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 */ 73 74 #include "opt_inet.h" 75 #include "opt_inet6.h" 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/sysctl.h> 81 #include <sys/malloc.h> 82 #include <sys/mbuf.h> 83 #include <sys/md5.h> 84 #include <sys/proc.h> /* for proc0 declaration */ 85 #include <sys/random.h> 86 #include <sys/socket.h> 87 #include <sys/socketvar.h> 88 #include <sys/in_cksum.h> 89 90 #include <sys/msgport2.h> 91 #include <net/netmsg2.h> 92 #include <net/netisr2.h> 93 94 #include <net/if.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/ip.h> 100 #include <netinet/in_var.h> 101 #include <netinet/in_pcb.h> 102 #include <netinet/ip_var.h> 103 #include <netinet/ip6.h> 104 #ifdef INET6 105 #include <netinet/icmp6.h> 106 #include <netinet6/nd6.h> 107 #endif 108 #include <netinet6/ip6_var.h> 109 #include <netinet6/in6_pcb.h> 110 #include <netinet/tcp.h> 111 #include <netinet/tcp_fsm.h> 112 #include <netinet/tcp_seq.h> 113 #include <netinet/tcp_timer.h> 114 #include <netinet/tcp_timer2.h> 115 #include <netinet/tcp_var.h> 116 #include <netinet6/tcp6_var.h> 117 118 static int tcp_syncookies = 1; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 120 &tcp_syncookies, 0, 121 "Use TCP SYN cookies if the syncache overflows"); 122 123 static void syncache_drop(struct syncache *, struct syncache_head *); 124 static void syncache_free(struct syncache *); 125 static void syncache_insert(struct syncache *, struct syncache_head *); 126 static struct syncache *syncache_lookup(struct in_conninfo *, 127 struct syncache_head **); 128 static int syncache_respond(struct syncache *, struct mbuf *); 129 static struct socket *syncache_socket(struct syncache *, struct socket *, 130 struct mbuf *); 131 static void syncache_timer(void *); 132 static u_int32_t syncookie_generate(struct syncache *); 133 static struct syncache *syncookie_lookup(struct in_conninfo *, 134 struct tcphdr *, struct socket *); 135 136 /* 137 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 138 * 4 retransmits corresponds to a timeout of (3 + 3 + 3 + 3 + 3 == 15) seconds 139 * or (1 + 1 + 2 + 4 + 8 == 16) seconds if RFC6298 is used, the odds are that 140 * the user has given up attempting to connect by then. 141 */ 142 #define SYNCACHE_MAXREXMTS 4 143 144 /* Arbitrary values */ 145 #define TCP_SYNCACHE_HASHSIZE 512 146 #define TCP_SYNCACHE_BUCKETLIMIT 30 147 148 static void syncache_timer_handler(netmsg_t); 149 static int syncache_sysctl_count(SYSCTL_HANDLER_ARGS); 150 151 struct tcp_syncache { 152 u_int hashsize; 153 u_int hashmask; 154 u_int bucket_limit; 155 u_int cache_limit; 156 u_int rexmt_limit; 157 u_int hash_secret; 158 }; 159 static struct tcp_syncache tcp_syncache; 160 161 struct syncache_timerq { 162 TAILQ_HEAD(, syncache) list; 163 struct callout timeo; 164 struct netmsg_base nm; 165 }; 166 167 struct tcp_syncache_percpu { 168 struct syncache_head *hashbase; 169 u_int cache_count; 170 struct syncache_timerq timerq[SYNCACHE_MAXREXMTS + 1]; 171 }; 172 173 static struct tcp_syncache_percpu *tcp_syncache_percpu[MAXCPU]; 174 175 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 176 177 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 178 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 179 180 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 181 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 182 183 SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, count, (CTLTYPE_INT | CTLFLAG_RD), 184 0, 0, syncache_sysctl_count, "I", "Current number of entries in syncache"); 185 186 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 187 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 188 189 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 190 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 191 192 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 193 194 #define SYNCACHE_HASH(inc, mask) \ 195 ((tcp_syncache.hash_secret ^ \ 196 (inc)->inc_faddr.s_addr ^ \ 197 ((inc)->inc_faddr.s_addr >> 16) ^ \ 198 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 199 200 #define SYNCACHE_HASH6(inc, mask) \ 201 ((tcp_syncache.hash_secret ^ \ 202 (inc)->inc6_faddr.s6_addr32[0] ^ \ 203 (inc)->inc6_faddr.s6_addr32[3] ^ \ 204 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 205 206 #define ENDPTS_EQ(a, b) ( \ 207 (a)->ie_fport == (b)->ie_fport && \ 208 (a)->ie_lport == (b)->ie_lport && \ 209 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 210 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 211 ) 212 213 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 214 215 static __inline int 216 syncache_rto(int slot) 217 { 218 if (tcp_low_rtobase) 219 return (TCPTV_RTOBASE * tcp_syn_backoff_low[slot]); 220 else 221 return (TCPTV_RTOBASE * tcp_syn_backoff[slot]); 222 } 223 224 static __inline void 225 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu, 226 struct syncache *sc, int slot) 227 { 228 struct syncache_timerq *tq; 229 int rto; 230 231 KASSERT(slot <= SYNCACHE_MAXREXMTS, 232 ("syncache: invalid slot %d", slot)); 233 234 if (slot > 0) { 235 /* 236 * Record the time that we spent in SYN|ACK 237 * retransmition. 238 * 239 * Needed by RFC3390 and RFC6298. 