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("$FreeBSD$"); 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 * 585 * RFC 793 page 37: 586 * In all states except SYN-SENT, all reset (RST) segments 587 * are validated by checking their SEQ-fields. A reset is 588 * valid if its sequence number is in the window. 589 * 590 * RFC 793 page 69: 591 * There are four cases for the acceptability test for an incoming 592 * segment: 593 * 594 * Segment Receive Test 595 * Length Window 596 * ------- ------- ------------------------------------------- 597 * 0 0 SEG.SEQ = RCV.NXT 598 * 0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND 599 * >0 0 not acceptable 600 * >0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND 601 * or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND 602 * 603 * Note that when receiving a SYN segment in the LISTEN state, 604 * IRS is set to SEG.SEQ and RCV.NXT is set to SEG.SEQ+1, as 605 * described in RFC 793, page 66. 606 */ 607 if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) && 608 SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) || 609 (sc->sc_wnd == 0 && th->th_seq == sc->sc_irs + 1)) { 610 if (V_tcp_insecure_rst || 611 th->th_seq == sc->sc_irs + 1) { 612 syncache_drop(sc, sch); 613 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 614 log(LOG_DEBUG, 615 "%s; %s: Our SYN|ACK was rejected, " 616 "connection attempt aborted by remote " 617 "endpoint\n", 618 s, __func__); 619 TCPSTAT_INC(tcps_sc_reset); 620 } else { 621 TCPSTAT_INC(tcps_badrst); 622 /* Send challenge ACK. */ 623 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 624 log(LOG_DEBUG, "%s; %s: RST with invalid " 625 " SEQ %u != NXT %u (+WND %u), " 626 "sending challenge ACK\n", 627 s, __func__, 628 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 629 syncache_respond(sc, sch, m, TH_ACK); 630 } 631 } else { 632 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 633 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 634 "NXT %u (+WND %u), segment ignored\n", 635 s, __func__, 636 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 637 TCPSTAT_INC(tcps_badrst); 638 } 639 640 done: 641 if (s != NULL) 642 free(s, M_TCPLOG); 643 SCH_UNLOCK(sch); 644 } 645 646 void 647 syncache_badack(struct in_conninfo *inc) 648 { 649 struct syncache *sc; 650 struct syncache_head *sch; 651 652 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 653 SCH_LOCK_ASSERT(sch); 654 if (sc != NULL) { 655 syncache_drop(sc, sch); 656 TCPSTAT_INC(tcps_sc_badack); 657 } 658 SCH_UNLOCK(sch); 659 } 660 661 void 662 syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq) 663 { 664 struct syncache *sc; 665 struct syncache_head *sch; 666 667 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 668 SCH_LOCK_ASSERT(sch); 669 if (sc == NULL) 670 goto done; 671 672 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 673 if (ntohl(th_seq) != sc->sc_iss) 674 goto done; 675 676 /* 677 * If we've rertransmitted 3 times and this is our second error, 678 * we remove the entry. Otherwise, we allow it to continue on. 679 * This prevents us from incorrectly nuking an entry during a 680 * spurious network outage. 681 * 682 * See tcp_notify(). 683 */ 684 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 685 sc->sc_flags |= SCF_UNREACH; 686 goto done; 687 } 688 syncache_drop(sc, sch); 689 TCPSTAT_INC(tcps_sc_unreach); 690 done: 691 SCH_UNLOCK(sch); 692 } 693 694 /* 695 * Build a new TCP socket structure from a syncache entry. 696 * 697 * On success return the newly created socket with its underlying inp locked. 698 */ 699 static struct socket * 700 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 701 { 702 struct tcp_function_block *blk; 703 struct inpcb *inp = NULL; 704 struct socket *so; 705 struct tcpcb *tp; 706 int error; 707 char *s; 708 709 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 710 711 /* 712 * Ok, create the full blown connection, and set things up 713 * as they would have been set up if we had created the 714 * connection when the SYN arrived. If we can't create 715 * the connection, abort it. 716 */ 717 so = sonewconn(lso, 0); 718 if (so == NULL) { 719 /* 720 * Drop the connection; we will either send a RST or 721 * have the peer retransmit its SYN again after its 722 * RTO and try again. 723 */ 724 TCPSTAT_INC(tcps_listendrop); 725 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 726 log(LOG_DEBUG, "%s; %s: Socket create failed " 727 "due to limits or memory shortage\n", 728 s, __func__); 729 free(s, M_TCPLOG); 730 } 731 goto abort2; 732 } 733 #ifdef MAC 734 mac_socketpeer_set_from_mbuf(m, so); 735 #endif 736 737 inp = sotoinpcb(so); 738 inp->inp_inc.inc_fibnum = so->so_fibnum; 739 INP_WLOCK(inp); 740 /* 741 * Exclusive pcbinfo lock is not required in syncache socket case even 742 * if two inpcb locks can be acquired simultaneously: 743 * - the inpcb in LISTEN state, 744 * - the newly created inp. 745 * 746 * In this case, an inp cannot be at same time in LISTEN state and 747 * just created by an accept() call. 748 */ 749 INP_HASH_WLOCK(&V_tcbinfo); 750 751 /* Insert new socket into PCB hash list. */ 752 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 753 #ifdef INET6 754 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 755 inp->inp_vflag &= ~INP_IPV4; 756 inp->inp_vflag |= INP_IPV6; 757 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 758 } else { 759 inp->inp_vflag &= ~INP_IPV6; 760 inp->inp_vflag |= INP_IPV4; 761 #endif 762 inp->inp_laddr = sc->sc_inc.inc_laddr; 763 #ifdef INET6 764 } 765 #endif 766 767 /* 768 * If there's an mbuf and it has a flowid, then let's initialise the 769 * inp with that particular flowid. 770 */ 771 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) { 772 inp->inp_flowid = m->m_pkthdr.flowid; 773 inp->inp_flowtype = M_HASHTYPE_GET(m); 774 } 775 776 /* 777 * Install in the reservation hash table for now, but don't yet 778 * install a connection group since the full 4-tuple isn't yet 779 * configured. 780 */ 781 inp->inp_lport = sc->sc_inc.inc_lport; 782 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 783 /* 784 * Undo the assignments above if we failed to 785 * put the PCB on the hash lists. 786 */ 787 #ifdef INET6 788 if (sc->sc_inc.inc_flags & INC_ISIPV6) 789 inp->in6p_laddr = in6addr_any; 790 else 791 #endif 792 inp->inp_laddr.s_addr = INADDR_ANY; 793 inp->inp_lport = 0; 794 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 795 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 796 "with error %i\n", 797 s, __func__, error); 798 free(s, M_TCPLOG); 799 } 800 INP_HASH_WUNLOCK(&V_tcbinfo); 801 goto abort; 802 } 803 #ifdef INET6 804 if (inp->inp_vflag & INP_IPV6PROTO) { 805 struct inpcb *oinp = sotoinpcb(lso); 806 807 /* 808 * Inherit socket options from the listening socket. 