/*      $FreeBSD: src/sys/netinet6/nd6_nbr.c,v 1.4.2.6 2003/01/23 21:06:47 sam Exp $    */
/*      $KAME: nd6_nbr.c,v 1.86 2002/01/21 02:33:04 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 "opt_inet.h"
#include "opt_inet6.h"
#include "opt_carp.h"

#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>
#include <sys/syslog.h>
#include <sys/queue.h>
#include <sys/callout.h>
#include <sys/mutex.h>
#include <sys/resourcevar.h>

#include <sys/thread2.h>
#include <sys/mutex2.h>

#include <net/if.h>
#include <net/if_types.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <net/netisr2.h>
#include <net/netmsg2.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>

#include <net/net_osdep.h>

#ifdef CARP
#include <netinet/ip_carp.h>
#endif


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

struct dadq;
static struct dadq *nd6_dad_find(struct ifaddr *);
static void nd6_dad_starttimer(struct dadq *, int);
static void nd6_dad_stoptimer(struct dadq *);
static void nd6_dad_timer(void *);
static void nd6_dad_timer_handler(netmsg_t);
static void nd6_dad_ns_output(struct dadq *);
static void nd6_dad_ns_input(struct ifaddr *);
static void nd6_dad_na_input(struct ifaddr *);
static struct dadq *nd6_dad_create(struct ifaddr *);
static void nd6_dad_destroy(struct dadq *);
static void nd6_dad_duplicated(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(struct mbuf *m, int off, int icmp6len)
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct ifnet *cmpifp;
        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 tlladdr;
        union nd_opts ndopts;
        struct sockaddr_dl *proxydl = NULL;

        /*
         * Collapse interfaces to the bridge for comparison and
         * mac (llinfo) purposes.
         */
        cmpifp = ifp;
        if (ifp->if_bridge)
                cmpifp = ifp->if_bridge;

#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
        ip6 = mtod(m, struct ip6_hdr *); /* adjust pointer for safety */
        taddr6 = nd_ns->nd_ns_target;

        if (ip6->ip6_hlim != 255) {
                nd6log((LOG_ERR,
                    "nd6_ns_input: invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst), if_name(ifp)));
                goto bad;
        }

        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 {
                        nd6log((LOG_INFO, "nd6_ns_input: bad DAD packet "
                            "(wrong ip6 dst)\n"));
                        goto bad;
                }
        } else if (!nd6_onlink_ns_rfc4861) {
                struct sockaddr_in6 src_sa6;

                /*
                 * According to recent IETF discussions, it is not a good idea
                 * to accept a NS from an address which would not be deemed
                 * to be a neighbor otherwise.  This point is expected to be
                 * clarified in future revisions of the specification.
                 */
                bzero(&src_sa6, sizeof(src_sa6));
                src_sa6.sin6_family = AF_INET6;
                src_sa6.sin6_len = sizeof(src_sa6);
                src_sa6.sin6_addr = saddr6;
                if (nd6_is_addr_neighbor(&src_sa6, ifp) == 0) {
                        nd6log((LOG_INFO, "nd6_ns_input: "
                            "NS packet from non-neighbor\n"));
                        goto bad;
                }
        }

        if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
                nd6log((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) {
                nd6log((LOG_INFO,
                    "nd6_ns_input: 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, "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 or anycast address for which I'm offering proxy
         *     service.
         * (3) "tentative" address on which DAD is being performed.
         */
        /* (1) and (3) check. */
#ifdef CARP
        if (ifp->if_carp)
                ifa = carp_iamatch6(ifp->if_carp, &taddr6);
        if (!ifa)
                ifa = (struct ifaddr *)in6ifa_ifpwithaddr(ifp, &taddr6);
#else
        ifa = (struct ifaddr *)in6ifa_ifpwithaddr(ifp, &taddr6);
#endif

