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 * Copyright (c) 1982, 1986, 1988, 1993 3 * The Regents of the University of California. 4 * Copyright (c) 2005 Andre Oppermann, Internet Business Solutions AG. 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 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD: releng/11.0/sys/netinet/ip_options.c 298995 2016-05-03 18:05:43Z pfg $"); 34 35 #include "opt_ipstealth.h" 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/mbuf.h> 40 #include <sys/domain.h> 41 #include <sys/protosw.h> 42 #include <sys/socket.h> 43 #include <sys/time.h> 44 #include <sys/kernel.h> 45 #include <sys/syslog.h> 46 #include <sys/sysctl.h> 47 48 #include <net/if.h> 49 #include <net/if_types.h> 50 #include <net/if_var.h> 51 #include <net/if_dl.h> 52 #include <net/route.h> 53 #include <net/netisr.h> 54 #include <net/vnet.h> 55 56 #include <netinet/in.h> 57 #include <netinet/in_fib.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/in_var.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #include <netinet/ip_options.h> 64 #include <netinet/ip_icmp.h> 65 #include <machine/in_cksum.h> 66 67 #include <sys/socketvar.h> 68 69 static VNET_DEFINE(int, ip_dosourceroute); 70 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, 71 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0, 72 "Enable forwarding source routed IP packets"); 73 #define V_ip_dosourceroute VNET(ip_dosourceroute) 74 75 static VNET_DEFINE(int, ip_acceptsourceroute); 76 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute, 77 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0, 78 "Enable accepting source routed IP packets"); 79 #define V_ip_acceptsourceroute VNET(ip_acceptsourceroute) 80 81 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */ 82 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW, 83 &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)"); 84 85 static void save_rte(struct mbuf *m, u_char *, struct in_addr); 86 87 /* 88 * Do option processing on a datagram, possibly discarding it if bad options 89 * are encountered, or forwarding it if source-routed. 90 * 91 * The pass argument is used when operating in the IPSTEALTH mode to tell 92 * what options to process: [LS]SRR (pass 0) or the others (pass 1). The 93 * reason for as many as two passes is that when doing IPSTEALTH, non-routing 94 * options should be processed only if the packet is for us. 95 * 96 * Returns 1 if packet has been forwarded/freed, 0 if the packet should be 97 * processed further. 98 */ 99 int 100 ip_dooptions(struct mbuf *m, int pass) 101 { 102 struct ip *ip = mtod(m, struct ip *); 103 u_char *cp; 104 struct in_ifaddr *ia; 105 int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0; 106 struct in_addr *sin, dst; 107 uint32_t ntime; 108 struct nhop4_extended nh_ext; 109 struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET }; 110 111 /* Ignore or reject packets with IP options. */ 112 if (V_ip_doopts == 0) 113 return 0; 114 else if (V_ip_doopts == 2) { 115 type = ICMP_UNREACH; 116 code = ICMP_UNREACH_FILTER_PROHIB; 117 goto bad; 118 } 119 120 dst = ip->ip_dst; 121 cp = (u_char *)(ip + 1); 122 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 123 for (; cnt > 0; cnt -= optlen, cp += optlen) { 124 opt = cp[IPOPT_OPTVAL]; 125 if (opt == IPOPT_EOL) 126 break; 127 if (opt == IPOPT_NOP) 128 optlen = 1; 129 else { 130 if (cnt < IPOPT_OLEN + sizeof(*cp)) { 131 code = &cp[IPOPT_OLEN] - (u_char *)ip; 132 goto bad; 133 } 134 optlen = cp[IPOPT_OLEN]; 135 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) { 136 code = &cp[IPOPT_OLEN] - (u_char *)ip; 137 goto bad; 138 } 139 } 140 switch (opt) { 141 142 default: 143 break; 144 145 /* 146 * Source routing with record. Find interface with current 147 * destination address. If none on this machine then drop if 148 * strictly routed, or do nothing if loosely routed. Record 149 * interface address and bring up next address component. If 150 * strictly routed make sure next address is on directly 151 * accessible net. 152 */ 153 case IPOPT_LSRR: 154 case IPOPT_SSRR: 155 #ifdef IPSTEALTH 156 if (V_ipstealth && pass > 0) 157 break; 158 #endif 159 if (optlen < IPOPT_OFFSET + sizeof(*cp)) { 160 code = &cp[IPOPT_OLEN] - (u_char *)ip; 161 goto bad; 162 } 163 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) { 164 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 165 goto bad; 166 } 167 ipaddr.sin_addr = ip->ip_dst; 168 if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr) 169 == 0) { 170 if (opt == IPOPT_SSRR) { 171 type = ICMP_UNREACH; 172 code = ICMP_UNREACH_SRCFAIL; 173 goto bad; 174 } 175 if (!V_ip_dosourceroute) 176 goto nosourcerouting; 177 /* 178 * Loose routing, and not at next destination 179 * yet; nothing to do except forward. 180 */ 181 break; 182 } 183 off--; /* 0 origin */ 184 if (off > optlen - (int)sizeof(struct in_addr)) { 185 /* 186 * End of source route. Should be for us. 187 */ 188 if (!V_ip_acceptsourceroute) 189 goto nosourcerouting; 190 save_rte(m, cp, ip->ip_src); 191 break; 192 } 193 #ifdef IPSTEALTH 194 if (V_ipstealth) 195 goto dropit; 196 #endif 197 if (!V_ip_dosourceroute) { 198 if (V_ipforwarding) { 199 char buf[16]; /* aaa.bbb.ccc.ddd\0 */ 200 /* 201 * Acting as a router, so generate 202 * ICMP 203 */ 204 nosourcerouting: 205 strcpy(buf, inet_ntoa(ip->ip_dst)); 206 log(LOG_WARNING, 207 "attempted source route from %s to %s\n", 208 inet_ntoa(ip->ip_src), buf); 209 type = ICMP_UNREACH; 210 code = ICMP_UNREACH_SRCFAIL; 211 goto bad; 212 } else { 213 /* 214 * Not acting as a router, so 215 * silently drop. 216 */ 217 #ifdef IPSTEALTH 218 dropit: 219 #endif 220 IPSTAT_INC(ips_cantforward); 221 m_freem(m); 222 return (1); 223 } 224 } 225 226 /* 227 * locate outgoing interface 228 */ 229 (void)memcpy(&ipaddr.sin_addr, cp + off, 230 sizeof(ipaddr.sin_addr)); 231 232 type = ICMP_UNREACH; 233 code = ICMP_UNREACH_SRCFAIL; 234 235 if (opt == IPOPT_SSRR) { 236 #define INA struct in_ifaddr * 237 #define SA struct sockaddr * 238 ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr, 239 RT_ALL_FIBS); 240 if (ia == NULL) 241 ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0, 242 RT_ALL_FIBS); 243 if (ia == NULL) 244 goto bad; 245 246 memcpy(cp + off, &(IA_SIN(ia)->sin_addr), 247 sizeof(struct in_addr)); 248 ifa_free(&ia->ia_ifa); 249 } else { 250 /* XXX MRT 0 for routing */ 251 if (fib4_lookup_nh_ext(M_GETFIB(m), 252 ipaddr.sin_addr, 0, 0, &nh_ext) != 0) 253 goto bad; 254 255 memcpy(cp + off, &nh_ext.nh_src, 256 sizeof(struct in_addr)); 257 } 258 259 ip->ip_dst = ipaddr.sin_addr; 260 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 261 /* 262 * Let ip_intr's mcast routing check handle mcast pkts 263 */ 264 forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr)); 265 break; 266 267 case IPOPT_RR: 268 #ifdef IPSTEALTH 269 if (V_ipstealth && pass == 0) 270 break; 271 #endif 272 if (optlen < IPOPT_OFFSET + sizeof(*cp)) { 273 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 274 goto bad; 275 } 276 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) { 277 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 278 goto bad; 279 } 280 /* 281 * If no space remains, ignore. 