xnu-792.6.76.tar.gz

[apple/xnu.git] / bsd / netinet / ip_fw2.c

/*
 * Copyright (c) 2002 Luigi Rizzo, Universita` di Pisa
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/netinet/ip_fw2.c,v 1.6.2.18 2003/10/17 11:01:03 scottl Exp $
 */

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

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

#ifndef INET
#error IPFIREWALL requires INET.
#endif /* INET */

#ifdef IPFW2
#include <machine/spl.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/ucred.h>
#include <net/if.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/in_pcb.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>
#include <netinet/ip_fw.h>
#include <netinet/ip_divert.h>

#if DUMMYNET
#include <netinet/ip_dummynet.h>
#endif /* DUMMYNET */

#include <netinet/tcp.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>

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

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

#include "ip_fw2_compat.h"

#include <sys/kern_event.h>
#include <stdarg.h>

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

/*
 * XXX This one should go in sys/mbuf.h. It is used to avoid that
 * a firewall-generated packet loops forever through the firewall.
 */
#ifndef M_SKIP_FIREWALL
#define M_SKIP_FIREWALL         0x4000
#endif

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

int fw_verbose;
static int verbose_limit;

#define IPFW_DEFAULT_RULE       65535

#define IPFW_RULE_INACTIVE 1

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

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

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

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

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

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

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

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

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

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

#endif /* SYSCTL_NODE */


static ip_fw_chk_t      ipfw_chk;

/* firewall lock */
lck_grp_t         *ipfw_mutex_grp;
lck_grp_attr_t    *ipfw_mutex_grp_attr;
lck_attr_t        *ipfw_mutex_attr;
lck_mtx_t         *ipfw_mutex;

extern  void    ipfwsyslog( int level, char *format,...);

#if DUMMYNET
ip_dn_ruledel_t *ip_dn_ruledel_ptr = NULL;      /* hook into dummynet */
#endif /* DUMMYNET */

#define KEV_LOG_SUBCLASS 10
#define IPFWLOGEVENT    0

#define         ipfwstring      "ipfw:"
static          size_t          ipfwstringlen;

#define dolog( a ) {            \
        if ( fw_verbose == 2 )          /* Apple logging, log to ipfw.log */ \
                ipfwsyslog a ;  \ 
        else log a ;            \
}

void    ipfwsyslog( int level, char *format,...)
{
#define         msgsize         100

    struct kev_msg        ev_msg;
    va_list             ap;
    char                msgBuf[msgsize];
    char                *dptr = msgBuf;
    unsigned char       pri;
    int                 loglen;

        va_start( ap, format );
        loglen = vsnprintf(msgBuf, msgsize, format, ap);
        va_end( ap );

        ev_msg.vendor_code    = KEV_VENDOR_APPLE;
        ev_msg.kev_class      = KEV_NETWORK_CLASS;
        ev_msg.kev_subclass   = KEV_LOG_SUBCLASS;
        ev_msg.event_code         = IPFWLOGEVENT;

        /* get rid of the trailing \n */
        dptr[loglen-1] = 0;

        pri = LOG_PRI(level);

        /* remove "ipfw:" prefix if logging to ipfw log */
        if ( !(strncmp( ipfwstring, msgBuf, ipfwstringlen))){
                dptr = msgBuf+ipfwstringlen;
        }
        
        ev_msg.dv[0].data_ptr = &pri;
        ev_msg.dv[0].data_length = 1;
        ev_msg.dv[1].data_ptr    = dptr;
        ev_msg.dv[1].data_length = 100; /* bug in kern_post_msg, it can't handle size > 256-msghdr */
        ev_msg.dv[2].data_length = 0;

        kev_post_msg(&ev_msg);
}

/*
 * This macro maps an ip pointer into a layer3 header pointer of type T
 */
#define L3HDR(T, ip) ((T *)((u_int32_t *)(ip) + (ip)->ip_hl))

static __inline int
icmptype_match(struct ip *ip, ipfw_insn_u32 *cmd)
{
        int type = L3HDR(struct icmp,ip)->icmp_type;

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

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

static int
is_icmp_query(struct ip *ip)
{
        int type = L3HDR(struct icmp, ip)->icmp_type;
        return (type <= ICMP_MAXTYPE && (TT & (1<<type)) );
}
#undef TT

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

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

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

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

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

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

                default:
                        break;

                case IPOPT_LSRR:
                        bits |= IP_FW_IPOPT_LSRR;
                        break;

                case IPOPT_SSRR:
                        bits |= IP_FW_IPOPT_SSRR;
                        break;

                case IPOPT_RR:
                        bits |= IP_FW_IPOPT_RR;
                        break;

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

static int
tcpopts_match(struct ip *ip, ipfw_insn *cmd)
{
        int optlen, bits = 0;
        struct tcphdr *tcp = L3HDR(struct tcphdr,ip);
        u_char *cp = (u_char *)(tcp + 1);
        int x = (tcp->th_off << 2) - sizeof(struct tcphdr);

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

                switch (opt) {

                default:
                        break;

                case TCPOPT_MAXSEG:
                        bits |= IP_FW_TCPOPT_MSS;
                        break;

                case TCPOPT_WINDOW:
                        bits |= IP_FW_TCPOPT_WINDOW;
                        break;

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

                case TCPOPT_TIMESTAMP:
                        bits |= IP_FW_TCPOPT_TS;
                        break;

                case TCPOPT_CC:
                case TCPOPT_CCNEW:
                case TCPOPT_CCECHO:
                        bits |= IP_FW_TCPOPT_CC;
                        break;
                }
        }
        return (flags_match(cmd, bits));
}

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

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

/*
 * 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. This is 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 knob is purposely reminisent of the Cisco IOS command,
 *
 *   ip verify unicast reverse-path
 *
 * which implements the same functionality. But note that syntax is
 * misleading. The check may be performed on all IP packets whether unicast,
 * multicast, or broadcast.
 */
static int
verify_rev_path(struct in_addr src, struct ifnet *ifp)
{
        static struct route ro;
        struct sockaddr_in *dst;

        dst = (struct sockaddr_in *)&(ro.ro_dst);

        /* Check if we've cached the route from the previous call. */
        if (src.s_addr != dst->sin_addr.s_addr) {
                ro.ro_rt = NULL;

                bzero(dst, sizeof(*dst));
                dst->sin_family = AF_INET;
                dst->sin_len = sizeof(*dst);
                dst->sin_addr = src;

                rtalloc_ign(&ro, RTF_CLONING|RTF_PRCLONING);
        }

        if ((ro.ro_rt == NULL) || (ifp == NULL) ||
            (ro.ro_rt->rt_ifp->if_index != ifp->if_index))
                return 0;

        return 1;
}


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

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

/*
 * We enter here when we have a rule with O_LOG.
 * XXX this function alone takes about 2Kbytes of code!
 */
static void
ipfw_log(struct ip_fw *f, u_int hlen, struct ether_header *eh,
        struct mbuf *m, struct ifnet *oif)
{
        char *action;
        int limit_reached = 0;
        char ipv4str[MAX_IPv4_STR_LEN];
        char action2[40], proto[48], fragment[28];
        
        fragment[0] = '\0';
        proto[0] = '\0';

