fixed a bug that uRPF does not work properly for an IPv6 packet bound for the sending...

[FreeBSD/FreeBSD.git] / 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.
 *
 * $FreeBSD$
 */

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

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

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

#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 <netgraph/ng_ipfw.h>

#include <altq/if_altq.h>

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

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

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

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

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

static int fw_verbose;
static int verbose_limit;

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

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

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");

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

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

static int fw_deny_unknown_exthdrs = 1;


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

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

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

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

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

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

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

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

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

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

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

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

                default:
                        break;

                case IPOPT_LSRR:
                        bits |= IP_FW_IPOPT_LSRR;
                        break;

                case IPOPT_SSRR:
                        bits |= IP_FW_IPOPT_SSRR;
                        break;

                case IPOPT_RR:
                        bits |= IP_FW_IPOPT_RR;
                        break;

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

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

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

                switch (opt) {

                default:
                        break;

                case TCPOPT_MAXSEG:
                        bits |= IP_FW_TCPOPT_MSS;
                        break;

                case TCPOPT_WINDOW:
                        bits |= IP_FW_TCPOPT_WINDOW;
                        break;

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

                case TCPOPT_TIMESTAMP:
                        bits |= IP_FW_TCPOPT_TS;
                        break;

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

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

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

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

        bzero(&ro, sizeof(ro));

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

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

        /* if ifp is provided, check for equality with rtentry */
        if (ifp != NULL && ro.ro_rt->rt_ifp != ifp) {
                RTFREE(ro.ro_rt);
                return 0;
        }

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

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

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

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

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

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

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

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

        bzero(&ro, sizeof(ro));

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

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

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

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

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

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

}
static __inline int
hash_packet6(struct ipfw_flow_id *id)
{
        u_int32_t i;
        i = (id->dst_ip6.__u6_addr.__u6_addr32[0]) ^
            (id->dst_ip6.__u6_addr.__u6_addr32[1]) ^
            (id->dst_ip6.__u6_addr.__u6_addr32[2]) ^
            (id->dst_ip6.__u6_addr.__u6_addr32[3]) ^
            (id->dst_port) ^ (id->src_port) ^ (id->flow_id6);
        return i;
}

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

        return (0);
}

static void
send_reject6(struct ip_fw_args *args, int code, u_short offset, u_int hlen)
{
        if (code == ICMP6_UNREACH_RST && offset == 0 &&
            args->f_id.proto == IPPROTO_TCP) {
                struct ip6_hdr *ip6;
                struct tcphdr *tcp;
                tcp_seq ack, seq;
                int flags;
                struct {
                        struct ip6_hdr ip6;
                        struct tcphdr th;
                } ti;

                if (args->m->m_len < (hlen+sizeof(struct tcphdr))) {
                        args->m = m_pullup(args->m, hlen+sizeof(struct tcphdr));
                        if (args->m == NULL)
                                return;
                }

                ip6 = mtod(args->m, struct ip6_hdr *);
                tcp = (struct tcphdr *)(mtod(args->m, char *) + hlen);

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

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

                if (ti.th.th_flags & TH_ACK) {
                        ack = 0;
                        seq = ti.th.th_ack;
                        flags = TH_RST;
                } else {
                        ack = ti.th.th_seq;
                        if (((args->m)->m_flags & M_PKTHDR) != 0) {
                                ack += (args->m)->m_pkthdr.len - hlen
                                        - (ti.th.th_off << 2);
                        } else if (ip6->ip6_plen) {
                                ack += ntohs(ip6->ip6_plen) + sizeof(*ip6)
                                        - hlen - (ti.th.th_off << 2);
                        } else {
                                m_freem(args->m);
                                return;
                        }
                        if (tcp->th_flags & TH_SYN)
                                ack++;
                        seq = 0;
                        flags = TH_RST|TH_ACK;
                }
                bcopy(&ti, ip6, sizeof(ti));
                tcp_respond(NULL, ip6, (struct tcphdr *)(ip6 + 1),
                        args->m, ack, seq, flags);

        } else if (code != ICMP6_UNREACH_RST) { /* Send an ICMPv6 unreach. */
                icmp6_error(args->m, ICMP6_DST_UNREACH, code, 0);

