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[netbsd-mini2440.git] / sys / netinet6 / ip6_forward.c

/*      $NetBSD: ip6_forward.c,v 1.66 2009/03/18 16:00:23 cegger Exp $  */
/*      $KAME: ip6_forward.c,v 1.109 2002/09/11 08:10:17 sakane Exp $   */

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

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ip6_forward.c,v 1.66 2009/03/18 16:00:23 cegger Exp $");

#include "opt_ipsec.h"
#include "opt_pfil_hooks.h"

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

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

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6_private.h>
#include <netinet6/scope6_var.h>
#include <netinet/icmp6.h>
#include <netinet6/nd6.h>

#ifdef IPSEC
#include <netinet6/ipsec.h>
#include <netinet6/ipsec_private.h>
#include <netkey/key.h>
#endif /* IPSEC */

#ifdef FAST_IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/ipsec6.h>
#include <netipsec/key.h>
#include <netipsec/xform.h>
#endif /* FAST_IPSEC */

#ifdef PFIL_HOOKS
#include <net/pfil.h>
#endif

#include <net/net_osdep.h>

struct  route ip6_forward_rt;

#ifdef PFIL_HOOKS
extern struct pfil_head inet6_pfil_hook;        /* XXX */
#endif

/*
 * Forward a packet.  If some error occurs return the sender
 * an icmp packet.  Note we can't always generate a meaningful
 * icmp message because icmp doesn't have a large enough repertoire
 * of codes and types.
 *
 * If not forwarding, just drop the packet.  This could be confusing
 * if ipforwarding was zero but some routing protocol was advancing
 * us as a gateway to somewhere.  However, we must let the routing
 * protocol deal with that.
 *
 */

void
ip6_forward(struct mbuf *m, int srcrt)
{
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        const struct sockaddr_in6 *dst;
        struct rtentry *rt;
        int error = 0, type = 0, code = 0;
        struct mbuf *mcopy = NULL;
        struct ifnet *origifp;  /* maybe unnecessary */
        u_int32_t inzone, outzone;
        struct in6_addr src_in6, dst_in6;
#ifdef IPSEC
        struct secpolicy *sp = NULL;
        int ipsecrt = 0;
#endif
#ifdef FAST_IPSEC
    struct secpolicy *sp = NULL;
    int needipsec = 0;
    int s;
#endif

        /*
         * Clear any in-bound checksum flags for this packet.
         */
        m->m_pkthdr.csum_flags = 0;

#ifdef IPSEC
        /*
         * Check AH/ESP integrity.
         */
        /*
         * Don't increment ip6s_cantforward because this is the check
         * before forwarding packet actually.
         */
        if (ipsec6_in_reject(m, NULL)) {
                IPSEC6_STATINC(IPSEC_STAT_IN_POLVIO);
                m_freem(m);
                return;
        }
#endif /* IPSEC */

        /*
         * Do not forward packets to multicast destination (should be handled
         * by ip6_mforward().
         * Do not forward packets with unspecified source.  It was discussed
         * in July 2000, on ipngwg mailing list.
         */
        if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
            IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
            IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
                IP6_STATINC(IP6_STAT_CANTFORWARD);
                /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
                if (ip6_log_time + ip6_log_interval < time_second) {
                        ip6_log_time = time_second;
                        log(LOG_DEBUG,
                            "cannot forward "
                            "from %s to %s nxt %d received on %s\n",
                            ip6_sprintf(&ip6->ip6_src),
                            ip6_sprintf(&ip6->ip6_dst),
                            ip6->ip6_nxt,
                            if_name(m->m_pkthdr.rcvif));
                }
                m_freem(m);
                return;
        }

        if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
                /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
                icmp6_error(m, ICMP6_TIME_EXCEEDED,
                                ICMP6_TIME_EXCEED_TRANSIT, 0);
                return;
        }
        ip6->ip6_hlim -= IPV6_HLIMDEC;

