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