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

/*
 * Copyright (c) 2003-2017 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) 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/sysctl.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/mcache.h>

#include <mach/mach_time.h>
#include <mach/sdt.h>
#include <pexpert/pexpert.h>
#include <dev/random/randomdev.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 <net/ntstat.h>
#include <net/init.h>
#include <net/net_osdep.h>
#include <net/net_perf.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/kpi_ipfilter_var.h>
#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/scope6_var.h>
#include <netinet6/ip6protosw.h>

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

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

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

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

struct ip6protosw *ip6_protox[IPPROTO_MAX];

static lck_grp_attr_t   *in6_ifaddr_rwlock_grp_attr;
static lck_grp_t        *in6_ifaddr_rwlock_grp;
static lck_attr_t       *in6_ifaddr_rwlock_attr;
decl_lck_rw_data(, in6_ifaddr_rwlock);

/* Protected by in6_ifaddr_rwlock */
struct in6_ifaddr *in6_ifaddrs = NULL;

#define IN6_IFSTAT_REQUIRE_ALIGNED_64(f)        \
        _CASSERT(!(offsetof(struct in6_ifstat, f) % sizeof (uint64_t)))

#define ICMP6_IFSTAT_REQUIRE_ALIGNED_64(f)      \
        _CASSERT(!(offsetof(struct icmp6_ifstat, f) % sizeof (uint64_t)))

struct ip6stat ip6stat;

decl_lck_mtx_data(, proxy6_lock);
decl_lck_mtx_data(static, dad6_mutex_data);
decl_lck_mtx_data(static, nd6_mutex_data);
decl_lck_mtx_data(static, prefix6_mutex_data);
lck_mtx_t               *dad6_mutex = &dad6_mutex_data;
lck_mtx_t               *nd6_mutex = &nd6_mutex_data;
lck_mtx_t               *prefix6_mutex = &prefix6_mutex_data;
#ifdef ENABLE_ADDRSEL
decl_lck_mtx_data(static, addrsel_mutex_data);
lck_mtx_t               *addrsel_mutex = &addrsel_mutex_data;
#endif
static lck_attr_t       *ip6_mutex_attr;
static lck_grp_t        *ip6_mutex_grp;
static lck_grp_attr_t   *ip6_mutex_grp_attr;

extern int loopattach_done;
extern void addrsel_policy_init(void);

static int sysctl_reset_ip6_input_stats SYSCTL_HANDLER_ARGS;
static int sysctl_ip6_input_measure_bins SYSCTL_HANDLER_ARGS;
static int sysctl_ip6_input_getperf SYSCTL_HANDLER_ARGS;
static void ip6_init_delayed(void);
static int ip6_hopopts_input(u_int32_t *, u_int32_t *, struct mbuf **, int *);

#if NSTF
extern void stfattach(void);
#endif /* NSTF */

SYSCTL_DECL(_net_inet6_ip6);

static uint32_t ip6_adj_clear_hwcksum = 0;
SYSCTL_UINT(_net_inet6_ip6, OID_AUTO, adj_clear_hwcksum,
        CTLFLAG_RW | CTLFLAG_LOCKED, &ip6_adj_clear_hwcksum, 0,
        "Invalidate hwcksum info when adjusting length");

static uint32_t ip6_adj_partial_sum = 1;
SYSCTL_UINT(_net_inet6_ip6, OID_AUTO, adj_partial_sum,
        CTLFLAG_RW | CTLFLAG_LOCKED, &ip6_adj_partial_sum, 0,
        "Perform partial sum adjustment of trailing bytes at IP layer");

static int ip6_input_measure = 0;
SYSCTL_PROC(_net_inet6_ip6, OID_AUTO, input_perf,
        CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
        &ip6_input_measure, 0, sysctl_reset_ip6_input_stats, "I", "Do time measurement");

static uint64_t ip6_input_measure_bins = 0;
SYSCTL_PROC(_net_inet6_ip6, OID_AUTO, input_perf_bins,
        CTLTYPE_QUAD | CTLFLAG_RW | CTLFLAG_LOCKED, &ip6_input_measure_bins, 0,
        sysctl_ip6_input_measure_bins, "I",
        "bins for chaining performance data histogram");

static net_perf_t net_perf;
SYSCTL_PROC(_net_inet6_ip6, OID_AUTO, input_perf_data,
        CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED,
        0, 0, sysctl_ip6_input_getperf, "S,net_perf",
        "IP6 input performance data (struct net_perf, net/net_perf.h)");

/*
 * On platforms which require strict alignment (currently for anything but
 * i386 or x86_64), check if the IP header pointer is 32-bit aligned; if not,
 * copy the contents of the mbuf chain into a new chain, and free the original
 * one.  Create some head room in the first mbuf of the new chain, in case
 * it's needed later on.
 *
 * RFC 2460 says that IPv6 headers are 64-bit aligned, but network interfaces
 * mostly align to 32-bit boundaries.  Care should be taken never to use 64-bit
 * load/store operations on the fields in IPv6 headers.
 */
#if defined(__i386__) || defined(__x86_64__)
#define IP6_HDR_ALIGNMENT_FIXUP(_m, _ifp, _action) do { } while (0)
#else /* !__i386__ && !__x86_64__ */
#define IP6_HDR_ALIGNMENT_FIXUP(_m, _ifp, _action) do {                 \
        if (!IP6_HDR_ALIGNED_P(mtod(_m, caddr_t))) {                    \
                struct mbuf *_n;                                        \
                struct ifnet *__ifp = (_ifp);                           \
                atomic_add_64(&(__ifp)->if_alignerrs, 1);               \
                if (((_m)->m_flags & M_PKTHDR) &&                       \
                    (_m)->m_pkthdr.pkt_hdr != NULL)                     \
                        (_m)->m_pkthdr.pkt_hdr = NULL;                  \
                _n = m_defrag_offset(_m, max_linkhdr, M_NOWAIT);        \
                if (_n == NULL) {                                       \
                        ip6stat.ip6s_toosmall++;                        \
                        m_freem(_m);                                    \
                        (_m) = NULL;                                    \
                        _action;                                        \
                } else {                                                \
                        VERIFY(_n != (_m));                             \
                        (_m) = _n;                                      \
                }                                                       \
        }                                                               \
} while (0)
#endif /* !__i386__ && !__x86_64__ */

static void
ip6_proto_input(protocol_family_t protocol, mbuf_t packet)
{
#pragma unused(protocol)
#if INET
        struct timeval start_tv;
        if (ip6_input_measure)
                net_perf_start_time(&net_perf, &start_tv);
#endif /* INET */
        ip6_input(packet);
#if INET
        if (ip6_input_measure) {
                net_perf_measure_time(&net_perf, &start_tv, 1);
                net_perf_histogram(&net_perf, 1);
        }
#endif /* INET */
}

