1 /*- 2 * Copyright (c) 2001 Networks Associates Technology, Inc. 3 * All rights reserved. 4 * 5 * This software was developed for the FreeBSD Project by Jonathan Lemon 6 * and NAI Labs, the Security Research Division of Network Associates, Inc. 7 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 8 * DARPA CHATS research program. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. The name of the author may not be used to endorse or promote 19 * products derived from this software without specific prior written 20 * permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $FreeBSD$ 35 */ 36 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_mac.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/sysctl.h> 46 #include <sys/malloc.h> 47 #include <sys/mac.h> 48 #include <sys/mbuf.h> 49 #include <sys/md5.h> 50 #include <sys/proc.h> /* for proc0 declaration */ 51 #include <sys/random.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 55 #include <net/if.h> 56 #include <net/route.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_var.h> 62 #include <netinet/in_pcb.h> 63 #include <netinet/ip_var.h> 64 #ifdef INET6 65 #include <netinet/ip6.h> 66 #include <netinet/icmp6.h> 67 #include <netinet6/nd6.h> 68 #include <netinet6/ip6_var.h> 69 #include <netinet6/in6_pcb.h> 70 #endif 71 #include <netinet/tcp.h> 72 #ifdef TCPDEBUG 73 #include <netinet/tcpip.h> 74 #endif 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #ifdef TCPDEBUG 80 #include <netinet/tcp_debug.h> 81 #endif 82 #ifdef INET6 83 #include <netinet6/tcp6_var.h> 84 #endif 85 86 #ifdef IPSEC 87 #include <netinet6/ipsec.h> 88 #ifdef INET6 89 #include <netinet6/ipsec6.h> 90 #endif 91 #endif /*IPSEC*/ 92 93 #ifdef FAST_IPSEC 94 #include <netipsec/ipsec.h> 95 #ifdef INET6 96 #include <netipsec/ipsec6.h> 97 #endif 98 #include <netipsec/key.h> 99 #endif /*FAST_IPSEC*/ 100 101 #include <machine/in_cksum.h> 102 #include <vm/uma.h> 103 104 static int tcp_syncookies = 1; 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 106 &tcp_syncookies, 0, 107 "Use TCP SYN cookies if the syncache overflows"); 108 109 static void syncache_drop(struct syncache *, struct syncache_head *); 110 static void syncache_free(struct syncache *); 111 static void syncache_insert(struct syncache *, struct syncache_head *); 112 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 113 #ifdef TCPDEBUG 114 static int syncache_respond(struct syncache *, struct mbuf *, struct socket *); 115 #else 116 static int syncache_respond(struct syncache *, struct mbuf *); 117 #endif 118 static struct socket *syncache_socket(struct syncache *, struct socket *, 119 struct mbuf *m); 120 static void syncache_timer(void *); 121 static u_int32_t syncookie_generate(struct syncache *); 122 static struct syncache *syncookie_lookup(struct in_conninfo *, 123 struct tcphdr *, struct socket *); 124 125 /* 126 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 127 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 128 * the odds are that the user has given up attempting to connect by then. 129 */ 130 #define SYNCACHE_MAXREXMTS 3 131 132 /* Arbitrary values */ 133 #define TCP_SYNCACHE_HASHSIZE 512 134 #define TCP_SYNCACHE_BUCKETLIMIT 30 135 136 struct tcp_syncache { 137 struct syncache_head *hashbase; 138 uma_zone_t zone; 139 u_int hashsize; 140 u_int hashmask; 141 u_int bucket_limit; 142 u_int cache_count; 143 u_int cache_limit; 144 u_int rexmt_limit; 145 u_int hash_secret; 146 u_int next_reseed; 147 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 148 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 149 }; 150 static struct tcp_syncache tcp_syncache; 151 152 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 153 154 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 155 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 156 157 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 158 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 159 160 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 161 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 162 163 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 164 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 165 166 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 167 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 168 169 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 170 171 #define SYNCACHE_HASH(inc, mask) \ 172 ((tcp_syncache.hash_secret ^ \ 173 (inc)->inc_faddr.s_addr ^ \ 174 ((inc)->inc_faddr.s_addr >> 16) ^ \ 175 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 176 177 #define SYNCACHE_HASH6(inc, mask) \ 178 ((tcp_syncache.hash_secret ^ \ 179 (inc)->inc6_faddr.s6_addr32[0] ^ \ 180 (inc)->inc6_faddr.s6_addr32[3] ^ \ 181 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 182 183 #define ENDPTS_EQ(a, b) ( \ 184 (a)->ie_fport == (b)->ie_fport && \ 185 (a)->ie_lport == (b)->ie_lport && \ 186 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 187 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 188 ) 189 190 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 191 192 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 193 sc->sc_rxtslot = (slot); \ 194 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \ 195 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \ 196 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \ 197 callout_reset(&tcp_syncache.tt_timerq[(slot)], \ 198 TCPTV_RTOBASE * tcp_backoff[(slot)], \ 199 syncache_timer, (void *)((intptr_t)(slot))); \ 200 } while (0) 201 202 static void 203 syncache_free(struct syncache *sc) 204 { 205 struct rtentry *rt; 206 207 if (sc->sc_ipopts) 208 (void) m_free(sc->sc_ipopts); 209 #ifdef INET6 210 if (sc->sc_inc.inc_isipv6) 211 rt = sc->sc_route6.ro_rt; 212 else 213 #endif 214 rt = sc->sc_route.ro_rt; 215 if (rt != NULL) { 216 /* 217 * If this is the only reference to a protocol cloned 218 * route, remove it immediately. 