/src/bind9/lib/dns/resolver.c

Source (jump to first uncovered line)
/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * SPDX-License-Identifier: MPL-2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, you can obtain one at https://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */

/*! \file */

#include <ctype.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdint.h>

#include <isc/ascii.h>
#include <isc/async.h>
#include <isc/atomic.h>
#include <isc/counter.h>
#include <isc/hash.h>
#include <isc/hashmap.h>
#include <isc/hex.h>
#include <isc/log.h>
#include <isc/loop.h>
#include <isc/mutex.h>
#include <isc/random.h>
#include <isc/refcount.h>
#include <isc/result.h>
#include <isc/rwlock.h>
#include <isc/siphash.h>
#include <isc/stats.h>
#include <isc/string.h>
#include <isc/tid.h>
#include <isc/time.h>
#include <isc/timer.h>
#include <isc/util.h>

#include <dns/acl.h>
#include <dns/adb.h>
#include <dns/cache.h>
#include <dns/db.h>
#include <dns/dispatch.h>
#include <dns/dns64.h>
#include <dns/dnstap.h>
#include <dns/ds.h>
#include <dns/ede.h>
#include <dns/edns.h>
#include <dns/forward.h>
#include <dns/keytable.h>
#include <dns/message.h>
#include <dns/name.h>
#include <dns/nametree.h>
#include <dns/ncache.h>
#include <dns/nsec.h>
#include <dns/nsec3.h>
#include <dns/opcode.h>
#include <dns/peer.h>
#include <dns/rcode.h>
#include <dns/rdata.h>
#include <dns/rdataclass.h>
#include <dns/rdatalist.h>
#include <dns/rdataset.h>
#include <dns/rdatastruct.h>
#include <dns/rdatatype.h>
#include <dns/resolver.h>
#include <dns/rootns.h>
#include <dns/stats.h>
#include <dns/tsig.h>
#include <dns/validator.h>
#include <dns/zone.h>

#ifdef WANT_QUERYTRACE
#define RTRACE(m)                                                       \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER, \
          ISC_LOG_DEBUG(3), "res %p: %s", res, (m))
#define RRTRACE(r, m)                                                   \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER, \
          ISC_LOG_DEBUG(3), "res %p: %s", (r), (m))
#define FCTXTRACE(m)                                                         \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,      \
          ISC_LOG_DEBUG(3), "fctx %p(%s): %s", fctx, fctx->info, \
          (m))
#define FCTXTRACE2(m1, m2)                                              \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER, \
          ISC_LOG_DEBUG(3), "fctx %p(%s): %s %s", fctx,     \
          fctx->info, (m1), (m2))
#define FCTXTRACE3(m, res)                                                    \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,       \
          ISC_LOG_DEBUG(3), "fctx %p(%s): [result: %s] %s", fctx, \
          fctx->info, isc_result_totext(res), (m))
#define FCTXTRACE4(m1, m2, res)                                            \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,    \
          ISC_LOG_DEBUG(3), "fctx %p(%s): [result: %s] %s %s", \
          fctx, fctx->info, isc_result_totext(res), (m1), (m2))
#define FCTXTRACE5(m1, m2, v)                                           \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER, \
          ISC_LOG_DEBUG(3), "fctx %p(%s): %s %s%u", fctx,   \
          fctx->info, (m1), (m2), (v))
#define FCTXTRACEN(m1, name, res)                                    \
  do {                                                         \
    if (isc_log_wouldlog(ISC_LOG_DEBUG(3))) {            \
      char dbuf[DNS_NAME_FORMATSIZE];              \
      dns_name_format((name), dbuf, sizeof(dbuf)); \
      FCTXTRACE4((m1), dbuf, (res));               \
    }                                                    \
  } while (0)
#define FTRACE(m)                                                            \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,      \
          ISC_LOG_DEBUG(3), "fetch %p (fctx %p(%s)): %s", fetch, \
          fetch->private, fetch->private->info, (m))
#define QTRACE(m)                                                        \
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,  \
          ISC_LOG_DEBUG(3), "resquery %p (fctx %p(%s)): %s", \
          query, query->fctx, query->fctx->info, (m))
#else /* ifdef WANT_QUERYTRACE */
#define RTRACE(m)          \
  do {               \
    UNUSED(m); \
  } while (0)
#define RRTRACE(r, m)      \
  do {               \
    UNUSED(r); \
    UNUSED(m); \
  } while (0)
#define FCTXTRACE(m)          \
  do {                  \
    UNUSED(fctx); \
    UNUSED(m);    \
  } while (0)
#define FCTXTRACE2(m1, m2)    \
  do {                  \
    UNUSED(fctx); \
    UNUSED(m1);   \
    UNUSED(m2);   \
  } while (0)
#define FCTXTRACE3(m1, res)   \
  do {                  \
    UNUSED(fctx); \
    UNUSED(m1);   \
    UNUSED(res);  \
  } while (0)
#define FCTXTRACE4(m1, m2, res) \
  do {                    \
    UNUSED(fctx);   \
    UNUSED(m1);     \
    UNUSED(m2);     \
    UNUSED(res);    \
  } while (0)
#define FCTXTRACE5(m1, m2, v) \
  do {                  \
    UNUSED(fctx); \
    UNUSED(m1);   \
    UNUSED(m2);   \
    UNUSED(v);    \
  } while (0)
#define FCTXTRACEN(m1, name, res) FCTXTRACE4(m1, name, res)
#define FTRACE(m)          \
  do {               \
    UNUSED(m); \
  } while (0)
#define QTRACE(m)          \
  do {               \
    UNUSED(m); \
  } while (0)
#endif /* WANT_QUERYTRACE */

/*
 * The maximum time we will wait for a single query.
 */
#define MAX_SINGLE_QUERY_TIMEOUT    9000U
#define MAX_SINGLE_QUERY_TIMEOUT_US (MAX_SINGLE_QUERY_TIMEOUT * US_PER_MS)

/*
 * The default maximum number of validations and validation failures per-fetch
 */
#ifndef DEFAULT_MAX_VALIDATIONS
#define DEFAULT_MAX_VALIDATIONS 16
#endif
#ifndef DEFAULT_MAX_VALIDATION_FAILURES
#define DEFAULT_MAX_VALIDATION_FAILURES 1
#endif

/*
 * A minumum sane timeout value for the whole query to live when e.g. talking to
 * a backend server and a quick timeout is preferred by the user.
 *
 * IMPORTANT: if changing this value, note there is a documented behavior when
 * values of 'resolver-query-timeout' less than or equal to 300 are treated as
 * seconds and converted to milliseconds before applying the limits, that's
 * why the value of 301 was chosen as the absolute minimum in order to not break
 * backward compatibility.
 */
#define MINIMUM_QUERY_TIMEOUT 301U

/*
 * The default time in seconds for the whole query to live.
 * We want to allow an individual query time to complete / timeout.
 */
#ifndef DEFAULT_QUERY_TIMEOUT
#define DEFAULT_QUERY_TIMEOUT (MAX_SINGLE_QUERY_TIMEOUT + 1000U)
#endif /* ifndef DEFAULT_QUERY_TIMEOUT */

/* The maximum time in seconds for the whole query to live. */
#ifndef MAXIMUM_QUERY_TIMEOUT
#define MAXIMUM_QUERY_TIMEOUT 30000
#endif /* ifndef MAXIMUM_QUERY_TIMEOUT */

/* The default maximum number of recursions to follow before giving up. */
#ifndef DEFAULT_RECURSION_DEPTH
#define DEFAULT_RECURSION_DEPTH 7
#endif /* ifndef DEFAULT_RECURSION_DEPTH */

/* The default maximum number of iterative queries to allow before giving up. */
#ifndef DEFAULT_MAX_QUERIES
#define DEFAULT_MAX_QUERIES 50
#endif /* ifndef DEFAULT_MAX_QUERIES */

/*
 * After NS_FAIL_LIMIT attempts to fetch a name server address,
 * if the number of addresses in the NS RRset exceeds NS_RR_LIMIT,
 * stop trying to fetch, in order to avoid wasting resources.
 */
#define NS_FAIL_LIMIT 4
#define NS_RR_LIMIT   5
/*
 * IP address lookups are performed for at most NS_PROCESSING_LIMIT NS RRs in
 * any NS RRset encountered, to avoid excessive resource use while processing
 * large delegations.
 */
#define NS_PROCESSING_LIMIT 20

STATIC_ASSERT(NS_PROCESSING_LIMIT > NS_RR_LIMIT,
        "The maximum number of NS RRs processed for each "
        "delegation "
        "(NS_PROCESSING_LIMIT) must be larger than the large "
        "delegation "
        "threshold (NS_RR_LIMIT).");

/* Hash table for zone counters */
#ifndef RES_DOMAIN_HASH_BITS
#define RES_DOMAIN_HASH_BITS 12
#endif /* ifndef RES_DOMAIN_HASH_BITS */

/*%
 * Maximum EDNS0 input packet size.
 */
#define RECV_BUFFER_SIZE 4096 /* XXXRTH  Constant. */

/*%
 * This defines the maximum number of timeouts we will permit before we
 * disable EDNS0 on the query.
 */
#define MAX_EDNS0_TIMEOUTS 3

typedef struct fetchctx fetchctx_t;

typedef struct query {
  /* Locked by loop event serialization. */
  unsigned int magic;
  isc_refcount_t references;
  fetchctx_t *fctx;
  dns_message_t *rmessage;
  dns_dispatchmgr_t *dispatchmgr;
  dns_dispatch_t *dispatch;
  dns_adbaddrinfo_t *addrinfo;
  isc_time_t start;
  dns_messageid_t id;
  dns_dispentry_t *dispentry;
  ISC_LINK(struct query) link;
  isc_buffer_t buffer;
  isc_buffer_t *tsig;
  dns_tsigkey_t *tsigkey;
  int ednsversion;
  unsigned int options;
  unsigned int attributes;
  unsigned int udpsize;
  unsigned char data[512];
} resquery_t;

#if DNS_RESOLVER_TRACE
#define resquery_ref(ptr)   resquery__ref(ptr, __func__, __FILE__, __LINE__)
#define resquery_unref(ptr) resquery__unref(ptr, __func__, __FILE__, __LINE__)
#define resquery_attach(ptr, ptrp) \
  resquery__attach(ptr, ptrp, __func__, __FILE__, __LINE__)
#define resquery_detach(ptrp) \
  resquery__detach(ptrp, __func__, __FILE__, __LINE__)
ISC_REFCOUNT_TRACE_DECL(resquery);
#else
ISC_REFCOUNT_DECL(resquery);
#endif

struct tried {
  isc_sockaddr_t addr;
  unsigned int count;
  ISC_LINK(struct tried) link;
};

#define QUERY_MAGIC    ISC_MAGIC('Q', '!', '!', '!')
#define VALID_QUERY(query) ISC_MAGIC_VALID(query, QUERY_MAGIC)

#define RESQUERY_ATTR_CANCELED 0x02

#define RESQUERY_CONNECTING(q) ((q)->connects > 0)
#define RESQUERY_CANCELED(q)   (((q)->attributes & RESQUERY_ATTR_CANCELED) != 0)
#define RESQUERY_SENDING(q)    ((q)->sends > 0)

typedef enum {
  fetchstate_active,
  fetchstate_done /*%< Fetch completion events posted. */
} fetchstate_t;

typedef enum {
  badns_unreachable = 0,
  badns_response,
  badns_validation,
  badns_forwarder,
} badnstype_t;

#define FCTXCOUNT_MAGIC    ISC_MAGIC('F', 'C', 'n', 't')
#define VALID_FCTXCOUNT(counter) ISC_MAGIC_VALID(counter, FCTXCOUNT_MAGIC)

typedef struct fctxcount fctxcount_t;
struct fctxcount {
  unsigned int magic;
  isc_mem_t *mctx;
  isc_mutex_t lock;
  dns_fixedname_t dfname;
  dns_name_t *domain;
  uint_fast32_t count;
  uint_fast32_t allowed;
  uint_fast32_t dropped;
  isc_stdtime_t logged;
};

struct fetchctx {
  /*% Not locked. */
  unsigned int magic;
  dns_resolver_t *res;
  dns_fixedname_t fname;
  dns_name_t *name;
  dns_rdatatype_t type;
  unsigned int options;
  fctxcount_t *counter;
  char *info;
  isc_mem_t *mctx;
  isc_stdtime_t now;

  isc_loop_t *loop;
  isc_tid_t tid;

  dns_edectx_t edectx;

  /* Atomic */
  isc_refcount_t references;

  /*% Locked by lock. */
  isc_mutex_t lock;
  fetchstate_t state;
  bool cloned;
  bool spilled;
  uint_fast32_t allowed;
  uint_fast32_t dropped;
  ISC_LIST(dns_fetchresponse_t) resps;

  /*% Locked by loop event serialization. */
  dns_fixedname_t dfname;
  dns_name_t *domain;
  dns_rdataset_t nameservers;
  atomic_uint_fast32_t attributes;
  isc_timer_t *timer;
  isc_time_t expires;
  isc_interval_t interval;
  dns_message_t *qmessage;
  ISC_LIST(resquery_t) queries;
  dns_adbfindlist_t finds;
  dns_adbfind_t *find;
  /*
   * altfinds are names and/or addresses of dual stack servers that
   * should be used when iterative resolution to a server is not
   * possible because the address family of that server is not usable.
   */
  dns_adbfindlist_t altfinds;
  dns_adbfind_t *altfind;
  dns_adbaddrinfolist_t forwaddrs;
  dns_adbaddrinfolist_t altaddrs;
  dns_forwarderlist_t forwarders;
  dns_fwdpolicy_t fwdpolicy;
  isc_sockaddrlist_t bad;
  ISC_LIST(struct tried) edns;
  ISC_LIST(dns_validator_t) validators;
  dns_db_t *cache;
  dns_adb_t *adb;
  bool ns_ttl_ok;
  uint32_t ns_ttl;
  isc_counter_t *qc;
  isc_counter_t *gqc;
  bool minimized;
  unsigned int qmin_labels;
  isc_result_t qmin_warning;
  bool force_qmin_warning;
  bool ip6arpaskip;
  bool forwarding;
  dns_fixedname_t qminfname;
  dns_name_t *qminname;
  dns_rdatatype_t qmintype;
  dns_fetch_t *qminfetch;
  dns_rdataset_t qminrrset;
  dns_rdataset_t qminsigrrset;
  dns_fixedname_t qmindcfname;
  dns_name_t *qmindcname;
  dns_fixedname_t fwdfname;
  dns_name_t *fwdname;

  /*%
   * The number of events we're waiting for.
   */
  atomic_uint_fast32_t pending;

  /*%
   * The number of times we've "restarted" the current
   * nameserver set.  This acts as a failsafe to prevent
   * us from pounding constantly on a particular set of
   * servers that, for whatever reason, are not giving
   * us useful responses, but are responding in such a
   * way that they are not marked "bad".
   */
  unsigned int restarts;

  /*%
   * The number of timeouts that have occurred since we
   * last successfully received a response packet.  This
   * is used for EDNS0 black hole detection.
   */
  unsigned int timeouts;

  /*%
   * Look aside state for DS lookups.
   */
  dns_fixedname_t nsfname;
  dns_name_t *nsname;

  dns_fetch_t *nsfetch;
  dns_rdataset_t nsrrset;

  /*%
   * Number of queries that reference this context.
   */
  atomic_uint_fast32_t nqueries; /* Bucket lock. */

  /*%
   * Random numbers to use for mixing up server addresses.
   */
  uint32_t rand_buf;
  uint32_t rand_bits;

  /*%
   * Fetch-local statistics for detailed logging.
   */
  isc_result_t result;  /*%< fetch result */
  isc_result_t vresult; /*%< validation result */
  isc_time_t start;
  uint64_t duration;
  bool logged;
  unsigned int querysent;
  unsigned int referrals;
  unsigned int lamecount;
  unsigned int quotacount;
  unsigned int neterr;
  unsigned int badresp;
  unsigned int adberr;
  unsigned int findfail;
  unsigned int valfail;
  bool timeout;
  dns_adbaddrinfo_t *addrinfo;
  unsigned int depth;
  char clientstr[ISC_SOCKADDR_FORMATSIZE];

  isc_counter_t *nvalidations;
  isc_counter_t *nfails;
};

#define FCTX_MAGIC   ISC_MAGIC('F', '!', '!', '!')
#define VALID_FCTX(fctx) ISC_MAGIC_VALID(fctx, FCTX_MAGIC)

#define FCTX_ATTR_HAVEANSWER 0x0001
#define FCTX_ATTR_GLUING     0x0002
#define FCTX_ATTR_ADDRWAIT   0x0004
#define FCTX_ATTR_WANTCACHE  0x0010
#define FCTX_ATTR_WANTNCACHE 0x0020
#define FCTX_ATTR_NEEDEDNS0  0x0040
#define FCTX_ATTR_TRIEDFIND  0x0080
#define FCTX_ATTR_TRIEDALT   0x0100

#define HAVE_ANSWER(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_HAVEANSWER) != 0)
#define GLUING(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_GLUING) != 0)
#define ADDRWAIT(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_ADDRWAIT) != 0)
#define SHUTTINGDOWN(f) ((f)->state == fetchstate_done)
#define WANTCACHE(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_WANTCACHE) != 0)
#define WANTNCACHE(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_WANTNCACHE) != 0)
#define NEEDEDNS0(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_NEEDEDNS0) != 0)
#define TRIEDFIND(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_TRIEDFIND) != 0)
#define TRIEDALT(f) \
  ((atomic_load_acquire(&(f)->attributes) & FCTX_ATTR_TRIEDALT) != 0)

#define FCTX_ATTR_SET(f, a) atomic_fetch_or_release(&(f)->attributes, (a))
#define FCTX_ATTR_CLR(f, a) atomic_fetch_and_release(&(f)->attributes, ~(a))

#define CHECKNTA(f) (((f)->options & DNS_FETCHOPT_NONTA) == 0)

typedef struct {
  dns_adbaddrinfo_t *addrinfo;
  fetchctx_t *fctx;
} dns_valarg_t;

struct dns_fetch {
  unsigned int magic;
  isc_mem_t *mctx;
  dns_resolver_t *res;
  fetchctx_t *private;
};

#define DNS_FETCH_MAGIC        ISC_MAGIC('F', 't', 'c', 'h')
#define DNS_FETCH_VALID(fetch) ISC_MAGIC_VALID(fetch, DNS_FETCH_MAGIC)

typedef struct alternate {
  bool isaddress;
  union {
    isc_sockaddr_t addr;
    struct {
      dns_name_t name;
      in_port_t port;
    } _n;
  } _u;
  ISC_LINK(struct alternate) link;
} alternate_t;

struct dns_resolver {
  /* Unlocked. */
  unsigned int magic;
  isc_mem_t *mctx;
  isc_mutex_t lock;
  isc_mutex_t primelock;
  dns_rdataclass_t rdclass;
  dns_view_t *view;
  bool frozen;
  unsigned int options;
  isc_tlsctx_cache_t *tlsctx_cache;
  dns_dispatchset_t *dispatches4;
  dns_dispatchset_t *dispatches6;

  isc_hashmap_t *fctxs;
  isc_rwlock_t fctxs_lock;

  isc_hashmap_t *counters;
  isc_rwlock_t counters_lock;

  uint32_t lame_ttl;
  ISC_LIST(alternate_t) alternates;
  dns_nametree_t *algorithms;
  dns_nametree_t *digests;
  unsigned int spillatmax;
  unsigned int spillatmin;
  isc_timer_t *spillattimer;
  bool zero_no_soa_ttl;
  unsigned int query_timeout;
  unsigned int maxdepth;
  unsigned int maxqueries;
  isc_result_t quotaresp[2];
  isc_stats_t *stats;
  dns_stats_t *querystats;

  /* Additions for serve-stale feature. */
  unsigned int retryinterval; /* in milliseconds */
  unsigned int nonbackofftries;

  /* Atomic */
  isc_refcount_t references;
  atomic_uint_fast32_t zspill; /* fetches-per-zone */
  atomic_bool exiting;
  atomic_bool priming;

  atomic_uint_fast32_t maxvalidations;
  atomic_uint_fast32_t maxvalidationfails;

  /* Locked by lock. */
  unsigned int spillat; /* clients-per-query */

  /* Locked by primelock. */
  dns_fetch_t *primefetch;

  uint32_t nloops;

  isc_mempool_t **namepools;
  isc_mempool_t **rdspools;
};

#define RES_MAGIC     ISC_MAGIC('R', 'e', 's', '!')
#define VALID_RESOLVER(res) ISC_MAGIC_VALID(res, RES_MAGIC)

/*%
 * Private addrinfo flags.
 */
enum {
  FCTX_ADDRINFO_MARK = 1 << 0,
  FCTX_ADDRINFO_FORWARDER = 1 << 1,
  FCTX_ADDRINFO_EDNSOK = 1 << 2,
  FCTX_ADDRINFO_NOCOOKIE = 1 << 3,
  FCTX_ADDRINFO_BADCOOKIE = 1 << 4,
  FCTX_ADDRINFO_DUALSTACK = 1 << 5,
  FCTX_ADDRINFO_NOEDNS0 = 1 << 6,
};

#define UNMARKED(a)    (((a)->flags & FCTX_ADDRINFO_MARK) == 0)
#define ISFORWARDER(a) (((a)->flags & FCTX_ADDRINFO_FORWARDER) != 0)
#define NOCOOKIE(a)    (((a)->flags & FCTX_ADDRINFO_NOCOOKIE) != 0)
#define EDNSOK(a)      (((a)->flags & FCTX_ADDRINFO_EDNSOK) != 0)
#define BADCOOKIE(a)   (((a)->flags & FCTX_ADDRINFO_BADCOOKIE) != 0)
#define ISDUALSTACK(a) (((a)->flags & FCTX_ADDRINFO_DUALSTACK) != 0)

#define NXDOMAIN(r)   (((r)->attributes.nxdomain))
#define NEGATIVE(r)   (((r)->attributes.negative))
#define STATICSTUB(r) (((r)->attributes.staticstub))

#ifdef ENABLE_AFL
bool dns_fuzzing_resolver = false;
void
dns_resolver_setfuzzing(void) {
  dns_fuzzing_resolver = true;
}
#endif /* ifdef ENABLE_AFL */

static unsigned char ip6_arpa_data[] = "\003IP6\004ARPA";
static const dns_name_t ip6_arpa = DNS_NAME_INITABSOLUTE(ip6_arpa_data);

static void
dns_resolver__destroy(dns_resolver_t *res);
static isc_result_t
resquery_send(resquery_t *query);
static void
resquery_response(isc_result_t eresult, isc_region_t *region, void *arg);
static void
resquery_response_continue(void *arg, isc_result_t result);
static void
resquery_connected(isc_result_t eresult, isc_region_t *region, void *arg);
static void
fctx_try(fetchctx_t *fctx, bool retrying);
static void
fctx_shutdown(void *arg);
static void
fctx_minimize_qname(fetchctx_t *fctx);
static void
fctx_destroy(fetchctx_t *fctx);
static isc_result_t
negcache(dns_message_t *message, fetchctx_t *fctx, const dns_name_t *name,
   isc_stdtime_t now, bool optout, bool secure, dns_rdataset_t *added,
   dns_dbnode_t **nodep);
static void
validated(void *arg);
static void
maybe_cancel_validators(fetchctx_t *fctx);
static void
add_bad(fetchctx_t *fctx, dns_message_t *rmessage, dns_adbaddrinfo_t *addrinfo,
  isc_result_t reason, badnstype_t badtype);
static void
findnoqname(fetchctx_t *fctx, dns_message_t *message, dns_name_t *name,
      dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset);

#define fctx_done_detach(fctxp, result)                                 \
  if (fctx__done(*fctxp, result, __func__, __FILE__, __LINE__)) { \
    fetchctx_detach(fctxp);                                 \
  }

#define fctx_done_unref(fctx, result)                                 \
  if (fctx__done(fctx, result, __func__, __FILE__, __LINE__)) { \
    fetchctx_unref(fctx);                                 \
  }

#if DNS_RESOLVER_TRACE
#define fetchctx_ref(ptr)   fetchctx__ref(ptr, __func__, __FILE__, __LINE__)
#define fetchctx_unref(ptr) fetchctx__unref(ptr, __func__, __FILE__, __LINE__)
#define fetchctx_attach(ptr, ptrp) \
  fetchctx__attach(ptr, ptrp, __func__, __FILE__, __LINE__)
#define fetchctx_detach(ptrp) \
  fetchctx__detach(ptrp, __func__, __FILE__, __LINE__)
ISC_REFCOUNT_TRACE_DECL(fetchctx);
#else
ISC_REFCOUNT_DECL(fetchctx);
#endif

static bool
fctx__done(fetchctx_t *fctx, isc_result_t result, const char *func,
     const char *file, unsigned int line);

static void
resume_qmin(void *arg);

static void
clone_results(fetchctx_t *fctx);

static isc_result_t
get_attached_fctx(dns_resolver_t *res, isc_loop_t *loop, const dns_name_t *name,
      dns_rdatatype_t type, const dns_name_t *domain,
      dns_rdataset_t *nameservers, const isc_sockaddr_t *client,
      unsigned int options, unsigned int depth, isc_counter_t *qc,
      isc_counter_t *gqc, fetchctx_t **fctxp, bool *new_fctx);

/*%
 * The structure and functions defined below implement the resolver
 * query (resquery) response handling logic.
 *
 * When a resolver query is sent and a response is received, the
 * resquery_response() event handler is run, which calls the rctx_*()
 * functions.  The respctx_t structure maintains state from function
 * to function.
 *
 * The call flow is described below:
 *
 * 1. resquery_response():
 *    - Initialize a respctx_t structure (rctx_respinit()).
 *    - Check for dispatcher failure (rctx_dispfail()).
 *    - Parse the response (rctx_parse()).
 *    - Log the response (rctx_logpacket()).
 *    - Check the parsed response for an OPT record and handle
 *      EDNS (rctx_opt(), rctx_edns()).
 *    - Check for a bad or lame server (rctx_badserver(), rctx_lameserver()).
 *    - If RCODE and ANCOUNT suggest this is a positive answer, and
 *      if so, call rctx_answer(): go to step 2.
 *    - If RCODE and NSCOUNT suggest this is a negative answer or a
 *      referral, call rctx_answer_none(): go to step 4.
 *    - Check the additional section for data that should be cached
 *      (rctx_additional()).
 *    - Clean up and finish by calling rctx_done(): go to step 5.
 *
 * 2. rctx_answer():
 *    - If the answer appears to be positive, call rctx_answer_positive():
 *      go to step 3.
 *    - If the response is a malformed delegation (with glue or NS records
 *      in the answer section), call rctx_answer_none(): go to step 4.
 *
 * 3. rctx_answer_positive():
 *    - Initialize the portions of respctx_t needed for processing an answer
 *      (rctx_answer_init()).
 *    - Scan the answer section to find records that are responsive to the
 *      query (rctx_answer_scan()).
 *    - For whichever type of response was found, call a separate routine
 *      to handle it: matching QNAME/QTYPE (rctx_answer_match()),
 *      CNAME (rctx_answer_cname()), covering DNAME (rctx_answer_dname()),
 *      or any records returned in response to a query of type ANY
 *      (rctx_answer_any()).
 *    - Scan the authority section for NS or other records that may be
 *      included with a positive answer (rctx_authority_scan()).
 *
 * 4. rctx_answer_none():
 *    - Determine whether this is an NXDOMAIN, NXRRSET, or referral.
 *    - If referral, set up the resolver to follow the delegation
 *      (rctx_referral()).
 *    - If NXDOMAIN/NXRRSET, scan the authority section for NS and SOA
 *      records included with a negative response (rctx_authority_negative()),
 *      then for DNSSEC proof of nonexistence (rctx_authority_dnssec()).
 *
 * 5. rctx_done():
 *    - Set up chasing of DS records if needed (rctx_chaseds()).
 *    - If the response wasn't intended for us, wait for another response
 *      from the dispatcher (rctx_next()).
 *    - If there is a problem with the responding server, set up another
 *      query to a different server (rctx_nextserver()).
 *    - If there is a problem that might be temporary or dependent on
 *      EDNS options, set up another query to the same server with changed
 *      options (rctx_resend()).
 *    - Shut down the fetch context.
 */

typedef struct respctx {
  resquery_t *query;
  fetchctx_t *fctx;
  isc_mem_t *mctx;
  isc_result_t result;
  isc_buffer_t buffer;
  unsigned int retryopts; /* updated options to pass to
         * fctx_query() when resending */

  dns_rdatatype_t type; /* type being sought (set to
             * ANY if qtype was SIG or RRSIG) */
  bool aa;        /* authoritative answer? */
  dns_trust_t trust;    /* answer trust level */
  bool chaining;        /* CNAME/DNAME processing? */
  bool next_server;     /* give up, try the next server
             * */

  badnstype_t broken_type; /* type of name server problem
          * */
  isc_result_t broken_server;

  bool get_nameservers; /* get a new NS rrset at
             * zone cut? */
  bool resend;        /* resend this query? */
  bool nextitem;        /* invalid response; keep
             * listening for the correct one */
  bool truncated;       /* response was truncated */
  bool no_response;     /* no response was received */
  bool negative;        /* is this a negative response? */

  isc_stdtime_t now; /* time info */
  isc_time_t tnow;
  isc_time_t *finish;

  unsigned int dname_labels;
  unsigned int domain_labels; /* range of permissible number
             * of
             * labels in a DNAME */

  dns_name_t *aname;     /* answer name */
  dns_rdataset_t *ardataset; /* answer rdataset */

  dns_name_t *cname;     /* CNAME name */
  dns_rdataset_t *crdataset; /* CNAME rdataset */

  dns_name_t *dname;     /* DNAME name */
  dns_rdataset_t *drdataset; /* DNAME rdataset */

  dns_name_t *ns_name;       /* NS name */
  dns_rdataset_t *ns_rdataset; /* NS rdataset */

  dns_name_t *soa_name; /* SOA name in a negative answer */
  dns_name_t *ds_name;  /* DS name in a negative answer */

  dns_name_t *found_name;     /* invalid name in negative
             * response */
  dns_rdatatype_t found_type; /* invalid type in negative
             * response */

  dns_rdataset_t *opt; /* OPT rdataset */

  dns_rdataset_t *vrdataset;
  dns_rdataset_t *vsigrdataset;
} respctx_t;

static void
rctx_respinit(resquery_t *query, fetchctx_t *fctx, isc_result_t result,
        isc_region_t *region, respctx_t *rctx);

static void
rctx_answer_init(respctx_t *rctx);

static void
rctx_answer_scan(respctx_t *rctx);

static void
rctx_authority_positive(respctx_t *rctx);

static isc_result_t
rctx_answer_any(respctx_t *rctx);

static isc_result_t
rctx_answer_match(respctx_t *rctx);

static isc_result_t
rctx_answer_cname(respctx_t *rctx);

static isc_result_t
rctx_answer_dname(respctx_t *rctx);

static isc_result_t
rctx_answer_positive(respctx_t *rctx);

static isc_result_t
rctx_authority_negative(respctx_t *rctx);

static isc_result_t
rctx_authority_dnssec(respctx_t *rctx);

static void
rctx_additional(respctx_t *rctx);

static isc_result_t
rctx_referral(respctx_t *rctx);

static isc_result_t
rctx_answer_none(respctx_t *rctx);

static void
rctx_nextserver(respctx_t *rctx, dns_message_t *message,
    dns_adbaddrinfo_t *addrinfo, isc_result_t result);

static void
rctx_resend(respctx_t *rctx, dns_adbaddrinfo_t *addrinfo);

static isc_result_t
rctx_next(respctx_t *rctx);

static void
rctx_chaseds(respctx_t *rctx, dns_message_t *message,
       dns_adbaddrinfo_t *addrinfo, isc_result_t result);

static void
rctx_done(respctx_t *rctx, isc_result_t result);

static void
rctx_logpacket(respctx_t *rctx);

static void
rctx_opt(respctx_t *rctx);

static void
rctx_edns(respctx_t *rctx);

static isc_result_t
rctx_parse(respctx_t *rctx);

static isc_result_t
rctx_badserver(respctx_t *rctx, isc_result_t result);

static isc_result_t
rctx_answer(respctx_t *rctx);

static isc_result_t
rctx_lameserver(respctx_t *rctx);

static isc_result_t
rctx_dispfail(respctx_t *rctx);

static isc_result_t
rctx_timedout(respctx_t *rctx);

static void
rctx_ncache(respctx_t *rctx);

/*%
 * Increment resolver-related statistics counters.
 */
static void
inc_stats(dns_resolver_t *res, isc_statscounter_t counter) {
  if (res->stats != NULL) {
    isc_stats_increment(res->stats, counter);
  }
}

static void
dec_stats(dns_resolver_t *res, isc_statscounter_t counter) {
  if (res->stats != NULL) {
    isc_stats_decrement(res->stats, counter);
  }
}

static void
set_stats(dns_resolver_t *res, isc_statscounter_t counter, uint64_t val) {
  if (res->stats != NULL) {
    isc_stats_set(res->stats, val, counter);
  }
}

static void
valcreate(fetchctx_t *fctx, dns_message_t *message, dns_adbaddrinfo_t *addrinfo,
    dns_name_t *name, dns_rdatatype_t type, dns_rdataset_t *rdataset,
    dns_rdataset_t *sigrdataset) {
  dns_validator_t *validator = NULL;
  dns_valarg_t *valarg = NULL;
  unsigned int valoptions = 0;
  isc_result_t result;

  valarg = isc_mem_get(fctx->mctx, sizeof(*valarg));
  *valarg = (dns_valarg_t){
    .addrinfo = addrinfo,
  };

  fetchctx_attach(fctx, &valarg->fctx);

  /* Set up validator options */
  if ((fctx->options & DNS_FETCHOPT_NOCDFLAG) != 0) {
    valoptions |= DNS_VALIDATOR_NOCDFLAG;
  }

  if ((fctx->options & DNS_FETCHOPT_NONTA) != 0) {
    valoptions |= DNS_VALIDATOR_NONTA;
  }

  if (!ISC_LIST_EMPTY(fctx->validators)) {
    valoptions |= DNS_VALIDATOR_DEFER;
  }

  result = dns_validator_create(
    fctx->res->view, name, type, rdataset, sigrdataset, message,
    valoptions, fctx->loop, validated, valarg, fctx->nvalidations,
    fctx->nfails, fctx->qc, fctx->gqc, &fctx->edectx, &validator);
  RUNTIME_CHECK(result == ISC_R_SUCCESS);
  inc_stats(fctx->res, dns_resstatscounter_val);
  ISC_LIST_APPEND(fctx->validators, validator, link);
}

static void
resquery_destroy(resquery_t *query) {
  fetchctx_t *fctx = query->fctx;

  query->magic = 0;

  if (ISC_LINK_LINKED(query, link)) {
    ISC_LIST_UNLINK(fctx->queries, query, link);
  }

  if (query->tsig != NULL) {
    isc_buffer_free(&query->tsig);
  }

  if (query->tsigkey != NULL) {
    dns_tsigkey_detach(&query->tsigkey);
  }

  if (query->dispentry != NULL) {
    dns_dispatch_done(&query->dispentry);
  }

  if (query->dispatch != NULL) {
    dns_dispatch_detach(&query->dispatch);
  }

  LOCK(&fctx->lock);
  atomic_fetch_sub_release(&fctx->nqueries, 1);
  UNLOCK(&fctx->lock);

  if (query->rmessage != NULL) {
    dns_message_detach(&query->rmessage);
  }

  isc_mem_put(fctx->mctx, query, sizeof(*query));

  fetchctx_detach(&fctx);
}

#if DNS_RESOLVER_TRACE
ISC_REFCOUNT_TRACE_IMPL(resquery, resquery_destroy);
#else
ISC_REFCOUNT_IMPL(resquery, resquery_destroy);
#endif

/*%
 * Update EDNS statistics for a server after not getting a response to a UDP
 * query sent to it.
 */
static void
update_edns_stats(resquery_t *query) {
  fetchctx_t *fctx = query->fctx;

  if ((query->options & DNS_FETCHOPT_TCP) != 0) {
    return;
  }

  if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
    dns_adb_ednsto(fctx->adb, query->addrinfo);
  } else {
    dns_adb_timeout(fctx->adb, query->addrinfo);
  }
}

static void
fctx_expired(void *arg);

/*
 * Start the maximum lifetime timer for the fetch. This will
 * trigger if, for example, some ADB or validator dependency
 * loop occurs and causes a fetch to hang.
 */
static void
fctx_starttimer(fetchctx_t *fctx) {
  isc_interval_t interval;
  isc_time_t now;
  isc_time_t expires;

  isc_interval_set(&interval, 2, 0);
  isc_time_add(&fctx->expires, &interval, &expires);

  now = isc_time_now();
  if (isc_time_compare(&expires, &now) <= 0) {
    isc_interval_set(&interval, 0, 1);
  } else {
    isc_time_subtract(&expires, &now, &interval);
  }

  isc_timer_start(fctx->timer, isc_timertype_once, &interval);
}

static void
fctx_stoptimer(fetchctx_t *fctx) {
  isc_timer_stop(fctx->timer);
}

static void
fctx_cancelquery(resquery_t **queryp, isc_time_t *finish, bool no_response,
     bool age_untried) {
  resquery_t *query = NULL;
  fetchctx_t *fctx = NULL;
  isc_stdtime_t now = isc_stdtime_now();

  REQUIRE(queryp != NULL);

  query = *queryp;
  fctx = query->fctx;

  if (RESQUERY_CANCELED(query)) {
    return;
  }

  FCTXTRACE("cancelquery");

  query->attributes |= RESQUERY_ATTR_CANCELED;

  /*
   * Should we update the RTT?
   */
  if (finish != NULL || no_response) {
    unsigned int rtt, factor;
    if (finish != NULL) {
      /*
       * We have both the start and finish times for this
       * packet, so we can compute a real RTT.
       */
      unsigned int rttms;

      rtt = (unsigned int)isc_time_microdiff(finish,
                     &query->start);
      rttms = rtt / US_PER_MS;
      factor = DNS_ADB_RTTADJDEFAULT;

      if (rttms < DNS_RESOLVER_QRYRTTCLASS0) {
        inc_stats(fctx->res,
            dns_resstatscounter_queryrtt0);
      } else if (rttms < DNS_RESOLVER_QRYRTTCLASS1) {
        inc_stats(fctx->res,
            dns_resstatscounter_queryrtt1);
      } else if (rttms < DNS_RESOLVER_QRYRTTCLASS2) {
        inc_stats(fctx->res,
            dns_resstatscounter_queryrtt2);
      } else if (rttms < DNS_RESOLVER_QRYRTTCLASS3) {
        inc_stats(fctx->res,
            dns_resstatscounter_queryrtt3);
      } else if (rttms < DNS_RESOLVER_QRYRTTCLASS4) {
        inc_stats(fctx->res,
            dns_resstatscounter_queryrtt4);
      } else {
        inc_stats(fctx->res,
            dns_resstatscounter_queryrtt5);
      }
    } else {
      uint32_t value;
      uint32_t mask;

      update_edns_stats(query);

      /*
       * If "forward first;" is used and a forwarder timed
       * out, do not attempt to query it again in this fetch
       * context.
       */
      if (fctx->fwdpolicy == dns_fwdpolicy_first &&
          ISFORWARDER(query->addrinfo))
      {
        add_bad(fctx, query->rmessage, query->addrinfo,
          ISC_R_TIMEDOUT, badns_forwarder);
      }

      /*
       * We don't have an RTT for this query.  Maybe the
       * packet was lost, or maybe this server is very
       * slow.  We don't know.  Increase the RTT.
       */
      INSIST(no_response);
      value = isc_random32();
      if (query->addrinfo->srtt > 800000) {
        mask = 0x3fff;
      } else if (query->addrinfo->srtt > 400000) {
        mask = 0x7fff;
      } else if (query->addrinfo->srtt > 200000) {
        mask = 0xffff;
      } else if (query->addrinfo->srtt > 100000) {
        mask = 0x1ffff;
      } else if (query->addrinfo->srtt > 50000) {
        mask = 0x3ffff;
      } else if (query->addrinfo->srtt > 25000) {
        mask = 0x7ffff;
      } else {
        mask = 0xfffff;
      }

      /*
       * Don't adjust timeout on EDNS queries unless we have
       * seen a EDNS response.
       */
      if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0 &&
          !EDNSOK(query->addrinfo))
      {
        mask >>= 2;
      }

      rtt = query->addrinfo->srtt + (value & mask);
      if (rtt > MAX_SINGLE_QUERY_TIMEOUT_US) {
        rtt = MAX_SINGLE_QUERY_TIMEOUT_US;
      }
      if (rtt > fctx->res->query_timeout * US_PER_MS) {
        rtt = fctx->res->query_timeout * US_PER_MS;
      }

      /*
       * Replace the current RTT with our value.
       */
      factor = DNS_ADB_RTTADJREPLACE;
    }

    dns_adb_adjustsrtt(fctx->adb, query->addrinfo, rtt, factor);
  }

  if ((query->options & DNS_FETCHOPT_TCP) == 0) {
    /* Inform the ADB that we're ending a UDP fetch */
    dns_adb_endudpfetch(fctx->adb, query->addrinfo);
  }

  /*
   * Age RTTs of servers not tried.
   */
  if (finish != NULL || age_untried) {
    ISC_LIST_FOREACH(fctx->forwaddrs, addrinfo, publink) {
      if (UNMARKED(addrinfo)) {
        dns_adb_agesrtt(fctx->adb, addrinfo, now);
      }
    }
  }

  if ((finish != NULL || age_untried) && TRIEDFIND(fctx)) {
    ISC_LIST_FOREACH(fctx->finds, find, publink) {
      ISC_LIST_FOREACH(find->list, addrinfo, publink) {
        if (UNMARKED(addrinfo)) {
          dns_adb_agesrtt(fctx->adb, addrinfo,
              now);
        }
      }
    }
  }

  if ((finish != NULL || age_untried) && TRIEDALT(fctx)) {
    ISC_LIST_FOREACH(fctx->altaddrs, addrinfo, publink) {
      if (UNMARKED(addrinfo)) {
        dns_adb_agesrtt(fctx->adb, addrinfo, now);
      }
    }
    ISC_LIST_FOREACH(fctx->altfinds, find, publink) {
      ISC_LIST_FOREACH(find->list, addrinfo, publink) {
        if (UNMARKED(addrinfo)) {
          dns_adb_agesrtt(fctx->adb, addrinfo,
              now);
        }
      }
    }
  }

  /*
   * Check for any outstanding dispatch responses and if they
   * exist, cancel them.
   */
  if (query->dispentry != NULL) {
    dns_dispatch_done(&query->dispentry);
  }

