FreeBSD kernel IPv4 code
tcp_syncache.c
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1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2001 McAfee, Inc.
5 * Copyright (c) 2006,2013 Andre Oppermann, Internet Business Solutions AG
6 * All rights reserved.
7 *
8 * This software was developed for the FreeBSD Project by Jonathan Lemon
9 * and McAfee Research, the Security Research Division of McAfee, Inc. under
10 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
11 * DARPA CHATS research program. [2001 McAfee, Inc.]
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/cdefs.h>
36__FBSDID("$FreeBSD$");
37
38#include "opt_inet.h"
39#include "opt_inet6.h"
40#include "opt_ipsec.h"
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/hash.h>
45#include <sys/refcount.h>
46#include <sys/kernel.h>
47#include <sys/sysctl.h>
48#include <sys/limits.h>
49#include <sys/lock.h>
50#include <sys/mutex.h>
51#include <sys/malloc.h>
52#include <sys/mbuf.h>
53#include <sys/proc.h> /* for proc0 declaration */
54#include <sys/random.h>
55#include <sys/socket.h>
56#include <sys/socketvar.h>
57#include <sys/syslog.h>
58#include <sys/ucred.h>
59
60#include <sys/md5.h>
61#include <crypto/siphash/siphash.h>
62
63#include <vm/uma.h>
64
65#include <net/if.h>
66#include <net/if_var.h>
67#include <net/route.h>
68#include <net/vnet.h>
69
70#include <netinet/in.h>
71#include <netinet/in_kdtrace.h>
72#include <netinet/in_systm.h>
73#include <netinet/ip.h>
74#include <netinet/in_var.h>
75#include <netinet/in_pcb.h>
76#include <netinet/ip_var.h>
77#include <netinet/ip_options.h>
78#ifdef INET6
79#include <netinet/ip6.h>
80#include <netinet/icmp6.h>
81#include <netinet6/nd6.h>
82#include <netinet6/ip6_var.h>
83#include <netinet6/in6_pcb.h>
84#endif
85#include <netinet/tcp.h>
86#include <netinet/tcp_fastopen.h>
87#include <netinet/tcp_fsm.h>
88#include <netinet/tcp_seq.h>
89#include <netinet/tcp_timer.h>
90#include <netinet/tcp_var.h>
91#include <netinet/tcp_syncache.h>
92#include <netinet/tcp_ecn.h>
93#ifdef INET6
94#include <netinet6/tcp6_var.h>
95#endif
96#ifdef TCP_OFFLOAD
97#include <netinet/toecore.h>
98#endif
99#include <netinet/udp.h>
100#include <netinet/udp_var.h>
101
102#include <netipsec/ipsec_support.h>
103
104#include <machine/in_cksum.h>
105
106#include <security/mac/mac_framework.h>
107
108VNET_DEFINE_STATIC(int, tcp_syncookies) = 1;
109#define V_tcp_syncookies VNET(tcp_syncookies)
110SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_VNET | CTLFLAG_RW,
111 &VNET_NAME(tcp_syncookies), 0,
112 "Use TCP SYN cookies if the syncache overflows");
113
114VNET_DEFINE_STATIC(int, tcp_syncookiesonly) = 0;
115#define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
116SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_VNET | CTLFLAG_RW,
117 &VNET_NAME(tcp_syncookiesonly), 0,
118 "Use only TCP SYN cookies");
119
120VNET_DEFINE_STATIC(int, functions_inherit_listen_socket_stack) = 1;
121#define V_functions_inherit_listen_socket_stack \
122 VNET(functions_inherit_listen_socket_stack)
123SYSCTL_INT(_net_inet_tcp, OID_AUTO, functions_inherit_listen_socket_stack,
124 CTLFLAG_VNET | CTLFLAG_RW,
125 &VNET_NAME(functions_inherit_listen_socket_stack), 0,
126 "Inherit listen socket's stack");
127
128#ifdef TCP_OFFLOAD
129#define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL)
130#endif
131
132static void syncache_drop(struct syncache *, struct syncache_head *);
133static void syncache_free(struct syncache *);
134static void syncache_insert(struct syncache *, struct syncache_head *);
135static int syncache_respond(struct syncache *, const struct mbuf *, int);
136static struct socket *syncache_socket(struct syncache *, struct socket *,
137 struct mbuf *m);
138static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
139 int docallout);
140static void syncache_timer(void *);
141
142static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t,
143 uint8_t *, uintptr_t);
144static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *);
145static struct syncache
146 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
147 struct syncache *, struct tcphdr *, struct tcpopt *,
148 struct socket *, uint16_t);
149static void syncache_pause(struct in_conninfo *);
150static void syncache_unpause(void *);
151static void syncookie_reseed(void *);
152#ifdef INVARIANTS
153static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
154 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
155 struct socket *lso, uint16_t port);
156#endif
157
158/*
159 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
160 * 3 retransmits corresponds to a timeout with default values of
161 * tcp_rexmit_initial * ( 1 +
162 * tcp_backoff[1] +
163 * tcp_backoff[2] +
164 * tcp_backoff[3]) + 3 * tcp_rexmit_slop,
165 * 1000 ms * (1 + 2 + 4 + 8) + 3 * 200 ms = 15600 ms,
166 * the odds are that the user has given up attempting to connect by then.
167 */
168#define SYNCACHE_MAXREXMTS 3
169
170/* Arbitrary values */
171#define TCP_SYNCACHE_HASHSIZE 512
172#define TCP_SYNCACHE_BUCKETLIMIT 30
173
174VNET_DEFINE_STATIC(struct tcp_syncache, tcp_syncache);
175#define V_tcp_syncache VNET(tcp_syncache)
176
177static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache,
178 CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
179 "TCP SYN cache");
180
181SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
182 &VNET_NAME(tcp_syncache.bucket_limit), 0,
183 "Per-bucket hash limit for syncache");
184
185SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
186 &VNET_NAME(tcp_syncache.cache_limit), 0,
187 "Overall entry limit for syncache");
188
189SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET,
190 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache");
191
192SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN,
193 &VNET_NAME(tcp_syncache.hashsize), 0,
194 "Size of TCP syncache hashtable");
195
196SYSCTL_BOOL(_net_inet_tcp_syncache, OID_AUTO, see_other, CTLFLAG_VNET |
197 CTLFLAG_RW, &VNET_NAME(tcp_syncache.see_other), 0,
198 "All syncache(4) entries are visible, ignoring UID/GID, jail(2) "
199 "and mac(4) checks");
200
201static int
202sysctl_net_inet_tcp_syncache_rexmtlimit_check(SYSCTL_HANDLER_ARGS)
203{
204 int error;
205 u_int new;
206
207 new = V_tcp_syncache.rexmt_limit;
208 error = sysctl_handle_int(oidp, &new, 0, req);
209 if ((error == 0) && (req->newptr != NULL)) {
210 if (new > TCP_MAXRXTSHIFT)
211 error = EINVAL;
212 else
213 V_tcp_syncache.rexmt_limit = new;
214 }
215 return (error);
216}
217
218SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit,
219 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
220 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
221 sysctl_net_inet_tcp_syncache_rexmtlimit_check, "UI",
222 "Limit on SYN/ACK retransmissions");
223
224VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
225SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
226 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
227 "Send reset on socket allocation failure");
228
229static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
230
231#define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
232#define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
233#define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
234
235/*
236 * Requires the syncache entry to be already removed from the bucket list.
237 */
238static void
239syncache_free(struct syncache *sc)
240{
241
242 if (sc->sc_ipopts)
243 (void) m_free(sc->sc_ipopts);
244 if (sc->sc_cred)
245 crfree(sc->sc_cred);
246#ifdef MAC
247 mac_syncache_destroy(&sc->sc_label);
248#endif
249
250 uma_zfree(V_tcp_syncache.zone, sc);
251}
252
253void
254syncache_init(void)
255{
256 int i;
257
258 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
259 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
260 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
261 V_tcp_syncache.hash_secret = arc4random();
262
263 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
264 &V_tcp_syncache.hashsize);
265 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
266 &V_tcp_syncache.bucket_limit);
267 if (!powerof2(V_tcp_syncache.hashsize) ||
268 V_tcp_syncache.hashsize == 0) {
269 printf("WARNING: syncache hash size is not a power of 2.\n");
270 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
271 }
272 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
273
274 /* Set limits. */
275 V_tcp_syncache.cache_limit =
276 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
277 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
278 &V_tcp_syncache.cache_limit);
279
280 /* Allocate the hash table. */
281 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
282 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
283
284#ifdef VIMAGE
285 V_tcp_syncache.vnet = curvnet;
286#endif
287
288 /* Initialize the hash buckets. */
289 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
290 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
291 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
292 NULL, MTX_DEF);
293 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
294 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
295 V_tcp_syncache.hashbase[i].sch_length = 0;
296 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache;
297 V_tcp_syncache.hashbase[i].sch_last_overflow =
298 -(SYNCOOKIE_LIFETIME + 1);
299 }
300
301 /* Create the syncache entry zone. */
302 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
303 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
304 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone,
305 V_tcp_syncache.cache_limit);
306
307 /* Start the SYN cookie reseeder callout. */
308 callout_init(&V_tcp_syncache.secret.reseed, 1);
309 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0);
310 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0);
311 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz,
312 syncookie_reseed, &V_tcp_syncache);
313
314 /* Initialize the pause machinery. */
315 mtx_init(&V_tcp_syncache.pause_mtx, "tcp_sc_pause", NULL, MTX_DEF);
316 callout_init_mtx(&V_tcp_syncache.pause_co, &V_tcp_syncache.pause_mtx,
317 0);
318 V_tcp_syncache.pause_until = time_uptime - TCP_SYNCACHE_PAUSE_TIME;
319 V_tcp_syncache.pause_backoff = 0;
320 V_tcp_syncache.paused = false;
321}
322
323#ifdef VIMAGE
324void
325syncache_destroy(void)
326{
327 struct syncache_head *sch;
328 struct syncache *sc, *nsc;
329 int i;
330
331 /*
332 * Stop the re-seed timer before freeing resources. No need to
333 * possibly schedule it another time.
334 */
335 callout_drain(&V_tcp_syncache.secret.reseed);
336
337 /* Stop the SYN cache pause callout. */
338 mtx_lock(&V_tcp_syncache.pause_mtx);
339 if (callout_stop(&V_tcp_syncache.pause_co) == 0) {
340 mtx_unlock(&V_tcp_syncache.pause_mtx);
341 callout_drain(&V_tcp_syncache.pause_co);
342 } else
343 mtx_unlock(&V_tcp_syncache.pause_mtx);
344
345 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
346 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
347 sch = &V_tcp_syncache.hashbase[i];
348 callout_drain(&sch->sch_timer);
349
350 SCH_LOCK(sch);
351 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
352 syncache_drop(sc, sch);
353 SCH_UNLOCK(sch);
354 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
355 ("%s: sch->sch_bucket not empty", __func__));
356 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
357 __func__, sch->sch_length));
358 mtx_destroy(&sch->sch_mtx);
359 }
360
361 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0,
362 ("%s: cache_count not 0", __func__));
363
364 /* Free the allocated global resources. */
365 uma_zdestroy(V_tcp_syncache.zone);
366 free(V_tcp_syncache.hashbase, M_SYNCACHE);
367 mtx_destroy(&V_tcp_syncache.pause_mtx);
368}
369#endif
370
371/*
372 * Inserts a syncache entry into the specified bucket row.
373 * Locks and unlocks the syncache_head autonomously.
374 */
375static void
376syncache_insert(struct syncache *sc, struct syncache_head *sch)
377{
378 struct syncache *sc2;
379
380 SCH_LOCK(sch);
381
382 /*
383 * Make sure that we don't overflow the per-bucket limit.
384 * If the bucket is full, toss the oldest element.
385 */
386 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
387 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
388 ("sch->sch_length incorrect"));
389 syncache_pause(&sc->sc_inc);
390 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
391 sch->sch_last_overflow = time_uptime;
392 syncache_drop(sc2, sch);
393 }
394
395 /* Put it into the bucket. */
396 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
397 sch->sch_length++;
398
399#ifdef TCP_OFFLOAD
400 if (ADDED_BY_TOE(sc)) {
401 struct toedev *tod = sc->sc_tod;
402
403 tod->tod_syncache_added(tod, sc->sc_todctx);
404 }
405#endif
406
407 /* Reinitialize the bucket row's timer. */
408 if (sch->sch_length == 1)
409 sch->sch_nextc = ticks + INT_MAX;
410 syncache_timeout(sc, sch, 1);
411
412 SCH_UNLOCK(sch);
413
414 TCPSTATES_INC(TCPS_SYN_RECEIVED);
415 TCPSTAT_INC(tcps_sc_added);
416}
417
418/*
419 * Remove and free entry from syncache bucket row.
420 * Expects locked syncache head.
421 */
422static void
423syncache_drop(struct syncache *sc, struct syncache_head *sch)
424{
425
426 SCH_LOCK_ASSERT(sch);
427
428 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
429 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
430 sch->sch_length--;
431
432#ifdef TCP_OFFLOAD
433 if (ADDED_BY_TOE(sc)) {
434 struct toedev *tod = sc->sc_tod;
435
436 tod->tod_syncache_removed(tod, sc->sc_todctx);
437 }
438#endif
439
440 syncache_free(sc);
441}
442
443/*
444 * Engage/reengage time on bucket row.