/*
 * 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 *pp, struct domain *dp)
{
        static int ip6_initialized = 0;
        struct protosw *pr;
        struct timeval tv;
        int i;
        domain_unguard_t unguard;

        domain_proto_mtx_lock_assert_held();
        VERIFY((pp->pr_flags & (PR_INITIALIZED|PR_ATTACHED)) == PR_ATTACHED);

        _CASSERT((sizeof (struct ip6_hdr) +
            sizeof (struct icmp6_hdr)) <= _MHLEN);

        if (ip6_initialized)
                return;
        ip6_initialized = 1;

        eventhandler_lists_ctxt_init(&in6_evhdlr_ctxt);
        (void)EVENTHANDLER_REGISTER(&in6_evhdlr_ctxt, in6_event,
            in6_eventhdlr_callback, eventhandler_entry_dummy_arg,
            EVENTHANDLER_PRI_ANY);

        for (i = 0; i < IN6_EVENT_MAX; i++)
                VERIFY(in6_event2kev_array[i].in6_event_code == i);

        pr = pffindproto_locked(PF_INET6, IPPROTO_RAW, SOCK_RAW);
        if (pr == NULL) {
                panic("%s: Unable to find [PF_INET6,IPPROTO_RAW,SOCK_RAW]\n",
                    __func__);
                /* NOTREACHED */
        }

        /* Initialize the entire ip6_protox[] array to IPPROTO_RAW. */
        for (i = 0; i < IPPROTO_MAX; i++)
                ip6_protox[i] = (struct ip6protosw *)pr;
        /*
         * Cycle through IP protocols and put them into the appropriate place
         * in ip6_protox[], skipping protocols IPPROTO_{IP,RAW}.
         */
        VERIFY(dp == inet6domain && dp->dom_family == PF_INET6);
        TAILQ_FOREACH(pr, &dp->dom_protosw, pr_entry) {
                VERIFY(pr->pr_domain == dp);
                if (pr->pr_protocol != 0 && pr->pr_protocol != IPPROTO_RAW) {
                        /* Be careful to only index valid IP protocols. */
                        if (pr->pr_protocol < IPPROTO_MAX)
                                ip6_protox[pr->pr_protocol] =
                                    (struct ip6protosw *)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();

        lck_mtx_init(dad6_mutex, ip6_mutex_grp, ip6_mutex_attr);
        lck_mtx_init(nd6_mutex, ip6_mutex_grp, ip6_mutex_attr);
        lck_mtx_init(prefix6_mutex, ip6_mutex_grp, ip6_mutex_attr);
        scope6_init(ip6_mutex_grp, ip6_mutex_attr);

#ifdef ENABLE_ADDRSEL
        lck_mtx_init(addrsel_mutex, ip6_mutex_grp, ip6_mutex_attr);
#endif

        lck_mtx_init(&proxy6_lock, ip6_mutex_grp, ip6_mutex_attr);

        in6_ifaddr_rwlock_grp_attr = lck_grp_attr_alloc_init();
        in6_ifaddr_rwlock_grp = lck_grp_alloc_init("in6_ifaddr_rwlock",
            in6_ifaddr_rwlock_grp_attr);
        in6_ifaddr_rwlock_attr = lck_attr_alloc_init();
        lck_rw_init(&in6_ifaddr_rwlock, in6_ifaddr_rwlock_grp,
            in6_ifaddr_rwlock_attr);

        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_receive);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_hdrerr);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_toobig);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_noroute);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_addrerr);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_protounknown);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_truncated);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_discard);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_deliver);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_forward);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_request);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_discard);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_fragok);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_fragfail);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_fragcreat);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_reass_reqd);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_reass_ok);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_reass_fail);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_mcast);
        IN6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_mcast);

        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_msg);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_error);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_dstunreach);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_adminprohib);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_timeexceed);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_paramprob);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_pkttoobig);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_echo);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_echoreply);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_routersolicit);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_routeradvert);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_neighborsolicit);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_neighboradvert);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_redirect);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_mldquery);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_mldreport);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_in_mlddone);

        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_msg);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_error);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_dstunreach);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_adminprohib);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_timeexceed);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_paramprob);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_pkttoobig);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_echo);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_echoreply);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_routersolicit);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_routeradvert);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_neighborsolicit);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_neighboradvert);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_redirect);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_mldquery);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_mldreport);
        ICMP6_IFSTAT_REQUIRE_ALIGNED_64(ifs6_out_mlddone);

        getmicrotime(&tv);
        ip6_desync_factor =
            (RandomULong() ^ tv.tv_usec) % MAX_TEMP_DESYNC_FACTOR;

        in6_ifaddr_init();
        ip6_moptions_init();
        nd6_init();
        frag6_init();
        icmp6_init(NULL, dp);
        addrsel_policy_init();

        /*
         * P2P interfaces often route the local address to the loopback
         * interface. At this point, lo0 hasn't been initialized yet, which
         * means that we need to delay the IPv6 configuration of lo0.
         */
        net_init_add(ip6_init_delayed);

        unguard = domain_unguard_deploy();
        i = proto_register_input(PF_INET6, ip6_proto_input, NULL, 0);
        if (i != 0) {
                panic("%s: failed to register PF_INET6 protocol: %d\n",
                    __func__, i);
                /* NOTREACHED */
        }
        domain_unguard_release(unguard);
}

static void
ip6_init_delayed(void)
{
        (void) in6_ifattach_prelim(lo_ifp);

