[apple/xnu.git] / bsd / netinet6 / ip6_input.c

/*
 * Copyright (c) 2003-2008 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@
 */
/*      $FreeBSD: src/sys/netinet6/ip6_input.c,v 1.11.2.10 2001/07/24 19:10:18 brooks Exp $     */
/*      $KAME: ip6_input.c,v 1.194 2001/05/27 13:28:35 itojun Exp $     */

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * 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. Neither the name of the project 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 PROJECT 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 PROJECT 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.
 */

/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)ip_input.c  8.2 (Berkeley) 1/4/94
 */


#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/proc.h>
#include <sys/kauth.h>

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

#include <netinet/in.h>
#include <netinet/in_systm.h>
#if INET
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#endif /*INET*/
#include <netinet/ip6.h>
#include <netinet6/in6_var.h>
#include <netinet6/ip6_var.h>
#include <netinet/in_pcb.h>
#include <netinet/icmp6.h>
#include <netinet6/in6_ifattach.h>
#include <netinet6/nd6.h>
#include <netinet6/in6_prefix.h>

#if IPSEC
#include <netinet6/ipsec.h>
#if INET6
#include <netinet6/ipsec6.h>
#endif
extern int ipsec_bypass;
#endif

#include <netinet6/ip6_fw.h>

#include <netinet/kpi_ipfilter_var.h>

#include <netinet6/ip6protosw.h>

/* we need it for NLOOP. */
#include "loop.h"
#include "faith.h"

#include <net/net_osdep.h>

#if PF
#include <net/pfvar.h>
#endif /* PF */

extern struct domain inet6domain;
extern struct ip6protosw inet6sw[];

struct ip6protosw *  ip6_protox[IPPROTO_MAX];
static int ip6qmaxlen = IFQ_MAXLEN;
struct in6_ifaddr *in6_ifaddrs;

int ip6_forward_srcrt;                  /* XXX */
int ip6_sourcecheck;                    /* XXX */
int ip6_sourcecheck_interval;           /* XXX */
const int int6intrq_present = 1;

int ip6_ours_check_algorithm;
int in6_init2done = 0;


#if IPFW2
/* firewall hooks */
ip6_fw_chk_t *ip6_fw_chk_ptr;
ip6_fw_ctl_t *ip6_fw_ctl_ptr;
int ip6_fw_enable = 1;
#endif

struct ip6stat ip6stat;

#ifdef __APPLE__
struct ifqueue ip6intrq;
lck_mtx_t               *ip6_mutex;
lck_mtx_t               *dad6_mutex;
lck_mtx_t               *nd6_mutex;
lck_mtx_t               *prefix6_mutex;
lck_mtx_t               *scope6_mutex;
lck_attr_t              *ip6_mutex_attr;
lck_grp_t               *ip6_mutex_grp;
lck_grp_attr_t          *ip6_mutex_grp_attr;
extern lck_mtx_t        *inet6_domain_mutex;
#endif
extern int loopattach_done;

static void ip6_init2(void *);
static struct ip6aux *ip6_setdstifaddr(struct mbuf *, struct in6_ifaddr *);

static int ip6_hopopts_input(u_int32_t *, u_int32_t *, struct mbuf **, int *);
#if PULLDOWN_TEST
static struct mbuf *ip6_pullexthdr(struct mbuf *, size_t, int);
#endif

#ifdef __APPLE__
void gifattach(void);
void faithattach(void);
void stfattach(void);
#endif

extern lck_mtx_t *domain_proto_mtx;


static void
ip6_proto_input(
        __unused protocol_family_t      protocol,
        mbuf_t                          packet)
{
        ip6_input(packet);
}

/*
 * IP6 initialization: fill in IP6 protocol switch table.
 * All protocols not implemented in kernel go to raw IP6 protocol handler.
 */
void
ip6_init()
{
        struct ip6protosw *pr;
        int i;
        struct timeval tv;

#if DIAGNOSTIC
        if (sizeof(struct protosw) != sizeof(struct ip6protosw))
                panic("sizeof(protosw) != sizeof(ip6protosw)");
#endif
        pr = (struct ip6protosw *)pffindproto_locked(PF_INET6, IPPROTO_RAW, SOCK_RAW);
        if (pr == 0)
                panic("ip6_init");
        for (i = 0; i < IPPROTO_MAX; i++)
                ip6_protox[i] = pr;
        for (pr = (struct ip6protosw*)inet6domain.dom_protosw; pr; pr = pr->pr_next) {
                if(!(pr->pr_domain)) continue;    /* If uninitialized, skip */
                if (pr->pr_domain->dom_family == PF_INET6 &&
                    pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW) {
                        ip6_protox[pr->pr_protocol] = pr;
                }
        }

        ip6_mutex_grp_attr  = lck_grp_attr_alloc_init();

        ip6_mutex_grp = lck_grp_alloc_init("ip6", ip6_mutex_grp_attr);
        ip6_mutex_attr = lck_attr_alloc_init();

        if ((ip6_mutex = lck_mtx_alloc_init(ip6_mutex_grp, ip6_mutex_attr)) == NULL) {
                panic("ip6_init: can't alloc ip6_mutex\n");
        }
        if ((dad6_mutex = lck_mtx_alloc_init(ip6_mutex_grp, ip6_mutex_attr)) == NULL) {
                panic("ip6_init: can't alloc dad6_mutex\n");
        }
        if ((nd6_mutex = lck_mtx_alloc_init(ip6_mutex_grp, ip6_mutex_attr)) == NULL) {
                panic("ip6_init: can't alloc nd6_mutex\n");
        }

        if ((prefix6_mutex = lck_mtx_alloc_init(ip6_mutex_grp, ip6_mutex_attr)) == NULL) {
                panic("ip6_init: can't alloc prefix6_mutex\n");
        }

        if ((scope6_mutex = lck_mtx_alloc_init(ip6_mutex_grp, ip6_mutex_attr)) == NULL) {
                panic("ip6_init: can't alloc scope6_mutex\n");
        }


        inet6domain.dom_flags = DOM_REENTRANT;  

        ip6intrq.ifq_maxlen = ip6qmaxlen;
        in6_ifaddr_init();
        nd6_init();
        frag6_init();
        icmp6_init();
        /*
         * in many cases, random() here does NOT return random number
         * as initialization during bootstrap time occur in fixed order.
         */
        microtime(&tv);
        ip6_flow_seq = random() ^ tv.tv_usec;
        microtime(&tv);
        ip6_desync_factor = (random() ^ tv.tv_usec) % MAX_TEMP_DESYNC_FACTOR;
        timeout(ip6_init2, (caddr_t)0, 1 * hz);

        lck_mtx_unlock(domain_proto_mtx);       
        proto_register_input(PF_INET6, ip6_proto_input, NULL, 0);
        lck_mtx_lock(domain_proto_mtx); 
}

static void
ip6_init2(
        __unused void *dummy)
{
        /*
         * to route local address of p2p link to loopback,
         * assign loopback address first.
         */
        if (loopattach_done == 0) {
                timeout(ip6_init2, (caddr_t)0, 1 * hz);
                return;
        }
        (void) in6_ifattach(lo_ifp, NULL, NULL);

#ifdef __APPLE__
        /* nd6_timer_init */
        timeout(nd6_timer, (caddr_t)0, hz);

