root/sys/netinet6/icmp6.c
/*      $NetBSD: icmp6.c,v 1.259 2026/03/24 21:32:17 christos Exp $     */
/*      $KAME: icmp6.c,v 1.217 2001/06/20 15:03:29 jinmei 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. 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_icmp.c   8.2 (Berkeley) 1/4/94
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: icmp6.c,v 1.259 2026/03/24 21:32:17 christos Exp $");

#ifdef _KERNEL_OPT
#include "opt_compat_netbsd.h"
#include "opt_inet.h"
#include "opt_ipsec.h"
#endif

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

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

#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip6.h>
#include <netinet/wqinput.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6_private.h>
#include <netinet/icmp6.h>
#include <netinet6/icmp6_private.h>
#include <netinet6/mld6_var.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/in6_ifattach.h>
#include <netinet6/ip6protosw.h>
#include <netinet6/nd6.h>
#include <netinet6/scope6_var.h>

#ifdef IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/ipsec6.h>
#include <netipsec/key.h>
#endif

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

/* Ensure that non packed structures are the desired size. */
__CTASSERT(sizeof(struct icmp6_hdr) == 8);
__CTASSERT(sizeof(struct icmp6_nodeinfo) == 16);
__CTASSERT(sizeof(struct icmp6_namelookup) == 20);
__CTASSERT(sizeof(struct icmp6_router_renum) == 16);

__CTASSERT(sizeof(struct nd_router_solicit) == 8);
__CTASSERT(sizeof(struct nd_router_advert) == 16);
__CTASSERT(sizeof(struct nd_neighbor_solicit) == 24);
__CTASSERT(sizeof(struct nd_neighbor_advert) == 24);
__CTASSERT(sizeof(struct nd_redirect) == 40);
__CTASSERT(sizeof(struct nd_opt_hdr) == 2);
__CTASSERT(sizeof(struct nd_opt_route_info) == 8);
__CTASSERT(sizeof(struct nd_opt_prefix_info) == 32);
__CTASSERT(sizeof(struct nd_opt_rd_hdr) == 8);
__CTASSERT(sizeof(struct nd_opt_mtu) == 8);
__CTASSERT(sizeof(struct nd_opt_nonce) == 2 + ND_OPT_NONCE_LEN);
__CTASSERT(sizeof(struct nd_opt_rdnss) == 8);
__CTASSERT(sizeof(struct nd_opt_dnssl) == 8);

__CTASSERT(sizeof(struct mld_hdr) == 24);
__CTASSERT(sizeof(struct ni_reply_fqdn) == 8);
__CTASSERT(sizeof(struct rr_pco_match) == 24);
__CTASSERT(sizeof(struct rr_pco_use) == 32);
__CTASSERT(sizeof(struct rr_result) == 24);

extern struct domain inet6domain;

percpu_t *icmp6stat_percpu;

extern struct inpcbtable raw6cbtable;
extern int icmp6errppslim;
static int icmp6errpps_count = 0;
static struct timeval icmp6errppslim_last;
extern int icmp6_nodeinfo;

bool icmp6_dynamic_rt_msg = false;

/*
 * List of callbacks to notify when Path MTU changes are made.
 */
struct icmp6_mtudisc_callback {
        LIST_ENTRY(icmp6_mtudisc_callback) mc_list;
        void (*mc_func)(struct in6_addr *);
};

LIST_HEAD(, icmp6_mtudisc_callback) icmp6_mtudisc_callbacks =
    LIST_HEAD_INITIALIZER(&icmp6_mtudisc_callbacks);

static struct rttimer_queue *icmp6_mtudisc_timeout_q = NULL;
extern int pmtu_expire;

/* XXX do these values make any sense? */
static int icmp6_mtudisc_hiwat = 1280;
static int icmp6_mtudisc_lowat = 256;

/*
 * keep track of # of redirect routes.
 */
static struct rttimer_queue *icmp6_redirect_timeout_q = NULL;

/* XXX experimental, turned off */
static int icmp6_redirect_hiwat = -1;
static int icmp6_redirect_lowat = -1;

/* Protect mtudisc and redirect stuffs */
static kmutex_t icmp6_mtx __cacheline_aligned;

static bool icmp6_reflect_pmtu = false;

static void icmp6_errcount(u_int, int, int);
static int icmp6_rip6_input(struct mbuf **, int);
static void icmp6_reflect(struct mbuf *, size_t);
static int icmp6_ratelimit(const struct in6_addr *, const int, const int);
static const char *icmp6_redirect_diag(char *, size_t, struct in6_addr *,
    struct in6_addr *, struct in6_addr *);
static void icmp6_redirect_input(struct mbuf *, int);
static struct mbuf *ni6_input(struct mbuf *, int);
static struct mbuf *ni6_nametodns(const char *, int, int);
static int ni6_dnsmatch(const char *, int, const char *, int);
static int ni6_addrs(struct icmp6_nodeinfo *, struct ifnet **, char *,
    struct psref *);
static int ni6_store_addrs(struct icmp6_nodeinfo *, struct icmp6_nodeinfo *,
    struct ifnet *, int);
static int icmp6_notify_error(struct mbuf *, int, int, int);
static struct rtentry *icmp6_mtudisc_clone(struct sockaddr *);
static void icmp6_mtudisc_timeout(struct rtentry *, struct rttimer *);
static void icmp6_redirect_timeout(struct rtentry *, struct rttimer *);
static void sysctl_net_inet6_icmp6_setup(struct sysctllog **);

/* workqueue-based pr_input */
static struct wqinput *icmp6_wqinput;
static void _icmp6_input(struct mbuf *m, int off, int proto);

void
icmp6_init(void)
{

        sysctl_net_inet6_icmp6_setup(NULL);
        mld_init();

        mutex_init(&icmp6_mtx, MUTEX_DEFAULT, IPL_NONE);
        mutex_enter(&icmp6_mtx);
        icmp6_mtudisc_timeout_q = rt_timer_queue_create(pmtu_expire);
        icmp6_redirect_timeout_q = rt_timer_queue_create(icmp6_redirtimeout);
        mutex_exit(&icmp6_mtx);

        icmp6stat_percpu = percpu_alloc(sizeof(uint64_t) * ICMP6_NSTATS);

        icmp6_wqinput = wqinput_create("icmp6", _icmp6_input);
}

static void
icmp6_errcount(u_int base, int type, int code)
{
        switch (type) {
        case ICMP6_DST_UNREACH:
                switch (code) {
                case ICMP6_DST_UNREACH_NOROUTE:
                        ICMP6_STATINC(base + ICMP6_ERRSTAT_DST_UNREACH_NOROUTE);
                        return;
                case ICMP6_DST_UNREACH_ADMIN:
                        ICMP6_STATINC(base + ICMP6_ERRSTAT_DST_UNREACH_ADMIN);
                        return;
                case ICMP6_DST_UNREACH_BEYONDSCOPE:
                        ICMP6_STATINC(base +
                                      ICMP6_ERRSTAT_DST_UNREACH_BEYONDSCOPE);
                        return;
                case ICMP6_DST_UNREACH_ADDR:
                        ICMP6_STATINC(base + ICMP6_ERRSTAT_DST_UNREACH_ADDR);
                        return;
                case ICMP6_DST_UNREACH_NOPORT:
                        ICMP6_STATINC(base + ICMP6_ERRSTAT_DST_UNREACH_NOPORT);
                        return;
                }
                break;
        case ICMP6_PACKET_TOO_BIG:
                ICMP6_STATINC(base + ICMP6_ERRSTAT_PACKET_TOO_BIG);
                return;
        case ICMP6_TIME_EXCEEDED:
                switch (code) {
                case ICMP6_TIME_EXCEED_TRANSIT:
                        ICMP6_STATINC(base + ICMP6_ERRSTAT_TIME_EXCEED_TRANSIT);
                        return;
                case ICMP6_TIME_EXCEED_REASSEMBLY:
                        ICMP6_STATINC(base +
                                      ICMP6_ERRSTAT_TIME_EXCEED_REASSEMBLY);
                        return;
                }
                break;
        case ICMP6_PARAM_PROB:
                switch (code) {
                case ICMP6_PARAMPROB_HEADER:
                        ICMP6_STATINC(base + ICMP6_ERRSTAT_PARAMPROB_HEADER);
                        return;
                case ICMP6_PARAMPROB_NEXTHEADER:
                        ICMP6_STATINC(base +
                                      ICMP6_ERRSTAT_PARAMPROB_NEXTHEADER);
                        return;
                case ICMP6_PARAMPROB_OPTION:
                        ICMP6_STATINC(base + ICMP6_ERRSTAT_PARAMPROB_OPTION);
                        return;
                }
                break;
        case ND_REDIRECT:
                ICMP6_STATINC(base + ICMP6_ERRSTAT_REDIRECT);
                return;
        }
        ICMP6_STATINC(base + ICMP6_ERRSTAT_UNKNOWN);
}

/*
 * Register a Path MTU Discovery callback.
 */
void
icmp6_mtudisc_callback_register(void (*func)(struct in6_addr *))
{
        struct icmp6_mtudisc_callback *mc, *new;

        new = kmem_alloc(sizeof(*mc), KM_SLEEP);

        mutex_enter(&icmp6_mtx);
        for (mc = LIST_FIRST(&icmp6_mtudisc_callbacks); mc != NULL;
             mc = LIST_NEXT(mc, mc_list)) {
                if (mc->mc_func == func) {
                        mutex_exit(&icmp6_mtx);
                        kmem_free(new, sizeof(*mc));
                        return;
                }
        }

        new->mc_func = func;
        LIST_INSERT_HEAD(&icmp6_mtudisc_callbacks, new, mc_list);
        mutex_exit(&icmp6_mtx);
}

/*
 * A wrapper function for icmp6_error() necessary when the erroneous packet
 * may not contain enough scope zone information.
 */
void
icmp6_error2(struct mbuf *m, int type, int code, int param,
        struct ifnet *ifp, struct in6_addr *src)
{
        struct ip6_hdr *ip6;

        KASSERT(ifp != NULL);

        if (m->m_len < sizeof(struct ip6_hdr)) {
                m = m_pullup(m, sizeof(struct ip6_hdr));
                if (m == NULL)
                        return;
        }

        ip6 = mtod(m, struct ip6_hdr *);

        if (in6_setscope(&ip6->ip6_src, ifp, NULL) != 0)
                goto out;
        if (in6_setscope(&ip6->ip6_dst, ifp, NULL) != 0)
                goto out;

        *src = ip6->ip6_src;
        icmp6_error(m, type, code, param);
        return;

out:
        m_freem(m);
}

/*
 * Generate an error packet of type error in response to bad IP6 packet.
 */
void
icmp6_error(struct mbuf *m, int type, int code, int param)
{
        struct ip6_hdr *oip6, *nip6;
        struct icmp6_hdr *icmp6;
        u_int preplen;
        int off;
        int nxt;

        ICMP6_STATINC(ICMP6_STAT_ERROR);

        /* count per-type-code statistics */
        icmp6_errcount(ICMP6_STAT_OUTERRHIST, type, code);

        if (m->m_flags & M_DECRYPTED) {
                ICMP6_STATINC(ICMP6_STAT_CANTERROR);
                goto freeit;
        }

        if (M_UNWRITABLE(m, sizeof(struct ip6_hdr)) &&
            (m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL)
                return;
        oip6 = mtod(m, struct ip6_hdr *);

        /*
         * If the destination address of the erroneous packet is a multicast
         * address, or the packet was sent using link-layer multicast,
         * we should basically suppress sending an error (RFC 2463, Section
         * 2.4).
         * We have two exceptions (the item e.2 in that section):
         * - the Packet Too Big message can be sent for path MTU discovery.
         * - the Parameter Problem Message that can be allowed an icmp6 error
         *   in the option type field.  This check has been done in
         *   ip6_unknown_opt(), so we can just check the type and code.
         */
        if ((m->m_flags & (M_BCAST|M_MCAST) ||
             IN6_IS_ADDR_MULTICAST(&oip6->ip6_dst)) &&
            (type != ICMP6_PACKET_TOO_BIG &&
             (type != ICMP6_PARAM_PROB ||
              code != ICMP6_PARAMPROB_OPTION)))
                goto freeit;

        /*
         * RFC 2463, 2.4 (e.5): source address check.
         * XXX: the case of anycast source?
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&oip6->ip6_src) ||
            IN6_IS_ADDR_MULTICAST(&oip6->ip6_src))
                goto freeit;

        /*
         * If we are about to send ICMPv6 against ICMPv6 error/redirect,
         * don't do it.
         */
        nxt = -1;
        off = ip6_lasthdr(m, 0, IPPROTO_IPV6, &nxt);
        if (off >= 0 && nxt == IPPROTO_ICMPV6) {
                struct icmp6_hdr *icp;

