1 /*- 2 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the project nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $ 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_ipstealth.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/malloc.h> 43 #include <sys/mbuf.h> 44 #include <sys/domain.h> 45 #include <sys/protosw.h> 46 #include <sys/socket.h> 47 #include <sys/errno.h> 48 #include <sys/time.h> 49 #include <sys/kernel.h> 50 #include <sys/syslog.h> 51 52 #include <net/if.h> 53 #include <net/route.h> 54 #include <net/pfil.h> 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 <netinet6/scope6_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 <netipsec/ipsec.h> 72 #include <netipsec/ipsec6.h> 73 #include <netipsec/key.h> 74 #endif /* IPSEC */ 75 76 #include <netinet6/ip6protosw.h> 77 78 /* 79 * Forward a packet. If some error occurs return the sender 80 * an icmp packet. Note we can't always generate a meaningful 81 * icmp message because icmp doesn't have a large enough repertoire 82 * of codes and types. 83 * 84 * If not forwarding, just drop the packet. This could be confusing 85 * if ipforwarding was zero but some routing protocol was advancing 86 * us as a gateway to somewhere. However, we must let the routing 87 * protocol deal with that. 88 * 89 */ 90 void 91 ip6_forward(struct mbuf *m, int srcrt) 92 { 93 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 94 struct sockaddr_in6 *dst = NULL; 95 struct rtentry *rt = NULL; 96 struct route_in6 rin6; 97 int error, type = 0, code = 0; 98 struct mbuf *mcopy = NULL; 99 struct ifnet *origifp; /* maybe unnecessary */ 100 u_int32_t inzone, outzone; 101 struct in6_addr src_in6, dst_in6; 102 #ifdef IPSEC 103 struct secpolicy *sp = NULL; 104 int ipsecrt = 0; 105 #endif 106 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN]; 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 V_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 the 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 V_ip6stat.ip6s_cantforward++; 133 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 134 if (V_ip6_log_time + V_ip6_log_interval < time_second) { 135 V_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(ip6bufs, &ip6->ip6_src), 140 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 141 ip6->ip6_nxt, 142 if_name(m->m_pkthdr.rcvif)); 143 } 144 m_freem(m); 145 return; 146 } 147 148 #ifdef IPSTEALTH 149 if (!V_ip6stealth) { 150 #endif 151 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 152 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 153 icmp6_error(m, ICMP6_TIME_EXCEEDED, 154 ICMP6_TIME_EXCEED_TRANSIT, 0); 155 return; 156 } 157 ip6->ip6_hlim -= IPV6_HLIMDEC; 158 159 #ifdef IPSTEALTH 160 } 161 #endif 162 163 /* 164 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 165 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 166 * we need to generate an ICMP6 message to the src. 167 * Thanks to M_EXT, in most cases copy will not occur. 168 * 169 * It is important to save it before IPsec processing as IPsec 170 * processing may modify the mbuf. 171 */ 172 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 173 174 #ifdef IPSEC 175 /* get a security policy for this packet */ 176 sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, 177 IP_FORWARDING, &error); 178 if (sp == NULL) { 179 V_ipsec6stat.out_inval++; 180 V_ip6stat.ip6s_cantforward++; 181 if (mcopy) { 182 #if 0 183 /* XXX: what icmp ? */ 184 #else 185 m_freem(mcopy); 186 #endif 187 } 188 m_freem(m); 189 return; 190 } 191 192 error = 0; 193 194 /* check policy */ 195 switch (sp->policy) { 196 case IPSEC_POLICY_DISCARD: 197 /* 198 * This packet is just discarded. 