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

#if NSTF
        stfattach();
#endif /* NSTF */
}

static void
ip6_input_adjust(struct mbuf *m, struct ip6_hdr *ip6, uint32_t plen,
    struct ifnet *inifp)
{
        boolean_t adjust = TRUE;
        uint32_t tot_len = sizeof (*ip6) + plen;

        ASSERT(m_pktlen(m) > tot_len);

        /*
         * Invalidate hardware checksum info if ip6_adj_clear_hwcksum
         * is set; useful to handle buggy drivers.  Note that this
         * should not be enabled by default, as we may get here due
         * to link-layer padding.
         */
        if (ip6_adj_clear_hwcksum &&
            (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) &&
            !(inifp->if_flags & IFF_LOOPBACK) &&
            !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
                m->m_pkthdr.csum_flags &= ~CSUM_DATA_VALID;
                m->m_pkthdr.csum_data = 0;
                ip6stat.ip6s_adj_hwcsum_clr++;
        }

        /*
         * If partial checksum information is available, subtract
         * out the partial sum of postpended extraneous bytes, and
         * update the checksum metadata accordingly.  By doing it
         * here, the upper layer transport only needs to adjust any
         * prepended extraneous bytes (else it will do both.)
         */
        if (ip6_adj_partial_sum &&
            (m->m_pkthdr.csum_flags & (CSUM_DATA_VALID|CSUM_PARTIAL)) ==
            (CSUM_DATA_VALID|CSUM_PARTIAL)) {
                m->m_pkthdr.csum_rx_val = m_adj_sum16(m,
                    m->m_pkthdr.csum_rx_start, m->m_pkthdr.csum_rx_start,
                    (tot_len - m->m_pkthdr.csum_rx_start),
                    m->m_pkthdr.csum_rx_val);
        } else if ((m->m_pkthdr.csum_flags &
            (CSUM_DATA_VALID|CSUM_PARTIAL)) ==
            (CSUM_DATA_VALID|CSUM_PARTIAL)) {
                /*
                 * If packet has partial checksum info and we decided not
                 * to subtract the partial sum of postpended extraneous
                 * bytes here (not the default case), leave that work to
                 * be handled by the other layers.  For now, only TCP, UDP
                 * layers are capable of dealing with this.  For all other
                 * protocols (including fragments), trim and ditch the
                 * partial sum as those layers might not implement partial
                 * checksumming (or adjustment) at all.
                 */
                if (ip6->ip6_nxt == IPPROTO_TCP ||
                    ip6->ip6_nxt == IPPROTO_UDP) {
                        adjust = FALSE;
                } else {
                        m->m_pkthdr.csum_flags &= ~CSUM_DATA_VALID;
                        m->m_pkthdr.csum_data = 0;
                        ip6stat.ip6s_adj_hwcsum_clr++;
                }
        }

        if (adjust) {
                ip6stat.ip6s_adj++;
                if (m->m_len == m->m_pkthdr.len) {
                        m->m_len = tot_len;
                        m->m_pkthdr.len = tot_len;
                } else {
                        m_adj(m, tot_len - m->m_pkthdr.len);
                }
        }
}

void
ip6_input(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 *inifp, *deliverifp = NULL;
        ipfilter_t inject_ipfref = NULL;
        int seen = 1;
        struct in6_ifaddr *ia6 = NULL;
        struct sockaddr_in6 *dst6;
#if DUMMYNET
        struct m_tag *tag;
#endif /* DUMMYNET */
        struct {
                struct route_in6 rin6;
#if DUMMYNET
                struct ip_fw_args args;
#endif /* DUMMYNET */
        } ip6ibz;
#define rin6    ip6ibz.rin6
#define args    ip6ibz.args

        /* zero out {rin6, args} */
        bzero(&ip6ibz, sizeof (ip6ibz));

        /*
         * Check if the packet we received is valid after interface filter
         * processing
         */
        MBUF_INPUT_CHECK(m, m->m_pkthdr.rcvif);
        inifp = m->m_pkthdr.rcvif;
        VERIFY(inifp != NULL);

        /* Perform IP header alignment fixup, if needed */
        IP6_HDR_ALIGNMENT_FIXUP(m, inifp, return);

        m->m_pkthdr.pkt_flags &= ~PKTF_FORWARDED;
#if IPSEC
        /*
         * should the inner packet be considered authentic?
         * see comment in ah4_input().
         */
        m->m_flags &= ~M_AUTHIPHDR;
        m->m_flags &= ~M_AUTHIPDGM;
#endif /* IPSEC */

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

#if DUMMYNET
        if ((tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID,
            KERNEL_TAG_TYPE_DUMMYNET, NULL)) != NULL) {
                struct dn_pkt_tag       *dn_tag;

                dn_tag = (struct dn_pkt_tag *)(tag+1);

                args.fwa_pf_rule = dn_tag->dn_pf_rule;

                m_tag_delete(m, tag);
        }

        if (args.fwa_pf_rule) {
                ip6 = mtod(m, struct ip6_hdr *); /* In case PF got disabled */

                goto check_with_pf;
        }
#endif /* DUMMYNET */

        /*
         * No need to proccess packet twice if we've already seen it.
         */
        inject_ipfref = ipf_get_inject_filter(m);
        if (inject_ipfref != NULL) {
                ip6 = mtod(m, struct ip6_hdr *);
                nxt = ip6->ip6_nxt;
                seen = 0;
                goto injectit;
        } else {
                seen = 1;
        }

