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sys/netinet/tcp_syncache.c
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1 /*- 2 * Copyright (c) 2001 McAfee, Inc. 3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG 4 * All rights reserved. 5 * 6 * This software was developed for the FreeBSD Project by Jonathan Lemon 7 * and McAfee Research, the Security Research Division of McAfee, Inc. under 8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 9 * DARPA CHATS research program. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD: releng/8.0/sys/netinet/tcp_syncache.c 196019 2009-08-01 19:26:27Z rwatson $"); 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 { 281 282 /* XXX walk the cache, free remaining objects, stop timers */ 283 284 uma_zdestroy(V_tcp_syncache.zone); 285 FREE(V_tcp_syncache.hashbase, M_SYNCACHE); 286 } 287 #endif 288 289 /* 290 * Inserts a syncache entry into the specified bucket row. 291 * Locks and unlocks the syncache_head autonomously. 292 */ 293 static void 294 syncache_insert(struct syncache *sc, struct syncache_head *sch) 295 { 296 struct syncache *sc2; 297 298 SCH_LOCK(sch); 299 300 /* 301 * Make sure that we don't overflow the per-bucket limit. 302 * If the bucket is full, toss the oldest element. 303 */ 304 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 305 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 306 ("sch->sch_length incorrect")); 307 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 308 syncache_drop(sc2, sch); 309 TCPSTAT_INC(tcps_sc_bucketoverflow); 310 } 311 312 /* Put it into the bucket. */ 313 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 314 sch->sch_length++; 315 316 /* Reinitialize the bucket row's timer. */ 317 if (sch->sch_length == 1) 318 sch->sch_nextc = ticks + INT_MAX; 319 syncache_timeout(sc, sch, 1); 320 321 SCH_UNLOCK(sch); 322 323 V_tcp_syncache.cache_count++; 324 TCPSTAT_INC(tcps_sc_added); 325 } 326 327 /* 328 * Remove and free entry from syncache bucket row. 329 * Expects locked syncache head. 330 */ 331 static void 332 syncache_drop(struct syncache *sc, struct syncache_head *sch) 333 { 334 335 SCH_LOCK_ASSERT(sch); 336 337 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 338 sch->sch_length--; 339 340 #ifndef TCP_OFFLOAD_DISABLE 341 if (sc->sc_tu) 342 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 343 #endif 344 syncache_free(sc); 345 V_tcp_syncache.cache_count--; 346 } 347 348 /* 349 * Engage/reengage time on bucket row. 350 */ 351 static void 352 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 353 { 354 sc->sc_rxttime = ticks + 355 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 356 sc->sc_rxmits++; 357 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 358 sch->sch_nextc = sc->sc_rxttime; 359 if (docallout) 360 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 361 syncache_timer, (void *)sch); 362 } 363 } 364 365 /* 366 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 367 * If we have retransmitted an entry the maximum number of times, expire it. 368 * One separate timer for each bucket row. 369 */ 370 static void 371 syncache_timer(void *xsch) 372 { 373 struct syncache_head *sch = (struct syncache_head *)xsch; 374 struct syncache *sc, *nsc; 375 int tick = ticks; 376 char *s; 377 378 CURVNET_SET(sch->sch_vnet); 379 380 /* NB: syncache_head has already been locked by the callout. */ 381 SCH_LOCK_ASSERT(sch); 382 383 /* 384 * In the following cycle we may remove some entries and/or 385 * advance some timeouts, so re-initialize the bucket timer. 386 */ 387 sch->sch_nextc = tick + INT_MAX; 388 389 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 390 /* 391 * We do not check if the listen socket still exists 392 * and accept the case where the listen socket may be 393 * gone by the time we resend the SYN/ACK. We do 394 * not expect this to happens often. If it does, 395 * then the RST will be sent by the time the remote 396 * host does the SYN/ACK->ACK. 397 */ 398 if (TSTMP_GT(sc->sc_rxttime, tick)) { 399 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 400 sch->sch_nextc = sc->sc_rxttime; 401 continue; 402 } 403 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 404 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 405 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 406 "giving up and removing syncache entry\n", 407 s, __func__); 408 free(s, M_TCPLOG); 409 } 410 syncache_drop(sc, sch); 411 TCPSTAT_INC(tcps_sc_stale); 412 continue; 413 } 414 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 415 log(LOG_DEBUG, "%s; %s: Response timeout, " 416 "retransmitting (%u) SYN|ACK\n", 417 s, __func__, sc->sc_rxmits); 418 free(s, M_TCPLOG); 419 } 420 421 (void) syncache_respond(sc); 422 TCPSTAT_INC(tcps_sc_retransmitted); 423 syncache_timeout(sc, sch, 0); 424 } 425 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 426 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 427 syncache_timer, (void *)(sch)); 428 CURVNET_RESTORE(); 429 } 430 431 /* 432 * Find an entry in the syncache. 433 * Returns always with locked syncache_head plus a matching entry or NULL. 434 */ 435 struct syncache * 436 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 437 { 438 struct syncache *sc; 439 struct syncache_head *sch; 440 441 #ifdef INET6 442 if (inc->inc_flags & INC_ISIPV6) { 443 sch = &V_tcp_syncache.hashbase[ 444 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 445 *schp = sch; 446 447 SCH_LOCK(sch); 448 449 /* Circle through bucket row to find matching entry. */ 450 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 451 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 452 return (sc); 453 } 454 } else 455 #endif 456 { 457 sch = &V_tcp_syncache.hashbase[ 458 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 459 *schp = sch; 460 461 SCH_LOCK(sch); 462 463 /* Circle through bucket row to find matching entry. */ 464 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 465 #ifdef INET6 466 if (sc->sc_inc.inc_flags & INC_ISIPV6) 467 continue; 468 #endif 469 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 470 return (sc); 471 } 472 } 473 SCH_LOCK_ASSERT(*schp); 474 return (NULL); /* always returns with locked sch */ 475 } 476 477 /* 478 * This function is called when we get a RST for a 479 * non-existent connection, so that we can see if the 480 * connection is in the syn cache. If it is, zap it. 481 */ 482 void 483 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 484 { 485 struct syncache *sc; 486 struct syncache_head *sch; 487 char *s = NULL; 488 489 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 490 SCH_LOCK_ASSERT(sch); 491 492 /* 493 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 494 * See RFC 793 page 65, section SEGMENT ARRIVES. 