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