1 /* $NetBSD: ip6_forward.c,v 1.35 2003/07/03 05:03:55 itojun Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.109 2002/09/11 08:10:17 sakane 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 1.35 2003/07/03 05:03:55 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 106 107 #ifdef IPSEC 108 /* 109 * Check AH/ESP integrity. 110 */ 111 /* 112 * Don't increment ip6s_cantforward because this is the check 113 * before forwarding packet actually. 114 */ 115 if (ipsec6_in_reject(m, NULL)) { 116 ipsec6stat.in_polvio++; 117 m_freem(m); 118 return; 119 } 120 #endif /* IPSEC */ 121 122 /* 123 * Do not forward packets to multicast destination (should be handled 124 * by ip6_mforward(). 125 * Do not forward packets with unspecified source. It was discussed 126 * in July 2000, on ipngwg mailing list. 127 */ 128 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 129 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 130 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 131 ip6stat.ip6s_cantforward++; 132 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 133 if (ip6_log_time + ip6_log_interval < time.tv_sec) { 134 ip6_log_time = time.tv_sec; 135 log(LOG_DEBUG, 136 "cannot forward " 137 "from %s to %s nxt %d received on %s\n", 138 ip6_sprintf(&ip6->ip6_src), 139 ip6_sprintf(&ip6->ip6_dst), 140 ip6->ip6_nxt, 141 if_name(m->m_pkthdr.rcvif)); 142 } 143 m_freem(m); 144 return; 145 } 146 147 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 148 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 149 icmp6_error(m, ICMP6_TIME_EXCEEDED, 150 ICMP6_TIME_EXCEED_TRANSIT, 0); 151 return; 152 } 153 ip6->ip6_hlim -= IPV6_HLIMDEC; 154 155 /* 156 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 157 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 158 * we need to generate an ICMP6 message to the src. 159 * Thanks to M_EXT, in most cases copy will not occur. 160 * 161 * It is important to save it before IPsec processing as IPsec 162 * processing may modify the mbuf. 163 */ 164 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 165 166 #ifdef IPSEC 167 /* get a security policy for this packet */ 168 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, 169 IP_FORWARDING, &error); 170 if (sp == NULL) { 171 ipsec6stat.out_inval++; 172 ip6stat.ip6s_cantforward++; 173 if (mcopy) { 174 #if 0 175 /* XXX: what icmp ? */ 176 #else 177 m_freem(mcopy); 178 #endif 179 } 180 m_freem(m); 181 return; 182 } 183 184 error = 0; 185 186 /* check policy */ 187 switch (sp->policy) { 188 case IPSEC_POLICY_DISCARD: 189 /* 190 * This packet is just discarded. 191 */ 192 ipsec6stat.out_polvio++; 193 ip6stat.ip6s_cantforward++; 194 key_freesp(sp); 195 if (mcopy) { 196 #if 0 197 /* XXX: what icmp ? */ 198 #else 199 m_freem(mcopy); 200 #endif 201 } 202 m_freem(m); 203 return; 204 205 case IPSEC_POLICY_BYPASS: 206 case IPSEC_POLICY_NONE: 207 /* no need to do IPsec. */ 208 key_freesp(sp); 209 goto skip_ipsec; 210 211 case IPSEC_POLICY_IPSEC: 212 if (sp->req == NULL) { 213 /* XXX should be panic ? */ 214 printf("ip6_forward: No IPsec request specified.\n"); 215 ip6stat.ip6s_cantforward++; 216 key_freesp(sp); 217 if (mcopy) { 218 #if 0 219 /* XXX: what icmp ? */ 220 #else 221 m_freem(mcopy); 222 #endif 223 } 224 m_freem(m); 225 return; 226 } 227 /* do IPsec */ 228 break; 229 230 case IPSEC_POLICY_ENTRUST: 231 default: 232 /* should be panic ?? */ 233 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 234 key_freesp(sp); 235 goto skip_ipsec; 236 } 237 238 { 239 struct ipsecrequest *isr = NULL; 240 struct ipsec_output_state state; 241 242 /* 243 * when the kernel forwards a packet, it is not proper to apply 244 * IPsec transport mode to the packet is not proper. this check 245 * avoid from this. 246 * at present, if there is even a transport mode SA request in the 247 * security policy, the kernel does not apply IPsec to the packet. 248 * this check is not enough because the following case is valid. 249 * ipsec esp/tunnel/xxx-xxx/require esp/transport//require; 250 */ 251 for (isr = sp->req; isr; isr = isr->next) { 252 if (isr->saidx.mode == IPSEC_MODE_TRANSPORT) 253 goto skip_ipsec; 254 } 255 256 /* 257 * All the extension headers will become inaccessible 258 * (since they can be encrypted). 259 * Don't panic, we need no more updates to extension headers 260 * on inner IPv6 packet (since they are now encapsulated). 