        /* router renumbering prefix list maintenance */
        timeout(in6_rr_timer, (caddr_t)0, hz);

        /* timer for regeneranation of temporary addresses randomize ID */
        timeout(in6_tmpaddrtimer, (caddr_t)0,
                (ip6_temp_preferred_lifetime - ip6_desync_factor -
                       ip6_temp_regen_advance) * hz);

#if NGIF
        gifattach();
#endif
#if NFAITH
        faithattach();
#endif
#if NSTF
        stfattach();
#endif
#else
        /* nd6_timer_init */

        callout_init(&nd6_timer_ch);
        callout_reset(&nd6_timer_ch, hz, nd6_timer, NULL);

        /* router renumbering prefix list maintenance */
        callout_init(&in6_rr_timer_ch);
        callout_reset(&in6_rr_timer_ch, hz, in6_rr_timer, NULL);

        /* timer for regeneranation of temporary addresses randomize ID */
        callout_reset(&in6_tmpaddrtimer_ch,
                      (ip6_temp_preferred_lifetime - ip6_desync_factor -
                       ip6_temp_regen_advance) * hz,
                      in6_tmpaddrtimer, NULL);
#endif

        in6_init2done = 1;
}

#if __FreeBSD__
/* cheat */
/* This must be after route_init(), which is now SI_ORDER_THIRD */
SYSINIT(netinet6init2, SI_SUB_PROTO_DOMAIN, SI_ORDER_MIDDLE, ip6_init2, NULL);
#endif

/*
 * ip6_forward_rt contains the route entry that was recently used during
 * the forwarding of an IPv6 packet and thus acts as a route cache.  Access
 * to this variable is protected by the global lock ip6_mutex.
 */
static struct route_in6 ip6_forward_rt;

void
ip6_input(m)
        struct mbuf *m;
{
        struct ip6_hdr *ip6;
        int off = sizeof(struct ip6_hdr), nest;
        u_int32_t plen;
        u_int32_t rtalert = ~0;
        int nxt = 0, ours = 0;
        struct ifnet *deliverifp = NULL;
        ipfilter_t inject_ipfref = 0;
        int seen;

        /*
         * No need to proccess packet twice if we've 
         * already seen it
         */
        inject_ipfref = ipf_get_inject_filter(m);
        if (inject_ipfref != 0) {
                ip6 = mtod(m, struct ip6_hdr *);
                nxt = ip6->ip6_nxt;
                seen = 0;
                goto injectit;
        } else
                seen = 1;
        
#if IPSEC
        /*
         * should the inner packet be considered authentic?
         * see comment in ah4_input().
         */
        if (m) {
                m->m_flags &= ~M_AUTHIPHDR;
                m->m_flags &= ~M_AUTHIPDGM;
        }
#endif

        /*
         * make sure we don't have onion peering information into m_aux.
         */
        ip6_delaux(m);

        lck_mtx_lock(ip6_mutex);
        /*
         * mbuf statistics
         */
        if (m->m_flags & M_EXT) {
                if (m->m_next)
                        ip6stat.ip6s_mext2m++;
                else
                        ip6stat.ip6s_mext1++;
        } else {
#define M2MMAX  (sizeof(ip6stat.ip6s_m2m)/sizeof(ip6stat.ip6s_m2m[0]))
                if (m->m_next) {
                        if (m->m_flags & M_LOOP) {
                                ip6stat.ip6s_m2m[ifnet_index(lo_ifp)]++;        /* XXX */
                        } else if (m->m_pkthdr.rcvif->if_index < M2MMAX)
                                ip6stat.ip6s_m2m[m->m_pkthdr.rcvif->if_index]++;
                        else
                                ip6stat.ip6s_m2m[0]++;
                } else
                        ip6stat.ip6s_m1++;
#undef M2MMAX
        }

        in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_receive);
        ip6stat.ip6s_total++;

#ifndef PULLDOWN_TEST
        /*
         * L2 bridge code and some other code can return mbuf chain
         * that does not conform to KAME requirement.  too bad.
         * XXX: fails to join if interface MTU > MCLBYTES.  jumbogram?
         */
        if (m && m->m_next != NULL && m->m_pkthdr.len < MCLBYTES) {
                struct mbuf *n;

                MGETHDR(n, M_DONTWAIT, MT_HEADER);      /* MAC-OK */
                if (n)
                        M_COPY_PKTHDR(n, m);
                if (n && m->m_pkthdr.len > MHLEN) {
                        MCLGET(n, M_DONTWAIT);
                        if ((n->m_flags & M_EXT) == 0) {
                                m_freem(n);
                                n = NULL;
                        }
                }
                if (n == NULL) {
                        m_freem(m);
                        lck_mtx_unlock(ip6_mutex);
                        return; /*ENOBUFS*/
                }

                m_copydata(m, 0, m->m_pkthdr.len, mtod(n, caddr_t));
                n->m_len = m->m_pkthdr.len;
                m_freem(m);
                m = n;
        }
        IP6_EXTHDR_CHECK(m, 0, sizeof(struct ip6_hdr),
                {lck_mtx_unlock(ip6_mutex); return;}); 
#endif

        if (m->m_len < sizeof(struct ip6_hdr)) {
                struct ifnet *inifp;
                inifp = m->m_pkthdr.rcvif;
                if ((m = m_pullup(m, sizeof(struct ip6_hdr))) == 0) {
                        ip6stat.ip6s_toosmall++;
                        in6_ifstat_inc(inifp, ifs6_in_hdrerr);
                        lck_mtx_unlock(ip6_mutex);
                        return;
                }
        }

        ip6 = mtod(m, struct ip6_hdr *);

        if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
                ip6stat.ip6s_badvers++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_hdrerr);
                goto bad;
        }

        ip6stat.ip6s_nxthist[ip6->ip6_nxt]++;

#if IPFW2
        /*
         * Check with the firewall...
         */
        if (ip6_fw_enable && ip6_fw_chk_ptr) {
                u_short port = 0;
                /* If ipfw says divert, we have to just drop packet */
                /* use port as a dummy argument */
                if ((*ip6_fw_chk_ptr)(&ip6, NULL, &port, &m)) {
                        m_freem(m);
                        m = NULL;
                }
                if (!m) {
                        lck_mtx_unlock(ip6_mutex);
                        return;
                }
        }
#endif

        /*
         * Check against address spoofing/corruption.
         */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src) ||
            IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
                /*
                 * XXX: "badscope" is not very suitable for a multicast source.
                 */
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
                goto bad;
        }
        if ((IN6_IS_ADDR_LOOPBACK(&ip6->ip6_src) ||
             IN6_IS_ADDR_LOOPBACK(&ip6->ip6_dst)) &&
            (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) == 0) {
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
                goto bad;
        }

