/src/libpcap/gencode.c

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/*
 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#ifdef _WIN32
  #include <ws2tcpip.h>
#else
  #include <sys/socket.h>

  #ifdef __NetBSD__
    #include <sys/param.h>
  #endif

  #include <netinet/in.h>
  #include <arpa/inet.h>
#endif /* _WIN32 */

#include <stdlib.h>
#include <string.h>
#include <memory.h>
#include <setjmp.h>
#include <stdarg.h>
#include <stdio.h>

#ifdef MSDOS
#include "pcap-dos.h"
#endif

#include "pcap-int.h"

#include "extract.h"

#include "ethertype.h"
#include "nlpid.h"
#include "llc.h"
#include "gencode.h"
#include "ieee80211.h"
#include "atmuni31.h"
#include "sunatmpos.h"
#include "pflog.h"
#include "ppp.h"
#include "pcap/sll.h"
#include "pcap/ipnet.h"
#include "arcnet.h"
#include "diag-control.h"

#include "scanner.h"

#if defined(linux)
#include <linux/types.h>
#include <linux/if_packet.h>
#include <linux/filter.h>
#endif

#ifndef offsetof
#define offsetof(s, e) ((size_t)&((s *)0)->e)
#endif

#ifdef _WIN32
  #ifdef INET6
    #if defined(__MINGW32__) && defined(DEFINE_ADDITIONAL_IPV6_STUFF)
/* IPv6 address */
struct in6_addr
  {
    union
      {
  uint8_t   u6_addr8[16];
  uint16_t  u6_addr16[8];
  uint32_t  u6_addr32[4];
      } in6_u;
#define s6_addr     in6_u.u6_addr8
#define s6_addr16   in6_u.u6_addr16
#define s6_addr32   in6_u.u6_addr32
#define s6_addr64   in6_u.u6_addr64
  };

typedef unsigned short  sa_family_t;

#define __SOCKADDR_COMMON(sa_prefix) \
  sa_family_t sa_prefix##family

/* Ditto, for IPv6.  */
struct sockaddr_in6
  {
    __SOCKADDR_COMMON (sin6_);
    uint16_t sin6_port;   /* Transport layer port # */
    uint32_t sin6_flowinfo; /* IPv6 flow information */
    struct in6_addr sin6_addr;  /* IPv6 address */
  };

      #ifndef EAI_ADDRFAMILY
struct addrinfo {
  int ai_flags; /* AI_PASSIVE, AI_CANONNAME */
  int ai_family;  /* PF_xxx */
  int ai_socktype;  /* SOCK_xxx */
  int ai_protocol;  /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
  size_t  ai_addrlen; /* length of ai_addr */
  char  *ai_canonname;  /* canonical name for hostname */
  struct sockaddr *ai_addr; /* binary address */
  struct addrinfo *ai_next; /* next structure in linked list */
};
      #endif /* EAI_ADDRFAMILY */
    #endif /* defined(__MINGW32__) && defined(DEFINE_ADDITIONAL_IPV6_STUFF) */
  #endif /* INET6 */
#else /* _WIN32 */
  #include <netdb.h>  /* for "struct addrinfo" */
#endif /* _WIN32 */
#include <pcap/namedb.h>

#include "nametoaddr.h"

#define ETHERMTU  1500

#ifndef IPPROTO_HOPOPTS
#define IPPROTO_HOPOPTS 0
#endif
#ifndef IPPROTO_ROUTING
#define IPPROTO_ROUTING 43
#endif
#ifndef IPPROTO_FRAGMENT
#define IPPROTO_FRAGMENT 44
#endif
#ifndef IPPROTO_DSTOPTS
#define IPPROTO_DSTOPTS 60
#endif
#ifndef IPPROTO_SCTP
#define IPPROTO_SCTP 132
#endif

#define GENEVE_PORT 6081

#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif

#define JMP(c) ((c)|BPF_JMP|BPF_K)

/*
 * "Push" the current value of the link-layer header type and link-layer
 * header offset onto a "stack", and set a new value.  (It's not a
 * full-blown stack; we keep only the top two items.)
 */
#define PUSH_LINKHDR(cs, new_linktype, new_is_variable, new_constant_part, new_reg) \
{ \
  (cs)->prevlinktype = (cs)->linktype; \
  (cs)->off_prevlinkhdr = (cs)->off_linkhdr; \
  (cs)->linktype = (new_linktype); \
  (cs)->off_linkhdr.is_variable = (new_is_variable); \
  (cs)->off_linkhdr.constant_part = (new_constant_part); \
  (cs)->off_linkhdr.reg = (new_reg); \
  (cs)->is_geneve = 0; \
}

/*
 * Offset "not set" value.
 */
#define OFFSET_NOT_SET  0xffffffffU

/*
 * Absolute offsets, which are offsets from the beginning of the raw
 * packet data, are, in the general case, the sum of a variable value
 * and a constant value; the variable value may be absent, in which
 * case the offset is only the constant value, and the constant value
 * may be zero, in which case the offset is only the variable value.
 *
 * bpf_abs_offset is a structure containing all that information:
 *
 *   is_variable is 1 if there's a variable part.
 *
 *   constant_part is the constant part of the value, possibly zero;
 *
 *   if is_variable is 1, reg is the register number for a register
 *   containing the variable value if the register has been assigned,
 *   and -1 otherwise.
 */
typedef struct {
  int is_variable;
  u_int constant_part;
  int reg;
} bpf_abs_offset;

/*
 * Value passed to gen_load_a() to indicate what the offset argument
 * is relative to the beginning of.
 */
enum e_offrel {
  OR_PACKET,    /* full packet data */
  OR_LINKHDR,   /* link-layer header */
  OR_PREVLINKHDR,   /* previous link-layer header */
  OR_LLC,     /* 802.2 LLC header */
  OR_PREVMPLSHDR,   /* previous MPLS header */
  OR_LINKTYPE,    /* link-layer type */
  OR_LINKPL,    /* link-layer payload */
  OR_LINKPL_NOSNAP, /* link-layer payload, with no SNAP header at the link layer */
  OR_TRAN_IPV4,   /* transport-layer header, with IPv4 network layer */
  OR_TRAN_IPV6    /* transport-layer header, with IPv6 network layer */
};

/*
 * We divy out chunks of memory rather than call malloc each time so
 * we don't have to worry about leaking memory.  It's probably
 * not a big deal if all this memory was wasted but if this ever
 * goes into a library that would probably not be a good idea.
 *
 * XXX - this *is* in a library....
 */
#define NCHUNKS 16
#define CHUNK0SIZE 1024
struct chunk {
  size_t n_left;
  void *m;
};

/*
 * A chunk can store any of:
 *  - a string (guaranteed alignment 1 but present for completeness)
 *  - a block
 *  - an slist
 *  - an arth
 * For this simple allocator every allocated chunk gets rounded up to the
 * alignment needed for any chunk.
 */
struct chunk_align {
  char dummy;
  union {
    char c;
    struct block b;
    struct slist s;
    struct arth a;
  } u;
};
#define CHUNK_ALIGN (offsetof(struct chunk_align, u))

/* Code generator state */

struct _compiler_state {
  jmp_buf top_ctx;
  pcap_t *bpf_pcap;
  int error_set;

  struct icode ic;

  int snaplen;

  int linktype;
  int prevlinktype;
  int outermostlinktype;

  bpf_u_int32 netmask;
  int no_optimize;

  /* Hack for handling VLAN and MPLS stacks. */
  u_int label_stack_depth;
  u_int vlan_stack_depth;

  /* XXX */
  u_int pcap_fddipad;

  /*
   * As errors are handled by a longjmp, anything allocated must
   * be freed in the longjmp handler, so it must be reachable
   * from that handler.
   *
   * One thing that's allocated is the result of pcap_nametoaddrinfo();
   * it must be freed with freeaddrinfo().  This variable points to
   * any addrinfo structure that would need to be freed.
   */
  struct addrinfo *ai;

  /*
   * Another thing that's allocated is the result of pcap_ether_aton();
   * it must be freed with free().  This variable points to any
   * address that would need to be freed.
   */
  u_char *e;

  /*
   * Various code constructs need to know the layout of the packet.
   * These values give the necessary offsets from the beginning
   * of the packet data.
   */

  /*
   * Absolute offset of the beginning of the link-layer header.
   */
  bpf_abs_offset off_linkhdr;

  /*
   * If we're checking a link-layer header for a packet encapsulated
   * in another protocol layer, this is the equivalent information
   * for the previous layers' link-layer header from the beginning
   * of the raw packet data.
   */
  bpf_abs_offset off_prevlinkhdr;

  /*
   * This is the equivalent information for the outermost layers'
   * link-layer header.
   */
  bpf_abs_offset off_outermostlinkhdr;

  /*
   * Absolute offset of the beginning of the link-layer payload.
   */
  bpf_abs_offset off_linkpl;

  /*
   * "off_linktype" is the offset to information in the link-layer
   * header giving the packet type. This is an absolute offset
   * from the beginning of the packet.
   *
   * For Ethernet, it's the offset of the Ethernet type field; this
   * means that it must have a value that skips VLAN tags.
   *
   * For link-layer types that always use 802.2 headers, it's the
   * offset of the LLC header; this means that it must have a value
   * that skips VLAN tags.
   *
   * For PPP, it's the offset of the PPP type field.
   *
   * For Cisco HDLC, it's the offset of the CHDLC type field.
   *
   * For BSD loopback, it's the offset of the AF_ value.
   *
   * For Linux cooked sockets, it's the offset of the type field.
   *
   * off_linktype.constant_part is set to OFFSET_NOT_SET for no
   * encapsulation, in which case, IP is assumed.
   */
  bpf_abs_offset off_linktype;

  /*
   * TRUE if the link layer includes an ATM pseudo-header.
   */
  int is_atm;

  /*
   * TRUE if "geneve" appeared in the filter; it causes us to
   * generate code that checks for a Geneve header and assume
   * that later filters apply to the encapsulated payload.
   */
  int is_geneve;

  /*
   * TRUE if we need variable length part of VLAN offset
   */
  int is_vlan_vloffset;

  /*
   * These are offsets for the ATM pseudo-header.
   */
  u_int off_vpi;
  u_int off_vci;
  u_int off_proto;

  /*
   * These are offsets for the MTP2 fields.
   */
  u_int off_li;
  u_int off_li_hsl;

  /*
   * These are offsets for the MTP3 fields.
   */
  u_int off_sio;
  u_int off_opc;
  u_int off_dpc;
  u_int off_sls;

  /*
   * This is the offset of the first byte after the ATM pseudo_header,
   * or -1 if there is no ATM pseudo-header.
   */
  u_int off_payload;

  /*
   * These are offsets to the beginning of the network-layer header.
   * They are relative to the beginning of the link-layer payload
   * (i.e., they don't include off_linkhdr.constant_part or
   * off_linkpl.constant_part).
   *
   * If the link layer never uses 802.2 LLC:
   *
   *  "off_nl" and "off_nl_nosnap" are the same.
   *
   * If the link layer always uses 802.2 LLC:
   *
   *  "off_nl" is the offset if there's a SNAP header following
   *  the 802.2 header;
   *
   *  "off_nl_nosnap" is the offset if there's no SNAP header.
   *
   * If the link layer is Ethernet:
   *
   *  "off_nl" is the offset if the packet is an Ethernet II packet
   *  (we assume no 802.3+802.2+SNAP);
   *
   *  "off_nl_nosnap" is the offset if the packet is an 802.3 packet
   *  with an 802.2 header following it.
   */
  u_int off_nl;
  u_int off_nl_nosnap;

  /*
   * Here we handle simple allocation of the scratch registers.
   * If too many registers are alloc'd, the allocator punts.
   */
  int regused[BPF_MEMWORDS];
  int curreg;

  /*
   * Memory chunks.
   */
  struct chunk chunks[NCHUNKS];
  int cur_chunk;
};

/*
 * For use by routines outside this file.
 */
/* VARARGS */
void
bpf_set_error(compiler_state_t *cstate, const char *fmt, ...)
{
  va_list ap;

  /*
   * If we've already set an error, don't override it.
   * The lexical analyzer reports some errors by setting
   * the error and then returning a LEX_ERROR token, which
   * is not recognized by any grammar rule, and thus forces
   * the parse to stop.  We don't want the error reported
   * by the lexical analyzer to be overwritten by the syntax
   * error.
   */
  if (!cstate->error_set) {
    va_start(ap, fmt);
    (void)vsnprintf(cstate->bpf_pcap->errbuf, PCAP_ERRBUF_SIZE,
        fmt, ap);
    va_end(ap);
    cstate->error_set = 1;
  }
}

/*
 * For use *ONLY* in routines in this file.
 */
static void PCAP_NORETURN bpf_error(compiler_state_t *, const char *, ...)
    PCAP_PRINTFLIKE(2, 3);

/* VARARGS */
static void PCAP_NORETURN
bpf_error(compiler_state_t *cstate, const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  (void)vsnprintf(cstate->bpf_pcap->errbuf, PCAP_ERRBUF_SIZE,
      fmt, ap);
  va_end(ap);
  longjmp(cstate->top_ctx, 1);
  /*NOTREACHED*/
#ifdef _AIX
  PCAP_UNREACHABLE
#endif /* _AIX */
}

static int init_linktype(compiler_state_t *, pcap_t *);

static void init_regs(compiler_state_t *);
static int alloc_reg(compiler_state_t *);
static void free_reg(compiler_state_t *, int);

static void initchunks(compiler_state_t *cstate);
static void *newchunk_nolongjmp(compiler_state_t *cstate, size_t);
static void *newchunk(compiler_state_t *cstate, size_t);
static void freechunks(compiler_state_t *cstate);
static inline struct block *new_block(compiler_state_t *cstate, int);
static inline struct slist *new_stmt(compiler_state_t *cstate, int);
static struct block *gen_retblk(compiler_state_t *cstate, int);
static inline void syntax(compiler_state_t *cstate);

static void backpatch(struct block *, struct block *);
static void merge(struct block *, struct block *);
static struct block *gen_cmp(compiler_state_t *, enum e_offrel, u_int,
    u_int, bpf_u_int32);
static struct block *gen_cmp_gt(compiler_state_t *, enum e_offrel, u_int,
    u_int, bpf_u_int32);
static struct block *gen_cmp_ge(compiler_state_t *, enum e_offrel, u_int,
    u_int, bpf_u_int32);
static struct block *gen_cmp_lt(compiler_state_t *, enum e_offrel, u_int,
    u_int, bpf_u_int32);
static struct block *gen_cmp_le(compiler_state_t *, enum e_offrel, u_int,
    u_int, bpf_u_int32);
static struct block *gen_mcmp(compiler_state_t *, enum e_offrel, u_int,
    u_int, bpf_u_int32, bpf_u_int32);
static struct block *gen_bcmp(compiler_state_t *, enum e_offrel, u_int,
    u_int, const u_char *);
static struct block *gen_ncmp(compiler_state_t *, enum e_offrel, u_int,
    u_int, bpf_u_int32, int, int, bpf_u_int32);
static struct slist *gen_load_absoffsetrel(compiler_state_t *, bpf_abs_offset *,
    u_int, u_int);
static struct slist *gen_load_a(compiler_state_t *, enum e_offrel, u_int,
    u_int);
static struct slist *gen_loadx_iphdrlen(compiler_state_t *);
static struct block *gen_uncond(compiler_state_t *, int);
static inline struct block *gen_true(compiler_state_t *);
static inline struct block *gen_false(compiler_state_t *);
static struct block *gen_ether_linktype(compiler_state_t *, bpf_u_int32);
static struct block *gen_ipnet_linktype(compiler_state_t *, bpf_u_int32);
static struct block *gen_linux_sll_linktype(compiler_state_t *, bpf_u_int32);
static struct slist *gen_load_pflog_llprefixlen(compiler_state_t *);
static struct slist *gen_load_prism_llprefixlen(compiler_state_t *);
static struct slist *gen_load_avs_llprefixlen(compiler_state_t *);
static struct slist *gen_load_radiotap_llprefixlen(compiler_state_t *);
static struct slist *gen_load_ppi_llprefixlen(compiler_state_t *);
static void insert_compute_vloffsets(compiler_state_t *, struct block *);
static struct slist *gen_abs_offset_varpart(compiler_state_t *,
    bpf_abs_offset *);
static bpf_u_int32 ethertype_to_ppptype(bpf_u_int32);
static struct block *gen_linktype(compiler_state_t *, bpf_u_int32);
static struct block *gen_snap(compiler_state_t *, bpf_u_int32, bpf_u_int32);
static struct block *gen_llc_linktype(compiler_state_t *, bpf_u_int32);
static struct block *gen_hostop(compiler_state_t *, bpf_u_int32, bpf_u_int32,
    int, bpf_u_int32, u_int, u_int);
#ifdef INET6
static struct block *gen_hostop6(compiler_state_t *, struct in6_addr *,
    struct in6_addr *, int, bpf_u_int32, u_int, u_int);
#endif
static struct block *gen_ahostop(compiler_state_t *, const u_char *, int);
static struct block *gen_ehostop(compiler_state_t *, const u_char *, int);
static struct block *gen_fhostop(compiler_state_t *, const u_char *, int);
static struct block *gen_thostop(compiler_state_t *, const u_char *, int);
static struct block *gen_wlanhostop(compiler_state_t *, const u_char *, int);
static struct block *gen_ipfchostop(compiler_state_t *, const u_char *, int);
static struct block *gen_dnhostop(compiler_state_t *, bpf_u_int32, int);
static struct block *gen_mpls_linktype(compiler_state_t *, bpf_u_int32);
static struct block *gen_host(compiler_state_t *, bpf_u_int32, bpf_u_int32,
    int, int, int);
#ifdef INET6
static struct block *gen_host6(compiler_state_t *, struct in6_addr *,
    struct in6_addr *, int, int, int);
#endif
#ifndef INET6
static struct block *gen_gateway(compiler_state_t *, const u_char *,
    struct addrinfo *, int, int);
#endif
static struct block *gen_ipfrag(compiler_state_t *);
static struct block *gen_portatom(compiler_state_t *, int, bpf_u_int32);
static struct block *gen_portrangeatom(compiler_state_t *, u_int, bpf_u_int32,
    bpf_u_int32);
static struct block *gen_portatom6(compiler_state_t *, int, bpf_u_int32);
static struct block *gen_portrangeatom6(compiler_state_t *, u_int, bpf_u_int32,
    bpf_u_int32);
static struct block *gen_portop(compiler_state_t *, u_int, u_int, int);
static struct block *gen_port(compiler_state_t *, u_int, int, int);
static struct block *gen_portrangeop(compiler_state_t *, u_int, u_int,
    bpf_u_int32, int);
static struct block *gen_portrange(compiler_state_t *, u_int, u_int, int, int);
struct block *gen_portop6(compiler_state_t *, u_int, u_int, int);
static struct block *gen_port6(compiler_state_t *, u_int, int, int);
static struct block *gen_portrangeop6(compiler_state_t *, u_int, u_int,
    bpf_u_int32, int);
static struct block *gen_portrange6(compiler_state_t *, u_int, u_int, int, int);
static int lookup_proto(compiler_state_t *, const char *, int);
#if !defined(NO_PROTOCHAIN)
static struct block *gen_protochain(compiler_state_t *, bpf_u_int32, int);
#endif /* !defined(NO_PROTOCHAIN) */
static struct block *gen_proto(compiler_state_t *, bpf_u_int32, int, int);
static struct slist *xfer_to_x(compiler_state_t *, struct arth *);
static struct slist *xfer_to_a(compiler_state_t *, struct arth *);
static struct block *gen_mac_multicast(compiler_state_t *, int);
static struct block *gen_len(compiler_state_t *, int, int);
static struct block *gen_check_802_11_data_frame(compiler_state_t *);
static struct block *gen_geneve_ll_check(compiler_state_t *cstate);

static struct block *gen_ppi_dlt_check(compiler_state_t *);
static struct block *gen_atmfield_code_internal(compiler_state_t *, int,
    bpf_u_int32, int, int);
static struct block *gen_atmtype_llc(compiler_state_t *);
static struct block *gen_msg_abbrev(compiler_state_t *, int type);

static void
initchunks(compiler_state_t *cstate)
{
  int i;

  for (i = 0; i < NCHUNKS; i++) {
    cstate->chunks[i].n_left = 0;
    cstate->chunks[i].m = NULL;
  }
  cstate->cur_chunk = 0;
}

static void *
newchunk_nolongjmp(compiler_state_t *cstate, size_t n)
{
  struct chunk *cp;
  int k;
  size_t size;

  /* Round up to chunk alignment. */
  n = (n + CHUNK_ALIGN - 1) & ~(CHUNK_ALIGN - 1);

  cp = &cstate->chunks[cstate->cur_chunk];
  if (n > cp->n_left) {
    ++cp;
    k = ++cstate->cur_chunk;
    if (k >= NCHUNKS) {
      bpf_set_error(cstate, "out of memory");
      return (NULL);
    }
    size = CHUNK0SIZE << k;
    cp->m = (void *)malloc(size);
    if (cp->m == NULL) {
      bpf_set_error(cstate, "out of memory");
      return (NULL);
    }
    memset((char *)cp->m, 0, size);
    cp->n_left = size;
    if (n > size) {
      bpf_set_error(cstate, "out of memory");
      return (NULL);
    }
  }
  cp->n_left -= n;
  return (void *)((char *)cp->m + cp->n_left);
}

static void *
newchunk(compiler_state_t *cstate, size_t n)
{
  void *p;

  p = newchunk_nolongjmp(cstate, n);
  if (p == NULL) {
    longjmp(cstate->top_ctx, 1);
    /*NOTREACHED*/
  }
  return (p);
}

static void
freechunks(compiler_state_t *cstate)
{
  int i;

  for (i = 0; i < NCHUNKS; ++i)
    if (cstate->chunks[i].m != NULL)
      free(cstate->chunks[i].m);
}

/*
 * A strdup whose allocations are freed after code generation is over.
 * This is used by the lexical analyzer, so it can't longjmp; it just
 * returns NULL on an allocation error, and the callers must check
 * for it.
 */
char *
sdup(compiler_state_t *cstate, const char *s)
{
  size_t n = strlen(s) + 1;
  char *cp = newchunk_nolongjmp(cstate, n);

  if (cp == NULL)
    return (NULL);
  pcap_strlcpy(cp, s, n);
  return (cp);
}

static inline struct block *
new_block(compiler_state_t *cstate, int code)
{
  struct block *p;

  p = (struct block *)newchunk(cstate, sizeof(*p));
  p->s.code = code;
  p->head = p;

  return p;
}

static inline struct slist *
new_stmt(compiler_state_t *cstate, int code)
{
  struct slist *p;

  p = (struct slist *)newchunk(cstate, sizeof(*p));
  p->s.code = code;

  return p;
}

static struct block *
gen_retblk(compiler_state_t *cstate, int v)
{
  struct block *b = new_block(cstate, BPF_RET|BPF_K);

  b->s.k = v;
  return b;
}

static inline PCAP_NORETURN_DEF void
syntax(compiler_state_t *cstate)
{
  bpf_error(cstate, "syntax error in filter expression");
}

int
pcap_compile(pcap_t *p, struct bpf_program *program,
       const char *buf, int optimize, bpf_u_int32 mask)
{
#ifdef _WIN32
  static int done = 0;
#endif
  compiler_state_t cstate;
  const char * volatile xbuf = buf;
  yyscan_t scanner = NULL;
  volatile YY_BUFFER_STATE in_buffer = NULL;
  u_int len;
  int  rc;

  /*
   * If this pcap_t hasn't been activated, it doesn't have a
   * link-layer type, so we can't use it.
   */
  if (!p->activated) {
    snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
        "not-yet-activated pcap_t passed to pcap_compile");
    return (PCAP_ERROR);
  }

#ifdef _WIN32
  if (!done)
    pcap_wsockinit();
  done = 1;
#endif

#ifdef ENABLE_REMOTE
  /*
   * If the device on which we're capturing need to be notified
   * that a new filter is being compiled, do so.
   *
   * This allows them to save a copy of it, in case, for example,
   * they're implementing a form of remote packet capture, and
   * want the remote machine to filter out the packets in which
   * it's sending the packets it's captured.
   *
   * XXX - the fact that we happen to be compiling a filter
   * doesn't necessarily mean we'll be installing it as the
   * filter for this pcap_t; we might be running it from userland
   * on captured packets to do packet classification.  We really
   * need a better way of handling this, but this is all that
   * the WinPcap remote capture code did.
   */
  if (p->save_current_filter_op != NULL)
    (p->save_current_filter_op)(p, buf);
#endif

  initchunks(&cstate);
  cstate.no_optimize = 0;
#ifdef INET6
  cstate.ai = NULL;
#endif
  cstate.e = NULL;
  cstate.ic.root = NULL;
  cstate.ic.cur_mark = 0;
  cstate.bpf_pcap = p;
  cstate.error_set = 0;
  init_regs(&cstate);

  cstate.netmask = mask;

  cstate.snaplen = pcap_snapshot(p);
  if (cstate.snaplen == 0) {
    snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
       "snaplen of 0 rejects all packets");
    rc = PCAP_ERROR;
    goto quit;
  }

  if (pcap_lex_init(&scanner) != 0)
    pcap_fmt_errmsg_for_errno(p->errbuf, PCAP_ERRBUF_SIZE,
        errno, "can't initialize scanner");
  in_buffer = pcap__scan_string(xbuf ? xbuf : "", scanner);

  /*
   * Associate the compiler state with the lexical analyzer
   * state.
   */
  pcap_set_extra(&cstate, scanner);

  if (init_linktype(&cstate, p) == -1) {
    rc = PCAP_ERROR;
    goto quit;
  }
  if (pcap_parse(scanner, &cstate) != 0) {
#ifdef INET6
    if (cstate.ai != NULL)
      freeaddrinfo(cstate.ai);
#endif
    if (cstate.e != NULL)
      free(cstate.e);
    rc = PCAP_ERROR;
    goto quit;
  }

  if (cstate.ic.root == NULL) {
    /*
     * Catch errors reported by gen_retblk().
     */
    if (setjmp(cstate.top_ctx)) {
      rc = PCAP_ERROR;
      goto quit;
    }
    cstate.ic.root = gen_retblk(&cstate, cstate.snaplen);
  }

  if (optimize && !cstate.no_optimize) {
    if (bpf_optimize(&cstate.ic, p->errbuf) == -1) {
      /* Failure */
      rc = PCAP_ERROR;
      goto quit;
    }
    if (cstate.ic.root == NULL ||
        (cstate.ic.root->s.code == (BPF_RET|BPF_K) && cstate.ic.root->s.k == 0)) {
      (void)snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
          "expression rejects all packets");
      rc = PCAP_ERROR;
      goto quit;
    }
  }
  program->bf_insns = icode_to_fcode(&cstate.ic,
      cstate.ic.root, &len, p->errbuf);
  if (program->bf_insns == NULL) {
    /* Failure */
    rc = PCAP_ERROR;
    goto quit;
  }
  program->bf_len = len;

  rc = 0;  /* We're all okay */

quit:
  /*
   * Clean up everything for the lexical analyzer.
   */
  if (in_buffer != NULL)
    pcap__delete_buffer(in_buffer, scanner);
  if (scanner != NULL)
    pcap_lex_destroy(scanner);

  /*
   * Clean up our own allocated memory.
   */
  freechunks(&cstate);

  return (rc);
}

/*
 * entry point for using the compiler with no pcap open
 * pass in all the stuff that is needed explicitly instead.
 */
int
pcap_compile_nopcap(int snaplen_arg, int linktype_arg,
        struct bpf_program *program,
       const char *buf, int optimize, bpf_u_int32 mask)
{
  pcap_t *p;
  int ret;

  p = pcap_open_dead(linktype_arg, snaplen_arg);
  if (p == NULL)
    return (PCAP_ERROR);
  ret = pcap_compile(p, program, buf, optimize, mask);
  pcap_close(p);
  return (ret);
}

/*
 * Clean up a "struct bpf_program" by freeing all the memory allocated
 * in it.
 */
void
pcap_freecode(struct bpf_program *program)
{
  program->bf_len = 0;
  if (program->bf_insns != NULL) {
    free((char *)program->bf_insns);
    program->bf_insns = NULL;
  }
}

/*
 * Backpatch the blocks in 'list' to 'target'.  The 'sense' field indicates
 * which of the jt and jf fields has been resolved and which is a pointer
 * back to another unresolved block (or nil).  At least one of the fields
 * in each block is already resolved.
 */
static void
backpatch(struct block *list, struct block *target)
{
  struct block *next;

  while (list) {
    if (!list->sense) {
      next = JT(list);
      JT(list) = target;
    } else {
      next = JF(list);
      JF(list) = target;
    }
    list = next;
  }
}

/*
 * Merge the lists in b0 and b1, using the 'sense' field to indicate
 * which of jt and jf is the link.
 */
static void
merge(struct block *b0, struct block *b1)
{
  register struct block **p = &b0;

  /* Find end of list. */
  while (*p)
    p = !((*p)->sense) ? &JT(*p) : &JF(*p);

  /* Concatenate the lists. */
  *p = b1;
}

int
finish_parse(compiler_state_t *cstate, struct block *p)
{
  struct block *ppi_dlt_check;

  /*
   * Catch errors reported by us and routines below us, and return -1
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (-1);

  /*
   * Insert before the statements of the first (root) block any
   * statements needed to load the lengths of any variable-length
   * headers into registers.
   *
   * XXX - a fancier strategy would be to insert those before the
   * statements of all blocks that use those lengths and that
   * have no predecessors that use them, so that we only compute
   * the lengths if we need them.  There might be even better
   * approaches than that.
   *
   * However, those strategies would be more complicated, and
   * as we don't generate code to compute a length if the
   * program has no tests that use the length, and as most
   * tests will probably use those lengths, we would just
   * postpone computing the lengths so that it's not done
   * for tests that fail early, and it's not clear that's
   * worth the effort.
   */
  insert_compute_vloffsets(cstate, p->head);

  /*
   * For DLT_PPI captures, generate a check of the per-packet
   * DLT value to make sure it's DLT_IEEE802_11.
   *
   * XXX - TurboCap cards use DLT_PPI for Ethernet.
   * Can we just define some DLT_ETHERNET_WITH_PHDR pseudo-header
   * with appropriate Ethernet information and use that rather
   * than using something such as DLT_PPI where you don't know
   * the link-layer header type until runtime, which, in the
   * general case, would force us to generate both Ethernet *and*
   * 802.11 code (*and* anything else for which PPI is used)
   * and choose between them early in the BPF program?
   */
  ppi_dlt_check = gen_ppi_dlt_check(cstate);
  if (ppi_dlt_check != NULL)
    gen_and(ppi_dlt_check, p);

  backpatch(p, gen_retblk(cstate, cstate->snaplen));
  p->sense = !p->sense;
  backpatch(p, gen_retblk(cstate, 0));
  cstate->ic.root = p->head;
  return (0);
}

void
gen_and(struct block *b0, struct block *b1)
{
  backpatch(b0, b1->head);
  b0->sense = !b0->sense;
  b1->sense = !b1->sense;
  merge(b1, b0);
  b1->sense = !b1->sense;
  b1->head = b0->head;
}

void
gen_or(struct block *b0, struct block *b1)
{
  b0->sense = !b0->sense;
  backpatch(b0, b1->head);
  b0->sense = !b0->sense;
  merge(b1, b0);
  b1->head = b0->head;
}

void
gen_not(struct block *b)
{
  b->sense = !b->sense;
}

static struct block *
gen_cmp(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, bpf_u_int32 v)
{
  return gen_ncmp(cstate, offrel, offset, size, 0xffffffff, BPF_JEQ, 0, v);
}

static struct block *
gen_cmp_gt(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, bpf_u_int32 v)
{
  return gen_ncmp(cstate, offrel, offset, size, 0xffffffff, BPF_JGT, 0, v);
}

static struct block *
gen_cmp_ge(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, bpf_u_int32 v)
{
  return gen_ncmp(cstate, offrel, offset, size, 0xffffffff, BPF_JGE, 0, v);
}

static struct block *
gen_cmp_lt(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, bpf_u_int32 v)
{
  return gen_ncmp(cstate, offrel, offset, size, 0xffffffff, BPF_JGE, 1, v);
}

static struct block *
gen_cmp_le(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, bpf_u_int32 v)
{
  return gen_ncmp(cstate, offrel, offset, size, 0xffffffff, BPF_JGT, 1, v);
}

static struct block *
gen_mcmp(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, bpf_u_int32 v, bpf_u_int32 mask)
{
  return gen_ncmp(cstate, offrel, offset, size, mask, BPF_JEQ, 0, v);
}

static struct block *
gen_bcmp(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, const u_char *v)
{
  register struct block *b, *tmp;

  b = NULL;
  while (size >= 4) {
    register const u_char *p = &v[size - 4];

    tmp = gen_cmp(cstate, offrel, offset + size - 4, BPF_W,
        EXTRACT_BE_U_4(p));
    if (b != NULL)
      gen_and(b, tmp);
    b = tmp;
    size -= 4;
  }
  while (size >= 2) {
    register const u_char *p = &v[size - 2];

    tmp = gen_cmp(cstate, offrel, offset + size - 2, BPF_H,
        EXTRACT_BE_U_2(p));
    if (b != NULL)
      gen_and(b, tmp);
    b = tmp;
    size -= 2;
  }
  if (size > 0) {
    tmp = gen_cmp(cstate, offrel, offset, BPF_B, v[0]);
    if (b != NULL)
      gen_and(b, tmp);
    b = tmp;
  }
  return b;
}

/*
 * AND the field of size "size" at offset "offset" relative to the header
 * specified by "offrel" with "mask", and compare it with the value "v"
 * with the test specified by "jtype"; if "reverse" is true, the test
 * should test the opposite of "jtype".
 */
static struct block *
gen_ncmp(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size, bpf_u_int32 mask, int jtype, int reverse,
    bpf_u_int32 v)
{
  struct slist *s, *s2;
  struct block *b;

  s = gen_load_a(cstate, offrel, offset, size);

  if (mask != 0xffffffff) {
    s2 = new_stmt(cstate, BPF_ALU|BPF_AND|BPF_K);
    s2->s.k = mask;
    sappend(s, s2);
  }

  b = new_block(cstate, JMP(jtype));
  b->stmts = s;
  b->s.k = v;
  if (reverse && (jtype == BPF_JGT || jtype == BPF_JGE))
    gen_not(b);
  return b;
}

static int
init_linktype(compiler_state_t *cstate, pcap_t *p)
{
  cstate->pcap_fddipad = p->fddipad;

  /*
   * We start out with only one link-layer header.
   */
  cstate->outermostlinktype = pcap_datalink(p);
  cstate->off_outermostlinkhdr.constant_part = 0;
  cstate->off_outermostlinkhdr.is_variable = 0;
  cstate->off_outermostlinkhdr.reg = -1;

  cstate->prevlinktype = cstate->outermostlinktype;
  cstate->off_prevlinkhdr.constant_part = 0;
  cstate->off_prevlinkhdr.is_variable = 0;
  cstate->off_prevlinkhdr.reg = -1;

  cstate->linktype = cstate->outermostlinktype;
  cstate->off_linkhdr.constant_part = 0;
  cstate->off_linkhdr.is_variable = 0;
  cstate->off_linkhdr.reg = -1;

  /*
   * XXX
   */
  cstate->off_linkpl.constant_part = 0;
  cstate->off_linkpl.is_variable = 0;
  cstate->off_linkpl.reg = -1;

  cstate->off_linktype.constant_part = 0;
  cstate->off_linktype.is_variable = 0;
  cstate->off_linktype.reg = -1;

  /*
   * Assume it's not raw ATM with a pseudo-header, for now.
   */
  cstate->is_atm = 0;
  cstate->off_vpi = OFFSET_NOT_SET;
  cstate->off_vci = OFFSET_NOT_SET;
  cstate->off_proto = OFFSET_NOT_SET;
  cstate->off_payload = OFFSET_NOT_SET;

  /*
   * And not Geneve.
   */
  cstate->is_geneve = 0;

  /*
   * No variable length VLAN offset by default
   */
  cstate->is_vlan_vloffset = 0;

