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ip_fw2.c

/*-
 * Copyright (c) 2002 Luigi Rizzo, Universita` di Pisa
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/netinet/ip_fw2.c,v 1.106.2.40 2007/06/07 09:50:53 bz Exp $
 */

#define        DEB(x)
#define        DDB(x) x

/*
 * Implement IP packet firewall (new version)
 */

#if !defined(KLD_MODULE)
#include "opt_ipfw.h"
#include "opt_ip6fw.h"
#include "opt_ipdivert.h"
#include "opt_ipdn.h"
#include "opt_inet.h"
#ifndef INET
#error IPFIREWALL requires INET.
#endif /* INET */
#endif
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include "opt_mac.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/condvar.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>
#include <sys/jail.h>
#include <sys/mac.h>
#include <sys/module.h>
#include <sys/proc.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/ucred.h>
#include <net/if.h>
#include <net/radix.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/in_pcb.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>
#include <netinet/ip_fw.h>
#include <netinet/ip_divert.h>
#include <netinet/ip_dummynet.h>
#include <netinet/ip_carp.h>
#include <netinet/pim.h>
#include <netinet/tcp.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>

#include <netgraph/ng_ipfw.h>

#include <altq/if_altq.h>

#ifdef IPSEC
#include <netinet6/ipsec.h>
#endif

#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#ifdef INET6
#include <netinet6/scope6_var.h>
#endif

#include <netinet/if_ether.h> /* XXX for ETHERTYPE_IP */

#include <machine/in_cksum.h> /* XXX for in_cksum */

/*
 * set_disable contains one bit per set value (0..31).
 * If the bit is set, all rules with the corresponding set
 * are disabled. Set RESVD_SET(31) is reserved for the default rule
 * and rules that are not deleted by the flush command,
 * and CANNOT be disabled.
 * Rules in set RESVD_SET can only be deleted explicitly.
 */
static u_int32_t set_disable;

static int fw_verbose;
static int verbose_limit;

static struct callout ipfw_timeout;
static uma_zone_t ipfw_dyn_rule_zone;
#define     IPFW_DEFAULT_RULE 65535

/*
 * Data structure to cache our ucred related
 * information. This structure only gets used if
 * the user specified UID/GID based constraints in
 * a firewall rule.
 */
struct ip_fw_ugid {
      gid_t       fw_groups[NGROUPS];
      int         fw_ngroups;
      uid_t       fw_uid;
      int         fw_prid;
};

#define     IPFW_TABLES_MAX         128
struct ip_fw_chain {
      struct ip_fw      *rules;           /* list of rules */
      struct ip_fw      *reap;            /* list of rules to reap */
      struct radix_node_head *tables[IPFW_TABLES_MAX];
      struct mtx  mtx;        /* lock guarding rule list */
      int         busy_count; /* busy count for rw locks */
      int         want_write;
      struct cv   cv;
};
#define     IPFW_LOCK_INIT(_chain) \
      mtx_init(&(_chain)->mtx, "IPFW static rules", NULL, \
            MTX_DEF | MTX_RECURSE)
#define     IPFW_LOCK_DESTROY(_chain)     mtx_destroy(&(_chain)->mtx)
#define     IPFW_WLOCK_ASSERT(_chain)     do {                    \
      mtx_assert(&(_chain)->mtx, MA_OWNED);                       \
      NET_ASSERT_GIANT();                                   \
} while (0)

static __inline void
IPFW_RLOCK(struct ip_fw_chain *chain)
{
      mtx_lock(&chain->mtx);
      chain->busy_count++;
      mtx_unlock(&chain->mtx);
}

static __inline void
IPFW_RUNLOCK(struct ip_fw_chain *chain)
{
      mtx_lock(&chain->mtx);
      chain->busy_count--;
      if (chain->busy_count == 0 && chain->want_write)
            cv_signal(&chain->cv);
      mtx_unlock(&chain->mtx);
}

static __inline void
IPFW_WLOCK(struct ip_fw_chain *chain)
{
      mtx_lock(&chain->mtx);
      chain->want_write++;
      while (chain->busy_count > 0)
            cv_wait(&chain->cv, &chain->mtx);
}

static __inline void
IPFW_WUNLOCK(struct ip_fw_chain *chain)
{
      chain->want_write--;
      cv_signal(&chain->cv);
      mtx_unlock(&chain->mtx);
}

/*
 * list of rules for layer 3
 */
static struct ip_fw_chain layer3_chain;

MALLOC_DEFINE(M_IPFW, "IpFw/IpAcct", "IpFw/IpAcct chain's");
MALLOC_DEFINE(M_IPFW_TBL, "ipfw_tbl", "IpFw tables");

struct table_entry {
      struct radix_node rn[2];
      struct sockaddr_in      addr, mask;
      u_int32_t         value;
};

static int fw_debug = 1;
static int autoinc_step = 100; /* bounded to 1..1000 in add_rule() */

#ifdef SYSCTL_NODE
SYSCTL_NODE(_net_inet_ip, OID_AUTO, fw, CTLFLAG_RW, 0, "Firewall");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, enable,
    CTLFLAG_RW | CTLFLAG_SECURE3,
    &fw_enable, 0, "Enable ipfw");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, autoinc_step, CTLFLAG_RW,
    &autoinc_step, 0, "Rule number autincrement step");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, one_pass,
    CTLFLAG_RW | CTLFLAG_SECURE3,
    &fw_one_pass, 0,
    "Only do a single pass through ipfw when using dummynet(4)");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, debug, CTLFLAG_RW,
    &fw_debug, 0, "Enable printing of debug ip_fw statements");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, verbose,
    CTLFLAG_RW | CTLFLAG_SECURE3,
    &fw_verbose, 0, "Log matches to ipfw rules");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, verbose_limit, CTLFLAG_RW,
    &verbose_limit, 0, "Set upper limit of matches of ipfw rules logged");

/*
 * Description of dynamic rules.
 *
 * Dynamic rules are stored in lists accessed through a hash table
 * (ipfw_dyn_v) whose size is curr_dyn_buckets. This value can
 * be modified through the sysctl variable dyn_buckets which is
 * updated when the table becomes empty.
 *
 * XXX currently there is only one list, ipfw_dyn.
 *
 * When a packet is received, its address fields are first masked
 * with the mask defined for the rule, then hashed, then matched
 * against the entries in the corresponding list.
 * Dynamic rules can be used for different purposes:
 *  + stateful rules;
 *  + enforcing limits on the number of sessions;
 *  + in-kernel NAT (not implemented yet)
 *
 * The lifetime of dynamic rules is regulated by dyn_*_lifetime,
 * measured in seconds and depending on the flags.
 *
 * The total number of dynamic rules is stored in dyn_count.
 * The max number of dynamic rules is dyn_max. When we reach
 * the maximum number of rules we do not create anymore. This is
 * done to avoid consuming too much memory, but also too much
 * time when searching on each packet (ideally, we should try instead
 * to put a limit on the length of the list on each bucket...).
 *
 * Each dynamic rule holds a pointer to the parent ipfw rule so
 * we know what action to perform. Dynamic rules are removed when
 * the parent rule is deleted. XXX we should make them survive.
 *
 * There are some limitations with dynamic rules -- we do not
 * obey the 'randomized match', and we do not do multiple
 * passes through the firewall. XXX check the latter!!!
 */
static ipfw_dyn_rule **ipfw_dyn_v = NULL;
static u_int32_t dyn_buckets = 256; /* must be power of 2 */
static u_int32_t curr_dyn_buckets = 256; /* must be power of 2 */

static struct mtx ipfw_dyn_mtx;           /* mutex guarding dynamic rules */
#define     IPFW_DYN_LOCK_INIT() \
      mtx_init(&ipfw_dyn_mtx, "IPFW dynamic rules", NULL, MTX_DEF)
#define     IPFW_DYN_LOCK_DESTROY() mtx_destroy(&ipfw_dyn_mtx)
#define     IPFW_DYN_LOCK()         mtx_lock(&ipfw_dyn_mtx)
#define     IPFW_DYN_UNLOCK() mtx_unlock(&ipfw_dyn_mtx)
#define     IPFW_DYN_LOCK_ASSERT()  mtx_assert(&ipfw_dyn_mtx, MA_OWNED)

/*
 * Timeouts for various events in handing dynamic rules.
 */
static u_int32_t dyn_ack_lifetime = 300;
static u_int32_t dyn_syn_lifetime = 20;
static u_int32_t dyn_fin_lifetime = 1;
static u_int32_t dyn_rst_lifetime = 1;
static u_int32_t dyn_udp_lifetime = 10;
static u_int32_t dyn_short_lifetime = 5;

/*
 * Keepalives are sent if dyn_keepalive is set. They are sent every
 * dyn_keepalive_period seconds, in the last dyn_keepalive_interval
 * seconds of lifetime of a rule.
 * dyn_rst_lifetime and dyn_fin_lifetime should be strictly lower
 * than dyn_keepalive_period.
 */

static u_int32_t dyn_keepalive_interval = 20;
static u_int32_t dyn_keepalive_period = 5;
static u_int32_t dyn_keepalive = 1; /* do send keepalives */

static u_int32_t static_count;      /* # of static rules */
static u_int32_t static_len;  /* size in bytes of static rules */
static u_int32_t dyn_count;         /* # of dynamic rules */
static u_int32_t dyn_max = 4096;    /* max # of dynamic rules */

SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_buckets, CTLFLAG_RW,
    &dyn_buckets, 0, "Number of dyn. buckets");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, curr_dyn_buckets, CTLFLAG_RD,
    &curr_dyn_buckets, 0, "Current Number of dyn. buckets");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_count, CTLFLAG_RD,
    &dyn_count, 0, "Number of dyn. rules");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_max, CTLFLAG_RW,
    &dyn_max, 0, "Max number of dyn. rules");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, static_count, CTLFLAG_RD,
    &static_count, 0, "Number of static rules");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_ack_lifetime, CTLFLAG_RW,
    &dyn_ack_lifetime, 0, "Lifetime of dyn. rules for acks");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_syn_lifetime, CTLFLAG_RW,
    &dyn_syn_lifetime, 0, "Lifetime of dyn. rules for syn");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_fin_lifetime, CTLFLAG_RW,
    &dyn_fin_lifetime, 0, "Lifetime of dyn. rules for fin");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_rst_lifetime, CTLFLAG_RW,
    &dyn_rst_lifetime, 0, "Lifetime of dyn. rules for rst");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_udp_lifetime, CTLFLAG_RW,
    &dyn_udp_lifetime, 0, "Lifetime of dyn. rules for UDP");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_short_lifetime, CTLFLAG_RW,
    &dyn_short_lifetime, 0, "Lifetime of dyn. rules for other situations");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, dyn_keepalive, CTLFLAG_RW,
    &dyn_keepalive, 0, "Enable keepalives for dyn. rules");

#ifdef INET6
/*
 * IPv6 specific variables
 */
SYSCTL_DECL(_net_inet6_ip6);

static struct sysctl_ctx_list ip6_fw_sysctl_ctx;
static struct sysctl_oid *ip6_fw_sysctl_tree;
#endif /* INET6 */
#endif /* SYSCTL_NODE */

static int fw_deny_unknown_exthdrs = 1;


/*
 * L3HDR maps an ipv4 pointer into a layer3 header pointer of type T
 * Other macros just cast void * into the appropriate type
 */
#define     L3HDR(T, ip)      ((T *)((u_int32_t *)(ip) + (ip)->ip_hl))
#define     TCP(p)            ((struct tcphdr *)(p))
#define     UDP(p)            ((struct udphdr *)(p))
#define     ICMP(p)           ((struct icmphdr *)(p))
#define     ICMP6(p)    ((struct icmp6_hdr *)(p))

static __inline int
icmptype_match(struct icmphdr *icmp, ipfw_insn_u32 *cmd)
{
      int type = icmp->icmp_type;

      return (type <= ICMP_MAXTYPE && (cmd->d[0] & (1<<type)) );
}

#define TT  ( (1 << ICMP_ECHO) | (1 << ICMP_ROUTERSOLICIT) | \
    (1 << ICMP_TSTAMP) | (1 << ICMP_IREQ) | (1 << ICMP_MASKREQ) )

static int
is_icmp_query(struct icmphdr *icmp)
{
      int type = icmp->icmp_type;

      return (type <= ICMP_MAXTYPE && (TT & (1<<type)) );
}
#undef TT

/*
 * The following checks use two arrays of 8 or 16 bits to store the
 * bits that we want set or clear, respectively. They are in the
 * low and high half of cmd->arg1 or cmd->d[0].
 *
 * We scan options and store the bits we find set. We succeed if
 *
 *    (want_set & ~bits) == 0 && (want_clear & ~bits) == want_clear
 *
 * The code is sometimes optimized not to store additional variables.
 */

static int
flags_match(ipfw_insn *cmd, u_int8_t bits)
{
      u_char want_clear;
      bits = ~bits;

      if ( ((cmd->arg1 & 0xff) & bits) != 0)
            return 0; /* some bits we want set were clear */
      want_clear = (cmd->arg1 >> 8) & 0xff;
      if ( (want_clear & bits) != want_clear)
            return 0; /* some bits we want clear were set */
      return 1;
}

static int
ipopts_match(struct ip *ip, ipfw_insn *cmd)
{
      int optlen, bits = 0;
      u_char *cp = (u_char *)(ip + 1);
      int x = (ip->ip_hl << 2) - sizeof (struct ip);

      for (; x > 0; x -= optlen, cp += optlen) {
            int opt = cp[IPOPT_OPTVAL];

            if (opt == IPOPT_EOL)
                  break;
            if (opt == IPOPT_NOP)
                  optlen = 1;
            else {
                  optlen = cp[IPOPT_OLEN];
                  if (optlen <= 0 || optlen > x)
                        return 0; /* invalid or truncated */
            }
            switch (opt) {

            default:
                  break;

            case IPOPT_LSRR:
                  bits |= IP_FW_IPOPT_LSRR;
                  break;

            case IPOPT_SSRR:
                  bits |= IP_FW_IPOPT_SSRR;
                  break;

            case IPOPT_RR:
                  bits |= IP_FW_IPOPT_RR;
                  break;

            case IPOPT_TS:
                  bits |= IP_FW_IPOPT_TS;
                  break;
            }
      }
      return (flags_match(cmd, bits));
}

static int
tcpopts_match(struct tcphdr *tcp, ipfw_insn *cmd)
{
      int optlen, bits = 0;
      u_char *cp = (u_char *)(tcp + 1);
      int x = (tcp->th_off << 2) - sizeof(struct tcphdr);

      for (; x > 0; x -= optlen, cp += optlen) {
            int opt = cp[0];
            if (opt == TCPOPT_EOL)
                  break;
            if (opt == TCPOPT_NOP)
                  optlen = 1;
            else {
                  optlen = cp[1];
                  if (optlen <= 0)
                        break;
            }

            switch (opt) {

            default:
                  break;

            case TCPOPT_MAXSEG:
                  bits |= IP_FW_TCPOPT_MSS;
                  break;

            case TCPOPT_WINDOW:
                  bits |= IP_FW_TCPOPT_WINDOW;
                  break;

            case TCPOPT_SACK_PERMITTED:
            case TCPOPT_SACK:
                  bits |= IP_FW_TCPOPT_SACK;
                  break;

            case TCPOPT_TIMESTAMP:
                  bits |= IP_FW_TCPOPT_TS;
                  break;

            }
      }
      return (flags_match(cmd, bits));
}

static int
iface_match(struct ifnet *ifp, ipfw_insn_if *cmd)
{
      if (ifp == NULL)  /* no iface with this packet, match fails */
            return 0;
      /* Check by name or by IP address */
      if (cmd->name[0] != '\0') { /* match by name */
            /* Check name */
            if (cmd->p.glob) {
                  if (fnmatch(cmd->name, ifp->if_xname, 0) == 0)
                        return(1);
            } else {
                  if (strncmp(ifp->if_xname, cmd->name, IFNAMSIZ) == 0)
                        return(1);
            }
      } else {
            struct ifaddr *ia;

            /* XXX lock? */
            TAILQ_FOREACH(ia, &ifp->if_addrhead, ifa_link) {
                  if (ia->ifa_addr == NULL)
                        continue;
                  if (ia->ifa_addr->sa_family != AF_INET)
                        continue;
                  if (cmd->p.ip.s_addr == ((struct sockaddr_in *)
                      (ia->ifa_addr))->sin_addr.s_addr)
                        return(1);  /* match */
            }
      }
      return(0);  /* no match, fail ... */
}

/*
 * The verify_path function checks if a route to the src exists and
 * if it is reachable via ifp (when provided).
 * 
 * The 'verrevpath' option checks that the interface that an IP packet
 * arrives on is the same interface that traffic destined for the
 * packet's source address would be routed out of.  The 'versrcreach'
 * option just checks that the source address is reachable via any route
 * (except default) in the routing table.  These two are a measure to block
 * forged packets.  This is also commonly known as "anti-spoofing" or Unicast
 * Reverse Path Forwarding (Unicast RFP) in Cisco-ese. The name of the knobs
 * is purposely reminiscent of the Cisco IOS command,
 *
 *   ip verify unicast reverse-path
 *   ip verify unicast source reachable-via any
 *
 * which implements the same functionality. But note that syntax is
 * misleading. The check may be performed on all IP packets whether unicast,
 * multicast, or broadcast.
 */
static int
verify_path(struct in_addr src, struct ifnet *ifp)
{
      struct route ro;
      struct sockaddr_in *dst;

      bzero(&ro, sizeof(ro));

      dst = (struct sockaddr_in *)&(ro.ro_dst);
      dst->sin_family = AF_INET;
      dst->sin_len = sizeof(*dst);
      dst->sin_addr = src;
      rtalloc_ign(&ro, RTF_CLONING);

      if (ro.ro_rt == NULL)
            return 0;

      /*
       * If ifp is provided, check for equality with rtentry.
       * We should use rt->rt_ifa->ifa_ifp, instead of rt->rt_ifp,
       * in order to pass packets injected back by if_simloop():
       * if useloopback == 1 routing entry (via lo0) for our own address
       * may exist, so we need to handle routing assymetry.
       */
      if (ifp != NULL && ro.ro_rt->rt_ifa->ifa_ifp != ifp) {
            RTFREE(ro.ro_rt);
            return 0;
      }

      /* if no ifp provided, check if rtentry is not default route */
      if (ifp == NULL &&
           satosin(rt_key(ro.ro_rt))->sin_addr.s_addr == INADDR_ANY) {
            RTFREE(ro.ro_rt);
            return 0;
      }

      /* or if this is a blackhole/reject route */
      if (ifp == NULL && ro.ro_rt->rt_flags & (RTF_REJECT|RTF_BLACKHOLE)) {
            RTFREE(ro.ro_rt);
            return 0;
      }

