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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/7.3/sys/netinet/tcp_syncache.c 196010 2009-08-01 07:09:50Z julian $"); 35 36 #include "opt_inet.h" 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_mac.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 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 int tcp_syncookies = 1; 101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 102 &tcp_syncookies, 0, 103 "Use TCP SYN cookies if the syncache overflows"); 104 105 static int tcp_syncookiesonly = 0; 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW, 107 &tcp_syncookiesonly, 0, 108 "Use only TCP SYN cookies"); 109 110 #define SYNCOOKIE_SECRET_SIZE 8 /* dwords */ 111 #define SYNCOOKIE_LIFETIME 16 /* seconds */ 112 113 struct syncache { 114 TAILQ_ENTRY(syncache) sc_hash; 115 struct in_conninfo sc_inc; /* addresses */ 116 int sc_rxttime; /* retransmit time */ 117 u_int16_t sc_rxmits; /* retransmit counter */ 118 u_int32_t sc_tsreflect; /* timestamp to reflect */ 119 u_int32_t sc_ts; /* our timestamp to send */ 120 u_int32_t sc_tsoff; /* ts offset w/ syncookies */ 121 u_int32_t sc_flowlabel; /* IPv6 flowlabel */ 122 tcp_seq sc_irs; /* seq from peer */ 123 tcp_seq sc_iss; /* our ISS */ 124 struct mbuf *sc_ipopts; /* source route */ 125 u_int16_t sc_peer_mss; /* peer's MSS */ 126 u_int16_t sc_wnd; /* advertised window */ 127 u_int8_t sc_ip_ttl; /* IPv4 TTL */ 128 u_int8_t sc_ip_tos; /* IPv4 TOS */ 129 u_int8_t sc_requested_s_scale:4, 130 sc_requested_r_scale:4; 131 u_int8_t sc_flags; 132 #ifndef TCP_OFFLOAD_DISABLE 133 struct toe_usrreqs *sc_tu; /* TOE operations */ 134 void *sc_toepcb; /* TOE protocol block */ 135 #endif 136 #ifdef MAC 137 struct label *sc_label; /* MAC label reference */ 138 #endif 139 struct ucred *sc_cred; /* cred cache for jail checks */ 140 }; 141 142 /* 143 * Flags for the sc_flags field. 144 */ 145 #define SCF_NOOPT 0x01 /* no TCP options */ 146 #define SCF_WINSCALE 0x02 /* negotiated window scaling */ 147 #define SCF_TIMESTAMP 0x04 /* negotiated timestamps */ 148 /* MSS is implicit */ 149 #define SCF_UNREACH 0x10 /* icmp unreachable received */ 150 #define SCF_SIGNATURE 0x20 /* send MD5 digests */ 151 #define SCF_SACK 0x80 /* send SACK option */ 152 153 #ifdef TCP_OFFLOAD_DISABLE 154 #define TOEPCB_ISSET(sc) (0) 155 #else 156 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL) 157 #endif 158 159 160 struct syncache_head { 161 struct mtx sch_mtx; 162 TAILQ_HEAD(sch_head, syncache) sch_bucket; 163 struct callout sch_timer; 164 int sch_nextc; 165 u_int sch_length; 166 u_int sch_oddeven; 167 u_int32_t sch_secbits_odd[SYNCOOKIE_SECRET_SIZE]; 168 u_int32_t sch_secbits_even[SYNCOOKIE_SECRET_SIZE]; 169 u_int sch_reseed; /* time_uptime, seconds */ 170 }; 171 172 static void syncache_drop(struct syncache *, struct syncache_head *); 173 static void syncache_free(struct syncache *); 174 static void syncache_insert(struct syncache *, struct syncache_head *); 175 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 176 static int syncache_respond(struct syncache *); 177 static struct socket *syncache_socket(struct syncache *, struct socket *, 178 struct mbuf *m); 179 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 180 int docallout); 181 static void syncache_timer(void *); 182 static void syncookie_generate(struct syncache_head *, struct syncache *, 183 u_int32_t *); 184 static struct syncache 185 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 186 struct syncache *, struct tcpopt *, struct tcphdr *, 187 struct socket *); 188 189 /* 190 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 191 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 192 * the odds are that the user has given up attempting to connect by then. 193 */ 194 #define SYNCACHE_MAXREXMTS 3 195 196 /* Arbitrary values */ 197 #define TCP_SYNCACHE_HASHSIZE 512 198 #define TCP_SYNCACHE_BUCKETLIMIT 30 199 200 struct tcp_syncache { 201 struct syncache_head *hashbase; 202 uma_zone_t zone; 203 u_int hashsize; 204 u_int hashmask; 205 u_int bucket_limit; 206 u_int cache_count; /* XXX: unprotected */ 207 u_int cache_limit; 208 u_int rexmt_limit; 209 u_int hash_secret; 210 }; 211 static struct tcp_syncache tcp_syncache; 212 213 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 214 215 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 216 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 217 218 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 219 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 220 221 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 222 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 223 224 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 225 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 226 227 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 228 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 229 230 int tcp_sc_rst_sock_fail = 1; 231 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, CTLFLAG_RW, 232 &tcp_sc_rst_sock_fail, 0, "Send reset on socket allocation failure"); 233 234 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 235 236 #define SYNCACHE_HASH(inc, mask) \ 237 ((tcp_syncache.hash_secret ^ \ 238 (inc)->inc_faddr.s_addr ^ \ 239 ((inc)->inc_faddr.s_addr >> 16) ^ \ 240 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 241 242 #define SYNCACHE_HASH6(inc, mask) \ 243 ((tcp_syncache.hash_secret ^ \ 244 (inc)->inc6_faddr.s6_addr32[0] ^ \ 245 (inc)->inc6_faddr.s6_addr32[3] ^ \ 246 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 247 248 #define ENDPTS_EQ(a, b) ( \ 249 (a)->ie_fport == (b)->ie_fport && \ 250 (a)->ie_lport == (b)->ie_lport && \ 251 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 252 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 253 ) 254 255 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 256 257 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 258 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 259 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 260 261 /* 262 * Requires the syncache entry to be already removed from the bucket list. 263 */ 264 static void 265 syncache_free(struct syncache *sc) 266 { 267 if (sc->sc_ipopts) 268 (void) m_free(sc->sc_ipopts); 269 if (sc->sc_cred) 270 crfree(sc->sc_cred); 271 #ifdef MAC 272 mac_destroy_syncache(&sc->sc_label); 273 #endif 274 275 uma_zfree(tcp_syncache.zone, sc); 276 } 277 278 void 279 syncache_init(void) 280 { 281 int i; 282 283 tcp_syncache.cache_count = 0; 284 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 285 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 286 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 287 tcp_syncache.hash_secret = arc4random(); 288 289 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 290 &tcp_syncache.hashsize); 291 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 292 &tcp_syncache.bucket_limit); 293 if (!powerof2(tcp_syncache.hashsize) || tcp_syncache.hashsize == 0) { 294 printf("WARNING: syncache hash size is not a power of 2.