Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/netipsec/ipsec_output.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
1 /* $NetBSD: ipsec_output.c,v 1.17.2.2 2007/10/31 12:39:30 liamjfoy Exp $ */ 2 3 /*- 4 * Copyright (c) 2002, 2003 Sam Leffler, Errno Consulting 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 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * $FreeBSD: /repoman/r/ncvs/src/sys/netipsec/ipsec_output.c,v 1.3.2.2 2003/03/28 20:32:53 sam Exp $ 29 */ 30 31 #include <sys/cdefs.h> 32 __KERNEL_RCSID(0, "$NetBSD: ipsec_output.c,v 1.17.2.2 2007/10/31 12:39:30 liamjfoy Exp $"); 33 34 /* 35 * IPsec output processing. 36 */ 37 #include "opt_inet.h" 38 #ifdef __FreeBSD__ 39 #include "opt_inet6.h" 40 #endif 41 #include "opt_ipsec.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/mbuf.h> 46 #include <sys/domain.h> 47 #include <sys/protosw.h> 48 #include <sys/socket.h> 49 #include <sys/errno.h> 50 #include <sys/syslog.h> 51 52 #include <net/if.h> 53 #include <net/route.h> 54 55 #include <netinet/in.h> 56 #include <netinet/in_systm.h> 57 #include <netinet/ip.h> 58 #include <netinet/ip_var.h> 59 #include <netinet/in_var.h> 60 #include <netinet/ip_ecn.h> 61 #ifdef INET6 62 # ifdef __FreeBSD__ 63 # include <netinet6/ip6_ecn.h> 64 # endif 65 #endif 66 67 #include <netinet/ip6.h> 68 #ifdef INET6 69 #include <netinet6/ip6_var.h> 70 #endif 71 #include <netinet/in_pcb.h> 72 #ifdef INET6 73 #include <netinet/icmp6.h> 74 #endif 75 76 #include <netipsec/ipsec.h> 77 #include <netipsec/ipsec_var.h> 78 #ifdef INET6 79 #include <netipsec/ipsec6.h> 80 #endif 81 #include <netipsec/ah_var.h> 82 #include <netipsec/esp_var.h> 83 #include <netipsec/ipcomp_var.h> 84 85 #include <netipsec/xform.h> 86 87 #include <netipsec/key.h> 88 #include <netipsec/keydb.h> 89 #include <netipsec/key_debug.h> 90 #include <netipsec/ipsec_osdep.h> 91 92 #include <net/net_osdep.h> /* ovbcopy() in ipsec6_encapsulate() */ 93 94 int 95 ipsec_process_done(struct mbuf *m, struct ipsecrequest *isr) 96 { 97 struct tdb_ident *tdbi; 98 struct m_tag *mtag; 99 struct secasvar *sav; 100 struct secasindex *saidx; 101 int error; 102 103 IPSEC_SPLASSERT_SOFTNET("ipsec_process_done"); 104 105 IPSEC_ASSERT(m != NULL, ("ipsec_process_done: null mbuf")); 106 IPSEC_ASSERT(isr != NULL, ("ipsec_process_done: null ISR")); 107 sav = isr->sav; 108 IPSEC_ASSERT(sav != NULL, ("ipsec_process_done: null SA")); 109 IPSEC_ASSERT(sav->sah != NULL, ("ipsec_process_done: null SAH")); 110 111 saidx = &sav->sah->saidx; 112 switch (saidx->dst.sa.sa_family) { 113 #ifdef INET 114 case AF_INET: 115 /* Fix the header length, for AH processing. */ 116 mtod(m, struct ip *)->ip_len = htons(m->m_pkthdr.len); 117 break; 118 #endif /* INET */ 119 #ifdef INET6 120 case AF_INET6: 121 /* Fix the header length, for AH processing. */ 122 if (m->m_pkthdr.len < sizeof (struct ip6_hdr)) { 123 error = ENXIO; 124 goto bad; 125 } 126 if (m->m_pkthdr.len - sizeof (struct ip6_hdr) > IPV6_MAXPACKET) { 127 /* No jumbogram support. */ 128 error = ENXIO; /*?*/ 129 goto bad; 130 } 131 mtod(m, struct ip6_hdr *)->ip6_plen = 132 htons(m->m_pkthdr.len - sizeof(struct ip6_hdr)); 133 break; 134 #endif /* INET6 */ 135 default: 136 DPRINTF(("ipsec_process_done: unknown protocol family %u\n", 137 saidx->dst.sa.sa_family)); 138 error = ENXIO; 139 goto bad; 140 } 141 142 /* 143 * Add a record of what we've done or what needs to be done to the 144 * packet. 