                IP6_EXTHDR_GET(icp, struct icmp6_hdr *, m, off,
                        sizeof(*icp));
                if (icp == NULL) {
                        ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                        return;
                }
                if (icp->icmp6_type < ICMP6_ECHO_REQUEST ||
                    icp->icmp6_type == ND_REDIRECT) {
                        /*
                         * ICMPv6 error
                         * Special case: for redirect (which is
                         * informational) we must not send icmp6 error.
                         */
                        ICMP6_STATINC(ICMP6_STAT_CANTERROR);
                        goto freeit;
                } else {
                        /* ICMPv6 informational - send the error */
                }
        } else {
                /* non-ICMPv6 - send the error */
        }

        oip6 = mtod(m, struct ip6_hdr *); /* adjust pointer */

        /* Finally, do rate limitation check. */
        if (icmp6_ratelimit(&oip6->ip6_src, type, code)) {
                ICMP6_STATINC(ICMP6_STAT_TOOFREQ);
                goto freeit;
        }

        /*
         * OK, ICMP6 can be generated.
         */

        if (m->m_pkthdr.len >= ICMPV6_PLD_MAXLEN)
                m_adj(m, ICMPV6_PLD_MAXLEN - m->m_pkthdr.len);

        preplen = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
        M_PREPEND(m, preplen, M_DONTWAIT);
        if (m && M_UNWRITABLE(m, preplen))
                m = m_pullup(m, preplen);
        if (m == NULL) {
                nd6log(LOG_DEBUG, "ENOBUFS in icmp6_error %d\n", __LINE__);
                return;
        }

        nip6 = mtod(m, struct ip6_hdr *);
        nip6->ip6_src  = oip6->ip6_src;
        nip6->ip6_dst  = oip6->ip6_dst;

        in6_clearscope(&oip6->ip6_src);
        in6_clearscope(&oip6->ip6_dst);

        icmp6 = (struct icmp6_hdr *)(nip6 + 1);
        icmp6->icmp6_type = type;
        icmp6->icmp6_code = code;
        icmp6->icmp6_pptr = htonl((u_int32_t)param);

        /*
         * icmp6_reflect() is designed to be in the input path.
         * icmp6_error() can be called from both input and output path,
         * and if we are in output path rcvif could contain bogus value.
         * clear m->m_pkthdr.rcvif for safety, we should have enough scope
         * information in ip header (nip6).
         */
        m_reset_rcvif(m);

        ICMP6_STATINC(ICMP6_STAT_OUTHIST + type);

        /* header order: IPv6 - ICMPv6 */
        icmp6_reflect(m, sizeof(struct ip6_hdr));

        return;

freeit:
        /*
         * If we can't tell whether or not we can generate ICMP6, free it.
         */
        m_freem(m);
}

/*
 * Process a received ICMP6 message.
 */
static void
_icmp6_input(struct mbuf *m, int off, int proto)
{
        struct mbuf *n;
        struct ip6_hdr *ip6, *nip6;
        struct icmp6_hdr *icmp6, *nicmp6;
        int icmp6len = m->m_pkthdr.len - off;
        int code, sum;
        struct ifnet *rcvif;
        struct psref psref;
        char ip6buf[INET6_ADDRSTRLEN], ip6buf2[INET6_ADDRSTRLEN];

        rcvif = m_get_rcvif_psref(m, &psref);
        if (__predict_false(rcvif == NULL))
                goto freeit;

#define ICMP6_MAXLEN (sizeof(*nip6) + sizeof(*nicmp6) + 4)
        KASSERT(ICMP6_MAXLEN < MCLBYTES);
        icmp6_ifstat_inc(rcvif, ifs6_in_msg);

        /*
         * Locate icmp6 structure in mbuf, and check
         * that not corrupted and of at least minimum length
         */

        if (icmp6len < sizeof(struct icmp6_hdr)) {
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                icmp6_ifstat_inc(rcvif, ifs6_in_error);
                goto freeit;
        }

        if (m->m_len < sizeof(struct ip6_hdr)) {
                m = m_pullup(m, sizeof(struct ip6_hdr));
                if (m == NULL) {
                        ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                        icmp6_ifstat_inc(rcvif, ifs6_in_error);
                        goto freeit;
                }
        }

        ip6 = mtod(m, struct ip6_hdr *);
        IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, m, off, sizeof(*icmp6));
        if (icmp6 == NULL) {
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                icmp6_ifstat_inc(rcvif, ifs6_in_error);
                goto freeit;
        }

        /*
         * Enforce alignment requirements that are violated in
         * some cases, see kern/50766 for details.
         */
        if (ACCESSIBLE_POINTER(icmp6, struct ip6_hdr) == 0) {
                m = m_copyup(m, off + sizeof(struct icmp6_hdr), 0);
                if (m == NULL) {
                        ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                        icmp6_ifstat_inc(rcvif, ifs6_in_error);
                        goto freeit;
                }
                ip6 = mtod(m, struct ip6_hdr *);
                icmp6 = (struct icmp6_hdr *)(mtod(m, char *) + off);
        }
        KASSERT(ACCESSIBLE_POINTER(icmp6, struct ip6_hdr));

        /*
         * calculate the checksum
         */
        if ((sum = in6_cksum(m, IPPROTO_ICMPV6, off, icmp6len)) != 0) {
                nd6log(LOG_ERR, "ICMP6 checksum error(%d|%x) %s\n",
                    icmp6->icmp6_type, sum, IN6_PRINT(ip6buf, &ip6->ip6_src));
                ICMP6_STATINC(ICMP6_STAT_CHECKSUM);
                icmp6_ifstat_inc(rcvif, ifs6_in_error);
                goto freeit;
        }

#if defined(NFAITH) && 0 < NFAITH
        if (faithprefix(&ip6->ip6_dst)) {
                /*
                 * Deliver very specific ICMP6 type only.
                 * This is important to deliver TOOBIG.  Otherwise PMTUD
                 * will not work.
                 */
                switch (icmp6->icmp6_type) {
                case ICMP6_DST_UNREACH:
                case ICMP6_PACKET_TOO_BIG:
                case ICMP6_TIME_EXCEEDED:
                        break;
                default:
                        goto freeit;
                }
        }
#endif

        code = icmp6->icmp6_code;
        ICMP6_STATINC(ICMP6_STAT_INHIST + icmp6->icmp6_type);

        switch (icmp6->icmp6_type) {
        case ICMP6_DST_UNREACH:
                icmp6_ifstat_inc(rcvif, ifs6_in_dstunreach);
                switch (code) {
                case ICMP6_DST_UNREACH_NOROUTE:
                        code = PRC_UNREACH_NET;
                        break;
                case ICMP6_DST_UNREACH_ADMIN:
                        icmp6_ifstat_inc(rcvif, ifs6_in_adminprohib);
                        code = PRC_UNREACH_PROTOCOL; /* is this a good code? */
                        break;
                case ICMP6_DST_UNREACH_ADDR:
                        code = PRC_HOSTDEAD;
                        break;
                case ICMP6_DST_UNREACH_BEYONDSCOPE:
                        /* I mean "source address was incorrect." */
                        code = PRC_UNREACH_NET;
                        break;
                case ICMP6_DST_UNREACH_NOPORT:
                        code = PRC_UNREACH_PORT;
                        break;
                default:
                        goto badcode;
                }
                goto deliver;

        case ICMP6_PACKET_TOO_BIG:
                icmp6_ifstat_inc(rcvif, ifs6_in_pkttoobig);

                /*
                 * MTU is checked in icmp6_mtudisc.
                 */
                code = PRC_MSGSIZE;

                /*
                 * Updating the path MTU will be done after examining
                 * intermediate extension headers.
                 */
                goto deliver;

        case ICMP6_TIME_EXCEEDED:
                icmp6_ifstat_inc(rcvif, ifs6_in_timeexceed);
                switch (code) {
                case ICMP6_TIME_EXCEED_TRANSIT:
                        code = PRC_TIMXCEED_INTRANS;
                        break;
                case ICMP6_TIME_EXCEED_REASSEMBLY:
                        code = PRC_TIMXCEED_REASS;
                        break;
                default:
                        goto badcode;
                }
                goto deliver;

        case ICMP6_PARAM_PROB:
                icmp6_ifstat_inc(rcvif, ifs6_in_paramprob);
                switch (code) {
                case ICMP6_PARAMPROB_NEXTHEADER:
                        code = PRC_UNREACH_PROTOCOL;
                        break;
                case ICMP6_PARAMPROB_HEADER:
                case ICMP6_PARAMPROB_OPTION:
                        code = PRC_PARAMPROB;
                        break;
                default:
                        goto badcode;
                }
                goto deliver;

        case ICMP6_ECHO_REQUEST:
                icmp6_ifstat_inc(rcvif, ifs6_in_echo);
                if (code != 0)
                        goto badcode;
                /*
                 * Copy mbuf to send to two data paths: userland socket(s),
                 * and to the querier (echo reply).
                 * m: a copy for socket, n: a copy for querier
                 *
                 * If the first mbuf is shared, or the first mbuf is too short,
                 * copy the first part of the data into a fresh mbuf.
                 * Otherwise, we will wrongly overwrite both copies.
                 */
                if ((n = m_copypacket(m, M_DONTWAIT)) == NULL) {
                        /* Give up local */
                        n = m;
                        m = NULL;
                } else if (M_UNWRITABLE(n, off + sizeof(struct icmp6_hdr))) {
                        struct mbuf *n0 = n;

                        /*
                         * Prepare an internal mbuf.  m_pullup() doesn't
                         * always copy the length we specified.
                         */
                        if ((n = m_dup(n0, 0, M_COPYALL, M_DONTWAIT)) == NULL) {
                                /* Give up local */
                                n = m;
                                m = NULL;
                        }
                        m_freem(n0);
                }
                IP6_EXTHDR_GET(nicmp6, struct icmp6_hdr *, n, off,
                    sizeof(*nicmp6));
                if (nicmp6 == NULL)
                        goto freeit;
                nicmp6->icmp6_type = ICMP6_ECHO_REPLY;
                nicmp6->icmp6_code = 0;
                if (n) {
                        net_stat_ref_t icmp6s = ICMP6_STAT_GETREF();
                        _NET_STATINC_REF(icmp6s, ICMP6_STAT_REFLECT);
                        _NET_STATINC_REF(icmp6s,
                            ICMP6_STAT_OUTHIST + ICMP6_ECHO_REPLY);
                        ICMP6_STAT_PUTREF();
                        icmp6_reflect(n, off);
                }
                if (!m)
                        goto freeit;
                break;

        case ICMP6_ECHO_REPLY:
                icmp6_ifstat_inc(rcvif, ifs6_in_echoreply);
                if (code != 0)
                        goto badcode;
                break;

        case MLD_LISTENER_QUERY:
        case MLD_LISTENER_REPORT:
                if (icmp6len < sizeof(struct mld_hdr))
                        goto badlen;
                if (icmp6->icmp6_type == MLD_LISTENER_QUERY) /* XXX: ugly... */
                        icmp6_ifstat_inc(rcvif, ifs6_in_mldquery);
                else
                        icmp6_ifstat_inc(rcvif, ifs6_in_mldreport);
                if ((n = m_copypacket(m, M_DONTWAIT)) == NULL) {
                        /* give up local */
                        mld_input(m, off);
                        m = NULL;
                        goto freeit;
                }
                mld_input(n, off);
                /* m stays. */
                break;

        case MLD_LISTENER_DONE:
                icmp6_ifstat_inc(rcvif, ifs6_in_mlddone);
                if (icmp6len < sizeof(struct mld_hdr))  /* necessary? */
                        goto badlen;
                break;          /* nothing to be done in kernel */

        case MLD_MTRACE_RESP:
        case MLD_MTRACE:
                /* XXX: these two are experimental.  not officially defined. */
                /* XXX: per-interface statistics? */
                break;          /* just pass it to applications */

        case ICMP6_WRUREQUEST:  /* ICMP6_FQDN_QUERY */
            {
                enum { WRU, FQDN } mode;

                if (!icmp6_nodeinfo)
                        break;

                if (icmp6len == sizeof(struct icmp6_hdr) + 4)
                        mode = WRU;
                else if (icmp6len >= sizeof(struct icmp6_nodeinfo))
                        mode = FQDN;
                else
                        goto badlen;

                if (mode == FQDN) {
                        n = m_copypacket(m, M_DONTWAIT);
                        if (n)
                                n = ni6_input(n, off);
                } else {
                        u_char *p;
                        int maxhlen;

                        if ((icmp6_nodeinfo & 5) != 5)
                                break;

                        if (code != 0)
                                goto badcode;
                        MGETHDR(n, M_DONTWAIT, m->m_type);
                        if (n && ICMP6_MAXLEN > MHLEN) {
                                MCLGET(n, M_DONTWAIT);
                                if ((n->m_flags & M_EXT) == 0) {
                                        m_free(n);
                                        n = NULL;
                                }
                        }
                        if (n == NULL) {
                                /* Give up remote */
                                break;
                        }
                        m_reset_rcvif(n);
                        n->m_len = 0;
                        maxhlen = M_TRAILINGSPACE(n) - ICMP6_MAXLEN;
                        if (maxhlen < 0) {
                                m_free(n);
                                break;
                        }
                        if (maxhlen > hostnamelen)
                                maxhlen = hostnamelen;
                        /*
                         * Copy IPv6 and ICMPv6 only.
                         */
                        nip6 = mtod(n, struct ip6_hdr *);
                        memcpy(nip6, ip6, sizeof(struct ip6_hdr));
                        nicmp6 = (struct icmp6_hdr *)(nip6 + 1);
                        memcpy(nicmp6, icmp6, sizeof(struct icmp6_hdr));

