/src/unbound/iterator/iterator.c

Source
/*
 * iterator/iterator.c - iterative resolver DNS query response module
 *
 * Copyright (c) 2007, NLnet Labs. All rights reserved.
 *
 * This software is open source.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * Neither the name of the NLNET LABS nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * \file
 *
 * This file contains a module that performs recursive iterative DNS query
 * processing.
 */

#include "config.h"
#include "iterator/iterator.h"
#include "iterator/iter_utils.h"
#include "iterator/iter_hints.h"
#include "iterator/iter_fwd.h"
#include "iterator/iter_donotq.h"
#include "iterator/iter_delegpt.h"
#include "iterator/iter_resptype.h"
#include "iterator/iter_scrub.h"
#include "iterator/iter_priv.h"
#include "validator/val_neg.h"
#include "services/cache/dns.h"
#include "services/cache/rrset.h"
#include "services/cache/infra.h"
#include "services/authzone.h"
#include "util/module.h"
#include "util/netevent.h"
#include "util/net_help.h"
#include "util/regional.h"
#include "util/data/dname.h"
#include "util/data/msgencode.h"
#include "util/fptr_wlist.h"
#include "util/config_file.h"
#include "util/random.h"
#include "sldns/rrdef.h"
#include "sldns/wire2str.h"
#include "sldns/str2wire.h"
#include "sldns/parseutil.h"
#include "sldns/sbuffer.h"

/* number of packets */
int MAX_GLOBAL_QUOTA = 200;
/* in msec */
int UNKNOWN_SERVER_NICENESS = 376;
/* in msec */
int USEFUL_SERVER_TOP_TIMEOUT = 120000;
/* Equals USEFUL_SERVER_TOP_TIMEOUT*4 */
int BLACKLIST_PENALTY = (120000*4);
/** Timeout when only a single probe query per IP is allowed. */
int PROBE_MAXRTO = PROBE_MAXRTO_DEFAULT; /* in msec */

static void target_count_increase_nx(struct iter_qstate* iq, int num);

int 
iter_init(struct module_env* env, int id)
{
  struct iter_env* iter_env = (struct iter_env*)calloc(1,
    sizeof(struct iter_env));
  if(!iter_env) {
    log_err("malloc failure");
    return 0;
  }
  env->modinfo[id] = (void*)iter_env;

  lock_basic_init(&iter_env->queries_ratelimit_lock);
  lock_protect(&iter_env->queries_ratelimit_lock,
      &iter_env->num_queries_ratelimited,
    sizeof(iter_env->num_queries_ratelimited));

  if(!iter_apply_cfg(iter_env, env->cfg)) {
    log_err("iterator: could not apply configuration settings.");
    return 0;
  }

  return 1;
}

void 
iter_deinit(struct module_env* env, int id)
{
  struct iter_env* iter_env;
  if(!env || !env->modinfo[id])
    return;
  iter_env = (struct iter_env*)env->modinfo[id];
  lock_basic_destroy(&iter_env->queries_ratelimit_lock);
  free(iter_env->target_fetch_policy);
  priv_delete(iter_env->priv);
  donotq_delete(iter_env->donotq);
  caps_white_delete(iter_env->caps_white);
  free(iter_env);
  env->modinfo[id] = NULL;
}

/** new query for iterator */
static int
iter_new(struct module_qstate* qstate, int id)
{
  struct iter_qstate* iq = (struct iter_qstate*)regional_alloc(
    qstate->region, sizeof(struct iter_qstate));
  qstate->minfo[id] = iq;
  if(!iq) 
    return 0;
  memset(iq, 0, sizeof(*iq));
  iq->state = INIT_REQUEST_STATE;
  iq->final_state = FINISHED_STATE;
  iq->an_prepend_list = NULL;
  iq->an_prepend_last = NULL;
  iq->ns_prepend_list = NULL;
  iq->ns_prepend_last = NULL;
  iq->dp = NULL;
  iq->depth = 0;
  iq->num_target_queries = 0;
  iq->num_current_queries = 0;
  iq->query_restart_count = 0;
  iq->referral_count = 0;
  iq->sent_count = 0;
  iq->ratelimit_ok = 0;
  iq->target_count = NULL;
  iq->dp_target_count = 0;
  iq->wait_priming_stub = 0;
  iq->refetch_glue = 0;
  iq->dnssec_expected = 0;
  iq->dnssec_lame_query = 0;
  iq->chase_flags = qstate->query_flags;
  /* Start with the (current) qname. */
  iq->qchase = qstate->qinfo;
  outbound_list_init(&iq->outlist);
  iq->minimise_count = 0;
  iq->timeout_count = 0;
  if (qstate->env->cfg->qname_minimisation)
    iq->minimisation_state = INIT_MINIMISE_STATE;
  else
    iq->minimisation_state = DONOT_MINIMISE_STATE;
  
  memset(&iq->qinfo_out, 0, sizeof(struct query_info));
  return 1;
}

/**
 * Transition to the next state. This can be used to advance a currently
 * processing event. It cannot be used to reactivate a forEvent.
 *
 * @param iq: iterator query state
 * @param nextstate The state to transition to.
 * @return true. This is so this can be called as the return value for the
 *         actual process*State() methods. (Transitioning to the next state
 *         implies further processing).
 */
static int
next_state(struct iter_qstate* iq, enum iter_state nextstate)
{
  /* If transitioning to a "response" state, make sure that there is a
   * response */
  if(iter_state_is_responsestate(nextstate)) {
    if(iq->response == NULL) {
      log_err("transitioning to response state sans "
        "response.");
    }
  }
  iq->state = nextstate;
  return 1;
}

/**
 * Transition an event to its final state. Final states always either return
 * a result up the module chain, or reactivate a dependent event. Which
 * final state to transition to is set in the module state for the event when
 * it was created, and depends on the original purpose of the event.
 *
 * The response is stored in the qstate->buf buffer.
 *
 * @param iq: iterator query state
 * @return false. This is so this method can be used as the return value for
 *         the processState methods. (Transitioning to the final state
 */
static int
final_state(struct iter_qstate* iq)
{
  return next_state(iq, iq->final_state);
}

/**
 * Callback routine to handle errors in parent query states
 * @param qstate: query state that failed.
 * @param id: module id.
 * @param super: super state.
 */
static void
error_supers(struct module_qstate* qstate, int id, struct module_qstate* super)
{
  struct iter_env* ie = (struct iter_env*)qstate->env->modinfo[id];
  struct iter_qstate* super_iq = (struct iter_qstate*)super->minfo[id];

  if(qstate->qinfo.qtype == LDNS_RR_TYPE_A ||
    qstate->qinfo.qtype == LDNS_RR_TYPE_AAAA) {
    /* mark address as failed. */
    struct delegpt_ns* dpns = NULL;
    super_iq->num_target_queries--; 
    if(super_iq->dp)
      dpns = delegpt_find_ns(super_iq->dp, 
        qstate->qinfo.qname, qstate->qinfo.qname_len);
    if(!dpns) {
      /* not interested */
      /* this can happen, for eg. qname minimisation asked
       * for an NXDOMAIN to be validated, and used qtype
       * A for that, and the error of that, the name, is
       * not listed in super_iq->dp */
      verbose(VERB_ALGO, "subq error, but not interested");
      log_query_info(VERB_ALGO, "superq", &super->qinfo);
      return;
    } else {
      /* see if the failure did get (parent-lame) info */
      if(!cache_fill_missing(super->env, super_iq->qchase.qclass,
        super->region, super_iq->dp, 0))
        log_err("out of memory adding missing");
    }
    delegpt_mark_neg(dpns, qstate->qinfo.qtype);
    if((dpns->got4 == 2 || (!ie->supports_ipv4 && !ie->nat64.use_nat64)) &&
      (dpns->got6 == 2 || !ie->supports_ipv6)) {
      dpns->resolved = 1; /* mark as failed */
      target_count_increase_nx(super_iq, 1);
    }
  }
  if(qstate->qinfo.qtype == LDNS_RR_TYPE_NS) {
    /* prime failed to get delegation */
    super_iq->dp = NULL;
  }
  /* evaluate targets again */
  super_iq->state = QUERYTARGETS_STATE; 
  /* super becomes runnable, and will process this change */
}

/**
 * Return an error to the client
 * @param qstate: our query state
 * @param id: module id
 * @param rcode: error code (DNS errcode).
 * @return: 0 for use by caller, to make notation easy, like:
 *  return error_response(..). 
 */
static int
error_response(struct module_qstate* qstate, int id, int rcode)
{
  verbose(VERB_QUERY, "return error response %s", 
    sldns_lookup_by_id(sldns_rcodes, rcode)?
    sldns_lookup_by_id(sldns_rcodes, rcode)->name:"??");
  qstate->return_rcode = rcode;
  qstate->return_msg = NULL;
  qstate->ext_state[id] = module_finished;
  return 0;
}

/**
 * Return an error to the client and cache the error code in the
 * message cache (so per qname, qtype, qclass).
 * @param qstate: our query state
 * @param id: module id
 * @param rcode: error code (DNS errcode).
 * @return: 0 for use by caller, to make notation easy, like:
 *  return error_response(..). 
 */
static int
error_response_cache(struct module_qstate* qstate, int id, int rcode)
{
  struct reply_info err;
  struct msgreply_entry* msg;
  if(qstate->no_cache_store) {
    return error_response(qstate, id, rcode);
  }
  if(qstate->prefetch_leeway > NORR_TTL) {
    verbose(VERB_ALGO, "error response for prefetch in cache");
    /* attempt to adjust the cache entry prefetch */
    if(dns_cache_prefetch_adjust(qstate->env, &qstate->qinfo,
      NORR_TTL, qstate->query_flags))
      return error_response(qstate, id, rcode);
    /* if that fails (not in cache), fall through to store err */
  }
  if((msg=msg_cache_lookup(qstate->env,
    qstate->qinfo.qname, qstate->qinfo.qname_len,
    qstate->qinfo.qtype, qstate->qinfo.qclass,
    qstate->query_flags, 0,
    qstate->env->cfg->serve_expired)) != NULL) {
    struct reply_info* rep = (struct reply_info*)msg->entry.data;
    if(qstate->env->cfg->serve_expired && rep) {
      if(qstate->env->cfg->serve_expired_ttl_reset &&
        *qstate->env->now + qstate->env->cfg->serve_expired_ttl
        > rep->serve_expired_ttl) {
        verbose(VERB_ALGO, "reset serve-expired-ttl for "
          "response in cache");
        rep->serve_expired_ttl = *qstate->env->now +
          qstate->env->cfg->serve_expired_ttl;
      }
      verbose(VERB_ALGO, "set serve-expired-norec-ttl for "
        "response in cache");
      rep->serve_expired_norec_ttl = NORR_TTL +
        *qstate->env->now;
    }
    if(rep && (FLAGS_GET_RCODE(rep->flags) ==
      LDNS_RCODE_NOERROR ||
      FLAGS_GET_RCODE(rep->flags) ==
      LDNS_RCODE_NXDOMAIN ||
      FLAGS_GET_RCODE(rep->flags) ==
      LDNS_RCODE_YXDOMAIN) &&
      (qstate->env->cfg->serve_expired ||
      *qstate->env->now <= rep->ttl)) {
      /* we have a good entry, don't overwrite */
      lock_rw_unlock(&msg->entry.lock);
      return error_response(qstate, id, rcode);
    }
    lock_rw_unlock(&msg->entry.lock);
    /* nothing interesting is cached (already error response or
     * expired good record when we don't serve expired), so this
     * servfail cache entry is useful (stops waste of time on this
     * servfail NORR_TTL) */
  }
  /* store in cache */
  memset(&err, 0, sizeof(err));
  err.flags = (uint16_t)(BIT_QR | BIT_RA);
  FLAGS_SET_RCODE(err.flags, rcode);
  err.qdcount = 1;
  err.ttl = NORR_TTL;
  err.prefetch_ttl = PREFETCH_TTL_CALC(err.ttl);
  err.serve_expired_ttl = NORR_TTL;
  /* do not waste time trying to validate this servfail */
  err.security = sec_status_indeterminate;
  verbose(VERB_ALGO, "store error response in message cache");
  iter_dns_store(qstate->env, &qstate->qinfo, &err, 0, 0, 0, NULL,
    qstate->query_flags, qstate->qstarttime, qstate->is_valrec);
  return error_response(qstate, id, rcode);
}

/** check if prepend item is duplicate item */
static int
prepend_is_duplicate(struct ub_packed_rrset_key** sets, size_t to,
  struct ub_packed_rrset_key* dup)
{
  size_t i;
  for(i=0; i<to; i++) {
    if(sets[i]->rk.type == dup->rk.type &&
      sets[i]->rk.rrset_class == dup->rk.rrset_class &&
      sets[i]->rk.dname_len == dup->rk.dname_len &&
      query_dname_compare(sets[i]->rk.dname, dup->rk.dname)
      == 0)
      return 1;
  }
  return 0;
}

/** prepend the prepend list in the answer and authority section of dns_msg */
static int
iter_prepend(struct iter_qstate* iq, struct dns_msg* msg, 
  struct regional* region)
{
  struct iter_prep_list* p;
  struct ub_packed_rrset_key** sets;
  size_t num_an = 0, num_ns = 0;;
  for(p = iq->an_prepend_list; p; p = p->next)
    num_an++;
  for(p = iq->ns_prepend_list; p; p = p->next)
    num_ns++;
  if(num_an + num_ns == 0)
    return 1;
  verbose(VERB_ALGO, "prepending %d rrsets", (int)num_an + (int)num_ns);
  if(num_an > RR_COUNT_MAX || num_ns > RR_COUNT_MAX ||
    msg->rep->rrset_count > RR_COUNT_MAX) return 0; /* overflow */
  sets = regional_alloc(region, (num_an+num_ns+msg->rep->rrset_count) *
    sizeof(struct ub_packed_rrset_key*));
  if(!sets) 
    return 0;
  /* ANSWER section */
  num_an = 0;
  for(p = iq->an_prepend_list; p; p = p->next) {
    sets[num_an++] = p->rrset;
    if(ub_packed_rrset_ttl(p->rrset) < msg->rep->ttl) {
      msg->rep->ttl = ub_packed_rrset_ttl(p->rrset);
      msg->rep->prefetch_ttl = PREFETCH_TTL_CALC(msg->rep->ttl);
      msg->rep->serve_expired_ttl = msg->rep->ttl + SERVE_EXPIRED_TTL;
    }
  }
  memcpy(sets+num_an, msg->rep->rrsets, msg->rep->an_numrrsets *
    sizeof(struct ub_packed_rrset_key*));
  /* AUTH section */
  num_ns = 0;
  for(p = iq->ns_prepend_list; p; p = p->next) {
    if(prepend_is_duplicate(sets+msg->rep->an_numrrsets+num_an,
      num_ns, p->rrset) || prepend_is_duplicate(
      msg->rep->rrsets+msg->rep->an_numrrsets, 
      msg->rep->ns_numrrsets, p->rrset))
      continue;
    sets[msg->rep->an_numrrsets + num_an + num_ns++] = p->rrset;
    if(ub_packed_rrset_ttl(p->rrset) < msg->rep->ttl) {
      msg->rep->ttl = ub_packed_rrset_ttl(p->rrset);
      msg->rep->prefetch_ttl = PREFETCH_TTL_CALC(msg->rep->ttl);
      msg->rep->serve_expired_ttl = msg->rep->ttl + SERVE_EXPIRED_TTL;
    }
  }
  memcpy(sets + num_an + msg->rep->an_numrrsets + num_ns, 
    msg->rep->rrsets + msg->rep->an_numrrsets, 
    (msg->rep->ns_numrrsets + msg->rep->ar_numrrsets) *
    sizeof(struct ub_packed_rrset_key*));

  /* NXDOMAIN rcode can stay if we prepended DNAME/CNAMEs, because
   * this is what recursors should give. */
  msg->rep->rrset_count += num_an + num_ns;
  msg->rep->an_numrrsets += num_an;
  msg->rep->ns_numrrsets += num_ns;
  msg->rep->rrsets = sets;
  return 1;
}

/**
 * Find rrset in ANSWER prepend list.
 * to avoid duplicate DNAMEs when a DNAME is traversed twice.
 * @param iq: iterator query state.
 * @param rrset: rrset to add.
 * @return false if not found
 */
static int
iter_find_rrset_in_prepend_answer(struct iter_qstate* iq,
  struct ub_packed_rrset_key* rrset)
{
  struct iter_prep_list* p = iq->an_prepend_list;
  while(p) {
    if(ub_rrset_compare(p->rrset, rrset) == 0 &&
      rrsetdata_equal((struct packed_rrset_data*)p->rrset
      ->entry.data, (struct packed_rrset_data*)rrset
      ->entry.data))
      return 1;
    p = p->next;
  }
  return 0;
}

/**
 * Add rrset to ANSWER prepend list
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param rrset: rrset to add.
 * @return false on failure (malloc).
 */
static int
iter_add_prepend_answer(struct module_qstate* qstate, struct iter_qstate* iq,
  struct ub_packed_rrset_key* rrset)
{
  struct iter_prep_list* p = (struct iter_prep_list*)regional_alloc(
    qstate->region, sizeof(struct iter_prep_list));
  if(!p)
    return 0;
  p->rrset = rrset;
  p->next = NULL;
  /* add at end */
  if(iq->an_prepend_last)
    iq->an_prepend_last->next = p;
  else  iq->an_prepend_list = p;
  iq->an_prepend_last = p;
  return 1;
}

/**
 * Add rrset to AUTHORITY prepend list
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param rrset: rrset to add.
 * @return false on failure (malloc).
 */
static int
iter_add_prepend_auth(struct module_qstate* qstate, struct iter_qstate* iq,
  struct ub_packed_rrset_key* rrset)
{
  struct iter_prep_list* p = (struct iter_prep_list*)regional_alloc(
    qstate->region, sizeof(struct iter_prep_list));
  if(!p)
    return 0;
  p->rrset = rrset;
  p->next = NULL;
  /* add at end */
  if(iq->ns_prepend_last)
    iq->ns_prepend_last->next = p;
  else  iq->ns_prepend_list = p;
  iq->ns_prepend_last = p;
  return 1;
}

/**
 * Given a CNAME response (defined as a response containing a CNAME or DNAME
 * that does not answer the request), process the response, modifying the
 * state as necessary. This follows the CNAME/DNAME chain and returns the
 * final query name.
 *
 * sets the new query name, after following the CNAME/DNAME chain.
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param msg: the response.
 * @param mname: returned target new query name.
 * @param mname_len: length of mname.
 * @return false on (malloc) error.
 */
static int
handle_cname_response(struct module_qstate* qstate, struct iter_qstate* iq,
        struct dns_msg* msg, uint8_t** mname, size_t* mname_len)
{
  size_t i;
  /* Start with the (current) qname. */
  *mname = iq->qchase.qname;
  *mname_len = iq->qchase.qname_len;

  /* Iterate over the ANSWER rrsets in order, looking for CNAMEs and 
   * DNAMES. */
  for(i=0; i<msg->rep->an_numrrsets; i++) {
    struct ub_packed_rrset_key* r = msg->rep->rrsets[i];
    /* If there is a (relevant) DNAME, add it to the list.
     * We always expect there to be CNAME that was generated 
     * by this DNAME following, so we don't process the DNAME 
     * directly.  */
    if(ntohs(r->rk.type) == LDNS_RR_TYPE_DNAME &&
      dname_strict_subdomain_c(*mname, r->rk.dname) &&
      !iter_find_rrset_in_prepend_answer(iq, r)) {
      if(!iter_add_prepend_answer(qstate, iq, r))
        return 0;
      continue;
    }

    if(ntohs(r->rk.type) == LDNS_RR_TYPE_CNAME &&
      query_dname_compare(*mname, r->rk.dname) == 0 &&
      !iter_find_rrset_in_prepend_answer(iq, r)) {
      /* Add this relevant CNAME rrset to the prepend list.*/
      if(!iter_add_prepend_answer(qstate, iq, r))
        return 0;
      get_cname_target(r, mname, mname_len);
    }

    /* Other rrsets in the section are ignored. */
  }
  /* add authority rrsets to authority prepend, for wildcarded CNAMEs */
  for(i=msg->rep->an_numrrsets; i<msg->rep->an_numrrsets +
    msg->rep->ns_numrrsets; i++) {
    struct ub_packed_rrset_key* r = msg->rep->rrsets[i];
    /* only add NSEC/NSEC3, as they may be needed for validation */
    if(ntohs(r->rk.type) == LDNS_RR_TYPE_NSEC ||
      ntohs(r->rk.type) == LDNS_RR_TYPE_NSEC3) {
      if(!iter_add_prepend_auth(qstate, iq, r))
        return 0;
    }
  }
  return 1;
}

/** fill fail address for later recovery */
static void
fill_fail_addr(struct iter_qstate* iq, struct sockaddr_storage* addr,
  socklen_t addrlen)
{
  if(addrlen == 0) {
    iq->fail_addr_type = 0;
    return;
  }
  if(((struct sockaddr_in*)addr)->sin_family == AF_INET) {
    iq->fail_addr_type = 4;
    memcpy(&iq->fail_addr.in,
      &((struct sockaddr_in*)addr)->sin_addr,
      sizeof(iq->fail_addr.in));
  }
#ifdef AF_INET6
  else if(((struct sockaddr_in*)addr)->sin_family == AF_INET6) {
    iq->fail_addr_type = 6;
    memcpy(&iq->fail_addr.in6,
      &((struct sockaddr_in6*)addr)->sin6_addr,
      sizeof(iq->fail_addr.in6));
  }
#endif
  else {
    iq->fail_addr_type = 0;
  }
}

/** print fail addr to string */
static void
print_fail_addr(struct iter_qstate* iq, char* buf, size_t len)
{
  if(iq->fail_addr_type == 4) {
    if(inet_ntop(AF_INET, &iq->fail_addr.in, buf,
      (socklen_t)len) == 0)
      (void)strlcpy(buf, "(inet_ntop error)", len);
  }
#ifdef AF_INET6
  else if(iq->fail_addr_type == 6) {
    if(inet_ntop(AF_INET6, &iq->fail_addr.in6, buf,
      (socklen_t)len) == 0)
      (void)strlcpy(buf, "(inet_ntop error)", len);
  }
#endif
  else
    (void)strlcpy(buf, "", len);
}

