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