282 */ 283 off--; /* 0 origin */ 284 if (off > optlen - (int)sizeof(struct in_addr)) 285 break; 286 (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst, 287 sizeof(ipaddr.sin_addr)); 288 /* 289 * Locate outgoing interface; if we're the 290 * destination, use the incoming interface (should be 291 * same). 292 */ 293 if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) { 294 memcpy(cp + off, &(IA_SIN(ia)->sin_addr), 295 sizeof(struct in_addr)); 296 ifa_free(&ia->ia_ifa); 297 } else if (fib4_lookup_nh_ext(M_GETFIB(m), 298 ipaddr.sin_addr, 0, 0, &nh_ext) == 0) { 299 memcpy(cp + off, &nh_ext.nh_src, 300 sizeof(struct in_addr)); 301 } else { 302 type = ICMP_UNREACH; 303 code = ICMP_UNREACH_HOST; 304 goto bad; 305 } 306 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 307 break; 308 309 case IPOPT_TS: 310 #ifdef IPSTEALTH 311 if (V_ipstealth && pass == 0) 312 break; 313 #endif 314 code = cp - (u_char *)ip; 315 if (optlen < 4 || optlen > 40) { 316 code = &cp[IPOPT_OLEN] - (u_char *)ip; 317 goto bad; 318 } 319 if ((off = cp[IPOPT_OFFSET]) < 5) { 320 code = &cp[IPOPT_OLEN] - (u_char *)ip; 321 goto bad; 322 } 323 if (off > optlen - (int)sizeof(int32_t)) { 324 cp[IPOPT_OFFSET + 1] += (1 << 4); 325 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) { 326 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 327 goto bad; 328 } 329 break; 330 } 331 off--; /* 0 origin */ 332 sin = (struct in_addr *)(cp + off); 333 switch (cp[IPOPT_OFFSET + 1] & 0x0f) { 334 335 case IPOPT_TS_TSONLY: 336 break; 337 338 case IPOPT_TS_TSANDADDR: 339 if (off + sizeof(uint32_t) + 340 sizeof(struct in_addr) > optlen) { 341 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 342 goto bad; 343 } 344 ipaddr.sin_addr = dst; 345 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr, 346 m->m_pkthdr.rcvif); 347 if (ia == NULL) 348 continue; 349 (void)memcpy(sin, &IA_SIN(ia)->sin_addr, 350 sizeof(struct in_addr)); 351 ifa_free(&ia->ia_ifa); 352 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 353 off += sizeof(struct in_addr); 354 break; 355 356 case IPOPT_TS_PRESPEC: 357 if (off + sizeof(uint32_t) + 358 sizeof(struct in_addr) > optlen) { 359 code = &cp[IPOPT_OFFSET] - (u_char *)ip; 360 goto bad; 361 } 362 (void)memcpy(&ipaddr.sin_addr, sin, 363 sizeof(struct in_addr)); 364 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0) 365 continue; 366 cp[IPOPT_OFFSET] += sizeof(struct in_addr); 367 off += sizeof(struct in_addr); 368 break; 369 370 default: 371 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip; 372 goto bad; 373 } 374 ntime = iptime(); 375 (void)memcpy(cp + off, &ntime, sizeof(uint32_t)); 376 cp[IPOPT_OFFSET] += sizeof(uint32_t); 377 } 378 } 379 if (forward && V_ipforwarding) { 380 ip_forward(m, 1); 381 return (1); 382 } 383 return (0); 384 bad: 385 icmp_error(m, type, code, 0, 0); 386 IPSTAT_INC(ips_badoptions); 387 return (1); 388 } 389 390 /* 391 * Save incoming source route for use in replies, to be picked up later by 392 * ip_srcroute if the receiver is interested. 