        /*
         * The following check is not documented in specs.  A malicious
         * party may be able to use IPv4 mapped addr to confuse tcp/udp stack
         * and bypass security checks (act as if it was from 127.0.0.1 by using
         * IPv6 src ::ffff:127.0.0.1).  Be cautious.
         *
         * This check chokes if we are in an SIIT cloud.  As none of BSDs
         * support IPv4-less kernel compilation, we cannot support SIIT
         * environment at all.  So, it makes more sense for us to reject any
         * malicious packets for non-SIIT environment, than try to do a
         * partical support for SIIT environment.
         */
        if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
            IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
                goto bad;
        }
#if 0
        /*
         * Reject packets with IPv4 compatible addresses (auto tunnel).
         *
         * The code forbids auto tunnel relay case in RFC1933 (the check is
         * stronger than RFC1933).  We may want to re-enable it if mech-xx
         * is revised to forbid relaying case.
         */
        if (IN6_IS_ADDR_V4COMPAT(&ip6->ip6_src) ||
            IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
                goto bad;
        }
#endif

#if PF
        /* Invoke inbound packet filter */
        lck_mtx_unlock(ip6_mutex);
        if (pf_af_hook(m->m_pkthdr.rcvif, NULL, &m, AF_INET6, TRUE) != 0) {
                if (m != NULL) {
                        panic("%s: unexpected packet %p\n", __func__, m);
                        /* NOTREACHED */
                }
                /* Already freed by callee */
                return;
        }
        ip6 = mtod(m, struct ip6_hdr *);
        lck_mtx_lock(ip6_mutex);
#endif /* PF */

        /* drop packets if interface ID portion is already filled */
        if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) == 0) {
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src) &&
                    ip6->ip6_src.s6_addr16[1]) {
                        ip6stat.ip6s_badscope++;
                        goto bad;
                }
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst) &&
                    ip6->ip6_dst.s6_addr16[1]) {
                        ip6stat.ip6s_badscope++;
                        goto bad;
                }
        }

        if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src))
                ip6->ip6_src.s6_addr16[1]
                        = htons(m->m_pkthdr.rcvif->if_index);
        if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst))
                ip6->ip6_dst.s6_addr16[1]
                        = htons(m->m_pkthdr.rcvif->if_index);

#if 0 /* this case seems to be unnecessary. (jinmei, 20010401) */
        /*
         * We use rt->rt_ifp to determine if the address is ours or not.
         * If rt_ifp is lo0, the address is ours.
         * The problem here is, rt->rt_ifp for fe80::%lo0/64 is set to lo0,
         * so any address under fe80::%lo0/64 will be mistakenly considered
         * local.  The special case is supplied to handle the case properly
         * by actually looking at interface addresses
         * (using in6ifa_ifpwithaddr).
         */
        if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) != 0 &&
            IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_dst)) {
            struct in6_ifaddr *ia6;
                if (!(ia6 = in6ifa_ifpwithaddr(m->m_pkthdr.rcvif, &ip6->ip6_dst))) {
                        lck_mtx_unlock(ip6_mutex);
                        icmp6_error(m, ICMP6_DST_UNREACH,
                            ICMP6_DST_UNREACH_ADDR, 0);
                        /* m is already freed */
                        return;
                }
                ifafree(&ia6->ia_ifa);

                ours = 1;
                deliverifp = m->m_pkthdr.rcvif;
                goto hbhcheck;
        }
#endif

        /*
         * Multicast check
         */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                struct  in6_multi *in6m = 0;
                struct ifnet *ifp = m->m_pkthdr.rcvif;

                in6_ifstat_inc(ifp, ifs6_in_mcast);
                /*
                 * See if we belong to the destination multicast group on the
                 * arrival interface.
                 */
                ifnet_lock_shared(ifp);
                IN6_LOOKUP_MULTI(ip6->ip6_dst, ifp, in6m);
                ifnet_lock_done(ifp);
                if (in6m)
                        ours = 1;
#if MROUTING
                else if (!ip6_mrouter) {
#else
                else {
#endif
                        ip6stat.ip6s_notmember++;
                        ip6stat.ip6s_cantforward++;
                        in6_ifstat_inc(ifp, ifs6_in_discard);
                        goto bad;
                }
                deliverifp = ifp;
                goto hbhcheck;
        }

        if (ip6_forward_rt.ro_rt != NULL)
                RT_LOCK(ip6_forward_rt.ro_rt);
        /*
         *  Unicast check
         */
        if (ip6_forward_rt.ro_rt != NULL &&
            (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) &&
            IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
            &((struct sockaddr_in6 *)(&ip6_forward_rt.ro_dst))->sin6_addr) &&
            ip6_forward_rt.ro_rt->generation_id == route_generation) {
                ip6stat.ip6s_forward_cachehit++;
        } else {
                struct sockaddr_in6 *dst6;

                if (ip6_forward_rt.ro_rt != NULL) {
                        /* route is down/stale or destination is different */
                        ip6stat.ip6s_forward_cachemiss++;
                        RT_UNLOCK(ip6_forward_rt.ro_rt);
                        rtfree(ip6_forward_rt.ro_rt);
                        ip6_forward_rt.ro_rt = NULL;
                }

                bzero(&ip6_forward_rt.ro_dst, sizeof(struct sockaddr_in6));
                dst6 = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
                dst6->sin6_len = sizeof(struct sockaddr_in6);
                dst6->sin6_family = AF_INET6;
                dst6->sin6_addr = ip6->ip6_dst;
#if SCOPEDROUTING
                ip6_forward_rt.ro_dst.sin6_scope_id =
                        in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_dst);
#endif

                rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
                if (ip6_forward_rt.ro_rt != NULL)
                        RT_LOCK(ip6_forward_rt.ro_rt);
        }

#define rt6_key(r) ((struct sockaddr_in6 *)((r)->rt_nodes->rn_key))

        /*
         * Accept the packet if the forwarding interface to the destination
         * according to the routing table is the loopback interface,
         * unless the associated route has a gateway.
         * Note that this approach causes to accept a packet if there is a
         * route to the loopback interface for the destination of the packet.
         * But we think it's even useful in some situations, e.g. when using
         * a special daemon which wants to intercept the packet.
         *
         * XXX: some OSes automatically make a cloned route for the destination
         * of an outgoing packet.  If the outgoing interface of the packet
         * is a loopback one, the kernel would consider the packet to be
         * accepted, even if we have no such address assinged on the interface.
         * We check the cloned flag of the route entry to reject such cases,
         * assuming that route entries for our own addresses are not made by
         * cloning (it should be true because in6_addloop explicitly installs
         * the host route).  However, we might have to do an explicit check
         * while it would be less efficient.  Or, should we rather install a
         * reject route for such a case?
         */
        if (ip6_forward_rt.ro_rt != NULL &&
            (ip6_forward_rt.ro_rt->rt_flags &
             (RTF_HOST|RTF_GATEWAY)) == RTF_HOST &&
#if RTF_WASCLONED
            !(ip6_forward_rt.ro_rt->rt_flags & RTF_WASCLONED) &&
#endif
#if 0
            /*
             * The check below is redundant since the comparison of
             * the destination and the key of the rtentry has
             * already done through looking up the routing table.
             */
            IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
                                &rt6_key(ip6_forward_rt.ro_rt)->sin6_addr)
#endif
            ip6_forward_rt.ro_rt->rt_ifp->if_type == IFT_LOOP) {
                struct in6_ifaddr *ia6 =
                        (struct in6_ifaddr *)ip6_forward_rt.ro_rt->rt_ifa;

                /*
                 * record address information into m_aux.
                 */
                (void)ip6_setdstifaddr(m, ia6);

