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 * tcp_rexmit_initial * ( 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 = tcp_rexmit_initial; 428 else 429 TCPT_RANGESET(rexmt, 430 tcp_rexmit_initial * tcp_backoff[sc->sc_rxmits], 431 tcp_rexmit_min, TCPTV_REXMTMAX); 432 sc->sc_rxttime = ticks + rexmt; 433 sc->sc_rxmits++; 434 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 435 sch->sch_nextc = sc->sc_rxttime; 436 if (docallout) 437 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 438 syncache_timer, (void *)sch); 439 } 440 } 441 442 /* 443 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 444 * If we have retransmitted an entry the maximum number of times, expire it. 445 * One separate timer for each bucket row. 446 */ 447 static void 448 syncache_timer(void *xsch) 449 { 450 struct syncache_head *sch = (struct syncache_head *)xsch; 451 struct syncache *sc, *nsc; 452 int tick = ticks; 453 char *s; 454 455 CURVNET_SET(sch->sch_sc->vnet); 456 457 /* NB: syncache_head has already been locked by the callout. */ 458 SCH_LOCK_ASSERT(sch); 459 460 /* 461 * In the following cycle we may remove some entries and/or 462 * advance some timeouts, so re-initialize the bucket timer. 463 */ 464 sch->sch_nextc = tick + INT_MAX; 465 466 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 467 /* 468 * We do not check if the listen socket still exists 469 * and accept the case where the listen socket may be 470 * gone by the time we resend the SYN/ACK. We do 471 * not expect this to happens often. If it does, 472 * then the RST will be sent by the time the remote 473 * host does the SYN/ACK->ACK. 474 */ 475 if (TSTMP_GT(sc->sc_rxttime, tick)) { 476 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 477 sch->sch_nextc = sc->sc_rxttime; 478 continue; 479 } 480 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 481 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 482 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 483 "giving up and removing syncache entry\n", 484 s, __func__); 485 free(s, M_TCPLOG); 486 } 487 syncache_drop(sc, sch); 488 TCPSTAT_INC(tcps_sc_stale); 489 continue; 490 } 491 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 492 log(LOG_DEBUG, "%s; %s: Response timeout, " 493 "retransmitting (%u) SYN|ACK\n", 494 s, __func__, sc->sc_rxmits); 495 free(s, M_TCPLOG); 496 } 497 498 syncache_respond(sc, sch, NULL, TH_SYN|TH_ACK); 499 TCPSTAT_INC(tcps_sc_retransmitted); 500 syncache_timeout(sc, sch, 0); 501 } 502 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 503 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 504 syncache_timer, (void *)(sch)); 505 CURVNET_RESTORE(); 506 } 507 508 /* 509 * Find an entry in the syncache. 510 * Returns always with locked syncache_head plus a matching entry or NULL. 511 */ 512 static struct syncache * 513 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 514 { 515 struct syncache *sc; 516 struct syncache_head *sch; 517 uint32_t hash; 518 519 /* 520 * The hash is built on foreign port + local port + foreign address. 521 * We rely on the fact that struct in_conninfo starts with 16 bits 522 * of foreign port, then 16 bits of local port then followed by 128 523 * bits of foreign address. In case of IPv4 address, the first 3 524 * 32-bit words of the address always are zeroes. 525 */ 526 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5, 527 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask; 528 529 sch = &V_tcp_syncache.hashbase[hash]; 530 *schp = sch; 531 SCH_LOCK(sch); 532 533 /* Circle through bucket row to find matching entry. */ 534 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 535 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie, 536 sizeof(struct in_endpoints)) == 0) 537 break; 538 539 return (sc); /* Always returns with locked sch. */ 540 } 541 542 /* 543 * This function is called when we get a RST for a 544 * non-existent connection, so that we can see if the 545 * connection is in the syn cache. If it is, zap it. 546 * If required send a challenge ACK. 547 */ 548 void 549 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m) 550 { 551 struct syncache *sc; 552 struct syncache_head *sch; 553 char *s = NULL; 554 555 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 556 SCH_LOCK_ASSERT(sch); 557 558 /* 559 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 560 * See RFC 793 page 65, section SEGMENT ARRIVES. 561 */ 562 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 563 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 564 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 565 "FIN flag set, segment ignored\n", s, __func__); 566 TCPSTAT_INC(tcps_badrst); 567 goto done; 568 } 569 570 /* 571 * No corresponding connection was found in syncache. 572 * If syncookies are enabled and possibly exclusively 573 * used, or we are under memory pressure, a valid RST 574 * may not find a syncache entry. In that case we're 575 * done and no SYN|ACK retransmissions will happen. 576 * Otherwise the RST was misdirected or spoofed. 577 */ 578 if (sc == NULL) { 579 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 580 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 581 "syncache entry (possibly syncookie only), " 582 "segment ignored\n", s, __func__); 583 TCPSTAT_INC(tcps_badrst); 584 goto done; 585 } 586 587 /* 588 * If the RST bit is set, check the sequence number to see 589 * if this is a valid reset segment. 590 * 591 * RFC 793 page 37: 592 * In all states except SYN-SENT, all reset (RST) segments 593 * are validated by checking their SEQ-fields. A reset is 594 * valid if its sequence number is in the window. 595 * 596 * RFC 793 page 69: 597 * There are four cases for the acceptability test for an incoming 598 * segment: 599 * 600 * Segment Receive Test 601 * Length Window 602 * ------- ------- ------------------------------------------- 603 * 0 0 SEG.SEQ = RCV.NXT 604 * 0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND 605 * >0 0 not acceptable 606 * >0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND 607 * or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND 608 * 609 * Note that when receiving a SYN segment in the LISTEN state, 610 * IRS is set to SEG.SEQ and RCV.NXT is set to SEG.SEQ+1, as 611 * described in RFC 793, page 66. 612 */ 613 if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) && 614 SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) || 615 (sc->sc_wnd == 0 && th->th_seq == sc->sc_irs + 1)) { 616 if (V_tcp_insecure_rst || 617 th->th_seq == sc->sc_irs + 1) { 618 syncache_drop(sc, sch); 619 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 620 log(LOG_DEBUG, 621 "%s; %s: Our SYN|ACK was rejected, " 622 "connection attempt aborted by remote " 623 "endpoint\n", 624 s, __func__); 625 TCPSTAT_INC(tcps_sc_reset); 626 } else { 627 TCPSTAT_INC(tcps_badrst); 628 /* Send challenge ACK. */ 629 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 630 log(LOG_DEBUG, "%s; %s: RST with invalid " 631 " SEQ %u != NXT %u (+WND %u), " 632 "sending challenge ACK\n", 633 s, __func__, 634 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 635 syncache_respond(sc, sch, m, TH_ACK); 636 } 637 } else { 638 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 639 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 640 "NXT %u (+WND %u), segment ignored\n", 641 s, __func__, 642 th->th_seq, sc->sc_irs + 1, sc->sc_wnd); 643 TCPSTAT_INC(tcps_badrst); 644 } 645 646 done: 647 if (s != NULL) 648 free(s, M_TCPLOG); 649 SCH_UNLOCK(sch); 650 } 651 652 void 653 syncache_badack(struct in_conninfo *inc) 654 { 655 struct syncache *sc; 656 struct syncache_head *sch; 657 658 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 659 SCH_LOCK_ASSERT(sch); 660 if (sc != NULL) { 661 syncache_drop(sc, sch); 662 TCPSTAT_INC(tcps_sc_badack); 663 } 664 SCH_UNLOCK(sch); 665 } 666 667 void 668 syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq) 669 { 670 struct syncache *sc; 671 struct syncache_head *sch; 672 673 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 674 SCH_LOCK_ASSERT(sch); 675 if (sc == NULL) 676 goto done; 677 678 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 679 if (ntohl(th_seq) != sc->sc_iss) 680 goto done; 681 682 /* 683 * If we've rertransmitted 3 times and this is our second error, 684 * we remove the entry. Otherwise, we allow it to continue on. 685 * This prevents us from incorrectly nuking an entry during a 686 * spurious network outage. 