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 with default values of 158 * TCPTV_RTOBASE * ( 1 + 159 * tcp_backoff[1] + 160 * tcp_backoff[2] + 161 * tcp_backoff[3]) + 3 * tcp_rexmit_slop, 162 * 1000 ms * (1 + 2 + 4 + 8) + 3 * 200 ms = 15600 ms, 163 * the odds are that the user has given up attempting to connect by then. 164 */ 165 #define SYNCACHE_MAXREXMTS 3 166 167 /* Arbitrary values */ 168 #define TCP_SYNCACHE_HASHSIZE 512 169 #define TCP_SYNCACHE_BUCKETLIMIT 30 170 171 VNET_DEFINE_STATIC(struct tcp_syncache, tcp_syncache); 172 #define V_tcp_syncache VNET(tcp_syncache) 173 174 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, 175 "TCP SYN cache"); 176 177 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN, 178 &VNET_NAME(tcp_syncache.bucket_limit), 0, 179 "Per-bucket hash limit for syncache"); 180 181 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN, 182 &VNET_NAME(tcp_syncache.cache_limit), 0, 183 "Overall entry limit for syncache"); 184 185 SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET, 186 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache"); 187 188 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN, 189 &VNET_NAME(tcp_syncache.hashsize), 0, 190 "Size of TCP syncache hashtable"); 191 192 static int 193 sysctl_net_inet_tcp_syncache_rexmtlimit_check(SYSCTL_HANDLER_ARGS) 194 { 195 int error; 196 u_int new; 197 198 new = V_tcp_syncache.rexmt_limit; 199 error = sysctl_handle_int(oidp, &new, 0, req); 200 if ((error == 0) && (req->newptr != NULL)) { 201 if (new > TCP_MAXRXTSHIFT) 202 error = EINVAL; 203 else 204 V_tcp_syncache.rexmt_limit = new; 205 } 206 return (error); 207 } 208 209 SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, 210 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW, 211 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 212 sysctl_net_inet_tcp_syncache_rexmtlimit_check, "UI", 213 "Limit on SYN/ACK retransmissions"); 214 215 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 216 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 217 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 218 "Send reset on socket allocation failure"); 219 220 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 221 222 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 223 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 224 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 225 226 /* 227 * Requires the syncache entry to be already removed from the bucket list. 228 */ 229 static void 230 syncache_free(struct syncache *sc) 231 { 232 233 if (sc->sc_ipopts) 234 (void) m_free(sc->sc_ipopts); 235 if (sc->sc_cred) 236 crfree(sc->sc_cred); 237 #ifdef MAC 238 mac_syncache_destroy(&sc->sc_label); 239 #endif 240 241 uma_zfree(V_tcp_syncache.zone, sc); 242 } 243 244 void 245 syncache_init(void) 246 { 247 int i; 248 249 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 250 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 251 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 252 V_tcp_syncache.hash_secret = arc4random(); 253 254 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 255 &V_tcp_syncache.hashsize); 256 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 257 &V_tcp_syncache.bucket_limit); 258 if (!powerof2(V_tcp_syncache.hashsize) || 259 V_tcp_syncache.hashsize == 0) { 260 printf("WARNING: syncache hash size is not a power of 2.\n"); 261 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 262 } 263 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 264 265 /* Set limits. */ 266 V_tcp_syncache.cache_limit = 267 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 268 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 269 &V_tcp_syncache.cache_limit); 270 271 /* Allocate the hash table. */ 272 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 273 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 274 275 #ifdef VIMAGE 276 V_tcp_syncache.vnet = curvnet; 277 #endif 278 279 /* Initialize the hash buckets. */ 280 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 281 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 282 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 283 NULL, MTX_DEF); 284 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 285 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 286 V_tcp_syncache.hashbase[i].sch_length = 0; 287 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache; 288 V_tcp_syncache.hashbase[i].sch_last_overflow = 289 -(SYNCOOKIE_LIFETIME + 1); 290 } 291 292 /* Create the syncache entry zone. */ 293 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 294 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 295 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone, 296 V_tcp_syncache.cache_limit); 297 298 /* Start the SYN cookie reseeder callout. */ 299 callout_init(&V_tcp_syncache.secret.reseed, 1); 300 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0); 301 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0); 302 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz, 303 syncookie_reseed, &V_tcp_syncache); 304 } 305 306 #ifdef VIMAGE 307 void 308 syncache_destroy(void) 309 { 310 struct syncache_head *sch; 311 struct syncache *sc, *nsc; 312 int i; 313 314 /* 315 * Stop the re-seed timer before freeing resources. No need to 316 * possibly schedule it another time. 317 */ 318 callout_drain(&V_tcp_syncache.secret.reseed); 319 320 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 321 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 322 323 sch = &V_tcp_syncache.hashbase[i]; 324 callout_drain(&sch->sch_timer); 325 326 SCH_LOCK(sch); 327 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 328 syncache_drop(sc, sch); 329 SCH_UNLOCK(sch); 330 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 331 ("%s: sch->sch_bucket not empty", __func__)); 332 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 333 __func__, sch->sch_length)); 334 mtx_destroy(&sch->sch_mtx); 335 } 336 337 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0, 338 ("%s: cache_count not 0", __func__)); 339 340 /* Free the allocated global resources. */ 341 uma_zdestroy(V_tcp_syncache.zone); 342 free(V_tcp_syncache.hashbase, M_SYNCACHE); 343 } 344 #endif 345 346 /* 347 * Inserts a syncache entry into the specified bucket row. 348 * Locks and unlocks the syncache_head autonomously. 349 */ 350 static void 351 syncache_insert(struct syncache *sc, struct syncache_head *sch) 352 { 353 struct syncache *sc2; 354 355 SCH_LOCK(sch); 356 357 /* 358 * Make sure that we don't overflow the per-bucket limit. 359 * If the bucket is full, toss the oldest element. 360 */ 361 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 362 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 363 ("sch->sch_length incorrect")); 364 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 365 sch->sch_last_overflow = time_uptime; 366 syncache_drop(sc2, sch); 367 TCPSTAT_INC(tcps_sc_bucketoverflow); 368 } 369 370 /* Put it into the bucket. */ 371 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 372 sch->sch_length++; 373 374 #ifdef TCP_OFFLOAD 375 if (ADDED_BY_TOE(sc)) { 376 struct toedev *tod = sc->sc_tod; 377 378 tod->tod_syncache_added(tod, sc->sc_todctx); 379 } 380 #endif 381 382 /* Reinitialize the bucket row's timer. */ 383 if (sch->sch_length == 1) 384 sch->sch_nextc = ticks + INT_MAX; 385 syncache_timeout(sc, sch, 1); 386 387 SCH_UNLOCK(sch); 388 389 TCPSTATES_INC(TCPS_SYN_RECEIVED); 390 TCPSTAT_INC(tcps_sc_added); 391 } 392 393 /* 394 * Remove and free entry from syncache bucket row. 395 * Expects locked syncache head. 396 */ 397 static void 398 syncache_drop(struct syncache *sc, struct syncache_head *sch) 399 { 400 401 SCH_LOCK_ASSERT(sch); 402 403 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 404 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 405 sch->sch_length--; 406 407 #ifdef TCP_OFFLOAD 408 if (ADDED_BY_TOE(sc)) { 409 struct toedev *tod = sc->sc_tod; 410 411 tod->tod_syncache_removed(tod, sc->sc_todctx); 412 } 413 #endif 414 415 syncache_free(sc); 416 } 417 418 /* 419 * Engage/reengage time on bucket row. 420 */ 421 static void 422 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 423 { 424 int rexmt; 425 426 if (sc->sc_rxmits == 0) 427 rexmt = TCPTV_RTOBASE; 428 else 429 TCPT_RANGESET(rexmt, TCPTV_RTOBASE * tcp_backoff[sc->sc_rxmits], 430 tcp_rexmit_min, TCPTV_REXMTMAX); 431 sc->sc_rxttime = ticks + rexmt; 432 sc->sc_rxmits++; 433 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 434 sch->sch_nextc = sc->sc_rxttime; 435 if (docallout) 436 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 437 syncache_timer, (void *)sch); 438 } 439 } 440 441 /* 442 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 443 * If we have retransmitted an entry the maximum number of times, expire it. 444 * One separate timer for each bucket row. 445 */ 446 static void 447 syncache_timer(void *xsch) 448 { 449 struct syncache_head *sch = (struct syncache_head *)xsch; 450 struct syncache *sc, *nsc; 451 int tick = ticks; 452 char *s; 453 454 CURVNET_SET(sch->sch_sc->vnet); 455 456 /* NB: syncache_head has already been locked by the callout. */ 457 SCH_LOCK_ASSERT(sch); 458 459 /* 460 * In the following cycle we may remove some entries and/or 461 * advance some timeouts, so re-initialize the bucket timer. 