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 *, const struct mbuf *, int); 134 static struct socket *syncache_socket(struct syncache *, struct socket *, 135 struct mbuf *m); 136 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 137 int docallout); 138 static void syncache_timer(void *); 139 140 static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t, 141 uint8_t *, uintptr_t); 142 static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *); 143 static struct syncache 144 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 145 struct syncache *, struct tcphdr *, struct tcpopt *, 146 struct socket *); 147 static void syncookie_reseed(void *); 148 #ifdef INVARIANTS 149 static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 150 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 151 struct socket *lso); 152 #endif 153 154 /* 155 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 156 * 3 retransmits corresponds to a timeout with default values of 157 * tcp_rexmit_initial * ( 1 + 158 * tcp_backoff[1] + 159 * tcp_backoff[2] + 160 * tcp_backoff[3]) + 3 * tcp_rexmit_slop, 161 * 1000 ms * (1 + 2 + 4 + 8) + 3 * 200 ms = 15600 ms, 162 * the odds are that the user has given up attempting to connect by then. 163 */ 164 #define SYNCACHE_MAXREXMTS 3 165 166 /* Arbitrary values */ 167 #define TCP_SYNCACHE_HASHSIZE 512 168 #define TCP_SYNCACHE_BUCKETLIMIT 30 169 170 VNET_DEFINE_STATIC(struct tcp_syncache, tcp_syncache); 171 #define V_tcp_syncache VNET(tcp_syncache) 172 173 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, 174 "TCP SYN cache"); 175 176 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN, 177 &VNET_NAME(tcp_syncache.bucket_limit), 0, 178 "Per-bucket hash limit for syncache"); 179 180 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN, 181 &VNET_NAME(tcp_syncache.cache_limit), 0, 182 "Overall entry limit for syncache"); 183 184 SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET, 185 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache"); 186 187 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN, 188 &VNET_NAME(tcp_syncache.hashsize), 0, 189 "Size of TCP syncache hashtable"); 190 191 static int 192 sysctl_net_inet_tcp_syncache_rexmtlimit_check(SYSCTL_HANDLER_ARGS) 193 { 194 int error; 195 u_int new; 196 197 new = V_tcp_syncache.rexmt_limit; 198 error = sysctl_handle_int(oidp, &new, 0, req); 199 if ((error == 0) && (req->newptr != NULL)) { 200 if (new > TCP_MAXRXTSHIFT) 201 error = EINVAL; 202 else 203 V_tcp_syncache.rexmt_limit = new; 204 } 205 return (error); 206 } 207 208 SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, 209 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW, 210 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 211 sysctl_net_inet_tcp_syncache_rexmtlimit_check, "UI", 212 "Limit on SYN/ACK retransmissions"); 213 214 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 215 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 216 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 217 "Send reset on socket allocation failure"); 218 219 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 220 221 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 222 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 223 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 224 225 /* 226 * Requires the syncache entry to be already removed from the bucket list. 227 */ 228 static void 229 syncache_free(struct syncache *sc) 230 { 231 232 if (sc->sc_ipopts) 233 (void) m_free(sc->sc_ipopts); 234 if (sc->sc_cred) 235 crfree(sc->sc_cred); 236 #ifdef MAC 237 mac_syncache_destroy(&sc->sc_label); 238 #endif 239 240 uma_zfree(V_tcp_syncache.zone, sc); 241 } 242 243 void 244 syncache_init(void) 245 { 246 int i; 247 248 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 249 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 250 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 251 V_tcp_syncache.hash_secret = arc4random(); 252 253 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 254 &V_tcp_syncache.hashsize); 255 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 256 &V_tcp_syncache.bucket_limit); 257 if (!powerof2(V_tcp_syncache.hashsize) || 258 V_tcp_syncache.hashsize == 0) { 259 printf("WARNING: syncache hash size is not a power of 2.\n"); 260 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 261 } 262 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 263 264 /* Set limits. */ 265 V_tcp_syncache.cache_limit = 266 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 267 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 268 &V_tcp_syncache.cache_limit); 269 270 /* Allocate the hash table. */ 271 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 272 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 273 274 #ifdef VIMAGE 275 V_tcp_syncache.vnet = curvnet; 276 #endif 277 278 /* Initialize the hash buckets. */ 279 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 280 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 281 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 282 NULL, MTX_DEF); 283 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 284 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 285 V_tcp_syncache.hashbase[i].sch_length = 0; 286 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache; 287 V_tcp_syncache.hashbase[i].sch_last_overflow = 288 -(SYNCOOKIE_LIFETIME + 1); 289 } 290 291 /* Create the syncache entry zone. */ 292 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 293 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 294 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone, 295 V_tcp_syncache.cache_limit); 296 297 /* Start the SYN cookie reseeder callout. */ 298 callout_init(&V_tcp_syncache.secret.reseed, 1); 299 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0); 300 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0); 301 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz, 302 syncookie_reseed, &V_tcp_syncache); 303 } 304 305 #ifdef VIMAGE 306 void 307 syncache_destroy(void) 308 { 309 struct syncache_head *sch; 310 struct syncache *sc, *nsc; 311 int i; 312 313 /* 314 * Stop the re-seed timer before freeing resources. No need to 315 * possibly schedule it another time. 316 */ 317 callout_drain(&V_tcp_syncache.secret.reseed); 318 319 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 320 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 321 322 sch = &V_tcp_syncache.hashbase[i]; 323 callout_drain(&sch->sch_timer); 324 325 SCH_LOCK(sch); 326 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 327 syncache_drop(sc, sch); 328 SCH_UNLOCK(sch); 329 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 330 ("%s: sch->sch_bucket not empty", __func__)); 331 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 332 __func__, sch->sch_length)); 333 mtx_destroy(&sch->sch_mtx); 334 } 335 336 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0, 337 ("%s: cache_count not 0", __func__)); 338 339 /* Free the allocated global resources. */ 340 uma_zdestroy(V_tcp_syncache.zone); 341 free(V_tcp_syncache.hashbase, M_SYNCACHE); 342 } 343 #endif 344 345 /* 346 * Inserts a syncache entry into the specified bucket row. 347 * Locks and unlocks the syncache_head autonomously. 348 */ 349 static void 350 syncache_insert(struct syncache *sc, struct syncache_head *sch) 351 { 352 struct syncache *sc2; 353 354 SCH_LOCK(sch); 355 356 /* 357 * Make sure that we don't overflow the per-bucket limit. 