687 * 688 * See tcp_notify(). 689 */ 690 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 691 sc->sc_flags |= SCF_UNREACH; 692 goto done; 693 } 694 syncache_drop(sc, sch); 695 TCPSTAT_INC(tcps_sc_unreach); 696 done: 697 SCH_UNLOCK(sch); 698 } 699 700 /* 701 * Build a new TCP socket structure from a syncache entry. 702 * 703 * On success return the newly created socket with its underlying inp locked. 704 */ 705 static struct socket * 706 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 707 { 708 struct tcp_function_block *blk; 709 struct inpcb *inp = NULL; 710 struct socket *so; 711 struct tcpcb *tp; 712 int error; 713 char *s; 714 715 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 716 717 /* 718 * Ok, create the full blown connection, and set things up 719 * as they would have been set up if we had created the 720 * connection when the SYN arrived. If we can't create 721 * the connection, abort it. 722 */ 723 so = sonewconn(lso, 0); 724 if (so == NULL) { 725 /* 726 * Drop the connection; we will either send a RST or 727 * have the peer retransmit its SYN again after its 728 * RTO and try again. 729 */ 730 TCPSTAT_INC(tcps_listendrop); 731 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 732 log(LOG_DEBUG, "%s; %s: Socket create failed " 733 "due to limits or memory shortage\n", 734 s, __func__); 735 free(s, M_TCPLOG); 736 } 737 goto abort2; 738 } 739 #ifdef MAC 740 mac_socketpeer_set_from_mbuf(m, so); 741 #endif 742 743 inp = sotoinpcb(so); 744 inp->inp_inc.inc_fibnum = so->so_fibnum; 745 INP_WLOCK(inp); 746 /* 747 * Exclusive pcbinfo lock is not required in syncache socket case even 748 * if two inpcb locks can be acquired simultaneously: 749 * - the inpcb in LISTEN state, 750 * - the newly created inp. 751 * 752 * In this case, an inp cannot be at same time in LISTEN state and 753 * just created by an accept() call. 754 */ 755 INP_HASH_WLOCK(&V_tcbinfo); 756 757 /* Insert new socket into PCB hash list. */ 758 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 759 #ifdef INET6 760 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 761 inp->inp_vflag &= ~INP_IPV4; 762 inp->inp_vflag |= INP_IPV6; 763 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 764 } else { 765 inp->inp_vflag &= ~INP_IPV6; 766 inp->inp_vflag |= INP_IPV4; 767 #endif 768 inp->inp_laddr = sc->sc_inc.inc_laddr; 769 #ifdef INET6 770 } 771 #endif 772 773 /* 774 * If there's an mbuf and it has a flowid, then let's initialise the 775 * inp with that particular flowid. 776 */ 777 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) { 778 inp->inp_flowid = m->m_pkthdr.flowid; 779 inp->inp_flowtype = M_HASHTYPE_GET(m); 780 } 781 782 /* 783 * Install in the reservation hash table for now, but don't yet 784 * install a connection group since the full 4-tuple isn't yet 785 * configured. 786 */ 787 inp->inp_lport = sc->sc_inc.inc_lport; 788 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 789 /* 790 * Undo the assignments above if we failed to 791 * put the PCB on the hash lists. 792 */ 793 #ifdef INET6 794 if (sc->sc_inc.inc_flags & INC_ISIPV6) 795 inp->in6p_laddr = in6addr_any; 796 else 797 #endif 798 inp->inp_laddr.s_addr = INADDR_ANY; 799 inp->inp_lport = 0; 800 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 801 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 802 "with error %i\n", 803 s, __func__, error); 804 free(s, M_TCPLOG); 805 } 806 INP_HASH_WUNLOCK(&V_tcbinfo); 807 goto abort; 808 } 809 #ifdef INET6 810 if (inp->inp_vflag & INP_IPV6PROTO) { 811 struct inpcb *oinp = sotoinpcb(lso); 812 813 /* 814 * Inherit socket options from the listening socket. 815 * Note that in6p_inputopts are not (and should not be) 816 * copied, since it stores previously received options and is 817 * used to detect if each new option is different than the 818 * previous one and hence should be passed to a user. 819 * If we copied in6p_inputopts, a user would not be able to 820 * receive options just after calling the accept system call. 821 */ 822 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 823 if (oinp->in6p_outputopts) 824 inp->in6p_outputopts = 825 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 826 } 827 828 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 829 struct in6_addr laddr6; 830 struct sockaddr_in6 sin6; 831 832 sin6.sin6_family = AF_INET6; 833 sin6.sin6_len = sizeof(sin6); 834 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 835 sin6.sin6_port = sc->sc_inc.inc_fport; 836 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 837 laddr6 = inp->in6p_laddr; 838 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 839 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 840 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 841 thread0.td_ucred, m)) != 0) { 842 inp->in6p_laddr = laddr6; 843 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 844 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 845 "with error %i\n", 846 s, __func__, error); 847 free(s, M_TCPLOG); 848 } 849 INP_HASH_WUNLOCK(&V_tcbinfo); 850 goto abort; 851 } 852 /* Override flowlabel from in6_pcbconnect. */ 853 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 854 inp->inp_flow |= sc->sc_flowlabel; 855 } 856 #endif /* INET6 */ 857 #if defined(INET) && defined(INET6) 858 else 859 #endif 860 #ifdef INET 861 { 862 struct in_addr laddr; 863 struct sockaddr_in sin; 864 865 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 866 867 if (inp->inp_options == NULL) { 868 inp->inp_options = sc->sc_ipopts; 869 sc->sc_ipopts = NULL; 870 } 871 872 sin.sin_family = AF_INET; 873 sin.sin_len = sizeof(sin); 874 sin.sin_addr = sc->sc_inc.inc_faddr; 875 sin.sin_port = sc->sc_inc.inc_fport; 876 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 877 laddr = inp->inp_laddr; 878 if (inp->inp_laddr.s_addr == INADDR_ANY) 879 inp->inp_laddr = sc->sc_inc.inc_laddr; 880 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 881 thread0.td_ucred, m)) != 0) { 882 inp->inp_laddr = laddr; 883 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 884 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 885 "with error %i\n", 886 s, __func__, error); 887 free(s, M_TCPLOG); 888 } 889 INP_HASH_WUNLOCK(&V_tcbinfo); 890 goto abort; 891 } 892 } 893 #endif /* INET */ 894 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 895 /* Copy old policy into new socket's. */ 896 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0) 897 printf("syncache_socket: could not copy policy\n"); 898 #endif 899 INP_HASH_WUNLOCK(&V_tcbinfo); 900 tp = intotcpcb(inp); 901 tcp_state_change(tp, TCPS_SYN_RECEIVED); 902 tp->iss = sc->sc_iss; 903 tp->irs = sc->sc_irs; 904 tcp_rcvseqinit(tp); 905 tcp_sendseqinit(tp); 906 blk = sototcpcb(lso)->t_fb; 907 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) { 908 /* 909 * Our parents t_fb was not the default, 910 * we need to release our ref on tp->t_fb and 911 * pickup one on the new entry. 