        /*
         * mbuf statistics
         */
        if (m->m_flags & M_EXT) {
                if (m->m_next != NULL)
                        ip6stat.ip6s_mext2m++;
                else
                        ip6stat.ip6s_mext1++;
        } else {
#define M2MMAX  (sizeof (ip6stat.ip6s_m2m) / sizeof (ip6stat.ip6s_m2m[0]))
                if (m->m_next != NULL) {
                        if (m->m_pkthdr.pkt_flags & PKTF_LOOP) {
                                /* XXX */
                                ip6stat.ip6s_m2m[ifnet_index(lo_ifp)]++;
                        } else if (inifp->if_index < M2MMAX) {
                                ip6stat.ip6s_m2m[inifp->if_index]++;
                        } else {
                                ip6stat.ip6s_m2m[0]++;
                        }
                } else {
                        ip6stat.ip6s_m1++;
                }
#undef M2MMAX
        }

        /*
         * Drop the packet if IPv6 operation is disabled on the interface.
         */
        if (inifp->if_eflags & IFEF_IPV6_DISABLED)
                goto bad;

        in6_ifstat_inc_na(inifp, ifs6_in_receive);
        ip6stat.ip6s_total++;

        /*
         * 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_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)
                        goto bad;

                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), { goto done; });

        if (m->m_len < sizeof (struct ip6_hdr)) {
                if ((m = m_pullup(m, sizeof (struct ip6_hdr))) == 0) {
                        ip6stat.ip6s_toosmall++;
                        in6_ifstat_inc(inifp, ifs6_in_hdrerr);
                        goto done;
                }
        }

        ip6 = mtod(m, struct ip6_hdr *);

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

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

        /*
         * Check against address spoofing/corruption.
         */
        if (!(m->m_pkthdr.pkt_flags & PKTF_LOOP) &&
            IN6_IS_ADDR_LOOPBACK(&ip6->ip6_src)) {
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(inifp, ifs6_in_addrerr);
                goto bad;
        }
        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(inifp, ifs6_in_addrerr);
                goto bad;
        }
        if (IN6_IS_ADDR_MC_INTFACELOCAL(&ip6->ip6_dst) &&
            !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
                /*
                 * In this case, the packet should come from the loopback
                 * interface.  However, we cannot just check the if_flags,
                 * because ip6_mloopback() passes the "actual" interface
                 * as the outgoing/incoming interface.
                 */
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(inifp, 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
         * partial 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(inifp, 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(inifp, ifs6_in_addrerr);
                goto bad;
        }
#endif

        /*
         * Naively assume we can attribute inbound data to the route we would
         * use to send to this destination. Asymetric routing breaks this
         * assumption, but it still allows us to account for traffic from
         * a remote node in the routing table.
         * this has a very significant performance impact so we bypass
         * if nstat_collect is disabled. We may also bypass if the
         * protocol is tcp in the future because tcp will have a route that
         * we can use to attribute the data to. That does mean we would not
         * account for forwarded tcp traffic.
         */
        if (nstat_collect) {
                struct rtentry *rte =
                    ifnet_cached_rtlookup_inet6(inifp, &ip6->ip6_src);
                if (rte != NULL) {
                        nstat_route_rx(rte, 1, m->m_pkthdr.len, 0);
                        rtfree(rte);
                }
        }

        /* for consistency */
        m->m_pkthdr.pkt_proto = ip6->ip6_nxt;

#if DUMMYNET
check_with_pf:
#endif /* DUMMYNET */
#if PF
        /* Invoke inbound packet filter */
        if (PF_IS_ENABLED) {
                int error;
#if DUMMYNET
                error = pf_af_hook(inifp, NULL, &m, AF_INET6, TRUE, &args);
#else /* !DUMMYNET */
                error = pf_af_hook(inifp, NULL, &m, AF_INET6, TRUE, NULL);
#endif /* !DUMMYNET */
                if (error != 0 || m == NULL) {
                        if (m != NULL) {
                                panic("%s: unexpected packet %p\n",
                                    __func__, m);
                                /* NOTREACHED */
                        }
                        /* Already freed by callee */
                        goto done;
                }
                ip6 = mtod(m, struct ip6_hdr *);
        }
#endif /* PF */

        /* drop packets if interface ID portion is already filled */
        if (!(inifp->if_flags & IFF_LOOPBACK) &&
            !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src) &&
                    ip6->ip6_src.s6_addr16[1]) {
                        ip6stat.ip6s_badscope++;
                        goto bad;
                }
                if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst) &&
                    ip6->ip6_dst.s6_addr16[1]) {
                        ip6stat.ip6s_badscope++;
                        goto bad;
                }
        }

        if (m->m_pkthdr.pkt_flags & PKTF_IFAINFO) {
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src))
                        ip6->ip6_src.s6_addr16[1] =
                            htons(m->m_pkthdr.src_ifindex);
                if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst))
                        ip6->ip6_dst.s6_addr16[1] =
                            htons(m->m_pkthdr.dst_ifindex);
        } else {
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src))
                        ip6->ip6_src.s6_addr16[1] = htons(inifp->if_index);
                if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst))
                        ip6->ip6_dst.s6_addr16[1] = htons(inifp->if_index);
        }

        /*
         * Multicast check
         */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                struct  in6_multi *in6m = NULL;

                in6_ifstat_inc_na(inifp, ifs6_in_mcast);
                /*
                 * See if we belong to the destination multicast group on the
                 * arrival interface.
                 */
                in6_multihead_lock_shared();
                IN6_LOOKUP_MULTI(&ip6->ip6_dst, inifp, in6m);
                in6_multihead_lock_done();
                if (in6m != NULL) {
                        IN6M_REMREF(in6m);
                        ours = 1;
                } else if (!nd6_prproxy) {
                        ip6stat.ip6s_notmember++;
                        ip6stat.ip6s_cantforward++;
                        in6_ifstat_inc(inifp, ifs6_in_discard);
                        goto bad;
                }
                deliverifp = inifp;
                VERIFY(ia6 == NULL);
                goto hbhcheck;
        }