/** add response specific error information for log servfail */
static void
errinf_reply(struct module_qstate* qstate, struct iter_qstate* iq)
{
  if(qstate->env->cfg->val_log_level < 2 && !qstate->env->cfg->log_servfail)
    return;
  if((qstate->reply && qstate->reply->remote_addrlen != 0) ||
    (iq->fail_addr_type != 0)) {
    char from[256], frm[512];
    if(qstate->reply && qstate->reply->remote_addrlen != 0)
      addr_to_str(&qstate->reply->remote_addr,
        qstate->reply->remote_addrlen, from,
        sizeof(from));
    else
      print_fail_addr(iq, from, sizeof(from));
    snprintf(frm, sizeof(frm), "from %s", from);
    errinf(qstate, frm);
  }
  if(iq->scrub_failures || iq->parse_failures) {
    if(iq->scrub_failures)
      errinf(qstate, "upstream response failed scrub");
    if(iq->parse_failures)
      errinf(qstate, "could not parse upstream response");
  } else if(iq->response == NULL && iq->timeout_count != 0) {
    errinf(qstate, "upstream server timeout");
  } else if(iq->response == NULL) {
    errinf(qstate, "no server to query");
    if(iq->dp) {
      if(iq->dp->target_list == NULL)
        errinf(qstate, "no addresses for nameservers");
      else  errinf(qstate, "nameserver addresses not usable");
      if(iq->dp->nslist == NULL)
        errinf(qstate, "have no nameserver names");
      if(iq->dp->bogus)
        errinf(qstate, "NS record was dnssec bogus");
    }
  }
  if(iq->response && iq->response->rep) {
    if(FLAGS_GET_RCODE(iq->response->rep->flags) != 0) {
      char rcode[256], rc[32];
      (void)sldns_wire2str_rcode_buf(
        FLAGS_GET_RCODE(iq->response->rep->flags),
        rc, sizeof(rc));
      snprintf(rcode, sizeof(rcode), "got %s", rc);
      errinf(qstate, rcode);
    } else {
      /* rcode NOERROR */
      if(iq->response->rep->an_numrrsets == 0) {
        errinf(qstate, "nodata answer");
      }
    }
  }
}

/** see if last resort is possible - does config allow queries to parent */
static int
can_have_last_resort(struct module_env* env, uint8_t* nm, size_t ATTR_UNUSED(nmlen),
  uint16_t qclass, int* have_dp, struct delegpt** retdp,
  struct regional* region)
{
  struct delegpt* dp = NULL;
  int nolock = 0;
  /* do not process a last resort (the parent side) if a stub
   * or forward is configured, because we do not want to go 'above'
   * the configured servers */
  if(!dname_is_root(nm) &&
    (dp = hints_find(env->hints, nm, qclass, nolock)) &&
    /* has_parent side is turned off for stub_first, where we
     * are allowed to go to the parent */
    dp->has_parent_side_NS) {
    if(retdp) *retdp = delegpt_copy(dp, region);
    lock_rw_unlock(&env->hints->lock);
    if(have_dp) *have_dp = 1;
    return 0;
  }
  if(dp) {
    lock_rw_unlock(&env->hints->lock);
    dp = NULL;
  }
  if((dp = forwards_find(env->fwds, nm, qclass, nolock)) &&
    /* has_parent_side is turned off for forward_first, where
     * we are allowed to go to the parent */
    dp->has_parent_side_NS) {
    if(retdp) *retdp = delegpt_copy(dp, region);
    lock_rw_unlock(&env->fwds->lock);
    if(have_dp) *have_dp = 1;
    return 0;
  }
  /* lock_() calls are macros that could be nothing, surround in {} */
  if(dp) { lock_rw_unlock(&env->fwds->lock); }
  return 1;
}

/** see if target name is caps-for-id whitelisted */
static int
is_caps_whitelisted(struct iter_env* ie, struct iter_qstate* iq)
{
  if(!ie->caps_white) return 0; /* no whitelist, or no capsforid */
  return name_tree_lookup(ie->caps_white, iq->qchase.qname,
    iq->qchase.qname_len, dname_count_labels(iq->qchase.qname),
    iq->qchase.qclass) != NULL;
}

/**
 * Create target count structure for this query. This is always explicitly
 * created for the parent query.
 */
static void
target_count_create(struct iter_qstate* iq)
{
  if(!iq->target_count) {
    iq->target_count = (int*)calloc(TARGET_COUNT_MAX, sizeof(int));
    /* if calloc fails we simply do not track this number */
    if(iq->target_count) {
      iq->target_count[TARGET_COUNT_REF] = 1;
      iq->nxns_dp = (uint8_t**)calloc(1, sizeof(uint8_t*));
    }
  }
}

static void
target_count_increase(struct iter_qstate* iq, int num)
{
  target_count_create(iq);
  if(iq->target_count)
    iq->target_count[TARGET_COUNT_QUERIES] += num;
  iq->dp_target_count++;
}

static void
target_count_increase_nx(struct iter_qstate* iq, int num)
{
  target_count_create(iq);
  if(iq->target_count)
    iq->target_count[TARGET_COUNT_NX] += num;
}

static void
target_count_increase_global_quota(struct iter_qstate* iq, int num)
{
  target_count_create(iq);
  if(iq->target_count)
    iq->target_count[TARGET_COUNT_GLOBAL_QUOTA] += num;
}

/**
 * Generate a subrequest.
 * Generate a local request event. Local events are tied to this module, and
 * have a corresponding (first tier) event that is waiting for this event to
 * resolve to continue.
 *
 * @param qname The query name for this request.
 * @param qnamelen length of qname
 * @param qtype The query type for this request.
 * @param qclass The query class for this request.
 * @param qstate The event that is generating this event.
 * @param id: module id.
 * @param iq: The iterator state that is generating this event.
 * @param initial_state The initial response state (normally this
 *          is QUERY_RESP_STATE, unless it is known that the request won't
 *          need iterative processing
 * @param finalstate The final state for the response to this request.
 * @param subq_ret: if newly allocated, the subquerystate, or NULL if it does
 *  not need initialisation.
 * @param v: if true, validation is done on the subquery.
 * @param detached: true if this qstate should not attach to the subquery
 * @return false on error (malloc).
 */
static int
generate_sub_request(uint8_t* qname, size_t qnamelen, uint16_t qtype, 
  uint16_t qclass, struct module_qstate* qstate, int id,
  struct iter_qstate* iq, enum iter_state initial_state, 
  enum iter_state finalstate, struct module_qstate** subq_ret, int v,
  int detached)
{
  struct module_qstate* subq = NULL;
  struct iter_qstate* subiq = NULL;
  uint16_t qflags = 0; /* OPCODE QUERY, no flags */
  struct query_info qinf;
  int prime = (finalstate == PRIME_RESP_STATE)?1:0;
  int valrec = 0;
  qinf.qname = qname;
  qinf.qname_len = qnamelen;
  qinf.qtype = qtype;
  qinf.qclass = qclass;
  qinf.local_alias = NULL;

  /* RD should be set only when sending the query back through the INIT
   * state. */
  if(initial_state == INIT_REQUEST_STATE)
    qflags |= BIT_RD;
  /* We set the CD flag so we can send this through the "head" of 
   * the resolution chain, which might have a validator. We are 
   * uninterested in validating things not on the direct resolution 
   * path.  */
  if(!v) {
    qflags |= BIT_CD;
    valrec = 1;
  }
  
  if(detached) {
    struct mesh_state* sub = NULL;
    fptr_ok(fptr_whitelist_modenv_add_sub(
      qstate->env->add_sub));
    if(!(*qstate->env->add_sub)(qstate, &qinf, NULL,
      qflags, prime, valrec, &subq, &sub)){
      return 0;
    }
  }
  else {
    /* attach subquery, lookup existing or make a new one */
    fptr_ok(fptr_whitelist_modenv_attach_sub(
      qstate->env->attach_sub));
    if(!(*qstate->env->attach_sub)(qstate, &qinf, NULL, qflags,
      prime, valrec, &subq)) {
      return 0;
    }
  }
  *subq_ret = subq;
  if(subq) {
    /* initialise the new subquery */
    subq->curmod = id;
    subq->ext_state[id] = module_state_initial;
    subq->minfo[id] = regional_alloc(subq->region, 
      sizeof(struct iter_qstate));
    if(!subq->minfo[id]) {
      log_err("init subq: out of memory");
      fptr_ok(fptr_whitelist_modenv_kill_sub(
        qstate->env->kill_sub));
      (*qstate->env->kill_sub)(subq);
      return 0;
    }
    subiq = (struct iter_qstate*)subq->minfo[id];
    memset(subiq, 0, sizeof(*subiq));
    subiq->num_target_queries = 0;
    target_count_create(iq);
    subiq->target_count = iq->target_count;
    if(iq->target_count) {
      iq->target_count[TARGET_COUNT_REF] ++; /* extra reference */
      subiq->nxns_dp = iq->nxns_dp;
    }
    subiq->dp_target_count = 0;
    subiq->num_current_queries = 0;
    subiq->depth = iq->depth+1;
    outbound_list_init(&subiq->outlist);
    subiq->state = initial_state;
    subiq->final_state = finalstate;
    subiq->qchase = subq->qinfo;
    subiq->chase_flags = subq->query_flags;
    subiq->refetch_glue = 0;
    if(qstate->env->cfg->qname_minimisation)
      subiq->minimisation_state = INIT_MINIMISE_STATE;
    else
      subiq->minimisation_state = DONOT_MINIMISE_STATE;
    memset(&subiq->qinfo_out, 0, sizeof(struct query_info));
  }
  return 1;
}

/**
 * Generate and send a root priming request.
 * @param qstate: the qtstate that triggered the need to prime.
 * @param iq: iterator query state.
 * @param id: module id.
 * @param qclass: the class to prime.
 * @return 0 on failure
 */
static int
prime_root(struct module_qstate* qstate, struct iter_qstate* iq, int id,
  uint16_t qclass)
{
  struct delegpt* dp;
  struct module_qstate* subq;
  int nolock = 0;
  verbose(VERB_DETAIL, "priming . %s NS", 
    sldns_lookup_by_id(sldns_rr_classes, (int)qclass)?
    sldns_lookup_by_id(sldns_rr_classes, (int)qclass)->name:"??");
  dp = hints_find_root(qstate->env->hints, qclass, nolock);
  if(!dp) {
    verbose(VERB_ALGO, "Cannot prime due to lack of hints");
    return 0;
  }
  /* Priming requests start at the QUERYTARGETS state, skipping 
   * the normal INIT state logic (which would cause an infloop). */
  if(!generate_sub_request((uint8_t*)"\000", 1, LDNS_RR_TYPE_NS, 
    qclass, qstate, id, iq, QUERYTARGETS_STATE, PRIME_RESP_STATE,
    &subq, 0, 0)) {
    lock_rw_unlock(&qstate->env->hints->lock);
    verbose(VERB_ALGO, "could not prime root");
    return 0;
  }
  if(subq) {
    struct iter_qstate* subiq = 
      (struct iter_qstate*)subq->minfo[id];
    /* Set the initial delegation point to the hint.
     * copy dp, it is now part of the root prime query. 
     * dp was part of in the fixed hints structure. */
    subiq->dp = delegpt_copy(dp, subq->region);
    lock_rw_unlock(&qstate->env->hints->lock);
    if(!subiq->dp) {
      log_err("out of memory priming root, copydp");
      fptr_ok(fptr_whitelist_modenv_kill_sub(
        qstate->env->kill_sub));
      (*qstate->env->kill_sub)(subq);
      return 0;
    }
    /* there should not be any target queries. */
    subiq->num_target_queries = 0; 
    subiq->dnssec_expected = iter_indicates_dnssec(
      qstate->env, subiq->dp, NULL, subq->qinfo.qclass);
  } else {
    lock_rw_unlock(&qstate->env->hints->lock);
  }
  
  /* this module stops, our submodule starts, and does the query. */
  qstate->ext_state[id] = module_wait_subquery;
  return 1;
}

/**
 * Generate and process a stub priming request. This method tests for the
 * need to prime a stub zone, so it is safe to call for every request.
 *
 * @param qstate: the qtstate that triggered the need to prime.
 * @param iq: iterator query state.
 * @param id: module id.
 * @param qname: request name.
 * @param qclass: request class.
 * @return true if a priming subrequest was made, false if not. The will only
 *         issue a priming request if it detects an unprimed stub.
 *         Uses value of 2 to signal during stub-prime in root-prime situation
 *         that a noprime-stub is available and resolution can continue.
 */
static int
prime_stub(struct module_qstate* qstate, struct iter_qstate* iq, int id,
  uint8_t* qname, uint16_t qclass)
{
  /* Lookup the stub hint. This will return null if the stub doesn't 
   * need to be re-primed. */
  struct iter_hints_stub* stub;
  struct delegpt* stub_dp;
  struct module_qstate* subq;
  int nolock = 0;

  if(!qname) return 0;
  stub = hints_lookup_stub(qstate->env->hints, qname, qclass, iq->dp,
    nolock);
  /* The stub (if there is one) does not need priming. */
  if(!stub) return 0;
  stub_dp = stub->dp;
  /* if we have an auth_zone dp, and stub is equal, don't prime stub
   * yet, unless we want to fallback and avoid the auth_zone */
  if(!iq->auth_zone_avoid && iq->dp && iq->dp->auth_dp && 
    query_dname_compare(iq->dp->name, stub_dp->name) == 0) {
    lock_rw_unlock(&qstate->env->hints->lock);
    return 0;
  }

  /* is it a noprime stub (always use) */
  if(stub->noprime) {
    int r = 0;
    if(iq->dp == NULL) r = 2;
    /* copy the dp out of the fixed hints structure, so that
     * it can be changed when servicing this query */
    iq->dp = delegpt_copy(stub_dp, qstate->region);
    lock_rw_unlock(&qstate->env->hints->lock);
    if(!iq->dp) {
      log_err("out of memory priming stub");
      errinf(qstate, "malloc failure, priming stub");
      (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      return 1; /* return 1 to make module stop, with error */
    }
    log_nametypeclass(VERB_DETAIL, "use stub", iq->dp->name,
      LDNS_RR_TYPE_NS, qclass);
    return r;
  }

  /* Otherwise, we need to (re)prime the stub. */
  log_nametypeclass(VERB_DETAIL, "priming stub", stub_dp->name, 
    LDNS_RR_TYPE_NS, qclass);

  /* Stub priming events start at the QUERYTARGETS state to avoid the
   * redundant INIT state processing. */
  if(!generate_sub_request(stub_dp->name, stub_dp->namelen, 
    LDNS_RR_TYPE_NS, qclass, qstate, id, iq,
    QUERYTARGETS_STATE, PRIME_RESP_STATE, &subq, 0, 0)) {
    lock_rw_unlock(&qstate->env->hints->lock);
    verbose(VERB_ALGO, "could not prime stub");
    errinf(qstate, "could not generate lookup for stub prime");
    (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    return 1; /* return 1 to make module stop, with error */
  }
  if(subq) {
    struct iter_qstate* subiq = 
      (struct iter_qstate*)subq->minfo[id];

    /* Set the initial delegation point to the hint. */
    /* make copy to avoid use of stub dp by different qs/threads */
    subiq->dp = delegpt_copy(stub_dp, subq->region);
    lock_rw_unlock(&qstate->env->hints->lock);
    if(!subiq->dp) {
      log_err("out of memory priming stub, copydp");
      fptr_ok(fptr_whitelist_modenv_kill_sub(
        qstate->env->kill_sub));
      (*qstate->env->kill_sub)(subq);
      errinf(qstate, "malloc failure, in stub prime");
      (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      return 1; /* return 1 to make module stop, with error */
    }
    /* there should not be any target queries -- although there 
     * wouldn't be anyway, since stub hints never have 
     * missing targets. */
    subiq->num_target_queries = 0; 
    subiq->wait_priming_stub = 1;
    subiq->dnssec_expected = iter_indicates_dnssec(
      qstate->env, subiq->dp, NULL, subq->qinfo.qclass);
  } else {
    lock_rw_unlock(&qstate->env->hints->lock);
  }
  
  /* this module stops, our submodule starts, and does the query. */
  qstate->ext_state[id] = module_wait_subquery;
  return 1;
}

/**
 * Generate a delegation point for an auth zone (unless cached dp is better)
 * false on alloc failure.
 */
static int
auth_zone_delegpt(struct module_qstate* qstate, struct iter_qstate* iq,
  uint8_t* delname, size_t delnamelen)
{
  struct auth_zone* z;
  if(iq->auth_zone_avoid)
    return 1;
  if(!delname) {
    delname = iq->qchase.qname;
    delnamelen = iq->qchase.qname_len;
  }
  lock_rw_rdlock(&qstate->env->auth_zones->lock);
  z = auth_zones_find_zone(qstate->env->auth_zones, delname, delnamelen,
    qstate->qinfo.qclass);
  if(!z) {
    lock_rw_unlock(&qstate->env->auth_zones->lock);
    return 1;
  }
  lock_rw_rdlock(&z->lock);
  lock_rw_unlock(&qstate->env->auth_zones->lock);
  if(z->for_upstream) {
    if(iq->dp && query_dname_compare(z->name, iq->dp->name) == 0
      && iq->dp->auth_dp && qstate->blacklist &&
      z->fallback_enabled) {
      /* cache is blacklisted and fallback, and we
       * already have an auth_zone dp */
      if(verbosity>=VERB_ALGO) {
        char buf[LDNS_MAX_DOMAINLEN];
        dname_str(z->name, buf);
        verbose(VERB_ALGO, "auth_zone %s "
          "fallback because cache blacklisted",
          buf);
      }
      lock_rw_unlock(&z->lock);
      iq->dp = NULL;
      return 1;
    }
    if(iq->dp==NULL || dname_subdomain_c(z->name, iq->dp->name)) {
      struct delegpt* dp;
      if(qstate->blacklist && z->fallback_enabled) {
        /* cache is blacklisted because of a DNSSEC
         * validation failure, and the zone allows
         * fallback to the internet, query there. */
        if(verbosity>=VERB_ALGO) {
          char buf[LDNS_MAX_DOMAINLEN];
          dname_str(z->name, buf);
          verbose(VERB_ALGO, "auth_zone %s "
            "fallback because cache blacklisted",
            buf);
        }
        lock_rw_unlock(&z->lock);
        return 1;
      }
      dp = (struct delegpt*)regional_alloc_zero(
        qstate->region, sizeof(*dp));
      if(!dp) {
        log_err("alloc failure");
        if(z->fallback_enabled) {
          lock_rw_unlock(&z->lock);
          return 1; /* just fallback */
        }
        lock_rw_unlock(&z->lock);
        errinf(qstate, "malloc failure");
        return 0;
      }
      dp->name = regional_alloc_init(qstate->region,
        z->name, z->namelen);
      if(!dp->name) {
        log_err("alloc failure");
        if(z->fallback_enabled) {
          lock_rw_unlock(&z->lock);
          return 1; /* just fallback */
        }
        lock_rw_unlock(&z->lock);
        errinf(qstate, "malloc failure");
        return 0;
      }
      dp->namelen = z->namelen;
      dp->namelabs = z->namelabs;
      dp->auth_dp = 1;
      iq->dp = dp;
    }
  }

  lock_rw_unlock(&z->lock);
  return 1;
}

/**
 * Generate A and AAAA checks for glue that is in-zone for the referral
 * we just got to obtain authoritative information on the addresses.
 *
 * @param qstate: the qtstate that triggered the need to prime.
 * @param iq: iterator query state.
 * @param id: module id.
 */
static void
generate_a_aaaa_check(struct module_qstate* qstate, struct iter_qstate* iq, 
  int id)
{
  struct iter_env* ie = (struct iter_env*)qstate->env->modinfo[id];
  struct module_qstate* subq;
  size_t i;
  struct reply_info* rep = iq->response->rep;
  struct ub_packed_rrset_key* s;
  log_assert(iq->dp);

  if(iq->depth == ie->max_dependency_depth)
    return;
  /* walk through additional, and check if in-zone,
   * only relevant A, AAAA are left after scrub anyway */
  for(i=rep->an_numrrsets+rep->ns_numrrsets; i<rep->rrset_count; i++) {
    s = rep->rrsets[i];
    /* check *ALL* addresses that are transmitted in additional*/
    /* is it an address ? */
    if( !(ntohs(s->rk.type)==LDNS_RR_TYPE_A ||
      ntohs(s->rk.type)==LDNS_RR_TYPE_AAAA)) {
      continue;
    }
    /* is this query the same as the A/AAAA check for it */
    if(qstate->qinfo.qtype == ntohs(s->rk.type) &&
      qstate->qinfo.qclass == ntohs(s->rk.rrset_class) &&
      query_dname_compare(qstate->qinfo.qname, 
        s->rk.dname)==0 &&
      (qstate->query_flags&BIT_RD) && 
      !(qstate->query_flags&BIT_CD))
      continue;

    /* generate subrequest for it */
    log_nametypeclass(VERB_ALGO, "schedule addr fetch", 
      s->rk.dname, ntohs(s->rk.type), 
      ntohs(s->rk.rrset_class));
    if(!generate_sub_request(s->rk.dname, s->rk.dname_len, 
      ntohs(s->rk.type), ntohs(s->rk.rrset_class),
      qstate, id, iq,
      INIT_REQUEST_STATE, FINISHED_STATE, &subq, 1, 0)) {
      verbose(VERB_ALGO, "could not generate addr check");
      return;
    }
    /* ignore subq - not need for more init */
  }
}

/**
 * Generate a NS check request to obtain authoritative information
 * on an NS rrset.
 *
 * @param qstate: the qstate that triggered the need to prime.
 * @param iq: iterator query state.
 * @param id: module id.
 */
static void
generate_ns_check(struct module_qstate* qstate, struct iter_qstate* iq, int id)
{
  struct iter_env* ie = (struct iter_env*)qstate->env->modinfo[id];
  struct module_qstate* subq;
  log_assert(iq->dp);

  if(iq->depth == ie->max_dependency_depth)
    return;
  if(!can_have_last_resort(qstate->env, iq->dp->name, iq->dp->namelen,
    iq->qchase.qclass, NULL, NULL, NULL))
    return;
  /* is this query the same as the nscheck? */
  if(qstate->qinfo.qtype == LDNS_RR_TYPE_NS &&
    query_dname_compare(iq->dp->name, qstate->qinfo.qname)==0 &&
    (qstate->query_flags&BIT_RD) && !(qstate->query_flags&BIT_CD)){
    /* spawn off A, AAAA queries for in-zone glue to check */
    generate_a_aaaa_check(qstate, iq, id);
    return;
  }
  /* no need to get the NS record for DS, it is above the zonecut */
  if(qstate->qinfo.qtype == LDNS_RR_TYPE_DS)
    return;

  log_nametypeclass(VERB_ALGO, "schedule ns fetch", 
    iq->dp->name, LDNS_RR_TYPE_NS, iq->qchase.qclass);
  if(!generate_sub_request(iq->dp->name, iq->dp->namelen, 
    LDNS_RR_TYPE_NS, iq->qchase.qclass, qstate, id, iq,
    INIT_REQUEST_STATE, FINISHED_STATE, &subq, 1, 0)) {
    verbose(VERB_ALGO, "could not generate ns check");
    return;
  }
  if(subq) {
    struct iter_qstate* subiq = 
      (struct iter_qstate*)subq->minfo[id];