        /*
         * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
         * size of IPv6 + ICMPv6 headers) bytes of the packet in case
         * we need to generate an ICMP6 message to the src.
         * Thanks to M_EXT, in most cases copy will not occur.
         *
         * It is important to save it before IPsec processing as IPsec
         * processing may modify the mbuf.
         */
        mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));

#ifdef IPSEC
        /* get a security policy for this packet */
        sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
            IP_FORWARDING, &error);
        if (sp == NULL) {
                IPSEC6_STATINC(IPSEC_STAT_OUT_INVAL);
                IP6_STATINC(IP6_STAT_CANTFORWARD);
                if (mcopy) {
#if 0
                        /* XXX: what icmp ? */
#else
                        m_freem(mcopy);
#endif
                }
                m_freem(m);
                return;
        }

        error = 0;

        /* check policy */
        switch (sp->policy) {
        case IPSEC_POLICY_DISCARD:
                /*
                 * This packet is just discarded.
                 */
                IPSEC6_STATINC(IPSEC_STAT_OUT_POLVIO);
                IP6_STATINC(IP6_STAT_CANTFORWARD);
                key_freesp(sp);
                if (mcopy) {
#if 0
                        /* XXX: what icmp ? */
#else
                        m_freem(mcopy);
#endif
                }
                m_freem(m);
                return;

        case IPSEC_POLICY_BYPASS:
        case IPSEC_POLICY_NONE:
                /* no need to do IPsec. */
                key_freesp(sp);
                goto skip_ipsec;

        case IPSEC_POLICY_IPSEC:
                if (sp->req == NULL) {
                        /* XXX should be panic ? */
                        printf("ip6_forward: No IPsec request specified.\n");
                        IP6_STATINC(IP6_STAT_CANTFORWARD);
                        key_freesp(sp);
                        if (mcopy) {
#if 0
                                /* XXX: what icmp ? */
#else
                                m_freem(mcopy);
#endif
                        }
                        m_freem(m);
                        return;
                }
                /* do IPsec */
                break;

        case IPSEC_POLICY_ENTRUST:
        default:
                /* should be panic ?? */
                printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
                key_freesp(sp);
                goto skip_ipsec;
        }

    {
        struct ipsecrequest *isr = NULL;
        struct ipsec_output_state state;

        /*
         * when the kernel forwards a packet, it is not proper to apply
         * IPsec transport mode to the packet is not proper.  this check
         * avoid from this.
         * at present, if there is even a transport mode SA request in the
         * security policy, the kernel does not apply IPsec to the packet.
         * this check is not enough because the following case is valid.
         *      ipsec esp/tunnel/xxx-xxx/require esp/transport//require;
         */
        for (isr = sp->req; isr; isr = isr->next) {
                if (isr->saidx.mode == IPSEC_MODE_ANY)
                        goto doipsectunnel;
                if (isr->saidx.mode == IPSEC_MODE_TUNNEL)
                        goto doipsectunnel;
        }

        /*
         * if there's no need for tunnel mode IPsec, skip.
         */
        if (!isr)
                goto skip_ipsec;

    doipsectunnel:
        /*
         * All the extension headers will become inaccessible
         * (since they can be encrypted).
         * Don't panic, we need no more updates to extension headers
         * on inner IPv6 packet (since they are now encapsulated).
         *
         * IPv6 [ESP|AH] IPv6 [extension headers] payload
         */
        memset(&state, 0, sizeof(state));
        state.m = m;
        state.ro = NULL;        /* update at ipsec6_output_tunnel() */
        state.dst = NULL;       /* update at ipsec6_output_tunnel() */

        error = ipsec6_output_tunnel(&state, sp, 0);

        m = state.m;
        key_freesp(sp);

