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 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/malloc.h> 41 #include <sys/mbuf.h> 42 #include <sys/domain.h> 43 #include <sys/protosw.h> 44 #include <sys/socket.h> 45 #include <sys/errno.h> 46 #include <sys/time.h> 47 #include <sys/kernel.h> 48 #include <sys/syslog.h> 49 50 #include <net/if.h> 51 #include <net/route.h> 52 #ifdef PFIL_HOOKS 53 #include <net/pfil.h> 54 #endif 55 56 #include <netinet/in.h> 57 #include <netinet/in_var.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/ip_var.h> 61 #include <netinet6/in6_var.h> 62 #include <netinet/ip6.h> 63 #include <netinet6/ip6_var.h> 64 #include <netinet/icmp6.h> 65 #include <netinet6/nd6.h> 66 67 #include <netinet/in_pcb.h> 68 69 #ifdef IPSEC 70 #include <netinet6/ipsec.h> 71 #ifdef INET6 72 #include <netinet6/ipsec6.h> 73 #endif 74 #include <netkey/key.h> 75 #endif /* IPSEC */ 76 77 #ifdef FAST_IPSEC 78 #include <netipsec/ipsec.h> 79 #include <netipsec/ipsec6.h> 80 #include <netipsec/key.h> 81 #define IPSEC 82 #endif /* FAST_IPSEC */ 83 84 #include <netinet6/ip6_fw.h> 85 86 #include <net/net_osdep.h> 87 88 #include <netinet6/ip6protosw.h> 89 90 struct route_in6 ip6_forward_rt; 91 92 /* 93 * Forward a packet. If some error occurs return the sender 94 * an icmp packet. Note we can't always generate a meaningful 95 * icmp message because icmp doesn't have a large enough repertoire 96 * of codes and types. 97 * 98 * If not forwarding, just drop the packet. This could be confusing 99 * if ipforwarding was zero but some routing protocol was advancing 100 * us as a gateway to somewhere. However, we must let the routing 101 * protocol deal with that. 102 * 103 */ 104 105 void 106 ip6_forward(m, srcrt) 107 struct mbuf *m; 108 int srcrt; 109 { 110 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 111 struct sockaddr_in6 *dst; 112 struct rtentry *rt; 113 int error, type = 0, code = 0; 114 struct mbuf *mcopy = NULL; 115 struct ifnet *origifp; /* maybe unnecessary */ 116 #ifdef PFIL_HOOKS 117 struct packet_filter_hook *pfh; 118 struct mbuf *m1; 119 int rv; 120 #endif /* PFIL_HOOKS */ 121 #ifdef IPSEC 122 struct secpolicy *sp = NULL; 123 #endif 124 125 #ifdef IPSEC 126 /* 127 * Check AH/ESP integrity. 128 */ 129 /* 130 * Don't increment ip6s_cantforward because this is the check 131 * before forwarding packet actually. 132 */ 133 if (ipsec6_in_reject(m, NULL)) { 134 #if !defined(FAST_IPSEC) 135 ipsec6stat.in_polvio++; 136 #endif 137 m_freem(m); 138 return; 139 } 140 #endif /* IPSEC */ 141 142 /* 143 * Do not forward packets to multicast destination (should be handled 144 * by ip6_mforward(). 145 * Do not forward packets with unspecified source. It was discussed 146 * in July 2000, on ipngwg mailing list. 147 */ 148 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 149 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 150 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 151 ip6stat.ip6s_cantforward++; 152 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 153 if (ip6_log_time + ip6_log_interval < time_second) { 154 ip6_log_time = time_second; 155 log(LOG_DEBUG, 156 "cannot forward " 157 "from %s to %s nxt %d received on %s\n", 158 ip6_sprintf(&ip6->ip6_src), 159 ip6_sprintf(&ip6->ip6_dst), 160 ip6->ip6_nxt, 161 if_name(m->m_pkthdr.rcvif)); 162 } 163 m_freem(m); 164 return; 165 } 166 167 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 168 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 169 icmp6_error(m, ICMP6_TIME_EXCEEDED, 170 ICMP6_TIME_EXCEED_TRANSIT, 0); 171 return; 172 } 173 ip6->ip6_hlim -= IPV6_HLIMDEC; 174 175 /* 176 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 177 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 178 * we need to generate an ICMP6 message to the src. 179 * Thanks to M_EXT, in most cases copy will not occur. 