      /* found valid route */
      RTFREE(ro.ro_rt);
      return 1;
}

#ifdef INET6
/*
 * ipv6 specific rules here...
 */
static __inline int
icmp6type_match (int type, ipfw_insn_u32 *cmd)
{
      return (type <= ICMP6_MAXTYPE && (cmd->d[type/32] & (1<<(type%32)) ) );
}

static int
flow6id_match( int curr_flow, ipfw_insn_u32 *cmd )
{
      int i;
      for (i=0; i <= cmd->o.arg1; ++i )
            if (curr_flow == cmd->d[i] )
                  return 1;
      return 0;
}

/* support for IP6_*_ME opcodes */
static int
search_ip6_addr_net (struct in6_addr * ip6_addr)
{
      struct ifnet *mdc;
      struct ifaddr *mdc2;
      struct in6_ifaddr *fdm;
      struct in6_addr copia;

      TAILQ_FOREACH(mdc, &ifnet, if_link)
            TAILQ_FOREACH(mdc2, &mdc->if_addrlist, ifa_list) {
                  if (!mdc2->ifa_addr)
                        continue;
                  if (mdc2->ifa_addr->sa_family == AF_INET6) {
                        fdm = (struct in6_ifaddr *)mdc2;
                        copia = fdm->ia_addr.sin6_addr;
                        /* need for leaving scope_id in the sock_addr */
                        in6_clearscope(&copia);
                        if (IN6_ARE_ADDR_EQUAL(ip6_addr, &copia))
                              return 1;
                  }
            }
      return 0;
}

static int
verify_path6(struct in6_addr *src, struct ifnet *ifp)
{
      struct route_in6 ro;
      struct sockaddr_in6 *dst;

      bzero(&ro, sizeof(ro));

      dst = (struct sockaddr_in6 * )&(ro.ro_dst);
      dst->sin6_family = AF_INET6;
      dst->sin6_len = sizeof(*dst);
      dst->sin6_addr = *src;
      rtalloc_ign((struct route *)&ro, RTF_CLONING);

      if (ro.ro_rt == NULL)
            return 0;

      /* 
       * if ifp is provided, check for equality with rtentry
       * We should use rt->rt_ifa->ifa_ifp, instead of rt->rt_ifp,
       * to support the case of sending packets to an address of our own.
       * (where the former interface is the first argument of if_simloop()
       *  (=ifp), the latter is lo0)
       */
      if (ifp != NULL && ro.ro_rt->rt_ifa->ifa_ifp != ifp) {
            RTFREE(ro.ro_rt);
            return 0;
      }

      /* if no ifp provided, check if rtentry is not default route */
      if (ifp == NULL &&
          IN6_IS_ADDR_UNSPECIFIED(&satosin6(rt_key(ro.ro_rt))->sin6_addr)) {
            RTFREE(ro.ro_rt);
            return 0;
      }

      /* or if this is a blackhole/reject route */
      if (ifp == NULL && ro.ro_rt->rt_flags & (RTF_REJECT|RTF_BLACKHOLE)) {
            RTFREE(ro.ro_rt);
            return 0;
      }

      /* found valid route */
      RTFREE(ro.ro_rt);
      return 1;

}
static __inline int
hash_packet6(struct ipfw_flow_id *id)
{
      u_int32_t i;
      i = (id->dst_ip6.__u6_addr.__u6_addr32[2]) ^
          (id->dst_ip6.__u6_addr.__u6_addr32[3]) ^
          (id->src_ip6.__u6_addr.__u6_addr32[2]) ^
          (id->src_ip6.__u6_addr.__u6_addr32[3]) ^
          (id->dst_port) ^ (id->src_port);
      return i;
}

static int
is_icmp6_query(int icmp6_type)
{
      if ((icmp6_type <= ICMP6_MAXTYPE) &&
          (icmp6_type == ICMP6_ECHO_REQUEST ||
          icmp6_type == ICMP6_MEMBERSHIP_QUERY ||
          icmp6_type == ICMP6_WRUREQUEST ||
          icmp6_type == ICMP6_FQDN_QUERY ||
          icmp6_type == ICMP6_NI_QUERY))
            return (1);

      return (0);
}

static void
send_reject6(struct ip_fw_args *args, int code, u_short offset, u_int hlen, struct ip6_hdr *ip6)
{
      struct mbuf *m;

      m = args->m;
      if (code == ICMP6_UNREACH_RST && offset == 0 &&
          args->f_id.proto == IPPROTO_TCP) {
            struct tcphdr *tcp;
            tcp_seq ack, seq;
            int flags;
            struct {
                  struct ip6_hdr ip6;
                  struct tcphdr th;
            } ti;
            tcp = (struct tcphdr *)((char *)ip6 + hlen);

            if ((tcp->th_flags & TH_RST) != 0) {
                  m_freem(m);
                  args->m = NULL;
                  return;
            }

            ti.ip6 = *ip6;
            ti.th = *tcp;
            ti.th.th_seq = ntohl(ti.th.th_seq);
            ti.th.th_ack = ntohl(ti.th.th_ack);
            ti.ip6.ip6_nxt = IPPROTO_TCP;

            if (ti.th.th_flags & TH_ACK) {
                  ack = 0;
                  seq = ti.th.th_ack;
                  flags = TH_RST;
            } else {
                  ack = ti.th.th_seq;
                  if ((m->m_flags & M_PKTHDR) != 0) {
                        /*
                         * total new data to ACK is:
                         * total packet length,
                         * minus the header length,
                         * minus the tcp header length.
                         */
                        ack += m->m_pkthdr.len - hlen
                              - (ti.th.th_off << 2);
                  } else if (ip6->ip6_plen) {
                        ack += ntohs(ip6->ip6_plen) + sizeof(*ip6) -
                            hlen - (ti.th.th_off << 2);
                  } else {
                        m_freem(m);
                        return;
                  }
                  if (tcp->th_flags & TH_SYN)
                        ack++;
                  seq = 0;
                  flags = TH_RST|TH_ACK;
            }
            bcopy(&ti, ip6, sizeof(ti));
            /*
             * m is only used to recycle the mbuf
             * The data in it is never read so we don't need
             * to correct the offsets or anything
             */
            tcp_respond(NULL, ip6, tcp, m, ack, seq, flags);
      } else if (code != ICMP6_UNREACH_RST) { /* Send an ICMPv6 unreach. */
#if 0
            /*
             * Unlike above, the mbufs need to line up with the ip6 hdr,
             * as the contents are read. We need to m_adj() the
             * needed amount.
             * The mbuf will however be thrown away so we can adjust it.
             * Remember we did an m_pullup on it already so we
             * can make some assumptions about contiguousness.
             */
            if (args->L3offset)
                  m_adj(m, args->L3offset);
#endif
            icmp6_error(m, ICMP6_DST_UNREACH, code, 0);
      } else
            m_freem(m);

      args->m = NULL;
}

#endif /* INET6 */

static u_int64_t norule_counter;    /* counter for ipfw_log(NULL...) */

#define SNPARGS(buf, len) buf + len, sizeof(buf) > len ? sizeof(buf) - len : 0
#define SNP(buf) buf, sizeof(buf)

/*
 * We enter here when we have a rule with O_LOG.
 * XXX this function alone takes about 2Kbytes of code!
 */
static void
ipfw_log(struct ip_fw *f, u_int hlen, struct ip_fw_args *args,
      struct mbuf *m, struct ifnet *oif, u_short offset, uint32_t tablearg, struct ip  *ip)
{
      struct ether_header *eh = args->eh;
      char *action;
      int limit_reached = 0;
      char action2[40], proto[128], fragment[32];

      fragment[0] = '\0';
      proto[0] = '\0';

      if (f == NULL) {  /* bogus pkt */
            if (verbose_limit != 0 && norule_counter >= verbose_limit)
                  return;
            norule_counter++;
            if (norule_counter == verbose_limit)
                  limit_reached = verbose_limit;
            action = "Refuse";
      } else {    /* O_LOG is the first action, find the real one */
            ipfw_insn *cmd = ACTION_PTR(f);
            ipfw_insn_log *l = (ipfw_insn_log *)cmd;

            if (l->max_log != 0 && l->log_left == 0)
                  return;
            l->log_left--;
            if (l->log_left == 0)
                  limit_reached = l->max_log;
            cmd += F_LEN(cmd);      /* point to first action */
            if (cmd->opcode == O_ALTQ) {
                  ipfw_insn_altq *altq = (ipfw_insn_altq *)cmd;

                  snprintf(SNPARGS(action2, 0), "Altq %d",
                        altq->qid);
                  cmd += F_LEN(cmd);
            }
            if (cmd->opcode == O_PROB)
                  cmd += F_LEN(cmd);

            if (cmd->opcode == O_TAG)
                  cmd += F_LEN(cmd);

            action = action2;
            switch (cmd->opcode) {
            case O_DENY:
                  action = "Deny";
                  break;

            case O_REJECT:
                  if (cmd->arg1==ICMP_REJECT_RST)
                        action = "Reset";
                  else if (cmd->arg1==ICMP_UNREACH_HOST)
                        action = "Reject";
                  else
                        snprintf(SNPARGS(action2, 0), "Unreach %d",
                              cmd->arg1);
                  break;

            case O_UNREACH6:
                  if (cmd->arg1==ICMP6_UNREACH_RST)
                        action = "Reset";
                  else
                        snprintf(SNPARGS(action2, 0), "Unreach %d",
                              cmd->arg1);
                  break;

            case O_ACCEPT:
                  action = "Accept";
                  break;
            case O_COUNT:
                  action = "Count";
                  break;
            case O_DIVERT:
                  snprintf(SNPARGS(action2, 0), "Divert %d",
                        cmd->arg1);
                  break;
            case O_TEE:
                  snprintf(SNPARGS(action2, 0), "Tee %d",
                        cmd->arg1);
                  break;
            case O_SKIPTO:
                  snprintf(SNPARGS(action2, 0), "SkipTo %d",
                        cmd->arg1);
                  break;
            case O_PIPE:
                  snprintf(SNPARGS(action2, 0), "Pipe %d",
                        cmd->arg1);
                  break;
            case O_QUEUE:
                  snprintf(SNPARGS(action2, 0), "Queue %d",
                        cmd->arg1);
                  break;
            case O_FORWARD_IP: {
                  ipfw_insn_sa *sa = (ipfw_insn_sa *)cmd;
                  int len;
                  struct in_addr dummyaddr;
                  if (sa->sa.sin_addr.s_addr == INADDR_ANY)
                        dummyaddr.s_addr = htonl(tablearg);
                  else
                        dummyaddr.s_addr = sa->sa.sin_addr.s_addr;

                  len = snprintf(SNPARGS(action2, 0), "Forward to %s",
                        inet_ntoa(dummyaddr));

                  if (sa->sa.sin_port)
                        snprintf(SNPARGS(action2, len), ":%d",
                            sa->sa.sin_port);
                  }
                  break;
            case O_NETGRAPH:
                  snprintf(SNPARGS(action2, 0), "Netgraph %d",
                        cmd->arg1);
                  break;
            case O_NGTEE:
                  snprintf(SNPARGS(action2, 0), "Ngtee %d",
                        cmd->arg1);
                  break;
            default:
                  action = "UNKNOWN";
                  break;
            }
      }

      if (hlen == 0) {  /* non-ip */
            snprintf(SNPARGS(proto, 0), "MAC");

      } else {
            int len;
            char src[48], dst[48];
            struct icmphdr *icmp;
            struct tcphdr *tcp;
            struct udphdr *udp;
#ifdef INET6
            struct ip6_hdr *ip6 = NULL;
            struct icmp6_hdr *icmp6;
#endif
            src[0] = '\0';
            dst[0] = '\0';
#ifdef INET6
            if (IS_IP6_FLOW_ID(&(args->f_id))) {
                  snprintf(src, sizeof(src), "[%s]",
                      ip6_sprintf(&args->f_id.src_ip6));
                  snprintf(dst, sizeof(dst), "[%s]",
                      ip6_sprintf(&args->f_id.dst_ip6));

                  ip6 = (struct ip6_hdr *)ip;
                  tcp = (struct tcphdr *)(((char *)ip) + hlen);
                  udp = (struct udphdr *)(((char *)ip) + hlen);
            } else
#endif
            {
                  tcp = L3HDR(struct tcphdr, ip);
                  udp = L3HDR(struct udphdr, ip);

                  inet_ntoa_r(ip->ip_src, src);
                  inet_ntoa_r(ip->ip_dst, dst);
            }

            switch (args->f_id.proto) {
            case IPPROTO_TCP:
                  len = snprintf(SNPARGS(proto, 0), "TCP %s", src);
                  if (offset == 0)
                        snprintf(SNPARGS(proto, len), ":%d %s:%d",
                            ntohs(tcp->th_sport),
                            dst,
                            ntohs(tcp->th_dport));
                  else
                        snprintf(SNPARGS(proto, len), " %s", dst);
                  break;

            case IPPROTO_UDP:
                  len = snprintf(SNPARGS(proto, 0), "UDP %s", src);
                  if (offset == 0)
                        snprintf(SNPARGS(proto, len), ":%d %s:%d",
                            ntohs(udp->uh_sport),
                            dst,
                            ntohs(udp->uh_dport));
                  else
                        snprintf(SNPARGS(proto, len), " %s", dst);
                  break;

            case IPPROTO_ICMP:
                  icmp = L3HDR(struct icmphdr, ip);
                  if (offset == 0)
                        len = snprintf(SNPARGS(proto, 0),
                            "ICMP:%u.%u ",
                            icmp->icmp_type, icmp->icmp_code);
                  else
                        len = snprintf(SNPARGS(proto, 0), "ICMP ");
                  len += snprintf(SNPARGS(proto, len), "%s", src);
                  snprintf(SNPARGS(proto, len), " %s", dst);
                  break;
#ifdef INET6
            case IPPROTO_ICMPV6:
                  icmp6 = (struct icmp6_hdr *)(((char *)ip) + hlen);
                  if (offset == 0)
                        len = snprintf(SNPARGS(proto, 0),
                            "ICMPv6:%u.%u ",
                            icmp6->icmp6_type, icmp6->icmp6_code);
                  else
                        len = snprintf(SNPARGS(proto, 0), "ICMPv6 ");
                  len += snprintf(SNPARGS(proto, len), "%s", src);
                  snprintf(SNPARGS(proto, len), " %s", dst);
                  break;
#endif
            default:
                  len = snprintf(SNPARGS(proto, 0), "P:%d %s",
                      args->f_id.proto, src);
                  snprintf(SNPARGS(proto, len), " %s", dst);
                  break;
            }

#ifdef INET6
            if (IS_IP6_FLOW_ID(&(args->f_id))) {
                  if (offset & (IP6F_OFF_MASK | IP6F_MORE_FRAG))
                        snprintf(SNPARGS(fragment, 0),
                            " (frag %08x:%d@%d%s)",
                            args->f_id.frag_id6,
                            ntohs(ip6->ip6_plen) - hlen,
                            ntohs(offset & IP6F_OFF_MASK) << 3,
                            (offset & IP6F_MORE_FRAG) ? "+" : "");
            } else
#endif
            {
                  int ip_off, ip_len;
                  if (eh != NULL) { /* layer 2 packets are as on the wire */
                        ip_off = ntohs(ip->ip_off);
                        ip_len = ntohs(ip->ip_len);
                  } else {
                        ip_off = ip->ip_off;
                        ip_len = ip->ip_len;
                  }
                  if (ip_off & (IP_MF | IP_OFFMASK))
                        snprintf(SNPARGS(fragment, 0),
                            " (frag %d:%d@%d%s)",
                            ntohs(ip->ip_id), ip_len - (ip->ip_hl << 2),
                            offset << 3,
                            (ip_off & IP_MF) ? "+" : "");
            }
      }
      if (oif || m->m_pkthdr.rcvif)
            log(LOG_SECURITY | LOG_INFO,
                "ipfw: %d %s %s %s via %s%s\n",
                f ? f->rulenum : -1,
                action, proto, oif ? "out" : "in",
                oif ? oif->if_xname : m->m_pkthdr.rcvif->if_xname,
                fragment);
      else
            log(LOG_SECURITY | LOG_INFO,
                "ipfw: %d %s %s [no if info]%s\n",
                f ? f->rulenum : -1,
                action, proto, fragment);
      if (limit_reached)
            log(LOG_SECURITY | LOG_NOTICE,
                "ipfw: limit %d reached on entry %d\n",
                limit_reached, f ? f->rulenum : -1);
}

/*
 * IMPORTANT: the hash function for dynamic rules must be commutative
 * in source and destination (ip,port), because rules are bidirectional
 * and we want to find both in the same bucket.
 */
static __inline int
hash_packet(struct ipfw_flow_id *id)
{
      u_int32_t i;

#ifdef INET6
      if (IS_IP6_FLOW_ID(id)) 
            i = hash_packet6(id);
      else
#endif /* INET6 */
      i = (id->dst_ip) ^ (id->src_ip) ^ (id->dst_port) ^ (id->src_port);
      i &= (curr_dyn_buckets - 1);
      return i;
}

/**
 * unlink a dynamic rule from a chain. prev is a pointer to
 * the previous one, q is a pointer to the rule to delete,
 * head is a pointer to the head of the queue.
 * Modifies q and potentially also head.
 */
#define UNLINK_DYN_RULE(prev, head, q) {                    \
      ipfw_dyn_rule *old_q = q;                             \
                                                      \
      /* remove a refcount to the parent */                       \
      if (q->dyn_type == O_LIMIT)                           \
            q->parent->count--;                             \
      DEB(printf("ipfw: unlink entry 0x%08x %d -> 0x%08x %d, %d left\n",\
            (q->id.src_ip), (q->id.src_port),               \
            (q->id.dst_ip), (q->id.dst_port), dyn_count-1 ); )    \
      if (prev != NULL)                               \
            prev->next = q = q->next;                       \
      else                                            \
            head = q = q->next;                             \
      dyn_count--;                                          \
      uma_zfree(ipfw_dyn_rule_zone, old_q); }

#define TIME_LEQ(a,b)       ((int)((a)-(b)) <= 0)

/**
 * Remove dynamic rules pointing to "rule", or all of them if rule == NULL.
 *
 * If keep_me == NULL, rules are deleted even if not expired,
 * otherwise only expired rules are removed.
 *
 * The value of the second parameter is also used to point to identify
 * a rule we absolutely do not want to remove (e.g. because we are
 * holding a reference to it -- this is the case with O_LIMIT_PARENT
 * rules). The pointer is only used for comparison, so any non-null
 * value will do.
 */
static void
remove_dyn_rule(struct ip_fw *rule, ipfw_dyn_rule *keep_me)
{
      static u_int32_t last_remove = 0;

