/*      $NetBSD: nd6_nbr.c,v 1.186 2025/04/28 11:39:10 joe Exp $        */
/*      $KAME: nd6_nbr.c,v 1.61 2001/02/10 16:06:14 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: nd6_nbr.c,v 1.186 2025/04/28 11:39:10 joe Exp $");

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#include "opt_net_mpsafe.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kmem.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sockio.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#include <sys/ioctl.h>
#include <sys/syslog.h>
#include <sys/queue.h>
#include <sys/callout.h>
#include <sys/cprng.h>

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

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet6/in6_var.h>
#include <netinet6/in6_ifattach.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet6/nd6.h>
#include <netinet/icmp6.h>
#include <netinet6/icmp6_private.h>

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

struct dadq;
static struct dadq *nd6_dad_find(struct ifaddr *, struct nd_opt_nonce *, bool *);
static bool nd6_dad_ownnonce(struct ifaddr *, struct nd_opt_nonce *nonce);
static void nd6_dad_starttimer(struct dadq *, int);
static void nd6_dad_destroytimer(struct dadq *);
static void nd6_dad_timer(struct dadq *);
static void nd6_dad_ns_output(struct dadq *, struct ifaddr *);
static void nd6_dad_input(struct ifaddr *, struct nd_opt_nonce *,
    const struct sockaddr_dl *);
static void nd6_dad_duplicated(struct ifaddr *, struct dadq *,
    const struct sockaddr_dl *);

static int dad_maxtry = 15;     /* max # of *tries* to transmit DAD packet */

/*
 * Input a Neighbor Solicitation Message.
 *
 * Based on RFC 2461
 * Based on RFC 2462 (duplicate address detection)
 */
void
nd6_ns_input(struct mbuf *m, int off, int icmp6len)
{
        struct ifnet *ifp, *ifpc;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_neighbor_solicit *nd_ns;
        struct in6_addr saddr6 = ip6->ip6_src;
        struct in6_addr daddr6 = ip6->ip6_dst;
        struct in6_addr taddr6;
        struct in6_addr myaddr6;
        char *lladdr = NULL;
        struct ifaddr *ifa = NULL;
        int lladdrlen = 0;
        int anycast = 0, proxy = 0, tentative = 0;
        int router = ip6_forwarding;
        int tlladdr;
        union nd_opts ndopts;
        const struct sockaddr_dl *proxydl = NULL;
        struct psref psref;
        struct psref psref_c;
        struct psref psref_ia;
        char ip6buf[INET6_ADDRSTRLEN], ip6buf2[INET6_ADDRSTRLEN];

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

        IP6_EXTHDR_GET(nd_ns, struct nd_neighbor_solicit *, m, off, icmp6len);
        if (nd_ns == NULL) {
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                m_put_rcvif_psref(ifp, &psref);
                return;
        }
        ip6 = mtod(m, struct ip6_hdr *); /* adjust pointer for safety */
        taddr6 = nd_ns->nd_ns_target;
        if (in6_setscope(&taddr6, ifp, NULL) != 0)
                goto bad;

        if (ip6->ip6_hlim != 255) {
                nd6log(LOG_ERR, "invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, IN6_PRINT(ip6buf, &ip6->ip6_src),
                    IN6_PRINT(ip6buf2, &ip6->ip6_dst), if_name(ifp));
                goto bad;
        }

        if (IN6_IS_ADDR_UNSPECIFIED(&saddr6)) {
                /* dst has to be a solicited node multicast address. */
                /* don't check ifindex portion */
                if (daddr6.s6_addr16[0] == IPV6_ADDR_INT16_MLL &&
                    daddr6.s6_addr32[1] == 0 &&
                    daddr6.s6_addr32[2] == IPV6_ADDR_INT32_ONE &&
                    daddr6.s6_addr8[12] == 0xff) {
                        ; /* good */
                } else {
                        nd6log(LOG_INFO, "bad DAD packet (wrong ip6 dst)\n");
                        goto bad;
                }
        } else {
                struct sockaddr_in6 ssin6;

                /*
                 * Make sure the source address is from a neighbor's address.
                 */
                sockaddr_in6_init(&ssin6, &saddr6, 0, 0, 0);
                if (nd6_is_addr_neighbor(&ssin6, ifp) == 0) {
                        nd6log(LOG_INFO,
                            "NS packet from non-neighbor %s on %s\n",
                            IN6_PRINT(ip6buf, &saddr6), if_name(ifp));
                        goto bad;
                }
        }

        if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
                nd6log(LOG_INFO, "bad NS target (multicast)\n");
                goto bad;
        }

        icmp6len -= sizeof(*nd_ns);
        nd6_option_init(nd_ns + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                nd6log(LOG_INFO, "invalid ND option, ignored\n");
                /* nd6_options have incremented stats */
                goto freeit;
        }

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

        if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src) && lladdr) {
                nd6log(LOG_INFO,
                    "bad DAD packet (link-layer address option)\n");
                goto bad;
        }

        /*
         * Attaching target link-layer address to the NA?
         * (RFC 2461 7.2.4)
         *
         * NS IP dst is multicast                       MUST add
         * Otherwise                                    MAY be omitted
         *
         * In this implementation, we omit the target link-layer address
         * in the "MAY" case.
         */
#if 0 /* too much! */
        ifa = (struct ifaddr *)in6ifa_ifpwithaddr(ifp, &daddr6);
        if (ifa && (((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_ANYCAST))
                tlladdr = 0;
        else
#endif
        if (!IN6_IS_ADDR_MULTICAST(&daddr6))
                tlladdr = 0;
        else
                tlladdr = 1;

        /*
         * Target address (taddr6) must be either:
         * (1) Valid unicast/anycast address for my receiving interface,
         * (2) Unicast address for which I'm offering proxy service, or
         * (3) "tentative" address on which DAD is being performed.
         */
        /* (1) and (3) check. */
#if NCARP > 0
        if (ifp->if_carp && ifp->if_type != IFT_CARP) {
                int s = pserialize_read_enter();
                ifa = carp_iamatch6(ifp->if_carp, &taddr6);
                if (ifa != NULL) {
                        ifa_acquire(ifa, &psref_ia);
                        if (ifa->ifa_ifp && ifa->ifa_ifp != ifp) {
                                ifpc = ifa->ifa_ifp;
                                if_acquire(ifpc, &psref_c);
                        }
                }

                pserialize_read_exit(s);
        } else
                ifa = NULL;
        if (!ifa)
                ifa = (struct ifaddr *)in6ifa_ifpwithaddr_psref(ifp, &taddr6,
                    &psref_ia);
#else
        ifa = (struct ifaddr *)in6ifa_ifpwithaddr_psref(ifp, &taddr6,
            &psref_ia);
#endif

