/*      $OpenBSD: icmp6.c,v 1.281 2025/11/12 19:11:10 bluhm 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 "carp.h"
#include "pf.h"

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

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

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet/icmp6.h>
#include <netinet6/mld6_var.h>
#include <netinet/in_pcb.h>
#include <netinet6/nd6.h>
#include <netinet6/ip6protosw.h>

#if NCARP > 0
#include <netinet/ip_carp.h>
#endif

#if NPF > 0
#include <net/pfvar.h>
#endif

/*
 * Locks used to protect data:
 *      a       atomic
 */

struct cpumem *icmp6counters;

extern int icmp6errppslim;
static int icmp6errpps_count = 0;
static struct timeval icmp6errppslim_last;

/*
 * 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 sockaddr_in6 *, u_int);
};

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

struct rttimer_queue icmp6_mtudisc_timeout_q;

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

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

void    icmp6_errcount(int, int);
int     icmp6_ratelimit(const struct in6_addr *, const int, const int);
int     icmp6_notify_error(struct mbuf *, int, int, int);
void    icmp6_mtudisc_timeout(struct rtentry *, u_int);

void
icmp6_init(void)
{
        mld6_init();
        rt_timer_queue_init(&icmp6_mtudisc_timeout_q, ip6_mtudisc_timeout,
            &icmp6_mtudisc_timeout);
        rt_timer_queue_init(&icmp6_redirect_timeout_q, icmp6_redirtimeout,
            NULL);
        icmp6counters = counters_alloc(icp6s_ncounters);
}

void
icmp6_errcount(int type, int code)
{
        enum icmp6stat_counters c = icp6s_ounknown;

        switch (type) {
        case ICMP6_DST_UNREACH:
                switch (code) {
                case ICMP6_DST_UNREACH_NOROUTE:
                        c = icp6s_odst_unreach_noroute;
                        break;
                case ICMP6_DST_UNREACH_ADMIN:
                        c = icp6s_odst_unreach_admin;
                        break;
                case ICMP6_DST_UNREACH_BEYONDSCOPE:
                        c = icp6s_odst_unreach_beyondscope;
                        break;
                case ICMP6_DST_UNREACH_ADDR:
                        c = icp6s_odst_unreach_addr;
                        break;
                case ICMP6_DST_UNREACH_NOPORT:
                        c = icp6s_odst_unreach_noport;
                        break;
                }
                break;
        case ICMP6_PACKET_TOO_BIG:
                c = icp6s_opacket_too_big;
                break;
        case ICMP6_TIME_EXCEEDED:
                switch (code) {
                case ICMP6_TIME_EXCEED_TRANSIT:
                        c = icp6s_otime_exceed_transit;
                        break;
                case ICMP6_TIME_EXCEED_REASSEMBLY:
                        c = icp6s_otime_exceed_reassembly;
                        break;
                }
                break;
        case ICMP6_PARAM_PROB:
                switch (code) {
                case ICMP6_PARAMPROB_HEADER:
                        c = icp6s_oparamprob_header;
                        break;
                case ICMP6_PARAMPROB_NEXTHEADER:
                        c = icp6s_oparamprob_nextheader;
                        break;
                case ICMP6_PARAMPROB_OPTION:
                        c = icp6s_oparamprob_option;
                        break;
                }
                break;
        case ND_REDIRECT:
                c = icp6s_oredirect;
                break;
        }

        icmp6stat_inc(c);
}

/*
 * Register a Path MTU Discovery callback.
 */
void
icmp6_mtudisc_callback_register(void (*func)(struct sockaddr_in6 *, u_int))
{
        struct icmp6_mtudisc_callback *mc;

        LIST_FOREACH(mc, &icmp6_mtudisc_callbacks, mc_list) {
                if (mc->mc_func == func)
                        return;
        }

        mc = malloc(sizeof(*mc), M_PCB, M_NOWAIT);
        if (mc == NULL)
                panic("%s", __func__);

        mc->mc_func = func;
        LIST_INSERT_HEAD(&icmp6_mtudisc_callbacks, mc, mc_list);
}

struct mbuf *
icmp6_do_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;

        icmp6stat_inc(icp6s_error);

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

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

                icp = ip6_exthdr_get(&m, off, sizeof(*icp));
                if (icp == NULL) {
                        icmp6stat_inc(icp6s_tooshort);
                        return (NULL);
                }
                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.
                         */
                        icmp6stat_inc(icp6s_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)) {
                icmp6stat_inc(icp6s_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->m_len < preplen)
                m = m_pullup(m, preplen);
        if (m == NULL)
                return (NULL);

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

        if (IN6_IS_SCOPE_EMBED(&oip6->ip6_src))
                oip6->ip6_src.s6_addr16[1] = 0;
        if (IN6_IS_SCOPE_EMBED(&oip6->ip6_dst))
                oip6->ip6_dst.s6_addr16[1] = 0;

        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.ph_ifidx for safety, we should have enough
         * scope information in ip header (nip6).
         */
        m->m_pkthdr.ph_ifidx = 0;

        icmp6stat_inc(icp6s_outhist + type);

        return (m);

  freeit:
        /*
         * If we can't tell whether or not we can generate ICMP6, free it.
         */
        return (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 mbuf     *n;

        n = icmp6_do_error(m, type, code, param);
        if (n != NULL) {
                /* header order: IPv6 - ICMPv6 */
                if (!icmp6_reflect(&n, sizeof(struct ip6_hdr), NULL))
                        ip6_send(n);
        }
}

