1 /*-
2 * Copyright (c) 2001 McAfee, Inc.
3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG
4 * All rights reserved.
5 *
6 * This software was developed for the FreeBSD Project by Jonathan Lemon
7 * and McAfee Research, the Security Research Division of McAfee, Inc. under
8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
9 * DARPA CHATS research program.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
35
36 #include "opt_inet.h"
37 #include "opt_inet6.h"
38 #include "opt_ipsec.h"
39 #include "opt_pcbgroup.h"
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/kernel.h>
44 #include <sys/sysctl.h>
45 #include <sys/limits.h>
46 #include <sys/lock.h>
47 #include <sys/mutex.h>
48 #include <sys/malloc.h>
49 #include <sys/mbuf.h>
50 #include <sys/md5.h>
51 #include <sys/proc.h> /* for proc0 declaration */
52 #include <sys/random.h>
53 #include <sys/socket.h>
54 #include <sys/socketvar.h>
55 #include <sys/syslog.h>
56 #include <sys/ucred.h>
57
58 #include <vm/uma.h>
59
60 #include <net/if.h>
61 #include <net/route.h>
62 #include <net/vnet.h>
63
64 #include <netinet/in.h>
65 #include <netinet/in_systm.h>
66 #include <netinet/ip.h>
67 #include <netinet/in_var.h>
68 #include <netinet/in_pcb.h>
69 #include <netinet/ip_var.h>
70 #include <netinet/ip_options.h>
71 #ifdef INET6
72 #include <netinet/ip6.h>
73 #include <netinet/icmp6.h>
74 #include <netinet6/nd6.h>
75 #include <netinet6/ip6_var.h>
76 #include <netinet6/in6_pcb.h>
77 #endif
78 #include <netinet/tcp.h>
79 #include <netinet/tcp_fsm.h>
80 #include <netinet/tcp_seq.h>
81 #include <netinet/tcp_timer.h>
82 #include <netinet/tcp_var.h>
83 #include <netinet/tcp_syncache.h>
84 #ifdef INET6
85 #include <netinet6/tcp6_var.h>
86 #endif
87 #ifdef TCP_OFFLOAD
88 #include <netinet/toecore.h>
89 #endif
90
91 #ifdef IPSEC
92 #include <netipsec/ipsec.h>
93 #ifdef INET6
94 #include <netipsec/ipsec6.h>
95 #endif
96 #include <netipsec/key.h>
97 #endif /*IPSEC*/
98
99 #include <machine/in_cksum.h>
100
101 #include <security/mac/mac_framework.h>
102
103 static VNET_DEFINE(int, tcp_syncookies) = 1;
104 #define V_tcp_syncookies VNET(tcp_syncookies)
105 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
106 &VNET_NAME(tcp_syncookies), 0,
107 "Use TCP SYN cookies if the syncache overflows");
108
109 static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
110 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
111 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW,
112 &VNET_NAME(tcp_syncookiesonly), 0,
113 "Use only TCP SYN cookies");
114
115 #ifdef TCP_OFFLOAD
116 #define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL)
117 #endif
118
119 static void syncache_drop(struct syncache *, struct syncache_head *);
120 static void syncache_free(struct syncache *);
121 static void syncache_insert(struct syncache *, struct syncache_head *);
122 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
123 static int syncache_respond(struct syncache *);
124 static struct socket *syncache_socket(struct syncache *, struct socket *,
125 struct mbuf *m);
126 static int syncache_sysctl_count(SYSCTL_HANDLER_ARGS);
127 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
128 int docallout);
129 static void syncache_timer(void *);
130 static void syncookie_generate(struct syncache_head *, struct syncache *,
131 u_int32_t *);
132 static struct syncache
133 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
134 struct syncache *, struct tcpopt *, struct tcphdr *,
135 struct socket *);
136
137 /*
138 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
139 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
140 * the odds are that the user has given up attempting to connect by then.