        /* (2) check. */
        if (ifa == NULL) {
                struct rtentry *rt;
                struct sockaddr_in6 tsin6;

                sockaddr_in6_init(&tsin6, &taddr6, 0, 0, 0);

                rt = rtalloc1(sin6tosa(&tsin6), 0);
                if (rt && (rt->rt_flags & RTF_ANNOUNCE) != 0 &&
                    rt->rt_gateway->sa_family == AF_LINK) {
                        /*
                         * proxy NDP for single entry
                         */
                        ifa = (struct ifaddr *)in6ifa_ifpforlinklocal_psref(ifp,
                                IN6_IFF_NOTREADY|IN6_IFF_ANYCAST, &psref_ia);
                        if (ifa) {
                                proxy = 1;
                                proxydl = satocsdl(rt->rt_gateway);
                                router = 0;     /* XXX */
                        }
                }
                if (rt)
                        rt_unref(rt);
        }
        if (ifa == NULL) {
                /*
                 * We've got an NS packet, and we don't have that address
                 * assigned for us.  We MUST silently ignore it.
                 * See RFC2461 7.2.3.
                 */
                goto freeit;
        }
        myaddr6 = *IFA_IN6(ifa);
        anycast = ((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_ANYCAST;
        tentative = ((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_TENTATIVE;
        if (((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_DUPLICATED)
                goto freeit;

        if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                nd6log(LOG_INFO, "lladdrlen mismatch for %s "
                    "(if %d, NS packet %d)\n",
                    IN6_PRINT(ip6buf, &taddr6),
                    ifp->if_addrlen, lladdrlen - 2);
                goto bad;
        }

        if (IN6_ARE_ADDR_EQUAL(&myaddr6, &saddr6)) {
                nd6log(LOG_INFO, "duplicate IP6 address %s\n",
                    IN6_PRINT(ip6buf, &saddr6));
                goto freeit;
        }

        /*
         * We have neighbor solicitation packet, with target address equals to
         * one of my tentative address.
         *
         * src addr     how to process?
         * ---          ---
         * multicast    of course, invalid (rejected in ip6_input)
         * unicast      somebody is doing address resolution -> ignore
         * unspec       dup address detection
         *
         * The processing is defined in RFC 2462.
         */
        if (tentative) {
                /*
                 * If source address is unspecified address, it is for
                 * duplicate address detection.
                 *
                 * If not, the packet is for address resolution;
                 * silently ignore it.
                 */
                if (IN6_IS_ADDR_UNSPECIFIED(&saddr6)) {
                        struct sockaddr_dl sdl, *sdlp;

                        if (lladdr != NULL)
                                sdlp = sockaddr_dl_init(&sdl, sizeof(sdl),
                                    ifp->if_index, ifp->if_type,
                                    NULL, 0, lladdr, lladdrlen);
                        else
                                sdlp = NULL;
                        nd6_dad_input(ifa, ndopts.nd_opts_nonce, sdlp);
                }
                goto freeit;
        }

        /*
         * It looks that sender is performing DAD.
         * Check that the nonce is not being used by the same address
         * on another interface.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&saddr6) && ndopts.nd_opts_nonce != NULL) {
                if (nd6_dad_ownnonce(ifa, ndopts.nd_opts_nonce))
                        goto freeit;
        }

        ifa_release(ifa, &psref_ia);
        ifa = NULL;

        /*
         * If the source address is unspecified address, entries must not
         * be created or updated.
         * It looks that sender is performing DAD.  Output NA toward
         * all-node multicast address, to tell the sender that I'm using
         * the address.
         * S bit ("solicited") must be zero.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&saddr6)) {
                struct in6_addr in6_all;

                in6_all = in6addr_linklocal_allnodes;
                if (in6_setscope(&in6_all, ifp, NULL) != 0)
                        goto bad;
                nd6_na_output(ifpc, &in6_all, &taddr6,
                    ((anycast || proxy || !tlladdr) ? 0 : ND_NA_FLAG_OVERRIDE) |
                    (ip6_forwarding ? ND_NA_FLAG_ROUTER : 0),
                    tlladdr, (const struct sockaddr *)proxydl);
                goto freeit;
        }

        nd6_cache_lladdr(ifpc, &saddr6, lladdr, lladdrlen, ND_NEIGHBOR_SOLICIT, 0);

        nd6_na_output(ifp, &saddr6, &taddr6,
            ((anycast || proxy || !tlladdr) ? 0 : ND_NA_FLAG_OVERRIDE) |
            (router ? ND_NA_FLAG_ROUTER : 0) | ND_NA_FLAG_SOLICITED,
            tlladdr, (const struct sockaddr *)proxydl);
 freeit:
        ifa_release(ifa, &psref_ia);
        m_put_rcvif_psref(ifp, &psref);
        if (ifp != ifpc)
                if_put(ifpc, &psref_c);

        m_freem(m);
        return;

 bad:
        nd6log(LOG_ERR, "src=%s\n", IN6_PRINT(ip6buf, &saddr6));
        nd6log(LOG_ERR, "dst=%s\n", IN6_PRINT(ip6buf, &daddr6));
        nd6log(LOG_ERR, "tgt=%s\n", IN6_PRINT(ip6buf, &taddr6));
        ICMP6_STATINC(ICMP6_STAT_BADNS);
        ifa_release(ifa, &psref_ia);
        m_put_rcvif_psref(ifp, &psref);
        m_freem(m);
}

/*
 * Output a Neighbor Solicitation Message. Caller specifies:
 *      - ICMP6 header source IP6 address
 *      - ND6 header target IP6 address
 *      - ND6 header source datalink address
 *
 * Based on RFC 2461
 * Based on RFC 2462 (duplicate address detection)
 */
void
nd6_ns_output(struct ifnet *ifp, const struct in6_addr *daddr6,
    const struct in6_addr *taddr6,
    const struct in6_addr *hsrc,
    const uint8_t *nonce        /* duplicate address detection */)
{
        struct mbuf *m;
        struct ip6_hdr *ip6;
        struct nd_neighbor_solicit *nd_ns;
        const struct in6_addr *src;
        struct in6_addr src_in;
        struct ip6_moptions im6o;
        int icmp6len;
        int maxlen;
        const void *mac;
        struct route ro;

        if (IN6_IS_ADDR_MULTICAST(taddr6))
                return;

        memset(&ro, 0, sizeof(ro));