    /* make copy to avoid use of stub dp by different qs/threads */
    /* refetch glue to start higher up the tree */
    subiq->refetch_glue = 1;
    subiq->dp = delegpt_copy(iq->dp, subq->region);
    if(!subiq->dp) {
      log_err("out of memory generating ns check, copydp");
      fptr_ok(fptr_whitelist_modenv_kill_sub(
        qstate->env->kill_sub));
      (*qstate->env->kill_sub)(subq);
      return;
    }
  }
}

/**
 * Generate a DNSKEY prefetch query to get the DNSKEY for the DS record we
 * just got in a referral (where we have dnssec_expected, thus have trust
 * anchors above it).  Note that right after calling this routine the
 * iterator detached subqueries (because of following the referral), and thus
 * the DNSKEY query becomes detached, its return stored in the cache for
 * later lookup by the validator.  This cache lookup by the validator avoids
 * the roundtrip incurred by the DNSKEY query.  The DNSKEY query is now
 * performed at about the same time the original query is sent to the domain,
 * thus the two answers are likely to be returned at about the same time,
 * saving a roundtrip from the validated lookup.
 *
 * @param qstate: the qtstate that triggered the need to prime.
 * @param iq: iterator query state.
 * @param id: module id.
 */
static void
generate_dnskey_prefetch(struct module_qstate* qstate, 
  struct iter_qstate* iq, int id)
{
  struct module_qstate* subq;
  log_assert(iq->dp);

  /* is this query the same as the prefetch? */
  if(qstate->qinfo.qtype == LDNS_RR_TYPE_DNSKEY &&
    query_dname_compare(iq->dp->name, qstate->qinfo.qname)==0 &&
    (qstate->query_flags&BIT_RD) && !(qstate->query_flags&BIT_CD)){
    return;
  }
  /* we do not generate this prefetch when the query list is full,
   * the query is fetched, if needed, when the validator wants it.
   * At that time the validator waits for it, after spawning it.
   * This means there is one state that uses cpu and a socket, the
   * spawned while this one waits, and not several at the same time,
   * if we had created the lookup here. And this helps to keep
   * the total load down, but the query still succeeds to resolve. */
  if(mesh_jostle_exceeded(qstate->env->mesh))
    return;

  /* if the DNSKEY is in the cache this lookup will stop quickly */
  log_nametypeclass(VERB_ALGO, "schedule dnskey prefetch", 
    iq->dp->name, LDNS_RR_TYPE_DNSKEY, iq->qchase.qclass);
  if(!generate_sub_request(iq->dp->name, iq->dp->namelen, 
    LDNS_RR_TYPE_DNSKEY, iq->qchase.qclass, qstate, id, iq,
    INIT_REQUEST_STATE, FINISHED_STATE, &subq, 0, 0)) {
    /* we'll be slower, but it'll work */
    verbose(VERB_ALGO, "could not generate dnskey prefetch");
    return;
  }
  if(subq) {
    struct iter_qstate* subiq = 
      (struct iter_qstate*)subq->minfo[id];
    /* this qstate has the right delegation for the dnskey lookup*/
    /* make copy to avoid use of stub dp by different qs/threads */
    subiq->dp = delegpt_copy(iq->dp, subq->region);
    /* if !subiq->dp, it'll start from the cache, no problem */
  }
}

/**
 * See if the query needs forwarding.
 * 
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @return true if the request is forwarded, false if not.
 *  If returns true but, iq->dp is NULL then a malloc failure occurred.
 */
static int
forward_request(struct module_qstate* qstate, struct iter_qstate* iq)
{
  struct delegpt* dp;
  uint8_t* delname = iq->qchase.qname;
  size_t delnamelen = iq->qchase.qname_len;
  int nolock = 0;
  if(iq->refetch_glue && iq->dp) {
    delname = iq->dp->name;
    delnamelen = iq->dp->namelen;
  }
  /* strip one label off of DS query to lookup higher for it */
  if( (iq->qchase.qtype == LDNS_RR_TYPE_DS || iq->refetch_glue)
    && !dname_is_root(iq->qchase.qname))
    dname_remove_label(&delname, &delnamelen);
  dp = forwards_lookup(qstate->env->fwds, delname, iq->qchase.qclass,
    nolock);
  if(!dp) return 0;
  /* send recursion desired to forward addr */
  iq->chase_flags |= BIT_RD; 
  iq->dp = delegpt_copy(dp, qstate->region);
  lock_rw_unlock(&qstate->env->fwds->lock);
  /* iq->dp checked by caller */
  verbose(VERB_ALGO, "forwarding request");
  return 1;
}

/** 
 * Process the initial part of the request handling. This state roughly
 * corresponds to resolver algorithms steps 1 (find answer in cache) and 2
 * (find the best servers to ask).
 *
 * Note that all requests start here, and query restarts revisit this state.
 *
 * This state either generates: 1) a response, from cache or error, 2) a
 * priming event, or 3) forwards the request to the next state (init2,
 * generally).
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @return true if the event needs more request processing immediately,
 *         false if not.
 */
static int
processInitRequest(struct module_qstate* qstate, struct iter_qstate* iq,
  struct iter_env* ie, int id)
{
  uint8_t dpname_storage[LDNS_MAX_DOMAINLEN+1];
  uint8_t* delname, *dpname=NULL;
  size_t delnamelen, dpnamelen=0;
  struct dns_msg* msg = NULL;

  log_query_info(VERB_DETAIL, "resolving", &qstate->qinfo);
  /* check effort */

  /* We enforce a maximum number of query restarts. This is primarily a
   * cheap way to prevent CNAME loops. */
  if(iq->query_restart_count > ie->max_query_restarts) {
    verbose(VERB_QUERY, "request has exceeded the maximum number"
      " of query restarts with %d", iq->query_restart_count);
    errinf(qstate, "request has exceeded the maximum number "
      "restarts (eg. indirections)");
    if(iq->qchase.qname)
      errinf_dname(qstate, "stop at", iq->qchase.qname);
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }

  /* We enforce a maximum recursion/dependency depth -- in general, 
   * this is unnecessary for dependency loops (although it will 
   * catch those), but it provides a sensible limit to the amount 
   * of work required to answer a given query. */
  verbose(VERB_ALGO, "request has dependency depth of %d", iq->depth);
  if(iq->depth > ie->max_dependency_depth) {
    verbose(VERB_QUERY, "request has exceeded the maximum "
      "dependency depth with depth of %d", iq->depth);
    errinf(qstate, "request has exceeded the maximum dependency "
      "depth (eg. nameserver lookup recursion)");
    return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
  }

  /* If the request is qclass=ANY, setup to generate each class */
  if(qstate->qinfo.qclass == LDNS_RR_CLASS_ANY) {
    iq->qchase.qclass = 0;
    return next_state(iq, COLLECT_CLASS_STATE);
  }

  /*
   * If we are restricted by a forward-zone or a stub-zone, we
   * can't re-fetch glue for this delegation point.
   * we won’t try to re-fetch glue if the iq->dp is null.
   */
  if (iq->refetch_glue &&
          iq->dp &&
          !can_have_last_resort(qstate->env, iq->dp->name,
               iq->dp->namelen, iq->qchase.qclass, NULL, NULL, NULL)) {
      iq->refetch_glue = 0;
  }

  /* Resolver Algorithm Step 1 -- Look for the answer in local data. */

  /* This either results in a query restart (CNAME cache response), a
   * terminating response (ANSWER), or a cache miss (null). */

  /* Check RPZ for override */
  if(qstate->env->auth_zones) {
    /* apply rpz qname triggers, like after cname */
    struct dns_msg* forged_response =
      rpz_callback_from_iterator_cname(qstate, iq);
    if(forged_response) {
      uint8_t* sname = 0;
      size_t slen = 0;
      int count = 0;
      while(forged_response && reply_find_rrset_section_an(
        forged_response->rep, iq->qchase.qname,
        iq->qchase.qname_len, LDNS_RR_TYPE_CNAME,
        iq->qchase.qclass) &&
        iq->qchase.qtype != LDNS_RR_TYPE_CNAME &&
        count++ < ie->max_query_restarts) {
        /* another cname to follow */
        if(!handle_cname_response(qstate, iq, forged_response,
          &sname, &slen)) {
          errinf(qstate, "malloc failure, CNAME info");
          return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
        }
        iq->qchase.qname = sname;
        iq->qchase.qname_len = slen;
        forged_response =
          rpz_callback_from_iterator_cname(qstate, iq);
      }
      if(forged_response != NULL) {
        qstate->ext_state[id] = module_finished;
        qstate->return_rcode = LDNS_RCODE_NOERROR;
        qstate->return_msg = forged_response;
        iq->response = forged_response;
        next_state(iq, FINISHED_STATE);
        if(!iter_prepend(iq, qstate->return_msg, qstate->region)) {
          log_err("rpz: after cached cname, prepend rrsets: out of memory");
          return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
        }
        qstate->return_msg->qinfo = qstate->qinfo;
        return 0;
      }
      /* Follow the CNAME response */
      iq->dp = NULL;
      iq->refetch_glue = 0;
      iq->query_restart_count++;
      iq->sent_count = 0;
      iq->dp_target_count = 0;
      sock_list_insert(&qstate->reply_origin, NULL, 0, qstate->region);
      if(qstate->env->cfg->qname_minimisation)
        iq->minimisation_state = INIT_MINIMISE_STATE;
      return next_state(iq, INIT_REQUEST_STATE);
    }
  }

  if (iter_stub_fwd_no_cache(qstate, &iq->qchase, &dpname, &dpnamelen,
    dpname_storage, sizeof(dpname_storage))) {
    /* Asked to not query cache. */
    verbose(VERB_ALGO, "no-cache set, going to the network");
    qstate->no_cache_lookup = 1;
    qstate->no_cache_store = 1;
    msg = NULL;
  } else if(qstate->blacklist) {
    /* if cache, or anything else, was blacklisted then
     * getting older results from cache is a bad idea, no cache */
    verbose(VERB_ALGO, "cache blacklisted, going to the network");
    msg = NULL;
  } else if(!qstate->no_cache_lookup) {
    msg = dns_cache_lookup(qstate->env, iq->qchase.qname, 
      iq->qchase.qname_len, iq->qchase.qtype, 
      iq->qchase.qclass, qstate->query_flags,
      qstate->region, qstate->env->scratch, 0, dpname,
      dpnamelen);
    if(!msg && qstate->env->neg_cache &&
      iter_qname_indicates_dnssec(qstate->env, &iq->qchase)) {
      /* lookup in negative cache; may result in
       * NOERROR/NODATA or NXDOMAIN answers that need validation */
      msg = val_neg_getmsg(qstate->env->neg_cache, &iq->qchase,
        qstate->region, qstate->env->rrset_cache,
        qstate->env->scratch_buffer, 
        *qstate->env->now, 1/*add SOA*/, NULL, 
        qstate->env->cfg);
    }
    /* item taken from cache does not match our query name, thus
     * security needs to be re-examined later */
    if(msg && query_dname_compare(qstate->qinfo.qname,
      iq->qchase.qname) != 0)
      msg->rep->security = sec_status_unchecked;
  }
  if(msg) {
    /* handle positive cache response */
    enum response_type type = response_type_from_cache(msg, 
      &iq->qchase);
    if(verbosity >= VERB_ALGO) {
      log_dns_msg("msg from cache lookup", &msg->qinfo, 
        msg->rep);
      verbose(VERB_ALGO, "msg ttl is %d, prefetch ttl %d", 
        (int)msg->rep->ttl, 
        (int)msg->rep->prefetch_ttl);
    }

    if(type == RESPONSE_TYPE_CNAME) {
      uint8_t* sname = 0;
      size_t slen = 0;
      verbose(VERB_ALGO, "returning CNAME response from "
        "cache");
      if(!handle_cname_response(qstate, iq, msg, 
        &sname, &slen)) {
        errinf(qstate, "failed to prepend CNAME "
          "components, malloc failure");
        return error_response(qstate, id, 
          LDNS_RCODE_SERVFAIL);
      }
      iq->qchase.qname = sname;
      iq->qchase.qname_len = slen;
      /* This *is* a query restart, even if it is a cheap 
       * one. */
      iq->dp = NULL;
      iq->refetch_glue = 0;
      iq->query_restart_count++;
      iq->sent_count = 0;
      iq->dp_target_count = 0;
      sock_list_insert(&qstate->reply_origin, NULL, 0, qstate->region);
      if(qstate->env->cfg->qname_minimisation)
        iq->minimisation_state = INIT_MINIMISE_STATE;
      return next_state(iq, INIT_REQUEST_STATE);
    }
    /* if from cache, NULL, else insert 'cache IP' len=0 */
    if(qstate->reply_origin)
      sock_list_insert(&qstate->reply_origin, NULL, 0, qstate->region);
    if(FLAGS_GET_RCODE(msg->rep->flags) == LDNS_RCODE_SERVFAIL)
      errinf(qstate, "SERVFAIL in cache");
    /* it is an answer, response, to final state */
    verbose(VERB_ALGO, "returning answer from cache.");
    iq->response = msg;
    return final_state(iq);
  }

  /* attempt to forward the request */
  if(forward_request(qstate, iq))
  {
    if(!iq->dp) {
      log_err("alloc failure for forward dp");
      errinf(qstate, "malloc failure for forward zone");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    if(!cache_fill_missing(qstate->env, iq->qchase.qclass,
      qstate->region, iq->dp, 0)) {
      errinf(qstate, "malloc failure, copy extra info into delegation point");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    if((qstate->query_flags&BIT_RD)==0) {
      /* If the server accepts RD=0 queries and forwards
       * with RD=1, then if the server is listed as an NS
       * entry, it starts query loops. Stop that loop by
       * disallowing the query. The RD=0 was previously used
       * to check the cache with allow_snoop. For stubs,
       * the iterator pass would have primed the stub and
       * then cached information can be used for further
       * queries. */
      verbose(VERB_ALGO, "cannot forward RD=0 query, to stop query loops");
      errinf(qstate, "cannot forward RD=0 query");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    iq->refetch_glue = 0;
    iq->minimisation_state = DONOT_MINIMISE_STATE;
    /* the request has been forwarded.
     * forwarded requests need to be immediately sent to the 
     * next state, QUERYTARGETS. */
    return next_state(iq, QUERYTARGETS_STATE);
  }

  /* Resolver Algorithm Step 2 -- find the "best" servers. */

  /* first, adjust for DS queries. To avoid the grandparent problem, 
   * we just look for the closest set of server to the parent of qname.
   * When re-fetching glue we also need to ask the parent.
   */
  if(iq->refetch_glue) {
    if(!iq->dp) {
      log_err("internal or malloc fail: no dp for refetch");
      errinf(qstate, "malloc failure, for delegation info");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    delname = iq->dp->name;
    delnamelen = iq->dp->namelen;
  } else {
    delname = iq->qchase.qname;
    delnamelen = iq->qchase.qname_len;
  }
  if(iq->qchase.qtype == LDNS_RR_TYPE_DS || iq->refetch_glue ||
     (iq->qchase.qtype == LDNS_RR_TYPE_NS && qstate->prefetch_leeway
     && can_have_last_resort(qstate->env, delname, delnamelen, iq->qchase.qclass, NULL, NULL, NULL))) {
    /* remove first label from delname, root goes to hints,
     * but only to fetch glue, not for qtype=DS. */
    /* also when prefetching an NS record, fetch it again from
     * its parent, just as if it expired, so that you do not
     * get stuck on an older nameserver that gives old NSrecords */
    if(dname_is_root(delname) && (iq->refetch_glue ||
      (iq->qchase.qtype == LDNS_RR_TYPE_NS &&
      qstate->prefetch_leeway)))
      delname = NULL; /* go to root priming */
    else  dname_remove_label(&delname, &delnamelen);
  }
  /* delname is the name to lookup a delegation for. If NULL rootprime */
  while(1) {
    
    /* Lookup the delegation in the cache. If null, then the 
     * cache needs to be primed for the qclass. */
    if(delname)
         iq->dp = dns_cache_find_delegation(qstate->env, delname, 
      delnamelen, iq->qchase.qtype, iq->qchase.qclass, 
      qstate->region, &iq->deleg_msg,
      *qstate->env->now+qstate->prefetch_leeway, 1,
      dpname, dpnamelen);
    else iq->dp = NULL;

    /* If the cache has returned nothing, then we have a 
     * root priming situation. */
    if(iq->dp == NULL) {
      int r;
      int nolock = 0;
      /* if under auth zone, no prime needed */
      if(!auth_zone_delegpt(qstate, iq, delname, delnamelen))
        return error_response(qstate, id, 
          LDNS_RCODE_SERVFAIL);
      if(iq->dp) /* use auth zone dp */
        return next_state(iq, INIT_REQUEST_2_STATE);
      /* if there is a stub, then no root prime needed */
      r = prime_stub(qstate, iq, id, delname,
        iq->qchase.qclass);
      if(r == 2)
        break; /* got noprime-stub-zone, continue */
      else if(r)
        return 0; /* stub prime request made */
      if(forwards_lookup_root(qstate->env->fwds,
        iq->qchase.qclass, nolock)) {
        lock_rw_unlock(&qstate->env->fwds->lock);
        /* forward zone root, no root prime needed */
        /* fill in some dp - safety belt */
        iq->dp = hints_find_root(qstate->env->hints,
          iq->qchase.qclass, nolock);
        if(!iq->dp) {
          log_err("internal error: no hints dp");
          errinf(qstate, "no hints for this class");
          return error_response_cache(qstate, id,
            LDNS_RCODE_SERVFAIL);
        }
        iq->dp = delegpt_copy(iq->dp, qstate->region);
        lock_rw_unlock(&qstate->env->hints->lock);
        if(!iq->dp) {
          log_err("out of memory in safety belt");
          errinf(qstate, "malloc failure, in safety belt");
          return error_response(qstate, id, 
            LDNS_RCODE_SERVFAIL);
        }
        return next_state(iq, INIT_REQUEST_2_STATE);
      }
      /* Note that the result of this will set a new
       * DelegationPoint based on the result of priming. */
      if(!prime_root(qstate, iq, id, iq->qchase.qclass))
        return error_response(qstate, id, 
          LDNS_RCODE_REFUSED);

      /* priming creates and sends a subordinate query, with 
       * this query as the parent. So further processing for 
       * this event will stop until reactivated by the 
       * results of priming. */
      return 0;
    }
    if(!iq->ratelimit_ok && qstate->prefetch_leeway)
      iq->ratelimit_ok = 1; /* allow prefetches, this keeps
      otherwise valid data in the cache */

    /* see if this dp not useless.
     * It is useless if:
     *  o all NS items are required glue.
     *    or the query is for NS item that is required glue.
     *  o no addresses are provided.
     *  o RD qflag is on.
     * Instead, go up one level, and try to get even further
     * If the root was useless, use safety belt information.
     * Only check cache returns, because replies for servers
     * could be useless but lead to loops (bumping into the
     * same server reply) if useless-checked.
     */
    if(iter_dp_is_useless(&qstate->qinfo, qstate->query_flags,
      iq->dp, ie->supports_ipv4, ie->supports_ipv6,
      ie->nat64.use_nat64)) {
      int have_dp = 0;
      if(!can_have_last_resort(qstate->env, iq->dp->name, iq->dp->namelen, iq->qchase.qclass, &have_dp, &iq->dp, qstate->region)) {
        if(have_dp) {
          verbose(VERB_QUERY, "cache has stub "
            "or fwd but no addresses, "
            "fallback to config");
          if(have_dp && !iq->dp) {
            log_err("out of memory in "
              "stub/fwd fallback");
            errinf(qstate, "malloc failure, for fallback to config");
            return error_response(qstate,
                id, LDNS_RCODE_SERVFAIL);
          }
          break;
        }
        verbose(VERB_ALGO, "useless dp "
          "but cannot go up, servfail");
        delegpt_log(VERB_ALGO, iq->dp);
        errinf(qstate, "no useful nameservers, "
          "and cannot go up");
        errinf_dname(qstate, "for zone", iq->dp->name);
        return error_response(qstate, id, 
          LDNS_RCODE_SERVFAIL);
      }
      if(dname_is_root(iq->dp->name)) {
        /* use safety belt */
        int nolock = 0;
        verbose(VERB_QUERY, "Cache has root NS but "
        "no addresses. Fallback to the safety belt.");
        iq->dp = hints_find_root(qstate->env->hints,
          iq->qchase.qclass, nolock);
        /* note deleg_msg is from previous lookup,
         * but RD is on, so it is not used */
        if(!iq->dp) {
          log_err("internal error: no hints dp");
          return error_response(qstate, id, 
            LDNS_RCODE_REFUSED);
        }
        iq->dp = delegpt_copy(iq->dp, qstate->region);
        lock_rw_unlock(&qstate->env->hints->lock);
        if(!iq->dp) {
          log_err("out of memory in safety belt");
          errinf(qstate, "malloc failure, in safety belt, for root");
          return error_response(qstate, id, 
            LDNS_RCODE_SERVFAIL);
        }
        break;
      } else {
        verbose(VERB_ALGO, 
          "cache delegation was useless:");
        delegpt_log(VERB_ALGO, iq->dp);
        /* go up */
        delname = iq->dp->name;
        delnamelen = iq->dp->namelen;
        dname_remove_label(&delname, &delnamelen);
      }
    } else break;
  }

  verbose(VERB_ALGO, "cache delegation returns delegpt");
  delegpt_log(VERB_ALGO, iq->dp);

  /* Otherwise, set the current delegation point and move on to the 
   * next state. */
  return next_state(iq, INIT_REQUEST_2_STATE);
}