        } else
                m_freem(args->m);

        args->m = NULL;
}

#endif /* INET6 */

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

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

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

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

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

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

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

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

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

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

                case O_ACCEPT:
                        action = "Accept";
                        break;
                case O_COUNT:
                        action = "Count";
                        break;
                case O_DIVERT:
                        snprintf(SNPARGS(action2, 0), "Divert %d",
                                cmd->arg1);
                        break;
                case O_TEE:
                        snprintf(SNPARGS(action2, 0), "Tee %d",
                                cmd->arg1);
                        break;
                case O_SKIPTO:
                        snprintf(SNPARGS(action2, 0), "SkipTo %d",
                                cmd->arg1);
                        break;
                case O_PIPE:
                        snprintf(SNPARGS(action2, 0), "Pipe %d",
                                cmd->arg1);
                        break;
                case O_QUEUE:
                        snprintf(SNPARGS(action2, 0), "Queue %d",
                                cmd->arg1);
                        break;
                case O_FORWARD_IP: {
                        ipfw_insn_sa *sa = (ipfw_insn_sa *)cmd;
                        int len;

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

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

        } else {
                int len;
                char src[48], dst[48];
                struct icmphdr *icmp;
                struct tcphdr *tcp;
                struct udphdr *udp;
                /* Initialize to make compiler happy. */
                struct ip *ip = NULL;
#ifdef INET6
                struct ip6_hdr *ip6 = NULL;
                struct icmp6_hdr *icmp6;
#endif
                src[0] = '\0';
                dst[0] = '\0';
#ifdef INET6
                if (args->f_id.addr_type == 6) {
                        snprintf(src, sizeof(src), "[%s]",
                            ip6_sprintf(&args->f_id.src_ip6));
                        snprintf(dst, sizeof(dst), "[%s]",
                            ip6_sprintf(&args->f_id.dst_ip6));

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

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

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

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

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

#ifdef INET6
                if (args->f_id.addr_type == 6) {
                        if (offset & (IP6F_OFF_MASK | IP6F_MORE_FRAG))
                                snprintf(SNPARGS(fragment, 0),
                                    " (frag %08x:%d@%d%s)",
                                    args->f_id.frag_id6,
                                    ntohs(ip6->ip6_plen) - hlen,
                                    ntohs(offset & IP6F_OFF_MASK) << 3,
                                    (offset & IP6F_MORE_FRAG) ? "+" : "");
                } else
#endif
                {
                        int ip_off, ip_len;
                        if (eh != NULL) { /* layer 2 packets are as on the wire */
                                ip_off = ntohs(ip->ip_off);
                                ip_len = ntohs(ip->ip_len);
                        } else {
                                ip_off = ip->ip_off;
                                ip_len = ip->ip_len;
                        }
                        if (ip_off & (IP_MF | IP_OFFMASK))
                                snprintf(SNPARGS(fragment, 0),
                                    " (frag %d:%d@%d%s)",
                                    ntohs(ip->ip_id), ip_len - (ip->ip_hl << 2),
                                    offset << 3,
                                    (ip_off & IP_MF) ? "+" : "");
                }
        }
        if (oif || m->m_pkthdr.rcvif)
                log(LOG_SECURITY | LOG_INFO,
                    "ipfw: %d %s %s %s via %s%s\n",
                    f ? f->rulenum : -1,
                    action, proto, oif ? "out" : "in",
                    oif ? oif->if_xname : m->m_pkthdr.rcvif->if_xname,
                    fragment);
        else
                log(LOG_SECURITY | LOG_INFO,
                    "ipfw: %d %s %s [no if info]%s\n",
                    f ? f->rulenum : -1,
                    action, proto, fragment);
        if (limit_reached)
                log(LOG_SECURITY | LOG_NOTICE,
                    "ipfw: limit %d reached on entry %d\n",
                    limit_reached, f ? f->rulenum : -1);
}

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

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

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

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

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

#define FORCE (keep_me == NULL)

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

        IPFW_DYN_LOCK_ASSERT();

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

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


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

        IPFW_DYN_LOCK_ASSERT();

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

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

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

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

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

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

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

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

static void
realloc_dynamic_table(void)
{
        IPFW_DYN_LOCK_ASSERT();

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

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

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

        IPFW_DYN_LOCK_ASSERT();

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

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

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

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

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

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

        IPFW_DYN_LOCK_ASSERT();