  /*
   * And assume we're not doing SS7.
   */
  cstate->off_li = OFFSET_NOT_SET;
  cstate->off_li_hsl = OFFSET_NOT_SET;
  cstate->off_sio = OFFSET_NOT_SET;
  cstate->off_opc = OFFSET_NOT_SET;
  cstate->off_dpc = OFFSET_NOT_SET;
  cstate->off_sls = OFFSET_NOT_SET;

  cstate->label_stack_depth = 0;
  cstate->vlan_stack_depth = 0;

  switch (cstate->linktype) {

  case DLT_ARCNET:
    cstate->off_linktype.constant_part = 2;
    cstate->off_linkpl.constant_part = 6;
    cstate->off_nl = 0;   /* XXX in reality, variable! */
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_ARCNET_LINUX:
    cstate->off_linktype.constant_part = 4;
    cstate->off_linkpl.constant_part = 8;
    cstate->off_nl = 0;   /* XXX in reality, variable! */
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_EN10MB:
    cstate->off_linktype.constant_part = 12;
    cstate->off_linkpl.constant_part = 14;  /* Ethernet header length */
    cstate->off_nl = 0;   /* Ethernet II */
    cstate->off_nl_nosnap = 3;  /* 802.3+802.2 */
    break;

  case DLT_SLIP:
    /*
     * SLIP doesn't have a link level type.  The 16 byte
     * header is hacked into our SLIP driver.
     */
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = 16;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_SLIP_BSDOS:
    /* XXX this may be the same as the DLT_PPP_BSDOS case */
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    /* XXX end */
    cstate->off_linkpl.constant_part = 24;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_NULL:
  case DLT_LOOP:
    cstate->off_linktype.constant_part = 0;
    cstate->off_linkpl.constant_part = 4;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_ENC:
    cstate->off_linktype.constant_part = 0;
    cstate->off_linkpl.constant_part = 12;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_PPP:
  case DLT_PPP_PPPD:
  case DLT_C_HDLC:   /* BSD/OS Cisco HDLC */
  case DLT_HDLC:     /* NetBSD (Cisco) HDLC */
  case DLT_PPP_SERIAL:   /* NetBSD sync/async serial PPP */
    cstate->off_linktype.constant_part = 2; /* skip HDLC-like framing */
    cstate->off_linkpl.constant_part = 4; /* skip HDLC-like framing and protocol field */
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_PPP_ETHER:
    /*
     * This does no include the Ethernet header, and
     * only covers session state.
     */
    cstate->off_linktype.constant_part = 6;
    cstate->off_linkpl.constant_part = 8;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_PPP_BSDOS:
    cstate->off_linktype.constant_part = 5;
    cstate->off_linkpl.constant_part = 24;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_FDDI:
    /*
     * FDDI doesn't really have a link-level type field.
     * We set "off_linktype" to the offset of the LLC header.
     *
     * To check for Ethernet types, we assume that SSAP = SNAP
     * is being used and pick out the encapsulated Ethernet type.
     * XXX - should we generate code to check for SNAP?
     */
    cstate->off_linktype.constant_part = 13;
    cstate->off_linktype.constant_part += cstate->pcap_fddipad;
    cstate->off_linkpl.constant_part = 13;  /* FDDI MAC header length */
    cstate->off_linkpl.constant_part += cstate->pcap_fddipad;
    cstate->off_nl = 8;   /* 802.2+SNAP */
    cstate->off_nl_nosnap = 3;  /* 802.2 */
    break;

  case DLT_IEEE802:
    /*
     * Token Ring doesn't really have a link-level type field.
     * We set "off_linktype" to the offset of the LLC header.
     *
     * To check for Ethernet types, we assume that SSAP = SNAP
     * is being used and pick out the encapsulated Ethernet type.
     * XXX - should we generate code to check for SNAP?
     *
     * XXX - the header is actually variable-length.
     * Some various Linux patched versions gave 38
     * as "off_linktype" and 40 as "off_nl"; however,
     * if a token ring packet has *no* routing
     * information, i.e. is not source-routed, the correct
     * values are 20 and 22, as they are in the vanilla code.
     *
     * A packet is source-routed iff the uppermost bit
     * of the first byte of the source address, at an
     * offset of 8, has the uppermost bit set.  If the
     * packet is source-routed, the total number of bytes
     * of routing information is 2 plus bits 0x1F00 of
     * the 16-bit value at an offset of 14 (shifted right
     * 8 - figure out which byte that is).
     */
    cstate->off_linktype.constant_part = 14;
    cstate->off_linkpl.constant_part = 14;  /* Token Ring MAC header length */
    cstate->off_nl = 8;   /* 802.2+SNAP */
    cstate->off_nl_nosnap = 3;  /* 802.2 */
    break;

  case DLT_PRISM_HEADER:
  case DLT_IEEE802_11_RADIO_AVS:
  case DLT_IEEE802_11_RADIO:
    cstate->off_linkhdr.is_variable = 1;
    /* Fall through, 802.11 doesn't have a variable link
     * prefix but is otherwise the same. */
    /* FALLTHROUGH */

  case DLT_IEEE802_11:
    /*
     * 802.11 doesn't really have a link-level type field.
     * We set "off_linktype.constant_part" to the offset of
     * the LLC header.
     *
     * To check for Ethernet types, we assume that SSAP = SNAP
     * is being used and pick out the encapsulated Ethernet type.
     * XXX - should we generate code to check for SNAP?
     *
     * We also handle variable-length radio headers here.
     * The Prism header is in theory variable-length, but in
     * practice it's always 144 bytes long.  However, some
     * drivers on Linux use ARPHRD_IEEE80211_PRISM, but
     * sometimes or always supply an AVS header, so we
     * have to check whether the radio header is a Prism
     * header or an AVS header, so, in practice, it's
     * variable-length.
     */
    cstate->off_linktype.constant_part = 24;
    cstate->off_linkpl.constant_part = 0; /* link-layer header is variable-length */
    cstate->off_linkpl.is_variable = 1;
    cstate->off_nl = 8;   /* 802.2+SNAP */
    cstate->off_nl_nosnap = 3;  /* 802.2 */
    break;

  case DLT_PPI:
    /*
     * At the moment we treat PPI the same way that we treat
     * normal Radiotap encoded packets. The difference is in
     * the function that generates the code at the beginning
     * to compute the header length.  Since this code generator
     * of PPI supports bare 802.11 encapsulation only (i.e.
     * the encapsulated DLT should be DLT_IEEE802_11) we
     * generate code to check for this too.
     */
    cstate->off_linktype.constant_part = 24;
    cstate->off_linkpl.constant_part = 0; /* link-layer header is variable-length */
    cstate->off_linkpl.is_variable = 1;
    cstate->off_linkhdr.is_variable = 1;
    cstate->off_nl = 8;   /* 802.2+SNAP */
    cstate->off_nl_nosnap = 3;  /* 802.2 */
    break;

  case DLT_ATM_RFC1483:
  case DLT_ATM_CLIP: /* Linux ATM defines this */
    /*
     * assume routed, non-ISO PDUs
     * (i.e., LLC = 0xAA-AA-03, OUT = 0x00-00-00)
     *
     * XXX - what about ISO PDUs, e.g. CLNP, ISIS, ESIS,
     * or PPP with the PPP NLPID (e.g., PPPoA)?  The
     * latter would presumably be treated the way PPPoE
     * should be, so you can do "pppoe and udp port 2049"
     * or "pppoa and tcp port 80" and have it check for
     * PPPo{A,E} and a PPP protocol of IP and....
     */
    cstate->off_linktype.constant_part = 0;
    cstate->off_linkpl.constant_part = 0; /* packet begins with LLC header */
    cstate->off_nl = 8;   /* 802.2+SNAP */
    cstate->off_nl_nosnap = 3;  /* 802.2 */
    break;

  case DLT_SUNATM:
    /*
     * Full Frontal ATM; you get AALn PDUs with an ATM
     * pseudo-header.
     */
    cstate->is_atm = 1;
    cstate->off_vpi = SUNATM_VPI_POS;
    cstate->off_vci = SUNATM_VCI_POS;
    cstate->off_proto = PROTO_POS;
    cstate->off_payload = SUNATM_PKT_BEGIN_POS;
    cstate->off_linktype.constant_part = cstate->off_payload;
    cstate->off_linkpl.constant_part = cstate->off_payload; /* if LLC-encapsulated */
    cstate->off_nl = 8;   /* 802.2+SNAP */
    cstate->off_nl_nosnap = 3;  /* 802.2 */
    break;

  case DLT_RAW:
  case DLT_IPV4:
  case DLT_IPV6:
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = 0;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_LINUX_SLL: /* fake header for Linux cooked socket v1 */
    cstate->off_linktype.constant_part = 14;
    cstate->off_linkpl.constant_part = 16;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_LINUX_SLL2: /* fake header for Linux cooked socket v2 */
    cstate->off_linktype.constant_part = 0;
    cstate->off_linkpl.constant_part = 20;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_LTALK:
    /*
     * LocalTalk does have a 1-byte type field in the LLAP header,
     * but really it just indicates whether there is a "short" or
     * "long" DDP packet following.
     */
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = 0;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_IP_OVER_FC:
    /*
     * RFC 2625 IP-over-Fibre-Channel doesn't really have a
     * link-level type field.  We set "off_linktype" to the
     * offset of the LLC header.
     *
     * To check for Ethernet types, we assume that SSAP = SNAP
     * is being used and pick out the encapsulated Ethernet type.
     * XXX - should we generate code to check for SNAP? RFC
     * 2625 says SNAP should be used.
     */
    cstate->off_linktype.constant_part = 16;
    cstate->off_linkpl.constant_part = 16;
    cstate->off_nl = 8;   /* 802.2+SNAP */
    cstate->off_nl_nosnap = 3;  /* 802.2 */
    break;

  case DLT_FRELAY:
    /*
     * XXX - we should set this to handle SNAP-encapsulated
     * frames (NLPID of 0x80).
     */
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = 0;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

                /*
                 * the only BPF-interesting FRF.16 frames are non-control frames;
                 * Frame Relay has a variable length link-layer
                 * so lets start with offset 4 for now and increments later on (FIXME);
                 */
  case DLT_MFR:
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = 0;
    cstate->off_nl = 4;
    cstate->off_nl_nosnap = 0;  /* XXX - for now -> no 802.2 LLC */
    break;

  case DLT_APPLE_IP_OVER_IEEE1394:
    cstate->off_linktype.constant_part = 16;
    cstate->off_linkpl.constant_part = 18;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

  case DLT_SYMANTEC_FIREWALL:
    cstate->off_linktype.constant_part = 6;
    cstate->off_linkpl.constant_part = 44;
    cstate->off_nl = 0;   /* Ethernet II */
    cstate->off_nl_nosnap = 0;  /* XXX - what does it do with 802.3 packets? */
    break;

  case DLT_PFLOG:
    cstate->off_linktype.constant_part = 0;
    cstate->off_linkpl.constant_part = 0; /* link-layer header is variable-length */
    cstate->off_linkpl.is_variable = 1;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */
    break;

        case DLT_JUNIPER_MFR:
        case DLT_JUNIPER_MLFR:
        case DLT_JUNIPER_MLPPP:
        case DLT_JUNIPER_PPP:
        case DLT_JUNIPER_CHDLC:
        case DLT_JUNIPER_FRELAY:
    cstate->off_linktype.constant_part = 4;
    cstate->off_linkpl.constant_part = 4;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = OFFSET_NOT_SET; /* no 802.2 LLC */
                break;

  case DLT_JUNIPER_ATM1:
    cstate->off_linktype.constant_part = 4;   /* in reality variable between 4-8 */
    cstate->off_linkpl.constant_part = 4; /* in reality variable between 4-8 */
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 10;
    break;

  case DLT_JUNIPER_ATM2:
    cstate->off_linktype.constant_part = 8;   /* in reality variable between 8-12 */
    cstate->off_linkpl.constant_part = 8; /* in reality variable between 8-12 */
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 10;
    break;

    /* frames captured on a Juniper PPPoE service PIC
     * contain raw ethernet frames */
  case DLT_JUNIPER_PPPOE:
        case DLT_JUNIPER_ETHER:
    cstate->off_linkpl.constant_part = 14;
    cstate->off_linktype.constant_part = 16;
    cstate->off_nl = 18;    /* Ethernet II */
    cstate->off_nl_nosnap = 21; /* 802.3+802.2 */
    break;

  case DLT_JUNIPER_PPPOE_ATM:
    cstate->off_linktype.constant_part = 4;
    cstate->off_linkpl.constant_part = 6;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = OFFSET_NOT_SET; /* no 802.2 LLC */
    break;

  case DLT_JUNIPER_GGSN:
    cstate->off_linktype.constant_part = 6;
    cstate->off_linkpl.constant_part = 12;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = OFFSET_NOT_SET; /* no 802.2 LLC */
    break;

  case DLT_JUNIPER_ES:
    cstate->off_linktype.constant_part = 6;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET; /* not really a network layer but raw IP addresses */
    cstate->off_nl = OFFSET_NOT_SET; /* not really a network layer but raw IP addresses */
    cstate->off_nl_nosnap = OFFSET_NOT_SET; /* no 802.2 LLC */
    break;

  case DLT_JUNIPER_MONITOR:
    cstate->off_linktype.constant_part = 12;
    cstate->off_linkpl.constant_part = 12;
    cstate->off_nl = 0;     /* raw IP/IP6 header */
    cstate->off_nl_nosnap = OFFSET_NOT_SET; /* no 802.2 LLC */
    break;

  case DLT_BACNET_MS_TP:
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_JUNIPER_SERVICES:
    cstate->off_linktype.constant_part = 12;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET; /* L3 proto location dep. on cookie type */
    cstate->off_nl = OFFSET_NOT_SET; /* L3 proto location dep. on cookie type */
    cstate->off_nl_nosnap = OFFSET_NOT_SET; /* no 802.2 LLC */
    break;

  case DLT_JUNIPER_VP:
    cstate->off_linktype.constant_part = 18;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_JUNIPER_ST:
    cstate->off_linktype.constant_part = 18;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_JUNIPER_ISM:
    cstate->off_linktype.constant_part = 8;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_JUNIPER_VS:
  case DLT_JUNIPER_SRX_E2E:
  case DLT_JUNIPER_FIBRECHANNEL:
  case DLT_JUNIPER_ATM_CEMIC:
    cstate->off_linktype.constant_part = 8;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_MTP2:
    cstate->off_li = 2;
    cstate->off_li_hsl = 4;
    cstate->off_sio = 3;
    cstate->off_opc = 4;
    cstate->off_dpc = 4;
    cstate->off_sls = 7;
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_MTP2_WITH_PHDR:
    cstate->off_li = 6;
    cstate->off_li_hsl = 8;
    cstate->off_sio = 7;
    cstate->off_opc = 8;
    cstate->off_dpc = 8;
    cstate->off_sls = 11;
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_ERF:
    cstate->off_li = 22;
    cstate->off_li_hsl = 24;
    cstate->off_sio = 23;
    cstate->off_opc = 24;
    cstate->off_dpc = 24;
    cstate->off_sls = 27;
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_PFSYNC:
    cstate->off_linktype.constant_part = OFFSET_NOT_SET;
    cstate->off_linkpl.constant_part = 4;
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = 0;
    break;

  case DLT_AX25_KISS:
    /*
     * Currently, only raw "link[N:M]" filtering is supported.
     */
    cstate->off_linktype.constant_part = OFFSET_NOT_SET; /* variable, min 15, max 71 steps of 7 */
    cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
    cstate->off_nl = OFFSET_NOT_SET; /* variable, min 16, max 71 steps of 7 */
    cstate->off_nl_nosnap = OFFSET_NOT_SET; /* no 802.2 LLC */
    break;

  case DLT_IPNET:
    cstate->off_linktype.constant_part = 1;
    cstate->off_linkpl.constant_part = 24;  /* ipnet header length */
    cstate->off_nl = 0;
    cstate->off_nl_nosnap = OFFSET_NOT_SET;
    break;

  case DLT_NETANALYZER:
    cstate->off_linkhdr.constant_part = 4;  /* Ethernet header is past 4-byte pseudo-header */
    cstate->off_linktype.constant_part = cstate->off_linkhdr.constant_part + 12;
    cstate->off_linkpl.constant_part = cstate->off_linkhdr.constant_part + 14;  /* pseudo-header+Ethernet header length */
    cstate->off_nl = 0;   /* Ethernet II */
    cstate->off_nl_nosnap = 3;  /* 802.3+802.2 */
    break;

  case DLT_NETANALYZER_TRANSPARENT:
    cstate->off_linkhdr.constant_part = 12; /* MAC header is past 4-byte pseudo-header, preamble, and SFD */
    cstate->off_linktype.constant_part = cstate->off_linkhdr.constant_part + 12;
    cstate->off_linkpl.constant_part = cstate->off_linkhdr.constant_part + 14;  /* pseudo-header+preamble+SFD+Ethernet header length */
    cstate->off_nl = 0;   /* Ethernet II */
    cstate->off_nl_nosnap = 3;  /* 802.3+802.2 */
    break;

  default:
    /*
     * For values in the range in which we've assigned new
     * DLT_ values, only raw "link[N:M]" filtering is supported.
     */
    if (cstate->linktype >= DLT_MATCHING_MIN &&
        cstate->linktype <= DLT_MATCHING_MAX) {
      cstate->off_linktype.constant_part = OFFSET_NOT_SET;
      cstate->off_linkpl.constant_part = OFFSET_NOT_SET;
      cstate->off_nl = OFFSET_NOT_SET;
      cstate->off_nl_nosnap = OFFSET_NOT_SET;
    } else {
      bpf_set_error(cstate, "unknown data link type %d (min %d, max %d)",
          cstate->linktype, DLT_MATCHING_MIN, DLT_MATCHING_MAX);
      return (-1);
    }
    break;
  }

  cstate->off_outermostlinkhdr = cstate->off_prevlinkhdr = cstate->off_linkhdr;
  return (0);
}

/*
 * Load a value relative to the specified absolute offset.
 */
static struct slist *
gen_load_absoffsetrel(compiler_state_t *cstate, bpf_abs_offset *abs_offset,
    u_int offset, u_int size)
{
  struct slist *s, *s2;

  s = gen_abs_offset_varpart(cstate, abs_offset);

  /*
   * If "s" is non-null, it has code to arrange that the X register
   * contains the variable part of the absolute offset, so we
   * generate a load relative to that, with an offset of
   * abs_offset->constant_part + offset.
   *
   * Otherwise, we can do an absolute load with an offset of
   * abs_offset->constant_part + offset.
   */
  if (s != NULL) {
    /*
     * "s" points to a list of statements that puts the
     * variable part of the absolute offset into the X register.
     * Do an indirect load, to use the X register as an offset.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_IND|size);
    s2->s.k = abs_offset->constant_part + offset;
    sappend(s, s2);
  } else {
    /*
     * There is no variable part of the absolute offset, so
     * just do an absolute load.
     */
    s = new_stmt(cstate, BPF_LD|BPF_ABS|size);
    s->s.k = abs_offset->constant_part + offset;
  }
  return s;
}

/*
 * Load a value relative to the beginning of the specified header.
 */
static struct slist *
gen_load_a(compiler_state_t *cstate, enum e_offrel offrel, u_int offset,
    u_int size)
{
  struct slist *s, *s2;

  /*
   * Squelch warnings from compilers that *don't* assume that
   * offrel always has a valid enum value and therefore don't
   * assume that we'll always go through one of the case arms.
   *
   * If we have a default case, compilers that *do* assume that
   * will then complain about the default case code being
   * unreachable.
   *
   * Damned if you do, damned if you don't.
   */
  s = NULL;

  switch (offrel) {

  case OR_PACKET:
                s = new_stmt(cstate, BPF_LD|BPF_ABS|size);
                s->s.k = offset;
    break;

  case OR_LINKHDR:
    s = gen_load_absoffsetrel(cstate, &cstate->off_linkhdr, offset, size);
    break;

  case OR_PREVLINKHDR:
    s = gen_load_absoffsetrel(cstate, &cstate->off_prevlinkhdr, offset, size);
    break;

  case OR_LLC:
    s = gen_load_absoffsetrel(cstate, &cstate->off_linkpl, offset, size);
    break;

  case OR_PREVMPLSHDR:
    s = gen_load_absoffsetrel(cstate, &cstate->off_linkpl, cstate->off_nl - 4 + offset, size);
    break;

  case OR_LINKPL:
    s = gen_load_absoffsetrel(cstate, &cstate->off_linkpl, cstate->off_nl + offset, size);
    break;

  case OR_LINKPL_NOSNAP:
    s = gen_load_absoffsetrel(cstate, &cstate->off_linkpl, cstate->off_nl_nosnap + offset, size);
    break;

  case OR_LINKTYPE:
    s = gen_load_absoffsetrel(cstate, &cstate->off_linktype, offset, size);
    break;

  case OR_TRAN_IPV4:
    /*
     * Load the X register with the length of the IPv4 header
     * (plus the offset of the link-layer header, if it's
     * preceded by a variable-length header such as a radio
     * header), in bytes.
     */
    s = gen_loadx_iphdrlen(cstate);

    /*
     * Load the item at {offset of the link-layer payload} +
     * {offset, relative to the start of the link-layer
     * paylod, of the IPv4 header} + {length of the IPv4 header} +
     * {specified offset}.
     *
     * If the offset of the link-layer payload is variable,
     * the variable part of that offset is included in the
     * value in the X register, and we include the constant
     * part in the offset of the load.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_IND|size);
    s2->s.k = cstate->off_linkpl.constant_part + cstate->off_nl + offset;
    sappend(s, s2);
    break;

  case OR_TRAN_IPV6:
    s = gen_load_absoffsetrel(cstate, &cstate->off_linkpl, cstate->off_nl + 40 + offset, size);
    break;
  }
  return s;
}

/*
 * Generate code to load into the X register the sum of the length of
 * the IPv4 header and the variable part of the offset of the link-layer
 * payload.
 */
static struct slist *
gen_loadx_iphdrlen(compiler_state_t *cstate)
{
  struct slist *s, *s2;

  s = gen_abs_offset_varpart(cstate, &cstate->off_linkpl);
  if (s != NULL) {
    /*
     * The offset of the link-layer payload has a variable
     * part.  "s" points to a list of statements that put
     * the variable part of that offset into the X register.
     *
     * The 4*([k]&0xf) addressing mode can't be used, as we
     * don't have a constant offset, so we have to load the
     * value in question into the A register and add to it
     * the value from the X register.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_IND|BPF_B);
    s2->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
    sappend(s, s2);
    s2 = new_stmt(cstate, BPF_ALU|BPF_AND|BPF_K);
    s2->s.k = 0xf;
    sappend(s, s2);
    s2 = new_stmt(cstate, BPF_ALU|BPF_LSH|BPF_K);
    s2->s.k = 2;
    sappend(s, s2);

    /*
     * The A register now contains the length of the IP header.
     * We need to add to it the variable part of the offset of
     * the link-layer payload, which is still in the X
     * register, and move the result into the X register.
     */
    sappend(s, new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X));
    sappend(s, new_stmt(cstate, BPF_MISC|BPF_TAX));
  } else {
    /*
     * The offset of the link-layer payload is a constant,
     * so no code was generated to load the (non-existent)
     * variable part of that offset.
     *
     * This means we can use the 4*([k]&0xf) addressing
     * mode.  Load the length of the IPv4 header, which
     * is at an offset of cstate->off_nl from the beginning of
     * the link-layer payload, and thus at an offset of
     * cstate->off_linkpl.constant_part + cstate->off_nl from the beginning
     * of the raw packet data, using that addressing mode.
     */
    s = new_stmt(cstate, BPF_LDX|BPF_MSH|BPF_B);
    s->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
  }
  return s;
}


static struct block *
gen_uncond(compiler_state_t *cstate, int rsense)
{
  struct block *b;
  struct slist *s;

  s = new_stmt(cstate, BPF_LD|BPF_IMM);
  s->s.k = !rsense;
  b = new_block(cstate, JMP(BPF_JEQ));
  b->stmts = s;

  return b;
}

static inline struct block *
gen_true(compiler_state_t *cstate)
{
  return gen_uncond(cstate, 1);
}

static inline struct block *
gen_false(compiler_state_t *cstate)
{
  return gen_uncond(cstate, 0);
}

/*
 * Byte-swap a 32-bit number.
 * ("htonl()" or "ntohl()" won't work - we want to byte-swap even on
 * big-endian platforms.)
 */
#define SWAPLONG(y) \
((((y)&0xff)<<24) | (((y)&0xff00)<<8) | (((y)&0xff0000)>>8) | (((y)>>24)&0xff))

/*
 * Generate code to match a particular packet type.
 *
 * "proto" is an Ethernet type value, if > ETHERMTU, or an LLC SAP
 * value, if <= ETHERMTU.  We use that to determine whether to
 * match the type/length field or to check the type/length field for
 * a value <= ETHERMTU to see whether it's a type field and then do
 * the appropriate test.
 */
static struct block *
gen_ether_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
{
  struct block *b0, *b1;

  switch (ll_proto) {

  case LLCSAP_ISONS:
  case LLCSAP_IP:
  case LLCSAP_NETBEUI:
    /*
     * OSI protocols and NetBEUI always use 802.2 encapsulation,
     * so we check the DSAP and SSAP.
     *
     * LLCSAP_IP checks for IP-over-802.2, rather
     * than IP-over-Ethernet or IP-over-SNAP.
     *
     * XXX - should we check both the DSAP and the
     * SSAP, like this, or should we check just the
     * DSAP, as we do for other types <= ETHERMTU
     * (i.e., other SAP values)?
     */
    b0 = gen_cmp_gt(cstate, OR_LINKTYPE, 0, BPF_H, ETHERMTU);
    gen_not(b0);
    b1 = gen_cmp(cstate, OR_LLC, 0, BPF_H, (ll_proto << 8) | ll_proto);
    gen_and(b0, b1);
    return b1;

  case LLCSAP_IPX:
    /*
     * Check for;
     *
     *  Ethernet_II frames, which are Ethernet
     *  frames with a frame type of ETHERTYPE_IPX;
     *
     *  Ethernet_802.3 frames, which are 802.3
     *  frames (i.e., the type/length field is
     *  a length field, <= ETHERMTU, rather than
     *  a type field) with the first two bytes
     *  after the Ethernet/802.3 header being
     *  0xFFFF;
     *
     *  Ethernet_802.2 frames, which are 802.3
     *  frames with an 802.2 LLC header and
     *  with the IPX LSAP as the DSAP in the LLC
     *  header;
     *
     *  Ethernet_SNAP frames, which are 802.3
     *  frames with an LLC header and a SNAP
     *  header and with an OUI of 0x000000
     *  (encapsulated Ethernet) and a protocol
     *  ID of ETHERTYPE_IPX in the SNAP header.
     *
     * XXX - should we generate the same code both
     * for tests for LLCSAP_IPX and for ETHERTYPE_IPX?
     */

    /*
     * This generates code to check both for the
     * IPX LSAP (Ethernet_802.2) and for Ethernet_802.3.
     */
    b0 = gen_cmp(cstate, OR_LLC, 0, BPF_B, LLCSAP_IPX);
    b1 = gen_cmp(cstate, OR_LLC, 0, BPF_H, 0xFFFF);
    gen_or(b0, b1);

    /*
     * Now we add code to check for SNAP frames with
     * ETHERTYPE_IPX, i.e. Ethernet_SNAP.
     */
    b0 = gen_snap(cstate, 0x000000, ETHERTYPE_IPX);
    gen_or(b0, b1);

    /*
     * Now we generate code to check for 802.3
     * frames in general.
     */
    b0 = gen_cmp_gt(cstate, OR_LINKTYPE, 0, BPF_H, ETHERMTU);
    gen_not(b0);

    /*
     * Now add the check for 802.3 frames before the
     * check for Ethernet_802.2 and Ethernet_802.3,
     * as those checks should only be done on 802.3
     * frames, not on Ethernet frames.
     */
    gen_and(b0, b1);

    /*
     * Now add the check for Ethernet_II frames, and
     * do that before checking for the other frame
     * types.
     */
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ETHERTYPE_IPX);
    gen_or(b0, b1);
    return b1;

  case ETHERTYPE_ATALK:
  case ETHERTYPE_AARP:
    /*
     * EtherTalk (AppleTalk protocols on Ethernet link
     * layer) may use 802.2 encapsulation.
     */

    /*
     * Check for 802.2 encapsulation (EtherTalk phase 2?);
     * we check for an Ethernet type field less than
     * 1500, which means it's an 802.3 length field.
     */
    b0 = gen_cmp_gt(cstate, OR_LINKTYPE, 0, BPF_H, ETHERMTU);
    gen_not(b0);

    /*
     * 802.2-encapsulated ETHERTYPE_ATALK packets are
     * SNAP packets with an organization code of
     * 0x080007 (Apple, for Appletalk) and a protocol
     * type of ETHERTYPE_ATALK (Appletalk).
     *
     * 802.2-encapsulated ETHERTYPE_AARP packets are
     * SNAP packets with an organization code of
     * 0x000000 (encapsulated Ethernet) and a protocol
     * type of ETHERTYPE_AARP (Appletalk ARP).
     */
    if (ll_proto == ETHERTYPE_ATALK)
      b1 = gen_snap(cstate, 0x080007, ETHERTYPE_ATALK);
    else  /* ll_proto == ETHERTYPE_AARP */
      b1 = gen_snap(cstate, 0x000000, ETHERTYPE_AARP);
    gen_and(b0, b1);

    /*
     * Check for Ethernet encapsulation (Ethertalk
     * phase 1?); we just check for the Ethernet
     * protocol type.
     */
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ll_proto);

    gen_or(b0, b1);
    return b1;

  default:
    if (ll_proto <= ETHERMTU) {
      /*
       * This is an LLC SAP value, so the frames
       * that match would be 802.2 frames.
       * Check that the frame is an 802.2 frame
       * (i.e., that the length/type field is
       * a length field, <= ETHERMTU) and
       * then check the DSAP.
       */
      b0 = gen_cmp_gt(cstate, OR_LINKTYPE, 0, BPF_H, ETHERMTU);
      gen_not(b0);
      b1 = gen_cmp(cstate, OR_LINKTYPE, 2, BPF_B, ll_proto);
      gen_and(b0, b1);
      return b1;
    } else {
      /*
       * This is an Ethernet type, so compare
       * the length/type field with it (if
       * the frame is an 802.2 frame, the length
       * field will be <= ETHERMTU, and, as
       * "ll_proto" is > ETHERMTU, this test
       * will fail and the frame won't match,
       * which is what we want).
       */
      return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ll_proto);
    }
  }
}

static struct block *
gen_loopback_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
{
  /*
   * For DLT_NULL, the link-layer header is a 32-bit word
   * containing an AF_ value in *host* byte order, and for
   * DLT_ENC, the link-layer header begins with a 32-bit
   * word containing an AF_ value in host byte order.
   *
   * In addition, if we're reading a saved capture file,
   * the host byte order in the capture may not be the
   * same as the host byte order on this machine.
   *
   * For DLT_LOOP, the link-layer header is a 32-bit
   * word containing an AF_ value in *network* byte order.
   */
  if (cstate->linktype == DLT_NULL || cstate->linktype == DLT_ENC) {
    /*
     * The AF_ value is in host byte order, but the BPF
     * interpreter will convert it to network byte order.
     *
     * If this is a save file, and it's from a machine
     * with the opposite byte order to ours, we byte-swap
     * the AF_ value.
     *
     * Then we run it through "htonl()", and generate
     * code to compare against the result.
     */
    if (cstate->bpf_pcap->rfile != NULL && cstate->bpf_pcap->swapped)
      ll_proto = SWAPLONG(ll_proto);
    ll_proto = htonl(ll_proto);
  }
  return (gen_cmp(cstate, OR_LINKHDR, 0, BPF_W, ll_proto));
}

/*
 * "proto" is an Ethernet type value and for IPNET, if it is not IPv4
 * or IPv6 then we have an error.
 */
static struct block *
gen_ipnet_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
{
  switch (ll_proto) {

  case ETHERTYPE_IP:
    return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B, IPH_AF_INET);
    /*NOTREACHED*/

  case ETHERTYPE_IPV6:
    return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B, IPH_AF_INET6);
    /*NOTREACHED*/

  default:
    break;
  }

  return gen_false(cstate);
}

/*
 * Generate code to match a particular packet type.
 *
 * "ll_proto" is an Ethernet type value, if > ETHERMTU, or an LLC SAP
 * value, if <= ETHERMTU.  We use that to determine whether to
 * match the type field or to check the type field for the special
 * LINUX_SLL_P_802_2 value and then do the appropriate test.
 */
static struct block *
gen_linux_sll_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
{
  struct block *b0, *b1;

  switch (ll_proto) {

  case LLCSAP_ISONS:
  case LLCSAP_IP:
  case LLCSAP_NETBEUI:
    /*
     * OSI protocols and NetBEUI always use 802.2 encapsulation,
     * so we check the DSAP and SSAP.
     *
     * LLCSAP_IP checks for IP-over-802.2, rather
     * than IP-over-Ethernet or IP-over-SNAP.
     *
     * XXX - should we check both the DSAP and the
     * SSAP, like this, or should we check just the
     * DSAP, as we do for other types <= ETHERMTU
     * (i.e., other SAP values)?
     */
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, LINUX_SLL_P_802_2);
    b1 = gen_cmp(cstate, OR_LLC, 0, BPF_H, (ll_proto << 8) | ll_proto);
    gen_and(b0, b1);
    return b1;

  case LLCSAP_IPX:
    /*
     *  Ethernet_II frames, which are Ethernet
     *  frames with a frame type of ETHERTYPE_IPX;
     *
     *  Ethernet_802.3 frames, which have a frame
     *  type of LINUX_SLL_P_802_3;
     *
     *  Ethernet_802.2 frames, which are 802.3
     *  frames with an 802.2 LLC header (i.e, have
     *  a frame type of LINUX_SLL_P_802_2) and
     *  with the IPX LSAP as the DSAP in the LLC
     *  header;
     *
     *  Ethernet_SNAP frames, which are 802.3
     *  frames with an LLC header and a SNAP
     *  header and with an OUI of 0x000000
     *  (encapsulated Ethernet) and a protocol
     *  ID of ETHERTYPE_IPX in the SNAP header.
     *
     * First, do the checks on LINUX_SLL_P_802_2
     * frames; generate the check for either
     * Ethernet_802.2 or Ethernet_SNAP frames, and
     * then put a check for LINUX_SLL_P_802_2 frames
     * before it.
     */
    b0 = gen_cmp(cstate, OR_LLC, 0, BPF_B, LLCSAP_IPX);
    b1 = gen_snap(cstate, 0x000000, ETHERTYPE_IPX);
    gen_or(b0, b1);
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, LINUX_SLL_P_802_2);
    gen_and(b0, b1);

    /*
     * Now check for 802.3 frames and OR that with
     * the previous test.
     */
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, LINUX_SLL_P_802_3);
    gen_or(b0, b1);

    /*
     * Now add the check for Ethernet_II frames, and
     * do that before checking for the other frame
     * types.
     */
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ETHERTYPE_IPX);
    gen_or(b0, b1);
    return b1;

  case ETHERTYPE_ATALK:
  case ETHERTYPE_AARP:
    /*
     * EtherTalk (AppleTalk protocols on Ethernet link
     * layer) may use 802.2 encapsulation.
     */

    /*
     * Check for 802.2 encapsulation (EtherTalk phase 2?);
     * we check for the 802.2 protocol type in the
     * "Ethernet type" field.
     */
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, LINUX_SLL_P_802_2);

    /*
     * 802.2-encapsulated ETHERTYPE_ATALK packets are
     * SNAP packets with an organization code of
     * 0x080007 (Apple, for Appletalk) and a protocol
     * type of ETHERTYPE_ATALK (Appletalk).
     *
     * 802.2-encapsulated ETHERTYPE_AARP packets are
     * SNAP packets with an organization code of
     * 0x000000 (encapsulated Ethernet) and a protocol
     * type of ETHERTYPE_AARP (Appletalk ARP).
     */
    if (ll_proto == ETHERTYPE_ATALK)
      b1 = gen_snap(cstate, 0x080007, ETHERTYPE_ATALK);
    else  /* ll_proto == ETHERTYPE_AARP */
      b1 = gen_snap(cstate, 0x000000, ETHERTYPE_AARP);
    gen_and(b0, b1);

    /*
     * Check for Ethernet encapsulation (Ethertalk
     * phase 1?); we just check for the Ethernet
     * protocol type.
     */
    b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ll_proto);

    gen_or(b0, b1);
    return b1;

  default:
    if (ll_proto <= ETHERMTU) {
      /*
       * This is an LLC SAP value, so the frames
       * that match would be 802.2 frames.
       * Check for the 802.2 protocol type
       * in the "Ethernet type" field, and
       * then check the DSAP.
       */
      b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, LINUX_SLL_P_802_2);
      b1 = gen_cmp(cstate, OR_LINKHDR, cstate->off_linkpl.constant_part, BPF_B,
           ll_proto);
      gen_and(b0, b1);
      return b1;
    } else {
      /*
       * This is an Ethernet type, so compare
       * the length/type field with it (if
       * the frame is an 802.2 frame, the length
       * field will be <= ETHERMTU, and, as
       * "ll_proto" is > ETHERMTU, this test
       * will fail and the frame won't match,
       * which is what we want).
       */
      return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ll_proto);
    }
  }
}

/*
 * Load a value relative to the beginning of the link-layer header after the
 * pflog header.
 */
static struct slist *
gen_load_pflog_llprefixlen(compiler_state_t *cstate)
{
  struct slist *s1, *s2;

  /*
   * Generate code to load the length of the pflog header into
   * the register assigned to hold that length, if one has been
   * assigned.  (If one hasn't been assigned, no code we've
   * generated uses that prefix, so we don't need to generate any
   * code to load it.)
   */
  if (cstate->off_linkpl.reg != -1) {
    /*
     * The length is in the first byte of the header.
     */
    s1 = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
    s1->s.k = 0;

    /*
     * Round it up to a multiple of 4.
     * Add 3, and clear the lower 2 bits.
     */
    s2 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
    s2->s.k = 3;
    sappend(s1, s2);
    s2 = new_stmt(cstate, BPF_ALU|BPF_AND|BPF_K);
    s2->s.k = 0xfffffffc;
    sappend(s1, s2);

