1 /* $NetBSD: ip6_forward.c,v 1.27 2001/12/18 03:04:03 itojun Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.74 2001/06/12 23:54:55 itojun 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 <sys/cdefs.h> 34 __KERNEL_RCSID(0, "$NetBSD: ip6_forward.c,v 1.27 2001/12/18 03:04:03 itojun Exp $"); 35 36 #include "opt_ipsec.h" 37 #include "opt_pfil_hooks.h" 38 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/malloc.h> 42 #include <sys/mbuf.h> 43 #include <sys/domain.h> 44 #include <sys/protosw.h> 45 #include <sys/socket.h> 46 #include <sys/errno.h> 47 #include <sys/time.h> 48 #include <sys/kernel.h> 49 #include <sys/syslog.h> 50 51 #include <net/if.h> 52 #include <net/route.h> 53 54 #include <netinet/in.h> 55 #include <netinet/in_var.h> 56 #include <netinet/ip_var.h> 57 #include <netinet/ip6.h> 58 #include <netinet6/ip6_var.h> 59 #include <netinet/icmp6.h> 60 #include <netinet6/nd6.h> 61 62 #ifdef IPSEC 63 #include <netinet6/ipsec.h> 64 #include <netkey/key.h> 65 #endif /* IPSEC */ 66 67 #ifdef PFIL_HOOKS 68 #include <net/pfil.h> 69 #endif 70 71 #include <net/net_osdep.h> 72 73 struct route_in6 ip6_forward_rt; 74 75 #ifdef PFIL_HOOKS 76 extern struct pfil_head inet6_pfil_hook; /* XXX */ 77 #endif 78 79 /* 80 * Forward a packet. If some error occurs return the sender 81 * an icmp packet. Note we can't always generate a meaningful 82 * icmp message because icmp doesn't have a large enough repertoire 83 * of codes and types. 84 * 85 * If not forwarding, just drop the packet. This could be confusing 86 * if ipforwarding was zero but some routing protocol was advancing 87 * us as a gateway to somewhere. However, we must let the routing 88 * protocol deal with that. 89 * 90 */ 91 92 void 93 ip6_forward(m, srcrt) 94 struct mbuf *m; 95 int srcrt; 96 { 97 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 98 struct sockaddr_in6 *dst; 99 struct rtentry *rt; 100 int error, type = 0, code = 0; 101 struct mbuf *mcopy = NULL; 102 struct ifnet *origifp; /* maybe unnecessary */ 103 #ifdef IPSEC 104 struct secpolicy *sp = NULL; 105 #endif 106 long time_second = time.tv_sec; 107 108 #ifdef IPSEC 109 /* 110 * Check AH/ESP integrity. 111 */ 112 /* 113 * Don't increment ip6s_cantforward because this is the check 114 * before forwarding packet actually. 115 */ 116 if (ipsec6_in_reject(m, NULL)) { 117 ipsec6stat.in_polvio++; 118 m_freem(m); 119 return; 120 } 121 #endif /* IPSEC */ 122 123 /* 124 * Do not forward packets to multicast destination (should be handled 125 * by ip6_mforward(). 126 * Do not forward packets with unspecified source. It was discussed 127 * in July 2000, on ipngwg mailing list. 128 */ 129 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 130 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 131 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 132 ip6stat.ip6s_cantforward++; 133 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 134 if (ip6_log_time + ip6_log_interval < time_second) { 135 ip6_log_time = time_second; 136 log(LOG_DEBUG, 137 "cannot forward " 138 "from %s to %s nxt %d received on %s\n", 139 ip6_sprintf(&ip6->ip6_src), 140 ip6_sprintf(&ip6->ip6_dst), 141 ip6->ip6_nxt, 142 if_name(m->m_pkthdr.rcvif)); 143 } 144 m_freem(m); 145 return; 146 } 147 148 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 149 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 150 icmp6_error(m, ICMP6_TIME_EXCEEDED, 151 ICMP6_TIME_EXCEED_TRANSIT, 0); 152 return; 153 } 154 ip6->ip6_hlim -= IPV6_HLIMDEC; 155 156 /* 157 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 158 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 159 * we need to generate an ICMP6 message to the src. 160 * Thanks to M_EXT, in most cases copy will not occur. 