462 */ 463 sch->sch_nextc = tick + INT_MAX; 464 465 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 466 /* 467 * We do not check if the listen socket still exists 468 * and accept the case where the listen socket may be 469 * gone by the time we resend the SYN/ACK. We do 470 * not expect this to happens often. If it does, 471 * then the RST will be sent by the time the remote 472 * host does the SYN/ACK->ACK. 473 */ 474 if (TSTMP_GT(sc->sc_rxttime, tick)) { 475 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 476 sch->sch_nextc = sc->sc_rxttime; 477 continue; 478 } 479 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 480 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 481 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 482 "giving up and removing syncache entry\n", 483 s, __func__); 484 free(s, M_TCPLOG); 485 } 486 syncache_drop(sc, sch); 487 TCPSTAT_INC(tcps_sc_stale); 488 continue; 489 } 490 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 491 log(LOG_DEBUG, "%s; %s: Response timeout, " 492 "retransmitting (%u) SYN|ACK\n", 493 s, __func__, sc->sc_rxmits); 494 free(s, M_TCPLOG); 495 } 496 497 syncache_respond(sc, sch, NULL, TH_SYN|TH_ACK); 498 TCPSTAT_INC(tcps_sc_retransmitted); 499 syncache_timeout(sc, sch, 0); 500 } 501 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 502 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 503 syncache_timer, (void *)(sch)); 504 CURVNET_RESTORE(); 505 } 506 507 /* 508 * Find an entry in the syncache. 509 * Returns always with locked syncache_head plus a matching entry or NULL. 510 */ 511 static struct syncache * 512 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 513 { 514 struct syncache *sc; 515 struct syncache_head *sch; 516 uint32_t hash; 517 518 /* 519 * The hash is built on foreign port + local port + foreign address. 520 * We rely on the fact that struct in_conninfo starts with 16 bits 521 * of foreign port, then 16 bits of local port then followed by 128 522 * bits of foreign address. In case of IPv4 address, the first 3 523 * 32-bit words of the address always are zeroes. 524 */ 525 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5, 526 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask; 527 528 sch = &V_tcp_syncache.hashbase[hash]; 529 *schp = sch; 530 SCH_LOCK(sch); 531 532 /* Circle through bucket row to find matching entry. */ 533 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 534 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie, 535 sizeof(struct in_endpoints)) == 0) 536 break; 537 538 return (sc); /* Always returns with locked sch. */ 539 } 540 541 /* 542 * This function is called when we get a RST for a 543 * non-existent connection, so that we can see if the 544 * connection is in the syn cache. If it is, zap it. 545 * If required send a challenge ACK. 546 */ 547 void 548 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m) 549 { 550 struct syncache *sc; 551 struct syncache_head *sch; 552 char *s = NULL; 553 554 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 555 SCH_LOCK_ASSERT(sch); 556 557 /* 558 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 559 * See RFC 793 page 65, section SEGMENT ARRIVES. 560 */ 561 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 562 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 563 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 564 "FIN flag set, segment ignored\n", s, __func__); 565 TCPSTAT_INC(tcps_badrst); 566 goto done; 567 } 568 569 /* 570 * No corresponding connection was found in syncache. 571 * If syncookies are enabled and possibly exclusively 572 * used, or we are under memory pressure, a valid RST 573 * may not find a syncache entry. In that case we're 574 * done and no SYN|ACK retransmissions will happen. 575 * Otherwise the RST was misdirected or spoofed. 576 */ 577 if (sc == NULL) { 578 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 579 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 580 "syncache entry (possibly syncookie only), " 581 "segment ignored\n", s, __func__); 582 TCPSTAT_INC(tcps_badrst); 583 goto done; 584 } 585 586 /* 587 * If the RST bit is set, check the sequence number to see 588 * if this is a valid reset segment. 589 * 590 * RFC 793 page 37: 591 * In all states except SYN-SENT, all reset (RST) segments 592 * are validated by checking their SEQ-fields. A reset is 593 * valid if its sequence number is in the window. 594 * 595 * RFC 793 page 69: 596 * There are four cases for the acceptability test for an incoming 597 * segment: 598 * 599 * Segment Receive Test 600 * Length Window 601 * ------- ------- ------------------------------------------- 602 * 0 0 SEG.SEQ = RCV.NXT 603 * 0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND 604 * >0 0 not acceptable 605 * >0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND 606 * or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND 607 * 608 * Note that when receiving a SYN segment in the LISTEN state, 609 * IRS is set to SEG.SEQ and RCV.NXT is set to SEG.SEQ+1, as 610 * described in RFC 793, page 66. 611 */ 612 if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) && 613 SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) || 614 (sc->sc_wnd == 0 && th->th_seq == sc->sc_irs + 1)) { 615 if (V_tcp_insecure_rst || 616 th->th_seq == sc->sc_irs + 1) { 617 syncache_drop(sc, sch); 618 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 619 log(LOG_DEBUG, 620 "%s; %s: Our SYN|ACK was rejected, " 621 "connection attempt aborted by remote " 622 "endpoint\n", 623 s, __func__); 624 TCPSTAT_INC(tcps_sc_reset); 625 } else { 626 TCPSTAT_INC(tcps_badrst); 627 /* Send challenge ACK. */ 628 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 629 log(LOG_DEBUG, "%s; %s: RST with invalid " 630 " SEQ %u != NXT %u (+WND %u), " 631 "sending challenge ACK\n", 632 s, __func__, 633 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 634 syncache_respond(sc, sch, m, TH_ACK); 635 } 636 } else { 637 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 638 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 639 "NXT %u (+WND %u), segment ignored\n", 640 s, __func__, 641 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 642 TCPSTAT_INC(tcps_badrst); 643 } 644 645 done: 646 if (s != NULL) 647 free(s, M_TCPLOG); 648 SCH_UNLOCK(sch); 649 } 650 651 void 652 syncache_badack(struct in_conninfo *inc) 653 { 654 struct syncache *sc; 655 struct syncache_head *sch; 656 657 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 658 SCH_LOCK_ASSERT(sch); 659 if (sc != NULL) { 660 syncache_drop(sc, sch); 661 TCPSTAT_INC(tcps_sc_badack); 662 } 663 SCH_UNLOCK(sch); 664 } 665 666 void 667 syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq) 668 { 669 struct syncache *sc; 670 struct syncache_head *sch; 671 672 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 673 SCH_LOCK_ASSERT(sch); 674 if (sc == NULL) 675 goto done; 676 677 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 678 if (ntohl(th_seq) != sc->sc_iss) 679 goto done; 680 681 /* 682 * If we've rertransmitted 3 times and this is our second error, 683 * we remove the entry. Otherwise, we allow it to continue on. 684 * This prevents us from incorrectly nuking an entry during a 685 * spurious network outage. 686 * 687 * See tcp_notify(). 688 */ 689 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 690 sc->sc_flags |= SCF_UNREACH; 691 goto done; 692 } 693 syncache_drop(sc, sch); 694 TCPSTAT_INC(tcps_sc_unreach); 695 done: 696 SCH_UNLOCK(sch); 697 } 698 699 /* 700 * Build a new TCP socket structure from a syncache entry. 701 * 702 * On success return the newly created socket with its underlying inp locked. 