1 /*- 2 * Copyright (c) 2001 McAfee, Inc. 3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG 4 * All rights reserved. 5 * 6 * This software was developed for the FreeBSD Project by Jonathan Lemon 7 * and McAfee Research, the Security Research Division of McAfee, Inc. under 8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 9 * DARPA CHATS research program. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include "opt_inet.h" 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_pcbgroup.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/kernel.h> 44 #include <sys/sysctl.h> 45 #include <sys/limits.h> 46 #include <sys/lock.h> 47 #include <sys/mutex.h> 48 #include <sys/malloc.h> 49 #include <sys/mbuf.h> 50 #include <sys/md5.h> 51 #include <sys/proc.h> /* for proc0 declaration */ 52 #include <sys/random.h> 53 #include <sys/socket.h> 54 #include <sys/socketvar.h> 55 #include <sys/syslog.h> 56 #include <sys/ucred.h> 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 #include <net/vnet.h> 63 64 #include <netinet/in.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/ip.h> 67 #include <netinet/in_var.h> 68 #include <netinet/in_pcb.h> 69 #include <netinet/ip_var.h> 70 #include <netinet/ip_options.h> 71 #ifdef INET6 72 #include <netinet/ip6.h> 73 #include <netinet/icmp6.h> 74 #include <netinet6/nd6.h> 75 #include <netinet6/ip6_var.h> 76 #include <netinet6/in6_pcb.h> 77 #endif 78 #include <netinet/tcp.h> 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #include <netinet/tcp_syncache.h> 84 #include <netinet/tcp_offload.h> 85 #ifdef INET6 86 #include <netinet6/tcp6_var.h> 87 #endif 88 89 #ifdef IPSEC 90 #include <netipsec/ipsec.h> 91 #ifdef INET6 92 #include <netipsec/ipsec6.h> 93 #endif 94 #include <netipsec/key.h> 95 #endif /*IPSEC*/ 96 97 #include <machine/in_cksum.h> 98 99 #include <security/mac/mac_framework.h> 100 101 static VNET_DEFINE(int, tcp_syncookies) = 1; 102 #define V_tcp_syncookies VNET(tcp_syncookies) 103 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 104 &VNET_NAME(tcp_syncookies), 0, 105 "Use TCP SYN cookies if the syncache overflows"); 106 107 static VNET_DEFINE(int, tcp_syncookiesonly) = 0; 108 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly) 109 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW, 110 &VNET_NAME(tcp_syncookiesonly), 0, 111 "Use only TCP SYN cookies"); 112 113 #ifdef TCP_OFFLOAD_DISABLE 114 #define TOEPCB_ISSET(sc) (0) 115 #else 116 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL) 117 #endif 118 119 static void syncache_drop(struct syncache *, struct syncache_head *); 120 static void syncache_free(struct syncache *); 121 static void syncache_insert(struct syncache *, struct syncache_head *); 122 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 123 static int syncache_respond(struct syncache *); 124 static struct socket *syncache_socket(struct syncache *, struct socket *, 125 struct mbuf *m); 126 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 127 int docallout); 128 static void syncache_timer(void *); 129 static void syncookie_generate(struct syncache_head *, struct syncache *, 130 u_int32_t *); 131 static struct syncache 132 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 133 struct syncache *, struct tcpopt *, struct tcphdr *, 134 struct socket *); 135 136 /* 137 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 138 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 139 * the odds are that the user has given up attempting to connect by then. 140 */ 141 #define SYNCACHE_MAXREXMTS 3 142 143 /* Arbitrary values */ 144 #define TCP_SYNCACHE_HASHSIZE 512 145 #define TCP_SYNCACHE_BUCKETLIMIT 30 146 147 static VNET_DEFINE(struct tcp_syncache, tcp_syncache); 148 #define V_tcp_syncache VNET(tcp_syncache) 149 150 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, 151 "TCP SYN cache"); 152 153 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 154 &VNET_NAME(tcp_syncache.bucket_limit), 0, 155 "Per-bucket hash limit for syncache"); 156 157 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 158 &VNET_NAME(tcp_syncache.cache_limit), 0, 159 "Overall entry limit for syncache"); 160 161 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 162 &VNET_NAME(tcp_syncache.cache_count), 0, 163 "Current number of entries in syncache"); 164 165 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 166 &VNET_NAME(tcp_syncache.hashsize), 0, 167 "Size of TCP syncache hashtable"); 168 169 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 170 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 171 "Limit on SYN/ACK retransmissions"); 172 173 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 174 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 175 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 176 "Send reset on socket allocation failure"); 177 178 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 179 180 #define SYNCACHE_HASH(inc, mask) \ 181 ((V_tcp_syncache.hash_secret ^ \ 182 (inc)->inc_faddr.s_addr ^ \ 183 ((inc)->inc_faddr.s_addr >> 16) ^ \ 184 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 185 186 #define SYNCACHE_HASH6(inc, mask) \ 187 ((V_tcp_syncache.hash_secret ^ \ 188 (inc)->inc6_faddr.s6_addr32[0] ^ \ 189 (inc)->inc6_faddr.s6_addr32[3] ^ \ 190 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 191 192 #define ENDPTS_EQ(a, b) ( \ 193 (a)->ie_fport == (b)->ie_fport && \ 194 (a)->ie_lport == (b)->ie_lport && \ 195 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 196 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 197 ) 198 199 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 200 201 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 202 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 203 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 204 205 /* 206 * Requires the syncache entry to be already removed from the bucket list. 207 */ 208 static void 209 syncache_free(struct syncache *sc) 210 { 211 212 if (sc->sc_ipopts) 213 (void) m_free(sc->sc_ipopts); 214 if (sc->sc_cred) 215 crfree(sc->sc_cred); 216 #ifdef MAC 217 mac_syncache_destroy(&sc->sc_label); 218 #endif 219 220 uma_zfree(V_tcp_syncache.zone, sc); 221 } 222 223 void 224 syncache_init(void) 225 { 226 int i; 227 228 V_tcp_syncache.cache_count = 0; 229 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 230 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 231 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 232 V_tcp_syncache.hash_secret = arc4random(); 233 234 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 235 &V_tcp_syncache.hashsize); 236 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 237 &V_tcp_syncache.bucket_limit); 238 if (!powerof2(V_tcp_syncache.hashsize) || 239 V_tcp_syncache.hashsize == 0) { 240 printf("WARNING: syncache hash size is not a power of 2.