1 /* 2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * All advertising materials mentioning features or use of this software 53 * must display the following acknowledgement: 54 * This product includes software developed by Jeffrey M. Hsu. 55 * 56 * Copyright (c) 2001 Networks Associates Technologies, Inc. 57 * All rights reserved. 58 * 59 * This software was developed for the FreeBSD Project by Jonathan Lemon 60 * and NAI Labs, the Security Research Division of Network Associates, Inc. 61 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 62 * DARPA CHATS research program. 63 * 64 * Redistribution and use in source and binary forms, with or without 65 * modification, are permitted provided that the following conditions 66 * are met: 67 * 1. Redistributions of source code must retain the above copyright 68 * notice, this list of conditions and the following disclaimer. 69 * 2. Redistributions in binary form must reproduce the above copyright 70 * notice, this list of conditions and the following disclaimer in the 71 * documentation and/or other materials provided with the distribution. 72 * 3. The name of the author may not be used to endorse or promote 73 * products derived from this software without specific prior written 74 * permission. 75 * 76 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 77 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 78 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 79 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 80 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 81 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 82 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 83 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 84 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 85 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 86 * SUCH DAMAGE. 87 * 88 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.5.2.14 2003/02/24 04:02:27 silby Exp $ 89 * $DragonFly: src/sys/netinet/tcp_syncache.c,v 1.16 2004/08/08 06:33:24 hsu Exp $ 90 */ 91 92 #include "opt_inet6.h" 93 #include "opt_ipsec.h" 94 95 #include <sys/param.h> 96 #include <sys/systm.h> 97 #include <sys/kernel.h> 98 #include <sys/sysctl.h> 99 #include <sys/malloc.h> 100 #include <sys/mbuf.h> 101 #include <sys/md5.h> 102 #include <sys/proc.h> /* for proc0 declaration */ 103 #include <sys/random.h> 104 #include <sys/socket.h> 105 #include <sys/socketvar.h> 106 #include <sys/in_cksum.h> 107 108 #include <net/if.h> 109 #include <net/route.h> 110 111 #include <netinet/in.h> 112 #include <netinet/in_systm.h> 113 #include <netinet/ip.h> 114 #include <netinet/in_var.h> 115 #include <netinet/in_pcb.h> 116 #include <netinet/ip_var.h> 117 #include <netinet/ip6.h> 118 #ifdef INET6 119 #include <netinet/icmp6.h> 120 #include <netinet6/nd6.h> 121 #endif 122 #include <netinet6/ip6_var.h> 123 #include <netinet6/in6_pcb.h> 124 #include <netinet/tcp.h> 125 #include <netinet/tcp_fsm.h> 126 #include <netinet/tcp_seq.h> 127 #include <netinet/tcp_timer.h> 128 #include <netinet/tcp_var.h> 129 #include <netinet6/tcp6_var.h> 130 131 #ifdef IPSEC 132 #include <netinet6/ipsec.h> 133 #ifdef INET6 134 #include <netinet6/ipsec6.h> 135 #endif 136 #include <netproto/key/key.h> 137 #endif /*IPSEC*/ 138 139 #ifdef FAST_IPSEC 140 #include <netipsec/ipsec.h> 141 #ifdef INET6 142 #include <netipsec/ipsec6.h> 143 #endif 144 #include <netipsec/key.h> 145 #define IPSEC 146 #endif /*FAST_IPSEC*/ 147 148 #include <vm/vm_zone.h> 149 150 static int tcp_syncookies = 1; 151 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 152 &tcp_syncookies, 0, 153 "Use TCP SYN cookies if the syncache overflows"); 154 155 static void syncache_drop(struct syncache *, struct syncache_head *); 156 static void syncache_free(struct syncache *); 157 static void syncache_insert(struct syncache *, struct syncache_head *); 158 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 159 static int syncache_respond(struct syncache *, struct mbuf *); 160 static struct socket *syncache_socket(struct syncache *, struct socket *); 161 static void syncache_timer(void *); 162 static u_int32_t syncookie_generate(struct syncache *); 163 static struct syncache *syncookie_lookup(struct in_conninfo *, 164 struct tcphdr *, struct socket *); 165 166 /* 167 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 168 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 169 * the odds are that the user has given up attempting to connect by then. 170 */ 171 #define SYNCACHE_MAXREXMTS 3 172 173 /* Arbitrary values */ 174 #define TCP_SYNCACHE_HASHSIZE 512 175 #define TCP_SYNCACHE_BUCKETLIMIT 30 176 177 struct tcp_syncache { 178 struct syncache_head *hashbase; 179 struct vm_zone *zone; 180 u_int hashsize; 181 u_int hashmask; 182 u_int bucket_limit; 183 u_int cache_count; 184 u_int cache_limit; 185 u_int rexmt_limit; 186 u_int