358 * If the bucket is full, toss the oldest element. 359 */ 360 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 361 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 362 ("sch->sch_length incorrect")); 363 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 364 sch->sch_last_overflow = time_uptime; 365 syncache_drop(sc2, sch); 366 TCPSTAT_INC(tcps_sc_bucketoverflow); 367 } 368 369 /* Put it into the bucket. */ 370 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 371 sch->sch_length++; 372 373 #ifdef TCP_OFFLOAD 374 if (ADDED_BY_TOE(sc)) { 375 struct toedev *tod = sc->sc_tod; 376 377 tod->tod_syncache_added(tod, sc->sc_todctx); 378 } 379 #endif 380 381 /* Reinitialize the bucket row's timer. */ 382 if (sch->sch_length == 1) 383 sch->sch_nextc = ticks + INT_MAX; 384 syncache_timeout(sc, sch, 1); 385 386 SCH_UNLOCK(sch); 387 388 TCPSTATES_INC(TCPS_SYN_RECEIVED); 389 TCPSTAT_INC(tcps_sc_added); 390 } 391 392 /* 393 * Remove and free entry from syncache bucket row. 394 * Expects locked syncache head. 395 */ 396 static void 397 syncache_drop(struct syncache *sc, struct syncache_head *sch) 398 { 399 400 SCH_LOCK_ASSERT(sch); 401 402 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 403 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 404 sch->sch_length--; 405 406 #ifdef TCP_OFFLOAD 407 if (ADDED_BY_TOE(sc)) { 408 struct toedev *tod = sc->sc_tod; 409 410 tod->tod_syncache_removed(tod, sc->sc_todctx); 411 } 412 #endif 413 414 syncache_free(sc); 415 } 416 417 /* 418 * Engage/reengage time on bucket row. 419 */ 420 static void 421 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 422 { 423 int rexmt; 424 425 if (sc->sc_rxmits == 0) 426 rexmt = tcp_rexmit_initial; 427 else 428 TCPT_RANGESET(rexmt, 429 tcp_rexmit_initial * 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, 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, 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 #ifdef NUMA 780 inp->inp_numa_domain = m->m_pkthdr.numa_domain; 781 #endif 782 } 783 784 /* 785 * Install in the reservation hash table for now, but don't yet 786 * install a connection group since the full 4-tuple isn't yet 787 * configured. 788 */ 789 inp->inp_lport = sc->sc_inc.inc_lport; 790 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 791 /* 792 * Undo the assignments above if we failed to 793 * put the PCB on the hash lists. 794 */ 795 #ifdef INET6 796 if (sc->sc_inc.inc_flags & INC_ISIPV6) 797 inp->in6p_laddr = in6addr_any; 798 else 799 #endif 800 inp->inp_laddr.s_addr = INADDR_ANY; 801 inp->inp_lport = 0; 802 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 803 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 804 "with error %i\n", 805 s, __func__, error); 806 free(s, M_TCPLOG); 807 } 808 INP_HASH_WUNLOCK(&V_tcbinfo); 809 goto abort; 810 } 811 #ifdef INET6 812 if (inp->inp_vflag & INP_IPV6PROTO) { 813 struct inpcb *oinp = sotoinpcb(lso); 814 815 /* 816 * Inherit socket options from the listening socket. 817 * Note that in6p_inputopts are not (and should not be) 818 * copied, since it stores previously received options and is 819 * used to detect if each new option is different than the 820 * previous one and hence should be passed to a user. 821 * If we copied in6p_inputopts, a user would not be able to 822 * receive options just after calling the accept system call. 823 */ 824 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 825 if (oinp->in6p_outputopts) 826 inp->in6p_outputopts = 827 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 828 } 829 830 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 831 struct in6_addr laddr6; 832 struct sockaddr_in6 sin6; 833 834 sin6.sin6_family = AF_INET6; 835 sin6.sin6_len = sizeof(sin6); 836 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 837 sin6.sin6_port = sc->sc_inc.inc_fport; 838 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 839 laddr6 = inp->in6p_laddr; 840 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 841 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 842 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 843 thread0.td_ucred, m)) != 0) { 844 inp->in6p_laddr = laddr6; 845 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 846 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 847 "with error %i\n", 848 s, __func__, error); 849 free(s, M_TCPLOG); 850 } 851 INP_HASH_WUNLOCK(&V_tcbinfo); 852 goto abort; 853 } 854 /* Override flowlabel from in6_pcbconnect. */ 855 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 856 inp->inp_flow |= sc->sc_flowlabel; 857 } 858 #endif /* INET6 */ 859 #if defined(INET) && defined(INET6) 860 else 861 #endif 862 #ifdef INET 863 { 864 struct in_addr laddr; 865 struct sockaddr_in sin; 866 867 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 868 869 if (inp->inp_options == NULL) { 870 inp->inp_options = sc->sc_ipopts; 871 sc->sc_ipopts = NULL; 872 } 873 874 sin.sin_family = AF_INET; 875 sin.sin_len = sizeof(sin); 876 sin.sin_addr = sc->sc_inc.inc_faddr; 877 sin.sin_port = sc->sc_inc.inc_fport; 878 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 879 laddr = inp->inp_laddr; 880 if (inp->inp_laddr.s_addr == INADDR_ANY) 881 inp->inp_laddr = sc->sc_inc.inc_laddr; 882 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 883 thread0.td_ucred, m)) != 0) { 884 inp->inp_laddr = laddr; 885 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 886 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 887 "with error %i\n", 888 s, __func__, error); 889 free(s, M_TCPLOG); 890 } 891 INP_HASH_WUNLOCK(&V_tcbinfo); 892 goto abort; 893 } 894 } 895 #endif /* INET */ 896 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 897 /* Copy old policy into new socket's. */ 898 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0) 899 printf("syncache_socket: could not copy policy\n"); 900 #endif 901 INP_HASH_WUNLOCK(&V_tcbinfo); 902 tp = intotcpcb(inp); 903 tcp_state_change(tp, TCPS_SYN_RECEIVED); 904 tp->iss = sc->sc_iss; 905 tp->irs = sc->sc_irs; 906 tcp_rcvseqinit(tp); 907 tcp_sendseqinit(tp); 908 blk = sototcpcb(lso)->t_fb; 909 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) { 910 /* 911 * Our parents t_fb was not the default, 912 * we need to release our ref on tp->t_fb and 913 * pickup one on the new entry. 914 */ 915 struct tcp_function_block *rblk; 916 917 rblk = find_and_ref_tcp_fb(blk); 918 KASSERT(rblk != NULL, 919 ("cannot find blk %p out of syncache?", blk)); 920 if (tp->t_fb->tfb_tcp_fb_fini) 921 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0); 922 refcount_release(&tp->t_fb->tfb_refcnt); 923 tp->t_fb = rblk; 924 /* 925 * XXXrrs this is quite dangerous, it is possible 926 * for the new function to fail to init. We also 927 * are not asking if the handoff_is_ok though at 928 * the very start thats probalbly ok. 929 */ 930 if (tp->t_fb->tfb_tcp_fb_init) { 931 (*tp->t_fb->tfb_tcp_fb_init)(tp); 932 } 933 } 934 tp->snd_wl1 = sc->sc_irs; 935 tp->snd_max = tp->iss + 1; 936 tp->snd_nxt = tp->iss + 1; 937 tp->rcv_up = sc->sc_irs + 1; 938 tp->rcv_wnd = sc->sc_wnd; 939 tp->rcv_adv += tp->rcv_wnd; 940 tp->last_ack_sent = tp->rcv_nxt; 941 942 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 943 if (sc->sc_flags & SCF_NOOPT) 944 tp->t_flags |= TF_NOOPT; 945 else { 946 if (sc->sc_flags & SCF_WINSCALE) { 947 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 948 tp->snd_scale = sc->sc_requested_s_scale; 949 tp->request_r_scale = sc->sc_requested_r_scale; 950 } 951 if (sc->sc_flags & SCF_TIMESTAMP) { 952 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 953 tp->ts_recent = sc->sc_tsreflect; 954 tp->ts_recent_age = tcp_ts_getticks(); 955 tp->ts_offset = sc->sc_tsoff; 956 } 957 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 958 if (sc->sc_flags & SCF_SIGNATURE) 959 tp->t_flags |= TF_SIGNATURE; 960 #endif 961 if (sc->sc_flags & SCF_SACK) 962 tp->t_flags |= TF_SACK_PERMIT; 963 } 964 965 if (sc->sc_flags & SCF_ECN) 966 tp->t_flags |= TF_ECN_PERMIT; 967 968 /* 969 * Set up MSS and get cached values from tcp_hostcache. 