\n"); 241 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 242 } 243 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 244 245 /* Set limits. */ 246 V_tcp_syncache.cache_limit = 247 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 248 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 249 &V_tcp_syncache.cache_limit); 250 251 /* Allocate the hash table. */ 252 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 253 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 254 255 /* Initialize the hash buckets. */ 256 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 257 #ifdef VIMAGE 258 V_tcp_syncache.hashbase[i].sch_vnet = curvnet; 259 #endif 260 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 261 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 262 NULL, MTX_DEF); 263 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 264 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 265 V_tcp_syncache.hashbase[i].sch_length = 0; 266 } 267 268 /* Create the syncache entry zone. */ 269 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 270 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 271 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit); 272 } 273 274 #ifdef VIMAGE 275 void 276 syncache_destroy(void) 277 { 278 struct syncache_head *sch; 279 struct syncache *sc, *nsc; 280 int i; 281 282 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 283 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 284 285 sch = &V_tcp_syncache.hashbase[i]; 286 callout_drain(&sch->sch_timer); 287 288 SCH_LOCK(sch); 289 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 290 syncache_drop(sc, sch); 291 SCH_UNLOCK(sch); 292 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 293 ("%s: sch->sch_bucket not empty", __func__)); 294 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 295 __func__, sch->sch_length)); 296 mtx_destroy(&sch->sch_mtx); 297 } 298 299 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0", 300 __func__, V_tcp_syncache.cache_count)); 301 302 /* Free the allocated global resources. */ 303 uma_zdestroy(V_tcp_syncache.zone); 304 free(V_tcp_syncache.hashbase, M_SYNCACHE); 305 } 306 #endif 307 308 /* 309 * Inserts a syncache entry into the specified bucket row. 310 * Locks and unlocks the syncache_head autonomously. 311 */ 312 static void 313 syncache_insert(struct syncache *sc, struct syncache_head *sch) 314 { 315 struct syncache *sc2; 316 317 SCH_LOCK(sch); 318 319 /* 320 * Make sure that we don't overflow the per-bucket limit. 321 * If the bucket is full, toss the oldest element. 322 */ 323 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 324 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 325 ("sch->sch_length incorrect")); 326 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 327 syncache_drop(sc2, sch); 328 TCPSTAT_INC(tcps_sc_bucketoverflow); 329 } 330 331 /* Put it into the bucket. */ 332 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 333 sch->sch_length++; 334 335 /* Reinitialize the bucket row's timer. */ 336 if (sch->sch_length == 1) 337 sch->sch_nextc = ticks + INT_MAX; 338 syncache_timeout(sc, sch, 1); 339 340 SCH_UNLOCK(sch); 341 342 V_tcp_syncache.cache_count++; 343 TCPSTAT_INC(tcps_sc_added); 344 } 345 346 /* 347 * Remove and free entry from syncache bucket row. 348 * Expects locked syncache head. 349 */ 350 static void 351 syncache_drop(struct syncache *sc, struct syncache_head *sch) 352 { 353 354 SCH_LOCK_ASSERT(sch); 355 356 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 357 sch->sch_length--; 358 359 #ifndef TCP_OFFLOAD_DISABLE 360 if (sc->sc_tu) 361 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 362 #endif 363 syncache_free(sc); 364 V_tcp_syncache.cache_count--; 365 } 366 367 /* 368 * Engage/reengage time on bucket row. 369 */ 370 static void 371 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 372 { 373 sc->sc_rxttime = ticks + 374 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 375 sc->sc_rxmits++; 376 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 377 sch->sch_nextc = sc->sc_rxttime; 378 if (docallout) 379 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 380 syncache_timer, (void *)sch); 381 } 382 } 383 384 /* 385 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 386 * If we have retransmitted an entry the maximum number of times, expire it. 387 * One separate timer for each bucket row. 388 */ 389 static void 390 syncache_timer(void *xsch) 391 { 392 struct syncache_head *sch = (struct syncache_head *)xsch; 393 struct syncache *sc, *nsc; 394 int tick = ticks; 395 char *s; 396 397 CURVNET_SET(sch->sch_vnet); 398 399 /* NB: syncache_head has already been locked by the callout. */ 400 SCH_LOCK_ASSERT(sch); 401 402 /* 403 * In the following cycle we may remove some entries and/or 404 * advance some timeouts, so re-initialize the bucket timer. 405 */ 406 sch->sch_nextc = tick + INT_MAX; 407 408 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 409 /* 410 * We do not check if the listen socket still exists 411 * and accept the case where the listen socket may be 412 * gone by the time we resend the SYN/ACK. We do 413 * not expect this to happens often. If it does, 414 * then the RST will be sent by the time the remote 415 * host does the SYN/ACK->ACK. 416 */ 417 if (TSTMP_GT(sc->sc_rxttime, tick)) { 418 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 419 sch->sch_nextc = sc->sc_rxttime; 420 continue; 421 } 422 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 423 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 424 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 425 "giving up and removing syncache entry\n", 426 s, __func__); 427 free(s, M_TCPLOG); 428 } 429 syncache_drop(sc, sch); 430 TCPSTAT_INC(tcps_sc_stale); 431 continue; 432 } 433 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 434 log(LOG_DEBUG, "%s; %s: Response timeout, " 435 "retransmitting (%u) SYN|ACK\n", 436 s, __func__, sc->sc_rxmits); 437 free(s, M_TCPLOG); 438 } 439 440 (void) syncache_respond(sc); 441 TCPSTAT_INC(tcps_sc_retransmitted); 442 syncache_timeout(sc, sch, 0); 443 } 444 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 445 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 446 syncache_timer, (void *)(sch)); 447 CURVNET_RESTORE(); 448 } 449 450 /* 451 * Find an entry in the syncache. 452 * Returns always with locked syncache_head plus a matching entry or NULL. 453 */ 454 struct syncache * 455 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 456 { 457 struct syncache *sc; 458 struct syncache_head *sch; 459 460 #ifdef INET6 461 if (inc->inc_flags & INC_ISIPV6) { 462 sch = &V_tcp_syncache.hashbase[ 463 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 464 *schp = sch; 465 466 SCH_LOCK(sch); 467 468 /* Circle through bucket row to find matching entry. */ 469 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 470 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 471 return (sc); 472 } 473 } else 474 #endif 475 { 476 sch = &V_tcp_syncache.hashbase[ 477 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 478 *schp = sch; 479 480 SCH_LOCK(sch); 481 482 /* Circle through bucket row to find matching entry. */ 483 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 484 #ifdef INET6 485 if (sc->sc_inc.inc_flags & INC_ISIPV6) 486 continue; 487 #endif 488 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 489 return (sc); 490 } 491 } 492 SCH_LOCK_ASSERT(*schp); 493 return (NULL); /* always returns with locked sch */ 494 } 495 496 /* 497 * This function is called when we get a RST for a 498 * non-existent connection, so that we can see if the 499 * connection is in the syn cache. If it is, zap it. 500 */ 501 void 502 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 503 { 504 struct syncache *sc; 505 struct syncache_head *sch; 506 char *s = NULL; 507 508 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 509 SCH_LOCK_ASSERT(sch); 510 511 /* 512 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 513 * See RFC 793 page 65, section SEGMENT ARRIVES. 