703 */ 704 static struct socket * 705 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 706 { 707 struct tcp_function_block *blk; 708 struct inpcb *inp = NULL; 709 struct socket *so; 710 struct tcpcb *tp; 711 int error; 712 char *s; 713 714 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 715 716 /* 717 * Ok, create the full blown connection, and set things up 718 * as they would have been set up if we had created the 719 * connection when the SYN arrived. If we can't create 720 * the connection, abort it. 721 */ 722 so = sonewconn(lso, 0); 723 if (so == NULL) { 724 /* 725 * Drop the connection; we will either send a RST or 726 * have the peer retransmit its SYN again after its 727 * RTO and try again. 728 */ 729 TCPSTAT_INC(tcps_listendrop); 730 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 731 log(LOG_DEBUG, "%s; %s: Socket create failed " 732 "due to limits or memory shortage\n", 733 s, __func__); 734 free(s, M_TCPLOG); 735 } 736 goto abort2; 737 } 738 #ifdef MAC 739 mac_socketpeer_set_from_mbuf(m, so); 740 #endif 741 742 inp = sotoinpcb(so); 743 inp->inp_inc.inc_fibnum = so->so_fibnum; 744 INP_WLOCK(inp); 745 /* 746 * Exclusive pcbinfo lock is not required in syncache socket case even 747 * if two inpcb locks can be acquired simultaneously: 748 * - the inpcb in LISTEN state, 749 * - the newly created inp. 750 * 751 * In this case, an inp cannot be at same time in LISTEN state and 752 * just created by an accept() call. 753 */ 754 INP_HASH_WLOCK(&V_tcbinfo); 755 756 /* Insert new socket into PCB hash list. */ 757 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 758 #ifdef INET6 759 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 760 inp->inp_vflag &= ~INP_IPV4; 761 inp->inp_vflag |= INP_IPV6; 762 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 763 } else { 764 inp->inp_vflag &= ~INP_IPV6; 765 inp->inp_vflag |= INP_IPV4; 766 #endif 767 inp->inp_laddr = sc->sc_inc.inc_laddr; 768 #ifdef INET6 769 } 770 #endif 771 772 /* 773 * If there's an mbuf and it has a flowid, then let's initialise the 774 * inp with that particular flowid. 775 */ 776 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) { 777 inp->inp_flowid = m->m_pkthdr.flowid; 778 inp->inp_flowtype = M_HASHTYPE_GET(m); 779 } 780 781 /* 782 * Install in the reservation hash table for now, but don't yet 783 * install a connection group since the full 4-tuple isn't yet 784 * configured. 785 */ 786 inp->inp_lport = sc->sc_inc.inc_lport; 787 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 788 /* 789 * Undo the assignments above if we failed to 790 * put the PCB on the hash lists. 791 */ 792 #ifdef INET6 793 if (sc->sc_inc.inc_flags & INC_ISIPV6) 794 inp->in6p_laddr = in6addr_any; 795 else 796 #endif 797 inp->inp_laddr.s_addr = INADDR_ANY; 798 inp->inp_lport = 0; 799 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 800 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 801 "with error %i\n", 802 s, __func__, error); 803 free(s, M_TCPLOG); 804 } 805 INP_HASH_WUNLOCK(&V_tcbinfo); 806 goto abort; 807 } 808 #ifdef INET6 809 if (inp->inp_vflag & INP_IPV6PROTO) { 810 struct inpcb *oinp = sotoinpcb(lso); 811 812 /* 813 * Inherit socket options from the listening socket. 814 * Note that in6p_inputopts are not (and should not be) 815 * copied, since it stores previously received options and is 816 * used to detect if each new option is different than the 817 * previous one and hence should be passed to a user. 818 * If we copied in6p_inputopts, a user would not be able to 819 * receive options just after calling the accept system call. 820 */ 821 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 822 if (oinp->in6p_outputopts) 823 inp->in6p_outputopts = 824 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 825 } 826 827 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 828 struct in6_addr laddr6; 829 struct sockaddr_in6 sin6; 830 831 sin6.sin6_family = AF_INET6; 832 sin6.sin6_len = sizeof(sin6); 833 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 834 sin6.sin6_port = sc->sc_inc.inc_fport; 835 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 836 laddr6 = inp->in6p_laddr; 837 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 838 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 839 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 840 thread0.td_ucred, m)) != 0) { 841 inp->in6p_laddr = laddr6; 842 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 843 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 844 "with error %i\n", 845 s, __func__, error); 846 free(s, M_TCPLOG); 847 } 848 INP_HASH_WUNLOCK(&V_tcbinfo); 849 goto abort; 850 } 851 /* Override flowlabel from in6_pcbconnect. */ 852 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 853 inp->inp_flow |= sc->sc_flowlabel; 854 } 855 #endif /* INET6 */ 856 #if defined(INET) && defined(INET6) 857 else 858 #endif 859 #ifdef INET 860 { 861 struct in_addr laddr; 862 struct sockaddr_in sin; 863 864 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 865 866 if (inp->inp_options == NULL) { 867 inp->inp_options = sc->sc_ipopts; 868 sc->sc_ipopts = NULL; 869 } 870 871 sin.sin_family = AF_INET; 872 sin.sin_len = sizeof(sin); 873 sin.sin_addr = sc->sc_inc.inc_faddr; 874 sin.sin_port = sc->sc_inc.inc_fport; 875 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 876 laddr = inp->inp_laddr; 877 if (inp->inp_laddr.s_addr == INADDR_ANY) 878 inp->inp_laddr = sc->sc_inc.inc_laddr; 879 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 880 thread0.td_ucred, m)) != 0) { 881 inp->inp_laddr = laddr; 882 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 883 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 884 "with error %i\n", 885 s, __func__, error); 886 free(s, M_TCPLOG); 887 } 888 INP_HASH_WUNLOCK(&V_tcbinfo); 889 goto abort; 890 } 891 } 892 #endif /* INET */ 893 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 894 /* Copy old policy into new socket's. */ 895 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0) 896 printf("syncache_socket: could not copy policy\n"); 897 #endif 898 INP_HASH_WUNLOCK(&V_tcbinfo); 899 tp = intotcpcb(inp); 900 tcp_state_change(tp, TCPS_SYN_RECEIVED); 901 tp->iss = sc->sc_iss; 902 tp->irs = sc->sc_irs; 903 tcp_rcvseqinit(tp); 904 tcp_sendseqinit(tp); 905 blk = sototcpcb(lso)->t_fb; 906 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) { 907 /* 908 * Our parents t_fb was not the default, 909 * we need to release our ref on tp->t_fb and 910 * pickup one on the new entry. 911 */ 912 struct tcp_function_block *rblk; 913 914 rblk = find_and_ref_tcp_fb(blk); 915 KASSERT(rblk != NULL, 916 ("cannot find blk %p out of syncache?", blk)); 917 if (tp->t_fb->tfb_tcp_fb_fini) 918 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0); 919 refcount_release(&tp->t_fb->tfb_refcnt); 920 tp->t_fb = rblk; 921 /* 922 * XXXrrs this is quite dangerous, it is possible 923 * for the new function to fail to init. We also 924 * are not asking if the handoff_is_ok though at 925 * the very start thats probalbly ok. 926 */ 927 if (tp->t_fb->tfb_tcp_fb_init) { 928 (*tp->t_fb->tfb_tcp_fb_init)(tp); 929 } 930 } 931 tp->snd_wl1 = sc->sc_irs; 932 tp->snd_max = tp->iss + 1; 933 tp->snd_nxt = tp->iss + 1; 934 tp->rcv_up = sc->sc_irs + 1; 935 tp->rcv_wnd = sc->sc_wnd; 936 tp->rcv_adv += tp->rcv_wnd; 937 tp->last_ack_sent = tp->rcv_nxt; 938 939 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 940 if (sc->sc_flags & SCF_NOOPT) 941 tp->t_flags |= TF_NOOPT; 942 else { 943 if (sc->sc_flags & SCF_WINSCALE) { 944 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 945 tp->snd_scale = sc->sc_requested_s_scale; 946 tp->request_r_scale = sc->sc_requested_r_scale; 947 } 948 if (sc->sc_flags & SCF_TIMESTAMP) { 949 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 950 tp->ts_recent = sc->sc_tsreflect; 951 tp->ts_recent_age = tcp_ts_getticks(); 952 tp->ts_offset = sc->sc_tsoff; 953 } 954 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 955 if (sc->sc_flags & SCF_SIGNATURE) 956 tp->t_flags |= TF_SIGNATURE; 957 #endif 958 if (sc->sc_flags & SCF_SACK) 959 tp->t_flags |= TF_SACK_PERMIT; 960 } 961 962 if (sc->sc_flags & SCF_ECN) 963 tp->t_flags |= TF_ECN_PERMIT; 964 965 /* 966 * Set up MSS and get cached values from tcp_hostcache. 967 * This might overwrite some of the defaults we just set. 968 */ 969 tcp_mss(tp, sc->sc_peer_mss); 970 971 /* 972 * If the SYN,ACK was retransmitted, indicate that CWND to be 973 * limited to one segment in cc_conn_init(). 974 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 975 */ 976 if (sc->sc_rxmits > 1) 977 tp->snd_cwnd = 1; 978 979 #ifdef TCP_OFFLOAD 980 /* 981 * Allow a TOE driver to install its hooks. Note that we hold the 982 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a 983 * new connection before the TOE driver has done its thing. 