                        p = (u_char *)(nicmp6 + 1);
                        memset(p, 0, 4);
                        memcpy(p + 4, hostname, maxhlen); /* meaningless TTL */

                        m_copy_pkthdr(n, m);
                        n->m_pkthdr.len = n->m_len = sizeof(struct ip6_hdr) +
                                sizeof(struct icmp6_hdr) + 4 + maxhlen;
                        nicmp6->icmp6_type = ICMP6_WRUREPLY;
                        nicmp6->icmp6_code = 0;
                }
                if (n) {
                        net_stat_ref_t icmp6s = ICMP6_STAT_GETREF();
                        _NET_STATINC_REF(icmp6s, ICMP6_STAT_REFLECT);
                        _NET_STATINC_REF(icmp6s,
                            ICMP6_STAT_OUTHIST + ICMP6_WRUREPLY);
                        ICMP6_STAT_PUTREF();
                        icmp6_reflect(n, sizeof(struct ip6_hdr));
                }
                break;
            }

        case ICMP6_WRUREPLY:
                if (code != 0)
                        goto badcode;
                break;

        case ND_ROUTER_SOLICIT:
                icmp6_ifstat_inc(rcvif, ifs6_in_routersolicit);
                /* FALLTHROUGH */
        case ND_ROUTER_ADVERT:
                if (icmp6->icmp6_type == ND_ROUTER_ADVERT)
                        icmp6_ifstat_inc(rcvif, ifs6_in_routeradvert);
                if (code != 0)
                        goto badcode;
                if ((icmp6->icmp6_type == ND_ROUTER_SOLICIT &&
                    icmp6len < sizeof(struct nd_router_solicit)) ||
                    (icmp6->icmp6_type == ND_ROUTER_ADVERT &&
                    icmp6len < sizeof(struct nd_router_advert)))
                        goto badlen;
                if ((n = m_copypacket(m, M_DONTWAIT)) == NULL) {
                        /* give up local */
                        nd6_rtr_cache(m, off, icmp6len, icmp6->icmp6_type);
                        m = NULL;
                        goto freeit;
                }
                nd6_rtr_cache(n, off, icmp6len, icmp6->icmp6_type);
                /* m stays. */
                break;

        case ND_NEIGHBOR_SOLICIT:
                icmp6_ifstat_inc(rcvif, ifs6_in_neighborsolicit);
                if (code != 0)
                        goto badcode;
                if (icmp6len < sizeof(struct nd_neighbor_solicit))
                        goto badlen;
                if ((n = m_copypacket(m, M_DONTWAIT)) == NULL) {
                        /* give up local */
                        nd6_ns_input(m, off, icmp6len);
                        m = NULL;
                        goto freeit;
                }
                nd6_ns_input(n, off, icmp6len);
                /* m stays. */
                break;

        case ND_NEIGHBOR_ADVERT:
                icmp6_ifstat_inc(rcvif, ifs6_in_neighboradvert);
                if (code != 0)
                        goto badcode;
                if (icmp6len < sizeof(struct nd_neighbor_advert))
                        goto badlen;
                if ((n = m_copypacket(m, M_DONTWAIT)) == NULL) {
                        /* give up local */
                        nd6_na_input(m, off, icmp6len);
                        m = NULL;
                        goto freeit;
                }
                nd6_na_input(n, off, icmp6len);
                /* m stays. */
                break;

        case ND_REDIRECT:
                icmp6_ifstat_inc(rcvif, ifs6_in_redirect);
                if (code != 0)
                        goto badcode;
                if (icmp6len < sizeof(struct nd_redirect))
                        goto badlen;
                if ((n = m_copypacket(m, M_DONTWAIT)) == NULL) {
                        /* give up local */
                        icmp6_redirect_input(m, off);
                        m = NULL;
                        goto freeit;
                }
                icmp6_redirect_input(n, off);
                /* m stays. */
                break;

        case ICMP6_ROUTER_RENUMBERING:
                if (code != ICMP6_ROUTER_RENUMBERING_COMMAND &&
                    code != ICMP6_ROUTER_RENUMBERING_RESULT)
                        goto badcode;
                if (icmp6len < sizeof(struct icmp6_router_renum))
                        goto badlen;
                break;

        default:
                nd6log(LOG_DEBUG,
                    "unknown type %d(src=%s, dst=%s, ifid=%d)\n",
                    icmp6->icmp6_type,
                    IN6_PRINT(ip6buf, &ip6->ip6_src),
                    IN6_PRINT(ip6buf2, &ip6->ip6_dst),
                    rcvif ? rcvif->if_index : 0);
                if (icmp6->icmp6_type < ICMP6_ECHO_REQUEST) {
                        /* ICMPv6 error: MUST deliver it by spec... */
                        code = PRC_NCMDS;
                        /* deliver */
                } else {
                        /* ICMPv6 informational: MUST not deliver */
                        break;
                }
        deliver:
                if (icmp6_notify_error(m, off, icmp6len, code)) {
                        /* In this case, m should've been freed. */
                        m_put_rcvif_psref(rcvif, &psref);
                        return;
                }
                break;

        badcode:
                ICMP6_STATINC(ICMP6_STAT_BADCODE);
                break;

        badlen:
                ICMP6_STATINC(ICMP6_STAT_BADLEN);
                break;
        }
        m_put_rcvif_psref(rcvif, &psref);

        /* deliver the packet to appropriate sockets */
        icmp6_rip6_input(&m, off);

        return;

freeit:
        m_put_rcvif_psref(rcvif, &psref);
        m_freem(m);
        return;
}

int
icmp6_input(struct mbuf **mp, int *offp, int proto)
{

        wqinput_input(icmp6_wqinput, *mp, *offp, proto);

        return IPPROTO_DONE;
}

static int
icmp6_notify_error(struct mbuf *m, int off, int icmp6len, int code)
{
        struct icmp6_hdr *icmp6;
        struct ip6_hdr *eip6;
        u_int32_t notifymtu;
        struct sockaddr_in6 icmp6src, icmp6dst;

        if (icmp6len < sizeof(struct icmp6_hdr) + sizeof(struct ip6_hdr)) {
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                goto freeit;
        }
        IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, m, off,
            sizeof(*icmp6) + sizeof(struct ip6_hdr));
        if (icmp6 == NULL) {
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                return (-1);
        }
        eip6 = (struct ip6_hdr *)(icmp6 + 1);

        /* Detect the upper level protocol */
        {
                void *(*ctlfunc)(int, const struct sockaddr *, void *);
                u_int8_t nxt = eip6->ip6_nxt;
                int eoff = off + sizeof(struct icmp6_hdr) +
                        sizeof(struct ip6_hdr);
                struct ip6ctlparam ip6cp;
                struct in6_addr *finaldst = NULL;
                int icmp6type = icmp6->icmp6_type;
                struct ip6_frag *fh;
                struct ip6_rthdr *rth;
                struct ifnet *rcvif;
                int s;

                while (1) { /* XXX: should avoid infinite loop explicitly? */
                        struct ip6_ext *eh;

                        switch (nxt) {
                        case IPPROTO_HOPOPTS:
                        case IPPROTO_DSTOPTS:
                        case IPPROTO_AH:
                                IP6_EXTHDR_GET(eh, struct ip6_ext *, m,
                                    eoff, sizeof(*eh));
                                if (eh == NULL) {
                                        ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                                        return (-1);
                                }

                                if (nxt == IPPROTO_AH)
                                        eoff += (eh->ip6e_len + 2) << 2;
                                else
                                        eoff += (eh->ip6e_len + 1) << 3;
                                nxt = eh->ip6e_nxt;
                                break;
                        case IPPROTO_ROUTING:
                                /* Ignore the option. */
                                IP6_EXTHDR_GET(rth, struct ip6_rthdr *, m,
                                    eoff, sizeof(*rth));
                                if (rth == NULL) {
                                        ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                                        return (-1);
                                }

                                eoff += (rth->ip6r_len + 1) << 3;
                                nxt = rth->ip6r_nxt;
                                break;
                        case IPPROTO_FRAGMENT:
                                IP6_EXTHDR_GET(fh, struct ip6_frag *, m,
                                    eoff, sizeof(*fh));
                                if (fh == NULL) {
                                        ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                                        return (-1);
                                }
                                /*
                                 * Data after a fragment header is meaningless
                                 * unless it is the first fragment, but
                                 * we'll go to the notify label for path MTU
                                 * discovery.
                                 */
                                if (fh->ip6f_offlg & IP6F_OFF_MASK)
                                        goto notify;

                                eoff += sizeof(struct ip6_frag);
                                nxt = fh->ip6f_nxt;
                                break;
                        default:
                                /*
                                 * This case includes ESP and the No Next
                                 * Header.  In such cases going to the notify
                                 * label does not have any meaning
                                 * (i.e. ctlfunc will be NULL), but we go
                                 * anyway since we might have to update
                                 * path MTU information.
                                 */
                                goto notify;
                        }
                }
          notify:
                IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, m, off,
                    sizeof(*icmp6) + sizeof(struct ip6_hdr));
                if (icmp6 == NULL) {
                        ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                        return (-1);
                }

                /*
                 * retrieve parameters from the inner IPv6 header, and convert
                 * them into sockaddr structures.
                 * XXX: there is no guarantee that the source or destination
                 * addresses of the inner packet are in the same scope zone as
                 * the addresses of the icmp packet.  But there is no other
                 * way to determine the zone.
                 */
                eip6 = (struct ip6_hdr *)(icmp6 + 1);

                rcvif = m_get_rcvif(m, &s);
                if (__predict_false(rcvif == NULL))
                        goto freeit;
                sockaddr_in6_init(&icmp6dst,
                    (finaldst == NULL) ? &eip6->ip6_dst : finaldst, 0, 0, 0);
                if (in6_setscope(&icmp6dst.sin6_addr, rcvif, NULL)) {
                        m_put_rcvif(rcvif, &s);
                        goto freeit;
                }
                sockaddr_in6_init(&icmp6src, &eip6->ip6_src, 0, 0, 0);
                if (in6_setscope(&icmp6src.sin6_addr, rcvif, NULL)) {
                        m_put_rcvif(rcvif, &s);
                        goto freeit;
                }
                m_put_rcvif(rcvif, &s);

                icmp6src.sin6_flowinfo =
                        (eip6->ip6_flow & IPV6_FLOWLABEL_MASK);

                if (finaldst == NULL)
                        finaldst = &eip6->ip6_dst;
                ip6cp.ip6c_m = m;
                ip6cp.ip6c_icmp6 = icmp6;
                ip6cp.ip6c_ip6 = (struct ip6_hdr *)(icmp6 + 1);
                ip6cp.ip6c_off = eoff;
                ip6cp.ip6c_finaldst = finaldst;
                ip6cp.ip6c_src = &icmp6src;
                ip6cp.ip6c_nxt = nxt;

                if (icmp6type == ICMP6_PACKET_TOO_BIG) {
                        notifymtu = ntohl(icmp6->icmp6_mtu);
                        ip6cp.ip6c_cmdarg = (void *)&notifymtu;
                }

                ctlfunc = inet6sw[ip6_protox[nxt]].pr_ctlinput;
                if (ctlfunc) {
                        (void)(*ctlfunc)(code, sin6tosa(&icmp6dst), &ip6cp);
                }
        }
        return (0);

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

void
icmp6_mtudisc_update(struct ip6ctlparam *ip6cp, int validated)
{
        unsigned long rtcount;
        struct icmp6_mtudisc_callback *mc;
        struct in6_addr *dst = ip6cp->ip6c_finaldst;
        struct icmp6_hdr *icmp6 = ip6cp->ip6c_icmp6;
        struct mbuf *m = ip6cp->ip6c_m; /* will be necessary for scope issue */
        u_int mtu = ntohl(icmp6->icmp6_mtu);
        struct rtentry *rt = NULL;
        struct sockaddr_in6 sin6;
        struct ifnet *rcvif;
        int s;

        /*
         * The MTU should not be less than the minimal IPv6 MTU except for the
         * hack in ip6_output/ip6_setpmtu where we always include a frag header.
         * In that one case, the MTU might be less than 1280.
         */
        if (__predict_false(mtu < IPV6_MMTU - sizeof(struct ip6_frag))) {
                /* is the mtu even sane? */
                if (mtu < sizeof(struct ip6_hdr) + sizeof(struct ip6_frag) + 8)
                        return;
                if (!validated)
                        return;
                mtu = IPV6_MMTU - sizeof(struct ip6_frag);
        }

