FreeBSD/Linux Kernel Cross Reference
sys/netinet/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 1.70.2.17 2006/02/23 23:06:24 emaste Exp $
     */
    
    #define        DEB(x)
    #define        DDB(x) x
    
    /*
     * Implement IP packet firewall (new version)
     */
    
    #if !defined(KLD_MODULE)
    #include "opt_ipfw.h"
    #include "opt_ipdn.h"
    #include "opt_ipdivert.h"
    #include "opt_inet.h"
    #include "opt_ipsec.h"
    #ifndef INET
    #error IPFIREWALL requires INET.
    #endif /* INET */
    #endif
    
    #define IPFW2   1
    #if IPFW2
    #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/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/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 <altq/if_altq.h>
    
    #ifdef IPSEC
    #include <netinet6/ipsec.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;
   };
   
   struct ip_fw_chain {
           struct ip_fw    *rules;         /* list of rules */
           struct ip_fw    *reap;          /* list of rules to reap */
           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;
   };
   
   #define IPFW_TABLES_MAX         128
   static struct ip_fw_table {
           struct radix_node_head  *rnh;
           int                     modified;
           in_addr_t               last_addr;
           int                     last_match;
           u_int32_t               last_value;
   } ipfw_tables[IPFW_TABLES_MAX];
   
   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");
   
   #endif /* SYSCTL_NODE */
   
   
   /*
    * This macro maps an ip pointer into a layer3 header pointer of type T
    */
   #define L3HDR(T, ip) ((T *)((u_int32_t *)(ip) + (ip)->ip_hl))
   
   static __inline int
   icmptype_match(struct ip *ip, ipfw_insn_u32 *cmd)
   {
           int type = L3HDR(struct icmp,ip)->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 ip *ip)
   {
           int type = L3HDR(struct icmp, ip)->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 ip *ip, ipfw_insn *cmd)
   {
           int optlen, bits = 0;
           struct tcphdr *tcp = L3HDR(struct tcphdr,ip);
           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;
   
                   case TCPOPT_CC:
                   case TCPOPT_CCNEW:
                   case TCPOPT_CCECHO:
                           bits |= IP_FW_TCPOPT_CC;
                           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;
   }
   
   
   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 ether_header *eh,
           struct mbuf *m, struct ifnet *oif)
   {
           char *action;
           int limit_reached = 0;
           char action2[40], proto[48], fragment[28];
   
           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);
   
                   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_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;
   
                           len = snprintf(SNPARGS(action2, 0), "Forward to %s",
                                   inet_ntoa(sa->sa.sin_addr));
                           if (sa->sa.sin_port)
                                   snprintf(SNPARGS(action2, len), ":%d",
                                       sa->sa.sin_port);
                           }
                           break;
                   default:
                           action = "UNKNOWN";
                           break;
                   }
           }
   
           if (hlen == 0) {        /* non-ip */
                   snprintf(SNPARGS(proto, 0), "MAC");
           } else {
                   struct ip *ip = mtod(m, struct ip *);
                   /* these three are all aliases to the same thing */
                   struct icmp *const icmp = L3HDR(struct icmp, ip);
                   struct tcphdr *const tcp = (struct tcphdr *)icmp;
                   struct udphdr *const udp = (struct udphdr *)icmp;
   
                   int ip_off, offset, ip_len;
   
                   int 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;
                   }
                   offset = ip_off & IP_OFFMASK;
                   switch (ip->ip_p) {
                   case IPPROTO_TCP:
                           len = snprintf(SNPARGS(proto, 0), "TCP %s",
                               inet_ntoa(ip->ip_src));
                           if (offset == 0)
                                   snprintf(SNPARGS(proto, len), ":%d %s:%d",
                                       ntohs(tcp->th_sport),
                                       inet_ntoa(ip->ip_dst),
                                       ntohs(tcp->th_dport));
                           else
                                   snprintf(SNPARGS(proto, len), " %s",
                                       inet_ntoa(ip->ip_dst));
                           break;
   
