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], CALLOUT_MPSAFE); 272 } 273 274 /* 275 * Allocate the syncache entries. Allow the zone to allocate one 276 * more entry than cache limit, so a new entry can bump out an 277 * older one. 278 */ 279 tcp_syncache.cache_limit -= 1; 280 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 281 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 282 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 283 } 284 285 static void 286 syncache_insert(sc, sch) 287 struct syncache *sc; 288 struct syncache_head *sch; 289 { 290 struct syncache *sc2; 291 int s, i; 292 293 /* 294 * Make sure that we don't overflow the per-bucket 295 * limit or the total cache size limit. 296 */ 297 s = splnet(); 298 if (sch->sch_length >= tcp_syncache.bucket_limit) { 299 /* 300 * The bucket is full, toss the oldest element. 301 */ 302 sc2 = TAILQ_FIRST(&sch->sch_bucket); 303 sc2->sc_tp->ts_recent = ticks; 304 syncache_drop(sc2, sch); 305 tcpstat.tcps_sc_bucketoverflow++; 306 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 307 /* 308 * The cache is full. Toss the oldest entry in the 309 * entire cache. This is the front entry in the 310 * first non-empty timer queue with the largest 311 * timeout value. 312 */ 313 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 314 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 315 if (sc2 != NULL) 316 break; 317 } 318 sc2->sc_tp->ts_recent = ticks; 319 syncache_drop(sc2, NULL); 320 tcpstat.tcps_sc_cacheoverflow++; 321 } 322 323 /* Initialize the entry's timer. */ 324 SYNCACHE_TIMEOUT(sc, 0); 325 326 /* Put it into the bucket. */ 327 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 328 sch->sch_length++; 329 tcp_syncache.cache_count++; 330 tcpstat.tcps_sc_added++; 331 splx(s); 332 } 333 334 static void 335 syncache_drop(sc, sch) 336 struct syncache *sc; 337 struct syncache_head *sch; 338 { 339 int s; 340 341 if (sch == NULL) { 342 #ifdef INET6 343 if (sc->sc_inc.inc_isipv6) { 344 sch = &tcp_syncache.hashbase[ 345 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 346 } else 347 #endif 348 { 349 sch = &tcp_syncache.hashbase[ 350 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 351 } 352 } 353 354 s = splnet(); 355 356 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 357 sch->sch_length--; 358 tcp_syncache.cache_count--; 359 360 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 361 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 362 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 363 splx(s); 364 365 syncache_free(sc); 366 } 367 368 /* 369 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 370 * If we have retransmitted an entry the maximum number of times, expire it. 371 */ 372 static void 373 syncache_timer(xslot) 374 void *xslot; 375 { 376 intptr_t slot = (intptr_t)xslot; 377 struct syncache *sc, *nsc; 378 struct inpcb *inp; 379 int s; 380 381 s = splnet(); 382 INP_INFO_WLOCK(&tcbinfo); 383 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 384 !callout_active(&tcp_syncache.tt_timerq[slot])) { 385 INP_INFO_WUNLOCK(&tcbinfo); 386 splx(s); 387 return; 388 } 389 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 390 391 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 392 while (nsc != NULL) { 393 if (ticks < nsc->sc_rxttime) 394 break; 395 sc = nsc; 396 inp = sc->sc_tp->t_inpcb; 397 if (slot == SYNCACHE_MAXREXMTS || 398 slot >= tcp_syncache.rexmt_limit || 399 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) { 400 nsc = TAILQ_NEXT(sc, sc_timerq); 401 syncache_drop(sc, NULL); 402 tcpstat.tcps_sc_stale++; 403 continue; 404 } 405 /* 406 * syncache_respond() may call back into the syncache to 407 * to modify another entry, so do not obtain the next 408 * entry on the timer chain until it has completed. 409 */ 410 #ifdef TCPDEBUG 411 (void) syncache_respond(sc, NULL, NULL); 412 #else 413 (void) syncache_respond(sc, NULL); 414 #endif 415 nsc = TAILQ_NEXT(sc, sc_timerq); 416 tcpstat.tcps_sc_retransmitted++; 417 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 418 SYNCACHE_TIMEOUT(sc, slot + 1); 419 } 420 if (nsc != NULL) 421 callout_reset(&tcp_syncache.tt_timerq[slot], 422 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 423 INP_INFO_WUNLOCK(&tcbinfo); 424 splx(s); 425 } 426 427 /* 428 * Find an entry in the syncache. 