240 */ 241 sc->sc_rxtused += syncache_rto(slot - 1); 242 } 243 sc->sc_rxtslot = slot; 244 245 rto = syncache_rto(slot); 246 sc->sc_rxttime = ticks + rto; 247 248 tq = &syncache_percpu->timerq[slot]; 249 TAILQ_INSERT_TAIL(&tq->list, sc, sc_timerq); 250 if (!callout_active(&tq->timeo)) 251 callout_reset(&tq->timeo, rto, syncache_timer, &tq->nm); 252 } 253 254 static void 255 syncache_free(struct syncache *sc) 256 { 257 struct rtentry *rt; 258 #ifdef INET6 259 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 260 #else 261 const boolean_t isipv6 = FALSE; 262 #endif 263 264 if (sc->sc_ipopts) 265 m_free(sc->sc_ipopts); 266 267 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt; 268 if (rt != NULL) { 269 /* 270 * If this is the only reference to a protocol-cloned 271 * route, remove it immediately. 272 */ 273 if ((rt->rt_flags & (RTF_WASCLONED | RTF_LLINFO)) == 274 RTF_WASCLONED && rt->rt_refcnt == 1) { 275 rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway, 276 rt_mask(rt), rt->rt_flags, NULL); 277 } 278 RTFREE(rt); 279 } 280 kfree(sc, M_SYNCACHE); 281 } 282 283 static void 284 syncache_init_dispatch(netmsg_t nm) 285 { 286 struct tcp_syncache_percpu *syncache_percpu; 287 int i; 288 289 ASSERT_NETISR_NCPUS(mycpuid); 290 291 syncache_percpu = kmalloc(sizeof(*syncache_percpu), M_SYNCACHE, 292 M_WAITOK | M_ZERO); 293 294 /* Allocate the hash table. */ 295 syncache_percpu->hashbase = kmalloc(tcp_syncache.hashsize * 296 sizeof(struct syncache_head), 297 M_SYNCACHE, M_WAITOK | M_ZERO); 298 299 /* Initialize the hash buckets. */ 300 for (i = 0; i < tcp_syncache.hashsize; i++) { 301 struct syncache_head *bucket; 302 303 bucket = &syncache_percpu->hashbase[i]; 304 TAILQ_INIT(&bucket->sch_bucket); 305 bucket->sch_length = 0; 306 } 307 308 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 309 struct syncache_timerq *tq = 310 &syncache_percpu->timerq[i]; 311 312 /* Initialize the timer queues. */ 313 TAILQ_INIT(&tq->list); 314 callout_init_mp(&tq->timeo); 315 316 netmsg_init(&tq->nm, NULL, &netisr_adone_rport, 317 MSGF_PRIORITY, syncache_timer_handler); 318 tq->nm.lmsg.u.ms_result = i; 319 } 320 321 tcp_syncache_percpu[mycpuid] = syncache_percpu; 322 323 netisr_forwardmsg(&nm->base, mycpuid + 1); 324 } 325 326 void 327 syncache_init(void) 328 { 329 struct netmsg_base nm; 330 331 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 332 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 333 tcp_syncache.cache_limit = 334 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 335 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 336 tcp_syncache.hash_secret = karc4random(); 337 338 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 339 &tcp_syncache.hashsize); 340 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 341 &tcp_syncache.cache_limit); 342 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 343 &tcp_syncache.bucket_limit); 344 if (!powerof2(tcp_syncache.hashsize)) { 345 kprintf("WARNING: syncache hash size is not a power of 2.\n"); 346 tcp_syncache.hashsize = 512; /* safe default */ 347 } 348 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 349 350 netmsg_init(&nm, NULL, &curthread->td_msgport, 0, 351 syncache_init_dispatch); 352 netisr_domsg_global(&nm); 353 } 354 355 static void 356 syncache_insert(struct syncache *sc, struct syncache_head *sch) 357 { 358 struct tcp_syncache_percpu *syncache_percpu; 359 struct syncache *sc2; 360 int i; 361 362 syncache_percpu = tcp_syncache_percpu[mycpu->gd_cpuid]; 363 364 /* 365 * Make sure that we don't overflow the per-bucket 366 * limit or the total cache size limit. 367 */ 368 if (sch->sch_length >= tcp_syncache.bucket_limit) { 369 /* 370 * The bucket is full, toss the oldest element. 371 */ 372 sc2 = TAILQ_FIRST(&sch->sch_bucket); 373 if (sc2->sc_tp != NULL) 374 sc2->sc_tp->ts_recent = ticks; 375 syncache_drop(sc2, sch); 376 tcpstat.tcps_sc_bucketoverflow++; 377 } else if (syncache_percpu->cache_count >= tcp_syncache.cache_limit) { 378 /* 379 * The cache is full. Toss the oldest entry in the 380 * entire cache. This is the front entry in the 381 * first non-empty timer queue with the largest 382 * timeout value. 383 */ 384 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 385 sc2 = TAILQ_FIRST(&syncache_percpu->timerq[i].list); 386 if (sc2 != NULL) 387 break; 388 } 389 if (sc2->sc_tp != NULL) 390 sc2->sc_tp->ts_recent = ticks; 391 syncache_drop(sc2, NULL); 392 tcpstat.tcps_sc_cacheoverflow++; 393 } 394 395 /* Initialize the entry's timer. */ 396 syncache_timeout(syncache_percpu, sc, 0); 397 398 /* Put it into the bucket. */ 399 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 400 sch->sch_length++; 401 syncache_percpu->cache_count++; 402 tcpstat.tcps_sc_added++; 403 } 404 405 void 406 syncache_destroy(struct tcpcb *tp, struct tcpcb *tp_inh) 407 { 408 struct tcp_syncache_percpu *syncache_percpu; 409 int i; 410 411 ASSERT_NETISR_NCPUS(mycpuid); 412 413 syncache_percpu = tcp_syncache_percpu[mycpu->gd_cpuid]; 414 for (i = 0; i < tcp_syncache.hashsize; i++) { 415 struct syncache_head *bucket; 416 struct syncache *sc; 417 418 bucket = &syncache_percpu->hashbase[i]; 419 TAILQ_FOREACH(sc, &bucket->sch_bucket, sc_hash) { 420 if (sc->sc_tp == tp) 421 sc->sc_tp = tp_inh; 422 } 423 } 424 } 425 426 static void 427 syncache_drop(struct syncache *sc, struct syncache_head *sch) 428 { 429 struct tcp_syncache_percpu *syncache_percpu; 430 #ifdef INET6 431 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 