        if (error) {
                /* mbuf is already reclaimed in ipsec6_output_tunnel. */
                switch (error) {
                case EHOSTUNREACH:
                case ENETUNREACH:
                case EMSGSIZE:
                case ENOBUFS:
                case ENOMEM:
                        break;
                default:
                        printf("ip6_forward (ipsec): error code %d\n", error);
                        /* FALLTHROUGH */
                case ENOENT:
                        /* don't show these error codes to the user */
                        break;
                }
                IP6_STATINC(IP6_STAT_CANTFORWARD);
                if (mcopy) {
#if 0
                        /* XXX: what icmp ? */
#else
                        m_freem(mcopy);
#endif
                }
                m_freem(m);
                return;
        }

        if (ip6 != mtod(m, struct ip6_hdr *)) {
                /*
                 * now tunnel mode headers are added.  we are originating
                 * packet instead of forwarding the packet.
                 */
                ip6_output(m, NULL, NULL, IPV6_FORWARDING/*XXX*/, NULL, NULL,
                    NULL);
                goto freecopy;
        }

        /* adjust pointer */
        rt = state.ro ? rtcache_validate(state.ro) : NULL;
        dst = (const struct sockaddr_in6 *)state.dst;
        if (dst != NULL && rt != NULL) {
                ipsecrt = 1;
                goto skip_routing;
        }
    }
    skip_ipsec:
#endif /* IPSEC */
#ifdef FAST_IPSEC
        /* Check the security policy (SP) for the packet */

        sp = ipsec6_check_policy(m,NULL,0,&needipsec,&error);
        if (error != 0) {
                /*
                 * Hack: -EINVAL is used to signal that a packet
                 * should be silently discarded.  This is typically
                 * because we asked key management for an SA and
                 * it was delayed (e.g. kicked up to IKE).
                 */
        if (error == -EINVAL)
                error = 0;
        goto freecopy;
        }
#endif /* FAST_IPSEC */

        if (srcrt) {
                union {
                        struct sockaddr         dst;
                        struct sockaddr_in6     dst6;
                } u;

                sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0);
                if ((rt = rtcache_lookup(&ip6_forward_rt, &u.dst)) == NULL) {
                        IP6_STATINC(IP6_STAT_NOROUTE);
                        /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
                        if (mcopy) {
                                icmp6_error(mcopy, ICMP6_DST_UNREACH,
                                            ICMP6_DST_UNREACH_NOROUTE, 0);
                        }
                        m_freem(m);
                        return;
                }
        } else if ((rt = rtcache_validate(&ip6_forward_rt)) == NULL &&
                   (rt = rtcache_update(&ip6_forward_rt, 1)) == NULL) {
                /*
                 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to
                 * ip6->ip6_dst
                 */
                IP6_STATINC(IP6_STAT_NOROUTE);
                /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
                if (mcopy) {
                        icmp6_error(mcopy, ICMP6_DST_UNREACH,
                            ICMP6_DST_UNREACH_NOROUTE, 0);
                }
                m_freem(m);
                return;
        }
        dst = satocsin6(rtcache_getdst(&ip6_forward_rt));
#ifdef IPSEC
    skip_routing:;
#endif /* IPSEC */

        /*
         * Source scope check: if a packet can't be delivered to its
         * destination for the reason that the destination is beyond the scope
         * of the source address, discard the packet and return an icmp6
         * destination unreachable error with Code 2 (beyond scope of source
         * address).  We use a local copy of ip6_src, since in6_setscope()
         * will possibly modify its first argument.
         * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1]
         */
        src_in6 = ip6->ip6_src;
        if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
                /* XXX: this should not happen */
                uint64_t *ip6s = IP6_STAT_GETREF();
                ip6s[IP6_STAT_CANTFORWARD]++;
                ip6s[IP6_STAT_BADSCOPE]++;
                IP6_STAT_PUTREF();
                m_freem(m);
                return;
        }
        if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
                uint64_t *ip6s = IP6_STAT_GETREF();
                ip6s[IP6_STAT_CANTFORWARD]++;
                ip6s[IP6_STAT_BADSCOPE]++;
                IP6_STAT_PUTREF();
                m_freem(m);
                return;
        }
        if (inzone != outzone
#ifdef IPSEC
            && !ipsecrt
#endif
            ) {
                uint64_t *ip6s = IP6_STAT_GETREF();
                ip6s[IP6_STAT_CANTFORWARD]++;
                ip6s[IP6_STAT_BADSCOPE]++;
                IP6_STAT_PUTREF();
                in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);