429 */ 430 struct syncache * 431 syncache_lookup(inc, schp) 432 struct in_conninfo *inc; 433 struct syncache_head **schp; 434 { 435 struct syncache *sc; 436 struct syncache_head *sch; 437 int s; 438 439 #ifdef INET6 440 if (inc->inc_isipv6) { 441 sch = &tcp_syncache.hashbase[ 442 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 443 *schp = sch; 444 s = splnet(); 445 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 446 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 447 splx(s); 448 return (sc); 449 } 450 } 451 splx(s); 452 } else 453 #endif 454 { 455 sch = &tcp_syncache.hashbase[ 456 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 457 *schp = sch; 458 s = splnet(); 459 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 460 #ifdef INET6 461 if (sc->sc_inc.inc_isipv6) 462 continue; 463 #endif 464 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 465 splx(s); 466 return (sc); 467 } 468 } 469 splx(s); 470 } 471 return (NULL); 472 } 473 474 /* 475 * This function is called when we get a RST for a 476 * non-existent connection, so that we can see if the 477 * connection is in the syn cache. If it is, zap it. 478 */ 479 void 480 syncache_chkrst(inc, th) 481 struct in_conninfo *inc; 482 struct tcphdr *th; 483 { 484 struct syncache *sc; 485 struct syncache_head *sch; 486 487 sc = syncache_lookup(inc, &sch); 488 if (sc == NULL) 489 return; 490 /* 491 * If the RST bit is set, check the sequence number to see 492 * if this is a valid reset segment. 493 * RFC 793 page 37: 494 * In all states except SYN-SENT, all reset (RST) segments 495 * are validated by checking their SEQ-fields. A reset is 496 * valid if its sequence number is in the window. 497 * 498 * The sequence number in the reset segment is normally an 499 * echo of our outgoing acknowlegement numbers, but some hosts 500 * send a reset with the sequence number at the rightmost edge 501 * of our receive window, and we have to handle this case. 502 */ 503 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 504 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 505 syncache_drop(sc, sch); 506 tcpstat.tcps_sc_reset++; 507 } 508 } 509 510 void 511 syncache_badack(inc) 512 struct in_conninfo *inc; 513 { 514 struct syncache *sc; 515 struct syncache_head *sch; 516 517 sc = syncache_lookup(inc, &sch); 518 if (sc != NULL) { 519 syncache_drop(sc, sch); 520 tcpstat.tcps_sc_badack++; 521 } 522 } 523 524 void 525 syncache_unreach(inc, th) 526 struct in_conninfo *inc; 527 struct tcphdr *th; 528 { 529 struct syncache *sc; 530 struct syncache_head *sch; 531 532 /* we are called at splnet() here */ 533 sc = syncache_lookup(inc, &sch); 534 if (sc == NULL) 535 return; 536 537 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 538 if (ntohl(th->th_seq) != sc->sc_iss) 539 return; 540 541 /* 542 * If we've rertransmitted 3 times and this is our second error, 543 * we remove the entry. Otherwise, we allow it to continue on. 544 * This prevents us from incorrectly nuking an entry during a 545 * spurious network outage. 546 * 547 * See tcp_notify(). 548 */ 549 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 550 sc->sc_flags |= SCF_UNREACH; 551 return; 552 } 553 syncache_drop(sc, sch); 554 tcpstat.tcps_sc_unreach++; 555 } 556 557 /* 558 * Build a new TCP socket structure from a syncache entry. 559 */ 560 static struct socket * 561 syncache_socket(sc, lso, m) 562 struct syncache *sc; 563 struct socket *lso; 564 struct mbuf *m; 565 { 566 struct inpcb *inp = NULL; 567 struct socket *so; 568 struct tcpcb *tp; 569 570 /* 571 * Ok, create the full blown connection, and set things up 572 * as they would have been set up if we had created the 573 * connection when the SYN arrived. If we can't create 574 * the connection, abort it. 575 */ 576 so = sonewconn(lso, SS_ISCONNECTED); 577 if (so == NULL) { 578 /* 579 * Drop the connection; we will send a RST if the peer 580 * retransmits the ACK, 581 */ 582 tcpstat.tcps_listendrop++; 583 goto abort; 584 } 585 #ifdef MAC 586 mac_set_socket_peer_from_mbuf(m, so); 587 #endif 588 589 inp = sotoinpcb(so); 590 591 /* 592 * Insert new socket into hash list. 593 */ 594 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 595 #ifdef INET6 596 if (sc->sc_inc.inc_isipv6) { 597 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 598 } else { 599 inp->inp_vflag &= ~INP_IPV6; 600 inp->inp_vflag |= INP_IPV4; 601 #endif 602 inp->inp_laddr = sc->sc_inc.inc_laddr; 603 #ifdef INET6 604 } 605 #endif 606 inp->inp_lport = sc->sc_inc.inc_lport; 607 if (in_pcbinshash(inp) != 0) { 608 /* 609 * Undo the assignments above if we failed to 610 * put the PCB on the hash lists. 