        /* estimate the size of message */
        maxlen = sizeof(*ip6) + sizeof(*nd_ns);
        maxlen += (sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7;
        KASSERTMSG(max_linkhdr + maxlen <= MCLBYTES,
            "max_linkhdr + maxlen > MCLBYTES (%d + %d > %d)",
            max_linkhdr, maxlen, MCLBYTES);

        MGETHDR(m, M_DONTWAIT, MT_DATA);
        if (m && max_linkhdr + maxlen >= MHLEN) {
                MCLGET(m, M_DONTWAIT);
                if ((m->m_flags & M_EXT) == 0) {
                        m_free(m);
                        m = NULL;
                }
        }
        if (m == NULL)
                return;
        m_reset_rcvif(m);

        if (daddr6 == NULL || IN6_IS_ADDR_MULTICAST(daddr6)) {
                m->m_flags |= M_MCAST;
                im6o.im6o_multicast_if_index = if_get_index(ifp);
                im6o.im6o_multicast_hlim = 255;
                im6o.im6o_multicast_loop = 0;
        }

        icmp6len = sizeof(*nd_ns);
        m->m_pkthdr.len = m->m_len = sizeof(*ip6) + icmp6len;
        m->m_data += max_linkhdr;       /* or m_align() equivalent? */

        /* fill neighbor solicitation packet */
        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;
        if (daddr6)
                ip6->ip6_dst = *daddr6;
        else {
                ip6->ip6_dst.s6_addr16[0] = IPV6_ADDR_INT16_MLL;
                ip6->ip6_dst.s6_addr16[1] = 0;
                ip6->ip6_dst.s6_addr32[1] = 0;
                ip6->ip6_dst.s6_addr32[2] = IPV6_ADDR_INT32_ONE;
                ip6->ip6_dst.s6_addr32[3] = taddr6->s6_addr32[3];
                ip6->ip6_dst.s6_addr8[12] = 0xff;
                if (in6_setscope(&ip6->ip6_dst, ifp, NULL) != 0)
                        goto bad;
        }
        if (nonce == NULL) {
                int s;
                /*
                 * RFC2461 7.2.2:
                 * "If the source address of the packet prompting the
                 * solicitation is the same as one of the addresses assigned
                 * to the outgoing interface, that address SHOULD be placed
                 * in the IP Source Address of the outgoing solicitation.
                 * Otherwise, any one of the addresses assigned to the
                 * interface should be used."
                 *
                 * We use the source address for the prompting packet
                 * (hsrc), if:
                 * - hsrc is given from the caller (by giving "ln"), and
                 * - hsrc belongs to the outgoing interface.
                 * Otherwise, we perform the source address selection as usual.
                 */
                s = pserialize_read_enter();
                if (hsrc && in6ifa_ifpwithaddr(ifp, hsrc)) {
                        pserialize_read_exit(s);
                        src = hsrc;
                } else {
                        int error;
                        struct sockaddr_in6 dst_sa;

                        pserialize_read_exit(s);

                        sockaddr_in6_init(&dst_sa, &ip6->ip6_dst, 0, 0, 0);

                        error = in6_selectsrc(&dst_sa, NULL,
                            NULL, &ro, NULL, NULL, NULL, &src_in);
                        if (error != 0) {
                                char ip6buf[INET6_ADDRSTRLEN];
                                nd6log(LOG_DEBUG, "source can't be "
                                    "determined: dst=%s, error=%d\n",
                                    IN6_PRINT(ip6buf, &dst_sa.sin6_addr),
                                    error);
                                goto bad;
                        }
                        src = &src_in;
                }
        } else {
                /*
                 * Source address for DAD packet must always be IPv6
                 * unspecified address. (0::0)
                 * We actually don't have to 0-clear the address (we did it
                 * above), but we do so here explicitly to make the intention
                 * clearer.
                 */
                memset(&src_in, 0, sizeof(src_in));
                src = &src_in;
        }
        ip6->ip6_src = *src;
        nd_ns = (struct nd_neighbor_solicit *)(ip6 + 1);
        nd_ns->nd_ns_type = ND_NEIGHBOR_SOLICIT;
        nd_ns->nd_ns_code = 0;
        nd_ns->nd_ns_reserved = 0;
        nd_ns->nd_ns_target = *taddr6;
        in6_clearscope(&nd_ns->nd_ns_target); /* XXX */

        /*
         * Add source link-layer address option.
         *
         *                              spec            implementation
         *                              ---             ---
         * DAD packet                   MUST NOT        do not add the option
         * there's no link layer address:
         *                              impossible      do not add the option
         * there's link layer address:
         *      Multicast NS            MUST add one    add the option
         *      Unicast NS              SHOULD add one  add the option
         */
        if (nonce == NULL && (mac = nd6_ifptomac(ifp))) {
                int optlen = sizeof(struct nd_opt_hdr) + ifp->if_addrlen;
                struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)(nd_ns + 1);
                /* 8 byte alignments... */
                optlen = (optlen + 7) & ~7;

                m->m_pkthdr.len += optlen;
                m->m_len += optlen;
                icmp6len += optlen;
                memset((void *)nd_opt, 0, optlen);
                nd_opt->nd_opt_type = ND_OPT_SOURCE_LINKADDR;
                nd_opt->nd_opt_len = optlen >> 3;
                memcpy((void *)(nd_opt + 1), mac, ifp->if_addrlen);
        }

        /* Add a nonce option (RFC 3971) to detect looped back NS messages.
         * This behavior is documented in RFC 7527. */
        if (nonce != NULL) {
                int optlen = sizeof(struct nd_opt_hdr) + ND_OPT_NONCE_LEN;
                struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)(nd_ns + 1);

