[apple/xnu.git] / bsd / netinet6 / nd6_nbr.c

/*      $KAME: nd6_nbr.c,v 1.32 2000/03/21 11:37:30 itojun Exp $        */

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if (defined(__FreeBSD__) && __FreeBSD__ >= 3) || defined(__NetBSD__)
#include "opt_inet.h"
#if __NetBSD__  /*XXX*/
#include "opt_ipsec.h"
#endif
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#if !(defined(__FreeBSD__) && __FreeBSD__ >= 3)
#include <sys/ioctl.h>
#endif
#include <sys/syslog.h>
#include <kern/queue.h>

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

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

#ifdef __OpenBSD__      /*don't confuse KAME ipsec with OpenBSD ipsec*/
#undef IPSEC
#endif

#if IPSEC
#include <netinet6/ipsec.h>
#endif

#include <net/net_osdep.h>

#define SDL(s) ((struct sockaddr_dl *)s)

struct dadq;
static struct dadq *nd6_dad_find __P((struct ifaddr *));
static void nd6_dad_timer __P((struct ifaddr *));
static void nd6_dad_timer_funnel __P((struct ifaddr *));
static void nd6_dad_ns_output __P((struct dadq *, struct ifaddr *));
static void nd6_dad_ns_input __P((struct ifaddr *));
static void nd6_dad_na_input __P((struct ifaddr *));

static int dad_ignore_ns = 0;   /* ignore NS in DAD - specwise incorrect*/
static int dad_maxtry = 15;     /* max # of *tries* to transmit DAD packet */

/*
 * Input an Neighbor Solicitation Message.
 *
 * Based on RFC 2461
 * Based on RFC 2462 (duplicated address detection)
 */
void
nd6_ns_input(m, off, icmp6len)
        struct mbuf *m;
        int off, icmp6len;
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        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;
        int lladdrlen = 0;
        int anycast = 0, proxy = 0, tentative = 0;
        int tlladdr;
        union nd_opts ndopts;
        struct sockaddr_dl *proxydl = NULL;

        if (ip6->ip6_hlim != 255) {
                log(LOG_ERR,
                    "nd6_ns_input: invalid hlim %d\n", ip6->ip6_hlim);
                goto freeit;
        }

        if (IN6_IS_ADDR_UNSPECIFIED(&saddr6)) {
                /* dst has to be solicited node multicast address. */
                if (daddr6.s6_addr16[0] == IPV6_ADDR_INT16_MLL
                    /*don't check ifindex portion*/
                    && daddr6.s6_addr32[1] == 0
                    && daddr6.s6_addr32[2] == IPV6_ADDR_INT32_ONE
                    && daddr6.s6_addr8[12] == 0xff) {
                        ; /*good*/
                } else {
                        log(LOG_INFO, "nd6_ns_input: bad DAD packet "
                                "(wrong ip6 dst)\n");
                        goto bad;
                }
        }

#ifndef PULLDOWN_TEST
        IP6_EXTHDR_CHECK(m, off, icmp6len,);
        nd_ns = (struct nd_neighbor_solicit *)((caddr_t)ip6 + off);
#else
        IP6_EXTHDR_GET(nd_ns, struct nd_neighbor_solicit *, m, off, icmp6len);
        if (nd_ns == NULL) {
                icmp6stat.icp6s_tooshort++;
                return;
        }
#endif
        taddr6 = nd_ns->nd_ns_target;

        if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
                log(LOG_INFO, "nd6_ns_input: bad NS target (multicast)\n");
                goto bad;
        }

        if (IN6_IS_SCOPE_LINKLOCAL(&taddr6))
                taddr6.s6_addr16[1] = htons(ifp->if_index);

        icmp6len -= sizeof(*nd_ns);
        nd6_option_init(nd_ns + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                log(LOG_INFO, "nd6_ns_input: invalid ND option, ignored\n");
                goto bad;
        }

        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) {
                log(LOG_INFO, "nd6_ns_input: 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 unicast/anycast                 MUST NOT add
         * NS IP dst is solicited-node multicast        MUST add
         *
         * In implementation, we add target link-layer address by default.
         * We do not add one in MUST NOT cases.
         */
#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. */
        ifa = (struct ifaddr *)in6ifa_ifpwithaddr(ifp, &taddr6);

