1 /*- 2 * Copyright (c) 2001 McAfee, Inc. 3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG 4 * All rights reserved. 5 * 6 * This software was developed for the FreeBSD Project by Jonathan Lemon 7 * and McAfee Research, the Security Research Division of McAfee, Inc. under 8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 9 * DARPA CHATS research program. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include "opt_inet.h" 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_pcbgroup.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/kernel.h> 44 #include <sys/sysctl.h> 45 #include <sys/limits.h> 46 #include <sys/lock.h> 47 #include <sys/mutex.h> 48 #include <sys/malloc.h> 49 #include <sys/mbuf.h> 50 #include <sys/md5.h> 51 #include <sys/proc.h> /* for proc0 declaration */ 52 #include <sys/random.h> 53 #include <sys/socket.h> 54 #include <sys/socketvar.h> 55 #include <sys/syslog.h> 56 #include <sys/ucred.h> 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 #include <net/vnet.h> 63 64 #include <netinet/in.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/ip.h> 67 #include <netinet/in_var.h> 68 #include <netinet/in_pcb.h> 69 #include <netinet/ip_var.h> 70 #include <netinet/ip_options.h> 71 #ifdef INET6 72 #include <netinet/ip6.h> 73 #include <netinet/icmp6.h> 74 #include <netinet6/nd6.h> 75 #include <netinet6/ip6_var.h> 76 #include <netinet6/in6_pcb.h> 77 #endif 78 #include <netinet/tcp.h> 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #include <netinet/tcp_syncache.h> 84 #ifdef INET6 85 #include <netinet6/tcp6_var.h> 86 #endif 87 #ifdef TCP_OFFLOAD 88 #include <netinet/toecore.h> 89 #endif 90 91 #ifdef IPSEC 92 #include <netipsec/ipsec.h> 93 #ifdef INET6 94 #include <netipsec/ipsec6.h> 95 #endif 96 #include <netipsec/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 #include <security/mac/mac_framework.h> 102 103 static VNET_DEFINE(int, tcp_syncookies) = 1; 104 #define V_tcp_syncookies VNET(tcp_syncookies) 105 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 106 &VNET_NAME(tcp_syncookies), 0, 107 "Use TCP SYN cookies if the syncache overflows"); 108 109 static VNET_DEFINE(int, tcp_syncookiesonly) = 0; 110 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly) 111 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW, 112 &VNET_NAME(tcp_syncookiesonly), 0, 113 "Use only TCP SYN cookies"); 114 115 #ifdef TCP_OFFLOAD 116 #define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL) 117 #endif 118 119 static void syncache_drop(struct syncache *, struct syncache_head *); 120 static void syncache_free(struct syncache *); 121 static void syncache_insert(struct syncache *, struct syncache_head *); 122 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 123 static int syncache_respond(struct syncache *); 124 static struct socket *syncache_socket(struct syncache *, struct socket *, 125 struct mbuf *m); 126 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 127 int docallout); 128 static void syncache_timer(void *); 129 static void syncookie_generate(struct syncache_head *, struct syncache *, 130 u_int32_t *); 131 static struct syncache 132 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 133 struct syncache *, struct tcpopt *, struct tcphdr *, 134 struct socket *); 135 136 /* 137 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 138 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 139 * the odds are that the user has given up attempting to connect by then. 140 */ 141 #define SYNCACHE_MAXREXMTS 3 142 143 /* Arbitrary values */ 144 #define TCP_SYNCACHE_HASHSIZE 512 145 #define TCP_SYNCACHE_BUCKETLIMIT 30 146 147 static VNET_DEFINE(struct tcp_syncache, tcp_syncache); 148 #define V_tcp_syncache VNET(tcp_syncache) 149 150 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, 151 "TCP SYN cache"); 152 153 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 154 &VNET_NAME(tcp_syncache.bucket_limit), 0, 155 "Per-bucket hash limit for syncache"); 156 157 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 158 &VNET_NAME(tcp_syncache.cache_limit), 0, 159 "Overall entry limit for syncache"); 160 161 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 162 &VNET_NAME(tcp_syncache.cache_count), 0, 163 "Current number of entries in syncache"); 164 165 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 166 &VNET_NAME(tcp_syncache.hashsize), 0, 167 "Size of TCP syncache hashtable"); 168 169 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 170 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 171 "Limit on SYN/ACK retransmissions"); 172 173 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 174 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 175 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 176 "Send reset on socket allocation failure"); 177 178 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 179 180 #define SYNCACHE_HASH(inc, mask) \ 181 ((V_tcp_syncache.hash_secret ^ \ 182 (inc)->inc_faddr.s_addr ^ \ 183 ((inc)->inc_faddr.s_addr >> 16) ^ \ 184 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 185 186 #define SYNCACHE_HASH6(inc, mask) \ 187 ((V_tcp_syncache.hash_secret ^ \ 188 (inc)->inc6_faddr.s6_addr32[0] ^ \ 189 (inc)->inc6_faddr.s6_addr32[3] ^ \ 190 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 191 192 #define ENDPTS_EQ(a, b) ( \ 193 (a)->ie_fport == (b)->ie_fport && \ 194 (a)->ie_lport == (b)->ie_lport && \ 195 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 196 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 197 ) 198 199 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 200 201 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 202 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 203 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 204 205 /* 206 * Requires the syncache entry to be already removed from the bucket list. 207 */ 208 static void 209 syncache_free(struct syncache *sc) 210 { 211 212 if (sc->sc_ipopts) 213 (void) m_free(sc->sc_ipopts); 214 if (sc->sc_cred) 215 crfree(sc->sc_cred); 216 #ifdef MAC 217 mac_syncache_destroy(&sc->sc_label); 218 #endif 219 220 uma_zfree(V_tcp_syncache.zone, sc); 221 } 222 223 void 224 syncache_init(void) 225 { 226 int i; 227 228 V_tcp_syncache.cache_count = 0; 229 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 230 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 231 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 232 V_tcp_syncache.hash_secret = arc4random(); 233 234 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 235 &V_tcp_syncache.hashsize); 236 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 237 &V_tcp_syncache.bucket_limit); 238 if (!powerof2(V_tcp_syncache.hashsize) || 239 V_tcp_syncache.hashsize == 0) { 240 printf("WARNING: syncache hash size is not a power of 2.