/*      $NetBSD: ipsec_output.c,v 1.87 2024/07/05 04:31:54 rin Exp $    */

/*
 * Copyright (c) 2002, 2003 Sam Leffler, Errno Consulting
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 * $FreeBSD: sys/netipsec/ipsec_output.c,v 1.3.2.2 2003/03/28 20:32:53 sam Exp $
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ipsec_output.c,v 1.87 2024/07/05 04:31:54 rin Exp $");

#if defined(_KERNEL_OPT)
#include "opt_inet.h"
#include "opt_net_mpsafe.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/errno.h>
#include <sys/syslog.h>

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

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/in_var.h>
#include <netinet/ip_ecn.h>

#include <netinet/ip6.h>
#ifdef INET6
#include <netinet6/ip6_var.h>
#endif
#include <netinet/in_pcb.h>
#ifdef INET6
#include <netinet/icmp6.h>
#endif
#include <netinet/udp.h>

#include <netipsec/ipsec.h>
#include <netipsec/ipsec_var.h>
#include <netipsec/ipsec_private.h>
#ifdef INET6
#include <netipsec/ipsec6.h>
#endif
#include <netipsec/ah_var.h>
#include <netipsec/esp_var.h>
#include <netipsec/ipcomp_var.h>

#include <netipsec/xform.h>

#include <netipsec/key.h>
#include <netipsec/keydb.h>
#include <netipsec/key_debug.h>

static percpu_t *ipsec_rtcache_percpu __cacheline_aligned;

/*
 * Add a IPSEC_OUT_DONE tag to mark that we have finished the ipsec processing
 * It will be used by ip{,6}_output to check if we have already or not
 * processed this packet.
 */
static int
ipsec_register_done(struct mbuf *m, int *error)
{
        struct m_tag *mtag;

        mtag = m_tag_get(PACKET_TAG_IPSEC_OUT_DONE, 0, M_NOWAIT);
        if (mtag == NULL) {
                IPSECLOG(LOG_DEBUG, "could not get packet tag\n");
                *error = ENOMEM;
                return -1;
        }

        m_tag_prepend(m, mtag);
        return 0;
}

static int
ipsec_reinject_ipstack(struct mbuf *m, int af, int flags)
{
        int rv = -1;
        struct route *ro;

        KASSERT(af == AF_INET || af == AF_INET6);

        KERNEL_LOCK_UNLESS_NET_MPSAFE();
        ro = rtcache_percpu_getref(ipsec_rtcache_percpu);
        switch (af) {
#ifdef INET
        case AF_INET:
                rv = ip_output(m, NULL, ro, IP_RAWOUTPUT|IP_NOIPNEWID,
                    NULL, NULL);
                break;
#endif
#ifdef INET6
        case AF_INET6:
                /*
                 * We don't need massage, IPv6 header fields are always in
                 * net endian.
                 */
                rv = ip6_output(m, NULL, ro, flags, NULL, NULL, NULL);
                break;
#endif
        }
        rtcache_percpu_putref(ipsec_rtcache_percpu);
        KERNEL_UNLOCK_UNLESS_NET_MPSAFE();

        return rv;
}

int
ipsec_process_done(struct mbuf *m, const struct ipsecrequest *isr,
    struct secasvar *sav, int flags)
{
        struct secasindex *saidx;
        int error;
#ifdef INET
        struct ip *ip;
#endif
#ifdef INET6
        struct ip6_hdr *ip6;
#endif
        struct mbuf *mo;
        struct udphdr *udp = NULL;
        int hlen, roff, iphlen;

        KASSERT(m != NULL);
        KASSERT(isr != NULL);
        KASSERT(sav != NULL);

        saidx = &sav->sah->saidx;

        if (sav->natt_type != 0) {
                hlen = sizeof(struct udphdr);

                switch (saidx->dst.sa.sa_family) {
#ifdef INET
                case AF_INET:
                        ip = mtod(m, struct ip *);
                        mo = m_makespace(m, sizeof(struct ip), hlen, &roff);
                        iphlen = ip->ip_hl << 2;
                        break;
#endif
#ifdef INET6
                case AF_INET6:
                        ip6 = mtod(m, struct ip6_hdr *);
                        mo = m_makespace(m, sizeof(struct ip6_hdr), hlen, &roff);
                        iphlen = sizeof(*ip6);
                        break;
#endif
                default:
                        IPSECLOG(LOG_DEBUG, "unknown protocol family %u\n",
                            saidx->dst.sa.sa_family);
                        error = ENXIO;
                        goto bad;
                }

