xnu-792.25.20.tar.gz

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

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *      @(#)ip_input.c  8.2 (Berkeley) 1/4/94
 * $FreeBSD: src/sys/netinet/ip_input.c,v 1.130.2.25 2001/08/29 21:41:37 jesper Exp $
 */

#define _IP_VHL

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/sysctl.h>

#include <kern/queue.h>
#include <kern/locks.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <net/kpi_protocol.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>
#include <sys/socketvar.h>

#include <netinet/ip_fw.h>
#include <netinet/ip_divert.h>

#include <netinet/kpi_ipfilter_var.h>

/* needed for AUTOCONFIGURING: */
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netinet/bootp.h>

#include <sys/kdebug.h>

#define DBG_LAYER_BEG           NETDBG_CODE(DBG_NETIP, 0)
#define DBG_LAYER_END           NETDBG_CODE(DBG_NETIP, 2)
#define DBG_FNC_IP_INPUT        NETDBG_CODE(DBG_NETIP, (2 << 8))


#if IPSEC
#include <netinet6/ipsec.h>
#include <netkey/key.h>
#endif

#include "faith.h"
#if defined(NFAITH) && NFAITH > 0
#include <net/if_types.h>
#endif

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

#if IPSEC
extern int ipsec_bypass;
extern lck_mtx_t *sadb_mutex;
#endif

int rsvp_on = 0;
static int ip_rsvp_on;
struct socket *ip_rsvpd;

int     ipforwarding = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_FORWARDING, forwarding, CTLFLAG_RW,
    &ipforwarding, 0, "Enable IP forwarding between interfaces");

static int      ipsendredirects = 1; /* XXX */
SYSCTL_INT(_net_inet_ip, IPCTL_SENDREDIRECTS, redirect, CTLFLAG_RW,
    &ipsendredirects, 0, "Enable sending IP redirects");

int     ip_defttl = IPDEFTTL;
SYSCTL_INT(_net_inet_ip, IPCTL_DEFTTL, ttl, CTLFLAG_RW,
    &ip_defttl, 0, "Maximum TTL on IP packets");

static int      ip_dosourceroute = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
    &ip_dosourceroute, 0, "Enable forwarding source routed IP packets");

static int      ip_acceptsourceroute = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute, 
    CTLFLAG_RW, &ip_acceptsourceroute, 0, 
    "Enable accepting source routed IP packets");

static int      ip_keepfaith = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_KEEPFAITH, keepfaith, CTLFLAG_RW,
        &ip_keepfaith,  0,
        "Enable packet capture for FAITH IPv4->IPv6 translater daemon");

static int      nipq = 0;       /* total # of reass queues */
static int      maxnipq;
SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfragpackets, CTLFLAG_RW,
        &maxnipq, 0,
        "Maximum number of IPv4 fragment reassembly queue entries");

static int    maxfragsperpacket;
SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfragsperpacket, CTLFLAG_RW,
        &maxfragsperpacket, 0,
        "Maximum number of IPv4 fragments allowed per packet");

static int    maxfrags;
SYSCTL_INT(_net_inet_ip, OID_AUTO, maxfrags, CTLFLAG_RW,
        &maxfrags, 0, "Maximum number of IPv4 fragments allowed");

static int    currentfrags = 0;

/*
 * XXX - Setting ip_checkinterface mostly implements the receive side of
 * the Strong ES model described in RFC 1122, but since the routing table
 * and transmit implementation do not implement the Strong ES model,
 * setting this to 1 results in an odd hybrid.
 *
 * XXX - ip_checkinterface currently must be disabled if you use ipnat
 * to translate the destination address to another local interface.
 *
 * XXX - ip_checkinterface must be disabled if you add IP aliases
 * to the loopback interface instead of the interface where the
 * packets for those addresses are received.
 */
static int      ip_checkinterface = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, check_interface, CTLFLAG_RW,
    &ip_checkinterface, 0, "Verify packet arrives on correct interface");

#if DIAGNOSTIC
static int      ipprintfs = 0;
#endif

extern  struct domain inetdomain;
extern  struct protosw inetsw[];
struct protosw *ip_protox[IPPROTO_MAX];
static int      ipqmaxlen = IFQ_MAXLEN;
struct  in_ifaddrhead in_ifaddrhead; /* first inet address */
struct  ifqueue ipintrq;
SYSCTL_INT(_net_inet_ip, IPCTL_INTRQMAXLEN, intr_queue_maxlen, CTLFLAG_RW,
    &ipintrq.ifq_maxlen, 0, "Maximum size of the IP input queue");
SYSCTL_INT(_net_inet_ip, IPCTL_INTRQDROPS, intr_queue_drops, CTLFLAG_RD,
    &ipintrq.ifq_drops, 0, "Number of packets dropped from the IP input queue");

struct ipstat ipstat;
SYSCTL_STRUCT(_net_inet_ip, IPCTL_STATS, stats, CTLFLAG_RD,
    &ipstat, ipstat, "IP statistics (struct ipstat, netinet/ip_var.h)");

/* Packet reassembly stuff */
#define IPREASS_NHASH_LOG2      6
#define IPREASS_NHASH           (1 << IPREASS_NHASH_LOG2)
#define IPREASS_HMASK           (IPREASS_NHASH - 1)
#define IPREASS_HASH(x,y) \
        (((((x) & 0xF) | ((((x) >> 8) & 0xF) << 4)) ^ (y)) & IPREASS_HMASK)

static struct ipq ipq[IPREASS_NHASH];
static TAILQ_HEAD(ipq_list, ipq) ipq_list =
        TAILQ_HEAD_INITIALIZER(ipq_list);
const  int    ipintrq_present = 1;
lck_mtx_t                       *ip_mutex;
lck_attr_t              *ip_mutex_attr;
lck_grp_t                       *ip_mutex_grp;
lck_grp_attr_t  *ip_mutex_grp_attr;
lck_mtx_t               *inet_domain_mutex;
extern lck_mtx_t                *domain_proto_mtx;

#if IPCTL_DEFMTU
SYSCTL_INT(_net_inet_ip, IPCTL_DEFMTU, mtu, CTLFLAG_RW,
    &ip_mtu, 0, "Default MTU");
#endif

#if IPSTEALTH
static int      ipstealth = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, stealth, CTLFLAG_RW,
    &ipstealth, 0, "");
#endif


/* Firewall hooks */
ip_fw_chk_t *ip_fw_chk_ptr;
int fw_enable = 1 ;
int fw_one_pass = 1;

#if DUMMYNET
ip_dn_io_t *ip_dn_io_ptr;
#endif

int (*fr_checkp)(struct ip *, int, struct ifnet *, int, struct mbuf **) = NULL;

SYSCTL_NODE(_net_inet_ip, OID_AUTO, linklocal, CTLFLAG_RW, 0, "link local");

struct ip_linklocal_stat ip_linklocal_stat;
SYSCTL_STRUCT(_net_inet_ip_linklocal, OID_AUTO, stat, CTLFLAG_RD,
        &ip_linklocal_stat, ip_linklocal_stat,
        "Number of link local packets with TTL less than 255");

SYSCTL_NODE(_net_inet_ip_linklocal, OID_AUTO, in, CTLFLAG_RW, 0, "link local input");

int ip_linklocal_in_allowbadttl = 1;
SYSCTL_INT(_net_inet_ip_linklocal_in, OID_AUTO, allowbadttl, CTLFLAG_RW,
        &ip_linklocal_in_allowbadttl, 0,
        "Allow incoming link local packets with TTL less than 255");


/*
 * We need to save the IP options in case a protocol wants to respond
 * to an incoming packet over the same route if the packet got here
 * using IP source routing.  This allows connection establishment and
 * maintenance when the remote end is on a network that is not known
 * to us.
 */
static int      ip_nhops = 0;
static  struct ip_srcrt {
        struct  in_addr dst;                    /* final destination */
        char    nop;                            /* one NOP to align */
        char    srcopt[IPOPT_OFFSET + 1];       /* OPTVAL, OLEN and OFFSET */
        struct  in_addr route[MAX_IPOPTLEN/sizeof(struct in_addr)];
} ip_srcrt;

#ifdef __APPLE__
extern struct mbuf*     m_dup(register struct mbuf *m, int how);
#endif

static void     save_rte(u_char *, struct in_addr);
static int      ip_dooptions(struct mbuf *, int, struct sockaddr_in *, struct route *ipforward_rt);
static void     ip_forward(struct mbuf *, int, struct sockaddr_in *, struct route *ipforward_rt);
static void     ip_freef(struct ipq *);
#if IPDIVERT
#ifdef IPDIVERT_44
static struct   mbuf *ip_reass(struct mbuf *,
                        struct ipq *, struct ipq *, u_int32_t *, u_int16_t *);
#else
static struct   mbuf *ip_reass(struct mbuf *,
                        struct ipq *, struct ipq *, u_int16_t *, u_int16_t *);
#endif
#else
static struct   mbuf *ip_reass(struct mbuf *, struct ipq *, struct ipq *);
#endif
void    ipintr(void);

#if RANDOM_IP_ID
extern u_short ip_id;
#endif

extern u_long  route_generation;
extern int apple_hwcksum_rx;

