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 * All advertising materials mentioning features or use of this software 36 * must display the following acknowledgement: 37 * This product includes software developed by Jeffrey M. Hsu. 38 * 39 * Copyright (c) 2001 Networks Associates Technologies, Inc. 40 * All rights reserved. 41 * 42 * This software was developed for the FreeBSD Project by Jonathan Lemon 43 * and NAI Labs, the Security Research Division of Network Associates, Inc. 44 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 45 * DARPA CHATS research program. 46 * 47 * Redistribution and use in source and binary forms, with or without 48 * modification, are permitted provided that the following conditions 49 * are met: 50 * 1. Redistributions of source code must retain the above copyright 51 * notice, this list of conditions and the following disclaimer. 52 * 2. Redistributions in binary form must reproduce the above copyright 53 * notice, this list of conditions and the following disclaimer in the 54 * documentation and/or other materials provided with the distribution. 55 * 3. The name of the author may not be used to endorse or promote 56 * products derived from this software without specific prior written 57 * permission. 58 * 59 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 62 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 69 * SUCH DAMAGE. 70 * 71 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.5.2.14 2003/02/24 04:02:27 silby Exp $ 72 * $DragonFly: src/sys/netinet/tcp_syncache.c,v 1.35 2008/11/22 11:03:35 sephe Exp $ 73 */ 74 75 #include "opt_inet.h" 76 #include "opt_inet6.h" 77 #include "opt_ipsec.h" 78 79 #include <sys/param.h> 80 #include <sys/systm.h> 81 #include <sys/kernel.h> 82 #include <sys/sysctl.h> 83 #include <sys/malloc.h> 84 #include <sys/mbuf.h> 85 #include <sys/md5.h> 86 #include <sys/proc.h> /* for proc0 declaration */ 87 #include <sys/random.h> 88 #include <sys/socket.h> 89 #include <sys/socketvar.h> 90 #include <sys/in_cksum.h> 91 92 #include <sys/msgport2.h> 93 #include <net/netmsg2.h> 94 95 #include <net/if.h> 96 #include <net/route.h> 97 98 #include <netinet/in.h> 99 #include <netinet/in_systm.h> 100 #include <netinet/ip.h> 101 #include <netinet/in_var.h> 102 #include <netinet/in_pcb.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/ip6.h> 105 #ifdef INET6 106 #include <netinet/icmp6.h> 107 #include <netinet6/nd6.h> 108 #endif 109 #include <netinet6/ip6_var.h> 110 #include <netinet6/in6_pcb.h> 111 #include <netinet/tcp.h> 112 #include <netinet/tcp_fsm.h> 113 #include <netinet/tcp_seq.h> 114 #include <netinet/tcp_timer.h> 115 #include <netinet/tcp_timer2.h> 116 #include <netinet/tcp_var.h> 117 #include <netinet6/tcp6_var.h> 118 119 #ifdef IPSEC 120 #include <netinet6/ipsec.h> 121 #ifdef INET6 122 #include <netinet6/ipsec6.h> 123 #endif 124 #include <netproto/key/key.h> 125 #endif /*IPSEC*/ 126 127 #ifdef FAST_IPSEC 128 #include <netproto/ipsec/ipsec.h> 129 #ifdef INET6 130 #include <netproto/ipsec/ipsec6.h> 131 #endif 132 #include <netproto/ipsec/key.h> 133 #define IPSEC 134 #endif /*FAST_IPSEC*/ 135 136 static int tcp_syncookies = 1; 137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 138 &tcp_syncookies, 0, 139 "Use TCP SYN cookies if the syncache overflows"); 140 141 static void syncache_drop(struct syncache *, struct syncache_head *); 142 static void syncache_free(struct syncache *); 143 static void syncache_insert(struct syncache *, struct syncache_head *); 144 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 145 static int syncache_respond(struct syncache *, struct mbuf *); 146 static struct socket *syncache_socket(struct syncache *, struct socket *, 147 struct mbuf *); 148 static void syncache_timer(void *); 149 static u_int32_t syncookie_generate(struct syncache *); 150 static struct syncache *syncookie_lookup(struct in_conninfo *, 151 struct tcphdr *, struct socket *); 152 153 /* 154 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 155 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 156 * the odds are that the user has given up attempting to connect by then. 157 */ 158 #define SYNCACHE_MAXREXMTS 3 159 160 /* Arbitrary values */ 161 #define TCP_SYNCACHE_HASHSIZE 512 162 #define TCP_SYNCACHE_BUCKETLIMIT 30 163 164 struct netmsg_sc_timer { 165 struct netmsg_base base; 166 struct msgrec *nm_mrec; /* back pointer to containing msgrec */ 167 }; 168 169 struct msgrec { 170 struct netmsg_sc_timer msg; 171 lwkt_port_t port; /* constant after init */ 172 int slot; /* constant after init */ 173 }; 174 175 static void syncache_timer_handler(netmsg_t); 176 177 struct tcp_syncache { 178 u_int hashsize; 179 u_int hashmask; 180 u_int bucket_limit; 181 u_int cache_limit; 182 u_int rexmt_limit; 183 u_int hash_secret; 184 }; 185 static struct tcp_syncache tcp_syncache; 186 187 TAILQ_HEAD(syncache_list, syncache); 188 189 struct tcp_syncache_percpu { 190 struct syncache_head *hashbase; 191 u_int cache_count; 192 struct syncache_list timerq[SYNCACHE_MAXREXMTS + 1]; 193 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 194 struct msgrec mrec[SYNCACHE_MAXREXMTS + 1]; 195 }; 196 static struct tcp_syncache_percpu tcp_syncache_percpu[MAXCPU]; 197 198 static struct lwkt_port syncache_null_rport; 199 200 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 201 202 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 203 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 204 205 