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sys/netinet/tcp_syncache.c
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1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2001 McAfee, Inc. 5 * Copyright (c) 2006,2013 Andre Oppermann, Internet Business Solutions AG 6 * All rights reserved. 7 * 8 * This software was developed for the FreeBSD Project by Jonathan Lemon 9 * and McAfee Research, the Security Research Division of McAfee, Inc. under 10 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 11 * DARPA CHATS research program. [2001 McAfee, Inc.] 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 __FBSDID("$FreeBSD: releng/12.0/sys/netinet/tcp_syncache.c 339430 2018-10-18 19:21:18Z tuexen $"); 37 38 #include "opt_inet.h" 39 #include "opt_inet6.h" 40 #include "opt_ipsec.h" 41 #include "opt_pcbgroup.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/hash.h> 46 #include <sys/refcount.h> 47 #include <sys/kernel.h> 48 #include <sys/sysctl.h> 49 #include <sys/limits.h> 50 #include <sys/lock.h> 51 #include <sys/mutex.h> 52 #include <sys/malloc.h> 53 #include <sys/mbuf.h> 54 #include <sys/proc.h> /* for proc0 declaration */ 55 #include <sys/random.h> 56 #include <sys/socket.h> 57 #include <sys/socketvar.h> 58 #include <sys/syslog.h> 59 #include <sys/ucred.h> 60 61 #include <sys/md5.h> 62 #include <crypto/siphash/siphash.h> 63 64 #include <vm/uma.h> 65 66 #include <net/if.h> 67 #include <net/if_var.h> 68 #include <net/route.h> 69 #include <net/vnet.h> 70 71 #include <netinet/in.h> 72 #include <netinet/in_kdtrace.h> 73 #include <netinet/in_systm.h> 74 #include <netinet/ip.h> 75 #include <netinet/in_var.h> 76 #include <netinet/in_pcb.h> 77 #include <netinet/ip_var.h> 78 #include <netinet/ip_options.h> 79 #ifdef INET6 80 #include <netinet/ip6.h> 81 #include <netinet/icmp6.h> 82 #include <netinet6/nd6.h> 83 #include <netinet6/ip6_var.h> 84 #include <netinet6/in6_pcb.h> 85 #endif 86 #include <netinet/tcp.h> 87 #include <netinet/tcp_fastopen.h> 88 #include <netinet/tcp_fsm.h> 89 #include <netinet/tcp_seq.h> 90 #include <netinet/tcp_timer.h> 91 #include <netinet/tcp_var.h> 92 #include <netinet/tcp_syncache.h> 93 #ifdef INET6 94 #include <netinet6/tcp6_var.h> 95 #endif 96 #ifdef TCP_OFFLOAD 97 #include <netinet/toecore.h> 98 #endif 99 100 #include <netipsec/ipsec_support.h> 101 102 #include <machine/in_cksum.h> 103 104 #include <security/mac/mac_framework.h> 105 106 VNET_DEFINE_STATIC(int, tcp_syncookies) = 1; 107 #define V_tcp_syncookies VNET(tcp_syncookies) 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_VNET | CTLFLAG_RW, 109 &VNET_NAME(tcp_syncookies), 0, 110 "Use TCP SYN cookies if the syncache overflows"); 111 112 VNET_DEFINE_STATIC(int, tcp_syncookiesonly) = 0; 113 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly) 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_VNET | CTLFLAG_RW, 115 &VNET_NAME(tcp_syncookiesonly), 0, 116 "Use only TCP SYN cookies"); 117 118 VNET_DEFINE_STATIC(int, functions_inherit_listen_socket_stack) = 1; 119 #define V_functions_inherit_listen_socket_stack \ 120 VNET(functions_inherit_listen_socket_stack) 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, functions_inherit_listen_socket_stack, 122 CTLFLAG_VNET | CTLFLAG_RW, 123 &VNET_NAME(functions_inherit_listen_socket_stack), 0, 124 "Inherit listen socket's stack"); 125 126 #ifdef TCP_OFFLOAD 127 #define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL) 128 #endif 129 130 static void syncache_drop(struct syncache *, struct syncache_head *); 131 static void syncache_free(struct syncache *); 132 static void syncache_insert(struct syncache *, struct syncache_head *); 133 static int syncache_respond(struct syncache *, struct syncache_head *, 134 const struct mbuf *, int); 135 static struct socket *syncache_socket(struct syncache *, struct socket *, 136 struct mbuf *m); 137 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 138 int docallout); 139 static void syncache_timer(void *); 140 141 static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t, 142 uint8_t *, uintptr_t); 143 static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *); 144 static struct syncache 145 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 146 struct syncache *, struct tcphdr *, struct tcpopt *, 147 struct socket *); 148 static void syncookie_reseed(void *); 149 #ifdef INVARIANTS 150 static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 151 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 152 struct socket *lso); 153 #endif 154 155 /* 156 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 157 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 158 * the odds are that the user has given up attempting to connect by then. 159 */ 160 #define SYNCACHE_MAXREXMTS 3 161 162 /* Arbitrary values */ 163 #define TCP_SYNCACHE_HASHSIZE 512 164 #define TCP_SYNCACHE_BUCKETLIMIT 30 165 166 VNET_DEFINE_STATIC(struct tcp_syncache, tcp_syncache); 167 #define V_tcp_syncache VNET(tcp_syncache) 168 169 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, 170 "TCP SYN cache"); 171 172 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN, 173 &VNET_NAME(tcp_syncache.bucket_limit), 0, 174 "Per-bucket hash limit for syncache"); 175 176 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN, 177 &VNET_NAME(tcp_syncache.cache_limit), 0, 178 "Overall entry limit for syncache"); 179 180 SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET, 181 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache"); 182 183 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN, 184 &VNET_NAME(tcp_syncache.hashsize), 0, 185 "Size of TCP syncache hashtable"); 186 187 static int 188 sysctl_net_inet_tcp_syncache_rexmtlimit_check(SYSCTL_HANDLER_ARGS) 189 { 190 int error; 191 u_int new; 192 193 new = V_tcp_syncache.rexmt_limit; 194 error = sysctl_handle_int(oidp, &new, 0, req); 195 if ((error == 0) && (req->newptr != NULL)) { 196 if (new > TCP_MAXRXTSHIFT) 197 error = EINVAL; 198 else 199 V_tcp_syncache.rexmt_limit = new; 200 } 201 return (error); 202 } 203 204 SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, 205 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW, 206 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 207 sysctl_net_inet_tcp_syncache_rexmtlimit_check, "UI", 208 "Limit on SYN/ACK retransmissions"); 209 210 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 211 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 212 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 213 "Send reset on socket allocation failure"); 214 215 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 216 217 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 218 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 219 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 220 221 /* 222 * Requires the syncache entry to be already removed from the bucket list. 223 */ 224 static void 225 syncache_free(struct syncache *sc) 226 { 227 228 if (sc->sc_ipopts) 229 (void) m_free(sc->sc_ipopts); 230 if (sc->sc_cred) 231 crfree(sc->sc_cred); 232 #ifdef MAC 233 mac_syncache_destroy(&sc->sc_label); 234 #endif 235 236 uma_zfree(V_tcp_syncache.zone, sc); 237 } 238 239 void 240 syncache_init(void) 241 { 242 int i; 243 244 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 245 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 246 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 247 V_tcp_syncache.hash_secret = arc4random(); 248 249 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 250 &V_tcp_syncache.hashsize); 251 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 252 &V_tcp_syncache.bucket_limit); 253 if (!powerof2(V_tcp_syncache.hashsize) || 254 V_tcp_syncache.hashsize == 0) { 255 printf("WARNING: syncache hash size is not a power of 2.