611 */ 612 #ifdef INET6 613 if (sc->sc_inc.inc_isipv6) 614 inp->in6p_laddr = in6addr_any; 615 else 616 #endif 617 inp->inp_laddr.s_addr = INADDR_ANY; 618 inp->inp_lport = 0; 619 goto abort; 620 } 621 #ifdef IPSEC 622 /* copy old policy into new socket's */ 623 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 624 printf("syncache_expand: could not copy policy\n"); 625 #endif 626 #ifdef FAST_IPSEC 627 /* copy old policy into new socket's */ 628 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 629 printf("syncache_expand: could not copy policy\n"); 630 #endif 631 #ifdef INET6 632 if (sc->sc_inc.inc_isipv6) { 633 struct inpcb *oinp = sotoinpcb(lso); 634 struct in6_addr laddr6; 635 struct sockaddr_in6 *sin6; 636 /* 637 * Inherit socket options from the listening socket. 638 * Note that in6p_inputopts are not (and should not be) 639 * copied, since it stores previously received options and is 640 * used to detect if each new option is different than the 641 * previous one and hence should be passed to a user. 642 * If we copied in6p_inputopts, a user would not be able to 643 * receive options just after calling the accept system call. 644 */ 645 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 646 if (oinp->in6p_outputopts) 647 inp->in6p_outputopts = 648 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 649 inp->in6p_route = sc->sc_route6; 650 sc->sc_route6.ro_rt = NULL; 651 652 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, 653 M_SONAME, M_NOWAIT | M_ZERO); 654 if (sin6 == NULL) 655 goto abort; 656 sin6->sin6_family = AF_INET6; 657 sin6->sin6_len = sizeof(*sin6); 658 sin6->sin6_addr = sc->sc_inc.inc6_faddr; 659 sin6->sin6_port = sc->sc_inc.inc_fport; 660 laddr6 = inp->in6p_laddr; 661 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 662 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 663 if (in6_pcbconnect(inp, (struct sockaddr *)sin6, &thread0)) { 664 inp->in6p_laddr = laddr6; 665 FREE(sin6, M_SONAME); 666 goto abort; 667 } 668 FREE(sin6, M_SONAME); 669 } else 670 #endif 671 { 672 struct in_addr laddr; 673 struct sockaddr_in *sin; 674 675 inp->inp_options = ip_srcroute(); 676 if (inp->inp_options == NULL) { 677 inp->inp_options = sc->sc_ipopts; 678 sc->sc_ipopts = NULL; 679 } 680 inp->inp_route = sc->sc_route; 681 sc->sc_route.ro_rt = NULL; 682 683 MALLOC(sin, struct sockaddr_in *, sizeof *sin, 684 M_SONAME, M_NOWAIT | M_ZERO); 685 if (sin == NULL) 686 goto abort; 687 sin->sin_family = AF_INET; 688 sin->sin_len = sizeof(*sin); 689 sin->sin_addr = sc->sc_inc.inc_faddr; 690 sin->sin_port = sc->sc_inc.inc_fport; 691 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 692 laddr = inp->inp_laddr; 693 if (inp->inp_laddr.s_addr == INADDR_ANY) 694 inp->inp_laddr = sc->sc_inc.inc_laddr; 695 if (in_pcbconnect(inp, (struct sockaddr *)sin, &thread0)) { 696 inp->inp_laddr = laddr; 697 FREE(sin, M_SONAME); 698 goto abort; 699 } 700 FREE(sin, M_SONAME); 701 } 702 703 tp = intotcpcb(inp); 704 tp->t_state = TCPS_SYN_RECEIVED; 705 tp->iss = sc->sc_iss; 706 tp->irs = sc->sc_irs; 707 tcp_rcvseqinit(tp); 708 tcp_sendseqinit(tp); 709 tp->snd_wl1 = sc->sc_irs; 710 tp->rcv_up = sc->sc_irs + 1; 711 tp->rcv_wnd = sc->sc_wnd; 712 tp->rcv_adv += tp->rcv_wnd; 713 714 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 715 if (sc->sc_flags & SCF_NOOPT) 716 tp->t_flags |= TF_NOOPT; 717 if (sc->sc_flags & SCF_WINSCALE) { 718 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 719 tp->requested_s_scale = sc->sc_requested_s_scale; 720 tp->request_r_scale = sc->sc_request_r_scale; 721 } 722 if (sc->sc_flags & SCF_TIMESTAMP) { 723 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 724 tp->ts_recent = sc->sc_tsrecent; 725 tp->ts_recent_age = ticks; 726 } 727 if (sc->sc_flags & SCF_CC) { 728 /* 729 * Initialization of the tcpcb for transaction; 730 * set SND.WND = SEG.WND, 731 * initialize CCsend and CCrecv. 