/** 
 * Process the second part of the initial request handling. This state
 * basically exists so that queries that generate root priming events have
 * the same init processing as ones that do not. Request events that reach
 * this state must have a valid currentDelegationPoint set.
 *
 * This part is primarily handling stub zone priming. Events that reach this
 * state must have a current delegation point.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @return true if the event needs more request processing immediately,
 *         false if not.
 */
static int
processInitRequest2(struct module_qstate* qstate, struct iter_qstate* iq,
  int id)
{
  uint8_t* delname;
  size_t delnamelen;
  log_query_info(VERB_QUERY, "resolving (init part 2): ", 
    &qstate->qinfo);

  delname = iq->qchase.qname;
  delnamelen = iq->qchase.qname_len;
  if(iq->refetch_glue) {
    struct iter_hints_stub* stub;
    int nolock = 0;
    if(!iq->dp) {
      log_err("internal or malloc fail: no dp for refetch");
      errinf(qstate, "malloc failure, no delegation info");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    /* Do not send queries above stub, do not set delname to dp if
     * this is above stub without stub-first. */
    stub = hints_lookup_stub(
      qstate->env->hints, iq->qchase.qname, iq->qchase.qclass,
      iq->dp, nolock);
    if(!stub || !stub->dp->has_parent_side_NS || 
      dname_subdomain_c(iq->dp->name, stub->dp->name)) {
      delname = iq->dp->name;
      delnamelen = iq->dp->namelen;
    }
    /* lock_() calls are macros that could be nothing, surround in {} */
    if(stub) { lock_rw_unlock(&qstate->env->hints->lock); }
  }
  if(iq->qchase.qtype == LDNS_RR_TYPE_DS || iq->refetch_glue) {
    if(!dname_is_root(delname))
      dname_remove_label(&delname, &delnamelen);
    iq->refetch_glue = 0; /* if CNAME causes restart, no refetch */
  }

  /* see if we have an auth zone to answer from, improves dp from cache
   * (if any dp from cache) with auth zone dp, if that is lower */
  if(!auth_zone_delegpt(qstate, iq, delname, delnamelen))
    return error_response(qstate, id, LDNS_RCODE_SERVFAIL);

  /* Check to see if we need to prime a stub zone. */
  if(prime_stub(qstate, iq, id, delname, iq->qchase.qclass)) {
    /* A priming sub request was made */
    return 0;
  }

  /* most events just get forwarded to the next state. */
  return next_state(iq, INIT_REQUEST_3_STATE);
}

/** 
 * Process the third part of the initial request handling. This state exists
 * as a separate state so that queries that generate stub priming events
 * will get the tail end of the init process but not repeat the stub priming
 * check.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @return true, advancing the event to the QUERYTARGETS_STATE.
 */
static int
processInitRequest3(struct module_qstate* qstate, struct iter_qstate* iq, 
  int id)
{
  log_query_info(VERB_QUERY, "resolving (init part 3): ", 
    &qstate->qinfo);
  /* if the cache reply dp equals a validation anchor or msg has DS,
   * then DNSSEC RRSIGs are expected in the reply */
  iq->dnssec_expected = iter_indicates_dnssec(qstate->env, iq->dp, 
    iq->deleg_msg, iq->qchase.qclass);

  /* If the RD flag wasn't set, then we just finish with the 
   * cached referral as the response. */
  if(!(qstate->query_flags & BIT_RD) && iq->deleg_msg) {
    iq->response = iq->deleg_msg;
    if(verbosity >= VERB_ALGO && iq->response)
      log_dns_msg("no RD requested, using delegation msg", 
        &iq->response->qinfo, iq->response->rep);
    if(qstate->reply_origin)
      sock_list_insert(&qstate->reply_origin, NULL, 0, qstate->region);
    return final_state(iq);
  }
  /* After this point, unset the RD flag -- this query is going to 
   * be sent to an auth. server. */
  iq->chase_flags &= ~BIT_RD;

  /* if dnssec expected, fetch key for the trust-anchor or cached-DS */
  if(iq->dnssec_expected && qstate->env->cfg->prefetch_key &&
    !(qstate->query_flags&BIT_CD)) {
    generate_dnskey_prefetch(qstate, iq, id);
    fptr_ok(fptr_whitelist_modenv_detach_subs(
      qstate->env->detach_subs));
    (*qstate->env->detach_subs)(qstate);
  }

  /* Jump to the next state. */
  return next_state(iq, QUERYTARGETS_STATE);
}

/**
 * Given a basic query, generate a parent-side "target" query. 
 * These are subordinate queries for missing delegation point target addresses,
 * for which only the parent of the delegation provides correct IP addresses.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @param name: target qname.
 * @param namelen: target qname length.
 * @param qtype: target qtype (either A or AAAA).
 * @param qclass: target qclass.
 * @return true on success, false on failure.
 */
static int
generate_parentside_target_query(struct module_qstate* qstate, 
  struct iter_qstate* iq, int id, uint8_t* name, size_t namelen, 
  uint16_t qtype, uint16_t qclass)
{
  struct module_qstate* subq;
  if(!generate_sub_request(name, namelen, qtype, qclass, qstate, 
    id, iq, INIT_REQUEST_STATE, FINISHED_STATE, &subq, 0, 0))
    return 0;
  if(subq) {
    struct iter_qstate* subiq = 
      (struct iter_qstate*)subq->minfo[id];
    /* blacklist the cache - we want to fetch parent stuff */
    sock_list_insert(&subq->blacklist, NULL, 0, subq->region);
    subiq->query_for_pside_glue = 1;
    if(dname_subdomain_c(name, iq->dp->name)) {
      subiq->dp = delegpt_copy(iq->dp, subq->region);
      subiq->dnssec_expected = iter_indicates_dnssec(
        qstate->env, subiq->dp, NULL, 
        subq->qinfo.qclass);
      subiq->refetch_glue = 1;
    } else {
      subiq->dp = dns_cache_find_delegation(qstate->env, 
        name, namelen, qtype, qclass, subq->region,
        &subiq->deleg_msg,
        *qstate->env->now+subq->prefetch_leeway,
        1, NULL, 0);
      /* if no dp, then it's from root, refetch unneeded */
      if(subiq->dp) { 
        subiq->dnssec_expected = iter_indicates_dnssec(
          qstate->env, subiq->dp, NULL, 
          subq->qinfo.qclass);
        subiq->refetch_glue = 1;
      }
    }
  }
  log_nametypeclass(VERB_QUERY, "new pside target", name, qtype, qclass);
  return 1;
}

/**
 * Given a basic query, generate a "target" query. These are subordinate
 * queries for missing delegation point target addresses.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @param name: target qname.
 * @param namelen: target qname length.
 * @param qtype: target qtype (either A or AAAA).
 * @param qclass: target qclass.
 * @return true on success, false on failure.
 */
static int
generate_target_query(struct module_qstate* qstate, struct iter_qstate* iq,
        int id, uint8_t* name, size_t namelen, uint16_t qtype, uint16_t qclass)
{
  struct module_qstate* subq;
  if(!generate_sub_request(name, namelen, qtype, qclass, qstate, 
    id, iq, INIT_REQUEST_STATE, FINISHED_STATE, &subq, 0, 0))
    return 0;
  log_nametypeclass(VERB_QUERY, "new target", name, qtype, qclass);
  return 1;
}

/**
 * Given an event at a certain state, generate zero or more target queries
 * for it's current delegation point.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @param maxtargets: The maximum number of targets to query for.
 *  if it is negative, there is no maximum number of targets.
 * @param num: returns the number of queries generated and processed, 
 *  which may be zero if there were no missing targets.
 * @return 0 on success, nonzero on error. 1 means temporary failure and
 *  2 means the failure can be cached.
 */
static int
query_for_targets(struct module_qstate* qstate, struct iter_qstate* iq,
        struct iter_env* ie, int id, int maxtargets, int* num)
{
  int query_count = 0;
  struct delegpt_ns* ns;
  int missing;
  int toget = 0;

  iter_mark_cycle_targets(qstate, iq->dp);
  missing = (int)delegpt_count_missing_targets(iq->dp, NULL);
  log_assert(maxtargets != 0); /* that would not be useful */

  /* Generate target requests. Basically, any missing targets
   * are queried for here, regardless if it is necessary to do
   * so to continue processing. */
  if(maxtargets < 0 || maxtargets > missing)
    toget = missing;
  else  toget = maxtargets;
  if(toget == 0) {
    *num = 0;
    return 0;
  }

  /* now that we are sure that a target query is going to be made,
   * check the limits. */
  if(iq->depth == ie->max_dependency_depth)
    return 1;
  if(iq->depth > 0 && iq->target_count &&
    iq->target_count[TARGET_COUNT_QUERIES] > MAX_TARGET_COUNT) {
    char s[LDNS_MAX_DOMAINLEN];
    dname_str(qstate->qinfo.qname, s);
    verbose(VERB_QUERY, "request %s has exceeded the maximum "
      "number of glue fetches %d", s,
      iq->target_count[TARGET_COUNT_QUERIES]);
    return 2;
  }
  if(iq->dp_target_count > MAX_DP_TARGET_COUNT) {
    char s[LDNS_MAX_DOMAINLEN];
    dname_str(qstate->qinfo.qname, s);
    verbose(VERB_QUERY, "request %s has exceeded the maximum "
      "number of glue fetches %d to a single delegation point",
      s, iq->dp_target_count);
    return 2;
  }

  /* select 'toget' items from the total of 'missing' items */
  log_assert(toget <= missing);

  /* loop over missing targets */
  for(ns = iq->dp->nslist; ns; ns = ns->next) {
    if(ns->resolved)
      continue;

    /* randomly select this item with probability toget/missing */
    if(!iter_ns_probability(qstate->env->rnd, toget, missing)) {
      /* do not select this one, next; select toget number
       * of items from a list one less in size */
      missing --;
      continue;
    }

    if(ie->supports_ipv6 &&
      ((ns->lame && !ns->done_pside6) ||
      (!ns->lame && !ns->got6))) {
      /* Send the AAAA request. */
      if(!generate_target_query(qstate, iq, id, 
        ns->name, ns->namelen,
        LDNS_RR_TYPE_AAAA, iq->qchase.qclass)) {
        *num = query_count;
        if(query_count > 0)
          qstate->ext_state[id] = module_wait_subquery;
        return 1;
      }
      query_count++;
      /* If the mesh query list is full, exit the loop here.
       * This makes the routine spawn one query at a time,
       * and this means there is no query state load
       * increase, because the spawned state uses cpu and a
       * socket while this state waits for that spawned
       * state. Next time we can look up further targets */
      if(mesh_jostle_exceeded(qstate->env->mesh)) {
        /* If no ip4 query is possible, that makes
         * this ns resolved. */
        if(!((ie->supports_ipv4 || ie->nat64.use_nat64) &&
          ((ns->lame && !ns->done_pside4) ||
          (!ns->lame && !ns->got4)))) {
          ns->resolved = 1;
        }
        break;
      }
    }
    /* Send the A request. */
    if((ie->supports_ipv4 || ie->nat64.use_nat64) &&
      ((ns->lame && !ns->done_pside4) ||
      (!ns->lame && !ns->got4))) {
      if(!generate_target_query(qstate, iq, id, 
        ns->name, ns->namelen, 
        LDNS_RR_TYPE_A, iq->qchase.qclass)) {
        *num = query_count;
        if(query_count > 0)
          qstate->ext_state[id] = module_wait_subquery;
        return 1;
      }
      query_count++;
      /* If the mesh query list is full, exit the loop. */
      if(mesh_jostle_exceeded(qstate->env->mesh)) {
        /* With the ip6 query already checked for,
         * this makes the ns resolved. It is no longer
         * a missing target. */
        ns->resolved = 1;
        break;
      }
    }

    /* mark this target as in progress. */
    ns->resolved = 1;
    missing--;
    toget--;
    if(toget == 0)
      break;
  }
  *num = query_count;
  if(query_count > 0)
    qstate->ext_state[id] = module_wait_subquery;

  return 0;
}

/**
 * Called by processQueryTargets when it would like extra targets to query
 * but it seems to be out of options.  At last resort some less appealing
 * options are explored.  If there are no more options, the result is SERVFAIL
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @return true if the event requires more request processing immediately,
 *         false if not. 
 */
static int
processLastResort(struct module_qstate* qstate, struct iter_qstate* iq,
  struct iter_env* ie, int id)
{
  struct delegpt_ns* ns;
  int query_count = 0;
  verbose(VERB_ALGO, "No more query targets, attempting last resort");
  log_assert(iq->dp);

  if(!can_have_last_resort(qstate->env, iq->dp->name, iq->dp->namelen,
    iq->qchase.qclass, NULL, NULL, NULL)) {
    /* fail -- no more targets, no more hope of targets, no hope 
     * of a response. */
    errinf(qstate, "all the configured stub or forward servers failed,");
    errinf_dname(qstate, "at zone", iq->dp->name);
    errinf_reply(qstate, iq);
    verbose(VERB_QUERY, "configured stub or forward servers failed -- returning SERVFAIL");
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }
  iq->dp->fallback_to_parent_side_NS = 1;
  if(qstate->env->cfg->harden_unverified_glue) {
    if(!cache_fill_missing(qstate->env, iq->qchase.qclass,
      qstate->region, iq->dp, PACKED_RRSET_UNVERIFIED_GLUE))
      log_err("out of memory in cache_fill_missing");
    if(iq->dp->usable_list) {
      verbose(VERB_ALGO, "try unverified glue from cache");
      return next_state(iq, QUERYTARGETS_STATE);
    }
  }
  if(!iq->dp->has_parent_side_NS && dname_is_root(iq->dp->name)) {
    struct delegpt* dp;
    int nolock = 0;
    dp = hints_find_root(qstate->env->hints,
      iq->qchase.qclass, nolock);
    if(dp) {
      struct delegpt_addr* a;
      iq->chase_flags &= ~BIT_RD; /* go to authorities */
      for(ns = dp->nslist; ns; ns=ns->next) {
        (void)delegpt_add_ns(iq->dp, qstate->region,
          ns->name, ns->lame, ns->tls_auth_name,
          ns->port);
      }
      for(a = dp->target_list; a; a=a->next_target) {
        (void)delegpt_add_addr(iq->dp, qstate->region,
          &a->addr, a->addrlen, a->bogus,
          a->lame, a->tls_auth_name, -1, NULL);
      }
      lock_rw_unlock(&qstate->env->hints->lock);
      /* copy over some configuration since we update the
       * delegation point in place */
      iq->dp->tcp_upstream = dp->tcp_upstream;
      iq->dp->ssl_upstream = dp->ssl_upstream;
    }
    iq->dp->has_parent_side_NS = 1;
  } else if(!iq->dp->has_parent_side_NS) {
    if(!iter_lookup_parent_NS_from_cache(qstate->env, iq->dp,
      qstate->region, &qstate->qinfo) 
      || !iq->dp->has_parent_side_NS) {
      /* if: malloc failure in lookup go up to try */
      /* if: no parent NS in cache - go up one level */
      verbose(VERB_ALGO, "try to grab parent NS");
      iq->store_parent_NS = iq->dp;
      iq->chase_flags &= ~BIT_RD; /* go to authorities */
      iq->deleg_msg = NULL;
      iq->refetch_glue = 1;
      iq->query_restart_count++;
      iq->sent_count = 0;
      iq->dp_target_count = 0;
      if(qstate->env->cfg->qname_minimisation)
        iq->minimisation_state = INIT_MINIMISE_STATE;
      return next_state(iq, INIT_REQUEST_STATE);
    }
  }
  /* see if that makes new names available */
  if(!cache_fill_missing(qstate->env, iq->qchase.qclass, 
    qstate->region, iq->dp, 0))
    log_err("out of memory in cache_fill_missing");
  if(iq->dp->usable_list) {
    verbose(VERB_ALGO, "try parent-side-name, w. glue from cache");
    return next_state(iq, QUERYTARGETS_STATE);
  }
  /* try to fill out parent glue from cache */
  if(iter_lookup_parent_glue_from_cache(qstate->env, iq->dp,
    qstate->region, &qstate->qinfo)) {
    /* got parent stuff from cache, see if we can continue */
    verbose(VERB_ALGO, "try parent-side glue from cache");
    return next_state(iq, QUERYTARGETS_STATE);
  }
  /* query for an extra name added by the parent-NS record */
  if(delegpt_count_missing_targets(iq->dp, NULL) > 0) {
    int qs = 0, ret;
    verbose(VERB_ALGO, "try parent-side target name");
    if((ret=query_for_targets(qstate, iq, ie, id, 1, &qs))!=0) {
      errinf(qstate, "could not fetch nameserver");
      errinf_dname(qstate, "at zone", iq->dp->name);
      if(ret == 1)
        return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    iq->num_target_queries += qs;
    target_count_increase(iq, qs);
    if(qs != 0) {
      qstate->ext_state[id] = module_wait_subquery;
      return 0; /* and wait for them */
    }
  }
  if(iq->depth == ie->max_dependency_depth) {
    verbose(VERB_QUERY, "maxdepth and need more nameservers, fail");
    errinf(qstate, "cannot fetch more nameservers because at max dependency depth");
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }
  if(iq->depth > 0 && iq->target_count &&
    iq->target_count[TARGET_COUNT_QUERIES] > MAX_TARGET_COUNT) {
    char s[LDNS_MAX_DOMAINLEN];
    dname_str(qstate->qinfo.qname, s);
    verbose(VERB_QUERY, "request %s has exceeded the maximum "
      "number of glue fetches %d", s,
      iq->target_count[TARGET_COUNT_QUERIES]);
    errinf(qstate, "exceeded the maximum number of glue fetches");
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }
  /* mark cycle targets for parent-side lookups */
  iter_mark_pside_cycle_targets(qstate, iq->dp);
  /* see if we can issue queries to get nameserver addresses */
  /* this lookup is not randomized, but sequential. */
  for(ns = iq->dp->nslist; ns; ns = ns->next) {
    /* if this nameserver is at a delegation point, but that
     * delegation point is a stub and we cannot go higher, skip*/
    if( ((ie->supports_ipv6 && !ns->done_pside6) ||
        ((ie->supports_ipv4 || ie->nat64.use_nat64) && !ns->done_pside4)) &&
        !can_have_last_resort(qstate->env, ns->name, ns->namelen,
      iq->qchase.qclass, NULL, NULL, NULL)) {
      log_nametypeclass(VERB_ALGO, "cannot pside lookup ns "
        "because it is also a stub/forward,",
        ns->name, LDNS_RR_TYPE_NS, iq->qchase.qclass);
      if(ie->supports_ipv6) ns->done_pside6 = 1;
      if(ie->supports_ipv4 || ie->nat64.use_nat64) ns->done_pside4 = 1;
      continue;
    }
    /* query for parent-side A and AAAA for nameservers */
    if(ie->supports_ipv6 && !ns->done_pside6) {
      /* Send the AAAA request. */
      if(!generate_parentside_target_query(qstate, iq, id, 
        ns->name, ns->namelen,
        LDNS_RR_TYPE_AAAA, iq->qchase.qclass)) {
        errinf_dname(qstate, "could not generate nameserver AAAA lookup for", ns->name);
        return error_response(qstate, id,
          LDNS_RCODE_SERVFAIL);
      }
      ns->done_pside6 = 1;
      query_count++;
      if(mesh_jostle_exceeded(qstate->env->mesh)) {
        /* Wait for the lookup; do not spawn multiple
         * lookups at a time. */
        verbose(VERB_ALGO, "try parent-side glue lookup");
        iq->num_target_queries += query_count;
        target_count_increase(iq, query_count);
        qstate->ext_state[id] = module_wait_subquery;
        return 0;
      }
    }
    if((ie->supports_ipv4 || ie->nat64.use_nat64) && !ns->done_pside4) {
      /* Send the A request. */
      if(!generate_parentside_target_query(qstate, iq, id, 
        ns->name, ns->namelen, 
        LDNS_RR_TYPE_A, iq->qchase.qclass)) {
        errinf_dname(qstate, "could not generate nameserver A lookup for", ns->name);
        return error_response(qstate, id,
          LDNS_RCODE_SERVFAIL);
      }
      ns->done_pside4 = 1;
      query_count++;
    }
    if(query_count != 0) { /* suspend to await results */
      verbose(VERB_ALGO, "try parent-side glue lookup");
      iq->num_target_queries += query_count;
      target_count_increase(iq, query_count);
      qstate->ext_state[id] = module_wait_subquery;
      return 0;
    }
  }

  /* if this was a parent-side glue query itself, then store that
   * failure in cache. */
  if(!qstate->no_cache_store && iq->query_for_pside_glue
    && !iq->pside_glue)
      iter_store_parentside_neg(qstate->env, &qstate->qinfo,
        iq->deleg_msg?iq->deleg_msg->rep:
        (iq->response?iq->response->rep:NULL));

  errinf(qstate, "all servers for this domain failed,");
  errinf_dname(qstate, "at zone", iq->dp->name);
  errinf_reply(qstate, iq);
  verbose(VERB_QUERY, "out of query targets -- returning SERVFAIL");
  /* fail -- no more targets, no more hope of targets, no hope 
   * of a response. */
  return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
}

/** 
 * Try to find the NS record set that will resolve a qtype DS query. Due
 * to grandparent/grandchild reasons we did not get a proper lookup right
 * away.  We need to create type NS queries until we get the right parent
 * for this lookup.  We remove labels from the query to find the right point.
 * If we end up at the old dp name, then there is no solution.
 * 
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @return true if the event requires more immediate processing, false if
 *         not. This is generally only true when forwarding the request to
 *         the final state (i.e., on answer).
 */
static int
processDSNSFind(struct module_qstate* qstate, struct iter_qstate* iq, int id)
{
  struct module_qstate* subq = NULL;
  verbose(VERB_ALGO, "processDSNSFind");

  if(!iq->dsns_point) {
    /* initialize */
    iq->dsns_point = iq->qchase.qname;
    iq->dsns_point_len = iq->qchase.qname_len;
  }
  /* robustcheck for internal error: we are not underneath the dp */
  if(!dname_subdomain_c(iq->dsns_point, iq->dp->name)) {
    errinf_dname(qstate, "for DS query parent-child nameserver search the query is not under the zone", iq->dp->name);
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }

  /* go up one (more) step, until we hit the dp, if so, end */
  dname_remove_label(&iq->dsns_point, &iq->dsns_point_len);
  if(query_dname_compare(iq->dsns_point, iq->dp->name) == 0) {
    /* there was no inbetween nameserver, use the old delegation
     * point again.  And this time, because dsns_point is nonNULL
     * we are going to accept the (bad) result */
    iq->state = QUERYTARGETS_STATE;
    return 1;
  }
  iq->state = DSNS_FIND_STATE;

