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sys/netinet/tcp_syncache.c
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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: releng/8.1/sys/netinet/tcp_syncache.c 207695 2010-05-06 06:44:19Z bz $"); 35 36 #include "opt_inet.h" 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/kernel.h> 43 #include <sys/sysctl.h> 44 #include <sys/limits.h> 45 #include <sys/lock.h> 46 #include <sys/mutex.h> 47 #include <sys/malloc.h> 48 #include <sys/mbuf.h> 49 #include <sys/md5.h> 50 #include <sys/proc.h> /* for proc0 declaration */ 51 #include <sys/random.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 #include <sys/syslog.h> 55 #include <sys/ucred.h> 56 57 #include <vm/uma.h> 58 59 #include <net/if.h> 60 #include <net/route.h> 61 #include <net/vnet.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/in_var.h> 67 #include <netinet/in_pcb.h> 68 #include <netinet/ip_var.h> 69 #include <netinet/ip_options.h> 70 #ifdef INET6 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/nd6.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/in6_pcb.h> 76 #endif 77 #include <netinet/tcp.h> 78 #include <netinet/tcp_fsm.h> 79 #include <netinet/tcp_seq.h> 80 #include <netinet/tcp_timer.h> 81 #include <netinet/tcp_var.h> 82 #include <netinet/tcp_syncache.h> 83 #include <netinet/tcp_offload.h> 84 #ifdef INET6 85 #include <netinet6/tcp6_var.h> 86 #endif 87 88 #ifdef IPSEC 89 #include <netipsec/ipsec.h> 90 #ifdef INET6 91 #include <netipsec/ipsec6.h> 92 #endif 93 #include <netipsec/key.h> 94 #endif /*IPSEC*/ 95 96 #include <machine/in_cksum.h> 97 98 #include <security/mac/mac_framework.h> 99 100 static VNET_DEFINE(int, tcp_syncookies) = 1; 101 #define V_tcp_syncookies VNET(tcp_syncookies) 102 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 103 &VNET_NAME(tcp_syncookies), 0, 104 "Use TCP SYN cookies if the syncache overflows"); 105 106 static VNET_DEFINE(int, tcp_syncookiesonly) = 0; 107 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly) 108 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW, 109 &VNET_NAME(tcp_syncookiesonly), 0, 110 "Use only TCP SYN cookies"); 111 112 #ifdef TCP_OFFLOAD_DISABLE 113 #define TOEPCB_ISSET(sc) (0) 114 #else 115 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL) 116 #endif 117 118 static void syncache_drop(struct syncache *, struct syncache_head *); 119 static void syncache_free(struct syncache *); 120 static void syncache_insert(struct syncache *, struct syncache_head *); 121 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 122 static int syncache_respond(struct syncache *); 123 static struct socket *syncache_socket(struct syncache *, struct socket *, 124 struct mbuf *m); 125 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 126 int docallout); 127 static void syncache_timer(void *); 128 static void syncookie_generate(struct syncache_head *, struct syncache *, 129 u_int32_t *); 130 static struct syncache 131 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 132 struct syncache *, struct tcpopt *, struct tcphdr *, 133 struct socket *); 134 135 /* 136 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 137 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 138 * the odds are that the user has given up attempting to connect by then. 139 */ 140 #define SYNCACHE_MAXREXMTS 3 141 142 /* Arbitrary values */ 143 #define TCP_SYNCACHE_HASHSIZE 512 144 #define TCP_SYNCACHE_BUCKETLIMIT 30 145 146 static VNET_DEFINE(struct tcp_syncache, tcp_syncache); 147 #define V_tcp_syncache VNET(tcp_syncache) 148 149 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 150 151 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 152 &VNET_NAME(tcp_syncache.bucket_limit), 0, 153 "Per-bucket hash limit for syncache"); 154 155 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 156 &VNET_NAME(tcp_syncache.cache_limit), 0, 157 "Overall entry limit for syncache"); 158 159 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 160 &VNET_NAME(tcp_syncache.cache_count), 0, 161 "Current number of entries in syncache"); 162 163 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 164 &VNET_NAME(tcp_syncache.hashsize), 0, 165 "Size of TCP syncache hashtable"); 166 167 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 168 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 169 "Limit on SYN/ACK retransmissions"); 170 171 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 172 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 173 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 174 "Send reset on socket allocation failure"); 175 176 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 177 178 #define SYNCACHE_HASH(inc, mask) \ 179 ((V_tcp_syncache.hash_secret ^ \ 180 (inc)->inc_faddr.s_addr ^ \ 181 ((inc)->inc_faddr.s_addr >> 16) ^ \ 182 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 183 184 #define SYNCACHE_HASH6(inc, mask) \ 185 ((V_tcp_syncache.hash_secret ^ \ 186 (inc)->inc6_faddr.s6_addr32[0] ^ \ 187 (inc)->inc6_faddr.s6_addr32[3] ^ \ 188 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 189 190 #define ENDPTS_EQ(a, b) ( \ 191 (a)->ie_fport == (b)->ie_fport && \ 192 (a)->ie_lport == (b)->ie_lport && \ 193 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 194 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 195 ) 196 197 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 198 199 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 200 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 201 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 202 203 /* 204 * Requires the syncache entry to be already removed from the bucket list. 205 */ 206 static void 207 syncache_free(struct syncache *sc) 208 { 209 210 if (sc->sc_ipopts) 211 (void) m_free(sc->sc_ipopts); 212 if (sc->sc_cred) 213 crfree(sc->sc_cred); 214 #ifdef MAC 215 mac_syncache_destroy(&sc->sc_label); 216 #endif 217 218 uma_zfree(V_tcp_syncache.zone, sc); 219 } 220 221 void 222 syncache_init(void) 223 { 224 int i; 225 226 V_tcp_syncache.cache_count = 0; 227 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 228 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 229 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 230 V_tcp_syncache.hash_secret = arc4random(); 231 232 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 233 &V_tcp_syncache.hashsize); 234 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 235 &V_tcp_syncache.bucket_limit); 236 if (!powerof2(V_tcp_syncache.hashsize) || 237 V_tcp_syncache.hashsize == 0) { 238 printf("WARNING: syncache hash size is not a power of 2.