432 #else 433 const boolean_t isipv6 = FALSE; 434 #endif 435 436 syncache_percpu = tcp_syncache_percpu[mycpu->gd_cpuid]; 437 438 if (sch == NULL) { 439 if (isipv6) { 440 sch = &syncache_percpu->hashbase[ 441 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 442 } else { 443 sch = &syncache_percpu->hashbase[ 444 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 445 } 446 } 447 448 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 449 sch->sch_length--; 450 syncache_percpu->cache_count--; 451 452 /* 453 * Cleanup 454 */ 455 sc->sc_tp = NULL; 456 457 /* 458 * Remove the entry from the syncache timer/timeout queue. Note 459 * that we do not try to stop any running timer since we do not know 460 * whether the timer's message is in-transit or not. Since timeouts 461 * are fairly long, taking an unneeded callout does not detrimentally 462 * effect performance. 463 */ 464 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot].list, sc, 465 sc_timerq); 466 467 syncache_free(sc); 468 } 469 470 /* 471 * Place a timeout message on the TCP thread's message queue. 472 * This routine runs in soft interrupt context. 473 * 474 * An invariant is for this routine to be called, the callout must 475 * have been active. Note that the callout is not deactivated until 476 * after the message has been processed in syncache_timer_handler() below. 477 */ 478 static void 479 syncache_timer(void *p) 480 { 481 struct netmsg_base *msg = p; 482 483 KKASSERT(mycpuid < netisr_ncpus); 484 485 crit_enter(); 486 if (msg->lmsg.ms_flags & MSGF_DONE) 487 netisr_sendmsg_oncpu(msg); 488 crit_exit(); 489 } 490 491 /* 492 * Service a timer message queued by timer expiration. 493 * This routine runs in the TCP protocol thread. 494 * 495 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 496 * If we have retransmitted an entry the maximum number of times, expire it. 497 * 498 * When we finish processing timed-out entries, we restart the timer if there 499 * are any entries still on the queue and deactivate it otherwise. Only after 500 * a timer has been deactivated here can it be restarted by syncache_timeout(). 501 */ 502 static void 503 syncache_timer_handler(netmsg_t msg) 504 { 505 struct tcp_syncache_percpu *syncache_percpu; 506 struct syncache *nsc; 507 struct syncache_timerq *tq; 508 int slot; 509 510 ASSERT_NETISR_NCPUS(mycpuid); 511 512 /* Reply ASAP. */ 513 crit_enter(); 514 netisr_replymsg(&msg->base, 0); 515 crit_exit(); 516 517 syncache_percpu = tcp_syncache_percpu[mycpu->gd_cpuid]; 518 519 slot = msg->lmsg.u.ms_result; 520 KASSERT(slot <= SYNCACHE_MAXREXMTS, 521 ("syncache: invalid slot %d", slot)); 522 tq = &syncache_percpu->timerq[slot]; 523 524 nsc = TAILQ_FIRST(&tq->list); 525 while (nsc != NULL) { 526 struct syncache *sc; 527 528 if (ticks < nsc->sc_rxttime) 529 break; /* finished because timerq sorted by time */ 530 531 sc = nsc; 532 if (sc->sc_tp == NULL) { 533 nsc = TAILQ_NEXT(sc, sc_timerq); 534 syncache_drop(sc, NULL); 535 tcpstat.tcps_sc_stale++; 536 continue; 537 } 538 if (slot == SYNCACHE_MAXREXMTS || 539 slot >= tcp_syncache.rexmt_limit || 540 sc->sc_tp->t_inpcb->inp_gencnt != sc->sc_inp_gencnt) { 541 nsc = TAILQ_NEXT(sc, sc_timerq); 542 syncache_drop(sc, NULL); 543 tcpstat.tcps_sc_stale++; 544 continue; 545 } 546 /* 547 * syncache_respond() may call back into the syncache to 548 * to modify another entry, so do not obtain the next 549 * entry on the timer chain until it has completed. 550 */ 551 syncache_respond(sc, NULL); 552 tcpstat.tcps_sc_retransmitted++; 553 nsc = TAILQ_NEXT(sc, sc_timerq); 554 TAILQ_REMOVE(&tq->list, sc, sc_timerq); 555 syncache_timeout(syncache_percpu, sc, slot + 1); 556 } 557 558 if (nsc != NULL) { 559 callout_reset(&tq->timeo, nsc->sc_rxttime - ticks, 560 syncache_timer, &tq->nm); 561 } else { 562 callout_deactivate(&tq->timeo); 563 } 564 } 565 566 /* 567 * Find an entry in the syncache. 568 */ 569 static struct syncache * 570 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 571 { 572 struct tcp_syncache_percpu *syncache_percpu; 573 struct syncache *sc; 574 struct syncache_head *sch; 575 576 syncache_percpu = tcp_syncache_percpu[mycpu->gd_cpuid]; 577 #ifdef INET6 578 if (inc->inc_isipv6) { 579 sch = &syncache_percpu->hashbase[ 580 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 581 *schp = sch; 582 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 583 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 584 return (sc); 585 } else 586 #endif 587 { 588 sch = &syncache_percpu->hashbase[ 589 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 590 *schp = sch; 591 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 592 #ifdef INET6 593 if (sc->sc_inc.inc_isipv6) 594 continue; 595 #endif 596 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 597 return (sc); 598 } 599 } 600 return (NULL); 601 } 602 603 /* 604 * This function is called when we get a RST for a 605 * non-existent connection, so that we can see if the 606 * connection is in the syn cache. If it is, zap it. 607 */ 608 void 609 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 610 { 611 struct syncache *sc; 612 struct syncache_head *sch; 613 614 ASSERT_NETISR_NCPUS(mycpuid); 615 616 sc = syncache_lookup(inc, &sch); 617 if (sc == NULL) { 618 return; 619 } 620 /* 621 * If the RST bit is set, check the sequence number to see 622 * if this is a valid reset segment. 