\n"); 295 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 296 } 297 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 298 299 /* Set limits. */ 300 tcp_syncache.cache_limit = 301 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 302 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 303 &tcp_syncache.cache_limit); 304 305 /* Allocate the hash table. */ 306 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 307 tcp_syncache.hashsize * sizeof(struct syncache_head), 308 M_SYNCACHE, M_WAITOK | M_ZERO); 309 310 /* Initialize the hash buckets. */ 311 for (i = 0; i < tcp_syncache.hashsize; i++) { 312 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 313 mtx_init(&tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 314 NULL, MTX_DEF); 315 callout_init_mtx(&tcp_syncache.hashbase[i].sch_timer, 316 &tcp_syncache.hashbase[i].sch_mtx, 0); 317 tcp_syncache.hashbase[i].sch_length = 0; 318 } 319 320 /* Create the syncache entry zone. */ 321 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 322 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 323 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 324 } 325 326 /* 327 * Inserts a syncache entry into the specified bucket row. 328 * Locks and unlocks the syncache_head autonomously. 329 */ 330 static void 331 syncache_insert(struct syncache *sc, struct syncache_head *sch) 332 { 333 struct syncache *sc2; 334 335 SCH_LOCK(sch); 336 337 /* 338 * Make sure that we don't overflow the per-bucket limit. 339 * If the bucket is full, toss the oldest element. 340 */ 341 if (sch->sch_length >= tcp_syncache.bucket_limit) { 342 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 343 ("sch->sch_length incorrect")); 344 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 345 syncache_drop(sc2, sch); 346 tcpstat.tcps_sc_bucketoverflow++; 347 } 348 349 /* Put it into the bucket. */ 350 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 351 sch->sch_length++; 352 353 /* Reinitialize the bucket row's timer. */ 354 if (sch->sch_length == 1) 355 sch->sch_nextc = ticks + INT_MAX; 356 syncache_timeout(sc, sch, 1); 357 358 SCH_UNLOCK(sch); 359 360 tcp_syncache.cache_count++; 361 tcpstat.tcps_sc_added++; 362 } 363 364 /* 365 * Remove and free entry from syncache bucket row. 366 * Expects locked syncache head. 367 */ 368 static void 369 syncache_drop(struct syncache *sc, struct syncache_head *sch) 370 { 371 372 SCH_LOCK_ASSERT(sch); 373 374 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 375 sch->sch_length--; 376 377 #ifndef TCP_OFFLOAD_DISABLE 378 if (sc->sc_tu) 379 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 380 #endif 381 syncache_free(sc); 382 tcp_syncache.cache_count--; 383 } 384 385 /* 386 * Engage/reengage time on bucket row. 387 */ 388 static void 389 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 390 { 391 sc->sc_rxttime = ticks + 392 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 393 sc->sc_rxmits++; 394 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 395 sch->sch_nextc = sc->sc_rxttime; 396 if (docallout) 397 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 398 syncache_timer, (void *)sch); 399 } 400 } 401 402 /* 403 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 404 * If we have retransmitted an entry the maximum number of times, expire it. 405 * One separate timer for each bucket row. 406 */ 407 static void 408 syncache_timer(void *xsch) 409 { 410 struct syncache_head *sch = (struct syncache_head *)xsch; 411 struct syncache *sc, *nsc; 412 int tick = ticks; 413 char *s; 414 415 /* NB: syncache_head has already been locked by the callout. */ 416 SCH_LOCK_ASSERT(sch); 417 418 /* 419 * In the following cycle we may remove some entries and/or 420 * advance some timeouts, so re-initialize the bucket timer. 421 */ 422 sch->sch_nextc = tick + INT_MAX; 423 424 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 425 /* 426 * We do not check if the listen socket still exists 427 * and accept the case where the listen socket may be 428 * gone by the time we resend the SYN/ACK. We do 429 * not expect this to happens often. If it does, 430 * then the RST will be sent by the time the remote 431 * host does the SYN/ACK->ACK. 432 */ 433 if (TSTMP_GT(sc->sc_rxttime, tick)) { 434 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 435 sch->sch_nextc = sc->sc_rxttime; 436 continue; 437 } 438 439 if (sc->sc_rxmits > tcp_syncache.rexmt_limit) { 440 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 441 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 442 "giving up and removing syncache entry\n", 443 s, __func__); 444 free(s, M_TCPLOG); 445 } 446 syncache_drop(sc, sch); 447 tcpstat.tcps_sc_stale++; 448 continue; 449 } 450 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 451 log(LOG_DEBUG, "%s; %s: Response timeout, " 452 "retransmitting (%u) SYN|ACK\n", 453 s, __func__, sc->sc_rxmits); 454 free(s, M_TCPLOG); 455 } 456 457 (void) syncache_respond(sc); 458 tcpstat.tcps_sc_retransmitted++; 459 syncache_timeout(sc, sch, 0); 460 } 461 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 462 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 463 syncache_timer, (void *)(sch)); 464 } 465 466 /* 467 * Find an entry in the syncache. 468 * Returns always with locked syncache_head plus a matching entry or NULL. 469 */ 470 struct syncache * 471 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 472 { 473 struct syncache *sc; 474 struct syncache_head *sch; 475 476 #ifdef INET6 477 if (inc->inc_flags & INC_ISIPV6) { 478 sch = &tcp_syncache.hashbase[ 479 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 480 *schp = sch; 481 482 SCH_LOCK(sch); 483 484 /* Circle through bucket row to find matching entry. */ 485 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 486 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 487 return (sc); 488 } 489 } else 490 #endif 491 { 492 sch = &tcp_syncache.hashbase[ 493 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 494 *schp = sch; 495 496 SCH_LOCK(sch); 497 498 /* Circle through bucket row to find matching entry. */ 499 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 500 #ifdef INET6 501 if (sc->sc_inc.inc_flags & INC_ISIPV6) 502 continue; 503 #endif 504 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 505 return (sc); 506 } 507 } 508 SCH_LOCK_ASSERT(*schp); 509 return (NULL); /* always returns with locked sch */ 510 } 511 512 /* 513 * This function is called when we get a RST for a 514 * non-existent connection, so that we can see if the 515 * connection is in the syn cache. If it is, zap it. 516 */ 517 void 518 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 519 { 520 struct syncache *sc; 521 struct syncache_head *sch; 522 char *s = NULL; 523 524 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 525 SCH_LOCK_ASSERT(sch); 526 527 /* 528 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 529 * See RFC 793 page 65, section SEGMENT ARRIVES. 