/* $OpenBSD: ip6_forward.c,v 1.112 2023/07/07 08:05:02 bluhm 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 "pf.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if NPF > 0 #include #endif #ifdef IPSEC #include #include #include #include #endif #include #include #include /* * 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, struct rtentry *rt, int srcrt) { struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); struct sockaddr_in6 *sin6; struct route_in6 ro; struct ifnet *ifp = NULL; int error = 0, type = 0, code = 0, destmtu = 0; struct mbuf *mcopy = NULL; #ifdef IPSEC struct tdb *tdb = NULL; #endif /* IPSEC */ char src6[INET6_ADDRSTRLEN], dst6[INET6_ADDRSTRLEN]; /* * 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)) { time_t uptime; ip6stat_inc(ip6s_cantforward); uptime = getuptime(); if (ip6_log_time + ip6_log_interval < uptime) { ip6_log_time = uptime; inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); log(LOG_DEBUG, "cannot forward " "from %s to %s nxt %d received on interface %u\n", src6, dst6, ip6->ip6_nxt, m->m_pkthdr.ph_ifidx); } m_freem(m); goto out; } if (ip6->ip6_hlim <= IPV6_HLIMDEC) { icmp6_error(m, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT, 0); goto out; } 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_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), M_NOWAIT); #if NPF > 0 reroute: #endif #ifdef IPSEC if (ipsec_in_use) { error = ip6_output_ipsec_lookup(m, NULL, &tdb); if (error) { /* * -EINVAL is used to indicate that the packet should * be silently dropped, typically because we've asked * key management for an SA. */ if (error == -EINVAL) /* Should silently drop packet */ error = 0; m_freem(m); goto freecopy; } } #endif /* IPSEC */ memset(&ro, 0, sizeof(ro)); sin6 = &ro.ro_dst; sin6->sin6_family = AF_INET6; sin6->sin6_len = sizeof(*sin6); sin6->sin6_addr = ip6->ip6_dst; if (!rtisvalid(rt)) { rtfree(rt); rt = rtalloc_mpath(sin6tosa(sin6), &ip6->ip6_src.s6_addr32[0], m->m_pkthdr.ph_rtableid); if (rt == NULL) { ip6stat_inc(ip6s_noroute); if (mcopy) { icmp6_error(mcopy, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE, 0); } m_freem(m); goto out; } } /* * 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.ph_ifidx, &ip6->ip6_src) != in6_addr2scopeid(rt->rt_ifidx, &ip6->ip6_src)) { time_t uptime; ip6stat_inc(ip6s_cantforward); ip6stat_inc(ip6s_badscope); uptime = getuptime(); if (ip6_log_time + ip6_log_interval < uptime) { ip6_log_time = uptime; inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); log(LOG_DEBUG, "cannot forward " "src %s, dst %s, nxt %d, rcvif %u, outif %u\n", src6, dst6, ip6->ip6_nxt, m->m_pkthdr.ph_ifidx, rt->rt_ifidx); } if (mcopy) icmp6_error(mcopy, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_BEYONDSCOPE, 0); m_freem(m); goto out; } #ifdef IPSEC /* * Check if the packet needs encapsulation. * ipsp_process_packet will never come back to here. */ if (tdb != NULL) { /* Callee frees mbuf */ ro.ro_rt = rt; ro.ro_tableid = m->m_pkthdr.ph_rtableid; error = ip6_output_ipsec_send(tdb, m, &ro, 0, 1); rt = ro.ro_rt; if (error) goto senderr; goto freecopy; } #endif /* IPSEC */ if (rt->rt_flags & RTF_GATEWAY) sin6 = satosin6(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. */ ifp = if_get(rt->rt_ifidx); if (ifp == NULL) { m_freem(m); goto freecopy; } if (rt->rt_ifidx == m->m_pkthdr.ph_ifidx && !srcrt && ip6_sendredirects && (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { if ((ifp->if_flags & IFF_POINTOPOINT) && nd6_is_addr_neighbor(&ro.ro_dst, 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. */ if (mcopy) icmp6_error(mcopy, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 0); m_freem(m); goto out; } type = ND_REDIRECT; } /* * Fake scoped addresses. Note that even link-local source or * destination 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 (IN6_IS_SCOPE_EMBED(&ip6->ip6_src)) ip6->ip6_src.s6_addr16[1] = 0; if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst)) ip6->ip6_dst.s6_addr16[1] = 0; #if NPF > 0 if (pf_test(AF_INET6, PF_FWD, ifp, &m) != PF_PASS) { m_freem(m); goto senderr; } if (m == NULL) goto senderr; ip6 = mtod(m, struct ip6_hdr *); if ((m->m_pkthdr.pf.flags & (PF_TAG_REROUTE | PF_TAG_GENERATED)) == (PF_TAG_REROUTE | PF_TAG_GENERATED)) { /* already rerun the route lookup, go on */ m->m_pkthdr.pf.flags &= ~(PF_TAG_GENERATED | PF_TAG_REROUTE); } else if (m->m_pkthdr.pf.flags & PF_TAG_REROUTE) { /* tag as generated to skip over pf_test on rerun */ m->m_pkthdr.pf.flags |= PF_TAG_GENERATED; srcrt = 1; rtfree(rt); rt = NULL; if_put(ifp); ifp = NULL; goto reroute; } #endif error = if_output_tso(ifp, &m, sin6tosa(sin6), rt, ifp->if_mtu); if (error) ip6stat_inc(ip6s_cantforward); else if (m == NULL) ip6stat_inc(ip6s_forward); if (error || m == NULL) goto senderr; if (mcopy != NULL) icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, ifp->if_mtu); m_freem(m); goto out; senderr: if (mcopy == NULL) goto out; switch (error) { case 0: if (type == ND_REDIRECT) { icmp6_redirect_output(mcopy, rt); ip6stat_inc(ip6s_redirectsent); goto out; } goto freecopy; case EMSGSIZE: type = ICMP6_PACKET_TOO_BIG; code = 0; if (rt != NULL) { if (rt->rt_mtu) { destmtu = rt->rt_mtu; } else { struct ifnet *destifp; destifp = if_get(rt->rt_ifidx); if (destifp != NULL) destmtu = destifp->if_mtu; if_put(destifp); } } ip6stat_inc(ip6s_cantfrag); if (destmtu == 0) goto freecopy; break; case EACCES: /* * pf(4) blocked the packet. There is no need to send an ICMP * packet back since pf(4) takes care of it. */ 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, destmtu); goto out; freecopy: m_freem(mcopy); out: rtfree(rt); if_put(ifp); #ifdef IPSEC tdb_unref(tdb); #endif /* IPSEC */ }