/*      $NetBSD: ip_encap.c,v 1.78 2025/02/26 04:49:45 andvar Exp $     */
/*      $KAME: ip_encap.c,v 1.73 2001/10/02 08:30:58 itojun Exp $       */

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * My grandfather said that there's a devil inside tunnelling technology...
 *
 * We have surprisingly many protocols that want packets with IP protocol
 * #4 or #41.  Here's a list of protocols that want protocol #41:
 *      RFC1933 configured tunnel
 *      RFC1933 automatic tunnel
 *      RFC2401 IPsec tunnel
 *      RFC2473 IPv6 generic packet tunnelling
 *      RFC2529 6over4 tunnel
 *      RFC3056 6to4 tunnel
 *      isatap tunnel
 *      mobile-ip6 (uses RFC2473)
 * Here's a list of protocol that want protocol #4:
 *      RFC1853 IPv4-in-IPv4 tunnelling
 *      RFC2003 IPv4 encapsulation within IPv4
 *      RFC2344 reverse tunnelling for mobile-ip4
 *      RFC2401 IPsec tunnel
 * Well, what can I say.  They impose different en/decapsulation mechanism
 * from each other, so they need separate protocol handler.  The only one
 * we can easily determine by protocol # is IPsec, which always has
 * AH/ESP/IPComp header right after outer IP header.
 *
 * So, clearly good old protosw does not work for protocol #4 and #41.
 * The code will let you match protocol via src/dst address pair.
 */
/* XXX is M_NETADDR correct? */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ip_encap.c,v 1.78 2025/02/26 04:49:45 andvar Exp $");

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

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/socket.h>
#include <sys/socketvar.h> /* for softnet_lock */
#include <sys/sockio.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/queue.h>
#include <sys/kmem.h>
#include <sys/mutex.h>
#include <sys/condvar.h>
#include <sys/psref.h>
#include <sys/pslist.h>
#include <sys/thmap.h>

#include <net/if.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_encap.h>
#ifdef MROUTING
#include <netinet/ip_mroute.h>
#endif /* MROUTING */

#ifdef INET6
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6protosw.h> /* for struct ip6ctlparam */
#include <netinet6/in6_var.h>
#include <netinet6/in6_pcb.h>
#include <netinet/icmp6.h>
#endif

#ifdef NET_MPSAFE
#define ENCAP_MPSAFE    1
#endif

enum direction { INBOUND, OUTBOUND };

#ifdef INET
static struct encaptab *encap4_lookup(struct mbuf *, int, int, enum direction,
    struct psref *);
#endif
#ifdef INET6
static struct encaptab *encap6_lookup(struct mbuf *, int, int, enum direction,
    struct psref *);
#endif
static int encap_add(struct encaptab *);
static int encap_remove(struct encaptab *);
static void encap_afcheck(int, const struct sockaddr *, const struct sockaddr *);
static void encap_key_init(struct encap_key *, const struct sockaddr *,
    const struct sockaddr *);
static void encap_key_inc(struct encap_key *);

/*
 * In encap[46]_lookup(), ep->func can sleep(e.g. rtalloc1) while walking
 * encap_table. So, it cannot use pserialize_read_enter()
 */
static struct {
        struct pslist_head      list;
        pserialize_t            psz;
        struct psref_class      *elem_class; /* for the element of et_list */
} encaptab  __cacheline_aligned = {
        .list = PSLIST_INITIALIZER,
};
#define encap_table encaptab.list

static struct {
        kmutex_t        lock;
        kcondvar_t      cv;
        struct lwp      *busy;
} encap_whole __cacheline_aligned;

static thmap_t *encap_map[2];   /* 0 for AF_INET, 1 for AF_INET6 */

static bool encap_initialized = false;
/*
 * must be done before other encap interfaces initialization.
 */
void
encapinit(void)
{

        if (encap_initialized)
                return;

        encaptab.psz = pserialize_create();
        encaptab.elem_class = psref_class_create("encapelem", IPL_SOFTNET);

        mutex_init(&encap_whole.lock, MUTEX_DEFAULT, IPL_NONE);
        cv_init(&encap_whole.cv, "ip_encap cv");
        encap_whole.busy = NULL;

        encap_initialized = true;
}

void
encap_init(void)
{
        static int initialized = 0;

        if (initialized)
                return;
        initialized++;
#if 0
        /*
         * we cannot use LIST_INIT() here, since drivers may want to call
         * encap_attach(), on driver attach.  encap_init() will be called
         * on AF_INET{,6} initialization, which happens after driver
         * initialization - using LIST_INIT() here can nuke encap_attach()
         * from drivers.
         */
        PSLIST_INIT(&encap_table);
#endif

        encap_map[0] = thmap_create(0, NULL, THMAP_NOCOPY);
#ifdef INET6
        encap_map[1] = thmap_create(0, NULL, THMAP_NOCOPY);
#endif
}