                   case IPPROTO_UDP:
                           len = snprintf(SNPARGS(proto, 0), "UDP %s",
                                   inet_ntoa(ip->ip_src));
                           if (offset == 0)
                                   snprintf(SNPARGS(proto, len), ":%d %s:%d",
                                       ntohs(udp->uh_sport),
                                       inet_ntoa(ip->ip_dst),
                                       ntohs(udp->uh_dport));
                           else
                                   snprintf(SNPARGS(proto, len), " %s",
                                       inet_ntoa(ip->ip_dst));
                           break;
   
                   case IPPROTO_ICMP:
                           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",
                               inet_ntoa(ip->ip_src));
                           snprintf(SNPARGS(proto, len), " %s",
                               inet_ntoa(ip->ip_dst));
                           break;
   
                   default:
                           len = snprintf(SNPARGS(proto, 0), "P:%d %s", ip->ip_p,
                               inet_ntoa(ip->ip_src));
                           snprintf(SNPARGS(proto, len), " %s",
                               inet_ntoa(ip->ip_dst));
                           break;
                   }
   
                   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;
   
           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_second)
                   return;
           last_remove = time_second;
   
           /*
            * 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_second ))
                                           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_second)) { /* 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 (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_second + 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_second + 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_second + 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_second + dyn_rst_lifetime;
                           break;
                   }
           } else if (pkt->proto == IPPROTO_UDP) {
                   q->expire = time_second + dyn_udp_lifetime;
           } else {
                   /* other protocols */
                  q->expire = time_second + 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_second + 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) {
                  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_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) {
                                  q->expire = time_second + 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)
  {
          static int last_log;
  
          ipfw_dyn_rule *q;
  
          DEB(printf("ipfw: install state type %d 0x%08x %u -> 0x%08x %u\n",
              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_second) {
                          last_log = time_second;
                          printf("ipfw: install_state: entry already present, done\n");
                  }
                  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_second) {
                          last_log = time_second;
                          printf("ipfw: install_state: Too many dynamic rules\n");
                  }
                  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 */
              {
                  u_int16_t limit_mask = cmd->limit_mask;
                  struct ipfw_flow_id id;
                  ipfw_dyn_rule *parent;
  
                  DEB(printf("ipfw: installing dyn-limit rule %d\n",
                      cmd->conn_limit);)
  
                  id.dst_ip = id.src_ip = 0;
                  id.dst_port = id.src_port = 0;
                  id.proto = args->f_id.proto;
  
                  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;
                  parent = lookup_dyn_parent(&id, rule);
                  if (parent == NULL) {
                          printf("ipfw: add parent failed\n");
                          IPFW_DYN_UNLOCK();
                          return 1;
                  }
                  if (parent->count >= cmd->conn_limit) {
                          /*
                           * See if we can remove some expired rule.
                           */
                          remove_dyn_rule(rule, parent);
                          if (parent->count >= cmd->conn_limit) {
                                  if (fw_verbose && last_log != time_second) {
                                          last_log = time_second;
                                          log(LOG_SECURITY | LOG_DEBUG,
                                              "drop session, too many entries\n");
                                  }
                                  IPFW_DYN_UNLOCK();
                                  return 1;
                          }
                  }
                  add_dyn_rule(&args->f_id, O_LIMIT, (struct ip_fw *)parent);
              }
                  break;
          default:
                  printf("ipfw: unknown dynamic rule type %u\n", cmd->o.opcode);
                  IPFW_DYN_UNLOCK();
                  return 1;
          }
          lookup_dyn_rule_locked(&args->f_id, NULL, NULL); /* XXX just set lifetime */
          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_
   */
  static struct mbuf *
  send_pkt(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;
          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, int offset, int ip_len)
  {
  
          if (code != ICMP_REJECT_RST) { /* Send an ICMP unreach */
                  /* We need the IP header in host order for icmp_error(). */
                  if (args->eh != NULL) {
                          struct ip *ip = mtod(args->m, struct ip *);
                          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->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_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 void
  init_tables(void)
  {
          int i;
  
          for (i = 0; i < IPFW_TABLES_MAX; i++) {
                  rn_inithead((void **)&ipfw_tables[i].rnh, 32);
                  ipfw_tables[i].modified = 1;
          }
  }
  