\n"); 256 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 257 } 258 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 259 260 /* Set limits. */ 261 V_tcp_syncache.cache_limit = 262 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 263 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 264 &V_tcp_syncache.cache_limit); 265 266 /* Allocate the hash table. */ 267 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 268 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 269 270 #ifdef VIMAGE 271 V_tcp_syncache.vnet = curvnet; 272 #endif 273 274 /* Initialize the hash buckets. */ 275 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 276 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 277 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 278 NULL, MTX_DEF); 279 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 280 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 281 V_tcp_syncache.hashbase[i].sch_length = 0; 282 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache; 283 V_tcp_syncache.hashbase[i].sch_last_overflow = 284 -(SYNCOOKIE_LIFETIME + 1); 285 } 286 287 /* Create the syncache entry zone. */ 288 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 289 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 290 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone, 291 V_tcp_syncache.cache_limit); 292 293 /* Start the SYN cookie reseeder callout. */ 294 callout_init(&V_tcp_syncache.secret.reseed, 1); 295 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0); 296 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0); 297 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz, 298 syncookie_reseed, &V_tcp_syncache); 299 } 300 301 #ifdef VIMAGE 302 void 303 syncache_destroy(void) 304 { 305 struct syncache_head *sch; 306 struct syncache *sc, *nsc; 307 int i; 308 309 /* 310 * Stop the re-seed timer before freeing resources. No need to 311 * possibly schedule it another time. 312 */ 313 callout_drain(&V_tcp_syncache.secret.reseed); 314 315 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 316 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 317 318 sch = &V_tcp_syncache.hashbase[i]; 319 callout_drain(&sch->sch_timer); 320 321 SCH_LOCK(sch); 322 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 323 syncache_drop(sc, sch); 324 SCH_UNLOCK(sch); 325 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 326 ("%s: sch->sch_bucket not empty", __func__)); 327 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 328 __func__, sch->sch_length)); 329 mtx_destroy(&sch->sch_mtx); 330 } 331 332 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0, 333 ("%s: cache_count not 0", __func__)); 334 335 /* Free the allocated global resources. */ 336 uma_zdestroy(V_tcp_syncache.zone); 337 free(V_tcp_syncache.hashbase, M_SYNCACHE); 338 } 339 #endif 340 341 /* 342 * Inserts a syncache entry into the specified bucket row. 343 * Locks and unlocks the syncache_head autonomously. 344 */ 345 static void 346 syncache_insert(struct syncache *sc, struct syncache_head *sch) 347 { 348 struct syncache *sc2; 349 350 SCH_LOCK(sch); 351 352 /* 353 * Make sure that we don't overflow the per-bucket limit. 354 * If the bucket is full, toss the oldest element. 355 */ 356 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 357 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 358 ("sch->sch_length incorrect")); 359 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 360 sch->sch_last_overflow = time_uptime; 361 syncache_drop(sc2, sch); 362 TCPSTAT_INC(tcps_sc_bucketoverflow); 363 } 364 365 /* Put it into the bucket. */ 366 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 367 sch->sch_length++; 368 369 #ifdef TCP_OFFLOAD 370 if (ADDED_BY_TOE(sc)) { 371 struct toedev *tod = sc->sc_tod; 372 373 tod->tod_syncache_added(tod, sc->sc_todctx); 374 } 375 #endif 376 377 /* Reinitialize the bucket row's timer. */ 378 if (sch->sch_length == 1) 379 sch->sch_nextc = ticks + INT_MAX; 380 syncache_timeout(sc, sch, 1); 381 382 SCH_UNLOCK(sch); 383 384 TCPSTATES_INC(TCPS_SYN_RECEIVED); 385 TCPSTAT_INC(tcps_sc_added); 386 } 387 388 /* 389 * Remove and free entry from syncache bucket row. 390 * Expects locked syncache head. 391 */ 392 static void 393 syncache_drop(struct syncache *sc, struct syncache_head *sch) 394 { 395 396 SCH_LOCK_ASSERT(sch); 397 398 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 399 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 400 sch->sch_length--; 401 402 #ifdef TCP_OFFLOAD 403 if (ADDED_BY_TOE(sc)) { 404 struct toedev *tod = sc->sc_tod; 405 406 tod->tod_syncache_removed(tod, sc->sc_todctx); 407 } 408 #endif 409 410 syncache_free(sc); 411 } 412 413 /* 414 * Engage/reengage time on bucket row. 415 */ 416 static void 417 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 418 { 419 int rexmt; 420 421 if (sc->sc_rxmits == 0) 422 rexmt = TCPTV_RTOBASE; 423 else 424 TCPT_RANGESET(rexmt, TCPTV_RTOBASE * tcp_syn_backoff[sc->sc_rxmits], 425 tcp_rexmit_min, TCPTV_REXMTMAX); 426 sc->sc_rxttime = ticks + rexmt; 427 sc->sc_rxmits++; 428 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 429 sch->sch_nextc = sc->sc_rxttime; 430 if (docallout) 431 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 432 syncache_timer, (void *)sch); 433 } 434 } 435 436 /* 437 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 438 * If we have retransmitted an entry the maximum number of times, expire it. 439 * One separate timer for each bucket row. 440 */ 441 static void 442 syncache_timer(void *xsch) 443 { 444 struct syncache_head *sch = (struct syncache_head *)xsch; 445 struct syncache *sc, *nsc; 446 int tick = ticks; 447 char *s; 448 449 CURVNET_SET(sch->sch_sc->vnet); 450 451 /* NB: syncache_head has already been locked by the callout. */ 452 SCH_LOCK_ASSERT(sch); 453 454 /* 455 * In the following cycle we may remove some entries and/or 456 * advance some timeouts, so re-initialize the bucket timer. 457 */ 458 sch->sch_nextc = tick + INT_MAX; 459 460 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 461 /* 462 * We do not check if the listen socket still exists 463 * and accept the case where the listen socket may be 464 * gone by the time we resend the SYN/ACK. We do 465 * not expect this to happens often. If it does, 466 * then the RST will be sent by the time the remote 467 * host does the SYN/ACK->ACK. 468 */ 469 if (TSTMP_GT(sc->sc_rxttime, tick)) { 470 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 471 sch->sch_nextc = sc->sc_rxttime; 472 continue; 473 } 474 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 475 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 476 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 477 "giving up and removing syncache entry\n", 478 s, __func__); 479 free(s, M_TCPLOG); 480 } 481 syncache_drop(sc, sch); 482 TCPSTAT_INC(tcps_sc_stale); 483 continue; 484 } 485 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 486 log(LOG_DEBUG, "%s; %s: Response timeout, " 487 "retransmitting (%u) SYN|ACK\n", 488 s, __func__, sc->sc_rxmits); 489 free(s, M_TCPLOG); 490 } 491 492 syncache_respond(sc, sch, NULL, TH_SYN|TH_ACK); 493 TCPSTAT_INC(tcps_sc_retransmitted); 494 syncache_timeout(sc, sch, 0); 495 } 496 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 497 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 498 syncache_timer, (void *)(sch)); 499 CURVNET_RESTORE(); 500 } 501 502 /* 503 * Find an entry in the syncache. 504 * Returns always with locked syncache_head plus a matching entry or NULL. 505 */ 506 static struct syncache * 507 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 508 { 509 struct syncache *sc; 510 struct syncache_head *sch; 511 uint32_t hash; 512 513 /* 514 * The hash is built on foreign port + local port + foreign address. 515 * We rely on the fact that struct in_conninfo starts with 16 bits 516 * of foreign port, then 16 bits of local port then followed by 128 517 * bits of foreign address. In case of IPv4 address, the first 3 518 * 32-bit words of the address always are zeroes. 519 */ 520 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5, 521 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask; 522 523 sch = &V_tcp_syncache.hashbase[hash]; 524 *schp = sch; 525 SCH_LOCK(sch); 526 527 /* Circle through bucket row to find matching entry. */ 528 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 529 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie, 530 sizeof(struct in_endpoints)) == 0) 531 break; 532 533 return (sc); /* Always returns with locked sch. */ 534 } 535 536 /* 537 * This function is called when we get a RST for a 538 * non-existent connection, so that we can see if the 539 * connection is in the syn cache. If it is, zap it. 540 * If required send a challenge ACK. 541 */ 542 void 543 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m) 544 { 545 struct syncache *sc; 546 struct syncache_head *sch; 547 char *s = NULL; 548 549 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 550 SCH_LOCK_ASSERT(sch); 551 552 /* 553 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 554 * See RFC 793 page 65, section SEGMENT ARRIVES. 555 */ 556 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 557 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 558 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 559 "FIN flag set, segment ignored\n", s, __func__); 560 TCPSTAT_INC(tcps_badrst); 561 goto done; 562 } 563 564 /* 565 * No corresponding connection was found in syncache. 566 * If syncookies are enabled and possibly exclusively 567 * used, or we are under memory pressure, a valid RST 568 * may not find a syncache entry. In that case we're 569 * done and no SYN|ACK retransmissions will happen. 570 * Otherwise the RST was misdirected or spoofed. 571 */ 572 if (sc == NULL) { 573 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 574 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 575 "syncache entry (possibly syncookie only), " 576 "segment ignored\n", s, __func__); 577 TCPSTAT_INC(tcps_badrst); 578 goto done; 579 } 580 581 /* 582 * If the RST bit is set, check the sequence number to see 583 * if this is a valid reset segment. 584 * RFC 793 page 37: 585 * In all states except SYN-SENT, all reset (RST) segments 586 * are validated by checking their SEQ-fields. A reset is 587 * valid if its sequence number is in the window. 