  LOCK(&fctx->lock);
  if (ISC_LINK_LINKED(query, link)) {
    ISC_LIST_UNLINK(fctx->queries, query, link);
  }
  UNLOCK(&fctx->lock);

  resquery_detach(queryp);
}

static void
fctx_cleanup(fetchctx_t *fctx) {
  REQUIRE(ISC_LIST_EMPTY(fctx->queries));

  ISC_LIST_FOREACH(fctx->finds, find, publink) {
    ISC_LIST_UNLINK(fctx->finds, find, publink);
    dns_adb_destroyfind(&find);
    fetchctx_unref(fctx);
  }
  fctx->find = NULL;

  ISC_LIST_FOREACH(fctx->altfinds, find, publink) {
    ISC_LIST_UNLINK(fctx->altfinds, find, publink);
    dns_adb_destroyfind(&find);
    fetchctx_unref(fctx);
  }
  fctx->altfind = NULL;

  ISC_LIST_FOREACH(fctx->forwaddrs, addr, publink) {
    ISC_LIST_UNLINK(fctx->forwaddrs, addr, publink);
    dns_adb_freeaddrinfo(fctx->adb, &addr);
  }

  ISC_LIST_FOREACH(fctx->altaddrs, addr, publink) {
    ISC_LIST_UNLINK(fctx->altaddrs, addr, publink);
    dns_adb_freeaddrinfo(fctx->adb, &addr);
  }
}

static void
fctx_cancelqueries(fetchctx_t *fctx, bool no_response, bool age_untried) {
  ISC_LIST(resquery_t) queries;

  FCTXTRACE("cancelqueries");

  ISC_LIST_INIT(queries);

  /*
   * Move the queries to a local list so we can cancel
   * them without holding the lock.
   */
  LOCK(&fctx->lock);
  ISC_LIST_MOVE(queries, fctx->queries);
  UNLOCK(&fctx->lock);

  ISC_LIST_FOREACH(queries, query, link) {
    /*
     * Note that we have to unlink the query here,
     * because if it's still linked in fctx_cancelquery(),
     * then it will try to unlink it from fctx->queries.
     */
    ISC_LIST_UNLINK(queries, query, link);
    fctx_cancelquery(&query, NULL, no_response, age_untried);
  }
}

static void
fcount_logspill(fetchctx_t *fctx, fctxcount_t *counter, bool final) {
  char dbuf[DNS_NAME_FORMATSIZE];
  isc_stdtime_t now;

  if (!isc_log_wouldlog(ISC_LOG_INFO)) {
    return;
  }

  /* Do not log a message if there were no dropped fetches. */
  if (counter->dropped == 0) {
    return;
  }

  /* Do not log the cumulative message if the previous log is recent. */
  now = isc_stdtime_now();
  if (!final && counter->logged > now - 60) {
    return;
  }

  dns_name_format(fctx->domain, dbuf, sizeof(dbuf));

  if (!final) {
    isc_log_write(DNS_LOGCATEGORY_SPILL, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_INFO,
            "too many simultaneous fetches for %s "
            "(allowed %" PRIuFAST32 " spilled %" PRIuFAST32
            "; %s)",
            dbuf, counter->allowed, counter->dropped,
            counter->dropped == 1 ? "initial trigger event"
                : "cumulative since "
                  "initial trigger event");
  } else {
    isc_log_write(DNS_LOGCATEGORY_SPILL, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_INFO,
            "fetch counters for %s now being discarded "
            "(allowed %" PRIuFAST32 " spilled %" PRIuFAST32
            "; cumulative since initial trigger event)",
            dbuf, counter->allowed, counter->dropped);
  }

  counter->logged = now;
}

static bool
fcount_match(void *node, const void *key) {
  const fctxcount_t *counter = node;
  const dns_name_t *domain = key;

  return dns_name_equal(counter->domain, domain);
}

static isc_result_t
fcount_incr(fetchctx_t *fctx, bool force) {
  isc_result_t result = ISC_R_SUCCESS;
  dns_resolver_t *res = NULL;
  fctxcount_t *counter = NULL;
  uint32_t hashval;
  uint_fast32_t spill;
  isc_rwlocktype_t locktype = isc_rwlocktype_read;

  REQUIRE(fctx != NULL);
  res = fctx->res;
  REQUIRE(res != NULL);
  INSIST(fctx->counter == NULL);

  /* Skip any counting if fetches-per-zone is disabled */
  spill = atomic_load_acquire(&res->zspill);
  if (spill == 0) {
    return ISC_R_SUCCESS;
  }

  hashval = dns_name_hash(fctx->domain);

  RWLOCK(&res->counters_lock, locktype);
  result = isc_hashmap_find(res->counters, hashval, fcount_match,
          fctx->domain, (void **)&counter);
  switch (result) {
  case ISC_R_SUCCESS:
    break;
  case ISC_R_NOTFOUND:
    counter = isc_mem_get(fctx->mctx, sizeof(*counter));
    *counter = (fctxcount_t){
      .magic = FCTXCOUNT_MAGIC,
    };
    isc_mem_attach(fctx->mctx, &counter->mctx);
    isc_mutex_init(&counter->lock);
    counter->domain = dns_fixedname_initname(&counter->dfname);
    dns_name_copy(fctx->domain, counter->domain);

    UPGRADELOCK(&res->counters_lock, locktype);

    void *found = NULL;
    result = isc_hashmap_add(res->counters, hashval, fcount_match,
           counter->domain, counter, &found);
    if (result == ISC_R_EXISTS) {
      isc_mutex_destroy(&counter->lock);
      isc_mem_putanddetach(&counter->mctx, counter,
               sizeof(*counter));
      counter = found;
      result = ISC_R_SUCCESS;
    }

    INSIST(result == ISC_R_SUCCESS);
    break;
  default:
    UNREACHABLE();
  }
  INSIST(VALID_FCTXCOUNT(counter));

  INSIST(spill > 0);
  LOCK(&counter->lock);
  if (++counter->count > spill && !force) {
    counter->count--;
    INSIST(counter->count > 0);
    counter->dropped++;
    fcount_logspill(fctx, counter, false);
    result = ISC_R_QUOTA;
  } else {
    counter->allowed++;
    fctx->counter = counter;
  }
  UNLOCK(&counter->lock);
  RWUNLOCK(&res->counters_lock, locktype);

  return result;
}

static bool
match_ptr(void *node, const void *key) {
  return node == key;
}

static void
fcount_decr(fetchctx_t *fctx) {
  REQUIRE(fctx != NULL);

  fctxcount_t *counter = fctx->counter;
  if (counter == NULL) {
    return;
  }
  fctx->counter = NULL;

  /*
   * FIXME: This should not require a write lock, but should be
   * implemented using reference counting later, otherwise we would could
   * encounter ABA problem here - the count could go up and down when we
   * switch from read to write lock.
   */
  RWLOCK(&fctx->res->counters_lock, isc_rwlocktype_write);

  LOCK(&counter->lock);
  INSIST(VALID_FCTXCOUNT(counter));
  INSIST(counter->count > 0);
  if (--counter->count > 0) {
    UNLOCK(&counter->lock);
    RWUNLOCK(&fctx->res->counters_lock, isc_rwlocktype_write);
    return;
  }

  isc_result_t result = isc_hashmap_delete(fctx->res->counters,
             dns_name_hash(counter->domain),
             match_ptr, counter);
  INSIST(result == ISC_R_SUCCESS);

  fcount_logspill(fctx, counter, true);
  UNLOCK(&counter->lock);

  isc_mutex_destroy(&counter->lock);
  isc_mem_putanddetach(&counter->mctx, counter, sizeof(*counter));

  RWUNLOCK(&fctx->res->counters_lock, isc_rwlocktype_write);
}

static void
spillattimer_countdown(void *arg);

static void
fctx_sendevents(fetchctx_t *fctx, isc_result_t result) {
  unsigned int count = 0;
  bool logit = false;
  isc_time_t now;
  unsigned int old_spillat;
  unsigned int new_spillat = 0; /* initialized to silence
               * compiler warnings */

  LOCK(&fctx->lock);

  REQUIRE(fctx->state == fetchstate_done);

  FCTXTRACE("sendevents");

  /*
   * Keep some record of fetch result for logging later (if required).
   */
  fctx->result = result;
  now = isc_time_now();
  fctx->duration = isc_time_microdiff(&now, &fctx->start);

  ISC_LIST_FOREACH(fctx->resps, resp, link) {
    ISC_LIST_UNLINK(fctx->resps, resp, link);

    count++;

    resp->vresult = fctx->vresult;
    if (!HAVE_ANSWER(fctx)) {
      resp->result = result;
    }

    INSIST(resp->result != ISC_R_SUCCESS ||
           dns_rdataset_isassociated(resp->rdataset) ||
           dns_rdatatype_ismulti(fctx->type));

    /*
     * Negative results must be indicated in resp->result.
     */
    if (dns_rdataset_isassociated(resp->rdataset) &&
        NEGATIVE(resp->rdataset))
    {
      INSIST(resp->result == DNS_R_NCACHENXDOMAIN ||
             resp->result == DNS_R_NCACHENXRRSET);
    }

    /*
     * Finalize the EDE context so it becomes "constant", and
     * assign it to all clients.
     */
    if (resp->edectx != NULL) {
      dns_ede_copy(resp->edectx, &fctx->edectx);
    }

    FCTXTRACE("post response event");
    isc_async_run(resp->loop, resp->cb, resp);
  }
  UNLOCK(&fctx->lock);

  if (HAVE_ANSWER(fctx) && fctx->spilled &&
      (count < fctx->res->spillatmax || fctx->res->spillatmax == 0))
  {
    LOCK(&fctx->res->lock);
    if (count == fctx->res->spillat &&
        !atomic_load_acquire(&fctx->res->exiting))
    {
      old_spillat = fctx->res->spillat;
      fctx->res->spillat += 5;
      if (fctx->res->spillat > fctx->res->spillatmax &&
          fctx->res->spillatmax != 0)
      {
        fctx->res->spillat = fctx->res->spillatmax;
      }
      new_spillat = fctx->res->spillat;
      if (new_spillat != old_spillat) {
        logit = true;
      }

      /* Timer not running */
      if (fctx->res->spillattimer == NULL) {
        isc_interval_t i;

        isc_timer_create(
          isc_loop(), spillattimer_countdown,
          fctx->res, &fctx->res->spillattimer);

        isc_interval_set(&i, 20 * 60, 0);
        isc_timer_start(fctx->res->spillattimer,
            isc_timertype_ticker, &i);
      }
    }
    UNLOCK(&fctx->res->lock);
    if (logit) {
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
              "clients-per-query increased to %u",
              new_spillat);
    }
  }
}

static uint32_t
fctx_hash(fetchctx_t *fctx) {
  isc_hash32_t hash32;
  isc_hash32_init(&hash32);
  isc_hash32_hash(&hash32, fctx->name->ndata, fctx->name->length, false);
  isc_hash32_hash(&hash32, &fctx->options, sizeof(fctx->options), true);
  isc_hash32_hash(&hash32, &fctx->type, sizeof(fctx->type), true);
  return isc_hash32_finalize(&hash32);
}

static bool
fctx_match(void *node, const void *key) {
  const fetchctx_t *fctx0 = node;
  const fetchctx_t *fctx1 = key;

  return fctx0->options == fctx1->options && fctx0->type == fctx1->type &&
         dns_name_equal(fctx0->name, fctx1->name);
}

static bool
fctx__done(fetchctx_t *fctx, isc_result_t result, const char *func,
     const char *file, unsigned int line) {
  bool no_response = false;
  bool age_untried = false;

  REQUIRE(fctx != NULL);
  REQUIRE(fctx->tid == isc_tid());

  FCTXTRACE("done");

#ifdef DNS_RESOLVER_TRACE
  fprintf(stderr, "%s:%s:%s:%u:(%p): %s\n", __func__, func, file, line,
    fctx, isc_result_totext(result));
#else
  UNUSED(file);
  UNUSED(line);
  UNUSED(func);
#endif

  LOCK(&fctx->lock);
  /* We need to do this under the lock for intra-thread synchronization */
  if (fctx->state == fetchstate_done) {
    UNLOCK(&fctx->lock);
    return false;
  }
  fctx->state = fetchstate_done;
  FCTX_ATTR_CLR(fctx, FCTX_ATTR_ADDRWAIT);
  UNLOCK(&fctx->lock);

  /* The fctx will get deleted either here or in get_attached_fctx() */
  RWLOCK(&fctx->res->fctxs_lock, isc_rwlocktype_write);
  (void)isc_hashmap_delete(fctx->res->fctxs, fctx_hash(fctx), match_ptr,
         fctx);
  RWUNLOCK(&fctx->res->fctxs_lock, isc_rwlocktype_write);

  if (result == ISC_R_SUCCESS) {
    if (fctx->qmin_warning != ISC_R_SUCCESS) {
      isc_log_write(DNS_LOGCATEGORY_LAME_SERVERS,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
              "success resolving '%s' after disabling "
              "qname minimization due to '%s'",
              fctx->info,
              isc_result_totext(fctx->qmin_warning));
    }

    /*
     * A success result indicates we got a response to a
     * query. That query should be canceled already. If
     * there still are any outstanding queries attached to the
     * same fctx, then those have *not* gotten a response,
     * so we set 'no_response' to true here: that way, when
     * we run fctx_cancelqueries() below, the SRTTs will
     * be adjusted.
     */
    no_response = true;
  } else if (result == ISC_R_TIMEDOUT) {
    age_untried = true;
  }

  fctx->qmin_warning = ISC_R_SUCCESS;

  fctx_cancelqueries(fctx, no_response, age_untried);
  fctx_stoptimer(fctx);

  /*
   * Cancel all pending validators.  Note that this must be done
   * without the fctx lock held, since that could cause
   * deadlock.
   */
  maybe_cancel_validators(fctx);

  if (fctx->nsfetch != NULL) {
    dns_resolver_cancelfetch(fctx->nsfetch);
  }

  if (fctx->qminfetch != NULL) {
    dns_resolver_cancelfetch(fctx->qminfetch);
  }

  /*
   * Shut down anything still running on behalf of this
   * fetch, and clean up finds and addresses.
   */
  fctx_sendevents(fctx, result);
  fctx_cleanup(fctx);

  isc_timer_destroy(&fctx->timer);

  return true;
}

static void
resquery_senddone(isc_result_t eresult, isc_region_t *region, void *arg) {
  resquery_t *query = (resquery_t *)arg;
  resquery_t *copy = query;
  fetchctx_t *fctx = NULL;

  QTRACE("senddone");

  UNUSED(region);

  REQUIRE(VALID_QUERY(query));
  fctx = query->fctx;
  REQUIRE(VALID_FCTX(fctx));
  REQUIRE(fctx->tid == isc_tid());

  if (RESQUERY_CANCELED(query)) {
    goto detach;
  }

  /*
   * See the note in resquery_connected() about reference
   * counting on error conditions.
   */
  switch (eresult) {
  case ISC_R_SUCCESS:
  case ISC_R_CANCELED:
  case ISC_R_SHUTTINGDOWN:
    break;

  case ISC_R_HOSTDOWN:
  case ISC_R_HOSTUNREACH:
  case ISC_R_NETDOWN:
  case ISC_R_NETUNREACH:
  case ISC_R_NOPERM:
  case ISC_R_ADDRNOTAVAIL:
  case ISC_R_CONNREFUSED:
  case ISC_R_CONNECTIONRESET:
  case ISC_R_TIMEDOUT:
    /* No route to remote. */
    FCTXTRACE3("query canceled in resquery_senddone(): "
         "no route to host; no response",
         eresult);
    add_bad(fctx, query->rmessage, query->addrinfo, eresult,
      badns_unreachable);
    fctx_cancelquery(&copy, NULL, true, false);
    FCTX_ATTR_CLR(fctx, FCTX_ATTR_ADDRWAIT);
    fctx_try(fctx, true);
    break;

  default:
    FCTXTRACE3("query canceled in resquery_senddone() "
         "due to unexpected result; responding",
         eresult);
    fctx_cancelquery(&copy, NULL, false, false);
    fctx_done_detach(&fctx, eresult);
    break;
  }

detach:
  resquery_detach(&query);
}

static isc_result_t
fctx_addopt(dns_message_t *message, unsigned int version, uint16_t udpsize,
      dns_ednsopt_t *ednsopts, size_t count) {
  dns_rdataset_t *rdataset = NULL;
  isc_result_t result;

  result = dns_message_buildopt(message, &rdataset, version, udpsize,
              DNS_MESSAGEEXTFLAG_DO, ednsopts, count);
  if (result != ISC_R_SUCCESS) {
    return result;
  }
  return dns_message_setopt(message, rdataset);
}

static void
fctx_setretryinterval(fetchctx_t *fctx, unsigned int rtt) {
  unsigned int seconds, us;
  uint64_t limit;
  isc_time_t now;

  /*
   * Has this fetch already expired?
   */
  now = isc_time_now();
  limit = isc_time_microdiff(&fctx->expires, &now);
  if (limit < US_PER_MS) {
    FCTXTRACE("fetch already expired");
    isc_interval_set(&fctx->interval, 0, 0);
    return;
  }

  us = fctx->res->retryinterval * US_PER_MS;

  /*
   * Exponential backoff after the first few tries.
   */
  if (fctx->restarts > fctx->res->nonbackofftries) {
    int shift = fctx->restarts - fctx->res->nonbackofftries;
    if (shift > 6) {
      shift = 6;
    }
    us <<= shift;
  }

  /*
   * Add a fudge factor to the expected rtt based on the current
   * estimate.
   */
  if (rtt < 50000) {
    rtt += 50000;
  } else if (rtt < 100000) {
    rtt += 100000;
  } else {
    rtt += 200000;
  }

  /*
   * Always wait for at least the expected rtt.
   */
  if (us < rtt) {
    us = rtt;
  }

  /*
   * But don't wait past the the final expiration of the fetch,
   * or for more than 10 seconds total.
   */
  if (us > limit) {
    us = limit;
  }
  if (us > MAX_SINGLE_QUERY_TIMEOUT_US) {
    us = MAX_SINGLE_QUERY_TIMEOUT_US;
  }
  if (us > fctx->res->query_timeout * US_PER_MS) {
    us = fctx->res->query_timeout * US_PER_MS;
  }

  seconds = us / US_PER_SEC;
  us -= seconds * US_PER_SEC;
  isc_interval_set(&fctx->interval, seconds, us * NS_PER_US);
}

static isc_result_t
fctx_query(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
     unsigned int options) {
  isc_result_t result;
  dns_resolver_t *res = NULL;
  dns_dns64_t *dns64 = NULL;
  resquery_t *query = NULL;
  isc_sockaddr_t addr, sockaddr;
  bool have_addr = false;
  unsigned int srtt;
  isc_tlsctx_cache_t *tlsctx_cache = NULL;

  FCTXTRACE("query");

  res = fctx->res;

  srtt = addrinfo->srtt;

  if (addrinfo->transport != NULL) {
    switch (dns_transport_get_type(addrinfo->transport)) {
    case DNS_TRANSPORT_TLS:
      options |= DNS_FETCHOPT_TCP;
      tlsctx_cache = res->tlsctx_cache;
      break;
    case DNS_TRANSPORT_TCP:
    case DNS_TRANSPORT_HTTP:
      options |= DNS_FETCHOPT_TCP;
      break;
    default:
      break;
    }
  }

  /*
   * Maybe apply DNS64 mappings to IPv4 addresses.
   */
  sockaddr = addrinfo->sockaddr;
  dns64 = ISC_LIST_HEAD(fctx->res->view->dns64);
  if (isc_sockaddr_pf(&sockaddr) == AF_INET &&
      fctx->res->view->usedns64 && dns64 != NULL)
  {
    struct in6_addr aaaa;

    result = dns_dns64_aaaafroma(
      dns64, NULL, NULL, fctx->res->view->aclenv, 0,
      (unsigned char *)&sockaddr.type.sin.sin_addr.s_addr,
      aaaa.s6_addr);
    if (result == ISC_R_SUCCESS) {
      char sockaddrbuf1[ISC_SOCKADDR_FORMATSIZE];
      char sockaddrbuf2[ISC_SOCKADDR_FORMATSIZE];

      /* format old address */
      isc_sockaddr_format(&sockaddr, sockaddrbuf1,
              sizeof(sockaddrbuf1));

      /* replace address */
      isc_sockaddr_fromin6(&sockaddr, &aaaa,
               ntohs(sockaddr.type.sin.sin_port));
      addrinfo->sockaddr = sockaddr;

      /* format new address */
      isc_sockaddr_format(&sockaddr, sockaddrbuf2,
              sizeof(sockaddrbuf2));
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_DEBUG(3),
              "Using DNS64 address %s to talk to %s\n",
              sockaddrbuf2, sockaddrbuf1);
    }
  }

  /*
   * Check if the address is in the peers list and has a special
   * confguration.
   */
  if (res->view->peers != NULL) {
    dns_peer_t *peer = NULL;
    isc_netaddr_t dstip;
    bool usetcp = false;
    isc_netaddr_fromsockaddr(&dstip, &sockaddr);
    result = dns_peerlist_peerbyaddr(res->view->peers, &dstip,
             &peer);
    if (result == ISC_R_SUCCESS) {
      result = dns_peer_getquerysource(peer, &addr);
      if (result == ISC_R_SUCCESS) {
        have_addr = true;
      }
      result = dns_peer_getforcetcp(peer, &usetcp);
      if (result == ISC_R_SUCCESS && usetcp) {
        options |= DNS_FETCHOPT_TCP;
      }
    }
  }

  /*
   * Allow an additional second for the kernel to resend the SYN
   * (or SYN without ECN in the case of stupid firewalls blocking
   * ECN negotiation) over the current RTT estimate.
   */
  if ((options & DNS_FETCHOPT_TCP) != 0) {
    srtt += US_PER_SEC;
  }

  /*
   * A forwarder needs to make multiple queries. Give it at least
   * a second to do these in.
   */
  if (ISFORWARDER(addrinfo) && srtt < US_PER_SEC) {
    srtt = US_PER_SEC;
  }

  fctx_setretryinterval(fctx, srtt);
  if (isc_interval_iszero(&fctx->interval)) {
    FCTXTRACE("fetch expired");
    dns_ede_add(&fctx->edectx, DNS_EDE_NOREACHABLEAUTH, NULL);
    return ISC_R_TIMEDOUT;
  }

  INSIST(ISC_LIST_EMPTY(fctx->validators));

  query = isc_mem_get(fctx->mctx, sizeof(*query));
  *query = (resquery_t){
    .options = options,
    .addrinfo = addrinfo,
    .dispatchmgr = res->view->dispatchmgr,
    .link = ISC_LINK_INITIALIZER,
  };

#if DNS_RESOLVER_TRACE
  fprintf(stderr, "rctx_init:%s:%s:%d:%p->references = 1\n", __func__,
    __FILE__, __LINE__, query);
#endif
  isc_refcount_init(&query->references, 1);

  /*
   * Note that the caller MUST guarantee that 'addrinfo' will
   * remain valid until this query is canceled.
   */

  dns_message_create(fctx->mctx, fctx->res->namepools[fctx->tid],
         fctx->res->rdspools[fctx->tid],
         DNS_MESSAGE_INTENTPARSE, &query->rmessage);
  query->start = isc_time_now();

  /*
   * If this is a TCP query, then we need to make a socket and
   * a dispatch for it here.  Otherwise we use the resolver's
   * shared dispatch.
   */
  if ((query->options & DNS_FETCHOPT_TCP) != 0) {
    int pf;

    pf = isc_sockaddr_pf(&sockaddr);
    if (!have_addr) {
      switch (pf) {
      case PF_INET:
        result = dns_dispatch_getlocaladdress(
          res->dispatches4->dispatches[0], &addr);
        break;
      case PF_INET6:
        result = dns_dispatch_getlocaladdress(
          res->dispatches6->dispatches[0], &addr);
        break;
      default:
        result = ISC_R_NOTIMPLEMENTED;
        break;
      }
      if (result != ISC_R_SUCCESS) {
        goto cleanup_query;
      }
    }
    isc_sockaddr_setport(&addr, 0);

    result = dns_dispatch_createtcp(res->view->dispatchmgr, &addr,
            &sockaddr, addrinfo->transport,
            DNS_DISPATCHOPT_UNSHARED,
            &query->dispatch);
    if (result != ISC_R_SUCCESS) {
      goto cleanup_query;
    }

    FCTXTRACE("connecting via TCP");
  } else {
    if (have_addr) {
      result = dns_dispatch_createudp(res->view->dispatchmgr,
              &addr,
              &query->dispatch);
      if (result != ISC_R_SUCCESS) {
        goto cleanup_query;
      }
    } else {
      switch (isc_sockaddr_pf(&sockaddr)) {
      case PF_INET:
        dns_dispatch_attach(
          dns_resolver_dispatchv4(res),
          &query->dispatch);
        break;
      case PF_INET6:
        dns_dispatch_attach(
          dns_resolver_dispatchv6(res),
          &query->dispatch);
        break;
      default:
        result = ISC_R_NOTIMPLEMENTED;
        goto cleanup_query;
      }
    }

    /*
     * We should always have a valid dispatcher here.  If we
     * don't support a protocol family, then its dispatcher
     * will be NULL, but we shouldn't be finding addresses
     * for protocol types we don't support, so the
     * dispatcher we found should never be NULL.
     */
    INSIST(query->dispatch != NULL);
  }

  LOCK(&fctx->lock);
  INSIST(!SHUTTINGDOWN(fctx));
  fetchctx_attach(fctx, &query->fctx);
  query->magic = QUERY_MAGIC;

  if ((query->options & DNS_FETCHOPT_TCP) == 0) {
    if (dns_adb_overquota(fctx->adb, addrinfo)) {
      UNLOCK(&fctx->lock);
      result = ISC_R_QUOTA;
      goto cleanup_dispatch;
    }

    /* Inform the ADB that we're starting a UDP fetch */
    dns_adb_beginudpfetch(fctx->adb, addrinfo);
  }

  ISC_LIST_APPEND(fctx->queries, query, link);
  atomic_fetch_add_relaxed(&fctx->nqueries, 1);
  UNLOCK(&fctx->lock);

  /* Set up the dispatch and set the query ID */
  const unsigned int timeout_ms = isc_interval_ms(&fctx->interval);
  result = dns_dispatch_add(query->dispatch, fctx->loop, 0, timeout_ms,
          timeout_ms, &sockaddr, addrinfo->transport,
          tlsctx_cache, resquery_connected,
          resquery_senddone, resquery_response, query,
          &query->id, &query->dispentry);
  if (result != ISC_R_SUCCESS) {
    goto cleanup_udpfetch;
  }

  /* Connect the socket */
  resquery_ref(query);
  result = dns_dispatch_connect(query->dispentry);

  if (result != ISC_R_SUCCESS && (query->options & DNS_FETCHOPT_TCP) != 0)
  {
    int log_level = ISC_LOG_NOTICE;
    if (isc_log_wouldlog(log_level)) {
      char peerbuf[ISC_SOCKADDR_FORMATSIZE];

      isc_sockaddr_format(&sockaddr, peerbuf,
              ISC_SOCKADDR_FORMATSIZE);

      isc_log_write(
        DNS_LOGCATEGORY_RESOLVER,
        DNS_LOGMODULE_RESOLVER, log_level,
        "Unable to establish a connection to %s: %s\n",
        peerbuf, isc_result_totext(result));
    }
    dns_dispatch_done(&query->dispentry);
    goto cleanup_fetch;
  } else {
    RUNTIME_CHECK(result == ISC_R_SUCCESS);
  }

  return result;

cleanup_udpfetch:
  if (!RESQUERY_CANCELED(query)) {
    if ((query->options & DNS_FETCHOPT_TCP) == 0) {
      /* Inform the ADB that we're ending a UDP fetch */
      dns_adb_endudpfetch(fctx->adb, addrinfo);
    }
  }

cleanup_fetch:
  LOCK(&fctx->lock);
  if (ISC_LINK_LINKED(query, link)) {
    atomic_fetch_sub_release(&fctx->nqueries, 1);
    ISC_LIST_UNLINK(fctx->queries, query, link);
  }
  UNLOCK(&fctx->lock);

cleanup_dispatch:
  fetchctx_detach(&query->fctx);

  if (query->dispatch != NULL) {
    dns_dispatch_detach(&query->dispatch);
  }

cleanup_query:
  query->magic = 0;
  dns_message_detach(&query->rmessage);
  isc_mem_put(fctx->mctx, query, sizeof(*query));

  return result;
}

static struct tried *
triededns(fetchctx_t *fctx, isc_sockaddr_t *address) {
  ISC_LIST_FOREACH(fctx->edns, tried, link) {
    if (isc_sockaddr_equal(&tried->addr, address)) {
      return tried;
    }
  }

  return NULL;
}

static void
add_triededns(fetchctx_t *fctx, isc_sockaddr_t *address) {
  struct tried *tried = triededns(fctx, address);
  if (tried != NULL) {
    tried->count++;
    return;
  }

  tried = isc_mem_get(fctx->mctx, sizeof(*tried));
  tried->addr = *address;
  tried->count = 1;
  ISC_LIST_INITANDAPPEND(fctx->edns, tried, link);
}

static size_t
addr2buf(void *buf, const size_t bufsize, const isc_sockaddr_t *sockaddr) {
  isc_netaddr_t netaddr;
  isc_netaddr_fromsockaddr(&netaddr, sockaddr);
  switch (netaddr.family) {
  case AF_INET:
    INSIST(bufsize >= 4);
    memmove(buf, &netaddr.type.in, 4);
    return 4;
  case AF_INET6:
    INSIST(bufsize >= 16);
    memmove(buf, &netaddr.type.in6, 16);
    return 16;
  default:
    UNREACHABLE();
  }
  return 0;
}

static size_t
add_serveraddr(uint8_t *buf, const size_t bufsize, const resquery_t *query) {
  return addr2buf(buf, bufsize, &query->addrinfo->sockaddr);
}

/*
 * Client cookie is 8 octets.
 * Server cookie is [8..32] octets.
 */
#define CLIENT_COOKIE_SIZE 8U
#define COOKIE_BUFFER_SIZE (8U + 32U)

static void
compute_cc(const resquery_t *query, uint8_t *cookie, const size_t len) {
  INSIST(len >= CLIENT_COOKIE_SIZE);
  STATIC_ASSERT(sizeof(query->fctx->res->view->secret) >=
            ISC_SIPHASH24_KEY_LENGTH,
          "The view->secret size can't fit SipHash 2-4 key "
          "length");

  uint8_t buf[16] ISC_NONSTRING = { 0 };
  size_t buflen = add_serveraddr(buf, sizeof(buf), query);

  uint8_t digest[ISC_SIPHASH24_TAG_LENGTH] ISC_NONSTRING = { 0 };
  isc_siphash24(query->fctx->res->view->secret, buf, buflen, true,
          digest);
  memmove(cookie, digest, CLIENT_COOKIE_SIZE);
}

static bool
issecuredomain(fetchctx_t *fctx, const dns_name_t *name, dns_rdatatype_t type,
         isc_stdtime_t now, bool *ntap) {
  dns_name_t suffix;
  unsigned int labels;

  /*
   * For DS variants we need to check fom the parent domain,
   * since there may be a negative trust anchor for the name,
   * while the enclosing domain where the DS record lives is
   * under a secure entry point.
   */
  labels = dns_name_countlabels(name);
  if (dns_rdatatype_atparent(type) && labels > 1) {
    dns_name_init(&suffix);
    dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
    name = &suffix;
  }

  return dns_view_issecuredomain(fctx->res->view, name, now,
               CHECKNTA(fctx), ntap);
}

static isc_result_t
resquery_send(resquery_t *query) {
  isc_result_t result;
  fetchctx_t *fctx = query->fctx;
  dns_resolver_t *res = fctx->res;
  isc_buffer_t buffer;
  dns_name_t *qname = NULL;
  dns_rdataset_t *qrdataset = NULL;
  isc_region_t r;
  isc_netaddr_t ipaddr;
  dns_tsigkey_t *tsigkey = NULL;
  dns_peer_t *peer = NULL;
  dns_compress_t cctx;
  bool useedns;
  bool tcp = ((query->options & DNS_FETCHOPT_TCP) != 0);
  dns_ednsopt_t ednsopts[DNS_EDNSOPTIONS];
  unsigned int ednsopt = 0;
  uint16_t hint = 0, udpsize = 0; /* No EDNS */
  isc_sockaddr_t localaddr, *la = NULL;
#ifdef HAVE_DNSTAP
  unsigned char zone[DNS_NAME_MAXWIRE];
  dns_transport_type_t transport_type;
  dns_dtmsgtype_t dtmsgtype;
  isc_region_t zr;
  isc_buffer_t zb;
#endif /* HAVE_DNSTAP */

  QTRACE("send");

  if (atomic_load_acquire(&res->exiting)) {
    FCTXTRACE("resquery_send: resolver shutting down");
    return ISC_R_SHUTTINGDOWN;
  }

  dns_message_gettempname(fctx->qmessage, &qname);
  dns_message_gettemprdataset(fctx->qmessage, &qrdataset);

  fctx->qmessage->opcode = dns_opcode_query;

  /*
   * Set up question.
   */
  dns_name_clone(fctx->name, qname);
  dns_rdataset_makequestion(qrdataset, res->rdclass, fctx->type);
  ISC_LIST_APPEND(qname->list, qrdataset, link);
  dns_message_addname(fctx->qmessage, qname, DNS_SECTION_QUESTION);

  /*
   * Set RD if the client has requested that we do a recursive
   * query, or if we're sending to a forwarder.
   */
  if ((query->options & DNS_FETCHOPT_RECURSIVE) != 0 ||
      ISFORWARDER(query->addrinfo))
  {
    fctx->qmessage->flags |= DNS_MESSAGEFLAG_RD;
  }

  /*
   * Set CD if the client says not to validate, or if the
   * question is under a secure entry point and this is a
   * recursive/forward query -- unless the client said not to.
   */
  if ((query->options & DNS_FETCHOPT_NOCDFLAG) != 0) {
    /* Do nothing */
  } else if ((query->options & DNS_FETCHOPT_NOVALIDATE) != 0 ||
       (query->options & DNS_FETCHOPT_TRYCD) != 0)
  {
    fctx->qmessage->flags |= DNS_MESSAGEFLAG_CD;
  } else if (res->view->enablevalidation &&
       ((fctx->qmessage->flags & DNS_MESSAGEFLAG_RD) != 0))
  {
    query->options |= DNS_FETCHOPT_TRYCD;
  }

  /*
   * We don't have to set opcode because it defaults to query.
   */
  fctx->qmessage->id = query->id;

  /*
   * Convert the question to wire format.
   */
  dns_compress_init(&cctx, fctx->mctx, 0);

  isc_buffer_init(&buffer, query->data, sizeof(query->data));
  result = dns_message_renderbegin(fctx->qmessage, &cctx, &buffer);
  if (result != ISC_R_SUCCESS) {
    goto cleanup_message;
  }

  result = dns_message_rendersection(fctx->qmessage, DNS_SECTION_QUESTION,
             0);
  if (result != ISC_R_SUCCESS) {
    goto cleanup_message;
  }

  isc_netaddr_fromsockaddr(&ipaddr, &query->addrinfo->sockaddr);
  (void)dns_peerlist_peerbyaddr(fctx->res->view->peers, &ipaddr, &peer);

  /*
   * The ADB does not know about servers with "edns no".  Check
   * this, and then inform the ADB for future use.
   */
  if ((query->addrinfo->flags & FCTX_ADDRINFO_NOEDNS0) == 0 &&
      peer != NULL &&
      dns_peer_getsupportedns(peer, &useedns) == ISC_R_SUCCESS &&
      !useedns)
  {
    query->options |= DNS_FETCHOPT_NOEDNS0;
    dns_adb_changeflags(fctx->adb, query->addrinfo,
            FCTX_ADDRINFO_NOEDNS0,
            FCTX_ADDRINFO_NOEDNS0);
  }

  /* Sync NOEDNS0 flag in addrinfo->flags and options now. */
  if ((query->addrinfo->flags & FCTX_ADDRINFO_NOEDNS0) != 0) {
    query->options |= DNS_FETCHOPT_NOEDNS0;
  }

  if (fctx->timeout && (query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
    isc_sockaddr_t *sockaddr = &query->addrinfo->sockaddr;
    struct tried *tried;

    /*
     * If this is the first timeout for this server in this
     * fetch context, try setting EDNS UDP buffer size to
     * the largest UDP response size we have seen from this
     * server so far.
     *
     * If this server has already timed out twice or more in
     * this fetch context, force TCP.
     */
    if ((tried = triededns(fctx, sockaddr)) != NULL) {
      if (tried->count == 1U) {
        hint = dns_adb_getudpsize(fctx->adb,
                query->addrinfo);
      } else if (tried->count >= 2U) {
        if ((query->options & DNS_FETCHOPT_TCP) == 0) {
          /*
           * Inform the ADB that we're ending a
           * UDP fetch, and turn the query into
           * a TCP query.
           */
          dns_adb_endudpfetch(fctx->adb,
                  query->addrinfo);
          query->options |= DNS_FETCHOPT_TCP;
        }
      }
    }
  }
  fctx->timeout = false;

  /*
   * Use EDNS0, unless the caller doesn't want it, or we know that
   * the remote server doesn't like it.
   */
  if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
    if ((query->addrinfo->flags & FCTX_ADDRINFO_NOEDNS0) == 0) {
      uint16_t peerudpsize = 0;
      unsigned int version = DNS_EDNS_VERSION;
      unsigned int flags = query->addrinfo->flags;
      bool reqnsid = res->view->requestnsid;
      bool sendcookie = res->view->sendcookie;
      bool reqzoneversion = res->view->requestzoneversion;
      bool tcpkeepalive = false;
      unsigned char cookie[COOKIE_BUFFER_SIZE];
      uint16_t padding = 0;

      /*
       * Set the default UDP size to what was
       * configured as 'edns-buffer-size'
       */
      udpsize = res->view->udpsize;

      /*
       * This server timed out for the first time in
       * this fetch context and we received a response
       * from it before (either in this fetch context
       * or in a different one).  Set 'udpsize' to the
       * size of the largest UDP response we have
       * received from this server so far.
       */
      if (hint != 0U) {
        udpsize = hint;
      }

      /*
       * If a fixed EDNS UDP buffer size is configured
       * for this server, make sure we obey that.
       */
      if (peer != NULL) {
        (void)dns_peer_getudpsize(peer, &peerudpsize);
        if (peerudpsize != 0) {
          udpsize = peerudpsize;
        }
      }

      if ((flags & DNS_FETCHOPT_EDNSVERSIONSET) != 0) {
        version = flags & DNS_FETCHOPT_EDNSVERSIONMASK;
        version >>= DNS_FETCHOPT_EDNSVERSIONSHIFT;
      }

      /* Request NSID/COOKIE/VERSION for current peer?
       */
      if (peer != NULL) {
        uint8_t ednsversion;
        result = dns_peer_getednsversion(peer,
                 &ednsversion);
        if (result == ISC_R_SUCCESS &&
            ednsversion < version)
        {
          version = ednsversion;
        }
        (void)dns_peer_getrequestnsid(peer, &reqnsid);
        (void)dns_peer_getrequestzoneversion(
          peer, &reqzoneversion);
        (void)dns_peer_getsendcookie(peer, &sendcookie);
      }
      if (NOCOOKIE(query->addrinfo)) {
        sendcookie = false;
      }
      if (reqnsid) {
        INSIST(ednsopt < DNS_EDNSOPTIONS);
        ednsopts[ednsopt].code = DNS_OPT_NSID;
        ednsopts[ednsopt].length = 0;
        ednsopts[ednsopt].value = NULL;
        ednsopt++;
      }
      if (reqzoneversion) {
        INSIST(ednsopt < DNS_EDNSOPTIONS);
        ednsopts[ednsopt].code = DNS_OPT_ZONEVERSION;
        ednsopts[ednsopt].length = 0;
        ednsopts[ednsopt].value = NULL;
        ednsopt++;
      }
      if (sendcookie) {
        INSIST(ednsopt < DNS_EDNSOPTIONS);
        ednsopts[ednsopt].code = DNS_OPT_COOKIE;
        ednsopts[ednsopt].length =
          (uint16_t)dns_adb_getcookie(
            query->addrinfo, cookie,
            sizeof(cookie));
        if (ednsopts[ednsopt].length != 0) {
          ednsopts[ednsopt].value = cookie;
          inc_stats(
            fctx->res,
            dns_resstatscounter_cookieout);
        } else {
          compute_cc(query, cookie,
               CLIENT_COOKIE_SIZE);
          ednsopts[ednsopt].value = cookie;
          ednsopts[ednsopt].length =
            CLIENT_COOKIE_SIZE;
          inc_stats(
            fctx->res,
            dns_resstatscounter_cookienew);
        }
        ednsopt++;
      }

      /* Add TCP keepalive option if appropriate */
      if ((peer != NULL) && tcp) {
        (void)dns_peer_gettcpkeepalive(peer,
                     &tcpkeepalive);
      }
      if (tcpkeepalive) {
        INSIST(ednsopt < DNS_EDNSOPTIONS);
        ednsopts[ednsopt].code = DNS_OPT_TCP_KEEPALIVE;
        ednsopts[ednsopt].length = 0;
        ednsopts[ednsopt].value = NULL;
        ednsopt++;
      }

      /* Add PAD for current peer? Require TCP for now
       */
      if ((peer != NULL) && tcp) {
        (void)dns_peer_getpadding(peer, &padding);
      }
      if (padding != 0) {
        INSIST(ednsopt < DNS_EDNSOPTIONS);
        ednsopts[ednsopt].code = DNS_OPT_PAD;
        ednsopts[ednsopt].length = 0;
        ednsopt++;
        dns_message_setpadding(fctx->qmessage, padding);
      }

      query->ednsversion = version;
      result = fctx_addopt(fctx->qmessage, version, udpsize,
               ednsopts, ednsopt);
      if (result == ISC_R_SUCCESS) {
        if (reqnsid) {
          query->options |= DNS_FETCHOPT_WANTNSID;
        }
        if (reqzoneversion) {
          query->options |=
            DNS_FETCHOPT_WANTZONEVERSION;
        }
      } else if (result != ISC_R_SUCCESS) {
        /*
         * We couldn't add the OPT, but we'll
         * press on. We're not using EDNS0, so
         * set the NOEDNS0 bit.
         */
        query->options |= DNS_FETCHOPT_NOEDNS0;
        query->ednsversion = -1;
        udpsize = 0;
      }
    } else {
      /*
       * We know this server doesn't like EDNS0, so we
       * won't use it.  Set the NOEDNS0 bit since
       * we're not using EDNS0.
       */
      query->options |= DNS_FETCHOPT_NOEDNS0;
      query->ednsversion = -1;
    }
  } else {
    query->ednsversion = -1;
  }