#ifdef INET
static struct encaptab *
encap4_lookup(struct mbuf *m, int off, int proto, enum direction dir,
    struct psref *match_psref)
{
        struct ip *ip;
        struct ip_pack4 pack;
        struct encaptab *ep, *match;
        int prio, matchprio;
        int s;
        thmap_t *emap = encap_map[0];
        struct encap_key key;

        KASSERT(m->m_len >= sizeof(*ip));

        ip = mtod(m, struct ip *);

        memset(&pack, 0, sizeof(pack));
        pack.p.sp_len = sizeof(pack);
        pack.mine.sin_family = pack.yours.sin_family = AF_INET;
        pack.mine.sin_len = pack.yours.sin_len = sizeof(struct sockaddr_in);
        if (dir == INBOUND) {
                pack.mine.sin_addr = ip->ip_dst;
                pack.yours.sin_addr = ip->ip_src;
        } else {
                pack.mine.sin_addr = ip->ip_src;
                pack.yours.sin_addr = ip->ip_dst;
        }

        match = NULL;
        matchprio = 0;

        s = pserialize_read_enter();

        encap_key_init(&key, sintosa(&pack.mine), sintosa(&pack.yours));
        while ((ep = thmap_get(emap, &key, sizeof(key))) != NULL) {
                struct psref elem_psref;

                KASSERT(ep->af == AF_INET);

                if (ep->proto >= 0 && ep->proto != proto) {
                        encap_key_inc(&key);
                        continue;
                }

                psref_acquire(&elem_psref, &ep->psref,
                    encaptab.elem_class);
                if (ep->func) {
                        pserialize_read_exit(s);
                        prio = (*ep->func)(m, off, proto, ep->arg);
                        s = pserialize_read_enter();
                } else {
                        prio = pack.mine.sin_len + pack.yours.sin_len;
                }

                if (prio <= 0) {
                        psref_release(&elem_psref, &ep->psref,
                            encaptab.elem_class);
                        encap_key_inc(&key);
                        continue;
                }
                if (prio > matchprio) {
                        /* release last matched ep */
                        if (match != NULL)
                                psref_release(match_psref, &match->psref,
                                    encaptab.elem_class);

                        psref_copy(match_psref, &elem_psref,
                            encaptab.elem_class);
                        matchprio = prio;
                        match = ep;
                }

                psref_release(&elem_psref, &ep->psref,
                    encaptab.elem_class);
                encap_key_inc(&key);
        }

        PSLIST_READER_FOREACH(ep, &encap_table, struct encaptab, chain) {
                struct psref elem_psref;

                if (ep->af != AF_INET)
                        continue;
                if (ep->proto >= 0 && ep->proto != proto)
                        continue;

                psref_acquire(&elem_psref, &ep->psref,
                    encaptab.elem_class);
                pserialize_read_exit(s);
                /* ep->func is sleepable. e.g. rtalloc1 */
                prio = (*ep->func)(m, off, proto, ep->arg);
                s = pserialize_read_enter();

                /*
                 * We prioritize the matches by using bit length of the
                 * matches.  user-supplied matching function
                 * should return the bit length of the matches (for example,
                 * if both src/dst are matched for IPv4, 64 should be returned).
                 * 0 or negative return value means "it did not match".
                 *
                 * We need to loop through all the possible candidates
                 * to get the best match - the search takes O(n) for
                 * n attachments (i.e. interfaces).
                 */
                if (prio <= 0) {
                        psref_release(&elem_psref, &ep->psref,
                            encaptab.elem_class);
                        continue;
                }
                if (prio > matchprio) {
                        /* release last matched ep */
                        if (match != NULL)
                                psref_release(match_psref, &match->psref,
                                    encaptab.elem_class);