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

/**
 * Install dynamic state for rule type cmd->o.opcode
 *
 * Returns 1 (failure) if state is not installed because of errors or because
 * session limitations are enforced.
 */
static int
install_state(struct ip_fw *rule, ipfw_insn_limit *cmd,
        struct ip_fw_args *args)
{
        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_uptime) {
                        last_log = time_uptime;
                        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_uptime) {
                        last_log = time_uptime;
                        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 (IS_IP6_FLOW_ID (&(args->f_id))) {
                        if (limit_mask & DYN_SRC_ADDR)
                                id.src_ip6 = args->f_id.src_ip6;
                        if (limit_mask & DYN_DST_ADDR)
                                id.dst_ip6 = args->f_id.dst_ip6;
                } else {
                        if (limit_mask & DYN_SRC_ADDR)
                                id.src_ip = args->f_id.src_ip;
                        if (limit_mask & DYN_DST_ADDR)
                                id.dst_ip = args->f_id.dst_ip;
                }
                if (limit_mask & DYN_SRC_PORT)
                        id.src_port = args->f_id.src_port;
                if (limit_mask & DYN_DST_PORT)
                        id.dst_port = args->f_id.dst_port;
                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_uptime) {
                                        last_log = time_uptime;
                                        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_DATA);
        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, u_short 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)
 *      args->cookie    a cookie depending on rule action
 *
 * Return value:
 *
 *      IP_FW_PASS      the packet must be accepted
 *      IP_FW_DENY      the packet must be dropped
 *      IP_FW_DIVERT    divert packet, port in m_tag
 *      IP_FW_TEE       tee packet, port in m_tag
 *      IP_FW_DUMMYNET  to dummynet, pipe in args->cookie
 *      IP_FW_NETGRAPH  into netgraph, cookie args->cookie
 *
 */

int
ipfw_chk(struct ip_fw_args *args)
{
        /*
         * Local variables 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, ip_input).
         *      If non-NULL, ipfw_chk has been called on the outbound path
         *      (ether_output, ip_output).
         */
        struct ifnet *oif = args->oif;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

                        default:
                                break;
                        }
                }

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

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

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

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

        /*
         * Now scan the rules, and parse microinstructions for each rule.
         */
        for (; f; f = f->next) {
                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 a
                                 * packet with the ports info.
                                 */
                                if (offset!=0)
                                        break;
                                if (is_ipv6) /* XXX to be fixed later */
                                        break;
                                if (proto == IPPROTO_TCP ||
                                    proto == IPPROTO_UDP)
                                        match = check_uidgid(
                                                    (ipfw_insn_u32 *)cmd,
                                                    proto, oif,
                                                    dst_ip, dst_port,
                                                    src_ip, src_port, &fw_ugid_cache,
                                                    &ugid_lookup, args->inp);
                                break;

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

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

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

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

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

                        case O_MAC_TYPE:
                                if (args->eh != NULL) {
                                        u_int16_t 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 = (offset != 0);
                                break;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

                        case O_IPOPT:
                                match = (is_ipv4 &&
                                    ipopts_match(mtod(m, struct ip *), cmd) );
                                break;

                        case O_IPVER:
                                match = (is_ipv4 &&
                                    cmd->arg1 == mtod(m, struct ip *)->ip_v);
                                break;

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

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

                        case O_IPPRECEDENCE:
                                match = (is_ipv4 &&
                                    (cmd->arg1 == (mtod(m, struct ip *)->ip_tos & 0xe0)) );
                                break;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

                        case O_IP6_DST:
                                match = is_ipv6 &&
                                IN6_ARE_ADDR_EQUAL(&args->f_id.dst_ip6,
                                    &((ipfw_insn_ip6 *)cmd)->addr6);
                                break;
                        case O_IP6_SRC_MASK:
                                if (is_ipv6) {
                                        ipfw_insn_ip6 *te = (ipfw_insn_ip6 *)cmd;
                                        struct in6_addr p = args->f_id.src_ip6;

                                        APPLY_MASK(&p, &te->mask6);
                                        match = IN6_ARE_ADDR_EQUAL(&te->addr6, &p);
                                }
                                break;

                        case O_IP6_DST_MASK:
                                if (is_ipv6) {
                                        ipfw_insn_ip6 *te = (ipfw_insn_ip6 *)cmd;
                                        struct in6_addr p = args->f_id.dst_ip6;

                                        APPLY_MASK(&p, &te->mask6);
                                        match = IN6_ARE_ADDR_EQUAL(&te->addr6, &p);
                                }
                                break;

