xnu-1228.7.58.tar.gz

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

/*
 * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * Copyright (c) 1982, 1986, 1988, 1990, 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_output.c 8.3 (Berkeley) 1/21/94
 * $FreeBSD: src/sys/netinet/ip_output.c,v 1.99.2.16 2001/07/19 06:37:26 kris Exp $
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#define _IP_VHL

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <kern/locks.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/route.h>

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

#include <netinet/kpi_ipfilter_var.h>

#if CONFIG_MACF_NET
#include <security/mac_framework.h>
#endif

#include "faith.h"

#include <net/dlil.h>
#include <sys/kdebug.h>
#include <libkern/OSAtomic.h>

#define DBG_LAYER_BEG           NETDBG_CODE(DBG_NETIP, 1)
#define DBG_LAYER_END           NETDBG_CODE(DBG_NETIP, 3)
#define DBG_FNC_IP_OUTPUT       NETDBG_CODE(DBG_NETIP, (1 << 8) | 1)
#define DBG_FNC_IPSEC4_OUTPUT   NETDBG_CODE(DBG_NETIP, (2 << 8) | 1)

#define SWAP16(v) ((((v) & 0xff) << 8) | ((v) >> 8))

#if IPSEC
#include <netinet6/ipsec.h>
#include <netkey/key.h>
#if IPSEC_DEBUG
#include <netkey/key_debug.h>
#else
#define KEYDEBUG(lev,arg)
#endif
#endif /*IPSEC*/

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

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

#if IPFIREWALL_FORWARD_DEBUG
#define print_ip(a)      printf("%ld.%ld.%ld.%ld",(ntohl(a.s_addr)>>24)&0xFF,\
                                                  (ntohl(a.s_addr)>>16)&0xFF,\
                                                  (ntohl(a.s_addr)>>8)&0xFF,\
                                                  (ntohl(a.s_addr))&0xFF);
#endif


u_short ip_id;

static struct mbuf *ip_insertoptions(struct mbuf *, struct mbuf *, int *);
static struct ifnet *ip_multicast_if(struct in_addr *, int *);
static void     ip_mloopback(struct ifnet *, struct mbuf *,
        struct sockaddr_in *, int);
static int      ip_getmoptions(struct sockopt *, struct ip_moptions *);
static int      ip_pcbopts(int, struct mbuf **, struct mbuf *);
static int      ip_setmoptions(struct sockopt *, struct ip_moptions **);

static void ip_out_cksum_stats(int, u_int32_t);

int ip_createmoptions(struct ip_moptions **imop);
int ip_addmembership(struct ip_moptions *imo, struct ip_mreq *mreq);
int ip_dropmembership(struct ip_moptions *imo, struct ip_mreq *mreq);
int     ip_optcopy(struct ip *, struct ip *);
void in_delayed_cksum_offset(struct mbuf *, int );
void in_cksum_offset(struct mbuf* , size_t );

extern int (*fr_checkp)(struct ip *, int, struct ifnet *, int, struct mbuf **);

extern u_long  route_generation;

extern  struct protosw inetsw[];

extern struct ip_linklocal_stat ip_linklocal_stat;
extern lck_mtx_t *ip_mutex;

/* temporary: for testing */
#if IPSEC
extern int ipsec_bypass;
#endif

static int      ip_maxchainsent = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, maxchainsent, CTLFLAG_RW,
    &ip_maxchainsent, 0, "use dlil_output_list");
#if DEBUG
static int forge_ce = 0;
SYSCTL_INT(_net_inet_ip, OID_AUTO, forge_ce, CTLFLAG_RW,
    &forge_ce, 0, "Forge ECN CE");
#endif /* DEBUG */
/*
 * IP output.  The packet in mbuf chain m contains a skeletal IP
 * header (with len, off, ttl, proto, tos, src, dst).
 * The mbuf chain containing the packet will be freed.
 * The mbuf opt, if present, will not be freed.
 */
int
ip_output(
        struct mbuf *m0,
        struct mbuf *opt,
        struct route *ro,
        int flags,
        struct ip_moptions *imo,
        struct ifnet *ifp)
{
        int error;
        error = ip_output_list(m0, 0, opt, ro, flags, imo, ifp);
        return error;
}

/*
 * Returns:     0                       Success
 *              ENOMEM
 *              EADDRNOTAVAIL
 *              ENETUNREACH
 *              EHOSTUNREACH
 *              EACCES
 *              EMSGSIZE
 *              ENOBUFS
 *      ipsec4_getpolicybyaddr:???      [IPSEC 4th argument, contents modified]
 *      ipsec4_getpolicybysock:???      [IPSEC 4th argument, contents modified]
 *      key_spdacquire:???              [IPSEC]
 *      ipsec4_output:???               [IPSEC]
 *      <fr_checkp>:???                 [firewall]
 *      ip_dn_io_ptr:???                [dummynet]
 *      dlil_output:???                 [DLIL]
 *      dlil_output_list:???            [DLIL]
 *
 * Notes:       The ipsec4_getpolicyby{addr|sock} function error returns are
 *              only used as the error return from this function where one of
 *              these functions fails to return a policy.
 */
int
ip_output_list(
        struct mbuf *m0,
        int packetchain,
        struct mbuf *opt,
        struct route *ro,
        int flags,
        struct ip_moptions *imo,
#if CONFIG_FORCE_OUT_IFP
        struct ifnet *pdp_ifp
#else
        __unused struct ifnet *unused_ifp
#endif
        )
{
        struct ip *ip, *mhip;
        struct ifnet *ifp = NULL;
        struct mbuf *m = m0;
        int hlen = sizeof (struct ip);
        int len = 0, off, error = 0;
        struct sockaddr_in *dst = NULL;
        struct in_ifaddr *ia = NULL;
        int isbroadcast, sw_csum;
        struct in_addr pkt_dst;
#if IPSEC
        struct route iproute;
        struct socket *so = NULL;
        struct secpolicy *sp = NULL;
#endif
#if IPFIREWALL_FORWARD
        int fwd_rewrite_src = 0;
#endif
#if IPFIREWALL
        struct ip_fw_args args;
#endif
        int didfilter = 0;
        ipfilter_t inject_filter_ref = 0;
        struct m_tag    *tag;
        struct route    saved_route;
        struct mbuf * packetlist;
        int pktcnt = 0;
        

        KERNEL_DEBUG(DBG_FNC_IP_OUTPUT | DBG_FUNC_START, 0,0,0,0,0);

        packetlist = m0;
#if IPFIREWALL
        args.next_hop = NULL;
        args.eh = NULL;
        args.rule = NULL;
        args.divert_rule = 0;                   /* divert cookie */
        
        /* Grab info from mtags prepended to the chain */
#if DUMMYNET
        if ((tag = m_tag_locate(m0, 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;
                opt = NULL;
                saved_route = dn_tag->ro;
                ro = &saved_route;
                        
                imo = NULL;
                dst = dn_tag->dn_dst;
                ifp = dn_tag->ifp;
                flags = dn_tag->flags;
                
                m_tag_delete(m0, tag);
        }
#endif /* DUMMYNET */

#if IPDIVERT
        if ((tag = m_tag_locate(m0, 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(m0, tag);
        }
#endif /* IPDIVERT */

        if ((tag = m_tag_locate(m0, 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(m0, tag);
        }
#endif /* IPFIREWALL */

        m = m0;
        
#if     DIAGNOSTIC
        if ( !m || (m->m_flags & M_PKTHDR) != 0)
                panic("ip_output no HDR");
        if (!ro)
                panic("ip_output no route, proto = %d",
                      mtod(m, struct ip *)->ip_p);
#endif

#if IPFIREWALL
        if (args.rule != NULL) {        /* dummynet already saw us */
            ip = mtod(m, struct ip *);
            hlen = IP_VHL_HL(ip->ip_vhl) << 2 ;
            lck_mtx_lock(rt_mtx);
            if (ro->ro_rt != NULL) 
                ia = (struct in_ifaddr *)ro->ro_rt->rt_ifa;
            if (ia)
                ifaref(&ia->ia_ifa);
            lck_mtx_unlock(rt_mtx);
#if IPSEC
            if (ipsec_bypass == 0 && (flags & IP_NOIPSEC) == 0) {
                so = ipsec_getsocket(m);
                (void)ipsec_setsocket(m, NULL);
                }
#endif
            goto sendit;
        }
#endif /* IPFIREWALL */

#if IPSEC
        if (ipsec_bypass == 0 && (flags & IP_NOIPSEC) == 0) {
                so = ipsec_getsocket(m);
                (void)ipsec_setsocket(m, NULL);
        }
#endif
loopit: 
        /*
         * No need to proccess packet twice if we've 
         * already seen it
         */
        inject_filter_ref = ipf_get_inject_filter(m);

        if (opt) {
                m = ip_insertoptions(m, opt, &len);
                hlen = len;
        }
        ip = mtod(m, struct ip *);
#if IPFIREWALL
        pkt_dst = args.next_hop ? args.next_hop->sin_addr : ip->ip_dst;
#else
        pkt_dst = ip->ip_dst;
#endif

        /*
         * Fill in IP header.
         */
        if ((flags & (IP_FORWARDING|IP_RAWOUTPUT)) == 0) {
                ip->ip_vhl = IP_MAKE_VHL(IPVERSION, hlen >> 2);
                ip->ip_off &= IP_DF;
#if RANDOM_IP_ID
                ip->ip_id = ip_randomid();
#else
                ip->ip_id = htons(ip_id++);
#endif
                OSAddAtomic(1, (SInt32*)&ipstat.ips_localout);
        } else {
                hlen = IP_VHL_HL(ip->ip_vhl) << 2;
        }
        
#if DEBUG
        /* For debugging, we let the stack forge congestion */
        if (forge_ce != 0 &&
                ((ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_ECT1 ||
                 (ip->ip_tos & IPTOS_ECN_MASK) == IPTOS_ECN_ECT0)) {
                ip->ip_tos = (ip->ip_tos & ~IPTOS_ECN_MASK) | IPTOS_ECN_CE;
                forge_ce--;
        }
#endif /* DEBUG */

        KERNEL_DEBUG(DBG_LAYER_BEG, ip->ip_dst.s_addr, 
                     ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);
        
        dst = (struct sockaddr_in *)&ro->ro_dst;

