1 /*- 2 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the project nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $ 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipfw.h" 38 #include "opt_ipsec.h" 39 #include "opt_ipstealth.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/malloc.h> 44 #include <sys/mbuf.h> 45 #include <sys/domain.h> 46 #include <sys/protosw.h> 47 #include <sys/socket.h> 48 #include <sys/errno.h> 49 #include <sys/time.h> 50 #include <sys/kernel.h> 51 #include <sys/syslog.h> 52 53 #include <net/if.h> 54 #include <net/if_var.h> 55 #include <net/netisr.h> 56 #include <net/route.h> 57 #include <net/pfil.h> 58 59 #include <netinet/in.h> 60 #include <netinet/in_var.h> 61 #include <netinet/in_systm.h> 62 #include <netinet/ip.h> 63 #include <netinet/ip_var.h> 64 #include <netinet6/in6_var.h> 65 #include <netinet/ip6.h> 66 #include <netinet6/ip6_var.h> 67 #include <netinet6/scope6_var.h> 68 #include <netinet/icmp6.h> 69 #include <netinet6/nd6.h> 70 71 #include <netinet/in_pcb.h> 72 73 #ifdef IPSEC 74 #include <netinet6/ip6_ipsec.h> 75 #include <netipsec/ipsec.h> 76 #include <netipsec/ipsec6.h> 77 #include <netipsec/key.h> 78 #endif /* IPSEC */ 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 = NULL; 97 struct rtentry *rt = NULL; 98 struct route_in6 rin6; 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 src_in6, dst_in6, odst; 104 #ifdef IPSEC 105 struct secpolicy *sp = NULL; 106 #endif 107 #ifdef SCTP 108 int sw_csum; 109 #endif 110 struct m_tag *fwd_tag; 111 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN]; 112 113 /* 114 * Do not forward packets to multicast destination (should be handled 115 * by ip6_mforward(). 116 * Do not forward packets with unspecified source. It was discussed 117 * in July 2000, on the ipngwg mailing list. 118 */ 119 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 120 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 121 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 122 IP6STAT_INC(ip6s_cantforward); 123 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 124 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 125 V_ip6_log_time = time_uptime; 126 log(LOG_DEBUG, 127 "cannot forward " 128 "from %s to %s nxt %d received on %s\n", 129 ip6_sprintf(ip6bufs, &ip6->ip6_src), 130 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 131 ip6->ip6_nxt, 132 if_name(m->m_pkthdr.rcvif)); 133 } 134 m_freem(m); 135 return; 136 } 137 #ifdef IPSEC 138 /* 139 * Check if this packet has an active SA and needs to be dropped 140 * instead of forwarded. 141 */ 142 if (ip6_ipsec_fwd(m) != 0) { 143 IP6STAT_INC(ip6s_cantforward); 144 m_freem(m); 145 return; 146 } 147 #endif /* IPSEC */ 148 149 #ifdef IPSTEALTH 150 if (!V_ip6stealth) { 151 #endif 152 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 153 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 154 icmp6_error(m, ICMP6_TIME_EXCEEDED, 155 ICMP6_TIME_EXCEED_TRANSIT, 0); 156 return; 157 } 158 ip6->ip6_hlim -= IPV6_HLIMDEC; 159 160 #ifdef IPSTEALTH 161 } 162 #endif 163 164 /* 165 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 166 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 167 * we need to generate an ICMP6 message to the src. 168 * Thanks to M_EXT, in most cases copy will not occur. 169 * 170 * It is important to save it before IPsec processing as IPsec 171 * processing may modify the mbuf. 172 */ 173 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 174 175 #ifdef IPSEC 176 /* get a security policy for this packet */ 177 sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, &error); 178 if (sp == NULL) { 179 IPSEC6STAT_INC(ips_out_inval); 180 IP6STAT_INC(ip6s_cantforward); 181 if (mcopy) { 182 #if 0 183 /* XXX: what icmp ? */ 184 #else 185 m_freem(mcopy); 186 #endif 187 } 188 m_freem(m); 189 return; 190 } 191 192 error = 0; 193 194 /* check policy */ 195 switch (sp->policy) { 196 case IPSEC_POLICY_DISCARD: 197 /* 198 * This packet is just discarded. 