145 */ 146 mtag = m_tag_get(PACKET_TAG_IPSEC_OUT_DONE, 147 sizeof(struct tdb_ident), M_NOWAIT); 148 if (mtag == NULL) { 149 DPRINTF(("ipsec_process_done: could not get packet tag\n")); 150 error = ENOMEM; 151 goto bad; 152 } 153 154 tdbi = (struct tdb_ident *)(mtag + 1); 155 tdbi->dst = saidx->dst; 156 tdbi->proto = saidx->proto; 157 tdbi->spi = sav->spi; 158 m_tag_prepend(m, mtag); 159 160 /* 161 * If there's another (bundled) SA to apply, do so. 162 * Note that this puts a burden on the kernel stack size. 163 * If this is a problem we'll need to introduce a queue 164 * to set the packet on so we can unwind the stack before 165 * doing further processing. 166 */ 167 if (isr->next) { 168 newipsecstat.ips_out_bundlesa++; 169 switch ( saidx->dst.sa.sa_family ) { 170 #ifdef INET 171 case AF_INET: 172 return ipsec4_process_packet(m, isr->next, 0,0); 173 #endif /* INET */ 174 #ifdef INET6 175 case AF_INET6: 176 return ipsec6_process_packet(m,isr->next); 177 #endif /* INET6 */ 178 default : 179 DPRINTF(("ipsec_process_done: unknown protocol family %u\n", 180 saidx->dst.sa.sa_family)); 181 error = ENXIO; 182 goto bad; 183 } 184 } 185 186 /* 187 * We're done with IPsec processing, transmit the packet using the 188 * appropriate network protocol (IP or IPv6). SPD lookup will be 189 * performed again there. 190 */ 191 switch (saidx->dst.sa.sa_family) { 192 #ifdef INET 193 struct ip *ip; 194 case AF_INET: 195 ip = mtod(m, struct ip *); 196 #ifdef __FreeBSD__ 197 /* FreeBSD ip_output() expects ip_len, ip_off in host endian */ 198 ip->ip_len = ntohs(ip->ip_len); 199 ip->ip_off = ntohs(ip->ip_off); 200 #endif /* __FreeBSD_ */ 201 return ip_output(m, NULL, NULL, IP_RAWOUTPUT, 202 (struct ip_moptions *)NULL, (struct socket *)NULL); 203 204 #endif /* INET */ 205 #ifdef INET6 206 case AF_INET6: 207 /* 208 * We don't need massage, IPv6 header fields are always in 209 * net endian. 210 */ 211 return ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 212 #endif /* INET6 */ 213 } 214 panic("ipsec_process_done"); 215 bad: 216 m_freem(m); 217 KEY_FREESAV(&sav); 218 return (error); 219 } 220 221 static struct ipsecrequest * 222 ipsec_nextisr( 223 struct mbuf *m, 224 struct ipsecrequest *isr, 225 int af, 226 struct secasindex *saidx, 227 int *error 228 ) 229 { 230 #define IPSEC_OSTAT(x,y,z) (isr->saidx.proto == IPPROTO_ESP ? (x)++ : \ 231 isr->saidx.proto == IPPROTO_AH ? (y)++ : (z)++) 232 struct secasvar *sav; 233 234 IPSEC_SPLASSERT_SOFTNET("ipsec_nextisr"); 235 IPSEC_ASSERT(af == AF_INET || af == AF_INET6, 236 ("ipsec_nextisr: invalid address family %u", af)); 237 again: 238 /* 239 * Craft SA index to search for proper SA. Note that 240 * we only fillin unspecified SA peers for transport 241 * mode; for tunnel mode they must already be filled in. 242 */ 243 *saidx = isr->saidx; 244 if (isr->saidx.mode == IPSEC_MODE_TRANSPORT) { 245 /* Fillin unspecified SA peers only for transport mode */ 246 if (af == AF_INET) { 247 struct sockaddr_in *sin; 248 struct ip *ip = mtod(m, struct ip *); 249 250 if (saidx->src.sa.sa_len == 0) { 251 sin = &saidx->src.sin; 