tcp_syncache.c revision 193332
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: head/sys/netinet/tcp_syncache.c 193332 2009-06-02 18:26:17Z rwatson $"); 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 103static struct tcp_syncache tcp_syncache; 104static int tcp_syncookies; 105static int tcp_syncookiesonly; 106int tcp_sc_rst_sock_fail; 107#endif 108 109SYSCTL_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 113SYSCTL_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 123static void syncache_drop(struct syncache *, struct syncache_head *); 124static void syncache_free(struct syncache *); 125static void syncache_insert(struct syncache *, struct syncache_head *); 126struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 127static int syncache_respond(struct syncache *); 128static struct socket *syncache_socket(struct syncache *, struct socket *, 129 struct mbuf *m); 130static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 131 int docallout); 132static void syncache_timer(void *); 133static void syncookie_generate(struct syncache_head *, struct syncache *, 134 u_int32_t *); 135static 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 151SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 152 153SYSCTL_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 157SYSCTL_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 161SYSCTL_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 165SYSCTL_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 169SYSCTL_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 173SYSCTL_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 177static 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 */ 207static void 208syncache_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 223void 224syncache_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 */ 283static void 284syncache_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 */ 322static void 323syncache_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 */ 343static void 344syncache_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 */ 362static void 363syncache_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 */ 428struct syncache * 429syncache_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 */ 476void 477syncache_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 545done: 546 if (s != NULL) 547 free(s, M_TCPLOG); 548 SCH_UNLOCK(sch); 549} 550 551void 552syncache_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 567void 568syncache_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); 597done: 598 SCH_UNLOCK(sch); 599} 600 601/* 602 * Build a new TCP socket structure from a syncache entry. 603 */ 604static struct socket * 605syncache_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 mac_socketpeer_set_from_mbuf(m, so); 639#endif 640 641 inp = sotoinpcb(so); 642 inp->inp_inc.inc_fibnum = sc->sc_inc.inc_fibnum; 643 so->so_fibnum = sc->sc_inc.inc_fibnum; 644 INP_WLOCK(inp); 645 646 /* Insert new socket into PCB hash list. */ 647 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 648#ifdef INET6 649 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 650 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 651 } else { 652 inp->inp_vflag &= ~INP_IPV6; 653 inp->inp_vflag |= INP_IPV4; 654#endif 655 inp->inp_laddr = sc->sc_inc.inc_laddr; 656#ifdef INET6 657 } 658#endif 659 inp->inp_lport = sc->sc_inc.inc_lport; 660 if (in_pcbinshash(inp) != 0) { 661 /* 662 * Undo the assignments above if we failed to 663 * put the PCB on the hash lists. 664 */ 665#ifdef INET6 666 if (sc->sc_inc.inc_flags & INC_ISIPV6) 667 inp->in6p_laddr = in6addr_any; 668 else 669#endif 670 inp->inp_laddr.s_addr = INADDR_ANY; 671 inp->inp_lport = 0; 672 goto abort; 673 } 674#ifdef IPSEC 675 /* Copy old policy into new socket's. */ 676 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 677 printf("syncache_socket: could not copy policy\n"); 678#endif 679#ifdef INET6 680 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 681 struct inpcb *oinp = sotoinpcb(lso); 682 struct in6_addr laddr6; 683 struct sockaddr_in6 sin6; 684 /* 685 * Inherit socket options from the listening socket. 