970 * This might overwrite some of the defaults we just set. 971 */ 972 tcp_mss(tp, sc->sc_peer_mss); 973 974 /* 975 * If the SYN,ACK was retransmitted, indicate that CWND to be 976 * limited to one segment in cc_conn_init(). 977 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 978 */ 979 if (sc->sc_rxmits > 1) 980 tp->snd_cwnd = 1; 981 982 #ifdef TCP_OFFLOAD 983 /* 984 * Allow a TOE driver to install its hooks. Note that we hold the 985 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a 986 * new connection before the TOE driver has done its thing. 987 */ 988 if (ADDED_BY_TOE(sc)) { 989 struct toedev *tod = sc->sc_tod; 990 991 tod->tod_offload_socket(tod, sc->sc_todctx, so); 992 } 993 #endif 994 /* 995 * Copy and activate timers. 996 */ 997 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 998 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 999 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 1000 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 1001 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 1002 1003 TCPSTAT_INC(tcps_accepts); 1004 return (so); 1005 1006 abort: 1007 INP_WUNLOCK(inp); 1008 abort2: 1009 if (so != NULL) 1010 soabort(so); 1011 return (NULL); 1012 } 1013 1014 /* 1015 * This function gets called when we receive an ACK for a 1016 * socket in the LISTEN state. We look up the connection 1017 * in the syncache, and if its there, we pull it out of 1018 * the cache and turn it into a full-blown connection in 1019 * the SYN-RECEIVED state. 1020 * 1021 * On syncache_socket() success the newly created socket 1022 * has its underlying inp locked. 1023 */ 1024 int 1025 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1026 struct socket **lsop, struct mbuf *m) 1027 { 1028 struct syncache *sc; 1029 struct syncache_head *sch; 1030 struct syncache scs; 1031 char *s; 1032 1033 /* 1034 * Global TCP locks are held because we manipulate the PCB lists 1035 * and create a new socket. 1036 */ 1037 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1038 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 1039 ("%s: can handle only ACK", __func__)); 1040 1041 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 1042 SCH_LOCK_ASSERT(sch); 1043 1044 #ifdef INVARIANTS 1045 /* 1046 * Test code for syncookies comparing the syncache stored 1047 * values with the reconstructed values from the cookie. 1048 */ 1049 if (sc != NULL) 1050 syncookie_cmp(inc, sch, sc, th, to, *lsop); 1051 #endif 1052 1053 if (sc == NULL) { 1054 /* 1055 * There is no syncache entry, so see if this ACK is 1056 * a returning syncookie. To do this, first: 1057 * A. Check if syncookies are used in case of syncache 1058 * overflows 1059 * B. See if this socket has had a syncache entry dropped in 1060 * the recent past. We don't want to accept a bogus 1061 * syncookie if we've never received a SYN or accept it 1062 * twice. 1063 * C. check that the syncookie is valid. If it is, then 1064 * cobble up a fake syncache entry, and return. 1065 */ 1066 if (!V_tcp_syncookies) { 1067 SCH_UNLOCK(sch); 1068 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1069 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1070 "segment rejected (syncookies disabled)\n", 1071 s, __func__); 1072 goto failed; 1073 } 1074 if (!V_tcp_syncookiesonly && 1075 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) { 1076 SCH_UNLOCK(sch); 1077 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1078 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 1079 "segment rejected (no syncache entry)\n", 1080 s, __func__); 1081 goto failed; 1082 } 1083 bzero(&scs, sizeof(scs)); 1084 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop); 1085 SCH_UNLOCK(sch); 1086 if (sc == NULL) { 1087 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1088 log(LOG_DEBUG, "%s; %s: Segment failed " 1089 "SYNCOOKIE authentication, segment rejected " 1090 "(probably spoofed)\n", s, __func__); 1091 goto failed; 1092 } 1093 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1094 /* If received ACK has MD5 signature, check it. */ 1095 if ((to->to_flags & TOF_SIGNATURE) != 0 && 1096 (!TCPMD5_ENABLED() || 1097 TCPMD5_INPUT(m, th, to->to_signature) != 0)) { 1098 /* Drop the ACK. */ 1099 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1100 log(LOG_DEBUG, "%s; %s: Segment rejected, " 1101 "MD5 signature doesn't match.\n", 1102 s, __func__); 1103 free(s, M_TCPLOG); 1104 } 1105 TCPSTAT_INC(tcps_sig_err_sigopt); 1106 return (-1); /* Do not send RST */ 1107 } 1108 #endif /* TCP_SIGNATURE */ 1109 } else { 1110 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1111 /* 1112 * If listening socket requested TCP digests, check that 1113 * received ACK has signature and it is correct. 1114 * If not, drop the ACK and leave sc entry in th cache, 1115 * because SYN was received with correct signature. 1116 */ 1117 if (sc->sc_flags & SCF_SIGNATURE) { 1118 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1119 /* No signature */ 1120 TCPSTAT_INC(tcps_sig_err_nosigopt); 1121 SCH_UNLOCK(sch); 1122 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1123 log(LOG_DEBUG, "%s; %s: Segment " 1124 "rejected, MD5 signature wasn't " 1125 "provided.\n", s, __func__); 1126 free(s, M_TCPLOG); 1127 } 1128 return (-1); /* Do not send RST */ 1129 } 1130 if (!TCPMD5_ENABLED() || 1131 TCPMD5_INPUT(m, th, to->to_signature) != 0) { 1132 /* Doesn't match or no SA */ 1133 SCH_UNLOCK(sch); 1134 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1135 log(LOG_DEBUG, "%s; %s: Segment " 1136 "rejected, MD5 signature doesn't " 1137 "match.\n", s, __func__); 1138 free(s, M_TCPLOG); 1139 } 1140 return (-1); /* Do not send RST */ 1141 } 1142 } 1143 #endif /* TCP_SIGNATURE */ 1144 1145 /* 1146 * RFC 7323 PAWS: If we have a timestamp on this segment and 1147 * it's less than ts_recent, drop it. 1148 * XXXMT: RFC 7323 also requires to send an ACK. 1149 * In tcp_input.c this is only done for TCP segments 1150 * with user data, so be consistent here and just drop 1151 * the segment. 1152 */ 1153 if (sc->sc_flags & SCF_TIMESTAMP && to->to_flags & TOF_TS && 1154 TSTMP_LT(to->to_tsval, sc->sc_tsreflect)) { 1155 SCH_UNLOCK(sch); 1156 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1157 log(LOG_DEBUG, 1158 "%s; %s: SEG.TSval %u < TS.Recent %u, " 1159 "segment dropped\n", s, __func__, 1160 to->to_tsval, sc->sc_tsreflect); 1161 free(s, M_TCPLOG); 1162 } 1163 return (-1); /* Do not send RST */ 1164 } 1165 1166 /* 1167 * Pull out the entry to unlock the bucket row. 1168 * 1169 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not 1170 * tcp_state_change(). The tcpcb is not existent at this 1171 * moment. A new one will be allocated via syncache_socket-> 1172 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then 1173 * syncache_socket() will change it to TCPS_SYN_RECEIVED. 