Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/netinet/ip_options.c
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1 /* 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1993 5 * The Regents of the University of California. 6 * Copyright (c) 2005 Andre Oppermann, Internet Business Solutions AG. 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD: releng/12.0/sys/netinet/ip_options.c 339251 2018-10-09 13:26:06Z jtl $"); 36 37 #include "opt_ipstealth.h" 38 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/mbuf.h> 42 #include <sys/domain.h> 43 #include <sys/protosw.h> 44 #include <sys/socket.h> 45 #include <sys/time.h> 46 #include <sys/kernel.h> 47 #include <sys/syslog.h> 48 #include <sys/sysctl.h> 49 50 #include <net/if.h> 51 #include <net/if_types.h> 52 #include <net/if_var.h> 53 #include <net/if_dl.h> 54 #include <net/route.h> 55 #include <net/netisr.h> 56 #include <net/vnet.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_fib.h> 60 #include <netinet/in_systm.h> 61 #include <netinet/in_var.h> 62 #include <netinet/ip.h> 63 #include <netinet/in_pcb.h> 64 #include <netinet/ip_var.h> 65 #include <netinet/ip_options.h> 66 #include <netinet/ip_icmp.h> 67 #include <machine/in_cksum.h> 68 69 #include <sys/socketvar.h> 70 71 VNET_DEFINE_STATIC(int, ip_dosourceroute); 72 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, 73 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0, 74 "Enable forwarding source routed IP packets"); 75 #define V_ip_dosourceroute VNET(ip_dosourceroute) 76 77 VNET_DEFINE_STATIC(int, ip_acceptsourceroute); 78 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute, 79 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0, 80 "Enable accepting source routed IP packets"); 81 #define V_ip_acceptsourceroute VNET(ip_acceptsourceroute) 82 83 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */ 84 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW, 85 &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)"); 86 87 static void save_rte(struct mbuf *m, u_char *, struct in_addr); 88 89 /* 90 * Do option processing on a datagram, possibly discarding it if bad options 91 * are encountered, or forwarding it if source-routed. 92 * 93 * The pass argument is used when operating in the IPSTEALTH mode to tell 94 * what options to process: [LS]SRR (pass 0) or the others (pass 1). The 95 * reason for as many as two passes is that when doing IPSTEALTH, non-routing 96 * options should be processed only if the packet is for us. 97 * 98 * Returns 1 if packet has been forwarded/freed, 0 if the packet should be 99 * processed further. 100 */ 101 int 102 ip_dooptions(struct mbuf *m, int pass) 103 { 104 struct ip *ip = mtod(m, struct ip *); 105 u_char *cp; 106 struct in_ifaddr *ia; 107 int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0; 108 struct in_addr *sin, dst; 109 uint32_t ntime; 110 struct nhop4_extended nh_ext; 111 struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET }; 112 113 /* Ignore or reject packets with IP options. */ 114 if (V_ip_doopts == 0) 115 return 0; 116 else if (V_ip_doopts == 2) { 117 type = ICMP_UNREACH; 118 code = ICMP_UNREACH_FILTER_PROHIB; 119 goto bad_unlocked; 120 } 121 122 NET_EPOCH_ENTER(); 123 dst = ip->ip_dst; 124 cp = (u_char *)(ip + 1); 125 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 126 for (; cnt > 0; cnt -= optlen, cp += optlen) { 127 opt = cp[IPOPT_OPTVAL]; 128 