912 */ 913 struct tcp_function_block *rblk; 914 915 rblk = find_and_ref_tcp_fb(blk); 916 KASSERT(rblk != NULL, 917 ("cannot find blk %p out of syncache?", blk)); 918 if (tp->t_fb->tfb_tcp_fb_fini) 919 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0); 920 refcount_release(&tp->t_fb->tfb_refcnt); 921 tp->t_fb = rblk; 922 /* 923 * XXXrrs this is quite dangerous, it is possible 924 * for the new function to fail to init. We also 925 * are not asking if the handoff_is_ok though at 926 * the very start thats probalbly ok. 927 */ 928 if (tp->t_fb->tfb_tcp_fb_init) { 929 (*tp->t_fb->tfb_tcp_fb_init)(tp); 930 } 931 } 932 tp->snd_wl1 = sc->sc_irs; 933 tp->snd_max = tp->iss + 1; 934 tp->snd_nxt = tp->iss + 1; 935 tp->rcv_up = sc->sc_irs + 1; 936 tp->rcv_wnd = sc->sc_wnd; 937 tp->rcv_adv += tp->rcv_wnd; 938 tp->last_ack_sent = tp->rcv_nxt; 939 940 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 941 if (sc->sc_flags & SCF_NOOPT) 942 tp->t_flags |= TF_NOOPT; 943 else { 944 if (sc->sc_flags & SCF_WINSCALE) { 945 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 946 tp->snd_scale = sc->sc_requested_s_scale; 947 tp->request_r_scale = sc->sc_requested_r_scale; 948 } 949 if (sc->sc_flags & SCF_TIMESTAMP) { 950 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 951 tp->ts_recent = sc->sc_tsreflect; 952 tp->ts_recent_age = tcp_ts_getticks(); 953 tp->ts_offset = sc->sc_tsoff; 954 } 955 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 956 if (sc->sc_flags & SCF_SIGNATURE) 957 tp->t_flags |= TF_SIGNATURE; 958 #endif 959 if (sc->sc_flags & SCF_SACK) 960 tp->t_flags |= TF_SACK_PERMIT; 961 } 962 963 if (sc->sc_flags & SCF_ECN) 964 tp->t_flags |= TF_ECN_PERMIT; 965 966 /* 967 * Set up MSS and get cached values from tcp_hostcache. 968 * This might overwrite some of the defaults we just set. 969 */ 970 tcp_mss(tp, sc->sc_peer_mss); 971 972 /* 973 * If the SYN,ACK was retransmitted, indicate that CWND to be 974 * limited to one segment in cc_conn_init(). 975 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 976 */ 977 if (sc->sc_rxmits > 1) 978 tp->snd_cwnd = 1; 979 980 #ifdef TCP_OFFLOAD 981 /* 982 * Allow a TOE driver to install its hooks. Note that we hold the 983 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a 984 * new connection before the TOE driver has done its thing. 985 */ 986 if (ADDED_BY_TOE(sc)) { 987 struct toedev *tod = sc->sc_tod; 988 989 tod->tod_offload_socket(tod, sc->sc_todctx, so); 990 } 991 #endif 992 /* 993 * Copy and activate timers. 994 */ 995 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 996 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 997 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 998 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 999 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 1000 1001 TCPSTAT_INC(tcps_accepts); 1002 return (so); 1003 1004 abort: 1005 INP_WUNLOCK(inp); 1006 abort2: 1007 if (so != NULL) 1008 soabort(so); 1009 return (NULL); 1010 } 1011 1012 /* 1013 * This function gets called when we receive an ACK for a 1014 * socket in the LISTEN state. We look up the connection 1015 * in the syncache, and if its there, we pull it out of 1016 * the cache and turn it into a full-blown connection in 1017 * the SYN-RECEIVED state. 1018 * 1019 * On syncache_socket() success the newly created socket 1020 * has its underlying inp locked. 1021 */ 1022 int 1023 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1024 struct socket **lsop, struct mbuf *m) 1025 { 1026 struct syncache *sc; 1027 struct syncache_head *sch; 1028 struct syncache scs; 1029 char *s; 1030 1031 /* 1032 * Global TCP locks are held because we manipulate the PCB lists 1033 * and create a new socket. 1034 */ 1035 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1036 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 1037 ("%s: can handle only ACK", __func__)); 1038 1039 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 1040 SCH_LOCK_ASSERT(sch); 1041 1042 #ifdef INVARIANTS 1043 /* 1044 * Test code for syncookies comparing the syncache stored 1045 * values with the reconstructed values from the cookie. 1046 */ 1047 if (sc != NULL) 1048 syncookie_cmp(inc, sch, sc, th, to, *lsop); 1049 #endif 1050 1051 if (sc == NULL) { 1052 /* 1053 * There is no syncache entry, so see if this ACK is 1054 * a returning syncookie. To do this, first: 1055 * A. Check if syncookies are used in case of syncache 1056 * overflows 1057 * B. See if this socket has had a syncache entry dropped in 1058 * the recent past. We don't want to accept a bogus 1059 * syncookie if we've never received a SYN or accept it 1060 * twice. 1061 * C. check that the syncookie is valid. If it is, then 1062 * cobble up a fake syncache entry, and return. 1063 */ 1064 if (!V_tcp_syncookies) { 1065 SCH_UNLOCK(sch); 1066 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1067 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1068 "segment rejected (syncookies disabled)\n", 1069 s, __func__); 1070 goto failed; 1071 } 1072 if (!V_tcp_syncookiesonly && 1073 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) { 1074 SCH_UNLOCK(sch); 1075 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1076 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1077 "segment rejected (no syncache entry)\n", 1078 s, __func__); 1079 goto failed; 1080 } 1081 bzero(&scs, sizeof(scs)); 1082 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop); 1083 SCH_UNLOCK(sch); 1084 if (sc == NULL) { 1085 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1086 log(LOG_DEBUG, "%s; %s: Segment failed " 1087 "SYNCOOKIE authentication, segment rejected " 1088 "(probably spoofed)\n", s, __func__); 1089 goto failed; 1090 } 1091 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1092 /* If received ACK has MD5 signature, check it. */ 1093 if ((to->to_flags & TOF_SIGNATURE) != 0 && 1094 (!TCPMD5_ENABLED() || 1095 TCPMD5_INPUT(m, th, to->to_signature) != 0)) { 1096 /* Drop the ACK. */ 1097 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1098 log(LOG_DEBUG, "%s; %s: Segment rejected, " 1099 "MD5 signature doesn't match.\n", 1100 s, __func__); 1101 free(s, M_TCPLOG); 1102 } 1103 TCPSTAT_INC(tcps_sig_err_sigopt); 1104 return (-1); /* Do not send RST */ 1105 } 1106 #endif /* TCP_SIGNATURE */ 1107 } else { 1108 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1109 /* 1110 * If listening socket requested TCP digests, check that 1111 * received ACK has signature and it is correct. 1112 * If not, drop the ACK and leave sc entry in th cache, 1113 * because SYN was received with correct signature. 1114 */ 1115 if (sc->sc_flags & SCF_SIGNATURE) { 1116 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1117 /* No signature */ 1118 TCPSTAT_INC(tcps_sig_err_nosigopt); 1119 SCH_UNLOCK(sch); 1120 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1121 log(LOG_DEBUG, "%s; %s: Segment " 1122 "rejected, MD5 signature wasn't " 1123 "provided.\n", s, __func__); 1124 free(s, M_TCPLOG); 1125 } 1126 return (-1); /* Do not send RST */ 1127 } 1128 if (!TCPMD5_ENABLED() || 1129 TCPMD5_INPUT(m, th, to->to_signature) != 0) { 1130 /* Doesn't match or no SA */ 1131 SCH_UNLOCK(sch); 1132 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1133 log(LOG_DEBUG, "%s; %s: Segment " 1134 "rejected, MD5 signature doesn't " 1135 "match.