xref: /freebsd/sys/netpfil/ipfw/ip_fw2.c (revision 4a77657cbc011ea657ccb079fff6b58b295eccb0)

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2002-2009 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.
 */

#include <sys/cdefs.h>
/*
 * The FreeBSD IP packet firewall, main file
 */

#include "opt_ipfw.h"
#include "opt_ipdivert.h"
#include "opt_inet.h"
#ifndef INET
#error "IPFIREWALL requires INET"
#endif /* INET */
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/condvar.h>
#include <sys/counter.h>
#include <sys/eventhandler.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/jail.h>
#include <sys/module.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/rmlock.h>
#include <sys/sdt.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/ucred.h>
#include <net/ethernet.h> /* for ETHERTYPE_IP */
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_private.h>
#include <net/route.h>
#include <net/route/nhop.h>
#include <net/pfil.h>
#include <net/vnet.h>
#include <net/if_pfsync.h>

#include <netpfil/pf/pf_mtag.h>

#include <netinet/in.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_carp.h>
#include <netinet/pim.h>
#include <netinet/tcp_var.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netinet/sctp.h>
#include <netinet/sctp_crc32.h>
#include <netinet/sctp_header.h>

#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <netinet/in_fib.h>
#ifdef INET6
#include <netinet6/in6_fib.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/scope6_var.h>
#include <netinet6/ip6_var.h>
#endif

#include <net/if_gre.h> /* for struct grehdr */

#include <netpfil/ipfw/ip_fw_private.h>

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

#ifdef MAC
#include <security/mac/mac_framework.h>
#endif

#define	IPFW_PROBE(probe, arg0, arg1, arg2, arg3, arg4, arg5)		\
    SDT_PROBE6(ipfw, , , probe, arg0, arg1, arg2, arg3, arg4, arg5)

SDT_PROVIDER_DEFINE(ipfw);
SDT_PROBE_DEFINE6(ipfw, , , rule__matched,
    "int",			/* retval */
    "int",			/* af */
    "void *",			/* src addr */
    "void *",			/* dst addr */
    "struct ip_fw_args *",	/* args */
    "struct ip_fw *"		/* rule */);

/*
 * static variables followed by global ones.
 * All ipfw global variables are here.
 */

VNET_DEFINE_STATIC(int, fw_deny_unknown_exthdrs);
#define	V_fw_deny_unknown_exthdrs	VNET(fw_deny_unknown_exthdrs)

VNET_DEFINE_STATIC(int, fw_permit_single_frag6) = 1;
#define	V_fw_permit_single_frag6	VNET(fw_permit_single_frag6)

#ifdef IPFIREWALL_DEFAULT_TO_ACCEPT
static int default_to_accept = 1;
#else
static int default_to_accept;
#endif

VNET_DEFINE(int, autoinc_step);
VNET_DEFINE(int, fw_one_pass) = 1;

VNET_DEFINE(unsigned int, fw_tables_max);
VNET_DEFINE(unsigned int, fw_tables_sets) = 0;	/* Don't use set-aware tables */
/* Use 128 tables by default */
static unsigned int default_fw_tables = IPFW_TABLES_DEFAULT;

#ifndef IPFIREWALL_LINEAR_SKIPTO
VNET_DEFINE(int, skipto_cache) = 0;
#else
VNET_DEFINE(int, skipto_cache) = 1;
#endif

static uint32_t jump(struct ip_fw_chain *chain, struct ip_fw *f,
    uint32_t num, int tablearg, bool jump_backwards);

/*
 * Each rule belongs to one of 32 different sets (0..31).
 * The variable set_disable contains one bit per set.
 * If the bit is set, all rules in 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 individually.
 */
VNET_DEFINE(u_int32_t, set_disable);
#define	V_set_disable			VNET(set_disable)

VNET_DEFINE(int, fw_verbose);
/* counter for ipfw_log(NULL...) */
VNET_DEFINE(u_int64_t, norule_counter);
VNET_DEFINE(int, verbose_limit);

/* layer3_chain contains the list of rules for layer 3 */
VNET_DEFINE(struct ip_fw_chain, layer3_chain);

/* ipfw_vnet_ready controls when we are open for business */
VNET_DEFINE(int, ipfw_vnet_ready) = 0;

VNET_DEFINE(int, ipfw_nat_ready) = 0;

ipfw_nat_t *ipfw_nat_ptr = NULL;
struct cfg_nat *(*lookup_nat_ptr)(struct nat_list *, int);
ipfw_nat_cfg_t *ipfw_nat_cfg_ptr;
ipfw_nat_cfg_t *ipfw_nat_del_ptr;
ipfw_nat_cfg_t *ipfw_nat_get_cfg_ptr;
ipfw_nat_cfg_t *ipfw_nat_get_log_ptr;

#ifdef SYSCTL_NODE
uint32_t dummy_def = IPFW_DEFAULT_RULE;
static int sysctl_ipfw_table_num(SYSCTL_HANDLER_ARGS);
static int sysctl_ipfw_tables_sets(SYSCTL_HANDLER_ARGS);

SYSBEGIN(f3)

SYSCTL_NODE(_net_inet_ip, OID_AUTO, fw, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Firewall");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, one_pass,
    CTLFLAG_VNET | CTLFLAG_RW | CTLFLAG_SECURE3, &VNET_NAME(fw_one_pass), 0,
    "Only do a single pass through ipfw when using dummynet(4)");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, autoinc_step,
    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(autoinc_step), 0,
    "Rule number auto-increment step");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, verbose,
    CTLFLAG_VNET | CTLFLAG_RW | CTLFLAG_SECURE3, &VNET_NAME(fw_verbose), 0,
    "Log matches to ipfw rules");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, verbose_limit,
    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(verbose_limit), 0,
    "Set upper limit of matches of ipfw rules logged");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, skipto_cache,
    CTLFLAG_VNET | CTLFLAG_RD, &VNET_NAME(skipto_cache), 0,
    "Status of linear skipto cache: 1 - enabled, 0 - disabled.");
SYSCTL_UINT(_net_inet_ip_fw, OID_AUTO, default_rule, CTLFLAG_RD,
    &dummy_def, 0,
    "The default/max possible rule number.");
SYSCTL_PROC(_net_inet_ip_fw, OID_AUTO, tables_max,
    CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE,
    0, 0, sysctl_ipfw_table_num, "IU",
    "Maximum number of concurrently used tables");
SYSCTL_PROC(_net_inet_ip_fw, OID_AUTO, tables_sets,
    CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE,
    0, 0, sysctl_ipfw_tables_sets, "IU",
    "Use per-set namespace for tables");
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, default_to_accept, CTLFLAG_RDTUN,
    &default_to_accept, 0,
    "Make the default rule accept all packets.");
TUNABLE_INT("net.inet.ip.fw.tables_max", (int *)&default_fw_tables);
SYSCTL_INT(_net_inet_ip_fw, OID_AUTO, static_count,
    CTLFLAG_VNET | CTLFLAG_RD, &VNET_NAME(layer3_chain.n_rules), 0,
    "Number of static rules");

#ifdef INET6
SYSCTL_DECL(_net_inet6_ip6);
SYSCTL_NODE(_net_inet6_ip6, OID_AUTO, fw, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "Firewall");
SYSCTL_INT(_net_inet6_ip6_fw, OID_AUTO, deny_unknown_exthdrs,
    CTLFLAG_VNET | CTLFLAG_RW | CTLFLAG_SECURE,
    &VNET_NAME(fw_deny_unknown_exthdrs), 0,
    "Deny packets with unknown IPv6 Extension Headers");
SYSCTL_INT(_net_inet6_ip6_fw, OID_AUTO, permit_single_frag6,
    CTLFLAG_VNET | CTLFLAG_RW | CTLFLAG_SECURE,
    &VNET_NAME(fw_permit_single_frag6), 0,
    "Permit single packet IPv6 fragments");
#endif /* INET6 */

SYSEND

#endif /* SYSCTL_NODE */

/*
 * Some macros used in the various matching options.
 * 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	SCTP(p)		((struct sctphdr *)(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));
}

/*
 * Parse TCP options. The logic copied from tcp_dooptions().
 */
static int
tcpopts_parse(const struct tcphdr *tcp, uint16_t *mss)
{
	const u_char *cp = (const u_char *)(tcp + 1);
	int optlen, bits = 0;
	int cnt = (tcp->th_off << 2) - sizeof(struct tcphdr);

	for (; cnt > 0; cnt -= optlen, cp += optlen) {
		int opt = cp[0];
		if (opt == TCPOPT_EOL)
			break;
		if (opt == TCPOPT_NOP)
			optlen = 1;
		else {
			if (cnt < 2)
				break;
			optlen = cp[1];
			if (optlen < 2 || optlen > cnt)
				break;
		}

		switch (opt) {
		default:
			break;

		case TCPOPT_MAXSEG:
			if (optlen != TCPOLEN_MAXSEG)
				break;
			bits |= IP_FW_TCPOPT_MSS;
			if (mss != NULL)
				*mss = be16dec(cp + 2);
			break;

		case TCPOPT_WINDOW:
			if (optlen == TCPOLEN_WINDOW)
				bits |= IP_FW_TCPOPT_WINDOW;
			break;

		case TCPOPT_SACK_PERMITTED:
			if (optlen == TCPOLEN_SACK_PERMITTED)
				bits |= IP_FW_TCPOPT_SACK;
			break;

		case TCPOPT_SACK:
			if (optlen > 2 && (optlen - 2) % TCPOLEN_SACK == 0)
				bits |= IP_FW_TCPOPT_SACK;
			break;

		case TCPOPT_TIMESTAMP:
			if (optlen == TCPOLEN_TIMESTAMP)
				bits |= IP_FW_TCPOPT_TS;
			break;
		}
	}
	return (bits);
}

static int
tcpopts_match(struct tcphdr *tcp, ipfw_insn *cmd)
{

	return (flags_match(cmd, tcpopts_parse(tcp, NULL)));
}

static int
iface_match(struct ifnet *ifp, ipfw_insn_if *cmd, struct ip_fw_chain *chain,
    uint32_t *tablearg)
{

	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 */
		if (cmd->name[0] == '\1') /* use tablearg to match */
			return ipfw_lookup_table(chain, cmd->p.kidx, 0,
			    &ifp->if_index, tablearg);
		/* 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 {
#if !defined(USERSPACE) && defined(__FreeBSD__)	/* and OSX too ? */
		struct ifaddr *ia;

		NET_EPOCH_ASSERT();

		CK_STAILQ_FOREACH(ia, &ifp->if_addrhead, ifa_link) {
			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 */
		}
#endif /* __FreeBSD__ */
	}
	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 the syntax
 * is misleading, and 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, u_int fib)
{
#if defined(USERSPACE) || !defined(__FreeBSD__)
	return 0;
#else
	struct nhop_object *nh;

	nh = fib4_lookup(fib, src, 0, NHR_NONE, 0);
	if (nh == NULL)
		return (0);

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

	/* if no ifp provided, check if rtentry is not default route */
	if (ifp == NULL && (nh->nh_flags & NHF_DEFAULT) != 0)
		return (0);

	/* or if this is a blackhole/reject route */
	if (ifp == NULL && (nh->nh_flags & (NHF_REJECT|NHF_BLACKHOLE)) != 0)
		return (0);

	/* found valid route */
	return 1;
#endif /* __FreeBSD__ */
}

/*
 * Generate an SCTP packet containing an ABORT chunk. The verification tag
 * is given by vtag. The T-bit is set in the ABORT chunk if and only if
 * reflected is not 0.
 */

static struct mbuf *
ipfw_send_abort(struct mbuf *replyto, struct ipfw_flow_id *id, u_int32_t vtag,
    int reflected)
{
	struct mbuf *m;
	struct ip *ip;
#ifdef INET6
	struct ip6_hdr *ip6;
#endif
	struct sctphdr *sctp;
	struct sctp_chunkhdr *chunk;
	u_int16_t hlen, plen, tlen;

	MGETHDR(m, M_NOWAIT, MT_DATA);
	if (m == NULL)
		return (NULL);