495 */ 496 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 497 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 498 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 499 "FIN flag set, segment ignored\n", s, __func__); 500 TCPSTAT_INC(tcps_badrst); 501 goto done; 502 } 503 504 /* 505 * No corresponding connection was found in syncache. 506 * If syncookies are enabled and possibly exclusively 507 * used, or we are under memory pressure, a valid RST 508 * may not find a syncache entry. In that case we're 509 * done and no SYN|ACK retransmissions will happen. 510 * Otherwise the the RST was misdirected or spoofed. 511 */ 512 if (sc == NULL) { 513 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 514 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 515 "syncache entry (possibly syncookie only), " 516 "segment ignored\n", s, __func__); 517 TCPSTAT_INC(tcps_badrst); 518 goto done; 519 } 520 521 /* 522 * If the RST bit is set, check the sequence number to see 523 * if this is a valid reset segment. 524 * RFC 793 page 37: 525 * In all states except SYN-SENT, all reset (RST) segments 526 * are validated by checking their SEQ-fields. A reset is 527 * valid if its sequence number is in the window. 528 * 529 * The sequence number in the reset segment is normally an 530 * echo of our outgoing acknowlegement numbers, but some hosts 531 * send a reset with the sequence number at the rightmost edge 532 * of our receive window, and we have to handle this case. 533 */ 534 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 535 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 536 syncache_drop(sc, sch); 537 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 538 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 539 "connection attempt aborted by remote endpoint\n", 540 s, __func__); 541 TCPSTAT_INC(tcps_sc_reset); 542 } else { 543 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 544 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 545 "IRS %u (+WND %u), segment ignored\n", 546 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 547 TCPSTAT_INC(tcps_badrst); 548 } 549 550 done: 551 if (s != NULL) 552 free(s, M_TCPLOG); 553 SCH_UNLOCK(sch); 554 } 555 556 void 557 syncache_badack(struct in_conninfo *inc) 558 { 559 struct syncache *sc; 560 struct syncache_head *sch; 561 562 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 563 SCH_LOCK_ASSERT(sch); 564 if (sc != NULL) { 565 syncache_drop(sc, sch); 566 TCPSTAT_INC(tcps_sc_badack); 567 } 568 SCH_UNLOCK(sch); 569 } 570 571 void 572 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 573 { 574 struct syncache *sc; 575 struct syncache_head *sch; 576 577 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 578 SCH_LOCK_ASSERT(sch); 579 if (sc == NULL) 580 goto done; 581 582 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 583 if (ntohl(th->th_seq) != sc->sc_iss) 584 goto done; 585 586 /* 587 * If we've rertransmitted 3 times and this is our second error, 588 * we remove the entry. Otherwise, we allow it to continue on. 589 * This prevents us from incorrectly nuking an entry during a 590 * spurious network outage. 591 * 592 * See tcp_notify(). 593 */ 594 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 595 sc->sc_flags |= SCF_UNREACH; 596 goto done; 597 } 598 syncache_drop(sc, sch); 599 TCPSTAT_INC(tcps_sc_unreach); 600 done: 601 SCH_UNLOCK(sch); 602 } 603 604 /* 605 * Build a new TCP socket structure from a syncache entry. 606 */ 607 static struct socket * 608 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 609 { 610 struct inpcb *inp = NULL; 611 struct socket *so; 612 struct tcpcb *tp; 613 char *s; 614 615 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 616 617 /* 618 * Ok, create the full blown connection, and set things up 619 * as they would have been set up if we had created the 620 * connection when the SYN arrived. If we can't create 621 * the connection, abort it. 622 */ 623 so = sonewconn(lso, SS_ISCONNECTED); 624 if (so == NULL) { 625 /* 626 * Drop the connection; we will either send a RST or 627 * have the peer retransmit its SYN again after its 628 * RTO and try again. 629 */ 630 TCPSTAT_INC(tcps_listendrop); 631 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 632 log(LOG_DEBUG, "%s; %s: Socket create failed " 633 "due to limits or memory shortage\n", 634 s, __func__); 635 free(s, M_TCPLOG); 636 } 637 goto abort2; 638 } 639 #ifdef MAC 640 mac_socketpeer_set_from_mbuf(m, so); 641 #endif 642 643 inp = sotoinpcb(so); 644 inp->inp_inc.inc_fibnum = so->so_fibnum; 645 INP_WLOCK(inp); 646 647 /* Insert new socket into PCB hash list. */ 648 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 649 #ifdef INET6 650 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 651 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 652 } else { 653 inp->inp_vflag &= ~INP_IPV6; 654 inp->inp_vflag |= INP_IPV4; 655 #endif 656 inp->inp_laddr = sc->sc_inc.inc_laddr; 657 #ifdef INET6 658 } 659 #endif 660 inp->inp_lport = sc->sc_inc.inc_lport; 661 if (in_pcbinshash(inp) != 0) { 662 /* 663 * Undo the assignments above if we failed to 664 * put the PCB on the hash lists. 