                        psref_copy(match_psref, &elem_psref,
                            encaptab.elem_class);
                        matchprio = prio;
                        match = ep;
                }
                KASSERTMSG((match == NULL) || psref_held(&match->psref,
                        encaptab.elem_class),
                    "current match = %p, but not hold its psref", match);

                psref_release(&elem_psref, &ep->psref,
                    encaptab.elem_class);
        }
        pserialize_read_exit(s);

        return match;
}

void
encap4_input(struct mbuf *m, int off, int proto)
{
        const struct encapsw *esw;
        struct encaptab *match;
        struct psref match_psref;

        match = encap4_lookup(m, off, proto, INBOUND, &match_psref);
        if (match) {
                /* found a match, "match" has the best one */
                esw = match->esw;
                if (esw && esw->encapsw4.pr_input) {
                        (*esw->encapsw4.pr_input)(m, off, proto, match->arg);
                        psref_release(&match_psref, &match->psref,
                            encaptab.elem_class);
                } else {
                        psref_release(&match_psref, &match->psref,
                            encaptab.elem_class);
                        m_freem(m);
                }
                return;
        }

        /* last resort: inject to raw socket */
        SOFTNET_LOCK_IF_NET_MPSAFE();
        rip_input(m, off, proto);
        SOFTNET_UNLOCK_IF_NET_MPSAFE();
}
#endif

#ifdef INET6
static struct encaptab *
encap6_lookup(struct mbuf *m, int off, int proto, enum direction dir,
    struct psref *match_psref)
{
        struct ip6_hdr *ip6;
        struct ip_pack6 pack;
        int prio, matchprio;
        int s;
        struct encaptab *ep, *match;
        thmap_t *emap = encap_map[1];
        struct encap_key key;

        KASSERT(m->m_len >= sizeof(*ip6));

        ip6 = mtod(m, struct ip6_hdr *);

        memset(&pack, 0, sizeof(pack));
        pack.p.sp_len = sizeof(pack);
        pack.mine.sin6_family = pack.yours.sin6_family = AF_INET6;
        pack.mine.sin6_len = pack.yours.sin6_len = sizeof(struct sockaddr_in6);
        if (dir == INBOUND) {
                pack.mine.sin6_addr = ip6->ip6_dst;
                pack.yours.sin6_addr = ip6->ip6_src;
        } else {
                pack.mine.sin6_addr = ip6->ip6_src;
                pack.yours.sin6_addr = ip6->ip6_dst;
        }

        match = NULL;
        matchprio = 0;

        s = pserialize_read_enter();

        encap_key_init(&key, sin6tosa(&pack.mine), sin6tosa(&pack.yours));
        while ((ep = thmap_get(emap, &key, sizeof(key))) != NULL) {
                struct psref elem_psref;

                KASSERT(ep->af == AF_INET6);

                if (ep->proto >= 0 && ep->proto != proto) {
                        encap_key_inc(&key);
                        continue;
                }

                psref_acquire(&elem_psref, &ep->psref,
                    encaptab.elem_class);
                if (ep->func) {
                        pserialize_read_exit(s);
                        prio = (*ep->func)(m, off, proto, ep->arg);
                        s = pserialize_read_enter();
                } else {
                        prio = pack.mine.sin6_len + pack.yours.sin6_len;
                }

                if (prio <= 0) {
                        psref_release(&elem_psref, &ep->psref,
                            encaptab.elem_class);
                        encap_key_inc(&key);
                        continue;
                }
                if (prio > matchprio) {
                        /* release last matched ep */
                        if (match != NULL)
                                psref_release(match_psref, &match->psref,
                                    encaptab.elem_class);

                        psref_copy(match_psref, &elem_psref,
                            encaptab.elem_class);
                        matchprio = prio;
                        match = ep;
                }
                psref_release(&elem_psref, &ep->psref,
                    encaptab.elem_class);
                encap_key_inc(&key);
        }

        PSLIST_READER_FOREACH(ep, &encap_table, struct encaptab, chain) {
                struct psref elem_psref;

                if (ep->af != AF_INET6)
                        continue;
                if (ep->proto >= 0 && ep->proto != proto)
                        continue;

                psref_acquire(&elem_psref, &ep->psref,
                    encaptab.elem_class);

                pserialize_read_exit(s);
                /* ep->func is sleepable. e.g. rtalloc1 */
                prio = (*ep->func)(m, off, proto, ep->arg);
                s = pserialize_read_enter();