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 206 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 207 208 /* XXX JH */ 209 #if 0 210 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 211 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 212 #endif 213 214 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 215 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 216 217 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 218 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 219 220 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 221 222 #define SYNCACHE_HASH(inc, mask) \ 223 ((tcp_syncache.hash_secret ^ \ 224 (inc)->inc_faddr.s_addr ^ \ 225 ((inc)->inc_faddr.s_addr >> 16) ^ \ 226 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 227 228 #define SYNCACHE_HASH6(inc, mask) \ 229 ((tcp_syncache.hash_secret ^ \ 230 (inc)->inc6_faddr.s6_addr32[0] ^ \ 231 (inc)->inc6_faddr.s6_addr32[3] ^ \ 232 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 233 234 #define ENDPTS_EQ(a, b) ( \ 235 (a)->ie_fport == (b)->ie_fport && \ 236 (a)->ie_lport == (b)->ie_lport && \ 237 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 238 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 239 ) 240 241 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 242 243 static __inline void 244 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu, 245 struct syncache *sc, int slot) 246 { 247 sc->sc_rxtslot = slot; 248 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot]; 249 TAILQ_INSERT_TAIL(&syncache_percpu->timerq[slot], sc, sc_timerq); 250 if (!callout_active(&syncache_percpu->tt_timerq[slot])) { 251 callout_reset(&syncache_percpu->tt_timerq[slot], 252 TCPTV_RTOBASE * tcp_backoff[slot], 253 syncache_timer, 254 &syncache_percpu->mrec[slot]); 255 } 256 } 257 258 static void 259 syncache_free(struct syncache *sc) 260 { 261 struct rtentry *rt; 262 #ifdef INET6 263 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 264 #else 265 const boolean_t isipv6 = FALSE; 266 #endif 267 268 if (sc->sc_ipopts) 269 m_free(sc->sc_ipopts); 270 271 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt; 272 if (rt != NULL) { 273 /* 274 * If this is the only reference to a protocol-cloned 275 * route, remove it immediately. 276 */ 277 if ((rt->rt_flags & RTF_WASCLONED) && rt->rt_refcnt == 1) 278 rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway, 279 rt_mask(rt), rt->rt_flags, NULL); 280 RTFREE(rt); 281 } 282 kfree(sc, M_SYNCACHE); 283 } 284 285 void 286 syncache_init(void) 287 { 288 int i, cpu; 289 290 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 291 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 292 tcp_syncache.cache_limit = 293 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 294 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 295 tcp_syncache.hash_secret = karc4random(); 296 297 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 298 &tcp_syncache.hashsize); 299 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 300 &tcp_syncache.cache_limit); 301 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 302 &tcp_syncache.bucket_limit); 303 if (!powerof2(tcp_syncache.hashsize)) { 304 kprintf("WARNING: syncache hash size is not a power of 2.\n"); 305 tcp_syncache.hashsize = 512; /* safe default */ 306 } 307 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 308 309 lwkt_initport_replyonly_null(&syncache_null_rport); 310 311 for (cpu = 0; cpu < ncpus2; cpu++) { 312 struct tcp_syncache_percpu *syncache_percpu; 313 314 syncache_percpu = &tcp_syncache_percpu[cpu]; 315 /* Allocate the hash table. */ 316 MALLOC(syncache_percpu->hashbase, struct syncache_head *, 317 tcp_syncache.hashsize * sizeof(struct syncache_head), 318 M_SYNCACHE, M_WAITOK); 319 320 /* Initialize the hash buckets. */ 321 for (i = 0; i < tcp_syncache.hashsize; i++) { 322 struct syncache_head *bucket; 323 324 bucket = &syncache_percpu->hashbase[i]; 325 TAILQ_INIT(&bucket->sch_bucket); 326 bucket->sch_length = 0; 327 } 328 329 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 330 /* Initialize the timer queues. */ 331 TAILQ_INIT(&syncache_percpu->timerq[i]); 332 callout_init(&syncache_percpu->tt_timerq[i]); 333 334 syncache_percpu->mrec[i].slot = i; 335 syncache_percpu->mrec[i].port = cpu_portfn(cpu); 336 syncache_percpu->mrec[i].msg.nm_mrec = 337 &syncache_percpu->mrec[i]; 338 netmsg_init(&syncache_percpu->mrec[i].msg.base, 339 NULL, &syncache_null_rport, 340 0, syncache_timer_handler); 341 } 342 } 343 } 344 345 static void 346 syncache_insert(struct syncache *sc, struct syncache_head *sch) 347 { 348 struct tcp_syncache_percpu *syncache_percpu; 349 struct syncache *sc2; 350 int i; 351 352 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 353 354 /* 355 * Make sure that we don't overflow the per-bucket 356 * limit or the total cache size limit. 357 */ 358 if (sch->sch_length >= tcp_syncache.bucket_limit) { 359 /* 360 * The bucket is full, toss the oldest element. 361 */ 362 sc2 = TAILQ_FIRST(&sch->sch_bucket); 363 sc2->sc_tp->ts_recent = ticks; 364 syncache_drop(sc2, sch); 365 tcpstat.tcps_sc_bucketoverflow++; 366 } else if (syncache_percpu->cache_count >= tcp_syncache.cache_limit) { 367 /* 368 * The cache is full. Toss the oldest entry in the 369 * entire cache. This is the front entry in the 370 * first non-empty timer queue with the largest 371 * timeout value. 