        /*
         * allow non-validated cases if memory is plenty, to make traffic
         * from non-connected pcb happy.
         */
        mutex_enter(&icmp6_mtx);
        rtcount = rt_timer_count(icmp6_mtudisc_timeout_q);
        if (validated) {
                if (0 <= icmp6_mtudisc_hiwat && rtcount > icmp6_mtudisc_hiwat) {
                        mutex_exit(&icmp6_mtx);
                        return;
                } else if (0 <= icmp6_mtudisc_lowat &&
                    rtcount > icmp6_mtudisc_lowat) {
                        /*
                         * XXX nuke a victim, install the new one.
                         */
                }
        } else {
                if (0 <= icmp6_mtudisc_lowat && rtcount > icmp6_mtudisc_lowat) {
                        mutex_exit(&icmp6_mtx);
                        return;
                }
        }
        mutex_exit(&icmp6_mtx);

        memset(&sin6, 0, sizeof(sin6));
        sin6.sin6_family = PF_INET6;
        sin6.sin6_len = sizeof(struct sockaddr_in6);
        sin6.sin6_addr = *dst;
        rcvif = m_get_rcvif(m, &s);
        if (__predict_false(rcvif == NULL))
                return;
        if (in6_setscope(&sin6.sin6_addr, rcvif, NULL)) {
                m_put_rcvif(rcvif, &s);
                return;
        }
        m_put_rcvif(rcvif, &s);

        rt = icmp6_mtudisc_clone(sin6tosa(&sin6));

        if (rt && (rt->rt_flags & RTF_HOST) &&
            !(rt->rt_rmx.rmx_locks & RTV_MTU) &&
            (rt->rt_rmx.rmx_mtu > mtu || rt->rt_rmx.rmx_mtu == 0)) {
                if (mtu < rt->rt_ifp->if_mtu) {
                        ICMP6_STATINC(ICMP6_STAT_PMTUCHG);
                        rt->rt_rmx.rmx_mtu = mtu;
                }
        }
        if (rt) {
                rt_unref(rt);
        }

        /*
         * Notify protocols that the MTU for this destination
         * has changed.
         */
        mutex_enter(&icmp6_mtx);
        for (mc = LIST_FIRST(&icmp6_mtudisc_callbacks); mc != NULL;
             mc = LIST_NEXT(mc, mc_list))
                (*mc->mc_func)(&sin6.sin6_addr);
        mutex_exit(&icmp6_mtx);
}

/*
 * Process a Node Information Query packet, based on
 * draft-ietf-ipngwg-icmp-name-lookups-07.
 *
 * Spec incompatibilities:
 * - IPv6 Subject address handling
 * - IPv4 Subject address handling support missing
 * - Proxy reply (answer even if it's not for me)
 * - joins NI group address at in6_ifattach() time only, does not cope
 *   with hostname changes by sethostname(3)
 */
static struct mbuf *
ni6_input(struct mbuf *m, int off)
{
        struct icmp6_nodeinfo *ni6, *nni6;
        struct mbuf *n = NULL;
        u_int16_t qtype;
        int subjlen;
        int replylen = sizeof(struct ip6_hdr) + sizeof(struct icmp6_nodeinfo);
        struct ni_reply_fqdn *fqdn;
        int addrs;              /* for NI_QTYPE_NODEADDR */
        struct ifnet *ifp = NULL; /* for NI_QTYPE_NODEADDR */
        struct sockaddr_in6 sin6; /* ip6_dst */
        struct in6_addr in6_subj; /* subject address */
        struct ip6_hdr *ip6;
        int oldfqdn = 0;        /* if 1, return pascal string (03 draft) */
        char *subj = NULL;
        struct ifnet *rcvif;
        int s, ss;
        struct ifaddr *ifa;
        struct psref psref;

        ip6 = mtod(m, struct ip6_hdr *);
        IP6_EXTHDR_GET(ni6, struct icmp6_nodeinfo *, m, off, sizeof(*ni6));
        if (ni6 == NULL) {
                /* m is already reclaimed */
                return NULL;
        }
        KASSERT((m->m_flags & M_PKTHDR) != 0);

        /*
         * Validate IPv6 destination address.
         *
         * The Responder must discard the Query without further processing
         * unless it is one of the Responder's unicast or anycast addresses, or
         * a link-local scope multicast address which the Responder has joined.
         * [icmp-name-lookups-07, Section 4.]
         */
        sockaddr_in6_init(&sin6, &ip6->ip6_dst, 0, 0, 0);
        /* XXX scopeid */
        ss = pserialize_read_enter();
        ifa = ifa_ifwithaddr(sin6tosa(&sin6));
        if (ifa != NULL) {
                ; /* unicast/anycast, fine */
        } else if (IN6_IS_ADDR_MC_LINKLOCAL(&sin6.sin6_addr)) {
                ; /* link-local multicast, fine */
        } else {
                pserialize_read_exit(ss);
                goto bad;
        }
        pserialize_read_exit(ss);

        /* validate query Subject field. */
        qtype = ntohs(ni6->ni_qtype);
        subjlen = m->m_pkthdr.len - off - sizeof(struct icmp6_nodeinfo);
        switch (qtype) {
        case NI_QTYPE_NOOP:
        case NI_QTYPE_SUPTYPES:
                /* 07 draft */
                if (ni6->ni_code == ICMP6_NI_SUBJ_FQDN && subjlen == 0)
                        break;
                /* FALLTHROUGH */
        case NI_QTYPE_FQDN:
        case NI_QTYPE_NODEADDR:
        case NI_QTYPE_IPV4ADDR:
                switch (ni6->ni_code) {
                case ICMP6_NI_SUBJ_IPV6:
#if ICMP6_NI_SUBJ_IPV6 != 0
                case 0:
#endif
                        /*
                         * backward compatibility - try to accept 03 draft
                         * format, where no Subject is present.
                         */
                        if (qtype == NI_QTYPE_FQDN && ni6->ni_code == 0 &&
                            subjlen == 0) {
                                oldfqdn++;
                                break;
                        }
#if ICMP6_NI_SUBJ_IPV6 != 0
                        if (ni6->ni_code != ICMP6_NI_SUBJ_IPV6)
                                goto bad;
#endif

                        if (subjlen != sizeof(sin6.sin6_addr))
                                goto bad;

                        /*
                         * Validate Subject address.
                         *
                         * Not sure what exactly "address belongs to the node"
                         * means in the spec, is it just unicast, or what?
                         *
                         * At this moment we consider Subject address as
                         * "belong to the node" if the Subject address equals
                         * to the IPv6 destination address; validation for
                         * IPv6 destination address should have done enough
                         * check for us.
                         *
                         * We do not do proxy at this moment.
                         */
                        /* m_pulldown instead of copy? */
                        m_copydata(m, off + sizeof(struct icmp6_nodeinfo),
                            subjlen, (void *)&in6_subj);
                        rcvif = m_get_rcvif(m, &s);
                        if (__predict_false(rcvif == NULL))
                                goto bad;
                        if (in6_setscope(&in6_subj, rcvif, NULL)) {
                                m_put_rcvif(rcvif, &s);
                                goto bad;
                        }
                        m_put_rcvif(rcvif, &s);

                        subj = (char *)&in6_subj;
                        if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &in6_subj))
                                break;

                        /*
                         * XXX if we are to allow other cases, we should really
                         * be careful about scope here.
                         * basically, we should disallow queries toward IPv6
                         * destination X with subject Y, if scope(X) > scope(Y).
                         * if we allow scope(X) > scope(Y), it will result in
                         * information leakage across scope boundary.
                         */
                        goto bad;

                case ICMP6_NI_SUBJ_FQDN:
                        /*
                         * Validate Subject name with gethostname(3).
                         *
                         * The behavior may need some debate, since:
                         * - we are not sure if the node has FQDN as
                         *   hostname (returned by gethostname(3)).
                         * - the code does wildcard match for truncated names.
                         *   however, we are not sure if we want to perform
                         *   wildcard match, if gethostname(3) side has
                         *   truncated hostname.
                         */
                        n = ni6_nametodns(hostname, hostnamelen, 0);
                        if (!n || n->m_next || n->m_len == 0)
                                goto bad;
                        IP6_EXTHDR_GET(subj, char *, m,
                            off + sizeof(struct icmp6_nodeinfo), subjlen);
                        if (subj == NULL)
                                goto bad;
                        if (!ni6_dnsmatch(subj, subjlen, mtod(n, const char *),
                            n->m_len)) {
                                goto bad;
                        }
                        m_freem(n);
                        n = NULL;
                        break;

                case ICMP6_NI_SUBJ_IPV4:        /* XXX: to be implemented? */
                default:
                        goto bad;
                }
                break;
        }

        /* refuse based on configuration.  XXX ICMP6_NI_REFUSED? */
        switch (qtype) {
        case NI_QTYPE_FQDN:
                if ((icmp6_nodeinfo & 1) == 0)
                        goto bad;
                break;
        case NI_QTYPE_NODEADDR:
        case NI_QTYPE_IPV4ADDR:
                if ((icmp6_nodeinfo & 2) == 0)
                        goto bad;
                break;
        }

        /* guess reply length */
        switch (qtype) {
        case NI_QTYPE_NOOP:
                break;          /* no reply data */
        case NI_QTYPE_SUPTYPES:
                replylen += sizeof(u_int32_t);
                break;
        case NI_QTYPE_FQDN:
                /* will append an mbuf */
                replylen += offsetof(struct ni_reply_fqdn, ni_fqdn_namelen);
                break;
        case NI_QTYPE_NODEADDR:
                addrs = ni6_addrs(ni6, &ifp, subj, &psref);
                replylen += addrs *
                    (sizeof(struct in6_addr) + sizeof(u_int32_t));
                if (replylen > MCLBYTES)
                        replylen = MCLBYTES; /* XXX: will truncate pkt later */
                break;
        case NI_QTYPE_IPV4ADDR:
                /* unsupported - should respond with unknown Qtype? */
                goto bad;
        default:
                /*
                 * XXX: We must return a reply with the ICMP6 code
                 * `unknown Qtype' in this case.  However we regard the case
                 * as an FQDN query for backward compatibility.
                 * Older versions set a random value to this field,
                 * so it rarely varies in the defined qtypes.
                 * But the mechanism is not reliable...
                 * maybe we should obsolete older versions.
                 */
                qtype = NI_QTYPE_FQDN;
                /* will append an mbuf */
                replylen += offsetof(struct ni_reply_fqdn, ni_fqdn_namelen);
                oldfqdn++;
                break;
        }

        /* allocate an mbuf to reply. */
        MGETHDR(n, M_DONTWAIT, m->m_type);
        if (n == NULL) {
                goto bad;
        }
        m_move_pkthdr(n, m);
        if (replylen > MHLEN) {
                if (replylen > MCLBYTES) {
                        /*
                         * XXX: should we try to allocate more? But MCLBYTES
                         * is probably much larger than IPV6_MMTU...
                         */
                        goto bad;
                }
                MCLGET(n, M_DONTWAIT);
                if ((n->m_flags & M_EXT) == 0) {
                        goto bad;
                }
        }
        n->m_pkthdr.len = n->m_len = replylen;

        /* copy mbuf header and IPv6 + Node Information base headers */
        bcopy(mtod(m, void *), mtod(n, void *), sizeof(struct ip6_hdr));
        nni6 = (struct icmp6_nodeinfo *)(mtod(n, struct ip6_hdr *) + 1);
        bcopy((void *)ni6, (void *)nni6, sizeof(struct icmp6_nodeinfo));

        /* qtype dependent procedure */
        switch (qtype) {
        case NI_QTYPE_NOOP:
                nni6->ni_code = ICMP6_NI_SUCCESS;
                nni6->ni_flags = 0;
                break;
        case NI_QTYPE_SUPTYPES:
        {
                u_int32_t v;
                nni6->ni_code = ICMP6_NI_SUCCESS;
                nni6->ni_flags = htons(0x0000); /* raw bitmap */
                /* supports NOOP, SUPTYPES, FQDN, and NODEADDR */
                v = (u_int32_t)htonl(0x0000000f);
                memcpy(nni6 + 1, &v, sizeof(u_int32_t));
                break;
        }
        case NI_QTYPE_FQDN:
                nni6->ni_code = ICMP6_NI_SUCCESS;
                fqdn = (struct ni_reply_fqdn *)(mtod(n, char *) +
                    sizeof(struct ip6_hdr) + sizeof(struct icmp6_nodeinfo));
                nni6->ni_flags = 0; /* XXX: meaningless TTL */
                fqdn->ni_fqdn_ttl = 0;  /* ditto. */
                /*
                 * XXX do we really have FQDN in variable "hostname"?
                 */
                n->m_next = ni6_nametodns(hostname, hostnamelen, oldfqdn);
                if (n->m_next == NULL)
                        goto bad;
                /* XXX we assume that n->m_next is not a chain */
                if (n->m_next->m_next != NULL)
                        goto bad;
                n->m_pkthdr.len += n->m_next->m_len;
                break;
        case NI_QTYPE_NODEADDR:
        {
                int lenlim, copied;

                nni6->ni_code = ICMP6_NI_SUCCESS;
                n->m_pkthdr.len = n->m_len = sizeof(struct ip6_hdr) +
                    sizeof(struct icmp6_nodeinfo);
                lenlim = M_TRAILINGSPACE(n);
                copied = ni6_store_addrs(ni6, nni6, ifp, lenlim);
                if_put(ifp, &psref);
                ifp = NULL;
                /* update mbuf length */
                n->m_pkthdr.len = n->m_len = sizeof(struct ip6_hdr) +
                    sizeof(struct icmp6_nodeinfo) + copied;
                break;
        }
        default:
                panic("%s: impossible", __func__);
                break;
        }

        nni6->ni_type = ICMP6_NI_REPLY;
        m_freem(m);
        return n;

bad:
        if_put(ifp, &psref);
        m_freem(m);
        m_freem(n);
        return NULL;
}