686 * Note that in6p_inputopts are not (and should not be) 687 * copied, since it stores previously received options and is 688 * used to detect if each new option is different than the 689 * previous one and hence should be passed to a user. 690 * If we copied in6p_inputopts, a user would not be able to 691 * receive options just after calling the accept system call. 692 */ 693 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 694 if (oinp->in6p_outputopts) 695 inp->in6p_outputopts = 696 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 697 698 sin6.sin6_family = AF_INET6; 699 sin6.sin6_len = sizeof(sin6); 700 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 701 sin6.sin6_port = sc->sc_inc.inc_fport; 702 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 703 laddr6 = inp->in6p_laddr; 704 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 705 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 706 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 707 thread0.td_ucred)) { 708 inp->in6p_laddr = laddr6; 709 goto abort; 710 } 711 /* Override flowlabel from in6_pcbconnect. */ 712 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 713 inp->inp_flow |= sc->sc_flowlabel; 714 } else 715#endif 716 { 717 struct in_addr laddr; 718 struct sockaddr_in sin; 719 720 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 721 722 if (inp->inp_options == NULL) { 723 inp->inp_options = sc->sc_ipopts; 724 sc->sc_ipopts = NULL; 725 } 726 727 sin.sin_family = AF_INET; 728 sin.sin_len = sizeof(sin); 729 sin.sin_addr = sc->sc_inc.inc_faddr; 730 sin.sin_port = sc->sc_inc.inc_fport; 731 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 732 laddr = inp->inp_laddr; 733 if (inp->inp_laddr.s_addr == INADDR_ANY) 734 inp->inp_laddr = sc->sc_inc.inc_laddr; 735 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 736 thread0.td_ucred)) { 737 inp->inp_laddr = laddr; 738 goto abort; 739 } 740 } 741 tp = intotcpcb(inp); 742 tp->t_state = TCPS_SYN_RECEIVED; 743 tp->iss = sc->sc_iss; 744 tp->irs = sc->sc_irs; 745 tcp_rcvseqinit(tp); 746 tcp_sendseqinit(tp); 747 tp->snd_wl1 = sc->sc_irs; 748 tp->snd_max = tp->iss + 1; 749 tp->snd_nxt = tp->iss + 1; 750 tp->rcv_up = sc->sc_irs + 1; 751 tp->rcv_wnd = sc->sc_wnd; 752 tp->rcv_adv += tp->rcv_wnd; 753 tp->last_ack_sent = tp->rcv_nxt; 754 755 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 756 if (sc->sc_flags & SCF_NOOPT) 757 tp->t_flags |= TF_NOOPT; 758 else { 759 if (sc->sc_flags & SCF_WINSCALE) { 760 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 761 tp->snd_scale = sc->sc_requested_s_scale; 762 tp->request_r_scale = sc->sc_requested_r_scale; 763 } 764 if (sc->sc_flags & SCF_TIMESTAMP) { 765 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 766 tp->ts_recent = sc->sc_tsreflect; 767 tp->ts_recent_age = ticks; 768 tp->ts_offset = sc->sc_tsoff; 769 } 770#ifdef TCP_SIGNATURE 771 if (sc->sc_flags & SCF_SIGNATURE) 772 tp->t_flags |= TF_SIGNATURE; 773#endif 774 if (sc->sc_flags & SCF_SACK) 775 tp->t_flags |= TF_SACK_PERMIT; 776 } 777 778 if (sc->sc_flags & SCF_ECN) 779 tp->t_flags |= TF_ECN_PERMIT; 780 781 /* 782 * Set up MSS and get cached values from tcp_hostcache. 783 * This might overwrite some of the defaults we just set. 784 */ 785 tcp_mss(tp, sc->sc_peer_mss); 786 787 /* 788 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 789 */ 790 if (sc->sc_rxmits) 791 tp->snd_cwnd = tp->t_maxseg; 792 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 793 794 INP_WUNLOCK(inp); 795 796 TCPSTAT_INC(tcps_accepts); 797 return (so); 798 799abort: 800 INP_WUNLOCK(inp); 801abort2: 802 if (so != NULL) 803 soabort(so); 804 return (NULL); 805} 806 807/* 808 * This function gets called when we receive an ACK for a 809 * socket in the LISTEN state. We look up the connection 810 * in the syncache, and if its there, we pull it out of 811 * the cache and turn it into a full-blown connection in 812 * the SYN-RECEIVED state. 813 */ 814int 815syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 816 struct socket **lsop, struct mbuf *m) 817{ 818 INIT_VNET_INET(curvnet); 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); 924failed: 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 933int 934tcp_offload_syncache_expand(struct in_conninfo *inc, struct tcpopt *to, 935 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 936{ 937 INIT_VNET_INET(curvnet); 938 int rc; 939 940 INP_INFO_WLOCK(&V_tcbinfo); 941 rc = syncache_expand(inc, to, th, lsop, m); 942 INP_INFO_WUNLOCK(&V_tcbinfo); 943 944 return (rc); 945} 946 947/* 948 * Given a LISTEN socket and an inbound SYN request, add 949 * this to the syn cache, and send back a segment: 950 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 951 * to the source. 