445 */
446static void
447syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
448{
449 int rexmt;
450
451 if (sc->sc_rxmits == 0)
452 rexmt = tcp_rexmit_initial;
453 else
454 TCPT_RANGESET(rexmt,
455 tcp_rexmit_initial * tcp_backoff[sc->sc_rxmits],
456 tcp_rexmit_min, TCPTV_REXMTMAX);
457 sc->sc_rxttime = ticks + rexmt;
458 sc->sc_rxmits++;
459 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
460 sch->sch_nextc = sc->sc_rxttime;
461 if (docallout)
462 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
463 syncache_timer, (void *)sch);
464 }
465}
466
467/*
468 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
469 * If we have retransmitted an entry the maximum number of times, expire it.
470 * One separate timer for each bucket row.
471 */
472static void
473syncache_timer(void *xsch)
474{
475 struct syncache_head *sch = (struct syncache_head *)xsch;
476 struct syncache *sc, *nsc;
477 struct epoch_tracker et;
478 int tick = ticks;
479 char *s;
480 bool paused;
481
482 CURVNET_SET(sch->sch_sc->vnet);
483
484 /* NB: syncache_head has already been locked by the callout. */
485 SCH_LOCK_ASSERT(sch);
486
487 /*
488 * In the following cycle we may remove some entries and/or
489 * advance some timeouts, so re-initialize the bucket timer.
490 */
491 sch->sch_nextc = tick + INT_MAX;
492
493 /*
494 * If we have paused processing, unconditionally remove
495 * all syncache entries.
496 */
497 mtx_lock(&V_tcp_syncache.pause_mtx);
498 paused = V_tcp_syncache.paused;
499 mtx_unlock(&V_tcp_syncache.pause_mtx);
500
501 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
502 if (paused) {
503 syncache_drop(sc, sch);
504 continue;
505 }
506 /*
507 * We do not check if the listen socket still exists
508 * and accept the case where the listen socket may be
509 * gone by the time we resend the SYN/ACK. We do
510 * not expect this to happens often. If it does,
511 * then the RST will be sent by the time the remote
512 * host does the SYN/ACK->ACK.
513 */
514 if (TSTMP_GT(sc->sc_rxttime, tick)) {
515 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
516 sch->sch_nextc = sc->sc_rxttime;
517 continue;
518 }
519 if (sc->sc_rxmits > V_tcp_ecn_maxretries) {
520 sc->sc_flags &= ~SCF_ECN;
521 }
522 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
523 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
524 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
525 "giving up and removing syncache entry\n",
526 s, __func__);
527 free(s, M_TCPLOG);
528 }
529 syncache_drop(sc, sch);
530 TCPSTAT_INC(tcps_sc_stale);
531 continue;
532 }
533 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
534 log(LOG_DEBUG, "%s; %s: Response timeout, "
535 "retransmitting (%u) SYN|ACK\n",
536 s, __func__, sc->sc_rxmits);
537 free(s, M_TCPLOG);
538 }
539
540 NET_EPOCH_ENTER(et);
541 syncache_respond(sc, NULL, TH_SYN|TH_ACK);
542 NET_EPOCH_EXIT(et);
543 TCPSTAT_INC(tcps_sc_retransmitted);
544 syncache_timeout(sc, sch, 0);
545 }
546 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
547 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
548 syncache_timer, (void *)(sch));
549 CURVNET_RESTORE();
550}
551
552/*
553 * Returns true if the system is only using cookies at the moment.
554 * This could be due to a sysadmin decision to only use cookies, or it
555 * could be due to the system detecting an attack.
556 */
557static inline bool
558syncache_cookiesonly(void)
559{
560
561 return (V_tcp_syncookies && (V_tcp_syncache.paused ||
562 V_tcp_syncookiesonly));
563}
564
565/*
566 * Find the hash bucket for the given connection.
567 */
568static struct syncache_head *
569syncache_hashbucket(struct in_conninfo *inc)
570{
571 uint32_t hash;
572
573 /*
574 * The hash is built on foreign port + local port + foreign address.
575 * We rely on the fact that struct in_conninfo starts with 16 bits
576 * of foreign port, then 16 bits of local port then followed by 128
577 * bits of foreign address. In case of IPv4 address, the first 3
578 * 32-bit words of the address always are zeroes.
579 */
580 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5,
581 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask;
582
583 return (&V_tcp_syncache.hashbase[hash]);
584}
585
586/*
587 * Find an entry in the syncache.
588 * Returns always with locked syncache_head plus a matching entry or NULL.
589 */
590static struct syncache *
591syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
592{
593 struct syncache *sc;
594 struct syncache_head *sch;
595
596 *schp = sch = syncache_hashbucket(inc);
597 SCH_LOCK(sch);
598
599 /* Circle through bucket row to find matching entry. */
600 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
601 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie,
602 sizeof(struct in_endpoints)) == 0)
603 break;
604
605 return (sc); /* Always returns with locked sch. */
606}
607
608/*
609 * This function is called when we get a RST for a
610 * non-existent connection, so that we can see if the
611 * connection is in the syn cache. If it is, zap it.
612 * If required send a challenge ACK.
613 */
614void
615syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m,
616 uint16_t port)
617{
618 struct syncache *sc;
619 struct syncache_head *sch;
620 char *s = NULL;
621
622 if (syncache_cookiesonly())
623 return;
624 sc = syncache_lookup(inc, &sch); /* returns locked sch */
625 SCH_LOCK_ASSERT(sch);
626
627 /*
628 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
629 * See RFC 793 page 65, section SEGMENT ARRIVES.
630 */
631 if (tcp_get_flags(th) & (TH_ACK|TH_SYN|TH_FIN)) {
632 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
633 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
634 "FIN flag set, segment ignored\n", s, __func__);
635 TCPSTAT_INC(tcps_badrst);
636 goto done;
637 }
638
639 /*
640 * No corresponding connection was found in syncache.
641 * If syncookies are enabled and possibly exclusively
642 * used, or we are under memory pressure, a valid RST
643 * may not find a syncache entry. In that case we're
644 * done and no SYN|ACK retransmissions will happen.
645 * Otherwise the RST was misdirected or spoofed.
646 */
647 if (sc == NULL) {
648 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
649 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
650 "syncache entry (possibly syncookie only), "
651 "segment ignored\n", s, __func__);
652 TCPSTAT_INC(tcps_badrst);
653 goto done;
654 }
655
656 /* The remote UDP encaps port does not match. */
657 if (sc->sc_port != port) {
658 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
659 log(LOG_DEBUG, "%s; %s: Spurious RST with matching "
660 "syncache entry but non-matching UDP encaps port, "
661 "segment ignored\n", s, __func__);
662 TCPSTAT_INC(tcps_badrst);
663 goto done;
664 }
665
666 /*
667 * If the RST bit is set, check the sequence number to see
668 * if this is a valid reset segment.
669 *
670 * RFC 793 page 37:
671 * In all states except SYN-SENT, all reset (RST) segments
672 * are validated by checking their SEQ-fields. A reset is
673 * valid if its sequence number is in the window.
674 *
675 * RFC 793 page 69:
676 * There are four cases for the acceptability test for an incoming
677 * segment:
678 *
679 * Segment Receive Test
680 * Length Window
681 * ------- ------- -------------------------------------------
682 * 0 0 SEG.SEQ = RCV.NXT
683 * 0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND
684 * >0 0 not acceptable
685 * >0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND
686 * or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND
687 *
688 * Note that when receiving a SYN segment in the LISTEN state,
689 * IRS is set to SEG.SEQ and RCV.NXT is set to SEG.SEQ+1, as
690 * described in RFC 793, page 66.
691 */
692 if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) &&
693 SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) ||
694 (sc->sc_wnd == 0 && th->th_seq == sc->sc_irs + 1)) {
695 if (V_tcp_insecure_rst ||
696 th->th_seq == sc->sc_irs + 1) {
697 syncache_drop(sc, sch);
698 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
699 log(LOG_DEBUG,
700 "%s; %s: Our SYN|ACK was rejected, "
701 "connection attempt aborted by remote "
702 "endpoint\n",
703 s, __func__);
704 TCPSTAT_INC(tcps_sc_reset);
705 } else {
706 TCPSTAT_INC(tcps_badrst);
707 /* Send challenge ACK. */
708 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
709 log(LOG_DEBUG, "%s; %s: RST with invalid "
710 " SEQ %u != NXT %u (+WND %u), "
711 "sending challenge ACK\n",
712 s, __func__,
713 th->th_seq, sc->sc_irs + 1, sc->sc_wnd);
714 syncache_respond(sc, m, TH_ACK);
715 }
716 } else {
717 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
718 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
719 "NXT %u (+WND %u), segment ignored\n",
720 s, __func__,
721 th->th_seq, sc->sc_irs + 1, sc->sc_wnd);
722 TCPSTAT_INC(tcps_badrst);
723 }
724
725done:
726 if (s != NULL)
727 free(s, M_TCPLOG);
728 SCH_UNLOCK(sch);
729}
730
731void
732syncache_badack(struct in_conninfo *inc, uint16_t port)
733{
734 struct syncache *sc;
735 struct syncache_head *sch;
736
737 if (syncache_cookiesonly())
738 return;
739 sc = syncache_lookup(inc, &sch); /* returns locked sch */
740 SCH_LOCK_ASSERT(sch);
741 if ((sc != NULL) && (sc->sc_port == port)) {
742 syncache_drop(sc, sch);
743 TCPSTAT_INC(tcps_sc_badack);
744 }
745 SCH_UNLOCK(sch);
746}
747
748void
749syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq, uint16_t port)
750{
751 struct syncache *sc;
752 struct syncache_head *sch;
753
754 if (syncache_cookiesonly())
755 return;
756 sc = syncache_lookup(inc, &sch); /* returns locked sch */
757 SCH_LOCK_ASSERT(sch);
758 if (sc == NULL)
759 goto done;
760
761 /* If the port != sc_port, then it's a bogus ICMP msg */
762 if (port != sc->sc_port)
763 goto done;
764
765 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
766 if (ntohl(th_seq) != sc->sc_iss)
767 goto done;
768
769 /*
770 * If we've rertransmitted 3 times and this is our second error,
771 * we remove the entry. Otherwise, we allow it to continue on.
772 * This prevents us from incorrectly nuking an entry during a
773 * spurious network outage.
774 *
775 * See tcp_notify().
776 */
777 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
778 sc->sc_flags |= SCF_UNREACH;
779 goto done;
780 }
781 syncache_drop(sc, sch);
782 TCPSTAT_INC(tcps_sc_unreach);
783done:
784 SCH_UNLOCK(sch);
785}
786
787/*
788 * Build a new TCP socket structure from a syncache entry.
789 *
790 * On success return the newly created socket with its underlying inp locked.
791 */
792static struct socket *
793syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
794{
795 struct tcp_function_block *blk;
796 struct inpcb *inp = NULL;
797 struct socket *so;
798 struct tcpcb *tp;
799 int error;
800 char *s;
801
802 NET_EPOCH_ASSERT();
803
804 /*
805 * Ok, create the full blown connection, and set things up
806 * as they would have been set up if we had created the
807 * connection when the SYN arrived. If we can't create
808 * the connection, abort it.
809 */
810 so = sonewconn(lso, 0);
811 if (so == NULL) {
812 /*
813 * Drop the connection; we will either send a RST or
814 * have the peer retransmit its SYN again after its
815 * RTO and try again.
816 */
817 TCPSTAT_INC(tcps_listendrop);
818 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
819 log(LOG_DEBUG, "%s; %s: Socket create failed "
820 "due to limits or memory shortage\n",
821 s, __func__);
822 free(s, M_TCPLOG);
823 }
824 goto abort2;
825 }
826#ifdef MAC
827 mac_socketpeer_set_from_mbuf(m, so);
828#endif
829
830 inp = sotoinpcb(so);
831 inp->inp_inc.inc_fibnum = so->so_fibnum;
832 INP_WLOCK(inp);
833 /*
834 * Exclusive pcbinfo lock is not required in syncache socket case even
835 * if two inpcb locks can be acquired simultaneously:
836 * - the inpcb in LISTEN state,
837 * - the newly created inp.
838 *
839 * In this case, an inp cannot be at same time in LISTEN state and
840 * just created by an accept() call.
841 */
842 INP_HASH_WLOCK(&V_tcbinfo);
843
844 /* Insert new socket into PCB hash list. */
845 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
846#ifdef INET6
847 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
848 inp->inp_vflag &= ~INP_IPV4;
849 inp->inp_vflag |= INP_IPV6;
850 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
851 } else {
852 inp->inp_vflag &= ~INP_IPV6;
853 inp->inp_vflag |= INP_IPV4;
854#endif
855 inp->inp_ip_ttl = sc->sc_ip_ttl;
856 inp->inp_ip_tos = sc->sc_ip_tos;
857 inp->inp_laddr = sc->sc_inc.inc_laddr;
858#ifdef INET6
859 }
860#endif
861
862 /*
863 * If there's an mbuf and it has a flowid, then let's initialise the
864 * inp with that particular flowid.
865 */
866 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) {
867 inp->inp_flowid = m->m_pkthdr.flowid;
868 inp->inp_flowtype = M_HASHTYPE_GET(m);
869#ifdef NUMA
870 inp->inp_numa_domain = m->m_pkthdr.numa_domain;
871#endif
872 }
873
874 inp->inp_lport = sc->sc_inc.inc_lport;
875#ifdef INET6
876 if (inp->inp_vflag & INP_IPV6PROTO) {
877 struct inpcb *oinp = sotoinpcb(lso);
878
879 /*
880 * Inherit socket options from the listening socket.
881 * Note that in6p_inputopts are not (and should not be)
882 * copied, since it stores previously received options and is
883 * used to detect if each new option is different than the
884 * previous one and hence should be passed to a user.