#define FORCE (keep_me == NULL)

      ipfw_dyn_rule *prev, *q;
      int i, pass = 0, max_pass = 0;

      IPFW_DYN_LOCK_ASSERT();

      if (ipfw_dyn_v == NULL || dyn_count == 0)
            return;
      /* do not expire more than once per second, it is useless */
      if (!FORCE && last_remove == time_uptime)
            return;
      last_remove = time_uptime;

      /*
       * because O_LIMIT refer to parent rules, during the first pass only
       * remove child and mark any pending LIMIT_PARENT, and remove
       * them in a second pass.
       */
next_pass:
      for (i = 0 ; i < curr_dyn_buckets ; i++) {
            for (prev=NULL, q = ipfw_dyn_v[i] ; q ; ) {
                  /*
                   * Logic can become complex here, so we split tests.
                   */
                  if (q == keep_me)
                        goto next;
                  if (rule != NULL && rule != q->rule)
                        goto next; /* not the one we are looking for */
                  if (q->dyn_type == O_LIMIT_PARENT) {
                        /*
                         * handle parent in the second pass,
                         * record we need one.
                         */
                        max_pass = 1;
                        if (pass == 0)
                              goto next;
                        if (FORCE && q->count != 0 ) {
                              /* XXX should not happen! */
                              printf("ipfw: OUCH! cannot remove rule,"
                                   " count %d\n", q->count);
                        }
                  } else {
                        if (!FORCE &&
                            !TIME_LEQ( q->expire, time_uptime ))
                              goto next;
                  }
             if (q->dyn_type != O_LIMIT_PARENT || !q->count) {
                     UNLINK_DYN_RULE(prev, ipfw_dyn_v[i], q);
                     continue;
             }
next:
                  prev=q;
                  q=q->next;
            }
      }
      if (pass++ < max_pass)
            goto next_pass;
}


/**
 * lookup a dynamic rule.
 */
static ipfw_dyn_rule *
lookup_dyn_rule_locked(struct ipfw_flow_id *pkt, int *match_direction,
      struct tcphdr *tcp)
{
      /*
       * stateful ipfw extensions.
       * Lookup into dynamic session queue
       */
#define MATCH_REVERSE   0
#define MATCH_FORWARD   1
#define MATCH_NONE      2
#define MATCH_UNKNOWN   3
      int i, dir = MATCH_NONE;
      ipfw_dyn_rule *prev, *q=NULL;

      IPFW_DYN_LOCK_ASSERT();

      if (ipfw_dyn_v == NULL)
            goto done;  /* not found */
      i = hash_packet( pkt );
      for (prev=NULL, q = ipfw_dyn_v[i] ; q != NULL ; ) {
            if (q->dyn_type == O_LIMIT_PARENT && q->count)
                  goto next;
            if (TIME_LEQ( q->expire, time_uptime)) { /* expire entry */
                  UNLINK_DYN_RULE(prev, ipfw_dyn_v[i], q);
                  continue;
            }
            if (pkt->proto == q->id.proto &&
                q->dyn_type != O_LIMIT_PARENT) {
                  if (IS_IP6_FLOW_ID(pkt)) {
                      if (IN6_ARE_ADDR_EQUAL(&(pkt->src_ip6),
                        &(q->id.src_ip6)) &&
                      IN6_ARE_ADDR_EQUAL(&(pkt->dst_ip6),
                        &(q->id.dst_ip6)) &&
                      pkt->src_port == q->id.src_port &&
                      pkt->dst_port == q->id.dst_port ) {
                        dir = MATCH_FORWARD;
                        break;
                      }
                      if (IN6_ARE_ADDR_EQUAL(&(pkt->src_ip6),
                            &(q->id.dst_ip6)) &&
                        IN6_ARE_ADDR_EQUAL(&(pkt->dst_ip6),
                            &(q->id.src_ip6)) &&
                        pkt->src_port == q->id.dst_port &&
                        pkt->dst_port == q->id.src_port ) {
                            dir = MATCH_REVERSE;
                            break;
                      }
                  } else {
                      if (pkt->src_ip == q->id.src_ip &&
                        pkt->dst_ip == q->id.dst_ip &&
                        pkt->src_port == q->id.src_port &&
                        pkt->dst_port == q->id.dst_port ) {
                            dir = MATCH_FORWARD;
                            break;
                      }
                      if (pkt->src_ip == q->id.dst_ip &&
                        pkt->dst_ip == q->id.src_ip &&
                        pkt->src_port == q->id.dst_port &&
                        pkt->dst_port == q->id.src_port ) {
                            dir = MATCH_REVERSE;
                            break;
                      }
                  }
            }
next:
            prev = q;
            q = q->next;
      }
      if (q == NULL)
            goto done; /* q = NULL, not found */

      if ( prev != NULL) { /* found and not in front */
            prev->next = q->next;
            q->next = ipfw_dyn_v[i];
            ipfw_dyn_v[i] = q;
      }
      if (pkt->proto == IPPROTO_TCP) { /* update state according to flags */
            u_char flags = pkt->flags & (TH_FIN|TH_SYN|TH_RST);

#define BOTH_SYN  (TH_SYN | (TH_SYN << 8))
#define BOTH_FIN  (TH_FIN | (TH_FIN << 8))
            q->state |= (dir == MATCH_FORWARD ) ? flags : (flags << 8);
            switch (q->state) {
            case TH_SYN:                        /* opening */
                  q->expire = time_uptime + dyn_syn_lifetime;
                  break;

            case BOTH_SYN:                /* move to established */
            case BOTH_SYN | TH_FIN :      /* one side tries to close */
            case BOTH_SYN | (TH_FIN << 8) :
                  if (tcp) {
#define _SEQ_GE(a,b) ((int)(a) - (int)(b) >= 0)
                      u_int32_t ack = ntohl(tcp->th_ack);
                      if (dir == MATCH_FORWARD) {
                        if (q->ack_fwd == 0 || _SEQ_GE(ack, q->ack_fwd))
                            q->ack_fwd = ack;
                        else { /* ignore out-of-sequence */
                            break;
                        }
                      } else {
                        if (q->ack_rev == 0 || _SEQ_GE(ack, q->ack_rev))
                            q->ack_rev = ack;
                        else { /* ignore out-of-sequence */
                            break;
                        }
                      }
                  }
                  q->expire = time_uptime + dyn_ack_lifetime;
                  break;

            case BOTH_SYN | BOTH_FIN:     /* both sides closed */
                  if (dyn_fin_lifetime >= dyn_keepalive_period)
                        dyn_fin_lifetime = dyn_keepalive_period - 1;
                  q->expire = time_uptime + dyn_fin_lifetime;
                  break;

            default:
#if 0
                  /*
                   * reset or some invalid combination, but can also
                   * occur if we use keep-state the wrong way.
                   */
                  if ( (q->state & ((TH_RST << 8)|TH_RST)) == 0)
                        printf("invalid state: 0x%x\n", q->state);
#endif
                  if (dyn_rst_lifetime >= dyn_keepalive_period)
                        dyn_rst_lifetime = dyn_keepalive_period - 1;
                  q->expire = time_uptime + dyn_rst_lifetime;
                  break;
            }
      } else if (pkt->proto == IPPROTO_UDP) {
            q->expire = time_uptime + dyn_udp_lifetime;
      } else {
            /* other protocols */
            q->expire = time_uptime + dyn_short_lifetime;
      }
done:
      if (match_direction)
            *match_direction = dir;
      return q;
}

static ipfw_dyn_rule *
lookup_dyn_rule(struct ipfw_flow_id *pkt, int *match_direction,
      struct tcphdr *tcp)
{
      ipfw_dyn_rule *q;

      IPFW_DYN_LOCK();
      q = lookup_dyn_rule_locked(pkt, match_direction, tcp);
      if (q == NULL)
            IPFW_DYN_UNLOCK();
      /* NB: return table locked when q is not NULL */
      return q;
}

static void
realloc_dynamic_table(void)
{
      IPFW_DYN_LOCK_ASSERT();

      /*
       * Try reallocation, make sure we have a power of 2 and do
       * not allow more than 64k entries. In case of overflow,
       * default to 1024.
       */

      if (dyn_buckets > 65536)
            dyn_buckets = 1024;
      if ((dyn_buckets & (dyn_buckets-1)) != 0) { /* not a power of 2 */
            dyn_buckets = curr_dyn_buckets; /* reset */
            return;
      }
      curr_dyn_buckets = dyn_buckets;
      if (ipfw_dyn_v != NULL)
            free(ipfw_dyn_v, M_IPFW);
      for (;;) {
            ipfw_dyn_v = malloc(curr_dyn_buckets * sizeof(ipfw_dyn_rule *),
                   M_IPFW, M_NOWAIT | M_ZERO);
            if (ipfw_dyn_v != NULL || curr_dyn_buckets <= 2)
                  break;
            curr_dyn_buckets /= 2;
      }
}

/**
 * Install state of type 'type' for a dynamic session.
 * The hash table contains two type of rules:
 * - regular rules (O_KEEP_STATE)
 * - rules for sessions with limited number of sess per user
 *   (O_LIMIT). When they are created, the parent is
 *   increased by 1, and decreased on delete. In this case,
 *   the third parameter is the parent rule and not the chain.
 * - "parent" rules for the above (O_LIMIT_PARENT).
 */
static ipfw_dyn_rule *
add_dyn_rule(struct ipfw_flow_id *id, u_int8_t dyn_type, struct ip_fw *rule)
{
      ipfw_dyn_rule *r;
      int i;

      IPFW_DYN_LOCK_ASSERT();

      if (ipfw_dyn_v == NULL ||
          (dyn_count == 0 && dyn_buckets != curr_dyn_buckets)) {
            realloc_dynamic_table();
            if (ipfw_dyn_v == NULL)
                  return NULL; /* failed ! */
      }
      i = hash_packet(id);

      r = uma_zalloc(ipfw_dyn_rule_zone, M_NOWAIT | M_ZERO);
      if (r == NULL) {
            printf ("ipfw: sorry cannot allocate state\n");
            return NULL;
      }

      /* increase refcount on parent, and set pointer */
      if (dyn_type == O_LIMIT) {
            ipfw_dyn_rule *parent = (ipfw_dyn_rule *)rule;
            if ( parent->dyn_type != O_LIMIT_PARENT)
                  panic("invalid parent");
            parent->count++;
            r->parent = parent;
            rule = parent->rule;
      }

      r->id = *id;
      r->expire = time_uptime + dyn_syn_lifetime;
      r->rule = rule;
      r->dyn_type = dyn_type;
      r->pcnt = r->bcnt = 0;
      r->count = 0;

      r->bucket = i;
      r->next = ipfw_dyn_v[i];
      ipfw_dyn_v[i] = r;
      dyn_count++;
      DEB(printf("ipfw: add dyn entry ty %d 0x%08x %d -> 0x%08x %d, total %d\n",
         dyn_type,
         (r->id.src_ip), (r->id.src_port),
         (r->id.dst_ip), (r->id.dst_port),
         dyn_count ); )
      return r;
}

/**
 * lookup dynamic parent rule using pkt and rule as search keys.
 * If the lookup fails, then install one.
 */
static ipfw_dyn_rule *
lookup_dyn_parent(struct ipfw_flow_id *pkt, struct ip_fw *rule)
{
      ipfw_dyn_rule *q;
      int i;

      IPFW_DYN_LOCK_ASSERT();

      if (ipfw_dyn_v) {
            int is_v6 = IS_IP6_FLOW_ID(pkt);
            i = hash_packet( pkt );
            for (q = ipfw_dyn_v[i] ; q != NULL ; q=q->next)
                  if (q->dyn_type == O_LIMIT_PARENT &&
                      rule== q->rule &&
                      pkt->proto == q->id.proto &&
                      pkt->src_port == q->id.src_port &&
                      pkt->dst_port == q->id.dst_port &&
                      (
                        (is_v6 &&
                         IN6_ARE_ADDR_EQUAL(&(pkt->src_ip6),
                              &(q->id.src_ip6)) &&
                         IN6_ARE_ADDR_EQUAL(&(pkt->dst_ip6),
                              &(q->id.dst_ip6))) ||
                        (!is_v6 &&
                         pkt->src_ip == q->id.src_ip &&
                         pkt->dst_ip == q->id.dst_ip)
                      )
                  ) {
                        q->expire = time_uptime + dyn_short_lifetime;
                        DEB(printf("ipfw: lookup_dyn_parent found 0x%p\n",q);)
                        return q;
                  }
      }
      return add_dyn_rule(pkt, O_LIMIT_PARENT, rule);
}

/**
 * Install dynamic state for rule type cmd->o.opcode
 *
 * Returns 1 (failure) if state is not installed because of errors or because
 * session limitations are enforced.
 */
static int
install_state(struct ip_fw *rule, ipfw_insn_limit *cmd,
    struct ip_fw_args *args, uint32_t tablearg)
{
      static int last_log;
      ipfw_dyn_rule *q;
      struct in_addr da;
      char src[48], dst[48];

      src[0] = '\0';
      dst[0] = '\0';

      DEB(
      printf("ipfw: %s: type %d 0x%08x %u -> 0x%08x %u\n",
          __func__, cmd->o.opcode,
          (args->f_id.src_ip), (args->f_id.src_port),
          (args->f_id.dst_ip), (args->f_id.dst_port));
      )

      IPFW_DYN_LOCK();

      q = lookup_dyn_rule_locked(&args->f_id, NULL, NULL);

      if (q != NULL) {  /* should never occur */
            if (last_log != time_uptime) {
                  last_log = time_uptime;
                  printf("ipfw: %s: entry already present, done\n",
                      __func__);
            }
            IPFW_DYN_UNLOCK();
            return (0);
      }

      if (dyn_count >= dyn_max)
            /* Run out of slots, try to remove any expired rule. */
            remove_dyn_rule(NULL, (ipfw_dyn_rule *)1);

      if (dyn_count >= dyn_max) {
            if (last_log != time_uptime) {
                  last_log = time_uptime;
                  printf("ipfw: %s: Too many dynamic rules\n", __func__);
            }
            IPFW_DYN_UNLOCK();
            return (1); /* cannot install, notify caller */
      }

      switch (cmd->o.opcode) {
      case O_KEEP_STATE:      /* bidir rule */
            add_dyn_rule(&args->f_id, O_KEEP_STATE, rule);
            break;

      case O_LIMIT: {         /* limit number of sessions */
            struct ipfw_flow_id id;
            ipfw_dyn_rule *parent;
            uint32_t conn_limit;
            uint16_t limit_mask = cmd->limit_mask;

            conn_limit = (cmd->conn_limit == IP_FW_TABLEARG) ?
                tablearg : cmd->conn_limit;
              
            DEB(
            if (cmd->conn_limit == IP_FW_TABLEARG)
                  printf("ipfw: %s: O_LIMIT rule, conn_limit: %u "
                      "(tablearg)\n", __func__, conn_limit);
            else
                  printf("ipfw: %s: O_LIMIT rule, conn_limit: %u\n",
                      __func__, conn_limit);
            )

            id.dst_ip = id.src_ip = id.dst_port = id.src_port = 0;
            id.proto = args->f_id.proto;
            id.addr_type = args->f_id.addr_type;

            if (IS_IP6_FLOW_ID (&(args->f_id))) {
                  if (limit_mask & DYN_SRC_ADDR)
                        id.src_ip6 = args->f_id.src_ip6;
                  if (limit_mask & DYN_DST_ADDR)
                        id.dst_ip6 = args->f_id.dst_ip6;
            } else {
                  if (limit_mask & DYN_SRC_ADDR)
                        id.src_ip = args->f_id.src_ip;
                  if (limit_mask & DYN_DST_ADDR)
                        id.dst_ip = args->f_id.dst_ip;
            }
            if (limit_mask & DYN_SRC_PORT)
                  id.src_port = args->f_id.src_port;
            if (limit_mask & DYN_DST_PORT)
                  id.dst_port = args->f_id.dst_port;
            if ((parent = lookup_dyn_parent(&id, rule)) == NULL) {
                  printf("ipfw: %s: add parent failed\n", __func__);
                  IPFW_DYN_UNLOCK();
                  return (1);
            }

            if (parent->count >= conn_limit) {
                  /* See if we can remove some expired rule. */
                  remove_dyn_rule(rule, parent);
                  if (parent->count >= conn_limit) {
                        if (fw_verbose && last_log != time_uptime) {
                              last_log = time_uptime;
#ifdef INET6
                              /*
                               * XXX IPv6 flows are not
                               * supported yet.
                               * */
                              if (IS_IP6_FLOW_ID(&(args->f_id))) {
                                    snprintf(src, sizeof(src),
                                        "[%s]", ip6_sprintf(
                                          &args->f_id.src_ip6));
                                    snprintf(dst, sizeof(dst),
                                        "[%s]", ip6_sprintf(
                                          &args->f_id.dst_ip6));
                              } else
#endif
                              {
                                    da.s_addr =
                                        htonl(args->f_id.src_ip);
                                    inet_ntoa_r(da, src);
                                    da.s_addr =
                                        htonl(args->f_id.dst_ip);
                                    inet_ntoa_r(da, dst);
                              }
                              log(LOG_SECURITY | LOG_DEBUG,
                                  "%s %s:%u -> %s:%u, %s\n",
                                  "drop session",
                                  src, (args->f_id.src_port),
                                  dst, (args->f_id.dst_port),
                                  "too many entries");
                        }
                        IPFW_DYN_UNLOCK();
                        return (1);
                  }
            }
            add_dyn_rule(&args->f_id, O_LIMIT, (struct ip_fw *)parent);
            break;
      }
      default:
            printf("ipfw: %s: unknown dynamic rule type %u\n",
                __func__, cmd->o.opcode);
            IPFW_DYN_UNLOCK();
            return (1);
      }

      /* XXX just set lifetime */
      lookup_dyn_rule_locked(&args->f_id, NULL, NULL);

      IPFW_DYN_UNLOCK();
      return (0);
}

/*
 * Generate a TCP packet, containing either a RST or a keepalive.
 * When flags & TH_RST, we are sending a RST packet, because of a
 * "reset" action matched the packet.
 * Otherwise we are sending a keepalive, and flags & TH_
 * The 'replyto' mbuf is the mbuf being replied to, if any, and is required
 * so that MAC can label the reply appropriately.
 */
static struct mbuf *
send_pkt(struct mbuf *replyto, struct ipfw_flow_id *id, u_int32_t seq,
    u_int32_t ack, int flags)
{
      struct mbuf *m;
      struct ip *ip;
      struct tcphdr *tcp;

      MGETHDR(m, M_DONTWAIT, MT_HEADER);
      if (m == 0)
            return (NULL);
      m->m_pkthdr.rcvif = (struct ifnet *)0;

