1 /* $FreeBSD$ */ 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 #include "opt_ip6fw.h" 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 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 #ifdef PFIL_HOOKS 54 #include <net/pfil.h> 55 #endif 56 57 #include <netinet/in.h> 58 #include <netinet/in_var.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/ip_var.h> 62 #include <netinet6/in6_var.h> 63 #include <netinet/ip6.h> 64 #include <netinet6/ip6_var.h> 65 #include <netinet/icmp6.h> 66 #include <netinet6/nd6.h> 67 68 #include <netinet/in_pcb.h> 69 70 #ifdef IPSEC 71 #include <netinet6/ipsec.h> 72 #ifdef INET6 73 #include <netinet6/ipsec6.h> 74 #endif 75 #include <netkey/key.h> 76 #endif /* IPSEC */ 77 78 #ifdef FAST_IPSEC 79 #include <netipsec/ipsec.h> 80 #include <netipsec/ipsec6.h> 81 #include <netipsec/key.h> 82 #define IPSEC 83 #endif /* FAST_IPSEC */ 84 85 #include <netinet6/ip6_fw.h> 86 87 #include <net/net_osdep.h> 88 89 #include <netinet6/ip6protosw.h> 90 91 struct route_in6 ip6_forward_rt; 92 93 /* 94 * Forward a packet. If some error occurs return the sender 95 * an icmp packet. Note we can't always generate a meaningful 96 * icmp message because icmp doesn't have a large enough repertoire 97 * of codes and types. 98 * 99 * If not forwarding, just drop the packet. This could be confusing 100 * if ipforwarding was zero but some routing protocol was advancing 101 * us as a gateway to somewhere. However, we must let the routing 102 * protocol deal with that. 103 * 104 */ 105 106 void 107 ip6_forward(m, srcrt) 108 struct mbuf *m; 109 int srcrt; 110 { 111 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 112 struct sockaddr_in6 *dst; 113 struct rtentry *rt; 114 int error, type = 0, code = 0; 115 struct mbuf *mcopy = NULL; 116 struct ifnet *origifp; /* maybe unnecessary */ 117 #ifdef IPSEC 118 struct secpolicy *sp = NULL; 119 #endif 120 121 #ifdef IPSEC 122 /* 123 * Check AH/ESP integrity. 124 */ 125 /* 126 * Don't increment ip6s_cantforward because this is the check 127 * before forwarding packet actually. 128 */ 129 if (ipsec6_in_reject(m, NULL)) { 130 #if !defined(FAST_IPSEC) 131 ipsec6stat.in_polvio++; 132 #endif 133 m_freem(m); 134 return; 135 } 136 #endif /* IPSEC */ 137 138 /* 139 * Do not forward packets to multicast destination (should be handled 140 * by ip6_mforward(). 141 * Do not forward packets with unspecified source. It was discussed 142 * in July 2000, on ipngwg mailing list. 143 */ 144 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 145 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 146 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 147 ip6stat.ip6s_cantforward++; 148 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 149 if (ip6_log_time + ip6_log_interval < time_second) { 150 ip6_log_time = time_second; 151 log(LOG_DEBUG, 152 "cannot forward " 153 "from %s to %s nxt %d received on %s\n", 154 ip6_sprintf(&ip6->ip6_src), 155 ip6_sprintf(&ip6->ip6_dst), 156 ip6->ip6_nxt, 157 if_name(m->m_pkthdr.rcvif)); 158 } 159 m_freem(m); 160 return; 161 } 162 163 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 164 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 165 icmp6_error(m, ICMP6_TIME_EXCEEDED, 166 ICMP6_TIME_EXCEED_TRANSIT, 0); 167 return; 168 } 169 ip6->ip6_hlim -= IPV6_HLIMDEC; 170 171 /* 172 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 173 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 174 * we need to generate an ICMP6 message to the src. 175 * Thanks to M_EXT, in most cases copy will not occur. 