/*
 * Process a received ICMP6 message.
 */
int
icmp6_input(struct mbuf **mp, int *offp, int proto, int af,
    struct netstack *ns)
{
#if NCARP > 0
        struct ifnet *ifp;
#endif
        struct mbuf *m = *mp, *n;
        struct ip6_hdr *ip6, *nip6;
        struct icmp6_hdr *icmp6, *nicmp6;
        int off = *offp;
        int icmp6len = m->m_pkthdr.len - off;
        int code, sum, noff;

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

        ip6 = mtod(m, struct ip6_hdr *);
        if (icmp6len < sizeof(struct icmp6_hdr)) {
                icmp6stat_inc(icp6s_tooshort);
                goto freeit;
        }

        /*
         * calculate the checksum
         */
        icmp6 = ip6_exthdr_get(mp, off, sizeof(*icmp6));
        if (icmp6 == NULL) {
                icmp6stat_inc(icp6s_tooshort);
                return IPPROTO_DONE;
        }
        code = icmp6->icmp6_code;

        if ((sum = in6_cksum(m, IPPROTO_ICMPV6, off, icmp6len)) != 0) {
                icmp6stat_inc(icp6s_checksum);
                goto freeit;
        }

#if NPF > 0
        if (m->m_pkthdr.pf.flags & PF_TAG_DIVERTED) {
                switch (icmp6->icmp6_type) {
                /*
                 * These ICMP6 types map to other connections.  They must be
                 * delivered to pr_ctlinput() also for diverted connections.
                 */
                case ICMP6_DST_UNREACH:
                case ICMP6_PACKET_TOO_BIG:
                case ICMP6_TIME_EXCEEDED:
                case ICMP6_PARAM_PROB:
                        /*
                         * Do not use the divert-to property of the TCP or UDP
                         * rule when doing the PCB lookup for the raw socket.
                         */
                        m->m_pkthdr.pf.flags &=~ PF_TAG_DIVERTED;
                        break;
                default:
                        goto raw;
                }
        }
#endif /* NPF */

#if NCARP > 0
        ifp = if_get(m->m_pkthdr.ph_ifidx);
        if (ifp == NULL)
                goto freeit;

        if (icmp6->icmp6_type == ICMP6_ECHO_REQUEST &&
            carp_lsdrop(ifp, m, AF_INET6, ip6->ip6_src.s6_addr32,
            ip6->ip6_dst.s6_addr32, 1)) {
                if_put(ifp);
                goto freeit;
        }

        if_put(ifp);
#endif
        icmp6stat_inc(icp6s_inhist + icmp6->icmp6_type);

        switch (icmp6->icmp6_type) {
        case ICMP6_DST_UNREACH:
                switch (code) {
                case ICMP6_DST_UNREACH_NOROUTE:
                        code = PRC_UNREACH_NET;
                        break;
                case ICMP6_DST_UNREACH_ADMIN:
                        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_PARAMPROB;
                        break;
                case ICMP6_DST_UNREACH_NOPORT:
                        code = PRC_UNREACH_PORT;
                        break;
                default:
                        goto badcode;
                }
                goto deliver;

        case ICMP6_PACKET_TOO_BIG:
                /* MTU is checked in icmp6_mtudisc_update. */
                code = PRC_MSGSIZE;

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

        case ICMP6_TIME_EXCEEDED:
                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:
                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:
                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 ((n = m_copym(m, 0, M_COPYALL, M_DONTWAIT)) == NULL) {
                        /* Give up local */
                        n = m;
                        m = *mp = NULL;
                        goto deliverecho;
                }
                /*
                 * 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_flags & M_EXT) != 0 ||
                    n->m_len < off + sizeof(struct icmp6_hdr)) {
                        struct mbuf *n0 = n;
                        const int maxlen = sizeof(*nip6) + sizeof(*nicmp6);