	M_SETFIB(m, id->fib);
#ifdef MAC
	if (replyto != NULL)
		mac_netinet_firewall_reply(replyto, m);
	else
		mac_netinet_firewall_send(m);
#else
	(void)replyto;		/* don't warn about unused arg */
#endif

	switch (id->addr_type) {
	case 4:
		hlen = sizeof(struct ip);
		break;
#ifdef INET6
	case 6:
		hlen = sizeof(struct ip6_hdr);
		break;
#endif
	default:
		/* XXX: log me?!? */
		FREE_PKT(m);
		return (NULL);
	}
	plen = sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr);
	tlen = hlen + plen;
	m->m_data += max_linkhdr;
	m->m_flags |= M_SKIP_FIREWALL;
	m->m_pkthdr.len = m->m_len = tlen;
	m->m_pkthdr.rcvif = NULL;
	bzero(m->m_data, tlen);

	switch (id->addr_type) {
	case 4:
		ip = mtod(m, struct ip *);

		ip->ip_v = 4;
		ip->ip_hl = sizeof(struct ip) >> 2;
		ip->ip_tos = IPTOS_LOWDELAY;
		ip->ip_len = htons(tlen);
		ip->ip_id = htons(0);
		ip->ip_off = htons(0);
		ip->ip_ttl = V_ip_defttl;
		ip->ip_p = IPPROTO_SCTP;
		ip->ip_sum = 0;
		ip->ip_src.s_addr = htonl(id->dst_ip);
		ip->ip_dst.s_addr = htonl(id->src_ip);

		sctp = (struct sctphdr *)(ip + 1);
		break;
#ifdef INET6
	case 6:
		ip6 = mtod(m, struct ip6_hdr *);

		ip6->ip6_vfc = IPV6_VERSION;
		ip6->ip6_plen = htons(plen);
		ip6->ip6_nxt = IPPROTO_SCTP;
		ip6->ip6_hlim = IPV6_DEFHLIM;
		ip6->ip6_src = id->dst_ip6;
		ip6->ip6_dst = id->src_ip6;

		sctp = (struct sctphdr *)(ip6 + 1);
		break;
#endif
	}

	sctp->src_port = htons(id->dst_port);
	sctp->dest_port = htons(id->src_port);
	sctp->v_tag = htonl(vtag);
	sctp->checksum = htonl(0);

	chunk = (struct sctp_chunkhdr *)(sctp + 1);
	chunk->chunk_type = SCTP_ABORT_ASSOCIATION;
	chunk->chunk_flags = 0;
	if (reflected != 0) {
		chunk->chunk_flags |= SCTP_HAD_NO_TCB;
	}
	chunk->chunk_length = htons(sizeof(struct sctp_chunkhdr));

	sctp->checksum = sctp_calculate_cksum(m, hlen);

	return (m);
}

/*
 * Generate a TCP packet, containing either a RST or a keepalive.
 * When flags & TH_RST, we are sending a RST packet, because of a
 * "reset" action matched the packet.
 * Otherwise we are sending a keepalive, and flags & TH_
 * The 'replyto' mbuf is the mbuf being replied to, if any, and is required
 * so that MAC can label the reply appropriately.
 */
struct mbuf *
ipfw_send_pkt(struct mbuf *replyto, struct ipfw_flow_id *id, u_int32_t seq,
    u_int32_t ack, int flags)
{
	struct mbuf *m = NULL;		/* stupid compiler */
	struct ip *h = NULL;		/* stupid compiler */
#ifdef INET6
	struct ip6_hdr *h6 = NULL;
#endif
	struct tcphdr *th = NULL;
	int len, dir;

	MGETHDR(m, M_NOWAIT, MT_DATA);
	if (m == NULL)
		return (NULL);

	M_SETFIB(m, id->fib);
#ifdef MAC
	if (replyto != NULL)
		mac_netinet_firewall_reply(replyto, m);
	else
		mac_netinet_firewall_send(m);
#else
	(void)replyto;		/* don't warn about unused arg */
#endif

	switch (id->addr_type) {
	case 4:
		len = sizeof(struct ip) + sizeof(struct tcphdr);
		break;
#ifdef INET6
	case 6:
		len = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
		break;
#endif
	default:
		/* XXX: log me?!? */
		FREE_PKT(m);
		return (NULL);
	}
	dir = ((flags & (TH_SYN | TH_RST)) == TH_SYN);

	m->m_data += max_linkhdr;
	m->m_flags |= M_SKIP_FIREWALL;
	m->m_pkthdr.len = m->m_len = len;
	m->m_pkthdr.rcvif = NULL;
	bzero(m->m_data, len);

	switch (id->addr_type) {
	case 4:
		h = mtod(m, struct ip *);

		/* prepare for checksum */
		h->ip_p = IPPROTO_TCP;
		h->ip_len = htons(sizeof(struct tcphdr));
		if (dir) {
			h->ip_src.s_addr = htonl(id->src_ip);
			h->ip_dst.s_addr = htonl(id->dst_ip);
		} else {
			h->ip_src.s_addr = htonl(id->dst_ip);
			h->ip_dst.s_addr = htonl(id->src_ip);
		}

		th = (struct tcphdr *)(h + 1);
		break;
#ifdef INET6
	case 6:
		h6 = mtod(m, struct ip6_hdr *);

		/* prepare for checksum */
		h6->ip6_nxt = IPPROTO_TCP;
		h6->ip6_plen = htons(sizeof(struct tcphdr));
		if (dir) {
			h6->ip6_src = id->src_ip6;
			h6->ip6_dst = id->dst_ip6;
		} else {
			h6->ip6_src = id->dst_ip6;
			h6->ip6_dst = id->src_ip6;
		}

		th = (struct tcphdr *)(h6 + 1);
		break;
#endif
	}

	if (dir) {
		th->th_sport = htons(id->src_port);
		th->th_dport = htons(id->dst_port);
	} else {
		th->th_sport = htons(id->dst_port);
		th->th_dport = htons(id->src_port);
	}
	th->th_off = sizeof(struct tcphdr) >> 2;

	if (flags & TH_RST) {
		if (flags & TH_ACK) {
			th->th_seq = htonl(ack);
			tcp_set_flags(th, TH_RST);
		} else {
			if (flags & TH_SYN)
				seq++;
			th->th_ack = htonl(seq);
			tcp_set_flags(th, TH_RST | TH_ACK);
		}
	} else {
		/*
		 * Keepalive - use caller provided sequence numbers
		 */
		th->th_seq = htonl(seq);
		th->th_ack = htonl(ack);
		tcp_set_flags(th, TH_ACK);
	}

	switch (id->addr_type) {
	case 4:
		th->th_sum = in_cksum(m, len);

		/* finish the ip header */
		h->ip_v = 4;
		h->ip_hl = sizeof(*h) >> 2;
		h->ip_tos = IPTOS_LOWDELAY;
		h->ip_off = htons(0);
		h->ip_len = htons(len);
		h->ip_ttl = V_ip_defttl;
		h->ip_sum = 0;
		break;
#ifdef INET6
	case 6:
		th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(*h6),
		    sizeof(struct tcphdr));

		/* finish the ip6 header */
		h6->ip6_vfc |= IPV6_VERSION;
		h6->ip6_hlim = IPV6_DEFHLIM;
		break;
#endif
	}

	return (m);
}

#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 const struct in6_addr lla_mask = {{{
	0xff, 0xff, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
}}};

static int
ipfw_localip6(struct in6_addr *in6)
{
	struct rm_priotracker in6_ifa_tracker;
	struct in6_ifaddr *ia;

	if (IN6_IS_ADDR_MULTICAST(in6))
		return (0);

	if (!IN6_IS_ADDR_LINKLOCAL(in6))
		return (in6_localip(in6));

	IN6_IFADDR_RLOCK(&in6_ifa_tracker);
	CK_STAILQ_FOREACH(ia, &V_in6_ifaddrhead, ia_link) {
		if (!IN6_IS_ADDR_LINKLOCAL(&ia->ia_addr.sin6_addr))
			continue;
		if (IN6_ARE_MASKED_ADDR_EQUAL(&ia->ia_addr.sin6_addr,
		    in6, &lla_mask)) {
			IN6_IFADDR_RUNLOCK(&in6_ifa_tracker);
			return (1);
		}
	}
	IN6_IFADDR_RUNLOCK(&in6_ifa_tracker);
	return (0);
}

static int
verify_path6(struct in6_addr *src, struct ifnet *ifp, u_int fib)
{
	struct nhop_object *nh;

	if (IN6_IS_SCOPE_LINKLOCAL(src))
		return (1);

	nh = fib6_lookup(fib, src, 0, NHR_NONE, 0);
	if (nh == NULL)
		return (0);

	/* If ifp is provided, check for equality with route table. */
	if (ifp != NULL && ifp != nh->nh_aifp)
		return (0);

	/* if no ifp provided, check if rtentry is not default route */
	if (ifp == NULL && (nh->nh_flags & NHF_DEFAULT) != 0)
		return (0);

	/* or if this is a blackhole/reject route */
	if (ifp == NULL && (nh->nh_flags & (NHF_REJECT|NHF_BLACKHOLE)) != 0)
		return (0);

	/* found valid route */
	return 1;
}

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 int
map_icmp_unreach(int code)
{

	/* RFC 7915 p4.2 */
	switch (code) {
	case ICMP_UNREACH_NET:
	case ICMP_UNREACH_HOST:
	case ICMP_UNREACH_SRCFAIL:
	case ICMP_UNREACH_NET_UNKNOWN:
	case ICMP_UNREACH_HOST_UNKNOWN:
	case ICMP_UNREACH_TOSNET:
	case ICMP_UNREACH_TOSHOST:
		return (ICMP6_DST_UNREACH_NOROUTE);
	case ICMP_UNREACH_PORT:
		return (ICMP6_DST_UNREACH_NOPORT);
	default:
		/*
		 * Map the rest of codes into admit prohibited.
		 * XXX: unreach proto should be mapped into ICMPv6
		 * parameter problem, but we use only unreach type.
		 */
		return (ICMP6_DST_UNREACH_ADMIN);
	}
}

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

	m = args->m;
	if (code == ICMP6_UNREACH_RST && args->f_id.proto == IPPROTO_TCP) {
		const struct tcphdr * tcp;
		tcp = (const struct tcphdr *)((const char *)ip6 + hlen);

		if ((tcp_get_flags(tcp) & TH_RST) == 0) {
			struct mbuf *m0;
			m0 = ipfw_send_pkt(args->m, &(args->f_id),
			    ntohl(tcp->th_seq), ntohl(tcp->th_ack),
			    tcp_get_flags(tcp) | TH_RST);
			if (m0 != NULL)
				ip6_output(m0, NULL, NULL, 0, NULL, NULL,
				    NULL);
		}
		FREE_PKT(m);
	} else if (code == ICMP6_UNREACH_ABORT &&
	    args->f_id.proto == IPPROTO_SCTP) {
		struct mbuf *m0;
		const struct sctphdr *sctp;
		u_int32_t v_tag;
		int reflected;

		sctp = (const struct sctphdr *)((const char *)ip6 + hlen);
		reflected = 1;
		v_tag = ntohl(sctp->v_tag);
		/* Investigate the first chunk header if available */
		if (m->m_len >= hlen + sizeof(struct sctphdr) +
		    sizeof(struct sctp_chunkhdr)) {
			const struct sctp_chunkhdr *chunk;

			chunk = (const struct sctp_chunkhdr *)(sctp + 1);
			switch (chunk->chunk_type) {
			case SCTP_INITIATION:
				/*
				 * Packets containing an INIT chunk MUST have
				 * a zero v-tag.
				 */
				if (v_tag != 0) {
					v_tag = 0;
					break;
				}
				/* INIT chunk MUST NOT be bundled */
				if (m->m_pkthdr.len >
				    hlen + sizeof(struct sctphdr) +
				    ntohs(chunk->chunk_length) + 3) {
					break;
				}
				/* Use the initiate tag if available */
				if ((m->m_len >= hlen + sizeof(struct sctphdr) +
				    sizeof(struct sctp_chunkhdr) +
				    offsetof(struct sctp_init, a_rwnd))) {
					const struct sctp_init *init;

					init = (const struct sctp_init *)(chunk + 1);
					v_tag = ntohl(init->initiate_tag);
					reflected = 0;
				}
				break;
			case SCTP_ABORT_ASSOCIATION:
				/*
				 * If the packet contains an ABORT chunk, don't
				 * reply.
				 * XXX: We should search through all chunks,
				 * but do not do that to avoid attacks.
				 */
				v_tag = 0;
				break;
			}
		}
		if (v_tag == 0) {
			m0 = NULL;
		} else {
			m0 = ipfw_send_abort(args->m, &(args->f_id), v_tag,
			    reflected);
		}
		if (m0 != NULL)
			ip6_output(m0, NULL, NULL, 0, NULL, NULL, NULL);
		FREE_PKT(m);
	} else if (code != ICMP6_UNREACH_RST && code != ICMP6_UNREACH_ABORT) {
		/* Send an ICMPv6 unreach. */
#if 0
		/*
		 * Unlike above, the mbufs need to line up with the ip6 hdr,
		 * as the contents are read. We need to m_adj() the
		 * needed amount.
		 * The mbuf will however be thrown away so we can adjust it.
		 * Remember we did an m_pullup on it already so we
		 * can make some assumptions about contiguousness.
		 */
		if (args->L3offset)
			m_adj(m, args->L3offset);
#endif
		icmp6_error(m, ICMP6_DST_UNREACH, code, 0);
	} else
		FREE_PKT(m);