665 */ 666 #ifdef INET6 667 if (sc->sc_inc.inc_flags & INC_ISIPV6) 668 inp->in6p_laddr = in6addr_any; 669 else 670 #endif 671 inp->inp_laddr.s_addr = INADDR_ANY; 672 inp->inp_lport = 0; 673 goto abort; 674 } 675 #ifdef IPSEC 676 /* Copy old policy into new socket's. */ 677 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 678 printf("syncache_socket: could not copy policy\n"); 679 #endif 680 #ifdef INET6 681 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 682 struct inpcb *oinp = sotoinpcb(lso); 683 struct in6_addr laddr6; 684 struct sockaddr_in6 sin6; 685 /* 686 * Inherit socket options from the listening socket. 687 * Note that in6p_inputopts are not (and should not be) 688 * copied, since it stores previously received options and is 689 * used to detect if each new option is different than the 690 * previous one and hence should be passed to a user. 691 * If we copied in6p_inputopts, a user would not be able to 692 * receive options just after calling the accept system call. 693 */ 694 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 695 if (oinp->in6p_outputopts) 696 inp->in6p_outputopts = 697 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 698 699 sin6.sin6_family = AF_INET6; 700 sin6.sin6_len = sizeof(sin6); 701 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 702 sin6.sin6_port = sc->sc_inc.inc_fport; 703 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 704 laddr6 = inp->in6p_laddr; 705 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 706 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 707 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 708 thread0.td_ucred)) { 709 inp->in6p_laddr = laddr6; 710 goto abort; 711 } 712 /* Override flowlabel from in6_pcbconnect. */ 713 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 714 inp->inp_flow |= sc->sc_flowlabel; 715 } else 716 #endif 717 { 718 struct in_addr laddr; 719 struct sockaddr_in sin; 720 721 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 722 723 if (inp->inp_options == NULL) { 724 inp->inp_options = sc->sc_ipopts; 725 sc->sc_ipopts = NULL; 726 } 727 728 sin.sin_family = AF_INET; 729 sin.sin_len = sizeof(sin); 730 sin.sin_addr = sc->sc_inc.inc_faddr; 731 sin.sin_port = sc->sc_inc.inc_fport; 732 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 733 laddr = inp->inp_laddr; 734 if (inp->inp_laddr.s_addr == INADDR_ANY) 735 inp->inp_laddr = sc->sc_inc.inc_laddr; 736 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 737 thread0.td_ucred)) { 738 inp->inp_laddr = laddr; 739 goto abort; 740 } 741 } 742 tp = intotcpcb(inp); 743 tp->t_state = TCPS_SYN_RECEIVED; 744 tp->iss = sc->sc_iss; 745 tp->irs = sc->sc_irs; 746 tcp_rcvseqinit(tp); 747 tcp_sendseqinit(tp); 748 tp->snd_wl1 = sc->sc_irs; 749 tp->snd_max = tp->iss + 1; 750 tp->snd_nxt = tp->iss + 1; 751 tp->rcv_up = sc->sc_irs + 1; 752 tp->rcv_wnd = sc->sc_wnd; 753 tp->rcv_adv += tp->rcv_wnd; 754 tp->last_ack_sent = tp->rcv_nxt; 755 756 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 757 if (sc->sc_flags & SCF_NOOPT) 758 tp->t_flags |= TF_NOOPT; 759 else { 760 if (sc->sc_flags & SCF_WINSCALE) { 761 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 762 tp->snd_scale = sc->sc_requested_s_scale; 763 tp->request_r_scale = sc->sc_requested_r_scale; 764 } 765 if (sc->sc_flags & SCF_TIMESTAMP) { 766 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 767 tp->ts_recent = sc->sc_tsreflect; 768 tp->ts_recent_age = ticks; 769 tp->ts_offset = sc->sc_tsoff; 770 } 771 #ifdef TCP_SIGNATURE 772 if (sc->sc_flags & SCF_SIGNATURE) 773 tp->t_flags |= TF_SIGNATURE; 774 #endif 775 if (sc->sc_flags & SCF_SACK) 776 tp->t_flags |= TF_SACK_PERMIT; 777 } 778 779 if (sc->sc_flags & SCF_ECN) 780 tp->t_flags |= TF_ECN_PERMIT; 781 782 /* 783 * Set up MSS and get cached values from tcp_hostcache. 784 * This might overwrite some of the defaults we just set. 785 */ 786 tcp_mss(tp, sc->sc_peer_mss); 787 788 /* 789 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 790 */ 791 if (sc->sc_rxmits) 792 tp->snd_cwnd = tp->t_maxseg; 793 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 794 795 INP_WUNLOCK(inp); 796 797 TCPSTAT_INC(tcps_accepts); 798 return (so); 799 800 abort: 801 INP_WUNLOCK(inp); 802 abort2: 803 if (so != NULL) 804 soabort(so); 805 return (NULL); 806 } 807 808 /* 809 * This function gets called when we receive an ACK for a 810 * socket in the LISTEN state. We look up the connection 811 * in the syncache, and if its there, we pull it out of 812 * the cache and turn it into a full-blown connection in 813 * the SYN-RECEIVED state. 814 */ 815 int 816 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 817 struct socket **lsop, struct mbuf *m) 818 { 819 struct syncache *sc; 820 struct syncache_head *sch; 821 struct syncache scs; 822 char *s; 823 824 /* 825 * Global TCP locks are held because we manipulate the PCB lists 826 * and create a new socket. 827 */ 828 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 829 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 830 ("%s: can handle only ACK", __func__)); 831 832 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 833 SCH_LOCK_ASSERT(sch); 834 if (sc == NULL) { 835 /* 836 * There is no syncache entry, so see if this ACK is 837 * a returning syncookie. To do this, first: 838 * A. See if this socket has had a syncache entry dropped in 839 * the past. We don't want to accept a bogus syncookie 840 * if we've never received a SYN. 841 * B. check that the syncookie is valid. If it is, then 842 * cobble up a fake syncache entry, and return. 