/*
 * IP initialization: fill in IP protocol switch table.
 * All protocols not implemented in kernel go to raw IP protocol handler.
 */
void
ip_init()
{
        register struct protosw *pr;
        register int i;
        static ip_initialized = 0;
        struct timeval timenow;


        if (!ip_initialized)
        {
                TAILQ_INIT(&in_ifaddrhead);
                pr = pffindproto_locked(PF_INET, IPPROTO_RAW, SOCK_RAW);
                if (pr == 0)
                        panic("ip_init");
                for (i = 0; i < IPPROTO_MAX; i++)
                        ip_protox[i] = pr;
                for (pr = inetdomain.dom_protosw; pr; pr = pr->pr_next)
                {       if(!((unsigned int)pr->pr_domain)) continue;    /* If uninitialized, skip */
                        if (pr->pr_domain->dom_family == PF_INET &&
                            pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW)
                                ip_protox[pr->pr_protocol] = pr;
                }
                for (i = 0; i < IPREASS_NHASH; i++)
                    ipq[i].next = ipq[i].prev = &ipq[i];

        maxnipq = nmbclusters / 32;
        maxfrags = maxnipq * 2;
        maxfragsperpacket = 128; /* enough for 64k in 512 byte fragments */

#if RANDOM_IP_ID
                getmicrouptime(&timenow);
                ip_id = timenow.tv_sec & 0xffff;
#endif
                ipintrq.ifq_maxlen = ipqmaxlen;

                ipf_init();

                ip_mutex_grp_attr  = lck_grp_attr_alloc_init();

                ip_mutex_grp = lck_grp_alloc_init("ip", ip_mutex_grp_attr);

                ip_mutex_attr = lck_attr_alloc_init();

                if ((ip_mutex = lck_mtx_alloc_init(ip_mutex_grp, ip_mutex_attr)) == NULL) {
                        printf("ip_init: can't alloc ip_mutex\n");
                        return;
                }

                ip_initialized = 1;
        }
}

static void
ip_proto_input(
        protocol_family_t       protocol,
        mbuf_t                          packet)
{
        ip_input(packet);
}

/* Initialize the PF_INET domain, and add in the pre-defined protos */
void
in_dinit()
{       register int i;
        register struct protosw *pr;
        register struct domain *dp;
        static inetdomain_initted = 0;
        extern int in_proto_count; 

        if (!inetdomain_initted)
        {
                kprintf("Initing %d protosw entries\n", in_proto_count);
                dp = &inetdomain;
                dp->dom_flags = DOM_REENTRANT;

                for (i=0, pr = &inetsw[0]; i<in_proto_count; i++, pr++)
                        net_add_proto(pr, dp);
                inet_domain_mutex = dp->dom_mtx;
                inetdomain_initted = 1;
        
                lck_mtx_unlock(domain_proto_mtx);       
                proto_register_input(PF_INET, ip_proto_input, NULL);
                lck_mtx_lock(domain_proto_mtx); 
        }
}

__private_extern__ void
ip_proto_dispatch_in(
                                        struct mbuf     *m,
                                        int                     hlen,
                                        u_int8_t        proto,
                                        ipfilter_t      inject_ipfref)
{
        struct ipfilter *filter;
        int seen = (inject_ipfref == 0);
        int     changed_header = 0;
        struct ip *ip;

        if (!TAILQ_EMPTY(&ipv4_filters)) {      
                ipf_ref();
                TAILQ_FOREACH(filter, &ipv4_filters, ipf_link) {
                        if (seen == 0) {
                                if ((struct ipfilter *)inject_ipfref == filter)
                                        seen = 1;
                        } else if (filter->ipf_filter.ipf_input) {
                                errno_t result;
                
                                if (changed_header == 0) {
                                        changed_header = 1;
                                        ip = mtod(m, struct ip *);
                                        ip->ip_len = htons(ip->ip_len + hlen);
                                        ip->ip_off = htons(ip->ip_off);
                                        ip->ip_sum = 0;
                                        ip->ip_sum = in_cksum(m, hlen);
                                }
                                result = filter->ipf_filter.ipf_input(
                                        filter->ipf_filter.cookie, (mbuf_t*)&m, hlen, proto);
                                if (result == EJUSTRETURN) {
                                        ipf_unref();
                                        return;
                                }
                                if (result != 0) {
                                        ipf_unref();
                                        m_freem(m);
                                        return;
                                }
        }
                }
                ipf_unref();
        }
        /*
         * If there isn't a specific lock for the protocol
         * we're about to call, use the generic lock for AF_INET.
         * otherwise let the protocol deal with its own locking
         */
        ip = mtod(m, struct ip *);
        
        if (changed_header) {
                ip->ip_len = ntohs(ip->ip_len) - hlen;
                ip->ip_off = ntohs(ip->ip_off);
        }
        
        if (!(ip_protox[ip->ip_p]->pr_flags & PR_PROTOLOCK)) {
                lck_mtx_lock(inet_domain_mutex);
                (*ip_protox[ip->ip_p]->pr_input)(m, hlen);
                lck_mtx_unlock(inet_domain_mutex);
        }       
        else     
                (*ip_protox[ip->ip_p]->pr_input)(m, hlen);
                
}

/* 
 * ipforward_rt cleared in in_addroute()
 * when a new route is successfully created.
 */
static struct   sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };

/*
 * Ip input routine.  Checksum and byte swap header.  If fragmented
 * try to reassemble.  Process options.  Pass to next level.
 */
void
ip_input(struct mbuf *m)
{
        struct ip *ip;
        struct ipq *fp;
        struct in_ifaddr *ia = NULL;
        int    i, hlen, mff, checkif;
        u_short sum;
        struct in_addr pkt_dst;
        u_int32_t div_info = 0;         /* packet divert/tee info */
        struct ip_fw_args args;
        ipfilter_t inject_filter_ref = 0;
        struct m_tag    *tag;
        struct route    ipforward_rt = { 0 };
        
        lck_mtx_lock(ip_mutex);

        args.eh = NULL;
        args.oif = NULL;
        args.rule = NULL;
        args.divert_rule = 0;                   /* divert cookie */
        args.next_hop = NULL;

        /* Grab info from mtags prepended to the chain */
#if DUMMYNET
        if ((tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_DUMMYNET, NULL)) != NULL) {
                struct dn_pkt_tag       *dn_tag;
                
                dn_tag = (struct dn_pkt_tag *)(tag+1);
                args.rule = dn_tag->rule;
                
                m_tag_delete(m, tag);
        }
#endif /* DUMMYNET */

        if ((tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_DIVERT, NULL)) != NULL) {
                struct divert_tag       *div_tag;
                
                div_tag = (struct divert_tag *)(tag+1);
                args.divert_rule = div_tag->cookie;

                m_tag_delete(m, tag);
        }
        if ((tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_IPFORWARD, NULL)) != NULL) {
                struct ip_fwd_tag       *ipfwd_tag;
                
                ipfwd_tag = (struct ip_fwd_tag *)(tag+1);
                args.next_hop = ipfwd_tag->next_hop;

                m_tag_delete(m, tag);
        }
        
#if     DIAGNOSTIC
        if (m == NULL || (m->m_flags & M_PKTHDR) == 0)
                panic("ip_input no HDR");
#endif

        if (args.rule) {        /* dummynet already filtered us */
            ip = mtod(m, struct ip *);
            hlen = IP_VHL_HL(ip->ip_vhl) << 2;
            inject_filter_ref = ipf_get_inject_filter(m);
            goto iphack ;
        }
        
        /*
         * No need to proccess packet twice if we've 
         * already seen it
         */
        inject_filter_ref = ipf_get_inject_filter(m);
        if (inject_filter_ref != 0) {
                lck_mtx_unlock(ip_mutex);
                ip = mtod(m, struct ip *);
                hlen = IP_VHL_HL(ip->ip_vhl) << 2;
                ip->ip_len = ntohs(ip->ip_len) - hlen;
                ip->ip_off = ntohs(ip->ip_off);
                ip_proto_dispatch_in(m, hlen, ip->ip_p, inject_filter_ref);
                return;
        }

        ipstat.ips_total++;

        if (m->m_pkthdr.len < sizeof(struct ip))
                goto tooshort;

        if (m->m_len < sizeof (struct ip) &&
            (m = m_pullup(m, sizeof (struct ip))) == 0) {
                ipstat.ips_toosmall++;
                lck_mtx_unlock(ip_mutex);
                return;
        }
        ip = mtod(m, struct ip *);

        KERNEL_DEBUG(DBG_LAYER_BEG, ip->ip_dst.s_addr, 
                     ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);

        if (IP_VHL_V(ip->ip_vhl) != IPVERSION) {
                ipstat.ips_badvers++;
                goto bad;
        }

        hlen = IP_VHL_HL(ip->ip_vhl) << 2;
        if (hlen < sizeof(struct ip)) { /* minimum header length */
                ipstat.ips_badhlen++;
                goto bad;
        }
        if (hlen > m->m_len) {
                if ((m = m_pullup(m, hlen)) == 0) {
                        ipstat.ips_badhlen++;
                        lck_mtx_unlock(ip_mutex);
                        return;
                }
                ip = mtod(m, struct ip *);
        }

        /* 127/8 must not appear on wire - RFC1122 */
        if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
            (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
                if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) == 0) {
                        ipstat.ips_badaddr++;
                        goto bad;
                }
        }