530 */ 531 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 532 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 533 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 534 "FIN flag set, segment ignored\n", s, __func__); 535 tcpstat.tcps_badrst++; 536 goto done; 537 } 538 539 /* 540 * No corresponding connection was found in syncache. 541 * If syncookies are enabled and possibly exclusively 542 * used, or we are under memory pressure, a valid RST 543 * may not find a syncache entry. In that case we're 544 * done and no SYN|ACK retransmissions will happen. 545 * Otherwise the the RST was misdirected or spoofed. 546 */ 547 if (sc == NULL) { 548 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 549 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 550 "syncache entry (possibly syncookie only), " 551 "segment ignored\n", s, __func__); 552 tcpstat.tcps_badrst++; 553 goto done; 554 } 555 556 /* 557 * If the RST bit is set, check the sequence number to see 558 * if this is a valid reset segment. 559 * RFC 793 page 37: 560 * In all states except SYN-SENT, all reset (RST) segments 561 * are validated by checking their SEQ-fields. A reset is 562 * valid if its sequence number is in the window. 563 * 564 * The sequence number in the reset segment is normally an 565 * echo of our outgoing acknowlegement numbers, but some hosts 566 * send a reset with the sequence number at the rightmost edge 567 * of our receive window, and we have to handle this case. 568 */ 569 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 570 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 571 syncache_drop(sc, sch); 572 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 573 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 574 "connection attempt aborted by remote endpoint\n", 575 s, __func__); 576 tcpstat.tcps_sc_reset++; 577 } else { 578 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 579 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 580 "IRS %u (+WND %u), segment ignored\n", 581 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 582 tcpstat.tcps_badrst++; 583 } 584 585 done: 586 if (s != NULL) 587 free(s, M_TCPLOG); 588 SCH_UNLOCK(sch); 589 } 590 591 void 592 syncache_badack(struct in_conninfo *inc) 593 { 594 struct syncache *sc; 595 struct syncache_head *sch; 596 597 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 598 SCH_LOCK_ASSERT(sch); 599 if (sc != NULL) { 600 syncache_drop(sc, sch); 601 tcpstat.tcps_sc_badack++; 602 } 603 SCH_UNLOCK(sch); 604 } 605 606 void 607 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 608 { 609 struct syncache *sc; 610 struct syncache_head *sch; 611 612 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 613 SCH_LOCK_ASSERT(sch); 614 if (sc == NULL) 615 goto done; 616 617 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 618 if (ntohl(th->th_seq) != sc->sc_iss) 619 goto done; 620 621 /* 622 * If we've rertransmitted 3 times and this is our second error, 623 * we remove the entry. Otherwise, we allow it to continue on. 624 * This prevents us from incorrectly nuking an entry during a 625 * spurious network outage. 626 * 627 * See tcp_notify(). 628 */ 629 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 630 sc->sc_flags |= SCF_UNREACH; 631 goto done; 632 } 633 syncache_drop(sc, sch); 634 tcpstat.tcps_sc_unreach++; 635 done: 636 SCH_UNLOCK(sch); 637 } 638 639 /* 640 * Build a new TCP socket structure from a syncache entry. 641 */ 642 static struct socket * 643 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 644 { 645 struct inpcb *inp = NULL; 646 struct socket *so; 647 struct tcpcb *tp; 648 char *s; 649 650 INP_INFO_WLOCK_ASSERT(&tcbinfo); 651 652 /* 653 * Ok, create the full blown connection, and set things up 654 * as they would have been set up if we had created the 655 * connection when the SYN arrived. If we can't create 656 * the connection, abort it. 657 */ 658 so = sonewconn(lso, SS_ISCONNECTED); 659 if (so == NULL) { 660 /* 661 * Drop the connection; we will either send a RST or 662 * have the peer retransmit its SYN again after its 663 * RTO and try again. 664 */ 665 tcpstat.tcps_listendrop++; 666 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 667 log(LOG_DEBUG, "%s; %s: Socket create failed " 668 "due to limits or memory shortage\n", 669 s, __func__); 670 free(s, M_TCPLOG); 671 } 672 goto abort2; 673 } 674 #ifdef MAC 675 SOCK_LOCK(so); 676 mac_set_socket_peer_from_mbuf(m, so); 677 SOCK_UNLOCK(so); 678 #endif 679 680 inp = sotoinpcb(so); 681 inp->inp_inc.inc_fibnum = so->so_fibnum; 682 INP_WLOCK(inp); 683 684 /* Insert new socket into PCB hash list. */ 685 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 686 #ifdef INET6 687 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 688 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 689 } else { 690 inp->inp_vflag &= ~INP_IPV6; 691 inp->inp_vflag |= INP_IPV4; 692 #endif 693 inp->inp_laddr = sc->sc_inc.inc_laddr; 694 #ifdef INET6 695 } 696 #endif 697 inp->inp_lport = sc->sc_inc.inc_lport; 698 if (in_pcbinshash(inp) != 0) { 699 /* 700 * Undo the assignments above if we failed to 701 * put the PCB on the hash lists. 702 */ 703 #ifdef INET6 704 if (sc->sc_inc.inc_flags & INC_ISIPV6) 705 inp->in6p_laddr = in6addr_any; 706 else 707 #endif 708 inp->inp_laddr.s_addr = INADDR_ANY; 709 inp->inp_lport = 0; 710 goto abort; 711 } 712 #ifdef IPSEC 713 /* Copy old policy into new socket's. */ 714 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 715 printf("syncache_socket: could not copy policy\n"); 716 #endif 717 #ifdef INET6 718 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 719 struct inpcb *oinp = sotoinpcb(lso); 720 struct in6_addr laddr6; 721 struct sockaddr_in6 sin6; 722 /* 723 * Inherit socket options from the listening socket. 