        /*
         * (2) Check proxying.  Requires ip6_forwarding to be turned on.
         *
         *     If the packet is anycast the target route must be on a
         *     different interface because the anycast will get anything
         *     on the current interface.
         *
         *     If the packet is unicast the target route may be on the
         *     same interface.  If the gateway is a (typically manually
         *     configured) link address we can directly offer it.
         *     XXX for now we don't do this but instead offer ours and
         *     presumably relay.
         *
         *     WARNING! Since this is a subnet proxy the interface proxying
         *     the ND6 must be in promiscuous mode or it will not see the
         *     solicited multicast requests for various hosts being proxied.
         *
         *     WARNING! Since this is a subnet proxy we have to treat bridge
         *     interfaces as being the bridge itself so we do not proxy-nd6
         *     between bridge interfaces (which are effectively switched).
         *
         *     (In the specific-host-proxy case via RTF_ANNOUNCE, which is
         *     a bitch to configure, a specific multicast route is already
         *     added for that host <-- NOT RECOMMENDED).
         */
        if (!ifa && ip6_forwarding) {
                struct rtentry *rt;
                struct sockaddr_in6 tsin6;
                struct ifnet *rtifp;

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

                rt = rtpurelookup((struct sockaddr *)&tsin6);
                rtifp = rt ? rt->rt_ifp : NULL;
                if (rtifp && rtifp->if_bridge)
                        rtifp = rtifp->if_bridge;

                if (rt != NULL &&
                    ((rt->rt_flags & RTF_ANNOUNCE) == 0 &&
                     (rtifp->if_flags & IFF_ANNOUNCE) == 0)
                    ) {
                        static struct krate krate_nff = { .freq = 1 };
                        krateprintf(&krate_nff,
                                    "route %p not flagged RTF_ANNOUNCE "
                                    "rtifp %p "
                                    "target %04x:%04x:%04x:%04x:"
                                    "%04x:%04x:%04x:%04x\n",
                                    rt,
                                    rtifp,
                                    taddr6.s6_addr16[0],
                                    taddr6.s6_addr16[1],
                                    taddr6.s6_addr16[2],
                                    taddr6.s6_addr16[3],
                                    taddr6.s6_addr16[4],
                                    taddr6.s6_addr16[5],
                                    taddr6.s6_addr16[6],
                                    taddr6.s6_addr16[7]);
                }

                if (rt != NULL &&
                    ((rt->rt_flags & RTF_ANNOUNCE) ||
                     (rtifp->if_flags & IFF_ANNOUNCE)) &&
                    (cmpifp != rtifp || (m->m_flags & M_MCAST) == 0)) {
                        ifa = (struct ifaddr *)in6ifa_ifpforlinklocal(cmpifp,
                                IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
                        nd6log((LOG_INFO,
                               "nd6_ns_input: nd6 proxy %s(%s)<-%s ifa %p\n",
                               if_name(cmpifp), if_name(ifp),
                               if_name(rtifp), ifa));
                        if (ifa) {
                                proxy = 1;
                                /*
                                 * Manual link address on same interface
                                 * w/announce flag will proxy-arp using
                                 * target mac, else our mac is used.
                                 */
                                if (cmpifp == rtifp &&
                                    rt->rt_gateway->sa_family == AF_LINK) {
                                        proxydl = SDL(rt->rt_gateway);
                                }
                        }
                }
                if (rt != NULL)
                        --rt->rt_refcnt;
        }
        if (ifa == NULL) {
                /*
                 * We've got an 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 && ((cmpifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                nd6log((LOG_INFO, "nd6_ns_input: lladdrlen mismatch for %s "
                    "(if %d, NS packet %d)\n",
                    ip6_sprintf(&taddr6), cmpifp->if_addrlen, lladdrlen - 2));
                goto bad;
        }

        if (IN6_ARE_ADDR_EQUAL(&myaddr6, &saddr6)) {
                nd6log((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 = kin6addr_linklocal_allnodes;
                saddr6.s6_addr16[1] = htons(cmpifp->if_index);
                nd6_na_output(cmpifp, &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(cmpifp, &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:
        nd6log((LOG_ERR, "nd6_ns_input: src=%s\n", ip6_sprintf(&saddr6)));
        nd6log((LOG_ERR, "nd6_ns_input: dst=%s\n", ip6_sprintf(&daddr6)));
        nd6log((LOG_ERR, "nd6_ns_input: tgt=%s\n", ip6_sprintf(&taddr6)));
        icmp6stat.icp6s_badns++;
        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(struct ifnet *ifp, const struct in6_addr *daddr6,
              const struct in6_addr *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
                kprintf("nd6_ns_output: max_linkhdr + maxlen > MCLBYTES "
                    "(%d + %d > %d)\n", max_linkhdr, maxlen, MCLBYTES);
#endif
                return;
        }

        m = m_getb(max_linkhdr + maxlen, M_NOWAIT, MT_DATA, M_PKTHDR);
        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) {
                /*
                 * 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);
                                return;
                        }
                        ip6->ip6_src = ia->ia_addr.sin6_addr;
                }
        } 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;
        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 (!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);

        ip6_output(m, NULL, NULL, dad ? IPV6_DADOUTPUT : 0, &im6o, &outif, NULL);
        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(struct mbuf *m, int off, int icmp6len)
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        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;
        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) {
                nd6log((LOG_ERR,
                    "nd6_na_input: invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst), if_name(ifp)));
                goto bad;
        }