372 */ 373 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 374 sc2 = TAILQ_FIRST(&syncache_percpu->timerq[i]); 375 while (sc2 && (sc2->sc_flags & SCF_MARKER)) 376 sc2 = TAILQ_NEXT(sc2, sc_timerq); 377 if (sc2 != NULL) 378 break; 379 } 380 sc2->sc_tp->ts_recent = ticks; 381 syncache_drop(sc2, NULL); 382 tcpstat.tcps_sc_cacheoverflow++; 383 } 384 385 /* Initialize the entry's timer. */ 386 syncache_timeout(syncache_percpu, sc, 0); 387 388 /* Put it into the bucket. */ 389 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 390 sch->sch_length++; 391 syncache_percpu->cache_count++; 392 tcpstat.tcps_sc_added++; 393 } 394 395 void 396 syncache_destroy(struct tcpcb *tp) 397 { 398 struct tcp_syncache_percpu *syncache_percpu; 399 struct syncache_head *bucket; 400 struct syncache *sc; 401 int i; 402 403 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 404 sc = NULL; 405 406 for (i = 0; i < tcp_syncache.hashsize; i++) { 407 bucket = &syncache_percpu->hashbase[i]; 408 TAILQ_FOREACH(sc, &bucket->sch_bucket, sc_hash) { 409 if (sc->sc_tp == tp) { 410 sc->sc_tp = NULL; 411 tp->t_flags &= ~TF_SYNCACHE; 412 break; 413 } 414 } 415 } 416 kprintf("Warning: delete stale syncache for tp=%p, sc=%p\n", tp, sc); 417 } 418 419 static void 420 syncache_drop(struct syncache *sc, struct syncache_head *sch) 421 { 422 struct tcp_syncache_percpu *syncache_percpu; 423 #ifdef INET6 424 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 425 #else 426 const boolean_t isipv6 = FALSE; 427 #endif 428 429 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 430 431 if (sch == NULL) { 432 if (isipv6) { 433 sch = &syncache_percpu->hashbase[ 434 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 435 } else { 436 sch = &syncache_percpu->hashbase[ 437 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 438 } 439 } 440 441 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 442 sch->sch_length--; 443 syncache_percpu->cache_count--; 444 445 /* 446 * Cleanup 447 */ 448 if (sc->sc_tp) { 449 sc->sc_tp->t_flags &= ~TF_SYNCACHE; 450 sc->sc_tp = NULL; 451 } 452 453 /* 454 * Remove the entry from the syncache timer/timeout queue. Note 455 * that we do not try to stop any running timer since we do not know 456 * whether the timer's message is in-transit or not. Since timeouts 457 * are fairly long, taking an unneeded callout does not detrimentally 458 * effect performance. 459 */ 460 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], sc, sc_timerq); 461 462 syncache_free(sc); 463 } 464 465 /* 466 * Place a timeout message on the TCP thread's message queue. 467 * This routine runs in soft interrupt context. 468 * 469 * An invariant is for this routine to be called, the callout must 470 * have been active. Note that the callout is not deactivated until 471 * after the message has been processed in syncache_timer_handler() below. 472 */ 473 static void 474 syncache_timer(void *p) 475 { 476 struct netmsg_sc_timer *msg = p; 477 478 lwkt_sendmsg(msg->nm_mrec->port, &msg->base.lmsg); 479 } 480 481 /* 482 * Service a timer message queued by timer expiration. 483 * This routine runs in the TCP protocol thread. 484 * 485 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 486 * If we have retransmitted an entry the maximum number of times, expire it. 487 * 488 * When we finish processing timed-out entries, we restart the timer if there 489 * are any entries still on the queue and deactivate it otherwise. Only after 490 * a timer has been deactivated here can it be restarted by syncache_timeout(). 491 */ 492 static void 493 syncache_timer_handler(netmsg_t msg) 494 { 495 struct tcp_syncache_percpu *syncache_percpu; 496 struct syncache *sc; 497 struct syncache marker; 498 struct syncache_list *list; 499 struct inpcb *inp; 500 int slot; 501 502 slot = ((struct netmsg_sc_timer *)msg)->nm_mrec->slot; 503 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 504 505 list = &syncache_percpu->timerq[slot]; 506 507 /* 508 * Use a marker to keep our place in the scan. syncache_drop() 509 * can block and cause any next pointer we cache to become stale. 510 */ 511 marker.sc_flags = SCF_MARKER; 512 TAILQ_INSERT_HEAD(list, &marker, sc_timerq); 513 514 while ((sc = TAILQ_NEXT(&marker, sc_timerq)) != NULL) { 515 /* 516 * Move the marker. 517 */ 518 TAILQ_REMOVE(list, &marker, sc_timerq); 519 TAILQ_INSERT_AFTER(list, sc, &marker, sc_timerq); 520 521 if (sc->sc_flags & SCF_MARKER) 522 continue; 523 524 if (ticks < sc->sc_rxttime) 525 break; /* finished because timerq sorted by time */ 526 if (sc->sc_tp == NULL) { 527 syncache_drop(sc, NULL); 528 tcpstat.tcps_sc_stale++; 529 continue; 530 } 531 inp = sc->sc_tp->t_inpcb; 532 if (slot == SYNCACHE_MAXREXMTS || 533 slot >= tcp_syncache.rexmt_limit || 534 inp == NULL || 535 inp->inp_gencnt != sc->sc_inp_gencnt) { 536 syncache_drop(sc, NULL); 537 tcpstat.tcps_sc_stale++; 538 continue; 539 } 540 /* 541 * syncache_respond() may call back into the syncache to 542 * to modify another entry, so do not obtain the next 543 * entry on the timer chain until it has completed. 544 */ 545 syncache_respond(sc, NULL); 546 tcpstat.tcps_sc_retransmitted++; 547 TAILQ_REMOVE(list, sc, sc_timerq); 548 syncache_timeout(syncache_percpu, sc, slot + 1); 549 } 550 TAILQ_REMOVE(list, &marker, sc_timerq); 551 552 if (sc != NULL) { 553 callout_reset(&syncache_percpu->tt_timerq[slot], 554 sc->sc_rxttime - ticks, syncache_timer, 555 &syncache_percpu->mrec[slot]); 556 } else { 557 callout_deactivate(&syncache_percpu->tt_timerq[slot]); 558 } 559 lwkt_replymsg(&msg->base.lmsg, 0); 560 } 561 562 /* 563 * Find an entry in the syncache. 