724 * Note that in6p_inputopts are not (and should not be) 725 * copied, since it stores previously received options and is 726 * used to detect if each new option is different than the 727 * previous one and hence should be passed to a user. 728 * If we copied in6p_inputopts, a user would not be able to 729 * receive options just after calling the accept system call. 730 */ 731 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 732 if (oinp->in6p_outputopts) 733 inp->in6p_outputopts = 734 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 735 736 sin6.sin6_family = AF_INET6; 737 sin6.sin6_len = sizeof(sin6); 738 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 739 sin6.sin6_port = sc->sc_inc.inc_fport; 740 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 741 laddr6 = inp->in6p_laddr; 742 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 743 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 744 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 745 thread0.td_ucred)) { 746 inp->in6p_laddr = laddr6; 747 goto abort; 748 } 749 /* Override flowlabel from in6_pcbconnect. */ 750 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 751 inp->inp_flow |= sc->sc_flowlabel; 752 } else 753 #endif 754 { 755 struct in_addr laddr; 756 struct sockaddr_in sin; 757 758 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 759 760 if (inp->inp_options == NULL) { 761 inp->inp_options = sc->sc_ipopts; 762 sc->sc_ipopts = NULL; 763 } 764 765 sin.sin_family = AF_INET; 766 sin.sin_len = sizeof(sin); 767 sin.sin_addr = sc->sc_inc.inc_faddr; 768 sin.sin_port = sc->sc_inc.inc_fport; 769 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 770 laddr = inp->inp_laddr; 771 if (inp->inp_laddr.s_addr == INADDR_ANY) 772 inp->inp_laddr = sc->sc_inc.inc_laddr; 773 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 774 thread0.td_ucred)) { 775 inp->inp_laddr = laddr; 776 goto abort; 777 } 778 } 779 tp = intotcpcb(inp); 780 tp->t_state = TCPS_SYN_RECEIVED; 781 tp->iss = sc->sc_iss; 782 tp->irs = sc->sc_irs; 783 tcp_rcvseqinit(tp); 784 tcp_sendseqinit(tp); 785 tp->snd_wl1 = sc->sc_irs; 786 tp->snd_max = tp->iss + 1; 787 tp->snd_nxt = tp->iss + 1; 788 tp->rcv_up = sc->sc_irs + 1; 789 tp->rcv_wnd = sc->sc_wnd; 790 tp->rcv_adv += tp->rcv_wnd; 791 tp->last_ack_sent = tp->rcv_nxt; 792 793 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 794 if (sc->sc_flags & SCF_NOOPT) 795 tp->t_flags |= TF_NOOPT; 796 else { 797 if (sc->sc_flags & SCF_WINSCALE) { 798 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 799 tp->snd_scale = sc->sc_requested_s_scale; 800 tp->request_r_scale = sc->sc_requested_r_scale; 801 } 802 if (sc->sc_flags & SCF_TIMESTAMP) { 803 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 804 tp->ts_recent = sc->sc_tsreflect; 805 tp->ts_recent_age = ticks; 806 tp->ts_offset = sc->sc_tsoff; 807 } 808 #ifdef TCP_SIGNATURE 809 if (sc->sc_flags & SCF_SIGNATURE) 810 tp->t_flags |= TF_SIGNATURE; 811 #endif 812 if (sc->sc_flags & SCF_SACK) 813 tp->t_flags |= TF_SACK_PERMIT; 814 } 815 816 /* 817 * Set up MSS and get cached values from tcp_hostcache. 818 * This might overwrite some of the defaults we just set. 819 */ 820 tcp_mss(tp, sc->sc_peer_mss); 821 822 /* 823 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 824 */ 825 if (sc->sc_rxmits) 826 tp->snd_cwnd = tp->t_maxseg; 827 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 828 829 INP_WUNLOCK(inp); 830 831 tcpstat.tcps_accepts++; 832 return (so); 833 834 abort: 835 INP_WUNLOCK(inp); 836 abort2: 837 if (so != NULL) 838 soabort(so); 839 return (NULL); 840 } 841 842 /* 843 * This function gets called when we receive an ACK for a 844 * socket in the LISTEN state. We look up the connection 845 * in the syncache, and if its there, we pull it out of 846 * the cache and turn it into a full-blown connection in 847 * the SYN-RECEIVED state. 848 */ 849 int 850 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 851 struct socket **lsop, struct mbuf *m) 852 { 853 struct syncache *sc; 854 struct syncache_head *sch; 855 struct syncache scs; 856 char *s; 857 858 /* 859 * Global TCP locks are held because we manipulate the PCB lists 860 * and create a new socket. 861 */ 862 INP_INFO_WLOCK_ASSERT(&tcbinfo); 863 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 864 ("%s: can handle only ACK", __func__)); 865 866 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 867 SCH_LOCK_ASSERT(sch); 868 if (sc == NULL) { 869 /* 870 * There is no syncache entry, so see if this ACK is 871 * a returning syncookie. To do this, first: 872 * A. See if this socket has had a syncache entry dropped in 873 * the past. We don't want to accept a bogus syncookie 874 * if we've never received a SYN. 875 * B. check that the syncookie is valid. If it is, then 876 * cobble up a fake syncache entry, and return. 877 */ 878 if (!tcp_syncookies) { 879 SCH_UNLOCK(sch); 880 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 881 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 882 "segment rejected (syncookies disabled)\n", 883 s, __func__); 884 goto failed; 885 } 886 bzero(&scs, sizeof(scs)); 887 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 888 SCH_UNLOCK(sch); 889 if (sc == NULL) { 890 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 891 log(LOG_DEBUG, "%s; %s: Segment failed " 892 "SYNCOOKIE authentication, segment rejected " 893 "(probably spoofed)\n", s, __func__); 894 goto failed; 895 } 896 } else { 897 /* Pull out the entry to unlock the bucket row. */ 898 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 899 sch->sch_length--; 900 tcp_syncache.cache_count--; 901 SCH_UNLOCK(sch); 902 } 903 904 /* 905 * Segment validation: 906 * ACK must match our initial sequence number + 1 (the SYN|ACK). 907 */ 908 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 909 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 910 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 911 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 912 goto failed; 913 } 914 915 /* 916 * The SEQ must fall in the window starting at the received 917 * initial receive sequence number + 1 (the SYN). 918 */ 919 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 920 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 921 !TOEPCB_ISSET(sc)) { 922 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 923 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 924 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 925 goto failed; 926 } 927 #if 0 928 /* 929 * If timestamps were present in the SYN and we accepted 930 * them in our SYN|ACK we require them to be present from 931 * now on. And vice versa. 932 * 933 * Unfortunately, during testing of 7.0 some users found 934 * network devices that violate this constraint, so it must 935 * be disabled. 