if (opt == IPOPT_EOL) 129 break; 130 if (opt == IPOPT_NOP) 131 optlen = 1; 132 else { 133 if (cnt < IPOPT_OLEN + sizeof(*cp)) { 134 code = &cp[IPOPT_OLEN] - (u_char *)ip; 135 goto bad; 136 } 137 optlen = cp[IPOPT_OLEN]; 138 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) { 139 code = &cp[IPOPT_OLEN] - (u_char *)ip; 140 goto bad; 141 } 142 } 143 switch (opt) { 144 145 default: 146 break; 147 148 /* 149 * Source routing with record. Find interface with current 150 * destination address. If none on this machine then drop if 151 * strictly routed, or do nothing if loosely routed. Record 152 * interface address and bring up next address component. If 153 * strictly routed make sure next address is on directly 154 * accessible net. 155 */ 156 case IPOPT_LSRR: 157 case IPOPT_SSRR: 158 #ifdef IPSTEALTH 159 if (V_ipstealth && pass > 0) 160 break; 161 #endif 162 if (optlen < IPOPT_OFFSET + sizeof(*cp)) { 163 code = &cp[IPOPT_OLEN] - (u_char *)ip; 164 goto bad; 165 } 166 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) { 167 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 168 goto bad; 169 } 170 ipaddr.sin_addr = ip->ip_dst; 171 if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr) 172 == 0) { 173 if (opt == IPOPT_SSRR) { 174 type = ICMP_UNREACH; 175 code = ICMP_UNREACH_SRCFAIL; 176 goto bad; 177 } 178 if (!V_ip_dosourceroute) 179 goto nosourcerouting; 180 /* 181 * Loose routing, and not at next destination 182 * yet; nothing to do except forward. 183 */ 184 break; 185 } 186 off--; /* 0 origin */ 187 if (off > optlen - (int)sizeof(struct in_addr)) { 188 /* 189 * End of source route. Should be for us. 190 */ 191 if (!V_ip_acceptsourceroute) 192 goto nosourcerouting; 193 save_rte(m, cp, ip->ip_src); 194 break; 195 } 196 #ifdef IPSTEALTH 197 if (V_ipstealth) 198 goto dropit; 199 #endif 200 if (!V_ip_dosourceroute) { 201 if (V_ipforwarding) { 202 char srcbuf[INET_ADDRSTRLEN]; 203 char dstbuf[INET_ADDRSTRLEN]; 204 205 /* 206 * Acting as a router, so generate 207 * ICMP 208 */ 209 nosourcerouting: 210 log(LOG_WARNING, 211 "attempted source route from %s " 212 "to %s\n", 213 inet_ntoa_r(ip->ip_src, srcbuf), 214 inet_ntoa_r(ip->ip_dst, dstbuf)); 215 type = ICMP_UNREACH; 216 code = ICMP_UNREACH_SRCFAIL; 217 goto bad; 218 } else { 219 /* 220 * Not acting as a router, so 221 * silently drop. 222 */ 223 #ifdef IPSTEALTH 224 dropit: 225 #endif 226 IPSTAT_INC(ips_cantforward); 227 m_freem(m); 228 NET_EPOCH_EXIT(); 229 return (1); 230 } 231 } 232 233 /* 234 * locate outgoing interface 235 */ 236 (void)memcpy(&ipaddr.sin_addr, cp + off, 237 sizeof(ipaddr.sin_addr)); 238 239 type = ICMP_UNREACH; 240 code = ICMP_UNREACH_SRCFAIL; 241 242 if (opt == IPOPT_SSRR) { 243 #define INA struct in_ifaddr * 244 #define SA struct sockaddr * 245 ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr, 246 RT_ALL_FIBS); 247 if (ia == NULL) 248 ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0, 249 RT_ALL_FIBS); 250 if (ia == NULL) 251 goto bad; 252 253 memcpy(cp + off, &(IA_SIN(ia)->sin_addr), 254 sizeof(struct in_addr)); 255 } else { 256 /* XXX MRT 0 for routing */ 257 if (fib4_lookup_nh_ext(M_GETFIB(m), 258 ipaddr.sin_addr, 0, 0, &nh_ext) != 0) 259 goto bad; 260 261 memcpy(cp + off, &nh_ext.nh_src, 262 sizeof(struct in_addr)); 263 } 264 265 ip->ip_dst = ipaddr.sin_addr; 266 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 267 /* 268 * Let ip_intr's mcast routing