	args->m = NULL;
}

#endif /* INET6 */

/*
 * sends a reject message, consuming the mbuf passed as an argument.
 */
static void
send_reject(struct ip_fw_args *args, int code, uint16_t mtu, int iplen,
    const struct ip *ip)
{
#if 0
	/* XXX When ip is not guaranteed to be at mtod() we will
	 * need to account for this */
	 * The mbuf will however be thrown away so we can adjust it.
	 * Remember we did an m_pullup on it already so we
	 * can make some assumptions about contiguousness.
	 */
	if (args->L3offset)
		m_adj(m, args->L3offset);
#endif
	if (code != ICMP_REJECT_RST && code != ICMP_REJECT_ABORT) {
		/* Send an ICMP unreach */
		icmp_error(args->m, ICMP_UNREACH, code, 0L, mtu);
	} else if (code == ICMP_REJECT_RST && args->f_id.proto == IPPROTO_TCP) {
		struct tcphdr *const tcp =
		    L3HDR(struct tcphdr, mtod(args->m, struct ip *));
		if ( (tcp_get_flags(tcp) & TH_RST) == 0) {
			struct mbuf *m;
			m = ipfw_send_pkt(args->m, &(args->f_id),
				ntohl(tcp->th_seq), ntohl(tcp->th_ack),
				tcp_get_flags(tcp) | TH_RST);
			if (m != NULL)
				ip_output(m, NULL, NULL, 0, NULL, NULL);
		}
		FREE_PKT(args->m);
	} else if (code == ICMP_REJECT_ABORT &&
	    args->f_id.proto == IPPROTO_SCTP) {
		struct mbuf *m;
		struct sctphdr *sctp;
		struct sctp_chunkhdr *chunk;
		struct sctp_init *init;
		u_int32_t v_tag;
		int reflected;

		sctp = L3HDR(struct sctphdr, mtod(args->m, struct ip *));
		reflected = 1;
		v_tag = ntohl(sctp->v_tag);
		if (iplen >= (ip->ip_hl << 2) + sizeof(struct sctphdr) +
		    sizeof(struct sctp_chunkhdr)) {
			/* Look at the first chunk header if available */
			chunk = (struct sctp_chunkhdr *)(sctp + 1);
			switch (chunk->chunk_type) {
			case SCTP_INITIATION:
				/*
				 * Packets containing an INIT chunk MUST have
				 * a zero v-tag.
				 */
				if (v_tag != 0) {
					v_tag = 0;
					break;
				}
				/* INIT chunk MUST NOT be bundled */
				if (iplen >
				    (ip->ip_hl << 2) + sizeof(struct sctphdr) +
				    ntohs(chunk->chunk_length) + 3) {
					break;
				}
				/* Use the initiate tag if available */
				if ((iplen >= (ip->ip_hl << 2) +
				    sizeof(struct sctphdr) +
				    sizeof(struct sctp_chunkhdr) +
				    offsetof(struct sctp_init, a_rwnd))) {
					init = (struct sctp_init *)(chunk + 1);
					v_tag = ntohl(init->initiate_tag);
					reflected = 0;
				}
				break;
			case SCTP_ABORT_ASSOCIATION:
				/*
				 * If the packet contains an ABORT chunk, don't
				 * reply.
				 * XXX: We should search through all chunks,
				 * but do not do that to avoid attacks.
				 */
				v_tag = 0;
				break;
			}
		}
		if (v_tag == 0) {
			m = NULL;
		} else {
			m = ipfw_send_abort(args->m, &(args->f_id), v_tag,
			    reflected);
		}
		if (m != NULL)
			ip_output(m, NULL, NULL, 0, NULL, NULL);
		FREE_PKT(args->m);
	} else
		FREE_PKT(args->m);
	args->m = NULL;
}

/*
 * Support for uid/gid/jail lookup. These tests are expensive
 * (because we may need to look into the list of active sockets)
 * so we cache the results. ugid_lookupp is 0 if we have not
 * yet done a lookup, 1 if we succeeded, and -1 if we tried
 * and failed. The function always returns the match value.
 * We could actually spare the variable and use *uc, setting
 * it to '(void *)check_uidgid if we have no info, NULL if
 * we tried and failed, or any other value if successful.
 */
static int
check_uidgid(ipfw_insn_u32 *insn, struct ip_fw_args *args, int *ugid_lookupp,
    struct ucred **uc)
{
#if defined(USERSPACE)
	return 0;	// not supported in userspace
#else
#ifndef __FreeBSD__
	/* XXX */
	return cred_check(insn, proto, oif,
	    dst_ip, dst_port, src_ip, src_port,
	    (struct bsd_ucred *)uc, ugid_lookupp, ((struct mbuf *)inp)->m_skb);
#else  /* FreeBSD */
	struct in_addr src_ip, dst_ip;
	struct inpcbinfo *pi;
	struct ipfw_flow_id *id;
	struct inpcb *pcb, *inp;
	int lookupflags;
	int match;

	id = &args->f_id;
	inp = args->inp;

	/*
	 * 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 && *ugid_lookupp == 0) {
		INP_LOCK_ASSERT(inp);
		if (inp->inp_socket != NULL) {
			*uc = crhold(inp->inp_cred);
			*ugid_lookupp = 1;
		} else
			*ugid_lookupp = -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 (*ugid_lookupp == -1)
		return (0);
	if (id->proto == IPPROTO_TCP) {
		lookupflags = 0;
		pi = &V_tcbinfo;
	} else if (id->proto == IPPROTO_UDP) {
		lookupflags = INPLOOKUP_WILDCARD;
		pi = &V_udbinfo;
	} else if (id->proto == IPPROTO_UDPLITE) {
		lookupflags = INPLOOKUP_WILDCARD;
		pi = &V_ulitecbinfo;
	} else
		return 0;
	lookupflags |= INPLOOKUP_RLOCKPCB;
	match = 0;
	if (*ugid_lookupp == 0) {
		if (id->addr_type == 6) {
#ifdef INET6
			if (args->flags & IPFW_ARGS_IN)
				pcb = in6_pcblookup_mbuf(pi,
				    &id->src_ip6, htons(id->src_port),
				    &id->dst_ip6, htons(id->dst_port),
				    lookupflags, NULL, args->m);
			else
				pcb = in6_pcblookup_mbuf(pi,
				    &id->dst_ip6, htons(id->dst_port),
				    &id->src_ip6, htons(id->src_port),
				    lookupflags, args->ifp, args->m);
#else
			*ugid_lookupp = -1;
			return (0);
#endif
		} else {
			src_ip.s_addr = htonl(id->src_ip);
			dst_ip.s_addr = htonl(id->dst_ip);
			if (args->flags & IPFW_ARGS_IN)
				pcb = in_pcblookup_mbuf(pi,
				    src_ip, htons(id->src_port),
				    dst_ip, htons(id->dst_port),
				    lookupflags, NULL, args->m);
			else
				pcb = in_pcblookup_mbuf(pi,
				    dst_ip, htons(id->dst_port),
				    src_ip, htons(id->src_port),
				    lookupflags, args->ifp, args->m);
		}
		if (pcb != NULL) {
			INP_RLOCK_ASSERT(pcb);
			*uc = crhold(pcb->inp_cred);
			*ugid_lookupp = 1;
			INP_RUNLOCK(pcb);
		}
		if (*ugid_lookupp == 0) {
			/*
			 * We tried and failed, set the variable to -1
			 * so we will not try again on this packet.
			 */
			*ugid_lookupp = -1;
			return (0);
		}
	}
	if (insn->o.opcode == O_UID)
		match = ((*uc)->cr_uid == (uid_t)insn->d[0]);
	else if (insn->o.opcode == O_GID)
		match = groupmember((gid_t)insn->d[0], *uc);
	else if (insn->o.opcode == O_JAIL)
		match = ((*uc)->cr_prison->pr_id == (int)insn->d[0]);
	return (match);
#endif /* __FreeBSD__ */
#endif /* not supported in userspace */
}

/*
 * Helper function to set args with info on the rule after the matching
 * one. slot is precise, whereas we guess rule_id as they are
 * assigned sequentially.
 */
static inline void
set_match(struct ip_fw_args *args, int slot,
	struct ip_fw_chain *chain)
{
	args->rule.chain_id = chain->id;
	args->rule.slot = slot + 1; /* we use 0 as a marker */
	args->rule.rule_id = 1 + chain->map[slot]->id;
	args->rule.rulenum = chain->map[slot]->rulenum;
	args->flags |= IPFW_ARGS_REF;
}

static uint32_t
jump_lookup_pos(struct ip_fw_chain *chain, struct ip_fw *f, uint32_t num,
    int tablearg, bool jump_backwards)
{
	int f_pos, i;

	/*
	 * Make sure we do not jump backward.
	 */
	i = IP_FW_ARG_TABLEARG(chain, num, skipto);
	if (!jump_backwards && i <= f->rulenum)
		i = f->rulenum + 1;

	if (V_skipto_cache == 0)
		f_pos = ipfw_find_rule(chain, i, 0);
	else {
		/*
		 * Make sure we do not do out of bounds access.
		 */
		if (i >= IPFW_DEFAULT_RULE)
			i = IPFW_DEFAULT_RULE - 1;
		f_pos = chain->idxmap[i];
	}

	return (f_pos);
}

static uint32_t
jump(struct ip_fw_chain *chain, struct ip_fw *f, uint32_t num,
    int tablearg, bool jump_backwards)
{
	int f_pos;

	/* Can't use cache with IP_FW_TARG */
	if (num == IP_FW_TARG)
		return jump_lookup_pos(chain, f, num, tablearg, jump_backwards);

	/*
	 * If possible use cached f_pos (in f->cache.pos),
	 * whose version is written in f->cache.id (horrible hacks
	 * to avoid changing the ABI).
	 *
	 * Multiple threads can execute the same rule simultaneously,
	 * we need to ensure that cache.pos is updated before cache.id.
	 */

#ifdef __LP64__
	struct ip_fw_jump_cache cache;

	cache.raw_value = f->cache.raw_value;
	if (cache.id == chain->id)
		return (cache.pos);

	f_pos = jump_lookup_pos(chain, f, num, tablearg, jump_backwards);

	cache.pos = f_pos;
	cache.id = chain->id;
	f->cache.raw_value = cache.raw_value;
#else
	if (f->cache.id == chain->id) {
		/* Load pos after id */
		atomic_thread_fence_acq();
		return (f->cache.pos);
	}

	f_pos = jump_lookup_pos(chain, f, num, tablearg, jump_backwards);

	f->cache.pos = f_pos;
	/* Store id after pos */
	atomic_thread_fence_rel();
	f->cache.id = chain->id;
#endif /* !__LP64__ */
	return (f_pos);
}

#define	TARG(k, f)	IP_FW_ARG_TABLEARG(chain, k, f)

static inline int
tvalue_match(struct ip_fw_chain *ch, const ipfw_insn_table *cmd,
    uint32_t tablearg)
{
	uint32_t tvalue;

	switch (IPFW_TVALUE_TYPE(&cmd->o)) {
	case TVALUE_PIPE:
		tvalue = TARG_VAL(ch, tablearg, pipe);
		break;
	case TVALUE_DIVERT:
		tvalue = TARG_VAL(ch, tablearg, divert);
		break;
	case TVALUE_SKIPTO:
		tvalue = TARG_VAL(ch, tablearg, skipto);
		break;
	case TVALUE_NETGRAPH:
		tvalue = TARG_VAL(ch, tablearg, netgraph);
		break;
	case TVALUE_FIB:
		tvalue = TARG_VAL(ch, tablearg, fib);
		break;
	case TVALUE_NAT:
		tvalue = TARG_VAL(ch, tablearg, nat);
		break;
	case TVALUE_NH4:
		tvalue = TARG_VAL(ch, tablearg, nh4);
		break;
	case TVALUE_DSCP:
		tvalue = TARG_VAL(ch, tablearg, dscp);
		break;
	case TVALUE_LIMIT:
		tvalue = TARG_VAL(ch, tablearg, limit);
		break;
	case TVALUE_MARK:
		tvalue = TARG_VAL(ch, tablearg, mark);
		break;
	case TVALUE_TAG:
	default:
		tvalue = TARG_VAL(ch, tablearg, tag);
		break;
	}
	return (tvalue == cmd->value);
}