        /*
         * If there is a cached route,
         * check that it is to the same destination
         * and is still up.  If not, free it and try again.
         * The address family should also be checked in case of sharing the
         * cache with IPv6.
         */

        lck_mtx_lock(rt_mtx);
        if (ro->ro_rt != NULL) {
                if (ro->ro_rt->generation_id != route_generation &&
                    ((flags & (IP_ROUTETOIF | IP_FORWARDING)) == 0) &&
                    (ip->ip_src.s_addr != INADDR_ANY) &&
                    (ifa_foraddr(ip->ip_src.s_addr) == 0)) {
                        error = EADDRNOTAVAIL;
                        lck_mtx_unlock(rt_mtx);
                        goto bad;
                }
                if ((ro->ro_rt->rt_flags & RTF_UP) == 0 ||
                    dst->sin_family != AF_INET ||
                    dst->sin_addr.s_addr != pkt_dst.s_addr) {
                        rtfree_locked(ro->ro_rt);
                        ro->ro_rt = NULL;
                }
                if (ro->ro_rt && ro->ro_rt->generation_id != route_generation)
                        ro->ro_rt->generation_id = route_generation;
        }
        if (ro->ro_rt == NULL) {
                bzero(dst, sizeof(*dst));
                dst->sin_family = AF_INET;
                dst->sin_len = sizeof(*dst);
                dst->sin_addr = pkt_dst;
        }
        /*
         * If routing to interface only,
         * short circuit routing lookup.
         */
#define ifatoia(ifa)    ((struct in_ifaddr *)(ifa))
#define sintosa(sin)    ((struct sockaddr *)(sin))
        if (flags & IP_ROUTETOIF) {
                if (ia)
                        ifafree(&ia->ia_ifa);
                if ((ia = ifatoia(ifa_ifwithdstaddr(sintosa(dst)))) == 0) {
                        if ((ia = ifatoia(ifa_ifwithnet(sintosa(dst)))) == 0) {
                                OSAddAtomic(1, (SInt32*)&ipstat.ips_noroute);
                                error = ENETUNREACH;
                                lck_mtx_unlock(rt_mtx);
                                goto bad;
                        }
                }
                ifp = ia->ia_ifp;
                ip->ip_ttl = 1;
                isbroadcast = in_broadcast(dst->sin_addr, ifp);
        } else {

#if CONFIG_FORCE_OUT_IFP
                /* Check if this packet should be forced out a specific interface */
                if (ro->ro_rt == 0 && pdp_ifp != NULL) {
                        pdp_context_route_locked(pdp_ifp, ro);
                        
                        if (ro->ro_rt == NULL) {
                                OSAddAtomic(1, (UInt32*)&ipstat.ips_noroute);
                                error = EHOSTUNREACH;
                                lck_mtx_unlock(rt_mtx);
                                goto bad;
                        }
                }
#endif
                
                /*
                 * If this is the case, we probably don't want to allocate
                 * a protocol-cloned route since we didn't get one from the
                 * ULP.  This lets TCP do its thing, while not burdening
                 * forwarding or ICMP with the overhead of cloning a route.
                 * Of course, we still want to do any cloning requested by
                 * the link layer, as this is probably required in all cases
                 * for correct operation (as it is for ARP).
                 */
                
                if (ro->ro_rt == 0) {
                        unsigned long ign = RTF_PRCLONING;
                        /*
                         * We make an exception here: if the destination
                         * address is INADDR_BROADCAST, allocate a protocol-
                         * cloned host route so that we end up with a route
                         * marked with the RTF_BROADCAST flag.  Otherwise,
                         * we would end up referring to the default route,
                         * instead of creating a cloned host route entry.
                         * That would introduce inconsistencies between ULPs
                         * that allocate a route and those that don't.  The
                         * RTF_BROADCAST route is important since we'd want
                         * to send out undirected IP broadcast packets using
                         * link-level broadcast address.
                         *
                         * This exception will no longer be necessary when
                         * the RTF_PRCLONING scheme is no longer present.
                         */
                        if (dst->sin_addr.s_addr == INADDR_BROADCAST)
                                ign &= ~RTF_PRCLONING;

                        rtalloc_ign_locked(ro, ign);
                }
                if (ro->ro_rt == 0) {
                        OSAddAtomic(1, (SInt32*)&ipstat.ips_noroute);
                        error = EHOSTUNREACH;
                        lck_mtx_unlock(rt_mtx);
                        goto bad;
                }
                
                if (ia)
                        ifafree(&ia->ia_ifa);
                ia = ifatoia(ro->ro_rt->rt_ifa);
                if (ia)
                        ifaref(&ia->ia_ifa);
                ifp = ro->ro_rt->rt_ifp;
                ro->ro_rt->rt_use++;
                if (ro->ro_rt->rt_flags & RTF_GATEWAY)
                        dst = (struct sockaddr_in *)ro->ro_rt->rt_gateway;
                if (ro->ro_rt->rt_flags & RTF_HOST)
                        isbroadcast = (ro->ro_rt->rt_flags & RTF_BROADCAST);
                else
                        isbroadcast = in_broadcast(dst->sin_addr, ifp);
        }
        lck_mtx_unlock(rt_mtx);
        if (IN_MULTICAST(ntohl(pkt_dst.s_addr))) {
                struct in_multi *inm;

                m->m_flags |= M_MCAST;
                /*
                 * IP destination address is multicast.  Make sure "dst"
                 * still points to the address in "ro".  (It may have been
                 * changed to point to a gateway address, above.)
                 */
                dst = (struct sockaddr_in *)&ro->ro_dst;
                /*
                 * See if the caller provided any multicast options
                 */
                if (imo != NULL) {
                        if ((flags & IP_RAWOUTPUT) == 0) ip->ip_ttl = imo->imo_multicast_ttl;
                        if (imo->imo_multicast_ifp != NULL) {
                                ifp = imo->imo_multicast_ifp;
                        }
#if MROUTING
                        if (imo->imo_multicast_vif != -1 && 
                                ((flags & IP_RAWOUTPUT) == 0 || ip->ip_src.s_addr == INADDR_ANY))
                                ip->ip_src.s_addr =
                                        ip_mcast_src(imo->imo_multicast_vif);
#endif /* MROUTING */
                } else
                        if ((flags & IP_RAWOUTPUT) == 0) ip->ip_ttl = IP_DEFAULT_MULTICAST_TTL;
                /*
                 * Confirm that the outgoing interface supports multicast.
                 */
                if ((imo == NULL) || (imo->imo_multicast_vif == -1)) {
                        if ((ifp->if_flags & IFF_MULTICAST) == 0) {
                                OSAddAtomic(1, (SInt32*)&ipstat.ips_noroute);
                                error = ENETUNREACH;
                                goto bad;
                        }
                }
                /*
                 * If source address not specified yet, use address
                 * of outgoing interface.
                 */
                if (ip->ip_src.s_addr == INADDR_ANY) {
                        register struct in_ifaddr *ia1;
                        lck_mtx_lock(rt_mtx);   
                        TAILQ_FOREACH(ia1, &in_ifaddrhead, ia_link)
                                if (ia1->ia_ifp == ifp) {
                                        ip->ip_src = IA_SIN(ia1)->sin_addr;
                                        
                                        break;
                                }
                        lck_mtx_unlock(rt_mtx); 
                        if (ip->ip_src.s_addr == INADDR_ANY) {
                                error = ENETUNREACH;
                                goto bad;
                        }
                }

                ifnet_lock_shared(ifp);
                IN_LOOKUP_MULTI(pkt_dst, ifp, inm);
                ifnet_lock_done(ifp);
                if (inm != NULL &&
                   (imo == NULL || imo->imo_multicast_loop)) {
                        /*
                         * If we belong to the destination multicast group
                         * on the outgoing interface, and the caller did not
                         * forbid loopback, loop back a copy.
                         */
                        if (!TAILQ_EMPTY(&ipv4_filters)) {
                                struct ipfilter *filter;
                                int seen = (inject_filter_ref == 0);
                                struct ipf_pktopts *ippo = 0, ipf_pktopts;

                                if (imo) {                                              
                                        ippo = &ipf_pktopts;
                                        ipf_pktopts.ippo_mcast_ifnet = imo->imo_multicast_ifp;
                                        ipf_pktopts.ippo_mcast_ttl = imo->imo_multicast_ttl;
                                        ipf_pktopts.ippo_mcast_loop = imo->imo_multicast_loop;
                                }
                                
                                ipf_ref();
                                
                                /* 4135317 - always pass network byte order to filter */
                                HTONS(ip->ip_len);
                                HTONS(ip->ip_off);
                                
                                TAILQ_FOREACH(filter, &ipv4_filters, ipf_link) {
                                        if (seen == 0) {
                                                if ((struct ipfilter *)inject_filter_ref == filter)
                                                        seen = 1;
                                        } else if (filter->ipf_filter.ipf_output) {
                                                errno_t result;
                                                result = filter->ipf_filter.ipf_output(filter->ipf_filter.cookie, (mbuf_t*)&m, ippo);
                                                if (result == EJUSTRETURN) {
                                                        ipf_unref();
                                                        goto done;
                                                }
                                                if (result != 0) {
                                                        ipf_unref();
                                                        goto bad;
                                                }
                                        }
                                }
                                
                                /* set back to host byte order */
                                ip = mtod(m, struct ip *);
                                NTOHS(ip->ip_len);
                                NTOHS(ip->ip_off);
                                
                                ipf_unref();
                                didfilter = 1;
                        }
                        ip_mloopback(ifp, m, dst, hlen);
                }
#if MROUTING
                else {
                        /*
                         * If we are acting as a multicast router, perform
                         * multicast forwarding as if the packet had just
                         * arrived on the interface to which we are about
                         * to send.  The multicast forwarding function
                         * recursively calls this function, using the
                         * IP_FORWARDING flag to prevent infinite recursion.
                         *
                         * Multicasts that are looped back by ip_mloopback(),
                         * above, will be forwarded by the ip_input() routine,
                         * if necessary.
                         */
                        if (ip_mrouter && (flags & IP_FORWARDING) == 0) {
                                /*
                                 * Check if rsvp daemon is running. If not, don't
                                 * set ip_moptions. This ensures that the packet
                                 * is multicast and not just sent down one link
                                 * as prescribed by rsvpd.
                                 */
                                if (!rsvp_on)
                                  imo = NULL;
                                if (ip_mforward(ip, ifp, m, imo) != 0) {
                                        m_freem(m);
                                        goto done;
                                }
                        }
                }
#endif /* MROUTING */

                /*
                 * Multicasts with a time-to-live of zero may be looped-
                 * back, above, but must not be transmitted on a network.
                 * Also, multicasts addressed to the loopback interface
                 * are not sent -- the above call to ip_mloopback() will
                 * loop back a copy if this host actually belongs to the
                 * destination group on the loopback interface.
                 */
                if (ip->ip_ttl == 0 || ifp->if_flags & IFF_LOOPBACK) {
                        m_freem(m);
                        goto done;
                }

                goto sendit;
        }
#ifndef notdef
        /*
         * If source address not specified yet, use address
         * of outgoing interface.
         */
        if (ip->ip_src.s_addr == INADDR_ANY) {
                ip->ip_src = IA_SIN(ia)->sin_addr;
#if IPFIREWALL_FORWARD
                /* Keep note that we did this - if the firewall changes
                 * the next-hop, our interface may change, changing the
                 * default source IP. It's a shame so much effort happens
                 * twice. Oh well. 
                 */
                fwd_rewrite_src++;
#endif /* IPFIREWALL_FORWARD */
        }
#endif /* notdef */

        /*
         * Look for broadcast address and
         * and verify user is allowed to send
         * such a packet.
         */
        if (isbroadcast) {
                if ((ifp->if_flags & IFF_BROADCAST) == 0) {
                        error = EADDRNOTAVAIL;
                        goto bad;
                }
                if ((flags & IP_ALLOWBROADCAST) == 0) {
                        error = EACCES;
                        goto bad;
                }
                /* don't allow broadcast messages to be fragmented */
                if ((u_short)ip->ip_len > ifp->if_mtu) {
                        error = EMSGSIZE;
                        goto bad;
                }
                m->m_flags |= M_BCAST;
        } else {
                m->m_flags &= ~M_BCAST;
        }

sendit:
        /*
         * Force IP TTL to 255 following draft-ietf-zeroconf-ipv4-linklocal.txt
         */
        if (IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) || IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr))) {
                ip_linklocal_stat.iplls_out_total++;
                if (ip->ip_ttl != MAXTTL) {
                        ip_linklocal_stat.iplls_out_badttl++;
                        ip->ip_ttl = MAXTTL;
                }
        }

        if (!didfilter && !TAILQ_EMPTY(&ipv4_filters)) {
                struct ipfilter *filter;
                int seen = (inject_filter_ref == 0);
                
                ipf_ref();
                