514 */ 515 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 516 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 517 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 518 "FIN flag set, segment ignored\n", s, __func__); 519 TCPSTAT_INC(tcps_badrst); 520 goto done; 521 } 522 523 /* 524 * No corresponding connection was found in syncache. 525 * If syncookies are enabled and possibly exclusively 526 * used, or we are under memory pressure, a valid RST 527 * may not find a syncache entry. In that case we're 528 * done and no SYN|ACK retransmissions will happen. 529 * Otherwise the RST was misdirected or spoofed. 530 */ 531 if (sc == NULL) { 532 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 533 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 534 "syncache entry (possibly syncookie only), " 535 "segment ignored\n", s, __func__); 536 TCPSTAT_INC(tcps_badrst); 537 goto done; 538 } 539 540 /* 541 * If the RST bit is set, check the sequence number to see 542 * if this is a valid reset segment. 543 * RFC 793 page 37: 544 * In all states except SYN-SENT, all reset (RST) segments 545 * are validated by checking their SEQ-fields. A reset is 546 * valid if its sequence number is in the window. 547 * 548 * The sequence number in the reset segment is normally an 549 * echo of our outgoing acknowlegement numbers, but some hosts 550 * send a reset with the sequence number at the rightmost edge 551 * of our receive window, and we have to handle this case. 552 */ 553 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 554 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 555 syncache_drop(sc, sch); 556 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 557 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 558 "connection attempt aborted by remote endpoint\n", 559 s, __func__); 560 TCPSTAT_INC(tcps_sc_reset); 561 } else { 562 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 563 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 564 "IRS %u (+WND %u), segment ignored\n", 565 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 566 TCPSTAT_INC(tcps_badrst); 567 } 568 569 done: 570 if (s != NULL) 571 free(s, M_TCPLOG); 572 SCH_UNLOCK(sch); 573 } 574 575 void 576 syncache_badack(struct in_conninfo *inc) 577 { 578 struct syncache *sc; 579 struct syncache_head *sch; 580 581 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 582 SCH_LOCK_ASSERT(sch); 583 if (sc != NULL) { 584 syncache_drop(sc, sch); 585 TCPSTAT_INC(tcps_sc_badack); 586 } 587 SCH_UNLOCK(sch); 588 } 589 590 void 591 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 592 { 593 struct syncache *sc; 594 struct syncache_head *sch; 595 596 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 597 SCH_LOCK_ASSERT(sch); 598 if (sc == NULL) 599 goto done; 600 601 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 602 if (ntohl(th->th_seq) != sc->sc_iss) 603 goto done; 604 605 /* 606 * If we've rertransmitted 3 times and this is our second error, 607 * we remove the entry. Otherwise, we allow it to continue on. 608 * This prevents us from incorrectly nuking an entry during a 609 * spurious network outage. 610 * 611 * See tcp_notify(). 612 */ 613 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 614 sc->sc_flags |= SCF_UNREACH; 615 goto done; 616 } 617 syncache_drop(sc, sch); 618 TCPSTAT_INC(tcps_sc_unreach); 619 done: 620 SCH_UNLOCK(sch); 621 } 622 623 /* 624 * Build a new TCP socket structure from a syncache entry. 625 */ 626 static struct socket * 627 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 628 { 629 struct inpcb *inp = NULL; 630 struct socket *so; 631 struct tcpcb *tp; 632 int error; 633 char *s; 634 635 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 636 637 /* 638 * Ok, create the full blown connection, and set things up 639 * as they would have been set up if we had created the 640 * connection when the SYN arrived. If we can't create 641 * the connection, abort it. 642 */ 643 so = sonewconn(lso, SS_ISCONNECTED); 644 if (so == NULL) { 645 /* 646 * Drop the connection; we will either send a RST or 647 * have the peer retransmit its SYN again after its 648 * RTO and try again. 649 */ 650 TCPSTAT_INC(tcps_listendrop); 651 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 652 log(LOG_DEBUG, "%s; %s: Socket create failed " 653 "due to limits or memory shortage\n", 654 s, __func__); 655 free(s, M_TCPLOG); 656 } 657 goto abort2; 658 } 659 #ifdef MAC 660 mac_socketpeer_set_from_mbuf(m, so); 661 #endif 662 663 inp = sotoinpcb(so); 664 inp->inp_inc.inc_fibnum = so->so_fibnum; 665 INP_WLOCK(inp); 666 INP_HASH_WLOCK(&V_tcbinfo); 667 668 /* Insert new socket into PCB hash list. */ 669 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 670 #ifdef INET6 671 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 672 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 673 } else { 674 inp->inp_vflag &= ~INP_IPV6; 675 inp->inp_vflag |= INP_IPV4; 676 #endif 677 inp->inp_laddr = sc->sc_inc.inc_laddr; 678 #ifdef INET6 679 } 680 #endif 681 682 /* 683 * Install in the reservation hash table for now, but don't yet 684 * install a connection group since the full 4-tuple isn't yet 685 * configured. 686 */ 687 inp->inp_lport = sc->sc_inc.inc_lport; 688 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 689 /* 690 * Undo the assignments above if we failed to 691 * put the PCB on the hash lists. 692 */ 693 #ifdef INET6 694 if (sc->sc_inc.inc_flags & INC_ISIPV6) 695 inp->in6p_laddr = in6addr_any; 696 else 697 #endif 698 inp->inp_laddr.s_addr = INADDR_ANY; 699 inp->inp_lport = 0; 700 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 701 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 702 "with error %i\n", 703 s, __func__, error); 704 free(s, M_TCPLOG); 705 } 706 INP_HASH_WUNLOCK(&V_tcbinfo); 707 goto abort; 708 } 709 #ifdef IPSEC 710 /* Copy old policy into new socket's. */ 711 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 712 printf("syncache_socket: could not copy policy\n"); 713 #endif 714 #ifdef INET6 715 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 716 struct inpcb *oinp = sotoinpcb(lso); 717 struct in6_addr laddr6; 718 struct sockaddr_in6 sin6; 719 /* 720 * Inherit socket options from the listening socket. 