\n", s, __func__); 1136 free(s, M_TCPLOG); 1137 } 1138 return (-1); /* Do not send RST */ 1139 } 1140 } 1141 #endif /* TCP_SIGNATURE */ 1142 /* 1143 * Pull out the entry to unlock the bucket row. 1144 * 1145 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not 1146 * tcp_state_change(). The tcpcb is not existent at this 1147 * moment. A new one will be allocated via syncache_socket-> 1148 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then 1149 * syncache_socket() will change it to TCPS_SYN_RECEIVED. 1150 */ 1151 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 1152 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 1153 sch->sch_length--; 1154 #ifdef TCP_OFFLOAD 1155 if (ADDED_BY_TOE(sc)) { 1156 struct toedev *tod = sc->sc_tod; 1157 1158 tod->tod_syncache_removed(tod, sc->sc_todctx); 1159 } 1160 #endif 1161 SCH_UNLOCK(sch); 1162 } 1163 1164 /* 1165 * Segment validation: 1166 * ACK must match our initial sequence number + 1 (the SYN|ACK). 1167 */ 1168 if (th->th_ack != sc->sc_iss + 1) { 1169 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1170 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 1171 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 1172 goto failed; 1173 } 1174 1175 /* 1176 * The SEQ must fall in the window starting at the received 1177 * initial receive sequence number + 1 (the SYN). 1178 */ 1179 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 1180 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 1181 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1182 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 1183 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 1184 goto failed; 1185 } 1186 1187 /* 1188 * If timestamps were not negotiated during SYN/ACK they 1189 * must not appear on any segment during this session. 1190 */ 1191 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 1192 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1193 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1194 "segment rejected\n", s, __func__); 1195 goto failed; 1196 } 1197 1198 /* 1199 * If timestamps were negotiated during SYN/ACK they should 1200 * appear on every segment during this session. 1201 * XXXAO: This is only informal as there have been unverified 1202 * reports of non-compliants stacks. 1203 */ 1204 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) { 1205 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1206 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1207 "no action\n", s, __func__); 1208 free(s, M_TCPLOG); 1209 s = NULL; 1210 } 1211 } 1212 1213 *lsop = syncache_socket(sc, *lsop, m); 1214 1215 if (*lsop == NULL) 1216 TCPSTAT_INC(tcps_sc_aborted); 1217 else 1218 TCPSTAT_INC(tcps_sc_completed); 1219 1220 /* how do we find the inp for the new socket? */ 1221 if (sc != &scs) 1222 syncache_free(sc); 1223 return (1); 1224 failed: 1225 if (sc != NULL && sc != &scs) 1226 syncache_free(sc); 1227 if (s != NULL) 1228 free(s, M_TCPLOG); 1229 *lsop = NULL; 1230 return (0); 1231 } 1232 1233 static void 1234 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m, 1235 uint64_t response_cookie) 1236 { 1237 struct inpcb *inp; 1238 struct tcpcb *tp; 1239 unsigned int *pending_counter; 1240 1241 /* 1242 * Global TCP locks are held because we manipulate the PCB lists 1243 * and create a new socket. 1244 */ 1245 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1246 1247 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending; 1248 *lsop = syncache_socket(sc, *lsop, m); 1249 if (*lsop == NULL) { 1250 TCPSTAT_INC(tcps_sc_aborted); 1251 atomic_subtract_int(pending_counter, 1); 1252 } else { 1253 soisconnected(*lsop); 1254 inp = sotoinpcb(*lsop); 1255 tp = intotcpcb(inp); 1256 tp->t_flags |= TF_FASTOPEN; 1257 tp->t_tfo_cookie.server = response_cookie; 1258 tp->snd_max = tp->iss; 1259 tp->snd_nxt = tp->iss; 1260 tp->t_tfo_pending = pending_counter; 1261 TCPSTAT_INC(tcps_sc_completed); 1262 } 1263 } 1264 1265 /* 1266 * Given a LISTEN socket and an inbound SYN request, add 1267 * this to the syn cache, and send back a segment: 1268 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1269 * to the source. 1270 * 1271 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1272 * Doing so would require that we hold onto the data and deliver it 1273 * to the application. However, if we are the target of a SYN-flood 1274 * DoS attack, an attacker could send data which would eventually 1275 * consume all available buffer space if it were ACKed. By not ACKing 1276 * the data, we avoid this DoS scenario. 1277 * 1278 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO) 1279 * cookie is processed and a new socket is created. In this case, any data 1280 * accompanying the SYN will be queued to the socket by tcp_input() and will 1281 * be ACKed either when the application sends response data or the delayed 1282 * ACK timer expires, whichever comes first. 1283 */ 1284 int 1285 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1286 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1287 void *todctx) 1288 { 1289 struct tcpcb *tp; 1290 struct socket *so; 1291 struct syncache *sc = NULL; 1292 struct syncache_head *sch; 1293 struct mbuf *ipopts = NULL; 1294 u_int ltflags; 1295 int win, ip_ttl, ip_tos; 1296 char *s; 1297 int rv = 0; 1298 #ifdef INET6 1299 int autoflowlabel = 0; 1300 #endif 1301 #ifdef MAC 1302 struct label *maclabel; 1303 #endif 1304 struct syncache scs; 1305 struct ucred *cred; 1306 uint64_t tfo_response_cookie; 1307 unsigned int *tfo_pending = NULL; 1308 int tfo_cookie_valid = 0; 1309 int tfo_response_cookie_valid = 0; 1310 1311 INP_WLOCK_ASSERT(inp); /* listen socket */ 1312 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1313 ("%s: unexpected tcp flags", __func__)); 1314 1315 /* 1316 * Combine all so/tp operations very early to drop the INP lock as 1317 * soon as possible. 1318 */ 1319 so = *lsop; 1320 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so)); 1321 tp = sototcpcb(so); 1322 cred = crhold(so->so_cred); 1323 1324 #ifdef INET6 1325 if ((inc->inc_flags & INC_ISIPV6) && 1326 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1327 autoflowlabel = 1; 1328 #endif 1329 ip_ttl = inp->inp_ip_ttl; 1330 ip_tos = inp->inp_ip_tos; 1331 win = so->sol_sbrcv_hiwat; 1332 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1333 1334 if (V_tcp_fastopen_server_enable && IS_FASTOPEN(tp->t_flags) && 1335 (tp->t_tfo_pending != NULL) && 1336 (to->to_flags & TOF_FASTOPEN)) { 1337 /* 1338 * Limit the number of pending TFO connections to 1339 * approximately half of the queue limit. This prevents TFO 1340 * SYN floods from starving the service by filling the 1341 * listen queue with bogus TFO connections. 1342 */ 1343 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <= 1344 (so->sol_qlimit / 2)) { 1345 int result; 1346 1347 result = tcp_fastopen_check_cookie(inc, 1348 to->to_tfo_cookie, to->to_tfo_len, 1349 &tfo_response_cookie); 1350 tfo_cookie_valid = (result > 0); 1351 tfo_response_cookie_valid = (result >= 0); 1352 } 1353 1354 /* 1355 * Remember the TFO pending counter as it will have to be 1356 * decremented below if we don't make it to syncache_tfo_expand(). 1357 */ 1358 tfo_pending = tp->t_tfo_pending; 1359 } 1360 1361 /* By the time we drop the lock these should no longer be used. */ 1362 so = NULL; 1363 tp = NULL; 1364 1365 #ifdef MAC 1366 if (mac_syncache_init(&maclabel) != 0) { 1367 INP_WUNLOCK(inp); 1368 goto done; 1369 } else 1370 mac_syncache_create(maclabel, inp); 1371 #endif 1372 if (!tfo_cookie_valid) 1373 INP_WUNLOCK(inp); 1374 1375 /* 1376 * Remember the IP options, if any. 1377 */ 1378 #ifdef INET6 1379 if (!