623 * RFC 793 page 37: 624 * In all states except SYN-SENT, all reset (RST) segments 625 * are validated by checking their SEQ-fields. A reset is 626 * valid if its sequence number is in the window. 627 * 628 * The sequence number in the reset segment is normally an 629 * echo of our outgoing acknowlegement numbers, but some hosts 630 * send a reset with the sequence number at the rightmost edge 631 * of our receive window, and we have to handle this case. 632 */ 633 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 634 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 635 syncache_drop(sc, sch); 636 tcpstat.tcps_sc_reset++; 637 } 638 } 639 640 void 641 syncache_badack(struct in_conninfo *inc) 642 { 643 struct syncache *sc; 644 struct syncache_head *sch; 645 646 ASSERT_NETISR_NCPUS(mycpuid); 647 648 sc = syncache_lookup(inc, &sch); 649 if (sc != NULL) { 650 syncache_drop(sc, sch); 651 tcpstat.tcps_sc_badack++; 652 } 653 } 654 655 void 656 syncache_unreach(struct in_conninfo *inc, const struct tcphdr *th) 657 { 658 struct syncache *sc; 659 struct syncache_head *sch; 660 661 ASSERT_NETISR_NCPUS(mycpuid); 662 663 /* we are called at splnet() here */ 664 sc = syncache_lookup(inc, &sch); 665 if (sc == NULL) 666 return; 667 668 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 669 if (ntohl(th->th_seq) != sc->sc_iss) 670 return; 671 672 /* 673 * If we've rertransmitted 3 times and this is our second error, 674 * we remove the entry. Otherwise, we allow it to continue on. 675 * This prevents us from incorrectly nuking an entry during a 676 * spurious network outage. 677 * 678 * See tcp_notify(). 679 */ 680 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 681 sc->sc_flags |= SCF_UNREACH; 682 return; 683 } 684 syncache_drop(sc, sch); 685 tcpstat.tcps_sc_unreach++; 686 } 687 688 /* 689 * Build a new TCP socket structure from a syncache entry. 690 * 691 * This is called from the context of the SYN+ACK 692 */ 693 static struct socket * 694 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 695 { 696 struct inpcb *inp = NULL, *linp; 697 struct socket *so; 698 struct tcpcb *tp, *ltp; 699 lwkt_port_t port; 700 #ifdef INET6 701 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 702 #else 703 const boolean_t isipv6 = FALSE; 704 #endif 705 struct sockaddr_in sin_faddr; 706 struct sockaddr_in6 sin6_faddr; 707 struct sockaddr *faddr; 708 709 KASSERT(m->m_flags & M_HASH, ("mbuf has no hash")); 710 711 if (isipv6) { 712 faddr = (struct sockaddr *)&sin6_faddr; 713 sin6_faddr.sin6_family = AF_INET6; 714 sin6_faddr.sin6_len = sizeof(sin6_faddr); 715 sin6_faddr.sin6_addr = sc->sc_inc.inc6_faddr; 716 sin6_faddr.sin6_port = sc->sc_inc.inc_fport; 717 sin6_faddr.sin6_flowinfo = sin6_faddr.sin6_scope_id = 0; 718 } else { 719 faddr = (struct sockaddr *)&sin_faddr; 720 sin_faddr.sin_family = AF_INET; 721 sin_faddr.sin_len = sizeof(sin_faddr); 722 sin_faddr.sin_addr = sc->sc_inc.inc_faddr; 723 sin_faddr.sin_port = sc->sc_inc.inc_fport; 724 bzero(sin_faddr.sin_zero, sizeof(sin_faddr.sin_zero)); 725 } 726 727 /* 728 * Ok, create the full blown connection, and set things up 729 * as they would have been set up if we had created the 730 * connection when the SYN arrived. If we can't create 731 * the connection, abort it. 732 * 733 * Set the protocol processing port for the socket to the current 734 * port (that the connection came in on). 735 * 736 * NOTE: 737 * We don't keep a reference on the new socket, since its 738 * destruction will run in this thread (netisrN); there is no 739 * race here. 740 */ 741 so = sonewconn_faddr(lso, SS_ISCONNECTED, faddr, 742 FALSE /* don't ref */); 743 if (so == NULL) { 744 /* 745 * Drop the connection; we will send a RST if the peer 746 * retransmits the ACK, 747 */ 748 tcpstat.tcps_listendrop++; 749 goto abort; 750 } 751 752 /* 753 * Insert new socket into hash list. 754 */ 755 inp = so->so_pcb; 756 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 757 if (isipv6) { 758 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 759 } else { 760 KASSERT(INP_ISIPV4(inp), ("not inet pcb")); 761 inp->inp_laddr = sc->sc_inc.inc_laddr; 762 } 763 inp->inp_lport = sc->sc_inc.inc_lport; 764 765 linp = lso->so_pcb; 766 ltp = intotcpcb(linp); 767 768 tcp_pcbport_insert(ltp, inp); 769 770 if (isipv6) { 771 struct in6_addr laddr6; 772 /* 773 * Inherit socket options from the listening socket. 774 * Note that in6p_inputopts are not (and should not be) 775 * copied, since it stores previously received options and is 776 * used to detect if each new option is different than the 777 * previous one and hence should be passed to a user. 778 * If we copied in6p_inputopts, a user would not be able to 779 * receive options just after calling the accept system call. 780 */ 781 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS; 782 if (linp->in6p_outputopts) 783 inp->in6p_outputopts = 784 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT); 785 inp->in6p_route = sc->sc_route6; 786 sc->sc_route6.ro_rt = NULL; 787 788 laddr6 = inp->in6p_laddr; 789 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 790 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 791 if (in6_pcbconnect(inp, faddr, &thread0)) { 792 inp->in6p_laddr = laddr6; 793 goto abort; 794 } 795 port = tcp6_addrport(); 796 } else { 797 struct in_addr laddr; 798 799 inp->inp_options = ip_srcroute(m); 800 if (inp->inp_options == NULL) { 801 inp->inp_options = sc->sc_ipopts; 802 sc->sc_ipopts = NULL; 803 } 804 inp->inp_route = sc->sc_route; 805 sc->sc_route.ro_rt = NULL; 806 807 laddr = inp->inp_laddr; 808 if (inp->inp_laddr.s_addr == INADDR_ANY) 809 inp->inp_laddr = sc->sc_inc.inc_laddr; 810 if (in_pcbconnect(inp, faddr, &thread0)) { 811 inp->inp_laddr = laddr; 812 goto abort; 813 } 814 815 inp->inp_flags |= INP_HASH; 816 inp->inp_hashval = m->m_pkthdr.hash; 817 port = netisr_hashport(inp->inp_hashval); 818 } 819 820 /* 821 * The current port should be in the context of the SYN+ACK and 822 * so should match the tcp address port. 823 */ 824 KASSERT(port == &curthread->td_msgport, 825 ("TCP PORT MISMATCH %p vs %p\n", port, &curthread->td_msgport)); 826 827 tp = intotcpcb(inp); 828 TCP_STATE_CHANGE(tp, 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_wnd = sc->sc_sndwnd; 834 tp->snd_wl1 = sc->sc_irs; 835 tp->rcv_up = sc->sc_irs + 1; 836 tp->rcv_wnd = sc->sc_wnd; 837 tp->rcv_adv += tp->rcv_wnd; 838 839 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY); 840 if (sc->sc_flags & SCF_NOOPT) 841 tp->t_flags |= TF_NOOPT; 842 if (sc->sc_flags & SCF_WINSCALE) { 843 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE; 844 tp->snd_scale = sc->sc_requested_s_scale; 845 tp->request_r_scale = sc->sc_request_r_scale; 846 } 847 if (sc->sc_flags & SCF_TIMESTAMP) { 848 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP; 849 tp->ts_recent = sc->sc_tsrecent; 850 tp->ts_recent_age = ticks; 851 } 852 if (sc->sc_flags & SCF_SACK_PERMITTED) 853 tp->t_flags |= TF_SACK_PERMITTED; 854 855 #ifdef TCP_SIGNATURE 856 if (sc->sc_flags & SCF_SIGNATURE) 857 tp->t_flags |= TF_SIGNATURE; 858 #endif /* TCP_SIGNATURE */ 859 860 tp->t_rxtsyn = sc->sc_rxtused; 861 tcp_rmx_init(tp, sc->sc_peer_mss); 862 863 /* 864 * Inherit some properties from the listen socket 865 */ 866 tp->t_keepinit = ltp->t_keepinit; 867 tp->t_keepidle = ltp->t_keepidle; 868 tp->t_keepintvl = ltp->t_keepintvl; 869 tp->t_keepcnt = ltp->t_keepcnt; 870 tp->t_maxidle = ltp->t_maxidle; 871 872 tcp_create_timermsg(tp, port); 873 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepinit, tcp_timer_keep); 874 875 tcpstat.tcps_accepts++; 876 return (so); 877 878 abort: 879 if (so != NULL) 880 soabort_direct(so); 881 return (NULL); 882 } 883 884 /* 885 * This function gets called when we receive an ACK for a 886 * socket in the LISTEN state. We look up the connection 887 * in the syncache, and if its there, we pull it out of 888 * the cache and turn it into a full-blown connection in 889 * the SYN-RECEIVED state. 890 */ 891 int 892 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop, 893 struct mbuf *m) 894 { 895 struct syncache *sc; 896 struct syncache_head *sch; 897 struct socket *so; 898 899 ASSERT_NETISR_NCPUS(mycpuid); 900 901 sc = syncache_lookup(inc, &sch); 902 if (sc == NULL) { 903 /* 904 * There is no syncache entry, so see if this ACK is 905 * a returning syncookie. To do this, first: 906 * A. See if this socket has had a syncache entry dropped in 907 * the past. We don't want to accept a bogus syncookie 908 * if we've never received a SYN. 909 * B. check that the syncookie is valid. If it is, then 910 * cobble up a fake syncache entry, and return. 911 */ 912 if (!tcp_syncookies) 913 return (0); 914 sc = syncookie_lookup(inc, th, *sop); 915 if (sc == NULL) 916 return (0); 917 sch = NULL; 918 tcpstat.tcps_sc_recvcookie++; 919 } 920 921 /* 922 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 923 */ 924 if (th->th_ack != sc->sc_iss + 1) 925 return (0); 926 927 so = syncache_socket(sc, *sop, m); 928 if (so == NULL) { 929 #if 0 930 resetandabort: 931 /* XXXjlemon check this - is this correct? */ 932 tcp_respond(NULL, m, m, th, 933 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK); 934 #endif 935 m_freem(m); /* XXX only needed for above */ 936 tcpstat.tcps_sc_aborted++; 937 } else { 938 tcpstat.tcps_sc_completed++; 939 } 940 if (sch == NULL) 941 syncache_free(sc); 942 else 943 syncache_drop(sc, sch); 944 *sop = so; 945 return (1); 946 } 947 948 /* 949 * Given a LISTEN socket and an inbound SYN request, add 950 * this to the syn cache, and send back a segment: 951 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 952 * to the source. 953 * 954 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 955 * Doing so would require that we hold onto the data and deliver it 956 * to the application. However, if we are the target of a SYN-flood 957 * DoS attack, an attacker could send data which would eventually 958 * consume all available buffer space if it were ACKed. By not ACKing 959 * the data, we avoid this DoS scenario. 960 */ 961 int 962 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 963 struct socket *so, struct mbuf *m) 964 { 965 struct tcp_syncache_percpu *syncache_percpu; 966 struct tcpcb *tp; 967 struct syncache *sc = NULL; 968 struct syncache_head *sch; 969 struct mbuf *ipopts = NULL; 970 int win; 971 972 ASSERT_NETISR_NCPUS(mycpuid); 973 KASSERT(m->m_flags & M_HASH, ("mbuf has no hash")); 974 975 syncache_percpu = tcp_syncache_percpu[mycpu->gd_cpuid]; 976 tp = sototcpcb(so); 977 978 /* 979 * Remember the IP options, if any. 980 */ 981 #ifdef INET6 982 if (!inc->inc_isipv6) 983 #endif 984 ipopts = ip_srcroute(m); 985 986 /* 987 * See if we already have an entry for this connection. 