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 /* 1144 * RFC 7323 PAWS: If we have a timestamp on this segment and 1145 * it's less than ts_recent, drop it. 1146 * XXXMT: RFC 7323 also requires to send an ACK. 1147 * In tcp_input.c this is only done for TCP segments 1148 * with user data, so be consistent here and just drop 1149 * the segment. 1150 */ 1151 if (sc->sc_flags & SCF_TIMESTAMP && to->to_flags & TOF_TS && 1152 TSTMP_LT(to->to_tsval, sc->sc_tsreflect)) { 1153 SCH_UNLOCK(sch); 1154 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1155 log(LOG_DEBUG, 1156 "%s; %s: SEG.TSval %u < TS.Recent %u, " 1157 "segment dropped\n", s, __func__, 1158 to->to_tsval, sc->sc_tsreflect); 1159 free(s, M_TCPLOG); 1160 } 1161 return (-1); /* Do not send RST */ 1162 } 1163 1164 /* 1165 * Pull out the entry to unlock the bucket row. 1166 * 1167 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not 1168 * tcp_state_change(). The tcpcb is not existent at this 1169 * moment. A new one will be allocated via syncache_socket-> 1170 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then 1171 * syncache_socket() will change it to TCPS_SYN_RECEIVED. 1172 */ 1173 TCPSTATES_DEC(TCPS_SYN_RECEIVED); 1174 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 1175 sch->sch_length--; 1176 #ifdef TCP_OFFLOAD 1177 if (ADDED_BY_TOE(sc)) { 1178 struct toedev *tod = sc->sc_tod; 1179 1180 tod->tod_syncache_removed(tod, sc->sc_todctx); 1181 } 1182 #endif 1183 SCH_UNLOCK(sch); 1184 } 1185 1186 /* 1187 * Segment validation: 1188 * ACK must match our initial sequence number + 1 (the SYN|ACK). 1189 */ 1190 if (th->th_ack != sc->sc_iss + 1) { 1191 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1192 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 1193 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 1194 goto failed; 1195 } 1196 1197 /* 1198 * The SEQ must fall in the window starting at the received 1199 * initial receive sequence number + 1 (the SYN). 1200 */ 1201 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 1202 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 1203 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1204 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 1205 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 1206 goto failed; 1207 } 1208 1209 /* 1210 * If timestamps were not negotiated during SYN/ACK they 1211 * must not appear on any segment during this session. 1212 */ 1213 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 1214 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1215 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1216 "segment rejected\n", s, __func__); 1217 goto failed; 1218 } 1219 1220 /* 1221 * If timestamps were negotiated during SYN/ACK they should 1222 * appear on every segment during this session. 1223 * XXXAO: This is only informal as there have been unverified 1224 * reports of non-compliants stacks. 1225 */ 1226 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) { 1227 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1228 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1229 "no action\n", s, __func__); 1230 free(s, M_TCPLOG); 1231 s = NULL; 1232 } 1233 } 1234 1235 *lsop = syncache_socket(sc, *lsop, m); 1236 1237 if (*lsop == NULL) 1238 TCPSTAT_INC(tcps_sc_aborted); 1239 else 1240 TCPSTAT_INC(tcps_sc_completed); 1241 1242 /* how do we find the inp for the new socket? */ 1243 if (sc != &scs) 1244 syncache_free(sc); 1245 return (1); 1246 failed: 1247 if (sc != NULL && sc != &scs) 1248 syncache_free(sc); 1249 if (s != NULL) 1250 free(s, M_TCPLOG); 1251 *lsop = NULL; 1252 return (0); 1253 } 1254 1255 static void 1256 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m, 1257 uint64_t response_cookie) 1258 { 1259 struct inpcb *inp; 1260 struct tcpcb *tp; 1261 unsigned int *pending_counter; 1262 1263 /* 1264 * Global TCP locks are held because we manipulate the PCB lists 1265 * and create a new socket. 1266 */ 1267 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1268 1269 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending; 1270 *lsop = syncache_socket(sc, *lsop, m); 1271 if (*lsop == NULL) { 1272 TCPSTAT_INC(tcps_sc_aborted); 1273 atomic_subtract_int(pending_counter, 1); 1274 } else { 1275 soisconnected(*lsop); 1276 inp = sotoinpcb(*lsop); 1277 tp = intotcpcb(inp); 1278 tp->t_flags |= TF_FASTOPEN; 1279 tp->t_tfo_cookie.server = response_cookie; 1280 tp->snd_max = tp->iss; 1281 tp->snd_nxt = tp->iss; 1282 tp->t_tfo_pending = pending_counter; 1283 TCPSTAT_INC(tcps_sc_completed); 1284 } 1285 } 1286 1287 /* 1288 * Given a LISTEN socket and an inbound SYN request, add 1289 * this to the syn cache, and send back a segment: 1290 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1291 * to the source. 