                if (mo == NULL) {
                        char buf[IPSEC_ADDRSTRLEN];
                        IPSECLOG(LOG_DEBUG,
                            "failed to inject %u byte UDP for SA %s/%08lx\n",
                            hlen, ipsec_address(&saidx->dst, buf, sizeof(buf)),
                            (u_long)ntohl(sav->spi));
                        error = ENOBUFS;
                        goto bad;
                }

                udp = (struct udphdr *)(mtod(mo, char *) + roff);
                udp->uh_sport = key_portfromsaddr(&saidx->src);
                udp->uh_dport = key_portfromsaddr(&saidx->dst);
                udp->uh_sum = 0;
                udp->uh_ulen = htons(m->m_pkthdr.len - iphlen);
        }

        /*
         * Fix the header length, for AH processing.
         */
        switch (saidx->dst.sa.sa_family) {
#ifdef INET
        case AF_INET:
                ip = mtod(m, struct ip *);
                ip->ip_len = htons(m->m_pkthdr.len);
                /* IPv4 packet does not have to be set UDP checksum. */
                if (sav->natt_type != 0)
                        ip->ip_p = IPPROTO_UDP;
                break;
#endif
#ifdef INET6
        case AF_INET6:
                if (m->m_pkthdr.len < sizeof(struct ip6_hdr)) {
                        error = ENXIO;
                        goto bad;
                }
                if (m->m_pkthdr.len - sizeof(struct ip6_hdr) > IPV6_MAXPACKET) {
                        /* No jumbogram support. */
                        error = ENXIO;  /*?*/
                        goto bad;
                }
                ip6 = mtod(m, struct ip6_hdr *);
                ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(struct ip6_hdr));
                /* IPv6 packet should be set UDP checksum. */
                if (sav->natt_type != 0) {
                        ip6->ip6_nxt = IPPROTO_UDP;
                        ipsec6_udp_cksum(m);
                }
                break;
#endif
        default:
                IPSECLOG(LOG_DEBUG, "unknown protocol family %u\n",
                    saidx->dst.sa.sa_family);
                error = ENXIO;
                goto bad;
        }

        key_sa_recordxfer(sav, m);

        /*
         * If there's another (bundled) SA to apply, do so.
         * Note that this puts a burden on the kernel stack size.
         * If this is a problem we'll need to introduce a queue
         * to set the packet on so we can unwind the stack before
         * doing further processing.
         */
        if (isr->next) {
                IPSEC_STATINC(IPSEC_STAT_OUT_BUNDLESA);
                switch (saidx->dst.sa.sa_family) {
#ifdef INET
                case AF_INET:
                        return ipsec4_process_packet(m, isr->next, NULL);
#endif
#ifdef INET6
                case AF_INET6:
                        return ipsec6_process_packet(m, isr->next, flags);
#endif
                default:
                        IPSECLOG(LOG_DEBUG, "unknown protocol family %u\n",
                            saidx->dst.sa.sa_family);
                        error = ENXIO;
                        goto bad;
                }
        }

        /*
         * We're done with IPsec processing, mark the packet as processed,
         * and transmit it using the appropriate network protocol
         * (IPv4/IPv6).
         */

        if (ipsec_register_done(m, &error) < 0)
                goto bad;

        return ipsec_reinject_ipstack(m, saidx->dst.sa.sa_family, flags);

bad:
        m_freem(m);
        return error;
}

static void
ipsec_fill_saidx_bymbuf(struct secasindex *saidx, const struct mbuf *m,
    const int af)
{
        struct m_tag *mtag;
        u_int16_t natt_src = IPSEC_PORT_ANY;
        u_int16_t natt_dst = IPSEC_PORT_ANY;