988 * If we do, resend the SYN,ACK, and reset the retransmit timer. 989 * 990 * XXX 991 * The syncache should be re-initialized with the contents 992 * of the new SYN which may have different options. 993 */ 994 sc = syncache_lookup(inc, &sch); 995 if (sc != NULL) { 996 KASSERT(sc->sc_flags & SCF_HASH, ("syncache has no hash")); 997 KASSERT(sc->sc_hashval == m->m_pkthdr.hash, 998 ("syncache/mbuf hash mismatches")); 999 1000 tcpstat.tcps_sc_dupsyn++; 1001 if (ipopts) { 1002 /* 1003 * If we were remembering a previous source route, 1004 * forget it and use the new one we've been given. 1005 */ 1006 if (sc->sc_ipopts) 1007 m_free(sc->sc_ipopts); 1008 sc->sc_ipopts = ipopts; 1009 } 1010 /* 1011 * Update timestamp if present. 1012 */ 1013 if (sc->sc_flags & SCF_TIMESTAMP) 1014 sc->sc_tsrecent = to->to_tsval; 1015 1016 /* Just update the TOF_SACK_PERMITTED for now. */ 1017 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 1018 sc->sc_flags |= SCF_SACK_PERMITTED; 1019 else 1020 sc->sc_flags &= ~SCF_SACK_PERMITTED; 1021 1022 /* Update initial send window */ 1023 sc->sc_sndwnd = th->th_win; 1024 1025 /* 1026 * PCB may have changed, pick up new values. 1027 */ 1028 sc->sc_tp = tp; 1029 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1030 if (syncache_respond(sc, m) == 0) { 1031 TAILQ_REMOVE( 1032 &syncache_percpu->timerq[sc->sc_rxtslot].list, 1033 sc, sc_timerq); 1034 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot); 1035 tcpstat.tcps_sndacks++; 1036 tcpstat.tcps_sndtotal++; 1037 } 1038 return (1); 1039 } 1040 1041 /* 1042 * Fill in the syncache values. 1043 */ 1044 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1045 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1046 sc->sc_ipopts = ipopts; 1047 sc->sc_inc.inc_fport = inc->inc_fport; 1048 sc->sc_inc.inc_lport = inc->inc_lport; 1049 sc->sc_tp = tp; 1050 #ifdef INET6 1051 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1052 if (inc->inc_isipv6) { 1053 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1054 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1055 sc->sc_route6.ro_rt = NULL; 1056 } else 1057 #endif 1058 { 1059 sc->sc_inc.inc_faddr = inc->inc_faddr; 1060 sc->sc_inc.inc_laddr = inc->inc_laddr; 1061 sc->sc_route.ro_rt = NULL; 1062 } 1063 sc->sc_irs = th->th_seq; 1064 sc->sc_flags = SCF_HASH; 1065 sc->sc_hashval = m->m_pkthdr.hash; 1066 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 1067 if (tcp_syncookies) 1068 sc->sc_iss = syncookie_generate(sc); 1069 else 1070 sc->sc_iss = karc4random(); 1071 1072 /* Initial receive window: clip ssb_space to [0 .. TCP_MAXWIN] */ 1073 win = ssb_space(&so->so_rcv); 1074 win = imax(win, 0); 1075 win = imin(win, TCP_MAXWIN); 1076 sc->sc_wnd = win; 1077 1078 if (tcp_do_rfc1323) { 1079 /* 1080 * A timestamp received in a SYN makes 1081 * it ok to send timestamp requests and replies. 1082 */ 1083 if (to->to_flags & TOF_TS) { 1084 sc->sc_tsrecent = to->to_tsval; 1085 sc->sc_flags |= SCF_TIMESTAMP; 1086 } 1087 if (to->to_flags & TOF_SCALE) { 1088 int wscale = TCP_MIN_WINSHIFT; 1089 1090 /* Compute proper scaling value from buffer space */ 1091 while (wscale < TCP_MAX_WINSHIFT && 1092 (TCP_MAXWIN << wscale) < so->so_rcv.ssb_hiwat) { 1093 wscale++; 1094 } 1095 sc->sc_request_r_scale = wscale; 1096 sc->sc_requested_s_scale = to->to_requested_s_scale; 1097 sc->sc_flags |= SCF_WINSCALE; 1098 } 1099 } 1100 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 1101 sc->sc_flags |= SCF_SACK_PERMITTED; 1102 if (tp->t_flags & TF_NOOPT) 1103 sc->sc_flags = SCF_NOOPT; 1104 #ifdef TCP_SIGNATURE 1105 /* 1106 * If listening socket requested TCP digests, and received SYN 1107 * contains the option, flag this in the syncache so that 1108 * syncache_respond() will do the right thing with the SYN+ACK. 1109 * XXX Currently we always record the option by default and will 1110 * attempt to use it in syncache_respond(). 1111 */ 1112 if (to->to_flags & TOF_SIGNATURE) 1113 sc->sc_flags = SCF_SIGNATURE; 1114 #endif /* TCP_SIGNATURE */ 1115 sc->sc_sndwnd = th->th_win; 1116 1117 if (syncache_respond(sc, m) == 0) { 1118 syncache_insert(sc, sch); 1119 tcpstat.tcps_sndacks++; 1120 tcpstat.tcps_sndtotal++; 1121 } else { 1122 syncache_free(sc); 1123 tcpstat.tcps_sc_dropped++; 1124 } 1125 return (1); 1126 } 1127 1128 static int 1129 syncache_respond(struct syncache *sc, struct mbuf *m) 1130 { 1131 u_int8_t *optp; 1132 int optlen, error; 1133 u_int16_t tlen, hlen, mssopt; 1134 struct ip *ip = NULL; 1135 struct rtentry *rt; 1136 struct tcphdr *th; 1137 struct ip6_hdr *ip6 = NULL; 1138 #ifdef INET6 1139 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1140 #else 1141 const boolean_t isipv6 = FALSE; 1142 #endif 1143 1144 if (isipv6) { 1145 rt = tcp_rtlookup6(&sc->sc_inc); 1146 if (rt != NULL) 1147 mssopt = rt->rt_ifp->if_mtu - 1148 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1149 else 1150 mssopt = tcp_v6mssdflt; 1151 hlen = sizeof(struct ip6_hdr); 1152 } else { 1153 rt = tcp_rtlookup(&sc->sc_inc); 1154 if (rt != NULL) 1155 mssopt = rt->rt_ifp->if_mtu - 1156 (sizeof(struct ip) + sizeof(struct tcphdr)); 1157 else 1158 mssopt = tcp_mssdflt; 1159 hlen = sizeof(struct ip); 1160 } 1161 1162 /* Compute the size of the TCP options. */ 1163 if (sc->sc_flags & SCF_NOOPT) { 1164 optlen = 0; 1165 } else { 1166 optlen = TCPOLEN_MAXSEG + 1167 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1168 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1169 ((sc->sc_flags & SCF_SACK_PERMITTED) ? 