                /* 8-byte alignment is required. */
                optlen = (optlen + 7) & ~7;
                m->m_pkthdr.len += optlen;
                m->m_len += optlen;
                icmp6len += optlen;
                memset(nd_opt, 0, optlen);
                nd_opt->nd_opt_type = ND_OPT_NONCE;
                nd_opt->nd_opt_len = optlen >> 3;
                memcpy(nd_opt + 1, nonce, ND_OPT_NONCE_LEN);
        }

        ip6->ip6_plen = htons((u_int16_t)icmp6len);
        nd_ns->nd_ns_cksum = 0;
        nd_ns->nd_ns_cksum =
            in6_cksum(m, IPPROTO_ICMPV6, sizeof(*ip6), icmp6len);

        ip6_output(m, NULL, &ro, nonce != NULL ? IPV6_UNSPECSRC : 0,
            &im6o, NULL, NULL);
        icmp6_ifstat_inc(ifp, ifs6_out_msg);
        icmp6_ifstat_inc(ifp, ifs6_out_neighborsolicit);
        ICMP6_STATINC(ICMP6_STAT_OUTHIST + ND_NEIGHBOR_SOLICIT);

        rtcache_free(&ro);
        return;

  bad:
        rtcache_free(&ro);
        m_freem(m);
        return;
}

/*
 * Neighbor advertisement input handling.
 *
 * Based on RFC 2461
 * Based on RFC 2462 (duplicate address detection)
 *
 * the following items are not implemented yet:
 * - proxy advertisement delay rule (RFC2461 7.2.8, last paragraph, SHOULD)
 * - anycast advertisement delay rule (RFC2461 7.2.7, SHOULD)
 */
void
nd6_na_input(struct mbuf *m, int off, int icmp6len)
{
        struct ifnet *ifp;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_neighbor_advert *nd_na;
        struct in6_addr saddr6 = ip6->ip6_src;
        struct in6_addr daddr6 = ip6->ip6_dst;
        struct in6_addr taddr6;
        int flags;
        int is_router;
        int is_solicited;
        int is_override;
        int rt_cmd;
        char *lladdr = NULL;
        int lladdrlen = 0;
        struct ifaddr *ifa;
        struct llentry *ln = NULL;
        union nd_opts ndopts;
        struct sockaddr_in6 ssin6;
        struct psref psref;
        struct psref psref_ia;
        char ip6buf[INET6_ADDRSTRLEN], ip6buf2[INET6_ADDRSTRLEN];

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

        if (ip6->ip6_hlim != 255) {
                nd6log(LOG_ERR,
                    "invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, IN6_PRINT(ip6buf, &ip6->ip6_src),
                    IN6_PRINT(ip6buf2, &ip6->ip6_dst), if_name(ifp));
                goto bad;
        }

        IP6_EXTHDR_GET(nd_na, struct nd_neighbor_advert *, m, off, icmp6len);
        if (nd_na == NULL) {
                m_put_rcvif_psref(ifp, &psref);
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                return;
        }

        flags = nd_na->nd_na_flags_reserved;
        is_router = ((flags & ND_NA_FLAG_ROUTER) != 0);
        is_solicited = ((flags & ND_NA_FLAG_SOLICITED) != 0);
        is_override = ((flags & ND_NA_FLAG_OVERRIDE) != 0);

        taddr6 = nd_na->nd_na_target;
        if (in6_setscope(&taddr6, ifp, NULL)) {
                goto bad;
        }

        if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
                nd6log(LOG_ERR, "invalid target address %s\n",
                    IN6_PRINT(ip6buf, &taddr6));
                goto bad;
        }
        if (is_solicited && IN6_IS_ADDR_MULTICAST(&daddr6)) {
                nd6log(LOG_ERR, "a solicited adv is multicasted\n");
                goto bad;
        }

        icmp6len -= sizeof(*nd_na);
        nd6_option_init(nd_na + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                nd6log(LOG_INFO, "invalid ND option, ignored\n");
                /* nd6_options have incremented stats */
                goto freeit;
        }

        if (ndopts.nd_opts_tgt_lladdr != NULL) {
                struct ifnet *ifp_ll;
                struct psref psref_ll;

                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, NA packet %d)\n",
                            IN6_PRINT(ip6buf, &taddr6),
                            ifp->if_addrlen, lladdrlen - 2);
                        goto bad;
                }

                ifp_ll = if_get_bylla(lladdr, ifp->if_addrlen, &psref_ll);
                if (ifp_ll != NULL) {
                        /* it's from me, ignore it. */
                        if_put(ifp_ll, &psref_ll);
                        goto freeit;
                }
        }

        ifa = (struct ifaddr *)in6ifa_ifpwithaddr_psref(ifp, &taddr6, &psref_ia);

        /*
         * Target address matches one of my interface address.
         *
         * If my address is tentative, this means that there's somebody
         * already using the same address as mine.  This indicates DAD failure.
         * This is defined in RFC 2462.
         *
         * Otherwise, process as defined in RFC 2461.
         */
        if (ifa) {
                if (((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_TENTATIVE) {
                        struct sockaddr_dl sdl, *sdlp;

                        if (lladdr != NULL)
                                sdlp = sockaddr_dl_init(&sdl, sizeof(sdl),
                                    ifp->if_index, ifp->if_type,
                                    NULL, 0, lladdr, lladdrlen);
                        else
                                sdlp = NULL;
                        nd6_dad_input(ifa, NULL, sdlp);
                } else
                        log(LOG_ERR,
                            "nd6_na_input: duplicate IP6 address %s\n",
                            IN6_PRINT(ip6buf, &taddr6));
                ifa_release(ifa, &psref_ia);
                ifa = NULL;
                goto freeit;
        }

        /*
         * Make sure the source address is from a neighbor's address.
         */
        sockaddr_in6_init(&ssin6, &saddr6, 0, 0, 0);
        if (nd6_is_addr_neighbor(&ssin6, ifp) == 0) {
                nd6log(LOG_INFO, "ND packet from non-neighbor %s on %s\n",
                    IN6_PRINT(ip6buf, &saddr6), if_name(ifp));
                goto bad;
        }

        /*
         * If no neighbor cache entry is found, NA SHOULD silently be
         * discarded.
         */
        ln = nd6_lookup(&taddr6, ifp, true);
        if (ln == NULL)
                goto freeit;

        rt_cmd = 0;
        if (ln->ln_state <= ND_LLINFO_INCOMPLETE) {
                /*
                 * If the link-layer has address, and no lladdr option came,
                 * discard the packet.
                 */
                if (ifp->if_addrlen && !lladdr)
                        goto freeit;

                /*
                 * Record link-layer address, and update the state.
                 */
                memcpy(&ln->ll_addr, lladdr, ifp->if_addrlen);
                ln->la_flags |= LLE_VALID;
                rt_cmd = RTM_ADD;
                if (is_solicited) {
                        ln->ln_state = ND_LLINFO_REACHABLE;
                        ln->ln_byhint = 0;
                        if (!ND_IS_LLINFO_PERMANENT(ln))
                                nd_set_timer(ln, ND_TIMER_REACHABLE);
                } else {
                        ln->ln_state = ND_LLINFO_STALE;
                        nd_set_timer(ln, ND_TIMER_GC);
                }
        } else {
                bool llchange;