588 * 589 * The sequence number in the reset segment is normally an 590 * echo of our outgoing acknowlegement numbers, but some hosts 591 * send a reset with the sequence number at the rightmost edge 592 * of our receive window, and we have to handle this case. 593 */ 594 if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) && 595 SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) || 596 (sc->sc_wnd == 0 && th->th_seq == sc->sc_irs + 1)) { 597 if (V_tcp_insecure_rst || 598 th->th_seq == sc->sc_irs + 1) { 599 syncache_drop(sc, sch); 600 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 601 log(LOG_DEBUG, 602 "%s; %s: Our SYN|ACK was rejected, " 603 "connection attempt aborted by remote " 604 "endpoint\n", 605 s, __func__); 606 TCPSTAT_INC(tcps_sc_reset); 607 } else { 608 TCPSTAT_INC(tcps_badrst); 609 /* Send challenge ACK. */ 610 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 611 log(LOG_DEBUG, "%s; %s: RST with invalid " 612 " SEQ %u != NXT %u (+WND %u), " 613 "sending challenge ACK\n", 614 s, __func__, 615 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 616 syncache_respond(sc, sch, m, TH_ACK); 617 } 618 } else { 619 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 620 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 621 "NXT %u (+WND %u), segment ignored\n", 622 s, __func__, 623 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 624 TCPSTAT_INC(tcps_badrst); 625 } 626 627 done: 628 if (s != NULL) 629 free(s, M_TCPLOG); 630 SCH_UNLOCK(sch); 631 } 632 633 void 634 syncache_badack(struct in_conninfo *inc) 635 { 636 struct syncache *sc; 637 struct syncache_head *sch; 638 639 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 640 SCH_LOCK_ASSERT(sch); 641 if (sc != NULL) { 642 syncache_drop(sc, sch); 643 TCPSTAT_INC(tcps_sc_badack); 644 } 645 SCH_UNLOCK(sch); 646 } 647 648 void 649 syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq) 650 { 651 struct syncache *sc; 652 struct syncache_head *sch; 653 654 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 655 SCH_LOCK_ASSERT(sch); 656 if (sc == NULL) 657 goto done; 658 659 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 660 if (ntohl(th_seq) != sc->sc_iss) 661 goto done; 662 663 /* 664 * If we've rertransmitted 3 times and this is our second error, 665 * we remove the entry. Otherwise, we allow it to continue on. 666 * This prevents us from incorrectly nuking an entry during a 667 * spurious network outage. 668 * 669 * See tcp_notify(). 670 */ 671 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 672 sc->sc_flags |= SCF_UNREACH; 673 goto done; 674 } 675 syncache_drop(sc, sch); 676 TCPSTAT_INC(tcps_sc_unreach); 677 done: 678 SCH_UNLOCK(sch); 679 } 680 681 /* 682 * Build a new TCP socket structure from a syncache entry. 683 * 684 * On success return the newly created socket with its underlying inp locked. 685 */ 686 static struct socket * 687 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 688 { 689 struct tcp_function_block *blk; 690 struct inpcb *inp = NULL; 691 struct socket *so; 692 struct tcpcb *tp; 693 int error; 694 char *s; 695 696 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 697 698 /* 699 * Ok, create the full blown connection, and set things up 700 * as they would have been set up if we had created the 701 * connection when the SYN arrived. If we can't create 702 * the connection, abort it. 703 */ 704 so = sonewconn(lso, 0); 705 if (so == NULL) { 706 /* 707 * Drop the connection; we will either send a RST or 708 * have the peer retransmit its SYN again after its 709 * RTO and try again. 710 */ 711 TCPSTAT_INC(tcps_listendrop); 712 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 713 log(LOG_DEBUG, "%s; %s: Socket create failed " 714 "due to limits or memory shortage\n", 715 s, __func__); 716 free(s, M_TCPLOG); 717 } 718 goto abort2; 719 } 720 #ifdef MAC 721 mac_socketpeer_set_from_mbuf(m, so); 722 #endif 723 724 inp = sotoinpcb(so); 725 inp->inp_inc.inc_fibnum = so->so_fibnum; 726 INP_WLOCK(inp); 727 /* 728 * Exclusive pcbinfo lock is not required in syncache socket case even 729 * if two inpcb locks can be acquired simultaneously: 730 * - the inpcb in LISTEN state, 731 * - the newly created inp. 732 * 733 * In this case, an inp cannot be at same time in LISTEN state and 734 * just created by an accept() call. 735 */ 736 INP_HASH_WLOCK(&V_tcbinfo); 737 738 /* Insert new socket into PCB hash list. */ 739 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 740 #ifdef INET6 741 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 742 inp->inp_vflag &= ~INP_IPV4; 743 inp->inp_vflag |= INP_IPV6; 744 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 745 } else { 746 inp->inp_vflag &= ~INP_IPV6; 747 inp->inp_vflag |= INP_IPV4; 748 #endif 749 inp->inp_laddr = sc->sc_inc.inc_laddr; 750 #ifdef INET6 751 } 752 #endif 753 754 /* 755 * If there's an mbuf and it has a flowid, then let's initialise the 756 * inp with that particular flowid. 757 */ 758 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) { 759 inp->inp_flowid = m->m_pkthdr.flowid; 760 inp->inp_flowtype = M_HASHTYPE_GET(m); 761 } 762 763 /* 764 * Install in the reservation hash table for now, but don't yet 765 * install a connection group since the full 4-tuple isn't yet 766 * configured. 767 */ 768 inp->inp_lport = sc->sc_inc.inc_lport; 769 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 770 /* 771 * Undo the assignments above if we failed to 772 * put the PCB on the hash lists. 773 */ 774 #ifdef INET6 775 if (sc->sc_inc.inc_flags & INC_ISIPV6) 776 inp->in6p_laddr = in6addr_any; 777 else 778 #endif 779 inp->inp_laddr.s_addr = INADDR_ANY; 780 inp->inp_lport = 0; 781 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 782 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 783 "with error %i\n", 784 s, __func__, error); 785 free(s, M_TCPLOG); 786 } 787 INP_HASH_WUNLOCK(&V_tcbinfo); 788 goto abort; 789 } 790 #ifdef INET6 791 if (inp->inp_vflag & INP_IPV6PROTO) { 792 struct inpcb *oinp = sotoinpcb(lso); 793 794 /* 795 * Inherit socket options from the listening socket. 796 * Note that in6p_inputopts are not (and should not be) 797 * copied, since it stores previously received options and is 798 * used to detect if each new option is different than the 799 * previous one and hence should be passed to a user. 800 * If we copied in6p_inputopts, a user would not be able to 801 * receive options just after calling the accept system call. 802 */ 803 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 804 if (oinp->in6p_outputopts) 805 inp->in6p_outputopts = 806 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 807 } 808 809 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 810 struct in6_addr laddr6; 811 struct sockaddr_in6 sin6; 812 813 sin6.sin6_family = AF_INET6; 814 sin6.sin6_len = sizeof(sin6); 815 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 816 sin6.sin6_port = sc->sc_inc.inc_fport; 817 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 818 laddr6 = inp->in6p_laddr; 819 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 820 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 821 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 822 thread0.td_ucred, m)) != 0) { 823 inp->in6p_laddr = laddr6; 824 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 825 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 826 "with error %i\n", 827 s, __func__, error); 828 free(s, M_TCPLOG); 829 } 830 INP_HASH_WUNLOCK(&V_tcbinfo); 831 goto abort; 832 } 833 /* Override flowlabel from in6_pcbconnect. */ 834 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 835 inp->inp_flow |= sc->sc_flowlabel; 836 } 837 #endif /* INET6 */ 838 #if defined(INET) && defined(INET6) 839 else 840 #endif 841 #ifdef INET 842 { 843 struct in_addr laddr; 844 struct sockaddr_in sin; 845 846 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 847 848 if (inp->inp_options == NULL) { 849 inp->inp_options = sc->sc_ipopts; 850 sc->sc_ipopts = NULL; 851 } 852 853 sin.sin_family = AF_INET; 854 sin.sin_len = sizeof(sin); 855 sin.sin_addr = sc->sc_inc.inc_faddr; 856 sin.sin_port = sc->sc_inc.inc_fport; 857 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 858 laddr = inp->inp_laddr; 859 if (inp->inp_laddr.s_addr == INADDR_ANY) 860 inp->inp_laddr = sc->sc_inc.inc_laddr; 861 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 862 thread0.td_ucred, m)) != 0) { 863 inp->inp_laddr = laddr; 864 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 865 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 866 "with error %i\n", 867 s, __func__, error); 868 free(s, M_TCPLOG); 869 } 870 INP_HASH_WUNLOCK(&V_tcbinfo); 871 goto abort; 872 } 873 } 874 #endif /* INET */ 875 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 876 /* Copy old policy into new socket's. */ 877 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0) 878 printf("syncache_socket: could not copy policy\n"); 879 #endif 880 INP_HASH_WUNLOCK(&V_tcbinfo); 881 tp = intotcpcb(inp); 882 tcp_state_change(tp, TCPS_SYN_RECEIVED); 883 tp->iss = sc->sc_iss; 884 tp->irs = sc->sc_irs; 885 tcp_rcvseqinit(tp); 886 tcp_sendseqinit(tp); 887 blk = sototcpcb(lso)->t_fb; 888 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) { 889 /* 890 * Our parents t_fb was not the default, 891 * we need to release our ref on tp->t_fb and 892 * pickup one on the new entry. 