732 */ 733 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 734 tp->cc_send = sc->sc_cc_send; 735 tp->cc_recv = sc->sc_cc_recv; 736 } 737 738 tcp_mss(tp, sc->sc_peer_mss); 739 740 /* 741 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 742 */ 743 if (sc->sc_rxtslot != 0) 744 tp->snd_cwnd = tp->t_maxseg; 745 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 746 747 tcpstat.tcps_accepts++; 748 return (so); 749 750 abort: 751 if (so != NULL) 752 (void) soabort(so); 753 return (NULL); 754 } 755 756 /* 757 * This function gets called when we receive an ACK for a 758 * socket in the LISTEN state. We look up the connection 759 * in the syncache, and if its there, we pull it out of 760 * the cache and turn it into a full-blown connection in 761 * the SYN-RECEIVED state. 762 */ 763 int 764 syncache_expand(inc, th, sop, m) 765 struct in_conninfo *inc; 766 struct tcphdr *th; 767 struct socket **sop; 768 struct mbuf *m; 769 { 770 struct syncache *sc; 771 struct syncache_head *sch; 772 struct socket *so; 773 774 sc = syncache_lookup(inc, &sch); 775 if (sc == NULL) { 776 /* 777 * There is no syncache entry, so see if this ACK is 778 * a returning syncookie. To do this, first: 779 * A. See if this socket has had a syncache entry dropped in 780 * the past. We don't want to accept a bogus syncookie 781 * if we've never received a SYN. 782 * B. check that the syncookie is valid. If it is, then 783 * cobble up a fake syncache entry, and return. 784 */ 785 if (!tcp_syncookies) 786 return (0); 787 sc = syncookie_lookup(inc, th, *sop); 788 if (sc == NULL) 789 return (0); 790 sch = NULL; 791 tcpstat.tcps_sc_recvcookie++; 792 } 793 794 /* 795 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 796 */ 797 if (th->th_ack != sc->sc_iss + 1) 798 return (0); 799 800 so = syncache_socket(sc, *sop, m); 801 if (so == NULL) { 802 #if 0 803 resetandabort: 804 /* XXXjlemon check this - is this correct? */ 805 (void) tcp_respond(NULL, m, m, th, 806 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 807 #endif 808 m_freem(m); /* XXX only needed for above */ 809 tcpstat.tcps_sc_aborted++; 810 } else { 811 sc->sc_flags |= SCF_KEEPROUTE; 812 tcpstat.tcps_sc_completed++; 813 } 814 if (sch == NULL) 815 syncache_free(sc); 816 else 817 syncache_drop(sc, sch); 818 *sop = so; 819 return (1); 820 } 821 822 /* 823 * Given a LISTEN socket and an inbound SYN request, add 824 * this to the syn cache, and send back a segment: 825 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 826 * to the source. 827 * 828 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 829 * Doing so would require that we hold onto the data and deliver it 830 * to the application. However, if we are the target of a SYN-flood 831 * DoS attack, an attacker could send data which would eventually 832 * consume all available buffer space if it were ACKed. By not ACKing 833 * the data, we avoid this DoS scenario. 834 */ 835 int 836 syncache_add(inc, to, th, sop, m) 837 struct in_conninfo *inc; 838 struct tcpopt *to; 839 struct tcphdr *th; 840 struct socket **sop; 841 struct mbuf *m; 842 { 843 struct tcpcb *tp; 844 struct socket *so; 845 struct syncache *sc = NULL; 846 struct syncache_head *sch; 847 struct mbuf *ipopts = NULL; 848 struct rmxp_tao *taop; 849 int i, s, win; 850 851 so = *sop; 852 tp = sototcpcb(so); 853 854 /* 855 * Remember the IP options, if any. 856 */ 857 #ifdef INET6 858 if (!inc->inc_isipv6) 859 #endif 860 ipopts = ip_srcroute(); 861 862 /* 863 * See if we already have an entry for this connection. 864 * If we do, resend the SYN,ACK, and reset the retransmit timer. 865 * 866 * XXX 867 * should the syncache be re-initialized with the contents 868 * of the new SYN here (which may have different options?) 869 */ 870 sc = syncache_lookup(inc, &sch); 871 if (sc != NULL) { 872 tcpstat.tcps_sc_dupsyn++; 873 if (ipopts) { 874 /* 875 * If we were remembering a previous source route, 876 * forget it and use the new one we've been given. 