  /*
   * Record the UDP EDNS size chosen.
   */
  query->udpsize = udpsize;

  /*
   * If we need EDNS0 to do this query and aren't using it, we
   * lose.
   */
  if (NEEDEDNS0(fctx) && (query->options & DNS_FETCHOPT_NOEDNS0) != 0) {
    result = DNS_R_SERVFAIL;
    goto cleanup_message;
  }

  add_triededns(fctx, &query->addrinfo->sockaddr);

  /*
   * Clear CD if EDNS is not in use.
   */
  if ((query->options & DNS_FETCHOPT_NOEDNS0) != 0) {
    fctx->qmessage->flags &= ~DNS_MESSAGEFLAG_CD;
  }

  /*
   * Add TSIG record tailored to the current recipient.
   */
  result = dns_view_getpeertsig(fctx->res->view, &ipaddr, &tsigkey);
  if (result != ISC_R_SUCCESS && result != ISC_R_NOTFOUND) {
    goto cleanup_message;
  }

  if (tsigkey != NULL) {
    result = dns_message_settsigkey(fctx->qmessage, tsigkey);
    dns_tsigkey_detach(&tsigkey);
    if (result != ISC_R_SUCCESS) {
      goto cleanup_message;
    }
  }

  result = dns_message_rendersection(fctx->qmessage,
             DNS_SECTION_ADDITIONAL, 0);
  if (result != ISC_R_SUCCESS) {
    goto cleanup_message;
  }

  result = dns_message_renderend(fctx->qmessage);
  if (result != ISC_R_SUCCESS) {
    goto cleanup_message;
  }

#ifdef HAVE_DNSTAP
  memset(&zr, 0, sizeof(zr));
  isc_buffer_init(&zb, zone, sizeof(zone));
  dns_compress_setpermitted(&cctx, false);
  result = dns_name_towire(fctx->domain, &cctx, &zb);
  if (result == ISC_R_SUCCESS) {
    isc_buffer_usedregion(&zb, &zr);
  }
#endif /* HAVE_DNSTAP */

  if (dns_message_gettsigkey(fctx->qmessage) != NULL) {
    dns_tsigkey_attach(dns_message_gettsigkey(fctx->qmessage),
           &query->tsigkey);
    result = dns_message_getquerytsig(fctx->qmessage, fctx->mctx,
              &query->tsig);
    if (result != ISC_R_SUCCESS) {
      goto cleanup_message;
    }
  }

  /*
   * Log the outgoing packet.
   */
  result = dns_dispentry_getlocaladdress(query->dispentry, &localaddr);
  if (result == ISC_R_SUCCESS) {
    la = &localaddr;
  }

  dns_message_logpacketfromto(
    fctx->qmessage, "sending packet", la,
    &query->addrinfo->sockaddr, DNS_LOGCATEGORY_RESOLVER,
    DNS_LOGMODULE_PACKETS, ISC_LOG_DEBUG(11), fctx->mctx);

  /*
   * We're now done with the query message.
   */
  dns_compress_invalidate(&cctx);
  dns_message_reset(fctx->qmessage, DNS_MESSAGE_INTENTRENDER);

  isc_buffer_usedregion(&buffer, &r);

  resquery_ref(query);
  dns_dispatch_send(query->dispentry, &r);

  QTRACE("sent");

#ifdef HAVE_DNSTAP
  /*
   * Log the outgoing query via dnstap.
   */
  if ((fctx->qmessage->flags & DNS_MESSAGEFLAG_RD) != 0) {
    dtmsgtype = DNS_DTTYPE_FQ;
  } else {
    dtmsgtype = DNS_DTTYPE_RQ;
  }

  if (query->addrinfo->transport != NULL) {
    transport_type =
      dns_transport_get_type(query->addrinfo->transport);
  } else if ((query->options & DNS_FETCHOPT_TCP) != 0) {
    transport_type = DNS_TRANSPORT_TCP;
  } else {
    transport_type = DNS_TRANSPORT_UDP;
  }

  dns_dt_send(fctx->res->view, dtmsgtype, la, &query->addrinfo->sockaddr,
        transport_type, &zr, &query->start, NULL, &buffer);
#endif /* HAVE_DNSTAP */

  return ISC_R_SUCCESS;

cleanup_message:
  dns_compress_invalidate(&cctx);

  dns_message_reset(fctx->qmessage, DNS_MESSAGE_INTENTRENDER);

  /*
   * Stop the dispatcher from listening.
   */
  dns_dispatch_done(&query->dispentry);

  return result;
}

static void
resquery_connected(isc_result_t eresult, isc_region_t *region, void *arg) {
  resquery_t *query = (resquery_t *)arg;
  resquery_t *copy = query;
  isc_result_t result;
  fetchctx_t *fctx = NULL;
  dns_resolver_t *res = NULL;
  int pf;

  REQUIRE(VALID_QUERY(query));

  QTRACE("connected");

  UNUSED(region);

  fctx = query->fctx;

  REQUIRE(VALID_FCTX(fctx));
  REQUIRE(fctx->tid == isc_tid());

  res = fctx->res;

  if (RESQUERY_CANCELED(query)) {
    goto detach;
  }

  if (atomic_load_acquire(&fctx->res->exiting)) {
    eresult = ISC_R_SHUTTINGDOWN;
  }

  /*
   * The reference counting of resquery objects is complex:
   *
   * 1. attached in fctx_query()
   * 2. attached prior to dns_dispatch_connect(), detached in
   *    resquery_connected()
   * 3. attached prior to dns_dispatch_send(), detached in
   *    resquery_senddone()
   * 4. finally detached in fctx_cancelquery()
   *
   * On error conditions, it's necessary to call fctx_cancelquery()
   * from resquery_connected() or _senddone(), detaching twice
   * within the same function. To make it clear that's what's
   * happening, we cancel-and-detach 'copy' and detach 'query',
   * which are both pointing to the same object.
   */
  switch (eresult) {
  case ISC_R_SUCCESS:
    /*
     * We are connected. Send the query.
     */

    result = resquery_send(query);
    if (result != ISC_R_SUCCESS) {
      FCTXTRACE("query canceled: resquery_send() failed; "
          "responding");

      fctx_cancelquery(&copy, NULL, false, false);
      fctx_done_detach(&fctx, result);
      break;
    }

    fctx->querysent++;

    pf = isc_sockaddr_pf(&query->addrinfo->sockaddr);
    if (pf == PF_INET) {
      inc_stats(res, dns_resstatscounter_queryv4);
    } else {
      inc_stats(res, dns_resstatscounter_queryv6);
    }
    if (res->querystats != NULL) {
      dns_rdatatypestats_increment(res->querystats,
                 fctx->type);
    }
    break;

  case ISC_R_CANCELED:
  case ISC_R_SHUTTINGDOWN:
    FCTXTRACE3("shutdown in resquery_connected()", eresult);
    fctx_cancelquery(&copy, NULL, true, false);
    fctx_done_detach(&fctx, eresult);
    break;

  case ISC_R_HOSTDOWN:
  case ISC_R_HOSTUNREACH:
  case ISC_R_NETDOWN:
  case ISC_R_NETUNREACH:
  case ISC_R_CONNREFUSED:
  case ISC_R_NOPERM:
  case ISC_R_ADDRNOTAVAIL:
  case ISC_R_CONNECTIONRESET:
  case ISC_R_TIMEDOUT:
    /*
     * Do not query this server again in this fetch context.
     */
    FCTXTRACE3("query failed in resquery_connected(): "
         "no response",
         eresult);
    add_bad(fctx, query->rmessage, query->addrinfo, eresult,
      badns_unreachable);
    fctx_cancelquery(&copy, NULL, true, false);

    FCTX_ATTR_CLR(fctx, FCTX_ATTR_ADDRWAIT);
    fctx_try(fctx, true);
    break;

  default:
    FCTXTRACE3("query canceled in resquery_connected() "
         "due to unexpected result; responding",
         eresult);

    fctx_cancelquery(&copy, NULL, false, false);
    fctx_done_detach(&fctx, eresult);
    break;
  }

detach:
  resquery_detach(&query);
}

static void
fctx_finddone(void *arg) {
  dns_adbfind_t *find = (dns_adbfind_t *)arg;
  fetchctx_t *fctx = (fetchctx_t *)find->cbarg;
  bool want_try = false;
  bool want_done = false;
  uint_fast32_t pending;

  REQUIRE(VALID_FCTX(fctx));

  FCTXTRACE("finddone");

  REQUIRE(fctx->tid == isc_tid());

  LOCK(&fctx->lock);
  pending = atomic_fetch_sub_release(&fctx->pending, 1);
  INSIST(pending > 0);

  if (ADDRWAIT(fctx)) {
    /*
     * The fetch is waiting for a name to be found.
     */
    INSIST(!SHUTTINGDOWN(fctx));
    if (dns_adb_findstatus(find) == DNS_ADB_MOREADDRESSES) {
      FCTX_ATTR_CLR(fctx, FCTX_ATTR_ADDRWAIT);
      want_try = true;
    } else {
      fctx->findfail++;
      if (atomic_load_acquire(&fctx->pending) == 0) {
        FCTX_ATTR_CLR(fctx, FCTX_ATTR_ADDRWAIT);
        if (!ISC_LIST_EMPTY(fctx->res->alternates)) {
          want_try = true;
        } else {
          /*
           * We've got nothing else to wait for
           * and don't know the answer.  There's
           * nothing to do but fail the fctx.
           */
          want_done = true;
        }
      }
    }
  }

  UNLOCK(&fctx->lock);

  dns_adb_destroyfind(&find);

  if (want_done) {
    FCTXTRACE("fetch failed in finddone(); return "
        "ISC_R_FAILURE");

    fctx_done_unref(fctx, ISC_R_FAILURE);
  } else if (want_try) {
    fctx_try(fctx, true);
  }

  fetchctx_detach(&fctx);
}

static bool
bad_server(fetchctx_t *fctx, isc_sockaddr_t *address) {
  ISC_LIST_FOREACH(fctx->bad, sa, link) {
    if (isc_sockaddr_equal(sa, address)) {
      return true;
    }
  }

  return false;
}

static bool
mark_bad(fetchctx_t *fctx) {
  bool all_bad = true;

#ifdef ENABLE_AFL
  if (dns_fuzzing_resolver) {
    return false;
  }
#endif /* ifdef ENABLE_AFL */

  /*
   * Mark all known bad servers, so we don't try to talk to them
   * again.
   */

  /*
   * Mark any bad nameservers.
   */
  ISC_LIST_FOREACH(fctx->finds, curr, publink) {
    ISC_LIST_FOREACH(curr->list, addrinfo, publink) {
      if (bad_server(fctx, &addrinfo->sockaddr)) {
        addrinfo->flags |= FCTX_ADDRINFO_MARK;
      } else {
        all_bad = false;
      }
    }
  }

  /*
   * Mark any bad forwarders.
   */
  ISC_LIST_FOREACH(fctx->forwaddrs, addrinfo, publink) {
    if (bad_server(fctx, &addrinfo->sockaddr)) {
      addrinfo->flags |= FCTX_ADDRINFO_MARK;
    } else {
      all_bad = false;
    }
  }

  /*
   * Mark any bad alternates.
   */
  ISC_LIST_FOREACH(fctx->altfinds, curr, publink) {
    ISC_LIST_FOREACH(curr->list, addrinfo, publink) {
      if (bad_server(fctx, &addrinfo->sockaddr)) {
        addrinfo->flags |= FCTX_ADDRINFO_MARK;
      } else {
        all_bad = false;
      }
    }
  }

  ISC_LIST_FOREACH(fctx->altaddrs, addrinfo, publink) {
    if (bad_server(fctx, &addrinfo->sockaddr)) {
      addrinfo->flags |= FCTX_ADDRINFO_MARK;
    } else {
      all_bad = false;
    }
  }

  return all_bad;
}

static void
add_bad(fetchctx_t *fctx, dns_message_t *rmessage, dns_adbaddrinfo_t *addrinfo,
  isc_result_t reason, badnstype_t badtype) {
  char namebuf[DNS_NAME_FORMATSIZE];
  char addrbuf[ISC_SOCKADDR_FORMATSIZE];
  char classbuf[64];
  char typebuf[64];
  char code[64];
  isc_buffer_t b;
  isc_sockaddr_t *sa;
  const char *spc = "";
  isc_sockaddr_t *address = &addrinfo->sockaddr;

#ifdef ENABLE_AFL
  if (dns_fuzzing_resolver) {
    return;
  }
#endif /* ifdef ENABLE_AFL */

  if (reason == DNS_R_LAME) {
    fctx->lamecount++;
  } else {
    switch (badtype) {
    case badns_unreachable:
      fctx->neterr++;
      break;
    case badns_response:
      fctx->badresp++;
      break;
    case badns_validation:
      break; /* counted as 'valfail' */
    case badns_forwarder:
      /*
       * We were called to prevent the given forwarder
       * from being used again for this fetch context.
       */
      break;
    }
  }

  if (bad_server(fctx, address)) {
    /*
     * We already know this server is bad.
     */
    return;
  }

  FCTXTRACE("add_bad");

  sa = isc_mem_get(fctx->mctx, sizeof(*sa));
  *sa = *address;
  ISC_LIST_INITANDAPPEND(fctx->bad, sa, link);

  if (reason == DNS_R_LAME) { /* already logged */
    return;
  }

  if (reason == DNS_R_UNEXPECTEDRCODE &&
      rmessage->rcode == dns_rcode_servfail && ISFORWARDER(addrinfo))
  {
    return;
  }

  if (reason == DNS_R_UNEXPECTEDRCODE) {
    isc_buffer_init(&b, code, sizeof(code) - 1);
    dns_rcode_totext(rmessage->rcode, &b);
    code[isc_buffer_usedlength(&b)] = '\0';
    spc = " ";
  } else if (reason == DNS_R_UNEXPECTEDOPCODE) {
    isc_buffer_init(&b, code, sizeof(code) - 1);
    dns_opcode_totext((dns_opcode_t)rmessage->opcode, &b);
    code[isc_buffer_usedlength(&b)] = '\0';
    spc = " ";
  } else {
    code[0] = '\0';
  }
  dns_name_format(fctx->name, namebuf, sizeof(namebuf));
  dns_rdatatype_format(fctx->type, typebuf, sizeof(typebuf));
  dns_rdataclass_format(fctx->res->rdclass, classbuf, sizeof(classbuf));
  isc_sockaddr_format(address, addrbuf, sizeof(addrbuf));
  isc_log_write(DNS_LOGCATEGORY_LAME_SERVERS, DNS_LOGMODULE_RESOLVER,
          ISC_LOG_INFO, "%s%s%s resolving '%s/%s/%s': %s", code,
          spc, isc_result_totext(reason), namebuf, typebuf,
          classbuf, addrbuf);
}

/*
 * Sort addrinfo list by RTT.
 */
static void
sort_adbfind(dns_adbfind_t *find, unsigned int bias) {
  dns_adbaddrinfo_t *best, *curr;
  dns_adbaddrinfolist_t sorted;

  /* Lame N^2 bubble sort. */
  ISC_LIST_INIT(sorted);
  while (!ISC_LIST_EMPTY(find->list)) {
    unsigned int best_srtt;
    best = ISC_LIST_HEAD(find->list);
    best_srtt = best->srtt;
    if (isc_sockaddr_pf(&best->sockaddr) != AF_INET6) {
      best_srtt += bias;
    }
    curr = ISC_LIST_NEXT(best, publink);
    while (curr != NULL) {
      unsigned int curr_srtt = curr->srtt;
      if (isc_sockaddr_pf(&curr->sockaddr) != AF_INET6) {
        curr_srtt += bias;
      }
      if (curr_srtt < best_srtt) {
        best = curr;
        best_srtt = curr_srtt;
      }
      curr = ISC_LIST_NEXT(curr, publink);
    }
    ISC_LIST_UNLINK(find->list, best, publink);
    ISC_LIST_APPEND(sorted, best, publink);
  }
  find->list = sorted;
}

/*
 * Sort a list of finds by server RTT.
 */
static void
sort_finds(dns_adbfindlist_t *findlist, unsigned int bias) {
  dns_adbfind_t *best = NULL;
  dns_adbfindlist_t sorted;
  dns_adbaddrinfo_t *addrinfo, *bestaddrinfo;

  /* Sort each find's addrinfo list by SRTT. */
  ISC_LIST_FOREACH(*findlist, curr, publink) {
    sort_adbfind(curr, bias);
  }

  /* Lame N^2 bubble sort. */
  ISC_LIST_INIT(sorted);
  while (!ISC_LIST_EMPTY(*findlist)) {
    dns_adbfind_t *curr = NULL;
    unsigned int best_srtt;

    best = ISC_LIST_HEAD(*findlist);
    bestaddrinfo = ISC_LIST_HEAD(best->list);
    INSIST(bestaddrinfo != NULL);
    best_srtt = bestaddrinfo->srtt;
    if (isc_sockaddr_pf(&bestaddrinfo->sockaddr) != AF_INET6) {
      best_srtt += bias;
    }
    curr = ISC_LIST_NEXT(best, publink);
    while (curr != NULL) {
      unsigned int curr_srtt;
      addrinfo = ISC_LIST_HEAD(curr->list);
      INSIST(addrinfo != NULL);
      curr_srtt = addrinfo->srtt;
      if (isc_sockaddr_pf(&addrinfo->sockaddr) != AF_INET6) {
        curr_srtt += bias;
      }
      if (curr_srtt < best_srtt) {
        best = curr;
        best_srtt = curr_srtt;
      }
      curr = ISC_LIST_NEXT(curr, publink);
    }
    ISC_LIST_UNLINK(*findlist, best, publink);
    ISC_LIST_APPEND(sorted, best, publink);
  }
  *findlist = sorted;
}

/*
 * Return true iff the ADB find has a pending fetch for 'type'.  This is
 * used to find out whether we're in a loop, where a fetch is waiting for a
 * find which is waiting for that same fetch.
 *
 * Note: This could be done with either an equivalence check (e.g.,
 * query_pending == DNS_ADBFIND_INET) or with a bit check, as below.  If
 * we checked for equivalence, that would mean we could only detect a loop
 * when there is exactly one pending fetch, and we're it. If there were
 * pending fetches for *both* address families, then a loop would be
 * undetected.
 *
 * However, using a bit check means that in theory, an ADB find might be
 * aborted that could have succeeded, if the other fetch had returned an
 * answer.
 *
 * Since there's a good chance the server is broken and won't answer either
 * query, and since an ADB find with two pending fetches is a very rare
 * occurrance anyway, we regard this theoretical SERVFAIL as the lesser
 * evil.
 */
static bool
waiting_for(dns_adbfind_t *find, dns_rdatatype_t type) {
  switch (type) {
  case dns_rdatatype_a:
    return (find->query_pending & DNS_ADBFIND_INET) != 0;
  case dns_rdatatype_aaaa:
    return (find->query_pending & DNS_ADBFIND_INET6) != 0;
  default:
    return false;
  }
}

static void
findname(fetchctx_t *fctx, const dns_name_t *name, in_port_t port,
   unsigned int options, unsigned int flags, isc_stdtime_t now,
   bool *overquota, bool *need_alternate, unsigned int *no_addresses) {
  dns_adbfind_t *find = NULL;
  dns_resolver_t *res = fctx->res;
  bool unshared = ((fctx->options & DNS_FETCHOPT_UNSHARED) != 0);
  isc_result_t result;

  FCTXTRACE("FINDNAME");

  /*
   * If this name is a subdomain of the query domain, tell
   * the ADB to start looking using zone/hint data. This keeps us
   * from getting stuck if the nameserver is beneath the zone cut
   * and we don't know its address (e.g. because the A record has
   * expired).
   */
  if (dns_name_issubdomain(name, fctx->domain)) {
    options |= DNS_ADBFIND_STARTATZONE;
  }

  /*
   * Exempt prefetches from ADB quota.
   */
  if ((fctx->options & DNS_FETCHOPT_PREFETCH) != 0) {
    options |= DNS_ADBFIND_QUOTAEXEMPT;
  }

  /*
   * Pass through NOVALIDATE to any lookups ADB makes.
   */
  if ((fctx->options & DNS_FETCHOPT_NOVALIDATE) != 0) {
    options |= DNS_ADBFIND_NOVALIDATE;
  }

  /*
   * See what we know about this address.
   */
  INSIST(!SHUTTINGDOWN(fctx));
  fetchctx_ref(fctx);
  result = dns_adb_createfind(fctx->adb, fctx->loop, fctx_finddone, fctx,
            name, fctx->name, fctx->type, options, now,
            res->view->dstport, fctx->depth + 1,
            fctx->qc, fctx->gqc, &find);

  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
          ISC_LOG_DEBUG(3), "fctx %p(%s): createfind for %s - %s",
          fctx, fctx->info, fctx->clientstr,
          isc_result_totext(result));

  if (result != ISC_R_SUCCESS) {
    if (result == DNS_R_ALIAS) {
      char namebuf[DNS_NAME_FORMATSIZE];

      /*
       * XXXRTH  Follow the CNAME/DNAME chain?
       */
      dns_adb_destroyfind(&find);
      fctx->adberr++;
      dns_name_format(name, namebuf, sizeof(namebuf));
      isc_log_write(DNS_LOGCATEGORY_CNAME,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
              "skipping nameserver '%s' because it "
              "is a CNAME, while resolving '%s'",
              namebuf, fctx->info);
    }
    fetchctx_detach(&fctx);
    return;
  }

  if (!ISC_LIST_EMPTY(find->list)) {
    /*
     * We have at least some of the addresses for the
     * name.
     */
    INSIST((find->options & DNS_ADBFIND_WANTEVENT) == 0);
    if (flags != 0 || port != 0) {
      ISC_LIST_FOREACH(find->list, ai, publink) {
        ai->flags |= flags;
        if (port != 0) {
          isc_sockaddr_setport(&ai->sockaddr,
                   port);
        }
      }
    }
    if ((flags & FCTX_ADDRINFO_DUALSTACK) != 0) {
      ISC_LIST_APPEND(fctx->altfinds, find, publink);
    } else {
      ISC_LIST_APPEND(fctx->finds, find, publink);
    }
    return;
  }

  /*
   * We don't know any of the addresses for this name.
   *
   * The find may be waiting on a resolver fetch for a server
   * address. We need to make sure it isn't waiting on *this*
   * fetch, because if it is, we won't be answering it and it
   * won't be answering us.
   */
  if (waiting_for(find, fctx->type) && dns_name_equal(name, fctx->name)) {
    fctx->adberr++;
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_INFO, "loop detected resolving '%s'",
            fctx->info);

    if ((find->options & DNS_ADBFIND_WANTEVENT) != 0) {
      atomic_fetch_add_relaxed(&fctx->pending, 1);
      dns_adb_cancelfind(find);
    } else {
      dns_adb_destroyfind(&find);
      fetchctx_detach(&fctx);
    }
    return;
  }

  /*
   * We may be waiting for another fetch to complete, and
   * we'll get an event later when the find has what it needs.
   */
  if ((find->options & DNS_ADBFIND_WANTEVENT) != 0) {
    atomic_fetch_add_relaxed(&fctx->pending, 1);

    /*
     * Bootstrap.
     */
    if (need_alternate != NULL && !*need_alternate && unshared &&
        ((res->dispatches4 == NULL &&
          find->result_v6 != DNS_R_NXDOMAIN) ||
         (res->dispatches6 == NULL &&
          find->result_v4 != DNS_R_NXDOMAIN)))
    {
      *need_alternate = true;
    }
    if (no_addresses != NULL) {
      (*no_addresses)++;
    }
    return;
  }

  /*
   * No addresses and no pending events: the find failed.
   */
  if ((find->options & DNS_ADBFIND_OVERQUOTA) != 0) {
    if (overquota != NULL) {
      *overquota = true;
    }
    fctx->quotacount++; /* quota exceeded */
  } else {
    fctx->adberr++; /* unreachable server, etc. */
  }

  /*
   * If we know there are no addresses for the family we are using then
   * try to add an alternative server.
   */
  if (need_alternate != NULL && !*need_alternate &&
      ((res->dispatches4 == NULL && find->result_v6 == DNS_R_NXRRSET) ||
       (res->dispatches6 == NULL && find->result_v4 == DNS_R_NXRRSET)))
  {
    *need_alternate = true;
  }
  dns_adb_destroyfind(&find);
  fetchctx_detach(&fctx);
}

static bool
isstrictsubdomain(const dns_name_t *name1, const dns_name_t *name2) {
  int order;
  unsigned int nlabels;
  dns_namereln_t namereln;

  namereln = dns_name_fullcompare(name1, name2, &order, &nlabels);
  return namereln == dns_namereln_subdomain;
}

static isc_result_t
fctx_getaddresses(fetchctx_t *fctx) {
  isc_result_t result;
  dns_resolver_t *res;
  isc_stdtime_t now;
  unsigned int stdoptions = 0;
  dns_forwarder_t *fwd;
  dns_adbaddrinfo_t *ai;
  bool all_bad;
  dns_rdata_ns_t ns;
  bool need_alternate = false;
  bool all_spilled = false;
  unsigned int no_addresses = 0;
  unsigned int ns_processed = 0;

  FCTXTRACE5("getaddresses", "fctx->depth=", fctx->depth);

  /*
   * Don't pound on remote servers.  (Failsafe!)
   */
  fctx->restarts++;
  if (fctx->restarts > 100) {
    FCTXTRACE("too many restarts");
    return DNS_R_SERVFAIL;
  }

  res = fctx->res;

  if (fctx->depth > res->maxdepth) {
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(3),
            "too much NS indirection resolving '%s' "
            "(depth=%u, maxdepth=%u)",
            fctx->info, fctx->depth, res->maxdepth);
    return DNS_R_SERVFAIL;
  }

  /*
   * Forwarders.
   */

  INSIST(ISC_LIST_EMPTY(fctx->forwaddrs));
  INSIST(ISC_LIST_EMPTY(fctx->altaddrs));

  /*
   * If we have DNS_FETCHOPT_NOFORWARD set and forwarding policy
   * allows us to not forward - skip forwarders and go straight
   * to NSes. This is currently used to make sure that priming
   * query gets root servers' IP addresses in ADDITIONAL section.
   */
  if ((fctx->options & DNS_FETCHOPT_NOFORWARD) != 0 &&
      (fctx->fwdpolicy != dns_fwdpolicy_only))
  {
    goto normal_nses;
  }

  /*
   * If this fctx has forwarders, use them; otherwise use any
   * selective forwarders specified in the view; otherwise use the
   * resolver's forwarders (if any).
   */
  fwd = ISC_LIST_HEAD(fctx->forwarders);
  if (fwd == NULL) {
    dns_forwarders_t *forwarders = NULL;
    dns_name_t *name = fctx->name;
    dns_name_t suffix;

    /*
     * DS records are found in the parent server.
     * Strip label to get the correct forwarder (if any).
     */
    if (dns_rdatatype_atparent(fctx->type) &&
        dns_name_countlabels(name) > 1)
    {
      unsigned int labels;
      dns_name_init(&suffix);
      labels = dns_name_countlabels(name);
      dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
      name = &suffix;
    }

    result = dns_fwdtable_find(res->view->fwdtable, name,
             &forwarders);
    if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
      fwd = ISC_LIST_HEAD(forwarders->fwdrs);
      fctx->fwdpolicy = forwarders->fwdpolicy;
      dns_name_copy(&forwarders->name, fctx->fwdname);
      if (fctx->fwdpolicy == dns_fwdpolicy_only &&
          isstrictsubdomain(&forwarders->name, fctx->domain))
      {
        fcount_decr(fctx);
        dns_name_copy(&forwarders->name, fctx->domain);
        result = fcount_incr(fctx, true);
        if (result != ISC_R_SUCCESS) {
          dns_forwarders_detach(&forwarders);
          return result;
        }
      }
      dns_forwarders_detach(&forwarders);
    }
  }

  while (fwd != NULL) {
    if ((isc_sockaddr_pf(&fwd->addr) == AF_INET &&
         res->dispatches4 == NULL) ||
        (isc_sockaddr_pf(&fwd->addr) == AF_INET6 &&
         res->dispatches6 == NULL))
    {
      fwd = ISC_LIST_NEXT(fwd, link);
      continue;
    }
    ai = NULL;
    result = dns_adb_findaddrinfo(fctx->adb, &fwd->addr, &ai, 0);
    if (result == ISC_R_SUCCESS) {
      dns_adbaddrinfo_t *cur;
      ai->flags |= FCTX_ADDRINFO_FORWARDER;
      if (fwd->tlsname != NULL) {
        result = dns_view_gettransport(
          res->view, DNS_TRANSPORT_TLS,
          fwd->tlsname, &ai->transport);
        if (result != ISC_R_SUCCESS) {
          dns_adb_freeaddrinfo(fctx->adb, &ai);
          goto next;
        }
      }
      cur = ISC_LIST_HEAD(fctx->forwaddrs);
      while (cur != NULL && cur->srtt < ai->srtt) {
        cur = ISC_LIST_NEXT(cur, publink);
      }
      if (cur != NULL) {
        ISC_LIST_INSERTBEFORE(fctx->forwaddrs, cur, ai,
                  publink);
      } else {
        ISC_LIST_APPEND(fctx->forwaddrs, ai, publink);
      }
    }
  next:
    fwd = ISC_LIST_NEXT(fwd, link);
  }

  /*
   * If the forwarding policy is "only", we don't need the
   * addresses of the nameservers.
   */
  if (fctx->fwdpolicy == dns_fwdpolicy_only) {
    goto out;
  }

  /*
   * Normal nameservers.
   */
normal_nses:
  stdoptions = DNS_ADBFIND_WANTEVENT | DNS_ADBFIND_EMPTYEVENT;
  if (fctx->restarts == 1) {
    /*
     * To avoid sending out a flood of queries likely to
     * result in NXRRSET, we suppress fetches for address
     * families we don't have the first time through,
     * provided that we have addresses in some family we
     * can use.
     *
     * We don't want to set this option all the time, since
     * if fctx->restarts > 1, we've clearly been having
     * trouble with the addresses we had, so getting more
     * could help.
     */
    stdoptions |= DNS_ADBFIND_AVOIDFETCHES;
  }
  if (res->dispatches4 != NULL) {
    stdoptions |= DNS_ADBFIND_INET;
  }
  if (res->dispatches6 != NULL) {
    stdoptions |= DNS_ADBFIND_INET6;
  }

  if ((stdoptions & DNS_ADBFIND_ADDRESSMASK) == 0) {
    return DNS_R_SERVFAIL;
  }

  now = isc_stdtime_now();
  all_spilled = true; /* resets to false below after the first success */

  INSIST(ISC_LIST_EMPTY(fctx->finds));
  INSIST(ISC_LIST_EMPTY(fctx->altfinds));

  DNS_RDATASET_FOREACH(&fctx->nameservers) {
    dns_rdata_t rdata = DNS_RDATA_INIT;
    bool overquota = false;
    unsigned int static_stub = 0;

    dns_rdataset_current(&fctx->nameservers, &rdata);
    /*
     * Extract the name from the NS record.
     */
    result = dns_rdata_tostruct(&rdata, &ns, NULL);
    if (result != ISC_R_SUCCESS) {
      continue;
    }

    if (STATICSTUB(&fctx->nameservers) &&
        dns_name_equal(&ns.name, fctx->domain))
    {
      static_stub = DNS_ADBFIND_STATICSTUB;
    }

    if (no_addresses > NS_FAIL_LIMIT &&
        dns_rdataset_count(&fctx->nameservers) > NS_RR_LIMIT)
    {
      stdoptions |= DNS_ADBFIND_NOFETCH;
    }
    findname(fctx, &ns.name, 0, stdoptions | static_stub, 0, now,
       &overquota, &need_alternate, &no_addresses);

    if (!overquota) {
      all_spilled = false;
    }

    dns_rdata_reset(&rdata);
    dns_rdata_freestruct(&ns);

    if (++ns_processed >= NS_PROCESSING_LIMIT) {
      break;
    }
  }

  /*
   * Do we need to use 6 to 4?
   */
  if (need_alternate) {
    int family;
    family = (res->dispatches6 != NULL) ? AF_INET6 : AF_INET;
    ISC_LIST_FOREACH(res->alternates, a, link) {
      if (!a->isaddress) {
        findname(fctx, &a->_u._n.name, a->_u._n.port,
           stdoptions, FCTX_ADDRINFO_DUALSTACK,
           now, NULL, NULL, NULL);
        continue;
      }
      if (isc_sockaddr_pf(&a->_u.addr) != family) {
        continue;
      }
      ai = NULL;
      result = dns_adb_findaddrinfo(fctx->adb, &a->_u.addr,
                  &ai, 0);
      if (result == ISC_R_SUCCESS) {
        dns_adbaddrinfo_t *cur;
        ai->flags |= FCTX_ADDRINFO_FORWARDER;
        ai->flags |= FCTX_ADDRINFO_DUALSTACK;
        cur = ISC_LIST_HEAD(fctx->altaddrs);
        while (cur != NULL && cur->srtt < ai->srtt) {
          cur = ISC_LIST_NEXT(cur, publink);
        }
        if (cur != NULL) {
          ISC_LIST_INSERTBEFORE(fctx->altaddrs,
                    cur, ai, publink);
        } else {
          ISC_LIST_APPEND(fctx->altaddrs, ai,
              publink);
        }
      }
    }
  }

out:
  /*
   * Mark all known bad servers.
   */
  all_bad = mark_bad(fctx);

  /*
   * How are we doing?
   */
  if (all_bad) {
    /*
     * We've got no addresses.
     */
    if (atomic_load_acquire(&fctx->pending) > 0) {
      /*
       * We're fetching the addresses, but don't have
       * any yet.   Tell the caller to wait for an
       * answer.
       */
      result = DNS_R_WAIT;
    } else {
      /*
       * We've lost completely.  We don't know any
       * addresses, and the ADB has told us it can't
       * get them.
       */
      FCTXTRACE("no addresses");

      result = ISC_R_FAILURE;

      /*
       * If all of the addresses found were over the
       * fetches-per-server quota, increase the ServerQuota
       * counter and return the configured response.
       */
      if (all_spilled) {
        result = res->quotaresp[dns_quotatype_server];
        inc_stats(res, dns_resstatscounter_serverquota);
      }

      /*
       * If we are using a 'forward only' policy, and all
       * the forwarders are bad, increase the ForwardOnlyFail
       * counter.
       */
      if (fctx->fwdpolicy == dns_fwdpolicy_only) {
        inc_stats(res,
            dns_resstatscounter_forwardonlyfail);
      }
    }
  } else {
    /*
     * We've found some addresses.  We might still be
     * looking for more addresses.
     */
    sort_finds(&fctx->finds, res->view->v6bias);
    sort_finds(&fctx->altfinds, 0);
    result = ISC_R_SUCCESS;
  }

  return result;
}

static void
possibly_mark(fetchctx_t *fctx, dns_adbaddrinfo_t *addr) {
  isc_netaddr_t na;
  isc_sockaddr_t *sa = &addr->sockaddr;
  bool aborted = false;
  bool bogus;
  dns_acl_t *blackhole;
  isc_netaddr_t ipaddr;
  dns_peer_t *peer = NULL;
  dns_resolver_t *res = fctx->res;
  const char *msg = NULL;

  isc_netaddr_fromsockaddr(&ipaddr, sa);
  blackhole = dns_dispatchmgr_getblackhole(res->view->dispatchmgr);
  (void)dns_peerlist_peerbyaddr(res->view->peers, &ipaddr, &peer);

  if (blackhole != NULL) {
    int match;

    if ((dns_acl_match(&ipaddr, NULL, blackhole, res->view->aclenv,
           &match, NULL) == ISC_R_SUCCESS) &&
        match > 0)
    {
      aborted = true;
    }
  }

  if (peer != NULL && dns_peer_getbogus(peer, &bogus) == ISC_R_SUCCESS &&
      bogus)
  {
    aborted = true;
  }

  if (aborted) {
    addr->flags |= FCTX_ADDRINFO_MARK;
    msg = "ignoring blackholed / bogus server: ";
  } else if (isc_sockaddr_isnetzero(sa)) {
    addr->flags |= FCTX_ADDRINFO_MARK;
    msg = "ignoring net zero address: ";
  } else if (isc_sockaddr_ismulticast(sa)) {
    addr->flags |= FCTX_ADDRINFO_MARK;
    msg = "ignoring multicast address: ";
  } else if (isc_sockaddr_isexperimental(sa)) {
    addr->flags |= FCTX_ADDRINFO_MARK;
    msg = "ignoring experimental address: ";
  } else if (sa->type.sa.sa_family != AF_INET6) {
    return;
  } else if (IN6_IS_ADDR_V4MAPPED(&sa->type.sin6.sin6_addr)) {
    addr->flags |= FCTX_ADDRINFO_MARK;
    msg = "ignoring IPv6 mapped IPV4 address: ";
  } else if (IN6_IS_ADDR_V4COMPAT(&sa->type.sin6.sin6_addr)) {
    addr->flags |= FCTX_ADDRINFO_MARK;
    msg = "ignoring IPv6 compatibility IPV4 address: ";
  } else {
    return;
  }

  if (isc_log_wouldlog(ISC_LOG_DEBUG(3))) {
    char buf[ISC_NETADDR_FORMATSIZE];
    isc_netaddr_fromsockaddr(&na, sa);
    isc_netaddr_format(&na, buf, sizeof(buf));
    FCTXTRACE2(msg, buf);
  }
}

static dns_adbaddrinfo_t *
fctx_nextaddress(fetchctx_t *fctx) {
  dns_adbfind_t *find = NULL, *start = NULL;
  dns_adbaddrinfo_t *addrinfo = NULL, *faddrinfo = NULL;

  /*
   * Return the next untried address, if any.
   */

  /*
   * Find the first unmarked forwarder (if any).
   */
  ISC_LIST_FOREACH(fctx->forwaddrs, ai, publink) {
    if (!UNMARKED(ai)) {
      continue;
    }
    possibly_mark(fctx, ai);
    if (UNMARKED(ai)) {
      ai->flags |= FCTX_ADDRINFO_MARK;
      fctx->find = NULL;
      fctx->forwarding = true;

      /*
       * QNAME minimization is disabled when
       * forwarding, and has to remain disabled if
       * we switch back to normal recursion; otherwise
       * forwarding could leave us in an inconsistent
       * state.
       */
      fctx->minimized = false;
      return ai;
    }
  }

  /*
   * No forwarders.  Move to the next find.
   */
  fctx->forwarding = false;
  FCTX_ATTR_SET(fctx, FCTX_ATTR_TRIEDFIND);

  find = fctx->find;
  if (find == NULL) {
    find = ISC_LIST_HEAD(fctx->finds);
  } else {
    find = ISC_LIST_NEXT(find, publink);
    if (find == NULL) {
      find = ISC_LIST_HEAD(fctx->finds);
    }
  }

  /*
   * Find the first unmarked addrinfo.
   */
  if (find != NULL) {
    start = find;
    do {
      ISC_LIST_FOREACH(find->list, ai, publink) {
        if (!UNMARKED(ai)) {
          continue;
        }
        possibly_mark(fctx, ai);
        if (UNMARKED(ai)) {
          ai->flags |= FCTX_ADDRINFO_MARK;
          faddrinfo = ai;
          break;
        }
      }
      if (faddrinfo != NULL) {
        break;
      }
      find = ISC_LIST_NEXT(find, publink);
      if (find == NULL) {
        find = ISC_LIST_HEAD(fctx->finds);
      }
    } while (find != start);
  }

  fctx->find = find;
  if (faddrinfo != NULL) {
    return faddrinfo;
  }

  /*
   * No nameservers left.  Try alternates.
   */

  FCTX_ATTR_SET(fctx, FCTX_ATTR_TRIEDALT);

  find = fctx->altfind;
  if (find == NULL) {
    find = ISC_LIST_HEAD(fctx->altfinds);
  } else {
    find = ISC_LIST_NEXT(find, publink);
    if (find == NULL) {
      find = ISC_LIST_HEAD(fctx->altfinds);
    }
  }

  /*
   * Find the first unmarked addrinfo.
   */
  if (find != NULL) {
    start = find;
    do {
      ISC_LIST_FOREACH(find->list, ai, publink) {
        if (!UNMARKED(ai)) {
          continue;
        }
        possibly_mark(fctx, ai);
        if (UNMARKED(ai)) {
          ai->flags |= FCTX_ADDRINFO_MARK;
          faddrinfo = ai;
          break;
        }
      }
      if (faddrinfo != NULL) {
        break;
      }
      find = ISC_LIST_NEXT(find, publink);
      if (find == NULL) {
        find = ISC_LIST_HEAD(fctx->altfinds);
      }
    } while (find != start);
  }

  /*
   * See if we have a better alternate server by address.
   */
  ISC_LIST_FOREACH(fctx->altaddrs, ai, publink) {
    if (!UNMARKED(ai)) {
      continue;
    }
    possibly_mark(fctx, ai);
    if (UNMARKED(ai) &&
        (faddrinfo == NULL || ai->srtt < faddrinfo->srtt))
    {
      if (faddrinfo != NULL) {
        faddrinfo->flags &= ~FCTX_ADDRINFO_MARK;
      }
      ai->flags |= FCTX_ADDRINFO_MARK;
      addrinfo = ai;
      break;
    }
  }

  if (addrinfo == NULL) {
    addrinfo = faddrinfo;
    fctx->altfind = find;
  }

  return addrinfo;
}

static void
fctx_try(fetchctx_t *fctx, bool retrying) {
  isc_result_t result;
  dns_adbaddrinfo_t *addrinfo = NULL;
  dns_resolver_t *res = NULL;

  FCTXTRACE5("try", "fctx->qc=", isc_counter_used(fctx->qc));
  if (fctx->gqc != NULL) {
    FCTXTRACE5("try", "fctx->gqc=", isc_counter_used(fctx->gqc));
  }

  REQUIRE(!ADDRWAIT(fctx));
  REQUIRE(fctx->tid == isc_tid());

  res = fctx->res;

  /* We've already exceeded maximum query count */
  if (isc_counter_used(fctx->qc) > isc_counter_getlimit(fctx->qc)) {
    isc_log_write(
      DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
      ISC_LOG_DEBUG(3),
      "exceeded max queries resolving '%s' "
      "(max-recursion-queries, querycount=%u, maxqueries=%u)",
      fctx->info, isc_counter_used(fctx->qc),
      isc_counter_getlimit(fctx->qc));
    result = DNS_R_SERVFAIL;
    goto done;
  }

  if (fctx->gqc != NULL &&
      isc_counter_used(fctx->gqc) > isc_counter_getlimit(fctx->gqc))
  {
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(3),
            "exceeded global max queries resolving '%s' "
            "(max-query-count, querycount=%u, maxqueries=%u)",
            fctx->info, isc_counter_used(fctx->gqc),
            isc_counter_getlimit(fctx->gqc));
    result = DNS_R_SERVFAIL;
    goto done;
  }

  addrinfo = fctx_nextaddress(fctx);