        /*
         * Unicast check
         *
         * Fast path: see if the target is ourselves.
         */
        lck_rw_lock_shared(&in6_ifaddr_rwlock);
        for (ia6 = in6_ifaddrs; ia6 != NULL; ia6 = ia6->ia_next) {
                /*
                 * No reference is held on the address, as we just need
                 * to test for a few things while holding the RW lock.
                 */
                if (IN6_ARE_ADDR_EQUAL(&ia6->ia_addr.sin6_addr, &ip6->ip6_dst))
                        break;
        }

        if (ia6 != NULL) {
                /*
                 * For performance, test without acquiring the address lock;
                 * a lot of things in the address are set once and never
                 * changed (e.g. ia_ifp.)
                 */
                if (!(ia6->ia6_flags & IN6_IFF_NOTREADY)) {
                        /* this address is ready */
                        ours = 1;
                        deliverifp = ia6->ia_ifp;
                        /*
                         * record dst address information into mbuf.
                         */
                        (void) ip6_setdstifaddr_info(m, 0, ia6);
                        lck_rw_done(&in6_ifaddr_rwlock);
                        goto hbhcheck;
                }
                lck_rw_done(&in6_ifaddr_rwlock);
                ia6 = NULL;
                /* address is not ready, so discard the packet. */
                nd6log((LOG_INFO, "%s: packet to an unready address %s->%s\n",
                    __func__, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst)));
                goto bad;
        }
        lck_rw_done(&in6_ifaddr_rwlock);

        /*
         * Slow path: route lookup.
         */
        dst6 = SIN6(&rin6.ro_dst);
        dst6->sin6_len = sizeof (struct sockaddr_in6);
        dst6->sin6_family = AF_INET6;
        dst6->sin6_addr = ip6->ip6_dst;

        rtalloc_scoped_ign((struct route *)&rin6,
            RTF_PRCLONING, IFSCOPE_NONE);
        if (rin6.ro_rt != NULL)
                RT_LOCK_SPIN(rin6.ro_rt);

#define rt6_key(r) (SIN6((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 (rin6.ro_rt != NULL &&
            (rin6.ro_rt->rt_flags & (RTF_HOST|RTF_GATEWAY)) == RTF_HOST &&
#if RTF_WASCLONED
            !(rin6.ro_rt->rt_flags & RTF_WASCLONED) &&
#endif
            rin6.ro_rt->rt_ifp->if_type == IFT_LOOP) {
                ia6 = (struct in6_ifaddr *)rin6.ro_rt->rt_ifa;
                /*
                 * Packets to a tentative, duplicated, or somehow invalid
                 * address must not be accepted.
                 *
                 * For performance, test without acquiring the address lock;
                 * a lot of things in the address are set once and never
                 * changed (e.g. ia_ifp.)
                 */
                if (!(ia6->ia6_flags & IN6_IFF_NOTREADY)) {
                        /* this address is ready */
                        ours = 1;
                        deliverifp = ia6->ia_ifp;       /* correct? */
                        /*
                         * record dst address information into mbuf.
                         */
                        (void) ip6_setdstifaddr_info(m, 0, ia6);
                        RT_UNLOCK(rin6.ro_rt);
                        goto hbhcheck;
                }
                RT_UNLOCK(rin6.ro_rt);
                ia6 = NULL;
                /* address is not ready, so discard the packet. */
                nd6log((LOG_INFO, "%s: packet to an unready address %s->%s\n",
                    __func__, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst)));
                goto bad;
        }

        if (rin6.ro_rt != NULL)
                RT_UNLOCK(rin6.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(inifp, ifs6_in_discard);
                /*
                 * Raise a kernel event if the packet received on cellular
                 * interface is not intended for local host.
                 * For now limit it to ICMPv6 packets.
                 */
                if (inifp->if_type == IFT_CELLULAR &&
                    ip6->ip6_nxt == IPPROTO_ICMPV6)
                        in6_ifstat_inc(inifp, ifs6_cantfoward_icmp6);
                goto bad;
        }

hbhcheck:
        /*
         * record dst address information into mbuf, 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, etc.)
         */
        if (deliverifp != NULL && ia6 == NULL) {
                ia6 = in6_ifawithifp(deliverifp, &ip6->ip6_dst);
                if (ia6 != NULL) {
                        (void) ip6_setdstifaddr_info(m, 0, ia6);
                        IFA_REMREF(&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;

                /*
                 * Mark the packet to imply that HBH option has been checked.
                 * This can only be true is the packet came in unfragmented
                 * or if the option is in the first fragment
                 */
                m->m_pkthdr.pkt_flags |= PKTF_HBH_CHKED;
                if (ip6_hopopts_input(&plen, &rtalert, &m, &off)) {
#if 0   /* touches NULL pointer */
                        in6_ifstat_inc(inifp, ifs6_in_discard);
#endif
                        goto done;      /* 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_hopopts_input() must set a valid
                         * (non-zero) payload length to the variable plen.
                         */
                        ip6stat.ip6s_badoptions++;
                        in6_ifstat_inc(inifp, ifs6_in_discard);
                        in6_ifstat_inc(inifp, ifs6_in_hdrerr);
                        icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
                            (caddr_t)&ip6->ip6_plen - (caddr_t)ip6);
                        goto done;
                }
                /* ip6_hopopts_input() ensures that mbuf is contiguous */
                hbh = (struct ip6_hbh *)(ip6 + 1);
                nxt = hbh->ip6h_nxt;

                /*
                 * If we are acting as a router and the packet contains a
                 * router alert option, see if we know the option value.
                 * Currently, we only support the option value for MLD, in which
                 * case we should pass the packet to the multicast routing
                 * daemon.
                 */
                if (rtalert != ~0 && ip6_forwarding) {
                        switch (rtalert) {
                        case IP6OPT_RTALERT_MLD:
                                ours = 1;
                                break;
                        default:
                                /*
                                 * RFC2711 requires unrecognized values must be
                                 * silently ignored.
                                 */
                                break;
                        }
                }
        } 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(inifp, ifs6_in_truncated);
                goto bad;
        }
        if (m->m_pkthdr.len > sizeof (struct ip6_hdr) + plen) {
                ip6_input_adjust(m, ip6, plen, inifp);
        }