936 */ 937 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) { 938 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 939 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 940 "segment rejected\n", s, __func__); 941 goto failed; 942 } 943 #endif 944 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 945 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 946 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 947 "segment rejected\n", s, __func__); 948 goto failed; 949 } 950 /* 951 * If timestamps were negotiated the reflected timestamp 952 * must be equal to what we actually sent in the SYN|ACK. 953 */ 954 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 955 !TOEPCB_ISSET(sc)) { 956 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 957 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 958 "segment rejected\n", 959 s, __func__, to->to_tsecr, sc->sc_ts); 960 goto failed; 961 } 962 963 *lsop = syncache_socket(sc, *lsop, m); 964 965 if (*lsop == NULL) 966 tcpstat.tcps_sc_aborted++; 967 else 968 tcpstat.tcps_sc_completed++; 969 970 /* how do we find the inp for the new socket? */ 971 if (sc != &scs) 972 syncache_free(sc); 973 return (1); 974 failed: 975 if (sc != NULL && sc != &scs) 976 syncache_free(sc); 977 if (s != NULL) 978 free(s, M_TCPLOG); 979 *lsop = NULL; 980 return (0); 981 } 982 983 int 984 tcp_offload_syncache_expand(struct in_conninfo *inc, struct tcpopt *to, 985 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 986 { 987 int rc; 988 989 INP_INFO_WLOCK(&tcbinfo); 990 rc = syncache_expand(inc, to, th, lsop, m); 991 INP_INFO_WUNLOCK(&tcbinfo); 992 993 return (rc); 994 } 995 996 /* 997 * Given a LISTEN socket and an inbound SYN request, add 998 * this to the syn cache, and send back a segment: 999 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1000 * to the source. 1001 * 1002 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1003 * Doing so would require that we hold onto the data and deliver it 1004 * to the application. However, if we are the target of a SYN-flood 1005 * DoS attack, an attacker could send data which would eventually 1006 * consume all available buffer space if it were ACKed. By not ACKing 1007 * the data, we avoid this DoS scenario. 1008 */ 1009 static void 1010 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1011 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 1012 struct toe_usrreqs *tu, void *toepcb) 1013 { 1014 struct tcpcb *tp; 1015 struct socket *so; 1016 struct syncache *sc = NULL; 1017 struct syncache_head *sch; 1018 struct mbuf *ipopts = NULL; 1019 u_int32_t flowtmp; 1020 int win, sb_hiwat, ip_ttl, ip_tos, noopt; 1021 char *s; 1022 #ifdef INET6 1023 int autoflowlabel = 0; 1024 #endif 1025 #ifdef MAC 1026 struct label *maclabel; 1027 #endif 1028 struct syncache scs; 1029 struct ucred *cred; 1030 1031 INP_INFO_WLOCK_ASSERT(&tcbinfo); 1032 INP_WLOCK_ASSERT(inp); /* listen socket */ 1033 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1034 ("%s: unexpected tcp flags", __func__)); 1035 1036 /* 1037 * Combine all so/tp operations very early to drop the INP lock as 1038 * soon as possible. 1039 */ 1040 so = *lsop; 1041 tp = sototcpcb(so); 1042 cred = crhold(so->so_cred); 1043 1044 #ifdef INET6 1045 if ((inc->inc_flags & INC_ISIPV6) && 1046 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1047 autoflowlabel = 1; 1048 #endif 1049 ip_ttl = inp->inp_ip_ttl; 1050 ip_tos = inp->inp_ip_tos; 1051 win = sbspace(&so->so_rcv); 1052 sb_hiwat = so->so_rcv.sb_hiwat; 1053 noopt = (tp->t_flags & TF_NOOPT); 1054 1055 /* By the time we drop the lock these should no longer be used. */ 1056 so = NULL; 1057 tp = NULL; 1058 1059 #ifdef MAC 1060 if (mac_init_syncache(&maclabel) != 0) { 1061 INP_WUNLOCK(inp); 1062 INP_INFO_WUNLOCK(&tcbinfo); 1063 goto done; 1064 } else 1065 mac_init_syncache_from_inpcb(maclabel, inp); 1066 #endif 1067 INP_WUNLOCK(inp); 1068 INP_INFO_WUNLOCK(&tcbinfo); 1069 1070 /* 1071 * Remember the IP options, if any. 1072 */ 1073 #ifdef INET6 1074 if (!(inc->inc_flags & INC_ISIPV6)) 1075 #endif 1076 ipopts = (m) ? ip_srcroute(m) : NULL; 1077 1078 /* 1079 * See if we already have an entry for this connection. 1080 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1081 * 1082 * XXX: should the syncache be re-initialized with the contents 1083 * of the new SYN here (which may have different options?) 1084 * 1085 * XXX: We do not check the sequence number to see if this is a 1086 * real retransmit or a new connection attempt. The question is 1087 * how to handle such a case; either ignore it as spoofed, or 1088 * drop the current entry and create a new one? 1089 */ 1090 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1091 SCH_LOCK_ASSERT(sch); 1092 if (sc != NULL) { 1093 #ifndef TCP_OFFLOAD_DISABLE 1094 if (sc->sc_tu) 1095 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1096 sc->sc_toepcb); 1097 #endif 1098 tcpstat.tcps_sc_dupsyn++; 1099 if (ipopts) { 1100 /* 1101 * If we were remembering a previous source route, 1102 * forget it and use the new one we've been given. 1103 */ 1104 if (sc->sc_ipopts) 1105 (void) m_free(sc->sc_ipopts); 1106 sc->sc_ipopts = ipopts; 1107 } 1108 /* 1109 * Update timestamp if present. 1110 */ 1111 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1112 sc->sc_tsreflect = to->to_tsval; 1113 else 1114 sc->sc_flags &= ~SCF_TIMESTAMP; 1115 #ifdef MAC 1116 /* 1117 * Since we have already unconditionally allocated label 1118 * storage, free it up. The syncache entry will already 1119 * have an initialized label we can use. 1120 */ 1121 mac_destroy_syncache(&maclabel); 1122 KASSERT(sc->sc_label != NULL, 1123 ("%s: label not initialized", __func__)); 1124 #endif 1125 /* Retransmit SYN|ACK and reset retransmit count. */ 1126 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1127 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1128 "resetting timer and retransmitting SYN|ACK\n", 1129 s, __func__); 1130 free(s, M_TCPLOG); 1131 } 1132 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1133 sc->sc_rxmits = 0; 1134 syncache_timeout(sc, sch, 1); 1135 tcpstat.tcps_sndacks++; 1136 tcpstat.tcps_sndtotal++; 1137 } 1138 SCH_UNLOCK(sch); 1139 goto done; 1140 } 1141 1142 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO); 1143 if (sc == NULL) { 1144 /* 1145 * The zone allocator couldn't provide more entries. 1146 * Treat this as if the cache was full; drop the oldest 1147 * entry and insert the new one. 1148 */ 1149 tcpstat.tcps_sc_zonefail++; 1150 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1151 syncache_drop(sc, sch); 1152 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO); 1153 if (sc == NULL) { 1154 if (tcp_syncookies) { 1155 bzero(&scs, sizeof(scs)); 1156 sc = &scs; 1157 } else { 1158 SCH_UNLOCK(sch); 1159 if (ipopts) 1160 (void) m_free(ipopts); 1161 goto done; 1162 } 1163 } 1164 } 1165 1166 /* 1167 * Fill in the syncache values. 1168 */ 1169 #ifdef MAC 1170 sc->sc_label = maclabel; 1171 #endif 1172 sc->sc_cred = cred; 1173 cred = NULL; 1174 sc->sc_ipopts = ipopts; 1175 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1176 #ifdef INET6 1177 if (!(inc->inc_flags & INC_ISIPV6)) 1178 #endif 1179 { 1180 sc->sc_ip_tos = ip_tos; 1181 sc->sc_ip_ttl = ip_ttl; 1182 } 1183 #ifndef TCP_OFFLOAD_DISABLE 1184 sc->sc_tu = tu; 1185 sc->sc_toepcb = toepcb; 1186 #endif 1187 sc->sc_irs = th->th_seq; 1188 sc->sc_iss = arc4random(); 1189 sc->sc_flags = 0; 1190 sc->sc_flowlabel = 0; 1191 1192 /* 1193 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1194 * win was derived from socket earlier in the function. 