                /*
                 * packets to a tentative, duplicated, or somehow invalid
                 * address must not be accepted.
                 */
                if (!(ia6->ia6_flags & IN6_IFF_NOTREADY)) {
                        /* this address is ready */
                        ours = 1;
                        deliverifp = ia6->ia_ifp;       /* correct? */
                        /* Count the packet in the ip address stats */
#ifndef __APPLE__

                        ia6->ia_ifa.if_ipackets++;
                        ia6->ia_ifa.if_ibytes += m->m_pkthdr.len;
#endif
                        RT_UNLOCK(ip6_forward_rt.ro_rt);
                        goto hbhcheck;
                } else {
                        RT_UNLOCK(ip6_forward_rt.ro_rt);
                        /* address is not ready, so discard the packet. */
                        nd6log((LOG_INFO,
                            "ip6_input: packet to an unready address %s->%s\n",
                            ip6_sprintf(&ip6->ip6_src),
                            ip6_sprintf(&ip6->ip6_dst)));
                        goto bad;
                }
        }

        /*
         * FAITH(Firewall Aided Internet Translator)
         */
#if defined(NFAITH) && 0 < NFAITH
        if (ip6_keepfaith) {
                if (ip6_forward_rt.ro_rt && ip6_forward_rt.ro_rt->rt_ifp
                 && ip6_forward_rt.ro_rt->rt_ifp->if_type == IFT_FAITH) {
                        /* XXX do we need more sanity checks? */
                        ours = 1;
                        deliverifp = ip6_forward_rt.ro_rt->rt_ifp; /* faith */
                        RT_UNLOCK(ip6_forward_rt.ro_rt);
                        goto hbhcheck;
                }
        }
#endif
        if (ip6_forward_rt.ro_rt != NULL)
                RT_UNLOCK(ip6_forward_rt.ro_rt);

        /*
         * Now there is no reason to process the packet if it's not our own
         * and we're not a router.
         */
        if (!ip6_forwarding) {
                ip6stat.ip6s_cantforward++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
                goto bad;
        }

  hbhcheck:
        /*
         * record address information into m_aux, if we don't have one yet.
         * note that we are unable to record it, if the address is not listed
         * as our interface address (e.g. multicast addresses, addresses
         * within FAITH prefixes and such).
         */
        if (deliverifp && !ip6_getdstifaddr(m)) {
                struct in6_ifaddr *ia6;

                ia6 = in6_ifawithifp(deliverifp, &ip6->ip6_dst);
                if (ia6) {
                        if (!ip6_setdstifaddr(m, ia6)) {
                                /*
                                 * XXX maybe we should drop the packet here,
                                 * as we could not provide enough information
                                 * to the upper layers.
                                 */
                        }
                        ifafree(&ia6->ia_ifa);
                }
        }

        /*
         * Process Hop-by-Hop options header if it's contained.
         * m may be modified in ip6_hopopts_input().
         * If a JumboPayload option is included, plen will also be modified.
         */
        plen = (u_int32_t)ntohs(ip6->ip6_plen);
        if (ip6->ip6_nxt == IPPROTO_HOPOPTS) {
                struct ip6_hbh *hbh;

                if (ip6_hopopts_input(&plen, &rtalert, &m, &off)) {
#if 0   /*touches NULL pointer*/
                        in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
#endif
                        lck_mtx_unlock(ip6_mutex);
                        return; /* m have already been freed */
                }

                /* adjust pointer */
                ip6 = mtod(m, struct ip6_hdr *);

                /*
                 * if the payload length field is 0 and the next header field
                 * indicates Hop-by-Hop Options header, then a Jumbo Payload
                 * option MUST be included.
                 */
                if (ip6->ip6_plen == 0 && plen == 0) {
                        /*
                         * Note that if a valid jumbo payload option is
                         * contained, ip6_hoptops_input() must set a valid
                         * (non-zero) payload length to the variable plen. 
                         */
                        ip6stat.ip6s_badoptions++;
                        in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
                        in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_hdrerr);
                        lck_mtx_unlock(ip6_mutex);
                        icmp6_error(m, ICMP6_PARAM_PROB,
                                    ICMP6_PARAMPROB_HEADER,
                                    (caddr_t)&ip6->ip6_plen - (caddr_t)ip6);
                        return;
                }
#ifndef PULLDOWN_TEST
                /* ip6_hopopts_input() ensures that mbuf is contiguous */
                hbh = (struct ip6_hbh *)(ip6 + 1);
#else
                IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m, sizeof(struct ip6_hdr),
                        sizeof(struct ip6_hbh));
                if (hbh == NULL) {
                        ip6stat.ip6s_tooshort++;
                        lck_mtx_unlock(ip6_mutex);
                        return;
                }
#endif
                nxt = hbh->ip6h_nxt;

                /*
                 * accept the packet if a router alert option is included
                 * and we act as an IPv6 router.
                 */
                if (rtalert != ~0 && ip6_forwarding)
                        ours = 1;
        } else
                nxt = ip6->ip6_nxt;

        /*
         * Check that the amount of data in the buffers
         * is as at least much as the IPv6 header would have us expect.
         * Trim mbufs if longer than we expect.
         * Drop packet if shorter than we expect.
         */
        if (m->m_pkthdr.len - sizeof(struct ip6_hdr) < plen) {
                ip6stat.ip6s_tooshort++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
                goto bad;
        }
        if (m->m_pkthdr.len > sizeof(struct ip6_hdr) + plen) {
                if (m->m_len == m->m_pkthdr.len) {
                        m->m_len = sizeof(struct ip6_hdr) + plen;
                        m->m_pkthdr.len = sizeof(struct ip6_hdr) + plen;
                } else
                        m_adj(m, sizeof(struct ip6_hdr) + plen - m->m_pkthdr.len);
        }

        /*
         * Forward if desirable.
         */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                /*
                 * If we are acting as a multicast router, all
                 * incoming multicast packets are passed to the
                 * kernel-level multicast forwarding function.
                 * The packet is returned (relatively) intact; if
                 * ip6_mforward() returns a non-zero value, the packet
                 * must be discarded, else it may be accepted below.
                 */
#if MROUTING
                if (ip6_mrouter && ip6_mforward(ip6, m->m_pkthdr.rcvif, m)) {
                        ip6stat.ip6s_cantforward++;
                        m_freem(m);
                        lck_mtx_unlock(ip6_mutex);
                        return;
                }
#endif
                if (!ours) {
                        m_freem(m);
                        lck_mtx_unlock(ip6_mutex);
                        return;
                }
        } else if (!ours) {
                ip6_forward(m, &ip6_forward_rt, 0, 1);
                lck_mtx_unlock(ip6_mutex);
                return;
        }       

        ip6 = mtod(m, struct ip6_hdr *);

        /*
         * Malicious party may be able to use IPv4 mapped addr to confuse
         * tcp/udp stack and bypass security checks (act as if it was from
         * 127.0.0.1 by using IPv6 src ::ffff:127.0.0.1).  Be cautious.
         *
         * For SIIT end node behavior, you may want to disable the check.
         * However, you will  become vulnerable to attacks using IPv4 mapped
         * source.
         */
        if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
            IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
                goto bad;
        }