219 */ 220 if (rt->rt_flags & RTF_WASCLONED && 221 (sc->sc_flags & SCF_KEEPROUTE) == 0 && 222 rt->rt_refcnt == 1) 223 rtrequest(RTM_DELETE, rt_key(rt), 224 rt->rt_gateway, rt_mask(rt), 225 rt->rt_flags, NULL); 226 RTFREE(rt); 227 } 228 uma_zfree(tcp_syncache.zone, sc); 229 } 230 231 void 232 syncache_init(void) 233 { 234 int i; 235 236 tcp_syncache.cache_count = 0; 237 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 238 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 239 tcp_syncache.cache_limit = 240 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 241 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 242 tcp_syncache.next_reseed = 0; 243 tcp_syncache.hash_secret = arc4random(); 244 245 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 246 &tcp_syncache.hashsize); 247 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 248 &tcp_syncache.cache_limit); 249 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 250 &tcp_syncache.bucket_limit); 251 if (!powerof2(tcp_syncache.hashsize)) { 252 printf("WARNING: syncache hash size is not a power of 2.\n"); 253 tcp_syncache.hashsize = 512; /* safe default */ 254 } 255 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 256 257 /* Allocate the hash table. */ 258 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 259 tcp_syncache.hashsize * sizeof(struct syncache_head), 260 M_SYNCACHE, M_WAITOK); 261 262 /* Initialize the hash buckets. */ 263 for (i = 0; i < tcp_syncache.hashsize; i++) { 264 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 265 tcp_syncache.hashbase[i].sch_length = 0; 266 } 267 268 /* Initialize the timer queues. */ 269 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 270 TAILQ_INIT(&tcp_syncache.timerq[i]); 271 callout_init(&tcp_syncache.tt_timerq[i], 272 debug_mpsafenet ? CALLOUT_MPSAFE : 0); 273 } 274 275 /* 276 * Allocate the syncache entries. Allow the zone to allocate one 277 * more entry than cache limit, so a new entry can bump out an 278 * older one. 279 */ 280 tcp_syncache.cache_limit -= 1; 281 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 282 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 283 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 284 } 285 286 static void 287 syncache_insert(sc, sch) 288 struct syncache *sc; 289 struct syncache_head *sch; 290 { 291 struct syncache *sc2; 292 int i; 293 294 INP_INFO_WLOCK_ASSERT(&tcbinfo); 295 296 /* 297 * Make sure that we don't overflow the per-bucket 298 * limit or the total cache size limit. 299 */ 300 if (sch->sch_length >= tcp_syncache.bucket_limit) { 301 /* 302 * The bucket is full, toss the oldest element. 303 */ 304 sc2 = TAILQ_FIRST(&sch->sch_bucket); 305 sc2->sc_tp->ts_recent = ticks; 306 syncache_drop(sc2, sch); 307 tcpstat.tcps_sc_bucketoverflow++; 308 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 309 /* 310 * The cache is full. Toss the oldest entry in the 311 * entire cache. This is the front entry in the 312 * first non-empty timer queue with the largest 313 * timeout value. 314 */ 315 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 316 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 317 if (sc2 != NULL) 318 break; 319 } 320 sc2->sc_tp->ts_recent = ticks; 321 syncache_drop(sc2, NULL); 322 tcpstat.tcps_sc_cacheoverflow++; 323 } 324 325 /* Initialize the entry's timer. */ 326 SYNCACHE_TIMEOUT(sc, 0); 327 328 /* Put it into the bucket. */ 329 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 330 sch->sch_length++; 331 tcp_syncache.cache_count++; 332 tcpstat.tcps_sc_added++; 333 } 334 335 static void 336 syncache_drop(sc, sch) 337 struct syncache *sc; 338 struct syncache_head *sch; 339 { 340 INP_INFO_WLOCK_ASSERT(&tcbinfo); 341 342 if (sch == NULL) { 343 #ifdef INET6 344 if (sc->sc_inc.inc_isipv6) { 345 sch = &tcp_syncache.hashbase[ 346 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 347 } else 348 #endif 349 { 350 sch = &tcp_syncache.hashbase[ 351 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 352 } 353 } 354 355 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 356 sch->sch_length--; 357 tcp_syncache.cache_count--; 358 359 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 360 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 361 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 362 363 syncache_free(sc); 364 } 365 366 /* 367 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 368 * If we have retransmitted an entry the maximum number of times, expire it. 369 */ 370 static void 371 