1292 * 1293 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1294 * Doing so would require that we hold onto the data and deliver it 1295 * to the application. However, if we are the target of a SYN-flood 1296 * DoS attack, an attacker could send data which would eventually 1297 * consume all available buffer space if it were ACKed. By not ACKing 1298 * the data, we avoid this DoS scenario. 1299 * 1300 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO) 1301 * cookie is processed and a new socket is created. In this case, any data 1302 * accompanying the SYN will be queued to the socket by tcp_input() and will 1303 * be ACKed either when the application sends response data or the delayed 1304 * ACK timer expires, whichever comes first. 1305 */ 1306 int 1307 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1308 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1309 void *todctx) 1310 { 1311 struct tcpcb *tp; 1312 struct socket *so; 1313 struct syncache *sc = NULL; 1314 struct syncache_head *sch; 1315 struct mbuf *ipopts = NULL; 1316 u_int ltflags; 1317 int win, ip_ttl, ip_tos; 1318 char *s; 1319 int rv = 0; 1320 #ifdef INET6 1321 int autoflowlabel = 0; 1322 #endif 1323 #ifdef MAC 1324 struct label *maclabel; 1325 #endif 1326 struct syncache scs; 1327 struct ucred *cred; 1328 uint64_t tfo_response_cookie; 1329 unsigned int *tfo_pending = NULL; 1330 int tfo_cookie_valid = 0; 1331 int tfo_response_cookie_valid = 0; 1332 1333 INP_WLOCK_ASSERT(inp); /* listen socket */ 1334 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1335 ("%s: unexpected tcp flags", __func__)); 1336 1337 /* 1338 * Combine all so/tp operations very early to drop the INP lock as 1339 * soon as possible. 1340 */ 1341 so = *lsop; 1342 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so)); 1343 tp = sototcpcb(so); 1344 cred = crhold(so->so_cred); 1345 1346 #ifdef INET6 1347 if ((inc->inc_flags & INC_ISIPV6) && 1348 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1349 autoflowlabel = 1; 1350 #endif 1351 ip_ttl = inp->inp_ip_ttl; 1352 ip_tos = inp->inp_ip_tos; 1353 win = so->sol_sbrcv_hiwat; 1354 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1355 1356 if (V_tcp_fastopen_server_enable && IS_FASTOPEN(tp->t_flags) && 1357 (tp->t_tfo_pending != NULL) && 1358 (to->to_flags & TOF_FASTOPEN)) { 1359 /* 1360 * Limit the number of pending TFO connections to 1361 * approximately half of the queue limit. This prevents TFO 1362 * SYN floods from starving the service by filling the 1363 * listen queue with bogus TFO connections. 1364 */ 1365 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <= 1366 (so->sol_qlimit / 2)) { 1367 int result; 1368 1369 result = tcp_fastopen_check_cookie(inc, 1370 to->to_tfo_cookie, to->to_tfo_len, 1371 &tfo_response_cookie); 1372 tfo_cookie_valid = (result > 0); 1373 tfo_response_cookie_valid = (result >= 0); 1374 } 1375 1376 /* 1377 * Remember the TFO pending counter as it will have to be 1378 * decremented below if we don't make it to syncache_tfo_expand(). 1379 */ 1380 tfo_pending = tp->t_tfo_pending; 1381 } 1382 1383 /* By the time we drop the lock these should no longer be used. */ 1384 so = NULL; 1385 tp = NULL; 1386 1387 #ifdef MAC 1388 if (mac_syncache_init(&maclabel) != 0) { 1389 INP_WUNLOCK(inp); 1390 goto done; 1391 } else 1392 mac_syncache_create(maclabel, inp); 1393 #endif 1394 if (!tfo_cookie_valid) 1395 INP_WUNLOCK(inp); 1396 1397 /* 1398 * Remember the IP options, if any. 1399 */ 1400 #ifdef INET6 1401 if (!(inc->inc_flags & INC_ISIPV6)) 1402 #endif 1403 #ifdef INET 1404 ipopts = (m) ? ip_srcroute(m) : NULL; 1405 #else 1406 ipopts = NULL; 1407 #endif 1408 1409 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1410 /* 1411 * If listening socket requested TCP digests, check that received 1412 * SYN has signature and it is correct. If signature doesn't match 1413 * or TCP_SIGNATURE support isn't enabled, drop the packet. 1414 */ 1415 if (ltflags & TF_SIGNATURE) { 1416 if ((to->to_flags & TOF_SIGNATURE) == 0) { 1417 TCPSTAT_INC(tcps_sig_err_nosigopt); 1418 goto done; 1419 } 1420 if (!TCPMD5_ENABLED() || 1421 TCPMD5_INPUT(m, th, to->to_signature) != 0) 1422 goto done; 1423 } 1424 #endif /* TCP_SIGNATURE */ 1425 /* 1426 * See if we already have an entry for this connection. 1427 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1428 * 1429 * XXX: should the syncache be re-initialized with the contents 1430 * of the new SYN here (which may have different options?) 