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

                bzero(&tsin6, sizeof tsin6);            
                tsin6.sin6_len = sizeof(struct sockaddr_in6);
                tsin6.sin6_family = AF_INET6;
                tsin6.sin6_addr = taddr6;

                rt = rtalloc1((struct sockaddr *)&tsin6, 0
#if __FreeBSD__ || defined (__APPLE__)
                              , 0
#endif /* __FreeBSD__ */
                              );
                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(ifp,
                                IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
                        if (ifa) {
                                proxy = 1;
                                proxydl = SDL(rt->rt_gateway);
                        }
                }
                if (rt)
                        rtfree(rt);
        }
        if (!ifa) {
                /*
                 * We've got a NS packet, and we don't have that adddress
                 * 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) {
                log(LOG_INFO,
                    "nd6_ns_input: lladdrlen mismatch for %s "
                    "(if %d, NS packet %d)\n",
                        ip6_sprintf(&taddr6), ifp->if_addrlen, lladdrlen - 2);
        }

        if (IN6_ARE_ADDR_EQUAL(&myaddr6, &saddr6)) {
                log(LOG_INFO,
                    "nd6_ns_input: duplicate IP6 address %s\n",
                    ip6_sprintf(&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
                 * duplicated address detection.
                 *
                 * If not, the packet is for addess resolution;
                 * silently ignore it.
                 */
                if (IN6_IS_ADDR_UNSPECIFIED(&saddr6))
                        nd6_dad_ns_input(ifa);

                goto freeit;
        }

        /*
         * 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)) {
                saddr6 = in6addr_linklocal_allnodes;
                saddr6.s6_addr16[1] = htons(ifp->if_index);
                nd6_na_output(ifp, &saddr6, &taddr6,
                              ((anycast || proxy || !tlladdr)
                                      ? 0 : ND_NA_FLAG_OVERRIDE)
                                | (ip6_forwarding ? ND_NA_FLAG_ROUTER : 0),
                              tlladdr, (struct sockaddr *)proxydl);
                goto freeit;
        }

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

        nd6_na_output(ifp, &saddr6, &taddr6,
                      ((anycast || proxy || !tlladdr) ? 0 : ND_NA_FLAG_OVERRIDE)
                        | (ip6_forwarding ? ND_NA_FLAG_ROUTER : 0)
                        | ND_NA_FLAG_SOLICITED,
                      tlladdr, (struct sockaddr *)proxydl);
 freeit:
        m_freem(m);
        return;

 bad:
        log(LOG_ERR, "nd6_ns_input: src=%s\n", ip6_sprintf(&saddr6));
        log(LOG_ERR, "nd6_ns_input: dst=%s\n", ip6_sprintf(&daddr6));
        log(LOG_ERR, "nd6_ns_input: tgt=%s\n", ip6_sprintf(&taddr6));
        m_freem(m);
}

/*
 * Output an 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 (duplicated address detection)
 */
void
nd6_ns_output(ifp, daddr6, taddr6, ln, dad)
        struct ifnet *ifp;
        struct in6_addr *daddr6, *taddr6;
        struct llinfo_nd6 *ln;  /* for source address determination */
        int dad;        /* duplicated address detection */
{
        struct mbuf *m;
        struct ip6_hdr *ip6;
        struct nd_neighbor_solicit *nd_ns;
        struct in6_ifaddr *ia = NULL;
        struct ip6_moptions im6o;
        int icmp6len;
        int maxlen;
        caddr_t mac;
        struct ifnet *outif = NULL;
        
        if (IN6_IS_ADDR_MULTICAST(taddr6))
                return;

        /* estimate the size of message */
        maxlen = sizeof(*ip6) + sizeof(*nd_ns);
        maxlen += (sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7;
        if (max_linkhdr + maxlen >= MCLBYTES) {
#ifdef DIAGNOSTIC
                printf("nd6_ns_output: max_linkhdr + maxlen >= MCLBYTES "
                    "(%d + %d > %d)\n", max_linkhdr, maxlen, MCLBYTES);
#endif
                return;
        }