#define isupper(x) ('A' <= (x) && (x) <= 'Z')
#define isalpha(x) (('A' <= (x) && (x) <= 'Z') || ('a' <= (x) && (x) <= 'z'))
#define isalnum(x) (isalpha(x) || ('0' <= (x) && (x) <= '9'))
#define tolower(x) (isupper(x) ? (x) + 'a' - 'A' : (x))

/*
 * make a mbuf with DNS-encoded string.  no compression support.
 *
 * XXX names with less than 2 dots (like "foo" or "foo.section") will be
 * treated as truncated name (two \0 at the end).  this is a wild guess.
 *
 * old - return pascal string if non-zero
 */
static struct mbuf *
ni6_nametodns(const char *name, int namelen, int old)
{
        struct mbuf *m;
        char *cp, *ep;
        const char *p, *q;
        int i, len, nterm;

        if (old)
                len = namelen + 1;
        else
                len = MCLBYTES;

        /* because MAXHOSTNAMELEN is usually 256, we use cluster mbuf */
        MGET(m, M_DONTWAIT, MT_DATA);
        if (m && len > MLEN) {
                MCLGET(m, M_DONTWAIT);
                if ((m->m_flags & M_EXT) == 0)
                        goto fail;
        }
        if (!m)
                goto fail;
        m->m_next = NULL;

        if (old) {
                m->m_len = len;
                *mtod(m, char *) = namelen;
                memcpy(mtod(m, char *) + 1, name, namelen);
                return m;
        } else {
                m->m_len = 0;
                cp = mtod(m, char *);
                ep = mtod(m, char *) + M_TRAILINGSPACE(m);

                /* if not certain about my name, return empty buffer */
                if (namelen == 0)
                        return m;

                /*
                 * guess if it looks like shortened hostname, or FQDN.
                 * shortened hostname needs two trailing "\0".
                 */
                i = 0;
                for (p = name; p < name + namelen; p++) {
                        if (*p == '.')
                                i++;
                }
                if (i < 2)
                        nterm = 2;
                else
                        nterm = 1;

                p = name;
                while (cp < ep && p < name + namelen) {
                        i = 0;
                        for (q = p; q < name + namelen && *q && *q != '.'; q++)
                                i++;
                        /* result does not fit into mbuf */
                        if (cp + i + 1 >= ep)
                                goto fail;
                        /*
                         * DNS label length restriction, RFC1035 page 8.
                         * "i == 0" case is included here to avoid returning
                         * 0-length label on "foo..bar".
                         */
                        if (i <= 0 || i >= 64)
                                goto fail;
                        *cp++ = i;
                        if (!isalpha(p[0]) || !isalnum(p[i - 1]))
                                goto fail;
                        while (i > 0) {
                                if (!isalnum(*p) && *p != '-')
                                        goto fail;
                                if (isupper(*p)) {
                                        *cp++ = tolower(*p);
                                        p++;
                                } else
                                        *cp++ = *p++;
                                i--;
                        }
                        p = q;
                        if (p < name + namelen && *p == '.')
                                p++;
                }
                /* termination */
                if (cp + nterm >= ep)
                        goto fail;
                while (nterm-- > 0)
                        *cp++ = '\0';
                m->m_len = cp - mtod(m, char *);
                return m;
        }

        panic("should not reach here");
        /* NOTREACHED */

fail:
        m_freem(m);
        return NULL;
}

/*
 * check if two DNS-encoded string matches.  takes care of truncated
 * form (with \0\0 at the end).  no compression support.
 * XXX upper/lowercase match (see RFC2065)
 */
static int
ni6_dnsmatch(const char *a, int alen, const char *b, int blen)
{
        const char *a0, *b0;
        int l;

        /* simplest case - need validation? */
        if (alen == blen && memcmp(a, b, alen) == 0)
                return 1;

        a0 = a;
        b0 = b;

        /* termination is mandatory */
        if (alen < 2 || blen < 2)
                return 0;
        if (a0[alen - 1] != '\0' || b0[blen - 1] != '\0')
                return 0;
        alen--;
        blen--;

        while (a - a0 < alen && b - b0 < blen) {
                if (a - a0 + 1 > alen || b - b0 + 1 > blen)
                        return 0;

                if ((signed char)a[0] < 0 || (signed char)b[0] < 0)
                        return 0;
                /* we don't support compression yet */
                if (a[0] >= 64 || b[0] >= 64)
                        return 0;

                /* truncated case */
                if (a[0] == 0 && a - a0 == alen - 1)
                        return 1;
                if (b[0] == 0 && b - b0 == blen - 1)
                        return 1;
                if (a[0] == 0 || b[0] == 0)
                        return 0;

                if (a[0] != b[0])
                        return 0;
                l = a[0];
                if (a - a0 + 1 + l > alen || b - b0 + 1 + l > blen)
                        return 0;
                if (memcmp(a + 1, b + 1, l) != 0)
                        return 0;

                a += 1 + l;
                b += 1 + l;
        }

        if (a - a0 == alen && b - b0 == blen)
                return 1;
        else
                return 0;
}

/*
 * calculate the number of addresses to be returned in the node info reply.
 */
static int
ni6_addrs(struct icmp6_nodeinfo *ni6, struct ifnet **ifpp, char *subj,
    struct psref *psref)
{
        struct ifnet *ifp;
        struct in6_ifaddr *ia6;
        struct ifaddr *ifa;
        struct sockaddr_in6 *subj_ip6 = NULL; /* XXX pedant */
        int addrs = 0, addrsofif, iffound = 0;
        int niflags = ni6->ni_flags;
        int s;

        if ((niflags & NI_NODEADDR_FLAG_ALL) == 0) {
                switch (ni6->ni_code) {
                case ICMP6_NI_SUBJ_IPV6:
                        if (subj == NULL) /* must be impossible... */
                                return 0;
                        subj_ip6 = (struct sockaddr_in6 *)subj;
                        break;
                default:
                        /*
                         * XXX: we only support IPv6 subject address for
                         * this Qtype.
                         */
                        return 0;
                }
        }

        s = pserialize_read_enter();
        IFNET_READER_FOREACH(ifp) {
                addrsofif = 0;
                IFADDR_READER_FOREACH(ifa, ifp) {
                        if (ifa->ifa_addr->sa_family != AF_INET6)
                                continue;
                        ia6 = (struct in6_ifaddr *)ifa;

                        if ((niflags & NI_NODEADDR_FLAG_ALL) == 0 &&
                            IN6_ARE_ADDR_EQUAL(&subj_ip6->sin6_addr,
                             &ia6->ia_addr.sin6_addr))
                                iffound = 1;

                        /*
                         * IPv4-mapped addresses can only be returned by a
                         * Node Information proxy, since they represent
                         * addresses of IPv4-only nodes, which perforce do
                         * not implement this protocol.
                         * [icmp-name-lookups-07, Section 5.4]
                         * So we don't support NI_NODEADDR_FLAG_COMPAT in
                         * this function at this moment.
                         */

                        /* What do we have to do about ::1? */
                        switch (in6_addrscope(&ia6->ia_addr.sin6_addr)) {
                        case IPV6_ADDR_SCOPE_LINKLOCAL:
                                if ((niflags & NI_NODEADDR_FLAG_LINKLOCAL) == 0)
                                        continue;
                                break;
                        case IPV6_ADDR_SCOPE_SITELOCAL:
                                if ((niflags & NI_NODEADDR_FLAG_SITELOCAL) == 0)
                                        continue;
                                break;
                        case IPV6_ADDR_SCOPE_GLOBAL:
                                if ((niflags & NI_NODEADDR_FLAG_GLOBAL) == 0)
                                        continue;
                                break;
                        default:
                                continue;
                        }

                        /*
                         * check if anycast is okay.
                         * XXX: just experimental.  not in the spec.
                         */
                        if ((ia6->ia6_flags & IN6_IFF_ANYCAST) != 0 &&
                            (niflags & NI_NODEADDR_FLAG_ANYCAST) == 0)
                                continue; /* we need only unicast addresses */

                        addrsofif++; /* count the address */
                }
                if (iffound) {
                        if_acquire(ifp, psref);
                        pserialize_read_exit(s);
                        *ifpp = ifp;
                        return addrsofif;
                }

                addrs += addrsofif;
        }
        pserialize_read_exit(s);

        return addrs;
}

static int
ni6_store_addrs(struct icmp6_nodeinfo *ni6,
        struct icmp6_nodeinfo *nni6, struct ifnet *ifp0,
        int resid)
{
        struct ifnet *ifp;
        struct in6_ifaddr *ia6;
        struct ifaddr *ifa;
        struct ifnet *ifp_dep = NULL;
        int copied = 0, allow_deprecated = 0;
        u_char *cp = (u_char *)(nni6 + 1);
        int niflags = ni6->ni_flags;
        u_int32_t ltime;
        int s;

        if (ifp0 == NULL && !(niflags & NI_NODEADDR_FLAG_ALL))
                return 0;       /* needless to copy */

        s = pserialize_read_enter();
        ifp = ifp0 ? ifp0 : IFNET_READER_FIRST();
again:

        for (; ifp; ifp = IFNET_READER_NEXT(ifp))
        {
                IFADDR_READER_FOREACH(ifa, ifp) {
                        if (ifa->ifa_addr->sa_family != AF_INET6)
                                continue;
                        ia6 = (struct in6_ifaddr *)ifa;

                        if ((ia6->ia6_flags & IN6_IFF_DEPRECATED) != 0 &&
                            allow_deprecated == 0) {
                                /*
                                 * prefererred address should be put before
                                 * deprecated addresses.
                                 */

                                /* record the interface for later search */
                                if (ifp_dep == NULL)
                                        ifp_dep = ifp;

                                continue;
                        }
                        else if ((ia6->ia6_flags & IN6_IFF_DEPRECATED) == 0 &&
                                 allow_deprecated != 0)
                                continue; /* we now collect deprecated addrs */

                        /* What do we have to do about ::1? */
                        switch (in6_addrscope(&ia6->ia_addr.sin6_addr)) {
                        case IPV6_ADDR_SCOPE_LINKLOCAL:
                                if ((niflags & NI_NODEADDR_FLAG_LINKLOCAL) == 0)
                                        continue;
                                break;
                        case IPV6_ADDR_SCOPE_SITELOCAL:
                                if ((niflags & NI_NODEADDR_FLAG_SITELOCAL) == 0)
                                        continue;
                                break;
                        case IPV6_ADDR_SCOPE_GLOBAL:
                                if ((niflags & NI_NODEADDR_FLAG_GLOBAL) == 0)
                                        continue;
                                break;
                        default:
                                continue;
                        }

                        /*
                         * check if anycast is okay.
                         * XXX: just experimental.  not in the spec.
                         */
                        if ((ia6->ia6_flags & IN6_IFF_ANYCAST) != 0 &&
                            (niflags & NI_NODEADDR_FLAG_ANYCAST) == 0)
                                continue;

                        /* now we can copy the address */
                        if (resid < sizeof(struct in6_addr) +
                            sizeof(u_int32_t)) {
                                /*
                                 * We give up much more copy.
                                 * Set the truncate flag and return.
                                 */
                                nni6->ni_flags |= NI_NODEADDR_FLAG_TRUNCATE;
                                goto out;
                        }

                        /*
                         * Set the TTL of the address.
                         * The TTL value should be one of the following
                         * according to the specification:
                         *
                         * 1. The remaining lifetime of a DHCP lease on the
                         *    address, or
                         * 2. The remaining Valid Lifetime of a prefix from
                         *    which the address was derived through Stateless
                         *    Autoconfiguration.
                         *
                         * Note that we currently do not support stateful
                         * address configuration by DHCPv6, so the former
                         * case can't happen.
                         *
                         * TTL must be 2^31 > TTL >= 0.
                         */
                        if (ia6->ia6_lifetime.ia6t_expire == 0)
                                ltime = ND6_INFINITE_LIFETIME;
                        else {
                                if (ia6->ia6_lifetime.ia6t_expire >
                                    time_uptime)
                                        ltime = ia6->ia6_lifetime.ia6t_expire -
                                            time_uptime;
                                else
                                        ltime = 0;
                        }
                        if (ltime > 0x7fffffff)
                                ltime = 0x7fffffff;
                        ltime = htonl(ltime);

                        memcpy(cp, &ltime, sizeof(u_int32_t));
                        cp += sizeof(u_int32_t);

                        /* copy the address itself */
                        bcopy(&ia6->ia_addr.sin6_addr, cp,
                              sizeof(struct in6_addr));
                        in6_clearscope((struct in6_addr *)cp); /* XXX */
                        cp += sizeof(struct in6_addr);

                        resid -= (sizeof(struct in6_addr) + sizeof(u_int32_t));
                        copied += (sizeof(struct in6_addr) + sizeof(u_int32_t));
                }
                if (ifp0)       /* we need search only on the specified IF */
                        break;
        }

        if (allow_deprecated == 0 && ifp_dep != NULL) {
                ifp = ifp_dep;
                allow_deprecated = 1;

                goto again;
        }
out:
        pserialize_read_exit(s);
        return copied;
}