    /*
     * Now allocate a register to hold that value and store
     * it.
     */
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linkpl.reg;
    sappend(s1, s2);

    /*
     * Now move it into the X register.
     */
    s2 = new_stmt(cstate, BPF_MISC|BPF_TAX);
    sappend(s1, s2);

    return (s1);
  } else
    return (NULL);
}

static struct slist *
gen_load_prism_llprefixlen(compiler_state_t *cstate)
{
  struct slist *s1, *s2;
  struct slist *sjeq_avs_cookie;
  struct slist *sjcommon;

  /*
   * This code is not compatible with the optimizer, as
   * we are generating jmp instructions within a normal
   * slist of instructions
   */
  cstate->no_optimize = 1;

  /*
   * Generate code to load the length of the radio header into
   * the register assigned to hold that length, if one has been
   * assigned.  (If one hasn't been assigned, no code we've
   * generated uses that prefix, so we don't need to generate any
   * code to load it.)
   *
   * Some Linux drivers use ARPHRD_IEEE80211_PRISM but sometimes
   * or always use the AVS header rather than the Prism header.
   * We load a 4-byte big-endian value at the beginning of the
   * raw packet data, and see whether, when masked with 0xFFFFF000,
   * it's equal to 0x80211000.  If so, that indicates that it's
   * an AVS header (the masked-out bits are the version number).
   * Otherwise, it's a Prism header.
   *
   * XXX - the Prism header is also, in theory, variable-length,
   * but no known software generates headers that aren't 144
   * bytes long.
   */
  if (cstate->off_linkhdr.reg != -1) {
    /*
     * Load the cookie.
     */
    s1 = new_stmt(cstate, BPF_LD|BPF_W|BPF_ABS);
    s1->s.k = 0;

    /*
     * AND it with 0xFFFFF000.
     */
    s2 = new_stmt(cstate, BPF_ALU|BPF_AND|BPF_K);
    s2->s.k = 0xFFFFF000;
    sappend(s1, s2);

    /*
     * Compare with 0x80211000.
     */
    sjeq_avs_cookie = new_stmt(cstate, JMP(BPF_JEQ));
    sjeq_avs_cookie->s.k = 0x80211000;
    sappend(s1, sjeq_avs_cookie);

    /*
     * If it's AVS:
     *
     * The 4 bytes at an offset of 4 from the beginning of
     * the AVS header are the length of the AVS header.
     * That field is big-endian.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_W|BPF_ABS);
    s2->s.k = 4;
    sappend(s1, s2);
    sjeq_avs_cookie->s.jt = s2;

    /*
     * Now jump to the code to allocate a register
     * into which to save the header length and
     * store the length there.  (The "jump always"
     * instruction needs to have the k field set;
     * it's added to the PC, so, as we're jumping
     * over a single instruction, it should be 1.)
     */
    sjcommon = new_stmt(cstate, JMP(BPF_JA));
    sjcommon->s.k = 1;
    sappend(s1, sjcommon);

    /*
     * Now for the code that handles the Prism header.
     * Just load the length of the Prism header (144)
     * into the A register.  Have the test for an AVS
     * header branch here if we don't have an AVS header.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_W|BPF_IMM);
    s2->s.k = 144;
    sappend(s1, s2);
    sjeq_avs_cookie->s.jf = s2;

    /*
     * Now allocate a register to hold that value and store
     * it.  The code for the AVS header will jump here after
     * loading the length of the AVS header.
     */
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linkhdr.reg;
    sappend(s1, s2);
    sjcommon->s.jf = s2;

    /*
     * Now move it into the X register.
     */
    s2 = new_stmt(cstate, BPF_MISC|BPF_TAX);
    sappend(s1, s2);

    return (s1);
  } else
    return (NULL);
}

static struct slist *
gen_load_avs_llprefixlen(compiler_state_t *cstate)
{
  struct slist *s1, *s2;

  /*
   * Generate code to load the length of the AVS header into
   * the register assigned to hold that length, if one has been
   * assigned.  (If one hasn't been assigned, no code we've
   * generated uses that prefix, so we don't need to generate any
   * code to load it.)
   */
  if (cstate->off_linkhdr.reg != -1) {
    /*
     * The 4 bytes at an offset of 4 from the beginning of
     * the AVS header are the length of the AVS header.
     * That field is big-endian.
     */
    s1 = new_stmt(cstate, BPF_LD|BPF_W|BPF_ABS);
    s1->s.k = 4;

    /*
     * Now allocate a register to hold that value and store
     * it.
     */
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linkhdr.reg;
    sappend(s1, s2);

    /*
     * Now move it into the X register.
     */
    s2 = new_stmt(cstate, BPF_MISC|BPF_TAX);
    sappend(s1, s2);

    return (s1);
  } else
    return (NULL);
}

static struct slist *
gen_load_radiotap_llprefixlen(compiler_state_t *cstate)
{
  struct slist *s1, *s2;

  /*
   * Generate code to load the length of the radiotap header into
   * the register assigned to hold that length, if one has been
   * assigned.  (If one hasn't been assigned, no code we've
   * generated uses that prefix, so we don't need to generate any
   * code to load it.)
   */
  if (cstate->off_linkhdr.reg != -1) {
    /*
     * The 2 bytes at offsets of 2 and 3 from the beginning
     * of the radiotap header are the length of the radiotap
     * header; unfortunately, it's little-endian, so we have
     * to load it a byte at a time and construct the value.
     */

    /*
     * Load the high-order byte, at an offset of 3, shift it
     * left a byte, and put the result in the X register.
     */
    s1 = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
    s1->s.k = 3;
    s2 = new_stmt(cstate, BPF_ALU|BPF_LSH|BPF_K);
    sappend(s1, s2);
    s2->s.k = 8;
    s2 = new_stmt(cstate, BPF_MISC|BPF_TAX);
    sappend(s1, s2);

    /*
     * Load the next byte, at an offset of 2, and OR the
     * value from the X register into it.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
    sappend(s1, s2);
    s2->s.k = 2;
    s2 = new_stmt(cstate, BPF_ALU|BPF_OR|BPF_X);
    sappend(s1, s2);

    /*
     * Now allocate a register to hold that value and store
     * it.
     */
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linkhdr.reg;
    sappend(s1, s2);

    /*
     * Now move it into the X register.
     */
    s2 = new_stmt(cstate, BPF_MISC|BPF_TAX);
    sappend(s1, s2);

    return (s1);
  } else
    return (NULL);
}

/*
 * At the moment we treat PPI as normal Radiotap encoded
 * packets. The difference is in the function that generates
 * the code at the beginning to compute the header length.
 * Since this code generator of PPI supports bare 802.11
 * encapsulation only (i.e. the encapsulated DLT should be
 * DLT_IEEE802_11) we generate code to check for this too;
 * that's done in finish_parse().
 */
static struct slist *
gen_load_ppi_llprefixlen(compiler_state_t *cstate)
{
  struct slist *s1, *s2;

  /*
   * Generate code to load the length of the radiotap header
   * into the register assigned to hold that length, if one has
   * been assigned.
   */
  if (cstate->off_linkhdr.reg != -1) {
    /*
     * The 2 bytes at offsets of 2 and 3 from the beginning
     * of the radiotap header are the length of the radiotap
     * header; unfortunately, it's little-endian, so we have
     * to load it a byte at a time and construct the value.
     */

    /*
     * Load the high-order byte, at an offset of 3, shift it
     * left a byte, and put the result in the X register.
     */
    s1 = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
    s1->s.k = 3;
    s2 = new_stmt(cstate, BPF_ALU|BPF_LSH|BPF_K);
    sappend(s1, s2);
    s2->s.k = 8;
    s2 = new_stmt(cstate, BPF_MISC|BPF_TAX);
    sappend(s1, s2);

    /*
     * Load the next byte, at an offset of 2, and OR the
     * value from the X register into it.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
    sappend(s1, s2);
    s2->s.k = 2;
    s2 = new_stmt(cstate, BPF_ALU|BPF_OR|BPF_X);
    sappend(s1, s2);

    /*
     * Now allocate a register to hold that value and store
     * it.
     */
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linkhdr.reg;
    sappend(s1, s2);

    /*
     * Now move it into the X register.
     */
    s2 = new_stmt(cstate, BPF_MISC|BPF_TAX);
    sappend(s1, s2);

    return (s1);
  } else
    return (NULL);
}

/*
 * Load a value relative to the beginning of the link-layer header after the 802.11
 * header, i.e. LLC_SNAP.
 * The link-layer header doesn't necessarily begin at the beginning
 * of the packet data; there might be a variable-length prefix containing
 * radio information.
 */
static struct slist *
gen_load_802_11_header_len(compiler_state_t *cstate, struct slist *s, struct slist *snext)
{
  struct slist *s2;
  struct slist *sjset_data_frame_1;
  struct slist *sjset_data_frame_2;
  struct slist *sjset_qos;
  struct slist *sjset_radiotap_flags_present;
  struct slist *sjset_radiotap_ext_present;
  struct slist *sjset_radiotap_tsft_present;
  struct slist *sjset_tsft_datapad, *sjset_notsft_datapad;
  struct slist *s_roundup;

  if (cstate->off_linkpl.reg == -1) {
    /*
     * No register has been assigned to the offset of
     * the link-layer payload, which means nobody needs
     * it; don't bother computing it - just return
     * what we already have.
     */
    return (s);
  }

  /*
   * This code is not compatible with the optimizer, as
   * we are generating jmp instructions within a normal
   * slist of instructions
   */
  cstate->no_optimize = 1;

  /*
   * If "s" is non-null, it has code to arrange that the X register
   * contains the length of the prefix preceding the link-layer
   * header.
   *
   * Otherwise, the length of the prefix preceding the link-layer
   * header is "off_outermostlinkhdr.constant_part".
   */
  if (s == NULL) {
    /*
     * There is no variable-length header preceding the
     * link-layer header.
     *
     * Load the length of the fixed-length prefix preceding
     * the link-layer header (if any) into the X register,
     * and store it in the cstate->off_linkpl.reg register.
     * That length is off_outermostlinkhdr.constant_part.
     */
    s = new_stmt(cstate, BPF_LDX|BPF_IMM);
    s->s.k = cstate->off_outermostlinkhdr.constant_part;
  }

  /*
   * The X register contains the offset of the beginning of the
   * link-layer header; add 24, which is the minimum length
   * of the MAC header for a data frame, to that, and store it
   * in cstate->off_linkpl.reg, and then load the Frame Control field,
   * which is at the offset in the X register, with an indexed load.
   */
  s2 = new_stmt(cstate, BPF_MISC|BPF_TXA);
  sappend(s, s2);
  s2 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s2->s.k = 24;
  sappend(s, s2);
  s2 = new_stmt(cstate, BPF_ST);
  s2->s.k = cstate->off_linkpl.reg;
  sappend(s, s2);

  s2 = new_stmt(cstate, BPF_LD|BPF_IND|BPF_B);
  s2->s.k = 0;
  sappend(s, s2);

  /*
   * Check the Frame Control field to see if this is a data frame;
   * a data frame has the 0x08 bit (b3) in that field set and the
   * 0x04 bit (b2) clear.
   */
  sjset_data_frame_1 = new_stmt(cstate, JMP(BPF_JSET));
  sjset_data_frame_1->s.k = 0x08;
  sappend(s, sjset_data_frame_1);

  /*
   * If b3 is set, test b2, otherwise go to the first statement of
   * the rest of the program.
   */
  sjset_data_frame_1->s.jt = sjset_data_frame_2 = new_stmt(cstate, JMP(BPF_JSET));
  sjset_data_frame_2->s.k = 0x04;
  sappend(s, sjset_data_frame_2);
  sjset_data_frame_1->s.jf = snext;

  /*
   * If b2 is not set, this is a data frame; test the QoS bit.
   * Otherwise, go to the first statement of the rest of the
   * program.
   */
  sjset_data_frame_2->s.jt = snext;
  sjset_data_frame_2->s.jf = sjset_qos = new_stmt(cstate, JMP(BPF_JSET));
  sjset_qos->s.k = 0x80;  /* QoS bit */
  sappend(s, sjset_qos);

  /*
   * If it's set, add 2 to cstate->off_linkpl.reg, to skip the QoS
   * field.
   * Otherwise, go to the first statement of the rest of the
   * program.
   */
  sjset_qos->s.jt = s2 = new_stmt(cstate, BPF_LD|BPF_MEM);
  s2->s.k = cstate->off_linkpl.reg;
  sappend(s, s2);
  s2 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_IMM);
  s2->s.k = 2;
  sappend(s, s2);
  s2 = new_stmt(cstate, BPF_ST);
  s2->s.k = cstate->off_linkpl.reg;
  sappend(s, s2);

  /*
   * If we have a radiotap header, look at it to see whether
   * there's Atheros padding between the MAC-layer header
   * and the payload.
   *
   * Note: all of the fields in the radiotap header are
   * little-endian, so we byte-swap all of the values
   * we test against, as they will be loaded as big-endian
   * values.
   *
   * XXX - in the general case, we would have to scan through
   * *all* the presence bits, if there's more than one word of
   * presence bits.  That would require a loop, meaning that
   * we wouldn't be able to run the filter in the kernel.
   *
   * We assume here that the Atheros adapters that insert the
   * annoying padding don't have multiple antennae and therefore
   * do not generate radiotap headers with multiple presence words.
   */
  if (cstate->linktype == DLT_IEEE802_11_RADIO) {
    /*
     * Is the IEEE80211_RADIOTAP_FLAGS bit (0x0000002) set
     * in the first presence flag word?
     */
    sjset_qos->s.jf = s2 = new_stmt(cstate, BPF_LD|BPF_ABS|BPF_W);
    s2->s.k = 4;
    sappend(s, s2);

    sjset_radiotap_flags_present = new_stmt(cstate, JMP(BPF_JSET));
    sjset_radiotap_flags_present->s.k = SWAPLONG(0x00000002);
    sappend(s, sjset_radiotap_flags_present);

    /*
     * If not, skip all of this.
     */
    sjset_radiotap_flags_present->s.jf = snext;

    /*
     * Otherwise, is the "extension" bit set in that word?
     */
    sjset_radiotap_ext_present = new_stmt(cstate, JMP(BPF_JSET));
    sjset_radiotap_ext_present->s.k = SWAPLONG(0x80000000);
    sappend(s, sjset_radiotap_ext_present);
    sjset_radiotap_flags_present->s.jt = sjset_radiotap_ext_present;

    /*
     * If so, skip all of this.
     */
    sjset_radiotap_ext_present->s.jt = snext;

    /*
     * Otherwise, is the IEEE80211_RADIOTAP_TSFT bit set?
     */
    sjset_radiotap_tsft_present = new_stmt(cstate, JMP(BPF_JSET));
    sjset_radiotap_tsft_present->s.k = SWAPLONG(0x00000001);
    sappend(s, sjset_radiotap_tsft_present);
    sjset_radiotap_ext_present->s.jf = sjset_radiotap_tsft_present;

    /*
     * If IEEE80211_RADIOTAP_TSFT is set, the flags field is
     * at an offset of 16 from the beginning of the raw packet
     * data (8 bytes for the radiotap header and 8 bytes for
     * the TSFT field).
     *
     * Test whether the IEEE80211_RADIOTAP_F_DATAPAD bit (0x20)
     * is set.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_ABS|BPF_B);
    s2->s.k = 16;
    sappend(s, s2);
    sjset_radiotap_tsft_present->s.jt = s2;

    sjset_tsft_datapad = new_stmt(cstate, JMP(BPF_JSET));
    sjset_tsft_datapad->s.k = 0x20;
    sappend(s, sjset_tsft_datapad);

    /*
     * If IEEE80211_RADIOTAP_TSFT is not set, the flags field is
     * at an offset of 8 from the beginning of the raw packet
     * data (8 bytes for the radiotap header).
     *
     * Test whether the IEEE80211_RADIOTAP_F_DATAPAD bit (0x20)
     * is set.
     */
    s2 = new_stmt(cstate, BPF_LD|BPF_ABS|BPF_B);
    s2->s.k = 8;
    sappend(s, s2);
    sjset_radiotap_tsft_present->s.jf = s2;

    sjset_notsft_datapad = new_stmt(cstate, JMP(BPF_JSET));
    sjset_notsft_datapad->s.k = 0x20;
    sappend(s, sjset_notsft_datapad);

    /*
     * In either case, if IEEE80211_RADIOTAP_F_DATAPAD is
     * set, round the length of the 802.11 header to
     * a multiple of 4.  Do that by adding 3 and then
     * dividing by and multiplying by 4, which we do by
     * ANDing with ~3.
     */
    s_roundup = new_stmt(cstate, BPF_LD|BPF_MEM);
    s_roundup->s.k = cstate->off_linkpl.reg;
    sappend(s, s_roundup);
    s2 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_IMM);
    s2->s.k = 3;
    sappend(s, s2);
    s2 = new_stmt(cstate, BPF_ALU|BPF_AND|BPF_IMM);
    s2->s.k = (bpf_u_int32)~3;
    sappend(s, s2);
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linkpl.reg;
    sappend(s, s2);

    sjset_tsft_datapad->s.jt = s_roundup;
    sjset_tsft_datapad->s.jf = snext;
    sjset_notsft_datapad->s.jt = s_roundup;
    sjset_notsft_datapad->s.jf = snext;
  } else
    sjset_qos->s.jf = snext;

  return s;
}

static void
insert_compute_vloffsets(compiler_state_t *cstate, struct block *b)
{
  struct slist *s;

  /* There is an implicit dependency between the link
   * payload and link header since the payload computation
   * includes the variable part of the header. Therefore,
   * if nobody else has allocated a register for the link
   * header and we need it, do it now. */
  if (cstate->off_linkpl.reg != -1 && cstate->off_linkhdr.is_variable &&
      cstate->off_linkhdr.reg == -1)
    cstate->off_linkhdr.reg = alloc_reg(cstate);

  /*
   * For link-layer types that have a variable-length header
   * preceding the link-layer header, generate code to load
   * the offset of the link-layer header into the register
   * assigned to that offset, if any.
   *
   * XXX - this, and the next switch statement, won't handle
   * encapsulation of 802.11 or 802.11+radio information in
   * some other protocol stack.  That's significantly more
   * complicated.
   */
  switch (cstate->outermostlinktype) {

  case DLT_PRISM_HEADER:
    s = gen_load_prism_llprefixlen(cstate);
    break;

  case DLT_IEEE802_11_RADIO_AVS:
    s = gen_load_avs_llprefixlen(cstate);
    break;

  case DLT_IEEE802_11_RADIO:
    s = gen_load_radiotap_llprefixlen(cstate);
    break;

  case DLT_PPI:
    s = gen_load_ppi_llprefixlen(cstate);
    break;

  default:
    s = NULL;
    break;
  }

  /*
   * For link-layer types that have a variable-length link-layer
   * header, generate code to load the offset of the link-layer
   * payload into the register assigned to that offset, if any.
   */
  switch (cstate->outermostlinktype) {

  case DLT_IEEE802_11:
  case DLT_PRISM_HEADER:
  case DLT_IEEE802_11_RADIO_AVS:
  case DLT_IEEE802_11_RADIO:
  case DLT_PPI:
    s = gen_load_802_11_header_len(cstate, s, b->stmts);
    break;

  case DLT_PFLOG:
    s = gen_load_pflog_llprefixlen(cstate);
    break;
  }

  /*
   * If there is no initialization yet and we need variable
   * length offsets for VLAN, initialize them to zero
   */
  if (s == NULL && cstate->is_vlan_vloffset) {
    struct slist *s2;

    if (cstate->off_linkpl.reg == -1)
      cstate->off_linkpl.reg = alloc_reg(cstate);
    if (cstate->off_linktype.reg == -1)
      cstate->off_linktype.reg = alloc_reg(cstate);

    s = new_stmt(cstate, BPF_LD|BPF_W|BPF_IMM);
    s->s.k = 0;
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linkpl.reg;
    sappend(s, s2);
    s2 = new_stmt(cstate, BPF_ST);
    s2->s.k = cstate->off_linktype.reg;
    sappend(s, s2);
  }

  /*
   * If we have any offset-loading code, append all the
   * existing statements in the block to those statements,
   * and make the resulting list the list of statements
   * for the block.
   */
  if (s != NULL) {
    sappend(s, b->stmts);
    b->stmts = s;
  }
}

static struct block *
gen_ppi_dlt_check(compiler_state_t *cstate)
{
  struct slist *s_load_dlt;
  struct block *b;

  if (cstate->linktype == DLT_PPI)
  {
    /* Create the statements that check for the DLT
     */
    s_load_dlt = new_stmt(cstate, BPF_LD|BPF_W|BPF_ABS);
    s_load_dlt->s.k = 4;

    b = new_block(cstate, JMP(BPF_JEQ));

    b->stmts = s_load_dlt;
    b->s.k = SWAPLONG(DLT_IEEE802_11);
  }
  else
  {
    b = NULL;
  }

  return b;
}

/*
 * Take an absolute offset, and:
 *
 *    if it has no variable part, return NULL;
 *
 *    if it has a variable part, generate code to load the register
 *    containing that variable part into the X register, returning
 *    a pointer to that code - if no register for that offset has
 *    been allocated, allocate it first.
 *
 * (The code to set that register will be generated later, but will
 * be placed earlier in the code sequence.)
 */
static struct slist *
gen_abs_offset_varpart(compiler_state_t *cstate, bpf_abs_offset *off)
{
  struct slist *s;

  if (off->is_variable) {
    if (off->reg == -1) {
      /*
       * We haven't yet assigned a register for the
       * variable part of the offset of the link-layer
       * header; allocate one.
       */
      off->reg = alloc_reg(cstate);
    }

    /*
     * Load the register containing the variable part of the
     * offset of the link-layer header into the X register.
     */
    s = new_stmt(cstate, BPF_LDX|BPF_MEM);
    s->s.k = off->reg;
    return s;
  } else {
    /*
     * That offset isn't variable, there's no variable part,
     * so we don't need to generate any code.
     */
    return NULL;
  }
}

/*
 * Map an Ethernet type to the equivalent PPP type.
 */
static bpf_u_int32
ethertype_to_ppptype(bpf_u_int32 ll_proto)
{
  switch (ll_proto) {

  case ETHERTYPE_IP:
    ll_proto = PPP_IP;
    break;

  case ETHERTYPE_IPV6:
    ll_proto = PPP_IPV6;
    break;

  case ETHERTYPE_DN:
    ll_proto = PPP_DECNET;
    break;

  case ETHERTYPE_ATALK:
    ll_proto = PPP_APPLE;
    break;

  case ETHERTYPE_NS:
    ll_proto = PPP_NS;
    break;

  case LLCSAP_ISONS:
    ll_proto = PPP_OSI;
    break;

  case LLCSAP_8021D:
    /*
     * I'm assuming the "Bridging PDU"s that go
     * over PPP are Spanning Tree Protocol
     * Bridging PDUs.
     */
    ll_proto = PPP_BRPDU;
    break;

  case LLCSAP_IPX:
    ll_proto = PPP_IPX;
    break;
  }
  return (ll_proto);
}

/*
 * Generate any tests that, for encapsulation of a link-layer packet
 * inside another protocol stack, need to be done to check for those
 * link-layer packets (and that haven't already been done by a check
 * for that encapsulation).
 */
static struct block *
gen_prevlinkhdr_check(compiler_state_t *cstate)
{
  struct block *b0;

  if (cstate->is_geneve)
    return gen_geneve_ll_check(cstate);

  switch (cstate->prevlinktype) {

  case DLT_SUNATM:
    /*
     * This is LANE-encapsulated Ethernet; check that the LANE
     * packet doesn't begin with an LE Control marker, i.e.
     * that it's data, not a control message.
     *
     * (We've already generated a test for LANE.)
     */
    b0 = gen_cmp(cstate, OR_PREVLINKHDR, SUNATM_PKT_BEGIN_POS, BPF_H, 0xFF00);
    gen_not(b0);
    return b0;

  default:
    /*
     * No such tests are necessary.
     */
    return NULL;
  }
  /*NOTREACHED*/
}

/*
 * The three different values we should check for when checking for an
 * IPv6 packet with DLT_NULL.
 */
#define BSD_AFNUM_INET6_BSD 24  /* NetBSD, OpenBSD, BSD/OS, Npcap */
#define BSD_AFNUM_INET6_FREEBSD 28  /* FreeBSD */
#define BSD_AFNUM_INET6_DARWIN  30  /* macOS, iOS, other Darwin-based OSes */

/*
 * Generate code to match a particular packet type by matching the
 * link-layer type field or fields in the 802.2 LLC header.
 *
 * "proto" is an Ethernet type value, if > ETHERMTU, or an LLC SAP
 * value, if <= ETHERMTU.
 */
static struct block *
gen_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
{
  struct block *b0, *b1, *b2;
  const char *description;

  /* are we checking MPLS-encapsulated packets? */
  if (cstate->label_stack_depth > 0)
    return gen_mpls_linktype(cstate, ll_proto);

  switch (cstate->linktype) {

  case DLT_EN10MB:
  case DLT_NETANALYZER:
  case DLT_NETANALYZER_TRANSPARENT:
    /* Geneve has an EtherType regardless of whether there is an
     * L2 header. */
    if (!cstate->is_geneve)
      b0 = gen_prevlinkhdr_check(cstate);
    else
      b0 = NULL;

    b1 = gen_ether_linktype(cstate, ll_proto);
    if (b0 != NULL)
      gen_and(b0, b1);
    return b1;
    /*NOTREACHED*/

  case DLT_C_HDLC:
  case DLT_HDLC:
    switch (ll_proto) {

    case LLCSAP_ISONS:
      ll_proto = (ll_proto << 8 | LLCSAP_ISONS);
      /* fall through */

    default:
      return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ll_proto);
      /*NOTREACHED*/
    }

  case DLT_IEEE802_11:
  case DLT_PRISM_HEADER:
  case DLT_IEEE802_11_RADIO_AVS:
  case DLT_IEEE802_11_RADIO:
  case DLT_PPI:
    /*
     * Check that we have a data frame.
     */
    b0 = gen_check_802_11_data_frame(cstate);

    /*
     * Now check for the specified link-layer type.
     */
    b1 = gen_llc_linktype(cstate, ll_proto);
    gen_and(b0, b1);
    return b1;
    /*NOTREACHED*/

  case DLT_FDDI:
    /*
     * XXX - check for LLC frames.
     */
    return gen_llc_linktype(cstate, ll_proto);
    /*NOTREACHED*/

  case DLT_IEEE802:
    /*
     * XXX - check for LLC PDUs, as per IEEE 802.5.
     */
    return gen_llc_linktype(cstate, ll_proto);
    /*NOTREACHED*/

  case DLT_ATM_RFC1483:
  case DLT_ATM_CLIP:
  case DLT_IP_OVER_FC:
    return gen_llc_linktype(cstate, ll_proto);
    /*NOTREACHED*/

  case DLT_SUNATM:
    /*
     * Check for an LLC-encapsulated version of this protocol;
     * if we were checking for LANE, linktype would no longer
     * be DLT_SUNATM.
     *
     * Check for LLC encapsulation and then check the protocol.
     */
    b0 = gen_atmfield_code_internal(cstate, A_PROTOTYPE, PT_LLC, BPF_JEQ, 0);
    b1 = gen_llc_linktype(cstate, ll_proto);
    gen_and(b0, b1);
    return b1;
    /*NOTREACHED*/

  case DLT_LINUX_SLL:
    return gen_linux_sll_linktype(cstate, ll_proto);
    /*NOTREACHED*/

  case DLT_SLIP:
  case DLT_SLIP_BSDOS:
  case DLT_RAW:
    /*
     * These types don't provide any type field; packets
     * are always IPv4 or IPv6.
     *
     * XXX - for IPv4, check for a version number of 4, and,
     * for IPv6, check for a version number of 6?
     */
    switch (ll_proto) {

    case ETHERTYPE_IP:
      /* Check for a version number of 4. */
      return gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, 0x40, 0xF0);

    case ETHERTYPE_IPV6:
      /* Check for a version number of 6. */
      return gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, 0x60, 0xF0);

    default:
      return gen_false(cstate); /* always false */
    }
    /*NOTREACHED*/

  case DLT_IPV4:
    /*
     * Raw IPv4, so no type field.
     */
    if (ll_proto == ETHERTYPE_IP)
      return gen_true(cstate);  /* always true */

    /* Checking for something other than IPv4; always false */
    return gen_false(cstate);
    /*NOTREACHED*/

  case DLT_IPV6:
    /*
     * Raw IPv6, so no type field.
     */
    if (ll_proto == ETHERTYPE_IPV6)
      return gen_true(cstate);  /* always true */

    /* Checking for something other than IPv6; always false */
    return gen_false(cstate);
    /*NOTREACHED*/

  case DLT_PPP:
  case DLT_PPP_PPPD:
  case DLT_PPP_SERIAL:
  case DLT_PPP_ETHER:
    /*
     * We use Ethernet protocol types inside libpcap;
     * map them to the corresponding PPP protocol types.
     */
    return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H,
        ethertype_to_ppptype(ll_proto));
    /*NOTREACHED*/

  case DLT_PPP_BSDOS:
    /*
     * We use Ethernet protocol types inside libpcap;
     * map them to the corresponding PPP protocol types.
     */
    switch (ll_proto) {

    case ETHERTYPE_IP:
      /*
       * Also check for Van Jacobson-compressed IP.
       * XXX - do this for other forms of PPP?
       */
      b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, PPP_IP);
      b1 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, PPP_VJC);
      gen_or(b0, b1);
      b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, PPP_VJNC);
      gen_or(b1, b0);
      return b0;

    default:
      return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H,
          ethertype_to_ppptype(ll_proto));
    }
    /*NOTREACHED*/

  case DLT_NULL:
  case DLT_LOOP:
  case DLT_ENC:
    switch (ll_proto) {

    case ETHERTYPE_IP:
      return (gen_loopback_linktype(cstate, AF_INET));

    case ETHERTYPE_IPV6:
      /*
       * AF_ values may, unfortunately, be platform-
       * dependent; AF_INET isn't, because everybody
       * used 4.2BSD's value, but AF_INET6 is, because
       * 4.2BSD didn't have a value for it (given that
       * IPv6 didn't exist back in the early 1980's),
       * and they all picked their own values.
       *
       * This means that, if we're reading from a
       * savefile, we need to check for all the
       * possible values.
       *
       * If we're doing a live capture, we only need
       * to check for this platform's value; however,
       * Npcap uses 24, which isn't Windows's AF_INET6
       * value.  (Given the multiple different values,
       * programs that read pcap files shouldn't be
       * checking for their platform's AF_INET6 value
       * anyway, they should check for all of the
       * possible values. and they might as well do
       * that even for live captures.)
       */
      if (cstate->bpf_pcap->rfile != NULL) {
        /*
         * Savefile - check for all three
         * possible IPv6 values.
         */
        b0 = gen_loopback_linktype(cstate, BSD_AFNUM_INET6_BSD);
        b1 = gen_loopback_linktype(cstate, BSD_AFNUM_INET6_FREEBSD);
        gen_or(b0, b1);
        b0 = gen_loopback_linktype(cstate, BSD_AFNUM_INET6_DARWIN);
        gen_or(b0, b1);
        return (b1);
      } else {
        /*
         * Live capture, so we only need to
         * check for the value used on this
         * platform.
         */
#ifdef _WIN32
        /*
         * Npcap doesn't use Windows's AF_INET6,
         * as that collides with AF_IPX on
         * some BSDs (both have the value 23).
         * Instead, it uses 24.
         */
        return (gen_loopback_linktype(cstate, 24));
#else /* _WIN32 */
#ifdef AF_INET6
        return (gen_loopback_linktype(cstate, AF_INET6));
#else /* AF_INET6 */
        /*
         * I guess this platform doesn't support
         * IPv6, so we just reject all packets.
         */
        return gen_false(cstate);
#endif /* AF_INET6 */
#endif /* _WIN32 */
      }

    default:
      /*
       * Not a type on which we support filtering.
       * XXX - support those that have AF_ values
       * #defined on this platform, at least?
       */
      return gen_false(cstate);
    }

  case DLT_PFLOG:
    /*
     * af field is host byte order in contrast to the rest of
     * the packet.
     */
    if (ll_proto == ETHERTYPE_IP)
      return (gen_cmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, af),
          BPF_B, AF_INET));
    else if (ll_proto == ETHERTYPE_IPV6)
      return (gen_cmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, af),
          BPF_B, AF_INET6));
    else
      return gen_false(cstate);
    /*NOTREACHED*/

  case DLT_ARCNET:
  case DLT_ARCNET_LINUX:
    /*
     * XXX should we check for first fragment if the protocol
     * uses PHDS?
     */
    switch (ll_proto) {

    default:
      return gen_false(cstate);

    case ETHERTYPE_IPV6:
      return (gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B,
        ARCTYPE_INET6));

    case ETHERTYPE_IP:
      b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B,
          ARCTYPE_IP);
      b1 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B,
          ARCTYPE_IP_OLD);
      gen_or(b0, b1);
      return (b1);

    case ETHERTYPE_ARP:
      b0 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B,
          ARCTYPE_ARP);
      b1 = gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B,
          ARCTYPE_ARP_OLD);
      gen_or(b0, b1);
      return (b1);

    case ETHERTYPE_REVARP:
      return (gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B,
          ARCTYPE_REVARP));

    case ETHERTYPE_ATALK:
      return (gen_cmp(cstate, OR_LINKTYPE, 0, BPF_B,
          ARCTYPE_ATALK));
    }
    /*NOTREACHED*/

  case DLT_LTALK:
    switch (ll_proto) {
    case ETHERTYPE_ATALK:
      return gen_true(cstate);
    default:
      return gen_false(cstate);
    }
    /*NOTREACHED*/

  case DLT_FRELAY:
    /*
     * XXX - assumes a 2-byte Frame Relay header with
     * DLCI and flags.  What if the address is longer?
     */
    switch (ll_proto) {

    case ETHERTYPE_IP:
      /*
       * Check for the special NLPID for IP.
       */
      return gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, (0x03<<8) | 0xcc);

    case ETHERTYPE_IPV6:
      /*
       * Check for the special NLPID for IPv6.
       */
      return gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, (0x03<<8) | 0x8e);

    case LLCSAP_ISONS:
      /*
       * Check for several OSI protocols.
       *
       * Frame Relay packets typically have an OSI
       * NLPID at the beginning; we check for each
       * of them.
       *
       * What we check for is the NLPID and a frame
       * control field of UI, i.e. 0x03 followed
       * by the NLPID.
       */
      b0 = gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, (0x03<<8) | ISO8473_CLNP);
      b1 = gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, (0x03<<8) | ISO9542_ESIS);
      b2 = gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, (0x03<<8) | ISO10589_ISIS);
      gen_or(b1, b2);
      gen_or(b0, b2);
      return b2;

    default:
      return gen_false(cstate);
    }
    /*NOTREACHED*/

  case DLT_MFR:
    bpf_error(cstate, "Multi-link Frame Relay link-layer type filtering not implemented");

        case DLT_JUNIPER_MFR:
        case DLT_JUNIPER_MLFR:
        case DLT_JUNIPER_MLPPP:
  case DLT_JUNIPER_ATM1:
  case DLT_JUNIPER_ATM2:
  case DLT_JUNIPER_PPPOE:
  case DLT_JUNIPER_PPPOE_ATM:
        case DLT_JUNIPER_GGSN:
        case DLT_JUNIPER_ES:
        case DLT_JUNIPER_MONITOR:
        case DLT_JUNIPER_SERVICES:
        case DLT_JUNIPER_ETHER:
        case DLT_JUNIPER_PPP:
        case DLT_JUNIPER_FRELAY:
        case DLT_JUNIPER_CHDLC:
        case DLT_JUNIPER_VP:
        case DLT_JUNIPER_ST:
        case DLT_JUNIPER_ISM:
        case DLT_JUNIPER_VS:
        case DLT_JUNIPER_SRX_E2E:
        case DLT_JUNIPER_FIBRECHANNEL:
  case DLT_JUNIPER_ATM_CEMIC:

    /* just lets verify the magic number for now -
     * on ATM we may have up to 6 different encapsulations on the wire
     * and need a lot of heuristics to figure out that the payload
     * might be;
     *
     * FIXME encapsulation specific BPF_ filters
     */
    return gen_mcmp(cstate, OR_LINKHDR, 0, BPF_W, 0x4d474300, 0xffffff00); /* compare the magic number */

  case DLT_BACNET_MS_TP:
    return gen_mcmp(cstate, OR_LINKHDR, 0, BPF_W, 0x55FF0000, 0xffff0000);

  case DLT_IPNET:
    return gen_ipnet_linktype(cstate, ll_proto);

  case DLT_LINUX_IRDA:
    bpf_error(cstate, "IrDA link-layer type filtering not implemented");

  case DLT_DOCSIS:
    bpf_error(cstate, "DOCSIS link-layer type filtering not implemented");

  case DLT_MTP2:
  case DLT_MTP2_WITH_PHDR:
    bpf_error(cstate, "MTP2 link-layer type filtering not implemented");

  case DLT_ERF:
    bpf_error(cstate, "ERF link-layer type filtering not implemented");

  case DLT_PFSYNC:
    bpf_error(cstate, "PFSYNC link-layer type filtering not implemented");

  case DLT_LINUX_LAPD:
    bpf_error(cstate, "LAPD link-layer type filtering not implemented");

  case DLT_USB_FREEBSD:
  case DLT_USB_LINUX:
  case DLT_USB_LINUX_MMAPPED:
  case DLT_USBPCAP:
    bpf_error(cstate, "USB link-layer type filtering not implemented");

  case DLT_BLUETOOTH_HCI_H4:
  case DLT_BLUETOOTH_HCI_H4_WITH_PHDR:
    bpf_error(cstate, "Bluetooth link-layer type filtering not implemented");

  case DLT_CAN20B:
  case DLT_CAN_SOCKETCAN:
    bpf_error(cstate, "CAN link-layer type filtering not implemented");

  case DLT_IEEE802_15_4:
  case DLT_IEEE802_15_4_LINUX:
  case DLT_IEEE802_15_4_NONASK_PHY:
  case DLT_IEEE802_15_4_NOFCS:
  case DLT_IEEE802_15_4_TAP:
    bpf_error(cstate, "IEEE 802.15.4 link-layer type filtering not implemented");

  case DLT_IEEE802_16_MAC_CPS_RADIO:
    bpf_error(cstate, "IEEE 802.16 link-layer type filtering not implemented");

  case DLT_SITA:
    bpf_error(cstate, "SITA link-layer type filtering not implemented");

  case DLT_RAIF1:
    bpf_error(cstate, "RAIF1 link-layer type filtering not implemented");

  case DLT_IPMB_KONTRON:
  case DLT_IPMB_LINUX:
    bpf_error(cstate, "IPMB link-layer type filtering not implemented");

  case DLT_AX25_KISS:
    bpf_error(cstate, "AX.25 link-layer type filtering not implemented");

  case DLT_NFLOG:
    /* Using the fixed-size NFLOG header it is possible to tell only
     * the address family of the packet, other meaningful data is
     * either missing or behind TLVs.
     */
    bpf_error(cstate, "NFLOG link-layer type filtering not implemented");

  default:
    /*
     * Does this link-layer header type have a field
     * indicating the type of the next protocol?  If
     * so, off_linktype.constant_part will be the offset of that
     * field in the packet; if not, it will be OFFSET_NOT_SET.
     */
    if (cstate->off_linktype.constant_part != OFFSET_NOT_SET) {
      /*
       * Yes; assume it's an Ethernet type.  (If
       * it's not, it needs to be handled specially
       * above.)
       */
      return gen_cmp(cstate, OR_LINKTYPE, 0, BPF_H, ll_proto);
      /*NOTREACHED */
    } else {
      /*
       * No; report an error.
       */
      description = pcap_datalink_val_to_description_or_dlt(cstate->linktype);
      bpf_error(cstate, "%s link-layer type filtering not implemented",
          description);
      /*NOTREACHED */
    }
  }
}

/*
 * Check for an LLC SNAP packet with a given organization code and
 * protocol type; we check the entire contents of the 802.2 LLC and
 * snap headers, checking for DSAP and SSAP of SNAP and a control
 * field of 0x03 in the LLC header, and for the specified organization
 * code and protocol type in the SNAP header.
 */
static struct block *
gen_snap(compiler_state_t *cstate, bpf_u_int32 orgcode, bpf_u_int32 ptype)
{
  u_char snapblock[8];

  snapblock[0] = LLCSAP_SNAP;   /* DSAP = SNAP */
  snapblock[1] = LLCSAP_SNAP;   /* SSAP = SNAP */
  snapblock[2] = 0x03;      /* control = UI */
  snapblock[3] = (u_char)(orgcode >> 16); /* upper 8 bits of organization code */
  snapblock[4] = (u_char)(orgcode >> 8);  /* middle 8 bits of organization code */
  snapblock[5] = (u_char)(orgcode >> 0);  /* lower 8 bits of organization code */
  snapblock[6] = (u_char)(ptype >> 8);  /* upper 8 bits of protocol type */
  snapblock[7] = (u_char)(ptype >> 0);  /* lower 8 bits of protocol type */
  return gen_bcmp(cstate, OR_LLC, 0, 8, snapblock);
}

/*
 * Generate code to match frames with an LLC header.
 */
static struct block *
gen_llc_internal(compiler_state_t *cstate)
{
  struct block *b0, *b1;

  switch (cstate->linktype) {

  case DLT_EN10MB:
    /*
     * We check for an Ethernet type field less than
     * 1500, which means it's an 802.3 length field.
     */
    b0 = gen_cmp_gt(cstate, OR_LINKTYPE, 0, BPF_H, ETHERMTU);
    gen_not(b0);

    /*
     * Now check for the purported DSAP and SSAP not being
     * 0xFF, to rule out NetWare-over-802.3.
     */
    b1 = gen_cmp(cstate, OR_LLC, 0, BPF_H, 0xFFFF);
    gen_not(b1);
    gen_and(b0, b1);
    return b1;

  case DLT_SUNATM:
    /*
     * We check for LLC traffic.
     */
    b0 = gen_atmtype_llc(cstate);
    return b0;

  case DLT_IEEE802: /* Token Ring */
    /*
     * XXX - check for LLC frames.
     */
    return gen_true(cstate);

  case DLT_FDDI:
    /*
     * XXX - check for LLC frames.
     */
    return gen_true(cstate);

  case DLT_ATM_RFC1483:
    /*
     * For LLC encapsulation, these are defined to have an
     * 802.2 LLC header.
     *
     * For VC encapsulation, they don't, but there's no
     * way to check for that; the protocol used on the VC
     * is negotiated out of band.
     */
    return gen_true(cstate);

  case DLT_IEEE802_11:
  case DLT_PRISM_HEADER:
  case DLT_IEEE802_11_RADIO:
  case DLT_IEEE802_11_RADIO_AVS:
  case DLT_PPI:
    /*
     * Check that we have a data frame.
     */
    b0 = gen_check_802_11_data_frame(cstate);
    return b0;

  default:
    bpf_error(cstate, "'llc' not supported for %s",
        pcap_datalink_val_to_description_or_dlt(cstate->linktype));
    /*NOTREACHED*/
  }
}

struct block *
gen_llc(compiler_state_t *cstate)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  return gen_llc_internal(cstate);
}

struct block *
gen_llc_i(compiler_state_t *cstate)
{
  struct block *b0, *b1;
  struct slist *s;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Check whether this is an LLC frame.
   */
  b0 = gen_llc_internal(cstate);

  /*
   * Load the control byte and test the low-order bit; it must
   * be clear for I frames.
   */
  s = gen_load_a(cstate, OR_LLC, 2, BPF_B);
  b1 = new_block(cstate, JMP(BPF_JSET));
  b1->s.k = 0x01;
  b1->stmts = s;
  gen_not(b1);
  gen_and(b0, b1);
  return b1;
}

struct block *
gen_llc_s(compiler_state_t *cstate)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Check whether this is an LLC frame.
   */
  b0 = gen_llc_internal(cstate);

  /*
   * Now compare the low-order 2 bit of the control byte against
   * the appropriate value for S frames.
   */
  b1 = gen_mcmp(cstate, OR_LLC, 2, BPF_B, LLC_S_FMT, 0x03);
  gen_and(b0, b1);
  return b1;
}

struct block *
gen_llc_u(compiler_state_t *cstate)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Check whether this is an LLC frame.
   */
  b0 = gen_llc_internal(cstate);

  /*
   * Now compare the low-order 2 bit of the control byte against
   * the appropriate value for U frames.
   */
  b1 = gen_mcmp(cstate, OR_LLC, 2, BPF_B, LLC_U_FMT, 0x03);
  gen_and(b0, b1);
  return b1;
}

struct block *
gen_llc_s_subtype(compiler_state_t *cstate, bpf_u_int32 subtype)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Check whether this is an LLC frame.
   */
  b0 = gen_llc_internal(cstate);

  /*
   * Now check for an S frame with the appropriate type.
   */
  b1 = gen_mcmp(cstate, OR_LLC, 2, BPF_B, subtype, LLC_S_CMD_MASK);
  gen_and(b0, b1);
  return b1;
}

struct block *
gen_llc_u_subtype(compiler_state_t *cstate, bpf_u_int32 subtype)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Check whether this is an LLC frame.
   */
  b0 = gen_llc_internal(cstate);

  /*
   * Now check for a U frame with the appropriate type.
   */
  b1 = gen_mcmp(cstate, OR_LLC, 2, BPF_B, subtype, LLC_U_CMD_MASK);
  gen_and(b0, b1);
  return b1;
}

/*
 * Generate code to match a particular packet type, for link-layer types
 * using 802.2 LLC headers.
 *
 * This is *NOT* used for Ethernet; "gen_ether_linktype()" is used
 * for that - it handles the D/I/X Ethernet vs. 802.3+802.2 issues.
 *
 * "proto" is an Ethernet type value, if > ETHERMTU, or an LLC SAP
 * value, if <= ETHERMTU.  We use that to determine whether to
 * match the DSAP or both DSAP and LSAP or to check the OUI and
 * protocol ID in a SNAP header.
 */
static struct block *
gen_llc_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
{
  /*
   * XXX - handle token-ring variable-length header.
   */
  switch (ll_proto) {

  case LLCSAP_IP:
  case LLCSAP_ISONS:
  case LLCSAP_NETBEUI:
    /*
     * XXX - should we check both the DSAP and the
     * SSAP, like this, or should we check just the
     * DSAP, as we do for other SAP values?
     */
    return gen_cmp(cstate, OR_LLC, 0, BPF_H, (bpf_u_int32)
           ((ll_proto << 8) | ll_proto));

  case LLCSAP_IPX:
    /*
     * XXX - are there ever SNAP frames for IPX on
     * non-Ethernet 802.x networks?
     */
    return gen_cmp(cstate, OR_LLC, 0, BPF_B, LLCSAP_IPX);

  case ETHERTYPE_ATALK:
    /*
     * 802.2-encapsulated ETHERTYPE_ATALK packets are
     * SNAP packets with an organization code of
     * 0x080007 (Apple, for Appletalk) and a protocol
     * type of ETHERTYPE_ATALK (Appletalk).
     *
     * XXX - check for an organization code of
     * encapsulated Ethernet as well?
     */
    return gen_snap(cstate, 0x080007, ETHERTYPE_ATALK);

  default:
    /*
     * XXX - we don't have to check for IPX 802.3
     * here, but should we check for the IPX Ethertype?
     */
    if (ll_proto <= ETHERMTU) {
      /*
       * This is an LLC SAP value, so check
       * the DSAP.
       */
      return gen_cmp(cstate, OR_LLC, 0, BPF_B, ll_proto);
    } else {
      /*
       * This is an Ethernet type; we assume that it's
       * unlikely that it'll appear in the right place
       * at random, and therefore check only the
       * location that would hold the Ethernet type
       * in a SNAP frame with an organization code of
       * 0x000000 (encapsulated Ethernet).
       *
       * XXX - if we were to check for the SNAP DSAP and
       * LSAP, as per XXX, and were also to check for an
       * organization code of 0x000000 (encapsulated
       * Ethernet), we'd do
       *
       *  return gen_snap(cstate, 0x000000, ll_proto);
       *
       * here; for now, we don't, as per the above.
       * I don't know whether it's worth the extra CPU
       * time to do the right check or not.
       */
      return gen_cmp(cstate, OR_LLC, 6, BPF_H, ll_proto);
    }
  }
}

static struct block *
gen_hostop(compiler_state_t *cstate, bpf_u_int32 addr, bpf_u_int32 mask,
    int dir, bpf_u_int32 ll_proto, u_int src_off, u_int dst_off)
{
  struct block *b0, *b1;
  u_int offset;

  switch (dir) {

  case Q_SRC:
    offset = src_off;
    break;

  case Q_DST:
    offset = dst_off;
    break;

  case Q_AND:
    b0 = gen_hostop(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
    b1 = gen_hostop(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_hostop(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
    b1 = gen_hostop(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is not a valid qualifier for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is not a valid qualifier for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  default:
    abort();
    /*NOTREACHED*/
  }
  b0 = gen_linktype(cstate, ll_proto);
  b1 = gen_mcmp(cstate, OR_LINKPL, offset, BPF_W, addr, mask);
  gen_and(b0, b1);
  return b1;
}

#ifdef INET6
static struct block *
gen_hostop6(compiler_state_t *cstate, struct in6_addr *addr,
    struct in6_addr *mask, int dir, bpf_u_int32 ll_proto, u_int src_off,
    u_int dst_off)
{
  struct block *b0, *b1;
  u_int offset;
  uint32_t *a, *m;

  switch (dir) {

  case Q_SRC:
    offset = src_off;
    break;

  case Q_DST:
    offset = dst_off;
    break;

  case Q_AND:
    b0 = gen_hostop6(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
    b1 = gen_hostop6(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_hostop6(cstate, addr, mask, Q_SRC, ll_proto, src_off, dst_off);
    b1 = gen_hostop6(cstate, addr, mask, Q_DST, ll_proto, src_off, dst_off);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is not a valid qualifier for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is not a valid qualifier for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  default:
    abort();
    /*NOTREACHED*/
  }
  /* this order is important */
  a = (uint32_t *)addr;
  m = (uint32_t *)mask;
  b1 = gen_mcmp(cstate, OR_LINKPL, offset + 12, BPF_W, ntohl(a[3]), ntohl(m[3]));
  b0 = gen_mcmp(cstate, OR_LINKPL, offset + 8, BPF_W, ntohl(a[2]), ntohl(m[2]));
  gen_and(b0, b1);
  b0 = gen_mcmp(cstate, OR_LINKPL, offset + 4, BPF_W, ntohl(a[1]), ntohl(m[1]));
  gen_and(b0, b1);
  b0 = gen_mcmp(cstate, OR_LINKPL, offset + 0, BPF_W, ntohl(a[0]), ntohl(m[0]));
  gen_and(b0, b1);
  b0 = gen_linktype(cstate, ll_proto);
  gen_and(b0, b1);
  return b1;
}
#endif

static struct block *
gen_ehostop(compiler_state_t *cstate, const u_char *eaddr, int dir)
{
  register struct block *b0, *b1;

  switch (dir) {
  case Q_SRC:
    return gen_bcmp(cstate, OR_LINKHDR, 6, 6, eaddr);

  case Q_DST:
    return gen_bcmp(cstate, OR_LINKHDR, 0, 6, eaddr);

  case Q_AND:
    b0 = gen_ehostop(cstate, eaddr, Q_SRC);
    b1 = gen_ehostop(cstate, eaddr, Q_DST);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_ehostop(cstate, eaddr, Q_SRC);
    b1 = gen_ehostop(cstate, eaddr, Q_DST);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are only supported on 802.11 with 802.11 headers");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are only supported on 802.11 with 802.11 headers");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are only supported on 802.11 with 802.11 headers");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are only supported on 802.11 with 802.11 headers");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is only supported on 802.11 with 802.11 headers");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is only supported on 802.11 with 802.11 headers");
    /*NOTREACHED*/
  }
  abort();
  /*NOTREACHED*/
}

/*
 * Like gen_ehostop, but for DLT_FDDI
 */
static struct block *
gen_fhostop(compiler_state_t *cstate, const u_char *eaddr, int dir)
{
  struct block *b0, *b1;

  switch (dir) {
  case Q_SRC:
    return gen_bcmp(cstate, OR_LINKHDR, 6 + 1 + cstate->pcap_fddipad, 6, eaddr);

  case Q_DST:
    return gen_bcmp(cstate, OR_LINKHDR, 0 + 1 + cstate->pcap_fddipad, 6, eaddr);

  case Q_AND:
    b0 = gen_fhostop(cstate, eaddr, Q_SRC);
    b1 = gen_fhostop(cstate, eaddr, Q_DST);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_fhostop(cstate, eaddr, Q_SRC);
    b1 = gen_fhostop(cstate, eaddr, Q_DST);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is only supported on 802.11");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is only supported on 802.11");
    /*NOTREACHED*/
  }
  abort();
  /*NOTREACHED*/
}

/*
 * Like gen_ehostop, but for DLT_IEEE802 (Token Ring)
 */
static struct block *
gen_thostop(compiler_state_t *cstate, const u_char *eaddr, int dir)
{
  register struct block *b0, *b1;

  switch (dir) {
  case Q_SRC:
    return gen_bcmp(cstate, OR_LINKHDR, 8, 6, eaddr);

  case Q_DST:
    return gen_bcmp(cstate, OR_LINKHDR, 2, 6, eaddr);

  case Q_AND:
    b0 = gen_thostop(cstate, eaddr, Q_SRC);
    b1 = gen_thostop(cstate, eaddr, Q_DST);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_thostop(cstate, eaddr, Q_SRC);
    b1 = gen_thostop(cstate, eaddr, Q_DST);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is only supported on 802.11");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is only supported on 802.11");
    /*NOTREACHED*/
  }
  abort();
  /*NOTREACHED*/
}

/*
 * Like gen_ehostop, but for DLT_IEEE802_11 (802.11 wireless LAN) and
 * various 802.11 + radio headers.
 */
static struct block *
gen_wlanhostop(compiler_state_t *cstate, const u_char *eaddr, int dir)
{
  register struct block *b0, *b1, *b2;
  register struct slist *s;

#ifdef ENABLE_WLAN_FILTERING_PATCH
  /*
   * TODO GV 20070613
   * We need to disable the optimizer because the optimizer is buggy
   * and wipes out some LD instructions generated by the below
   * code to validate the Frame Control bits
   */
  cstate->no_optimize = 1;
#endif /* ENABLE_WLAN_FILTERING_PATCH */

  switch (dir) {
  case Q_SRC:
    /*
     * Oh, yuk.
     *
     *  For control frames, there is no SA.
     *
     *  For management frames, SA is at an
     *  offset of 10 from the beginning of
     *  the packet.
     *
     *  For data frames, SA is at an offset
     *  of 10 from the beginning of the packet
     *  if From DS is clear, at an offset of
     *  16 from the beginning of the packet
     *  if From DS is set and To DS is clear,
     *  and an offset of 24 from the beginning
     *  of the packet if From DS is set and To DS
     *  is set.
     */

    /*
     * Generate the tests to be done for data frames
     * with From DS set.
     *
     * First, check for To DS set, i.e. check "link[1] & 0x01".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x01; /* To DS */
    b1->stmts = s;

    /*
     * If To DS is set, the SA is at 24.
     */
    b0 = gen_bcmp(cstate, OR_LINKHDR, 24, 6, eaddr);
    gen_and(b1, b0);

    /*
     * Now, check for To DS not set, i.e. check
     * "!(link[1] & 0x01)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
    b2 = new_block(cstate, JMP(BPF_JSET));
    b2->s.k = 0x01; /* To DS */
    b2->stmts = s;
    gen_not(b2);

    /*
     * If To DS is not set, the SA is at 16.
     */
    b1 = gen_bcmp(cstate, OR_LINKHDR, 16, 6, eaddr);
    gen_and(b2, b1);

    /*
     * Now OR together the last two checks.  That gives
     * the complete set of checks for data frames with
     * From DS set.
     */
    gen_or(b1, b0);

    /*
     * Now check for From DS being set, and AND that with
     * the ORed-together checks.
     */
    s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x02; /* From DS */
    b1->stmts = s;
    gen_and(b1, b0);

    /*
     * Now check for data frames with From DS not set.
     */
    s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
    b2 = new_block(cstate, JMP(BPF_JSET));
    b2->s.k = 0x02; /* From DS */
    b2->stmts = s;
    gen_not(b2);

    /*
     * If From DS isn't set, the SA is at 10.
     */
    b1 = gen_bcmp(cstate, OR_LINKHDR, 10, 6, eaddr);
    gen_and(b2, b1);

    /*
     * Now OR together the checks for data frames with
     * From DS not set and for data frames with From DS
     * set; that gives the checks done for data frames.
     */
    gen_or(b1, b0);

    /*
     * Now check for a data frame.
     * I.e, check "link[0] & 0x08".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x08;
    b1->stmts = s;

    /*
     * AND that with the checks done for data frames.
     */
    gen_and(b1, b0);

    /*
     * If the high-order bit of the type value is 0, this
     * is a management frame.
     * I.e, check "!(link[0] & 0x08)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b2 = new_block(cstate, JMP(BPF_JSET));
    b2->s.k = 0x08;
    b2->stmts = s;
    gen_not(b2);

    /*
     * For management frames, the SA is at 10.
     */
    b1 = gen_bcmp(cstate, OR_LINKHDR, 10, 6, eaddr);
    gen_and(b2, b1);

    /*
     * OR that with the checks done for data frames.
     * That gives the checks done for management and
     * data frames.
     */
    gen_or(b1, b0);

    /*
     * If the low-order bit of the type value is 1,
     * this is either a control frame or a frame
     * with a reserved type, and thus not a
     * frame with an SA.
     *
     * I.e., check "!(link[0] & 0x04)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x04;
    b1->stmts = s;
    gen_not(b1);

    /*
     * AND that with the checks for data and management
     * frames.
     */
    gen_and(b1, b0);
    return b0;

  case Q_DST:
    /*
     * Oh, yuk.
     *
     *  For control frames, there is no DA.
     *
     *  For management frames, DA is at an
     *  offset of 4 from the beginning of
     *  the packet.
     *
     *  For data frames, DA is at an offset
     *  of 4 from the beginning of the packet
     *  if To DS is clear and at an offset of
     *  16 from the beginning of the packet
     *  if To DS is set.
     */

    /*
     * Generate the tests to be done for data frames.
     *
     * First, check for To DS set, i.e. "link[1] & 0x01".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x01; /* To DS */
    b1->stmts = s;

    /*
     * If To DS is set, the DA is at 16.
     */
    b0 = gen_bcmp(cstate, OR_LINKHDR, 16, 6, eaddr);
    gen_and(b1, b0);

    /*
     * Now, check for To DS not set, i.e. check
     * "!(link[1] & 0x01)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
    b2 = new_block(cstate, JMP(BPF_JSET));
    b2->s.k = 0x01; /* To DS */
    b2->stmts = s;
    gen_not(b2);

    /*
     * If To DS is not set, the DA is at 4.
     */
    b1 = gen_bcmp(cstate, OR_LINKHDR, 4, 6, eaddr);
    gen_and(b2, b1);

    /*
     * Now OR together the last two checks.  That gives
     * the complete set of checks for data frames.
     */
    gen_or(b1, b0);

    /*
     * Now check for a data frame.
     * I.e, check "link[0] & 0x08".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x08;
    b1->stmts = s;

    /*
     * AND that with the checks done for data frames.
     */
    gen_and(b1, b0);

    /*
     * If the high-order bit of the type value is 0, this
     * is a management frame.
     * I.e, check "!(link[0] & 0x08)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b2 = new_block(cstate, JMP(BPF_JSET));
    b2->s.k = 0x08;
    b2->stmts = s;
    gen_not(b2);

    /*
     * For management frames, the DA is at 4.
     */
    b1 = gen_bcmp(cstate, OR_LINKHDR, 4, 6, eaddr);
    gen_and(b2, b1);

    /*
     * OR that with the checks done for data frames.
     * That gives the checks done for management and
     * data frames.
     */
    gen_or(b1, b0);

    /*
     * If the low-order bit of the type value is 1,
     * this is either a control frame or a frame
     * with a reserved type, and thus not a
     * frame with an SA.
     *
     * I.e., check "!(link[0] & 0x04)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x04;
    b1->stmts = s;
    gen_not(b1);

    /*
     * AND that with the checks for data and management
     * frames.
     */
    gen_and(b1, b0);
    return b0;

  case Q_AND:
    b0 = gen_wlanhostop(cstate, eaddr, Q_SRC);
    b1 = gen_wlanhostop(cstate, eaddr, Q_DST);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_wlanhostop(cstate, eaddr, Q_SRC);
    b1 = gen_wlanhostop(cstate, eaddr, Q_DST);
    gen_or(b0, b1);
    return b1;

  /*
   * XXX - add BSSID keyword?
   */
  case Q_ADDR1:
    return (gen_bcmp(cstate, OR_LINKHDR, 4, 6, eaddr));

  case Q_ADDR2:
    /*
     * Not present in CTS or ACK control frames.
     */
    b0 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, IEEE80211_FC0_TYPE_CTL,
      IEEE80211_FC0_TYPE_MASK);
    gen_not(b0);
    b1 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, IEEE80211_FC0_SUBTYPE_CTS,
      IEEE80211_FC0_SUBTYPE_MASK);
    gen_not(b1);
    b2 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, IEEE80211_FC0_SUBTYPE_ACK,
      IEEE80211_FC0_SUBTYPE_MASK);
    gen_not(b2);
    gen_and(b1, b2);
    gen_or(b0, b2);
    b1 = gen_bcmp(cstate, OR_LINKHDR, 10, 6, eaddr);
    gen_and(b2, b1);
    return b1;

  case Q_ADDR3:
    /*
     * Not present in control frames.
     */
    b0 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, IEEE80211_FC0_TYPE_CTL,
      IEEE80211_FC0_TYPE_MASK);
    gen_not(b0);
    b1 = gen_bcmp(cstate, OR_LINKHDR, 16, 6, eaddr);
    gen_and(b0, b1);
    return b1;

  case Q_ADDR4:
    /*
     * Present only if the direction mask has both "From DS"
     * and "To DS" set.  Neither control frames nor management
     * frames should have both of those set, so we don't
     * check the frame type.
     */
    b0 = gen_mcmp(cstate, OR_LINKHDR, 1, BPF_B,
      IEEE80211_FC1_DIR_DSTODS, IEEE80211_FC1_DIR_MASK);
    b1 = gen_bcmp(cstate, OR_LINKHDR, 24, 6, eaddr);
    gen_and(b0, b1);
    return b1;

  case Q_RA:
    /*
     * Not present in management frames; addr1 in other
     * frames.
     */

    /*
     * If the high-order bit of the type value is 0, this
     * is a management frame.
     * I.e, check "(link[0] & 0x08)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x08;
    b1->stmts = s;

    /*
     * Check addr1.
     */
    b0 = gen_bcmp(cstate, OR_LINKHDR, 4, 6, eaddr);

    /*
     * AND that with the check of addr1.
     */
    gen_and(b1, b0);
    return (b0);

  case Q_TA:
    /*
     * Not present in management frames; addr2, if present,
     * in other frames.
     */

    /*
     * Not present in CTS or ACK control frames.
     */
    b0 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, IEEE80211_FC0_TYPE_CTL,
      IEEE80211_FC0_TYPE_MASK);
    gen_not(b0);
    b1 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, IEEE80211_FC0_SUBTYPE_CTS,
      IEEE80211_FC0_SUBTYPE_MASK);
    gen_not(b1);
    b2 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, IEEE80211_FC0_SUBTYPE_ACK,
      IEEE80211_FC0_SUBTYPE_MASK);
    gen_not(b2);
    gen_and(b1, b2);
    gen_or(b0, b2);

    /*
     * If the high-order bit of the type value is 0, this
     * is a management frame.
     * I.e, check "(link[0] & 0x08)".
     */
    s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
    b1 = new_block(cstate, JMP(BPF_JSET));
    b1->s.k = 0x08;
    b1->stmts = s;

    /*
     * AND that with the check for frames other than
     * CTS and ACK frames.
     */
    gen_and(b1, b2);

    /*
     * Check addr2.
     */
    b1 = gen_bcmp(cstate, OR_LINKHDR, 10, 6, eaddr);
    gen_and(b2, b1);
    return b1;
  }
  abort();
  /*NOTREACHED*/
}

/*
 * Like gen_ehostop, but for RFC 2625 IP-over-Fibre-Channel.
 * (We assume that the addresses are IEEE 48-bit MAC addresses,
 * as the RFC states.)
 */
static struct block *
gen_ipfchostop(compiler_state_t *cstate, const u_char *eaddr, int dir)
{
  register struct block *b0, *b1;

  switch (dir) {
  case Q_SRC:
    return gen_bcmp(cstate, OR_LINKHDR, 10, 6, eaddr);

  case Q_DST:
    return gen_bcmp(cstate, OR_LINKHDR, 2, 6, eaddr);

  case Q_AND:
    b0 = gen_ipfchostop(cstate, eaddr, Q_SRC);
    b1 = gen_ipfchostop(cstate, eaddr, Q_DST);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_ipfchostop(cstate, eaddr, Q_SRC);
    b1 = gen_ipfchostop(cstate, eaddr, Q_DST);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is only supported on 802.11");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is only supported on 802.11");
    /*NOTREACHED*/
  }
  abort();
  /*NOTREACHED*/
}

/*
 * This is quite tricky because there may be pad bytes in front of the
 * DECNET header, and then there are two possible data packet formats that
 * carry both src and dst addresses, plus 5 packet types in a format that
 * carries only the src node, plus 2 types that use a different format and
 * also carry just the src node.
 *
 * Yuck.
 *
 * Instead of doing those all right, we just look for data packets with
 * 0 or 1 bytes of padding.  If you want to look at other packets, that
 * will require a lot more hacking.
 *
 * To add support for filtering on DECNET "areas" (network numbers)
 * one would want to add a "mask" argument to this routine.  That would
 * make the filter even more inefficient, although one could be clever
 * and not generate masking instructions if the mask is 0xFFFF.
 */
static struct block *
gen_dnhostop(compiler_state_t *cstate, bpf_u_int32 addr, int dir)
{
  struct block *b0, *b1, *b2, *tmp;
  u_int offset_lh;  /* offset if long header is received */
  u_int offset_sh;  /* offset if short header is received */

  switch (dir) {

  case Q_DST:
    offset_sh = 1;  /* follows flags */
    offset_lh = 7;  /* flgs,darea,dsubarea,HIORD */
    break;

  case Q_SRC:
    offset_sh = 3;  /* follows flags, dstnode */
    offset_lh = 15; /* flgs,darea,dsubarea,did,sarea,ssub,HIORD */
    break;

  case Q_AND:
    /* Inefficient because we do our Calvinball dance twice */
    b0 = gen_dnhostop(cstate, addr, Q_SRC);
    b1 = gen_dnhostop(cstate, addr, Q_DST);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    /* Inefficient because we do our Calvinball dance twice */
    b0 = gen_dnhostop(cstate, addr, Q_SRC);
    b1 = gen_dnhostop(cstate, addr, Q_DST);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are not valid qualifiers for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is not a valid qualifier for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is not a valid qualifier for addresses other than 802.11 MAC addresses");
    /*NOTREACHED*/

  default:
    abort();
    /*NOTREACHED*/
  }
  b0 = gen_linktype(cstate, ETHERTYPE_DN);
  /* Check for pad = 1, long header case */
  tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_H,
      (bpf_u_int32)ntohs(0x0681), (bpf_u_int32)ntohs(0x07FF));
  b1 = gen_cmp(cstate, OR_LINKPL, 2 + 1 + offset_lh,
      BPF_H, (bpf_u_int32)ntohs((u_short)addr));
  gen_and(tmp, b1);
  /* Check for pad = 0, long header case */
  tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_B, (bpf_u_int32)0x06,
      (bpf_u_int32)0x7);
  b2 = gen_cmp(cstate, OR_LINKPL, 2 + offset_lh, BPF_H,
      (bpf_u_int32)ntohs((u_short)addr));
  gen_and(tmp, b2);
  gen_or(b2, b1);
  /* Check for pad = 1, short header case */
  tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_H,
      (bpf_u_int32)ntohs(0x0281), (bpf_u_int32)ntohs(0x07FF));
  b2 = gen_cmp(cstate, OR_LINKPL, 2 + 1 + offset_sh, BPF_H,
      (bpf_u_int32)ntohs((u_short)addr));
  gen_and(tmp, b2);
  gen_or(b2, b1);
  /* Check for pad = 0, short header case */
  tmp = gen_mcmp(cstate, OR_LINKPL, 2, BPF_B, (bpf_u_int32)0x02,
      (bpf_u_int32)0x7);
  b2 = gen_cmp(cstate, OR_LINKPL, 2 + offset_sh, BPF_H,
      (bpf_u_int32)ntohs((u_short)addr));
  gen_and(tmp, b2);
  gen_or(b2, b1);