984 */ 985 if (ADDED_BY_TOE(sc)) { 986 struct toedev *tod = sc->sc_tod; 987 988 tod->tod_offload_socket(tod, sc->sc_todctx, so); 989 } 990 #endif 991 /* 992 * Copy and activate timers. 993 */ 994 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 995 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 996 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 997 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 998 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 999 1000 TCPSTAT_INC(tcps_accepts); 1001 return (so); 1002 1003 abort: 1004 INP_WUNLOCK(inp); 1005 abort2: 1006 if (so != NULL) 1007 soabort(so); 1008 return (NULL); 1009 } 1010 1011 /* 1012 * This function gets called when we receive an ACK for a 1013 * socket in the LISTEN state. We look up the connection 1014 * in the syncache, and if its there, we pull it out of 1015 * the cache and turn it into a full-blown connection in 1016 * the SYN-RECEIVED state. 1017 * 1018 * On syncache_socket() success the newly created socket 1019 * has its underlying inp locked. 1020 */ 1021 int 1022 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1023 struct socket **lsop, struct mbuf *m) 1024 { 1025 struct syncache *sc; 1026 struct syncache_head *sch; 1027 struct syncache scs; 1028 char *s; 1029 1030 /* 1031 * Global TCP locks are held because we manipulate the PCB lists 1032 * and create a new socket. 1033 */ 1034 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1035 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 1036 ("%s: can handle only ACK", __func__)); 1037 1038 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 1039 SCH_LOCK_ASSERT(sch); 1040 1041 #ifdef INVARIANTS 1042 /* 1043 * Test code for syncookies comparing the syncache stored 1044 * values with the reconstructed values from the cookie. 1045 */ 1046 if (sc != NULL) 1047 syncookie_cmp(inc, sch, sc, th, to, *lsop); 1048 #endif 1049 1050 if (sc == NULL) { 1051 /* 1052 * There is no syncache entry, so see if this ACK is 1053 * a returning syncookie. To do this, first: 1054 * A. Check if syncookies are used in case of syncache 1055 * overflows 1056 * B. See if this socket has had a syncache entry dropped in 1057 * the recent past. We don't want to accept a bogus 1058 * syncookie if we've never received a SYN or accept it 1059 * twice. 1060 * C. check that the syncookie is valid. If it is, then 1061 * cobble up a fake syncache entry, and return. 1062 */ 1063 if (!V_tcp_syncookies) { 1064 SCH_UNLOCK(sch); 1065 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1066 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1067 "segment rejected (syncookies disabled)\n", 1068 s, __func__); 1069 goto failed; 1070 } 1071 if (!V_tcp_syncookiesonly && 1072 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) { 1073 SCH_UNLOCK(sch); 1074 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1075 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1076 "segment rejected (no syncache entry)\n", 1077 s, __func__); 1078 goto failed; 1079 } 1080 bzero(&scs, sizeof(scs)); 1081 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop); 1082 SCH_UNLOCK(sch); 1083 if (sc == NULL) { 1084 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1085 log(LOG_DEBUG, "%s; %s: Segment failed " 1086 "SYNCOOKIE authentication, segment rejected " 1087 "(probably spoofed)\n", s, __func__); 1088 goto failed; 1089 } 1090 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1091 /* If received ACK has MD5 signature, check it. */ 1092 if ((to->to_flags & TOF_SIGNATURE) != 0 && 1093 (!TCPMD5_ENABLED() || 1094 TCPMD5_INPUT(m, th, to->to_signature) != 0)) { 1095 /* Drop the ACK. */ 1096 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1097 log(LOG_DEBUG, "%s; %s: Segment rejected, " 1098 "MD5 signature doesn't match.\n", 1099 s, __func__); 1100 free(s, M_TCPLOG); 1101 } 1102 TCPSTAT_INC(tcps_sig_err_sigopt); 1103 return (-1); /* Do not send RST */ 1104 } 1105 #endif /* TCP_SIGNATURE */ 1106 } else { 1107 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1108 /* 1109 * If listening socket requested TCP digests, check that 1110 * received ACK has signature and it is correct. 1111 * If not, drop the ACK and leave sc entry in th cache, 1112 * because SYN was received with correct signature. 1113 */ 1114 if (sc->sc_flags & SCF_SIGNATURE) { 1115 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1116 /* No signature */ 1117 TCPSTAT_INC(tcps_sig_err_nosigopt); 1118 SCH_UNLOCK(sch); 1119 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1120 log(LOG_DEBUG, "%s; %s: Segment " 1121 "rejected, MD5 signature wasn't " 1122 "provided.\n", s, __func__); 1123 free(s, M_TCPLOG); 1124 } 1125 return (-1); /* Do not send RST */ 1126 } 1127 if (!TCPMD5_ENABLED() || 1128 TCPMD5_INPUT(m, th, to->to_signature) != 0) { 1129 /* Doesn't match or no SA */ 1130 SCH_UNLOCK(sch); 1131 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1132 log(LOG_DEBUG, "%s; %s: Segment " 1133 "rejected, MD5 signature doesn't " 1134 "match.\n", s, __func__); 1135 free(s, M_TCPLOG); 1136 } 1137 return (-1); /* Do not send RST */ 1138 } 1139 } 1140 #endif /* TCP_SIGNATURE */ 1141 /* 1142 * Pull out the entry to unlock the bucket row. 1143 * 1144 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not 1145 * tcp_state_change(). The tcpcb is not existent at this 1146 * moment. A new one will be allocated via syncache_socket-> 1147 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then 1148 * syncache_socket() will change it to TCPS_SYN_RECEIVED. 1149 */ 1150 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 1151 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 1152 sch->sch_length--; 1153 #ifdef TCP_OFFLOAD 1154 if (ADDED_BY_TOE(sc)) { 1155 struct toedev *tod = sc->sc_tod; 1156 1157 tod->tod_syncache_removed(tod, sc->sc_todctx); 1158 } 1159 #endif 1160 SCH_UNLOCK(sch); 1161 } 1162 1163 /* 1164 * Segment validation: 1165 * ACK must match our initial sequence number + 1 (the SYN|ACK). 1166 */ 1167 if (th->th_ack != sc->sc_iss + 1) { 1168 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1169 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 1170 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 1171 goto failed; 1172 } 1173 1174 /* 1175 * The SEQ must fall in the window starting at the received 1176 * initial receive sequence number + 1 (the SYN). 1177 */ 1178 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 1179 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 1180 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1181 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 1182 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 1183 goto failed; 1184 } 1185 1186 /* 1187 * If timestamps were not negotiated during SYN/ACK they 1188 * must not appear on any segment during this session. 1189 */ 1190 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 1191 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1192 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1193 "segment rejected\n", s, __func__); 1194 goto failed; 1195 } 1196 1197 /* 1198 * If timestamps were negotiated during SYN/ACK they should 1199 * appear on every segment during this session. 1200 * XXXAO: This is only informal as there have been unverified 1201 * reports of non-compliants stacks. 1202 */ 1203 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) { 1204 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1205 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1206 "no action\n", s, __func__); 1207 free(s, M_TCPLOG); 1208 s = NULL; 1209 } 1210 } 1211 1212 *lsop = syncache_socket(sc, *lsop, m); 1213 1214 if (*lsop == NULL) 1215 TCPSTAT_INC(tcps_sc_aborted); 1216 else 1217 TCPSTAT_INC(tcps_sc_completed); 1218 1219 /* how do we find the inp for the new socket? */ 1220 if (sc != &scs) 1221 syncache_free(sc); 1222 return (1); 1223 failed: 1224 if (sc != NULL && sc != &scs) 1225 syncache_free(sc); 1226 if (s != NULL) 1227 free(s, M_TCPLOG); 1228 *lsop = NULL; 1229 return (0); 1230 } 1231 1232 static void 1233 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m, 1234 uint64_t response_cookie) 1235 { 1236 struct inpcb *inp; 1237 struct tcpcb *tp; 1238 unsigned int *pending_counter; 1239 1240 /* 1241 * Global TCP locks are held because we manipulate the PCB lists 1242 * and create a new socket. 