                /* 4135317 - always pass network byte order to filter */
                HTONS(ip->ip_len);
                HTONS(ip->ip_off);
                
                TAILQ_FOREACH(filter, &ipv4_filters, ipf_link) {
                        if (seen == 0) {
                                if ((struct ipfilter *)inject_filter_ref == filter)
                                        seen = 1;
                        } else if (filter->ipf_filter.ipf_output) {
                                errno_t result;
                                result = filter->ipf_filter.ipf_output(filter->ipf_filter.cookie, (mbuf_t*)&m, 0);
                                if (result == EJUSTRETURN) {
                                        ipf_unref();
                                        goto done;
                                }
                                if (result != 0) {
                                        ipf_unref();
                                        goto bad;
                                }
                        }
                }
                
                /* set back to host byte order */
                ip = mtod(m, struct ip *);
                NTOHS(ip->ip_len);
                NTOHS(ip->ip_off);
                
                ipf_unref();
        }

#if IPSEC
        /* temporary for testing only: bypass ipsec alltogether */

        if (ipsec_bypass != 0 || (flags & IP_NOIPSEC) != 0)
                goto skip_ipsec;

        KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_START, 0,0,0,0,0);


        /* get SP for this packet */
        if (so == NULL)
                sp = ipsec4_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, flags, &error);
        else
                sp = ipsec4_getpolicybysock(m, IPSEC_DIR_OUTBOUND, so, &error);

        if (sp == NULL) {
                IPSEC_STAT_INCREMENT(ipsecstat.out_inval);              
                KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 0,0,0,0,0);
                goto bad;
        }

        error = 0;

        /* check policy */
        switch (sp->policy) {
        case IPSEC_POLICY_DISCARD:
        case IPSEC_POLICY_GENERATE:
                /*
                 * This packet is just discarded.
                 */
                IPSEC_STAT_INCREMENT(ipsecstat.out_polvio);
                KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 1,0,0,0,0);
                goto bad;

        case IPSEC_POLICY_BYPASS:
        case IPSEC_POLICY_NONE:
                /* no need to do IPsec. */
                KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 2,0,0,0,0);
                goto skip_ipsec;
        
        case IPSEC_POLICY_IPSEC:
                if (sp->req == NULL) {
                        /* acquire a policy */
                        error = key_spdacquire(sp);
                        KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 3,0,0,0,0);
                        goto bad;
                }
                break;

        case IPSEC_POLICY_ENTRUST:
        default:
                printf("ip_output: Invalid policy found. %d\n", sp->policy);
        }
    {
        struct ipsec_output_state state;
        bzero(&state, sizeof(state));
        state.m = m;
        if (flags & IP_ROUTETOIF) {
                state.ro = &iproute;
                bzero(&iproute, sizeof(iproute));
        } else
                state.ro = ro;
        state.dst = (struct sockaddr *)dst;

        ip->ip_sum = 0;

        /*
         * XXX
         * delayed checksums are not currently compatible with IPsec
         */
        if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
                in_delayed_cksum(m);
                m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
        }

        HTONS(ip->ip_len);
        HTONS(ip->ip_off);

        error = ipsec4_output(&state, sp, flags);
    
        m0 = m = state.m;
        
        if (flags & IP_ROUTETOIF) {
                /*
                 * if we have tunnel mode SA, we may need to ignore
                 * IP_ROUTETOIF.
                 */
                if (state.ro != &iproute || state.ro->ro_rt != NULL) {
                        flags &= ~IP_ROUTETOIF;
                        ro = state.ro;
                }
        } else
                ro = state.ro;

        dst = (struct sockaddr_in *)state.dst;
        if (error) {
                /* mbuf is already reclaimed in ipsec4_output. */
                m0 = NULL;
                switch (error) {
                case EHOSTUNREACH:
                case ENETUNREACH:
                case EMSGSIZE:
                case ENOBUFS:
                case ENOMEM:
                        break;
                default:
                        printf("ip4_output (ipsec): error code %d\n", error);
                        /*fall through*/
                case ENOENT:
                        /* don't show these error codes to the user */
                        error = 0;
                        break;
                }
                KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 4,0,0,0,0);
                goto bad;
        }
    }

        /* be sure to update variables that are affected by ipsec4_output() */
        ip = mtod(m, struct ip *);
        
#ifdef _IP_VHL
        hlen = IP_VHL_HL(ip->ip_vhl) << 2;
#else
        hlen = ip->ip_hl << 2;
#endif
        /* Check that there wasn't a route change and src is still valid */

        lck_mtx_lock(rt_mtx);
        if (ro->ro_rt && ro->ro_rt->generation_id != route_generation) {
                if (ifa_foraddr(ip->ip_src.s_addr) == 0 && ((flags & (IP_ROUTETOIF | IP_FORWARDING)) == 0)) {
                        error = EADDRNOTAVAIL;
                        lck_mtx_unlock(rt_mtx);
                        KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 5,0,0,0,0);
                        goto bad;
                }
                rtfree_locked(ro->ro_rt);
                ro->ro_rt = NULL;
        }

        if (ro->ro_rt == NULL) {
                if ((flags & IP_ROUTETOIF) == 0) {
                        printf("ip_output: "
                                "can't update route after IPsec processing\n");
                        error = EHOSTUNREACH;   /*XXX*/ 
                        lck_mtx_unlock(rt_mtx);
                        KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 6,0,0,0,0);
                        goto bad;
                }
        } else {
                if (ia)
                        ifafree(&ia->ia_ifa);
                ia = ifatoia(ro->ro_rt->rt_ifa);
                if (ia)
                        ifaref(&ia->ia_ifa);
                ifp = ro->ro_rt->rt_ifp;
        }
        lck_mtx_unlock(rt_mtx);

        /* make it flipped, again. */
        NTOHS(ip->ip_len);
        NTOHS(ip->ip_off);
        KERNEL_DEBUG(DBG_FNC_IPSEC4_OUTPUT | DBG_FUNC_END, 7,0xff,0xff,0xff,0xff);
        
        /* Pass to filters again */
        if (!TAILQ_EMPTY(&ipv4_filters)) {
                struct ipfilter *filter;
                
                ipf_ref();
                
                /* 4135317 - always pass network byte order to filter */
                HTONS(ip->ip_len);
                HTONS(ip->ip_off);
                
                TAILQ_FOREACH(filter, &ipv4_filters, ipf_link) {
                        if (filter->ipf_filter.ipf_output) {
                                errno_t result;
                                result = filter->ipf_filter.ipf_output(filter->ipf_filter.cookie, (mbuf_t*)&m, 0);
                                if (result == EJUSTRETURN) {
                                        ipf_unref();
                                        goto done;
                                }
                                if (result != 0) {
                                        ipf_unref();
                                        goto bad;
                                }
                        }
                }
                
                /* set back to host byte order */
                ip = mtod(m, struct ip *);
                NTOHS(ip->ip_len);
                NTOHS(ip->ip_off);
                
                ipf_unref();
        }
skip_ipsec:
#endif /*IPSEC*/

#if IPFIREWALL
        /*
         * IpHack's section.
         * - Xlate: translate packet's addr/port (NAT).
         * - Firewall: deny/allow/etc.
         * - Wrap: fake packet's addr/port <unimpl.>
         * - Encapsulate: put it in another IP and send out. <unimp.>
         */ 
        if (fr_checkp) {
                struct  mbuf    *m1 = m;

                if ((error = (*fr_checkp)(ip, hlen, ifp, 1, &m1)) || !m1) {
                        goto done;
                }
                ip = mtod(m0 = m = m1, struct ip *);
        }

        /*
         * Check with the firewall...
         * but not if we are already being fwd'd from a firewall.
         */
        if (fw_enable && IPFW_LOADED && !args.next_hop) {
                struct sockaddr_in *old = dst;

                args.m = m;
                args.next_hop = dst;
                args.oif = ifp;
                off = ip_fw_chk_ptr(&args);
                m = args.m;
                dst = args.next_hop;

                /*
                 * On return we must do the following:
                 * IP_FW_PORT_DENY_FLAG         -> drop the pkt (XXX new)
                 * 1<=off<= 0xffff   -> DIVERT
                 * (off & IP_FW_PORT_DYNT_FLAG) -> send to a DUMMYNET pipe
                 * (off & IP_FW_PORT_TEE_FLAG)  -> TEE the packet
                 * dst != old        -> IPFIREWALL_FORWARD
                 * off==0, dst==old  -> accept
                 * If some of the above modules is not compiled in, then
                 * we should't have to check the corresponding condition
                 * (because the ipfw control socket should not accept
                 * unsupported rules), but better play safe and drop
                 * packets in case of doubt.
                 */
                m0 = m;
                if ( (off & IP_FW_PORT_DENY_FLAG) || m == NULL) {
                        if (m)
                                m_freem(m);
                        error = EACCES ;
                        goto done ;
                }
                ip = mtod(m, struct ip *);
                
                if (off == 0 && dst == old) {/* common case */
                        goto pass ;
                }
#if DUMMYNET
                if (DUMMYNET_LOADED && (off & IP_FW_PORT_DYNT_FLAG) != 0) {
                    /*
                     * pass the pkt to dummynet. Need to include
                     * pipe number, m, ifp, ro, dst because these are
                     * not recomputed in the next pass.
                     * All other parameters have been already used and
                     * so they are not needed anymore. 
                     * XXX note: if the ifp or ro entry are deleted
                     * while a pkt is in dummynet, we are in trouble!
                     */ 
                    args.ro = ro;
                    args.dst = dst;
                    args.flags = flags;

                    error = ip_dn_io_ptr(m, off & 0xffff, DN_TO_IP_OUT,
                                &args);
                    goto done;
                }
#endif /* DUMMYNET */
#if IPDIVERT
                if (off != 0 && (off & IP_FW_PORT_DYNT_FLAG) == 0) {
                        struct mbuf *clone = NULL;

                        /* Clone packet if we're doing a 'tee' */
                        if ((off & IP_FW_PORT_TEE_FLAG) != 0)
                                clone = m_dup(m, M_DONTWAIT);
                        /*
                         * XXX
                         * delayed checksums are not currently compatible
                         * with divert sockets.
                         */
                        if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
                                in_delayed_cksum(m);
                                m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
                        }

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

                        /* Deliver packet to divert input routine */
                        divert_packet(m, 0, off & 0xffff, args.divert_rule);

                        /* If 'tee', continue with original packet */
                        if (clone != NULL) {
                                m0 = m = clone;
                                ip = mtod(m, struct ip *);
                                goto pass;
                        }
                        goto done;
                }
#endif

#if IPFIREWALL_FORWARD
                /* Here we check dst to make sure it's directly reachable on the
                 * interface we previously thought it was.
                 * If it isn't (which may be likely in some situations) we have
                 * to re-route it (ie, find a route for the next-hop and the
                 * associated interface) and set them here. This is nested
                 * forwarding which in most cases is undesirable, except where
                 * such control is nigh impossible. So we do it here.
                 * And I'm babbling.
                 */
                if (off == 0 && old != dst) {
                        struct in_ifaddr *ia_fw;