/*
 * XXX almost dup'ed code with rip6_input.
 */
static int
icmp6_rip6_input(struct mbuf **mp, int off)
{
        struct mbuf *m = *mp;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct inpcb *inp;
        struct inpcb *last = NULL;
        struct sockaddr_in6 rip6src;
        struct icmp6_hdr *icmp6;
        struct mbuf *n, *opts = NULL;

        IP6_EXTHDR_GET(icmp6, struct icmp6_hdr *, m, off, sizeof(*icmp6));
        if (icmp6 == NULL) {
                /* m is already reclaimed */
                return IPPROTO_DONE;
        }

        /*
         * XXX: the address may have embedded scope zone ID, which should be
         * hidden from applications.
         */
        sockaddr_in6_init(&rip6src, &ip6->ip6_src, 0, 0, 0);
        if (sa6_recoverscope(&rip6src)) {
                m_freem(m);
                return IPPROTO_DONE;
        }

        TAILQ_FOREACH(inp, &raw6cbtable.inpt_queue, inp_queue) {
                if (inp->inp_af != AF_INET6)
                        continue;
                if (in6p_ip6(inp).ip6_nxt != IPPROTO_ICMPV6)
                        continue;
                if (!IN6_IS_ADDR_UNSPECIFIED(&in6p_laddr(inp)) &&
                    !IN6_ARE_ADDR_EQUAL(&in6p_laddr(inp), &ip6->ip6_dst))
                        continue;
                if (!IN6_IS_ADDR_UNSPECIFIED(&in6p_faddr(inp)) &&
                    !IN6_ARE_ADDR_EQUAL(&in6p_faddr(inp), &ip6->ip6_src))
                        continue;
                if (in6p_icmp6filt(inp) &&
                    ICMP6_FILTER_WILLBLOCK(icmp6->icmp6_type,
                    in6p_icmp6filt(inp)))
                        continue;

                if (last == NULL) {
                        ;
                }
#ifdef IPSEC
                else if (ipsec_used && ipsec_in_reject(m, last)) {
                        /* do not inject data into pcb */
                }
#endif
                else if ((n = m_copypacket(m, M_DONTWAIT)) != NULL) {
                        if (last->inp_flags & IN6P_CONTROLOPTS ||
                            SOOPT_TIMESTAMP(last->inp_socket->so_options))
                                ip6_savecontrol(last, &opts, ip6, n);
                        /* strip intermediate headers */
                        m_adj(n, off);
                        if (sbappendaddr(&last->inp_socket->so_rcv,
                            sin6tosa(&rip6src), n, opts) == 0) {
                                soroverflow(last->inp_socket);
                                m_freem(n);
                                m_freem(opts);
                        } else {
                                sorwakeup(last->inp_socket);
                        }
                        opts = NULL;
                }

                last = inp;
        }

#ifdef IPSEC
        if (ipsec_used && last && ipsec_in_reject(m, last)) {
                m_freem(m);
                IP6_STATDEC(IP6_STAT_DELIVERED);
                /* do not inject data into pcb */
        } else
#endif
        if (last) {
                if (last->inp_flags & IN6P_CONTROLOPTS ||
                    SOOPT_TIMESTAMP(last->inp_socket->so_options))
                        ip6_savecontrol(last, &opts, ip6, m);
                /* strip intermediate headers */
                m_adj(m, off);
                if (sbappendaddr(&last->inp_socket->so_rcv,
                    sin6tosa(&rip6src), m, opts) == 0) {
                        soroverflow(last->inp_socket);
                        m_freem(m);
                        m_freem(opts);
                } else {
                        sorwakeup(last->inp_socket);
                }
        } else {
                m_freem(m);
                IP6_STATDEC(IP6_STAT_DELIVERED);
        }
        return IPPROTO_DONE;
}

/*
 * Reflect the ip6 packet back to the source.
 * OFF points to the icmp6 header, counted from the top of the mbuf.
 *
 * Note: RFC 1885 required that an echo reply should be truncated if it
 * did not fit in with (return) path MTU, and KAME code supported the
 * behavior.  However, as a clarification after the RFC, this limitation
 * was removed in a revised version of the spec, RFC 2463.  We had kept the
 * old behavior, with a (non-default) ifdef block, while the new version of
 * the spec was an internet-draft status, and even after the new RFC was
 * published.  But it would rather make sense to clean the obsoleted part
 * up, and to make the code simpler at this stage.
 */
static void
icmp6_reflect(struct mbuf *m, size_t off)
{
        struct ip6_hdr *ip6;
        struct icmp6_hdr *icmp6;
        const struct in6_ifaddr *ia;
        const struct ip6aux *ip6a;
        int plen;
        int type, code;
        struct ifnet *outif = NULL;
        struct in6_addr origdst;
        struct ifnet *rcvif;
        int s;
        bool ip6_src_filled = false;
        int flags;

        /* too short to reflect */
        if (off < sizeof(struct ip6_hdr)) {
                nd6log(LOG_DEBUG,
                    "sanity fail: off=%lx, sizeof(ip6)=%lx in %s:%d\n",
                    (u_long)off, (u_long)sizeof(struct ip6_hdr),
                    __FILE__, __LINE__);
                goto bad;
        }

        /*
         * If there are extra headers between IPv6 and ICMPv6, strip
         * off that header first.
         */
        CTASSERT(sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr) <= MHLEN);
        if (off > sizeof(struct ip6_hdr)) {
                size_t l;
                struct ip6_hdr nip6;

                l = off - sizeof(struct ip6_hdr);
                m_copydata(m, 0, sizeof(nip6), (void *)&nip6);
                m_adj(m, l);
                l = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
                if (m->m_len < l) {
                        if ((m = m_pullup(m, l)) == NULL)
                                return;
                }
                memcpy(mtod(m, void *), (void *)&nip6, sizeof(nip6));
        } else {
                size_t l = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
                if (m->m_len < l) {
                        if ((m = m_pullup(m, l)) == NULL)
                                return;
                }
        }

        plen = m->m_pkthdr.len - sizeof(struct ip6_hdr);
        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        icmp6 = (struct icmp6_hdr *)(ip6 + 1);
        type = icmp6->icmp6_type; /* keep type for statistics */
        code = icmp6->icmp6_code; /* ditto. */

        origdst = ip6->ip6_dst;
        /*
         * ip6_input() drops a packet if its src is multicast.
         * So, the src is never multicast.
         */
        ip6->ip6_dst = ip6->ip6_src;

        /*
         * If the incoming packet was addressed directly to us (i.e. unicast),
         * use dst as the src for the reply.
         * The IN6_IFF_NOTREADY case should be VERY rare, but is possible
         * (for example) when we encounter an error while forwarding procedure
         * destined to a duplicated address of ours.
         * Note that ip6_getdstifaddr() may fail if we are in an error handling
         * procedure of an outgoing packet of our own, in which case we need
         * to search in the ifaddr list.
         */
        if (IN6_IS_ADDR_MULTICAST(&origdst)) {
                ;
        } else if ((ip6a = ip6_getdstifaddr(m)) != NULL) {
                if ((ip6a->ip6a_flags &
                     (IN6_IFF_ANYCAST|IN6_IFF_NOTREADY)) == 0) {
                        ip6->ip6_src = ip6a->ip6a_src;
                        ip6_src_filled = true;
                }
        } else {
                union {
                        struct sockaddr_in6 sin6;
                        struct sockaddr sa;
                } u;
                int _s;
                struct ifaddr *ifa;

                sockaddr_in6_init(&u.sin6, &origdst, 0, 0, 0);

                _s = pserialize_read_enter();
                ifa = ifa_ifwithaddr(&u.sa);

                if (ifa != NULL) {
                        ia = ifatoia6(ifa);
                        if ((ia->ia6_flags &
                                 (IN6_IFF_ANYCAST|IN6_IFF_NOTREADY)) == 0) {
                                ip6->ip6_src = ia->ia_addr.sin6_addr;
                                ip6_src_filled = true;
                        }
                }
                pserialize_read_exit(_s);
        }

        if (!ip6_src_filled) {
                int e;
                struct sockaddr_in6 sin6;
                struct route ro;

                /*
                 * This case matches to multicasts, our anycast, or unicasts
                 * that we do not own.  Select a source address based on the
                 * source address of the erroneous packet.
                 */
                /* zone ID should be embedded */
                sockaddr_in6_init(&sin6, &ip6->ip6_dst, 0, 0, 0);

                memset(&ro, 0, sizeof(ro));
                e = in6_selectsrc(&sin6, NULL, NULL, &ro, NULL, NULL, NULL,
                    &ip6->ip6_src);
                rtcache_free(&ro);
                if (e != 0) {
                        char ip6buf[INET6_ADDRSTRLEN];
                        nd6log(LOG_DEBUG,
                            "source can't be determined: "
                            "dst=%s, error=%d\n",
                            IN6_PRINT(ip6buf, &sin6.sin6_addr), e);
                        goto bad;
                }
        }

        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        rcvif = m_get_rcvif(m, &s);
        if (rcvif) {
                /* XXX: This may not be the outgoing interface */
                ip6->ip6_hlim = ND_IFINFO(rcvif)->chlim;
        } else {
                ip6->ip6_hlim = ip6_defhlim;
        }
        m_put_rcvif(rcvif, &s);

        m->m_pkthdr.csum_flags = 0;
        icmp6->icmp6_cksum = 0;
        icmp6->icmp6_cksum = in6_cksum(m, IPPROTO_ICMPV6,
            sizeof(struct ip6_hdr), plen);

        /*
         * XXX option handling
         */

        m->m_flags &= ~(M_BCAST|M_MCAST);

        /*
         * Note for icmp6_reflect_pmtu == false
         * To avoid a "too big" situation at an intermediate router
         * and the path MTU discovery process, specify the IPV6_MINMTU flag.
         * Note that only echo and node information replies are affected,
         * since the length of ICMP6 errors is limited to the minimum MTU.
         */
        flags = icmp6_reflect_pmtu ? 0 : IPV6_MINMTU;
        if (ip6_output(m, NULL, NULL, flags, NULL, NULL, &outif) != 0 &&
            outif)
                icmp6_ifstat_inc(outif, ifs6_out_error);
        if (outif)
                icmp6_ifoutstat_inc(outif, type, code);

        return;

 bad:
        m_freem(m);
        return;
}

static const char *
icmp6_redirect_diag(char *buf, size_t buflen, struct in6_addr *src6,
    struct in6_addr *dst6,  struct in6_addr *tgt6)
{
        char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
        char ip6buft[INET6_ADDRSTRLEN];

        snprintf(buf, buflen, "(src=%s dst=%s tgt=%s)",
            IN6_PRINT(ip6bufs, src6), IN6_PRINT(ip6bufd, dst6),
            IN6_PRINT(ip6buft, tgt6));
        return buf;
}

static void
icmp6_redirect_input(struct mbuf *m, int off)
{
        struct ifnet *ifp;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_redirect *nd_rd;
        int icmp6len = m->m_pkthdr.len - off;
        char *lladdr = NULL;
        int lladdrlen = 0;
        struct rtentry *rt = NULL;
        int is_router;
        int is_onlink;
        struct in6_addr src6 = ip6->ip6_src;
        struct in6_addr redtgt6;
        struct in6_addr reddst6;
        union nd_opts ndopts;
        struct psref psref;
        char ip6buf[INET6_ADDRSTRLEN];
        char diagbuf[256];

        ifp = m_get_rcvif_psref(m, &psref);
        if (ifp == NULL)
                goto freeit;

        /* XXX if we are router, we don't update route by icmp6 redirect */
        if (ip6_forwarding)
                goto freeit;
        if (!icmp6_rediraccept)
                goto freeit;

        IP6_EXTHDR_GET(nd_rd, struct nd_redirect *, m, off, icmp6len);
        if (nd_rd == NULL) {
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                m_put_rcvif_psref(ifp, &psref);
                return;
        }
        redtgt6 = nd_rd->nd_rd_target;
        reddst6 = nd_rd->nd_rd_dst;

        if (in6_setscope(&redtgt6, ifp, NULL) ||
            in6_setscope(&reddst6, ifp, NULL)) {
                goto freeit;
        }

        /* validation */
        if (!IN6_IS_ADDR_LINKLOCAL(&src6)) {
                nd6log(LOG_ERR,
                    "ICMP6 redirect sent from %s rejected; "
                    "must be from linklocal\n", IN6_PRINT(ip6buf, &src6));
                goto bad;
        }
        if (ip6->ip6_hlim != 255) {
                nd6log(LOG_ERR,
                    "ICMP6 redirect sent from %s rejected; "
                    "hlim=%d (must be 255)\n",
                    IN6_PRINT(ip6buf, &src6), ip6->ip6_hlim);
                goto bad;
        }