(inc->inc_flags & INC_ISIPV6)) 1380 #endif 1381 #ifdef INET 1382 ipopts = (m) ? ip_srcroute(m) : NULL; 1383 #else 1384 ipopts = NULL; 1385 #endif 1386 1387 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1388 /* 1389 * If listening socket requested TCP digests, check that received 1390 * SYN has signature and it is correct. If signature doesn't match 1391 * or TCP_SIGNATURE support isn't enabled, drop the packet. 1392 */ 1393 if (ltflags & TF_SIGNATURE) { 1394 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1395 TCPSTAT_INC(tcps_sig_err_nosigopt); 1396 goto done; 1397 } 1398 if (!TCPMD5_ENABLED() || 1399 TCPMD5_INPUT(m, th, to->to_signature) != 0) 1400 goto done; 1401 } 1402 #endif /* TCP_SIGNATURE */ 1403 /* 1404 * See if we already have an entry for this connection. 1405 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1406 * 1407 * XXX: should the syncache be re-initialized with the contents 1408 * of the new SYN here (which may have different options?) 1409 * 1410 * XXX: We do not check the sequence number to see if this is a 1411 * real retransmit or a new connection attempt. The question is 1412 * how to handle such a case; either ignore it as spoofed, or 1413 * drop the current entry and create a new one? 1414 */ 1415 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1416 SCH_LOCK_ASSERT(sch); 1417 if (sc != NULL) { 1418 if (tfo_cookie_valid) 1419 INP_WUNLOCK(inp); 1420 TCPSTAT_INC(tcps_sc_dupsyn); 1421 if (ipopts) { 1422 /* 1423 * If we were remembering a previous source route, 1424 * forget it and use the new one we've been given. 1425 */ 1426 if (sc->sc_ipopts) 1427 (void) m_free(sc->sc_ipopts); 1428 sc->sc_ipopts = ipopts; 1429 } 1430 /* 1431 * Update timestamp if present. 1432 */ 1433 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1434 sc->sc_tsreflect = to->to_tsval; 1435 else 1436 sc->sc_flags &= ~SCF_TIMESTAMP; 1437 #ifdef MAC 1438 /* 1439 * Since we have already unconditionally allocated label 1440 * storage, free it up. The syncache entry will already 1441 * have an initialized label we can use. 1442 */ 1443 mac_syncache_destroy(&maclabel); 1444 #endif 1445 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1446 /* Retransmit SYN|ACK and reset retransmit count. */ 1447 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1448 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1449 "resetting timer and retransmitting SYN|ACK\n", 1450 s, __func__); 1451 free(s, M_TCPLOG); 1452 } 1453 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1454 sc->sc_rxmits = 0; 1455 syncache_timeout(sc, sch, 1); 1456 TCPSTAT_INC(tcps_sndacks); 1457 TCPSTAT_INC(tcps_sndtotal); 1458 } 1459 SCH_UNLOCK(sch); 1460 goto donenoprobe; 1461 } 1462 1463 if (tfo_cookie_valid) { 1464 bzero(&scs, sizeof(scs)); 1465 sc = &scs; 1466 goto skip_alloc; 1467 } 1468 1469 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1470 if (sc == NULL) { 1471 /* 1472 * The zone allocator couldn't provide more entries. 1473 * Treat this as if the cache was full; drop the oldest 1474 * entry and insert the new one. 1475 */ 1476 TCPSTAT_INC(tcps_sc_zonefail); 1477 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) { 1478 sch->sch_last_overflow = time_uptime; 1479 syncache_drop(sc, sch); 1480 } 1481 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1482 if (sc == NULL) { 1483 if (V_tcp_syncookies) { 1484 bzero(&scs, sizeof(scs)); 1485 sc = &scs; 1486 } else { 1487 SCH_UNLOCK(sch); 1488 if (ipopts) 1489 (void) m_free(ipopts); 1490 goto done; 1491 } 1492 } 1493 } 1494 1495 skip_alloc: 1496 if (!tfo_cookie_valid && tfo_response_cookie_valid) 1497 sc->sc_tfo_cookie = &tfo_response_cookie; 1498 1499 /* 1500 * Fill in the syncache values. 1501 */ 1502 #ifdef MAC 1503 sc->sc_label = maclabel; 1504 #endif 1505 sc->sc_cred = cred; 1506 cred = NULL; 1507 sc->sc_ipopts = ipopts; 1508 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1509 #ifdef INET6 1510 if (!(inc->inc_flags & INC_ISIPV6)) 1511 #endif 1512 { 1513 sc->sc_ip_tos = ip_tos; 1514 sc->sc_ip_ttl = ip_ttl; 1515 } 1516 #ifdef TCP_OFFLOAD 1517 sc->sc_tod = tod; 1518 sc->sc_todctx = todctx; 1519 #endif 1520 sc->sc_irs = th->th_seq; 1521 sc->sc_iss = arc4random(); 1522 sc->sc_flags = 0; 1523 sc->sc_flowlabel = 0; 1524 1525 /* 1526 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1527 * win was derived from socket earlier in the function. 1528 */ 1529 win = imax(win, 0); 1530 win = imin(win, TCP_MAXWIN); 1531 sc->sc_wnd = win; 1532 1533 if (V_tcp_do_rfc1323) { 1534 /* 1535 * A timestamp received in a SYN makes 1536 * it ok to send timestamp requests and replies. 1537 */ 1538 if (to->to_flags & TOF_TS) { 1539 sc->sc_tsreflect = to->to_tsval; 1540 sc->sc_flags |= SCF_TIMESTAMP; 1541 sc->sc_tsoff = tcp_new_ts_offset(inc); 1542 } 1543 if (to->to_flags & TOF_SCALE) { 1544 int wscale = 0; 1545 1546 /* 1547 * Pick the smallest possible scaling factor that 1548 * will still allow us to scale up to sb_max, aka 1549 * kern.ipc.maxsockbuf. 1550 * 1551 * We do this because there are broken firewalls that 1552 * will corrupt the window scale option, leading to 1553 * the other endpoint believing that our advertised 1554 * window is unscaled. At scale factors larger than 1555 * 5 the unscaled window will drop below 1500 bytes, 1556 * leading to serious problems when traversing these 1557 * broken firewalls. 1558 * 1559 * With the default maxsockbuf of 256K, a scale factor 1560 * of 3 will be chosen by this algorithm. Those who 1561 * choose a larger maxsockbuf should watch out 1562 * for the compatibility problems mentioned above. 1563 * 1564 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1565 * or <SYN,ACK>) segment itself is never scaled. 1566 */ 1567 while (wscale < TCP_MAX_WINSHIFT && 1568 (TCP_MAXWIN << wscale) < sb_max) 1569 wscale++; 1570 sc->sc_requested_r_scale = wscale; 1571 sc->sc_requested_s_scale = to->to_wscale; 1572 sc->sc_flags |= SCF_WINSCALE; 1573 } 1574 } 1575 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1576 /* 1577 * If listening socket requested TCP digests, flag this in the 1578 * syncache so that syncache_respond() will do the right thing 1579 * with the SYN+ACK. 1580 */ 1581 if (ltflags & TF_SIGNATURE) 1582 sc->sc_flags |= SCF_SIGNATURE; 1583 #endif /* TCP_SIGNATURE */ 1584 if (to->to_flags & TOF_SACKPERM) 1585 sc->sc_flags |= SCF_SACK; 1586 if (to->to_flags & TOF_MSS) 1587 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1588 if (ltflags & TF_NOOPT) 1589 sc->sc_flags |= SCF_NOOPT; 1590 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1591 sc->sc_flags |= SCF_ECN; 1592 1593 if (V_tcp_syncookies) 1594 sc->sc_iss = syncookie_generate(sch, sc); 1595 #ifdef INET6 1596 if (autoflowlabel) { 1597 if (V_tcp_syncookies) 1598 sc->sc_flowlabel = sc->sc_iss; 1599 else 1600 sc->sc_flowlabel = ip6_randomflowlabel(); 1601 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK; 1602 } 1603 #endif 1604 SCH_UNLOCK(sch); 1605 1606 if (tfo_cookie_valid) { 1607 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie); 1608 /* INP_WUNLOCK(inp) will be performed by the caller */ 1609 rv = 1; 1610 goto tfo_expanded; 1611 } 1612 1613 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1614 /* 1615 * Do a standard 3-way handshake. 1616 */ 1617 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1618 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1619 syncache_free(sc); 1620 else if (sc != &scs) 1621 syncache_insert(sc, sch); /* locks and unlocks sch */ 1622 TCPSTAT_INC(tcps_sndacks); 1623 TCPSTAT_INC(tcps_sndtotal); 1624 } else { 1625 if (sc != &scs) 1626 syncache_free(sc); 1627 TCPSTAT_INC(tcps_sc_dropped); 1628 } 1629 goto donenoprobe; 1630 1631 done: 1632 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1633 donenoprobe: 1634 if (m) { 1635 *lsop = NULL; 1636 m_freem(m); 1637 } 1638 /* 1639 * If tfo_pending is not NULL here, then a TFO SYN that did not 1640 * result in a new socket was processed and the associated pending 1641 * counter has not yet been decremented. All such TFO processing paths 1642 * transit this point. 