809 * Note that in6p_inputopts are not (and should not be) 810 * copied, since it stores previously received options and is 811 * used to detect if each new option is different than the 812 * previous one and hence should be passed to a user. 813 * If we copied in6p_inputopts, a user would not be able to 814 * receive options just after calling the accept system call. 815 */ 816 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 817 if (oinp->in6p_outputopts) 818 inp->in6p_outputopts = 819 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 820 } 821 822 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 823 struct in6_addr laddr6; 824 struct sockaddr_in6 sin6; 825 826 sin6.sin6_family = AF_INET6; 827 sin6.sin6_len = sizeof(sin6); 828 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 829 sin6.sin6_port = sc->sc_inc.inc_fport; 830 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 831 laddr6 = inp->in6p_laddr; 832 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 833 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 834 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 835 thread0.td_ucred, m)) != 0) { 836 inp->in6p_laddr = laddr6; 837 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 838 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 839 "with error %i\n", 840 s, __func__, error); 841 free(s, M_TCPLOG); 842 } 843 INP_HASH_WUNLOCK(&V_tcbinfo); 844 goto abort; 845 } 846 /* Override flowlabel from in6_pcbconnect. */ 847 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 848 inp->inp_flow |= sc->sc_flowlabel; 849 } 850 #endif /* INET6 */ 851 #if defined(INET) && defined(INET6) 852 else 853 #endif 854 #ifdef INET 855 { 856 struct in_addr laddr; 857 struct sockaddr_in sin; 858 859 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 860 861 if (inp->inp_options == NULL) { 862 inp->inp_options = sc->sc_ipopts; 863 sc->sc_ipopts = NULL; 864 } 865 866 sin.sin_family = AF_INET; 867 sin.sin_len = sizeof(sin); 868 sin.sin_addr = sc->sc_inc.inc_faddr; 869 sin.sin_port = sc->sc_inc.inc_fport; 870 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 871 laddr = inp->inp_laddr; 872 if (inp->inp_laddr.s_addr == INADDR_ANY) 873 inp->inp_laddr = sc->sc_inc.inc_laddr; 874 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 875 thread0.td_ucred, m)) != 0) { 876 inp->inp_laddr = laddr; 877 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 878 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 879 "with error %i\n", 880 s, __func__, error); 881 free(s, M_TCPLOG); 882 } 883 INP_HASH_WUNLOCK(&V_tcbinfo); 884 goto abort; 885 } 886 } 887 #endif /* INET */ 888 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 889 /* Copy old policy into new socket's. */ 890 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0) 891 printf("syncache_socket: could not copy policy\n"); 892 #endif 893 INP_HASH_WUNLOCK(&V_tcbinfo); 894 tp = intotcpcb(inp); 895 tcp_state_change(tp, TCPS_SYN_RECEIVED); 896 tp->iss = sc->sc_iss; 897 tp->irs = sc->sc_irs; 898 tcp_rcvseqinit(tp); 899 tcp_sendseqinit(tp); 900 blk = sototcpcb(lso)->t_fb; 901 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) { 902 /* 903 * Our parents t_fb was not the default, 904 * we need to release our ref on tp->t_fb and 905 * pickup one on the new entry. 906 */ 907 struct tcp_function_block *rblk; 908 909 rblk = find_and_ref_tcp_fb(blk); 910 KASSERT(rblk != NULL, 911 ("cannot find blk %p out of syncache?", blk)); 912 if (tp->t_fb->tfb_tcp_fb_fini) 913 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0); 914 refcount_release(&tp->t_fb->tfb_refcnt); 915 tp->t_fb = rblk; 916 /* 917 * XXXrrs this is quite dangerous, it is possible 918 * for the new function to fail to init. We also 919 * are not asking if the handoff_is_ok though at 920 * the very start thats probalbly ok. 921 */ 922 if (tp->t_fb->tfb_tcp_fb_init) { 923 (*tp->t_fb->tfb_tcp_fb_init)(tp); 924 } 925 } 926 tp->snd_wl1 = sc->sc_irs; 927 tp->snd_max = tp->iss + 1; 928 tp->snd_nxt = tp->iss + 1; 929 tp->rcv_up = sc->sc_irs + 1; 930 tp->rcv_wnd = sc->sc_wnd; 931 tp->rcv_adv += tp->rcv_wnd; 932 tp->last_ack_sent = tp->rcv_nxt; 933 934 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 935 if (sc->sc_flags & SCF_NOOPT) 936 tp->t_flags |= TF_NOOPT; 937 else { 938 if (sc->sc_flags & SCF_WINSCALE) { 939 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 940 tp->snd_scale = sc->sc_requested_s_scale; 941 tp->request_r_scale = sc->sc_requested_r_scale; 942 } 943 if (sc->sc_flags & SCF_TIMESTAMP) { 944 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 945 tp->ts_recent = sc->sc_tsreflect; 946 tp->ts_recent_age = tcp_ts_getticks(); 947 tp->ts_offset = sc->sc_tsoff; 948 } 949 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 950 if (sc->sc_flags & SCF_SIGNATURE) 951 tp->t_flags |= TF_SIGNATURE; 952 #endif 953 if (sc->sc_flags & SCF_SACK) 954 tp->t_flags |= TF_SACK_PERMIT; 955 } 956 957 if (sc->sc_flags & SCF_ECN) 958 tp->t_flags |= TF_ECN_PERMIT; 959 960 /* 961 * Set up MSS and get cached values from tcp_hostcache. 962 * This might overwrite some of the defaults we just set. 963 */ 964 tcp_mss(tp, sc->sc_peer_mss); 965 966 /* 967 * If the SYN,ACK was retransmitted, indicate that CWND to be 968 * limited to one segment in cc_conn_init(). 969 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 970 */ 971 if (sc->sc_rxmits > 1) 972 tp->snd_cwnd = 1; 973 974 #ifdef TCP_OFFLOAD 975 /* 976 * Allow a TOE driver to install its hooks. Note that we hold the 977 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a 978 * new connection before the TOE driver has done its thing. 979 */ 980 if (ADDED_BY_TOE(sc)) { 981 struct toedev *tod = sc->sc_tod; 982 983 tod->tod_offload_socket(tod, sc->sc_todctx, so); 984 } 985 #endif 986 /* 987 * Copy and activate timers. 988 */ 989 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 990 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 991 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 992 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 993 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 994 995 TCPSTAT_INC(tcps_accepts); 996 return (so); 997 998 abort: 999 INP_WUNLOCK(inp); 1000 abort2: 1001 if (so != NULL) 1002 soabort(so); 1003 return (NULL); 1004 } 1005 1006 /* 1007 * This function gets called when we receive an ACK for a 1008 * socket in the LISTEN state. We look up the connection 1009 * in the syncache, and if its there, we pull it out of 1010 * the cache and turn it into a full-blown connection in 1011 * the SYN-RECEIVED state. 1012 * 1013 * On syncache_socket() success the newly created socket 1014 * has its underlying inp locked. 1015 */ 1016 int 1017 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1018 struct socket **lsop, struct mbuf *m) 1019 { 1020 struct syncache *sc; 1021 struct syncache_head *sch; 1022 struct syncache scs; 1023 char *s; 1024 1025 /* 1026 * Global TCP locks are held because we manipulate the PCB lists 1027 * and create a new socket. 