  /* Try to find an address that isn't over quota */
  while (addrinfo != NULL && dns_adb_overquota(fctx->adb, addrinfo)) {
    addrinfo = fctx_nextaddress(fctx);
  }

  if (addrinfo == NULL) {
    /* We have no more addresses.  Start over. */
    fctx_cancelqueries(fctx, true, false);
    fctx_cleanup(fctx);
    result = fctx_getaddresses(fctx);
    switch (result) {
    case ISC_R_SUCCESS:
      break;
    case DNS_R_WAIT:
      /* Sleep waiting for addresses. */
      FCTXTRACE("addrwait");
      FCTX_ATTR_SET(fctx, FCTX_ATTR_ADDRWAIT);
      return;
    default:
      goto done;
    }

    addrinfo = fctx_nextaddress(fctx);

    while (addrinfo != NULL &&
           dns_adb_overquota(fctx->adb, addrinfo))
    {
      addrinfo = fctx_nextaddress(fctx);
    }

    /*
     * While we may have addresses from the ADB, they
     * might be bad ones.  In this case, return SERVFAIL.
     */
    if (addrinfo == NULL) {
      result = DNS_R_SERVFAIL;
      goto done;
    }
  }
  /*
   * We're minimizing and we're not yet at the final NS -
   * we need to launch a query for NS for 'upper' domain
   */
  if (fctx->minimized && !fctx->forwarding) {
    unsigned int options = fctx->options;

    options &= ~DNS_FETCHOPT_QMINIMIZE;

    /*
     * Is another QNAME minimization fetch still running?
     */
    if (fctx->qminfetch != NULL) {
      bool validfctx = (DNS_FETCH_VALID(fctx->qminfetch) &&
            VALID_FCTX(fctx->qminfetch->private));
      char namebuf[DNS_NAME_FORMATSIZE];
      char typebuf[DNS_RDATATYPE_FORMATSIZE];

      dns_name_format(fctx->qminname, namebuf,
          sizeof(namebuf));
      dns_rdatatype_format(fctx->qmintype, typebuf,
               sizeof(typebuf));
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_ERROR,
              "fctx %p(%s): attempting QNAME "
              "minimization fetch for %s/%s but "
              "fetch %p(%s) still running",
              fctx, fctx->info, namebuf, typebuf,
              fctx->qminfetch,
              validfctx ? fctx->qminfetch->private->info
            : "<invalid>");
      result = DNS_R_SERVFAIL;
      goto done;
    }

    /*
     * Turn on NOFOLLOW in relaxed mode so that QNAME minimization
     * doesn't cause additional queries to resolve the target of the
     * QNAME minimization request when a referral is returned.  This
     * will also reduce the impact of mis-matched NS RRsets where
     * the child's NS RRset is garbage.  If a delegation is
     * discovered DNS_R_DELEGATION will be returned to resume_qmin.
     */
    if ((options & DNS_FETCHOPT_QMIN_STRICT) == 0) {
      options |= DNS_FETCHOPT_NOFOLLOW;
    }

    fetchctx_ref(fctx);
    result = dns_resolver_createfetch(
      fctx->res, fctx->qminname, fctx->qmintype, fctx->domain,
      &fctx->nameservers, NULL, NULL, 0,
      options | DNS_FETCHOPT_QMINFETCH, 0, fctx->qc,
      fctx->gqc, fctx->loop, resume_qmin, fctx, &fctx->edectx,
      &fctx->qminrrset, &fctx->qminsigrrset,
      &fctx->qminfetch);
    if (result != ISC_R_SUCCESS) {
      fetchctx_unref(fctx);
      goto done;
    }
    return;
  }

  result = isc_counter_increment(fctx->qc);
  if (result != ISC_R_SUCCESS) {
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(3),
            "exceeded max queries resolving '%s' "
            "(max-recursion-queries, querycount=%u)",
            fctx->info, isc_counter_used(fctx->qc));
    goto done;
  }

  if (fctx->gqc != NULL) {
    result = isc_counter_increment(fctx->gqc);
    if (result != ISC_R_SUCCESS) {
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_DEBUG(3),
              "exceeded global max queries resolving "
              "'%s' (max-query-count, querycount=%u)",
              fctx->info, isc_counter_used(fctx->gqc));
      goto done;
    }
  }

  result = fctx_query(fctx, addrinfo, fctx->options);
  if (result != ISC_R_SUCCESS) {
    goto done;
  }
  if (retrying) {
    inc_stats(res, dns_resstatscounter_retry);
  }

done:
  if (result != ISC_R_SUCCESS) {
    fctx_done_detach(&fctx, result);
  }
}

static void
resume_qmin(void *arg) {
  dns_fetchresponse_t *resp = (dns_fetchresponse_t *)arg;
  fetchctx_t *fctx = resp->arg;
  dns_resolver_t *res = NULL;
  isc_result_t result;
  unsigned int findoptions = 0;
  dns_name_t *fname = NULL, *dcname = NULL;
  dns_fixedname_t ffixed, dcfixed;
  dns_rdataset_t rdataset;
  dns_rdataset_t sigrdataset;
  dns_db_t *db = NULL;
  dns_dbnode_t *node = NULL;
  bool fixup_result = false;

  REQUIRE(VALID_FCTX(fctx));

  res = fctx->res;

  REQUIRE(fctx->tid == isc_tid());

  FCTXTRACE("resume_qmin");

  fname = dns_fixedname_initname(&ffixed);
  dcname = dns_fixedname_initname(&dcfixed);

  dns_rdataset_init(&rdataset);
  dns_rdataset_init(&sigrdataset);

  if (resp->node != NULL) {
    dns_db_attachnode(resp->node, &node);
    dns_db_detachnode(&resp->node);
  }
  if (resp->db != NULL) {
    dns_db_attach(resp->db, &db);
    dns_db_detach(&resp->db);
  }

  if (dns_rdataset_isassociated(resp->rdataset)) {
    dns_rdataset_clone(resp->rdataset, &rdataset);
    dns_rdataset_disassociate(resp->rdataset);
  }
  if (dns_rdataset_isassociated(resp->sigrdataset)) {
    dns_rdataset_clone(resp->sigrdataset, &sigrdataset);
    dns_rdataset_disassociate(resp->sigrdataset);
  }
  dns_name_copy(resp->foundname, fname);

  result = resp->result;

  dns_resolver_freefresp(&resp);

  LOCK(&fctx->lock);
  if (SHUTTINGDOWN(fctx)) {
    result = ISC_R_SHUTTINGDOWN;
  }
  UNLOCK(&fctx->lock);

  dns_resolver_destroyfetch(&fctx->qminfetch);

  /*
   * Beware, the switch() below is little bit tricky - the order of the
   * branches is important.
   */
  switch (result) {
  case ISC_R_SHUTTINGDOWN:
  case ISC_R_CANCELED:
    goto cleanup;

  case DNS_R_NXDOMAIN:
  case DNS_R_NCACHENXDOMAIN:
  case DNS_R_FORMERR:
  case DNS_R_REMOTEFORMERR:
  case ISC_R_FAILURE:
  case ISC_R_TIMEDOUT:
    if ((fctx->options & DNS_FETCHOPT_QMIN_STRICT) != 0) {
      /* These results cause a hard fail in strict mode */
      goto cleanup;
    }

    if (result == DNS_R_NXDOMAIN &&
        fctx->qmin_labels == dns_name_countlabels(fctx->name))
    {
      LOCK(&fctx->lock);
      resp = ISC_LIST_HEAD(fctx->resps);
      if (resp != NULL) {
        if (dns_rdataset_isassociated(&rdataset)) {
          dns_rdataset_clone(&rdataset,
                 resp->rdataset);
        }
        if (dns_rdataset_isassociated(&sigrdataset) &&
            resp->sigrdataset != NULL)
        {
          dns_rdataset_clone(&sigrdataset,
                 resp->sigrdataset);
        }
        if (db != NULL) {
          dns_db_attach(db, &resp->db);
        }
        if (node != NULL) {
          dns_db_attachnode(node, &resp->node);
        }
        dns_name_copy(fname, resp->foundname);
        clone_results(fctx);
        UNLOCK(&fctx->lock);
        goto cleanup;
      }
      UNLOCK(&fctx->lock);
    }

    /* ...or disable minimization in relaxed mode */
    fctx->qmin_labels = DNS_NAME_MAXLABELS;

    /*
     * We store the result. If we succeed in the end
     * we'll issue a warning that the server is
     * broken.
     */
    fctx->qmin_warning = result;
    break;

  case ISC_R_SUCCESS:
  case DNS_R_DELEGATION:
  case DNS_R_NXRRSET:
  case DNS_R_NCACHENXRRSET:
  case DNS_R_CNAME:
  case DNS_R_DNAME:
    /*
     * We have previously detected a possible error of an
     * incorrect NXDOMAIN and now have a response that
     * indicates that it was an actual error.
     */
    if (fctx->qmin_warning == DNS_R_NCACHENXDOMAIN ||
        fctx->qmin_warning == DNS_R_NXDOMAIN)
    {
      fctx->force_qmin_warning = true;
    }

    /*
     * We have got a CNAME or DNAME respone to the NS query
     * so we are done in almost all cases.
     */
    if ((result == DNS_R_CNAME || result == DNS_R_DNAME) &&
        fctx->qmin_labels == dns_name_countlabels(fctx->name) &&
        fctx->type != dns_rdatatype_key &&
        fctx->type != dns_rdatatype_nsec &&
        fctx->type != dns_rdatatype_any &&
        fctx->type != dns_rdatatype_sig &&
        fctx->type != dns_rdatatype_rrsig)
    {
      LOCK(&fctx->lock);
      resp = ISC_LIST_HEAD(fctx->resps);
      if (resp != NULL) {
        if (dns_rdataset_isassociated(&rdataset)) {
          dns_rdataset_clone(&rdataset,
                 resp->rdataset);
        }
        if (dns_rdataset_isassociated(&sigrdataset) &&
            resp->sigrdataset != NULL)
        {
          dns_rdataset_clone(&sigrdataset,
                 resp->sigrdataset);
        }
        if (db != NULL) {
          dns_db_attach(db, &resp->db);
        }
        if (node != NULL) {
          dns_db_attachnode(node, &resp->node);
        }
        dns_name_copy(fname, resp->foundname);
        if (result == DNS_R_CNAME &&
            dns_rdataset_isassociated(&rdataset) &&
            fctx->type == dns_rdatatype_cname)
        {
          fixup_result = true;
        }
        clone_results(fctx);
        UNLOCK(&fctx->lock);
        goto cleanup;
      }
      UNLOCK(&fctx->lock);
    }

    /*
     * Any other result will *not* cause a failure in strict
     * mode, or cause minimization to be disabled in relaxed
     * mode.
     *
     * If DNS_R_DELEGATION is set here, it implies that
     * DNS_FETCHOPT_NOFOLLOW was set, and a delegation was
     * discovered but not followed; we will do so now.
     */
    break;

  default:
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(5),
            "QNAME minimization: unexpected result %s",
            isc_result_totext(result));
    break;
  }

  if (dns_rdataset_isassociated(&fctx->nameservers)) {
    dns_rdataset_disassociate(&fctx->nameservers);
  }

  if (dns_rdatatype_atparent(fctx->type)) {
    findoptions |= DNS_DBFIND_NOEXACT;
  }
  result = dns_view_findzonecut(res->view, fctx->name, fname, dcname,
              fctx->now, findoptions, true, true,
              &fctx->nameservers, NULL);
  FCTXTRACEN("resume_qmin findzonecut", fname, result);

  /*
   * DNS_R_NXDOMAIN here means we have not loaded the root zone
   * mirror yet - but DNS_R_NXDOMAIN is not a valid return value
   * when doing recursion, we need to patch it.
   *
   * CNAME or DNAME means zone were added with that record
   * after the start of a recursion. It means we do not have
   * initialized correct hevent->foundname and have to fail.
   */
  if (result == DNS_R_NXDOMAIN || result == DNS_R_CNAME ||
      result == DNS_R_DNAME)
  {
    result = DNS_R_SERVFAIL;
  }

  if (result != ISC_R_SUCCESS) {
    goto cleanup;
  }
  fcount_decr(fctx);

  dns_name_copy(fname, fctx->domain);

  result = fcount_incr(fctx, false);
  if (result != ISC_R_SUCCESS) {
    goto cleanup;
  }

  dns_name_copy(dcname, fctx->qmindcname);
  fctx->ns_ttl = fctx->nameservers.ttl;
  fctx->ns_ttl_ok = true;

  fctx_minimize_qname(fctx);

  if (!fctx->minimized) {
    /*
     * We have finished minimizing, but fctx->finds was
     * filled at the beginning of the run - now we need to
     * clear it before sending the final query to use proper
     * nameservers.
     */
    fctx_cancelqueries(fctx, false, false);
    fctx_cleanup(fctx);
  }

  fctx_try(fctx, true);

cleanup:
  if (node != NULL) {
    dns_db_detachnode(&node);
  }
  if (db != NULL) {
    dns_db_detach(&db);
  }
  if (dns_rdataset_isassociated(&rdataset)) {
    dns_rdataset_disassociate(&rdataset);
  }
  if (dns_rdataset_isassociated(&sigrdataset)) {
    dns_rdataset_disassociate(&sigrdataset);
  }
  if (result != ISC_R_SUCCESS) {
    /* An error occurred, tear down whole fctx */
    fctx_done_unref(fctx, fixup_result ? ISC_R_SUCCESS : result);
  }
  fetchctx_detach(&fctx);
}

static void
fctx_destroy(fetchctx_t *fctx) {
  dns_resolver_t *res = NULL;

  REQUIRE(VALID_FCTX(fctx));
  REQUIRE(ISC_LIST_EMPTY(fctx->resps));
  REQUIRE(ISC_LIST_EMPTY(fctx->queries));
  REQUIRE(ISC_LIST_EMPTY(fctx->finds));
  REQUIRE(ISC_LIST_EMPTY(fctx->altfinds));
  REQUIRE(atomic_load_acquire(&fctx->pending) == 0);
  REQUIRE(ISC_LIST_EMPTY(fctx->validators));
  REQUIRE(fctx->state != fetchstate_active);

  FCTXTRACE("destroy");

  fctx->magic = 0;

  res = fctx->res;

  dec_stats(res, dns_resstatscounter_nfetch);

  /* Free bad */
  ISC_LIST_FOREACH(fctx->bad, sa, link) {
    ISC_LIST_UNLINK(fctx->bad, sa, link);
    isc_mem_put(fctx->mctx, sa, sizeof(*sa));
  }

  ISC_LIST_FOREACH(fctx->edns, tried, link) {
    ISC_LIST_UNLINK(fctx->edns, tried, link);
    isc_mem_put(fctx->mctx, tried, sizeof(*tried));
  }

  if (fctx->nfails != NULL) {
    isc_counter_detach(&fctx->nfails);
  }
  if (fctx->nvalidations != NULL) {
    isc_counter_detach(&fctx->nvalidations);
  }
  isc_counter_detach(&fctx->qc);
  if (fctx->gqc != NULL) {
    isc_counter_detach(&fctx->gqc);
  }
  fcount_decr(fctx);
  dns_message_detach(&fctx->qmessage);
  if (dns_rdataset_isassociated(&fctx->nameservers)) {
    dns_rdataset_disassociate(&fctx->nameservers);
  }
  dns_db_detach(&fctx->cache);
  dns_adb_detach(&fctx->adb);

  dns_resolver_detach(&fctx->res);

  dns_ede_invalidate(&fctx->edectx);

  isc_mutex_destroy(&fctx->lock);

  isc_mem_free(fctx->mctx, fctx->info);
  isc_mem_putanddetach(&fctx->mctx, fctx, sizeof(*fctx));
}

static void
fctx_expired(void *arg) {
  fetchctx_t *fctx = (fetchctx_t *)arg;

  REQUIRE(VALID_FCTX(fctx));
  REQUIRE(fctx->tid == isc_tid());

  FCTXTRACE(isc_result_totext(ISC_R_TIMEDOUT));
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
          ISC_LOG_INFO, "gave up on resolving '%s'", fctx->info);

  dns_ede_add(&fctx->edectx, DNS_EDE_NOREACHABLEAUTH, NULL);

  fctx_done_detach(&fctx, DNS_R_SERVFAIL);
}

static void
fctx_shutdown(void *arg) {
  fetchctx_t *fctx = arg;

  REQUIRE(VALID_FCTX(fctx));

  fctx_done_unref(fctx, ISC_R_SHUTTINGDOWN);
  fetchctx_detach(&fctx);
}

static void
fctx_start(void *arg) {
  fetchctx_t *fctx = (fetchctx_t *)arg;

  REQUIRE(VALID_FCTX(fctx));

  FCTXTRACE("start");

  LOCK(&fctx->lock);
  if (SHUTTINGDOWN(fctx)) {
    UNLOCK(&fctx->lock);
    goto detach;
  }

  /*
   * Normal fctx startup.
   */
  fctx->state = fetchstate_active;
  UNLOCK(&fctx->lock);

  /*
   * As a backstop, we also set a timer to stop the fetch
   * if in-band netmgr timeouts don't work. It will fire two
   * seconds after the fetch should have finished. (This
   * should be enough of a gap to avoid the timer firing
   * while a response is being processed normally.)
   */
  fctx_starttimer(fctx);
  fctx_try(fctx, false);

detach:
  fetchctx_detach(&fctx);
}

/*
 * Fetch Creation, Joining, and Cancellation.
 */

static void
fctx_add_event(fetchctx_t *fctx, isc_loop_t *loop, const isc_sockaddr_t *client,
         dns_messageid_t id, isc_job_cb cb, void *arg,
         dns_edectx_t *edectx, dns_rdataset_t *rdataset,
         dns_rdataset_t *sigrdataset, dns_fetch_t *fetch) {
  dns_fetchresponse_t *resp = NULL;

  FCTXTRACE("addevent");

  resp = isc_mem_get(fctx->mctx, sizeof(*resp));
  *resp = (dns_fetchresponse_t){
    .result = DNS_R_SERVFAIL,
    .qtype = fctx->type,
    .rdataset = rdataset,
    .sigrdataset = sigrdataset,
    .fetch = fetch,
    .client = client,
    .id = id,
    .loop = loop,
    .cb = cb,
    .arg = arg,
    .link = ISC_LINK_INITIALIZER,
    .edectx = edectx,
  };
  isc_mem_attach(fctx->mctx, &resp->mctx);

  resp->foundname = dns_fixedname_initname(&resp->fname);

  /*
   * Store the sigrdataset in the first resp in case it is needed
   * by any of the events.
   */
  if (resp->sigrdataset != NULL) {
    ISC_LIST_PREPEND(fctx->resps, resp, link);
  } else {
    ISC_LIST_APPEND(fctx->resps, resp, link);
  }
}

static void
fctx_join(fetchctx_t *fctx, isc_loop_t *loop, const isc_sockaddr_t *client,
    dns_messageid_t id, isc_job_cb cb, void *arg, dns_edectx_t *edectx,
    dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset,
    dns_fetch_t *fetch) {
  FCTXTRACE("join");

  REQUIRE(!SHUTTINGDOWN(fctx));

  fctx_add_event(fctx, loop, client, id, cb, arg, edectx, rdataset,
           sigrdataset, fetch);

  fetch->magic = DNS_FETCH_MAGIC;
  fetchctx_attach(fctx, &fetch->private);
}

static void
log_ns_ttl(fetchctx_t *fctx, const char *where) {
  char namebuf[DNS_NAME_FORMATSIZE];
  char domainbuf[DNS_NAME_FORMATSIZE];

  dns_name_format(fctx->name, namebuf, sizeof(namebuf));
  dns_name_format(fctx->domain, domainbuf, sizeof(domainbuf));
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
          ISC_LOG_DEBUG(10),
          "log_ns_ttl: fctx %p: %s: %s (in '%s'?): %u %u", fctx,
          where, namebuf, domainbuf, fctx->ns_ttl_ok, fctx->ns_ttl);
}

static isc_result_t
fctx_create(dns_resolver_t *res, isc_loop_t *loop, const dns_name_t *name,
      dns_rdatatype_t type, const dns_name_t *domain,
      dns_rdataset_t *nameservers, const isc_sockaddr_t *client,
      unsigned int options, unsigned int depth, isc_counter_t *qc,
      isc_counter_t *gqc, fetchctx_t **fctxp) {
  fetchctx_t *fctx = NULL;
  isc_result_t result;
  isc_result_t iresult;
  isc_interval_t interval;
  unsigned int findoptions = 0;
  char buf[DNS_NAME_FORMATSIZE + DNS_RDATATYPE_FORMATSIZE + 1];
  isc_mem_t *mctx = isc_loop_getmctx(loop);
  size_t p;
  uint32_t nvalidations = atomic_load_relaxed(&res->maxvalidations);
  uint32_t nfails = atomic_load_relaxed(&res->maxvalidationfails);

  /*
   * Caller must be holding the lock for 'bucket'
   */
  REQUIRE(fctxp != NULL && *fctxp == NULL);

  fctx = isc_mem_get(mctx, sizeof(*fctx));
  *fctx = (fetchctx_t){
    .type = type,
    .qmintype = type,
    .options = options,
    .tid = isc_tid(),
    .state = fetchstate_active,
    .depth = depth,
    .qmin_labels = 1,
    .fwdpolicy = dns_fwdpolicy_none,
    .result = ISC_R_FAILURE,
    .loop = loop,
  };

  isc_mem_attach(mctx, &fctx->mctx);
  dns_resolver_attach(res, &fctx->res);

  isc_mutex_init(&fctx->lock);

  dns_ede_init(fctx->mctx, &fctx->edectx);

  /*
   * Make fctx->info point to a copy of a formatted string
   * "name/type". FCTXTRACE won't work until this is done.
   */
  dns_name_format(name, buf, sizeof(buf));
  p = strlcat(buf, "/", sizeof(buf));
  INSIST(p + DNS_RDATATYPE_FORMATSIZE < sizeof(buf));
  dns_rdatatype_format(type, buf + p, sizeof(buf) - p);
  fctx->info = isc_mem_strdup(fctx->mctx, buf);

  FCTXTRACE("create");

  if (nfails > 0) {
    isc_counter_create(mctx, nfails, &fctx->nfails);
  }

  if (nvalidations > 0) {
    isc_counter_create(mctx, nvalidations, &fctx->nvalidations);
  }

  if (qc != NULL) {
    isc_counter_attach(qc, &fctx->qc);
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(9),
            "fctx %p(%s): attached to counter %p (%d)", fctx,
            fctx->info, fctx->qc, isc_counter_used(fctx->qc));
  } else {
    isc_counter_create(fctx->mctx, res->maxqueries, &fctx->qc);
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(9),
            "fctx %p(%s): created counter %p", fctx,
            fctx->info, fctx->qc);
  }

  if (gqc != NULL) {
    isc_counter_attach(gqc, &fctx->gqc);
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(9),
            "fctx %p(%s): attached to counter %p (%d)", fctx,
            fctx->info, fctx->gqc,
            isc_counter_used(fctx->gqc));
  }

#if DNS_RESOLVER_TRACE
  fprintf(stderr, "fetchctx__init:%s:%s:%d:%p:%p->references = 1\n",
    __func__, __FILE__, __LINE__, fctx, fctx);
#endif
  isc_refcount_init(&fctx->references, 1);

  ISC_LIST_INIT(fctx->queries);
  ISC_LIST_INIT(fctx->finds);
  ISC_LIST_INIT(fctx->altfinds);
  ISC_LIST_INIT(fctx->forwaddrs);
  ISC_LIST_INIT(fctx->altaddrs);
  ISC_LIST_INIT(fctx->forwarders);
  ISC_LIST_INIT(fctx->bad);
  ISC_LIST_INIT(fctx->edns);
  ISC_LIST_INIT(fctx->validators);

  atomic_init(&fctx->attributes, 0);

  fctx->name = dns_fixedname_initname(&fctx->fname);
  fctx->nsname = dns_fixedname_initname(&fctx->nsfname);
  fctx->domain = dns_fixedname_initname(&fctx->dfname);
  fctx->qminname = dns_fixedname_initname(&fctx->qminfname);
  fctx->qmindcname = dns_fixedname_initname(&fctx->qmindcfname);
  fctx->fwdname = dns_fixedname_initname(&fctx->fwdfname);

  dns_name_copy(name, fctx->name);
  dns_name_copy(name, fctx->qminname);

  dns_rdataset_init(&fctx->nameservers);
  dns_rdataset_init(&fctx->qminrrset);
  dns_rdataset_init(&fctx->qminsigrrset);
  dns_rdataset_init(&fctx->nsrrset);

  fctx->start = isc_time_now();
  fctx->now = (isc_stdtime_t)fctx->start.seconds;

  if (client != NULL) {
    isc_sockaddr_format(client, fctx->clientstr,
            sizeof(fctx->clientstr));
  } else {
    strlcpy(fctx->clientstr, "<unknown>", sizeof(fctx->clientstr));
  }

  if (domain == NULL) {
    dns_forwarders_t *forwarders = NULL;
    unsigned int labels;
    const dns_name_t *fwdname = name;
    dns_name_t suffix;

    /*
     * DS records are found in the parent server. Strip one
     * leading label from the name (to be used in finding
     * the forwarder).
     */
    if (dns_rdatatype_atparent(fctx->type) &&
        dns_name_countlabels(name) > 1)
    {
      dns_name_init(&suffix);
      labels = dns_name_countlabels(name);
      dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
      fwdname = &suffix;
    }

    /* Find the forwarder for this name. */
    result = dns_fwdtable_find(fctx->res->view->fwdtable, fwdname,
             &forwarders);
    if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
      fctx->fwdpolicy = forwarders->fwdpolicy;
      dns_name_copy(&forwarders->name, fctx->fwdname);
      dns_forwarders_detach(&forwarders);
    }

    if (fctx->fwdpolicy == dns_fwdpolicy_only) {
      /*
       * We're in forward-only mode.  Set the query
       * domain.
       */
      dns_name_copy(fctx->fwdname, fctx->domain);
      dns_name_copy(fctx->fwdname, fctx->qmindcname);
      /*
       * Disable query minimization
       */
      options &= ~DNS_FETCHOPT_QMINIMIZE;
    } else {
      dns_fixedname_t dcfixed;
      dns_name_t *dcname = dns_fixedname_initname(&dcfixed);

      /*
       * The caller didn't supply a query domain and
       * nameservers, and we're not in forward-only
       * mode, so find the best nameservers to use.
       */
      if (dns_rdatatype_atparent(fctx->type)) {
        findoptions |= DNS_DBFIND_NOEXACT;
      }
      result = dns_view_findzonecut(
        res->view, name, fctx->fwdname, dcname,
        fctx->now, findoptions, true, true,
        &fctx->nameservers, NULL);
      if (result != ISC_R_SUCCESS) {
        goto cleanup_nameservers;
      }

      dns_name_copy(fctx->fwdname, fctx->domain);
      dns_name_copy(dcname, fctx->qmindcname);
      fctx->ns_ttl = fctx->nameservers.ttl;
      fctx->ns_ttl_ok = true;
    }
  } else {
    dns_name_copy(domain, fctx->domain);
    dns_name_copy(domain, fctx->qmindcname);
    dns_rdataset_clone(nameservers, &fctx->nameservers);
    fctx->ns_ttl = fctx->nameservers.ttl;
    fctx->ns_ttl_ok = true;
  }

  /*
   * Exempt prefetch queries from the fetches-per-zone quota check
   * also exempt QMIN fetches as the calling fetch has already
   * successfully called fcount_incr for this zone.
   */
  if ((fctx->options & DNS_FETCHOPT_PREFETCH) == 0 &&
      (fctx->options & DNS_FETCHOPT_QMINFETCH) == 0)
  {
    /*
     * Are there too many simultaneous queries for this domain?
     */
    result = fcount_incr(fctx, false);
    if (result != ISC_R_SUCCESS) {
      result = fctx->res->quotaresp[dns_quotatype_zone];
      inc_stats(res, dns_resstatscounter_zonequota);
      goto cleanup_nameservers;
    }
  }

  log_ns_ttl(fctx, "fctx_create");

  if (!dns_name_issubdomain(fctx->name, fctx->domain)) {
    dns_name_format(fctx->domain, buf, sizeof(buf));
    UNEXPECTED_ERROR("'%s' is not subdomain of '%s'", fctx->info,
         buf);
    result = ISC_R_UNEXPECTED;
    goto cleanup_fcount;
  }

  dns_message_create(fctx->mctx, fctx->res->namepools[fctx->tid],
         fctx->res->rdspools[fctx->tid],
         DNS_MESSAGE_INTENTRENDER, &fctx->qmessage);

  /*
   * Compute an expiration time for the entire fetch.
   */
  isc_interval_set(&interval, res->query_timeout / 1000,
       res->query_timeout % 1000 * 1000000);
  iresult = isc_time_nowplusinterval(&fctx->expires, &interval);
  if (iresult != ISC_R_SUCCESS) {
    UNEXPECTED_ERROR("isc_time_nowplusinterval: %s",
         isc_result_totext(iresult));
    result = ISC_R_UNEXPECTED;
    goto cleanup_qmessage;
  }

  /*
   * Default retry interval initialization.  We set the interval
   * now mostly so it won't be uninitialized.  It will be set to
   * the correct value before a query is issued.
   */
  isc_interval_set(&fctx->interval, 2, 0);

  /*
   * Attach to the view's cache and adb.
   */
  dns_db_attach(res->view->cachedb, &fctx->cache);
  dns_view_getadb(res->view, &fctx->adb);

  ISC_LIST_INIT(fctx->resps);
  fctx->magic = FCTX_MAGIC;

  /*
   * If qname minimization is enabled we need to trim
   * the name in fctx to proper length.
   */
  if ((options & DNS_FETCHOPT_QMINIMIZE) != 0) {
    fctx->ip6arpaskip = (options & DNS_FETCHOPT_QMIN_SKIP_IP6A) !=
              0 &&
            dns_name_issubdomain(fctx->name, &ip6_arpa);
    fctx_minimize_qname(fctx);
  }

  inc_stats(res, dns_resstatscounter_nfetch);

  isc_timer_create(fctx->loop, fctx_expired, fctx, &fctx->timer);

  *fctxp = fctx;

  return ISC_R_SUCCESS;

cleanup_qmessage:
  dns_message_detach(&fctx->qmessage);

cleanup_fcount:
  fcount_decr(fctx);

cleanup_nameservers:
  if (dns_rdataset_isassociated(&fctx->nameservers)) {
    dns_rdataset_disassociate(&fctx->nameservers);
  }
  isc_mem_free(fctx->mctx, fctx->info);
  if (fctx->nfails != NULL) {
    isc_counter_detach(&fctx->nfails);
  }
  if (fctx->nvalidations != NULL) {
    isc_counter_detach(&fctx->nvalidations);
  }
  isc_counter_detach(&fctx->qc);
  if (fctx->gqc != NULL) {
    isc_counter_detach(&fctx->gqc);
  }

  dns_resolver_detach(&fctx->res);
  isc_mem_putanddetach(&fctx->mctx, fctx, sizeof(*fctx));

  return result;
}

/*
 * Handle Responses
 */
static bool
is_lame(fetchctx_t *fctx, dns_message_t *message) {
  if (message->rcode != dns_rcode_noerror &&
      message->rcode != dns_rcode_yxdomain &&
      message->rcode != dns_rcode_nxdomain)
  {
    return false;
  }

  if (message->counts[DNS_SECTION_ANSWER] != 0) {
    return false;
  }

  if (message->counts[DNS_SECTION_AUTHORITY] == 0) {
    return false;
  }

  MSG_SECTION_FOREACH(message, DNS_SECTION_AUTHORITY, name) {
    ISC_LIST_FOREACH(name->list, rdataset, link) {
      dns_namereln_t namereln;
      int order;
      unsigned int labels;
      if (rdataset->type != dns_rdatatype_ns) {
        continue;
      }
      namereln = dns_name_fullcompare(name, fctx->domain,
              &order, &labels);
      if (namereln == dns_namereln_equal &&
          (message->flags & DNS_MESSAGEFLAG_AA) != 0)
      {
        return false;
      }
      if (namereln == dns_namereln_subdomain) {
        return false;
      }
      return true;
    }
  }

  return false;
}

static void
log_lame(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo) {
  char namebuf[DNS_NAME_FORMATSIZE];
  char domainbuf[DNS_NAME_FORMATSIZE];
  char addrbuf[ISC_SOCKADDR_FORMATSIZE];

  dns_name_format(fctx->name, namebuf, sizeof(namebuf));
  dns_name_format(fctx->domain, domainbuf, sizeof(domainbuf));
  isc_sockaddr_format(&addrinfo->sockaddr, addrbuf, sizeof(addrbuf));
  isc_log_write(DNS_LOGCATEGORY_LAME_SERVERS, DNS_LOGMODULE_RESOLVER,
          ISC_LOG_INFO, "lame server resolving '%s' (in '%s'?): %s",
          namebuf, domainbuf, addrbuf);
}

static void
log_formerr(fetchctx_t *fctx, const char *format, ...) {
  char nsbuf[ISC_SOCKADDR_FORMATSIZE];
  char msgbuf[2048];
  va_list args;

  va_start(args, format);
  vsnprintf(msgbuf, sizeof(msgbuf), format, args);
  va_end(args);

  isc_sockaddr_format(&fctx->addrinfo->sockaddr, nsbuf, sizeof(nsbuf));

  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
          ISC_LOG_NOTICE,
          "DNS format error from %s resolving %s for %s: %s", nsbuf,
          fctx->info, fctx->clientstr, msgbuf);
}

static isc_result_t
same_question(fetchctx_t *fctx, dns_message_t *message) {
  dns_name_t *name = NULL;
  dns_rdataset_t *rdataset = NULL;

  /*
   * Caller must be holding the fctx lock.
   */

  /*
   * XXXRTH  Currently we support only one question.
   */
  if (message->counts[DNS_SECTION_QUESTION] == 0) {
    if ((message->flags & DNS_MESSAGEFLAG_TC) != 0) {
      /*
       * If TC=1 and the question section is empty, we
       * accept the reply message as a truncated
       * answer, to be retried over TCP.
       *
       * It is really a FORMERR condition, but this is
       * a workaround to accept replies from some
       * implementations.
       *
       * Because the question section matching is not
       * performed, the worst that could happen is
       * that an attacker who gets past the ID and
       * source port checks can force the use of
       * TCP. This is considered an acceptable risk.
       */
      log_formerr(fctx, "empty question section, "
            "accepting it anyway as TC=1");
      return ISC_R_SUCCESS;
    } else {
      log_formerr(fctx, "empty question section");
      return DNS_R_FORMERR;
    }
  } else if (message->counts[DNS_SECTION_QUESTION] > 1) {
    log_formerr(fctx, "too many questions");
    return DNS_R_FORMERR;
  }

  if (ISC_LIST_EMPTY(message->sections[DNS_SECTION_QUESTION])) {
    return ISC_R_NOMORE;
  }
  name = ISC_LIST_HEAD(message->sections[DNS_SECTION_QUESTION]);
  rdataset = ISC_LIST_HEAD(name->list);
  INSIST(rdataset != NULL);
  INSIST(ISC_LIST_NEXT(rdataset, link) == NULL);

  if (fctx->type != rdataset->type ||
      fctx->res->rdclass != rdataset->rdclass ||
      !dns_name_equal(fctx->name, name))
  {
    char namebuf[DNS_NAME_FORMATSIZE];
    char classbuf[DNS_RDATACLASS_FORMATSIZE];
    char typebuf[DNS_RDATATYPE_FORMATSIZE];

    dns_name_format(name, namebuf, sizeof(namebuf));
    dns_rdataclass_format(rdataset->rdclass, classbuf,
              sizeof(classbuf));
    dns_rdatatype_format(rdataset->type, typebuf, sizeof(typebuf));
    log_formerr(fctx, "question section mismatch: got %s/%s/%s",
          namebuf, classbuf, typebuf);
    return DNS_R_FORMERR;
  }

  return ISC_R_SUCCESS;
}

static void
clone_results(fetchctx_t *fctx) {
  dns_fetchresponse_t *hresp = NULL;

  REQUIRE(!ISC_LIST_EMPTY(fctx->resps));

  /*
   * Set up any other resps to have the same data as the first.
   * Caller must be holding the appropriate lock.
   */

  FCTXTRACE("clone_results");

  ISC_LIST_FOREACH(fctx->resps, resp, link) {
    /* This is the head resp; keep a pointer and move on */
    if (hresp == NULL) {
      hresp = ISC_LIST_HEAD(fctx->resps);
      FCTXTRACEN("clone_results", hresp->foundname,
           hresp->result);
      continue;
    }

    resp->result = hresp->result;
    dns_name_copy(hresp->foundname, resp->foundname);
    dns_db_attach(hresp->db, &resp->db);
    dns_db_attachnode(hresp->node, &resp->node);

    INSIST(hresp->rdataset != NULL && resp->rdataset != NULL);
    if (dns_rdataset_isassociated(hresp->rdataset)) {
      dns_rdataset_clone(hresp->rdataset, resp->rdataset);
    }

    INSIST(hresp->sigrdataset != NULL || resp->sigrdataset == NULL);
    if (resp->sigrdataset != NULL && hresp->sigrdataset != NULL &&
        dns_rdataset_isassociated(hresp->sigrdataset))
    {
      dns_rdataset_clone(hresp->sigrdataset,
             resp->sigrdataset);
    }
  }

  fctx->cloned = true;
}

#define CACHE(r)      (((r)->attributes.cache))
#define ANSWER(r)     (((r)->attributes.answer))
#define ANSWERSIG(r)  (((r)->attributes.answersig))
#define EXTERNAL(r)   (((r)->attributes.external))
#define CHAINING(r)   (((r)->attributes.chaining))
#define CHASE(r)      (((r)->attributes.chase))
#define CHECKNAMES(r) (((r)->attributes.checknames))

/*
 * Cancel validators associated with '*fctx' if it is ready to be
 * destroyed (i.e., no queries waiting for it and no pending ADB finds).
 * Caller must hold fctx bucket lock.
 *
 * Requires:
 *      '*fctx' is shutting down.
 */
static void
maybe_cancel_validators(fetchctx_t *fctx) {
  if (atomic_load_acquire(&fctx->pending) != 0 ||
      atomic_load_acquire(&fctx->nqueries) != 0)
  {
    return;
  }

  REQUIRE(SHUTTINGDOWN(fctx));
  ISC_LIST_FOREACH(fctx->validators, validator, link) {
    dns_validator_cancel(validator);
  }
}

/*
 * typemap with just RRSIG(46) and NSEC(47) bits set.
 *
 * Bitmap calculation from dns_nsec_setbit:
 *
 *          46  47
 *  shift = 7 - (type % 8);   0 1
 *  mask = 1 << shift;    0x02  0x01
 *  array[type / 8] |= mask;
 *
 * Window (0), bitmap length (6), and bitmap.
 */
static const unsigned char minimal_typemap[] = { 0, 6, 0, 0, 0, 0, 0, 0x03 };

static bool
is_minimal_nsec(dns_rdataset_t *nsecset) {
  dns_rdataset_t rdataset = DNS_RDATASET_INIT;

  dns_rdataset_clone(nsecset, &rdataset);

  DNS_RDATASET_FOREACH(&rdataset) {
    isc_result_t result;
    dns_rdata_t rdata = DNS_RDATA_INIT;
    dns_rdata_nsec_t nsec;

    dns_rdataset_current(&rdataset, &rdata);
    result = dns_rdata_tostruct(&rdata, &nsec, NULL);
    RUNTIME_CHECK(result == ISC_R_SUCCESS);

    if (nsec.len == sizeof(minimal_typemap) &&
        memcmp(nsec.typebits, minimal_typemap, nsec.len) == 0)
    {
      dns_rdataset_disassociate(&rdataset);
      return true;
    }
  }
  dns_rdataset_disassociate(&rdataset);
  return false;
}

/*
 * If there is a SOA record in the type map then there must be a DNSKEY.
 */
static bool
check_soa_and_dnskey(dns_rdataset_t *nsecset) {
  dns_rdataset_t rdataset = DNS_RDATASET_INIT;

  dns_rdataset_clone(nsecset, &rdataset);

  DNS_RDATASET_FOREACH(&rdataset) {
    dns_rdata_t rdata = DNS_RDATA_INIT;
    dns_rdataset_current(&rdataset, &rdata);
    if (dns_nsec_typepresent(&rdata, dns_rdatatype_soa) &&
        (!dns_nsec_typepresent(&rdata, dns_rdatatype_dnskey) ||
         !dns_nsec_typepresent(&rdata, dns_rdatatype_ns)))
    {
      dns_rdataset_disassociate(&rdataset);
      return false;
    }
  }
  dns_rdataset_disassociate(&rdataset);
  return true;
}

/*
 * Look for NSEC next name that starts with the label '\000'.
 */
static bool
has_000_label(dns_rdataset_t *nsecset) {
  dns_rdataset_t rdataset = DNS_RDATASET_INIT;

  dns_rdataset_clone(nsecset, &rdataset);

