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 <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_ipstealth.h" 41 #include "opt_sctp.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/domain.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/errno.h> 51 #include <sys/time.h> 52 #include <sys/kernel.h> 53 #include <sys/syslog.h> 54 55 #include <net/if.h> 56 #include <net/if_var.h> 57 #include <net/if_private.h> 58 #include <net/netisr.h> 59 #include <net/route.h> 60 #include <net/route/nhop.h> 61 #include <net/pfil.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_var.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/ip.h> 67 #include <netinet/ip_var.h> 68 #include <netinet6/in6_var.h> 69 #include <netinet/ip6.h> 70 #include <netinet6/in6_fib.h> 71 #include <netinet6/ip6_var.h> 72 #include <netinet6/scope6_var.h> 73 #include <netinet/icmp6.h> 74 #include <netinet6/nd6.h> 75 76 #include <netinet/in_pcb.h> 77 78 #include <netipsec/ipsec_support.h> 79 80 /* 81 * Forward a packet. If some error occurs return the sender 82 * an icmp packet. Note we can't always generate a meaningful 83 * icmp message because icmp doesn't have a large enough repertoire 84 * of codes and types. 85 * 86 * If not forwarding, just drop the packet. This could be confusing 87 * if ipforwarding was zero but some routing protocol was advancing 88 * us as a gateway to somewhere. However, we must let the routing 89 * protocol deal with that. 90 * 91 */ 92 void 93 ip6_forward(struct mbuf *m, int srcrt) 94 { 95 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 96 struct sockaddr_in6 dst; 97 struct nhop_object *nh = NULL; 98 int error, type = 0, code = 0; 99 struct mbuf *mcopy = NULL; 100 struct ifnet *origifp; /* maybe unnecessary */ 101 u_int32_t inzone, outzone; 102 struct in6_addr odst; 103 struct m_tag *fwd_tag; 104 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN]; 105 106 /* 107 * Do not forward packets to multicast destination (should be handled 108 * by ip6_mforward(). 109 * Do not forward packets with unspecified source. It was discussed 110 * in July 2000, on the ipngwg mailing list. 111 */ 112 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 113 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 114 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 115 IP6STAT_INC(ip6s_cantforward); 116 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 117 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 118 V_ip6_log_time = time_uptime; 119 log(LOG_DEBUG, 120 "cannot forward " 121 "from %s to %s nxt %d received on %s\n", 122 ip6_sprintf(ip6bufs, &ip6->ip6_src), 123 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 124 ip6->ip6_nxt, 125 if_name(m->m_pkthdr.rcvif)); 126 } 127 m_freem(m); 128 return; 129 } 130 131 if ( 132 #ifdef IPSTEALTH 133 V_ip6stealth == 0 && 134 #endif 135 ip6->ip6_hlim <= IPV6_HLIMDEC) { 136 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 137 icmp6_error(m, ICMP6_TIME_EXCEEDED, 138 ICMP6_TIME_EXCEED_TRANSIT, 0); 139 return; 140 } 141 142 /* 143 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 144 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 145 * we need to generate an ICMP6 message to the src. 146 * Thanks to M_EXT, in most cases copy will not occur. 147 * 148 * It is important to save it before IPsec processing as IPsec 149 * processing may modify the mbuf. 150 */ 151 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 152 M_NOWAIT); 153 #ifdef IPSTEALTH 154 if (V_ip6stealth == 0) 155 #endif 156 ip6->ip6_hlim -= IPV6_HLIMDEC; 157 158 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 159 if (IPSEC_ENABLED(ipv6)) { 160 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) { 161 /* mbuf consumed by IPsec */ 162 m_freem(mcopy); 163 if (error != EINPROGRESS) 164 IP6STAT_INC(ip6s_cantforward); 165 return; 166 } 167 /* No IPsec processing required */ 168 } 169 #endif 170 /* 171 * ip6_forward() operates with IPv6 addresses with deembedded scope. 172 * 173 * There are 3 sources of IPv6 destination address: 174 * 175 * 1) ip6_input(), where ip6_dst contains deembedded address. 176 * In order to deal with forwarding of link-local packets, 177 * calculate the scope based on input interface (RFC 4007, clause 9). 178 * 2) packet filters changing ip6_dst directly. It would embed scope 179 * for LL addresses, so in6_localip() performs properly. 