885 * If we copied in6p_inputopts, a user would not be able to
886 * receive options just after calling the accept system call.
887 */
888 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
889 if (oinp->in6p_outputopts)
890 inp->in6p_outputopts =
891 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
892 inp->in6p_hops = oinp->in6p_hops;
893 }
894
895 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
896 struct in6_addr laddr6;
897 struct sockaddr_in6 sin6;
898
899 sin6.sin6_family = AF_INET6;
900 sin6.sin6_len = sizeof(sin6);
901 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
902 sin6.sin6_port = sc->sc_inc.inc_fport;
903 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
904 laddr6 = inp->in6p_laddr;
905 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
906 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
907 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
908 thread0.td_ucred, m, false)) != 0) {
909 inp->in6p_laddr = laddr6;
910 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
911 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
912 "with error %i\n",
913 s, __func__, error);
914 free(s, M_TCPLOG);
915 }
916 INP_HASH_WUNLOCK(&V_tcbinfo);
917 goto abort;
918 }
919 /* Override flowlabel from in6_pcbconnect. */
920 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
921 inp->inp_flow |= sc->sc_flowlabel;
922 }
923#endif /* INET6 */
924#if defined(INET) && defined(INET6)
925 else
926#endif
927#ifdef INET
928 {
929 struct in_addr laddr;
930 struct sockaddr_in sin;
931
932 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
933
934 if (inp->inp_options == NULL) {
935 inp->inp_options = sc->sc_ipopts;
936 sc->sc_ipopts = NULL;
937 }
938
939 sin.sin_family = AF_INET;
940 sin.sin_len = sizeof(sin);
941 sin.sin_addr = sc->sc_inc.inc_faddr;
942 sin.sin_port = sc->sc_inc.inc_fport;
943 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
944 laddr = inp->inp_laddr;
945 if (inp->inp_laddr.s_addr == INADDR_ANY)
946 inp->inp_laddr = sc->sc_inc.inc_laddr;
947 if ((error = in_pcbconnect(inp, (struct sockaddr *)&sin,
948 thread0.td_ucred, false)) != 0) {
949 inp->inp_laddr = laddr;
950 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
951 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
952 "with error %i\n",
953 s, __func__, error);
954 free(s, M_TCPLOG);
955 }
956 INP_HASH_WUNLOCK(&V_tcbinfo);
957 goto abort;
958 }
959 }
960#endif /* INET */
961#if defined(IPSEC) || defined(IPSEC_SUPPORT)
962 /* Copy old policy into new socket's. */
963 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0)
964 printf("syncache_socket: could not copy policy\n");
965#endif
966 INP_HASH_WUNLOCK(&V_tcbinfo);
967 tp = intotcpcb(inp);
968 tcp_state_change(tp, TCPS_SYN_RECEIVED);
969 tp->iss = sc->sc_iss;
970 tp->irs = sc->sc_irs;
971 tp->t_port = sc->sc_port;
972 tcp_rcvseqinit(tp);
973 tcp_sendseqinit(tp);
974 blk = sototcpcb(lso)->t_fb;
975 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) {
976 /*
977 * Our parents t_fb was not the default,
978 * we need to release our ref on tp->t_fb and
979 * pickup one on the new entry.
980 */
981 struct tcp_function_block *rblk;
982
983 rblk = find_and_ref_tcp_fb(blk);
984 KASSERT(rblk != NULL,
985 ("cannot find blk %p out of syncache?", blk));
986 if (tp->t_fb->tfb_tcp_fb_fini)
987 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0);
988 refcount_release(&tp->t_fb->tfb_refcnt);
989 tp->t_fb = rblk;
990 /*
991 * XXXrrs this is quite dangerous, it is possible
992 * for the new function to fail to init. We also
993 * are not asking if the handoff_is_ok though at
994 * the very start thats probalbly ok.
995 */
996 if (tp->t_fb->tfb_tcp_fb_init) {
997 (*tp->t_fb->tfb_tcp_fb_init)(tp);
998 }
999 }
1000 tp->snd_wl1 = sc->sc_irs;
1001 tp->snd_max = tp->iss + 1;
1002 tp->snd_nxt = tp->iss + 1;
1003 tp->rcv_up = sc->sc_irs + 1;
1004 tp->rcv_wnd = sc->sc_wnd;
1005 tp->rcv_adv += tp->rcv_wnd;
1006 tp->last_ack_sent = tp->rcv_nxt;
1007
1008 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
1009 if (sc->sc_flags & SCF_NOOPT)
1010 tp->t_flags |= TF_NOOPT;
1011 else {
1012 if (sc->sc_flags & SCF_WINSCALE) {
1013 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
1014 tp->snd_scale = sc->sc_requested_s_scale;
1015 tp->request_r_scale = sc->sc_requested_r_scale;
1016 }
1017 if (sc->sc_flags & SCF_TIMESTAMP) {
1018 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
1019 tp->ts_recent = sc->sc_tsreflect;
1020 tp->ts_recent_age = tcp_ts_getticks();
1021 tp->ts_offset = sc->sc_tsoff;
1022 }
1023#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1024 if (sc->sc_flags & SCF_SIGNATURE)
1025 tp->t_flags |= TF_SIGNATURE;
1026#endif
1027 if (sc->sc_flags & SCF_SACK)
1028 tp->t_flags |= TF_SACK_PERMIT;
1029 }
1030
1031 tcp_ecn_syncache_socket(tp, sc);
1032
1033 /*
1034 * Set up MSS and get cached values from tcp_hostcache.
1035 * This might overwrite some of the defaults we just set.
1036 */
1037 tcp_mss(tp, sc->sc_peer_mss);
1038
1039 /*
1040 * If the SYN,ACK was retransmitted, indicate that CWND to be
1041 * limited to one segment in cc_conn_init().
1042 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
1043 */
1044 if (sc->sc_rxmits > 1)
1045 tp->snd_cwnd = 1;
1046
1047#ifdef TCP_OFFLOAD
1048 /*
1049 * Allow a TOE driver to install its hooks. Note that we hold the
1050 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a
1051 * new connection before the TOE driver has done its thing.
1052 */
1053 if (ADDED_BY_TOE(sc)) {
1054 struct toedev *tod = sc->sc_tod;
1055
1056 tod->tod_offload_socket(tod, sc->sc_todctx, so);
1057 }
1058#endif
1059 /*
1060 * Copy and activate timers.
1061 */
1062 tp->t_keepinit = sototcpcb(lso)->t_keepinit;
1063 tp->t_keepidle = sototcpcb(lso)->t_keepidle;
1064 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
1065 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
1066 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
1067
1068 TCPSTAT_INC(tcps_accepts);
1069 return (so);
1070
1071abort:
1072 INP_WUNLOCK(inp);
1073abort2:
1074 if (so != NULL)
1075 soabort(so);
1076 return (NULL);
1077}
1078
1079/*
1080 * This function gets called when we receive an ACK for a
1081 * socket in the LISTEN state. We look up the connection
1082 * in the syncache, and if its there, we pull it out of
1083 * the cache and turn it into a full-blown connection in
1084 * the SYN-RECEIVED state.
1085 *
1086 * On syncache_socket() success the newly created socket
1087 * has its underlying inp locked.
1088 */
1089int
1090syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1091 struct socket **lsop, struct mbuf *m, uint16_t port)
1092{
1093 struct syncache *sc;
1094 struct syncache_head *sch;
1095 struct syncache scs;
1096 char *s;
1097 bool locked;
1098
1099 NET_EPOCH_ASSERT();
1100 KASSERT((tcp_get_flags(th) & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
1101 ("%s: can handle only ACK", __func__));
1102
1103 if (syncache_cookiesonly()) {
1104 sc = NULL;
1105 sch = syncache_hashbucket(inc);
1106 locked = false;
1107 } else {
1108 sc = syncache_lookup(inc, &sch); /* returns locked sch */
1109 locked = true;
1110 SCH_LOCK_ASSERT(sch);
1111 }
1112
1113#ifdef INVARIANTS
1114 /*
1115 * Test code for syncookies comparing the syncache stored
1116 * values with the reconstructed values from the cookie.
1117 */
1118 if (sc != NULL)
1119 syncookie_cmp(inc, sch, sc, th, to, *lsop, port);
1120#endif
1121
1122 if (sc == NULL) {
1123 /*
1124 * There is no syncache entry, so see if this ACK is
1125 * a returning syncookie. To do this, first:
1126 * A. Check if syncookies are used in case of syncache
1127 * overflows
1128 * B. See if this socket has had a syncache entry dropped in
1129 * the recent past. We don't want to accept a bogus
1130 * syncookie if we've never received a SYN or accept it
1131 * twice.
1132 * C. check that the syncookie is valid. If it is, then
1133 * cobble up a fake syncache entry, and return.
1134 */
1135 if (locked && !V_tcp_syncookies) {
1136 SCH_UNLOCK(sch);
1137 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1138 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
1139 "segment rejected (syncookies disabled)\n",
1140 s, __func__);
1141 goto failed;
1142 }
1143 if (locked && !V_tcp_syncookiesonly &&
1144 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) {
1145 SCH_UNLOCK(sch);
1146 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1147 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
1148 "segment rejected (no syncache entry)\n",
1149 s, __func__);
1150 goto failed;
1151 }
1152 bzero(&scs, sizeof(scs));
1153 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop, port);
1154 if (locked)
1155 SCH_UNLOCK(sch);
1156 if (sc == NULL) {
1157 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1158 log(LOG_DEBUG, "%s; %s: Segment failed "
1159 "SYNCOOKIE authentication, segment rejected "
1160 "(probably spoofed)\n", s, __func__);
1161 goto failed;
1162 }
1163#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1164 /* If received ACK has MD5 signature, check it. */
1165 if ((to->to_flags & TOF_SIGNATURE) != 0 &&
1166 (!TCPMD5_ENABLED() ||
1167 TCPMD5_INPUT(m, th, to->to_signature) != 0)) {
1168 /* Drop the ACK. */
1169 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1170 log(LOG_DEBUG, "%s; %s: Segment rejected, "
1171 "MD5 signature doesn't match.\n",
1172 s, __func__);
1173 free(s, M_TCPLOG);
1174 }
1175 TCPSTAT_INC(tcps_sig_err_sigopt);
1176 return (-1); /* Do not send RST */
1177 }
1178#endif /* TCP_SIGNATURE */
1179 } else {
1180 if (sc->sc_port != port) {
1181 SCH_UNLOCK(sch);
1182 return (0);
1183 }
1184#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1185 /*
1186 * If listening socket requested TCP digests, check that
1187 * received ACK has signature and it is correct.
1188 * If not, drop the ACK and leave sc entry in th cache,
1189 * because SYN was received with correct signature.
1190 */
1191 if (sc->sc_flags & SCF_SIGNATURE) {
1192 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1193 /* No signature */
1194 TCPSTAT_INC(tcps_sig_err_nosigopt);
1195 SCH_UNLOCK(sch);
1196 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1197 log(LOG_DEBUG, "%s; %s: Segment "
1198 "rejected, MD5 signature wasn't "
1199 "provided.\n", s, __func__);
1200 free(s, M_TCPLOG);
1201 }
1202 return (-1); /* Do not send RST */
1203 }
1204 if (!TCPMD5_ENABLED() ||
1205 TCPMD5_INPUT(m, th, to->to_signature) != 0) {
1206 /* Doesn't match or no SA */
1207 SCH_UNLOCK(sch);
1208 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1209 log(LOG_DEBUG, "%s; %s: Segment "
1210 "rejected, MD5 signature doesn't "
1211 "match.\n", s, __func__);
1212 free(s, M_TCPLOG);
1213 }
1214 return (-1); /* Do not send RST */
1215 }
1216 }
1217#endif /* TCP_SIGNATURE */
1218
1219 /*
1220 * RFC 7323 PAWS: If we have a timestamp on this segment and
1221 * it's less than ts_recent, drop it.
1222 * XXXMT: RFC 7323 also requires to send an ACK.
1223 * In tcp_input.c this is only done for TCP segments
1224 * with user data, so be consistent here and just drop
1225 * the segment.
1226 */
1227 if (sc->sc_flags & SCF_TIMESTAMP && to->to_flags & TOF_TS &&
1228 TSTMP_LT(to->to_tsval, sc->sc_tsreflect)) {
1229 SCH_UNLOCK(sch);
1230 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1231 log(LOG_DEBUG,
1232 "%s; %s: SEG.TSval %u < TS.Recent %u, "
1233 "segment dropped\n", s, __func__,
1234 to->to_tsval, sc->sc_tsreflect);
1235 free(s, M_TCPLOG);
1236 }
1237 return (-1); /* Do not send RST */
1238 }
1239
1240 /*
1241 * If timestamps were not negotiated during SYN/ACK and a
1242 * segment with a timestamp is received, ignore the
1243 * timestamp and process the packet normally.
1244 * See section 3.2 of RFC 7323.
1245 */
1246 if (!(sc->sc_flags & SCF_TIMESTAMP) &&
1247 (to->to_flags & TOF_TS)) {
1248 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1249 log(LOG_DEBUG, "%s; %s: Timestamp not "
1250 "expected, segment processed normally\n",
1251 s, __func__);
1252 free(s, M_TCPLOG);
1253 s = NULL;
1254 }
1255 }
1256
1257 /*
1258 * If timestamps were negotiated during SYN/ACK and a
1259 * segment without a timestamp is received, silently drop
1260 * the segment, unless the missing timestamps are tolerated.
1261 * See section 3.2 of RFC 7323.