                /*
                 * Check if the link-layer address has changed or not.
                 */
                if (lladdr == NULL)
                        llchange = false;
                else {
                        if (ln->la_flags & LLE_VALID) {
                                if (memcmp(lladdr, &ln->ll_addr, ifp->if_addrlen))
                                        llchange = true;
                                else
                                        llchange = false;
                        } else
                                llchange = true;
                }
                if (llchange)
                        rt_cmd = RTM_CHANGE;

                /*
                 * This is VERY complex.  Look at it with care.
                 *
                 * override solicit lladdr llchange     action
                 *                                      (L: record lladdr)
                 *
                 *      0       0       n       --      (2c)
                 *      0       0       y       n       (2b) L
                 *      0       0       y       y       (1)    REACHABLE->STALE
                 *      0       1       n       --      (2c)   *->REACHABLE
                 *      0       1       y       n       (2b) L *->REACHABLE
                 *      0       1       y       y       (1)    REACHABLE->STALE
                 *      1       0       n       --      (2a)
                 *      1       0       y       n       (2a) L
                 *      1       0       y       y       (2a) L *->STALE
                 *      1       1       n       --      (2a)   *->REACHABLE
                 *      1       1       y       n       (2a) L *->REACHABLE
                 *      1       1       y       y       (2a) L *->REACHABLE
                 */
                if (!is_override && lladdr != NULL && llchange) { /* (1) */
                        /*
                         * If state is REACHABLE, make it STALE.
                         * no other updates should be done.
                         */
                        if (ln->ln_state == ND_LLINFO_REACHABLE) {
                                ln->ln_state = ND_LLINFO_STALE;
                                nd_set_timer(ln, ND_TIMER_GC);
                        }
                        goto freeit;
                } else if (is_override                             /* (2a) */
                    || (!is_override && lladdr != NULL && !llchange) /* (2b) */
                    || lladdr == NULL) {                           /* (2c) */
                        /*
                         * Update link-local address, if any.
                         */
                        if (lladdr != NULL) {
                                memcpy(&ln->ll_addr, lladdr, ifp->if_addrlen);
                                ln->la_flags |= LLE_VALID;
                        }

                        /*
                         * If solicited, make the state REACHABLE.
                         * If not solicited and the link-layer address was
                         * changed, make it STALE.
                         */
                        if (is_solicited) {
                                ln->ln_state = ND_LLINFO_REACHABLE;
                                ln->ln_byhint = 0;
                                if (!ND_IS_LLINFO_PERMANENT(ln))
                                        nd_set_timer(ln, ND_TIMER_REACHABLE);
                        } else {
                                if (lladdr && llchange) {
                                        ln->ln_state = ND_LLINFO_STALE;
                                        nd_set_timer(ln, ND_TIMER_GC);
                                }
                        }
                }
                ln->ln_router = is_router;
        }
        /*
         * XXX: does this matter?
         * rt->rt_flags &= ~RTF_REJECT;
         */
        ln->ln_asked = 0;
        nd6_llinfo_release_pkts(ln, ifp);

        if (rt_cmd != 0) {
                struct sockaddr_in6 sin6;

                sockaddr_in6_init(&sin6, &ln->r_l3addr.addr6, 0, 0, 0);
                rt_clonedmsg(rt_cmd, sin6tosa(&ssin6), sin6tosa(&sin6),
                    (char *)&ln->ll_addr, ln->lle_tbl->llt_ifp);
        }

 freeit:
        if (ln != NULL)
                LLE_WUNLOCK(ln);

        m_put_rcvif_psref(ifp, &psref);
        m_freem(m);
        return;

 bad:
        if (ln != NULL)
                LLE_WUNLOCK(ln);

        ICMP6_STATINC(ICMP6_STAT_BADNA);
        m_put_rcvif_psref(ifp, &psref);
        m_freem(m);
}

/*
 * Neighbor advertisement output handling.
 *
 * Based on RFC 2461
 *
 * the following items are not implemented yet:
 * - proxy advertisement delay rule (RFC2461 7.2.8, last paragraph, SHOULD)
 * - anycast advertisement delay rule (RFC2461 7.2.7, SHOULD)
 */
void
nd6_na_output(
        struct ifnet *ifp,
        const struct in6_addr *daddr6_0,
        const struct in6_addr *taddr6,
        u_long flags,
        int tlladdr,            /* 1 if include target link-layer address */
        const struct sockaddr *sdl0)    /* sockaddr_dl (= proxy NA) or NULL */
{
        struct mbuf *m;
        struct ip6_hdr *ip6;
        struct nd_neighbor_advert *nd_na;
        struct ip6_moptions im6o;
        struct sockaddr *dst;
        union {
                struct sockaddr         dst;
                struct sockaddr_in6     dst6;
        } u;
        struct in6_addr daddr6;
        int icmp6len, maxlen, error;
        const void *mac;
        struct route ro;

        mac = NULL;
        memset(&ro, 0, sizeof(ro));

        daddr6 = *daddr6_0;     /* make a local copy for modification */

        /* estimate the size of message */
        maxlen = sizeof(*ip6) + sizeof(*nd_na);
        maxlen += (sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7;
        KASSERTMSG(max_linkhdr + maxlen <= MCLBYTES,
            "max_linkhdr + maxlen > MCLBYTES (%d + %d > %d)",
            max_linkhdr, maxlen, MCLBYTES);

        MGETHDR(m, M_DONTWAIT, MT_DATA);
        if (m && max_linkhdr + maxlen >= MHLEN) {
                MCLGET(m, M_DONTWAIT);
                if ((m->m_flags & M_EXT) == 0) {
                        m_free(m);
                        m = NULL;
                }
        }
        if (m == NULL)
                return;
        m_reset_rcvif(m);

        if (IN6_IS_ADDR_MULTICAST(&daddr6)) {
                m->m_flags |= M_MCAST;
                im6o.im6o_multicast_if_index = if_get_index(ifp);
                im6o.im6o_multicast_hlim = 255;
                im6o.im6o_multicast_loop = 0;
        }

        icmp6len = sizeof(*nd_na);
        m->m_pkthdr.len = m->m_len = sizeof(struct ip6_hdr) + icmp6len;
        m->m_data += max_linkhdr;       /* or m_align() equivalent? */