  static int
  add_table_entry(u_int16_t tbl, in_addr_t addr, u_int8_t mlen, u_int32_t value)
  {
          struct radix_node_head *rnh;
          struct table_entry *ent;
  
          if (tbl >= IPFW_TABLES_MAX)
                  return (EINVAL);
          rnh = ipfw_tables[tbl].rnh;
          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;
          RADIX_NODE_HEAD_LOCK(rnh);
          if (rnh->rnh_addaddr(&ent->addr, &ent->mask, rnh, (void *)ent) ==
              NULL) {
                  RADIX_NODE_HEAD_UNLOCK(rnh);
                  free(ent, M_IPFW_TBL);
                  return (EEXIST);
          }
          ipfw_tables[tbl].modified = 1;
          RADIX_NODE_HEAD_UNLOCK(rnh);
          return (0);
  }
  
  static int
  del_table_entry(u_int16_t tbl, in_addr_t addr, u_int8_t mlen)
  {
          struct radix_node_head *rnh;
          struct table_entry *ent;
          struct sockaddr_in sa, mask;
  
          if (tbl >= IPFW_TABLES_MAX)
                  return (EINVAL);
          rnh = ipfw_tables[tbl].rnh;
          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;
          RADIX_NODE_HEAD_LOCK(rnh);
          ent = (struct table_entry *)rnh->rnh_deladdr(&sa, &mask, rnh);
          if (ent == NULL) {
                  RADIX_NODE_HEAD_UNLOCK(rnh);
                  return (ESRCH);
          }
          ipfw_tables[tbl].modified = 1;
          RADIX_NODE_HEAD_UNLOCK(rnh);
          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(u_int16_t tbl)
  {
          struct radix_node_head *rnh;
  
          if (tbl >= IPFW_TABLES_MAX)
                  return (EINVAL);
          rnh = ipfw_tables[tbl].rnh;
          RADIX_NODE_HEAD_LOCK(rnh);
          rnh->rnh_walktree(rnh, flush_table_entry, rnh);
          ipfw_tables[tbl].modified = 1;
          RADIX_NODE_HEAD_UNLOCK(rnh);
          return (0);
  }
  
  static void
  flush_tables(void)
  {
          u_int16_t tbl;
  
          for (tbl = 0; tbl < IPFW_TABLES_MAX; tbl++)
                  flush_table(tbl);
  }
  
  static int
  lookup_table(u_int16_t tbl, in_addr_t addr, u_int32_t *val)
  {
          struct radix_node_head *rnh;
          struct ip_fw_table *table;
          struct table_entry *ent;
          struct sockaddr_in sa;
          int last_match;
  
          if (tbl >= IPFW_TABLES_MAX)
                  return (0);
          table = &ipfw_tables[tbl];
          rnh = table->rnh;
          RADIX_NODE_HEAD_LOCK(rnh);
          if (addr == table->last_addr && !table->modified) {
                  last_match = table->last_match;
                  if (last_match)
                          *val = table->last_value;
                  RADIX_NODE_HEAD_UNLOCK(rnh);
                  return (last_match);
          }
          table->modified = 0;
          sa.sin_len = 8;
          sa.sin_addr.s_addr = addr;
          ent = (struct table_entry *)(rnh->rnh_lookup(&sa, NULL, rnh));
          table->last_addr = addr;
          if (ent != NULL) {
                  table->last_value = *val = ent->value;
                  table->last_match = 1;
                  RADIX_NODE_HEAD_UNLOCK(rnh);
                  return (1);
          }
          table->last_match = 0;
          RADIX_NODE_HEAD_UNLOCK(rnh);
          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(u_int32_t tbl, u_int32_t *cnt)
  {
          struct radix_node_head *rnh;
  
          if (tbl >= IPFW_TABLES_MAX)
                  return (EINVAL);
          rnh = ipfw_tables[tbl].rnh;
          *cnt = 0;
          RADIX_NODE_HEAD_LOCK(rnh);
          rnh->rnh_walktree(rnh, count_table_entry, cnt);
          RADIX_NODE_HEAD_UNLOCK(rnh);
          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(ipfw_table *tbl)
  {
          struct radix_node_head *rnh;
  