564 */ 565 struct syncache * 566 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 567 { 568 struct tcp_syncache_percpu *syncache_percpu; 569 struct syncache *sc; 570 struct syncache_head *sch; 571 572 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 573 #ifdef INET6 574 if (inc->inc_isipv6) { 575 sch = &syncache_percpu->hashbase[ 576 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 577 *schp = sch; 578 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 579 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 580 return (sc); 581 } else 582 #endif 583 { 584 sch = &syncache_percpu->hashbase[ 585 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 586 *schp = sch; 587 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 588 #ifdef INET6 589 if (sc->sc_inc.inc_isipv6) 590 continue; 591 #endif 592 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 593 return (sc); 594 } 595 } 596 return (NULL); 597 } 598 599 /* 600 * This function is called when we get a RST for a 601 * non-existent connection, so that we can see if the 602 * connection is in the syn cache. If it is, zap it. 603 */ 604 void 605 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 606 { 607 struct syncache *sc; 608 struct syncache_head *sch; 609 610 sc = syncache_lookup(inc, &sch); 611 if (sc == NULL) { 612 return; 613 } 614 /* 615 * If the RST bit is set, check the sequence number to see 616 * if this is a valid reset segment. 617 * RFC 793 page 37: 618 * In all states except SYN-SENT, all reset (RST) segments 619 * are validated by checking their SEQ-fields. A reset is 620 * valid if its sequence number is in the window. 621 * 622 * The sequence number in the reset segment is normally an 623 * echo of our outgoing acknowlegement numbers, but some hosts 624 * send a reset with the sequence number at the rightmost edge 625 * of our receive window, and we have to handle this case. 626 */ 627 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 628 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 629 syncache_drop(sc, sch); 630 tcpstat.tcps_sc_reset++; 631 } 632 } 633 634 void 635 syncache_badack(struct in_conninfo *inc) 636 { 637 struct syncache *sc; 638 struct syncache_head *sch; 639 640 sc = syncache_lookup(inc, &sch); 641 if (sc != NULL) { 642 syncache_drop(sc, sch); 643 tcpstat.tcps_sc_badack++; 644 } 645 } 646 647 void 648 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 649 { 650 struct syncache *sc; 651 struct syncache_head *sch; 652 653 /* we are called at splnet() here */ 654 sc = syncache_lookup(inc, &sch); 655 if (sc == NULL) 656 return; 657 658 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 659 if (ntohl(th->th_seq) != sc->sc_iss) 660 return; 661 662 /* 663 * If we've rertransmitted 3 times and this is our second error, 664 * we remove the entry. Otherwise, we allow it to continue on. 665 * This prevents us from incorrectly nuking an entry during a 666 * spurious network outage. 667 * 668 * See tcp_notify(). 669 */ 670 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 671 sc->sc_flags |= SCF_UNREACH; 672 return; 673 } 674 syncache_drop(sc, sch); 675 tcpstat.tcps_sc_unreach++; 676 } 677 678 /* 679 * Build a new TCP socket structure from a syncache entry. 680 * 681 * This is called from the context of the SYN+ACK 682 */ 683 static struct socket * 684 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 685 { 686 struct inpcb *inp = NULL, *linp; 687 struct socket *so; 688 struct tcpcb *tp; 689 lwkt_port_t port; 690 #ifdef INET6 691 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 692 #else 693 const boolean_t isipv6 = FALSE; 694 #endif 695 696 /* 697 * Ok, create the full blown connection, and set things up 698 * as they would have been set up if we had created the 699 * connection when the SYN arrived. If we can't create 700 * the connection, abort it. 701 * 702 * Set the protocol processing port for the socket to the current 703 * port (that the connection came in on). 704 */ 705 so = sonewconn(lso, SS_ISCONNECTED); 706 if (so == NULL) { 707 /* 708 * Drop the connection; we will send a RST if the peer 709 * retransmits the ACK, 710 */ 711 tcpstat.tcps_listendrop++; 712 goto abort; 713 } 714 715 /* 716 * Insert new socket into hash list. 717 */ 718 inp = so->so_pcb; 719 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 720 if (isipv6) { 721 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 722 } else { 723 #ifdef INET6 724 inp->inp_vflag &= ~INP_IPV6; 725 inp->inp_vflag |= INP_IPV4; 726 inp->inp_flags &= ~IN6P_IPV6_V6ONLY; 727 #endif 728 inp->inp_laddr = sc->sc_inc.inc_laddr; 729 } 730 inp->inp_lport = sc->sc_inc.inc_lport; 731 if (in_pcbinsporthash(inp) != 0) { 732 /* 733 * Undo the assignments above if we failed to 734 * put the PCB on the hash lists. 735 */ 736 if (isipv6) 737 inp->in6p_laddr = kin6addr_any; 738 else 739 inp->inp_laddr.s_addr = INADDR_ANY; 740 inp->inp_lport = 0; 741 goto abort; 742 } 743 linp = lso->so_pcb; 744 #ifdef IPSEC 745 /* copy old policy into new socket's */ 746 if (ipsec_copy_policy(linp->inp_sp, inp->inp_sp)) 747 kprintf("syncache_expand: could not copy policy\n"); 748 #endif 749 if (isipv6) { 750 struct in6_addr laddr6; 751 struct sockaddr_in6 sin6; 752 /* 753 * Inherit socket options from the listening socket. 