  /* Combine with test for cstate->linktype */
  gen_and(b0, b1);
  return b1;
}

/*
 * Generate a check for IPv4 or IPv6 for MPLS-encapsulated packets;
 * test the bottom-of-stack bit, and then check the version number
 * field in the IP header.
 */
static struct block *
gen_mpls_linktype(compiler_state_t *cstate, bpf_u_int32 ll_proto)
{
  struct block *b0, *b1;

        switch (ll_proto) {

        case ETHERTYPE_IP:
                /* match the bottom-of-stack bit */
                b0 = gen_mcmp(cstate, OR_LINKPL, (u_int)-2, BPF_B, 0x01, 0x01);
                /* match the IPv4 version number */
                b1 = gen_mcmp(cstate, OR_LINKPL, 0, BPF_B, 0x40, 0xf0);
                gen_and(b0, b1);
                return b1;

        case ETHERTYPE_IPV6:
                /* match the bottom-of-stack bit */
                b0 = gen_mcmp(cstate, OR_LINKPL, (u_int)-2, BPF_B, 0x01, 0x01);
                /* match the IPv4 version number */
                b1 = gen_mcmp(cstate, OR_LINKPL, 0, BPF_B, 0x60, 0xf0);
                gen_and(b0, b1);
                return b1;

        default:
               /* FIXME add other L3 proto IDs */
               bpf_error(cstate, "unsupported protocol over mpls");
               /*NOTREACHED*/
        }
}

static struct block *
gen_host(compiler_state_t *cstate, bpf_u_int32 addr, bpf_u_int32 mask,
    int proto, int dir, int type)
{
  struct block *b0, *b1;
  const char *typestr;

  if (type == Q_NET)
    typestr = "net";
  else
    typestr = "host";

  switch (proto) {

  case Q_DEFAULT:
    b0 = gen_host(cstate, addr, mask, Q_IP, dir, type);
    /*
     * Only check for non-IPv4 addresses if we're not
     * checking MPLS-encapsulated packets.
     */
    if (cstate->label_stack_depth == 0) {
      b1 = gen_host(cstate, addr, mask, Q_ARP, dir, type);
      gen_or(b0, b1);
      b0 = gen_host(cstate, addr, mask, Q_RARP, dir, type);
      gen_or(b1, b0);
    }
    return b0;

  case Q_LINK:
    bpf_error(cstate, "link-layer modifier applied to %s", typestr);

  case Q_IP:
    return gen_hostop(cstate, addr, mask, dir, ETHERTYPE_IP, 12, 16);

  case Q_RARP:
    return gen_hostop(cstate, addr, mask, dir, ETHERTYPE_REVARP, 14, 24);

  case Q_ARP:
    return gen_hostop(cstate, addr, mask, dir, ETHERTYPE_ARP, 14, 24);

  case Q_SCTP:
    bpf_error(cstate, "'sctp' modifier applied to %s", typestr);

  case Q_TCP:
    bpf_error(cstate, "'tcp' modifier applied to %s", typestr);

  case Q_UDP:
    bpf_error(cstate, "'udp' modifier applied to %s", typestr);

  case Q_ICMP:
    bpf_error(cstate, "'icmp' modifier applied to %s", typestr);

  case Q_IGMP:
    bpf_error(cstate, "'igmp' modifier applied to %s", typestr);

  case Q_IGRP:
    bpf_error(cstate, "'igrp' modifier applied to %s", typestr);

  case Q_ATALK:
    bpf_error(cstate, "AppleTalk host filtering not implemented");

  case Q_DECNET:
    return gen_dnhostop(cstate, addr, dir);

  case Q_LAT:
    bpf_error(cstate, "LAT host filtering not implemented");

  case Q_SCA:
    bpf_error(cstate, "SCA host filtering not implemented");

  case Q_MOPRC:
    bpf_error(cstate, "MOPRC host filtering not implemented");

  case Q_MOPDL:
    bpf_error(cstate, "MOPDL host filtering not implemented");

  case Q_IPV6:
    bpf_error(cstate, "'ip6' modifier applied to ip host");

  case Q_ICMPV6:
    bpf_error(cstate, "'icmp6' modifier applied to %s", typestr);

  case Q_AH:
    bpf_error(cstate, "'ah' modifier applied to %s", typestr);

  case Q_ESP:
    bpf_error(cstate, "'esp' modifier applied to %s", typestr);

  case Q_PIM:
    bpf_error(cstate, "'pim' modifier applied to %s", typestr);

  case Q_VRRP:
    bpf_error(cstate, "'vrrp' modifier applied to %s", typestr);

  case Q_AARP:
    bpf_error(cstate, "AARP host filtering not implemented");

  case Q_ISO:
    bpf_error(cstate, "ISO host filtering not implemented");

  case Q_ESIS:
    bpf_error(cstate, "'esis' modifier applied to %s", typestr);

  case Q_ISIS:
    bpf_error(cstate, "'isis' modifier applied to %s", typestr);

  case Q_CLNP:
    bpf_error(cstate, "'clnp' modifier applied to %s", typestr);

  case Q_STP:
    bpf_error(cstate, "'stp' modifier applied to %s", typestr);

  case Q_IPX:
    bpf_error(cstate, "IPX host filtering not implemented");

  case Q_NETBEUI:
    bpf_error(cstate, "'netbeui' modifier applied to %s", typestr);

  case Q_ISIS_L1:
    bpf_error(cstate, "'l1' modifier applied to %s", typestr);

  case Q_ISIS_L2:
    bpf_error(cstate, "'l2' modifier applied to %s", typestr);

  case Q_ISIS_IIH:
    bpf_error(cstate, "'iih' modifier applied to %s", typestr);

  case Q_ISIS_SNP:
    bpf_error(cstate, "'snp' modifier applied to %s", typestr);

  case Q_ISIS_CSNP:
    bpf_error(cstate, "'csnp' modifier applied to %s", typestr);

  case Q_ISIS_PSNP:
    bpf_error(cstate, "'psnp' modifier applied to %s", typestr);

  case Q_ISIS_LSP:
    bpf_error(cstate, "'lsp' modifier applied to %s", typestr);

  case Q_RADIO:
    bpf_error(cstate, "'radio' modifier applied to %s", typestr);

  case Q_CARP:
    bpf_error(cstate, "'carp' modifier applied to %s", typestr);

  default:
    abort();
  }
  /*NOTREACHED*/
}

#ifdef INET6
static struct block *
gen_host6(compiler_state_t *cstate, struct in6_addr *addr,
    struct in6_addr *mask, int proto, int dir, int type)
{
  const char *typestr;

  if (type == Q_NET)
    typestr = "net";
  else
    typestr = "host";

  switch (proto) {

  case Q_DEFAULT:
    return gen_host6(cstate, addr, mask, Q_IPV6, dir, type);

  case Q_LINK:
    bpf_error(cstate, "link-layer modifier applied to ip6 %s", typestr);

  case Q_IP:
    bpf_error(cstate, "'ip' modifier applied to ip6 %s", typestr);

  case Q_RARP:
    bpf_error(cstate, "'rarp' modifier applied to ip6 %s", typestr);

  case Q_ARP:
    bpf_error(cstate, "'arp' modifier applied to ip6 %s", typestr);

  case Q_SCTP:
    bpf_error(cstate, "'sctp' modifier applied to ip6 %s", typestr);

  case Q_TCP:
    bpf_error(cstate, "'tcp' modifier applied to ip6 %s", typestr);

  case Q_UDP:
    bpf_error(cstate, "'udp' modifier applied to ip6 %s", typestr);

  case Q_ICMP:
    bpf_error(cstate, "'icmp' modifier applied to ip6 %s", typestr);

  case Q_IGMP:
    bpf_error(cstate, "'igmp' modifier applied to ip6 %s", typestr);

  case Q_IGRP:
    bpf_error(cstate, "'igrp' modifier applied to ip6 %s", typestr);

  case Q_ATALK:
    bpf_error(cstate, "AppleTalk modifier applied to ip6 %s", typestr);

  case Q_DECNET:
    bpf_error(cstate, "'decnet' modifier applied to ip6 %s", typestr);

  case Q_LAT:
    bpf_error(cstate, "'lat' modifier applied to ip6 %s", typestr);

  case Q_SCA:
    bpf_error(cstate, "'sca' modifier applied to ip6 %s", typestr);

  case Q_MOPRC:
    bpf_error(cstate, "'moprc' modifier applied to ip6 %s", typestr);

  case Q_MOPDL:
    bpf_error(cstate, "'mopdl' modifier applied to ip6 %s", typestr);

  case Q_IPV6:
    return gen_hostop6(cstate, addr, mask, dir, ETHERTYPE_IPV6, 8, 24);

  case Q_ICMPV6:
    bpf_error(cstate, "'icmp6' modifier applied to ip6 %s", typestr);

  case Q_AH:
    bpf_error(cstate, "'ah' modifier applied to ip6 %s", typestr);

  case Q_ESP:
    bpf_error(cstate, "'esp' modifier applied to ip6 %s", typestr);

  case Q_PIM:
    bpf_error(cstate, "'pim' modifier applied to ip6 %s", typestr);

  case Q_VRRP:
    bpf_error(cstate, "'vrrp' modifier applied to ip6 %s", typestr);

  case Q_AARP:
    bpf_error(cstate, "'aarp' modifier applied to ip6 %s", typestr);

  case Q_ISO:
    bpf_error(cstate, "'iso' modifier applied to ip6 %s", typestr);

  case Q_ESIS:
    bpf_error(cstate, "'esis' modifier applied to ip6 %s", typestr);

  case Q_ISIS:
    bpf_error(cstate, "'isis' modifier applied to ip6 %s", typestr);

  case Q_CLNP:
    bpf_error(cstate, "'clnp' modifier applied to ip6 %s", typestr);

  case Q_STP:
    bpf_error(cstate, "'stp' modifier applied to ip6 %s", typestr);

  case Q_IPX:
    bpf_error(cstate, "'ipx' modifier applied to ip6 %s", typestr);

  case Q_NETBEUI:
    bpf_error(cstate, "'netbeui' modifier applied to ip6 %s", typestr);

  case Q_ISIS_L1:
    bpf_error(cstate, "'l1' modifier applied to ip6 %s", typestr);

  case Q_ISIS_L2:
    bpf_error(cstate, "'l2' modifier applied to ip6 %s", typestr);

  case Q_ISIS_IIH:
    bpf_error(cstate, "'iih' modifier applied to ip6 %s", typestr);

  case Q_ISIS_SNP:
    bpf_error(cstate, "'snp' modifier applied to ip6 %s", typestr);

  case Q_ISIS_CSNP:
    bpf_error(cstate, "'csnp' modifier applied to ip6 %s", typestr);

  case Q_ISIS_PSNP:
    bpf_error(cstate, "'psnp' modifier applied to ip6 %s", typestr);

  case Q_ISIS_LSP:
    bpf_error(cstate, "'lsp' modifier applied to ip6 %s", typestr);

  case Q_RADIO:
    bpf_error(cstate, "'radio' modifier applied to ip6 %s", typestr);

  case Q_CARP:
    bpf_error(cstate, "'carp' modifier applied to ip6 %s", typestr);

  default:
    abort();
  }
  /*NOTREACHED*/
}
#endif

#ifndef INET6
static struct block *
gen_gateway(compiler_state_t *cstate, const u_char *eaddr,
    struct addrinfo *alist, int proto, int dir)
{
  struct block *b0, *b1, *tmp;
  struct addrinfo *ai;
  struct sockaddr_in *sin;

  if (dir != 0)
    bpf_error(cstate, "direction applied to 'gateway'");

  switch (proto) {
  case Q_DEFAULT:
  case Q_IP:
  case Q_ARP:
  case Q_RARP:
    switch (cstate->linktype) {
    case DLT_EN10MB:
    case DLT_NETANALYZER:
    case DLT_NETANALYZER_TRANSPARENT:
      b1 = gen_prevlinkhdr_check(cstate);
      b0 = gen_ehostop(cstate, eaddr, Q_OR);
      if (b1 != NULL)
        gen_and(b1, b0);
      break;
    case DLT_FDDI:
      b0 = gen_fhostop(cstate, eaddr, Q_OR);
      break;
    case DLT_IEEE802:
      b0 = gen_thostop(cstate, eaddr, Q_OR);
      break;
    case DLT_IEEE802_11:
    case DLT_PRISM_HEADER:
    case DLT_IEEE802_11_RADIO_AVS:
    case DLT_IEEE802_11_RADIO:
    case DLT_PPI:
      b0 = gen_wlanhostop(cstate, eaddr, Q_OR);
      break;
    case DLT_SUNATM:
      /*
       * This is LLC-multiplexed traffic; if it were
       * LANE, cstate->linktype would have been set to
       * DLT_EN10MB.
       */
      bpf_error(cstate,
          "'gateway' supported only on ethernet/FDDI/token ring/802.11/ATM LANE/Fibre Channel");
      break;
    case DLT_IP_OVER_FC:
      b0 = gen_ipfchostop(cstate, eaddr, Q_OR);
      break;
    default:
      bpf_error(cstate,
          "'gateway' supported only on ethernet/FDDI/token ring/802.11/ATM LANE/Fibre Channel");
    }
    b1 = NULL;
    for (ai = alist; ai != NULL; ai = ai->ai_next) {
      /*
       * Does it have an address?
       */
      if (ai->ai_addr != NULL) {
        /*
         * Yes.  Is it an IPv4 address?
         */
        if (ai->ai_addr->sa_family == AF_INET) {
          /*
           * Generate an entry for it.
           */
          sin = (struct sockaddr_in *)ai->ai_addr;
          tmp = gen_host(cstate,
              ntohl(sin->sin_addr.s_addr),
              0xffffffff, proto, Q_OR, Q_HOST);
          /*
           * Is it the *first* IPv4 address?
           */
          if (b1 == NULL) {
            /*
             * Yes, so start with it.
             */
            b1 = tmp;
          } else {
            /*
             * No, so OR it into the
             * existing set of
             * addresses.
             */
            gen_or(b1, tmp);
            b1 = tmp;
          }
        }
      }
    }
    if (b1 == NULL) {
      /*
       * No IPv4 addresses found.
       */
      return (NULL);
    }
    gen_not(b1);
    gen_and(b0, b1);
    return b1;
  }
  bpf_error(cstate, "illegal modifier of 'gateway'");
  /*NOTREACHED*/
}
#endif

static struct block *
gen_proto_abbrev_internal(compiler_state_t *cstate, int proto)
{
  struct block *b0;
  struct block *b1;

  switch (proto) {

  case Q_SCTP:
    b1 = gen_proto(cstate, IPPROTO_SCTP, Q_DEFAULT, Q_DEFAULT);
    break;

  case Q_TCP:
    b1 = gen_proto(cstate, IPPROTO_TCP, Q_DEFAULT, Q_DEFAULT);
    break;

  case Q_UDP:
    b1 = gen_proto(cstate, IPPROTO_UDP, Q_DEFAULT, Q_DEFAULT);
    break;

  case Q_ICMP:
    b1 = gen_proto(cstate, IPPROTO_ICMP, Q_IP, Q_DEFAULT);
    break;

#ifndef IPPROTO_IGMP
#define IPPROTO_IGMP  2
#endif

  case Q_IGMP:
    b1 = gen_proto(cstate, IPPROTO_IGMP, Q_IP, Q_DEFAULT);
    break;

#ifndef IPPROTO_IGRP
#define IPPROTO_IGRP  9
#endif
  case Q_IGRP:
    b1 = gen_proto(cstate, IPPROTO_IGRP, Q_IP, Q_DEFAULT);
    break;

#ifndef IPPROTO_PIM
#define IPPROTO_PIM 103
#endif

  case Q_PIM:
    b1 = gen_proto(cstate, IPPROTO_PIM, Q_DEFAULT, Q_DEFAULT);
    break;

#ifndef IPPROTO_VRRP
#define IPPROTO_VRRP  112
#endif

  case Q_VRRP:
    b1 = gen_proto(cstate, IPPROTO_VRRP, Q_IP, Q_DEFAULT);
    break;

#ifndef IPPROTO_CARP
#define IPPROTO_CARP  112
#endif

  case Q_CARP:
    b1 = gen_proto(cstate, IPPROTO_CARP, Q_IP, Q_DEFAULT);
    break;

  case Q_IP:
    b1 = gen_linktype(cstate, ETHERTYPE_IP);
    break;

  case Q_ARP:
    b1 = gen_linktype(cstate, ETHERTYPE_ARP);
    break;

  case Q_RARP:
    b1 = gen_linktype(cstate, ETHERTYPE_REVARP);
    break;

  case Q_LINK:
    bpf_error(cstate, "link layer applied in wrong context");

  case Q_ATALK:
    b1 = gen_linktype(cstate, ETHERTYPE_ATALK);
    break;

  case Q_AARP:
    b1 = gen_linktype(cstate, ETHERTYPE_AARP);
    break;

  case Q_DECNET:
    b1 = gen_linktype(cstate, ETHERTYPE_DN);
    break;

  case Q_SCA:
    b1 = gen_linktype(cstate, ETHERTYPE_SCA);
    break;

  case Q_LAT:
    b1 = gen_linktype(cstate, ETHERTYPE_LAT);
    break;

  case Q_MOPDL:
    b1 = gen_linktype(cstate, ETHERTYPE_MOPDL);
    break;

  case Q_MOPRC:
    b1 = gen_linktype(cstate, ETHERTYPE_MOPRC);
    break;

  case Q_IPV6:
    b1 = gen_linktype(cstate, ETHERTYPE_IPV6);
    break;

#ifndef IPPROTO_ICMPV6
#define IPPROTO_ICMPV6  58
#endif
  case Q_ICMPV6:
    b1 = gen_proto(cstate, IPPROTO_ICMPV6, Q_IPV6, Q_DEFAULT);
    break;

#ifndef IPPROTO_AH
#define IPPROTO_AH  51
#endif
  case Q_AH:
    b1 = gen_proto(cstate, IPPROTO_AH, Q_DEFAULT, Q_DEFAULT);
    break;

#ifndef IPPROTO_ESP
#define IPPROTO_ESP 50
#endif
  case Q_ESP:
    b1 = gen_proto(cstate, IPPROTO_ESP, Q_DEFAULT, Q_DEFAULT);
    break;

  case Q_ISO:
    b1 = gen_linktype(cstate, LLCSAP_ISONS);
    break;

  case Q_ESIS:
    b1 = gen_proto(cstate, ISO9542_ESIS, Q_ISO, Q_DEFAULT);
    break;

  case Q_ISIS:
    b1 = gen_proto(cstate, ISO10589_ISIS, Q_ISO, Q_DEFAULT);
    break;

  case Q_ISIS_L1: /* all IS-IS Level1 PDU-Types */
    b0 = gen_proto(cstate, ISIS_L1_LAN_IIH, Q_ISIS, Q_DEFAULT);
    b1 = gen_proto(cstate, ISIS_PTP_IIH, Q_ISIS, Q_DEFAULT); /* FIXME extract the circuit-type bits */
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L1_LSP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L1_CSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L1_PSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    break;

  case Q_ISIS_L2: /* all IS-IS Level2 PDU-Types */
    b0 = gen_proto(cstate, ISIS_L2_LAN_IIH, Q_ISIS, Q_DEFAULT);
    b1 = gen_proto(cstate, ISIS_PTP_IIH, Q_ISIS, Q_DEFAULT); /* FIXME extract the circuit-type bits */
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L2_LSP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L2_CSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L2_PSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    break;

  case Q_ISIS_IIH: /* all IS-IS Hello PDU-Types */
    b0 = gen_proto(cstate, ISIS_L1_LAN_IIH, Q_ISIS, Q_DEFAULT);
    b1 = gen_proto(cstate, ISIS_L2_LAN_IIH, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_PTP_IIH, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    break;

  case Q_ISIS_LSP:
    b0 = gen_proto(cstate, ISIS_L1_LSP, Q_ISIS, Q_DEFAULT);
    b1 = gen_proto(cstate, ISIS_L2_LSP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    break;

  case Q_ISIS_SNP:
    b0 = gen_proto(cstate, ISIS_L1_CSNP, Q_ISIS, Q_DEFAULT);
    b1 = gen_proto(cstate, ISIS_L2_CSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L1_PSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    b0 = gen_proto(cstate, ISIS_L2_PSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    break;

  case Q_ISIS_CSNP:
    b0 = gen_proto(cstate, ISIS_L1_CSNP, Q_ISIS, Q_DEFAULT);
    b1 = gen_proto(cstate, ISIS_L2_CSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    break;

  case Q_ISIS_PSNP:
    b0 = gen_proto(cstate, ISIS_L1_PSNP, Q_ISIS, Q_DEFAULT);
    b1 = gen_proto(cstate, ISIS_L2_PSNP, Q_ISIS, Q_DEFAULT);
    gen_or(b0, b1);
    break;

  case Q_CLNP:
    b1 = gen_proto(cstate, ISO8473_CLNP, Q_ISO, Q_DEFAULT);
    break;

  case Q_STP:
    b1 = gen_linktype(cstate, LLCSAP_8021D);
    break;

  case Q_IPX:
    b1 = gen_linktype(cstate, LLCSAP_IPX);
    break;

  case Q_NETBEUI:
    b1 = gen_linktype(cstate, LLCSAP_NETBEUI);
    break;

  case Q_RADIO:
    bpf_error(cstate, "'radio' is not a valid protocol type");

  default:
    abort();
  }
  return b1;
}

struct block *
gen_proto_abbrev(compiler_state_t *cstate, int proto)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  return gen_proto_abbrev_internal(cstate, proto);
}

static struct block *
gen_ipfrag(compiler_state_t *cstate)
{
  struct slist *s;
  struct block *b;

  /* not IPv4 frag other than the first frag */
  s = gen_load_a(cstate, OR_LINKPL, 6, BPF_H);
  b = new_block(cstate, JMP(BPF_JSET));
  b->s.k = 0x1fff;
  b->stmts = s;
  gen_not(b);

  return b;
}

/*
 * Generate a comparison to a port value in the transport-layer header
 * at the specified offset from the beginning of that header.
 *
 * XXX - this handles a variable-length prefix preceding the link-layer
 * header, such as the radiotap or AVS radio prefix, but doesn't handle
 * variable-length link-layer headers (such as Token Ring or 802.11
 * headers).
 */
static struct block *
gen_portatom(compiler_state_t *cstate, int off, bpf_u_int32 v)
{
  return gen_cmp(cstate, OR_TRAN_IPV4, off, BPF_H, v);
}

static struct block *
gen_portatom6(compiler_state_t *cstate, int off, bpf_u_int32 v)
{
  return gen_cmp(cstate, OR_TRAN_IPV6, off, BPF_H, v);
}

static struct block *
gen_portop(compiler_state_t *cstate, u_int port, u_int proto, int dir)
{
  struct block *b0, *b1, *tmp;

  /* ip proto 'proto' and not a fragment other than the first fragment */
  tmp = gen_cmp(cstate, OR_LINKPL, 9, BPF_B, proto);
  b0 = gen_ipfrag(cstate);
  gen_and(tmp, b0);

  switch (dir) {
  case Q_SRC:
    b1 = gen_portatom(cstate, 0, port);
    break;

  case Q_DST:
    b1 = gen_portatom(cstate, 2, port);
    break;

  case Q_AND:
    tmp = gen_portatom(cstate, 0, port);
    b1 = gen_portatom(cstate, 2, port);
    gen_and(tmp, b1);
    break;

  case Q_DEFAULT:
  case Q_OR:
    tmp = gen_portatom(cstate, 0, port);
    b1 = gen_portatom(cstate, 2, port);
    gen_or(tmp, b1);
    break;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are not valid qualifiers for ports");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are not valid qualifiers for ports");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are not valid qualifiers for ports");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are not valid qualifiers for ports");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is not a valid qualifier for ports");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is not a valid qualifier for ports");
    /*NOTREACHED*/

  default:
    abort();
    /*NOTREACHED*/
  }
  gen_and(b0, b1);

  return b1;
}

static struct block *
gen_port(compiler_state_t *cstate, u_int port, int ip_proto, int dir)
{
  struct block *b0, *b1, *tmp;

  /*
   * ether proto ip
   *
   * For FDDI, RFC 1188 says that SNAP encapsulation is used,
   * not LLC encapsulation with LLCSAP_IP.
   *
   * For IEEE 802 networks - which includes 802.5 token ring
   * (which is what DLT_IEEE802 means) and 802.11 - RFC 1042
   * says that SNAP encapsulation is used, not LLC encapsulation
   * with LLCSAP_IP.
   *
   * For LLC-encapsulated ATM/"Classical IP", RFC 1483 and
   * RFC 2225 say that SNAP encapsulation is used, not LLC
   * encapsulation with LLCSAP_IP.
   *
   * So we always check for ETHERTYPE_IP.
   */
  b0 = gen_linktype(cstate, ETHERTYPE_IP);

  switch (ip_proto) {
  case IPPROTO_UDP:
  case IPPROTO_TCP:
  case IPPROTO_SCTP:
    b1 = gen_portop(cstate, port, (u_int)ip_proto, dir);
    break;

  case PROTO_UNDEF:
    tmp = gen_portop(cstate, port, IPPROTO_TCP, dir);
    b1 = gen_portop(cstate, port, IPPROTO_UDP, dir);
    gen_or(tmp, b1);
    tmp = gen_portop(cstate, port, IPPROTO_SCTP, dir);
    gen_or(tmp, b1);
    break;

  default:
    abort();
  }
  gen_and(b0, b1);
  return b1;
}

struct block *
gen_portop6(compiler_state_t *cstate, u_int port, u_int proto, int dir)
{
  struct block *b0, *b1, *tmp;

  /* ip6 proto 'proto' */
  /* XXX - catch the first fragment of a fragmented packet? */
  b0 = gen_cmp(cstate, OR_LINKPL, 6, BPF_B, proto);

  switch (dir) {
  case Q_SRC:
    b1 = gen_portatom6(cstate, 0, port);
    break;

  case Q_DST:
    b1 = gen_portatom6(cstate, 2, port);
    break;

  case Q_AND:
    tmp = gen_portatom6(cstate, 0, port);
    b1 = gen_portatom6(cstate, 2, port);
    gen_and(tmp, b1);
    break;

  case Q_DEFAULT:
  case Q_OR:
    tmp = gen_portatom6(cstate, 0, port);
    b1 = gen_portatom6(cstate, 2, port);
    gen_or(tmp, b1);
    break;

  default:
    abort();
  }
  gen_and(b0, b1);

  return b1;
}

static struct block *
gen_port6(compiler_state_t *cstate, u_int port, int ip_proto, int dir)
{
  struct block *b0, *b1, *tmp;

  /* link proto ip6 */
  b0 = gen_linktype(cstate, ETHERTYPE_IPV6);

  switch (ip_proto) {
  case IPPROTO_UDP:
  case IPPROTO_TCP:
  case IPPROTO_SCTP:
    b1 = gen_portop6(cstate, port, (u_int)ip_proto, dir);
    break;

  case PROTO_UNDEF:
    tmp = gen_portop6(cstate, port, IPPROTO_TCP, dir);
    b1 = gen_portop6(cstate, port, IPPROTO_UDP, dir);
    gen_or(tmp, b1);
    tmp = gen_portop6(cstate, port, IPPROTO_SCTP, dir);
    gen_or(tmp, b1);
    break;

  default:
    abort();
  }
  gen_and(b0, b1);
  return b1;
}

/* gen_portrange code */
static struct block *
gen_portrangeatom(compiler_state_t *cstate, u_int off, bpf_u_int32 v1,
    bpf_u_int32 v2)
{
  struct block *b1, *b2;

  if (v1 > v2) {
    /*
     * Reverse the order of the ports, so v1 is the lower one.
     */
    bpf_u_int32 vtemp;

    vtemp = v1;
    v1 = v2;
    v2 = vtemp;
  }

  b1 = gen_cmp_ge(cstate, OR_TRAN_IPV4, off, BPF_H, v1);
  b2 = gen_cmp_le(cstate, OR_TRAN_IPV4, off, BPF_H, v2);

  gen_and(b1, b2);

  return b2;
}

static struct block *
gen_portrangeop(compiler_state_t *cstate, u_int port1, u_int port2,
    bpf_u_int32 proto, int dir)
{
  struct block *b0, *b1, *tmp;

  /* ip proto 'proto' and not a fragment other than the first fragment */
  tmp = gen_cmp(cstate, OR_LINKPL, 9, BPF_B, proto);
  b0 = gen_ipfrag(cstate);
  gen_and(tmp, b0);

  switch (dir) {
  case Q_SRC:
    b1 = gen_portrangeatom(cstate, 0, port1, port2);
    break;

  case Q_DST:
    b1 = gen_portrangeatom(cstate, 2, port1, port2);
    break;

  case Q_AND:
    tmp = gen_portrangeatom(cstate, 0, port1, port2);
    b1 = gen_portrangeatom(cstate, 2, port1, port2);
    gen_and(tmp, b1);
    break;

  case Q_DEFAULT:
  case Q_OR:
    tmp = gen_portrangeatom(cstate, 0, port1, port2);
    b1 = gen_portrangeatom(cstate, 2, port1, port2);
    gen_or(tmp, b1);
    break;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are not valid qualifiers for port ranges");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are not valid qualifiers for port ranges");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are not valid qualifiers for port ranges");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are not valid qualifiers for port ranges");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is not a valid qualifier for port ranges");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is not a valid qualifier for port ranges");
    /*NOTREACHED*/

  default:
    abort();
    /*NOTREACHED*/
  }
  gen_and(b0, b1);

  return b1;
}

static struct block *
gen_portrange(compiler_state_t *cstate, u_int port1, u_int port2, int ip_proto,
    int dir)
{
  struct block *b0, *b1, *tmp;

  /* link proto ip */
  b0 = gen_linktype(cstate, ETHERTYPE_IP);

  switch (ip_proto) {
  case IPPROTO_UDP:
  case IPPROTO_TCP:
  case IPPROTO_SCTP:
    b1 = gen_portrangeop(cstate, port1, port2, (bpf_u_int32)ip_proto,
        dir);
    break;

  case PROTO_UNDEF:
    tmp = gen_portrangeop(cstate, port1, port2, IPPROTO_TCP, dir);
    b1 = gen_portrangeop(cstate, port1, port2, IPPROTO_UDP, dir);
    gen_or(tmp, b1);
    tmp = gen_portrangeop(cstate, port1, port2, IPPROTO_SCTP, dir);
    gen_or(tmp, b1);
    break;

  default:
    abort();
  }
  gen_and(b0, b1);
  return b1;
}

static struct block *
gen_portrangeatom6(compiler_state_t *cstate, u_int off, bpf_u_int32 v1,
    bpf_u_int32 v2)
{
  struct block *b1, *b2;

  if (v1 > v2) {
    /*
     * Reverse the order of the ports, so v1 is the lower one.
     */
    bpf_u_int32 vtemp;

    vtemp = v1;
    v1 = v2;
    v2 = vtemp;
  }

  b1 = gen_cmp_ge(cstate, OR_TRAN_IPV6, off, BPF_H, v1);
  b2 = gen_cmp_le(cstate, OR_TRAN_IPV6, off, BPF_H, v2);

  gen_and(b1, b2);

  return b2;
}

static struct block *
gen_portrangeop6(compiler_state_t *cstate, u_int port1, u_int port2,
    bpf_u_int32 proto, int dir)
{
  struct block *b0, *b1, *tmp;

  /* ip6 proto 'proto' */
  /* XXX - catch the first fragment of a fragmented packet? */
  b0 = gen_cmp(cstate, OR_LINKPL, 6, BPF_B, proto);

  switch (dir) {
  case Q_SRC:
    b1 = gen_portrangeatom6(cstate, 0, port1, port2);
    break;

  case Q_DST:
    b1 = gen_portrangeatom6(cstate, 2, port1, port2);
    break;

  case Q_AND:
    tmp = gen_portrangeatom6(cstate, 0, port1, port2);
    b1 = gen_portrangeatom6(cstate, 2, port1, port2);
    gen_and(tmp, b1);
    break;

  case Q_DEFAULT:
  case Q_OR:
    tmp = gen_portrangeatom6(cstate, 0, port1, port2);
    b1 = gen_portrangeatom6(cstate, 2, port1, port2);
    gen_or(tmp, b1);
    break;

  default:
    abort();
  }
  gen_and(b0, b1);

  return b1;
}

static struct block *
gen_portrange6(compiler_state_t *cstate, u_int port1, u_int port2, int ip_proto,
    int dir)
{
  struct block *b0, *b1, *tmp;

  /* link proto ip6 */
  b0 = gen_linktype(cstate, ETHERTYPE_IPV6);

  switch (ip_proto) {
  case IPPROTO_UDP:
  case IPPROTO_TCP:
  case IPPROTO_SCTP:
    b1 = gen_portrangeop6(cstate, port1, port2, (bpf_u_int32)ip_proto,
        dir);
    break;

  case PROTO_UNDEF:
    tmp = gen_portrangeop6(cstate, port1, port2, IPPROTO_TCP, dir);
    b1 = gen_portrangeop6(cstate, port1, port2, IPPROTO_UDP, dir);
    gen_or(tmp, b1);
    tmp = gen_portrangeop6(cstate, port1, port2, IPPROTO_SCTP, dir);
    gen_or(tmp, b1);
    break;

  default:
    abort();
  }
  gen_and(b0, b1);
  return b1;
}

static int
lookup_proto(compiler_state_t *cstate, const char *name, int proto)
{
  register int v;

  switch (proto) {

  case Q_DEFAULT:
  case Q_IP:
  case Q_IPV6:
    v = pcap_nametoproto(name);
    if (v == PROTO_UNDEF)
      bpf_error(cstate, "unknown ip proto '%s'", name);
    break;

  case Q_LINK:
    /* XXX should look up h/w protocol type based on cstate->linktype */
    v = pcap_nametoeproto(name);
    if (v == PROTO_UNDEF) {
      v = pcap_nametollc(name);
      if (v == PROTO_UNDEF)
        bpf_error(cstate, "unknown ether proto '%s'", name);
    }
    break;

  case Q_ISO:
    if (strcmp(name, "esis") == 0)
      v = ISO9542_ESIS;
    else if (strcmp(name, "isis") == 0)
      v = ISO10589_ISIS;
    else if (strcmp(name, "clnp") == 0)
      v = ISO8473_CLNP;
    else
      bpf_error(cstate, "unknown osi proto '%s'", name);
    break;

  default:
    v = PROTO_UNDEF;
    break;
  }
  return v;
}

#if !defined(NO_PROTOCHAIN)
static struct block *
gen_protochain(compiler_state_t *cstate, bpf_u_int32 v, int proto)
{
  struct block *b0, *b;
  struct slist *s[100];
  int fix2, fix3, fix4, fix5;
  int ahcheck, again, end;
  int i, max;
  int reg2 = alloc_reg(cstate);

  memset(s, 0, sizeof(s));
  fix3 = fix4 = fix5 = 0;

  switch (proto) {
  case Q_IP:
  case Q_IPV6:
    break;
  case Q_DEFAULT:
    b0 = gen_protochain(cstate, v, Q_IP);
    b = gen_protochain(cstate, v, Q_IPV6);
    gen_or(b0, b);
    return b;
  default:
    bpf_error(cstate, "bad protocol applied for 'protochain'");
    /*NOTREACHED*/
  }

  /*
   * We don't handle variable-length prefixes before the link-layer
   * header, or variable-length link-layer headers, here yet.
   * We might want to add BPF instructions to do the protochain
   * work, to simplify that and, on platforms that have a BPF
   * interpreter with the new instructions, let the filtering
   * be done in the kernel.  (We already require a modified BPF
   * engine to do the protochain stuff, to support backward
   * branches, and backward branch support is unlikely to appear
   * in kernel BPF engines.)
   */
  if (cstate->off_linkpl.is_variable)
    bpf_error(cstate, "'protochain' not supported with variable length headers");

  /*
   * To quote a comment in optimize.c:
   *
   * "These data structures are used in a Cocke and Shwarz style
   * value numbering scheme.  Since the flowgraph is acyclic,
   * exit values can be propagated from a node's predecessors
   * provided it is uniquely defined."
   *
   * "Acyclic" means "no backward branches", which means "no
   * loops", so we have to turn the optimizer off.
   */
  cstate->no_optimize = 1;

  /*
   * s[0] is a dummy entry to protect other BPF insn from damage
   * by s[fix] = foo with uninitialized variable "fix".  It is somewhat
   * hard to find interdependency made by jump table fixup.
   */
  i = 0;
  s[i] = new_stmt(cstate, 0); /*dummy*/
  i++;

  switch (proto) {
  case Q_IP:
    b0 = gen_linktype(cstate, ETHERTYPE_IP);

    /* A = ip->ip_p */
    s[i] = new_stmt(cstate, BPF_LD|BPF_ABS|BPF_B);
    s[i]->s.k = cstate->off_linkpl.constant_part + cstate->off_nl + 9;
    i++;
    /* X = ip->ip_hl << 2 */
    s[i] = new_stmt(cstate, BPF_LDX|BPF_MSH|BPF_B);
    s[i]->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
    i++;
    break;

  case Q_IPV6:
    b0 = gen_linktype(cstate, ETHERTYPE_IPV6);

    /* A = ip6->ip_nxt */
    s[i] = new_stmt(cstate, BPF_LD|BPF_ABS|BPF_B);
    s[i]->s.k = cstate->off_linkpl.constant_part + cstate->off_nl + 6;
    i++;
    /* X = sizeof(struct ip6_hdr) */
    s[i] = new_stmt(cstate, BPF_LDX|BPF_IMM);
    s[i]->s.k = 40;
    i++;
    break;

  default:
    bpf_error(cstate, "unsupported proto to gen_protochain");
    /*NOTREACHED*/
  }

  /* again: if (A == v) goto end; else fall through; */
  again = i;
  s[i] = new_stmt(cstate, BPF_JMP|BPF_JEQ|BPF_K);
  s[i]->s.k = v;
  s[i]->s.jt = NULL;    /*later*/
  s[i]->s.jf = NULL;    /*update in next stmt*/
  fix5 = i;
  i++;

#ifndef IPPROTO_NONE
#define IPPROTO_NONE  59
#endif
  /* if (A == IPPROTO_NONE) goto end */
  s[i] = new_stmt(cstate, BPF_JMP|BPF_JEQ|BPF_K);
  s[i]->s.jt = NULL;  /*later*/
  s[i]->s.jf = NULL;  /*update in next stmt*/
  s[i]->s.k = IPPROTO_NONE;
  s[fix5]->s.jf = s[i];
  fix2 = i;
  i++;

  if (proto == Q_IPV6) {
    int v6start, v6end, v6advance, j;

    v6start = i;
    /* if (A == IPPROTO_HOPOPTS) goto v6advance */
    s[i] = new_stmt(cstate, BPF_JMP|BPF_JEQ|BPF_K);
    s[i]->s.jt = NULL;  /*later*/
    s[i]->s.jf = NULL;  /*update in next stmt*/
    s[i]->s.k = IPPROTO_HOPOPTS;
    s[fix2]->s.jf = s[i];
    i++;
    /* if (A == IPPROTO_DSTOPTS) goto v6advance */
    s[i - 1]->s.jf = s[i] = new_stmt(cstate, BPF_JMP|BPF_JEQ|BPF_K);
    s[i]->s.jt = NULL;  /*later*/
    s[i]->s.jf = NULL;  /*update in next stmt*/
    s[i]->s.k = IPPROTO_DSTOPTS;
    i++;
    /* if (A == IPPROTO_ROUTING) goto v6advance */
    s[i - 1]->s.jf = s[i] = new_stmt(cstate, BPF_JMP|BPF_JEQ|BPF_K);
    s[i]->s.jt = NULL;  /*later*/
    s[i]->s.jf = NULL;  /*update in next stmt*/
    s[i]->s.k = IPPROTO_ROUTING;
    i++;
    /* if (A == IPPROTO_FRAGMENT) goto v6advance; else goto ahcheck; */
    s[i - 1]->s.jf = s[i] = new_stmt(cstate, BPF_JMP|BPF_JEQ|BPF_K);
    s[i]->s.jt = NULL;  /*later*/
    s[i]->s.jf = NULL;  /*later*/
    s[i]->s.k = IPPROTO_FRAGMENT;
    fix3 = i;
    v6end = i;
    i++;

    /* v6advance: */
    v6advance = i;

    /*
     * in short,
     * A = P[X + packet head];
     * X = X + (P[X + packet head + 1] + 1) * 8;
     */
    /* A = P[X + packet head] */
    s[i] = new_stmt(cstate, BPF_LD|BPF_IND|BPF_B);
    s[i]->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
    i++;
    /* MEM[reg2] = A */
    s[i] = new_stmt(cstate, BPF_ST);
    s[i]->s.k = reg2;
    i++;
    /* A = P[X + packet head + 1]; */
    s[i] = new_stmt(cstate, BPF_LD|BPF_IND|BPF_B);
    s[i]->s.k = cstate->off_linkpl.constant_part + cstate->off_nl + 1;
    i++;
    /* A += 1 */
    s[i] = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
    s[i]->s.k = 1;
    i++;
    /* A *= 8 */
    s[i] = new_stmt(cstate, BPF_ALU|BPF_MUL|BPF_K);
    s[i]->s.k = 8;
    i++;
    /* A += X */
    s[i] = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X);
    s[i]->s.k = 0;
    i++;
    /* X = A; */
    s[i] = new_stmt(cstate, BPF_MISC|BPF_TAX);
    i++;
    /* A = MEM[reg2] */
    s[i] = new_stmt(cstate, BPF_LD|BPF_MEM);
    s[i]->s.k = reg2;
    i++;

    /* goto again; (must use BPF_JA for backward jump) */
    s[i] = new_stmt(cstate, BPF_JMP|BPF_JA);
    s[i]->s.k = again - i - 1;
    s[i - 1]->s.jf = s[i];
    i++;

    /* fixup */
    for (j = v6start; j <= v6end; j++)
      s[j]->s.jt = s[v6advance];
  } else {
    /* nop */
    s[i] = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
    s[i]->s.k = 0;
    s[fix2]->s.jf = s[i];
    i++;
  }

  /* ahcheck: */
  ahcheck = i;
  /* if (A == IPPROTO_AH) then fall through; else goto end; */
  s[i] = new_stmt(cstate, BPF_JMP|BPF_JEQ|BPF_K);
  s[i]->s.jt = NULL;  /*later*/
  s[i]->s.jf = NULL;  /*later*/
  s[i]->s.k = IPPROTO_AH;
  if (fix3)
    s[fix3]->s.jf = s[ahcheck];
  fix4 = i;
  i++;