180 * 181 * It is important to save it before IPsec processing as IPsec 182 * processing may modify the mbuf. 183 */ 184 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 185 186 #ifdef IPSEC 187 /* get a security policy for this packet */ 188 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 189 &error); 190 if (sp == NULL) { 191 ipsec6stat.out_inval++; 192 ip6stat.ip6s_cantforward++; 193 if (mcopy) { 194 #if 0 195 /* XXX: what icmp ? */ 196 #else 197 m_freem(mcopy); 198 #endif 199 } 200 m_freem(m); 201 return; 202 } 203 204 error = 0; 205 206 /* check policy */ 207 switch (sp->policy) { 208 case IPSEC_POLICY_DISCARD: 209 /* 210 * This packet is just discarded. 211 */ 212 ipsec6stat.out_polvio++; 213 ip6stat.ip6s_cantforward++; 214 key_freesp(sp); 215 if (mcopy) { 216 #if 0 217 /* XXX: what icmp ? */ 218 #else 219 m_freem(mcopy); 220 #endif 221 } 222 m_freem(m); 223 return; 224 225 case IPSEC_POLICY_BYPASS: 226 case IPSEC_POLICY_NONE: 227 /* no need to do IPsec. */ 228 key_freesp(sp); 229 goto skip_ipsec; 230 231 case IPSEC_POLICY_IPSEC: 232 if (sp->req == NULL) { 233 /* XXX should be panic ? */ 234 printf("ip6_forward: No IPsec request specified.\n"); 235 ip6stat.ip6s_cantforward++; 236 key_freesp(sp); 237 if (mcopy) { 238 #if 0 239 /* XXX: what icmp ? */ 240 #else 241 m_freem(mcopy); 242 #endif 243 } 244 m_freem(m); 245 return; 246 } 247 /* do IPsec */ 248 break; 249 250 case IPSEC_POLICY_ENTRUST: 251 default: 252 /* should be panic ?? */ 253 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 254 key_freesp(sp); 255 goto skip_ipsec; 256 } 257 258 { 259 struct ipsec_output_state state; 260 261 /* 262 * All the extension headers will become inaccessible 263 * (since they can be encrypted). 264 * Don't panic, we need no more updates to extension headers 265 * on inner IPv6 packet (since they are now encapsulated). 266 * 267 * IPv6 [ESP|AH] IPv6 [extension headers] payload 268 */ 269 bzero(&state, sizeof(state)); 270 state.m = m; 271 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 272 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 273 274 error = ipsec6_output_tunnel(&state, sp, 0); 275 276 m = state.m; 277 key_freesp(sp); 278 279 if (error) { 280 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 281 switch (error) { 282 case EHOSTUNREACH: 283 case ENETUNREACH: 284 case EMSGSIZE: 285 case ENOBUFS: 286 case ENOMEM: 287 break; 288 default: 289 printf("ip6_output (ipsec): error code %d\n", error); 290 /* fall through */ 291 case ENOENT: 292 /* don't show these error codes to the user */ 293 break; 294 } 295 ip6stat.ip6s_cantforward++; 296 if (mcopy) { 297 #if 0 298 /* XXX: what icmp ? */ 299 #else 300 m_freem(mcopy); 301 #endif 302 } 303 m_freem(m); 304 return; 305 } 306 } 307 skip_ipsec: 308 #endif /* IPSEC */ 309 310 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 311 if (!srcrt) { 312 /* 313 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 314 */ 315 if (ip6_forward_rt.ro_rt == 0 || 316 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 317 if (ip6_forward_rt.ro_rt) { 318 RTFREE(ip6_forward_rt.ro_rt); 319 ip6_forward_rt.ro_rt = 0; 320 } 321 /* this probably fails but give it a try again */ 322 rtalloc_ign((struct route *)&ip6_forward_rt, 323 RTF_PRCLONING); 324 } 325 326 if (ip6_forward_rt.ro_rt == 0) { 327 ip6stat.ip6s_noroute++; 328 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 329 if (mcopy) { 330 icmp6_error(mcopy, ICMP6_DST_UNREACH, 331 ICMP6_DST_UNREACH_NOROUTE, 0); 332 } 333 m_freem(m); 334 return; 335 } 336 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 337 