754 * Note that in6p_inputopts are not (and should not be) 755 * copied, since it stores previously received options and is 756 * used to detect if each new option is different than the 757 * previous one and hence should be passed to a user. 758 * If we copied in6p_inputopts, a user would not be able to 759 * receive options just after calling the accept system call. 760 */ 761 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS; 762 if (linp->in6p_outputopts) 763 inp->in6p_outputopts = 764 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT); 765 inp->in6p_route = sc->sc_route6; 766 sc->sc_route6.ro_rt = NULL; 767 768 sin6.sin6_family = AF_INET6; 769 sin6.sin6_len = sizeof sin6; 770 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 771 sin6.sin6_port = sc->sc_inc.inc_fport; 772 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 773 laddr6 = inp->in6p_laddr; 774 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 775 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 776 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) { 777 inp->in6p_laddr = laddr6; 778 goto abort; 779 } 780 } else { 781 struct in_addr laddr; 782 struct sockaddr_in sin; 783 784 inp->inp_options = ip_srcroute(m); 785 if (inp->inp_options == NULL) { 786 inp->inp_options = sc->sc_ipopts; 787 sc->sc_ipopts = NULL; 788 } 789 inp->inp_route = sc->sc_route; 790 sc->sc_route.ro_rt = NULL; 791 792 sin.sin_family = AF_INET; 793 sin.sin_len = sizeof sin; 794 sin.sin_addr = sc->sc_inc.inc_faddr; 795 sin.sin_port = sc->sc_inc.inc_fport; 796 bzero(sin.sin_zero, sizeof sin.sin_zero); 797 laddr = inp->inp_laddr; 798 if (inp->inp_laddr.s_addr == INADDR_ANY) 799 inp->inp_laddr = sc->sc_inc.inc_laddr; 800 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) { 801 inp->inp_laddr = laddr; 802 goto abort; 803 } 804 } 805 806 /* 807 * The current port should be in the context of the SYN+ACK and 808 * so should match the tcp address port. 809 * 810 * XXX we may be running on the netisr thread instead of a tcp 811 * thread, in which case port will not match 812 * curthread->td_msgport. 813 */ 814 if (isipv6) { 815 port = tcp6_addrport(); 816 } else { 817 port = tcp_addrport(inp->inp_faddr.s_addr, inp->inp_fport, 818 inp->inp_laddr.s_addr, inp->inp_lport); 819 } 820 if (port != &curthread->td_msgport) { 821 print_backtrace(-1); 822 kprintf("TCP PORT MISMATCH %p vs %p\n", 823 port, &curthread->td_msgport); 824 } 825 /*KKASSERT(port == &curthread->td_msgport);*/ 826 827 tp = intotcpcb(inp); 828 tp->t_state = TCPS_SYN_RECEIVED; 829 tp->iss = sc->sc_iss; 830 tp->irs = sc->sc_irs; 831 tcp_rcvseqinit(tp); 832 tcp_sendseqinit(tp); 833 tp->snd_wl1 = sc->sc_irs; 834 tp->rcv_up = sc->sc_irs + 1; 835 tp->rcv_wnd = sc->sc_wnd; 836 tp->rcv_adv += tp->rcv_wnd; 837 838 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY); 839 if (sc->sc_flags & SCF_NOOPT) 840 tp->t_flags |= TF_NOOPT; 841 if (sc->sc_flags & SCF_WINSCALE) { 842 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE; 843 tp->requested_s_scale = sc->sc_requested_s_scale; 844 tp->request_r_scale = sc->sc_request_r_scale; 845 } 846 if (sc->sc_flags & SCF_TIMESTAMP) { 847 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP; 848 tp->ts_recent = sc->sc_tsrecent; 849 tp->ts_recent_age = ticks; 850 } 851 if (sc->sc_flags & SCF_SACK_PERMITTED) 852 tp->t_flags |= TF_SACK_PERMITTED; 853 854 #ifdef TCP_SIGNATURE 855 if (sc->sc_flags & SCF_SIGNATURE) 856 tp->t_flags |= TF_SIGNATURE; 857 #endif /* TCP_SIGNATURE */ 858 859 860 tcp_mss(tp, sc->sc_peer_mss); 861 862 /* 863 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 864 */ 865 if (sc->sc_rxtslot != 0) 866 tp->snd_cwnd = tp->t_maxseg; 867 tcp_create_timermsg(tp, port); 868 tcp_callout_reset(tp, tp->tt_keep, tcp_keepinit, tcp_timer_keep); 869 870 tcpstat.tcps_accepts++; 871 return (so); 872 873 abort: 874 if (so != NULL) 875 soabort_oncpu(so); 876 return (NULL); 877 } 878 879 /* 880 * This function gets called when we receive an ACK for a 881 * socket in the LISTEN state. We look up the connection 882 * in the syncache, and if its there, we pull it out of 883 * the cache and turn it into a full-blown connection in 884 * the SYN-RECEIVED state. 885 */ 886 int 887 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop, 888 struct mbuf *m) 889 { 890 struct syncache *sc; 891 struct syncache_head *sch; 892 struct socket *so; 893 894 sc = syncache_lookup(inc, &sch); 895 if (sc == NULL) { 896 /* 897 * There is no syncache entry, so see if this ACK is 898 * a returning syncookie. To do this, first: 899 * A. See if this socket has had a syncache entry dropped in 900 * the past. We don't want to accept a bogus syncookie 901 * if we've never received a SYN. 902 * B. check that the syncookie is valid. If it is, then 903 * cobble up a fake syncache entry, and return. 904 */ 905 if (!tcp_syncookies) 906 return (0); 907 sc = syncookie_lookup(inc, th, *sop); 908 if (sc == NULL) 909 return (0); 910 sch = NULL; 911 tcpstat.tcps_sc_recvcookie++; 912 } 913 914 /* 915 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 916 */ 917 if (th->th_ack != sc->sc_iss + 1) 918 return (0); 919 920 so = syncache_socket(sc, *sop, m); 921 if (so == NULL) { 922 #if 0 923 resetandabort: 924 /* XXXjlemon check this - is this correct? */ 925 tcp_respond(NULL, m, m, th, 926 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK); 927 #endif 928 m_freem(m); /* XXX only needed for above */ 929 tcpstat.tcps_sc_aborted++; 930 } else { 931 tcpstat.tcps_sc_completed++; 932 } 933 if (sch == NULL) 934 syncache_free(sc); 935 else 936 syncache_drop(sc, sch); 937 *sop = so; 938 return (1); 939 } 940 941 /* 942 * Given a LISTEN socket and an inbound SYN request, add 943 * this to the syn cache, and send back a segment: 944 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 945 * to the source. 