  /*
   * in short,
   * A = P[X];
   * X = X + (P[X + 1] + 2) * 4;
   */
  /* A = X */
  s[i - 1]->s.jt = s[i] = new_stmt(cstate, BPF_MISC|BPF_TXA);
  i++;
  /* A = P[X + packet head]; */
  s[i] = new_stmt(cstate, BPF_LD|BPF_IND|BPF_B);
  s[i]->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
  i++;
  /* MEM[reg2] = A */
  s[i] = new_stmt(cstate, BPF_ST);
  s[i]->s.k = reg2;
  i++;
  /* A = X */
  s[i - 1]->s.jt = s[i] = new_stmt(cstate, BPF_MISC|BPF_TXA);
  i++;
  /* A += 1 */
  s[i] = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s[i]->s.k = 1;
  i++;
  /* X = A */
  s[i] = new_stmt(cstate, BPF_MISC|BPF_TAX);
  i++;
  /* A = P[X + packet head] */
  s[i] = new_stmt(cstate, BPF_LD|BPF_IND|BPF_B);
  s[i]->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
  i++;
  /* A += 2 */
  s[i] = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s[i]->s.k = 2;
  i++;
  /* A *= 4 */
  s[i] = new_stmt(cstate, BPF_ALU|BPF_MUL|BPF_K);
  s[i]->s.k = 4;
  i++;
  /* X = A; */
  s[i] = new_stmt(cstate, BPF_MISC|BPF_TAX);
  i++;
  /* A = MEM[reg2] */
  s[i] = new_stmt(cstate, BPF_LD|BPF_MEM);
  s[i]->s.k = reg2;
  i++;

  /* goto again; (must use BPF_JA for backward jump) */
  s[i] = new_stmt(cstate, BPF_JMP|BPF_JA);
  s[i]->s.k = again - i - 1;
  i++;

  /* end: nop */
  end = i;
  s[i] = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s[i]->s.k = 0;
  s[fix2]->s.jt = s[end];
  s[fix4]->s.jf = s[end];
  s[fix5]->s.jt = s[end];
  i++;

  /*
   * make slist chain
   */
  max = i;
  for (i = 0; i < max - 1; i++)
    s[i]->next = s[i + 1];
  s[max - 1]->next = NULL;

  /*
   * emit final check
   */
  b = new_block(cstate, JMP(BPF_JEQ));
  b->stmts = s[1];  /*remember, s[0] is dummy*/
  b->s.k = v;

  free_reg(cstate, reg2);

  gen_and(b0, b);
  return b;
}
#endif /* !defined(NO_PROTOCHAIN) */

static struct block *
gen_check_802_11_data_frame(compiler_state_t *cstate)
{
  struct slist *s;
  struct block *b0, *b1;

  /*
   * A data frame has the 0x08 bit (b3) in the frame control field set
   * and the 0x04 bit (b2) clear.
   */
  s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
  b0 = new_block(cstate, JMP(BPF_JSET));
  b0->s.k = 0x08;
  b0->stmts = s;

  s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
  b1 = new_block(cstate, JMP(BPF_JSET));
  b1->s.k = 0x04;
  b1->stmts = s;
  gen_not(b1);

  gen_and(b1, b0);

  return b0;
}

/*
 * Generate code that checks whether the packet is a packet for protocol
 * <proto> and whether the type field in that protocol's header has
 * the value <v>, e.g. if <proto> is Q_IP, it checks whether it's an
 * IP packet and checks the protocol number in the IP header against <v>.
 *
 * If <proto> is Q_DEFAULT, i.e. just "proto" was specified, it checks
 * against Q_IP and Q_IPV6.
 */
static struct block *
gen_proto(compiler_state_t *cstate, bpf_u_int32 v, int proto, int dir)
{
  struct block *b0, *b1;
  struct block *b2;

  if (dir != Q_DEFAULT)
    bpf_error(cstate, "direction applied to 'proto'");

  switch (proto) {
  case Q_DEFAULT:
    b0 = gen_proto(cstate, v, Q_IP, dir);
    b1 = gen_proto(cstate, v, Q_IPV6, dir);
    gen_or(b0, b1);
    return b1;

  case Q_LINK:
    return gen_linktype(cstate, v);

  case Q_IP:
    /*
     * For FDDI, RFC 1188 says that SNAP encapsulation is used,
     * not LLC encapsulation with LLCSAP_IP.
     *
     * For IEEE 802 networks - which includes 802.5 token ring
     * (which is what DLT_IEEE802 means) and 802.11 - RFC 1042
     * says that SNAP encapsulation is used, not LLC encapsulation
     * with LLCSAP_IP.
     *
     * For LLC-encapsulated ATM/"Classical IP", RFC 1483 and
     * RFC 2225 say that SNAP encapsulation is used, not LLC
     * encapsulation with LLCSAP_IP.
     *
     * So we always check for ETHERTYPE_IP.
     */
    b0 = gen_linktype(cstate, ETHERTYPE_IP);
    b1 = gen_cmp(cstate, OR_LINKPL, 9, BPF_B, v);
    gen_and(b0, b1);
    return b1;

  case Q_ARP:
    bpf_error(cstate, "arp does not encapsulate another protocol");
    /*NOTREACHED*/

  case Q_RARP:
    bpf_error(cstate, "rarp does not encapsulate another protocol");
    /*NOTREACHED*/

  case Q_SCTP:
    bpf_error(cstate, "'sctp proto' is bogus");
    /*NOTREACHED*/

  case Q_TCP:
    bpf_error(cstate, "'tcp proto' is bogus");
    /*NOTREACHED*/

  case Q_UDP:
    bpf_error(cstate, "'udp proto' is bogus");
    /*NOTREACHED*/

  case Q_ICMP:
    bpf_error(cstate, "'icmp proto' is bogus");
    /*NOTREACHED*/

  case Q_IGMP:
    bpf_error(cstate, "'igmp proto' is bogus");
    /*NOTREACHED*/

  case Q_IGRP:
    bpf_error(cstate, "'igrp proto' is bogus");
    /*NOTREACHED*/

  case Q_ATALK:
    bpf_error(cstate, "AppleTalk encapsulation is not specifiable");
    /*NOTREACHED*/

  case Q_DECNET:
    bpf_error(cstate, "DECNET encapsulation is not specifiable");
    /*NOTREACHED*/

  case Q_LAT:
    bpf_error(cstate, "LAT does not encapsulate another protocol");
    /*NOTREACHED*/

  case Q_SCA:
    bpf_error(cstate, "SCA does not encapsulate another protocol");
    /*NOTREACHED*/

  case Q_MOPRC:
    bpf_error(cstate, "MOPRC does not encapsulate another protocol");
    /*NOTREACHED*/

  case Q_MOPDL:
    bpf_error(cstate, "MOPDL does not encapsulate another protocol");
    /*NOTREACHED*/

  case Q_IPV6:
    b0 = gen_linktype(cstate, ETHERTYPE_IPV6);
    /*
     * Also check for a fragment header before the final
     * header.
     */
    b2 = gen_cmp(cstate, OR_LINKPL, 6, BPF_B, IPPROTO_FRAGMENT);
    b1 = gen_cmp(cstate, OR_LINKPL, 40, BPF_B, v);
    gen_and(b2, b1);
    b2 = gen_cmp(cstate, OR_LINKPL, 6, BPF_B, v);
    gen_or(b2, b1);
    gen_and(b0, b1);
    return b1;

  case Q_ICMPV6:
    bpf_error(cstate, "'icmp6 proto' is bogus");
    /*NOTREACHED*/

  case Q_AH:
    bpf_error(cstate, "'ah proto' is bogus");
    /*NOTREACHED*/

  case Q_ESP:
    bpf_error(cstate, "'esp proto' is bogus");
    /*NOTREACHED*/

  case Q_PIM:
    bpf_error(cstate, "'pim proto' is bogus");
    /*NOTREACHED*/

  case Q_VRRP:
    bpf_error(cstate, "'vrrp proto' is bogus");
    /*NOTREACHED*/

  case Q_AARP:
    bpf_error(cstate, "'aarp proto' is bogus");
    /*NOTREACHED*/

  case Q_ISO:
    switch (cstate->linktype) {

    case DLT_FRELAY:
      /*
       * Frame Relay packets typically have an OSI
       * NLPID at the beginning; "gen_linktype(cstate, LLCSAP_ISONS)"
       * generates code to check for all the OSI
       * NLPIDs, so calling it and then adding a check
       * for the particular NLPID for which we're
       * looking is bogus, as we can just check for
       * the NLPID.
       *
       * What we check for is the NLPID and a frame
       * control field value of UI, i.e. 0x03 followed
       * by the NLPID.
       *
       * XXX - assumes a 2-byte Frame Relay header with
       * DLCI and flags.  What if the address is longer?
       *
       * XXX - what about SNAP-encapsulated frames?
       */
      return gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, (0x03<<8) | v);
      /*NOTREACHED*/

    case DLT_C_HDLC:
    case DLT_HDLC:
      /*
       * Cisco uses an Ethertype lookalike - for OSI,
       * it's 0xfefe.
       */
      b0 = gen_linktype(cstate, LLCSAP_ISONS<<8 | LLCSAP_ISONS);
      /* OSI in C-HDLC is stuffed with a fudge byte */
      b1 = gen_cmp(cstate, OR_LINKPL_NOSNAP, 1, BPF_B, v);
      gen_and(b0, b1);
      return b1;

    default:
      b0 = gen_linktype(cstate, LLCSAP_ISONS);
      b1 = gen_cmp(cstate, OR_LINKPL_NOSNAP, 0, BPF_B, v);
      gen_and(b0, b1);
      return b1;
    }

  case Q_ESIS:
    bpf_error(cstate, "'esis proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS:
    b0 = gen_proto(cstate, ISO10589_ISIS, Q_ISO, Q_DEFAULT);
    /*
     * 4 is the offset of the PDU type relative to the IS-IS
     * header.
     */
    b1 = gen_cmp(cstate, OR_LINKPL_NOSNAP, 4, BPF_B, v);
    gen_and(b0, b1);
    return b1;

  case Q_CLNP:
    bpf_error(cstate, "'clnp proto' is not supported");
    /*NOTREACHED*/

  case Q_STP:
    bpf_error(cstate, "'stp proto' is bogus");
    /*NOTREACHED*/

  case Q_IPX:
    bpf_error(cstate, "'ipx proto' is bogus");
    /*NOTREACHED*/

  case Q_NETBEUI:
    bpf_error(cstate, "'netbeui proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS_L1:
    bpf_error(cstate, "'l1 proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS_L2:
    bpf_error(cstate, "'l2 proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS_IIH:
    bpf_error(cstate, "'iih proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS_SNP:
    bpf_error(cstate, "'snp proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS_CSNP:
    bpf_error(cstate, "'csnp proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS_PSNP:
    bpf_error(cstate, "'psnp proto' is bogus");
    /*NOTREACHED*/

  case Q_ISIS_LSP:
    bpf_error(cstate, "'lsp proto' is bogus");
    /*NOTREACHED*/

  case Q_RADIO:
    bpf_error(cstate, "'radio proto' is bogus");
    /*NOTREACHED*/

  case Q_CARP:
    bpf_error(cstate, "'carp proto' is bogus");
    /*NOTREACHED*/

  default:
    abort();
    /*NOTREACHED*/
  }
  /*NOTREACHED*/
}

struct block *
gen_scode(compiler_state_t *cstate, const char *name, struct qual q)
{
  int proto = q.proto;
  int dir = q.dir;
  int tproto;
  u_char *eaddr;
  bpf_u_int32 mask, addr;
  struct addrinfo *res, *res0;
  struct sockaddr_in *sin4;
#ifdef INET6
  int tproto6;
  struct sockaddr_in6 *sin6;
  struct in6_addr mask128;
#endif /*INET6*/
  struct block *b, *tmp;
  int port, real_proto;
  int port1, port2;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (q.addr) {

  case Q_NET:
    addr = pcap_nametonetaddr(name);
    if (addr == 0)
      bpf_error(cstate, "unknown network '%s'", name);
    /* Left justify network addr and calculate its network mask */
    mask = 0xffffffff;
    while (addr && (addr & 0xff000000) == 0) {
      addr <<= 8;
      mask <<= 8;
    }
    return gen_host(cstate, addr, mask, proto, dir, q.addr);

  case Q_DEFAULT:
  case Q_HOST:
    if (proto == Q_LINK) {
      switch (cstate->linktype) {

      case DLT_EN10MB:
      case DLT_NETANALYZER:
      case DLT_NETANALYZER_TRANSPARENT:
        eaddr = pcap_ether_hostton(name);
        if (eaddr == NULL)
          bpf_error(cstate,
              "unknown ether host '%s'", name);
        tmp = gen_prevlinkhdr_check(cstate);
        b = gen_ehostop(cstate, eaddr, dir);
        if (tmp != NULL)
          gen_and(tmp, b);
        free(eaddr);
        return b;

      case DLT_FDDI:
        eaddr = pcap_ether_hostton(name);
        if (eaddr == NULL)
          bpf_error(cstate,
              "unknown FDDI host '%s'", name);
        b = gen_fhostop(cstate, eaddr, dir);
        free(eaddr);
        return b;

      case DLT_IEEE802:
        eaddr = pcap_ether_hostton(name);
        if (eaddr == NULL)
          bpf_error(cstate,
              "unknown token ring host '%s'", name);
        b = gen_thostop(cstate, eaddr, dir);
        free(eaddr);
        return b;

      case DLT_IEEE802_11:
      case DLT_PRISM_HEADER:
      case DLT_IEEE802_11_RADIO_AVS:
      case DLT_IEEE802_11_RADIO:
      case DLT_PPI:
        eaddr = pcap_ether_hostton(name);
        if (eaddr == NULL)
          bpf_error(cstate,
              "unknown 802.11 host '%s'", name);
        b = gen_wlanhostop(cstate, eaddr, dir);
        free(eaddr);
        return b;

      case DLT_IP_OVER_FC:
        eaddr = pcap_ether_hostton(name);
        if (eaddr == NULL)
          bpf_error(cstate,
              "unknown Fibre Channel host '%s'", name);
        b = gen_ipfchostop(cstate, eaddr, dir);
        free(eaddr);
        return b;
      }

      bpf_error(cstate, "only ethernet/FDDI/token ring/802.11/ATM LANE/Fibre Channel supports link-level host name");
    } else if (proto == Q_DECNET) {
      unsigned short dn_addr;

      if (!__pcap_nametodnaddr(name, &dn_addr)) {
#ifdef  DECNETLIB
        bpf_error(cstate, "unknown decnet host name '%s'\n", name);
#else
        bpf_error(cstate, "decnet name support not included, '%s' cannot be translated\n",
          name);
#endif
      }
      /*
       * I don't think DECNET hosts can be multihomed, so
       * there is no need to build up a list of addresses
       */
      return (gen_host(cstate, dn_addr, 0, proto, dir, q.addr));
    } else {
#ifdef INET6
      memset(&mask128, 0xff, sizeof(mask128));
#endif
      res0 = res = pcap_nametoaddrinfo(name);
      if (res == NULL)
        bpf_error(cstate, "unknown host '%s'", name);
      cstate->ai = res;
      b = tmp = NULL;
      tproto = proto;
#ifdef INET6
      tproto6 = proto;
#endif
      if (cstate->off_linktype.constant_part == OFFSET_NOT_SET &&
          tproto == Q_DEFAULT) {
        tproto = Q_IP;
#ifdef INET6
        tproto6 = Q_IPV6;
#endif
      }
      for (res = res0; res; res = res->ai_next) {
        switch (res->ai_family) {
        case AF_INET:
#ifdef INET6
          if (tproto == Q_IPV6)
            continue;
#endif

          sin4 = (struct sockaddr_in *)
            res->ai_addr;
          tmp = gen_host(cstate, ntohl(sin4->sin_addr.s_addr),
            0xffffffff, tproto, dir, q.addr);
          break;
#ifdef INET6
        case AF_INET6:
          if (tproto6 == Q_IP)
            continue;

          sin6 = (struct sockaddr_in6 *)
            res->ai_addr;
          tmp = gen_host6(cstate, &sin6->sin6_addr,
            &mask128, tproto6, dir, q.addr);
          break;
#endif
        default:
          continue;
        }
        if (b)
          gen_or(b, tmp);
        b = tmp;
      }
      cstate->ai = NULL;
      freeaddrinfo(res0);
      if (b == NULL) {
        bpf_error(cstate, "unknown host '%s'%s", name,
            (proto == Q_DEFAULT)
          ? ""
          : " for specified address family");
      }
      return b;
    }

  case Q_PORT:
    if (proto != Q_DEFAULT &&
        proto != Q_UDP && proto != Q_TCP && proto != Q_SCTP)
      bpf_error(cstate, "illegal qualifier of 'port'");
    if (pcap_nametoport(name, &port, &real_proto) == 0)
      bpf_error(cstate, "unknown port '%s'", name);
    if (proto == Q_UDP) {
      if (real_proto == IPPROTO_TCP)
        bpf_error(cstate, "port '%s' is tcp", name);
      else if (real_proto == IPPROTO_SCTP)
        bpf_error(cstate, "port '%s' is sctp", name);
      else
        /* override PROTO_UNDEF */
        real_proto = IPPROTO_UDP;
    }
    if (proto == Q_TCP) {
      if (real_proto == IPPROTO_UDP)
        bpf_error(cstate, "port '%s' is udp", name);

      else if (real_proto == IPPROTO_SCTP)
        bpf_error(cstate, "port '%s' is sctp", name);
      else
        /* override PROTO_UNDEF */
        real_proto = IPPROTO_TCP;
    }
    if (proto == Q_SCTP) {
      if (real_proto == IPPROTO_UDP)
        bpf_error(cstate, "port '%s' is udp", name);

      else if (real_proto == IPPROTO_TCP)
        bpf_error(cstate, "port '%s' is tcp", name);
      else
        /* override PROTO_UNDEF */
        real_proto = IPPROTO_SCTP;
    }
    if (port < 0)
      bpf_error(cstate, "illegal port number %d < 0", port);
    if (port > 65535)
      bpf_error(cstate, "illegal port number %d > 65535", port);
    b = gen_port(cstate, port, real_proto, dir);
    gen_or(gen_port6(cstate, port, real_proto, dir), b);
    return b;

  case Q_PORTRANGE:
    if (proto != Q_DEFAULT &&
        proto != Q_UDP && proto != Q_TCP && proto != Q_SCTP)
      bpf_error(cstate, "illegal qualifier of 'portrange'");
    if (pcap_nametoportrange(name, &port1, &port2, &real_proto) == 0)
      bpf_error(cstate, "unknown port in range '%s'", name);
    if (proto == Q_UDP) {
      if (real_proto == IPPROTO_TCP)
        bpf_error(cstate, "port in range '%s' is tcp", name);
      else if (real_proto == IPPROTO_SCTP)
        bpf_error(cstate, "port in range '%s' is sctp", name);
      else
        /* override PROTO_UNDEF */
        real_proto = IPPROTO_UDP;
    }
    if (proto == Q_TCP) {
      if (real_proto == IPPROTO_UDP)
        bpf_error(cstate, "port in range '%s' is udp", name);
      else if (real_proto == IPPROTO_SCTP)
        bpf_error(cstate, "port in range '%s' is sctp", name);
      else
        /* override PROTO_UNDEF */
        real_proto = IPPROTO_TCP;
    }
    if (proto == Q_SCTP) {
      if (real_proto == IPPROTO_UDP)
        bpf_error(cstate, "port in range '%s' is udp", name);
      else if (real_proto == IPPROTO_TCP)
        bpf_error(cstate, "port in range '%s' is tcp", name);
      else
        /* override PROTO_UNDEF */
        real_proto = IPPROTO_SCTP;
    }
    if (port1 < 0)
      bpf_error(cstate, "illegal port number %d < 0", port1);
    if (port1 > 65535)
      bpf_error(cstate, "illegal port number %d > 65535", port1);
    if (port2 < 0)
      bpf_error(cstate, "illegal port number %d < 0", port2);
    if (port2 > 65535)
      bpf_error(cstate, "illegal port number %d > 65535", port2);

    b = gen_portrange(cstate, port1, port2, real_proto, dir);
    gen_or(gen_portrange6(cstate, port1, port2, real_proto, dir), b);
    return b;

  case Q_GATEWAY:
#ifndef INET6
    eaddr = pcap_ether_hostton(name);
    if (eaddr == NULL)
      bpf_error(cstate, "unknown ether host: %s", name);

    res = pcap_nametoaddrinfo(name);
    cstate->ai = res;
    if (res == NULL)
      bpf_error(cstate, "unknown host '%s'", name);
    b = gen_gateway(cstate, eaddr, res, proto, dir);
    cstate->ai = NULL;
    freeaddrinfo(res);
    if (b == NULL)
      bpf_error(cstate, "unknown host '%s'", name);
    return b;
#else
    bpf_error(cstate, "'gateway' not supported in this configuration");
#endif /*INET6*/

  case Q_PROTO:
    real_proto = lookup_proto(cstate, name, proto);
    if (real_proto >= 0)
      return gen_proto(cstate, real_proto, proto, dir);
    else
      bpf_error(cstate, "unknown protocol: %s", name);

#if !defined(NO_PROTOCHAIN)
  case Q_PROTOCHAIN:
    real_proto = lookup_proto(cstate, name, proto);
    if (real_proto >= 0)
      return gen_protochain(cstate, real_proto, proto);
    else
      bpf_error(cstate, "unknown protocol: %s", name);
#endif /* !defined(NO_PROTOCHAIN) */

  case Q_UNDEF:
    syntax(cstate);
    /*NOTREACHED*/
  }
  abort();
  /*NOTREACHED*/
}

struct block *
gen_mcode(compiler_state_t *cstate, const char *s1, const char *s2,
    bpf_u_int32 masklen, struct qual q)
{
  register int nlen, mlen;
  bpf_u_int32 n, m;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  nlen = __pcap_atoin(s1, &n);
  if (nlen < 0)
    bpf_error(cstate, "invalid IPv4 address '%s'", s1);
  /* Promote short ipaddr */
  n <<= 32 - nlen;

  if (s2 != NULL) {
    mlen = __pcap_atoin(s2, &m);
    if (mlen < 0)
      bpf_error(cstate, "invalid IPv4 address '%s'", s2);
    /* Promote short ipaddr */
    m <<= 32 - mlen;
    if ((n & ~m) != 0)
      bpf_error(cstate, "non-network bits set in \"%s mask %s\"",
          s1, s2);
  } else {
    /* Convert mask len to mask */
    if (masklen > 32)
      bpf_error(cstate, "mask length must be <= 32");
    if (masklen == 0) {
      /*
       * X << 32 is not guaranteed by C to be 0; it's
       * undefined.
       */
      m = 0;
    } else
      m = 0xffffffff << (32 - masklen);
    if ((n & ~m) != 0)
      bpf_error(cstate, "non-network bits set in \"%s/%d\"",
          s1, masklen);
  }

  switch (q.addr) {

  case Q_NET:
    return gen_host(cstate, n, m, q.proto, q.dir, q.addr);

  default:
    bpf_error(cstate, "Mask syntax for networks only");
    /*NOTREACHED*/
  }
  /*NOTREACHED*/
}

struct block *
gen_ncode(compiler_state_t *cstate, const char *s, bpf_u_int32 v, struct qual q)
{
  bpf_u_int32 mask;
  int proto;
  int dir;
  register int vlen;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  proto = q.proto;
  dir = q.dir;
  if (s == NULL)
    vlen = 32;
  else if (q.proto == Q_DECNET) {
    vlen = __pcap_atodn(s, &v);
    if (vlen == 0)
      bpf_error(cstate, "malformed decnet address '%s'", s);
  } else {
    vlen = __pcap_atoin(s, &v);
    if (vlen < 0)
      bpf_error(cstate, "invalid IPv4 address '%s'", s);
  }

  switch (q.addr) {

  case Q_DEFAULT:
  case Q_HOST:
  case Q_NET:
    if (proto == Q_DECNET)
      return gen_host(cstate, v, 0, proto, dir, q.addr);
    else if (proto == Q_LINK) {
      bpf_error(cstate, "illegal link layer address");
    } else {
      mask = 0xffffffff;
      if (s == NULL && q.addr == Q_NET) {
        /* Promote short net number */
        while (v && (v & 0xff000000) == 0) {
          v <<= 8;
          mask <<= 8;
        }
      } else {
        /* Promote short ipaddr */
        v <<= 32 - vlen;
        mask <<= 32 - vlen ;
      }
      return gen_host(cstate, v, mask, proto, dir, q.addr);
    }

  case Q_PORT:
    if (proto == Q_UDP)
      proto = IPPROTO_UDP;
    else if (proto == Q_TCP)
      proto = IPPROTO_TCP;
    else if (proto == Q_SCTP)
      proto = IPPROTO_SCTP;
    else if (proto == Q_DEFAULT)
      proto = PROTO_UNDEF;
    else
      bpf_error(cstate, "illegal qualifier of 'port'");

    if (v > 65535)
      bpf_error(cstate, "illegal port number %u > 65535", v);

      {
    struct block *b;
    b = gen_port(cstate, v, proto, dir);
    gen_or(gen_port6(cstate, v, proto, dir), b);
    return b;
      }

  case Q_PORTRANGE:
    if (proto == Q_UDP)
      proto = IPPROTO_UDP;
    else if (proto == Q_TCP)
      proto = IPPROTO_TCP;
    else if (proto == Q_SCTP)
      proto = IPPROTO_SCTP;
    else if (proto == Q_DEFAULT)
      proto = PROTO_UNDEF;
    else
      bpf_error(cstate, "illegal qualifier of 'portrange'");

    if (v > 65535)
      bpf_error(cstate, "illegal port number %u > 65535", v);

      {
    struct block *b;
    b = gen_portrange(cstate, v, v, proto, dir);
    gen_or(gen_portrange6(cstate, v, v, proto, dir), b);
    return b;
      }

  case Q_GATEWAY:
    bpf_error(cstate, "'gateway' requires a name");
    /*NOTREACHED*/

  case Q_PROTO:
    return gen_proto(cstate, v, proto, dir);

#if !defined(NO_PROTOCHAIN)
  case Q_PROTOCHAIN:
    return gen_protochain(cstate, v, proto);
#endif

  case Q_UNDEF:
    syntax(cstate);
    /*NOTREACHED*/

  default:
    abort();
    /*NOTREACHED*/
  }
  /*NOTREACHED*/
}

#ifdef INET6
struct block *
gen_mcode6(compiler_state_t *cstate, const char *s1, const char *s2,
    bpf_u_int32 masklen, struct qual q)
{
  struct addrinfo *res;
  struct in6_addr *addr;
  struct in6_addr mask;
  struct block *b;
  uint32_t *a, *m;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if (s2)
    bpf_error(cstate, "no mask %s supported", s2);

  res = pcap_nametoaddrinfo(s1);
  if (!res)
    bpf_error(cstate, "invalid ip6 address %s", s1);
  cstate->ai = res;
  if (res->ai_next)
    bpf_error(cstate, "%s resolved to multiple address", s1);
  addr = &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr;

  if (masklen > sizeof(mask.s6_addr) * 8)
    bpf_error(cstate, "mask length must be <= %u", (unsigned int)(sizeof(mask.s6_addr) * 8));
  memset(&mask, 0, sizeof(mask));
  memset(&mask.s6_addr, 0xff, masklen / 8);
  if (masklen % 8) {
    mask.s6_addr[masklen / 8] =
      (0xff << (8 - masklen % 8)) & 0xff;
  }

  a = (uint32_t *)addr;
  m = (uint32_t *)&mask;
  if ((a[0] & ~m[0]) || (a[1] & ~m[1])
   || (a[2] & ~m[2]) || (a[3] & ~m[3])) {
    bpf_error(cstate, "non-network bits set in \"%s/%d\"", s1, masklen);
  }

  switch (q.addr) {

  case Q_DEFAULT:
  case Q_HOST:
    if (masklen != 128)
      bpf_error(cstate, "Mask syntax for networks only");
    /* FALLTHROUGH */

  case Q_NET:
    b = gen_host6(cstate, addr, &mask, q.proto, q.dir, q.addr);
    cstate->ai = NULL;
    freeaddrinfo(res);
    return b;

  default:
    bpf_error(cstate, "invalid qualifier against IPv6 address");
    /*NOTREACHED*/
  }
}
#endif /*INET6*/

struct block *
gen_ecode(compiler_state_t *cstate, const char *s, struct qual q)
{
  struct block *b, *tmp;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if ((q.addr == Q_HOST || q.addr == Q_DEFAULT) && q.proto == Q_LINK) {
    cstate->e = pcap_ether_aton(s);
    if (cstate->e == NULL)
      bpf_error(cstate, "malloc");
    switch (cstate->linktype) {
    case DLT_EN10MB:
    case DLT_NETANALYZER:
    case DLT_NETANALYZER_TRANSPARENT:
      tmp = gen_prevlinkhdr_check(cstate);
      b = gen_ehostop(cstate, cstate->e, (int)q.dir);
      if (tmp != NULL)
        gen_and(tmp, b);
      break;
    case DLT_FDDI:
      b = gen_fhostop(cstate, cstate->e, (int)q.dir);
      break;
    case DLT_IEEE802:
      b = gen_thostop(cstate, cstate->e, (int)q.dir);
      break;
    case DLT_IEEE802_11:
    case DLT_PRISM_HEADER:
    case DLT_IEEE802_11_RADIO_AVS:
    case DLT_IEEE802_11_RADIO:
    case DLT_PPI:
      b = gen_wlanhostop(cstate, cstate->e, (int)q.dir);
      break;
    case DLT_IP_OVER_FC:
      b = gen_ipfchostop(cstate, cstate->e, (int)q.dir);
      break;
    default:
      free(cstate->e);
      cstate->e = NULL;
      bpf_error(cstate, "ethernet addresses supported only on ethernet/FDDI/token ring/802.11/ATM LANE/Fibre Channel");
      /*NOTREACHED*/
    }
    free(cstate->e);
    cstate->e = NULL;
    return (b);
  }
  bpf_error(cstate, "ethernet address used in non-ether expression");
  /*NOTREACHED*/
}

void
sappend(struct slist *s0, struct slist *s1)
{
  /*
   * This is definitely not the best way to do this, but the
   * lists will rarely get long.
   */
  while (s0->next)
    s0 = s0->next;
  s0->next = s1;
}

static struct slist *
xfer_to_x(compiler_state_t *cstate, struct arth *a)
{
  struct slist *s;

  s = new_stmt(cstate, BPF_LDX|BPF_MEM);
  s->s.k = a->regno;
  return s;
}

static struct slist *
xfer_to_a(compiler_state_t *cstate, struct arth *a)
{
  struct slist *s;

  s = new_stmt(cstate, BPF_LD|BPF_MEM);
  s->s.k = a->regno;
  return s;
}

/*
 * Modify "index" to use the value stored into its register as an
 * offset relative to the beginning of the header for the protocol
 * "proto", and allocate a register and put an item "size" bytes long
 * (1, 2, or 4) at that offset into that register, making it the register
 * for "index".
 */
static struct arth *
gen_load_internal(compiler_state_t *cstate, int proto, struct arth *inst,
    bpf_u_int32 size)
{
  int size_code;
  struct slist *s, *tmp;
  struct block *b;
  int regno = alloc_reg(cstate);

  free_reg(cstate, inst->regno);
  switch (size) {

  default:
    bpf_error(cstate, "data size must be 1, 2, or 4");
    /*NOTREACHED*/

  case 1:
    size_code = BPF_B;
    break;

  case 2:
    size_code = BPF_H;
    break;

  case 4:
    size_code = BPF_W;
    break;
  }
  switch (proto) {
  default:
    bpf_error(cstate, "unsupported index operation");

  case Q_RADIO:
    /*
     * The offset is relative to the beginning of the packet
     * data, if we have a radio header.  (If we don't, this
     * is an error.)
     */
    if (cstate->linktype != DLT_IEEE802_11_RADIO_AVS &&
        cstate->linktype != DLT_IEEE802_11_RADIO &&
        cstate->linktype != DLT_PRISM_HEADER)
      bpf_error(cstate, "radio information not present in capture");

    /*
     * Load into the X register the offset computed into the
     * register specified by "index".
     */
    s = xfer_to_x(cstate, inst);

    /*
     * Load the item at that offset.
     */
    tmp = new_stmt(cstate, BPF_LD|BPF_IND|size_code);
    sappend(s, tmp);
    sappend(inst->s, s);
    break;

  case Q_LINK:
    /*
     * The offset is relative to the beginning of
     * the link-layer header.
     *
     * XXX - what about ATM LANE?  Should the index be
     * relative to the beginning of the AAL5 frame, so
     * that 0 refers to the beginning of the LE Control
     * field, or relative to the beginning of the LAN
     * frame, so that 0 refers, for Ethernet LANE, to
     * the beginning of the destination address?
     */
    s = gen_abs_offset_varpart(cstate, &cstate->off_linkhdr);

    /*
     * If "s" is non-null, it has code to arrange that the
     * X register contains the length of the prefix preceding
     * the link-layer header.  Add to it the offset computed
     * into the register specified by "index", and move that
     * into the X register.  Otherwise, just load into the X
     * register the offset computed into the register specified
     * by "index".
     */
    if (s != NULL) {
      sappend(s, xfer_to_a(cstate, inst));
      sappend(s, new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X));
      sappend(s, new_stmt(cstate, BPF_MISC|BPF_TAX));
    } else
      s = xfer_to_x(cstate, inst);

    /*
     * Load the item at the sum of the offset we've put in the
     * X register and the offset of the start of the link
     * layer header (which is 0 if the radio header is
     * variable-length; that header length is what we put
     * into the X register and then added to the index).
     */
    tmp = new_stmt(cstate, BPF_LD|BPF_IND|size_code);
    tmp->s.k = cstate->off_linkhdr.constant_part;
    sappend(s, tmp);
    sappend(inst->s, s);
    break;

  case Q_IP:
  case Q_ARP:
  case Q_RARP:
  case Q_ATALK:
  case Q_DECNET:
  case Q_SCA:
  case Q_LAT:
  case Q_MOPRC:
  case Q_MOPDL:
  case Q_IPV6:
    /*
     * The offset is relative to the beginning of
     * the network-layer header.
     * XXX - are there any cases where we want
     * cstate->off_nl_nosnap?
     */
    s = gen_abs_offset_varpart(cstate, &cstate->off_linkpl);

    /*
     * If "s" is non-null, it has code to arrange that the
     * X register contains the variable part of the offset
     * of the link-layer payload.  Add to it the offset
     * computed into the register specified by "index",
     * and move that into the X register.  Otherwise, just
     * load into the X register the offset computed into
     * the register specified by "index".
     */
    if (s != NULL) {
      sappend(s, xfer_to_a(cstate, inst));
      sappend(s, new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X));
      sappend(s, new_stmt(cstate, BPF_MISC|BPF_TAX));
    } else
      s = xfer_to_x(cstate, inst);

    /*
     * Load the item at the sum of the offset we've put in the
     * X register, the offset of the start of the network
     * layer header from the beginning of the link-layer
     * payload, and the constant part of the offset of the
     * start of the link-layer payload.
     */
    tmp = new_stmt(cstate, BPF_LD|BPF_IND|size_code);
    tmp->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
    sappend(s, tmp);
    sappend(inst->s, s);

    /*
     * Do the computation only if the packet contains
     * the protocol in question.
     */
    b = gen_proto_abbrev_internal(cstate, proto);
    if (inst->b)
      gen_and(inst->b, b);
    inst->b = b;
    break;

  case Q_SCTP:
  case Q_TCP:
  case Q_UDP:
  case Q_ICMP:
  case Q_IGMP:
  case Q_IGRP:
  case Q_PIM:
  case Q_VRRP:
  case Q_CARP:
    /*
     * The offset is relative to the beginning of
     * the transport-layer header.
     *
     * Load the X register with the length of the IPv4 header
     * (plus the offset of the link-layer header, if it's
     * a variable-length header), in bytes.
     *
     * XXX - are there any cases where we want
     * cstate->off_nl_nosnap?
     * XXX - we should, if we're built with
     * IPv6 support, generate code to load either
     * IPv4, IPv6, or both, as appropriate.
     */
    s = gen_loadx_iphdrlen(cstate);

    /*
     * The X register now contains the sum of the variable
     * part of the offset of the link-layer payload and the
     * length of the network-layer header.
     *
     * Load into the A register the offset relative to
     * the beginning of the transport layer header,
     * add the X register to that, move that to the
     * X register, and load with an offset from the
     * X register equal to the sum of the constant part of
     * the offset of the link-layer payload and the offset,
     * relative to the beginning of the link-layer payload,
     * of the network-layer header.
     */
    sappend(s, xfer_to_a(cstate, inst));
    sappend(s, new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X));
    sappend(s, new_stmt(cstate, BPF_MISC|BPF_TAX));
    sappend(s, tmp = new_stmt(cstate, BPF_LD|BPF_IND|size_code));
    tmp->s.k = cstate->off_linkpl.constant_part + cstate->off_nl;
    sappend(inst->s, s);