1243 */ 1244 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1245 1246 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending; 1247 *lsop = syncache_socket(sc, *lsop, m); 1248 if (*lsop == NULL) { 1249 TCPSTAT_INC(tcps_sc_aborted); 1250 atomic_subtract_int(pending_counter, 1); 1251 } else { 1252 soisconnected(*lsop); 1253 inp = sotoinpcb(*lsop); 1254 tp = intotcpcb(inp); 1255 tp->t_flags |= TF_FASTOPEN; 1256 tp->t_tfo_cookie.server = response_cookie; 1257 tp->snd_max = tp->iss; 1258 tp->snd_nxt = tp->iss; 1259 tp->t_tfo_pending = pending_counter; 1260 TCPSTAT_INC(tcps_sc_completed); 1261 } 1262 } 1263 1264 /* 1265 * Given a LISTEN socket and an inbound SYN request, add 1266 * this to the syn cache, and send back a segment: 1267 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1268 * to the source. 1269 * 1270 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1271 * Doing so would require that we hold onto the data and deliver it 1272 * to the application. However, if we are the target of a SYN-flood 1273 * DoS attack, an attacker could send data which would eventually 1274 * consume all available buffer space if it were ACKed. By not ACKing 1275 * the data, we avoid this DoS scenario. 1276 * 1277 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO) 1278 * cookie is processed and a new socket is created. In this case, any data 1279 * accompanying the SYN will be queued to the socket by tcp_input() and will 1280 * be ACKed either when the application sends response data or the delayed 1281 * ACK timer expires, whichever comes first. 1282 */ 1283 int 1284 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1285 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1286 void *todctx) 1287 { 1288 struct tcpcb *tp; 1289 struct socket *so; 1290 struct syncache *sc = NULL; 1291 struct syncache_head *sch; 1292 struct mbuf *ipopts = NULL; 1293 u_int ltflags; 1294 int win, ip_ttl, ip_tos; 1295 char *s; 1296 int rv = 0; 1297 #ifdef INET6 1298 int autoflowlabel = 0; 1299 #endif 1300 #ifdef MAC 1301 struct label *maclabel; 1302 #endif 1303 struct syncache scs; 1304 struct ucred *cred; 1305 uint64_t tfo_response_cookie; 1306 unsigned int *tfo_pending = NULL; 1307 int tfo_cookie_valid = 0; 1308 int tfo_response_cookie_valid = 0; 1309 1310 INP_WLOCK_ASSERT(inp); /* listen socket */ 1311 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1312 ("%s: unexpected tcp flags", __func__)); 1313 1314 /* 1315 * Combine all so/tp operations very early to drop the INP lock as 1316 * soon as possible. 1317 */ 1318 so = *lsop; 1319 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so)); 1320 tp = sototcpcb(so); 1321 cred = crhold(so->so_cred); 1322 1323 #ifdef INET6 1324 if ((inc->inc_flags & INC_ISIPV6) && 1325 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1326 autoflowlabel = 1; 1327 #endif 1328 ip_ttl = inp->inp_ip_ttl; 1329 ip_tos = inp->inp_ip_tos; 1330 win = so->sol_sbrcv_hiwat; 1331 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1332 1333 if (V_tcp_fastopen_server_enable && IS_FASTOPEN(tp->t_flags) && 1334 (tp->t_tfo_pending != NULL) && 1335 (to->to_flags & TOF_FASTOPEN)) { 1336 /* 1337 * Limit the number of pending TFO connections to 1338 * approximately half of the queue limit. This prevents TFO 1339 * SYN floods from starving the service by filling the 1340 * listen queue with bogus TFO connections. 1341 */ 1342 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <= 1343 (so->sol_qlimit / 2)) { 1344 int result; 1345 1346 result = tcp_fastopen_check_cookie(inc, 1347 to->to_tfo_cookie, to->to_tfo_len, 1348 &tfo_response_cookie); 1349 tfo_cookie_valid = (result > 0); 1350 tfo_response_cookie_valid = (result >= 0); 1351 } 1352 1353 /* 1354 * Remember the TFO pending counter as it will have to be 1355 * decremented below if we don't make it to syncache_tfo_expand(). 1356 */ 1357 tfo_pending = tp->t_tfo_pending; 1358 } 1359 1360 /* By the time we drop the lock these should no longer be used. */ 1361 so = NULL; 1362 tp = NULL; 1363 1364 #ifdef MAC 1365 if (mac_syncache_init(&maclabel) != 0) { 1366 INP_WUNLOCK(inp); 1367 goto done; 1368 } else 1369 mac_syncache_create(maclabel, inp); 1370 #endif 1371 if (!tfo_cookie_valid) 1372 INP_WUNLOCK(inp); 1373 1374 /* 1375 * Remember the IP options, if any. 1376 */ 1377 #ifdef INET6 1378 if (!(inc->inc_flags & INC_ISIPV6)) 1379 #endif 1380 #ifdef INET 1381 ipopts = (m) ? ip_srcroute(m) : NULL; 1382 #else 1383 ipopts = NULL; 1384 #endif 1385 1386 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1387 /* 1388 * If listening socket requested TCP digests, check that received 1389 * SYN has signature and it is correct. If signature doesn't match 1390 * or TCP_SIGNATURE support isn't enabled, drop the packet. 1391 */ 1392 if (ltflags & TF_SIGNATURE) { 1393 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1394 TCPSTAT_INC(tcps_sig_err_nosigopt); 1395 goto done; 1396 } 1397 if (!TCPMD5_ENABLED() || 1398 TCPMD5_INPUT(m, th, to->to_signature) != 0) 1399 goto done; 1400 } 1401 #endif /* TCP_SIGNATURE */ 1402 /* 1403 * See if we already have an entry for this connection. 1404 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1405 * 1406 * XXX: should the syncache be re-initialized with the contents 1407 * of the new SYN here (which may have different options?) 1408 * 1409 * XXX: We do not check the sequence number to see if this is a 1410 * real retransmit or a new connection attempt. The question is 1411 * how to handle such a case; either ignore it as spoofed, or 1412 * drop the current entry and create a new one? 1413 */ 1414 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1415 SCH_LOCK_ASSERT(sch); 1416 if (sc != NULL) { 1417 if (tfo_cookie_valid) 1418 INP_WUNLOCK(inp); 1419 TCPSTAT_INC(tcps_sc_dupsyn); 1420 if (ipopts) { 1421 /* 1422 * If we were remembering a previous source route, 1423 * forget it and use the new one we've been given. 1424 */ 1425 if (sc->sc_ipopts) 1426 (void) m_free(sc->sc_ipopts); 1427 sc->sc_ipopts = ipopts; 1428 } 1429 /* 1430 * Update timestamp if present. 1431 */ 1432 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1433 sc->sc_tsreflect = to->to_tsval; 1434 else 1435 sc->sc_flags &= ~SCF_TIMESTAMP; 1436 #ifdef MAC 1437 /* 1438 * Since we have already unconditionally allocated label 1439 * storage, free it up. The syncache entry will already 1440 * have an initialized label we can use. 1441 */ 1442 mac_syncache_destroy(&maclabel); 1443 #endif 1444 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1445 /* Retransmit SYN|ACK and reset retransmit count. */ 1446 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1447 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1448 "resetting timer and retransmitting SYN|ACK\n", 1449 s, __func__); 1450 free(s, M_TCPLOG); 1451 } 1452 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1453 sc->sc_rxmits = 0; 1454 syncache_timeout(sc, sch, 1); 1455 TCPSTAT_INC(tcps_sndacks); 1456 TCPSTAT_INC(tcps_sndtotal); 1457 } 1458 SCH_UNLOCK(sch); 1459 goto donenoprobe; 1460 } 1461 1462 if (tfo_cookie_valid) { 1463 bzero(&scs, sizeof(scs)); 1464 sc = &scs; 1465 goto skip_alloc; 1466 } 1467 1468 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1469 if (sc == NULL) { 1470 /* 1471 * The zone allocator couldn't provide more entries. 1472 * Treat this as if the cache was full; drop the oldest 1473 * entry and insert the new one. 1474 */ 1475 TCPSTAT_INC(tcps_sc_zonefail); 1476 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) { 1477 sch->sch_last_overflow = time_uptime; 1478 syncache_drop(sc, sch); 1479 } 1480 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1481 if (sc == NULL) { 1482 if (V_tcp_syncookies) { 1483 bzero(&scs, sizeof(scs)); 1484 sc = &scs; 1485 } else { 1486 SCH_UNLOCK(sch); 1487 if (ipopts) 1488 (void) m_free(ipopts); 1489 goto done; 1490 } 1491 } 1492 } 1493 1494 skip_alloc: 1495 if (!tfo_cookie_valid && tfo_response_cookie_valid) 1496 sc->sc_tfo_cookie = &tfo_response_cookie; 1497 1498 /* 1499 * Fill in the syncache values. 1500 */ 1501 #ifdef MAC 1502 sc->sc_label = maclabel; 1503 #endif 1504 sc->sc_cred = cred; 1505 cred = NULL; 1506 sc->sc_ipopts = ipopts; 1507 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1508 #ifdef INET6 1509 if (!(inc->inc_flags & INC_ISIPV6)) 1510 #endif 1511 { 1512 sc->sc_ip_tos = ip_tos; 1513 sc->sc_ip_ttl = ip_ttl; 1514 } 1515 #ifdef TCP_OFFLOAD 1516 sc->sc_tod = tod; 1517 sc->sc_todctx = todctx; 1518 #endif 1519 sc->sc_irs = th->th_seq; 1520 sc->sc_iss = arc4random(); 1521 sc->sc_flags = 0; 1522 sc->sc_flowlabel = 0; 1523 1524 /* 1525 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1526 * win was derived from socket earlier in the function. 1527 */ 1528 win = imax(win, 0); 1529 win = imin(win, TCP_MAXWIN); 1530 sc->sc_wnd = win; 1531 1532 if (V_tcp_do_rfc1323) { 1533 /* 1534 * A timestamp received in a SYN makes 1535 * it ok to send timestamp requests and replies. 