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

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

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

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

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

                        if (f->reserved_1 == IPFW_RULE_INACTIVE) {
                                break;
                        }
                        len = snprintf(SNPARGS(action2, 0), "Forward to %s",
                                inet_ntop(AF_INET, &sa->sa.sin_addr, ipv4str, sizeof(ipv4str)));
                        if (sa->sa.sin_port)
                                snprintf(SNPARGS(action2, len), ":%d",
                                    sa->sa.sin_port);
                        }
                        break;
                default:
                        action = "UNKNOWN";
                        break;
                }
        }

        if (hlen == 0) {        /* non-ip */
                snprintf(SNPARGS(proto, 0), "MAC");
        } else {
                struct ip *ip = mtod(m, struct ip *);
                /* these three are all aliases to the same thing */
                struct icmp *const icmp = L3HDR(struct icmp, ip);
                struct tcphdr *const tcp = (struct tcphdr *)icmp;
                struct udphdr *const udp = (struct udphdr *)icmp;

                int ip_off, offset, ip_len;

                int len;

                if (eh != NULL) { /* layer 2 packets are as on the wire */
                        ip_off = ntohs(ip->ip_off);
                        ip_len = ntohs(ip->ip_len);
                } else {
                        ip_off = ip->ip_off;
                        ip_len = ip->ip_len;
                }
                offset = ip_off & IP_OFFMASK;
                switch (ip->ip_p) {
                case IPPROTO_TCP:
                        len = snprintf(SNPARGS(proto, 0), "TCP %s",
                            inet_ntop(AF_INET, &ip->ip_src, ipv4str, sizeof(ipv4str)));
                        if (offset == 0)
                                snprintf(SNPARGS(proto, len), ":%d %s:%d",
                                    ntohs(tcp->th_sport),
                                    inet_ntop(AF_INET, &ip->ip_dst, ipv4str, sizeof(ipv4str)),
                                    ntohs(tcp->th_dport));
                        else
                                snprintf(SNPARGS(proto, len), " %s",
                                    inet_ntop(AF_INET, &ip->ip_dst, ipv4str, sizeof(ipv4str)));
                        break;

                case IPPROTO_UDP:
                        len = snprintf(SNPARGS(proto, 0), "UDP %s",
                                inet_ntop(AF_INET, &ip->ip_src, ipv4str, sizeof(ipv4str)));
                        if (offset == 0)
                                snprintf(SNPARGS(proto, len), ":%d %s:%d",
                                    ntohs(udp->uh_sport),
                                    inet_ntop(AF_INET, &ip->ip_dst, ipv4str, sizeof(ipv4str)),
                                    ntohs(udp->uh_dport));
                        else
                                snprintf(SNPARGS(proto, len), " %s",
                                    inet_ntop(AF_INET, &ip->ip_dst, ipv4str, sizeof(ipv4str)));
                        break;

                case IPPROTO_ICMP:
                        if (offset == 0)
                                len = snprintf(SNPARGS(proto, 0),
                                    "ICMP:%u.%u ",
                                    icmp->icmp_type, icmp->icmp_code);
                        else
                                len = snprintf(SNPARGS(proto, 0), "ICMP ");
                        len += snprintf(SNPARGS(proto, len), "%s",
                            inet_ntop(AF_INET, &ip->ip_src, ipv4str, sizeof(ipv4str)));
                        snprintf(SNPARGS(proto, len), " %s",
                            inet_ntop(AF_INET, &ip->ip_dst, ipv4str, sizeof(ipv4str)));
                        break;

                default:
                        len = snprintf(SNPARGS(proto, 0), "P:%d %s", ip->ip_p,
                            inet_ntop(AF_INET, &ip->ip_src, ipv4str, sizeof(ipv4str)));
                        snprintf(SNPARGS(proto, len), " %s",
                            inet_ntop(AF_INET, &ip->ip_dst, ipv4str, sizeof(ipv4str)));
                        break;
                }

                if (ip_off & (IP_MF | IP_OFFMASK))
                        snprintf(SNPARGS(fragment, 0), " (frag %d:%d@%d%s)",
                             ntohs(ip->ip_id), ip_len - (ip->ip_hl << 2),
                             offset << 3,
                             (ip_off & IP_MF) ? "+" : "");
        }
        if (oif || m->m_pkthdr.rcvif)
        {
                dolog((LOG_AUTHPRIV | LOG_INFO,
                    "ipfw: %d %s %s %s via %s%d%s\n",
                    f ? f->rulenum : -1,
                    action, proto, oif ? "out" : "in",
                    oif ? oif->if_name : m->m_pkthdr.rcvif->if_name,
                    oif ? oif->if_unit : m->m_pkthdr.rcvif->if_unit,
                    fragment)); 
        }
        else{
                dolog((LOG_AUTHPRIV | LOG_INFO,
                    "ipfw: %d %s %s [no if info]%s\n",
                    f ? f->rulenum : -1,
                    action, proto, fragment));
        }
        if (limit_reached){
                dolog((LOG_AUTHPRIV | LOG_NOTICE,
                    "ipfw: limit %d reached on entry %d\n",
                    limit_reached, f ? f->rulenum : -1));
        }
}

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

        i = (id->dst_ip) ^ (id->src_ip) ^ (id->dst_port) ^ (id->src_port);
        i &= (curr_dyn_buckets - 1);
        return i;
}

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

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

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

#define FORCE (keep_me == NULL)

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

        getmicrotime(&timenow);

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

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


/**
 * lookup a dynamic rule.
 */
static ipfw_dyn_rule *
lookup_dyn_rule(struct ipfw_flow_id *pkt, int *match_direction,
        struct tcphdr *tcp)
{
        /*
         * stateful ipfw extensions.
         * Lookup into dynamic session queue
         */
#define MATCH_REVERSE   0
#define MATCH_FORWARD   1
#define MATCH_NONE      2
#define MATCH_UNKNOWN   3
#define BOTH_SYN        (TH_SYN | (TH_SYN << 8))
#define BOTH_FIN        (TH_FIN | (TH_FIN << 8))

        int i, dir = MATCH_NONE;
        ipfw_dyn_rule *prev, *q=NULL;
        struct timeval timenow;

        getmicrotime(&timenow);

        if (ipfw_dyn_v == NULL)
                goto done;      /* not found */
        i = hash_packet( pkt );
        for (prev=NULL, q = ipfw_dyn_v[i] ; q != NULL ; ) {
                if (q->dyn_type == O_LIMIT_PARENT && q->count)
                        goto next;
                if (TIME_LEQ( q->expire, timenow.tv_sec)) { /* expire entry */
                        int     dounlink = 1;

                        /* check if entry is TCP */
                        if ( q->id.proto == IPPROTO_TCP )
                        {
                                /* do not delete an established TCP connection which hasn't been closed by both sides */
                                if ( (q->state & (BOTH_SYN | BOTH_FIN)) != (BOTH_SYN | BOTH_FIN) )
                                        dounlink = 0;
                        }
                        if ( dounlink ){
                                UNLINK_DYN_RULE(prev, ipfw_dyn_v[i], q);
                                continue;
                        }
                }
                if (pkt->proto == q->id.proto &&
                    q->dyn_type != O_LIMIT_PARENT) {
                        if (pkt->src_ip == q->id.src_ip &&
                            pkt->dst_ip == q->id.dst_ip &&
                            pkt->src_port == q->id.src_port &&
                            pkt->dst_port == q->id.dst_port ) {
                                dir = MATCH_FORWARD;
                                break;
                        }
                        if (pkt->src_ip == q->id.dst_ip &&
                            pkt->dst_ip == q->id.src_ip &&
                            pkt->src_port == q->id.dst_port &&
                            pkt->dst_port == q->id.src_port ) {
                                dir = MATCH_REVERSE;
                                break;
                        }
                }
next:
                prev = q;
                q = q->next;
        }
        if (q == NULL)
                goto done; /* q = NULL, not found */

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

                q->state |= (dir == MATCH_FORWARD ) ? flags : (flags << 8);
                switch (q->state) {
                case TH_SYN:                            /* opening */
                        q->expire = timenow.tv_sec + dyn_syn_lifetime;
                        break;

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

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

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

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

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

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

        getmicrotime(&timenow);

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

        r = _MALLOC(sizeof *r, M_IPFW, M_NOWAIT | M_ZERO);
        if (r == NULL) {
#if IPFW_DEBUG
                printf ("ipfw: sorry cannot allocate state\n");
#endif
                return NULL;
        }

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

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

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

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

        getmicrotime(&timenow);

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

/**
 * Install dynamic state for rule type cmd->o.opcode
 *
 * Returns 1 (failure) if state is not installed because of errors or because
 * session limitations are enforced.
 */
static int
install_state(struct ip_fw *rule, ipfw_insn_limit *cmd,
        struct ip_fw_args *args)
{
        static int last_log;
        struct timeval timenow;

        ipfw_dyn_rule *q;
        getmicrotime(&timenow);