hash_secret; 187 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 188 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 189 }; 190 static struct tcp_syncache tcp_syncache; 191 192 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 193 194 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 195 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 196 197 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 198 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 199 200 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 201 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 202 203 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 204 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 205 206 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 207 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 208 209 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 210 211 #define SYNCACHE_HASH(inc, mask) \ 212 ((tcp_syncache.hash_secret ^ \ 213 (inc)->inc_faddr.s_addr ^ \ 214 ((inc)->inc_faddr.s_addr >> 16) ^ \ 215 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 216 217 #define SYNCACHE_HASH6(inc, mask) \ 218 ((tcp_syncache.hash_secret ^ \ 219 (inc)->inc6_faddr.s6_addr32[0] ^ \ 220 (inc)->inc6_faddr.s6_addr32[3] ^ \ 221 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 222 223 #define ENDPTS_EQ(a, b) ( \ 224 (a)->ie_fport == (b)->ie_fport && \ 225 (a)->ie_lport == (b)->ie_lport && \ 226 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 227 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 228 ) 229 230 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 231 232 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 233 sc->sc_rxtslot = slot; \ 234 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot]; \ 235 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[slot], sc, sc_timerq); \ 236 if (!callout_active(&tcp_syncache.tt_timerq[slot])) \ 237 callout_reset(&tcp_syncache.tt_timerq[slot], \ 238 TCPTV_RTOBASE * tcp_backoff[slot], \ 239 syncache_timer, (void *)((intptr_t)slot)); \ 240 } while (0) 241 242 static void 243 syncache_free(struct syncache *sc) 244 { 245 struct rtentry *rt; 246 #ifdef INET6 247 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 248 #else 249 const boolean_t isipv6 = FALSE; 250 #endif 251 252 if (sc->sc_ipopts) 253 (void) m_free(sc->sc_ipopts); 254 if (isipv6) 255 rt = sc->sc_route6.ro_rt; 256 else 257 rt = sc->sc_route.ro_rt; 258 if (rt != NULL) { 259 /* 260 * If this is the only reference to a protocol cloned 261 * route, remove it immediately. 262 */ 263 if (rt->rt_flags & RTF_WASCLONED && 264 (sc->sc_flags & SCF_KEEPROUTE) == 0 && 265 rt->rt_refcnt == 1) 266 rtrequest(RTM_DELETE, rt_key(rt), 267 rt->rt_gateway, rt_mask(rt), 268 rt->rt_flags, NULL); 269 RTFREE(rt); 270 } 271 zfree(tcp_syncache.zone, sc); 272 } 273 274 void 275 syncache_init(void) 276 { 277 int i; 278 279 tcp_syncache.cache_count = 0; 280 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 281 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 282 tcp_syncache.cache_limit = 283 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 284 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 285 tcp_syncache.hash_secret = arc4random(); 286 287 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 288 &tcp_syncache.hashsize); 289 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 290 &tcp_syncache.cache_limit); 291 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 292 &tcp_syncache.bucket_limit); 293 if (!powerof2(tcp_syncache.hashsize)) { 294 printf("WARNING: syncache hash size is not a power of 2.\n"); 295 tcp_syncache.hashsize = 512; /* safe default */ 296 } 297 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 298 299 /* Allocate the hash table. */ 300 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 301 tcp_syncache.hashsize * sizeof(struct syncache_head), 302 M_SYNCACHE, M_WAITOK); 303 304 /* Initialize the hash buckets. */ 305 for (i = 0; i < tcp_syncache.hashsize; i++) { 306 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 307 tcp_syncache.hashbase[i].sch_length = 0; 308 } 309 310 /* Initialize the timer queues. */ 311 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 312 TAILQ_INIT(&tcp_syncache.timerq[i]); 313 callout_init(&tcp_syncache.tt_timerq[i]); 314 } 315 316 /* 317 * Allocate the syncache entries. Allow the zone to allocate one 318 * more entry than cache limit, so a new entry can bump out an 319 * older one. 320 */ 321 tcp_syncache.zone = zinit("syncache", sizeof(struct syncache), 322 tcp_syncache.cache_limit, ZONE_INTERRUPT, 0); 323 tcp_syncache.cache_limit -= 1; 324 } 325 326 static void 327 syncache_insert(sc, sch) 328 struct syncache *sc; 329 struct syncache_head *sch; 330 { 331 struct syncache *sc2; 332 int i; 333 334 /* 335 * Make sure that we don't overflow the per-bucket 336 * limit or the total cache size limit. 