/*
 * 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->L3offset	Number of bytes bypassed if we came from L2.
 *			e.g. often sizeof(eh)  ** NOTYET **
 *	args->ifp	Incoming or outgoing interface.
 *	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->next_hop6	IPv6 next hop we are forwarding to (out).
 *	args->f_id	Addresses grabbed from the packet (out)
 * 	args->rule.info	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
 *		args->rule contains the matching rule,
 *		args->rule.info has additional information.
 *
 */
int
ipfw_chk(struct ip_fw_args *args)
{

	/*
	 * Local variables holding state while processing 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.
	 *
	 * 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.
	 *	OR
	 * args->mem	Pointer to contigous memory chunk.
	 * ip	Is the beginning of the ip(4 or 6) header.
	 * eh	Ethernet header in case if input is Layer2.
	 */
	struct mbuf *m;
	struct ip *ip;
	struct ether_header *eh;

	/*
	 * 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.
	 */
#ifndef __FreeBSD__
	struct bsd_ucred ucred_cache;
#else
	struct ucred *ucred_cache = NULL;
#endif
	uint32_t f_pos = 0;	/* index of current rule in the array */
	int ucred_lookup = 0;
	int retval = 0;
	struct ifnet *oif, *iif;

	/*
	 * 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|ip6f_mf == 0 means there is no Fragment Header
	 *	or there is a single packet fragment (fragment header added
	 *	without needed).  We will treat a single packet fragment as if
	 *	there was no fragment header (or log/block depending on the
	 *	V_fw_permit_single_frag6 sysctl setting).
	 */
	u_short offset = 0;
	u_short ip6f_mf = 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.
	 */
	uint8_t proto;
	uint16_t src_port, dst_port;		/* NOTE: host format	*/
	struct in_addr src_ip, dst_ip;		/* NOTE: network format	*/
	int iplen = 0;
	int pktlen;

	struct ipfw_dyn_info dyn_info;
	struct ip_fw *q = NULL;
	struct ip_fw_chain *chain = &V_layer3_chain;

	/*
	 * 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;
#ifdef INET6
	uint8_t	icmp6_type = 0;
#endif
	uint16_t ext_hd = 0;	/* bits vector for extension header filtering */
	/* end of ipv6 variables */

	int is_ipv4 = 0;

	int done = 0;		/* flag to exit the outer loop */
	IPFW_RLOCK_TRACKER;
	bool mem;
	bool need_send_reject = false;
	int reject_code;
	uint16_t reject_mtu;

	if ((mem = (args->flags & IPFW_ARGS_LENMASK))) {
		if (args->flags & IPFW_ARGS_ETHER) {
			eh = (struct ether_header *)args->mem;
			if (eh->ether_type == htons(ETHERTYPE_VLAN))
				ip = (struct ip *)
				    ((struct ether_vlan_header *)eh + 1);
			else
				ip = (struct ip *)(eh + 1);
		} else {
			eh = NULL;
			ip = (struct ip *)args->mem;
		}
		pktlen = IPFW_ARGS_LENGTH(args->flags);
		args->f_id.fib = args->ifp->if_fib;	/* best guess */
	} else {
		m = args->m;
		if (m->m_flags & M_SKIP_FIREWALL || (! V_ipfw_vnet_ready))
			return (IP_FW_PASS);	/* accept */
		if (args->flags & IPFW_ARGS_ETHER) {
	                /* We need some amount of data to be contiguous. */
			if (m->m_len < min(m->m_pkthdr.len, max_protohdr) &&
			    (args->m = m = m_pullup(m, min(m->m_pkthdr.len,
			    max_protohdr))) == NULL)
				goto pullup_failed;
			eh = mtod(m, struct ether_header *);
			ip = (struct ip *)(eh + 1);
		} else {
			eh = NULL;
			ip = mtod(m, struct ip *);
		}
		pktlen = m->m_pkthdr.len;
		args->f_id.fib = M_GETFIB(m); /* mbuf not altered */
	}

	dst_ip.s_addr = 0;		/* make sure it is initialized */
	src_ip.s_addr = 0;		/* make sure it is initialized */
	src_port = dst_port = 0;

	DYN_INFO_INIT(&dyn_info);
/*
 * 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)	PULLUP_LEN(_len, p, sizeof(T))
#define	EHLEN	(eh != NULL ? ((char *)ip - (char *)eh) : 0)
#define	_PULLUP_LOCKED(_len, p, T, unlock)			\
do {								\
	int x = (_len) + T + EHLEN;				\
	if (mem) {						\
		if (__predict_false(pktlen < x)) {		\
			unlock;					\
			goto pullup_failed;			\
		}						\
		p = (char *)args->mem + (_len) + EHLEN;		\
	} else {						\
		if (__predict_false((m)->m_len < x)) {		\
			args->m = m = m_pullup(m, x);		\
			if (m == NULL) {			\
				unlock;				\
				goto pullup_failed;		\
			}					\
		}						\
		p = mtod(m, char *) + (_len) + EHLEN;		\
	}							\
} while (0)

#define	PULLUP_LEN(_len, p, T)	_PULLUP_LOCKED(_len, p, T, )
#define	PULLUP_LEN_LOCKED(_len, p, T)	\
    _PULLUP_LOCKED(_len, p, T, IPFW_PF_RUNLOCK(chain));	\
    UPDATE_POINTERS()
/*
 * In case pointers got stale after pullups, update them.
 */
#define	UPDATE_POINTERS()					\
do {								\
	if (!mem) {						\
		if (eh != NULL) {				\
			eh = mtod(m, struct ether_header *);	\
			ip = (struct ip *)(eh + 1);		\
		} else						\
			ip = mtod(m, struct ip *);		\
		args->m = m;					\
	}							\
} while (0)

	/* Identify IP packets and fill up variables. */
	if (pktlen >= sizeof(struct ip6_hdr) &&
	    (eh == NULL || eh->ether_type == htons(ETHERTYPE_IPV6)) &&
	    ip->ip_v == 6) {
		struct ip6_hdr *ip6 = (struct ip6_hdr *)ip;

		is_ipv6 = 1;
		args->flags |= IPFW_ARGS_IP6;
		hlen = sizeof(struct ip6_hdr);
		proto = ip6->ip6_nxt;
		/* Search extension headers to find upper layer protocols */
		while (ulp == NULL && offset == 0) {
			switch (proto) {
			case IPPROTO_ICMPV6:
				PULLUP_TO(hlen, ulp, struct icmp6_hdr);
#ifdef INET6
				icmp6_type = ICMP6(ulp)->icmp6_type;
#endif
				break;

			case IPPROTO_TCP:
				PULLUP_TO(hlen, ulp, struct tcphdr);
				dst_port = TCP(ulp)->th_dport;
				src_port = TCP(ulp)->th_sport;
				/* save flags for dynamic rules */
				args->f_id._flags = tcp_get_flags(TCP(ulp));
				break;

			case IPPROTO_SCTP:
				if (pktlen >= hlen + sizeof(struct sctphdr) +
				    sizeof(struct sctp_chunkhdr) +
				    offsetof(struct sctp_init, a_rwnd))
					PULLUP_LEN(hlen, ulp,
					    sizeof(struct sctphdr) +
					    sizeof(struct sctp_chunkhdr) +
					    offsetof(struct sctp_init, a_rwnd));
				else if (pktlen >= hlen + sizeof(struct sctphdr))
					PULLUP_LEN(hlen, ulp, pktlen - hlen);
				else
					PULLUP_LEN(hlen, ulp,
					    sizeof(struct sctphdr));
				src_port = SCTP(ulp)->src_port;
				dst_port = SCTP(ulp)->dest_port;
				break;

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

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

			case IPPROTO_ROUTING:	/* RFC 2460 */
				PULLUP_TO(hlen, ulp, struct ip6_rthdr);
				switch (((struct ip6_rthdr *)ulp)->ip6r_type) {
				case 0:
					ext_hd |= EXT_RTHDR0;
					break;
				case 2:
					ext_hd |= EXT_RTHDR2;
					break;
				default:
					if (V_fw_verbose)
						printf("IPFW2: IPV6 - Unknown "
						    "Routing Header type(%d)\n",
						    ((struct ip6_rthdr *)
						    ulp)->ip6r_type);
					if (V_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;
				ip6f_mf = ((struct ip6_frag *)ulp)->ip6f_offlg &
					IP6F_MORE_FRAG;
				if (V_fw_permit_single_frag6 == 0 &&
				    offset == 0 && ip6f_mf == 0) {
					if (V_fw_verbose)
						printf("IPFW2: IPV6 - Invalid "
						    "Fragment Header\n");
					if (V_fw_deny_unknown_exthdrs)
					    return (IP_FW_DENY);
					break;
				}
				args->f_id.extra =
				    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 */
				/*
				 * Packet ends here, and IPv6 header has
				 * already been pulled up. If ip6e_len!=0
				 * then octets must be ignored.
				 */
				ulp = ip; /* non-NULL to get out of loop. */
				break;

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

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

			case IPPROTO_GRE:	/* RFC 1701 */
				/* XXX GRE header check? */
				PULLUP_TO(hlen, ulp, struct grehdr);
				break;

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

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

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

			case IPPROTO_PFSYNC:
				PULLUP_TO(hlen, ulp, struct pfsync_header);
				break;

			default:
				if (V_fw_verbose)
					printf("IPFW2: IPV6 - Unknown "
					    "Extension Header(%d), ext_hd=%x\n",
					     proto, ext_hd);
				if (V_fw_deny_unknown_exthdrs)
				    return (IP_FW_DENY);
				PULLUP_TO(hlen, ulp, struct ip6_ext);
				break;
			} /*switch */
		}
		UPDATE_POINTERS();
		ip6 = (struct ip6_hdr *)ip;
		args->f_id.addr_type = 6;
		args->f_id.src_ip6 = ip6->ip6_src;
		args->f_id.dst_ip6 = ip6->ip6_dst;
		args->f_id.flow_id6 = ntohl(ip6->ip6_flow);
		iplen = ntohs(ip6->ip6_plen) + sizeof(*ip6);
	} else if (pktlen >= sizeof(struct ip) &&
	    (eh == NULL || eh->ether_type == htons(ETHERTYPE_IP)) &&
	    ip->ip_v == 4) {
		is_ipv4 = 1;
		args->flags |= IPFW_ARGS_IP4;
		hlen = ip->ip_hl << 2;
		/*
		 * Collect parameters into local variables for faster
		 * matching.
		 */
		proto = ip->ip_p;
		src_ip = ip->ip_src;
		dst_ip = ip->ip_dst;
		offset = ntohs(ip->ip_off) & IP_OFFMASK;
		iplen = ntohs(ip->ip_len);

		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;
				/* save flags for dynamic rules */
				args->f_id._flags = tcp_get_flags(TCP(ulp));
				break;

			case IPPROTO_SCTP:
				if (pktlen >= hlen + sizeof(struct sctphdr) +
				    sizeof(struct sctp_chunkhdr) +
				    offsetof(struct sctp_init, a_rwnd))
					PULLUP_LEN(hlen, ulp,
					    sizeof(struct sctphdr) +
					    sizeof(struct sctp_chunkhdr) +
					    offsetof(struct sctp_init, a_rwnd));
				else if (pktlen >= hlen + sizeof(struct sctphdr))
					PULLUP_LEN(hlen, ulp, pktlen - hlen);
				else
					PULLUP_LEN(hlen, ulp,
					    sizeof(struct sctphdr));
				src_port = SCTP(ulp)->src_port;
				dst_port = SCTP(ulp)->dest_port;
				break;

			case IPPROTO_UDP:
			case IPPROTO_UDPLITE:
				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;
			}
		} else {
			if (offset == 1 && proto == IPPROTO_TCP) {
				/* RFC 3128 */
				goto pullup_failed;
			}
		}

		UPDATE_POINTERS();
		args->f_id.addr_type = 4;
		args->f_id.src_ip = ntohl(src_ip.s_addr);
		args->f_id.dst_ip = ntohl(dst_ip.s_addr);
	} else {
		proto = 0;
		dst_ip.s_addr = src_ip.s_addr = 0;

		args->f_id.addr_type = 1; /* XXX */
	}
#undef PULLUP_TO
	pktlen = iplen < pktlen ? iplen: pktlen;