        /*
         * Tell launch routine the next header
         */
        ip6stat.ip6s_delivered++;
        in6_ifstat_inc(deliverifp, ifs6_in_deliver);

        lck_mtx_unlock(ip6_mutex);
injectit:
        nest = 0;

        while (nxt != IPPROTO_DONE) {
                struct ipfilter *filter;
                
                if (ip6_hdrnestlimit && (++nest > ip6_hdrnestlimit)) {
                        ip6stat.ip6s_toomanyhdr++;
                        goto badunlocked;
                }

                /*
                 * protection against faulty packet - there should be
                 * more sanity checks in header chain processing.
                 */
                if (m->m_pkthdr.len < off) {
                        ip6stat.ip6s_tooshort++;
                        in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
                        goto badunlocked;
                }

#if 0
                /*
                 * do we need to do it for every header?  yeah, other
                 * functions can play with it (like re-allocate and copy).
                 */
                mhist = ip6_addaux(m);
                if (mhist && M_TRAILINGSPACE(mhist) >= sizeof(nxt)) {
                        hist = mtod(mhist, caddr_t) + mhist->m_len;
                        bcopy(&nxt, hist, sizeof(nxt));
                        mhist->m_len += sizeof(nxt);
                } else {
                        ip6stat.ip6s_toomanyhdr++;
                        goto bad;
                }
#endif

#if IPSEC
                /*
                 * enforce IPsec policy checking if we are seeing last header.
                 * note that we do not visit this with protocols with pcb layer
                 * code - like udp/tcp/raw ip.
                 */
                if ((ipsec_bypass == 0) && (ip6_protox[nxt]->pr_flags & PR_LASTHDR) != 0) {
                        if (ipsec6_in_reject(m, NULL)) {
                                IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio);
                                goto badunlocked;
                    }
                }
#endif

                /*
                 * Call IP filter
                 */
                if (!TAILQ_EMPTY(&ipv6_filters)) {
                        ipf_ref();
                        TAILQ_FOREACH(filter, &ipv6_filters, ipf_link) {
                                if (seen == 0) {
                                        if ((struct ipfilter *)inject_ipfref == filter)
                                                seen = 1;
                                } else if (filter->ipf_filter.ipf_input) {
                                        errno_t result;
                                        
                                        result = filter->ipf_filter.ipf_input(
                                                filter->ipf_filter.cookie, (mbuf_t*)&m, off, nxt);
                                        if (result == EJUSTRETURN) {
                                                ipf_unref();
                                                return;
                                        }
                                        if (result != 0) {
                                                ipf_unref();
                                                m_freem(m);
                                                return;
                                        }
                                }
                        }
                        ipf_unref();
                }
                if (!(ip6_protox[nxt]->pr_flags & PR_PROTOLOCK)) {
                        lck_mtx_lock(inet6_domain_mutex);
                        nxt = (*ip6_protox[nxt]->pr_input)(&m, &off);
                        lck_mtx_unlock(inet6_domain_mutex);
                }
                else
                        nxt = (*ip6_protox[nxt]->pr_input)(&m, &off);
        }
        return;
 bad:
        lck_mtx_unlock(ip6_mutex);
 badunlocked:
        m_freem(m);
        return;
}

/*
 * set/grab in6_ifaddr correspond to IPv6 destination address.
 * XXX backward compatibility wrapper
 */
static struct ip6aux *
ip6_setdstifaddr(struct mbuf *m, struct in6_ifaddr *ia6)
{
        struct ip6aux *n;

        n = ip6_addaux(m);
        if (n)
                n->ip6a_dstia6 = ia6;
        return (struct ip6aux *)n;      /* NULL if failed to set */
}

struct in6_ifaddr *
ip6_getdstifaddr(m)
        struct mbuf *m;
{
        struct ip6aux *n;

        n = ip6_findaux(m);
        if (n)
                return n->ip6a_dstia6;
        else
                return NULL;
}

/*
 * Hop-by-Hop options header processing. If a valid jumbo payload option is
 * included, the real payload length will be stored in plenp.
 */
static int
ip6_hopopts_input(plenp, rtalertp, mp, offp)
        u_int32_t *plenp;
        u_int32_t *rtalertp;    /* XXX: should be stored more smart way */
        struct mbuf **mp;
        int *offp;
{
        struct mbuf *m = *mp;
        int off = *offp, hbhlen;
        struct ip6_hbh *hbh;
        u_int8_t *opt;

        /* validation of the length of the header */
#ifndef PULLDOWN_TEST
        IP6_EXTHDR_CHECK(m, off, sizeof(*hbh), return -1);
        hbh = (struct ip6_hbh *)(mtod(m, caddr_t) + off);
        hbhlen = (hbh->ip6h_len + 1) << 3;

        IP6_EXTHDR_CHECK(m, off, hbhlen, return -1);
        hbh = (struct ip6_hbh *)(mtod(m, caddr_t) + off);
#else
        IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m,
                sizeof(struct ip6_hdr), sizeof(struct ip6_hbh));
        if (hbh == NULL) {
                ip6stat.ip6s_tooshort++;
                return -1;
        }
        hbhlen = (hbh->ip6h_len + 1) << 3;
        IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m, sizeof(struct ip6_hdr),
                hbhlen);
        if (hbh == NULL) {
                ip6stat.ip6s_tooshort++;
                return -1;
        }
#endif
        off += hbhlen;
        hbhlen -= sizeof(struct ip6_hbh);
        opt = (u_int8_t *)hbh + sizeof(struct ip6_hbh);

        if (ip6_process_hopopts(m, (u_int8_t *)hbh + sizeof(struct ip6_hbh),
                                hbhlen, rtalertp, plenp) < 0)
                return(-1);

        *offp = off;
        *mp = m;
        return(0);
}

/*
 * Search header for all Hop-by-hop options and process each option.
 * This function is separate from ip6_hopopts_input() in order to
 * handle a case where the sending node itself process its hop-by-hop
 * options header. In such a case, the function is called from ip6_output().
 *
 * The function assumes that hbh header is located right after the IPv6 header
 * (RFC2460 p7), opthead is pointer into data content in m, and opthead to
 * opthead + hbhlen is located in continuous memory region.
 */
int
ip6_process_hopopts(m, opthead, hbhlen, rtalertp, plenp)
        struct mbuf *m;
        u_int8_t *opthead;
        int hbhlen;
        u_int32_t *rtalertp;
        u_int32_t *plenp;
{
        struct ip6_hdr *ip6;
        int optlen = 0;
        u_int8_t *opt = opthead;
        u_int16_t rtalert_val;
        u_int32_t jumboplen;
        const int erroff = sizeof(struct ip6_hdr) + sizeof(struct ip6_hbh);

        for (; hbhlen > 0; hbhlen -= optlen, opt += optlen) {
                switch (*opt) {
                case IP6OPT_PAD1:
                        optlen = 1;
                        break;
                case IP6OPT_PADN:
                        if (hbhlen < IP6OPT_MINLEN) {
                                ip6stat.ip6s_toosmall++;
                                goto bad;
                        }
                        optlen = *(opt + 1) + 2;
                        break;
                case IP6OPT_RTALERT:
                        /* XXX may need check for alignment */
                        if (hbhlen < IP6OPT_RTALERT_LEN) {
                                ip6stat.ip6s_toosmall++;
                                goto bad;
                        }
                        if (*(opt + 1) != IP6OPT_RTALERT_LEN - 2) {
                                /* XXX stat */
                                lck_mtx_unlock(ip6_mutex);
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 1 - opthead);
                                lck_mtx_lock(ip6_mutex);
                                return(-1);
                        }
                        optlen = IP6OPT_RTALERT_LEN;
                        bcopy((caddr_t)(opt + 2), (caddr_t)&rtalert_val, 2);
                        *rtalertp = ntohs(rtalert_val);
                        break;
                case IP6OPT_JUMBO:
                        /* XXX may need check for alignment */
                        if (hbhlen < IP6OPT_JUMBO_LEN) {
                                ip6stat.ip6s_toosmall++;
                                goto bad;
                        }
                        if (*(opt + 1) != IP6OPT_JUMBO_LEN - 2) {
                                /* XXX stat */
                                lck_mtx_unlock(ip6_mutex);
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 1 - opthead);
                                lck_mtx_lock(ip6_mutex);
                                return(-1);
                        }
                        optlen = IP6OPT_JUMBO_LEN;

