xnu-2050.7.9.tar.gz

[apple/xnu.git] / bsd / netinet6 / nd6_prproxy.c

/*
 * Copyright (c) 2011-2012 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

/*
 * Prefix-based Neighbor Discovery Proxy
 *
 * When an interface is marked with the ND6_IFF_PROXY_PREFIXES flag, all
 * of current and future non-scoped on-link prefixes configured on the
 * interface will be shared with the scoped variant of such prefixes on
 * other interfaces.  This allows for one or more prefixes to be shared
 * across multiple links, with full support for Duplicate Addres Detection,
 * Address Resolution and Neighbor Unreachability Detection.
 *
 * A non-scoped prefix may be configured statically, or dynamically via
 * Router Advertisement.  An interface is said to be an "upstream" interface
 * when it is marked with ND6_IFF_PROXY_PREFIXES and has at least one prefix
 * that is non-scoped (global, not scoped.)  Such prefixes are marked with
 * the NDPRF_PRPROXY flag.
 *
 * A scoped prefix typically gets configured by way of adding an address
 * to a "downstream" interface, when the added address is part of an existing
 * prefix that is allowed to be shared (i.e. NDPRF_PRPROXY prefixes.)  Unlike
 * non-scoped prefixes, however, scoped prefixes will never be marked with
 * the NDPRF_PRPROXY flag.
 *
 * The setting of NDPRF_PRPROXY depends on whether the prefix is on-link;
 * an off-link prefix on an interface marked with ND6_IFF_PROXY_PREFIXES
 * will not cause NDPRF_PRPROXY to be set (it will only happen when that
 * prefix goes on-link.)  Likewise, a previously on-link prefix that has
 * transitioned to off-link will cause its NDPRF_PRPROXY flag to be cleared.
 *
 * Prefix proxying relies on IPv6 Scoped Routing to be in effect, as it would
 * otherwise be impossible to install scoped prefix route entries in the
 * routing table.  By default, such cloning prefix routes will generate cloned
 * routes that are scoped according to their interfaces.  Because prefix
 * proxying is essentially creating a larger network comprised of multiple
 * links sharing a prefix, we need to treat the cloned routes as if they
 * weren't scoped route entries.  This requires marking such cloning prefix
 * routes with the RTF_PROXY flag, which serves as an indication that the
 * route entry (and its clones) are part of a proxied prefix, and that the
 * entries are non-scoped.
 *
 * In order to handle solicited-node destined ND packets (Address Resolution,
 * Neighbor Unreachability Detection), prefix proxying also requires that the
 * "upstream" and "downstream" interfaces be configured for all-multicast mode.
 *
 * The setting and clearing of RTF_PROXY flag, as well as the entering and
 * exiting of all-multicast mode on those interfaces happen when a prefix
 * transitions between on-link and off-link (vice versa.)
 *
 * Note that this is not a strict implementation of RFC 4389, but rather a
 * derivative based on similar concept.  In particular, we only proxy NS and
 * NA packets; RA packets are never proxied.  Care should be taken to enable
 * prefix proxying only on non-looping network topology.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <sys/sysctl.h>
#include <sys/mcache.h>
#include <sys/protosw.h>

#include <kern/queue.h>
#include <kern/zalloc.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_types.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 <netinet/icmp6.h>
#include <netinet6/nd6.h>
#include <netinet6/scope6_var.h>

struct nd6_prproxy_prelist {
        SLIST_ENTRY(nd6_prproxy_prelist) ndprl_le;
        struct nd_prefix *ndprl_pr;             /* prefix */
        struct nd_prefix *ndprl_up;             /* non-NULL for upstream */
        struct ifnet    *ndprl_fwd_ifp;         /* outgoing interface */
        boolean_t       ndprl_sol;              /* unicast solicitor? */
        struct in6_addr ndprl_sol_saddr;        /* solicitor's address */
};

/*
 * Soliciting node (source) record.
 */
struct nd6_prproxy_solsrc {
        TAILQ_ENTRY(nd6_prproxy_solsrc) solsrc_tqe;
        struct in6_addr solsrc_saddr;           /* soliciting (src) address */
        struct ifnet    *solsrc_ifp;            /* iface where NS arrived on */
};

/*
 * Solicited node (target) record.
 */
struct nd6_prproxy_soltgt {
        RB_ENTRY(nd6_prproxy_soltgt) soltgt_link; /* RB tree links */
        struct soltgt_key_s {
                struct in6_addr taddr;          /* solicited (tgt) address */
        } soltgt_key;
        u_int64_t       soltgt_expire;          /* expiration time */
        u_int32_t       soltgt_cnt;             /* total # of solicitors */
        TAILQ_HEAD(, nd6_prproxy_solsrc) soltgt_q;
};

SLIST_HEAD(nd6_prproxy_prelist_head, nd6_prproxy_prelist);

static void nd6_prproxy_prelist_setroute(boolean_t enable,
    struct nd6_prproxy_prelist_head *, struct nd6_prproxy_prelist_head *);
static struct nd6_prproxy_prelist *nd6_ndprl_alloc(int);
static void nd6_ndprl_free(struct nd6_prproxy_prelist *);
static struct nd6_prproxy_solsrc *nd6_solsrc_alloc(int);
static void nd6_solsrc_free(struct nd6_prproxy_solsrc *);
static boolean_t nd6_solsrc_enq(struct nd_prefix *, struct ifnet *,
    struct in6_addr *, struct in6_addr *);
static boolean_t nd6_solsrc_deq(struct nd_prefix *, struct in6_addr *,
    struct in6_addr *, struct ifnet **);
static struct nd6_prproxy_soltgt *nd6_soltgt_alloc(int);
static void nd6_soltgt_free(struct nd6_prproxy_soltgt *);
static void nd6_soltgt_prune(struct nd6_prproxy_soltgt *, u_int32_t);
static __inline int soltgt_cmp(const struct nd6_prproxy_soltgt *,
    const struct nd6_prproxy_soltgt *);
static void nd6_prproxy_sols_purge(struct nd_prefix *, u_int64_t);

RB_PROTOTYPE_SC_PREV(__private_extern__, prproxy_sols_tree, nd6_prproxy_soltgt,
    soltgt_link, soltgt_cmp);

/*
 * Time (in seconds) before a target record expires (is idle).
 */
#define ND6_TGT_SOLS_EXPIRE                     5

/*
 * Maximum number of queued soliciting (source) records per target.
 */
#define ND6_MAX_SRC_SOLS_DEFAULT                4

/*
 * Maximum number of queued solicited (target) records per prefix.
 */
#define ND6_MAX_TGT_SOLS_DEFAULT                8

static u_int32_t nd6_max_tgt_sols = ND6_MAX_TGT_SOLS_DEFAULT;
static u_int32_t nd6_max_src_sols = ND6_MAX_SRC_SOLS_DEFAULT;

static unsigned int ndprl_size;                 /* size of zone element */
static struct zone *ndprl_zone;                 /* nd6_prproxy_prelist zone */