843 */ 844 if (!V_tcp_syncookies) { 845 SCH_UNLOCK(sch); 846 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 847 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 848 "segment rejected (syncookies disabled)\n", 849 s, __func__); 850 goto failed; 851 } 852 bzero(&scs, sizeof(scs)); 853 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 854 SCH_UNLOCK(sch); 855 if (sc == NULL) { 856 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 857 log(LOG_DEBUG, "%s; %s: Segment failed " 858 "SYNCOOKIE authentication, segment rejected " 859 "(probably spoofed)\n", s, __func__); 860 goto failed; 861 } 862 } else { 863 /* Pull out the entry to unlock the bucket row. */ 864 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 865 sch->sch_length--; 866 V_tcp_syncache.cache_count--; 867 SCH_UNLOCK(sch); 868 } 869 870 /* 871 * Segment validation: 872 * ACK must match our initial sequence number + 1 (the SYN|ACK). 873 */ 874 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 875 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 876 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 877 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 878 goto failed; 879 } 880 881 /* 882 * The SEQ must fall in the window starting at the received 883 * initial receive sequence number + 1 (the SYN). 884 */ 885 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 886 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 887 !TOEPCB_ISSET(sc)) { 888 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 889 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 890 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 891 goto failed; 892 } 893 894 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 895 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 896 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 897 "segment rejected\n", s, __func__); 898 goto failed; 899 } 900 /* 901 * If timestamps were negotiated the reflected timestamp 902 * must be equal to what we actually sent in the SYN|ACK. 903 */ 904 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 905 !TOEPCB_ISSET(sc)) { 906 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 907 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 908 "segment rejected\n", 909 s, __func__, to->to_tsecr, sc->sc_ts); 910 goto failed; 911 } 912 913 *lsop = syncache_socket(sc, *lsop, m); 914 915 if (*lsop == NULL) 916 TCPSTAT_INC(tcps_sc_aborted); 917 else 918 TCPSTAT_INC(tcps_sc_completed); 919 920 /* how do we find the inp for the new socket? */ 921 if (sc != &scs) 922 syncache_free(sc); 923 return (1); 924 failed: 925 if (sc != NULL && sc != &scs) 926 syncache_free(sc); 927 if (s != NULL) 928 free(s, M_TCPLOG); 929 *lsop = NULL; 930 return (0); 931 } 932 933 int 934 tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo, 935 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 936 { 937 struct tcpopt to; 938 int rc; 939 940 bzero(&to, sizeof(struct tcpopt)); 941 to.to_mss = toeo->to_mss; 942 to.to_wscale = toeo->to_wscale; 943 to.to_flags = toeo->to_flags; 944 945 INP_INFO_WLOCK(&V_tcbinfo); 946 rc = syncache_expand(inc, &to, th, lsop, m); 947 INP_INFO_WUNLOCK(&V_tcbinfo); 948 949 return (rc); 950 } 951 952 /* 953 * Given a LISTEN socket and an inbound SYN request, add 954 * this to the syn cache, and send back a segment: 955 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 956 * to the source. 957 * 958 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 959 * Doing so would require that we hold onto the data and deliver it 960 * to the application. However, if we are the target of a SYN-flood 961 * DoS attack, an attacker could send data which would eventually 962 * consume all available buffer space if it were ACKed. By not ACKing 963 * the data, we avoid this DoS scenario. 964 */ 965 static void 966 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 967 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 968 struct toe_usrreqs *tu, void *toepcb) 969 { 970 struct tcpcb *tp; 971 struct socket *so; 972 struct syncache *sc = NULL; 973 struct syncache_head *sch; 974 struct mbuf *ipopts = NULL; 975 u_int32_t flowtmp; 976 int win, sb_hiwat, ip_ttl, ip_tos, noopt; 977 char *s; 978 #ifdef INET6 979 int autoflowlabel = 0; 980 #endif 981 #ifdef MAC 982 struct label *maclabel; 983 #endif 984 struct syncache scs; 985 struct ucred *cred; 986 987 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 988 INP_WLOCK_ASSERT(inp); /* listen socket */ 989 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 990 ("%s: unexpected tcp flags", __func__)); 991 992 /* 993 * Combine all so/tp operations very early to drop the INP lock as 994 * soon as possible. 995 */ 996 so = *lsop; 997 tp = sototcpcb(so); 998 cred = crhold(so->so_cred); 999 1000 #ifdef INET6 1001 if ((inc->inc_flags & INC_ISIPV6) && 1002 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1003 autoflowlabel = 1; 1004 #endif 1005 ip_ttl = inp->inp_ip_ttl; 1006 ip_tos = inp->inp_ip_tos; 1007 win = sbspace(&so->so_rcv); 1008 sb_hiwat = so->so_rcv.sb_hiwat; 1009 noopt = (tp->t_flags & TF_NOOPT); 1010 1011 /* By the time we drop the lock these should no longer be used. */ 1012 so = NULL; 1013 tp = NULL; 1014 1015 #ifdef MAC 1016 if (mac_syncache_init(&maclabel) != 0) { 1017 INP_WUNLOCK(inp); 1018 INP_INFO_WUNLOCK(&V_tcbinfo); 1019 goto done; 1020 } else 1021 mac_syncache_create(maclabel, inp); 1022 #endif 1023 INP_WUNLOCK(inp); 1024 INP_INFO_WUNLOCK(&V_tcbinfo); 1025 1026 /* 1027 * Remember the IP options, if any. 1028 */ 1029 #ifdef INET6 1030 if (!(inc->inc_flags & INC_ISIPV6)) 1031 #endif 1032 ipopts = (m) ? ip_srcroute(m) : NULL; 1033 1034 /* 1035 * See if we already have an entry for this connection. 1036 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1037 * 1038 * XXX: should the syncache be re-initialized with the contents 1039 * of the new SYN here (which may have different options?) 