952 * 953 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 954 * Doing so would require that we hold onto the data and deliver it 955 * to the application. However, if we are the target of a SYN-flood 956 * DoS attack, an attacker could send data which would eventually 957 * consume all available buffer space if it were ACKed. By not ACKing 958 * the data, we avoid this DoS scenario. 959 */ 960static void 961_syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 962 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 963 struct toe_usrreqs *tu, void *toepcb) 964{ 965 INIT_VNET_INET(inp->inp_vnet); 966 struct tcpcb *tp; 967 struct socket *so; 968 struct syncache *sc = NULL; 969 struct syncache_head *sch; 970 struct mbuf *ipopts = NULL; 971 u_int32_t flowtmp; 972 int win, sb_hiwat, ip_ttl, ip_tos, noopt; 973 char *s; 974#ifdef INET6 975 int autoflowlabel = 0; 976#endif 977#ifdef MAC 978 struct label *maclabel; 979#endif 980 struct syncache scs; 981 struct ucred *cred; 982 983 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 984 INP_WLOCK_ASSERT(inp); /* listen socket */ 985 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 986 ("%s: unexpected tcp flags", __func__)); 987 988 /* 989 * Combine all so/tp operations very early to drop the INP lock as 990 * soon as possible. 991 */ 992 so = *lsop; 993 tp = sototcpcb(so); 994 cred = crhold(so->so_cred); 995 996#ifdef INET6 997 if ((inc->inc_flags & INC_ISIPV6) && 998 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 999 autoflowlabel = 1; 1000#endif 1001 ip_ttl = inp->inp_ip_ttl; 1002 ip_tos = inp->inp_ip_tos; 1003 win = sbspace(&so->so_rcv); 1004 sb_hiwat = so->so_rcv.sb_hiwat; 1005 noopt = (tp->t_flags & TF_NOOPT); 1006 1007 /* By the time we drop the lock these should no longer be used. */ 1008 so = NULL; 1009 tp = NULL; 1010 1011#ifdef MAC 1012 if (mac_syncache_init(&maclabel) != 0) { 1013 INP_WUNLOCK(inp); 1014 INP_INFO_WUNLOCK(&V_tcbinfo); 1015 goto done; 1016 } else 1017 mac_syncache_create(maclabel, inp); 1018#endif 1019 INP_WUNLOCK(inp); 1020 INP_INFO_WUNLOCK(&V_tcbinfo); 1021 1022 /* 1023 * Remember the IP options, if any. 1024 */ 1025#ifdef INET6 1026 if (!(inc->inc_flags & INC_ISIPV6)) 1027#endif 1028 ipopts = (m) ? ip_srcroute(m) : NULL; 1029 1030 /* 1031 * See if we already have an entry for this connection. 1032 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1033 * 1034 * XXX: should the syncache be re-initialized with the contents 1035 * of the new SYN here (which may have different options?) 1036 * 1037 * XXX: We do not check the sequence number to see if this is a 1038 * real retransmit or a new connection attempt. The question is 1039 * how to handle such a case; either ignore it as spoofed, or 1040 * drop the current entry and create a new one? 1041 */ 1042 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1043 SCH_LOCK_ASSERT(sch); 1044 if (sc != NULL) { 1045#ifndef TCP_OFFLOAD_DISABLE 1046 if (sc->sc_tu) 1047 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1048 sc->sc_toepcb); 1049#endif 1050 TCPSTAT_INC(tcps_sc_dupsyn); 1051 if (ipopts) { 1052 /* 1053 * If we were remembering a previous source route, 1054 * forget it and use the new one we've been given. 1055 */ 1056 if (sc->sc_ipopts) 1057 (void) m_free(sc->sc_ipopts); 1058 sc->sc_ipopts = ipopts; 1059 } 1060 /* 1061 * Update timestamp if present. 1062 */ 1063 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1064 sc->sc_tsreflect = to->to_tsval; 1065 else 1066 sc->sc_flags &= ~SCF_TIMESTAMP; 1067#ifdef MAC 1068 /* 1069 * Since we have already unconditionally allocated label 1070 * storage, free it up. The syncache entry will already 1071 * have an initialized label we can use. 1072 */ 1073 mac_syncache_destroy(&maclabel); 1074#endif 1075 /* Retransmit SYN|ACK and reset retransmit count. */ 1076 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1077 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1078 "resetting timer and retransmitting SYN|ACK\n", 1079 s, __func__); 1080 free(s, M_TCPLOG); 1081 } 1082 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1083 sc->sc_rxmits = 0; 1084 syncache_timeout(sc, sch, 1); 1085 TCPSTAT_INC(tcps_sndacks); 1086 TCPSTAT_INC(tcps_sndtotal); 1087 } 1088 SCH_UNLOCK(sch); 1089 goto done; 1090 } 1091 1092 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1093 if (sc == NULL) { 1094 /* 1095 * The zone allocator couldn't provide more entries. 