        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;

        if (daddr6 == NULL || IN6_IS_ADDR_MULTICAST(daddr6)) {
                m->m_flags |= M_MCAST;
                im6o.im6o_multicast_ifp = 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 MH_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] = htons(ifp->if_index);
                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 (!dad) {
#if 0   /* KAME way, exact address scope match */
                /*
                 * Select a source whose scope is the same as that of the dest.
                 * Typically, the dest is link-local solicitation multicast
                 * (i.e. neighbor discovery) or link-local/global unicast
                 * (i.e. neighbor un-reachability detection).
                 */
                ia = in6_ifawithifp(ifp, &ip6->ip6_dst);
                if (ia == NULL) {
                        m_freem(m);
                        return;
                }
                ip6->ip6_src = ia->ia_addr.sin6_addr;
#else   /* spec-wise correct */
                /*
                 * 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
                 * (saddr6), if:
                 * - saddr6 is given from the caller (by giving "ln"), and
                 * - saddr6 belongs to the outgoing interface.
                 * Otherwise, we perform a scope-wise match.
                 */
                struct ip6_hdr *hip6;           /*hold ip6*/
                struct in6_addr *saddr6;

                if (ln && ln->ln_hold) {
                        hip6 = mtod(ln->ln_hold, struct ip6_hdr *);
                        /* XXX pullup? */
                        if (sizeof(*hip6) < ln->ln_hold->m_len)
                                saddr6 = &hip6->ip6_src;
                        else
                                saddr6 = NULL;
                } else
                        saddr6 = NULL;
                if (saddr6 && in6ifa_ifpwithaddr(ifp, saddr6))
                        bcopy(saddr6, &ip6->ip6_src, sizeof(*saddr6));
                else {
                        ia = in6_ifawithifp(ifp, &ip6->ip6_dst);
                        if (ia == NULL) {
                                m_freem(m);     /*XXX*/
                                return;
                        }
                        ip6->ip6_src = ia->ia_addr.sin6_addr;
                }
#endif
        } else {
                /*
                 * Source address for DAD packet must always be IPv6
                 * unspecified address. (0::0)
                 */
                bzero(&ip6->ip6_src, sizeof(ip6->ip6_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;

        if (IN6_IS_SCOPE_LINKLOCAL(&nd_ns->nd_ns_target))
                nd_ns->nd_ns_target.s6_addr16[1] = 0;

        /*
         * 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 (!dad && (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;
                bzero((caddr_t)nd_opt, optlen);
                nd_opt->nd_opt_type = ND_OPT_SOURCE_LINKADDR;
                nd_opt->nd_opt_len = optlen >> 3;
                bcopy(mac, (caddr_t)(nd_opt + 1), ifp->if_addrlen);
        }

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

#if IPSEC
        /* Don't lookup socket */
        ipsec_setsocket(m, NULL);
#endif
        ip6_output(m, NULL, NULL, dad ? IPV6_DADOUTPUT : 0, &im6o, &outif);
        if (outif) {
                icmp6_ifstat_inc(outif, ifs6_out_msg);
                icmp6_ifstat_inc(outif, ifs6_out_neighborsolicit);
        }
        icmp6stat.icp6s_outhist[ND_NEIGHBOR_SOLICIT]++;
}

/*
 * Neighbor advertisement input handling.
 *
 * Based on RFC 2461
 * Based on RFC 2462 (duplicated 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(m, off, icmp6len)
        struct mbuf *m;
        int off, icmp6len;
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_neighbor_advert *nd_na;
#if 0
        struct in6_addr saddr6 = ip6->ip6_src;
#endif
        struct in6_addr daddr6 = ip6->ip6_dst;
        struct in6_addr taddr6;
        int flags;
        int is_router;
        int is_solicited;
        int is_override;
        char *lladdr = NULL;
        int lladdrlen = 0;
        struct ifaddr *ifa;
        struct llinfo_nd6 *ln;
        struct rtentry *rt;
        struct sockaddr_dl *sdl;
        union nd_opts ndopts;

        if (ip6->ip6_hlim != 255) {
                log(LOG_ERR,
                    "nd6_na_input: invalid hlim %d\n", ip6->ip6_hlim);
                goto freeit;
        }