1262 */
1263 if ((sc->sc_flags & SCF_TIMESTAMP) &&
1264 !(to->to_flags & TOF_TS)) {
1265 if (V_tcp_tolerate_missing_ts) {
1266 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1267 log(LOG_DEBUG,
1268 "%s; %s: Timestamp missing, "
1269 "segment processed normally\n",
1270 s, __func__);
1271 free(s, M_TCPLOG);
1272 }
1273 } else {
1274 SCH_UNLOCK(sch);
1275 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1276 log(LOG_DEBUG,
1277 "%s; %s: Timestamp missing, "
1278 "segment silently dropped\n",
1279 s, __func__);
1280 free(s, M_TCPLOG);
1281 }
1282 return (-1); /* Do not send RST */
1283 }
1284 }
1285
1286 /*
1287 * Pull out the entry to unlock the bucket row.
1288 *
1289 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not
1290 * tcp_state_change(). The tcpcb is not existent at this
1291 * moment. A new one will be allocated via syncache_socket->
1292 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then
1293 * syncache_socket() will change it to TCPS_SYN_RECEIVED.
1294 */
1295 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
1296 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
1297 sch->sch_length--;
1298#ifdef TCP_OFFLOAD
1299 if (ADDED_BY_TOE(sc)) {
1300 struct toedev *tod = sc->sc_tod;
1301
1302 tod->tod_syncache_removed(tod, sc->sc_todctx);
1303 }
1304#endif
1305 SCH_UNLOCK(sch);
1306 }
1307
1308 /*
1309 * Segment validation:
1310 * ACK must match our initial sequence number + 1 (the SYN|ACK).
1311 */
1312 if (th->th_ack != sc->sc_iss + 1) {
1313 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1314 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
1315 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
1316 goto failed;
1317 }
1318
1319 /*
1320 * The SEQ must fall in the window starting at the received
1321 * initial receive sequence number + 1 (the SYN).
1322 */
1323 if (SEQ_LEQ(th->th_seq, sc->sc_irs) ||
1324 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
1325 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1326 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
1327 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
1328 goto failed;
1329 }
1330
1331 *lsop = syncache_socket(sc, *lsop, m);
1332
1333 if (*lsop == NULL)
1334 TCPSTAT_INC(tcps_sc_aborted);
1335 else
1336 TCPSTAT_INC(tcps_sc_completed);
1337
1338/* how do we find the inp for the new socket? */
1339 if (sc != &scs)
1340 syncache_free(sc);
1341 return (1);
1342failed:
1343 if (sc != NULL && sc != &scs)
1344 syncache_free(sc);
1345 if (s != NULL)
1346 free(s, M_TCPLOG);
1347 *lsop = NULL;
1348 return (0);
1349}
1350
1351static struct socket *
1352syncache_tfo_expand(struct syncache *sc, struct socket *lso, struct mbuf *m,
1353 uint64_t response_cookie)
1354{
1355 struct inpcb *inp;
1356 struct tcpcb *tp;
1357 unsigned int *pending_counter;
1358 struct socket *so;
1359
1360 NET_EPOCH_ASSERT();
1361
1362 pending_counter = intotcpcb(sotoinpcb(lso))->t_tfo_pending;
1363 so = syncache_socket(sc, lso, m);
1364 if (so == NULL) {
1365 TCPSTAT_INC(tcps_sc_aborted);
1366 atomic_subtract_int(pending_counter, 1);
1367 } else {
1368 soisconnected(so);
1369 inp = sotoinpcb(so);
1370 tp = intotcpcb(inp);
1371 tp->t_flags |= TF_FASTOPEN;
1372 tp->t_tfo_cookie.server = response_cookie;
1373 tp->snd_max = tp->iss;
1374 tp->snd_nxt = tp->iss;
1375 tp->t_tfo_pending = pending_counter;
1376 TCPSTAT_INC(tcps_sc_completed);
1377 }
1378
1379 return (so);
1380}
1381
1382/*
1383 * Given a LISTEN socket and an inbound SYN request, add
1384 * this to the syn cache, and send back a segment:
1385 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1386 * to the source.
1387 *
1388 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1389 * Doing so would require that we hold onto the data and deliver it
1390 * to the application. However, if we are the target of a SYN-flood
1391 * DoS attack, an attacker could send data which would eventually
1392 * consume all available buffer space if it were ACKed. By not ACKing
1393 * the data, we avoid this DoS scenario.
1394 *
1395 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO)
1396 * cookie is processed and a new socket is created. In this case, any data
1397 * accompanying the SYN will be queued to the socket by tcp_input() and will
1398 * be ACKed either when the application sends response data or the delayed
1399 * ACK timer expires, whichever comes first.
1400 */
1401struct socket *
1402syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1403 struct inpcb *inp, struct socket *so, struct mbuf *m, void *tod,
1404 void *todctx, uint8_t iptos, uint16_t port)
1405{
1406 struct tcpcb *tp;
1407 struct socket *rv = NULL;
1408 struct syncache *sc = NULL;
1409 struct syncache_head *sch;
1410 struct mbuf *ipopts = NULL;
1411 u_int ltflags;
1412 int win, ip_ttl, ip_tos;
1413 char *s;
1414#ifdef INET6
1415 int autoflowlabel = 0;
1416#endif
1417#ifdef MAC
1418 struct label *maclabel;
1419#endif
1420 struct syncache scs;
1421 struct ucred *cred;
1422 uint64_t tfo_response_cookie;
1423 unsigned int *tfo_pending = NULL;
1424 int tfo_cookie_valid = 0;
1425 int tfo_response_cookie_valid = 0;
1426 bool locked;
1427
1428 INP_RLOCK_ASSERT(inp); /* listen socket */
1429 KASSERT((tcp_get_flags(th) & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1430 ("%s: unexpected tcp flags", __func__));
1431
1432 /*
1433 * Combine all so/tp operations very early to drop the INP lock as
1434 * soon as possible.
1435 */
1436 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so));
1437 tp = sototcpcb(so);
1438 cred = V_tcp_syncache.see_other ? NULL : crhold(so->so_cred);
1439
1440#ifdef INET6
1441 if (inc->inc_flags & INC_ISIPV6) {
1442 if (inp->inp_flags & IN6P_AUTOFLOWLABEL) {
1443 autoflowlabel = 1;
1444 }
1445 ip_ttl = in6_selecthlim(inp, NULL);
1446 if ((inp->in6p_outputopts == NULL) ||
1447 (inp->in6p_outputopts->ip6po_tclass == -1)) {
1448 ip_tos = 0;
1449 } else {
1450 ip_tos = inp->in6p_outputopts->ip6po_tclass;
1451 }
1452 }
1453#endif
1454#if defined(INET6) && defined(INET)
1455 else
1456#endif
1457#ifdef INET
1458 {
1459 ip_ttl = inp->inp_ip_ttl;
1460 ip_tos = inp->inp_ip_tos;
1461 }
1462#endif
1463 win = so->sol_sbrcv_hiwat;
1464 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1465
1466 if (V_tcp_fastopen_server_enable && IS_FASTOPEN(tp->t_flags) &&
1467 (tp->t_tfo_pending != NULL) &&
1468 (to->to_flags & TOF_FASTOPEN)) {
1469 /*
1470 * Limit the number of pending TFO connections to
1471 * approximately half of the queue limit. This prevents TFO
1472 * SYN floods from starving the service by filling the
1473 * listen queue with bogus TFO connections.
1474 */
1475 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <=
1476 (so->sol_qlimit / 2)) {
1477 int result;
1478
1479 result = tcp_fastopen_check_cookie(inc,
1480 to->to_tfo_cookie, to->to_tfo_len,
1481 &tfo_response_cookie);
1482 tfo_cookie_valid = (result > 0);
1483 tfo_response_cookie_valid = (result >= 0);
1484 }
1485
1486 /*
1487 * Remember the TFO pending counter as it will have to be
1488 * decremented below if we don't make it to syncache_tfo_expand().
1489 */
1490 tfo_pending = tp->t_tfo_pending;
1491 }
1492
1493#ifdef MAC
1494 if (mac_syncache_init(&maclabel) != 0) {
1495 INP_RUNLOCK(inp);
1496 goto done;
1497 } else
1498 mac_syncache_create(maclabel, inp);
1499#endif
1500 if (!tfo_cookie_valid)
1501 INP_RUNLOCK(inp);
1502
1503 /*
1504 * Remember the IP options, if any.
1505 */
1506#ifdef INET6
1507 if (!(inc->inc_flags & INC_ISIPV6))
1508#endif
1509#ifdef INET
1510 ipopts = (m) ? ip_srcroute(m) : NULL;
1511#else
1512 ipopts = NULL;
1513#endif
1514
1515#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1516 /*
1517 * When the socket is TCP-MD5 enabled check that,
1518 * - a signed packet is valid
1519 * - a non-signed packet does not have a security association
1520 *
1521 * If a signed packet fails validation or a non-signed packet has a
1522 * security association, the packet will be dropped.
1523 */
1524 if (ltflags & TF_SIGNATURE) {
1525 if (to->to_flags & TOF_SIGNATURE) {
1526 if (!TCPMD5_ENABLED() ||
1527 TCPMD5_INPUT(m, th, to->to_signature) != 0)
1528 goto done;
1529 } else {
1530 if (TCPMD5_ENABLED() &&
1531 TCPMD5_INPUT(m, NULL, NULL) != ENOENT)
1532 goto done;
1533 }
1534 } else if (to->to_flags & TOF_SIGNATURE)
1535 goto done;
1536#endif /* TCP_SIGNATURE */
1537 /*
1538 * See if we already have an entry for this connection.
1539 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1540 *
1541 * XXX: should the syncache be re-initialized with the contents
1542 * of the new SYN here (which may have different options?)
1543 *
1544 * XXX: We do not check the sequence number to see if this is a
1545 * real retransmit or a new connection attempt. The question is
1546 * how to handle such a case; either ignore it as spoofed, or
1547 * drop the current entry and create a new one?
1548 */
1549 if (syncache_cookiesonly()) {
1550 sc = NULL;
1551 sch = syncache_hashbucket(inc);
1552 locked = false;
1553 } else {
1554 sc = syncache_lookup(inc, &sch); /* returns locked sch */
1555 locked = true;
1556 SCH_LOCK_ASSERT(sch);
1557 }
1558 if (sc != NULL) {
1559 if (tfo_cookie_valid)
1560 INP_RUNLOCK(inp);
1561 TCPSTAT_INC(tcps_sc_dupsyn);
1562 if (ipopts) {
1563 /*
1564 * If we were remembering a previous source route,
1565 * forget it and use the new one we've been given.
1566 */
1567 if (sc->sc_ipopts)
1568 (void) m_free(sc->sc_ipopts);
1569 sc->sc_ipopts = ipopts;
1570 }
1571 /*
1572 * Update timestamp if present.
1573 */
1574 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1575 sc->sc_tsreflect = to->to_tsval;
1576 else
1577 sc->sc_flags &= ~SCF_TIMESTAMP;
1578 /*
1579 * Disable ECN if needed.
1580 */
1581 if ((sc->sc_flags & SCF_ECN) &&
1582 ((tcp_get_flags(th) & (TH_ECE|TH_CWR)) != (TH_ECE|TH_CWR))) {
1583 sc->sc_flags &= ~SCF_ECN;
1584 }
1585#ifdef MAC
1586 /*
1587 * Since we have already unconditionally allocated label
1588 * storage, free it up. The syncache entry will already
1589 * have an initialized label we can use.
1590 */
1591 mac_syncache_destroy(&maclabel);
1592#endif
1593 TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
1594 /* Retransmit SYN|ACK and reset retransmit count. */
1595 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1596 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1597 "resetting timer and retransmitting SYN|ACK\n",
1598 s, __func__);
1599 free(s, M_TCPLOG);
1600 }
1601 if (syncache_respond(sc, m, TH_SYN|TH_ACK) == 0) {
1602 sc->sc_rxmits = 0;
1603 syncache_timeout(sc, sch, 1);
1604 TCPSTAT_INC(tcps_sndacks);
1605 TCPSTAT_INC(tcps_sndtotal);
1606 }
1607 SCH_UNLOCK(sch);
1608 goto donenoprobe;
1609 }
1610
1611 if (tfo_cookie_valid) {
1612 bzero(&scs, sizeof(scs));
1613 sc = &scs;
1614 goto skip_alloc;
1615 }
1616
1617 /*
1618 * Skip allocating a syncache entry if we are just going to discard
1619 * it later.
1620 */
1621 if (!locked) {
1622 bzero(&scs, sizeof(scs));
1623 sc = &scs;
1624 } else
1625 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1626 if (sc == NULL) {
1627 /*
1628 * The zone allocator couldn't provide more entries.
1629 * Treat this as if the cache was full; drop the oldest
1630 * entry and insert the new one.
1631 */
1632 TCPSTAT_INC(tcps_sc_zonefail);
1633 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) {
1634 sch->sch_last_overflow = time_uptime;
1635 syncache_drop(sc, sch);
1636 syncache_pause(inc);
1637 }
1638 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1639 if (sc == NULL) {
1640 if (V_tcp_syncookies) {
1641 bzero(&scs, sizeof(scs));
1642 sc = &scs;
1643 } else {
1644 KASSERT(locked,
1645 ("%s: bucket unexpectedly unlocked",
1646 __func__));
1647 SCH_UNLOCK(sch);
1648 if (ipopts)
1649 (void) m_free(ipopts);
1650 goto done;
1651 }
1652 }
1653 }
1654
1655skip_alloc:
1656 if (!tfo_cookie_valid && tfo_response_cookie_valid)
1657 sc->sc_tfo_cookie = &tfo_response_cookie;
1658
1659 /*
1660 * Fill in the syncache values.