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

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

        if (q != NULL) { /* should never occur */
                if (last_log != timenow.tv_sec) {
                        last_log = timenow.tv_sec;
                        printf("ipfw: install_state: entry already present, done\n");
                }
                return 0;
        }

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

        if (dyn_count >= dyn_max) {
                if (last_log != timenow.tv_sec) {
                        last_log = timenow.tv_sec;
                        printf("ipfw: install_state: Too many dynamic rules\n");
                }
                return 1; /* cannot install, notify caller */
        }

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

        case O_LIMIT: /* limit number of sessions */
            {
                u_int16_t limit_mask = cmd->limit_mask;
                struct ipfw_flow_id id;
                ipfw_dyn_rule *parent;

                DEB(printf("ipfw: installing dyn-limit rule %d\n",
                    cmd->conn_limit);)

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

                if (limit_mask & DYN_SRC_ADDR)
                        id.src_ip = args->f_id.src_ip;
                if (limit_mask & DYN_DST_ADDR)
                        id.dst_ip = args->f_id.dst_ip;
                if (limit_mask & DYN_SRC_PORT)
                        id.src_port = args->f_id.src_port;
                if (limit_mask & DYN_DST_PORT)
                        id.dst_port = args->f_id.dst_port;
                parent = lookup_dyn_parent(&id, rule);
                if (parent == NULL) {
                        printf("ipfw: add parent failed\n");
                        return 1;
                }
                if (parent->count >= cmd->conn_limit) {
                        /*
                         * See if we can remove some expired rule.
                         */
                        remove_dyn_rule(rule, parent);
                        if (parent->count >= cmd->conn_limit) {
                                if (fw_verbose && last_log != timenow.tv_sec) {
                                        last_log = timenow.tv_sec;
                                        dolog((LOG_AUTHPRIV | LOG_DEBUG,
                                            "drop session, too many entries\n"));
                                }
                                return 1;
                        }
                }
                add_dyn_rule(&args->f_id, O_LIMIT, (struct ip_fw *)parent);
            }
                break;
        default:
                printf("ipfw: unknown dynamic rule type %u\n", cmd->o.opcode);
                return 1;
        }
        lookup_dyn_rule(&args->f_id, NULL, NULL); /* XXX just set lifetime */
        return 0;
}

/*
 * Transmit a TCP packet, containing either a RST or a keepalive.
 * When flags & TH_RST, we are sending a RST packet, because of a
 * "reset" action matched the packet.
 * Otherwise we are sending a keepalive, and flags & TH_
 */
static void
send_pkt(struct ipfw_flow_id *id, u_int32_t seq, u_int32_t ack, int flags)
{
        struct mbuf *m;
        struct ip *ip;
        struct tcphdr *tcp;
        struct route sro;       /* fake route */

        MGETHDR(m, M_DONTWAIT, MT_HEADER);
        if (m == 0)
                return;
        m->m_pkthdr.rcvif = (struct ifnet *)0;
        m->m_pkthdr.len = m->m_len = sizeof(struct ip) + sizeof(struct tcphdr);
        m->m_data += max_linkhdr;

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

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

        if (code != ICMP_REJECT_RST) { /* Send an ICMP unreach */
                /* We need the IP header in host order for icmp_error(). */
                if (args->eh != NULL) {
                        struct ip *ip = mtod(args->m, struct ip *);
                        ip->ip_len = ntohs(ip->ip_len);
                        ip->ip_off = ntohs(ip->ip_off);
                }
                args->m->m_flags |= M_SKIP_FIREWALL;
                icmp_error(args->m, ICMP_UNREACH, code, 0L, 0);
        } else if (offset == 0 && args->f_id.proto == IPPROTO_TCP) {
                struct tcphdr *const tcp =
                    L3HDR(struct tcphdr, mtod(args->m, struct ip *));
                if ( (tcp->th_flags & TH_RST) == 0) {
                        send_pkt(&(args->f_id), ntohl(tcp->th_seq),
                                ntohl(tcp->th_ack),
                                tcp->th_flags | TH_RST);
                }
                m_freem(args->m);
        } else
                m_freem(args->m);
        args->m = NULL;
}

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

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

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

/*
 * The main check routine for the firewall.
 *
 * All arguments are in args so we can modify them and return them
 * back to the caller.
 *
 * Parameters:
 *
 *      args->m (in/out) The packet; we set to NULL when/if we nuke it.
 *              Starts with the IP header.
 *      args->eh (in)   Mac header if present, or NULL for layer3 packet.
 *      args->oif       Outgoing interface, or NULL if packet is incoming.
 *              The incoming interface is in the mbuf. (in)
 *      args->divert_rule (in/out)
 *              Skip up to the first rule past this rule number;
 *              upon return, non-zero port number for divert or tee.
 *
 *      args->rule      Pointer to the last matching rule (in/out)
 *      args->next_hop  Socket we are forwarding to (out).
 *      args->f_id      Addresses grabbed from the packet (out)
 *
 * Return value:
 *
 *      IP_FW_PORT_DENY_FLAG    the packet must be dropped.
 *      0       The packet is to be accepted and routed normally OR
 *              the packet was denied/rejected and has been dropped;
 *              in the latter case, *m is equal to NULL upon return.
 *      port    Divert the packet to port, with these caveats:
 *
 *              - If IP_FW_PORT_TEE_FLAG is set, tee the packet instead
 *                of diverting it (ie, 'ipfw tee').
 *
 *              - If IP_FW_PORT_DYNT_FLAG is set, interpret the lower
 *                16 bits as a dummynet pipe number instead of diverting
 */

static int
ipfw_chk(struct ip_fw_args *args)
{
        /*
         * Local variables hold state during the processing of a packet.
         *
         * IMPORTANT NOTE: to speed up the processing of rules, there
         * are some assumption on the values of the variables, which
         * are documented here. Should you change them, please check
         * the implementation of the various instructions to make sure
         * that they still work.
         *
         * args->eh     The MAC header. It is non-null for a layer2
         *      packet, it is NULL for a layer-3 packet.
         *
         * m | args->m  Pointer to the mbuf, as received from the caller.
         *      It may change if ipfw_chk() does an m_pullup, or if it
         *      consumes the packet because it calls send_reject().
         *      XXX This has to change, so that ipfw_chk() never modifies
         *      or consumes the buffer.
         * ip   is simply an alias of the value of m, and it is kept
         *      in sync with it (the packet is  supposed to start with
         *      the ip header).
         */
        struct mbuf *m = args->m;
        struct ip *ip = mtod(m, struct ip *);

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

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

        /*
         * hlen The length of the IPv4 header.
         *      hlen >0 means we have an IPv4 packet.
         */
        u_int hlen = 0;         /* hlen >0 means we have an IP pkt */

        /*
         * offset       The offset of a fragment. offset != 0 means that
         *      we have a fragment at this offset of an IPv4 packet.
         *      offset == 0 means that (if this is an IPv4 packet)
         *      this is the first or only fragment.
         */
        u_short offset = 0;

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

        if (m->m_flags & M_SKIP_FIREWALL) {
                return 0;       /* accept */
        }

        lck_mtx_lock(ipfw_mutex);

        getmicrotime(&timenow);
        /*
         * dyn_dir = MATCH_UNKNOWN when rules unchecked,
         *      MATCH_NONE when checked and not matched (q = NULL),
         *      MATCH_FORWARD or MATCH_REVERSE otherwise (q != NULL)
         */

        pktlen = m->m_pkthdr.len;
        if (args->eh == NULL ||         /* layer 3 packet */
                ( m->m_pkthdr.len >= sizeof(struct ip) &&
                    ntohs(args->eh->ether_type) == ETHERTYPE_IP))
                        hlen = ip->ip_hl << 2;

        /*
         * Collect parameters into local variables for faster matching.
         */
        if (hlen == 0) {        /* do not grab addresses for non-ip pkts */
                proto = args->f_id.proto = 0;   /* mark f_id invalid */
                goto after_ip_checks;
        }