syncache_timer(xslot) 372 void *xslot; 373 { 374 intptr_t slot = (intptr_t)xslot; 375 struct syncache *sc, *nsc; 376 struct inpcb *inp; 377 378 INP_INFO_WLOCK(&tcbinfo); 379 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 380 !callout_active(&tcp_syncache.tt_timerq[slot])) { 381 /* XXX can this happen? */ 382 INP_INFO_WUNLOCK(&tcbinfo); 383 return; 384 } 385 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 386 387 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 388 while (nsc != NULL) { 389 if (ticks < nsc->sc_rxttime) 390 break; 391 sc = nsc; 392 inp = sc->sc_tp->t_inpcb; 393 if (slot == SYNCACHE_MAXREXMTS || 394 slot >= tcp_syncache.rexmt_limit || 395 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) { 396 nsc = TAILQ_NEXT(sc, sc_timerq); 397 syncache_drop(sc, NULL); 398 tcpstat.tcps_sc_stale++; 399 continue; 400 } 401 /* 402 * syncache_respond() may call back into the syncache to 403 * to modify another entry, so do not obtain the next 404 * entry on the timer chain until it has completed. 405 */ 406 #ifdef TCPDEBUG 407 (void) syncache_respond(sc, NULL, NULL); 408 #else 409 (void) syncache_respond(sc, NULL); 410 #endif 411 nsc = TAILQ_NEXT(sc, sc_timerq); 412 tcpstat.tcps_sc_retransmitted++; 413 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 414 SYNCACHE_TIMEOUT(sc, slot + 1); 415 } 416 if (nsc != NULL) 417 callout_reset(&tcp_syncache.tt_timerq[slot], 418 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 419 INP_INFO_WUNLOCK(&tcbinfo); 420 } 421 422 /* 423 * Find an entry in the syncache. 424 */ 425 struct syncache * 426 syncache_lookup(inc, schp) 427 struct in_conninfo *inc; 428 struct syncache_head **schp; 429 { 430 struct syncache *sc; 431 struct syncache_head *sch; 432 433 INP_INFO_WLOCK_ASSERT(&tcbinfo); 434 435 #ifdef INET6 436 if (inc->inc_isipv6) { 437 sch = &tcp_syncache.hashbase[ 438 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 439 *schp = sch; 440 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 441 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 442 return (sc); 443 } 444 } else 445 #endif 446 { 447 sch = &tcp_syncache.hashbase[ 448 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 449 *schp = sch; 450 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 451 #ifdef INET6 452 if (sc->sc_inc.inc_isipv6) 453 continue; 454 #endif 455 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 456 return (sc); 457 } 458 } 459 return (NULL); 460 } 461 462 /* 463 * This function is called when we get a RST for a 464 * non-existent connection, so that we can see if the 465 * connection is in the syn cache. If it is, zap it. 466 */ 467 void 468 syncache_chkrst(inc, th) 469 struct in_conninfo *inc; 470 struct tcphdr *th; 471 { 472 struct syncache *sc; 473 struct syncache_head *sch; 474 475 INP_INFO_WLOCK_ASSERT(&tcbinfo); 476 477 sc = syncache_lookup(inc, &sch); 478 if (sc == NULL) 479 return; 480 /* 481 * If the RST bit is set, check the sequence number to see 482 * if this is a valid reset segment. 483 * RFC 793 page 37: 484 * In all states except SYN-SENT, all reset (RST) segments 485 * are validated by checking their SEQ-fields. A reset is 486 * valid if its sequence number is in the window. 487 * 488 * The sequence number in the reset segment is normally an 489 * echo of our outgoing acknowlegement numbers, but some hosts 490 * send a reset with the sequence number at the rightmost edge 491 * of our receive window, and we have to handle this case. 492 */ 493 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 494 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 495 syncache_drop(sc, sch); 496 tcpstat.tcps_sc_reset++; 497 } 498 } 499 500 void 501 syncache_badack(inc) 502 struct in_conninfo *inc; 503 { 504 struct syncache *sc; 505 struct syncache_head *sch; 506 507 INP_INFO_WLOCK_ASSERT(&tcbinfo); 508 509 sc = syncache_lookup(inc, &sch); 510 if (sc != NULL) { 511 syncache_drop(sc, sch); 512 tcpstat.tcps_sc_badack++; 513 } 514 } 515 516 void 517 syncache_unreach(inc, th) 518 struct in_conninfo *inc; 519 struct tcphdr *th; 520 { 521 struct syncache *sc; 522 struct syncache_head *sch; 523 524 INP_INFO_WLOCK_ASSERT(&tcbinfo); 525 526 /* we are called at splnet() here */ 527 sc = syncache_lookup(inc, &sch); 528 if (sc == NULL) 529 return; 530 531 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 532 if (ntohl(th->th_seq) != sc->sc_iss) 533 return; 534 535 /* 536 * If we've rertransmitted 3 times and this is our second error, 537 * we remove the entry. Otherwise, we allow it to continue on. 538 * This prevents us from incorrectly nuking an entry during a 539 * spurious network outage. 540 * 541 * See tcp_notify(). 542 */ 543 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 544 sc->sc_flags |= SCF_UNREACH; 545 return; 546 } 547 syncache_drop(sc, sch); 548 tcpstat.tcps_sc_unreach++; 549 } 550 551 /* 552 * Build a new TCP socket structure from a syncache entry. 