#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)) {
                nd6log((LOG_ERR,
                    "nd6_na_input: invalid target address %s\n",
                    ip6_sprintf(&taddr6)));
                goto bad;
        }
        if (IN6_IS_ADDR_MULTICAST(&daddr6))
                if (is_solicited) {
                        nd6log((LOG_ERR,
                            "nd6_na_input: 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,
                    "nd6_na_input: invalid ND option, ignored\n"));
                /* nd6_options have incremented stats */
                goto freeit;
        }

        if (ndopts.nd_opts_tgt_lladdr) {
                struct ifnet *ifp_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, "nd6_na_input: lladdrlen mismatch "
                            "for %s (if %d, NA packet %d)\n", ip6_sprintf(&taddr6),
                            ifp->if_addrlen, lladdrlen - 2));
                        goto bad;
                }

                /* If it's from me, ignore it. */
                ifp_ll = if_bylla(lladdr, ifp->if_addrlen);
                if (ifp_ll != NULL)
                        goto freeit;
        }

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

        if (!nd6_onlink_ns_rfc4861) {
                /*
                 * Make sure the source address is from a neighbor's address.
                 */
                struct sockaddr_in6 src_sa6;

                bzero(&src_sa6, sizeof(src_sa6));
                src_sa6.sin6_family = AF_INET6;
                src_sa6.sin6_len = sizeof(src_sa6);
                src_sa6.sin6_addr = saddr6;
                if (nd6_is_addr_neighbor(&src_sa6, ifp) == 0) {
                        nd6log((LOG_INFO, "nd6_na_input: "
                            "NA packet from non-neighbor\n"));
                        goto bad;
                }
        }

        /*
         * 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;
                        ln->ln_byhint = 0;
                        if (ln->ln_expire) {
                                ln->ln_expire = time_uptime +
                                    ND_IFINFO(rt->rt_ifp)->reachable;
                        }
                } else {
                        ln->ln_state = ND6_LLINFO_STALE;
                        ln->ln_expire = time_uptime + nd6_gctimer;
                }
                if ((ln->ln_router = is_router) != 0) {
                        /*
                         * This means a router's state has changed from
                         * non-reachable to probably reachable, and might
                         * affect the status of associated prefixes..
                         */
                        pfxlist_onlink_check();
                }
        } 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;
                                ln->ln_expire = time_uptime + nd6_gctimer;
                        }
                        goto freeit;
                } else if (is_override                             /* (2a) */
                        || (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;
                                ln->ln_byhint = 0;
                                if (ln->ln_expire) {
                                        ln->ln_expire = time_uptime +
                                            ND_IFINFO(ifp)->reachable;
                                }
                        } else {
                                if (lladdr && llchange) {
                                        ln->ln_state = ND6_LLINFO_STALE;
                                        ln->ln_expire = time_uptime + nd6_gctimer;
                                }
                        }
                }

                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;

                        in6 = &((struct sockaddr_in6 *)rt_key(rt))->sin6_addr;

                        /*
                         * Lock to protect the default router list.
                         * XXX: this might be unnecessary, since this function
                         * is only called under the network software interrupt
                         * context.  However, we keep it just for safety.
                         */
                        mtx_lock(&nd6_mtx);
                        dr = defrouter_lookup(in6, rt->rt_ifp);
                        if (dr)
                                defrtrlist_del(dr);
                        mtx_unlock(&nd6_mtx);