  /* spawn NS lookup (validation not needed, this is for DS lookup) */
  log_nametypeclass(VERB_ALGO, "fetch nameservers", 
    iq->dsns_point, LDNS_RR_TYPE_NS, iq->qchase.qclass);
  if(!generate_sub_request(iq->dsns_point, iq->dsns_point_len, 
    LDNS_RR_TYPE_NS, iq->qchase.qclass, qstate, id, iq,
    INIT_REQUEST_STATE, FINISHED_STATE, &subq, 0, 0)) {
    errinf_dname(qstate, "for DS query parent-child nameserver search, could not generate NS lookup for", iq->dsns_point);
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }

  return 0;
}

/**
 * Check if we wait responses for sent queries and update the iterator's
 * external state.
 */
static void
check_waiting_queries(struct iter_qstate* iq, struct module_qstate* qstate,
  int id)
{
  if(iq->num_target_queries>0 && iq->num_current_queries>0) {
    verbose(VERB_ALGO, "waiting for %d targets to "
      "resolve or %d outstanding queries to "
      "respond", iq->num_target_queries,
      iq->num_current_queries);
    qstate->ext_state[id] = module_wait_reply;
  } else if(iq->num_target_queries>0) {
    verbose(VERB_ALGO, "waiting for %d targets to "
      "resolve", iq->num_target_queries);
    qstate->ext_state[id] = module_wait_subquery;
  } else {
    verbose(VERB_ALGO, "waiting for %d "
      "outstanding queries to respond",
      iq->num_current_queries);
    qstate->ext_state[id] = module_wait_reply;
  }
}
  
/** 
 * This is the request event state where the request will be sent to one of
 * its current query targets. This state also handles issuing target lookup
 * queries for missing target IP addresses. Queries typically iterate on
 * this state, both when they are just trying different targets for a given
 * delegation point, and when they change delegation points. This state
 * roughly corresponds to RFC 1034 algorithm steps 3 and 4.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @return true if the event requires more request processing immediately,
 *         false if not. This state only returns true when it is generating
 *         a SERVFAIL response because the query has hit a dead end.
 */
static int
processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
  struct iter_env* ie, int id)
{
  int tf_policy;
  struct delegpt_addr* target;
  struct outbound_entry* outq;
  int auth_fallback = 0;
  uint8_t* qout_orig = NULL;
  size_t qout_orig_len = 0;
  int sq_check_ratelimit = 1;
  int sq_was_ratelimited = 0;
  int can_do_promisc = 0;

  /* NOTE: a request will encounter this state for each target it
   * needs to send a query to. That is, at least one per referral,
   * more if some targets timeout or return throwaway answers. */

  log_query_info(VERB_QUERY, "processQueryTargets:", &qstate->qinfo);
  verbose(VERB_ALGO, "processQueryTargets: targetqueries %d, "
    "currentqueries %d sentcount %d", iq->num_target_queries, 
    iq->num_current_queries, iq->sent_count);

  /* Make sure that we haven't run away */
  if(iq->referral_count > MAX_REFERRAL_COUNT) {
    verbose(VERB_QUERY, "request has exceeded the maximum "
      "number of referrrals with %d", iq->referral_count);
    errinf(qstate, "exceeded the maximum of referrals");
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }
  if(iq->sent_count > ie->max_sent_count) {
    verbose(VERB_QUERY, "request has exceeded the maximum "
      "number of sends with %d", iq->sent_count);
    errinf(qstate, "exceeded the maximum number of sends");
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }

  /* Check if we reached MAX_TARGET_NX limit without a fallback activation. */
  if(iq->target_count && !*iq->nxns_dp &&
    iq->target_count[TARGET_COUNT_NX] > MAX_TARGET_NX) {
    struct delegpt_ns* ns;
    /* If we can wait for resolution, do so. */
    if(iq->num_target_queries>0 || iq->num_current_queries>0) {
      check_waiting_queries(iq, qstate, id);
      return 0;
    }
    verbose(VERB_ALGO, "request has exceeded the maximum "
      "number of nxdomain nameserver lookups (%d) with %d",
      MAX_TARGET_NX, iq->target_count[TARGET_COUNT_NX]);
    /* Check for dp because we require one below */
    if(!iq->dp) {
      verbose(VERB_QUERY, "Failed to get a delegation, "
        "giving up");
      errinf(qstate, "failed to get a delegation (eg. prime "
        "failure)");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    /* We reached the limit but we already have parent side
     * information; stop resolution */
    if(iq->dp->has_parent_side_NS) {
      verbose(VERB_ALGO, "parent-side information is "
        "already present for the delegation point, no "
        "fallback possible");
      errinf(qstate, "exceeded the maximum nameserver nxdomains");
      return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    verbose(VERB_ALGO, "initiating parent-side fallback for "
      "nxdomain nameserver lookups");
    /* Mark all the current NSes as resolved to allow for parent
     * fallback */
    for(ns=iq->dp->nslist; ns; ns=ns->next) {
      ns->resolved = 1;
    }
    /* Note the delegation point that triggered the NXNS fallback;
     * no reason for shared queries to keep trying there.
     * This also marks the fallback activation. */
    *iq->nxns_dp = malloc(iq->dp->namelen);
    if(!*iq->nxns_dp) {
      verbose(VERB_ALGO, "out of memory while initiating "
        "fallback");
      errinf(qstate, "exceeded the maximum nameserver "
        "nxdomains (malloc)");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    memcpy(*iq->nxns_dp, iq->dp->name, iq->dp->namelen);
  } else if(iq->target_count && *iq->nxns_dp) {
    /* Handle the NXNS fallback case. */
    /* If we can wait for resolution, do so. */
    if(iq->num_target_queries>0 || iq->num_current_queries>0) {
      check_waiting_queries(iq, qstate, id);
      return 0;
    }
    /* Check for dp because we require one below */
    if(!iq->dp) {
      verbose(VERB_QUERY, "Failed to get a delegation, "
        "giving up");
      errinf(qstate, "failed to get a delegation (eg. prime "
        "failure)");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }

    if(iq->target_count[TARGET_COUNT_NX] > MAX_TARGET_NX_FALLBACK) {
      verbose(VERB_ALGO, "request has exceeded the maximum "
        "number of fallback nxdomain nameserver "
        "lookups (%d) with %d", MAX_TARGET_NX_FALLBACK,
        iq->target_count[TARGET_COUNT_NX]);
      errinf(qstate, "exceeded the maximum nameserver nxdomains");
      return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
    }

    if(!iq->dp->has_parent_side_NS) {
      struct delegpt_ns* ns;
      if(!dname_canonical_compare(*iq->nxns_dp, iq->dp->name)) {
        verbose(VERB_ALGO, "this delegation point "
          "initiated the fallback, marking the "
          "nslist as resolved");
        for(ns=iq->dp->nslist; ns; ns=ns->next) {
          ns->resolved = 1;
        }
      }
    }
  }
  
  /* Make sure we have a delegation point, otherwise priming failed
   * or another failure occurred */
  if(!iq->dp) {
    verbose(VERB_QUERY, "Failed to get a delegation, giving up");
    errinf(qstate, "failed to get a delegation (eg. prime failure)");
    return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
  }
  if(!ie->supports_ipv6)
    delegpt_no_ipv6(iq->dp);
  if(!ie->supports_ipv4 && !ie->nat64.use_nat64)
    delegpt_no_ipv4(iq->dp);
  delegpt_log(VERB_ALGO, iq->dp);

  if(iq->num_current_queries>0) {
    /* already busy answering a query, this restart is because
     * more delegpt addrs became available, wait for existing
     * query. */
    verbose(VERB_ALGO, "woke up, but wait for outstanding query");
    qstate->ext_state[id] = module_wait_reply;
    return 0;
  }

  if(iq->minimisation_state == INIT_MINIMISE_STATE
    && !(iq->chase_flags & BIT_RD)) {
    /* (Re)set qinfo_out to (new) delegation point, except when
     * qinfo_out is already a subdomain of dp. This happens when
     * increasing by more than one label at once (QNAMEs with more
     * than MAX_MINIMISE_COUNT labels). */
    if(!(iq->qinfo_out.qname_len 
      && dname_subdomain_c(iq->qchase.qname, 
        iq->qinfo_out.qname)
      && dname_subdomain_c(iq->qinfo_out.qname, 
        iq->dp->name))) {
      iq->qinfo_out.qname = iq->dp->name;
      iq->qinfo_out.qname_len = iq->dp->namelen;
      iq->qinfo_out.qtype = LDNS_RR_TYPE_A;
      iq->qinfo_out.qclass = iq->qchase.qclass;
      iq->qinfo_out.local_alias = NULL;
      iq->minimise_count = 0;
    }

    iq->minimisation_state = MINIMISE_STATE;
  }
  if(iq->minimisation_state == MINIMISE_STATE) {
    int qchaselabs = dname_count_labels(iq->qchase.qname);
    int labdiff = qchaselabs -
      dname_count_labels(iq->qinfo_out.qname);

    qout_orig = iq->qinfo_out.qname;
    qout_orig_len = iq->qinfo_out.qname_len;
    iq->qinfo_out.qname = iq->qchase.qname;
    iq->qinfo_out.qname_len = iq->qchase.qname_len;
    iq->minimise_count++;
    iq->timeout_count = 0;

    iter_dec_attempts(iq->dp, 1, ie->outbound_msg_retry);

    /* Limit number of iterations for QNAMEs with more
     * than MAX_MINIMISE_COUNT labels. Send first MINIMISE_ONE_LAB
     * labels of QNAME always individually.
     */
    if(qchaselabs > MAX_MINIMISE_COUNT && labdiff > 1 && 
      iq->minimise_count > MINIMISE_ONE_LAB) {
      if(iq->minimise_count < MAX_MINIMISE_COUNT) {
        int multilabs = qchaselabs - 1 - 
          MINIMISE_ONE_LAB;
        int extralabs = multilabs / 
          MINIMISE_MULTIPLE_LABS;

        if (MAX_MINIMISE_COUNT - iq->minimise_count >= 
          multilabs % MINIMISE_MULTIPLE_LABS)
          /* Default behaviour is to add 1 label
           * every iteration. Therefore, decrement
           * the extralabs by 1 */
          extralabs--;
        if (extralabs < labdiff)
          labdiff -= extralabs;
        else
          labdiff = 1;
      }
      /* Last minimised iteration, send all labels with
       * QTYPE=NS */
      else
        labdiff = 1;
    }

    if(labdiff > 1) {
      verbose(VERB_QUERY, "removing %d labels", labdiff-1);
      dname_remove_labels(&iq->qinfo_out.qname, 
        &iq->qinfo_out.qname_len, 
        labdiff-1);
    }
    if(labdiff < 1 || (labdiff < 2 
      && (iq->qchase.qtype == LDNS_RR_TYPE_DS
      || iq->qchase.qtype == LDNS_RR_TYPE_A)))
      /* Stop minimising this query, resolve "as usual" */
      iq->minimisation_state = DONOT_MINIMISE_STATE;
    else if(!qstate->no_cache_lookup) {
      struct dns_msg* msg = dns_cache_lookup(qstate->env, 
        iq->qinfo_out.qname, iq->qinfo_out.qname_len, 
        iq->qinfo_out.qtype, iq->qinfo_out.qclass, 
        qstate->query_flags, qstate->region, 
        qstate->env->scratch, 0, iq->dp->name,
        iq->dp->namelen);
      if(msg && FLAGS_GET_RCODE(msg->rep->flags) ==
        LDNS_RCODE_NOERROR)
        /* no need to send query if it is already 
         * cached as NOERROR */
        return 1;
      if(msg && FLAGS_GET_RCODE(msg->rep->flags) ==
        LDNS_RCODE_NXDOMAIN &&
        qstate->env->need_to_validate &&
        qstate->env->cfg->harden_below_nxdomain) {
        if(msg->rep->security == sec_status_secure) {
          iq->response = msg;
          return final_state(iq);
        }
        if(msg->rep->security == sec_status_unchecked) {
          struct module_qstate* subq = NULL;
          if(!generate_sub_request(
            iq->qinfo_out.qname,
            iq->qinfo_out.qname_len,
            iq->qinfo_out.qtype,
            iq->qinfo_out.qclass,
            qstate, id, iq,
            INIT_REQUEST_STATE,
            FINISHED_STATE, &subq, 1, 1))
            verbose(VERB_ALGO,
            "could not validate NXDOMAIN "
            "response");
        }
      }
      if(msg && FLAGS_GET_RCODE(msg->rep->flags) ==
        LDNS_RCODE_NXDOMAIN) {
        /* return and add a label in the next
         * minimisation iteration.
         */
        return 1;
      }
    }
  }
  if(iq->minimisation_state == SKIP_MINIMISE_STATE) {
    if(iq->timeout_count < MAX_MINIMISE_TIMEOUT_COUNT)
      /* Do not increment qname, continue incrementing next 
       * iteration */
      iq->minimisation_state = MINIMISE_STATE;
    else if(!qstate->env->cfg->qname_minimisation_strict)
      /* Too many time-outs detected for this QNAME and QTYPE.
       * We give up, disable QNAME minimisation. */
      iq->minimisation_state = DONOT_MINIMISE_STATE;
  }
  if(iq->minimisation_state == DONOT_MINIMISE_STATE)
    iq->qinfo_out = iq->qchase;

  /* now find an answer to this query */
  /* see if authority zones have an answer */
  /* now we know the dp, we can check the auth zone for locally hosted
   * contents */
  if(!iq->auth_zone_avoid && qstate->blacklist) {
    if(auth_zones_can_fallback(qstate->env->auth_zones,
      iq->dp->name, iq->dp->namelen, iq->qinfo_out.qclass)) {
      /* if cache is blacklisted and this zone allows us
       * to fallback to the internet, then do so, and
       * fetch results from the internet servers */
      iq->auth_zone_avoid = 1;
    }
  }
  if(iq->auth_zone_avoid) {
    iq->auth_zone_avoid = 0;
    auth_fallback = 1;
  } else if(auth_zones_lookup(qstate->env->auth_zones, &iq->qinfo_out,
    qstate->region, &iq->response, &auth_fallback, iq->dp->name,
    iq->dp->namelen)) {
    /* use this as a response to be processed by the iterator */
    if(verbosity >= VERB_ALGO) {
      log_dns_msg("msg from auth zone",
        &iq->response->qinfo, iq->response->rep);
    }
    if((iq->chase_flags&BIT_RD) && !(iq->response->rep->flags&BIT_AA)) {
      verbose(VERB_ALGO, "forwarder, ignoring referral from auth zone");
    } else {
      qstate->env->mesh->num_query_authzone_up++;
      iq->num_current_queries++;
      iq->chase_to_rd = 0;
      iq->dnssec_lame_query = 0;
      iq->auth_zone_response = 1;
      return next_state(iq, QUERY_RESP_STATE);
    }
  }
  iq->auth_zone_response = 0;
  if(auth_fallback == 0) {
    /* like we got servfail from the auth zone lookup, and
     * no internet fallback */
    verbose(VERB_ALGO, "auth zone lookup failed, no fallback,"
      " servfail");
    errinf(qstate, "auth zone lookup failed, fallback is off");
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }
  if(iq->dp->auth_dp) {
    /* we wanted to fallback, but had no delegpt, only the
     * auth zone generated delegpt, create an actual one */
    iq->auth_zone_avoid = 1;
    return next_state(iq, INIT_REQUEST_STATE);
  }
  /* but mostly, fallback==1 (like, when no such auth zone exists)
   * and we continue with lookups */

  tf_policy = 0;
  /* < not <=, because although the array is large enough for <=, the
   * generated query will immediately be discarded due to depth and
   * that servfail is cached, which is not good as opportunism goes. */
  if(iq->depth < ie->max_dependency_depth
    && iq->num_target_queries == 0
    && (!iq->target_count || iq->target_count[TARGET_COUNT_NX]==0)
    && iq->sent_count < TARGET_FETCH_STOP) {
    can_do_promisc = 1;
  }
  /* if the mesh query list is full, then do not waste cpu and sockets to
   * fetch promiscuous targets. They can be looked up when needed. */
  if(!iq->dp->fallback_to_parent_side_NS && can_do_promisc
    && !mesh_jostle_exceeded(qstate->env->mesh)) {
    tf_policy = ie->target_fetch_policy[iq->depth];
  }

  /* if in 0x20 fallback get as many targets as possible */
  if(iq->caps_fallback) {
    int extra = 0, ret;
    size_t naddr, nres, navail;
    if((ret=query_for_targets(qstate, iq, ie, id, -1, &extra))!=0) {
      errinf(qstate, "could not fetch nameservers for 0x20 fallback");
      if(ret == 1)
        return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    iq->num_target_queries += extra;
    target_count_increase(iq, extra);
    if(iq->num_target_queries > 0) {
      /* wait to get all targets, we want to try em */
      verbose(VERB_ALGO, "wait for all targets for fallback");
      qstate->ext_state[id] = module_wait_reply;
      /* undo qname minimise step because we'll get back here
       * to do it again */
      if(qout_orig && iq->minimise_count > 0) {
        iq->minimise_count--;
        iq->qinfo_out.qname = qout_orig;
        iq->qinfo_out.qname_len = qout_orig_len;
      }
      return 0;
    }
    /* did we do enough fallback queries already? */
    delegpt_count_addr(iq->dp, &naddr, &nres, &navail);
    /* the current caps_server is the number of fallbacks sent.
     * the original query is one that matched too, so we have
     * caps_server+1 number of matching queries now */
    if(iq->caps_server+1 >= naddr*3 ||
      iq->caps_server*2+2 >= (size_t)ie->max_sent_count) {
      /* *2 on sentcount check because ipv6 may fail */
      /* we're done, process the response */
      verbose(VERB_ALGO, "0x20 fallback had %d responses "
        "match for %d wanted, done.", 
        (int)iq->caps_server+1, (int)naddr*3);
      iq->response = iq->caps_response;
      iq->caps_fallback = 0;
      iter_dec_attempts(iq->dp, 3, ie->outbound_msg_retry); /* space for fallback */
      iq->num_current_queries++; /* RespState decrements it*/
      iq->referral_count++; /* make sure we don't loop */
      iq->sent_count = 0;
      iq->dp_target_count = 0;
      iq->state = QUERY_RESP_STATE;
      return 1;
    }
    verbose(VERB_ALGO, "0x20 fallback number %d", 
      (int)iq->caps_server);

  /* if there is a policy to fetch missing targets 
   * opportunistically, do it. we rely on the fact that once a 
   * query (or queries) for a missing name have been issued, 
   * they will not show up again. */
  } else if(tf_policy != 0) {
    int extra = 0;
    verbose(VERB_ALGO, "attempt to get extra %d targets", 
      tf_policy);
    (void)query_for_targets(qstate, iq, ie, id, tf_policy, &extra);
    /* errors ignored, these targets are not strictly necessary for
     * this result, we do not have to reply with SERVFAIL */
    iq->num_target_queries += extra;
    target_count_increase(iq, extra);
  }

  /* Add the current set of unused targets to our queue. */
  delegpt_add_unused_targets(iq->dp);

  if(qstate->env->auth_zones) {
    uint8_t* sname = NULL;
    size_t snamelen = 0;
    /* apply rpz triggers at query time; nameserver IP and dname */
    struct dns_msg* forged_response_after_cname;
    struct dns_msg* forged_response = rpz_callback_from_iterator_module(qstate, iq);
    int count = 0;
    while(forged_response && reply_find_rrset_section_an(
      forged_response->rep, iq->qchase.qname,
      iq->qchase.qname_len, LDNS_RR_TYPE_CNAME,
      iq->qchase.qclass) &&
      iq->qchase.qtype != LDNS_RR_TYPE_CNAME &&
      count++ < ie->max_query_restarts) {
      /* another cname to follow */
      if(!handle_cname_response(qstate, iq, forged_response,
        &sname, &snamelen)) {
        errinf(qstate, "malloc failure, CNAME info");
        return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      }
      iq->qchase.qname = sname;
      iq->qchase.qname_len = snamelen;
      forged_response_after_cname =
        rpz_callback_from_iterator_cname(qstate, iq);
      if(forged_response_after_cname) {
        forged_response = forged_response_after_cname;
      } else {
        /* Follow the CNAME with a query restart */
        iq->deleg_msg = NULL;
        iq->dp = NULL;
        iq->dsns_point = NULL;
        iq->auth_zone_response = 0;
        iq->refetch_glue = 0;
        iq->query_restart_count++;
        iq->sent_count = 0;
        iq->dp_target_count = 0;
        if(qstate->env->cfg->qname_minimisation)
          iq->minimisation_state = INIT_MINIMISE_STATE;
        outbound_list_clear(&iq->outlist);
        iq->num_current_queries = 0;
        fptr_ok(fptr_whitelist_modenv_detach_subs(
          qstate->env->detach_subs));
        (*qstate->env->detach_subs)(qstate);
        iq->num_target_queries = 0;
        return next_state(iq, INIT_REQUEST_STATE);
      }
    }
    if(forged_response != NULL) {
      qstate->ext_state[id] = module_finished;
      qstate->return_rcode = LDNS_RCODE_NOERROR;
      qstate->return_msg = forged_response;
      iq->response = forged_response;
      next_state(iq, FINISHED_STATE);
      if(!iter_prepend(iq, qstate->return_msg, qstate->region)) {
        log_err("rpz: prepend rrsets: out of memory");
        return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      }
      return 0;
    }
  }

  /* Select the next usable target, filtering out unsuitable targets. */
  target = iter_server_selection(ie, qstate->env, iq->dp,
    iq->dp->name, iq->dp->namelen, iq->qchase.qtype,
    &iq->dnssec_lame_query, &iq->chase_to_rd,
    iq->num_target_queries, qstate->blacklist,
    qstate->prefetch_leeway);

  /* If no usable target was selected... */
  if(!target) {
    /* Here we distinguish between three states: generate a new 
     * target query, just wait, or quit (with a SERVFAIL).
     * We have the following information: number of active 
     * target queries, number of active current queries, 
     * the presence of missing targets at this delegation 
     * point, and the given query target policy. */
    