393 */ 394 static void 395 save_rte(struct mbuf *m, u_char *option, struct in_addr dst) 396 { 397 unsigned olen; 398 struct ipopt_tag *opts; 399 400 opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS, 401 sizeof(struct ipopt_tag), M_NOWAIT); 402 if (opts == NULL) 403 return; 404 405 olen = option[IPOPT_OLEN]; 406 if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) { 407 m_tag_free((struct m_tag *)opts); 408 return; 409 } 410 bcopy(option, opts->ip_srcrt.srcopt, olen); 411 opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr); 412 opts->ip_srcrt.dst = dst; 413 m_tag_prepend(m, (struct m_tag *)opts); 414 } 415 416 /* 417 * Retrieve incoming source route for use in replies, in the same form used 418 * by setsockopt. The first hop is placed before the options, will be 419 * removed later. 420 */ 421 struct mbuf * 422 ip_srcroute(struct mbuf *m0) 423 { 424 struct in_addr *p, *q; 425 struct mbuf *m; 426 struct ipopt_tag *opts; 427 428 opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL); 429 if (opts == NULL) 430 return (NULL); 431 432 if (opts->ip_nhops == 0) 433 return (NULL); 434 m = m_get(M_NOWAIT, MT_DATA); 435 if (m == NULL) 436 return (NULL); 437 438 #define OPTSIZ (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt)) 439 440 /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */ 441 m->m_len = opts->ip_nhops * sizeof(struct in_addr) + 442 sizeof(struct in_addr) + OPTSIZ; 443 444 /* 445 * First, save first hop for return route. 446 */ 447 p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]); 448 *(mtod(m, struct in_addr *)) = *p--; 449 450 /* 451 * Copy option fields and padding (nop) to mbuf. 452 */ 453 opts->ip_srcrt.nop = IPOPT_NOP; 454 opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF; 455 (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr), 456 &(opts->ip_srcrt.nop), OPTSIZ); 457 q = (struct in_addr *)(mtod(m, caddr_t) + 458 sizeof(struct in_addr) + OPTSIZ); 459 #undef OPTSIZ 460 /* 461 * Record return path as an IP source route, reversing the path 462 * (pointers are now aligned). 463 */ 464 while (p >= opts->ip_srcrt.route) { 465 *q++ = *p--; 466 } 467 /* 468 * Last hop goes to final destination. 469 */ 470 *q = opts->ip_srcrt.dst; 471 m_tag_delete(m0, (struct m_tag *)opts); 472 return (m); 473 } 474 475 /* 476 * Strip out IP options, at higher level protocol in the kernel. 477 */ 478 void 479 ip_stripoptions(struct mbuf *m) 480 { 481 struct ip *ip = mtod(m, struct ip *); 482 int olen; 483 484 olen = (ip->ip_hl << 2) - sizeof(struct ip); 485 m->m_len -= olen; 486 if (m->m_flags & M_PKTHDR) 487 m->m_pkthdr.len -= olen; 488 ip->ip_len = htons(ntohs(ip->ip_len) - olen); 489 ip->ip_hl = sizeof(struct ip) >> 2; 490 491 bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1), 492 (size_t )(m->m_len - sizeof(struct ip))); 493 } 494 495 /* 496 * Insert IP options into preformed packet. Adjust IP destination as 497 * required for IP source routing, as indicated by a non-zero in_addr at the 498 * start of the options. 499 * 500 * XXX This routine assumes that the packet has no options in place. 