1643 */ 1644 if (tfo_pending != NULL) 1645 tcp_fastopen_decrement_counter(tfo_pending); 1646 1647 tfo_expanded: 1648 if (cred != NULL) 1649 crfree(cred); 1650 #ifdef MAC 1651 if (sc == &scs) 1652 mac_syncache_destroy(&maclabel); 1653 #endif 1654 return (rv); 1655 } 1656 1657 /* 1658 * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment, 1659 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL. 1660 */ 1661 static int 1662 syncache_respond(struct syncache *sc, struct syncache_head *sch, 1663 const struct mbuf *m0, int flags) 1664 { 1665 struct ip *ip = NULL; 1666 struct mbuf *m; 1667 struct tcphdr *th = NULL; 1668 int optlen, error = 0; /* Make compiler happy */ 1669 u_int16_t hlen, tlen, mssopt; 1670 struct tcpopt to; 1671 #ifdef INET6 1672 struct ip6_hdr *ip6 = NULL; 1673 #endif 1674 hlen = 1675 #ifdef INET6 1676 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1677 #endif 1678 sizeof(struct ip); 1679 tlen = hlen + sizeof(struct tcphdr); 1680 1681 /* Determine MSS we advertize to other end of connection. */ 1682 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss); 1683 1684 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1685 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1686 ("syncache: mbuf too small")); 1687 1688 /* Create the IP+TCP header from scratch. */ 1689 m = m_gethdr(M_NOWAIT, MT_DATA); 1690 if (m == NULL) 1691 return (ENOBUFS); 1692 #ifdef MAC 1693 mac_syncache_create_mbuf(sc->sc_label, m); 1694 #endif 1695 m->m_data += max_linkhdr; 1696 m->m_len = tlen; 1697 m->m_pkthdr.len = tlen; 1698 m->m_pkthdr.rcvif = NULL; 1699 1700 #ifdef INET6 1701 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1702 ip6 = mtod(m, struct ip6_hdr *); 1703 ip6->ip6_vfc = IPV6_VERSION; 1704 ip6->ip6_nxt = IPPROTO_TCP; 1705 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1706 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1707 ip6->ip6_plen = htons(tlen - hlen); 1708 /* ip6_hlim is set after checksum */ 1709 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1710 ip6->ip6_flow |= sc->sc_flowlabel; 1711 1712 th = (struct tcphdr *)(ip6 + 1); 1713 } 1714 #endif 1715 #if defined(INET6) && defined(INET) 1716 else 1717 #endif 1718 #ifdef INET 1719 { 1720 ip = mtod(m, struct ip *); 1721 ip->ip_v = IPVERSION; 1722 ip->ip_hl = sizeof(struct ip) >> 2; 1723 ip->ip_len = htons(tlen); 1724 ip->ip_id = 0; 1725 ip->ip_off = 0; 1726 ip->ip_sum = 0; 1727 ip->ip_p = IPPROTO_TCP; 1728 ip->ip_src = sc->sc_inc.inc_laddr; 1729 ip->ip_dst = sc->sc_inc.inc_faddr; 1730 ip->ip_ttl = sc->sc_ip_ttl; 1731 ip->ip_tos = sc->sc_ip_tos; 1732 1733 /* 1734 * See if we should do MTU discovery. Route lookups are 1735 * expensive, so we will only unset the DF bit if: 1736 * 1737 * 1) path_mtu_discovery is disabled 1738 * 2) the SCF_UNREACH flag has been set 1739 */ 1740 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1741 ip->ip_off |= htons(IP_DF); 1742 1743 th = (struct tcphdr *)(ip + 1); 1744 } 1745 #endif /* INET */ 1746 th->th_sport = sc->sc_inc.inc_lport; 1747 th->th_dport = sc->sc_inc.inc_fport; 1748 1749 if (flags & TH_SYN) 1750 th->th_seq = htonl(sc->sc_iss); 1751 else 1752 th->th_seq = htonl(sc->sc_iss + 1); 1753 th->th_ack = htonl(sc->sc_irs + 1); 1754 th->th_off = sizeof(struct tcphdr) >> 2; 1755 th->th_x2 = 0; 1756 th->th_flags = flags; 1757 th->th_win = htons(sc->sc_wnd); 1758 th->th_urp = 0; 1759 1760 if ((flags & TH_SYN) && (sc->sc_flags & SCF_ECN)) { 1761 th->th_flags |= TH_ECE; 1762 TCPSTAT_INC(tcps_ecn_shs); 1763 } 1764 1765 /* Tack on the TCP options. */ 1766 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1767 to.to_flags = 0; 1768 1769 if (flags & TH_SYN) { 1770 to.to_mss = mssopt; 1771 to.to_flags = TOF_MSS; 1772 if (sc->sc_flags & SCF_WINSCALE) { 1773 to.to_wscale = sc->sc_requested_r_scale; 1774 to.to_flags |= TOF_SCALE; 1775 } 1776 if (sc->sc_flags & SCF_SACK) 1777 to.to_flags |= TOF_SACKPERM; 1778 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1779 if (sc->sc_flags & SCF_SIGNATURE) 1780 to.to_flags |= TOF_SIGNATURE; 1781 #endif 1782 if (sc->sc_tfo_cookie) { 1783 to.to_flags |= TOF_FASTOPEN; 1784 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 1785 to.to_tfo_cookie = sc->sc_tfo_cookie; 1786 /* don't send cookie again when retransmitting response */ 1787 sc->sc_tfo_cookie = NULL; 1788 } 1789 } 1790 if (sc->sc_flags & SCF_TIMESTAMP) { 1791 to.to_tsval = sc->sc_tsoff + tcp_ts_getticks(); 1792 to.to_tsecr = sc->sc_tsreflect; 1793 to.to_flags |= TOF_TS; 1794 } 1795 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1796 1797 /* Adjust headers by option size. */ 1798 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1799 m->m_len += optlen; 1800 m->m_pkthdr.len += optlen; 1801 #ifdef INET6 1802 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1803 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1804 else 1805 #endif 1806 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 1807 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1808 if (sc->sc_flags & SCF_SIGNATURE) { 1809 KASSERT(to.to_flags & TOF_SIGNATURE, 1810 ("tcp_addoptions() didn't set tcp_signature")); 1811 1812 /* NOTE: to.to_signature is inside of mbuf */ 1813 if (!TCPMD5_ENABLED() || 1814 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) { 1815 m_freem(m); 1816 return (EACCES); 1817 } 1818 } 1819 #endif 1820 } else 1821 optlen = 0; 1822 1823 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1824 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1825 /* 1826 * If we have peer's SYN and it has a flowid, then let's assign it to 1827 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid 1828 * to SYN|ACK due to lack of inp here. 1829 */ 1830 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) { 1831 m->m_pkthdr.flowid = m0->m_pkthdr.flowid; 1832 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0)); 1833 } 1834 #ifdef INET6 1835 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1836 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1837 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1838 IPPROTO_TCP, 0); 1839 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1840 #ifdef TCP_OFFLOAD 1841 if (ADDED_BY_TOE(sc)) { 1842 struct toedev *tod = sc->sc_tod; 1843 1844 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1845 1846 return (error); 1847 } 1848 #endif 1849 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th); 1850 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1851 } 1852 #endif 1853 #if defined(INET6) && defined(INET) 1854 else 1855 #endif 1856 #ifdef INET 1857 { 1858 m->m_pkthdr.csum_flags = CSUM_TCP; 1859 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1860 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1861 #ifdef TCP_OFFLOAD 1862 if (ADDED_BY_TOE(sc)) { 1863 struct toedev *tod = sc->sc_tod; 1864 1865 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1866 1867 return (error); 1868 } 1869 #endif 1870 TCP_PROBE5(send, NULL, NULL, ip, NULL, th); 1871 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1872 } 1873 #endif 1874 return (error); 1875 } 1876 1877 /* 1878 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks 1879 * that exceed the capacity of the syncache by avoiding the storage of any 1880 * of the SYNs we receive. Syncookies defend against blind SYN flooding 1881 * attacks where the attacker does not have access to our responses. 