1661 */
1662#ifdef MAC
1663 sc->sc_label = maclabel;
1664#endif
1665 sc->sc_cred = cred;
1666 sc->sc_port = port;
1667 cred = NULL;
1668 sc->sc_ipopts = ipopts;
1669 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1670 sc->sc_ip_tos = ip_tos;
1671 sc->sc_ip_ttl = ip_ttl;
1672#ifdef TCP_OFFLOAD
1673 sc->sc_tod = tod;
1674 sc->sc_todctx = todctx;
1675#endif
1676 sc->sc_irs = th->th_seq;
1677 sc->sc_flags = 0;
1678 sc->sc_flowlabel = 0;
1679
1680 /*
1681 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1682 * win was derived from socket earlier in the function.
1683 */
1684 win = imax(win, 0);
1685 win = imin(win, TCP_MAXWIN);
1686 sc->sc_wnd = win;
1687
1688 if (V_tcp_do_rfc1323 &&
1689 !(ltflags & TF_NOOPT)) {
1690 /*
1691 * A timestamp received in a SYN makes
1692 * it ok to send timestamp requests and replies.
1693 */
1694 if (to->to_flags & TOF_TS) {
1695 sc->sc_tsreflect = to->to_tsval;
1696 sc->sc_flags |= SCF_TIMESTAMP;
1697 sc->sc_tsoff = tcp_new_ts_offset(inc);
1698 }
1699 if (to->to_flags & TOF_SCALE) {
1700 int wscale = 0;
1701
1702 /*
1703 * Pick the smallest possible scaling factor that
1704 * will still allow us to scale up to sb_max, aka
1705 * kern.ipc.maxsockbuf.
1706 *
1707 * We do this because there are broken firewalls that
1708 * will corrupt the window scale option, leading to
1709 * the other endpoint believing that our advertised
1710 * window is unscaled. At scale factors larger than
1711 * 5 the unscaled window will drop below 1500 bytes,
1712 * leading to serious problems when traversing these
1713 * broken firewalls.
1714 *
1715 * With the default maxsockbuf of 256K, a scale factor
1716 * of 3 will be chosen by this algorithm. Those who
1717 * choose a larger maxsockbuf should watch out
1718 * for the compatibility problems mentioned above.
1719 *
1720 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1721 * or <SYN,ACK>) segment itself is never scaled.
1722 */
1723 while (wscale < TCP_MAX_WINSHIFT &&
1724 (TCP_MAXWIN << wscale) < sb_max)
1725 wscale++;
1726 sc->sc_requested_r_scale = wscale;
1727 sc->sc_requested_s_scale = to->to_wscale;
1728 sc->sc_flags |= SCF_WINSCALE;
1729 }
1730 }
1731#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1732 /*
1733 * If incoming packet has an MD5 signature, flag this in the
1734 * syncache so that syncache_respond() will do the right thing
1735 * with the SYN+ACK.
1736 */
1737 if (to->to_flags & TOF_SIGNATURE)
1738 sc->sc_flags |= SCF_SIGNATURE;
1739#endif /* TCP_SIGNATURE */
1740 if (to->to_flags & TOF_SACKPERM)
1741 sc->sc_flags |= SCF_SACK;
1742 if (to->to_flags & TOF_MSS)
1743 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1744 if (ltflags & TF_NOOPT)
1745 sc->sc_flags |= SCF_NOOPT;
1746 /* ECN Handshake */
1747 if (V_tcp_do_ecn)
1748 sc->sc_flags |= tcp_ecn_syncache_add(tcp_get_flags(th), iptos);
1749
1750 if (V_tcp_syncookies)
1751 sc->sc_iss = syncookie_generate(sch, sc);
1752 else
1753 sc->sc_iss = arc4random();
1754#ifdef INET6
1755 if (autoflowlabel) {
1756 if (V_tcp_syncookies)
1757 sc->sc_flowlabel = sc->sc_iss;
1758 else
1759 sc->sc_flowlabel = ip6_randomflowlabel();
1760 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK;
1761 }
1762#endif
1763 if (locked)
1764 SCH_UNLOCK(sch);
1765
1766 if (tfo_cookie_valid) {
1767 rv = syncache_tfo_expand(sc, so, m, tfo_response_cookie);
1768 /* INP_RUNLOCK(inp) will be performed by the caller */
1769 goto tfo_expanded;
1770 }
1771
1772 TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
1773 /*
1774 * Do a standard 3-way handshake.
1775 */
1776 if (syncache_respond(sc, m, TH_SYN|TH_ACK) == 0) {
1777 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1778 syncache_free(sc);
1779 else if (sc != &scs)
1780 syncache_insert(sc, sch); /* locks and unlocks sch */
1781 TCPSTAT_INC(tcps_sndacks);
1782 TCPSTAT_INC(tcps_sndtotal);
1783 } else {
1784 if (sc != &scs)
1785 syncache_free(sc);
1786 TCPSTAT_INC(tcps_sc_dropped);
1787 }
1788 goto donenoprobe;
1789
1790done:
1791 TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
1792donenoprobe:
1793 if (m)
1794 m_freem(m);
1795 /*
1796 * If tfo_pending is not NULL here, then a TFO SYN that did not
1797 * result in a new socket was processed and the associated pending
1798 * counter has not yet been decremented. All such TFO processing paths
1799 * transit this point.
1800 */
1801 if (tfo_pending != NULL)
1802 tcp_fastopen_decrement_counter(tfo_pending);
1803
1804tfo_expanded:
1805 if (cred != NULL)
1806 crfree(cred);
1807#ifdef MAC
1808 if (sc == &scs)
1809 mac_syncache_destroy(&maclabel);
1810#endif
1811 return (rv);
1812}
1813
1814/*
1815 * Send SYN|ACK or ACK to the peer. Either in response to a peer's segment,
1816 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL.
1817 */
1818static int
1819syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
1820{
1821 struct ip *ip = NULL;
1822 struct mbuf *m;
1823 struct tcphdr *th = NULL;
1824 struct udphdr *udp = NULL;
1825 int optlen, error = 0; /* Make compiler happy */
1826 u_int16_t hlen, tlen, mssopt, ulen;
1827 struct tcpopt to;
1828#ifdef INET6
1829 struct ip6_hdr *ip6 = NULL;
1830#endif
1831
1832 NET_EPOCH_ASSERT();
1833
1834 hlen =
1835#ifdef INET6
1836 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1837#endif
1838 sizeof(struct ip);
1839 tlen = hlen + sizeof(struct tcphdr);
1840 if (sc->sc_port) {
1841 tlen += sizeof(struct udphdr);
1842 }
1843 /* Determine MSS we advertize to other end of connection. */
1844 mssopt = tcp_mssopt(&sc->sc_inc);
1845 if (sc->sc_port)
1846 mssopt -= V_tcp_udp_tunneling_overhead;
1847 mssopt = max(mssopt, V_tcp_minmss);
1848
1849 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1850 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1851 ("syncache: mbuf too small: hlen %u, sc_port %u, max_linkhdr %d + "
1852 "tlen %d + TCP_MAXOLEN %ju <= MHLEN %d", hlen, sc->sc_port,
1853 max_linkhdr, tlen, (uintmax_t)TCP_MAXOLEN, MHLEN));
1854
1855 /* Create the IP+TCP header from scratch. */
1856 m = m_gethdr(M_NOWAIT, MT_DATA);
1857 if (m == NULL)
1858 return (ENOBUFS);
1859#ifdef MAC
1860 mac_syncache_create_mbuf(sc->sc_label, m);
1861#endif
1862 m->m_data += max_linkhdr;
1863 m->m_len = tlen;
1864 m->m_pkthdr.len = tlen;
1865 m->m_pkthdr.rcvif = NULL;
1866
1867#ifdef INET6
1868 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1869 ip6 = mtod(m, struct ip6_hdr *);
1870 ip6->ip6_vfc = IPV6_VERSION;
1871 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1872 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1873 ip6->ip6_plen = htons(tlen - hlen);
1874 /* ip6_hlim is set after checksum */
1875 /* Zero out traffic class and flow label. */
1876 ip6->ip6_flow &= ~IPV6_FLOWINFO_MASK;
1877 ip6->ip6_flow |= sc->sc_flowlabel;
1878 if (sc->sc_port != 0) {
1879 ip6->ip6_nxt = IPPROTO_UDP;
1880 udp = (struct udphdr *)(ip6 + 1);
1881 udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1882 udp->uh_dport = sc->sc_port;
1883 ulen = (tlen - sizeof(struct ip6_hdr));
1884 th = (struct tcphdr *)(udp + 1);
1885 } else {
1886 ip6->ip6_nxt = IPPROTO_TCP;
1887 th = (struct tcphdr *)(ip6 + 1);
1888 }
1889 ip6->ip6_flow |= htonl(sc->sc_ip_tos << 20);
1890 }
1891#endif
1892#if defined(INET6) && defined(INET)
1893 else
1894#endif
1895#ifdef INET
1896 {
1897 ip = mtod(m, struct ip *);
1898 ip->ip_v = IPVERSION;
1899 ip->ip_hl = sizeof(struct ip) >> 2;
1900 ip->ip_len = htons(tlen);
1901 ip->ip_id = 0;
1902 ip->ip_off = 0;
1903 ip->ip_sum = 0;
1904 ip->ip_src = sc->sc_inc.inc_laddr;
1905 ip->ip_dst = sc->sc_inc.inc_faddr;
1906 ip->ip_ttl = sc->sc_ip_ttl;
1907 ip->ip_tos = sc->sc_ip_tos;
1908
1909 /*
1910 * See if we should do MTU discovery. Route lookups are
1911 * expensive, so we will only unset the DF bit if:
1912 *
1913 * 1) path_mtu_discovery is disabled
1914 * 2) the SCF_UNREACH flag has been set
1915 */
1916 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1917 ip->ip_off |= htons(IP_DF);
1918 if (sc->sc_port == 0) {
1919 ip->ip_p = IPPROTO_TCP;
1920 th = (struct tcphdr *)(ip + 1);
1921 } else {
1922 ip->ip_p = IPPROTO_UDP;
1923 udp = (struct udphdr *)(ip + 1);
1924 udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1925 udp->uh_dport = sc->sc_port;
1926 ulen = (tlen - sizeof(struct ip));
1927 th = (struct tcphdr *)(udp + 1);
1928 }
1929 }
1930#endif /* INET */
1931 th->th_sport = sc->sc_inc.inc_lport;
1932 th->th_dport = sc->sc_inc.inc_fport;
1933
1934 if (flags & TH_SYN)
1935 th->th_seq = htonl(sc->sc_iss);
1936 else
1937 th->th_seq = htonl(sc->sc_iss + 1);
1938 th->th_ack = htonl(sc->sc_irs + 1);
1939 th->th_off = sizeof(struct tcphdr) >> 2;
1940 th->th_win = htons(sc->sc_wnd);
1941 th->th_urp = 0;
1942
1943 flags = tcp_ecn_syncache_respond(flags, sc);
1944 tcp_set_flags(th, flags);
1945
1946 /* Tack on the TCP options. */
1947 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1948 to.to_flags = 0;
1949
1950 if (flags & TH_SYN) {
1951 to.to_mss = mssopt;
1952 to.to_flags = TOF_MSS;
1953 if (sc->sc_flags & SCF_WINSCALE) {
1954 to.to_wscale = sc->sc_requested_r_scale;
1955 to.to_flags |= TOF_SCALE;
1956 }
1957 if (sc->sc_flags & SCF_SACK)
1958 to.to_flags |= TOF_SACKPERM;
1959#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1960 if (sc->sc_flags & SCF_SIGNATURE)
1961 to.to_flags |= TOF_SIGNATURE;
1962#endif
1963 if (sc->sc_tfo_cookie) {
1964 to.to_flags |= TOF_FASTOPEN;
1965 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
1966 to.to_tfo_cookie = sc->sc_tfo_cookie;
1967 /* don't send cookie again when retransmitting response */
1968 sc->sc_tfo_cookie = NULL;
1969 }
1970 }
1971 if (sc->sc_flags & SCF_TIMESTAMP) {
1972 to.to_tsval = sc->sc_tsoff + tcp_ts_getticks();
1973 to.to_tsecr = sc->sc_tsreflect;
1974 to.to_flags |= TOF_TS;
1975 }
1976 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1977
1978 /* Adjust headers by option size. */
1979 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1980 m->m_len += optlen;
1981 m->m_pkthdr.len += optlen;
1982#ifdef INET6
1983 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1984 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1985 else
1986#endif
1987 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
1988#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1989 if (sc->sc_flags & SCF_SIGNATURE) {
1990 KASSERT(to.to_flags & TOF_SIGNATURE,
1991 ("tcp_addoptions() didn't set tcp_signature"));
1992
1993 /* NOTE: to.to_signature is inside of mbuf */
1994 if (!TCPMD5_ENABLED() ||
1995 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) {
1996 m_freem(m);
1997 return (EACCES);
1998 }
1999 }
2000#endif
2001 } else
2002 optlen = 0;
2003
2004 if (udp) {
2005 ulen += optlen;
2006 udp->uh_ulen = htons(ulen);
2007 }
2008 M_SETFIB(m, sc->sc_inc.inc_fibnum);
2009 /*
2010 * If we have peer's SYN and it has a flowid, then let's assign it to
2011 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid
2012 * to SYN|ACK due to lack of inp here.
