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