176 * 177 * It is important to save it before IPsec processing as IPsec 178 * processing may modify the mbuf. 179 */ 180 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 181 182 #ifdef IPSEC 183 /* get a security policy for this packet */ 184 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 185 &error); 186 if (sp == NULL) { 187 ipsec6stat.out_inval++; 188 ip6stat.ip6s_cantforward++; 189 if (mcopy) { 190 #if 0 191 /* XXX: what icmp ? */ 192 #else 193 m_freem(mcopy); 194 #endif 195 } 196 m_freem(m); 197 return; 198 } 199 200 error = 0; 201 202 /* check policy */ 203 switch (sp->policy) { 204 case IPSEC_POLICY_DISCARD: 205 /* 206 * This packet is just discarded. 207 */ 208 ipsec6stat.out_polvio++; 209 ip6stat.ip6s_cantforward++; 210 key_freesp(sp); 211 if (mcopy) { 212 #if 0 213 /* XXX: what icmp ? */ 214 #else 215 m_freem(mcopy); 216 #endif 217 } 218 m_freem(m); 219 return; 220 221 case IPSEC_POLICY_BYPASS: 222 case IPSEC_POLICY_NONE: 223 /* no need to do IPsec. */ 224 key_freesp(sp); 225 goto skip_ipsec; 226 227 case IPSEC_POLICY_IPSEC: 228 if (sp->req == NULL) { 229 /* XXX should be panic ? */ 230 printf("ip6_forward: No IPsec request specified.\n"); 231 ip6stat.ip6s_cantforward++; 232 key_freesp(sp); 233 if (mcopy) { 234 #if 0 235 /* XXX: what icmp ? */ 236 #else 237 m_freem(mcopy); 238 #endif 239 } 240 m_freem(m); 241 return; 242 } 243 /* do IPsec */ 244 break; 245 246 case IPSEC_POLICY_ENTRUST: 247 default: 248 /* should be panic ?? */ 249 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 250 key_freesp(sp); 251 goto skip_ipsec; 252 } 253 254 { 255 struct ipsec_output_state state; 256 257 /* 258 * All the extension headers will become inaccessible 259 * (since they can be encrypted). 260 * Don't panic, we need no more updates to extension headers 261 * on inner IPv6 packet (since they are now encapsulated). 262 * 263 * IPv6 [ESP|AH] IPv6 [extension headers] payload 264 */ 265 bzero(&state, sizeof(state)); 266 state.m = m; 267 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 268 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 269 270 error = ipsec6_output_tunnel(&state, sp, 0); 271 272 m = state.m; 273 key_freesp(sp); 274 275 if (error) { 276 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 277 switch (error) { 278 case EHOSTUNREACH: 279 case ENETUNREACH: 280 case EMSGSIZE: 281 case ENOBUFS: 282 case ENOMEM: 283 break; 284 default: 285 printf("ip6_output (ipsec): error code %d\n", error); 286 /* fall through */ 287 case ENOENT: 288 /* don't show these error codes to the user */ 289 break; 290 } 291 ip6stat.ip6s_cantforward++; 292 if (mcopy) { 293 #if 0 294 /* XXX: what icmp ? */ 295 #else 296 m_freem(mcopy); 297 #endif 298 } 299 m_freem(m); 300 return; 301 } 302 } 303 skip_ipsec: 304 #endif /* IPSEC */ 305 306 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 307 if (!srcrt) { 308 /* 309 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 310 */ 311 if (ip6_forward_rt.ro_rt == 0 || 312 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 313 if (ip6_forward_rt.ro_rt) { 314 RTFREE(ip6_forward_rt.ro_rt); 315 ip6_forward_rt.ro_rt = 0; 316 } 317 /* this probably fails but give it a try again */ 318 rtalloc_ign((struct route *)&ip6_forward_rt, 319 RTF_PRCLONING); 320 } 321 322 if (ip6_forward_rt.ro_rt == 0) { 323 ip6stat.ip6s_noroute++; 324 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 325 if (mcopy) { 326 icmp6_error(mcopy, ICMP6_DST_UNREACH, 327 ICMP6_DST_UNREACH_NOROUTE, 0); 328 } 329 m_freem(m); 330 return; 331 } 332 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 333 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 334 if (ip6_forward_rt.ro_rt) { 335 