1096 * Treat this as if the cache was full; drop the oldest 1097 * entry and insert the new one. 1098 */ 1099 TCPSTAT_INC(tcps_sc_zonefail); 1100 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1101 syncache_drop(sc, sch); 1102 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1103 if (sc == NULL) { 1104 if (V_tcp_syncookies) { 1105 bzero(&scs, sizeof(scs)); 1106 sc = &scs; 1107 } else { 1108 SCH_UNLOCK(sch); 1109 if (ipopts) 1110 (void) m_free(ipopts); 1111 goto done; 1112 } 1113 } 1114 } 1115 1116 /* 1117 * Fill in the syncache values. 1118 */ 1119#ifdef MAC 1120 sc->sc_label = maclabel; 1121#endif 1122 sc->sc_cred = cred; 1123 cred = NULL; 1124 sc->sc_ipopts = ipopts; 1125 /* XXX-BZ this fib assignment is just useless. */ 1126 sc->sc_inc.inc_fibnum = inp->inp_inc.inc_fibnum; 1127 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1128#ifdef INET6 1129 if (!(inc->inc_flags & INC_ISIPV6)) 1130#endif 1131 { 1132 sc->sc_ip_tos = ip_tos; 1133 sc->sc_ip_ttl = ip_ttl; 1134 } 1135#ifndef TCP_OFFLOAD_DISABLE 1136 sc->sc_tu = tu; 1137 sc->sc_toepcb = toepcb; 1138#endif 1139 sc->sc_irs = th->th_seq; 1140 sc->sc_iss = arc4random(); 1141 sc->sc_flags = 0; 1142 sc->sc_flowlabel = 0; 1143 1144 /* 1145 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1146 * win was derived from socket earlier in the function. 1147 */ 1148 win = imax(win, 0); 1149 win = imin(win, TCP_MAXWIN); 1150 sc->sc_wnd = win; 1151 1152 if (V_tcp_do_rfc1323) { 1153 /* 1154 * A timestamp received in a SYN makes 1155 * it ok to send timestamp requests and replies. 1156 */ 1157 if (to->to_flags & TOF_TS) { 1158 sc->sc_tsreflect = to->to_tsval; 1159 sc->sc_ts = ticks; 1160 sc->sc_flags |= SCF_TIMESTAMP; 1161 } 1162 if (to->to_flags & TOF_SCALE) { 1163 int wscale = 0; 1164 1165 /* 1166 * Pick the smallest possible scaling factor that 1167 * will still allow us to scale up to sb_max, aka 1168 * kern.ipc.maxsockbuf. 1169 * 1170 * We do this because there are broken firewalls that 1171 * will corrupt the window scale option, leading to 1172 * the other endpoint believing that our advertised 1173 * window is unscaled. At scale factors larger than 1174 * 5 the unscaled window will drop below 1500 bytes, 1175 * leading to serious problems when traversing these 1176 * broken firewalls. 1177 * 1178 * With the default maxsockbuf of 256K, a scale factor 1179 * of 3 will be chosen by this algorithm. Those who 1180 * choose a larger maxsockbuf should watch out 1181 * for the compatiblity problems mentioned above. 1182 * 1183 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1184 * or <SYN,ACK>) segment itself is never scaled. 1185 */ 1186 while (wscale < TCP_MAX_WINSHIFT && 1187 (TCP_MAXWIN << wscale) < sb_max) 1188 wscale++; 1189 sc->sc_requested_r_scale = wscale; 1190 sc->sc_requested_s_scale = to->to_wscale; 1191 sc->sc_flags |= SCF_WINSCALE; 1192 } 1193 } 1194#ifdef TCP_SIGNATURE 1195 /* 1196 * If listening socket requested TCP digests, and received SYN 1197 * contains the option, flag this in the syncache so that 1198 * syncache_respond() will do the right thing with the SYN+ACK. 1199 * XXX: Currently we always record the option by default and will 1200 * attempt to use it in syncache_respond(). 1201 */ 1202 if (to->to_flags & TOF_SIGNATURE) 1203 sc->sc_flags |= SCF_SIGNATURE; 1204#endif 1205 if (to->to_flags & TOF_SACKPERM) 1206 sc->sc_flags |= SCF_SACK; 1207 if (to->to_flags & TOF_MSS) 1208 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1209 if (noopt) 1210 sc->sc_flags |= SCF_NOOPT; 1211 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1212 sc->sc_flags |= SCF_ECN; 1213 1214 if (V_tcp_syncookies) { 1215 syncookie_generate(sch, sc, &flowtmp); 1216#ifdef INET6 1217 if (autoflowlabel) 1218 sc->sc_flowlabel = flowtmp; 1219#endif 1220 } else { 1221#ifdef INET6 1222 if (autoflowlabel) 1223 sc->sc_flowlabel = 1224 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1225#endif 1226 } 1227 SCH_UNLOCK(sch); 1228 1229 /* 1230 * Do a standard 3-way handshake. 