553 */ 554 static struct socket * 555 syncache_socket(sc, lso, m) 556 struct syncache *sc; 557 struct socket *lso; 558 struct mbuf *m; 559 { 560 struct inpcb *inp = NULL; 561 struct socket *so; 562 struct tcpcb *tp; 563 564 GIANT_REQUIRED; /* XXX until socket locking */ 565 INP_INFO_WLOCK_ASSERT(&tcbinfo); 566 567 /* 568 * Ok, create the full blown connection, and set things up 569 * as they would have been set up if we had created the 570 * connection when the SYN arrived. If we can't create 571 * the connection, abort it. 572 */ 573 so = sonewconn(lso, SS_ISCONNECTED); 574 if (so == NULL) { 575 /* 576 * Drop the connection; we will send a RST if the peer 577 * retransmits the ACK, 578 */ 579 tcpstat.tcps_listendrop++; 580 goto abort2; 581 } 582 #ifdef MAC 583 mac_set_socket_peer_from_mbuf(m, so); 584 #endif 585 586 inp = sotoinpcb(so); 587 INP_LOCK(inp); 588 589 /* 590 * Insert new socket into hash list. 591 */ 592 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 593 #ifdef INET6 594 if (sc->sc_inc.inc_isipv6) { 595 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 596 } else { 597 inp->inp_vflag &= ~INP_IPV6; 598 inp->inp_vflag |= INP_IPV4; 599 #endif 600 inp->inp_laddr = sc->sc_inc.inc_laddr; 601 #ifdef INET6 602 } 603 #endif 604 inp->inp_lport = sc->sc_inc.inc_lport; 605 if (in_pcbinshash(inp) != 0) { 606 /* 607 * Undo the assignments above if we failed to 608 * put the PCB on the hash lists. 609 */ 610 #ifdef INET6 611 if (sc->sc_inc.inc_isipv6) 612 inp->in6p_laddr = in6addr_any; 613 else 614 #endif 615 inp->inp_laddr.s_addr = INADDR_ANY; 616 inp->inp_lport = 0; 617 goto abort; 618 } 619 #ifdef IPSEC 620 /* copy old policy into new socket's */ 621 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 622 printf("syncache_expand: could not copy policy\n"); 623 #endif 624 #ifdef FAST_IPSEC 625 /* copy old policy into new socket's */ 626 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 627 printf("syncache_expand: could not copy policy\n"); 628 #endif 629 #ifdef INET6 630 if (sc->sc_inc.inc_isipv6) { 631 struct inpcb *oinp = sotoinpcb(lso); 632 struct in6_addr laddr6; 633 struct sockaddr_in6 *sin6; 634 /* 635 * Inherit socket options from the listening socket. 636 * Note that in6p_inputopts are not (and should not be) 637 * copied, since it stores previously received options and is 638 * used to detect if each new option is different than the 639 * previous one and hence should be passed to a user. 640 * If we copied in6p_inputopts, a user would not be able to 641 * receive options just after calling the accept system call. 642 */ 643 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 644 if (oinp->in6p_outputopts) 645 inp->in6p_outputopts = 646 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 647 inp->in6p_route = sc->sc_route6; 648 sc->sc_route6.ro_rt = NULL; 649 650 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, 651 M_SONAME, M_NOWAIT | M_ZERO); 652 if (sin6 == NULL) 653 goto abort; 654 sin6->sin6_family = AF_INET6; 655 sin6->sin6_len = sizeof(*sin6); 656 sin6->sin6_addr = sc->sc_inc.inc6_faddr; 657 sin6->sin6_port = sc->sc_inc.inc_fport; 658 laddr6 = inp->in6p_laddr; 659 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 660 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 661 if (in6_pcbconnect(inp, (struct sockaddr *)sin6, &thread0)) { 662 inp->in6p_laddr = laddr6; 663 FREE(sin6, M_SONAME); 664 goto abort; 665 } 666 FREE(sin6, M_SONAME); 667 } else 668 #endif 669 { 670 struct in_addr laddr; 671 struct sockaddr_in *sin; 672 673 inp->inp_options = ip_srcroute(); 674 if (inp->inp_options == NULL) { 675 inp->inp_options = sc->sc_ipopts; 676 sc->sc_ipopts = NULL; 677 } 678 inp->inp_route = sc->sc_route; 679 sc->sc_route.ro_rt = NULL; 680 681 MALLOC(sin, struct sockaddr_in *, sizeof *sin, 682 M_SONAME, M_NOWAIT | M_ZERO); 683 if (sin == NULL) 684 goto abort; 685 sin->sin_family = AF_INET; 686 sin->sin_len = sizeof(*sin); 687 sin->sin_addr = sc->sc_inc.inc_faddr; 688 sin->sin_port = sc->sc_inc.inc_fport; 689 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 690 laddr = inp->inp_laddr; 691 if (inp->inp_laddr.s_addr == INADDR_ANY) 692 inp->inp_laddr = sc->sc_inc.inc_laddr; 693 if (in_pcbconnect(inp, (struct sockaddr *)sin, &thread0)) { 694 inp->inp_laddr = laddr; 695 FREE(sin, M_SONAME); 696 goto abort; 697 } 698 FREE(sin, M_SONAME); 699 } 700 701 tp = intotcpcb(inp); 702 tp->t_state = TCPS_SYN_RECEIVED; 703 tp->iss = sc->sc_iss; 704 tp->irs = sc->sc_irs; 705 tcp_rcvseqinit(tp); 706 tcp_sendseqinit(tp); 707 tp->snd_wl1 = sc->sc_irs; 708 tp->rcv_up = sc->sc_irs + 1; 709 tp->rcv_wnd = sc->sc_wnd; 710 tp->rcv_adv += tp->rcv_wnd; 711 712 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 713 if (sc->sc_flags & SCF_NOOPT) 714 tp->t_flags |= TF_NOOPT; 715 if (sc->sc_flags & SCF_WINSCALE) { 716 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 717 tp->requested_s_scale = sc->sc_requested_s_scale; 718 tp->request_r_scale = sc->sc_request_r_scale; 719 } 720 if (sc->sc_flags & SCF_TIMESTAMP) { 721 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 722 tp->ts_recent = sc->sc_tsrecent; 723 tp->ts_recent_age = ticks; 724 } 725 if (sc->sc_flags & SCF_CC) { 726 /* 727 * Initialization of the tcpcb for transaction; 728 * set SND.WND = SEG.WND, 729 * initialize CCsend and CCrecv. 