1174 */ 1175 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 1176 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 1177 sch->sch_length--; 1178 #ifdef TCP_OFFLOAD 1179 if (ADDED_BY_TOE(sc)) { 1180 struct toedev *tod = sc->sc_tod; 1181 1182 tod->tod_syncache_removed(tod, sc->sc_todctx); 1183 } 1184 #endif 1185 SCH_UNLOCK(sch); 1186 } 1187 1188 /* 1189 * Segment validation: 1190 * ACK must match our initial sequence number + 1 (the SYN|ACK). 1191 */ 1192 if (th->th_ack != sc->sc_iss + 1) { 1193 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1194 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 1195 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 1196 goto failed; 1197 } 1198 1199 /* 1200 * The SEQ must fall in the window starting at the received 1201 * initial receive sequence number + 1 (the SYN). 1202 */ 1203 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 1204 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 1205 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1206 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 1207 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 1208 goto failed; 1209 } 1210 1211 /* 1212 * If timestamps were not negotiated during SYN/ACK they 1213 * must not appear on any segment during this session. 1214 */ 1215 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 1216 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1217 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1218 "segment rejected\n", s, __func__); 1219 goto failed; 1220 } 1221 1222 /* 1223 * If timestamps were negotiated during SYN/ACK they should 1224 * appear on every segment during this session. 1225 * XXXAO: This is only informal as there have been unverified 1226 * reports of non-compliants stacks. 1227 */ 1228 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) { 1229 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1230 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1231 "no action\n", s, __func__); 1232 free(s, M_TCPLOG); 1233 s = NULL; 1234 } 1235 } 1236 1237 *lsop = syncache_socket(sc, *lsop, m); 1238 1239 if (*lsop == NULL) 1240 TCPSTAT_INC(tcps_sc_aborted); 1241 else 1242 TCPSTAT_INC(tcps_sc_completed); 1243 1244 /* how do we find the inp for the new socket? */ 1245 if (sc != &scs) 1246 syncache_free(sc); 1247 return (1); 1248 failed: 1249 if (sc != NULL && sc != &scs) 1250 syncache_free(sc); 1251 if (s != NULL) 1252 free(s, M_TCPLOG); 1253 *lsop = NULL; 1254 return (0); 1255 } 1256 1257 static void 1258 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m, 1259 uint64_t response_cookie) 1260 { 1261 struct inpcb *inp; 1262 struct tcpcb *tp; 1263 unsigned int *pending_counter; 1264 1265 /* 1266 * Global TCP locks are held because we manipulate the PCB lists 1267 * and create a new socket. 1268 */ 1269 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1270 1271 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending; 1272 *lsop = syncache_socket(sc, *lsop, m); 1273 if (*lsop == NULL) { 1274 TCPSTAT_INC(tcps_sc_aborted); 1275 atomic_subtract_int(pending_counter, 1); 1276 } else { 1277 soisconnected(*lsop); 1278 inp = sotoinpcb(*lsop); 1279 tp = intotcpcb(inp); 1280 tp->t_flags |= TF_FASTOPEN; 1281 tp->t_tfo_cookie.server = response_cookie; 1282 tp->snd_max = tp->iss; 1283 tp->snd_nxt = tp->iss; 1284 tp->t_tfo_pending = pending_counter; 1285 TCPSTAT_INC(tcps_sc_completed); 1286 } 1287 } 1288 1289 /* 1290 * Given a LISTEN socket and an inbound SYN request, add 1291 * this to the syn cache, and send back a segment: 1292 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1293 * to the source. 1294 * 1295 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1296 * Doing so would require that we hold onto the data and deliver it 1297 * to the application. However, if we are the target of a SYN-flood 1298 * DoS attack, an attacker could send data which would eventually 1299 * consume all available buffer space if it were ACKed. By not ACKing 1300 * the data, we avoid this DoS scenario. 1301 * 1302 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO) 1303 * cookie is processed and a new socket is created. In this case, any data 1304 * accompanying the SYN will be queued to the socket by tcp_input() and will 1305 * be ACKed either when the application sends response data or the delayed 1306 * ACK timer expires, whichever comes first. 1307 */ 1308 int 1309 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1310 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1311 void *todctx) 1312 { 1313 struct tcpcb *tp; 1314 struct socket *so; 1315 struct syncache *sc = NULL; 1316 struct syncache_head *sch; 1317 struct mbuf *ipopts = NULL; 1318 u_int ltflags; 1319 int win, ip_ttl, ip_tos; 1320 char *s; 1321 int rv = 0; 1322 #ifdef INET6 1323 int autoflowlabel = 0; 1324 #endif 1325 #ifdef MAC 1326 struct label *maclabel; 1327 #endif 1328 struct syncache scs; 1329 struct ucred *cred; 1330 uint64_t tfo_response_cookie; 1331 unsigned int *tfo_pending = NULL; 1332 int tfo_cookie_valid = 0; 1333 int tfo_response_cookie_valid = 0; 1334 1335 INP_WLOCK_ASSERT(inp); /* listen socket */ 1336 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1337 ("%s: unexpected tcp flags", __func__)); 1338 1339 /* 1340 * Combine all so/tp operations very early to drop the INP lock as 1341 * soon as possible. 1342 */ 1343 so = *lsop; 1344 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so)); 1345 tp = sototcpcb(so); 1346 cred = crhold(so->so_cred); 1347 1348 #ifdef INET6 1349 if ((inc->inc_flags & INC_ISIPV6) && 1350 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1351 autoflowlabel = 1; 1352 #endif 1353 ip_ttl = inp->inp_ip_ttl; 1354 ip_tos = inp->inp_ip_tos; 1355 win = so->sol_sbrcv_hiwat; 1356 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1357 1358 if (V_tcp_fastopen_server_enable && IS_FASTOPEN(tp->t_flags) && 1359 (tp->t_tfo_pending != NULL) && 1360 (to->to_flags & TOF_FASTOPEN)) { 1361 /* 1362 * Limit the number of pending TFO connections to 1363 * approximately half of the queue limit. This prevents TFO 1364 * SYN floods from starving the service by filling the 1365 * listen queue with bogus TFO connections. 1366 */ 1367 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <= 1368 (so->sol_qlimit / 2)) { 1369 int result; 1370 1371 result = tcp_fastopen_check_cookie(inc, 1372 to->to_tfo_cookie, to->to_tfo_len, 1373 &tfo_response_cookie); 1374 tfo_cookie_valid = (result > 0); 1375 tfo_response_cookie_valid = (result >= 0); 1376 } 1377 1378 /* 1379 * Remember the TFO pending counter as it will have to be 1380 * decremented below if we don't make it to syncache_tfo_expand(). 1381 */ 1382 tfo_pending = tp->t_tfo_pending; 1383 } 1384 1385 /* By the time we drop the lock these should no longer be used. */ 1386 so = NULL; 1387 tp = NULL; 1388 1389 #ifdef MAC 1390 if (mac_syncache_init(&maclabel) != 0) { 1391 INP_WUNLOCK(inp); 1392 goto done; 1393 } else 1394 mac_syncache_create(maclabel, inp); 1395 #endif 1396 if (!tfo_cookie_valid) 1397 INP_WUNLOCK(inp); 1398 1399 /* 1400 * Remember the IP options, if any. 1401 */ 1402 #ifdef INET6 1403 if (!(inc->inc_flags & INC_ISIPV6)) 1404 #endif 1405 #ifdef INET 1406 ipopts = (m) ? ip_srcroute(m) : NULL; 1407 #else 1408 ipopts = NULL; 1409 #endif 1410 1411 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1412 /* 1413 * If listening socket requested TCP digests, check that received 1414 * SYN has signature and it is correct. If signature doesn't match 1415 * or TCP_SIGNATURE support isn't enabled, drop the packet. 