                        /*
                         * IPv6 packets that have non 0 payload length
                         * must not contain a jumbo payload option.
                         */
                        ip6 = mtod(m, struct ip6_hdr *);
                        if (ip6->ip6_plen) {
                                ip6stat.ip6s_badoptions++;
                                lck_mtx_unlock(ip6_mutex);
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt - opthead);
                                lck_mtx_lock(ip6_mutex);
                                return(-1);
                        }

                        /*
                         * We may see jumbolen in unaligned location, so
                         * we'd need to perform bcopy().
                         */
                        bcopy(opt + 2, &jumboplen, sizeof(jumboplen));
                        jumboplen = (u_int32_t)htonl(jumboplen);

#if 1
                        /*
                         * if there are multiple jumbo payload options,
                         * *plenp will be non-zero and the packet will be
                         * rejected.
                         * the behavior may need some debate in ipngwg -
                         * multiple options does not make sense, however,
                         * there's no explicit mention in specification.
                         */
                        if (*plenp != 0) {
                                ip6stat.ip6s_badoptions++;
                                lck_mtx_unlock(ip6_mutex);
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 2 - opthead);
                                lck_mtx_lock(ip6_mutex);
                                return(-1);
                        }
#endif

                        /*
                         * jumbo payload length must be larger than 65535.
                         */
                        if (jumboplen <= IPV6_MAXPACKET) {
                                ip6stat.ip6s_badoptions++;
                                lck_mtx_unlock(ip6_mutex);
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 2 - opthead);
                                lck_mtx_lock(ip6_mutex);
                                return(-1);
                        }
                        *plenp = jumboplen;

                        break;
                default:                /* unknown option */
                        if (hbhlen < IP6OPT_MINLEN) {
                                ip6stat.ip6s_toosmall++;
                                goto bad;
                        }
                        optlen = ip6_unknown_opt(opt, m,
                            erroff + opt - opthead, 1);
                        if (optlen == -1) {
                                /* ip6_unknown opt unlocked ip6_mutex */
                                return(-1);
                        }
                        optlen += 2;
                        break;
                }
        }

        return(0);

  bad:  
        m_freem(m);
        return(-1);
}

/*
 * Unknown option processing.
 * The third argument `off' is the offset from the IPv6 header to the option,
 * which is necessary if the IPv6 header the and option header and IPv6 header
 * is not continuous in order to return an ICMPv6 error.
 */
int
ip6_unknown_opt(optp, m, off, locked)
        u_int8_t *optp;
        struct mbuf *m;
        int off;
        int locked;
{
        struct ip6_hdr *ip6;

        switch (IP6OPT_TYPE(*optp)) {
        case IP6OPT_TYPE_SKIP: /* ignore the option */
                return((int)*(optp + 1));
        case IP6OPT_TYPE_DISCARD:       /* silently discard */
                m_freem(m);
                return(-1);
        case IP6OPT_TYPE_FORCEICMP: /* send ICMP even if multicasted */
                ip6stat.ip6s_badoptions++;
                if (locked)
                        lck_mtx_unlock(ip6_mutex);
                icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_OPTION, off);
                if (locked)
                        lck_mtx_lock(ip6_mutex);
                return(-1);
        case IP6OPT_TYPE_ICMP: /* send ICMP if not multicasted */
                ip6stat.ip6s_badoptions++;
                ip6 = mtod(m, struct ip6_hdr *);
                if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
                    (m->m_flags & (M_BCAST|M_MCAST)))
                        m_freem(m);
                else {
                        if (locked)
                                lck_mtx_unlock(ip6_mutex);
                        icmp6_error(m, ICMP6_PARAM_PROB,
                                    ICMP6_PARAMPROB_OPTION, off);
                        if (locked)
                                lck_mtx_lock(ip6_mutex);
                }
                return(-1);
        }

        m_freem(m);             /* XXX: NOTREACHED */
        return(-1);
}

/*
 * Create the "control" list for this pcb.
 * The function will not modify mbuf chain at all.
 *
 * with KAME mbuf chain restriction:
 * The routine will be called from upper layer handlers like tcp6_input().
 * Thus the routine assumes that the caller (tcp6_input) have already
 * called IP6_EXTHDR_CHECK() and all the extension headers are located in the
 * very first mbuf on the mbuf chain.
 */
void
ip6_savecontrol(in6p, mp, ip6, m)
        struct inpcb *in6p;
        struct mbuf **mp;
        struct ip6_hdr *ip6;
        struct mbuf *m;
{
        int rthdr_exist = 0;

#if SO_TIMESTAMP
        if ((in6p->in6p_socket->so_options & SO_TIMESTAMP) != 0) {
                struct timeval tv;

                microtime(&tv);
                *mp = sbcreatecontrol((caddr_t) &tv, sizeof(tv),
                                      SCM_TIMESTAMP, SOL_SOCKET);
                if (*mp) {
                        mp = &(*mp)->m_next;
                }
        }
#endif

        /* some OSes call this logic with IPv4 packet, for SO_TIMESTAMP */
        if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION)
                return;

        /* RFC 2292 sec. 5 */
        if ((in6p->in6p_flags & IN6P_PKTINFO) != 0) {
                struct in6_pktinfo pi6;
                bcopy(&ip6->ip6_dst, &pi6.ipi6_addr, sizeof(struct in6_addr));
                if (IN6_IS_SCOPE_LINKLOCAL(&pi6.ipi6_addr))
                        pi6.ipi6_addr.s6_addr16[1] = 0;
                pi6.ipi6_ifindex = (m && m->m_pkthdr.rcvif)
                                        ? m->m_pkthdr.rcvif->if_index
                                        : 0;
                *mp = sbcreatecontrol((caddr_t) &pi6,
                        sizeof(struct in6_pktinfo), IPV6_PKTINFO,
                        IPPROTO_IPV6);
                if (*mp)
                        mp = &(*mp)->m_next;
        }

        if ((in6p->in6p_flags & IN6P_HOPLIMIT) != 0) {
                int hlim = ip6->ip6_hlim & 0xff;
                *mp = sbcreatecontrol((caddr_t) &hlim,
                        sizeof(int), IPV6_HOPLIMIT, IPPROTO_IPV6);
                if (*mp)
                        mp = &(*mp)->m_next;
        }

        if ((in6p->in6p_flags & IN6P_TCLASS) != 0) {
                u_int32_t flowinfo;
                int tclass;

                flowinfo = (u_int32_t)ntohl(ip6->ip6_flow & IPV6_FLOWINFO_MASK);
                flowinfo >>= 20;

                tclass = flowinfo & 0xff;
                *mp = sbcreatecontrol((caddr_t) &tclass, sizeof(tclass),
                    IPV6_TCLASS, IPPROTO_IPV6);
                if (*mp)
                        mp = &(*mp)->m_next;
        }