#define NDPRL_ZONE_MAX  256                     /* maximum elements in zone */
#define NDPRL_ZONE_NAME "nd6_prproxy_prelist"   /* name for zone */

static unsigned int solsrc_size;                /* size of zone element */
static struct zone *solsrc_zone;                /* nd6_prproxy_solsrc zone */

#define SOLSRC_ZONE_MAX  256                    /* maximum elements in zone */
#define SOLSRC_ZONE_NAME "nd6_prproxy_solsrc"   /* name for zone */

static unsigned int soltgt_size;                /* size of zone element */
static struct zone *soltgt_zone;                /* nd6_prproxy_soltgt zone */

#define SOLTGT_ZONE_MAX  256                    /* maximum elements in zone */
#define SOLTGT_ZONE_NAME "nd6_prproxy_soltgt"   /* name for zone */

/* The following is protected by ndpr_lock */
RB_GENERATE_PREV(prproxy_sols_tree, nd6_prproxy_soltgt,
    soltgt_link, soltgt_cmp);

/* The following is protected by proxy6_lock (for updates) */
u_int32_t nd6_prproxy;

extern lck_mtx_t *nd6_mutex;

SYSCTL_DECL(_net_inet6_icmp6);

SYSCTL_UINT(_net_inet6_icmp6, OID_AUTO, nd6_maxsolstgt,
    CTLFLAG_RW | CTLFLAG_LOCKED, &nd6_max_tgt_sols, ND6_MAX_TGT_SOLS_DEFAULT,
    "maximum number of outstanding solicited targets per prefix");

SYSCTL_UINT(_net_inet6_icmp6, OID_AUTO, nd6_maxproxiedsol,
    CTLFLAG_RW | CTLFLAG_LOCKED, &nd6_max_src_sols, ND6_MAX_SRC_SOLS_DEFAULT,
    "maximum number of outstanding solicitations per target");

SYSCTL_UINT(_net_inet6_icmp6, OID_AUTO, prproxy_cnt,
    CTLFLAG_RD | CTLFLAG_LOCKED, &nd6_prproxy, 0,
    "total number of proxied prefixes");

/*
 * Called by nd6_init() during initialization time.
 */
void
nd6_prproxy_init(void)
{
        ndprl_size = sizeof (struct nd6_prproxy_prelist);
        ndprl_zone = zinit(ndprl_size, NDPRL_ZONE_MAX * ndprl_size, 0,
            NDPRL_ZONE_NAME);
        if (ndprl_zone == NULL)
                panic("%s: failed allocating ndprl_zone", __func__);

        zone_change(ndprl_zone, Z_EXPAND, TRUE);
        zone_change(ndprl_zone, Z_CALLERACCT, FALSE);

        solsrc_size = sizeof (struct nd6_prproxy_solsrc);
        solsrc_zone = zinit(solsrc_size, SOLSRC_ZONE_MAX * solsrc_size, 0,
            SOLSRC_ZONE_NAME);
        if (solsrc_zone == NULL)
                panic("%s: failed allocating solsrc_zone", __func__);

        zone_change(solsrc_zone, Z_EXPAND, TRUE);
        zone_change(solsrc_zone, Z_CALLERACCT, FALSE);

        soltgt_size = sizeof (struct nd6_prproxy_soltgt);
        soltgt_zone = zinit(soltgt_size, SOLTGT_ZONE_MAX * soltgt_size, 0,
            SOLTGT_ZONE_NAME);
        if (soltgt_zone == NULL)
                panic("%s: failed allocating soltgt_zone", __func__);

        zone_change(soltgt_zone, Z_EXPAND, TRUE);
        zone_change(soltgt_zone, Z_CALLERACCT, FALSE);
}

static struct nd6_prproxy_prelist *
nd6_ndprl_alloc(int how)
{
        struct nd6_prproxy_prelist *ndprl;

        ndprl = (how == M_WAITOK) ? zalloc(ndprl_zone) :
            zalloc_noblock(ndprl_zone);
        if (ndprl != NULL)
                bzero(ndprl, ndprl_size);

        return (ndprl);
}

static void
nd6_ndprl_free(struct nd6_prproxy_prelist *ndprl)
{
        zfree(ndprl_zone, ndprl);
}

/*
 * Apply routing function on the affected upstream and downstream prefixes,
 * i.e. either set or clear RTF_PROXY on the cloning prefix route; all route
 * entries that were cloned off these prefixes will be blown away.  Caller
 * must have acquried proxy6_lock and must not be holding nd6_mutex.
 */
static void
nd6_prproxy_prelist_setroute(boolean_t enable,
    struct nd6_prproxy_prelist_head *up_head,
    struct nd6_prproxy_prelist_head *down_head)
{
        struct nd6_prproxy_prelist *up, *down, *ndprl_tmp;
        struct nd_prefix *pr;

        lck_mtx_assert(&proxy6_lock, LCK_MTX_ASSERT_OWNED);
        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

        SLIST_FOREACH_SAFE(up, up_head, ndprl_le, ndprl_tmp) {
                struct rtentry *rt;
                boolean_t prproxy;

                SLIST_REMOVE(up_head, up, nd6_prproxy_prelist, ndprl_le);
                pr = up->ndprl_pr;
                VERIFY(up->ndprl_up == NULL);

                NDPR_LOCK(pr);
                prproxy = (pr->ndpr_stateflags & NDPRF_PRPROXY);
                VERIFY(!prproxy || ((pr->ndpr_stateflags & NDPRF_ONLINK) &&
                    !(pr->ndpr_stateflags & NDPRF_IFSCOPE)));

                nd6_prproxy_sols_reap(pr);
                VERIFY(pr->ndpr_prproxy_sols_cnt == 0);
                VERIFY(RB_EMPTY(&pr->ndpr_prproxy_sols));

                if (enable && pr->ndpr_allmulti_cnt == 0) {
                        nd6_prproxy++;
                        pr->ndpr_allmulti_cnt++;
                        if_allmulti(pr->ndpr_ifp, TRUE);
                } else if (!enable && pr->ndpr_allmulti_cnt > 0) {
                        nd6_prproxy--;
                        pr->ndpr_allmulti_cnt--;
                        if_allmulti(pr->ndpr_ifp, FALSE);
                }

                if ((rt = pr->ndpr_rt) != NULL) {
                        if ((enable && prproxy) || (!enable && !prproxy))
                                RT_ADDREF(rt);
                        else
                                rt = NULL;
                        NDPR_UNLOCK(pr);
                } else {
                        NDPR_UNLOCK(pr);
                }
                NDPR_REMREF(pr);
                if (rt != NULL) {
                        rt_set_proxy(rt, enable);
                        rtfree(rt);
                }
                nd6_ndprl_free(up);
        }