721 * Note that in6p_inputopts are not (and should not be) 722 * copied, since it stores previously received options and is 723 * used to detect if each new option is different than the 724 * previous one and hence should be passed to a user. 725 * If we copied in6p_inputopts, a user would not be able to 726 * receive options just after calling the accept system call. 727 */ 728 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 729 if (oinp->in6p_outputopts) 730 inp->in6p_outputopts = 731 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 732 733 sin6.sin6_family = AF_INET6; 734 sin6.sin6_len = sizeof(sin6); 735 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 736 sin6.sin6_port = sc->sc_inc.inc_fport; 737 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 738 laddr6 = inp->in6p_laddr; 739 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 740 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 741 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 742 thread0.td_ucred, m)) != 0) { 743 inp->in6p_laddr = laddr6; 744 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 745 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 746 "with error %i\n", 747 s, __func__, error); 748 free(s, M_TCPLOG); 749 } 750 INP_HASH_WUNLOCK(&V_tcbinfo); 751 goto abort; 752 } 753 /* Override flowlabel from in6_pcbconnect. */ 754 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 755 inp->inp_flow |= sc->sc_flowlabel; 756 } 757 #endif /* INET6 */ 758 #if defined(INET) && defined(INET6) 759 else 760 #endif 761 #ifdef INET 762 { 763 struct in_addr laddr; 764 struct sockaddr_in sin; 765 766 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 767 768 if (inp->inp_options == NULL) { 769 inp->inp_options = sc->sc_ipopts; 770 sc->sc_ipopts = NULL; 771 } 772 773 sin.sin_family = AF_INET; 774 sin.sin_len = sizeof(sin); 775 sin.sin_addr = sc->sc_inc.inc_faddr; 776 sin.sin_port = sc->sc_inc.inc_fport; 777 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 778 laddr = inp->inp_laddr; 779 if (inp->inp_laddr.s_addr == INADDR_ANY) 780 inp->inp_laddr = sc->sc_inc.inc_laddr; 781 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 782 thread0.td_ucred, m)) != 0) { 783 inp->inp_laddr = laddr; 784 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 785 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 786 "with error %i\n", 787 s, __func__, error); 788 free(s, M_TCPLOG); 789 } 790 INP_HASH_WUNLOCK(&V_tcbinfo); 791 goto abort; 792 } 793 } 794 #endif /* INET */ 795 INP_HASH_WUNLOCK(&V_tcbinfo); 796 tp = intotcpcb(inp); 797 tp->t_state = TCPS_SYN_RECEIVED; 798 tp->iss = sc->sc_iss; 799 tp->irs = sc->sc_irs; 800 tcp_rcvseqinit(tp); 801 tcp_sendseqinit(tp); 802 tp->snd_wl1 = sc->sc_irs; 803 tp->snd_max = tp->iss + 1; 804 tp->snd_nxt = tp->iss + 1; 805 tp->rcv_up = sc->sc_irs + 1; 806 tp->rcv_wnd = sc->sc_wnd; 807 tp->rcv_adv += tp->rcv_wnd; 808 tp->last_ack_sent = tp->rcv_nxt; 809 810 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 811 if (sc->sc_flags & SCF_NOOPT) 812 tp->t_flags |= TF_NOOPT; 813 else { 814 if (sc->sc_flags & SCF_WINSCALE) { 815 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 816 tp->snd_scale = sc->sc_requested_s_scale; 817 tp->request_r_scale = sc->sc_requested_r_scale; 818 } 819 if (sc->sc_flags & SCF_TIMESTAMP) { 820 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 821 tp->ts_recent = sc->sc_tsreflect; 822 tp->ts_recent_age = tcp_ts_getticks(); 823 tp->ts_offset = sc->sc_tsoff; 824 } 825 #ifdef TCP_SIGNATURE 826 if (sc->sc_flags & SCF_SIGNATURE) 827 tp->t_flags |= TF_SIGNATURE; 828 #endif 829 if (sc->sc_flags & SCF_SACK) 830 tp->t_flags |= TF_SACK_PERMIT; 831 } 832 833 if (sc->sc_flags & SCF_ECN) 834 tp->t_flags |= TF_ECN_PERMIT; 835 836 /* 837 * Set up MSS and get cached values from tcp_hostcache. 838 * This might overwrite some of the defaults we just set. 839 */ 840 tcp_mss(tp, sc->sc_peer_mss); 841 842 /* 843 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 844 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 845 */ 846 if (sc->sc_rxmits > 1) 847 tp->snd_cwnd = tp->t_maxseg; 848 849 /* 850 * Copy and activate timers. 851 */ 852 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 853 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 854 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 855 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 856 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 857 858 INP_WUNLOCK(inp); 859 860 TCPSTAT_INC(tcps_accepts); 861 return (so); 862 863 abort: 864 INP_WUNLOCK(inp); 865 abort2: 866 if (so != NULL) 867 soabort(so); 868 return (NULL); 869 } 870 871 /* 872 * This function gets called when we receive an ACK for a 873 * socket in the LISTEN state. We look up the connection 874 * in the syncache, and if its there, we pull it out of 875 * the cache and turn it into a full-blown connection in 876 * the SYN-RECEIVED state. 877 */ 878 int 879 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 880 struct socket **lsop, struct mbuf *m) 881 { 882 struct syncache *sc; 883 struct syncache_head *sch; 884 struct syncache scs; 885 char *s; 886 887 /* 888 * Global TCP locks are held because we manipulate the PCB lists 889 * and create a new socket. 890 */ 891 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 892 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 893 ("%s: can handle only ACK", __func__)); 894 895 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 896 SCH_LOCK_ASSERT(sch); 897 if (sc == NULL) { 898 /* 899 * There is no syncache entry, so see if this ACK is 900 * a returning syncookie. To do this, first: 901 * A. See if this socket has had a syncache entry dropped in 902 * the past. We don't want to accept a bogus syncookie 903 * if we've never received a SYN. 904 * B. check that the syncookie is valid. If it is, then 905 * cobble up a fake syncache entry, and return. 906 */ 907 if (!V_tcp_syncookies) { 908 SCH_UNLOCK(sch); 909 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 910 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 911 "segment rejected (syncookies disabled)\n", 912 s, __func__); 913 goto failed; 914 } 915 bzero(&scs, sizeof(scs)); 916 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 917 SCH_UNLOCK(sch); 918 if (sc == NULL) { 919 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 920 log(LOG_DEBUG, "%s; %s: Segment failed " 921 "SYNCOOKIE authentication, segment rejected " 922 "(probably spoofed)\n", s, __func__); 923 goto failed; 924 } 925 } else { 926 /* Pull out the entry to unlock the bucket row. */ 927 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 928 sch->sch_length--; 929 V_tcp_syncache.cache_count--; 930 SCH_UNLOCK(sch); 931 } 932 933 /* 934 * Segment validation: 935 * ACK must match our initial sequence number + 1 (the SYN|ACK). 936 */ 937 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 938 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 939 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 940 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 941 goto failed; 942 } 943 944 /* 945 * The SEQ must fall in the window starting at the received 946 * initial receive sequence number + 1 (the SYN). 