1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the project nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $ 32 */ 33 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_ipstealth.h" 38 #include "opt_sctp.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/if_var.h> 54 #include <net/if_private.h> 55 #include <net/netisr.h> 56 #include <net/route.h> 57 #include <net/route/nhop.h> 58 #include <net/pfil.h> 59 60 #include <netinet/in.h> 61 #include <netinet/in_var.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/ip.h> 64 #include <netinet/ip_var.h> 65 #include <netinet6/in6_var.h> 66 #include <netinet/ip6.h> 67 #include <netinet6/in6_fib.h> 68 #include <netinet6/ip6_var.h> 69 #include <netinet6/scope6_var.h> 70 #include <netinet/icmp6.h> 71 #include <netinet6/nd6.h> 72 73 #include <netinet/in_pcb.h> 74 75 #include <netipsec/ipsec_support.h> 76 77 #if defined(SCTP) || defined(SCTP_SUPPORT) 78 #include <netinet/sctp_crc32.h> 79 #endif 80 81 /* 82 * Forward a packet. If some error occurs return the sender 83 * an icmp packet. Note we can't always generate a meaningful 84 * icmp message because icmp doesn't have a large enough repertoire 85 * of codes and types. 86 * 87 * If not forwarding, just drop the packet. This could be confusing 88 * if ipforwarding was zero but some routing protocol was advancing 89 * us as a gateway to somewhere. However, we must let the routing 90 * protocol deal with that. 91 * 92 */ 93 void 94 ip6_forward(struct mbuf *m, int srcrt) 95 { 96 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 97 struct sockaddr_in6 dst; 98 struct nhop_object *nh = NULL; 99 int error, type = 0, code = 0; 100 struct mbuf *mcopy = NULL; 101 struct ifnet *origifp; /* maybe unnecessary */ 102 u_int32_t inzone, outzone; 103 struct in6_addr odst; 104 struct m_tag *fwd_tag; 105 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN]; 106 107 /* 108 * Do not forward packets to multicast destination (should be handled 109 * by ip6_mforward(). 110 * Do not forward packets with unspecified source. It was discussed 111 * in July 2000, on the ipngwg mailing list. 112 */ 113 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 114 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 115 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src) || 116 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) { 117 IP6STAT_INC(ip6s_cantforward); 118 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 119 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) { 120 log(LOG_DEBUG, 121 "cannot forward " 122 "from %s to %s nxt %d received on %s\n", 123 ip6_sprintf(ip6bufs, &ip6->ip6_src), 124 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 125 ip6->ip6_nxt, 126 if_name(m->m_pkthdr.rcvif)); 127 } 128 m_freem(m); 129 return; 130 } 131 132 if ( 133 #ifdef IPSTEALTH 134 V_ip6stealth == 0 && 135 #endif 136 ip6->ip6_hlim <= IPV6_HLIMDEC) { 137 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 138 icmp6_error(m, ICMP6_TIME_EXCEEDED, 139 ICMP6_TIME_EXCEED_TRANSIT, 0); 140 return; 141 } 142 143 /* 144 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 145 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 146 * we need to generate an ICMP6 message to the src. 147 * Thanks to M_EXT, in most cases copy will not occur. 148 * 149 * It is important to save it before IPsec processing as IPsec 150 * processing may modify the mbuf. 151 */ 152 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 153 M_NOWAIT); 154 #ifdef IPSTEALTH 155 if (V_ip6stealth == 0) 156 #endif 157 ip6->ip6_hlim -= IPV6_HLIMDEC; 158 159 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 160 if (IPSEC_ENABLED(ipv6)) { 161 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) { 162 /* mbuf consumed by IPsec */ 163 m_freem(mcopy); 164 if (error != EINPROGRESS) 165 IP6STAT_INC(ip6s_cantforward); 166 return; 167 } 168 /* No IPsec processing required */ 169 } 170 #endif 171 /* 172 * ip6_forward() operates with IPv6 addresses with deembedded scope. 173 * 174 * There are 3 sources of IPv6 destination address: 175 * 176 * 1) ip6_input(), where ip6_dst contains deembedded address. 177 * In order to deal with forwarding of link-local packets, 178 * calculate the scope based on input interface (RFC 4007, clause 9). 179 * 2) packet filters changing ip6_dst directly. It would embed scope 180 * for LL addresses, so in6_localip() performs properly. 181 * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed 182 * scope for the nexthop. 