/* $NetBSD: ip6_forward.c,v 1.96.2.1 2019/09/24 03:10:35 martin 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 __KERNEL_RCSID(0, "$NetBSD: ip6_forward.c,v 1.96.2.1 2019/09/24 03:10:35 martin Exp $"); #ifdef _KERNEL_OPT #include "opt_gateway.h" #include "opt_ipsec.h" #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef IPSEC #include #include #include #endif extern percpu_t *ip6_forward_rt_percpu; extern pfil_head_t *inet6_pfil_hook; /* XXX */ static void __printflike(4, 5) ip6_cantforward(const struct ip6_hdr *ip6, const struct ifnet *srcifp, const struct ifnet *dstifp, const char *fmt, ...) { char sbuf[INET6_ADDRSTRLEN], dbuf[INET6_ADDRSTRLEN]; char reason[256]; va_list ap; uint64_t *ip6s; /* update statistics */ ip6s = IP6_STAT_GETREF(); ip6s[IP6_STAT_CANTFORWARD]++; if (dstifp) ip6s[IP6_STAT_BADSCOPE]++; IP6_STAT_PUTREF(); if (dstifp) in6_ifstat_inc(dstifp, ifs6_in_discard); if (ip6_log_time + ip6_log_interval >= time_uptime) return; ip6_log_time = time_uptime; va_start(ap, fmt); vsnprintf(reason, sizeof(reason), fmt, ap); va_end(ap); log(LOG_DEBUG, "Cannot forward from %s@%s to %s@%s nxt %d (%s)\n", IN6_PRINT(sbuf, &ip6->ip6_src), srcifp ? if_name(srcifp) : "?", IN6_PRINT(dbuf, &ip6->ip6_dst), dstifp ? if_name(dstifp) : "?", ip6->ip6_nxt, reason); } /* * 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 = NULL; int error = 0, type = 0, code = 0; struct mbuf *mcopy = NULL; struct ifnet *origifp; /* maybe unnecessary */ uint32_t inzone, outzone; struct in6_addr src_in6, dst_in6; struct ifnet *rcvif = NULL; struct psref psref; struct route *ro = NULL; #ifdef IPSEC int needipsec = 0; struct secpolicy *sp = NULL; #endif /* * Clear any in-bound checksum flags for this packet. */ m->m_pkthdr.csum_flags = 0; rcvif = m_get_rcvif_psref(m, &psref); if (__predict_false(rcvif == NULL)) goto drop; /* * 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_cantforward(ip6, rcvif, NULL, ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" : IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" : "unspec/src"); goto drop; } 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); 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_DONTWAIT); #ifdef IPSEC if (ipsec_used) { /* 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; m_freem(m); goto freecopy; } } #endif ro = rtcache_percpu_getref(ip6_forward_rt_percpu); if (srcrt) { union { struct sockaddr dst; struct sockaddr_in6 dst6; } u; sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); rt = rtcache_lookup(ro, &u.dst); if (rt == 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); } goto drop; } } else if ((rt = rtcache_validate(ro)) == NULL && (rt = rtcache_update(ro, 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); } goto drop; } dst = satocsin6(rtcache_getdst(ro)); /* * 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; inzone = outzone = ~0; if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 || in6_setscope(&src_in6, rcvif, &inzone) != 0 || inzone != outzone) { ip6_cantforward(ip6, rcvif, rt->rt_ifp, "src[%s] inzone %d outzone %d", in6_getscopename(&ip6->ip6_src), inzone, outzone); if (mcopy) icmp6_error(mcopy, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_BEYONDSCOPE, 0); goto drop; } #ifdef IPSEC /* * If we need to encapsulate the packet, do it here. * ipsec6_process_packet will send the packet using ip6_output. */ if (needipsec) { int s = splsoftnet(); error = ipsec6_process_packet(m, sp->req); splx(s); /* m is freed */ if (mcopy) goto freecopy; goto out; } #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; inzone = outzone = ~0; if (in6_setscope(&dst_in6, rcvif, &inzone) != 0 || in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || inzone != outzone) { ip6_cantforward(ip6, rcvif, rt->rt_ifp, "dst[%s] inzone %d outzone %d", in6_getscopename(&ip6->ip6_dst), inzone, outzone); if (mcopy) icmp6_error(mcopy, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_BEYONDSCOPE, 0); goto drop; } 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); } goto drop; } 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 == rcvif && !srcrt && ip6_sendredirects && (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && nd6_is_addr_neighbor(satocsin6(rtcache_getdst(ro)), 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); goto drop; } 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 ((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 { char ip6bufs[INET6_ADDRSTRLEN]; char ip6bufd[INET6_ADDRSTRLEN]; printf("ip6_forward: outgoing interface is loopback. " "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", IN6_PRINT(ip6bufs, &ip6->ip6_src), IN6_PRINT(ip6bufd, &ip6->ip6_dst), ip6->ip6_nxt, if_name(rcvif), if_name(rt->rt_ifp)); } /* we can just use rcvif in forwarding. */ origifp = 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 ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT)) != 0) { IP6_STATINC(IP6_STAT_PFILDROP_OUT); goto senderr; } if (m == NULL) { IP6_STATINC(IP6_STAT_PFILDROP_OUT); goto freecopy; } ip6 = mtod(m, struct ip6_hdr *); error = ip6_if_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 /* Need to release rt here */ rtcache_unref(rt, ro); rt = NULL; if (mcopy->m_flags & M_CANFASTFWD) ip6flow_create(ro, mcopy); #endif if (mcopy) goto freecopy; } } senderr: if (mcopy == NULL) goto out; switch (error) { case 0: if (type == ND_REDIRECT) { icmp6_redirect_output(mcopy, rt); goto out; } 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); goto out; freecopy: m_freem(mcopy); goto out; drop: m_freem(m); out: #ifdef IPSEC if (sp != NULL) KEY_SP_UNREF(&sp); #endif rtcache_unref(rt, ro); if (ro != NULL) rtcache_percpu_putref(ip6_forward_rt_percpu); if (rcvif != NULL) m_put_rcvif_psref(rcvif, &psref); return; }