947 */ 948 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 949 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 950 !TOEPCB_ISSET(sc)) { 951 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 952 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 953 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 954 goto failed; 955 } 956 957 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 958 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 959 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 960 "segment rejected\n", s, __func__); 961 goto failed; 962 } 963 /* 964 * If timestamps were negotiated the reflected timestamp 965 * must be equal to what we actually sent in the SYN|ACK. 966 */ 967 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 968 !TOEPCB_ISSET(sc)) { 969 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 970 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 971 "segment rejected\n", 972 s, __func__, to->to_tsecr, sc->sc_ts); 973 goto failed; 974 } 975 976 *lsop = syncache_socket(sc, *lsop, m); 977 978 if (*lsop == NULL) 979 TCPSTAT_INC(tcps_sc_aborted); 980 else 981 TCPSTAT_INC(tcps_sc_completed); 982 983 /* how do we find the inp for the new socket? */ 984 if (sc != &scs) 985 syncache_free(sc); 986 return (1); 987 failed: 988 if (sc != NULL && sc != &scs) 989 syncache_free(sc); 990 if (s != NULL) 991 free(s, M_TCPLOG); 992 *lsop = NULL; 993 return (0); 994 } 995 996 int 997 tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo, 998 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 999 { 1000 struct tcpopt to; 1001 int rc; 1002 1003 bzero(&to, sizeof(struct tcpopt)); 1004 to.to_mss = toeo->to_mss; 1005 to.to_wscale = toeo->to_wscale; 1006 to.to_flags = toeo->to_flags; 1007 1008 INP_INFO_WLOCK(&V_tcbinfo); 1009 rc = syncache_expand(inc, &to, th, lsop, m); 1010 INP_INFO_WUNLOCK(&V_tcbinfo); 1011 1012 return (rc); 1013 } 1014 1015 /* 1016 * Given a LISTEN socket and an inbound SYN request, add 1017 * this to the syn cache, and send back a segment: 1018 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1019 * to the source. 1020 * 1021 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1022 * Doing so would require that we hold onto the data and deliver it 1023 * to the application. However, if we are the target of a SYN-flood 1024 * DoS attack, an attacker could send data which would eventually 1025 * consume all available buffer space if it were ACKed. By not ACKing 1026 * the data, we avoid this DoS scenario. 1027 */ 1028 static void 1029 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1030 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 1031 struct toe_usrreqs *tu, void *toepcb) 1032 { 1033 struct tcpcb *tp; 1034 struct socket *so; 1035 struct syncache *sc = NULL; 1036 struct syncache_head *sch; 1037 struct mbuf *ipopts = NULL; 1038 u_int32_t flowtmp; 1039 u_int ltflags; 1040 int win, sb_hiwat, ip_ttl, ip_tos; 1041 char *s; 1042 #ifdef INET6 1043 int autoflowlabel = 0; 1044 #endif 1045 #ifdef MAC 1046 struct label *maclabel; 1047 #endif 1048 struct syncache scs; 1049 struct ucred *cred; 1050 1051 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1052 INP_WLOCK_ASSERT(inp); /* listen socket */ 1053 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1054 ("%s: unexpected tcp flags", __func__)); 1055 1056 /* 1057 * Combine all so/tp operations very early to drop the INP lock as 1058 * soon as possible. 1059 */ 1060 so = *lsop; 1061 tp = sototcpcb(so); 1062 cred = crhold(so->so_cred); 1063 1064 #ifdef INET6 1065 if ((inc->inc_flags & INC_ISIPV6) && 1066 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1067 autoflowlabel = 1; 1068 #endif 1069 ip_ttl = inp->inp_ip_ttl; 1070 ip_tos = inp->inp_ip_tos; 1071 win = sbspace(&so->so_rcv); 1072 sb_hiwat = so->so_rcv.sb_hiwat; 1073 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1074 1075 /* By the time we drop the lock these should no longer be used. */ 1076 so = NULL; 1077 tp = NULL; 1078 1079 #ifdef MAC 1080 if (mac_syncache_init(&maclabel) != 0) { 1081 INP_WUNLOCK(inp); 1082 INP_INFO_WUNLOCK(&V_tcbinfo); 1083 goto done; 1084 } else 1085 mac_syncache_create(maclabel, inp); 1086 #endif 1087 INP_WUNLOCK(inp); 1088 INP_INFO_WUNLOCK(&V_tcbinfo); 1089 1090 /* 1091 * Remember the IP options, if any. 1092 */ 1093 #ifdef INET6 1094 if (!(inc->inc_flags & INC_ISIPV6)) 1095 #endif 1096 #ifdef INET 1097 ipopts = (m) ? ip_srcroute(m) : NULL; 1098 #else 1099 ipopts = NULL; 1100 #endif 1101 1102 /* 1103 * See if we already have an entry for this connection. 1104 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1105 * 1106 * XXX: should the syncache be re-initialized with the contents 1107 * of the new SYN here (which may have different options?) 1108 * 1109 * XXX: We do not check the sequence number to see if this is a 1110 * real retransmit or a new connection attempt. The question is 1111 * how to handle such a case; either ignore it as spoofed, or 1112 * drop the current entry and create a new one? 1113 */ 1114 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1115 SCH_LOCK_ASSERT(sch); 1116 if (sc != NULL) { 1117 #ifndef TCP_OFFLOAD_DISABLE 1118 if (sc->sc_tu) 1119 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1120 sc->sc_toepcb); 1121 #endif 1122 TCPSTAT_INC(tcps_sc_dupsyn); 1123 if (ipopts) { 1124 /* 1125 * If we were remembering a previous source route, 1126 * forget it and use the new one we've been given. 1127 */ 1128 if (sc->sc_ipopts) 1129 (void) m_free(sc->sc_ipopts); 1130 sc->sc_ipopts = ipopts; 1131 } 1132 /* 1133 * Update timestamp if present. 1134 */ 1135 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1136 sc->sc_tsreflect = to->to_tsval; 1137 else 1138 sc->sc_flags &= ~SCF_TIMESTAMP; 1139 #ifdef MAC 1140 /* 1141 * Since we have already unconditionally allocated label 1142 * storage, free it up. The syncache entry will already 1143 * have an initialized label we can use. 1144 */ 1145 mac_syncache_destroy(&maclabel); 1146 #endif 1147 /* Retransmit SYN|ACK and reset retransmit count. */ 1148 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1149 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1150 "resetting timer and retransmitting SYN|ACK\n", 1151 s, __func__); 1152 free(s, M_TCPLOG); 1153 } 1154 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1155 sc->sc_rxmits = 0; 1156 syncache_timeout(sc, sch, 1); 1157 TCPSTAT_INC(tcps_sndacks); 1158 TCPSTAT_INC(tcps_sndtotal); 1159 } 1160 SCH_UNLOCK(sch); 1161 goto done; 1162 } 1163 1164 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1165 if (sc == NULL) { 1166 /* 1167 * The zone allocator couldn't provide more entries. 1168 * Treat this as if the cache was full; drop the oldest 1169 * entry and insert the new one. 1170 */ 1171 TCPSTAT_INC(tcps_sc_zonefail); 1172 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1173 syncache_drop(sc, sch); 1174 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1175 if (sc == NULL) { 1176 if (V_tcp_syncookies) { 1177 bzero(&scs, sizeof(scs)); 1178 sc = &scs; 1179 } else { 1180 SCH_UNLOCK(sch); 1181 if (ipopts) 1182 (void) m_free(ipopts); 1183 goto done; 1184 } 1185 } 1186 } 1187 1188 /* 1189 * Fill in the syncache values. 1190 */ 1191 #ifdef MAC 1192 sc->sc_label = maclabel; 1193 #endif 1194 sc->sc_cred = cred; 1195 cred = NULL; 1196 sc->sc_ipopts = ipopts; 1197 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1198 #ifdef INET6 1199 if (!