1028 */ 1029 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1030 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 1031 ("%s: can handle only ACK", __func__)); 1032 1033 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 1034 SCH_LOCK_ASSERT(sch); 1035 1036 #ifdef INVARIANTS 1037 /* 1038 * Test code for syncookies comparing the syncache stored 1039 * values with the reconstructed values from the cookie. 1040 */ 1041 if (sc != NULL) 1042 syncookie_cmp(inc, sch, sc, th, to, *lsop); 1043 #endif 1044 1045 if (sc == NULL) { 1046 /* 1047 * There is no syncache entry, so see if this ACK is 1048 * a returning syncookie. To do this, first: 1049 * A. Check if syncookies are used in case of syncache 1050 * overflows 1051 * B. See if this socket has had a syncache entry dropped in 1052 * the recent past. We don't want to accept a bogus 1053 * syncookie if we've never received a SYN or accept it 1054 * twice. 1055 * C. check that the syncookie is valid. If it is, then 1056 * cobble up a fake syncache entry, and return. 1057 */ 1058 if (!V_tcp_syncookies) { 1059 SCH_UNLOCK(sch); 1060 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1061 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1062 "segment rejected (syncookies disabled)\n", 1063 s, __func__); 1064 goto failed; 1065 } 1066 if (!V_tcp_syncookiesonly && 1067 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) { 1068 SCH_UNLOCK(sch); 1069 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1070 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1071 "segment rejected (no syncache entry)\n", 1072 s, __func__); 1073 goto failed; 1074 } 1075 bzero(&scs, sizeof(scs)); 1076 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop); 1077 SCH_UNLOCK(sch); 1078 if (sc == NULL) { 1079 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1080 log(LOG_DEBUG, "%s; %s: Segment failed " 1081 "SYNCOOKIE authentication, segment rejected " 1082 "(probably spoofed)\n", s, __func__); 1083 goto failed; 1084 } 1085 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1086 /* If received ACK has MD5 signature, check it. */ 1087 if ((to->to_flags & TOF_SIGNATURE) != 0 && 1088 (!TCPMD5_ENABLED() || 1089 TCPMD5_INPUT(m, th, to->to_signature) != 0)) { 1090 /* Drop the ACK. */ 1091 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1092 log(LOG_DEBUG, "%s; %s: Segment rejected, " 1093 "MD5 signature doesn't match.\n", 1094 s, __func__); 1095 free(s, M_TCPLOG); 1096 } 1097 TCPSTAT_INC(tcps_sig_err_sigopt); 1098 return (-1); /* Do not send RST */ 1099 } 1100 #endif /* TCP_SIGNATURE */ 1101 } else { 1102 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1103 /* 1104 * If listening socket requested TCP digests, check that 1105 * received ACK has signature and it is correct. 1106 * If not, drop the ACK and leave sc entry in th cache, 1107 * because SYN was received with correct signature. 1108 */ 1109 if (sc->sc_flags & SCF_SIGNATURE) { 1110 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1111 /* No signature */ 1112 TCPSTAT_INC(tcps_sig_err_nosigopt); 1113 SCH_UNLOCK(sch); 1114 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1115 log(LOG_DEBUG, "%s; %s: Segment " 1116 "rejected, MD5 signature wasn't " 1117 "provided.\n", s, __func__); 1118 free(s, M_TCPLOG); 1119 } 1120 return (-1); /* Do not send RST */ 1121 } 1122 if (!TCPMD5_ENABLED() || 1123 TCPMD5_INPUT(m, th, to->to_signature) != 0) { 1124 /* Doesn't match or no SA */ 1125 SCH_UNLOCK(sch); 1126 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1127 log(LOG_DEBUG, "%s; %s: Segment " 1128 "rejected, MD5 signature doesn't " 1129 "match.\n", s, __func__); 1130 free(s, M_TCPLOG); 1131 } 1132 return (-1); /* Do not send RST */ 1133 } 1134 } 1135 #endif /* TCP_SIGNATURE */ 1136 /* 1137 * Pull out the entry to unlock the bucket row. 1138 * 1139 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not 1140 * tcp_state_change(). The tcpcb is not existent at this 1141 * moment. A new one will be allocated via syncache_socket-> 1142 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then 1143 * syncache_socket() will change it to TCPS_SYN_RECEIVED. 1144 */ 1145 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 1146 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 1147 sch->sch_length--; 1148 #ifdef TCP_OFFLOAD 1149 if (ADDED_BY_TOE(sc)) { 1150 struct toedev *tod = sc->sc_tod; 1151 1152 tod->tod_syncache_removed(tod, sc->sc_todctx); 1153 } 1154 #endif 1155 SCH_UNLOCK(sch); 1156 } 1157 1158 /* 1159 * Segment validation: 1160 * ACK must match our initial sequence number + 1 (the SYN|ACK). 1161 */ 1162 if (th->th_ack != sc->sc_iss + 1) { 1163 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1164 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 1165 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 1166 goto failed; 1167 } 1168 1169 /* 1170 * The SEQ must fall in the window starting at the received 1171 * initial receive sequence number + 1 (the SYN). 1172 */ 1173 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 1174 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 1175 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1176 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 1177 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 1178 goto failed; 1179 } 1180 1181 /* 1182 * If timestamps were not negotiated during SYN/ACK they 1183 * must not appear on any segment during this session. 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 not expected, " 1188 "segment rejected\n", s, __func__); 1189 goto failed; 1190 } 1191 1192 /* 1193 * If timestamps were negotiated during SYN/ACK they should 1194 * appear on every segment during this session. 1195 * XXXAO: This is only informal as there have been unverified 1196 * reports of non-compliants stacks. 1197 */ 1198 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) { 1199 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1200 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1201 "no action\n", s, __func__); 1202 free(s, M_TCPLOG); 1203 s = NULL; 1204 } 1205 } 1206 1207 *lsop = syncache_socket(sc, *lsop, m); 1208 1209 if (*lsop == NULL) 1210 TCPSTAT_INC(tcps_sc_aborted); 1211 else 1212 TCPSTAT_INC(tcps_sc_completed); 1213 1214 /* how do we find the inp for the new socket? */ 1215 if (sc != &scs) 1216 syncache_free(sc); 1217 return (1); 1218 failed: 1219 if (sc != NULL && sc != &scs) 1220 syncache_free(sc); 1221 if (s != NULL) 1222 free(s, M_TCPLOG); 1223 *lsop = NULL; 1224 return (0); 1225 } 1226 1227 static void 1228 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m, 1229 uint64_t response_cookie) 1230 { 1231 struct inpcb *inp; 1232 struct tcpcb *tp; 1233 unsigned int *pending_counter; 1234 1235 /* 1236 * Global TCP locks are held because we manipulate the PCB lists 1237 * and create a new socket. 