                        if (dr == NULL && !ip6_forwarding &&
                            (ND_IFINFO(rt->rt_ifp)->flags &
                             ND6_IFF_ACCEPT_RTADV) != 0) {
                                /*
                                 * 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);
                        }
                }
                ln->ln_router = is_router;
        }
        rt->rt_flags &= ~RTF_REJECT;
        ln->ln_asked = 0;
        if (ln->ln_hold) {
                /*
                 * we assume ifp is not a loopback here, so just set the 2nd
                 * argument as the 1st one.
                 */
                nd6_output(ifp, ifp, ln->ln_hold,
                           (struct sockaddr_in6 *)rt_key(rt), rt);
                ln->ln_hold = NULL;
        }

freeit:
        m_freem(m);
        return;

bad:
        icmp6stat.icp6s_badna++;
        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,
              const struct in6_addr *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
                kprintf("nd6_na_output: max_linkhdr + maxlen > MCLBYTES "
                    "(%d + %d > %d)\n", max_linkhdr, maxlen, MCLBYTES);
#endif
                return;
        }

        m = m_getb(max_linkhdr + maxlen, M_NOWAIT, MT_DATA, M_PKTHDR);
        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;
        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.
         */
        mac = NULL;
        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) {
#ifdef CARP
                        if (ifp->if_carp)
                                mac = carp_macmatch6(ifp->if_carp, m, taddr6);
                        if (mac == NULL)
                                mac = nd6_ifptomac(ifp);
#else
                        mac = nd6_ifptomac(ifp);
#endif
                } 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 (mac != NULL) {
                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);

        ip6_output(m, NULL, NULL, 0, &im6o, &outif, NULL);
        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(struct ifnet *ifp)
{
        switch (ifp->if_type) {
        case IFT_ETHER:
        case IFT_IEEE1394:
#ifdef IFT_L2VLAN
        case IFT_L2VLAN:
#endif
#ifdef IFT_IEEE80211
        case IFT_IEEE80211:
#endif
#ifdef IFT_CARP
        case IFT_CARP:
#endif
                return ((caddr_t)(ifp + 1));
        default:
                return NULL;
        }
}

struct netmsg_dad {
        struct netmsg_base      base;
        struct dadq             *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;
        struct callout dad_timer_ch;
        struct netmsg_dad dad_nmsg;
};
TAILQ_HEAD(dadq_head, dadq);

static struct dadq_head dadq = TAILQ_HEAD_INITIALIZER(dadq);

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

        ASSERT_NETISR0;

        TAILQ_FOREACH(dp, &dadq, dad_list) {
                if (dp->dad_ifa == ifa)
                        return dp;
        }
        return NULL;
}

static void
nd6_dad_starttimer(struct dadq *dp, int ticks)
{
        ASSERT_NETISR0;
        callout_reset(&dp->dad_timer_ch, ticks, nd6_dad_timer, dp);
}

static void
nd6_dad_stoptimer(struct dadq *dp)
{
        ASSERT_NETISR0;
        callout_stop(&dp->dad_timer_ch);
}

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

        ASSERT_NETISR0;

        /*
         * If we don't need DAD, don't do it.
         * There are several cases:
         * - DAD is disabled globally (ip6_dad_count == 0) or on the interface
         * - 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) ||
            ip6_dad_count == 0 ||
            (ND_IFINFO(ifa->ifa_ifp)->flags & ND6_IFF_NO_DAD)) {
                ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
                in6_newaddrmsg(ifa);
                return;
        }
        if (!(ifa->ifa_ifp->if_flags & IFF_UP))
                return;
        if (nd6_dad_find(ifa) != NULL) {
                /* DAD already in progress */
                return;
        }

        dp = nd6_dad_create(ifa);
        nd6log((LOG_DEBUG, "%s: starting DAD for %s\n", if_name(ifa->ifa_ifp),
            ip6_sprintf(&ia->ia_addr.sin6_addr)));

        /*
         * Send NS packet for DAD, dp->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.
         */
        if (tick == NULL) {
                nd6_dad_ns_output(dp);
                nd6_dad_starttimer(dp,
                    ND_IFINFO(ifa->ifa_ifp)->retrans * hz / 1000);
        } else {
                int ntick;

                if (*tick == 0)
                        ntick = krandom() % (MAX_RTR_SOLICITATION_DELAY * hz);
                else
                        ntick = *tick + krandom() % (hz / 2);
                *tick = ntick;
                nd6_dad_starttimer(dp, ntick);
        }
}

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

        ASSERT_NETISR0;

        dp = nd6_dad_find(ifa);
        if (!dp) {
                /* DAD wasn't started yet */
                return;
        }
        nd6_dad_destroy(dp);
}

static struct dadq *
nd6_dad_create(struct ifaddr *ifa)
{
        struct netmsg_dad *dm;
        struct dadq *dp;