#ifndef PULLDOWN_TEST
        IP6_EXTHDR_CHECK(m, off, icmp6len,);
        nd_na = (struct nd_neighbor_advert *)((caddr_t)ip6 + off);
#else
        IP6_EXTHDR_GET(nd_na, struct nd_neighbor_advert *, m, off, icmp6len);
        if (nd_na == NULL) {
                icmp6stat.icp6s_tooshort++;
                return;
        }
#endif
        taddr6 = nd_na->nd_na_target;
        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);

        if (IN6_IS_SCOPE_LINKLOCAL(&taddr6))
                taddr6.s6_addr16[1] = htons(ifp->if_index);

        if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
                log(LOG_ERR,
                    "nd6_na_input: invalid target address %s\n",
                    ip6_sprintf(&taddr6));
                goto freeit;
        }
        if (IN6_IS_ADDR_MULTICAST(&daddr6))
                if (is_solicited) {
                        log(LOG_ERR,
                            "nd6_na_input: a solicited adv is multicasted\n");
                        goto freeit;
                }

        icmp6len -= sizeof(*nd_na);
        nd6_option_init(nd_na + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                log(LOG_INFO, "nd6_na_input: invalid ND option, ignored\n");
                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;
        }

        ifa = (struct ifaddr *)in6ifa_ifpwithaddr(ifp, &taddr6);

        /*
         * 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
         && (((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_TENTATIVE)) {
                nd6_dad_na_input(ifa);
                goto freeit;
        }

        /* Just for safety, maybe unnecessery. */
        if (ifa) {
                log(LOG_ERR,
                    "nd6_na_input: duplicate IP6 address %s\n",
                    ip6_sprintf(&taddr6));
                goto freeit;
        }

        if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                log(LOG_INFO,
                    "nd6_na_input: lladdrlen mismatch for %s "
                    "(if %d, NA packet %d)\n",
                        ip6_sprintf(&taddr6), ifp->if_addrlen, lladdrlen - 2);
        }

        /*
         * If no neighbor cache entry is found, NA SHOULD silently be discarded.
         */
        rt = nd6_lookup(&taddr6, 0, ifp);
        if ((rt == NULL) ||
           ((ln = (struct llinfo_nd6 *)rt->rt_llinfo) == NULL) ||
           ((sdl = SDL(rt->rt_gateway)) == NULL))
                goto freeit;

        if (ln->ln_state == ND6_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.
                 */
                sdl->sdl_alen = ifp->if_addrlen;
                bcopy(lladdr, LLADDR(sdl), ifp->if_addrlen);
                if (is_solicited) {
                        ln->ln_state = ND6_LLINFO_REACHABLE;
                        if (ln->ln_expire)
#if !(defined(__FreeBSD__) && __FreeBSD__ >= 3) && !defined(__APPLE__)
                                ln->ln_expire = time.tv_sec +
#else
                                ln->ln_expire = time_second +
#endif
                                        nd_ifinfo[rt->rt_ifp->if_index].reachable;
                } else
                        ln->ln_state = ND6_LLINFO_STALE;
                ln->ln_router = is_router;
        } else {
                int llchange;

                /*
                 * Check if the link-layer address has changed or not.
                 */
                if (!lladdr)
                        llchange = 0;
                else {
                        if (sdl->sdl_alen) {
                                if (bcmp(lladdr, LLADDR(sdl), ifp->if_addrlen))
                                        llchange = 1;
                                else
                                        llchange = 0;
                        } else
                                llchange = 1;
                }

                /*
                 * 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 && llchange)) {        /* (1) */
                        /*
                         * If state is REACHABLE, make it STALE.
                         * no other updates should be done.
                         */
                        if (ln->ln_state == ND6_LLINFO_REACHABLE)
                                ln->ln_state = ND6_LLINFO_STALE;
                        goto freeit;
                } else if (is_override                             /* (2a) */
                        || (!is_override && (lladdr && !llchange)) /* (2b) */
                        || !lladdr) {                              /* (2c) */
                        /*
                         * Update link-local address, if any.
                         */
                        if (lladdr) {
                                sdl->sdl_alen = ifp->if_addrlen;
                                bcopy(lladdr, LLADDR(sdl), ifp->if_addrlen);
                        }