141 */
142 #define SYNCACHE_MAXREXMTS 3
143
144 /* Arbitrary values */
145 #define TCP_SYNCACHE_HASHSIZE 512
146 #define TCP_SYNCACHE_BUCKETLIMIT 30
147
148 static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
149 #define V_tcp_syncache VNET(tcp_syncache)
150
151 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0,
152 "TCP SYN cache");
153
154 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
155 &VNET_NAME(tcp_syncache.bucket_limit), 0,
156 "Per-bucket hash limit for syncache");
157
158 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
159 &VNET_NAME(tcp_syncache.cache_limit), 0,
160 "Overall entry limit for syncache");
161
162 SYSCTL_VNET_PROC(_net_inet_tcp_syncache, OID_AUTO, count, (CTLTYPE_UINT|CTLFLAG_RD),
163 NULL, 0, &syncache_sysctl_count, "IU",
164 "Current number of entries in syncache");
165
166 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
167 &VNET_NAME(tcp_syncache.hashsize), 0,
168 "Size of TCP syncache hashtable");
169
170 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
171 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
172 "Limit on SYN/ACK retransmissions");
173
174 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
175 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
176 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
177 "Send reset on socket allocation failure");
178
179 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
180
181 #define SYNCACHE_HASH(inc, mask) \
182 ((V_tcp_syncache.hash_secret ^ \
183 (inc)->inc_faddr.s_addr ^ \
184 ((inc)->inc_faddr.s_addr >> 16) ^ \
185 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
186
187 #define SYNCACHE_HASH6(inc, mask) \
188 ((V_tcp_syncache.hash_secret ^ \
189 (inc)->inc6_faddr.s6_addr32[0] ^ \
190 (inc)->inc6_faddr.s6_addr32[3] ^ \
191 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
192
193 #define ENDPTS_EQ(a, b) ( \
194 (a)->ie_fport == (b)->ie_fport && \
195 (a)->ie_lport == (b)->ie_lport && \
196 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
197 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
198 )
199
200 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
201
202 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
203 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
204 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
205
206 /*
207 * Requires the syncache entry to be already removed from the bucket list.
208 */
209 static void
210 syncache_free(struct syncache *sc)
211 {
212
213 if (sc->sc_ipopts)
214 (void) m_free(sc->sc_ipopts);
215 if (sc->sc_cred)
216 crfree(sc->sc_cred);
217 #ifdef MAC
218 mac_syncache_destroy(&sc->sc_label);
219 #endif
220
221 uma_zfree(V_tcp_syncache.zone, sc);
222 }
223
224 void
225 syncache_init(void)
226 {
227 int i;
228
229 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
230 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
231 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
232 V_tcp_syncache.hash_secret = arc4random();
233
234 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
235 &V_tcp_syncache.hashsize);
236 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
237 &V_tcp_syncache.bucket_limit);
238 if (!powerof2(V_tcp_syncache.hashsize) ||
239 V_tcp_syncache.hashsize == 0) {
240 printf("WARNING: syncache hash size is not a power of 2.\n");
241 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
242 }
243 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
244
245 /* Set limits. */
246 V_tcp_syncache.cache_limit =
247 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
248 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
249 &V_tcp_syncache.cache_limit);
250
251 /* Allocate the hash table. */
252 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
253 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
254
255 /* Initialize the hash buckets. */
256 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
257 #ifdef VIMAGE
258 V_tcp_syncache.hashbase[i].sch_vnet = curvnet;
259 #endif
260 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
261 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
262 NULL, MTX_DEF);
263 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
264 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
265 V_tcp_syncache.hashbase[i].sch_length = 0;
266 }
267
268 /* Create the syncache entry zone. */
269 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
270 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
271 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone,
272 V_tcp_syncache.cache_limit);
273 }
274
275 #ifdef VIMAGE
276 void
277 syncache_destroy(void)
278 {
279 struct syncache_head *sch;
280 struct syncache *sc, *nsc;
281 int i;
282
283 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
284 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
285
286 sch = &V_tcp_syncache.hashbase[i];
287 callout_drain(&sch->sch_timer);
288
289 SCH_LOCK(sch);
290 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
291 syncache_drop(sc, sch);
292 SCH_UNLOCK(sch);
293 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
294 ("%s: sch->sch_bucket not empty", __func__));
295 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
296 __func__, sch->sch_length));
297 mtx_destroy(&sch->sch_mtx);
298 }
299
300 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0,
301 ("%s: cache_count not 0", __func__));
302
303 /* Free the allocated global resources. */
304 uma_zdestroy(V_tcp_syncache.zone);
305 free(V_tcp_syncache.hashbase, M_SYNCACHE);
306 }
307 #endif
308
309 static int
310 syncache_sysctl_count(SYSCTL_HANDLER_ARGS)
311 {
312 int count;
313
314 count = uma_zone_get_cur(V_tcp_syncache.zone);
315 return (sysctl_handle_int(oidp, &count, 0, req));
316 }
317
318 /*
319 * Inserts a syncache entry into the specified bucket row.
320 * Locks and unlocks the syncache_head autonomously.
321 */
322 static void
323 syncache_insert(struct syncache *sc, struct syncache_head *sch)
324 {
325 struct syncache *sc2;
326
327 SCH_LOCK(sch);
328
329 /*
330 * Make sure that we don't overflow the per-bucket limit.
331 * If the bucket is full, toss the oldest element.