                        /*
                         * Prepare an internal mbuf.  m_pullup() doesn't
                         * always copy the length we specified.
                         */
                        if (maxlen >= MCLBYTES) {
                                /* Give up remote */
                                m_freem(n0);
                                break;
                        }
                        MGETHDR(n, M_DONTWAIT, n0->m_type);
                        if (n && maxlen >= MHLEN) {
                                MCLGET(n, M_DONTWAIT);
                                if ((n->m_flags & M_EXT) == 0) {
                                        m_free(n);
                                        n = NULL;
                                }
                        }
                        if (n == NULL) {
                                /* Give up local */
                                m_freem(n0);
                                n = m;
                                m = *mp = NULL;
                                goto deliverecho;
                        }
                        M_MOVE_PKTHDR(n, n0);
                        /*
                         * Copy IPv6 and ICMPv6 only.
                         */
                        nip6 = mtod(n, struct ip6_hdr *);
                        bcopy(ip6, nip6, sizeof(struct ip6_hdr));
                        nicmp6 = (struct icmp6_hdr *)(nip6 + 1);
                        bcopy(icmp6, nicmp6, sizeof(struct icmp6_hdr));
                        noff = sizeof(struct ip6_hdr);
                        n->m_len = noff + sizeof(struct icmp6_hdr);
                        /*
                         * Adjust mbuf.  ip6_plen will be adjusted in
                         * ip6_output().
                         * n->m_pkthdr.len == n0->m_pkthdr.len at this point.
                         */
                        n->m_pkthdr.len += noff + sizeof(struct icmp6_hdr);
                        n->m_pkthdr.len -= (off + sizeof(struct icmp6_hdr));
                        m_adj(n0, off + sizeof(struct icmp6_hdr));
                        n->m_next = n0;
                } else {
         deliverecho:
                        nicmp6 = ip6_exthdr_get(&n, off, sizeof(*nicmp6));
                        noff = off;
                }
                if (n) {
                        nicmp6->icmp6_type = ICMP6_ECHO_REPLY;
                        nicmp6->icmp6_code = 0;
                        icmp6stat_inc(icp6s_reflect);
                        icmp6stat_inc(icp6s_outhist + ICMP6_ECHO_REPLY);
                        if (!icmp6_reflect(&n, noff, NULL))
                                ip6_send(n);
                }
                if (!m)
                        goto freeit;
                break;

        case ICMP6_ECHO_REPLY:
                if (code != 0)
                        goto badcode;
                break;

        case MLD_LISTENER_QUERY:
        case MLD_LISTENER_REPORT:
                if (icmp6len < sizeof(struct mld_hdr))
                        goto badlen;
                if ((n = m_copym(m, 0, M_COPYALL, M_DONTWAIT)) == NULL) {
                        /* give up local */
                        mld6_input(m, off);
                        m = NULL;
                        goto freeit;
                }
                mld6_input(n, off);
                /* m stays. */
                break;

        case MLD_LISTENER_DONE:
                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 */
                /* IPv6 Node Information Queries are not supported */
                break;
        case ICMP6_WRUREPLY:
                break;

        case ND_ROUTER_SOLICIT:
        case ND_ROUTER_ADVERT:
                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_copym(m, 0, M_COPYALL, 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:
                if (code != 0)
                        goto badcode;
                if (icmp6len < sizeof(struct nd_neighbor_solicit))
                        goto badlen;
                if ((n = m_copym(m, 0, M_COPYALL, 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:
                if (code != 0)
                        goto badcode;
                if (icmp6len < sizeof(struct nd_neighbor_advert))
                        goto badlen;
                if ((n = m_copym(m, 0, M_COPYALL, 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:
                if (code != 0)
                        goto badcode;
                if (icmp6len < sizeof(struct nd_redirect))
                        goto badlen;
                if ((n = m_copym(m, 0, M_COPYALL, 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:
                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. */
                        return (IPPROTO_DONE);
                }
                break;

badcode:
                icmp6stat_inc(icp6s_badcode);
                break;

badlen:
                icmp6stat_inc(icp6s_badlen);
                break;
        }

#if NPF > 0
raw:
#endif
        /* deliver the packet to appropriate sockets */
        return rip6_input(mp, offp, proto, af, ns);

 freeit:
        m_freem(m);
        return IPPROTO_DONE;
}

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)) {
                icmp6stat_inc(icp6s_tooshort);
                goto freeit;
        }
        icmp6 = ip6_exthdr_get(&m, off,
            sizeof(*icmp6) + sizeof(struct ip6_hdr));
        if (icmp6 == NULL) {
                icmp6stat_inc(icp6s_tooshort);
                return (-1);
        }
        eip6 = (struct ip6_hdr *)(icmp6 + 1);

        /* Detect the upper level protocol */
        {
                void (*ctlfunc)(int, struct sockaddr *, u_int, 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 ip6_rthdr0 *rth0;
                int rthlen;

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

                        switch (nxt) {
                        case IPPROTO_HOPOPTS:
                        case IPPROTO_DSTOPTS:
                        case IPPROTO_AH:
                                eh = ip6_exthdr_get(&m, eoff, sizeof(*eh));
                                if (eh == NULL) {
                                        icmp6stat_inc(icp6s_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:
                                /*
                                 * When the erroneous packet contains a
                                 * routing header, we should examine the
                                 * header to determine the final destination.
                                 * Otherwise, we can't properly update
                                 * information that depends on the final
                                 * destination (e.g. path MTU).
                                 */
                                rth  = ip6_exthdr_get(&m, eoff, sizeof(*rth));
                                if (rth == NULL) {
                                        icmp6stat_inc(icp6s_tooshort);
                                        return (-1);
                                }
                                rthlen = (rth->ip6r_len + 1) << 3;
                                /*
                                 * XXX: currently there is no
                                 * officially defined type other
                                 * than type-0.
                                 * Note that if the segment left field
                                 * is 0, all intermediate hops must
                                 * have been passed.
                                 */
                                if (rth->ip6r_segleft &&
                                    rth->ip6r_type == IPV6_RTHDR_TYPE_0) {
                                        int hops;