252 sin->sin_len = sizeof(*sin); 253 sin->sin_family = AF_INET; 254 sin->sin_port = IPSEC_PORT_ANY; 255 sin->sin_addr = ip->ip_src; 256 } 257 if (saidx->dst.sa.sa_len == 0) { 258 sin = &saidx->dst.sin; 259 sin->sin_len = sizeof(*sin); 260 sin->sin_family = AF_INET; 261 sin->sin_port = IPSEC_PORT_ANY; 262 sin->sin_addr = ip->ip_dst; 263 } 264 } else { 265 struct sockaddr_in6 *sin6; 266 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 267 268 if (saidx->src.sin6.sin6_len == 0) { 269 sin6 = (struct sockaddr_in6 *)&saidx->src; 270 sin6->sin6_len = sizeof(*sin6); 271 sin6->sin6_family = AF_INET6; 272 sin6->sin6_port = IPSEC_PORT_ANY; 273 sin6->sin6_addr = ip6->ip6_src; 274 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) { 275 /* fix scope id for comparing SPD */ 276 sin6->sin6_addr.s6_addr16[1] = 0; 277 sin6->sin6_scope_id = 278 ntohs(ip6->ip6_src.s6_addr16[1]); 279 } 280 } 281 if (saidx->dst.sin6.sin6_len == 0) { 282 sin6 = (struct sockaddr_in6 *)&saidx->dst; 283 sin6->sin6_len = sizeof(*sin6); 284 sin6->sin6_family = AF_INET6; 285 sin6->sin6_port = IPSEC_PORT_ANY; 286 sin6->sin6_addr = ip6->ip6_dst; 287 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) { 288 /* fix scope id for comparing SPD */ 289 sin6->sin6_addr.s6_addr16[1] = 0; 290 sin6->sin6_scope_id = 291 ntohs(ip6->ip6_dst.s6_addr16[1]); 292 } 293 } 294 } 295 } 296 297 /* 298 * Lookup SA and validate it. 299 */ 300 *error = key_checkrequest(isr, saidx); 301 if (*error != 0) { 302 /* 303 * IPsec processing is required, but no SA found. 304 * I assume that key_acquire() had been called 305 * to get/establish the SA. Here I discard 306 * this packet because it is responsibility for 307 * upper layer to retransmit the packet. 308 */ 309 newipsecstat.ips_out_nosa++; 310 goto bad; 311 } 312 sav = isr->sav; 313 if (sav == NULL) { /* XXX valid return */ 314 IPSEC_ASSERT(ipsec_get_reqlevel(isr) == IPSEC_LEVEL_USE, 315 ("ipsec_nextisr: no SA found, but required; level %u", 316 ipsec_get_reqlevel(isr))); 317 isr = isr->next; 318 if (isr == NULL) { 319 /*XXXstatistic??*/ 320 *error = EINVAL; /*XXX*/ 321 return isr; 322 } 323 goto again; 324 } 325 326 /* 327 * Check system global policy controls. 328 */ 329 if ((isr->saidx.proto == IPPROTO_ESP && !esp_enable) || 330 (isr->saidx.proto == IPPROTO_AH && !ah_enable) || 331 (isr->saidx.proto == IPPROTO_IPCOMP && !ipcomp_enable)) { 332 DPRINTF(("ipsec_nextisr: IPsec outbound packet dropped due" 333 " to policy (check your sysctls)\n")); 334 IPSEC_OSTAT(espstat.esps_pdrops, ahstat.ahs_pdrops, 335 ipcompstat.ipcomps_pdrops); 336 *error = EHOSTUNREACH; 337 goto bad; 338 } 339 340 /* 341 * Sanity check the SA contents for the caller 342 * before they invoke the xform output method. 343 */ 344 if (sav->tdb_xform == NULL) { 345 DPRINTF(("ipsec_nextisr: no transform for SA\n")); 346 IPSEC_OSTAT(espstat.esps_noxform, ahstat.ahs_noxform, 347 ipcompstat.ipcomps_noxform); 348 *error = EHOSTUNREACH; 349 goto bad; 350 } 351 return isr; 352 bad: 353 IPSEC_ASSERT(*error != 0, ("ipsec_nextisr: error return w/ no error code")); 354 return NULL; 355 #undef IPSEC_OSTAT 356 } 357 358 #ifdef INET 359 /* 360 * IPsec output logic for IPv4. 