        SLIST_FOREACH_SAFE(down, down_head, ndprl_le, ndprl_tmp) {
                struct nd_prefix *pr_up;
                struct rtentry *rt;
                boolean_t prproxy;

                SLIST_REMOVE(down_head, down, nd6_prproxy_prelist, ndprl_le);
                pr = down->ndprl_pr;
                pr_up = down->ndprl_up;
                VERIFY(pr_up != NULL);

                NDPR_LOCK(pr_up);
                prproxy = (pr_up->ndpr_stateflags & NDPRF_PRPROXY);
                VERIFY(!prproxy || ((pr_up->ndpr_stateflags & NDPRF_ONLINK) &&
                    !(pr_up->ndpr_stateflags & NDPRF_IFSCOPE)));
                NDPR_UNLOCK(pr_up);

                NDPR_LOCK(pr);
                if (enable && pr->ndpr_allmulti_cnt == 0) {
                        pr->ndpr_allmulti_cnt++;
                        if_allmulti(pr->ndpr_ifp, TRUE);
                } else if (!enable && pr->ndpr_allmulti_cnt > 0) {
                        pr->ndpr_allmulti_cnt--;
                        if_allmulti(pr->ndpr_ifp, FALSE);
                }

                if ((rt = pr->ndpr_rt) != NULL) {
                        if ((enable && prproxy) || (!enable && !prproxy))
                                RT_ADDREF(rt);
                        else
                                rt = NULL;
                        NDPR_UNLOCK(pr);
                } else {
                        NDPR_UNLOCK(pr);
                }
                NDPR_REMREF(pr);
                NDPR_REMREF(pr_up);
                if (rt != NULL) {
                        rt_set_proxy(rt, enable);
                        rtfree(rt);
                }
                nd6_ndprl_free(down);
        }
}

/*
 * Enable/disable prefix proxying on an interface; typically called
 * as part of handling SIOCSIFINFO_FLAGS[IFEF_IPV6_ROUTER].
 */
int
nd6_if_prproxy(struct ifnet *ifp, boolean_t enable)
{
        SLIST_HEAD(, nd6_prproxy_prelist) up_head;
        SLIST_HEAD(, nd6_prproxy_prelist) down_head;
        struct nd6_prproxy_prelist *up, *down;
        struct nd_prefix *pr;

        /* Can't be enabled if we are an advertising router on the interface */
        ifnet_lock_shared(ifp);
        if (enable && (ifp->if_eflags & IFEF_IPV6_ROUTER)) {
                ifnet_lock_done(ifp);
                return (EBUSY);
        }
        ifnet_lock_done(ifp);

        SLIST_INIT(&up_head);
        SLIST_INIT(&down_head);

        /*
         * Serialize the clearing/setting of NDPRF_PRPROXY.
         */
        lck_mtx_lock(&proxy6_lock);

        /*
         * First build a list of upstream prefixes on this interface for
         * which we need to enable/disable prefix proxy functionality.
         */
        lck_mtx_lock(nd6_mutex);
        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if (IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr) ||
                    (!enable && !(pr->ndpr_stateflags & NDPRF_PRPROXY)) ||
                    (enable && (pr->ndpr_stateflags & NDPRF_PRPROXY)) ||
                    (pr->ndpr_stateflags & NDPRF_IFSCOPE) ||
                    pr->ndpr_ifp != ifp) {
                        NDPR_UNLOCK(pr);
                        continue;
                }

                /*
                 * At present, in order for the prefix to be eligible
                 * as a proxying/proxied prefix, we require that the
                 * prefix route entry be marked as a cloning route with
                 * RTF_PROXY; i.e. nd6_need_cache() needs to return
                 * true for the interface type.
                 */
                if (enable && (pr->ndpr_stateflags & NDPRF_ONLINK) &&
                    nd6_need_cache(ifp)) {
                        pr->ndpr_stateflags |= NDPRF_PRPROXY;
                        NDPR_ADDREF_LOCKED(pr);
                        NDPR_UNLOCK(pr);
                } else if (!enable) {
                        pr->ndpr_stateflags &= ~NDPRF_PRPROXY;
                        NDPR_ADDREF_LOCKED(pr);
                        NDPR_UNLOCK(pr);
                } else {
                        NDPR_UNLOCK(pr);
                        pr = NULL;      /* don't go further */
                }

                if (pr == NULL)
                        continue;

                up = nd6_ndprl_alloc(M_WAITOK);
                if (up == NULL) {
                        NDPR_REMREF(pr);
                        continue;
                }

                up->ndprl_pr = pr;      /* keep reference from above */
                SLIST_INSERT_HEAD(&up_head, up, ndprl_le);
        }

        /*
         * Now build a list of matching (scoped) downstream prefixes on other
         * interfaces which need to be enabled/disabled accordingly.  Note that
         * the NDPRF_PRPROXY is never set/cleared on the downstream prefixes.
         */
        SLIST_FOREACH(up, &up_head, ndprl_le) {
                struct nd_prefix *fwd;
                struct in6_addr pr_addr;
                u_char pr_len;

                pr = up->ndprl_pr;

                NDPR_LOCK(pr);
                bcopy(&pr->ndpr_prefix.sin6_addr, &pr_addr, sizeof (pr_addr));
                pr_len = pr->ndpr_plen;
                NDPR_UNLOCK(pr);

                for (fwd = nd_prefix.lh_first; fwd; fwd = fwd->ndpr_next) {
                        NDPR_LOCK(fwd);
                        if (!(fwd->ndpr_stateflags & NDPRF_ONLINK) ||
                            !(fwd->ndpr_stateflags & NDPRF_IFSCOPE) ||
                            fwd->ndpr_plen != pr_len ||
                            !in6_are_prefix_equal(&fwd->ndpr_prefix.sin6_addr,
                            &pr_addr, pr_len)) {
                                NDPR_UNLOCK(fwd);
                                continue;
                        }
                        NDPR_UNLOCK(fwd);

                        down = nd6_ndprl_alloc(M_WAITOK);
                        if (down == NULL)
                                continue;

                        NDPR_ADDREF(fwd);
                        down->ndprl_pr = fwd;
                        NDPR_ADDREF(pr);
                        down->ndprl_up = pr;
                        SLIST_INSERT_HEAD(&down_head, down, ndprl_le);
                }
        }
        lck_mtx_unlock(nd6_mutex);

        /*
         * Apply routing function on prefixes; callee will free resources.
         */
        nd6_prproxy_prelist_setroute(enable,
            (struct nd6_prproxy_prelist_head *)&up_head,
            (struct nd6_prproxy_prelist_head *)&down_head);