\n"); 241 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 242 } 243 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 244 245 /* Set limits. */ 246 V_tcp_syncache.cache_limit = 247 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 248 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 249 &V_tcp_syncache.cache_limit); 250 251 /* Allocate the hash table. */ 252 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 253 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 254 255 /* Initialize the hash buckets. */ 256 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 257 #ifdef VIMAGE 258 V_tcp_syncache.hashbase[i].sch_vnet = curvnet; 259 #endif 260 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 261 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 262 NULL, MTX_DEF); 263 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 264 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 265 V_tcp_syncache.hashbase[i].sch_length = 0; 266 } 267 268 /* Create the syncache entry zone. */ 269 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 270 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 271 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit); 272 } 273 274 #ifdef VIMAGE 275 void 276 syncache_destroy(void) 277 { 278 struct syncache_head *sch; 279 struct syncache *sc, *nsc; 280 int i; 281 282 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 283 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 284 285 sch = &V_tcp_syncache.hashbase[i]; 286 callout_drain(&sch->sch_timer); 287 288 SCH_LOCK(sch); 289 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 290 syncache_drop(sc, sch); 291 SCH_UNLOCK(sch); 292 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 293 ("%s: sch->sch_bucket not empty", __func__)); 294 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 295 __func__, sch->sch_length)); 296 mtx_destroy(&sch->sch_mtx); 297 } 298 299 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0", 300 __func__, V_tcp_syncache.cache_count)); 301 302 /* Free the allocated global resources. */ 303 uma_zdestroy(V_tcp_syncache.zone); 304 free(V_tcp_syncache.hashbase, M_SYNCACHE); 305 } 306 #endif 307 308 /* 309 * Inserts a syncache entry into the specified bucket row. 310 * Locks and unlocks the syncache_head autonomously. 311 */ 312 static void 313 syncache_insert(struct syncache *sc, struct syncache_head *sch) 314 { 315 struct syncache *sc2; 316 317 SCH_LOCK(sch); 318 319 /* 320 * Make sure that we don't overflow the per-bucket limit. 321 * If the bucket is full, toss the oldest element. 322 */ 323 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 324 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 325 ("sch->sch_length incorrect")); 326 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 327 syncache_drop(sc2, sch); 328 TCPSTAT_INC(tcps_sc_bucketoverflow); 329 } 330 331 /* Put it into the bucket. */ 332 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 333 sch->sch_length++; 334 335 #ifdef TCP_OFFLOAD 336 if (ADDED_BY_TOE(sc)) { 337 struct toedev *tod = sc->sc_tod; 338 339 tod->tod_syncache_added(tod, sc->sc_todctx); 340 } 341 #endif 342 343 /* Reinitialize the bucket row's timer. */ 344 if (sch->sch_length == 1) 345 sch->sch_nextc = ticks + INT_MAX; 346 syncache_timeout(sc, sch, 1); 347 348 SCH_UNLOCK(sch); 349 350 V_tcp_syncache.cache_count++; 351 TCPSTAT_INC(tcps_sc_added); 352 } 353 354 /* 355 * Remove and free entry from syncache bucket row. 356 * Expects locked syncache head. 357 */ 358 static void 359 syncache_drop(struct syncache *sc, struct syncache_head *sch) 360 { 361 362 SCH_LOCK_ASSERT(sch); 363 364 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 365 sch->sch_length--; 366 367 #ifdef TCP_OFFLOAD 368 if (ADDED_BY_TOE(sc)) { 369 struct toedev *tod = sc->sc_tod; 370 371 tod->tod_syncache_removed(tod, sc->sc_todctx); 372 } 373 #endif 374 375 syncache_free(sc); 376 V_tcp_syncache.cache_count--; 377 } 378 379 /* 380 * Engage/reengage time on bucket row. 381 */ 382 static void 383 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 384 { 385 sc->sc_rxttime = ticks + 386 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 387 sc->sc_rxmits++; 388 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 389 sch->sch_nextc = sc->sc_rxttime; 390 if (docallout) 391 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 392 syncache_timer, (void *)sch); 393 } 394 } 395 396 /* 397 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 398 * If we have retransmitted an entry the maximum number of times, expire it. 399 * One separate timer for each bucket row. 400 */ 401 static void 402 syncache_timer(void *xsch) 403 { 404 struct syncache_head *sch = (struct syncache_head *)xsch; 405 struct syncache *sc, *nsc; 406 int tick = ticks; 407 char *s; 408 409 CURVNET_SET(sch->sch_vnet); 410 411 /* NB: syncache_head has already been locked by the callout. */ 412 SCH_LOCK_ASSERT(sch); 413 414 /* 415 * In the following cycle we may remove some entries and/or 416 * advance some timeouts, so re-initialize the bucket timer. 417 */ 418 sch->sch_nextc = tick + INT_MAX; 419 420 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 421 /* 422 * We do not check if the listen socket still exists 423 * and accept the case where the listen socket may be 424 * gone by the time we resend the SYN/ACK. We do 425 * not expect this to happens often. If it does, 426 * then the RST will be sent by the time the remote 427 * host does the SYN/ACK->ACK. 428 */ 429 if (TSTMP_GT(sc->sc_rxttime, tick)) { 430 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 431 sch->sch_nextc = sc->sc_rxttime; 432 continue; 433 } 434 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 435 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 436 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 437 "giving up and removing syncache entry\n", 438 s, __func__); 439 free(s, M_TCPLOG); 440 } 441 syncache_drop(sc, sch); 442 TCPSTAT_INC(tcps_sc_stale); 443 continue; 444 } 445 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 446 log(LOG_DEBUG, "%s; %s: Response timeout, " 447 "retransmitting (%u) SYN|ACK\n", 448 s, __func__, sc->sc_rxmits); 449 free(s, M_TCPLOG); 450 } 451 452 (void) syncache_respond(sc); 453 TCPSTAT_INC(tcps_sc_retransmitted); 454 syncache_timeout(sc, sch, 0); 455 } 456 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 457 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 458 syncache_timer, (void *)(sch)); 459 CURVNET_RESTORE(); 460 } 461 462 /* 463 * Find an entry in the syncache. 