501 */ 502 struct mbuf * 503 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen) 504 { 505 struct ipoption *p = mtod(opt, struct ipoption *); 506 struct mbuf *n; 507 struct ip *ip = mtod(m, struct ip *); 508 unsigned optlen; 509 510 optlen = opt->m_len - sizeof(p->ipopt_dst); 511 if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) { 512 *phlen = 0; 513 return (m); /* XXX should fail */ 514 } 515 if (p->ipopt_dst.s_addr) 516 ip->ip_dst = p->ipopt_dst; 517 if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) { 518 n = m_gethdr(M_NOWAIT, MT_DATA); 519 if (n == NULL) { 520 *phlen = 0; 521 return (m); 522 } 523 m_move_pkthdr(n, m); 524 n->m_pkthdr.rcvif = NULL; 525 n->m_pkthdr.len += optlen; 526 m->m_len -= sizeof(struct ip); 527 m->m_data += sizeof(struct ip); 528 n->m_next = m; 529 m = n; 530 m->m_len = optlen + sizeof(struct ip); 531 m->m_data += max_linkhdr; 532 bcopy(ip, mtod(m, void *), sizeof(struct ip)); 533 } else { 534 m->m_data -= optlen; 535 m->m_len += optlen; 536 m->m_pkthdr.len += optlen; 537 bcopy(ip, mtod(m, void *), sizeof(struct ip)); 538 } 539 ip = mtod(m, struct ip *); 540 bcopy(p->ipopt_list, ip + 1, optlen); 541 *phlen = sizeof(struct ip) + optlen; 542 ip->ip_v = IPVERSION; 543 ip->ip_hl = *phlen >> 2; 544 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 545 return (m); 546 } 547 548 /* 549 * Copy options from ip to jp, omitting those not copied during 550 * fragmentation. 551 */ 552 int 553 ip_optcopy(struct ip *ip, struct ip *jp) 554 { 555 u_char *cp, *dp; 556 int opt, optlen, cnt; 557 558 cp = (u_char *)(ip + 1); 559 dp = (u_char *)(jp + 1); 560 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 561 for (; cnt > 0; cnt -= optlen, cp += optlen) { 562 opt = cp[0]; 563 if (opt == IPOPT_EOL) 564 break; 565 if (opt == IPOPT_NOP) { 566 /* Preserve for IP mcast tunnel's LSRR alignment. */ 567 *dp++ = IPOPT_NOP; 568 optlen = 1; 569 continue; 570 } 571 572 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp), 573 ("ip_optcopy: malformed ipv4 option")); 574 optlen = cp[IPOPT_OLEN]; 575 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt, 576 ("ip_optcopy: malformed ipv4 option")); 577 578 /* Bogus lengths should have been caught by ip_dooptions. */ 579 if (optlen > cnt) 580 optlen = cnt; 581 if (IPOPT_COPIED(opt)) { 582 bcopy(cp, dp, optlen); 583 dp += optlen; 584 } 585 } 586 for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++) 587 *dp++ = IPOPT_EOL; 588 return (optlen); 589 } 590 591 /* 592 * Set up IP options in pcb for insertion in output packets. Store in mbuf 593 * with pointer in pcbopt, adding pseudo-option with destination address if 594 * source routed. 595 */ 596 int 597 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m) 598 { 599 int cnt, optlen; 600 u_char *cp; 601 struct mbuf **pcbopt; 602 u_char opt; 603 604 INP_WLOCK_ASSERT(inp); 605 606 pcbopt = &inp->inp_options; 607 608 /* turn off any old options */ 609 if (*pcbopt) 610 (void)m_free(*pcbopt); 611 *pcbopt = NULL; 612 if (m == NULL || m->m_len == 0) { 613 /* 614 * Only turning off any previous options. 615 */ 616 if (m != NULL) 617 (void)m_free(m); 618 return (0); 619 } 620 621 if (m->m_len % sizeof(int32_t)) 622 goto bad; 623 /* 624 * IP first-hop destination address will be stored before actual 625 * options; move other options back and clear it when none present. 