1231 */ 1232 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1233 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1234 syncache_free(sc); 1235 else if (sc != &scs) 1236 syncache_insert(sc, sch); /* locks and unlocks sch */ 1237 TCPSTAT_INC(tcps_sndacks); 1238 TCPSTAT_INC(tcps_sndtotal); 1239 } else { 1240 if (sc != &scs) 1241 syncache_free(sc); 1242 TCPSTAT_INC(tcps_sc_dropped); 1243 } 1244 1245done: 1246 if (cred != NULL) 1247 crfree(cred); 1248#ifdef MAC 1249 if (sc == &scs) 1250 mac_syncache_destroy(&maclabel); 1251#endif 1252 if (m) { 1253 1254 *lsop = NULL; 1255 m_freem(m); 1256 } 1257} 1258 1259static int 1260syncache_respond(struct syncache *sc) 1261{ 1262 INIT_VNET_INET(curvnet); 1263 struct ip *ip = NULL; 1264 struct mbuf *m; 1265 struct tcphdr *th; 1266 int optlen, error; 1267 u_int16_t hlen, tlen, mssopt; 1268 struct tcpopt to; 1269#ifdef INET6 1270 struct ip6_hdr *ip6 = NULL; 1271#endif 1272 1273 hlen = 1274#ifdef INET6 1275 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1276#endif 1277 sizeof(struct ip); 1278 tlen = hlen + sizeof(struct tcphdr); 1279 1280 /* Determine MSS we advertize to other end of connection. */ 1281 mssopt = tcp_mssopt(&sc->sc_inc); 1282 if (sc->sc_peer_mss) 1283 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1284 1285 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1286 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1287 ("syncache: mbuf too small")); 1288 1289 /* Create the IP+TCP header from scratch. */ 1290 m = m_gethdr(M_DONTWAIT, MT_DATA); 1291 if (m == NULL) 1292 return (ENOBUFS); 1293#ifdef MAC 1294 mac_syncache_create_mbuf(sc->sc_label, m); 1295#endif 1296 m->m_data += max_linkhdr; 1297 m->m_len = tlen; 1298 m->m_pkthdr.len = tlen; 1299 m->m_pkthdr.rcvif = NULL; 1300 1301#ifdef INET6 1302 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1303 ip6 = mtod(m, struct ip6_hdr *); 1304 ip6->ip6_vfc = IPV6_VERSION; 1305 ip6->ip6_nxt = IPPROTO_TCP; 1306 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1307 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1308 ip6->ip6_plen = htons(tlen - hlen); 1309 /* ip6_hlim is set after checksum */ 1310 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1311 ip6->ip6_flow |= sc->sc_flowlabel; 1312 1313 th = (struct tcphdr *)(ip6 + 1); 1314 } else 1315#endif 1316 { 1317 ip = mtod(m, struct ip *); 1318 ip->ip_v = IPVERSION; 1319 ip->ip_hl = sizeof(struct ip) >> 2; 1320 ip->ip_len = tlen; 1321 ip->ip_id = 0; 1322 ip->ip_off = 0; 1323 ip->ip_sum = 0; 1324 ip->ip_p = IPPROTO_TCP; 1325 ip->ip_src = sc->sc_inc.inc_laddr; 1326 ip->ip_dst = sc->sc_inc.inc_faddr; 1327 ip->ip_ttl = sc->sc_ip_ttl; 1328 ip->ip_tos = sc->sc_ip_tos; 1329 1330 /* 1331 * See if we should do MTU discovery. Route lookups are 1332 * expensive, so we will only unset the DF bit if: 1333 * 1334 * 1) path_mtu_discovery is disabled 1335 * 2) the SCF_UNREACH flag has been set 1336 */ 1337 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1338 ip->ip_off |= IP_DF; 1339 1340 th = (struct tcphdr *)(ip + 1); 1341 } 1342 th->th_sport = sc->sc_inc.inc_lport; 1343 th->th_dport = sc->sc_inc.inc_fport; 1344 1345 th->th_seq = htonl(sc->sc_iss); 1346 th->th_ack = htonl(sc->sc_irs + 1); 1347 th->th_off = sizeof(struct tcphdr) >> 2; 1348 th->th_x2 = 0; 1349 th->th_flags = TH_SYN|TH_ACK; 1350 th->th_win = htons(sc->sc_wnd); 1351 th->th_urp = 0; 1352 1353 if (sc->sc_flags & SCF_ECN) { 1354 th->th_flags |= TH_ECE; 1355 TCPSTAT_INC(tcps_ecn_shs); 1356 } 1357 1358 /* Tack on the TCP options. */ 1359 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1360 to.to_flags = 0; 1361 1362 to.to_mss = mssopt; 1363 to.to_flags = TOF_MSS; 1364 if (sc->sc_flags & SCF_WINSCALE) { 1365 to.to_wscale = sc->sc_requested_r_scale; 1366 to.to_flags |= TOF_SCALE; 1367 } 1368 if (sc->sc_flags & SCF_TIMESTAMP) { 1369 /* Virgin timestamp or TCP cookie enhanced one. */ 1370 to.to_tsval = sc->sc_ts; 1371 to.to_tsecr = sc->sc_tsreflect; 1372 to.to_flags |= TOF_TS; 1373 } 1374 if (sc->sc_flags & SCF_SACK) 1375 to.to_flags |= TOF_SACKPERM; 1376#ifdef TCP_SIGNATURE 1377 if (sc->sc_flags & SCF_SIGNATURE) 1378 to.to_flags |= TOF_SIGNATURE; 1379#endif 1380 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1381 1382 /* Adjust headers by option size. */ 1383 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1384 m->m_len += optlen; 1385 m->m_pkthdr.len += optlen; 1386 1387#ifdef TCP_SIGNATURE 1388 if (sc->sc_flags & SCF_SIGNATURE) 1389 tcp_signature_compute(m, 0, 0, optlen, 1390 to.to_signature, IPSEC_DIR_OUTBOUND); 1391#endif 1392#ifdef INET6 1393 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1394 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1395 else 1396#endif 1397 ip->ip_len += optlen; 1398 } else 1399 optlen = 0; 1400 1401#ifdef INET6 1402 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1403 th->th_sum = 0; 1404 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1405 tlen + optlen - hlen); 1406 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1407 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1408 } else 1409#endif 1410 { 1411 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1412 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1413 m->m_pkthdr.csum_flags = CSUM_TCP; 1414 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1415 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1416 } 1417 return (error); 1418} 1419 1420void 1421syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1422 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1423{ 1424 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1425} 1426 1427void 1428tcp_offload_syncache_add(struct in_conninfo *inc, struct tcpopt *to, 1429 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1430 struct toe_usrreqs *tu, void *toepcb) 1431{ 1432 INIT_VNET_INET(curvnet); 1433 1434 INP_INFO_WLOCK(&V_tcbinfo); 1435 INP_WLOCK(inp); 1436 _syncache_add(inc, to, th, inp, lsop, NULL, tu, toepcb); 1437} 1438 1439/* 1440 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1441 * receive and to be able to handle SYN floods from bogus source addresses 1442 * (where we will never receive any reply). SYN floods try to exhaust all 1443 * our memory and available slots in the SYN cache table to cause a denial 1444 * of service to legitimate users of the local host. 1445 * 1446 * The idea of SYN cookies is to encode and include all necessary information 1447 * about the connection setup state within the SYN-ACK we send back and thus 1448 * to get along without keeping any local state until the ACK to the SYN-ACK 1449 * arrives (if ever). Everything we need to know should be available from 1450 * the information we encoded in the SYN-ACK. 1451 * 1452 * More information about the theory behind SYN cookies and its first 1453 * discussion and specification can be found at: 1454 * http://cr.yp.to/syncookies.html (overview) 1455 * http://cr.yp.to/syncookies/archive (gory details) 1456 * 1457 * This implementation extends the orginal idea and first implementation 1458 * of FreeBSD by using not only the initial sequence number field to store 1459 * information but also the timestamp field if present. This way we can 1460 * keep track of the entire state we need to know to recreate the session in 1461 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1462 * these days. For those that do not we still have to live with the known 1463 * shortcomings of the ISN only SYN cookies. 1464 * 1465 * Cookie layers: 1466 * 1467 * Initial sequence number we send: 1468 * 31|................................|0 1469 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1470 * D = MD5 Digest (first dword) 1471 * M = MSS index 1472 * R = Rotation of secret 1473 * P = Odd or Even secret 1474 * 1475 * The MD5 Digest is computed with over following parameters: 1476 * a) randomly rotated secret 1477 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1478 * c) the received initial sequence number from remote host 1479 * d) the rotation offset and odd/even bit 1480 * 1481 * Timestamp we send: 1482 * 31|................................|0 1483 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1484 * D = MD5 Digest (third dword) (only as filler) 1485 * S = Requested send window scale 1486 * R = Requested receive window scale 1487 * A = SACK allowed 1488 * 5 = TCP-MD5 enabled (not implemented yet) 1489 * XORed with MD5 Digest (forth dword) 1490 * 1491 * The timestamp isn't cryptographically secure and doesn't need to be. 1492 * The double use of the MD5 digest dwords ties it to a specific remote/ 1493 * local host/port, remote initial sequence number and our local time 1494 * limited secret. A received timestamp is reverted (XORed) and then 1495 * the contained MD5 dword is compared to the computed one to ensure the 1496 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1497 * have been tampered with but this isn't different from supplying bogus 1498 * values in the SYN in the first place. 