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/pfil.h> 60 61 #include <netinet/in.h> 62 #include <netinet/in_var.h> 63 #include <netinet/in_systm.h> 64 #include <netinet/ip.h> 65 #include <netinet/ip_var.h> 66 #include <netinet6/in6_var.h> 67 #include <netinet/ip6.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 /* 78 * Forward a packet. If some error occurs return the sender 79 * an icmp packet. Note we can't always generate a meaningful 80 * icmp message because icmp doesn't have a large enough repertoire 81 * of codes and types. 82 * 83 * If not forwarding, just drop the packet. This could be confusing 84 * if ipforwarding was zero but some routing protocol was advancing 85 * us as a gateway to somewhere. However, we must let the routing 86 * protocol deal with that. 87 * 88 */ 89 void 90 ip6_forward(struct mbuf *m, int srcrt) 91 { 92 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 93 struct sockaddr_in6 *dst = NULL; 94 struct rtentry *rt = NULL; 95 struct route_in6 rin6; 96 int error, type = 0, code = 0; 97 struct mbuf *mcopy = NULL; 98 struct ifnet *origifp; /* maybe unnecessary */ 99 u_int32_t inzone, outzone; 100 struct in6_addr src_in6, dst_in6, odst; 101 struct m_tag *fwd_tag; 102 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN]; 103 104 /* 105 * Do not forward packets to multicast destination (should be handled 106 * by ip6_mforward(). 107 * Do not forward packets with unspecified source. It was discussed 108 * in July 2000, on the ipngwg mailing list. 109 */ 110 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 111 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 112 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 113 IP6STAT_INC(ip6s_cantforward); 114 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 115 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 116 V_ip6_log_time = time_uptime; 117 log(LOG_DEBUG, 118 "cannot forward " 119 "from %s to %s nxt %d received on %s\n", 120 ip6_sprintf(ip6bufs, &ip6->ip6_src), 121 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 122 ip6->ip6_nxt, 123 if_name(m->m_pkthdr.rcvif)); 124 } 125 m_freem(m); 126 return; 127 } 128 129 if ( 130 #ifdef IPSTEALTH 131 V_ip6stealth == 0 && 132 #endif 133 ip6->ip6_hlim <= IPV6_HLIMDEC) { 134 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 135 icmp6_error(m, ICMP6_TIME_EXCEEDED, 136 ICMP6_TIME_EXCEED_TRANSIT, 0); 137 return; 138 } 139 140 /* 141 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 142 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 143 * we need to generate an ICMP6 message to the src. 144 * Thanks to M_EXT, in most cases copy will not occur. 145 * 146 * It is important to save it before IPsec processing as IPsec 147 * processing may modify the mbuf. 148 */ 149 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 150 M_NOWAIT); 151 #ifdef IPSTEALTH 152 if (V_ip6stealth == 0) 153 #endif 154 ip6->ip6_hlim -= IPV6_HLIMDEC; 155 156 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 157 if (IPSEC_ENABLED(ipv6)) { 158 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) { 159 /* mbuf consumed by IPsec */ 160 m_freem(mcopy); 161 if (error != EINPROGRESS) 162 IP6STAT_INC(ip6s_cantforward); 163 return; 164 } 165 /* No IPsec processing required */ 166 } 167 #endif 168 again: 169 bzero(&rin6, sizeof(struct route_in6)); 170 dst = (struct sockaddr_in6 *)&rin6.ro_dst; 171 dst->sin6_len = sizeof(struct sockaddr_in6); 172 dst->sin6_family = AF_INET6; 173 dst->sin6_addr = ip6->ip6_dst; 174 again2: 175 rin6.ro_rt = in6_rtalloc1((struct sockaddr *)dst, 0, 0, M_GETFIB(m)); 176 rt = rin6.ro_rt; 177 if (rin6.ro_rt != NULL) 178 RT_UNLOCK(rin6.ro_rt); 179 else { 180 IP6STAT_INC(ip6s_noroute); 181 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 182 if (mcopy) { 183 icmp6_error(mcopy, ICMP6_DST_UNREACH, 184 ICMP6_DST_UNREACH_NOROUTE, 0); 185 } 186 goto bad; 187 } 188 189 /* 190 * Source scope check: if a packet can't be delivered to its 191 * destination for the reason that the destination is beyond the scope 192 * of the source address, discard the packet and return an icmp6 193 * destination unreachable error with Code 2 (beyond scope of source 194 * address). We use a local copy of ip6_src, since in6_setscope() 195 * will possibly modify its first argument. 