730 */ 731 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 732 tp->cc_send = sc->sc_cc_send; 733 tp->cc_recv = sc->sc_cc_recv; 734 } 735 736 tcp_mss(tp, sc->sc_peer_mss); 737 738 /* 739 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 740 */ 741 if (sc->sc_rxtslot != 0) 742 tp->snd_cwnd = tp->t_maxseg; 743 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 744 745 INP_UNLOCK(inp); 746 747 tcpstat.tcps_accepts++; 748 return (so); 749 750 abort: 751 INP_UNLOCK(inp); 752 abort2: 753 if (so != NULL) 754 (void) soabort(so); 755 return (NULL); 756 } 757 758 /* 759 * This function gets called when we receive an ACK for a 760 * socket in the LISTEN state. We look up the connection 761 * in the syncache, and if its there, we pull it out of 762 * the cache and turn it into a full-blown connection in 763 * the SYN-RECEIVED state. 764 */ 765 int 766 syncache_expand(inc, th, sop, m) 767 struct in_conninfo *inc; 768 struct tcphdr *th; 769 struct socket **sop; 770 struct mbuf *m; 771 { 772 struct syncache *sc; 773 struct syncache_head *sch; 774 struct socket *so; 775 776 INP_INFO_WLOCK_ASSERT(&tcbinfo); 777 778 sc = syncache_lookup(inc, &sch); 779 if (sc == NULL) { 780 /* 781 * There is no syncache entry, so see if this ACK is 782 * a returning syncookie. To do this, first: 783 * A. See if this socket has had a syncache entry dropped in 784 * the past. We don't want to accept a bogus syncookie 785 * if we've never received a SYN. 786 * B. check that the syncookie is valid. If it is, then 787 * cobble up a fake syncache entry, and return. 788 */ 789 if (!tcp_syncookies) 790 return (0); 791 sc = syncookie_lookup(inc, th, *sop); 792 if (sc == NULL) 793 return (0); 794 sch = NULL; 795 tcpstat.tcps_sc_recvcookie++; 796 } 797 798 /* 799 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 800 */ 801 if (th->th_ack != sc->sc_iss + 1) 802 return (0); 803 804 so = syncache_socket(sc, *sop, m); 805 if (so == NULL) { 806 #if 0 807 resetandabort: 808 /* XXXjlemon check this - is this correct? */ 809 (void) tcp_respond(NULL, m, m, th, 810 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 811 #endif 812 m_freem(m); /* XXX only needed for above */ 813 tcpstat.tcps_sc_aborted++; 814 } else { 815 sc->sc_flags |= SCF_KEEPROUTE; 816 tcpstat.tcps_sc_completed++; 817 } 818 if (sch == NULL) 819 syncache_free(sc); 820 else 821 syncache_drop(sc, sch); 822 *sop = so; 823 return (1); 824 } 825 826 /* 827 * Given a LISTEN socket and an inbound SYN request, add 828 * this to the syn cache, and send back a segment: 829 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 830 * to the source. 831 * 832 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 833 * Doing so would require that we hold onto the data and deliver it 834 * to the application. However, if we are the target of a SYN-flood 835 * DoS attack, an attacker could send data which would eventually 836 * consume all available buffer space if it were ACKed. By not ACKing 837 * the data, we avoid this DoS scenario. 838 */ 839 int 840 syncache_add(inc, to, th, sop, m) 841 struct in_conninfo *inc; 842 struct tcpopt *to; 843 struct tcphdr *th; 844 struct socket **sop; 845 struct mbuf *m; 846 { 847 struct tcpcb *tp; 848 struct socket *so; 849 struct syncache *sc = NULL; 850 struct syncache_head *sch; 851 struct mbuf *ipopts = NULL; 852 struct rmxp_tao *taop; 853 int i, win; 854 855 INP_INFO_WLOCK_ASSERT(&tcbinfo); 856 857 so = *sop; 858 tp = sototcpcb(so); 859 860 /* 861 * Remember the IP options, if any. 862 */ 863 #ifdef INET6 864 if (!inc->inc_isipv6) 865 #endif 866 ipopts = ip_srcroute(); 867 868 /* 869 * See if we already have an entry for this connection. 870 * If we do, resend the SYN,ACK, and reset the retransmit timer. 871 * 872 * XXX 873 * should the syncache be re-initialized with the contents 874 * of the new SYN here (which may have different options?) 875 */ 876 sc = syncache_lookup(inc, &sch); 877 if (sc != NULL) { 878 tcpstat.tcps_sc_dupsyn++; 879 if (ipopts) { 880 /* 881 * If we were remembering a previous source route, 882 * forget it and use the new one we've been given. 883 */ 884 if (sc->sc_ipopts) 885 (void) m_free(sc->sc_ipopts); 886 sc->sc_ipopts = ipopts; 887 } 888 /* 889 * Update timestamp if present. 890 */ 891 if (sc->sc_flags & SCF_TIMESTAMP) 892 sc->sc_tsrecent = to->to_tsval; 893 /* 894 * PCB may have changed, pick up new values. 895 */ 896 sc->sc_tp = tp; 897 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 898 #ifdef TCPDEBUG 899 if (syncache_respond(sc, m, so) == 0) { 900 #else 901 if (syncache_respond(sc, m) == 0) { 902 #endif 903 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 904 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 905 sc, sc_timerq); 906 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 907 tcpstat.tcps_sndacks++; 908 tcpstat.tcps_sndtotal++; 909 } 910 *sop = NULL; 911 return (1); 912 } 913 914 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 915 if (sc == NULL) { 916 /* 917 * The zone allocator couldn't provide more entries. 918 * Treat this as if the cache was full; drop the oldest 919 * entry and insert the new one. 920 */ 921 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 922 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 923 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 924 if (sc != NULL) 925 break; 926 } 927 sc->sc_tp->ts_recent = ticks; 928 syncache_drop(sc, NULL); 929 tcpstat.tcps_sc_zonefail++; 930 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 931 if (sc == NULL) { 932 if (ipopts) 933 (void) m_free(ipopts); 934 return (0); 935 } 936 } 937 938 /* 939 * Fill in the syncache values. 