    {
        /* ip6->ip6_src must be equal to gw for icmp6->icmp6_reddst */
        struct sockaddr_in6 sin6;
        struct in6_addr *gw6;

        sockaddr_in6_init(&sin6, &reddst6, 0, 0, 0);
        rt = rtalloc1(sin6tosa(&sin6), 0);
        if (rt) {
                if (rt->rt_gateway == NULL ||
                    rt->rt_gateway->sa_family != AF_INET6) {
                        nd6log(LOG_ERR,
                            "ICMP6 redirect rejected; no route "
                            "with inet6 gateway found for redirect dst: %s\n",
                            icmp6_redirect_diag(diagbuf, sizeof(diagbuf),
                            &src6, &reddst6, &redtgt6));
                        rt_unref(rt);
                        goto bad;
                }

                gw6 = &(((struct sockaddr_in6 *)rt->rt_gateway)->sin6_addr);
                if (memcmp(&src6, gw6, sizeof(struct in6_addr)) != 0) {
                        nd6log(LOG_ERR,
                            "ICMP6 redirect rejected; "
                            "not equal to gw-for-src=%s (must be same): %s\n",
                            IN6_PRINT(ip6buf, gw6),
                            icmp6_redirect_diag(diagbuf, sizeof(diagbuf),
                            &src6, &reddst6, &redtgt6));
                        rt_unref(rt);
                        goto bad;
                }
        } else {
                nd6log(LOG_ERR, "ICMP6 redirect rejected; "
                    "no route found for redirect dst: %s\n",
                    icmp6_redirect_diag(diagbuf, sizeof(diagbuf),
                    &src6, &reddst6, &redtgt6));
                goto bad;
        }
        rt_unref(rt);
        rt = NULL;
    }

        if (IN6_IS_ADDR_MULTICAST(&reddst6)) {
                nd6log(LOG_ERR, "ICMP6 redirect rejected; "
                    "redirect dst must be unicast: %s\n",
                    icmp6_redirect_diag(diagbuf, sizeof(diagbuf),
                    &src6, &reddst6, &redtgt6));
                goto bad;
        }

        is_router = is_onlink = 0;
        if (IN6_IS_ADDR_LINKLOCAL(&redtgt6))
                is_router = 1;  /* router case */
        if (memcmp(&redtgt6, &reddst6, sizeof(redtgt6)) == 0)
                is_onlink = 1;  /* on-link destination case */
        if (!is_router && !is_onlink) {
                nd6log(LOG_ERR, "ICMP6 redirect rejected; "
                    "neither router case nor onlink case: %s\n",
                    icmp6_redirect_diag(diagbuf, sizeof(diagbuf),
                    &src6, &reddst6, &redtgt6));
                goto bad;
        }
        /* validation passed */

        icmp6len -= sizeof(*nd_rd);
        nd6_option_init(nd_rd + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                nd6log(LOG_INFO, "invalid ND option, rejected: %s\n",
                    icmp6_redirect_diag(diagbuf, sizeof(diagbuf),
                    &src6, &reddst6, &redtgt6));
                /* nd6_options have incremented stats */
                goto freeit;
        }

        if (ndopts.nd_opts_tgt_lladdr) {
                lladdr = (char *)(ndopts.nd_opts_tgt_lladdr + 1);
                lladdrlen = ndopts.nd_opts_tgt_lladdr->nd_opt_len << 3;
        }

        if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                nd6log(LOG_INFO, "lladdrlen mismatch for %s "
                    "(if %d, icmp6 packet %d): %s\n",
                    IN6_PRINT(ip6buf, &redtgt6),
                    ifp->if_addrlen, lladdrlen - 2,
                    icmp6_redirect_diag(diagbuf, sizeof(diagbuf),
                    &src6, &reddst6, &redtgt6));
                goto bad;
        }

        /* RFC 2461 8.3 */
        nd6_cache_lladdr(ifp, &redtgt6, lladdr, lladdrlen, ND_REDIRECT,
            is_onlink ? ND_REDIRECT_ONLINK : ND_REDIRECT_ROUTER);

        m_put_rcvif_psref(ifp, &psref);
        ifp = NULL;

        if (!is_onlink) {       /* better router case.  perform rtredirect. */
                /* perform rtredirect */
                struct sockaddr_in6 sdst;
                struct sockaddr_in6 sgw;
                struct sockaddr_in6 ssrc;
                unsigned long rtcount;
                struct rtentry *newrt = NULL;

                /*
                 * do not install redirect route, if the number of entries
                 * is too much (> hiwat).  note that, the node (= host) will
                 * work just fine even if we do not install redirect route
                 * (there will be additional hops, though).
                 */
                mutex_enter(&icmp6_mtx);
                rtcount = rt_timer_count(icmp6_redirect_timeout_q);
                if (0 <= ip6_maxdynroutes && rtcount >= ip6_maxdynroutes) {
                        mutex_exit(&icmp6_mtx);
                        goto freeit;
                }
                if (0 <= icmp6_redirect_hiwat && rtcount > icmp6_redirect_hiwat) {
                        mutex_exit(&icmp6_mtx);
                        goto freeit;
                } else if (0 <= icmp6_redirect_lowat &&
                    rtcount > icmp6_redirect_lowat) {
                        /*
                         * XXX nuke a victim, install the new one.
                         */
                }

                memset(&sdst, 0, sizeof(sdst));
                memset(&sgw, 0, sizeof(sgw));
                memset(&ssrc, 0, sizeof(ssrc));
                sdst.sin6_family = sgw.sin6_family = ssrc.sin6_family = AF_INET6;
                sdst.sin6_len = sgw.sin6_len = ssrc.sin6_len =
                    sizeof(struct sockaddr_in6);
                bcopy(&redtgt6, &sgw.sin6_addr, sizeof(struct in6_addr));
                bcopy(&reddst6, &sdst.sin6_addr, sizeof(struct in6_addr));
                bcopy(&src6, &ssrc.sin6_addr, sizeof(struct in6_addr));
                rtredirect(sin6tosa(&sdst), sin6tosa(&sgw), NULL,
                    RTF_GATEWAY | RTF_HOST, sin6tosa(&ssrc), &newrt);

                if (newrt) {
                        (void)rt_timer_add(newrt, icmp6_redirect_timeout,
                            icmp6_redirect_timeout_q);
                        rt_unref(newrt);
                }
                mutex_exit(&icmp6_mtx);
        }
        /* finally update cached route in each socket via pfctlinput */
        {
                struct sockaddr_in6 sdst;

                sockaddr_in6_init(&sdst, &reddst6, 0, 0, 0);
                pfctlinput(PRC_REDIRECT_HOST, sin6tosa(&sdst));
#if defined(IPSEC)
                if (ipsec_used)
                        key_sa_routechange(sin6tosa(&sdst));
#endif
        }

freeit:
        if (ifp != NULL)
                m_put_rcvif_psref(ifp, &psref);
        m_freem(m);
        return;

bad:
        m_put_rcvif_psref(ifp, &psref);
        ICMP6_STATINC(ICMP6_STAT_BADREDIRECT);
        m_freem(m);
}

void
icmp6_redirect_output(struct mbuf *m0, struct rtentry *rt)
{
        struct ifnet *ifp;      /* my outgoing interface */
        struct in6_addr *ifp_ll6;
        struct in6_addr *nexthop;
        struct ip6_hdr *sip6;   /* m0 as struct ip6_hdr */
        struct mbuf *m = NULL;  /* newly allocated one */
        struct ip6_hdr *ip6;    /* m as struct ip6_hdr */
        struct nd_redirect *nd_rd;
        size_t maxlen;
        u_char *p;
        struct sockaddr_in6 src_sa;

        icmp6_errcount(ICMP6_STAT_OUTERRHIST, ND_REDIRECT, 0);

        /* if we are not router, we don't send icmp6 redirect */
        if (!ip6_forwarding)
                goto fail;

        /* sanity check */
        KASSERT(m0 != NULL);
        KASSERT(rt != NULL);

        ifp = rt->rt_ifp;

        /*
         * Address check:
         *  the source address must identify a neighbor, and
         *  the destination address must not be a multicast address
         *  [RFC 2461, sec 8.2]
         */
        sip6 = mtod(m0, struct ip6_hdr *);
        sockaddr_in6_init(&src_sa, &sip6->ip6_src, 0, 0, 0);
        if (nd6_is_addr_neighbor(&src_sa, ifp) == 0)
                goto fail;
        if (IN6_IS_ADDR_MULTICAST(&sip6->ip6_dst))
                goto fail;      /* what should we do here? */

        /* rate limit */
        if (icmp6_ratelimit(&sip6->ip6_src, ND_REDIRECT, 0))
                goto fail;

        /*
         * Since we are going to append up to 1280 bytes (= IPV6_MMTU),
         * we almost always ask for an mbuf cluster for simplicity.
         * (MHLEN < IPV6_MMTU is almost always true)
         */
        MGETHDR(m, M_DONTWAIT, MT_HEADER);
        if (m && IPV6_MMTU >= MHLEN) {
#if IPV6_MMTU >= MCLBYTES
                MEXTMALLOC(m, IPV6_MMTU, M_NOWAIT);
#else
                MCLGET(m, M_DONTWAIT);
#endif
        }

        if (!m)
                goto fail;
        m_reset_rcvif(m);
        m->m_len = 0;
        maxlen = M_TRAILINGSPACE(m);
        maxlen = uimin(IPV6_MMTU, maxlen);

        /* just for safety */
        if (maxlen < sizeof(struct ip6_hdr) + sizeof(struct nd_redirect) +
            ((sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7)) {
                goto fail;
        }

        {
                /* get ip6 linklocal address for ifp(my outgoing interface). */
                struct in6_ifaddr *ia;
                int s = pserialize_read_enter();
                if ((ia = in6ifa_ifpforlinklocal(ifp,
                                                 IN6_IFF_NOTREADY|
                                                 IN6_IFF_ANYCAST)) == NULL) {
                        pserialize_read_exit(s);
                        goto fail;
                }
                ifp_ll6 = &ia->ia_addr.sin6_addr;
                pserialize_read_exit(s);
        }

        /* get ip6 linklocal address for the router. */
        if (rt->rt_gateway && (rt->rt_flags & RTF_GATEWAY)) {
                struct sockaddr_in6 *sin6;
                sin6 = (struct sockaddr_in6 *)rt->rt_gateway;
                nexthop = &sin6->sin6_addr;
                if (!IN6_IS_ADDR_LINKLOCAL(nexthop))
                        nexthop = NULL;
        } else
                nexthop = NULL;

        /* ip6 */
        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        /* ip6->ip6_plen will be set later */
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        ip6->ip6_hlim = 255;
        /* ip6->ip6_src must be linklocal addr for my outgoing if. */
        bcopy(ifp_ll6, &ip6->ip6_src, sizeof(struct in6_addr));
        bcopy(&sip6->ip6_src, &ip6->ip6_dst, sizeof(struct in6_addr));

        /* ND Redirect */
        nd_rd = (struct nd_redirect *)(ip6 + 1);
        nd_rd->nd_rd_type = ND_REDIRECT;
        nd_rd->nd_rd_code = 0;
        nd_rd->nd_rd_reserved = 0;
        if (rt->rt_flags & RTF_GATEWAY) {
                /*
                 * nd_rd->nd_rd_target must be a link-local address in
                 * better router cases.
                 */
                if (!nexthop)
                        goto fail;
                bcopy(nexthop, &nd_rd->nd_rd_target,
                      sizeof(nd_rd->nd_rd_target));
                bcopy(&sip6->ip6_dst, &nd_rd->nd_rd_dst,
                      sizeof(nd_rd->nd_rd_dst));
        } else {
                /* make sure redtgt == reddst */
                nexthop = &sip6->ip6_dst;
                bcopy(&sip6->ip6_dst, &nd_rd->nd_rd_target,
                      sizeof(nd_rd->nd_rd_target));
                bcopy(&sip6->ip6_dst, &nd_rd->nd_rd_dst,
                      sizeof(nd_rd->nd_rd_dst));
        }

        p = (u_char *)(nd_rd + 1);

        {
                /* target lladdr option */
                struct llentry *ln = NULL;
                int len, pad;
                struct nd_opt_hdr *nd_opt;
                char *lladdr;

                ln = nd6_lookup(nexthop, ifp, false);
                if (ln == NULL)
                        goto nolladdropt;
                len = sizeof(*nd_opt) + ifp->if_addrlen;
                len = (len + 7) & ~7;   /* round by 8 */
                pad = len - (sizeof(*nd_opt) + ifp->if_addrlen);

                /* safety check */
                if (len + (p - (u_char *)ip6) > maxlen) {
                        LLE_RUNLOCK(ln);
                        goto nolladdropt;
                }

                if (ln->la_flags & LLE_VALID) {
                        nd_opt = (struct nd_opt_hdr *)p;
                        nd_opt->nd_opt_type = ND_OPT_TARGET_LINKADDR;
                        nd_opt->nd_opt_len = len >> 3;
                        lladdr = (char *)(nd_opt + 1);
                        memcpy(lladdr, &ln->ll_addr, ifp->if_addrlen);
                        memset(lladdr + ifp->if_addrlen, 0, pad);
                        p += len;
                }
                LLE_RUNLOCK(ln);
        }
nolladdropt:

        m->m_pkthdr.len = m->m_len = p - (u_char *)ip6;

        /* just to be safe */
        if (m0->m_flags & M_DECRYPTED)
                goto noredhdropt;
        if (p - (u_char *)ip6 > maxlen)
                goto noredhdropt;