1431 * 1432 * XXX: We do not check the sequence number to see if this is a 1433 * real retransmit or a new connection attempt. The question is 1434 * how to handle such a case; either ignore it as spoofed, or 1435 * drop the current entry and create a new one? 1436 */ 1437 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1438 SCH_LOCK_ASSERT(sch); 1439 if (sc != NULL) { 1440 if (tfo_cookie_valid) 1441 INP_WUNLOCK(inp); 1442 TCPSTAT_INC(tcps_sc_dupsyn); 1443 if (ipopts) { 1444 /* 1445 * If we were remembering a previous source route, 1446 * forget it and use the new one we've been given. 1447 */ 1448 if (sc->sc_ipopts) 1449 (void) m_free(sc->sc_ipopts); 1450 sc->sc_ipopts = ipopts; 1451 } 1452 /* 1453 * Update timestamp if present. 1454 */ 1455 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1456 sc->sc_tsreflect = to->to_tsval; 1457 else 1458 sc->sc_flags &= ~SCF_TIMESTAMP; 1459 #ifdef MAC 1460 /* 1461 * Since we have already unconditionally allocated label 1462 * storage, free it up. The syncache entry will already 1463 * have an initialized label we can use. 1464 */ 1465 mac_syncache_destroy(&maclabel); 1466 #endif 1467 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1468 /* Retransmit SYN|ACK and reset retransmit count. */ 1469 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1470 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1471 "resetting timer and retransmitting SYN|ACK\n", 1472 s, __func__); 1473 free(s, M_TCPLOG); 1474 } 1475 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1476 sc->sc_rxmits = 0; 1477 syncache_timeout(sc, sch, 1); 1478 TCPSTAT_INC(tcps_sndacks); 1479 TCPSTAT_INC(tcps_sndtotal); 1480 } 1481 SCH_UNLOCK(sch); 1482 goto donenoprobe; 1483 } 1484 1485 if (tfo_cookie_valid) { 1486 bzero(&scs, sizeof(scs)); 1487 sc = &scs; 1488 goto skip_alloc; 1489 } 1490 1491 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1492 if (sc == NULL) { 1493 /* 1494 * The zone allocator couldn't provide more entries. 1495 * Treat this as if the cache was full; drop the oldest 1496 * entry and insert the new one. 1497 */ 1498 TCPSTAT_INC(tcps_sc_zonefail); 1499 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) { 1500 sch->sch_last_overflow = time_uptime; 1501 syncache_drop(sc, sch); 1502 } 1503 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1504 if (sc == NULL) { 1505 if (V_tcp_syncookies) { 1506 bzero(&scs, sizeof(scs)); 1507 sc = &scs; 1508 } else { 1509 SCH_UNLOCK(sch); 1510 if (ipopts) 1511 (void) m_free(ipopts); 1512 goto done; 1513 } 1514 } 1515 } 1516 1517 skip_alloc: 1518 if (!tfo_cookie_valid && tfo_response_cookie_valid) 1519 sc->sc_tfo_cookie = &tfo_response_cookie; 1520 1521 /* 1522 * Fill in the syncache values. 1523 */ 1524 #ifdef MAC 1525 sc->sc_label = maclabel; 1526 #endif 1527 sc->sc_cred = cred; 1528 cred = NULL; 1529 sc->sc_ipopts = ipopts; 1530 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1531 #ifdef INET6 1532 if (!(inc->inc_flags & INC_ISIPV6)) 1533 #endif 1534 { 1535 sc->sc_ip_tos = ip_tos; 1536 sc->sc_ip_ttl = ip_ttl; 1537 } 1538 #ifdef TCP_OFFLOAD 1539 sc->sc_tod = tod; 1540 sc->sc_todctx = todctx; 1541 #endif 1542 sc->sc_irs = th->th_seq; 1543 sc->sc_iss = arc4random(); 1544 sc->sc_flags = 0; 1545 sc->sc_flowlabel = 0; 1546 1547 /* 1548 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1549 * win was derived from socket earlier in the function. 1550 */ 1551 win = imax(win, 0); 1552 win = imin(win, TCP_MAXWIN); 1553 sc->sc_wnd = win; 1554 1555 if (V_tcp_do_rfc1323) { 1556 /* 1557 * A timestamp received in a SYN makes 1558 * it ok to send timestamp requests and replies. 1559 */ 1560 if (to->to_flags & TOF_TS) { 1561 sc->sc_tsreflect = to->to_tsval; 1562 sc->sc_flags |= SCF_TIMESTAMP; 1563 sc->sc_tsoff = tcp_new_ts_offset(inc); 1564 } 1565 if (to->to_flags & TOF_SCALE) { 1566 int wscale = 0; 1567 1568 /* 1569 * Pick the smallest possible scaling factor that 1570 * will still allow us to scale up to sb_max, aka 1571 * kern.ipc.maxsockbuf. 1572 * 1573 * We do this because there are broken firewalls that 1574 * will corrupt the window scale option, leading to 1575 * the other endpoint believing that our advertised 1576 * window is unscaled. At scale factors larger than 1577 * 5 the unscaled window will drop below 1500 bytes, 1578 * leading to serious problems when traversing these 1579 * broken firewalls. 1580 * 1581 * With the default maxsockbuf of 256K, a scale factor 1582 * of 3 will be chosen by this algorithm. Those who 1583 * choose a larger maxsockbuf should watch out 1584 * for the compatibility problems mentioned above. 1585 * 1586 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1587 * or <SYN,ACK>) segment itself is never scaled. 