                /* see encap4_lookup() for issues here */
                if (prio <= 0) {
                        psref_release(&elem_psref, &ep->psref,
                            encaptab.elem_class);
                        continue;
                }
                if (prio > matchprio) {
                        /* release last matched ep */
                        if (match != NULL)
                                psref_release(match_psref, &match->psref,
                                    encaptab.elem_class);

                        psref_copy(match_psref, &elem_psref,
                            encaptab.elem_class);
                        matchprio = prio;
                        match = ep;
                }
                KASSERTMSG((match == NULL) || psref_held(&match->psref,
                        encaptab.elem_class),
                    "current match = %p, but not hold its psref", match);

                psref_release(&elem_psref, &ep->psref,
                    encaptab.elem_class);
        }
        pserialize_read_exit(s);

        return match;
}

int
encap6_input(struct mbuf **mp, int *offp, int proto)
{
        struct mbuf *m = *mp;
        const struct encapsw *esw;
        struct encaptab *match;
        struct psref match_psref;
        int rv;

        match = encap6_lookup(m, *offp, proto, INBOUND, &match_psref);

        if (match) {
                /* found a match */
                esw = match->esw;
                if (esw && esw->encapsw6.pr_input) {
                        int ret;
                        ret = (*esw->encapsw6.pr_input)(mp, offp, proto,
                            match->arg);
                        psref_release(&match_psref, &match->psref,
                            encaptab.elem_class);
                        return ret;
                } else {
                        psref_release(&match_psref, &match->psref,
                            encaptab.elem_class);
                        m_freem(m);
                        return IPPROTO_DONE;
                }
        }

        /* last resort: inject to raw socket */
        SOFTNET_LOCK_IF_NET_MPSAFE();
        rv = rip6_input(mp, offp, proto);
        SOFTNET_UNLOCK_IF_NET_MPSAFE();
        return rv;
}
#endif

static int
encap_add(struct encaptab *ep)
{

        KASSERT(encap_lock_held());

        PSLIST_WRITER_INSERT_HEAD(&encap_table, ep, chain);

        return 0;
}

static int
encap_remove(struct encaptab *ep)
{
        int error = 0;

        KASSERT(encap_lock_held());

        PSLIST_WRITER_REMOVE(ep, chain);

        return error;
}

static void
encap_afcheck(int af, const struct sockaddr *sp, const struct sockaddr *dp)
{

        KASSERT(sp != NULL && dp != NULL);
        KASSERT(sp->sa_len == dp->sa_len);
        KASSERT(af == sp->sa_family && af == dp->sa_family);

        socklen_t len __diagused = sockaddr_getsize_by_family(af);
        KASSERT(len != 0 && len == sp->sa_len && len == dp->sa_len);
}

const struct encaptab *
encap_attach_func(int af, int proto,
    encap_priofunc_t *func,
    const struct encapsw *esw, void *arg)
{
        struct encaptab *ep;
        int error;
#ifndef ENCAP_MPSAFE
        int s;

        s = splsoftnet();
#endif

        ASSERT_SLEEPABLE();

        /* sanity check on args */
        KASSERT(func != NULL);
        KASSERT(af == AF_INET
#ifdef INET6
            || af == AF_INET6
#endif
        );

        ep = kmem_alloc(sizeof(*ep), KM_SLEEP);
        memset(ep, 0, sizeof(*ep));

        ep->af = af;
        ep->proto = proto;
        ep->func = func;
        ep->esw = esw;
        ep->arg = arg;
        psref_target_init(&ep->psref, encaptab.elem_class);

        error = encap_add(ep);
        if (error)
                goto gc;

        error = 0;
#ifndef ENCAP_MPSAFE
        splx(s);
#endif
        return ep;

gc:
        kmem_free(ep, sizeof(*ep));
#ifndef ENCAP_MPSAFE
        splx(s);
#endif
        return NULL;
}

static void
encap_key_init(struct encap_key *key,
    const struct sockaddr *local, const struct sockaddr *remote)
{

        memset(key, 0, sizeof(*key));

        sockaddr_copy(&key->local_sa, sizeof(key->local_u), local);
        sockaddr_copy(&key->remote_sa, sizeof(key->remote_u), remote);
}