361 */ 362 int 363 ipsec4_process_packet( 364 struct mbuf *m, 365 struct ipsecrequest *isr, 366 int flags, 367 int tunalready 368 ) 369 { 370 struct secasindex saidx; 371 struct secasvar *sav; 372 struct ip *ip; 373 int s, error, i, off; 374 375 IPSEC_ASSERT(m != NULL, ("ipsec4_process_packet: null mbuf")); 376 IPSEC_ASSERT(isr != NULL, ("ipsec4_process_packet: null isr")); 377 378 s = splsoftnet(); /* insure SA contents don't change */ 379 380 isr = ipsec_nextisr(m, isr, AF_INET, &saidx, &error); 381 if (isr == NULL) 382 goto bad; 383 384 sav = isr->sav; 385 if (!tunalready) { 386 union sockaddr_union *dst = &sav->sah->saidx.dst; 387 int setdf; 388 389 /* 390 * Collect IP_DF state from the outer header. 391 */ 392 if (dst->sa.sa_family == AF_INET) { 393 if (m->m_len < sizeof (struct ip) && 394 (m = m_pullup(m, sizeof (struct ip))) == NULL) { 395 error = ENOBUFS; 396 goto bad; 397 } 398 ip = mtod(m, struct ip *); 399 /* Honor system-wide control of how to handle IP_DF */ 400 switch (ip4_ipsec_dfbit) { 401 case 0: /* clear in outer header */ 402 case 1: /* set in outer header */ 403 setdf = ip4_ipsec_dfbit; 404 break; 405 default: /* propagate to outer header */ 406 setdf = ip->ip_off; 407 #ifndef __FreeBSD__ 408 /* On FreeBSD, ip_off and ip_len assumed in host endian. */ 409 setdf = ntohs(setdf); 410 #endif 411 setdf = htons(setdf & IP_DF); 412 break; 413 } 414 } else { 415 ip = NULL; /* keep compiler happy */ 416 setdf = 0; 417 } 418 /* Do the appropriate encapsulation, if necessary */ 419 if (isr->saidx.mode == IPSEC_MODE_TUNNEL || /* Tunnel requ'd */ 420 dst->sa.sa_family != AF_INET || /* PF mismatch */ 421 #if 0 422 (sav->flags & SADB_X_SAFLAGS_TUNNEL) || /* Tunnel requ'd */ 423 sav->tdb_xform->xf_type == XF_IP4 || /* ditto */ 424 #endif 425 (dst->sa.sa_family == AF_INET && /* Proxy */ 426 dst->sin.sin_addr.s_addr != INADDR_ANY && 427 dst->sin.sin_addr.s_addr != ip->ip_dst.s_addr)) { 428 struct mbuf *mp; 429 430 /* Fix IPv4 header checksum and length */ 431 if (m->m_len < sizeof (struct ip) && 432 (m = m_pullup(m, sizeof (struct ip))) == NULL) { 433 error = ENOBUFS; 434 goto bad; 435 } 436 ip = mtod(m, struct ip *); 437 ip->ip_len = htons(m->m_pkthdr.len); 438 ip->ip_sum = 0; 439 #ifdef _IP_VHL 440 if (ip->ip_vhl == IP_VHL_BORING) 441 ip->ip_sum = in_cksum_hdr(ip); 442 else 443 ip->ip_sum = in_cksum(m, 444 _IP_VHL_HL(ip->ip_vhl) << 2); 445 #else 446 ip->ip_sum = in_cksum(m, ip->ip_hl << 2); 447 #endif 448 449 /* Encapsulate the packet */ 450 error = ipip_output(m, isr, &mp, 0, 0); 451 if (mp == NULL && !error) { 452 /* Should never happen. */ 453 DPRINTF(("ipsec4_process_packet: ipip_output " 454 "returns no mbuf and no error!")); 455 error = EFAULT; 456 } 457 if (error) { 458 if (mp) { 459 /* XXX: Should never happen! */ 460 m_freem(mp); 461 } 462 m = NULL; /* ipip_output() already freed it */ 463 goto bad; 464 } 465 m = mp, mp = NULL; 466 /* 467 * ipip_output clears IP_DF in the new header. If 468 * we need to propagate IP_DF from the outer header, 469 * then we have to do it here. 470 * 471 * XXX shouldn't assume what ipip_output does. 472 */ 473 if (dst->sa.sa_family == AF_INET && setdf) { 474 if (m->m_len < sizeof (struct ip) && 475 (m = m_pullup(m, sizeof (struct ip))) == NULL) { 476 error = ENOBUFS; 477 goto bad; 478 } 479 ip = mtod(m, struct ip *); 480 ip->ip_off |= IP_OFF_CONVERT(IP_DF); 481 } 482 } 483 } 484 485 /* 486 * Dispatch to the appropriate IPsec transform logic. The 487 * packet will be returned for transmission after crypto 488 * processing, etc. are completed. For encapsulation we 489 * bypass this call because of the explicit call done above 490 * (necessary to deal with IP_DF handling for IPv4). 