464 * Returns always with locked syncache_head plus a matching entry or NULL. 465 */ 466 struct syncache * 467 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 468 { 469 struct syncache *sc; 470 struct syncache_head *sch; 471 472 #ifdef INET6 473 if (inc->inc_flags & INC_ISIPV6) { 474 sch = &V_tcp_syncache.hashbase[ 475 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 476 *schp = sch; 477 478 SCH_LOCK(sch); 479 480 /* Circle through bucket row to find matching entry. */ 481 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 482 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 483 return (sc); 484 } 485 } else 486 #endif 487 { 488 sch = &V_tcp_syncache.hashbase[ 489 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 490 *schp = sch; 491 492 SCH_LOCK(sch); 493 494 /* Circle through bucket row to find matching entry. */ 495 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 496 #ifdef INET6 497 if (sc->sc_inc.inc_flags & INC_ISIPV6) 498 continue; 499 #endif 500 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 501 return (sc); 502 } 503 } 504 SCH_LOCK_ASSERT(*schp); 505 return (NULL); /* always returns with locked sch */ 506 } 507 508 /* 509 * This function is called when we get a RST for a 510 * non-existent connection, so that we can see if the 511 * connection is in the syn cache. If it is, zap it. 512 */ 513 void 514 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 515 { 516 struct syncache *sc; 517 struct syncache_head *sch; 518 char *s = NULL; 519 520 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 521 SCH_LOCK_ASSERT(sch); 522 523 /* 524 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 525 * See RFC 793 page 65, section SEGMENT ARRIVES. 526 */ 527 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 528 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 529 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 530 "FIN flag set, segment ignored\n", s, __func__); 531 TCPSTAT_INC(tcps_badrst); 532 goto done; 533 } 534 535 /* 536 * No corresponding connection was found in syncache. 537 * If syncookies are enabled and possibly exclusively 538 * used, or we are under memory pressure, a valid RST 539 * may not find a syncache entry. In that case we're 540 * done and no SYN|ACK retransmissions will happen. 541 * Otherwise the RST was misdirected or spoofed. 542 */ 543 if (sc == NULL) { 544 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 545 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 546 "syncache entry (possibly syncookie only), " 547 "segment ignored\n", s, __func__); 548 TCPSTAT_INC(tcps_badrst); 549 goto done; 550 } 551 552 /* 553 * If the RST bit is set, check the sequence number to see 554 * if this is a valid reset segment. 555 * RFC 793 page 37: 556 * In all states except SYN-SENT, all reset (RST) segments 557 * are validated by checking their SEQ-fields. A reset is 558 * valid if its sequence number is in the window. 559 * 560 * The sequence number in the reset segment is normally an 561 * echo of our outgoing acknowlegement numbers, but some hosts 562 * send a reset with the sequence number at the rightmost edge 563 * of our receive window, and we have to handle this case. 564 */ 565 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 566 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 567 syncache_drop(sc, sch); 568 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 569 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 570 "connection attempt aborted by remote endpoint\n", 571 s, __func__); 572 TCPSTAT_INC(tcps_sc_reset); 573 } else { 574 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 575 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 576 "IRS %u (+WND %u), segment ignored\n", 577 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 578 TCPSTAT_INC(tcps_badrst); 579 } 580 581 done: 582 if (s != NULL) 583 free(s, M_TCPLOG); 584 SCH_UNLOCK(sch); 585 } 586 587 void 588 syncache_badack(struct in_conninfo *inc) 589 { 590 struct syncache *sc; 591 struct syncache_head *sch; 592 593 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 594 SCH_LOCK_ASSERT(sch); 595 if (sc != NULL) { 596 syncache_drop(sc, sch); 597 TCPSTAT_INC(tcps_sc_badack); 598 } 599 SCH_UNLOCK(sch); 600 } 601 602 void 603 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 604 { 605 struct syncache *sc; 606 struct syncache_head *sch; 607 608 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 609 SCH_LOCK_ASSERT(sch); 610 if (sc == NULL) 611 goto done; 612 613 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 614 if (ntohl(th->th_seq) != sc->sc_iss) 615 goto done; 616 617 /* 618 * If we've rertransmitted 3 times and this is our second error, 619 * we remove the entry. Otherwise, we allow it to continue on. 620 * This prevents us from incorrectly nuking an entry during a 621 * spurious network outage. 622 * 623 * See tcp_notify(). 624 */ 625 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 626 sc->sc_flags |= SCF_UNREACH; 627 goto done; 628 } 629 syncache_drop(sc, sch); 630 TCPSTAT_INC(tcps_sc_unreach); 631 done: 632 SCH_UNLOCK(sch); 633 } 634 635 /* 636 * Build a new TCP socket structure from a syncache entry. 637 */ 638 static struct socket * 639 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 640 { 641 struct inpcb *inp = NULL; 642 struct socket *so; 643 struct tcpcb *tp; 644 int error; 645 char *s; 646 647 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 648 649 /* 650 * Ok, create the full blown connection, and set things up 651 * as they would have been set up if we had created the 652 * connection when the SYN arrived. If we can't create 653 * the connection, abort it. 654 */ 655 so = sonewconn(lso, SS_ISCONNECTED); 656 if (so == NULL) { 657 /* 658 * Drop the connection; we will either send a RST or 659 * have the peer retransmit its SYN again after its 660 * RTO and try again. 661 */ 662 TCPSTAT_INC(tcps_listendrop); 663 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 664 log(LOG_DEBUG, "%s; %s: Socket create failed " 665 "due to limits or memory shortage\n", 666 s, __func__); 667 free(s, M_TCPLOG); 668 } 669 goto abort2; 670 } 671 #ifdef MAC 672 mac_socketpeer_set_from_mbuf(m, so); 673 #endif 674 675 inp = sotoinpcb(so); 676 inp->inp_inc.inc_fibnum = so->so_fibnum; 677 INP_WLOCK(inp); 678 INP_HASH_WLOCK(&V_tcbinfo); 679 680 /* Insert new socket into PCB hash list. */ 681 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 682 #ifdef INET6 683 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 684 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 685 } else { 686 inp->inp_vflag &= ~INP_IPV6; 687 inp->inp_vflag |= INP_IPV4; 688 #endif 689 inp->inp_laddr = sc->sc_inc.inc_laddr; 690 #ifdef INET6 691 } 692 #endif 693 694 /* 695 * Install in the reservation hash table for now, but don't yet 696 * install a connection group since the full 4-tuple isn't yet 697 * configured. 698 */ 699 inp->inp_lport = sc->sc_inc.inc_lport; 700 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 701 /* 702 * Undo the assignments above if we failed to 703 * put the PCB on the hash lists. 704 */ 705 #ifdef INET6 706 if (sc->sc_inc.inc_flags & INC_ISIPV6) 707 inp->in6p_laddr = in6addr_any; 708 else 709 #endif 710 inp->inp_laddr.s_addr = INADDR_ANY; 711 inp->inp_lport = 0; 712 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 713 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 714 "with error %i\n", 715 s, __func__, error); 716 free(s, M_TCPLOG); 717 } 718 INP_HASH_WUNLOCK(&V_tcbinfo); 719 goto abort; 720 } 721 #ifdef IPSEC 722 /* Copy old policy into new socket's. */ 723 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 724 printf("syncache_socket: could not copy policy\n"); 725 #endif 726 #ifdef INET6 727 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 728 struct inpcb *oinp = sotoinpcb(lso); 729 struct in6_addr laddr6; 730 struct sockaddr_in6 sin6; 731 /* 732 * Inherit socket options from the listening socket. 