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 338 if (ip6_forward_rt.ro_rt) { 339 RTFREE(ip6_forward_rt.ro_rt); 340 ip6_forward_rt.ro_rt = 0; 341 } 342 bzero(dst, sizeof(*dst)); 343 dst->sin6_len = sizeof(struct sockaddr_in6); 344 dst->sin6_family = AF_INET6; 345 dst->sin6_addr = ip6->ip6_dst; 346 347 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 348 if (ip6_forward_rt.ro_rt == 0) { 349 ip6stat.ip6s_noroute++; 350 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 351 if (mcopy) { 352 icmp6_error(mcopy, ICMP6_DST_UNREACH, 353 ICMP6_DST_UNREACH_NOROUTE, 0); 354 } 355 m_freem(m); 356 return; 357 } 358 } 359 rt = ip6_forward_rt.ro_rt; 360 361 /* 362 * Scope check: if a packet can't be delivered to its destination 363 * for the reason that the destination is beyond the scope of the 364 * source address, discard the packet and return an icmp6 destination 365 * unreachable error with Code 2 (beyond scope of source address). 366 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1] 367 */ 368 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 369 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 370 ip6stat.ip6s_cantforward++; 371 ip6stat.ip6s_badscope++; 372 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 373 374 if (ip6_log_time + ip6_log_interval < time_second) { 375 ip6_log_time = time_second; 376 log(LOG_DEBUG, 377 "cannot forward " 378 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 379 ip6_sprintf(&ip6->ip6_src), 380 ip6_sprintf(&ip6->ip6_dst), 381 ip6->ip6_nxt, 382 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 383 } 384 if (mcopy) 385 icmp6_error(mcopy, ICMP6_DST_UNREACH, 386 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 387 m_freem(m); 388 return; 389 } 390 391 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 392 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 393 if (mcopy) { 394 u_long mtu; 395 #ifdef IPSEC 396 struct secpolicy *sp; 397 int ipsecerror; 398 size_t ipsechdrsiz; 399 #endif 400 401 mtu = rt->rt_ifp->if_mtu; 402 #ifdef IPSEC 403 /* 404 * When we do IPsec tunnel ingress, we need to play 405 * with if_mtu value (decrement IPsec header size 406 * from mtu value). The code is much simpler than v4 407 * case, as we have the outgoing interface for 408 * encapsulated packet as "rt->rt_ifp". 409 */ 410 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 411 IP_FORWARDING, &ipsecerror); 412 if (sp) { 413 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 414 IPSEC_DIR_OUTBOUND, NULL); 415 if (ipsechdrsiz < mtu) 416 mtu -= ipsechdrsiz; 417 } 418 419 /* 420 * if mtu becomes less than minimum MTU, 421 * tell minimum MTU (and I'll need to fragment it). 422 */ 423 if (mtu < IPV6_MMTU) 424 mtu = IPV6_MMTU; 425 #endif 426 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 427 } 428 m_freem(m); 429 return; 430 } 431 432 if (rt->rt_flags & RTF_GATEWAY) 433 dst = (struct sockaddr_in6 *)rt->rt_gateway; 434 435 /* 436 * If we are to forward the packet using the same interface 437 * as one we got the packet from, perhaps we should send a redirect 438 * to sender to shortcut a hop. 439 * Only send redirect if source is sending directly to us, 440 * and if packet was not source routed (or has any options). 441 * Also, don't send redirect if forwarding using a route 442 * modified by a redirect. 443 */ 444 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 445 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 446 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 447 /* 448 * If the incoming interface is equal to the outgoing 449 * one, and the link attached to the interface is 450 * point-to-point, then it will be highly probable 451 * that a routing loop occurs. Thus, we immediately 452 * drop the packet and send an ICMPv6 error message. 