\n"); 239 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 240 } 241 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 242 243 /* Set limits. */ 244 V_tcp_syncache.cache_limit = 245 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 246 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 247 &V_tcp_syncache.cache_limit); 248 249 /* Allocate the hash table. */ 250 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 251 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 252 253 /* Initialize the hash buckets. */ 254 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 255 #ifdef VIMAGE 256 V_tcp_syncache.hashbase[i].sch_vnet = curvnet; 257 #endif 258 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 259 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 260 NULL, MTX_DEF); 261 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 262 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 263 V_tcp_syncache.hashbase[i].sch_length = 0; 264 } 265 266 /* Create the syncache entry zone. */ 267 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 268 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 269 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit); 270 } 271 272 #ifdef VIMAGE 273 void 274 syncache_destroy(void) 275 { 276 struct syncache_head *sch; 277 struct syncache *sc, *nsc; 278 int i; 279 280 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 281 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 282 283 sch = &V_tcp_syncache.hashbase[i]; 284 callout_drain(&sch->sch_timer); 285 286 SCH_LOCK(sch); 287 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 288 syncache_drop(sc, sch); 289 SCH_UNLOCK(sch); 290 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 291 ("%s: sch->sch_bucket not empty", __func__)); 292 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 293 __func__, sch->sch_length)); 294 mtx_destroy(&sch->sch_mtx); 295 } 296 297 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0", 298 __func__, V_tcp_syncache.cache_count)); 299 300 /* Free the allocated global resources. */ 301 uma_zdestroy(V_tcp_syncache.zone); 302 free(V_tcp_syncache.hashbase, M_SYNCACHE); 303 } 304 #endif 305 306 /* 307 * Inserts a syncache entry into the specified bucket row. 308 * Locks and unlocks the syncache_head autonomously. 309 */ 310 static void 311 syncache_insert(struct syncache *sc, struct syncache_head *sch) 312 { 313 struct syncache *sc2; 314 315 SCH_LOCK(sch); 316 317 /* 318 * Make sure that we don't overflow the per-bucket limit. 319 * If the bucket is full, toss the oldest element. 320 */ 321 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 322 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 323 ("sch->sch_length incorrect")); 324 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 325 syncache_drop(sc2, sch); 326 TCPSTAT_INC(tcps_sc_bucketoverflow); 327 } 328 329 /* Put it into the bucket. */ 330 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 331 sch->sch_length++; 332 333 /* Reinitialize the bucket row's timer. */ 334 if (sch->sch_length == 1) 335 sch->sch_nextc = ticks + INT_MAX; 336 syncache_timeout(sc, sch, 1); 337 338 SCH_UNLOCK(sch); 339 340 V_tcp_syncache.cache_count++; 341 TCPSTAT_INC(tcps_sc_added); 342 } 343 344 /* 345 * Remove and free entry from syncache bucket row. 346 * Expects locked syncache head. 347 */ 348 static void 349 syncache_drop(struct syncache *sc, struct syncache_head *sch) 350 { 351 352 SCH_LOCK_ASSERT(sch); 353 354 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 355 sch->sch_length--; 356 357 #ifndef TCP_OFFLOAD_DISABLE 358 if (sc->sc_tu) 359 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 360 #endif 361 syncache_free(sc); 362 V_tcp_syncache.cache_count--; 363 } 364 365 /* 366 * Engage/reengage time on bucket row. 367 */ 368 static void 369 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 370 { 371 sc->sc_rxttime = ticks + 372 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 373 sc->sc_rxmits++; 374 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 375 sch->sch_nextc = sc->sc_rxttime; 376 if (docallout) 377 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 378 syncache_timer, (void *)sch); 379 } 380 } 381 382 /* 383 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 384 * If we have retransmitted an entry the maximum number of times, expire it. 385 * One separate timer for each bucket row. 386 */ 387 static void 388 syncache_timer(void *xsch) 389 { 390 struct syncache_head *sch = (struct syncache_head *)xsch; 391 struct syncache *sc, *nsc; 392 int tick = ticks; 393 char *s; 394 395 CURVNET_SET(sch->sch_vnet); 396 397 /* NB: syncache_head has already been locked by the callout. */ 398 SCH_LOCK_ASSERT(sch); 399 400 /* 401 * In the following cycle we may remove some entries and/or 402 * advance some timeouts, so re-initialize the bucket timer. 403 */ 404 sch->sch_nextc = tick + INT_MAX; 405 406 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 407 /* 408 * We do not check if the listen socket still exists 409 * and accept the case where the listen socket may be 410 * gone by the time we resend the SYN/ACK. We do 411 * not expect this to happens often. If it does, 412 * then the RST will be sent by the time the remote 413 * host does the SYN/ACK->ACK. 414 */ 415 if (TSTMP_GT(sc->sc_rxttime, tick)) { 416 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 417 sch->sch_nextc = sc->sc_rxttime; 418 continue; 419 } 420 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 421 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 422 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 423 "giving up and removing syncache entry\n", 424 s, __func__); 425 free(s, M_TCPLOG); 426 } 427 syncache_drop(sc, sch); 428 TCPSTAT_INC(tcps_sc_stale); 429 continue; 430 } 431 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 432 log(LOG_DEBUG, "%s; %s: Response timeout, " 433 "retransmitting (%u) SYN|ACK\n", 434 s, __func__, sc->sc_rxmits); 435 free(s, M_TCPLOG); 436 } 437 438 (void) syncache_respond(sc); 439 TCPSTAT_INC(tcps_sc_retransmitted); 440 syncache_timeout(sc, sch, 0); 441 } 442 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 443 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 444 syncache_timer, (void *)(sch)); 445 CURVNET_RESTORE(); 446 } 447 448 /* 449 * Find an entry in the syncache. 450 * Returns always with locked syncache_head plus a matching entry or NULL. 451 */ 452 struct syncache * 453 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 454 { 455 struct syncache *sc; 456 struct syncache_head *sch; 457 458 #ifdef INET6 459 if (inc->inc_flags & INC_ISIPV6) { 460 sch = &V_tcp_syncache.hashbase[ 461 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 462 *schp = sch; 463 464 SCH_LOCK(sch); 465 466 /* Circle through bucket row to find matching entry. */ 467 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 468 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 469 return (sc); 470 } 471 } else 472 #endif 473 { 474 sch = &V_tcp_syncache.hashbase[ 475 SYNCACHE_HASH(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 #ifdef INET6 483 if (sc->sc_inc.inc_flags & INC_ISIPV6) 484 continue; 485 #endif 486 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 487 return (sc); 488 } 489 } 490 SCH_LOCK_ASSERT(*schp); 491 return (NULL); /* always returns with locked sch */ 492 } 493 494 /* 495 * This function is called when we get a RST for a 496 * non-existent connection, so that we can see if the 497 * connection is in the syn cache. If it is, zap it. 498 */ 499 void 500 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 501 { 502 struct syncache *sc; 503 struct syncache_head *sch; 504 char *s = NULL; 505 506 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 507 SCH_LOCK_ASSERT(sch); 508 509 /* 510 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 511 * See RFC 793 page 65, section SEGMENT ARRIVES. 