1040 * 1041 * XXX: We do not check the sequence number to see if this is a 1042 * real retransmit or a new connection attempt. The question is 1043 * how to handle such a case; either ignore it as spoofed, or 1044 * drop the current entry and create a new one? 1045 */ 1046 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1047 SCH_LOCK_ASSERT(sch); 1048 if (sc != NULL) { 1049 #ifndef TCP_OFFLOAD_DISABLE 1050 if (sc->sc_tu) 1051 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1052 sc->sc_toepcb); 1053 #endif 1054 TCPSTAT_INC(tcps_sc_dupsyn); 1055 if (ipopts) { 1056 /* 1057 * If we were remembering a previous source route, 1058 * forget it and use the new one we've been given. 1059 */ 1060 if (sc->sc_ipopts) 1061 (void) m_free(sc->sc_ipopts); 1062 sc->sc_ipopts = ipopts; 1063 } 1064 /* 1065 * Update timestamp if present. 1066 */ 1067 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1068 sc->sc_tsreflect = to->to_tsval; 1069 else 1070 sc->sc_flags &= ~SCF_TIMESTAMP; 1071 #ifdef MAC 1072 /* 1073 * Since we have already unconditionally allocated label 1074 * storage, free it up. The syncache entry will already 1075 * have an initialized label we can use. 1076 */ 1077 mac_syncache_destroy(&maclabel); 1078 #endif 1079 /* Retransmit SYN|ACK and reset retransmit count. */ 1080 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1081 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1082 "resetting timer and retransmitting SYN|ACK\n", 1083 s, __func__); 1084 free(s, M_TCPLOG); 1085 } 1086 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1087 sc->sc_rxmits = 0; 1088 syncache_timeout(sc, sch, 1); 1089 TCPSTAT_INC(tcps_sndacks); 1090 TCPSTAT_INC(tcps_sndtotal); 1091 } 1092 SCH_UNLOCK(sch); 1093 goto done; 1094 } 1095 1096 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1097 if (sc == NULL) { 1098 /* 1099 * The zone allocator couldn't provide more entries. 1100 * Treat this as if the cache was full; drop the oldest 1101 * entry and insert the new one. 1102 */ 1103 TCPSTAT_INC(tcps_sc_zonefail); 1104 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1105 syncache_drop(sc, sch); 1106 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1107 if (sc == NULL) { 1108 if (V_tcp_syncookies) { 1109 bzero(&scs, sizeof(scs)); 1110 sc = &scs; 1111 } else { 1112 SCH_UNLOCK(sch); 1113 if (ipopts) 1114 (void) m_free(ipopts); 1115 goto done; 1116 } 1117 } 1118 } 1119 1120 /* 1121 * Fill in the syncache values. 1122 */ 1123 #ifdef MAC 1124 sc->sc_label = maclabel; 1125 #endif 1126 sc->sc_cred = cred; 1127 cred = NULL; 1128 sc->sc_ipopts = ipopts; 1129 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1130 #ifdef INET6 1131 if (!(inc->inc_flags & INC_ISIPV6)) 1132 #endif 1133 { 1134 sc->sc_ip_tos = ip_tos; 1135 sc->sc_ip_ttl = ip_ttl; 1136 } 1137 #ifndef TCP_OFFLOAD_DISABLE 1138 sc->sc_tu = tu; 1139 sc->sc_toepcb = toepcb; 1140 #endif 1141 sc->sc_irs = th->th_seq; 1142 sc->sc_iss = arc4random(); 1143 sc->sc_flags = 0; 1144 sc->sc_flowlabel = 0; 1145 1146 /* 1147 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1148 * win was derived from socket earlier in the function. 1149 */ 1150 win = imax(win, 0); 1151 win = imin(win, TCP_MAXWIN); 1152 sc->sc_wnd = win; 1153 1154 if (V_tcp_do_rfc1323) { 1155 /* 1156 * A timestamp received in a SYN makes 1157 * it ok to send timestamp requests and replies. 1158 */ 1159 if (to->to_flags & TOF_TS) { 1160 sc->sc_tsreflect = to->to_tsval; 1161 sc->sc_ts = ticks; 1162 sc->sc_flags |= SCF_TIMESTAMP; 1163 } 1164 if (to->to_flags & TOF_SCALE) { 1165 int wscale = 0; 1166 1167 /* 1168 * Pick the smallest possible scaling factor that 1169 * will still allow us to scale up to sb_max, aka 1170 * kern.ipc.maxsockbuf. 1171 * 1172 * We do this because there are broken firewalls that 1173 * will corrupt the window scale option, leading to 1174 * the other endpoint believing that our advertised 1175 * window is unscaled. At scale factors larger than 1176 * 5 the unscaled window will drop below 1500 bytes, 1177 * leading to serious problems when traversing these 1178 * broken firewalls. 1179 * 1180 * With the default maxsockbuf of 256K, a scale factor 1181 * of 3 will be chosen by this algorithm. Those who 1182 * choose a larger maxsockbuf should watch out 1183 * for the compatiblity problems mentioned above. 1184 * 1185 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1186 * or <SYN,ACK>) segment itself is never scaled. 1187 */ 1188 while (wscale < TCP_MAX_WINSHIFT && 1189 (TCP_MAXWIN << wscale) < sb_max) 1190 wscale++; 1191 sc->sc_requested_r_scale = wscale; 1192 sc->sc_requested_s_scale = to->to_wscale; 1193 sc->sc_flags |= SCF_WINSCALE; 1194 } 1195 } 1196 #ifdef TCP_SIGNATURE 1197 /* 1198 * If listening socket requested TCP digests, and received SYN 1199 * contains the option, flag this in the syncache so that 1200 * syncache_respond() will do the right thing with the SYN+ACK. 1201 * XXX: Currently we always record the option by default and will 1202 * attempt to use it in syncache_respond(). 1203 */ 1204 if (to->to_flags & TOF_SIGNATURE) 1205 sc->sc_flags |= SCF_SIGNATURE; 1206 #endif 1207 if (to->to_flags & TOF_SACKPERM) 1208 sc->sc_flags |= SCF_SACK; 1209 if (to->to_flags & TOF_MSS) 1210 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1211 if (noopt) 1212 sc->sc_flags |= SCF_NOOPT; 1213 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1214 sc->sc_flags |= SCF_ECN; 1215 1216 if (V_tcp_syncookies) { 1217 syncookie_generate(sch, sc, &flowtmp); 1218 #ifdef INET6 1219 if (autoflowlabel) 1220 sc->sc_flowlabel = flowtmp; 1221 #endif 1222 } else { 1223 #ifdef INET6 1224 if (autoflowlabel) 1225 sc->sc_flowlabel = 1226 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1227 #endif 1228 } 1229 SCH_UNLOCK(sch); 1230 1231 /* 1232 * Do a standard 3-way handshake. 