733 * Note that in6p_inputopts are not (and should not be) 734 * copied, since it stores previously received options and is 735 * used to detect if each new option is different than the 736 * previous one and hence should be passed to a user. 737 * If we copied in6p_inputopts, a user would not be able to 738 * receive options just after calling the accept system call. 739 */ 740 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 741 if (oinp->in6p_outputopts) 742 inp->in6p_outputopts = 743 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 744 745 sin6.sin6_family = AF_INET6; 746 sin6.sin6_len = sizeof(sin6); 747 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 748 sin6.sin6_port = sc->sc_inc.inc_fport; 749 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 750 laddr6 = inp->in6p_laddr; 751 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 752 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 753 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 754 thread0.td_ucred, m)) != 0) { 755 inp->in6p_laddr = laddr6; 756 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 757 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 758 "with error %i\n", 759 s, __func__, error); 760 free(s, M_TCPLOG); 761 } 762 INP_HASH_WUNLOCK(&V_tcbinfo); 763 goto abort; 764 } 765 /* Override flowlabel from in6_pcbconnect. */ 766 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 767 inp->inp_flow |= sc->sc_flowlabel; 768 } 769 #endif /* INET6 */ 770 #if defined(INET) && defined(INET6) 771 else 772 #endif 773 #ifdef INET 774 { 775 struct in_addr laddr; 776 struct sockaddr_in sin; 777 778 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 779 780 if (inp->inp_options == NULL) { 781 inp->inp_options = sc->sc_ipopts; 782 sc->sc_ipopts = NULL; 783 } 784 785 sin.sin_family = AF_INET; 786 sin.sin_len = sizeof(sin); 787 sin.sin_addr = sc->sc_inc.inc_faddr; 788 sin.sin_port = sc->sc_inc.inc_fport; 789 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 790 laddr = inp->inp_laddr; 791 if (inp->inp_laddr.s_addr == INADDR_ANY) 792 inp->inp_laddr = sc->sc_inc.inc_laddr; 793 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 794 thread0.td_ucred, m)) != 0) { 795 inp->inp_laddr = laddr; 796 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 797 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 798 "with error %i\n", 799 s, __func__, error); 800 free(s, M_TCPLOG); 801 } 802 INP_HASH_WUNLOCK(&V_tcbinfo); 803 goto abort; 804 } 805 } 806 #endif /* INET */ 807 INP_HASH_WUNLOCK(&V_tcbinfo); 808 tp = intotcpcb(inp); 809 tp->t_state = TCPS_SYN_RECEIVED; 810 tp->iss = sc->sc_iss; 811 tp->irs = sc->sc_irs; 812 tcp_rcvseqinit(tp); 813 tcp_sendseqinit(tp); 814 tp->snd_wl1 = sc->sc_irs; 815 tp->snd_max = tp->iss + 1; 816 tp->snd_nxt = tp->iss + 1; 817 tp->rcv_up = sc->sc_irs + 1; 818 tp->rcv_wnd = sc->sc_wnd; 819 tp->rcv_adv += tp->rcv_wnd; 820 tp->last_ack_sent = tp->rcv_nxt; 821 822 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 823 if (sc->sc_flags & SCF_NOOPT) 824 tp->t_flags |= TF_NOOPT; 825 else { 826 if (sc->sc_flags & SCF_WINSCALE) { 827 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 828 tp->snd_scale = sc->sc_requested_s_scale; 829 tp->request_r_scale = sc->sc_requested_r_scale; 830 } 831 if (sc->sc_flags & SCF_TIMESTAMP) { 832 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 833 tp->ts_recent = sc->sc_tsreflect; 834 tp->ts_recent_age = tcp_ts_getticks(); 835 tp->ts_offset = sc->sc_tsoff; 836 } 837 #ifdef TCP_SIGNATURE 838 if (sc->sc_flags & SCF_SIGNATURE) 839 tp->t_flags |= TF_SIGNATURE; 840 #endif 841 if (sc->sc_flags & SCF_SACK) 842 tp->t_flags |= TF_SACK_PERMIT; 843 } 844 845 if (sc->sc_flags & SCF_ECN) 846 tp->t_flags |= TF_ECN_PERMIT; 847 848 /* 849 * Set up MSS and get cached values from tcp_hostcache. 850 * This might overwrite some of the defaults we just set. 851 */ 852 tcp_mss(tp, sc->sc_peer_mss); 853 854 /* 855 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 856 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 857 */ 858 if (sc->sc_rxmits > 1) 859 tp->snd_cwnd = tp->t_maxseg; 860 861 #ifdef TCP_OFFLOAD 862 /* 863 * Allow a TOE driver to install its hooks. Note that we hold the 864 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a 865 * new connection before the TOE driver has done its thing. 866 */ 867 if (ADDED_BY_TOE(sc)) { 868 struct toedev *tod = sc->sc_tod; 869 870 tod->tod_offload_socket(tod, sc->sc_todctx, so); 871 } 872 #endif 873 /* 874 * Copy and activate timers. 875 */ 876 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 877 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 878 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 879 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 880 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 881 882 INP_WUNLOCK(inp); 883 884 TCPSTAT_INC(tcps_accepts); 885 return (so); 886 887 abort: 888 INP_WUNLOCK(inp); 889 abort2: 890 if (so != NULL) 891 soabort(so); 892 return (NULL); 893 } 894 895 /* 896 * This function gets called when we receive an ACK for a 897 * socket in the LISTEN state. We look up the connection 898 * in the syncache, and if its there, we pull it out of 899 * the cache and turn it into a full-blown connection in 900 * the SYN-RECEIVED state. 901 */ 902 int 903 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 904 struct socket **lsop, struct mbuf *m) 905 { 906 struct syncache *sc; 907 struct syncache_head *sch; 908 struct syncache scs; 909 char *s; 910 911 /* 912 * Global TCP locks are held because we manipulate the PCB lists 913 * and create a new socket. 914 */ 915 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 916 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 917 ("%s: can handle only ACK", __func__)); 918 919 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 920 SCH_LOCK_ASSERT(sch); 921 if (sc == NULL) { 922 /* 923 * There is no syncache entry, so see if this ACK is 924 * a returning syncookie. To do this, first: 925 * A. See if this socket has had a syncache entry dropped in 926 * the past. We don't want to accept a bogus syncookie 927 * if we've never received a SYN. 928 * B. check that the syncookie is valid. If it is, then 929 * cobble up a fake syncache entry, and return. 930 */ 931 if (!V_tcp_syncookies) { 932 SCH_UNLOCK(sch); 933 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 934 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 935 "segment rejected (syncookies disabled)\n", 936 s, __func__); 937 goto failed; 938 } 939 bzero(&scs, sizeof(scs)); 940 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 941 SCH_UNLOCK(sch); 942 if (sc == NULL) { 943 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 944 log(LOG_DEBUG, "%s; %s: Segment failed " 945 "SYNCOOKIE authentication, segment rejected " 946 "(probably spoofed)\n", s, __func__); 947 goto failed; 948 } 949 } else { 950 /* Pull out the entry to unlock the bucket row. */ 951 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 952 sch->sch_length--; 953 #ifdef TCP_OFFLOAD 954 if (ADDED_BY_TOE(sc)) { 955 struct toedev *tod = sc->sc_tod; 956 957 tod->tod_syncache_removed(tod, sc->sc_todctx); 958 } 959 #endif 960 V_tcp_syncache.cache_count--; 961 SCH_UNLOCK(sch); 962 } 963 964 /* 965 * Segment validation: 966 * ACK must match our initial sequence number + 1 (the SYN|ACK). 