          if (tbl->tbl >= IPFW_TABLES_MAX)
                  return (EINVAL);
          rnh = ipfw_tables[tbl->tbl].rnh;
          tbl->cnt = 0;
          RADIX_NODE_HEAD_LOCK(rnh);
          rnh->rnh_walktree(rnh, dump_table_entry, tbl);
          RADIX_NODE_HEAD_UNLOCK(rnh);
          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 = 1;
                  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->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)
   *
   * Return value:
   *
   *      IP_FW_PORT_DENY_FLAG    the packet must be dropped.
   *      0       The packet is to be accepted and routed normally OR
   *              the packet was denied/rejected and has been dropped;
   *              in the latter case, *m is equal to NULL upon return.
   *      port    Divert the packet to port, with these caveats:
   *
   *              - If IP_FW_PORT_TEE_FLAG is set, tee the packet instead
   *                of diverting it (ie, 'ipfw tee').
   *
   *              - If IP_FW_PORT_DYNT_FLAG is set, interpret the lower
   *                16 bits as a dummynet pipe number instead of diverting
   */
  
  int
  ipfw_chk(struct ip_fw_args *args)
  {
          /*
           * Local variables hold 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.
           *
           * 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 simply an alias of the value of m, and it is kept
           *      in sync with it (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 IPv4 header.
           *      hlen >0 means we have an IPv4 packet.
           */
          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.
           */
          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;
          int dyn_dir = MATCH_UNKNOWN;
          ipfw_dyn_rule *q = NULL;
          struct ip_fw_chain *chain = &layer3_chain;
          struct m_tag *mtag;
  
          if (m->m_flags & M_SKIP_FIREWALL)
                  return 0;       /* accept */
          /*
           * dyn_dir = MATCH_UNKNOWN when rules unchecked,
           *      MATCH_NONE when checked and not matched (q = NULL),
           *      MATCH_FORWARD or MATCH_REVERSE otherwise (q != NULL)
           */
  
          pktlen = m->m_pkthdr.len;
          if (args->eh == NULL ||         /* layer 3 packet */
                  ( m->m_pkthdr.len >= sizeof(struct ip) &&
                      ntohs(args->eh->ether_type) == ETHERTYPE_IP))
                          hlen = ip->ip_hl << 2;
  
          /*
           * Collect parameters into local variables for faster matching.
           */
          if (hlen == 0) {        /* do not grab addresses for non-ip pkts */
                  proto = args->f_id.proto = 0;   /* mark f_id invalid */
                  goto after_ip_checks;
          }
  
          proto = args->f_id.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;
  
  #define PULLUP_TO(len)                                          \
                  do {                                            \
                          if ((m)->m_len < (len)) {               \
                              args->m = m = m_pullup(m, (len));   \
                              if (m == 0)                         \
                                  goto pullup_failed;             \
                              ip = mtod(m, struct ip *);          \
                          }                                       \
                  } while (0)
  
          if (offset == 0) {
                  switch (proto) {
                  case IPPROTO_TCP:
                      {
                          struct tcphdr *tcp;
  
                          PULLUP_TO(hlen + sizeof(struct tcphdr));
                          tcp = L3HDR(struct tcphdr, ip);
                          dst_port = tcp->th_dport;
                          src_port = tcp->th_sport;
                          args->f_id.flags = tcp->th_flags;
                          }
                          break;
  
                  case IPPROTO_UDP:
                      {
                          struct udphdr *udp;
  
                          PULLUP_TO(hlen + sizeof(struct udphdr));
                          udp = L3HDR(struct udphdr, ip);
                          dst_port = udp->uh_dport;
                          src_port = udp->uh_sport;
                          }
                          break;
  
                  case IPPROTO_ICMP:
                          PULLUP_TO(hlen + 4);    /* type, code and checksum. */
                          args->f_id.flags = L3HDR(struct icmp, ip)->icmp_type;
                          break;
  
                  default:
                          break;
                  }
  #undef PULLUP_TO
          }
  
          args->f_id.src_ip = ntohl(src_ip.s_addr);
          args->f_id.dst_ip = ntohl(dst_ip.s_addr);
          args->f_id.src_port = src_port = ntohs(src_port);
          args->f_id.dst_port = dst_port = ntohs(dst_port);
  
  after_ip_checks:
          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 0;
                  }
  