1233 */ 1234 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1235 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1236 syncache_free(sc); 1237 else if (sc != &scs) 1238 syncache_insert(sc, sch); /* locks and unlocks sch */ 1239 TCPSTAT_INC(tcps_sndacks); 1240 TCPSTAT_INC(tcps_sndtotal); 1241 } else { 1242 if (sc != &scs) 1243 syncache_free(sc); 1244 TCPSTAT_INC(tcps_sc_dropped); 1245 } 1246 1247 done: 1248 if (cred != NULL) 1249 crfree(cred); 1250 #ifdef MAC 1251 if (sc == &scs) 1252 mac_syncache_destroy(&maclabel); 1253 #endif 1254 if (m) { 1255 1256 *lsop = NULL; 1257 m_freem(m); 1258 } 1259 } 1260 1261 static int 1262 syncache_respond(struct syncache *sc) 1263 { 1264 struct ip *ip = NULL; 1265 struct mbuf *m; 1266 struct tcphdr *th; 1267 int optlen, error; 1268 u_int16_t hlen, tlen, mssopt; 1269 struct tcpopt to; 1270 #ifdef INET6 1271 struct ip6_hdr *ip6 = NULL; 1272 #endif 1273 1274 hlen = 1275 #ifdef INET6 1276 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1277 #endif 1278 sizeof(struct ip); 1279 tlen = hlen + sizeof(struct tcphdr); 1280 1281 /* Determine MSS we advertize to other end of connection. */ 1282 mssopt = tcp_mssopt(&sc->sc_inc); 1283 if (sc->sc_peer_mss) 1284 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1285 1286 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1287 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1288 ("syncache: mbuf too small")); 1289 1290 /* Create the IP+TCP header from scratch. */ 1291 m = m_gethdr(M_DONTWAIT, MT_DATA); 1292 if (m == NULL) 1293 return (ENOBUFS); 1294 #ifdef MAC 1295 mac_syncache_create_mbuf(sc->sc_label, m); 1296 #endif 1297 m->m_data += max_linkhdr; 1298 m->m_len = tlen; 1299 m->m_pkthdr.len = tlen; 1300 m->m_pkthdr.rcvif = NULL; 1301 1302 #ifdef INET6 1303 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1304 ip6 = mtod(m, struct ip6_hdr *); 1305 ip6->ip6_vfc = IPV6_VERSION; 1306 ip6->ip6_nxt = IPPROTO_TCP; 1307 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1308 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1309 ip6->ip6_plen = htons(tlen - hlen); 1310 /* ip6_hlim is set after checksum */ 1311 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1312 ip6->ip6_flow |= sc->sc_flowlabel; 1313 1314 th = (struct tcphdr *)(ip6 + 1); 1315 } else 1316 #endif 1317 { 1318 ip = mtod(m, struct ip *); 1319 ip->ip_v = IPVERSION; 1320 ip->ip_hl = sizeof(struct ip) >> 2; 1321 ip->ip_len = tlen; 1322 ip->ip_id = 0; 1323 ip->ip_off = 0; 1324 ip->ip_sum = 0; 1325 ip->ip_p = IPPROTO_TCP; 1326 ip->ip_src = sc->sc_inc.inc_laddr; 1327 ip->ip_dst = sc->sc_inc.inc_faddr; 1328 ip->ip_ttl = sc->sc_ip_ttl; 1329 ip->ip_tos = sc->sc_ip_tos; 1330 1331 /* 1332 * See if we should do MTU discovery. Route lookups are 1333 * expensive, so we will only unset the DF bit if: 1334 * 1335 * 1) path_mtu_discovery is disabled 1336 * 2) the SCF_UNREACH flag has been set 1337 */ 1338 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1339 ip->ip_off |= IP_DF; 1340 1341 th = (struct tcphdr *)(ip + 1); 1342 } 1343 th->th_sport = sc->sc_inc.inc_lport; 1344 th->th_dport = sc->sc_inc.inc_fport; 1345 1346 th->th_seq = htonl(sc->sc_iss); 1347 th->th_ack = htonl(sc->sc_irs + 1); 1348 th->th_off = sizeof(struct tcphdr) >> 2; 1349 th->th_x2 = 0; 1350 th->th_flags = TH_SYN|TH_ACK; 1351 th->th_win = htons(sc->sc_wnd); 1352 th->th_urp = 0; 1353 1354 if (sc->sc_flags & SCF_ECN) { 1355 th->th_flags |= TH_ECE; 1356 TCPSTAT_INC(tcps_ecn_shs); 1357 } 1358 1359 /* Tack on the TCP options. */ 1360 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1361 to.to_flags = 0; 1362 1363 to.to_mss = mssopt; 1364 to.to_flags = TOF_MSS; 1365 if (sc->sc_flags & SCF_WINSCALE) { 1366 to.to_wscale = sc->sc_requested_r_scale; 1367 to.to_flags |= TOF_SCALE; 1368 } 1369 if (sc->sc_flags & SCF_TIMESTAMP) { 1370 /* Virgin timestamp or TCP cookie enhanced one. */ 1371 to.to_tsval = sc->sc_ts; 1372 to.to_tsecr = sc->sc_tsreflect; 1373 to.to_flags |= TOF_TS; 1374 } 1375 if (sc->sc_flags & SCF_SACK) 1376 to.to_flags |= TOF_SACKPERM; 1377 #ifdef TCP_SIGNATURE 1378 if (sc->sc_flags & SCF_SIGNATURE) 1379 to.to_flags |= TOF_SIGNATURE; 1380 #endif 1381 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1382 1383 /* Adjust headers by option size. */ 1384 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1385 m->m_len += optlen; 1386 m->m_pkthdr.len += optlen; 1387 1388 #ifdef TCP_SIGNATURE 1389 if (sc->sc_flags & SCF_SIGNATURE) 1390 tcp_signature_compute(m, 0, 0, optlen, 1391 to.to_signature, IPSEC_DIR_OUTBOUND); 1392 #endif 1393 #ifdef INET6 1394 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1395 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1396 else 1397 #endif 1398 ip->ip_len += optlen; 1399 } else 1400 optlen = 0; 1401 1402 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1403 #ifdef INET6 1404 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1405 th->th_sum = 0; 1406 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1407 tlen + optlen - hlen); 1408 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1409 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1410 } else 1411 #endif 1412 { 1413 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1414 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1415 m->m_pkthdr.csum_flags = CSUM_TCP; 1416 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1417 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1418 } 1419 return (error); 1420 } 1421 1422 void 1423 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1424 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1425 { 1426 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1427 } 1428 1429 void 1430 tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo, 1431 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1432 struct toe_usrreqs *tu, void *toepcb) 1433 { 1434 struct tcpopt to; 1435 1436 bzero(&to, sizeof(struct tcpopt)); 1437 to.to_mss = toeo->to_mss; 1438 to.to_wscale = toeo->to_wscale; 1439 to.to_flags = toeo->to_flags; 1440 1441 INP_INFO_WLOCK(&V_tcbinfo); 1442 INP_WLOCK(inp); 1443 1444 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb); 1445 } 1446 1447 /* 1448 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1449 * receive and to be able to handle SYN floods from bogus source addresses 1450 * (where we will never receive any reply). SYN floods try to exhaust all 1451 * our memory and available slots in the SYN cache table to cause a denial 1452 * of service to legitimate users of the local host. 1453 * 1454 * The idea of SYN cookies is to encode and include all necessary information 1455 * about the connection setup state within the SYN-ACK we send back and thus 1456 * to get along without keeping any local state until the ACK to the SYN-ACK 1457 * arrives (if ever). Everything we need to know should be available from 1458 * the information we encoded in the SYN-ACK. 1459 * 1460 * More information about the theory behind SYN cookies and its first 1461 * discussion and specification can be found at: 1462 * http://cr.yp.to/syncookies.html (overview) 1463 * http://cr.yp.to/syncookies/archive (gory details) 1464 * 1465 * This implementation extends the orginal idea and first implementation 1466 * of FreeBSD by using not only the initial sequence number field to store 1467 * information but also the timestamp field if present. This way we can 1468 * keep track of the entire state we need to know to recreate the session in 1469 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1470 * these days. For those that do not we still have to live with the known 1471 * shortcomings of the ISN only SYN cookies. 1472 * 1473 * Cookie layers: 1474 * 1475 * Initial sequence number we send: 1476 * 31|................................|0 1477 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1478 * D = MD5 Digest (first dword) 1479 * M = MSS index 1480 * R = Rotation of secret 1481 * P = Odd or Even secret 1482 * 1483 * The MD5 Digest is computed with over following parameters: 1484 * a) randomly rotated secret 1485 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1486 * c) the received initial sequence number from remote host 1487 * d) the rotation offset and odd/even bit 1488 * 1489 * Timestamp we send: 1490 * 31|................................|0 1491 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1492 * D = MD5 Digest (third dword) (only as filler) 1493 * S = Requested send window scale 1494 * R = Requested receive window scale 1495 * A = SACK allowed 1496 * 5 = TCP-MD5 enabled (not implemented yet) 1497 * XORed with MD5 Digest (forth dword) 1498 * 1499 * The timestamp isn't cryptographically secure and doesn't need to be. 1500 * The double use of the MD5 digest dwords ties it to a specific remote/ 1501 * local host/port, remote initial sequence number and our local time 1502 * limited secret. A received timestamp is reverted (XORed) and then 1503 * the contained MD5 dword is compared to the computed one to ensure the 1504 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1505 * have been tampered with but this isn't different from supplying bogus 1506 * values in the SYN in the first place. 1507 * 1508 * Some problems with SYN cookies remain however: 1509 * Consider the problem of a recreated (and retransmitted) cookie. If the 1510 * original SYN was accepted, the connection is established. The second 1511 * SYN is inflight, and if it arrives with an ISN that falls within the 1512 * receive window, the connection is killed. 1513 * 1514 * Notes: 1515 * A heuristic to determine when to accept syn cookies is not necessary. 1516 * An ACK flood would cause the syncookie verification to be attempted, 1517 * but a SYN flood causes syncookies to be generated. Both are of equal 1518 * cost, so there's no point in trying to optimize the ACK flood case. 1519 * Also, if you don't process certain ACKs for some reason, then all someone 1520 * would have to do is launch a SYN and ACK flood at the same time, which 1521 * would stop cookie verification and defeat the entire purpose of syncookies. 1522 */ 1523 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1524 1525 static void 1526 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1527 u_int32_t *flowlabel) 1528 { 1529 MD5_CTX ctx; 1530 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1531 u_int32_t data; 1532 u_int32_t *secbits; 1533 u_int off, pmss, mss; 1534 int i; 1535 1536 SCH_LOCK_ASSERT(sch); 1537 1538 /* Which of the two secrets to use. */ 1539 secbits = sch->sch_oddeven ? 1540 sch->sch_secbits_odd : sch->sch_secbits_even; 1541 1542 /* Reseed secret if too old. */ 1543 if (sch->sch_reseed < time_uptime) { 1544 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1545 secbits = sch->sch_oddeven ? 1546 sch->sch_secbits_odd : sch->sch_secbits_even; 1547 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1548 secbits[i] = arc4random(); 1549 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1550 } 1551 1552 /* Secret rotation offset. */ 1553 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1554 1555 /* Maximum segment size calculation. */ 1556 pmss = 1557 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1558 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1559 if (tcp_sc_msstab[mss] <= pmss) 1560 break; 1561 1562 /* Fold parameters and MD5 digest into the ISN we will send. */ 1563 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1564 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1565 data |= mss << 4; /* mss, 3 bits */ 1566 1567 MD5Init(&ctx); 1568 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1569 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1570 MD5Update(&ctx, secbits, off); 1571 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1572 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1573 MD5Update(&ctx, &data, sizeof(data)); 1574 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1575 1576 data |= (md5_buffer[0] << 7); 1577 sc->sc_iss = data; 1578 1579 #ifdef INET6 1580 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1581 #endif 1582 1583 /* Additional parameters are stored in the timestamp if present. */ 1584 if (sc->sc_flags & SCF_TIMESTAMP) { 1585 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1586 