940 */ 941 bzero(sc, sizeof(*sc)); 942 sc->sc_tp = tp; 943 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 944 sc->sc_ipopts = ipopts; 945 sc->sc_inc.inc_fport = inc->inc_fport; 946 sc->sc_inc.inc_lport = inc->inc_lport; 947 #ifdef INET6 948 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 949 if (inc->inc_isipv6) { 950 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 951 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 952 sc->sc_route6.ro_rt = NULL; 953 } else 954 #endif 955 { 956 sc->sc_inc.inc_faddr = inc->inc_faddr; 957 sc->sc_inc.inc_laddr = inc->inc_laddr; 958 sc->sc_route.ro_rt = NULL; 959 } 960 sc->sc_irs = th->th_seq; 961 sc->sc_flags = 0; 962 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 963 if (tcp_syncookies) 964 sc->sc_iss = syncookie_generate(sc); 965 else 966 sc->sc_iss = arc4random(); 967 968 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 969 win = sbspace(&so->so_rcv); 970 win = imax(win, 0); 971 win = imin(win, TCP_MAXWIN); 972 sc->sc_wnd = win; 973 974 if (tcp_do_rfc1323) { 975 /* 976 * A timestamp received in a SYN makes 977 * it ok to send timestamp requests and replies. 978 */ 979 if (to->to_flags & TOF_TS) { 980 sc->sc_tsrecent = to->to_tsval; 981 sc->sc_flags |= SCF_TIMESTAMP; 982 } 983 if (to->to_flags & TOF_SCALE) { 984 int wscale = 0; 985 986 /* Compute proper scaling value from buffer space */ 987 while (wscale < TCP_MAX_WINSHIFT && 988 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 989 wscale++; 990 sc->sc_request_r_scale = wscale; 991 sc->sc_requested_s_scale = to->to_requested_s_scale; 992 sc->sc_flags |= SCF_WINSCALE; 993 } 994 } 995 if (tcp_do_rfc1644) { 996 /* 997 * A CC or CC.new option received in a SYN makes 998 * it ok to send CC in subsequent segments. 999 */ 1000 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 1001 sc->sc_cc_recv = to->to_cc; 1002 sc->sc_cc_send = CC_INC(tcp_ccgen); 1003 sc->sc_flags |= SCF_CC; 1004 } 1005 } 1006 if (tp->t_flags & TF_NOOPT) 1007 sc->sc_flags = SCF_NOOPT; 1008 1009 /* 1010 * XXX 1011 * We have the option here of not doing TAO (even if the segment 1012 * qualifies) and instead fall back to a normal 3WHS via the syncache. 1013 * This allows us to apply synflood protection to TAO-qualifying SYNs 1014 * also. However, there should be a hueristic to determine when to 1015 * do this, and is not present at the moment. 1016 */ 1017 1018 /* 1019 * Perform TAO test on incoming CC (SEG.CC) option, if any. 1020 * - compare SEG.CC against cached CC from the same host, if any. 1021 * - if SEG.CC > chached value, SYN must be new and is accepted 1022 * immediately: save new CC in the cache, mark the socket 1023 * connected, enter ESTABLISHED state, turn on flag to 1024 * send a SYN in the next segment. 1025 * A virtual advertised window is set in rcv_adv to 1026 * initialize SWS prevention. Then enter normal segment 1027 * processing: drop SYN, process data and FIN. 1028 * - otherwise do a normal 3-way handshake. 1029 */ 1030 taop = tcp_gettaocache(&sc->sc_inc); 1031 if ((to->to_flags & TOF_CC) != 0) { 1032 if (((tp->t_flags & TF_NOPUSH) != 0) && 1033 sc->sc_flags & SCF_CC && 1034 taop != NULL && taop->tao_cc != 0 && 1035 CC_GT(to->to_cc, taop->tao_cc)) { 1036 sc->sc_rxtslot = 0; 1037 so = syncache_socket(sc, *sop, m); 1038 if (so != NULL) { 1039 sc->sc_flags |= SCF_KEEPROUTE; 1040 taop->tao_cc = to->to_cc; 1041 *sop = so; 1042 } 1043 syncache_free(sc); 1044 return (so != NULL); 1045 } 1046 } else { 1047 /* 1048 * No CC option, but maybe CC.NEW: invalidate cached value. 1049 */ 1050 if (taop != NULL) 1051 taop->tao_cc = 0; 1052 } 1053 /* 1054 * TAO test failed or there was no CC option, 1055 * do a standard 3-way handshake. 1056 */ 1057 #ifdef TCPDEBUG 1058 if (syncache_respond(sc, m, so) == 0) { 1059 #else 1060 if (syncache_respond(sc, m) == 0) { 1061 #endif 1062 syncache_insert(sc, sch); 1063 tcpstat.tcps_sndacks++; 1064 tcpstat.tcps_sndtotal++; 1065 } else { 1066 syncache_free(sc); 1067 tcpstat.tcps_sc_dropped++; 1068 } 1069 *sop = NULL; 1070 return (1); 1071 } 1072 1073 #ifdef TCPDEBUG 1074 static int 1075 syncache_respond(sc, m, so) 1076 struct syncache *sc; 1077 struct mbuf *m; 1078 struct socket *so; 1079 #else 1080 static int 1081 syncache_respond(sc, m) 1082 struct syncache *sc; 1083 struct mbuf *m; 1084 #endif 1085 { 1086 u_int8_t *optp; 1087 int optlen, error; 1088 u_int16_t tlen, hlen, mssopt; 1089 struct ip *ip = NULL; 1090 struct rtentry *rt; 1091 struct tcphdr *th; 1092 struct inpcb *inp; 1093 #ifdef INET6 1094 struct ip6_hdr *ip6 = NULL; 1095 #endif 1096 1097 #ifdef INET6 1098 if (sc->sc_inc.inc_isipv6) { 1099 rt = tcp_rtlookup6(&sc->sc_inc); 1100 if (rt != NULL) 1101 mssopt = rt->rt_ifp->if_mtu - 1102 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1103 else 1104 mssopt = tcp_v6mssdflt; 1105 hlen = sizeof(struct ip6_hdr); 1106 } else 1107 #endif 1108 { 1109 rt = tcp_rtlookup(&sc->sc_inc); 1110 if (rt != NULL) 1111 mssopt = rt->rt_ifp->if_mtu - 1112 (sizeof(struct ip) + sizeof(struct tcphdr)); 1113 else 1114 mssopt = tcp_mssdflt; 1115 hlen = sizeof(struct ip); 1116 } 1117 1118 /* Compute the size of the TCP options. */ 1119 if (sc->sc_flags & SCF_NOOPT) { 1120 optlen = 0; 1121 } else { 1122 optlen = TCPOLEN_MAXSEG + 1123 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1124 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1125 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1126 } 1127 tlen = hlen + sizeof(struct tcphdr) + optlen; 1128 1129 /* 1130 * XXX 1131 * assume that the entire packet will fit in a header mbuf 1132 */ 1133 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1134 1135 /* 1136 * XXX shouldn't this reuse the mbuf if possible ? 