196 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1] 197 */ 198 src_in6 = ip6->ip6_src; 199 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) { 200 /* XXX: this should not happen */ 201 IP6STAT_INC(ip6s_cantforward); 202 IP6STAT_INC(ip6s_badscope); 203 goto bad; 204 } 205 if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) { 206 IP6STAT_INC(ip6s_cantforward); 207 IP6STAT_INC(ip6s_badscope); 208 goto bad; 209 } 210 if (inzone != outzone) { 211 IP6STAT_INC(ip6s_cantforward); 212 IP6STAT_INC(ip6s_badscope); 213 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 214 215 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 216 V_ip6_log_time = time_uptime; 217 log(LOG_DEBUG, 218 "cannot forward " 219 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 220 ip6_sprintf(ip6bufs, &ip6->ip6_src), 221 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 222 ip6->ip6_nxt, 223 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 224 } 225 if (mcopy) 226 icmp6_error(mcopy, ICMP6_DST_UNREACH, 227 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 228 goto bad; 229 } 230 231 /* 232 * Destination scope check: if a packet is going to break the scope 233 * zone of packet's destination address, discard it. This case should 234 * usually be prevented by appropriately-configured routing table, but 235 * we need an explicit check because we may mistakenly forward the 236 * packet to a different zone by (e.g.) a default route. 237 */ 238 dst_in6 = ip6->ip6_dst; 239 if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 || 240 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 241 inzone != outzone) { 242 IP6STAT_INC(ip6s_cantforward); 243 IP6STAT_INC(ip6s_badscope); 244 goto bad; 245 } 246 247 if (rt->rt_flags & RTF_GATEWAY) 248 dst = (struct sockaddr_in6 *)rt->rt_gateway; 249 250 /* 251 * If we are to forward the packet using the same interface 252 * as one we got the packet from, perhaps we should send a redirect 253 * to sender to shortcut a hop. 254 * Only send redirect if source is sending directly to us, 255 * and if packet was not source routed (or has any options). 256 * Also, don't send redirect if forwarding using a route 257 * modified by a redirect. 258 */ 259 if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 260 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) 261 type = ND_REDIRECT; 262 263 /* 264 * Fake scoped addresses. Note that even link-local source or 265 * destinaion can appear, if the originating node just sends the 266 * packet to us (without address resolution for the destination). 267 * Since both icmp6_error and icmp6_redirect_output fill the embedded 268 * link identifiers, we can do this stuff after making a copy for 269 * returning an error. 270 */ 271 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 272 /* 273 * See corresponding comments in ip6_output. 274 * XXX: but is it possible that ip6_forward() sends a packet 275 * to a loopback interface? I don't think so, and thus 276 * I bark here. (jinmei@kame.net) 277 * XXX: it is common to route invalid packets to loopback. 278 * also, the codepath will be visited on use of ::1 in 279 * rthdr. (itojun) 280 */ 281 #if 1 282 if (0) 283 #else 284 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 285 #endif 286 { 287 printf("ip6_forward: outgoing interface is loopback. " 288 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 289 ip6_sprintf(ip6bufs, &ip6->ip6_src), 290 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 291 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 292 if_name(rt->rt_ifp)); 293 } 294 295 /* we can just use rcvif in forwarding. */ 296 origifp = m->m_pkthdr.rcvif; 297 } 298 else 299 origifp = rt->rt_ifp; 300 /* 301 * clear embedded scope identifiers if necessary. 