626 */ 627 if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN]) 628 goto bad; 629 cnt = m->m_len; 630 m->m_len += sizeof(struct in_addr); 631 cp = mtod(m, u_char *) + sizeof(struct in_addr); 632 bcopy(mtod(m, void *), cp, (unsigned)cnt); 633 bzero(mtod(m, void *), sizeof(struct in_addr)); 634 635 for (; cnt > 0; cnt -= optlen, cp += optlen) { 636 opt = cp[IPOPT_OPTVAL]; 637 if (opt == IPOPT_EOL) 638 break; 639 if (opt == IPOPT_NOP) 640 optlen = 1; 641 else { 642 if (cnt < IPOPT_OLEN + sizeof(*cp)) 643 goto bad; 644 optlen = cp[IPOPT_OLEN]; 645 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) 646 goto bad; 647 } 648 switch (opt) { 649 650 default: 651 break; 652 653 case IPOPT_LSRR: 654 case IPOPT_SSRR: 655 /* 656 * User process specifies route as: 657 * 658 * ->A->B->C->D 659 * 660 * D must be our final destination (but we can't 661 * check that since we may not have connected yet). 662 * A is first hop destination, which doesn't appear 663 * in actual IP option, but is stored before the 664 * options. 665 */ 666 /* XXX-BZ PRIV_NETINET_SETHDROPTS? */ 667 if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr)) 668 goto bad; 669 m->m_len -= sizeof(struct in_addr); 670 cnt -= sizeof(struct in_addr); 671 optlen -= sizeof(struct in_addr); 672 cp[IPOPT_OLEN] = optlen; 673 /* 674 * Move first hop before start of options. 675 */ 676 bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t), 677 sizeof(struct in_addr)); 678 /* 679 * Then copy rest of options back 680 * to close up the deleted entry. 681 */ 682 bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)), 683 &cp[IPOPT_OFFSET+1], 684 (unsigned)cnt - (IPOPT_MINOFF - 1)); 685 break; 686 } 687 } 688 if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr)) 689 goto bad; 690 *pcbopt = m; 691 return (0); 692 693 bad: 694 (void)m_free(m); 695 return (EINVAL); 696 } 697 698 /* 699 * Check for the presence of the IP Router Alert option [RFC2113] 700 * in the header of an IPv4 datagram. 701 * 702 * This call is not intended for use from the forwarding path; it is here 703 * so that protocol domains may check for the presence of the option. 704 * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert 705 * option does not have much relevance to the implementation, though this 706 * may change in future. 707 * Router alert options SHOULD be passed if running in IPSTEALTH mode and 708 * we are not the endpoint. 709 * Length checks on individual options should already have been performed 710 * by ip_dooptions() therefore they are folded under INVARIANTS here. 711 * 712 * Return zero if not present or options are invalid, non-zero if present. 713 */ 714 int 715 ip_checkrouteralert(struct mbuf *m) 716 { 717 struct ip *ip = mtod(m, struct ip *); 718 u_char *cp; 719 int opt, optlen, cnt, found_ra; 720 721 found_ra = 0; 722 cp = (u_char *)(ip + 1); 723 cnt = (ip->ip_hl << 2) - sizeof (struct ip); 724 for (; cnt > 0; cnt -= optlen, cp += optlen) { 725 opt = cp[IPOPT_OPTVAL]; 726 if (opt == IPOPT_EOL) 727 break; 728 if (opt == IPOPT_NOP) 729 optlen = 1; 730 else { 731 #ifdef INVARIANTS 732 if (cnt < IPOPT_OLEN + sizeof(*cp)) 733 break; 734 #endif 735 optlen = cp[IPOPT_OLEN]; 736 #ifdef INVARIANTS 737 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) 738 break; 739 #endif 740 } 741 switch (opt) { 742 case IPOPT_RA: 743 #ifdef INVARIANTS 744 if (optlen != IPOPT_OFFSET + sizeof(uint16_t) || 745 (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0)) 746 break; 747 else 748 #endif 749 found_ra = 1; 750 break; 751 default: 752 break; 753 } 754 } 755 756 return (found_ra); 757 }
Cache object: 70dd3b8ddf76c039f384e2a2ab7e602d
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