491 * 492 * NB: m & sav are ``passed to caller'' who's reponsible for 493 * for reclaiming their resources. 494 */ 495 if (sav->tdb_xform->xf_type != XF_IP4) { 496 ip = mtod(m, struct ip *); 497 i = ip->ip_hl << 2; 498 off = offsetof(struct ip, ip_p); 499 error = (*sav->tdb_xform->xf_output)(m, isr, NULL, i, off); 500 } else { 501 error = ipsec_process_done(m, isr); 502 } 503 splx(s); 504 return error; 505 bad: 506 splx(s); 507 if (m) 508 m_freem(m); 509 return error; 510 } 511 #endif 512 513 #ifdef INET6 514 int 515 ipsec6_process_packet( 516 struct mbuf *m, 517 struct ipsecrequest *isr 518 ) 519 { 520 struct secasindex saidx; 521 struct secasvar *sav; 522 struct ip6_hdr *ip6; 523 int s, error, i, off; 524 525 IPSEC_ASSERT(m != NULL, ("ipsec6_process_packet: null mbuf")); 526 IPSEC_ASSERT(isr != NULL, ("ipsec6_process_packet: null isr")); 527 528 s = splsoftnet(); /* insure SA contents don't change */ 529 isr = ipsec_nextisr(m, isr, AF_INET6, &saidx, &error); 530 if (isr == NULL) { 531 // XXX Should we send a notification ? 532 goto bad; 533 } 534 535 sav = isr->sav; 536 if (sav->tdb_xform->xf_type != XF_IP4) { 537 i = sizeof(struct ip6_hdr); 538 off = offsetof(struct ip6_hdr, ip6_nxt); 539 error = (*sav->tdb_xform->xf_output)(m, isr, NULL, i, off); 540 } else { 541 union sockaddr_union *dst = &sav->sah->saidx.dst; 542 543 ip6 = mtod(m, struct ip6_hdr *); 544 545 /* Do the appropriate encapsulation, if necessary */ 546 if (isr->saidx.mode == IPSEC_MODE_TUNNEL || /* Tunnel requ'd */ 547 dst->sa.sa_family != AF_INET6 || /* PF mismatch */ 548 ((dst->sa.sa_family == AF_INET6) && 549 (!IN6_IS_ADDR_UNSPECIFIED(&dst->sin6.sin6_addr)) && 550 (!IN6_ARE_ADDR_EQUAL(&dst->sin6.sin6_addr, 551 &ip6->ip6_dst))) 552 ) 553 { 554 struct mbuf *mp; 555 /* Fix IPv6 header payload length. */ 556 if (m->m_len < sizeof(struct ip6_hdr)) 557 if ((m = m_pullup(m,sizeof(struct ip6_hdr))) == NULL) 558 return ENOBUFS; 559 560 if (m->m_pkthdr.len - sizeof(*ip6) > IPV6_MAXPACKET) { 561 /* No jumbogram support. */ 562 m_freem(m); 563 return ENXIO; /*XXX*/ 564 } 565 ip6 = mtod(m, struct ip6_hdr *); 566 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 567 568 /* Encapsulate the packet */ 569 error = ipip_output(m, isr, &mp, 0, 0); 570 if (mp == NULL && !error) { 571 /* Should never happen. */ 572 DPRINTF(("ipsec6_process_packet: ipip_output " 573 "returns no mbuf and no error!")); 574 error = EFAULT; 575 } 576 577 if (error) { 578 if (mp) { 579 /* XXX: Should never happen! */ 580 m_freem(mp); 581 } 582 m = NULL; /* ipip_output() already freed it */ 583 goto bad; 584 } 585 586 m = mp; 587 mp = NULL; 588 } 589 590 error = ipsec_process_done(m,isr); 591 } 592 splx(s); 593 return error; 594 bad: 595 splx(s); 596 if (m) 597 m_freem(m); 598 return error; 599 } 600 #endif /*INET6*/
Cache object: 1071946cdd15a1017aef7d49974a5307
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]