        /*
         * Forward if desirable.
         */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                if (!ours && nd6_prproxy) {
                        /*
                         * If this isn't for us, this might be a Neighbor
                         * Solicitation (dst is solicited-node multicast)
                         * against an address in one of the proxied prefixes;
                         * if so, claim the packet and let icmp6_input()
                         * handle the rest.
                         */
                        ours = nd6_prproxy_isours(m, ip6, NULL, IFSCOPE_NONE);
                        VERIFY(!ours ||
                            (m->m_pkthdr.pkt_flags & PKTF_PROXY_DST));
                }
                if (!ours)
                        goto bad;
        } else if (!ours) {
                /*
                 * The unicast forwarding function might return the packet
                 * if we are proxying prefix(es), and if the packet is an
                 * ICMPv6 packet that has failed the zone checks, but is
                 * targetted towards a proxied address (this is optimized by
                 * way of RTF_PROXY test.)  If so, claim the packet as ours
                 * and let icmp6_input() handle the rest.  The packet's hop
                 * limit value is kept intact (it's not decremented).  This
                 * is for supporting Neighbor Unreachability Detection between
                 * proxied nodes on different links (src is link-local, dst
                 * is target address.)
                 */
                if ((m = ip6_forward(m, &rin6, 0)) == NULL)
                        goto done;
                VERIFY(rin6.ro_rt != NULL);
                VERIFY(m->m_pkthdr.pkt_flags & PKTF_PROXY_DST);
                deliverifp = rin6.ro_rt->rt_ifp;
                ours = 1;
        }

        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(inifp, ifs6_in_addrerr);
                goto bad;
        }

        /*
         * Tell launch routine the next header
         */
        ip6stat.ip6s_delivered++;
        in6_ifstat_inc_na(deliverifp, ifs6_in_deliver);

injectit:
        nest = 0;

        /*
         * Perform IP header alignment fixup again, if needed.  Note that
         * we do it once for the outermost protocol, and we assume each
         * protocol handler wouldn't mess with the alignment afterwards.
         */
        IP6_HDR_ALIGNMENT_FIXUP(m, inifp, return);

        while (nxt != IPPROTO_DONE) {
                struct ipfilter *filter;
                int (*pr_input)(struct mbuf **, int *, int);

                /*
                 * This would imply either IPPROTO_HOPOPTS was not the first
                 * option or it did not come in the first fragment.
                 */
                if (nxt == IPPROTO_HOPOPTS &&
                    (m->m_pkthdr.pkt_flags & PKTF_HBH_CHKED) == 0) {
                        /*
                         * This implies that HBH option was not contained
                         * in the first fragment
                         */
                        ip6stat.ip6s_badoptions++;
                        goto bad;
                }

                if (ip6_hdrnestlimit && (++nest > ip6_hdrnestlimit)) {
                        ip6stat.ip6s_toomanyhdr++;
                        goto bad;
                }

                /*
                 * 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(inifp, ifs6_in_truncated);
                        goto bad;
                }

#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 bad;
                        }
                }
#endif /* IPSEC */

                /*
                 * Call IP filter
                 */
                if (!TAILQ_EMPTY(&ipv6_filters) && !IFNET_IS_INTCOPROC(inifp)) {
                        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();
                                                goto done;
                                        }
                                        if (result != 0) {
                                                ipf_unref();
                                                goto bad;
                                        }
                                }
                        }
                        ipf_unref();
                }

                DTRACE_IP6(receive, struct mbuf *, m, struct inpcb *, NULL,
                    struct ip6_hdr *, ip6, struct ifnet *, inifp,
                    struct ip *, NULL, struct ip6_hdr *, ip6);

                if ((pr_input = ip6_protox[nxt]->pr_input) == NULL) {
                        m_freem(m);
                        m = NULL;
                        nxt = IPPROTO_DONE;
                } else if (!(ip6_protox[nxt]->pr_flags & PR_PROTOLOCK)) {
                        lck_mtx_lock(inet6_domain_mutex);
                        nxt = pr_input(&m, &off, nxt);
                        lck_mtx_unlock(inet6_domain_mutex);
                } else {
                        nxt = pr_input(&m, &off, nxt);
                }
        }
done:
        ROUTE_RELEASE(&rin6);
        return;
bad:
        m_freem(m);
        goto done;
}

void
ip6_setsrcifaddr_info(struct mbuf *m, uint32_t src_idx, struct in6_ifaddr *ia6)
{
        VERIFY(m->m_flags & M_PKTHDR);

        /*
         * If the source ifaddr is specified, pick up the information
         * from there; otherwise just grab the passed-in ifindex as the
         * caller may not have the ifaddr available.
         */
        if (ia6 != NULL) {
                m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
                m->m_pkthdr.src_ifindex = ia6->ia_ifp->if_index;

                /* See IN6_IFF comments in in6_var.h */
                m->m_pkthdr.src_iff = (ia6->ia6_flags & 0xffff);
        } else {
                m->m_pkthdr.src_iff = 0;
                m->m_pkthdr.src_ifindex = src_idx;
                if (src_idx != 0)
                        m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
        }
}

void
ip6_setdstifaddr_info(struct mbuf *m, uint32_t dst_idx, struct in6_ifaddr *ia6)
{
        VERIFY(m->m_flags & M_PKTHDR);

        /*
         * If the destination ifaddr is specified, pick up the information
         * from there; otherwise just grab the passed-in ifindex as the
         * caller may not have the ifaddr available.
         */
        if (ia6 != NULL) {
                m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
                m->m_pkthdr.dst_ifindex = ia6->ia_ifp->if_index;