967 */ 968 if (th->th_ack != sc->sc_iss + 1) { 969 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 970 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 971 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 972 goto failed; 973 } 974 975 /* 976 * The SEQ must fall in the window starting at the received 977 * initial receive sequence number + 1 (the SYN). 978 */ 979 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 980 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 981 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 982 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 983 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 984 goto failed; 985 } 986 987 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 988 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 989 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 990 "segment rejected\n", s, __func__); 991 goto failed; 992 } 993 /* 994 * If timestamps were negotiated the reflected timestamp 995 * must be equal to what we actually sent in the SYN|ACK. 996 */ 997 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts) { 998 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 999 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 1000 "segment rejected\n", 1001 s, __func__, to->to_tsecr, sc->sc_ts); 1002 goto failed; 1003 } 1004 1005 *lsop = syncache_socket(sc, *lsop, m); 1006 1007 if (*lsop == NULL) 1008 TCPSTAT_INC(tcps_sc_aborted); 1009 else 1010 TCPSTAT_INC(tcps_sc_completed); 1011 1012 /* how do we find the inp for the new socket? */ 1013 if (sc != &scs) 1014 syncache_free(sc); 1015 return (1); 1016 failed: 1017 if (sc != NULL && sc != &scs) 1018 syncache_free(sc); 1019 if (s != NULL) 1020 free(s, M_TCPLOG); 1021 *lsop = NULL; 1022 return (0); 1023 } 1024 1025 /* 1026 * Given a LISTEN socket and an inbound SYN request, add 1027 * this to the syn cache, and send back a segment: 1028 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1029 * to the source. 1030 * 1031 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1032 * Doing so would require that we hold onto the data and deliver it 1033 * to the application. However, if we are the target of a SYN-flood 1034 * DoS attack, an attacker could send data which would eventually 1035 * consume all available buffer space if it were ACKed. By not ACKing 1036 * the data, we avoid this DoS scenario. 1037 */ 1038 void 1039 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1040 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1041 void *todctx) 1042 { 1043 struct tcpcb *tp; 1044 struct socket *so; 1045 struct syncache *sc = NULL; 1046 struct syncache_head *sch; 1047 struct mbuf *ipopts = NULL; 1048 u_int32_t flowtmp; 1049 u_int ltflags; 1050 int win, sb_hiwat, ip_ttl, ip_tos; 1051 char *s; 1052 #ifdef INET6 1053 int autoflowlabel = 0; 1054 #endif 1055 #ifdef MAC 1056 struct label *maclabel; 1057 #endif 1058 struct syncache scs; 1059 struct ucred *cred; 1060 1061 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1062 INP_WLOCK_ASSERT(inp); /* listen socket */ 1063 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1064 ("%s: unexpected tcp flags", __func__)); 1065 1066 /* 1067 * Combine all so/tp operations very early to drop the INP lock as 1068 * soon as possible. 1069 */ 1070 so = *lsop; 1071 tp = sototcpcb(so); 1072 cred = crhold(so->so_cred); 1073 1074 #ifdef INET6 1075 if ((inc->inc_flags & INC_ISIPV6) && 1076 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1077 autoflowlabel = 1; 1078 #endif 1079 ip_ttl = inp->inp_ip_ttl; 1080 ip_tos = inp->inp_ip_tos; 1081 win = sbspace(&so->so_rcv); 1082 sb_hiwat = so->so_rcv.sb_hiwat; 1083 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1084 1085 /* By the time we drop the lock these should no longer be used. */ 1086 so = NULL; 1087 tp = NULL; 1088 1089 #ifdef MAC 1090 if (mac_syncache_init(&maclabel) != 0) { 1091 INP_WUNLOCK(inp); 1092 INP_INFO_WUNLOCK(&V_tcbinfo); 1093 goto done; 1094 } else 1095 mac_syncache_create(maclabel, inp); 1096 #endif 1097 INP_WUNLOCK(inp); 1098 INP_INFO_WUNLOCK(&V_tcbinfo); 1099 1100 /* 1101 * Remember the IP options, if any. 1102 */ 1103 #ifdef INET6 1104 if (!(inc->inc_flags & INC_ISIPV6)) 1105 #endif 1106 #ifdef INET 1107 ipopts = (m) ? ip_srcroute(m) : NULL; 1108 #else 1109 ipopts = NULL; 1110 #endif 1111 1112 /* 1113 * See if we already have an entry for this connection. 1114 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1115 * 1116 * XXX: should the syncache be re-initialized with the contents 1117 * of the new SYN here (which may have different options?) 1118 * 1119 * XXX: We do not check the sequence number to see if this is a 1120 * real retransmit or a new connection attempt. The question is 1121 * how to handle such a case; either ignore it as spoofed, or 1122 * drop the current entry and create a new one? 1123 */ 1124 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1125 SCH_LOCK_ASSERT(sch); 1126 if (sc != NULL) { 1127 TCPSTAT_INC(tcps_sc_dupsyn); 1128 if (ipopts) { 1129 /* 1130 * If we were remembering a previous source route, 1131 * forget it and use the new one we've been given. 1132 */ 1133 if (sc->sc_ipopts) 1134 (void) m_free(sc->sc_ipopts); 1135 sc->sc_ipopts = ipopts; 1136 } 1137 /* 1138 * Update timestamp if present. 1139 */ 1140 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1141 sc->sc_tsreflect = to->to_tsval; 1142 else 1143 sc->sc_flags &= ~SCF_TIMESTAMP; 1144 #ifdef MAC 1145 /* 1146 * Since we have already unconditionally allocated label 1147 * storage, free it up. The syncache entry will already 1148 * have an initialized label we can use. 1149 */ 1150 mac_syncache_destroy(&maclabel); 1151 #endif 1152 /* Retransmit SYN|ACK and reset retransmit count. */ 1153 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1154 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1155 "resetting timer and retransmitting SYN|ACK\n", 1156 s, __func__); 1157 free(s, M_TCPLOG); 1158 } 1159 if (syncache_respond(sc) == 0) { 1160 sc->sc_rxmits = 0; 1161 syncache_timeout(sc, sch, 1); 1162 TCPSTAT_INC(tcps_sndacks); 1163 TCPSTAT_INC(tcps_sndtotal); 1164 } 1165 SCH_UNLOCK(sch); 1166 goto done; 1167 } 1168 1169 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1170 if (sc == NULL) { 1171 /* 1172 * The zone allocator couldn't provide more entries. 1173 * Treat this as if the cache was full; drop the oldest 1174 * entry and insert the new one. 1175 */ 1176 TCPSTAT_INC(tcps_sc_zonefail); 1177 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1178 syncache_drop(sc, sch); 1179 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1180 if (sc == NULL) { 1181 if (V_tcp_syncookies) { 1182 bzero(&scs, sizeof(scs)); 1183 sc = &scs; 1184 } else { 1185 SCH_UNLOCK(sch); 1186 if (ipopts) 1187 (void) m_free(ipopts); 1188 goto done; 1189 } 1190 } 1191 } 1192 1193 /* 1194 * Fill in the syncache values. 