                        /*
                         * 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 = ND6_LLINFO_REACHABLE;
                                if (ln->ln_expire) {
#if !(defined(__FreeBSD__) && __FreeBSD__ >= 3) && !defined(__APPLE__)
                                        ln->ln_expire = time.tv_sec +
#else
                                        ln->ln_expire = time_second +
#endif
                                                nd_ifinfo[ifp->if_index].reachable;
                                }
                        } else {
                                if (lladdr && llchange)
                                        ln->ln_state = ND6_LLINFO_STALE;
                        }
                }

                if (ln->ln_router && !is_router) {
                        /*
                         * The peer dropped the router flag.
                         * Remove the sender from the Default Router List and
                         * update the Destination Cache entries.
                         */
                        struct nd_defrouter *dr;
                        struct in6_addr *in6;
                        int s;

                        in6 = &((struct sockaddr_in6 *)rt_key(rt))->sin6_addr;
#if __NetBSD__
                        s = splsoftnet();
#else
                        s = splnet();
#endif
                        dr = defrouter_lookup(in6, rt->rt_ifp);
                        if (dr)
                                defrtrlist_del(dr);
                        else if (!ip6_forwarding && ip6_accept_rtadv) {
                                /*
                                 * Even if the neighbor is not in the default
                                 * router list, the neighbor may be used
                                 * as a next hop for some destinations
                                 * (e.g. redirect case). So we must
                                 * call rt6_flush explicitly.
                                 */
                                rt6_flush(&ip6->ip6_src, rt->rt_ifp);
                        }
                        splx(s);
                }
                ln->ln_router = is_router;
        }
        rt->rt_flags &= ~RTF_REJECT;
        ln->ln_asked = 0;
        if (ln->ln_hold) {
#if OLDIP6OUTPUT
                (*ifp->if_output)(ifp, ln->ln_hold, rt_key(rt), rt);
#else
                nd6_output(ifp, ln->ln_hold,
                           (struct sockaddr_in6 *)rt_key(rt), rt);
#endif
                ln->ln_hold = 0;
        }

 freeit:
        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(ifp, daddr6, taddr6, flags, tlladdr, sdl0)
        struct ifnet *ifp;
        struct in6_addr *daddr6, *taddr6;
        u_long flags;
        int tlladdr;            /* 1 if include target link-layer address */
        struct sockaddr *sdl0;  /* sockaddr_dl (= proxy NA) or NULL */
{
        struct mbuf *m;
        struct ip6_hdr *ip6;
        struct nd_neighbor_advert *nd_na;
        struct in6_ifaddr *ia = NULL;
        struct ip6_moptions im6o;
        int icmp6len;
        int maxlen;
        caddr_t mac;
        struct ifnet *outif = NULL;

        /* estimate the size of message */
        maxlen = sizeof(*ip6) + sizeof(*nd_na);
        maxlen += (sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7;
        if (max_linkhdr + maxlen >= MCLBYTES) {
#ifdef DIAGNOSTIC
                printf("nd6_na_output: max_linkhdr + maxlen >= MCLBYTES "
                    "(%d + %d > %d)\n", max_linkhdr, maxlen, MCLBYTES);
#endif
                return;
        }

        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;

        if (IN6_IS_ADDR_MULTICAST(daddr6)) {
                m->m_flags |= M_MCAST;
                im6o.im6o_multicast_ifp = 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 MH_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 */
                ip6->ip6_dst.s6_addr16[0] = IPV6_ADDR_INT16_MLL;
                ip6->ip6_dst.s6_addr16[1] = htons(ifp->if_index);
                ip6->ip6_dst.s6_addr32[1] = 0;
                ip6->ip6_dst.s6_addr32[2] = 0;
                ip6->ip6_dst.s6_addr32[3] = IPV6_ADDR_INT32_ONE;
                flags &= ~ND_NA_FLAG_SOLICITED;
        } else
                ip6->ip6_dst = *daddr6;

        /*
         * Select a source whose scope is the same as that of the dest.
         */
        ia = in6_ifawithifp(ifp, &ip6->ip6_dst);
        if (ia == NULL) {
                m_freem(m);
                return;
        }
        ip6->ip6_src = ia->ia_addr.sin6_addr;
        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;
        if (IN6_IS_SCOPE_LINKLOCAL(&nd_na->nd_na_target))
                nd_na->nd_na_target.s6_addr16[1] = 0;