check handle mcast pkts 269 */ 270 forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr)); 271 break; 272 273 case IPOPT_RR: 274 #ifdef IPSTEALTH 275 if (V_ipstealth && pass == 0) 276 break; 277 #endif 278 if (optlen < IPOPT_OFFSET + sizeof(*cp)) { 279 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 280 goto bad; 281 } 282 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) { 283 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 284 goto bad; 285 } 286 /* 287 * If no space remains, ignore. 288 */ 289 off--; /* 0 origin */ 290 if (off > optlen - (int)sizeof(struct in_addr)) 291 break; 292 (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst, 293 sizeof(ipaddr.sin_addr)); 294 /* 295 * Locate outgoing interface; if we're the 296 * destination, use the incoming interface (should be 297 * same). 298 */ 299 if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) { 300 memcpy(cp + off, &(IA_SIN(ia)->sin_addr), 301 sizeof(struct in_addr)); 302 } else if (fib4_lookup_nh_ext(M_GETFIB(m), 303 ipaddr.sin_addr, 0, 0, &nh_ext) == 0) { 304 memcpy(cp + off, &nh_ext.nh_src, 305 sizeof(struct in_addr)); 306 } else { 307 type = ICMP_UNREACH; 308 code = ICMP_UNREACH_HOST; 309 goto bad; 310 } 311 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 312 break; 313 314 case IPOPT_TS: 315 #ifdef IPSTEALTH 316 if (V_ipstealth && pass == 0) 317 break; 318 #endif 319 code = cp - (u_char *)ip; 320 if (optlen < 4 || optlen > 40) { 321 code = &cp[IPOPT_OLEN] - (u_char *)ip; 322 goto bad; 323 } 324 if ((off = cp[IPOPT_OFFSET]) < 5) { 325 code = &cp[IPOPT_OLEN] - (u_char *)ip; 326 goto bad; 327 } 328 if (off > optlen - (int)sizeof(int32_t)) { 329 cp[IPOPT_OFFSET + 1] += (1 << 4); 330 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) { 331 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 332 goto bad; 333 } 334 break; 335 } 336 off--; /* 0 origin */ 337 sin = (struct in_addr *)(cp + off); 338 switch (cp[IPOPT_OFFSET + 1] & 0x0f) { 339 340 case IPOPT_TS_TSONLY: 341 break; 342 343 case IPOPT_TS_TSANDADDR: 344 if (off + sizeof(uint32_t) + 345 sizeof(struct in_addr) > optlen) { 346 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 347 goto bad; 348 } 349 ipaddr.sin_addr = dst; 350 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr, 351 m->m_pkthdr.rcvif); 352 if (ia == NULL) 353 continue; 354 (void)memcpy(sin, &IA_SIN(ia)->sin_addr, 355 sizeof(struct in_addr)); 356 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 357 off += sizeof(struct in_addr); 358 break; 359 360 case IPOPT_TS_PRESPEC: 361 if (off + sizeof(uint32_t) + 362 sizeof(struct in_addr) > optlen) { 363 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 364 goto bad; 365 } 366 (void)memcpy(&ipaddr.sin_addr, sin, 367 sizeof(struct in_addr)); 368 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0) 369 continue; 370 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 371 off += sizeof(struct in_addr); 372 break; 373 374 default: 375 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip; 376 goto bad; 377 } 378 ntime = iptime(); 379 (void)memcpy(cp + off, &ntime, sizeof(uint32_t)); 380 cp[IPOPT_OFFSET] += sizeof(uint32_t); 381 } 382 } 383 NET_EPOCH_EXIT(); 384 if (forward && V_ipforwarding) { 385 ip_forward(m, 1); 386 return (1); 387 } 388 return (0); 389 bad: 390 NET_EPOCH_EXIT(); 391 bad_unlocked: 392 icmp_error(m, type, code, 0, 0); 393 IPSTAT_INC(ips_badoptions); 394 return (1); 395 } 396 397 /* 398 * Save incoming source route for use in replies, to be picked up later by 399 * ip_srcroute if the receiver is interested. 