1 /* $OpenBSD: ip6_forward.c,v 1.100 2021/01/11 13:28:54 bluhm Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei Exp $ */ 3 4 /* 5 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the project nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #include "pf.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/mbuf.h> 38 #include <sys/domain.h> 39 #include <sys/protosw.h> 40 #include <sys/socket.h> 41 #include <sys/errno.h> 42 #include <sys/time.h> 43 #include <sys/kernel.h> 44 #include <sys/syslog.h> 45 46 #include <net/if.h> 47 #include <net/if_var.h> 48 #include <net/if_enc.h> 49 #include <net/route.h> 50 51 #include <netinet/in.h> 52 #include <netinet/ip_var.h> 53 #include <netinet6/in6_var.h> 54 #include <netinet/ip6.h> 55 #include <netinet6/ip6_var.h> 56 #include <netinet/icmp6.h> 57 #include <netinet6/nd6.h> 58 59 #if NPF > 0 60 #include <net/pfvar.h> 61 #endif 62 63 #ifdef IPSEC 64 #include <netinet/ip_ipsp.h> 65 #include <netinet/ip_ah.h> 66 #include <netinet/ip_esp.h> 67 #include <netinet/udp.h> 68 #include <netinet/tcp.h> 69 #endif 70 71 /* 72 * Forward a packet. If some error occurs return the sender 73 * an icmp packet. Note we can't always generate a meaningful 74 * icmp message because icmp doesn't have a large enough repertoire 75 * of codes and types. 76 * 77 * If not forwarding, just drop the packet. This could be confusing 78 * if ipforwarding was zero but some routing protocol was advancing 79 * us as a gateway to somewhere. However, we must let the routing 80 * protocol deal with that. 81 * 82 */ 83 84 void 85 ip6_forward(struct mbuf *m, struct rtentry *rt, int srcrt) 86 { 87 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 88 struct sockaddr_in6 *sin6; 89 struct route_in6 ro; 90 struct ifnet *ifp = NULL; 91 int error = 0, type = 0, code = 0; 92 struct mbuf *mcopy = NULL; 93 #ifdef IPSEC 94 struct tdb *tdb = NULL; 95 #endif /* IPSEC */ 96 char src6[INET6_ADDRSTRLEN], dst6[INET6_ADDRSTRLEN]; 97 98 /* 99 * Do not forward packets to multicast destination (should be handled 100 * by ip6_mforward(). 101 * Do not forward packets with unspecified source. It was discussed 102 * in July 2000, on ipngwg mailing list. 103 */ 104 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 105 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 106 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 107 ip6stat_inc(ip6s_cantforward); 108 if (ip6_log_time + ip6_log_interval < getuptime()) { 109 ip6_log_time = getuptime(); 110 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 111 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 112 log(LOG_DEBUG, 113 "cannot forward " 114 "from %s to %s nxt %d received on interface %u\n", 115 src6, dst6, 116 ip6->ip6_nxt, 117 m->m_pkthdr.ph_ifidx); 118 } 119 m_freem(m); 120 goto out; 121 } 122 123 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 124 icmp6_error(m, ICMP6_TIME_EXCEEDED, 125 ICMP6_TIME_EXCEED_TRANSIT, 0); 126 goto out; 127 } 128 ip6->ip6_hlim -= IPV6_HLIMDEC; 129 130 /* 131 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 132 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 133 * we need to generate an ICMP6 message to the src. 134 * Thanks to M_EXT, in most cases copy will not occur. 