1 /* $OpenBSD: ip6_forward.c,v 1.26 2003/06/24 07:47:54 itojun 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/malloc.h> 38 #include <sys/mbuf.h> 39 #include <sys/domain.h> 40 #include <sys/protosw.h> 41 #include <sys/socket.h> 42 #include <sys/errno.h> 43 #include <sys/time.h> 44 #include <sys/kernel.h> 45 #include <sys/syslog.h> 46 47 #include <net/if.h> 48 #include <net/route.h> 49 50 #include <netinet/in.h> 51 #include <netinet/in_var.h> 52 #include <netinet/ip_var.h> 53 #include <netinet/ip6.h> 54 #include <netinet6/ip6_var.h> 55 #include <netinet/icmp6.h> 56 #include <netinet6/nd6.h> 57 58 #if NPF > 0 59 #include <net/pfvar.h> 60 #endif 61 62 #ifdef IPSEC 63 #include <netinet/ip_ah.h> 64 #include <netinet/ip_esp.h> 65 #include <netinet/udp.h> 66 #include <netinet/tcp.h> 67 #include <net/pfkeyv2.h> 68 #endif 69 70 struct route_in6 ip6_forward_rt; 71 72 /* 73 * Forward a packet. If some error occurs return the sender 74 * an icmp packet. Note we can't always generate a meaningful 75 * icmp message because icmp doesn't have a large enough repertoire 76 * of codes and types. 77 * 78 * If not forwarding, just drop the packet. This could be confusing 79 * if ipforwarding was zero but some routing protocol was advancing 80 * us as a gateway to somewhere. However, we must let the routing 81 * protocol deal with that. 82 * 83 */ 84 85 void 86 ip6_forward(m, srcrt) 87 struct mbuf *m; 88 int srcrt; 89 { 90 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 91 struct sockaddr_in6 *dst; 92 struct rtentry *rt; 93 int error, type = 0, code = 0; 94 struct mbuf *mcopy = NULL; 95 struct ifnet *origifp; /* maybe unnecessary */ 96 #ifdef IPSEC 97 u_int8_t sproto = 0; 98 struct m_tag *mtag; 99 union sockaddr_union sdst; 100 struct tdb_ident *tdbi; 101 u_int32_t sspi; 102 struct tdb *tdb; 103 int s; 104 #endif /* IPSEC */ 105 106 /* 107 * Do not forward packets to multicast destination (should be handled 108 * by ip6_mforward(). 109 * Do not forward packets with unspecified source. It was discussed 110 * in July 2000, on ipngwg mailing list. 111 */ 112 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 113 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 114 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 115 ip6stat.ip6s_cantforward++; 116 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 117 if (ip6_log_time + ip6_log_interval < time.tv_sec) { 118 ip6_log_time = time.tv_sec; 119 log(LOG_DEBUG, 120 "cannot forward " 121 "from %s to %s nxt %d received on %s\n", 122 ip6_sprintf(&ip6->ip6_src), 123 ip6_sprintf(&ip6->ip6_dst), 124 ip6->ip6_nxt, 125 m->m_pkthdr.rcvif->if_xname); 126 } 127 m_freem(m); 128 return; 129 } 130 131 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 132 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 133 icmp6_error(m, ICMP6_TIME_EXCEEDED, 134 ICMP6_TIME_EXCEED_TRANSIT, 0); 135 return; 136 } 137 ip6->ip6_hlim -= IPV6_HLIMDEC; 138 139 #ifdef IPSEC 140 s = splnet(); 141 142 /* 143 * Check if there was an outgoing SA bound to the flow 144 * from a transport protocol. 145 */ 146 147 /* Do we have any pending SAs to apply ? */ 148 mtag = m_tag_find(m, PACKET_TAG_IPSEC_PENDING_TDB, NULL); 149 if (mtag != NULL) { 150 #ifdef DIAGNOSTIC 151 if (mtag->m_tag_len != sizeof (struct tdb_ident)) 152 panic("ip6_forward: tag of length %d (should be %d", 153 mtag->m_tag_len, sizeof (struct tdb_ident)); 154 #endif 155 tdbi = (struct tdb_ident *)(mtag + 1); 156 tdb = gettdb(tdbi->spi, &tdbi->dst, tdbi->proto); 157 if (tdb == NULL) 158 error = -EINVAL; 159 m_tag_delete(m, mtag); 160 } else 161 tdb = ipsp_spd_lookup(m, AF_INET6, sizeof(struct ip6_hdr), 162 &error, IPSP_DIRECTION_OUT, NULL, NULL); 163 164 if (tdb == NULL) { 165 splx(s); 166 167 if (error == 0) { 168 /* 169 * No IPsec processing required, we'll just send the 170 * packet out. 171 */ 172 sproto = 0; 173 174 /* Fall through to routing/multicast handling */ 175 } else { 176 /* 177 * -EINVAL is used to indicate that the packet should 178 * be silently dropped, typically because we've asked 179 * key management for an SA. 180 */ 181 if (error == -EINVAL) /* Should silently drop packet */ 182 error = 0; 183 184 goto freecopy; 185 } 186 } else { 187 /* Loop detection */ 188 for (mtag = m_tag_first(m); mtag != NULL; 189 mtag = m_tag_next(m, mtag)) { 190 if (mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_DONE && 191 mtag->m_tag_id != 192 PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED) 193 continue; 194 tdbi = (struct tdb_ident *)(mtag + 1); 195 if (tdbi->spi == tdb->tdb_spi && 196 tdbi->proto == tdb->tdb_sproto && 197 !bcmp(&tdbi->dst, &tdb->tdb_dst, 198 sizeof(union sockaddr_union))) { 199 splx(s); 200 sproto = 0; /* mark as no-IPsec-needed */ 201 goto done_spd; 202 } 203 } 204 205 /* We need to do IPsec */ 206 bcopy(&tdb->tdb_dst, &sdst, sizeof(sdst)); 207 sspi = tdb->tdb_spi; 208 sproto = tdb->tdb_sproto; 209 splx(s); 210 } 211 212 /* Fall through to the routing/multicast handling code */ 213 done_spd: 214 #endif /* IPSEC */ 215 216 /* 217 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 218 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 219 * we need to generate an ICMP6 message to the src. 220 * Thanks to M_EXT, in most cases copy will not occur. 221 * 222 * It is important to save it before IPsec processing as IPsec 223 * processing may modify the mbuf. 224 */ 225 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 226 227 dst = &ip6_forward_rt.ro_dst; 228 if (!srcrt) { 229 /* 230 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 231 */ 232 if (ip6_forward_rt.ro_rt == 0 || 233 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 234 if (ip6_forward_rt.ro_rt) { 235 RTFREE(ip6_forward_rt.ro_rt); 236 ip6_forward_rt.ro_rt = 0; 237 } 238 /* this probably fails but give it a try again */ 239 rtalloc((struct route *)&ip6_forward_rt); 240 } 241 242 if (ip6_forward_rt.ro_rt == 0) { 243 ip6stat.ip6s_noroute++; 244 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 245 if (mcopy) { 246 icmp6_error(mcopy, ICMP6_DST_UNREACH, 247 ICMP6_DST_UNREACH_NOROUTE, 0); 248 } 249 m_freem(m); 250 return; 251 } 252 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 253 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 254 if (ip6_forward_rt.ro_rt) { 255 RTFREE(ip6_forward_rt.ro_rt); 256 ip6_forward_rt.ro_rt = 0; 257 } 258 bzero(dst, sizeof(*dst)); 259 dst->sin6_len = sizeof(struct sockaddr_in6); 260 dst->sin6_family = AF_INET6; 261 dst->sin6_addr = ip6->ip6_dst; 262 263 rtalloc((struct route *)&ip6_forward_rt); 264 265 if (ip6_forward_rt.ro_rt == 0) { 266 ip6stat.ip6s_noroute++; 267 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 268 if (mcopy) { 269 icmp6_error(mcopy, ICMP6_DST_UNREACH, 270 ICMP6_DST_UNREACH_NOROUTE, 0); 271 } 272 m_freem(m); 273 return; 274 } 275 } 276 rt = ip6_forward_rt.ro_rt; 277 278 /* 279 * Scope check: if a packet can't be delivered to its destination 280 * for the reason that the destination is beyond the scope of the 281 * source address, discard the packet and return an icmp6 destination 282 * unreachable error with Code 2 (beyond scope of source address). 283 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 284 */ 285 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 286 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 287 ip6stat.ip6s_cantforward++; 288 ip6stat.ip6s_badscope++; 289 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 290 291 if (ip6_log_time + ip6_log_interval < time.tv_sec) { 292 ip6_log_time = time.tv_sec; 293 log(LOG_DEBUG, 294 "cannot forward " 295 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 296 ip6_sprintf(&ip6->ip6_src), 297 ip6_sprintf(&ip6->ip6_dst), 298 ip6->ip6_nxt, 299 m->m_pkthdr.rcvif->if_xname, rt->rt_ifp->if_xname); 300 } 301 if (mcopy) 302 icmp6_error(mcopy, ICMP6_DST_UNREACH, 303 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 304 m_freem(m); 305 return; 306 } 307 308 #ifdef IPSEC 309 /* 310 * Check if the packet needs encapsulation. 311 * ipsp_process_packet will never come back to here. 312 * XXX ipsp_process_packet() calls ip6_output(), and there'll be no 313 * PMTU notification. is it okay? 314 */ 315 if (sproto != 0) { 316 s = splnet(); 317 318 tdb = gettdb(sspi, &sdst, sproto); 319 if (tdb == NULL) { 320 splx(s); 321 error = EHOSTUNREACH; 322 m_freem(m); 323 goto senderr; /*XXX*/ 324 } 325 326 m->m_flags &= ~(M_BCAST | M_MCAST); /* just in case */ 327 328 /* Callee frees mbuf */ 329 error = ipsp_process_packet(m, tdb, AF_INET6, 0); 330 splx(s); 331 m_freem(mcopy); 332 return; /* Nothing more to be done */ 333 } 334 #endif /* IPSEC */ 335 336 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 337 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 338 if (mcopy) { 339 u_long mtu; 340 341 mtu = IN6_LINKMTU(rt->rt_ifp); 342 343 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 344 } 345 m_freem(m); 346 return; 347 } 348 349 if (rt->rt_flags & RTF_GATEWAY) 350 dst = (struct sockaddr_in6 *)rt->rt_gateway; 351 352 /* 353 * If we are to forward the packet using the same interface 354 * as one we got the packet from, perhaps we should send a redirect 355 * to sender to shortcut a hop. 356 * Only send redirect if source is sending directly to us, 357 * and if packet was not source routed (or has any options). 