                        /* It's changed... */
                        /* There must be a better way to do this next line... */
                        static struct route sro_fwd, *ro_fwd = &sro_fwd;
#if IPFIREWALL_FORWARD_DEBUG
                        printf("IPFIREWALL_FORWARD: New dst ip: ");
                        print_ip(dst->sin_addr);
                        printf("\n");
#endif
                        /*
                         * We need to figure out if we have been forwarded
                         * to a local socket. If so then we should somehow 
                         * "loop back" to ip_input, and get directed to the
                         * PCB as if we had received this packet. This is
                         * because it may be dificult to identify the packets
                         * you want to forward until they are being output
                         * and have selected an interface. (e.g. locally
                         * initiated packets) If we used the loopback inteface,
                         * we would not be able to control what happens 
                         * as the packet runs through ip_input() as
                         * it is done through a ISR.
                         */
                        TAILQ_FOREACH(ia_fw, &in_ifaddrhead, ia_link) {
                                /*
                                 * If the addr to forward to is one
                                 * of ours, we pretend to
                                 * be the destination for this packet.
                                 */
                                if (IA_SIN(ia_fw)->sin_addr.s_addr ==
                                                 dst->sin_addr.s_addr)
                                        break;
                        }
                        if (ia) {
                                /* tell ip_input "dont filter" */
                                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) {
                                        error = ENOBUFS;
                                        goto bad;
                                }
                                
                                ipfwd_tag = (struct ip_fwd_tag *)(fwd_tag+1);
                                ipfwd_tag->next_hop = args.next_hop;

                                m_tag_prepend(m, fwd_tag);

                                if (m->m_pkthdr.rcvif == NULL)
                                        m->m_pkthdr.rcvif = ifunit("lo0");
                                if ((~IF_HWASSIST_CSUM_FLAGS(m->m_pkthdr.rcvif->if_hwassist) & 
                                                m->m_pkthdr.csum_flags) == 0) {
                                        if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
                                                m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
                                                m->m_pkthdr.csum_flags |=
                                                        CSUM_DATA_VALID | CSUM_PSEUDO_HDR;
                                                m->m_pkthdr.csum_data = 0xffff;
                                        }
                                        m->m_pkthdr.csum_flags |=
                                                CSUM_IP_CHECKED | CSUM_IP_VALID;
                                }
                                else if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
                                        in_delayed_cksum(m);
                                        m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
                                        ip->ip_sum = in_cksum(m, hlen);
                                }
                                HTONS(ip->ip_len);
                                HTONS(ip->ip_off);
                                
                                
                                /*  we need to call dlil_output to run filters
                                 *      and resync to avoid recursion loops.
                                 */
                                if (lo_ifp) {
                                        dlil_output(lo_ifp, PF_INET, m, 0, (struct sockaddr *)dst, 0);
                                }
                                else {
                                        printf("ip_output: no loopback ifp for forwarding!!!\n");
                                }
                                goto done;
                        }
                        /* Some of the logic for this was
                         * nicked from above.
                         *
                         * This rewrites the cached route in a local PCB.
                         * Is this what we want to do?
                         */
                        bcopy(dst, &ro_fwd->ro_dst, sizeof(*dst));

                        ro_fwd->ro_rt = 0;
                        lck_mtx_lock(rt_mtx);
                        rtalloc_ign_locked(ro_fwd, RTF_PRCLONING);

                        if (ro_fwd->ro_rt == 0) {
                                OSAddAtomic(1, (SInt32*)&ipstat.ips_noroute);
                                error = EHOSTUNREACH;
                                lck_mtx_unlock(rt_mtx);
                                goto bad;
                        }

                        ia_fw = ifatoia(ro_fwd->ro_rt->rt_ifa);
                        ifp = ro_fwd->ro_rt->rt_ifp;
                        ro_fwd->ro_rt->rt_use++;
                        if (ro_fwd->ro_rt->rt_flags & RTF_GATEWAY)
                                dst = (struct sockaddr_in *)ro_fwd->ro_rt->rt_gateway;
                        if (ro_fwd->ro_rt->rt_flags & RTF_HOST)
                                isbroadcast =
                                    (ro_fwd->ro_rt->rt_flags & RTF_BROADCAST);
                        else
                                isbroadcast = in_broadcast(dst->sin_addr, ifp);
                        rtfree_locked(ro->ro_rt);
                        ro->ro_rt = ro_fwd->ro_rt;
                        dst = (struct sockaddr_in *)&ro_fwd->ro_dst;
                        lck_mtx_unlock(rt_mtx);

                        /*
                         * If we added a default src ip earlier,
                         * which would have been gotten from the-then
                         * interface, do it again, from the new one.
                         */
                        if (fwd_rewrite_src)
                                ip->ip_src = IA_SIN(ia_fw)->sin_addr;
                        goto pass ;
                }
#endif /* IPFIREWALL_FORWARD */
                /*
                 * if we get here, none of the above matches, and 
                 * we have to drop the pkt
                 */
                m_freem(m);
                error = EACCES; /* not sure this is the right error msg */
                goto done;
        }
#endif /* IPFIREWALL */

pass:
#if __APPLE__
        /* Do not allow loopback address to wind up on a wire */
        if ((ifp->if_flags & IFF_LOOPBACK) == 0 &&
                 ((ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
                  (ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET)) {
                OSAddAtomic(1, (SInt32*)&ipstat.ips_badaddr);
                m_freem(m);
                /* 
                 * Do not simply drop the packet just like a firewall -- we want the 
                 * the application to feel the pain.
                 * Return ENETUNREACH like ip6_output does in some similar cases. 
                 * This can startle the otherwise clueless process that specifies
                 * loopback as the source address.
                 */
                error = ENETUNREACH;
                goto done;
        }
#endif
        m->m_pkthdr.csum_flags |= CSUM_IP;
        sw_csum = m->m_pkthdr.csum_flags 
                & ~IF_HWASSIST_CSUM_FLAGS(ifp->if_hwassist);

        if ((ifp->if_hwassist & CSUM_TCP_SUM16) != 0) {
                /*
                 * Special case code for GMACE
                 * frames that can be checksumed by GMACE SUM16 HW:
                 * frame >64, no fragments, no UDP
                 */
                if (apple_hwcksum_tx && (m->m_pkthdr.csum_flags & CSUM_TCP)
                        && (ip->ip_len > 50) && (ip->ip_len <= ifp->if_mtu)) {
                        /* Apple GMAC HW, expects STUFF_OFFSET << 16  | START_OFFSET */
                        u_short offset = (IP_VHL_HL(ip->ip_vhl) << 2) +14 ; /* IP+Enet header length */
                        u_short csumprev= m->m_pkthdr.csum_data & 0xFFFF;
                        m->m_pkthdr.csum_flags = CSUM_DATA_VALID | CSUM_TCP_SUM16; /* for GMAC */
                        m->m_pkthdr.csum_data = (csumprev + offset)  << 16 ;
                        m->m_pkthdr.csum_data += offset; 
                sw_csum = CSUM_DELAY_IP; /* do IP hdr chksum in software */
                }
                else {
                        /* let the software handle any UDP or TCP checksums */
                        sw_csum |= (CSUM_DELAY_DATA & m->m_pkthdr.csum_flags);
                }
        } else if (apple_hwcksum_tx == 0) {
                sw_csum |= (CSUM_DELAY_DATA | CSUM_DELAY_IP) &
                    m->m_pkthdr.csum_flags;
        }
        
        if (sw_csum & CSUM_DELAY_DATA) {
                in_delayed_cksum(m);
                sw_csum &= ~CSUM_DELAY_DATA;
                m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
        }

        if (apple_hwcksum_tx != 0) {
                m->m_pkthdr.csum_flags &=
                    IF_HWASSIST_CSUM_FLAGS(ifp->if_hwassist);
        } else {
                m->m_pkthdr.csum_flags = 0;
        }

        /*
         * If small enough for interface, or the interface will take
         * care of the fragmentation for us, can just send directly.
         */
        if ((u_short)ip->ip_len <= ifp->if_mtu ||
            ifp->if_hwassist & CSUM_FRAGMENT) {
                struct rtentry *rte;

                HTONS(ip->ip_len);
                HTONS(ip->ip_off);
                ip->ip_sum = 0;
                if (sw_csum & CSUM_DELAY_IP) {
                        ip->ip_sum = in_cksum(m, hlen);
                }
                
#ifndef __APPLE__
                /* Record statistics for this interface address. */
                if (!(flags & IP_FORWARDING) && ia != NULL) {
                        ia->ia_ifa.if_opackets++;
                        ia->ia_ifa.if_obytes += m->m_pkthdr.len;
                }
#endif

#if IPSEC
                /* clean ipsec history once it goes out of the node */
                if (ipsec_bypass == 0 && (flags & IP_NOIPSEC) == 0)
                        ipsec_delaux(m);
#endif
                if (packetchain == 0) {
                        lck_mtx_lock(rt_mtx);
                        if ((rte = ro->ro_rt) != NULL)
                                rtref(rte);
                        lck_mtx_unlock(rt_mtx);
                        error = ifnet_output(ifp, PF_INET, m, rte,
                            (struct sockaddr *)dst);
                        if (rte != NULL)
                                rtfree(rte);
                        goto done;
                }
                else { /* packet chaining allows us to reuse the route for all packets */
                        m = m->m_nextpkt;
                        if (m == NULL) {
                                if (pktcnt > ip_maxchainsent)
                                        ip_maxchainsent = pktcnt;
                                lck_mtx_lock(rt_mtx);
                                if ((rte = ro->ro_rt) != NULL)
                                        rtref(rte);
                                lck_mtx_unlock(rt_mtx);
                                //send
                                error = ifnet_output(ifp, PF_INET, packetlist,
                                    rte, (struct sockaddr *)dst);
                                if (rte != NULL)
                                        rtfree(rte);
                                pktcnt = 0;
                                goto done;
        
                        }
                        m0 = m;
                        pktcnt++;
                        goto loopit;
                }
        }
        /*
         * Too large for interface; fragment if possible.
         * Must be able to put at least 8 bytes per fragment.
         */
        if (ip->ip_off & IP_DF) {
                error = EMSGSIZE;
                /*
                 * This case can happen if the user changed the MTU
                 * of an interface after enabling IP on it.  Because
                 * most netifs don't keep track of routes pointing to
                 * them, there is no way for one to update all its
                 * routes when the MTU is changed.
                 */
                
                lck_mtx_lock(rt_mtx);
                if (ro->ro_rt && (ro->ro_rt->rt_flags & (RTF_UP | RTF_HOST))
                    && !(ro->ro_rt->rt_rmx.rmx_locks & RTV_MTU)
                    && (ro->ro_rt->rt_rmx.rmx_mtu > ifp->if_mtu)) {
                        ro->ro_rt->rt_rmx.rmx_mtu = ifp->if_mtu;
                }
                lck_mtx_unlock(rt_mtx);
                OSAddAtomic(1, (SInt32*)&ipstat.ips_cantfrag);
                goto bad;
        }
        len = (ifp->if_mtu - hlen) &~ 7;
        if (len < 8) {
                error = EMSGSIZE;
                goto bad;
        }