1588 */ 1589 while (wscale < TCP_MAX_WINSHIFT && 1590 (TCP_MAXWIN << wscale) < sb_max) 1591 wscale++; 1592 sc->sc_requested_r_scale = wscale; 1593 sc->sc_requested_s_scale = to->to_wscale; 1594 sc->sc_flags |= SCF_WINSCALE; 1595 } 1596 } 1597 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1598 /* 1599 * If listening socket requested TCP digests, flag this in the 1600 * syncache so that syncache_respond() will do the right thing 1601 * with the SYN+ACK. 1602 */ 1603 if (ltflags & TF_SIGNATURE) 1604 sc->sc_flags |= SCF_SIGNATURE; 1605 #endif /* TCP_SIGNATURE */ 1606 if (to->to_flags & TOF_SACKPERM) 1607 sc->sc_flags |= SCF_SACK; 1608 if (to->to_flags & TOF_MSS) 1609 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1610 if (ltflags & TF_NOOPT) 1611 sc->sc_flags |= SCF_NOOPT; 1612 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1613 sc->sc_flags |= SCF_ECN; 1614 1615 if (V_tcp_syncookies) 1616 sc->sc_iss = syncookie_generate(sch, sc); 1617 #ifdef INET6 1618 if (autoflowlabel) { 1619 if (V_tcp_syncookies) 1620 sc->sc_flowlabel = sc->sc_iss; 1621 else 1622 sc->sc_flowlabel = ip6_randomflowlabel(); 1623 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK; 1624 } 1625 #endif 1626 SCH_UNLOCK(sch); 1627 1628 if (tfo_cookie_valid) { 1629 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie); 1630 /* INP_WUNLOCK(inp) will be performed by the caller */ 1631 rv = 1; 1632 goto tfo_expanded; 1633 } 1634 1635 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1636 /* 1637 * Do a standard 3-way handshake. 1638 */ 1639 if (syncache_respond(sc, sch, m, TH_SYN|TH_ACK) == 0) { 1640 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1641 syncache_free(sc); 1642 else if (sc != &scs) 1643 syncache_insert(sc, sch); /* locks and unlocks sch */ 1644 TCPSTAT_INC(tcps_sndacks); 1645 TCPSTAT_INC(tcps_sndtotal); 1646 } else { 1647 if (sc != &scs) 1648 syncache_free(sc); 1649 TCPSTAT_INC(tcps_sc_dropped); 1650 } 1651 goto donenoprobe; 1652 1653 done: 1654 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 1655 donenoprobe: 1656 if (m) { 1657 *lsop = NULL; 1658 m_freem(m); 1659 } 1660 /* 1661 * If tfo_pending is not NULL here, then a TFO SYN that did not 1662 * result in a new socket was processed and the associated pending 1663 * counter has not yet been decremented. All such TFO processing paths 1664 * transit this point. 1665 */ 1666 if (tfo_pending != NULL) 1667 tcp_fastopen_decrement_counter(tfo_pending); 1668 1669 tfo_expanded: 1670 if (cred != NULL) 1671 crfree(cred); 1672 #ifdef MAC 1673 if (sc == &scs) 1674 mac_syncache_destroy(&maclabel); 1675 #endif 1676 return (rv); 1677 } 1678 1679 /* 1680 * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment, 1681 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL. 1682 */ 1683 static int 1684 syncache_respond(struct syncache *sc, struct syncache_head *sch, 1685 const struct mbuf *m0, int flags) 1686 { 1687 struct ip *ip = NULL; 1688 struct mbuf *m; 1689 struct tcphdr *th = NULL; 1690 int optlen, error = 0; /* Make compiler happy */ 1691 u_int16_t hlen, tlen, mssopt; 1692 struct tcpopt to; 1693 #ifdef INET6 1694 struct ip6_hdr *ip6 = NULL; 1695 #endif 1696 hlen = 1697 #ifdef INET6 1698 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1699 #endif 1700 sizeof(struct ip); 1701 tlen = hlen + sizeof(struct tcphdr); 1702 1703 /* Determine MSS we advertize to other end of connection. */ 1704 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss); 1705 1706 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1707 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1708 ("syncache: mbuf too small")); 1709 1710 /* Create the IP+TCP header from scratch. */ 1711 m = m_gethdr(M_NOWAIT, MT_DATA); 1712 if (m == NULL) 1713 return (ENOBUFS); 1714 #ifdef MAC 1715 mac_syncache_create_mbuf(sc->sc_label, m); 1716 #endif 1717 m->m_data += max_linkhdr; 1718 m->m_len = tlen; 1719 m->m_pkthdr.len = tlen; 1720 m->m_pkthdr.rcvif = NULL; 1721 1722 #ifdef INET6 1723 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1724 ip6 = mtod(m, struct ip6_hdr *); 1725 ip6->ip6_vfc = IPV6_VERSION; 1726 ip6->ip6_nxt = IPPROTO_TCP; 1727 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1728 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1729 ip6->ip6_plen = htons(tlen - hlen); 1730 /* ip6_hlim is set after checksum */ 1731 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1732 ip6->ip6_flow |= sc->sc_flowlabel; 1733 1734 th = (struct tcphdr *)(ip6 + 1); 1735 } 1736 #endif 1737 #if defined(INET6) && defined(INET) 1738 else 1739 #endif 1740 #ifdef INET 1741 { 1742 ip = mtod(m, struct ip *); 1743 ip->ip_v = IPVERSION; 1744 ip->ip_hl = sizeof(struct ip) >> 2; 1745 ip->ip_len = htons(tlen); 1746 ip->ip_id = 0; 1747 ip->ip_off = 0; 1748 ip->ip_sum = 0; 1749 ip->ip_p = IPPROTO_TCP; 1750 ip->ip_src = sc->sc_inc.inc_laddr; 1751 ip->ip_dst = sc->sc_inc.inc_faddr; 1752 ip->ip_ttl = sc->sc_ip_ttl; 1753 ip->ip_tos = sc->sc_ip_tos; 1754 1755 /* 1756 * See if we should do MTU discovery. Route lookups are 1757 * expensive, so we will only unset the DF bit if: 1758 * 1759 * 1) path_mtu_discovery is disabled 1760 * 2) the SCF_UNREACH flag has been set 1761 */ 1762 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1763 ip->ip_off |= htons(IP_DF); 1764 1765 th = (struct tcphdr *)(ip + 1); 1766 } 1767 #endif /* INET */ 1768 th->th_sport = sc->sc_inc.inc_lport; 1769 th->th_dport = sc->sc_inc.inc_fport; 1770 1771 if (flags & TH_SYN) 1772 th->th_seq = htonl(sc->sc_iss); 1773 else 1774 th->th_seq = htonl(sc->sc_iss + 1); 1775 th->th_ack = htonl(sc->sc_irs + 1); 1776 th->th_off = sizeof(struct tcphdr) >> 2; 1777 th->th_x2 = 0; 1778 th->th_flags = flags; 1779 th->th_win = htons(sc->sc_wnd); 1780 th->th_urp = 0; 1781 1782 if ((flags & TH_SYN) && (sc->sc_flags & SCF_ECN)) { 1783 th->th_flags |= TH_ECE; 1784 TCPSTAT_INC(tcps_ecn_shs); 1785 } 1786 1787 /* Tack on the TCP options. */ 1788 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1789 to.to_flags = 0; 1790 1791 if (flags & TH_SYN) { 1792 to.to_mss = mssopt; 1793 to.to_flags = TOF_MSS; 1794 if (sc->sc_flags & SCF_WINSCALE) { 1795 to.to_wscale = sc->sc_requested_r_scale; 1796 to.to_flags |= TOF_SCALE; 1797 } 1798 if (sc->sc_flags & SCF_SACK) 1799 to.to_flags |= TOF_SACKPERM; 1800 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1801 if (sc->sc_flags & SCF_SIGNATURE) 1802 to.to_flags |= TOF_SIGNATURE; 1803 #endif 1804 if (sc->sc_tfo_cookie) { 1805 to.to_flags |= TOF_FASTOPEN; 1806 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 1807 to.to_tfo_cookie = sc->sc_tfo_cookie; 1808 /* don't send cookie again when retransmitting response */ 1809 sc->sc_tfo_cookie = NULL; 1810 } 1811 } 1812 if (sc->sc_flags & SCF_TIMESTAMP) { 1813 to.to_tsval = sc->sc_tsoff + tcp_ts_getticks(); 1814 to.to_tsecr = sc->sc_tsreflect; 1815 to.to_flags |= TOF_TS; 1816 } 1817 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1818 1819 /* Adjust headers by option size. */ 1820 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1821 m->m_len += optlen; 1822 m->m_pkthdr.len += optlen; 1823 #ifdef INET6 1824 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1825 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1826 else 1827 #endif 1828 ip->ip_len = htons(ntohs(ip->ip_len) + optlen); 1829 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1830 if (sc->sc_flags & SCF_SIGNATURE) { 1831 KASSERT(to.to_flags & TOF_SIGNATURE, 1832 ("tcp_addoptions() didn't set tcp_signature")); 1833 1834 /* NOTE: to.to_signature is inside of mbuf */ 1835 if (!TCPMD5_ENABLED() || 1836 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) { 1837 m_freem(m); 1838 return (EACCES); 1839 } 1840 } 1841 #endif 1842 } else 1843 optlen = 0; 1844 1845 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1846 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1847 /* 1848 * If we have peer's SYN and it has a flowid, then let's assign it to 1849 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid 1850 * to SYN|ACK due to lack of inp here. 1851 */ 1852 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) { 1853 m->m_pkthdr.flowid = m0->m_pkthdr.flowid; 1854 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0)); 1855 } 1856 #ifdef INET6 1857 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1858 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1859 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1860 IPPROTO_TCP, 0); 1861 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1862 #ifdef TCP_OFFLOAD 1863 if (ADDED_BY_TOE(sc)) { 1864 struct toedev *tod = sc->sc_tod; 1865 1866 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1867 1868 return (error); 1869 } 1870 #endif 1871 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th); 1872 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1873 } 1874 #endif 1875 #if defined(INET6) && defined(INET) 1876 else 1877 #endif 1878 #ifdef INET 1879 { 1880 m->m_pkthdr.csum_flags = CSUM_TCP; 1881 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1882 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1883 #ifdef TCP_OFFLOAD 1884 if (ADDED_BY_TOE(sc)) { 1885 struct toedev *tod = sc->sc_tod; 1886 1887 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1888 1889 return (error); 1890 } 1891 #endif 1892 TCP_PROBE5(send, NULL, NULL, ip, NULL, th); 1893 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1894 } 1895 #endif 1896 return (error); 1897 } 1898 1899 /* 1900 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks 1901 * that exceed the capacity of the syncache by avoiding the storage of any 1902 * of the SYNs we receive. Syncookies defend against blind SYN flooding 1903 * attacks where the attacker does not have access to our responses. 