    /* Check for the wait condition. If this is true, then 
     * an action must be taken. */
    if(iq->num_target_queries==0 && iq->num_current_queries==0) {
      /* If there is nothing to wait for, then we need 
       * to distinguish between generating (a) new target 
       * query, or failing. */
      if(delegpt_count_missing_targets(iq->dp, NULL) > 0) {
        int qs = 0, ret;
        verbose(VERB_ALGO, "querying for next "
          "missing target");
        if((ret=query_for_targets(qstate, iq, ie, id, 
          1, &qs))!=0) {
          errinf(qstate, "could not fetch nameserver");
          errinf_dname(qstate, "at zone", iq->dp->name);
          if(ret == 1)
            return error_response(qstate, id,
              LDNS_RCODE_SERVFAIL);
          return error_response_cache(qstate, id,
            LDNS_RCODE_SERVFAIL);
        }
        if(qs == 0 && 
           delegpt_count_missing_targets(iq->dp, NULL) == 0){
          /* it looked like there were missing
           * targets, but they did not turn up.
           * Try the bad choices again (if any),
           * when we get back here missing==0,
           * so this is not a loop. */
          return 1;
        }
        if(qs == 0) {
          /* There should be targets now, and
           * if there are not, it should not
           * wait for no targets. Stop it from
           * waiting forever, or looping to
           * here, as a safeguard. */
          errinf(qstate, "could not generate nameserver lookups");
          errinf_dname(qstate, "at zone", iq->dp->name);
          return error_response(qstate, id,
            LDNS_RCODE_SERVFAIL);
        }
        iq->num_target_queries += qs;
        target_count_increase(iq, qs);
      }
      /* Since a target query might have been made, we 
       * need to check again. */
      if(iq->num_target_queries == 0) {
        /* if in capsforid fallback, instead of last
         * resort, we agree with the current reply
         * we have (if any) (our count of addrs bad)*/
        if(iq->caps_fallback && iq->caps_reply) {
          /* we're done, process the response */
          verbose(VERB_ALGO, "0x20 fallback had %d responses, "
            "but no more servers except "
            "last resort, done.", 
            (int)iq->caps_server+1);
          iq->response = iq->caps_response;
          iq->caps_fallback = 0;
          iter_dec_attempts(iq->dp, 3, ie->outbound_msg_retry); /* space for fallback */
          iq->num_current_queries++; /* RespState decrements it*/
          iq->referral_count++; /* make sure we don't loop */
          iq->sent_count = 0;
          iq->dp_target_count = 0;
          iq->state = QUERY_RESP_STATE;
          return 1;
        }
        return processLastResort(qstate, iq, ie, id);
      }
    }

    /* otherwise, we have no current targets, so submerge 
     * until one of the target or direct queries return. */
    verbose(VERB_ALGO, "no current targets");
    check_waiting_queries(iq, qstate, id);
    /* undo qname minimise step because we'll get back here
     * to do it again */
    if(qout_orig && iq->minimise_count > 0) {
      iq->minimise_count--;
      iq->qinfo_out.qname = qout_orig;
      iq->qinfo_out.qname_len = qout_orig_len;
    }
    return 0;
  }

  /* We have a target. We could have created promiscuous target
   * queries but we are currently under pressure (mesh_jostle_exceeded).
   * If we are configured to allow promiscuous target queries and haven't
   * gone out to the network for a target query for this delegation, then
   * it is possible to slip in a promiscuous one with a 1/10 chance. */
  if(can_do_promisc && tf_policy == 0 && iq->depth == 0
    && iq->depth < ie->max_dependency_depth
    && ie->target_fetch_policy[iq->depth] != 0
    && iq->dp_target_count == 0
    && !ub_random_max(qstate->env->rnd, 10)) {
    int extra = 0;
    verbose(VERB_ALGO, "available target exists in cache but "
      "attempt to get extra 1 target");
    (void)query_for_targets(qstate, iq, ie, id, 1, &extra);
    /* errors ignored, these targets are not strictly necessary for
    * this result, we do not have to reply with SERVFAIL */
    if(extra > 0) {
      iq->num_target_queries += extra;
      target_count_increase(iq, extra);
      check_waiting_queries(iq, qstate, id);
      /* undo qname minimise step because we'll get back here
       * to do it again */
      if(qout_orig && iq->minimise_count > 0) {
        iq->minimise_count--;
        iq->qinfo_out.qname = qout_orig;
        iq->qinfo_out.qname_len = qout_orig_len;
      }
      return 0;
    }
  }

  target_count_increase_global_quota(iq, 1);
  if(iq->target_count && iq->target_count[TARGET_COUNT_GLOBAL_QUOTA]
    > MAX_GLOBAL_QUOTA) {
    char s[LDNS_MAX_DOMAINLEN];
    dname_str(qstate->qinfo.qname, s);
    verbose(VERB_QUERY, "request %s has exceeded the maximum "
      "global quota on number of upstream queries %d", s,
      iq->target_count[TARGET_COUNT_GLOBAL_QUOTA]);
    return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
  }

  /* Do not check ratelimit for forwarding queries or if we already got a
   * pass. */
  sq_check_ratelimit = (!(iq->chase_flags & BIT_RD) && !iq->ratelimit_ok);
  /* We have a valid target. */
  if(verbosity >= VERB_QUERY) {
    log_query_info(VERB_QUERY, "sending query:", &iq->qinfo_out);
    log_name_addr(VERB_QUERY, "sending to target:", iq->dp->name,
      &target->addr, target->addrlen);
    verbose(VERB_ALGO, "dnssec status: %s%s",
      iq->dnssec_expected?"expected": "not expected",
      iq->dnssec_lame_query?" but lame_query anyway": "");
  }

  fptr_ok(fptr_whitelist_modenv_send_query(qstate->env->send_query));
  outq = (*qstate->env->send_query)(&iq->qinfo_out,
    iq->chase_flags | (iq->chase_to_rd?BIT_RD:0),
    /* unset CD if to forwarder(RD set) and not dnssec retry
     * (blacklist nonempty) and no trust-anchors are configured
     * above the qname or on the first attempt when dnssec is on */
    (qstate->env->cfg->disable_edns_do?0:EDNS_DO)|
    ((iq->chase_to_rd||(iq->chase_flags&BIT_RD)!=0)&&
    !qstate->blacklist&&(!iter_qname_indicates_dnssec(qstate->env,
    &iq->qinfo_out)||target->attempts==1)?0:BIT_CD),
    iq->dnssec_expected, iq->caps_fallback || is_caps_whitelisted(
    ie, iq), sq_check_ratelimit, &target->addr, target->addrlen,
    iq->dp->name, iq->dp->namelen,
    (iq->dp->tcp_upstream || qstate->env->cfg->tcp_upstream),
    (iq->dp->ssl_upstream || qstate->env->cfg->ssl_upstream),
    target->tls_auth_name, qstate, &sq_was_ratelimited);
  if(!outq) {
    if(sq_was_ratelimited) {
      lock_basic_lock(&ie->queries_ratelimit_lock);
      ie->num_queries_ratelimited++;
      lock_basic_unlock(&ie->queries_ratelimit_lock);
      verbose(VERB_ALGO, "query exceeded ratelimits");
      qstate->was_ratelimited = 1;
      errinf_dname(qstate, "exceeded ratelimit for zone",
        iq->dp->name);
      return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    log_addr(VERB_QUERY, "error sending query to auth server",
      &target->addr, target->addrlen);
    if(qstate->env->cfg->qname_minimisation)
      iq->minimisation_state = SKIP_MINIMISE_STATE;
    return next_state(iq, QUERYTARGETS_STATE);
  }
  outbound_list_insert(&iq->outlist, outq);
  iq->num_current_queries++;
  iq->sent_count++;
  qstate->ext_state[id] = module_wait_reply;

  return 0;
}

/** find NS rrset in given list */
static struct ub_packed_rrset_key*
find_NS(struct reply_info* rep, size_t from, size_t to)
{
  size_t i;
  for(i=from; i<to; i++) {
    if(ntohs(rep->rrsets[i]->rk.type) == LDNS_RR_TYPE_NS)
      return rep->rrsets[i];
  }
  return NULL;
}


/** 
 * Process the query response. All queries end up at this state first. This
 * process generally consists of analyzing the response and routing the
 * event to the next state (either bouncing it back to a request state, or
 * terminating the processing for this event).
 * 
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @return true if the event requires more immediate processing, false if
 *         not. This is generally only true when forwarding the request to
 *         the final state (i.e., on answer).
 */
static int
processQueryResponse(struct module_qstate* qstate, struct iter_qstate* iq,
  struct iter_env* ie, int id)
{
  int dnsseclame = 0, origtypecname = 0, orig_empty_nodata_found;
  enum response_type type;

  iq->num_current_queries--;

  if(!inplace_cb_query_response_call(qstate->env, qstate, iq->response))
    log_err("unable to call query_response callback");

  if(iq->response == NULL) {
    /* Don't increment qname when QNAME minimisation is enabled */
    if(qstate->env->cfg->qname_minimisation) {
      iq->minimisation_state = SKIP_MINIMISE_STATE;
    }
    iq->timeout_count++;
    iq->chase_to_rd = 0;
    iq->dnssec_lame_query = 0;
    verbose(VERB_ALGO, "query response was timeout");
    return next_state(iq, QUERYTARGETS_STATE);
  }
  iq->timeout_count = 0;
  orig_empty_nodata_found = iq->empty_nodata_found;
  type = response_type_from_server(
    (int)((iq->chase_flags&BIT_RD) || iq->chase_to_rd),
    iq->response, &iq->qinfo_out, iq->dp, &iq->empty_nodata_found);
  iq->chase_to_rd = 0;
  /* remove TC flag, if this is erroneously set by TCP upstream */
  iq->response->rep->flags &= ~BIT_TC;
  if(orig_empty_nodata_found != iq->empty_nodata_found &&
    iq->empty_nodata_found < EMPTY_NODATA_RETRY_COUNT) {
    /* try to search at another server */
    if(qstate->reply) {
      struct delegpt_addr* a = delegpt_find_addr(
        iq->dp, &qstate->reply->remote_addr,
        qstate->reply->remote_addrlen);
      /* make selection disprefer it */
      if(a) a->lame = 1;
    }
    return next_state(iq, QUERYTARGETS_STATE);
  }
  if(type == RESPONSE_TYPE_REFERRAL && (iq->chase_flags&BIT_RD) &&
    !iq->auth_zone_response) {
    /* When forwarding (RD bit is set), we handle referrals 
     * differently. No queries should be sent elsewhere */
    type = RESPONSE_TYPE_ANSWER;
  }
  if(!qstate->env->cfg->disable_dnssec_lame_check && iq->dnssec_expected 
                && !iq->dnssec_lame_query &&
    !(iq->chase_flags&BIT_RD) 
    && iq->sent_count < DNSSEC_LAME_DETECT_COUNT
    && type != RESPONSE_TYPE_LAME 
    && type != RESPONSE_TYPE_REC_LAME 
    && type != RESPONSE_TYPE_THROWAWAY 
    && type != RESPONSE_TYPE_UNTYPED) {
    /* a possible answer, see if it is missing DNSSEC */
    /* but not when forwarding, so we dont mark fwder lame */
    if(!iter_msg_has_dnssec(iq->response)) {
      /* Mark this address as dnsseclame in this dp,
       * because that will make serverselection disprefer
       * it, but also, once it is the only final option,
       * use dnssec-lame-bypass if it needs to query there.*/
      if(qstate->reply) {
        struct delegpt_addr* a = delegpt_find_addr(
          iq->dp, &qstate->reply->remote_addr,
          qstate->reply->remote_addrlen);
        if(a) a->dnsseclame = 1;
      }
      /* test the answer is from the zone we expected,
       * otherwise, (due to parent,child on same server), we
       * might mark the server,zone lame inappropriately */
      if(!iter_msg_from_zone(iq->response, iq->dp, type,
        iq->qchase.qclass))
        qstate->reply = NULL;
      type = RESPONSE_TYPE_LAME;
      dnsseclame = 1;
    }
  } else iq->dnssec_lame_query = 0;
  /* see if referral brings us close to the target */
  if(type == RESPONSE_TYPE_REFERRAL) {
    struct ub_packed_rrset_key* ns = find_NS(
      iq->response->rep, iq->response->rep->an_numrrsets,
      iq->response->rep->an_numrrsets 
      + iq->response->rep->ns_numrrsets);
    if(!ns) ns = find_NS(iq->response->rep, 0, 
        iq->response->rep->an_numrrsets);
    if(!ns || !dname_strict_subdomain_c(ns->rk.dname, iq->dp->name) 
      || !dname_subdomain_c(iq->qchase.qname, ns->rk.dname)){
      verbose(VERB_ALGO, "bad referral, throwaway");
      type = RESPONSE_TYPE_THROWAWAY;
    } else
      iter_scrub_ds(iq->response, ns, iq->dp->name);
  } else iter_scrub_ds(iq->response, NULL, NULL);
  if(type == RESPONSE_TYPE_THROWAWAY &&
    FLAGS_GET_RCODE(iq->response->rep->flags) == LDNS_RCODE_YXDOMAIN) {
    /* YXDOMAIN is a permanent error, no need to retry */
    type = RESPONSE_TYPE_ANSWER;
  }
  if(type == RESPONSE_TYPE_CNAME)
    origtypecname = 1;
  if(type == RESPONSE_TYPE_CNAME && iq->response->rep->an_numrrsets >= 1
    && ntohs(iq->response->rep->rrsets[0]->rk.type) == LDNS_RR_TYPE_DNAME) {
    uint8_t* sname = NULL;
    size_t snamelen = 0;
    get_cname_target(iq->response->rep->rrsets[0], &sname,
      &snamelen);
    if(snamelen && dname_subdomain_c(sname, iq->response->rep->rrsets[0]->rk.dname)) {
      /* DNAME to a subdomain loop; do not recurse */
      type = RESPONSE_TYPE_ANSWER;
    }
  }
  if(type == RESPONSE_TYPE_CNAME &&
    (iq->qchase.qtype == LDNS_RR_TYPE_CNAME ||
      iq->qchase.qtype == LDNS_RR_TYPE_ANY) &&
    iq->minimisation_state == MINIMISE_STATE &&
    query_dname_compare(iq->qchase.qname, iq->qinfo_out.qname) == 0) {
    /* The minimised query for full QTYPE and hidden QTYPE can be
     * classified as CNAME response type, even when the original
     * QTYPE=CNAME. This should be treated as answer response type.
     */
    /* For QTYPE=ANY, it is also considered the response, that
     * is what the classifier would say, if it saw qtype ANY,
     * and this same response was returned for that. The response
     * can already be treated as such an answer, without having
     * to send another query with a new qtype. */
    type = RESPONSE_TYPE_ANSWER;
  }

  /* handle each of the type cases */
  if(type == RESPONSE_TYPE_ANSWER) {
    /* ANSWER type responses terminate the query algorithm, 
     * so they sent on their */
    if(verbosity >= VERB_DETAIL) {
      verbose(VERB_DETAIL, "query response was %s",
        FLAGS_GET_RCODE(iq->response->rep->flags)
        ==LDNS_RCODE_NXDOMAIN?"NXDOMAIN ANSWER":
        (iq->response->rep->an_numrrsets?"ANSWER":
        "nodata ANSWER"));
    }
    /* if qtype is DS, check we have the right level of answer,
     * like grandchild answer but we need the middle, reject it */
    if(iq->qchase.qtype == LDNS_RR_TYPE_DS && !iq->dsns_point
      && !(iq->chase_flags&BIT_RD)
      && iter_ds_toolow(iq->response, iq->dp)
      && iter_dp_cangodown(&iq->qchase, iq->dp)) {
      /* close down outstanding requests to be discarded */
      outbound_list_clear(&iq->outlist);
      iq->num_current_queries = 0;
      fptr_ok(fptr_whitelist_modenv_detach_subs(
        qstate->env->detach_subs));
      (*qstate->env->detach_subs)(qstate);
      iq->num_target_queries = 0;
      return processDSNSFind(qstate, iq, id);
    }
    if(iq->qchase.qtype == LDNS_RR_TYPE_DNSKEY && SERVE_EXPIRED
      && qstate->is_valrec &&
      reply_find_answer_rrset(&iq->qchase, iq->response->rep) != NULL) {
      /* clean out the authority section, if any, so it
       * does not overwrite dnssec valid data in the
       * validation recursion lookup. */
      verbose(VERB_ALGO, "make DNSKEY minimal for serve "
        "expired");
      iter_make_minimal(iq->response->rep);
    }
    if(!qstate->no_cache_store)
      iter_dns_store(qstate->env, &iq->response->qinfo,
        iq->response->rep,
        iq->qchase.qtype != iq->response->qinfo.qtype,
        qstate->prefetch_leeway,
        iq->dp&&iq->dp->has_parent_side_NS,
        qstate->region, qstate->query_flags,
        qstate->qstarttime, qstate->is_valrec);
    /* close down outstanding requests to be discarded */
    outbound_list_clear(&iq->outlist);
    iq->num_current_queries = 0;
    fptr_ok(fptr_whitelist_modenv_detach_subs(
      qstate->env->detach_subs));
    (*qstate->env->detach_subs)(qstate);
    iq->num_target_queries = 0;
    if(qstate->reply)
      sock_list_insert(&qstate->reply_origin,
        &qstate->reply->remote_addr,
        qstate->reply->remote_addrlen, qstate->region);
    if(iq->minimisation_state != DONOT_MINIMISE_STATE
      && !(iq->chase_flags & BIT_RD)) {
      if(FLAGS_GET_RCODE(iq->response->rep->flags) != 
        LDNS_RCODE_NOERROR) {
        if(qstate->env->cfg->qname_minimisation_strict) {
          if(FLAGS_GET_RCODE(iq->response->rep->flags) ==
            LDNS_RCODE_NXDOMAIN) {
            iter_scrub_nxdomain(iq->response);
            return final_state(iq);
          }
          return error_response_cache(qstate, id,
            LDNS_RCODE_SERVFAIL);
        }
        /* Best effort qname-minimisation. 
         * Stop minimising and send full query when
         * RCODE is not NOERROR. */
        iq->minimisation_state = DONOT_MINIMISE_STATE;
      }
      if(FLAGS_GET_RCODE(iq->response->rep->flags) ==
        LDNS_RCODE_NXDOMAIN && !origtypecname) {
        /* Stop resolving when NXDOMAIN is DNSSEC
         * signed. Based on assumption that nameservers
         * serving signed zones do not return NXDOMAIN
         * for empty-non-terminals. */
        /* If this response is actually a CNAME type,
         * the nxdomain rcode may not be for the qname,
         * and so it is not the final response. */
        if(iq->dnssec_expected)
          return final_state(iq);
        /* Make subrequest to validate intermediate
         * NXDOMAIN if harden-below-nxdomain is
         * enabled. */
        if(qstate->env->cfg->harden_below_nxdomain &&
          qstate->env->need_to_validate) {
          struct module_qstate* subq = NULL;
          log_query_info(VERB_QUERY,
            "schedule NXDOMAIN validation:",
            &iq->response->qinfo);
          if(!generate_sub_request(
            iq->response->qinfo.qname,
            iq->response->qinfo.qname_len,
            iq->response->qinfo.qtype,
            iq->response->qinfo.qclass,
            qstate, id, iq,
            INIT_REQUEST_STATE,
            FINISHED_STATE, &subq, 1, 1))
            verbose(VERB_ALGO,
            "could not validate NXDOMAIN "
            "response");
        }
      }
      return next_state(iq, QUERYTARGETS_STATE);
    }
    return final_state(iq);
  } else if(type == RESPONSE_TYPE_REFERRAL) {
    struct delegpt* old_dp = NULL;
    /* REFERRAL type responses get a reset of the 
     * delegation point, and back to the QUERYTARGETS_STATE. */
    verbose(VERB_DETAIL, "query response was REFERRAL");

    /* if hardened, only store referral if we asked for it */
    if(!qstate->no_cache_store &&
    (!qstate->env->cfg->harden_referral_path ||
        (  qstate->qinfo.qtype == LDNS_RR_TYPE_NS 
      && (qstate->query_flags&BIT_RD) 
      && !(qstate->query_flags&BIT_CD)
         /* we know that all other NS rrsets are scrubbed
          * away, thus on referral only one is left.
          * see if that equals the query name... */
      && ( /* auth section, but sometimes in answer section*/
        reply_find_rrset_section_ns(iq->response->rep,
        iq->qchase.qname, iq->qchase.qname_len,
        LDNS_RR_TYPE_NS, iq->qchase.qclass)
        || reply_find_rrset_section_an(iq->response->rep,
        iq->qchase.qname, iq->qchase.qname_len,
        LDNS_RR_TYPE_NS, iq->qchase.qclass)
        )
        ))) {
      /* Store the referral under the current query */
      /* no prefetch-leeway, since its not the answer */
      iter_dns_store(qstate->env, &iq->response->qinfo,
        iq->response->rep, 1, 0, 0, NULL, 0,
        qstate->qstarttime, qstate->is_valrec);
      if(iq->store_parent_NS)
        iter_store_parentside_NS(qstate->env, 
          iq->response->rep);
      if(qstate->env->neg_cache)
        val_neg_addreferral(qstate->env->neg_cache, 
          iq->response->rep, iq->dp->name);
    }
    /* store parent-side-in-zone-glue, if directly queried for */
    if(!qstate->no_cache_store && iq->query_for_pside_glue
      && !iq->pside_glue) {
        iq->pside_glue = reply_find_rrset(iq->response->rep, 
          iq->qchase.qname, iq->qchase.qname_len, 
          iq->qchase.qtype, iq->qchase.qclass);
        if(iq->pside_glue) {
          log_rrset_key(VERB_ALGO, "found parent-side "
            "glue", iq->pside_glue);
          iter_store_parentside_rrset(qstate->env,
            iq->pside_glue);
        }
    }

    /* Reset the event state, setting the current delegation 
     * point to the referral. */
    iq->deleg_msg = iq->response;
    /* Keep current delegation point for label comparison */
    old_dp = iq->dp;
    iq->dp = delegpt_from_message(iq->response, qstate->region);
    if (qstate->env->cfg->qname_minimisation)
      iq->minimisation_state = INIT_MINIMISE_STATE;
    if(!iq->dp) {
      errinf(qstate, "malloc failure, for delegation point");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    if(old_dp->namelabs + 1 < iq->dp->namelabs) {
      /* We got a grandchild delegation (more than one label
       * difference) than expected. Check for in-between
       * delegations in the cache and remove them.
       * They could prove problematic when they expire
       * and rrset_expired_above() encounters them during
       * delegation cache lookups. */
      uint8_t* qname = iq->dp->name;
      size_t qnamelen = iq->dp->namelen;
      rrset_cache_remove_above(qstate->env->rrset_cache,
        &qname, &qnamelen, LDNS_RR_TYPE_NS,
        iq->qchase.qclass, *qstate->env->now,
        old_dp->name, old_dp->namelen);
    }
    if(!cache_fill_missing(qstate->env, iq->qchase.qclass, 
      qstate->region, iq->dp, 0)) {
      errinf(qstate, "malloc failure, copy extra info into delegation point");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    if(iq->store_parent_NS && query_dname_compare(iq->dp->name,
      iq->store_parent_NS->name) == 0)
      iter_merge_retry_counts(iq->dp, iq->store_parent_NS,
        ie->outbound_msg_retry);
    delegpt_log(VERB_ALGO, iq->dp);
    /* Count this as a referral. */
    iq->referral_count++;
    iq->sent_count = 0;
    iq->dp_target_count = 0;
    /* see if the next dp is a trust anchor, or a DS was sent
     * along, indicating dnssec is expected for next zone */
    iq->dnssec_expected = iter_indicates_dnssec(qstate->env, 
      iq->dp, iq->response, iq->qchase.qclass);
    /* if dnssec, validating then also fetch the key for the DS */
    if(iq->dnssec_expected && qstate->env->cfg->prefetch_key &&
      !(qstate->query_flags&BIT_CD))
      generate_dnskey_prefetch(qstate, iq, id);