1238 */ 1239 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1240 1241 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending; 1242 *lsop = syncache_socket(sc, *lsop, m); 1243 if (*lsop == NULL) { 1244 TCPSTAT_INC(tcps_sc_aborted); 1245 atomic_subtract_int(pending_counter, 1); 1246 } else { 1247 soisconnected(*lsop); 1248 inp = sotoinpcb(*lsop); 1249 tp = intotcpcb(inp); 1250 tp->t_flags |= TF_FASTOPEN; 1251 tp->t_tfo_cookie.server = response_cookie; 1252 tp->snd_max = tp->iss; 1253 tp->snd_nxt = tp->iss; 1254 tp->t_tfo_pending = pending_counter; 1255 TCPSTAT_INC(tcps_sc_completed); 1256 } 1257 } 1258 1259 /* 1260 * Given a LISTEN socket and an inbound SYN request, add 1261 * this to the syn cache, and send back a segment: 1262 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1263 * to the source. 1264 * 1265 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1266 * Doing so would require that we hold onto the data and deliver it 1267 * to the application. However, if we are the target of a SYN-flood 1268 * DoS attack, an attacker could send data which would eventually 1269 * consume all available buffer space if it were ACKed. By not ACKing 1270 * the data, we avoid this DoS scenario. 1271 * 1272 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO) 1273 * cookie is processed and a new socket is created. In this case, any data 1274 * accompanying the SYN will be queued to the socket by tcp_input() and will 1275 * be ACKed either when the application sends response data or the delayed 1276 * ACK timer expires, whichever comes first. 1277 */ 1278 int 1279 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1280 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1281 void *todctx) 1282 { 1283 struct tcpcb *tp; 1284 struct socket *so; 1285 struct syncache *sc = NULL; 1286 struct syncache_head *sch; 1287 struct mbuf *ipopts = NULL; 1288 u_int ltflags; 1289 int win, ip_ttl, ip_tos; 1290 char *s; 1291 int rv = 0; 1292 #ifdef INET6 1293 int autoflowlabel = 0; 1294 #endif 1295 #ifdef MAC 1296 struct label *maclabel; 1297 #endif 1298 struct syncache scs; 1299 struct ucred *cred; 1300 uint64_t tfo_response_cookie; 1301 unsigned int *tfo_pending = NULL; 1302 int tfo_cookie_valid = 0; 1303 int tfo_response_cookie_valid = 0; 1304 1305 INP_WLOCK_ASSERT(inp); /* listen socket */ 1306 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1307 ("%s: unexpected tcp flags", __func__)); 1308 1309 /* 1310 * Combine all so/tp operations very early to drop the INP lock as 1311 * soon as possible. 1312 */ 1313 so = *lsop; 1314 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so)); 1315 tp = sototcpcb(so); 1316 cred = crhold(so->so_cred); 1317 1318 #ifdef INET6 1319 if ((inc->inc_flags & INC_ISIPV6) && 1320 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1321 autoflowlabel = 1; 1322 #endif 1323 ip_ttl = inp->inp_ip_ttl; 1324 ip_tos = inp->inp_ip_tos; 1325 win = so->sol_sbrcv_hiwat; 1326 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1327 1328 if (V_tcp_fastopen_server_enable && IS_FASTOPEN(tp->t_flags) && 1329 (tp->t_tfo_pending != NULL) && 1330 (to->to_flags & TOF_FASTOPEN)) { 1331 /* 1332 * Limit the number of pending TFO connections to 1333 * approximately half of the queue limit. This prevents TFO 1334 * SYN floods from starving the service by filling the 1335 * listen queue with bogus TFO connections. 1336 */ 1337 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <= 1338 (so->sol_qlimit / 2)) { 1339 int result; 1340 1341 result = tcp_fastopen_check_cookie(inc, 1342 to->to_tfo_cookie, to->to_tfo_len, 1343 &tfo_response_cookie); 1344 tfo_cookie_valid = (result > 0); 1345 tfo_response_cookie_valid = (result >= 0); 1346 } 1347 1348 /* 1349 * Remember the TFO pending counter as it will have to be 1350 * decremented below if we don't make it to syncache_tfo_expand(). 1351 */ 1352 tfo_pending = tp->t_tfo_pending; 1353 } 1354 1355 /* By the time we drop the lock these should no longer be used. */ 1356 so = NULL; 1357 tp = NULL; 1358 1359 #ifdef MAC 1360 if (mac_syncache_init(&maclabel) != 0) { 1361 INP_WUNLOCK(inp); 1362 goto done; 1363 } else 1364 mac_syncache_create(maclabel, inp); 1365 #endif 1366 if (!tfo_cookie_valid) 1367 INP_WUNLOCK(inp); 1368 1369 /* 1370 * Remember the IP options, if any. 1371 */ 1372 #ifdef INET6 1373 if (!(inc->inc_flags & INC_ISIPV6)) 1374 #endif 1375 #ifdef INET 1376 ipopts = (m) ? ip_srcroute(m) : NULL; 1377 #else 1378 ipopts = NULL; 1379 #endif 1380 1381 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1382 /* 1383 * If listening socket requested TCP digests, check that received 1384 * SYN has signature and it is correct. If signature doesn't match 1385 * or TCP_SIGNATURE support isn't enabled, drop the packet. 1386 */ 1387 if (ltflags & TF_SIGNATURE) { 1388 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1389 TCPSTAT_INC(tcps_sig_err_nosigopt); 1390 goto done; 1391 } 1392 if (!TCPMD5_ENABLED() || 1393 TCPMD5_INPUT(m, th, to->to_signature) != 0) 1394 goto done; 1395 } 1396 #endif /* TCP_SIGNATURE */ 1397 /* 1398 * See if we already have an entry for this connection. 1399 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1400 * 1401 * XXX: should the syncache be re-initialized with the contents 1402 * of the new SYN here (which may have different options?) 1403 * 1404 * XXX: We do not check the sequence number to see if this is a 1405 * real retransmit or a new connection attempt. The question is 1406 * how to handle such a case; either ignore it as spoofed, or 1407 * drop the current entry and create a new one? 1408 */ 1409 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1410 SCH_LOCK_ASSERT(sch); 1411 if (sc != NULL) { 1412 if (tfo_cookie_valid) 1413 INP_WUNLOCK(inp); 1414 TCPSTAT_INC(tcps_sc_dupsyn); 1415 if (ipopts) { 1416 /* 1417 * If we were remembering a previous source route, 1418 * forget it and use the new one we've been given. 1419 */ 1420 if (sc->sc_ipopts) 1421 (void) m_free(sc->sc_ipopts); 1422 sc->sc_ipopts = ipopts; 1423 } 1424 /* 1425 * Update timestamp if present. 1426 */ 1427 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1428 sc->sc_tsreflect = to->to_tsval; 1429 else 1430 sc->sc_flags &= ~SCF_TIMESTAMP; 1431 #ifdef MAC 1432 /* 1433 * Since we have already unconditionally allocated label 1434 * storage, free it up. The syncache entry will already 1435 * have an initialized label we can use. 1436 */ 1437 mac_syncache_destroy(&maclabel); 1438 #endif 1439 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1440 /* Retransmit SYN|ACK and reset retransmit count. */ 1441 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1442 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1443 "resetting timer and retransmitting SYN|ACK\n", 1444 s, __func__); 1445 free(s, M_TCPLOG); 1446 } 1447 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1448 sc->sc_rxmits = 0; 1449 syncache_timeout(sc, sch, 1); 1450 TCPSTAT_INC(tcps_sndacks); 1451 TCPSTAT_INC(tcps_sndtotal); 1452 } 1453 SCH_UNLOCK(sch); 1454 goto donenoprobe; 1455 } 1456 1457 if (tfo_cookie_valid) { 1458 bzero(&scs, sizeof(scs)); 1459 sc = &scs; 1460 goto skip_alloc; 1461 } 1462 1463 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1464 if (sc == NULL) { 1465 /* 1466 * The zone allocator couldn't provide more entries. 