        VERIFY(SLIST_EMPTY(&up_head));
        VERIFY(SLIST_EMPTY(&down_head));

        lck_mtx_unlock(&proxy6_lock);

        return (0);
}

/*
 * Called from the input path to determine whether the packet is destined
 * to a proxied node; if so, mark the mbuf with MAUXF_PROXY_DST so that
 * icmp6_input() knows that this is not to be delivered to socket(s).
 */
boolean_t
nd6_prproxy_isours(struct mbuf *m, struct ip6_hdr *ip6, struct route_in6 *ro6,
    unsigned int ifscope)
{
        struct rtentry *rt;
        boolean_t ours = FALSE;

        if (ip6->ip6_hlim != IPV6_MAXHLIM || ip6->ip6_nxt != IPPROTO_ICMPV6)
                goto done;

        if (IN6_IS_ADDR_MC_NODELOCAL(&ip6->ip6_dst) ||
            IN6_IS_ADDR_MC_LINKLOCAL(&ip6->ip6_dst)) {
                VERIFY(ro6 == NULL);
                ours = TRUE;
                goto done;
        } else if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                goto done;
        }

        if (ro6 == NULL)
                goto done;

        if ((rt = ro6->ro_rt) != NULL)
                RT_LOCK(rt);

        if (rt == NULL || !(rt->rt_flags & RTF_UP) ||
            rt->generation_id != route_generation) {
                if (rt != NULL) {
                        RT_UNLOCK(rt);
                        rtfree(rt);
                        rt = ro6->ro_rt = NULL;
                }

                /* Caller must have ensured this condition (not srcrt) */
                VERIFY(IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
                    &ro6->ro_dst.sin6_addr));

                rtalloc_scoped_ign((struct route *)ro6, RTF_PRCLONING, ifscope);
                if ((rt = ro6->ro_rt) == NULL)
                        goto done;

                RT_LOCK(rt);
        }

        ours = (rt->rt_flags & RTF_PROXY) ? TRUE : FALSE;
        RT_UNLOCK(rt);

done:
        if (ours)
                m->m_pkthdr.aux_flags |= MAUXF_PROXY_DST;

        return (ours);
}

/*
 * Called when a prefix transitions between on-link and off-link.  Perform
 * routing (RTF_PROXY) and interface (all-multicast) related operations on
 * the affected prefixes.
 */
void
nd6_prproxy_prelist_update(struct nd_prefix *pr_cur, struct nd_prefix *pr_up)
{
        SLIST_HEAD(, nd6_prproxy_prelist) up_head;
        SLIST_HEAD(, nd6_prproxy_prelist) down_head;
        struct nd6_prproxy_prelist *up, *down;
        struct nd_prefix *pr;
        struct in6_addr pr_addr;
        boolean_t enable;
        u_char pr_len;

        SLIST_INIT(&up_head);
        SLIST_INIT(&down_head);
        VERIFY(pr_cur != NULL);

        lck_mtx_assert(&proxy6_lock, LCK_MTX_ASSERT_OWNED);

        /*
         * Upstream prefix.  If caller did not specify one, search for one
         * based on the information in current prefix.  Caller is expected
         * to have held an extra reference for the passed-in prefixes.
         */
        lck_mtx_lock(nd6_mutex);
        if (pr_up == NULL) {
                NDPR_LOCK(pr_cur);
                bcopy(&pr_cur->ndpr_prefix.sin6_addr, &pr_addr,
                    sizeof (pr_addr));
                pr_len = pr_cur->ndpr_plen;
                NDPR_UNLOCK(pr_cur);

                for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                        NDPR_LOCK(pr);
                        if (!(pr->ndpr_stateflags & NDPRF_ONLINK) ||
                            !(pr->ndpr_stateflags & NDPRF_PRPROXY) ||
                            pr->ndpr_plen != pr_len ||
                            !in6_are_prefix_equal(&pr->ndpr_prefix.sin6_addr,
                            &pr_addr, pr_len)) {
                                NDPR_UNLOCK(pr);
                                continue;
                        }
                        NDPR_UNLOCK(pr);
                        break;
                }

                if ((pr_up = pr) == NULL) {
                        lck_mtx_unlock(nd6_mutex);
                        goto done;
                }
                NDPR_LOCK(pr_up);
        } else {
                NDPR_LOCK(pr_up);
                bcopy(&pr_up->ndpr_prefix.sin6_addr, &pr_addr,
                    sizeof (pr_addr));
                pr_len = pr_up->ndpr_plen;
        }
        NDPR_LOCK_ASSERT_HELD(pr_up);
        /*
         * Upstream prefix could be offlink by now; therefore we cannot
         * assert that NDPRF_PRPROXY is set; however, we can insist that
         * it must not be a scoped prefix.
         */
        VERIFY(!(pr_up->ndpr_stateflags & NDPRF_IFSCOPE));
        enable = (pr_up->ndpr_stateflags & NDPRF_PRPROXY);
        NDPR_UNLOCK(pr_up);

        up = nd6_ndprl_alloc(M_WAITOK);
        if (up == NULL) {
                lck_mtx_unlock(nd6_mutex);
                goto done;
        }

        NDPR_ADDREF(pr_up);
        up->ndprl_pr = pr_up;
        SLIST_INSERT_HEAD(&up_head, up, ndprl_le);

        /*
         * Now build a list of matching (scoped) downstream prefixes on other
         * interfaces which need to be enabled/disabled accordingly.  Note that
         * the NDPRF_PRPROXY is never set/cleared on the downstream prefixes.
         */
        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if (!(pr->ndpr_stateflags & NDPRF_ONLINK) ||
                    !(pr->ndpr_stateflags & NDPRF_IFSCOPE) ||
                    pr->ndpr_plen != pr_len ||
                    !in6_are_prefix_equal(&pr->ndpr_prefix.sin6_addr,
                    &pr_addr, pr_len)) {
                        NDPR_UNLOCK(pr);
                        continue;
                }
                NDPR_UNLOCK(pr);

                down = nd6_ndprl_alloc(M_WAITOK);
                if (down == NULL)
                        continue;

                NDPR_ADDREF(pr);
                down->ndprl_pr = pr;
                NDPR_ADDREF(pr_up);
                down->ndprl_up = pr_up;
                SLIST_INSERT_HEAD(&down_head, down, ndprl_le);
        }
        lck_mtx_unlock(nd6_mutex);

        /*
         * Apply routing function on prefixes; callee will free resources.
         */
        nd6_prproxy_prelist_setroute(enable,
            (struct nd6_prproxy_prelist_head *)&up_head,
            (struct nd6_prproxy_prelist_head *)&down_head);

done:
        VERIFY(SLIST_EMPTY(&up_head));
        VERIFY(SLIST_EMPTY(&down_head));
}