135 * 136 * It is important to save it before IPsec processing as IPsec 137 * processing may modify the mbuf. 138 */ 139 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 140 M_NOWAIT); 141 142 #if NPF > 0 143 reroute: 144 #endif 145 146 #ifdef IPSEC 147 if (ipsec_in_use) { 148 tdb = ip6_output_ipsec_lookup(m, &error, NULL); 149 if (error != 0) { 150 /* 151 * -EINVAL is used to indicate that the packet should 152 * be silently dropped, typically because we've asked 153 * key management for an SA. 154 */ 155 if (error == -EINVAL) /* Should silently drop packet */ 156 error = 0; 157 158 m_freem(m); 159 goto freecopy; 160 } 161 } 162 #endif /* IPSEC */ 163 164 memset(&ro, 0, sizeof(ro)); 165 sin6 = &ro.ro_dst; 166 sin6->sin6_family = AF_INET6; 167 sin6->sin6_len = sizeof(*sin6); 168 sin6->sin6_addr = ip6->ip6_dst; 169 170 if (!rtisvalid(rt)) { 171 rtfree(rt); 172 rt = rtalloc_mpath(sin6tosa(sin6), &ip6->ip6_src.s6_addr32[0], 173 m->m_pkthdr.ph_rtableid); 174 if (rt == NULL) { 175 ip6stat_inc(ip6s_noroute); 176 if (mcopy) { 177 icmp6_error(mcopy, ICMP6_DST_UNREACH, 178 ICMP6_DST_UNREACH_NOROUTE, 0); 179 } 180 m_freem(m); 181 goto out; 182 } 183 } 184 185 /* 186 * Scope check: if a packet can't be delivered to its destination 187 * for the reason that the destination is beyond the scope of the 188 * source address, discard the packet and return an icmp6 destination 189 * unreachable error with Code 2 (beyond scope of source address). 190 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 191 */ 192 if (in6_addr2scopeid(m->m_pkthdr.ph_ifidx, &ip6->ip6_src) != 193 in6_addr2scopeid(rt->rt_ifidx, &ip6->ip6_src)) { 194 ip6stat_inc(ip6s_cantforward); 195 ip6stat_inc(ip6s_badscope); 196 197 if (ip6_log_time + ip6_log_interval < getuptime()) { 198 ip6_log_time = getuptime(); 199 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 200 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 201 log(LOG_DEBUG, 202 "cannot forward " 203 "src %s, dst %s, nxt %d, rcvif %u, outif %u\n", 204 src6, dst6, 205 ip6->ip6_nxt, 206 m->m_pkthdr.ph_ifidx, rt->rt_ifidx); 207 } 208 if (mcopy) 209 icmp6_error(mcopy, ICMP6_DST_UNREACH, 210 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 211 m_freem(m); 212 goto out; 213 } 214 215 #ifdef IPSEC 216 /* 217 * Check if the packet needs encapsulation. 218 * ipsp_process_packet will never come back to here. 219 */ 220 if (tdb != NULL) { 221 /* Callee frees mbuf */ 222 ro.ro_rt = rt; 223 ro.ro_tableid = m->m_pkthdr.ph_rtableid; 224 error = ip6_output_ipsec_send(tdb, m, &ro, 0, 1); 225 if (error) 226 goto senderr; 227 goto freecopy; 228 } 229 #endif /* IPSEC */ 230 231 if (rt->rt_flags & RTF_GATEWAY) 232 sin6 = satosin6(rt->rt_gateway); 233 234 /* 235 * If we are to forward the packet using the same interface 236 * as one we got the packet from, perhaps we should send a redirect 237 * to sender to shortcut a hop. 238 * Only send redirect if source is sending directly to us, 239 * and if packet was not source routed (or has any options). 240 * Also, don't send redirect if forwarding using a route 241 * modified by a redirect. 242 */ 243 ifp = if_get(rt->rt_ifidx); 244 if (ifp == NULL) { 245 m_freem(m); 246 goto freecopy; 247 } 248 if (rt->rt_ifidx == m->m_pkthdr.ph_ifidx && !srcrt && 249 ip6_sendredirects && 250 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 251 if ((ifp->if_flags & IFF_POINTOPOINT) && 252 nd6_is_addr_neighbor(&ro.ro_dst, ifp)) { 253 /* 254 * If the incoming interface is equal to the outgoing 255 * one, the link attached to the interface is 256 * point-to-point, and the IPv6 destination is 257 * regarded as on-link on the link, then it will be 258 * highly probable that the destination address does 259 * not exist on the link and that the packet is going 260 * to loop. Thus, we immediately drop the packet and 261 * send an ICMPv6 error message. 