1467 * Treat this as if the cache was full; drop the oldest 1468 * entry and insert the new one. 1469 */ 1470 TCPSTAT_INC(tcps_sc_zonefail); 1471 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) { 1472 sch->sch_last_overflow = time_uptime; 1473 syncache_drop(sc, sch); 1474 } 1475 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1476 if (sc == NULL) { 1477 if (V_tcp_syncookies) { 1478 bzero(&scs, sizeof(scs)); 1479 sc = &scs; 1480 } else { 1481 SCH_UNLOCK(sch); 1482 if (ipopts) 1483 (void) m_free(ipopts); 1484 goto done; 1485 } 1486 } 1487 } 1488 1489 skip_alloc: 1490 if (!tfo_cookie_valid && tfo_response_cookie_valid) 1491 sc->sc_tfo_cookie = &tfo_response_cookie; 1492 1493 /* 1494 * Fill in the syncache values. 1495 */ 1496 #ifdef MAC 1497 sc->sc_label = maclabel; 1498 #endif 1499 sc->sc_cred = cred; 1500 cred = NULL; 1501 sc->sc_ipopts = ipopts; 1502 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1503 #ifdef INET6 1504 if (!(inc->inc_flags & INC_ISIPV6)) 1505 #endif 1506 { 1507 sc->sc_ip_tos = ip_tos; 1508 sc->sc_ip_ttl = ip_ttl; 1509 } 1510 #ifdef TCP_OFFLOAD 1511 sc->sc_tod = tod; 1512 sc->sc_todctx = todctx; 1513 #endif 1514 sc->sc_irs = th->th_seq; 1515 sc->sc_iss = arc4random(); 1516 sc->sc_flags = 0; 1517 sc->sc_flowlabel = 0; 1518 1519 /* 1520 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1521 * win was derived from socket earlier in the function. 1522 */ 1523 win = imax(win, 0); 1524 win = imin(win, TCP_MAXWIN); 1525 sc->sc_wnd = win; 1526 1527 if (V_tcp_do_rfc1323) { 1528 /* 1529 * A timestamp received in a SYN makes 1530 * it ok to send timestamp requests and replies. 1531 */ 1532 if (to->to_flags & TOF_TS) { 1533 sc->sc_tsreflect = to->to_tsval; 1534 sc->sc_flags |= SCF_TIMESTAMP; 1535 sc->sc_tsoff = tcp_new_ts_offset(inc); 1536 } 1537 if (to->to_flags & TOF_SCALE) { 1538 int wscale = 0; 1539 1540 /* 1541 * Pick the smallest possible scaling factor that 1542 * will still allow us to scale up to sb_max, aka 1543 * kern.ipc.maxsockbuf. 1544 * 1545 * We do this because there are broken firewalls that 1546 * will corrupt the window scale option, leading to 1547 * the other endpoint believing that our advertised 1548 * window is unscaled. At scale factors larger than 1549 * 5 the unscaled window will drop below 1500 bytes, 1550 * leading to serious problems when traversing these 1551 * broken firewalls. 1552 * 1553 * With the default maxsockbuf of 256K, a scale factor 1554 * of 3 will be chosen by this algorithm. Those who 1555 * choose a larger maxsockbuf should watch out 1556 * for the compatibility problems mentioned above. 1557 * 1558 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1559 * or <SYN,ACK>) segment itself is never scaled. 1560 */ 1561 while (wscale < TCP_MAX_WINSHIFT && 1562 (TCP_MAXWIN << wscale) < sb_max) 1563 wscale++; 1564 sc->sc_requested_r_scale = wscale; 1565 sc->sc_requested_s_scale = to->to_wscale; 1566 sc->sc_flags |= SCF_WINSCALE; 1567 } 1568 } 1569 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1570 /* 1571 * If listening socket requested TCP digests, flag this in the 1572 * syncache so that syncache_respond() will do the right thing 1573 * with the SYN+ACK. 1574 */ 1575 if (ltflags & TF_SIGNATURE) 1576 sc->sc_flags |= SCF_SIGNATURE; 1577 #endif /* TCP_SIGNATURE */ 1578 if (to->to_flags & TOF_SACKPERM) 1579 sc->sc_flags |= SCF_SACK; 1580 if (to->to_flags & TOF_MSS) 1581 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1582 if (ltflags & TF_NOOPT) 1583 sc->sc_flags |= SCF_NOOPT; 1584 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1585 sc->sc_flags |= SCF_ECN; 1586 1587 if (V_tcp_syncookies) 1588 sc->sc_iss = syncookie_generate(sch, sc); 1589 #ifdef INET6 1590 if (autoflowlabel) { 1591 if (V_tcp_syncookies) 1592 sc->sc_flowlabel = sc->sc_iss; 1593 else 1594 sc->sc_flowlabel = ip6_randomflowlabel(); 1595 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK; 1596 } 1597 #endif 1598 SCH_UNLOCK(sch); 1599 1600 if (tfo_cookie_valid) { 1601 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie); 1602 /* INP_WUNLOCK(inp) will be performed by the caller */ 1603 rv = 1; 1604 goto tfo_expanded; 1605 } 1606 1607 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1608 /* 1609 * Do a standard 3-way handshake. 1610 */ 1611 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1612 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1613 syncache_free(sc); 1614 else if (sc != &scs) 1615 syncache_insert(sc, sch); /* locks and unlocks sch */ 1616 TCPSTAT_INC(tcps_sndacks); 1617 TCPSTAT_INC(tcps_sndtotal); 1618 } else { 1619 if (sc != &scs) 1620 syncache_free(sc); 1621 TCPSTAT_INC(tcps_sc_dropped); 1622 } 1623 goto donenoprobe; 1624 1625 done: 1626 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1627 donenoprobe: 1628 if (m) { 1629 *lsop = NULL; 1630 m_freem(m); 1631 } 1632 /* 1633 * If tfo_pending is not NULL here, then a TFO SYN that did not 1634 * result in a new socket was processed and the associated pending 1635 * counter has not yet been decremented. All such TFO processing paths 1636 * transit this point. 1637 */ 1638 if (tfo_pending != NULL) 1639 tcp_fastopen_decrement_counter(tfo_pending); 1640 1641 tfo_expanded: 1642 if (cred != NULL) 1643 crfree(cred); 1644 #ifdef MAC 1645 if (sc == &scs) 1646 mac_syncache_destroy(&maclabel); 1647 #endif 1648 return (rv); 1649 } 1650 1651 /* 1652 * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment, 1653 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL. 1654 */ 1655 static int 1656 syncache_respond(struct syncache *sc, struct syncache_head *sch, 1657 const struct mbuf *m0, int flags) 1658 { 1659 struct ip *ip = NULL; 1660 struct mbuf *m; 1661 struct tcphdr *th = NULL; 1662 int optlen, error = 0; /* Make compiler happy */ 1663 u_int16_t hlen, tlen, mssopt; 1664 struct tcpopt to; 1665 #ifdef INET6 1666 struct ip6_hdr *ip6 = NULL; 1667 #endif 1668 hlen = 1669 #ifdef INET6 1670 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1671 #endif 1672 sizeof(struct ip); 1673 tlen = hlen + sizeof(struct tcphdr); 1674 1675 /* Determine MSS we advertize to other end of connection. */ 1676 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss); 1677 1678 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1679 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1680 ("syncache: mbuf too small")); 1681 1682 /* Create the IP+TCP header from scratch. */ 1683 m = m_gethdr(M_NOWAIT, MT_DATA); 1684 if (m == NULL) 1685 return (ENOBUFS); 1686 #ifdef MAC 1687 mac_syncache_create_mbuf(sc->sc_label, m); 1688 #endif 1689 m->m_data += max_linkhdr; 1690 m->m_len = tlen; 1691 m->m_pkthdr.len = tlen; 1692 m->m_pkthdr.rcvif = NULL; 1693 1694 #ifdef INET6 1695 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1696 ip6 = mtod(m, struct ip6_hdr *); 