199 */ 200 IPSEC6STAT_INC(ips_out_polvio); 201 IP6STAT_INC(ip6s_cantforward); 202 KEY_FREESP(&sp); 203 if (mcopy) { 204 #if 0 205 /* XXX: what icmp ? */ 206 #else 207 m_freem(mcopy); 208 #endif 209 } 210 m_freem(m); 211 return; 212 213 case IPSEC_POLICY_BYPASS: 214 case IPSEC_POLICY_NONE: 215 /* no need to do IPsec. */ 216 KEY_FREESP(&sp); 217 goto skip_ipsec; 218 219 case IPSEC_POLICY_IPSEC: 220 if (sp->req == NULL) { 221 /* XXX should be panic ? */ 222 printf("ip6_forward: No IPsec request specified.\n"); 223 IP6STAT_INC(ip6s_cantforward); 224 KEY_FREESP(&sp); 225 if (mcopy) { 226 #if 0 227 /* XXX: what icmp ? */ 228 #else 229 m_freem(mcopy); 230 #endif 231 } 232 m_freem(m); 233 return; 234 } 235 /* do IPsec */ 236 break; 237 238 case IPSEC_POLICY_ENTRUST: 239 default: 240 /* should be panic ?? */ 241 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 242 KEY_FREESP(&sp); 243 goto skip_ipsec; 244 } 245 246 { 247 struct ipsecrequest *isr = NULL; 248 249 /* 250 * when the kernel forwards a packet, it is not proper to apply 251 * IPsec transport mode to the packet. This check avoid from this. 252 * at present, if there is even a transport mode SA request in the 253 * security policy, the kernel does not apply IPsec to the packet. 254 * this check is not enough because the following case is valid. 255 * ipsec esp/tunnel/xxx-xxx/require esp/transport//require; 256 */ 257 for (isr = sp->req; isr; isr = isr->next) { 258 if (isr->saidx.mode == IPSEC_MODE_ANY) 259 goto doipsectunnel; 260 if (isr->saidx.mode == IPSEC_MODE_TUNNEL) 261 goto doipsectunnel; 262 } 263 264 /* 265 * if there's no need for tunnel mode IPsec, skip. 266 */ 267 if (!isr) 268 goto skip_ipsec; 269 270 doipsectunnel: 271 /* 272 * All the extension headers will become inaccessible 273 * (since they can be encrypted). 274 * Don't panic, we need no more updates to extension headers 275 * on inner IPv6 packet (since they are now encapsulated). 276 * 277 * IPv6 [ESP|AH] IPv6 [extension headers] payload 278 */ 279 280 /* 281 * If we need to encapsulate the packet, do it here 282 * ipsec6_proces_packet will send the packet using ip6_output 283 */ 284 error = ipsec6_process_packet(m, sp->req); 285 /* Release SP if an error occured */ 286 if (error != 0) 287 KEY_FREESP(&sp); 288 if (error == EJUSTRETURN) { 289 /* 290 * We had a SP with a level of 'use' and no SA. We 291 * will just continue to process the packet without 292 * IPsec processing. 293 */ 294 error = 0; 295 goto skip_ipsec; 296 } 297 298 if (error) { 299 /* mbuf is already reclaimed in ipsec6_process_packet. */ 300 switch (error) { 301 case EHOSTUNREACH: 302 case ENETUNREACH: 303 case EMSGSIZE: 304 case ENOBUFS: 305 case ENOMEM: 306 break; 307 default: 308 printf("ip6_output (ipsec): error code %d\n", error); 309 /* FALLTHROUGH */ 310 case ENOENT: 311 /* don't show these error codes to the user */ 312 break; 313 } 314 IP6STAT_INC(ip6s_cantforward); 315 if (mcopy) { 316 #if 0 317 /* XXX: what icmp ? */ 318 #else 319 m_freem(mcopy); 320 #endif 321 } 322 return; 323 } else { 324 /* 325 * In the FAST IPSec case we have already 326 * re-injected the packet and it has been freed 327 * by the ipsec_done() function. So, just clean 328 * up after ourselves. 329 */ 330 m = NULL; 331 goto freecopy; 332 } 333 } 334 skip_ipsec: 335 #endif 336 again: 337 bzero(&rin6, sizeof(struct route_in6)); 338 dst = (struct sockaddr_in6 *)&rin6.ro_dst; 339 dst->sin6_len = sizeof(struct sockaddr_in6); 340 dst->sin6_family = AF_INET6; 341 dst->sin6_addr = ip6->ip6_dst; 342 again2: 343 rin6.ro_rt = in6_rtalloc1((struct sockaddr *)dst, 0, 0, M_GETFIB(m)); 344 rt = rin6.ro_rt; 345 if (rin6.ro_rt != NULL) 346 RT_UNLOCK(rin6.ro_rt); 347 else { 348 IP6STAT_INC(ip6s_noroute); 349 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 350 if (mcopy) { 351 icmp6_error(mcopy, ICMP6_DST_UNREACH, 352 ICMP6_DST_UNREACH_NOROUTE, 0); 353 } 354 goto bad; 355 } 356 357 /* 358 * Source scope check: if a packet can't be delivered to its 359 * destination for the reason that the destination is beyond the scope 360 * of the source address, discard the packet and return an icmp6 361 * destination unreachable error with Code 2 (beyond scope of source 362 * address). We use a local copy of ip6_src, since in6_setscope() 363 * will possibly modify its first argument. 