262 * For other routing loops, we dare to let the packet 263 * go to the loop, so that a remote diagnosing host 264 * can detect the loop by traceroute. 265 * type/code is based on suggestion by Rich Draves. 266 * not sure if it is the best pick. 267 */ 268 if (mcopy) 269 icmp6_error(mcopy, ICMP6_DST_UNREACH, 270 ICMP6_DST_UNREACH_ADDR, 0); 271 m_freem(m); 272 goto out; 273 } 274 type = ND_REDIRECT; 275 } 276 277 /* 278 * Fake scoped addresses. Note that even link-local source or 279 * destinaion can appear, if the originating node just sends the 280 * packet to us (without address resolution for the destination). 281 * Since both icmp6_error and icmp6_redirect_output fill the embedded 282 * link identifiers, we can do this stuff after making a copy for 283 * returning an error. 284 */ 285 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src)) 286 ip6->ip6_src.s6_addr16[1] = 0; 287 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst)) 288 ip6->ip6_dst.s6_addr16[1] = 0; 289 290 #if NPF > 0 291 if (pf_test(AF_INET6, PF_FWD, ifp, &m) != PF_PASS) { 292 m_freem(m); 293 goto senderr; 294 } 295 if (m == NULL) 296 goto senderr; 297 ip6 = mtod(m, struct ip6_hdr *); 298 if ((m->m_pkthdr.pf.flags & (PF_TAG_REROUTE | PF_TAG_GENERATED)) == 299 (PF_TAG_REROUTE | PF_TAG_GENERATED)) { 300 /* already rerun the route lookup, go on */ 301 m->m_pkthdr.pf.flags &= ~(PF_TAG_GENERATED | PF_TAG_REROUTE); 302 } else if (m->m_pkthdr.pf.flags & PF_TAG_REROUTE) { 303 /* tag as generated to skip over pf_test on rerun */ 304 m->m_pkthdr.pf.flags |= PF_TAG_GENERATED; 305 srcrt = 1; 306 rtfree(rt); 307 rt = NULL; 308 if_put(ifp); 309 ifp = NULL; 310 goto reroute; 311 } 312 #endif 313 in6_proto_cksum_out(m, ifp); 314 315 /* Check the size after pf_test to give pf a chance to refragment. */ 316 if (m->m_pkthdr.len > ifp->if_mtu) { 317 if (mcopy) 318 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 319 ifp->if_mtu); 320 m_freem(m); 321 goto out; 322 } 323 324 error = ifp->if_output(ifp, m, sin6tosa(sin6), rt); 325 if (error) { 326 ip6stat_inc(ip6s_cantforward); 327 } else { 328 ip6stat_inc(ip6s_forward); 329 if (type) 330 ip6stat_inc(ip6s_redirectsent); 331 else { 332 if (mcopy) 333 goto freecopy; 334 } 335 } 336 337 #if NPF > 0 || defined(IPSEC) 338 senderr: 339 #endif 340 if (mcopy == NULL) 341 goto out; 342 switch (error) { 343 case 0: 344 if (type == ND_REDIRECT) { 345 icmp6_redirect_output(mcopy, rt); 346 goto out; 347 } 348 goto freecopy; 349 350 case EMSGSIZE: 351 /* xxx MTU is constant in PPP? */ 352 goto freecopy; 353 354 case ENOBUFS: 355 /* Tell source to slow down like source quench in IP? */ 356 goto freecopy; 357 358 case ENETUNREACH: /* shouldn't happen, checked above */ 359 case EHOSTUNREACH: 360 case ENETDOWN: 361 case EHOSTDOWN: 362 default: 363 type = ICMP6_DST_UNREACH; 364 code = ICMP6_DST_UNREACH_ADDR; 365 break; 366 } 367 icmp6_error(mcopy, type, code, 0); 368 goto out; 369 370 freecopy: 371 m_freem(mcopy); 372 out: 373 rtfree(rt); 374 if_put(ifp); 375 } 376