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

#define PULLUP_TO(len)                                          \
                do {                                            \
                        if ((m)->m_len < (len)) {               \
                            args->m = m = m_pullup(m, (len));   \
                            if (m == 0)                         \
                                goto pullup_failed;             \
                            ip = mtod(m, struct ip *);          \
                        }                                       \
                } while (0)

        if (offset == 0) {
                switch (proto) {
                case IPPROTO_TCP:
                    {
                        struct tcphdr *tcp;

                        PULLUP_TO(hlen + sizeof(struct tcphdr));
                        tcp = L3HDR(struct tcphdr, ip);
                        dst_port = tcp->th_dport;
                        src_port = tcp->th_sport;
                        args->f_id.flags = tcp->th_flags;
                        }
                        break;

                case IPPROTO_UDP:
                    {
                        struct udphdr *udp;

                        PULLUP_TO(hlen + sizeof(struct udphdr));
                        udp = L3HDR(struct udphdr, ip);
                        dst_port = udp->uh_dport;
                        src_port = udp->uh_sport;
                        }
                        break;

                case IPPROTO_ICMP:
                        PULLUP_TO(hlen + 4);    /* type, code and checksum. */
                        args->f_id.flags = L3HDR(struct icmp, ip)->icmp_type;
                        break;

                default:
                        break;
                }
#undef PULLUP_TO
        }

        args->f_id.src_ip = ntohl(src_ip.s_addr);
        args->f_id.dst_ip = ntohl(dst_ip.s_addr);
        args->f_id.src_port = src_port = ntohs(src_port);
        args->f_id.dst_port = dst_port = ntohs(dst_port);

after_ip_checks:
        if (args->rule) {
                /*
                 * Packet has already been tagged. Look for the next rule
                 * to restart processing.
                 *
                 * If fw_one_pass != 0 then just accept it.
                 * XXX should not happen here, but optimized out in
                 * the caller.
                 */
                if (fw_one_pass) {
                        lck_mtx_unlock(ipfw_mutex);
                        return 0;
                }

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

                f = layer3_chain;
                if (args->eh == NULL && skipto != 0) {
                        if (skipto >= IPFW_DEFAULT_RULE) {
                                lck_mtx_unlock(ipfw_mutex);
                                return(IP_FW_PORT_DENY_FLAG); /* invalid */
                        }
                        while (f && f->rulenum <= skipto)
                                f = f->next;
                        if (f == NULL) {        /* drop packet */
                                lck_mtx_unlock(ipfw_mutex);
                                return(IP_FW_PORT_DENY_FLAG);
                        }
                }
        }
        args->divert_rule = 0;  /* reset to avoid confusion later */

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

again:
                if (f->reserved_1 == IPFW_RULE_INACTIVE) {
                        continue;
                }
                
                if (set_disable & (1 << f->set) )
                        continue;

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

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

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

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

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

#ifndef __APPLE__
                        case O_GID:
#endif
                        case O_UID:
                                /*
                                 * We only check offset == 0 && proto != 0,
                                 * as this ensures that we have an IPv4
                                 * packet with the ports info.
                                 */
                                if (offset!=0)
                                        break;
                                        
                            {
                                struct inpcbinfo *pi;
                                int wildcard;
                                struct inpcb *pcb;

                                if (proto == IPPROTO_TCP) {
                                        wildcard = 0;
                                        pi = &tcbinfo;
                                } else if (proto == IPPROTO_UDP) {
                                        wildcard = 1;
                                        pi = &udbinfo;
                                } else
                                        break;

                                pcb =  (oif) ?
                                        in_pcblookup_hash(pi,
                                            dst_ip, htons(dst_port),
                                            src_ip, htons(src_port),
                                            wildcard, oif) :
                                        in_pcblookup_hash(pi,
                                            src_ip, htons(src_port),
                                            dst_ip, htons(dst_port),
                                            wildcard, NULL);

                                if (pcb == NULL || pcb->inp_socket == NULL)
                                        break;
#if __FreeBSD_version < 500034
#define socheckuid(a,b) (kauth_cred_getuid((a)->so_cred) != (b))
#endif
                                if (cmd->opcode == O_UID) {
                                        match = 
#ifdef __APPLE__
                                                (pcb->inp_socket->so_uid == (uid_t)((ipfw_insn_u32 *)cmd)->d[0]);
#else
                                                !socheckuid(pcb->inp_socket,
                                                   (uid_t)((ipfw_insn_u32 *)cmd)->d[0]);
#endif
                                } 
#ifndef __APPLE__
                                else  {
                                        match = 0;
                                        kauth_cred_ismember_gid(pcb->inp_socket->so_cred, 
                                                (gid_t)((ipfw_insn_u32 *)cmd)->d[0], &match);
                                }
#endif
                                }

                        break;

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

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

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

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

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

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

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

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

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

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

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

                        case O_IP_SRC:
                                match = (hlen > 0 &&
                                    ((ipfw_insn_ip *)cmd)->addr.s_addr ==
                                    src_ip.s_addr);
                                break;

                        case O_IP_SRC_MASK:
                        case O_IP_DST_MASK:
                                if (hlen > 0) {
                                    uint32_t a =
                                        (cmd->opcode == O_IP_DST_MASK) ?
                                            dst_ip.s_addr : src_ip.s_addr;
                                    uint32_t *p = ((ipfw_insn_u32 *)cmd)->d;
                                    int i = cmdlen-1;

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

                        case O_IP_SRC_ME:
                                if (hlen > 0) {
                                        struct ifnet *tif;

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

                        case O_IP_DST_SET:
                        case O_IP_SRC_SET:
                                if (hlen > 0) {
                                        u_int32_t *d = (u_int32_t *)(cmd+1);
                                        u_int32_t addr =
                                            cmd->opcode == O_IP_DST_SET ?
                                                args->f_id.dst_ip :
                                                args->f_id.src_ip;

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

                        case O_IP_DST:
                                match = (hlen > 0 &&
                                    ((ipfw_insn_ip *)cmd)->addr.s_addr ==
                                    dst_ip.s_addr);
                                break;

                        case O_IP_DST_ME:
                                if (hlen > 0) {
                                        struct ifnet *tif;

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

                        case O_IP_SRCPORT:
                        case O_IP_DSTPORT:
                                /*
                                 * offset == 0 && proto != 0 is enough
                                 * to guarantee that we have an IPv4
                                 * packet with port info.
                                 */
                                if ((proto==IPPROTO_UDP || proto==IPPROTO_TCP)
                                    && offset == 0) {
                                        u_int16_t x =
                                            (cmd->opcode == O_IP_SRCPORT) ?
                                                src_port : dst_port ;
                                        u_int16_t *p =
                                            ((ipfw_insn_u16 *)cmd)->ports;
                                        int i;

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

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

                        case O_IPOPT:
                                match = (hlen > 0 && ipopts_match(ip, cmd) );
                                break;

                        case O_IPVER:
                                match = (hlen > 0 && cmd->arg1 == ip->ip_v);
                                break;

                        case O_IPID:
                        case O_IPLEN:
                        case O_IPTTL:
                                if (hlen > 0) { /* only for IP packets */
                                    uint16_t x;
                                    uint16_t *p;
                                    int i;

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

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

                        case O_IPTOS:
                                match = (hlen > 0 &&
                                    flags_match(cmd, ip->ip_tos));
                                break;

                        case O_TCPFLAGS:
                                match = (proto == IPPROTO_TCP && offset == 0 &&
                                    flags_match(cmd,
                                        L3HDR(struct tcphdr,ip)->th_flags));
                                break;

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

                        case O_TCPSEQ:
                                match = (proto == IPPROTO_TCP && offset == 0 &&
                                    ((ipfw_insn_u32 *)cmd)->d[0] ==
                                        L3HDR(struct tcphdr,ip)->th_seq);
                                break;

                        case O_TCPACK:
                                match = (proto == IPPROTO_TCP && offset == 0 &&
                                    ((ipfw_insn_u32 *)cmd)->d[0] ==
                                        L3HDR(struct tcphdr,ip)->th_ack);
                                break;

                        case O_TCPWIN:
                                match = (proto == IPPROTO_TCP && offset == 0 &&
                                    cmd->arg1 ==
                                        L3HDR(struct tcphdr,ip)->th_win);
                                break;