400 */ 401 static void 402 save_rte(struct mbuf *m, u_char *option, struct in_addr dst) 403 { 404 unsigned olen; 405 struct ipopt_tag *opts; 406 407 opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS, 408 sizeof(struct ipopt_tag), M_NOWAIT); 409 if (opts == NULL) 410 return; 411 412 olen = option[IPOPT_OLEN]; 413 if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) { 414 m_tag_free((struct m_tag *)opts); 415 return; 416 } 417 bcopy(option, opts->ip_srcrt.srcopt, olen); 418 opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr); 419 opts->ip_srcrt.dst = dst; 420 m_tag_prepend(m, (struct m_tag *)opts); 421 } 422 423 /* 424 * Retrieve incoming source route for use in replies, in the same form used 425 * by setsockopt. The first hop is placed before the options, will be 426 * removed later. 427 */ 428 struct mbuf * 429 ip_srcroute(struct mbuf *m0) 430 { 431 struct in_addr *p, *q; 432 struct mbuf *m; 433 struct ipopt_tag *opts; 434 435 opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL); 436 if (opts == NULL) 437 return (NULL); 438 439 if (opts->ip_nhops == 0) 440 return (NULL); 441 m = m_get(M_NOWAIT, MT_DATA); 442 if (m == NULL) 443 return (NULL); 444 445 #define OPTSIZ (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt)) 446 447 /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */ 448 m->m_len = opts->ip_nhops * sizeof(struct in_addr) + 449 sizeof(struct in_addr) + OPTSIZ; 450 451 /* 452 * First, save first hop for return route. 453 */ 454 p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]); 455 *(mtod(m, struct in_addr *)) = *p--; 456 457 /* 458 * Copy option fields and padding (nop) to mbuf. 459 */ 460 opts->ip_srcrt.nop = IPOPT_NOP; 461 opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF; 462 (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr), 463 &(opts->ip_srcrt.nop), OPTSIZ); 464 q = (struct in_addr *)(mtod(m, caddr_t) + 465 sizeof(struct in_addr) + OPTSIZ); 466 #undef OPTSIZ 467 /* 468 * Record return path as an IP source route, reversing the path 469 * (pointers are now aligned). 470 */ 471 while (p >= opts->ip_srcrt.route) { 472 *q++ = *p--; 473 } 474 /* 475 * Last hop goes to final destination. 476 */ 477 *q = opts->ip_srcrt.dst; 478 m_tag_delete(m0, (struct m_tag *)opts); 479 return (m); 480 } 481 482 /* 483 * Strip out IP options, at higher level protocol in the kernel. 484 */ 485 void 486 ip_stripoptions(struct mbuf *m) 487 { 488 struct ip *ip = mtod(m, struct ip *); 489 int olen; 490 491 olen = (ip->ip_hl << 2) - sizeof(struct ip); 492 m->m_len -= olen; 493 if (m->m_flags & M_PKTHDR) 494 m->m_pkthdr.len -= olen; 495 ip->ip_len = htons(ntohs(ip->ip_len) - olen); 496 ip->ip_hl = sizeof(struct ip) >> 2; 497 498 bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1), 499 (size_t )(m->m_len - sizeof(struct ip))); 500 } 501 502 /* 503 * Insert IP options into preformed packet. Adjust IP destination as 504 * required for IP source routing, as indicated by a non-zero in_addr at the 505 * start of the options. 506 * 507 * XXX This routine assumes that the packet has no options in place. 