1 /* $OpenBSD: ip6_forward.c,v 1.112 2023/07/07 08:05:02 bluhm Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei Exp $ */ 3 4 /* 5 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the project nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #include "pf.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/mbuf.h> 38 #include <sys/socket.h> 39 #include <sys/errno.h> 40 #include <sys/time.h> 41 #include <sys/kernel.h> 42 #include <sys/syslog.h> 43 44 #include <net/if.h> 45 #include <net/if_var.h> 46 #include <net/if_enc.h> 47 #include <net/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/ip_var.h> 51 #include <netinet6/in6_var.h> 52 #include <netinet/ip6.h> 53 #include <netinet6/ip6_var.h> 54 #include <netinet/icmp6.h> 55 #include <netinet6/nd6.h> 56 57 #if NPF > 0 58 #include <net/pfvar.h> 59 #endif 60 61 #ifdef IPSEC 62 #include <netinet/ip_ipsp.h> 63 #include <netinet/ip_ah.h> 64 #include <netinet/ip_esp.h> 65 #include <netinet/udp.h> 66 #endif 67 #include <netinet/tcp.h> 68 #include <netinet/tcp_timer.h> 69 #include <netinet/tcp_var.h> 70 71 /* 72 * Forward a packet. If some error occurs return the sender 73 * an icmp packet. Note we can't always generate a meaningful 74 * icmp message because icmp doesn't have a large enough repertoire 75 * of codes and types. 76 * 77 * If not forwarding, just drop the packet. This could be confusing 78 * if ipforwarding was zero but some routing protocol was advancing 79 * us as a gateway to somewhere. However, we must let the routing 80 * protocol deal with that. 81 * 82 */ 83 84 void 85 ip6_forward(struct mbuf *m, struct rtentry *rt, int srcrt) 86 { 87 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 88 struct sockaddr_in6 *sin6; 89 struct route_in6 ro; 90 struct ifnet *ifp = NULL; 91 int error = 0, type = 0, code = 0, destmtu = 0; 92 struct mbuf *mcopy = NULL; 93 #ifdef IPSEC 94 struct tdb *tdb = NULL; 95 #endif /* IPSEC */ 96 char src6[INET6_ADDRSTRLEN], dst6[INET6_ADDRSTRLEN]; 97 98 /* 99 * Do not forward packets to multicast destination (should be handled 100 * by ip6_mforward(). 101 * Do not forward packets with unspecified source. It was discussed 102 * in July 2000, on ipngwg mailing list. 103 */ 104 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 105 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 106 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 107 time_t uptime; 108 109 ip6stat_inc(ip6s_cantforward); 110 uptime = getuptime(); 111 112 if (ip6_log_time + ip6_log_interval < uptime) { 113 ip6_log_time = uptime; 114 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 115 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 116 log(LOG_DEBUG, 117 "cannot forward " 118 "from %s to %s nxt %d received on interface %u\n", 119 src6, dst6, 120 ip6->ip6_nxt, 121 m->m_pkthdr.ph_ifidx); 122 } 123 m_freem(m); 124 goto out; 125 } 126 127 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 128 icmp6_error(m, ICMP6_TIME_EXCEEDED, 129 ICMP6_TIME_EXCEED_TRANSIT, 0); 130 goto out; 131 } 132 ip6->ip6_hlim -= IPV6_HLIMDEC; 133 134 /* 135 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 136 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 137 * we need to generate an ICMP6 message to the src. 138 * Thanks to M_EXT, in most cases copy will not occur. 