1416 */ 1417 if (ltflags & TF_SIGNATURE) { 1418 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1419 TCPSTAT_INC(tcps_sig_err_nosigopt); 1420 goto done; 1421 } 1422 if (!TCPMD5_ENABLED() || 1423 TCPMD5_INPUT(m, th, to->to_signature) != 0) 1424 goto done; 1425 } 1426 #endif /* TCP_SIGNATURE */ 1427 /* 1428 * See if we already have an entry for this connection. 1429 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1430 * 1431 * XXX: should the syncache be re-initialized with the contents 1432 * of the new SYN here (which may have different options?) 1433 * 1434 * XXX: We do not check the sequence number to see if this is a 1435 * real retransmit or a new connection attempt. The question is 1436 * how to handle such a case; either ignore it as spoofed, or 1437 * drop the current entry and create a new one? 1438 */ 1439 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1440 SCH_LOCK_ASSERT(sch); 1441 if (sc != NULL) { 1442 if (tfo_cookie_valid) 1443 INP_WUNLOCK(inp); 1444 TCPSTAT_INC(tcps_sc_dupsyn); 1445 if (ipopts) { 1446 /* 1447 * If we were remembering a previous source route, 1448 * forget it and use the new one we've been given. 1449 */ 1450 if (sc->sc_ipopts) 1451 (void) m_free(sc->sc_ipopts); 1452 sc->sc_ipopts = ipopts; 1453 } 1454 /* 1455 * Update timestamp if present. 1456 */ 1457 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1458 sc->sc_tsreflect = to->to_tsval; 1459 else 1460 sc->sc_flags &= ~SCF_TIMESTAMP; 1461 #ifdef MAC 1462 /* 1463 * Since we have already unconditionally allocated label 1464 * storage, free it up. The syncache entry will already 1465 * have an initialized label we can use. 1466 */ 1467 mac_syncache_destroy(&maclabel); 1468 #endif 1469 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1470 /* Retransmit SYN|ACK and reset retransmit count. */ 1471 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1472 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1473 "resetting timer and retransmitting SYN|ACK\n", 1474 s, __func__); 1475 free(s, M_TCPLOG); 1476 } 1477 if (syncache_respond(sc, m, TH_SYN|TH_ACK) == 0) { 1478 sc->sc_rxmits = 0; 1479 syncache_timeout(sc, sch, 1); 1480 TCPSTAT_INC(tcps_sndacks); 1481 TCPSTAT_INC(tcps_sndtotal); 1482 } 1483 SCH_UNLOCK(sch); 1484 goto donenoprobe; 1485 } 1486 1487 if (tfo_cookie_valid) { 1488 bzero(&scs, sizeof(scs)); 1489 sc = &scs; 1490 goto skip_alloc; 1491 } 1492 1493 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1494 if (sc == NULL) { 1495 /* 1496 * The zone allocator couldn't provide more entries. 1497 * Treat this as if the cache was full; drop the oldest 1498 * entry and insert the new one. 1499 */ 1500 TCPSTAT_INC(tcps_sc_zonefail); 1501 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) { 1502 sch->sch_last_overflow = time_uptime; 1503 syncache_drop(sc, sch); 1504 } 1505 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1506 if (sc == NULL) { 1507 if (V_tcp_syncookies) { 1508 bzero(&scs, sizeof(scs)); 1509 sc = &scs; 1510 } else { 1511 SCH_UNLOCK(sch); 1512 if (ipopts) 1513 (void) m_free(ipopts); 1514 goto done; 1515 } 1516 } 1517 } 1518 1519 skip_alloc: 1520 if (!tfo_cookie_valid && tfo_response_cookie_valid) 1521 sc->sc_tfo_cookie = &tfo_response_cookie; 1522 1523 /* 1524 * Fill in the syncache values. 1525 */ 1526 #ifdef MAC 1527 sc->sc_label = maclabel; 1528 #endif 1529 sc->sc_cred = cred; 1530 cred = NULL; 1531 sc->sc_ipopts = ipopts; 1532 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1533 #ifdef INET6 1534 if (!(inc->inc_flags & INC_ISIPV6)) 1535 #endif 1536 { 1537 sc->sc_ip_tos = ip_tos; 1538 sc->sc_ip_ttl = ip_ttl; 1539 } 1540 #ifdef TCP_OFFLOAD 1541 sc->sc_tod = tod; 1542 sc->sc_todctx = todctx; 1543 #endif 1544 sc->sc_irs = th->th_seq; 1545 sc->sc_flags = 0; 1546 sc->sc_flowlabel = 0; 1547 1548 /* 1549 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1550 * win was derived from socket earlier in the function. 1551 */ 1552 win = imax(win, 0); 1553 win = imin(win, TCP_MAXWIN); 1554 sc->sc_wnd = win; 1555 1556 if (V_tcp_do_rfc1323) { 1557 /* 1558 * A timestamp received in a SYN makes 1559 * it ok to send timestamp requests and replies. 1560 */ 1561 if (to->to_flags & TOF_TS) { 1562 sc->sc_tsreflect = to->to_tsval; 1563 sc->sc_flags |= SCF_TIMESTAMP; 1564 sc->sc_tsoff = tcp_new_ts_offset(inc); 1565 } 1566 if (to->to_flags & TOF_SCALE) { 1567 int wscale = 0; 1568 1569 /* 1570 * Pick the smallest possible scaling factor that 1571 * will still allow us to scale up to sb_max, aka 1572 * kern.ipc.maxsockbuf. 1573 * 1574 * We do this because there are broken firewalls that 1575 * will corrupt the window scale option, leading to 1576 * the other endpoint believing that our advertised 1577 * window is unscaled. At scale factors larger than 1578 * 5 the unscaled window will drop below 1500 bytes, 1579 * leading to serious problems when traversing these 1580 * broken firewalls. 1581 * 1582 * With the default maxsockbuf of 256K, a scale factor 1583 * of 3 will be chosen by this algorithm. Those who 1584 * choose a larger maxsockbuf should watch out 1585 * for the compatibility problems mentioned above. 1586 * 1587 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1588 * or <SYN,ACK>) segment itself is never scaled. 1589 */ 1590 while (wscale < TCP_MAX_WINSHIFT && 1591 (TCP_MAXWIN << wscale) < sb_max) 1592 wscale++; 1593 sc->sc_requested_r_scale = wscale; 1594 sc->sc_requested_s_scale = to->to_wscale; 1595 sc->sc_flags |= SCF_WINSCALE; 1596 } 1597 } 1598 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1599 /* 1600 * If listening socket requested TCP digests, flag this in the 1601 * syncache so that syncache_respond() will do the right thing 1602 * with the SYN+ACK. 1603 */ 1604 if (ltflags & TF_SIGNATURE) 1605 sc->sc_flags |= SCF_SIGNATURE; 1606 #endif /* TCP_SIGNATURE */ 1607 if (to->to_flags & TOF_SACKPERM) 1608 sc->sc_flags |= SCF_SACK; 1609 if (to->to_flags & TOF_MSS) 1610 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1611 if (ltflags & TF_NOOPT) 1612 sc->sc_flags |= SCF_NOOPT; 1613 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1614 sc->sc_flags |= SCF_ECN; 1615 1616 if (V_tcp_syncookies) 1617 sc->sc_iss = syncookie_generate(sch, sc); 1618 else 1619 sc->sc_iss = arc4random(); 1620 #ifdef INET6 1621 if (autoflowlabel) { 1622 if (V_tcp_syncookies) 1623 sc->sc_flowlabel = sc->sc_iss; 1624 else 1625 sc->sc_flowlabel = ip6_randomflowlabel(); 1626 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK; 1627 } 1628 #endif 1629 SCH_UNLOCK(sch); 1630 1631 if (tfo_cookie_valid) { 1632 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie); 1633 /* INP_WUNLOCK(inp) will be performed by the caller */ 1634 rv = 1; 1635 goto tfo_expanded; 1636 } 1637 1638 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1639 /* 1640 * Do a standard 3-way handshake. 1641 */ 1642 if (syncache_respond(sc, m, TH_SYN|TH_ACK) == 0) { 1643 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1644 syncache_free(sc); 1645 else if (sc != &scs) 1646 syncache_insert(sc, sch); /* locks and unlocks sch */ 1647 TCPSTAT_INC(tcps_sndacks); 1648 TCPSTAT_INC(tcps_sndtotal); 1649 } else { 1650 if (sc != &scs) 1651 syncache_free(sc); 1652 TCPSTAT_INC(tcps_sc_dropped); 1653 } 1654 goto donenoprobe; 1655 1656 done: 1657 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1658 donenoprobe: 1659 if (m) { 1660 *lsop = NULL; 1661 m_freem(m); 1662 } 1663 /* 1664 * If tfo_pending is not NULL here, then a TFO SYN that did not 1665 * result in a new socket was processed and the associated pending 1666 * counter has not yet been decremented. All such TFO processing paths 1667 * transit this point. 