        /*
         * For NAT-T enabled ipsecif(4), set NAT-T port numbers
         * even if the saidx uses transport mode.
         *
         * See also ipsecif[46]_output().
         */
        mtag = m_tag_find(m, PACKET_TAG_IPSEC_NAT_T_PORTS);
        if (mtag) {
                u_int16_t *natt_ports;

                natt_ports = (u_int16_t *)(mtag + 1);
                natt_src = natt_ports[1];
                natt_dst = natt_ports[0];
        }

        if (af == AF_INET) {
                struct sockaddr_in *sin;
                struct ip *ip = mtod(m, struct ip *);

                if (saidx->src.sa.sa_len == 0) {
                        sin = &saidx->src.sin;
                        sin->sin_len = sizeof(*sin);
                        sin->sin_family = AF_INET;
                        sin->sin_port = natt_src;
                        sin->sin_addr = ip->ip_src;
                }
                if (saidx->dst.sa.sa_len == 0) {
                        sin = &saidx->dst.sin;
                        sin->sin_len = sizeof(*sin);
                        sin->sin_family = AF_INET;
                        sin->sin_port = natt_dst;
                        sin->sin_addr = ip->ip_dst;
                }
        } else {
                struct sockaddr_in6 *sin6;
                struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);

                if (saidx->src.sin6.sin6_len == 0) {
                        sin6 = (struct sockaddr_in6 *)&saidx->src;
                        sin6->sin6_len = sizeof(*sin6);
                        sin6->sin6_family = AF_INET6;
                        sin6->sin6_port = natt_src;
                        sin6->sin6_addr = ip6->ip6_src;
                        if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) {
                                /* fix scope id for comparing SPD */
                                sin6->sin6_addr.s6_addr16[1] = 0;
                                sin6->sin6_scope_id =
                                    ntohs(ip6->ip6_src.s6_addr16[1]);
                        }
                }
                if (saidx->dst.sin6.sin6_len == 0) {
                        sin6 = (struct sockaddr_in6 *)&saidx->dst;
                        sin6->sin6_len = sizeof(*sin6);
                        sin6->sin6_family = AF_INET6;
                        sin6->sin6_port = natt_dst;
                        sin6->sin6_addr = ip6->ip6_dst;
                        if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) {
                                /* fix scope id for comparing SPD */
                                sin6->sin6_addr.s6_addr16[1] = 0;
                                sin6->sin6_scope_id =
                                    ntohs(ip6->ip6_dst.s6_addr16[1]);
                        }
                }
        }
}

struct secasvar *
ipsec_lookup_sa(const struct ipsecrequest *isr, const struct mbuf *m)
{
        struct secasindex saidx;

        saidx = isr->saidx;
        if (isr->saidx.mode == IPSEC_MODE_TRANSPORT) {
                /* Fillin unspecified SA peers only for transport mode */
                ipsec_fill_saidx_bymbuf(&saidx, m, isr->saidx.dst.sa.sa_family);
        }

        return key_lookup_sa_bysaidx(&saidx);
}

/*
 * ipsec_nextisr can return :
 * - isr == NULL and error != 0 => something is bad : the packet must be
 *   discarded
 * - isr == NULL and error == 0 => no more rules to apply, ipsec processing
 *   is done, reinject it in ip stack
 * - isr != NULL (error == 0) => we need to apply one rule to the packet
 */
static const struct ipsecrequest *
ipsec_nextisr(struct mbuf *m, const struct ipsecrequest *isr, int af,
    int *error, struct secasvar **ret)
{
#define IPSEC_OSTAT(type)                                               \
do {                                                                    \
        switch (isr->saidx.proto) {                                     \
        case IPPROTO_ESP:                                               \
                ESP_STATINC(ESP_STAT_ ## type);                         \
                break;                                                  \
        case IPPROTO_AH:                                                \
                AH_STATINC(AH_STAT_ ## type);                           \
                break;                                                  \
        default:                                                        \
                IPCOMP_STATINC(IPCOMP_STAT_ ## type);                   \
                break;                                                  \
        }                                                               \
} while (/*CONSTCOND*/0)

        struct secasvar *sav = NULL;
        struct secasindex saidx;

        KASSERTMSG(af == AF_INET || af == AF_INET6,
            "invalid address family %u", af);
again:
        /*
         * Craft SA index to search for proper SA.  Note that
         * we only fillin unspecified SA peers for transport
         * mode; for tunnel mode they must already be filled in.
         */
        saidx = isr->saidx;
        if (isr->saidx.mode == IPSEC_MODE_TRANSPORT) {
                /* Fillin unspecified SA peers only for transport mode */
                ipsec_fill_saidx_bymbuf(&saidx, m, af);
        }