199 */ 200 V_ipsec6stat.out_polvio++; 201 V_ip6stat.ip6s_cantforward++; 202 KEY_FREESP(&sp); 203 if (mcopy) { 204 #if 0 205 /* XXX: what icmp ? */ 206 #else 207 m_freem(mcopy); 208 #endif 209 } 210 m_freem(m); 211 return; 212 213 case IPSEC_POLICY_BYPASS: 214 case IPSEC_POLICY_NONE: 215 /* no need to do IPsec. */ 216 KEY_FREESP(&sp); 217 goto skip_ipsec; 218 219 case IPSEC_POLICY_IPSEC: 220 if (sp->req == NULL) { 221 /* XXX should be panic ? */ 222 printf("ip6_forward: No IPsec request specified.\n"); 223 V_ip6stat.ip6s_cantforward++; 224 KEY_FREESP(&sp); 225 if (mcopy) { 226 #if 0 227 /* XXX: what icmp ? */ 228 #else 229 m_freem(mcopy); 230 #endif 231 } 232 m_freem(m); 233 return; 234 } 235 /* do IPsec */ 236 break; 237 238 case IPSEC_POLICY_ENTRUST: 239 default: 240 /* should be panic ?? */ 241 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 242 KEY_FREESP(&sp); 243 goto skip_ipsec; 244 } 245 246 { 247 struct ipsecrequest *isr = NULL; 248 struct ipsec_output_state state; 249 250 /* 251 * when the kernel forwards a packet, it is not proper to apply 252 * IPsec transport mode to the packet is not proper. this check 253 * avoid from this. 254 * at present, if there is even a transport mode SA request in the 255 * security policy, the kernel does not apply IPsec to the packet. 256 * this check is not enough because the following case is valid. 257 * ipsec esp/tunnel/xxx-xxx/require esp/transport//require; 258 */ 259 for (isr = sp->req; isr; isr = isr->next) { 260 if (isr->saidx.mode == IPSEC_MODE_ANY) 261 goto doipsectunnel; 262 if (isr->saidx.mode == IPSEC_MODE_TUNNEL) 263 goto doipsectunnel; 264 } 265 266 /* 267 * if there's no need for tunnel mode IPsec, skip. 268 */ 269 if (!isr) 270 goto skip_ipsec; 271 272 doipsectunnel: 273 /* 274 * All the extension headers will become inaccessible 275 * (since they can be encrypted). 276 * Don't panic, we need no more updates to extension headers 277 * on inner IPv6 packet (since they are now encapsulated). 278 * 279 * IPv6 [ESP|AH] IPv6 [extension headers] payload 280 */ 281 bzero(&state, sizeof(state)); 282 state.m = m; 283 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 284 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 285 286 error = ipsec6_output_tunnel(&state, sp, 0); 287 288 m = state.m; 289 KEY_FREESP(&sp); 290 291 if (error) { 292 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 293 switch (error) { 294 case EHOSTUNREACH: 295 case ENETUNREACH: 296 case EMSGSIZE: 297 case ENOBUFS: 298 case ENOMEM: 299 break; 300 default: 301 printf("ip6_output (ipsec): error code %d\n", error); 302 /* FALLTHROUGH */ 303 case ENOENT: 304 /* don't show these error codes to the user */ 305 break; 306 } 307 V_ip6stat.ip6s_cantforward++; 308 if (mcopy) { 309 #if 0 310 /* XXX: what icmp ? */ 311 #else 312 m_freem(mcopy); 313 #endif 314 } 315 m_freem(m); 316 return; 317 } else { 318 /* 319 * In the FAST IPSec case we have already 320 * re-injected the packet and it has been freed 321 * by the ipsec_done() function. So, just clean 322 * up after ourselves. 323 */ 324 m = NULL; 325 goto freecopy; 326 } 327 328 if ((m != NULL) && (ip6 != mtod(m, struct ip6_hdr *)) ){ 329 /* 330 * now tunnel mode headers are added. we are originating 331 * packet instead of forwarding the packet. 332 */ 333 ip6_output(m, NULL, NULL, IPV6_FORWARDING/*XXX*/, NULL, NULL, 334 NULL); 335 goto freecopy; 336 } 337 338 /* adjust pointer */ 339 dst = (struct sockaddr_in6 *)state.dst; 340 rt = state.ro ? state.ro->ro_rt : NULL; 341 if (dst != NULL && rt != NULL) 342 ipsecrt = 1; 343 } 344 if (ipsecrt) 345 goto skip_routing; 346 skip_ipsec: 347 #endif 348 349 bzero(&rin6, sizeof(struct route_in6)); 350 dst = (struct sockaddr_in6 *)&rin6.ro_dst; 351 dst->sin6_len = sizeof(struct sockaddr_in6); 352 dst->sin6_family = AF_INET6; 353 dst->sin6_addr = ip6->ip6_dst; 354 355 rin6.ro_rt = rtalloc1((struct sockaddr *)dst, 0, 0); 356 if (rin6.ro_rt != NULL) 357 RT_UNLOCK(rin6.ro_rt); 358 else { 359 V_ip6stat.ip6s_noroute++; 360 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 361 if (mcopy) { 362 icmp6_error(mcopy, ICMP6_DST_UNREACH, 363 ICMP6_DST_UNREACH_NOROUTE, 0); 364 } 365 goto bad; 366 } 367 rt = rin6.ro_rt; 368 #ifdef IPSEC 369 skip_routing: 370 #endif 371 372 /* 373 * Source scope check: if a packet can't be delivered to its 374 * destination for the reason that the destination is beyond the scope 375 * of the source address, discard the packet and return an icmp6 376 * destination unreachable error with Code 2 (beyond scope of source 377 * address). We use a local copy of ip6_src, since in6_setscope() 378 * will possibly modify its first argument. 