        /*
         * "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) {
                mac = NULL;
                /*
                 * 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) {
                        struct sockaddr_dl *sdl;
                        sdl = (struct sockaddr_dl *)sdl0;
                        if (sdl->sdl_alen == ifp->if_addrlen)
                                mac = LLADDR(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;
                bzero((caddr_t)nd_opt, optlen);
                nd_opt->nd_opt_type = ND_OPT_TARGET_LINKADDR;
                nd_opt->nd_opt_len = optlen >> 3;
                bcopy(mac, (caddr_t)(nd_opt + 1), ifp->if_addrlen);
        } else
                flags &= ~ND_NA_FLAG_OVERRIDE;

        ip6->ip6_plen = htons((u_short)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);

#if IPSEC
        /* Don't lookup socket */
        ipsec_setsocket(m, NULL);
#endif
        ip6_output(m, NULL, NULL, 0, &im6o, &outif);
        if (outif) {
                icmp6_ifstat_inc(outif, ifs6_out_msg);
                icmp6_ifstat_inc(outif, ifs6_out_neighboradvert);
        }
        icmp6stat.icp6s_outhist[ND_NEIGHBOR_ADVERT]++;
}

caddr_t
nd6_ifptomac(ifp)
        struct ifnet *ifp;
{
        switch (ifp->if_type) {
        case IFT_ARCNET:
        case IFT_ETHER:
        case IFT_FDDI:
#if __NetBSD__
                return LLADDR(ifp->if_sadl);
#else
                return ((caddr_t)(ifp + 1));
#endif
                break;
        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_icount;
        int dad_na_icount;
#if defined(__FreeBSD__) && __FreeBSD__ >= 3
        struct callout_handle dad_timer;
#endif
};

static struct dadq_head dadq;

static struct dadq *
nd6_dad_find(ifa)
        struct ifaddr *ifa;
{
        struct dadq *dp;

        for (dp = dadq.tqh_first; dp; dp = dp->dad_list.tqe_next) {
                if (dp->dad_ifa == ifa)
                        return dp;
        }
        return NULL;
}

/*
 * Start Duplicated Address Detection (DAD) for specified interface address.
 */
void
nd6_dad_start(ifa, tick)
        struct ifaddr *ifa;
        int *tick;      /* minimum delay ticks for IFF_UP event */
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct dadq *dp;
        static int dad_init = 0;

        if (!dad_init) {
                TAILQ_INIT(&dadq);
                dad_init++;
        }

        /*
         * If we don't need DAD, don't do it.
         * There are several cases:
         * - DAD is disabled (ip6_dad_count == 0)
         * - 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",
                        ip6_sprintf(&ia->ia_addr.sin6_addr),
                        ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
                return;
        }
        if (ia->ia6_flags & IN6_IFF_ANYCAST) {
                ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
                return;
        }
        if (!ip6_dad_count) {
                ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
                return;
        }
        if (!ifa->ifa_ifp)
                panic("nd6_dad_start: ifa->ifa_ifp == NULL");
        if (!(ifa->ifa_ifp->if_flags & IFF_UP))
                return;
        if (nd6_dad_find(ifa) != NULL) {
                /* DAD already in progress */
                return;
        }

        dp = _MALLOC(sizeof(*dp), M_IP6NDP, M_NOWAIT);
        if (dp == NULL) {
                log(LOG_ERR, "nd6_dad_start: memory allocation failed for "
                        "%s(%s)\n",
                        ip6_sprintf(&ia->ia_addr.sin6_addr),
                        ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
                return;
        }
        bzero(dp, sizeof(*dp));
        TAILQ_INSERT_TAIL(&dadq, (struct dadq *)dp, dad_list);

#if ND6_DEBUG
        log(LOG_DEBUG, "%s: starting DAD for %s\n", if_name(ifa->ifa_ifp),
            ip6_sprintf(&ia->ia_addr.sin6_addr));
#endif