1882 * 1883 * Syncookies encode and include all necessary information about the 1884 * connection setup within the SYN|ACK that we send back. That way we 1885 * can avoid keeping any local state until the ACK to our SYN|ACK returns 1886 * (if ever). Normally the syncache and syncookies are running in parallel 1887 * with the latter taking over when the former is exhausted. When matching 1888 * syncache entry is found the syncookie is ignored. 1889 * 1890 * The only reliable information persisting the 3WHS is our initial sequence 1891 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient 1892 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS 1893 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK 1894 * returns and signifies a legitimate connection if it matches the ACK. 1895 * 1896 * The available space of 32 bits to store the hash and to encode the SYN 1897 * option information is very tight and we should have at least 24 bits for 1898 * the MAC to keep the number of guesses by blind spoofing reasonably high. 1899 * 1900 * SYN option information we have to encode to fully restore a connection: 1901 * MSS: is imporant to chose an optimal segment size to avoid IP level 1902 * fragmentation along the path. The common MSS values can be encoded 1903 * in a 3-bit table. Uncommon values are captured by the next lower value 1904 * in the table leading to a slight increase in packetization overhead. 1905 * WSCALE: is necessary to allow large windows to be used for high delay- 1906 * bandwidth product links. Not scaling the window when it was initially 1907 * negotiated is bad for performance as lack of scaling further decreases 1908 * the apparent available send window. We only need to encode the WSCALE 1909 * we received from the remote end. Our end can be recalculated at any 1910 * time. The common WSCALE values can be encoded in a 3-bit table. 1911 * Uncommon values are captured by the next lower value in the table 1912 * making us under-estimate the available window size halving our 1913 * theoretically possible maximum throughput for that connection. 1914 * SACK: Greatly assists in packet loss recovery and requires 1 bit. 1915 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options 1916 * that are included in all segments on a connection. We enable them when 1917 * the ACK has them. 1918 * 1919 * Security of syncookies and attack vectors: 1920 * 1921 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod) 1922 * together with the gloabl secret to make it unique per connection attempt. 1923 * Thus any change of any of those parameters results in a different MAC output 1924 * in an unpredictable way unless a collision is encountered. 24 bits of the 1925 * MAC are embedded into the ISS. 1926 * 1927 * To prevent replay attacks two rotating global secrets are updated with a 1928 * new random value every 15 seconds. The life-time of a syncookie is thus 1929 * 15-30 seconds. 1930 * 1931 * Vector 1: Attacking the secret. This requires finding a weakness in the 1932 * MAC itself or the way it is used here. The attacker can do a chosen plain 1933 * text attack by varying and testing the all parameters under his control. 1934 * The strength depends on the size and randomness of the secret, and the 1935 * cryptographic security of the MAC function. Due to the constant updating 1936 * of the secret the attacker has at most 29.999 seconds to find the secret 1937 * and launch spoofed connections. After that he has to start all over again. 1938 * 1939 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC 1940 * size an average of 4,823 attempts are required for a 50% chance of success 1941 * to spoof a single syncookie (birthday collision paradox). However the 1942 * attacker is blind and doesn't know if one of his attempts succeeded unless 1943 * he has a side channel to interfere success from. A single connection setup 1944 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets. 1945 * This many attempts are required for each one blind spoofed connection. For 1946 * every additional spoofed connection he has to launch another N attempts. 1947 * Thus for a sustained rate 100 spoofed connections per second approximately 1948 * 1,800,000 packets per second would have to be sent. 1949 * 1950 * NB: The MAC function should be fast so that it doesn't become a CPU 1951 * exhaustion attack vector itself. 1952 * 1953 * References: 1954 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations 1955 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996 1956 * http://cr.yp.to/syncookies.html (overview) 1957 * http://cr.yp.to/syncookies/archive (details) 1958 * 1959 * 1960 * Schematic construction of a syncookie enabled Initial Sequence Number: 1961 * 0 1 2 3 1962 * 12345678901234567890123456789012 1963 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP| 1964 * 1965 * x 24 MAC (truncated) 1966 * W 3 Send Window Scale index 1967 * M 3 MSS index 1968 * S 1 SACK permitted 1969 * P 1 Odd/even secret 1970 */ 1971 1972 /* 1973 * Distribution and probability of certain MSS values. Those in between are 1974 * rounded down to the next lower one. 1975 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011] 1976 * .2% .3% 5% 7% 7% 20% 15% 45% 1977 */ 1978 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 }; 1979 1980 /* 1981 * Distribution and probability of certain WSCALE values. We have to map the 1982 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3 1983 * bits based on prevalence of certain values. Where we don't have an exact 1984 * match for are rounded down to the next lower one letting us under-estimate 1985 * the true available window. At the moment this would happen only for the 1986 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer 1987 * and window size). The absence of the WSCALE option (no scaling in either 1988 * direction) is encoded with index zero. 1989 * [WSCALE values histograms, Allman, 2012] 1990 * X 10 10 35 5 6 14 10% by host 1991 * X 11 4 5 5 18 49 3% by connections 1992 */ 1993 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 }; 1994 1995 /* 1996 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed 1997 * and good cryptographic properties. 1998 */ 1999 static uint32_t 2000 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags, 2001 uint8_t *secbits, uintptr_t secmod) 2002 { 2003 SIPHASH_CTX ctx; 2004 uint32_t siphash[2]; 2005 2006 SipHash24_Init(&ctx); 2007 SipHash_SetKey(&ctx, secbits); 2008 switch (inc->inc_flags & INC_ISIPV6) { 2009 #ifdef INET 2010 case 0: 2011 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr)); 2012 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr)); 2013 break; 2014 #endif 2015 #ifdef INET6 2016 case INC_ISIPV6: 2017 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr)); 2018 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr)); 2019 break; 2020 #endif 2021 } 2022 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport)); 2023 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport)); 2024 SipHash_Update(&ctx, &irs, sizeof(irs)); 2025 SipHash_Update(&ctx, &flags, sizeof(flags)); 2026 SipHash_Update(&ctx, &secmod, sizeof(secmod)); 2027 SipHash_Final((u_int8_t *)&siphash, &ctx); 2028 2029 return (siphash[0] ^ siphash[1]); 2030 } 2031 2032 static tcp_seq 2033 syncookie_generate(struct syncache_head *sch, struct syncache *sc) 2034 { 2035 u_int i, secbit, wscale; 2036 uint32_t iss, hash; 2037 uint8_t *secbits; 2038 union syncookie cookie; 2039 2040 SCH_LOCK_ASSERT(sch); 2041 2042 cookie.cookie = 0; 2043 2044 /* Map our computed MSS into the 3-bit index. */ 2045 for (i = nitems(tcp_sc_msstab) - 1; 2046 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0; 2047 i--) 2048 ; 2049 cookie.flags.mss_idx = i; 2050 2051 /* 2052 * Map the send window scale into the 3-bit index but only if 2053 * the wscale option was received. 