1668 */ 1669 if (tfo_pending != NULL) 1670 tcp_fastopen_decrement_counter(tfo_pending); 1671 1672 tfo_expanded: 1673 if (cred != NULL) 1674 crfree(cred); 1675 #ifdef MAC 1676 if (sc == &scs) 1677 mac_syncache_destroy(&maclabel); 1678 #endif 1679 return (rv); 1680 } 1681 1682 /* 1683 * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment, 1684 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL. 1685 */ 1686 static int 1687 syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags) 1688 { 1689 struct ip *ip = NULL; 1690 struct mbuf *m; 1691 struct tcphdr *th = NULL; 1692 int optlen, error = 0; /* Make compiler happy */ 1693 u_int16_t hlen, tlen, mssopt; 1694 struct tcpopt to; 1695 #ifdef INET6 1696 struct ip6_hdr *ip6 = NULL; 1697 #endif 1698 hlen = 1699 #ifdef INET6 1700 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1701 #endif 1702 sizeof(struct ip); 1703 tlen = hlen + sizeof(struct tcphdr); 1704 1705 /* Determine MSS we advertize to other end of connection. */ 1706 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss); 1707 1708 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1709 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1710 ("syncache: mbuf too small")); 1711 1712 /* Create the IP+TCP header from scratch. */ 1713 m = m_gethdr(M_NOWAIT, MT_DATA); 1714 if (m == NULL) 1715 return (ENOBUFS); 1716 #ifdef MAC 1717 mac_syncache_create_mbuf(sc->sc_label, m); 1718 #endif 1719 m->m_data += max_linkhdr; 1720 m->m_len = tlen; 1721 m->m_pkthdr.len = tlen; 1722 m->m_pkthdr.rcvif = NULL; 1723 1724 #ifdef INET6 1725 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1726 ip6 = mtod(m, struct ip6_hdr *); 1727 ip6->ip6_vfc = IPV6_VERSION; 1728 ip6->ip6_nxt = IPPROTO_TCP; 1729 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1730 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1731 ip6->ip6_plen = htons(tlen - hlen); 1732 /* ip6_hlim is set after checksum */ 1733 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1734 ip6->ip6_flow |= sc->sc_flowlabel; 1735 1736 th = (struct tcphdr *)(ip6 + 1); 1737 } 1738 #endif 1739 #if defined(INET6) && defined(INET) 1740 else 1741 #endif 1742 #ifdef INET 1743 { 1744 ip = mtod(m, struct ip *); 1745 ip->ip_v = IPVERSION; 1746 ip->ip_hl = sizeof(struct ip) >> 2; 1747 ip->ip_len = htons(tlen); 1748 ip->ip_id = 0; 1749 ip->ip_off = 0; 1750 ip->ip_sum = 0; 1751 ip->ip_p = IPPROTO_TCP; 1752 ip->ip_src = sc->sc_inc.inc_laddr; 1753 ip->ip_dst = sc->sc_inc.inc_faddr; 1754 ip->ip_ttl = sc->sc_ip_ttl; 1755 ip->ip_tos = sc->sc_ip_tos; 1756 1757 /* 1758 * See if we should do MTU discovery. Route lookups are 1759 * expensive, so we will only unset the DF bit if: 1760 * 1761 * 1) path_mtu_discovery is disabled 1762 * 2) the SCF_UNREACH flag has been set 1763 */ 1764 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1765 ip->ip_off |= htons(IP_DF); 1766 1767 th = (struct tcphdr *)(ip + 1); 1768 } 1769 #endif /* INET */ 1770 th->th_sport = sc->sc_inc.inc_lport; 1771 th->th_dport = sc->sc_inc.inc_fport; 1772 1773 if (flags & TH_SYN) 1774 th->th_seq = htonl(sc->sc_iss); 1775 else 1776 th->th_seq = htonl(sc->sc_iss + 1); 1777 th->th_ack = htonl(sc->sc_irs + 1); 1778 th->th_off = sizeof(struct tcphdr) >> 2; 1779 th->th_x2 = 0; 1780 th->th_flags = flags; 1781 th->th_win = htons(sc->sc_wnd); 1782 th->th_urp = 0; 1783 1784 if ((flags & TH_SYN) && (sc->sc_flags & SCF_ECN)) { 1785 th->th_flags |= TH_ECE; 1786 TCPSTAT_INC(tcps_ecn_shs); 1787 } 1788 1789 /* Tack on the TCP options. */ 1790 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1791 to.to_flags = 0; 1792 1793 if (flags & TH_SYN) { 1794 to.to_mss = mssopt; 1795 to.to_flags = TOF_MSS; 1796 if (sc->sc_flags & SCF_WINSCALE) { 1797 to.to_wscale = sc->sc_requested_r_scale; 1798 to.to_flags |= TOF_SCALE; 1799 } 1800 if (sc->sc_flags & SCF_SACK) 1801 to.to_flags |= TOF_SACKPERM; 1802 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1803 if (sc->sc_flags & SCF_SIGNATURE) 1804 to.to_flags |= TOF_SIGNATURE; 1805 #endif 1806 if (sc->sc_tfo_cookie) { 1807 to.to_flags |= TOF_FASTOPEN; 1808 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 1809 to.to_tfo_cookie = sc->sc_tfo_cookie; 1810 /* don't send cookie again when retransmitting response */ 1811 sc->sc_tfo_cookie = NULL; 1812 } 1813 } 1814 if (sc->sc_flags & SCF_TIMESTAMP) { 1815 to.to_tsval = sc->sc_tsoff + tcp_ts_getticks(); 1816 to.to_tsecr = sc->sc_tsreflect; 1817 to.to_flags |= TOF_TS; 1818 } 1819 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1820 1821 /* Adjust headers by option size. */ 1822 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1823 m->m_len += optlen; 1824 m->m_pkthdr.len += optlen; 1825 #ifdef INET6 1826 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1827 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1828 else 1829 #endif 1830 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 1831 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1832 if (sc->sc_flags & SCF_SIGNATURE) { 1833 KASSERT(to.to_flags & TOF_SIGNATURE, 1834 ("tcp_addoptions() didn't set tcp_signature")); 1835 1836 /* NOTE: to.to_signature is inside of mbuf */ 1837 if (!TCPMD5_ENABLED() || 1838 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) { 1839 m_freem(m); 1840 return (EACCES); 1841 } 1842 } 1843 #endif 1844 } else 1845 optlen = 0; 1846 1847 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1848 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1849 /* 1850 * If we have peer's SYN and it has a flowid, then let's assign it to 1851 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid 1852 * to SYN|ACK due to lack of inp here. 1853 */ 1854 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) { 1855 m->m_pkthdr.flowid = m0->m_pkthdr.flowid; 1856 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0)); 1857 } 1858 #ifdef INET6 1859 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1860 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1861 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1862 IPPROTO_TCP, 0); 1863 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1864 #ifdef TCP_OFFLOAD 1865 if (ADDED_BY_TOE(sc)) { 1866 struct toedev *tod = sc->sc_tod; 1867 1868 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1869 1870 return (error); 1871 } 1872 #endif 1873 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th); 1874 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1875 } 1876 #endif 1877 #if defined(INET6) && defined(INET) 1878 else 1879 #endif 1880 #ifdef INET 1881 { 1882 m->m_pkthdr.csum_flags = CSUM_TCP; 1883 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1884 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1885 #ifdef TCP_OFFLOAD 1886 if (ADDED_BY_TOE(sc)) { 1887 struct toedev *tod = sc->sc_tod; 1888 1889 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1890 1891 return (error); 1892 } 1893 #endif 1894 TCP_PROBE5(send, NULL, NULL, ip, NULL, th); 1895 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1896 } 1897 #endif 1898 return (error); 1899 } 1900 1901 /* 1902 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks 1903 * that exceed the capacity of the syncache by avoiding the storage of any 1904 * of the SYNs we receive. Syncookies defend against blind SYN flooding 1905 * attacks where the attacker does not have access to our responses. 