  DNS_RDATASET_FOREACH(&rdataset) {
    dns_rdata_t rdata = DNS_RDATA_INIT;
    dns_rdataset_current(&rdataset, &rdata);
    if (rdata.length > 1 && rdata.data[0] == 1 &&
        rdata.data[1] == 0)
    {
      dns_rdataset_disassociate(&rdataset);
      return true;
    }
  }
  dns_rdataset_disassociate(&rdataset);
  return false;
}

static isc_result_t
fctx_setresult(fetchctx_t *fctx, dns_rdataset_t *rdataset) {
  isc_result_t eresult = ISC_R_SUCCESS;

  if (NEGATIVE(rdataset)) {
    eresult = NXDOMAIN(rdataset) ? DNS_R_NCACHENXDOMAIN
               : DNS_R_NCACHENXRRSET;
  } else if (eresult == ISC_R_SUCCESS && rdataset->type != fctx->type) {
    switch (rdataset->type) {
    case dns_rdatatype_cname:
      eresult = DNS_R_CNAME;
      break;
    case dns_rdatatype_dname:
      eresult = DNS_R_DNAME;
      break;
    default:
      break;
    }
  }

  return eresult;
}

static inline dns_trust_t
gettrust(dns_rdataset_t *rdataset) {
  if (rdataset == NULL || !dns_rdataset_isassociated(rdataset)) {
    return dns_trust_none;
  }

  return rdataset->trust;
}

static inline dns_rdataset_t *
getrrsig(dns_name_t *name, dns_rdatatype_t type) {
  for (dns_rdataset_t *sig = ISC_LIST_HEAD(name->list); sig != NULL;
       sig = ISC_LIST_NEXT(sig, link))
  {
    if (dns_rdataset_issigtype(sig, type)) {
      return sig;
    }
  }

  return NULL;
}

static isc_result_t
cache_rrset(fetchctx_t *fctx, isc_stdtime_t now, dns_name_t *name,
      dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset,
      dns_dbnode_t **nodep, dns_rdataset_t *added,
      dns_rdataset_t *addedsig, bool need_validation) {
  isc_result_t result = ISC_R_SUCCESS;
  unsigned int options = 0;
  dns_dbnode_t *node = NULL;

  if (rdataset == NULL) {
    return ISC_R_NOTFOUND;
  }

  /*
   * If the trust level is glue, we must be caching a referral.
   * New referral data always takes precedence over the existing
   * cache contents. We also force a cache update if the fctx
   * has the _NOCACHED option.
   */
  if ((gettrust(rdataset) == dns_trust_glue &&
       dns_rdataset_matchestype(rdataset, dns_rdatatype_ns)) ||
      (fctx->options & DNS_FETCHOPT_NOCACHED) != 0)
  {
    options = DNS_DBADD_FORCE;
  } else if ((fctx->options & DNS_FETCHOPT_PREFETCH) != 0) {
    options = DNS_DBADD_PREFETCH;
  }

  /*
   * If the node pointer points to a node, attach to it.
   *
   * If it points to NULL, find or create the node and pass
   * it back to the caller.
   *
   * If there's no node pointer at all, find the node, but
   * detach it before returning.
   */
  if (nodep != NULL && *nodep != NULL) {
    dns_db_attachnode(*nodep, &node);
  } else {
    result = dns_db_findnode(fctx->cache, name, true, &node);
  }

  if (result == ISC_R_SUCCESS) {
    result = dns_db_addrdataset(fctx->cache, node, NULL, now,
              rdataset, options, added);
  }

  if (result == DNS_R_UNCHANGED) {
    /*
     * The cache wasn't updated because something was
     * already there. If the data was the same as what
     * we were trying to add, then sigrdataset might
     * still be useful.
     */
    if (!need_validation && added != NULL &&
        !dns_rdataset_equals(rdataset, added))
    {
      /* Skip adding the sigrdataset */
    } else {
      /* Carry on caching the sigrdataset */
      result = ISC_R_SUCCESS;
    }
  }

  if (result == ISC_R_SUCCESS && sigrdataset != NULL) {
    result = dns_db_addrdataset(fctx->cache, node, NULL, now,
              sigrdataset, options, addedsig);
    if (result != ISC_R_SUCCESS && result != DNS_R_UNCHANGED) {
      dns__rdataset_disassociate(added);
    }
  }

  if (result == DNS_R_UNCHANGED) {
    result = ISC_R_SUCCESS;
  }

  /*
   * If we're passing a node that we looked up back to the
   * caller, then we don't detach it.
   */
  if (nodep != NULL && *nodep == NULL) {
    *nodep = node;
  } else if (node != NULL) {
    dns_db_detachnode(&node);
  }

  return result;
}

static void
delete_rrset(fetchctx_t *fctx, dns_name_t *name, dns_rdatatype_t type) {
  isc_result_t result;
  dns_dbnode_t *node = NULL;

  result = dns_db_findnode(fctx->cache, name, false, &node);
  if (result != ISC_R_SUCCESS) {
    return;
  }

  dns_db_deleterdataset(fctx->cache, node, NULL, type, 0);
  dns_db_deleterdataset(fctx->cache, node, NULL, dns_rdatatype_rrsig,
            type);
  dns_db_detachnode(&node);
}

static void
fctx_cacheauthority(fetchctx_t *fctx, dns_message_t *message,
        isc_stdtime_t now) {
  isc_result_t result;

  /*
   * Cache any SOA/NS/NSEC records that happened to be validated.
   */
  MSG_SECTION_FOREACH(message, DNS_SECTION_AUTHORITY, name) {
    ISC_LIST_FOREACH(name->list, rdataset, link) {
      dns_rdataset_t *sigrdataset = NULL;

      if ((rdataset->type != dns_rdatatype_ns &&
           rdataset->type != dns_rdatatype_soa &&
           rdataset->type != dns_rdatatype_nsec) ||
          gettrust(rdataset) != dns_trust_secure)
      {
        continue;
      }

      sigrdataset = getrrsig(name, rdataset->type);
      if (gettrust(sigrdataset) != dns_trust_secure) {
        continue;
      }

      /*
       * Don't cache NSEC if missing NSEC or RRSIG types.
       */
      if (rdataset->type == dns_rdatatype_nsec &&
          !dns_nsec_requiredtypespresent(rdataset))
      {
        continue;
      }

      /*
       * Don't cache "white lies" but do cache
       * "black lies".
       */
      if (rdataset->type == dns_rdatatype_nsec &&
          !dns_name_equal(fctx->name, name) &&
          is_minimal_nsec(rdataset))
      {
        continue;
      }

      /*
       * Check SOA and DNSKEY consistency.
       */
      if (rdataset->type == dns_rdatatype_nsec &&
          !check_soa_and_dnskey(rdataset))
      {
        continue;
      }

      /*
       * Look for \000 label in next name.
       */
      if (rdataset->type == dns_rdatatype_nsec &&
          has_000_label(rdataset))
      {
        continue;
      }

      result = cache_rrset(fctx, now, name, rdataset,
               sigrdataset, NULL, NULL, NULL,
               false);
      if (result != ISC_R_SUCCESS) {
        continue;
      }
    }
  }
}

/*
 * The validator has finished.
 */
static void
validated(void *arg) {
  isc_result_t result = ISC_R_SUCCESS;
  dns_validator_t *val = (dns_validator_t *)arg;
  dns_valarg_t *valarg = val->arg;
  dns_validator_t *nextval = NULL;
  dns_adbaddrinfo_t *addrinfo = NULL;
  dns_dbnode_t *node = NULL;
  dns_fetchresponse_t *resp = NULL;
  dns_rdataset_t *ardataset = NULL, *asigrdataset = NULL;
  dns_message_t *message = NULL;
  fetchctx_t *fctx = NULL;
  dns_resolver_t *res = NULL;
  isc_stdtime_t now;
  bool done = false;
  bool negative = (val->rdataset == NULL);
  bool chaining = (val->result == ISC_R_SUCCESS) && !negative &&
      CHAINING(val->rdataset);

  fctx = valarg->fctx;
  valarg->fctx = NULL;

  REQUIRE(VALID_FCTX(fctx));
  REQUIRE(fctx->tid == isc_tid());

  res = fctx->res;
  addrinfo = valarg->addrinfo;

  message = val->message;
  fctx->vresult = val->result;

  FCTXTRACE("received validation completion event");

  isc_mem_put(fctx->mctx, valarg, sizeof(*valarg));

  LOCK(&fctx->lock);

  ISC_LIST_UNLINK(fctx->validators, val, link);

  if (SHUTTINGDOWN(fctx)) {
    goto cleanup;
  }

  now = isc_stdtime_now();

  /* Validation failed. */
  if (val->result != ISC_R_SUCCESS) {
    FCTXTRACE("validation failed");
    inc_stats(res, dns_resstatscounter_valfail);
    fctx->valfail++;
    result = fctx->vresult = val->result;
    if (result != DNS_R_BROKENCHAIN) {
      delete_rrset(fctx, val->name, val->type);
    } else if (!negative) {
      /*
       * Cache the data as pending for later validation.
       */
      cache_rrset(fctx, now, val->name, val->rdataset,
            val->sigrdataset, NULL, NULL, NULL, false);
    }

    add_bad(fctx, message, addrinfo, result, badns_validation);

    /* Start the next validator if there is one. */
    nextval = ISC_LIST_HEAD(fctx->validators);
    if (nextval != NULL) {
      goto cleanup;
    }

    /* A broken trust chain isn't recoverable. */
    if (result == DNS_R_BROKENCHAIN) {
      done = true;
      goto cleanup;
    }

    /*
     * Some other error, we can try again. We have to
     * unlock the fctx before calling fctx_try().
     */
    UNLOCK(&fctx->lock);
    fctx_try(fctx, true);
    goto cleanup_unlocked;
  }

  /*
   * For non-ANY responses, and all negative and chaining responses,
   * we pass an rdataset back to the caller. Otherwise the caller
   * iterates the node.
   */
  resp = ISC_LIST_HEAD(fctx->resps);
  if (resp != NULL &&
      (negative || chaining || !dns_rdatatype_ismulti(fctx->type)))
  {
    ardataset = resp->rdataset;
    asigrdataset = resp->sigrdataset;
  }

  /*
   * Validator proved nonexistence.
   */
  if (negative) {
    FCTXTRACE("nonexistence validation OK");
    inc_stats(res, dns_resstatscounter_valnegsuccess);

    result = negcache(message, fctx, val->name, now, val->optout,
          val->secure, ardataset, &node);
    if (result != ISC_R_SUCCESS) {
      done = true;
      goto cleanup;
    }
    goto answer_response;
  }

  /*
   * Validator proved a positive answer.
   */
  FCTXTRACE("validation OK");
  inc_stats(res, dns_resstatscounter_valsuccess);

  if (val->proofs[DNS_VALIDATOR_NOQNAMEPROOF] != NULL) {
    result = dns_rdataset_addnoqname(
      val->rdataset, val->proofs[DNS_VALIDATOR_NOQNAMEPROOF]);
    RUNTIME_CHECK(result == ISC_R_SUCCESS);
    INSIST(val->sigrdataset != NULL);
    val->sigrdataset->ttl = val->rdataset->ttl;
    if (val->proofs[DNS_VALIDATOR_CLOSESTENCLOSER] != NULL) {
      result = dns_rdataset_addclosest(
        val->rdataset,
        val->proofs[DNS_VALIDATOR_CLOSESTENCLOSER]);
      RUNTIME_CHECK(result == ISC_R_SUCCESS);
    }
  } else if (gettrust(val->rdataset) == dns_trust_answer) {
    findnoqname(fctx, message, val->name, val->rdataset,
          val->sigrdataset);
  }

  /*
   * The data was already cached as pending. Re-cache it as secure.
   */
  result = cache_rrset(fctx, now, val->name, val->rdataset,
           val->sigrdataset, &node, ardataset, asigrdataset,
           true);
  if (result != ISC_R_SUCCESS) {
    done = true;
    goto cleanup;
  }

  /*
   * If this was an ANY query, we might have more rdatasets
   * needing to be validated before we can respond.
   */
  if (!ISC_LIST_EMPTY(fctx->validators)) {
    INSIST(!negative);
    INSIST(dns_rdatatype_ismulti(fctx->type));

    nextval = ISC_LIST_HEAD(fctx->validators);
    goto cleanup;
  }

answer_response:
  fctx_cacheauthority(fctx, message, now);

  /*
   * Cache the wild card entry.
   */
  if (val->proofs[DNS_VALIDATOR_NOQNAMEPROOF] != NULL &&
      gettrust(val->rdataset) == dns_trust_secure &&
      gettrust(val->sigrdataset) == dns_trust_secure)
  {
    cache_rrset(fctx, now, dns_fixedname_name(&val->wild),
          val->rdataset, val->sigrdataset, NULL, NULL, NULL,
          true);
  }

  /*
   * We're responding with an answer, positive or negative,
   * not an error.
   */
  if (resp != NULL) {
    FCTX_ATTR_SET(fctx, FCTX_ATTR_HAVEANSWER);

    resp->result = fctx_setresult(fctx, resp->rdataset);
    dns_name_copy(val->name, resp->foundname);
    dns_db_attach(fctx->cache, &resp->db);
    dns_db_transfernode(fctx->cache, &node, &resp->node);
    clone_results(fctx);
  }

  done = true;

cleanup:
  UNLOCK(&fctx->lock);
cleanup_unlocked:

  if (node != NULL) {
    dns_db_detachnode(&node);
  }

  if (nextval != NULL) {
    dns_validator_send(nextval);
  }

  if (done) {
    fctx_done_unref(fctx, result);
  }

  /*
   * val->name points to name on a message on one of the
   * queries on the fetch context so the name has to be
   * released first with a dns_validator_shutdown() call.
   */
  dns_validator_shutdown(val);
  dns_validator_detach(&val);
  fetchctx_detach(&fctx);
  INSIST(node == NULL);
}

static void
fctx_log(void *arg, int level, const char *fmt, ...) {
  char msgbuf[2048];
  va_list args;
  fetchctx_t *fctx = arg;

  va_start(args, fmt);
  vsnprintf(msgbuf, sizeof(msgbuf), fmt, args);
  va_end(args);

  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER, level,
          "fctx %p(%s): %s", fctx, fctx->info, msgbuf);
}

static void
findnoqname(fetchctx_t *fctx, dns_message_t *message, dns_name_t *name,
      dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset) {
  isc_result_t result;
  dns_rdata_rrsig_t rrsig;
  unsigned int labels;
  dns_name_t *zonename = NULL;
  dns_fixedname_t fzonename;
  dns_name_t *closest = NULL;
  dns_fixedname_t fclosest;
  dns_name_t *nearest = NULL;
  dns_fixedname_t fnearest;
  dns_rdatatype_t found = dns_rdatatype_none;
  dns_name_t *noqname = NULL;
  dns_rdatatype_t type = rdataset->type;

  FCTXTRACE("findnoqname");

  if (dns_rdatatype_issig(rdataset->type) || sigrdataset == NULL) {
    return;
  }

  labels = dns_name_countlabels(name);

  result = ISC_R_NOTFOUND;
  DNS_RDATASET_FOREACH(sigrdataset) {
    dns_rdata_t rdata = DNS_RDATA_INIT;
    dns_rdataset_current(sigrdataset, &rdata);
    result = dns_rdata_tostruct(&rdata, &rrsig, NULL);
    RUNTIME_CHECK(result == ISC_R_SUCCESS);
    /* Wildcard has rrsig.labels < labels - 1. */
    if (rrsig.labels + 1U >= labels) {
      continue;
    }
    result = ISC_R_SUCCESS;
    break;
  }

  if (result != ISC_R_SUCCESS) {
    return;
  }

  zonename = dns_fixedname_initname(&fzonename);
  closest = dns_fixedname_initname(&fclosest);
  nearest = dns_fixedname_initname(&fnearest);

#define NXND(x) ((x) == ISC_R_SUCCESS)

  MSG_SECTION_FOREACH(message, DNS_SECTION_AUTHORITY, nsec) {
    ISC_LIST_FOREACH(nsec->list, nrdataset, link) {
      bool data = false, exists = false;
      bool optout = false, unknown = false;
      bool setclosest = false;
      bool setnearest = false;

      if (!dns_rdatatype_isnsec(nrdataset->type)) {
        continue;
      }

      if (nrdataset->type == dns_rdatatype_nsec &&
          NXND(dns_nsec_noexistnodata(
            type, name, nsec, nrdataset, &exists, &data,
            NULL, fctx_log, fctx)))
      {
        if (!exists) {
          noqname = nsec;
          found = dns_rdatatype_nsec;
        }
      }

      if (nrdataset->type == dns_rdatatype_nsec3 &&
          NXND(dns_nsec3_noexistnodata(
            type, name, nsec, nrdataset, zonename,
            &exists, &data, &optout, &unknown,
            &setclosest, &setnearest, closest, nearest,
            fctx_log, fctx)))
      {
        if (!exists && setnearest) {
          noqname = nsec;
          found = dns_rdatatype_nsec3;
        }
      }
    }
  }

  if (noqname != NULL) {
    sigrdataset = getrrsig(noqname, found);
    if (sigrdataset == NULL) {
      noqname = NULL;
    }
  }

  if (result == ISC_R_SUCCESS && noqname != NULL) {
    (void)dns_rdataset_addnoqname(rdataset, noqname);
  }

  return;
}

static isc_result_t
check_cacheable(dns_name_t *name, dns_rdataset_t *rdataset, bool fail) {
  /* This rdataset isn't marked for caching */
  if (!CACHE(rdataset)) {
    return DNS_R_CONTINUE;
  }

  /* See if there are any name errors */
  if (CHECKNAMES(rdataset)) {
    char namebuf[DNS_NAME_FORMATSIZE];
    char typebuf[DNS_RDATATYPE_FORMATSIZE];
    char classbuf[DNS_RDATATYPE_FORMATSIZE];

    dns_name_format(name, namebuf, sizeof(namebuf));
    dns_rdatatype_format(rdataset->type, typebuf, sizeof(typebuf));
    dns_rdataclass_format(rdataset->rdclass, classbuf,
              sizeof(classbuf));
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_NOTICE, "check-names %s %s/%s/%s",
            fail ? "failure" : "warning", namebuf, typebuf,
            classbuf);
    if (fail) {
      if (ANSWER(rdataset)) {
        return DNS_R_BADNAME;
      }

      return DNS_R_CONTINUE;
    }
  }

  /*
   * We do not attempt to cache or validate glue or out-of-bailiwick
   * data - even if there might be some performance benefit to doing
   * so - because it makes it simpler and safer.
   */
  if (EXTERNAL(rdataset)) {
    return DNS_R_CONTINUE;
  }

  return ISC_R_SUCCESS;
}

static void
fixttls(dns_view_t *view, dns_rdataset_t *rdataset,
  dns_rdataset_t *sigrdataset) {
  /*
   * Enforce the configured maximum and minimum cache TTL.
   */
  if (rdataset->ttl > view->maxcachettl) {
    rdataset->ttl = view->maxcachettl;
  }

  if (rdataset->ttl < view->mincachettl) {
    rdataset->ttl = view->mincachettl;
  }

  /*
   * Mark the rdataset as being prefetch eligible.
   */
  if (rdataset->ttl >= view->prefetch_eligible) {
    rdataset->attributes.prefetch = true;
  }

  /* Normalize the rdataset and sigrdataset TTLs */
  if (sigrdataset != NULL) {
    rdataset->ttl = ISC_MIN(rdataset->ttl, sigrdataset->ttl);
    sigrdataset->ttl = rdataset->ttl;
  }
}

static isc_result_t
rctx_cache_secure(respctx_t *rctx, dns_message_t *message, dns_name_t *name,
      dns_dbnode_t *node, dns_rdataset_t *rdataset,
      dns_rdataset_t *sigrdataset, bool need_validation) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;
  dns_rdataset_t *ardataset = NULL, *asigset = NULL;
  dns_fetchresponse_t *resp = ISC_LIST_HEAD(fctx->resps);

  /*
   * RRSIGs are validated as part of validating the type they cover.
   */
  if (dns_rdatatype_issig(rdataset->type)) {
    return ISC_R_SUCCESS;
  }

  /*
   * Ignore unrelated non-answer rdatasets that are missing
   * signatures.
   */
  if (sigrdataset == NULL && need_validation && !ANSWER(rdataset)) {
    return ISC_R_SUCCESS;
  }

  /*
   * Mark this rdataset/sigrdataset pair as "pending".
   */
  if (rdataset->trust == dns_trust_additional) {
    rdataset->trust = dns_trust_pending_additional;
  } else {
    rdataset->trust = dns_trust_pending_answer;
  }

  if (sigrdataset != NULL) {
    sigrdataset->trust = rdataset->trust;
  }

  if (ANSWER(rdataset) && need_validation) {
    if (!dns_rdatatype_ismulti(fctx->type)) {
      /*
       * This is The Answer.  We will validate it,
       * but first we finish caching the rest of the
       * response; it may contain useful keys.
       */
      INSIST(rctx->vrdataset == NULL &&
             rctx->vsigrdataset == NULL);
      rctx->vrdataset = rdataset;
      rctx->vsigrdataset = sigrdataset;
    } else {
      /*
       * This is one of (potentially) multiple answers to
       * an ANY query.  To keep things simple, we just
       * start the validator right away rather than
       * caching first and having to remember which
       * rdatasets needed validation.
       */
      valcreate(fctx, message, query->addrinfo, name,
          rdataset->type, rdataset, sigrdataset);
    }
  } else {
    if (ANSWER(rdataset)) {
      /*
       * We're not validating, but the client might
       * be, so look for the NOQNAME proof.
       */
      findnoqname(fctx, message, name, rdataset, sigrdataset);

      /*
       * If this was not an ANY query - or if it was,
       * but we got a CNAME/DNAME - then we need to
       * set up rdatasets to send back to the caller.
       */
      if (resp != NULL &&
          (!dns_rdatatype_ismulti(fctx->type) ||
           CHAINING(rdataset)))
      {
        ardataset = resp->rdataset;
        asigset = resp->sigrdataset;
      }
    }

    /*
     * In this case we cache the rdataset and sigrdataset
     * (if any) in two steps, so we can do an extra check
     * in-between.
     */

    result = cache_rrset(fctx, rctx->now, name, rdataset,
             sigrdataset, &node, ardataset, asigset,
             need_validation);
    if (result != ISC_R_SUCCESS) {
      return result;
    }
  }

  return ISC_R_SUCCESS;
}

static isc_result_t
rctx_cache_insecure(respctx_t *rctx, dns_message_t *message, dns_name_t *name,
        dns_dbnode_t *node, dns_rdataset_t *rdataset,
        dns_rdataset_t *sigrdataset) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;
  dns_fetchresponse_t *resp = ISC_LIST_HEAD(fctx->resps);
  dns_rdataset_t *added = NULL;

  /*
   * If this was not an ANY query - or if it was, but we got a
   * CNAME/DNAME - then we need to set up an rdataset to send
   * back to the caller.
   */
  if (resp != NULL &&
      (!dns_rdatatype_ismulti(fctx->type) || CHAINING(rdataset)))
  {
    if (ANSWER(rdataset)) {
      added = resp->rdataset;
    } else if (ANSWERSIG(rdataset)) {
      added = resp->sigrdataset;
    }
  }

  /*
   * Look for the NOQNAME proof.
   */
  if (ANSWER(rdataset)) {
    findnoqname(fctx, message, name, rdataset, sigrdataset);
  }

  /*
   * Cache the rdataset.
   */
  result = cache_rrset(fctx, rctx->now, name, rdataset, NULL, &node,
           added, NULL, NULL);

  return result;
}

static isc_result_t
rctx_cachename(respctx_t *rctx, dns_message_t *message, dns_name_t *name) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;
  dns_resolver_t *res = fctx->res;
  dns_rdataset_t *sigrdataset = NULL;
  dns_dbnode_t *node = NULL;

  FCTXTRACE("rctx_cachename");

  /*
   * The appropriate bucket lock must be held.
   */

  /*
   * Is DNSSEC validation required for this name?
   */
  bool secure_domain = issecuredomain(fctx, name, fctx->type, rctx->now,
              NULL);
  bool need_validation = secure_domain &&
             ((fctx->options & DNS_FETCHOPT_NOVALIDATE) == 0);

  /*
   * Find or create the cache node.
   */
  result = dns_db_findnode(fctx->cache, name, true, &node);
  if (result != ISC_R_SUCCESS) {
    return result;
  }

  /*
   * Cache or validate each cacheable rdataset.
   */
  bool fail = ((res->options & DNS_RESOLVER_CHECKNAMESFAIL) != 0);
  ISC_LIST_FOREACH(name->list, rdataset, link) {
    result = check_cacheable(name, rdataset, fail);
    if (result == DNS_R_CONTINUE) {
      result = ISC_R_SUCCESS;
      continue;
    } else if (result != ISC_R_SUCCESS) {
      goto cleanup;
    }

    /* Find the signature for this rdataset */
    sigrdataset = getrrsig(name, rdataset->type);

    /*
     * Make the TTL consistent with the configured
     * maximum and minimum
     */
    fixttls(res->view, rdataset, sigrdataset);

    if (secure_domain && gettrust(rdataset) != dns_trust_glue) {
      /*
       * If this is a secure domain and the rdataset
       * isn't glue, start a validator. The data will
       * be cached when the validator finishes.
       */
      result = rctx_cache_secure(rctx, message, name, node,
               rdataset, sigrdataset,
               need_validation);
    } else {
      /* Insecure domain or glue: cache the data now. */
      result = rctx_cache_insecure(rctx, message, name, node,
                 rdataset, sigrdataset);
    }
    if (result != ISC_R_SUCCESS) {
      goto cleanup;
    }
  }

  /*
   * If there was a delayed validation set up in
   * rctx_cache_secure(), run it now.
   */
  if (rctx->vrdataset != NULL) {
    dns_rdatatype_t vtype = fctx->type;
    if (CHAINING(rctx->vrdataset)) {
      vtype = rctx->vrdataset->type;
      INSIST(dns_rdatatype_isalias(vtype));
    }

    valcreate(fctx, message, query->addrinfo, name, vtype,
        rctx->vrdataset, rctx->vsigrdataset);
    rctx->vrdataset = NULL;
    rctx->vsigrdataset = NULL;
    goto cleanup;
  }

  /*
   * We're not validating and have an answer ready; pass
   * it back to the caller.
   */
  if (!need_validation && name->attributes.answer && !HAVE_ANSWER(fctx)) {
    dns_fetchresponse_t *resp = ISC_LIST_HEAD(fctx->resps);
    if (resp != NULL) {
      isc_result_t eresult = ISC_R_SUCCESS;

      if (dns_rdataset_isassociated(resp->rdataset)) {
        eresult = fctx_setresult(fctx, resp->rdataset);
      }

      resp->result = eresult;
      dns_name_copy(name, resp->foundname);
      dns_db_attach(fctx->cache, &resp->db);
      dns_db_transfernode(fctx->cache, &node, &resp->node);
      clone_results(fctx);

      FCTX_ATTR_SET(fctx, FCTX_ATTR_HAVEANSWER);
    }
  }

cleanup:
  if (node != NULL) {
    dns_db_detachnode(&node);
  }

  return result;
}

static isc_result_t
rctx_cachemessage(respctx_t *rctx) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;
  dns_message_t *message = query->rmessage;

  FCTXTRACE("rctx_cachemessage");

  FCTX_ATTR_CLR(fctx, FCTX_ATTR_WANTCACHE);

  LOCK(&fctx->lock);

  for (dns_section_t section = DNS_SECTION_ANSWER;
       section <= DNS_SECTION_ADDITIONAL; section++)
  {
    MSG_SECTION_FOREACH(message, section, name) {
      if (name->attributes.cache) {
        result = rctx_cachename(rctx, message, name);
        if (result != ISC_R_SUCCESS) {
          goto cleanup;
        }
      }
    }
  }

cleanup:
  UNLOCK(&fctx->lock);
  return result;
}

/*
 * Call dns_ncache_add() and then compute an appropriate eresult.
 */
static isc_result_t
negcache(dns_message_t *message, fetchctx_t *fctx, const dns_name_t *name,
   isc_stdtime_t now, bool optout, bool secure, dns_rdataset_t *added,
   dns_dbnode_t **nodep) {
  isc_result_t result;
  dns_ttl_t minttl = fctx->res->view->minncachettl;
  dns_ttl_t maxttl = fctx->res->view->maxncachettl;
  dns_rdatatype_t covers = fctx->type;
  dns_db_t *cache = fctx->cache;
  dns_dbnode_t *node = NULL;
  dns_rdataset_t rdataset = DNS_RDATASET_INIT;

  /* Set up a placeholder in case added was NULL */
  if (added == NULL) {
    added = &rdataset;
  }

  /*
   * Cache DS NXDOMAIN separately to other types.
   */
  if (message->rcode == dns_rcode_nxdomain &&
      fctx->type != dns_rdatatype_ds)
  {
    covers = dns_rdatatype_any;
  }

  /*
   * If the request was for an SOA record, set the cache time
   * to zero to facilitate locating the containing zone of
   * an arbitrary zone.
   */
  if (fctx->type == dns_rdatatype_soa && covers == dns_rdatatype_any &&
      fctx->res->zero_no_soa_ttl)
  {
    maxttl = 0;
  }

  /*
   * Don't warn about QNAME minimization NXDOMAIN errors
   * if the final result is NXDOMAIN anyway.
   */
  if (!fctx->force_qmin_warning && message->rcode == dns_rcode_nxdomain &&
      (fctx->qmin_warning == DNS_R_NXDOMAIN ||
       fctx->qmin_warning == DNS_R_NCACHENXDOMAIN))
  {
    fctx->qmin_warning = ISC_R_SUCCESS;
  }

  /*
   * Cache the negative entry.
   */
  result = dns_db_findnode(fctx->cache, name, true, &node);
  if (result != ISC_R_SUCCESS) {
    return result;
  }

  result = dns_ncache_add(message, cache, node, covers, now, minttl,
        maxttl, optout, secure, added);

  if (added == &rdataset && dns_rdataset_isassociated(added)) {
    dns_rdataset_disassociate(added);
  }

  *nodep = node;
  return result;
}

/*
 * rctx_ncache():
 * Cache the negatively cacheable parts of the message.  This may
 * also cause work to be queued to the DNSSEC validator.
 */
static void
rctx_ncache(respctx_t *rctx) {
  isc_result_t result = ISC_R_SUCCESS;
  fetchctx_t *fctx = rctx->fctx;
  dns_name_t *name = fctx->name;
  dns_message_t *message = rctx->query->rmessage;
  dns_adbaddrinfo_t *addrinfo = rctx->query->addrinfo;
  dns_dbnode_t *node = NULL;
  dns_fetchresponse_t *resp = NULL;
  dns_rdataset_t *added = NULL;

  FCTXTRACE("rctx_ncache");

  if (!WANTNCACHE(fctx)) {
    goto done;
  }

  FCTX_ATTR_CLR(fctx, FCTX_ATTR_WANTNCACHE);

  /*
   * XXXMPA remove when we follow cnames and adjust the setting
   * of FCTX_ATTR_WANTNCACHE in rctx_answer_none().
   */
  INSIST(message->counts[DNS_SECTION_ANSWER] == 0);

  /*
   * Is DNSSEC validation required for this name?
   */
  bool secure_domain = issecuredomain(fctx, name, fctx->type, rctx->now,
              NULL);
  bool need_validation = secure_domain &&
             ((fctx->options & DNS_FETCHOPT_NOVALIDATE) == 0);

  if (secure_domain) {
    /*
     * Mark all rdatasets as pending. (We do this for
     * any domain under a trust anchor, regardless
     * of whether we're actually validating.)
     */
    MSG_SECTION_FOREACH(message, DNS_SECTION_AUTHORITY, tname) {
      ISC_LIST_FOREACH(tname->list, trdataset, link) {
        trdataset->trust = dns_trust_pending_answer;
      }
    }
  }

  if (need_validation) {
    /*
     * Start the validator for the negative response. It
     * will call validated() on completion; the caching of
     * negative answers will be done then.
     */
    valcreate(fctx, message, addrinfo, name, fctx->type, NULL,
        NULL);
    goto done;
  }

  /*
   * Cache the negative answer, and copy it into the fetch response.
   */
  LOCK(&fctx->lock);
  resp = ISC_LIST_HEAD(fctx->resps);
  if (!HAVE_ANSWER(fctx) && resp != NULL) {
    added = resp->rdataset;
  }

  result = negcache(message, fctx, name, rctx->now, false, false, added,
        &node);
  if (result != ISC_R_SUCCESS || HAVE_ANSWER(fctx)) {
    goto unlock;
  }

  FCTX_ATTR_SET(fctx, FCTX_ATTR_HAVEANSWER);
  if (resp != NULL) {
    resp->result = fctx_setresult(fctx, resp->rdataset);
    dns_name_copy(name, resp->foundname);
    dns_db_attach(fctx->cache, &resp->db);
    dns_db_transfernode(fctx->cache, &node, &resp->node);
    clone_results(fctx);
  }

unlock:
  UNLOCK(&fctx->lock);

  if (node != NULL) {
    dns_db_detachnode(&node);
  }

done:
  if (result != ISC_R_SUCCESS) {
    FCTXTRACE3("rctx_ncache complete", result);
  }
}

static void
mark_related(dns_name_t *name, dns_rdataset_t *rdataset, bool external,
       bool gluing) {
  name->attributes.cache = true;
  if (gluing) {
    rdataset->trust = dns_trust_glue;
    /*
     * Glue with 0 TTL causes problems.  We force the TTL to
     * 1 second to prevent this.
     */
    if (rdataset->ttl == 0) {
      rdataset->ttl = 1;
    }
  } else {
    rdataset->trust = dns_trust_additional;
  }

  /*
   * Avoid infinite loops by only marking new rdatasets.
   */
  if (!CACHE(rdataset)) {
    name->attributes.chase = true;
    rdataset->attributes.chase = true;
  }
  rdataset->attributes.cache = true;
  if (external) {
    rdataset->attributes.external = true;
  }
}

/*
 * Returns true if 'name' is external to the namespace for which
 * the server being queried can answer, either because it's not a
 * subdomain or because it's below a forward declaration or a
 * locally served zone.
 */
static inline bool
name_external(const dns_name_t *name, dns_rdatatype_t type, fetchctx_t *fctx) {
  isc_result_t result;
  dns_forwarders_t *forwarders = NULL;
  dns_name_t *apex = NULL;
  dns_name_t suffix;
  dns_zone_t *zone = NULL;
  unsigned int labels;
  dns_namereln_t rel;

  apex = (ISDUALSTACK(fctx->addrinfo) || !ISFORWARDER(fctx->addrinfo))
           ? fctx->domain
           : fctx->fwdname;

  /*
   * The name is outside the queried namespace.
   */
  rel = dns_name_fullcompare(name, apex, &(int){ 0 },
           &(unsigned int){ 0U });
  if (rel != dns_namereln_subdomain && rel != dns_namereln_equal) {
    return true;
  }

  /*
   * If the record lives in the parent zone, adjust the name so we
   * look for the correct zone or forward clause.
   */
  labels = dns_name_countlabels(name);
  if (dns_rdatatype_atparent(type) && labels > 1U) {
    dns_name_init(&suffix);
    dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
    name = &suffix;
  } else if (rel == dns_namereln_equal) {
    /* If 'name' is 'apex', no further checking is needed. */
    return false;
  }

  /*
   * If there is a locally served zone between 'apex' and 'name'
   * then don't cache.
   */
  dns_ztfind_t options = DNS_ZTFIND_NOEXACT | DNS_ZTFIND_MIRROR;
  result = dns_view_findzone(fctx->res->view, name, options, &zone);
  if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
    dns_name_t *zname = dns_zone_getorigin(zone);
    dns_namereln_t reln = dns_name_fullcompare(
      zname, apex, &(int){ 0 }, &(unsigned int){ 0U });
    dns_zone_detach(&zone);
    if (reln == dns_namereln_subdomain) {
      return true;
    }
  }

  /*
   * Look for a forward declaration below 'name'.
   */
  result = dns_fwdtable_find(fctx->res->view->fwdtable, name,
           &forwarders);

  if (ISFORWARDER(fctx->addrinfo)) {
    /*
     * See if the forwarder declaration is better.
     */
    if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
      bool better = !dns_name_equal(&forwarders->name,
                  fctx->fwdname);
      dns_forwarders_detach(&forwarders);
      return better;
    }

    /*
     * If the lookup failed, the configuration must have
     * changed: play it safe and don't cache.
     */
    return true;
  } else if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
    /*
     * If 'name' is covered by a 'forward only' clause then we
     * can't cache this response.
     */
    bool nocache = (forwarders->fwdpolicy == dns_fwdpolicy_only &&
        !ISC_LIST_EMPTY(forwarders->fwdrs));
    dns_forwarders_detach(&forwarders);
    return nocache;
  }

  return false;
}

static isc_result_t
check_section(void *arg, const dns_name_t *addname, dns_rdatatype_t type,
        dns_rdataset_t *found, dns_section_t section) {
  respctx_t *rctx = arg;
  fetchctx_t *fctx = rctx->fctx;
  isc_result_t result;
  dns_name_t *name = NULL;
  bool external;
  dns_rdatatype_t rtype;
  bool gluing;

  REQUIRE(VALID_FCTX(fctx));

#if CHECK_FOR_GLUE_IN_ANSWER
  if (section == DNS_SECTION_ANSWER && type != dns_rdatatype_a) {
    return ISC_R_SUCCESS;
  }
#endif /* if CHECK_FOR_GLUE_IN_ANSWER */

  gluing = (GLUING(fctx) || (fctx->type == dns_rdatatype_ns &&
           dns_name_equal(fctx->name, dns_rootname)));

  result = dns_message_findname(rctx->query->rmessage, section, addname,
              dns_rdatatype_any, 0, &name, NULL);
  if (result == ISC_R_SUCCESS) {
    external = name_external(name, type, fctx);
    if (type == dns_rdatatype_a) {
      ISC_LIST_FOREACH(name->list, rdataset, link) {
        if (dns_rdatatype_issig(rdataset->type)) {
          rtype = rdataset->covers;
        } else {
          rtype = rdataset->type;
        }
        if (dns_rdatatype_isaddr(rtype)) {
          mark_related(name, rdataset, external,
                 gluing);
        }
      }
    } else {
      dns_rdataset_t *rdataset = NULL;
      result = dns_message_findtype(name, type, 0, &rdataset);
      if (result == ISC_R_SUCCESS) {
        mark_related(name, rdataset, external, gluing);
        if (found != NULL) {
          dns_rdataset_clone(rdataset, found);
        }
        /*
         * Do we have its SIG too?
         */
        rdataset = NULL;
        result = dns_message_findtype(
          name, dns_rdatatype_rrsig, type,
          &rdataset);
        if (result == ISC_R_SUCCESS) {
          mark_related(name, rdataset, external,
                 gluing);
        }
      }
    }
  }

  return ISC_R_SUCCESS;
}

static isc_result_t
check_related(void *arg, const dns_name_t *addname, dns_rdatatype_t type,
        dns_rdataset_t *found DNS__DB_FLARG) {
  return check_section(arg, addname, type, found, DNS_SECTION_ADDITIONAL);
}

#ifndef CHECK_FOR_GLUE_IN_ANSWER
#define CHECK_FOR_GLUE_IN_ANSWER 0
#endif /* ifndef CHECK_FOR_GLUE_IN_ANSWER */

#if CHECK_FOR_GLUE_IN_ANSWER
static isc_result_t
check_answer(void *arg, const dns_name_t *addname, dns_rdatatype_t type,
       dns_rdataset_t *found) {
  return check_section(arg, addname, type, found, DNS_SECTION_ANSWER);
}
#endif /* if CHECK_FOR_GLUE_IN_ANSWER */

static bool
is_answeraddress_allowed(dns_view_t *view, dns_name_t *name,
       dns_rdataset_t *rdataset) {
  isc_result_t result;
  dns_rdata_t rdata = DNS_RDATA_INIT;
  struct in_addr ina;
  struct in6_addr in6a;
  isc_netaddr_t netaddr;
  char addrbuf[ISC_NETADDR_FORMATSIZE];
  char namebuf[DNS_NAME_FORMATSIZE];
  char classbuf[64];
  char typebuf[64];
  int match;

  /* By default, we allow any addresses. */
  if (view->denyansweracl == NULL) {
    return true;
  }

  /*
   * If the owner name matches one in the exclusion list, either
   * exactly or partially, allow it.
   */
  if (dns_nametree_covered(view->answeracl_exclude, name, NULL, 0)) {
    return true;
  }

  /*
   * Otherwise, search the filter list for a match for each
   * address record.  If a match is found, the address should be
   * filtered, so should the entire answer.
   */
  DNS_RDATASET_FOREACH(rdataset) {
    dns_rdata_reset(&rdata);
    dns_rdataset_current(rdataset, &rdata);
    if (rdataset->type == dns_rdatatype_a) {
      INSIST(rdata.length == sizeof(ina.s_addr));
      memmove(&ina.s_addr, rdata.data, sizeof(ina.s_addr));
      isc_netaddr_fromin(&netaddr, &ina);
    } else {
      INSIST(rdata.length == sizeof(in6a.s6_addr));
      memmove(in6a.s6_addr, rdata.data, sizeof(in6a.s6_addr));
      isc_netaddr_fromin6(&netaddr, &in6a);
    }

    result = dns_acl_match(&netaddr, NULL, view->denyansweracl,
               view->aclenv, &match, NULL);
    if (result == ISC_R_SUCCESS && match > 0) {
      isc_netaddr_format(&netaddr, addrbuf, sizeof(addrbuf));
      dns_name_format(name, namebuf, sizeof(namebuf));
      dns_rdatatype_format(rdataset->type, typebuf,
               sizeof(typebuf));
      dns_rdataclass_format(rdataset->rdclass, classbuf,
                sizeof(classbuf));
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
              "answer address %s denied for %s/%s/%s",
              addrbuf, namebuf, typebuf, classbuf);
      return false;
    }
  }

  return true;
}

static bool
is_answertarget_allowed(fetchctx_t *fctx, dns_name_t *qname, dns_name_t *rname,
      dns_rdataset_t *rdataset, bool *chainingp) {
  isc_result_t result;
  dns_name_t *tname = NULL;
  dns_rdata_cname_t cname;
  dns_rdata_dname_t dname;
  dns_view_t *view = fctx->res->view;
  dns_rdata_t rdata = DNS_RDATA_INIT;
  unsigned int nlabels;
  dns_fixedname_t fixed;
  dns_name_t prefix;
  int order;

  REQUIRE(rdataset != NULL);
  REQUIRE(dns_rdatatype_isalias(rdataset->type));

  /*
   * By default, we allow any target name.
   * If newqname != NULL we also need to extract the newqname.
   */
  if (chainingp == NULL && view->denyanswernames == NULL) {
    return true;
  }

  result = dns_rdataset_first(rdataset);
  RUNTIME_CHECK(result == ISC_R_SUCCESS);
  dns_rdataset_current(rdataset, &rdata);
  switch (rdataset->type) {
  case dns_rdatatype_cname:
    result = dns_rdata_tostruct(&rdata, &cname, NULL);
    RUNTIME_CHECK(result == ISC_R_SUCCESS);
    tname = &cname.cname;
    break;
  case dns_rdatatype_dname:
    if (dns_name_fullcompare(qname, rname, &order, &nlabels) !=
        dns_namereln_subdomain)
    {
      return true;
    }
    result = dns_rdata_tostruct(&rdata, &dname, NULL);
    RUNTIME_CHECK(result == ISC_R_SUCCESS);
    dns_name_init(&prefix);
    tname = dns_fixedname_initname(&fixed);
    nlabels = dns_name_countlabels(rname);
    dns_name_split(qname, nlabels, &prefix, NULL);
    result = dns_name_concatenate(&prefix, &dname.dname, tname);
    if (result == DNS_R_NAMETOOLONG) {
      SET_IF_NOT_NULL(chainingp, true);
      return true;
    }
    RUNTIME_CHECK(result == ISC_R_SUCCESS);
    break;
  default:
    UNREACHABLE();
  }