        /* IPv4 Link-Local Addresses as defined in <draft-ietf-zeroconf-ipv4-linklocal-05.txt> */
        if ((IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) || 
            IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)))) {
                ip_linklocal_stat.iplls_in_total++;
                if (ip->ip_ttl != MAXTTL) {
                        ip_linklocal_stat.iplls_in_badttl++;
                        /* Silently drop link local traffic with bad TTL */
                        if (!ip_linklocal_in_allowbadttl)
                                goto bad;
                }
        }
        if ((IF_HWASSIST_CSUM_FLAGS(m->m_pkthdr.rcvif->if_hwassist) == 0) 
            || (apple_hwcksum_rx == 0) ||
           ((m->m_pkthdr.csum_flags & CSUM_TCP_SUM16) && ip->ip_p != IPPROTO_TCP)) {
                        m->m_pkthdr.csum_flags = 0; /* invalidate HW generated checksum flags */
        }

        if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) {
                sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID);
        } else {
                sum = in_cksum(m, hlen);
        }
        if (sum) {
                ipstat.ips_badsum++;
                goto bad;
        }

        /*
         * Convert fields to host representation.
         */
        NTOHS(ip->ip_len);
        if (ip->ip_len < hlen) {
                ipstat.ips_badlen++;
                goto bad;
        }
        NTOHS(ip->ip_off);

        /*
         * Check that the amount of data in the buffers
         * is as at least much as the IP header would have us expect.
         * Trim mbufs if longer than we expect.
         * Drop packet if shorter than we expect.
         */
        if (m->m_pkthdr.len < ip->ip_len) {
tooshort:
                ipstat.ips_tooshort++;
                goto bad;
        }
        if (m->m_pkthdr.len > ip->ip_len) {
                /* Invalidate hwcksuming */
                m->m_pkthdr.csum_flags = 0;
                m->m_pkthdr.csum_data = 0;

                if (m->m_len == m->m_pkthdr.len) {
                        m->m_len = ip->ip_len;
                        m->m_pkthdr.len = ip->ip_len;
                } else
                        m_adj(m, ip->ip_len - m->m_pkthdr.len);
        }

#if IPSEC
        if (ipsec_bypass == 0 && ipsec_gethist(m, NULL))
                goto pass;
#endif

        /*
         * IpHack's section.
         * Right now when no processing on packet has done
         * and it is still fresh out of network we do our black
         * deals with it.
         * - Firewall: deny/allow/divert
         * - Xlate: translate packet's addr/port (NAT).
         * - Pipe: pass pkt through dummynet.
         * - Wrap: fake packet's addr/port <unimpl.>
         * - Encapsulate: put it in another IP and send out. <unimp.>
         */

#if defined(IPFIREWALL) && defined(DUMMYNET)
iphack:
#endif
        /*
         * Check if we want to allow this packet to be processed.
         * Consider it to be bad if not.
         */
        if (fr_checkp) {
                struct  mbuf    *m1 = m;

                if (fr_checkp(ip, hlen, m->m_pkthdr.rcvif, 0, &m1) || !m1) {
                        lck_mtx_unlock(ip_mutex);
                        return;
                }
                ip = mtod(m = m1, struct ip *);
        }
        if (fw_enable && IPFW_LOADED) {
#if IPFIREWALL_FORWARD
                /*
                 * If we've been forwarded from the output side, then
                 * skip the firewall a second time
                 */
                if (args.next_hop)
                        goto ours;
#endif  /* IPFIREWALL_FORWARD */

                args.m = m;
                lck_mtx_unlock(ip_mutex);

                i = ip_fw_chk_ptr(&args);
                m = args.m;

                if ( (i & IP_FW_PORT_DENY_FLAG) || m == NULL) { /* drop */
                        if (m)
                                m_freem(m);
                        return;
                }
                ip = mtod(m, struct ip *); /* just in case m changed */
                if (i == 0 && args.next_hop == NULL) {  /* common case */
                        lck_mtx_lock(ip_mutex);
                        goto pass;
                }
#if DUMMYNET
                if (DUMMYNET_LOADED && (i & IP_FW_PORT_DYNT_FLAG) != 0) {
                        /* Send packet to the appropriate pipe */
                        ip_dn_io_ptr(m, i&0xffff, DN_TO_IP_IN, &args);
                        return;
                }
#endif /* DUMMYNET */
#if IPDIVERT
                if (i != 0 && (i & IP_FW_PORT_DYNT_FLAG) == 0) {
                        /* Divert or tee packet */
                        lck_mtx_lock(ip_mutex);
                        div_info = i;
                        goto ours;
                }
#endif
#if IPFIREWALL_FORWARD
                if (i == 0 && args.next_hop != NULL) {
                        lck_mtx_lock(ip_mutex);
                        goto pass;
                }
#endif
                /*
                 * if we get here, the packet must be dropped
                 */
                m_freem(m);
                return;
        }
pass:

        /*
         * Process options and, if not destined for us,
         * ship it on.  ip_dooptions returns 1 when an
         * error was detected (causing an icmp message
         * to be sent and the original packet to be freed).
         */
        ip_nhops = 0;           /* for source routed packets */
        if (hlen > sizeof (struct ip) && ip_dooptions(m, 0, args.next_hop, &ipforward_rt)) {
                lck_mtx_unlock(ip_mutex);
                return;
        }

        /* greedy RSVP, snatches any PATH packet of the RSVP protocol and no
         * matter if it is destined to another node, or whether it is 
         * a multicast one, RSVP wants it! and prevents it from being forwarded
         * anywhere else. Also checks if the rsvp daemon is running before
         * grabbing the packet.
         */
        if (rsvp_on && ip->ip_p==IPPROTO_RSVP) 
                goto ours;

        /*
         * Check our list of addresses, to see if the packet is for us.
         * If we don't have any addresses, assume any unicast packet
         * we receive might be for us (and let the upper layers deal
         * with it).
         */
        if (TAILQ_EMPTY(&in_ifaddrhead) &&
            (m->m_flags & (M_MCAST|M_BCAST)) == 0)
                goto ours;

        /*
         * Cache the destination address of the packet; this may be
         * changed by use of 'ipfw fwd'.
         */
        pkt_dst = args.next_hop == NULL ?
            ip->ip_dst : args.next_hop->sin_addr;

        /*
         * Enable a consistency check between the destination address
         * and the arrival interface for a unicast packet (the RFC 1122
         * strong ES model) if IP forwarding is disabled and the packet
         * is not locally generated and the packet is not subject to
         * 'ipfw fwd'.
         *
         * XXX - Checking also should be disabled if the destination
         * address is ipnat'ed to a different interface.
         *
         * XXX - Checking is incompatible with IP aliases added
         * to the loopback interface instead of the interface where
         * the packets are received.
         */
        checkif = ip_checkinterface && (ipforwarding == 0) && 
            ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) == 0) &&
            (args.next_hop == NULL);

        lck_mtx_lock(rt_mtx);
        TAILQ_FOREACH(ia, &in_ifaddrhead, ia_link) {
#define satosin(sa)     ((struct sockaddr_in *)(sa))

                if (IA_SIN(ia)->sin_addr.s_addr == INADDR_ANY) {
                        lck_mtx_unlock(rt_mtx);
                        goto ours;
                }
                
                /*
                 * If the address matches, verify that the packet
                 * arrived via the correct interface if checking is
                 * enabled.
                 */
                if (IA_SIN(ia)->sin_addr.s_addr == pkt_dst.s_addr && 
                    (!checkif || ia->ia_ifp == m->m_pkthdr.rcvif)) {
                        lck_mtx_unlock(rt_mtx);
                        goto ours;
                }
                /*
                 * Only accept broadcast packets that arrive via the
                 * matching interface.  Reception of forwarded directed
                 * broadcasts would be handled via ip_forward() and
                 * ether_output() with the loopback into the stack for
                 * SIMPLEX interfaces handled by ether_output().
                 */
                if ((!checkif || ia->ia_ifp == m->m_pkthdr.rcvif) &&
                    ia->ia_ifp && ia->ia_ifp->if_flags & IFF_BROADCAST) {
                        if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
                            pkt_dst.s_addr) {
                                lck_mtx_unlock(rt_mtx);
                                goto ours;
                        }
                        if (ia->ia_netbroadcast.s_addr == pkt_dst.s_addr) {
                                lck_mtx_unlock(rt_mtx);
                                goto ours;
                        }
                }
        }
        lck_mtx_unlock(rt_mtx);
        if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
                struct in_multi *inm;
                if (ip_mrouter) {
                        /*
                         * If we are acting as a multicast router, all
                         * incoming multicast packets are passed to the
                         * kernel-level multicast forwarding function.
                         * The packet is returned (relatively) intact; if
                         * ip_mforward() returns a non-zero value, the packet
                         * must be discarded, else it may be accepted below.
                         */
                        if (ip_mforward &&
                            ip_mforward(ip, m->m_pkthdr.rcvif, m, 0) != 0) {
                                ipstat.ips_cantforward++;
                                m_freem(m);
                                lck_mtx_unlock(ip_mutex);
                                return;
                        }

                        /*
                         * The process-level routing daemon needs to receive
                         * all multicast IGMP packets, whether or not this
                         * host belongs to their destination groups.
                         */
                        if (ip->ip_p == IPPROTO_IGMP)
                                goto ours;
                        ipstat.ips_forward++;
                }
                /*
                 * See if we belong to the destination multicast group on the
                 * arrival interface.
                 */
                IN_LOOKUP_MULTI(ip->ip_dst, m->m_pkthdr.rcvif, inm);
                if (inm == NULL) {
                        ipstat.ips_notmember++;
                        m_freem(m);
                        lck_mtx_unlock(ip_mutex);
                        return;
                }
                goto ours;
        }
        if (ip->ip_dst.s_addr == (u_long)INADDR_BROADCAST)
                goto ours;
        if (ip->ip_dst.s_addr == INADDR_ANY)
                goto ours;