1536 */ 1537 if (to->to_flags & TOF_TS) { 1538 sc->sc_tsreflect = to->to_tsval; 1539 sc->sc_flags |= SCF_TIMESTAMP; 1540 sc->sc_tsoff = tcp_new_ts_offset(inc); 1541 } 1542 if (to->to_flags & TOF_SCALE) { 1543 int wscale = 0; 1544 1545 /* 1546 * Pick the smallest possible scaling factor that 1547 * will still allow us to scale up to sb_max, aka 1548 * kern.ipc.maxsockbuf. 1549 * 1550 * We do this because there are broken firewalls that 1551 * will corrupt the window scale option, leading to 1552 * the other endpoint believing that our advertised 1553 * window is unscaled. At scale factors larger than 1554 * 5 the unscaled window will drop below 1500 bytes, 1555 * leading to serious problems when traversing these 1556 * broken firewalls. 1557 * 1558 * With the default maxsockbuf of 256K, a scale factor 1559 * of 3 will be chosen by this algorithm. Those who 1560 * choose a larger maxsockbuf should watch out 1561 * for the compatibility problems mentioned above. 1562 * 1563 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1564 * or <SYN,ACK>) segment itself is never scaled. 1565 */ 1566 while (wscale < TCP_MAX_WINSHIFT && 1567 (TCP_MAXWIN << wscale) < sb_max) 1568 wscale++; 1569 sc->sc_requested_r_scale = wscale; 1570 sc->sc_requested_s_scale = to->to_wscale; 1571 sc->sc_flags |= SCF_WINSCALE; 1572 } 1573 } 1574 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1575 /* 1576 * If listening socket requested TCP digests, flag this in the 1577 * syncache so that syncache_respond() will do the right thing 1578 * with the SYN+ACK. 1579 */ 1580 if (ltflags & TF_SIGNATURE) 1581 sc->sc_flags |= SCF_SIGNATURE; 1582 #endif /* TCP_SIGNATURE */ 1583 if (to->to_flags & TOF_SACKPERM) 1584 sc->sc_flags |= SCF_SACK; 1585 if (to->to_flags & TOF_MSS) 1586 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1587 if (ltflags & TF_NOOPT) 1588 sc->sc_flags |= SCF_NOOPT; 1589 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1590 sc->sc_flags |= SCF_ECN; 1591 1592 if (V_tcp_syncookies) 1593 sc->sc_iss = syncookie_generate(sch, sc); 1594 #ifdef INET6 1595 if (autoflowlabel) { 1596 if (V_tcp_syncookies) 1597 sc->sc_flowlabel = sc->sc_iss; 1598 else 1599 sc->sc_flowlabel = ip6_randomflowlabel(); 1600 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK; 1601 } 1602 #endif 1603 SCH_UNLOCK(sch); 1604 1605 if (tfo_cookie_valid) { 1606 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie); 1607 /* INP_WUNLOCK(inp) will be performed by the caller */ 1608 rv = 1; 1609 goto tfo_expanded; 1610 } 1611 1612 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1613 /* 1614 * Do a standard 3-way handshake. 1615 */ 1616 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1617 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1618 syncache_free(sc); 1619 else if (sc != &scs) 1620 syncache_insert(sc, sch); /* locks and unlocks sch */ 1621 TCPSTAT_INC(tcps_sndacks); 1622 TCPSTAT_INC(tcps_sndtotal); 1623 } else { 1624 if (sc != &scs) 1625 syncache_free(sc); 1626 TCPSTAT_INC(tcps_sc_dropped); 1627 } 1628 goto donenoprobe; 1629 1630 done: 1631 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1632 donenoprobe: 1633 if (m) { 1634 *lsop = NULL; 1635 m_freem(m); 1636 } 1637 /* 1638 * If tfo_pending is not NULL here, then a TFO SYN that did not 1639 * result in a new socket was processed and the associated pending 1640 * counter has not yet been decremented. All such TFO processing paths 1641 * transit this point. 1642 */ 1643 if (tfo_pending != NULL) 1644 tcp_fastopen_decrement_counter(tfo_pending); 1645 1646 tfo_expanded: 1647 if (cred != NULL) 1648 crfree(cred); 1649 #ifdef MAC 1650 if (sc == &scs) 1651 mac_syncache_destroy(&maclabel); 1652 #endif 1653 return (rv); 1654 } 1655 1656 /* 1657 * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment, 1658 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL. 1659 */ 1660 static int 1661 syncache_respond(struct syncache *sc, struct syncache_head *sch, 1662 const struct mbuf *m0, int flags) 1663 { 1664 struct ip *ip = NULL; 1665 struct mbuf *m; 1666 struct tcphdr *th = NULL; 1667 int optlen, error = 0; /* Make compiler happy */ 1668 u_int16_t hlen, tlen, mssopt; 1669 struct tcpopt to; 1670 #ifdef INET6 1671 struct ip6_hdr *ip6 = NULL; 1672 #endif 1673 hlen = 1674 #ifdef INET6 1675 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1676 #endif 1677 sizeof(struct ip); 1678 tlen = hlen + sizeof(struct tcphdr); 1679 1680 /* Determine MSS we advertize to other end of connection. */ 1681 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss); 1682 1683 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1684 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1685 ("syncache: mbuf too small")); 1686 1687 /* Create the IP+TCP header from scratch. */ 1688 m = m_gethdr(M_NOWAIT, MT_DATA); 1689 if (m == NULL) 1690 return (ENOBUFS); 1691 #ifdef MAC 1692 mac_syncache_create_mbuf(sc->sc_label, m); 1693 #endif 1694 m->m_data += max_linkhdr; 1695 m->m_len = tlen; 1696 m->m_pkthdr.len = tlen; 1697 m->m_pkthdr.rcvif = NULL; 1698 1699 #ifdef INET6 1700 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1701 ip6 = mtod(m, struct ip6_hdr *); 1702 ip6->ip6_vfc = IPV6_VERSION; 1703 ip6->ip6_nxt = IPPROTO_TCP; 1704 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1705 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1706 ip6->ip6_plen = htons(tlen - hlen); 1707 /* ip6_hlim is set after checksum */ 1708 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1709 ip6->ip6_flow |= sc->sc_flowlabel; 1710 1711 th = (struct tcphdr *)(ip6 + 1); 1712 } 1713 #endif 1714 #if defined(INET6) && defined(INET) 1715 else 1716 #endif 1717 #ifdef INET 1718 { 1719 ip = mtod(m, struct ip *); 1720 ip->ip_v = IPVERSION; 1721 ip->ip_hl = sizeof(struct ip) >> 2; 1722 ip->ip_len = htons(tlen); 1723 ip->ip_id = 0; 1724 ip->ip_off = 0; 1725 ip->ip_sum = 0; 1726 ip->ip_p = IPPROTO_TCP; 1727 ip->ip_src = sc->sc_inc.inc_laddr; 1728 ip->ip_dst = sc->sc_inc.inc_faddr; 1729 ip->ip_ttl = sc->sc_ip_ttl; 1730 ip->ip_tos = sc->sc_ip_tos; 1731 1732 /* 1733 * See if we should do MTU discovery. Route lookups are 1734 * expensive, so we will only unset the DF bit if: 1735 * 1736 * 1) path_mtu_discovery is disabled 1737 * 2) the SCF_UNREACH flag has been set 1738 */ 1739 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1740 ip->ip_off |= htons(IP_DF); 1741 1742 th = (struct tcphdr *)(ip + 1); 1743 } 1744 #endif /* INET */ 1745 th->th_sport = sc->sc_inc.inc_lport; 1746 th->th_dport = sc->sc_inc.inc_fport; 1747 1748 if (flags & TH_SYN) 1749 th->th_seq = htonl(sc->sc_iss); 1750 else 1751 th->th_seq = htonl(sc->sc_iss + 1); 1752 th->th_ack = htonl(sc->sc_irs + 1); 1753 th->th_off = sizeof(struct tcphdr) >> 2; 1754 th->th_x2 = 0; 1755 th->th_flags = flags; 1756 th->th_win = htons(sc->sc_wnd); 1757 th->th_urp = 0; 1758 1759 if ((flags & TH_SYN) && (sc->sc_flags & SCF_ECN)) { 1760 th->th_flags |= TH_ECE; 1761 TCPSTAT_INC(tcps_ecn_shs); 1762 } 1763 1764 /* Tack on the TCP options. */ 1765 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1766 to.to_flags = 0; 1767 1768 if (flags & TH_SYN) { 1769 to.to_mss = mssopt; 1770 to.to_flags = TOF_MSS; 1771 if (sc->sc_flags & SCF_WINSCALE) { 1772 to.to_wscale = sc->sc_requested_r_scale; 1773 to.to_flags |= TOF_SCALE; 1774 } 1775 if (sc->sc_flags & SCF_SACK) 1776 to.to_flags |= TOF_SACKPERM; 1777 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1778 if (sc->sc_flags & SCF_SIGNATURE) 1779 to.to_flags |= TOF_SIGNATURE; 1780 #endif 1781 if (sc->sc_tfo_cookie) { 1782 to.to_flags |= TOF_FASTOPEN; 1783 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 1784 to.to_tfo_cookie = sc->sc_tfo_cookie; 1785 /* don't send cookie again when retransmitting response */ 1786 sc->sc_tfo_cookie = NULL; 1787 } 1788 } 1789 if (sc->sc_flags & SCF_TIMESTAMP) { 1790 to.to_tsval = sc->sc_tsoff + tcp_ts_getticks(); 1791 to.to_tsecr = sc->sc_tsreflect; 1792 to.to_flags |= TOF_TS; 1793 } 1794 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1795 1796 /* Adjust headers by option size. */ 1797 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1798 m->m_len += optlen; 1799 m->m_pkthdr.len += optlen; 1800 #ifdef INET6 1801 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1802 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1803 else 1804 #endif 1805 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 1806 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1807 if (sc->sc_flags & SCF_SIGNATURE) { 1808 KASSERT(to.to_flags & TOF_SIGNATURE, 1809 ("tcp_addoptions() didn't set tcp_signature")); 1810 1811 /* NOTE: to.to_signature is inside of mbuf */ 1812 if (!TCPMD5_ENABLED() || 1813 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) { 