139 * 140 * It is important to save it before IPsec processing as IPsec 141 * processing may modify the mbuf. 142 */ 143 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 144 M_NOWAIT); 145 146 #if NPF > 0 147 reroute: 148 #endif 149 150 #ifdef IPSEC 151 if (ipsec_in_use) { 152 error = ip6_output_ipsec_lookup(m, NULL, &tdb); 153 if (error) { 154 /* 155 * -EINVAL is used to indicate that the packet should 156 * be silently dropped, typically because we've asked 157 * key management for an SA. 158 */ 159 if (error == -EINVAL) /* Should silently drop packet */ 160 error = 0; 161 162 m_freem(m); 163 goto freecopy; 164 } 165 } 166 #endif /* IPSEC */ 167 168 memset(&ro, 0, sizeof(ro)); 169 sin6 = &ro.ro_dst; 170 sin6->sin6_family = AF_INET6; 171 sin6->sin6_len = sizeof(*sin6); 172 sin6->sin6_addr = ip6->ip6_dst; 173 174 if (!rtisvalid(rt)) { 175 rtfree(rt); 176 rt = rtalloc_mpath(sin6tosa(sin6), &ip6->ip6_src.s6_addr32[0], 177 m->m_pkthdr.ph_rtableid); 178 if (rt == NULL) { 179 ip6stat_inc(ip6s_noroute); 180 if (mcopy) { 181 icmp6_error(mcopy, ICMP6_DST_UNREACH, 182 ICMP6_DST_UNREACH_NOROUTE, 0); 183 } 184 m_freem(m); 185 goto out; 186 } 187 } 188 189 /* 190 * Scope check: if a packet can't be delivered to its destination 191 * for the reason that the destination is beyond the scope of the 192 * source address, discard the packet and return an icmp6 destination 193 * unreachable error with Code 2 (beyond scope of source address). 194 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 195 */ 196 if (in6_addr2scopeid(m->m_pkthdr.ph_ifidx, &ip6->ip6_src) != 197 in6_addr2scopeid(rt->rt_ifidx, &ip6->ip6_src)) { 198 time_t uptime; 199 200 ip6stat_inc(ip6s_cantforward); 201 ip6stat_inc(ip6s_badscope); 202 uptime = getuptime(); 203 204 if (ip6_log_time + ip6_log_interval < uptime) { 205 ip6_log_time = uptime; 206 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 207 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 208 log(LOG_DEBUG, 209 "cannot forward " 210 "src %s, dst %s, nxt %d, rcvif %u, outif %u\n", 211 src6, dst6, 212 ip6->ip6_nxt, 213 m->m_pkthdr.ph_ifidx, rt->rt_ifidx); 214 } 215 if (mcopy) 216 icmp6_error(mcopy, ICMP6_DST_UNREACH, 217 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 218 m_freem(m); 219 goto out; 220 } 221 222 #ifdef IPSEC 223 /* 224 * Check if the packet needs encapsulation. 225 * ipsp_process_packet will never come back to here. 226 */ 227 if (tdb != NULL) { 228 /* Callee frees mbuf */ 229 ro.ro_rt = rt; 230 ro.ro_tableid = m->m_pkthdr.ph_rtableid; 231 error = ip6_output_ipsec_send(tdb, m, &ro, 0, 1); 232 rt = ro.ro_rt; 233 if (error) 234 goto senderr; 235 goto freecopy; 236 } 237 #endif /* IPSEC */ 238 239 if (rt->rt_flags & RTF_GATEWAY) 240 sin6 = satosin6(rt->rt_gateway); 241 242 /* 243 * If we are to forward the packet using the same interface 244 * as one we got the packet from, perhaps we should send a redirect 245 * to sender to shortcut a hop. 246 * Only send redirect if source is sending directly to us, 247 * and if packet was not source routed (or has any options). 248 * Also, don't send redirect if forwarding using a route 249 * modified by a redirect. 250 */ 251 ifp = if_get(rt->rt_ifidx); 252 if (ifp == NULL) { 253 m_freem(m); 254 goto freecopy; 255 } 256 if (rt->rt_ifidx == m->m_pkthdr.ph_ifidx && !srcrt && 257 ip6_sendredirects && 258 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 259 if ((ifp->if_flags & IFF_POINTOPOINT) && 260 nd6_is_addr_neighbor(&ro.ro_dst, ifp)) { 261 /* 262 * If the incoming interface is equal to the outgoing 263 * one, the link attached to the interface is 264 * point-to-point, and the IPv6 destination is 265 * regarded as on-link on the link, then it will be 266 * highly probable that the destination address does 267 * not exist on the link and that the packet is going 268 * to loop. Thus, we immediately drop the packet and 269 * send an ICMPv6 error message. 