512 */ 513 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 514 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 515 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 516 "FIN flag set, segment ignored\n", s, __func__); 517 TCPSTAT_INC(tcps_badrst); 518 goto done; 519 } 520 521 /* 522 * No corresponding connection was found in syncache. 523 * If syncookies are enabled and possibly exclusively 524 * used, or we are under memory pressure, a valid RST 525 * may not find a syncache entry. In that case we're 526 * done and no SYN|ACK retransmissions will happen. 527 * Otherwise the the RST was misdirected or spoofed. 528 */ 529 if (sc == NULL) { 530 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 531 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 532 "syncache entry (possibly syncookie only), " 533 "segment ignored\n", s, __func__); 534 TCPSTAT_INC(tcps_badrst); 535 goto done; 536 } 537 538 /* 539 * If the RST bit is set, check the sequence number to see 540 * if this is a valid reset segment. 541 * RFC 793 page 37: 542 * In all states except SYN-SENT, all reset (RST) segments 543 * are validated by checking their SEQ-fields. A reset is 544 * valid if its sequence number is in the window. 545 * 546 * The sequence number in the reset segment is normally an 547 * echo of our outgoing acknowlegement numbers, but some hosts 548 * send a reset with the sequence number at the rightmost edge 549 * of our receive window, and we have to handle this case. 550 */ 551 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 552 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 553 syncache_drop(sc, sch); 554 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 555 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 556 "connection attempt aborted by remote endpoint\n", 557 s, __func__); 558 TCPSTAT_INC(tcps_sc_reset); 559 } else { 560 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 561 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 562 "IRS %u (+WND %u), segment ignored\n", 563 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 564 TCPSTAT_INC(tcps_badrst); 565 } 566 567 done: 568 if (s != NULL) 569 free(s, M_TCPLOG); 570 SCH_UNLOCK(sch); 571 } 572 573 void 574 syncache_badack(struct in_conninfo *inc) 575 { 576 struct syncache *sc; 577 struct syncache_head *sch; 578 579 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 580 SCH_LOCK_ASSERT(sch); 581 if (sc != NULL) { 582 syncache_drop(sc, sch); 583 TCPSTAT_INC(tcps_sc_badack); 584 } 585 SCH_UNLOCK(sch); 586 } 587 588 void 589 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 590 { 591 struct syncache *sc; 592 struct syncache_head *sch; 593 594 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 595 SCH_LOCK_ASSERT(sch); 596 if (sc == NULL) 597 goto done; 598 599 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 600 if (ntohl(th->th_seq) != sc->sc_iss) 601 goto done; 602 603 /* 604 * If we've rertransmitted 3 times and this is our second error, 605 * we remove the entry. Otherwise, we allow it to continue on. 606 * This prevents us from incorrectly nuking an entry during a 607 * spurious network outage. 608 * 609 * See tcp_notify(). 610 */ 611 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 612 sc->sc_flags |= SCF_UNREACH; 613 goto done; 614 } 615 syncache_drop(sc, sch); 616 TCPSTAT_INC(tcps_sc_unreach); 617 done: 618 SCH_UNLOCK(sch); 619 } 620 621 /* 622 * Build a new TCP socket structure from a syncache entry. 623 */ 624 static struct socket * 625 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 626 { 627 struct inpcb *inp = NULL; 628 struct socket *so; 629 struct tcpcb *tp; 630 char *s; 631 632 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 633 634 /* 635 * Ok, create the full blown connection, and set things up 636 * as they would have been set up if we had created the 637 * connection when the SYN arrived. If we can't create 638 * the connection, abort it. 639 */ 640 so = sonewconn(lso, SS_ISCONNECTED); 641 if (so == NULL) { 642 /* 643 * Drop the connection; we will either send a RST or 644 * have the peer retransmit its SYN again after its 645 * RTO and try again. 646 */ 647 TCPSTAT_INC(tcps_listendrop); 648 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 649 log(LOG_DEBUG, "%s; %s: Socket create failed " 650 "due to limits or memory shortage\n", 651 s, __func__); 652 free(s, M_TCPLOG); 653 } 654 goto abort2; 655 } 656 #ifdef MAC 657 mac_socketpeer_set_from_mbuf(m, so); 658 #endif 659 660 inp = sotoinpcb(so); 661 inp->inp_inc.inc_fibnum = so->so_fibnum; 662 INP_WLOCK(inp); 663 664 /* Insert new socket into PCB hash list. */ 665 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 666 #ifdef INET6 667 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 668 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 669 } else { 670 inp->inp_vflag &= ~INP_IPV6; 671 inp->inp_vflag |= INP_IPV4; 672 #endif 673 inp->inp_laddr = sc->sc_inc.inc_laddr; 674 #ifdef INET6 675 } 676 #endif 677 inp->inp_lport = sc->sc_inc.inc_lport; 678 if (in_pcbinshash(inp) != 0) { 679 /* 680 * Undo the assignments above if we failed to 681 * put the PCB on the hash lists. 682 */ 683 #ifdef INET6 684 if (sc->sc_inc.inc_flags & INC_ISIPV6) 685 inp->in6p_laddr = in6addr_any; 686 else 687 #endif 688 inp->inp_laddr.s_addr = INADDR_ANY; 689 inp->inp_lport = 0; 690 goto abort; 691 } 692 #ifdef IPSEC 693 /* Copy old policy into new socket's. */ 694 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 695 printf("syncache_socket: could not copy policy\n"); 696 #endif 697 #ifdef INET6 698 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 699 struct inpcb *oinp = sotoinpcb(lso); 700 struct in6_addr laddr6; 701 struct sockaddr_in6 sin6; 702 /* 703 * Inherit socket options from the listening socket. 