946 * 947 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 948 * Doing so would require that we hold onto the data and deliver it 949 * to the application. However, if we are the target of a SYN-flood 950 * DoS attack, an attacker could send data which would eventually 951 * consume all available buffer space if it were ACKed. By not ACKing 952 * the data, we avoid this DoS scenario. 953 */ 954 int 955 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 956 struct socket **sop, struct mbuf *m) 957 { 958 struct tcp_syncache_percpu *syncache_percpu; 959 struct tcpcb *tp; 960 struct socket *so; 961 struct syncache *sc = NULL; 962 struct syncache_head *sch; 963 struct mbuf *ipopts = NULL; 964 int win; 965 966 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 967 so = *sop; 968 tp = sototcpcb(so); 969 970 /* 971 * Remember the IP options, if any. 972 */ 973 #ifdef INET6 974 if (!inc->inc_isipv6) 975 #endif 976 ipopts = ip_srcroute(m); 977 978 /* 979 * See if we already have an entry for this connection. 980 * If we do, resend the SYN,ACK, and reset the retransmit timer. 981 * 982 * XXX 983 * The syncache should be re-initialized with the contents 984 * of the new SYN which may have different options. 985 */ 986 sc = syncache_lookup(inc, &sch); 987 if (sc != NULL) { 988 tcpstat.tcps_sc_dupsyn++; 989 if (ipopts) { 990 /* 991 * If we were remembering a previous source route, 992 * forget it and use the new one we've been given. 993 */ 994 if (sc->sc_ipopts) 995 m_free(sc->sc_ipopts); 996 sc->sc_ipopts = ipopts; 997 } 998 /* 999 * Update timestamp if present. 1000 */ 1001 if (sc->sc_flags & SCF_TIMESTAMP) 1002 sc->sc_tsrecent = to->to_tsval; 1003 1004 /* Just update the TOF_SACK_PERMITTED for now. */ 1005 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 1006 sc->sc_flags |= SCF_SACK_PERMITTED; 1007 else 1008 sc->sc_flags &= ~SCF_SACK_PERMITTED; 1009 1010 /* 1011 * PCB may have changed, pick up new values. 1012 */ 1013 if (sc->sc_tp) { 1014 sc->sc_tp->t_flags &= ~TF_SYNCACHE; 1015 tp->t_flags |= TF_SYNCACHE; 1016 } 1017 sc->sc_tp = tp; 1018 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1019 if (syncache_respond(sc, m) == 0) { 1020 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], 1021 sc, sc_timerq); 1022 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot); 1023 tcpstat.tcps_sndacks++; 1024 tcpstat.tcps_sndtotal++; 1025 } 1026 *sop = NULL; 1027 return (1); 1028 } 1029 1030 /* 1031 * Fill in the syncache values. 1032 */ 1033 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1034 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1035 sc->sc_ipopts = ipopts; 1036 sc->sc_inc.inc_fport = inc->inc_fport; 1037 sc->sc_inc.inc_lport = inc->inc_lport; 1038 sc->sc_tp = tp; 1039 tp->t_flags |= TF_SYNCACHE; 1040 #ifdef INET6 1041 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1042 if (inc->inc_isipv6) { 1043 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1044 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1045 sc->sc_route6.ro_rt = NULL; 1046 } else 1047 #endif 1048 { 1049 sc->sc_inc.inc_faddr = inc->inc_faddr; 1050 sc->sc_inc.inc_laddr = inc->inc_laddr; 1051 sc->sc_route.ro_rt = NULL; 1052 } 1053 sc->sc_irs = th->th_seq; 1054 sc->sc_flags = 0; 1055 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 1056 if (tcp_syncookies) 1057 sc->sc_iss = syncookie_generate(sc); 1058 else 1059 sc->sc_iss = karc4random(); 1060 1061 /* Initial receive window: clip ssb_space to [0 .. TCP_MAXWIN] */ 1062 win = ssb_space(&so->so_rcv); 1063 win = imax(win, 0); 1064 win = imin(win, TCP_MAXWIN); 1065 sc->sc_wnd = win; 1066 1067 if (tcp_do_rfc1323) { 1068 /* 1069 * A timestamp received in a SYN makes 1070 * it ok to send timestamp requests and replies. 1071 */ 1072 if (to->to_flags & TOF_TS) { 1073 sc->sc_tsrecent = to->to_tsval; 1074 sc->sc_flags |= SCF_TIMESTAMP; 1075 } 1076 if (to->to_flags & TOF_SCALE) { 1077 int wscale = TCP_MIN_WINSHIFT; 1078 1079 /* Compute proper scaling value from buffer space */ 1080 while (wscale < TCP_MAX_WINSHIFT && 1081 (TCP_MAXWIN << wscale) < so->so_rcv.ssb_hiwat) { 1082 wscale++; 1083 } 1084 sc->sc_request_r_scale = wscale; 1085 sc->sc_requested_s_scale = to->to_requested_s_scale; 1086 sc->sc_flags |= SCF_WINSCALE; 1087 } 1088 } 1089 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 1090 sc->sc_flags |= SCF_SACK_PERMITTED; 1091 if (tp->t_flags & TF_NOOPT) 1092 sc->sc_flags = SCF_NOOPT; 1093 #ifdef TCP_SIGNATURE 1094 /* 1095 * If listening socket requested TCP digests, and received SYN 1096 * contains the option, flag this in the syncache so that 1097 * syncache_respond() will do the right thing with the SYN+ACK. 1098 * XXX Currently we always record the option by default and will 1099 * attempt to use it in syncache_respond(). 