1170 TCPOLEN_SACK_PERMITTED_ALIGNED : 0); 1171 #ifdef TCP_SIGNATURE 1172 optlen += ((sc->sc_flags & SCF_SIGNATURE) ? 1173 (TCPOLEN_SIGNATURE + 2) : 0); 1174 #endif /* TCP_SIGNATURE */ 1175 } 1176 tlen = hlen + sizeof(struct tcphdr) + optlen; 1177 1178 /* 1179 * XXX 1180 * assume that the entire packet will fit in a header mbuf 1181 */ 1182 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1183 1184 /* 1185 * XXX shouldn't this reuse the mbuf if possible ? 1186 * Create the IP+TCP header from scratch. 1187 */ 1188 if (m) 1189 m_freem(m); 1190 1191 m = m_gethdr(M_NOWAIT, MT_HEADER); 1192 if (m == NULL) 1193 return (ENOBUFS); 1194 m->m_data += max_linkhdr; 1195 m->m_len = tlen; 1196 m->m_pkthdr.len = tlen; 1197 m->m_pkthdr.rcvif = NULL; 1198 if (tcp_prio_synack) 1199 m->m_flags |= M_PRIO; 1200 1201 if (isipv6) { 1202 ip6 = mtod(m, struct ip6_hdr *); 1203 ip6->ip6_vfc = IPV6_VERSION; 1204 ip6->ip6_nxt = IPPROTO_TCP; 1205 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1206 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1207 ip6->ip6_plen = htons(tlen - hlen); 1208 /* ip6_hlim is set after checksum */ 1209 /* ip6_flow = ??? */ 1210 1211 th = (struct tcphdr *)(ip6 + 1); 1212 } else { 1213 ip = mtod(m, struct ip *); 1214 ip->ip_v = IPVERSION; 1215 ip->ip_hl = sizeof(struct ip) >> 2; 1216 ip->ip_len = htons(tlen); 1217 ip->ip_id = 0; 1218 ip->ip_off = 0; 1219 ip->ip_sum = 0; 1220 ip->ip_p = IPPROTO_TCP; 1221 ip->ip_src = sc->sc_inc.inc_laddr; 1222 ip->ip_dst = sc->sc_inc.inc_faddr; 1223 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1224 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1225 1226 /* 1227 * See if we should do MTU discovery. Route lookups are 1228 * expensive, so we will only unset the DF bit if: 1229 * 1230 * 1) path_mtu_discovery is disabled 1231 * 2) the SCF_UNREACH flag has been set 1232 */ 1233 if (path_mtu_discovery 1234 && ((sc->sc_flags & SCF_UNREACH) == 0)) 1235 { 1236 ip->ip_off |= htons(IP_DF); 1237 } 1238 1239 th = (struct tcphdr *)(ip + 1); 1240 } 1241 th->th_sport = sc->sc_inc.inc_lport; 1242 th->th_dport = sc->sc_inc.inc_fport; 1243 1244 th->th_seq = htonl(sc->sc_iss); 1245 th->th_ack = htonl(sc->sc_irs + 1); 1246 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1247 th->th_x2 = 0; 1248 th->th_flags = TH_SYN | TH_ACK; 1249 th->th_win = htons(sc->sc_wnd); 1250 th->th_urp = 0; 1251 1252 /* Tack on the TCP options. */ 1253 if (optlen == 0) 1254 goto no_options; 1255 optp = (u_int8_t *)(th + 1); 1256 *optp++ = TCPOPT_MAXSEG; 1257 *optp++ = TCPOLEN_MAXSEG; 1258 *optp++ = (mssopt >> 8) & 0xff; 1259 *optp++ = mssopt & 0xff; 1260 1261 if (sc->sc_flags & SCF_WINSCALE) { 1262 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1263 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1264 sc->sc_request_r_scale); 1265 optp += 4; 1266 } 1267 1268 if (sc->sc_flags & SCF_TIMESTAMP) { 1269 u_int32_t *lp = (u_int32_t *)(optp); 1270 1271 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1272 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1273 *lp++ = htonl(ticks); 1274 *lp = htonl(sc->sc_tsrecent); 1275 optp += TCPOLEN_TSTAMP_APPA; 1276 } 1277 1278 #ifdef TCP_SIGNATURE 1279 /* 1280 * Handle TCP-MD5 passive opener response. 1281 */ 1282 if (sc->sc_flags & SCF_SIGNATURE) { 1283 u_int8_t *bp = optp; 1284 int i; 1285 1286 *bp++ = TCPOPT_SIGNATURE; 1287 *bp++ = TCPOLEN_SIGNATURE; 1288 for (i = 0; i < TCP_SIGLEN; i++) 1289 *bp++ = 0; 1290 tcpsignature_compute(m, 0, optlen, 1291 optp + 2, IPSEC_DIR_OUTBOUND); 1292 *bp++ = TCPOPT_NOP; 1293 *bp++ = TCPOPT_EOL; 1294 optp += TCPOLEN_SIGNATURE + 2; 1295 } 1296 #endif /* TCP_SIGNATURE */ 1297 1298 if (sc->sc_flags & SCF_SACK_PERMITTED) { 1299 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 1300 optp += TCPOLEN_SACK_PERMITTED_ALIGNED; 1301 } 1302 1303 no_options: 1304 if (isipv6) { 1305 struct route_in6 *ro6 = &sc->sc_route6; 1306 1307 th->th_sum = 0; 1308 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1309 ip6->ip6_hlim = in6_selecthlim(NULL, 1310 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1311 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1312 sc->sc_tp->t_inpcb); 1313 } else { 1314 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1315 htons(tlen - hlen + IPPROTO_TCP)); 1316 m->m_pkthdr.csum_flags = CSUM_TCP; 1317 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1318 m->m_pkthdr.csum_thlen = sizeof(struct tcphdr) + optlen; 1319 KASSERT(sc->sc_flags & SCF_HASH, ("syncache has no hash")); 1320 m_sethash(m, sc->sc_hashval); 1321 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 1322 IP_DEBUGROUTE, NULL, sc->sc_tp->t_inpcb); 1323 } 1324 return (error); 1325 } 1326 1327 /* 1328 * cookie layers: 1329 * 1330 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1331 * | peer iss | 1332 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1333 * | 0 |(A)| | 1334 * (A): peer mss index 1335 */ 1336 1337 /* 1338 * The values below are chosen to minimize the size of the tcp_secret 1339 * table, as well as providing roughly a 16 second lifetime for the cookie. 