#ifdef MAC
      if (replyto != NULL)
            mac_create_mbuf_netlayer(replyto, m);
      else
            mac_create_mbuf_from_firewall(m);
#else
      (void)replyto;          /* don't warn about unused arg */
#endif

      m->m_pkthdr.len = m->m_len = sizeof(struct ip) + sizeof(struct tcphdr);
      m->m_data += max_linkhdr;

      ip = mtod(m, struct ip *);
      bzero(ip, m->m_len);
      tcp = (struct tcphdr *)(ip + 1); /* no IP options */
      ip->ip_p = IPPROTO_TCP;
      tcp->th_off = 5;
      /*
       * Assume we are sending a RST (or a keepalive in the reverse
       * direction), swap src and destination addresses and ports.
       */
      ip->ip_src.s_addr = htonl(id->dst_ip);
      ip->ip_dst.s_addr = htonl(id->src_ip);
      tcp->th_sport = htons(id->dst_port);
      tcp->th_dport = htons(id->src_port);
      if (flags & TH_RST) {   /* we are sending a RST */
            if (flags & TH_ACK) {
                  tcp->th_seq = htonl(ack);
                  tcp->th_ack = htonl(0);
                  tcp->th_flags = TH_RST;
            } else {
                  if (flags & TH_SYN)
                        seq++;
                  tcp->th_seq = htonl(0);
                  tcp->th_ack = htonl(seq);
                  tcp->th_flags = TH_RST | TH_ACK;
            }
      } else {
            /*
             * We are sending a keepalive. flags & TH_SYN determines
             * the direction, forward if set, reverse if clear.
             * NOTE: seq and ack are always assumed to be correct
             * as set by the caller. This may be confusing...
             */
            if (flags & TH_SYN) {
                  /*
                   * we have to rewrite the correct addresses!
                   */
                  ip->ip_dst.s_addr = htonl(id->dst_ip);
                  ip->ip_src.s_addr = htonl(id->src_ip);
                  tcp->th_dport = htons(id->dst_port);
                  tcp->th_sport = htons(id->src_port);
            }
            tcp->th_seq = htonl(seq);
            tcp->th_ack = htonl(ack);
            tcp->th_flags = TH_ACK;
      }
      /*
       * set ip_len to the payload size so we can compute
       * the tcp checksum on the pseudoheader
       * XXX check this, could save a couple of words ?
       */
      ip->ip_len = htons(sizeof(struct tcphdr));
      tcp->th_sum = in_cksum(m, m->m_pkthdr.len);
      /*
       * now fill fields left out earlier
       */
      ip->ip_ttl = ip_defttl;
      ip->ip_len = m->m_pkthdr.len;
      m->m_flags |= M_SKIP_FIREWALL;
      return (m);
}

/*
 * sends a reject message, consuming the mbuf passed as an argument.
 */
static void
send_reject(struct ip_fw_args *args, int code, u_short offset, int ip_len, struct ip *ip)
{

#if 0
      /* XXX When ip is not guaranteed to be at mtod() we will
       * need to account for this */
       * The mbuf will however be thrown away so we can adjust it.
       * Remember we did an m_pullup on it already so we
       * can make some assumptions about contiguousness.
       */
      if (args->L3offset)
            m_adj(m, args->L3offset);
#endif
      if (code != ICMP_REJECT_RST) { /* Send an ICMP unreach */
            /* We need the IP header in host order for icmp_error(). */
            if (args->eh != NULL) {
                  ip->ip_len = ntohs(ip->ip_len);
                  ip->ip_off = ntohs(ip->ip_off);
            }
            icmp_error(args->m, ICMP_UNREACH, code, 0L, 0);
      } else if (offset == 0 && args->f_id.proto == IPPROTO_TCP) {
            struct tcphdr *const tcp =
                L3HDR(struct tcphdr, mtod(args->m, struct ip *));
            if ( (tcp->th_flags & TH_RST) == 0) {
                  struct mbuf *m;
                  m = send_pkt(args->m, &(args->f_id),
                        ntohl(tcp->th_seq), ntohl(tcp->th_ack),
                        tcp->th_flags | TH_RST);
                  if (m != NULL)
                        ip_output(m, NULL, NULL, 0, NULL, NULL);
            }
            m_freem(args->m);
      } else
            m_freem(args->m);
      args->m = NULL;
}

/**
 *
 * Given an ip_fw *, lookup_next_rule will return a pointer
 * to the next rule, which can be either the jump
 * target (for skipto instructions) or the next one in the list (in
 * all other cases including a missing jump target).
 * The result is also written in the "next_rule" field of the rule.
 * Backward jumps are not allowed, so start looking from the next
 * rule...
 *
 * This never returns NULL -- in case we do not have an exact match,
 * the next rule is returned. When the ruleset is changed,
 * pointers are flushed so we are always correct.
 */

static struct ip_fw *
lookup_next_rule(struct ip_fw *me)
{
      struct ip_fw *rule = NULL;
      ipfw_insn *cmd;

      /* look for action, in case it is a skipto */
      cmd = ACTION_PTR(me);
      if (cmd->opcode == O_LOG)
            cmd += F_LEN(cmd);
      if (cmd->opcode == O_ALTQ)
            cmd += F_LEN(cmd);
      if (cmd->opcode == O_TAG)
            cmd += F_LEN(cmd);
      if ( cmd->opcode == O_SKIPTO )
            for (rule = me->next; rule ; rule = rule->next)
                  if (rule->rulenum >= cmd->arg1)
                        break;
      if (rule == NULL)             /* failure or not a skipto */
            rule = me->next;
      me->next_rule = rule;
      return rule;
}

static int
add_table_entry(struct ip_fw_chain *ch, uint16_t tbl, in_addr_t addr,
      uint8_t mlen, uint32_t value)
{
      struct radix_node_head *rnh;
      struct table_entry *ent;

      if (tbl >= IPFW_TABLES_MAX)
            return (EINVAL);
      rnh = ch->tables[tbl];
      ent = malloc(sizeof(*ent), M_IPFW_TBL, M_NOWAIT | M_ZERO);
      if (ent == NULL)
            return (ENOMEM);
      ent->value = value;
      ent->addr.sin_len = ent->mask.sin_len = 8;
      ent->mask.sin_addr.s_addr = htonl(mlen ? ~((1 << (32 - mlen)) - 1) : 0);
      ent->addr.sin_addr.s_addr = addr & ent->mask.sin_addr.s_addr;
      IPFW_WLOCK(&layer3_chain);
      if (rnh->rnh_addaddr(&ent->addr, &ent->mask, rnh, (void *)ent) ==
          NULL) {
            IPFW_WUNLOCK(&layer3_chain);
            free(ent, M_IPFW_TBL);
            return (EEXIST);
      }
      IPFW_WUNLOCK(&layer3_chain);
      return (0);
}

static int
del_table_entry(struct ip_fw_chain *ch, uint16_t tbl, in_addr_t addr,
      uint8_t mlen)
{
      struct radix_node_head *rnh;
      struct table_entry *ent;
      struct sockaddr_in sa, mask;

      if (tbl >= IPFW_TABLES_MAX)
            return (EINVAL);
      rnh = ch->tables[tbl];
      sa.sin_len = mask.sin_len = 8;
      mask.sin_addr.s_addr = htonl(mlen ? ~((1 << (32 - mlen)) - 1) : 0);
      sa.sin_addr.s_addr = addr & mask.sin_addr.s_addr;
      IPFW_WLOCK(ch);
      ent = (struct table_entry *)rnh->rnh_deladdr(&sa, &mask, rnh);
      if (ent == NULL) {
            IPFW_WUNLOCK(ch);
            return (ESRCH);
      }
      IPFW_WUNLOCK(ch);
      free(ent, M_IPFW_TBL);
      return (0);
}

static int
flush_table_entry(struct radix_node *rn, void *arg)
{
      struct radix_node_head * const rnh = arg;
      struct table_entry *ent;

      ent = (struct table_entry *)
          rnh->rnh_deladdr(rn->rn_key, rn->rn_mask, rnh);
      if (ent != NULL)
            free(ent, M_IPFW_TBL);
      return (0);
}

static int
flush_table(struct ip_fw_chain *ch, uint16_t tbl)
{
      struct radix_node_head *rnh;

      IPFW_WLOCK_ASSERT(ch);

      if (tbl >= IPFW_TABLES_MAX)
            return (EINVAL);
      rnh = ch->tables[tbl];
      KASSERT(rnh != NULL, ("NULL IPFW table"));
      rnh->rnh_walktree(rnh, flush_table_entry, rnh);
      return (0);
}

static void
flush_tables(struct ip_fw_chain *ch)
{
      uint16_t tbl;

      IPFW_WLOCK_ASSERT(ch);

      for (tbl = 0; tbl < IPFW_TABLES_MAX; tbl++)
            flush_table(ch, tbl);
}

static int
init_tables(struct ip_fw_chain *ch)
{ 
      int i;
      uint16_t j;

      for (i = 0; i < IPFW_TABLES_MAX; i++) {
            if (!rn_inithead((void **)&ch->tables[i], 32)) {
                  for (j = 0; j < i; j++) {
                        (void) flush_table(ch, j);
                  }
                  return (ENOMEM);
            }
      }
      return (0);
}

static int
lookup_table(struct ip_fw_chain *ch, uint16_t tbl, in_addr_t addr,
      uint32_t *val)
{
      struct radix_node_head *rnh;
      struct table_entry *ent;
      struct sockaddr_in sa;

      if (tbl >= IPFW_TABLES_MAX)
            return (0);
      rnh = ch->tables[tbl];
      sa.sin_len = 8;
      sa.sin_addr.s_addr = addr;
      ent = (struct table_entry *)(rnh->rnh_lookup(&sa, NULL, rnh));
      if (ent != NULL) {
            *val = ent->value;
            return (1);
      }
      return (0);
}

static int
count_table_entry(struct radix_node *rn, void *arg)
{
      u_int32_t * const cnt = arg;

      (*cnt)++;
      return (0);
}

static int
count_table(struct ip_fw_chain *ch, uint32_t tbl, uint32_t *cnt)
{
      struct radix_node_head *rnh;

      if (tbl >= IPFW_TABLES_MAX)
            return (EINVAL);
      rnh = ch->tables[tbl];
      *cnt = 0;
      rnh->rnh_walktree(rnh, count_table_entry, cnt);
      return (0);
}

static int
dump_table_entry(struct radix_node *rn, void *arg)
{
      struct table_entry * const n = (struct table_entry *)rn;
      ipfw_table * const tbl = arg;
      ipfw_table_entry *ent;

      if (tbl->cnt == tbl->size)
            return (1);
      ent = &tbl->ent[tbl->cnt];
      ent->tbl = tbl->tbl;
      if (in_nullhost(n->mask.sin_addr))
            ent->masklen = 0;
      else
            ent->masklen = 33 - ffs(ntohl(n->mask.sin_addr.s_addr));
      ent->addr = n->addr.sin_addr.s_addr;
      ent->value = n->value;
      tbl->cnt++;
      return (0);
}

static int
dump_table(struct ip_fw_chain *ch, ipfw_table *tbl)
{
      struct radix_node_head *rnh;

      if (tbl->tbl >= IPFW_TABLES_MAX)
            return (EINVAL);
      rnh = ch->tables[tbl->tbl];
      tbl->cnt = 0;
      rnh->rnh_walktree(rnh, dump_table_entry, tbl);
      return (0);
}

static void
fill_ugid_cache(struct inpcb *inp, struct ip_fw_ugid *ugp)
{
      struct ucred *cr;

      if (inp->inp_socket != NULL) {
            cr = inp->inp_socket->so_cred;
            ugp->fw_prid = jailed(cr) ?
                cr->cr_prison->pr_id : -1;
            ugp->fw_uid = cr->cr_uid;
            ugp->fw_ngroups = cr->cr_ngroups;
            bcopy(cr->cr_groups, ugp->fw_groups,
                sizeof(ugp->fw_groups));
      }
}

static int
check_uidgid(ipfw_insn_u32 *insn,
      int proto, struct ifnet *oif,
      struct in_addr dst_ip, u_int16_t dst_port,
      struct in_addr src_ip, u_int16_t src_port,
      struct ip_fw_ugid *ugp, int *lookup, struct inpcb *inp)
{
      struct inpcbinfo *pi;
      int wildcard;
      struct inpcb *pcb;
      int match;
      gid_t *gp;

      /*
       * Check to see if the UDP or TCP stack supplied us with
       * the PCB. If so, rather then holding a lock and looking
       * up the PCB, we can use the one that was supplied.
       */
      if (inp && *lookup == 0) {
            INP_LOCK_ASSERT(inp);
            if (inp->inp_socket != NULL) {
                  fill_ugid_cache(inp, ugp);
                  *lookup = 1;
            }
      }
      /*
       * If we have already been here and the packet has no
       * PCB entry associated with it, then we can safely
       * assume that this is a no match.
       */
      if (*lookup == -1)
            return (0);
      if (proto == IPPROTO_TCP) {
            wildcard = 0;
            pi = &tcbinfo;
      } else if (proto == IPPROTO_UDP) {
            wildcard = INPLOOKUP_WILDCARD;
            pi = &udbinfo;
      } else
            return 0;
      match = 0;
      if (*lookup == 0) {
            INP_INFO_RLOCK(pi);
            pcb =  (oif) ?
                  in_pcblookup_hash(pi,
                        dst_ip, htons(dst_port),
                        src_ip, htons(src_port),
                        wildcard, oif) :
                  in_pcblookup_hash(pi,
                        src_ip, htons(src_port),
                        dst_ip, htons(dst_port),
                        wildcard, NULL);
            if (pcb != NULL) {
                  INP_LOCK(pcb);
                  if (pcb->inp_socket != NULL) {
                        fill_ugid_cache(pcb, ugp);
                        *lookup = 1;
                  }
                  INP_UNLOCK(pcb);
            }
            INP_INFO_RUNLOCK(pi);
            if (*lookup == 0) {
                  /*
                   * If the lookup did not yield any results, there
                   * is no sense in coming back and trying again. So
                   * we can set lookup to -1 and ensure that we wont
                   * bother the pcb system again.
                   */
                  *lookup = -1;
                  return (0);
            }
      } 
      if (insn->o.opcode == O_UID)
            match = (ugp->fw_uid == (uid_t)insn->d[0]);
      else if (insn->o.opcode == O_GID) {
            for (gp = ugp->fw_groups;
                  gp < &ugp->fw_groups[ugp->fw_ngroups]; gp++)
                  if (*gp == (gid_t)insn->d[0]) {
                        match = 1;
                        break;
                  }
      } else if (insn->o.opcode == O_JAIL)
            match = (ugp->fw_prid == (int)insn->d[0]);
      return match;
}

/*
 * The main check routine for the firewall.
 *
 * All arguments are in args so we can modify them and return them
 * back to the caller.
 *
 * Parameters:
 *
 *    args->m     (in/out) The packet; we set to NULL when/if we nuke it.
 *          Starts with the IP header.
 *    args->eh (in)     Mac header if present, or NULL for layer3 packet.
 *    args->L3offset    Number of bytes bypassed if we came from L2.
 *                e.g. often sizeof(eh)  ** NOTYET **
 *    args->oif   Outgoing interface, or NULL if packet is incoming.
 *          The incoming interface is in the mbuf. (in)
 *    args->divert_rule (in/out)
 *          Skip up to the first rule past this rule number;
 *          upon return, non-zero port number for divert or tee.
 *
 *    args->rule  Pointer to the last matching rule (in/out)
 *    args->next_hop    Socket we are forwarding to (out).
 *    args->f_id  Addresses grabbed from the packet (out)
 *    args->cookie      a cookie depending on rule action
 *
 * Return value:
 *
 *    IP_FW_PASS  the packet must be accepted
 *    IP_FW_DENY  the packet must be dropped
 *    IP_FW_DIVERT      divert packet, port in m_tag
 *    IP_FW_TEE   tee packet, port in m_tag
 *    IP_FW_DUMMYNET    to dummynet, pipe in args->cookie
 *    IP_FW_NETGRAPH    into netgraph, cookie args->cookie
 *
 */
int
ipfw_chk(struct ip_fw_args *args)
{
      /*
       * Local variables holding state during the processing of a packet:
       *
       * IMPORTANT NOTE: to speed up the processing of rules, there
       * are some assumption on the values of the variables, which
       * are documented here. Should you change them, please check
       * the implementation of the various instructions to make sure
       * that they still work.
       *
       * args->eh The MAC header. It is non-null for a layer2
       *    packet, it is NULL for a layer-3 packet.
       * **notyet**
       * args->L3offset Offset in the packet to the L3 (IP or equiv.) header.
       *
       * m | args->m    Pointer to the mbuf, as received from the caller.
       *    It may change if ipfw_chk() does an m_pullup, or if it
       *    consumes the packet because it calls send_reject().
       *    XXX This has to change, so that ipfw_chk() never modifies
       *    or consumes the buffer.
       * ip is the beginning of the ip(4 or 6) header.
       *    Calculated by adding the L3offset to the start of data.
       *    (Until we start using L3offset, the packet is
       *    supposed to start with the ip header).
       */
      struct mbuf *m = args->m;
      struct ip *ip = mtod(m, struct ip *);

      /*
       * For rules which contain uid/gid or jail constraints, cache
       * a copy of the users credentials after the pcb lookup has been
       * executed. This will speed up the processing of rules with
       * these types of constraints, as well as decrease contention
       * on pcb related locks.
       */
      struct ip_fw_ugid fw_ugid_cache;
      int ugid_lookup = 0;

      /*
       * divinput_flags If non-zero, set to the IP_FW_DIVERT_*_FLAG
       *    associated with a packet input on a divert socket.  This
       *    will allow to distinguish traffic and its direction when
       *    it originates from a divert socket.
       */
      u_int divinput_flags = 0;

      /*
       * oif | args->oif      If NULL, ipfw_chk has been called on the
       *    inbound path (ether_input, bdg_forward, ip_input).
       *    If non-NULL, ipfw_chk has been called on the outbound path
       *    (ether_output, ip_output).
       */
      struct ifnet *oif = args->oif;

      struct ip_fw *f = NULL;       /* matching rule */
      int retval = 0;

      /*
       * hlen     The length of the IP header.
       */
      u_int hlen = 0;         /* hlen >0 means we have an IP pkt */

      /*
       * offset   The offset of a fragment. offset != 0 means that
       *    we have a fragment at this offset of an IPv4 packet.
       *    offset == 0 means that (if this is an IPv4 packet)
       *    this is the first or only fragment.
       *    For IPv6 offset == 0 means there is no Fragment Header. 
       *    If offset != 0 for IPv6 always use correct mask to
       *    get the correct offset because we add IP6F_MORE_FRAG
       *    to be able to dectect the first fragment which would
       *    otherwise have offset = 0.
       */
      u_short offset = 0;