358 * Also, don't send redirect if forwarding using a route 359 * modified by a redirect. 360 */ 361 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 362 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 363 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 364 nd6_is_addr_neighbor((struct sockaddr_in6 *)&ip6_forward_rt.ro_dst, rt->rt_ifp)) { 365 /* 366 * If the incoming interface is equal to the outgoing 367 * one, the link attached to the interface is 368 * point-to-point, and the IPv6 destination is 369 * regarded as on-link on the link, then it will be 370 * highly probable that the destination address does 371 * not exist on the link and that the packet is going 372 * to loop. Thus, we immediately drop the packet and 373 * send an ICMPv6 error message. 374 * For other routing loops, we dare to let the packet 375 * go to the loop, so that a remote diagnosing host 376 * can detect the loop by traceroute. 377 * type/code is based on suggestion by Rich Draves. 378 * not sure if it is the best pick. 379 */ 380 icmp6_error(mcopy, ICMP6_DST_UNREACH, 381 ICMP6_DST_UNREACH_ADDR, 0); 382 m_freem(m); 383 return; 384 } 385 type = ND_REDIRECT; 386 } 387 388 /* 389 * Fake scoped addresses. Note that even link-local source or 390 * destinaion can appear, if the originating node just sends the 391 * packet to us (without address resolution for the destination). 392 * Since both icmp6_error and icmp6_redirect_output fill the embedded 393 * link identifiers, we can do this stuff after making a copy for 394 * returning an error. 395 */ 396 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 397 /* 398 * See corresponding comments in ip6_output. 399 * XXX: but is it possible that ip6_forward() sends a packet 400 * to a loopback interface? I don't think so, and thus 401 * I bark here. (jinmei@kame.net) 402 * XXX: it is common to route invalid packets to loopback. 403 * also, the codepath will be visited on use of ::1 in 404 * rthdr. (itojun) 405 */ 406 #if 1 407 if (0) 408 #else 409 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 410 #endif 411 { 412 printf("ip6_forward: outgoing interface is loopback. " 413 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 414 ip6_sprintf(&ip6->ip6_src), 415 ip6_sprintf(&ip6->ip6_dst), 416 ip6->ip6_nxt, m->m_pkthdr.rcvif->if_xname, 417 rt->rt_ifp->if_xname); 418 } 419 420 /* we can just use rcvif in forwarding. */ 421 origifp = m->m_pkthdr.rcvif; 422 } 423 else 424 origifp = rt->rt_ifp; 425 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 426 ip6->ip6_src.s6_addr16[1] = 0; 427 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 428 ip6->ip6_dst.s6_addr16[1] = 0; 429 430 #if NPF > 0 431 if (pf_test6(PF_OUT, rt->rt_ifp, &m) != PF_PASS) { 432 m_freem(m); 433 goto senderr; 434 } 435 if (m == NULL) 436 goto senderr; 437 438 ip6 = mtod(m, struct ip6_hdr *); 439 #endif 440 441 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 442 if (error) { 443 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 444 ip6stat.ip6s_cantforward++; 445 } else { 446 ip6stat.ip6s_forward++; 447 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 448 if (type) 449 ip6stat.ip6s_redirectsent++; 450 else { 451 if (mcopy) 452 goto freecopy; 453 } 454 } 455 456 #if NPF > 0 457 senderr: 458 #endif 459 if (mcopy == NULL) 460 return; 461 switch (error) { 462 case 0: 463 if (type == ND_REDIRECT) { 464 icmp6_redirect_output(mcopy, rt); 465 return; 466 } 467 goto freecopy; 468 469 case EMSGSIZE: 470 /* xxx MTU is constant in PPP? */ 471 goto freecopy; 472 473 case ENOBUFS: 474 /* Tell source to slow down like source quench in IP? */ 475 goto freecopy; 476 477 case ENETUNREACH: /* shouldn't happen, checked above */ 478 case EHOSTUNREACH: 479 case ENETDOWN: 480 case EHOSTDOWN: 481 default: 482 type = ICMP6_DST_UNREACH; 483 code = ICMP6_DST_UNREACH_ADDR; 484 break; 485 } 486 icmp6_error(mcopy, type, code, 0); 487 return; 488 489 freecopy: 490 m_freem(mcopy); 491 return; 492 } 493