2013 */
2014 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) {
2015 m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
2016 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0));
2017 }
2018#ifdef INET6
2019 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
2020 if (sc->sc_port) {
2021 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
2022 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
2023 udp->uh_sum = in6_cksum_pseudo(ip6, ulen,
2024 IPPROTO_UDP, 0);
2025 th->th_sum = htons(0);
2026 } else {
2027 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
2028 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
2029 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
2030 IPPROTO_TCP, 0);
2031 }
2032 ip6->ip6_hlim = sc->sc_ip_ttl;
2033#ifdef TCP_OFFLOAD
2034 if (ADDED_BY_TOE(sc)) {
2035 struct toedev *tod = sc->sc_tod;
2036
2037 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
2038
2039 return (error);
2040 }
2041#endif
2042 TCP_PROBE5(send, NULL, NULL, ip6, NULL, th);
2043 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
2044 }
2045#endif
2046#if defined(INET6) && defined(INET)
2047 else
2048#endif
2049#ifdef INET
2050 {
2051 if (sc->sc_port) {
2052 m->m_pkthdr.csum_flags = CSUM_UDP;
2053 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
2054 udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
2055 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
2056 th->th_sum = htons(0);
2057 } else {
2058 m->m_pkthdr.csum_flags = CSUM_TCP;
2059 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
2060 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
2061 htons(tlen + optlen - hlen + IPPROTO_TCP));
2062 }
2063#ifdef TCP_OFFLOAD
2064 if (ADDED_BY_TOE(sc)) {
2065 struct toedev *tod = sc->sc_tod;
2066
2067 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
2068
2069 return (error);
2070 }
2071#endif
2072 TCP_PROBE5(send, NULL, NULL, ip, NULL, th);
2073 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
2074 }
2075#endif
2076 return (error);
2077}
2078
2079/*
2080 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks
2081 * that exceed the capacity of the syncache by avoiding the storage of any
2082 * of the SYNs we receive. Syncookies defend against blind SYN flooding
2083 * attacks where the attacker does not have access to our responses.
2084 *
2085 * Syncookies encode and include all necessary information about the
2086 * connection setup within the SYN|ACK that we send back. That way we
2087 * can avoid keeping any local state until the ACK to our SYN|ACK returns
2088 * (if ever). Normally the syncache and syncookies are running in parallel
2089 * with the latter taking over when the former is exhausted. When matching
2090 * syncache entry is found the syncookie is ignored.
2091 *
2092 * The only reliable information persisting the 3WHS is our initial sequence
2093 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient
2094 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS
2095 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK
2096 * returns and signifies a legitimate connection if it matches the ACK.
2097 *
2098 * The available space of 32 bits to store the hash and to encode the SYN
2099 * option information is very tight and we should have at least 24 bits for
2100 * the MAC to keep the number of guesses by blind spoofing reasonably high.
2101 *
2102 * SYN option information we have to encode to fully restore a connection:
2103 * MSS: is imporant to chose an optimal segment size to avoid IP level
2104 * fragmentation along the path. The common MSS values can be encoded
2105 * in a 3-bit table. Uncommon values are captured by the next lower value
2106 * in the table leading to a slight increase in packetization overhead.
2107 * WSCALE: is necessary to allow large windows to be used for high delay-
2108 * bandwidth product links. Not scaling the window when it was initially
2109 * negotiated is bad for performance as lack of scaling further decreases
2110 * the apparent available send window. We only need to encode the WSCALE
2111 * we received from the remote end. Our end can be recalculated at any
2112 * time. The common WSCALE values can be encoded in a 3-bit table.
2113 * Uncommon values are captured by the next lower value in the table
2114 * making us under-estimate the available window size halving our
2115 * theoretically possible maximum throughput for that connection.
2116 * SACK: Greatly assists in packet loss recovery and requires 1 bit.
2117 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options
2118 * that are included in all segments on a connection. We enable them when
2119 * the ACK has them.
2120 *
2121 * Security of syncookies and attack vectors:
2122 *
2123 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod)
2124 * together with the gloabl secret to make it unique per connection attempt.
2125 * Thus any change of any of those parameters results in a different MAC output
2126 * in an unpredictable way unless a collision is encountered. 24 bits of the
2127 * MAC are embedded into the ISS.
2128 *
2129 * To prevent replay attacks two rotating global secrets are updated with a
2130 * new random value every 15 seconds. The life-time of a syncookie is thus
2131 * 15-30 seconds.
2132 *
2133 * Vector 1: Attacking the secret. This requires finding a weakness in the
2134 * MAC itself or the way it is used here. The attacker can do a chosen plain
2135 * text attack by varying and testing the all parameters under his control.
2136 * The strength depends on the size and randomness of the secret, and the
2137 * cryptographic security of the MAC function. Due to the constant updating
2138 * of the secret the attacker has at most 29.999 seconds to find the secret
2139 * and launch spoofed connections. After that he has to start all over again.
2140 *
2141 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC
2142 * size an average of 4,823 attempts are required for a 50% chance of success
2143 * to spoof a single syncookie (birthday collision paradox). However the
2144 * attacker is blind and doesn't know if one of his attempts succeeded unless
2145 * he has a side channel to interfere success from. A single connection setup
2146 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets.
2147 * This many attempts are required for each one blind spoofed connection. For
2148 * every additional spoofed connection he has to launch another N attempts.
2149 * Thus for a sustained rate 100 spoofed connections per second approximately
2150 * 1,800,000 packets per second would have to be sent.
2151 *
2152 * NB: The MAC function should be fast so that it doesn't become a CPU
2153 * exhaustion attack vector itself.
2154 *
2155 * References:
2156 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations
2157 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996
2158 * http://cr.yp.to/syncookies.html (overview)
2159 * http://cr.yp.to/syncookies/archive (details)
2160 *
2161 *
2162 * Schematic construction of a syncookie enabled Initial Sequence Number:
2163 * 0 1 2 3
2164 * 12345678901234567890123456789012
2165 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP|
2166 *
2167 * x 24 MAC (truncated)
2168 * W 3 Send Window Scale index
2169 * M 3 MSS index
2170 * S 1 SACK permitted
2171 * P 1 Odd/even secret
2172 */
2173
2174/*
2175 * Distribution and probability of certain MSS values. Those in between are
2176 * rounded down to the next lower one.
2177 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011]
2178 * .2% .3% 5% 7% 7% 20% 15% 45%
2179 */
2180static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 };
2181
2182/*
2183 * Distribution and probability of certain WSCALE values. We have to map the
2184 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3
2185 * bits based on prevalence of certain values. Where we don't have an exact
2186 * match for are rounded down to the next lower one letting us under-estimate
2187 * the true available window. At the moment this would happen only for the
2188 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer
2189 * and window size). The absence of the WSCALE option (no scaling in either
2190 * direction) is encoded with index zero.
2191 * [WSCALE values histograms, Allman, 2012]
2192 * X 10 10 35 5 6 14 10% by host
2193 * X 11 4 5 5 18 49 3% by connections
2194 */
2195static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 };
2196
2197/*
2198 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed
2199 * and good cryptographic properties.
2200 */
2201static uint32_t
2202syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags,
2203 uint8_t *secbits, uintptr_t secmod)
2204{
2205 SIPHASH_CTX ctx;
2206 uint32_t siphash[2];
2207
2208 SipHash24_Init(&ctx);
2209 SipHash_SetKey(&ctx, secbits);
2210 switch (inc->inc_flags & INC_ISIPV6) {
2211#ifdef INET
2212 case 0:
2213 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr));
2214 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr));
2215 break;
2216#endif
2217#ifdef INET6
2218 case INC_ISIPV6:
2219 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr));
2220 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr));
2221 break;
2222#endif
2223 }
2224 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport));
2225 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport));
2226 SipHash_Update(&ctx, &irs, sizeof(irs));
2227 SipHash_Update(&ctx, &flags, sizeof(flags));
2228 SipHash_Update(&ctx, &secmod, sizeof(secmod));
2229 SipHash_Final((u_int8_t *)&siphash, &ctx);
2230
2231 return (siphash[0] ^ siphash[1]);
2232}
2233
2234static tcp_seq
2235syncookie_generate(struct syncache_head *sch, struct syncache *sc)
2236{
2237 u_int i, secbit, wscale;
2238 uint32_t iss, hash;
2239 uint8_t *secbits;
2240 union syncookie cookie;
2241
2242 cookie.cookie = 0;
2243
2244 /* Map our computed MSS into the 3-bit index. */
2245 for (i = nitems(tcp_sc_msstab) - 1;
2246 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0;
2247 i--)
2248 ;
2249 cookie.flags.mss_idx = i;
2250
2251 /*
2252 * Map the send window scale into the 3-bit index but only if
2253 * the wscale option was received.
2254 */
2255 if (sc->sc_flags & SCF_WINSCALE) {
2256 wscale = sc->sc_requested_s_scale;
2257 for (i = nitems(tcp_sc_wstab) - 1;
2258 tcp_sc_wstab[i] > wscale && i > 0;
2259 i--)
2260 ;
2261 cookie.flags.wscale_idx = i;
2262 }
2263
2264 /* Can we do SACK? */
2265 if (sc->sc_flags & SCF_SACK)
2266 cookie.flags.sack_ok = 1;
2267
2268 /* Which of the two secrets to use. */
2269 secbit = V_tcp_syncache.secret.oddeven & 0x1;
2270 cookie.flags.odd_even = secbit;
2271
2272 secbits = V_tcp_syncache.secret.key[secbit];
2273 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits,
2274 (uintptr_t)sch);
2275
2276 /*
2277 * Put the flags into the hash and XOR them to get better ISS number
2278 * variance. This doesn't enhance the cryptographic strength and is
2279 * done to prevent the 8 cookie bits from showing up directly on the
2280 * wire.
2281 */
2282 iss = hash & ~0xff;
2283 iss |= cookie.cookie ^ (hash >> 24);
2284
2285 TCPSTAT_INC(tcps_sc_sendcookie);
2286 return (iss);
2287}
2288
2289static struct syncache *
2290syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
2291 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2292 struct socket *lso, uint16_t port)
2293{
2294 uint32_t hash;
2295 uint8_t *secbits;
2296 tcp_seq ack, seq;
2297 int wnd, wscale = 0;
2298 union syncookie cookie;
2299
2300 /*
2301 * Pull information out of SYN-ACK/ACK and revert sequence number
2302 * advances.
2303 */
2304 ack = th->th_ack - 1;
2305 seq = th->th_seq - 1;
2306
2307 /*
2308 * Unpack the flags containing enough information to restore the
2309 * connection.
2310 */
2311 cookie.cookie = (ack & 0xff) ^ (ack >> 24);
2312
2313 /* Which of the two secrets to use. */
2314 secbits = V_tcp_syncache.secret.key[cookie.flags.odd_even];
2315
2316 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch);
2317
2318 /* The recomputed hash matches the ACK if this was a genuine cookie. */
2319 if ((ack & ~0xff) != (hash & ~0xff))
2320 return (NULL);
2321
2322 /* Fill in the syncache values. */
2323 sc->sc_flags = 0;
2324 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
2325 sc->sc_ipopts = NULL;
2326
2327 sc->sc_irs = seq;
2328 sc->sc_iss = ack;
2329
2330 switch (inc->inc_flags & INC_ISIPV6) {
2331#ifdef INET
2332 case 0:
2333 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl;
2334 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos;
2335 break;
2336#endif
2337#ifdef INET6
2338 case INC_ISIPV6:
2339 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL)
2340 sc->sc_flowlabel =
2341 htonl(sc->sc_iss) & IPV6_FLOWLABEL_MASK;
2342 break;
2343#endif
2344 }
2345
2346 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx];
2347
2348 /* We can simply recompute receive window scale we sent earlier. */
2349 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max)
2350 wscale++;
2351
2352 /* Only use wscale if it was enabled in the orignal SYN. */
2353 if (cookie.flags.wscale_idx > 0) {
2354 sc->sc_requested_r_scale = wscale;
2355 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx];
2356 sc->sc_flags |= SCF_WINSCALE;
2357 }
2358
2359 wnd = lso->sol_sbrcv_hiwat;
2360 wnd = imax(wnd, 0);
2361 wnd = imin(wnd, TCP_MAXWIN);
2362 sc->sc_wnd = wnd;
2363
2364 if (cookie.flags.sack_ok)
2365 sc->sc_flags |= SCF_SACK;
2366
2367 if (to->to_flags & TOF_TS) {
2368 sc->sc_flags |= SCF_TIMESTAMP;
2369 sc->sc_tsreflect = to->to_tsval;
2370 sc->sc_tsoff = tcp_new_ts_offset(inc);
2371 }
2372
2373 if (to->to_flags & TOF_SIGNATURE)
2374 sc->sc_flags |= SCF_SIGNATURE;
2375
2376 sc->sc_rxmits = 0;
2377
2378 sc->sc_port = port;
2379
2380 TCPSTAT_INC(tcps_sc_recvcookie);
2381 return (sc);
2382}
2383
2384#ifdef INVARIANTS
2385static int
2386syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
2387 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2388 struct socket *lso, uint16_t port)
2389{
2390 struct syncache scs, *scx;
2391 char *s;
2392
2393 bzero(&scs, sizeof(scs));
2394 scx = syncookie_lookup(inc, sch, &scs, th, to, lso, port);
2395
2396 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL)
2397 return (0);
2398
2399 if (scx != NULL) {
2400 if (sc->sc_peer_mss != scx->sc_peer_mss)
2401 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n",
2402 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss);
2403
2404 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale)
2405 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n",
2406 s, __func__, sc->sc_requested_r_scale,
2407 scx->sc_requested_r_scale);
2408
2409 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale)
2410 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n",
2411 s, __func__, sc->sc_requested_s_scale,
2412 scx->sc_requested_s_scale);
2413
2414 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK))
2415 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__);
2416 }
2417
2418 if (s != NULL)
2419 free(s, M_TCPLOG);
2420 return (0);
2421}
2422#endif /* INVARIANTS */
2423
2424static void
2425syncookie_reseed(void *arg)
2426{
2427 struct tcp_syncache *sc = arg;
2428 uint8_t *secbits;
2429 int secbit;
2430
2431 /*
2432 * Reseeding the secret doesn't have to be protected by a lock.