180 * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed 181 * scope for the nexthop. 182 */ 183 bzero(&dst, sizeof(struct sockaddr_in6)); 184 dst.sin6_family = AF_INET6; 185 dst.sin6_addr = ip6->ip6_dst; 186 dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif); 187 again: 188 nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id, 189 NHR_REF, m->m_pkthdr.flowid); 190 if (nh == NULL) { 191 IP6STAT_INC(ip6s_noroute); 192 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 193 if (mcopy) { 194 icmp6_error(mcopy, ICMP6_DST_UNREACH, 195 ICMP6_DST_UNREACH_NOROUTE, 0); 196 } 197 goto bad; 198 } 199 200 if (nh->nh_flags & (NHF_BLACKHOLE | NHF_REJECT)) { 201 IP6STAT_INC(ip6s_cantforward); 202 if ((nh->nh_flags & NHF_REJECT) && (mcopy != NULL)) { 203 icmp6_error(mcopy, ICMP6_DST_UNREACH, 204 ICMP6_DST_UNREACH_REJECT, 0); 205 } 206 goto bad; 207 } 208 209 /* 210 * Source scope check: if a packet can't be delivered to its 211 * destination for the reason that the destination is beyond the scope 212 * of the source address, discard the packet and return an icmp6 213 * destination unreachable error with Code 2 (beyond scope of source 214 * address). 215 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1] 216 */ 217 outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp); 218 inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif); 219 if (inzone != outzone) { 220 IP6STAT_INC(ip6s_cantforward); 221 IP6STAT_INC(ip6s_badscope); 222 in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard); 223 224 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 225 V_ip6_log_time = time_uptime; 226 log(LOG_DEBUG, 227 "cannot forward " 228 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 229 ip6_sprintf(ip6bufs, &ip6->ip6_src), 230 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 231 ip6->ip6_nxt, 232 if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp)); 233 } 234 if (mcopy) 235 icmp6_error(mcopy, ICMP6_DST_UNREACH, 236 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 237 goto bad; 238 } 239 240 /* 241 * Destination scope check: if a packet is going to break the scope 242 * zone of packet's destination address, discard it. This case should 243 * usually be prevented by appropriately-configured routing table, but 244 * we need an explicit check because we may mistakenly forward the 245 * packet to a different zone by (e.g.) a default route. 246 */ 247 inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif); 248 outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp); 249 250 if (inzone != outzone) { 251 IP6STAT_INC(ip6s_cantforward); 252 IP6STAT_INC(ip6s_badscope); 253 goto bad; 254 } 255 256 if (nh->nh_flags & NHF_GATEWAY) { 257 /* Store gateway address in deembedded form */ 258 dst.sin6_addr = nh->gw6_sa.sin6_addr; 259 dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr)); 260 in6_clearscope(&dst.sin6_addr); 261 } 262 263 /* 264 * If we are to forward the packet using the same interface 265 * as one we got the packet from, perhaps we should send a redirect 266 * to sender to shortcut a hop. 267 * Only send redirect if source is sending directly to us, 268 * and if packet was not source routed (or has any options). 269 * Also, don't send redirect if forwarding using a route 270 * modified by a redirect. 271 */ 272 if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt && 273 (nh->nh_flags & NHF_REDIRECT) == 0) 274 type = ND_REDIRECT; 275 276 /* 277 * Fake scoped addresses. Note that even link-local source or 278 * destinaion can appear, if the originating node just sends the 279 * packet to us (without address resolution for the destination). 280 * Since both icmp6_error and icmp6_redirect_output fill the embedded 281 * link identifiers, we can do this stuff after making a copy for 282 * returning an error. 283 */ 284 if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) { 285 /* 286 * See corresponding comments in ip6_output. 287 * XXX: but is it possible that ip6_forward() sends a packet 288 * to a loopback interface? I don't think so, and thus 289 * I bark here. (jinmei@kame.net) 290 * XXX: it is common to route invalid packets to loopback. 