	/* Properly initialize the rest of f_id */
	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_PF_RLOCK(chain);
	if (! V_ipfw_vnet_ready) { /* shutting down, leave NOW. */
		IPFW_PF_RUNLOCK(chain);
		return (IP_FW_PASS);	/* accept */
	}
	if (args->flags & IPFW_ARGS_REF) {
		/*
		 * Packet has already been tagged as a result of a previous
		 * match on rule args->rule aka args->rule_id (PIPE, QUEUE,
		 * REASS, NETGRAPH, DIVERT/TEE...)
		 * Validate the slot and continue from the next one
		 * if still present, otherwise do a lookup.
		 */
		f_pos = (args->rule.chain_id == chain->id) ?
		    args->rule.slot :
		    ipfw_find_rule(chain, args->rule.rulenum,
			args->rule.rule_id);
	} else {
		f_pos = 0;
	}

	if (args->flags & IPFW_ARGS_IN) {
		iif = args->ifp;
		oif = NULL;
	} else {
		MPASS(args->flags & IPFW_ARGS_OUT);
		iif = mem ? NULL : m_rcvif(m);
		oif = args->ifp;
	}

	/*
	 * Now scan the rules, and parse microinstructions for each rule.
	 * We have two nested loops and an inner switch. Sometimes we
	 * need to break out of one or both loops, or re-enter one of
	 * the loops with updated variables. Loop variables are:
	 *
	 *	f_pos (outer loop) points to the current rule.
	 *		On output it points to the matching rule.
	 *	done (outer loop) is used as a flag to break the loop.
	 *	l (inner loop)	residual length of current rule.
	 *		cmd points to the current microinstruction.
	 *
	 * We break the inner loop by setting l=0 and possibly
	 * cmdlen=0 if we don't want to advance cmd.
	 * We break the outer loop by setting done=1
	 * We can restart the inner loop by setting l>0 and f_pos, f, cmd
	 * as needed.
	 */
	for (; f_pos < chain->n_rules; f_pos++) {
		ipfw_insn *cmd;
		uint32_t tablearg = 0;
		int l, cmdlen, skip_or; /* skip rest of OR block */
		struct ip_fw *f;

		f = chain->map[f_pos];
		if (V_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 (proto == IPPROTO_TCP ||
				    proto == IPPROTO_UDP ||
				    proto == IPPROTO_UDPLITE)
					match = check_uidgid(
						    (ipfw_insn_u32 *)cmd,
						    args, &ucred_lookup,
#ifdef __FreeBSD__
						    &ucred_cache);
#else
						    (void *)&ucred_cache);
#endif
				break;

			case O_RECV:
				match = iface_match(iif, (ipfw_insn_if *)cmd,
				    chain, &tablearg);
				break;

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

			case O_VIA:
				match = iface_match(args->ifp,
				    (ipfw_insn_if *)cmd, chain, &tablearg);
				break;

			case O_MACADDR2:
				if (args->flags & IPFW_ARGS_ETHER) {
					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 *)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->flags & IPFW_ARGS_ETHER) {
					u_int16_t *p =
					    ((ipfw_insn_u16 *)cmd)->ports;
					int i;

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

			case O_FRAG:
				if (is_ipv4) {
					/*
					 * Since flags_match() works with
					 * uint8_t we pack ip_off into 8 bits.
					 * For this match offset is a boolean.
					 */
					match = flags_match(cmd,
					    ((ntohs(ip->ip_off) & ~IP_OFFMASK)
					    >> 8) | (offset != 0));
				} else {
					/*
					 * Compatibility: historically bare
					 * "frag" would match IPv6 fragments.
					 */
					match = (cmd->arg1 == 0x1 &&
					    (offset != 0));
				}
				break;

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

			case O_LAYER2:
				match = (args->flags & IPFW_ARGS_ETHER);
				break;

			case O_DIVERTED:
				if ((args->flags & IPFW_ARGS_REF) == 0)
					break;
				/*
				 * For diverted packets, args->rule.info
				 * contains the divert port (in host format)
				 * reason and direction.
				 */
				match = ((args->rule.info & IPFW_IS_MASK) ==
				    IPFW_IS_DIVERT) && (
				    ((args->rule.info & IPFW_INFO_IN) ?
					1: 2) & cmd->arg1);
				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_DST_LOOKUP:
				if (IPFW_LOOKUP_TYPE(cmd) != LOOKUP_NONE) {
				  void *pkey = NULL;
				  uint32_t key, vidx;
				  uint16_t keylen = 0; /* zero if can't match the packet */
				  uint8_t lookup_type;

				lookup_type = IPFW_LOOKUP_TYPE(cmd);

				switch (lookup_type) {
				case LOOKUP_DST_IP:
				case LOOKUP_SRC_IP:
					if (is_ipv4) {
						keylen = sizeof(in_addr_t);
						if (lookup_type == LOOKUP_DST_IP)
							pkey = &dst_ip;
						else
							pkey = &src_ip;
					} else if (is_ipv6) {
						keylen = sizeof(struct in6_addr);
						if (lookup_type == LOOKUP_DST_IP)
							pkey = &args->f_id.dst_ip6;
						else
							pkey = &args->f_id.src_ip6;
					} else /* only for L3 */
						break;
				case LOOKUP_DSCP:
					if (is_ipv4)
						key = ip->ip_tos >> 2;
					else if (is_ipv6)
						key = IPV6_DSCP(
						    (struct ip6_hdr *)ip) >> 2;
					else
						break; /* only for L3 */

					key &= 0x3f;
					if (cmdlen == F_INSN_SIZE(ipfw_insn_table))
						key &= insntod(cmd, table)->value;
					pkey = &key;
					keylen = sizeof(key);
					break;
				case LOOKUP_DST_PORT:
				case LOOKUP_SRC_PORT:
					/* only for L3 */
					if (is_ipv6 == 0 && is_ipv4 == 0) {
						break;
					}
					/* Skip fragments */
					if (offset != 0) {
						break;
					}
					/* Skip proto without ports */
					if (proto != IPPROTO_TCP &&
					    proto != IPPROTO_UDP &&
					    proto != IPPROTO_UDPLITE &&
					    proto != IPPROTO_SCTP)
						break;
					if (lookup_type == LOOKUP_DST_PORT)
						key = dst_port;
					else
						key = src_port;
					pkey = &key;
					if (cmdlen == F_INSN_SIZE(ipfw_insn_table))
						key &= insntod(cmd, table)->value;
					keylen = sizeof(key);
					break;
				case LOOKUP_DST_MAC:
				case LOOKUP_SRC_MAC:
					/* only for L2 */
					if ((args->flags & IPFW_ARGS_ETHER) == 0)
						break;

					pkey = lookup_type == LOOKUP_DST_MAC ?
					    eh->ether_dhost : eh->ether_shost;
					keylen = ETHER_ADDR_LEN;
					break;
#ifndef USERSPACE
				case LOOKUP_UID:
				case LOOKUP_JAIL:
					check_uidgid(insntod(cmd, u32),
					    args, &ucred_lookup,
#ifdef __FreeBSD__
					    &ucred_cache);
					if (lookup_type == LOOKUP_UID)
						key = ucred_cache->cr_uid;
					else if (lookup_type == LOOKUP_JAIL)
						key = ucred_cache->cr_prison->pr_id;
#else /* !__FreeBSD__ */
					    (void *)&ucred_cache);
					if (lookup_type == LOOKUP_UID)
						key = ucred_cache.uid;
					else if (lookup_type == LOOKUP_JAIL)
						key = ucred_cache.xid;
#endif /* !__FreeBSD__ */
					pkey = &key;
					if (cmdlen == F_INSN_SIZE(ipfw_insn_table))
						key &= insntod(cmd, table)->value;
					keylen = sizeof(key);
					break;
#endif /* !USERSPACE */
				case LOOKUP_MARK:
					key = args->rule.pkt_mark;
					if (cmdlen == F_INSN_SIZE(ipfw_insn_table))
						key &= insntod(cmd, table)->value;
					pkey = &key;
					keylen = sizeof(key);
					break;
				case LOOKUP_RULENUM:
					key = f->rulenum;
					if (cmdlen == F_INSN_SIZE(ipfw_insn_table))
						key &= insntod(cmd, table)->value;
					pkey = &key;
					keylen = sizeof(key);
					break;
				}
				/* unknown key type */
				if (keylen == 0)
					break;
				match = ipfw_lookup_table(chain,
				    insntod(cmd, kidx)->kidx, keylen,
				    pkey, &vidx);

				if (match)
					tablearg = vidx;
				break;
			}
				/* LOOKUP_NONE */
				/* FALLTHROUGH */
			case O_IP_SRC_LOOKUP:
			{
				void *pkey;
				uint32_t vidx;
				uint16_t keylen;

				if (is_ipv4) {
					keylen = sizeof(in_addr_t);
					if (cmd->opcode == O_IP_DST_LOOKUP)
						pkey = &dst_ip;
					else
						pkey = &src_ip;
				} else if (is_ipv6) {
					keylen = sizeof(struct in6_addr);
					if (cmd->opcode == O_IP_DST_LOOKUP)
						pkey = &args->f_id.dst_ip6;
					else
						pkey = &args->f_id.src_ip6;
				} else
					break;
				match = ipfw_lookup_table(chain,
				    insntod(cmd, kidx)->kidx,
				    keylen, pkey, &vidx);
				if (!match)
					break;
				if (cmdlen == F_INSN_SIZE(ipfw_insn_table)) {
					match = tvalue_match(chain,
					    insntod(cmd, table), vidx);
					if (!match)
						break;
				}
				tablearg = vidx;
				break;
			}

			case O_MAC_SRC_LOOKUP:
			case O_MAC_DST_LOOKUP:
			{
				void *pkey;
				uint32_t vidx;
				uint16_t keylen = ETHER_ADDR_LEN;

				/* Need ether frame */
				if ((args->flags & IPFW_ARGS_ETHER) == 0)
					break;

				if (cmd->opcode == O_MAC_DST_LOOKUP)
					pkey = eh->ether_dhost;
				else
					pkey = eh->ether_shost;

				match = ipfw_lookup_table(chain,
				    insntod(cmd, kidx)->kidx,
				    keylen, pkey, &vidx);
				if (!match)
					break;
				if (cmdlen == F_INSN_SIZE(ipfw_insn_table)) {
					match = tvalue_match(chain,
					    insntod(cmd, table), vidx);
					if (!match)
						break;
				}
				tablearg = vidx;
				break;
			}

			case O_IP_FLOW_LOOKUP:
			{
				uint32_t vidx = 0;

				match = ipfw_lookup_table(chain,
				    insntod(cmd, kidx)->kidx, 0,
				    &args->f_id, &vidx);
				if (!match)
					break;
				if (cmdlen == F_INSN_SIZE(ipfw_insn_table))
					match = tvalue_match(chain,
					    insntod(cmd, table), vidx);
				if (match)
					tablearg = vidx;
				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) {
					match = in_localip(src_ip);
					break;
				}
#ifdef INET6
				/* FALLTHROUGH */
			case O_IP6_SRC_ME:
				match = is_ipv6 &&
				    ipfw_localip6(&args->f_id.src_ip6);
#endif
				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) {
					match = in_localip(dst_ip);
					break;
				}
#ifdef INET6
				/* FALLTHROUGH */
			case O_IP6_DST_ME:
				match = is_ipv6 &&
				    ipfw_localip6(&args->f_id.dst_ip6);
#endif
				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_UDPLITE ||
				    proto == IPPROTO_TCP ||
				    proto == IPPROTO_SCTP) && offset == 0) {
					u_int16_t x =
					    (cmd->opcode == O_IP_SRCPORT) ?
						src_port : dst_port ;
					u_int16_t *p =
					    ((ipfw_insn_u16 *)cmd)->ports;
					int i;

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

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

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

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

			case O_IPVER:
				match = ((is_ipv4 || is_ipv6) &&
				    cmd->arg1 == ip->ip_v);
				break;

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

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

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

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

			case O_DSCP:
			    {
				uint32_t *p;
				uint16_t x;

				p = ((ipfw_insn_u32 *)cmd)->d;

				if (is_ipv4)
					x = ip->ip_tos >> 2;
				else if (is_ipv6) {
					x = IPV6_DSCP(
					    (struct ip6_hdr *)ip) >> 2;
					x &= 0x3f;
				} else
					break;