893 */ 894 struct tcp_function_block *rblk; 895 896 rblk = find_and_ref_tcp_fb(blk); 897 KASSERT(rblk != NULL, 898 ("cannot find blk %p out of syncache?", blk)); 899 if (tp->t_fb->tfb_tcp_fb_fini) 900 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0); 901 refcount_release(&tp->t_fb->tfb_refcnt); 902 tp->t_fb = rblk; 903 /* 904 * XXXrrs this is quite dangerous, it is possible 905 * for the new function to fail to init. We also 906 * are not asking if the handoff_is_ok though at 907 * the very start thats probalbly ok. 908 */ 909 if (tp->t_fb->tfb_tcp_fb_init) { 910 (*tp->t_fb->tfb_tcp_fb_init)(tp); 911 } 912 } 913 tp->snd_wl1 = sc->sc_irs; 914 tp->snd_max = tp->iss + 1; 915 tp->snd_nxt = tp->iss + 1; 916 tp->rcv_up = sc->sc_irs + 1; 917 tp->rcv_wnd = sc->sc_wnd; 918 tp->rcv_adv += tp->rcv_wnd; 919 tp->last_ack_sent = tp->rcv_nxt; 920 921 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 922 if (sc->sc_flags & SCF_NOOPT) 923 tp->t_flags |= TF_NOOPT; 924 else { 925 if (sc->sc_flags & SCF_WINSCALE) { 926 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 927 tp->snd_scale = sc->sc_requested_s_scale; 928 tp->request_r_scale = sc->sc_requested_r_scale; 929 } 930 if (sc->sc_flags & SCF_TIMESTAMP) { 931 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 932 tp->ts_recent = sc->sc_tsreflect; 933 tp->ts_recent_age = tcp_ts_getticks(); 934 tp->ts_offset = sc->sc_tsoff; 935 } 936 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 937 if (sc->sc_flags & SCF_SIGNATURE) 938 tp->t_flags |= TF_SIGNATURE; 939 #endif 940 if (sc->sc_flags & SCF_SACK) 941 tp->t_flags |= TF_SACK_PERMIT; 942 } 943 944 if (sc->sc_flags & SCF_ECN) 945 tp->t_flags |= TF_ECN_PERMIT; 946 947 /* 948 * Set up MSS and get cached values from tcp_hostcache. 949 * This might overwrite some of the defaults we just set. 950 */ 951 tcp_mss(tp, sc->sc_peer_mss); 952 953 /* 954 * If the SYN,ACK was retransmitted, indicate that CWND to be 955 * limited to one segment in cc_conn_init(). 956 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 957 */ 958 if (sc->sc_rxmits > 1) 959 tp->snd_cwnd = 1; 960 961 #ifdef TCP_OFFLOAD 962 /* 963 * Allow a TOE driver to install its hooks. Note that we hold the 964 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a 965 * new connection before the TOE driver has done its thing. 966 */ 967 if (ADDED_BY_TOE(sc)) { 968 struct toedev *tod = sc->sc_tod; 969 970 tod->tod_offload_socket(tod, sc->sc_todctx, so); 971 } 972 #endif 973 /* 974 * Copy and activate timers. 975 */ 976 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 977 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 978 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 979 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 980 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 981 982 TCPSTAT_INC(tcps_accepts); 983 return (so); 984 985 abort: 986 INP_WUNLOCK(inp); 987 abort2: 988 if (so != NULL) 989 soabort(so); 990 return (NULL); 991 } 992 993 /* 994 * This function gets called when we receive an ACK for a 995 * socket in the LISTEN state. We look up the connection 996 * in the syncache, and if its there, we pull it out of 997 * the cache and turn it into a full-blown connection in 998 * the SYN-RECEIVED state. 999 * 1000 * On syncache_socket() success the newly created socket 1001 * has its underlying inp locked. 1002 */ 1003 int 1004 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1005 struct socket **lsop, struct mbuf *m) 1006 { 1007 struct syncache *sc; 1008 struct syncache_head *sch; 1009 struct syncache scs; 1010 char *s; 1011 1012 /* 1013 * Global TCP locks are held because we manipulate the PCB lists 1014 * and create a new socket. 1015 */ 1016 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1017 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 1018 ("%s: can handle only ACK", __func__)); 1019 1020 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 1021 SCH_LOCK_ASSERT(sch); 1022 1023 #ifdef INVARIANTS 1024 /* 1025 * Test code for syncookies comparing the syncache stored 1026 * values with the reconstructed values from the cookie. 1027 */ 1028 if (sc != NULL) 1029 syncookie_cmp(inc, sch, sc, th, to, *lsop); 1030 #endif 1031 1032 if (sc == NULL) { 1033 /* 1034 * There is no syncache entry, so see if this ACK is 1035 * a returning syncookie. To do this, first: 1036 * A. Check if syncookies are used in case of syncache 1037 * overflows 1038 * B. See if this socket has had a syncache entry dropped in 1039 * the recent past. We don't want to accept a bogus 1040 * syncookie if we've never received a SYN or accept it 1041 * twice. 1042 * C. check that the syncookie is valid. If it is, then 1043 * cobble up a fake syncache entry, and return. 1044 */ 1045 if (!V_tcp_syncookies) { 1046 SCH_UNLOCK(sch); 1047 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1048 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1049 "segment rejected (syncookies disabled)\n", 1050 s, __func__); 1051 goto failed; 1052 } 1053 if (!V_tcp_syncookiesonly && 1054 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) { 1055 SCH_UNLOCK(sch); 1056 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1057 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1058 "segment rejected (no syncache entry)\n", 1059 s, __func__); 1060 goto failed; 1061 } 1062 bzero(&scs, sizeof(scs)); 1063 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop); 1064 SCH_UNLOCK(sch); 1065 if (sc == NULL) { 1066 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1067 log(LOG_DEBUG, "%s; %s: Segment failed " 1068 "SYNCOOKIE authentication, segment rejected " 1069 "(probably spoofed)\n", s, __func__); 1070 goto failed; 1071 } 1072 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1073 /* If received ACK has MD5 signature, check it. */ 1074 if ((to->to_flags & TOF_SIGNATURE) != 0 && 1075 (!TCPMD5_ENABLED() || 1076 TCPMD5_INPUT(m, th, to->to_signature) != 0)) { 1077 /* Drop the ACK. */ 1078 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1079 log(LOG_DEBUG, "%s; %s: Segment rejected, " 1080 "MD5 signature doesn't match.\n", 1081 s, __func__); 1082 free(s, M_TCPLOG); 1083 } 1084 TCPSTAT_INC(tcps_sig_err_sigopt); 1085 return (-1); /* Do not send RST */ 1086 } 1087 #endif /* TCP_SIGNATURE */ 1088 } else { 1089 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1090 /* 1091 * If listening socket requested TCP digests, check that 1092 * received ACK has signature and it is correct. 1093 * If not, drop the ACK and leave sc entry in th cache, 1094 * because SYN was received with correct signature. 1095 */ 1096 if (sc->sc_flags & SCF_SIGNATURE) { 1097 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1098 /* No signature */ 1099 TCPSTAT_INC(tcps_sig_err_nosigopt); 1100 SCH_UNLOCK(sch); 1101 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1102 log(LOG_DEBUG, "%s; %s: Segment " 1103 "rejected, MD5 signature wasn't " 1104 "provided.\n", s, __func__); 1105 free(s, M_TCPLOG); 1106 } 1107 return (-1); /* Do not send RST */ 1108 } 1109 if (!TCPMD5_ENABLED() || 1110 TCPMD5_INPUT(m, th, to->to_signature) != 0) { 1111 /* Doesn't match or no SA */ 1112 SCH_UNLOCK(sch); 1113 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1114 log(LOG_DEBUG, "%s; %s: Segment " 1115 "rejected, MD5 signature doesn't " 1116 "match.\n", s, __func__); 1117 free(s, M_TCPLOG); 1118 } 1119 return (-1); /* Do not send RST */ 1120 } 1121 } 1122 #endif /* TCP_SIGNATURE */ 1123 /* 1124 * Pull out the entry to unlock the bucket row. 1125 * 1126 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not 1127 * tcp_state_change(). The tcpcb is not existent at this 1128 * moment. A new one will be allocated via syncache_socket-> 1129 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then 1130 * syncache_socket() will change it to TCPS_SYN_RECEIVED. 1131 */ 1132 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 1133 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 1134 sch->sch_length--; 1135 #ifdef TCP_OFFLOAD 1136 if (ADDED_BY_TOE(sc)) { 1137 struct toedev *tod = sc->sc_tod; 1138 1139 tod->tod_syncache_removed(tod, sc->sc_todctx); 1140 } 1141 #endif 1142 SCH_UNLOCK(sch); 1143 } 1144 1145 /* 1146 * Segment validation: 1147 * ACK must match our initial sequence number + 1 (the SYN|ACK). 1148 */ 1149 if (th->th_ack != sc->sc_iss + 1) { 1150 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1151 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 1152 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 1153 goto failed; 1154 } 1155 1156 /* 1157 * The SEQ must fall in the window starting at the received 1158 * initial receive sequence number + 1 (the SYN). 1159 */ 1160 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 1161 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 1162 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1163 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 1164 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 1165 goto failed; 1166 } 1167 1168 /* 1169 * If timestamps were not negotiated during SYN/ACK they 1170 * must not appear on any segment during this session. 