1100 */ 1101 if (to->to_flags & TOF_SIGNATURE) 1102 sc->sc_flags = SCF_SIGNATURE; 1103 #endif /* TCP_SIGNATURE */ 1104 1105 if (syncache_respond(sc, m) == 0) { 1106 syncache_insert(sc, sch); 1107 tcpstat.tcps_sndacks++; 1108 tcpstat.tcps_sndtotal++; 1109 } else { 1110 syncache_free(sc); 1111 tcpstat.tcps_sc_dropped++; 1112 } 1113 *sop = NULL; 1114 return (1); 1115 } 1116 1117 static int 1118 syncache_respond(struct syncache *sc, struct mbuf *m) 1119 { 1120 u_int8_t *optp; 1121 int optlen, error; 1122 u_int16_t tlen, hlen, mssopt; 1123 struct ip *ip = NULL; 1124 struct rtentry *rt; 1125 struct tcphdr *th; 1126 struct ip6_hdr *ip6 = NULL; 1127 #ifdef INET6 1128 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1129 #else 1130 const boolean_t isipv6 = FALSE; 1131 #endif 1132 1133 if (isipv6) { 1134 rt = tcp_rtlookup6(&sc->sc_inc); 1135 if (rt != NULL) 1136 mssopt = rt->rt_ifp->if_mtu - 1137 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1138 else 1139 mssopt = tcp_v6mssdflt; 1140 hlen = sizeof(struct ip6_hdr); 1141 } else { 1142 rt = tcp_rtlookup(&sc->sc_inc); 1143 if (rt != NULL) 1144 mssopt = rt->rt_ifp->if_mtu - 1145 (sizeof(struct ip) + sizeof(struct tcphdr)); 1146 else 1147 mssopt = tcp_mssdflt; 1148 hlen = sizeof(struct ip); 1149 } 1150 1151 /* Compute the size of the TCP options. */ 1152 if (sc->sc_flags & SCF_NOOPT) { 1153 optlen = 0; 1154 } else { 1155 optlen = TCPOLEN_MAXSEG + 1156 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1157 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1158 ((sc->sc_flags & SCF_SACK_PERMITTED) ? 1159 TCPOLEN_SACK_PERMITTED_ALIGNED : 0); 1160 #ifdef TCP_SIGNATURE 1161 optlen += ((sc->sc_flags & SCF_SIGNATURE) ? 1162 (TCPOLEN_SIGNATURE + 2) : 0); 1163 #endif /* TCP_SIGNATURE */ 1164 } 1165 tlen = hlen + sizeof(struct tcphdr) + optlen; 1166 1167 /* 1168 * XXX 1169 * assume that the entire packet will fit in a header mbuf 1170 */ 1171 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1172 1173 /* 1174 * XXX shouldn't this reuse the mbuf if possible ? 1175 * Create the IP+TCP header from scratch. 1176 */ 1177 if (m) 1178 m_freem(m); 1179 1180 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 1181 if (m == NULL) 1182 return (ENOBUFS); 1183 m->m_data += max_linkhdr; 1184 m->m_len = tlen; 1185 m->m_pkthdr.len = tlen; 1186 m->m_pkthdr.rcvif = NULL; 1187 1188 if (isipv6) { 1189 ip6 = mtod(m, struct ip6_hdr *); 1190 ip6->ip6_vfc = IPV6_VERSION; 1191 ip6->ip6_nxt = IPPROTO_TCP; 1192 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1193 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1194 ip6->ip6_plen = htons(tlen - hlen); 1195 /* ip6_hlim is set after checksum */ 1196 /* ip6_flow = ??? */ 1197 1198 th = (struct tcphdr *)(ip6 + 1); 1199 } else { 1200 ip = mtod(m, struct ip *); 1201 ip->ip_v = IPVERSION; 1202 ip->ip_hl = sizeof(struct ip) >> 2; 1203 ip->ip_len = tlen; 1204 ip->ip_id = 0; 1205 ip->ip_off = 0; 1206 ip->ip_sum = 0; 1207 ip->ip_p = IPPROTO_TCP; 1208 ip->ip_src = sc->sc_inc.inc_laddr; 1209 ip->ip_dst = sc->sc_inc.inc_faddr; 1210 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1211 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1212 1213 /* 1214 * See if we should do MTU discovery. Route lookups are 1215 * expensive, so we will only unset the DF bit if: 1216 * 1217 * 1) path_mtu_discovery is disabled 1218 * 2) the SCF_UNREACH flag has been set 1219 */ 1220 if (path_mtu_discovery 1221 && ((sc->sc_flags & SCF_UNREACH) == 0)) { 1222 ip->ip_off |= IP_DF; 1223 } 1224 1225 th = (struct tcphdr *)(ip + 1); 1226 } 1227 th->th_sport = sc->sc_inc.inc_lport; 1228 th->th_dport = sc->sc_inc.inc_fport; 1229 1230 th->th_seq = htonl(sc->sc_iss); 1231 th->th_ack = htonl(sc->sc_irs + 1); 1232 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1233 th->th_x2 = 0; 1234 th->th_flags = TH_SYN | TH_ACK; 1235 th->th_win = htons(sc->sc_wnd); 1236 th->th_urp = 0; 1237 1238 /* Tack on the TCP options. */ 1239 if (optlen == 0) 1240 goto no_options; 1241 optp = (u_int8_t *)(th + 1); 1242 *optp++ = TCPOPT_MAXSEG; 1243 *optp++ = TCPOLEN_MAXSEG; 1244 *optp++ = (mssopt >> 8) & 0xff; 1245 *optp++ = mssopt & 0xff; 1246 1247 if (sc->sc_flags & SCF_WINSCALE) { 1248 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1249 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1250 sc->sc_request_r_scale); 1251 optp += 4; 1252 } 1253 1254 if (sc->sc_flags & SCF_TIMESTAMP) { 1255 u_int32_t *lp = (u_int32_t *)(optp); 1256 1257 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1258 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1259 *lp++ = htonl(ticks); 1260 *lp = htonl(sc->sc_tsrecent); 1261 optp += TCPOLEN_TSTAMP_APPA; 1262 } 1263 1264 #ifdef TCP_SIGNATURE 1265 /* 1266 * Handle TCP-MD5 passive opener response. 1267 */ 1268 if (sc->sc_flags & SCF_SIGNATURE) { 1269 u_int8_t *bp = optp; 1270 int i; 1271 1272 *bp++ = TCPOPT_SIGNATURE; 1273 *bp++ = TCPOLEN_SIGNATURE; 1274 for (i = 0; i < TCP_SIGLEN; i++) 1275 *bp++ = 0; 1276 tcpsignature_compute(m, 0, optlen, 1277 optp + 2, IPSEC_DIR_OUTBOUND); 1278 *bp++ = TCPOPT_NOP; 1279 *bp++ = TCPOPT_EOL; 1280 optp += TCPOLEN_SIGNATURE + 2; 1281 } 1282 #endif /* TCP_SIGNATURE */ 1283 1284 if (sc->sc_flags & SCF_SACK_PERMITTED) { 1285 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 1286 optp += TCPOLEN_SACK_PERMITTED_ALIGNED; 1287 } 1288 1289 no_options: 1290 if (isipv6) { 1291 struct route_in6 *ro6 = &sc->sc_route6; 1292 1293 th->th_sum = 0; 1294 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1295 ip6->ip6_hlim = in6_selecthlim(NULL, 1296 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1297 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1298 sc->sc_tp->t_inpcb); 1299 } else { 1300 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1301 htons(tlen - hlen + IPPROTO_TCP)); 1302 m->m_pkthdr.csum_flags = CSUM_TCP; 1303 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1304 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 1305 IP_DEBUGROUTE, NULL, sc->sc_tp->t_inpcb); 1306 } 1307 return (error); 1308 } 1309 1310 /* 1311 * cookie layers: 1312 * 1313 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1314 * | peer iss | 1315 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1316 * | 0 |(A)| | 1317 * (A): peer mss index 1318 */ 1319 1320 /* 1321 * The values below are chosen to minimize the size of the tcp_secret 1322 * table, as well as providing roughly a 16 second lifetime for the cookie. 