                  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_PORT_DENY_FLAG); /* invalid */
                          }
                          while (f && f->rulenum <= skipto)
                                  f = f->next;
                          if (f == NULL) {        /* drop packet */
                                  IPFW_RUNLOCK(chain);
                                  return(IP_FW_PORT_DENY_FLAG);
                          }
                  }
          }
          /* 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) {
                  int l, cmdlen;
                  ipfw_insn *cmd;
                  int 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 an IPv4
                                   * packet with the ports info.
                                   */
                                  if (offset!=0)
                                          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 t =
                                              ntohs(args->eh->ether_type);
                                          u_int16_t *p =
                                              ((ipfw_insn_u16 *)cmd)->ports;
                                          int i;
  
                                          for (i = cmdlen - 1; !match && i>0;
                                              i--, p += 2)
                                                  match = (t>=p[0] && t<=p[1]);
                                  }
                                  break;
  
                          case O_FRAG:
                                  match = (hlen > 0 && 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 = (hlen > 0 &&
                                      ((ipfw_insn_ip *)cmd)->addr.s_addr ==
                                      src_ip.s_addr);
                                  break;
  
                          case O_IP_SRC_LOOKUP:
                          case O_IP_DST_LOOKUP:
                                  if (hlen > 0) {
                                      uint32_t a =
                                          (cmd->opcode == O_IP_DST_LOOKUP) ?
                                              dst_ip.s_addr : src_ip.s_addr;
                                      uint32_t v;
  
                                      match = lookup_table(cmd->arg1, a, &v);
                                      if (!match)
                                          break;
                                      if (cmdlen == F_INSN_SIZE(ipfw_insn_u32))
                                          match =
                                              ((ipfw_insn_u32 *)cmd)->d[0] == v;
                                  }
                                  break;
  
                          case O_IP_SRC_MASK:
                          case O_IP_DST_MASK:
                                  if (hlen > 0) {
                                      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 (hlen > 0) {
                                          struct ifnet *tif;
  
                                          INADDR_TO_IFP(src_ip, tif);
                                          match = (tif != NULL);
                                  }
                                  break;
  
                          case O_IP_DST_SET:
                          case O_IP_SRC_SET:
                                  if (hlen > 0) {
                                          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 = (hlen > 0 &&
                                      ((ipfw_insn_ip *)cmd)->addr.s_addr ==
                                      dst_ip.s_addr);
                                  break;
  
                          case O_IP_DST_ME:
                                  if (hlen > 0) {
                                          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 an IPv4
                                   * 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(ip, (ipfw_insn_u32 *)cmd) );
                                  break;
  
                          case O_IPOPT:
                                  match = (hlen > 0 && ipopts_match(ip, cmd) );
                                  break;
  
                          case O_IPVER:
                                  match = (hlen > 0 && cmd->arg1 == ip->ip_v);
                                  break;
  
                          case O_IPID:
                          case O_IPLEN:
                          case O_IPTTL:
                                  if (hlen > 0) { /* 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 = (hlen > 0 &&
                                      (cmd->arg1 == (ip->ip_tos & 0xe0)) );
                                  break;
  
                          case O_IPTOS:
                                  match = (hlen > 0 &&
                                      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 = L3HDR(struct tcphdr,ip);
                                      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,
                                          L3HDR(struct tcphdr,ip)->th_flags));
                                  break;
  
                          case O_TCPOPTS:
                                  match = (proto == IPPROTO_TCP && offset == 0 &&
                                      tcpopts_match(ip, cmd));
                                  break;
  
                          case O_TCPSEQ:
                                  match = (proto == IPPROTO_TCP && offset == 0 &&
                                      ((ipfw_insn_u32 *)cmd)->d[0] ==
                                          L3HDR(struct tcphdr,ip)->th_seq);
                                  break;
  