        /* fill neighbor advertisement packet */
        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        ip6->ip6_hlim = 255;
        if (IN6_IS_ADDR_UNSPECIFIED(&daddr6)) {
                /* reply to DAD */
                daddr6.s6_addr16[0] = IPV6_ADDR_INT16_MLL;
                daddr6.s6_addr16[1] = 0;
                daddr6.s6_addr32[1] = 0;
                daddr6.s6_addr32[2] = 0;
                daddr6.s6_addr32[3] = IPV6_ADDR_INT32_ONE;
                if (in6_setscope(&daddr6, ifp, NULL))
                        goto bad;

                flags &= ~ND_NA_FLAG_SOLICITED;
        }
        ip6->ip6_dst = daddr6;
        sockaddr_in6_init(&u.dst6, &daddr6, 0, 0, 0);
        dst = &u.dst;
        if (rtcache_setdst(&ro, dst) != 0)
                goto bad;

        /*
         * Select a source whose scope is the same as that of the dest.
         */
        error = in6_selectsrc(satosin6(dst), NULL, NULL, &ro, NULL, NULL, NULL,
            &ip6->ip6_src);
        if (error != 0) {
                char ip6buf[INET6_ADDRSTRLEN];
                nd6log(LOG_DEBUG, "source can't be "
                    "determined: dst=%s, error=%d\n",
                    IN6_PRINT(ip6buf, &satocsin6(dst)->sin6_addr), error);
                goto bad;
        }
        nd_na = (struct nd_neighbor_advert *)(ip6 + 1);
        nd_na->nd_na_type = ND_NEIGHBOR_ADVERT;
        nd_na->nd_na_code = 0;
        nd_na->nd_na_target = *taddr6;
        in6_clearscope(&nd_na->nd_na_target); /* XXX */

        /*
         * "tlladdr" indicates NS's condition for adding tlladdr or not.
         * see nd6_ns_input() for details.
         * Basically, if NS packet is sent to unicast/anycast addr,
         * target lladdr option SHOULD NOT be included.
         */
        if (tlladdr) {
                /*
                 * sdl0 != NULL indicates proxy NA.  If we do proxy, use
                 * lladdr in sdl0.  If we are not proxying (sending NA for
                 * my address) use lladdr configured for the interface.
                 */
                if (sdl0 == NULL)
                        mac = nd6_ifptomac(ifp);
                else if (sdl0->sa_family == AF_LINK) {
                        const struct sockaddr_dl *sdl;
                        sdl = satocsdl(sdl0);
                        if (sdl->sdl_alen == ifp->if_addrlen)
                                mac = CLLADDR(sdl);
                }
        }
        if (tlladdr && mac) {
                int optlen = sizeof(struct nd_opt_hdr) + ifp->if_addrlen;
                struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)(nd_na + 1);

                /* roundup to 8 bytes alignment! */
                optlen = (optlen + 7) & ~7;

                m->m_pkthdr.len += optlen;
                m->m_len += optlen;
                icmp6len += optlen;
                memset((void *)nd_opt, 0, optlen);
                nd_opt->nd_opt_type = ND_OPT_TARGET_LINKADDR;
                nd_opt->nd_opt_len = optlen >> 3;
                memcpy((void *)(nd_opt + 1), mac, ifp->if_addrlen);
        } else
                flags &= ~ND_NA_FLAG_OVERRIDE;

        ip6->ip6_plen = htons((u_int16_t)icmp6len);
        nd_na->nd_na_flags_reserved = flags;
        nd_na->nd_na_cksum = 0;
        nd_na->nd_na_cksum =
            in6_cksum(m, IPPROTO_ICMPV6, sizeof(struct ip6_hdr), icmp6len);

        ip6_output(m, NULL, NULL, 0, &im6o, NULL, NULL);

        icmp6_ifstat_inc(ifp, ifs6_out_msg);
        icmp6_ifstat_inc(ifp, ifs6_out_neighboradvert);
        ICMP6_STATINC(ICMP6_STAT_OUTHIST + ND_NEIGHBOR_ADVERT);

        rtcache_free(&ro);
        return;

  bad:
        rtcache_free(&ro);
        m_freem(m);
        return;
}

const void *
nd6_ifptomac(const struct ifnet *ifp)
{
        switch (ifp->if_type) {
        case IFT_ARCNET:
        case IFT_ETHER:
        case IFT_IEEE1394:
        case IFT_PROPVIRTUAL:
        case IFT_CARP:
        case IFT_L2VLAN:
        case IFT_IEEE80211:
                return CLLADDR(ifp->if_sadl);
        default:
                return NULL;
        }
}

TAILQ_HEAD(dadq_head, dadq);
struct dadq {
        TAILQ_ENTRY(dadq) dad_list;
        struct ifaddr *dad_ifa;
        int dad_count;                  /* max NS to send */
        int dad_ns_tcount;              /* # of trials to send NS */
        int dad_ns_ocount;              /* NS sent so far */
        int dad_ns_lcount;              /* looped back NS */
        struct callout dad_timer_ch;
#define ND_OPT_NONCE_STORE      3       /* dad_count should not exceed this */
        /*
         * The default ip6_dad_count is 1 as specified by RFC 4862 and
         * practically must users won't exceed this.
         * A storage of 3 is defaulted to here, in-case the administrator wants
         * to match the equivalent behaviour in our ARP implementation.
         * This constraint could be removed by sending the on wire nonce as
         * hmac(key, dad_ns_ocount), but that would increase the nonce size
         * sent on the wire.
         */
        uint8_t dad_nonce[ND_OPT_NONCE_STORE][ND_OPT_NONCE_LEN];
};

static struct dadq_head dadq;
static kmutex_t nd6_dad_lock;

void
nd6_nbr_init(void)
{

        TAILQ_INIT(&dadq);
        mutex_init(&nd6_dad_lock, MUTEX_DEFAULT, IPL_NONE);
}

static struct dadq *
nd6_dad_find(struct ifaddr *ifa, struct nd_opt_nonce *nonce, bool *found_nonce)
{
        struct in6_addr *myaddr6, *dadaddr6;
        bool match_ifa;
        struct dadq *dp;
        int i, nonce_max;

        KASSERT(mutex_owned(&nd6_dad_lock));
        KASSERT(ifa != NULL);

        myaddr6 = IFA_IN6(ifa);
        if (nonce != NULL &&
            nonce->nd_opt_nonce_len != (ND_OPT_NONCE_LEN + 2) / 8)
                nonce = NULL;
        match_ifa = nonce == NULL || found_nonce == NULL || *found_nonce == false;
        if (found_nonce != NULL)
                *found_nonce = false;