877 */ 878 if (sc->sc_ipopts) 879 (void) m_free(sc->sc_ipopts); 880 sc->sc_ipopts = ipopts; 881 } 882 /* 883 * Update timestamp if present. 884 */ 885 if (sc->sc_flags & SCF_TIMESTAMP) 886 sc->sc_tsrecent = to->to_tsval; 887 /* 888 * PCB may have changed, pick up new values. 889 */ 890 sc->sc_tp = tp; 891 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 892 #ifdef TCPDEBUG 893 if (syncache_respond(sc, m, so) == 0) { 894 #else 895 if (syncache_respond(sc, m) == 0) { 896 #endif 897 s = splnet(); 898 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 899 sc, sc_timerq); 900 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 901 splx(s); 902 tcpstat.tcps_sndacks++; 903 tcpstat.tcps_sndtotal++; 904 } 905 *sop = NULL; 906 return (1); 907 } 908 909 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 910 if (sc == NULL) { 911 /* 912 * The zone allocator couldn't provide more entries. 913 * Treat this as if the cache was full; drop the oldest 914 * entry and insert the new one. 915 */ 916 s = splnet(); 917 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 918 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 919 if (sc != NULL) 920 break; 921 } 922 sc->sc_tp->ts_recent = ticks; 923 syncache_drop(sc, NULL); 924 splx(s); 925 tcpstat.tcps_sc_zonefail++; 926 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 927 if (sc == NULL) { 928 if (ipopts) 929 (void) m_free(ipopts); 930 return (0); 931 } 932 } 933 934 /* 935 * Fill in the syncache values. 936 */ 937 bzero(sc, sizeof(*sc)); 938 sc->sc_tp = tp; 939 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 940 sc->sc_ipopts = ipopts; 941 sc->sc_inc.inc_fport = inc->inc_fport; 942 sc->sc_inc.inc_lport = inc->inc_lport; 943 #ifdef INET6 944 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 945 if (inc->inc_isipv6) { 946 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 947 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 948 sc->sc_route6.ro_rt = NULL; 949 } else 950 #endif 951 { 952 sc->sc_inc.inc_faddr = inc->inc_faddr; 953 sc->sc_inc.inc_laddr = inc->inc_laddr; 954 sc->sc_route.ro_rt = NULL; 955 } 956 sc->sc_irs = th->th_seq; 957 sc->sc_flags = 0; 958 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 959 if (tcp_syncookies) 960 sc->sc_iss = syncookie_generate(sc); 961 else 962 sc->sc_iss = arc4random(); 963 964 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 965 win = sbspace(&so->so_rcv); 966 win = imax(win, 0); 967 win = imin(win, TCP_MAXWIN); 968 sc->sc_wnd = win; 969 970 if (tcp_do_rfc1323) { 971 /* 972 * A timestamp received in a SYN makes 973 * it ok to send timestamp requests and replies. 974 */ 975 if (to->to_flags & TOF_TS) { 976 sc->sc_tsrecent = to->to_tsval; 977 sc->sc_flags |= SCF_TIMESTAMP; 978 } 979 if (to->to_flags & TOF_SCALE) { 980 int wscale = 0; 981 982 /* Compute proper scaling value from buffer space */ 983 while (wscale < TCP_MAX_WINSHIFT && 984 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 985 wscale++; 986 sc->sc_request_r_scale = wscale; 987 sc->sc_requested_s_scale = to->to_requested_s_scale; 988 sc->sc_flags |= SCF_WINSCALE; 989 } 990 } 991 if (tcp_do_rfc1644) { 992 /* 993 * A CC or CC.new option received in a SYN makes 994 * it ok to send CC in subsequent segments. 995 */ 996 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 997 sc->sc_cc_recv = to->to_cc; 998 sc->sc_cc_send = CC_INC(tcp_ccgen); 999 sc->sc_flags |= SCF_CC; 1000 } 1001 } 1002 if (tp->t_flags & TF_NOOPT) 1003 sc->sc_flags = SCF_NOOPT; 1004 1005 /* 1006 * XXX 1007 * We have the option here of not doing TAO (even if the segment 1008 * qualifies) and instead fall back to a normal 3WHS via the syncache. 1009 * This allows us to apply synflood protection to TAO-qualifying SYNs 1010 * also. However, there should be a hueristic to determine when to 1011 * do this, and is not present at the moment. 1012 */ 1013 1014 /* 1015 * Perform TAO test on incoming CC (SEG.CC) option, if any. 1016 * - compare SEG.CC against cached CC from the same host, if any. 1017 * - if SEG.CC > chached value, SYN must be new and is accepted 1018 * immediately: save new CC in the cache, mark the socket 1019 * connected, enter ESTABLISHED state, turn on flag to 1020 * send a SYN in the next segment. 