/*      $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.4.2.7 2003/01/24 05:11:35 sam Exp $        */
/*      $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 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.
 */

#include "opt_ip6fw.h"
#include "opt_inet.h"
#include "opt_inet6.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 <net/pfil.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_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 <netinet/in_pcb.h>

#include <net/ip6fw/ip6_fw.h>

#include <net/net_osdep.h>

/*
 * See ip6_forward_rt define in ip6_fw.h
 */
struct  route_in6 ip6_forward_rt_array[MAXCPU];

/*
 * 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 *);
        struct sockaddr_in6 *dst;
        struct rtentry *rt;
        int error, type = 0, code = 0;
        struct mbuf *mcopy = NULL;
        struct ifnet *origifp;  /* maybe unnecessary */
        u_int32_t srczone, dstzone;

        /*
         * 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 the 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)) {
                ip6stat.ip6s_cantforward++;
                /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
                if (ip6_log_time + ip6_log_interval < time_uptime) {
                        ip6_log_time = time_uptime;
                        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.
         */
        mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
                        M_NOWAIT);

        dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
        if (!srcrt) {
                /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */
                if (ip6_forward_rt.ro_rt == NULL ||
                    !(ip6_forward_rt.ro_rt->rt_flags & RTF_UP)) {
                        if (ip6_forward_rt.ro_rt) {
                                RTFREE(ip6_forward_rt.ro_rt);
                                ip6_forward_rt.ro_rt = 0;
                        }

                        /* this probably fails but give it a try again */
                        rtalloc_ign((struct route *)&ip6_forward_rt,
                                    RTF_PRCLONING);
                }

                if (ip6_forward_rt.ro_rt == NULL) {
                        ip6stat.ip6s_noroute++;
                        in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
                        if (mcopy) {
                                icmp6_error(mcopy, ICMP6_DST_UNREACH,
                                            ICMP6_DST_UNREACH_NOROUTE, 0);
                        }
                        m_freem(m);
                        return;
                }
        } else if ((rt = ip6_forward_rt.ro_rt) == NULL ||
                   !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
                if (ip6_forward_rt.ro_rt) {
                        RTFREE(ip6_forward_rt.ro_rt);
                        ip6_forward_rt.ro_rt = 0;
                }
                bzero(dst, sizeof(*dst));
                dst->sin6_len = sizeof(struct sockaddr_in6);
                dst->sin6_family = AF_INET6;
                dst->sin6_addr = ip6->ip6_dst;

                rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
                if (ip6_forward_rt.ro_rt == NULL) {
                        ip6stat.ip6s_noroute++;
                        in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
                        if (mcopy) {
                                icmp6_error(mcopy, ICMP6_DST_UNREACH,
                                            ICMP6_DST_UNREACH_NOROUTE, 0);
                        }
                        m_freem(m);
                        return;
                }
        }
        rt = ip6_forward_rt.ro_rt;

        /*
         * 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).
         * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
         */
        if (in6_addr2zoneid(m->m_pkthdr.rcvif, &ip6->ip6_src, &srczone) ||
            in6_addr2zoneid(rt->rt_ifp, &ip6->ip6_src, &dstzone) ||
            srczone != dstzone) {
                ip6stat.ip6s_cantforward++;
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);

                if (ip6_log_time + ip6_log_interval < time_uptime) {
                        ip6_log_time = time_uptime;
                        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;
        }

        if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
                in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
                if (mcopy) {
                        u_long mtu;

                        mtu = IN6_LINKMTU(rt->rt_ifp);
                        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 &&
            (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) {
                if (rt->rt_ifp->if_flags & IFF_POINTOPOINT) {
                        /*
                         * If the incoming interface is equal to the outgoing
                         * one, and the link attached to the interface is
                         * point-to-point, then it will be highly probable
                         * that a routing loop occurs. Thus, we immediately
                         * drop the packet and send an ICMPv6 error message.
                         *
                         * 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;
        }

        /*
         * Check with the firewall...
         */
        if (ip6_fw_enable && ip6_fw_chk_ptr) {
                u_short port = 0;
                /* If ipfw says divert, we have to just drop packet */
                if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
                        m_freem(m);
                        goto freecopy;
                }
                if (!m)
                        goto freecopy;
        }

        /*
         * 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) {
                /*
                 * 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
                {
                        kprintf("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);

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

        error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
        if (error) {
                in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
                ip6stat.ip6s_cantforward++;
        } else {
                ip6stat.ip6s_forward++;
                in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
                if (type)
                        ip6stat.ip6s_redirectsent++;
                else {
                        if (mcopy)
                                goto freecopy;
                }
        }
senderr:
        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;
}