                                        rth0 = ip6_exthdr_get(&m, eoff, rthlen);
                                        if (rth0 == NULL) {
                                                icmp6stat_inc(icp6s_tooshort);
                                                return (-1);
                                        }
                                        /* just ignore a bogus header */
                                        if ((rth0->ip6r0_len % 2) == 0 &&
                                            (hops = rth0->ip6r0_len/2)) {
                                                finaldst = (struct in6_addr *)
                                                    (rth0 + 1) + (hops - 1);
                                        }
                                }
                                eoff += rthlen;
                                nxt = rth->ip6r_nxt;
                                break;
                        case IPPROTO_FRAGMENT:
                                fh = ip6_exthdr_get(&m, eoff, sizeof(*fh));
                                if (fh == NULL) {
                                        icmp6stat_inc(icp6s_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:
                icmp6 = ip6_exthdr_get(&m, off,
                    sizeof(*icmp6) + sizeof(struct ip6_hdr));
                if (icmp6 == NULL) {
                        icmp6stat_inc(icp6s_tooshort);
                        return (-1);
                }

                eip6 = (struct ip6_hdr *)(icmp6 + 1);
                bzero(&icmp6dst, sizeof(icmp6dst));
                icmp6dst.sin6_len = sizeof(struct sockaddr_in6);
                icmp6dst.sin6_family = AF_INET6;
                if (finaldst == NULL)
                        icmp6dst.sin6_addr = eip6->ip6_dst;
                else
                        icmp6dst.sin6_addr = *finaldst;
                icmp6dst.sin6_scope_id = in6_addr2scopeid(m->m_pkthdr.ph_ifidx,
                    &icmp6dst.sin6_addr);
                if (in6_embedscope(&icmp6dst.sin6_addr, &icmp6dst,
                    NULL, NULL)) {
                        /* interface went away */
                        goto freeit;
                }

                /*
                 * retrieve parameters from the inner IPv6 header, and convert
                 * them into sockaddr structures.
                 */
                bzero(&icmp6src, sizeof(icmp6src));
                icmp6src.sin6_len = sizeof(struct sockaddr_in6);
                icmp6src.sin6_family = AF_INET6;
                icmp6src.sin6_addr = eip6->ip6_src;
                icmp6src.sin6_scope_id = in6_addr2scopeid(m->m_pkthdr.ph_ifidx,
                    &icmp6src.sin6_addr);
                if (in6_embedscope(&icmp6src.sin6_addr, &icmp6src,
                    NULL, NULL)) {
                        /* interface went away */
                        goto freeit;
                }
                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 NPF > 0
                pf_pkt_addr_changed(m);
#endif

                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)
                        (*ctlfunc)(code, sin6tosa(&icmp6dst),
                            m->m_pkthdr.ph_rtableid, &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;

        if (mtu < IPV6_MMTU)
                return;

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

        bzero(&sin6, sizeof(sin6));
        sin6.sin6_family = PF_INET6;
        sin6.sin6_len = sizeof(struct sockaddr_in6);
        sin6.sin6_addr = *dst;
        /* XXX normally, this won't happen */
        if (IN6_IS_ADDR_LINKLOCAL(dst)) {
                sin6.sin6_addr.s6_addr16[1] = htons(m->m_pkthdr.ph_ifidx);
        }
        sin6.sin6_scope_id = in6_addr2scopeid(m->m_pkthdr.ph_ifidx,
            &sin6.sin6_addr);

        rt = icmp6_mtudisc_clone(&sin6, m->m_pkthdr.ph_rtableid, 0);

        if (rt != NULL && ISSET(rt->rt_flags, RTF_HOST) &&
            !(rt->rt_locks & RTV_MTU)) {
                u_int rtmtu;

                rtmtu = atomic_load_int(&rt->rt_mtu);
                if (rtmtu > mtu || rtmtu == 0) {
                        struct ifnet *ifp;

                        ifp = if_get(rt->rt_ifidx);
                        if (ifp != NULL && mtu < ifp->if_mtu) {
                                icmp6stat_inc(icp6s_pmtuchg);
                                atomic_cas_uint(&rt->rt_mtu, rtmtu, mtu);
                        }
                        if_put(ifp);
                }
        }
        rtfree(rt);

        /*
         * Notify protocols that the MTU for this destination
         * has changed.
         */
        LIST_FOREACH(mc, &icmp6_mtudisc_callbacks, mc_list)
                (*mc->mc_func)(&sin6, m->m_pkthdr.ph_rtableid);
}

/*
 * Reflect the ip6 packet back to the source.
 * OFF points to the icmp6 header, counted from the top of the mbuf.
 */
int
icmp6_reflect(struct mbuf **mp, size_t off, struct sockaddr *sa)
{
        struct mbuf *m = *mp;
        struct rtentry *rt = NULL;
        struct ip6_hdr *ip6;
        struct icmp6_hdr *icmp6;
        struct in6_addr t, *src = NULL;
        struct sockaddr_in6 sa6_src, sa6_dst;
        u_int rtableid;
        u_int8_t pfflags;

        CTASSERT(sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr) <= MHLEN);

        /* too short to reflect */
        if (off < sizeof(struct ip6_hdr))
                goto bad;

        if (m->m_pkthdr.ph_loopcnt++ >= M_MAXLOOP) {
                m_freemp(mp);
                return (ELOOP);
        }
        rtableid = m->m_pkthdr.ph_rtableid;
        pfflags = m->m_pkthdr.pf.flags;
        m_resethdr(m);
        m->m_pkthdr.ph_rtableid = rtableid;
        m->m_pkthdr.pf.flags = pfflags & PF_TAG_GENERATED;