                /* See IN6_IFF comments in in6_var.h */
                m->m_pkthdr.dst_iff = (ia6->ia6_flags & 0xffff);
        } else {
                m->m_pkthdr.dst_iff = 0;
                m->m_pkthdr.dst_ifindex = dst_idx;
                if (dst_idx != 0)
                        m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
        }
}

int
ip6_getsrcifaddr_info(struct mbuf *m, uint32_t *src_idx, uint32_t *ia6f)
{
        VERIFY(m->m_flags & M_PKTHDR);

        if (!(m->m_pkthdr.pkt_flags & PKTF_IFAINFO))
                return (-1);

        if (src_idx != NULL)
                *src_idx = m->m_pkthdr.src_ifindex;

        if (ia6f != NULL)
                *ia6f = m->m_pkthdr.src_iff;

        return (0);
}

int
ip6_getdstifaddr_info(struct mbuf *m, uint32_t *dst_idx, uint32_t *ia6f)
{
        VERIFY(m->m_flags & M_PKTHDR);

        if (!(m->m_pkthdr.pkt_flags & PKTF_IFAINFO))
                return (-1);

        if (dst_idx != NULL)
                *dst_idx = m->m_pkthdr.dst_ifindex;

        if (ia6f != NULL)
                *ia6f = m->m_pkthdr.dst_iff;

        return (0);
}

/*
 * 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(uint32_t *plenp, uint32_t *rtalertp, 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 */
        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);
        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(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_ROUTER_ALERT:
                        /* 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 */
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 1 - opthead);
                                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 */
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 1 - opthead);
                                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++;
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt - opthead);
                                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++;
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 2 - opthead);
                                return (-1);
                        }
#endif

                        /*
                         * jumbo payload length must be larger than 65535.
                         */
                        if (jumboplen <= IPV6_MAXPACKET) {
                                ip6stat.ip6s_badoptions++;
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                            ICMP6_PARAMPROB_HEADER,
                                            erroff + opt + 2 - opthead);
                                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);
                        if (optlen == -1) {
                                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(uint8_t *optp, struct mbuf *m, int off)
{
        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++;
                icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_OPTION, off);
                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 {
                        icmp6_error(m, ICMP6_PARAM_PROB,
                            ICMP6_PARAMPROB_OPTION, off);
                }
                return (-1);
        }

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

/*
 * Create the "control" list for this pcb.
 * These functions 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.
 *
 * ip6_savecontrol_v4 will handle those options that are possible to be
 * set on a v4-mapped socket.
 * ip6_savecontrol will directly call ip6_savecontrol_v4 to handle those
 * options and handle the v6-only ones itself.
 */
struct mbuf **
ip6_savecontrol_v4(struct inpcb *inp, struct mbuf *m, struct mbuf **mp,
    int *v4only)
{
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);

        if ((inp->inp_socket->so_options & SO_TIMESTAMP) != 0) {
                struct timeval tv;

                getmicrotime(&tv);
                mp = sbcreatecontrol_mbuf((caddr_t)&tv, sizeof (tv),
                    SCM_TIMESTAMP, SOL_SOCKET, mp);
                if (*mp == NULL)
                        return (NULL);
        }
        if ((inp->inp_socket->so_options & SO_TIMESTAMP_MONOTONIC) != 0) {
                uint64_t time;

                time = mach_absolute_time();
                mp = sbcreatecontrol_mbuf((caddr_t)&time, sizeof (time),
                    SCM_TIMESTAMP_MONOTONIC, SOL_SOCKET, mp);
                if (*mp == NULL)
                        return (NULL);
        }
        if ((inp->inp_socket->so_flags & SOF_RECV_TRAFFIC_CLASS) != 0) {
                int tc = m_get_traffic_class(m);

                mp = sbcreatecontrol_mbuf((caddr_t)&tc, sizeof (tc),
                    SO_TRAFFIC_CLASS, SOL_SOCKET, mp);
                if (*mp == NULL)
                        return (NULL);
        }

        if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
                if (v4only != NULL)
                        *v4only = 1;
                return (mp);
        }

#define IS2292(inp, x, y)       (((inp)->inp_flags & IN6P_RFC2292) ? (x) : (y))
        /* RFC 2292 sec. 5 */
        if ((inp->inp_flags & IN6P_PKTINFO) != 0) {
                struct in6_pktinfo pi6;

                bcopy(&ip6->ip6_dst, &pi6.ipi6_addr, sizeof (struct in6_addr));
                in6_clearscope(&pi6.ipi6_addr); /* XXX */
                pi6.ipi6_ifindex =
                    (m && m->m_pkthdr.rcvif) ? m->m_pkthdr.rcvif->if_index : 0;

                mp = sbcreatecontrol_mbuf((caddr_t)&pi6,
                    sizeof (struct in6_pktinfo),
                    IS2292(inp, IPV6_2292PKTINFO, IPV6_PKTINFO),
                    IPPROTO_IPV6, mp);
                if (*mp == NULL)
                        return (NULL);
        }

        if ((inp->inp_flags & IN6P_HOPLIMIT) != 0) {
                int hlim = ip6->ip6_hlim & 0xff;

                mp = sbcreatecontrol_mbuf((caddr_t)&hlim, sizeof (int),
                    IS2292(inp, IPV6_2292HOPLIMIT, IPV6_HOPLIMIT),
                    IPPROTO_IPV6, mp);
                if (*mp == NULL)
                        return (NULL);
        }

        if (v4only != NULL)
                *v4only = 0;
        return (mp);
}

int
ip6_savecontrol(struct inpcb *in6p, struct mbuf *m, struct mbuf **mp)
{
        struct mbuf **np;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        int v4only = 0;

        *mp = NULL;
        np = ip6_savecontrol_v4(in6p, m, mp, &v4only);
        if (np == NULL)
                goto no_mbufs;

        mp = np;
        if (v4only)
                return (0);

        if ((in6p->inp_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_mbuf((caddr_t)&tclass, sizeof (tclass),
                    IPV6_TCLASS, IPPROTO_IPV6, mp);
                if (*mp == NULL)
                        goto no_mbufs;
        }

        /*
         * 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 also RFC 2292 section 6 (or RFC 3542 section 8).
         */
        if ((in6p->inp_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 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;
                        hbh = (struct ip6_hbh *)(ip6 + 1);
                        hbhlen = (hbh->ip6h_len + 1) << 3;