364 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1] 365 */ 366 src_in6 = ip6->ip6_src; 367 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) { 368 /* XXX: this should not happen */ 369 IP6STAT_INC(ip6s_cantforward); 370 IP6STAT_INC(ip6s_badscope); 371 goto bad; 372 } 373 if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) { 374 IP6STAT_INC(ip6s_cantforward); 375 IP6STAT_INC(ip6s_badscope); 376 goto bad; 377 } 378 if (inzone != outzone) { 379 IP6STAT_INC(ip6s_cantforward); 380 IP6STAT_INC(ip6s_badscope); 381 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 382 383 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 384 V_ip6_log_time = time_uptime; 385 log(LOG_DEBUG, 386 "cannot forward " 387 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 388 ip6_sprintf(ip6bufs, &ip6->ip6_src), 389 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 390 ip6->ip6_nxt, 391 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 392 } 393 if (mcopy) 394 icmp6_error(mcopy, ICMP6_DST_UNREACH, 395 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 396 goto bad; 397 } 398 399 /* 400 * Destination scope check: if a packet is going to break the scope 401 * zone of packet's destination address, discard it. This case should 402 * usually be prevented by appropriately-configured routing table, but 403 * we need an explicit check because we may mistakenly forward the 404 * packet to a different zone by (e.g.) a default route. 405 */ 406 dst_in6 = ip6->ip6_dst; 407 if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 || 408 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 409 inzone != outzone) { 410 IP6STAT_INC(ip6s_cantforward); 411 IP6STAT_INC(ip6s_badscope); 412 goto bad; 413 } 414 415 if (rt->rt_flags & RTF_GATEWAY) 416 dst = (struct sockaddr_in6 *)rt->rt_gateway; 417 418 /* 419 * If we are to forward the packet using the same interface 420 * as one we got the packet from, perhaps we should send a redirect 421 * to sender to shortcut a hop. 422 * Only send redirect if source is sending directly to us, 423 * and if packet was not source routed (or has any options). 424 * Also, don't send redirect if forwarding using a route 425 * modified by a redirect. 426 */ 427 if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 428 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 429 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 430 /* 431 * If the incoming interface is equal to the outgoing 432 * one, and the link attached to the interface is 433 * point-to-point, then it will be highly probable 434 * that a routing loop occurs. Thus, we immediately 435 * drop the packet and send an ICMPv6 error message. 436 * 437 * type/code is based on suggestion by Rich Draves. 438 * not sure if it is the best pick. 439 */ 440 icmp6_error(mcopy, ICMP6_DST_UNREACH, 441 ICMP6_DST_UNREACH_ADDR, 0); 442 goto bad; 443 } 444 type = ND_REDIRECT; 445 } 446 447 /* 448 * Fake scoped addresses. Note that even link-local source or 449 * destinaion can appear, if the originating node just sends the 450 * packet to us (without address resolution for the destination). 451 * Since both icmp6_error and icmp6_redirect_output fill the embedded 452 * link identifiers, we can do this stuff after making a copy for 453 * returning an error. 454 */ 455 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 456 /* 457 * See corresponding comments in ip6_output. 458 * XXX: but is it possible that ip6_forward() sends a packet 459 * to a loopback interface? I don't think so, and thus 460 * I bark here. (jinmei@kame.net) 461 * XXX: it is common to route invalid packets to loopback. 462 * also, the codepath will be visited on use of ::1 in 463 * rthdr. (itojun) 464 */ 465 #if 1 466 if (0) 467 #else 468 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 469 #endif 470 { 471 printf("ip6_forward: outgoing interface is loopback. " 472 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 473 ip6_sprintf(ip6bufs, &ip6->ip6_src), 474 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 475 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 476 if_name(rt->rt_ifp)); 477 } 478 479 /* we can just use rcvif in forwarding. */ 480 origifp = m->m_pkthdr.rcvif; 481 } 482 else 483 origifp = rt->rt_ifp; 484 /* 485 * clear embedded scope identifiers if necessary. 