337 */ 338 if (sch->sch_length >= tcp_syncache.bucket_limit) { 339 /* 340 * The bucket is full, toss the oldest element. 341 */ 342 sc2 = TAILQ_FIRST(&sch->sch_bucket); 343 sc2->sc_tp->ts_recent = ticks; 344 syncache_drop(sc2, sch); 345 tcpstat.tcps_sc_bucketoverflow++; 346 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 347 /* 348 * The cache is full. Toss the oldest entry in the 349 * entire cache. This is the front entry in the 350 * first non-empty timer queue with the largest 351 * timeout value. 352 */ 353 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 354 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 355 if (sc2 != NULL) 356 break; 357 } 358 sc2->sc_tp->ts_recent = ticks; 359 syncache_drop(sc2, NULL); 360 tcpstat.tcps_sc_cacheoverflow++; 361 } 362 363 /* Initialize the entry's timer. */ 364 SYNCACHE_TIMEOUT(sc, 0); 365 366 /* Put it into the bucket. */ 367 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 368 sch->sch_length++; 369 tcp_syncache.cache_count++; 370 tcpstat.tcps_sc_added++; 371 } 372 373 static void 374 syncache_drop(sc, sch) 375 struct syncache *sc; 376 struct syncache_head *sch; 377 { 378 #ifdef INET6 379 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 380 #else 381 const boolean_t isipv6 = FALSE; 382 #endif 383 384 if (sch == NULL) { 385 if (isipv6) { 386 sch = &tcp_syncache.hashbase[ 387 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 388 } else { 389 sch = &tcp_syncache.hashbase[ 390 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 391 } 392 } 393 394 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 395 sch->sch_length--; 396 tcp_syncache.cache_count--; 397 398 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 399 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 400 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 401 402 syncache_free(sc); 403 } 404 405 /* 406 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 407 * If we have retransmitted an entry the maximum number of times, expire it. 408 */ 409 static void 410 syncache_timer(xslot) 411 void *xslot; 412 { 413 intptr_t slot = (intptr_t)xslot; 414 struct syncache *sc, *nsc; 415 struct inpcb *inp; 416 int s; 417 418 s = splnet(); 419 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 420 !callout_active(&tcp_syncache.tt_timerq[slot])) { 421 splx(s); 422 return; 423 } 424 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 425 426 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 427 while (nsc != NULL) { 428 if (ticks < nsc->sc_rxttime) 429 break; 430 sc = nsc; 431 inp = sc->sc_tp->t_inpcb; 432 if (slot == SYNCACHE_MAXREXMTS || 433 slot >= tcp_syncache.rexmt_limit || 434 inp->inp_gencnt != sc->sc_inp_gencnt) { 435 nsc = TAILQ_NEXT(sc, sc_timerq); 436 syncache_drop(sc, NULL); 437 tcpstat.tcps_sc_stale++; 438 continue; 439 } 440 /* 441 * syncache_respond() may call back into the syncache to 442 * to modify another entry, so do not obtain the next 443 * entry on the timer chain until it has completed. 444 */ 445 (void) syncache_respond(sc, NULL); 446 nsc = TAILQ_NEXT(sc, sc_timerq); 447 tcpstat.tcps_sc_retransmitted++; 448 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 449 SYNCACHE_TIMEOUT(sc, slot + 1); 450 } 451 if (nsc != NULL) 452 callout_reset(&tcp_syncache.tt_timerq[slot], 453 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 454 splx(s); 455 } 456 457 /* 458 * Find an entry in the syncache. 459 */ 460 struct syncache * 461 syncache_lookup(inc, schp) 462 struct in_conninfo *inc; 463 struct syncache_head **schp; 464 { 465 struct syncache *sc; 466 struct syncache_head *sch; 467 468 #ifdef INET6 469 if (inc->inc_isipv6) { 470 sch = &tcp_syncache.hashbase[ 471 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 472 *schp = sch; 473 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 474 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 475 return (sc); 476 } else 477 #endif 478 { 479 sch = &tcp_syncache.hashbase[ 480 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 481 *schp = sch; 482 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 483 #ifdef INET6 484 if (sc->sc_inc.inc_isipv6) 485 continue; 486 #endif 487 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 488 return (sc); 489 } 490 } 491 return (NULL); 492 } 493 494 /* 495 * This function is called when we get a RST for a 496 * non-existent connection, so that we can see if the 497 * connection is in the syn cache. If it is, zap it. 498 */ 499 void 500 syncache_chkrst(inc, th) 501 struct in_conninfo *inc; 502 struct tcphdr *th; 503 { 504 struct syncache *sc; 505 struct syncache_head *sch; 506 507 sc = syncache_lookup(inc, &sch); 508 if (sc == NULL) 509 return; 510 /* 511 * If the RST bit is set, check the sequence number to see 512 * if this is a valid reset segment. 