261 * 262 * IPv6 [ESP|AH] IPv6 [extension headers] payload 263 */ 264 bzero(&state, sizeof(state)); 265 state.m = m; 266 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 267 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 268 269 error = ipsec6_output_tunnel(&state, sp, 0); 270 271 m = state.m; 272 #if 0 /* XXX allocate a route (ro, dst) again later */ 273 ro = (struct route_in6 *)state.ro; 274 dst = (struct sockaddr_in6 *)state.dst; 275 #endif 276 key_freesp(sp); 277 278 if (error) { 279 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 280 switch (error) { 281 case EHOSTUNREACH: 282 case ENETUNREACH: 283 case EMSGSIZE: 284 case ENOBUFS: 285 case ENOMEM: 286 break; 287 default: 288 printf("ip6_output (ipsec): error code %d\n", error); 289 /* FALLTHROUGH */ 290 case ENOENT: 291 /* don't show these error codes to the user */ 292 break; 293 } 294 ip6stat.ip6s_cantforward++; 295 if (mcopy) { 296 #if 0 297 /* XXX: what icmp ? */ 298 #else 299 m_freem(mcopy); 300 #endif 301 } 302 m_freem(m); 303 return; 304 } 305 } 306 skip_ipsec: 307 #endif /* IPSEC */ 308 309 dst = &ip6_forward_rt.ro_dst; 310 if (!srcrt) { 311 /* 312 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 313 */ 314 if (ip6_forward_rt.ro_rt == 0 || 315 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 316 if (ip6_forward_rt.ro_rt) { 317 RTFREE(ip6_forward_rt.ro_rt); 318 ip6_forward_rt.ro_rt = 0; 319 } 320 /* this probably fails but give it a try again */ 321 rtalloc((struct route *)&ip6_forward_rt); 322 } 323 324 if (ip6_forward_rt.ro_rt == 0) { 325 ip6stat.ip6s_noroute++; 326 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 327 if (mcopy) { 328 icmp6_error(mcopy, ICMP6_DST_UNREACH, 329 ICMP6_DST_UNREACH_NOROUTE, 0); 330 } 331 m_freem(m); 332 return; 333 } 334 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 335 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 336 if (ip6_forward_rt.ro_rt) { 337 RTFREE(ip6_forward_rt.ro_rt); 338 ip6_forward_rt.ro_rt = 0; 339 } 340 bzero(dst, sizeof(*dst)); 341 dst->sin6_len = sizeof(struct sockaddr_in6); 342 dst->sin6_family = AF_INET6; 343 dst->sin6_addr = ip6->ip6_dst; 344 345 rtalloc((struct route *)&ip6_forward_rt); 346 if (ip6_forward_rt.ro_rt == 0) { 347 ip6stat.ip6s_noroute++; 348 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 349 if (mcopy) { 350 icmp6_error(mcopy, ICMP6_DST_UNREACH, 351 ICMP6_DST_UNREACH_NOROUTE, 0); 352 } 353 m_freem(m); 354 return; 355 } 356 } 357 rt = ip6_forward_rt.ro_rt; 358 359 /* 360 * Scope check: if a packet can't be delivered to its destination 361 * for the reason that the destination is beyond the scope of the 362 * source address, discard the packet and return an icmp6 destination 363 * unreachable error with Code 2 (beyond scope of source address). 364 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 365 */ 366 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 367 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 368 ip6stat.ip6s_cantforward++; 369 ip6stat.ip6s_badscope++; 370 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 371 372 if (ip6_log_time + ip6_log_interval < time.tv_sec) { 373 ip6_log_time = time.tv_sec; 374 log(LOG_DEBUG, 375 "cannot forward " 376 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 377 ip6_sprintf(&ip6->ip6_src), 378 ip6_sprintf(&ip6->ip6_dst), 379 ip6->ip6_nxt, 380 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 381 } 382 if (mcopy) 383 icmp6_error(mcopy, ICMP6_DST_UNREACH, 384 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 385 m_freem(m); 386 return; 387 } 388 389 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 390 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 391 if (mcopy) { 392 u_long mtu; 393 #ifdef IPSEC 394 struct secpolicy *sp; 395 int ipsecerror; 396 size_t ipsechdrsiz; 397 #endif 398 399 mtu = IN6_LINKMTU(rt->rt_ifp); 400 #ifdef IPSEC 401 /* 402 * When we do IPsec tunnel ingress, we need to play 403 * with the link value (decrement IPsec header size 404 * from mtu value). The code is much simpler than v4 405 * case, as we have the outgoing interface for 406 * encapsulated packet as "rt->rt_ifp". 407 */ 408 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 409 IP_FORWARDING, &ipsecerror); 410 if (sp) { 411 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 412 IPSEC_DIR_OUTBOUND, NULL); 413 if (ipsechdrsiz < mtu) 414 mtu -= ipsechdrsiz; 415 } 416 417 /* 418 * if mtu becomes less than minimum MTU, 419 * tell minimum MTU (and I'll need to fragment it). 