(inc->inc_flags & INC_ISIPV6)) 1200 #endif 1201 { 1202 sc->sc_ip_tos = ip_tos; 1203 sc->sc_ip_ttl = ip_ttl; 1204 } 1205 #ifndef TCP_OFFLOAD_DISABLE 1206 sc->sc_tu = tu; 1207 sc->sc_toepcb = toepcb; 1208 #endif 1209 sc->sc_irs = th->th_seq; 1210 sc->sc_iss = arc4random(); 1211 sc->sc_flags = 0; 1212 sc->sc_flowlabel = 0; 1213 1214 /* 1215 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1216 * win was derived from socket earlier in the function. 1217 */ 1218 win = imax(win, 0); 1219 win = imin(win, TCP_MAXWIN); 1220 sc->sc_wnd = win; 1221 1222 if (V_tcp_do_rfc1323) { 1223 /* 1224 * A timestamp received in a SYN makes 1225 * it ok to send timestamp requests and replies. 1226 */ 1227 if (to->to_flags & TOF_TS) { 1228 sc->sc_tsreflect = to->to_tsval; 1229 sc->sc_ts = tcp_ts_getticks(); 1230 sc->sc_flags |= SCF_TIMESTAMP; 1231 } 1232 if (to->to_flags & TOF_SCALE) { 1233 int wscale = 0; 1234 1235 /* 1236 * Pick the smallest possible scaling factor that 1237 * will still allow us to scale up to sb_max, aka 1238 * kern.ipc.maxsockbuf. 1239 * 1240 * We do this because there are broken firewalls that 1241 * will corrupt the window scale option, leading to 1242 * the other endpoint believing that our advertised 1243 * window is unscaled. At scale factors larger than 1244 * 5 the unscaled window will drop below 1500 bytes, 1245 * leading to serious problems when traversing these 1246 * broken firewalls. 1247 * 1248 * With the default maxsockbuf of 256K, a scale factor 1249 * of 3 will be chosen by this algorithm. Those who 1250 * choose a larger maxsockbuf should watch out 1251 * for the compatiblity problems mentioned above. 1252 * 1253 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1254 * or <SYN,ACK>) segment itself is never scaled. 1255 */ 1256 while (wscale < TCP_MAX_WINSHIFT && 1257 (TCP_MAXWIN << wscale) < sb_max) 1258 wscale++; 1259 sc->sc_requested_r_scale = wscale; 1260 sc->sc_requested_s_scale = to->to_wscale; 1261 sc->sc_flags |= SCF_WINSCALE; 1262 } 1263 } 1264 #ifdef TCP_SIGNATURE 1265 /* 1266 * If listening socket requested TCP digests, and received SYN 1267 * contains the option, flag this in the syncache so that 1268 * syncache_respond() will do the right thing with the SYN+ACK. 1269 * XXX: Currently we always record the option by default and will 1270 * attempt to use it in syncache_respond(). 1271 */ 1272 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE) 1273 sc->sc_flags |= SCF_SIGNATURE; 1274 #endif 1275 if (to->to_flags & TOF_SACKPERM) 1276 sc->sc_flags |= SCF_SACK; 1277 if (to->to_flags & TOF_MSS) 1278 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1279 if (ltflags & TF_NOOPT) 1280 sc->sc_flags |= SCF_NOOPT; 1281 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1282 sc->sc_flags |= SCF_ECN; 1283 1284 if (V_tcp_syncookies) { 1285 syncookie_generate(sch, sc, &flowtmp); 1286 #ifdef INET6 1287 if (autoflowlabel) 1288 sc->sc_flowlabel = flowtmp; 1289 #endif 1290 } else { 1291 #ifdef INET6 1292 if (autoflowlabel) 1293 sc->sc_flowlabel = 1294 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1295 #endif 1296 } 1297 SCH_UNLOCK(sch); 1298 1299 /* 1300 * Do a standard 3-way handshake. 1301 */ 1302 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1303 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1304 syncache_free(sc); 1305 else if (sc != &scs) 1306 syncache_insert(sc, sch); /* locks and unlocks sch */ 1307 TCPSTAT_INC(tcps_sndacks); 1308 TCPSTAT_INC(tcps_sndtotal); 1309 } else { 1310 if (sc != &scs) 1311 syncache_free(sc); 1312 TCPSTAT_INC(tcps_sc_dropped); 1313 } 1314 1315 done: 1316 if (cred != NULL) 1317 crfree(cred); 1318 #ifdef MAC 1319 if (sc == &scs) 1320 mac_syncache_destroy(&maclabel); 1321 #endif 1322 if (m) { 1323 1324 *lsop = NULL; 1325 m_freem(m); 1326 } 1327 } 1328 1329 static int 1330 syncache_respond(struct syncache *sc) 1331 { 1332 struct ip *ip = NULL; 1333 struct mbuf *m; 1334 struct tcphdr *th = NULL; 1335 int optlen, error = 0; /* Make compiler happy */ 1336 u_int16_t hlen, tlen, mssopt; 1337 struct tcpopt to; 1338 #ifdef INET6 1339 struct ip6_hdr *ip6 = NULL; 1340 #endif 1341 1342 hlen = 1343 #ifdef INET6 1344 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1345 #endif 1346 sizeof(struct ip); 1347 tlen = hlen + sizeof(struct tcphdr); 1348 1349 /* Determine MSS we advertize to other end of connection. */ 1350 mssopt = tcp_mssopt(&sc->sc_inc); 1351 if (sc->sc_peer_mss) 1352 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1353 1354 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1355 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1356 ("syncache: mbuf too small")); 1357 1358 /* Create the IP+TCP header from scratch. */ 1359 m = m_gethdr(M_DONTWAIT, MT_DATA); 1360 if (m == NULL) 1361 return (ENOBUFS); 1362 #ifdef MAC 1363 mac_syncache_create_mbuf(sc->sc_label, m); 1364 #endif 1365 m->m_data += max_linkhdr; 1366 m->m_len = tlen; 1367 m->m_pkthdr.len = tlen; 1368 m->m_pkthdr.rcvif = NULL; 1369 1370 #ifdef INET6 1371 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1372 ip6 = mtod(m, struct ip6_hdr *); 1373 ip6->ip6_vfc = IPV6_VERSION; 1374 ip6->ip6_nxt = IPPROTO_TCP; 1375 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1376 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1377 ip6->ip6_plen = htons(tlen - hlen); 1378 /* ip6_hlim is set after checksum */ 1379 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1380 ip6->ip6_flow |= sc->sc_flowlabel; 1381 1382 th = (struct tcphdr *)(ip6 + 1); 1383 } 1384 #endif 1385 #if defined(INET6) && defined(INET) 1386 else 1387 #endif 1388 #ifdef INET 1389 { 1390 ip = mtod(m, struct ip *); 1391 ip->ip_v = IPVERSION; 1392 ip->ip_hl = sizeof(struct ip) >> 2; 1393 ip->ip_len = tlen; 1394 ip->ip_id = 0; 1395 ip->ip_off = 0; 1396 ip->ip_sum = 0; 1397 ip->ip_p = IPPROTO_TCP; 1398 ip->ip_src = sc->sc_inc.inc_laddr; 1399 ip->ip_dst = sc->sc_inc.inc_faddr; 1400 ip->ip_ttl = sc->sc_ip_ttl; 1401 ip->ip_tos = sc->sc_ip_tos; 1402 1403 /* 1404 * See if we should do MTU discovery. Route lookups are 1405 * expensive, so we will only unset the DF bit if: 1406 * 1407 * 1) path_mtu_discovery is disabled 1408 * 2) the SCF_UNREACH flag has been set 1409 */ 1410 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1411 ip->ip_off |= IP_DF; 1412 1413 th = (struct tcphdr *)(ip + 1); 1414 } 1415 #endif /* INET */ 1416 th->th_sport = sc->sc_inc.inc_lport; 1417 th->th_dport = sc->sc_inc.inc_fport; 1418 1419 th->th_seq = htonl(sc->sc_iss); 1420 th->th_ack = htonl(sc->sc_irs + 1); 1421 th->th_off = sizeof(struct tcphdr) >> 2; 1422 th->th_x2 = 0; 1423 th->th_flags = TH_SYN|TH_ACK; 1424 th->th_win = htons(sc->sc_wnd); 1425 th->th_urp = 0; 1426 1427 if (sc->sc_flags & SCF_ECN) { 1428 th->th_flags |= TH_ECE; 1429 TCPSTAT_INC(tcps_ecn_shs); 1430 } 1431 1432 /* Tack on the TCP options. */ 1433 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1434 to.to_flags = 0; 1435 1436 to.to_mss = mssopt; 1437 to.to_flags = TOF_MSS; 1438 if (sc->sc_flags & SCF_WINSCALE) { 1439 to.to_wscale = sc->sc_requested_r_scale; 1440 to.to_flags |= TOF_SCALE; 1441 } 1442 if (sc->sc_flags & SCF_TIMESTAMP) { 1443 /* Virgin timestamp or TCP cookie