/*
 * Given an interface address, determine whether or not the address
 * is part of of a proxied prefix.
 */
boolean_t
nd6_prproxy_ifaddr(struct in6_ifaddr *ia)
{
        struct nd_prefix *pr;
        struct in6_addr addr, pr_mask;
        u_int32_t pr_len;
        boolean_t proxied = FALSE;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

        IFA_LOCK(&ia->ia_ifa);
        bcopy(&ia->ia_addr.sin6_addr, &addr, sizeof (addr));
        bcopy(&ia->ia_prefixmask.sin6_addr, &pr_mask, sizeof (pr_mask));
        pr_len = ia->ia_plen;
        IFA_UNLOCK(&ia->ia_ifa);

        lck_mtx_lock(nd6_mutex);
        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if ((pr->ndpr_stateflags & NDPRF_ONLINK) &&
                    (pr->ndpr_stateflags & NDPRF_PRPROXY) &&
                    in6_are_prefix_equal(&pr->ndpr_prefix.sin6_addr,
                    &addr, pr_len)) {
                        NDPR_UNLOCK(pr);
                        proxied = TRUE;
                        break;
                }
                NDPR_UNLOCK(pr);
        }
        lck_mtx_unlock(nd6_mutex);

        return (proxied);
}

/*
 * Perform automatic proxy function with NS output.
 *
 * If the target address matches a global prefix obtained from a router
 * advertisement received on an interface with the ND6_IFF_PROXY_PREFIXES
 * flag set, then we send solicitations for the target address to all other
 * interfaces where a matching prefix is currently on-link, in addition to
 * the original interface.
 */
void
nd6_prproxy_ns_output(struct ifnet *ifp, struct in6_addr *daddr,
    struct in6_addr *taddr, struct llinfo_nd6 *ln)
{
        SLIST_HEAD(, nd6_prproxy_prelist) ndprl_head;
        struct nd6_prproxy_prelist *ndprl, *ndprl_tmp;
        struct nd_prefix *pr, *fwd;
        struct ifnet *fwd_ifp;
        struct in6_addr pr_addr;
        u_char pr_len;

        SLIST_INIT(&ndprl_head);

        lck_mtx_lock(nd6_mutex);

        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if (!(pr->ndpr_stateflags & NDPRF_ONLINK) ||
                    !(pr->ndpr_stateflags & NDPRF_PRPROXY) ||
                    !IN6_ARE_MASKED_ADDR_EQUAL(&pr->ndpr_prefix.sin6_addr,
                    taddr, &pr->ndpr_mask)) {
                        NDPR_UNLOCK(pr);
                        continue;
                }

                VERIFY(!(pr->ndpr_stateflags & NDPRF_IFSCOPE));
                bcopy(&pr->ndpr_prefix.sin6_addr, &pr_addr, sizeof (pr_addr));
                pr_len = pr->ndpr_plen;
                NDPR_UNLOCK(pr);

                for (fwd = nd_prefix.lh_first; fwd; fwd = fwd->ndpr_next) {
                        NDPR_LOCK(fwd);
                        if (!(fwd->ndpr_stateflags & NDPRF_ONLINK) ||
                            fwd->ndpr_ifp == ifp ||
                            fwd->ndpr_plen != pr_len ||
                            !in6_are_prefix_equal(&fwd->ndpr_prefix.sin6_addr,
                            &pr_addr, pr_len)) {
                                NDPR_UNLOCK(fwd);
                                continue;
                        }

                        fwd_ifp = fwd->ndpr_ifp;
                        NDPR_UNLOCK(fwd);

                        ndprl = nd6_ndprl_alloc(M_WAITOK);
                        if (ndprl == NULL)
                                continue;

                        NDPR_ADDREF(fwd);
                        ndprl->ndprl_pr = fwd;
                        ndprl->ndprl_fwd_ifp = fwd_ifp;

                        SLIST_INSERT_HEAD(&ndprl_head, ndprl, ndprl_le);
                }
                break;
        }

        lck_mtx_unlock(nd6_mutex);

        SLIST_FOREACH_SAFE(ndprl, &ndprl_head, ndprl_le, ndprl_tmp) {
                SLIST_REMOVE(&ndprl_head, ndprl, nd6_prproxy_prelist, ndprl_le);

                pr = ndprl->ndprl_pr;
                fwd_ifp = ndprl->ndprl_fwd_ifp;

                if ((fwd_ifp->if_eflags & IFEF_IPV6_ND6ALT) != 0) {
                        NDPR_REMREF(pr);
                        nd6_ndprl_free(ndprl);
                        continue;
                }

                NDPR_LOCK(pr);
                if (pr->ndpr_stateflags & NDPRF_ONLINK) {
                        NDPR_UNLOCK(pr);
                        nd6log2((LOG_DEBUG,
                            "%s%d: Sending cloned NS who has %s on %s%d\n",
                            fwd_ifp->if_name, fwd_ifp->if_unit,
                            ip6_sprintf(taddr), ifp->if_name,
                            ifp->if_unit));

                        nd6_ns_output(fwd_ifp, daddr, taddr, NULL, 0);
                } else {
                        NDPR_UNLOCK(pr);
                }
                NDPR_REMREF(pr);

                nd6_ndprl_free(ndprl);
        }
        VERIFY(SLIST_EMPTY(&ndprl_head));

        nd6_ns_output(ifp, daddr, taddr, ln, 0);
}

/*
 * Perform automatic proxy function with NS input.
 *
 * If the target address matches a global prefix obtained from a router
 * advertisement received on an interface with the ND6_IFF_PROXY_PREFIXES
 * flag set, then we send solicitations for the target address to all other
 * interfaces where a matching prefix is currently on-link.
 */
void
nd6_prproxy_ns_input(struct ifnet *ifp, struct in6_addr *saddr,
    char *lladdr, int lladdrlen, struct in6_addr *daddr, struct in6_addr *taddr)
{
        SLIST_HEAD(, nd6_prproxy_prelist) ndprl_head;
        struct nd6_prproxy_prelist *ndprl, *ndprl_tmp;
        struct nd_prefix *pr, *fwd;
        struct ifnet *fwd_ifp;
        struct in6_addr pr_addr;
        u_char pr_len;
        boolean_t solrec = FALSE;

        SLIST_INIT(&ndprl_head);

        lck_mtx_lock(nd6_mutex);

        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if (!(pr->ndpr_stateflags & NDPRF_ONLINK) ||
                    !(pr->ndpr_stateflags & NDPRF_PRPROXY) ||
                    !IN6_ARE_MASKED_ADDR_EQUAL(&pr->ndpr_prefix.sin6_addr,
                    taddr, &pr->ndpr_mask)) {
                        NDPR_UNLOCK(pr);
                        continue;
                }

                VERIFY(!(pr->ndpr_stateflags & NDPRF_IFSCOPE));
                bcopy(&pr->ndpr_prefix.sin6_addr, &pr_addr, sizeof (pr_addr));
                pr_len = pr->ndpr_plen;