  SET_IF_NOT_NULL(chainingp, true);

  if (view->denyanswernames == NULL) {
    return true;
  }

  /*
   * If the owner name matches one in the exclusion list, either
   * exactly or partially, allow it.
   */
  if (dns_nametree_covered(view->answernames_exclude, qname, NULL, 0)) {
    return true;
  }

  /*
   * If the target name is a subdomain of the search domain, allow
   * it.
   *
   * Note that if BIND is configured as a forwarding DNS server,
   * the search domain will always match the root domain ("."), so
   * we must also check whether forwarding is enabled so that
   * filters can be applied; see GL #1574.
   */
  if (!fctx->forwarding && dns_name_issubdomain(tname, fctx->domain)) {
    return true;
  }

  /*
   * Otherwise, apply filters.
   */
  if (dns_nametree_covered(view->denyanswernames, tname, NULL, 0)) {
    char qnamebuf[DNS_NAME_FORMATSIZE];
    char tnamebuf[DNS_NAME_FORMATSIZE];
    char classbuf[64];
    char typebuf[64];
    dns_name_format(qname, qnamebuf, sizeof(qnamebuf));
    dns_name_format(tname, tnamebuf, sizeof(tnamebuf));
    dns_rdatatype_format(rdataset->type, typebuf, sizeof(typebuf));
    dns_rdataclass_format(view->rdclass, classbuf,
              sizeof(classbuf));
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_NOTICE, "%s target %s denied for %s/%s",
            typebuf, tnamebuf, qnamebuf, classbuf);
    return false;
  }

  return true;
}

static void
trim_ns_ttl(fetchctx_t *fctx, dns_name_t *name, dns_rdataset_t *rdataset) {
  if (fctx->ns_ttl_ok && rdataset->ttl > fctx->ns_ttl) {
    char ns_namebuf[DNS_NAME_FORMATSIZE];
    char namebuf[DNS_NAME_FORMATSIZE];
    char tbuf[DNS_RDATATYPE_FORMATSIZE];

    dns_name_format(name, ns_namebuf, sizeof(ns_namebuf));
    dns_name_format(fctx->name, namebuf, sizeof(namebuf));
    dns_rdatatype_format(fctx->type, tbuf, sizeof(tbuf));

    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_DEBUG(10),
            "fctx %p: trimming ttl of %s/NS for %s/%s: "
            "%u -> %u",
            fctx, ns_namebuf, namebuf, tbuf, rdataset->ttl,
            fctx->ns_ttl);
    rdataset->ttl = fctx->ns_ttl;
  }
}

static bool
validinanswer(dns_rdataset_t *rdataset, fetchctx_t *fctx) {
  if (rdataset->type == dns_rdatatype_nsec3) {
    /*
     * NSEC3 records are not allowed to
     * appear in the answer section.
     */
    log_formerr(fctx, "NSEC3 in answer");
    return false;
  }
  if (rdataset->type == dns_rdatatype_tkey) {
    /*
     * TKEY is not a valid record in a
     * response to any query we can make.
     */
    log_formerr(fctx, "TKEY in answer");
    return false;
  }
  if (rdataset->rdclass != fctx->res->rdclass) {
    log_formerr(fctx, "Mismatched class in answer");
    return false;
  }
  return true;
}

#if DNS_RESOLVER_TRACE
ISC_REFCOUNT_TRACE_IMPL(fetchctx, fctx_destroy);
#else
ISC_REFCOUNT_IMPL(fetchctx, fctx_destroy);
#endif

static void
resume_dslookup(void *arg) {
  dns_fetchresponse_t *resp = (dns_fetchresponse_t *)arg;
  fetchctx_t *fctx = resp->arg;
  isc_loop_t *loop = resp->loop;
  isc_result_t result;
  dns_resolver_t *res = NULL;
  dns_rdataset_t *frdataset = NULL, *nsrdataset = NULL;
  dns_rdataset_t nameservers;
  dns_fixedname_t fixed;
  dns_name_t *domain = NULL;
  unsigned int n;
  dns_fetch_t *fetch = NULL;

  REQUIRE(VALID_FCTX(fctx));

  res = fctx->res;

  REQUIRE(fctx->tid == isc_tid());

  FCTXTRACE("resume_dslookup");

  if (resp->node != NULL) {
    dns_db_detachnode(&resp->node);
  }
  if (resp->db != NULL) {
    dns_db_detach(&resp->db);
  }

  /* Preserve data from resp before freeing it. */
  frdataset = resp->rdataset; /* a.k.a. fctx->nsrrset */
  result = resp->result;

  dns_resolver_freefresp(&resp);

  LOCK(&fctx->lock);
  if (SHUTTINGDOWN(fctx)) {
    result = ISC_R_SHUTTINGDOWN;
  }
  UNLOCK(&fctx->lock);

  fetch = fctx->nsfetch;
  fctx->nsfetch = NULL;

  FTRACE("resume_dslookup");

  switch (result) {
  case ISC_R_SUCCESS:
    FCTXTRACE("resuming DS lookup");

    if (dns_rdataset_isassociated(&fctx->nameservers)) {
      dns_rdataset_disassociate(&fctx->nameservers);
    }
    dns_rdataset_clone(frdataset, &fctx->nameservers);

    /*
     * Disassociate now the NS's are saved.
     */
    if (dns_rdataset_isassociated(frdataset)) {
      dns_rdataset_disassociate(frdataset);
    }

    fctx->ns_ttl = fctx->nameservers.ttl;
    fctx->ns_ttl_ok = true;
    log_ns_ttl(fctx, "resume_dslookup");

    fcount_decr(fctx);
    dns_name_copy(fctx->nsname, fctx->domain);
    result = fcount_incr(fctx, false);
    if (result != ISC_R_SUCCESS) {
      goto cleanup;
    }

    /* Try again. */
    fctx_try(fctx, true);
    break;

  case ISC_R_SHUTTINGDOWN:
  case ISC_R_CANCELED:
    /* Don't try anymore. */
    /* Can't be done in cleanup. */
    if (dns_rdataset_isassociated(frdataset)) {
      dns_rdataset_disassociate(frdataset);
    }
    goto cleanup;

  default:
    /*
     * Disassociate for the next dns_resolver_createfetch call.
     */
    if (dns_rdataset_isassociated(frdataset)) {
      dns_rdataset_disassociate(frdataset);
    }

    /*
     * If the chain of resume_dslookup() invocations managed to
     * chop off enough labels from the original DS owner name to
     * reach the top of the namespace, no further progress can be
     * made.  Interrupt the DS chasing process, returning SERVFAIL.
     */
    if (dns_name_equal(fctx->nsname, fetch->private->domain)) {
      result = DNS_R_SERVFAIL;
      goto cleanup;
    }

    /* Get nameservers from fetch before we destroy it. */
    dns_rdataset_init(&nameservers);
    if (dns_rdataset_isassociated(&fetch->private->nameservers)) {
      dns_rdataset_clone(&fetch->private->nameservers,
             &nameservers);
      nsrdataset = &nameservers;

      /* Get domain from fetch before we destroy it. */
      domain = dns_fixedname_initname(&fixed);
      dns_name_copy(fetch->private->domain, domain);
    }

    n = dns_name_countlabels(fctx->nsname);
    dns_name_getlabelsequence(fctx->nsname, 1, n - 1, fctx->nsname);

    FCTXTRACE("continuing to look for parent's NS records");

    fetchctx_ref(fctx);
    result = dns_resolver_createfetch(
      res, fctx->nsname, dns_rdatatype_ns, domain, nsrdataset,
      NULL, NULL, 0, fctx->options, 0, fctx->qc, fctx->gqc,
      loop, resume_dslookup, fctx, &fctx->edectx,
      &fctx->nsrrset, NULL, &fctx->nsfetch);
    if (result != ISC_R_SUCCESS) {
      fetchctx_unref(fctx);
      if (result == DNS_R_DUPLICATE) {
        result = DNS_R_SERVFAIL;
      }
    }

    if (dns_rdataset_isassociated(&nameservers)) {
      dns_rdataset_disassociate(&nameservers);
    }
  }

cleanup:
  dns_resolver_destroyfetch(&fetch);

  if (result != ISC_R_SUCCESS) {
    /* An error occurred, tear down whole fctx */
    fctx_done_unref(fctx, result);
  }

  fetchctx_detach(&fctx);
}

static void
checknamessection(dns_message_t *message, dns_section_t section) {
  MSG_SECTION_FOREACH(message, section, name) {
    ISC_LIST_FOREACH(name->list, rdataset, link) {
      DNS_RDATASET_FOREACH(rdataset) {
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_rdataset_current(rdataset, &rdata);
        if (!dns_rdata_checkowner(name, rdata.rdclass,
                rdata.type, false) ||
            !dns_rdata_checknames(&rdata, name, NULL))
        {
          rdataset->attributes.checknames = true;
        }
      }
    }
  }
}

static void
checknames(dns_message_t *message) {
  checknamessection(message, DNS_SECTION_ANSWER);
  checknamessection(message, DNS_SECTION_AUTHORITY);
  checknamessection(message, DNS_SECTION_ADDITIONAL);
}

static void
make_hex(unsigned char *src, size_t srclen, char *buf, size_t buflen) {
  isc_buffer_t b;
  isc_region_t r;
  isc_result_t result;

  r.base = src;
  r.length = srclen;
  isc_buffer_init(&b, buf, buflen);
  result = isc_hex_totext(&r, 0, "", &b);
  RUNTIME_CHECK(result == ISC_R_SUCCESS);
  isc_buffer_putuint8(&b, '\0');
}

static void
make_printable(unsigned char *src, size_t srclen, char *buf, size_t buflen) {
  INSIST(buflen > srclen);
  while (srclen-- > 0) {
    unsigned char c = *src++;
    *buf++ = isprint(c) ? c : '.';
  }
  *buf = '\0';
}

/*
 * Log server NSID at log level 'level'
 */
static void
log_nsid(isc_buffer_t *opt, size_t nsid_len, resquery_t *query, int level,
   isc_mem_t *mctx) {
  char addrbuf[ISC_SOCKADDR_FORMATSIZE], *buf = NULL, *pbuf = NULL;
  size_t buflen;

  REQUIRE(nsid_len <= UINT16_MAX);

  /* Allocate buffer for storing hex version of the NSID */
  buflen = nsid_len * 2 + 1;
  buf = isc_mem_get(mctx, buflen);
  pbuf = isc_mem_get(mctx, nsid_len + 1);

  /* Convert to hex */
  make_hex(isc_buffer_current(opt), nsid_len, buf, buflen);

  /* Make printable version */
  make_printable(isc_buffer_current(opt), nsid_len, pbuf, nsid_len + 1);

  isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
          sizeof(addrbuf));
  isc_log_write(DNS_LOGCATEGORY_NSID, DNS_LOGMODULE_RESOLVER, level,
          "received NSID %s (\"%s\") from %s", buf, pbuf, addrbuf);

  isc_mem_put(mctx, pbuf, nsid_len + 1);
  isc_mem_put(mctx, buf, buflen);
}

static void
log_zoneversion(unsigned char *version, size_t version_len, unsigned char *nsid,
    size_t nsid_len, resquery_t *query, int level,
    isc_mem_t *mctx) {
  char addrbuf[ISC_SOCKADDR_FORMATSIZE];
  char namebuf[DNS_NAME_FORMATSIZE];
  size_t nsid_buflen = 0;
  char *nsid_buf = NULL;
  char *nsid_pbuf = NULL;
  const char *nsid_hex = "";
  const char *nsid_print = "";
  const char *sep_1 = "";
  const char *sep_2 = "";
  const char *sep_3 = "";
  dns_name_t suffix = DNS_NAME_INITEMPTY;
  unsigned int labels;

  REQUIRE(version_len <= UINT16_MAX);

  /*
   * Don't log reflected ZONEVERSION option.
   */
  if (version_len == 0) {
    return;
  }

  /* Enforced by dns_rdata_fromwire. */
  INSIST(version_len >= 2);

  /*
   * Sanity check on label count.
   */
  labels = version[0] + 1;
  if (dns_name_countlabels(query->fctx->name) < labels) {
    return;
  }

  /*
   * Get zone name.
   */
  dns_name_split(query->fctx->name, labels, NULL, &suffix);
  dns_name_format(&suffix, namebuf, sizeof(namebuf));

  if (nsid != NULL) {
    nsid_buflen = nsid_len * 2 + 1;
    nsid_hex = nsid_buf = isc_mem_get(mctx, nsid_buflen);
    nsid_print = nsid_pbuf = isc_mem_get(mctx, nsid_len + 1);

    /* Convert to hex */
    make_hex(nsid, nsid_len, nsid_buf, nsid_buflen);

    /* Convert to printable */
    make_printable(nsid, nsid_len, nsid_pbuf, nsid_len + 1);

    sep_1 = " (NSID ";
    sep_2 = " (";
    sep_3 = "))";
  }

  isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
          sizeof(addrbuf));
  if (version[1] == 0 && version_len == 6) {
    uint32_t serial = version[2] << 24 | version[3] << 2 |
          version[4] << 8 | version[5];
    isc_log_write(DNS_LOGCATEGORY_ZONEVERSION,
            DNS_LOGMODULE_RESOLVER, level,
            "received ZONEVERSION serial %u from %s for %s "
            "zone %s%s%s%s%s%s",
            serial, addrbuf, query->fctx->info, namebuf,
            sep_1, nsid_hex, sep_2, nsid_print, sep_3);
  } else {
    size_t version_buflen = version_len * 2 + 1;
    char *version_hex = isc_mem_get(mctx, version_buflen);
    char *version_pbuf = isc_mem_get(mctx, version_len - 1);

    /* Convert to hex */
    make_hex(version + 2, version_len - 2, version_hex,
       version_buflen);

    /* Convert to printable */
    make_printable(version + 2, version_len - 2, version_pbuf,
             version_len - 1);

    isc_log_write(DNS_LOGCATEGORY_ZONEVERSION,
            DNS_LOGMODULE_RESOLVER, level,
            "received ZONEVERSION type %u value %s (%s) from "
            "%s for %s zone %s%s%s%s%s%s",
            version[1], version_hex, version_pbuf, addrbuf,
            query->fctx->info, namebuf, sep_1, nsid_hex,
            sep_2, nsid_print, sep_3);
    isc_mem_put(mctx, version_hex, version_buflen);
    isc_mem_put(mctx, version_pbuf, version_len - 1);
  }

  if (nsid_pbuf != NULL) {
    isc_mem_put(mctx, nsid_pbuf, nsid_len + 1);
  }
  if (nsid_buf != NULL) {
    isc_mem_put(mctx, nsid_buf, nsid_buflen);
  }
}

static bool
betterreferral(respctx_t *rctx) {
  dns_message_t *msg = rctx->query->rmessage;

  MSG_SECTION_FOREACH(msg, DNS_SECTION_AUTHORITY, name) {
    if (!isstrictsubdomain(name, rctx->fctx->domain)) {
      continue;
    }

    ISC_LIST_FOREACH(name->list, rdataset, link) {
      if (rdataset->type == dns_rdatatype_ns) {
        return true;
      }
    }
  }
  return false;
}

/*
 * Handles responses received in response to iterative queries sent by
 * resquery_send(). Sets up a response context (respctx_t).
 */
static void
resquery_response(isc_result_t eresult, isc_region_t *region, void *arg) {
  isc_result_t result;
  resquery_t *query = (resquery_t *)arg;
  fetchctx_t *fctx = NULL;
  respctx_t *rctx = NULL;

  if (eresult == ISC_R_CANCELED) {
    return;
  }

  REQUIRE(VALID_QUERY(query));
  fctx = query->fctx;
  REQUIRE(VALID_FCTX(fctx));
  REQUIRE(fctx->tid == isc_tid());

  QTRACE("response");

  if (eresult == ISC_R_SUCCESS) {
    if (isc_sockaddr_pf(&query->addrinfo->sockaddr) == PF_INET) {
      inc_stats(fctx->res, dns_resstatscounter_responsev4);
    } else {
      inc_stats(fctx->res, dns_resstatscounter_responsev6);
    }
  }

  rctx = isc_mem_get(fctx->mctx, sizeof(*rctx));
  rctx_respinit(query, fctx, eresult, region, rctx);

  if (eresult == ISC_R_SHUTTINGDOWN ||
      atomic_load_acquire(&fctx->res->exiting))
  {
    result = ISC_R_SHUTTINGDOWN;
    FCTXTRACE("resolver shutting down");
    rctx->finish = NULL;
    rctx_done(rctx, result);
    goto cleanup;
  }

  result = rctx_timedout(rctx);
  if (result == ISC_R_COMPLETE) {
    goto cleanup;
  }

  fctx->addrinfo = query->addrinfo;
  fctx->timeout = false;
  fctx->timeouts = 0;

  /*
   * Check whether the dispatcher has failed; if so we're done
   */
  result = rctx_dispfail(rctx);
  if (result == ISC_R_COMPLETE) {
    goto cleanup;
  }

  if (query->tsig != NULL) {
    dns_message_setquerytsig(query->rmessage, query->tsig);
  }

  if (query->tsigkey != NULL) {
    result = dns_message_settsigkey(query->rmessage,
            query->tsigkey);
    if (result != ISC_R_SUCCESS) {
      FCTXTRACE3("unable to set tsig key", result);
      rctx_done(rctx, result);
      goto cleanup;
    }
  }

  dns_message_setclass(query->rmessage, fctx->res->rdclass);

  if ((rctx->retryopts & DNS_FETCHOPT_TCP) == 0) {
    if ((rctx->retryopts & DNS_FETCHOPT_NOEDNS0) == 0) {
      dns_adb_setudpsize(
        fctx->adb, query->addrinfo,
        isc_buffer_usedlength(&rctx->buffer));
    } else {
      dns_adb_plainresponse(fctx->adb, query->addrinfo);
    }
  }

  /*
   * Parse response message.
   */
  result = rctx_parse(rctx);
  if (result == ISC_R_COMPLETE) {
    goto cleanup;
  }

  /*
   * Log the incoming packet.
   */
  rctx_logpacket(rctx);

  if (query->rmessage->rdclass != fctx->res->rdclass) {
    rctx->resend = true;
    FCTXTRACE("bad class");
    rctx_done(rctx, result);
    goto cleanup;
  }

  /*
   * Process receive opt record.
   */
  rctx->opt = dns_message_getopt(query->rmessage);
  if (rctx->opt != NULL) {
    rctx_opt(rctx);
  }

  if (query->rmessage->cc_bad &&
      (rctx->retryopts & DNS_FETCHOPT_TCP) == 0)
  {
    /*
     * If the COOKIE is bad, assume it is an attack and
     * keep listening for a good answer.
     */
    rctx->nextitem = true;
    if (isc_log_wouldlog(ISC_LOG_INFO)) {
      char addrbuf[ISC_SOCKADDR_FORMATSIZE];
      isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
              sizeof(addrbuf));
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
              "bad cookie from %s", addrbuf);
    }
    rctx_done(rctx, result);
    goto cleanup;
  }

  /*
   * Is the question the same as the one we asked?
   * NOERROR/NXDOMAIN/YXDOMAIN/REFUSED/SERVFAIL/BADCOOKIE must
   * have the same question. FORMERR/NOTIMP if they have a
   * question section then it must match.
   */
  switch (query->rmessage->rcode) {
  case dns_rcode_notimp:
  case dns_rcode_formerr:
    if (query->rmessage->counts[DNS_SECTION_QUESTION] == 0) {
      break;
    }
    FALLTHROUGH;
  case dns_rcode_nxrrset: /* Not expected. */
  case dns_rcode_badcookie:
  case dns_rcode_noerror:
  case dns_rcode_nxdomain:
  case dns_rcode_yxdomain:
  case dns_rcode_refused:
  case dns_rcode_servfail:
  default:
    result = same_question(fctx, query->rmessage);
    if (result != ISC_R_SUCCESS) {
      FCTXTRACE3("question section invalid", result);
      rctx->nextitem = true;
      rctx_done(rctx, result);
      goto cleanup;
    }
    break;
  }

  if (query->rmessage->tsigkey == NULL && query->rmessage->tsig == NULL &&
      query->rmessage->sig0 != NULL)
  {
    /*
     * If the message is not TSIG-signed (which has priorty) and is
     * SIG(0)-signed (which consumes more resources), then run an
     * asynchronous check.
     */
    result = dns_message_checksig_async(
      query->rmessage, fctx->res->view, fctx->loop,
      resquery_response_continue, rctx);
    INSIST(result == DNS_R_WAIT);
  } else {
    /*
     * If the message is signed, check the signature.  If not, this
     * returns success anyway.
     */
    result = dns_message_checksig(query->rmessage, fctx->res->view);
    resquery_response_continue(rctx, result);
  }

  return;

cleanup:
  isc_mem_putanddetach(&rctx->mctx, rctx, sizeof(*rctx));
}

static isc_result_t
rctx_cookiecheck(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;

  /*
   * If TSIG signed, sent via TCP, or cookie present,
   * no need to continue.
   */
  if (dns_message_gettsig(query->rmessage, NULL) != NULL ||
      query->rmessage->cc_ok || query->rmessage->cc_bad ||
      (rctx->retryopts & DNS_FETCHOPT_TCP) != 0)
  {
    return ISC_R_SUCCESS;
  }

  /*
   * If we've had a cookie from the same server previously,
   * retry with TCP. This may be a misconfigured anycast server
   * or an attempt to send a spoofed response.
   */
  if (dns_adb_getcookie(query->addrinfo, NULL, 0) > CLIENT_COOKIE_SIZE) {
    if (isc_log_wouldlog(ISC_LOG_INFO)) {
      char addrbuf[ISC_SOCKADDR_FORMATSIZE];
      isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
              sizeof(addrbuf));
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
              "missing expected cookie "
              "from %s",
              addrbuf);
    }
    rctx->retryopts |= DNS_FETCHOPT_TCP;
    rctx->resend = true;
    rctx_done(rctx, ISC_R_SUCCESS);
    return ISC_R_COMPLETE;
  }

  /*
   * Retry over TCP if require-cookie is true.
   */
  if (fctx->res->view->peers != NULL) {
    isc_result_t result;
    dns_peer_t *peer = NULL;
    bool required = false;
    isc_netaddr_t netaddr;

    isc_netaddr_fromsockaddr(&netaddr, &query->addrinfo->sockaddr);
    result = dns_peerlist_peerbyaddr(fctx->res->view->peers,
             &netaddr, &peer);
    if (result == ISC_R_SUCCESS) {
      dns_peer_getrequirecookie(peer, &required);
    }
    if (!required) {
      return ISC_R_SUCCESS;
    }

    if (isc_log_wouldlog(ISC_LOG_INFO)) {
      char addrbuf[ISC_SOCKADDR_FORMATSIZE];
      isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
              sizeof(addrbuf));
      isc_log_write(DNS_LOGCATEGORY_RESOLVER,
              DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
              "missing required "
              "cookie from %s",
              addrbuf);
    }

    rctx->retryopts |= DNS_FETCHOPT_TCP;
    rctx->resend = true;
    rctx_done(rctx, ISC_R_SUCCESS);
    return ISC_R_COMPLETE;
  }

  return ISC_R_SUCCESS;
}

static void
resquery_response_continue(void *arg, isc_result_t result) {
  respctx_t *rctx = arg;
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;

  QTRACE("response_continue");

  if (result != ISC_R_SUCCESS) {
    FCTXTRACE3("signature check failed", result);
    if (result == DNS_R_UNEXPECTEDTSIG ||
        result == DNS_R_EXPECTEDTSIG)
    {
      rctx->nextitem = true;
    }
    rctx_done(rctx, result);
    goto cleanup;
  }

  /*
   * The dispatcher should ensure we only get responses with QR
   * set.
   */
  INSIST((query->rmessage->flags & DNS_MESSAGEFLAG_QR) != 0);

  /*
   * Check for cookie issues.
   */
  result = rctx_cookiecheck(rctx);
  if (result == ISC_R_COMPLETE) {
    goto cleanup;
  }

  /*
   * Check for EDNS issues.
   */
  rctx_edns(rctx);

  /*
   * Deal with truncated responses by retrying using TCP.
   */
  if ((query->rmessage->flags & DNS_MESSAGEFLAG_TC) != 0) {
    rctx->truncated = true;
  }

  if (rctx->truncated) {
    inc_stats(fctx->res, dns_resstatscounter_truncated);
    if ((rctx->retryopts & DNS_FETCHOPT_TCP) != 0) {
      rctx->broken_server = DNS_R_TRUNCATEDTCP;
      rctx->next_server = true;
    } else {
      rctx->retryopts |= DNS_FETCHOPT_TCP;
      rctx->resend = true;
    }
    FCTXTRACE3("message truncated", result);
    rctx_done(rctx, result);
    goto cleanup;
  }

  /*
   * Is it a query response?
   */
  if (query->rmessage->opcode != dns_opcode_query) {
    rctx->broken_server = DNS_R_UNEXPECTEDOPCODE;
    rctx->next_server = true;
    FCTXTRACE("invalid message opcode");
    rctx_done(rctx, result);
    goto cleanup;
  }

  /*
   * Update statistics about erroneous responses.
   */
  switch (query->rmessage->rcode) {
  case dns_rcode_noerror:
    /* no error */
    break;
  case dns_rcode_nxdomain:
    inc_stats(fctx->res, dns_resstatscounter_nxdomain);
    break;
  case dns_rcode_servfail:
    inc_stats(fctx->res, dns_resstatscounter_servfail);
    break;
  case dns_rcode_formerr:
    inc_stats(fctx->res, dns_resstatscounter_formerr);
    break;
  case dns_rcode_refused:
    inc_stats(fctx->res, dns_resstatscounter_refused);
    break;
  case dns_rcode_badvers:
    inc_stats(fctx->res, dns_resstatscounter_badvers);
    break;
  case dns_rcode_badcookie:
    inc_stats(fctx->res, dns_resstatscounter_badcookie);
    break;
  default:
    inc_stats(fctx->res, dns_resstatscounter_othererror);
    break;
  }

  /*
   * Bad server?
   */
  result = rctx_badserver(rctx, result);
  if (result == ISC_R_COMPLETE) {
    goto cleanup;
  }

  /*
   * Lame server?
   */
  result = rctx_lameserver(rctx);
  if (result == ISC_R_COMPLETE) {
    goto cleanup;
  }

  /*
   * Optionally call dns_rdata_checkowner() and
   * dns_rdata_checknames() to validate the names in the response
   * message.
   */
  if ((fctx->res->options & DNS_RESOLVER_CHECKNAMES) != 0) {
    checknames(query->rmessage);
  }

  /*
   * Clear cache bits.
   */
  FCTX_ATTR_CLR(fctx, FCTX_ATTR_WANTNCACHE | FCTX_ATTR_WANTCACHE);

  /*
   * Did we get any answers?
   */
  if (query->rmessage->counts[DNS_SECTION_ANSWER] > 0 &&
      (query->rmessage->rcode == dns_rcode_noerror ||
       query->rmessage->rcode == dns_rcode_yxdomain ||
       query->rmessage->rcode == dns_rcode_nxdomain))
  {
    result = rctx_answer(rctx);
    if (result == ISC_R_COMPLETE) {
      goto cleanup;
    }
  } else if (query->rmessage->counts[DNS_SECTION_AUTHORITY] > 0 ||
       query->rmessage->rcode == dns_rcode_noerror ||
       query->rmessage->rcode == dns_rcode_nxdomain)
  {
    /*
     * This might be an NXDOMAIN, NXRRSET, or referral.
     * Call rctx_answer_none() to determine which it is.
     */
    result = rctx_answer_none(rctx);
    switch (result) {
    case ISC_R_SUCCESS:
    case DNS_R_CHASEDSSERVERS:
      break;
    case DNS_R_DELEGATION:
      /*
       * With NOFOLLOW we want to pass return
       * DNS_R_DELEGATION to resume_qmin.
       */
      if ((fctx->options & DNS_FETCHOPT_NOFOLLOW) == 0) {
        result = ISC_R_SUCCESS;
      }
      break;
    default:
      /*
       * Something has gone wrong.
       */
      if (result == DNS_R_FORMERR) {
        rctx->next_server = true;
      }
      FCTXTRACE3("rctx_answer_none", result);
      rctx_done(rctx, result);
      goto cleanup;
    }
  } else {
    /*
     * The server is insane.
     */
    /* XXXRTH Log */
    rctx->broken_server = DNS_R_UNEXPECTEDRCODE;
    rctx->next_server = true;
    FCTXTRACE("broken server: unexpected rcode");
    rctx_done(rctx, result);
    goto cleanup;
  }

  /*
   * Follow additional section data chains.
   */
  rctx_additional(rctx);

  /*
   * Cache the cacheable parts of the message.  This may also
   * cause work to be queued to the DNSSEC validator.
   */
  if (WANTCACHE(fctx)) {
    isc_result_t tresult;
    tresult = rctx_cachemessage(rctx);
    if (tresult != ISC_R_SUCCESS) {
      FCTXTRACE3("rctx_cachemessage complete", tresult);
      rctx_done(rctx, tresult);
      goto cleanup;
    }
  }

  /*
   * Negative caching
   */
  rctx_ncache(rctx);

  FCTXTRACE("resquery_response done");
  rctx_done(rctx, result);

cleanup:
  isc_mem_putanddetach(&rctx->mctx, rctx, sizeof(*rctx));
}

/*
 * rctx_respinit():
 * Initialize the response context structure 'rctx' to all zeroes, then
 * set the loop, event, query and fctx information from
 * resquery_response().
 */
static void
rctx_respinit(resquery_t *query, fetchctx_t *fctx, isc_result_t result,
        isc_region_t *region, respctx_t *rctx) {
  *rctx = (respctx_t){ .result = result,
           .query = query,
           .fctx = fctx,
           .broken_type = badns_response,
           .retryopts = query->options };
  if (result == ISC_R_SUCCESS) {
    REQUIRE(region != NULL);
    isc_buffer_init(&rctx->buffer, region->base, region->length);
    isc_buffer_add(&rctx->buffer, region->length);
  } else {
    isc_buffer_initnull(&rctx->buffer);
  }
  rctx->tnow = isc_time_now();
  rctx->finish = &rctx->tnow;
  rctx->now = (isc_stdtime_t)isc_time_seconds(&rctx->tnow);
  isc_mem_attach(fctx->mctx, &rctx->mctx);
}

/*
 * rctx_answer_init():
 * Clear and reinitialize those portions of 'rctx' that will be needed
 * when scanning the answer section of the response message. This can be
 * called more than once if scanning needs to be restarted (though
 * currently there are no cases in which this occurs).
 */
static void
rctx_answer_init(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  rctx->aa = ((rctx->query->rmessage->flags & DNS_MESSAGEFLAG_AA) != 0);
  if (rctx->aa) {
    rctx->trust = dns_trust_authanswer;
  } else {
    rctx->trust = dns_trust_answer;
  }

  /*
   * There can be multiple RRSIG and SIG records at a name so
   * we treat these types as a subset of ANY.
   */
  rctx->type = fctx->type;
  if (dns_rdatatype_issig(fctx->type)) {
    rctx->type = dns_rdatatype_any;
  }

  /*
   * Bigger than any valid DNAME label count.
   */
  rctx->dname_labels = dns_name_countlabels(fctx->name);
  rctx->domain_labels = dns_name_countlabels(fctx->domain);

  rctx->found_type = dns_rdatatype_none;

  rctx->aname = NULL;
  rctx->ardataset = NULL;

  rctx->cname = NULL;
  rctx->crdataset = NULL;

  rctx->dname = NULL;
  rctx->drdataset = NULL;

  rctx->ns_name = NULL;
  rctx->ns_rdataset = NULL;

  rctx->soa_name = NULL;
  rctx->ds_name = NULL;
  rctx->found_name = NULL;

  rctx->vrdataset = NULL;
  rctx->vsigrdataset = NULL;
}

/*
 * rctx_dispfail():
 * Handle the case where the dispatcher failed
 */
static isc_result_t
rctx_dispfail(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  if (rctx->result == ISC_R_SUCCESS) {
    return ISC_R_SUCCESS;
  }

  /*
   * There's no hope for this response.
   */
  rctx->next_server = true;

  /*
   * If this is a network failure, the operation is cancelled,
   * or the network manager is being shut down, we mark the server
   * as bad so that we won't try it for this fetch again. Also
   * adjust finish and no_response so that we penalize this
   * address in SRTT adjustments later.
   */
  switch (rctx->result) {
  case ISC_R_EOF:
  case ISC_R_HOSTDOWN:
  case ISC_R_HOSTUNREACH:
  case ISC_R_NETDOWN:
  case ISC_R_NETUNREACH:
  case ISC_R_CONNREFUSED:
  case ISC_R_CONNECTIONRESET:
  case ISC_R_INVALIDPROTO:
  case ISC_R_CANCELED:
  case ISC_R_SHUTTINGDOWN:
    rctx->broken_server = rctx->result;
    rctx->broken_type = badns_unreachable;
    rctx->finish = NULL;
    rctx->no_response = true;
    break;
  default:
    break;
  }

  FCTXTRACE3("dispatcher failure", rctx->result);
  rctx_done(rctx, ISC_R_SUCCESS);
  return ISC_R_COMPLETE;
}

/*
 * rctx_timedout():
 * Handle the case where a dispatch read timed out.
 */
static isc_result_t
rctx_timedout(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  if (rctx->result == ISC_R_TIMEDOUT) {
    isc_time_t now;

    inc_stats(fctx->res, dns_resstatscounter_querytimeout);
    FCTX_ATTR_CLR(fctx, FCTX_ATTR_ADDRWAIT);
    fctx->timeout = true;
    fctx->timeouts++;

    rctx->no_response = true;
    rctx->finish = NULL;

    now = isc_time_now();
    /* netmgr timeouts are accurate to the millisecond */
    if (isc_time_microdiff(&fctx->expires, &now) < US_PER_MS) {
      FCTXTRACE("query timed out; stopped trying to make "
          "fetch happen");
      dns_ede_add(&fctx->edectx, DNS_EDE_NOREACHABLEAUTH,
            NULL);
    } else {
      FCTXTRACE("query timed out; trying next server");
      /* try next server */
      rctx->next_server = true;
    }

    rctx_done(rctx, rctx->result);
    return ISC_R_COMPLETE;
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_parse():
 * Parse the response message.
 */
static isc_result_t
rctx_parse(respctx_t *rctx) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;

  result = dns_message_parse(query->rmessage, &rctx->buffer, 0);
  if (result == ISC_R_SUCCESS) {
    return ISC_R_SUCCESS;
  }

  FCTXTRACE3("message failed to parse", result);

  switch (result) {
  case ISC_R_UNEXPECTEDEND:
    if (query->rmessage->question_ok &&
        (query->rmessage->flags & DNS_MESSAGEFLAG_TC) != 0 &&
        (rctx->retryopts & DNS_FETCHOPT_TCP) == 0)
    {
      /*
       * We defer retrying via TCP for a bit so we can
       * check out this message further.
       */
      rctx->truncated = true;
      return ISC_R_SUCCESS;
    }

    /*
     * Either the message ended prematurely,
     * and/or wasn't marked as being truncated,
     * and/or this is a response to a query we
     * sent over TCP.  In all of these cases,
     * something is wrong with the remote
     * server and we don't want to retry using
     * TCP.
     */
    if ((rctx->retryopts & DNS_FETCHOPT_NOEDNS0) == 0) {
      /*
       * The problem might be that they
       * don't understand EDNS0.  Turn it
       * off and try again.
       */
      rctx->retryopts |= DNS_FETCHOPT_NOEDNS0;
      rctx->resend = true;
      inc_stats(fctx->res, dns_resstatscounter_edns0fail);
    } else {
      rctx->broken_server = result;
      rctx->next_server = true;
    }

    rctx_done(rctx, result);
    break;
  case DNS_R_FORMERR:
    if ((rctx->retryopts & DNS_FETCHOPT_NOEDNS0) == 0) {
      /*
       * The problem might be that they
       * don't understand EDNS0.  Turn it
       * off and try again.
       */
      rctx->retryopts |= DNS_FETCHOPT_NOEDNS0;
      rctx->resend = true;
      inc_stats(fctx->res, dns_resstatscounter_edns0fail);
    } else {
      rctx->broken_server = DNS_R_UNEXPECTEDRCODE;
      rctx->next_server = true;
    }

    rctx_done(rctx, result);
    break;
  default:
    /*
     * Something bad has happened.
     */
    rctx_done(rctx, result);
    break;
  }

  return ISC_R_COMPLETE;
}

/*
 * rctx_opt():
 * Process the OPT record in the response.
 */
static void
rctx_opt(respctx_t *rctx) {
  resquery_t *query = rctx->query;
  fetchctx_t *fctx = rctx->fctx;
  dns_rdata_t rdata;
  isc_buffer_t optbuf;
  isc_result_t result;
  bool seen_cookie = false;
  bool seen_nsid = false;
  bool seen_zoneversion = false;
  unsigned char *nsid = NULL;
  uint16_t nsidlen = 0;
  unsigned char *zoneversion = NULL;
  uint16_t zoneversionlen = 0;

  result = dns_rdataset_first(rctx->opt);
  if (result != ISC_R_SUCCESS) {
    return;
  }

  dns_rdata_init(&rdata);
  dns_rdataset_current(rctx->opt, &rdata);
  isc_buffer_init(&optbuf, rdata.data, rdata.length);
  isc_buffer_add(&optbuf, rdata.length);

  while (isc_buffer_remaininglength(&optbuf) >= 4) {
    uint16_t optcode;
    uint16_t optlen;
    unsigned char *optvalue;
    unsigned char cookie[CLIENT_COOKIE_SIZE];
    optcode = isc_buffer_getuint16(&optbuf);
    optlen = isc_buffer_getuint16(&optbuf);
    INSIST(optlen <= isc_buffer_remaininglength(&optbuf));
    switch (optcode) {
    case DNS_OPT_NSID:
      if (seen_nsid) {
        break;
      }
      seen_nsid = true;
      nsid = isc_buffer_current(&optbuf);
      nsidlen = optlen;
      if ((query->options & DNS_FETCHOPT_WANTNSID) != 0) {
        log_nsid(&optbuf, optlen, query, ISC_LOG_INFO,
           fctx->mctx);
      }
      break;
    case DNS_OPT_COOKIE:
      /* Only process the first cookie option. */
      if (seen_cookie) {
        break;
      }
      seen_cookie = true;

      optvalue = isc_buffer_current(&optbuf);
      compute_cc(query, cookie, sizeof(cookie));
      INSIST(query->rmessage->cc_bad == 0 &&
             query->rmessage->cc_ok == 0);

      inc_stats(fctx->res, dns_resstatscounter_cookiein);

      if (optlen < CLIENT_COOKIE_SIZE ||
          memcmp(cookie, optvalue, CLIENT_COOKIE_SIZE) != 0)
      {
        query->rmessage->cc_bad = 1;
        break;
      }

      /* Cookie OK */
      if (optlen == CLIENT_COOKIE_SIZE) {
        query->rmessage->cc_echoed = 1;
      } else {
        query->rmessage->cc_ok = 1;
        inc_stats(fctx->res,
            dns_resstatscounter_cookieok);
        dns_adb_setcookie(fctx->adb, query->addrinfo,
              optvalue, optlen);
      }
      break;
    case DNS_OPT_ZONEVERSION:
      if (seen_zoneversion) {
        break;
      }
      seen_zoneversion = true;
      zoneversion = isc_buffer_current(&optbuf);
      zoneversionlen = optlen;
      break;
    default:
      break;
    }
    isc_buffer_forward(&optbuf, optlen);
  }
  INSIST(isc_buffer_remaininglength(&optbuf) == 0U);

  if ((query->options & DNS_FETCHOPT_WANTZONEVERSION) != 0 &&
      zoneversion != NULL)
  {
    log_zoneversion(zoneversion, zoneversionlen, nsid, nsidlen,
        query, ISC_LOG_INFO, fctx->mctx);
  }
}

/*
 * rctx_edns():
 * Determine whether the remote server is using EDNS correctly or
 * incorrectly and record that information if needed.
 */
static void
rctx_edns(respctx_t *rctx) {
  resquery_t *query = rctx->query;
  fetchctx_t *fctx = rctx->fctx;

  /*
   * If we get a non error EDNS response record the fact so we
   * won't fallback to plain DNS in the future for this server.
   */
  if (rctx->opt != NULL && !EDNSOK(query->addrinfo) &&
      (rctx->retryopts & DNS_FETCHOPT_NOEDNS0) == 0 &&
      (query->rmessage->rcode == dns_rcode_noerror ||
       query->rmessage->rcode == dns_rcode_nxdomain ||
       query->rmessage->rcode == dns_rcode_refused ||
       query->rmessage->rcode == dns_rcode_yxdomain))
  {
    dns_adb_changeflags(fctx->adb, query->addrinfo,
            FCTX_ADDRINFO_EDNSOK, FCTX_ADDRINFO_EDNSOK);
  }
}

/*
 * rctx_answer():
 * We might have answers, or we might have a malformed delegation with
 * records in the answer section. Call rctx_answer_positive() or
 * rctx_answer_none() as appropriate.
 */
static isc_result_t
rctx_answer(respctx_t *rctx) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;

  if ((query->rmessage->flags & DNS_MESSAGEFLAG_AA) != 0 ||
      ISFORWARDER(query->addrinfo))
  {
    result = rctx_answer_positive(rctx);
    if (result != ISC_R_SUCCESS) {
      FCTXTRACE3("rctx_answer_positive (AA/fwd)", result);
    }
  } else if (fctx->type != dns_rdatatype_ns && !betterreferral(rctx)) {
    result = rctx_answer_positive(rctx);
    if (result != ISC_R_SUCCESS) {
      FCTXTRACE3("rctx_answer_positive (!NS)", result);
    }
  } else {
    /*
     * This may be a delegation.
     */

    result = rctx_answer_none(rctx);
    if (result != ISC_R_SUCCESS) {
      FCTXTRACE3("rctx_answer_none", result);
    }

    if (result == DNS_R_DELEGATION) {
      /*
       * With NOFOLLOW we want to return DNS_R_DELEGATION to
       * resume_qmin.
       */
      if ((rctx->fctx->options & DNS_FETCHOPT_NOFOLLOW) != 0)
      {
        return result;
      }
      result = ISC_R_SUCCESS;
    } else {
      /*
       * At this point, AA is not set, the response
       * is not a referral, and the server is not a
       * forwarder.  It is technically lame and it's
       * easier to treat it as such than to figure out
       * some more elaborate course of action.
       */
      rctx->broken_server = DNS_R_LAME;
      rctx->next_server = true;
      FCTXTRACE3("rctx_answer lame", result);
      rctx_done(rctx, result);
      return ISC_R_COMPLETE;
    }
  }

  if (result != ISC_R_SUCCESS) {
    if (result == DNS_R_FORMERR) {
      rctx->next_server = true;
    }
    FCTXTRACE3("rctx_answer failed", result);
    rctx_done(rctx, result);
    return ISC_R_COMPLETE;
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_answer_positive():
 * Handles positive responses. Depending which type of answer this is
 * (matching QNAME/QTYPE, CNAME, DNAME, ANY) calls the proper routine
 * to handle it (rctx_answer_match(), rctx_answer_cname(),
 * rctx_answer_dname(), rctx_answer_any()).
 */
static isc_result_t
rctx_answer_positive(respctx_t *rctx) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;