513 * RFC 793 page 37: 514 * In all states except SYN-SENT, all reset (RST) segments 515 * are validated by checking their SEQ-fields. A reset is 516 * valid if its sequence number is in the window. 517 * 518 * The sequence number in the reset segment is normally an 519 * echo of our outgoing acknowlegement numbers, but some hosts 520 * send a reset with the sequence number at the rightmost edge 521 * of our receive window, and we have to handle this case. 522 */ 523 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 524 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 525 syncache_drop(sc, sch); 526 tcpstat.tcps_sc_reset++; 527 } 528 } 529 530 void 531 syncache_badack(inc) 532 struct in_conninfo *inc; 533 { 534 struct syncache *sc; 535 struct syncache_head *sch; 536 537 sc = syncache_lookup(inc, &sch); 538 if (sc != NULL) { 539 syncache_drop(sc, sch); 540 tcpstat.tcps_sc_badack++; 541 } 542 } 543 544 void 545 syncache_unreach(inc, th) 546 struct in_conninfo *inc; 547 struct tcphdr *th; 548 { 549 struct syncache *sc; 550 struct syncache_head *sch; 551 552 /* we are called at splnet() here */ 553 sc = syncache_lookup(inc, &sch); 554 if (sc == NULL) 555 return; 556 557 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 558 if (ntohl(th->th_seq) != sc->sc_iss) 559 return; 560 561 /* 562 * If we've rertransmitted 3 times and this is our second error, 563 * we remove the entry. Otherwise, we allow it to continue on. 564 * This prevents us from incorrectly nuking an entry during a 565 * spurious network outage. 566 * 567 * See tcp_notify(). 568 */ 569 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 570 sc->sc_flags |= SCF_UNREACH; 571 return; 572 } 573 syncache_drop(sc, sch); 574 tcpstat.tcps_sc_unreach++; 575 } 576 577 /* 578 * Build a new TCP socket structure from a syncache entry. 579 */ 580 static struct socket * 581 syncache_socket(sc, lso) 582 struct syncache *sc; 583 struct socket *lso; 584 { 585 struct inpcb *inp = NULL; 586 struct socket *so; 587 struct tcpcb *tp; 588 #ifdef INET6 589 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 590 #else 591 const boolean_t isipv6 = FALSE; 592 #endif 593 594 /* 595 * Ok, create the full blown connection, and set things up 596 * as they would have been set up if we had created the 597 * connection when the SYN arrived. If we can't create 598 * the connection, abort it. 599 */ 600 so = sonewconn(lso, SS_ISCONNECTED); 601 if (so == NULL) { 602 /* 603 * Drop the connection; we will send a RST if the peer 604 * retransmits the ACK, 605 */ 606 tcpstat.tcps_listendrop++; 607 goto abort; 608 } 609 610 inp = sotoinpcb(so); 611 612 /* 613 * Insert new socket into hash list. 614 */ 615 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 616 if (isipv6) { 617 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 618 } else { 619 #ifdef INET6 620 inp->inp_vflag &= ~INP_IPV6; 621 inp->inp_vflag |= INP_IPV4; 622 #endif 623 inp->inp_laddr = sc->sc_inc.inc_laddr; 624 } 625 inp->inp_lport = sc->sc_inc.inc_lport; 626 if (in_pcbinsporthash(inp) != 0) { 627 /* 628 * Undo the assignments above if we failed to 629 * put the PCB on the hash lists. 630 */ 631 if (isipv6) 632 inp->in6p_laddr = in6addr_any; 633 else 634 inp->inp_laddr.s_addr = INADDR_ANY; 635 inp->inp_lport = 0; 636 goto abort; 637 } 638 #ifdef IPSEC 639 /* copy old policy into new socket's */ 640 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 641 printf("syncache_expand: could not copy policy\n"); 642 #endif 643 if (isipv6) { 644 struct inpcb *oinp = sotoinpcb(lso); 645 struct in6_addr laddr6; 646 struct sockaddr_in6 sin6; 647 /* 648 * Inherit socket options from the listening socket. 649 * Note that in6p_inputopts are not (and should not be) 650 * copied, since it stores previously received options and is 651 * used to detect if each new option is different than the 652 * previous one and hence should be passed to a user. 653 * If we copied in6p_inputopts, a user would not be able to 654 * receive options just after calling the accept system call. 655 */ 656 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 657 if (oinp->in6p_outputopts) 658 inp->in6p_outputopts = 659 ip6_copypktopts(oinp->in6p_outputopts, M_INTWAIT); 660 inp->in6p_route = sc->sc_route6; 661 sc->sc_route6.ro_rt = NULL; 662 663 sin6.sin6_family = AF_INET6; 664 sin6.sin6_len = sizeof sin6; 665 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 666 sin6.sin6_port = sc->sc_inc.inc_fport; 667 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 668 laddr6 = inp->in6p_laddr; 669 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 670 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 671 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) { 672 inp->in6p_laddr = laddr6; 673 goto abort; 674 } 675 } else { 676 struct in_addr laddr; 677 struct sockaddr_in sin; 678 679 inp->inp_options = ip_srcroute(); 680 if (inp->inp_options == NULL) { 681 inp->inp_options = sc->sc_ipopts; 682 sc->sc_ipopts = NULL; 683 } 684 inp->inp_route = sc->sc_route; 685 sc->sc_route.ro_rt = NULL; 686 687 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(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 goto abort; 698 } 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 tcpstat.tcps_accepts++; 746 return (so); 747 748 abort: 749 if (so != NULL) 750 (void) soabort(so); 751 return (NULL); 752 } 753 754 /* 755 * This function gets called when we receive an ACK for a 756 * socket in the LISTEN state. We look up the connection 757 * in the syncache, and if its there, we pull it out of 758 * the cache and turn it into a full-blown connection in 759 * the SYN-RECEIVED state. 