                /*
                 * If this is a NS for NUD/AR, record it so that we know
                 * how to forward the NA reply later on (if/when it arrives.)
                 * Give up if we fail to save the NS info.
                 */
                if ((solrec = !IN6_IS_ADDR_UNSPECIFIED(saddr)) &&
                    !nd6_solsrc_enq(pr, ifp, saddr, taddr)) {
                        NDPR_UNLOCK(pr);
                        solrec = FALSE;
                        break;                  /* bail out */
                } else {
                        NDPR_UNLOCK(pr);
                }

                for (fwd = nd_prefix.lh_first; fwd; fwd = fwd->ndpr_next) {
                        NDPR_LOCK(fwd);
                        if (!(fwd->ndpr_stateflags & NDPRF_ONLINK) ||
                            fwd->ndpr_ifp == ifp ||
                            fwd->ndpr_plen != pr_len ||
                            !in6_are_prefix_equal(&fwd->ndpr_prefix.sin6_addr,
                            &pr_addr, pr_len)) {
                                NDPR_UNLOCK(fwd);
                                continue;
                        }

                        fwd_ifp = fwd->ndpr_ifp;
                        NDPR_UNLOCK(fwd);

                        ndprl = nd6_ndprl_alloc(M_WAITOK);
                        if (ndprl == NULL)
                                continue;

                        NDPR_ADDREF(fwd);
                        ndprl->ndprl_pr = fwd;
                        ndprl->ndprl_fwd_ifp = fwd_ifp;
                        ndprl->ndprl_sol = solrec;

                        SLIST_INSERT_HEAD(&ndprl_head, ndprl, ndprl_le);
                }
                break;
        }

        lck_mtx_unlock(nd6_mutex);

        /*
         * If this is a recorded solicitation (NS for NUD/AR), create
         * or update the neighbor cache entry for the soliciting node.
         * Later on, when the NA reply arrives, we will need this cache
         * entry in order to send the NA back to the original solicitor.
         * Without a neighbor cache entry, we'd end up with an endless
         * cycle of NS ping-pong between the us (the proxy) and the node
         * which is soliciting for the address.
         */
        if (solrec) {
                VERIFY(!IN6_IS_ADDR_UNSPECIFIED(saddr));
                nd6_cache_lladdr(ifp, saddr, lladdr, lladdrlen,
                    ND_NEIGHBOR_SOLICIT, 0);
        }

        SLIST_FOREACH_SAFE(ndprl, &ndprl_head, ndprl_le, ndprl_tmp) {
                SLIST_REMOVE(&ndprl_head, ndprl, nd6_prproxy_prelist, ndprl_le);

                pr = ndprl->ndprl_pr;
                fwd_ifp = ndprl->ndprl_fwd_ifp;

                if ((fwd_ifp->if_eflags & IFEF_IPV6_ND6ALT) != 0) {
                        NDPR_REMREF(pr);
                        nd6_ndprl_free(ndprl);
                        continue;
                }

                NDPR_LOCK(pr);
                if (pr->ndpr_stateflags & NDPRF_ONLINK) {
                        NDPR_UNLOCK(pr);
                        nd6log2((LOG_DEBUG,
                            "%s%d: Forwarding NS (%s) from %s to %s who has %s "
                            "on %s%d\n", fwd_ifp->if_name, fwd_ifp->if_unit,
                            ndprl->ndprl_sol ? "NUD/AR" : "DAD",
                            ip6_sprintf(saddr), ip6_sprintf(daddr),
                            ip6_sprintf(taddr), ifp->if_name, ifp->if_unit));

                        nd6_ns_output(fwd_ifp, ndprl->ndprl_sol ? taddr : NULL,
                            taddr, NULL, !ndprl->ndprl_sol);
                } else {
                        NDPR_UNLOCK(pr);
                }
                NDPR_REMREF(pr);

                nd6_ndprl_free(ndprl);
        }
        VERIFY(SLIST_EMPTY(&ndprl_head));
}

/*
 * Perform automatic proxy function with NA input.
 *
 * If the target address matches a global prefix obtained from a router
 * advertisement received on an interface with the ND6_IFF_PROXY_PREFIXES flag
 * set, then we send neighbor advertisements for the target address on all
 * other interfaces where a matching prefix is currently on link.
 */
void
nd6_prproxy_na_input(struct ifnet *ifp, struct in6_addr *saddr,
    struct in6_addr *daddr0, struct in6_addr *taddr, int flags)
{
        SLIST_HEAD(, nd6_prproxy_prelist) ndprl_head;
        struct nd6_prproxy_prelist *ndprl, *ndprl_tmp;
        struct nd_prefix *pr;
        struct ifnet *fwd_ifp;
        struct in6_addr daddr;

        SLIST_INIT(&ndprl_head);


        lck_mtx_lock(nd6_mutex);

        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if (!(pr->ndpr_stateflags & NDPRF_ONLINK) ||
                    !(pr->ndpr_stateflags & NDPRF_PRPROXY) ||
                    !IN6_ARE_MASKED_ADDR_EQUAL(&pr->ndpr_prefix.sin6_addr,
                    taddr, &pr->ndpr_mask)) {
                        NDPR_UNLOCK(pr);
                        continue;
                }

                VERIFY(!(pr->ndpr_stateflags & NDPRF_IFSCOPE));
                /*
                 * If this is a NA for NUD, see if there is a record created
                 * for the corresponding NS; upon success, we get back the
                 * interface where the NS originally arrived on, as well as
                 * the soliciting node's address.  Give up if we can't find it.
                 */
                if (!IN6_IS_ADDR_MULTICAST(daddr0)) {
                        fwd_ifp = NULL;
                        bzero(&daddr, sizeof (daddr));
                        if (!nd6_solsrc_deq(pr, taddr, &daddr, &fwd_ifp)) {
                                NDPR_UNLOCK(pr);
                                break;          /* bail out */
                        }
                        VERIFY(!IN6_IS_ADDR_UNSPECIFIED(&daddr) && fwd_ifp);
                        NDPR_UNLOCK(pr);

                        ndprl = nd6_ndprl_alloc(M_WAITOK);
                        if (ndprl == NULL)
                                break;          /* bail out */

                        ndprl->ndprl_fwd_ifp = fwd_ifp;
                        ndprl->ndprl_sol = TRUE;
                        ndprl->ndprl_sol_saddr = *(&daddr);

                        SLIST_INSERT_HEAD(&ndprl_head, ndprl, ndprl_le);
                } else {
                        struct nd_prefix *fwd;
                        struct in6_addr pr_addr;
                        u_char pr_len;

                        bcopy(&pr->ndpr_prefix.sin6_addr, &pr_addr,
                            sizeof (pr_addr));
                        pr_len = pr->ndpr_plen;
                        NDPR_UNLOCK(pr);