1906 * 1907 * Syncookies encode and include all necessary information about the 1908 * connection setup within the SYN|ACK that we send back. That way we 1909 * can avoid keeping any local state until the ACK to our SYN|ACK returns 1910 * (if ever). Normally the syncache and syncookies are running in parallel 1911 * with the latter taking over when the former is exhausted. When matching 1912 * syncache entry is found the syncookie is ignored. 1913 * 1914 * The only reliable information persisting the 3WHS is our initial sequence 1915 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient 1916 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS 1917 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK 1918 * returns and signifies a legitimate connection if it matches the ACK. 1919 * 1920 * The available space of 32 bits to store the hash and to encode the SYN 1921 * option information is very tight and we should have at least 24 bits for 1922 * the MAC to keep the number of guesses by blind spoofing reasonably high. 1923 * 1924 * SYN option information we have to encode to fully restore a connection: 1925 * MSS: is imporant to chose an optimal segment size to avoid IP level 1926 * fragmentation along the path. The common MSS values can be encoded 1927 * in a 3-bit table. Uncommon values are captured by the next lower value 1928 * in the table leading to a slight increase in packetization overhead. 1929 * WSCALE: is necessary to allow large windows to be used for high delay- 1930 * bandwidth product links. Not scaling the window when it was initially 1931 * negotiated is bad for performance as lack of scaling further decreases 1932 * the apparent available send window. We only need to encode the WSCALE 1933 * we received from the remote end. Our end can be recalculated at any 1934 * time. The common WSCALE values can be encoded in a 3-bit table. 1935 * Uncommon values are captured by the next lower value in the table 1936 * making us under-estimate the available window size halving our 1937 * theoretically possible maximum throughput for that connection. 1938 * SACK: Greatly assists in packet loss recovery and requires 1 bit. 1939 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options 1940 * that are included in all segments on a connection. We enable them when 1941 * the ACK has them. 1942 * 1943 * Security of syncookies and attack vectors: 1944 * 1945 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod) 1946 * together with the gloabl secret to make it unique per connection attempt. 1947 * Thus any change of any of those parameters results in a different MAC output 1948 * in an unpredictable way unless a collision is encountered. 24 bits of the 1949 * MAC are embedded into the ISS. 1950 * 1951 * To prevent replay attacks two rotating global secrets are updated with a 1952 * new random value every 15 seconds. The life-time of a syncookie is thus 1953 * 15-30 seconds. 1954 * 1955 * Vector 1: Attacking the secret. This requires finding a weakness in the 1956 * MAC itself or the way it is used here. The attacker can do a chosen plain 1957 * text attack by varying and testing the all parameters under his control. 1958 * The strength depends on the size and randomness of the secret, and the 1959 * cryptographic security of the MAC function. Due to the constant updating 1960 * of the secret the attacker has at most 29.999 seconds to find the secret 1961 * and launch spoofed connections. After that he has to start all over again. 1962 * 1963 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC 1964 * size an average of 4,823 attempts are required for a 50% chance of success 1965 * to spoof a single syncookie (birthday collision paradox). However the 1966 * attacker is blind and doesn't know if one of his attempts succeeded unless 1967 * he has a side channel to interfere success from. A single connection setup 1968 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets. 1969 * This many attempts are required for each one blind spoofed connection. For 1970 * every additional spoofed connection he has to launch another N attempts. 1971 * Thus for a sustained rate 100 spoofed connections per second approximately 1972 * 1,800,000 packets per second would have to be sent. 1973 * 1974 * NB: The MAC function should be fast so that it doesn't become a CPU 1975 * exhaustion attack vector itself. 1976 * 1977 * References: 1978 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations 1979 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996 1980 * http://cr.yp.to/syncookies.html (overview) 1981 * http://cr.yp.to/syncookies/archive (details) 1982 * 1983 * 1984 * Schematic construction of a syncookie enabled Initial Sequence Number: 1985 * 0 1 2 3 1986 * 12345678901234567890123456789012 1987 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP| 1988 * 1989 * x 24 MAC (truncated) 1990 * W 3 Send Window Scale index 1991 * M 3 MSS index 1992 * S 1 SACK permitted 1993 * P 1 Odd/even secret 1994 */ 1995 1996 /* 1997 * Distribution and probability of certain MSS values. Those in between are 1998 * rounded down to the next lower one. 1999 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011] 2000 * .2% .3% 5% 7% 7% 20% 15% 45% 2001 */ 2002 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 }; 2003 2004 /* 2005 * Distribution and probability of certain WSCALE values. We have to map the 2006 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3 2007 * bits based on prevalence of certain values. Where we don't have an exact 2008 * match for are rounded down to the next lower one letting us under-estimate 2009 * the true available window. At the moment this would happen only for the 2010 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer 2011 * and window size). The absence of the WSCALE option (no scaling in either 2012 * direction) is encoded with index zero. 2013 * [WSCALE values histograms, Allman, 2012] 2014 * X 10 10 35 5 6 14 10% by host 2015 * X 11 4 5 5 18 49 3% by connections 2016 */ 2017 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 }; 2018 2019 /* 2020 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed 2021 * and good cryptographic properties. 2022 */ 2023 static uint32_t 2024 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags, 2025 uint8_t *secbits, uintptr_t secmod) 2026 { 2027 SIPHASH_CTX ctx; 2028 uint32_t siphash[2]; 2029 2030 SipHash24_Init(&ctx); 2031 SipHash_SetKey(&ctx, secbits); 2032 switch (inc->inc_flags & INC_ISIPV6) { 2033 #ifdef INET 2034 case 0: 2035 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr)); 2036 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr)); 2037 break; 2038 #endif 2039 #ifdef INET6 2040 case INC_ISIPV6: 2041 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr)); 2042 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr)); 2043 break; 2044 #endif 2045 } 2046 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport)); 2047 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport)); 2048 SipHash_Update(&ctx, &irs, sizeof(irs)); 2049 SipHash_Update(&ctx, &flags, sizeof(flags)); 2050 SipHash_Update(&ctx, &secmod, sizeof(secmod)); 2051 SipHash_Final((u_int8_t *)&siphash, &ctx); 2052 2053 return (siphash[0] ^ siphash[1]); 2054 } 2055 2056 static tcp_seq 2057 syncookie_generate(struct syncache_head *sch, struct syncache *sc) 2058 { 2059 u_int i, secbit, wscale; 2060 uint32_t iss, hash; 2061 uint8_t *secbits; 2062 union syncookie cookie; 2063 2064 cookie.cookie = 0; 2065 2066 /* Map our computed MSS into the 3-bit index. */ 2067 for (i = nitems(tcp_sc_msstab) - 1; 2068 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0; 2069 i--) 2070 ; 2071 cookie.flags.mss_idx = i; 2072 2073 /* 2074 * Map the send window scale into the 3-bit index but only if 2075 * the wscale option was received. 