  FCTXTRACE("rctx_answer_positive");

  rctx_answer_init(rctx);
  rctx_answer_scan(rctx);

  /*
   * Determine which type of positive answer this is:
   * type ANY, CNAME, DNAME, or an answer matching QNAME/QTYPE.
   * Call the appropriate routine to handle the answer type.
   */
  if (rctx->aname != NULL && rctx->type == dns_rdatatype_any) {
    result = rctx_answer_any(rctx);
    if (result == ISC_R_COMPLETE) {
      return rctx->result;
    }
  } else if (rctx->aname != NULL) {
    result = rctx_answer_match(rctx);
    if (result == ISC_R_COMPLETE) {
      return rctx->result;
    }
  } else if (rctx->cname != NULL) {
    result = rctx_answer_cname(rctx);
    if (result == ISC_R_COMPLETE) {
      return rctx->result;
    }
  } else if (rctx->dname != NULL) {
    result = rctx_answer_dname(rctx);
    if (result == ISC_R_COMPLETE) {
      return rctx->result;
    }
  } else {
    log_formerr(fctx, "reply has no answer");
    return DNS_R_FORMERR;
  }

  /*
   * This response is now potentially cacheable.
   */
  FCTX_ATTR_SET(fctx, FCTX_ATTR_WANTCACHE);

  /*
   * Did chaining end before we got the final answer?
   */
  if (rctx->chaining) {
    return ISC_R_SUCCESS;
  }

  /*
   * We didn't end with an incomplete chain, so the rcode should
   * be "no error".
   */
  if (rctx->query->rmessage->rcode != dns_rcode_noerror) {
    log_formerr(fctx, "CNAME/DNAME chain complete, but RCODE "
          "indicates error");
    return DNS_R_FORMERR;
  }

  /*
   * Cache records in the authority section, if
   * there are any suitable for caching.
   */
  rctx_authority_positive(rctx);

  log_ns_ttl(fctx, "rctx_answer");

  if (rctx->ns_rdataset != NULL &&
      dns_name_equal(fctx->domain, rctx->ns_name) &&
      !dns_name_equal(rctx->ns_name, dns_rootname))
  {
    trim_ns_ttl(fctx, rctx->ns_name, rctx->ns_rdataset);
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_answer_scan():
 * Perform a single pass over the answer section of a response, looking
 * for an answer that matches QNAME/QTYPE, or a CNAME matching QNAME, or
 * a covering DNAME. If more than one rdataset is found matching these
 * criteria, then only one is kept. Order of preference is 1) the
 * shortest DNAME, 2) the first matching answer, or 3) the first CNAME.
 */
static void
rctx_answer_scan(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;
  dns_message_t *msg = rctx->query->rmessage;

  MSG_SECTION_FOREACH(msg, DNS_SECTION_ANSWER, name) {
    int order;
    unsigned int nlabels;
    dns_namereln_t namereln;

    namereln = dns_name_fullcompare(fctx->name, name, &order,
            &nlabels);
    switch (namereln) {
    case dns_namereln_equal:
      ISC_LIST_FOREACH(name->list, rdataset, link) {
        if (rdataset->type == rctx->type ||
            rctx->type == dns_rdatatype_any)
        {
          rctx->aname = name;
          if (rctx->type != dns_rdatatype_any) {
            rctx->ardataset = rdataset;
          }
          break;
        }
        if (rdataset->type == dns_rdatatype_cname) {
          rctx->cname = name;
          rctx->crdataset = rdataset;
          break;
        }
      }
      break;

    case dns_namereln_subdomain:
      /*
       * Don't accept DNAME from parent namespace.
       */
      if (name_external(name, dns_rdatatype_dname, fctx)) {
        continue;
      }

      /*
       * In-scope DNAME records must have at least
       * as many labels as the domain being queried.
       * They also must be less that qname's labels
       * and any previously found dname.
       */
      if (nlabels >= rctx->dname_labels ||
          nlabels < rctx->domain_labels)
      {
        continue;
      }

      /*
       * We are looking for the shortest DNAME if
       * there are multiple ones (which there
       * shouldn't be).
       */
      ISC_LIST_FOREACH(name->list, rdataset, link) {
        if (rdataset->type != dns_rdatatype_dname) {
          continue;
        }
        rctx->dname = name;
        rctx->drdataset = rdataset;
        rctx->dname_labels = nlabels;
        break;
      }
      break;
    default:
      break;
    }
  }

  /*
   * If a DNAME was found, then any CNAME or other answer matching
   * QNAME that may also have been found must be ignored.
   * Similarly, if a matching answer was found along with a CNAME,
   * the CNAME must be ignored.
   */
  if (rctx->dname != NULL) {
    rctx->aname = NULL;
    rctx->ardataset = NULL;
    rctx->cname = NULL;
    rctx->crdataset = NULL;
  } else if (rctx->aname != NULL) {
    rctx->cname = NULL;
    rctx->crdataset = NULL;
  }
}

/*
 * rctx_answer_any():
 * Handle responses to queries of type ANY. Scan the answer section,
 * and as long as each RRset is of a type that is valid in the answer
 * section, and the rdata isn't filtered, cache it.
 */
static isc_result_t
rctx_answer_any(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  ISC_LIST_FOREACH(rctx->aname->list, rdataset, link) {
    if (!validinanswer(rdataset, fctx)) {
      rctx->result = DNS_R_FORMERR;
      return ISC_R_COMPLETE;
    }

    if (dns_rdatatype_issig(fctx->type) &&
        rdataset->type != fctx->type)
    {
      continue;
    }

    if (dns_rdatatype_isaddr(rdataset->type) &&
        !is_answeraddress_allowed(fctx->res->view, rctx->aname,
                rdataset))
    {
      rctx->result = DNS_R_SERVFAIL;
      return ISC_R_COMPLETE;
    }

    if (dns_rdatatype_isalias(rdataset->type) &&
        !is_answertarget_allowed(fctx, fctx->name, rctx->aname,
               rdataset, NULL))
    {
      rctx->result = DNS_R_SERVFAIL;
      return ISC_R_COMPLETE;
    }

    rctx->aname->attributes.cache = true;
    rctx->aname->attributes.answer = true;
    if (dns_rdatatype_issig(rdataset->type)) {
      rdataset->attributes.answersig = true;
    } else {
      rdataset->attributes.answer = true;
    }
    rdataset->attributes.cache = true;
    rdataset->trust = rctx->trust;
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_answer_match():
 * Handle responses that match the QNAME/QTYPE of the resolver query.
 * If QTYPE is valid in the answer section and the rdata isn't filtered,
 * the answer can be cached. If there is additional section data related
 * to the answer, it can be cached as well.
 */
static isc_result_t
rctx_answer_match(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  if (!validinanswer(rctx->ardataset, fctx)) {
    rctx->result = DNS_R_FORMERR;
    return ISC_R_COMPLETE;
  }

  if (dns_rdatatype_isaddr(rctx->ardataset->type) &&
      !is_answeraddress_allowed(fctx->res->view, rctx->aname,
              rctx->ardataset))
  {
    rctx->result = DNS_R_SERVFAIL;
    return ISC_R_COMPLETE;
  }
  if (dns_rdatatype_isalias(rctx->ardataset->type) &&
      rctx->type != rctx->ardataset->type &&
      rctx->type != dns_rdatatype_any &&
      !is_answertarget_allowed(fctx, fctx->name, rctx->aname,
             rctx->ardataset, NULL))
  {
    rctx->result = DNS_R_SERVFAIL;
    return ISC_R_COMPLETE;
  }

  rctx->aname->attributes.cache = true;
  rctx->aname->attributes.answer = true;
  rctx->ardataset->attributes.answer = true;
  rctx->ardataset->attributes.cache = true;
  rctx->ardataset->trust = rctx->trust;
  (void)dns_rdataset_additionaldata(rctx->ardataset, rctx->aname,
            check_related, rctx,
            DNS_RDATASET_MAXADDITIONAL);

  ISC_LIST_FOREACH(rctx->aname->list, sigrdataset, link) {
    if (!validinanswer(sigrdataset, fctx)) {
      rctx->result = DNS_R_FORMERR;
      return ISC_R_COMPLETE;
    }

    if (!dns_rdataset_issigtype(sigrdataset, rctx->type)) {
      continue;
    }

    sigrdataset->attributes.answersig = true;
    sigrdataset->attributes.cache = true;
    sigrdataset->trust = rctx->trust;
    break;
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_answer_cname():
 * Handle answers containing a CNAME. Cache the CNAME, and flag that
 * there may be additional chain answers to find.
 */
static isc_result_t
rctx_answer_cname(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  if (!validinanswer(rctx->crdataset, fctx)) {
    rctx->result = DNS_R_FORMERR;
    return ISC_R_COMPLETE;
  }

  if (rctx->type == dns_rdatatype_rrsig ||
      rctx->type == dns_rdatatype_key || rctx->type == dns_rdatatype_nsec)
  {
    char buf[DNS_RDATATYPE_FORMATSIZE];
    dns_rdatatype_format(rctx->type, buf, sizeof(buf));
    log_formerr(fctx, "CNAME response for %s RR", buf);
    rctx->result = DNS_R_FORMERR;
    return ISC_R_COMPLETE;
  }

  if (!is_answertarget_allowed(fctx, fctx->name, rctx->cname,
             rctx->crdataset, NULL))
  {
    rctx->result = DNS_R_SERVFAIL;
    return ISC_R_COMPLETE;
  }

  rctx->cname->attributes.cache = true;
  rctx->cname->attributes.answer = true;
  rctx->cname->attributes.chaining = true;
  rctx->crdataset->attributes.answer = true;
  rctx->crdataset->attributes.cache = true;
  rctx->crdataset->attributes.chaining = true;
  rctx->crdataset->trust = rctx->trust;

  ISC_LIST_FOREACH(rctx->cname->list, sigrdataset, link) {
    if (!validinanswer(sigrdataset, fctx)) {
      rctx->result = DNS_R_FORMERR;
      return ISC_R_COMPLETE;
    }

    if (sigrdataset->type != dns_rdatatype_rrsig ||
        sigrdataset->covers != dns_rdatatype_cname)
    {
      continue;
    }

    sigrdataset->attributes.answersig = true;
    sigrdataset->attributes.cache = true;
    sigrdataset->trust = rctx->trust;
    break;
  }

  rctx->chaining = true;
  return ISC_R_SUCCESS;
}

/*
 * rctx_answer_dname():
 * Handle responses with covering DNAME records.
 */
static isc_result_t
rctx_answer_dname(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  if (!validinanswer(rctx->drdataset, fctx)) {
    rctx->result = DNS_R_FORMERR;
    return ISC_R_COMPLETE;
  }

  if (!is_answertarget_allowed(fctx, fctx->name, rctx->dname,
             rctx->drdataset, &rctx->chaining))
  {
    rctx->result = DNS_R_SERVFAIL;
    return ISC_R_COMPLETE;
  }

  rctx->dname->attributes.cache = true;
  rctx->dname->attributes.answer = true;
  rctx->dname->attributes.chaining = true;
  rctx->drdataset->attributes.answer = true;
  rctx->drdataset->attributes.cache = true;
  rctx->drdataset->attributes.chaining = true;
  rctx->drdataset->trust = rctx->trust;

  ISC_LIST_FOREACH(rctx->dname->list, sigrdataset, link) {
    if (!validinanswer(sigrdataset, fctx)) {
      rctx->result = DNS_R_FORMERR;
      return ISC_R_COMPLETE;
    }

    if (sigrdataset->type != dns_rdatatype_rrsig ||
        sigrdataset->covers != dns_rdatatype_dname)
    {
      continue;
    }

    sigrdataset->attributes.answersig = true;
    sigrdataset->attributes.cache = true;
    sigrdataset->trust = rctx->trust;
    break;
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_authority_positive():
 * Examine the records in the authority section (if there are any) for a
 * positive answer.  We expect the names for all rdatasets in this
 * section to be subdomains of the domain being queried; any that are
 * not are skipped.  We expect to find only *one* owner name; any names
 * after the first one processed are ignored. We expect to find only
 * rdatasets of type NS, RRSIG, or SIG; all others are ignored. Whatever
 * remains can be cached at trust level authauthority or additional
 * (depending on whether the AA bit was set on the answer).
 */
static void
rctx_authority_positive(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  dns_message_t *msg = rctx->query->rmessage;
  MSG_SECTION_FOREACH(msg, DNS_SECTION_AUTHORITY, name) {
    if (!name_external(name, dns_rdatatype_ns, fctx)) {
      /*
       * We expect to find NS or SIG NS rdatasets, and
       * nothing else.
       */
      ISC_LIST_FOREACH(name->list, rdataset, link) {
        if (dns_rdataset_matchestype(rdataset,
                   dns_rdatatype_ns))
        {
          name->attributes.cache = true;
          rdataset->attributes.cache = true;

          if (rctx->aa) {
            rdataset->trust =
              dns_trust_authauthority;
          } else {
            rdataset->trust =
              dns_trust_additional;
          }

          if (rdataset->type == dns_rdatatype_ns)
          {
            rctx->ns_name = name;
            rctx->ns_rdataset = rdataset;
          }
          /*
           * Mark any additional data
           * related to this rdataset.
           */
          (void)dns_rdataset_additionaldata(
            rdataset, name, check_related,
            rctx,
            DNS_RDATASET_MAXADDITIONAL);
          return;
        }
      }
    }
  }
}

/*
 * rctx_answer_none():
 * Handles a response without an answer: this is either a negative
 * response (NXDOMAIN or NXRRSET) or a referral. Determine which it is,
 * then either scan the authority section for negative caching and
 * DNSSEC proof of nonexistence, or else call rctx_referral().
 */
static isc_result_t
rctx_answer_none(respctx_t *rctx) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;

  FCTXTRACE("rctx_answer_none");

  rctx_answer_init(rctx);

  /*
   * Sometimes we can tell if its a negative response by looking
   * at the message header.
   */
  if (rctx->query->rmessage->rcode == dns_rcode_nxdomain ||
      (rctx->query->rmessage->counts[DNS_SECTION_ANSWER] == 0 &&
       rctx->query->rmessage->counts[DNS_SECTION_AUTHORITY] == 0))
  {
    rctx->negative = true;
  }

  /*
   * Process the authority section
   */
  result = rctx_authority_negative(rctx);
  if (result == ISC_R_COMPLETE) {
    return rctx->result;
  }

  log_ns_ttl(fctx, "rctx_answer_none");

  if (rctx->ns_rdataset != NULL &&
      dns_name_equal(fctx->domain, rctx->ns_name) &&
      !dns_name_equal(rctx->ns_name, dns_rootname))
  {
    trim_ns_ttl(fctx, rctx->ns_name, rctx->ns_rdataset);
  }

  /*
   * A negative response has a SOA record (Type 2)
   * and a optional NS RRset (Type 1) or it has neither
   * a SOA or a NS RRset (Type 3, handled above) or
   * rcode is NXDOMAIN (handled above) in which case
   * the NS RRset is allowed (Type 4).
   */
  if (rctx->soa_name != NULL) {
    rctx->negative = true;
  }

  /*
   * Process DNSSEC records in the authority section.
   */
  result = rctx_authority_dnssec(rctx);
  if (result == ISC_R_COMPLETE) {
    return rctx->result;
  }

  /*
   * Trigger lookups for DNS nameservers.
   */
  if (rctx->negative &&
      rctx->query->rmessage->rcode == dns_rcode_noerror &&
      fctx->type == dns_rdatatype_ds && rctx->soa_name != NULL &&
      dns_name_equal(rctx->soa_name, fctx->name) &&
      !dns_name_equal(fctx->name, dns_rootname))
  {
    return DNS_R_CHASEDSSERVERS;
  }

  /*
   * Did we find anything?
   */
  if (!rctx->negative && rctx->ns_name == NULL) {
    /*
     * The responder is insane.
     */
    if (rctx->found_name == NULL) {
      log_formerr(fctx, "invalid response");
      return DNS_R_FORMERR;
    }
    if (!dns_name_issubdomain(rctx->found_name, fctx->domain)) {
      char nbuf[DNS_NAME_FORMATSIZE];
      char dbuf[DNS_NAME_FORMATSIZE];
      char tbuf[DNS_RDATATYPE_FORMATSIZE];

      dns_rdatatype_format(rctx->found_type, tbuf,
               sizeof(tbuf));
      dns_name_format(rctx->found_name, nbuf, sizeof(nbuf));
      dns_name_format(fctx->domain, dbuf, sizeof(dbuf));

      log_formerr(fctx,
            "Name %s (%s) not subdomain"
            " of zone %s -- invalid response",
            nbuf, tbuf, dbuf);
    } else {
      log_formerr(fctx, "invalid response");
    }
    return DNS_R_FORMERR;
  }

  /*
   * If we found both NS and SOA, they should be the same name.
   */
  if (rctx->ns_name != NULL && rctx->soa_name != NULL &&
      rctx->ns_name != rctx->soa_name)
  {
    log_formerr(fctx, "NS/SOA mismatch");
    return DNS_R_FORMERR;
  }

  /*
   * Handle a referral.
   */
  result = rctx_referral(rctx);
  if (result == ISC_R_COMPLETE) {
    return rctx->result;
  }

  /*
   * Since we're not doing a referral, we don't want to cache any
   * NS RRs we may have found.
   */
  if (rctx->ns_name != NULL) {
    rctx->ns_name->attributes.cache = false;
  }

  if (rctx->negative) {
    FCTX_ATTR_SET(fctx, FCTX_ATTR_WANTNCACHE);
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_authority_negative():
 * Scan the authority section of a negative answer, handling
 * NS and SOA records. (Note that this function does *not* handle
 * DNSSEC records; those are addressed separately in
 * rctx_authority_dnssec() below.)
 */
static isc_result_t
rctx_authority_negative(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;
  dns_section_t section;

  section = DNS_SECTION_AUTHORITY;

  dns_message_t *msg = rctx->query->rmessage;
  MSG_SECTION_FOREACH(msg, section, name) {
    if (!dns_name_issubdomain(name, fctx->domain)) {
      continue;
    }

    ISC_LIST_FOREACH(name->list, rdataset, link) {
      dns_rdatatype_t type = rdataset->type;
      if (dns_rdatatype_issig(rdataset->type)) {
        type = rdataset->covers;
      }
      if ((type == dns_rdatatype_ns ||
           type == dns_rdatatype_soa) &&
          !dns_name_issubdomain(fctx->name, name))
      {
        char qbuf[DNS_NAME_FORMATSIZE];
        char nbuf[DNS_NAME_FORMATSIZE];
        char tbuf[DNS_RDATATYPE_FORMATSIZE];
        dns_rdatatype_format(type, tbuf, sizeof(tbuf));
        dns_name_format(name, nbuf, sizeof(nbuf));
        dns_name_format(fctx->name, qbuf, sizeof(qbuf));
        log_formerr(fctx,
              "unrelated %s %s in "
              "%s authority section",
              tbuf, nbuf, qbuf);
        break;
      }

      switch (type) {
      case dns_rdatatype_ns:
        /*
         * NS or RRSIG NS.
         *
         * Only one set of NS RRs is allowed.
         */
        if (rdataset->type == dns_rdatatype_ns) {
          if (rctx->ns_name != NULL &&
              name != rctx->ns_name)
          {
            log_formerr(fctx, "multiple NS "
                  "RRsets "
                  "in "
                  "authority "
                  "section");
            rctx->result = DNS_R_FORMERR;
            return ISC_R_COMPLETE;
          }
          rctx->ns_name = name;
          rctx->ns_rdataset = rdataset;
        }
        name->attributes.cache = true;
        rdataset->attributes.cache = true;
        rdataset->trust = dns_trust_glue;
        break;
      case dns_rdatatype_soa:
        /*
         * SOA, or RRSIG SOA.
         *
         * Only one SOA is allowed.
         */
        if (rdataset->type == dns_rdatatype_soa) {
          if (rctx->soa_name != NULL &&
              name != rctx->soa_name)
          {
            log_formerr(fctx, "multiple "
                  "SOA RRs "
                  "in "
                  "authority "
                  "section");
            rctx->result = DNS_R_FORMERR;
            return ISC_R_COMPLETE;
          }
          rctx->soa_name = name;
        }
        name->attributes.ncache = true;
        rdataset->attributes.ncache = true;
        if (rctx->aa) {
          rdataset->trust =
            dns_trust_authauthority;
        } else if (ISFORWARDER(fctx->addrinfo)) {
          rdataset->trust = dns_trust_answer;
        } else {
          rdataset->trust = dns_trust_additional;
        }
        break;
      default:
        continue;
      }
    }
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_authority_dnssec():
 *
 * Scan the authority section of a negative answer or referral,
 * handling DNSSEC records (i.e. NSEC, NSEC3, DS).
 */
static isc_result_t
rctx_authority_dnssec(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;

  dns_message_t *msg = rctx->query->rmessage;
  MSG_SECTION_FOREACH(msg, DNS_SECTION_AUTHORITY, name) {
    if (!dns_name_issubdomain(name, fctx->domain)) {
      /*
       * Invalid name found; preserve it for logging
       * later.
       */
      rctx->found_name = name;
      rctx->found_type = ISC_LIST_HEAD(name->list)->type;
      continue;
    }

    ISC_LIST_FOREACH(name->list, rdataset, link) {
      bool secure_domain = false;
      dns_rdatatype_t type = rdataset->type;

      if (dns_rdatatype_issig(type)) {
        type = rdataset->covers;
      }

      switch (type) {
      case dns_rdatatype_nsec:
      case dns_rdatatype_nsec3:
        if (rctx->negative) {
          name->attributes.ncache = true;
          rdataset->attributes.ncache = true;
        } else if (type == dns_rdatatype_nsec) {
          name->attributes.cache = true;
          rdataset->attributes.cache = true;
        }

        if (rctx->aa) {
          rdataset->trust =
            dns_trust_authauthority;
        } else if (ISFORWARDER(fctx->addrinfo)) {
          rdataset->trust = dns_trust_answer;
        } else {
          rdataset->trust = dns_trust_additional;
        }
        /*
         * No additional data needs to be
         * marked.
         */
        break;
      case dns_rdatatype_ds:
        /*
         * DS or SIG DS.
         *
         * These should only be here if this is
         * a referral, and there should only be
         * one DS RRset.
         */
        if (rctx->ns_name == NULL) {
          log_formerr(fctx, "DS with no "
                "referral");
          rctx->result = DNS_R_FORMERR;
          return ISC_R_COMPLETE;
        }

        if (rdataset->type == dns_rdatatype_ds) {
          if (rctx->ds_name != NULL &&
              name != rctx->ds_name)
          {
            log_formerr(fctx, "DS doesn't "
                  "match "
                  "referral "
                  "(NS)");
            rctx->result = DNS_R_FORMERR;
            return ISC_R_COMPLETE;
          }
          rctx->ds_name = name;
        }

        name->attributes.cache = true;
        rdataset->attributes.cache = true;

        secure_domain = issecuredomain(fctx, name,
                     dns_rdatatype_ds,
                     fctx->now, NULL);
        if (secure_domain) {
          rdataset->trust =
            dns_trust_pending_answer;
        } else if (rctx->aa) {
          rdataset->trust =
            dns_trust_authauthority;
        } else if (ISFORWARDER(fctx->addrinfo)) {
          rdataset->trust = dns_trust_answer;
        } else {
          rdataset->trust = dns_trust_additional;
        }
        break;
      default:
        continue;
      }
    }
  }

  return ISC_R_SUCCESS;
}

/*
 * rctx_referral():
 * Handles referral responses. Check for sanity, find glue as needed,
 * and update the fetch context to follow the delegation.
 */
static isc_result_t
rctx_referral(respctx_t *rctx) {
  isc_result_t result;
  fetchctx_t *fctx = rctx->fctx;

  if (rctx->negative || rctx->ns_name == NULL) {
    return ISC_R_SUCCESS;
  }

  /*
   * We already know ns_name is a subdomain of fctx->domain.
   * If ns_name is equal to fctx->domain, we're not making
   * progress.  We return DNS_R_FORMERR so that we'll keep
   * trying other servers.
   */
  if (dns_name_equal(rctx->ns_name, fctx->domain)) {
    log_formerr(fctx, "non-improving referral");
    rctx->result = DNS_R_FORMERR;
    return ISC_R_COMPLETE;
  }

  /*
   * If the referral name is not a parent of the query
   * name, consider the responder insane.
   */
  if (!dns_name_issubdomain(fctx->name, rctx->ns_name)) {
    /* Logged twice */
    log_formerr(fctx, "referral to non-parent");
    FCTXTRACE("referral to non-parent");
    rctx->result = DNS_R_FORMERR;
    return ISC_R_COMPLETE;
  }

  /*
   * Mark any additional data related to this rdataset.
   * It's important that we do this before we change the
   * query domain.
   */
  INSIST(rctx->ns_rdataset != NULL);
  FCTX_ATTR_SET(fctx, FCTX_ATTR_GLUING);
  /*
   * We want to append **all** the GLUE records here.
   */
  (void)dns_rdataset_additionaldata(rctx->ns_rdataset, rctx->ns_name,
            check_related, rctx, 0);
#if CHECK_FOR_GLUE_IN_ANSWER
  /*
   * Look in the answer section for "glue" that is incorrectly
   * returned as a answer.  This is needed if the server also
   * minimizes the response size by not adding records to the
   * additional section that are in the answer section or if
   * the record gets dropped due to message size constraints.
   */
  if (rctx->glue_in_answer && dns_rdatatype_isaddr(fctx->type)) {
    (void)dns_rdataset_additionaldata(
      rctx->ns_rdataset, rctx->ns_name, check_answer, fctx);
  }
#endif /* if CHECK_FOR_GLUE_IN_ANSWER */
  FCTX_ATTR_CLR(fctx, FCTX_ATTR_GLUING);

  /*
   * NS rdatasets with 0 TTL cause problems.
   * dns_view_findzonecut() will not find them when we
   * try to follow the referral, and we'll SERVFAIL
   * because the best nameservers are now above QDOMAIN.
   * We force the TTL to 1 second to prevent this.
   */
  if (rctx->ns_rdataset->ttl == 0) {
    rctx->ns_rdataset->ttl = 1;
  }

  /*
   * Set the current query domain to the referral name.
   *
   * XXXRTH  We should check if we're in forward-only mode, and
   *    if so we should bail out.
   */
  INSIST(dns_name_countlabels(fctx->domain) > 0);
  fcount_decr(fctx);

  if (dns_rdataset_isassociated(&fctx->nameservers)) {
    dns_rdataset_disassociate(&fctx->nameservers);
  }

  dns_name_copy(rctx->ns_name, fctx->domain);

  if ((fctx->options & DNS_FETCHOPT_QMINIMIZE) != 0) {
    dns_name_copy(rctx->ns_name, fctx->qmindcname);

    fctx_minimize_qname(fctx);
  }

  result = fcount_incr(fctx, false);
  if (result != ISC_R_SUCCESS) {
    rctx->result = result;
    return ISC_R_COMPLETE;
  }

  FCTX_ATTR_SET(fctx, FCTX_ATTR_WANTCACHE);
  fctx->ns_ttl_ok = false;
  log_ns_ttl(fctx, "DELEGATION");
  rctx->result = DNS_R_DELEGATION;

  /*
   * Reinitialize 'rctx' to prepare for following the delegation:
   * set the get_nameservers and next_server flags appropriately
   * and reset the fetch context counters.
   *
   */
  if ((rctx->fctx->options & DNS_FETCHOPT_NOFOLLOW) == 0) {
    rctx->get_nameservers = true;
    rctx->next_server = true;
    rctx->fctx->restarts = 0;
    rctx->fctx->referrals++;
    rctx->fctx->querysent = 0;
    rctx->fctx->lamecount = 0;
    rctx->fctx->quotacount = 0;
    rctx->fctx->neterr = 0;
    rctx->fctx->badresp = 0;
    rctx->fctx->adberr = 0;
  }

  return ISC_R_COMPLETE;
}

/*
 * rctx_additional():
 * Scan the additional section of a response to find records related
 * to answers we were interested in.
 */
static void
rctx_additional(respctx_t *rctx) {
  bool rescan;
  dns_section_t section = DNS_SECTION_ADDITIONAL;

again:
  rescan = false;

  dns_message_t *msg = rctx->query->rmessage;
  MSG_SECTION_FOREACH(msg, section, name) {
    if (!name->attributes.chase) {
      continue;
    }
    name->attributes.chase = false;
    ISC_LIST_FOREACH(name->list, rdataset, link) {
      if (CHASE(rdataset)) {
        rdataset->attributes.chase = false;
        (void)dns_rdataset_additionaldata(
          rdataset, name, check_related, rctx,
          DNS_RDATASET_MAXADDITIONAL);
        rescan = true;
      }
    }
  }
  if (rescan) {
    goto again;
  }
}

/*
 * rctx_nextserver():
 * We found something wrong with the remote server, but it may be
 * useful to try another one.
 */
static void
rctx_nextserver(respctx_t *rctx, dns_message_t *message,
    dns_adbaddrinfo_t *addrinfo, isc_result_t result) {
  fetchctx_t *fctx = rctx->fctx;
  bool retrying = true;

  if (result == DNS_R_FORMERR) {
    rctx->broken_server = DNS_R_FORMERR;
  }
  if (rctx->broken_server != ISC_R_SUCCESS) {
    /*
     * Add this server to the list of bad servers for
     * this fctx.
     */
    add_bad(fctx, message, addrinfo, rctx->broken_server,
      rctx->broken_type);
  }

  if (rctx->get_nameservers) {
    dns_fixedname_t foundname, founddc;
    dns_name_t *name, *fname, *dcname;
    unsigned int findoptions = 0;

    fname = dns_fixedname_initname(&foundname);
    dcname = dns_fixedname_initname(&founddc);

    if (result != ISC_R_SUCCESS) {
      fctx_done_detach(&rctx->fctx, DNS_R_SERVFAIL);
      return;
    }
    if (dns_rdatatype_atparent(fctx->type)) {
      findoptions |= DNS_DBFIND_NOEXACT;
    }
    /* FIXME: Why??? */
    if ((rctx->retryopts & DNS_FETCHOPT_UNSHARED) == 0) {
      name = fctx->name;
    } else {
      name = fctx->domain;
    }
    result = dns_view_findzonecut(
      fctx->res->view, name, fname, dcname, fctx->now,
      findoptions, true, true, &fctx->nameservers, NULL);
    if (result != ISC_R_SUCCESS) {
      FCTXTRACE("couldn't find a zonecut");
      fctx_done_detach(&rctx->fctx, DNS_R_SERVFAIL);
      return;
    }
    if (!dns_name_issubdomain(fname, fctx->domain)) {
      /*
       * The best nameservers are now above our
       * QDOMAIN.
       */
      FCTXTRACE("nameservers now above QDOMAIN");
      fctx_done_detach(&rctx->fctx, DNS_R_SERVFAIL);
      return;
    }

    fcount_decr(fctx);

    dns_name_copy(fname, fctx->domain);
    dns_name_copy(dcname, fctx->qmindcname);

    result = fcount_incr(fctx, true);
    if (result != ISC_R_SUCCESS) {
      fctx_done_detach(&rctx->fctx, DNS_R_SERVFAIL);
      return;
    }
    fctx->ns_ttl = fctx->nameservers.ttl;
    fctx->ns_ttl_ok = true;
    fctx_cancelqueries(fctx, true, false);
    fctx_cleanup(fctx);
    retrying = false;
  }

  /*
   * Try again.
   */
  fctx_try(fctx, retrying);
}

/*
 * rctx_resend():
 *
 * Resend the query, probably with the options changed. Calls
 * fctx_query(), passing rctx->retryopts (which is based on
 * query->options, but may have been updated since the last time
 * fctx_query() was called).
 */
static void
rctx_resend(respctx_t *rctx, dns_adbaddrinfo_t *addrinfo) {
  fetchctx_t *fctx = rctx->fctx;
  isc_result_t result;

  FCTXTRACE("resend");
  inc_stats(fctx->res, dns_resstatscounter_retry);
  result = fctx_query(fctx, addrinfo, rctx->retryopts);
  if (result != ISC_R_SUCCESS) {
    fctx_done_detach(&rctx->fctx, result);
  }
}

/*
 * rctx_next():
 * We got what appeared to be a response but it didn't match the
 * question or the cookie; it may have been meant for someone else, or
 * it may be a spoofing attack. Drop it and continue listening for the
 * response we wanted.
 */
static isc_result_t
rctx_next(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;
  isc_result_t result;

  FCTXTRACE("nextitem");
  inc_stats(rctx->fctx->res, dns_resstatscounter_nextitem);
  INSIST(rctx->query->dispentry != NULL);
  dns_message_reset(rctx->query->rmessage, DNS_MESSAGE_INTENTPARSE);
  result = dns_dispatch_getnext(rctx->query->dispentry);
  return result;
}

/*
 * rctx_chaseds():
 * Look up the parent zone's NS records so that DS records can be
 * fetched.
 */
static void
rctx_chaseds(respctx_t *rctx, dns_message_t *message,
       dns_adbaddrinfo_t *addrinfo, isc_result_t result) {
  fetchctx_t *fctx = rctx->fctx;
  unsigned int n;

  add_bad(fctx, message, addrinfo, result, rctx->broken_type);
  fctx_cancelqueries(fctx, true, false);
  fctx_cleanup(fctx);

  n = dns_name_countlabels(fctx->name);
  dns_name_getlabelsequence(fctx->name, 1, n - 1, fctx->nsname);

  FCTXTRACE("suspending DS lookup to find parent's NS records");

  fetchctx_ref(fctx);
  result = dns_resolver_createfetch(
    fctx->res, fctx->nsname, dns_rdatatype_ns, NULL, NULL, NULL,
    NULL, 0, fctx->options, 0, fctx->qc, fctx->gqc, fctx->loop,
    resume_dslookup, fctx, &fctx->edectx, &fctx->nsrrset, NULL,
    &fctx->nsfetch);
  if (result != ISC_R_SUCCESS) {
    if (result == DNS_R_DUPLICATE) {
      result = DNS_R_SERVFAIL;
    }
    fctx_done_detach(&rctx->fctx, result);
    fetchctx_detach(&fctx);
    return;
  }
}

/*
 * rctx_done():
 * This resolver query response is finished, either because we
 * encountered a problem or because we've gotten all the information
 * from it that we can.  We either wait for another response, resend the
 * query to the same server, resend to a new server, or clean up and
 * shut down the fetch.
 */
static void
rctx_done(respctx_t *rctx, isc_result_t result) {
  resquery_t *query = rctx->query;
  fetchctx_t *fctx = rctx->fctx;
  dns_adbaddrinfo_t *addrinfo = query->addrinfo;
  dns_message_t *message = NULL;

  /*
   * Need to attach to the message until the scope
   * of this function ends, since there are many places
   * where the message is used and/or may be destroyed
   * before this function ends.
   */
  dns_message_attach(query->rmessage, &message);

  FCTXTRACE4("query canceled in rctx_done();",
       rctx->no_response ? "no response" : "responding", result);

#ifdef ENABLE_AFL
  if (dns_fuzzing_resolver &&
      (rctx->next_server || rctx->resend || rctx->nextitem))
  {
    fctx_cancelquery(&query, rctx->finish, rctx->no_response,
         false);
    fctx_done_detach(&rctx->fctx, DNS_R_SERVFAIL);
    goto detach;
  }
#endif /* ifdef ENABLE_AFL */

  if (rctx->nextitem) {
    REQUIRE(!rctx->next_server);
    REQUIRE(!rctx->resend);

    result = rctx_next(rctx);
    if (result == ISC_R_SUCCESS) {
      goto detach;
    }
  }

  /* Cancel the query */
  fctx_cancelquery(&query, rctx->finish, rctx->no_response, false);

  /*
   * If nobody's waiting for results, don't resend or try next server.
   */
  LOCK(&fctx->lock);
  if (ISC_LIST_EMPTY(fctx->resps)) {
    rctx->next_server = false;
    rctx->resend = false;
  }
  UNLOCK(&fctx->lock);

  if (rctx->next_server) {
    rctx_nextserver(rctx, message, addrinfo, result);
  } else if (rctx->resend) {
    rctx_resend(rctx, addrinfo);
  } else if (result == DNS_R_CHASEDSSERVERS) {
    rctx_chaseds(rctx, message, addrinfo, result);
  } else if (result == ISC_R_SUCCESS && !HAVE_ANSWER(fctx)) {
    /*
     * All has gone well so far, but we are waiting for the DNSSEC
     * validator to validate the answer.
     */
    FCTXTRACE("wait for validator");
    fctx_cancelqueries(fctx, true, false);
  } else {
    /*
     * We're done.
     */
    fctx_done_detach(&rctx->fctx, result);
  }

detach:
  dns_message_detach(&message);
}

/*
 * rctx_logpacket():
 * Log the incoming packet; also log to DNSTAP if configured.
 */
static void
rctx_logpacket(respctx_t *rctx) {
  fetchctx_t *fctx = rctx->fctx;
  isc_result_t result;
  isc_sockaddr_t localaddr, *la = NULL;
#ifdef HAVE_DNSTAP
  unsigned char zone[DNS_NAME_MAXWIRE];
  dns_transport_type_t transport_type;
  dns_dtmsgtype_t dtmsgtype;
  dns_compress_t cctx;
  isc_region_t zr;
  isc_buffer_t zb;
#endif /* HAVE_DNSTAP */

  result = dns_dispentry_getlocaladdress(rctx->query->dispentry,
                 &localaddr);
  if (result == ISC_R_SUCCESS) {
    la = &localaddr;
  }

  dns_message_logpacketfromto(
    rctx->query->rmessage, "received packet",
    &rctx->query->addrinfo->sockaddr, la, DNS_LOGCATEGORY_RESOLVER,
    DNS_LOGMODULE_PACKETS, ISC_LOG_DEBUG(10), fctx->mctx);

#ifdef HAVE_DNSTAP
  /*
   * Log the response via dnstap.
   */
  memset(&zr, 0, sizeof(zr));
  dns_compress_init(&cctx, fctx->mctx, 0);
  dns_compress_setpermitted(&cctx, false);
  isc_buffer_init(&zb, zone, sizeof(zone));
  result = dns_name_towire(fctx->domain, &cctx, &zb);
  if (result == ISC_R_SUCCESS) {
    isc_buffer_usedregion(&zb, &zr);
  }
  dns_compress_invalidate(&cctx);

  if ((fctx->qmessage->flags & DNS_MESSAGEFLAG_RD) != 0) {
    dtmsgtype = DNS_DTTYPE_FR;
  } else {
    dtmsgtype = DNS_DTTYPE_RR;
  }

  if (rctx->query->addrinfo->transport != NULL) {
    transport_type = dns_transport_get_type(
      rctx->query->addrinfo->transport);
  } else if ((rctx->query->options & DNS_FETCHOPT_TCP) != 0) {
    transport_type = DNS_TRANSPORT_TCP;
  } else {
    transport_type = DNS_TRANSPORT_UDP;
  }

  dns_dt_send(fctx->res->view, dtmsgtype, la,
        &rctx->query->addrinfo->sockaddr, transport_type, &zr,
        &rctx->query->start, NULL, &rctx->buffer);
#endif /* HAVE_DNSTAP */
}

/*
 * rctx_badserver():
 * Is the remote server broken, or does it dislike us?
 */
static isc_result_t
rctx_badserver(respctx_t *rctx, isc_result_t result) {
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;
  isc_buffer_t b;
  char code[64];
  dns_rcode_t rcode = rctx->query->rmessage->rcode;

  QTRACE("rctx_badserver");

  if (rcode == dns_rcode_noerror || rcode == dns_rcode_yxdomain ||
      rcode == dns_rcode_nxdomain)
  {
    return ISC_R_SUCCESS;
  }

  if ((rcode == dns_rcode_formerr) && rctx->opt == NULL &&
      (rctx->retryopts & DNS_FETCHOPT_NOEDNS0) == 0)
  {
    /*
     * It's very likely they don't like EDNS0.
     */
    rctx->retryopts |= DNS_FETCHOPT_NOEDNS0;
    rctx->resend = true;
    /*
     * Remember that they may not like EDNS0.
     */
    inc_stats(fctx->res, dns_resstatscounter_edns0fail);
  } else if (rcode == dns_rcode_formerr) {
    if (query->rmessage->cc_echoed) {
      /*
       * Retry without DNS COOKIE.
       */
      query->addrinfo->flags |= FCTX_ADDRINFO_NOCOOKIE;
      rctx->resend = true;
      log_formerr(fctx, "server sent FORMERR with echoed DNS "
            "COOKIE");
    } else {
      /*
       * The server (or forwarder) doesn't understand us,
       * but others might.
       */
      rctx->next_server = true;
      rctx->broken_server = DNS_R_REMOTEFORMERR;
      log_formerr(fctx, "server sent FORMERR");
    }
  } else if (rcode == dns_rcode_badvers) {
    unsigned int version;
#if DNS_EDNS_VERSION > 0
    unsigned int flags, mask;
#endif /* if DNS_EDNS_VERSION > 0 */

    INSIST(rctx->opt != NULL);
    version = (rctx->opt->ttl >> 16) & 0xff;
#if DNS_EDNS_VERSION > 0
    flags = (version << DNS_FETCHOPT_EDNSVERSIONSHIFT) |
      DNS_FETCHOPT_EDNSVERSIONSET;
    mask = DNS_FETCHOPT_EDNSVERSIONMASK |
           DNS_FETCHOPT_EDNSVERSIONSET;
#endif /* if DNS_EDNS_VERSION > 0 */

    /*
     * Record that we got a good EDNS response.
     */
    if (query->ednsversion > (int)version &&
        !EDNSOK(query->addrinfo))
    {
      dns_adb_changeflags(fctx->adb, query->addrinfo,
              FCTX_ADDRINFO_EDNSOK,
              FCTX_ADDRINFO_EDNSOK);
    }