                        for (fwd = nd_prefix.lh_first; fwd;
                            fwd = fwd->ndpr_next) {
                                NDPR_LOCK(fwd);
                                if (!(fwd->ndpr_stateflags & NDPRF_ONLINK) ||
                                    fwd->ndpr_ifp == ifp ||
                                    fwd->ndpr_plen != pr_len ||
                                    !in6_are_prefix_equal(
                                    &fwd->ndpr_prefix.sin6_addr,
                                    &pr_addr, pr_len)) {
                                        NDPR_UNLOCK(fwd);
                                        continue;
                                }

                                fwd_ifp = fwd->ndpr_ifp;
                                NDPR_UNLOCK(fwd);

                                ndprl = nd6_ndprl_alloc(M_WAITOK);
                                if (ndprl == NULL)
                                        continue;

                                NDPR_ADDREF(fwd);
                                ndprl->ndprl_pr = fwd;
                                ndprl->ndprl_fwd_ifp = fwd_ifp;

                                SLIST_INSERT_HEAD(&ndprl_head, ndprl, ndprl_le);
                        }
                }
                break;
        }

        lck_mtx_unlock(nd6_mutex);

        SLIST_FOREACH_SAFE(ndprl, &ndprl_head, ndprl_le, ndprl_tmp) {
                boolean_t send_na;

                SLIST_REMOVE(&ndprl_head, ndprl, nd6_prproxy_prelist, ndprl_le);

                pr = ndprl->ndprl_pr;
                fwd_ifp = ndprl->ndprl_fwd_ifp;

                if (ndprl->ndprl_sol) {
                        VERIFY(pr == NULL);
                        daddr = *(&ndprl->ndprl_sol_saddr);
                        VERIFY(!IN6_IS_ADDR_UNSPECIFIED(&daddr));
                        send_na = (in6_setscope(&daddr, fwd_ifp, NULL) == 0);
                } else {
                        VERIFY(pr != NULL);
                        daddr = *daddr0;
                        NDPR_LOCK(pr);
                        send_na = ((pr->ndpr_stateflags & NDPRF_ONLINK) &&
                            in6_setscope(&daddr, fwd_ifp, NULL) == 0);
                        NDPR_UNLOCK(pr);
                }

                if (send_na) {
                        if (!ndprl->ndprl_sol) {
                                nd6log2((LOG_DEBUG,
                                    "%s%d: Forwarding NA (DAD) from %s to %s "
                                    "tgt is %s on %s%d\n",
                                    fwd_ifp->if_name, fwd_ifp->if_unit,
                                    ip6_sprintf(saddr), ip6_sprintf(&daddr),
                                    ip6_sprintf(taddr), ifp->if_name,
                                    ifp->if_unit));
                        } else {
                                nd6log2((LOG_DEBUG,
                                    "%s%d: Forwarding NA (NUD/AR) from %s to "
                                    "%s (was %s) tgt is %s on %s%d\n",
                                    fwd_ifp->if_name, fwd_ifp->if_unit,
                                    ip6_sprintf(saddr), ip6_sprintf(&daddr),
                                    ip6_sprintf(daddr0), ip6_sprintf(taddr),
                                    ifp->if_name, ifp->if_unit));
                        }

                        nd6_na_output(fwd_ifp, &daddr, taddr, flags, 1, NULL);
                }

                if (pr != NULL)
                        NDPR_REMREF(pr);

                nd6_ndprl_free(ndprl);
        }
        VERIFY(SLIST_EMPTY(&ndprl_head));
}

static struct nd6_prproxy_solsrc *
nd6_solsrc_alloc(int how)
{
        struct nd6_prproxy_solsrc *ssrc;

        ssrc = (how == M_WAITOK) ? zalloc(solsrc_zone) :
            zalloc_noblock(solsrc_zone);
        if (ssrc != NULL)
                bzero(ssrc, solsrc_size);

        return (ssrc);
}

static void
nd6_solsrc_free(struct nd6_prproxy_solsrc *ssrc)
{
        zfree(solsrc_zone, ssrc);
}

static void
nd6_prproxy_sols_purge(struct nd_prefix *pr, u_int64_t max_stgt)
{
        struct nd6_prproxy_soltgt *soltgt, *tmp;
        u_int64_t expire = (max_stgt > 0) ? net_uptime() : 0;

        NDPR_LOCK_ASSERT_HELD(pr);

        /* Either trim all or those that have expired or are idle */
        RB_FOREACH_SAFE(soltgt, prproxy_sols_tree,
            &pr->ndpr_prproxy_sols, tmp) {
                VERIFY(pr->ndpr_prproxy_sols_cnt > 0);
                if (expire == 0 || soltgt->soltgt_expire <= expire ||
                    soltgt->soltgt_cnt == 0) {
                        pr->ndpr_prproxy_sols_cnt--;
                        RB_REMOVE(prproxy_sols_tree,
                            &pr->ndpr_prproxy_sols, soltgt);
                        nd6_soltgt_free(soltgt);
                }
        }

        if (max_stgt == 0 || pr->ndpr_prproxy_sols_cnt < max_stgt) {
                VERIFY(max_stgt != 0 || (pr->ndpr_prproxy_sols_cnt == 0 &&
                    RB_EMPTY(&pr->ndpr_prproxy_sols)));
                return;
        }

        /* Brute force; mercilessly evict entries until we are under limit */
        RB_FOREACH_SAFE(soltgt, prproxy_sols_tree,
            &pr->ndpr_prproxy_sols, tmp) {
                VERIFY(pr->ndpr_prproxy_sols_cnt > 0);
                pr->ndpr_prproxy_sols_cnt--;
                RB_REMOVE(prproxy_sols_tree, &pr->ndpr_prproxy_sols, soltgt);
                nd6_soltgt_free(soltgt);
                if (pr->ndpr_prproxy_sols_cnt < max_stgt)
                        break;
        }
}

/*
 * Purges all solicitation records on a given prefix.
 * Caller is responsible for holding prefix lock.
 */
void
nd6_prproxy_sols_reap(struct nd_prefix *pr)
{
        nd6_prproxy_sols_purge(pr, 0);
}

/*
 * Purges expired or idle solicitation records on a given prefix.
 * Caller is responsible for holding prefix lock.
 */
void
nd6_prproxy_sols_prune(struct nd_prefix *pr, u_int32_t max_stgt)
{
        nd6_prproxy_sols_purge(pr, max_stgt);
}

/*
 * Enqueue a soliciation record in the target record of a prefix.
 */
static boolean_t
nd6_solsrc_enq(struct nd_prefix *pr, struct ifnet *ifp,
    struct in6_addr *saddr, struct in6_addr *taddr)
{
        struct nd6_prproxy_soltgt find, *soltgt;
        struct nd6_prproxy_solsrc *ssrc;
        u_int32_t max_stgt = nd6_max_tgt_sols;
        u_int32_t max_ssrc = nd6_max_src_sols;