2433 * It only must be ensured that the new random values are visible
2434 * to all CPUs in a SMP environment. The atomic with release
2435 * semantics ensures that.
2436 */
2437 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1;
2438 secbits = sc->secret.key[secbit];
2439 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0);
2440 atomic_add_rel_int(&sc->secret.oddeven, 1);
2441
2442 /* Reschedule ourself. */
2443 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz);
2444}
2445
2446/*
2447 * We have overflowed a bucket. Let's pause dealing with the syncache.
2448 * This function will increment the bucketoverflow statistics appropriately
2449 * (once per pause when pausing is enabled; otherwise, once per overflow).
2450 */
2451static void
2452syncache_pause(struct in_conninfo *inc)
2453{
2454 time_t delta;
2455 const char *s;
2456
2457 /* XXX:
2458 * 2. Add sysctl read here so we don't get the benefit of this
2459 * change without the new sysctl.
2460 */
2461
2462 /*
2463 * Try an unlocked read. If we already know that another thread
2464 * has activated the feature, there is no need to proceed.
2465 */
2466 if (V_tcp_syncache.paused)
2467 return;
2468
2469 /* Are cookied enabled? If not, we can't pause. */
2470 if (!V_tcp_syncookies) {
2471 TCPSTAT_INC(tcps_sc_bucketoverflow);
2472 return;
2473 }
2474
2475 /*
2476 * We may be the first thread to find an overflow. Get the lock
2477 * and evaluate if we need to take action.
2478 */
2479 mtx_lock(&V_tcp_syncache.pause_mtx);
2480 if (V_tcp_syncache.paused) {
2481 mtx_unlock(&V_tcp_syncache.pause_mtx);
2482 return;
2483 }
2484
2485 /* Activate protection. */
2486 V_tcp_syncache.paused = true;
2487 TCPSTAT_INC(tcps_sc_bucketoverflow);
2488
2489 /*
2490 * Determine the last backoff time. If we are seeing a re-newed
2491 * attack within that same time after last reactivating the syncache,
2492 * consider it an extension of the same attack.
2493 */
2494 delta = TCP_SYNCACHE_PAUSE_TIME << V_tcp_syncache.pause_backoff;
2495 if (V_tcp_syncache.pause_until + delta - time_uptime > 0) {
2496 if (V_tcp_syncache.pause_backoff < TCP_SYNCACHE_MAX_BACKOFF) {
2497 delta <<= 1;
2498 V_tcp_syncache.pause_backoff++;
2499 }
2500 } else {
2501 delta = TCP_SYNCACHE_PAUSE_TIME;
2502 V_tcp_syncache.pause_backoff = 0;
2503 }
2504
2505 /* Log a warning, including IP addresses, if able. */
2506 if (inc != NULL)
2507 s = tcp_log_addrs(inc, NULL, NULL, NULL);
2508 else
2509 s = (const char *)NULL;
2510 log(LOG_WARNING, "TCP syncache overflow detected; using syncookies for "
2511 "the next %lld seconds%s%s%s\n", (long long)delta,
2512 (s != NULL) ? " (last SYN: " : "", (s != NULL) ? s : "",
2513 (s != NULL) ? ")" : "");
2514 free(__DECONST(void *, s), M_TCPLOG);
2515
2516 /* Use the calculated delta to set a new pause time. */
2517 V_tcp_syncache.pause_until = time_uptime + delta;
2518 callout_reset(&V_tcp_syncache.pause_co, delta * hz, syncache_unpause,
2519 &V_tcp_syncache);
2520 mtx_unlock(&V_tcp_syncache.pause_mtx);
2521}
2522
2523/* Evaluate whether we need to unpause. */
2524static void
2525syncache_unpause(void *arg)
2526{
2527 struct tcp_syncache *sc;
2528 time_t delta;
2529
2530 sc = arg;
2531 mtx_assert(&sc->pause_mtx, MA_OWNED | MA_NOTRECURSED);
2532 callout_deactivate(&sc->pause_co);
2533
2534 /*
2535 * Check to make sure we are not running early. If the pause
2536 * time has expired, then deactivate the protection.
2537 */
2538 if ((delta = sc->pause_until - time_uptime) > 0)
2539 callout_schedule(&sc->pause_co, delta * hz);
2540 else
2541 sc->paused = false;
2542}
2543
2544/*
2545 * Exports the syncache entries to userland so that netstat can display
2546 * them alongside the other sockets. This function is intended to be
2547 * called only from tcp_pcblist.
2548 *
2549 * Due to concurrency on an active system, the number of pcbs exported
2550 * may have no relation to max_pcbs. max_pcbs merely indicates the
2551 * amount of space the caller allocated for this function to use.
2552 */
2553int
2554syncache_pcblist(struct sysctl_req *req)
2555{
2556 struct xtcpcb xt;
2557 struct syncache *sc;
2558 struct syncache_head *sch;
2559 int error, i;
2560
2561 bzero(&xt, sizeof(xt));
2562 xt.xt_len = sizeof(xt);
2563 xt.t_state = TCPS_SYN_RECEIVED;
2564 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP;
2565 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket);
2566 xt.xt_inp.xi_socket.so_type = SOCK_STREAM;
2567 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING;
2568
2569 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
2570 sch = &V_tcp_syncache.hashbase[i];
2571 SCH_LOCK(sch);
2572 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
2573 if (sc->sc_cred != NULL &&
2574 cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
2575 continue;
2576 if (sc->sc_inc.inc_flags & INC_ISIPV6)
2577 xt.xt_inp.inp_vflag = INP_IPV6;
2578 else
2579 xt.xt_inp.inp_vflag = INP_IPV4;
2580 xt.xt_encaps_port = sc->sc_port;
2581 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc,
2582 sizeof (struct in_conninfo));
2583 error = SYSCTL_OUT(req, &xt, sizeof xt);
2584 if (error) {
2585 SCH_UNLOCK(sch);
2586 return (0);
2587 }
2588 }
2589 SCH_UNLOCK(sch);
2590 }
2591
2592 return (0);
2593}
uint32_t
__uint32_t uint32_t
Definition: in.h:62
uint16_t
__uint16_t uint16_t
Definition: in.h:57
uint8_t
__uint8_t uint8_t
Definition: in.h:52
INADDR_ANY
#define INADDR_ANY
Definition: in.h:48
IPPROTO_TCP
#define IPPROTO_TCP
Definition: in.h:45
IPPROTO_UDP
#define IPPROTO_UDP
Definition: in.h:46
in_pseudo
u_short in_pseudo(u_int32_t a, u_int32_t b, u_int32_t c)
Definition: in_cksum.c:197
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const struct encaptab * cookie
Definition: in_gif.c:396
in_kdtrace.h
TCP_PROBE5
#define TCP_PROBE5(probe, arg0, arg1, arg2, arg3, arg4)
Definition: in_kdtrace.h:47
in_pcb.h
INP_IPV4
#define INP_IPV4
Definition: in_pcb.h:613
INC_ISIPV6
#define INC_ISIPV6
Definition: in_pcb.h:124
INP_WLOCK
#define INP_WLOCK(inp)
Definition: in_pcb.h:518
INP_HASH_WUNLOCK
#define INP_HASH_WUNLOCK(ipi)
Definition: in_pcb.h:573
INP_CONTROLOPTS
#define INP_CONTROLOPTS
Definition: in_pcb.h:653
INP_IPV6PROTO
#define INP_IPV6PROTO
Definition: in_pcb.h:615
INP_RUNLOCK
#define INP_RUNLOCK(inp)
Definition: in_pcb.h:521
sotoinpcb
#define sotoinpcb(so)
Definition: in_pcb.h:701
in_pcbconnect
int in_pcbconnect(struct inpcb *, struct sockaddr *, struct ucred *, bool)
INP_HASH_WLOCK
#define INP_HASH_WLOCK(ipi)
Definition: in_pcb.h:572
IN6P_AUTOFLOWLABEL
#define IN6P_AUTOFLOWLABEL
Definition: in_pcb.h:643
INP_WUNLOCK
#define INP_WUNLOCK(inp)
Definition: in_pcb.h:522
INP_RLOCK_ASSERT
#define INP_RLOCK_ASSERT(inp)
Definition: in_pcb.h:528
INP_IPV6
#define INP_IPV6
Definition: in_pcb.h:614
in_systm.h
in_var.h
IPV6_FLOWLABEL_MASK
#define IPV6_FLOWLABEL_MASK
Definition: ip6.h:100
IPV6_VERSION
#define IPV6_VERSION
Definition: ip6.h:95
ip_ttl
u_char ip_ttl
Definition: ip.h:16
ip_tos
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Definition: ip.h:8
IPVERSION
#define IPVERSION
Definition: ip.h:46
IP_DF
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Definition: ip.h:13
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u_int16_t count
Definition: ip_fw.h:18
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struct mbuf * ip_srcroute(struct mbuf *m0)
Definition: ip_options.c:426
ip_options.h
ip_output
int ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags, struct ip_moptions *imo, struct inpcb *inp)
Definition: ip_output.c:320
ip_var.h
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Definition: in.h:83
in_addr::s_addr
in_addr_t s_addr
Definition: in.h:84
in_conninfo
Definition: in_pcb.h:113
in_conninfo::inc_flags
u_int8_t inc_flags
Definition: in_pcb.h:114
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u_int16_t inc_fibnum
Definition: in_pcb.h:116
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struct in_endpoints inc_ie
Definition: in_pcb.h:118
in_endpoints
Definition: in_pcb.h:96
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Definition: in_pcb.h:217
inpcb::in6p_outputopts
struct ip6_pktopts * in6p_outputopts
Definition: in_pcb.h:286
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short in6p_hops
Definition: in_pcb.h:293
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Definition: in_pcb.h:246
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Definition: in_pcb.h:260
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u_int32_t inp_flow
Definition: in_pcb.h:259
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Definition: in_pcb.h:279
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Definition: in_pcb.h:261
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struct in6_addr ip6_dst
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Definition: in.h:102
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uint8_t key[2][SYNCOOKIE_SECRET_SIZE]
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volatile u_int oddeven
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Definition: tcp_syncache.h:117
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Definition: tcp_syncache.h:134
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Definition: tcp_syncache.h:140
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Definition: tcp_syncache.h:127
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Definition: tcp_syncache.h:139
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Definition: tcp_syncache.h:136
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Definition: tcp_var.h:132
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Definition: tcp_var.h:246
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Definition: tcp_var.h:174
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Definition: tcp_var.h:194
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Definition: tcp_var.h:151
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Definition: tcp_var.h:170
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Definition: tcp_var.h:148
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union tcpcb::@55 t_tfo_cookie
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Definition: tcp_var.h:169
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Definition: tcp_var.h:157
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Definition: tcp_var.h:189
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Definition: tcp_var.h:248
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Definition: tcp_var.h:193
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Definition: tcp_var.h:146
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struct tcp_function_block * t_fb
Definition: tcp_var.h:135
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Definition: tcp_var.h:164
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u_int8_t to_tfo_len
Definition: tcp_var.h:595
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Definition: tcp_var.h:590
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Definition: tcp_var.h:587
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Definition: tcp_var.h:592
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u_int8_t * to_tfo_cookie
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u_int32_t to_tsecr
Definition: tcp_var.h:588
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Definition: toecore.h:48
toedev::tod_syncache_respond
int(* tod_syncache_respond)(struct toedev *, void *, struct mbuf *)
Definition: toecore.h:105
toedev::tod_offload_socket
void(* tod_offload_socket)(struct toedev *, void *, struct socket *)
Definition: toecore.h:106
toedev::tod_syncache_removed
void(* tod_syncache_removed)(struct toedev *, void *)
Definition: toecore.h:104