2054 */ 2055 if (sc->sc_flags & SCF_WINSCALE) { 2056 wscale = sc->sc_requested_s_scale; 2057 for (i = nitems(tcp_sc_wstab) - 1; 2058 tcp_sc_wstab[i] > wscale && i > 0; 2059 i--) 2060 ; 2061 cookie.flags.wscale_idx = i; 2062 } 2063 2064 /* Can we do SACK? */ 2065 if (sc->sc_flags & SCF_SACK) 2066 cookie.flags.sack_ok = 1; 2067 2068 /* Which of the two secrets to use. */ 2069 secbit = sch->sch_sc->secret.oddeven & 0x1; 2070 cookie.flags.odd_even = secbit; 2071 2072 secbits = sch->sch_sc->secret.key[secbit]; 2073 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits, 2074 (uintptr_t)sch); 2075 2076 /* 2077 * Put the flags into the hash and XOR them to get better ISS number 2078 * variance. This doesn't enhance the cryptographic strength and is 2079 * done to prevent the 8 cookie bits from showing up directly on the 2080 * wire. 2081 */ 2082 iss = hash & ~0xff; 2083 iss |= cookie.cookie ^ (hash >> 24); 2084 2085 TCPSTAT_INC(tcps_sc_sendcookie); 2086 return (iss); 2087 } 2088 2089 static struct syncache * 2090 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 2091 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2092 struct socket *lso) 2093 { 2094 uint32_t hash; 2095 uint8_t *secbits; 2096 tcp_seq ack, seq; 2097 int wnd, wscale = 0; 2098 union syncookie cookie; 2099 2100 SCH_LOCK_ASSERT(sch); 2101 2102 /* 2103 * Pull information out of SYN-ACK/ACK and revert sequence number 2104 * advances. 2105 */ 2106 ack = th->th_ack - 1; 2107 seq = th->th_seq - 1; 2108 2109 /* 2110 * Unpack the flags containing enough information to restore the 2111 * connection. 2112 */ 2113 cookie.cookie = (ack & 0xff) ^ (ack >> 24); 2114 2115 /* Which of the two secrets to use. */ 2116 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even]; 2117 2118 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch); 2119 2120 /* The recomputed hash matches the ACK if this was a genuine cookie. */ 2121 if ((ack & ~0xff) != (hash & ~0xff)) 2122 return (NULL); 2123 2124 /* Fill in the syncache values. */ 2125 sc->sc_flags = 0; 2126 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 2127 sc->sc_ipopts = NULL; 2128 2129 sc->sc_irs = seq; 2130 sc->sc_iss = ack; 2131 2132 switch (inc->inc_flags & INC_ISIPV6) { 2133 #ifdef INET 2134 case 0: 2135 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl; 2136 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos; 2137 break; 2138 #endif 2139 #ifdef INET6 2140 case INC_ISIPV6: 2141 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL) 2142 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK; 2143 break; 2144 #endif 2145 } 2146 2147 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx]; 2148 2149 /* We can simply recompute receive window scale we sent earlier. */ 2150 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max) 2151 wscale++; 2152 2153 /* Only use wscale if it was enabled in the orignal SYN. */ 2154 if (cookie.flags.wscale_idx > 0) { 2155 sc->sc_requested_r_scale = wscale; 2156 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx]; 2157 sc->sc_flags |= SCF_WINSCALE; 2158 } 2159 2160 wnd = lso->sol_sbrcv_hiwat; 2161 wnd = imax(wnd, 0); 2162 wnd = imin(wnd, TCP_MAXWIN); 2163 sc->sc_wnd = wnd; 2164 2165 if (cookie.flags.sack_ok) 2166 sc->sc_flags |= SCF_SACK; 2167 2168 if (to->to_flags & TOF_TS) { 2169 sc->sc_flags |= SCF_TIMESTAMP; 2170 sc->sc_tsreflect = to->to_tsval; 2171 sc->sc_tsoff = tcp_new_ts_offset(inc); 2172 } 2173 2174 if (to->to_flags & TOF_SIGNATURE) 2175 sc->sc_flags |= SCF_SIGNATURE; 2176 2177 sc->sc_rxmits = 0; 2178 2179 TCPSTAT_INC(tcps_sc_recvcookie); 2180 return (sc); 2181 } 2182 2183 #ifdef INVARIANTS 2184 static int 2185 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 2186 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2187 struct socket *lso) 2188 { 2189 struct syncache scs, *scx; 2190 char *s; 2191 2192 bzero(&scs, sizeof(scs)); 2193 scx = syncookie_lookup(inc, sch, &scs, th, to, lso); 2194 2195 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL) 2196 return (0); 2197 2198 if (scx != NULL) { 2199 if (sc->sc_peer_mss != scx->sc_peer_mss) 2200 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n", 2201 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss); 2202 2203 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale) 2204 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n", 2205 s, __func__, sc->sc_requested_r_scale, 2206 scx->sc_requested_r_scale); 2207 2208 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale) 2209 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n", 2210 s, __func__, sc->sc_requested_s_scale, 2211 scx->sc_requested_s_scale); 2212 2213 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK)) 2214 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__); 2215 } 2216 2217 if (s != NULL) 2218 free(s, M_TCPLOG); 2219 return (0); 2220 } 2221 #endif /* INVARIANTS */ 2222 2223 static void 2224 syncookie_reseed(void *arg) 2225 { 2226 struct tcp_syncache *sc = arg; 2227 uint8_t *secbits; 2228 int secbit; 2229 2230 /* 2231 * Reseeding the secret doesn't have to be protected by a lock. 2232 * It only must be ensured that the new random values are visible 2233 * to all CPUs in a SMP environment. The atomic with release 2234 * semantics ensures that. 2235 */ 2236 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1; 2237 secbits = sc->secret.key[secbit]; 2238 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0); 2239 atomic_add_rel_int(&sc->secret.oddeven, 1); 2240 2241 /* Reschedule ourself. */ 2242 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz); 2243 } 2244 2245 /* 2246 * Exports the syncache entries to userland so that netstat can display 2247 * them alongside the other sockets. This function is intended to be 2248 * called only from tcp_pcblist. 2249 * 2250 * Due to concurrency on an active system, the number of pcbs exported 2251 * may have no relation to max_pcbs. max_pcbs merely indicates the 2252 * amount of space the caller allocated for this function to use. 2253 */ 2254 int 2255 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 2256 { 2257 struct xtcpcb xt; 2258 struct syncache *sc; 2259 struct syncache_head *sch; 2260 int count, error, i; 2261 2262 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 2263 sch = &V_tcp_syncache.hashbase[i]; 2264 SCH_LOCK(sch); 2265 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 2266 if (count >= max_pcbs) { 2267 SCH_UNLOCK(sch); 2268 goto exit; 2269 } 2270 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 2271 continue; 2272 bzero(&xt, sizeof(xt)); 2273 xt.xt_len = sizeof(xt); 2274 if (sc->sc_inc.inc_flags & INC_ISIPV6) 2275 xt.xt_inp.inp_vflag = INP_IPV6; 2276 else 2277 xt.xt_inp.inp_vflag = INP_IPV4; 2278 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, 2279 sizeof (struct in_conninfo)); 2280 xt.t_state = TCPS_SYN_RECEIVED; 2281 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP; 2282 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket); 2283 xt.xt_inp.xi_socket.so_type = SOCK_STREAM; 2284 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING; 2285 error = SYSCTL_OUT(req, &xt, sizeof xt); 2286 if (error) { 2287 SCH_UNLOCK(sch); 2288 goto exit; 2289 } 2290 count++; 2291 } 2292 SCH_UNLOCK(sch); 2293 } 2294 exit: 2295 *pcbs_exported = count; 2296 return error; 2297 } 2298