                        case O_ESTAB:
                                /* reject packets which have SYN only */
                                /* XXX should i also check for TH_ACK ? */
                                match = (proto == IPPROTO_TCP && offset == 0 &&
                                    (L3HDR(struct tcphdr,ip)->th_flags &
                                     (TH_RST | TH_ACK | TH_SYN)) != TH_SYN);
                                break;

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

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

                        case O_VERREVPATH:
                                /* Outgoing packets automatically pass/match */
                                match = ((oif != NULL) ||
                                    (m->m_pkthdr.rcvif == NULL) ||
                                    verify_rev_path(src_ip, m->m_pkthdr.rcvif));
                                break;

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

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

                        case O_PROBE_STATE:
                        case O_CHECK_STATE:
                                /*
                                 * dynamic rules are checked at the first
                                 * keep-state or check-state occurrence,
                                 * with the result being stored in dyn_dir.
                                 * The compiler introduces a PROBE_STATE
                                 * instruction for us when we have a
                                 * KEEP_STATE (because PROBE_STATE needs
                                 * to be run first).
                                 */
                                if (dyn_dir == MATCH_UNKNOWN &&
                                    (q = lookup_dyn_rule(&args->f_id,
                                     &dyn_dir, proto == IPPROTO_TCP ?
                                        L3HDR(struct tcphdr, ip) : NULL))
                                        != NULL) {
                                        /*
                                         * Found dynamic entry, update stats
                                         * and jump to the 'action' part of
                                         * the parent rule.
                                         */
                                        q->pcnt++;
                                        q->bcnt += pktlen;
                                        f = q->rule;
                                        cmd = ACTION_PTR(f);
                                        l = f->cmd_len - f->act_ofs;
                                        goto check_body;
                                }
                                /*
                                 * Dynamic entry not found. If CHECK_STATE,
                                 * skip to next rule, if PROBE_STATE just
                                 * ignore and continue with next opcode.
                                 */
                                if (cmd->opcode == O_CHECK_STATE)
                                        goto next_rule;
                                match = 1;
                                break;

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

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

                        case O_DIVERT:
                        case O_TEE:
                                if (args->eh) /* not on layer 2 */
                                        break;
                                args->divert_rule = f->rulenum;
                                retval = (cmd->opcode == O_DIVERT) ?
                                    cmd->arg1 :
                                    cmd->arg1 | IP_FW_PORT_TEE_FLAG;
                                goto done;

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

                        case O_REJECT:
                                /*
                                 * Drop the packet and send a reject notice
                                 * if the packet is not ICMP (or is an ICMP
                                 * query), and it is not multicast/broadcast.
                                 */
                                if (hlen > 0 &&
                                    (proto != IPPROTO_ICMP ||
                                     is_icmp_query(ip)) &&
                                    !(m->m_flags & (M_BCAST|M_MCAST)) &&
                                    !IN_MULTICAST(dst_ip.s_addr)) {
                                        send_reject(args, cmd->arg1,
                                            offset,ip_len);
                                        m = args->m;
                                }
                                /* FALLTHROUGH */
                        case O_DENY:
                                retval = IP_FW_PORT_DENY_FLAG;
                                goto done;

                        case O_FORWARD_IP:
                                if (args->eh)   /* not valid on layer2 pkts */
                                        break;
                                if (!q || dyn_dir == MATCH_FORWARD)
                                        args->next_hop =
                                            &((ipfw_insn_sa *)cmd)->sa;
                                retval = 0;
                                goto done;

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

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

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

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

next_rule:;             /* try next rule                */

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

done:
        /* Update statistics */
        f->pcnt++;
        f->bcnt += pktlen;
        f->timestamp = timenow.tv_sec;
        lck_mtx_unlock(ipfw_mutex);
        return retval;

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

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

        for (rule = layer3_chain; rule; rule = rule->next)
                rule->next_rule = NULL;
}

/*
 * When pipes/queues are deleted, clear the "pipe_ptr" pointer to a given
 * pipe/queue, or to all of them (match == NULL).
 * Must be called at splimp().
 */
void
flush_pipe_ptrs(struct dn_flow_set *match)
{
        struct ip_fw *rule;

        for (rule = layer3_chain; rule; rule = rule->next) {
                ipfw_insn_pipe *cmd = (ipfw_insn_pipe *)ACTION_PTR(rule);

                if (cmd->o.opcode != O_PIPE && cmd->o.opcode != O_QUEUE)
                        continue;
                /*
                 * XXX Use bcmp/bzero to handle pipe_ptr to overcome
                 * possible alignment problems on 64-bit architectures.
                 * This code is seldom used so we do not worry too
                 * much about efficiency.
                 */
                if (match == NULL ||
                    !bcmp(&cmd->pipe_ptr, &match, sizeof(match)) )
                        bzero(&cmd->pipe_ptr, sizeof(cmd->pipe_ptr));
        }
}

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

        if (*head == NULL && input_rule->rulenum != IPFW_DEFAULT_RULE)
                return (EINVAL);

        rule = _MALLOC(l, M_IPFW, M_WAIT);
        if (rule == NULL) {
                printf("ipfw2: add_rule MALLOC failed\n");
                return (ENOSPC);
        }
        
        bzero(rule, l);
        bcopy(input_rule, rule, l);

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

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

        if (*head == NULL) {    /* default rule */
                *head = rule;
                goto done;
        }

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

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

/**
 * Free storage associated with a static rule (including derived
 * dynamic rules).
 * The caller is in charge of clearing rule pointers to avoid
 * dangling pointers.
 * @return a pointer to the next entry.
 * Arguments are not checked, so they better be correct.
 * Must be called at splimp().
 */
static struct ip_fw *
delete_rule(struct ip_fw **head, struct ip_fw *prev, struct ip_fw *rule)
{
        struct ip_fw *n;
        int l = RULESIZE(rule);

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

#if DUMMYNET
        if (DUMMYNET_LOADED)
                ip_dn_ruledel_ptr(rule);
#endif /* DUMMYNET */
        _FREE(rule, M_IPFW);
        return n;
}

#if DEBUG_INACTIVE_RULES
static void
print_chain(struct ip_fw **chain)
{
        struct ip_fw *rule = *chain;
        
        for (; rule; rule = rule->next) {
                ipfw_insn       *cmd = ACTION_PTR(rule);
                
                printf("ipfw: rule->rulenum = %d\n", rule->rulenum);
                
                if (rule->reserved_1 == IPFW_RULE_INACTIVE) {
                        printf("ipfw: rule->reserved = IPFW_RULE_INACTIVE\n");
                }
                
                switch (cmd->opcode) {
                        case O_DENY:
                                printf("ipfw: ACTION: Deny\n");
                                break;
        
                        case O_REJECT:
                                if (cmd->arg1==ICMP_REJECT_RST)
                                        printf("ipfw: ACTION: Reset\n");
                                else if (cmd->arg1==ICMP_UNREACH_HOST)
                                        printf("ipfw: ACTION: Reject\n");
                                break;
        
                        case O_ACCEPT:
                                printf("ipfw: ACTION: Accept\n");
                                break;
                        case O_COUNT:
                                printf("ipfw: ACTION: Count\n");
                                break;
                        case O_DIVERT:
                                printf("ipfw: ACTION: Divert\n");
                                break;
                        case O_TEE:
                                printf("ipfw: ACTION: Tee\n");
                                break;
                        case O_SKIPTO:
                                printf("ipfw: ACTION: SkipTo\n");
                                break;
                        case O_PIPE:
                                printf("ipfw: ACTION: Pipe\n");
                                break;
                        case O_QUEUE:
                                printf("ipfw: ACTION: Queue\n");
                                break;
                        case O_FORWARD_IP:
                                printf("ipfw: ACTION: Forward\n");
                                break;
                        default:
                                printf("ipfw: invalid action! %d\n", cmd->opcode);
                }
        }
}
#endif /* DEBUG_INACTIVE_RULES */

static void
flush_inactive(void *param)
{
        struct ip_fw *inactive_rule = (struct ip_fw *)param;
        struct ip_fw *rule, *prev;
        
        lck_mtx_lock(ipfw_mutex);
        
        for (rule = layer3_chain, prev = NULL; rule; ) {
                if (rule == inactive_rule && rule->reserved_1 == IPFW_RULE_INACTIVE) {
                        struct ip_fw *n = rule;
                        