        /*
         * 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.
         */
        dp->dad_ifa = ifa;
        ifa->ifa_refcnt++;      /*just for safety*/
        dp->dad_count = ip6_dad_count;
        dp->dad_ns_icount = dp->dad_na_icount = 0;
        dp->dad_ns_ocount = dp->dad_ns_tcount = 0;
        if (!tick) {
                nd6_dad_ns_output(dp, ifa);
#if defined(__FreeBSD__) && __FreeBSD__ >= 3
                dp->dad_timer =
#endif
                timeout((void (*) __P((void *)))nd6_dad_timer_funnel, (void *)ifa,
                        nd_ifinfo[ifa->ifa_ifp->if_index].retrans * hz / 1000);
        } else {
                int ntick;

                if (*tick == 0)
                        ntick = random() % (MAX_RTR_SOLICITATION_DELAY * hz);
                else
                        ntick = *tick + random() % (hz / 2);
                *tick = ntick;
#if defined(__FreeBSD__) && __FreeBSD__ >= 3
                dp->dad_timer =
#endif
                timeout((void (*) __P((void *)))nd6_dad_timer_funnel, (void *)ifa,
                        ntick);
        }
}

static void     
nd6_dad_timer_funnel(ifa)
        struct ifaddr *ifa;
{
                
#ifdef __APPLE__
        boolean_t       funnel_state;
        funnel_state = thread_funnel_set(network_flock, TRUE);
#endif  
        nd6_dad_timer(ifa);
#ifdef __APPLE__
        (void) thread_funnel_set(network_flock, FALSE);
#endif

} 

static void
nd6_dad_timer(ifa)
        struct ifaddr *ifa;
{
        int s;
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct dadq *dp;

#if __NetBSD__
        s = splsoftnet();       /*XXX*/
#else
        s = splnet();           /*XXX*/
#endif

        /* Sanity check */
        if (ia == NULL) {
                log(LOG_ERR, "nd6_dad_timer: called with null parameter\n");
                goto done;
        }
        dp = nd6_dad_find(ifa);
        if (dp == NULL) {
                log(LOG_ERR, "nd6_dad_timer: DAD structure not found\n");
                goto done;
        }
        if (ia->ia6_flags & IN6_IFF_DUPLICATED) {
                log(LOG_ERR, "nd6_dad_timer: called with duplicated address "
                        "%s(%s)\n",
                        ip6_sprintf(&ia->ia_addr.sin6_addr),
                        ifa->ifa_ifp ? 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",
                        ip6_sprintf(&ia->ia_addr.sin6_addr),
                        ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
                goto done;
        }

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

                TAILQ_REMOVE(&dadq, (struct dadq *)dp, dad_list);
                _FREE(dp, M_IP6NDP);
                dp = NULL;
                IFAFREE(ifa);
                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);
#if defined(__FreeBSD__) && __FreeBSD__ >= 3
                dp->dad_timer =
#endif
                timeout((void (*) __P((void *)))nd6_dad_timer_funnel, (void *)ifa,
                        nd_ifinfo[ifa->ifa_ifp->if_index].retrans * hz / 1000);
        } else {
                /*
                 * We have transmitted sufficient number of DAD packets.
                 * See what we've got.
                 */
                int duplicate;

                duplicate = 0;

                if (dp->dad_na_icount) {
                        /*
                         * the check is in nd6_dad_na_input(),
                         * but just in case
                         */
                        duplicate++;
                }

                if (dp->dad_ns_icount) {
#if 0 /*heuristics*/
                        /*
                         * if
                         * - we have sent many(?) DAD NS, and
                         * - the number of NS we sent equals to the
                         *   number of NS we've got, and
                         * - we've got no NA
                         * we may have a faulty network card/driver which
                         * loops back multicasts to myself.
                         */
                        if (3 < dp->dad_count
                         && dp->dad_ns_icount == dp->dad_count
                         && dp->dad_na_icount == 0) {
                                log(LOG_INFO, "DAD questionable for %s(%s): "
                                        "network card loops back multicast?\n",
                                        ip6_sprintf(&ia->ia_addr.sin6_addr),
                                        if_name(ifa->ifa_ifp));
                                /* XXX consider it a duplicate or not? */
                                /* duplicate++; */
                        } else {
                                /* We've seen NS, means DAD has failed. */
                                duplicate++;
                        }
#else
                        /* We've seen NS, means DAD has failed. */
                        duplicate++;
#endif
                }

                if (duplicate) {
                        /* (*dp) will be freed in nd6_dad_duplicated() */
                        dp = NULL;
                        nd6_dad_duplicated(ifa);
                } else {
                        /*
                         * We are done with DAD.  No NA came, no NS came.
                         * duplicated address found.
                         */
                        ia->ia6_flags &= ~IN6_IFF_TENTATIVE;

