/* $OpenBSD: ip6_forward.c,v 1.124 2024/07/19 16:58:32 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 #if NPF > 0 #include #endif #include #include #include #include #include #include #include #include #include #include #include #ifdef IPSEC #include #include #include #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 ip6_forwarding 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 route *ro, int flags) { struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); struct route iproute; struct rtentry *rt; struct sockaddr *dst; struct ifnet *ifp = NULL; u_int rtableid = m->m_pkthdr.ph_rtableid; u_int ifidx = m->m_pkthdr.ph_ifidx; u_int8_t loopcnt = m->m_pkthdr.ph_loopcnt; u_int icmp_len; char icmp_buf[MHLEN]; CTASSERT(sizeof(struct ip6_hdr) + sizeof(struct tcphdr) + MAX_TCPOPTLEN <= sizeof(icmp_buf)); u_short mflags, pfflags; struct mbuf *mcopy; int error = 0, type = 0, code = 0, destmtu = 0; #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, ifidx); } m_freem(m); goto done; } if (ip6->ip6_hlim <= IPV6_HLIMDEC) { icmp6_error(m, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT, 0); goto done; } 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. * For small packets copy original onto stack instead of mbuf. * * For final protocol header like TCP or UDP, full header chain in * ICMP6 packet is not necessary. In this case only copy small * part of original packet and save it on stack instead of mbuf. * Although this violates RFC 4443 2.4. (c), it avoids additional * mbuf allocations. Also pf nat and rdr do not affect the shared * mbuf cluster. * * It is important to save it before IPsec processing as IPsec * processing may modify the mbuf. */ switch (ip6->ip6_nxt) { case IPPROTO_TCP: icmp_len = sizeof(struct ip6_hdr) + sizeof(struct tcphdr) + MAX_TCPOPTLEN; break; case IPPROTO_UDP: icmp_len = sizeof(struct ip6_hdr) + sizeof(struct udphdr); break; case IPPROTO_ESP: icmp_len = sizeof(struct ip6_hdr) + 2 * sizeof(u_int32_t); break; default: icmp_len = ICMPV6_PLD_MAXLEN; break; } if (icmp_len > m->m_pkthdr.len) icmp_len = m->m_pkthdr.len; if (icmp_len <= sizeof(icmp_buf)) { mflags = m->m_flags; pfflags = m->m_pkthdr.pf.flags; m_copydata(m, 0, icmp_len, icmp_buf); mcopy = NULL; } else { mcopy = m_copym(m, 0, icmp_len, M_NOWAIT); icmp_len = 0; } #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 */ if (ro == NULL) { ro = &iproute; ro->ro_rt = NULL; } rt = route6_mpath(ro, &ip6->ip6_dst, &ip6->ip6_src, m->m_pkthdr.ph_rtableid); if (rt == NULL) { ip6stat_inc(ip6s_noroute); type = ICMP6_DST_UNREACH; code = ICMP6_DST_UNREACH_NOROUTE; m_freem(m); goto icmperror; } dst = &ro->ro_dstsa; /* * 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(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, ifidx, rt->rt_ifidx); } type = ICMP6_DST_UNREACH; code = ICMP6_DST_UNREACH_BEYONDSCOPE; m_freem(m); goto icmperror; } #ifdef IPSEC /* * Check if the packet needs encapsulation. * ipsp_process_packet will never come back to here. */ if (tdb != NULL) { /* Callee frees mbuf */ 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) dst = 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 == ifidx && !ISSET(rt->rt_flags, RTF_DYNAMIC|RTF_MODIFIED) && !ISSET(flags, IPV6_REDIRECT) && atomic_load_int(&ip6_sendredirects)) { if ((ifp->if_flags & IFF_POINTOPOINT) && nd6_is_addr_neighbor(&ro->ro_dstsin6, 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. */ type = ICMP6_DST_UNREACH; code = ICMP6_DST_UNREACH_ADDR; m_freem(m); goto icmperror; } 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; SET(flags, IPV6_REDIRECT); if (ro == &iproute) rtfree(ro->ro_rt); ro = NULL; if_put(ifp); ifp = NULL; goto reroute; } #endif #ifdef IPSEC if (ISSET(flags, IPV6_FORWARDING) && ISSET(flags, IPV6_FORWARDING_IPSEC) && !ISSET(m->m_pkthdr.ph_tagsset, PACKET_TAG_IPSEC_IN_DONE)) { error = EHOSTUNREACH; goto senderr; } #endif error = if_output_tso(ifp, &m, dst, rt, ifp->if_mtu); if (error) ip6stat_inc(ip6s_cantforward); else if (m == NULL) ip6stat_inc(ip6s_forward); if (error || m == NULL) goto senderr; type = ICMP6_PACKET_TOO_BIG; destmtu = ifp->if_mtu; m_freem(m); goto icmperror; senderr: if (mcopy == NULL && icmp_len == 0) goto done; switch (error) { case 0: if (type == ND_REDIRECT) { if (icmp_len != 0) { mcopy = m_gethdr(M_DONTWAIT, MT_DATA); if (mcopy == NULL) goto done; mcopy->m_len = mcopy->m_pkthdr.len = icmp_len; mcopy->m_flags |= (mflags & M_COPYFLAGS); mcopy->m_pkthdr.ph_rtableid = rtableid; mcopy->m_pkthdr.ph_ifidx = ifidx; mcopy->m_pkthdr.ph_loopcnt = loopcnt; mcopy->m_pkthdr.pf.flags |= (pfflags & PF_TAG_GENERATED); memcpy(mcopy->m_data, icmp_buf, icmp_len); } if (mcopy != NULL) { icmp6_redirect_output(mcopy, rt); ip6stat_inc(ip6s_redirectsent); } goto done; } goto freecopy; case EMSGSIZE: type = ICMP6_PACKET_TOO_BIG; 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; } icmperror: if (icmp_len != 0) { mcopy = m_gethdr(M_DONTWAIT, MT_DATA); if (mcopy == NULL) goto done; mcopy->m_len = mcopy->m_pkthdr.len = icmp_len; mcopy->m_flags |= (mflags & M_COPYFLAGS); mcopy->m_pkthdr.ph_rtableid = rtableid; mcopy->m_pkthdr.ph_ifidx = ifidx; mcopy->m_pkthdr.ph_loopcnt = loopcnt; mcopy->m_pkthdr.pf.flags |= (pfflags & PF_TAG_GENERATED); memcpy(mcopy->m_data, icmp_buf, icmp_len); } if (mcopy != NULL) icmp6_error(mcopy, type, code, destmtu); goto done; freecopy: m_freem(mcopy); done: if (ro == &iproute) rtfree(ro->ro_rt); if_put(ifp); #ifdef IPSEC tdb_unref(tdb); #endif /* IPSEC */ }