        /*
         * Lookup SA and validate it.
         */
        *error = key_checkrequest(isr, &saidx, &sav);
        if (*error != 0) {
                /*
                 * IPsec processing is required, but no SA found.
                 * I assume that key_acquire() had been called
                 * to get/establish the SA. Here I discard
                 * this packet because it is responsibility for
                 * upper layer to retransmit the packet.
                 */
                IPSEC_STATINC(IPSEC_STAT_OUT_NOSA);
                goto bad;
        }
        /* sav may be NULL here if we have an USE rule */
        if (sav == NULL) {
                KASSERTMSG(ipsec_get_reqlevel(isr) == IPSEC_LEVEL_USE,
                    "no SA found, but required; level %u",
                    ipsec_get_reqlevel(isr));
                isr = isr->next;
                /*
                 * No more rules to apply, return NULL isr and no error.
                 * It can happen when the last rules are USE rules.
                 */
                if (isr == NULL) {
                        *ret = NULL;
                        *error = 0;
                        return isr;
                }
                goto again;
        }

        /*
         * Check system global policy controls.
         */
        if ((isr->saidx.proto == IPPROTO_ESP && !esp_enable) ||
            (isr->saidx.proto == IPPROTO_AH && !ah_enable) ||
            (isr->saidx.proto == IPPROTO_IPCOMP && !ipcomp_enable)) {
                IPSECLOG(LOG_DEBUG, "IPsec outbound packet dropped due"
                    " to policy (check your sysctls)\n");
                IPSEC_OSTAT(PDROPS);
                *error = EHOSTUNREACH;
                KEY_SA_UNREF(&sav);
                goto bad;
        }

        /*
         * Sanity check the SA contents for the caller
         * before they invoke the xform output method.
         */
        KASSERT(sav->tdb_xform != NULL);
        *ret = sav;
        return isr;

bad:
        KASSERTMSG(*error != 0, "error return w/ no error code");
        return NULL;
#undef IPSEC_OSTAT
}

#ifdef INET
/*
 * IPsec output logic for IPv4.
 */
int
ipsec4_process_packet(struct mbuf *m, const struct ipsecrequest *isr,
    u_long *mtu)
{
        struct secasvar *sav = NULL;
        struct ip *ip;
        int error, i, off;
        union sockaddr_union *dst;
        int setdf;

        KASSERT(m != NULL);
        KASSERT(m->m_nextpkt == NULL);
        KASSERT(isr != NULL);

        isr = ipsec_nextisr(m, isr, AF_INET, &error, &sav);
        if (isr == NULL) {
                if (error != 0) {
                        goto bad;
                } else {
                        if (ipsec_register_done(m, &error) < 0)
                                goto bad;

                        return ipsec_reinject_ipstack(m, AF_INET, 0);
                }
        }
        KASSERT(sav != NULL);

        if (m->m_len < sizeof(struct ip) &&
            (m = m_pullup(m, sizeof(struct ip))) == NULL) {
                error = ENOBUFS;
                goto unrefsav;
        }

        /*
         * Check if we need to handle NAT-T fragmentation.
         */
        if (isr == isr->sp->req) { /* Check only if called from ipsec4_output */
                KASSERT(mtu != NULL);
                ip = mtod(m, struct ip *);
                if (!(sav->natt_type & UDP_ENCAP_ESPINUDP)) {
                        goto noneed;
                }
                if (ntohs(ip->ip_len) <= sav->esp_frag)
                        goto noneed;
                *mtu = sav->esp_frag;
                KEY_SA_UNREF(&sav);
                return 0;
        }
noneed:
        dst = &sav->sah->saidx.dst;

        /*
         * Collect IP_DF state from the outer header.
         */
        if (dst->sa.sa_family == AF_INET) {
                ip = mtod(m, struct ip *);
                /* Honor system-wide control of how to handle IP_DF */
                switch (ip4_ipsec_dfbit) {
                case 0:                 /* clear in outer header */
                case 1:                 /* set in outer header */
                        setdf = ip4_ipsec_dfbit;
                        break;
                default:                /* propagate to outer header */
                        setdf = ip->ip_off;
                        setdf = ntohs(setdf);
                        setdf = htons(setdf & IP_DF);
                        break;
                }
        } else {
                ip = NULL;              /* keep compiler happy */
                setdf = 0;
        }