enhanced one. */ 1444 to.to_tsval = sc->sc_ts; 1445 to.to_tsecr = sc->sc_tsreflect; 1446 to.to_flags |= TOF_TS; 1447 } 1448 if (sc->sc_flags & SCF_SACK) 1449 to.to_flags |= TOF_SACKPERM; 1450 #ifdef TCP_SIGNATURE 1451 if (sc->sc_flags & SCF_SIGNATURE) 1452 to.to_flags |= TOF_SIGNATURE; 1453 #endif 1454 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1455 1456 /* Adjust headers by option size. */ 1457 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1458 m->m_len += optlen; 1459 m->m_pkthdr.len += optlen; 1460 1461 #ifdef TCP_SIGNATURE 1462 if (sc->sc_flags & SCF_SIGNATURE) 1463 tcp_signature_compute(m, 0, 0, optlen, 1464 to.to_signature, IPSEC_DIR_OUTBOUND); 1465 #endif 1466 #ifdef INET6 1467 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1468 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1469 else 1470 #endif 1471 ip->ip_len += optlen; 1472 } else 1473 optlen = 0; 1474 1475 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1476 #ifdef INET6 1477 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1478 th->th_sum = 0; 1479 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1480 tlen + optlen - hlen); 1481 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1482 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1483 } 1484 #endif 1485 #if defined(INET6) && defined(INET) 1486 else 1487 #endif 1488 #ifdef INET 1489 { 1490 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1491 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1492 m->m_pkthdr.csum_flags = CSUM_TCP; 1493 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1494 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1495 } 1496 #endif 1497 return (error); 1498 } 1499 1500 void 1501 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1502 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1503 { 1504 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1505 } 1506 1507 void 1508 tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo, 1509 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1510 struct toe_usrreqs *tu, void *toepcb) 1511 { 1512 struct tcpopt to; 1513 1514 bzero(&to, sizeof(struct tcpopt)); 1515 to.to_mss = toeo->to_mss; 1516 to.to_wscale = toeo->to_wscale; 1517 to.to_flags = toeo->to_flags; 1518 1519 INP_INFO_WLOCK(&V_tcbinfo); 1520 INP_WLOCK(inp); 1521 1522 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb); 1523 } 1524 1525 /* 1526 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1527 * receive and to be able to handle SYN floods from bogus source addresses 1528 * (where we will never receive any reply). SYN floods try to exhaust all 1529 * our memory and available slots in the SYN cache table to cause a denial 1530 * of service to legitimate users of the local host. 1531 * 1532 * The idea of SYN cookies is to encode and include all necessary information 1533 * about the connection setup state within the SYN-ACK we send back and thus 1534 * to get along without keeping any local state until the ACK to the SYN-ACK 1535 * arrives (if ever). Everything we need to know should be available from 1536 * the information we encoded in the SYN-ACK. 1537 * 1538 * More information about the theory behind SYN cookies and its first 1539 * discussion and specification can be found at: 1540 * http://cr.yp.to/syncookies.html (overview) 1541 * http://cr.yp.to/syncookies/archive (gory details) 1542 * 1543 * This implementation extends the orginal idea and first implementation 1544 * of FreeBSD by using not only the initial sequence number field to store 1545 * information but also the timestamp field if present. This way we can 1546 * keep track of the entire state we need to know to recreate the session in 1547 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1548 * these days. For those that do not we still have to live with the known 1549 * shortcomings of the ISN only SYN cookies. 1550 * 1551 * Cookie layers: 1552 * 1553 * Initial sequence number we send: 1554 * 31|................................|0 1555 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1556 * D = MD5 Digest (first dword) 1557 * M = MSS index 1558 * R = Rotation of secret 1559 * P = Odd or Even secret 1560 * 1561 * The MD5 Digest is computed with over following parameters: 1562 * a) randomly rotated secret 1563 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1564 * c) the received initial sequence number from remote host 1565 * d) the rotation offset and odd/even bit 1566 * 1567 * Timestamp we send: 1568 * 31|................................|0 1569 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1570 * D = MD5 Digest (third dword) (only as filler) 1571 * S = Requested send window scale 1572 * R = Requested receive window scale 1573 * A = SACK allowed 1574 * 5 = TCP-MD5 enabled (not implemented yet) 1575 * XORed with MD5 Digest (forth dword) 1576 * 1577 * The timestamp isn't cryptographically secure and doesn't need to be. 1578 * The double use of the MD5 digest dwords ties it to a specific remote/ 1579 * local host/port, remote initial sequence number and our local time 1580 * limited secret. A received timestamp is reverted (XORed) and then 1581 * the contained MD5 dword is compared to the computed one to ensure the 1582 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1583 * have been tampered with but this isn't different from supplying bogus 1584 * values in the SYN in the first place. 1585 * 1586 * Some problems with SYN cookies remain however: 1587 * Consider the problem of a recreated (and retransmitted) cookie. If the 1588 * original SYN was accepted, the connection is established. The second 1589 * SYN is inflight, and if it arrives with an ISN that falls within the 1590 * receive window, the connection is killed. 1591 * 1592 * Notes: 1593 * A heuristic to determine when to accept syn cookies is not necessary. 1594 * An ACK flood would cause the syncookie verification to be attempted, 1595 * but a SYN flood causes syncookies to be generated. Both are of equal 1596 * cost, so there's no point in trying to optimize the ACK flood case. 1597 * Also, if you don't process certain ACKs for some reason, then all someone 1598 * would have to do is launch a SYN and ACK flood at the same time, which 1599 * would stop cookie verification and defeat the entire purpose of syncookies. 1600 */ 1601 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1602 1603 static void 1604 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1605 u_int32_t *flowlabel) 1606 { 1607 MD5_CTX ctx; 1608 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1609 u_int32_t data; 1610 u_int32_t *secbits; 1611 u_int off, pmss, mss; 1612 int i; 1613 1614 SCH_LOCK_ASSERT(sch); 1615 1616 /* Which of the two secrets to use. */ 1617 secbits = sch->sch_oddeven ? 1618 sch->sch_secbits_odd : sch->sch_secbits_even; 1619 1620 /* Reseed secret if too old. */ 1621 if (sch->sch_reseed < time_uptime) { 1622 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1623 secbits = sch->sch_oddeven ? 