704 * Note that in6p_inputopts are not (and should not be) 705 * copied, since it stores previously received options and is 706 * used to detect if each new option is different than the 707 * previous one and hence should be passed to a user. 708 * If we copied in6p_inputopts, a user would not be able to 709 * receive options just after calling the accept system call. 710 */ 711 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 712 if (oinp->in6p_outputopts) 713 inp->in6p_outputopts = 714 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 715 716 sin6.sin6_family = AF_INET6; 717 sin6.sin6_len = sizeof(sin6); 718 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 719 sin6.sin6_port = sc->sc_inc.inc_fport; 720 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 721 laddr6 = inp->in6p_laddr; 722 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 723 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 724 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 725 thread0.td_ucred)) { 726 inp->in6p_laddr = laddr6; 727 goto abort; 728 } 729 /* Override flowlabel from in6_pcbconnect. */ 730 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 731 inp->inp_flow |= sc->sc_flowlabel; 732 } else 733 #endif 734 { 735 struct in_addr laddr; 736 struct sockaddr_in sin; 737 738 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 739 740 if (inp->inp_options == NULL) { 741 inp->inp_options = sc->sc_ipopts; 742 sc->sc_ipopts = NULL; 743 } 744 745 sin.sin_family = AF_INET; 746 sin.sin_len = sizeof(sin); 747 sin.sin_addr = sc->sc_inc.inc_faddr; 748 sin.sin_port = sc->sc_inc.inc_fport; 749 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 750 laddr = inp->inp_laddr; 751 if (inp->inp_laddr.s_addr == INADDR_ANY) 752 inp->inp_laddr = sc->sc_inc.inc_laddr; 753 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 754 thread0.td_ucred)) { 755 inp->inp_laddr = laddr; 756 goto abort; 757 } 758 } 759 tp = intotcpcb(inp); 760 tp->t_state = TCPS_SYN_RECEIVED; 761 tp->iss = sc->sc_iss; 762 tp->irs = sc->sc_irs; 763 tcp_rcvseqinit(tp); 764 tcp_sendseqinit(tp); 765 tp->snd_wl1 = sc->sc_irs; 766 tp->snd_max = tp->iss + 1; 767 tp->snd_nxt = tp->iss + 1; 768 tp->rcv_up = sc->sc_irs + 1; 769 tp->rcv_wnd = sc->sc_wnd; 770 tp->rcv_adv += tp->rcv_wnd; 771 tp->last_ack_sent = tp->rcv_nxt; 772 773 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 774 if (sc->sc_flags & SCF_NOOPT) 775 tp->t_flags |= TF_NOOPT; 776 else { 777 if (sc->sc_flags & SCF_WINSCALE) { 778 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 779 tp->snd_scale = sc->sc_requested_s_scale; 780 tp->request_r_scale = sc->sc_requested_r_scale; 781 } 782 if (sc->sc_flags & SCF_TIMESTAMP) { 783 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 784 tp->ts_recent = sc->sc_tsreflect; 785 tp->ts_recent_age = ticks; 786 tp->ts_offset = sc->sc_tsoff; 787 } 788 #ifdef TCP_SIGNATURE 789 if (sc->sc_flags & SCF_SIGNATURE) 790 tp->t_flags |= TF_SIGNATURE; 791 #endif 792 if (sc->sc_flags & SCF_SACK) 793 tp->t_flags |= TF_SACK_PERMIT; 794 } 795 796 if (sc->sc_flags & SCF_ECN) 797 tp->t_flags |= TF_ECN_PERMIT; 798 799 /* 800 * Set up MSS and get cached values from tcp_hostcache. 801 * This might overwrite some of the defaults we just set. 802 */ 803 tcp_mss(tp, sc->sc_peer_mss); 804 805 /* 806 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 807 */ 808 if (sc->sc_rxmits) 809 tp->snd_cwnd = tp->t_maxseg; 810 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 811 812 INP_WUNLOCK(inp); 813 814 TCPSTAT_INC(tcps_accepts); 815 return (so); 816 817 abort: 818 INP_WUNLOCK(inp); 819 abort2: 820 if (so != NULL) 821 soabort(so); 822 return (NULL); 823 } 824 825 /* 826 * This function gets called when we receive an ACK for a 827 * socket in the LISTEN state. We look up the connection 828 * in the syncache, and if its there, we pull it out of 829 * the cache and turn it into a full-blown connection in 830 * the SYN-RECEIVED state. 831 */ 832 int 833 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 834 struct socket **lsop, struct mbuf *m) 835 { 836 struct syncache *sc; 837 struct syncache_head *sch; 838 struct syncache scs; 839 char *s; 840 841 /* 842 * Global TCP locks are held because we manipulate the PCB lists 843 * and create a new socket. 844 */ 845 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 846 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 847 ("%s: can handle only ACK", __func__)); 848 849 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 850 SCH_LOCK_ASSERT(sch); 851 if (sc == NULL) { 852 /* 853 * There is no syncache entry, so see if this ACK is 854 * a returning syncookie. To do this, first: 855 * A. See if this socket has had a syncache entry dropped in 856 * the past. We don't want to accept a bogus syncookie 857 * if we've never received a SYN. 858 * B. check that the syncookie is valid. If it is, then 859 * cobble up a fake syncache entry, and return. 860 */ 861 if (!V_tcp_syncookies) { 862 SCH_UNLOCK(sch); 863 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 864 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 865 "segment rejected (syncookies disabled)\n", 866 s, __func__); 867 goto failed; 868 } 869 bzero(&scs, sizeof(scs)); 870 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 871 SCH_UNLOCK(sch); 872 if (sc == NULL) { 873 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 874 log(LOG_DEBUG, "%s; %s: Segment failed " 875 "SYNCOOKIE authentication, segment rejected " 876 "(probably spoofed)\n", s, __func__); 877 goto failed; 878 } 879 } else { 880 /* Pull out the entry to unlock the bucket row. */ 881 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 882 sch->sch_length--; 883 V_tcp_syncache.cache_count--; 884 SCH_UNLOCK(sch); 885 } 886 887 /* 888 * Segment validation: 889 * ACK must match our initial sequence number + 1 (the SYN|ACK). 890 */ 891 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 892 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 893 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 894 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 895 goto failed; 896 } 897 898 /* 899 * The SEQ must fall in the window starting at the received 900 * initial receive sequence number + 1 (the SYN). 