1697 ip6->ip6_vfc = IPV6_VERSION; 1698 ip6->ip6_nxt = IPPROTO_TCP; 1699 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1700 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1701 ip6->ip6_plen = htons(tlen - hlen); 1702 /* ip6_hlim is set after checksum */ 1703 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1704 ip6->ip6_flow |= sc->sc_flowlabel; 1705 1706 th = (struct tcphdr *)(ip6 + 1); 1707 } 1708 #endif 1709 #if defined(INET6) && defined(INET) 1710 else 1711 #endif 1712 #ifdef INET 1713 { 1714 ip = mtod(m, struct ip *); 1715 ip->ip_v = IPVERSION; 1716 ip->ip_hl = sizeof(struct ip) >> 2; 1717 ip->ip_len = htons(tlen); 1718 ip->ip_id = 0; 1719 ip->ip_off = 0; 1720 ip->ip_sum = 0; 1721 ip->ip_p = IPPROTO_TCP; 1722 ip->ip_src = sc->sc_inc.inc_laddr; 1723 ip->ip_dst = sc->sc_inc.inc_faddr; 1724 ip->ip_ttl = sc->sc_ip_ttl; 1725 ip->ip_tos = sc->sc_ip_tos; 1726 1727 /* 1728 * See if we should do MTU discovery. Route lookups are 1729 * expensive, so we will only unset the DF bit if: 1730 * 1731 * 1) path_mtu_discovery is disabled 1732 * 2) the SCF_UNREACH flag has been set 1733 */ 1734 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1735 ip->ip_off |= htons(IP_DF); 1736 1737 th = (struct tcphdr *)(ip + 1); 1738 } 1739 #endif /* INET */ 1740 th->th_sport = sc->sc_inc.inc_lport; 1741 th->th_dport = sc->sc_inc.inc_fport; 1742 1743 if (flags & TH_SYN) 1744 th->th_seq = htonl(sc->sc_iss); 1745 else 1746 th->th_seq = htonl(sc->sc_iss + 1); 1747 th->th_ack = htonl(sc->sc_irs + 1); 1748 th->th_off = sizeof(struct tcphdr) >> 2; 1749 th->th_x2 = 0; 1750 th->th_flags = flags; 1751 th->th_win = htons(sc->sc_wnd); 1752 th->th_urp = 0; 1753 1754 if ((flags & TH_SYN) && (sc->sc_flags & SCF_ECN)) { 1755 th->th_flags |= TH_ECE; 1756 TCPSTAT_INC(tcps_ecn_shs); 1757 } 1758 1759 /* Tack on the TCP options. */ 1760 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1761 to.to_flags = 0; 1762 1763 if (flags & TH_SYN) { 1764 to.to_mss = mssopt; 1765 to.to_flags = TOF_MSS; 1766 if (sc->sc_flags & SCF_WINSCALE) { 1767 to.to_wscale = sc->sc_requested_r_scale; 1768 to.to_flags |= TOF_SCALE; 1769 } 1770 if (sc->sc_flags & SCF_SACK) 1771 to.to_flags |= TOF_SACKPERM; 1772 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1773 if (sc->sc_flags & SCF_SIGNATURE) 1774 to.to_flags |= TOF_SIGNATURE; 1775 #endif 1776 if (sc->sc_tfo_cookie) { 1777 to.to_flags |= TOF_FASTOPEN; 1778 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 1779 to.to_tfo_cookie = sc->sc_tfo_cookie; 1780 /* don't send cookie again when retransmitting response */ 1781 sc->sc_tfo_cookie = NULL; 1782 } 1783 } 1784 if (sc->sc_flags & SCF_TIMESTAMP) { 1785 to.to_tsval = sc->sc_tsoff + tcp_ts_getticks(); 1786 to.to_tsecr = sc->sc_tsreflect; 1787 to.to_flags |= TOF_TS; 1788 } 1789 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1790 1791 /* Adjust headers by option size. */ 1792 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1793 m->m_len += optlen; 1794 m->m_pkthdr.len += optlen; 1795 #ifdef INET6 1796 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1797 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1798 else 1799 #endif 1800 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 1801 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1802 if (sc->sc_flags & SCF_SIGNATURE) { 1803 KASSERT(to.to_flags & TOF_SIGNATURE, 1804 ("tcp_addoptions() didn't set tcp_signature")); 1805 1806 /* NOTE: to.to_signature is inside of mbuf */ 1807 if (!TCPMD5_ENABLED() || 1808 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) { 1809 m_freem(m); 1810 return (EACCES); 1811 } 1812 } 1813 #endif 1814 } else 1815 optlen = 0; 1816 1817 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1818 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1819 /* 1820 * If we have peer's SYN and it has a flowid, then let's assign it to 1821 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid 1822 * to SYN|ACK due to lack of inp here. 1823 */ 1824 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) { 1825 m->m_pkthdr.flowid = m0->m_pkthdr.flowid; 1826 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0)); 1827 } 1828 #ifdef INET6 1829 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1830 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1831 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1832 IPPROTO_TCP, 0); 1833 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1834 #ifdef TCP_OFFLOAD 1835 if (ADDED_BY_TOE(sc)) { 1836 struct toedev *tod = sc->sc_tod; 1837 1838 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1839 1840 return (error); 1841 } 1842 #endif 1843 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th); 1844 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1845 } 1846 #endif 1847 #if defined(INET6) && defined(INET) 1848 else 1849 #endif 1850 #ifdef INET 1851 { 1852 m->m_pkthdr.csum_flags = CSUM_TCP; 1853 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1854 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1855 #ifdef TCP_OFFLOAD 1856 if (ADDED_BY_TOE(sc)) { 1857 struct toedev *tod = sc->sc_tod; 1858 1859 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1860 1861 return (error); 1862 } 1863 #endif 1864 TCP_PROBE5(send, NULL, NULL, ip, NULL, th); 1865 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1866 } 1867 #endif 1868 return (error); 1869 } 1870 1871 /* 1872 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks 1873 * that exceed the capacity of the syncache by avoiding the storage of any 1874 * of the SYNs we receive. Syncookies defend against blind SYN flooding 1875 * attacks where the attacker does not have access to our responses. 1876 * 1877 * Syncookies encode and include all necessary information about the 1878 * connection setup within the SYN|ACK that we send back. That way we 1879 * can avoid keeping any local state until the ACK to our SYN|ACK returns 1880 * (if ever). Normally the syncache and syncookies are running in parallel 1881 * with the latter taking over when the former is exhausted. When matching 1882 * syncache entry is found the syncookie is ignored. 1883 * 1884 * The only reliable information persisting the 3WHS is our initial sequence 1885 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient 1886 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS 1887 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK 1888 * returns and signifies a legitimate connection if it matches the ACK. 1889 * 1890 * The available space of 32 bits to store the hash and to encode the SYN 1891 * option information is very tight and we should have at least 24 bits for 1892 * the MAC to keep the number of guesses by blind spoofing reasonably high. 1893 * 1894 * SYN option information we have to encode to fully restore a connection: 1895 * MSS: is imporant to chose an optimal segment size to avoid IP level 1896 * fragmentation along the path. The common MSS values can be encoded 1897 * in a 3-bit table. Uncommon values are captured by the next lower value 1898 * in the table leading to a slight increase in packetization overhead. 