2076 */ 2077 if (sc->sc_flags & SCF_WINSCALE) { 2078 wscale = sc->sc_requested_s_scale; 2079 for (i = nitems(tcp_sc_wstab) - 1; 2080 tcp_sc_wstab[i] > wscale && i > 0; 2081 i--) 2082 ; 2083 cookie.flags.wscale_idx = i; 2084 } 2085 2086 /* Can we do SACK? */ 2087 if (sc->sc_flags & SCF_SACK) 2088 cookie.flags.sack_ok = 1; 2089 2090 /* Which of the two secrets to use. */ 2091 secbit = V_tcp_syncache.secret.oddeven & 0x1; 2092 cookie.flags.odd_even = secbit; 2093 2094 secbits = V_tcp_syncache.secret.key[secbit]; 2095 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits, 2096 (uintptr_t)sch); 2097 2098 /* 2099 * Put the flags into the hash and XOR them to get better ISS number 2100 * variance. This doesn't enhance the cryptographic strength and is 2101 * done to prevent the 8 cookie bits from showing up directly on the 2102 * wire. 2103 */ 2104 iss = hash & ~0xff; 2105 iss |= cookie.cookie ^ (hash >> 24); 2106 2107 TCPSTAT_INC(tcps_sc_sendcookie); 2108 return (iss); 2109 } 2110 2111 static struct syncache * 2112 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 2113 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2114 struct socket *lso) 2115 { 2116 uint32_t hash; 2117 uint8_t *secbits; 2118 tcp_seq ack, seq; 2119 int wnd, wscale = 0; 2120 union syncookie cookie; 2121 2122 /* 2123 * Pull information out of SYN-ACK/ACK and revert sequence number 2124 * advances. 2125 */ 2126 ack = th->th_ack - 1; 2127 seq = th->th_seq - 1; 2128 2129 /* 2130 * Unpack the flags containing enough information to restore the 2131 * connection. 2132 */ 2133 cookie.cookie = (ack & 0xff) ^ (ack >> 24); 2134 2135 /* Which of the two secrets to use. */ 2136 secbits = V_tcp_syncache.secret.key[cookie.flags.odd_even]; 2137 2138 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch); 2139 2140 /* The recomputed hash matches the ACK if this was a genuine cookie. */ 2141 if ((ack & ~0xff) != (hash & ~0xff)) 2142 return (NULL); 2143 2144 /* Fill in the syncache values. */ 2145 sc->sc_flags = 0; 2146 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 2147 sc->sc_ipopts = NULL; 2148 2149 sc->sc_irs = seq; 2150 sc->sc_iss = ack; 2151 2152 switch (inc->inc_flags & INC_ISIPV6) { 2153 #ifdef INET 2154 case 0: 2155 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl; 2156 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos; 2157 break; 2158 #endif 2159 #ifdef INET6 2160 case INC_ISIPV6: 2161 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL) 2162 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK; 2163 break; 2164 #endif 2165 } 2166 2167 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx]; 2168 2169 /* We can simply recompute receive window scale we sent earlier. */ 2170 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max) 2171 wscale++; 2172 2173 /* Only use wscale if it was enabled in the orignal SYN. */ 2174 if (cookie.flags.wscale_idx > 0) { 2175 sc->sc_requested_r_scale = wscale; 2176 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx]; 2177 sc->sc_flags |= SCF_WINSCALE; 2178 } 2179 2180 wnd = lso->sol_sbrcv_hiwat; 2181 wnd = imax(wnd, 0); 2182 wnd = imin(wnd, TCP_MAXWIN); 2183 sc->sc_wnd = wnd; 2184 2185 if (cookie.flags.sack_ok) 2186 sc->sc_flags |= SCF_SACK; 2187 2188 if (to->to_flags & TOF_TS) { 2189 sc->sc_flags |= SCF_TIMESTAMP; 2190 sc->sc_tsreflect = to->to_tsval; 2191 sc->sc_tsoff = tcp_new_ts_offset(inc); 2192 } 2193 2194 if (to->to_flags & TOF_SIGNATURE) 2195 sc->sc_flags |= SCF_SIGNATURE; 2196 2197 sc->sc_rxmits = 0; 2198 2199 TCPSTAT_INC(tcps_sc_recvcookie); 2200 return (sc); 2201 } 2202 2203 #ifdef INVARIANTS 2204 static int 2205 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 2206 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2207 struct socket *lso) 2208 { 2209 struct syncache scs, *scx; 2210 char *s; 2211 2212 bzero(&scs, sizeof(scs)); 2213 scx = syncookie_lookup(inc, sch, &scs, th, to, lso); 2214 2215 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL) 2216 return (0); 2217 2218 if (scx != NULL) { 2219 if (sc->sc_peer_mss != scx->sc_peer_mss) 2220 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n", 2221 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss); 2222 2223 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale) 2224 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n", 2225 s, __func__, sc->sc_requested_r_scale, 2226 scx->sc_requested_r_scale); 2227 2228 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale) 2229 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n", 2230 s, __func__, sc->sc_requested_s_scale, 2231 scx->sc_requested_s_scale); 2232 2233 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK)) 2234 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__); 2235 } 2236 2237 if (s != NULL) 2238 free(s, M_TCPLOG); 2239 return (0); 2240 } 2241 #endif /* INVARIANTS */ 2242 2243 static void 2244 syncookie_reseed(void *arg) 2245 { 2246 struct tcp_syncache *sc = arg; 2247 uint8_t *secbits; 2248 int secbit; 2249 2250 /* 2251 * Reseeding the secret doesn't have to be protected by a lock. 2252 * It only must be ensured that the new random values are visible 2253 * to all CPUs in a SMP environment. The atomic with release 2254 * semantics ensures that. 2255 */ 2256 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1; 2257 secbits = sc->secret.key[secbit]; 2258 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0); 2259 atomic_add_rel_int(&sc->secret.oddeven, 1); 2260 2261 /* Reschedule ourself. */ 2262 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz); 2263 } 2264 2265 /* 2266 * Exports the syncache entries to userland so that netstat can display 2267 * them alongside the other sockets. This function is intended to be 2268 * called only from tcp_pcblist. 2269 * 2270 * Due to concurrency on an active system, the number of pcbs exported 2271 * may have no relation to max_pcbs. max_pcbs merely indicates the 2272 * amount of space the caller allocated for this function to use. 2273 */ 2274 int 2275 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 2276 { 2277 struct xtcpcb xt; 2278 struct syncache *sc; 2279 struct syncache_head *sch; 2280 int count, error, i; 2281 2282 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 2283 sch = &V_tcp_syncache.hashbase[i]; 2284 SCH_LOCK(sch); 2285 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 2286 if (count >= max_pcbs) { 2287 SCH_UNLOCK(sch); 2288 goto exit; 2289 } 2290 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 2291 continue; 2292 bzero(&xt, sizeof(xt)); 2293 xt.xt_len = sizeof(xt); 2294 if (sc->sc_inc.inc_flags & INC_ISIPV6) 2295 xt.xt_inp.inp_vflag = INP_IPV6; 2296 else 2297 xt.xt_inp.inp_vflag = INP_IPV4; 2298 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, 2299 sizeof (struct in_conninfo)); 2300 xt.t_state = TCPS_SYN_RECEIVED; 2301 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP; 2302 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket); 2303 xt.xt_inp.xi_socket.so_type = SOCK_STREAM; 2304 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING; 2305 error = SYSCTL_OUT(req, &xt, sizeof xt); 2306 if (error) { 2307 SCH_UNLOCK(sch); 2308 goto exit; 2309 } 2310 count++; 2311 } 2312 SCH_UNLOCK(sch); 2313 } 2314 exit: 2315 *pcbs_exported = count; 2316 return error; 2317 } 2318