486 * in6_clearscope will touch the addresses only when necessary. 487 */ 488 in6_clearscope(&ip6->ip6_src); 489 in6_clearscope(&ip6->ip6_dst); 490 491 /* Jump over all PFIL processing if hooks are not active. */ 492 if (!PFIL_HOOKED(&V_inet6_pfil_hook)) 493 goto pass; 494 495 odst = ip6->ip6_dst; 496 /* Run through list of hooks for output packets. */ 497 error = pfil_run_hooks(&V_inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, NULL); 498 if (error != 0 || m == NULL) 499 goto freecopy; /* consumed by filter */ 500 ip6 = mtod(m, struct ip6_hdr *); 501 502 /* See if destination IP address was changed by packet filter. */ 503 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) { 504 m->m_flags |= M_SKIP_FIREWALL; 505 /* If destination is now ourself drop to ip6_input(). */ 506 if (in6_localip(&ip6->ip6_dst)) 507 m->m_flags |= M_FASTFWD_OURS; 508 else { 509 RTFREE(rt); 510 goto again; /* Redo the routing table lookup. */ 511 } 512 } 513 514 /* See if local, if yes, send it to netisr. */ 515 if (m->m_flags & M_FASTFWD_OURS) { 516 if (m->m_pkthdr.rcvif == NULL) 517 m->m_pkthdr.rcvif = V_loif; 518 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) { 519 m->m_pkthdr.csum_flags |= 520 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR; 521 m->m_pkthdr.csum_data = 0xffff; 522 } 523 #ifdef SCTP 524 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6) 525 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID; 526 #endif 527 error = netisr_queue(NETISR_IPV6, m); 528 goto out; 529 } 530 /* Or forward to some other address? */ 531 if ((m->m_flags & M_IP6_NEXTHOP) && 532 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) { 533 dst = (struct sockaddr_in6 *)&rin6.ro_dst; 534 bcopy((fwd_tag+1), dst, sizeof(struct sockaddr_in6)); 535 m->m_flags |= M_SKIP_FIREWALL; 536 m->m_flags &= ~M_IP6_NEXTHOP; 537 m_tag_delete(m, fwd_tag); 538 RTFREE(rt); 539 goto again2; 540 } 541 542 pass: 543 /* See if the size was changed by the packet filter. */ 544 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 545 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 546 if (mcopy) { 547 u_long mtu; 548 #ifdef IPSEC 549 size_t ipsechdrsiz; 550 #endif /* IPSEC */ 551 552 mtu = IN6_LINKMTU(rt->rt_ifp); 553 #ifdef IPSEC 554 /* 555 * When we do IPsec tunnel ingress, we need to play 556 * with the link value (decrement IPsec header size 557 * from mtu value). The code is much simpler than v4 558 * case, as we have the outgoing interface for 559 * encapsulated packet as "rt->rt_ifp". 560 */ 561 ipsechdrsiz = ipsec_hdrsiz(mcopy, IPSEC_DIR_OUTBOUND, 562 NULL); 563 if (ipsechdrsiz < mtu) 564 mtu -= ipsechdrsiz; 565 /* 566 * if mtu becomes less than minimum MTU, 567 * tell minimum MTU (and I'll need to fragment it). 568 */ 569 if (mtu < IPV6_MMTU) 570 mtu = IPV6_MMTU; 571 #endif /* IPSEC */ 572 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 573 } 574 goto bad; 575 } 576 577 error = nd6_output_ifp(rt->rt_ifp, origifp, m, dst, NULL); 578 if (error) { 579 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 580 IP6STAT_INC(ip6s_cantforward); 581 } else { 582 IP6STAT_INC(ip6s_forward); 583 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 584 if (type) 585 IP6STAT_INC(ip6s_redirectsent); 586 else { 587 if (mcopy) 588 goto freecopy; 589 } 590 } 591 592 if (mcopy == NULL) 593 goto out; 594 switch (error) { 595 case 0: 596 if (type == ND_REDIRECT) { 597 icmp6_redirect_output(mcopy, rt); 598 goto out; 599 } 600 goto freecopy; 601 602 case EMSGSIZE: 603 /* xxx MTU is constant in PPP? */ 604 goto freecopy; 605 606 case ENOBUFS: 607 /* Tell source to slow down like source quench in IP? */ 608 goto freecopy; 609 610 case ENETUNREACH: /* shouldn't happen, checked above */ 611 case EHOSTUNREACH: 612 case ENETDOWN: 613 case EHOSTDOWN: 614 default: 615 type = ICMP6_DST_UNREACH; 616 code = ICMP6_DST_UNREACH_ADDR; 617 break; 618 } 619 icmp6_error(mcopy, type, code, 0); 620 goto out; 621 622 freecopy: 623 m_freem(mcopy); 624 goto out; 625 bad: 626 m_freem(m); 627 out: 628 if (rt != NULL) 629 RTFREE(rt); 630 } 631