1899 * WSCALE: is necessary to allow large windows to be used for high delay- 1900 * bandwidth product links. Not scaling the window when it was initially 1901 * negotiated is bad for performance as lack of scaling further decreases 1902 * the apparent available send window. We only need to encode the WSCALE 1903 * we received from the remote end. Our end can be recalculated at any 1904 * time. The common WSCALE values can be encoded in a 3-bit table. 1905 * Uncommon values are captured by the next lower value in the table 1906 * making us under-estimate the available window size halving our 1907 * theoretically possible maximum throughput for that connection. 1908 * SACK: Greatly assists in packet loss recovery and requires 1 bit. 1909 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options 1910 * that are included in all segments on a connection. We enable them when 1911 * the ACK has them. 1912 * 1913 * Security of syncookies and attack vectors: 1914 * 1915 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod) 1916 * together with the gloabl secret to make it unique per connection attempt. 1917 * Thus any change of any of those parameters results in a different MAC output 1918 * in an unpredictable way unless a collision is encountered. 24 bits of the 1919 * MAC are embedded into the ISS. 1920 * 1921 * To prevent replay attacks two rotating global secrets are updated with a 1922 * new random value every 15 seconds. The life-time of a syncookie is thus 1923 * 15-30 seconds. 1924 * 1925 * Vector 1: Attacking the secret. This requires finding a weakness in the 1926 * MAC itself or the way it is used here. The attacker can do a chosen plain 1927 * text attack by varying and testing the all parameters under his control. 1928 * The strength depends on the size and randomness of the secret, and the 1929 * cryptographic security of the MAC function. Due to the constant updating 1930 * of the secret the attacker has at most 29.999 seconds to find the secret 1931 * and launch spoofed connections. After that he has to start all over again. 1932 * 1933 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC 1934 * size an average of 4,823 attempts are required for a 50% chance of success 1935 * to spoof a single syncookie (birthday collision paradox). However the 1936 * attacker is blind and doesn't know if one of his attempts succeeded unless 1937 * he has a side channel to interfere success from. A single connection setup 1938 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets. 1939 * This many attempts are required for each one blind spoofed connection. For 1940 * every additional spoofed connection he has to launch another N attempts. 1941 * Thus for a sustained rate 100 spoofed connections per second approximately 1942 * 1,800,000 packets per second would have to be sent. 1943 * 1944 * NB: The MAC function should be fast so that it doesn't become a CPU 1945 * exhaustion attack vector itself. 1946 * 1947 * References: 1948 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations 1949 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996 1950 * http://cr.yp.to/syncookies.html (overview) 1951 * http://cr.yp.to/syncookies/archive (details) 1952 * 1953 * 1954 * Schematic construction of a syncookie enabled Initial Sequence Number: 1955 * 0 1 2 3 1956 * 12345678901234567890123456789012 1957 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP| 1958 * 1959 * x 24 MAC (truncated) 1960 * W 3 Send Window Scale index 1961 * M 3 MSS index 1962 * S 1 SACK permitted 1963 * P 1 Odd/even secret 1964 */ 1965 1966 /* 1967 * Distribution and probability of certain MSS values. Those in between are 1968 * rounded down to the next lower one. 1969 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011] 1970 * .2% .3% 5% 7% 7% 20% 15% 45% 1971 */ 1972 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 }; 1973 1974 /* 1975 * Distribution and probability of certain WSCALE values. We have to map the 1976 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3 1977 * bits based on prevalence of certain values. Where we don't have an exact 1978 * match for are rounded down to the next lower one letting us under-estimate 1979 * the true available window. At the moment this would happen only for the 1980 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer 1981 * and window size). The absence of the WSCALE option (no scaling in either 1982 * direction) is encoded with index zero. 1983 * [WSCALE values histograms, Allman, 2012] 1984 * X 10 10 35 5 6 14 10% by host 1985 * X 11 4 5 5 18 49 3% by connections 1986 */ 1987 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 }; 1988 1989 /* 1990 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed 1991 * and good cryptographic properties. 1992 */ 1993 static uint32_t 1994 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags, 1995 uint8_t *secbits, uintptr_t secmod) 1996 { 1997 SIPHASH_CTX ctx; 1998 uint32_t siphash[2]; 1999 2000 SipHash24_Init(&ctx); 2001 SipHash_SetKey(&ctx, secbits); 2002 switch (inc->inc_flags & INC_ISIPV6) { 2003 #ifdef INET 2004 case 0: 2005 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr)); 2006 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr)); 2007 break; 2008 #endif 2009 #ifdef INET6 2010 case INC_ISIPV6: 2011 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr)); 2012 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr)); 2013 break; 2014 #endif 2015 } 2016 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport)); 2017 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport)); 2018 SipHash_Update(&ctx, &irs, sizeof(irs)); 2019 SipHash_Update(&ctx, &flags, sizeof(flags)); 2020 SipHash_Update(&ctx, &secmod, sizeof(secmod)); 2021 SipHash_Final((u_int8_t *)&siphash, &ctx); 2022 2023 return (siphash[0] ^ siphash[1]); 2024 } 2025 2026 static tcp_seq 2027 syncookie_generate(struct syncache_head *sch, struct syncache *sc) 2028 { 2029 u_int i, secbit, wscale; 2030 uint32_t iss, hash; 2031 uint8_t *secbits; 2032 union syncookie cookie; 2033 2034 SCH_LOCK_ASSERT(sch); 2035 2036 cookie.cookie = 0; 2037 2038 /* Map our computed MSS into the 3-bit index. */ 2039 for (i = nitems(tcp_sc_msstab) - 1; 2040 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0; 2041 i--) 2042 ; 2043 cookie.flags.mss_idx = i; 2044 2045 /* 2046 * Map the send window scale into the 3-bit index but only if 2047 * the wscale option was received. 