        /*
         * if the interface will not calculate checksums on
         * fragmented packets, then do it here.
         */
        if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA &&
            (ifp->if_hwassist & CSUM_IP_FRAGS) == 0) {
                in_delayed_cksum(m);
                m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
        }


    {
        int mhlen, firstlen = len;
        struct mbuf **mnext = &m->m_nextpkt;
        int nfrags = 1;

        /*
         * Loop through length of segment after first fragment,
         * make new header and copy data of each part and link onto chain.
         */
        m0 = m;
        mhlen = sizeof (struct ip);
        for (off = hlen + len; off < (u_short)ip->ip_len; off += len) {
                MGETHDR(m, M_DONTWAIT, MT_HEADER);      /* MAC-OK */
                if (m == 0) {
                        error = ENOBUFS;
                        OSAddAtomic(1, (SInt32*)&ipstat.ips_odropped);
                        goto sendorfree;
                }
                m->m_flags |= (m0->m_flags & M_MCAST) | M_FRAG;
                m->m_data += max_linkhdr;
                mhip = mtod(m, struct ip *);
                *mhip = *ip;
                if (hlen > sizeof (struct ip)) {
                        mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
                        mhip->ip_vhl = IP_MAKE_VHL(IPVERSION, mhlen >> 2);
                }
                m->m_len = mhlen;
                mhip->ip_off = ((off - hlen) >> 3) + (ip->ip_off & ~IP_MF);
                if (ip->ip_off & IP_MF)
                        mhip->ip_off |= IP_MF;
                if (off + len >= (u_short)ip->ip_len)
                        len = (u_short)ip->ip_len - off;
                else
                        mhip->ip_off |= IP_MF;
                mhip->ip_len = htons((u_short)(len + mhlen));
                m->m_next = m_copy(m0, off, len);
                if (m->m_next == 0) {
                        (void) m_free(m);
                        error = ENOBUFS;        /* ??? */
                        OSAddAtomic(1, (SInt32*)&ipstat.ips_odropped);
                        goto sendorfree;
                }
                m->m_pkthdr.len = mhlen + len;
                m->m_pkthdr.rcvif = 0;
                m->m_pkthdr.csum_flags = m0->m_pkthdr.csum_flags;
                m->m_pkthdr.socket_id = m0->m_pkthdr.socket_id;
#if CONFIG_MACF_NET
                mac_netinet_fragment(m0, m);
#endif
                HTONS(mhip->ip_off);
                mhip->ip_sum = 0;
                if (sw_csum & CSUM_DELAY_IP) {
                        mhip->ip_sum = in_cksum(m, mhlen);
                }
                *mnext = m;
                mnext = &m->m_nextpkt;
                nfrags++;
        }
        OSAddAtomic(nfrags, (SInt32*)&ipstat.ips_ofragments);

        /* set first/last markers for fragment chain */
        m->m_flags |= M_LASTFRAG;
        m0->m_flags |= M_FIRSTFRAG | M_FRAG;
        m0->m_pkthdr.csum_data = nfrags;

        /*
         * Update first fragment by trimming what's been copied out
         * and updating header, then send each fragment (in order).
         */
        m = m0;
        m_adj(m, hlen + firstlen - (u_short)ip->ip_len);
        m->m_pkthdr.len = hlen + firstlen;
        ip->ip_len = htons((u_short)m->m_pkthdr.len);
        ip->ip_off |= IP_MF;
        HTONS(ip->ip_off);
        ip->ip_sum = 0;
        if (sw_csum & CSUM_DELAY_IP) {
                ip->ip_sum = in_cksum(m, hlen);
        }
sendorfree:

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

        for (m = m0; m; m = m0) {
                m0 = m->m_nextpkt;
                m->m_nextpkt = 0;
#if IPSEC
                /* clean ipsec history once it goes out of the node */
                if (ipsec_bypass == 0 && (flags & IP_NOIPSEC) == 0)
                        ipsec_delaux(m);
#endif
                if (error == 0) {
                        struct rtentry *rte;
#ifndef __APPLE__
                        /* Record statistics for this interface address. */
                        if (ia != NULL) {
                                ia->ia_ifa.if_opackets++;
                                ia->ia_ifa.if_obytes += m->m_pkthdr.len;
                        }
#endif
                        if ((packetchain != 0)  && (pktcnt > 0))
                                panic("ip_output: mix of packet in packetlist is wrong=%p", packetlist);
                        lck_mtx_lock(rt_mtx);
                        if ((rte = ro->ro_rt) != NULL)
                                rtref(rte);
                        lck_mtx_unlock(rt_mtx);
                        error = ifnet_output(ifp, PF_INET, m, rte,
                            (struct sockaddr *)dst);
                        if (rte != NULL)
                                rtfree(rte);
                } else
                        m_freem(m);
        }

        if (error == 0)
                OSAddAtomic(1, (SInt32*)&ipstat.ips_fragmented);
    }
done:
        if (ia) {
                ifafree(&ia->ia_ifa);
                ia = NULL;
        }
#if IPSEC
        if (ipsec_bypass == 0 && (flags & IP_NOIPSEC) == 0) {
        if (ro == &iproute && ro->ro_rt) {
                rtfree(ro->ro_rt);
                ro->ro_rt = NULL;
        }
        if (sp != NULL) {
                KEYDEBUG(KEYDEBUG_IPSEC_STAMP,
                        printf("DP ip_output call free SP:%x\n", sp));
                key_freesp(sp, KEY_SADB_UNLOCKED);
        }
        }
#endif /* IPSEC */

        KERNEL_DEBUG(DBG_FNC_IP_OUTPUT | DBG_FUNC_END, error,0,0,0,0);
        return (error);
bad:
        m_freem(m0);
        goto done;
}

static void
ip_out_cksum_stats(int proto, u_int32_t len)
{
        switch (proto) {
        case IPPROTO_TCP:
                tcp_out_cksum_stats(len);
                break;
        case IPPROTO_UDP:
                udp_out_cksum_stats(len);
                break;
        default:
                /* keep only TCP or UDP stats for now */
                break;
        }
}

void
in_delayed_cksum_offset(struct mbuf *m0, int ip_offset)
{
        struct ip *ip;
        unsigned char buf[sizeof(struct ip)];
        u_short csum, offset, ip_len;
        struct mbuf *m = m0;
        
        while (ip_offset >= m->m_len) {
                ip_offset -= m->m_len;
                m = m->m_next;
                if (m == NULL) {
                        printf("in_delayed_cksum_withoffset failed - ip_offset wasn't in the packet\n");
                        return;
                }
        }
        
        /* Sometimes the IP header is not contiguous, yes this can happen! */
        if (ip_offset + sizeof(struct ip) > m->m_len) {
#if DEBUG               
                printf("delayed m_pullup, m->len: %ld  off: %d\n",
                        m->m_len, ip_offset);
#endif
                m_copydata(m, ip_offset, sizeof(struct ip), (caddr_t) buf);
                
                ip = (struct ip *)buf;
        } else {
                ip = (struct ip*)(m->m_data + ip_offset);
        }
        
        /* Gross */
        if (ip_offset) {
                m->m_len -= ip_offset;
                m->m_data += ip_offset;
        }
        
        offset = IP_VHL_HL(ip->ip_vhl) << 2 ;

        /*
         * We could be in the context of an IP or interface filter; in the
         * former case, ip_len would be in host (correct) order while for
         * the latter it would be in network order.  Because of this, we
         * attempt to interpret the length field by comparing it against
         * the actual packet length.  If the comparison fails, byte swap
         * the length and check again.  If it still fails, then the packet
         * is bogus and we give up.
         */
        ip_len = ip->ip_len;
        if (ip_len != (m0->m_pkthdr.len - ip_offset)) {
                ip_len = SWAP16(ip_len);
                if (ip_len != (m0->m_pkthdr.len - ip_offset)) {
                        printf("in_delayed_cksum_offset: ip_len %d (%d) "
                            "doesn't match actual length %d\n", ip->ip_len,
                            ip_len, (m0->m_pkthdr.len - ip_offset));
                        return;
                }
        }

        csum = in_cksum_skip(m, ip_len, offset);

        /* Update stats */
        ip_out_cksum_stats(ip->ip_p, ip_len - offset);

        if (m0->m_pkthdr.csum_flags & CSUM_UDP && csum == 0)
                csum = 0xffff;
        offset += m0->m_pkthdr.csum_data & 0xFFFF;        /* checksum offset */

        /* Gross */
        if (ip_offset) {
                if (M_LEADINGSPACE(m) < ip_offset)
                        panic("in_delayed_cksum_offset - chain modified!\n");
                m->m_len += ip_offset;
                m->m_data -= ip_offset;
        }

        if (offset > ip_len) /* bogus offset */
                return;

        /* Insert the checksum in the existing chain */
        if (offset + ip_offset + sizeof(u_short) > m->m_len) {
                char tmp[2];
                
#if DEBUG
                printf("delayed m_copyback, m->len: %ld  off: %d  p: %d\n",
                    m->m_len, offset + ip_offset, ip->ip_p);
#endif
                *(u_short *)tmp = csum;
                m_copyback(m, offset + ip_offset, 2, tmp);
        } else
                *(u_short *)(m->m_data + offset + ip_offset) = csum;
}

void
in_delayed_cksum(struct mbuf *m)
{
        in_delayed_cksum_offset(m, 0);
}

void
in_cksum_offset(struct mbuf* m, size_t ip_offset)
{
        struct ip* ip = NULL;
        int hlen = 0;
        unsigned char buf[sizeof(struct ip)];
        int swapped = 0;
        
        while (ip_offset >= m->m_len) {
                ip_offset -= m->m_len;
                m = m->m_next;
                if (m == NULL) {
                        printf("in_cksum_offset failed - ip_offset wasn't in the packet\n");
                        return;
                }
        }
        
        /* Sometimes the IP header is not contiguous, yes this can happen! */
        if (ip_offset + sizeof(struct ip) > m->m_len) {

#if DEBUG
                printf("in_cksum_offset - delayed m_pullup, m->len: %ld  off: %lu\n",
                        m->m_len, ip_offset);
#endif  
                m_copydata(m, ip_offset, sizeof(struct ip), (caddr_t) buf);

                ip = (struct ip *)buf;
                ip->ip_sum = 0;
                m_copyback(m, ip_offset + offsetof(struct ip, ip_sum), 2, (caddr_t)&ip->ip_sum);
        } else {
                ip = (struct ip*)(m->m_data + ip_offset);
                ip->ip_sum = 0;
        }
        
        /* Gross */
        if (ip_offset) {
                m->m_len -= ip_offset;
                m->m_data += ip_offset;
        }

#ifdef _IP_VHL
        hlen = IP_VHL_HL(ip->ip_vhl) << 2;
#else
        hlen = ip->ip_hl << 2;
#endif
        /*
         * We could be in the context of an IP or interface filter; in the
         * former case, ip_len would be in host order while for the latter
         * it would be in network (correct) order.  Because of this, we
         * attempt to interpret the length field by comparing it against
         * the actual packet length.  If the comparison fails, byte swap
         * the length and check again.  If it still fails, then the packet
         * is bogus and we give up.
         */
        if (ntohs(ip->ip_len) != (m->m_pkthdr.len - ip_offset)) {
                ip->ip_len = SWAP16(ip->ip_len);
                swapped = 1;
                if (ntohs(ip->ip_len) != (m->m_pkthdr.len - ip_offset)) {
                        ip->ip_len = SWAP16(ip->ip_len);
                        printf("in_cksum_offset: ip_len %d (%d) "
                            "doesn't match actual length %lu\n",
                            ip->ip_len, SWAP16(ip->ip_len),
                            (m->m_pkthdr.len - ip_offset));
                        return;
                }
        }

        ip->ip_sum = 0;
        ip->ip_sum = in_cksum(m, hlen);
        if (swapped)
                ip->ip_len = SWAP16(ip->ip_len);

