Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/bsd/netinet6/ip6_forward.c
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1 /* $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.16 2002/10/16 02:25:05 sam Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 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 34 #include <sys/param.h> 35 #include <sys/systm.h> 36 #include <sys/malloc.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/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/in_var.h> 51 #include <netinet/in_systm.h> 52 #include <netinet/ip.h> 53 #include <netinet/ip_var.h> 54 #include <netinet6/in6_var.h> 55 #include <netinet/ip6.h> 56 #include <netinet6/ip6_var.h> 57 #include <netinet/icmp6.h> 58 #include <netinet6/nd6.h> 59 60 #include <netinet/in_pcb.h> 61 62 #if IPSEC 63 #include <netinet6/ipsec.h> 64 #if INET6 65 #include <netinet6/ipsec6.h> 66 #endif 67 #include <netkey/key.h> 68 extern int ipsec_bypass; 69 #endif /* IPSEC */ 70 71 #include <netinet6/ip6_fw.h> 72 73 #include <net/net_osdep.h> 74 75 struct route_in6 ip6_forward_rt; 76 77 /* 78 * Forward a packet. If some error occurs return the sender 79 * an icmp packet. Note we can't always generate a meaningful 80 * icmp message because icmp doesn't have a large enough repertoire 81 * of codes and types. 82 * 83 * If not forwarding, just drop the packet. This could be confusing 84 * if ipforwarding was zero but some routing protocol was advancing 85 * us as a gateway to somewhere. However, we must let the routing 86 * protocol deal with that. 87 * 88 */ 89 90 void 91 ip6_forward(m, srcrt) 92 struct mbuf *m; 93 int srcrt; 94 { 95 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 96 struct sockaddr_in6 *dst; 97 struct rtentry *rt; 98 int error, type = 0, code = 0; 99 struct mbuf *mcopy = NULL; 100 struct ifnet *origifp; /* maybe unnecessary */ 101 #if IPSEC 102 struct secpolicy *sp = NULL; 103 #endif 104 105 #if IPSEC 106 /* 107 * Check AH/ESP integrity. 108 */ 109 /* 110 * Don't increment ip6s_cantforward because this is the check 111 * before forwarding packet actually. 112 */ 113 if (ipsec_bypass == 0 && ipsec6_in_reject(m, NULL)) { 114 ipsec6stat.in_polvio++; 115 m_freem(m); 116 return; 117 } 118 #endif /*IPSEC*/ 119 120 /* 121 * Do not forward packets to multicast destination (should be handled 122 * by ip6_mforward(). 123 * Do not forward packets with unspecified source. It was discussed 124 * in July 2000, on ipngwg mailing list. 125 */ 126 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 127 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 128 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 129 ip6stat.ip6s_cantforward++; 130 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 131 if (ip6_log_time + ip6_log_interval < time_second) { 132 ip6_log_time = time_second; 133 log(LOG_DEBUG, 134 "cannot forward " 135 "from %s to %s nxt %d received on %s\n", 136 ip6_sprintf(&ip6->ip6_src), 137 ip6_sprintf(&ip6->ip6_dst), 138 ip6->ip6_nxt, 139 if_name(m->m_pkthdr.rcvif)); 140 } 141 m_freem(m); 142 return; 143 } 144 145 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 146 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 147 icmp6_error(m, ICMP6_TIME_EXCEEDED, 148 ICMP6_TIME_EXCEED_TRANSIT, 0); 149 return; 150 } 151 ip6->ip6_hlim -= IPV6_HLIMDEC; 152 153 /* 154 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 155 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 156 * we need to generate an ICMP6 message to the src. 157 * Thanks to M_EXT, in most cases copy will not occur. 