760 */ 761 int 762 syncache_expand(inc, th, sop, m) 763 struct in_conninfo *inc; 764 struct tcphdr *th; 765 struct socket **sop; 766 struct mbuf *m; 767 { 768 struct syncache *sc; 769 struct syncache_head *sch; 770 struct socket *so; 771 772 sc = syncache_lookup(inc, &sch); 773 if (sc == NULL) { 774 /* 775 * There is no syncache entry, so see if this ACK is 776 * a returning syncookie. To do this, first: 777 * A. See if this socket has had a syncache entry dropped in 778 * the past. We don't want to accept a bogus syncookie 779 * if we've never received a SYN. 780 * B. check that the syncookie is valid. If it is, then 781 * cobble up a fake syncache entry, and return. 782 */ 783 if (!tcp_syncookies) 784 return (0); 785 sc = syncookie_lookup(inc, th, *sop); 786 if (sc == NULL) 787 return (0); 788 sch = NULL; 789 tcpstat.tcps_sc_recvcookie++; 790 } 791 792 /* 793 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 794 */ 795 if (th->th_ack != sc->sc_iss + 1) 796 return (0); 797 798 so = syncache_socket(sc, *sop); 799 if (so == NULL) { 800 #if 0 801 resetandabort: 802 /* XXXjlemon check this - is this correct? */ 803 (void) tcp_respond(NULL, m, m, th, 804 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK); 805 #endif 806 m_freem(m); /* XXX only needed for above */ 807 tcpstat.tcps_sc_aborted++; 808 } else { 809 sc->sc_flags |= SCF_KEEPROUTE; 810 tcpstat.tcps_sc_completed++; 811 } 812 if (sch == NULL) 813 syncache_free(sc); 814 else 815 syncache_drop(sc, sch); 816 *sop = so; 817 return (1); 818 } 819 820 /* 821 * Given a LISTEN socket and an inbound SYN request, add 822 * this to the syn cache, and send back a segment: 823 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 824 * to the source. 825 * 826 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 827 * Doing so would require that we hold onto the data and deliver it 828 * to the application. However, if we are the target of a SYN-flood 829 * DoS attack, an attacker could send data which would eventually 830 * consume all available buffer space if it were ACKed. By not ACKing 831 * the data, we avoid this DoS scenario. 832 */ 833 int 834 syncache_add(inc, to, th, sop, m) 835 struct in_conninfo *inc; 836 struct tcpopt *to; 837 struct tcphdr *th; 838 struct socket **sop; 839 struct mbuf *m; 840 { 841 struct tcpcb *tp; 842 struct socket *so; 843 struct syncache *sc = NULL; 844 struct syncache_head *sch; 845 struct mbuf *ipopts = NULL; 846 struct rmxp_tao *taop; 847 int win; 848 849 so = *sop; 850 tp = sototcpcb(so); 851 852 /* 853 * Remember the IP options, if any. 854 */ 855 #ifdef INET6 856 if (!inc->inc_isipv6) 857 #endif 858 ipopts = ip_srcroute(); 859 860 /* 861 * See if we already have an entry for this connection. 862 * If we do, resend the SYN,ACK, and reset the retransmit timer. 863 * 864 * XXX 865 * should the syncache be re-initialized with the contents 866 * of the new SYN here (which may have different options?) 867 */ 868 sc = syncache_lookup(inc, &sch); 869 if (sc != NULL) { 870 tcpstat.tcps_sc_dupsyn++; 871 if (ipopts) { 872 /* 873 * If we were remembering a previous source route, 874 * forget it and use the new one we've been given. 875 */ 876 if (sc->sc_ipopts) 877 (void) m_free(sc->sc_ipopts); 878 sc->sc_ipopts = ipopts; 879 } 880 /* 881 * Update timestamp if present. 882 */ 883 if (sc->sc_flags & SCF_TIMESTAMP) 884 sc->sc_tsrecent = to->to_tsval; 885 /* 886 * PCB may have changed, pick up new values. 887 */ 888 sc->sc_tp = tp; 889 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 890 if (syncache_respond(sc, m) == 0) { 891 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 892 sc, sc_timerq); 893 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 894 tcpstat.tcps_sndacks++; 895 tcpstat.tcps_sndtotal++; 896 } 897 *sop = NULL; 898 return (1); 899 } 900 901 /* 902 * This allocation is guaranteed to succeed because we 903 * preallocate one more syncache entry than cache_limit. 904 */ 905 sc = zalloc(tcp_syncache.zone); 906 907 /* 908 * Fill in the syncache values. 