                          case O_TCPACK:
                                  match = (proto == IPPROTO_TCP && offset == 0 &&
                                      ((ipfw_insn_u32 *)cmd)->d[0] ==
                                          L3HDR(struct tcphdr,ip)->th_ack);
                                  break;
  
                          case O_TCPWIN:
                                  match = (proto == IPPROTO_TCP && offset == 0 &&
                                      cmd->arg1 ==
                                          L3HDR(struct tcphdr,ip)->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 &&
                                      (L3HDR(struct tcphdr,ip)->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 (hlen != 0)
                                          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->eh, m, oif);
                                  match = 1;
                                  break;
  
                          case O_PROB:
                                  match = (random()<((ipfw_insn_u32 *)cmd)->d[0]);
                                  break;
  
                          case O_VERREVPATH:
                                  /* Outgoing packets automatically pass/match */
                                  match = (hlen > 0 && ((oif != NULL) ||
                                      (m->m_pkthdr.rcvif == NULL) ||
                                      verify_path(src_ip, m->m_pkthdr.rcvif)));
                                  break;
  
                          case O_VERSRCREACH:
                                  /* Outgoing packets automatically pass/match */
                                  match = (hlen > 0 && ((oif != NULL) ||
                                       verify_path(src_ip, NULL)));
                                  break;
  
                          case O_ANTISPOOF:
                                  /* Outgoing packets automatically pass/match */
                                  if (oif == NULL && hlen > 0 &&
                                      in_localaddr(src_ip))
                                          match = 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;
  
                          /*
                           * 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_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)) {
                                          retval = IP_FW_PORT_DENY_FLAG;
                                          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 ?
                                          L3HDR(struct tcphdr, ip) : 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 */
                                  retval = cmd->arg1 | IP_FW_PORT_DYNT_FLAG;
                                  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_PORT_DENY_FLAG;
                                  }
                                  dt = (struct divert_tag *)(mtag+1);
                                  dt->cookie = f->rulenum;
                                  dt->info = (cmd->opcode == O_DIVERT) ?
                                      cmd->arg1 :
                                      cmd->arg1 | IP_FW_PORT_TEE_FLAG;
                                  m_tag_prepend(m, mtag);
                                  retval = dt->info;
                                  goto done;
                          }
  
                          case O_COUNT:
                          case O_SKIPTO:
                                  f->pcnt++;      /* update stats */
                                  f->bcnt += pktlen;
                                  f->timestamp = time_second;
                                  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 && offset == 0 &&
                                      (proto != IPPROTO_ICMP ||
                                       is_icmp_query(ip)) &&
                                      !(m->m_flags & (M_BCAST|M_MCAST)) &&
                                      !IN_MULTICAST(ntohl(dst_ip.s_addr))) {
                                          send_reject(args, cmd->arg1,
                                              offset,ip_len);
                                          m = args->m;
                                  }
                                  /* FALLTHROUGH */
                          case O_DENY:
                                  retval = IP_FW_PORT_DENY_FLAG;
                                  goto done;
  
                          case O_FORWARD_IP:
                                  if (args->eh)   /* not valid on layer2 pkts */
                                          break;
                                  if (!q || dyn_dir == MATCH_FORWARD)
                                          args->next_hop =
                                              &((ipfw_insn_sa *)cmd)->sa;
                                  retval = 0;
                                  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_PORT_DENY_FLAG);
  
  done:
          /* Update statistics */
          f->pcnt++;
          f->bcnt += pktlen;
          f->timestamp = time_second;
          IPFW_RUNLOCK(chain);
          return retval;
  
  pullup_failed:
          if (fw_verbose)
                  printf("ipfw: pullup failed\n");
          return(IP_FW_PORT_DENY_FLAG);
  }
  
  /*
   * 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;
  }
  
  /*
   * When pipes/queues are deleted, clear the "pipe_ptr" pointer to a given
   * pipe/queue, or to all of them (match == NULL).
   */
  void
  flush_pipe_ptrs(struct dn_flow_set *match)
  {
          struct ip_fw *rule;
  