332 */
333 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
334 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
335 ("sch->sch_length incorrect"));
336 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
337 syncache_drop(sc2, sch);
338 TCPSTAT_INC(tcps_sc_bucketoverflow);
339 }
340
341 /* Put it into the bucket. */
342 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
343 sch->sch_length++;
344
345 #ifdef TCP_OFFLOAD
346 if (ADDED_BY_TOE(sc)) {
347 struct toedev *tod = sc->sc_tod;
348
349 tod->tod_syncache_added(tod, sc->sc_todctx);
350 }
351 #endif
352
353 /* Reinitialize the bucket row's timer. */
354 if (sch->sch_length == 1)
355 sch->sch_nextc = ticks + INT_MAX;
356 syncache_timeout(sc, sch, 1);
357
358 SCH_UNLOCK(sch);
359
360 TCPSTAT_INC(tcps_sc_added);
361 }
362
363 /*
364 * Remove and free entry from syncache bucket row.
365 * Expects locked syncache head.
366 */
367 static void
368 syncache_drop(struct syncache *sc, struct syncache_head *sch)
369 {
370
371 SCH_LOCK_ASSERT(sch);
372
373 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
374 sch->sch_length--;
375
376 #ifdef TCP_OFFLOAD
377 if (ADDED_BY_TOE(sc)) {
378 struct toedev *tod = sc->sc_tod;
379
380 tod->tod_syncache_removed(tod, sc->sc_todctx);
381 }
382 #endif
383
384 syncache_free(sc);
385 }
386
387 /*
388 * Engage/reengage time on bucket row.
389 */
390 static void
391 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
392 {
393 sc->sc_rxttime = ticks +
394 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
395 sc->sc_rxmits++;
396 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
397 sch->sch_nextc = sc->sc_rxttime;
398 if (docallout)
399 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
400 syncache_timer, (void *)sch);
401 }
402 }
403
404 /*
405 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
406 * If we have retransmitted an entry the maximum number of times, expire it.
407 * One separate timer for each bucket row.
408 */
409 static void
410 syncache_timer(void *xsch)
411 {
412 struct syncache_head *sch = (struct syncache_head *)xsch;
413 struct syncache *sc, *nsc;
414 int tick = ticks;
415 char *s;
416
417 CURVNET_SET(sch->sch_vnet);
418
419 /* NB: syncache_head has already been locked by the callout. */
420 SCH_LOCK_ASSERT(sch);
421
422 /*
423 * In the following cycle we may remove some entries and/or
424 * advance some timeouts, so re-initialize the bucket timer.
425 */
426 sch->sch_nextc = tick + INT_MAX;
427
428 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
429 /*
430 * We do not check if the listen socket still exists
431 * and accept the case where the listen socket may be
432 * gone by the time we resend the SYN/ACK. We do
433 * not expect this to happens often. If it does,
434 * then the RST will be sent by the time the remote
435 * host does the SYN/ACK->ACK.
436 */
437 if (TSTMP_GT(sc->sc_rxttime, tick)) {
438 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
439 sch->sch_nextc = sc->sc_rxttime;
440 continue;
441 }
442 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
443 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
444 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
445 "giving up and removing syncache entry\n",
446 s, __func__);
447 free(s, M_TCPLOG);
448 }
449 syncache_drop(sc, sch);
450 TCPSTAT_INC(tcps_sc_stale);
451 continue;
452 }
453 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
454 log(LOG_DEBUG, "%s; %s: Response timeout, "
455 "retransmitting (%u) SYN|ACK\n",
456 s, __func__, sc->sc_rxmits);
457 free(s, M_TCPLOG);
458 }
459
460 (void) syncache_respond(sc);
461 TCPSTAT_INC(tcps_sc_retransmitted);
462 syncache_timeout(sc, sch, 0);
463 }
464 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
465 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
466 syncache_timer, (void *)(sch));
467 CURVNET_RESTORE();
468 }
469
470 /*
471 * Find an entry in the syncache.
472 * Returns always with locked syncache_head plus a matching entry or NULL.
473 */
474 struct syncache *
475 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
476 {
477 struct syncache *sc;
478 struct syncache_head *sch;
479
480 #ifdef INET6
481 if (inc->inc_flags & INC_ISIPV6) {
482 sch = &V_tcp_syncache.hashbase[
483 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)];
484 *schp = sch;
485
486 SCH_LOCK(sch);
487
488 /* Circle through bucket row to find matching entry. */
489 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
490 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
491 return (sc);
492 }
493 } else
494 #endif
495 {
496 sch = &V_tcp_syncache.hashbase[
497 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)];
498 *schp = sch;
499
500 SCH_LOCK(sch);
501
502 /* Circle through bucket row to find matching entry. */
503 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
504 #ifdef INET6
505 if (sc->sc_inc.inc_flags & INC_ISIPV6)
506 continue;
507 #endif
508 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
509 return (sc);
510 }
511 }
512 SCH_LOCK_ASSERT(*schp);
513 return (NULL); /* always returns with locked sch */
514 }
515
516 /*
517 * This function is called when we get a RST for a
518 * non-existent connection, so that we can see if the
519 * connection is in the syn cache. If it is, zap it.