901 */ 902 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 903 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 904 !TOEPCB_ISSET(sc)) { 905 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 906 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 907 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 908 goto failed; 909 } 910 911 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 912 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 913 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 914 "segment rejected\n", s, __func__); 915 goto failed; 916 } 917 /* 918 * If timestamps were negotiated the reflected timestamp 919 * must be equal to what we actually sent in the SYN|ACK. 920 */ 921 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 922 !TOEPCB_ISSET(sc)) { 923 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 924 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 925 "segment rejected\n", 926 s, __func__, to->to_tsecr, sc->sc_ts); 927 goto failed; 928 } 929 930 *lsop = syncache_socket(sc, *lsop, m); 931 932 if (*lsop == NULL) 933 TCPSTAT_INC(tcps_sc_aborted); 934 else 935 TCPSTAT_INC(tcps_sc_completed); 936 937 /* how do we find the inp for the new socket? */ 938 if (sc != &scs) 939 syncache_free(sc); 940 return (1); 941 failed: 942 if (sc != NULL && sc != &scs) 943 syncache_free(sc); 944 if (s != NULL) 945 free(s, M_TCPLOG); 946 *lsop = NULL; 947 return (0); 948 } 949 950 int 951 tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo, 952 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 953 { 954 struct tcpopt to; 955 int rc; 956 957 bzero(&to, sizeof(struct tcpopt)); 958 to.to_mss = toeo->to_mss; 959 to.to_wscale = toeo->to_wscale; 960 to.to_flags = toeo->to_flags; 961 962 INP_INFO_WLOCK(&V_tcbinfo); 963 rc = syncache_expand(inc, &to, th, lsop, m); 964 INP_INFO_WUNLOCK(&V_tcbinfo); 965 966 return (rc); 967 } 968 969 /* 970 * Given a LISTEN socket and an inbound SYN request, add 971 * this to the syn cache, and send back a segment: 972 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 973 * to the source. 974 * 975 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 976 * Doing so would require that we hold onto the data and deliver it 977 * to the application. However, if we are the target of a SYN-flood 978 * DoS attack, an attacker could send data which would eventually 979 * consume all available buffer space if it were ACKed. By not ACKing 980 * the data, we avoid this DoS scenario. 981 */ 982 static void 983 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 984 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 985 struct toe_usrreqs *tu, void *toepcb) 986 { 987 struct tcpcb *tp; 988 struct socket *so; 989 struct syncache *sc = NULL; 990 struct syncache_head *sch; 991 struct mbuf *ipopts = NULL; 992 u_int32_t flowtmp; 993 int win, sb_hiwat, ip_ttl, ip_tos, noopt; 994 char *s; 995 #ifdef INET6 996 int autoflowlabel = 0; 997 #endif 998 #ifdef MAC 999 struct label *maclabel; 1000 #endif 1001 struct syncache scs; 1002 struct ucred *cred; 1003 1004 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1005 INP_WLOCK_ASSERT(inp); /* listen socket */ 1006 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1007 ("%s: unexpected tcp flags", __func__)); 1008 1009 /* 1010 * Combine all so/tp operations very early to drop the INP lock as 1011 * soon as possible. 1012 */ 1013 so = *lsop; 1014 tp = sototcpcb(so); 1015 cred = crhold(so->so_cred); 1016 1017 #ifdef INET6 1018 if ((inc->inc_flags & INC_ISIPV6) && 1019 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1020 autoflowlabel = 1; 1021 #endif 1022 ip_ttl = inp->inp_ip_ttl; 1023 ip_tos = inp->inp_ip_tos; 1024 win = sbspace(&so->so_rcv); 1025 sb_hiwat = so->so_rcv.sb_hiwat; 1026 noopt = (tp->t_flags & TF_NOOPT); 1027 1028 /* By the time we drop the lock these should no longer be used. */ 1029 so = NULL; 1030 tp = NULL; 1031 1032 #ifdef MAC 1033 if (mac_syncache_init(&maclabel) != 0) { 1034 INP_WUNLOCK(inp); 1035 INP_INFO_WUNLOCK(&V_tcbinfo); 1036 goto done; 1037 } else 1038 mac_syncache_create(maclabel, inp); 1039 #endif 1040 INP_WUNLOCK(inp); 1041 INP_INFO_WUNLOCK(&V_tcbinfo); 1042 1043 /* 1044 * Remember the IP options, if any. 1045 */ 1046 #ifdef INET6 1047 if (!(inc->inc_flags & INC_ISIPV6)) 1048 #endif 1049 ipopts = (m) ? ip_srcroute(m) : NULL; 1050 1051 /* 1052 * See if we already have an entry for this connection. 1053 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1054 * 1055 * XXX: should the syncache be re-initialized with the contents 1056 * of the new SYN here (which may have different options?) 1057 * 1058 * XXX: We do not check the sequence number to see if this is a 1059 * real retransmit or a new connection attempt. The question is 1060 * how to handle such a case; either ignore it as spoofed, or 1061 * drop the current entry and create a new one? 1062 */ 1063 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1064 SCH_LOCK_ASSERT(sch); 1065 if (sc != NULL) { 1066 #ifndef TCP_OFFLOAD_DISABLE 1067 if (sc->sc_tu) 1068 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1069 sc->sc_toepcb); 1070 #endif 1071 TCPSTAT_INC(tcps_sc_dupsyn); 1072 if (ipopts) { 1073 /* 1074 * If we were remembering a previous source route, 1075 * forget it and use the new one we've been given. 1076 */ 1077 if (sc->sc_ipopts) 1078 (void) m_free(sc->sc_ipopts); 1079 sc->sc_ipopts = ipopts; 1080 } 1081 /* 1082 * Update timestamp if present. 1083 */ 1084 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1085 sc->sc_tsreflect = to->to_tsval; 1086 else 1087 sc->sc_flags &= ~SCF_TIMESTAMP; 1088 #ifdef MAC 1089 /* 1090 * Since we have already unconditionally allocated label 1091 * storage, free it up. The syncache entry will already 1092 * have an initialized label we can use. 1093 */ 1094 mac_syncache_destroy(&maclabel); 1095 #endif 1096 /* Retransmit SYN|ACK and reset retransmit count. */ 1097 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1098 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1099 "resetting timer and retransmitting SYN|ACK\n", 1100 s, __func__); 1101 free(s, M_TCPLOG); 1102 } 1103 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1104 sc->sc_rxmits = 0; 1105 syncache_timeout(sc, sch, 1); 1106 TCPSTAT_INC(tcps_sndacks); 1107 TCPSTAT_INC(tcps_sndtotal); 1108 } 1109 SCH_UNLOCK(sch); 1110 goto done; 1111 } 1112 1113 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1114 if (sc == NULL) { 1115 /* 1116 * The zone allocator couldn't provide more entries. 1117 * Treat this as if the cache was full; drop the oldest 1118 * entry and insert the new one. 1119 */ 1120 TCPSTAT_INC(tcps_sc_zonefail); 1121 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1122 syncache_drop(sc, sch); 1123 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1124 if (sc == NULL) { 1125 if (V_tcp_syncookies) { 1126 bzero(&scs, sizeof(scs)); 1127 sc = &scs; 1128 } else { 1129 SCH_UNLOCK(sch); 1130 if (ipopts) 1131 (void) m_free(ipopts); 1132 goto done; 1133 } 1134 } 1135 } 1136 1137 /* 1138 * Fill in the syncache values. 1139 */ 1140 #ifdef MAC 1141 sc->sc_label = maclabel; 1142 #endif 1143 sc->sc_cred = cred; 1144 cred = NULL; 1145 sc->sc_ipopts = ipopts; 1146 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1147 #ifdef INET6 1148 if (!(inc->inc_flags & INC_ISIPV6)) 1149 #endif 1150 { 1151 sc->sc_ip_tos = ip_tos; 1152 sc->sc_ip_ttl = ip_ttl; 1153 } 1154 #ifndef TCP_OFFLOAD_DISABLE 1155 sc->sc_tu = tu; 1156 sc->sc_toepcb = toepcb; 1157 #endif 1158 sc->sc_irs = th->th_seq; 1159 sc->sc_iss = arc4random(); 1160 sc->sc_flags = 0; 1161 sc->sc_flowlabel = 0; 1162 1163 /* 1164 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1165 * win was derived from socket earlier in the function. 1166 */ 1167 win = imax(win, 0); 1168 win = imin(win, TCP_MAXWIN); 1169 sc->sc_wnd = win; 1170 1171 if (V_tcp_do_rfc1323) { 1172 /* 1173 * A timestamp received in a SYN makes 1174 * it ok to send timestamp requests and replies. 