1137 * Create the IP+TCP header from scratch. 1138 */ 1139 if (m) 1140 m_freem(m); 1141 1142 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1143 if (m == NULL) 1144 return (ENOBUFS); 1145 m->m_data += max_linkhdr; 1146 m->m_len = tlen; 1147 m->m_pkthdr.len = tlen; 1148 m->m_pkthdr.rcvif = NULL; 1149 inp = sc->sc_tp->t_inpcb; 1150 INP_LOCK(inp); 1151 #ifdef MAC 1152 mac_create_mbuf_from_socket(inp->inp_socket, m); 1153 #endif 1154 1155 #ifdef INET6 1156 if (sc->sc_inc.inc_isipv6) { 1157 ip6 = mtod(m, struct ip6_hdr *); 1158 ip6->ip6_vfc = IPV6_VERSION; 1159 ip6->ip6_nxt = IPPROTO_TCP; 1160 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1161 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1162 ip6->ip6_plen = htons(tlen - hlen); 1163 /* ip6_hlim is set after checksum */ 1164 /* ip6_flow = ??? */ 1165 1166 th = (struct tcphdr *)(ip6 + 1); 1167 } else 1168 #endif 1169 { 1170 ip = mtod(m, struct ip *); 1171 ip->ip_v = IPVERSION; 1172 ip->ip_hl = sizeof(struct ip) >> 2; 1173 ip->ip_len = tlen; 1174 ip->ip_id = 0; 1175 ip->ip_off = 0; 1176 ip->ip_sum = 0; 1177 ip->ip_p = IPPROTO_TCP; 1178 ip->ip_src = sc->sc_inc.inc_laddr; 1179 ip->ip_dst = sc->sc_inc.inc_faddr; 1180 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1181 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1182 1183 /* 1184 * See if we should do MTU discovery. Route lookups are 1185 * expensive, so we will only unset the DF bit if: 1186 * 1187 * 1) path_mtu_discovery is disabled 1188 * 2) the SCF_UNREACH flag has been set 1189 */ 1190 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1191 ip->ip_off |= IP_DF; 1192 1193 th = (struct tcphdr *)(ip + 1); 1194 } 1195 th->th_sport = sc->sc_inc.inc_lport; 1196 th->th_dport = sc->sc_inc.inc_fport; 1197 1198 th->th_seq = htonl(sc->sc_iss); 1199 th->th_ack = htonl(sc->sc_irs + 1); 1200 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1201 th->th_x2 = 0; 1202 th->th_flags = TH_SYN|TH_ACK; 1203 th->th_win = htons(sc->sc_wnd); 1204 th->th_urp = 0; 1205 1206 /* Tack on the TCP options. */ 1207 if (optlen != 0) { 1208 optp = (u_int8_t *)(th + 1); 1209 *optp++ = TCPOPT_MAXSEG; 1210 *optp++ = TCPOLEN_MAXSEG; 1211 *optp++ = (mssopt >> 8) & 0xff; 1212 *optp++ = mssopt & 0xff; 1213 1214 if (sc->sc_flags & SCF_WINSCALE) { 1215 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1216 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1217 sc->sc_request_r_scale); 1218 optp += 4; 1219 } 1220 1221 if (sc->sc_flags & SCF_TIMESTAMP) { 1222 u_int32_t *lp = (u_int32_t *)(optp); 1223 1224 /* Form timestamp option per appendix A of RFC 1323. */ 1225 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1226 *lp++ = htonl(ticks); 1227 *lp = htonl(sc->sc_tsrecent); 1228 optp += TCPOLEN_TSTAMP_APPA; 1229 } 1230 1231 /* 1232 * Send CC and CC.echo if we received CC from our peer. 1233 */ 1234 if (sc->sc_flags & SCF_CC) { 1235 u_int32_t *lp = (u_int32_t *)(optp); 1236 1237 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1238 *lp++ = htonl(sc->sc_cc_send); 1239 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1240 *lp = htonl(sc->sc_cc_recv); 1241 optp += TCPOLEN_CC_APPA * 2; 1242 } 1243 } 1244 1245 #ifdef INET6 1246 if (sc->sc_inc.inc_isipv6) { 1247 struct route_in6 *ro6 = &sc->sc_route6; 1248 1249 th->th_sum = 0; 1250 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1251 ip6->ip6_hlim = in6_selecthlim(NULL, 1252 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1253 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, inp); 1254 } else 1255 #endif 1256 { 1257 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1258 htons(tlen - hlen + IPPROTO_TCP)); 1259 m->m_pkthdr.csum_flags = CSUM_TCP; 1260 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1261 #ifdef TCPDEBUG 1262 /* 1263 * Trace. 1264 */ 1265 if (so != NULL && so->so_options & SO_DEBUG) { 1266 struct tcpcb *tp = sototcpcb(so); 1267 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1268 mtod(m, void *), th, 0); 1269 } 1270 #endif 1271 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL,inp); 1272 } 1273 INP_UNLOCK(inp); 1274 return (error); 1275 } 1276 1277 /* 1278 * cookie layers: 1279 * 1280 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1281 * | peer iss | 1282 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1283 * | 0 |(A)| | 1284 * (A): peer mss index 1285 */ 1286 1287 /* 1288 * The values below are chosen to minimize the size of the tcp_secret 1289 * table, as well as providing roughly a 16 second lifetime for the cookie. 