        /*
         * If there are extra headers between IPv6 and ICMPv6, strip
         * off that header first.
         */
        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), (caddr_t)&nip6);
                m_adj(m, l);
                l = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
                if (m->m_len < l) {
                        if ((m = *mp = m_pullup(m, l)) == NULL)
                                return (EMSGSIZE);
                }
                memcpy(mtod(m, caddr_t), &nip6, sizeof(nip6));
        } else /* off == sizeof(struct ip6_hdr) */ {
                size_t l;
                l = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
                if (m->m_len < l) {
                        if ((m = *mp = m_pullup(m, l)) == NULL)
                                return (EMSGSIZE);
                }
        }
        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        icmp6 = (struct icmp6_hdr *)(ip6 + 1);

        t = 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;

        /*
         * XXX: make sure to embed scope zone information, using
         * already embedded IDs or the received interface (if any).
         * Note that rcvif may be NULL.
         * TODO: scoped routing case (XXX).
         */
        bzero(&sa6_src, sizeof(sa6_src));
        sa6_src.sin6_family = AF_INET6;
        sa6_src.sin6_len = sizeof(sa6_src);
        sa6_src.sin6_addr = ip6->ip6_dst;
        bzero(&sa6_dst, sizeof(sa6_dst));
        sa6_dst.sin6_family = AF_INET6;
        sa6_dst.sin6_len = sizeof(sa6_dst);
        sa6_dst.sin6_addr = t;

        if (sa == NULL) {
                /*
                 * If the incoming packet was addressed directly to us (i.e.
                 * unicast), use dst as the src for the reply. The
                 * IN6_IFF_TENTATIVE|IN6_IFF_DUPLICATED case would be VERY rare,
                 * but is possible (for example) when we encounter an error
                 * while forwarding procedure destined to a duplicated address
                 * of ours.
                 */
                rt = rtalloc(sin6tosa(&sa6_dst), 0, rtableid);
                if (rtisvalid(rt) && ISSET(rt->rt_flags, RTF_LOCAL) &&
                    !ISSET(ifatoia6(rt->rt_ifa)->ia6_flags,
                    IN6_IFF_ANYCAST|IN6_IFF_TENTATIVE|IN6_IFF_DUPLICATED)) {
                        src = &t;
                }
                rtfree(rt);
                rt = NULL;
                sa = sin6tosa(&sa6_src);
        }

        if (src == NULL) {
                struct in6_ifaddr *ia6;

                /*
                 * 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.
                 */
                rt = rtalloc(sa, RT_RESOLVE, rtableid);
                if (!rtisvalid(rt)) {
                        rtfree(rt);
                        goto bad;
                }
                ia6 = in6_ifawithscope(rt->rt_ifa->ifa_ifp, &t, rtableid, rt);
                if (ia6 != NULL)
                        src = &ia6->ia_addr.sin6_addr;
                if (src == NULL)
                        src = &ifatoia6(rt->rt_ifa)->ia_addr.sin6_addr;

                /* route sourceaddr may override src address selection */
                if (ISSET(rt->rt_flags, RTF_GATEWAY)) {
                        struct sockaddr *sourceaddr;

                        sourceaddr = rtable_getsource(rtableid, AF_INET6);
                        if (sourceaddr != NULL) {
                                struct ifaddr *ifa;
                                ifa = ifa_ifwithaddr(sourceaddr, rtableid);
                                if (ifa != NULL &&
                                    ISSET(ifa->ifa_ifp->if_flags, IFF_UP))
                                        src = &satosin6(sourceaddr)->sin6_addr;
                        }
                }
        }

        ip6->ip6_src = *src;
        rtfree(rt);

        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        ip6->ip6_hlim = atomic_load_int(&ip6_defhlim);

        icmp6->icmp6_cksum = 0;
        m->m_pkthdr.csum_flags = M_ICMP_CSUM_OUT;

        /*
         * XXX option handling
         */

        m->m_flags &= ~(M_BCAST|M_MCAST);
        return (0);

 bad:
        m_freemp(mp);
        return (EHOSTUNREACH);
}

void
icmp6_fasttimo(void)
{
        mld6_fasttimo();
}

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 = ntohs(ip6->ip6_plen);
        char *lladdr = NULL;
        int lladdrlen = 0;
        struct rtentry *rt = NULL;
        int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
        int is_router;
        int is_onlink;
        struct in6_addr src6 = ip6->ip6_src;
        struct in6_addr redtgt6;
        struct in6_addr reddst6;
        struct nd_opts ndopts;

        ifp = if_get(m->m_pkthdr.ph_ifidx);
        if (ifp == NULL)
                return;

        /* if we are router, we don't update route by icmp6 redirect */
        if (i_am_router)
                goto freeit;
        if (!(ifp->if_xflags & IFXF_AUTOCONF6))
                goto freeit;

        nd_rd = ip6_exthdr_get(&m, off, icmp6len);
        if (nd_rd == NULL) {
                icmp6stat_inc(icp6s_tooshort);
                if_put(ifp);
                return;
        }
        redtgt6 = nd_rd->nd_rd_target;
        reddst6 = nd_rd->nd_rd_dst;

        if (IN6_IS_ADDR_LINKLOCAL(&redtgt6))
                redtgt6.s6_addr16[1] = htons(ifp->if_index);
        if (IN6_IS_ADDR_LINKLOCAL(&reddst6))
                reddst6.s6_addr16[1] = htons(ifp->if_index);