1175 */ 1176 if (to->to_flags & TOF_TS) { 1177 sc->sc_tsreflect = to->to_tsval; 1178 sc->sc_ts = ticks; 1179 sc->sc_flags |= SCF_TIMESTAMP; 1180 } 1181 if (to->to_flags & TOF_SCALE) { 1182 int wscale = 0; 1183 1184 /* 1185 * Pick the smallest possible scaling factor that 1186 * will still allow us to scale up to sb_max, aka 1187 * kern.ipc.maxsockbuf. 1188 * 1189 * We do this because there are broken firewalls that 1190 * will corrupt the window scale option, leading to 1191 * the other endpoint believing that our advertised 1192 * window is unscaled. At scale factors larger than 1193 * 5 the unscaled window will drop below 1500 bytes, 1194 * leading to serious problems when traversing these 1195 * broken firewalls. 1196 * 1197 * With the default maxsockbuf of 256K, a scale factor 1198 * of 3 will be chosen by this algorithm. Those who 1199 * choose a larger maxsockbuf should watch out 1200 * for the compatiblity problems mentioned above. 1201 * 1202 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1203 * or <SYN,ACK>) segment itself is never scaled. 1204 */ 1205 while (wscale < TCP_MAX_WINSHIFT && 1206 (TCP_MAXWIN << wscale) < sb_max) 1207 wscale++; 1208 sc->sc_requested_r_scale = wscale; 1209 sc->sc_requested_s_scale = to->to_wscale; 1210 sc->sc_flags |= SCF_WINSCALE; 1211 } 1212 } 1213 #ifdef TCP_SIGNATURE 1214 /* 1215 * If listening socket requested TCP digests, and received SYN 1216 * contains the option, flag this in the syncache so that 1217 * syncache_respond() will do the right thing with the SYN+ACK. 1218 * XXX: Currently we always record the option by default and will 1219 * attempt to use it in syncache_respond(). 1220 */ 1221 if (to->to_flags & TOF_SIGNATURE) 1222 sc->sc_flags |= SCF_SIGNATURE; 1223 #endif 1224 if (to->to_flags & TOF_SACKPERM) 1225 sc->sc_flags |= SCF_SACK; 1226 if (to->to_flags & TOF_MSS) 1227 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1228 if (noopt) 1229 sc->sc_flags |= SCF_NOOPT; 1230 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1231 sc->sc_flags |= SCF_ECN; 1232 1233 if (V_tcp_syncookies) { 1234 syncookie_generate(sch, sc, &flowtmp); 1235 #ifdef INET6 1236 if (autoflowlabel) 1237 sc->sc_flowlabel = flowtmp; 1238 #endif 1239 } else { 1240 #ifdef INET6 1241 if (autoflowlabel) 1242 sc->sc_flowlabel = 1243 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1244 #endif 1245 } 1246 SCH_UNLOCK(sch); 1247 1248 /* 1249 * Do a standard 3-way handshake. 1250 */ 1251 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1252 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1253 syncache_free(sc); 1254 else if (sc != &scs) 1255 syncache_insert(sc, sch); /* locks and unlocks sch */ 1256 TCPSTAT_INC(tcps_sndacks); 1257 TCPSTAT_INC(tcps_sndtotal); 1258 } else { 1259 if (sc != &scs) 1260 syncache_free(sc); 1261 TCPSTAT_INC(tcps_sc_dropped); 1262 } 1263 1264 done: 1265 if (cred != NULL) 1266 crfree(cred); 1267 #ifdef MAC 1268 if (sc == &scs) 1269 mac_syncache_destroy(&maclabel); 1270 #endif 1271 if (m) { 1272 1273 *lsop = NULL; 1274 m_freem(m); 1275 } 1276 } 1277 1278 static int 1279 syncache_respond(struct syncache *sc) 1280 { 1281 struct ip *ip = NULL; 1282 struct mbuf *m; 1283 struct tcphdr *th; 1284 int optlen, error; 1285 u_int16_t hlen, tlen, mssopt; 1286 struct tcpopt to; 1287 #ifdef INET6 1288 struct ip6_hdr *ip6 = NULL; 1289 #endif 1290 1291 hlen = 1292 #ifdef INET6 1293 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1294 #endif 1295 sizeof(struct ip); 1296 tlen = hlen + sizeof(struct tcphdr); 1297 1298 /* Determine MSS we advertize to other end of connection. */ 1299 mssopt = tcp_mssopt(&sc->sc_inc); 1300 if (sc->sc_peer_mss) 1301 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1302 1303 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1304 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1305 ("syncache: mbuf too small")); 1306 1307 /* Create the IP+TCP header from scratch. */ 1308 m = m_gethdr(M_DONTWAIT, MT_DATA); 1309 if (m == NULL) 1310 return (ENOBUFS); 1311 #ifdef MAC 1312 mac_syncache_create_mbuf(sc->sc_label, m); 1313 #endif 1314 m->m_data += max_linkhdr; 1315 m->m_len = tlen; 1316 m->m_pkthdr.len = tlen; 1317 m->m_pkthdr.rcvif = NULL; 1318 1319 #ifdef INET6 1320 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1321 ip6 = mtod(m, struct ip6_hdr *); 1322 ip6->ip6_vfc = IPV6_VERSION; 1323 ip6->ip6_nxt = IPPROTO_TCP; 1324 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1325 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1326 ip6->ip6_plen = htons(tlen - hlen); 1327 /* ip6_hlim is set after checksum */ 1328 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1329 ip6->ip6_flow |= sc->sc_flowlabel; 1330 1331 th = (struct tcphdr *)(ip6 + 1); 1332 } else 1333 #endif 1334 { 1335 ip = mtod(m, struct ip *); 1336 ip->ip_v = IPVERSION; 1337 ip->ip_hl = sizeof(struct ip) >> 2; 1338 ip->ip_len = tlen; 1339 ip->ip_id = 0; 1340 ip->ip_off = 0; 1341 ip->ip_sum = 0; 1342 ip->ip_p = IPPROTO_TCP; 1343 ip->ip_src = sc->sc_inc.inc_laddr; 1344 ip->ip_dst = sc->sc_inc.inc_faddr; 1345 ip->ip_ttl = sc->sc_ip_ttl; 1346 ip->ip_tos = sc->sc_ip_tos; 1347 1348 /* 1349 * See if we should do MTU discovery. Route lookups are 1350 * expensive, so we will only unset the DF bit if: 1351 * 1352 * 1) path_mtu_discovery is disabled 1353 * 2) the SCF_UNREACH flag has been set 1354 */ 1355 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1356 ip->ip_off |= IP_DF; 1357 1358 th = (struct tcphdr *)(ip + 1); 1359 } 1360 th->th_sport = sc->sc_inc.inc_lport; 1361 th->th_dport = sc->sc_inc.inc_fport; 1362 1363 th->th_seq = htonl(sc->sc_iss); 1364 th->th_ack = htonl(sc->sc_irs + 1); 1365 th->th_off = sizeof(struct tcphdr) >> 2; 1366 th->th_x2 = 0; 1367 th->th_flags = TH_SYN|TH_ACK; 1368 th->th_win = htons(sc->sc_wnd); 1369 th->th_urp = 0; 1370 1371 if (sc->sc_flags & SCF_ECN) { 1372 th->th_flags |= TH_ECE; 1373 TCPSTAT_INC(tcps_ecn_shs); 1374 } 1375 1376 /* Tack on the TCP options. */ 1377 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1378 to.to_flags = 0; 1379 1380 to.to_mss = mssopt; 1381 to.to_flags = TOF_MSS; 1382 if (sc->sc_flags & SCF_WINSCALE) { 1383 to.to_wscale = sc->sc_requested_r_scale; 1384 to.to_flags |= TOF_SCALE; 1385 } 1386 if (sc->sc_flags & SCF_TIMESTAMP) { 1387 /* Virgin timestamp or TCP cookie enhanced one. */ 1388 to.to_tsval = sc->sc_ts; 1389 to.to_tsecr = sc->sc_tsreflect; 1390 to.to_flags |= TOF_TS; 1391 } 1392 if (sc->sc_flags & SCF_SACK) 1393 to.to_flags |= TOF_SACKPERM; 1394 #ifdef TCP_SIGNATURE 1395 if (sc->sc_flags & SCF_SIGNATURE) 1396 to.to_flags |= TOF_SIGNATURE; 1397 #endif 1398 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1399 1400 /* Adjust headers by option size. */ 1401 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1402 m->m_len += optlen; 1403 m->m_pkthdr.len += optlen; 1404 1405 #ifdef TCP_SIGNATURE 1406 if (sc->sc_flags & SCF_SIGNATURE) 1407 tcp_signature_compute(m, 0, 0, optlen, 1408 to.to_signature, IPSEC_DIR_OUTBOUND); 1409 #endif 1410 #ifdef INET6 1411 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1412 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1413 else 1414 #endif 1415 ip->ip_len += optlen; 1416 } else 1417 optlen = 0; 1418 1419 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1420 #ifdef INET6 1421 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1422 th->th_sum = 0; 1423 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1424 tlen + optlen - hlen); 1425 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1426 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1427 } else 1428 #endif 1429 { 1430 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1431 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1432 m->m_pkthdr.csum_flags = CSUM_TCP; 1433 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1434 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1435 } 1436 return (error); 1437 } 1438 1439 void 1440 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1441 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1442 { 1443 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1444 } 1445 1446 void 1447 tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo, 1448 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1449 struct toe_usrreqs *tu, void *toepcb) 1450 { 1451 struct tcpopt to; 1452 1453 bzero(&to, sizeof(struct tcpopt)); 1454 to.to_mss = toeo->to_mss; 1455 to.to_wscale = toeo->to_wscale; 1456 to.to_flags = toeo->to_flags; 1457 1458 INP_INFO_WLOCK(&V_tcbinfo); 1459 INP_WLOCK(inp); 1460 1461 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb); 1462 } 1463 1464 /* 1465 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1466 * receive and to be able to handle SYN floods from bogus source addresses 1467 * (where we will never receive any reply). SYN floods try to exhaust all 1468 * our memory and available slots in the SYN cache table to cause a denial 1469 * of service to legitimate users of the local host. 1470 * 1471 * The idea of SYN cookies is to encode and include all necessary information 1472 * about the connection setup state within the SYN-ACK we send back and thus 1473 * to get along without keeping any local state until the ACK to the SYN-ACK 1474 * arrives (if ever). Everything we need to know should be available from 1475 * the information we encoded in the SYN-ACK. 1476 * 1477 * More information about the theory behind SYN cookies and its first 1478 * discussion and specification can be found at: 1479 * http://cr.yp.to/syncookies.html (overview) 1480 * http://cr.yp.to/syncookies/archive (gory details) 1481 * 1482 * This implementation extends the orginal idea and first implementation 1483 * of FreeBSD by using not only the initial sequence number field to store 1484 * information but also the timestamp field if present. This way we can 1485 * keep track of the entire state we need to know to recreate the session in 1486 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1487 * these days. For those that do not we still have to live with the known 1488 * shortcomings of the ISN only SYN cookies. 1489 * 1490 * Cookie layers: 1491 * 1492 * Initial sequence number we send: 1493 * 31|................................|0 1494 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1495 * D = MD5 Digest (first dword) 1496 * M = MSS index 1497 * R = Rotation of secret 1498 * P = Odd or Even secret 1499 * 1500 * The MD5 Digest is computed with over following parameters: 1501 * a) randomly rotated secret 1502 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1503 * c) the received initial sequence number from remote host 1504 * d) the rotation offset and odd/even bit 1505 * 1506 * Timestamp we send: 1507 * 31|................................|0 1508 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1509 * D = MD5 Digest (third dword) (only as filler) 1510 * S = Requested send window scale 1511 * R = Requested receive window scale 1512 * A = SACK allowed 1513 * 5 = TCP-MD5 enabled (not implemented yet) 1514 * XORed with MD5 Digest (forth dword) 1515 * 1516 * The timestamp isn't cryptographically secure and doesn't need to be. 1517 * The double use of the MD5 digest dwords ties it to a specific remote/ 1518 * local host/port, remote initial sequence number and our local time 1519 * limited secret. A received timestamp is reverted (XORed) and then 1520 * the contained MD5 dword is compared to the computed one to ensure the 1521 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1522 * have been tampered with but this isn't different from supplying bogus 1523 * values in the SYN in the first place. 1524 * 1525 * Some problems with SYN cookies remain however: 1526 * Consider the problem of a recreated (and retransmitted) cookie. If the 1527 * original SYN was accepted, the connection is established. The second 1528 * SYN is inflight, and if it arrives with an ISN that falls within the 1529 * receive window, the connection is killed. 1530 * 1531 * Notes: 1532 * A heuristic to determine when to accept syn cookies is not necessary. 1533 * An ACK flood would cause the syncookie verification to be attempted, 1534 * but a SYN flood causes syncookies to be generated. Both are of equal 1535 * cost, so there's no point in trying to optimize the ACK flood case. 1536 * Also, if you don't process certain ACKs for some reason, then all someone 1537 * would have to do is launch a SYN and ACK flood at the same time, which 1538 * would stop cookie verification and defeat the entire purpose of syncookies. 1539 */ 1540 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1541 1542 static void 1543 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1544 u_int32_t *flowlabel) 1545 { 1546 MD5_CTX ctx; 1547 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1548 u_int32_t data; 1549 u_int32_t *secbits; 1550 u_int off, pmss, mss; 1551 int i; 1552 1553 SCH_LOCK_ASSERT(sch); 1554 1555 /* Which of the two secrets to use. */ 1556 secbits = sch->sch_oddeven ? 1557 sch->sch_secbits_odd : sch->sch_secbits_even; 1558 1559 /* Reseed secret if too old. */ 1560 if (sch->sch_reseed < time_uptime) { 1561 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1562 secbits = sch->sch_oddeven ? 