183 */ 184 bzero(&dst, sizeof(struct sockaddr_in6)); 185 dst.sin6_family = AF_INET6; 186 dst.sin6_addr = ip6->ip6_dst; 187 dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif); 188 again: 189 nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id, 190 NHR_REF, m->m_pkthdr.flowid); 191 if (nh == NULL) { 192 IP6STAT_INC(ip6s_noroute); 193 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 194 if (mcopy) { 195 icmp6_error(mcopy, ICMP6_DST_UNREACH, 196 ICMP6_DST_UNREACH_NOROUTE, 0); 197 } 198 goto bad; 199 } 200 201 if (nh->nh_flags & (NHF_BLACKHOLE | NHF_REJECT)) { 202 IP6STAT_INC(ip6s_cantforward); 203 if (mcopy != NULL) { 204 if (nh->nh_flags & NHF_REJECT) { 205 icmp6_error(mcopy, ICMP6_DST_UNREACH, 206 ICMP6_DST_UNREACH_REJECT, 0); 207 } else 208 m_freem(mcopy); 209 } 210 goto bad; 211 } 212 213 /* 214 * Source scope check: if a packet can't be delivered to its 215 * destination for the reason that the destination is beyond the scope 216 * of the source address, discard the packet and return an icmp6 217 * destination unreachable error with Code 2 (beyond scope of source 218 * address). 219 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1] 220 */ 221 outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp); 222 inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif); 223 if (inzone != outzone) { 224 IP6STAT_INC(ip6s_cantforward); 225 IP6STAT_INC(ip6s_badscope); 226 in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard); 227 228 if (V_ip6_log_cannot_forward && ip6_log_ratelimit()) { 229 log(LOG_DEBUG, 230 "cannot forward " 231 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 232 ip6_sprintf(ip6bufs, &ip6->ip6_src), 233 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 234 ip6->ip6_nxt, 235 if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp)); 236 } 237 if (mcopy) 238 icmp6_error(mcopy, ICMP6_DST_UNREACH, 239 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 240 goto bad; 241 } 242 243 /* 244 * Destination scope check: if a packet is going to break the scope 245 * zone of packet's destination address, discard it. This case should 246 * usually be prevented by appropriately-configured routing table, but 247 * we need an explicit check because we may mistakenly forward the 248 * packet to a different zone by (e.g.) a default route. 249 */ 250 inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif); 251 outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp); 252 253 if (inzone != outzone) { 254 IP6STAT_INC(ip6s_cantforward); 255 IP6STAT_INC(ip6s_badscope); 256 goto bad; 257 } 258 259 if (nh->nh_flags & NHF_GATEWAY) { 260 /* Store gateway address in deembedded form */ 261 dst.sin6_addr = nh->gw6_sa.sin6_addr; 262 dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr)); 263 in6_clearscope(&dst.sin6_addr); 264 } 265 266 /* 267 * If we are to forward the packet using the same interface 268 * as one we got the packet from, perhaps we should send a redirect 269 * to sender to shortcut a hop. 270 * Only send redirect if source is sending directly to us, 271 * and if packet was not source routed (or has any options). 272 * Also, don't send redirect if forwarding using a route 273 * modified by a redirect. 274 */ 275 if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt && 276 (nh->nh_flags & NHF_REDIRECT) == 0) 277 type = ND_REDIRECT; 278 279 /* 280 * Fake scoped addresses. Note that even link-local source or 281 * destinaion can appear, if the originating node just sends the 282 * packet to us (without address resolution for the destination). 283 * Since both icmp6_error and icmp6_redirect_output fill the embedded 284 * link identifiers, we can do this stuff after making a copy for 285 * returning an error. 286 */ 287 if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) { 288 /* 289 * See corresponding comments in ip6_output. 290 * XXX: but is it possible that ip6_forward() sends a packet 291 * to a loopback interface? I don't think so, and thus 292 * I bark here. (jinmei@kame.net) 293 * XXX: it is common to route invalid packets to loopback. 294 * also, the codepath will be visited on use of ::1 in 295 * rthdr. (itojun) 296 */ 297 #if 1 298 if (0) 299 #else 300 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 301 #endif 302 { 303 printf("ip6_forward: outgoing interface is loopback. " 304 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 305 ip6_sprintf(ip6bufs, &ip6->ip6_src), 306 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 307 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 308 if_name(nh->nh_ifp)); 309 } 310 311 /* we can just use rcvif in forwarding. */ 312 origifp = m->m_pkthdr.rcvif; 313 } 314 else 315 origifp = nh->nh_ifp; 316 /* 317 * clear embedded scope identifiers if necessary. 318 * in6_clearscope will touch the addresses only when necessary. 