                        if (prev == NULL) {
                                layer3_chain = rule->next;
                        }
                        else {
                                prev->next = rule->next;
                        }
                        rule = rule->next;
                        _FREE(n, M_IPFW);
                }
                else {
                        prev = rule;
                        rule = rule->next;
                }
        }
        
#if DEBUG_INACTIVE_RULES
        print_chain(&layer3_chain);
#endif
        lck_mtx_unlock(ipfw_mutex);
}

static void
mark_inactive(struct ip_fw **prev, struct ip_fw **rule)
{
        int                     l = RULESIZE(*rule);

        if ((*rule)->reserved_1 != IPFW_RULE_INACTIVE) {
                (*rule)->reserved_1 = IPFW_RULE_INACTIVE;
                static_count--;
                static_len -= l;
                
                timeout(flush_inactive, *rule, 30*hz); /* 30 sec. */
        }
        
        *prev = *rule;
        *rule = (*rule)->next;
}

/*
 * Deletes all rules from a chain (except rules in set RESVD_SET
 * unless kill_default = 1).
 * Must be called at splimp().
 */
static void
free_chain(struct ip_fw **chain, int kill_default)
{
        struct ip_fw *prev, *rule;

        flush_rule_ptrs(); /* more efficient to do outside the loop */
        for (prev = NULL, rule = *chain; rule ; )
                if (kill_default || rule->set != RESVD_SET) {
                        ipfw_insn       *cmd = ACTION_PTR(rule);
                        
                        /* skip over forwarding rules so struct isn't 
                         * deleted while pointer is still in use elsewhere
                         */
                        if (cmd->opcode == O_FORWARD_IP) {
                                mark_inactive(&prev, &rule);
                        }
                        else {
                                rule = delete_rule(chain, prev, rule);
                        }
                }
                else {
                        prev = rule;
                        rule = rule->next;
                }
}

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

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

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

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

                /*
                 * flush pointers outside the loop, then delete all matching
                 * rules. prev remains the same throughout the cycle.
                 */
                flush_rule_ptrs();
                while (rule->rulenum == rulenum) {
                        ipfw_insn       *cmd = ACTION_PTR(rule);
                        
                        /* keep forwarding rules around so struct isn't 
                         * deleted while pointer is still in use elsewhere
                         */
                        if (cmd->opcode == O_FORWARD_IP) {
                                mark_inactive(&prev, &rule);
                        }
                        else {
                                rule = delete_rule(chain, prev, rule);
                        }
                }
                break;

        case 1: /* delete all rules with given set number */
                flush_rule_ptrs();
                while (rule->rulenum < IPFW_DEFAULT_RULE) {
                        if (rule->set == rulenum) {
                                ipfw_insn       *cmd = ACTION_PTR(rule);
                                
                                /* keep forwarding rules around so struct isn't 
                                 * deleted while pointer is still in use elsewhere
                                 */
                                if (cmd->opcode == O_FORWARD_IP) {
                                        mark_inactive(&prev, &rule);
                                }
                                else {
                                        rule = delete_rule(chain, prev, rule);
                                }
                        }
                        else {
                                prev = rule;
                                rule = rule->next;
                        }
                }
                break;

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

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

        case 4: /* swap two sets */
                for (; rule->rulenum < IPFW_DEFAULT_RULE; rule = rule->next)
                        if (rule->set == rulenum)
                                rule->set = new_set;
                        else if (rule->set == new_set)
                                rule->set = rulenum;
                break;
        }
        return 0;
}

/*
 * Clear counters for a specific rule.
 */
static void
clear_counters(struct ip_fw *rule, int log_only)
{
        ipfw_insn_log *l = (ipfw_insn_log *)ACTION_PTR(rule);

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

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

        if (rulenum == 0) {
                norule_counter = 0;
                for (rule = layer3_chain; rule; rule = rule->next)
                        clear_counters(rule, log_only);
                msg = log_only ? "ipfw: All logging counts reset.\n" :
                                "ipfw: Accounting cleared.\n";
        } else {
                int cleared = 0;
                /*
                 * We can have multiple rules with the same number, so we
                 * need to clear them all.
                 */
                for (rule = layer3_chain; rule; rule = rule->next)
                        if (rule->rulenum == rulenum) {
                                while (rule && rule->rulenum == rulenum) {
                                        clear_counters(rule, log_only);
                                        rule = rule->next;
                                }
                                cleared = 1;
                                break;
                        }
                if (!cleared)   /* we did not find any matching rules */
                        return (EINVAL);
                msg = log_only ? "ipfw: Entry %d logging count reset.\n" :
                                "ipfw: Entry %d cleared.\n";
        }
        if (fw_verbose)
        {
                dolog((LOG_AUTHPRIV | LOG_NOTICE, msg, rulenum));
        }
        return (0);
}

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

        if (size < sizeof(*rule)) {
                printf("ipfw: rule too short\n");
                return (EINVAL);
        }
        /* first, check for valid size */
        l = RULESIZE(rule);
        if (l != size) {
                printf("ipfw: size mismatch (have %d want %d)\n", size, l);
                return (EINVAL);
        }
        /*
         * Now go for the individual checks. Very simple ones, basically only
         * instruction sizes.
         */
        for (l = rule->cmd_len, cmd = rule->cmd ;
                        l > 0 ; l -= cmdlen, cmd += cmdlen) {
                cmdlen = F_LEN(cmd);
                if (cmdlen > l) {
                        printf("ipfw: opcode %d size truncated\n",
                            cmd->opcode);
                        return EINVAL;
                }
                DEB(printf("ipfw: opcode %d\n", cmd->opcode);)
                switch (cmd->opcode) {
                case O_PROBE_STATE:
                case O_KEEP_STATE:
                case O_PROTO:
                case O_IP_SRC_ME:
                case O_IP_DST_ME:
                case O_LAYER2:
                case O_IN:
                case O_FRAG:
                case O_IPOPT:
                case O_IPTOS:
                case O_IPPRECEDENCE:
                case O_IPVER:
                case O_TCPWIN:
                case O_TCPFLAGS:
                case O_TCPOPTS:
                case O_ESTAB:
                case O_VERREVPATH:
                case O_IPSEC:
                        if (cmdlen != F_INSN_SIZE(ipfw_insn))
                                goto bad_size;
                        break;
                case O_UID:
#ifndef __APPLE__
                case O_GID:
#endif /* __APPLE__ */
                case O_IP_SRC:
                case O_IP_DST:
                case O_TCPSEQ:
                case O_TCPACK:
                case O_PROB:
                case O_ICMPTYPE:
                        if (cmdlen != F_INSN_SIZE(ipfw_insn_u32))
                                goto bad_size;
                        break;

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

                case O_LOG:
                        if (cmdlen != F_INSN_SIZE(ipfw_insn_log))
                                goto bad_size;
                                
                        /* enforce logging limit */
                        if (fw_verbose &&
                                ((ipfw_insn_log *)cmd)->max_log == 0 && verbose_limit != 0) {
                                ((ipfw_insn_log *)cmd)->max_log = verbose_limit;
                        }

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

                        break;

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

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

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

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

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

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

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

                case O_FORWARD_IP:
                        if (cmdlen != F_INSN_SIZE(ipfw_insn_sa))
                                goto bad_size;
                        goto check_action;

                case O_FORWARD_MAC: /* XXX not implemented yet */
                case O_CHECK_STATE:
                case O_COUNT:
                case O_ACCEPT:
                case O_DENY:
                case O_REJECT:
                case O_SKIPTO:
                case O_DIVERT:
                case O_TEE:
                        if (cmdlen != F_INSN_SIZE(ipfw_insn))
                                goto bad_size;
check_action:
                        if (have_action) {
                                printf("ipfw: opcode %d, multiple actions"
                                        " not allowed\n",
                                        cmd->opcode);
                                return EINVAL;
                        }
                        have_action = 1;
                        if (l != cmdlen) {
                                printf("ipfw: opcode %d, action must be"
                                        " last opcode\n",
                                        cmd->opcode);
                                return EINVAL;
                        }
                        break;
                default:
                        printf("ipfw: opcode %d, unknown opcode\n",
                                cmd->opcode);
                        return EINVAL;
                }
        }
        if (have_action == 0) {
                printf("ipfw: missing action\n");
                return EINVAL;
        }
        return 0;