                if (ip6_log_time + ip6_log_interval < time_second) {
                        ip6_log_time = time_second;
                        log(LOG_DEBUG,
                            "cannot forward "
                            "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
                            ip6_sprintf(&ip6->ip6_src),
                            ip6_sprintf(&ip6->ip6_dst),
                            ip6->ip6_nxt,
                            if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
                }
                if (mcopy)
                        icmp6_error(mcopy, ICMP6_DST_UNREACH,
                                    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
                m_freem(m);
                return;
        }
#ifdef FAST_IPSEC
    /*
     * If we need to encapsulate the packet, do it here
     * ipsec6_proces_packet will send the packet using ip6_output 
     */
        if (needipsec) {
                s = splsoftnet();
                error = ipsec6_process_packet(m,sp->req);
                splx(s);
                if (mcopy)
                        goto freecopy;
    }
#endif   



        /*
         * Destination scope check: if a packet is going to break the scope
         * zone of packet's destination address, discard it.  This case should
         * usually be prevented by appropriately-configured routing table, but
         * we need an explicit check because we may mistakenly forward the
         * packet to a different zone by (e.g.) a default route.
         */
        dst_in6 = ip6->ip6_dst;
        if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
            in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
            inzone != outzone) {
                uint64_t *ip6s = IP6_STAT_GETREF();
                ip6s[IP6_STAT_CANTFORWARD]++;
                ip6s[IP6_STAT_BADSCOPE]++;
                IP6_STAT_PUTREF();
                m_freem(m);
                return;
        }

        if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
                in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
                if (mcopy) {
                        u_long mtu;
#ifdef IPSEC
                        struct secpolicy *xsp;
                        int ipsecerror;
                        size_t ipsechdrsiz;
#endif

                        mtu = IN6_LINKMTU(rt->rt_ifp);
#ifdef IPSEC
                        /*
                         * When we do IPsec tunnel ingress, we need to play
                         * with the link value (decrement IPsec header size
                         * from mtu value).  The code is much simpler than v4
                         * case, as we have the outgoing interface for
                         * encapsulated packet as "rt->rt_ifp".
                         */
                        xsp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
                                IP_FORWARDING, &ipsecerror);
                        if (xsp) {
                                ipsechdrsiz = ipsec6_hdrsiz(mcopy,
                                        IPSEC_DIR_OUTBOUND, NULL);
                                if (ipsechdrsiz < mtu)
                                        mtu -= ipsechdrsiz;
                        }

                        /*
                         * if mtu becomes less than minimum MTU,
                         * tell minimum MTU (and I'll need to fragment it).
                         */
                        if (mtu < IPV6_MMTU)
                                mtu = IPV6_MMTU;
#endif
                        icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
                }
                m_freem(m);
                return;
        }

        if (rt->rt_flags & RTF_GATEWAY)
                dst = (struct sockaddr_in6 *)rt->rt_gateway;