      /*
       * Local copies of addresses. They are only valid if we have
       * an IP packet.
       *
       * proto    The protocol. Set to 0 for non-ip packets,
       *    or to the protocol read from the packet otherwise.
       *    proto != 0 means that we have an IPv4 packet.
       *
       * src_port, dst_port   port numbers, in HOST format. Only
       *    valid for TCP and UDP packets.
       *
       * src_ip, dst_ip ip addresses, in NETWORK format.
       *    Only valid for IPv4 packets.
       */
      u_int8_t proto;
      u_int16_t src_port = 0, dst_port = 0;     /* NOTE: host format    */
      struct in_addr src_ip, dst_ip;            /* NOTE: network format */
      u_int16_t ip_len=0;
      int pktlen;
      u_int16_t   etype = 0;  /* Host order stored ether type */

      /*
       * dyn_dir = MATCH_UNKNOWN when rules unchecked,
       *    MATCH_NONE when checked and not matched (q = NULL),
       *    MATCH_FORWARD or MATCH_REVERSE otherwise (q != NULL)
       */
      int dyn_dir = MATCH_UNKNOWN;
      ipfw_dyn_rule *q = NULL;
      struct ip_fw_chain *chain = &layer3_chain;
      struct m_tag *mtag;

      /*
       * We store in ulp a pointer to the upper layer protocol header.
       * In the ipv4 case this is easy to determine from the header,
       * but for ipv6 we might have some additional headers in the middle.
       * ulp is NULL if not found.
       */
      void *ulp = NULL;       /* upper layer protocol pointer. */
      /* XXX ipv6 variables */
      int is_ipv6 = 0;
      u_int16_t ext_hd = 0;   /* bits vector for extension header filtering */
      /* end of ipv6 variables */
      int is_ipv4 = 0;

      if (m->m_flags & M_SKIP_FIREWALL)
            return (IP_FW_PASS);    /* accept */

      pktlen = m->m_pkthdr.len;
      proto = args->f_id.proto = 0; /* mark f_id invalid */
            /* XXX 0 is a valid proto: IP/IPv6 Hop-by-Hop Option */

/*
 * PULLUP_TO(len, p, T) makes sure that len + sizeof(T) is contiguous,
 * then it sets p to point at the offset "len" in the mbuf. WARNING: the
 * pointer might become stale after other pullups (but we never use it
 * this way).
 */
#define PULLUP_TO(len, p, T)                                \
do {                                                  \
      int x = (len) + sizeof(T);                            \
      if ((m)->m_len < x) {                                 \
            args->m = m = m_pullup(m, x);                   \
            if (m == NULL)                                  \
                  goto pullup_failed;                       \
      }                                               \
      p = (mtod(m, char *) + (len));                              \
} while (0)

      /*
       * if we have an ether header,
       */
      if (args->eh)
            etype = ntohs(args->eh->ether_type);

      /* Identify IP packets and fill up variables. */
      if (pktlen >= sizeof(struct ip6_hdr) &&
          (args->eh == NULL || etype == ETHERTYPE_IPV6) && ip->ip_v == 6) {
            struct ip6_hdr *ip6 = (struct ip6_hdr *)ip;
            is_ipv6 = 1;
            args->f_id.addr_type = 6;
            hlen = sizeof(struct ip6_hdr);
            proto = ip6->ip6_nxt;

            /* Search extension headers to find upper layer protocols */
            while (ulp == NULL) {
                  switch (proto) {
                  case IPPROTO_ICMPV6:
                        PULLUP_TO(hlen, ulp, struct icmp6_hdr);
                        args->f_id.flags = ICMP6(ulp)->icmp6_type;
                        break;

                  case IPPROTO_TCP:
                        PULLUP_TO(hlen, ulp, struct tcphdr);
                        dst_port = TCP(ulp)->th_dport;
                        src_port = TCP(ulp)->th_sport;
                        args->f_id.flags = TCP(ulp)->th_flags;
                        break;

                  case IPPROTO_UDP:
                        PULLUP_TO(hlen, ulp, struct udphdr);
                        dst_port = UDP(ulp)->uh_dport;
                        src_port = UDP(ulp)->uh_sport;
                        break;

                  case IPPROTO_HOPOPTS:   /* RFC 2460 */
                        PULLUP_TO(hlen, ulp, struct ip6_hbh);
                        ext_hd |= EXT_HOPOPTS;
                        hlen += (((struct ip6_hbh *)ulp)->ip6h_len + 1) << 3;
                        proto = ((struct ip6_hbh *)ulp)->ip6h_nxt;
                        ulp = NULL;
                        break;

                  case IPPROTO_ROUTING:   /* RFC 2460 */
                        PULLUP_TO(hlen, ulp, struct ip6_rthdr);
                        switch (((struct ip6_rthdr *)ulp)->ip6r_type) {
                        case 0:
                              ext_hd |= EXT_RTHDR0;
                              break;
                        case 2:
                              ext_hd |= EXT_RTHDR2;
                              break;
                        default:
                              printf("IPFW2: IPV6 - Unknown Routing "
                                  "Header type(%d)\n",
                                  ((struct ip6_rthdr *)ulp)->ip6r_type);
                              if (fw_deny_unknown_exthdrs)
                                  return (IP_FW_DENY);
                              break;
                        }
                        ext_hd |= EXT_ROUTING;
                        hlen += (((struct ip6_rthdr *)ulp)->ip6r_len + 1) << 3;
                        proto = ((struct ip6_rthdr *)ulp)->ip6r_nxt;
                        ulp = NULL;
                        break;

                  case IPPROTO_FRAGMENT:  /* RFC 2460 */
                        PULLUP_TO(hlen, ulp, struct ip6_frag);
                        ext_hd |= EXT_FRAGMENT;
                        hlen += sizeof (struct ip6_frag);
                        proto = ((struct ip6_frag *)ulp)->ip6f_nxt;
                        offset = ((struct ip6_frag *)ulp)->ip6f_offlg &
                              IP6F_OFF_MASK;
                        /* Add IP6F_MORE_FRAG for offset of first
                         * fragment to be != 0. */
                        offset |= ((struct ip6_frag *)ulp)->ip6f_offlg &
                              IP6F_MORE_FRAG;
                        if (offset == 0) {
                              printf("IPFW2: IPV6 - Invalid Fragment "
                                  "Header\n");
                              if (fw_deny_unknown_exthdrs)
                                  return (IP_FW_DENY);
                              break;
                        }
                        args->f_id.frag_id6 =
                            ntohl(((struct ip6_frag *)ulp)->ip6f_ident);
                        ulp = NULL;
                        break;

                  case IPPROTO_DSTOPTS:   /* RFC 2460 */
                        PULLUP_TO(hlen, ulp, struct ip6_hbh);
                        ext_hd |= EXT_DSTOPTS;
                        hlen += (((struct ip6_hbh *)ulp)->ip6h_len + 1) << 3;
                        proto = ((struct ip6_hbh *)ulp)->ip6h_nxt;
                        ulp = NULL;
                        break;

                  case IPPROTO_AH:  /* RFC 2402 */
                        PULLUP_TO(hlen, ulp, struct ip6_ext);
                        ext_hd |= EXT_AH;
                        hlen += (((struct ip6_ext *)ulp)->ip6e_len + 2) << 2;
                        proto = ((struct ip6_ext *)ulp)->ip6e_nxt;
                        ulp = NULL;
                        break;

                  case IPPROTO_ESP: /* RFC 2406 */
                        PULLUP_TO(hlen, ulp, uint32_t);     /* SPI, Seq# */
                        /* Anything past Seq# is variable length and
                         * data past this ext. header is encrypted. */
                        ext_hd |= EXT_ESP;
                        break;

                  case IPPROTO_NONE:      /* RFC 2460 */
                        PULLUP_TO(hlen, ulp, struct ip6_ext);
                        /* Packet ends here. if ip6e_len!=0 octets
                         * must be ignored. */
                        break;

                  case IPPROTO_OSPFIGP:
                        /* XXX OSPF header check? */
                        PULLUP_TO(hlen, ulp, struct ip6_ext);
                        break;

                  case IPPROTO_PIM:
                        /* XXX PIM header check? */
                        PULLUP_TO(hlen, ulp, struct pim);
                        break;

                  case IPPROTO_CARP:
                        PULLUP_TO(hlen, ulp, struct carp_header);
                        if (((struct carp_header *)ulp)->carp_version !=
                            CARP_VERSION) 
                              return (IP_FW_DENY);
                        if (((struct carp_header *)ulp)->carp_type !=
                            CARP_ADVERTISEMENT) 
                              return (IP_FW_DENY);
                        break;

                  case IPPROTO_IPV6:      /* RFC 2893 */
                        PULLUP_TO(hlen, ulp, struct ip6_hdr);
                        break;

                  case IPPROTO_IPV4:      /* RFC 2893 */
                        PULLUP_TO(hlen, ulp, struct ip);
                        break;

                  default:
                        printf("IPFW2: IPV6 - Unknown Extension "
                            "Header(%d), ext_hd=%x\n", proto, ext_hd);
                        if (fw_deny_unknown_exthdrs)
                            return (IP_FW_DENY);
                        PULLUP_TO(hlen, ulp, struct ip6_ext);
                        break;
                  } /*switch */
            }
            ip = mtod(m, struct ip *);
            ip6 = (struct ip6_hdr *)ip;
            args->f_id.src_ip6 = ip6->ip6_src;
            args->f_id.dst_ip6 = ip6->ip6_dst;
            args->f_id.src_ip = 0;
            args->f_id.dst_ip = 0;
            args->f_id.flow_id6 = ntohl(ip6->ip6_flow);
      } else if (pktlen >= sizeof(struct ip) &&
          (args->eh == NULL || etype == ETHERTYPE_IP) && ip->ip_v == 4) {
            is_ipv4 = 1;
            hlen = ip->ip_hl << 2;
            args->f_id.addr_type = 4;

            /*
             * Collect parameters into local variables for faster matching.
             */
            proto = ip->ip_p;
            src_ip = ip->ip_src;
            dst_ip = ip->ip_dst;
            if (args->eh != NULL) { /* layer 2 packets are as on the wire */
                  offset = ntohs(ip->ip_off) & IP_OFFMASK;
                  ip_len = ntohs(ip->ip_len);
            } else {
                  offset = ip->ip_off & IP_OFFMASK;
                  ip_len = ip->ip_len;
            }
            pktlen = ip_len < pktlen ? ip_len : pktlen;

            if (offset == 0) {
                  switch (proto) {
                  case IPPROTO_TCP:
                        PULLUP_TO(hlen, ulp, struct tcphdr);
                        dst_port = TCP(ulp)->th_dport;
                        src_port = TCP(ulp)->th_sport;
                        args->f_id.flags = TCP(ulp)->th_flags;
                        break;

                  case IPPROTO_UDP:
                        PULLUP_TO(hlen, ulp, struct udphdr);
                        dst_port = UDP(ulp)->uh_dport;
                        src_port = UDP(ulp)->uh_sport;
                        break;

                  case IPPROTO_ICMP:
                        PULLUP_TO(hlen, ulp, struct icmphdr);
                        args->f_id.flags = ICMP(ulp)->icmp_type;
                        break;

                  default:
                        break;
                  }
            }

            ip = mtod(m, struct ip *);
            args->f_id.src_ip = ntohl(src_ip.s_addr);
            args->f_id.dst_ip = ntohl(dst_ip.s_addr);
      }
#undef PULLUP_TO
      if (proto) { /* we may have port numbers, store them */
            args->f_id.proto = proto;
            args->f_id.src_port = src_port = ntohs(src_port);
            args->f_id.dst_port = dst_port = ntohs(dst_port);
      }

      IPFW_RLOCK(chain);
      mtag = m_tag_find(m, PACKET_TAG_DIVERT, NULL);
      if (args->rule) {
            /*
             * Packet has already been tagged. Look for the next rule
             * to restart processing.
             *
             * If fw_one_pass != 0 then just accept it.
             * XXX should not happen here, but optimized out in
             * the caller.
             */
            if (fw_one_pass) {
                  IPFW_RUNLOCK(chain);
                  return (IP_FW_PASS);
            }

            f = args->rule->next_rule;
            if (f == NULL)
                  f = lookup_next_rule(args->rule);
      } else {
            /*
             * Find the starting rule. It can be either the first
             * one, or the one after divert_rule if asked so.
             */
            int skipto = mtag ? divert_cookie(mtag) : 0;

            f = chain->rules;
            if (args->eh == NULL && skipto != 0) {
                  if (skipto >= IPFW_DEFAULT_RULE) {
                        IPFW_RUNLOCK(chain);
                        return (IP_FW_DENY); /* invalid */
                  }
                  while (f && f->rulenum <= skipto)
                        f = f->next;
                  if (f == NULL) {  /* drop packet */
                        IPFW_RUNLOCK(chain);
                        return (IP_FW_DENY);
                  }
            }
      }
      /* reset divert rule to avoid confusion later */
      if (mtag) {
            divinput_flags = divert_info(mtag) &
                (IP_FW_DIVERT_OUTPUT_FLAG | IP_FW_DIVERT_LOOPBACK_FLAG);
            m_tag_delete(m, mtag);
      }

      /*
       * Now scan the rules, and parse microinstructions for each rule.
       */
      for (; f; f = f->next) {
            ipfw_insn *cmd;
            uint32_t tablearg = 0;
            int l, cmdlen, skip_or; /* skip rest of OR block */

again:
            if (set_disable & (1 << f->set) )
                  continue;

            skip_or = 0;
            for (l = f->cmd_len, cmd = f->cmd ; l > 0 ;
                l -= cmdlen, cmd += cmdlen) {
                  int match;

                  /*
                   * check_body is a jump target used when we find a
                   * CHECK_STATE, and need to jump to the body of
                   * the target rule.
                   */

check_body:
                  cmdlen = F_LEN(cmd);
                  /*
                   * An OR block (insn_1 || .. || insn_n) has the
                   * F_OR bit set in all but the last instruction.
                   * The first match will set "skip_or", and cause
                   * the following instructions to be skipped until
                   * past the one with the F_OR bit clear.
                   */
                  if (skip_or) {          /* skip this instruction */
                        if ((cmd->len & F_OR) == 0)
                              skip_or = 0;      /* next one is good */
                        continue;
                  }
                  match = 0; /* set to 1 if we succeed */

                  switch (cmd->opcode) {
                  /*
                   * The first set of opcodes compares the packet's
                   * fields with some pattern, setting 'match' if a
                   * match is found. At the end of the loop there is
                   * logic to deal with F_NOT and F_OR flags associated
                   * with the opcode.
                   */
                  case O_NOP:
                        match = 1;
                        break;

                  case O_FORWARD_MAC:
                        printf("ipfw: opcode %d unimplemented\n",
                            cmd->opcode);
                        break;

                  case O_GID:
                  case O_UID:
                  case O_JAIL:
                        /*
                         * We only check offset == 0 && proto != 0,
                         * as this ensures that we have a
                         * packet with the ports info.
                         */
                        if (offset!=0)
                              break;
                        if (is_ipv6) /* XXX to be fixed later */
                              break;
                        if (proto == IPPROTO_TCP ||
                            proto == IPPROTO_UDP)
                              match = check_uidgid(
                                        (ipfw_insn_u32 *)cmd,
                                        proto, oif,
                                        dst_ip, dst_port,
                                        src_ip, src_port, &fw_ugid_cache,
                                        &ugid_lookup, args->inp);
                        break;

                  case O_RECV:
                        match = iface_match(m->m_pkthdr.rcvif,
                            (ipfw_insn_if *)cmd);
                        break;

                  case O_XMIT:
                        match = iface_match(oif, (ipfw_insn_if *)cmd);
                        break;

                  case O_VIA:
                        match = iface_match(oif ? oif :
                            m->m_pkthdr.rcvif, (ipfw_insn_if *)cmd);
                        break;

                  case O_MACADDR2:
                        if (args->eh != NULL) { /* have MAC header */
                              u_int32_t *want = (u_int32_t *)
                                    ((ipfw_insn_mac *)cmd)->addr;
                              u_int32_t *mask = (u_int32_t *)
                                    ((ipfw_insn_mac *)cmd)->mask;
                              u_int32_t *hdr = (u_int32_t *)args->eh;

                              match =
                                  ( want[0] == (hdr[0] & mask[0]) &&
                                    want[1] == (hdr[1] & mask[1]) &&
                                    want[2] == (hdr[2] & mask[2]) );
                        }
                        break;

                  case O_MAC_TYPE:
                        if (args->eh != NULL) {
                              u_int16_t *p =
                                  ((ipfw_insn_u16 *)cmd)->ports;
                              int i;

                              for (i = cmdlen - 1; !match && i>0;
                                  i--, p += 2)
                                    match = (etype >= p[0] &&
                                        etype <= p[1]);
                        }
                        break;

                  case O_FRAG:
                        match = (offset != 0);
                        break;

                  case O_IN:  /* "out" is "not in" */
                        match = (oif == NULL);
                        break;

                  case O_LAYER2:
                        match = (args->eh != NULL);
                        break;

                  case O_DIVERTED:
                        match = (cmd->arg1 & 1 && divinput_flags &
                            IP_FW_DIVERT_LOOPBACK_FLAG) ||
                              (cmd->arg1 & 2 && divinput_flags &
                            IP_FW_DIVERT_OUTPUT_FLAG);
                        break;

                  case O_PROTO:
                        /*
                         * We do not allow an arg of 0 so the
                         * check of "proto" only suffices.
                         */
                        match = (proto == cmd->arg1);
                        break;

                  case O_IP_SRC:
                        match = is_ipv4 &&
                            (((ipfw_insn_ip *)cmd)->addr.s_addr ==
                            src_ip.s_addr);
                        break;

                  case O_IP_SRC_LOOKUP:
                  case O_IP_DST_LOOKUP:
                        if (is_ipv4) {
                            uint32_t a =
                              (cmd->opcode == O_IP_DST_LOOKUP) ?
                                  dst_ip.s_addr : src_ip.s_addr;
                            uint32_t v;

                            match = lookup_table(chain, cmd->arg1, a,
                              &v);
                            if (!match)
                              break;
                            if (cmdlen == F_INSN_SIZE(ipfw_insn_u32))
                              match =
                                  ((ipfw_insn_u32 *)cmd)->d[0] == v;
                            else
                              tablearg = v;
                        }
                        break;

                  case O_IP_SRC_MASK:
                  case O_IP_DST_MASK:
                        if (is_ipv4) {
                            uint32_t a =
                              (cmd->opcode == O_IP_DST_MASK) ?
                                  dst_ip.s_addr : src_ip.s_addr;
                            uint32_t *p = ((ipfw_insn_u32 *)cmd)->d;
                            int i = cmdlen-1;