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

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

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

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

                        case O_IP6:
                                match = is_ipv6;
                                break;
#endif

                        case O_IP4:
                                match = is_ipv4;
                                break;

                        /*
                         * 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_DENY;
                                        goto done; /* error/limit violation */
                                }
                                match = 1;
                                break;

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

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

                        case O_PIPE:
                        case O_QUEUE:
                                args->rule = f; /* report matching rule */
                                args->cookie = cmd->arg1;
                                retval = IP_FW_DUMMYNET;
                                goto done;

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

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

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

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

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

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

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

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

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

next_rule:;             /* try next rule                */

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

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

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

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

        IPFW_WLOCK_ASSERT(chain);

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

/*
 * 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);
        }
        /*
         * Now go for the individual checks. Very simple ones, basically only
         * instruction sizes.
         */
        for (l = rule->cmd_len, cmd = rule->cmd ;
                        l > 0 ; l -= cmdlen, cmd += cmdlen) {
                cmdlen = F_LEN(cmd);
                if (cmdlen > l) {
                        printf("ipfw: opcode %d size truncated\n",
                            cmd->opcode);
                        return EINVAL;
                }
                DEB(printf("ipfw: opcode %d\n", cmd->opcode);)
                switch (cmd->opcode) {
                case O_PROBE_STATE:
                case O_KEEP_STATE:
                case O_PROTO:
                case O_IP_SRC_ME:
                case O_IP_DST_ME:
                case O_LAYER2:
                case O_IN:
                case O_FRAG:
                case O_DIVERTED:
                case O_IPOPT:
                case O_IPTOS:
                case O_IPPRECEDENCE:
                case O_IPVER:
                case O_TCPWIN:
                case O_TCPFLAGS:
                case O_TCPOPTS:
                case O_ESTAB:
                case O_VERREVPATH:
                case O_VERSRCREACH:
                case O_ANTISPOOF:
                case O_IPSEC:
#ifdef INET6
                case O_IP6_SRC_ME:
                case O_IP6_DST_ME:
                case O_EXT_HDR:
                case O_IP6:
#endif
                case O_IP4:
                        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:
                        if (ip_divert_ptr == NULL)
                                return EINVAL;
                        else
                                goto check_size;
                case O_NETGRAPH:
                case O_NGTEE:
                        if (!NG_IPFW_LOADED)
                                return EINVAL;
                        else
                                goto check_size;
                case O_FORWARD_MAC: /* XXX not implemented yet */
                case O_CHECK_STATE:
                case O_COUNT:
                case O_ACCEPT:
                case O_DENY:
                case O_REJECT:
#ifdef INET6
                case O_UNREACH6:
#endif
                case O_SKIPTO:
check_size:
                        if (cmdlen != F_INSN_SIZE(ipfw_insn))
                                goto bad_size;
check_action:
                        if (have_action) {
                                printf("ipfw: opcode %d, multiple actions"
                                        " not allowed\n",
                                        cmd->opcode);
                                return EINVAL;
                        }
                        have_action = 1;
                        if (l != cmdlen) {
                                printf("ipfw: opcode %d, action must be"
                                        " last opcode\n",
                                        cmd->opcode);
                                return EINVAL;
                        }
                        break;
#ifdef INET6
                case O_IP6_SRC:
                case O_IP6_DST:
                        if (cmdlen != F_INSN_SIZE(struct in6_addr) +
                            F_INSN_SIZE(ipfw_insn))
                                goto bad_size;
                        break;

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

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

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

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

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

        /* 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_uptime) ?
                                                0 : dst->expire - time_uptime ;
                                        bp += sizeof(ipfw_dyn_rule);
                                }
                        }
                IPFW_DYN_UNLOCK();
                if (last != NULL) /* mark last dynamic rule */
                        bzero(&last->next, sizeof(last));
        }
        return (bp - (char *)buf);
}


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

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

        /*
         * Disallow modifications in really-really secure mode, but still allow
         * the logging counters to be reset.
         */
        if (sopt->sopt_name == IP_FW_ADD ||
            (sopt->sopt_dir == SOPT_SET && sopt->sopt_name != IP_FW_RESETLOG)) {
#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_uptime+dyn_keepalive_interval,
                            q->expire))
                                continue;       /* too early */
                        if (TIME_LEQ(q->expire, time_uptime))
                                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;

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

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

        bzero(&default_rule, sizeof default_rule);

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

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

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

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

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

        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);

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

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