270 * For other routing loops, we dare to let the packet 271 * go to the loop, so that a remote diagnosing host 272 * can detect the loop by traceroute. 273 * type/code is based on suggestion by Rich Draves. 274 * not sure if it is the best pick. 275 */ 276 if (mcopy) 277 icmp6_error(mcopy, ICMP6_DST_UNREACH, 278 ICMP6_DST_UNREACH_ADDR, 0); 279 m_freem(m); 280 goto out; 281 } 282 type = ND_REDIRECT; 283 } 284 285 /* 286 * Fake scoped addresses. Note that even link-local source or 287 * destination can appear, if the originating node just sends the 288 * packet to us (without address resolution for the destination). 289 * Since both icmp6_error and icmp6_redirect_output fill the embedded 290 * link identifiers, we can do this stuff after making a copy for 291 * returning an error. 292 */ 293 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src)) 294 ip6->ip6_src.s6_addr16[1] = 0; 295 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst)) 296 ip6->ip6_dst.s6_addr16[1] = 0; 297 298 #if NPF > 0 299 if (pf_test(AF_INET6, PF_FWD, ifp, &m) != PF_PASS) { 300 m_freem(m); 301 goto senderr; 302 } 303 if (m == NULL) 304 goto senderr; 305 ip6 = mtod(m, struct ip6_hdr *); 306 if ((m->m_pkthdr.pf.flags & (PF_TAG_REROUTE | PF_TAG_GENERATED)) == 307 (PF_TAG_REROUTE | PF_TAG_GENERATED)) { 308 /* already rerun the route lookup, go on */ 309 m->m_pkthdr.pf.flags &= ~(PF_TAG_GENERATED | PF_TAG_REROUTE); 310 } else if (m->m_pkthdr.pf.flags & PF_TAG_REROUTE) { 311 /* tag as generated to skip over pf_test on rerun */ 312 m->m_pkthdr.pf.flags |= PF_TAG_GENERATED; 313 srcrt = 1; 314 rtfree(rt); 315 rt = NULL; 316 if_put(ifp); 317 ifp = NULL; 318 goto reroute; 319 } 320 #endif 321 322 error = if_output_tso(ifp, &m, sin6tosa(sin6), rt, ifp->if_mtu); 323 if (error) 324 ip6stat_inc(ip6s_cantforward); 325 else if (m == NULL) 326 ip6stat_inc(ip6s_forward); 327 if (error || m == NULL) 328 goto senderr; 329 330 if (mcopy != NULL) 331 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, ifp->if_mtu); 332 m_freem(m); 333 goto out; 334 335 senderr: 336 if (mcopy == NULL) 337 goto out; 338 339 switch (error) { 340 case 0: 341 if (type == ND_REDIRECT) { 342 icmp6_redirect_output(mcopy, rt); 343 ip6stat_inc(ip6s_redirectsent); 344 goto out; 345 } 346 goto freecopy; 347 348 case EMSGSIZE: 349 type = ICMP6_PACKET_TOO_BIG; 350 code = 0; 351 if (rt != NULL) { 352 if (rt->rt_mtu) { 353 destmtu = rt->rt_mtu; 354 } else { 355 struct ifnet *destifp; 356 357 destifp = if_get(rt->rt_ifidx); 358 if (destifp != NULL) 359 destmtu = destifp->if_mtu; 360 if_put(destifp); 361 } 362 } 363 ip6stat_inc(ip6s_cantfrag); 364 if (destmtu == 0) 365 goto freecopy; 366 break; 367 368 case EACCES: 369 /* 370 * pf(4) blocked the packet. There is no need to send an ICMP 371 * packet back since pf(4) takes care of it. 372 */ 373 goto freecopy; 374 375 case ENOBUFS: 376 /* Tell source to slow down like source quench in IP? */ 377 goto freecopy; 378 379 case ENETUNREACH: /* shouldn't happen, checked above */ 380 case EHOSTUNREACH: 381 case ENETDOWN: 382 case EHOSTDOWN: 383 default: 384 type = ICMP6_DST_UNREACH; 385 code = ICMP6_DST_UNREACH_ADDR; 386 break; 387 } 388 icmp6_error(mcopy, type, code, destmtu); 389 goto out; 390 391 freecopy: 392 m_freem(mcopy); 393 out: 394 rtfree(rt); 395 if_put(ifp); 396 #ifdef IPSEC 397 tdb_unref(tdb); 398 #endif /* IPSEC */ 399 } 400