        /* Allow DHCP/BootP responses through */
        if (m->m_pkthdr.rcvif != NULL
            && (m->m_pkthdr.rcvif->if_eflags & IFEF_AUTOCONFIGURING)
            && hlen == sizeof(struct ip)
            && ip->ip_p == IPPROTO_UDP) {
                struct udpiphdr *ui;
                if (m->m_len < sizeof(struct udpiphdr)
                    && (m = m_pullup(m, sizeof(struct udpiphdr))) == 0) {
                        udpstat.udps_hdrops++;
                        lck_mtx_unlock(ip_mutex);
                        return;
                }
                ui = mtod(m, struct udpiphdr *);
                if (ntohs(ui->ui_dport) == IPPORT_BOOTPC) {
                        goto ours;
                }
                ip = mtod(m, struct ip *); /* in case it changed */
        }

#if defined(NFAITH) && 0 < NFAITH
        /*
         * FAITH(Firewall Aided Internet Translator)
         */
        if (m->m_pkthdr.rcvif && m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
                if (ip_keepfaith) {
                        if (ip->ip_p == IPPROTO_TCP || ip->ip_p == IPPROTO_ICMP) 
                                goto ours;
                }
                m_freem(m);
                lck_mtx_unlock(ip_mutex);
                return;
        }
#endif
        lck_mtx_unlock(ip_mutex);
        /*
         * Not for us; forward if possible and desirable.
         */
        if (ipforwarding == 0) {
                ipstat.ips_cantforward++;
                m_freem(m);
        } else {
                ip_forward(m, 0, args.next_hop, &ipforward_rt);
        }
        return;

ours:
#ifndef __APPLE__
        /* Darwin does not have an if_data in ifaddr */
        /* Count the packet in the ip address stats */
        if (ia != NULL) {
                ia->ia_ifa.if_ipackets++;
                ia->ia_ifa.if_ibytes += m->m_pkthdr.len;
        }
#endif

        /*
         * If offset or IP_MF are set, must reassemble.
         * Otherwise, nothing need be done.
         * (We could look in the reassembly queue to see
         * if the packet was previously fragmented,
         * but it's not worth the time; just let them time out.)
         */
        if (ip->ip_off & (IP_MF | IP_OFFMASK | IP_RF)) {

                /* If maxnipq is 0, never accept fragments. */
                if (maxnipq == 0) {
                        ipstat.ips_fragments++;
                        ipstat.ips_fragdropped++;
                        goto bad;
                }
                
                /*
                 * If we will exceed the number of fragments in queues, timeout the
                 * oldest fragemented packet to make space.
                 */
                if (currentfrags >= maxfrags) {
                        fp = TAILQ_LAST(&ipq_list, ipq_list);
                        ipstat.ips_fragtimeout += fp->ipq_nfrags;
                        
                        if (ip->ip_id == fp->ipq_id &&
                                ip->ip_src.s_addr == fp->ipq_src.s_addr &&
                                ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
                                ip->ip_p == fp->ipq_p) {
                                /*
                                 * If we match the fragment queue we were going to
                                 * discard, drop this packet too.
                                 */
                                ipstat.ips_fragdropped++;
                                ip_freef(fp);
                                goto bad;
                        }
                        
                        ip_freef(fp);
                }

                sum = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
                /*
                 * Look for queue of fragments
                 * of this datagram.
                 */
                for (fp = ipq[sum].next; fp != &ipq[sum]; fp = fp->next)
                        if (ip->ip_id == fp->ipq_id &&
                            ip->ip_src.s_addr == fp->ipq_src.s_addr &&
                            ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
                            ip->ip_p == fp->ipq_p)
                                goto found;

                /*
                 * Enforce upper bound on number of fragmented packets
                 * for which we attempt reassembly;
                 * If maxnipq is -1, accept all fragments without limitation.
                 */
                if ((nipq > maxnipq) && (maxnipq > 0)) {
                    /*
                     * drop the oldest fragment before proceeding further
                     */
                    fp = TAILQ_LAST(&ipq_list, ipq_list);
                    ipstat.ips_fragtimeout += fp->ipq_nfrags;
                    ip_freef(fp);
                }

                fp = NULL;

found:
                /*
                 * Adjust ip_len to not reflect header,
                 * convert offset of this to bytes.
                 */
                ip->ip_len -= hlen;
                if (ip->ip_off & IP_MF) {
                        /*
                         * Make sure that fragments have a data length
                                 * that's a non-zero multiple of 8 bytes.
                         */
                        if (ip->ip_len == 0 || (ip->ip_len & 0x7) != 0) {
                                ipstat.ips_toosmall++; /* XXX */
                                goto bad;
                        }
                        m->m_flags |= M_FRAG;
                } else {
                        /* Clear the flag in case packet comes from loopback */
                        m->m_flags &= ~M_FRAG;
                }
                ip->ip_off <<= 3;

                /*
                 * Attempt reassembly; if it succeeds, proceed.
                 * ip_reass() will return a different mbuf, and update
                 * the divert info in div_info and args.divert_rule.
                 */
                        ipstat.ips_fragments++;
                        m->m_pkthdr.header = ip;
#if IPDIVERT
                        m = ip_reass(m,
                            fp, &ipq[sum], &div_info, &args.divert_rule);
#else
                        m = ip_reass(m, fp, &ipq[sum]);
#endif
                        if (m == 0) {
                                lck_mtx_unlock(ip_mutex);
                                return;
                        }
                        ipstat.ips_reassembled++;
                        ip = mtod(m, struct ip *);
                        /* Get the header length of the reassembled packet */
                        hlen = IP_VHL_HL(ip->ip_vhl) << 2;
#if IPDIVERT
                        /* Restore original checksum before diverting packet */
                        if (div_info != 0) {
                                ip->ip_len += hlen;
                                HTONS(ip->ip_len);
                                HTONS(ip->ip_off);
                                ip->ip_sum = 0;
                                ip->ip_sum = in_cksum(m, hlen);
                                NTOHS(ip->ip_off);
                                NTOHS(ip->ip_len);
                                ip->ip_len -= hlen;
                        }
#endif
                } else
                ip->ip_len -= hlen;

#if IPDIVERT
        /*
         * Divert or tee packet to the divert protocol if required.
         *
         * If div_info is zero then cookie should be too, so we shouldn't
         * need to clear them here.  Assume divert_packet() does so also.
         */
        if (div_info != 0) {
                struct mbuf *clone = NULL;

                /* Clone packet if we're doing a 'tee' */
                if ((div_info & IP_FW_PORT_TEE_FLAG) != 0)
                        clone = m_dup(m, M_DONTWAIT);

                /* Restore packet header fields to original values */
                ip->ip_len += hlen;
                HTONS(ip->ip_len);
                HTONS(ip->ip_off);

                /* Deliver packet to divert input routine */
                ipstat.ips_delivered++;
                lck_mtx_unlock(ip_mutex);
                divert_packet(m, 1, div_info & 0xffff, args.divert_rule);

                /* If 'tee', continue with original packet */
                if (clone == NULL) {
                        return;
                }
                lck_mtx_lock(ip_mutex);
                m = clone;
                ip = mtod(m, struct ip *);
        }
#endif

#if IPSEC
        /*
         * enforce IPsec policy checking if we are seeing last header.
         * note that we do not visit this with protocols with pcb layer
         * code - like udp/tcp/raw ip.
         */
        if (ipsec_bypass == 0 && (ip_protox[ip->ip_p]->pr_flags & PR_LASTHDR) != 0) {
                lck_mtx_lock(sadb_mutex);
                if (ipsec4_in_reject(m, NULL)) {
                        ipsecstat.in_polvio++;
                        lck_mtx_unlock(sadb_mutex);
                        goto bad;
                }
                lck_mtx_unlock(sadb_mutex);
        }
#endif

        /*
         * Switch out to protocol's input routine.
         */
        ipstat.ips_delivered++;
        {
                if (args.next_hop && ip->ip_p == IPPROTO_TCP) {
                        /* TCP needs IPFORWARD info if available */
                        struct m_tag *fwd_tag;
                        struct ip_fwd_tag       *ipfwd_tag;
                        
                        fwd_tag = m_tag_alloc(KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_IPFORWARD,
                                        sizeof(struct sockaddr_in), M_NOWAIT);
                        if (fwd_tag == NULL) {
                                goto bad;
                        }
                        
                        ipfwd_tag = (struct ip_fwd_tag *)(fwd_tag+1);
                        ipfwd_tag->next_hop = args.next_hop;

                        m_tag_prepend(m, fwd_tag);
        
                        KERNEL_DEBUG(DBG_LAYER_END, ip->ip_dst.s_addr, 
                             ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);
        
                        lck_mtx_unlock(ip_mutex);
        
                        /* TCP deals with its own locking */
                        ip_proto_dispatch_in(m, hlen, ip->ip_p, 0);
                } else {
                        KERNEL_DEBUG(DBG_LAYER_END, ip->ip_dst.s_addr, 
                             ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);
                
                        lck_mtx_unlock(ip_mutex);
                        ip_proto_dispatch_in(m, hlen, ip->ip_p, 0);
                }
                
                return;
        }
bad:
        KERNEL_DEBUG(DBG_LAYER_END, 0,0,0,0,0);
        lck_mtx_unlock(ip_mutex);
        m_freem(m);
}