1499 * 1500 * Some problems with SYN cookies remain however: 1501 * Consider the problem of a recreated (and retransmitted) cookie. If the 1502 * original SYN was accepted, the connection is established. The second 1503 * SYN is inflight, and if it arrives with an ISN that falls within the 1504 * receive window, the connection is killed. 1505 * 1506 * Notes: 1507 * A heuristic to determine when to accept syn cookies is not necessary. 1508 * An ACK flood would cause the syncookie verification to be attempted, 1509 * but a SYN flood causes syncookies to be generated. Both are of equal 1510 * cost, so there's no point in trying to optimize the ACK flood case. 1511 * Also, if you don't process certain ACKs for some reason, then all someone 1512 * would have to do is launch a SYN and ACK flood at the same time, which 1513 * would stop cookie verification and defeat the entire purpose of syncookies. 1514 */ 1515static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1516 1517static void 1518syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1519 u_int32_t *flowlabel) 1520{ 1521 INIT_VNET_INET(curvnet); 1522 MD5_CTX ctx; 1523 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1524 u_int32_t data; 1525 u_int32_t *secbits; 1526 u_int off, pmss, mss; 1527 int i; 1528 1529 SCH_LOCK_ASSERT(sch); 1530 1531 /* Which of the two secrets to use. */ 1532 secbits = sch->sch_oddeven ? 1533 sch->sch_secbits_odd : sch->sch_secbits_even; 1534 1535 /* Reseed secret if too old. */ 1536 if (sch->sch_reseed < time_uptime) { 1537 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1538 secbits = sch->sch_oddeven ? 1539 sch->sch_secbits_odd : sch->sch_secbits_even; 1540 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1541 secbits[i] = arc4random(); 1542 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1543 } 1544 1545 /* Secret rotation offset. */ 1546 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1547 1548 /* Maximum segment size calculation. */ 1549 pmss = 1550 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1551 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1552 if (tcp_sc_msstab[mss] <= pmss) 1553 break; 1554 1555 /* Fold parameters and MD5 digest into the ISN we will send. */ 1556 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1557 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1558 data |= mss << 4; /* mss, 3 bits */ 1559 1560 MD5Init(&ctx); 1561 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1562 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1563 MD5Update(&ctx, secbits, off); 1564 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1565 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1566 MD5Update(&ctx, &data, sizeof(data)); 1567 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1568 1569 data |= (md5_buffer[0] << 7); 1570 sc->sc_iss = data; 1571 1572#ifdef INET6 1573 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1574#endif 1575 1576 /* Additional parameters are stored in the timestamp if present. */ 1577 if (sc->sc_flags & SCF_TIMESTAMP) { 1578 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1579 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1580 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1581 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1582 data |= md5_buffer[2] << 10; /* more digest bits */ 1583 data ^= md5_buffer[3]; 1584 sc->sc_ts = data; 1585 sc->sc_tsoff = data - ticks; /* after XOR */ 1586 } 1587 1588 TCPSTAT_INC(tcps_sc_sendcookie); 1589} 1590 1591static struct syncache * 1592syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1593 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1594 struct socket *so) 1595{ 1596 INIT_VNET_INET(curvnet); 1597 MD5_CTX ctx; 1598 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1599 u_int32_t data = 0; 1600 u_int32_t *secbits; 1601 tcp_seq ack, seq; 1602 int off, mss, wnd, flags; 1603 1604 SCH_LOCK_ASSERT(sch); 1605 1606 /* 1607 * Pull information out of SYN-ACK/ACK and 1608 * revert sequence number advances. 