RTFREE(ip6_forward_rt.ro_rt); 336 ip6_forward_rt.ro_rt = 0; 337 } 338 bzero(dst, sizeof(*dst)); 339 dst->sin6_len = sizeof(struct sockaddr_in6); 340 dst->sin6_family = AF_INET6; 341 dst->sin6_addr = ip6->ip6_dst; 342 343 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 344 if (ip6_forward_rt.ro_rt == 0) { 345 ip6stat.ip6s_noroute++; 346 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 347 if (mcopy) { 348 icmp6_error(mcopy, ICMP6_DST_UNREACH, 349 ICMP6_DST_UNREACH_NOROUTE, 0); 350 } 351 m_freem(m); 352 return; 353 } 354 } 355 rt = ip6_forward_rt.ro_rt; 356 357 /* 358 * Scope check: if a packet can't be delivered to its destination 359 * for the reason that the destination is beyond the scope of the 360 * source address, discard the packet and return an icmp6 destination 361 * unreachable error with Code 2 (beyond scope of source address). 362 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1] 363 */ 364 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 365 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 366 ip6stat.ip6s_cantforward++; 367 ip6stat.ip6s_badscope++; 368 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 369 370 if (ip6_log_time + ip6_log_interval < time_second) { 371 ip6_log_time = time_second; 372 log(LOG_DEBUG, 373 "cannot forward " 374 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 375 ip6_sprintf(&ip6->ip6_src), 376 ip6_sprintf(&ip6->ip6_dst), 377 ip6->ip6_nxt, 378 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 379 } 380 if (mcopy) 381 icmp6_error(mcopy, ICMP6_DST_UNREACH, 382 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 383 m_freem(m); 384 return; 385 } 386 387 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 388 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 389 if (mcopy) { 390 u_long mtu; 391 #ifdef IPSEC 392 struct secpolicy *sp; 393 int ipsecerror; 394 size_t ipsechdrsiz; 395 #endif 396 397 mtu = rt->rt_ifp->if_mtu; 398 #ifdef IPSEC 399 /* 400 * When we do IPsec tunnel ingress, we need to play 401 * with if_mtu value (decrement IPsec header size 402 * from mtu value). The code is much simpler than v4 403 * case, as we have the outgoing interface for 404 * encapsulated packet as "rt->rt_ifp". 405 */ 406 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 407 IP_FORWARDING, &ipsecerror); 408 if (sp) { 409 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 410 IPSEC_DIR_OUTBOUND, NULL); 411 if (ipsechdrsiz < mtu) 412 mtu -= ipsechdrsiz; 413 } 414 415 /* 416 * if mtu becomes less than minimum MTU, 417 * tell minimum MTU (and I'll need to fragment it). 418 */ 419 if (mtu < IPV6_MMTU) 420 mtu = IPV6_MMTU; 421 #endif 422 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 423 } 424 m_freem(m); 425 return; 426 } 427 428 if (rt->rt_flags & RTF_GATEWAY) 429 dst = (struct sockaddr_in6 *)rt->rt_gateway; 430 431 /* 432 * If we are to forward the packet using the same interface 433 * as one we got the packet from, perhaps we should send a redirect 434 * to sender to shortcut a hop. 435 * Only send redirect if source is sending directly to us, 436 * and if packet was not source routed (or has any options). 437 * Also, don't send redirect if forwarding using a route 438 * modified by a redirect. 439 */ 440 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 441 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 442 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 443 /* 444 * If the incoming interface is equal to the outgoing 445 * one, and the link attached to the interface is 446 * point-to-point, then it will be highly probable 447 * that a routing loop occurs. Thus, we immediately 448 * drop the packet and send an ICMPv6 error message. 