				/* DSCP bitmask is stored as low_u32 high_u32 */
				if (x >= 32)
					match = *(p + 1) & (1 << (x - 32));
				else
					match = *p & (1 << x);
			    }
				break;

			case O_TCPDATALEN:
				if (proto == IPPROTO_TCP && offset == 0) {
				    struct tcphdr *tcp;
				    uint16_t x;
				    uint16_t *p;
				    int i;
#ifdef INET6
				    if (is_ipv6) {
					    struct ip6_hdr *ip6;

					    ip6 = (struct ip6_hdr *)ip;
					    if (ip6->ip6_plen == 0) {
						    /*
						     * Jumbo payload is not
						     * supported by this
						     * opcode.
						     */
						    break;
					    }
					    x = iplen - hlen;
				    } else
#endif /* INET6 */
					    x = iplen - (ip->ip_hl << 2);
				    tcp = TCP(ulp);
				    x -= 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:
				/*
				 * Note that this is currently only set up to
				 * match the lower 8 TCP header flag bits, not
				 * the full compliment of all 12 flags.
				 */
				match = (proto == IPPROTO_TCP && offset == 0 &&
				    flags_match(cmd, tcp_get_flags(TCP(ulp))));
				break;

			case O_TCPOPTS:
				if (proto == IPPROTO_TCP && offset == 0 && ulp){
					PULLUP_LEN_LOCKED(hlen, ulp,
					    (TCP(ulp)->th_off << 2));
					match = 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_TCPMSS:
				if (proto == IPPROTO_TCP &&
				    (args->f_id._flags & TH_SYN) != 0 &&
				    ulp != NULL) {
					uint16_t mss, *p;
					int i;

					PULLUP_LEN_LOCKED(hlen, ulp,
					    (TCP(ulp)->th_off << 2));
					if ((tcpopts_parse(TCP(ulp), &mss) &
					    IP_FW_TCPOPT_MSS) == 0)
						break;
					if (cmdlen == 1) {
						match = (cmd->arg1 == mss);
						break;
					}
					/* Otherwise we have ranges. */
					p = ((ipfw_insn_u16 *)cmd)->ports;
					i = cmdlen - 1;
					for (; !match && i > 0; i--, p += 2)
						match = (mss >= p[0] &&
						    mss <= p[1]);
				}
				break;

			case O_TCPWIN:
				if (proto == IPPROTO_TCP && offset == 0) {
				    uint16_t x;
				    uint16_t *p;
				    int i;

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

			case O_ALTQ: {
				struct pf_mtag *at;
				struct m_tag *mtag;
				ipfw_insn_altq *altq = (ipfw_insn_altq *)cmd;

				/*
				 * ALTQ uses mbuf tags from another
				 * packet filtering system - pf(4).
				 * We allocate a tag in its format
				 * and fill it in, pretending to be pf(4).
				 */
				match = 1;
				at = pf_find_mtag(m);
				if (at != NULL && at->qid != 0)
					break;
				mtag = m_tag_get(PACKET_TAG_PF,
				    sizeof(struct pf_mtag), M_NOWAIT | M_ZERO);
				if (mtag == NULL) {
					/*
					 * Let the packet fall back to the
					 * default ALTQ.
					 */
					break;
				}
				m_tag_prepend(m, mtag);
				at = (struct pf_mtag *)(mtag + 1);
				at->qid = altq->qid;
				at->hdr = ip;
				break;
			}

			case O_LOG:
				ipfw_log(chain, f, hlen, args,
				    offset | ip6f_mf, tablearg, ip, eh);
				match = 1;
				break;

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

			case O_VERREVPATH:
				/* Outgoing packets automatically pass/match */
				match = (args->flags & IPFW_ARGS_OUT ||
				    (
#ifdef INET6
				    is_ipv6 ?
					verify_path6(&(args->f_id.src_ip6),
					    iif, args->f_id.fib) :
#endif
				    verify_path(src_ip, iif, args->f_id.fib)));
				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, args->f_id.fib) :
#endif
				    verify_path(src_ip, NULL, args->f_id.fib))));
				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), iif,
						args->f_id.fib) :
#endif
					    verify_path(src_ip, iif,
					        args->f_id.fib);
				else
					match = 1;
				break;

			case O_IPSEC:
				match = (m_tag_find(m,
				    PACKET_TAG_IPSEC_IN_DONE, NULL) != NULL);
				/* otherwise no match */
				break;

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

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

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

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

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

			case O_IP6:
				match = is_ipv6;
				break;
#endif

			case O_IP4:
				match = is_ipv4;
				break;

			case O_TAG: {
				struct m_tag *mtag;
				uint32_t tag = TARG(cmd->arg1, tag);

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

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

			case O_FIB: /* try match the specified fib */
				if (args->f_id.fib == cmd->arg1)
					match = 1;
				break;

			case O_SOCKARG:	{
#ifndef USERSPACE	/* not supported in userspace */
				struct inpcb *inp = args->inp;
				struct inpcbinfo *pi;
				bool inp_locked = false;

				if (proto == IPPROTO_TCP)
					pi = &V_tcbinfo;
				else if (proto == IPPROTO_UDP)
					pi = &V_udbinfo;
				else if (proto == IPPROTO_UDPLITE)
					pi = &V_ulitecbinfo;
				else
					break;

				/*
				 * XXXRW: so_user_cookie should almost
				 * certainly be inp_user_cookie?
				 */

				/*
				 * For incoming packet lookup the inpcb
				 * using the src/dest ip/port tuple.
				 */
				if (is_ipv4 && inp == NULL) {
					inp = in_pcblookup(pi,
					    src_ip, htons(src_port),
					    dst_ip, htons(dst_port),
					    INPLOOKUP_RLOCKPCB, NULL);
					inp_locked = true;
				}
#ifdef INET6
				if (is_ipv6 && inp == NULL) {
					inp = in6_pcblookup(pi,
					    &args->f_id.src_ip6,
					    htons(src_port),
					    &args->f_id.dst_ip6,
					    htons(dst_port),
					    INPLOOKUP_RLOCKPCB, NULL);
					inp_locked = true;
				}
#endif /* INET6 */
				if (inp != NULL) {
					if (inp->inp_socket) {
						tablearg =
						    inp->inp_socket->so_user_cookie;
						if (tablearg)
							match = 1;
					}
					if (inp_locked)
						INP_RUNLOCK(inp);
				}
#endif /* !USERSPACE */
				break;
			}

			case O_TAGGED: {
				struct m_tag *mtag;
				uint32_t tag = TARG(cmd->arg1, tag);

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

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

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

					p = ((ipfw_insn_u16 *)cmd)->ports;
					i = cmdlen - 1;
					for(; !match && i > 0; i--, p += 2)
						match =
						    mtag->m_tag_id >= p[0] &&
						    mtag->m_tag_id <= p[1];
				}
				break;
			}

			case O_MARK: {
				uint32_t mark;
				if (cmd->arg1 == IP_FW_TARG)
					mark = TARG_VAL(chain, tablearg, mark);
				else
					mark = insntoc(cmd, u32)->d[0];
				match =
				    (args->rule.pkt_mark &
				    insntoc(cmd, u32)->d[1]) ==
				    (mark & insntoc(cmd, u32)->d[1]);
				break;
			}

			/*
			 * The second set of opcodes represents 'actions',
			 * i.e. the terminal part of a rule once the packet
			 * matches all previous patterns.
			 * Typically there is only one action for each rule,
			 * and the opcode is stored at the end of the rule
			 * (but there are exceptions -- see below).
			 *
			 * In general, here we set retval and terminate the
			 * outer loop (would be a 'break 3' in some language,
			 * but we need to set l=0, done=1)
			 *
			 * Exceptions:
			 * O_COUNT and O_SKIPTO actions:
			 *   instead of terminating, we jump to the next rule
			 *   (setting l=0), or to the SKIPTO target (setting
			 *   f/f_len, cmd and l as needed), respectively.
			 *
			 * O_TAG, O_LOG and O_ALTQ action parameters:
			 *   perform some action and set match = 1;
			 *
			 * O_LIMIT and O_KEEP_STATE: these opcodes are
			 *   not real 'actions', and are stored right
			 *   before the 'action' part of the rule (one
			 *   exception is O_SKIP_ACTION which could be
			 *   between these opcodes and 'action' one).
			 *   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 (set retval,
			 *   break loops with l=0, done=1)
			 *
			 * 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
			 *   if an entry is found, or
			 *   (CHECK_STATE only) a jump to the next rule if
			 *   the entry is not found.
			 *   The result of the lookup is cached so that
			 *   further instances of these opcodes become NOPs.
			 *   The jump to the next rule is done by setting
			 *   l=0, cmdlen=0.
			 *
			 * O_SKIP_ACTION: this opcode is not a real 'action'
			 *  either, and is stored right before the 'action'
			 *  part of the rule, right after the O_KEEP_STATE
			 *  opcode. It causes match failure so the real
			 *  'action' could be executed only if the rule
			 *  is checked via dynamic rule from the state
			 *  table, as in such case execution starts
			 *  from the true 'action' opcode directly.
			 *
			 */
			case O_LIMIT:
			case O_KEEP_STATE:
				if (ipfw_dyn_install_state(chain, f,
				    (ipfw_insn_limit *)cmd, args, ulp,
				    pktlen, &dyn_info, tablearg)) {
					/* error or limit violation */
					retval = IP_FW_DENY;
					l = 0;	/* exit inner loop */
					done = 1; /* exit outer loop */
				}
				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_info.
				 * 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_LOOKUP_NEEDED(&dyn_info, cmd) &&
				    (q = ipfw_dyn_lookup_state(args, ulp,
				    pktlen, cmd, &dyn_info)) != NULL) {
					/*
					 * Found dynamic entry, jump to the
					 * 'action' part of the parent rule
					 * by setting f, cmd, l and clearing
					 * cmdlen.
					 */
					f = q;
					f_pos = dyn_info.f_pos;
					cmd = ACTION_PTR(f);
					l = f->cmd_len - f->act_ofs;
					cmdlen = 0;
					continue;
				}
				/*
				 * 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)
					l = 0;	/* exit inner loop */
				match = 1;
				break;

			case O_SKIP_ACTION:
				match = 0;	/* skip to the next rule */
				l = 0;		/* exit inner loop */
				break;

			case O_ACCEPT:
				retval = 0;	/* accept */
				l = 0;		/* exit inner loop */
				done = 1;	/* exit outer loop */
				break;

			case O_PIPE:
			case O_QUEUE:
				set_match(args, f_pos, chain);
				args->rule.info = TARG(cmd->arg1, pipe);
				if (cmd->opcode == O_PIPE)
					args->rule.info |= IPFW_IS_PIPE;
				if (V_fw_one_pass)
					args->rule.info |= IPFW_ONEPASS;
				retval = IP_FW_DUMMYNET;
				l = 0;          /* exit inner loop */
				done = 1;       /* exit outer loop */
				break;

			case O_DIVERT:
			case O_TEE:
				if (args->flags & IPFW_ARGS_ETHER)
					break;	/* not on layer 2 */
				/* otherwise this is terminal */
				l = 0;		/* exit inner loop */
				done = 1;	/* exit outer loop */
				retval = (cmd->opcode == O_DIVERT) ?
					IP_FW_DIVERT : IP_FW_TEE;
				set_match(args, f_pos, chain);
				args->rule.info = TARG(cmd->arg1, divert);
				break;

			case O_COUNT:
				IPFW_INC_RULE_COUNTER(f, pktlen);
				l = 0;		/* exit inner loop */
				break;

			case O_SKIPTO:
			    IPFW_INC_RULE_COUNTER(f, pktlen);
			    f_pos = jump(chain, f,
				insntod(cmd, u32)->d[0], tablearg, false);
			    /*
			     * Skip disabled rules, and re-enter
			     * the inner loop with the correct
			     * f_pos, f, l and cmd.
			     * Also clear cmdlen and skip_or
			     */
			    for (; f_pos < chain->n_rules - 1 &&
				    (V_set_disable &
				     (1 << chain->map[f_pos]->set));
				    f_pos++)
				;
			    /* Re-enter the inner loop at the skipto rule. */
			    f = chain->map[f_pos];
			    l = f->cmd_len;
			    cmd = f->cmd;
			    match = 1;
			    cmdlen = 0;
			    skip_or = 0;
			    continue;
			    break;	/* not reached */

			case O_CALLRETURN: {
				/*
				 * Implementation of `subroutine' call/return,
				 * in the stack carried in an mbuf tag. This
				 * is different from `skipto' in that any call
				 * address is possible (`skipto' must prevent
				 * backward jumps to avoid endless loops).
				 * We have `return' action when F_NOT flag is
				 * present. The `m_tag_id' field is used as
				 * stack pointer.
				 */
				struct m_tag *mtag;
				uint32_t jmpto, *stack;