/*
 * Take incoming datagram fragment and try to reassemble it into
 * whole datagram.  If a chain for reassembly of this datagram already
 * exists, then it is given as fp; otherwise have to make a chain.
 *
 * When IPDIVERT enabled, keep additional state with each packet that
 * tells us if we need to divert or tee the packet we're building.
 */

static struct mbuf *
#if IPDIVERT
ip_reass(m, fp, where, divinfo, divcookie)
#else
ip_reass(m, fp, where)
#endif
        register struct mbuf *m;
        register struct ipq *fp;
        struct   ipq    *where;
#if IPDIVERT
#ifdef IPDIVERT_44
        u_int32_t *divinfo;
#else
        u_int16_t *divinfo;
#endif
        u_int16_t *divcookie;
#endif
{
        struct ip *ip = mtod(m, struct ip *);
        register struct mbuf *p = 0, *q, *nq;
        struct mbuf *t;
        int hlen = IP_VHL_HL(ip->ip_vhl) << 2;
        int i, next;

        /*
         * Presence of header sizes in mbufs
         * would confuse code below.
         */
        m->m_data += hlen;
        m->m_len -= hlen;

        if (m->m_pkthdr.csum_flags & CSUM_TCP_SUM16) 
                m->m_pkthdr.csum_flags = 0;
        /*
         * If first fragment to arrive, create a reassembly queue.
         */
        if (fp == 0) {
                if ((t = m_get(M_DONTWAIT, MT_FTABLE)) == NULL)
                        goto dropfrag;
                fp = mtod(t, struct ipq *);
                insque((void*)fp, (void*)where);
                nipq++;
                fp->ipq_nfrags = 1;
                fp->ipq_ttl = IPFRAGTTL;
                fp->ipq_p = ip->ip_p;
                fp->ipq_id = ip->ip_id;
                fp->ipq_src = ip->ip_src;
                fp->ipq_dst = ip->ip_dst;
                fp->ipq_frags = m;
                m->m_nextpkt = NULL;
#if IPDIVERT
#ifdef IPDIVERT_44
                fp->ipq_div_info = 0;
#else
                fp->ipq_divert = 0;
#endif
                fp->ipq_div_cookie = 0;
#endif
                TAILQ_INSERT_HEAD(&ipq_list, fp, ipq_list);
                goto inserted;
        } else {
                fp->ipq_nfrags++;
        }

#define GETIP(m)        ((struct ip*)((m)->m_pkthdr.header))

        /*
         * Find a segment which begins after this one does.
         */
        for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
                if (GETIP(q)->ip_off > ip->ip_off)
                        break;

        /*
         * If there is a preceding segment, it may provide some of
         * our data already.  If so, drop the data from the incoming
         * segment.  If it provides all of our data, drop us, otherwise
         * stick new segment in the proper place.
         *
         * If some of the data is dropped from the the preceding
         * segment, then it's checksum is invalidated.
         */
        if (p) {
                i = GETIP(p)->ip_off + GETIP(p)->ip_len - ip->ip_off;
                if (i > 0) {
                        if (i >= ip->ip_len)
                                goto dropfrag;
                        m_adj(m, i);
                        m->m_pkthdr.csum_flags = 0;
                        ip->ip_off += i;
                        ip->ip_len -= i;
                }
                m->m_nextpkt = p->m_nextpkt;
                p->m_nextpkt = m;
        } else {
                m->m_nextpkt = fp->ipq_frags;
                fp->ipq_frags = m;
        }

        /*
         * While we overlap succeeding segments trim them or,
         * if they are completely covered, dequeue them.
         */
        for (; q != NULL && ip->ip_off + ip->ip_len > GETIP(q)->ip_off;
             q = nq) {
                i = (ip->ip_off + ip->ip_len) -
                    GETIP(q)->ip_off;
                if (i < GETIP(q)->ip_len) {
                        GETIP(q)->ip_len -= i;
                        GETIP(q)->ip_off += i;
                        m_adj(q, i);
                        q->m_pkthdr.csum_flags = 0;
                        break;
                }
                nq = q->m_nextpkt;
                m->m_nextpkt = nq;
                ipstat.ips_fragdropped++;
                fp->ipq_nfrags--;
                m_freem(q);
        }

inserted:
        currentfrags++;

#if IPDIVERT
        /*
         * Transfer firewall instructions to the fragment structure.
         * Only trust info in the fragment at offset 0.
         */
        if (ip->ip_off == 0) {
#ifdef IPDIVERT_44
        fp->ipq_div_info = *divinfo;
#else
        fp->ipq_divert = *divinfo;
#endif
        fp->ipq_div_cookie = *divcookie;
        }
        *divinfo = 0;
        *divcookie = 0;
#endif

        /*
         * Check for complete reassembly and perform frag per packet
         * limiting.
         *
         * Frag limiting is performed here so that the nth frag has
         * a chance to complete the packet before we drop the packet.
         * As a result, n+1 frags are actually allowed per packet, but
         * only n will ever be stored. (n = maxfragsperpacket.)
         *
         */
        next = 0;
        for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt) {
                if (GETIP(q)->ip_off != next) {
                        if (fp->ipq_nfrags > maxfragsperpacket) {
                                ipstat.ips_fragdropped += fp->ipq_nfrags;
                                ip_freef(fp);
                        }
                        return (0);
                }
                next += GETIP(q)->ip_len;
        }
        /* Make sure the last packet didn't have the IP_MF flag */
        if (p->m_flags & M_FRAG) {
                if (fp->ipq_nfrags > maxfragsperpacket) {
                        ipstat.ips_fragdropped += fp->ipq_nfrags;
                        ip_freef(fp);
                }
                return (0);
        }

        /*
         * Reassembly is complete.  Make sure the packet is a sane size.
         */
        q = fp->ipq_frags;
        ip = GETIP(q);
        if (next + (IP_VHL_HL(ip->ip_vhl) << 2) > IP_MAXPACKET) {
                ipstat.ips_toolong++;
                ipstat.ips_fragdropped += fp->ipq_nfrags;
                ip_freef(fp);
                return (0);
        }

        /*
         * Concatenate fragments.
         */
        m = q;
        t = m->m_next;
        m->m_next = 0;
        m_cat(m, t);
        nq = q->m_nextpkt;
        q->m_nextpkt = 0;
        for (q = nq; q != NULL; q = nq) {
                nq = q->m_nextpkt;
                q->m_nextpkt = NULL;
                if (q->m_pkthdr.csum_flags & CSUM_TCP_SUM16) 
                        m->m_pkthdr.csum_flags = 0;
                else {
                        m->m_pkthdr.csum_flags &= q->m_pkthdr.csum_flags;
                        m->m_pkthdr.csum_data += q->m_pkthdr.csum_data;
                }
                m_cat(m, q);
        }

#if IPDIVERT
        /*
         * Extract firewall instructions from the fragment structure.
         */
#ifdef IPDIVERT_44
        *divinfo = fp->ipq_div_info;
#else
        *divinfo = fp->ipq_divert;
#endif
        *divcookie = fp->ipq_div_cookie;
#endif

        /*
         * Create header for new ip packet by
         * modifying header of first packet;
         * dequeue and discard fragment reassembly header.
         * Make header visible.
         */
        ip->ip_len = next;
        ip->ip_src = fp->ipq_src;
        ip->ip_dst = fp->ipq_dst;
        remque((void*)fp);
        TAILQ_REMOVE(&ipq_list, fp, ipq_list);
        currentfrags -= fp->ipq_nfrags;
        nipq--;
        (void) m_free(dtom(fp));
        m->m_len += (IP_VHL_HL(ip->ip_vhl) << 2);
        m->m_data -= (IP_VHL_HL(ip->ip_vhl) << 2);
        /* some debugging cruft by sklower, below, will go away soon */
        if (m->m_flags & M_PKTHDR) { /* XXX this should be done elsewhere */
                register int plen = 0;
                for (t = m; t; t = t->m_next)
                        plen += t->m_len;
                m->m_pkthdr.len = plen;
        }
        return (m);

dropfrag:
#if IPDIVERT
        *divinfo = 0;
        *divcookie = 0;
#endif
        ipstat.ips_fragdropped++;
        if (fp != 0)
                fp->ipq_nfrags--;
        m_freem(m);
        return (0);

#undef GETIP
}

/*
 * Free a fragment reassembly header and all
 * associated datagrams.
 */
static void
ip_freef(fp)
        struct ipq *fp;
{
        currentfrags -= fp->ipq_nfrags;
        m_freem_list(fp->ipq_frags);
        remque((void*)fp);
        TAILQ_REMOVE(&ipq_list, fp, ipq_list);
        (void) m_free(dtom(fp));
        nipq--;
}

/*
 * IP timer processing;
 * if a timer expires on a reassembly
 * queue, discard it.
 */
void
ip_slowtimo()
{
        register struct ipq *fp;
        int i;
        lck_mtx_lock(ip_mutex);
        for (i = 0; i < IPREASS_NHASH; i++) {
                fp = ipq[i].next;
                if (fp == 0)
                        continue;
                while (fp != &ipq[i]) {
                        --fp->ipq_ttl;
                        fp = fp->next;
                        if (fp->prev->ipq_ttl == 0) {
                                ipstat.ips_fragtimeout += fp->prev->ipq_nfrags;
                                ip_freef(fp->prev);
                        }
                }
        }
        /*
         * If we are over the maximum number of fragments
         * (due to the limit being lowered), drain off
         * enough to get down to the new limit.
         */
        if (maxnipq >= 0 && nipq > maxnipq) {
        for (i = 0; i < IPREASS_NHASH; i++) {
                        while (nipq > maxnipq &&
                                (ipq[i].next != &ipq[i])) {
                                ipstat.ips_fragdropped +=
                                    ipq[i].next->ipq_nfrags;
                                ip_freef(ipq[i].next);
                        }
                }
        }
        ipflow_slowtimo();
        lck_mtx_unlock(ip_mutex);
}