                            for (; !match && i>0; i-= 2, p+= 2)
                              match = (p[0] == (a & p[1]));
                        }
                        break;

                  case O_IP_SRC_ME:
                        if (is_ipv4) {
                              struct ifnet *tif;

                              INADDR_TO_IFP(src_ip, tif);
                              match = (tif != NULL);
                        }
                        break;

                  case O_IP_DST_SET:
                  case O_IP_SRC_SET:
                        if (is_ipv4) {
                              u_int32_t *d = (u_int32_t *)(cmd+1);
                              u_int32_t addr =
                                  cmd->opcode == O_IP_DST_SET ?
                                    args->f_id.dst_ip :
                                    args->f_id.src_ip;

                                  if (addr < d[0])
                                        break;
                                  addr -= d[0]; /* subtract base */
                                  match = (addr < cmd->arg1) &&
                                    ( d[ 1 + (addr>>5)] &
                                      (1<<(addr & 0x1f)) );
                        }
                        break;

                  case O_IP_DST:
                        match = is_ipv4 &&
                            (((ipfw_insn_ip *)cmd)->addr.s_addr ==
                            dst_ip.s_addr);
                        break;

                  case O_IP_DST_ME:
                        if (is_ipv4) {
                              struct ifnet *tif;

                              INADDR_TO_IFP(dst_ip, tif);
                              match = (tif != NULL);
                        }
                        break;

                  case O_IP_SRCPORT:
                  case O_IP_DSTPORT:
                        /*
                         * offset == 0 && proto != 0 is enough
                         * to guarantee that we have a
                         * packet with port info.
                         */
                        if ((proto==IPPROTO_UDP || proto==IPPROTO_TCP)
                            && offset == 0) {
                              u_int16_t x =
                                  (cmd->opcode == O_IP_SRCPORT) ?
                                    src_port : dst_port ;
                              u_int16_t *p =
                                  ((ipfw_insn_u16 *)cmd)->ports;
                              int i;

                              for (i = cmdlen - 1; !match && i>0;
                                  i--, p += 2)
                                    match = (x>=p[0] && x<=p[1]);
                        }
                        break;

                  case O_ICMPTYPE:
                        match = (offset == 0 && proto==IPPROTO_ICMP &&
                            icmptype_match(ICMP(ulp), (ipfw_insn_u32 *)cmd) );
                        break;

#ifdef INET6
                  case O_ICMP6TYPE:
                        match = is_ipv6 && offset == 0 &&
                            proto==IPPROTO_ICMPV6 &&
                            icmp6type_match(
                              ICMP6(ulp)->icmp6_type,
                              (ipfw_insn_u32 *)cmd);
                        break;
#endif /* INET6 */

                  case O_IPOPT:
                        match = (is_ipv4 &&
                            ipopts_match(ip, cmd) );
                        break;

                  case O_IPVER:
                        match = (is_ipv4 &&
                            cmd->arg1 == ip->ip_v);
                        break;

                  case O_IPID:
                  case O_IPLEN:
                  case O_IPTTL:
                        if (is_ipv4) {    /* only for IP packets */
                            uint16_t x;
                            uint16_t *p;
                            int i;

                            if (cmd->opcode == O_IPLEN)
                              x = ip_len;
                            else if (cmd->opcode == O_IPTTL)
                              x = ip->ip_ttl;
                            else /* must be IPID */
                              x = ntohs(ip->ip_id);
                            if (cmdlen == 1) {
                              match = (cmd->arg1 == x);
                              break;
                            }
                            /* otherwise we have ranges */
                            p = ((ipfw_insn_u16 *)cmd)->ports;
                            i = cmdlen - 1;
                            for (; !match && i>0; i--, p += 2)
                              match = (x >= p[0] && x <= p[1]);
                        }
                        break;

                  case O_IPPRECEDENCE:
                        match = (is_ipv4 &&
                            (cmd->arg1 == (ip->ip_tos & 0xe0)) );
                        break;

                  case O_IPTOS:
                        match = (is_ipv4 &&
                            flags_match(cmd, ip->ip_tos));
                        break;

                  case O_TCPDATALEN:
                        if (proto == IPPROTO_TCP && offset == 0) {
                            struct tcphdr *tcp;
                            uint16_t x;
                            uint16_t *p;
                            int i;

                            tcp = TCP(ulp);
                            x = ip_len -
                              ((ip->ip_hl + tcp->th_off) << 2);
                            if (cmdlen == 1) {
                              match = (cmd->arg1 == x);
                              break;
                            }
                            /* otherwise we have ranges */
                            p = ((ipfw_insn_u16 *)cmd)->ports;
                            i = cmdlen - 1;
                            for (; !match && i>0; i--, p += 2)
                              match = (x >= p[0] && x <= p[1]);
                        }
                        break;

                  case O_TCPFLAGS:
                        match = (proto == IPPROTO_TCP && offset == 0 &&
                            flags_match(cmd, TCP(ulp)->th_flags));
                        break;

                  case O_TCPOPTS:
                        match = (proto == IPPROTO_TCP && offset == 0 &&
                            tcpopts_match(TCP(ulp), cmd));
                        break;

                  case O_TCPSEQ:
                        match = (proto == IPPROTO_TCP && offset == 0 &&
                            ((ipfw_insn_u32 *)cmd)->d[0] ==
                              TCP(ulp)->th_seq);
                        break;

                  case O_TCPACK:
                        match = (proto == IPPROTO_TCP && offset == 0 &&
                            ((ipfw_insn_u32 *)cmd)->d[0] ==
                              TCP(ulp)->th_ack);
                        break;

                  case O_TCPWIN:
                        match = (proto == IPPROTO_TCP && offset == 0 &&
                            cmd->arg1 == TCP(ulp)->th_win);
                        break;

                  case O_ESTAB:
                        /* reject packets which have SYN only */
                        /* XXX should i also check for TH_ACK ? */
                        match = (proto == IPPROTO_TCP && offset == 0 &&
                            (TCP(ulp)->th_flags &
                             (TH_RST | TH_ACK | TH_SYN)) != TH_SYN);
                        break;

                  case O_ALTQ: {
                        struct altq_tag *at;
                        ipfw_insn_altq *altq = (ipfw_insn_altq *)cmd;

                        match = 1;
                        mtag = m_tag_find(m, PACKET_TAG_PF_QID, NULL);
                        if (mtag != NULL)
                              break;
                        mtag = m_tag_get(PACKET_TAG_PF_QID,
                                    sizeof(struct altq_tag),
                                    M_NOWAIT);
                        if (mtag == NULL) {
                              /*
                               * Let the packet fall back to the
                               * default ALTQ.
                               */
                              break;
                        }
                        at = (struct altq_tag *)(mtag+1);
                        at->qid = altq->qid;
                        if (is_ipv4)
                              at->af = AF_INET;
                        else
                              at->af = AF_LINK;
                        at->hdr = ip;
                        m_tag_prepend(m, mtag);
                        break;
                  }

                  case O_LOG:
                        if (fw_verbose)
                              ipfw_log(f, hlen, args, m,
                                  oif, offset, tablearg, ip);
                        match = 1;
                        break;

                  case O_PROB:
                        match = (random()<((ipfw_insn_u32 *)cmd)->d[0]);
                        break;

                  case O_VERREVPATH:
                        /* Outgoing packets automatically pass/match */
                        match = ((oif != NULL) ||
                            (m->m_pkthdr.rcvif == NULL) ||
                            (
#ifdef INET6
                            is_ipv6 ?
                              verify_path6(&(args->f_id.src_ip6),
                                  m->m_pkthdr.rcvif) :
#endif
                            verify_path(src_ip, m->m_pkthdr.rcvif)));
                        break;

                  case O_VERSRCREACH:
                        /* Outgoing packets automatically pass/match */
                        match = (hlen > 0 && ((oif != NULL) ||
#ifdef INET6
                            is_ipv6 ?
                                verify_path6(&(args->f_id.src_ip6),
                                    NULL) :
#endif
                            verify_path(src_ip, NULL)));
                        break;

                  case O_ANTISPOOF:
                        /* Outgoing packets automatically pass/match */
                        if (oif == NULL && hlen > 0 &&
                            (  (is_ipv4 && in_localaddr(src_ip))
#ifdef INET6
                            || (is_ipv6 &&
                                in6_localaddr(&(args->f_id.src_ip6)))
#endif
                            ))
                              match =
#ifdef INET6
                                  is_ipv6 ? verify_path6(
                                      &(args->f_id.src_ip6),
                                      m->m_pkthdr.rcvif) :
#endif
                                  verify_path(src_ip,
                                      m->m_pkthdr.rcvif);
                        else
                              match = 1;
                        break;

                  case O_IPSEC:
#ifdef FAST_IPSEC
                        match = (m_tag_find(m,
                            PACKET_TAG_IPSEC_IN_DONE, NULL) != NULL);
#endif
#ifdef IPSEC
                        match = (ipsec_getnhist(m) != 0);
#endif
                        /* otherwise no match */
                        break;

#ifdef INET6
                  case O_IP6_SRC:
                        match = is_ipv6 &&
                            IN6_ARE_ADDR_EQUAL(&args->f_id.src_ip6,
                            &((ipfw_insn_ip6 *)cmd)->addr6);
                        break;

                  case O_IP6_DST:
                        match = is_ipv6 &&
                        IN6_ARE_ADDR_EQUAL(&args->f_id.dst_ip6,
                            &((ipfw_insn_ip6 *)cmd)->addr6);
                        break;
                  case O_IP6_SRC_MASK:
                  case O_IP6_DST_MASK:
                        if (is_ipv6) {
                              int i = cmdlen - 1;
                              struct in6_addr p;
                              struct in6_addr *d =
                                  &((ipfw_insn_ip6 *)cmd)->addr6;

                              for (; !match && i > 0; d += 2,
                                  i -= F_INSN_SIZE(struct in6_addr)
                                  * 2) {
                                    p = (cmd->opcode ==
                                        O_IP6_SRC_MASK) ?
                                        args->f_id.src_ip6:
                                        args->f_id.dst_ip6;
                                    APPLY_MASK(&p, &d[1]);
                                    match =
                                        IN6_ARE_ADDR_EQUAL(&d[0],
                                        &p);
                              }
                        }
                        break;

                  case O_IP6_SRC_ME:
                        match= is_ipv6 && search_ip6_addr_net(&args->f_id.src_ip6);
                        break;

                  case O_IP6_DST_ME:
                        match= is_ipv6 && search_ip6_addr_net(&args->f_id.dst_ip6);
                        break;

                  case O_FLOW6ID:
                        match = is_ipv6 &&
                            flow6id_match(args->f_id.flow_id6,
                            (ipfw_insn_u32 *) cmd);
                        break;

                  case O_EXT_HDR:
                        match = is_ipv6 &&
                            (ext_hd & ((ipfw_insn *) cmd)->arg1);
                        break;

                  case O_IP6:
                        match = is_ipv6;
                        break;
#endif

                  case O_IP4:
                        match = is_ipv4;
                        break;

                  case O_TAG: {
                        uint32_t tag = (cmd->arg1 == IP_FW_TABLEARG) ?
                            tablearg : cmd->arg1;

                        /* Packet is already tagged with this tag? */
                        mtag = m_tag_locate(m, MTAG_IPFW, tag, NULL);

                        /* We have `untag' action when F_NOT flag is
                         * present. And we must remove this mtag from
                         * mbuf and reset `match' to zero (`match' will
                         * be inversed later).
                         * Otherwise we should allocate new mtag and
                         * push it into mbuf.
                         */
                        if (cmd->len & F_NOT) { /* `untag' action */
                              if (mtag != NULL)
                                    m_tag_delete(m, mtag);
                        } else if (mtag == NULL) {
                              if ((mtag = m_tag_alloc(MTAG_IPFW,
                                  tag, 0, M_NOWAIT)) != NULL)
                                    m_tag_prepend(m, mtag);
                        }
                        match = (cmd->len & F_NOT) ? 0: 1;
                        break;
                  }

                  case O_TAGGED: {
                        uint32_t tag = (cmd->arg1 == IP_FW_TABLEARG) ?
                            tablearg : cmd->arg1;

                        if (cmdlen == 1) {
                              match = m_tag_locate(m, MTAG_IPFW,
                                  tag, NULL) != NULL;
                              break;
                        }

                        /* we have ranges */
                        for (mtag = m_tag_first(m);
                            mtag != NULL && !match;
                            mtag = m_tag_next(m, mtag)) {
                              uint16_t *p;
                              int i;

                              if (mtag->m_tag_cookie != MTAG_IPFW)
                                    continue;

                              p = ((ipfw_insn_u16 *)cmd)->ports;
                              i = cmdlen - 1;
                              for(; !match && i > 0; i--, p += 2)
                                    match =
                                        mtag->m_tag_id >= p[0] &&
                                        mtag->m_tag_id <= p[1];
                        }
                        break;
                  }
                        
                  /*
                   * The second set of opcodes represents 'actions',
                   * i.e. the terminal part of a rule once the packet
                   * matches all previous patterns.
                   * Typically there is only one action for each rule,
                   * and the opcode is stored at the end of the rule
                   * (but there are exceptions -- see below).
                   *
                   * In general, here we set retval and terminate the
                   * outer loop (would be a 'break 3' in some language,
                   * but we need to do a 'goto done').
                   *
                   * Exceptions:
                   * O_COUNT and O_SKIPTO actions:
                   *   instead of terminating, we jump to the next rule
                   *   ('goto next_rule', equivalent to a 'break 2'),
                   *   or to the SKIPTO target ('goto again' after
                   *   having set f, cmd and l), respectively.
                   *
                   * O_TAG, O_LOG and O_ALTQ action parameters:
                   *   perform some action and set match = 1;
                   *
                   * O_LIMIT and O_KEEP_STATE: these opcodes are
                   *   not real 'actions', and are stored right
                   *   before the 'action' part of the rule.
                   *   These opcodes try to install an entry in the
                   *   state tables; if successful, we continue with
                   *   the next opcode (match=1; break;), otherwise
                   *   the packet *   must be dropped
                   *   ('goto done' after setting retval);
                   *
                   * O_PROBE_STATE and O_CHECK_STATE: these opcodes
                   *   cause a lookup of the state table, and a jump
                   *   to the 'action' part of the parent rule
                   *   ('goto check_body') if an entry is found, or
                   *   (CHECK_STATE only) a jump to the next rule if
                   *   the entry is not found ('goto next_rule').
                   *   The result of the lookup is cached to make
                   *   further instances of these opcodes are
                   *   effectively NOPs.
                   */
                  case O_LIMIT:
                  case O_KEEP_STATE:
                        if (install_state(f,
                            (ipfw_insn_limit *)cmd, args, tablearg)) {
                              retval = IP_FW_DENY;
                              goto done; /* error/limit violation */
                        }
                        match = 1;
                        break;

                  case O_PROBE_STATE:
                  case O_CHECK_STATE:
                        /*
                         * dynamic rules are checked at the first
                         * keep-state or check-state occurrence,
                         * with the result being stored in dyn_dir.
                         * The compiler introduces a PROBE_STATE
                         * instruction for us when we have a
                         * KEEP_STATE (because PROBE_STATE needs
                         * to be run first).
                         */
                        if (dyn_dir == MATCH_UNKNOWN &&
                            (q = lookup_dyn_rule(&args->f_id,
                             &dyn_dir, proto == IPPROTO_TCP ?
                              TCP(ulp) : NULL))
                              != NULL) {
                              /*
                               * Found dynamic entry, update stats
                               * and jump to the 'action' part of
                               * the parent rule.
                               */
                              q->pcnt++;
                              q->bcnt += pktlen;
                              f = q->rule;
                              cmd = ACTION_PTR(f);
                              l = f->cmd_len - f->act_ofs;
                              IPFW_DYN_UNLOCK();
                              goto check_body;
                        }
                        /*
                         * Dynamic entry not found. If CHECK_STATE,
                         * skip to next rule, if PROBE_STATE just
                         * ignore and continue with next opcode.
                         */
                        if (cmd->opcode == O_CHECK_STATE)
                              goto next_rule;
                        match = 1;
                        break;

                  case O_ACCEPT:
                        retval = 0; /* accept */
                        goto done;

                  case O_PIPE:
                  case O_QUEUE:
                        args->rule = f; /* report matching rule */
                        if (cmd->arg1 == IP_FW_TABLEARG)
                              args->cookie = tablearg;
                        else
                              args->cookie = cmd->arg1;
                        retval = IP_FW_DUMMYNET;
                        goto done;

                  case O_DIVERT:
                  case O_TEE: {
                        struct divert_tag *dt;

                        if (args->eh) /* not on layer 2 */
                              break;
                        mtag = m_tag_get(PACKET_TAG_DIVERT,
                                    sizeof(struct divert_tag),
                                    M_NOWAIT);
                        if (mtag == NULL) {
                              /* XXX statistic */
                              /* drop packet */
                              IPFW_RUNLOCK(chain);
                              return (IP_FW_DENY);
                        }
                        dt = (struct divert_tag *)(mtag+1);
                        dt->cookie = f->rulenum;
                        if (cmd->arg1 == IP_FW_TABLEARG)
                              dt->info = tablearg;
                        else
                              dt->info = cmd->arg1;
                        m_tag_prepend(m, mtag);
                        retval = (cmd->opcode == O_DIVERT) ?
                            IP_FW_DIVERT : IP_FW_TEE;
                        goto done;
                  }

                  case O_COUNT:
                  case O_SKIPTO:
                        f->pcnt++;  /* update stats */
                        f->bcnt += pktlen;
                        f->timestamp = time_uptime;
                        if (cmd->opcode == O_COUNT)
                              goto next_rule;
                        /* handle skipto */
                        if (f->next_rule == NULL)
                              lookup_next_rule(f);
                        f = f->next_rule;
                        goto again;

                  case O_REJECT:
                        /*
                         * Drop the packet and send a reject notice
                         * if the packet is not ICMP (or is an ICMP
                         * query), and it is not multicast/broadcast.
                         */
                        if (hlen > 0 && is_ipv4 && offset == 0 &&
                            (proto != IPPROTO_ICMP ||
                             is_icmp_query(ICMP(ulp))) &&
                            !(m->m_flags & (M_BCAST|M_MCAST)) &&
                            !IN_MULTICAST(ntohl(dst_ip.s_addr))) {
                              send_reject(args, cmd->arg1,
                                  offset,ip_len, ip);
                              m = args->m;
                        }
                        /* FALLTHROUGH */
#ifdef INET6
                  case O_UNREACH6:
                        if (hlen > 0 && is_ipv6 &&
                            (proto != IPPROTO_ICMPV6 ||
                             (is_icmp6_query(args->f_id.flags) == 1)) &&
                            !(m->m_flags & (M_BCAST|M_MCAST)) &&
                            !IN6_IS_ADDR_MULTICAST(&args->f_id.dst_ip6)) {
                              send_reject6(args, cmd->arg1,
                                  offset, hlen, (struct ip6_hdr *)ip);
                              m = args->m;
                        }
                        /* FALLTHROUGH */
#endif
                  case O_DENY:
                        retval = IP_FW_DENY;
                        goto done;

                  case O_FORWARD_IP: {
                        struct sockaddr_in *sa;
                        sa = &(((ipfw_insn_sa *)cmd)->sa);
                        if (args->eh)     /* not valid on layer2 pkts */
                              break;
                        if (!q || dyn_dir == MATCH_FORWARD) {
                              if (sa->sin_addr.s_addr == INADDR_ANY) {
                                    bcopy(sa, &args->hopstore,
                                          sizeof(*sa));
                                    args->hopstore.sin_addr.s_addr =
                                        htonl(tablearg);
                                    args->next_hop =
                                        &args->hopstore;
                              } else {
                                    args->next_hop = sa;
                              }
                        }
                        retval = IP_FW_PASS;
                      }
                      goto done;

                  case O_NETGRAPH:
                  case O_NGTEE:
                        args->rule = f;   /* report matching rule */
                        if (cmd->arg1 == IP_FW_TABLEARG)
                              args->cookie = tablearg;
                        else
                              args->cookie = cmd->arg1;
                        retval = (cmd->opcode == O_NETGRAPH) ?
                            IP_FW_NETGRAPH : IP_FW_NGTEE;
                        goto done;

                  default:
                        panic("-- unknown opcode %d\n", cmd->opcode);
                  } /* end of switch() on opcodes */

                  if (cmd->len & F_NOT)
                        match = !match;

                  if (match) {
                        if (cmd->len & F_OR)
                              skip_or = 1;
                  } else {
                        if (!(cmd->len & F_OR)) /* not an OR block, */
                              break;            /* try next rule    */
                  }