291 * also, the codepath will be visited on use of ::1 in 292 * rthdr. (itojun) 293 */ 294 #if 1 295 if (0) 296 #else 297 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 298 #endif 299 { 300 printf("ip6_forward: outgoing interface is loopback. " 301 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 302 ip6_sprintf(ip6bufs, &ip6->ip6_src), 303 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 304 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 305 if_name(nh->nh_ifp)); 306 } 307 308 /* we can just use rcvif in forwarding. */ 309 origifp = m->m_pkthdr.rcvif; 310 } 311 else 312 origifp = nh->nh_ifp; 313 /* 314 * clear embedded scope identifiers if necessary. 315 * in6_clearscope will touch the addresses only when necessary. 316 */ 317 in6_clearscope(&ip6->ip6_src); 318 in6_clearscope(&ip6->ip6_dst); 319 320 /* Jump over all PFIL processing if hooks are not active. */ 321 if (!PFIL_HOOKED_OUT(V_inet6_pfil_head)) 322 goto pass; 323 324 odst = ip6->ip6_dst; 325 /* Run through list of hooks for forwarded packets. */ 326 if (pfil_mbuf_out(V_inet6_pfil_head, &m, nh->nh_ifp, 327 NULL) != PFIL_PASS) 328 goto freecopy; 329 ip6 = mtod(m, struct ip6_hdr *); 330 331 /* See if destination IP address was changed by packet filter. */ 332 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) { 333 m->m_flags |= M_SKIP_FIREWALL; 334 /* If destination is now ourself drop to ip6_input(). */ 335 if (in6_localip(&ip6->ip6_dst)) 336 m->m_flags |= M_FASTFWD_OURS; 337 else { 338 NH_FREE(nh); 339 340 /* Update address and scopeid. Assume scope is embedded */ 341 dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst)); 342 dst.sin6_addr = ip6->ip6_dst; 343 in6_clearscope(&dst.sin6_addr); 344 goto again; /* Redo the routing table lookup. */ 345 } 346 } 347 348 /* See if local, if yes, send it to netisr. */ 349 if (m->m_flags & M_FASTFWD_OURS) { 350 if (m->m_pkthdr.rcvif == NULL) 351 m->m_pkthdr.rcvif = V_loif; 352 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) { 353 m->m_pkthdr.csum_flags |= 354 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR; 355 m->m_pkthdr.csum_data = 0xffff; 356 } 357 #if defined(SCTP) || defined(SCTP_SUPPORT) 358 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6) 359 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID; 360 #endif 361 error = netisr_queue(NETISR_IPV6, m); 362 goto out; 363 } 364 /* Or forward to some other address? */ 365 if ((m->m_flags & M_IP6_NEXTHOP) && 366 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) { 367 struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1); 368 369 /* Update address and scopeid. Assume scope is embedded */ 370 dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr)); 371 dst.sin6_addr = gw6->sin6_addr; 372 in6_clearscope(&dst.sin6_addr); 373 374 m->m_flags |= M_SKIP_FIREWALL; 375 m->m_flags &= ~M_IP6_NEXTHOP; 376 m_tag_delete(m, fwd_tag); 377 NH_FREE(nh); 378 goto again; 379 } 380 381 pass: 382 /* See if the size was changed by the packet filter. */ 383 /* TODO: change to nh->nh_mtu */ 384 if (m->m_pkthdr.len > IN6_LINKMTU(nh->nh_ifp)) { 385 in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig); 386 if (mcopy) 387 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 388 IN6_LINKMTU(nh->nh_ifp)); 389 goto bad; 390 } 391 392 /* Currently LLE layer stores embedded IPv6 addresses */ 393 if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) { 394 in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id); 395 dst.sin6_scope_id = 0; 396 } 397 error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL); 398 if (error) { 399 in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard); 400 IP6STAT_INC(ip6s_cantforward); 401 } else { 402 IP6STAT_INC(ip6s_forward); 403 in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward); 404 if (type) 405 IP6STAT_INC(ip6s_redirectsent); 406 else { 407 if (mcopy) 408 goto freecopy; 409 } 410 } 411 412 if (mcopy == NULL) 413 goto out; 414 switch (error) { 415 case 0: 416 if (type == ND_REDIRECT) { 417 icmp6_redirect_output(mcopy, nh); 418 goto out; 419 } 420 goto freecopy; 421 422 case EMSGSIZE: 423 /* xxx MTU is constant in PPP? */ 424 goto freecopy; 425 426 case ENOBUFS: 427 /* Tell source to slow down like source quench in IP? */ 428 goto freecopy; 429 430 case ENETUNREACH: /* shouldn't happen, checked above */ 431 case EHOSTUNREACH: 432 case ENETDOWN: 433 case EHOSTDOWN: 434 default: 435 type = ICMP6_DST_UNREACH; 436 code = ICMP6_DST_UNREACH_ADDR; 437 break; 438 } 439 icmp6_error(mcopy, type, code, 0); 440 goto out; 441 442 freecopy: 443 m_freem(mcopy); 444 goto out; 445 bad: 446 m_freem(m); 447 out: 448 if (nh != NULL) 449 NH_FREE(nh); 450 } 451