    /* spawn off NS and addr to auth servers for the NS we just
     * got in the referral. This gets authoritative answer
     * (answer section trust level) rrset. 
     * right after, we detach the subs, answer goes to cache. */
    if(qstate->env->cfg->harden_referral_path)
      generate_ns_check(qstate, iq, id);

    /* stop current outstanding queries. 
     * FIXME: should the outstanding queries be waited for and
     * handled? Say by a subquery that inherits the outbound_entry.
     */
    outbound_list_clear(&iq->outlist);
    iq->num_current_queries = 0;
    fptr_ok(fptr_whitelist_modenv_detach_subs(
      qstate->env->detach_subs));
    (*qstate->env->detach_subs)(qstate);
    iq->num_target_queries = 0;
    iq->response = NULL;
    iq->fail_addr_type = 0;
    verbose(VERB_ALGO, "cleared outbound list for next round");
    return next_state(iq, QUERYTARGETS_STATE);
  } else if(type == RESPONSE_TYPE_CNAME) {
    uint8_t* sname = NULL;
    size_t snamelen = 0;
    /* CNAME type responses get a query restart (i.e., get a 
     * reset of the query state and go back to INIT_REQUEST_STATE).
     */
    verbose(VERB_DETAIL, "query response was CNAME");
    if(verbosity >= VERB_ALGO)
      log_dns_msg("cname msg", &iq->response->qinfo, 
        iq->response->rep);
    /* if qtype is DS, check we have the right level of answer,
     * like grandchild answer but we need the middle, reject it */
    if(iq->qchase.qtype == LDNS_RR_TYPE_DS && !iq->dsns_point
      && !(iq->chase_flags&BIT_RD)
      && iter_ds_toolow(iq->response, iq->dp)
      && iter_dp_cangodown(&iq->qchase, iq->dp)) {
      outbound_list_clear(&iq->outlist);
      iq->num_current_queries = 0;
      fptr_ok(fptr_whitelist_modenv_detach_subs(
        qstate->env->detach_subs));
      (*qstate->env->detach_subs)(qstate);
      iq->num_target_queries = 0;
      return processDSNSFind(qstate, iq, id);
    }
    if(iq->minimisation_state == MINIMISE_STATE &&
      query_dname_compare(iq->qchase.qname,
      iq->qinfo_out.qname) != 0) {
      verbose(VERB_ALGO, "continue query minimisation, "
        "downwards, after CNAME response for "
        "intermediate label");
      /* continue query minimisation, downwards */
      return next_state(iq, QUERYTARGETS_STATE);
    }
    /* Process the CNAME response. */
    if(!handle_cname_response(qstate, iq, iq->response, 
      &sname, &snamelen)) {
      errinf(qstate, "malloc failure, CNAME info");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    /* cache the CNAME response under the current query */
    /* NOTE : set referral=1, so that rrsets get stored but not 
     * the partial query answer (CNAME only). */
    /* prefetchleeway applied because this updates answer parts */
    if(!qstate->no_cache_store)
      iter_dns_store(qstate->env, &iq->response->qinfo,
        iq->response->rep, 1, qstate->prefetch_leeway,
        iq->dp&&iq->dp->has_parent_side_NS, NULL,
        qstate->query_flags, qstate->qstarttime,
        qstate->is_valrec);
    /* set the current request's qname to the new value. */
    iq->qchase.qname = sname;
    iq->qchase.qname_len = snamelen;
    if(qstate->env->auth_zones) {
      /* apply rpz qname triggers after cname */
      struct dns_msg* forged_response =
        rpz_callback_from_iterator_cname(qstate, iq);
      int count = 0;
      while(forged_response && reply_find_rrset_section_an(
        forged_response->rep, iq->qchase.qname,
        iq->qchase.qname_len, LDNS_RR_TYPE_CNAME,
        iq->qchase.qclass) &&
        iq->qchase.qtype != LDNS_RR_TYPE_CNAME &&
        count++ < ie->max_query_restarts) {
        /* another cname to follow */
        if(!handle_cname_response(qstate, iq, forged_response,
          &sname, &snamelen)) {
          errinf(qstate, "malloc failure, CNAME info");
          return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
        }
        iq->qchase.qname = sname;
        iq->qchase.qname_len = snamelen;
        forged_response =
          rpz_callback_from_iterator_cname(qstate, iq);
      }
      if(forged_response != NULL) {
        qstate->ext_state[id] = module_finished;
        qstate->return_rcode = LDNS_RCODE_NOERROR;
        qstate->return_msg = forged_response;
        iq->response = forged_response;
        next_state(iq, FINISHED_STATE);
        if(!iter_prepend(iq, qstate->return_msg, qstate->region)) {
          log_err("rpz: after cname, prepend rrsets: out of memory");
          return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
        }
        qstate->return_msg->qinfo = qstate->qinfo;
        return 0;
      }
    }
    /* Clear the query state, since this is a query restart. */
    iq->deleg_msg = NULL;
    iq->dp = NULL;
    iq->dsns_point = NULL;
    iq->auth_zone_response = 0;
    iq->sent_count = 0;
    iq->dp_target_count = 0;
    iq->query_restart_count++;
    if(qstate->env->cfg->qname_minimisation)
      iq->minimisation_state = INIT_MINIMISE_STATE;

    /* stop current outstanding queries. 
     * FIXME: should the outstanding queries be waited for and
     * handled? Say by a subquery that inherits the outbound_entry.
     */
    outbound_list_clear(&iq->outlist);
    iq->num_current_queries = 0;
    fptr_ok(fptr_whitelist_modenv_detach_subs(
      qstate->env->detach_subs));
    (*qstate->env->detach_subs)(qstate);
    iq->num_target_queries = 0;
    if(qstate->reply)
      sock_list_insert(&qstate->reply_origin,
        &qstate->reply->remote_addr,
        qstate->reply->remote_addrlen, qstate->region);
    verbose(VERB_ALGO, "cleared outbound list for query restart");
    /* go to INIT_REQUEST_STATE for new qname. */
    return next_state(iq, INIT_REQUEST_STATE);
  } else if(type == RESPONSE_TYPE_LAME) {
    /* Cache the LAMEness. */
    verbose(VERB_DETAIL, "query response was %sLAME",
      dnsseclame?"DNSSEC ":"");
    if(!dname_subdomain_c(iq->qchase.qname, iq->dp->name)) {
      log_err("mark lame: mismatch in qname and dpname");
      /* throwaway this reply below */
    } else if(qstate->reply) {
      /* need addr for lameness cache, but we may have
       * gotten this from cache, so test to be sure */
      if(!infra_set_lame(qstate->env->infra_cache,
        &qstate->reply->remote_addr,
        qstate->reply->remote_addrlen,
        iq->dp->name, iq->dp->namelen,
        *qstate->env->now, dnsseclame, 0,
        iq->qchase.qtype))
        log_err("mark host lame: out of memory");
    }
  } else if(type == RESPONSE_TYPE_REC_LAME) {
    /* Cache the LAMEness. */
    verbose(VERB_DETAIL, "query response REC_LAME: "
      "recursive but not authoritative server");
    if(!dname_subdomain_c(iq->qchase.qname, iq->dp->name)) {
      log_err("mark rec_lame: mismatch in qname and dpname");
      /* throwaway this reply below */
    } else if(qstate->reply) {
      /* need addr for lameness cache, but we may have
       * gotten this from cache, so test to be sure */
      verbose(VERB_DETAIL, "mark as REC_LAME");
      if(!infra_set_lame(qstate->env->infra_cache, 
        &qstate->reply->remote_addr,
        qstate->reply->remote_addrlen,
        iq->dp->name, iq->dp->namelen,
        *qstate->env->now, 0, 1, iq->qchase.qtype))
        log_err("mark host lame: out of memory");
    } 
  } else if(type == RESPONSE_TYPE_THROWAWAY) {
    /* LAME and THROWAWAY responses are handled the same way. 
     * In this case, the event is just sent directly back to 
     * the QUERYTARGETS_STATE without resetting anything, 
     * because, clearly, the next target must be tried. */
    verbose(VERB_DETAIL, "query response was THROWAWAY");
  } else {
    log_warn("A query response came back with an unknown type: %d",
      (int)type);
  }

  /* LAME, THROWAWAY and "unknown" all end up here.
   * Recycle to the QUERYTARGETS state to hopefully try a 
   * different target. */
  if (qstate->env->cfg->qname_minimisation &&
    !qstate->env->cfg->qname_minimisation_strict)
    iq->minimisation_state = DONOT_MINIMISE_STATE;
  if(iq->auth_zone_response) {
    /* can we fallback? */
    iq->auth_zone_response = 0;
    if(!auth_zones_can_fallback(qstate->env->auth_zones,
      iq->dp->name, iq->dp->namelen, qstate->qinfo.qclass)) {
      verbose(VERB_ALGO, "auth zone response bad, and no"
        " fallback possible, servfail");
      errinf_dname(qstate, "response is bad, no fallback, "
        "for auth zone", iq->dp->name);
      return error_response_cache(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    verbose(VERB_ALGO, "auth zone response was bad, "
      "fallback enabled");
    iq->auth_zone_avoid = 1;
    if(iq->dp->auth_dp) {
      /* we are using a dp for the auth zone, with no
       * nameservers, get one first */
      iq->dp = NULL;
      return next_state(iq, INIT_REQUEST_STATE);
    }
  }
  return next_state(iq, QUERYTARGETS_STATE);
}

/**
 * Return priming query results to interested super querystates.
 * 
 * Sets the delegation point and delegation message (not nonRD queries).
 * This is a callback from walk_supers.
 *
 * @param qstate: priming query state that finished.
 * @param id: module id.
 * @param forq: the qstate for which priming has been done.
 */
static void
prime_supers(struct module_qstate* qstate, int id, struct module_qstate* forq)
{
  struct iter_qstate* foriq = (struct iter_qstate*)forq->minfo[id];
  struct delegpt* dp = NULL;

  log_assert(qstate->is_priming || foriq->wait_priming_stub);
  log_assert(qstate->return_rcode == LDNS_RCODE_NOERROR);
  /* Convert our response to a delegation point */
  dp = delegpt_from_message(qstate->return_msg, forq->region);
  if(!dp) {
    /* if there is no convertible delegation point, then 
     * the ANSWER type was (presumably) a negative answer. */
    verbose(VERB_ALGO, "prime response was not a positive "
      "ANSWER; failing");
    foriq->dp = NULL;
    foriq->state = QUERYTARGETS_STATE;
    return;
  }

  log_query_info(VERB_DETAIL, "priming successful for", &qstate->qinfo);
  delegpt_log(VERB_ALGO, dp);
  foriq->dp = dp;
  foriq->deleg_msg = dns_copy_msg(qstate->return_msg, forq->region);
  if(!foriq->deleg_msg) {
    log_err("copy prime response: out of memory");
    foriq->dp = NULL;
    foriq->state = QUERYTARGETS_STATE;
    return;
  }

  /* root priming responses go to init stage 2, priming stub 
   * responses to to stage 3. */
  if(foriq->wait_priming_stub) {
    foriq->state = INIT_REQUEST_3_STATE;
    foriq->wait_priming_stub = 0;
  } else foriq->state = INIT_REQUEST_2_STATE;
  /* because we are finished, the parent will be reactivated */
}

/** 
 * This handles the response to a priming query. This is used to handle both
 * root and stub priming responses. This is basically the equivalent of the
 * QUERY_RESP_STATE, but will not handle CNAME responses and will treat
 * REFERRALs as ANSWERS. It will also update and reactivate the originating
 * event.
 *
 * @param qstate: query state.
 * @param id: module id.
 * @return true if the event needs more immediate processing, false if not.
 *         This state always returns false.
 */
static int
processPrimeResponse(struct module_qstate* qstate, int id)
{
  struct iter_qstate* iq = (struct iter_qstate*)qstate->minfo[id];
  enum response_type type;
  iq->response->rep->flags &= ~(BIT_RD|BIT_RA); /* ignore rec-lame */
  type = response_type_from_server(
    (int)((iq->chase_flags&BIT_RD) || iq->chase_to_rd), 
    iq->response, &iq->qchase, iq->dp, NULL);
  if(type == RESPONSE_TYPE_ANSWER) {
    qstate->return_rcode = LDNS_RCODE_NOERROR;
    qstate->return_msg = iq->response;
  } else {
    errinf(qstate, "prime response did not get an answer");
    errinf_dname(qstate, "for", qstate->qinfo.qname);
    qstate->return_rcode = LDNS_RCODE_SERVFAIL;
    qstate->return_msg = NULL;
  }

  /* validate the root or stub after priming (if enabled).
   * This is the same query as the prime query, but with validation.
   * Now that we are primed, the additional queries that validation
   * may need can be resolved. */
  if(qstate->env->cfg->harden_referral_path) {
    struct module_qstate* subq = NULL;
    log_nametypeclass(VERB_ALGO, "schedule prime validation", 
      qstate->qinfo.qname, qstate->qinfo.qtype,
      qstate->qinfo.qclass);
    if(!generate_sub_request(qstate->qinfo.qname, 
      qstate->qinfo.qname_len, qstate->qinfo.qtype,
      qstate->qinfo.qclass, qstate, id, iq,
      INIT_REQUEST_STATE, FINISHED_STATE, &subq, 1, 0)) {
      verbose(VERB_ALGO, "could not generate prime check");
    }
    generate_a_aaaa_check(qstate, iq, id);
  }

  /* This event is finished. */
  qstate->ext_state[id] = module_finished;
  return 0;
}

/** 
 * Do final processing on responses to target queries. Events reach this
 * state after the iterative resolution algorithm terminates. This state is
 * responsible for reactivating the original event, and housekeeping related
 * to received target responses (caching, updating the current delegation
 * point, etc).
 * Callback from walk_supers for every super state that is interested in 
 * the results from this query.
 *
 * @param qstate: query state.
 * @param id: module id.
 * @param forq: super query state.
 */
static void
processTargetResponse(struct module_qstate* qstate, int id,
  struct module_qstate* forq)
{
  struct iter_env* ie = (struct iter_env*)qstate->env->modinfo[id];
  struct iter_qstate* iq = (struct iter_qstate*)qstate->minfo[id];
  struct iter_qstate* foriq = (struct iter_qstate*)forq->minfo[id];
  struct ub_packed_rrset_key* rrset;
  struct delegpt_ns* dpns;
  log_assert(qstate->return_rcode == LDNS_RCODE_NOERROR);

  foriq->state = QUERYTARGETS_STATE;
  log_query_info(VERB_ALGO, "processTargetResponse", &qstate->qinfo);
  log_query_info(VERB_ALGO, "processTargetResponse super", &forq->qinfo);

  /* Tell the originating event that this target query has finished
   * (regardless if it succeeded or not). */
  foriq->num_target_queries--;

  /* check to see if parent event is still interested (in orig name).  */
  if(!foriq->dp) {
    verbose(VERB_ALGO, "subq: parent not interested, was reset");
    return; /* not interested anymore */
  }
  dpns = delegpt_find_ns(foriq->dp, qstate->qinfo.qname,
      qstate->qinfo.qname_len);
  if(!dpns) {
    /* If not interested, just stop processing this event */
    verbose(VERB_ALGO, "subq: parent not interested anymore");
    /* could be because parent was jostled out of the cache,
       and a new identical query arrived, that does not want it*/
    return;
  }

  /* if iq->query_for_pside_glue then add the pside_glue (marked lame) */
  if(iq->pside_glue) {
    /* if the pside_glue is NULL, then it could not be found,
     * the done_pside is already set when created and a cache
     * entry created in processFinished so nothing to do here */
    log_rrset_key(VERB_ALGO, "add parentside glue to dp", 
      iq->pside_glue);
    if(!delegpt_add_rrset(foriq->dp, forq->region, 
      iq->pside_glue, 1, NULL))
      log_err("out of memory adding pside glue");
  }

  /* This response is relevant to the current query, so we
   * add (attempt to add, anyway) this target(s) and reactivate
   * the original event.
   * NOTE: we could only look for the AnswerRRset if the
   * response type was ANSWER. */
  rrset = reply_find_answer_rrset(&iq->qchase, qstate->return_msg->rep);
  if(rrset) {
    int additions = 0;
    /* if CNAMEs have been followed - add new NS to delegpt. */
    /* BTW. RFC 1918 says NS should not have got CNAMEs. Robust. */
    if(!delegpt_find_ns(foriq->dp, rrset->rk.dname,
      rrset->rk.dname_len)) {
      /* if dpns->lame then set newcname ns lame too */
      if(!delegpt_add_ns(foriq->dp, forq->region,
        rrset->rk.dname, dpns->lame, dpns->tls_auth_name,
        dpns->port))
        log_err("out of memory adding cnamed-ns");
    }
    /* if dpns->lame then set the address(es) lame too */
    if(!delegpt_add_rrset(foriq->dp, forq->region, rrset, 
      dpns->lame, &additions))
      log_err("out of memory adding targets");
    if(!additions) {
      /* no new addresses, increase the nxns counter, like
       * this could be a list of wildcards with no new
       * addresses */
      target_count_increase_nx(foriq, 1);
    }
    verbose(VERB_ALGO, "added target response");
    delegpt_log(VERB_ALGO, foriq->dp);
  } else {
    verbose(VERB_ALGO, "iterator TargetResponse failed");
    delegpt_mark_neg(dpns, qstate->qinfo.qtype);
    if((dpns->got4 == 2 || (!ie->supports_ipv4 && !ie->nat64.use_nat64)) &&
      (dpns->got6 == 2 || !ie->supports_ipv6)) {
      dpns->resolved = 1; /* fail the target */
      /* do not count cached answers */
      if(qstate->reply_origin && qstate->reply_origin->len != 0) {
        target_count_increase_nx(foriq, 1);
      }
    }
  }
}

/**
 * Process response for DS NS Find queries, that attempt to find the delegation
 * point where we ask the DS query from.
 *
 * @param qstate: query state.
 * @param id: module id.
 * @param forq: super query state.
 */
static void
processDSNSResponse(struct module_qstate* qstate, int id,
  struct module_qstate* forq)
{
  struct iter_qstate* foriq = (struct iter_qstate*)forq->minfo[id];

  /* if the finished (iq->response) query has no NS set: continue
   * up to look for the right dp; nothing to change, do DPNSstate */
  if(qstate->return_rcode != LDNS_RCODE_NOERROR)
    return; /* seek further */
  /* find the NS RRset (without allowing CNAMEs) */
  if(!reply_find_rrset(qstate->return_msg->rep, qstate->qinfo.qname,
    qstate->qinfo.qname_len, LDNS_RR_TYPE_NS,
    qstate->qinfo.qclass)){
    return; /* seek further */
  }

  /* else, store as DP and continue at querytargets */
  foriq->state = QUERYTARGETS_STATE;
  foriq->dp = delegpt_from_message(qstate->return_msg, forq->region);
  if(!foriq->dp) {
    log_err("out of memory in dsns dp alloc");
    errinf(qstate, "malloc failure, in DS search");
    return; /* dp==NULL in QUERYTARGETS makes SERVFAIL */
  }
  /* success, go query the querytargets in the new dp (and go down) */
}

/**
 * Process response for qclass=ANY queries for a particular class.
 * Append to result or error-exit.
 *
 * @param qstate: query state.
 * @param id: module id.
 * @param forq: super query state.
 */
static void
processClassResponse(struct module_qstate* qstate, int id,
  struct module_qstate* forq)
{
  struct iter_qstate* foriq = (struct iter_qstate*)forq->minfo[id];
  struct dns_msg* from = qstate->return_msg;
  log_query_info(VERB_ALGO, "processClassResponse", &qstate->qinfo);
  log_query_info(VERB_ALGO, "processClassResponse super", &forq->qinfo);
  if(qstate->return_rcode != LDNS_RCODE_NOERROR) {
    /* cause servfail for qclass ANY query */
    foriq->response = NULL;
    foriq->state = FINISHED_STATE;
    return;
  }
  /* append result */
  if(!foriq->response) {
    /* allocate the response: copy RCODE, sec_state */
    foriq->response = dns_copy_msg(from, forq->region);
    if(!foriq->response) {
      log_err("malloc failed for qclass ANY response"); 
      foriq->state = FINISHED_STATE;
      return;
    }
    foriq->response->qinfo.qclass = forq->qinfo.qclass;
    /* qclass ANY does not receive the AA flag on replies */
    foriq->response->rep->authoritative = 0; 
  } else {
    struct dns_msg* to = foriq->response;
    /* add _from_ this response _to_ existing collection */
    /* if there are records, copy RCODE */
    /* lower sec_state if this message is lower */
    if(from->rep->rrset_count != 0) {
      size_t n = from->rep->rrset_count+to->rep->rrset_count;
      struct ub_packed_rrset_key** dest, **d;
      /* copy appropriate rcode */
      to->rep->flags = from->rep->flags;
      /* copy rrsets */
      if(from->rep->rrset_count > RR_COUNT_MAX ||
        to->rep->rrset_count > RR_COUNT_MAX) {
        log_err("malloc failed (too many rrsets) in collect ANY"); 
        foriq->state = FINISHED_STATE;
        return; /* integer overflow protection */
      }
      dest = regional_alloc(forq->region, sizeof(dest[0])*n);
      if(!dest) {
        log_err("malloc failed in collect ANY"); 
        foriq->state = FINISHED_STATE;
        return;
      }
      d = dest;
      /* copy AN */
      memcpy(dest, to->rep->rrsets, to->rep->an_numrrsets
        * sizeof(dest[0]));
      dest += to->rep->an_numrrsets;
      memcpy(dest, from->rep->rrsets, from->rep->an_numrrsets
        * sizeof(dest[0]));
      dest += from->rep->an_numrrsets;
      /* copy NS */
      memcpy(dest, to->rep->rrsets+to->rep->an_numrrsets,
        to->rep->ns_numrrsets * sizeof(dest[0]));
      dest += to->rep->ns_numrrsets;
      memcpy(dest, from->rep->rrsets+from->rep->an_numrrsets,
        from->rep->ns_numrrsets * sizeof(dest[0]));
      dest += from->rep->ns_numrrsets;
      /* copy AR */
      memcpy(dest, to->rep->rrsets+to->rep->an_numrrsets+
        to->rep->ns_numrrsets,
        to->rep->ar_numrrsets * sizeof(dest[0]));
      dest += to->rep->ar_numrrsets;
      memcpy(dest, from->rep->rrsets+from->rep->an_numrrsets+
        from->rep->ns_numrrsets,
        from->rep->ar_numrrsets * sizeof(dest[0]));
      /* update counts */
      to->rep->rrsets = d;
      to->rep->an_numrrsets += from->rep->an_numrrsets;
      to->rep->ns_numrrsets += from->rep->ns_numrrsets;
      to->rep->ar_numrrsets += from->rep->ar_numrrsets;
      to->rep->rrset_count = n;
    }
    if(from->rep->security < to->rep->security) /* lowest sec */
      to->rep->security = from->rep->security;
    if(from->rep->qdcount != 0) /* insert qd if appropriate */
      to->rep->qdcount = from->rep->qdcount;
    if(from->rep->ttl < to->rep->ttl) /* use smallest TTL */
      to->rep->ttl = from->rep->ttl;
    if(from->rep->prefetch_ttl < to->rep->prefetch_ttl)
      to->rep->prefetch_ttl = from->rep->prefetch_ttl;
    if(from->rep->serve_expired_ttl < to->rep->serve_expired_ttl)
      to->rep->serve_expired_ttl = from->rep->serve_expired_ttl;
    if(from->rep->serve_expired_norec_ttl < to->rep->serve_expired_norec_ttl)
      to->rep->serve_expired_norec_ttl = from->rep->serve_expired_norec_ttl;
  }
  /* are we done? */
  foriq->num_current_queries --;
  if(foriq->num_current_queries == 0)
    foriq->state = FINISHED_STATE;
}
  