1904 * 1905 * Syncookies encode and include all necessary information about the 1906 * connection setup within the SYN|ACK that we send back. That way we 1907 * can avoid keeping any local state until the ACK to our SYN|ACK returns 1908 * (if ever). Normally the syncache and syncookies are running in parallel 1909 * with the latter taking over when the former is exhausted. When matching 1910 * syncache entry is found the syncookie is ignored. 1911 * 1912 * The only reliable information persisting the 3WHS is our initial sequence 1913 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient 1914 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS 1915 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK 1916 * returns and signifies a legitimate connection if it matches the ACK. 1917 * 1918 * The available space of 32 bits to store the hash and to encode the SYN 1919 * option information is very tight and we should have at least 24 bits for 1920 * the MAC to keep the number of guesses by blind spoofing reasonably high. 1921 * 1922 * SYN option information we have to encode to fully restore a connection: 1923 * MSS: is imporant to chose an optimal segment size to avoid IP level 1924 * fragmentation along the path. The common MSS values can be encoded 1925 * in a 3-bit table. Uncommon values are captured by the next lower value 1926 * in the table leading to a slight increase in packetization overhead. 1927 * WSCALE: is necessary to allow large windows to be used for high delay- 1928 * bandwidth product links. Not scaling the window when it was initially 1929 * negotiated is bad for performance as lack of scaling further decreases 1930 * the apparent available send window. We only need to encode the WSCALE 1931 * we received from the remote end. Our end can be recalculated at any 1932 * time. The common WSCALE values can be encoded in a 3-bit table. 1933 * Uncommon values are captured by the next lower value in the table 1934 * making us under-estimate the available window size halving our 1935 * theoretically possible maximum throughput for that connection. 1936 * SACK: Greatly assists in packet loss recovery and requires 1 bit. 1937 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options 1938 * that are included in all segments on a connection. We enable them when 1939 * the ACK has them. 1940 * 1941 * Security of syncookies and attack vectors: 1942 * 1943 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod) 1944 * together with the gloabl secret to make it unique per connection attempt. 1945 * Thus any change of any of those parameters results in a different MAC output 1946 * in an unpredictable way unless a collision is encountered. 24 bits of the 1947 * MAC are embedded into the ISS. 1948 * 1949 * To prevent replay attacks two rotating global secrets are updated with a 1950 * new random value every 15 seconds. The life-time of a syncookie is thus 1951 * 15-30 seconds. 1952 * 1953 * Vector 1: Attacking the secret. This requires finding a weakness in the 1954 * MAC itself or the way it is used here. The attacker can do a chosen plain 1955 * text attack by varying and testing the all parameters under his control. 1956 * The strength depends on the size and randomness of the secret, and the 1957 * cryptographic security of the MAC function. Due to the constant updating 1958 * of the secret the attacker has at most 29.999 seconds to find the secret 1959 * and launch spoofed connections. After that he has to start all over again. 1960 * 1961 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC 1962 * size an average of 4,823 attempts are required for a 50% chance of success 1963 * to spoof a single syncookie (birthday collision paradox). However the 1964 * attacker is blind and doesn't know if one of his attempts succeeded unless 1965 * he has a side channel to interfere success from. A single connection setup 1966 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets. 1967 * This many attempts are required for each one blind spoofed connection. For 1968 * every additional spoofed connection he has to launch another N attempts. 1969 * Thus for a sustained rate 100 spoofed connections per second approximately 1970 * 1,800,000 packets per second would have to be sent. 1971 * 1972 * NB: The MAC function should be fast so that it doesn't become a CPU 1973 * exhaustion attack vector itself. 