449 * 450 * type/code is based on suggestion by Rich Draves. 451 * not sure if it is the best pick. 452 */ 453 icmp6_error(mcopy, ICMP6_DST_UNREACH, 454 ICMP6_DST_UNREACH_ADDR, 0); 455 m_freem(m); 456 return; 457 } 458 type = ND_REDIRECT; 459 } 460 461 /* 462 * Check with the firewall... 463 */ 464 if (ip6_fw_enable && ip6_fw_chk_ptr) { 465 u_short port = 0; 466 /* If ipfw says divert, we have to just drop packet */ 467 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 468 m_freem(m); 469 goto freecopy; 470 } 471 if (!m) 472 goto freecopy; 473 } 474 475 /* 476 * Fake scoped addresses. Note that even link-local source or 477 * destinaion can appear, if the originating node just sends the 478 * packet to us (without address resolution for the destination). 479 * Since both icmp6_error and icmp6_redirect_output fill the embedded 480 * link identifiers, we can do this stuff after making a copy for 481 * returning an error. 482 */ 483 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 484 /* 485 * See corresponding comments in ip6_output. 486 * XXX: but is it possible that ip6_forward() sends a packet 487 * to a loopback interface? I don't think so, and thus 488 * I bark here. (jinmei@kame.net) 489 * XXX: it is common to route invalid packets to loopback. 490 * also, the codepath will be visited on use of ::1 in 491 * rthdr. (itojun) 492 */ 493 #if 1 494 if (0) 495 #else 496 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 497 #endif 498 { 499 printf("ip6_forward: outgoing interface is loopback. " 500 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 501 ip6_sprintf(&ip6->ip6_src), 502 ip6_sprintf(&ip6->ip6_dst), 503 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 504 if_name(rt->rt_ifp)); 505 } 506 507 /* we can just use rcvif in forwarding. */ 508 origifp = m->m_pkthdr.rcvif; 509 } 510 else 511 origifp = rt->rt_ifp; 512 #ifndef SCOPEDROUTING 513 /* 514 * clear embedded scope identifiers if necessary. 515 * in6_clearscope will touch the addresses only when necessary. 516 */ 517 in6_clearscope(&ip6->ip6_src); 518 in6_clearscope(&ip6->ip6_dst); 519 #endif 520 521 #ifdef PFIL_HOOKS 522 /* 523 * Run through list of hooks for output packets. 524 */ 525 error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT); 526 if (error != 0) 527 goto senderr; 528 if (m == NULL) 529 goto freecopy; 530 ip6 = mtod(m, struct ip6_hdr *); 531 #endif /* PFIL_HOOKS */ 532 533 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 534 if (error) { 535 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 536 ip6stat.ip6s_cantforward++; 537 } else { 538 ip6stat.ip6s_forward++; 539 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 540 if (type) 541 ip6stat.ip6s_redirectsent++; 542 else { 543 if (mcopy) 544 goto freecopy; 545 } 546 } 547 #ifdef PFIL_HOOKS 548 senderr: 549 #endif 550 if (mcopy == NULL) 551 return; 552 switch (error) { 553 case 0: 554 #if 1 555 if (type == ND_REDIRECT) { 556 icmp6_redirect_output(mcopy, rt); 557 return; 558 } 559 #endif 560 goto freecopy; 561 562 case EMSGSIZE: 563 /* xxx MTU is constant in PPP? */ 564 goto freecopy; 565 566 case ENOBUFS: 567 /* Tell source to slow down like source quench in IP? */ 568 goto freecopy; 569 570 case ENETUNREACH: /* shouldn't happen, checked above */ 571 case EHOSTUNREACH: 572 case ENETDOWN: 573 case EHOSTDOWN: 574 default: 575 type = ICMP6_DST_UNREACH; 576 code = ICMP6_DST_UNREACH_ADDR; 577 break; 578 } 579 icmp6_error(mcopy, type, code, 0); 580 return; 581 582 freecopy: 583 m_freem(mcopy); 584 return; 585 } 586