        ASSERT_NETISR0;

        dp = kmalloc(sizeof(*dp), M_IP6NDP, M_INTWAIT | M_ZERO);
        callout_init_mp(&dp->dad_timer_ch);

        dm = &dp->dad_nmsg;
        netmsg_init(&dm->base, NULL, &netisr_adone_rport,
            MSGF_DROPABLE | MSGF_PRIORITY, nd6_dad_timer_handler);
        dm->dadq = dp;

        dp->dad_ifa = ifa;
        IFAREF(ifa);    /* just for safety */

        /* Send NS packet for DAD, ip6_dad_count times. */
        dp->dad_count = ip6_dad_count;

        TAILQ_INSERT_TAIL(&dadq, dp, dad_list);

        return dp;
}

static void
nd6_dad_destroy(struct dadq *dp)
{
        struct lwkt_msg *lmsg = &dp->dad_nmsg.base.lmsg;

        ASSERT_NETISR0;

        TAILQ_REMOVE(&dadq, dp, dad_list);

        nd6_dad_stoptimer(dp);

        crit_enter();
        if ((lmsg->ms_flags & MSGF_DONE) == 0)
                lwkt_dropmsg(lmsg);
        crit_exit();

        IFAFREE(dp->dad_ifa);
        kfree(dp, M_IP6NDP);
}

static void
nd6_dad_timer(void *xdp)
{
        struct dadq *dp = xdp;
        struct lwkt_msg *lmsg = &dp->dad_nmsg.base.lmsg;

        KASSERT(mycpuid == 0, ("dad timer not on cpu0"));

        crit_enter();
        if (lmsg->ms_flags & MSGF_DONE)
                lwkt_sendmsg_oncpu(netisr_cpuport(0), lmsg);
        crit_exit();
}

static void
nd6_dad_timer_handler(netmsg_t msg)
{
        struct netmsg_dad *dm = (struct netmsg_dad *)msg;
        struct dadq *dp = dm->dadq;
        struct ifaddr *ifa = dp->dad_ifa;
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;

        ASSERT_NETISR0;

        /* Reply ASAP */
        crit_enter();
        lwkt_replymsg(&dm->base.lmsg, 0);
        crit_exit();

        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 destroy;
        }
        if (!(ia->ia6_flags & IN6_IFF_TENTATIVE)) {
                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 destroy;
        }

        /* Timed out 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)));
                goto destroy;
        }

        /* 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);
                nd6_dad_starttimer(dp,
                    ND_IFINFO(ifa->ifa_ifp)->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;
                        in6_newaddrmsg(ifa);
                        nd6log((LOG_DEBUG,
                            "%s: DAD complete for %s - no duplicates found\n",
                            if_name(ifa->ifa_ifp),
                            ip6_sprintf(&ia->ia_addr.sin6_addr)));
                        goto destroy;
                }
        }
        return;
destroy:
        nd6_dad_destroy(dp);
}

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

        ASSERT_NETISR0;

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

        /*
         * We are done with DAD, with duplicated address found. (failure)
         */
        log(LOG_ERR, "%s: DAD detected duplicate IPv6 address %s: "
            "NS in/out=%d/%d, NA in=%d\n",
            if_name(ifa->ifa_ifp), ip6_sprintf(&ia->ia_addr.sin6_addr),
            dp->dad_ns_icount, dp->dad_ns_ocount, dp->dad_na_icount);

        ia->ia6_flags &= ~IN6_IFF_TENTATIVE;
        ia->ia6_flags |= IN6_IFF_DUPLICATED;
        in6_newaddrmsg(ifa);

        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));

        nd6_dad_destroy(dp);
}

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

        ASSERT_NETISR0;

        dp->dad_ns_tcount++;
        if (!(ifp->if_flags & IFF_UP)) {
#if 0
                kprintf("%s: interface down?\n", if_name(ifp));
#endif
                return;
        }
        if (!(ifp->if_flags & IFF_RUNNING)) {
#if 0
                kprintf("%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(struct ifaddr *ifa)
{
        struct in6_ifaddr *ia;
        const struct in6_addr *taddr6;
        struct dadq *dp;
        int duplicate;

        ASSERT_NETISR0;

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

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

        /* Quickhack - completely ignore DAD NS packets */
        if (dad_ignore_ns) {
                nd6log((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(struct ifaddr *ifa)
{
        struct dadq *dp;

        ASSERT_NETISR0;

        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);
}