1974 * 1975 * References: 1976 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations 1977 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996 1978 * http://cr.yp.to/syncookies.html (overview) 1979 * http://cr.yp.to/syncookies/archive (details) 1980 * 1981 * 1982 * Schematic construction of a syncookie enabled Initial Sequence Number: 1983 * 0 1 2 3 1984 * 12345678901234567890123456789012 1985 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP| 1986 * 1987 * x 24 MAC (truncated) 1988 * W 3 Send Window Scale index 1989 * M 3 MSS index 1990 * S 1 SACK permitted 1991 * P 1 Odd/even secret 1992 */ 1993 1994 /* 1995 * Distribution and probability of certain MSS values. Those in between are 1996 * rounded down to the next lower one. 1997 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011] 1998 * .2% .3% 5% 7% 7% 20% 15% 45% 1999 */ 2000 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 }; 2001 2002 /* 2003 * Distribution and probability of certain WSCALE values. We have to map the 2004 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3 2005 * bits based on prevalence of certain values. Where we don't have an exact 2006 * match for are rounded down to the next lower one letting us under-estimate 2007 * the true available window. At the moment this would happen only for the 2008 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer 2009 * and window size). The absence of the WSCALE option (no scaling in either 2010 * direction) is encoded with index zero. 2011 * [WSCALE values histograms, Allman, 2012] 2012 * X 10 10 35 5 6 14 10% by host 2013 * X 11 4 5 5 18 49 3% by connections 2014 */ 2015 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 }; 2016 2017 /* 2018 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed 2019 * and good cryptographic properties. 2020 */ 2021 static uint32_t 2022 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags, 2023 uint8_t *secbits, uintptr_t secmod) 2024 { 2025 SIPHASH_CTX ctx; 2026 uint32_t siphash[2]; 2027 2028 SipHash24_Init(&ctx); 2029 SipHash_SetKey(&ctx, secbits); 2030 switch (inc->inc_flags & INC_ISIPV6) { 2031 #ifdef INET 2032 case 0: 2033 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr)); 2034 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr)); 2035 break; 2036 #endif 2037 #ifdef INET6 2038 case INC_ISIPV6: 2039 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr)); 2040 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr)); 2041 break; 2042 #endif 2043 } 2044 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport)); 2045 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport)); 2046 SipHash_Update(&ctx, &irs, sizeof(irs)); 2047 SipHash_Update(&ctx, &flags, sizeof(flags)); 2048 SipHash_Update(&ctx, &secmod, sizeof(secmod)); 2049 SipHash_Final((u_int8_t *)&siphash, &ctx); 2050 2051 return (siphash[0] ^ siphash[1]); 2052 } 2053 2054 static tcp_seq 2055 syncookie_generate(struct syncache_head *sch, struct syncache *sc) 2056 { 2057 u_int i, secbit, wscale; 2058 uint32_t iss, hash; 2059 uint8_t *secbits; 2060 union syncookie cookie; 2061 2062 SCH_LOCK_ASSERT(sch); 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 = sch->sch_sc->secret.oddeven & 0x1; 2092 cookie.flags.odd_even = secbit; 2093 2094 secbits = sch->sch_sc->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 SCH_LOCK_ASSERT(sch); 2123 2124 /* 2125 * Pull information out of SYN-ACK/ACK and revert sequence number 2126 * advances. 2127 */ 2128 ack = th->th_ack - 1; 2129 seq = th->th_seq - 1; 2130 2131 /* 2132 * Unpack the flags containing enough information to restore the 2133 * connection. 2134 */ 2135 cookie.cookie = (ack & 0xff) ^ (ack >> 24); 2136 2137 /* Which of the two secrets to use. */ 2138 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even]; 2139 2140 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch); 2141 2142 /* The recomputed hash matches the ACK if this was a genuine cookie. */ 2143 if ((ack & ~0xff) != (hash & ~0xff)) 2144 return (NULL); 2145 2146 /* Fill in the syncache values. */ 2147 sc->sc_flags = 0; 2148 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 2149 sc->sc_ipopts = NULL; 2150 2151 sc->sc_irs = seq; 2152 sc->sc_iss = ack; 2153 2154 switch (inc->inc_flags & INC_ISIPV6) { 2155 #ifdef INET 2156 case 0: 2157 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl; 2158 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos; 2159 break; 2160 #endif 2161 #ifdef INET6 2162 case INC_ISIPV6: 2163 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL) 2164 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK; 2165 break; 2166 #endif 2167 } 2168 2169 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx]; 