1021 * A virtual advertised window is set in rcv_adv to 1022 * initialize SWS prevention. Then enter normal segment 1023 * processing: drop SYN, process data and FIN. 1024 * - otherwise do a normal 3-way handshake. 1025 */ 1026 taop = tcp_gettaocache(&sc->sc_inc); 1027 if ((to->to_flags & TOF_CC) != 0) { 1028 if (((tp->t_flags & TF_NOPUSH) != 0) && 1029 sc->sc_flags & SCF_CC && 1030 taop != NULL && taop->tao_cc != 0 && 1031 CC_GT(to->to_cc, taop->tao_cc)) { 1032 sc->sc_rxtslot = 0; 1033 so = syncache_socket(sc, *sop, m); 1034 if (so != NULL) { 1035 sc->sc_flags |= SCF_KEEPROUTE; 1036 taop->tao_cc = to->to_cc; 1037 *sop = so; 1038 } 1039 syncache_free(sc); 1040 return (so != NULL); 1041 } 1042 } else { 1043 /* 1044 * No CC option, but maybe CC.NEW: invalidate cached value. 1045 */ 1046 if (taop != NULL) 1047 taop->tao_cc = 0; 1048 } 1049 /* 1050 * TAO test failed or there was no CC option, 1051 * do a standard 3-way handshake. 1052 */ 1053 #ifdef TCPDEBUG 1054 if (syncache_respond(sc, m, so) == 0) { 1055 #else 1056 if (syncache_respond(sc, m) == 0) { 1057 #endif 1058 syncache_insert(sc, sch); 1059 tcpstat.tcps_sndacks++; 1060 tcpstat.tcps_sndtotal++; 1061 } else { 1062 syncache_free(sc); 1063 tcpstat.tcps_sc_dropped++; 1064 } 1065 *sop = NULL; 1066 return (1); 1067 } 1068 1069 #ifdef TCPDEBUG 1070 static int 1071 syncache_respond(sc, m, so) 1072 struct syncache *sc; 1073 struct mbuf *m; 1074 struct socket *so; 1075 #else 1076 static int 1077 syncache_respond(sc, m) 1078 struct syncache *sc; 1079 struct mbuf *m; 1080 #endif 1081 { 1082 u_int8_t *optp; 1083 int optlen, error; 1084 u_int16_t tlen, hlen, mssopt; 1085 struct ip *ip = NULL; 1086 struct rtentry *rt; 1087 struct tcphdr *th; 1088 #ifdef INET6 1089 struct ip6_hdr *ip6 = NULL; 1090 #endif 1091 1092 #ifdef INET6 1093 if (sc->sc_inc.inc_isipv6) { 1094 rt = tcp_rtlookup6(&sc->sc_inc); 1095 if (rt != NULL) 1096 mssopt = rt->rt_ifp->if_mtu - 1097 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1098 else 1099 mssopt = tcp_v6mssdflt; 1100 hlen = sizeof(struct ip6_hdr); 1101 } else 1102 #endif 1103 { 1104 rt = tcp_rtlookup(&sc->sc_inc); 1105 if (rt != NULL) 1106 mssopt = rt->rt_ifp->if_mtu - 1107 (sizeof(struct ip) + sizeof(struct tcphdr)); 1108 else 1109 mssopt = tcp_mssdflt; 1110 hlen = sizeof(struct ip); 1111 } 1112 1113 /* Compute the size of the TCP options. */ 1114 if (sc->sc_flags & SCF_NOOPT) { 1115 optlen = 0; 1116 } else { 1117 optlen = TCPOLEN_MAXSEG + 1118 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1119 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1120 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1121 } 1122 tlen = hlen + sizeof(struct tcphdr) + optlen; 1123 1124 /* 1125 * XXX 1126 * assume that the entire packet will fit in a header mbuf 1127 */ 1128 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1129 1130 /* 1131 * XXX shouldn't this reuse the mbuf if possible ? 1132 * Create the IP+TCP header from scratch. 1133 */ 1134 if (m) 1135 m_freem(m); 1136 1137 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1138 if (m == NULL) 1139 return (ENOBUFS); 1140 m->m_data += max_linkhdr; 1141 m->m_len = tlen; 1142 m->m_pkthdr.len = tlen; 1143 m->m_pkthdr.rcvif = NULL; 1144 #ifdef MAC 1145 mac_create_mbuf_from_socket(sc->sc_tp->t_inpcb->inp_socket, m); 1146 #endif 1147 1148 #ifdef INET6 1149 if (sc->sc_inc.inc_isipv6) { 1150 ip6 = mtod(m, struct ip6_hdr *); 1151 ip6->ip6_vfc = IPV6_VERSION; 1152 ip6->ip6_nxt = IPPROTO_TCP; 1153 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1154 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1155 ip6->ip6_plen = htons(tlen - hlen); 1156 /* ip6_hlim is set after checksum */ 1157 /* ip6_flow = ??? */ 1158 1159 th = (struct tcphdr *)(ip6 + 1); 1160 } else 1161 #endif 1162 { 1163 ip = mtod(m, struct ip *); 1164 ip->ip_v = IPVERSION; 1165 ip->ip_hl = sizeof(struct ip) >> 2; 1166 ip->ip_len = tlen; 1167 ip->ip_id = 0; 1168 ip->ip_off = 0; 1169 ip->ip_sum = 0; 1170 ip->ip_p = IPPROTO_TCP; 1171 ip->ip_src = sc->sc_inc.inc_laddr; 1172 ip->ip_dst = sc->sc_inc.inc_faddr; 1173 