379 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1] 380 */ 381 src_in6 = ip6->ip6_src; 382 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) { 383 /* XXX: this should not happen */ 384 V_ip6stat.ip6s_cantforward++; 385 V_ip6stat.ip6s_badscope++; 386 goto bad; 387 } 388 if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) { 389 V_ip6stat.ip6s_cantforward++; 390 V_ip6stat.ip6s_badscope++; 391 goto bad; 392 } 393 if (inzone != outzone 394 #ifdef IPSEC 395 && !ipsecrt 396 #endif 397 ) { 398 V_ip6stat.ip6s_cantforward++; 399 V_ip6stat.ip6s_badscope++; 400 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 401 402 if (V_ip6_log_time + V_ip6_log_interval < time_second) { 403 V_ip6_log_time = time_second; 404 log(LOG_DEBUG, 405 "cannot forward " 406 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 407 ip6_sprintf(ip6bufs, &ip6->ip6_src), 408 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 409 ip6->ip6_nxt, 410 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 411 } 412 if (mcopy) 413 icmp6_error(mcopy, ICMP6_DST_UNREACH, 414 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 415 goto bad; 416 } 417 418 /* 419 * Destination scope check: if a packet is going to break the scope 420 * zone of packet's destination address, discard it. This case should 421 * usually be prevented by appropriately-configured routing table, but 422 * we need an explicit check because we may mistakenly forward the 423 * packet to a different zone by (e.g.) a default route. 424 */ 425 dst_in6 = ip6->ip6_dst; 426 if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 || 427 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 428 inzone != outzone) { 429 V_ip6stat.ip6s_cantforward++; 430 V_ip6stat.ip6s_badscope++; 431 goto bad; 432 } 433 434 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 435 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 436 if (mcopy) { 437 u_long mtu; 438 #ifdef IPSEC 439 struct secpolicy *sp; 440 int ipsecerror; 441 size_t ipsechdrsiz; 442 #endif /* IPSEC */ 443 444 mtu = IN6_LINKMTU(rt->rt_ifp); 445 #ifdef IPSEC 446 /* 447 * When we do IPsec tunnel ingress, we need to play 448 * with the link value (decrement IPsec header size 449 * from mtu value). The code is much simpler than v4 450 * case, as we have the outgoing interface for 451 * encapsulated packet as "rt->rt_ifp". 452 */ 453 sp = ipsec_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 454 IP_FORWARDING, &ipsecerror); 455 if (sp) { 456 ipsechdrsiz = ipsec_hdrsiz(mcopy, 457 IPSEC_DIR_OUTBOUND, NULL); 458 if (ipsechdrsiz < mtu) 459 mtu -= ipsechdrsiz; 460 } 461 462 /* 463 * if mtu becomes less than minimum MTU, 464 * tell minimum MTU (and I'll need to fragment it). 465 */ 466 if (mtu < IPV6_MMTU) 467 mtu = IPV6_MMTU; 468 #endif /* IPSEC */ 469 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 470 } 471 goto bad; 472 } 473 474 if (rt->rt_flags & RTF_GATEWAY) 475 dst = (struct sockaddr_in6 *)rt->rt_gateway; 476 477 /* 478 * If we are to forward the packet using the same interface 479 * as one we got the packet from, perhaps we should send a redirect 480 * to sender to shortcut a hop. 481 * Only send redirect if source is sending directly to us, 482 * and if packet was not source routed (or has any options). 483 * Also, don't send redirect if forwarding using a route 484 * modified by a redirect. 