2170 2171 /* We can simply recompute receive window scale we sent earlier. */ 2172 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max) 2173 wscale++; 2174 2175 /* Only use wscale if it was enabled in the orignal SYN. */ 2176 if (cookie.flags.wscale_idx > 0) { 2177 sc->sc_requested_r_scale = wscale; 2178 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx]; 2179 sc->sc_flags |= SCF_WINSCALE; 2180 } 2181 2182 wnd = lso->sol_sbrcv_hiwat; 2183 wnd = imax(wnd, 0); 2184 wnd = imin(wnd, TCP_MAXWIN); 2185 sc->sc_wnd = wnd; 2186 2187 if (cookie.flags.sack_ok) 2188 sc->sc_flags |= SCF_SACK; 2189 2190 if (to->to_flags & TOF_TS) { 2191 sc->sc_flags |= SCF_TIMESTAMP; 2192 sc->sc_tsreflect = to->to_tsval; 2193 sc->sc_tsoff = tcp_new_ts_offset(inc); 2194 } 2195 2196 if (to->to_flags & TOF_SIGNATURE) 2197 sc->sc_flags |= SCF_SIGNATURE; 2198 2199 sc->sc_rxmits = 0; 2200 2201 TCPSTAT_INC(tcps_sc_recvcookie); 2202 return (sc); 2203 } 2204 2205 #ifdef INVARIANTS 2206 static int 2207 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch, 2208 struct syncache *sc, struct tcphdr *th, struct tcpopt *to, 2209 struct socket *lso) 2210 { 2211 struct syncache scs, *scx; 2212 char *s; 2213 2214 bzero(&scs, sizeof(scs)); 2215 scx = syncookie_lookup(inc, sch, &scs, th, to, lso); 2216 2217 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL) 2218 return (0); 2219 2220 if (scx != NULL) { 2221 if (sc->sc_peer_mss != scx->sc_peer_mss) 2222 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n", 2223 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss); 2224 2225 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale) 2226 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n", 2227 s, __func__, sc->sc_requested_r_scale, 2228 scx->sc_requested_r_scale); 2229 2230 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale) 2231 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n", 2232 s, __func__, sc->sc_requested_s_scale, 2233 scx->sc_requested_s_scale); 2234 2235 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK)) 2236 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__); 2237 } 2238 2239 if (s != NULL) 2240 free(s, M_TCPLOG); 2241 return (0); 2242 } 2243 #endif /* INVARIANTS */ 2244 2245 static void 2246 syncookie_reseed(void *arg) 2247 { 2248 struct tcp_syncache *sc = arg; 2249 uint8_t *secbits; 2250 int secbit; 2251 2252 /* 2253 * Reseeding the secret doesn't have to be protected by a lock. 2254 * It only must be ensured that the new random values are visible 2255 * to all CPUs in a SMP environment. The atomic with release 2256 * semantics ensures that. 2257 */ 2258 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1; 2259 secbits = sc->secret.key[secbit]; 2260 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0); 2261 atomic_add_rel_int(&sc->secret.oddeven, 1); 2262 2263 /* Reschedule ourself. */ 2264 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz); 2265 } 2266 2267 /* 2268 * Exports the syncache entries to userland so that netstat can display 2269 * them alongside the other sockets. This function is intended to be 2270 * called only from tcp_pcblist. 2271 * 2272 * Due to concurrency on an active system, the number of pcbs exported 2273 * may have no relation to max_pcbs. max_pcbs merely indicates the 2274 * amount of space the caller allocated for this function to use. 2275 */ 2276 int 2277 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 2278 { 2279 struct xtcpcb xt; 2280 struct syncache *sc; 2281 struct syncache_head *sch; 2282 int count, error, i; 2283 2284 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 2285 sch = &V_tcp_syncache.hashbase[i]; 2286 SCH_LOCK(sch); 2287 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 2288 if (count >= max_pcbs) { 2289 SCH_UNLOCK(sch); 2290 goto exit; 2291 } 2292 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 2293 continue; 2294 bzero(&xt, sizeof(xt)); 2295 xt.xt_len = sizeof(xt); 2296 if (sc->sc_inc.inc_flags & INC_ISIPV6) 2297 xt.xt_inp.inp_vflag = INP_IPV6; 2298 else 2299 xt.xt_inp.inp_vflag = INP_IPV4; 2300 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, 2301 sizeof (struct in_conninfo)); 2302 xt.t_state = TCPS_SYN_RECEIVED; 2303 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP; 2304 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket); 2305 xt.xt_inp.xi_socket.so_type = SOCK_STREAM; 2306 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING; 2307 error = SYSCTL_OUT(req, &xt, sizeof xt); 2308 if (error) { 2309 SCH_UNLOCK(sch); 2310 goto exit; 2311 } 2312 count++; 2313 } 2314 SCH_UNLOCK(sch); 2315 } 2316 exit: 2317 *pcbs_exported = count; 2318 return error; 2319 } 2320