508 */ 509 struct mbuf * 510 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen) 511 { 512 struct ipoption *p = mtod(opt, struct ipoption *); 513 struct mbuf *n; 514 struct ip *ip = mtod(m, struct ip *); 515 unsigned optlen; 516 517 optlen = opt->m_len - sizeof(p->ipopt_dst); 518 if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) { 519 *phlen = 0; 520 return (m); /* XXX should fail */ 521 } 522 if (p->ipopt_dst.s_addr) 523 ip->ip_dst = p->ipopt_dst; 524 if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) { 525 n = m_gethdr(M_NOWAIT, MT_DATA); 526 if (n == NULL) { 527 *phlen = 0; 528 return (m); 529 } 530 m_move_pkthdr(n, m); 531 n->m_pkthdr.rcvif = NULL; 532 n->m_pkthdr.len += optlen; 533 m->m_len -= sizeof(struct ip); 534 m->m_data += sizeof(struct ip); 535 n->m_next = m; 536 m = n; 537 m->m_len = optlen + sizeof(struct ip); 538 m->m_data += max_linkhdr; 539 bcopy(ip, mtod(m, void *), sizeof(struct ip)); 540 } else { 541 m->m_data -= optlen; 542 m->m_len += optlen; 543 m->m_pkthdr.len += optlen; 544 bcopy(ip, mtod(m, void *), sizeof(struct ip)); 545 } 546 ip = mtod(m, struct ip *); 547 bcopy(p->ipopt_list, ip + 1, optlen); 548 *phlen = sizeof(struct ip) + optlen; 549 ip->ip_v = IPVERSION; 550 ip->ip_hl = *phlen >> 2; 551 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 552 return (m); 553 } 554 555 /* 556 * Copy options from ip to jp, omitting those not copied during 557 * fragmentation. 558 */ 559 int 560 ip_optcopy(struct ip *ip, struct ip *jp) 561 { 562 u_char *cp, *dp; 563 int opt, optlen, cnt; 564 565 cp = (u_char *)(ip + 1); 566 dp = (u_char *)(jp + 1); 567 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 568 for (; cnt > 0; cnt -= optlen, cp += optlen) { 569 opt = cp[0]; 570 if (opt == IPOPT_EOL) 571 break; 572 if (opt == IPOPT_NOP) { 573 /* Preserve for IP mcast tunnel's LSRR alignment. */ 574 *dp++ = IPOPT_NOP; 575 optlen = 1; 576 continue; 577 } 578 579 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp), 580 ("ip_optcopy: malformed ipv4 option")); 581 optlen = cp[IPOPT_OLEN]; 582 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt, 583 ("ip_optcopy: malformed ipv4 option")); 584 585 /* Bogus lengths should have been caught by ip_dooptions. */ 586 if (optlen > cnt) 587 optlen = cnt; 588 if (IPOPT_COPIED(opt)) { 589 bcopy(cp, dp, optlen); 590 dp += optlen; 591 } 592 } 593 for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++) 594 *dp++ = IPOPT_EOL; 595 return (optlen); 596 } 597 598 /* 599 * Set up IP options in pcb for insertion in output packets. Store in mbuf 600 * with pointer in pcbopt, adding pseudo-option with destination address if 601 * source routed. 602 */ 603 int 604 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m) 605 { 606 int cnt, optlen; 607 u_char *cp; 608 struct mbuf **pcbopt; 609 u_char opt; 610 611 INP_WLOCK_ASSERT(inp); 612 613 pcbopt = &inp->inp_options; 614 615 /* turn off any old options */ 616 if (*pcbopt) 617 (void)m_free(*pcbopt); 618 *pcbopt = NULL; 619 if (m == NULL || m->m_len == 0) { 620 /* 621 * Only turning off any previous options. 622 */ 623 if (m != NULL) 624 (void)m_free(m); 625 return (0); 626 } 627 628 if (m->m_len % sizeof(int32_t)) 629 goto bad; 630 /* 631 * IP first-hop destination address will be stored before actual 632 * options; move other options back and clear it when none present. 