161 * 162 * It is important to save it before IPsec processing as IPsec 163 * processing may modify the mbuf. 164 */ 165 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 166 167 #ifdef IPSEC 168 /* get a security policy for this packet */ 169 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 170 &error); 171 if (sp == NULL) { 172 ipsec6stat.out_inval++; 173 ip6stat.ip6s_cantforward++; 174 if (mcopy) { 175 #if 0 176 /* XXX: what icmp ? */ 177 #else 178 m_freem(mcopy); 179 #endif 180 } 181 m_freem(m); 182 return; 183 } 184 185 error = 0; 186 187 /* check policy */ 188 switch (sp->policy) { 189 case IPSEC_POLICY_DISCARD: 190 /* 191 * This packet is just discarded. 192 */ 193 ipsec6stat.out_polvio++; 194 ip6stat.ip6s_cantforward++; 195 key_freesp(sp); 196 if (mcopy) { 197 #if 0 198 /* XXX: what icmp ? */ 199 #else 200 m_freem(mcopy); 201 #endif 202 } 203 m_freem(m); 204 return; 205 206 case IPSEC_POLICY_BYPASS: 207 case IPSEC_POLICY_NONE: 208 /* no need to do IPsec. */ 209 key_freesp(sp); 210 goto skip_ipsec; 211 212 case IPSEC_POLICY_IPSEC: 213 if (sp->req == NULL) { 214 /* XXX should be panic ? */ 215 printf("ip6_forward: No IPsec request specified.\n"); 216 ip6stat.ip6s_cantforward++; 217 key_freesp(sp); 218 if (mcopy) { 219 #if 0 220 /* XXX: what icmp ? */ 221 #else 222 m_freem(mcopy); 223 #endif 224 } 225 m_freem(m); 226 return; 227 } 228 /* do IPsec */ 229 break; 230 231 case IPSEC_POLICY_ENTRUST: 232 default: 233 /* should be panic ?? */ 234 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 235 key_freesp(sp); 236 goto skip_ipsec; 237 } 238 239 { 240 struct ipsec_output_state state; 241 242 /* 243 * All the extension headers will become inaccessible 244 * (since they can be encrypted). 245 * Don't panic, we need no more updates to extension headers 246 * on inner IPv6 packet (since they are now encapsulated). 247 * 248 * IPv6 [ESP|AH] IPv6 [extension headers] payload 249 */ 250 bzero(&state, sizeof(state)); 251 state.m = m; 252 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 253 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 254 255 error = ipsec6_output_tunnel(&state, sp, 0); 256 257 m = state.m; 258 #if 0 /* XXX allocate a route (ro, dst) again later */ 259 ro = (struct route_in6 *)state.ro; 260 dst = (struct sockaddr_in6 *)state.dst; 261 #endif 262 key_freesp(sp); 263 264 if (error) { 265 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 266 switch (error) { 267 case EHOSTUNREACH: 268 case ENETUNREACH: 269 case EMSGSIZE: 270 case ENOBUFS: 271 case ENOMEM: 272 break; 273 default: 274 printf("ip6_output (ipsec): error code %d\n", error); 275 /* fall through */ 276 case ENOENT: 277 /* don't show these error codes to the user */ 278 break; 279 } 280 ip6stat.ip6s_cantforward++; 281 if (mcopy) { 282 #if 0 283 /* XXX: what icmp ? */ 284 #else 285 m_freem(mcopy); 286 #endif 287 } 288 m_freem(m); 289 return; 290 } 291 } 292 skip_ipsec: 293 #endif /* IPSEC */ 294 295 dst = &ip6_forward_rt.ro_dst; 296 if (!srcrt) { 297 /* 298 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 299 */ 300 if (ip6_forward_rt.ro_rt == 0 || 301 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 302 if (ip6_forward_rt.ro_rt) { 303 RTFREE(ip6_forward_rt.ro_rt); 304 ip6_forward_rt.ro_rt = 0; 305 } 306 /* this probably fails but give it a try again */ 307 rtalloc((struct route *)&ip6_forward_rt); 308 } 309 310 if (ip6_forward_rt.ro_rt == 0) { 311 ip6stat.ip6s_noroute++; 312 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 313 if (mcopy) { 314 icmp6_error(mcopy, ICMP6_DST_UNREACH, 315 ICMP6_DST_UNREACH_NOROUTE, 0); 316 } 317 m_freem(m); 318 return; 319 } 320 