158 * 159 * It is important to save it before IPsec processing as IPsec 160 * processing may modify the mbuf. 161 */ 162 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 163 164 #if IPSEC 165 if (ipsec_bypass != 0) 166 goto skip_ipsec; 167 168 /* 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 key_freesp(sp); 259 260 if (error) { 261 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 262 switch (error) { 263 case EHOSTUNREACH: 264 case ENETUNREACH: 265 case EMSGSIZE: 266 case ENOBUFS: 267 case ENOMEM: 268 break; 269 default: 270 printf("ip6_output (ipsec): error code %d\n", error); 271 /* fall through */ 272 case ENOENT: 273 /* don't show these error codes to the user */ 274 break; 275 } 276 ip6stat.ip6s_cantforward++; 277 if (mcopy) { 278 #if 0 279 /* XXX: what icmp ? */ 280 #else 281 m_freem(mcopy); 282 #endif 283 } 284 m_freem(m); 285 return; 286 } 287 } 288 skip_ipsec: 289 #endif /* IPSEC */ 290 291 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 292 if (!srcrt) { 293 /* 294 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 295 */ 296 if (ip6_forward_rt.ro_rt == 0 || 297 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 298 if (ip6_forward_rt.ro_rt) { 299 rtfree(ip6_forward_rt.ro_rt); 300 ip6_forward_rt.ro_rt = 0; 301 } 302 /* this probably fails but give it a try again */ 303 rtalloc_ign((struct route *)&ip6_forward_rt, 304 RTF_PRCLONING); 305 } 306 307 if (ip6_forward_rt.ro_rt == 0) { 308 ip6stat.ip6s_noroute++; 309 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 310 if (mcopy) { 311 icmp6_error(mcopy, ICMP6_DST_UNREACH, 312 ICMP6_DST_UNREACH_NOROUTE, 0); 313 } 314 m_freem(m); 315 return; 316 } 317 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 318 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 319 if (ip6_forward_rt.ro_rt) { 320 rtfree(ip6_forward_rt.ro_rt); 321 ip6_forward_rt.ro_rt = 0; 322 } 323 bzero(dst, sizeof(*dst)); 324 dst->sin6_len = sizeof(struct sockaddr_in6); 325 dst->sin6_family = AF_INET6; 326 dst->sin6_addr = ip6->ip6_dst; 327 328 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 329 if (ip6_forward_rt.ro_rt == 0) { 330 ip6stat.ip6s_noroute++; 331 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 332 if (mcopy) { 333 icmp6_error(mcopy, ICMP6_DST_UNREACH, 334 ICMP6_DST_UNREACH_NOROUTE, 0); 335 } 336 m_freem(m); 337 return; 338 } 339 } 340 rt = ip6_forward_rt.ro_rt; 341 342 /* 343 * Scope check: if a packet can't be delivered to its destination 344 * for the reason that the destination is beyond the scope of the 345 * source address, discard the packet and return an icmp6 destination 346 * unreachable error with Code 2 (beyond scope of source address). 347 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1] 348 */ 349 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 350 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 351 ip6stat.ip6s_cantforward++; 352 ip6stat.ip6s_badscope++; 353 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 354 355 if (ip6_log_time + ip6_log_interval < time_second) { 356 ip6_log_time = time_second; 357 log(LOG_DEBUG, 358 "cannot forward " 359 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 360 ip6_sprintf(&ip6->ip6_src), 361 ip6_sprintf(&ip6->ip6_dst), 362 ip6->ip6_nxt, 363 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 364 } 365 if (mcopy) 366 icmp6_error(mcopy, ICMP6_DST_UNREACH, 367 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 368 m_freem(m); 369 return; 370 } 371 372 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 373 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 374 if (mcopy) { 375 u_long mtu; 376 #if IPSEC 377 struct secpolicy *sp; 378 int ipsecerror; 379 size_t ipsechdrsiz; 380 #endif 381 382 mtu = rt->rt_ifp->if_mtu; 383 #if IPSEC 384 /* 385 * When we do IPsec tunnel ingress, we need to play 386 * with if_mtu value (decrement IPsec header size 387 * from mtu value). The code is much simpler than v4 388 * case, as we have the outgoing interface for 389 * encapsulated packet as "rt->rt_ifp". 390 */ 391 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 392 IP_FORWARDING, &ipsecerror); 393 if (sp) { 394 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 395 IPSEC_DIR_OUTBOUND, NULL); 396 if (ipsechdrsiz < mtu) 397 mtu -= ipsechdrsiz; 398 } 399 400 /* 401 * if mtu becomes less than minimum MTU, 402 * tell minimum MTU (and I'll need to fragment it). 