        /* validation */
        if (!IN6_IS_ADDR_LINKLOCAL(&src6))
                goto bad;
        if (ip6->ip6_hlim != 255)
                goto bad;
        if (IN6_IS_ADDR_MULTICAST(&reddst6))
                goto bad;

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

        bzero(&sin6, sizeof(sin6));
        sin6.sin6_family = AF_INET6;
        sin6.sin6_len = sizeof(struct sockaddr_in6);
        memcpy(&sin6.sin6_addr, &reddst6, sizeof(reddst6));
        rt = rtalloc(sin6tosa(&sin6), 0, m->m_pkthdr.ph_rtableid);
        if (!rt)
                goto bad;

        if (rt->rt_gateway == NULL || rt->rt_gateway->sa_family != AF_INET6) {
                rtfree(rt);
                goto bad;
        }

        gw6 = &(satosin6(rt->rt_gateway)->sin6_addr);
        if (bcmp(&src6, gw6, sizeof(struct in6_addr)) != 0) {
                rtfree(rt);
                goto bad;
        }
        rtfree(rt);
        rt = NULL;
    }

        is_router = is_onlink = 0;
        if (IN6_IS_ADDR_LINKLOCAL(&redtgt6))
                is_router = 1;  /* router case */
        if (bcmp(&redtgt6, &reddst6, sizeof(redtgt6)) == 0)
                is_onlink = 1;  /* on-link destination case */
        if (!is_router && !is_onlink)
                goto bad;

        /* validation passed */

        icmp6len -= sizeof(*nd_rd);
        if (nd6_options(nd_rd + 1, icmp6len, &ndopts) < 0)
                /* 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)
                goto bad;

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

        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).
                 */
                rtcount = rt_timer_queue_count(&icmp6_redirect_timeout_q);
                if (rtcount >= atomic_load_int(&ip6_maxdynroutes))
                        goto freeit;

                bzero(&sdst, sizeof(sdst));
                bzero(&sgw, sizeof(sgw));
                bzero(&ssrc, 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);
                memcpy(&sgw.sin6_addr, &redtgt6, sizeof(struct in6_addr));
                memcpy(&sdst.sin6_addr, &reddst6, sizeof(struct in6_addr));
                memcpy(&ssrc.sin6_addr, &src6, sizeof(struct in6_addr));
                rtredirect(sin6tosa(&sdst), sin6tosa(&sgw), sin6tosa(&ssrc),
                    &newrt, m->m_pkthdr.ph_rtableid);
                if (newrt != NULL && icmp6_redirtimeout > 0) {
                        rt_timer_add(newrt, &icmp6_redirect_timeout_q,
                            m->m_pkthdr.ph_rtableid);
                }
                rtfree(newrt);
        }
        /* finally update cached route in each socket via pfctlinput */
        {
                struct sockaddr_in6 sdst;

                bzero(&sdst, sizeof(sdst));
                sdst.sin6_family = AF_INET6;
                sdst.sin6_len = sizeof(struct sockaddr_in6);
                memcpy(&sdst.sin6_addr, &reddst6, sizeof(struct in6_addr));
                pfctlinput(PRC_REDIRECT_HOST, sin6tosa(&sdst));
        }

 freeit:
        if_put(ifp);
        m_freem(m);
        return;

 bad:
        if_put(ifp);
        icmp6stat_inc(icp6s_badredirect);
        m_freem(m);
}

void
icmp6_redirect_output(struct mbuf *m0, struct rtentry *rt)
{
        struct ifnet *ifp = NULL;
        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;
        int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);

        icmp6_errcount(ND_REDIRECT, 0);

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

        /* sanity check */
        if (m0 == NULL || !rtisvalid(rt))
                goto fail;

        ifp = if_get(rt->rt_ifidx);
        if (ifp == NULL)
                goto fail;

        /*
         * 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 *);
        bzero(&src_sa, sizeof(src_sa));
        src_sa.sin6_family = AF_INET6;
        src_sa.sin6_len = sizeof(src_sa);
        src_sa.sin6_addr = sip6->ip6_src;
        /* we don't currently use sin6_scope_id, but eventually use it */
        src_sa.sin6_scope_id = in6_addr2scopeid(ifp->if_index, &sip6->ip6_src);
        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)
         */
#if IPV6_MMTU >= MCLBYTES
# error assumption failed about IPV6_MMTU and MCLBYTES
#endif
        MGETHDR(m, M_DONTWAIT, MT_HEADER);
        if (m && IPV6_MMTU >= MHLEN)
                MCLGET(m, M_DONTWAIT);
        if (!m)
                goto fail;
        m->m_pkthdr.ph_ifidx = 0;
        m->m_len = 0;
        maxlen = m_trailingspace(m);
        maxlen = min(IPV6_MMTU, maxlen);
        /* just for safety */
        if (maxlen < sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr) +
            ((sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7)) {
                goto fail;
        }