302 * in6_clearscope will touch the addresses only when necessary. 303 */ 304 in6_clearscope(&ip6->ip6_src); 305 in6_clearscope(&ip6->ip6_dst); 306 307 /* Jump over all PFIL processing if hooks are not active. */ 308 if (!PFIL_HOOKED(&V_inet6_pfil_hook)) 309 goto pass; 310 311 odst = ip6->ip6_dst; 312 /* Run through list of hooks for forwarded packets. */ 313 error = pfil_run_hooks(&V_inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, 314 PFIL_FWD, NULL); 315 if (error != 0 || m == NULL) 316 goto freecopy; /* consumed by filter */ 317 ip6 = mtod(m, struct ip6_hdr *); 318 319 /* See if destination IP address was changed by packet filter. */ 320 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) { 321 m->m_flags |= M_SKIP_FIREWALL; 322 /* If destination is now ourself drop to ip6_input(). */ 323 if (in6_localip(&ip6->ip6_dst)) 324 m->m_flags |= M_FASTFWD_OURS; 325 else { 326 RTFREE(rt); 327 goto again; /* Redo the routing table lookup. */ 328 } 329 } 330 331 /* See if local, if yes, send it to netisr. */ 332 if (m->m_flags & M_FASTFWD_OURS) { 333 if (m->m_pkthdr.rcvif == NULL) 334 m->m_pkthdr.rcvif = V_loif; 335 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) { 336 m->m_pkthdr.csum_flags |= 337 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR; 338 m->m_pkthdr.csum_data = 0xffff; 339 } 340 #if defined(SCTP) || defined(SCTP_SUPPORT) 341 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6) 342 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID; 343 #endif 344 error = netisr_queue(NETISR_IPV6, m); 345 goto out; 346 } 347 /* Or forward to some other address? */ 348 if ((m->m_flags & M_IP6_NEXTHOP) && 349 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) { 350 dst = (struct sockaddr_in6 *)&rin6.ro_dst; 351 bcopy((fwd_tag+1), dst, sizeof(struct sockaddr_in6)); 352 m->m_flags |= M_SKIP_FIREWALL; 353 m->m_flags &= ~M_IP6_NEXTHOP; 354 m_tag_delete(m, fwd_tag); 355 RTFREE(rt); 356 goto again2; 357 } 358 359 pass: 360 /* See if the size was changed by the packet filter. */ 361 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 362 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 363 if (mcopy) 364 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 365 IN6_LINKMTU(rt->rt_ifp)); 366 goto bad; 367 } 368 369 error = nd6_output_ifp(rt->rt_ifp, origifp, m, dst, NULL); 370 if (error) { 371 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 372 IP6STAT_INC(ip6s_cantforward); 373 } else { 374 IP6STAT_INC(ip6s_forward); 375 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 376 if (type) 377 IP6STAT_INC(ip6s_redirectsent); 378 else { 379 if (mcopy) 380 goto freecopy; 381 } 382 } 383 384 if (mcopy == NULL) 385 goto out; 386 switch (error) { 387 case 0: 388 if (type == ND_REDIRECT) { 389 icmp6_redirect_output(mcopy, rt); 390 goto out; 391 } 392 goto freecopy; 393 394 case EMSGSIZE: 395 /* xxx MTU is constant in PPP? */ 396 goto freecopy; 397 398 case ENOBUFS: 399 /* Tell source to slow down like source quench in IP? */ 400 goto freecopy; 401 402 case ENETUNREACH: /* shouldn't happen, checked above */ 403 case EHOSTUNREACH: 404 case ENETDOWN: 405 case EHOSTDOWN: 406 default: 407 type = ICMP6_DST_UNREACH; 408 code = ICMP6_DST_UNREACH_ADDR; 409 break; 410 } 411 icmp6_error(mcopy, type, code, 0); 412 goto out; 413 414 freecopy: 415 m_freem(mcopy); 416 goto out; 417 bad: 418 m_freem(m); 419 out: 420 if (rt != NULL) 421 RTFREE(rt); 422 }
Cache object: 49d5d6a45afbab821c314d8f1d8f30dd
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