            }     /* end of inner for, scan opcodes */

next_rule:;       /* try next rule        */

      }           /* end of outer for, scan rules */
      printf("ipfw: ouch!, skip past end of rules, denying packet\n");
      IPFW_RUNLOCK(chain);
      return (IP_FW_DENY);

done:
      /* Update statistics */
      f->pcnt++;
      f->bcnt += pktlen;
      f->timestamp = time_uptime;
      IPFW_RUNLOCK(chain);
      return (retval);

pullup_failed:
      if (fw_verbose)
            printf("ipfw: pullup failed\n");
      return (IP_FW_DENY);
}

/*
 * When a rule is added/deleted, clear the next_rule pointers in all rules.
 * These will be reconstructed on the fly as packets are matched.
 */
static void
flush_rule_ptrs(struct ip_fw_chain *chain)
{
      struct ip_fw *rule;

      IPFW_WLOCK_ASSERT(chain);

      for (rule = chain->rules; rule; rule = rule->next)
            rule->next_rule = NULL;
}

/*
 * Add a new rule to the list. Copy the rule into a malloc'ed area, then
 * possibly create a rule number and add the rule to the list.
 * Update the rule_number in the input struct so the caller knows it as well.
 */
static int
add_rule(struct ip_fw_chain *chain, struct ip_fw *input_rule)
{
      struct ip_fw *rule, *f, *prev;
      int l = RULESIZE(input_rule);

      if (chain->rules == NULL && input_rule->rulenum != IPFW_DEFAULT_RULE)
            return (EINVAL);

      rule = malloc(l, M_IPFW, M_NOWAIT | M_ZERO);
      if (rule == NULL)
            return (ENOSPC);

      bcopy(input_rule, rule, l);

      rule->next = NULL;
      rule->next_rule = NULL;

      rule->pcnt = 0;
      rule->bcnt = 0;
      rule->timestamp = 0;

      IPFW_WLOCK(chain);

      if (chain->rules == NULL) {   /* default rule */
            chain->rules = rule;
            goto done;
        }

      /*
       * If rulenum is 0, find highest numbered rule before the
       * default rule, and add autoinc_step
       */
      if (autoinc_step < 1)
            autoinc_step = 1;
      else if (autoinc_step > 1000)
            autoinc_step = 1000;
      if (rule->rulenum == 0) {
            /*
             * locate the highest numbered rule before default
             */
            for (f = chain->rules; f; f = f->next) {
                  if (f->rulenum == IPFW_DEFAULT_RULE)
                        break;
                  rule->rulenum = f->rulenum;
            }
            if (rule->rulenum < IPFW_DEFAULT_RULE - autoinc_step)
                  rule->rulenum += autoinc_step;
            input_rule->rulenum = rule->rulenum;
      }

      /*
       * Now insert the new rule in the right place in the sorted list.
       */
      for (prev = NULL, f = chain->rules; f; prev = f, f = f->next) {
            if (f->rulenum > rule->rulenum) { /* found the location */
                  if (prev) {
                        rule->next = f;
                        prev->next = rule;
                  } else { /* head insert */
                        rule->next = chain->rules;
                        chain->rules = rule;
                  }
                  break;
            }
      }
      flush_rule_ptrs(chain);
done:
      static_count++;
      static_len += l;
      IPFW_WUNLOCK(chain);
      DEB(printf("ipfw: installed rule %d, static count now %d\n",
            rule->rulenum, static_count);)
      return (0);
}

/**
 * Remove a static rule (including derived * dynamic rules)
 * and place it on the ``reap list'' for later reclamation.
 * The caller is in charge of clearing rule pointers to avoid
 * dangling pointers.
 * @return a pointer to the next entry.
 * Arguments are not checked, so they better be correct.
 */
static struct ip_fw *
remove_rule(struct ip_fw_chain *chain, struct ip_fw *rule, struct ip_fw *prev)
{
      struct ip_fw *n;
      int l = RULESIZE(rule);

      IPFW_WLOCK_ASSERT(chain);

      n = rule->next;
      IPFW_DYN_LOCK();
      remove_dyn_rule(rule, NULL /* force removal */);
      IPFW_DYN_UNLOCK();
      if (prev == NULL)
            chain->rules = n;
      else
            prev->next = n;
      static_count--;
      static_len -= l;

      rule->next = chain->reap;
      chain->reap = rule;

      return n;
}

/**
 * Reclaim storage associated with a list of rules.  This is
 * typically the list created using remove_rule.
 */
static void
reap_rules(struct ip_fw *head)
{
      struct ip_fw *rule;

      while ((rule = head) != NULL) {
            head = head->next;
            if (DUMMYNET_LOADED)
                  ip_dn_ruledel_ptr(rule);
            free(rule, M_IPFW);
      }
}

/*
 * Remove all rules from a chain (except rules in set RESVD_SET
 * unless kill_default = 1).  The caller is responsible for
 * reclaiming storage for the rules left in chain->reap.
 */
static void
free_chain(struct ip_fw_chain *chain, int kill_default)
{
      struct ip_fw *prev, *rule;

      IPFW_WLOCK_ASSERT(chain);

      flush_rule_ptrs(chain); /* more efficient to do outside the loop */
      for (prev = NULL, rule = chain->rules; rule ; )
            if (kill_default || rule->set != RESVD_SET)
                  rule = remove_rule(chain, rule, prev);
            else {
                  prev = rule;
                  rule = rule->next;
            }
}

/**
 * Remove all rules with given number, and also do set manipulation.
 * Assumes chain != NULL && *chain != NULL.
 *
 * The argument is an u_int32_t. The low 16 bit are the rule or set number,
 * the next 8 bits are the new set, the top 8 bits are the command:
 *
 *    0     delete rules with given number
 *    1     delete rules with given set number
 *    2     move rules with given number to new set
 *    3     move rules with given set number to new set
 *    4     swap sets with given numbers
 */
static int
del_entry(struct ip_fw_chain *chain, u_int32_t arg)
{
      struct ip_fw *prev = NULL, *rule;
      u_int16_t rulenum;      /* rule or old_set */
      u_int8_t cmd, new_set;

      rulenum = arg & 0xffff;
      cmd = (arg >> 24) & 0xff;
      new_set = (arg >> 16) & 0xff;

      if (cmd > 4)
            return EINVAL;
      if (new_set > RESVD_SET)
            return EINVAL;
      if (cmd == 0 || cmd == 2) {
            if (rulenum >= IPFW_DEFAULT_RULE)
                  return EINVAL;
      } else {
            if (rulenum > RESVD_SET)      /* old_set */
                  return EINVAL;
      }

      IPFW_WLOCK(chain);
      rule = chain->rules;
      chain->reap = NULL;
      switch (cmd) {
      case 0:     /* delete rules with given number */
            /*
             * locate first rule to delete
             */
            for (; rule->rulenum < rulenum; prev = rule, rule = rule->next)
                  ;
            if (rule->rulenum != rulenum) {
                  IPFW_WUNLOCK(chain);
                  return EINVAL;
            }

            /*
             * flush pointers outside the loop, then delete all matching
             * rules. prev remains the same throughout the cycle.
             */
            flush_rule_ptrs(chain);
            while (rule->rulenum == rulenum)
                  rule = remove_rule(chain, rule, prev);
            break;

      case 1:     /* delete all rules with given set number */
            flush_rule_ptrs(chain);
            rule = chain->rules;
            while (rule->rulenum < IPFW_DEFAULT_RULE)
                  if (rule->set == rulenum)
                        rule = remove_rule(chain, rule, prev);
                  else {
                        prev = rule;
                        rule = rule->next;
                  }
            break;

      case 2:     /* move rules with given number to new set */
            rule = chain->rules;
            for (; rule->rulenum < IPFW_DEFAULT_RULE; rule = rule->next)
                  if (rule->rulenum == rulenum)
                        rule->set = new_set;
            break;

      case 3: /* move rules with given set number to new set */
            for (; rule->rulenum < IPFW_DEFAULT_RULE; rule = rule->next)
                  if (rule->set == rulenum)
                        rule->set = new_set;
            break;

      case 4: /* swap two sets */
            for (; rule->rulenum < IPFW_DEFAULT_RULE; rule = rule->next)
                  if (rule->set == rulenum)
                        rule->set = new_set;
                  else if (rule->set == new_set)
                        rule->set = rulenum;
            break;
      }
      /*
       * Look for rules to reclaim.  We grab the list before
       * releasing the lock then reclaim them w/o the lock to
       * avoid a LOR with dummynet.
       */
      rule = chain->reap;
      chain->reap = NULL;
      IPFW_WUNLOCK(chain);
      if (rule)
            reap_rules(rule);
      return 0;
}

/*
 * Clear counters for a specific rule.
 * The enclosing "table" is assumed locked.
 */
static void
clear_counters(struct ip_fw *rule, int log_only)
{
      ipfw_insn_log *l = (ipfw_insn_log *)ACTION_PTR(rule);

      if (log_only == 0) {
            rule->bcnt = rule->pcnt = 0;
            rule->timestamp = 0;
      }
      if (l->o.opcode == O_LOG)
            l->log_left = l->max_log;
}

/**
 * Reset some or all counters on firewall rules.
 * @arg frwl is null to clear all entries, or contains a specific
 * rule number.
 * @arg log_only is 1 if we only want to reset logs, zero otherwise.
 */
static int
zero_entry(struct ip_fw_chain *chain, int rulenum, int log_only)
{
      struct ip_fw *rule;
      char *msg;

      IPFW_WLOCK(chain);
      if (rulenum == 0) {
            norule_counter = 0;
            for (rule = chain->rules; rule; rule = rule->next)
                  clear_counters(rule, log_only);
            msg = log_only ? "ipfw: All logging counts reset.\n" :
                        "ipfw: Accounting cleared.\n";
      } else {
            int cleared = 0;
            /*
             * We can have multiple rules with the same number, so we
             * need to clear them all.
             */
            for (rule = chain->rules; rule; rule = rule->next)
                  if (rule->rulenum == rulenum) {
                        while (rule && rule->rulenum == rulenum) {
                              clear_counters(rule, log_only);
                              rule = rule->next;
                        }
                        cleared = 1;
                        break;
                  }
            if (!cleared) {   /* we did not find any matching rules */
                  IPFW_WUNLOCK(chain);
                  return (EINVAL);
            }
            msg = log_only ? "ipfw: Entry %d logging count reset.\n" :
                        "ipfw: Entry %d cleared.\n";
      }
      IPFW_WUNLOCK(chain);

      if (fw_verbose)
            log(LOG_SECURITY | LOG_NOTICE, msg, rulenum);
      return (0);
}

/*
 * Check validity of the structure before insert.
 * Fortunately rules are simple, so this mostly need to check rule sizes.
 */
static int
check_ipfw_struct(struct ip_fw *rule, int size)
{
      int l, cmdlen = 0;
      int have_action=0;
      ipfw_insn *cmd;

      if (size < sizeof(*rule)) {
            printf("ipfw: rule too short\n");
            return (EINVAL);
      }
      /* first, check for valid size */
      l = RULESIZE(rule);
      if (l != size) {
            printf("ipfw: size mismatch (have %d want %d)\n", size, l);
            return (EINVAL);
      }
      if (rule->act_ofs >= rule->cmd_len) {
            printf("ipfw: bogus action offset (%u > %u)\n",
                rule->act_ofs, rule->cmd_len - 1);
            return (EINVAL);
      }
      /*
       * Now go for the individual checks. Very simple ones, basically only
       * instruction sizes.
       */
      for (l = rule->cmd_len, cmd = rule->cmd ;
                  l > 0 ; l -= cmdlen, cmd += cmdlen) {
            cmdlen = F_LEN(cmd);
            if (cmdlen > l) {
                  printf("ipfw: opcode %d size truncated\n",
                      cmd->opcode);
                  return EINVAL;
            }
            DEB(printf("ipfw: opcode %d\n", cmd->opcode);)
            switch (cmd->opcode) {
            case O_PROBE_STATE:
            case O_KEEP_STATE:
            case O_PROTO:
            case O_IP_SRC_ME:
            case O_IP_DST_ME:
            case O_LAYER2:
            case O_IN:
            case O_FRAG:
            case O_DIVERTED:
            case O_IPOPT:
            case O_IPTOS:
            case O_IPPRECEDENCE:
            case O_IPVER:
            case O_TCPWIN:
            case O_TCPFLAGS:
            case O_TCPOPTS:
            case O_ESTAB:
            case O_VERREVPATH:
            case O_VERSRCREACH:
            case O_ANTISPOOF:
            case O_IPSEC:
#ifdef INET6
            case O_IP6_SRC_ME:
            case O_IP6_DST_ME:
            case O_EXT_HDR:
            case O_IP6:
#endif
            case O_IP4:
            case O_TAG:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn))
                        goto bad_size;
                  break;

            case O_UID:
            case O_GID:
            case O_JAIL:
            case O_IP_SRC:
            case O_IP_DST:
            case O_TCPSEQ:
            case O_TCPACK:
            case O_PROB:
            case O_ICMPTYPE:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_u32))
                        goto bad_size;
                  break;

            case O_LIMIT:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_limit))
                        goto bad_size;
                  break;

            case O_LOG:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_log))
                        goto bad_size;

                  ((ipfw_insn_log *)cmd)->log_left =
                      ((ipfw_insn_log *)cmd)->max_log;

                  break;

            case O_IP_SRC_MASK:
            case O_IP_DST_MASK:
                  /* only odd command lengths */
                  if ( !(cmdlen & 1) || cmdlen > 31)
                        goto bad_size;
                  break;

            case O_IP_SRC_SET:
            case O_IP_DST_SET:
                  if (cmd->arg1 == 0 || cmd->arg1 > 256) {
                        printf("ipfw: invalid set size %d\n",
                              cmd->arg1);
                        return EINVAL;
                  }
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_u32) +
                      (cmd->arg1+31)/32 )
                        goto bad_size;
                  break;

            case O_IP_SRC_LOOKUP:
            case O_IP_DST_LOOKUP:
                  if (cmd->arg1 >= IPFW_TABLES_MAX) {
                        printf("ipfw: invalid table number %d\n",
                            cmd->arg1);
                        return (EINVAL);
                  }
                  if (cmdlen != F_INSN_SIZE(ipfw_insn) &&
                      cmdlen != F_INSN_SIZE(ipfw_insn_u32))
                        goto bad_size;
                  break;

            case O_MACADDR2:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_mac))
                        goto bad_size;
                  break;

            case O_NOP:
            case O_IPID:
            case O_IPTTL:
            case O_IPLEN:
            case O_TCPDATALEN:
            case O_TAGGED:
                  if (cmdlen < 1 || cmdlen > 31)
                        goto bad_size;
                  break;

            case O_MAC_TYPE:
            case O_IP_SRCPORT:
            case O_IP_DSTPORT: /* XXX artificial limit, 30 port pairs */
                  if (cmdlen < 2 || cmdlen > 31)
                        goto bad_size;
                  break;

            case O_RECV:
            case O_XMIT:
            case O_VIA:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_if))
                        goto bad_size;
                  break;

            case O_ALTQ:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_altq))
                        goto bad_size;
                  break;

            case O_PIPE:
            case O_QUEUE:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_pipe))
                        goto bad_size;
                  goto check_action;

            case O_FORWARD_IP:
#ifdef      IPFIREWALL_FORWARD
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_sa))
                        goto bad_size;
                  goto check_action;
#else
                  return EINVAL;
#endif

            case O_DIVERT:
            case O_TEE:
                  if (ip_divert_ptr == NULL)
                        return EINVAL;
                  else
                        goto check_size;
            case O_NETGRAPH:
            case O_NGTEE:
                  if (!NG_IPFW_LOADED)
                        return EINVAL;
                  else
                        goto check_size;
            case O_FORWARD_MAC: /* XXX not implemented yet */
            case O_CHECK_STATE:
            case O_COUNT:
            case O_ACCEPT:
            case O_DENY:
            case O_REJECT:
#ifdef INET6
            case O_UNREACH6:
#endif
            case O_SKIPTO:
check_size:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn))
                        goto bad_size;
check_action:
                  if (have_action) {
                        printf("ipfw: opcode %d, multiple actions"
                              " not allowed\n",
                              cmd->opcode);
                        return EINVAL;
                  }
                  have_action = 1;
                  if (l != cmdlen) {
                        printf("ipfw: opcode %d, action must be"
                              " last opcode\n",
                              cmd->opcode);
                        return EINVAL;
                  }
                  break;
#ifdef INET6
            case O_IP6_SRC:
            case O_IP6_DST:
                  if (cmdlen != F_INSN_SIZE(struct in6_addr) +
                      F_INSN_SIZE(ipfw_insn))
                        goto bad_size;
                  break;

            case O_FLOW6ID:
                  if (cmdlen != F_INSN_SIZE(ipfw_insn_u32) +
                      ((ipfw_insn_u32 *)cmd)->o.arg1)
                        goto bad_size;
                  break;

            case O_IP6_SRC_MASK:
            case O_IP6_DST_MASK:
                  if ( !(cmdlen & 1) || cmdlen > 127)
                        goto bad_size;
                  break;
            case O_ICMP6TYPE:
                  if( cmdlen != F_INSN_SIZE( ipfw_insn_icmp6 ) )
                        goto bad_size;
                  break;
#endif

            default:
                  switch (cmd->opcode) {
#ifndef INET6
                  case O_IP6_SRC_ME:
                  case O_IP6_DST_ME:
                  case O_EXT_HDR:
                  case O_IP6:
                  case O_UNREACH6:
                  case O_IP6_SRC:
                  case O_IP6_DST:
                  case O_FLOW6ID:
                  case O_IP6_SRC_MASK:
                  case O_IP6_DST_MASK:
                  case O_ICMP6TYPE:
                        printf("ipfw: no IPv6 support in kernel\n");
                        return EPROTONOSUPPORT;
#endif
                  default:
                        printf("ipfw: opcode %d, unknown opcode\n",
                              cmd->opcode);
                        return EINVAL;
                  }
            }
      }
      if (have_action == 0) {
            printf("ipfw: missing action\n");
            return EINVAL;
      }
      return 0;

bad_size:
      printf("ipfw: opcode %d size %d wrong\n",
            cmd->opcode, cmdlen);
      return EINVAL;
}