#define	IS_CALL		((cmd->len & F_NOT) == 0)
#define	IS_RETURN	((cmd->len & F_NOT) != 0)
				/*
				 * Hand-rolled version of m_tag_locate() with
				 * wildcard `type'.
				 * If not already tagged, allocate new tag.
				 */
				mtag = m_tag_first(m);
				while (mtag != NULL) {
					if (mtag->m_tag_cookie ==
					    MTAG_IPFW_CALL)
						break;
					mtag = m_tag_next(m, mtag);
				}

				/*
				 * We keep ruleset id in the first element
				 * of stack. If it doesn't match chain->id,
				 * then we can't trust information in the
				 * stack, since rules were changed.
				 * We reset stack pointer to be able reuse
				 * tag if it will be needed.
				 */
				if (mtag != NULL) {
					stack = (uint32_t *)(mtag + 1);
					if (stack[0] != chain->id) {
						stack[0] = chain->id;
						mtag->m_tag_id = 0;
					}
				}

				/*
				 * If there is no mtag or stack is empty,
				 * `return` continues with next rule.
				 */
				if (IS_RETURN && (mtag == NULL ||
				    mtag->m_tag_id == 0)) {
					l = 0;		/* exit inner loop */
					break;
				}

				if (mtag == NULL) {
					MPASS(IS_CALL);
					mtag = m_tag_alloc(MTAG_IPFW_CALL, 0,
					    IPFW_CALLSTACK_SIZE *
					    sizeof(uint32_t), M_NOWAIT);
					if (mtag != NULL) {
						m_tag_prepend(m, mtag);
						stack = (uint32_t *)(mtag + 1);
						stack[0] = chain->id;
					}
				}

				if (mtag == NULL) {
					printf("ipfw: rule %u: failed to "
					    "allocate call stack. "
					    "Denying packet.\n",
					    f->rulenum);
					l = 0;		/* exit inner loop */
					done = 1;	/* exit outer loop */
					retval = IP_FW_DENY; /* drop packet */
					break;
				}

				if (IS_CALL && mtag->m_tag_id >=
				    IPFW_CALLSTACK_SIZE - 1) {
					printf("ipfw: rule %u: call stack "
					    "overflow. Denying packet.\n",
					    f->rulenum);
					l = 0;		/* exit inner loop */
					done = 1;	/* exit outer loop */
					retval = IP_FW_DENY; /* drop packet */
					break;
				}

				MPASS(stack == (uint32_t *)(mtag + 1));
				IPFW_INC_RULE_COUNTER(f, pktlen);

				if (IS_CALL) {
					stack[++mtag->m_tag_id] = f_pos;
					f_pos = jump(chain, f,
					    insntod(cmd, u32)->d[0],
					    tablearg, true);
				} else {	/* `return' action */
					jmpto = stack[mtag->m_tag_id--];
					if (cmd->arg1 == RETURN_NEXT_RULE)
						f_pos = jmpto + 1;
					else /* RETURN_NEXT_RULENUM */
						f_pos = ipfw_find_rule(chain,
						    chain->map[
						    jmpto]->rulenum + 1, 0);
				}

				/*
				 * Skip disabled rules, and re-enter
				 * the inner loop with the correct
				 * f_pos, f, l and cmd.
				 * Also clear cmdlen and skip_or
				 */
				MPASS(f_pos < chain->n_rules - 1);
				for (; f_pos < chain->n_rules - 1 &&
				    (V_set_disable &
				    (1 << chain->map[f_pos]->set)); f_pos++)
					;
				/*
				 * Re-enter the inner loop at the dest
				 * rule.
				 */
				f = chain->map[f_pos];
				l = f->cmd_len;
				cmd = f->cmd;
				cmdlen = 0;
				skip_or = 0;
				continue;
				break;	/* NOTREACHED */
			}
#undef IS_CALL
#undef IS_RETURN

			case O_REJECT:
				/*
				 * Drop the packet and send a reject notice
				 * if the packet is not ICMP (or is an ICMP
				 * query), and it is not multicast/broadcast.
				 */
				if (hlen > 0 && is_ipv4 && offset == 0 &&
				    (proto != IPPROTO_ICMP ||
				     is_icmp_query(ICMP(ulp))) &&
				    !(m->m_flags & (M_BCAST|M_MCAST)) &&
				    !IN_MULTICAST(ntohl(dst_ip.s_addr))) {
					KASSERT(!need_send_reject,
					    ("o_reject - need_send_reject was set previously"));
					if ((reject_code = cmd->arg1) == ICMP_UNREACH_NEEDFRAG &&
					    cmd->len == F_INSN_SIZE(ipfw_insn_u16)) {
						reject_mtu =
						    ((ipfw_insn_u16 *)cmd)->ports[0];
					} else {
						reject_mtu = 0;
					}
					need_send_reject = true;
				}
				/* FALLTHROUGH */
#ifdef INET6
			case O_UNREACH6:
				if (hlen > 0 && is_ipv6 &&
				    ((offset & IP6F_OFF_MASK) == 0) &&
				    (proto != IPPROTO_ICMPV6 ||
				     (is_icmp6_query(icmp6_type) == 1)) &&
				    !(m->m_flags & (M_BCAST|M_MCAST)) &&
				    !IN6_IS_ADDR_MULTICAST(
					&args->f_id.dst_ip6)) {
					KASSERT(!need_send_reject,
					    ("o_unreach6 - need_send_reject was set previously"));
					reject_code = cmd->arg1;
					if (cmd->opcode == O_REJECT) {
						reject_code =
						    map_icmp_unreach(reject_code);
					}
					need_send_reject = true;
				}
				/* FALLTHROUGH */
#endif
			case O_DENY:
				retval = IP_FW_DENY;
				l = 0;		/* exit inner loop */
				done = 1;	/* exit outer loop */
				break;

			case O_FORWARD_IP:
				if (args->flags & IPFW_ARGS_ETHER)
					break;	/* not valid on layer2 pkts */
				if (q != f ||
				    dyn_info.direction == MATCH_FORWARD) {
				    struct sockaddr_in *sa;

				    sa = &(((ipfw_insn_sa *)cmd)->sa);
				    if (sa->sin_addr.s_addr == INADDR_ANY) {
#ifdef INET6
					/*
					 * We use O_FORWARD_IP opcode for
					 * fwd rule with tablearg, but tables
					 * now support IPv6 addresses. And
					 * when we are inspecting IPv6 packet,
					 * we can use nh6 field from
					 * table_value as next_hop6 address.
					 */
					if (is_ipv6) {
						struct ip_fw_nh6 *nh6;

						args->flags |= IPFW_ARGS_NH6;
						nh6 = &args->hopstore6;
						nh6->sin6_addr = TARG_VAL(
						    chain, tablearg, nh6);
						nh6->sin6_port = sa->sin_port;
						nh6->sin6_scope_id = TARG_VAL(
						    chain, tablearg, zoneid);
					} else
#endif
					{
						args->flags |= IPFW_ARGS_NH4;
						args->hopstore.sin_port =
						    sa->sin_port;
						sa = &args->hopstore;
						sa->sin_family = AF_INET;
						sa->sin_len = sizeof(*sa);
						sa->sin_addr.s_addr = htonl(
						    TARG_VAL(chain, tablearg,
						    nh4));
					}
				    } else {
					    args->flags |= IPFW_ARGS_NH4PTR;
					    args->next_hop = sa;
				    }
				}
				retval = IP_FW_PASS;
				l = 0;          /* exit inner loop */
				done = 1;       /* exit outer loop */
				break;

#ifdef INET6
			case O_FORWARD_IP6:
				if (args->flags & IPFW_ARGS_ETHER)
					break;	/* not valid on layer2 pkts */
				if (q != f ||
				    dyn_info.direction == MATCH_FORWARD) {
					struct sockaddr_in6 *sin6;

					sin6 = &(((ipfw_insn_sa6 *)cmd)->sa);
					args->flags |= IPFW_ARGS_NH6PTR;
					args->next_hop6 = sin6;
				}
				retval = IP_FW_PASS;
				l = 0;		/* exit inner loop */
				done = 1;	/* exit outer loop */
				break;
#endif

			case O_NETGRAPH:
			case O_NGTEE:
				set_match(args, f_pos, chain);
				args->rule.info = TARG(cmd->arg1, netgraph);
				if (V_fw_one_pass)
					args->rule.info |= IPFW_ONEPASS;
				retval = (cmd->opcode == O_NETGRAPH) ?
				    IP_FW_NETGRAPH : IP_FW_NGTEE;
				l = 0;          /* exit inner loop */
				done = 1;       /* exit outer loop */
				break;

			case O_SETFIB: {
				uint32_t fib;

				IPFW_INC_RULE_COUNTER(f, pktlen);
				fib = TARG(cmd->arg1, fib) & 0x7FFF;
				if (fib >= rt_numfibs)
					fib = 0;
				M_SETFIB(m, fib);
				args->f_id.fib = fib; /* XXX */
				l = 0;		/* exit inner loop */
				break;
		        }

			case O_SETDSCP: {
				uint16_t code;

				code = TARG(cmd->arg1, dscp) & 0x3F;
				l = 0;		/* exit inner loop */
				if (is_ipv4) {
					uint16_t old;

					old = *(uint16_t *)ip;
					ip->ip_tos = (code << 2) |
					    (ip->ip_tos & 0x03);
					ip->ip_sum = cksum_adjust(ip->ip_sum,
					    old, *(uint16_t *)ip);
				} else if (is_ipv6) {
					/* update cached value */
					args->f_id.flow_id6 =
					    ntohl(*(uint32_t *)ip) & ~0x0FC00000;
					args->f_id.flow_id6 |= code << 22;

					*((uint32_t *)ip) =
					    htonl(args->f_id.flow_id6);
				} else
					break;

				IPFW_INC_RULE_COUNTER(f, pktlen);
				break;
			}

			case O_NAT:
				l = 0;          /* exit inner loop */
				done = 1;       /* exit outer loop */
				/*
				 * Ensure that we do not invoke NAT handler for
				 * non IPv4 packets. Libalias expects only IPv4.
				 */
				if (!is_ipv4 || !IPFW_NAT_LOADED) {
				    retval = IP_FW_DENY;
				    break;
				}

				struct cfg_nat *t;
				int nat_id;

				args->rule.info = 0;
				set_match(args, f_pos, chain);
				/* Check if this is 'global' nat rule */
				if (cmd->arg1 == IP_FW_NAT44_GLOBAL) {
					retval = ipfw_nat_ptr(args, NULL, m);
					break;
				}
				t = ((ipfw_insn_nat *)cmd)->nat;
				if (t == NULL) {
					nat_id = TARG(cmd->arg1, nat);
					t = (*lookup_nat_ptr)(&chain->nat, nat_id);

					if (t == NULL) {
					    retval = IP_FW_DENY;
					    break;
					}
					if (cmd->arg1 != IP_FW_TARG)
					    ((ipfw_insn_nat *)cmd)->nat = t;
				}
				retval = ipfw_nat_ptr(args, t, m);
				break;

			case O_REASS: {
				int ip_off;

				l = 0;	/* in any case exit inner loop */
				if (is_ipv6) /* IPv6 is not supported yet */
					break;
				IPFW_INC_RULE_COUNTER(f, pktlen);
				ip_off = ntohs(ip->ip_off);

				/* if not fragmented, go to next rule */
				if ((ip_off & (IP_MF | IP_OFFMASK)) == 0)
				    break;

				args->m = m = ip_reass(m);

				/*
				 * do IP header checksum fixup.
				 */
				if (m == NULL) { /* fragment got swallowed */
				    retval = IP_FW_DENY;
				} else { /* good, packet complete */
				    int hlen;

				    ip = mtod(m, struct ip *);
				    hlen = ip->ip_hl << 2;
				    ip->ip_sum = 0;
				    if (hlen == sizeof(struct ip))
					ip->ip_sum = in_cksum_hdr(ip);
				    else
					ip->ip_sum = in_cksum(m, hlen);
				    retval = IP_FW_REASS;
				    args->rule.info = 0;
				    set_match(args, f_pos, chain);
				}
				done = 1;	/* exit outer loop */
				break;
			}

			case O_SETMARK: {
				l = 0;		/* exit inner loop */
				args->rule.pkt_mark = (
				    (cmd->arg1 == IP_FW_TARG) ?
				    TARG_VAL(chain, tablearg, mark) :
				    insntoc(cmd, u32)->d[0]);