420 */ 421 if (mtu < IPV6_MMTU) 422 mtu = IPV6_MMTU; 423 #endif 424 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 425 } 426 m_freem(m); 427 return; 428 } 429 430 if (rt->rt_flags & RTF_GATEWAY) 431 dst = (struct sockaddr_in6 *)rt->rt_gateway; 432 433 /* 434 * If we are to forward the packet using the same interface 435 * as one we got the packet from, perhaps we should send a redirect 436 * to sender to shortcut a hop. 437 * Only send redirect if source is sending directly to us, 438 * and if packet was not source routed (or has any options). 439 * Also, don't send redirect if forwarding using a route 440 * modified by a redirect. 441 */ 442 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 443 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 444 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 445 nd6_is_addr_neighbor((struct sockaddr_in6 *)&ip6_forward_rt.ro_dst, rt->rt_ifp)) { 446 /* 447 * If the incoming interface is equal to the outgoing 448 * one, the link attached to the interface is 449 * point-to-point, and the IPv6 destination is 450 * regarded as on-link on the link, then it will be 451 * highly probable that the destination address does 452 * not exist on the link and that the packet is going 453 * to loop. Thus, we immediately drop the packet and 454 * send an ICMPv6 error message. 455 * For other routing loops, we dare to let the packet 456 * go to the loop, so that a remote diagnosing host 457 * can detect the loop by traceroute. 458 * type/code is based on suggestion by Rich Draves. 459 * not sure if it is the best pick. 460 */ 461 icmp6_error(mcopy, ICMP6_DST_UNREACH, 462 ICMP6_DST_UNREACH_ADDR, 0); 463 m_freem(m); 464 return; 465 } 466 type = ND_REDIRECT; 467 } 468 469 /* 470 * Fake scoped addresses. Note that even link-local source or 471 * destinaion can appear, if the originating node just sends the 472 * packet to us (without address resolution for the destination). 473 * Since both icmp6_error and icmp6_redirect_output fill the embedded 474 * link identifiers, we can do this stuff after making a copy for 475 * returning an error. 476 */ 477 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 478 /* 479 * See corresponding comments in ip6_output. 480 * XXX: but is it possible that ip6_forward() sends a packet 481 * to a loopback interface? I don't think so, and thus 482 * I bark here. (jinmei@kame.net) 483 * XXX: it is common to route invalid packets to loopback. 484 * also, the codepath will be visited on use of ::1 in 485 * rthdr. (itojun) 486 */ 487 #if 1 488 if (0) 489 #else 490 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 491 #endif 492 { 493 printf("ip6_forward: outgoing interface is loopback. " 494 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 495 ip6_sprintf(&ip6->ip6_src), 496 ip6_sprintf(&ip6->ip6_dst), 497 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 498 if_name(rt->rt_ifp)); 499 } 500 501 /* we can just use rcvif in forwarding. */ 502 origifp = m->m_pkthdr.rcvif; 503 } 504 else 505 origifp = rt->rt_ifp; 506 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 507 ip6->ip6_src.s6_addr16[1] = 0; 508 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 509 ip6->ip6_dst.s6_addr16[1] = 0; 510 511 #ifdef PFIL_HOOKS 512 /* 513 * Run through list of hooks for output packets. 514 */ 515 if ((error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, 516 PFIL_OUT)) != 0) 517 goto senderr; 518 if (m == NULL) 519 goto freecopy; 520 ip6 = mtod(m, struct ip6_hdr *); 521 #endif /* PFIL_HOOKS */ 522 523 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 524 if (error) { 525 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 526 ip6stat.ip6s_cantforward++; 527 } else { 528 ip6stat.ip6s_forward++; 529 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 530 if (type) 531 ip6stat.ip6s_redirectsent++; 532 else { 533 if (mcopy) 534 goto freecopy; 535 } 536 } 537 538 #ifdef PFIL_HOOKS 539 senderr: 540 #endif 541 if (mcopy == NULL) 542 return; 543 switch (error) { 544 case 0: 545 if (type == ND_REDIRECT) { 546 icmp6_redirect_output(mcopy, rt); 547 return; 548 } 549 goto freecopy; 550 551 case EMSGSIZE: 552 /* xxx MTU is constant in PPP? */ 553 goto freecopy; 554 555 case ENOBUFS: 556 /* Tell source to slow down like source quench in IP? */ 557 goto freecopy; 558 559 case ENETUNREACH: /* shouldn't happen, checked above */ 560 case EHOSTUNREACH: 561 case ENETDOWN: 562 case EHOSTDOWN: 563 default: 564 type = ICMP6_DST_UNREACH; 565 code = ICMP6_DST_UNREACH_ADDR; 566 break; 567 } 568 icmp6_error(mcopy, type, code, 0); 569 return; 570 571 freecopy: 572 m_freem(mcopy); 573 return; 574 } 575