                        /*
                         * XXX: We copy the whole header even if a
                         * jumbo payload option is included, the option which
                         * is to be removed before returning according to
                         * RFC2292.
                         * Note: this constraint is removed in RFC3542
                         */
                        mp = sbcreatecontrol_mbuf((caddr_t)hbh, hbhlen,
                            IS2292(in6p, IPV6_2292HOPOPTS, IPV6_HOPOPTS),
                            IPPROTO_IPV6, mp);

                        if (*mp == NULL) {
                                goto no_mbufs;
                        }
                }
        }

        if ((in6p->inp_flags & (IN6P_RTHDR | IN6P_DSTOPTS)) != 0) {
                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 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;
                        }

                        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;

                        switch (nxt) {
                        case IPPROTO_DSTOPTS:
                                if (!(in6p->inp_flags & IN6P_DSTOPTS))
                                        break;

                                mp = sbcreatecontrol_mbuf((caddr_t)ip6e, elen,
                                    IS2292(in6p, IPV6_2292DSTOPTS,
                                    IPV6_DSTOPTS), IPPROTO_IPV6, mp);
                                if (*mp == NULL) {
                                        goto no_mbufs;
                                }
                                break;
                        case IPPROTO_ROUTING:
                                if (!(in6p->inp_flags & IN6P_RTHDR))
                                        break;

                                mp = sbcreatecontrol_mbuf((caddr_t)ip6e, elen,
                                    IS2292(in6p, IPV6_2292RTHDR, IPV6_RTHDR),
                                    IPPROTO_IPV6, mp);
                                if (*mp == NULL) {
                                        goto no_mbufs;
                                }
                                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).
                                 */
                                goto loopend;

                        }

                        /* proceed with the next header. */
                        off += elen;
                        nxt = ip6e->ip6e_nxt;
                        ip6e = NULL;
                }
loopend:
                ;
        }
        return (0);
no_mbufs:
        ip6stat.ip6s_pktdropcntrl++;
        /* XXX increment a stat to show the failure */
        return (ENOBUFS);
}
#undef IS2292

void
ip6_notify_pmtu(struct inpcb *in6p, struct sockaddr_in6 *dst, u_int32_t *mtu)
{
        struct socket *so;
        struct mbuf *m_mtu;
        struct ip6_mtuinfo mtuctl;

        so =  in6p->inp_socket;

        if ((in6p->inp_flags & IN6P_MTU) == 0)
                return;

        if (mtu == NULL)
                return;

#ifdef DIAGNOSTIC
        if (so == NULL) {               /* I believe this is impossible */
                panic("ip6_notify_pmtu: socket is NULL");
                /* NOTREACHED */
        }
#endif

        if (IN6_IS_ADDR_UNSPECIFIED(&in6p->in6p_faddr) &&
            (so->so_proto == NULL || so->so_proto->pr_protocol == IPPROTO_TCP))
                return;

        if (!IN6_IS_ADDR_UNSPECIFIED(&in6p->in6p_faddr) &&
            !IN6_ARE_ADDR_EQUAL(&in6p->in6p_faddr, &dst->sin6_addr))
                return;

        bzero(&mtuctl, sizeof (mtuctl));        /* zero-clear for safety */
        mtuctl.ip6m_mtu = *mtu;
        mtuctl.ip6m_addr = *dst;
        if (sa6_recoverscope(&mtuctl.ip6m_addr, TRUE))
                return;

        if ((m_mtu = sbcreatecontrol((caddr_t)&mtuctl, sizeof (mtuctl),
            IPV6_PATHMTU, IPPROTO_IPV6)) == NULL)
                return;

        if (sbappendaddr(&so->so_rcv, SA(dst), NULL, m_mtu, NULL) == 0) {
                m_freem(m_mtu);
                /* XXX: should count statistics */
        } else {
                sorwakeup(so);
        }
}

/*
 * 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(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(struct mbuf *m, int off, int proto, int *nxtp)
{
        struct ip6_hdr ip6;
        struct ip6_ext ip6e;
        struct ip6_frag fh;

        /* just in case */
        VERIFY(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);
        }
}

/*
 * get offset for the last header in the chain.  m will be kept untainted.
 */
int
ip6_lasthdr(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_create(KERNEL_MODULE_TAG_ID, KERNEL_TAG_TYPE_INET6,
                    sizeof (struct ip6aux), M_DONTWAIT, m);

                /* 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_INET6, 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_INET6, NULL);
        if (tag) {
                m_tag_delete(m, tag);
        }
}

/*
 * Drain callback
 */
void
ip6_drain(void)
{
        frag6_drain();          /* fragments */
        in6_rtqdrain();         /* protocol cloned routes */
        nd6_drain(NULL);        /* cloned routes: ND6 */
}

/*
 * 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
};

static int
sysctl_reset_ip6_input_stats SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)
        int error, i;

        i = ip6_input_measure;
        error = sysctl_handle_int(oidp, &i, 0, req);
        if (error || req->newptr == USER_ADDR_NULL)
                goto done;
        /* impose bounds */
        if (i < 0 || i > 1) {
                error = EINVAL;
                goto done;
        }
        if (ip6_input_measure != i && i == 1) {
                net_perf_initialize(&net_perf, ip6_input_measure_bins);
        }
        ip6_input_measure = i;
done:
        return (error);
}

static int
sysctl_ip6_input_measure_bins SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)
        int error;
        uint64_t i;

        i = ip6_input_measure_bins;
        error = sysctl_handle_quad(oidp, &i, 0, req);
        if (error || req->newptr == USER_ADDR_NULL)
                goto done;
        /* validate data */
        if (!net_perf_validate_bins(i)) {
                error = EINVAL;
                goto done;
        }
        ip6_input_measure_bins = i;
done:
        return (error);
}

static int
sysctl_ip6_input_getperf SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        if (req->oldptr == USER_ADDR_NULL)
                req->oldlen = (size_t)sizeof (struct ipstat);

        return (SYSCTL_OUT(req, &net_perf, MIN(sizeof (net_perf), req->oldlen)));
}