1195 */ 1196 #ifdef MAC 1197 sc->sc_label = maclabel; 1198 #endif 1199 sc->sc_cred = cred; 1200 cred = NULL; 1201 sc->sc_ipopts = ipopts; 1202 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1203 #ifdef INET6 1204 if (!(inc->inc_flags & INC_ISIPV6)) 1205 #endif 1206 { 1207 sc->sc_ip_tos = ip_tos; 1208 sc->sc_ip_ttl = ip_ttl; 1209 } 1210 #ifdef TCP_OFFLOAD 1211 sc->sc_tod = tod; 1212 sc->sc_todctx = todctx; 1213 #endif 1214 sc->sc_irs = th->th_seq; 1215 sc->sc_iss = arc4random(); 1216 sc->sc_flags = 0; 1217 sc->sc_flowlabel = 0; 1218 1219 /* 1220 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1221 * win was derived from socket earlier in the function. 1222 */ 1223 win = imax(win, 0); 1224 win = imin(win, TCP_MAXWIN); 1225 sc->sc_wnd = win; 1226 1227 if (V_tcp_do_rfc1323) { 1228 /* 1229 * A timestamp received in a SYN makes 1230 * it ok to send timestamp requests and replies. 1231 */ 1232 if (to->to_flags & TOF_TS) { 1233 sc->sc_tsreflect = to->to_tsval; 1234 sc->sc_ts = tcp_ts_getticks(); 1235 sc->sc_flags |= SCF_TIMESTAMP; 1236 } 1237 if (to->to_flags & TOF_SCALE) { 1238 int wscale = 0; 1239 1240 /* 1241 * Pick the smallest possible scaling factor that 1242 * will still allow us to scale up to sb_max, aka 1243 * kern.ipc.maxsockbuf. 1244 * 1245 * We do this because there are broken firewalls that 1246 * will corrupt the window scale option, leading to 1247 * the other endpoint believing that our advertised 1248 * window is unscaled. At scale factors larger than 1249 * 5 the unscaled window will drop below 1500 bytes, 1250 * leading to serious problems when traversing these 1251 * broken firewalls. 1252 * 1253 * With the default maxsockbuf of 256K, a scale factor 1254 * of 3 will be chosen by this algorithm. Those who 1255 * choose a larger maxsockbuf should watch out 1256 * for the compatiblity problems mentioned above. 1257 * 1258 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1259 * or <SYN,ACK>) segment itself is never scaled. 1260 */ 1261 while (wscale < TCP_MAX_WINSHIFT && 1262 (TCP_MAXWIN << wscale) < sb_max) 1263 wscale++; 1264 sc->sc_requested_r_scale = wscale; 1265 sc->sc_requested_s_scale = to->to_wscale; 1266 sc->sc_flags |= SCF_WINSCALE; 1267 } 1268 } 1269 #ifdef TCP_SIGNATURE 1270 /* 1271 * If listening socket requested TCP digests, and received SYN 1272 * contains the option, flag this in the syncache so that 1273 * syncache_respond() will do the right thing with the SYN+ACK. 1274 * XXX: Currently we always record the option by default and will 1275 * attempt to use it in syncache_respond(). 1276 */ 1277 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE) 1278 sc->sc_flags |= SCF_SIGNATURE; 1279 #endif 1280 if (to->to_flags & TOF_SACKPERM) 1281 sc->sc_flags |= SCF_SACK; 1282 if (to->to_flags & TOF_MSS) 1283 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1284 if (ltflags & TF_NOOPT) 1285 sc->sc_flags |= SCF_NOOPT; 1286 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1287 sc->sc_flags |= SCF_ECN; 1288 1289 if (V_tcp_syncookies) { 1290 syncookie_generate(sch, sc, &flowtmp); 1291 #ifdef INET6 1292 if (autoflowlabel) 1293 sc->sc_flowlabel = flowtmp; 1294 #endif 1295 } else { 1296 #ifdef INET6 1297 if (autoflowlabel) 1298 sc->sc_flowlabel = 1299 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1300 #endif 1301 } 1302 SCH_UNLOCK(sch); 1303 1304 /* 1305 * Do a standard 3-way handshake. 1306 */ 1307 if (syncache_respond(sc) == 0) { 1308 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1309 syncache_free(sc); 1310 else if (sc != &scs) 1311 syncache_insert(sc, sch); /* locks and unlocks sch */ 1312 TCPSTAT_INC(tcps_sndacks); 1313 TCPSTAT_INC(tcps_sndtotal); 1314 } else { 1315 if (sc != &scs) 1316 syncache_free(sc); 1317 TCPSTAT_INC(tcps_sc_dropped); 1318 } 1319 1320 done: 1321 if (cred != NULL) 1322 crfree(cred); 1323 #ifdef MAC 1324 if (sc == &scs) 1325 mac_syncache_destroy(&maclabel); 1326 #endif 1327 if (m) { 1328 1329 *lsop = NULL; 1330 m_freem(m); 1331 } 1332 } 1333 1334 static int 1335 syncache_respond(struct syncache *sc) 1336 { 1337 struct ip *ip = NULL; 1338 struct mbuf *m; 1339 struct tcphdr *th = NULL; 1340 int optlen, error = 0; /* Make compiler happy */ 1341 u_int16_t hlen, tlen, mssopt; 1342 struct tcpopt to; 1343 #ifdef INET6 1344 struct ip6_hdr *ip6 = NULL; 1345 #endif 1346 1347 hlen = 1348 #ifdef INET6 1349 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1350 #endif 1351 sizeof(struct ip); 1352 tlen = hlen + sizeof(struct tcphdr); 1353 1354 /* Determine MSS we advertize to other end of connection. */ 1355 mssopt = tcp_mssopt(&sc->sc_inc); 1356 if (sc->sc_peer_mss) 1357 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1358 1359 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1360 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1361 ("syncache: mbuf too small")); 1362 1363 /* Create the IP+TCP header from scratch. */ 1364 m = m_gethdr(M_DONTWAIT, MT_DATA); 1365 if (m == NULL) 1366 return (ENOBUFS); 1367 #ifdef MAC 1368 mac_syncache_create_mbuf(sc->sc_label, m); 1369 #endif 1370 m->m_data += max_linkhdr; 1371 m->m_len = tlen; 1372 m->m_pkthdr.len = tlen; 1373 m->m_pkthdr.rcvif = NULL; 1374 1375 #ifdef INET6 1376 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1377 ip6 = mtod(m, struct ip6_hdr *); 1378 ip6->ip6_vfc = IPV6_VERSION; 1379 ip6->ip6_nxt = IPPROTO_TCP; 1380 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1381 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1382 ip6->ip6_plen = htons(tlen - hlen); 1383 /* ip6_hlim is set after checksum */ 1384 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1385 ip6->ip6_flow |= sc->sc_flowlabel; 1386 1387 th = (struct tcphdr *)(ip6 + 1); 1388 } 1389 #endif 1390 #if defined(INET6) && defined(INET) 1391 else 1392 #endif 1393 #ifdef INET 1394 { 1395 ip = mtod(m, struct ip *); 1396 ip->ip_v = IPVERSION; 1397 ip->ip_hl = sizeof(struct ip) >> 2; 1398 ip->ip_len = tlen; 1399 ip->ip_id = 0; 1400 ip->ip_off = 0; 1401 ip->ip_sum = 0; 1402 ip->ip_p = IPPROTO_TCP; 1403 ip->ip_src = sc->sc_inc.inc_laddr; 1404 ip->ip_dst = sc->sc_inc.inc_faddr; 1405 ip->ip_ttl = sc->sc_ip_ttl; 1406 ip->ip_tos = sc->sc_ip_tos; 1407 1408 /* 1409 * See if we should do MTU discovery. Route lookups are 1410 * expensive, so we will only unset the DF bit if: 1411 * 1412 * 1) path_mtu_discovery is disabled 1413 * 2) the SCF_UNREACH flag has been set 1414 */ 1415 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1416 ip->ip_off |= IP_DF; 1417 1418 th = (struct tcphdr *)(ip + 1); 1419 } 1420 #endif /* INET */ 1421 th->th_sport = sc->sc_inc.inc_lport; 1422 th->th_dport = sc->sc_inc.inc_fport; 1423 1424 th->th_seq = htonl(sc->sc_iss); 1425 th->th_ack = htonl(sc->sc_irs + 1); 1426 th->th_off = sizeof(struct tcphdr) >> 2; 1427 th->th_x2 = 0; 1428 th->th_flags = TH_SYN|TH_ACK; 1429 th->th_win = htons(sc->sc_wnd); 1430 th->th_urp = 0; 1431 1432 if (sc->sc_flags & SCF_ECN) { 1433 th->th_flags |= TH_ECE; 1434 TCPSTAT_INC(tcps_ecn_shs); 1435 } 1436 1437 /* Tack on the TCP options. */ 1438 