        /*
         * If we are to forward the packet using the same interface
         * as one we got the packet from, perhaps we should send a redirect
         * to sender to shortcut a hop.
         * Only send redirect if source is sending directly to us,
         * and if packet was not source routed (or has any options).
         * Also, don't send redirect if forwarding using a route
         * modified by a redirect.
         */
        if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && ip6_sendredirects &&
#ifdef IPSEC
            !ipsecrt &&
#endif
            (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
                if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) &&
                    nd6_is_addr_neighbor(
                        satocsin6(rtcache_getdst(&ip6_forward_rt)),
                        rt->rt_ifp)) {
                        /*
                         * If the incoming interface is equal to the outgoing
                         * one, the link attached to the interface is
                         * point-to-point, and the IPv6 destination is
                         * regarded as on-link on the link, then it will be
                         * highly probable that the destination address does
                         * not exist on the link and that the packet is going
                         * to loop.  Thus, we immediately drop the packet and
                         * send an ICMPv6 error message.
                         * For other routing loops, we dare to let the packet
                         * go to the loop, so that a remote diagnosing host
                         * can detect the loop by traceroute.
                         * type/code is based on suggestion by Rich Draves.
                         * not sure if it is the best pick.
                         */
                        icmp6_error(mcopy, ICMP6_DST_UNREACH,
                                    ICMP6_DST_UNREACH_ADDR, 0);
                        m_freem(m);
                        return;
                }
                type = ND_REDIRECT;
        }

        /*
         * Fake scoped addresses. Note that even link-local source or
         * destinaion can appear, if the originating node just sends the
         * packet to us (without address resolution for the destination).
         * Since both icmp6_error and icmp6_redirect_output fill the embedded
         * link identifiers, we can do this stuff after making a copy for
         * returning an error.
         */
        if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
                /*
                 * See corresponding comments in ip6_output.
                 * XXX: but is it possible that ip6_forward() sends a packet
                 *      to a loopback interface? I don't think so, and thus
                 *      I bark here. (jinmei@kame.net)
                 * XXX: it is common to route invalid packets to loopback.
                 *      also, the codepath will be visited on use of ::1 in
                 *      rthdr. (itojun)
                 */
#if 1
                if (0)
#else
                if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
#endif
                {
                        printf("ip6_forward: outgoing interface is loopback. "
                               "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
                               ip6_sprintf(&ip6->ip6_src),
                               ip6_sprintf(&ip6->ip6_dst),
                               ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
                               if_name(rt->rt_ifp));
                }

                /* we can just use rcvif in forwarding. */
                origifp = m->m_pkthdr.rcvif;
        }
        else
                origifp = rt->rt_ifp;
        /*
         * clear embedded scope identifiers if necessary.
         * in6_clearscope will touch the addresses only when necessary.
         */
        in6_clearscope(&ip6->ip6_src);
        in6_clearscope(&ip6->ip6_dst);

#ifdef PFIL_HOOKS
        /*
         * Run through list of hooks for output packets.
         */
        if ((error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp,
            PFIL_OUT)) != 0)
                goto senderr;
        if (m == NULL)
                goto freecopy;
        ip6 = mtod(m, struct ip6_hdr *);
#endif /* PFIL_HOOKS */

        error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
        if (error) {
                in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
                IP6_STATINC(IP6_STAT_CANTFORWARD);
        } else {
                IP6_STATINC(IP6_STAT_FORWARD);
                in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
                if (type)
                        IP6_STATINC(IP6_STAT_REDIRECTSENT);
                else {
#ifdef GATEWAY
                        if (m->m_flags & M_CANFASTFWD)
                                ip6flow_create(&ip6_forward_rt, m);
#endif
                        if (mcopy)
                                goto freecopy;
                }
        }

#ifdef PFIL_HOOKS
 senderr:
#endif
        if (mcopy == NULL)
                return;
        switch (error) {
        case 0:
                if (type == ND_REDIRECT) {
                        icmp6_redirect_output(mcopy, rt);
                        return;
                }
                goto freecopy;

        case EMSGSIZE:
                /* xxx MTU is constant in PPP? */
                goto freecopy;

        case ENOBUFS:
                /* Tell source to slow down like source quench in IP? */
                goto freecopy;

        case ENETUNREACH:       /* shouldn't happen, checked above */
        case EHOSTUNREACH:
        case ENETDOWN:
        case EHOSTDOWN:
        default:
                type = ICMP6_DST_UNREACH;
                code = ICMP6_DST_UNREACH_ADDR;
                break;
        }
        icmp6_error(mcopy, type, code, 0);
        return;

 freecopy:
        m_freem(mcopy);
        return;
}