/* $OpenBSD: ip6_forward.c,v 1.16 2001/07/18 09:56:49 itojun Exp $ */ /* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef IPSEC_IPV6FWD #include #include #include #endif /* IPSEC_IPV6FWD */ struct route_in6 ip6_forward_rt; /* * 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(m, srcrt) 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; long time_second = time.tv_sec; struct ifnet *origifp; /* maybe unnecessary */ #ifdef IPSEC_IPV6FWD struct secpolicy *sp = NULL; #endif #ifdef IPSEC_IPV6FWD /* * Check AH/ESP integrity. */ /* * Don't increment ip6s_cantforward because this is the check * before forwarding packet actually. */ if (ipsec6_in_reject(m, NULL)) { ipsec6stat.in_polvio++; m_freem(m); return; } #endif /*IPSEC_IPV6FWD*/ /* * 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)) { ip6stat.ip6s_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, m->m_pkthdr.rcvif->if_xname); } 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_IPV6FWD /* get a security policy for this packet */ sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, 0, &error); if (sp == NULL) { ipsec6stat.out_inval++; ip6stat.ip6s_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. */ ipsec6stat.out_polvio++; ip6stat.ip6s_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"); ip6stat.ip6s_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 ipsec_output_state state; /* * 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 */ bzero(&state, 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; #if 0 /* XXX allocate a route (ro, dst) again later */ ro = (struct route_in6 *)state.ro; dst = (struct sockaddr_in6 *)state.dst; #endif 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_output (ipsec): error code %d\n", error); /*fall through*/ case ENOENT: /* don't show these error codes to the user */ break; } ip6stat.ip6s_cantforward++; if (mcopy) { #if 0 /* XXX: what icmp ? */ #else m_freem(mcopy); #endif } m_freem(m); return; } } skip_ipsec: #endif /* IPSEC_IPV6FWD */ dst = &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 == 0 || (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 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((struct route *)&ip6_forward_rt); } if (ip6_forward_rt.ro_rt == 0) { ip6stat.ip6s_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 = ip6_forward_rt.ro_rt) == 0 || !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((struct route *)&ip6_forward_rt); if (ip6_forward_rt.ro_rt == 0) { ip6stat.ip6s_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; } } 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-v3-00.txt, Section 3.1] */ if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { ip6stat.ip6s_cantforward++; ip6stat.ip6s_badscope++; 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, m->m_pkthdr.rcvif->if_xname, rt->rt_ifp->if_xname); } if (mcopy) icmp6_error(mcopy, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_BEYONDSCOPE, 0); m_freem(m); return; } if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); if (mcopy) { u_long mtu; #ifdef IPSEC_IPV6FWD struct secpolicy *sp; int ipsecerror; size_t ipsechdrsiz; #endif mtu = rt->rt_ifp->if_mtu; #ifdef IPSEC_IPV6FWD /* * When we do IPsec tunnel ingress, we need to play * with if_mtu 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". */ sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, IP_FORWARDING, &ipsecerror); if (sp) { 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 && (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && nd6_is_addr_neighbor((struct sockaddr_in6 *)&ip6_forward_rt.ro_dst, 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, m->m_pkthdr.rcvif->if_xname, rt->rt_ifp->if_xname); } /* we can just use rcvif in forwarding. */ origifp = m->m_pkthdr.rcvif; } else origifp = rt->rt_ifp; if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) ip6->ip6_src.s6_addr16[1] = 0; if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) ip6->ip6_dst.s6_addr16[1] = 0; #ifdef OLDIP6OUTPUT error = (*rt->rt_ifp->if_output)(rt->rt_ifp, m, (struct sockaddr *)dst, ip6_forward_rt.ro_rt); #else error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); #endif 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; } } if (mcopy == NULL) return; switch (error) { case 0: #if 1 if (type == ND_REDIRECT) { icmp6_redirect_output(mcopy, rt); return; } #endif 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; }