        /* Do the appropriate encapsulation, if necessary */
        if (isr->saidx.mode == IPSEC_MODE_TUNNEL || /* Tunnel requ'd */
            dst->sa.sa_family != AF_INET ||         /* PF mismatch */
            (dst->sa.sa_family == AF_INET &&        /* Proxy */
             dst->sin.sin_addr.s_addr != INADDR_ANY &&
             dst->sin.sin_addr.s_addr != ip->ip_dst.s_addr)) {
                struct mbuf *mp;

                /* Fix IPv4 header checksum and length */
                ip = mtod(m, struct ip *);
                ip->ip_len = htons(m->m_pkthdr.len);
                ip->ip_sum = 0;
                ip->ip_sum = in_cksum(m, ip->ip_hl << 2);

                /* Encapsulate the packet */
                error = ipip_output(m, sav, &mp);
                if (mp == NULL && !error) {
                        /* Should never happen. */
                        IPSECLOG(LOG_DEBUG,
                            "ipip_output returns no mbuf and no error!");
                        error = EFAULT;
                }
                if (error) {
                        if (mp) {
                                /* XXX: Should never happen! */
                                m_freem(mp);
                        }
                        m = NULL; /* ipip_output() already freed it */
                        goto unrefsav;
                }
                m = mp, mp = NULL;

                /*
                 * ipip_output clears IP_DF in the new header.  If
                 * we need to propagate IP_DF from the outer header,
                 * then we have to do it here.
                 *
                 * XXX shouldn't assume what ipip_output does.
                 */
                if (dst->sa.sa_family == AF_INET && setdf) {
                        if (m->m_len < sizeof(struct ip) &&
                            (m = m_pullup(m, sizeof(struct ip))) == NULL) {
                                error = ENOBUFS;
                                goto unrefsav;
                        }
                        ip = mtod(m, struct ip *);
                        ip->ip_off |= htons(IP_DF);
                }
        }

        /*
         * Dispatch to the appropriate IPsec transform logic.  The
         * packet will be returned for transmission after crypto
         * processing, etc. are completed.  For encapsulation we
         * bypass this call because of the explicit call done above
         * (necessary to deal with IP_DF handling for IPv4).
         *
         * NB: m & sav are ``passed to caller'' who's responsible for
         *     for reclaiming their resources.
         */
        if (sav->tdb_xform->xf_type != XF_IP4) {
                if (dst->sa.sa_family == AF_INET) {
                        ip = mtod(m, struct ip *);
                        i = ip->ip_hl << 2;
                        off = offsetof(struct ip, ip_p);
                } else {
                        i = sizeof(struct ip6_hdr);
                        off = offsetof(struct ip6_hdr, ip6_nxt);
                }
                error = (*sav->tdb_xform->xf_output)(m, isr, sav, i, off, 0);
        } else {
                error = ipsec_process_done(m, isr, sav, 0);
        }
        KEY_SA_UNREF(&sav);
        return error;

unrefsav:
        KEY_SA_UNREF(&sav);
bad:
        m_freem(m);
        return error;
}
#endif

#ifdef INET6
static int
compute_ipsec_pos(struct mbuf *m, int *i, int *off)
{
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct ip6_ext ip6e;
        int dstopt = 0;
        int nxt;

        *i = sizeof(struct ip6_hdr);
        *off = offsetof(struct ip6_hdr, ip6_nxt);
        nxt = ip6->ip6_nxt;

        /*
         * chase mbuf chain to find the appropriate place to
         * put AH/ESP/IPcomp header.
         *     IPv6 hbh dest1 rthdr ah* [esp* dest2 payload]
         */
        while (1) {
                switch (nxt) {
                case IPPROTO_AH:
                case IPPROTO_ESP:
                case IPPROTO_IPCOMP:
                        /*
                         * We should not skip security header added
                         * beforehand.
                         */
                        return 0;

                case IPPROTO_HOPOPTS:
                case IPPROTO_DSTOPTS:
                case IPPROTO_ROUTING:
                        if (*i + sizeof(ip6e) > m->m_pkthdr.len) {
                                return EINVAL;
                        }

                        /*
                         * If we see 2nd destination option header,
                         * we should stop there.
                         */
                        if (nxt == IPPROTO_DSTOPTS && dstopt)
                                return 0;

                        if (nxt == IPPROTO_DSTOPTS) {
                                /*
                                 * Seen 1st or 2nd destination option.
                                 * next time we see one, it must be 2nd.
                                 */
                                dstopt = 1;
                        } else if (nxt == IPPROTO_ROUTING) {
                                /*
                                 * If we see destination option next
                                 * time, it must be dest2.
                                 */
                                dstopt = 2;
                        }