/*
 * Copy the static and dynamic rules to the supplied buffer
 * and return the amount of space actually used.
 */
static size_t
ipfw_getrules(struct ip_fw_chain *chain, void *buf, size_t space)
{
      char *bp = buf;
      char *ep = bp + space;
      struct ip_fw *rule;
      int i;
      time_t      boot_seconds;

        boot_seconds = boottime.tv_sec;
      /* XXX this can take a long time and locking will block packet flow */
      IPFW_RLOCK(chain);
      for (rule = chain->rules; rule ; rule = rule->next) {
            /*
             * Verify the entry fits in the buffer in case the
             * rules changed between calculating buffer space and
             * now.  This would be better done using a generation
             * number but should suffice for now.
             */
            i = RULESIZE(rule);
            if (bp + i <= ep) {
                  bcopy(rule, bp, i);
                  /*
                   * XXX HACK. Store the disable mask in the "next" pointer
                   * in a wild attempt to keep the ABI the same.
                   * Why do we do this on EVERY rule?
                   */
                  bcopy(&set_disable, &(((struct ip_fw *)bp)->next_rule),
                      sizeof(set_disable));
                  if (((struct ip_fw *)bp)->timestamp)
                        ((struct ip_fw *)bp)->timestamp += boot_seconds;
                  bp += i;
            }
      }
      IPFW_RUNLOCK(chain);
      if (ipfw_dyn_v) {
            ipfw_dyn_rule *p, *last = NULL;

            IPFW_DYN_LOCK();
            for (i = 0 ; i < curr_dyn_buckets; i++)
                  for (p = ipfw_dyn_v[i] ; p != NULL; p = p->next) {
                        if (bp + sizeof *p <= ep) {
                              ipfw_dyn_rule *dst =
                                    (ipfw_dyn_rule *)bp;
                              bcopy(p, dst, sizeof *p);
                              bcopy(&(p->rule->rulenum), &(dst->rule),
                                  sizeof(p->rule->rulenum));
                              /*
                               * store a non-null value in "next".
                               * The userland code will interpret a
                               * NULL here as a marker
                               * for the last dynamic rule.
                               */
                              bcopy(&dst, &dst->next, sizeof(dst));
                              last = dst;
                              dst->expire =
                                  TIME_LEQ(dst->expire, time_uptime) ?
                                    0 : dst->expire - time_uptime ;
                              bp += sizeof(ipfw_dyn_rule);
                        }
                  }
            IPFW_DYN_UNLOCK();
            if (last != NULL) /* mark last dynamic rule */
                  bzero(&last->next, sizeof(last));
      }
      return (bp - (char *)buf);
}


/**
 * {set|get}sockopt parser.
 */
static int
ipfw_ctl(struct sockopt *sopt)
{
#define     RULE_MAXSIZE      (256*sizeof(u_int32_t))
      int error, rule_num;
      size_t size;
      struct ip_fw *buf, *rule;
      u_int32_t rulenum[2];

      error = suser(sopt->sopt_td);
      if (error)
            return (error);

      /*
       * Disallow modifications in really-really secure mode, but still allow
       * the logging counters to be reset.
       */
      if (sopt->sopt_name == IP_FW_ADD ||
          (sopt->sopt_dir == SOPT_SET && sopt->sopt_name != IP_FW_RESETLOG)) {
            error = securelevel_ge(sopt->sopt_td->td_ucred, 3);
            if (error)
                  return (error);
      }

      error = 0;

      switch (sopt->sopt_name) {
      case IP_FW_GET:
            /*
             * pass up a copy of the current rules. Static rules
             * come first (the last of which has number IPFW_DEFAULT_RULE),
             * followed by a possibly empty list of dynamic rule.
             * The last dynamic rule has NULL in the "next" field.
             *
             * Note that the calculated size is used to bound the
             * amount of data returned to the user.  The rule set may
             * change between calculating the size and returning the
             * data in which case we'll just return what fits.
             */
            size = static_len;      /* size of static rules */
            if (ipfw_dyn_v)         /* add size of dyn.rules */
                  size += (dyn_count * sizeof(ipfw_dyn_rule));

            /*
             * XXX todo: if the user passes a short length just to know
             * how much room is needed, do not bother filling up the
             * buffer, just jump to the sooptcopyout.
             */
            buf = malloc(size, M_TEMP, M_WAITOK);
            error = sooptcopyout(sopt, buf,
                        ipfw_getrules(&layer3_chain, buf, size));
            free(buf, M_TEMP);
            break;

      case IP_FW_FLUSH:
            /*
             * Normally we cannot release the lock on each iteration.
             * We could do it here only because we start from the head all
             * the times so there is no risk of missing some entries.
             * On the other hand, the risk is that we end up with
             * a very inconsistent ruleset, so better keep the lock
             * around the whole cycle.
             *
             * XXX this code can be improved by resetting the head of
             * the list to point to the default rule, and then freeing
             * the old list without the need for a lock.
             */

            IPFW_WLOCK(&layer3_chain);
            layer3_chain.reap = NULL;
            free_chain(&layer3_chain, 0 /* keep default rule */);
            rule = layer3_chain.reap;
            layer3_chain.reap = NULL;
            IPFW_WUNLOCK(&layer3_chain);
            if (rule != NULL)
                  reap_rules(rule);
            break;

      case IP_FW_ADD:
            rule = malloc(RULE_MAXSIZE, M_TEMP, M_WAITOK);
            error = sooptcopyin(sopt, rule, RULE_MAXSIZE,
                  sizeof(struct ip_fw) );
            if (error == 0)
                  error = check_ipfw_struct(rule, sopt->sopt_valsize);
            if (error == 0) {
                  error = add_rule(&layer3_chain, rule);
                  size = RULESIZE(rule);
                  if (!error && sopt->sopt_dir == SOPT_GET)
                        error = sooptcopyout(sopt, rule, size);
            }
            free(rule, M_TEMP);
            break;

      case IP_FW_DEL:
            /*
             * IP_FW_DEL is used for deleting single rules or sets,
             * and (ab)used to atomically manipulate sets. Argument size
             * is used to distinguish between the two:
             *    sizeof(u_int32_t)
             *    delete single rule or set of rules,
             *    or reassign rules (or sets) to a different set.
             *    2*sizeof(u_int32_t)
             *    atomic disable/enable sets.
             *    first u_int32_t contains sets to be disabled,
             *    second u_int32_t contains sets to be enabled.
             */
            error = sooptcopyin(sopt, rulenum,
                  2*sizeof(u_int32_t), sizeof(u_int32_t));
            if (error)
                  break;
            size = sopt->sopt_valsize;
            if (size == sizeof(u_int32_t))      /* delete or reassign */
                  error = del_entry(&layer3_chain, rulenum[0]);
            else if (size == 2*sizeof(u_int32_t)) /* set enable/disable */
                  set_disable =
                      (set_disable | rulenum[0]) & ~rulenum[1] &
                      ~(1<<RESVD_SET); /* set RESVD_SET always enabled */
            else
                  error = EINVAL;
            break;

      case IP_FW_ZERO:
      case IP_FW_RESETLOG: /* argument is an int, the rule number */
            rule_num = 0;
            if (sopt->sopt_val != 0) {
                error = sooptcopyin(sopt, &rule_num,
                      sizeof(int), sizeof(int));
                if (error)
                  break;
            }
            error = zero_entry(&layer3_chain, rule_num,
                  sopt->sopt_name == IP_FW_RESETLOG);
            break;

      case IP_FW_TABLE_ADD:
            {
                  ipfw_table_entry ent;

                  error = sooptcopyin(sopt, &ent,
                      sizeof(ent), sizeof(ent));
                  if (error)
                        break;
                  error = add_table_entry(&layer3_chain, ent.tbl,
                      ent.addr, ent.masklen, ent.value);
            }
            break;

      case IP_FW_TABLE_DEL:
            {
                  ipfw_table_entry ent;

                  error = sooptcopyin(sopt, &ent,
                      sizeof(ent), sizeof(ent));
                  if (error)
                        break;
                  error = del_table_entry(&layer3_chain, ent.tbl,
                      ent.addr, ent.masklen);
            }
            break;

      case IP_FW_TABLE_FLUSH:
            {
                  u_int16_t tbl;

                  error = sooptcopyin(sopt, &tbl,
                      sizeof(tbl), sizeof(tbl));
                  if (error)
                        break;
                  IPFW_WLOCK(&layer3_chain);
                  error = flush_table(&layer3_chain, tbl);
                  IPFW_WUNLOCK(&layer3_chain);
            }
            break;

      case IP_FW_TABLE_GETSIZE:
            {
                  u_int32_t tbl, cnt;

                  if ((error = sooptcopyin(sopt, &tbl, sizeof(tbl),
                      sizeof(tbl))))
                        break;
                  IPFW_RLOCK(&layer3_chain);
                  error = count_table(&layer3_chain, tbl, &cnt);
                  IPFW_RUNLOCK(&layer3_chain);
                  if (error)
                        break;
                  error = sooptcopyout(sopt, &cnt, sizeof(cnt));
            }
            break;

      case IP_FW_TABLE_LIST:
            {
                  ipfw_table *tbl;

                  if (sopt->sopt_valsize < sizeof(*tbl)) {
                        error = EINVAL;
                        break;
                  }
                  size = sopt->sopt_valsize;
                  tbl = malloc(size, M_TEMP, M_WAITOK);
                  error = sooptcopyin(sopt, tbl, size, sizeof(*tbl));
                  if (error) {
                        free(tbl, M_TEMP);
                        break;
                  }
                  tbl->size = (size - sizeof(*tbl)) /
                      sizeof(ipfw_table_entry);
                  IPFW_RLOCK(&layer3_chain);
                  error = dump_table(&layer3_chain, tbl);
                  IPFW_RUNLOCK(&layer3_chain);
                  if (error) {
                        free(tbl, M_TEMP);
                        break;
                  }
                  error = sooptcopyout(sopt, tbl, size);
                  free(tbl, M_TEMP);
            }
            break;

      default:
            printf("ipfw: ipfw_ctl invalid option %d\n", sopt->sopt_name);
            error = EINVAL;
      }

      return (error);
#undef RULE_MAXSIZE
}

/**
 * dummynet needs a reference to the default rule, because rules can be
 * deleted while packets hold a reference to them. When this happens,
 * dummynet changes the reference to the default rule (it could well be a
 * NULL pointer, but this way we do not need to check for the special
 * case, plus here he have info on the default behaviour).
 */
struct ip_fw *ip_fw_default_rule;

/*
 * This procedure is only used to handle keepalives. It is invoked
 * every dyn_keepalive_period
 */
static void
ipfw_tick(void * __unused unused)
{
      struct mbuf *m0, *m, *mnext, **mtailp;
      int i;
      ipfw_dyn_rule *q;

      if (dyn_keepalive == 0 || ipfw_dyn_v == NULL || dyn_count == 0)
            goto done;

      /*
       * We make a chain of packets to go out here -- not deferring
       * until after we drop the IPFW dynamic rule lock would result
       * in a lock order reversal with the normal packet input -> ipfw
       * call stack.
       */
      m0 = NULL;
      mtailp = &m0;
      IPFW_DYN_LOCK();
      for (i = 0 ; i < curr_dyn_buckets ; i++) {
            for (q = ipfw_dyn_v[i] ; q ; q = q->next ) {
                  if (q->dyn_type == O_LIMIT_PARENT)
                        continue;
                  if (q->id.proto != IPPROTO_TCP)
                        continue;
                  if ( (q->state & BOTH_SYN) != BOTH_SYN)
                        continue;
                  if (TIME_LEQ( time_uptime+dyn_keepalive_interval,
                      q->expire))
                        continue;   /* too early */
                  if (TIME_LEQ(q->expire, time_uptime))
                        continue;   /* too late, rule expired */

                  *mtailp = send_pkt(NULL, &(q->id), q->ack_rev - 1,
                        q->ack_fwd, TH_SYN);
                  if (*mtailp != NULL)
                        mtailp = &(*mtailp)->m_nextpkt;
                  *mtailp = send_pkt(NULL, &(q->id), q->ack_fwd - 1,
                        q->ack_rev, 0);
                  if (*mtailp != NULL)
                        mtailp = &(*mtailp)->m_nextpkt;
            }
      }
      IPFW_DYN_UNLOCK();
      for (m = mnext = m0; m != NULL; m = mnext) {
            mnext = m->m_nextpkt;
            m->m_nextpkt = NULL;
            ip_output(m, NULL, NULL, 0, NULL, NULL);
      }
done:
      callout_reset(&ipfw_timeout, dyn_keepalive_period*hz, ipfw_tick, NULL);
}

int
ipfw_init(void)
{
      struct ip_fw default_rule;
      int error;

#ifdef INET6
      /* Setup IPv6 fw sysctl tree. */
      sysctl_ctx_init(&ip6_fw_sysctl_ctx);
      ip6_fw_sysctl_tree = SYSCTL_ADD_NODE(&ip6_fw_sysctl_ctx,
            SYSCTL_STATIC_CHILDREN(_net_inet6_ip6), OID_AUTO, "fw",
            CTLFLAG_RW | CTLFLAG_SECURE, 0, "Firewall");
      SYSCTL_ADD_INT(&ip6_fw_sysctl_ctx, SYSCTL_CHILDREN(ip6_fw_sysctl_tree),
            OID_AUTO, "deny_unknown_exthdrs", CTLFLAG_RW | CTLFLAG_SECURE,
            &fw_deny_unknown_exthdrs, 0,
            "Deny packets with unknown IPv6 Extension Headers");
#endif

      layer3_chain.rules = NULL;
      layer3_chain.want_write = 0;
      layer3_chain.busy_count = 0;
      cv_init(&layer3_chain.cv, "Condition variable for IPFW rw locks");
      IPFW_LOCK_INIT(&layer3_chain);
      ipfw_dyn_rule_zone = uma_zcreate("IPFW dynamic rule",
          sizeof(ipfw_dyn_rule), NULL, NULL, NULL, NULL,
          UMA_ALIGN_PTR, 0);
      IPFW_DYN_LOCK_INIT();
      callout_init(&ipfw_timeout, NET_CALLOUT_MPSAFE);

      bzero(&default_rule, sizeof default_rule);

      default_rule.act_ofs = 0;
      default_rule.rulenum = IPFW_DEFAULT_RULE;
      default_rule.cmd_len = 1;
      default_rule.set = RESVD_SET;

      default_rule.cmd[0].len = 1;
      default_rule.cmd[0].opcode =
#ifdef IPFIREWALL_DEFAULT_TO_ACCEPT
                        1 ? O_ACCEPT :
#endif
                        O_DENY;

      error = add_rule(&layer3_chain, &default_rule);
      if (error != 0) {
            printf("ipfw2: error %u initializing default rule "
                  "(support disabled)\n", error);
            IPFW_DYN_LOCK_DESTROY();
            IPFW_LOCK_DESTROY(&layer3_chain);
            uma_zdestroy(ipfw_dyn_rule_zone);
            return (error);
      }

      ip_fw_default_rule = layer3_chain.rules;
      printf("ipfw2 "
#ifdef INET6
            "(+ipv6) "
#endif
            "initialized, divert %s, "
            "rule-based forwarding "
#ifdef IPFIREWALL_FORWARD
            "enabled, "
#else
            "disabled, "
#endif
            "default to %s, logging ",
#ifdef IPDIVERT
            "enabled",
#else
            "loadable",
#endif
            default_rule.cmd[0].opcode == O_ACCEPT ? "accept" : "deny");

#ifdef IPFIREWALL_VERBOSE
      fw_verbose = 1;
#endif
#ifdef IPFIREWALL_VERBOSE_LIMIT
      verbose_limit = IPFIREWALL_VERBOSE_LIMIT;
#endif
      if (fw_verbose == 0)
            printf("disabled\n");
      else if (verbose_limit == 0)
            printf("unlimited\n");
      else
            printf("limited to %d packets/entry by default\n",
                verbose_limit);

      error = init_tables(&layer3_chain);
      if (error) {
            IPFW_DYN_LOCK_DESTROY();
            IPFW_LOCK_DESTROY(&layer3_chain);
            uma_zdestroy(ipfw_dyn_rule_zone);
            return (error);
      }
      ip_fw_ctl_ptr = ipfw_ctl;
      ip_fw_chk_ptr = ipfw_chk;
      callout_reset(&ipfw_timeout, hz, ipfw_tick, NULL);

      return (0);
}

void
ipfw_destroy(void)
{
      struct ip_fw *reap;

      ip_fw_chk_ptr = NULL;
      ip_fw_ctl_ptr = NULL;
      callout_drain(&ipfw_timeout);
      IPFW_WLOCK(&layer3_chain);
      flush_tables(&layer3_chain);
      layer3_chain.reap = NULL;
      free_chain(&layer3_chain, 1 /* kill default rule */);
      reap = layer3_chain.reap, layer3_chain.reap = NULL;
      IPFW_WUNLOCK(&layer3_chain);
      if (reap != NULL)
            reap_rules(reap);
      IPFW_DYN_LOCK_DESTROY();
      uma_zdestroy(ipfw_dyn_rule_zone);
      IPFW_LOCK_DESTROY(&layer3_chain);

#ifdef INET6
      /* Free IPv6 fw sysctl tree. */
      sysctl_ctx_free(&ip6_fw_sysctl_ctx);
#endif

      printf("IP firewall unloaded\n");
}

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