1171 */ 1172 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 1173 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1174 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1175 "segment rejected\n", s, __func__); 1176 goto failed; 1177 } 1178 1179 /* 1180 * If timestamps were negotiated during SYN/ACK they should 1181 * appear on every segment during this session. 1182 * XXXAO: This is only informal as there have been unverified 1183 * reports of non-compliants stacks. 1184 */ 1185 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) { 1186 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1187 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1188 "no action\n", s, __func__); 1189 free(s, M_TCPLOG); 1190 s = NULL; 1191 } 1192 } 1193 1194 *lsop = syncache_socket(sc, *lsop, m); 1195 1196 if (*lsop == NULL) 1197 TCPSTAT_INC(tcps_sc_aborted); 1198 else 1199 TCPSTAT_INC(tcps_sc_completed); 1200 1201 /* how do we find the inp for the new socket? */ 1202 if (sc != &scs) 1203 syncache_free(sc); 1204 return (1); 1205 failed: 1206 if (sc != NULL && sc != &scs) 1207 syncache_free(sc); 1208 if (s != NULL) 1209 free(s, M_TCPLOG); 1210 *lsop = NULL; 1211 return (0); 1212 } 1213 1214 static void 1215 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m, 1216 uint64_t response_cookie) 1217 { 1218 struct inpcb *inp; 1219 struct tcpcb *tp; 1220 unsigned int *pending_counter; 1221 1222 /* 1223 * Global TCP locks are held because we manipulate the PCB lists 1224 * and create a new socket. 1225 */ 1226 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1227 1228 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending; 1229 *lsop = syncache_socket(sc, *lsop, m); 1230 if (*lsop == NULL) { 1231 TCPSTAT_INC(tcps_sc_aborted); 1232 atomic_subtract_int(pending_counter, 1); 1233 } else { 1234 soisconnected(*lsop); 1235 inp = sotoinpcb(*lsop); 1236 tp = intotcpcb(inp); 1237 tp->t_flags |= TF_FASTOPEN; 1238 tp->t_tfo_cookie.server = response_cookie; 1239 tp->snd_max = tp->iss; 1240 tp->snd_nxt = tp->iss; 1241 tp->t_tfo_pending = pending_counter; 1242 TCPSTAT_INC(tcps_sc_completed); 1243 } 1244 } 1245 1246 /* 1247 * Given a LISTEN socket and an inbound SYN request, add 1248 * this to the syn cache, and send back a segment: 1249 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1250 * to the source. 1251 * 1252 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1253 * Doing so would require that we hold onto the data and deliver it 1254 * to the application. However, if we are the target of a SYN-flood 1255 * DoS attack, an attacker could send data which would eventually 1256 * consume all available buffer space if it were ACKed. By not ACKing 1257 * the data, we avoid this DoS scenario. 1258 * 1259 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO) 1260 * cookie is processed and a new socket is created. In this case, any data 1261 * accompanying the SYN will be queued to the socket by tcp_input() and will 1262 * be ACKed either when the application sends response data or the delayed 1263 * ACK timer expires, whichever comes first. 1264 */ 1265 int 1266 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1267 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1268 void *todctx) 1269 { 1270 struct tcpcb *tp; 1271 struct socket *so; 1272 struct syncache *sc = NULL; 1273 struct syncache_head *sch; 1274 struct mbuf *ipopts = NULL; 1275 u_int ltflags; 1276 int win, ip_ttl, ip_tos; 1277 char *s; 1278 int rv = 0; 1279 #ifdef INET6 1280 int autoflowlabel = 0; 1281 #endif 1282 #ifdef MAC 1283 struct label *maclabel; 1284 #endif 1285 struct syncache scs; 1286 struct ucred *cred; 1287 uint64_t tfo_response_cookie; 1288 unsigned int *tfo_pending = NULL; 1289 int tfo_cookie_valid = 0; 1290 int tfo_response_cookie_valid = 0; 1291 1292 INP_WLOCK_ASSERT(inp); /* listen socket */ 1293 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1294 ("%s: unexpected tcp flags", __func__)); 1295 1296 /* 1297 * Combine all so/tp operations very early to drop the INP lock as 1298 * soon as possible. 1299 */ 1300 so = *lsop; 1301 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so)); 1302 tp = sototcpcb(so); 1303 cred = crhold(so->so_cred); 1304 1305 #ifdef INET6 1306 if ((inc->inc_flags & INC_ISIPV6) && 1307 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1308 autoflowlabel = 1; 1309 #endif 1310 ip_ttl = inp->inp_ip_ttl; 1311 ip_tos = inp->inp_ip_tos; 1312 win = so->sol_sbrcv_hiwat; 1313 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1314 1315 if (V_tcp_fastopen_server_enable && IS_FASTOPEN(tp->t_flags) && 1316 (tp->t_tfo_pending != NULL) && 1317 (to->to_flags & TOF_FASTOPEN)) { 1318 /* 1319 * Limit the number of pending TFO connections to 1320 * approximately half of the queue limit. This prevents TFO 1321 * SYN floods from starving the service by filling the 1322 * listen queue with bogus TFO connections. 1323 */ 1324 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <= 1325 (so->sol_qlimit / 2)) { 1326 int result; 1327 1328 result = tcp_fastopen_check_cookie(inc, 1329 to->to_tfo_cookie, to->to_tfo_len, 1330 &tfo_response_cookie); 1331 tfo_cookie_valid = (result > 0); 1332 tfo_response_cookie_valid = (result >= 0); 1333 } 1334 1335 /* 1336 * Remember the TFO pending counter as it will have to be 1337 * decremented below if we don't make it to syncache_tfo_expand(). 1338 */ 1339 tfo_pending = tp->t_tfo_pending; 1340 } 1341 1342 /* By the time we drop the lock these should no longer be used. */ 1343 so = NULL; 1344 tp = NULL; 1345 1346 #ifdef MAC 1347 if (mac_syncache_init(&maclabel) != 0) { 1348 INP_WUNLOCK(inp); 1349 goto done; 1350 } else 1351 mac_syncache_create(maclabel, inp); 1352 #endif 1353 if (!tfo_cookie_valid) 1354 INP_WUNLOCK(inp); 1355 1356 /* 1357 * Remember the IP options, if any. 1358 */ 1359 #ifdef INET6 1360 if (!(inc->inc_flags & INC_ISIPV6)) 1361 #endif 1362 #ifdef INET 1363 ipopts = (m) ? ip_srcroute(m) : NULL; 1364 #else 1365 ipopts = NULL; 1366 #endif 1367 1368 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1369 /* 1370 * If listening socket requested TCP digests, check that received 1371 * SYN has signature and it is correct. If signature doesn't match 1372 * or TCP_SIGNATURE support isn't enabled, drop the packet. 1373 */ 1374 if (ltflags & TF_SIGNATURE) { 1375 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1376 TCPSTAT_INC(tcps_sig_err_nosigopt); 1377 goto done; 1378 } 1379 if (!TCPMD5_ENABLED() || 1380 TCPMD5_INPUT(m, th, to->to_signature) != 0) 1381 goto done; 1382 } 1383 #endif /* TCP_SIGNATURE */ 1384 /* 1385 * See if we already have an entry for this connection. 1386 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1387 * 1388 * XXX: should the syncache be re-initialized with the contents 1389 * of the new SYN here (which may have different options?) 1390 * 1391 * XXX: We do not check the sequence number to see if this is a 1392 * real retransmit or a new connection attempt. The question is 1393 * how to handle such a case; either ignore it as spoofed, or 1394 * drop the current entry and create a new one? 1395 */ 1396 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1397 SCH_LOCK_ASSERT(sch); 1398 if (sc != NULL) { 1399 if (tfo_cookie_valid) 1400 INP_WUNLOCK(inp); 1401 TCPSTAT_INC(tcps_sc_dupsyn); 1402 if (ipopts) { 1403 /* 1404 * If we were remembering a previous source route, 1405 * forget it and use the new one we've been given. 1406 */ 1407 if (sc->sc_ipopts) 1408 (void) m_free(sc->sc_ipopts); 1409 sc->sc_ipopts = ipopts; 1410 } 1411 /* 1412 * Update timestamp if present. 1413 */ 1414 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1415 sc->sc_tsreflect = to->to_tsval; 1416 else 1417 sc->sc_flags &= ~SCF_TIMESTAMP; 1418 #ifdef MAC 1419 /* 1420 * Since we have already unconditionally allocated label 1421 * storage, free it up. The syncache entry will already 1422 * have an initialized label we can use. 1423 */ 1424 mac_syncache_destroy(&maclabel); 1425 #endif 1426 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1427 /* Retransmit SYN|ACK and reset retransmit count. */ 1428 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1429 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1430 "resetting timer and retransmitting SYN|ACK\n", 1431 s, __func__); 1432 free(s, M_TCPLOG); 1433 } 1434 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1435 sc->sc_rxmits = 0; 1436 syncache_timeout(sc, sch, 1); 1437 TCPSTAT_INC(tcps_sndacks); 1438 TCPSTAT_INC(tcps_sndtotal); 1439 } 1440 SCH_UNLOCK(sch); 1441 goto donenoprobe; 1442 } 1443 1444 if (tfo_cookie_valid) { 1445 bzero(&scs, sizeof(scs)); 1446 sc = &scs; 1447 goto skip_alloc; 1448 } 1449 1450 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1451 if (sc == NULL) { 1452 /* 1453 * The zone allocator couldn't provide more entries. 