static void
encap_key_inc(struct encap_key *key)
{

        (key->seq)++;
}

static void
encap_key_dec(struct encap_key *key)
{

        (key->seq)--;
}

static void
encap_key_copy(struct encap_key *dst, const struct encap_key *src)
{

        memset(dst, 0, sizeof(*dst));
        *dst = *src;
}

/*
 * src is always my side, and dst is always remote side.
 * Return value will be necessary as input (cookie) for encap_detach().
 */
const struct encaptab *
encap_attach_addr(int af, int proto,
    const struct sockaddr *src, const struct sockaddr *dst,
    encap_priofunc_t *func,
    const struct encapsw *esw, void *arg)
{
        struct encaptab *ep;
        size_t l;
        thmap_t *emap;
        void *retep;
        struct ip_pack4 *pack4;
#ifdef INET6
        struct ip_pack6 *pack6;
#endif

        ASSERT_SLEEPABLE();

        encap_afcheck(af, src, dst);

        switch (af) {
        case AF_INET:
                l = sizeof(*pack4);
                emap = encap_map[0];
                break;
#ifdef INET6
        case AF_INET6:
                l = sizeof(*pack6);
                emap = encap_map[1];
                break;
#endif
        default:
                return NULL;
        }

        ep = kmem_zalloc(sizeof(*ep), KM_SLEEP);
        ep->addrpack = kmem_zalloc(l, KM_SLEEP);
        ep->addrpack->sa_len = l & 0xff;
        ep->af = af;
        ep->proto = proto;
        ep->flag = IP_ENCAP_ADDR_ENABLE;
        switch (af) {
        case AF_INET:
                pack4 = (struct ip_pack4 *)ep->addrpack;
                ep->src = (struct sockaddr *)&pack4->mine;
                ep->dst = (struct sockaddr *)&pack4->yours;
                break;
#ifdef INET6
        case AF_INET6:
                pack6 = (struct ip_pack6 *)ep->addrpack;
                ep->src = (struct sockaddr *)&pack6->mine;
                ep->dst = (struct sockaddr *)&pack6->yours;
                break;
#endif
        }
        memcpy(ep->src, src, src->sa_len);
        memcpy(ep->dst, dst, dst->sa_len);
        ep->esw = esw;
        ep->arg = arg;
        ep->func = func;
        psref_target_init(&ep->psref, encaptab.elem_class);

        encap_key_init(&ep->key, src, dst);
        while ((retep = thmap_put(emap, &ep->key, sizeof(ep->key), ep)) != ep)
                encap_key_inc(&ep->key);
        return ep;
}


/* XXX encap4_ctlinput() is necessary if we set DF=1 on outer IPv4 header */

#ifdef INET6
void *
encap6_ctlinput(int cmd, const struct sockaddr *sa, void *d0)
{
        void *d = d0;
        struct ip6_hdr *ip6;
        struct mbuf *m;
        int off;
        struct ip6ctlparam *ip6cp = NULL;
        int nxt;
        int s;
        struct encaptab *ep;
        const struct encapsw *esw;

        if (sa->sa_family != AF_INET6 ||
            sa->sa_len != sizeof(struct sockaddr_in6))
                return NULL;

        if ((unsigned)cmd >= PRC_NCMDS)
                return NULL;
        if (cmd == PRC_HOSTDEAD)
                d = NULL;
        else if (cmd == PRC_MSGSIZE)
                ; /* special code is present, see below */
        else if (inet6ctlerrmap[cmd] == 0)
                return NULL;

        /* if the parameter is from icmp6, decode it. */
        if (d != NULL) {
                ip6cp = (struct ip6ctlparam *)d;
                m = ip6cp->ip6c_m;
                ip6 = ip6cp->ip6c_ip6;
                off = ip6cp->ip6c_off;
                nxt = ip6cp->ip6c_nxt;

                if (ip6 && cmd == PRC_MSGSIZE) {
                        int valid = 0;
                        struct encaptab *match;
                        struct psref elem_psref;

                        /*
                        * Check to see if we have a valid encap configuration.
                        */
                        match = encap6_lookup(m, off, nxt, OUTBOUND,
                            &elem_psref);
                        if (match) {
                                valid++;
                                psref_release(&elem_psref, &match->psref,
                                    encaptab.elem_class);
                        }

                        /*
                        * Depending on the value of "valid" and routing table
                        * size (mtudisc_{hi,lo}wat), we will:
                        * - recalculate the new MTU and create the
                        *   corresponding routing entry, or
                        * - ignore the MTU change notification.
                        */
                        icmp6_mtudisc_update((struct ip6ctlparam *)d, valid);
                }
        } else {
                m = NULL;
                ip6 = NULL;
                nxt = -1;
        }