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1439 to.to_flags = 0; 1440 1441 to.to_mss = mssopt; 1442 to.to_flags = TOF_MSS; 1443 if (sc->sc_flags & SCF_WINSCALE) { 1444 to.to_wscale = sc->sc_requested_r_scale; 1445 to.to_flags |= TOF_SCALE; 1446 } 1447 if (sc->sc_flags & SCF_TIMESTAMP) { 1448 /* Virgin timestamp or TCP cookie enhanced one. */ 1449 to.to_tsval = sc->sc_ts; 1450 to.to_tsecr = sc->sc_tsreflect; 1451 to.to_flags |= TOF_TS; 1452 } 1453 if (sc->sc_flags & SCF_SACK) 1454 to.to_flags |= TOF_SACKPERM; 1455 #ifdef TCP_SIGNATURE 1456 if (sc->sc_flags & SCF_SIGNATURE) 1457 to.to_flags |= TOF_SIGNATURE; 1458 #endif 1459 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1460 1461 /* Adjust headers by option size. */ 1462 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1463 m->m_len += optlen; 1464 m->m_pkthdr.len += optlen; 1465 1466 #ifdef TCP_SIGNATURE 1467 if (sc->sc_flags & SCF_SIGNATURE) 1468 tcp_signature_compute(m, 0, 0, optlen, 1469 to.to_signature, IPSEC_DIR_OUTBOUND); 1470 #endif 1471 #ifdef INET6 1472 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1473 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1474 else 1475 #endif 1476 ip->ip_len += optlen; 1477 } else 1478 optlen = 0; 1479 1480 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1481 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1482 #ifdef INET6 1483 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1484 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1485 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1486 IPPROTO_TCP, 0); 1487 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1488 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1489 } 1490 #endif 1491 #if defined(INET6) && defined(INET) 1492 else 1493 #endif 1494 #ifdef INET 1495 { 1496 m->m_pkthdr.csum_flags = CSUM_TCP; 1497 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1498 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1499 #ifdef TCP_OFFLOAD 1500 if (ADDED_BY_TOE(sc)) { 1501 struct toedev *tod = sc->sc_tod; 1502 1503 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1504 1505 return (error); 1506 } 1507 #endif 1508 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1509 } 1510 #endif 1511 return (error); 1512 } 1513 1514 /* 1515 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1516 * receive and to be able to handle SYN floods from bogus source addresses 1517 * (where we will never receive any reply). SYN floods try to exhaust all 1518 * our memory and available slots in the SYN cache table to cause a denial 1519 * of service to legitimate users of the local host. 1520 * 1521 * The idea of SYN cookies is to encode and include all necessary information 1522 * about the connection setup state within the SYN-ACK we send back and thus 1523 * to get along without keeping any local state until the ACK to the SYN-ACK 1524 * arrives (if ever). Everything we need to know should be available from 1525 * the information we encoded in the SYN-ACK. 1526 * 1527 * More information about the theory behind SYN cookies and its first 1528 * discussion and specification can be found at: 1529 * http://cr.yp.to/syncookies.html (overview) 1530 * http://cr.yp.to/syncookies/archive (gory details) 1531 * 1532 * This implementation extends the orginal idea and first implementation 1533 * of FreeBSD by using not only the initial sequence number field to store 1534 * information but also the timestamp field if present. This way we can 1535 * keep track of the entire state we need to know to recreate the session in 1536 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1537 * these days. For those that do not we still have to live with the known 1538 * shortcomings of the ISN only SYN cookies. 1539 * 1540 * Cookie layers: 1541 * 1542 * Initial sequence number we send: 1543 * 31|................................|0 1544 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1545 * D = MD5 Digest (first dword) 1546 * M = MSS index 1547 * R = Rotation of secret 1548 * P = Odd or Even secret 1549 * 1550 * The MD5 Digest is computed with over following parameters: 1551 * a) randomly rotated secret 1552 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1553 * c) the received initial sequence number from remote host 1554 * d) the rotation offset and odd/even bit 1555 * 1556 * Timestamp we send: 1557 * 31|................................|0 1558 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1559 * D = MD5 Digest (third dword) (only as filler) 1560 * S = Requested send window scale 1561 * R = Requested receive window scale 1562 * A = SACK allowed 1563 * 5 = TCP-MD5 enabled (not implemented yet) 1564 * XORed with MD5 Digest (forth dword) 1565 * 1566 * The timestamp isn't cryptographically secure and doesn't need to be. 1567 * The double use of the MD5 digest dwords ties it to a specific remote/ 1568 * local host/port, remote initial sequence number and our local time 1569 * limited secret. A received timestamp is reverted (XORed) and then 1570 * the contained MD5 dword is compared to the computed one to ensure the 1571 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1572 * have been tampered with but this isn't different from supplying bogus 1573 * values in the SYN in the first place. 1574 * 1575 * Some problems with SYN cookies remain however: 1576 * Consider the problem of a recreated (and retransmitted) cookie. If the 1577 * original SYN was accepted, the connection is established. The second 1578 * SYN is inflight, and if it arrives with an ISN that falls within the 1579 * receive window, the connection is killed. 1580 * 1581 * Notes: 1582 * A heuristic to determine when to accept syn cookies is not necessary. 1583 * An ACK flood would cause the syncookie verification to be attempted, 1584 * but a SYN flood causes syncookies to be generated. Both are of equal 1585 * cost, so there's no point in trying to optimize the ACK flood case. 1586 * Also, if you don't process certain ACKs for some reason, then all someone 1587 * would have to do is launch a SYN and ACK flood at the same time, which 1588 * would stop cookie verification and defeat the entire purpose of syncookies. 1589 */ 1590 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1591 1592 static void 1593 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1594 u_int32_t *flowlabel) 1595 { 1596 MD5_CTX ctx; 1597 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1598 u_int32_t data; 1599 u_int32_t *secbits; 1600 u_int off, pmss, mss; 1601 int i; 1602 1603 SCH_LOCK_ASSERT(sch); 1604 1605 /* Which of the two secrets to use. */ 1606 secbits = sch->sch_oddeven ? 1607 sch->sch_secbits_odd : sch->sch_secbits_even; 1608 1609 /* Reseed secret if too old. */ 1610 if (sch->sch_reseed < time_uptime) { 1611 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1612 secbits = sch->sch_oddeven ? 