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


/**
 * {set|get}sockopt parser.
 */
static int
ipfw_ctl(struct sockopt *sopt)
{
#define RULE_MAXSIZE    (256*sizeof(u_int32_t))
        u_int32_t api_version;
        int command;
        int error, s;
        size_t size;
        struct ip_fw *bp , *buf, *rule;
        
        /* copy of orig sopt to send to ipfw_get_command_and_version() */
        struct sockopt tmp_sopt = *sopt; 
        struct timeval timenow;

        getmicrotime(&timenow);
        
        /*
         * Disallow modifications in really-really secure mode, but still allow
         * the logging counters to be reset.
         */
        if (sopt->sopt_name == IP_FW_ADD ||
            (sopt->sopt_dir == SOPT_SET && sopt->sopt_name != IP_FW_RESETLOG)) {
#if __FreeBSD_version >= 500034
                error = securelevel_ge(sopt->sopt_td->td_ucred, 3);
                if (error)
                        return (error);
#else /* FreeBSD 4.x */
                if (securelevel >= 3)
                        return (EPERM);
#endif
        }

        /* first get the command and version, then do conversion as necessary */
        error = ipfw_get_command_and_version(&tmp_sopt, &command, &api_version);
        
        if (error) {
                /* error getting the version */
                return error;
        }
        
        switch (command) {
        case IP_FW_GET:
                /*
                 * pass up a copy of the current rules. Static rules
                 * come first (the last of which has number IPFW_DEFAULT_RULE),
                 * followed by a possibly empty list of dynamic rule.
                 * The last dynamic rule has NULL in the "next" field.
                 */
                lck_mtx_lock(ipfw_mutex);
                size = static_len;      /* size of static rules */
                if (ipfw_dyn_v)         /* add size of dyn.rules */
                        size += (dyn_count * sizeof(ipfw_dyn_rule));

                /*
                 * XXX todo: if the user passes a short length just to know
                 * how much room is needed, do not bother filling up the
                 * buffer, just jump to the sooptcopyout.
                 */
                buf = _MALLOC(size, M_TEMP, M_WAITOK);
                if (buf == 0) {
                        lck_mtx_unlock(ipfw_mutex);
                        error = ENOBUFS;
                        break;
                }
                
                bzero(buf, size);

                bp = buf;
                for (rule = layer3_chain; rule ; rule = rule->next) {
                        int i = RULESIZE(rule);
                        
                        if (rule->reserved_1 == IPFW_RULE_INACTIVE) {
                                continue;
                        }
                        bcopy(rule, bp, i);
                        bcopy(&set_disable, &(bp->next_rule),
                            sizeof(set_disable));
                        bp = (struct ip_fw *)((char *)bp + i);
                }
                if (ipfw_dyn_v) {
                        int i;
                        ipfw_dyn_rule *p, *dst, *last = NULL;

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

                /* convert back if necessary and copyout */
                if (api_version == IP_FW_VERSION_0) {
                        int     i, len = 0;
                        struct ip_old_fw        *buf2, *rule_vers0;
                        
                        buf2 = _MALLOC(static_count * sizeof(struct ip_old_fw), M_TEMP, M_WAITOK);
                        if (buf2 == 0) {
                                error = ENOBUFS;
                        }
                        
                        if (!error) {
                                bp = buf;
                                rule_vers0 = buf2;
                                
                                for (i = 0; i < static_count; i++) {
                                        /* static rules have different sizes */
                                        int j = RULESIZE(bp);
                                        ipfw_convert_from_latest(bp, rule_vers0, api_version);
                                        bp = (struct ip_fw *)((char *)bp + j);
                                        len += sizeof(*rule_vers0);
                                        rule_vers0++;
                                }
                                error = sooptcopyout(sopt, buf2, len);
                                _FREE(buf2, M_TEMP);
                        }
                } else if (api_version == IP_FW_VERSION_1) {
                        int     i, len = 0, buf_size;
                        struct ip_fw_compat     *buf2, *rule_vers1;
                        struct ipfw_dyn_rule_compat     *dyn_rule_vers1, *dyn_last = NULL;
                        ipfw_dyn_rule   *p;

                        buf_size = static_count * sizeof(struct ip_fw_compat) +
                                                dyn_count * sizeof(struct ipfw_dyn_rule_compat);
                                                
                        buf2 = _MALLOC(buf_size, M_TEMP, M_WAITOK);
                        if (buf2 == 0) {
                                error = ENOBUFS;
                        }
                        
                        if (!error) {
                                bp = buf;
                                rule_vers1 = buf2;
                                
                                /* first do static rules */
                                for (i = 0; i < static_count; i++) {
                                        /* static rules have different sizes */
                                        int j = RULESIZE(bp);
                                        ipfw_convert_from_latest(bp, rule_vers1, api_version);
                                        bp = (struct ip_fw *)((char *)bp + j);
                                        len += sizeof(*rule_vers1);
                                        rule_vers1++;
                                }
                        
                                /* now do dynamic rules */
                                dyn_rule_vers1 = (struct ipfw_dyn_rule_compat *)rule_vers1;
                                if (ipfw_dyn_v) {
                                        for (i = 0; i < curr_dyn_buckets; i++) {
                                                for ( p = ipfw_dyn_v[i] ; p != NULL ; p = p->next) {
                                                        (int) dyn_rule_vers1->chain = p->rule->rulenum;
                                                        dyn_rule_vers1->id = p->id;
                                                        dyn_rule_vers1->mask = p->id;
                                                        dyn_rule_vers1->type = p->dyn_type;
                                                        dyn_rule_vers1->expire = p->expire;
                                                        dyn_rule_vers1->pcnt = p->pcnt;
                                                        dyn_rule_vers1->bcnt = p->bcnt;
                                                        dyn_rule_vers1->bucket = p->bucket;
                                                        dyn_rule_vers1->state = p->state;
                                                        
                                                        dyn_rule_vers1->next = dyn_rule_vers1;
                                                        dyn_last = dyn_rule_vers1;
                                                        
                                                        len += sizeof(*dyn_rule_vers1);
                                                        dyn_rule_vers1++;
                                                }
                                        }
                                        
                                        if (dyn_last != NULL) {
                                                dyn_last->next = NULL;
                                        }
                                }
                                
                                error = sooptcopyout(sopt, buf2, len);
                                _FREE(buf2, M_TEMP);
                        }
                } else {
                        error = sooptcopyout(sopt, buf, size);
                }
                
                _FREE(buf, M_TEMP);
                break;

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

                lck_mtx_lock(ipfw_mutex);
                free_chain(&layer3_chain, 0 /* keep default rule */);
#if DEBUG_INACTIVE_RULES
                        print_chain(&layer3_chain);
#endif
                lck_mtx_unlock(ipfw_mutex);
                break;

        case IP_FW_ADD:
                rule = _MALLOC(RULE_MAXSIZE, M_TEMP, M_WAITOK);
                if (rule == 0) {
                        error = ENOBUFS;
                        break;
                }
                
                bzero(rule, RULE_MAXSIZE);

                if (api_version != IP_FW_CURRENT_API_VERSION) {
                        error = ipfw_convert_to_latest(sopt, rule, api_version);
                }
                else {
                        error = sooptcopyin(sopt, rule, RULE_MAXSIZE,
                                sizeof(struct ip_fw) );
                }
                
                if (!error) {
                        if ((api_version == IP_FW_VERSION_0) || (api_version == IP_FW_VERSION_1)) {
                                /* the rule has already been checked so just
                                 * adjust sopt_valsize to match what would be expected.
                                 */
                                sopt->sopt_valsize = RULESIZE(rule);
                        }
                        error = check_ipfw_struct(rule, sopt->sopt_valsize);
                        if (!error) {
                                lck_mtx_lock(ipfw_mutex);
                                error = add_rule(&layer3_chain, rule);
                                lck_mtx_unlock(ipfw_mutex);
                                