/*
 * Drain off all datagram fragments.
 */
void
ip_drain()
{
        int     i;

        lck_mtx_lock(ip_mutex);
        for (i = 0; i < IPREASS_NHASH; i++) {
                while (ipq[i].next != &ipq[i]) {
                        ipstat.ips_fragdropped += ipq[i].next->ipq_nfrags;
                        ip_freef(ipq[i].next);
                }
        }
        lck_mtx_unlock(ip_mutex);
        in_rtqdrain();
}

/*
 * Do option processing on a datagram,
 * possibly discarding it if bad options are encountered,
 * or forwarding it if source-routed.
 * The pass argument is used when operating in the IPSTEALTH
 * mode to tell what options to process:
 * [LS]SRR (pass 0) or the others (pass 1).
 * The reason for as many as two passes is that when doing IPSTEALTH,
 * non-routing options should be processed only if the packet is for us.
 * Returns 1 if packet has been forwarded/freed,
 * 0 if the packet should be processed further.
 */
static int
ip_dooptions(struct mbuf *m, int pass, struct sockaddr_in *next_hop, struct route *ipforward_rt)
{
        register struct ip *ip = mtod(m, struct ip *);
        register u_char *cp;
        register struct ip_timestamp *ipt;
        register struct in_ifaddr *ia;
        int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
        struct in_addr *sin, dst;
        n_time ntime;

        dst = ip->ip_dst;
        cp = (u_char *)(ip + 1);
        cnt = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof (struct ip);
        for (; cnt > 0; cnt -= optlen, cp += optlen) {
                opt = cp[IPOPT_OPTVAL];
                if (opt == IPOPT_EOL)
                        break;
                if (opt == IPOPT_NOP)
                        optlen = 1;
                else {
                        if (cnt < IPOPT_OLEN + sizeof(*cp)) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                        optlen = cp[IPOPT_OLEN];
                        if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                }
                switch (opt) {

                default:
                        break;

                /*
                 * Source routing with record.
                 * Find interface with current destination address.
                 * If none on this machine then drop if strictly routed,
                 * or do nothing if loosely routed.
                 * Record interface address and bring up next address
                 * component.  If strictly routed make sure next
                 * address is on directly accessible net.
                 */
                case IPOPT_LSRR:
                case IPOPT_SSRR:
                        if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
                                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                                goto bad;
                        }
                        if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        ipaddr.sin_addr = ip->ip_dst;
                        ia = (struct in_ifaddr *)
                                ifa_ifwithaddr((struct sockaddr *)&ipaddr);
                        if (ia == 0) {
                                if (opt == IPOPT_SSRR) {
                                        type = ICMP_UNREACH;
                                        code = ICMP_UNREACH_SRCFAIL;
                                        goto bad;
                                }
                                if (!ip_dosourceroute)
                                        goto nosourcerouting;
                                /*
                                 * Loose routing, and not at next destination
                                 * yet; nothing to do except forward.
                                 */
                                break;
                        }
                        else {
                                ifafree(&ia->ia_ifa);
                                ia = NULL;
                        }
                        off--;                  /* 0 origin */
                        if (off > optlen - (int)sizeof(struct in_addr)) {
                                /*
                                 * End of source route.  Should be for us.
                                 */
                                if (!ip_acceptsourceroute)
                                        goto nosourcerouting;
                                save_rte(cp, ip->ip_src);
                                break;
                        }

                        if (!ip_dosourceroute) {
                                if (ipforwarding) {
                                        char buf[MAX_IPv4_STR_LEN];
                                        char buf2[MAX_IPv4_STR_LEN];
                                        /*
                                         * Acting as a router, so generate ICMP
                                         */
nosourcerouting:
                                        log(LOG_WARNING,
                                            "attempted source route from %s to %s\n",
                                            inet_ntop(AF_INET, &ip->ip_src, buf, sizeof(buf)),
                                            inet_ntop(AF_INET, &ip->ip_dst, buf2, sizeof(buf2)));
                                        type = ICMP_UNREACH;
                                        code = ICMP_UNREACH_SRCFAIL;
                                        goto bad;
                                } else {
                                        /*
                                         * Not acting as a router, so silently drop.
                                         */
                                        ipstat.ips_cantforward++;
                                        m_freem(m);
                                        return (1);
                                }
                        }

                        /*
                         * locate outgoing interface
                         */
                        (void)memcpy(&ipaddr.sin_addr, cp + off,
                            sizeof(ipaddr.sin_addr));

                        if (opt == IPOPT_SSRR) {
#define INA     struct in_ifaddr *
#define SA      struct sockaddr *
                            if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == 0) {
                                        ia = (INA)ifa_ifwithnet((SA)&ipaddr);
                                }
                        } else {
                                ia = ip_rtaddr(ipaddr.sin_addr, ipforward_rt);
                        }
                        if (ia == 0) {
                                type = ICMP_UNREACH;
                                code = ICMP_UNREACH_SRCFAIL;
                                goto bad;
                        }
                        ip->ip_dst = ipaddr.sin_addr;
                        (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
                            sizeof(struct in_addr));
                        ifafree(&ia->ia_ifa);
                        ia = NULL;
                        cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                        /*
                         * Let ip_intr's mcast routing check handle mcast pkts
                         */
                        forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
                        break;

                case IPOPT_RR:
                        if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                                goto bad;
                        }
                        /*
                         * If no space remains, ignore.
                         */
                        off--;                  /* 0 origin */
                        if (off > optlen - (int)sizeof(struct in_addr))
                                break;
                        (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
                            sizeof(ipaddr.sin_addr));
                        /*
                         * locate outgoing interface; if we're the destination,
                         * use the incoming interface (should be same).
                         */
                        if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == 0) {
                                if ((ia = ip_rtaddr(ipaddr.sin_addr, ipforward_rt)) == 0) {
                                        type = ICMP_UNREACH;
                                        code = ICMP_UNREACH_HOST;
                                        goto bad;
                                }
                        }
                        (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
                            sizeof(struct in_addr));
                        ifafree(&ia->ia_ifa);
                        ia = NULL;
                        cp[IPOPT_OFFSET] += sizeof(struct in_addr);
                        break;

                case IPOPT_TS:
                        code = cp - (u_char *)ip;
                        ipt = (struct ip_timestamp *)cp;
                        if (ipt->ipt_len < 4 || ipt->ipt_len > 40) {
                                code = (u_char *)&ipt->ipt_len - (u_char *)ip;
                                goto bad;
                        }
                        if (ipt->ipt_ptr < 5) {
                                code = (u_char *)&ipt->ipt_ptr - (u_char *)ip;
                                goto bad;
                        }
                        if (ipt->ipt_ptr >
                            ipt->ipt_len - (int)sizeof(int32_t)) {
                                if (++ipt->ipt_oflw == 0) {
                                        code = (u_char *)&ipt->ipt_ptr -
                                            (u_char *)ip;
                                        goto bad;
                                }
                                break;
                        }
                        sin = (struct in_addr *)(cp + ipt->ipt_ptr - 1);
                        switch (ipt->ipt_flg) {

                        case IPOPT_TS_TSONLY:
                                break;

                        case IPOPT_TS_TSANDADDR:
                                if (ipt->ipt_ptr - 1 + sizeof(n_time) +
                                    sizeof(struct in_addr) > ipt->ipt_len) {
                                        code = (u_char *)&ipt->ipt_ptr -
                                            (u_char *)ip;
                                        goto bad;
                                }
                                ipaddr.sin_addr = dst;
                                ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
                                                            m->m_pkthdr.rcvif);
                                if (ia == 0)
                                        continue;
                                (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
                                    sizeof(struct in_addr));
                                ipt->ipt_ptr += sizeof(struct in_addr);
                                ifafree(&ia->ia_ifa);
                                ia = NULL;
                                break;

                        case IPOPT_TS_PRESPEC:
                                if (ipt->ipt_ptr - 1 + sizeof(n_time) +
                                    sizeof(struct in_addr) > ipt->ipt_len) {
                                        code = (u_char *)&ipt->ipt_ptr -
                                            (u_char *)ip;
                                        goto bad;
                                }
                                (void)memcpy(&ipaddr.sin_addr, sin,
                                    sizeof(struct in_addr));
                                if ((ia = (struct in_ifaddr*)ifa_ifwithaddr((SA)&ipaddr)) == 0)
                                        continue;
                                ifafree(&ia->ia_ifa);
                                ia = NULL;
                                ipt->ipt_ptr += sizeof(struct in_addr);
                                break;

                        default:
                                /* XXX can't take &ipt->ipt_flg */
                                code = (u_char *)&ipt->ipt_ptr -
                                    (u_char *)ip + 1;
                                goto bad;
                        }
                        ntime = iptime();
                        (void)memcpy(cp + ipt->ipt_ptr - 1, &ntime,
                            sizeof(n_time));
                        ipt->ipt_ptr += sizeof(n_time);
                }
        }
        if (forward && ipforwarding) {
                ip_forward(m, 1, next_hop, ipforward_rt);
                return (1);
        }
        return (0);
bad:
        ip->ip_len -= IP_VHL_HL(ip->ip_vhl) << 2;   /* XXX icmp_error adds in hdr length */
        lck_mtx_unlock(ip_mutex);
        icmp_error(m, type, code, 0, 0);
        lck_mtx_lock(ip_mutex);
        ipstat.ips_badoptions++;
        return (1);
}