1340 */ 1341 1342 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1343 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1344 1345 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1346 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1347 #define SYNCOOKIE_TIMEOUT \ 1348 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1349 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1350 1351 static struct { 1352 u_int32_t ts_secbits[4]; 1353 u_int ts_expire; 1354 } tcp_secret[SYNCOOKIE_NSECRETS]; 1355 1356 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1357 1358 static MD5_CTX syn_ctx; 1359 1360 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1361 1362 struct md5_add { 1363 u_int32_t laddr, faddr; 1364 u_int32_t secbits[4]; 1365 u_int16_t lport, fport; 1366 }; 1367 1368 #ifdef CTASSERT 1369 CTASSERT(sizeof(struct md5_add) == 28); 1370 #endif 1371 1372 /* 1373 * Consider the problem of a recreated (and retransmitted) cookie. If the 1374 * original SYN was accepted, the connection is established. The second 1375 * SYN is inflight, and if it arrives with an ISN that falls within the 1376 * receive window, the connection is killed. 1377 * 1378 * However, since cookies have other problems, this may not be worth 1379 * worrying about. 1380 */ 1381 1382 static u_int32_t 1383 syncookie_generate(struct syncache *sc) 1384 { 1385 u_int32_t md5_buffer[4]; 1386 u_int32_t data; 1387 int idx, i; 1388 struct md5_add add; 1389 #ifdef INET6 1390 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1391 #else 1392 const boolean_t isipv6 = FALSE; 1393 #endif 1394 1395 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1396 if (tcp_secret[idx].ts_expire < ticks) { 1397 for (i = 0; i < 4; i++) 1398 tcp_secret[idx].ts_secbits[i] = karc4random(); 1399 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1400 } 1401 for (data = NELEM(tcp_msstab) - 1; data > 0; data--) 1402 if (tcp_msstab[data] <= sc->sc_peer_mss) 1403 break; 1404 data = (data << SYNCOOKIE_WNDBITS) | idx; 1405 data ^= sc->sc_irs; /* peer's iss */ 1406 MD5Init(&syn_ctx); 1407 if (isipv6) { 1408 MD5Add(sc->sc_inc.inc6_laddr); 1409 MD5Add(sc->sc_inc.inc6_faddr); 1410 add.laddr = 0; 1411 add.faddr = 0; 1412 } else { 1413 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1414 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1415 } 1416 add.lport = sc->sc_inc.inc_lport; 1417 add.fport = sc->sc_inc.inc_fport; 1418 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1419 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1420 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1421 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1422 MD5Add(add); 1423 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1424 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1425 return (data); 1426 } 1427 1428 static struct syncache * 1429 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so) 1430 { 1431 u_int32_t md5_buffer[4]; 1432 struct syncache *sc; 1433 u_int32_t data; 1434 int wnd, idx; 1435 struct md5_add add; 1436 1437 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1438 idx = data & SYNCOOKIE_WNDMASK; 1439 if (tcp_secret[idx].ts_expire < ticks || 1440 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1441 return (NULL); 1442 MD5Init(&syn_ctx); 1443 #ifdef INET6 1444 if (inc->inc_isipv6) { 1445 MD5Add(inc->inc6_laddr); 1446 MD5Add(inc->inc6_faddr); 1447 add.laddr = 0; 1448 add.faddr = 0; 1449 } else 1450 #endif 1451 { 1452 add.laddr = inc->inc_laddr.s_addr; 1453 add.faddr = inc->inc_faddr.s_addr; 1454 } 1455 add.lport = inc->inc_lport; 1456 add.fport = inc->inc_fport; 1457 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1458 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1459 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1460 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1461 MD5Add(add); 1462 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1463 data ^= md5_buffer[0]; 1464 if (data & ~SYNCOOKIE_DATAMASK) 1465 return (NULL); 1466 data = data >> SYNCOOKIE_WNDBITS; 1467 1468 /* 1469 * Fill in the syncache values. 1470 * XXX duplicate code from syncache_add 1471 */ 1472 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1473 sc->sc_ipopts = NULL; 1474 sc->sc_inc.inc_fport = inc->inc_fport; 1475 sc->sc_inc.inc_lport = inc->inc_lport; 1476 #ifdef INET6 1477 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1478 if (inc->inc_isipv6) { 1479 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1480 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1481 sc->sc_route6.ro_rt = NULL; 1482 } else 1483 #endif 1484 { 1485 sc->sc_inc.inc_faddr = inc->inc_faddr; 1486 sc->sc_inc.inc_laddr = inc->inc_laddr; 1487 sc->sc_route.ro_rt = NULL; 1488 } 1489 sc->sc_irs = th->th_seq - 1; 1490 sc->sc_iss = th->th_ack - 1; 1491 wnd = ssb_space(&so->so_rcv); 1492 wnd = imax(wnd, 0); 1493 wnd = imin(wnd, TCP_MAXWIN); 1494 sc->sc_wnd = wnd; 1495 sc->sc_flags = 0; 1496 sc->sc_rxtslot = 0; 1497 sc->sc_peer_mss = tcp_msstab[data]; 1498 return (sc); 1499 } 1500 1501 static int 1502 syncache_sysctl_count(SYSCTL_HANDLER_ARGS) 1503 { 1504 u_int count = 0; 1505 int cpu; 1506 1507 for (cpu = 0; cpu < netisr_ncpus; ++cpu) 1508 count += tcp_syncache_percpu[cpu]->cache_count; 1509 return sysctl_handle_int(oidp, &count, 0, req); 1510 } 1511