#if ND6_DEBUG
                        log(LOG_INFO,
                            "%s: DAD complete for %s - no duplicates found\n",
                            if_name(ifa->ifa_ifp),
                            ip6_sprintf(&ia->ia_addr.sin6_addr));
#endif

                        TAILQ_REMOVE(&dadq, (struct dadq *)dp, dad_list);
                        _FREE(dp, M_IP6NDP);
                        dp = NULL;
                        IFAFREE(ifa);
                }
        }

done:
        splx(s);
}

void
nd6_dad_duplicated(ifa)
        struct ifaddr *ifa;
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct dadq *dp;

        dp = nd6_dad_find(ifa);
        if (dp == NULL) {
                log(LOG_ERR, "nd6_dad_duplicated: DAD structure not found\n");
                return;
        }

        log(LOG_ERR, "%s: DAD detected duplicate IPv6 address %s: %d NS, "
            "%d NA\n", if_name(ifa->ifa_ifp),
            ip6_sprintf(&ia->ia_addr.sin6_addr),
            dp->dad_ns_icount, dp->dad_na_icount);

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

        /* We are done with DAD, with duplicated address found. (failure) */
        untimeout((void (*) __P((void *)))nd6_dad_timer_funnel, (void *)ifa
#if defined(__FreeBSD__) && __FreeBSD__ >= 3
                , dp->dad_timer
#endif
                );

        log(LOG_ERR, "%s: DAD complete for %s - duplicate found\n",
            if_name(ifa->ifa_ifp), ip6_sprintf(&ia->ia_addr.sin6_addr));
        log(LOG_ERR, "%s: manual intervention required\n",
            if_name(ifa->ifa_ifp));

        TAILQ_REMOVE(&dadq, (struct dadq *)dp, dad_list);
        _FREE(dp, M_IP6NDP);
        dp = NULL;
        IFAFREE(ifa);
}

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

        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_ocount++;
        nd6_ns_output(ifp, NULL, &ia->ia_addr.sin6_addr, NULL, 1);
}

static void
nd6_dad_ns_input(ifa)
        struct ifaddr *ifa;
{
        struct in6_ifaddr *ia;
        struct ifnet *ifp;
        struct in6_addr *taddr6;
        struct dadq *dp;
        int duplicate;

        if (!ifa)
                panic("ifa == NULL in nd6_dad_ns_input");

        ia = (struct in6_ifaddr *)ifa;
        ifp = ifa->ifa_ifp;
        taddr6 = &ia->ia_addr.sin6_addr;
        duplicate = 0;
        dp = nd6_dad_find(ifa);

        /*
         * If it is from myself, ignore this.
         */
        if (ifp && (ifp->if_flags & IFF_LOOPBACK))
                return;

        /* Quickhack - completely ignore DAD NS packets */
        if (dad_ignore_ns) {
                log(LOG_INFO, "nd6_dad_ns_input: ignoring DAD NS packet for "
                    "address %s(%s)\n", ip6_sprintf(taddr6),
                    if_name(ifa->ifa_ifp));
                return;
        }

        /*
         * if I'm yet to start DAD, someone else started using this address
         * first.  I have a duplicate and you win.
         */
        if (!dp || dp->dad_ns_ocount == 0)
                duplicate++;

        /* XXX more checks for loopback situation - see nd6_dad_timer too */

        if (duplicate) {
                dp = NULL;      /* will be freed in nd6_dad_duplicated() */
                nd6_dad_duplicated(ifa);
        } else {
                /*
                 * not sure if I got a duplicate.
                 * increment ns count and see what happens.
                 */
                if (dp)
                        dp->dad_ns_icount++;
        }
}

static void
nd6_dad_na_input(ifa)
        struct ifaddr *ifa;
{
        struct dadq *dp;

        if (!ifa)
                panic("ifa == NULL in nd6_dad_na_input");

        dp = nd6_dad_find(ifa);
        if (dp)
                dp->dad_na_icount++;

        /* remove the address. */
        nd6_dad_duplicated(ifa);
}