/*
 * Given address of next destination (final or next hop),
 * return internet address info of interface to be used to get there.
 */
struct in_ifaddr *
ip_rtaddr(dst, rt)
        struct in_addr dst;
        struct route *rt;
{
        register struct sockaddr_in *sin;

        sin = (struct sockaddr_in *)&rt->ro_dst;

        lck_mtx_lock(rt_mtx);
        if (rt->ro_rt == 0 || dst.s_addr != sin->sin_addr.s_addr ||
                rt->ro_rt->generation_id != route_generation) {
                if (rt->ro_rt) {
                        rtfree_locked(rt->ro_rt);
                        rt->ro_rt = 0;
                }
                sin->sin_family = AF_INET;
                sin->sin_len = sizeof(*sin);
                sin->sin_addr = dst;

                rtalloc_ign_locked(rt, RTF_PRCLONING);
        }
        if (rt->ro_rt == 0) {
                lck_mtx_unlock(rt_mtx);
                return ((struct in_ifaddr *)0);
        }

        if (rt->ro_rt->rt_ifa)
                ifaref(rt->ro_rt->rt_ifa);
        lck_mtx_unlock(rt_mtx);
        return ((struct in_ifaddr *) rt->ro_rt->rt_ifa);
}

/*
 * Save incoming source route for use in replies,
 * to be picked up later by ip_srcroute if the receiver is interested.
 */
void
save_rte(option, dst)
        u_char *option;
        struct in_addr dst;
{
        unsigned olen;

        olen = option[IPOPT_OLEN];
#if DIAGNOSTIC
        if (ipprintfs)
                printf("save_rte: olen %d\n", olen);
#endif
        if (olen > sizeof(ip_srcrt) - (1 + sizeof(dst)))
                return;
        bcopy(option, ip_srcrt.srcopt, olen);
        ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
        ip_srcrt.dst = dst;
}

/*
 * Retrieve incoming source route for use in replies,
 * in the same form used by setsockopt.
 * The first hop is placed before the options, will be removed later.
 */
struct mbuf *
ip_srcroute()
{
        register struct in_addr *p, *q;
        register struct mbuf *m;

        if (ip_nhops == 0)
                return ((struct mbuf *)0);
        m = m_get(M_DONTWAIT, MT_HEADER);
        if (m == 0)
                return ((struct mbuf *)0);

#define OPTSIZ  (sizeof(ip_srcrt.nop) + sizeof(ip_srcrt.srcopt))

        /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
        m->m_len = ip_nhops * sizeof(struct in_addr) + sizeof(struct in_addr) +
            OPTSIZ;
#if DIAGNOSTIC
        if (ipprintfs)
                printf("ip_srcroute: nhops %d mlen %d", ip_nhops, m->m_len);
#endif

        /*
         * First save first hop for return route
         */
        p = &ip_srcrt.route[ip_nhops - 1];
        *(mtod(m, struct in_addr *)) = *p--;
#if DIAGNOSTIC
        if (ipprintfs)
                printf(" hops %lx", (u_long)ntohl(mtod(m, struct in_addr *)->s_addr));
#endif

        /*
         * Copy option fields and padding (nop) to mbuf.
         */
        ip_srcrt.nop = IPOPT_NOP;
        ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
        (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
            &ip_srcrt.nop, OPTSIZ);
        q = (struct in_addr *)(mtod(m, caddr_t) +
            sizeof(struct in_addr) + OPTSIZ);
#undef OPTSIZ
        /*
         * Record return path as an IP source route,
         * reversing the path (pointers are now aligned).
         */
        while (p >= ip_srcrt.route) {
#if DIAGNOSTIC
                if (ipprintfs)
                        printf(" %lx", (u_long)ntohl(q->s_addr));
#endif
                *q++ = *p--;
        }
        /*
         * Last hop goes to final destination.
         */
        *q = ip_srcrt.dst;
#if DIAGNOSTIC
        if (ipprintfs)
                printf(" %lx\n", (u_long)ntohl(q->s_addr));
#endif
        return (m);
}

/*
 * Strip out IP options, at higher
 * level protocol in the kernel.
 * Second argument is buffer to which options
 * will be moved, and return value is their length.
 * XXX should be deleted; last arg currently ignored.
 */
void
ip_stripoptions(m, mopt)
        register struct mbuf *m;
        struct mbuf *mopt;
{
        register int i;
        struct ip *ip = mtod(m, struct ip *);
        register caddr_t opts;
        int olen;

        olen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof (struct ip);
        opts = (caddr_t)(ip + 1);
        i = m->m_len - (sizeof (struct ip) + olen);
        bcopy(opts + olen, opts, (unsigned)i);
        m->m_len -= olen;
        if (m->m_flags & M_PKTHDR)
                m->m_pkthdr.len -= olen;
        ip->ip_vhl = IP_MAKE_VHL(IPVERSION, sizeof(struct ip) >> 2);
}

u_char inetctlerrmap[PRC_NCMDS] = {
        0,              0,              0,              0,
        0,              EMSGSIZE,       EHOSTDOWN,      EHOSTUNREACH,
        EHOSTUNREACH,   EHOSTUNREACH,   ECONNREFUSED,   ECONNREFUSED,
        EMSGSIZE,       EHOSTUNREACH,   0,              0,
        0,              0,              0,              0,
        ENOPROTOOPT,    ECONNREFUSED
};

/*
 * Forward a packet.  If some error occurs return the sender
 * an icmp packet.  Note we can't always generate a meaningful
 * icmp message because icmp doesn't have a large enough repertoire
 * of codes and types.
 *
 * If not forwarding, just drop the packet.  This could be confusing
 * if ipforwarding was zero but some routing protocol was advancing
 * us as a gateway to somewhere.  However, we must let the routing
 * protocol deal with that.
 *
 * The srcrt parameter indicates whether the packet is being forwarded
 * via a source route.
 */
static void
ip_forward(struct mbuf *m, int srcrt, struct sockaddr_in *next_hop, struct route *ipforward_rt)
{
        register struct ip *ip = mtod(m, struct ip *);
        register struct sockaddr_in *sin;
        register struct rtentry *rt;
        int error, type = 0, code = 0;
        struct mbuf *mcopy;
        n_long dest;
        struct in_addr pkt_dst;
        struct ifnet *destifp;
#if IPSEC
        struct ifnet dummyifp;
#endif

        dest = 0;
        /*
         * Cache the destination address of the packet; this may be
         * changed by use of 'ipfw fwd'.
         */
        pkt_dst = next_hop ? next_hop->sin_addr : ip->ip_dst;

#if DIAGNOSTIC
        if (ipprintfs)
                printf("forward: src %lx dst %lx ttl %x\n",
                    (u_long)ip->ip_src.s_addr, (u_long)pkt_dst.s_addr,
                    ip->ip_ttl);
#endif


        if (m->m_flags & (M_BCAST|M_MCAST) || in_canforward(pkt_dst) == 0) {
                ipstat.ips_cantforward++;
                m_freem(m);
                return;
        }
#if IPSTEALTH
        if (!ipstealth) {
#endif
                if (ip->ip_ttl <= IPTTLDEC) {
                        icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS,
                            dest, 0);
                        return;
                }
#if IPSTEALTH
        }
#endif

        sin = (struct sockaddr_in *)&ipforward_rt->ro_dst;
        if ((rt = ipforward_rt->ro_rt) == 0 ||
            pkt_dst.s_addr != sin->sin_addr.s_addr ||
            ipforward_rt->ro_rt->generation_id != route_generation) {
                if (ipforward_rt->ro_rt) {
                        rtfree(ipforward_rt->ro_rt);
                        ipforward_rt->ro_rt = 0;
                }
                sin->sin_family = AF_INET;
                sin->sin_len = sizeof(*sin);
                sin->sin_addr = pkt_dst;

                rtalloc_ign(ipforward_rt, RTF_PRCLONING);
                if (ipforward_rt->ro_rt == 0) {
                        icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, dest, 0);
                        return;
                }
                rt = ipforward_rt->ro_rt;
        }

        /*
         * Save the IP header and at most 8 bytes of the payload,
         * in case we need to generate an ICMP message to the src.
         *
         * We don't use m_copy() because it might return a reference
         * to a shared cluster. Both this function and ip_output()
         * assume exclusive access to the IP header in `m', so any
         * data in a cluster may change before we reach icmp_error().
         */
        MGET(mcopy, M_DONTWAIT, m->m_type);
        if (mcopy != NULL) {
                M_COPY_PKTHDR(mcopy, m);
                mcopy->m_len = imin((IP_VHL_HL(ip->ip_vhl) << 2) + 8,
                    (int)ip->ip_len);
                m_copydata(m, 0, mcopy->m_len, mtod(mcopy, caddr_t));
        }

#if IPSTEALTH
        if (!ipstealth) {
#endif
                ip->ip_ttl -= IPTTLDEC;
#if IPSTEALTH
        }
#endif