1323 */ 1324 1325 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1326 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1327 1328 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1329 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1330 #define SYNCOOKIE_TIMEOUT \ 1331 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1332 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1333 1334 static struct { 1335 u_int32_t ts_secbits[4]; 1336 u_int ts_expire; 1337 } tcp_secret[SYNCOOKIE_NSECRETS]; 1338 1339 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1340 1341 static MD5_CTX syn_ctx; 1342 1343 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1344 1345 struct md5_add { 1346 u_int32_t laddr, faddr; 1347 u_int32_t secbits[4]; 1348 u_int16_t lport, fport; 1349 }; 1350 1351 #ifdef CTASSERT 1352 CTASSERT(sizeof(struct md5_add) == 28); 1353 #endif 1354 1355 /* 1356 * Consider the problem of a recreated (and retransmitted) cookie. If the 1357 * original SYN was accepted, the connection is established. The second 1358 * SYN is inflight, and if it arrives with an ISN that falls within the 1359 * receive window, the connection is killed. 1360 * 1361 * However, since cookies have other problems, this may not be worth 1362 * worrying about. 1363 */ 1364 1365 static u_int32_t 1366 syncookie_generate(struct syncache *sc) 1367 { 1368 u_int32_t md5_buffer[4]; 1369 u_int32_t data; 1370 int idx, i; 1371 struct md5_add add; 1372 #ifdef INET6 1373 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1374 #else 1375 const boolean_t isipv6 = FALSE; 1376 #endif 1377 1378 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1379 if (tcp_secret[idx].ts_expire < ticks) { 1380 for (i = 0; i < 4; i++) 1381 tcp_secret[idx].ts_secbits[i] = karc4random(); 1382 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1383 } 1384 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1385 if (tcp_msstab[data] <= sc->sc_peer_mss) 1386 break; 1387 data = (data << SYNCOOKIE_WNDBITS) | idx; 1388 data ^= sc->sc_irs; /* peer's iss */ 1389 MD5Init(&syn_ctx); 1390 if (isipv6) { 1391 MD5Add(sc->sc_inc.inc6_laddr); 1392 MD5Add(sc->sc_inc.inc6_faddr); 1393 add.laddr = 0; 1394 add.faddr = 0; 1395 } else { 1396 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1397 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1398 } 1399 add.lport = sc->sc_inc.inc_lport; 1400 add.fport = sc->sc_inc.inc_fport; 1401 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1402 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1403 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1404 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1405 MD5Add(add); 1406 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1407 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1408 return (data); 1409 } 1410 1411 static struct syncache * 1412 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so) 1413 { 1414 u_int32_t md5_buffer[4]; 1415 struct syncache *sc; 1416 u_int32_t data; 1417 int wnd, idx; 1418 struct md5_add add; 1419 1420 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1421 idx = data & SYNCOOKIE_WNDMASK; 1422 if (tcp_secret[idx].ts_expire < ticks || 1423 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1424 return (NULL); 1425 MD5Init(&syn_ctx); 1426 #ifdef INET6 1427 if (inc->inc_isipv6) { 1428 MD5Add(inc->inc6_laddr); 1429 MD5Add(inc->inc6_faddr); 1430 add.laddr = 0; 1431 add.faddr = 0; 1432 } else 1433 #endif 1434 { 1435 add.laddr = inc->inc_laddr.s_addr; 1436 add.faddr = inc->inc_faddr.s_addr; 1437 } 1438 add.lport = inc->inc_lport; 1439 add.fport = inc->inc_fport; 1440 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1441 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1442 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1443 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1444 MD5Add(add); 1445 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1446 data ^= md5_buffer[0]; 1447 if (data & ~SYNCOOKIE_DATAMASK) 1448 return (NULL); 1449 data = data >> SYNCOOKIE_WNDBITS; 1450 1451 /* 1452 * Fill in the syncache values. 1453 * XXX duplicate code from syncache_add 1454 */ 1455 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1456 sc->sc_ipopts = NULL; 1457 sc->sc_inc.inc_fport = inc->inc_fport; 1458 sc->sc_inc.inc_lport = inc->inc_lport; 1459 #ifdef INET6 1460 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1461 if (inc->inc_isipv6) { 1462 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1463 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1464 sc->sc_route6.ro_rt = NULL; 1465 } else 1466 #endif 1467 { 1468 sc->sc_inc.inc_faddr = inc->inc_faddr; 1469 sc->sc_inc.inc_laddr = inc->inc_laddr; 1470 sc->sc_route.ro_rt = NULL; 1471 } 1472 sc->sc_irs = th->th_seq - 1; 1473 sc->sc_iss = th->th_ack - 1; 1474 wnd = ssb_space(&so->so_rcv); 1475 wnd = imax(wnd, 0); 1476 wnd = imin(wnd, TCP_MAXWIN); 1477 sc->sc_wnd = wnd; 1478 sc->sc_flags = 0; 1479 sc->sc_rxtslot = 0; 1480 sc->sc_peer_mss = tcp_msstab[data]; 1481 return (sc); 1482 } 1483