485 */ 486 if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 487 #ifdef IPSEC 488 !ipsecrt && 489 #endif /* IPSEC */ 490 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 491 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 492 /* 493 * If the incoming interface is equal to the outgoing 494 * one, and the link attached to the interface is 495 * point-to-point, then it will be highly probable 496 * that a routing loop occurs. Thus, we immediately 497 * drop the packet and send an ICMPv6 error message. 498 * 499 * type/code is based on suggestion by Rich Draves. 500 * not sure if it is the best pick. 501 */ 502 icmp6_error(mcopy, ICMP6_DST_UNREACH, 503 ICMP6_DST_UNREACH_ADDR, 0); 504 goto bad; 505 } 506 type = ND_REDIRECT; 507 } 508 509 /* 510 * Fake scoped addresses. Note that even link-local source or 511 * destinaion can appear, if the originating node just sends the 512 * packet to us (without address resolution for the destination). 513 * Since both icmp6_error and icmp6_redirect_output fill the embedded 514 * link identifiers, we can do this stuff after making a copy for 515 * returning an error. 516 */ 517 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 518 /* 519 * See corresponding comments in ip6_output. 520 * XXX: but is it possible that ip6_forward() sends a packet 521 * to a loopback interface? I don't think so, and thus 522 * I bark here. (jinmei@kame.net) 523 * XXX: it is common to route invalid packets to loopback. 524 * also, the codepath will be visited on use of ::1 in 525 * rthdr. (itojun) 526 */ 527 #if 1 528 if (0) 529 #else 530 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 531 #endif 532 { 533 printf("ip6_forward: outgoing interface is loopback. " 534 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 535 ip6_sprintf(ip6bufs, &ip6->ip6_src), 536 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 537 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 538 if_name(rt->rt_ifp)); 539 } 540 541 /* we can just use rcvif in forwarding. */ 542 origifp = m->m_pkthdr.rcvif; 543 } 544 else 545 origifp = rt->rt_ifp; 546 /* 547 * clear embedded scope identifiers if necessary. 548 * in6_clearscope will touch the addresses only when necessary. 549 */ 550 in6_clearscope(&ip6->ip6_src); 551 in6_clearscope(&ip6->ip6_dst); 552 553 /* Jump over all PFIL processing if hooks are not active. */ 554 if (!PFIL_HOOKED(&V_inet6_pfil_hook)) 555 goto pass; 556 557 /* Run through list of hooks for output packets. */ 558 error = pfil_run_hooks(&V_inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, NULL); 559 if (error != 0) 560 goto senderr; 561 if (m == NULL) 562 goto freecopy; 563 ip6 = mtod(m, struct ip6_hdr *); 564 565 pass: 566 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 567 if (error) { 568 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 569 V_ip6stat.ip6s_cantforward++; 570 } else { 571 V_ip6stat.ip6s_forward++; 572 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 573 if (type) 574 V_ip6stat.ip6s_redirectsent++; 575 else { 576 if (mcopy) 577 goto freecopy; 578 } 579 } 580 581 senderr: 582 if (mcopy == NULL) 583 goto out; 584 switch (error) { 585 case 0: 586 if (type == ND_REDIRECT) { 587 icmp6_redirect_output(mcopy, rt); 588 goto out; 589 } 590 goto freecopy; 591 592 case EMSGSIZE: 593 /* xxx MTU is constant in PPP? */ 594 goto freecopy; 595 596 case ENOBUFS: 597 /* Tell source to slow down like source quench in IP? */ 598 goto freecopy; 599 600 case ENETUNREACH: /* shouldn't happen, checked above */ 601 case EHOSTUNREACH: 602 case ENETDOWN: 603 case EHOSTDOWN: 604 default: 605 type = ICMP6_DST_UNREACH; 606 code = ICMP6_DST_UNREACH_ADDR; 607 break; 608 } 609 icmp6_error(mcopy, type, code, 0); 610 goto out; 611 612 freecopy: 613 m_freem(mcopy); 614 goto out; 615 bad: 616 m_freem(m); 617 out: 618 if (rt != NULL 619 #ifdef IPSEC 620 && !ipsecrt 621 #endif 622 ) 623 RTFREE(rt); 624 } 625