        /*
         * If forwarding packet using same interface that it came in on,
         * perhaps should send a redirect to sender to shortcut a hop.
         * Only send redirect if source is sending directly to us,
         * and if packet was not source routed (or has any options).
         * Also, don't send redirect if forwarding using a default route
         * or a route modified by a redirect.
         */
#define satosin(sa)     ((struct sockaddr_in *)(sa))
        if (rt->rt_ifp == m->m_pkthdr.rcvif &&
            (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0 &&
            satosin(rt_key(rt))->sin_addr.s_addr != 0 &&
            ipsendredirects && !srcrt) {
#define RTA(rt) ((struct in_ifaddr *)(rt->rt_ifa))
                u_long src = ntohl(ip->ip_src.s_addr);

                if (RTA(rt) &&
                    (src & RTA(rt)->ia_subnetmask) == RTA(rt)->ia_subnet) {
                    if (rt->rt_flags & RTF_GATEWAY)
                        dest = satosin(rt->rt_gateway)->sin_addr.s_addr;
                    else
                        dest = pkt_dst.s_addr;
                    /* Router requirements says to only send host redirects */
                    type = ICMP_REDIRECT;
                    code = ICMP_REDIRECT_HOST;
#if DIAGNOSTIC
                    if (ipprintfs)
                        printf("redirect (%d) to %lx\n", code, (u_long)dest);
#endif
                }
        }

    {
        if (next_hop) {
                /* Pass IPFORWARD info if available */
                struct m_tag *tag;
                struct ip_fwd_tag       *ipfwd_tag;
                
                tag = m_tag_alloc(KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_IPFORWARD,
                                sizeof(struct sockaddr_in), M_NOWAIT);
                if (tag == NULL) {
                        error = ENOBUFS;
                        m_freem(m);
                        return;
                }
                
                ipfwd_tag = (struct ip_fwd_tag *)(tag+1);
                ipfwd_tag->next_hop = next_hop;

                m_tag_prepend(m, tag);
        }
        error = ip_output_list(m, 0, (struct mbuf *)0, ipforward_rt, 
                          IP_FORWARDING, 0);
    }
        if (error)
                ipstat.ips_cantforward++;
        else {
                ipstat.ips_forward++;
                if (type)
                        ipstat.ips_redirectsent++;
                else {
                        if (mcopy) {
                                ipflow_create(ipforward_rt, mcopy);
                                m_freem(mcopy);
                        }
                        return;
                }
        }
        if (mcopy == NULL)
                return;
        destifp = NULL;

        switch (error) {

        case 0:                         /* forwarded, but need redirect */
                /* type, code set above */
                break;

        case ENETUNREACH:               /* shouldn't happen, checked above */
        case EHOSTUNREACH:
        case ENETDOWN:
        case EHOSTDOWN:
        default:
                type = ICMP_UNREACH;
                code = ICMP_UNREACH_HOST;
                break;

        case EMSGSIZE:
                type = ICMP_UNREACH;
                code = ICMP_UNREACH_NEEDFRAG;
#ifndef IPSEC
                if (ipforward_rt->ro_rt)
                        destifp = ipforward_rt->ro_rt->rt_ifp;
#else
                /*
                 * If the packet is routed over IPsec tunnel, tell the
                 * originator the tunnel MTU.
                 *      tunnel MTU = if MTU - sizeof(IP) - ESP/AH hdrsiz
                 * XXX quickhack!!!
                 */
                if (ipforward_rt->ro_rt) {
                        struct secpolicy *sp = NULL;
                        int ipsecerror;
                        int ipsechdr;
                        struct route *ro;

                        if (ipsec_bypass) {
                                destifp = ipforward_rt->ro_rt->rt_ifp;
                                ipstat.ips_cantfrag++;
                                break;
                        }
                        lck_mtx_lock(sadb_mutex);
                        sp = ipsec4_getpolicybyaddr(mcopy,
                                                    IPSEC_DIR_OUTBOUND,
                                                    IP_FORWARDING,
                                                    &ipsecerror);

                        if (sp == NULL)
                                destifp = ipforward_rt->ro_rt->rt_ifp;
                        else {
                                /* count IPsec header size */
                                ipsechdr = ipsec4_hdrsiz(mcopy,
                                                         IPSEC_DIR_OUTBOUND,
                                                         NULL);

                                /*
                                 * find the correct route for outer IPv4
                                 * header, compute tunnel MTU.
                                 *
                                 * XXX BUG ALERT
                                 * The "dummyifp" code relies upon the fact
                                 * that icmp_error() touches only ifp->if_mtu.
                                 */
                                /*XXX*/
                                destifp = NULL;
                                if (sp->req != NULL
                                 && sp->req->sav != NULL
                                 && sp->req->sav->sah != NULL) {
                                        ro = &sp->req->sav->sah->sa_route;
                                        if (ro->ro_rt && ro->ro_rt->rt_ifp) {
                                                dummyifp.if_mtu =
                                                    ro->ro_rt->rt_ifp->if_mtu;
                                                dummyifp.if_mtu -= ipsechdr;
                                                destifp = &dummyifp;
                                        }
                                }

                                key_freesp(sp);
                        }
                        lck_mtx_unlock(sadb_mutex);
                }
#endif /*IPSEC*/
                ipstat.ips_cantfrag++;
                break;

        case ENOBUFS:
                type = ICMP_SOURCEQUENCH;
                code = 0;
                break;

        case EACCES:                    /* ipfw denied packet */
                m_freem(mcopy);
                return;
        }
        icmp_error(mcopy, type, code, dest, destifp);
}

void
ip_savecontrol(
        register struct inpcb *inp,
        register struct mbuf **mp,
        register struct ip *ip,
        register struct mbuf *m)
{
        if (inp->inp_socket->so_options & SO_TIMESTAMP) {
                struct timeval tv;

                microtime(&tv);
                *mp = sbcreatecontrol((caddr_t) &tv, sizeof(tv),
                        SCM_TIMESTAMP, SOL_SOCKET);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
        if (inp->inp_flags & INP_RECVDSTADDR) {
                *mp = sbcreatecontrol((caddr_t) &ip->ip_dst,
                    sizeof(struct in_addr), IP_RECVDSTADDR, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
#ifdef notyet
        /* XXX
         * Moving these out of udp_input() made them even more broken
         * than they already were.
         */
        /* options were tossed already */
        if (inp->inp_flags & INP_RECVOPTS) {
                *mp = sbcreatecontrol((caddr_t) opts_deleted_above,
                    sizeof(struct in_addr), IP_RECVOPTS, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
        /* ip_srcroute doesn't do what we want here, need to fix */
        if (inp->inp_flags & INP_RECVRETOPTS) {
                *mp = sbcreatecontrol((caddr_t) ip_srcroute(),
                    sizeof(struct in_addr), IP_RECVRETOPTS, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
#endif
        if (inp->inp_flags & INP_RECVIF) {
                struct ifnet *ifp;
                struct sdlbuf {
                        struct sockaddr_dl sdl;
                        u_char  pad[32];
                } sdlbuf;
                struct sockaddr_dl *sdp;
                struct sockaddr_dl *sdl2 = &sdlbuf.sdl;

                ifnet_head_lock_shared();
                if (((ifp = m->m_pkthdr.rcvif)) 
                && ( ifp->if_index && (ifp->if_index <= if_index))) {
                        struct ifaddr *ifa = ifnet_addrs[ifp->if_index - 1];
                        
                        if (!ifa || !ifa->ifa_addr)
                                goto makedummy;
                        
                        sdp = (struct sockaddr_dl *)ifa->ifa_addr;
                        /*
                         * Change our mind and don't try copy.
                         */
                        if ((sdp->sdl_family != AF_LINK)
                        || (sdp->sdl_len > sizeof(sdlbuf))) {
                                goto makedummy;
                        }
                        bcopy(sdp, sdl2, sdp->sdl_len);
                } else {
makedummy:      
                        sdl2->sdl_len
                                = offsetof(struct sockaddr_dl, sdl_data[0]);
                        sdl2->sdl_family = AF_LINK;
                        sdl2->sdl_index = 0;
                        sdl2->sdl_nlen = sdl2->sdl_alen = sdl2->sdl_slen = 0;
                }
                ifnet_head_done();
                *mp = sbcreatecontrol((caddr_t) sdl2, sdl2->sdl_len,
                        IP_RECVIF, IPPROTO_IP);
                if (*mp)
                        mp = &(*mp)->m_next;
        }
        if (inp->inp_flags & INP_RECVTTL) {
                *mp = sbcreatecontrol((caddr_t)&ip->ip_ttl, sizeof(ip->ip_ttl), IP_RECVTTL, IPPROTO_IP);
                if (*mp) mp = &(*mp)->m_next;
        }
}

int
ip_rsvp_init(struct socket *so)
{
        if (so->so_type != SOCK_RAW ||
            so->so_proto->pr_protocol != IPPROTO_RSVP)
          return EOPNOTSUPP;

        if (ip_rsvpd != NULL)
          return EADDRINUSE;

        ip_rsvpd = so;
        /*
         * This may seem silly, but we need to be sure we don't over-increment
         * the RSVP counter, in case something slips up.
         */
        if (!ip_rsvp_on) {
                ip_rsvp_on = 1;
                rsvp_on++;
        }

        return 0;
}

int
ip_rsvp_done(void)
{
        ip_rsvpd = NULL;
        /*
         * This may seem silly, but we need to be sure we don't over-decrement
         * the RSVP counter, in case something slips up.
         */
        if (ip_rsvp_on) {
                ip_rsvp_on = 0;
                rsvp_on--;
        }
        return 0;
}