403 */ 404 if (mtu < IPV6_MMTU) 405 mtu = IPV6_MMTU; 406 #endif 407 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 408 } 409 m_freem(m); 410 return; 411 } 412 413 if (rt->rt_flags & RTF_GATEWAY) 414 dst = (struct sockaddr_in6 *)rt->rt_gateway; 415 416 /* 417 * If we are to forward the packet using the same interface 418 * as one we got the packet from, perhaps we should send a redirect 419 * to sender to shortcut a hop. 420 * Only send redirect if source is sending directly to us, 421 * and if packet was not source routed (or has any options). 422 * Also, don't send redirect if forwarding using a route 423 * modified by a redirect. 424 */ 425 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 426 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 427 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 428 /* 429 * If the incoming interface is equal to the outgoing 430 * one, and the link attached to the interface is 431 * point-to-point, then it will be highly probable 432 * that a routing loop occurs. Thus, we immediately 433 * drop the packet and send an ICMPv6 error message. 434 * 435 * type/code is based on suggestion by Rich Draves. 436 * not sure if it is the best pick. 437 */ 438 icmp6_error(mcopy, ICMP6_DST_UNREACH, 439 ICMP6_DST_UNREACH_ADDR, 0); 440 m_freem(m); 441 return; 442 } 443 type = ND_REDIRECT; 444 } 445 446 /* 447 * Check with the firewall... 448 */ 449 if (ip6_fw_enable && ip6_fw_chk_ptr) { 450 u_short port = 0; 451 /* If ipfw says divert, we have to just drop packet */ 452 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 453 m_freem(m); 454 goto freecopy; 455 } 456 if (!m) 457 goto freecopy; 458 } 459 460 /* 461 * Fake scoped addresses. Note that even link-local source or 462 * destinaion can appear, if the originating node just sends the 463 * packet to us (without address resolution for the destination). 464 * Since both icmp6_error and icmp6_redirect_output fill the embedded 465 * link identifiers, we can do this stuff after making a copy for 466 * returning an error. 467 */ 468 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 469 /* 470 * See corresponding comments in ip6_output. 471 * XXX: but is it possible that ip6_forward() sends a packet 472 * to a loopback interface? I don't think so, and thus 473 * I bark here. (jinmei@kame.net) 474 * XXX: it is common to route invalid packets to loopback. 475 * also, the codepath will be visited on use of ::1 in 476 * rthdr. (itojun) 477 */ 478 #if 1 479 if (0) 480 #else 481 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 482 #endif 483 { 484 printf("ip6_forward: outgoing interface is loopback. " 485 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 486 ip6_sprintf(&ip6->ip6_src), 487 ip6_sprintf(&ip6->ip6_dst), 488 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 489 if_name(rt->rt_ifp)); 490 } 491 492 /* we can just use rcvif in forwarding. */ 493 origifp = m->m_pkthdr.rcvif; 494 } 495 else 496 origifp = rt->rt_ifp; 497 #ifndef SCOPEDROUTING 498 /* 499 * clear embedded scope identifiers if necessary. 500 * in6_clearscope will touch the addresses only when necessary. 501 */ 502 in6_clearscope(&ip6->ip6_src); 503 in6_clearscope(&ip6->ip6_dst); 504 #endif 505 506 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 507 if (error) { 508 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 509 ip6stat.ip6s_cantforward++; 510 } else { 511 ip6stat.ip6s_forward++; 512 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 513 if (type) 514 ip6stat.ip6s_redirectsent++; 515 else { 516 if (mcopy) 517 goto freecopy; 518 } 519 } 520 if (mcopy == NULL) 521 return; 522 523 switch (error) { 524 case 0: 525 #if 1 526 if (type == ND_REDIRECT) { 527 icmp6_redirect_output(mcopy, rt); 528 return; 529 } 530 #endif 531 goto freecopy; 532 533 case EMSGSIZE: 534 /* xxx MTU is constant in PPP? */ 535 goto freecopy; 536 537 case ENOBUFS: 538 /* Tell source to slow down like source quench in IP? */ 539 goto freecopy; 540 541 case ENETUNREACH: /* shouldn't happen, checked above */ 542 case EHOSTUNREACH: 543 case ENETDOWN: 544 case EHOSTDOWN: 545 default: 546 type = ICMP6_DST_UNREACH; 547 code = ICMP6_DST_UNREACH_ADDR; 548 break; 549 } 550 icmp6_error(mcopy, type, code, 0); 551 return; 552 553 freecopy: 554 m_freem(mcopy); 555 return; 556 }
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