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1174 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1175 1176 /* 1177 * See if we should do MTU discovery. Route lookups are 1178 * expensive, so we will only unset the DF bit if: 1179 * 1180 * 1) path_mtu_discovery is disabled 1181 * 2) the SCF_UNREACH flag has been set 1182 */ 1183 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1184 ip->ip_off |= IP_DF; 1185 1186 th = (struct tcphdr *)(ip + 1); 1187 } 1188 th->th_sport = sc->sc_inc.inc_lport; 1189 th->th_dport = sc->sc_inc.inc_fport; 1190 1191 th->th_seq = htonl(sc->sc_iss); 1192 th->th_ack = htonl(sc->sc_irs + 1); 1193 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1194 th->th_x2 = 0; 1195 th->th_flags = TH_SYN|TH_ACK; 1196 th->th_win = htons(sc->sc_wnd); 1197 th->th_urp = 0; 1198 1199 /* Tack on the TCP options. */ 1200 if (optlen != 0) { 1201 optp = (u_int8_t *)(th + 1); 1202 *optp++ = TCPOPT_MAXSEG; 1203 *optp++ = TCPOLEN_MAXSEG; 1204 *optp++ = (mssopt >> 8) & 0xff; 1205 *optp++ = mssopt & 0xff; 1206 1207 if (sc->sc_flags & SCF_WINSCALE) { 1208 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1209 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1210 sc->sc_request_r_scale); 1211 optp += 4; 1212 } 1213 1214 if (sc->sc_flags & SCF_TIMESTAMP) { 1215 u_int32_t *lp = (u_int32_t *)(optp); 1216 1217 /* Form timestamp option per appendix A of RFC 1323. */ 1218 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1219 *lp++ = htonl(ticks); 1220 *lp = htonl(sc->sc_tsrecent); 1221 optp += TCPOLEN_TSTAMP_APPA; 1222 } 1223 1224 /* 1225 * Send CC and CC.echo if we received CC from our peer. 1226 */ 1227 if (sc->sc_flags & SCF_CC) { 1228 u_int32_t *lp = (u_int32_t *)(optp); 1229 1230 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1231 *lp++ = htonl(sc->sc_cc_send); 1232 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1233 *lp = htonl(sc->sc_cc_recv); 1234 optp += TCPOLEN_CC_APPA * 2; 1235 } 1236 } 1237 1238 #ifdef INET6 1239 if (sc->sc_inc.inc_isipv6) { 1240 struct route_in6 *ro6 = &sc->sc_route6; 1241 1242 th->th_sum = 0; 1243 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1244 ip6->ip6_hlim = in6_selecthlim(NULL, 1245 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1246 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1247 sc->sc_tp->t_inpcb); 1248 } else 1249 #endif 1250 { 1251 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1252 htons(tlen - hlen + IPPROTO_TCP)); 1253 m->m_pkthdr.csum_flags = CSUM_TCP; 1254 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1255 #ifdef TCPDEBUG 1256 /* 1257 * Trace. 1258 */ 1259 if (so != NULL && so->so_options & SO_DEBUG) { 1260 struct tcpcb *tp = sototcpcb(so); 1261 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1262 mtod(m, void *), th, 0); 1263 } 1264 #endif 1265 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL, 1266 sc->sc_tp->t_inpcb); 1267 } 1268 return (error); 1269 } 1270 1271 /* 1272 * cookie layers: 1273 * 1274 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1275 * | peer iss | 1276 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1277 * | 0 |(A)| | 1278 * (A): peer mss index 1279 */ 1280 1281 /* 1282 * The values below are chosen to minimize the size of the tcp_secret 1283 * table, as well as providing roughly a 16 second lifetime for the cookie. 1284 */ 1285 1286 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1287 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1288 1289 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1290 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1291 #define SYNCOOKIE_TIMEOUT \ 1292 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1293 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1294 1295 static struct { 1296 u_int32_t ts_secbits[4]; 1297 u_int ts_expire; 1298 } tcp_secret[SYNCOOKIE_NSECRETS]; 1299 1300 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1301 1302 static MD5_CTX syn_ctx; 1303 1304 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1305 1306 struct md5_add { 1307 u_int32_t laddr, faddr; 1308 u_int32_t secbits[4]; 1309 u_int16_t lport, fport; 1310 }; 1311 1312 #ifdef CTASSERT 1313 CTASSERT(sizeof(struct md5_add) == 28); 1314 #endif 1315 1316 /* 1317 * Consider the problem of a recreated (and retransmitted) cookie. If the 1318 * original SYN was accepted, the connection is established. The second 1319 * SYN is inflight, and if it arrives with an ISN that falls within the 1320 * receive window, the connection is killed. 