909 */ 910 sc->sc_tp = tp; 911 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 912 sc->sc_ipopts = ipopts; 913 sc->sc_inc.inc_fport = inc->inc_fport; 914 sc->sc_inc.inc_lport = inc->inc_lport; 915 #ifdef INET6 916 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 917 if (inc->inc_isipv6) { 918 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 919 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 920 sc->sc_route6.ro_rt = NULL; 921 } else 922 #endif 923 { 924 sc->sc_inc.inc_faddr = inc->inc_faddr; 925 sc->sc_inc.inc_laddr = inc->inc_laddr; 926 sc->sc_route.ro_rt = NULL; 927 } 928 sc->sc_irs = th->th_seq; 929 sc->sc_flags = 0; 930 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 931 if (tcp_syncookies) 932 sc->sc_iss = syncookie_generate(sc); 933 else 934 sc->sc_iss = arc4random(); 935 936 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 937 win = sbspace(&so->so_rcv); 938 win = imax(win, 0); 939 win = imin(win, TCP_MAXWIN); 940 sc->sc_wnd = win; 941 942 if (tcp_do_rfc1323) { 943 /* 944 * A timestamp received in a SYN makes 945 * it ok to send timestamp requests and replies. 946 */ 947 if (to->to_flags & TOF_TS) { 948 sc->sc_tsrecent = to->to_tsval; 949 sc->sc_flags |= SCF_TIMESTAMP; 950 } 951 if (to->to_flags & TOF_SCALE) { 952 int wscale = 0; 953 954 /* Compute proper scaling value from buffer space */ 955 while (wscale < TCP_MAX_WINSHIFT && 956 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 957 wscale++; 958 sc->sc_request_r_scale = wscale; 959 sc->sc_requested_s_scale = to->to_requested_s_scale; 960 sc->sc_flags |= SCF_WINSCALE; 961 } 962 } 963 if (tcp_do_rfc1644) { 964 /* 965 * A CC or CC.new option received in a SYN makes 966 * it ok to send CC in subsequent segments. 967 */ 968 if (to->to_flags & (TOF_CC | TOF_CCNEW)) { 969 sc->sc_cc_recv = to->to_cc; 970 sc->sc_cc_send = CC_INC(tcp_ccgen); 971 sc->sc_flags |= SCF_CC; 972 } 973 } 974 if (tp->t_flags & TF_NOOPT) 975 sc->sc_flags = SCF_NOOPT; 976 977 /* 978 * XXX 979 * We have the option here of not doing TAO (even if the segment 980 * qualifies) and instead fall back to a normal 3WHS via the syncache. 981 * This allows us to apply synflood protection to TAO-qualifying SYNs 982 * also. However, there should be a hueristic to determine when to 983 * do this, and is not present at the moment. 984 */ 985 986 /* 987 * Perform TAO test on incoming CC (SEG.CC) option, if any. 988 * - compare SEG.CC against cached CC from the same host, if any. 989 * - if SEG.CC > chached value, SYN must be new and is accepted 990 * immediately: save new CC in the cache, mark the socket 991 * connected, enter ESTABLISHED state, turn on flag to 992 * send a SYN in the next segment. 993 * A virtual advertised window is set in rcv_adv to 994 * initialize SWS prevention. Then enter normal segment 995 * processing: drop SYN, process data and FIN. 996 * - otherwise do a normal 3-way handshake. 997 */ 998 taop = tcp_gettaocache(&sc->sc_inc); 999 if ((to->to_flags & TOF_CC) != 0) { 1000 if (((tp->t_flags & TF_NOPUSH) != 0) && 1001 sc->sc_flags & SCF_CC && 1002 taop != NULL && taop->tao_cc != 0 && 1003 CC_GT(to->to_cc, taop->tao_cc)) { 1004 sc->sc_rxtslot = 0; 1005 so = syncache_socket(sc, *sop); 1006 if (so != NULL) { 1007 sc->sc_flags |= SCF_KEEPROUTE; 1008 taop->tao_cc = to->to_cc; 1009 *sop = so; 1010 } 1011 syncache_free(sc); 1012 return (so != NULL); 1013 } 1014 } else { 1015 /* 1016 * No CC option, but maybe CC.NEW: invalidate cached value. 1017 */ 1018 if (taop != NULL) 1019 taop->tao_cc = 0; 1020 } 1021 /* 1022 * TAO test failed or there was no CC option, 1023 * do a standard 3-way handshake. 1024 */ 1025 if (syncache_respond(sc, m) == 0) { 1026 syncache_insert(sc, sch); 1027 tcpstat.tcps_sndacks++; 1028 tcpstat.tcps_sndtotal++; 1029 } else { 1030 syncache_free(sc); 1031 tcpstat.tcps_sc_dropped++; 1032 } 1033 *sop = NULL; 1034 return (1); 1035 } 1036 1037 static int 1038 syncache_respond(sc, m) 1039 struct syncache *sc; 1040 struct mbuf *m; 1041 { 1042 u_int8_t *optp; 1043 int optlen, error; 1044 u_int16_t tlen, hlen, mssopt; 1045 struct ip *ip = NULL; 1046 struct rtentry *rt; 1047 struct tcphdr *th; 1048 struct ip6_hdr *ip6 = NULL; 1049 #ifdef INET6 1050 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1051 #else 1052 const boolean_t isipv6 = FALSE; 1053 #endif 1054 1055 if (isipv6) { 1056 rt = tcp_rtlookup6(&sc->sc_inc); 1057 if (rt != NULL) 1058 mssopt = rt->rt_ifp->if_mtu - 1059 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1060 else 1061 mssopt = tcp_v6mssdflt; 1062 hlen = sizeof(struct ip6_hdr); 1063 } else { 1064 rt = tcp_rtlookup(&sc->sc_inc); 1065 if (rt != NULL) 1066 mssopt = rt->rt_ifp->if_mtu - 1067 (sizeof(struct ip) + sizeof(struct tcphdr)); 1068 else 1069 mssopt = tcp_mssdflt; 1070 hlen = sizeof(struct ip); 1071 } 1072 1073 /* Compute the size of the TCP options. */ 1074 if (sc->sc_flags & SCF_NOOPT) { 1075 optlen = 0; 1076 } else { 1077 optlen = TCPOLEN_MAXSEG + 1078 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1079 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1080 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1081 } 1082 tlen = hlen + sizeof(struct tcphdr) + optlen; 1083 1084 /* 1085 * XXX 1086 * assume that the entire packet will fit in a header mbuf 1087 */ 1088 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1089 1090 /* 1091 * XXX shouldn't this reuse the mbuf if possible ? 