1290 */ 1291 1292 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1293 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1294 1295 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1296 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1297 #define SYNCOOKIE_TIMEOUT \ 1298 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1299 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1300 1301 static struct { 1302 u_int32_t ts_secbits[4]; 1303 u_int ts_expire; 1304 } tcp_secret[SYNCOOKIE_NSECRETS]; 1305 1306 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1307 1308 static MD5_CTX syn_ctx; 1309 1310 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1311 1312 struct md5_add { 1313 u_int32_t laddr, faddr; 1314 u_int32_t secbits[4]; 1315 u_int16_t lport, fport; 1316 }; 1317 1318 #ifdef CTASSERT 1319 CTASSERT(sizeof(struct md5_add) == 28); 1320 #endif 1321 1322 /* 1323 * Consider the problem of a recreated (and retransmitted) cookie. If the 1324 * original SYN was accepted, the connection is established. The second 1325 * SYN is inflight, and if it arrives with an ISN that falls within the 1326 * receive window, the connection is killed. 1327 * 1328 * However, since cookies have other problems, this may not be worth 1329 * worrying about. 1330 */ 1331 1332 static u_int32_t 1333 syncookie_generate(struct syncache *sc) 1334 { 1335 u_int32_t md5_buffer[4]; 1336 u_int32_t data; 1337 int idx, i; 1338 struct md5_add add; 1339 1340 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1341 1342 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1343 if (tcp_secret[idx].ts_expire < ticks) { 1344 for (i = 0; i < 4; i++) 1345 tcp_secret[idx].ts_secbits[i] = arc4random(); 1346 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1347 } 1348 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1349 if (tcp_msstab[data] <= sc->sc_peer_mss) 1350 break; 1351 data = (data << SYNCOOKIE_WNDBITS) | idx; 1352 data ^= sc->sc_irs; /* peer's iss */ 1353 MD5Init(&syn_ctx); 1354 #ifdef INET6 1355 if (sc->sc_inc.inc_isipv6) { 1356 MD5Add(sc->sc_inc.inc6_laddr); 1357 MD5Add(sc->sc_inc.inc6_faddr); 1358 add.laddr = 0; 1359 add.faddr = 0; 1360 } else 1361 #endif 1362 { 1363 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1364 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1365 } 1366 add.lport = sc->sc_inc.inc_lport; 1367 add.fport = sc->sc_inc.inc_fport; 1368 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1369 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1370 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1371 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1372 MD5Add(add); 1373 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1374 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1375 return (data); 1376 } 1377 1378 static struct syncache * 1379 syncookie_lookup(inc, th, so) 1380 struct in_conninfo *inc; 1381 struct tcphdr *th; 1382 struct socket *so; 1383 { 1384 u_int32_t md5_buffer[4]; 1385 struct syncache *sc; 1386 u_int32_t data; 1387 int wnd, idx; 1388 struct md5_add add; 1389 1390 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1391 1392 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1393 idx = data & SYNCOOKIE_WNDMASK; 1394 if (tcp_secret[idx].ts_expire < ticks || 1395 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1396 return (NULL); 1397 MD5Init(&syn_ctx); 1398 #ifdef INET6 1399 if (inc->inc_isipv6) { 1400 MD5Add(inc->inc6_laddr); 1401 MD5Add(inc->inc6_faddr); 1402 add.laddr = 0; 1403 add.faddr = 0; 1404 } else 1405 #endif 1406 { 1407 add.laddr = inc->inc_laddr.s_addr; 1408 add.faddr = inc->inc_faddr.s_addr; 1409 } 1410 add.lport = inc->inc_lport; 1411 add.fport = inc->inc_fport; 1412 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1413 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1414 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1415 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1416 MD5Add(add); 1417 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1418 data ^= md5_buffer[0]; 1419 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1420 return (NULL); 1421 data = data >> SYNCOOKIE_WNDBITS; 1422 1423 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1424 if (sc == NULL) 1425 return (NULL); 1426 /* 1427 * Fill in the syncache values. 1428 * XXX duplicate code from syncache_add 1429 */ 1430 sc->sc_ipopts = NULL; 1431 sc->sc_inc.inc_fport = inc->inc_fport; 1432 sc->sc_inc.inc_lport = inc->inc_lport; 1433 #ifdef INET6 1434 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1435 if (inc->inc_isipv6) { 1436 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1437 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1438 sc->sc_route6.ro_rt = NULL; 1439 } else 1440 #endif 1441 { 1442 sc->sc_inc.inc_faddr = inc->inc_faddr; 1443 sc->sc_inc.inc_laddr = inc->inc_laddr; 1444 sc->sc_route.ro_rt = NULL; 1445 } 1446 sc->sc_irs = th->th_seq - 1; 1447 sc->sc_iss = th->th_ack - 1; 1448 wnd = sbspace(&so->so_rcv); 1449 wnd = imax(wnd, 0); 1450 wnd = imin(wnd, TCP_MAXWIN); 1451 sc->sc_wnd = wnd; 1452 sc->sc_flags = 0; 1453 sc->sc_rxtslot = 0; 1454 sc->sc_peer_mss = tcp_msstab[data]; 1455 return (sc); 1456 } 1457