1321 * 1322 * However, since cookies have other problems, this may not be worth 1323 * worrying about. 1324 */ 1325 1326 static u_int32_t 1327 syncookie_generate(struct syncache *sc) 1328 { 1329 u_int32_t md5_buffer[4]; 1330 u_int32_t data; 1331 int idx, i; 1332 struct md5_add add; 1333 1334 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1335 if (tcp_secret[idx].ts_expire < ticks) { 1336 for (i = 0; i < 4; i++) 1337 tcp_secret[idx].ts_secbits[i] = arc4random(); 1338 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1339 } 1340 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1341 if (tcp_msstab[data] <= sc->sc_peer_mss) 1342 break; 1343 data = (data << SYNCOOKIE_WNDBITS) | idx; 1344 data ^= sc->sc_irs; /* peer's iss */ 1345 MD5Init(&syn_ctx); 1346 #ifdef INET6 1347 if (sc->sc_inc.inc_isipv6) { 1348 MD5Add(sc->sc_inc.inc6_laddr); 1349 MD5Add(sc->sc_inc.inc6_faddr); 1350 add.laddr = 0; 1351 add.faddr = 0; 1352 } else 1353 #endif 1354 { 1355 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1356 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1357 } 1358 add.lport = sc->sc_inc.inc_lport; 1359 add.fport = sc->sc_inc.inc_fport; 1360 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1361 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1362 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1363 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1364 MD5Add(add); 1365 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1366 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1367 return (data); 1368 } 1369 1370 static struct syncache * 1371 syncookie_lookup(inc, th, so) 1372 struct in_conninfo *inc; 1373 struct tcphdr *th; 1374 struct socket *so; 1375 { 1376 u_int32_t md5_buffer[4]; 1377 struct syncache *sc; 1378 u_int32_t data; 1379 int wnd, idx; 1380 struct md5_add add; 1381 1382 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1383 idx = data & SYNCOOKIE_WNDMASK; 1384 if (tcp_secret[idx].ts_expire < ticks || 1385 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1386 return (NULL); 1387 MD5Init(&syn_ctx); 1388 #ifdef INET6 1389 if (inc->inc_isipv6) { 1390 MD5Add(inc->inc6_laddr); 1391 MD5Add(inc->inc6_faddr); 1392 add.laddr = 0; 1393 add.faddr = 0; 1394 } else 1395 #endif 1396 { 1397 add.laddr = inc->inc_laddr.s_addr; 1398 add.faddr = inc->inc_faddr.s_addr; 1399 } 1400 add.lport = inc->inc_lport; 1401 add.fport = inc->inc_fport; 1402 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1403 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1404 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1405 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1406 MD5Add(add); 1407 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1408 data ^= md5_buffer[0]; 1409 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1410 return (NULL); 1411 data = data >> SYNCOOKIE_WNDBITS; 1412 1413 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1414 if (sc == NULL) 1415 return (NULL); 1416 /* 1417 * Fill in the syncache values. 1418 * XXX duplicate code from syncache_add 1419 */ 1420 sc->sc_ipopts = NULL; 1421 sc->sc_inc.inc_fport = inc->inc_fport; 1422 sc->sc_inc.inc_lport = inc->inc_lport; 1423 #ifdef INET6 1424 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1425 if (inc->inc_isipv6) { 1426 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1427 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1428 sc->sc_route6.ro_rt = NULL; 1429 } else 1430 #endif 1431 { 1432 sc->sc_inc.inc_faddr = inc->inc_faddr; 1433 sc->sc_inc.inc_laddr = inc->inc_laddr; 1434 sc->sc_route.ro_rt = NULL; 1435 } 1436 sc->sc_irs = th->th_seq - 1; 1437 sc->sc_iss = th->th_ack - 1; 1438 wnd = sbspace(&so->so_rcv); 1439 wnd = imax(wnd, 0); 1440 wnd = imin(wnd, TCP_MAXWIN); 1441 sc->sc_wnd = wnd; 1442 sc->sc_flags = 0; 1443 sc->sc_rxtslot = 0; 1444 sc->sc_peer_mss = tcp_msstab[data]; 1445 return (sc); 1446 } 1447