1624 sch->sch_secbits_odd : sch->sch_secbits_even; 1625 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1626 secbits[i] = arc4random(); 1627 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1628 } 1629 1630 /* Secret rotation offset. */ 1631 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1632 1633 /* Maximum segment size calculation. */ 1634 pmss = 1635 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1636 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1637 if (tcp_sc_msstab[mss] <= pmss) 1638 break; 1639 1640 /* Fold parameters and MD5 digest into the ISN we will send. */ 1641 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1642 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1643 data |= mss << 4; /* mss, 3 bits */ 1644 1645 MD5Init(&ctx); 1646 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1647 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1648 MD5Update(&ctx, secbits, off); 1649 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1650 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1651 MD5Update(&ctx, &data, sizeof(data)); 1652 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1653 1654 data |= (md5_buffer[0] << 7); 1655 sc->sc_iss = data; 1656 1657 #ifdef INET6 1658 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1659 #endif 1660 1661 /* Additional parameters are stored in the timestamp if present. */ 1662 if (sc->sc_flags & SCF_TIMESTAMP) { 1663 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1664 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1665 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1666 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1667 data |= md5_buffer[2] << 10; /* more digest bits */ 1668 data ^= md5_buffer[3]; 1669 sc->sc_ts = data; 1670 sc->sc_tsoff = data - tcp_ts_getticks(); /* after XOR */ 1671 } 1672 1673 TCPSTAT_INC(tcps_sc_sendcookie); 1674 } 1675 1676 static struct syncache * 1677 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1678 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1679 struct socket *so) 1680 { 1681 MD5_CTX ctx; 1682 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1683 u_int32_t data = 0; 1684 u_int32_t *secbits; 1685 tcp_seq ack, seq; 1686 int off, mss, wnd, flags; 1687 1688 SCH_LOCK_ASSERT(sch); 1689 1690 /* 1691 * Pull information out of SYN-ACK/ACK and 1692 * revert sequence number advances. 1693 */ 1694 ack = th->th_ack - 1; 1695 seq = th->th_seq - 1; 1696 off = (ack >> 1) & 0x7; 1697 mss = (ack >> 4) & 0x7; 1698 flags = ack & 0x7f; 1699 1700 /* Which of the two secrets to use. */ 1701 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1702 1703 /* 1704 * The secret wasn't updated for the lifetime of a syncookie, 1705 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1706 */ 1707 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1708 return (NULL); 1709 } 1710 1711 /* Recompute the digest so we can compare it. */ 1712 MD5Init(&ctx); 1713 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1714 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1715 MD5Update(&ctx, secbits, off); 1716 MD5Update(&ctx, inc, sizeof(*inc)); 1717 MD5Update(&ctx, &seq, sizeof(seq)); 1718 MD5Update(&ctx, &flags, sizeof(flags)); 1719 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1720 1721 /* Does the digest part of or ACK'ed ISS match? */ 1722 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1723 return (NULL); 1724 1725 /* Does the digest part of our reflected timestamp match? */ 1726 if (to->to_flags & TOF_TS) { 1727 data = md5_buffer[3] ^ to->to_tsecr; 1728 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1729 return (NULL); 1730 } 1731 1732 /* Fill in the syncache values. */ 1733 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1734 sc->sc_ipopts = NULL; 1735 1736 sc->sc_irs = seq; 1737 sc->sc_iss = ack; 1738 1739 #ifdef INET6 1740 if (inc->inc_flags & INC_ISIPV6) { 1741 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1742 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1743 } else 1744 #endif 1745 { 1746 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1747 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1748 } 1749 1750 /* Additional parameters that were encoded in the timestamp. */ 1751 if (data) { 1752 sc->sc_flags |= SCF_TIMESTAMP; 1753 sc->sc_tsreflect = to->to_tsval; 1754 sc->sc_ts = to->to_tsecr; 1755 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks(); 1756 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1757 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1758 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1759 TCP_MAX_WINSHIFT); 1760 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1761 TCP_MAX_WINSHIFT); 1762 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1763 sc->sc_flags |= SCF_WINSCALE; 1764 } else 1765 sc->sc_flags |= SCF_NOOPT; 1766 1767 wnd = sbspace(&so->so_rcv); 1768 wnd = imax(wnd, 0); 1769 wnd = imin(wnd, TCP_MAXWIN); 1770 sc->sc_wnd = wnd; 1771 1772 sc->sc_rxmits = 0; 1773 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1774 1775 TCPSTAT_INC(tcps_sc_recvcookie); 1776 return (sc); 1777 } 1778 1779 /* 1780 * Returns the current number of syncache entries. This number 1781 * will probably change before you get around to calling 1782 * syncache_pcblist. 1783 */ 1784 1785 int 1786 syncache_pcbcount(void) 1787 { 1788 struct syncache_head *sch; 1789 int count, i; 1790 1791 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1792 /* No need to lock for a read. */ 1793 sch = &V_tcp_syncache.hashbase[i]; 1794 count += sch->sch_length; 1795 } 1796 return count; 1797 } 1798 1799 /* 1800 * Exports the syncache entries to userland so that netstat can display 1801 * them alongside the other sockets. This function is intended to be 1802 * called only from tcp_pcblist. 1803 * 1804 * Due to concurrency on an active system, the number of pcbs exported 1805 * may have no relation to max_pcbs. max_pcbs merely indicates the 1806 * amount of space the caller allocated for this function to use. 1807 */ 1808 int 1809 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1810 { 1811 struct xtcpcb xt; 1812 struct syncache *sc; 1813 struct syncache_head *sch; 1814 int count, error, i; 1815 1816 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1817 sch = &V_tcp_syncache.hashbase[i]; 1818 SCH_LOCK(sch); 1819 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1820 if (count >= max_pcbs) { 1821 SCH_UNLOCK(sch); 1822 goto exit; 1823 } 1824 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1825 continue; 1826 bzero(&xt, sizeof(xt)); 1827 xt.xt_len = sizeof(xt); 1828 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1829 xt.xt_inp.inp_vflag = INP_IPV6; 1830 else 1831 xt.xt_inp.inp_vflag = INP_IPV4; 1832 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1833 xt.xt_tp.t_inpcb = &xt.xt_inp; 1834 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1835 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1836 xt.xt_socket.xso_len = sizeof (struct xsocket); 1837 xt.xt_socket.so_type = SOCK_STREAM; 1838 xt.xt_socket.so_state = SS_ISCONNECTING; 1839 error = SYSCTL_OUT(req, &xt, sizeof xt); 1840 if (error) { 1841 SCH_UNLOCK(sch); 1842 goto exit; 1843 } 1844 count++; 1845 } 1846 SCH_UNLOCK(sch); 1847 } 1848 exit: 1849 *pcbs_exported = count; 1850 return error; 1851 } 1852