                        /* skip this header */
                        m_copydata(m, *i, sizeof(ip6e), &ip6e);
                        nxt = ip6e.ip6e_nxt;
                        *off = *i + offsetof(struct ip6_ext, ip6e_nxt);
                        *i += (ip6e.ip6e_len + 1) << 3;
                        if (*i > m->m_pkthdr.len) {
                                return EINVAL;
                        }
                        break;
                default:
                        return 0;
                }
        }

        return 0;
}

static int
in6_sa_equal_addrwithscope(const struct sockaddr_in6 *sa,
    const struct in6_addr *ia)
{
        struct in6_addr ia2;

        memcpy(&ia2, &sa->sin6_addr, sizeof(ia2));
        if (IN6_IS_SCOPE_LINKLOCAL(&sa->sin6_addr))
                ia2.s6_addr16[1] = htons(sa->sin6_scope_id);

        return IN6_ARE_ADDR_EQUAL(ia, &ia2);
}

int
ipsec6_process_packet(struct mbuf *m, const struct ipsecrequest *isr, int flags)
{
        struct secasvar *sav = NULL;
        struct ip6_hdr *ip6;
        int error, i, off;
        union sockaddr_union *dst;

        KASSERT(m != NULL);
        KASSERT(m->m_nextpkt == NULL);
        KASSERT(isr != NULL);

        isr = ipsec_nextisr(m, isr, AF_INET6, &error, &sav);
        if (isr == NULL) {
                if (error != 0) {
                        /* XXX Should we send a notification ? */
                        goto bad;
                } else {
                        if (ipsec_register_done(m, &error) < 0)
                                goto bad;

                        return ipsec_reinject_ipstack(m, AF_INET6, flags);
                }
        }

        KASSERT(sav != NULL);
        dst = &sav->sah->saidx.dst;

        if (m->m_len < sizeof(struct ip6_hdr)) {
                if ((m = m_pullup(m,sizeof(struct ip6_hdr))) == NULL) {
                        error = ENOBUFS;
                        goto unrefsav;
                }
        }
        ip6 = mtod(m, struct ip6_hdr *);

        /* Do the appropriate encapsulation, if necessary */
        if (isr->saidx.mode == IPSEC_MODE_TUNNEL || /* Tunnel requ'd */
            dst->sa.sa_family != AF_INET6 ||        /* AF mismatch */
            ((dst->sa.sa_family == AF_INET6) &&
             (!IN6_IS_ADDR_UNSPECIFIED(&dst->sin6.sin6_addr)) &&
             (!in6_sa_equal_addrwithscope(&dst->sin6, &ip6->ip6_dst)))) {
                struct mbuf *mp;

                if (m->m_pkthdr.len - sizeof(*ip6) > IPV6_MAXPACKET) {
                        /* No jumbogram support. */
                        error = ENXIO;   /*XXX*/
                        goto unrefsav;
                }

                /* Fix IPv6 header payload length. */
                ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));

                /* Encapsulate the packet */
                error = ipip_output(m, sav, &mp);
                if (mp == NULL && !error) {
                        /* Should never happen. */
                        IPSECLOG(LOG_DEBUG,
                            "ipip_output returns no mbuf and no error!");
                        error = EFAULT;
                }

                if (error) {
                        if (mp) {
                                /* XXX: Should never happen! */
                                m_freem(mp);
                        }
                        m = NULL; /* ipip_output() already freed it */
                        goto unrefsav;
                }

                m = mp;
                mp = NULL;
        }

        if (dst->sa.sa_family == AF_INET) {
                struct ip *ip;
                ip = mtod(m, struct ip *);
                i = ip->ip_hl << 2;
                off = offsetof(struct ip, ip_p);
        } else {
                error = compute_ipsec_pos(m, &i, &off);
                if (error)
                        goto unrefsav;
        }
        error = (*sav->tdb_xform->xf_output)(m, isr, sav, i, off, flags);
        KEY_SA_UNREF(&sav);
        return error;

unrefsav:
        KEY_SA_UNREF(&sav);
bad:
        m_freem(m);
        return error;
}
#endif /* INET6 */

void
ipsec_output_init(void)
{

        ipsec_rtcache_percpu = rtcache_percpu_alloc();
}