        /* Gross */
        if (ip_offset) {
                if (M_LEADINGSPACE(m) < ip_offset)
                        panic("in_cksum_offset - chain modified!\n");
                m->m_len += ip_offset;
                m->m_data -= ip_offset;
        }

        /* Insert the checksum in the existing chain if IP header not contiguous */
        if (ip_offset + sizeof(struct ip) > m->m_len) {
                char tmp[2];

#if DEBUG
                printf("in_cksum_offset m_copyback, m->len: %lu  off: %lu  p: %d\n",
                    m->m_len, ip_offset + offsetof(struct ip, ip_sum), ip->ip_p);
#endif
                *(u_short *)tmp = ip->ip_sum;
                m_copyback(m, ip_offset + offsetof(struct ip, ip_sum), 2, tmp);
        }
}

/*
 * Insert IP options into preformed packet.
 * Adjust IP destination as required for IP source routing,
 * as indicated by a non-zero in_addr at the start of the options.
 *
 * XXX This routine assumes that the packet has no options in place.
 */
static struct mbuf *
ip_insertoptions(m, opt, phlen)
        register struct mbuf *m;
        struct mbuf *opt;
        int *phlen;
{
        register struct ipoption *p = mtod(opt, struct ipoption *);
        struct mbuf *n;
        register struct ip *ip = mtod(m, struct ip *);
        unsigned optlen;

        optlen = opt->m_len - sizeof(p->ipopt_dst);
        if (optlen + (u_short)ip->ip_len > IP_MAXPACKET)
                return (m);             /* XXX should fail */
        if (p->ipopt_dst.s_addr)
                ip->ip_dst = p->ipopt_dst;
        if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
                MGETHDR(n, M_DONTWAIT, MT_HEADER);      /* MAC-OK */
                if (n == 0)
                        return (m);
                n->m_pkthdr.rcvif = 0;
#if CONFIG_MACF_NET
                mac_mbuf_label_copy(m, n);
#endif
                n->m_pkthdr.len = m->m_pkthdr.len + optlen;
                m->m_len -= sizeof(struct ip);
                m->m_data += sizeof(struct ip);
                n->m_next = m;
                m = n;
                m->m_len = optlen + sizeof(struct ip);
                m->m_data += max_linkhdr;
                (void)memcpy(mtod(m, void *), ip, sizeof(struct ip));
        } else {
                m->m_data -= optlen;
                m->m_len += optlen;
                m->m_pkthdr.len += optlen;
                ovbcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
        }
        ip = mtod(m, struct ip *);
        bcopy(p->ipopt_list, ip + 1, optlen);
        *phlen = sizeof(struct ip) + optlen;
        ip->ip_vhl = IP_MAKE_VHL(IPVERSION, *phlen >> 2);
        ip->ip_len += optlen;
        return (m);
}

/*
 * Copy options from ip to jp,
 * omitting those not copied during fragmentation.
 */
int
ip_optcopy(ip, jp)
        struct ip *ip, *jp;
{
        register u_char *cp, *dp;
        int opt, optlen, cnt;

        cp = (u_char *)(ip + 1);
        dp = (u_char *)(jp + 1);
        cnt = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof (struct ip);
        for (; cnt > 0; cnt -= optlen, cp += optlen) {
                opt = cp[0];
                if (opt == IPOPT_EOL)
                        break;
                if (opt == IPOPT_NOP) {
                        /* Preserve for IP mcast tunnel's LSRR alignment. */
                        *dp++ = IPOPT_NOP;
                        optlen = 1;
                        continue;
                }
#if DIAGNOSTIC
                if (cnt < IPOPT_OLEN + sizeof(*cp))
                        panic("malformed IPv4 option passed to ip_optcopy");
#endif
                optlen = cp[IPOPT_OLEN];
#if DIAGNOSTIC
                if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
                        panic("malformed IPv4 option passed to ip_optcopy");
#endif
                /* bogus lengths should have been caught by ip_dooptions */
                if (optlen > cnt)
                        optlen = cnt;
                if (IPOPT_COPIED(opt)) {
                        bcopy(cp, dp, optlen);
                        dp += optlen;
                }
        }
        for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
                *dp++ = IPOPT_EOL;
        return (optlen);
}

/*
 * IP socket option processing.
 */
int
ip_ctloutput(so, sopt)
        struct socket *so;
        struct sockopt *sopt;
{
        struct  inpcb *inp = sotoinpcb(so);
        int     error, optval;

        error = optval = 0;
        if (sopt->sopt_level != IPPROTO_IP) {
                return (EINVAL);
        }

        switch (sopt->sopt_dir) {
        case SOPT_SET:
                switch (sopt->sopt_name) {
                case IP_OPTIONS:
#ifdef notyet
                case IP_RETOPTS:
#endif
                {
                        struct mbuf *m;
                        if (sopt->sopt_valsize > MLEN) {
                                error = EMSGSIZE;
                                break;
                        }
                        MGET(m, sopt->sopt_p ? M_WAIT : M_DONTWAIT, MT_HEADER);
                        if (m == 0) {
                                error = ENOBUFS;
                                break;
                        }
                        m->m_len = sopt->sopt_valsize;
                        error = sooptcopyin(sopt, mtod(m, char *), m->m_len,
                                            m->m_len);
                        if (error)
                                break;
                        
                        return (ip_pcbopts(sopt->sopt_name, &inp->inp_options,
                                           m));
                }

                case IP_TOS:
                case IP_TTL:
                case IP_RECVOPTS:
                case IP_RECVRETOPTS:
                case IP_RECVDSTADDR:
                case IP_RECVIF:
                case IP_RECVTTL:
#if defined(NFAITH) && NFAITH > 0
                case IP_FAITH:
#endif
                        error = sooptcopyin(sopt, &optval, sizeof optval,
                                            sizeof optval);
                        if (error)
                                break;

                        switch (sopt->sopt_name) {
                        case IP_TOS:
                                inp->inp_ip_tos = optval;
                                break;

                        case IP_TTL:
                                inp->inp_ip_ttl = optval;
                                break;
#define OPTSET(bit) \
        if (optval) \
                inp->inp_flags |= bit; \
        else \
                inp->inp_flags &= ~bit;

                        case IP_RECVOPTS:
                                OPTSET(INP_RECVOPTS);
                                break;

                        case IP_RECVRETOPTS:
                                OPTSET(INP_RECVRETOPTS);
                                break;

                        case IP_RECVDSTADDR:
                                OPTSET(INP_RECVDSTADDR);
                                break;

                        case IP_RECVIF:
                                OPTSET(INP_RECVIF);
                                break;

                        case IP_RECVTTL:
                                OPTSET(INP_RECVTTL);
                                break;

#if defined(NFAITH) && NFAITH > 0
                        case IP_FAITH:
                                OPTSET(INP_FAITH);
                                break;
#endif
                        }
                        break;
#undef OPTSET

#if CONFIG_FORCE_OUT_IFP                
                case IP_FORCE_OUT_IFP: {
                        char    ifname[IFNAMSIZ];
                        ifnet_t ifp;
                        
                        /* Verify interface name parameter is sane */
                        if (sopt->sopt_valsize > sizeof(ifname)) {
                                error = EINVAL;
                                break;
                        }
                        
                        /* Copy the interface name */
                        if (sopt->sopt_valsize != 0) {
                                error = sooptcopyin(sopt, ifname, sizeof(ifname), sopt->sopt_valsize);
                                if (error)
                                        break;
                        }
                        
                        if (sopt->sopt_valsize == 0 || ifname[0] == 0) {
                                // Set pdp_ifp to NULL
                                inp->pdp_ifp = NULL;
                                
                                // Flush the route
                                if (inp->inp_route.ro_rt) {
                                        rtfree(inp->inp_route.ro_rt);
                                        inp->inp_route.ro_rt = NULL;
                                }
                                
                                break;
                        }
                        
                        /* Verify name is NULL terminated */
                        if (ifname[sopt->sopt_valsize - 1] != 0) {
                                error = EINVAL;
                                break;
                        }
                        
                        if (ifnet_find_by_name(ifname, &ifp) != 0) {
                                error = ENXIO;
                                break;
                        }
                        
                        /* Won't actually free. Since we don't release this later, we should do it now. */
                        ifnet_release(ifp);
                        
                        /* This only works for point-to-point interfaces */
                        if ((ifp->if_flags & IFF_POINTOPOINT) == 0) {
                                error = ENOTSUP;
                                break;
                        }
                        
                        inp->pdp_ifp = ifp;
                }
                break;
#endif
                case IP_MULTICAST_IF:
                case IP_MULTICAST_VIF:
                case IP_MULTICAST_TTL:
                case IP_MULTICAST_LOOP:
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                        error = ip_setmoptions(sopt, &inp->inp_moptions);
                        break;

                case IP_PORTRANGE:
                        error = sooptcopyin(sopt, &optval, sizeof optval,
                                            sizeof optval);
                        if (error)
                                break;

                        switch (optval) {
                        case IP_PORTRANGE_DEFAULT:
                                inp->inp_flags &= ~(INP_LOWPORT);
                                inp->inp_flags &= ~(INP_HIGHPORT);
                                break;

                        case IP_PORTRANGE_HIGH:
                                inp->inp_flags &= ~(INP_LOWPORT);
                                inp->inp_flags |= INP_HIGHPORT;
                                break;

                        case IP_PORTRANGE_LOW:
                                inp->inp_flags &= ~(INP_HIGHPORT);
                                inp->inp_flags |= INP_LOWPORT;
                                break;

                        default:
                                error = EINVAL;
                                break;
                        }
                        break;

#if IPSEC
                case IP_IPSEC_POLICY:
                {
                        caddr_t req = NULL;
                        size_t len = 0;
                        int priv;
                        struct mbuf *m;
                        int optname;

                        if (sopt->sopt_valsize > MCLBYTES) {
                                error = EMSGSIZE;
                                break;
                        }
                        if ((error = soopt_getm(sopt, &m)) != 0) /* XXX */
                                break;
                        if ((error = soopt_mcopyin(sopt, m)) != 0) /* XXX */
                                break;
                        priv = (sopt->sopt_p != NULL &&
                                proc_suser(sopt->sopt_p) != 0) ? 0 : 1;
                        if (m) {
                                req = mtod(m, caddr_t);
                                len = m->m_len;
                        }
                        optname = sopt->sopt_name;
                        error = ipsec4_set_policy(inp, optname, req, len, priv);
                        m_freem(m);
                        break;
                }
#endif /*IPSEC*/

#if TRAFFIC_MGT
                case IP_TRAFFIC_MGT_BACKGROUND:
                {
                        unsigned        background = 0;
                        error = sooptcopyin(sopt, &background, sizeof(background), sizeof(background));
                        if (error) 
                                break;

                        if (background) 
                                so->so_traffic_mgt_flags |= TRAFFIC_MGT_SO_BACKGROUND;
                        else 
                                so->so_traffic_mgt_flags &= ~TRAFFIC_MGT_SO_BACKGROUND;