1609 */ 1610 ack = th->th_ack - 1; 1611 seq = th->th_seq - 1; 1612 off = (ack >> 1) & 0x7; 1613 mss = (ack >> 4) & 0x7; 1614 flags = ack & 0x7f; 1615 1616 /* Which of the two secrets to use. */ 1617 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1618 1619 /* 1620 * The secret wasn't updated for the lifetime of a syncookie, 1621 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1622 */ 1623 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1624 return (NULL); 1625 } 1626 1627 /* Recompute the digest so we can compare it. */ 1628 MD5Init(&ctx); 1629 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1630 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1631 MD5Update(&ctx, secbits, off); 1632 MD5Update(&ctx, inc, sizeof(*inc)); 1633 MD5Update(&ctx, &seq, sizeof(seq)); 1634 MD5Update(&ctx, &flags, sizeof(flags)); 1635 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1636 1637 /* Does the digest part of or ACK'ed ISS match? */ 1638 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1639 return (NULL); 1640 1641 /* Does the digest part of our reflected timestamp match? */ 1642 if (to->to_flags & TOF_TS) { 1643 data = md5_buffer[3] ^ to->to_tsecr; 1644 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1645 return (NULL); 1646 } 1647 1648 /* Fill in the syncache values. */ 1649 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1650 sc->sc_ipopts = NULL; 1651 1652 sc->sc_irs = seq; 1653 sc->sc_iss = ack; 1654 1655#ifdef INET6 1656 if (inc->inc_flags & INC_ISIPV6) { 1657 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1658 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1659 } else 1660#endif 1661 { 1662 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1663 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1664 } 1665 1666 /* Additional parameters that were encoded in the timestamp. */ 1667 if (data) { 1668 sc->sc_flags |= SCF_TIMESTAMP; 1669 sc->sc_tsreflect = to->to_tsval; 1670 sc->sc_ts = to->to_tsecr; 1671 sc->sc_tsoff = to->to_tsecr - ticks; 1672 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1673 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1674 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1675 TCP_MAX_WINSHIFT); 1676 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1677 TCP_MAX_WINSHIFT); 1678 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1679 sc->sc_flags |= SCF_WINSCALE; 1680 } else 1681 sc->sc_flags |= SCF_NOOPT; 1682 1683 wnd = sbspace(&so->so_rcv); 1684 wnd = imax(wnd, 0); 1685 wnd = imin(wnd, TCP_MAXWIN); 1686 sc->sc_wnd = wnd; 1687 1688 sc->sc_rxmits = 0; 1689 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1690 1691 TCPSTAT_INC(tcps_sc_recvcookie); 1692 return (sc); 1693} 1694 1695/* 1696 * Returns the current number of syncache entries. This number 1697 * will probably change before you get around to calling 1698 * syncache_pcblist. 1699 */ 1700 1701int 1702syncache_pcbcount(void) 1703{ 1704 INIT_VNET_INET(curvnet); 1705 struct syncache_head *sch; 1706 int count, i; 1707 1708 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1709 /* No need to lock for a read. */ 1710 sch = &V_tcp_syncache.hashbase[i]; 1711 count += sch->sch_length; 1712 } 1713 return count; 1714} 1715 1716/* 1717 * Exports the syncache entries to userland so that netstat can display 1718 * them alongside the other sockets. This function is intended to be 1719 * called only from tcp_pcblist. 1720 * 1721 * Due to concurrency on an active system, the number of pcbs exported 1722 * may have no relation to max_pcbs. max_pcbs merely indicates the 1723 * amount of space the caller allocated for this function to use. 1724 */ 1725int 1726syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1727{ 1728 INIT_VNET_INET(curvnet); 1729 struct xtcpcb xt; 1730 struct syncache *sc; 1731 struct syncache_head *sch; 1732 int count, error, i; 1733 1734 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1735 sch = &V_tcp_syncache.hashbase[i]; 1736 SCH_LOCK(sch); 1737 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1738 if (count >= max_pcbs) { 1739 SCH_UNLOCK(sch); 1740 goto exit; 1741 } 1742 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1743 continue; 1744 bzero(&xt, sizeof(xt)); 1745 xt.xt_len = sizeof(xt); 1746 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1747 xt.xt_inp.inp_vflag = INP_IPV6; 1748 else 1749 xt.xt_inp.inp_vflag = INP_IPV4; 1750 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1751 xt.xt_tp.t_inpcb = &xt.xt_inp; 1752 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1753 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1754 xt.xt_socket.xso_len = sizeof (struct xsocket); 1755 xt.xt_socket.so_type = SOCK_STREAM; 1756 xt.xt_socket.so_state = SS_ISCONNECTING; 1757 error = SYSCTL_OUT(req, &xt, sizeof xt); 1758 if (error) { 1759 SCH_UNLOCK(sch); 1760 goto exit; 1761 } 1762 count++; 1763 } 1764 SCH_UNLOCK(sch); 1765 } 1766exit: 1767 *pcbs_exported = count; 1768 return error; 1769} 1770