1563 sch->sch_secbits_odd : sch->sch_secbits_even; 1564 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1565 secbits[i] = arc4random(); 1566 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1567 } 1568 1569 /* Secret rotation offset. */ 1570 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1571 1572 /* Maximum segment size calculation. */ 1573 pmss = 1574 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1575 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1576 if (tcp_sc_msstab[mss] <= pmss) 1577 break; 1578 1579 /* Fold parameters and MD5 digest into the ISN we will send. */ 1580 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1581 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1582 data |= mss << 4; /* mss, 3 bits */ 1583 1584 MD5Init(&ctx); 1585 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1586 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1587 MD5Update(&ctx, secbits, off); 1588 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1589 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1590 MD5Update(&ctx, &data, sizeof(data)); 1591 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1592 1593 data |= (md5_buffer[0] << 7); 1594 sc->sc_iss = data; 1595 1596 #ifdef INET6 1597 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1598 #endif 1599 1600 /* Additional parameters are stored in the timestamp if present. */ 1601 if (sc->sc_flags & SCF_TIMESTAMP) { 1602 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1603 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1604 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1605 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1606 data |= md5_buffer[2] << 10; /* more digest bits */ 1607 data ^= md5_buffer[3]; 1608 sc->sc_ts = data; 1609 sc->sc_tsoff = data - ticks; /* after XOR */ 1610 } 1611 1612 TCPSTAT_INC(tcps_sc_sendcookie); 1613 } 1614 1615 static struct syncache * 1616 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1617 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1618 struct socket *so) 1619 { 1620 MD5_CTX ctx; 1621 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1622 u_int32_t data = 0; 1623 u_int32_t *secbits; 1624 tcp_seq ack, seq; 1625 int off, mss, wnd, flags; 1626 1627 SCH_LOCK_ASSERT(sch); 1628 1629 /* 1630 * Pull information out of SYN-ACK/ACK and 1631 * revert sequence number advances. 1632 */ 1633 ack = th->th_ack - 1; 1634 seq = th->th_seq - 1; 1635 off = (ack >> 1) & 0x7; 1636 mss = (ack >> 4) & 0x7; 1637 flags = ack & 0x7f; 1638 1639 /* Which of the two secrets to use. */ 1640 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1641 1642 /* 1643 * The secret wasn't updated for the lifetime of a syncookie, 1644 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1645 */ 1646 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1647 return (NULL); 1648 } 1649 1650 /* Recompute the digest so we can compare it. */ 1651 MD5Init(&ctx); 1652 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1653 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1654 MD5Update(&ctx, secbits, off); 1655 MD5Update(&ctx, inc, sizeof(*inc)); 1656 MD5Update(&ctx, &seq, sizeof(seq)); 1657 MD5Update(&ctx, &flags, sizeof(flags)); 1658 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1659 1660 /* Does the digest part of or ACK'ed ISS match? */ 1661 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1662 return (NULL); 1663 1664 /* Does the digest part of our reflected timestamp match? */ 1665 if (to->to_flags & TOF_TS) { 1666 data = md5_buffer[3] ^ to->to_tsecr; 1667 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1668 return (NULL); 1669 } 1670 1671 /* Fill in the syncache values. */ 1672 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1673 sc->sc_ipopts = NULL; 1674 1675 sc->sc_irs = seq; 1676 sc->sc_iss = ack; 1677 1678 #ifdef INET6 1679 if (inc->inc_flags & INC_ISIPV6) { 1680 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1681 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1682 } else 1683 #endif 1684 { 1685 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1686 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1687 } 1688 1689 /* Additional parameters that were encoded in the timestamp. */ 1690 if (data) { 1691 sc->sc_flags |= SCF_TIMESTAMP; 1692 sc->sc_tsreflect = to->to_tsval; 1693 sc->sc_ts = to->to_tsecr; 1694 sc->sc_tsoff = to->to_tsecr - ticks; 1695 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1696 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1697 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1698 TCP_MAX_WINSHIFT); 1699 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1700 TCP_MAX_WINSHIFT); 1701 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1702 sc->sc_flags |= SCF_WINSCALE; 1703 } else 1704 sc->sc_flags |= SCF_NOOPT; 1705 1706 wnd = sbspace(&so->so_rcv); 1707 wnd = imax(wnd, 0); 1708 wnd = imin(wnd, TCP_MAXWIN); 1709 sc->sc_wnd = wnd; 1710 1711 sc->sc_rxmits = 0; 1712 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1713 1714 TCPSTAT_INC(tcps_sc_recvcookie); 1715 return (sc); 1716 } 1717 1718 /* 1719 * Returns the current number of syncache entries. This number 1720 * will probably change before you get around to calling 1721 * syncache_pcblist. 1722 */ 1723 1724 int 1725 syncache_pcbcount(void) 1726 { 1727 struct syncache_head *sch; 1728 int count, i; 1729 1730 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1731 /* No need to lock for a read. */ 1732 sch = &V_tcp_syncache.hashbase[i]; 1733 count += sch->sch_length; 1734 } 1735 return count; 1736 } 1737 1738 /* 1739 * Exports the syncache entries to userland so that netstat can display 1740 * them alongside the other sockets. This function is intended to be 1741 * called only from tcp_pcblist. 1742 * 1743 * Due to concurrency on an active system, the number of pcbs exported 1744 * may have no relation to max_pcbs. max_pcbs merely indicates the 1745 * amount of space the caller allocated for this function to use. 1746 */ 1747 int 1748 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1749 { 1750 struct xtcpcb xt; 1751 struct syncache *sc; 1752 struct syncache_head *sch; 1753 int count, error, i; 1754 1755 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1756 sch = &V_tcp_syncache.hashbase[i]; 1757 SCH_LOCK(sch); 1758 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1759 if (count >= max_pcbs) { 1760 SCH_UNLOCK(sch); 1761 goto exit; 1762 } 1763 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1764 continue; 1765 bzero(&xt, sizeof(xt)); 1766 xt.xt_len = sizeof(xt); 1767 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1768 xt.xt_inp.inp_vflag = INP_IPV6; 1769 else 1770 xt.xt_inp.inp_vflag = INP_IPV4; 1771 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1772 xt.xt_tp.t_inpcb = &xt.xt_inp; 1773 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1774 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1775 xt.xt_socket.xso_len = sizeof (struct xsocket); 1776 xt.xt_socket.so_type = SOCK_STREAM; 1777 xt.xt_socket.so_state = SS_ISCONNECTING; 1778 error = SYSCTL_OUT(req, &xt, sizeof xt); 1779 if (error) { 1780 SCH_UNLOCK(sch); 1781 goto exit; 1782 } 1783 count++; 1784 } 1785 SCH_UNLOCK(sch); 1786 } 1787 exit: 1788 *pcbs_exported = count; 1789 return error; 1790 }
Cache object: 2319b1a965fe32a581ffb42c6d061715
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