                        break;
                }
#endif /* TRAFFIC_MGT */

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;

        case SOPT_GET:
                switch (sopt->sopt_name) {
                case IP_OPTIONS:
                case IP_RETOPTS:
                        if (inp->inp_options)
                                error = sooptcopyout(sopt, 
                                                     mtod(inp->inp_options,
                                                          char *),
                                                     inp->inp_options->m_len);
                        else
                                sopt->sopt_valsize = 0;
                        break;

                case IP_TOS:
                case IP_TTL:
                case IP_RECVOPTS:
                case IP_RECVRETOPTS:
                case IP_RECVDSTADDR:
                case IP_RECVIF:
                case IP_RECVTTL:
                case IP_PORTRANGE:
#if defined(NFAITH) && NFAITH > 0
                case IP_FAITH:
#endif
                        switch (sopt->sopt_name) {

                        case IP_TOS:
                                optval = inp->inp_ip_tos;
                                break;

                        case IP_TTL:
                                optval = inp->inp_ip_ttl;
                                break;

#define OPTBIT(bit)     (inp->inp_flags & bit ? 1 : 0)

                        case IP_RECVOPTS:
                                optval = OPTBIT(INP_RECVOPTS);
                                break;

                        case IP_RECVRETOPTS:
                                optval = OPTBIT(INP_RECVRETOPTS);
                                break;

                        case IP_RECVDSTADDR:
                                optval = OPTBIT(INP_RECVDSTADDR);
                                break;

                        case IP_RECVIF:
                                optval = OPTBIT(INP_RECVIF);
                                break;

                        case IP_RECVTTL:
                                optval = OPTBIT(INP_RECVTTL);
                                break;

                        case IP_PORTRANGE:
                                if (inp->inp_flags & INP_HIGHPORT)
                                        optval = IP_PORTRANGE_HIGH;
                                else if (inp->inp_flags & INP_LOWPORT)
                                        optval = IP_PORTRANGE_LOW;
                                else
                                        optval = 0;
                                break;

#if defined(NFAITH) && NFAITH > 0
                        case IP_FAITH:
                                optval = OPTBIT(INP_FAITH);
                                break;
#endif
                        }
                        error = sooptcopyout(sopt, &optval, sizeof optval);
                        break;

                case IP_MULTICAST_IF:
                case IP_MULTICAST_VIF:
                case IP_MULTICAST_TTL:
                case IP_MULTICAST_LOOP:
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                        error = ip_getmoptions(sopt, inp->inp_moptions);
                        break;

#if IPSEC
                case IP_IPSEC_POLICY:
                {
                        struct mbuf *m = NULL;
                        caddr_t req = NULL;
                        size_t len = 0;

                        if (m != 0) {
                                req = mtod(m, caddr_t);
                                len = m->m_len;
                        }
                        error = ipsec4_get_policy(sotoinpcb(so), req, len, &m);
                        if (error == 0)
                                error = soopt_mcopyout(sopt, m); /* XXX */
                        if (error == 0)
                                m_freem(m);
                        break;
                }
#endif /*IPSEC*/

#if TRAFFIC_MGT
                case IP_TRAFFIC_MGT_BACKGROUND:
                {
                        unsigned        background = so->so_traffic_mgt_flags;
                        return (sooptcopyout(sopt, &background, sizeof(background)));
                        break;
                }
#endif /* TRAFFIC_MGT */

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;
        }
        return (error);
}

/*
 * Set up IP options in pcb for insertion in output packets.
 * Store in mbuf with pointer in pcbopt, adding pseudo-option
 * with destination address if source routed.
 */
static int
ip_pcbopts(
        __unused int optname,
        struct mbuf **pcbopt,
        register struct mbuf *m)
{
        register int cnt, optlen;
        register u_char *cp;
        u_char opt;

        /* turn off any old options */
        if (*pcbopt)
                (void)m_free(*pcbopt);
        *pcbopt = 0;
        if (m == (struct mbuf *)0 || m->m_len == 0) {
                /*
                 * Only turning off any previous options.
                 */
                if (m)
                        (void)m_free(m);
                return (0);
        }

#ifndef vax
        if (m->m_len % sizeof(int32_t))
                goto bad;
#endif
        /*
         * IP first-hop destination address will be stored before
         * actual options; move other options back
         * and clear it when none present.
         */
        if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
                goto bad;
        cnt = m->m_len;
        m->m_len += sizeof(struct in_addr);
        cp = mtod(m, u_char *) + sizeof(struct in_addr);
        ovbcopy(mtod(m, caddr_t), (caddr_t)cp, (unsigned)cnt);
        bzero(mtod(m, caddr_t), sizeof(struct in_addr));

        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))
                                goto bad;
                        optlen = cp[IPOPT_OLEN];
                        if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
                                goto bad;
                }
                switch (opt) {

                default:
                        break;

                case IPOPT_LSRR:
                case IPOPT_SSRR:
                        /*
                         * user process specifies route as:
                         *      ->A->B->C->D
                         * D must be our final destination (but we can't
                         * check that since we may not have connected yet).
                         * A is first hop destination, which doesn't appear in
                         * actual IP option, but is stored before the options.
                         */
                        if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
                                goto bad;
                        m->m_len -= sizeof(struct in_addr);
                        cnt -= sizeof(struct in_addr);
                        optlen -= sizeof(struct in_addr);
                        cp[IPOPT_OLEN] = optlen;
                        /*
                         * Move first hop before start of options.
                         */
                        bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
                            sizeof(struct in_addr));
                        /*
                         * Then copy rest of options back
                         * to close up the deleted entry.
                         */
                        ovbcopy((caddr_t)(&cp[IPOPT_OFFSET+1] +
                            sizeof(struct in_addr)),
                            (caddr_t)&cp[IPOPT_OFFSET+1],
                            (unsigned)cnt + sizeof(struct in_addr));
                        break;
                }
        }
        if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
                goto bad;
        *pcbopt = m;
        return (0);

bad:
        (void)m_free(m);
        return (EINVAL);
}

/*
 * XXX
 * The whole multicast option thing needs to be re-thought.
 * Several of these options are equally applicable to non-multicast
 * transmission, and one (IP_MULTICAST_TTL) totally duplicates a
 * standard option (IP_TTL).
 */

/*
 * following RFC1724 section 3.3, 0.0.0.0/8 is interpreted as interface index.
 */
static struct ifnet *
ip_multicast_if(a, ifindexp)
        struct in_addr *a;
        int *ifindexp;
{
        int ifindex;
        struct ifnet *ifp;

        if (ifindexp)
                *ifindexp = 0;
        if (ntohl(a->s_addr) >> 24 == 0) {
                ifindex = ntohl(a->s_addr) & 0xffffff;
                ifnet_head_lock_shared();
                if (ifindex < 0 || if_index < ifindex) {
                        ifnet_head_done();
                        return NULL;
                }
                ifp = ifindex2ifnet[ifindex];
                ifnet_head_done();
                if (ifindexp)
                        *ifindexp = ifindex;
        } else {
                INADDR_TO_IFP(*a, ifp);
        }
        return ifp;
}

/*
 * Set the IP multicast options in response to user setsockopt().
 */
static int
ip_setmoptions(sopt, imop)
        struct sockopt *sopt;
        struct ip_moptions **imop;
{
        int error = 0;
        int i;
        struct in_addr addr;
        struct ip_mreq mreq;
        struct ifnet *ifp = NULL;
        struct ip_moptions *imo = *imop;
        int ifindex;

        if (imo == NULL) {
                /*
                 * No multicast option buffer attached to the pcb;
                 * allocate one and initialize to default values.
                 */
                error = ip_createmoptions(imop);
                if (error != 0)
                        return error;
                imo = *imop;
        }

        switch (sopt->sopt_name) {
        /* store an index number for the vif you wanna use in the send */
#if MROUTING
        case IP_MULTICAST_VIF:
                if (legal_vif_num == 0) {
                        error = EOPNOTSUPP;
                        break;
                }
                error = sooptcopyin(sopt, &i, sizeof i, sizeof i);
                if (error)
                        break;
                if (!legal_vif_num(i) && (i != -1)) {
                        error = EINVAL;
                        break;
                }
                imo->imo_multicast_vif = i;
                break;
#endif /* MROUTING */

        case IP_MULTICAST_IF:
                /*
                 * Select the interface for outgoing multicast packets.
                 */
                error = sooptcopyin(sopt, &addr, sizeof addr, sizeof addr);
                if (error)
                        break;
                /*
                 * INADDR_ANY is used to remove a previous selection.
                 * When no interface is selected, a default one is
                 * chosen every time a multicast packet is sent.
                 */
                if (addr.s_addr == INADDR_ANY) {
                        imo->imo_multicast_ifp = NULL;
                        break;
                }
                /*
                 * The selected interface is identified by its local
                 * IP address.  Find the interface and confirm that
                 * it supports multicasting.
                 */
                ifp = ip_multicast_if(&addr, &ifindex);
                if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                imo->imo_multicast_ifp = ifp;
                if (ifindex)
                        imo->imo_multicast_addr = addr;
                else
                        imo->imo_multicast_addr.s_addr = INADDR_ANY;
                break;

        case IP_MULTICAST_TTL:
                /*
                 * Set the IP time-to-live for outgoing multicast packets.
                 * The original multicast API required a char argument,
                 * which is inconsistent with the rest of the socket API.
                 * We allow either a char or an int.
                 */
                if (sopt->sopt_valsize == 1) {
                        u_char ttl;
                        error = sooptcopyin(sopt, &ttl, 1, 1);
                        if (error)
                                break;
                        imo->imo_multicast_ttl = ttl;
                } else {
                        u_int ttl;
                        error = sooptcopyin(sopt, &ttl, sizeof ttl, 
                                            sizeof ttl);
                        if (error)
                                break;
                        if (ttl > 255)
                                error = EINVAL;
                        else
                                imo->imo_multicast_ttl = ttl;
                }
                break;

        case IP_MULTICAST_LOOP:
                /*
                 * Set the loopback flag for outgoing multicast packets.
                 * Must be zero or one.  The original multicast API required a
                 * char argument, which is inconsistent with the rest
                 * of the socket API.  We allow either a char or an int.
                 */
                if (sopt->sopt_valsize == 1) {
                        u_char loop;
                        error = sooptcopyin(sopt, &loop, 1, 1);
                        if (error)
                                break;
                        imo->imo_multicast_loop = !!loop;
                } else {
                        u_int loop;
                        error = sooptcopyin(sopt, &loop, sizeof loop,
                                            sizeof loop);
                        if (error)
                                break;
                        imo->imo_multicast_loop = !!loop;
                }
                break;

        case IP_ADD_MEMBERSHIP:
                /*
                 * Add a multicast group membership.
                 * Group must be a valid IP multicast address.
                 */
                error = sooptcopyin(sopt, &mreq, sizeof mreq, sizeof mreq);
                if (error)
                        break;
                
                error = ip_addmembership(imo, &mreq);
                break;

        case IP_DROP_MEMBERSHIP:
                /*
                 * Drop a multicast group membership.
                 * Group must be a valid IP multicast address.
                 */
                error = sooptcopyin(sopt, &mreq, sizeof mreq, sizeof mreq);
                if (error)
                        break;
                
                error = ip_dropmembership(imo, &mreq);
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }

        /*
         * If all options have default values, no need to keep the mbuf.
         */
        if (imo->imo_multicast_ifp == NULL &&
            imo->imo_multicast_vif == (u_long)-1 &&
            imo->imo_multicast_ttl == IP_DEFAULT_MULTICAST_TTL &&
            imo->imo_multicast_loop == IP_DEFAULT_MULTICAST_LOOP &&
            imo->imo_num_memberships == 0) {
                FREE(*imop, M_IPMOPTS);
                *imop = NULL;
        }

        return (error);
}

/*
 * Set the IP multicast options in response to user setsockopt().
 */
__private_extern__ int
ip_createmoptions(
        struct ip_moptions **imop)
{
        struct ip_moptions *imo;
        imo = (struct ip_moptions*) _MALLOC(sizeof(*imo), M_IPMOPTS,
                M_WAITOK);

        if (imo == NULL)
                return (ENOBUFS);
        *imop = imo;
        imo->imo_multicast_ifp = NULL;
        imo->imo_multicast_addr.s_addr = INADDR_ANY;
        imo->imo_multicast_vif = -1;
        imo->imo_multicast_ttl = IP_DEFAULT_MULTICAST_TTL;
        imo->imo_multicast_loop = IP_DEFAULT_MULTICAST_LOOP;
        imo->imo_num_memberships = 0;
        
        return 0;
}

/*
 * Add membership to an IPv4 multicast.
 */
__private_extern__ int
ip_addmembership(
        struct ip_moptions *imo,
        struct ip_mreq *mreq)
{
        struct route ro;
        struct sockaddr_in *dst;
        struct ifnet *ifp = NULL;
        int error = 0;
        int i;
        
        if (!IN_MULTICAST(ntohl(mreq->imr_multiaddr.s_addr))) {
                error = EINVAL;
                return error;
        }
        /*
         * If no interface address was provided, use the interface of
         * the route to the given multicast address.
         */
        if (mreq->imr_interface.s_addr == INADDR_ANY) {
                bzero((caddr_t)&ro, sizeof(ro));
                dst = (struct sockaddr_in *)&ro.ro_dst;
                dst->sin_len = sizeof(*dst);
                dst->sin_family = AF_INET;
                dst->sin_addr = mreq->imr_multiaddr;
                lck_mtx_lock(rt_mtx);
                rtalloc_ign_locked(&ro, 0UL);
                if (ro.ro_rt != NULL) {
                        ifp = ro.ro_rt->rt_ifp;
                        rtfree_locked(ro.ro_rt);
                }
                else {
                        /* If there's no default route, try using loopback */
                        mreq->imr_interface.s_addr = INADDR_LOOPBACK;
                }
                lck_mtx_unlock(rt_mtx);
        }
        
        if (ifp == NULL) {
                ifp = ip_multicast_if(&mreq->imr_interface, NULL);
        }

        /*
         * See if we found an interface, and confirm that it
         * supports multicast.
         */
        if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
                error = EADDRNOTAVAIL;
                return error;
        }
        /*
         * See if the membership already exists or if all the
         * membership slots are full.
         */
        for (i = 0; i < imo->imo_num_memberships; ++i) {
                if (imo->imo_membership[i]->inm_ifp == ifp &&
                        imo->imo_membership[i]->inm_addr.s_addr
                                        == mreq->imr_multiaddr.s_addr)
                        break;
        }
        if (i < imo->imo_num_memberships) {
                error = EADDRINUSE;
                return error;
        }
        if (i == IP_MAX_MEMBERSHIPS) {
                error = ETOOMANYREFS;
                return error;
        }
        /*
         * Everything looks good; add a new record to the multicast
         * address list for the given interface.
         */
        if ((imo->imo_membership[i] =
                in_addmulti(&mreq->imr_multiaddr, ifp)) == NULL) {
                error = ENOBUFS;
                return error;
        }
        ++imo->imo_num_memberships;
        
        return error;
}

/*
 * Drop membership of an IPv4 multicast.
 */
__private_extern__ int
ip_dropmembership(
        struct ip_moptions *imo,
        struct ip_mreq *mreq)
{
        int error = 0;
        struct ifnet* ifp = NULL;
        int i;
        
        if (!IN_MULTICAST(ntohl(mreq->imr_multiaddr.s_addr))) {
                error = EINVAL;
                return error;
        }

        /*
         * If an interface address was specified, get a pointer
         * to its ifnet structure.
         */
        if (mreq->imr_interface.s_addr == INADDR_ANY)
                ifp = NULL;
        else {
                ifp = ip_multicast_if(&mreq->imr_interface, NULL);
                if (ifp == NULL) {
                        error = EADDRNOTAVAIL;
                        return error;
                }
        }
        /*
         * Find the membership in the membership array.
         */
        for (i = 0; i < imo->imo_num_memberships; ++i) {
                if ((ifp == NULL ||
                         imo->imo_membership[i]->inm_ifp == ifp) &&
                         imo->imo_membership[i]->inm_addr.s_addr ==
                         mreq->imr_multiaddr.s_addr)
                        break;
        }
        if (i == imo->imo_num_memberships) {
                error = EADDRNOTAVAIL;
                return error;
        }
        /*
         * Give up the multicast address record to which the
         * membership points.
         */
        in_delmulti(&imo->imo_membership[i]);
        /*
         * Remove the gap in the membership array.
         */
        for (++i; i < imo->imo_num_memberships; ++i)
                imo->imo_membership[i-1] = imo->imo_membership[i];
        --imo->imo_num_memberships;
        
        return error;
}

/*
 * Return the IP multicast options in response to user getsockopt().
 */
static int
ip_getmoptions(sopt, imo)
        struct sockopt *sopt;
        register struct ip_moptions *imo;
{
        struct in_addr addr;
        struct in_ifaddr *ia;
        int error, optval;
        u_char coptval;

        error = 0;
        switch (sopt->sopt_name) {
#if MROUTING
        case IP_MULTICAST_VIF: 
                if (imo != NULL)
                        optval = imo->imo_multicast_vif;
                else
                        optval = -1;
                error = sooptcopyout(sopt, &optval, sizeof optval);
                break;
#endif /* MROUTING */

        case IP_MULTICAST_IF:
                if (imo == NULL || imo->imo_multicast_ifp == NULL)
                        addr.s_addr = INADDR_ANY;
                else if (imo->imo_multicast_addr.s_addr) {
                        /* return the value user has set */
                        addr = imo->imo_multicast_addr;
                } else {
                        IFP_TO_IA(imo->imo_multicast_ifp, ia);
                        addr.s_addr = (ia == NULL) ? INADDR_ANY
                                : IA_SIN(ia)->sin_addr.s_addr;
                }
                error = sooptcopyout(sopt, &addr, sizeof addr);
                break;

        case IP_MULTICAST_TTL:
                if (imo == 0)
                        optval = coptval = IP_DEFAULT_MULTICAST_TTL;
                else
                        optval = coptval = imo->imo_multicast_ttl;
                if (sopt->sopt_valsize == 1)
                        error = sooptcopyout(sopt, &coptval, 1);
                else
                        error = sooptcopyout(sopt, &optval, sizeof optval);
                break;

        case IP_MULTICAST_LOOP:
                if (imo == 0)
                        optval = coptval = IP_DEFAULT_MULTICAST_LOOP;
                else
                        optval = coptval = imo->imo_multicast_loop;
                if (sopt->sopt_valsize == 1)
                        error = sooptcopyout(sopt, &coptval, 1);
                else
                        error = sooptcopyout(sopt, &optval, sizeof optval);
                break;

        default:
                error = ENOPROTOOPT;
                break;
        }
        return (error);
}

/*
 * Discard the IP multicast options.
 */
void
ip_freemoptions(imo)
        register struct ip_moptions *imo;
{
        register int i;

        if (imo != NULL) {
                for (i = 0; i < imo->imo_num_memberships; ++i)
                        in_delmulti(&imo->imo_membership[i]);
                FREE(imo, M_IPMOPTS);
        }
}

/*
 * Routine called from ip_output() to loop back a copy of an IP multicast
 * packet to the input queue of a specified interface.  Note that this
 * calls the output routine of the loopback "driver", but with an interface
 * pointer that might NOT be a loopback interface -- evil, but easier than
 * replicating that code here.
 */
static void
ip_mloopback(ifp, m, dst, hlen)
        struct ifnet *ifp;
        register struct mbuf *m;
        register struct sockaddr_in *dst;
        int hlen;
{
        register struct ip *ip;
        struct mbuf *copym;
        int sw_csum = (apple_hwcksum_tx == 0);

        copym = m_copy(m, 0, M_COPYALL);
        if (copym != NULL && (copym->m_flags & M_EXT || copym->m_len < hlen))
                copym = m_pullup(copym, hlen);

        if (copym == NULL)
                return;

        /*
         * We don't bother to fragment if the IP length is greater
         * than the interface's MTU.  Can this possibly matter?
         */
        ip = mtod(copym, struct ip *);
        HTONS(ip->ip_len);
        HTONS(ip->ip_off);
        ip->ip_sum = 0;
        ip->ip_sum = in_cksum(copym, hlen);
        /*
         * NB:
         * It's not clear whether there are any lingering
         * reentrancy problems in other areas which might
         * be exposed by using ip_input directly (in
         * particular, everything which modifies the packet
         * in-place).  Yet another option is using the
         * protosw directly to deliver the looped back
         * packet.  For the moment, we'll err on the side
         * of safety by using if_simloop().
         */
#if 1 /* XXX */
        if (dst->sin_family != AF_INET) {
                printf("ip_mloopback: bad address family %d\n",
                                        dst->sin_family);
                dst->sin_family = AF_INET;
        }
#endif

        /*
         * Mark checksum as valid or calculate checksum for loopback.
         *
         * This is done this way because we have to embed the ifp of
         * the interface we will send the original copy of the packet
         * out on in the mbuf. ip_input will check if_hwassist of the
         * embedded ifp and ignore all csum_flags if if_hwassist is 0.
         * The UDP checksum has not been calculated yet.
         */
        if (sw_csum || (copym->m_pkthdr.csum_flags & CSUM_DELAY_DATA)) {
                if (!sw_csum && IF_HWASSIST_CSUM_FLAGS(ifp->if_hwassist)) {
                        copym->m_pkthdr.csum_flags |=
                            CSUM_DATA_VALID | CSUM_PSEUDO_HDR |
                            CSUM_IP_CHECKED | CSUM_IP_VALID;
                        copym->m_pkthdr.csum_data = 0xffff;
                } else {
                        NTOHS(ip->ip_len);
                        in_delayed_cksum(copym);
                        HTONS(ip->ip_len);
                }
        }

        /*
         * TedW: 
         * We need to send all loopback traffic down to dlil in case 
         * a filter has tapped-in.
         */

        /*
         * Stuff the 'real' ifp into the pkthdr, to be used in matching
         *  in ip_input(); we need the loopback ifp/dl_tag passed as args
         *  to make the loopback driver compliant with the data link
         *  requirements.
         */
        if (lo_ifp) {
                copym->m_pkthdr.rcvif = ifp;
                dlil_output(lo_ifp, PF_INET, copym, 0,
                    (struct sockaddr *) dst, 0);
        } else {
                printf("Warning: ip_output call to dlil_find_dltag failed!\n");
                m_freem(copym);
        }
}