453 * 454 * type/code is based on suggestion by Rich Draves. 455 * not sure if it is the best pick. 456 */ 457 icmp6_error(mcopy, ICMP6_DST_UNREACH, 458 ICMP6_DST_UNREACH_ADDR, 0); 459 m_freem(m); 460 return; 461 } 462 type = ND_REDIRECT; 463 } 464 465 /* 466 * Check with the firewall... 467 */ 468 if (ip6_fw_enable && ip6_fw_chk_ptr) { 469 u_short port = 0; 470 /* If ipfw says divert, we have to just drop packet */ 471 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 472 m_freem(m); 473 goto freecopy; 474 } 475 if (!m) 476 goto freecopy; 477 } 478 479 /* 480 * Fake scoped addresses. Note that even link-local source or 481 * destinaion can appear, if the originating node just sends the 482 * packet to us (without address resolution for the destination). 483 * Since both icmp6_error and icmp6_redirect_output fill the embedded 484 * link identifiers, we can do this stuff after making a copy for 485 * returning an error. 486 */ 487 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 488 /* 489 * See corresponding comments in ip6_output. 490 * XXX: but is it possible that ip6_forward() sends a packet 491 * to a loopback interface? I don't think so, and thus 492 * I bark here. (jinmei@kame.net) 493 * XXX: it is common to route invalid packets to loopback. 494 * also, the codepath will be visited on use of ::1 in 495 * rthdr. (itojun) 496 */ 497 #if 1 498 if (0) 499 #else 500 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 501 #endif 502 { 503 printf("ip6_forward: outgoing interface is loopback. " 504 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 505 ip6_sprintf(&ip6->ip6_src), 506 ip6_sprintf(&ip6->ip6_dst), 507 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 508 if_name(rt->rt_ifp)); 509 } 510 511 /* we can just use rcvif in forwarding. */ 512 origifp = m->m_pkthdr.rcvif; 513 } 514 else 515 origifp = rt->rt_ifp; 516 #ifndef SCOPEDROUTING 517 /* 518 * clear embedded scope identifiers if necessary. 519 * in6_clearscope will touch the addresses only when necessary. 520 */ 521 in6_clearscope(&ip6->ip6_src); 522 in6_clearscope(&ip6->ip6_dst); 523 #endif 524 525 #ifdef PFIL_HOOKS 526 /* 527 * Run through list of hooks for output packets. 528 */ 529 m1 = m; 530 pfh = pfil_hook_get(PFIL_OUT, &inet6sw[ip6_protox[IPPROTO_IPV6]].pr_pfh); 531 for (; pfh; pfh = pfh->pfil_link.tqe_next) 532 if (pfh->pfil_func) { 533 rv = pfh->pfil_func(ip6, sizeof(*ip6), 534 rt->rt_ifp, 1, &m1); 535 if (rv) { 536 error = EHOSTUNREACH; 537 goto freecopy; 538 } 539 m = m1; 540 if (m == NULL) 541 goto freecopy; 542 ip6 = mtod(m, struct ip6_hdr *); 543 } 544 #endif /* PFIL_HOOKS */ 545 546 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 547 if (error) { 548 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 549 ip6stat.ip6s_cantforward++; 550 } else { 551 ip6stat.ip6s_forward++; 552 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 553 if (type) 554 ip6stat.ip6s_redirectsent++; 555 else { 556 if (mcopy) 557 goto freecopy; 558 } 559 } 560 if (mcopy == NULL) 561 return; 562 switch (error) { 563 case 0: 564 #if 1 565 if (type == ND_REDIRECT) { 566 icmp6_redirect_output(mcopy, rt); 567 return; 568 } 569 #endif 570 goto freecopy; 571 572 case EMSGSIZE: 573 /* xxx MTU is constant in PPP? */ 574 goto freecopy; 575 576 case ENOBUFS: 577 /* Tell source to slow down like source quench in IP? */ 578 goto freecopy; 579 580 case ENETUNREACH: /* shouldn't happen, checked above */ 581 case EHOSTUNREACH: 582 case ENETDOWN: 583 case EHOSTDOWN: 584 default: 585 type = ICMP6_DST_UNREACH; 586 code = ICMP6_DST_UNREACH_ADDR; 587 break; 588 } 589 icmp6_error(mcopy, type, code, 0); 590 return; 591 592 freecopy: 593 m_freem(mcopy); 594 return; 595 } 596