    /*
     * Do the computation only if the packet contains
     * the protocol in question - which is true only
     * if this is an IP datagram and is the first or
     * only fragment of that datagram.
     */
    gen_and(gen_proto_abbrev_internal(cstate, proto), b = gen_ipfrag(cstate));
    if (inst->b)
      gen_and(inst->b, b);
    gen_and(gen_proto_abbrev_internal(cstate, Q_IP), b);
    inst->b = b;
    break;
  case Q_ICMPV6:
        /*
        * Do the computation only if the packet contains
        * the protocol in question.
        */
        b = gen_proto_abbrev_internal(cstate, Q_IPV6);
        if (inst->b) {
            gen_and(inst->b, b);
        }
        inst->b = b;

        /*
        * Check if we have an icmp6 next header
        */
        b = gen_cmp(cstate, OR_LINKPL, 6, BPF_B, 58);
        if (inst->b) {
            gen_and(inst->b, b);
        }
        inst->b = b;


        s = gen_abs_offset_varpart(cstate, &cstate->off_linkpl);
        /*
        * If "s" is non-null, it has code to arrange that the
        * X register contains the variable part of the offset
        * of the link-layer payload.  Add to it the offset
        * computed into the register specified by "index",
        * and move that into the X register.  Otherwise, just
        * load into the X register the offset computed into
        * the register specified by "index".
        */
        if (s != NULL) {
            sappend(s, xfer_to_a(cstate, inst));
            sappend(s, new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X));
            sappend(s, new_stmt(cstate, BPF_MISC|BPF_TAX));
        } else {
            s = xfer_to_x(cstate, inst);
        }

        /*
        * Load the item at the sum of the offset we've put in the
        * X register, the offset of the start of the network
        * layer header from the beginning of the link-layer
        * payload, and the constant part of the offset of the
        * start of the link-layer payload.
        */
        tmp = new_stmt(cstate, BPF_LD|BPF_IND|size_code);
        tmp->s.k = cstate->off_linkpl.constant_part + cstate->off_nl + 40;

        sappend(s, tmp);
        sappend(inst->s, s);

        break;
  }
  inst->regno = regno;
  s = new_stmt(cstate, BPF_ST);
  s->s.k = regno;
  sappend(inst->s, s);

  return inst;
}

struct arth *
gen_load(compiler_state_t *cstate, int proto, struct arth *inst,
    bpf_u_int32 size)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  return gen_load_internal(cstate, proto, inst, size);
}

static struct block *
gen_relation_internal(compiler_state_t *cstate, int code, struct arth *a0,
    struct arth *a1, int reversed)
{
  struct slist *s0, *s1, *s2;
  struct block *b, *tmp;

  s0 = xfer_to_x(cstate, a1);
  s1 = xfer_to_a(cstate, a0);
  if (code == BPF_JEQ) {
    s2 = new_stmt(cstate, BPF_ALU|BPF_SUB|BPF_X);
    b = new_block(cstate, JMP(code));
    sappend(s1, s2);
  }
  else
    b = new_block(cstate, BPF_JMP|code|BPF_X);
  if (reversed)
    gen_not(b);

  sappend(s0, s1);
  sappend(a1->s, s0);
  sappend(a0->s, a1->s);

  b->stmts = a0->s;

  free_reg(cstate, a0->regno);
  free_reg(cstate, a1->regno);

  /* 'and' together protocol checks */
  if (a0->b) {
    if (a1->b) {
      gen_and(a0->b, tmp = a1->b);
    }
    else
      tmp = a0->b;
  } else
    tmp = a1->b;

  if (tmp)
    gen_and(tmp, b);

  return b;
}

struct block *
gen_relation(compiler_state_t *cstate, int code, struct arth *a0,
    struct arth *a1, int reversed)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  return gen_relation_internal(cstate, code, a0, a1, reversed);
}

struct arth *
gen_loadlen(compiler_state_t *cstate)
{
  int regno;
  struct arth *a;
  struct slist *s;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  regno = alloc_reg(cstate);
  a = (struct arth *)newchunk(cstate, sizeof(*a));
  s = new_stmt(cstate, BPF_LD|BPF_LEN);
  s->next = new_stmt(cstate, BPF_ST);
  s->next->s.k = regno;
  a->s = s;
  a->regno = regno;

  return a;
}

static struct arth *
gen_loadi_internal(compiler_state_t *cstate, bpf_u_int32 val)
{
  struct arth *a;
  struct slist *s;
  int reg;

  a = (struct arth *)newchunk(cstate, sizeof(*a));

  reg = alloc_reg(cstate);

  s = new_stmt(cstate, BPF_LD|BPF_IMM);
  s->s.k = val;
  s->next = new_stmt(cstate, BPF_ST);
  s->next->s.k = reg;
  a->s = s;
  a->regno = reg;

  return a;
}

struct arth *
gen_loadi(compiler_state_t *cstate, bpf_u_int32 val)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  return gen_loadi_internal(cstate, val);
}

/*
 * The a_arg dance is to avoid annoying whining by compilers that
 * a might be clobbered by longjmp - yeah, it might, but *WHO CARES*?
 * It's not *used* after setjmp returns.
 */
struct arth *
gen_neg(compiler_state_t *cstate, struct arth *a_arg)
{
  struct arth *a = a_arg;
  struct slist *s;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  s = xfer_to_a(cstate, a);
  sappend(a->s, s);
  s = new_stmt(cstate, BPF_ALU|BPF_NEG);
  s->s.k = 0;
  sappend(a->s, s);
  s = new_stmt(cstate, BPF_ST);
  s->s.k = a->regno;
  sappend(a->s, s);

  return a;
}

/*
 * The a0_arg dance is to avoid annoying whining by compilers that
 * a0 might be clobbered by longjmp - yeah, it might, but *WHO CARES*?
 * It's not *used* after setjmp returns.
 */
struct arth *
gen_arth(compiler_state_t *cstate, int code, struct arth *a0_arg,
    struct arth *a1)
{
  struct arth *a0 = a0_arg;
  struct slist *s0, *s1, *s2;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Disallow division by, or modulus by, zero; we do this here
   * so that it gets done even if the optimizer is disabled.
   *
   * Also disallow shifts by a value greater than 31; we do this
   * here, for the same reason.
   */
  if (code == BPF_DIV) {
    if (a1->s->s.code == (BPF_LD|BPF_IMM) && a1->s->s.k == 0)
      bpf_error(cstate, "division by zero");
  } else if (code == BPF_MOD) {
    if (a1->s->s.code == (BPF_LD|BPF_IMM) && a1->s->s.k == 0)
      bpf_error(cstate, "modulus by zero");
  } else if (code == BPF_LSH || code == BPF_RSH) {
    if (a1->s->s.code == (BPF_LD|BPF_IMM) && a1->s->s.k > 31)
      bpf_error(cstate, "shift by more than 31 bits");
  }
  s0 = xfer_to_x(cstate, a1);
  s1 = xfer_to_a(cstate, a0);
  s2 = new_stmt(cstate, BPF_ALU|BPF_X|code);

  sappend(s1, s2);
  sappend(s0, s1);
  sappend(a1->s, s0);
  sappend(a0->s, a1->s);

  free_reg(cstate, a0->regno);
  free_reg(cstate, a1->regno);

  s0 = new_stmt(cstate, BPF_ST);
  a0->regno = s0->s.k = alloc_reg(cstate);
  sappend(a0->s, s0);

  return a0;
}

/*
 * Initialize the table of used registers and the current register.
 */
static void
init_regs(compiler_state_t *cstate)
{
  cstate->curreg = 0;
  memset(cstate->regused, 0, sizeof cstate->regused);
}

/*
 * Return the next free register.
 */
static int
alloc_reg(compiler_state_t *cstate)
{
  int n = BPF_MEMWORDS;

  while (--n >= 0) {
    if (cstate->regused[cstate->curreg])
      cstate->curreg = (cstate->curreg + 1) % BPF_MEMWORDS;
    else {
      cstate->regused[cstate->curreg] = 1;
      return cstate->curreg;
    }
  }
  bpf_error(cstate, "too many registers needed to evaluate expression");
  /*NOTREACHED*/
}

/*
 * Return a register to the table so it can
 * be used later.
 */
static void
free_reg(compiler_state_t *cstate, int n)
{
  cstate->regused[n] = 0;
}

static struct block *
gen_len(compiler_state_t *cstate, int jmp, int n)
{
  struct slist *s;
  struct block *b;

  s = new_stmt(cstate, BPF_LD|BPF_LEN);
  b = new_block(cstate, JMP(jmp));
  b->stmts = s;
  b->s.k = n;

  return b;
}

struct block *
gen_greater(compiler_state_t *cstate, int n)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  return gen_len(cstate, BPF_JGE, n);
}

/*
 * Actually, this is less than or equal.
 */
struct block *
gen_less(compiler_state_t *cstate, int n)
{
  struct block *b;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  b = gen_len(cstate, BPF_JGT, n);
  gen_not(b);

  return b;
}

/*
 * This is for "byte {idx} {op} {val}"; "idx" is treated as relative to
 * the beginning of the link-layer header.
 * XXX - that means you can't test values in the radiotap header, but
 * as that header is difficult if not impossible to parse generally
 * without a loop, that might not be a severe problem.  A new keyword
 * "radio" could be added for that, although what you'd really want
 * would be a way of testing particular radio header values, which
 * would generate code appropriate to the radio header in question.
 */
struct block *
gen_byteop(compiler_state_t *cstate, int op, int idx, bpf_u_int32 val)
{
  struct block *b;
  struct slist *s;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (op) {
  default:
    abort();

  case '=':
    return gen_cmp(cstate, OR_LINKHDR, (u_int)idx, BPF_B, val);

  case '<':
    b = gen_cmp_lt(cstate, OR_LINKHDR, (u_int)idx, BPF_B, val);
    return b;

  case '>':
    b = gen_cmp_gt(cstate, OR_LINKHDR, (u_int)idx, BPF_B, val);
    return b;

  case '|':
    s = new_stmt(cstate, BPF_ALU|BPF_OR|BPF_K);
    break;

  case '&':
    s = new_stmt(cstate, BPF_ALU|BPF_AND|BPF_K);
    break;
  }
  s->s.k = val;
  b = new_block(cstate, JMP(BPF_JEQ));
  b->stmts = s;
  gen_not(b);

  return b;
}

static const u_char abroadcast[] = { 0x0 };

struct block *
gen_broadcast(compiler_state_t *cstate, int proto)
{
  bpf_u_int32 hostmask;
  struct block *b0, *b1, *b2;
  static const u_char ebroadcast[] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (proto) {

  case Q_DEFAULT:
  case Q_LINK:
    switch (cstate->linktype) {
    case DLT_ARCNET:
    case DLT_ARCNET_LINUX:
      return gen_ahostop(cstate, abroadcast, Q_DST);
    case DLT_EN10MB:
    case DLT_NETANALYZER:
    case DLT_NETANALYZER_TRANSPARENT:
      b1 = gen_prevlinkhdr_check(cstate);
      b0 = gen_ehostop(cstate, ebroadcast, Q_DST);
      if (b1 != NULL)
        gen_and(b1, b0);
      return b0;
    case DLT_FDDI:
      return gen_fhostop(cstate, ebroadcast, Q_DST);
    case DLT_IEEE802:
      return gen_thostop(cstate, ebroadcast, Q_DST);
    case DLT_IEEE802_11:
    case DLT_PRISM_HEADER:
    case DLT_IEEE802_11_RADIO_AVS:
    case DLT_IEEE802_11_RADIO:
    case DLT_PPI:
      return gen_wlanhostop(cstate, ebroadcast, Q_DST);
    case DLT_IP_OVER_FC:
      return gen_ipfchostop(cstate, ebroadcast, Q_DST);
    default:
      bpf_error(cstate, "not a broadcast link");
    }
    /*NOTREACHED*/

  case Q_IP:
    /*
     * We treat a netmask of PCAP_NETMASK_UNKNOWN (0xffffffff)
     * as an indication that we don't know the netmask, and fail
     * in that case.
     */
    if (cstate->netmask == PCAP_NETMASK_UNKNOWN)
      bpf_error(cstate, "netmask not known, so 'ip broadcast' not supported");
    b0 = gen_linktype(cstate, ETHERTYPE_IP);
    hostmask = ~cstate->netmask;
    b1 = gen_mcmp(cstate, OR_LINKPL, 16, BPF_W, 0, hostmask);
    b2 = gen_mcmp(cstate, OR_LINKPL, 16, BPF_W,
            ~0 & hostmask, hostmask);
    gen_or(b1, b2);
    gen_and(b0, b2);
    return b2;
  }
  bpf_error(cstate, "only link-layer/IP broadcast filters supported");
  /*NOTREACHED*/
}

/*
 * Generate code to test the low-order bit of a MAC address (that's
 * the bottom bit of the *first* byte).
 */
static struct block *
gen_mac_multicast(compiler_state_t *cstate, int offset)
{
  register struct block *b0;
  register struct slist *s;

  /* link[offset] & 1 != 0 */
  s = gen_load_a(cstate, OR_LINKHDR, offset, BPF_B);
  b0 = new_block(cstate, JMP(BPF_JSET));
  b0->s.k = 1;
  b0->stmts = s;
  return b0;
}

struct block *
gen_multicast(compiler_state_t *cstate, int proto)
{
  register struct block *b0, *b1, *b2;
  register struct slist *s;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (proto) {

  case Q_DEFAULT:
  case Q_LINK:
    switch (cstate->linktype) {
    case DLT_ARCNET:
    case DLT_ARCNET_LINUX:
      /* all ARCnet multicasts use the same address */
      return gen_ahostop(cstate, abroadcast, Q_DST);
    case DLT_EN10MB:
    case DLT_NETANALYZER:
    case DLT_NETANALYZER_TRANSPARENT:
      b1 = gen_prevlinkhdr_check(cstate);
      /* ether[0] & 1 != 0 */
      b0 = gen_mac_multicast(cstate, 0);
      if (b1 != NULL)
        gen_and(b1, b0);
      return b0;
    case DLT_FDDI:
      /*
       * XXX TEST THIS: MIGHT NOT PORT PROPERLY XXX
       *
       * XXX - was that referring to bit-order issues?
       */
      /* fddi[1] & 1 != 0 */
      return gen_mac_multicast(cstate, 1);
    case DLT_IEEE802:
      /* tr[2] & 1 != 0 */
      return gen_mac_multicast(cstate, 2);
    case DLT_IEEE802_11:
    case DLT_PRISM_HEADER:
    case DLT_IEEE802_11_RADIO_AVS:
    case DLT_IEEE802_11_RADIO:
    case DLT_PPI:
      /*
       * Oh, yuk.
       *
       *  For control frames, there is no DA.
       *
       *  For management frames, DA is at an
       *  offset of 4 from the beginning of
       *  the packet.
       *
       *  For data frames, DA is at an offset
       *  of 4 from the beginning of the packet
       *  if To DS is clear and at an offset of
       *  16 from the beginning of the packet
       *  if To DS is set.
       */

      /*
       * Generate the tests to be done for data frames.
       *
       * First, check for To DS set, i.e. "link[1] & 0x01".
       */
      s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
      b1 = new_block(cstate, JMP(BPF_JSET));
      b1->s.k = 0x01; /* To DS */
      b1->stmts = s;

      /*
       * If To DS is set, the DA is at 16.
       */
      b0 = gen_mac_multicast(cstate, 16);
      gen_and(b1, b0);

      /*
       * Now, check for To DS not set, i.e. check
       * "!(link[1] & 0x01)".
       */
      s = gen_load_a(cstate, OR_LINKHDR, 1, BPF_B);
      b2 = new_block(cstate, JMP(BPF_JSET));
      b2->s.k = 0x01; /* To DS */
      b2->stmts = s;
      gen_not(b2);

      /*
       * If To DS is not set, the DA is at 4.
       */
      b1 = gen_mac_multicast(cstate, 4);
      gen_and(b2, b1);

      /*
       * Now OR together the last two checks.  That gives
       * the complete set of checks for data frames.
       */
      gen_or(b1, b0);

      /*
       * Now check for a data frame.
       * I.e, check "link[0] & 0x08".
       */
      s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
      b1 = new_block(cstate, JMP(BPF_JSET));
      b1->s.k = 0x08;
      b1->stmts = s;

      /*
       * AND that with the checks done for data frames.
       */
      gen_and(b1, b0);

      /*
       * If the high-order bit of the type value is 0, this
       * is a management frame.
       * I.e, check "!(link[0] & 0x08)".
       */
      s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
      b2 = new_block(cstate, JMP(BPF_JSET));
      b2->s.k = 0x08;
      b2->stmts = s;
      gen_not(b2);

      /*
       * For management frames, the DA is at 4.
       */
      b1 = gen_mac_multicast(cstate, 4);
      gen_and(b2, b1);

      /*
       * OR that with the checks done for data frames.
       * That gives the checks done for management and
       * data frames.
       */
      gen_or(b1, b0);

      /*
       * If the low-order bit of the type value is 1,
       * this is either a control frame or a frame
       * with a reserved type, and thus not a
       * frame with an SA.
       *
       * I.e., check "!(link[0] & 0x04)".
       */
      s = gen_load_a(cstate, OR_LINKHDR, 0, BPF_B);
      b1 = new_block(cstate, JMP(BPF_JSET));
      b1->s.k = 0x04;
      b1->stmts = s;
      gen_not(b1);

      /*
       * AND that with the checks for data and management
       * frames.
       */
      gen_and(b1, b0);
      return b0;
    case DLT_IP_OVER_FC:
      b0 = gen_mac_multicast(cstate, 2);
      return b0;
    default:
      break;
    }
    /* Link not known to support multicasts */
    break;

  case Q_IP:
    b0 = gen_linktype(cstate, ETHERTYPE_IP);
    b1 = gen_cmp_ge(cstate, OR_LINKPL, 16, BPF_B, 224);
    gen_and(b0, b1);
    return b1;

  case Q_IPV6:
    b0 = gen_linktype(cstate, ETHERTYPE_IPV6);
    b1 = gen_cmp(cstate, OR_LINKPL, 24, BPF_B, 255);
    gen_and(b0, b1);
    return b1;
  }
  bpf_error(cstate, "link-layer multicast filters supported only on ethernet/FDDI/token ring/ARCNET/802.11/ATM LANE/Fibre Channel");
  /*NOTREACHED*/
}

struct block *
gen_ifindex(compiler_state_t *cstate, int ifindex)
{
  register struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Only some data link types support ifindex qualifiers.
   */
  switch (cstate->linktype) {
  case DLT_LINUX_SLL2:
    /* match packets on this interface */
    b0 = gen_cmp(cstate, OR_LINKHDR, 4, BPF_W, ifindex);
    break;
        default:
#if defined(linux)
    /*
     * This is Linux; we require PF_PACKET support.
     * If this is a *live* capture, we can look at
     * special meta-data in the filter expression;
     * if it's a savefile, we can't.
     */
    if (cstate->bpf_pcap->rfile != NULL) {
      /* We have a FILE *, so this is a savefile */
      bpf_error(cstate, "ifindex not supported on %s when reading savefiles",
          pcap_datalink_val_to_description_or_dlt(cstate->linktype));
      b0 = NULL;
      /*NOTREACHED*/
    }
    /* match ifindex */
    b0 = gen_cmp(cstate, OR_LINKHDR, SKF_AD_OFF + SKF_AD_IFINDEX, BPF_W,
                 ifindex);
#else /* defined(linux) */
    bpf_error(cstate, "ifindex not supported on %s",
        pcap_datalink_val_to_description_or_dlt(cstate->linktype));
    /*NOTREACHED*/
#endif /* defined(linux) */
  }
  return (b0);
}

/*
 * Filter on inbound (dir == 0) or outbound (dir == 1) traffic.
 * Outbound traffic is sent by this machine, while inbound traffic is
 * sent by a remote machine (and may include packets destined for a
 * unicast or multicast link-layer address we are not subscribing to).
 * These are the same definitions implemented by pcap_setdirection().
 * Capturing only unicast traffic destined for this host is probably
 * better accomplished using a higher-layer filter.
 */
struct block *
gen_inbound(compiler_state_t *cstate, int dir)
{
  register struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Only some data link types support inbound/outbound qualifiers.
   */
  switch (cstate->linktype) {
  case DLT_SLIP:
    b0 = gen_relation_internal(cstate, BPF_JEQ,
        gen_load_internal(cstate, Q_LINK, gen_loadi_internal(cstate, 0), 1),
        gen_loadi_internal(cstate, 0),
        dir);
    break;

  case DLT_IPNET:
    if (dir) {
      /* match outgoing packets */
      b0 = gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, IPNET_OUTBOUND);
    } else {
      /* match incoming packets */
      b0 = gen_cmp(cstate, OR_LINKHDR, 2, BPF_H, IPNET_INBOUND);
    }
    break;

  case DLT_LINUX_SLL:
    /* match outgoing packets */
    b0 = gen_cmp(cstate, OR_LINKHDR, 0, BPF_H, LINUX_SLL_OUTGOING);
    if (!dir) {
      /* to filter on inbound traffic, invert the match */
      gen_not(b0);
    }
    break;

  case DLT_LINUX_SLL2:
    /* match outgoing packets */
    b0 = gen_cmp(cstate, OR_LINKHDR, 10, BPF_B, LINUX_SLL_OUTGOING);
    if (!dir) {
      /* to filter on inbound traffic, invert the match */
      gen_not(b0);
    }
    break;

  case DLT_PFLOG:
    b0 = gen_cmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, dir), BPF_B,
        ((dir == 0) ? PF_IN : PF_OUT));
    break;

  case DLT_PPP_PPPD:
    if (dir) {
      /* match outgoing packets */
      b0 = gen_cmp(cstate, OR_LINKHDR, 0, BPF_B, PPP_PPPD_OUT);
    } else {
      /* match incoming packets */
      b0 = gen_cmp(cstate, OR_LINKHDR, 0, BPF_B, PPP_PPPD_IN);
    }
    break;

        case DLT_JUNIPER_MFR:
        case DLT_JUNIPER_MLFR:
        case DLT_JUNIPER_MLPPP:
  case DLT_JUNIPER_ATM1:
  case DLT_JUNIPER_ATM2:
  case DLT_JUNIPER_PPPOE:
  case DLT_JUNIPER_PPPOE_ATM:
        case DLT_JUNIPER_GGSN:
        case DLT_JUNIPER_ES:
        case DLT_JUNIPER_MONITOR:
        case DLT_JUNIPER_SERVICES:
        case DLT_JUNIPER_ETHER:
        case DLT_JUNIPER_PPP:
        case DLT_JUNIPER_FRELAY:
        case DLT_JUNIPER_CHDLC:
        case DLT_JUNIPER_VP:
        case DLT_JUNIPER_ST:
        case DLT_JUNIPER_ISM:
        case DLT_JUNIPER_VS:
        case DLT_JUNIPER_SRX_E2E:
        case DLT_JUNIPER_FIBRECHANNEL:
  case DLT_JUNIPER_ATM_CEMIC:

    /* juniper flags (including direction) are stored
     * the byte after the 3-byte magic number */
    if (dir) {
      /* match outgoing packets */
      b0 = gen_mcmp(cstate, OR_LINKHDR, 3, BPF_B, 0, 0x01);
    } else {
      /* match incoming packets */
      b0 = gen_mcmp(cstate, OR_LINKHDR, 3, BPF_B, 1, 0x01);
    }
    break;

  default:
    /*
     * If we have packet meta-data indicating a direction,
     * and that metadata can be checked by BPF code, check
     * it.  Otherwise, give up, as this link-layer type has
     * nothing in the packet data.
     *
     * Currently, the only platform where a BPF filter can
     * check that metadata is Linux with the in-kernel
     * BPF interpreter.  If other packet capture mechanisms
     * and BPF filters also supported this, it would be
     * nice.  It would be even better if they made that
     * metadata available so that we could provide it
     * with newer capture APIs, allowing it to be saved
     * in pcapng files.
     */
#if defined(linux)
    /*
     * This is Linux; we require PF_PACKET support.
     * If this is a *live* capture, we can look at
     * special meta-data in the filter expression;
     * if it's a savefile, we can't.
     */
    if (cstate->bpf_pcap->rfile != NULL) {
      /* We have a FILE *, so this is a savefile */
      bpf_error(cstate, "inbound/outbound not supported on %s when reading savefiles",
          pcap_datalink_val_to_description_or_dlt(cstate->linktype));
      /*NOTREACHED*/
    }
    /* match outgoing packets */
    b0 = gen_cmp(cstate, OR_LINKHDR, SKF_AD_OFF + SKF_AD_PKTTYPE, BPF_H,
                 PACKET_OUTGOING);
    if (!dir) {
      /* to filter on inbound traffic, invert the match */
      gen_not(b0);
    }
#else /* defined(linux) */
    bpf_error(cstate, "inbound/outbound not supported on %s",
        pcap_datalink_val_to_description_or_dlt(cstate->linktype));
    /*NOTREACHED*/
#endif /* defined(linux) */
  }
  return (b0);
}

/* PF firewall log matched interface */
struct block *
gen_pf_ifname(compiler_state_t *cstate, const char *ifname)
{
  struct block *b0;
  u_int len, off;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if (cstate->linktype != DLT_PFLOG) {
    bpf_error(cstate, "ifname supported only on PF linktype");
    /*NOTREACHED*/
  }
  len = sizeof(((struct pfloghdr *)0)->ifname);
  off = offsetof(struct pfloghdr, ifname);
  if (strlen(ifname) >= len) {
    bpf_error(cstate, "ifname interface names can only be %d characters",
        len-1);
    /*NOTREACHED*/
  }
  b0 = gen_bcmp(cstate, OR_LINKHDR, off, (u_int)strlen(ifname),
      (const u_char *)ifname);
  return (b0);
}

/* PF firewall log ruleset name */
struct block *
gen_pf_ruleset(compiler_state_t *cstate, char *ruleset)
{
  struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if (cstate->linktype != DLT_PFLOG) {
    bpf_error(cstate, "ruleset supported only on PF linktype");
    /*NOTREACHED*/
  }

  if (strlen(ruleset) >= sizeof(((struct pfloghdr *)0)->ruleset)) {
    bpf_error(cstate, "ruleset names can only be %ld characters",
        (long)(sizeof(((struct pfloghdr *)0)->ruleset) - 1));
    /*NOTREACHED*/
  }

  b0 = gen_bcmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, ruleset),
      (u_int)strlen(ruleset), (const u_char *)ruleset);
  return (b0);
}

/* PF firewall log rule number */
struct block *
gen_pf_rnr(compiler_state_t *cstate, int rnr)
{
  struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if (cstate->linktype != DLT_PFLOG) {
    bpf_error(cstate, "rnr supported only on PF linktype");
    /*NOTREACHED*/
  }

  b0 = gen_cmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, rulenr), BPF_W,
     (bpf_u_int32)rnr);
  return (b0);
}

/* PF firewall log sub-rule number */
struct block *
gen_pf_srnr(compiler_state_t *cstate, int srnr)
{
  struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if (cstate->linktype != DLT_PFLOG) {
    bpf_error(cstate, "srnr supported only on PF linktype");
    /*NOTREACHED*/
  }

  b0 = gen_cmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, subrulenr), BPF_W,
      (bpf_u_int32)srnr);
  return (b0);
}

/* PF firewall log reason code */
struct block *
gen_pf_reason(compiler_state_t *cstate, int reason)
{
  struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if (cstate->linktype != DLT_PFLOG) {
    bpf_error(cstate, "reason supported only on PF linktype");
    /*NOTREACHED*/
  }

  b0 = gen_cmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, reason), BPF_B,
      (bpf_u_int32)reason);
  return (b0);
}

/* PF firewall log action */
struct block *
gen_pf_action(compiler_state_t *cstate, int action)
{
  struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  if (cstate->linktype != DLT_PFLOG) {
    bpf_error(cstate, "action supported only on PF linktype");
    /*NOTREACHED*/
  }

  b0 = gen_cmp(cstate, OR_LINKHDR, offsetof(struct pfloghdr, action), BPF_B,
      (bpf_u_int32)action);
  return (b0);
}

/* IEEE 802.11 wireless header */
struct block *
gen_p80211_type(compiler_state_t *cstate, bpf_u_int32 type, bpf_u_int32 mask)
{
  struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (cstate->linktype) {

  case DLT_IEEE802_11:
  case DLT_PRISM_HEADER:
  case DLT_IEEE802_11_RADIO_AVS:
  case DLT_IEEE802_11_RADIO:
    b0 = gen_mcmp(cstate, OR_LINKHDR, 0, BPF_B, type, mask);
    break;

  default:
    bpf_error(cstate, "802.11 link-layer types supported only on 802.11");
    /*NOTREACHED*/
  }

  return (b0);
}

struct block *
gen_p80211_fcdir(compiler_state_t *cstate, bpf_u_int32 fcdir)
{
  struct block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (cstate->linktype) {

  case DLT_IEEE802_11:
  case DLT_PRISM_HEADER:
  case DLT_IEEE802_11_RADIO_AVS:
  case DLT_IEEE802_11_RADIO:
    break;

  default:
    bpf_error(cstate, "frame direction supported only with 802.11 headers");
    /*NOTREACHED*/
  }

  b0 = gen_mcmp(cstate, OR_LINKHDR, 1, BPF_B, fcdir,
      IEEE80211_FC1_DIR_MASK);

  return (b0);
}

struct block *
gen_acode(compiler_state_t *cstate, const char *s, struct qual q)
{
  struct block *b;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (cstate->linktype) {

  case DLT_ARCNET:
  case DLT_ARCNET_LINUX:
    if ((q.addr == Q_HOST || q.addr == Q_DEFAULT) &&
        q.proto == Q_LINK) {
      cstate->e = pcap_ether_aton(s);
      if (cstate->e == NULL)
        bpf_error(cstate, "malloc");
      b = gen_ahostop(cstate, cstate->e, (int)q.dir);
      free(cstate->e);
      cstate->e = NULL;
      return (b);
    } else
      bpf_error(cstate, "ARCnet address used in non-arc expression");
    /*NOTREACHED*/

  default:
    bpf_error(cstate, "aid supported only on ARCnet");
    /*NOTREACHED*/
  }
}

static struct block *
gen_ahostop(compiler_state_t *cstate, const u_char *eaddr, int dir)
{
  register struct block *b0, *b1;

  switch (dir) {
  /* src comes first, different from Ethernet */
  case Q_SRC:
    return gen_bcmp(cstate, OR_LINKHDR, 0, 1, eaddr);

  case Q_DST:
    return gen_bcmp(cstate, OR_LINKHDR, 1, 1, eaddr);

  case Q_AND:
    b0 = gen_ahostop(cstate, eaddr, Q_SRC);
    b1 = gen_ahostop(cstate, eaddr, Q_DST);
    gen_and(b0, b1);
    return b1;

  case Q_DEFAULT:
  case Q_OR:
    b0 = gen_ahostop(cstate, eaddr, Q_SRC);
    b1 = gen_ahostop(cstate, eaddr, Q_DST);
    gen_or(b0, b1);
    return b1;

  case Q_ADDR1:
    bpf_error(cstate, "'addr1' and 'address1' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR2:
    bpf_error(cstate, "'addr2' and 'address2' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR3:
    bpf_error(cstate, "'addr3' and 'address3' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_ADDR4:
    bpf_error(cstate, "'addr4' and 'address4' are only supported on 802.11");
    /*NOTREACHED*/

  case Q_RA:
    bpf_error(cstate, "'ra' is only supported on 802.11");
    /*NOTREACHED*/

  case Q_TA:
    bpf_error(cstate, "'ta' is only supported on 802.11");
    /*NOTREACHED*/
  }
  abort();
  /*NOTREACHED*/
}

static struct block *
gen_vlan_tpid_test(compiler_state_t *cstate)
{
  struct block *b0, *b1;

  /* check for VLAN, including 802.1ad and QinQ */
  b0 = gen_linktype(cstate, ETHERTYPE_8021Q);
  b1 = gen_linktype(cstate, ETHERTYPE_8021AD);
  gen_or(b0,b1);
  b0 = b1;
  b1 = gen_linktype(cstate, ETHERTYPE_8021QINQ);
  gen_or(b0,b1);

  return b1;
}

static struct block *
gen_vlan_vid_test(compiler_state_t *cstate, bpf_u_int32 vlan_num)
{
  if (vlan_num > 0x0fff) {
    bpf_error(cstate, "VLAN tag %u greater than maximum %u",
        vlan_num, 0x0fff);
  }
  return gen_mcmp(cstate, OR_LINKPL, 0, BPF_H, vlan_num, 0x0fff);
}

static struct block *
gen_vlan_no_bpf_extensions(compiler_state_t *cstate, bpf_u_int32 vlan_num,
    int has_vlan_tag)
{
  struct block *b0, *b1;

  b0 = gen_vlan_tpid_test(cstate);

  if (has_vlan_tag) {
    b1 = gen_vlan_vid_test(cstate, vlan_num);
    gen_and(b0, b1);
    b0 = b1;
  }

  /*
   * Both payload and link header type follow the VLAN tags so that
   * both need to be updated.
   */
  cstate->off_linkpl.constant_part += 4;
  cstate->off_linktype.constant_part += 4;

  return b0;
}

#if defined(SKF_AD_VLAN_TAG_PRESENT)
/* add v to variable part of off */
static void
gen_vlan_vloffset_add(compiler_state_t *cstate, bpf_abs_offset *off,
    bpf_u_int32 v, struct slist *s)
{
  struct slist *s2;

  if (!off->is_variable)
    off->is_variable = 1;
  if (off->reg == -1)
    off->reg = alloc_reg(cstate);

  s2 = new_stmt(cstate, BPF_LD|BPF_MEM);
  s2->s.k = off->reg;
  sappend(s, s2);
  s2 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_IMM);
  s2->s.k = v;
  sappend(s, s2);
  s2 = new_stmt(cstate, BPF_ST);
  s2->s.k = off->reg;
  sappend(s, s2);
}

/*
 * patch block b_tpid (VLAN TPID test) to update variable parts of link payload
 * and link type offsets first
 */
static void
gen_vlan_patch_tpid_test(compiler_state_t *cstate, struct block *b_tpid)
{
  struct slist s;

  /* offset determined at run time, shift variable part */
  s.next = NULL;
  cstate->is_vlan_vloffset = 1;
  gen_vlan_vloffset_add(cstate, &cstate->off_linkpl, 4, &s);
  gen_vlan_vloffset_add(cstate, &cstate->off_linktype, 4, &s);

  /* we get a pointer to a chain of or-ed blocks, patch first of them */
  sappend(s.next, b_tpid->head->stmts);
  b_tpid->head->stmts = s.next;
}

/*
 * patch block b_vid (VLAN id test) to load VID value either from packet
 * metadata (using BPF extensions) if SKF_AD_VLAN_TAG_PRESENT is true
 */
static void
gen_vlan_patch_vid_test(compiler_state_t *cstate, struct block *b_vid)
{
  struct slist *s, *s2, *sjeq;
  unsigned cnt;

  s = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
  s->s.k = SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT;

  /* true -> next instructions, false -> beginning of b_vid */
  sjeq = new_stmt(cstate, JMP(BPF_JEQ));
  sjeq->s.k = 1;
  sjeq->s.jf = b_vid->stmts;
  sappend(s, sjeq);

  s2 = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
  s2->s.k = SKF_AD_OFF + SKF_AD_VLAN_TAG;
  sappend(s, s2);
  sjeq->s.jt = s2;

  /* Jump to the test in b_vid. We need to jump one instruction before
   * the end of the b_vid block so that we only skip loading the TCI
   * from packet data and not the 'and' instruction extractging VID.
   */
  cnt = 0;
  for (s2 = b_vid->stmts; s2; s2 = s2->next)
    cnt++;
  s2 = new_stmt(cstate, JMP(BPF_JA));
  s2->s.k = cnt - 1;
  sappend(s, s2);

  /* insert our statements at the beginning of b_vid */
  sappend(s, b_vid->stmts);
  b_vid->stmts = s;
}

/*
 * Generate check for "vlan" or "vlan <id>" on systems with support for BPF
 * extensions.  Even if kernel supports VLAN BPF extensions, (outermost) VLAN
 * tag can be either in metadata or in packet data; therefore if the
 * SKF_AD_VLAN_TAG_PRESENT test is negative, we need to check link
 * header for VLAN tag. As the decision is done at run time, we need
 * update variable part of the offsets
 */
static struct block *
gen_vlan_bpf_extensions(compiler_state_t *cstate, bpf_u_int32 vlan_num,
    int has_vlan_tag)
{
        struct block *b0, *b_tpid, *b_vid = NULL;
        struct slist *s;

        /* generate new filter code based on extracting packet
         * metadata */
        s = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
        s->s.k = SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT;

        b0 = new_block(cstate, JMP(BPF_JEQ));
        b0->stmts = s;
        b0->s.k = 1;