        TAILQ_FOREACH(dp, &dadq, dad_list) {
                if (match_ifa) {
                        if (dp->dad_ifa != ifa)
                                continue;
                } else {
                        dadaddr6 = IFA_IN6(dp->dad_ifa);
                        if (!IN6_ARE_ADDR_EQUAL(myaddr6, dadaddr6))
                                continue;
                }

                if (nonce == NULL)
                        break;

                nonce_max = MIN(dp->dad_ns_ocount, ND_OPT_NONCE_STORE);
                for (i = 0; i < nonce_max; i++) {
                        if (memcmp(nonce->nd_opt_nonce,
                            dp->dad_nonce[i],
                            ND_OPT_NONCE_LEN) == 0)
                                break;
                }
                if (i < nonce_max) {
                        char ip6buf[INET6_ADDRSTRLEN];

                        *found_nonce = true;
                        log(LOG_DEBUG,
                            "%s: detected a looped back NS message for %s\n",
                            if_name(ifa->ifa_ifp), IN6_PRINT(ip6buf, myaddr6));
                        dp->dad_ns_lcount++;
                        continue;
                }

                break;
        }
        return dp;
}

static bool
nd6_dad_ownnonce(struct ifaddr *ifa, struct nd_opt_nonce *nonce)
{
        bool found_nonce = true;

        mutex_enter(&nd6_dad_lock);
        nd6_dad_find(ifa, nonce, &found_nonce);
        mutex_exit(&nd6_dad_lock);

        return found_nonce;
}

static void
nd6_dad_starttimer(struct dadq *dp, int ticks)
{

        callout_reset(&dp->dad_timer_ch, ticks,
            (void (*)(void *))nd6_dad_timer, dp);
}

static void
nd6_dad_stoptimer(struct dadq *dp)
{

        KASSERT(mutex_owned(&nd6_dad_lock));

        TAILQ_REMOVE(&dadq, dp, dad_list);
        /* Tell the timer that dp is being destroyed. */
        dp->dad_ifa = NULL;
        callout_halt(&dp->dad_timer_ch, &nd6_dad_lock);
}

static void
nd6_dad_destroytimer(struct dadq *dp)
{

        KASSERT(dp->dad_ifa == NULL);
        callout_destroy(&dp->dad_timer_ch);
        kmem_intr_free(dp, sizeof(*dp));
}

/*
 * Start Duplicate Address Detection (DAD) for specified interface address.
 *
 * Note that callout is used when xtick > 0 and not when xtick == 0.
 *
 * xtick: minimum delay ticks for IFF_UP event
 */
void
nd6_dad_start(struct ifaddr *ifa, int xtick)
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct dadq *dp;
        char ip6buf[INET6_ADDRSTRLEN];

        /*
         * If we don't need DAD, don't do it.
         * There are several cases:
         * - DAD is disabled
         * - the interface address is anycast
         */
        if (!(ia->ia6_flags & IN6_IFF_TENTATIVE)) {
                log(LOG_DEBUG,
                        "nd6_dad_start: called with non-tentative address "
                        "%s(%s)\n",
                        IN6_PRINT(ip6buf, &ia->ia_addr.sin6_addr),
                        if_name(ifa->ifa_ifp));
                return;
        }
        if (ia->ia6_flags & IN6_IFF_ANYCAST || !ip6_dad_enabled()) {
                ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
                rt_addrmsg(RTM_NEWADDR, ifa);
                return;
        }
        if (!(ifa->ifa_ifp->if_flags & IFF_UP))
                return;

        dp = kmem_intr_alloc(sizeof(*dp), KM_NOSLEEP);

        mutex_enter(&nd6_dad_lock);
        if (nd6_dad_find(ifa, NULL, NULL) != NULL) {
                mutex_exit(&nd6_dad_lock);
                /* DAD already in progress */
                if (dp != NULL)
                        kmem_intr_free(dp, sizeof(*dp));
                return;
        }

        if (dp == NULL) {
                mutex_exit(&nd6_dad_lock);
                log(LOG_ERR, "nd6_dad_start: memory allocation failed for "
                        "%s(%s)\n",
                        IN6_PRINT(ip6buf, &ia->ia_addr.sin6_addr),
                        if_name(ifa->ifa_ifp));
                return;
        }

        /*
         * Send NS packet for DAD, ip6_dad_count times.
         * Note that we must delay the first transmission, if this is the
         * first packet to be sent from the interface after interface
         * (re)initialization.
         */
        callout_init(&dp->dad_timer_ch, CALLOUT_MPSAFE);
        dp->dad_ifa = ifa;
        ifaref(ifa);    /* just for safety */
        dp->dad_count = ip6_dad_count;
        dp->dad_ns_ocount = dp->dad_ns_tcount = 0;
        dp->dad_ns_lcount = 0;
        TAILQ_INSERT_TAIL(&dadq, (struct dadq *)dp, dad_list);

        nd6log(LOG_DEBUG, "%s: starting DAD for %s\n", if_name(ifa->ifa_ifp),
            IN6_PRINT(ip6buf, &ia->ia_addr.sin6_addr));

        if (xtick == 0) {
                nd6_dad_ns_output(dp, ifa);
                nd6_dad_starttimer(dp,
                    (long)ND_IFINFO(ifa->ifa_ifp)->retrans * hz / 1000);
        } else
                nd6_dad_starttimer(dp, xtick);
        mutex_exit(&nd6_dad_lock);
}

/*
 * terminate DAD unconditionally.  used for address removals.
 */
void
nd6_dad_stop(struct ifaddr *ifa)
{
        struct dadq *dp;

        mutex_enter(&nd6_dad_lock);
        dp = nd6_dad_find(ifa, NULL, NULL);
        if (dp == NULL) {
                mutex_exit(&nd6_dad_lock);
                /* DAD wasn't started yet */
                return;
        }

        /* Prevent the timer from running anymore. */
        nd6_dad_stoptimer(dp);

        mutex_exit(&nd6_dad_lock);

        nd6_dad_destroytimer(dp);
        ifafree(ifa);
}

static void
nd6_dad_timer(struct dadq *dp)
{
        struct ifaddr *ifa;
        struct in6_ifaddr *ia;
        char ip6buf[INET6_ADDRSTRLEN];
        bool need_free = false;