				IPFW_INC_RULE_COUNTER(f, pktlen);
				break;
			}

			case O_EXTERNAL_ACTION:
				l = 0; /* in any case exit inner loop */
				retval = ipfw_run_eaction(chain, args,
				    cmd, &done);
				/*
				 * If both @retval and @done are zero,
				 * consider this as rule matching and
				 * update counters.
				 */
				if (retval == 0 && done == 0) {
					IPFW_INC_RULE_COUNTER(f, pktlen);
					/*
					 * Reset the result of the last
					 * dynamic state lookup.
					 * External action can change
					 * @args content, and it may be
					 * used for new state lookup later.
					 */
					DYN_INFO_INIT(&dyn_info);
				}
				break;

			default:
				panic("ipfw: rule %u: unknown opcode %d\n",
				    f->rulenum, cmd->opcode);
			} /* end of switch() on opcodes */
			/*
			 * if we get here with l=0, then match is irrelevant.
			 */

			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 loop, scan opcodes */
#undef PULLUP_LEN
#undef PULLUP_LEN_LOCKED

		if (done)
			break;

/* next_rule:; */	/* try next rule		*/

	}		/* end of outer for, scan rules */

	if (done) {
		struct ip_fw *rule = chain->map[f_pos];
		/* Update statistics */
		IPFW_INC_RULE_COUNTER(rule, pktlen);
		IPFW_PROBE(rule__matched, retval,
		    is_ipv4 ? AF_INET : AF_INET6,
		    is_ipv4 ? (uintptr_t)&src_ip :
		        (uintptr_t)&args->f_id.src_ip6,
		    is_ipv4 ? (uintptr_t)&dst_ip :
		        (uintptr_t)&args->f_id.dst_ip6,
		    args, rule);
	} else {
		retval = IP_FW_DENY;
		printf("ipfw: ouch!, skip past end of rules, denying packet\n");
	}
	IPFW_PF_RUNLOCK(chain);
	if (need_send_reject) {
#ifdef INET6
		if (is_ipv6)
			send_reject6(args, reject_code, hlen,
				     (struct ip6_hdr *)ip);
		else
#endif
			send_reject(args, reject_code, reject_mtu,
				    iplen, ip);
	}
#ifdef __FreeBSD__
	if (ucred_cache != NULL)
		crfree(ucred_cache);
#endif
	return (retval);

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

/*
 * Set maximum number of tables that can be used in given VNET ipfw instance.
 */
#ifdef SYSCTL_NODE
static int
sysctl_ipfw_table_num(SYSCTL_HANDLER_ARGS)
{
	int error;
	unsigned int ntables;

	ntables = V_fw_tables_max;

	error = sysctl_handle_int(oidp, &ntables, 0, req);
	/* Read operation or some error */
	if ((error != 0) || (req->newptr == NULL))
		return (error);

	return (ipfw_resize_tables(&V_layer3_chain, ntables));
}

/*
 * Switches table namespace between global and per-set.
 */
static int
sysctl_ipfw_tables_sets(SYSCTL_HANDLER_ARGS)
{
	int error;
	unsigned int sets;

	sets = V_fw_tables_sets;

	error = sysctl_handle_int(oidp, &sets, 0, req);
	/* Read operation or some error */
	if ((error != 0) || (req->newptr == NULL))
		return (error);

	return (ipfw_switch_tables_namespace(&V_layer3_chain, sets));
}
#endif

/*
 * Module and VNET glue
 */

/*
 * Stuff that must be initialised only on boot or module load
 */
static int
ipfw_init(void)
{
	int error = 0;

	/*
 	 * Only print out this stuff the first time around,
	 * when called from the sysinit code.
	 */
	printf("ipfw2 "
#ifdef INET6
		"(+ipv6) "
#endif
		"initialized, divert %s, nat %s, "
		"default to %s, logging ",
#ifdef IPDIVERT
		"enabled",
#else
		"loadable",
#endif
#ifdef IPFIREWALL_NAT
		"enabled",
#else
		"loadable",
#endif
		default_to_accept ? "accept" : "deny");

	/*
	 * Note: V_xxx variables can be accessed here but the vnet specific
	 * initializer may not have been called yet for the VIMAGE case.
	 * Tuneables will have been processed. We will print out values for
	 * the default vnet.
	 * XXX This should all be rationalized AFTER 8.0
	 */
	if (V_fw_verbose == 0)
		printf("disabled\n");
	else if (V_verbose_limit == 0)
		printf("unlimited\n");
	else
		printf("limited to %d packets/entry by default\n",
		    V_verbose_limit);

	/* Check user-supplied table count for validness */
	if (default_fw_tables > IPFW_TABLES_MAX)
	  default_fw_tables = IPFW_TABLES_MAX;

	ipfw_init_sopt_handler();
	ipfw_init_obj_rewriter();
	ipfw_iface_init();
	return (error);
}

/*
 * Called for the removal of the last instance only on module unload.
 */
static void
ipfw_destroy(void)
{

	ipfw_iface_destroy();
	ipfw_destroy_sopt_handler();
	ipfw_destroy_obj_rewriter();
	printf("IP firewall unloaded\n");
}

/*
 * Stuff that must be initialized for every instance
 * (including the first of course).
 */
static int
vnet_ipfw_init(const void *unused)
{
	int error, first;
	struct ip_fw *rule = NULL;
	struct ip_fw_chain *chain;

	chain = &V_layer3_chain;

	first = IS_DEFAULT_VNET(curvnet) ? 1 : 0;

	/* First set up some values that are compile time options */
	V_autoinc_step = 100;	/* bounded to 1..1000 in add_rule() */
	V_fw_deny_unknown_exthdrs = 1;
#ifdef IPFIREWALL_VERBOSE
	V_fw_verbose = 1;
#endif
#ifdef IPFIREWALL_VERBOSE_LIMIT
	V_verbose_limit = IPFIREWALL_VERBOSE_LIMIT;
#endif
#ifdef IPFIREWALL_NAT
	LIST_INIT(&chain->nat);
#endif

	/* Init shared services hash table */
	ipfw_init_srv(chain);

	ipfw_init_counters();
	/* Set initial number of tables */
	V_fw_tables_max = default_fw_tables;
	error = ipfw_init_tables(chain, first);
	if (error) {
		printf("ipfw2: setting up tables failed\n");
		free(chain->map, M_IPFW);
		free(rule, M_IPFW);
		return (ENOSPC);
	}

	IPFW_LOCK_INIT(chain);

	/* fill and insert the default rule */
	rule = ipfw_alloc_rule(chain, sizeof(struct ip_fw));
	rule->flags |= IPFW_RULE_NOOPT;
	rule->cmd_len = 1;
	rule->cmd[0].len = 1;
	rule->cmd[0].opcode = default_to_accept ? O_ACCEPT : O_DENY;
	chain->default_rule = rule;
	ipfw_add_protected_rule(chain, rule, 0);

	ipfw_dyn_init(chain);
	ipfw_eaction_init(chain, first);
	ipfw_init_skipto_cache(chain);
	ipfw_bpf_init(first);

	/* First set up some values that are compile time options */
	V_ipfw_vnet_ready = 1;		/* Open for business */

	/*
	 * Hook the sockopt handler and pfil hooks for ipv4 and ipv6.
	 * Even if the latter two fail we still keep the module alive
	 * because the sockopt and layer2 paths are still useful.
	 * ipfw[6]_hook return 0 on success, ENOENT on failure,
	 * so we can ignore the exact return value and just set a flag.
	 *
	 * Note that V_fw[6]_enable are manipulated by a SYSCTL_PROC so
	 * changes in the underlying (per-vnet) variables trigger
	 * immediate hook()/unhook() calls.
	 * In layer2 we have the same behaviour, except that V_ether_ipfw
	 * is checked on each packet because there are no pfil hooks.
	 */
	V_ip_fw_ctl_ptr = ipfw_ctl3;
	error = ipfw_attach_hooks();
	return (error);
}

/*
 * Called for the removal of each instance.
 */
static int
vnet_ipfw_uninit(const void *unused)
{
	struct ip_fw *reap;
	struct ip_fw_chain *chain = &V_layer3_chain;
	int i, last;

	V_ipfw_vnet_ready = 0; /* tell new callers to go away */
	/*
	 * disconnect from ipv4, ipv6, layer2 and sockopt.
	 * Then grab, release and grab again the WLOCK so we make
	 * sure the update is propagated and nobody will be in.
	 */
	ipfw_detach_hooks();
	V_ip_fw_ctl_ptr = NULL;

	last = IS_DEFAULT_VNET(curvnet) ? 1 : 0;

	IPFW_UH_WLOCK(chain);
	IPFW_UH_WUNLOCK(chain);

	ipfw_dyn_uninit(0);	/* run the callout_drain */

	IPFW_UH_WLOCK(chain);

	reap = NULL;
	IPFW_WLOCK(chain);
	for (i = 0; i < chain->n_rules; i++)
		ipfw_reap_add(chain, &reap, chain->map[i]);
	free(chain->map, M_IPFW);
	ipfw_destroy_skipto_cache(chain);
	IPFW_WUNLOCK(chain);
	IPFW_UH_WUNLOCK(chain);
	ipfw_destroy_tables(chain, last);
	ipfw_eaction_uninit(chain, last);
	if (reap != NULL)
		ipfw_reap_rules(reap);
	vnet_ipfw_iface_destroy(chain);
	ipfw_destroy_srv(chain);
	IPFW_LOCK_DESTROY(chain);
	ipfw_dyn_uninit(1);	/* free the remaining parts */
	ipfw_destroy_counters();
	ipfw_bpf_uninit(last);
	return (0);
}

/*
 * Module event handler.
 * In general we have the choice of handling most of these events by the
 * event handler or by the (VNET_)SYS(UN)INIT handlers. I have chosen to
 * use the SYSINIT handlers as they are more capable of expressing the
 * flow of control during module and vnet operations, so this is just
 * a skeleton. Note there is no SYSINIT equivalent of the module
 * SHUTDOWN handler, but we don't have anything to do in that case anyhow.
 */
static int
ipfw_modevent(module_t mod, int type, void *unused)
{
	int err = 0;

	switch (type) {
	case MOD_LOAD:
		/* Called once at module load or
	 	 * system boot if compiled in. */
		break;
	case MOD_QUIESCE:
		/* Called before unload. May veto unloading. */
		break;
	case MOD_UNLOAD:
		/* Called during unload. */
		break;
	case MOD_SHUTDOWN:
		/* Called during system shutdown. */
		break;
	default:
		err = EOPNOTSUPP;
		break;
	}
	return err;
}

static moduledata_t ipfwmod = {
	"ipfw",
	ipfw_modevent,
	0
};

/* Define startup order. */
#define	IPFW_SI_SUB_FIREWALL	SI_SUB_PROTO_FIREWALL
#define	IPFW_MODEVENT_ORDER	(SI_ORDER_ANY - 255) /* On boot slot in here. */
#define	IPFW_MODULE_ORDER	(IPFW_MODEVENT_ORDER + 1) /* A little later. */
#define	IPFW_VNET_ORDER		(IPFW_MODEVENT_ORDER + 2) /* Later still. */

DECLARE_MODULE(ipfw, ipfwmod, IPFW_SI_SUB_FIREWALL, IPFW_MODEVENT_ORDER);
FEATURE(ipfw_ctl3, "ipfw new sockopt calls");
MODULE_VERSION(ipfw, 3);
/* should declare some dependencies here */

/*
 * Starting up. Done in order after ipfwmod() has been called.
 * VNET_SYSINIT is also called for each existing vnet and each new vnet.
 */
SYSINIT(ipfw_init, IPFW_SI_SUB_FIREWALL, IPFW_MODULE_ORDER,
	    ipfw_init, NULL);
VNET_SYSINIT(vnet_ipfw_init, IPFW_SI_SUB_FIREWALL, IPFW_VNET_ORDER,
	    vnet_ipfw_init, NULL);

/*
 * Closing up shop. These are done in REVERSE ORDER, but still
 * after ipfwmod() has been called. Not called on reboot.
 * VNET_SYSUNINIT is also called for each exiting vnet as it exits.
 * or when the module is unloaded.
 */
SYSUNINIT(ipfw_destroy, IPFW_SI_SUB_FIREWALL, IPFW_MODULE_ORDER,
	    ipfw_destroy, NULL);
VNET_SYSUNINIT(vnet_ipfw_uninit, IPFW_SI_SUB_FIREWALL, IPFW_VNET_ORDER,
	    vnet_ipfw_uninit, NULL);
/* end of file */