        {
                /* get ip6 linklocal address for ifp(my outgoing interface). */
                struct in6_ifaddr *ia6;
                if ((ia6 = in6ifa_ifpforlinklocal(ifp, IN6_IFF_TENTATIVE|
                    IN6_IFF_DUPLICATED|IN6_IFF_ANYCAST)) == NULL)
                        goto fail;
                ifp_ll6 = &ia6->ia_addr.sin6_addr;
        }

        /* get ip6 linklocal address for the router. */
        if (rt->rt_gateway && (rt->rt_flags & RTF_GATEWAY)) {
                struct sockaddr_in6 *sin6;
                sin6 = satosin6(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 rtentry *nrt;
                int len;
                struct sockaddr_dl *sdl;
                struct nd_opt_hdr *nd_opt;
                char *lladdr;

                len = sizeof(*nd_opt) + ifp->if_addrlen;
                len = (len + 7) & ~7;   /* round by 8 */
                /* safety check */
                if (len + (p - (u_char *)ip6) > maxlen)
                        goto nolladdropt;
                nrt = nd6_lookup(nexthop, 0, ifp, ifp->if_rdomain);
                if ((nrt != NULL) &&
                    (nrt->rt_flags & (RTF_GATEWAY|RTF_LLINFO)) == RTF_LLINFO &&
                    (nrt->rt_gateway->sa_family == AF_LINK) &&
                    (sdl = satosdl(nrt->rt_gateway)) &&
                    sdl->sdl_alen) {
                        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);
                        bcopy(LLADDR(sdl), lladdr, ifp->if_addrlen);
                        p += len;
                }
                rtfree(nrt);
        }
  nolladdropt:;

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

        /* just to be safe */
        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;

                /*
                 * 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.
                         */
                        size_t 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;
                bzero(nd_opt_rh, 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;

        sip6 = mtod(m, struct ip6_hdr *);
        if (IN6_IS_ADDR_LINKLOCAL(&sip6->ip6_src))
                sip6->ip6_src.s6_addr16[1] = 0;
        if (IN6_IS_ADDR_LINKLOCAL(&sip6->ip6_dst))
                sip6->ip6_dst.s6_addr16[1] = 0;
#if 0
        if (IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_src))
                ip6->ip6_src.s6_addr16[1] = 0;
        if (IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_dst))
                ip6->ip6_dst.s6_addr16[1] = 0;
#endif
        if (IN6_IS_ADDR_LINKLOCAL(&nd_rd->nd_rd_target))
                nd_rd->nd_rd_target.s6_addr16[1] = 0;
        if (IN6_IS_ADDR_LINKLOCAL(&nd_rd->nd_rd_dst))
                nd_rd->nd_rd_dst.s6_addr16[1] = 0;

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

        nd_rd->nd_rd_cksum = 0;
        m->m_pkthdr.csum_flags = M_ICMP_CSUM_OUT;

        /* send the packet to outside... */
        ip6_output(m, NULL, NULL, 0, NULL, NULL);

        icmp6stat_inc(icp6s_outhist + ND_REDIRECT);

        if_put(ifp);
        return;

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

/*
 * ICMPv6 socket option processing.
 */
int
icmp6_ctloutput(int op, struct socket *so, int level, int optname,
    struct mbuf *m)
{
        int error = 0;
        struct inpcb *inp = sotoinpcb(so);

        if (level != IPPROTO_ICMPV6)
                return EINVAL;

        switch (op) {
        case PRCO_SETOPT:
                switch (optname) {
                case ICMP6_FILTER:
                    {
                        struct icmp6_filter *p;

                        if (m == NULL || m->m_len != sizeof(*p)) {
                                error = EMSGSIZE;
                                break;
                        }
                        p = mtod(m, struct icmp6_filter *);
                        if (!p || !inp->inp_icmp6filt) {
                                error = EINVAL;
                                break;
                        }
                        bcopy(p, inp->inp_icmp6filt,
                                sizeof(struct icmp6_filter));
                        error = 0;
                        break;
                    }

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;

        case PRCO_GETOPT:
                switch (optname) {
                case ICMP6_FILTER:
                    {
                        struct icmp6_filter *p;

                        if (!inp->inp_icmp6filt) {
                                error = EINVAL;
                                break;
                        }
                        m->m_len = sizeof(struct icmp6_filter);
                        p = mtod(m, struct icmp6_filter *);
                        bcopy(inp->inp_icmp6filt, p,
                                sizeof(struct icmp6_filter));
                        error = 0;
                        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?
 *
 * dst - not used at this moment
 * type - not used at this moment
 * code - not used at this moment
 */
int
icmp6_ratelimit(const struct in6_addr *dst, const int type, const int code)
{
        /* PPS limit */
        if (!ppsratecheck(&icmp6errppslim_last, &icmp6errpps_count,
            atomic_load_int(&icmp6errppslim)))
                return 1;       /* The packet is subject to rate limit */
        return 0;               /* okay to send */
}

struct rtentry *
icmp6_mtudisc_clone(struct sockaddr_in6 *dst, u_int rtableid, int ipsec)
{
        struct rtentry *rt;
        int    error;

        rt = rtalloc(sin6tosa(dst), RT_RESOLVE, rtableid);