1814 m_freem(m); 1815 return (EACCES); 1816 } 1817 } 1818 #endif 1819 } else 1820 optlen = 0; 1821 1822 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1823 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1824 /* 1825 * If we have peer's SYN and it has a flowid, then let's assign it to 1826 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid 1827 * to SYN|ACK due to lack of inp here. 1828 */ 1829 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) { 1830 m->m_pkthdr.flowid = m0->m_pkthdr.flowid; 1831 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0)); 1832 } 1833 #ifdef INET6 1834 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1835 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1836 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1837 IPPROTO_TCP, 0); 1838 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1839 #ifdef TCP_OFFLOAD 1840 if (ADDED_BY_TOE(sc)) { 1841 struct toedev *tod = sc->sc_tod; 1842 1843 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1844 1845 return (error); 1846 } 1847 #endif 1848 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th); 1849 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1850 } 1851 #endif 1852 #if defined(INET6) && defined(INET) 1853 else 1854 #endif 1855 #ifdef INET 1856 { 1857 m->m_pkthdr.csum_flags = CSUM_TCP; 1858 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1859 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1860 #ifdef TCP_OFFLOAD 1861 if (ADDED_BY_TOE(sc)) { 1862 struct toedev *tod = sc->sc_tod; 1863 1864 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1865 1866 return (error); 1867 } 1868 #endif 1869 TCP_PROBE5(send, NULL, NULL, ip, NULL, th); 1870 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1871 } 1872 #endif 1873 return (error); 1874 } 1875 1876 /* 1877 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks 1878 * that exceed the capacity of the syncache by avoiding the storage of any 1879 * of the SYNs we receive. Syncookies defend against blind SYN flooding 1880 * attacks where the attacker does not have access to our responses. 1881 * 1882 * Syncookies encode and include all necessary information about the 1883 * connection setup within the SYN|ACK that we send back. That way we 1884 * can avoid keeping any local state until the ACK to our SYN|ACK returns 1885 * (if ever). Normally the syncache and syncookies are running in parallel 1886 * with the latter taking over when the former is exhausted. When matching 1887 * syncache entry is found the syncookie is ignored. 1888 * 1889 * The only reliable information persisting the 3WHS is our initial sequence 1890 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient 1891 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS 1892 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK 1893 * returns and signifies a legitimate connection if it matches the ACK. 1894 * 1895 * The available space of 32 bits to store the hash and to encode the SYN 1896 * option information is very tight and we should have at least 24 bits for 1897 * the MAC to keep the number of guesses by blind spoofing reasonably high. 1898 * 1899 * SYN option information we have to encode to fully restore a connection: 1900 * MSS: is imporant to chose an optimal segment size to avoid IP level 1901 * fragmentation along the path. The common MSS values can be encoded 1902 * in a 3-bit table. Uncommon values are captured by the next lower value 1903 * in the table leading to a slight increase in packetization overhead. 1904 * WSCALE: is necessary to allow large windows to be used for high delay- 1905 * bandwidth product links. Not scaling the window when it was initially 1906 * negotiated is bad for performance as lack of scaling further decreases 1907 * the apparent available send window. We only need to encode the WSCALE 1908 * we received from the remote end. Our end can be recalculated at any 1909 * time. The common WSCALE values can be encoded in a 3-bit table. 1910 * Uncommon values are captured by the next lower value in the table 1911 * making us under-estimate the available window size halving our 1912 * theoretically possible maximum throughput for that connection. 1913 * SACK: Greatly assists in packet loss recovery and requires 1 bit. 1914 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options 1915 * that are included in all segments on a connection. We enable them when 1916 * the ACK has them. 1917 * 1918 * Security of syncookies and attack vectors: 1919 * 1920 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod) 1921 * together with the gloabl secret to make it unique per connection attempt. 1922 * Thus any change of any of those parameters results in a different MAC output 1923 * in an unpredictable way unless a collision is encountered. 24 bits of the 1924 * MAC are embedded into the ISS. 1925 * 1926 * To prevent replay attacks two rotating global secrets are updated with a 1927 * new random value every 15 seconds. The life-time of a syncookie is thus 1928 * 15-30 seconds. 1929 * 1930 * Vector 1: Attacking the secret. This requires finding a weakness in the 1931 * MAC itself or the way it is used here. The attacker can do a chosen plain 1932 * text attack by varying and testing the all parameters under his control. 1933 * The strength depends on the size and randomness of the secret, and the 1934 * cryptographic security of the MAC function. Due to the constant updating 1935 * of the secret the attacker has at most 29.999 seconds to find the secret 1936 * and launch spoofed connections. After that he has to start all over again. 1937 * 1938 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC 1939 * size an average of 4,823 attempts are required for a 50% chance of success 1940 * to spoof a single syncookie (birthday collision paradox). However the 1941 * attacker is blind and doesn't know if one of his attempts succeeded unless 1942 * he has a side channel to interfere success from. A single connection setup 1943 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets. 1944 * This many attempts are required for each one blind spoofed connection. For 1945 * every additional spoofed connection he has to launch another N attempts. 1946 * Thus for a sustained rate 100 spoofed connections per second approximately 1947 * 1,800,000 packets per second would have to be sent. 1948 * 1949 * NB: The MAC function should be fast so that it doesn't become a CPU 1950 * exhaustion attack vector itself. 1951 * 1952 * References: 1953 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations 1954 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996 1955 * http://cr.yp.to/syncookies.html (overview) 1956 * http://cr.yp.to/syncookies/archive (details) 1957 * 1958 * 1959 * Schematic construction of a syncookie enabled Initial Sequence Number: 1960 * 0 1 2 3 1961 * 12345678901234567890123456789012 1962 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP| 1963 * 1964 * x 24 MAC (truncated) 1965 * W 3 Send Window Scale index 1966 * M 3 MSS index 1967 * S 1 SACK permitted 1968 * P 1 Odd/even secret 1969 */ 1970 1971 /* 1972 * Distribution and probability of certain MSS values. Those in between are 1973 * rounded down to the next lower one. 1974 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011] 1975 * .2% .3% 5% 7% 7% 20% 15% 45% 1976 */ 1977 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 }; 1978 1979 /* 1980 * Distribution and probability of certain WSCALE values. We have to map the 1981 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3 1982 * bits based on prevalence of certain values. Where we don't have an exact 1983 * match for are rounded down to the next lower one letting us under-estimate 1984 * the true available window. At the moment this would happen only for the 1985 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer 1986 * and window size). The absence of the WSCALE option (no scaling in either 1987 * direction) is encoded with index zero. 1988 * [WSCALE values histograms, Allman, 2012] 1989 * X 10 10 35 5 6 14 10% by host 1990 * X 11 4 5 5 18 49 3% by connections 1991 */ 1992 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 }; 1993 1994 /* 1995 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed 1996 * and good cryptographic properties. 