toedev::tod_syncache_added
void(* tod_syncache_added)(struct toedev *, void *)
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Definition: udp.h:45
udphdr::uh_ulen
u_short uh_ulen
Definition: udp.h:48
udphdr::uh_sport
u_short uh_sport
Definition: udp.h:46
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u_short uh_sum
Definition: udp.h:49
udphdr::uh_dport
u_short uh_dport
Definition: udp.h:47
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uint16_t tcp_ecn_syncache_respond(uint16_t thflags, struct syncache *sc)
Definition: tcp_ecn.c:283
tcp_ecn_syncache_add
int tcp_ecn_syncache_add(uint16_t thflags, int iptos)
Definition: tcp_ecn.c:260
tcp_ecn_syncache_socket
void tcp_ecn_syncache_socket(struct tcpcb *tp, struct syncache *sc)
Definition: tcp_ecn.c:241
tcp_ecn.h
tcp_fastopen_check_cookie
int tcp_fastopen_check_cookie(struct in_conninfo *inc, uint8_t *cookie, unsigned int len, uint64_t *latest_cookie)
Definition: tcp_fastopen.c:610
tcp_fastopen_decrement_counter
void tcp_fastopen_decrement_counter(unsigned int *counter)
Definition: tcp_fastopen.c:479
tcp_fastopen.h
V_tcp_fastopen_server_enable
#define V_tcp_fastopen_server_enable
Definition: tcp_fastopen.h:46
TCP_FASTOPEN_COOKIE_LEN
#define TCP_FASTOPEN_COOKIE_LEN
Definition: tcp_fastopen.h:36
tcp_fsm.h
TCPS_SYN_RECEIVED
#define TCPS_SYN_RECEIVED
Definition: tcp_fsm.h:50
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int tcp_mssopt(struct in_conninfo *inc)
Definition: tcp_input.c:3891
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void tcp_mss(struct tcpcb *tp, int offer)
Definition: tcp_input.c:3814
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int tcp_addoptions(struct tcpopt *to, u_char *optp)
Definition: tcp_output.c:1790
tcp_seq.h
SEQ_GEQ
#define SEQ_GEQ(a, b)
Definition: tcp_seq.h:45
SEQ_GT
#define SEQ_GT(a, b)
Definition: tcp_seq.h:44
tcp_ts_getticks
static __inline uint32_t tcp_ts_getticks(void)
Definition: tcp_seq.h:89
TSTMP_LT
#define TSTMP_LT(a, b)
Definition: tcp_seq.h:59
SEQ_LEQ
#define SEQ_LEQ(a, b)
Definition: tcp_seq.h:43
tcp_rcvseqinit
#define tcp_rcvseqinit(tp)
Definition: tcp_seq.h:68
TSTMP_GT
#define TSTMP_GT(a, b)
Definition: tcp_seq.h:60
tcp_sendseqinit
#define tcp_sendseqinit(tp)
Definition: tcp_seq.h:71
SEQ_LT
#define SEQ_LT(a, b)
Definition: tcp_seq.h:42
tcp_log_addrs
char * tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr, const void *ip6hdr)
Definition: tcp_subr.c:3901
tcp_state_change
void tcp_state_change(struct tcpcb *tp, int newstate)
Definition: tcp_subr.c:3999
tcp_new_ts_offset
uint32_t tcp_new_ts_offset(struct in_conninfo *inc)
Definition: tcp_subr.c:3220
find_and_ref_tcp_fb
struct tcp_function_block * find_and_ref_tcp_fb(struct tcp_function_block *blk)
Definition: tcp_subr.c:467
sysctl_net_inet_tcp_syncache_rexmtlimit_check
static int sysctl_net_inet_tcp_syncache_rexmtlimit_check(SYSCTL_HANDLER_ARGS)
Definition: tcp_syncache.c:202
syncache_timer
static void syncache_timer(void *)
Definition: tcp_syncache.c:473
syncache_drop
static void syncache_drop(struct syncache *, struct syncache_head *)
Definition: tcp_syncache.c:423
VNET_DEFINE
VNET_DEFINE(int, tcp_sc_rst_sock_fail)
SYSCTL_UINT
SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET|CTLFLAG_RDTUN, &VNET_NAME(tcp_syncache.bucket_limit), 0, "Per-bucket hash limit for syncache")
syncookie_mac
static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t, uint8_t *, uintptr_t)
Definition: tcp_syncache.c:2202
SCH_LOCK_ASSERT
#define SCH_LOCK_ASSERT(sch)
Definition: tcp_syncache.c:233
syncache_tfo_expand
static struct socket * syncache_tfo_expand(struct syncache *sc, struct socket *lso, struct mbuf *m, uint64_t response_cookie)
Definition: tcp_syncache.c:1352
V_tcp_syncookiesonly
#define V_tcp_syncookiesonly
Definition: tcp_syncache.c:115
SCH_UNLOCK
#define SCH_UNLOCK(sch)
Definition: tcp_syncache.c:232
syncookie_reseed
static void syncookie_reseed(void *)
Definition: tcp_syncache.c:2425
syncache_socket
static struct socket * syncache_socket(struct syncache *, struct socket *, struct mbuf *m)
Definition: tcp_syncache.c:793
SCH_LOCK
#define SCH_LOCK(sch)
Definition: tcp_syncache.c:231
syncache_add
struct socket * syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, struct inpcb *inp, struct socket *so, struct mbuf *m, void *tod, void *todctx, uint8_t iptos, uint16_t port)
Definition: tcp_syncache.c:1402
syncache_insert
static void syncache_insert(struct syncache *, struct syncache_head *)
Definition: tcp_syncache.c:376
syncache_timeout
static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
Definition: tcp_syncache.c:447
syncookie_generate
static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *)
Definition: tcp_syncache.c:2235
V_tcp_syncookies
#define V_tcp_syncookies
Definition: tcp_syncache.c:109
syncache_unpause
static void syncache_unpause(void *)
Definition: tcp_syncache.c:2525
syncache_chkrst
void syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m, uint16_t port)
Definition: tcp_syncache.c:615
SYSCTL_BOOL
SYSCTL_BOOL(_net_inet_tcp_syncache, OID_AUTO, see_other, CTLFLAG_VNET|CTLFLAG_RW, &VNET_NAME(tcp_syncache.see_other), 0, "All syncache(4) entries are visible, ignoring UID/GID, jail(2) " "and mac(4) checks")
tcp_sc_wstab
static int tcp_sc_wstab[]
Definition: tcp_syncache.c:2195
SYSCTL_INT
SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_VNET|CTLFLAG_RW, &VNET_NAME(tcp_syncookies), 0, "Use TCP SYN cookies if the syncache overflows")
V_tcp_syncache
#define V_tcp_syncache
Definition: tcp_syncache.c:175
__FBSDID
__FBSDID("$FreeBSD$")
syncache_cookiesonly
static bool syncache_cookiesonly(void)
Definition: tcp_syncache.c:558
TCP_SYNCACHE_HASHSIZE
#define TCP_SYNCACHE_HASHSIZE
Definition: tcp_syncache.c:171
syncache_init
void syncache_init(void)
Definition: tcp_syncache.c:254
SYNCACHE_MAXREXMTS
#define SYNCACHE_MAXREXMTS
Definition: tcp_syncache.c:168
tcp_sc_msstab
static int tcp_sc_msstab[]
Definition: tcp_syncache.c:2180
syncache_pcblist
int syncache_pcblist(struct sysctl_req *req)
Definition: tcp_syncache.c:2554
SYSCTL_UMA_CUR
SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET, &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache")
syncache_hashbucket
static struct syncache_head * syncache_hashbucket(struct in_conninfo *inc)
Definition: tcp_syncache.c:569
TCP_SYNCACHE_BUCKETLIMIT
#define TCP_SYNCACHE_BUCKETLIMIT
Definition: tcp_syncache.c:172
syncookie_lookup
static struct syncache * syncookie_lookup(struct in_conninfo *, struct syncache_head *, struct syncache *, struct tcphdr *, struct tcpopt *, struct socket *, uint16_t)
Definition: tcp_syncache.c:2290
SYSCTL_NODE
static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW|CTLFLAG_MPSAFE, 0, "TCP SYN cache")
syncache_pause
static void syncache_pause(struct in_conninfo *)
Definition: tcp_syncache.c:2452
syncache_respond
static int syncache_respond(struct syncache *, const struct mbuf *, int)
Definition: tcp_syncache.c:1819
syncache_free
static void syncache_free(struct syncache *)
Definition: tcp_syncache.c:239
VNET_DEFINE_STATIC
VNET_DEFINE_STATIC(int, tcp_syncookies)
syncache_expand
int syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, struct socket **lsop, struct mbuf *m, uint16_t port)
Definition: tcp_syncache.c:1090
MALLOC_DEFINE
static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache")
syncache_badack
void syncache_badack(struct in_conninfo *inc, uint16_t port)
Definition: tcp_syncache.c:732
syncache_lookup
static struct syncache * syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
Definition: tcp_syncache.c:591
syncache_unreach
void syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq, uint16_t port)
Definition: tcp_syncache.c:749
SYSCTL_PROC
SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_VNET|CTLTYPE_UINT|CTLFLAG_RW|CTLFLAG_NEEDGIANT, &VNET_NAME(tcp_syncache.rexmt_limit), 0, sysctl_net_inet_tcp_syncache_rexmtlimit_check, "UI", "Limit on SYN/ACK retransmissions")
V_functions_inherit_listen_socket_stack
#define V_functions_inherit_listen_socket_stack
Definition: tcp_syncache.c:121
tcp_syncache.h
SYNCOOKIE_LIFETIME
#define SYNCOOKIE_LIFETIME
Definition: tcp_syncache.h:112
SYNCOOKIE_SECRET_SIZE
#define SYNCOOKIE_SECRET_SIZE
Definition: tcp_syncache.h:111
SCF_ECN
#define SCF_ECN
Definition: tcp_syncache.h:95
SCF_SIGNATURE
#define SCF_SIGNATURE
Definition: tcp_syncache.h:92
SCF_SACK
#define SCF_SACK
Definition: tcp_syncache.h:93
SCF_NOOPT
#define SCF_NOOPT
Definition: tcp_syncache.h:87
SCF_TIMESTAMP
#define SCF_TIMESTAMP
Definition: tcp_syncache.h:89
SCF_WINSCALE
#define SCF_WINSCALE
Definition: tcp_syncache.h:88
TCP_SYNCACHE_MAX_BACKOFF
#define TCP_SYNCACHE_MAX_BACKOFF
Definition: tcp_syncache.h:122
SCF_UNREACH
#define SCF_UNREACH
Definition: tcp_syncache.h:91
TCP_SYNCACHE_PAUSE_TIME
#define TCP_SYNCACHE_PAUSE_TIME
Definition: tcp_syncache.h:121
tcp_rexmit_min
int tcp_rexmit_min
Definition: tcp_timer.c:132
tcp_backoff
int tcp_backoff[TCP_MAXRXTSHIFT+1]
Definition: tcp_timer.c:254
tcp_rexmit_initial
int tcp_rexmit_initial
Definition: tcp_timer.c:126
tcp_timer_activate
void tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
Definition: tcp_timer.c:854
tcp_timer.h
TCP_MAXRXTSHIFT
#define TCP_MAXRXTSHIFT
Definition: tcp_timer.h:117
TP_KEEPINIT
#define TP_KEEPINIT(tp)
Definition: tcp_timer.h:180
TT_KEEP
#define TT_KEEP
Definition: tcp_timer.h:164
TCPT_RANGESET
#define TCPT_RANGESET(tv, value, tvmin, tvmax)
Definition: tcp_timer.h:136
TCPTV_REXMTMAX
#define TCPTV_REXMTMAX
Definition: tcp_timer.h:113
tcp_var.h
TOF_MSS
#define TOF_MSS
Definition: tcp_var.h:579
TF_SIGNATURE
#define TF_SIGNATURE
Definition: tcp_var.h:519
TOF_SIGNATURE
#define TOF_SIGNATURE
Definition: tcp_var.h:583
tcp_get_flags
static uint16_t tcp_get_flags(const struct tcphdr *th)
Definition: tcp_var.h:1265
TF_FASTOPEN
#define TF_FASTOPEN
Definition: tcp_var.h:528
TOF_FASTOPEN
#define TOF_FASTOPEN
Definition: tcp_var.h:585
tcp_set_flags
static void tcp_set_flags(struct tcphdr *th, uint16_t flags)
Definition: tcp_var.h:1271
TF_RCVD_SCALE
#define TF_RCVD_SCALE
Definition: tcp_var.h:503
TCPSTATES_DEC
#define TCPSTATES_DEC(state)
Definition: tcp_var.h:858
V_tcp_do_rfc1323
#define V_tcp_do_rfc1323
Definition: tcp_var.h:1039
V_tcp_udp_tunneling_port
#define V_tcp_udp_tunneling_port
Definition: tcp_var.h:1067
V_tcp_insecure_rst
#define V_tcp_insecure_rst
Definition: tcp_var.h:1050
V_tcp_udp_tunneling_overhead
#define V_tcp_udp_tunneling_overhead
Definition: tcp_var.h:1066
sototcpcb
#define sototcpcb(so)
Definition: tcp_var.h:647
TOF_SACKPERM
#define TOF_SACKPERM
Definition: tcp_var.h:581
V_tcp_do_ecn
#define V_tcp_do_ecn
Definition: tcp_var.h:1038
TF_NOPUSH
#define TF_NOPUSH
Definition: tcp_var.h:509
V_tcp_ecn_maxretries
#define V_tcp_ecn_maxretries
Definition: tcp_var.h:1048
intotcpcb
#define intotcpcb(ip)
Definition: tcp_var.h:645
TF_REQ_SCALE
#define TF_REQ_SCALE
Definition: tcp_var.h:502
TF_NOOPT
#define TF_NOOPT
Definition: tcp_var.h:500
TOF_SCALE
#define TOF_SCALE
Definition: tcp_var.h:580
TCPSTATES_INC
#define TCPSTATES_INC(state)
Definition: tcp_var.h:857
TF_RCVD_TSTMP
#define TF_RCVD_TSTMP
Definition: tcp_var.h:505
V_tcp_tolerate_missing_ts
#define V_tcp_tolerate_missing_ts
Definition: tcp_var.h:1040
TF_NODELAY
#define TF_NODELAY
Definition: tcp_var.h:499
TCPSTAT_INC
#define TCPSTAT_INC(name)
Definition: tcp_var.h:842
IS_FASTOPEN
#define IS_FASTOPEN(t_flags)
Definition: tcp_var.h:543
TF_SACK_PERMIT
#define TF_SACK_PERMIT
Definition: tcp_var.h:506
V_path_mtu_discovery
#define V_path_mtu_discovery
Definition: tcp_var.h:1029
V_tcp_minmss
#define V_tcp_minmss
Definition: tcp_var.h:1054
V_tcbinfo
#define V_tcbinfo
Definition: tcp_var.h:1030
TF_REQ_TSTMP
#define TF_REQ_TSTMP
Definition: tcp_var.h:504
TOF_TS
#define TOF_TS
Definition: tcp_var.h:582
udp_var.h