1092 * Create the IP+TCP header from scratch. 1093 */ 1094 if (m) 1095 m_freem(m); 1096 1097 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 1098 if (m == NULL) 1099 return (ENOBUFS); 1100 m->m_data += max_linkhdr; 1101 m->m_len = tlen; 1102 m->m_pkthdr.len = tlen; 1103 m->m_pkthdr.rcvif = NULL; 1104 1105 if (isipv6) { 1106 ip6 = mtod(m, struct ip6_hdr *); 1107 ip6->ip6_vfc = IPV6_VERSION; 1108 ip6->ip6_nxt = IPPROTO_TCP; 1109 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1110 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1111 ip6->ip6_plen = htons(tlen - hlen); 1112 /* ip6_hlim is set after checksum */ 1113 /* ip6_flow = ??? */ 1114 1115 th = (struct tcphdr *)(ip6 + 1); 1116 } else { 1117 ip = mtod(m, struct ip *); 1118 ip->ip_v = IPVERSION; 1119 ip->ip_hl = sizeof(struct ip) >> 2; 1120 ip->ip_len = tlen; 1121 ip->ip_id = 0; 1122 ip->ip_off = 0; 1123 ip->ip_sum = 0; 1124 ip->ip_p = IPPROTO_TCP; 1125 ip->ip_src = sc->sc_inc.inc_laddr; 1126 ip->ip_dst = sc->sc_inc.inc_faddr; 1127 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1128 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1129 1130 /* 1131 * See if we should do MTU discovery. Route lookups are 1132 * expensive, so we will only unset the DF bit if: 1133 * 1134 * 1) path_mtu_discovery is disabled 1135 * 2) the SCF_UNREACH flag has been set 1136 */ 1137 if (path_mtu_discovery 1138 && ((sc->sc_flags & SCF_UNREACH) == 0)) { 1139 ip->ip_off |= IP_DF; 1140 } 1141 1142 th = (struct tcphdr *)(ip + 1); 1143 } 1144 th->th_sport = sc->sc_inc.inc_lport; 1145 th->th_dport = sc->sc_inc.inc_fport; 1146 1147 th->th_seq = htonl(sc->sc_iss); 1148 th->th_ack = htonl(sc->sc_irs + 1); 1149 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1150 th->th_x2 = 0; 1151 th->th_flags = TH_SYN | TH_ACK; 1152 th->th_win = htons(sc->sc_wnd); 1153 th->th_urp = 0; 1154 1155 /* Tack on the TCP options. */ 1156 if (optlen == 0) 1157 goto no_options; 1158 optp = (u_int8_t *)(th + 1); 1159 *optp++ = TCPOPT_MAXSEG; 1160 *optp++ = TCPOLEN_MAXSEG; 1161 *optp++ = (mssopt >> 8) & 0xff; 1162 *optp++ = mssopt & 0xff; 1163 1164 if (sc->sc_flags & SCF_WINSCALE) { 1165 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1166 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1167 sc->sc_request_r_scale); 1168 optp += 4; 1169 } 1170 1171 if (sc->sc_flags & SCF_TIMESTAMP) { 1172 u_int32_t *lp = (u_int32_t *)(optp); 1173 1174 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1175 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1176 *lp++ = htonl(ticks); 1177 *lp = htonl(sc->sc_tsrecent); 1178 optp += TCPOLEN_TSTAMP_APPA; 1179 } 1180 1181 /* 1182 * Send CC and CC.echo if we received CC from our peer. 1183 */ 1184 if (sc->sc_flags & SCF_CC) { 1185 u_int32_t *lp = (u_int32_t *)(optp); 1186 1187 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1188 *lp++ = htonl(sc->sc_cc_send); 1189 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1190 *lp = htonl(sc->sc_cc_recv); 1191 optp += TCPOLEN_CC_APPA * 2; 1192 } 1193 1194 no_options: 1195 if (isipv6) { 1196 struct route_in6 *ro6 = &sc->sc_route6; 1197 1198 th->th_sum = 0; 1199 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1200 ip6->ip6_hlim = in6_selecthlim(NULL, 1201 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1202 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1203 sc->sc_tp->t_inpcb); 1204 } else { 1205 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1206 htons(tlen - hlen + IPPROTO_TCP)); 1207 m->m_pkthdr.csum_flags = CSUM_TCP; 1208 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1209 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL, 1210 sc->sc_tp->t_inpcb); 1211 } 1212 return (error); 1213 } 1214 1215 /* 1216 * cookie layers: 1217 * 1218 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1219 * | peer iss | 1220 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1221 * | 0 |(A)| | 1222 * (A): peer mss index 1223 */ 1224 1225 /* 1226 * The values below are chosen to minimize the size of the tcp_secret 1227 * table, as well as providing roughly a 16 second lifetime for the cookie. 