        NDPR_LOCK_ASSERT_HELD(pr);
        VERIFY(!(pr->ndpr_stateflags & NDPRF_IFSCOPE));
        VERIFY((pr->ndpr_stateflags & (NDPRF_ONLINK|NDPRF_PRPROXY)) ==
            (NDPRF_ONLINK|NDPRF_PRPROXY));
        VERIFY(!IN6_IS_ADDR_UNSPECIFIED(saddr));

        ssrc = nd6_solsrc_alloc(M_WAITOK);
        if (ssrc == NULL)
                return (FALSE);

        ssrc->solsrc_saddr = *saddr;
        ssrc->solsrc_ifp = ifp;

        find.soltgt_key.taddr = *taddr;         /* search key */

        soltgt = RB_FIND(prproxy_sols_tree, &pr->ndpr_prproxy_sols, &find);
        if (soltgt == NULL) {
                if (max_stgt != 0 && pr->ndpr_prproxy_sols_cnt >= max_stgt) {
                        VERIFY(!RB_EMPTY(&pr->ndpr_prproxy_sols));
                        nd6_prproxy_sols_prune(pr, max_stgt);
                        VERIFY(pr->ndpr_prproxy_sols_cnt < max_stgt);
                }

                soltgt = nd6_soltgt_alloc(M_WAITOK);
                if (soltgt == NULL) {
                        nd6_solsrc_free(ssrc);
                        return (FALSE);
                }

                soltgt->soltgt_key.taddr = *taddr;
                VERIFY(soltgt->soltgt_cnt == 0);
                VERIFY(TAILQ_EMPTY(&soltgt->soltgt_q));

                pr->ndpr_prproxy_sols_cnt++;
                VERIFY(pr->ndpr_prproxy_sols_cnt != 0);
                RB_INSERT(prproxy_sols_tree, &pr->ndpr_prproxy_sols, soltgt);
        }

        if (max_ssrc != 0 && soltgt->soltgt_cnt >= max_ssrc) {
                VERIFY(!TAILQ_EMPTY(&soltgt->soltgt_q));
                nd6_soltgt_prune(soltgt, max_ssrc);
                VERIFY(soltgt->soltgt_cnt < max_ssrc);
        }

        soltgt->soltgt_cnt++;
        VERIFY(soltgt->soltgt_cnt != 0);
        TAILQ_INSERT_TAIL(&soltgt->soltgt_q, ssrc, solsrc_tqe);
        if (soltgt->soltgt_cnt == 1)
                soltgt->soltgt_expire = net_uptime() + ND6_TGT_SOLS_EXPIRE;

        return (TRUE);
}

/*
 * Dequeue a solicitation record from a target record of a prefix.
 */
static boolean_t
nd6_solsrc_deq(struct nd_prefix *pr, struct in6_addr *taddr,
    struct in6_addr *daddr, struct ifnet **ifp)
{
        struct nd6_prproxy_soltgt find, *soltgt;
        struct nd6_prproxy_solsrc *ssrc;

        NDPR_LOCK_ASSERT_HELD(pr);
        VERIFY(!(pr->ndpr_stateflags & NDPRF_IFSCOPE));
        VERIFY((pr->ndpr_stateflags & (NDPRF_ONLINK|NDPRF_PRPROXY)) ==
            (NDPRF_ONLINK|NDPRF_PRPROXY));

        bzero(daddr, sizeof (*daddr));
        *ifp = NULL;

        find.soltgt_key.taddr = *taddr;         /* search key */

        soltgt = RB_FIND(prproxy_sols_tree, &pr->ndpr_prproxy_sols, &find);
        if (soltgt == NULL || soltgt->soltgt_cnt == 0) {
                VERIFY(soltgt == NULL || TAILQ_EMPTY(&soltgt->soltgt_q));
                return (FALSE);
        }

        VERIFY(soltgt->soltgt_cnt != 0);
        --soltgt->soltgt_cnt;
        ssrc = TAILQ_FIRST(&soltgt->soltgt_q);
        VERIFY(ssrc != NULL);
        TAILQ_REMOVE(&soltgt->soltgt_q, ssrc, solsrc_tqe);
        *daddr = *(&ssrc->solsrc_saddr);
        *ifp = ssrc->solsrc_ifp;
        nd6_solsrc_free(ssrc);

        return (TRUE);
}

static struct nd6_prproxy_soltgt *
nd6_soltgt_alloc(int how)
{
        struct nd6_prproxy_soltgt *soltgt;

        soltgt = (how == M_WAITOK) ? zalloc(soltgt_zone) :
            zalloc_noblock(soltgt_zone);
        if (soltgt != NULL) {
                bzero(soltgt, soltgt_size);
                TAILQ_INIT(&soltgt->soltgt_q);
        }
        return (soltgt);
}

static void
nd6_soltgt_free(struct nd6_prproxy_soltgt *soltgt)
{
        struct nd6_prproxy_solsrc *ssrc, *tssrc;

        TAILQ_FOREACH_SAFE(ssrc, &soltgt->soltgt_q, solsrc_tqe, tssrc) {
                VERIFY(soltgt->soltgt_cnt > 0);
                soltgt->soltgt_cnt--;
                TAILQ_REMOVE(&soltgt->soltgt_q, ssrc, solsrc_tqe);
                nd6_solsrc_free(ssrc);
        }

        VERIFY(soltgt->soltgt_cnt == 0);
        VERIFY(TAILQ_EMPTY(&soltgt->soltgt_q));

        zfree(soltgt_zone, soltgt);
}

static void
nd6_soltgt_prune(struct nd6_prproxy_soltgt *soltgt, u_int32_t max_ssrc)
{
        while (soltgt->soltgt_cnt >= max_ssrc) {
                struct nd6_prproxy_solsrc *ssrc;

                VERIFY(soltgt->soltgt_cnt != 0);
                --soltgt->soltgt_cnt;
                ssrc = TAILQ_FIRST(&soltgt->soltgt_q);
                VERIFY(ssrc != NULL);
                TAILQ_REMOVE(&soltgt->soltgt_q, ssrc, solsrc_tqe);
                nd6_solsrc_free(ssrc);
        }
}

/*
 * Solicited target tree comparison function.
 *
 * An ordered predicate is necessary; bcmp() is not documented to return
 * an indication of order, memcmp() is, and is an ISO C99 requirement.
 */
static __inline int
soltgt_cmp(const struct nd6_prproxy_soltgt *a,
    const struct nd6_prproxy_soltgt *b)
{
        return (memcmp(&a->soltgt_key, &b->soltgt_key, sizeof (a->soltgt_key)));
}