  /*
   * This is tricky. We need to insert the statements updating variable
   * parts of offsets before the traditional TPID and VID tests so
   * that they are called whenever SKF_AD_VLAN_TAG_PRESENT fails but
   * we do not want this update to affect those checks. That's why we
   * generate both test blocks first and insert the statements updating
   * variable parts of both offsets after that. This wouldn't work if
   * there already were variable length link header when entering this
   * function but gen_vlan_bpf_extensions() isn't called in that case.
   */
  b_tpid = gen_vlan_tpid_test(cstate);
  if (has_vlan_tag)
    b_vid = gen_vlan_vid_test(cstate, vlan_num);

  gen_vlan_patch_tpid_test(cstate, b_tpid);
  gen_or(b0, b_tpid);
  b0 = b_tpid;

  if (has_vlan_tag) {
    gen_vlan_patch_vid_test(cstate, b_vid);
    gen_and(b0, b_vid);
    b0 = b_vid;
  }

        return b0;
}
#endif

/*
 * support IEEE 802.1Q VLAN trunk over ethernet
 */
struct block *
gen_vlan(compiler_state_t *cstate, bpf_u_int32 vlan_num, int has_vlan_tag)
{
  struct  block *b0;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /* can't check for VLAN-encapsulated packets inside MPLS */
  if (cstate->label_stack_depth > 0)
    bpf_error(cstate, "no VLAN match after MPLS");

  /*
   * Check for a VLAN packet, and then change the offsets to point
   * to the type and data fields within the VLAN packet.  Just
   * increment the offsets, so that we can support a hierarchy, e.g.
   * "vlan 300 && vlan 200" to capture VLAN 200 encapsulated within
   * VLAN 100.
   *
   * XXX - this is a bit of a kludge.  If we were to split the
   * compiler into a parser that parses an expression and
   * generates an expression tree, and a code generator that
   * takes an expression tree (which could come from our
   * parser or from some other parser) and generates BPF code,
   * we could perhaps make the offsets parameters of routines
   * and, in the handler for an "AND" node, pass to subnodes
   * other than the VLAN node the adjusted offsets.
   *
   * This would mean that "vlan" would, instead of changing the
   * behavior of *all* tests after it, change only the behavior
   * of tests ANDed with it.  That would change the documented
   * semantics of "vlan", which might break some expressions.
   * However, it would mean that "(vlan and ip) or ip" would check
   * both for VLAN-encapsulated IP and IP-over-Ethernet, rather than
   * checking only for VLAN-encapsulated IP, so that could still
   * be considered worth doing; it wouldn't break expressions
   * that are of the form "vlan and ..." or "vlan N and ...",
   * which I suspect are the most common expressions involving
   * "vlan".  "vlan or ..." doesn't necessarily do what the user
   * would really want, now, as all the "or ..." tests would
   * be done assuming a VLAN, even though the "or" could be viewed
   * as meaning "or, if this isn't a VLAN packet...".
   */
  switch (cstate->linktype) {

  case DLT_EN10MB:
  case DLT_NETANALYZER:
  case DLT_NETANALYZER_TRANSPARENT:
#if defined(SKF_AD_VLAN_TAG_PRESENT)
    /* Verify that this is the outer part of the packet and
     * not encapsulated somehow. */
    if (cstate->vlan_stack_depth == 0 && !cstate->off_linkhdr.is_variable &&
        cstate->off_linkhdr.constant_part ==
        cstate->off_outermostlinkhdr.constant_part) {
      /*
       * Do we need special VLAN handling?
       */
      if (cstate->bpf_pcap->bpf_codegen_flags & BPF_SPECIAL_VLAN_HANDLING)
        b0 = gen_vlan_bpf_extensions(cstate, vlan_num,
            has_vlan_tag);
      else
        b0 = gen_vlan_no_bpf_extensions(cstate,
            vlan_num, has_vlan_tag);
    } else
#endif
      b0 = gen_vlan_no_bpf_extensions(cstate, vlan_num,
          has_vlan_tag);
                break;

  case DLT_IEEE802_11:
  case DLT_PRISM_HEADER:
  case DLT_IEEE802_11_RADIO_AVS:
  case DLT_IEEE802_11_RADIO:
    b0 = gen_vlan_no_bpf_extensions(cstate, vlan_num, has_vlan_tag);
    break;

  default:
    bpf_error(cstate, "no VLAN support for %s",
          pcap_datalink_val_to_description_or_dlt(cstate->linktype));
    /*NOTREACHED*/
  }

        cstate->vlan_stack_depth++;

  return (b0);
}

/*
 * support for MPLS
 *
 * The label_num_arg dance is to avoid annoying whining by compilers that
 * label_num might be clobbered by longjmp - yeah, it might, but *WHO CARES*?
 * It's not *used* after setjmp returns.
 */
struct block *
gen_mpls(compiler_state_t *cstate, bpf_u_int32 label_num_arg,
    int has_label_num)
{
  volatile bpf_u_int32 label_num = label_num_arg;
  struct  block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

        if (cstate->label_stack_depth > 0) {
            /* just match the bottom-of-stack bit clear */
            b0 = gen_mcmp(cstate, OR_PREVMPLSHDR, 2, BPF_B, 0, 0x01);
        } else {
            /*
             * We're not in an MPLS stack yet, so check the link-layer
             * type against MPLS.
             */
            switch (cstate->linktype) {

            case DLT_C_HDLC: /* fall through */
            case DLT_HDLC:
            case DLT_EN10MB:
            case DLT_NETANALYZER:
            case DLT_NETANALYZER_TRANSPARENT:
                    b0 = gen_linktype(cstate, ETHERTYPE_MPLS);
                    break;

            case DLT_PPP:
                    b0 = gen_linktype(cstate, PPP_MPLS_UCAST);
                    break;

                    /* FIXME add other DLT_s ...
                     * for Frame-Relay/and ATM this may get messy due to SNAP headers
                     * leave it for now */

            default:
                    bpf_error(cstate, "no MPLS support for %s",
                          pcap_datalink_val_to_description_or_dlt(cstate->linktype));
                    /*NOTREACHED*/
            }
        }

  /* If a specific MPLS label is requested, check it */
  if (has_label_num) {
    if (label_num > 0xFFFFF) {
      bpf_error(cstate, "MPLS label %u greater than maximum %u",
          label_num, 0xFFFFF);
    }
    label_num = label_num << 12; /* label is shifted 12 bits on the wire */
    b1 = gen_mcmp(cstate, OR_LINKPL, 0, BPF_W, label_num,
        0xfffff000); /* only compare the first 20 bits */
    gen_and(b0, b1);
    b0 = b1;
  }

        /*
         * Change the offsets to point to the type and data fields within
         * the MPLS packet.  Just increment the offsets, so that we
         * can support a hierarchy, e.g. "mpls 100000 && mpls 1024" to
         * capture packets with an outer label of 100000 and an inner
         * label of 1024.
         *
         * Increment the MPLS stack depth as well; this indicates that
         * we're checking MPLS-encapsulated headers, to make sure higher
         * level code generators don't try to match against IP-related
         * protocols such as Q_ARP, Q_RARP etc.
         *
         * XXX - this is a bit of a kludge.  See comments in gen_vlan().
         */
        cstate->off_nl_nosnap += 4;
        cstate->off_nl += 4;
        cstate->label_stack_depth++;
  return (b0);
}

/*
 * Support PPPOE discovery and session.
 */
struct block *
gen_pppoed(compiler_state_t *cstate)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /* check for PPPoE discovery */
  return gen_linktype(cstate, ETHERTYPE_PPPOED);
}

struct block *
gen_pppoes(compiler_state_t *cstate, bpf_u_int32 sess_num, int has_sess_num)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  /*
   * Test against the PPPoE session link-layer type.
   */
  b0 = gen_linktype(cstate, ETHERTYPE_PPPOES);

  /* If a specific session is requested, check PPPoE session id */
  if (has_sess_num) {
    if (sess_num > 0x0000ffff) {
      bpf_error(cstate, "PPPoE session number %u greater than maximum %u",
          sess_num, 0x0000ffff);
    }
    b1 = gen_mcmp(cstate, OR_LINKPL, 0, BPF_W, sess_num, 0x0000ffff);
    gen_and(b0, b1);
    b0 = b1;
  }

  /*
   * Change the offsets to point to the type and data fields within
   * the PPP packet, and note that this is PPPoE rather than
   * raw PPP.
   *
   * XXX - this is a bit of a kludge.  See the comments in
   * gen_vlan().
   *
   * The "network-layer" protocol is PPPoE, which has a 6-byte
   * PPPoE header, followed by a PPP packet.
   *
   * There is no HDLC encapsulation for the PPP packet (it's
   * encapsulated in PPPoES instead), so the link-layer type
   * starts at the first byte of the PPP packet.  For PPPoE,
   * that offset is relative to the beginning of the total
   * link-layer payload, including any 802.2 LLC header, so
   * it's 6 bytes past cstate->off_nl.
   */
  PUSH_LINKHDR(cstate, DLT_PPP, cstate->off_linkpl.is_variable,
      cstate->off_linkpl.constant_part + cstate->off_nl + 6, /* 6 bytes past the PPPoE header */
      cstate->off_linkpl.reg);

  cstate->off_linktype = cstate->off_linkhdr;
  cstate->off_linkpl.constant_part = cstate->off_linkhdr.constant_part + 2;

  cstate->off_nl = 0;
  cstate->off_nl_nosnap = 0;  /* no 802.2 LLC */

  return b0;
}

/* Check that this is Geneve and the VNI is correct if
 * specified. Parameterized to handle both IPv4 and IPv6. */
static struct block *
gen_geneve_check(compiler_state_t *cstate,
    struct block *(*gen_portfn)(compiler_state_t *, u_int, int, int),
    enum e_offrel offrel, bpf_u_int32 vni, int has_vni)
{
  struct block *b0, *b1;

  b0 = gen_portfn(cstate, GENEVE_PORT, IPPROTO_UDP, Q_DST);

  /* Check that we are operating on version 0. Otherwise, we
   * can't decode the rest of the fields. The version is 2 bits
   * in the first byte of the Geneve header. */
  b1 = gen_mcmp(cstate, offrel, 8, BPF_B, 0, 0xc0);
  gen_and(b0, b1);
  b0 = b1;

  if (has_vni) {
    if (vni > 0xffffff) {
      bpf_error(cstate, "Geneve VNI %u greater than maximum %u",
          vni, 0xffffff);
    }
    vni <<= 8; /* VNI is in the upper 3 bytes */
    b1 = gen_mcmp(cstate, offrel, 12, BPF_W, vni, 0xffffff00);
    gen_and(b0, b1);
    b0 = b1;
  }

  return b0;
}

/* The IPv4 and IPv6 Geneve checks need to do two things:
 * - Verify that this actually is Geneve with the right VNI.
 * - Place the IP header length (plus variable link prefix if
 *   needed) into register A to be used later to compute
 *   the inner packet offsets. */
static struct block *
gen_geneve4(compiler_state_t *cstate, bpf_u_int32 vni, int has_vni)
{
  struct block *b0, *b1;
  struct slist *s, *s1;

  b0 = gen_geneve_check(cstate, gen_port, OR_TRAN_IPV4, vni, has_vni);

  /* Load the IP header length into A. */
  s = gen_loadx_iphdrlen(cstate);

  s1 = new_stmt(cstate, BPF_MISC|BPF_TXA);
  sappend(s, s1);

  /* Forcibly append these statements to the true condition
   * of the protocol check by creating a new block that is
   * always true and ANDing them. */
  b1 = new_block(cstate, BPF_JMP|BPF_JEQ|BPF_X);
  b1->stmts = s;
  b1->s.k = 0;

  gen_and(b0, b1);

  return b1;
}

static struct block *
gen_geneve6(compiler_state_t *cstate, bpf_u_int32 vni, int has_vni)
{
  struct block *b0, *b1;
  struct slist *s, *s1;

  b0 = gen_geneve_check(cstate, gen_port6, OR_TRAN_IPV6, vni, has_vni);

  /* Load the IP header length. We need to account for a
   * variable length link prefix if there is one. */
  s = gen_abs_offset_varpart(cstate, &cstate->off_linkpl);
  if (s) {
    s1 = new_stmt(cstate, BPF_LD|BPF_IMM);
    s1->s.k = 40;
    sappend(s, s1);

    s1 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X);
    s1->s.k = 0;
    sappend(s, s1);
  } else {
    s = new_stmt(cstate, BPF_LD|BPF_IMM);
    s->s.k = 40;
  }

  /* Forcibly append these statements to the true condition
   * of the protocol check by creating a new block that is
   * always true and ANDing them. */
  s1 = new_stmt(cstate, BPF_MISC|BPF_TAX);
  sappend(s, s1);

  b1 = new_block(cstate, BPF_JMP|BPF_JEQ|BPF_X);
  b1->stmts = s;
  b1->s.k = 0;

  gen_and(b0, b1);

  return b1;
}

/* We need to store three values based on the Geneve header::
 * - The offset of the linktype.
 * - The offset of the end of the Geneve header.
 * - The offset of the end of the encapsulated MAC header. */
static struct slist *
gen_geneve_offsets(compiler_state_t *cstate)
{
  struct slist *s, *s1, *s_proto;

  /* First we need to calculate the offset of the Geneve header
   * itself. This is composed of the IP header previously calculated
   * (include any variable link prefix) and stored in A plus the
   * fixed sized headers (fixed link prefix, MAC length, and UDP
   * header). */
  s = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s->s.k = cstate->off_linkpl.constant_part + cstate->off_nl + 8;

  /* Stash this in X since we'll need it later. */
  s1 = new_stmt(cstate, BPF_MISC|BPF_TAX);
  sappend(s, s1);

  /* The EtherType in Geneve is 2 bytes in. Calculate this and
   * store it. */
  s1 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s1->s.k = 2;
  sappend(s, s1);

  cstate->off_linktype.reg = alloc_reg(cstate);
  cstate->off_linktype.is_variable = 1;
  cstate->off_linktype.constant_part = 0;

  s1 = new_stmt(cstate, BPF_ST);
  s1->s.k = cstate->off_linktype.reg;
  sappend(s, s1);

  /* Load the Geneve option length and mask and shift to get the
   * number of bytes. It is stored in the first byte of the Geneve
   * header. */
  s1 = new_stmt(cstate, BPF_LD|BPF_IND|BPF_B);
  s1->s.k = 0;
  sappend(s, s1);

  s1 = new_stmt(cstate, BPF_ALU|BPF_AND|BPF_K);
  s1->s.k = 0x3f;
  sappend(s, s1);

  s1 = new_stmt(cstate, BPF_ALU|BPF_MUL|BPF_K);
  s1->s.k = 4;
  sappend(s, s1);

  /* Add in the rest of the Geneve base header. */
  s1 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s1->s.k = 8;
  sappend(s, s1);

  /* Add the Geneve header length to its offset and store. */
  s1 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_X);
  s1->s.k = 0;
  sappend(s, s1);

  /* Set the encapsulated type as Ethernet. Even though we may
   * not actually have Ethernet inside there are two reasons this
   * is useful:
   * - The linktype field is always in EtherType format regardless
   *   of whether it is in Geneve or an inner Ethernet frame.
   * - The only link layer that we have specific support for is
   *   Ethernet. We will confirm that the packet actually is
   *   Ethernet at runtime before executing these checks. */
  PUSH_LINKHDR(cstate, DLT_EN10MB, 1, 0, alloc_reg(cstate));

  s1 = new_stmt(cstate, BPF_ST);
  s1->s.k = cstate->off_linkhdr.reg;
  sappend(s, s1);

  /* Calculate whether we have an Ethernet header or just raw IP/
   * MPLS/etc. If we have Ethernet, advance the end of the MAC offset
   * and linktype by 14 bytes so that the network header can be found
   * seamlessly. Otherwise, keep what we've calculated already. */

  /* We have a bare jmp so we can't use the optimizer. */
  cstate->no_optimize = 1;

  /* Load the EtherType in the Geneve header, 2 bytes in. */
  s1 = new_stmt(cstate, BPF_LD|BPF_IND|BPF_H);
  s1->s.k = 2;
  sappend(s, s1);

  /* Load X with the end of the Geneve header. */
  s1 = new_stmt(cstate, BPF_LDX|BPF_MEM);
  s1->s.k = cstate->off_linkhdr.reg;
  sappend(s, s1);

  /* Check if the EtherType is Transparent Ethernet Bridging. At the
   * end of this check, we should have the total length in X. In
   * the non-Ethernet case, it's already there. */
  s_proto = new_stmt(cstate, JMP(BPF_JEQ));
  s_proto->s.k = ETHERTYPE_TEB;
  sappend(s, s_proto);

  s1 = new_stmt(cstate, BPF_MISC|BPF_TXA);
  sappend(s, s1);
  s_proto->s.jt = s1;

  /* Since this is Ethernet, use the EtherType of the payload
   * directly as the linktype. Overwrite what we already have. */
  s1 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s1->s.k = 12;
  sappend(s, s1);

  s1 = new_stmt(cstate, BPF_ST);
  s1->s.k = cstate->off_linktype.reg;
  sappend(s, s1);

  /* Advance two bytes further to get the end of the Ethernet
   * header. */
  s1 = new_stmt(cstate, BPF_ALU|BPF_ADD|BPF_K);
  s1->s.k = 2;
  sappend(s, s1);

  /* Move the result to X. */
  s1 = new_stmt(cstate, BPF_MISC|BPF_TAX);
  sappend(s, s1);

  /* Store the final result of our linkpl calculation. */
  cstate->off_linkpl.reg = alloc_reg(cstate);
  cstate->off_linkpl.is_variable = 1;
  cstate->off_linkpl.constant_part = 0;

  s1 = new_stmt(cstate, BPF_STX);
  s1->s.k = cstate->off_linkpl.reg;
  sappend(s, s1);
  s_proto->s.jf = s1;

  cstate->off_nl = 0;

  return s;
}

/* Check to see if this is a Geneve packet. */
struct block *
gen_geneve(compiler_state_t *cstate, bpf_u_int32 vni, int has_vni)
{
  struct block *b0, *b1;
  struct slist *s;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  b0 = gen_geneve4(cstate, vni, has_vni);
  b1 = gen_geneve6(cstate, vni, has_vni);

  gen_or(b0, b1);
  b0 = b1;

  /* Later filters should act on the payload of the Geneve frame,
   * update all of the header pointers. Attach this code so that
   * it gets executed in the event that the Geneve filter matches. */
  s = gen_geneve_offsets(cstate);

  b1 = gen_true(cstate);
  sappend(s, b1->stmts);
  b1->stmts = s;

  gen_and(b0, b1);

  cstate->is_geneve = 1;

  return b1;
}

/* Check that the encapsulated frame has a link layer header
 * for Ethernet filters. */
static struct block *
gen_geneve_ll_check(compiler_state_t *cstate)
{
  struct block *b0;
  struct slist *s, *s1;

  /* The easiest way to see if there is a link layer present
   * is to check if the link layer header and payload are not
   * the same. */

  /* Geneve always generates pure variable offsets so we can
   * compare only the registers. */
  s = new_stmt(cstate, BPF_LD|BPF_MEM);
  s->s.k = cstate->off_linkhdr.reg;

  s1 = new_stmt(cstate, BPF_LDX|BPF_MEM);
  s1->s.k = cstate->off_linkpl.reg;
  sappend(s, s1);

  b0 = new_block(cstate, BPF_JMP|BPF_JEQ|BPF_X);
  b0->stmts = s;
  b0->s.k = 0;
  gen_not(b0);

  return b0;
}

static struct block *
gen_atmfield_code_internal(compiler_state_t *cstate, int atmfield,
    bpf_u_int32 jvalue, int jtype, int reverse)
{
  struct block *b0;

  switch (atmfield) {

  case A_VPI:
    if (!cstate->is_atm)
      bpf_error(cstate, "'vpi' supported only on raw ATM");
    if (cstate->off_vpi == OFFSET_NOT_SET)
      abort();
    b0 = gen_ncmp(cstate, OR_LINKHDR, cstate->off_vpi, BPF_B,
        0xffffffffU, jtype, reverse, jvalue);
    break;

  case A_VCI:
    if (!cstate->is_atm)
      bpf_error(cstate, "'vci' supported only on raw ATM");
    if (cstate->off_vci == OFFSET_NOT_SET)
      abort();
    b0 = gen_ncmp(cstate, OR_LINKHDR, cstate->off_vci, BPF_H,
        0xffffffffU, jtype, reverse, jvalue);
    break;

  case A_PROTOTYPE:
    if (cstate->off_proto == OFFSET_NOT_SET)
      abort(); /* XXX - this isn't on FreeBSD */
    b0 = gen_ncmp(cstate, OR_LINKHDR, cstate->off_proto, BPF_B,
        0x0fU, jtype, reverse, jvalue);
    break;

  case A_MSGTYPE:
    if (cstate->off_payload == OFFSET_NOT_SET)
      abort();
    b0 = gen_ncmp(cstate, OR_LINKHDR, cstate->off_payload + MSG_TYPE_POS, BPF_B,
        0xffffffffU, jtype, reverse, jvalue);
    break;

  case A_CALLREFTYPE:
    if (!cstate->is_atm)
      bpf_error(cstate, "'callref' supported only on raw ATM");
    if (cstate->off_proto == OFFSET_NOT_SET)
      abort();
    b0 = gen_ncmp(cstate, OR_LINKHDR, cstate->off_proto, BPF_B,
        0xffffffffU, jtype, reverse, jvalue);
    break;

  default:
    abort();
  }
  return b0;
}

static struct block *
gen_atmtype_metac(compiler_state_t *cstate)
{
  struct block *b0, *b1;

  b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
  b1 = gen_atmfield_code_internal(cstate, A_VCI, 1, BPF_JEQ, 0);
  gen_and(b0, b1);
  return b1;
}

static struct block *
gen_atmtype_sc(compiler_state_t *cstate)
{
  struct block *b0, *b1;

  b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
  b1 = gen_atmfield_code_internal(cstate, A_VCI, 5, BPF_JEQ, 0);
  gen_and(b0, b1);
  return b1;
}

static struct block *
gen_atmtype_llc(compiler_state_t *cstate)
{
  struct block *b0;

  b0 = gen_atmfield_code_internal(cstate, A_PROTOTYPE, PT_LLC, BPF_JEQ, 0);
  cstate->linktype = cstate->prevlinktype;
  return b0;
}

struct block *
gen_atmfield_code(compiler_state_t *cstate, int atmfield,
    bpf_u_int32 jvalue, int jtype, int reverse)
{
  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  return gen_atmfield_code_internal(cstate, atmfield, jvalue, jtype,
      reverse);
}

struct block *
gen_atmtype_abbrev(compiler_state_t *cstate, int type)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (type) {

  case A_METAC:
    /* Get all packets in Meta signalling Circuit */
    if (!cstate->is_atm)
      bpf_error(cstate, "'metac' supported only on raw ATM");
    b1 = gen_atmtype_metac(cstate);
    break;

  case A_BCC:
    /* Get all packets in Broadcast Circuit*/
    if (!cstate->is_atm)
      bpf_error(cstate, "'bcc' supported only on raw ATM");
    b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
    b1 = gen_atmfield_code_internal(cstate, A_VCI, 2, BPF_JEQ, 0);
    gen_and(b0, b1);
    break;

  case A_OAMF4SC:
    /* Get all cells in Segment OAM F4 circuit*/
    if (!cstate->is_atm)
      bpf_error(cstate, "'oam4sc' supported only on raw ATM");
    b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
    b1 = gen_atmfield_code_internal(cstate, A_VCI, 3, BPF_JEQ, 0);
    gen_and(b0, b1);
    break;

  case A_OAMF4EC:
    /* Get all cells in End-to-End OAM F4 Circuit*/
    if (!cstate->is_atm)
      bpf_error(cstate, "'oam4ec' supported only on raw ATM");
    b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
    b1 = gen_atmfield_code_internal(cstate, A_VCI, 4, BPF_JEQ, 0);
    gen_and(b0, b1);
    break;

  case A_SC:
    /*  Get all packets in connection Signalling Circuit */
    if (!cstate->is_atm)
      bpf_error(cstate, "'sc' supported only on raw ATM");
    b1 = gen_atmtype_sc(cstate);
    break;

  case A_ILMIC:
    /* Get all packets in ILMI Circuit */
    if (!cstate->is_atm)
      bpf_error(cstate, "'ilmic' supported only on raw ATM");
    b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
    b1 = gen_atmfield_code_internal(cstate, A_VCI, 16, BPF_JEQ, 0);
    gen_and(b0, b1);
    break;

  case A_LANE:
    /* Get all LANE packets */
    if (!cstate->is_atm)
      bpf_error(cstate, "'lane' supported only on raw ATM");
    b1 = gen_atmfield_code_internal(cstate, A_PROTOTYPE, PT_LANE, BPF_JEQ, 0);

    /*
     * Arrange that all subsequent tests assume LANE
     * rather than LLC-encapsulated packets, and set
     * the offsets appropriately for LANE-encapsulated
     * Ethernet.
     *
     * We assume LANE means Ethernet, not Token Ring.
     */
    PUSH_LINKHDR(cstate, DLT_EN10MB, 0,
        cstate->off_payload + 2,  /* Ethernet header */
        -1);
    cstate->off_linktype.constant_part = cstate->off_linkhdr.constant_part + 12;
    cstate->off_linkpl.constant_part = cstate->off_linkhdr.constant_part + 14;  /* Ethernet */
    cstate->off_nl = 0;     /* Ethernet II */
    cstate->off_nl_nosnap = 3;    /* 802.3+802.2 */
    break;

  case A_LLC:
    /* Get all LLC-encapsulated packets */
    if (!cstate->is_atm)
      bpf_error(cstate, "'llc' supported only on raw ATM");
    b1 = gen_atmtype_llc(cstate);
    break;

  default:
    abort();
  }
  return b1;
}

/*
 * Filtering for MTP2 messages based on li value
 * FISU, length is null
 * LSSU, length is 1 or 2
 * MSU, length is 3 or more
 * For MTP2_HSL, sequences are on 2 bytes, and length on 9 bits
 */
struct block *
gen_mtp2type_abbrev(compiler_state_t *cstate, int type)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (type) {

  case M_FISU:
    if ( (cstate->linktype != DLT_MTP2) &&
         (cstate->linktype != DLT_ERF) &&
         (cstate->linktype != DLT_MTP2_WITH_PHDR) )
      bpf_error(cstate, "'fisu' supported only on MTP2");
    /* gen_ncmp(cstate, offrel, offset, size, mask, jtype, reverse, value) */
    b0 = gen_ncmp(cstate, OR_PACKET, cstate->off_li, BPF_B,
        0x3fU, BPF_JEQ, 0, 0U);
    break;

  case M_LSSU:
    if ( (cstate->linktype != DLT_MTP2) &&
         (cstate->linktype != DLT_ERF) &&
         (cstate->linktype != DLT_MTP2_WITH_PHDR) )
      bpf_error(cstate, "'lssu' supported only on MTP2");
    b0 = gen_ncmp(cstate, OR_PACKET, cstate->off_li, BPF_B,
        0x3fU, BPF_JGT, 1, 2U);
    b1 = gen_ncmp(cstate, OR_PACKET, cstate->off_li, BPF_B,
        0x3fU, BPF_JGT, 0, 0U);
    gen_and(b1, b0);
    break;

  case M_MSU:
    if ( (cstate->linktype != DLT_MTP2) &&
         (cstate->linktype != DLT_ERF) &&
         (cstate->linktype != DLT_MTP2_WITH_PHDR) )
      bpf_error(cstate, "'msu' supported only on MTP2");
    b0 = gen_ncmp(cstate, OR_PACKET, cstate->off_li, BPF_B,
        0x3fU, BPF_JGT, 0, 2U);
    break;

  case MH_FISU:
    if ( (cstate->linktype != DLT_MTP2) &&
         (cstate->linktype != DLT_ERF) &&
         (cstate->linktype != DLT_MTP2_WITH_PHDR) )
      bpf_error(cstate, "'hfisu' supported only on MTP2_HSL");
    /* gen_ncmp(cstate, offrel, offset, size, mask, jtype, reverse, value) */
    b0 = gen_ncmp(cstate, OR_PACKET, cstate->off_li_hsl, BPF_H,
        0xff80U, BPF_JEQ, 0, 0U);
    break;

  case MH_LSSU:
    if ( (cstate->linktype != DLT_MTP2) &&
         (cstate->linktype != DLT_ERF) &&
         (cstate->linktype != DLT_MTP2_WITH_PHDR) )
      bpf_error(cstate, "'hlssu' supported only on MTP2_HSL");
    b0 = gen_ncmp(cstate, OR_PACKET, cstate->off_li_hsl, BPF_H,
        0xff80U, BPF_JGT, 1, 0x0100U);
    b1 = gen_ncmp(cstate, OR_PACKET, cstate->off_li_hsl, BPF_H,
        0xff80U, BPF_JGT, 0, 0U);
    gen_and(b1, b0);
    break;

  case MH_MSU:
    if ( (cstate->linktype != DLT_MTP2) &&
         (cstate->linktype != DLT_ERF) &&
         (cstate->linktype != DLT_MTP2_WITH_PHDR) )
      bpf_error(cstate, "'hmsu' supported only on MTP2_HSL");
    b0 = gen_ncmp(cstate, OR_PACKET, cstate->off_li_hsl, BPF_H,
        0xff80U, BPF_JGT, 0, 0x0100U);
    break;

  default:
    abort();
  }
  return b0;
}

/*
 * The jvalue_arg dance is to avoid annoying whining by compilers that
 * jvalue might be clobbered by longjmp - yeah, it might, but *WHO CARES*?
 * It's not *used* after setjmp returns.
 */
struct block *
gen_mtp3field_code(compiler_state_t *cstate, int mtp3field,
    bpf_u_int32 jvalue_arg, int jtype, int reverse)
{
  volatile bpf_u_int32 jvalue = jvalue_arg;
  struct block *b0;
  bpf_u_int32 val1 , val2 , val3;
  u_int newoff_sio;
  u_int newoff_opc;
  u_int newoff_dpc;
  u_int newoff_sls;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  newoff_sio = cstate->off_sio;
  newoff_opc = cstate->off_opc;
  newoff_dpc = cstate->off_dpc;
  newoff_sls = cstate->off_sls;
  switch (mtp3field) {

  case MH_SIO:
    newoff_sio += 3; /* offset for MTP2_HSL */
    /* FALLTHROUGH */

  case M_SIO:
    if (cstate->off_sio == OFFSET_NOT_SET)
      bpf_error(cstate, "'sio' supported only on SS7");
    /* sio coded on 1 byte so max value 255 */
    if(jvalue > 255)
            bpf_error(cstate, "sio value %u too big; max value = 255",
                jvalue);
    b0 = gen_ncmp(cstate, OR_PACKET, newoff_sio, BPF_B, 0xffffffffU,
        jtype, reverse, jvalue);
    break;

  case MH_OPC:
    newoff_opc += 3;

    /* FALLTHROUGH */
        case M_OPC:
          if (cstate->off_opc == OFFSET_NOT_SET)
      bpf_error(cstate, "'opc' supported only on SS7");
    /* opc coded on 14 bits so max value 16383 */
    if (jvalue > 16383)
            bpf_error(cstate, "opc value %u too big; max value = 16383",
                jvalue);
    /* the following instructions are made to convert jvalue
     * to the form used to write opc in an ss7 message*/
    val1 = jvalue & 0x00003c00;
    val1 = val1 >>10;
    val2 = jvalue & 0x000003fc;
    val2 = val2 <<6;
    val3 = jvalue & 0x00000003;
    val3 = val3 <<22;
    jvalue = val1 + val2 + val3;
    b0 = gen_ncmp(cstate, OR_PACKET, newoff_opc, BPF_W, 0x00c0ff0fU,
        jtype, reverse, jvalue);
    break;

  case MH_DPC:
    newoff_dpc += 3;
    /* FALLTHROUGH */

  case M_DPC:
          if (cstate->off_dpc == OFFSET_NOT_SET)
      bpf_error(cstate, "'dpc' supported only on SS7");
    /* dpc coded on 14 bits so max value 16383 */
    if (jvalue > 16383)
            bpf_error(cstate, "dpc value %u too big; max value = 16383",
                jvalue);
    /* the following instructions are made to convert jvalue
     * to the forme used to write dpc in an ss7 message*/
    val1 = jvalue & 0x000000ff;
    val1 = val1 << 24;
    val2 = jvalue & 0x00003f00;
    val2 = val2 << 8;
    jvalue = val1 + val2;
    b0 = gen_ncmp(cstate, OR_PACKET, newoff_dpc, BPF_W, 0xff3f0000U,
        jtype, reverse, jvalue);
    break;

  case MH_SLS:
    newoff_sls += 3;
    /* FALLTHROUGH */

  case M_SLS:
          if (cstate->off_sls == OFFSET_NOT_SET)
      bpf_error(cstate, "'sls' supported only on SS7");
    /* sls coded on 4 bits so max value 15 */
    if (jvalue > 15)
             bpf_error(cstate, "sls value %u too big; max value = 15",
                 jvalue);
    /* the following instruction is made to convert jvalue
     * to the forme used to write sls in an ss7 message*/
    jvalue = jvalue << 4;
    b0 = gen_ncmp(cstate, OR_PACKET, newoff_sls, BPF_B, 0xf0U,
        jtype, reverse, jvalue);
    break;

  default:
    abort();
  }
  return b0;
}

static struct block *
gen_msg_abbrev(compiler_state_t *cstate, int type)
{
  struct block *b1;

  /*
   * Q.2931 signalling protocol messages for handling virtual circuits
   * establishment and teardown
   */
  switch (type) {

  case A_SETUP:
    b1 = gen_atmfield_code_internal(cstate, A_MSGTYPE, SETUP, BPF_JEQ, 0);
    break;

  case A_CALLPROCEED:
    b1 = gen_atmfield_code_internal(cstate, A_MSGTYPE, CALL_PROCEED, BPF_JEQ, 0);
    break;

  case A_CONNECT:
    b1 = gen_atmfield_code_internal(cstate, A_MSGTYPE, CONNECT, BPF_JEQ, 0);
    break;

  case A_CONNECTACK:
    b1 = gen_atmfield_code_internal(cstate, A_MSGTYPE, CONNECT_ACK, BPF_JEQ, 0);
    break;

  case A_RELEASE:
    b1 = gen_atmfield_code_internal(cstate, A_MSGTYPE, RELEASE, BPF_JEQ, 0);
    break;

  case A_RELEASE_DONE:
    b1 = gen_atmfield_code_internal(cstate, A_MSGTYPE, RELEASE_DONE, BPF_JEQ, 0);
    break;

  default:
    abort();
  }
  return b1;
}

struct block *
gen_atmmulti_abbrev(compiler_state_t *cstate, int type)
{
  struct block *b0, *b1;

  /*
   * Catch errors reported by us and routines below us, and return NULL
   * on an error.
   */
  if (setjmp(cstate->top_ctx))
    return (NULL);

  switch (type) {

  case A_OAM:
    if (!cstate->is_atm)
      bpf_error(cstate, "'oam' supported only on raw ATM");
    /* OAM F4 type */
    b0 = gen_atmfield_code_internal(cstate, A_VCI, 3, BPF_JEQ, 0);
    b1 = gen_atmfield_code_internal(cstate, A_VCI, 4, BPF_JEQ, 0);
    gen_or(b0, b1);
    b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
    gen_and(b0, b1);
    break;

  case A_OAMF4:
    if (!cstate->is_atm)
      bpf_error(cstate, "'oamf4' supported only on raw ATM");
    /* OAM F4 type */
    b0 = gen_atmfield_code_internal(cstate, A_VCI, 3, BPF_JEQ, 0);
    b1 = gen_atmfield_code_internal(cstate, A_VCI, 4, BPF_JEQ, 0);
    gen_or(b0, b1);
    b0 = gen_atmfield_code_internal(cstate, A_VPI, 0, BPF_JEQ, 0);
    gen_and(b0, b1);
    break;

  case A_CONNECTMSG:
    /*
     * Get Q.2931 signalling messages for switched
     * virtual connection
     */
    if (!cstate->is_atm)
      bpf_error(cstate, "'connectmsg' supported only on raw ATM");
    b0 = gen_msg_abbrev(cstate, A_SETUP);
    b1 = gen_msg_abbrev(cstate, A_CALLPROCEED);
    gen_or(b0, b1);
    b0 = gen_msg_abbrev(cstate, A_CONNECT);
    gen_or(b0, b1);
    b0 = gen_msg_abbrev(cstate, A_CONNECTACK);
    gen_or(b0, b1);
    b0 = gen_msg_abbrev(cstate, A_RELEASE);
    gen_or(b0, b1);
    b0 = gen_msg_abbrev(cstate, A_RELEASE_DONE);
    gen_or(b0, b1);
    b0 = gen_atmtype_sc(cstate);
    gen_and(b0, b1);
    break;

  case A_METACONNECT:
    if (!cstate->is_atm)
      bpf_error(cstate, "'metaconnect' supported only on raw ATM");
    b0 = gen_msg_abbrev(cstate, A_SETUP);
    b1 = gen_msg_abbrev(cstate, A_CALLPROCEED);
    gen_or(b0, b1);
    b0 = gen_msg_abbrev(cstate, A_CONNECT);
    gen_or(b0, b1);
    b0 = gen_msg_abbrev(cstate, A_RELEASE);
    gen_or(b0, b1);
    b0 = gen_msg_abbrev(cstate, A_RELEASE_DONE);
    gen_or(b0, b1);
    b0 = gen_atmtype_metac(cstate);
    gen_and(b0, b1);
    break;

  default:
    abort();
  }
  return b1;
}

Coverage Report

Created: 2023-05-05 14:17