        KERNEL_LOCK_UNLESS_NET_MPSAFE();
        mutex_enter(&nd6_dad_lock);

        ifa = dp->dad_ifa;
        if (ifa == NULL) {
                /* dp is being destroyed by someone.  Do nothing. */
                goto done;
        }

        ia = (struct in6_ifaddr *)ifa;
        if (ia->ia6_flags & IN6_IFF_DUPLICATED) {
                log(LOG_ERR, "nd6_dad_timer: called with duplicate address "
                        "%s(%s)\n",
                        IN6_PRINT(ip6buf, &ia->ia_addr.sin6_addr),
                        if_name(ifa->ifa_ifp));
                goto done;
        }
        if ((ia->ia6_flags & IN6_IFF_TENTATIVE) == 0) {
                log(LOG_ERR, "nd6_dad_timer: called with non-tentative address "
                        "%s(%s)\n",
                        IN6_PRINT(ip6buf, &ia->ia_addr.sin6_addr),
                        if_name(ifa->ifa_ifp));
                goto done;
        }

        /* timeouted with IFF_{RUNNING,UP} check */
        if (dp->dad_ns_tcount > dad_maxtry) {
                nd6log(LOG_INFO, "%s: could not run DAD, driver problem?\n",
                        if_name(ifa->ifa_ifp));

                nd6_dad_stoptimer(dp);
                need_free = true;
                goto done;
        }

        /* Need more checks? */
        if (dp->dad_ns_ocount < dp->dad_count) {
                /*
                 * We have more NS to go.  Send NS packet for DAD.
                 */
                nd6_dad_ns_output(dp, ifa);
                nd6_dad_starttimer(dp,
                    (long)ND_IFINFO(ifa->ifa_ifp)->retrans * hz / 1000);
        } else {
                /*
                 * We are done with DAD.  No NA came, no NS came.
                 * No duplicate address found.
                 */
                ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
                rt_addrmsg(RTM_NEWADDR, ifa);

                nd6log(LOG_DEBUG,
                    "%s: DAD complete for %s - no duplicates found\n",
                    if_name(ifa->ifa_ifp),
                    IN6_PRINT(ip6buf, &ia->ia_addr.sin6_addr));

                nd6_dad_stoptimer(dp);
                need_free = true;
        }
done:
        mutex_exit(&nd6_dad_lock);

        if (need_free) {
                nd6_dad_destroytimer(dp);
                KASSERT(ifa != NULL);
                ifafree(ifa);
        }

        KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
}

static void
nd6_dad_duplicated(struct ifaddr *ifa, struct dadq *dp,
    const struct sockaddr_dl *from)
{
        struct in6_ifaddr *ia;
        struct ifnet *ifp;
        char ip6buf[INET6_ADDRSTRLEN], llabuf[LLA_ADDRSTRLEN], *llastr;

        KASSERT(mutex_owned(&nd6_dad_lock));
        KASSERT(ifa != NULL);

        ifp = ifa->ifa_ifp;
        ia = (struct in6_ifaddr *)ifa;

        ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
        ia->ia6_flags |= IN6_IFF_DUPLICATED;

        if (__predict_false(from == NULL))
                llastr = NULL;
        else
                llastr = lla_snprintf(llabuf, sizeof(llabuf),
                    CLLADDR(from), from->sdl_alen);

        log(LOG_ERR, "%s: DAD duplicate address %s from %s\n",
            if_name(ifp), IN6_PRINT(ip6buf, &ia->ia_addr.sin6_addr), llastr);

        /* Inform the routing socket that DAD has completed */
        rt_addrmsg_src(RTM_NEWADDR, ifa, (const struct sockaddr *)from);

        /*
         * If the address is a link-local address formed from an interface
         * identifier based on the hardware address which is supposed to be
         * uniquely assigned (e.g., EUI-64 for an Ethernet interface), IP
         * operation on the interface SHOULD be disabled.
         * [rfc2462bis-03 Section 5.4.5]
         */
        if (IN6_IS_ADDR_LINKLOCAL(&ia->ia_addr.sin6_addr)) {
                struct in6_addr in6;

                /*
                 * To avoid over-reaction, we only apply this logic when we are
                 * very sure that hardware addresses are supposed to be unique.
                 */
                switch (ifp->if_type) {
                case IFT_ETHER:
                case IFT_ATM:
                case IFT_IEEE1394:
                case IFT_IEEE80211:
                        in6 = ia->ia_addr.sin6_addr;
                        if (in6_get_hw_ifid(ifp, &in6) == 0 &&
                            IN6_ARE_ADDR_EQUAL(&ia->ia_addr.sin6_addr, &in6)) {
                                ND_IFINFO(ifp)->flags |= ND6_IFF_IFDISABLED;
                                log(LOG_ERR, "%s: possible hardware address "
                                    "duplication detected, disable IPv6\n",
                                    if_name(ifp));
                        }
                        break;
                }
        }
}

static void
nd6_dad_ns_output(struct dadq *dp, struct ifaddr *ifa)
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct ifnet *ifp = ifa->ifa_ifp;
        uint8_t *nonce;

        dp->dad_ns_tcount++;
        if ((ifp->if_flags & IFF_UP) == 0) {
#if 0
                printf("%s: interface down?\n", if_name(ifp));
#endif
                return;
        }
        if ((ifp->if_flags & IFF_RUNNING) == 0) {
#if 0
                printf("%s: interface not running?\n", if_name(ifp));
#endif
                return;
        }

        dp->dad_ns_tcount = 0;
        nonce = dp->dad_nonce[dp->dad_ns_ocount % ND_OPT_NONCE_STORE];
        cprng_fast(nonce, ND_OPT_NONCE_LEN);
        dp->dad_ns_ocount++;

        nd6_ns_output(ifp, NULL, &ia->ia_addr.sin6_addr, NULL, nonce);
}

static void
nd6_dad_input(struct ifaddr *ifa, struct nd_opt_nonce *nonce,
    const struct sockaddr_dl *from)
{
        struct dadq *dp;
        bool found_nonce = false;

        KASSERT(ifa != NULL);

        mutex_enter(&nd6_dad_lock);
        dp = nd6_dad_find(ifa, nonce, &found_nonce);
        if (!found_nonce) {
                nd6_dad_duplicated(ifa, dp, from);
                if (dp != NULL)
                        nd6_dad_stoptimer(dp);
        }
        mutex_exit(&nd6_dad_lock);
        if (dp != NULL) {
                nd6_dad_destroytimer(dp);
                ifafree(ifa);
        }
}