    /*
     * RFC 2671 was not clear that unknown options should
     * be ignored.  RFC 6891 is clear that that they
     * should be ignored. If we are supporting the
     * experimental EDNS > 0 then perform strict
     * version checking of badvers responses.  We won't
     * be sending COOKIE etc. in that case.
     */
#if DNS_EDNS_VERSION > 0
    if ((int)version < query->ednsversion) {
      dns_adb_changeflags(fctx->adb, query->addrinfo, flags,
              mask);
      rctx->resend = true;
    } else {
      rctx->broken_server = DNS_R_BADVERS;
      rctx->next_server = true;
    }
#else  /* if DNS_EDNS_VERSION > 0 */
    rctx->broken_server = DNS_R_BADVERS;
    rctx->next_server = true;
#endif /* if DNS_EDNS_VERSION > 0 */
  } else if (rcode == dns_rcode_badcookie && rctx->query->rmessage->cc_ok)
  {
    /*
     * We have recorded the new cookie.
     */
    if (BADCOOKIE(query->addrinfo)) {
      rctx->retryopts |= DNS_FETCHOPT_TCP;
    }
    query->addrinfo->flags |= FCTX_ADDRINFO_BADCOOKIE;
    rctx->resend = true;
  } else if (ISFORWARDER(query->addrinfo) &&
       query->rmessage->rcode == dns_rcode_servfail &&
       (query->options & DNS_FETCHOPT_TRYCD) != 0)
  {
    /*
     * We got a SERVFAIL from a forwarder with
     * CD=0; try again with CD=1.
     */
    rctx->retryopts |= DNS_FETCHOPT_TRYCD;
    rctx->resend = true;
  } else {
    rctx->broken_server = DNS_R_UNEXPECTEDRCODE;
    rctx->next_server = true;
  }

  isc_buffer_init(&b, code, sizeof(code) - 1);
  dns_rcode_totext(rcode, &b);
  code[isc_buffer_usedlength(&b)] = '\0';
  FCTXTRACE2("remote server broken: returned ", code);
  rctx_done(rctx, result);

  return ISC_R_COMPLETE;
}

/*
 * rctx_lameserver():
 * Is the server lame?
 */
static isc_result_t
rctx_lameserver(respctx_t *rctx) {
  isc_result_t result = ISC_R_SUCCESS;
  fetchctx_t *fctx = rctx->fctx;
  resquery_t *query = rctx->query;

  if (ISFORWARDER(query->addrinfo) || !is_lame(fctx, query->rmessage)) {
    return ISC_R_SUCCESS;
  }

  inc_stats(fctx->res, dns_resstatscounter_lame);
  log_lame(fctx, query->addrinfo);
  rctx->broken_server = DNS_R_LAME;
  rctx->next_server = true;
  FCTXTRACE("lame server");
  rctx_done(rctx, result);

  return ISC_R_COMPLETE;
}

/***
 *** Resolver Methods
 ***/
static void
dns_resolver__destroy(dns_resolver_t *res) {
  alternate_t *a = NULL;

  REQUIRE(!atomic_load_acquire(&res->priming));
  REQUIRE(res->primefetch == NULL);

  RTRACE("destroy");

  res->magic = 0;

  dns_nametree_detach(&res->algorithms);
  dns_nametree_detach(&res->digests);

  if (res->querystats != NULL) {
    dns_stats_detach(&res->querystats);
  }
  if (res->stats != NULL) {
    isc_stats_detach(&res->stats);
  }

  isc_mutex_destroy(&res->primelock);
  isc_mutex_destroy(&res->lock);

  INSIST(isc_hashmap_count(res->fctxs) == 0);
  isc_hashmap_destroy(&res->fctxs);
  isc_rwlock_destroy(&res->fctxs_lock);

  INSIST(isc_hashmap_count(res->counters) == 0);
  isc_hashmap_destroy(&res->counters);
  isc_rwlock_destroy(&res->counters_lock);

  if (res->dispatches4 != NULL) {
    dns_dispatchset_destroy(&res->dispatches4);
  }
  if (res->dispatches6 != NULL) {
    dns_dispatchset_destroy(&res->dispatches6);
  }
  while ((a = ISC_LIST_HEAD(res->alternates)) != NULL) {
    ISC_LIST_UNLINK(res->alternates, a, link);
    if (!a->isaddress) {
      dns_name_free(&a->_u._n.name, res->mctx);
    }
    isc_mem_put(res->mctx, a, sizeof(*a));
  }

  dns_view_weakdetach(&res->view);

  for (size_t i = 0; i < res->nloops; i++) {
    dns_message_destroypools(&res->namepools[i], &res->rdspools[i]);
  }
  isc_mem_cput(res->mctx, res->rdspools, res->nloops,
         sizeof(res->rdspools[0]));
  isc_mem_cput(res->mctx, res->namepools, res->nloops,
         sizeof(res->namepools[0]));

  isc_mem_putanddetach(&res->mctx, res, sizeof(*res));
}

static void
spillattimer_countdown(void *arg) {
  dns_resolver_t *res = (dns_resolver_t *)arg;
  unsigned int spillat = 0;

  REQUIRE(VALID_RESOLVER(res));

  if (atomic_load(&res->exiting)) {
    isc_timer_destroy(&res->spillattimer);
    return;
  }

  LOCK(&res->lock);
  INSIST(!atomic_load_acquire(&res->exiting));
  if (res->spillat > res->spillatmin) {
    spillat = --res->spillat;
  }
  if (res->spillat <= res->spillatmin) {
    isc_timer_destroy(&res->spillattimer);
  }
  UNLOCK(&res->lock);
  if (spillat > 0) {
    isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
            ISC_LOG_NOTICE,
            "clients-per-query decreased to %u", spillat);
  }
}

isc_result_t
dns_resolver_create(dns_view_t *view, unsigned int options,
        isc_tlsctx_cache_t *tlsctx_cache,
        dns_dispatch_t *dispatchv4, dns_dispatch_t *dispatchv6,
        dns_resolver_t **resp) {
  dns_resolver_t *res = NULL;

  /*
   * Create a resolver.
   */

  REQUIRE(DNS_VIEW_VALID(view));
  REQUIRE(resp != NULL && *resp == NULL);
  REQUIRE(tlsctx_cache != NULL);
  REQUIRE(dispatchv4 != NULL || dispatchv6 != NULL);

  res = isc_mem_get(view->mctx, sizeof(*res));
  *res = (dns_resolver_t){
    .rdclass = view->rdclass,
    .options = options,
    .tlsctx_cache = tlsctx_cache,
    .spillatmin = 10,
    .spillat = 10,
    .spillatmax = 100,
    .retryinterval = 800,
    .nonbackofftries = 3,
    .query_timeout = DEFAULT_QUERY_TIMEOUT,
    .maxdepth = DEFAULT_RECURSION_DEPTH,
    .maxqueries = DEFAULT_MAX_QUERIES,
    .alternates = ISC_LIST_INITIALIZER,
    .nloops = isc_loopmgr_nloops(),
    .maxvalidations = DEFAULT_MAX_VALIDATIONS,
    .maxvalidationfails = DEFAULT_MAX_VALIDATION_FAILURES,
  };

  RTRACE("create");

  dns_view_weakattach(view, &res->view);
  isc_mem_attach(view->mctx, &res->mctx);

  res->quotaresp[dns_quotatype_zone] = DNS_R_DROP;
  res->quotaresp[dns_quotatype_server] = DNS_R_SERVFAIL;

#if DNS_RESOLVER_TRACE
  fprintf(stderr, "dns_resolver__init:%s:%s:%d:%p->references = 1\n",
    __func__, __FILE__, __LINE__, res);
#endif
  isc_refcount_init(&res->references, 1);

  isc_hashmap_create(view->mctx, RES_DOMAIN_HASH_BITS, &res->fctxs);
  isc_rwlock_init(&res->fctxs_lock);

  isc_hashmap_create(view->mctx, RES_DOMAIN_HASH_BITS, &res->counters);
  isc_rwlock_init(&res->counters_lock);

  if (dispatchv4 != NULL) {
    dns_dispatchset_create(res->mctx, dispatchv4, &res->dispatches4,
               res->nloops);
  }

  if (dispatchv6 != NULL) {
    dns_dispatchset_create(res->mctx, dispatchv6, &res->dispatches6,
               res->nloops);
  }

  isc_mutex_init(&res->lock);
  isc_mutex_init(&res->primelock);

  dns_nametree_create(res->mctx, DNS_NAMETREE_BITS, "algorithms",
          &res->algorithms);
  dns_nametree_create(res->mctx, DNS_NAMETREE_BITS, "ds-digests",
          &res->digests);

  res->namepools = isc_mem_cget(res->mctx, res->nloops,
              sizeof(res->namepools[0]));
  res->rdspools = isc_mem_cget(res->mctx, res->nloops,
             sizeof(res->rdspools[0]));
  for (size_t i = 0; i < res->nloops; i++) {
    isc_loop_t *loop = isc_loop_get(i);
    isc_mem_t *pool_mctx = isc_loop_getmctx(loop);

    dns_message_createpools(pool_mctx, &res->namepools[i],
          &res->rdspools[i]);
  }

  res->magic = RES_MAGIC;

  *resp = res;

  return ISC_R_SUCCESS;
}

static void
prime_done(void *arg) {
  dns_fetchresponse_t *resp = (dns_fetchresponse_t *)arg;
  dns_resolver_t *res = resp->arg;
  dns_fetch_t *fetch = NULL;
  dns_db_t *db = NULL;

  REQUIRE(VALID_RESOLVER(res));

  int level = (resp->result == ISC_R_SUCCESS) ? ISC_LOG_DEBUG(1)
                : ISC_LOG_NOTICE;
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER, level,
          "resolver priming query complete: %s",
          isc_result_totext(resp->result));

  LOCK(&res->primelock);
  fetch = res->primefetch;
  res->primefetch = NULL;
  UNLOCK(&res->primelock);

  atomic_compare_exchange_enforced(&res->priming, &(bool){ true }, false);

  if (resp->result == ISC_R_SUCCESS && res->view->cache != NULL &&
      res->view->hints != NULL)
  {
    dns_cache_attachdb(res->view->cache, &db);
    dns_root_checkhints(res->view, res->view->hints, db);
    dns_db_detach(&db);
  }

  if (resp->node != NULL) {
    dns_db_detachnode(&resp->node);
  }
  if (resp->db != NULL) {
    dns_db_detach(&resp->db);
  }
  if (dns_rdataset_isassociated(resp->rdataset)) {
    dns_rdataset_disassociate(resp->rdataset);
  }
  INSIST(resp->sigrdataset == NULL);

  isc_mem_put(res->mctx, resp->rdataset, sizeof(*resp->rdataset));
  dns_resolver_freefresp(&resp);
  dns_resolver_destroyfetch(&fetch);
}

void
dns_resolver_prime(dns_resolver_t *res) {
  bool want_priming = false;
  isc_result_t result;

  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(res->frozen);

  RTRACE("dns_resolver_prime");

  if (!atomic_load_acquire(&res->exiting)) {
    want_priming = atomic_compare_exchange_strong_acq_rel(
      &res->priming, &(bool){ false }, true);
  }

  if (want_priming) {
    /*
     * To avoid any possible recursive locking problems, we
     * start the priming fetch like any other fetch, and
     * holding no resolver locks.  No one else will try to
     * start it because we're the ones who set res->priming
     * to true. Any other callers of dns_resolver_prime()
     * while we're running will see that res->priming is
     * already true and do nothing.
     */
    RTRACE("priming");

    dns_rdataset_t *rdataset = isc_mem_get(res->mctx,
                   sizeof(*rdataset));
    dns_rdataset_init(rdataset);

    LOCK(&res->primelock);
    result = dns_resolver_createfetch(
      res, dns_rootname, dns_rdatatype_ns, NULL, NULL, NULL,
      NULL, 0, DNS_FETCHOPT_NOFORWARD, 0, NULL, NULL,
      isc_loop(), prime_done, res, NULL, rdataset, NULL,
      &res->primefetch);
    UNLOCK(&res->primelock);

    if (result != ISC_R_SUCCESS) {
      isc_mem_put(res->mctx, rdataset, sizeof(*rdataset));
      atomic_compare_exchange_enforced(
        &res->priming, &(bool){ true }, false);
    }
    inc_stats(res, dns_resstatscounter_priming);
  }
}

void
dns_resolver_freeze(dns_resolver_t *res) {
  /*
   * Freeze resolver.
   */

  REQUIRE(VALID_RESOLVER(res));

  res->frozen = true;
}

void
dns_resolver_shutdown(dns_resolver_t *res) {
  isc_result_t result;
  bool is_false = false;

  REQUIRE(VALID_RESOLVER(res));

  RTRACE("shutdown");

  if (atomic_compare_exchange_strong(&res->exiting, &is_false, true)) {
    isc_hashmap_iter_t *it = NULL;

    RTRACE("exiting");

    RWLOCK(&res->fctxs_lock, isc_rwlocktype_write);
    isc_hashmap_iter_create(res->fctxs, &it);
    for (result = isc_hashmap_iter_first(it);
         result == ISC_R_SUCCESS;
         result = isc_hashmap_iter_next(it))
    {
      fetchctx_t *fctx = NULL;

      isc_hashmap_iter_current(it, (void **)&fctx);
      INSIST(fctx != NULL);

      fetchctx_ref(fctx);
      isc_async_run(fctx->loop, fctx_shutdown, fctx);
    }
    isc_hashmap_iter_destroy(&it);
    RWUNLOCK(&res->fctxs_lock, isc_rwlocktype_write);

    LOCK(&res->lock);
    if (res->spillattimer != NULL) {
      isc_timer_async_destroy(&res->spillattimer);
    }
    UNLOCK(&res->lock);
  }
}

#if DNS_RESOLVER_TRACE
ISC_REFCOUNT_TRACE_IMPL(dns_resolver, dns_resolver__destroy);
#else
ISC_REFCOUNT_IMPL(dns_resolver, dns_resolver__destroy);
#endif

static void
log_fetch(const dns_name_t *name, dns_rdatatype_t type) {
  char namebuf[DNS_NAME_FORMATSIZE];
  char typebuf[DNS_RDATATYPE_FORMATSIZE];
  int level = ISC_LOG_DEBUG(1);

  /*
   * If there's no chance of logging it, don't render (format) the
   * name and RDATA type (further below), and return early.
   */
  if (!isc_log_wouldlog(level)) {
    return;
  }

  dns_name_format(name, namebuf, sizeof(namebuf));
  dns_rdatatype_format(type, typebuf, sizeof(typebuf));

  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER, level,
          "fetch: %s/%s", namebuf, typebuf);
}

static void
fctx_minimize_qname(fetchctx_t *fctx) {
  isc_result_t result;
  unsigned int dlabels, nlabels;
  dns_name_t name;

  REQUIRE(VALID_FCTX(fctx));

  dns_name_init(&name);

  dlabels = dns_name_countlabels(fctx->qmindcname);
  nlabels = dns_name_countlabels(fctx->name);

  if (dlabels > fctx->qmin_labels) {
    fctx->qmin_labels = dlabels + 1;
  } else {
    fctx->qmin_labels++;
  }

  if (fctx->ip6arpaskip) {
    /*
     * For ip6.arpa we want to skip some of the labels, with
     * boundaries at /16, /32, /48, /56, /64 and /128
     * In 'label count' terms that's equal to
     *    7    11   15   17   19      35
     * We fix fctx->qmin_labels to point to the nearest
     * boundary
     */
    if (fctx->qmin_labels < 7) {
      fctx->qmin_labels = 7;
    } else if (fctx->qmin_labels < 11) {
      fctx->qmin_labels = 11;
    } else if (fctx->qmin_labels < 15) {
      fctx->qmin_labels = 15;
    } else if (fctx->qmin_labels < 17) {
      fctx->qmin_labels = 17;
    } else if (fctx->qmin_labels < 19) {
      fctx->qmin_labels = 19;
    } else if (fctx->qmin_labels < 35) {
      fctx->qmin_labels = 35;
    } else {
      fctx->qmin_labels = nlabels + 1;
    }
  } else if (fctx->qmin_labels > DNS_QMIN_MAXLABELS) {
    fctx->qmin_labels = DNS_NAME_MAXLABELS;
  }

  if (fctx->qmin_labels <= nlabels) {
    dns_rdataset_t rdataset;
    dns_fixedname_t fixed;
    dns_name_t *fname = dns_fixedname_initname(&fixed);
    dns_rdataset_init(&rdataset);
    do {
      /*
       * We want to query for qmin_labels from fctx->name.
       */
      dns_name_split(fctx->name, fctx->qmin_labels, NULL,
               &name);
      /*
       * Look to see if we have anything cached about NS
       * RRsets at this name and if so skip this name and
       * try with an additional label prepended.
       */
      result = dns_db_find(fctx->cache, &name, NULL,
               dns_rdatatype_ns, 0, 0, NULL,
               fname, &rdataset, NULL);
      if (dns_rdataset_isassociated(&rdataset)) {
        dns_rdataset_disassociate(&rdataset);
      }
      switch (result) {
      case ISC_R_SUCCESS:
      case DNS_R_CNAME:
      case DNS_R_DNAME:
      case DNS_R_NCACHENXDOMAIN:
      case DNS_R_NCACHENXRRSET:
        fctx->qmin_labels++;
        continue;
      default:
        break;
      }
      break;
    } while (fctx->qmin_labels <= nlabels);
  }

  /*
   * DS lookups come from the parent zone so we don't need to do a
   * NS lookup at the QNAME.  If the QTYPE is NS we are not leaking
   * the type if we just do the final NS lookup.
   */
  if (fctx->qmin_labels < nlabels ||
      (fctx->type != dns_rdatatype_ns && fctx->type != dns_rdatatype_ds &&
       fctx->qmin_labels == nlabels))
  {
    dns_name_copy(&name, fctx->qminname);
    fctx->qmintype = dns_rdatatype_ns;
    fctx->minimized = true;
  } else {
    /* Minimization is done, we'll ask for whole qname */
    dns_name_copy(fctx->name, fctx->qminname);
    fctx->qmintype = fctx->type;
    fctx->minimized = false;
  }

  char domainbuf[DNS_NAME_FORMATSIZE];
  dns_name_format(fctx->qminname, domainbuf, sizeof(domainbuf));
  isc_log_write(DNS_LOGCATEGORY_RESOLVER, DNS_LOGMODULE_RESOLVER,
          ISC_LOG_DEBUG(5),
          "QNAME minimization - %s minimized, qmintype %d "
          "qminname %s",
          fctx->minimized ? "" : "not", fctx->qmintype, domainbuf);
}

static isc_result_t
get_attached_fctx(dns_resolver_t *res, isc_loop_t *loop, const dns_name_t *name,
      dns_rdatatype_t type, const dns_name_t *domain,
      dns_rdataset_t *nameservers, const isc_sockaddr_t *client,
      unsigned int options, unsigned int depth, isc_counter_t *qc,
      isc_counter_t *gqc, fetchctx_t **fctxp, bool *new_fctx) {
  isc_result_t result;
  fetchctx_t key = {
    .name = UNCONST(name),
    .options = options,
    .type = type,
  };
  fetchctx_t *fctx = NULL;
  isc_rwlocktype_t locktype = isc_rwlocktype_read;
  uint32_t hashval = fctx_hash(&key);

again:
  RWLOCK(&res->fctxs_lock, locktype);
  result = isc_hashmap_find(res->fctxs, hashval, fctx_match, &key,
          (void **)&fctx);
  switch (result) {
  case ISC_R_SUCCESS:
    break;
  case ISC_R_NOTFOUND:
    result = fctx_create(res, loop, name, type, domain, nameservers,
             client, options, depth, qc, gqc, &fctx);
    if (result != ISC_R_SUCCESS) {
      RWUNLOCK(&res->fctxs_lock, locktype);
      return result;
    }

    UPGRADELOCK(&res->fctxs_lock, locktype);

    void *found = NULL;
    result = isc_hashmap_add(res->fctxs, hashval, fctx_match, fctx,
           fctx, &found);
    if (result == ISC_R_SUCCESS) {
      *new_fctx = true;
    } else {
      /*
       * The fctx_done() tries to acquire the fctxs_lock.
       * Destroy the newly created fetchctx directly.
       */
      fctx->state = fetchstate_done;
      isc_timer_destroy(&fctx->timer);

      fetchctx_detach(&fctx);
      fctx = found;
      result = ISC_R_SUCCESS;
    }
    break;
  default:
    UNREACHABLE();
  }
  INSIST(result == ISC_R_SUCCESS);
  fetchctx_ref(fctx);

  /*
   * We need to lock the fetch context before unlocking the hash table to
   * prevent other threads from looking up this thread before it has been
   * properly initialized and started.
   */
  LOCK(&fctx->lock);
  RWUNLOCK(&res->fctxs_lock, locktype);

  if (SHUTTINGDOWN(fctx) || fctx->cloned) {
    /*
     * This is the single place where fctx might get
     * accesses from a different thread, so we need to
     * double check whether fctxs is done (or cloned) and
     * help with the release if the fctx has been cloned.
     */
    UNLOCK(&fctx->lock);

    /* The fctx will get deleted either here or in fctx__done() */
    RWLOCK(&res->fctxs_lock, isc_rwlocktype_write);
    (void)isc_hashmap_delete(res->fctxs, fctx_hash(fctx), match_ptr,
           fctx);
    RWUNLOCK(&res->fctxs_lock, isc_rwlocktype_write);

    fetchctx_detach(&fctx);
    goto again;
  }

  /*
   * The function returns a locked fetch context,
   */
  *fctxp = fctx;

  return result;
}

isc_result_t
dns_resolver_createfetch(dns_resolver_t *res, const dns_name_t *name,
       dns_rdatatype_t type, const dns_name_t *domain,
       dns_rdataset_t *nameservers,
       dns_forwarders_t *forwarders,
       const isc_sockaddr_t *client, dns_messageid_t id,
       unsigned int options, unsigned int depth,
       isc_counter_t *qc, isc_counter_t *gqc,
       isc_loop_t *loop, isc_job_cb cb, void *arg,
       dns_edectx_t *edectx, dns_rdataset_t *rdataset,
       dns_rdataset_t *sigrdataset, dns_fetch_t **fetchp) {
  dns_fetch_t *fetch = NULL;
  fetchctx_t *fctx = NULL;
  isc_result_t result = ISC_R_SUCCESS;
  bool new_fctx = false;
  unsigned int count = 0;
  unsigned int spillat;
  unsigned int spillatmin;
  isc_mem_t *mctx = isc_loop_getmctx(loop);

  UNUSED(forwarders);

  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(res->frozen);
  /* XXXRTH  Check for meta type */
  if (domain != NULL) {
    REQUIRE(DNS_RDATASET_VALID(nameservers));
    REQUIRE(nameservers->type == dns_rdatatype_ns);
  } else {
    REQUIRE(nameservers == NULL);
  }
  REQUIRE(forwarders == NULL);
  REQUIRE(!dns_rdataset_isassociated(rdataset));
  REQUIRE(sigrdataset == NULL || !dns_rdataset_isassociated(sigrdataset));
  REQUIRE(fetchp != NULL && *fetchp == NULL);

  if (atomic_load_acquire(&res->exiting)) {
    return ISC_R_SHUTTINGDOWN;
  }

  log_fetch(name, type);

  fetch = isc_mem_get(mctx, sizeof(*fetch));
  *fetch = (dns_fetch_t){ 0 };

  dns_resolver_attach(res, &fetch->res);
  isc_mem_attach(mctx, &fetch->mctx);

  if ((options & DNS_FETCHOPT_UNSHARED) == 0) {
    /*
     * We don't save the unshared fetch context to a bucket because
     * we also would never match it again.
     */

    LOCK(&res->lock);
    spillat = res->spillat;
    spillatmin = res->spillatmin;
    UNLOCK(&res->lock);

    result = get_attached_fctx(res, loop, name, type, domain,
             nameservers, client, options, depth,
             qc, gqc, &fctx, &new_fctx);
    if (result != ISC_R_SUCCESS) {
      goto fail;
    }

    /* On success, the fctx is locked in get_attached_fctx() */
    INSIST(!SHUTTINGDOWN(fctx));

    /* Is this a duplicate? */
    if (client != NULL) {
      ISC_LIST_FOREACH(fctx->resps, resp, link) {
        if (resp->client != NULL && resp->id == id &&
            isc_sockaddr_equal(resp->client, client))
        {
          result = DNS_R_DUPLICATE;
          goto unlock;
        }

        count++;
      }
    }
    if (count >= spillatmin && spillatmin != 0) {
      if (count >= spillat) {
        fctx->spilled = true;
      }
      if (fctx->spilled) {
        inc_stats(res, dns_resstatscounter_clientquota);
        fctx->dropped++;
        result = DNS_R_DROP;
        goto unlock;
      }
    }
  } else {
    result = fctx_create(res, loop, name, type, domain, nameservers,
             client, options, depth, qc, gqc, &fctx);
    if (result != ISC_R_SUCCESS) {
      goto fail;
    }
    new_fctx = true;
  }

  RUNTIME_CHECK(fctx != NULL);

  if (fctx->depth > depth) {
    fctx->depth = depth;
  }

  fctx->allowed++;

  fctx_join(fctx, loop, client, id, cb, arg, edectx, rdataset,
      sigrdataset, fetch);

  if (new_fctx) {
    fetchctx_ref(fctx);
    isc_async_run(fctx->loop, fctx_start, fctx);
  }

unlock:
  if ((options & DNS_FETCHOPT_UNSHARED) == 0) {
    UNLOCK(&fctx->lock);
    fetchctx_unref(fctx);
  }

fail:
  if (result != ISC_R_SUCCESS) {
    dns_resolver_detach(&fetch->res);
    isc_mem_putanddetach(&fetch->mctx, fetch, sizeof(*fetch));
    return result;
  }

  FTRACE("created");
  *fetchp = fetch;

  return ISC_R_SUCCESS;
}

void
dns_resolver_cancelfetch(dns_fetch_t *fetch) {
  fetchctx_t *fctx = NULL;
  bool last_fetch = false;

  REQUIRE(DNS_FETCH_VALID(fetch));
  fctx = fetch->private;
  REQUIRE(VALID_FCTX(fctx));

  FTRACE("cancelfetch");

  LOCK(&fctx->lock);

  /*
   * Find the completion event associated with this fetch (as opposed
   * to those for other fetches that have joined the same fctx) and run
   * the callback asynchronously with a ISC_R_CANCELED result.
   */
  if (fctx->state != fetchstate_done) {
    ISC_LIST_FOREACH(fctx->resps, resp, link) {
      if (resp->fetch == fetch) {
        resp->result = ISC_R_CANCELED;
        ISC_LIST_UNLINK(fctx->resps, resp, link);
        isc_async_run(resp->loop, resp->cb, resp);
        break;
      }
    }
  }

  if (ISC_LIST_EMPTY(fctx->resps)) {
    last_fetch = true;
  }
  UNLOCK(&fctx->lock);

  if (last_fetch) {
    fetchctx_ref(fctx);
    isc_async_run(fctx->loop, fctx_shutdown, fctx);
  }
}

void
dns_resolver_destroyfetch(dns_fetch_t **fetchp) {
  dns_fetch_t *fetch = NULL;
  dns_resolver_t *res = NULL;
  fetchctx_t *fctx = NULL;

  REQUIRE(fetchp != NULL);
  fetch = *fetchp;
  *fetchp = NULL;
  REQUIRE(DNS_FETCH_VALID(fetch));
  fctx = fetch->private;
  REQUIRE(VALID_FCTX(fctx));
  res = fetch->res;

  FTRACE("destroyfetch");

  fetch->magic = 0;

  LOCK(&fctx->lock);
  /*
   * Sanity check: the caller should have gotten its event before
   * trying to destroy the fetch.
   */
  if (fctx->state != fetchstate_done) {
    ISC_LIST_FOREACH(fctx->resps, resp, link) {
      RUNTIME_CHECK(resp->fetch != fetch);
    }
  }
  UNLOCK(&fctx->lock);

  isc_mem_putanddetach(&fetch->mctx, fetch, sizeof(*fetch));

  fetchctx_detach(&fctx);
  dns_resolver_detach(&res);
}

void
dns_resolver_logfetch(dns_fetch_t *fetch, isc_logcategory_t category,
          isc_logmodule_t module, int level, bool duplicateok) {
  fetchctx_t *fctx = NULL;

  REQUIRE(DNS_FETCH_VALID(fetch));
  fctx = fetch->private;
  REQUIRE(VALID_FCTX(fctx));

  LOCK(&fctx->lock);

  if (!fctx->logged || duplicateok) {
    char domainbuf[DNS_NAME_FORMATSIZE];
    dns_name_format(fctx->domain, domainbuf, sizeof(domainbuf));
    isc_log_write(category, module, level,
            "fetch completed for %s in "
            "%" PRIu64 "."
            "%06" PRIu64 ": %s/%s "
            "[domain:%s,referral:%u,restart:%u,qrysent:%u,"
            "timeout:%u,lame:%u,quota:%u,neterr:%u,"
            "badresp:%u,adberr:%u,findfail:%u,valfail:%u]",
            fctx->info, fctx->duration / US_PER_SEC,
            fctx->duration % US_PER_SEC,
            isc_result_totext(fctx->result),
            isc_result_totext(fctx->vresult), domainbuf,
            fctx->referrals, fctx->restarts, fctx->querysent,
            fctx->timeouts, fctx->lamecount, fctx->quotacount,
            fctx->neterr, fctx->badresp, fctx->adberr,
            fctx->findfail, fctx->valfail);
    fctx->logged = true;
  }

  UNLOCK(&fctx->lock);
}

dns_dispatch_t *
dns_resolver_dispatchv4(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));
  return dns_dispatchset_get(resolver->dispatches4);
}

dns_dispatch_t *
dns_resolver_dispatchv6(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));
  return dns_dispatchset_get(resolver->dispatches6);
}

void
dns_resolver_addalternate(dns_resolver_t *res, const isc_sockaddr_t *alt,
        const dns_name_t *name, in_port_t port) {
  alternate_t *a;

  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(!res->frozen);
  REQUIRE((alt == NULL) ^ (name == NULL));

  a = isc_mem_get(res->mctx, sizeof(*a));
  if (alt != NULL) {
    a->isaddress = true;
    a->_u.addr = *alt;
  } else {
    a->isaddress = false;
    a->_u._n.port = port;
    dns_name_init(&a->_u._n.name);
    dns_name_dup(name, res->mctx, &a->_u._n.name);
  }
  ISC_LINK_INIT(a, link);
  ISC_LIST_APPEND(res->alternates, a, link);
}

isc_result_t
dns_resolver_disable_algorithm(dns_resolver_t *resolver, const dns_name_t *name,
             unsigned int alg) {
  REQUIRE(VALID_RESOLVER(resolver));

  if (alg >= DST_MAX_ALGS) {
    return ISC_R_RANGE;
  }

  return dns_nametree_add(resolver->algorithms, name, alg);
}

isc_result_t
dns_resolver_disable_ds_digest(dns_resolver_t *resolver, const dns_name_t *name,
             unsigned int digest_type) {
  REQUIRE(VALID_RESOLVER(resolver));

  if (digest_type > 255) {
    return ISC_R_RANGE;
  }

  return dns_nametree_add(resolver->digests, name, digest_type);
}

bool
dns_resolver_algorithm_supported(dns_resolver_t *resolver,
         const dns_name_t *name, unsigned int alg,
         unsigned char *private, size_t len) {
  REQUIRE(VALID_RESOLVER(resolver));

  if ((alg == DST_ALG_DH) || (alg == DST_ALG_INDIRECT)) {
    return false;
  }

  /*
   * Look up the DST algorithm identifier for private-OID
   * and private-DNS keys.
   */
  if (alg == DST_ALG_PRIVATEDNS && private != NULL) {
    isc_buffer_t b;
    isc_buffer_init(&b, private, len);
    isc_buffer_add(&b, len);
    alg = dst_algorithm_fromprivatedns(&b);
    if (alg == 0) {
      return false;
    }
  }

  if (alg == DST_ALG_PRIVATEOID && private != NULL) {
    isc_buffer_t b;
    isc_buffer_init(&b, private, len);
    isc_buffer_add(&b, len);
    alg = dst_algorithm_fromprivateoid(&b);
    if (alg == 0) {
      return false;
    }
  }
  if (dns_nametree_covered(resolver->algorithms, name, NULL, alg)) {
    return false;
  }

  return dst_algorithm_supported(alg);
}

bool
dns_resolver_ds_digest_supported(dns_resolver_t *resolver,
         const dns_name_t *name,
         unsigned int digest_type) {
  REQUIRE(VALID_RESOLVER(resolver));

  if (dns_nametree_covered(resolver->digests, name, NULL, digest_type)) {
    return false;
  }

  return dst_ds_digest_supported(digest_type);
}

void
dns_resolver_getclientsperquery(dns_resolver_t *resolver, uint32_t *cur,
        uint32_t *min, uint32_t *max) {
  REQUIRE(VALID_RESOLVER(resolver));

  LOCK(&resolver->lock);
  SET_IF_NOT_NULL(cur, resolver->spillat);
  SET_IF_NOT_NULL(min, resolver->spillatmin);
  SET_IF_NOT_NULL(max, resolver->spillatmax);
  UNLOCK(&resolver->lock);
}

void
dns_resolver_setclientsperquery(dns_resolver_t *resolver, uint32_t min,
        uint32_t max) {
  REQUIRE(VALID_RESOLVER(resolver));

  LOCK(&resolver->lock);
  resolver->spillatmin = resolver->spillat = min;
  resolver->spillatmax = max;
  UNLOCK(&resolver->lock);
}

void
dns_resolver_setfetchesperzone(dns_resolver_t *resolver, uint32_t clients) {
  REQUIRE(VALID_RESOLVER(resolver));

  atomic_store_release(&resolver->zspill, clients);
}

uint32_t
dns_resolver_getfetchesperzone(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));

  return atomic_load_relaxed(&resolver->zspill);
}

bool
dns_resolver_getzeronosoattl(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));

  return resolver->zero_no_soa_ttl;
}

void
dns_resolver_setzeronosoattl(dns_resolver_t *resolver, bool state) {
  REQUIRE(VALID_RESOLVER(resolver));

  resolver->zero_no_soa_ttl = state;
}

unsigned int
dns_resolver_getoptions(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));

  return resolver->options;
}

unsigned int
dns_resolver_gettimeout(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));

  return resolver->query_timeout;
}

void
dns_resolver_settimeout(dns_resolver_t *resolver, unsigned int timeout) {
  REQUIRE(VALID_RESOLVER(resolver));

  if (timeout < MINIMUM_QUERY_TIMEOUT) {
    timeout *= 1000;
  }

  if (timeout == 0) {
    timeout = DEFAULT_QUERY_TIMEOUT;
  }
  if (timeout > MAXIMUM_QUERY_TIMEOUT) {
    timeout = MAXIMUM_QUERY_TIMEOUT;
  }
  if (timeout < MINIMUM_QUERY_TIMEOUT) {
    timeout = MINIMUM_QUERY_TIMEOUT;
  }

  resolver->query_timeout = timeout;
}

void
dns_resolver_setmaxvalidations(dns_resolver_t *resolver, uint32_t max) {
  REQUIRE(VALID_RESOLVER(resolver));
  atomic_store(&resolver->maxvalidations, max);
}

void
dns_resolver_setmaxvalidationfails(dns_resolver_t *resolver, uint32_t max) {
  REQUIRE(VALID_RESOLVER(resolver));
  atomic_store(&resolver->maxvalidationfails, max);
}

void
dns_resolver_setmaxdepth(dns_resolver_t *resolver, unsigned int maxdepth) {
  REQUIRE(VALID_RESOLVER(resolver));
  resolver->maxdepth = maxdepth;
}

unsigned int
dns_resolver_getmaxdepth(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));
  return resolver->maxdepth;
}

void
dns_resolver_setmaxqueries(dns_resolver_t *resolver, unsigned int queries) {
  REQUIRE(VALID_RESOLVER(resolver));
  resolver->maxqueries = queries;
}

unsigned int
dns_resolver_getmaxqueries(dns_resolver_t *resolver) {
  REQUIRE(VALID_RESOLVER(resolver));
  return resolver->maxqueries;
}

void
dns_resolver_dumpfetches(dns_resolver_t *res, isc_statsformat_t format,
       FILE *fp) {
  isc_result_t result;
  isc_hashmap_iter_t *it = NULL;

  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(fp != NULL);
  REQUIRE(format == isc_statsformat_file);

  LOCK(&res->lock);
  fprintf(fp, "clients-per-query: %u/%u/%u\n", res->spillatmin,
    res->spillat, res->spillatmax);
  UNLOCK(&res->lock);

  RWLOCK(&res->fctxs_lock, isc_rwlocktype_read);
  isc_hashmap_iter_create(res->fctxs, &it);
  for (result = isc_hashmap_iter_first(it); result == ISC_R_SUCCESS;
       result = isc_hashmap_iter_next(it))
  {
    char typebuf[DNS_RDATATYPE_FORMATSIZE];
    char timebuf[1024];
    fetchctx_t *fctx = NULL;
    unsigned int resp_count = 0, query_count = 0;

    isc_hashmap_iter_current(it, (void **)&fctx);

    LOCK(&fctx->lock);
    dns_name_print(fctx->name, fp);

    isc_time_formatISO8601ms(&fctx->start, timebuf,
           sizeof(timebuf));

    dns_rdatatype_format(fctx->type, typebuf, sizeof(typebuf));

    fprintf(fp, "/%s (%s): started %s, ", typebuf,
      fctx->state == fetchstate_active ? "active" : "done",
      timebuf);

    ISC_LIST_FOREACH(fctx->resps, resp, link) {
      resp_count++;
    }

    ISC_LIST_FOREACH(fctx->queries, query, link) {
      query_count++;
    }

    if (isc_timer_running(fctx->timer)) {
      strlcpy(timebuf, "expires ", sizeof(timebuf));
      isc_time_formatISO8601ms(&fctx->expires, timebuf + 8,
             sizeof(timebuf) - 8);
    } else {
      strlcpy(timebuf, "not running", sizeof(timebuf));
    }

    fprintf(fp,
      "fetches: %u active (%" PRIuFAST32
      " allowed, %" PRIuFAST32
      " dropped%s), queries: %u, timer %s\n",
      resp_count, fctx->allowed, fctx->dropped,
      fctx->spilled ? ", spilled" : "", query_count, timebuf);

    UNLOCK(&fctx->lock);
  }
  isc_hashmap_iter_destroy(&it);
  RWUNLOCK(&res->fctxs_lock, isc_rwlocktype_read);
}

isc_result_t
dns_resolver_dumpquota(dns_resolver_t *res, isc_buffer_t **buf) {
  isc_result_t result;
  isc_hashmap_iter_t *it = NULL;
  uint_fast32_t spill;

  REQUIRE(VALID_RESOLVER(res));

  spill = atomic_load_acquire(&res->zspill);
  if (spill == 0) {
    return ISC_R_SUCCESS;
  }

  RWLOCK(&res->counters_lock, isc_rwlocktype_read);
  isc_hashmap_iter_create(res->counters, &it);
  for (result = isc_hashmap_iter_first(it); result == ISC_R_SUCCESS;
       result = isc_hashmap_iter_next(it))
  {
    fctxcount_t *counter = NULL;
    uint_fast32_t count, dropped, allowed;
    char nb[DNS_NAME_FORMATSIZE];
    char text[DNS_NAME_FORMATSIZE + BUFSIZ];

    isc_hashmap_iter_current(it, (void **)&counter);

    LOCK(&counter->lock);
    count = counter->count;
    dropped = counter->dropped;
    allowed = counter->allowed;
    UNLOCK(&counter->lock);

    if (count < spill) {
      continue;
    }

    dns_name_format(counter->domain, nb, sizeof(nb));
    snprintf(text, sizeof(text),
       "\n- %s: %" PRIuFAST32 " active (allowed %" PRIuFAST32
       " spilled %" PRIuFAST32 ")",
       nb, count, allowed, dropped);

    result = isc_buffer_reserve(*buf, strlen(text));
    if (result != ISC_R_SUCCESS) {
      goto cleanup;
    }
    isc_buffer_putstr(*buf, text);
  }
  if (result == ISC_R_NOMORE) {
    result = ISC_R_SUCCESS;
  }

cleanup:
  isc_hashmap_iter_destroy(&it);
  RWUNLOCK(&res->counters_lock, isc_rwlocktype_read);
  return result;
}

void
dns_resolver_setquotaresponse(dns_resolver_t *resolver, dns_quotatype_t which,
            isc_result_t resp) {
  REQUIRE(VALID_RESOLVER(resolver));
  REQUIRE(which == dns_quotatype_zone || which == dns_quotatype_server);
  REQUIRE(resp == DNS_R_DROP || resp == DNS_R_SERVFAIL);

  resolver->quotaresp[which] = resp;
}

isc_result_t
dns_resolver_getquotaresponse(dns_resolver_t *resolver, dns_quotatype_t which) {
  REQUIRE(VALID_RESOLVER(resolver));
  REQUIRE(which == dns_quotatype_zone || which == dns_quotatype_server);

  return resolver->quotaresp[which];
}

void
dns_resolver_setstats(dns_resolver_t *res, isc_stats_t *stats) {
  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(res->stats == NULL);

  isc_stats_attach(stats, &res->stats);

  /* initialize the bucket "counter"; it's a static value */
  set_stats(res, dns_resstatscounter_buckets, isc_loopmgr_nloops());
}

void
dns_resolver_getstats(dns_resolver_t *res, isc_stats_t **statsp) {
  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(statsp != NULL && *statsp == NULL);

  if (res->stats != NULL) {
    isc_stats_attach(res->stats, statsp);
  }
}

void
dns_resolver_incstats(dns_resolver_t *res, isc_statscounter_t counter) {
  REQUIRE(VALID_RESOLVER(res));

  isc_stats_increment(res->stats, counter);
}

void
dns_resolver_setquerystats(dns_resolver_t *res, dns_stats_t *stats) {
  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(res->querystats == NULL);

  dns_stats_attach(stats, &res->querystats);
}

void
dns_resolver_getquerystats(dns_resolver_t *res, dns_stats_t **statsp) {
  REQUIRE(VALID_RESOLVER(res));
  REQUIRE(statsp != NULL && *statsp == NULL);

  if (res->querystats != NULL) {
    dns_stats_attach(res->querystats, statsp);
  }
}

void
dns_resolver_freefresp(dns_fetchresponse_t **frespp) {
  REQUIRE(frespp != NULL);

  if (*frespp == NULL) {
    return;
  }

  dns_fetchresponse_t *fresp = *frespp;

  *frespp = NULL;
  isc_mem_putanddetach(&fresp->mctx, fresp, sizeof(*fresp));
}

Coverage Report

Created: 2025-08-26 06:59