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1587 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1588 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1589 data |= md5_buffer[2] << 10; /* more digest bits */ 1590 data ^= md5_buffer[3]; 1591 sc->sc_ts = data; 1592 sc->sc_tsoff = data - ticks; /* after XOR */ 1593 } 1594 1595 TCPSTAT_INC(tcps_sc_sendcookie); 1596 } 1597 1598 static struct syncache * 1599 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1600 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1601 struct socket *so) 1602 { 1603 MD5_CTX ctx; 1604 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1605 u_int32_t data = 0; 1606 u_int32_t *secbits; 1607 tcp_seq ack, seq; 1608 int off, mss, wnd, flags; 1609 1610 SCH_LOCK_ASSERT(sch); 1611 1612 /* 1613 * Pull information out of SYN-ACK/ACK and 1614 * revert sequence number advances. 1615 */ 1616 ack = th->th_ack - 1; 1617 seq = th->th_seq - 1; 1618 off = (ack >> 1) & 0x7; 1619 mss = (ack >> 4) & 0x7; 1620 flags = ack & 0x7f; 1621 1622 /* Which of the two secrets to use. */ 1623 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1624 1625 /* 1626 * The secret wasn't updated for the lifetime of a syncookie, 1627 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1628 */ 1629 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1630 return (NULL); 1631 } 1632 1633 /* Recompute the digest so we can compare it. */ 1634 MD5Init(&ctx); 1635 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1636 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1637 MD5Update(&ctx, secbits, off); 1638 MD5Update(&ctx, inc, sizeof(*inc)); 1639 MD5Update(&ctx, &seq, sizeof(seq)); 1640 MD5Update(&ctx, &flags, sizeof(flags)); 1641 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1642 1643 /* Does the digest part of or ACK'ed ISS match? */ 1644 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1645 return (NULL); 1646 1647 /* Does the digest part of our reflected timestamp match? */ 1648 if (to->to_flags & TOF_TS) { 1649 data = md5_buffer[3] ^ to->to_tsecr; 1650 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1651 return (NULL); 1652 } 1653 1654 /* Fill in the syncache values. */ 1655 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1656 sc->sc_ipopts = NULL; 1657 1658 sc->sc_irs = seq; 1659 sc->sc_iss = ack; 1660 1661 #ifdef INET6 1662 if (inc->inc_flags & INC_ISIPV6) { 1663 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1664 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1665 } else 1666 #endif 1667 { 1668 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1669 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1670 } 1671 1672 /* Additional parameters that were encoded in the timestamp. */ 1673 if (data) { 1674 sc->sc_flags |= SCF_TIMESTAMP; 1675 sc->sc_tsreflect = to->to_tsval; 1676 sc->sc_ts = to->to_tsecr; 1677 sc->sc_tsoff = to->to_tsecr - ticks; 1678 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1679 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1680 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1681 TCP_MAX_WINSHIFT); 1682 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1683 TCP_MAX_WINSHIFT); 1684 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1685 sc->sc_flags |= SCF_WINSCALE; 1686 } else 1687 sc->sc_flags |= SCF_NOOPT; 1688 1689 wnd = sbspace(&so->so_rcv); 1690 wnd = imax(wnd, 0); 1691 wnd = imin(wnd, TCP_MAXWIN); 1692 sc->sc_wnd = wnd; 1693 1694 sc->sc_rxmits = 0; 1695 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1696 1697 TCPSTAT_INC(tcps_sc_recvcookie); 1698 return (sc); 1699 } 1700 1701 /* 1702 * Returns the current number of syncache entries. This number 1703 * will probably change before you get around to calling 1704 * syncache_pcblist. 1705 */ 1706 1707 int 1708 syncache_pcbcount(void) 1709 { 1710 struct syncache_head *sch; 1711 int count, i; 1712 1713 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1714 /* No need to lock for a read. */ 1715 sch = &V_tcp_syncache.hashbase[i]; 1716 count += sch->sch_length; 1717 } 1718 return count; 1719 } 1720 1721 /* 1722 * Exports the syncache entries to userland so that netstat can display 1723 * them alongside the other sockets. This function is intended to be 1724 * called only from tcp_pcblist. 1725 * 1726 * Due to concurrency on an active system, the number of pcbs exported 1727 * may have no relation to max_pcbs. max_pcbs merely indicates the 1728 * amount of space the caller allocated for this function to use. 1729 */ 1730 int 1731 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1732 { 1733 struct xtcpcb xt; 1734 struct syncache *sc; 1735 struct syncache_head *sch; 1736 int count, error, i; 1737 1738 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1739 sch = &V_tcp_syncache.hashbase[i]; 1740 SCH_LOCK(sch); 1741 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1742 if (count >= max_pcbs) { 1743 SCH_UNLOCK(sch); 1744 goto exit; 1745 } 1746 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1747 continue; 1748 bzero(&xt, sizeof(xt)); 1749 xt.xt_len = sizeof(xt); 1750 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1751 xt.xt_inp.inp_vflag = INP_IPV6; 1752 else 1753 xt.xt_inp.inp_vflag = INP_IPV4; 1754 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1755 xt.xt_tp.t_inpcb = &xt.xt_inp; 1756 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1757 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1758 xt.xt_socket.xso_len = sizeof (struct xsocket); 1759 xt.xt_socket.so_type = SOCK_STREAM; 1760 xt.xt_socket.so_state = SS_ISCONNECTING; 1761 error = SYSCTL_OUT(req, &xt, sizeof xt); 1762 if (error) { 1763 SCH_UNLOCK(sch); 1764 goto exit; 1765 } 1766 count++; 1767 } 1768 SCH_UNLOCK(sch); 1769 } 1770 exit: 1771 *pcbs_exported = count; 1772 return error; 1773 }
Cache object: 3b110e604db658bc72562faedacff737
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