        /* inform all listeners */

        s = pserialize_read_enter();
        PSLIST_READER_FOREACH(ep, &encap_table, struct encaptab, chain) {
                struct psref elem_psref;

                if (ep->af != AF_INET6)
                        continue;
                if (ep->proto >= 0 && ep->proto != nxt)
                        continue;

                /* should optimize by looking at address pairs */

                /* XXX need to pass ep->arg or ep itself to listeners */
                psref_acquire(&elem_psref, &ep->psref,
                    encaptab.elem_class);
                esw = ep->esw;
                if (esw && esw->encapsw6.pr_ctlinput) {
                        pserialize_read_exit(s);
                        /* pr_ctlinput is sleepable. e.g. rtcache_free */
                        (*esw->encapsw6.pr_ctlinput)(cmd, sa, d, ep->arg);
                        s = pserialize_read_enter();
                }
                psref_release(&elem_psref, &ep->psref,
                    encaptab.elem_class);
        }
        pserialize_read_exit(s);

        rip6_ctlinput(cmd, sa, d0);
        return NULL;
}
#endif

static int
encap_detach_addr(const struct encaptab *ep)
{
        thmap_t *emap;
        struct encaptab *retep;
        struct encaptab *target;
        void *thgc;
        struct encap_key key;

        KASSERT(encap_lock_held());
        KASSERT(ep->flag & IP_ENCAP_ADDR_ENABLE);

        switch (ep->af) {
        case AF_INET:
                emap = encap_map[0];
                break;
#ifdef INET6
        case AF_INET6:
                emap = encap_map[1];
                break;
#endif
        default:
                return EINVAL;
        }

        retep = thmap_del(emap, &ep->key, sizeof(ep->key));
        if (retep != ep) {
                return ENOENT;
        }
        target = retep;

        /*
         * To keep continuity, decrement seq after detached encaptab.
         */
        encap_key_copy(&key, &ep->key);
        encap_key_inc(&key);
        while ((retep = thmap_del(emap, &key, sizeof(key))) != NULL) {
                void *pp;

                encap_key_dec(&retep->key);
                pp = thmap_put(emap, &retep->key, sizeof(retep->key), retep);
                KASSERT(retep == pp);

                encap_key_inc(&key);
        }

        thgc = thmap_stage_gc(emap);
        pserialize_perform(encaptab.psz);
        thmap_gc(emap, thgc);
        psref_target_destroy(&target->psref, encaptab.elem_class);
        kmem_free(target->addrpack, target->addrpack->sa_len);
        kmem_free(target, sizeof(*target));

        return 0;
}

int
encap_detach(const struct encaptab *cookie)
{
        const struct encaptab *ep = cookie;
        struct encaptab *p;
        int error;

        KASSERT(encap_lock_held());

        if (ep->flag & IP_ENCAP_ADDR_ENABLE)
                return encap_detach_addr(ep);

        PSLIST_WRITER_FOREACH(p, &encap_table, struct encaptab, chain) {
                if (p == ep) {
                        error = encap_remove(p);
                        if (error)
                                return error;
                        else
                                break;
                }
        }
        if (p == NULL)
                return ENOENT;

        pserialize_perform(encaptab.psz);
        psref_target_destroy(&p->psref,
            encaptab.elem_class);
        kmem_free(p, sizeof(*p));

        return 0;
}

int
encap_lock_enter(void)
{
        int error;

        mutex_enter(&encap_whole.lock);
        while (encap_whole.busy != NULL) {
                error = cv_wait_sig(&encap_whole.cv, &encap_whole.lock);
                if (error) {
                        mutex_exit(&encap_whole.lock);
                        return error;
                }
        }
        KASSERT(encap_whole.busy == NULL);
        encap_whole.busy = curlwp;
        mutex_exit(&encap_whole.lock);

        return 0;
}

void
encap_lock_exit(void)
{

        mutex_enter(&encap_whole.lock);
        KASSERT(encap_whole.busy == curlwp);
        encap_whole.busy = NULL;
        cv_broadcast(&encap_whole.cv);
        mutex_exit(&encap_whole.lock);
}

bool
encap_lock_held(void)
{

        return (encap_whole.busy == curlwp);
}