          IPFW_WLOCK(&layer3_chain);
          for (rule = layer3_chain.rules; rule; rule = rule->next) {
                  ipfw_insn_pipe *cmd = (ipfw_insn_pipe *)ACTION_PTR(rule);
  
                  if (cmd->o.opcode != O_PIPE && cmd->o.opcode != O_QUEUE)
                          continue;
                  /*
                   * XXX Use bcmp/bzero to handle pipe_ptr to overcome
                   * possible alignment problems on 64-bit architectures.
                   * This code is seldom used so we do not worry too
                   * much about efficiency.
                   */
                  if (match == NULL ||
                      !bcmp(&cmd->pipe_ptr, &match, sizeof(match)) )
                          bzero(&cmd->pipe_ptr, sizeof(cmd->pipe_ptr));
          }
          IPFW_WUNLOCK(&layer3_chain);
  }
  
  /*
   * 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);
          }
          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:
                          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:
                          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:
  #ifndef IPDIVERT
                          return EINVAL;
  #endif
                  case O_FORWARD_MAC: /* XXX not implemented yet */
                  case O_CHECK_STATE:
                  case O_COUNT:
                  case O_ACCEPT:
                  case O_DENY:
                  case O_REJECT:
                  case O_SKIPTO:
                          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;
                  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;
  
          /* 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);
                          bcopy(&set_disable, &(((struct ip_fw *)bp)->next_rule),
                              sizeof(set_disable));
                          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_second) ?
                                                  0 : dst->expire - time_second ;
                                          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)) {
  #if __FreeBSD_version >= 500034
                  error = securelevel_ge(sopt->sopt_td->td_ucred, 3);
                  if (error)
                          return (error);
  #else /* FreeBSD 4.x */
                  if (securelevel >= 3)
                          return (EPERM);
  #endif
          }
  
          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 (layer3_chain.reap != 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(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(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;
                          error = flush_table(tbl);
                  }
                  break;
  
          case IP_FW_TABLE_GETSIZE:
                  {
                          u_int32_t tbl, cnt;
  
                          if ((error = sooptcopyin(sopt, &tbl, sizeof(tbl),
                              sizeof(tbl))))
                                  break;
                          if ((error = count_table(tbl, &cnt)))
                                  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);
                          if (tbl == NULL) {
                                  error = ENOMEM;
                                  break;
                          }
                          error = sooptcopyin(sopt, tbl, size, sizeof(*tbl));
                          if (error) {
                                  free(tbl, M_TEMP);
                                  break;
                          }
                          tbl->size = (size - sizeof(*tbl)) /
                              sizeof(ipfw_table_entry);
                          error = dump_table(tbl);
                          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_second+dyn_keepalive_interval,
                              q->expire))
                                  continue;       /* too early */
                          if (TIME_LEQ(q->expire, time_second))
                                  continue;       /* too late, rule expired */
  
                          *mtailp = send_pkt(&(q->id), q->ack_rev - 1,
                                  q->ack_fwd, TH_SYN);
                          if (*mtailp != NULL)
                                  mtailp = &(*mtailp)->m_nextpkt;
                          *mtailp = send_pkt(&(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;
  
          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 zone",
              sizeof(ipfw_dyn_rule), NULL, NULL, NULL, NULL,
              UMA_ALIGN_PTR, 0);
          IPFW_DYN_LOCK_INIT();
          callout_init(&ipfw_timeout, debug_mpsafenet ? CALLOUT_MPSAFE : 0);
  
          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);
                  return (error);
          }
  
          ip_fw_default_rule = layer3_chain.rules;
          printf("ipfw2 initialized, divert %s, "
                  "rule-based forwarding "
  #ifdef IPFIREWALL_FORWARD
                  "enabled, "
  #else
                  "disabled, "
  #endif
                  "default to %s, logging ",
  #ifdef IPDIVERT
                  "enabled",
  #else
                  "disabled",
  #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);
  
          init_tables();
          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);
          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);
          flush_tables();
          IPFW_DYN_LOCK_DESTROY();
          uma_zdestroy(ipfw_dyn_rule_zone);
          IPFW_LOCK_DESTROY(&layer3_chain);
          printf("IP firewall unloaded\n");
  }
  
  #endif /* IPFW2 */