        /*
         * IPV6_HOPOPTS socket option.  Recall that we required super-user
         * privilege for the option (see ip6_ctloutput), but it might be too
         * strict, since there might be some hop-by-hop options which can be
         * returned to normal user.
         * See RFC 2292 section 6.
         */
        if ((in6p->in6p_flags & IN6P_HOPOPTS) != 0) {
                /*
                 * Check if a hop-by-hop options header is contatined in the
                 * received packet, and if so, store the options as ancillary
                 * data. Note that a hop-by-hop options header must be
                 * just after the IPv6 header, which fact is assured through
                 * the IPv6 input processing.
                 */
                ip6 = mtod(m, struct ip6_hdr *);
                if (ip6->ip6_nxt == IPPROTO_HOPOPTS) {
                        struct ip6_hbh *hbh;
                        int hbhlen = 0;
#if PULLDOWN_TEST
                        struct mbuf *ext;
#endif

#ifndef PULLDOWN_TEST
                        hbh = (struct ip6_hbh *)(ip6 + 1);
                        hbhlen = (hbh->ip6h_len + 1) << 3;
#else
                        ext = ip6_pullexthdr(m, sizeof(struct ip6_hdr),
                            ip6->ip6_nxt);
                        if (ext == NULL) {
                                ip6stat.ip6s_tooshort++;
                                return;
                        }
                        hbh = mtod(ext, struct ip6_hbh *);
                        hbhlen = (hbh->ip6h_len + 1) << 3;
                        if (hbhlen != ext->m_len) {
                                m_freem(ext);
                                ip6stat.ip6s_tooshort++;
                                return;
                        }
#endif

                        /*
                         * XXX: We copy whole the header even if a jumbo
                         * payload option is included, which option is to
                         * be removed before returning in the RFC 2292.
                         * Note: this constraint is removed in 2292bis.
                         */
                        *mp = sbcreatecontrol((caddr_t)hbh, hbhlen,
                                              IPV6_HOPOPTS, IPPROTO_IPV6);
                        if (*mp)
                                mp = &(*mp)->m_next;
#if PULLDOWN_TEST
                        m_freem(ext);
#endif
                }
        }

        /* IPV6_DSTOPTS and IPV6_RTHDR socket options */
        if ((in6p->in6p_flags & (IN6P_DSTOPTS | IN6P_RTHDRDSTOPTS)) != 0) {
                int proto, off, nxt;

                /*
                 * go through the header chain to see if a routing header is
                 * contained in the packet. We need this information to store
                 * destination options headers (if any) properly.
                 * XXX: performance issue. We should record this info when
                 * processing extension headers in incoming routine.
                 * (todo) use m_aux? 
                 */
                proto = IPPROTO_IPV6;
                off = 0;
                nxt = -1;
                while (1) {
                        int newoff;

                        newoff = ip6_nexthdr(m, off, proto, &nxt);
                        if (newoff < 0)
                                break;
                        if (newoff < off) /* invalid, check for safety */
                                break;
                        if ((proto = nxt) == IPPROTO_ROUTING) {
                                rthdr_exist = 1;
                                break;
                        }
                        off = newoff;
                }
        }

        if ((in6p->in6p_flags &
             (IN6P_RTHDR | IN6P_DSTOPTS | IN6P_RTHDRDSTOPTS)) != 0) {
                ip6 = mtod(m, struct ip6_hdr *);
                int nxt = ip6->ip6_nxt, off = sizeof(struct ip6_hdr);

                /*
                 * Search for destination options headers or routing
                 * header(s) through the header chain, and stores each
                 * header as ancillary data.
                 * Note that the order of the headers remains in
                 * the chain of ancillary data.
                 */
                while (1) {     /* is explicit loop prevention necessary? */
                        struct ip6_ext *ip6e = NULL;
                        int elen;
#if PULLDOWN_TEST
                        struct mbuf *ext = NULL;
#endif

                        /*
                         * if it is not an extension header, don't try to
                         * pull it from the chain.
                         */
                        switch (nxt) {
                        case IPPROTO_DSTOPTS:
                        case IPPROTO_ROUTING:
                        case IPPROTO_HOPOPTS:
                        case IPPROTO_AH: /* is it possible? */
                                break;
                        default:
                                goto loopend;
                        }

#ifndef PULLDOWN_TEST
                        if (off + sizeof(*ip6e) > m->m_len)
                                goto loopend;
                        ip6e = (struct ip6_ext *)(mtod(m, caddr_t) + off);
                        if (nxt == IPPROTO_AH)
                                elen = (ip6e->ip6e_len + 2) << 2;
                        else
                                elen = (ip6e->ip6e_len + 1) << 3;
                        if (off + elen > m->m_len)
                                goto loopend;
#else
                        ext = ip6_pullexthdr(m, off, nxt);
                        if (ext == NULL) {
                                ip6stat.ip6s_tooshort++;
                                return;
                        }
                        ip6e = mtod(ext, struct ip6_ext *);
                        if (nxt == IPPROTO_AH)
                                elen = (ip6e->ip6e_len + 2) << 2;
                        else
                                elen = (ip6e->ip6e_len + 1) << 3;
                        if (elen != ext->m_len) {
                                m_freem(ext);
                                ip6stat.ip6s_tooshort++;
                                return;
                        }
#endif

                        switch (nxt) {
                        case IPPROTO_DSTOPTS:
                                if ((in6p->in6p_flags & IN6P_DSTOPTS) == 0)
                                        break;

                                *mp = sbcreatecontrol((caddr_t)ip6e, elen,
                                                      IPV6_DSTOPTS,
                                                      IPPROTO_IPV6);
                                if (*mp)
                                        mp = &(*mp)->m_next;
                                break;
                        case IPPROTO_ROUTING:
                                if (!in6p->in6p_flags & IN6P_RTHDR)
                                        break;

                                *mp = sbcreatecontrol((caddr_t)ip6e, elen,
                                                      IPV6_RTHDR,
                                                      IPPROTO_IPV6);
                                if (*mp)
                                        mp = &(*mp)->m_next;
                                break;
                        case IPPROTO_HOPOPTS:
                        case IPPROTO_AH: /* is it possible? */
                                break;

                        default:
                                /*
                                 * other cases have been filtered in the above.
                                 * none will visit this case.  here we supply
                                 * the code just in case (nxt overwritten or
                                 * other cases).
                                 */
#if PULLDOWN_TEST
                                m_freem(ext);
#endif
                                goto loopend;

                        }

                        /* proceed with the next header. */
                        off += elen;
                        nxt = ip6e->ip6e_nxt;
                        ip6e = NULL;
#if PULLDOWN_TEST
                        m_freem(ext);
                        ext = NULL;
#endif
                }
          loopend:
                ;
        }