1454 * Treat this as if the cache was full; drop the oldest 1455 * entry and insert the new one. 1456 */ 1457 TCPSTAT_INC(tcps_sc_zonefail); 1458 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) { 1459 sch->sch_last_overflow = time_uptime; 1460 syncache_drop(sc, sch); 1461 } 1462 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1463 if (sc == NULL) { 1464 if (V_tcp_syncookies) { 1465 bzero(&scs, sizeof(scs)); 1466 sc = &scs; 1467 } else { 1468 SCH_UNLOCK(sch); 1469 if (ipopts) 1470 (void) m_free(ipopts); 1471 goto done; 1472 } 1473 } 1474 } 1475 1476 skip_alloc: 1477 if (!tfo_cookie_valid && tfo_response_cookie_valid) 1478 sc->sc_tfo_cookie = &tfo_response_cookie; 1479 1480 /* 1481 * Fill in the syncache values. 1482 */ 1483 #ifdef MAC 1484 sc->sc_label = maclabel; 1485 #endif 1486 sc->sc_cred = cred; 1487 cred = NULL; 1488 sc->sc_ipopts = ipopts; 1489 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1490 #ifdef INET6 1491 if (!(inc->inc_flags & INC_ISIPV6)) 1492 #endif 1493 { 1494 sc->sc_ip_tos = ip_tos; 1495 sc->sc_ip_ttl = ip_ttl; 1496 } 1497 #ifdef TCP_OFFLOAD 1498 sc->sc_tod = tod; 1499 sc->sc_todctx = todctx; 1500 #endif 1501 sc->sc_irs = th->th_seq; 1502 sc->sc_iss = arc4random(); 1503 sc->sc_flags = 0; 1504 sc->sc_flowlabel = 0; 1505 1506 /* 1507 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1508 * win was derived from socket earlier in the function. 1509 */ 1510 win = imax(win, 0); 1511 win = imin(win, TCP_MAXWIN); 1512 sc->sc_wnd = win; 1513 1514 if (V_tcp_do_rfc1323) { 1515 /* 1516 * A timestamp received in a SYN makes 1517 * it ok to send timestamp requests and replies. 1518 */ 1519 if (to->to_flags & TOF_TS) { 1520 sc->sc_tsreflect = to->to_tsval; 1521 sc->sc_flags |= SCF_TIMESTAMP; 1522 sc->sc_tsoff = tcp_new_ts_offset(inc); 1523 } 1524 if (to->to_flags & TOF_SCALE) { 1525 int wscale = 0; 1526 1527 /* 1528 * Pick the smallest possible scaling factor that 1529 * will still allow us to scale up to sb_max, aka 1530 * kern.ipc.maxsockbuf. 1531 * 1532 * We do this because there are broken firewalls that 1533 * will corrupt the window scale option, leading to 1534 * the other endpoint believing that our advertised 1535 * window is unscaled. At scale factors larger than 1536 * 5 the unscaled window will drop below 1500 bytes, 1537 * leading to serious problems when traversing these 1538 * broken firewalls. 1539 * 1540 * With the default maxsockbuf of 256K, a scale factor 1541 * of 3 will be chosen by this algorithm. Those who 1542 * choose a larger maxsockbuf should watch out 1543 * for the compatibility problems mentioned above. 1544 * 1545 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1546 * or <SYN,ACK>) segment itself is never scaled. 1547 */ 1548 while (wscale < TCP_MAX_WINSHIFT && 1549 (TCP_MAXWIN << wscale) < sb_max) 1550 wscale++; 1551 sc->sc_requested_r_scale = wscale; 1552 sc->sc_requested_s_scale = to->to_wscale; 1553 sc->sc_flags |= SCF_WINSCALE; 1554 } 1555 } 1556 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1557 /* 1558 * If listening socket requested TCP digests, flag this in the 1559 * syncache so that syncache_respond() will do the right thing 1560 * with the SYN+ACK. 1561 */ 1562 if (ltflags & TF_SIGNATURE) 1563 sc->sc_flags |= SCF_SIGNATURE; 1564 #endif /* TCP_SIGNATURE */ 1565 if (to->to_flags & TOF_SACKPERM) 1566 sc->sc_flags |= SCF_SACK; 1567 if (to->to_flags & TOF_MSS) 1568 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1569 if (ltflags & TF_NOOPT) 1570 sc->sc_flags |= SCF_NOOPT; 1571 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1572 sc->sc_flags |= SCF_ECN; 1573 1574 if (V_tcp_syncookies) 1575 sc->sc_iss = syncookie_generate(sch, sc); 1576 #ifdef INET6 1577 if (autoflowlabel) { 1578 if (V_tcp_syncookies) 1579 sc->sc_flowlabel = sc->sc_iss; 1580 else 1581 sc->sc_flowlabel = ip6_randomflowlabel(); 1582 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK; 1583 } 1584 #endif 1585 SCH_UNLOCK(sch); 1586 1587 if (tfo_cookie_valid) { 1588 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie); 1589 /* INP_WUNLOCK(inp) will be performed by the caller */ 1590 rv = 1; 1591 goto tfo_expanded; 1592 } 1593 1594 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1595 /* 1596 * Do a standard 3-way handshake. 1597 */ 1598 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1599 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1600 syncache_free(sc); 1601 else if (sc != &scs) 1602 syncache_insert(sc, sch); /* locks and unlocks sch */ 1603 TCPSTAT_INC(tcps_sndacks); 1604 TCPSTAT_INC(tcps_sndtotal); 1605 } else { 1606 if (sc != &scs) 1607 syncache_free(sc); 1608 TCPSTAT_INC(tcps_sc_dropped); 1609 } 1610 goto donenoprobe; 1611 1612 done: 1613 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1614 donenoprobe: 1615 if (m) { 1616 *lsop = NULL; 1617 m_freem(m); 1618 } 1619 /* 1620 * If tfo_pending is not NULL here, then a TFO SYN that did not 1621 * result in a new socket was processed and the associated pending 1622 * counter has not yet been decremented. All such TFO processing paths 1623 * transit this point. 1624 */ 1625 if (tfo_pending != NULL) 1626 tcp_fastopen_decrement_counter(tfo_pending); 1627 1628 tfo_expanded: 1629 if (cred != NULL) 1630 crfree(cred); 1631 #ifdef MAC 1632 if (sc == &scs) 1633 mac_syncache_destroy(&maclabel); 1634 #endif 1635 return (rv); 1636 } 1637 1638 /* 1639 * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment, 1640 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL. 1641 */ 1642 static int 1643 syncache_respond(struct syncache *sc, struct syncache_head *sch, 1644 const struct mbuf *m0, int flags) 1645 { 1646 struct ip *ip = NULL; 1647 struct mbuf *m; 1648 struct tcphdr *th = NULL; 1649 int optlen, error = 0; /* Make compiler happy */ 1650 u_int16_t hlen, tlen, mssopt; 1651 struct tcpopt to; 1652 #ifdef INET6 1653 struct ip6_hdr *ip6 = NULL; 1654 #endif 1655 hlen = 1656 #ifdef INET6 1657 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1658 #endif 1659 sizeof(struct ip); 1660 tlen = hlen + sizeof(struct tcphdr); 1661 1662 /* Determine MSS we advertize to other end of connection. */ 1663 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss); 1664 1665 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1666 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1667 ("syncache: mbuf too small")); 1668 1669 /* Create the IP+TCP header from scratch. */ 1670 m = m_gethdr(M_NOWAIT, MT_DATA); 1671 if (m == NULL) 1672 return (ENOBUFS); 1673 #ifdef MAC 1674 mac_syncache_create_mbuf(sc->sc_label, m); 1675 #endif 1676 m->m_data += max_linkhdr; 1677 m->m_len = tlen; 1678 m->m_pkthdr.len = tlen; 1679 m->m_pkthdr.rcvif = NULL; 1680 1681 #ifdef INET6 1682 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1683 ip6 = mtod(m, struct ip6_hdr *); 1684 ip6->ip6_vfc = IPV6_VERSION; 1685 ip6->ip6_nxt = IPPROTO_TCP; 1686 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1687 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1688 ip6->ip6_plen = htons(tlen - hlen); 1689 /* ip6_hlim is set after checksum */ 1690 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1691 ip6->ip6_flow |= sc->sc_flowlabel; 1692 1693 th = (struct tcphdr *)(ip6 + 1); 1694 } 1695 #endif 1696 #if defined(INET6) && defined(INET) 1697 else 1698 #endif 1699 #ifdef INET 1700 { 1701 ip = mtod(m, struct ip *); 1702 ip->ip_v = IPVERSION; 1703 ip->ip_hl = sizeof(struct ip) >> 2; 1704 ip->ip_len = htons(tlen); 1705 ip->ip_id = 0; 1706 ip->ip_off = 0; 1707 ip->ip_sum = 0; 1708 ip->ip_p = IPPROTO_TCP; 1709 ip->ip_src = sc->sc_inc.inc_laddr; 1710 ip->ip_dst = sc->sc_inc.inc_faddr; 1711 ip->ip_ttl = sc->sc_ip_ttl; 1712 ip->ip_tos = sc->sc_ip_tos; 1713 1714 /* 1715 * See if we should do MTU discovery. Route lookups are 1716 * expensive, so we will only unset the DF bit if: 1717 * 1718 * 1) path_mtu_discovery is disabled 1719 * 2) the SCF_UNREACH flag has been set 1720 */ 1721 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1722 ip->ip_off |= htons(IP_DF); 1723 1724 th = (struct tcphdr *)(ip + 1); 1725 } 1726 #endif /* INET */ 1727 th->th_sport = sc->sc_inc.inc_lport; 1728 th->th_dport = sc->sc_inc.inc_fport; 1729 1730 if (flags & TH_SYN) 1731 th->th_seq = htonl(sc->sc_iss); 1732 else 1733 th->th_seq = htonl(sc->sc_iss + 1); 1734 th->th_ack = htonl(sc->sc_irs + 1); 1735 th->th_off = sizeof(struct tcphdr) >> 2; 1736 th->th_x2 = 0; 1737 th->th_flags = flags; 1738 th->th_win = htons(sc->sc_wnd); 1739 th->th_urp = 0; 1740 1741 if ((flags & TH_SYN) && (sc->sc_flags & SCF_ECN)) { 1742 th->th_flags |= TH_ECE; 1743 TCPSTAT_INC(tcps_ecn_shs); 1744 } 1745 1746 /* Tack on the TCP options. */ 1747 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1748 to.to_flags = 0; 1749 1750 if (flags & TH_SYN) { 1751 to.to_mss = mssopt; 1752 to.to_flags = TOF_MSS; 1753 if (sc->sc_flags & SCF_WINSCALE) { 1754 to.to_wscale = sc->sc_requested_r_scale; 1755 to.to_flags |= TOF_SCALE; 1756 } 1757 if (sc->sc_flags & SCF_SACK) 1758 to.to_flags |= TOF_SACKPERM; 1759 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1760 if (sc->sc_flags & SCF_SIGNATURE) 1761 to.to_flags |= TOF_SIGNATURE; 1762 #endif 1763 if (sc->sc_tfo_cookie) { 1764 to.to_flags |= TOF_FASTOPEN; 1765 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 1766 to.to_tfo_cookie = sc->sc_tfo_cookie; 1767 /* don't send cookie again when retransmitting response */ 1768 sc->sc_tfo_cookie = NULL; 1769 } 1770 } 1771 if (sc->sc_flags & SCF_TIMESTAMP) { 1772 to.to_tsval = sc->sc_tsoff + tcp_ts_getticks(); 1773 to.to_tsecr = sc->sc_tsreflect; 1774 to.to_flags |= TOF_TS; 1775 } 1776 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1777 1778 /* Adjust headers by option size. */ 1779 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1780 m->m_len += optlen; 1781 m->m_pkthdr.len += optlen; 1782 #ifdef INET6 1783 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1784 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1785 else 1786 #endif 1787 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 1788 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1789 if (sc->sc_flags & SCF_SIGNATURE) { 1790 KASSERT(to.to_flags & TOF_SIGNATURE, 1791 ("tcp_addoptions() didn't set tcp_signature")); 1792 1793 /* NOTE: to.to_signature is inside of mbuf */ 1794 if (!TCPMD5_ENABLED() || 1795 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) { 1796 m_freem(m); 1797 return (EACCES); 1798 } 1799 } 1800 #endif 1801 } else 1802 optlen = 0; 1803 1804 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1805 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1806 /* 1807 * If we have peer's SYN and it has a flowid, then let's assign it to 1808 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid 1809 * to SYN|ACK due to lack of inp here. 1810 */ 1811 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) { 1812 m->m_pkthdr.flowid = m0->m_pkthdr.flowid; 1813 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0)); 1814 } 1815 #ifdef INET6 1816 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1817 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1818 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1819 IPPROTO_TCP, 0); 1820 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1821 #ifdef TCP_OFFLOAD 1822 if (ADDED_BY_TOE(sc)) { 1823 struct toedev *tod = sc->sc_tod; 1824 1825 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1826 1827 return (error); 1828 } 1829 #endif 1830 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th); 1831 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1832 } 1833 #endif 1834 #if defined(INET6) && defined(INET) 1835 else 1836 #endif 1837 #ifdef INET 1838 { 1839 m->m_pkthdr.csum_flags = CSUM_TCP; 1840 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1841 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1842 #ifdef TCP_OFFLOAD 1843 if (ADDED_BY_TOE(sc)) { 1844 struct toedev *tod = sc->sc_tod; 1845 1846 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1847 1848 return (error); 1849 } 1850 #endif 1851 TCP_PROBE5(send, NULL, NULL, ip, NULL, th); 1852 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1853 } 1854 #endif 1855 return (error); 1856 } 1857 1858 /* 1859 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks 1860 * that exceed the capacity of the syncache by avoiding the storage of any 1861 * of the SYNs we receive. Syncookies defend against blind SYN flooding 1862 * attacks where the attacker does not have access to our responses. 1863 * 1864 * Syncookies encode and include all necessary information about the 1865 * connection setup within the SYN|ACK that we send back. That way we 1866 * can avoid keeping any local state until the ACK to our SYN|ACK returns 1867 * (if ever). Normally the syncache and syncookies are running in parallel 1868 * with the latter taking over when the former is exhausted. When matching 1869 * syncache entry is found the syncookie is ignored. 1870 * 1871 * The only reliable information persisting the 3WHS is our initial sequence 1872 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient 1873 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS 1874 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK 1875 * returns and signifies a legitimate connection if it matches the ACK. 1876 * 1877 * The available space of 32 bits to store the hash and to encode the SYN 1878 * option information is very tight and we should have at least 24 bits for 1879 * the MAC to keep the number of guesses by blind spoofing reasonably high. 1880 * 1881 * SYN option information we have to encode to fully restore a connection: 1882 * MSS: is imporant to chose an optimal segment size to avoid IP level 1883 * fragmentation along the path. The common MSS values can be encoded 1884 * in a 3-bit table. Uncommon values are captured by the next lower value 1885 * in the table leading to a slight increase in packetization overhead. 1886 * WSCALE: is necessary to allow large windows to be used for high delay- 1887 * bandwidth product links. Not scaling the window when it was initially 1888 * negotiated is bad for performance as lack of scaling further decreases 1889 * the apparent available send window. We only need to encode the WSCALE 1890 * we received from the remote end. Our end can be recalculated at any 1891 * time. The common WSCALE values can be encoded in a 3-bit table. 1892 * Uncommon values are captured by the next lower value in the table 1893 * making us under-estimate the available window size halving our 1894 * theoretically possible maximum throughput for that connection. 1895 * SACK: Greatly assists in packet loss recovery and requires 1 bit. 1896 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options 1897 * that are included in all segments on a connection. We enable them when 1898 * the ACK has them. 1899 * 1900 * Security of syncookies and attack vectors: 1901 * 1902 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod) 1903 * together with the gloabl secret to make it unique per connection attempt. 1904 * Thus any change of any of those parameters results in a different MAC output 1905 * in an unpredictable way unless a collision is encountered. 24 bits of the 1906 * MAC are embedded into the ISS. 1907 * 1908 * To prevent replay attacks two rotating global secrets are updated with a 1909 * new random value every 15 seconds. The life-time of a syncookie is thus 1910 * 15-30 seconds. 1911 * 1912 * Vector 1: Attacking the secret. This requires finding a weakness in the 1913 * MAC itself or the way it is used here. The attacker can do a chosen plain 1914 * text attack by varying and testing the all parameters under his control. 1915 * The strength depends on the size and randomness of the secret, and the 1916 * cryptographic security of the MAC function. Due to the constant updating 1917 * of the secret the attacker has at most 29.999 seconds to find the secret 1918 * and launch spoofed connections. After that he has to start all over again. 1919 * 1920 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC 1921 * size an average of 4,823 attempts are required for a 50% chance of success 1922 * to spoof a single syncookie (birthday collision paradox). However the 1923 * attacker is blind and doesn't know if one of his attempts succeeded unless 1924 * he has a side channel to interfere success from. A single connection setup 1925 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets. 1926 * This many attempts are required for each one blind spoofed connection. For 1927 * every additional spoofed connection he has to launch another N attempts. 1928 * Thus for a sustained rate 100 spoofed connections per second approximately 1929 * 1,800,000 packets per second would have to be sent. 1930 * 1931 * NB: The MAC function should be fast so that it doesn't become a CPU 1932 * exhaustion attack vector itself. 1933 * 1934 * References: 1935 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations 1936 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996 1937 * http://cr.yp.to/syncookies.html (overview) 1938 * http://cr.yp.to/syncookies/archive (details) 1939 * 1940 * 1941 * Schematic construction of a syncookie enabled Initial Sequence Number: 1942 * 0 1 2 3 1943 * 12345678901234567890123456789012 1944 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP| 1945 * 1946 * x 24 MAC (truncated) 1947 * W 3 Send Window Scale index 1948 * M 3 MSS index 1949 * S 1 SACK permitted 1950 * P 1 Odd/even secret 1951 */ 1952 1953 /* 1954 * Distribution and probability of certain MSS values. Those in between are 1955 * rounded down to the next lower one. 1956 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011] 1957 * .2% .3% 5% 7% 7% 20% 15% 45% 1958 */ 1959 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 }; 1960 1961 /* 1962 * Distribution and probability of certain WSCALE values. We have to map the 1963 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3 1964 * bits based on prevalence of certain values. Where we don't have an exact 1965 * match for are rounded down to the next lower one letting us under-estimate 1966 * the true available window. At the moment this would happen only for the 1967 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer 1968 * and window size). The absence of the WSCALE option (no scaling in either 1969 * direction) is encoded with index zero. 1970 * [WSCALE values histograms, Allman, 2012] 1971 * X 10 10 35 5 6 14 10% by host 1972 * X 11 4 5 5 18 49 3% by connections 1973 */ 1974 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 }; 1975 1976 /* 1977 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed 1978 * and good cryptographic properties. 