        {
                /* redirected header option */
                int len;
                struct nd_opt_rd_hdr *nd_opt_rh;

                /*
                 * compute the maximum size for icmp6 redirect header option.
                 * XXX room for auth header?
                 */
                len = maxlen - (p - (u_char *)ip6);
                len &= ~7;

                if (len < sizeof(*nd_opt_rh)) {
                        goto noredhdropt;
                }

                /*
                 * Redirected header option spec (RFC2461 4.6.3) talks nothing
                 * about padding/truncate rule for the original IP packet.
                 * From the discussion on IPv6imp in Feb 1999,
                 * the consensus was:
                 * - "attach as much as possible" is the goal
                 * - pad if not aligned (original size can be guessed by
                 *   original ip6 header)
                 * Following code adds the padding if it is simple enough,
                 * and truncates if not.
                 */
                if (len - sizeof(*nd_opt_rh) < m0->m_pkthdr.len) {
                        /* not enough room, truncate */
                        m_adj(m0, (len - sizeof(*nd_opt_rh)) -
                            m0->m_pkthdr.len);
                } else {
                        /*
                         * enough room, truncate if not aligned.
                         * we don't pad here for simplicity.
                         */
                        int extra;

                        extra = m0->m_pkthdr.len % 8;
                        if (extra) {
                                /* truncate */
                                m_adj(m0, -extra);
                        }
                        len = m0->m_pkthdr.len + sizeof(*nd_opt_rh);
                }

                nd_opt_rh = (struct nd_opt_rd_hdr *)p;
                memset(nd_opt_rh, 0, sizeof(*nd_opt_rh));
                nd_opt_rh->nd_opt_rh_type = ND_OPT_REDIRECTED_HEADER;
                nd_opt_rh->nd_opt_rh_len = len >> 3;
                p += sizeof(*nd_opt_rh);
                m->m_pkthdr.len = m->m_len = p - (u_char *)ip6;

                /* connect m0 to m */
                m->m_pkthdr.len += m0->m_pkthdr.len;
                m_cat(m, m0);
                m0 = NULL;
        }
noredhdropt:
        m_freem(m0);
        m0 = NULL;

        /* XXX: clear embedded link IDs in the inner header */
        in6_clearscope(&sip6->ip6_src);
        in6_clearscope(&sip6->ip6_dst);
        in6_clearscope(&nd_rd->nd_rd_target);
        in6_clearscope(&nd_rd->nd_rd_dst);

        ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(struct ip6_hdr));

        nd_rd->nd_rd_cksum = 0;
        nd_rd->nd_rd_cksum =
            in6_cksum(m, IPPROTO_ICMPV6, sizeof(*ip6), ntohs(ip6->ip6_plen));

        /* send the packet to outside... */
        if (ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL) != 0)
                icmp6_ifstat_inc(ifp, ifs6_out_error);

        icmp6_ifstat_inc(ifp, ifs6_out_msg);
        icmp6_ifstat_inc(ifp, ifs6_out_redirect);
        ICMP6_STATINC(ICMP6_STAT_OUTHIST + ND_REDIRECT);

        return;

fail:
        m_freem(m);
        m_freem(m0);
}

/*
 * ICMPv6 socket option processing.
 */
int
icmp6_ctloutput(int op, struct socket *so, struct sockopt *sopt)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);

        if (sopt->sopt_level != IPPROTO_ICMPV6)
                return rip6_ctloutput(op, so, sopt);

        switch (op) {
        case PRCO_SETOPT:
                switch (sopt->sopt_name) {
                case ICMP6_FILTER:
                    {
                        struct icmp6_filter fil;

                        error = sockopt_get(sopt, &fil, sizeof(fil));
                        if (error)
                                break;
                        memcpy(in6p_icmp6filt(inp), &fil,
                            sizeof(struct icmp6_filter));
                        error = 0;
                        break;
                    }

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;

        case PRCO_GETOPT:
                switch (sopt->sopt_name) {
                case ICMP6_FILTER:
                    {
                        if (in6p_icmp6filt(inp) == NULL) {
                                error = EINVAL;
                                break;
                        }
                        error = sockopt_set(sopt, in6p_icmp6filt(inp),
                            sizeof(struct icmp6_filter));
                        break;
                    }

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;
        }

        return error;
}

/*
 * Perform rate limit check.
 * Returns 0 if it is okay to send the icmp6 packet.
 * Returns 1 if the router SHOULD NOT send this icmp6 packet due to rate
 * limitation.
 *
 * XXX per-destination/type check necessary?
 */
static int
icmp6_ratelimit(
        const struct in6_addr *dst,     /* not used at this moment */
        const int type,         /* not used at this moment */
        const int code)         /* not used at this moment */
{
        int ret;

        ret = 0;        /* okay to send */

        /* PPS limit */
        if (!ppsratecheck(&icmp6errppslim_last, &icmp6errpps_count,
            icmp6errppslim)) {
                /* The packet is subject to rate limit */
                ret++;
        }

        return ret;
}

static struct rtentry *
icmp6_mtudisc_clone(struct sockaddr *dst)
{
        struct rtentry *rt;
        int    error;

        rt = rtalloc1(dst, 1);
        if (rt == NULL)
                return NULL;

        /* If we didn't get a host route, allocate one */
        if ((rt->rt_flags & RTF_HOST) == 0) {
                struct rtentry *nrt;

                error = rtrequest(RTM_ADD, dst, rt->rt_gateway, NULL,
                    RTF_GATEWAY | RTF_HOST | RTF_DYNAMIC, &nrt);
                if (error) {
                        rt_unref(rt);
                        return NULL;
                }
                nrt->rt_rmx = rt->rt_rmx;
                rt_newmsg_dynamic(RTM_ADD, nrt);
                rt_unref(rt);
                rt = nrt;
        }

        mutex_enter(&icmp6_mtx);
        error = rt_timer_add(rt, icmp6_mtudisc_timeout,
                        icmp6_mtudisc_timeout_q);
        mutex_exit(&icmp6_mtx);

        if (error) {
                rt_unref(rt);
                return NULL;
        }

        return rt;      /* caller need to call rtfree() */
}

static void
icmp6_mtudisc_timeout(struct rtentry *rt, struct rttimer *r)
{
        struct rtentry *retrt;

        KASSERT(rt != NULL);
        rt_assert_referenced(rt);

        if ((rt->rt_flags & (RTF_DYNAMIC | RTF_HOST)) ==
            (RTF_DYNAMIC | RTF_HOST)) {
                rtrequest(RTM_DELETE, rt_getkey(rt),
                    rt->rt_gateway, rt_mask(rt), rt->rt_flags, &retrt);
                rt_newmsg_dynamic(RTM_DELETE, retrt);
                rt_unref(rt);
                rt_free(retrt);
        } else {
                if (!(rt->rt_rmx.rmx_locks & RTV_MTU))
                        rt->rt_rmx.rmx_mtu = 0;
        }
}

static void
icmp6_redirect_timeout(struct rtentry *rt, struct rttimer *r)
{
        struct rtentry *retrt;

        KASSERT(rt != NULL);
        rt_assert_referenced(rt);

        if ((rt->rt_flags & (RTF_GATEWAY | RTF_DYNAMIC | RTF_HOST)) ==
            (RTF_GATEWAY | RTF_DYNAMIC | RTF_HOST)) {
                rtrequest(RTM_DELETE, rt_getkey(rt),
                    rt->rt_gateway, rt_mask(rt), rt->rt_flags, &retrt);
                rt_newmsg_dynamic(RTM_DELETE, retrt);
                rt_unref(rt);
                rt_free(retrt);
        }
}

static int
sysctl_net_inet6_icmp6_stats(SYSCTLFN_ARGS)
{

        return (NETSTAT_SYSCTL(icmp6stat_percpu, ICMP6_NSTATS));
}

static int
sysctl_net_inet6_icmp6_redirtimeout(SYSCTLFN_ARGS)
{
        int error, tmp;
        struct sysctlnode node;

        mutex_enter(&icmp6_mtx);

        node = *rnode;
        node.sysctl_data = &tmp;
        tmp = icmp6_redirtimeout;
        error = sysctl_lookup(SYSCTLFN_CALL(&node));
        if (error || newp == NULL)
                goto out;
        if (tmp < 0) {
                error = EINVAL;
                goto out;
        }
        icmp6_redirtimeout = tmp;

        if (icmp6_redirect_timeout_q != NULL) {
                if (icmp6_redirtimeout == 0) {
                        rt_timer_queue_destroy(icmp6_redirect_timeout_q);
                } else {
                        rt_timer_queue_change(icmp6_redirect_timeout_q,
                            icmp6_redirtimeout);
                }
        } else if (icmp6_redirtimeout > 0) {
                icmp6_redirect_timeout_q =
                    rt_timer_queue_create(icmp6_redirtimeout);
        }
        error = 0;
out:
        mutex_exit(&icmp6_mtx);
        return error;
}

static void
sysctl_net_inet6_icmp6_setup(struct sysctllog **clog)
{

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "inet6", NULL,
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET6, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "icmp6",
                       SYSCTL_DESCR("ICMPv6 related settings"),
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6, CTL_EOL);

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_STRUCT, "stats",
                       SYSCTL_DESCR("ICMPv6 transmission statistics"),
                       sysctl_net_inet6_icmp6_stats, 0, NULL, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_STATS, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "rediraccept",
                       SYSCTL_DESCR("Accept and process redirect messages"),
                       NULL, 0, &icmp6_rediraccept, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_REDIRACCEPT, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "redirtimeout",
                       SYSCTL_DESCR("Redirect generated route lifetime"),
                       sysctl_net_inet6_icmp6_redirtimeout, 0,
                       &icmp6_redirtimeout, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_REDIRTIMEOUT, CTL_EOL);
#if 0 /* obsoleted */
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "errratelimit", NULL,
                       NULL, 0, &icmp6_errratelimit, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ERRRATELIMIT, CTL_EOL);
#endif
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_prune",
                       SYSCTL_DESCR("Neighbor discovery prune interval"),
                       NULL, 0, &nd6_prune, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_PRUNE, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_delay",
                       SYSCTL_DESCR("First probe delay time"),
                       NULL, 0, &nd6_nd_domain.nd_delay, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_DELAY, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_mmaxtries",
                       SYSCTL_DESCR("Number of multicast discovery attempts"),
                       NULL, 0, &nd6_nd_domain.nd_mmaxtries, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_MMAXTRIES, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_umaxtries",
                       SYSCTL_DESCR("Number of unicast discovery attempts"),
                       NULL, 0, &nd6_nd_domain.nd_umaxtries, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_UMAXTRIES, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_maxnudhint",
                       SYSCTL_DESCR("Maximum neighbor unreachable hint count"),
                       NULL, 0, &nd6_nd_domain.nd_maxnudhint, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_MAXNUDHINT, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "maxqueuelen",
                       SYSCTL_DESCR("max packet queue len for a unresolved ND"),
                       NULL, 1, &nd6_nd_domain.nd_maxqueuelen, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_MAXQLEN, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_useloopback",
                       SYSCTL_DESCR("Use loopback interface for local traffic"),
                       NULL, 0, &nd6_useloopback, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_USELOOPBACK, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_gctimer",
                       SYSCTL_DESCR("stale neighbor GC timer duration"),
                       NULL, 0, &nd6_nd_domain.nd_gctimer, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_GCTIMER, CTL_EOL);
#if 0 /* obsoleted */
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_proxyall", NULL,
                       NULL, 0, &nd6_proxyall, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_PROXYALL, CTL_EOL);
#endif
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nodeinfo",
                       SYSCTL_DESCR("Respond to node information requests"),
                       NULL, 0, &icmp6_nodeinfo, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_NODEINFO, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "errppslimit",
                       SYSCTL_DESCR("Maximum ICMP errors sent per second"),
                       NULL, 0, &icmp6errppslim, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ERRPPSLIMIT, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "mtudisc_hiwat",
                       SYSCTL_DESCR("Low mark on MTU Discovery route timers"),
                       NULL, 0, &icmp6_mtudisc_hiwat, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_MTUDISC_HIWAT, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "mtudisc_lowat",
                       SYSCTL_DESCR("Low mark on MTU Discovery route timers"),
                       NULL, 0, &icmp6_mtudisc_lowat, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_MTUDISC_LOWAT, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "nd6_debug",
                       SYSCTL_DESCR("Enable neighbor discovery debug output"),
                       NULL, 0, &nd6_debug, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_ND6_DEBUG, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_BOOL, "reflect_pmtu",
                       SYSCTL_DESCR("Use path MTU Discovery for icmpv6 reflect"),
                       NULL, 0, &icmp6_reflect_pmtu, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_REFLECT_PMTU, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_BOOL, "dynamic_rt_msg",
                       SYSCTL_DESCR("Send routing message for RTF_DYNAMIC"),
                       NULL, 0, &icmp6_dynamic_rt_msg, 0,
                       CTL_NET, PF_INET6, IPPROTO_ICMPV6,
                       ICMPV6CTL_DYNAMIC_RT_MSG, CTL_EOL);
}

void
icmp6_statinc(u_int stat)
{

        KASSERT(stat < ICMP6_NSTATS);
        ICMP6_STATINC(stat);
}