1997 */ 1998 static uint32_t 1999 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags, 2000 uint8_t *secbits, uintptr_t secmod) 2001 { 2002 SIPHASH_CTX ctx; 2003 uint32_t siphash[2]; 2004 2005 SipHash24_Init(&ctx); 2006 SipHash_SetKey(&ctx, secbits); 2007 switch (inc->inc_flags & INC_ISIPV6) { 2008 #ifdef INET 2009 case 0: 2010 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr)); 2011 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr)); 2012 break; 2013 #endif 2014 #ifdef INET6 2015 case INC_ISIPV6: 2016 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr)); 2017 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr)); 2018 break; 2019 #endif 2020 } 2021 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport)); 2022 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport)); 2023 SipHash_Update(&ctx, &irs, sizeof(irs)); 2024 SipHash_Update(&ctx, &flags, sizeof(flags)); 2025 SipHash_Update(&ctx, &secmod, sizeof(secmod)); 2026 SipHash_Final((u_int8_t *)&siphash, &ctx); 2027 2028 return (siphash[0] ^ siphash[1]); 2029 } 2030 2031 static tcp_seq 2032 syncookie_generate(struct syncache_head *sch, struct syncache *sc) 2033 { 2034 u_int i, secbit, wscale; 2035 uint32_t iss, hash; 2036 uint8_t *secbits; 2037 union syncookie cookie; 2038 2039 SCH_LOCK_ASSERT(sch); 2040 2041 cookie.cookie = 0; 2042 2043 /* Map our computed MSS into the 3-bit index. */ 2044 for (i = nitems(tcp_sc_msstab) - 1; 2045 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0; 2046 i--) 2047 ; 2048 cookie.flags.mss_idx = i; 2049 2050 /* 2051 * Map the send window scale into the 3-bit index but only if 2052 * the wscale option was received. 2053 */ 2054 if (sc->sc_flags & SCF_WINSCALE) { 2055 wscale = sc->sc_requested_s_scale; 2056 for (i = nitems(tcp_sc_wstab) - 1; 2057 tcp_sc_wstab[i] > wscale && i > 0; 2058 i--) 2059 ; 2060 cookie.flags.wscale_idx = i; 2061 } 2062 2063 /* Can we do SACK? */ 2064 if (sc->sc_flags & SCF_SACK) 2065 cookie.flags.sack_ok = 1; 2066 2067 /* Which of the two secrets to use. */ 2068 secbit = sch->sch_sc->secret.oddeven & 0x1; 2069 cookie.flags.odd_even = secbit; 2070 2071 secbits = sch->sch_sc->secret.key[secbit]; 2072 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits, 2073 (uintptr_t)sch); 2074 2075 /* 2076 * Put the flags into the hash and XOR them to get better ISS number 2077 * variance. This doesn't enhance the cryptographic strength and is 2078 * done to prevent the 8 cookie bits from showing up directly on the 2079 * wire. 2080 */ 2081 iss = hash & ~0xff; 2082 iss |= cookie.cookie ^ (hash >> 24); 2083 2084 TCPSTAT_INC(tcps_sc_sendcookie); 2085 return (iss); 2086 } 2087 2088 static struct syncache * 2089 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 2090 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2091 struct socket *lso) 2092 { 2093 uint32_t hash; 2094 uint8_t *secbits; 2095 tcp_seq ack, seq; 2096 int wnd, wscale = 0; 2097 union syncookie cookie; 2098 2099 SCH_LOCK_ASSERT(sch); 2100 2101 /* 2102 * Pull information out of SYN-ACK/ACK and revert sequence number 2103 * advances. 2104 */ 2105 ack = th->th_ack - 1; 2106 seq = th->th_seq - 1; 2107 2108 /* 2109 * Unpack the flags containing enough information to restore the 2110 * connection. 2111 */ 2112 cookie.cookie = (ack & 0xff) ^ (ack >> 24); 2113 2114 /* Which of the two secrets to use. */ 2115 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even]; 2116 2117 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch); 2118 2119 /* The recomputed hash matches the ACK if this was a genuine cookie. */ 2120 if ((ack & ~0xff) != (hash & ~0xff)) 2121 return (NULL); 2122 2123 /* Fill in the syncache values. */ 2124 sc->sc_flags = 0; 2125 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 2126 sc->sc_ipopts = NULL; 2127 2128 sc->sc_irs = seq; 2129 sc->sc_iss = ack; 2130 2131 switch (inc->inc_flags & INC_ISIPV6) { 2132 #ifdef INET 2133 case 0: 2134 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl; 2135 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos; 2136 break; 2137 #endif 2138 #ifdef INET6 2139 case INC_ISIPV6: 2140 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL) 2141 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK; 2142 break; 2143 #endif 2144 } 2145 2146 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx]; 2147 2148 /* We can simply recompute receive window scale we sent earlier. */ 2149 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max) 2150 wscale++; 2151 2152 /* Only use wscale if it was enabled in the orignal SYN. */ 2153 if (cookie.flags.wscale_idx > 0) { 2154 sc->sc_requested_r_scale = wscale; 2155 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx]; 2156 sc->sc_flags |= SCF_WINSCALE; 2157 } 2158 2159 wnd = lso->sol_sbrcv_hiwat; 2160 wnd = imax(wnd, 0); 2161 wnd = imin(wnd, TCP_MAXWIN); 2162 sc->sc_wnd = wnd; 2163 2164 if (cookie.flags.sack_ok) 2165 sc->sc_flags |= SCF_SACK; 2166 2167 if (to->to_flags & TOF_TS) { 2168 sc->sc_flags |= SCF_TIMESTAMP; 2169 sc->sc_tsreflect = to->to_tsval; 2170 sc->sc_tsoff = tcp_new_ts_offset(inc); 2171 } 2172 2173 if (to->to_flags & TOF_SIGNATURE) 2174 sc->sc_flags |= SCF_SIGNATURE; 2175 2176 sc->sc_rxmits = 0; 2177 2178 TCPSTAT_INC(tcps_sc_recvcookie); 2179 return (sc); 2180 } 2181 2182 #ifdef INVARIANTS 2183 static int 2184 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 2185 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2186 struct socket *lso) 2187 { 2188 struct syncache scs, *scx; 2189 char *s; 2190 2191 bzero(&scs, sizeof(scs)); 2192 scx = syncookie_lookup(inc, sch, &scs, th, to, lso); 2193 2194 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL) 2195 return (0); 2196 2197 if (scx != NULL) { 2198 if (sc->sc_peer_mss != scx->sc_peer_mss) 2199 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n", 2200 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss); 2201 2202 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale) 2203 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n", 2204 s, __func__, sc->sc_requested_r_scale, 2205 scx->sc_requested_r_scale); 2206 2207 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale) 2208 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n", 2209 s, __func__, sc->sc_requested_s_scale, 2210 scx->sc_requested_s_scale); 2211 2212 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK)) 2213 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__); 2214 } 2215 2216 if (s != NULL) 2217 free(s, M_TCPLOG); 2218 return (0); 2219 } 2220 #endif /* INVARIANTS */ 2221 2222 static void 2223 syncookie_reseed(void *arg) 2224 { 2225 struct tcp_syncache *sc = arg; 2226 uint8_t *secbits; 2227 int secbit; 2228 2229 /* 2230 * Reseeding the secret doesn't have to be protected by a lock. 2231 * It only must be ensured that the new random values are visible 2232 * to all CPUs in a SMP environment. The atomic with release 2233 * semantics ensures that. 2234 */ 2235 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1; 2236 secbits = sc->secret.key[secbit]; 2237 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0); 2238 atomic_add_rel_int(&sc->secret.oddeven, 1); 2239 2240 /* Reschedule ourself. */ 2241 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz); 2242 } 2243 2244 /* 2245 * Exports the syncache entries to userland so that netstat can display 2246 * them alongside the other sockets. This function is intended to be 2247 * called only from tcp_pcblist. 2248 * 2249 * Due to concurrency on an active system, the number of pcbs exported 2250 * may have no relation to max_pcbs. max_pcbs merely indicates the 2251 * amount of space the caller allocated for this function to use. 2252 */ 2253 int 2254 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 2255 { 2256 struct xtcpcb xt; 2257 struct syncache *sc; 2258 struct syncache_head *sch; 2259 int count, error, i; 2260 2261 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 2262 sch = &V_tcp_syncache.hashbase[i]; 2263 SCH_LOCK(sch); 2264 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 2265 if (count >= max_pcbs) { 2266 SCH_UNLOCK(sch); 2267 goto exit; 2268 } 2269 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 2270 continue; 2271 bzero(&xt, sizeof(xt)); 2272 xt.xt_len = sizeof(xt); 2273 if (sc->sc_inc.inc_flags & INC_ISIPV6) 2274 xt.xt_inp.inp_vflag = INP_IPV6; 2275 else 2276 xt.xt_inp.inp_vflag = INP_IPV4; 2277 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, 2278 sizeof (struct in_conninfo)); 2279 xt.t_state = TCPS_SYN_RECEIVED; 2280 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP; 2281 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket); 2282 xt.xt_inp.xi_socket.so_type = SOCK_STREAM; 2283 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING; 2284 error = SYSCTL_OUT(req, &xt, sizeof xt); 2285 if (error) { 2286 SCH_UNLOCK(sch); 2287 goto exit; 2288 } 2289 count++; 2290 } 2291 SCH_UNLOCK(sch); 2292 } 2293 exit: 2294 *pcbs_exported = count; 2295 return error; 2296 } 2297