1228 */ 1229 1230 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1231 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1232 1233 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1234 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1235 #define SYNCOOKIE_TIMEOUT \ 1236 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1237 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1238 1239 static struct { 1240 u_int32_t ts_secbits[4]; 1241 u_int ts_expire; 1242 } tcp_secret[SYNCOOKIE_NSECRETS]; 1243 1244 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1245 1246 static MD5_CTX syn_ctx; 1247 1248 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1249 1250 struct md5_add { 1251 u_int32_t laddr, faddr; 1252 u_int32_t secbits[4]; 1253 u_int16_t lport, fport; 1254 }; 1255 1256 #ifdef CTASSERT 1257 CTASSERT(sizeof(struct md5_add) == 28); 1258 #endif 1259 1260 /* 1261 * Consider the problem of a recreated (and retransmitted) cookie. If the 1262 * original SYN was accepted, the connection is established. The second 1263 * SYN is inflight, and if it arrives with an ISN that falls within the 1264 * receive window, the connection is killed. 1265 * 1266 * However, since cookies have other problems, this may not be worth 1267 * worrying about. 1268 */ 1269 1270 static u_int32_t 1271 syncookie_generate(struct syncache *sc) 1272 { 1273 u_int32_t md5_buffer[4]; 1274 u_int32_t data; 1275 int idx, i; 1276 struct md5_add add; 1277 #ifdef INET6 1278 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1279 #else 1280 const boolean_t isipv6 = FALSE; 1281 #endif 1282 1283 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1284 if (tcp_secret[idx].ts_expire < ticks) { 1285 for (i = 0; i < 4; i++) 1286 tcp_secret[idx].ts_secbits[i] = arc4random(); 1287 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1288 } 1289 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1290 if (tcp_msstab[data] <= sc->sc_peer_mss) 1291 break; 1292 data = (data << SYNCOOKIE_WNDBITS) | idx; 1293 data ^= sc->sc_irs; /* peer's iss */ 1294 MD5Init(&syn_ctx); 1295 if (isipv6) { 1296 MD5Add(sc->sc_inc.inc6_laddr); 1297 MD5Add(sc->sc_inc.inc6_faddr); 1298 add.laddr = 0; 1299 add.faddr = 0; 1300 } else { 1301 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1302 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1303 } 1304 add.lport = sc->sc_inc.inc_lport; 1305 add.fport = sc->sc_inc.inc_fport; 1306 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1307 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1308 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1309 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1310 MD5Add(add); 1311 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1312 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1313 return (data); 1314 } 1315 1316 static struct syncache * 1317 syncookie_lookup(inc, th, so) 1318 struct in_conninfo *inc; 1319 struct tcphdr *th; 1320 struct socket *so; 1321 { 1322 u_int32_t md5_buffer[4]; 1323 struct syncache *sc; 1324 u_int32_t data; 1325 int wnd, idx; 1326 struct md5_add add; 1327 1328 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1329 idx = data & SYNCOOKIE_WNDMASK; 1330 if (tcp_secret[idx].ts_expire < ticks || 1331 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1332 return (NULL); 1333 MD5Init(&syn_ctx); 1334 #ifdef INET6 1335 if (inc->inc_isipv6) { 1336 MD5Add(inc->inc6_laddr); 1337 MD5Add(inc->inc6_faddr); 1338 add.laddr = 0; 1339 add.faddr = 0; 1340 } else 1341 #endif 1342 { 1343 add.laddr = inc->inc_laddr.s_addr; 1344 add.faddr = inc->inc_faddr.s_addr; 1345 } 1346 add.lport = inc->inc_lport; 1347 add.fport = inc->inc_fport; 1348 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1349 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1350 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1351 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1352 MD5Add(add); 1353 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1354 data ^= md5_buffer[0]; 1355 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1356 return (NULL); 1357 data = data >> SYNCOOKIE_WNDBITS; 1358 1359 /* 1360 * This allocation is guaranteed to succeed because we 1361 * preallocate one more syncache entry than cache_limit. 1362 */ 1363 sc = zalloc(tcp_syncache.zone); 1364 1365 /* 1366 * Fill in the syncache values. 1367 * XXX duplicate code from syncache_add 1368 */ 1369 sc->sc_ipopts = NULL; 1370 sc->sc_inc.inc_fport = inc->inc_fport; 1371 sc->sc_inc.inc_lport = inc->inc_lport; 1372 #ifdef INET6 1373 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1374 if (inc->inc_isipv6) { 1375 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1376 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1377 sc->sc_route6.ro_rt = NULL; 1378 } else 1379 #endif 1380 { 1381 sc->sc_inc.inc_faddr = inc->inc_faddr; 1382 sc->sc_inc.inc_laddr = inc->inc_laddr; 1383 sc->sc_route.ro_rt = NULL; 1384 } 1385 sc->sc_irs = th->th_seq - 1; 1386 sc->sc_iss = th->th_ack - 1; 1387 wnd = sbspace(&so->so_rcv); 1388 wnd = imax(wnd, 0); 1389 wnd = imin(wnd, TCP_MAXWIN); 1390 sc->sc_wnd = wnd; 1391 sc->sc_flags = 0; 1392 sc->sc_rxtslot = 0; 1393 sc->sc_peer_mss = tcp_msstab[data]; 1394 return (sc); 1395 } 1396