2048 */ 2049 if (sc->sc_flags & SCF_WINSCALE) { 2050 wscale = sc->sc_requested_s_scale; 2051 for (i = nitems(tcp_sc_wstab) - 1; 2052 tcp_sc_wstab[i] > wscale && i > 0; 2053 i--) 2054 ; 2055 cookie.flags.wscale_idx = i; 2056 } 2057 2058 /* Can we do SACK? */ 2059 if (sc->sc_flags & SCF_SACK) 2060 cookie.flags.sack_ok = 1; 2061 2062 /* Which of the two secrets to use. */ 2063 secbit = sch->sch_sc->secret.oddeven & 0x1; 2064 cookie.flags.odd_even = secbit; 2065 2066 secbits = sch->sch_sc->secret.key[secbit]; 2067 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits, 2068 (uintptr_t)sch); 2069 2070 /* 2071 * Put the flags into the hash and XOR them to get better ISS number 2072 * variance. This doesn't enhance the cryptographic strength and is 2073 * done to prevent the 8 cookie bits from showing up directly on the 2074 * wire. 2075 */ 2076 iss = hash & ~0xff; 2077 iss |= cookie.cookie ^ (hash >> 24); 2078 2079 TCPSTAT_INC(tcps_sc_sendcookie); 2080 return (iss); 2081 } 2082 2083 static struct syncache * 2084 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 2085 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2086 struct socket *lso) 2087 { 2088 uint32_t hash; 2089 uint8_t *secbits; 2090 tcp_seq ack, seq; 2091 int wnd, wscale = 0; 2092 union syncookie cookie; 2093 2094 SCH_LOCK_ASSERT(sch); 2095 2096 /* 2097 * Pull information out of SYN-ACK/ACK and revert sequence number 2098 * advances. 2099 */ 2100 ack = th->th_ack - 1; 2101 seq = th->th_seq - 1; 2102 2103 /* 2104 * Unpack the flags containing enough information to restore the 2105 * connection. 2106 */ 2107 cookie.cookie = (ack & 0xff) ^ (ack >> 24); 2108 2109 /* Which of the two secrets to use. */ 2110 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even]; 2111 2112 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch); 2113 2114 /* The recomputed hash matches the ACK if this was a genuine cookie. */ 2115 if ((ack & ~0xff) != (hash & ~0xff)) 2116 return (NULL); 2117 2118 /* Fill in the syncache values. */ 2119 sc->sc_flags = 0; 2120 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 2121 sc->sc_ipopts = NULL; 2122 2123 sc->sc_irs = seq; 2124 sc->sc_iss = ack; 2125 2126 switch (inc->inc_flags & INC_ISIPV6) { 2127 #ifdef INET 2128 case 0: 2129 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl; 2130 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos; 2131 break; 2132 #endif 2133 #ifdef INET6 2134 case INC_ISIPV6: 2135 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL) 2136 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK; 2137 break; 2138 #endif 2139 } 2140 2141 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx]; 2142 2143 /* We can simply recompute receive window scale we sent earlier. */ 2144 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max) 2145 wscale++; 2146 2147 /* Only use wscale if it was enabled in the orignal SYN. */ 2148 if (cookie.flags.wscale_idx > 0) { 2149 sc->sc_requested_r_scale = wscale; 2150 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx]; 2151 sc->sc_flags |= SCF_WINSCALE; 2152 } 2153 2154 wnd = lso->sol_sbrcv_hiwat; 2155 wnd = imax(wnd, 0); 2156 wnd = imin(wnd, TCP_MAXWIN); 2157 sc->sc_wnd = wnd; 2158 2159 if (cookie.flags.sack_ok) 2160 sc->sc_flags |= SCF_SACK; 2161 2162 if (to->to_flags & TOF_TS) { 2163 sc->sc_flags |= SCF_TIMESTAMP; 2164 sc->sc_tsreflect = to->to_tsval; 2165 sc->sc_tsoff = tcp_new_ts_offset(inc); 2166 } 2167 2168 if (to->to_flags & TOF_SIGNATURE) 2169 sc->sc_flags |= SCF_SIGNATURE; 2170 2171 sc->sc_rxmits = 0; 2172 2173 TCPSTAT_INC(tcps_sc_recvcookie); 2174 return (sc); 2175 } 2176 2177 #ifdef INVARIANTS 2178 static int 2179 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 2180 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2181 struct socket *lso) 2182 { 2183 struct syncache scs, *scx; 2184 char *s; 2185 2186 bzero(&scs, sizeof(scs)); 2187 scx = syncookie_lookup(inc, sch, &scs, th, to, lso); 2188 2189 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL) 2190 return (0); 2191 2192 if (scx != NULL) { 2193 if (sc->sc_peer_mss != scx->sc_peer_mss) 2194 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n", 2195 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss); 2196 2197 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale) 2198 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n", 2199 s, __func__, sc->sc_requested_r_scale, 2200 scx->sc_requested_r_scale); 2201 2202 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale) 2203 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n", 2204 s, __func__, sc->sc_requested_s_scale, 2205 scx->sc_requested_s_scale); 2206 2207 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK)) 2208 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__); 2209 } 2210 2211 if (s != NULL) 2212 free(s, M_TCPLOG); 2213 return (0); 2214 } 2215 #endif /* INVARIANTS */ 2216 2217 static void 2218 syncookie_reseed(void *arg) 2219 { 2220 struct tcp_syncache *sc = arg; 2221 uint8_t *secbits; 2222 int secbit; 2223 2224 /* 2225 * Reseeding the secret doesn't have to be protected by a lock. 2226 * It only must be ensured that the new random values are visible 2227 * to all CPUs in a SMP environment. The atomic with release 2228 * semantics ensures that. 2229 */ 2230 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1; 2231 secbits = sc->secret.key[secbit]; 2232 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0); 2233 atomic_add_rel_int(&sc->secret.oddeven, 1); 2234 2235 /* Reschedule ourself. */ 2236 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz); 2237 } 2238 2239 /* 2240 * Exports the syncache entries to userland so that netstat can display 2241 * them alongside the other sockets. This function is intended to be 2242 * called only from tcp_pcblist. 2243 * 2244 * Due to concurrency on an active system, the number of pcbs exported 2245 * may have no relation to max_pcbs. max_pcbs merely indicates the 2246 * amount of space the caller allocated for this function to use. 2247 */ 2248 int 2249 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 2250 { 2251 struct xtcpcb xt; 2252 struct syncache *sc; 2253 struct syncache_head *sch; 2254 int count, error, i; 2255 2256 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 2257 sch = &V_tcp_syncache.hashbase[i]; 2258 SCH_LOCK(sch); 2259 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 2260 if (count >= max_pcbs) { 2261 SCH_UNLOCK(sch); 2262 goto exit; 2263 } 2264 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 2265 continue; 2266 bzero(&xt, sizeof(xt)); 2267 xt.xt_len = sizeof(xt); 2268 if (sc->sc_inc.inc_flags & INC_ISIPV6) 2269 xt.xt_inp.inp_vflag = INP_IPV6; 2270 else 2271 xt.xt_inp.inp_vflag = INP_IPV4; 2272 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, 2273 sizeof (struct in_conninfo)); 2274 xt.t_state = TCPS_SYN_RECEIVED; 2275 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP; 2276 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket); 2277 xt.xt_inp.xi_socket.so_type = SOCK_STREAM; 2278 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING; 2279 error = SYSCTL_OUT(req, &xt, sizeof xt); 2280 if (error) { 2281 SCH_UNLOCK(sch); 2282 goto exit; 2283 } 2284 count++; 2285 } 2286 SCH_UNLOCK(sch); 2287 } 2288 exit: 2289 *pcbs_exported = count; 2290 return error; 2291 } 2292