                                size = RULESIZE(rule);
                                if (!error && sopt->sopt_dir == SOPT_GET) {
                                        /* convert back if necessary and copyout */
                                        if (api_version == IP_FW_VERSION_0) {
                                                struct ip_old_fw        rule_vers0;
                                                
                                                ipfw_convert_from_latest(rule, &rule_vers0, api_version);
                                                sopt->sopt_valsize = sizeof(struct ip_old_fw);
                                                
                                                error = sooptcopyout(sopt, &rule_vers0, sizeof(struct ip_old_fw));
                                        } else if (api_version == IP_FW_VERSION_1) {
                                                struct ip_fw_compat     rule_vers1;
                
                                                ipfw_convert_from_latest(rule, &rule_vers1, api_version);
                                                sopt->sopt_valsize = sizeof(struct ip_fw_compat);
                                                
                                                error = sooptcopyout(sopt, &rule_vers1, sizeof(struct ip_fw_compat));
                                        } else {
                                                error = sooptcopyout(sopt, rule, size);
                                        }
                                }
                        }
                }
                
                _FREE(rule, M_TEMP);
                break;

        case IP_FW_DEL:
        {
                /*
                 * IP_FW_DEL is used for deleting single rules or sets,
                 * and (ab)used to atomically manipulate sets. 
                 * rule->rulenum != 0 indicates single rule delete
                 * rule->set_masks used to manipulate sets
                 * rule->set_masks[0] contains info on sets to be 
                 *      disabled, swapped, or moved
                 * rule->set_masks[1] contains sets to be enabled.
                 */
                 
                /* there is only a simple rule passed in
                 * (no cmds), so use a temp struct to copy
                 */
                struct ip_fw    temp_rule;
                u_int32_t       arg;
                u_int8_t        cmd;
                
                bzero(&temp_rule, sizeof(struct ip_fw));
                if (api_version != IP_FW_CURRENT_API_VERSION) {
                        error = ipfw_convert_to_latest(sopt, &temp_rule, api_version);
                }
                else {
                        error = sooptcopyin(sopt, &temp_rule, sizeof(struct ip_fw),
                                sizeof(struct ip_fw) );
                }

                if (!error) {
                        /* set_masks is used to distinguish between deleting
                         * single rules or atomically manipulating sets
                         */
                        lck_mtx_lock(ipfw_mutex);
                        
                        arg = temp_rule.set_masks[0];
                        cmd = (arg >> 24) & 0xff;
                        
                        if (temp_rule.rulenum) {
                                /* single rule */
                                error = del_entry(&layer3_chain, temp_rule.rulenum);
#if DEBUG_INACTIVE_RULES
                                print_chain(&layer3_chain);
#endif
                        }
                        else if (cmd) {
                                /* set reassignment - see comment above del_entry() for details */
                                error = del_entry(&layer3_chain, temp_rule.set_masks[0]);
#if DEBUG_INACTIVE_RULES
                                print_chain(&layer3_chain);
#endif
                        }
                        else if (temp_rule.set_masks[0] != 0 ||
                                temp_rule.set_masks[1] != 0) {
                                /* set enable/disable */
                                set_disable =
                                        (set_disable | temp_rule.set_masks[0]) & ~temp_rule.set_masks[1] &
                                        ~(1<<RESVD_SET); /* set RESVD_SET always enabled */
                        }
                                                
                        lck_mtx_unlock(ipfw_mutex);
                }
                break;
        }
        case IP_FW_ZERO:
        case IP_FW_RESETLOG: /* using rule->rulenum */
        {
                /* there is only a simple rule passed in
                 * (no cmds), so use a temp struct to copy
                 */
                struct ip_fw    temp_rule = { 0 };
                
                if (api_version != IP_FW_CURRENT_API_VERSION) {
                        error = ipfw_convert_to_latest(sopt, &temp_rule, api_version);
                }
                else {
                        if (sopt->sopt_val != 0) {
                                error = sooptcopyin(sopt, &temp_rule, sizeof(struct ip_fw),
                                        sizeof(struct ip_fw) );
                        }
                }

                if (!error) {
                        lck_mtx_lock(ipfw_mutex);
                        error = zero_entry(temp_rule.rulenum, sopt->sopt_name == IP_FW_RESETLOG);
                        lck_mtx_unlock(ipfw_mutex);
                }
                break;
        }
        default:
                printf("ipfw: ipfw_ctl invalid option %d\n", sopt->sopt_name);
                error = EINVAL;
        }

        return (error);
}

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

/*
 * This procedure is only used to handle keepalives. It is invoked
 * every dyn_keepalive_period
 */
static void
ipfw_tick(void * __unused unused)
{
        int i;
        int s;
        ipfw_dyn_rule *q;
        struct timeval timenow;


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

        getmicrotime(&timenow);

        lck_mtx_lock(ipfw_mutex);
        for (i = 0 ; i < curr_dyn_buckets ; i++) {
                for (q = ipfw_dyn_v[i] ; q ; q = q->next ) {
                        if (q->dyn_type == O_LIMIT_PARENT)
                                continue;
                        if (q->id.proto != IPPROTO_TCP)
                                continue;
                        if ( (q->state & BOTH_SYN) != BOTH_SYN)
                                continue;
                        if (TIME_LEQ( timenow.tv_sec+dyn_keepalive_interval,
                            q->expire))
                                continue;       /* too early */
                        if (TIME_LEQ(q->expire, timenow.tv_sec))
                                continue;       /* too late, rule expired */

                        send_pkt(&(q->id), q->ack_rev - 1, q->ack_fwd, TH_SYN);
                        send_pkt(&(q->id), q->ack_fwd - 1, q->ack_rev, 0);
                }
        }
        lck_mtx_unlock(ipfw_mutex);
done:
        timeout(ipfw_tick, NULL, dyn_keepalive_period*hz);
}

void
ipfw_init(void)
{
        struct ip_fw default_rule;

        /* setup locks */
        ipfw_mutex_grp_attr = lck_grp_attr_alloc_init();
        ipfw_mutex_grp = lck_grp_alloc_init("ipfw", ipfw_mutex_grp_attr);
        ipfw_mutex_attr = lck_attr_alloc_init();
        lck_attr_setdefault(ipfw_mutex_attr);

        if ((ipfw_mutex = lck_mtx_alloc_init(ipfw_mutex_grp, ipfw_mutex_attr)) == NULL) {
                printf("ipfw_init: can't alloc ipfw_mutex\n");
                return;
        }

        layer3_chain = NULL;

        bzero(&default_rule, sizeof default_rule);

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

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

        if (add_rule(&layer3_chain, &default_rule)) {
                printf("ipfw2: add_rule failed adding default rule\n");
                printf("ipfw2 failed initialization!!\n");
                fw_enable = 0;
        }
        else {
                ip_fw_default_rule = layer3_chain;
#if 0
                /* Radar 3920649, don't print unncessary messages to the log */
                printf("ipfw2 initialized, divert %s, "
                        "rule-based forwarding enabled, default to %s, logging ",
        #ifdef IPDIVERT
                        "enabled",
        #else
                        "disabled",
        #endif
                        default_rule.cmd[0].opcode == O_ACCEPT ? "accept" : "deny");
#endif
        
        #ifdef IPFIREWALL_VERBOSE
                fw_verbose = 1;
        #endif
        #ifdef IPFIREWALL_VERBOSE_LIMIT
                verbose_limit = IPFIREWALL_VERBOSE_LIMIT;
        #endif
                if (fw_verbose == 0)
                        printf("disabled\n");
                else if (verbose_limit == 0)
                        printf("unlimited\n");
                else
                        printf("limited to %d packets/entry by default\n",
                                verbose_limit);
        }

        ip_fw_chk_ptr = ipfw_chk;
        ip_fw_ctl_ptr = ipfw_ctl;

        ipfwstringlen = strlen( ipfwstring );

        timeout(ipfw_tick, NULL, hz);
}

#endif /* IPFW2 */