1613 sch->sch_secbits_odd : sch->sch_secbits_even; 1614 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1615 secbits[i] = arc4random(); 1616 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1617 } 1618 1619 /* Secret rotation offset. */ 1620 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1621 1622 /* Maximum segment size calculation. */ 1623 pmss = 1624 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1625 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1626 if (tcp_sc_msstab[mss] <= pmss) 1627 break; 1628 1629 /* Fold parameters and MD5 digest into the ISN we will send. */ 1630 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1631 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1632 data |= mss << 4; /* mss, 3 bits */ 1633 1634 MD5Init(&ctx); 1635 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1636 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1637 MD5Update(&ctx, secbits, off); 1638 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1639 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1640 MD5Update(&ctx, &data, sizeof(data)); 1641 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1642 1643 data |= (md5_buffer[0] << 7); 1644 sc->sc_iss = data; 1645 1646 #ifdef INET6 1647 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1648 #endif 1649 1650 /* Additional parameters are stored in the timestamp if present. */ 1651 if (sc->sc_flags & SCF_TIMESTAMP) { 1652 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1653 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1654 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1655 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1656 data |= md5_buffer[2] << 10; /* more digest bits */ 1657 data ^= md5_buffer[3]; 1658 sc->sc_ts = data; 1659 sc->sc_tsoff = data - tcp_ts_getticks(); /* after XOR */ 1660 } 1661 1662 TCPSTAT_INC(tcps_sc_sendcookie); 1663 } 1664 1665 static struct syncache * 1666 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1667 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1668 struct socket *so) 1669 { 1670 MD5_CTX ctx; 1671 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1672 u_int32_t data = 0; 1673 u_int32_t *secbits; 1674 tcp_seq ack, seq; 1675 int off, mss, wnd, flags; 1676 1677 SCH_LOCK_ASSERT(sch); 1678 1679 /* 1680 * Pull information out of SYN-ACK/ACK and 1681 * revert sequence number advances. 1682 */ 1683 ack = th->th_ack - 1; 1684 seq = th->th_seq - 1; 1685 off = (ack >> 1) & 0x7; 1686 mss = (ack >> 4) & 0x7; 1687 flags = ack & 0x7f; 1688 1689 /* Which of the two secrets to use. */ 1690 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1691 1692 /* 1693 * The secret wasn't updated for the lifetime of a syncookie, 1694 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1695 */ 1696 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1697 return (NULL); 1698 } 1699 1700 /* Recompute the digest so we can compare it. */ 1701 MD5Init(&ctx); 1702 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1703 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1704 MD5Update(&ctx, secbits, off); 1705 MD5Update(&ctx, inc, sizeof(*inc)); 1706 MD5Update(&ctx, &seq, sizeof(seq)); 1707 MD5Update(&ctx, &flags, sizeof(flags)); 1708 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1709 1710 /* Does the digest part of or ACK'ed ISS match? */ 1711 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1712 return (NULL); 1713 1714 /* Does the digest part of our reflected timestamp match? */ 1715 if (to->to_flags & TOF_TS) { 1716 data = md5_buffer[3] ^ to->to_tsecr; 1717 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1718 return (NULL); 1719 } 1720 1721 /* Fill in the syncache values. */ 1722 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1723 sc->sc_ipopts = NULL; 1724 1725 sc->sc_irs = seq; 1726 sc->sc_iss = ack; 1727 1728 #ifdef INET6 1729 if (inc->inc_flags & INC_ISIPV6) { 1730 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1731 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1732 } else 1733 #endif 1734 { 1735 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1736 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1737 } 1738 1739 /* Additional parameters that were encoded in the timestamp. */ 1740 if (data) { 1741 sc->sc_flags |= SCF_TIMESTAMP; 1742 sc->sc_tsreflect = to->to_tsval; 1743 sc->sc_ts = to->to_tsecr; 1744 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks(); 1745 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1746 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1747 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1748 TCP_MAX_WINSHIFT); 1749 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1750 TCP_MAX_WINSHIFT); 1751 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1752 sc->sc_flags |= SCF_WINSCALE; 1753 } else 1754 sc->sc_flags |= SCF_NOOPT; 1755 1756 wnd = sbspace(&so->so_rcv); 1757 wnd = imax(wnd, 0); 1758 wnd = imin(wnd, TCP_MAXWIN); 1759 sc->sc_wnd = wnd; 1760 1761 sc->sc_rxmits = 0; 1762 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1763 1764 TCPSTAT_INC(tcps_sc_recvcookie); 1765 return (sc); 1766 } 1767 1768 /* 1769 * Returns the current number of syncache entries. This number 1770 * will probably change before you get around to calling 1771 * syncache_pcblist. 1772 */ 1773 1774 int 1775 syncache_pcbcount(void) 1776 { 1777 struct syncache_head *sch; 1778 int count, i; 1779 1780 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1781 /* No need to lock for a read. */ 1782 sch = &V_tcp_syncache.hashbase[i]; 1783 count += sch->sch_length; 1784 } 1785 return count; 1786 } 1787 1788 /* 1789 * Exports the syncache entries to userland so that netstat can display 1790 * them alongside the other sockets. This function is intended to be 1791 * called only from tcp_pcblist. 1792 * 1793 * Due to concurrency on an active system, the number of pcbs exported 1794 * may have no relation to max_pcbs. max_pcbs merely indicates the 1795 * amount of space the caller allocated for this function to use. 1796 */ 1797 int 1798 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1799 { 1800 struct xtcpcb xt; 1801 struct syncache *sc; 1802 struct syncache_head *sch; 1803 int count, error, i; 1804 1805 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1806 sch = &V_tcp_syncache.hashbase[i]; 1807 SCH_LOCK(sch); 1808 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1809 if (count >= max_pcbs) { 1810 SCH_UNLOCK(sch); 1811 goto exit; 1812 } 1813 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1814 continue; 1815 bzero(&xt, sizeof(xt)); 1816 xt.xt_len = sizeof(xt); 1817 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1818 xt.xt_inp.inp_vflag = INP_IPV6; 1819 else 1820 xt.xt_inp.inp_vflag = INP_IPV4; 1821 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1822 xt.xt_tp.t_inpcb = &xt.xt_inp; 1823 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1824 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1825 xt.xt_socket.xso_len = sizeof (struct xsocket); 1826 xt.xt_socket.so_type = SOCK_STREAM; 1827 xt.xt_socket.so_state = SS_ISCONNECTING; 1828 error = SYSCTL_OUT(req, &xt, sizeof xt); 1829 if (error) { 1830 SCH_UNLOCK(sch); 1831 goto exit; 1832 } 1833 count++; 1834 } 1835 SCH_UNLOCK(sch); 1836 } 1837 exit: 1838 *pcbs_exported = count; 1839 return error; 1840 } 1841