1195 */ 1196 win = imax(win, 0); 1197 win = imin(win, TCP_MAXWIN); 1198 sc->sc_wnd = win; 1199 1200 if (tcp_do_rfc1323) { 1201 /* 1202 * A timestamp received in a SYN makes 1203 * it ok to send timestamp requests and replies. 1204 */ 1205 if (to->to_flags & TOF_TS) { 1206 sc->sc_tsreflect = to->to_tsval; 1207 sc->sc_ts = ticks; 1208 sc->sc_flags |= SCF_TIMESTAMP; 1209 } 1210 if (to->to_flags & TOF_SCALE) { 1211 int wscale = 0; 1212 1213 /* 1214 * Pick the smallest possible scaling factor that 1215 * will still allow us to scale up to sb_max, aka 1216 * kern.ipc.maxsockbuf. 1217 * 1218 * We do this because there are broken firewalls that 1219 * will corrupt the window scale option, leading to 1220 * the other endpoint believing that our advertised 1221 * window is unscaled. At scale factors larger than 1222 * 5 the unscaled window will drop below 1500 bytes, 1223 * leading to serious problems when traversing these 1224 * broken firewalls. 1225 * 1226 * With the default maxsockbuf of 256K, a scale factor 1227 * of 3 will be chosen by this algorithm. Those who 1228 * choose a larger maxsockbuf should watch out 1229 * for the compatiblity problems mentioned above. 1230 * 1231 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1232 * or <SYN,ACK>) segment itself is never scaled. 1233 */ 1234 while (wscale < TCP_MAX_WINSHIFT && 1235 (TCP_MAXWIN << wscale) < sb_max) 1236 wscale++; 1237 sc->sc_requested_r_scale = wscale; 1238 sc->sc_requested_s_scale = to->to_wscale; 1239 sc->sc_flags |= SCF_WINSCALE; 1240 } 1241 } 1242 #ifdef TCP_SIGNATURE 1243 /* 1244 * If listening socket requested TCP digests, and received SYN 1245 * contains the option, flag this in the syncache so that 1246 * syncache_respond() will do the right thing with the SYN+ACK. 1247 * XXX: Currently we always record the option by default and will 1248 * attempt to use it in syncache_respond(). 1249 */ 1250 if (to->to_flags & TOF_SIGNATURE) 1251 sc->sc_flags |= SCF_SIGNATURE; 1252 #endif 1253 if (to->to_flags & TOF_SACKPERM) 1254 sc->sc_flags |= SCF_SACK; 1255 if (to->to_flags & TOF_MSS) 1256 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1257 if (noopt) 1258 sc->sc_flags |= SCF_NOOPT; 1259 1260 if (tcp_syncookies) { 1261 syncookie_generate(sch, sc, &flowtmp); 1262 #ifdef INET6 1263 if (autoflowlabel) 1264 sc->sc_flowlabel = flowtmp; 1265 #endif 1266 } else { 1267 #ifdef INET6 1268 if (autoflowlabel) 1269 sc->sc_flowlabel = 1270 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1271 #endif 1272 } 1273 SCH_UNLOCK(sch); 1274 1275 /* 1276 * Do a standard 3-way handshake. 1277 */ 1278 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1279 if (tcp_syncookies && tcp_syncookiesonly && sc != &scs) 1280 syncache_free(sc); 1281 else if (sc != &scs) 1282 syncache_insert(sc, sch); /* locks and unlocks sch */ 1283 tcpstat.tcps_sndacks++; 1284 tcpstat.tcps_sndtotal++; 1285 } else { 1286 if (sc != &scs) 1287 syncache_free(sc); 1288 tcpstat.tcps_sc_dropped++; 1289 } 1290 1291 done: 1292 if (cred != NULL) 1293 crfree(cred); 1294 #ifdef MAC 1295 if (sc == &scs) 1296 mac_destroy_syncache(&maclabel); 1297 #endif 1298 *lsop = NULL; 1299 m_freem(m); 1300 } 1301 1302 static int 1303 syncache_respond(struct syncache *sc) 1304 { 1305 struct ip *ip = NULL; 1306 struct mbuf *m; 1307 struct tcphdr *th; 1308 int optlen, error; 1309 u_int16_t hlen, tlen, mssopt; 1310 struct tcpopt to; 1311 #ifdef INET6 1312 struct ip6_hdr *ip6 = NULL; 1313 #endif 1314 1315 hlen = 1316 #ifdef INET6 1317 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1318 #endif 1319 sizeof(struct ip); 1320 tlen = hlen + sizeof(struct tcphdr); 1321 1322 /* Determine MSS we advertize to other end of connection. */ 1323 mssopt = tcp_mssopt(&sc->sc_inc); 1324 if (sc->sc_peer_mss) 1325 mssopt = max( min(sc->sc_peer_mss, mssopt), tcp_minmss); 1326 1327 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1328 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1329 ("syncache: mbuf too small")); 1330 1331 /* Create the IP+TCP header from scratch. */ 1332 m = m_gethdr(M_DONTWAIT, MT_DATA); 1333 if (m == NULL) 1334 return (ENOBUFS); 1335 #ifdef MAC 1336 mac_create_mbuf_from_syncache(sc->sc_label, m); 1337 #endif 1338 m->m_data += max_linkhdr; 1339 m->m_len = tlen; 1340 m->m_pkthdr.len = tlen; 1341 m->m_pkthdr.rcvif = NULL; 1342 1343 #ifdef INET6 1344 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1345 ip6 = mtod(m, struct ip6_hdr *); 1346 ip6->ip6_vfc = IPV6_VERSION; 1347 ip6->ip6_nxt = IPPROTO_TCP; 1348 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1349 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1350 ip6->ip6_plen = htons(tlen - hlen); 1351 /* ip6_hlim is set after checksum */ 1352 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1353 ip6->ip6_flow |= sc->sc_flowlabel; 1354 1355 th = (struct tcphdr *)(ip6 + 1); 1356 } else 1357 #endif 1358 { 1359 ip = mtod(m, struct ip *); 1360 ip->ip_v = IPVERSION; 1361 ip->ip_hl = sizeof(struct ip) >> 2; 1362 ip->ip_len = tlen; 1363 ip->ip_id = 0; 1364 ip->ip_off = 0; 1365 ip->ip_sum = 0; 1366 ip->ip_p = IPPROTO_TCP; 1367 ip->ip_src = sc->sc_inc.inc_laddr; 1368 ip->ip_dst = sc->sc_inc.inc_faddr; 1369 ip->ip_ttl = sc->sc_ip_ttl; 1370 ip->ip_tos = sc->sc_ip_tos; 1371 1372 /* 1373 * See if we should do MTU discovery. Route lookups are 1374 * expensive, so we will only unset the DF bit if: 1375 * 1376 * 1) path_mtu_discovery is disabled 1377 * 2) the SCF_UNREACH flag has been set 1378 */ 1379 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1380 ip->ip_off |= IP_DF; 1381 1382 th = (struct tcphdr *)(ip + 1); 1383 } 1384 th->th_sport = sc->sc_inc.inc_lport; 1385 th->th_dport = sc->sc_inc.inc_fport; 1386 1387 th->th_seq = htonl(sc->sc_iss); 1388 th->th_ack = htonl(sc->sc_irs + 1); 1389 th->th_off = sizeof(struct tcphdr) >> 2; 1390 th->th_x2 = 0; 1391 th->th_flags = TH_SYN|TH_ACK; 1392 th->th_win = htons(sc->sc_wnd); 1393 th->th_urp = 0; 1394 1395 /* Tack on the TCP options. */ 1396 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1397 to.to_flags = 0; 1398 1399 to.to_mss = mssopt; 1400 to.to_flags = TOF_MSS; 1401 if (sc->sc_flags & SCF_WINSCALE) { 1402 to.to_wscale = sc->sc_requested_r_scale; 1403 to.to_flags |= TOF_SCALE; 1404 } 1405 if (sc->sc_flags & SCF_TIMESTAMP) { 1406 /* Virgin timestamp or TCP cookie enhanced one. */ 1407 to.to_tsval = sc->sc_ts; 1408 to.to_tsecr = sc->sc_tsreflect; 1409 to.to_flags |= TOF_TS; 1410 } 1411 if (sc->sc_flags & SCF_SACK) 1412 to.to_flags |= TOF_SACKPERM; 1413 #ifdef TCP_SIGNATURE 1414 if (sc->sc_flags & SCF_SIGNATURE) 1415 to.to_flags |= TOF_SIGNATURE; 1416 #endif 1417 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1418 1419 /* Adjust headers by option size. */ 1420 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1421 m->m_len += optlen; 1422 