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 321 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 322 if (ip6_forward_rt.ro_rt) { 323 RTFREE(ip6_forward_rt.ro_rt); 324 ip6_forward_rt.ro_rt = 0; 325 } 326 bzero(dst, sizeof(*dst)); 327 dst->sin6_len = sizeof(struct sockaddr_in6); 328 dst->sin6_family = AF_INET6; 329 dst->sin6_addr = ip6->ip6_dst; 330 331 rtalloc((struct route *)&ip6_forward_rt); 332 if (ip6_forward_rt.ro_rt == 0) { 333 ip6stat.ip6s_noroute++; 334 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 335 if (mcopy) { 336 icmp6_error(mcopy, ICMP6_DST_UNREACH, 337 ICMP6_DST_UNREACH_NOROUTE, 0); 338 } 339 m_freem(m); 340 return; 341 } 342 } 343 rt = ip6_forward_rt.ro_rt; 344 345 /* 346 * Scope check: if a packet can't be delivered to its destination 347 * for the reason that the destination is beyond the scope of the 348 * source address, discard the packet and return an icmp6 destination 349 * unreachable error with Code 2 (beyond scope of source address). 350 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 351 */ 352 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 353 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 354 ip6stat.ip6s_cantforward++; 355 ip6stat.ip6s_badscope++; 356 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 357 358 if (ip6_log_time + ip6_log_interval < time_second) { 359 ip6_log_time = time_second; 360 log(LOG_DEBUG, 361 "cannot forward " 362 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 363 ip6_sprintf(&ip6->ip6_src), 364 ip6_sprintf(&ip6->ip6_dst), 365 ip6->ip6_nxt, 366 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 367 } 368 if (mcopy) 369 icmp6_error(mcopy, ICMP6_DST_UNREACH, 370 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 371 m_freem(m); 372 return; 373 } 374 375 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 376 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 377 if (mcopy) { 378 u_long mtu; 379 #ifdef IPSEC 380 struct secpolicy *sp; 381 int ipsecerror; 382 size_t ipsechdrsiz; 383 #endif 384 385 mtu = rt->rt_ifp->if_mtu; 386 #ifdef IPSEC 387 /* 388 * When we do IPsec tunnel ingress, we need to play 389 * with if_mtu value (decrement IPsec header size 390 * from mtu value). The code is much simpler than v4 391 * case, as we have the outgoing interface for 392 * encapsulated packet as "rt->rt_ifp". 393 */ 394 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 395 IP_FORWARDING, &ipsecerror); 396 if (sp) { 397 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 398 IPSEC_DIR_OUTBOUND, NULL); 399 if (ipsechdrsiz < mtu) 400 mtu -= ipsechdrsiz; 401 } 402 403 /* 404 * if mtu becomes less than minimum MTU, 405 * tell minimum MTU (and I'll need to fragment it). 406 */ 407 if (mtu < IPV6_MMTU) 408 mtu = IPV6_MMTU; 409 #endif 410 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 411 } 412 m_freem(m); 413 return; 414 } 415 416 if (rt->rt_flags & RTF_GATEWAY) 417 dst = (struct sockaddr_in6 *)rt->rt_gateway; 418 419 /* 420 * If we are to forward the packet using the same interface 421 * as one we got the packet from, perhaps we should send a redirect 422 * to sender to shortcut a hop. 423 * Only send redirect if source is sending directly to us, 424 * and if packet was not source routed (or has any options). 425 * Also, don't send redirect if forwarding using a route 426 * modified by a redirect. 