1979 */ 1980 static uint32_t 1981 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags, 1982 uint8_t *secbits, uintptr_t secmod) 1983 { 1984 SIPHASH_CTX ctx; 1985 uint32_t siphash[2]; 1986 1987 SipHash24_Init(&ctx); 1988 SipHash_SetKey(&ctx, secbits); 1989 switch (inc->inc_flags & INC_ISIPV6) { 1990 #ifdef INET 1991 case 0: 1992 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr)); 1993 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr)); 1994 break; 1995 #endif 1996 #ifdef INET6 1997 case INC_ISIPV6: 1998 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr)); 1999 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr)); 2000 break; 2001 #endif 2002 } 2003 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport)); 2004 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport)); 2005 SipHash_Update(&ctx, &irs, sizeof(irs)); 2006 SipHash_Update(&ctx, &flags, sizeof(flags)); 2007 SipHash_Update(&ctx, &secmod, sizeof(secmod)); 2008 SipHash_Final((u_int8_t *)&siphash, &ctx); 2009 2010 return (siphash[0] ^ siphash[1]); 2011 } 2012 2013 static tcp_seq 2014 syncookie_generate(struct syncache_head *sch, struct syncache *sc) 2015 { 2016 u_int i, secbit, wscale; 2017 uint32_t iss, hash; 2018 uint8_t *secbits; 2019 union syncookie cookie; 2020 2021 SCH_LOCK_ASSERT(sch); 2022 2023 cookie.cookie = 0; 2024 2025 /* Map our computed MSS into the 3-bit index. */ 2026 for (i = nitems(tcp_sc_msstab) - 1; 2027 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0; 2028 i--) 2029 ; 2030 cookie.flags.mss_idx = i; 2031 2032 /* 2033 * Map the send window scale into the 3-bit index but only if 2034 * the wscale option was received. 2035 */ 2036 if (sc->sc_flags & SCF_WINSCALE) { 2037 wscale = sc->sc_requested_s_scale; 2038 for (i = nitems(tcp_sc_wstab) - 1; 2039 tcp_sc_wstab[i] > wscale && i > 0; 2040 i--) 2041 ; 2042 cookie.flags.wscale_idx = i; 2043 } 2044 2045 /* Can we do SACK? */ 2046 if (sc->sc_flags & SCF_SACK) 2047 cookie.flags.sack_ok = 1; 2048 2049 /* Which of the two secrets to use. */ 2050 secbit = sch->sch_sc->secret.oddeven & 0x1; 2051 cookie.flags.odd_even = secbit; 2052 2053 secbits = sch->sch_sc->secret.key[secbit]; 2054 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits, 2055 (uintptr_t)sch); 2056 2057 /* 2058 * Put the flags into the hash and XOR them to get better ISS number 2059 * variance. This doesn't enhance the cryptographic strength and is 2060 * done to prevent the 8 cookie bits from showing up directly on the 2061 * wire. 2062 */ 2063 iss = hash & ~0xff; 2064 iss |= cookie.cookie ^ (hash >> 24); 2065 2066 TCPSTAT_INC(tcps_sc_sendcookie); 2067 return (iss); 2068 } 2069 2070 static struct syncache * 2071 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 2072 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2073 struct socket *lso) 2074 { 2075 uint32_t hash; 2076 uint8_t *secbits; 2077 tcp_seq ack, seq; 2078 int wnd, wscale = 0; 2079 union syncookie cookie; 2080 2081 SCH_LOCK_ASSERT(sch); 2082 2083 /* 2084 * Pull information out of SYN-ACK/ACK and revert sequence number 2085 * advances. 2086 */ 2087 ack = th->th_ack - 1; 2088 seq = th->th_seq - 1; 2089 2090 /* 2091 * Unpack the flags containing enough information to restore the 2092 * connection. 2093 */ 2094 cookie.cookie = (ack & 0xff) ^ (ack >> 24); 2095 2096 /* Which of the two secrets to use. */ 2097 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even]; 2098 2099 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch); 2100 2101 /* The recomputed hash matches the ACK if this was a genuine cookie. */ 2102 if ((ack & ~0xff) != (hash & ~0xff)) 2103 return (NULL); 2104 2105 /* Fill in the syncache values. */ 2106 sc->sc_flags = 0; 2107 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 2108 sc->sc_ipopts = NULL; 2109 2110 sc->sc_irs = seq; 2111 sc->sc_iss = ack; 2112 2113 switch (inc->inc_flags & INC_ISIPV6) { 2114 #ifdef INET 2115 case 0: 2116 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl; 2117 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos; 2118 break; 2119 #endif 2120 #ifdef INET6 2121 case INC_ISIPV6: 2122 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL) 2123 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK; 2124 break; 2125 #endif 2126 } 2127 2128 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx]; 2129 2130 /* We can simply recompute receive window scale we sent earlier. */ 2131 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max) 2132 wscale++; 2133 2134 /* Only use wscale if it was enabled in the orignal SYN. */ 2135 if (cookie.flags.wscale_idx > 0) { 2136 sc->sc_requested_r_scale = wscale; 2137 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx]; 2138 sc->sc_flags |= SCF_WINSCALE; 2139 } 2140 2141 wnd = lso->sol_sbrcv_hiwat; 2142 wnd = imax(wnd, 0); 2143 wnd = imin(wnd, TCP_MAXWIN); 2144 sc->sc_wnd = wnd; 2145 2146 if (cookie.flags.sack_ok) 2147 sc->sc_flags |= SCF_SACK; 2148 2149 if (to->to_flags & TOF_TS) { 2150 sc->sc_flags |= SCF_TIMESTAMP; 2151 sc->sc_tsreflect = to->to_tsval; 2152 sc->sc_tsoff = tcp_new_ts_offset(inc); 2153 } 2154 2155 if (to->to_flags & TOF_SIGNATURE) 2156 sc->sc_flags |= SCF_SIGNATURE; 2157 2158 sc->sc_rxmits = 0; 2159 2160 TCPSTAT_INC(tcps_sc_recvcookie); 2161 return (sc); 2162 } 2163 2164 #ifdef INVARIANTS 2165 static int 2166 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 2167 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2168 struct socket *lso) 2169 { 2170 struct syncache scs, *scx; 2171 char *s; 2172 2173 bzero(&scs, sizeof(scs)); 2174 scx = syncookie_lookup(inc, sch, &scs, th, to, lso); 2175 2176 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL) 2177 return (0); 2178 2179 if (scx != NULL) { 2180 if (sc->sc_peer_mss != scx->sc_peer_mss) 2181 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n", 2182 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss); 2183 2184 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale) 2185 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n", 2186 s, __func__, sc->sc_requested_r_scale, 2187 scx->sc_requested_r_scale); 2188 2189 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale) 2190 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n", 2191 s, __func__, sc->sc_requested_s_scale, 2192 scx->sc_requested_s_scale); 2193 2194 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK)) 2195 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__); 2196 } 2197 2198 if (s != NULL) 2199 free(s, M_TCPLOG); 2200 return (0); 2201 } 2202 #endif /* INVARIANTS */ 2203 2204 static void 2205 syncookie_reseed(void *arg) 2206 { 2207 struct tcp_syncache *sc = arg; 2208 uint8_t *secbits; 2209 int secbit; 2210 2211 /* 2212 * Reseeding the secret doesn't have to be protected by a lock. 2213 * It only must be ensured that the new random values are visible 2214 * to all CPUs in a SMP environment. The atomic with release 2215 * semantics ensures that. 2216 */ 2217 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1; 2218 secbits = sc->secret.key[secbit]; 2219 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0); 2220 atomic_add_rel_int(&sc->secret.oddeven, 1); 2221 2222 /* Reschedule ourself. */ 2223 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz); 2224 } 2225 2226 /* 2227 * Exports the syncache entries to userland so that netstat can display 2228 * them alongside the other sockets. This function is intended to be 2229 * called only from tcp_pcblist. 2230 * 2231 * Due to concurrency on an active system, the number of pcbs exported 2232 * may have no relation to max_pcbs. max_pcbs merely indicates the 2233 * amount of space the caller allocated for this function to use. 2234 */ 2235 int 2236 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 2237 { 2238 struct xtcpcb xt; 2239 struct syncache *sc; 2240 struct syncache_head *sch; 2241 int count, error, i; 2242 2243 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 2244 sch = &V_tcp_syncache.hashbase[i]; 2245 SCH_LOCK(sch); 2246 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 2247 if (count >= max_pcbs) { 2248 SCH_UNLOCK(sch); 2249 goto exit; 2250 } 2251 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 2252 continue; 2253 bzero(&xt, sizeof(xt)); 2254 xt.xt_len = sizeof(xt); 2255 if (sc->sc_inc.inc_flags & INC_ISIPV6) 2256 xt.xt_inp.inp_vflag = INP_IPV6; 2257 else 2258 xt.xt_inp.inp_vflag = INP_IPV4; 2259 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, 2260 sizeof (struct in_conninfo)); 2261 xt.t_state = TCPS_SYN_RECEIVED; 2262 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP; 2263 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket); 2264 xt.xt_inp.xi_socket.so_type = SOCK_STREAM; 2265 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING; 2266 error = SYSCTL_OUT(req, &xt, sizeof xt); 2267 if (error) { 2268 SCH_UNLOCK(sch); 2269 goto exit; 2270 } 2271 count++; 2272 } 2273 SCH_UNLOCK(sch); 2274 } 2275 exit: 2276 *pcbs_exported = count; 2277 return error; 2278 }
Cache object: 67035c94c8a328adcf36c5cf0b42bdeb
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