        /* Check if the route is actually usable */
        if (!rtisvalid(rt))
                goto bad;
        /* IPsec needs the route only for PMTU, it can use reject for that */
        if (!ipsec && (rt->rt_flags & (RTF_REJECT|RTF_BLACKHOLE)))
                goto bad;

        /*
         * No PMTU for local routes and permanent neighbors,
         * ARP and NDP use the same expire timer as the route.
         */
        if (ISSET(rt->rt_flags, RTF_LOCAL) ||
            (ISSET(rt->rt_flags, RTF_LLINFO) && rt->rt_expire == 0))
                goto bad;

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

                memset(&info, 0, sizeof(info));
                info.rti_ifa = rt->rt_ifa;
                info.rti_flags = RTF_GATEWAY | RTF_HOST | RTF_DYNAMIC;
                info.rti_info[RTAX_DST] = sin6tosa(dst);
                info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
                info.rti_info[RTAX_LABEL] =
                    rtlabel_id2sa(rt->rt_labelid, &sa_rl);

                error = rtrequest(RTM_ADD, &info, rt->rt_priority, &nrt,
                    rtableid);
                if (error)
                        goto bad;
                nrt->rt_rmx = rt->rt_rmx;
                rtfree(rt);
                rt = nrt;
                rtm_send(rt, RTM_ADD, 0, rtableid);
        }
        error = rt_timer_add(rt, &icmp6_mtudisc_timeout_q, rtableid);
        if (error)
                goto bad;

        return (rt);
bad:
        rtfree(rt);
        return (NULL);
}

void
icmp6_mtudisc_timeout(struct rtentry *rt, u_int rtableid)
{
        struct ifnet *ifp;

        NET_ASSERT_LOCKED();

        ifp = if_get(rt->rt_ifidx);
        if (ifp == NULL)
                return;

        if ((rt->rt_flags & (RTF_DYNAMIC|RTF_HOST)) == (RTF_DYNAMIC|RTF_HOST)) {
                rtdeletemsg(rt, ifp, rtableid);
        } else {
                if (!(rt->rt_locks & RTV_MTU))
                        atomic_store_int(&rt->rt_mtu, 0);
        }

        if_put(ifp);
}

#ifndef SMALL_KERNEL
const struct sysctl_bounded_args icmpv6ctl_vars[] = {
        { ICMPV6CTL_ND6_DELAY, &nd6_delay, 0, INT_MAX },
        { ICMPV6CTL_ND6_UMAXTRIES, &nd6_umaxtries, 0, INT_MAX },
        { ICMPV6CTL_ND6_MMAXTRIES, &nd6_mmaxtries, 0, INT_MAX },
        { ICMPV6CTL_MTUDISC_HIWAT, &icmp6_mtudisc_hiwat, 0, INT_MAX },
        { ICMPV6CTL_MTUDISC_LOWAT, &icmp6_mtudisc_lowat, 0, INT_MAX },
        { ICMPV6CTL_ERRPPSLIMIT, &icmp6errppslim, -1, 1000 },
};

int
icmp6_sysctl_icmp6stat(void *oldp, size_t *oldlenp, void *newp)
{
        struct icmp6stat *icmp6stat;
        int ret;

        CTASSERT(sizeof(*icmp6stat) == icp6s_ncounters * sizeof(uint64_t));
        icmp6stat = malloc(sizeof(*icmp6stat), M_TEMP, M_WAITOK|M_ZERO);
        counters_read(icmp6counters, (uint64_t *)icmp6stat, icp6s_ncounters,
            NULL);
        ret = sysctl_rdstruct(oldp, oldlenp, newp,
            icmp6stat, sizeof(*icmp6stat));
        free(icmp6stat, M_TEMP, sizeof(*icmp6stat));

        return (ret);
}

int
icmp6_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
    void *newp, size_t newlen)
{
        int error;

        /* All sysctl names at this level are terminal. */
        if (namelen != 1)
                return (ENOTDIR);

        switch (name[0]) {
        case ICMPV6CTL_REDIRTIMEOUT: {
                int oldval, newval, error;

                oldval = newval = atomic_load_int(&icmp6_redirtimeout);
                error = sysctl_int_bounded(oldp, oldlenp, newp, newlen,
                    &newval, 0, INT_MAX);
                if (error == 0 && oldval != newval) {
                        rw_enter_write(&sysctl_lock);
                        atomic_store_int(&icmp6_redirtimeout, newval);
                        rt_timer_queue_change(&icmp6_redirect_timeout_q,
                            newval);
                        rw_exit_write(&sysctl_lock);
                }

                return (error);
        }
        case ICMPV6CTL_STATS:
                error = icmp6_sysctl_icmp6stat(oldp, oldlenp, newp);
                break;

        case ICMPV6CTL_ND6_QUEUED:
                error = sysctl_rdint(oldp, oldlenp, newp,
                    atomic_load_int(&ln_hold_total));
                break;

        default:
                error = sysctl_bounded_arr(icmpv6ctl_vars,
                    nitems(icmpv6ctl_vars), name, namelen, oldp, oldlenp, newp,
                    newlen);
                break;
        }

        return (error);
}
#endif /* SMALL_KERNEL */