427 */ 428 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 429 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 430 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 431 nd6_is_addr_neighbor((struct sockaddr_in6 *)&ip6_forward_rt.ro_dst, rt->rt_ifp)) { 432 /* 433 * If the incoming interface is equal to the outgoing 434 * one, the link attached to the interface is 435 * point-to-point, and the IPv6 destination is 436 * regarded as on-link on the link, then it will be 437 * highly probable that the destination address does 438 * not exist on the link and that the packet is going 439 * to loop. Thus, we immediately drop the packet and 440 * send an ICMPv6 error message. 441 * For other routing loops, we dare to let the packet 442 * go to the loop, so that a remote diagnosing host 443 * can detect the loop by traceroute. 444 * type/code is based on suggestion by Rich Draves. 445 * not sure if it is the best pick. 446 */ 447 icmp6_error(mcopy, ICMP6_DST_UNREACH, 448 ICMP6_DST_UNREACH_ADDR, 0); 449 m_freem(m); 450 return; 451 } 452 type = ND_REDIRECT; 453 } 454 455 /* 456 * Fake scoped addresses. Note that even link-local source or 457 * destinaion can appear, if the originating node just sends the 458 * packet to us (without address resolution for the destination). 459 * Since both icmp6_error and icmp6_redirect_output fill the embedded 460 * link identifiers, we can do this stuff after making a copy for 461 * returning an error. 462 */ 463 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 464 /* 465 * See corresponding comments in ip6_output. 466 * XXX: but is it possible that ip6_forward() sends a packet 467 * to a loopback interface? I don't think so, and thus 468 * I bark here. (jinmei@kame.net) 469 * XXX: it is common to route invalid packets to loopback. 470 * also, the codepath will be visited on use of ::1 in 471 * rthdr. (itojun) 472 */ 473 #if 1 474 if (0) 475 #else 476 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 477 #endif 478 { 479 printf("ip6_forward: outgoing interface is loopback. " 480 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 481 ip6_sprintf(&ip6->ip6_src), 482 ip6_sprintf(&ip6->ip6_dst), 483 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 484 if_name(rt->rt_ifp)); 485 } 486 487 /* we can just use rcvif in forwarding. */ 488 origifp = m->m_pkthdr.rcvif; 489 } 490 else 491 origifp = rt->rt_ifp; 492 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 493 ip6->ip6_src.s6_addr16[1] = 0; 494 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 495 ip6->ip6_dst.s6_addr16[1] = 0; 496 497 #ifdef PFIL_HOOKS 498 /* 499 * Run through list of hooks for output packets. 500 */ 501 if ((error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, 502 PFIL_OUT)) != 0) 503 goto senderr; 504 if (m == NULL) 505 goto freecopy; 506 ip6 = mtod(m, struct ip6_hdr *); 507 #endif /* PFIL_HOOKS */ 508 509 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 510 if (error) { 511 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 512 ip6stat.ip6s_cantforward++; 513 } else { 514 ip6stat.ip6s_forward++; 515 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 516 if (type) 517 ip6stat.ip6s_redirectsent++; 518 else { 519 if (mcopy) 520 goto freecopy; 521 } 522 } 523 524 #ifdef PFIL_HOOKS 525 senderr: 526 #endif 527 if (mcopy == NULL) 528 return; 529 switch (error) { 530 case 0: 531 #if 1 532 if (type == ND_REDIRECT) { 533 icmp6_redirect_output(mcopy, rt); 534 return; 535 } 536 #endif 537 goto freecopy; 538 539 case EMSGSIZE: 540 /* xxx MTU is constant in PPP? */ 541 goto freecopy; 542 543 case ENOBUFS: 544 /* Tell source to slow down like source quench in IP? */ 545 goto freecopy; 546 547 case ENETUNREACH: /* shouldn't happen, checked above */ 548 case EHOSTUNREACH: 549 case ENETDOWN: 550 case EHOSTDOWN: 551 default: 552 type = ICMP6_DST_UNREACH; 553 code = ICMP6_DST_UNREACH_ADDR; 554 break; 555 } 556 icmp6_error(mcopy, type, code, 0); 557 return; 558 559 freecopy: 560 m_freem(mcopy); 561 return; 562 } 563