633 */ 634 if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN]) 635 goto bad; 636 cnt = m->m_len; 637 m->m_len += sizeof(struct in_addr); 638 cp = mtod(m, u_char *) + sizeof(struct in_addr); 639 bcopy(mtod(m, void *), cp, (unsigned)cnt); 640 bzero(mtod(m, void *), sizeof(struct in_addr)); 641 642 for (; cnt > 0; cnt -= optlen, cp += optlen) { 643 opt = cp[IPOPT_OPTVAL]; 644 if (opt == IPOPT_EOL) 645 break; 646 if (opt == IPOPT_NOP) 647 optlen = 1; 648 else { 649 if (cnt < IPOPT_OLEN + sizeof(*cp)) 650 goto bad; 651 optlen = cp[IPOPT_OLEN]; 652 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) 653 goto bad; 654 } 655 switch (opt) { 656 657 default: 658 break; 659 660 case IPOPT_LSRR: 661 case IPOPT_SSRR: 662 /* 663 * User process specifies route as: 664 * 665 * ->A->B->C->D 666 * 667 * D must be our final destination (but we can't 668 * check that since we may not have connected yet). 669 * A is first hop destination, which doesn't appear 670 * in actual IP option, but is stored before the 671 * options. 672 */ 673 /* XXX-BZ PRIV_NETINET_SETHDROPTS? */ 674 if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr)) 675 goto bad; 676 m->m_len -= sizeof(struct in_addr); 677 cnt -= sizeof(struct in_addr); 678 optlen -= sizeof(struct in_addr); 679 cp[IPOPT_OLEN] = optlen; 680 /* 681 * Move first hop before start of options. 682 */ 683 bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t), 684 sizeof(struct in_addr)); 685 /* 686 * Then copy rest of options back 687 * to close up the deleted entry. 688 */ 689 bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)), 690 &cp[IPOPT_OFFSET+1], 691 (unsigned)cnt - (IPOPT_MINOFF - 1)); 692 break; 693 } 694 } 695 if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr)) 696 goto bad; 697 *pcbopt = m; 698 return (0); 699 700 bad: 701 (void)m_free(m); 702 return (EINVAL); 703 } 704 705 /* 706 * Check for the presence of the IP Router Alert option [RFC2113] 707 * in the header of an IPv4 datagram. 708 * 709 * This call is not intended for use from the forwarding path; it is here 710 * so that protocol domains may check for the presence of the option. 711 * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert 712 * option does not have much relevance to the implementation, though this 713 * may change in future. 714 * Router alert options SHOULD be passed if running in IPSTEALTH mode and 715 * we are not the endpoint. 716 * Length checks on individual options should already have been performed 717 * by ip_dooptions() therefore they are folded under INVARIANTS here. 718 * 719 * Return zero if not present or options are invalid, non-zero if present. 720 */ 721 int 722 ip_checkrouteralert(struct mbuf *m) 723 { 724 struct ip *ip = mtod(m, struct ip *); 725 u_char *cp; 726 int opt, optlen, cnt, found_ra; 727 728 found_ra = 0; 729 cp = (u_char *)(ip + 1); 730 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 731 for (; cnt > 0; cnt -= optlen, cp += optlen) { 732 opt = cp[IPOPT_OPTVAL]; 733 if (opt == IPOPT_EOL) 734 break; 735 if (opt == IPOPT_NOP) 736 optlen = 1; 737 else { 738 #ifdef INVARIANTS 739 if (cnt < IPOPT_OLEN + sizeof(*cp)) 740 break; 741 #endif 742 optlen = cp[IPOPT_OLEN]; 743 #ifdef INVARIANTS 744 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) 745 break; 746 #endif 747 } 748 switch (opt) { 749 case IPOPT_RA: 750 #ifdef INVARIANTS 751 if (optlen != IPOPT_OFFSET + sizeof(uint16_t) || 752 (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0)) 753 break; 754 else 755 #endif 756 found_ra = 1; 757 break; 758 default: 759 break; 760 } 761 } 762 763 return (found_ra); 764 }
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