319 */ 320 in6_clearscope(&ip6->ip6_src); 321 in6_clearscope(&ip6->ip6_dst); 322 323 /* Jump over all PFIL processing if hooks are not active. */ 324 if (!PFIL_HOOKED_OUT(V_inet6_pfil_head)) 325 goto pass; 326 327 odst = ip6->ip6_dst; 328 /* Run through list of hooks for forwarded packets. */ 329 if (pfil_mbuf_fwd(V_inet6_pfil_head, &m, nh->nh_ifp, 330 NULL) != PFIL_PASS) 331 goto freecopy; 332 ip6 = mtod(m, struct ip6_hdr *); 333 334 /* See if destination IP address was changed by packet filter. */ 335 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) { 336 m->m_flags |= M_SKIP_FIREWALL; 337 /* If destination is now ourself drop to ip6_input(). */ 338 if (in6_localip(&ip6->ip6_dst)) 339 m->m_flags |= M_FASTFWD_OURS; 340 else { 341 NH_FREE(nh); 342 343 /* Update address and scopeid. Assume scope is embedded */ 344 dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst)); 345 dst.sin6_addr = ip6->ip6_dst; 346 in6_clearscope(&dst.sin6_addr); 347 goto again; /* Redo the routing table lookup. */ 348 } 349 } 350 351 /* See if local, if yes, send it to netisr. */ 352 if (m->m_flags & M_FASTFWD_OURS) { 353 if (m->m_pkthdr.rcvif == NULL) 354 m->m_pkthdr.rcvif = V_loif; 355 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) { 356 m->m_pkthdr.csum_flags |= 357 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR; 358 m->m_pkthdr.csum_data = 0xffff; 359 } 360 #if defined(SCTP) || defined(SCTP_SUPPORT) 361 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6) 362 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID; 363 #endif 364 error = netisr_queue(NETISR_IPV6, m); 365 goto out; 366 } 367 /* Or forward to some other address? */ 368 if ((m->m_flags & M_IP6_NEXTHOP) && 369 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) { 370 struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1); 371 372 /* Update address and scopeid. Assume scope is embedded */ 373 dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr)); 374 dst.sin6_addr = gw6->sin6_addr; 375 in6_clearscope(&dst.sin6_addr); 376 377 m->m_flags |= M_SKIP_FIREWALL; 378 m->m_flags &= ~M_IP6_NEXTHOP; 379 m_tag_delete(m, fwd_tag); 380 NH_FREE(nh); 381 goto again; 382 } 383 384 pass: 385 /* See if the size was changed by the packet filter. */ 386 /* TODO: change to nh->nh_mtu */ 387 if (m->m_pkthdr.len > IN6_LINKMTU(nh->nh_ifp)) { 388 in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig); 389 if (mcopy) 390 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 391 IN6_LINKMTU(nh->nh_ifp)); 392 goto bad; 393 } 394 395 /* 396 * If TCP/UDP header still needs a valid checksum and interface will not 397 * calculate it for us, do it here. 398 */ 399 if (__predict_false(m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6 & 400 ~nh->nh_ifp->if_hwassist)) { 401 int offset = ip6_lasthdr(m, 0, IPPROTO_IPV6, NULL); 402 403 if (offset < sizeof(struct ip6_hdr) || offset > m->m_pkthdr.len) 404 goto bad; 405 in6_delayed_cksum(m, m->m_pkthdr.len - offset, offset); 406 m->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA_IPV6; 407 } 408 #if defined(SCTP) || defined(SCTP_SUPPORT) 409 if (__predict_false(m->m_pkthdr.csum_flags & CSUM_IP6_SCTP & 410 ~nh->nh_ifp->if_hwassist)) { 411 int offset = ip6_lasthdr(m, 0, IPPROTO_IPV6, NULL); 412 413 sctp_delayed_cksum(m, offset); 414 m->m_pkthdr.csum_flags &= ~CSUM_IP6_SCTP; 415 } 416 #endif 417 418 /* Currently LLE layer stores embedded IPv6 addresses */ 419 if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) { 420 in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id); 421 dst.sin6_scope_id = 0; 422 } 423 error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL); 424 if (error) { 425 in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard); 426 IP6STAT_INC(ip6s_cantforward); 427 } else { 428 IP6STAT_INC(ip6s_forward); 429 in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward); 430 if (type) 431 IP6STAT_INC(ip6s_redirectsent); 432 else { 433 if (mcopy) 434 goto freecopy; 435 } 436 } 437 438 if (mcopy == NULL) 439 goto out; 440 switch (error) { 441 case 0: 442 if (type == ND_REDIRECT) { 443 icmp6_redirect_output(mcopy, nh); 444 goto out; 445 } 446 goto freecopy; 447 448 case EMSGSIZE: 449 /* xxx MTU is constant in PPP? */ 450 goto freecopy; 451 452 case ENOBUFS: 453 /* Tell source to slow down like source quench in IP? */ 454 goto freecopy; 455 456 case ENETUNREACH: /* shouldn't happen, checked above */ 457 case EHOSTUNREACH: 458 case ENETDOWN: 459 case EHOSTDOWN: 460 default: 461 type = ICMP6_DST_UNREACH; 462 code = ICMP6_DST_UNREACH_ADDR; 463 break; 464 } 465 icmp6_error(mcopy, type, code, 0); 466 goto out; 467 468 freecopy: 469 m_freem(mcopy); 470 goto out; 471 bad: 472 m_freem(m); 473 out: 474 if (nh != NULL) 475 NH_FREE(nh); 476 } 477