m->m_pkthdr.len += optlen; 1423 1424 #ifdef TCP_SIGNATURE 1425 if (sc->sc_flags & SCF_SIGNATURE) 1426 tcp_signature_compute(m, 0, 0, optlen, 1427 to.to_signature, IPSEC_DIR_OUTBOUND); 1428 #endif 1429 #ifdef INET6 1430 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1431 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1432 else 1433 #endif 1434 ip->ip_len += optlen; 1435 } else 1436 optlen = 0; 1437 1438 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1439 #ifdef INET6 1440 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1441 th->th_sum = 0; 1442 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1443 tlen + optlen - hlen); 1444 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1445 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1446 } else 1447 #endif 1448 { 1449 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1450 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1451 m->m_pkthdr.csum_flags = CSUM_TCP; 1452 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1453 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1454 } 1455 return (error); 1456 } 1457 1458 void 1459 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1460 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1461 { 1462 1463 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1464 } 1465 1466 void 1467 tcp_offload_syncache_add(struct in_conninfo *inc, struct tcpopt *to, 1468 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1469 struct toe_usrreqs *tu, void *toepcb) 1470 { 1471 1472 1473 INP_INFO_WLOCK(&tcbinfo); 1474 INP_WLOCK(inp); 1475 _syncache_add(inc, to, th, inp, lsop, NULL, tu, toepcb); 1476 1477 } 1478 1479 /* 1480 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1481 * receive and to be able to handle SYN floods from bogus source addresses 1482 * (where we will never receive any reply). SYN floods try to exhaust all 1483 * our memory and available slots in the SYN cache table to cause a denial 1484 * of service to legitimate users of the local host. 1485 * 1486 * The idea of SYN cookies is to encode and include all necessary information 1487 * about the connection setup state within the SYN-ACK we send back and thus 1488 * to get along without keeping any local state until the ACK to the SYN-ACK 1489 * arrives (if ever). Everything we need to know should be available from 1490 * the information we encoded in the SYN-ACK. 1491 * 1492 * More information about the theory behind SYN cookies and its first 1493 * discussion and specification can be found at: 1494 * http://cr.yp.to/syncookies.html (overview) 1495 * http://cr.yp.to/syncookies/archive (gory details) 1496 * 1497 * This implementation extends the orginal idea and first implementation 1498 * of FreeBSD by using not only the initial sequence number field to store 1499 * information but also the timestamp field if present. This way we can 1500 * keep track of the entire state we need to know to recreate the session in 1501 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1502 * these days. For those that do not we still have to live with the known 1503 * shortcomings of the ISN only SYN cookies. 1504 * 1505 * Cookie layers: 1506 * 1507 * Initial sequence number we send: 1508 * 31|................................|0 1509 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1510 * D = MD5 Digest (first dword) 1511 * M = MSS index 1512 * R = Rotation of secret 1513 * P = Odd or Even secret 1514 * 1515 * The MD5 Digest is computed with over following parameters: 1516 * a) randomly rotated secret 1517 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1518 * c) the received initial sequence number from remote host 1519 * d) the rotation offset and odd/even bit 1520 * 1521 * Timestamp we send: 1522 * 31|................................|0 1523 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1524 * D = MD5 Digest (third dword) (only as filler) 1525 * S = Requested send window scale 1526 * R = Requested receive window scale 1527 * A = SACK allowed 1528 * 5 = TCP-MD5 enabled (not implemented yet) 1529 * XORed with MD5 Digest (forth dword) 1530 * 1531 * The timestamp isn't cryptographically secure and doesn't need to be. 1532 * The double use of the MD5 digest dwords ties it to a specific remote/ 1533 * local host/port, remote initial sequence number and our local time 1534 * limited secret. A received timestamp is reverted (XORed) and then 1535 * the contained MD5 dword is compared to the computed one to ensure the 1536 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1537 * have been tampered with but this isn't different from supplying bogus 1538 * values in the SYN in the first place. 1539 * 1540 * Some problems with SYN cookies remain however: 1541 * Consider the problem of a recreated (and retransmitted) cookie. If the 1542 * original SYN was accepted, the connection is established. The second 1543 * SYN is inflight, and if it arrives with an ISN that falls within the 1544 * receive window, the connection is killed. 1545 * 1546 * Notes: 1547 * A heuristic to determine when to accept syn cookies is not necessary. 1548 * An ACK flood would cause the syncookie verification to be attempted, 1549 * but a SYN flood causes syncookies to be generated. Both are of equal 1550 * cost, so there's no point in trying to optimize the ACK flood case. 1551 * Also, if you don't process certain ACKs for some reason, then all someone 1552 * would have to do is launch a SYN and ACK flood at the same time, which 1553 * would stop cookie verification and defeat the entire purpose of syncookies. 1554 */ 1555 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1556 1557 static void 1558 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1559 u_int32_t *flowlabel) 1560 { 1561 MD5_CTX ctx; 1562 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1563 u_int32_t data; 1564 u_int32_t *secbits; 1565 u_int off, pmss, mss; 1566 int i; 1567 1568 SCH_LOCK_ASSERT(sch); 1569 1570 /* Which of the two secrets to use. */ 1571 secbits = sch->sch_oddeven ? 1572 sch->sch_secbits_odd : sch->sch_secbits_even; 1573 1574 /* Reseed secret if too old. */ 1575 if (sch->sch_reseed < time_uptime) { 1576 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1577 secbits = sch->sch_oddeven ? 