/** 
 * Collect class ANY responses and make them into one response.  This
 * state is started and it creates queries for all classes (that have
 * root hints).  The answers are then collected.
 *
 * @param qstate: query state.
 * @param id: module id.
 * @return true if the event needs more immediate processing, false if not.
 */
static int
processCollectClass(struct module_qstate* qstate, int id)
{
  struct iter_qstate* iq = (struct iter_qstate*)qstate->minfo[id];
  struct module_qstate* subq;
  /* If qchase.qclass == 0 then send out queries for all classes.
   * Otherwise, do nothing (wait for all answers to arrive and the
   * processClassResponse to put them together, and that moves us
   * towards the Finished state when done. */
  if(iq->qchase.qclass == 0) {
    uint16_t c = 0;
    iq->qchase.qclass = LDNS_RR_CLASS_ANY;
    while(iter_get_next_root(qstate->env->hints,
      qstate->env->fwds, &c)) {
      /* generate query for this class */
      log_nametypeclass(VERB_ALGO, "spawn collect query",
        qstate->qinfo.qname, qstate->qinfo.qtype, c);
      if(!generate_sub_request(qstate->qinfo.qname,
        qstate->qinfo.qname_len, qstate->qinfo.qtype,
        c, qstate, id, iq, INIT_REQUEST_STATE,
        FINISHED_STATE, &subq, 
        (int)!(qstate->query_flags&BIT_CD), 0)) {
        errinf(qstate, "could not generate class ANY"
          " lookup query");
        return error_response(qstate, id, 
          LDNS_RCODE_SERVFAIL);
      }
      /* ignore subq, no special init required */
      iq->num_current_queries ++;
      if(c == 0xffff)
        break;
      else c++;
    }
    /* if no roots are configured at all, return */
    if(iq->num_current_queries == 0) {
      verbose(VERB_ALGO, "No root hints or fwds, giving up "
        "on qclass ANY");
      return error_response_cache(qstate, id, LDNS_RCODE_REFUSED);
    }
    /* return false, wait for queries to return */
  }
  /* if woke up here because of an answer, wait for more answers */
  return 0;
}

/** 
 * This handles the final state for first-tier responses (i.e., responses to
 * externally generated queries).
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @return true if the event needs more processing, false if not. Since this
 *         is the final state for an event, it always returns false.
 */
static int
processFinished(struct module_qstate* qstate, struct iter_qstate* iq,
  int id)
{
  log_query_info(VERB_QUERY, "finishing processing for", 
    &qstate->qinfo);

  /* store negative cache element for parent side glue. */
  if(!qstate->no_cache_store && iq->query_for_pside_glue
    && !iq->pside_glue)
      iter_store_parentside_neg(qstate->env, &qstate->qinfo,
        iq->deleg_msg?iq->deleg_msg->rep:
        (iq->response?iq->response->rep:NULL));
  if(!iq->response) {
    verbose(VERB_ALGO, "No response is set, servfail");
    errinf(qstate, "(no response found at query finish)");
    return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
  }

  /* Make sure that the RA flag is set (since the presence of 
   * this module means that recursion is available) */
  iq->response->rep->flags |= BIT_RA;

  /* Clear the AA flag */
  /* FIXME: does this action go here or in some other module? */
  iq->response->rep->flags &= ~BIT_AA;

  /* make sure QR flag is on */
  iq->response->rep->flags |= BIT_QR;

  /* explicitly set the EDE string to NULL */
  iq->response->rep->reason_bogus_str = NULL;
  if((qstate->env->cfg->val_log_level >= 2 ||
    qstate->env->cfg->log_servfail) && qstate->errinf &&
    !qstate->env->cfg->val_log_squelch) {
    char* err_str = errinf_to_str_misc(qstate);
    if(err_str) {
      verbose(VERB_ALGO, "iterator EDE: %s", err_str);
      iq->response->rep->reason_bogus_str = err_str;
    }
  }

  /* we have finished processing this query */
  qstate->ext_state[id] = module_finished;

  /* TODO:  we are using a private TTL, trim the response. */
  /* if (mPrivateTTL > 0){IterUtils.setPrivateTTL(resp, mPrivateTTL); } */

  /* prepend any items we have accumulated */
  if(iq->an_prepend_list || iq->ns_prepend_list) {
    if(!iter_prepend(iq, iq->response, qstate->region)) {
      log_err("prepend rrsets: out of memory");
      return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    }
    /* reset the query name back */
    iq->response->qinfo = qstate->qinfo;
    /* the security state depends on the combination */
    iq->response->rep->security = sec_status_unchecked;
    /* store message with the finished prepended items,
     * but only if we did recursion. The nonrecursion referral
     * from cache does not need to be stored in the msg cache. */
    if(!qstate->no_cache_store && (qstate->query_flags&BIT_RD)) {
      iter_dns_store(qstate->env, &qstate->qinfo, 
        iq->response->rep, 0, qstate->prefetch_leeway,
        iq->dp&&iq->dp->has_parent_side_NS,
        qstate->region, qstate->query_flags,
        qstate->qstarttime, qstate->is_valrec);
    }
  }
  qstate->return_rcode = LDNS_RCODE_NOERROR;
  qstate->return_msg = iq->response;
  return 0;
}

/*
 * Return priming query results to interested super querystates.
 * 
 * Sets the delegation point and delegation message (not nonRD queries).
 * This is a callback from walk_supers.
 *
 * @param qstate: query state that finished.
 * @param id: module id.
 * @param super: the qstate to inform.
 */
void
iter_inform_super(struct module_qstate* qstate, int id, 
  struct module_qstate* super)
{
  if(!qstate->is_priming && super->qinfo.qclass == LDNS_RR_CLASS_ANY)
    processClassResponse(qstate, id, super);
  else if(super->qinfo.qtype == LDNS_RR_TYPE_DS && ((struct iter_qstate*)
    super->minfo[id])->state == DSNS_FIND_STATE)
    processDSNSResponse(qstate, id, super);
  else if(qstate->return_rcode != LDNS_RCODE_NOERROR)
    error_supers(qstate, id, super);
  else if(qstate->is_priming)
    prime_supers(qstate, id, super);
  else  processTargetResponse(qstate, id, super);
}

/**
 * Handle iterator state.
 * Handle events. This is the real processing loop for events, responsible
 * for moving events through the various states. If a processing method
 * returns true, then it will be advanced to the next state. If false, then
 * processing will stop.
 *
 * @param qstate: query state.
 * @param ie: iterator shared global environment.
 * @param iq: iterator query state.
 * @param id: module id.
 */
static void
iter_handle(struct module_qstate* qstate, struct iter_qstate* iq,
  struct iter_env* ie, int id)
{
  int cont = 1;
  while(cont) {
    verbose(VERB_ALGO, "iter_handle processing q with state %s",
      iter_state_to_string(iq->state));
    switch(iq->state) {
      case INIT_REQUEST_STATE:
        cont = processInitRequest(qstate, iq, ie, id);
        break;
      case INIT_REQUEST_2_STATE:
        cont = processInitRequest2(qstate, iq, id);
        break;
      case INIT_REQUEST_3_STATE:
        cont = processInitRequest3(qstate, iq, id);
        break;
      case QUERYTARGETS_STATE:
        cont = processQueryTargets(qstate, iq, ie, id);
        break;
      case QUERY_RESP_STATE:
        cont = processQueryResponse(qstate, iq, ie, id);
        break;
      case PRIME_RESP_STATE:
        cont = processPrimeResponse(qstate, id);
        break;
      case COLLECT_CLASS_STATE:
        cont = processCollectClass(qstate, id);
        break;
      case DSNS_FIND_STATE:
        cont = processDSNSFind(qstate, iq, id);
        break;
      case FINISHED_STATE:
        cont = processFinished(qstate, iq, id);
        break;
      default:
        log_warn("iterator: invalid state: %d",
          iq->state);
        cont = 0;
        break;
    }
  }
}

/** 
 * This is the primary entry point for processing request events. Note that
 * this method should only be used by external modules.
 * @param qstate: query state.
 * @param ie: iterator shared global environment.
 * @param iq: iterator query state.
 * @param id: module id.
 */
static void
process_request(struct module_qstate* qstate, struct iter_qstate* iq,
  struct iter_env* ie, int id)
{
  /* external requests start in the INIT state, and finish using the
   * FINISHED state. */
  iq->state = INIT_REQUEST_STATE;
  iq->final_state = FINISHED_STATE;
  verbose(VERB_ALGO, "process_request: new external request event");
  iter_handle(qstate, iq, ie, id);
}

/** process authoritative server reply */
static void
process_response(struct module_qstate* qstate, struct iter_qstate* iq, 
  struct iter_env* ie, int id, struct outbound_entry* outbound,
  enum module_ev event)
{
  struct msg_parse* prs;
  struct edns_data edns;
  sldns_buffer* pkt;

  verbose(VERB_ALGO, "process_response: new external response event");
  iq->response = NULL;
  iq->state = QUERY_RESP_STATE;
  if(event == module_event_noreply || event == module_event_error) {
    if(event == module_event_noreply && iq->timeout_count >= 3 &&
      qstate->env->cfg->use_caps_bits_for_id &&
      !iq->caps_fallback && !is_caps_whitelisted(ie, iq)) {
      /* start fallback */
      iq->caps_fallback = 1;
      iq->caps_server = 0;
      iq->caps_reply = NULL;
      iq->caps_response = NULL;
      iq->caps_minimisation_state = DONOT_MINIMISE_STATE;
      iq->state = QUERYTARGETS_STATE;
      iq->num_current_queries--;
      /* need fresh attempts for the 0x20 fallback, if
       * that was the cause for the failure */
      iter_dec_attempts(iq->dp, 3, ie->outbound_msg_retry);
      verbose(VERB_DETAIL, "Capsforid: timeouts, starting fallback");
      goto handle_it;
    }
    goto handle_it;
  }
  if( (event != module_event_reply && event != module_event_capsfail)
    || !qstate->reply) {
    log_err("Bad event combined with response");
    outbound_list_remove(&iq->outlist, outbound);
    errinf(qstate, "module iterator received wrong internal event with a response message");
    (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    return;
  }

  /* parse message */
  fill_fail_addr(iq, &qstate->reply->remote_addr,
    qstate->reply->remote_addrlen);
  prs = (struct msg_parse*)regional_alloc(qstate->env->scratch, 
    sizeof(struct msg_parse));
  if(!prs) {
    log_err("out of memory on incoming message");
    /* like packet got dropped */
    goto handle_it;
  }
  memset(prs, 0, sizeof(*prs));
  memset(&edns, 0, sizeof(edns));
  pkt = qstate->reply->c->buffer;
  sldns_buffer_set_position(pkt, 0);
  if(parse_packet(pkt, prs, qstate->env->scratch) != LDNS_RCODE_NOERROR) {
    verbose(VERB_ALGO, "parse error on reply packet");
    iq->parse_failures++;
    goto handle_it;
  }
  /* edns is not examined, but removed from message to help cache */
  if(parse_extract_edns_from_response_msg(prs, &edns, qstate->env->scratch) !=
    LDNS_RCODE_NOERROR) {
    iq->parse_failures++;
    goto handle_it;
  }

  /* Copy the edns options we may got from the back end */
  qstate->edns_opts_back_in = NULL;
  if(edns.opt_list_in) {
    qstate->edns_opts_back_in = edns_opt_copy_region(edns.opt_list_in,
      qstate->region);
    if(!qstate->edns_opts_back_in) {
      log_err("out of memory on incoming message");
      /* like packet got dropped */
      goto handle_it;
    }
  }
  if(!inplace_cb_edns_back_parsed_call(qstate->env, qstate)) {
    log_err("unable to call edns_back_parsed callback");
    goto handle_it;
  }

  /* remove CD-bit, we asked for in case we handle validation ourself */
  prs->flags &= ~BIT_CD;

  /* normalize and sanitize: easy to delete items from linked lists */
  if(!scrub_message(pkt, prs, &iq->qinfo_out, iq->dp->name, 
    qstate->env->scratch, qstate->env, qstate, ie)) {
    /* if 0x20 enabled, start fallback, but we have no message */
    if(event == module_event_capsfail && !iq->caps_fallback) {
      iq->caps_fallback = 1;
      iq->caps_server = 0;
      iq->caps_reply = NULL;
      iq->caps_response = NULL;
      iq->caps_minimisation_state = DONOT_MINIMISE_STATE;
      iq->state = QUERYTARGETS_STATE;
      iq->num_current_queries--;
      verbose(VERB_DETAIL, "Capsforid: scrub failed, starting fallback with no response");
    }
    iq->scrub_failures++;
    goto handle_it;
  }

  /* allocate response dns_msg in region */
  iq->response = dns_alloc_msg(pkt, prs, qstate->region);
  if(!iq->response)
    goto handle_it;
  log_query_info(VERB_DETAIL, "response for", &qstate->qinfo);
  log_name_addr(VERB_DETAIL, "reply from", iq->dp->name,
    &qstate->reply->remote_addr, qstate->reply->remote_addrlen);
  if(verbosity >= VERB_ALGO)
    log_dns_msg("incoming scrubbed packet:", &iq->response->qinfo, 
      iq->response->rep);

  if(qstate->env->cfg->aggressive_nsec) {
    limit_nsec_ttl(iq->response);
  }
  if(event == module_event_capsfail || iq->caps_fallback) {
    if(qstate->env->cfg->qname_minimisation &&
      iq->minimisation_state != DONOT_MINIMISE_STATE) {
      /* Skip QNAME minimisation for next query, since that
       * one has to match the current query. */
      iq->minimisation_state = SKIP_MINIMISE_STATE;
    }
    /* for fallback we care about main answer, not additionals */
    /* removing that makes comparison more likely to succeed */
    caps_strip_reply(iq->response->rep);

    if(iq->caps_fallback &&
      iq->caps_minimisation_state != iq->minimisation_state) {
      /* QNAME minimisation state has changed, restart caps
       * fallback. */
      iq->caps_fallback = 0;
    }

    if(!iq->caps_fallback) {
      /* start fallback */
      iq->caps_fallback = 1;
      iq->caps_server = 0;
      iq->caps_reply = iq->response->rep;
      iq->caps_response = iq->response;
      iq->caps_minimisation_state = iq->minimisation_state;
      iq->state = QUERYTARGETS_STATE;
      iq->num_current_queries--;
      verbose(VERB_DETAIL, "Capsforid: starting fallback");
      goto handle_it;
    } else {
      /* check if reply is the same, otherwise, fail */
      if(!iq->caps_reply) {
        iq->caps_reply = iq->response->rep;
        iq->caps_response = iq->response;
        iq->caps_server = -1; /*become zero at ++,
        so that we start the full set of trials */
      } else if(caps_failed_rcode(iq->caps_reply) &&
        !caps_failed_rcode(iq->response->rep)) {
        /* prefer to upgrade to non-SERVFAIL */
        iq->caps_reply = iq->response->rep;
        iq->caps_response = iq->response;
      } else if(!caps_failed_rcode(iq->caps_reply) &&
        caps_failed_rcode(iq->response->rep)) {
        /* if we have non-SERVFAIL as answer then 
         * we can ignore SERVFAILs for the equality
         * comparison */
        /* no instructions here, skip other else */
      } else if(caps_failed_rcode(iq->caps_reply) &&
        caps_failed_rcode(iq->response->rep)) {
        /* failure is same as other failure in fallbk*/
        /* no instructions here, skip other else */
      } else if(!reply_equal(iq->response->rep, iq->caps_reply,
        qstate->env->scratch)) {
        verbose(VERB_DETAIL, "Capsforid fallback: "
          "getting different replies, failed");
        outbound_list_remove(&iq->outlist, outbound);
        errinf(qstate, "0x20 failed, then got different replies in fallback");
        (void)error_response_cache(qstate, id,
          LDNS_RCODE_SERVFAIL);
        return;
      }
      /* continue the fallback procedure at next server */
      iq->caps_server++;
      iq->state = QUERYTARGETS_STATE;
      iq->num_current_queries--;
      verbose(VERB_DETAIL, "Capsforid: reply is equal. "
        "go to next fallback");
      goto handle_it;
    }
  }
  iq->caps_fallback = 0; /* if we were in fallback, 0x20 is OK now */

handle_it:
  outbound_list_remove(&iq->outlist, outbound);
  iter_handle(qstate, iq, ie, id);
}

void 
iter_operate(struct module_qstate* qstate, enum module_ev event, int id,
  struct outbound_entry* outbound)
{
  struct iter_env* ie = (struct iter_env*)qstate->env->modinfo[id];
  struct iter_qstate* iq = (struct iter_qstate*)qstate->minfo[id];
  verbose(VERB_QUERY, "iterator[module %d] operate: extstate:%s event:%s", 
    id, strextstate(qstate->ext_state[id]), strmodulevent(event));
  if(iq) log_query_info(VERB_QUERY, "iterator operate: query", 
    &qstate->qinfo);
  if(iq && qstate->qinfo.qname != iq->qchase.qname)
    log_query_info(VERB_QUERY, "iterator operate: chased to", 
      &iq->qchase);

  /* perform iterator state machine */
  if((event == module_event_new || event == module_event_pass) && 
    iq == NULL) {
    if(!iter_new(qstate, id)) {
      errinf(qstate, "malloc failure, new iterator module allocation");
      (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      return;
    }
    iq = (struct iter_qstate*)qstate->minfo[id];
    process_request(qstate, iq, ie, id);
    return;
  }
  if(iq && event == module_event_pass) {
    iter_handle(qstate, iq, ie, id);
    return;
  }
  if(iq && outbound) {
    process_response(qstate, iq, ie, id, outbound, event);
    return;
  }
  if(event == module_event_error) {
    verbose(VERB_ALGO, "got called with event error, giving up");
    errinf(qstate, "iterator module got the error event");
    (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
    return;
  }

  log_err("bad event for iterator");
  errinf(qstate, "iterator module received wrong event");
  (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
}

void 
iter_clear(struct module_qstate* qstate, int id)
{
  struct iter_qstate* iq;
  if(!qstate)
    return;
  iq = (struct iter_qstate*)qstate->minfo[id];
  if(iq) {
    outbound_list_clear(&iq->outlist);
    if(iq->target_count && --iq->target_count[TARGET_COUNT_REF] == 0) {
      free(iq->target_count);
      if(*iq->nxns_dp) free(*iq->nxns_dp);
      free(iq->nxns_dp);
    }
    iq->num_current_queries = 0;
  }
  qstate->minfo[id] = NULL;
}

size_t 
iter_get_mem(struct module_env* env, int id)
{
  struct iter_env* ie = (struct iter_env*)env->modinfo[id];
  if(!ie)
    return 0;
  return sizeof(*ie) + sizeof(int)*((size_t)ie->max_dependency_depth+1)
    + donotq_get_mem(ie->donotq) + priv_get_mem(ie->priv);
}

/**
 * The iterator function block 
 */
static struct module_func_block iter_block = {
  "iterator",
  NULL, NULL, &iter_init, &iter_deinit, &iter_operate,
  &iter_inform_super, &iter_clear, &iter_get_mem
};

struct module_func_block* 
iter_get_funcblock(void)
{
  return &iter_block;
}

const char* 
iter_state_to_string(enum iter_state state)
{
  switch (state)
  {
  case INIT_REQUEST_STATE :
    return "INIT REQUEST STATE";
  case INIT_REQUEST_2_STATE :
    return "INIT REQUEST STATE (stage 2)";
  case INIT_REQUEST_3_STATE:
    return "INIT REQUEST STATE (stage 3)";
  case QUERYTARGETS_STATE :
    return "QUERY TARGETS STATE";
  case PRIME_RESP_STATE :
    return "PRIME RESPONSE STATE";
  case COLLECT_CLASS_STATE :
    return "COLLECT CLASS STATE";
  case DSNS_FIND_STATE :
    return "DSNS FIND STATE";
  case QUERY_RESP_STATE :
    return "QUERY RESPONSE STATE";
  case FINISHED_STATE :
    return "FINISHED RESPONSE STATE";
  default :
    return "UNKNOWN ITER STATE";
  }
}

int 
iter_state_is_responsestate(enum iter_state s)
{
  switch(s) {
    case INIT_REQUEST_STATE :
    case INIT_REQUEST_2_STATE :
    case INIT_REQUEST_3_STATE :
    case QUERYTARGETS_STATE :
    case COLLECT_CLASS_STATE :
      return 0;
    default:
      break;
  }
  return 1;
}

Coverage Report

Created: 2025-11-16 06:46