}

#if PULLDOWN_TEST
/*
 * pull single extension header from mbuf chain.  returns single mbuf that
 * contains the result, or NULL on error.
 */
static struct mbuf *
ip6_pullexthdr(m, off, nxt)
        struct mbuf *m;
        size_t off;
        int nxt;
{
        struct ip6_ext ip6e;
        size_t elen;
        struct mbuf *n;

#if DIAGNOSTIC
        switch (nxt) {
        case IPPROTO_DSTOPTS:
        case IPPROTO_ROUTING:
        case IPPROTO_HOPOPTS:
        case IPPROTO_AH: /* is it possible? */
                break;
        default:
                printf("ip6_pullexthdr: invalid nxt=%d\n", nxt);
        }
#endif

        m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
        if (nxt == IPPROTO_AH)
                elen = (ip6e.ip6e_len + 2) << 2;
        else
                elen = (ip6e.ip6e_len + 1) << 3;

        MGET(n, M_DONTWAIT, MT_DATA);
        if (n && elen >= MLEN) {
                MCLGET(n, M_DONTWAIT);
                if ((n->m_flags & M_EXT) == 0) {
                        m_free(n);
                        n = NULL;
                }
        }
        if (!n)
                return NULL;

        n->m_len = 0;
        if (elen >= M_TRAILINGSPACE(n)) {
                m_free(n);
                return NULL;
        }

        m_copydata(m, off, elen, mtod(n, caddr_t));
        n->m_len = elen;
        return n;
}
#endif

/*
 * Get pointer to the previous header followed by the header
 * currently processed.
 * XXX: This function supposes that
 *      M includes all headers,
 *      the next header field and the header length field of each header
 *      are valid, and
 *      the sum of each header length equals to OFF.
 * Because of these assumptions, this function must be called very
 * carefully. Moreover, it will not be used in the near future when
 * we develop `neater' mechanism to process extension headers.
 */
char *
ip6_get_prevhdr(m, off)
        struct mbuf *m;
        int off;
{
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);

        if (off == sizeof(struct ip6_hdr))
                return((char *) &ip6->ip6_nxt);
        else {
                int len, nxt;
                struct ip6_ext *ip6e = NULL;

                nxt = ip6->ip6_nxt;
                len = sizeof(struct ip6_hdr);
                while (len < off) {
                        ip6e = (struct ip6_ext *)(mtod(m, caddr_t) + len);

                        switch (nxt) {
                        case IPPROTO_FRAGMENT:
                                len += sizeof(struct ip6_frag);
                                break;
                        case IPPROTO_AH:
                                len += (ip6e->ip6e_len + 2) << 2;
                                break;
                        default:
                                len += (ip6e->ip6e_len + 1) << 3;
                                break;
                        }
                        nxt = ip6e->ip6e_nxt;
                }
                if (ip6e)
                        return((char *) &ip6e->ip6e_nxt);
                else
                        return NULL;
        }
}

/*
 * get next header offset.  m will be retained.
 */
int
ip6_nexthdr(m, off, proto, nxtp)
        struct mbuf *m;
        int off;
        int proto;
        int *nxtp;
{
        struct ip6_hdr ip6;
        struct ip6_ext ip6e;
        struct ip6_frag fh;

        /* just in case */
        if (m == NULL)
                panic("ip6_nexthdr: m == NULL");
        if ((m->m_flags & M_PKTHDR) == 0 || m->m_pkthdr.len < off)
                return -1;

        switch (proto) {
        case IPPROTO_IPV6:
                if (m->m_pkthdr.len < off + sizeof(ip6))
                        return -1;
                m_copydata(m, off, sizeof(ip6), (caddr_t)&ip6);
                if (nxtp)
                        *nxtp = ip6.ip6_nxt;
                off += sizeof(ip6);
                return off;

        case IPPROTO_FRAGMENT:
                /*
                 * terminate parsing if it is not the first fragment,
                 * it does not make sense to parse through it.
                 */
                if (m->m_pkthdr.len < off + sizeof(fh))
                        return -1;
                m_copydata(m, off, sizeof(fh), (caddr_t)&fh);
                /* IP6F_OFF_MASK = 0xfff8(BigEndian), 0xf8ff(LittleEndian) */
                if (fh.ip6f_offlg & IP6F_OFF_MASK)
                        return -1;
                if (nxtp)
                        *nxtp = fh.ip6f_nxt;
                off += sizeof(struct ip6_frag);
                return off;

        case IPPROTO_AH:
                if (m->m_pkthdr.len < off + sizeof(ip6e))
                        return -1;
                m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
                if (nxtp)
                        *nxtp = ip6e.ip6e_nxt;
                off += (ip6e.ip6e_len + 2) << 2;
                return off;

        case IPPROTO_HOPOPTS:
        case IPPROTO_ROUTING:
        case IPPROTO_DSTOPTS:
                if (m->m_pkthdr.len < off + sizeof(ip6e))
                        return -1;
                m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
                if (nxtp)
                        *nxtp = ip6e.ip6e_nxt;
                off += (ip6e.ip6e_len + 1) << 3;
                return off;

        case IPPROTO_NONE:
        case IPPROTO_ESP:
        case IPPROTO_IPCOMP:
                /* give up */
                return -1;

        default:
                return -1;
        }

        return -1;
}

/*
 * get offset for the last header in the chain.  m will be kept untainted.
 */
int
ip6_lasthdr(m, off, proto, nxtp)
        struct mbuf *m;
        int off;
        int proto;
        int *nxtp;
{
        int newoff;
        int nxt;

        if (!nxtp) {
                nxt = -1;
                nxtp = &nxt;
        }
        while (1) {
                newoff = ip6_nexthdr(m, off, proto, nxtp);
                if (newoff < 0)
                        return off;
                else if (newoff < off)
                        return -1;      /* invalid */
                else if (newoff == off)
                        return newoff;

                off = newoff;
                proto = *nxtp;
        }
}

struct ip6aux *
ip6_addaux(
        struct mbuf *m)
{
        struct m_tag            *tag;
        
        /* Check if one is already allocated */
        tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_INET6, NULL);
        if (tag == NULL) {
                /* Allocate a tag */
                tag = m_tag_alloc(KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_INET6,
                    sizeof (struct ip6aux), M_DONTWAIT);

                /* Attach it to the mbuf */
                if (tag) {
                        m_tag_prepend(m, tag);
                }
        }
        
        return tag ? (struct ip6aux*)(tag + 1) : NULL;
}

struct ip6aux *
ip6_findaux(
        struct mbuf *m)
{
        struct m_tag    *tag;
        
        tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_ENCAP, NULL);
        
        return tag ? (struct ip6aux*)(tag + 1) : NULL;
}

void
ip6_delaux(
        struct mbuf *m)
{
        struct m_tag    *tag;

        tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_ENCAP, NULL);
        if (tag) {
                m_tag_delete(m, tag);
        }
}

/*
 * System control for IP6
 */

u_char  inet6ctlerrmap[PRC_NCMDS] = {
        0,              0,              0,              0,
        0,              EMSGSIZE,       EHOSTDOWN,      EHOSTUNREACH,
        EHOSTUNREACH,   EHOSTUNREACH,   ECONNREFUSED,   ECONNREFUSED,
        EMSGSIZE,       EHOSTUNREACH,   0,              0,
        0,              0,              0,              0,
        ENOPROTOOPT
};