1578 sch->sch_secbits_odd : sch->sch_secbits_even; 1579 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1580 secbits[i] = arc4random(); 1581 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1582 } 1583 1584 /* Secret rotation offset. */ 1585 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1586 1587 /* Maximum segment size calculation. */ 1588 pmss = max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), tcp_minmss); 1589 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1590 if (tcp_sc_msstab[mss] <= pmss) 1591 break; 1592 1593 /* Fold parameters and MD5 digest into the ISN we will send. */ 1594 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1595 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1596 data |= mss << 4; /* mss, 3 bits */ 1597 1598 MD5Init(&ctx); 1599 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1600 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1601 MD5Update(&ctx, secbits, off); 1602 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1603 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1604 MD5Update(&ctx, &data, sizeof(data)); 1605 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1606 1607 data |= (md5_buffer[0] << 7); 1608 sc->sc_iss = data; 1609 1610 #ifdef INET6 1611 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1612 #endif 1613 1614 /* Additional parameters are stored in the timestamp if present. */ 1615 if (sc->sc_flags & SCF_TIMESTAMP) { 1616 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1617 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1618 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1619 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1620 data |= md5_buffer[2] << 10; /* more digest bits */ 1621 data ^= md5_buffer[3]; 1622 sc->sc_ts = data; 1623 sc->sc_tsoff = data - ticks; /* after XOR */ 1624 } 1625 1626 tcpstat.tcps_sc_sendcookie++; 1627 } 1628 1629 static struct syncache * 1630 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1631 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1632 struct socket *so) 1633 { 1634 MD5_CTX ctx; 1635 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1636 u_int32_t data = 0; 1637 u_int32_t *secbits; 1638 tcp_seq ack, seq; 1639 int off, mss, wnd, flags; 1640 1641 SCH_LOCK_ASSERT(sch); 1642 1643 /* 1644 * Pull information out of SYN-ACK/ACK and 1645 * revert sequence number advances. 1646 */ 1647 ack = th->th_ack - 1; 1648 seq = th->th_seq - 1; 1649 off = (ack >> 1) & 0x7; 1650 mss = (ack >> 4) & 0x7; 1651 flags = ack & 0x7f; 1652 1653 /* Which of the two secrets to use. */ 1654 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1655 1656 /* 1657 * The secret wasn't updated for the lifetime of a syncookie, 1658 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1659 */ 1660 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1661 return (NULL); 1662 } 1663 1664 /* Recompute the digest so we can compare it. */ 1665 MD5Init(&ctx); 1666 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1667 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1668 MD5Update(&ctx, secbits, off); 1669 MD5Update(&ctx, inc, sizeof(*inc)); 1670 MD5Update(&ctx, &seq, sizeof(seq)); 1671 MD5Update(&ctx, &flags, sizeof(flags)); 1672 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1673 1674 /* Does the digest part of or ACK'ed ISS match? */ 1675 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1676 return (NULL); 1677 1678 /* Does the digest part of our reflected timestamp match? */ 1679 if (to->to_flags & TOF_TS) { 1680 data = md5_buffer[3] ^ to->to_tsecr; 1681 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1682 return (NULL); 1683 } 1684 1685 /* Fill in the syncache values. */ 1686 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1687 sc->sc_ipopts = NULL; 1688 1689 sc->sc_irs = seq; 1690 sc->sc_iss = ack; 1691 1692 #ifdef INET6 1693 if (inc->inc_flags & INC_ISIPV6) { 1694 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1695 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1696 } else 1697 #endif 1698 { 1699 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1700 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1701 } 1702 1703 /* Additional parameters that were encoded in the timestamp. */ 1704 if (data) { 1705 sc->sc_flags |= SCF_TIMESTAMP; 1706 sc->sc_tsreflect = to->to_tsval; 1707 sc->sc_ts = to->to_tsecr; 1708 sc->sc_tsoff = to->to_tsecr - ticks; 1709 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1710 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1711 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1712 TCP_MAX_WINSHIFT); 1713 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1714 TCP_MAX_WINSHIFT); 1715 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1716 sc->sc_flags |= SCF_WINSCALE; 1717 } else 1718 sc->sc_flags |= SCF_NOOPT; 1719 1720 wnd = sbspace(&so->so_rcv); 1721 wnd = imax(wnd, 0); 1722 wnd = imin(wnd, TCP_MAXWIN); 1723 sc->sc_wnd = wnd; 1724 1725 sc->sc_rxmits = 0; 1726 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1727 1728 tcpstat.tcps_sc_recvcookie++; 1729 return (sc); 1730 } 1731 1732 /* 1733 * Returns the current number of syncache entries. This number 1734 * will probably change before you get around to calling 1735 * syncache_pcblist. 1736 */ 1737 1738 int 1739 syncache_pcbcount(void) 1740 { 1741 struct syncache_head *sch; 1742 int count, i; 1743 1744 for (count = 0, i = 0; i < tcp_syncache.hashsize; i++) { 1745 /* No need to lock for a read. */ 1746 sch = &tcp_syncache.hashbase[i]; 1747 count += sch->sch_length; 1748 } 1749 return count; 1750 } 1751 1752 /* 1753 * Exports the syncache entries to userland so that netstat can display 1754 * them alongside the other sockets. This function is intended to be 1755 * called only from tcp_pcblist. 1756 * 1757 * Due to concurrency on an active system, the number of pcbs exported 1758 * may have no relation to max_pcbs. max_pcbs merely indicates the 1759 * amount of space the caller allocated for this function to use. 1760 */ 1761 int 1762 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1763 { 1764 struct xtcpcb xt; 1765 struct syncache *sc; 1766 struct syncache_head *sch; 1767 int count, error, i; 1768 1769 for (count = 0, error = 0, i = 0; i < tcp_syncache.hashsize; i++) { 1770 sch = &tcp_syncache.hashbase[i]; 1771 SCH_LOCK(sch); 1772 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1773 if (count >= max_pcbs) { 1774 SCH_UNLOCK(sch); 1775 goto exit; 1776 } 1777 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1778 continue; 1779 bzero(&xt, sizeof(xt)); 1780 xt.xt_len = sizeof(xt); 1781 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1782 xt.xt_inp.inp_vflag = INP_IPV6; 1783 else 1784 xt.xt_inp.inp_vflag = INP_IPV4; 1785 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1786 xt.xt_tp.t_inpcb = &xt.xt_inp; 1787 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1788 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1789 xt.xt_socket.xso_len = sizeof (struct xsocket); 1790 xt.xt_socket.so_type = SOCK_STREAM; 1791 xt.xt_socket.so_state = SS_ISCONNECTING; 1792 error = SYSCTL_OUT(req, &xt, sizeof xt); 1793 if (error) { 1794 SCH_UNLOCK(sch); 1795 goto exit; 1796 } 1797 count++; 1798 } 1799 SCH_UNLOCK(sch); 1800 } 1801 exit: 1802 *pcbs_exported = count; 1803 return error; 1804 } 1805
Cache object: 9ec960a8d48fdf272aa06ae97ab6f348
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