520 */
521 void
522 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
523 {
524 struct syncache *sc;
525 struct syncache_head *sch;
526 char *s = NULL;
527
528 sc = syncache_lookup(inc, &sch); /* returns locked sch */
529 SCH_LOCK_ASSERT(sch);
530
531 /*
532 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
533 * See RFC 793 page 65, section SEGMENT ARRIVES.
534 */
535 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
536 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
537 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
538 "FIN flag set, segment ignored\n", s, __func__);
539 TCPSTAT_INC(tcps_badrst);
540 goto done;
541 }
542
543 /*
544 * No corresponding connection was found in syncache.
545 * If syncookies are enabled and possibly exclusively
546 * used, or we are under memory pressure, a valid RST
547 * may not find a syncache entry. In that case we're
548 * done and no SYN|ACK retransmissions will happen.
549 * Otherwise the RST was misdirected or spoofed.
550 */
551 if (sc == NULL) {
552 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
553 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
554 "syncache entry (possibly syncookie only), "
555 "segment ignored\n", s, __func__);
556 TCPSTAT_INC(tcps_badrst);
557 goto done;
558 }
559
560 /*
561 * If the RST bit is set, check the sequence number to see
562 * if this is a valid reset segment.
563 * RFC 793 page 37:
564 * In all states except SYN-SENT, all reset (RST) segments
565 * are validated by checking their SEQ-fields. A reset is
566 * valid if its sequence number is in the window.
567 *
568 * The sequence number in the reset segment is normally an
569 * echo of our outgoing acknowlegement numbers, but some hosts
570 * send a reset with the sequence number at the rightmost edge
571 * of our receive window, and we have to handle this case.
572 */
573 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
574 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
575 syncache_drop(sc, sch);
576 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
577 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
578 "connection attempt aborted by remote endpoint\n",
579 s, __func__);
580 TCPSTAT_INC(tcps_sc_reset);
581 } else {
582 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
583 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
584 "IRS %u (+WND %u), segment ignored\n",
585 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
586 TCPSTAT_INC(tcps_badrst);
587 }
588
589 done:
590 if (s != NULL)
591 free(s, M_TCPLOG);
592 SCH_UNLOCK(sch);
593 }
594
595 void
596 syncache_badack(struct in_conninfo *inc)
597 {
598 struct syncache *sc;
599 struct syncache_head *sch;
600
601 sc = syncache_lookup(inc, &sch); /* returns locked sch */
602 SCH_LOCK_ASSERT(sch);
603 if (sc != NULL) {
604 syncache_drop(sc, sch);
605 TCPSTAT_INC(tcps_sc_badack);
606 }
607 SCH_UNLOCK(sch);
608 }
609
610 void
611 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
612 {
613 struct syncache *sc;
614 struct syncache_head *sch;
615
616 sc = syncache_lookup(inc, &sch); /* returns locked sch */
617 SCH_LOCK_ASSERT(sch);
618 if (sc == NULL)
619 goto done;
620
621 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
622 if (ntohl(th->th_seq) != sc->sc_iss)
623 goto done;
624
625 /*
626 * If we've rertransmitted 3 times and this is our second error,
627 * we remove the entry. Otherwise, we allow it to continue on.
628 * This prevents us from incorrectly nuking an entry during a
629 * spurious network outage.
630 *
631 * See tcp_notify().
632 */
633 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
634 sc->sc_flags |= SCF_UNREACH;
635 goto done;
636 }
637 syncache_drop(sc, sch);
638 TCPSTAT_INC(tcps_sc_unreach);
639 done:
640 SCH_UNLOCK(sch);
641 }
642
643 /*
644 * Build a new TCP socket structure from a syncache entry.
645 */
646 static struct socket *
647 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
648 {
649 struct inpcb *inp = NULL;
650 struct socket *so;
651 struct tcpcb *tp;
652 int error;
653 char *s;
654
655 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
656
657 /*
658 * Ok, create the full blown connection, and set things up
659 * as they would have been set up if we had created the
660 * connection when the SYN arrived. If we can't create
661 * the connection, abort it.
662 */
663 so = sonewconn(lso, SS_ISCONNECTED);
664 if (so == NULL) {
665 /*
666 * Drop the connection; we will either send a RST or
667 * have the peer retransmit its SYN again after its
668 * RTO and try again.
669 */
670 TCPSTAT_INC(tcps_listendrop);
671 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
672 log(LOG_DEBUG, "%s; %s: Socket create failed "
673 "due to limits or memory shortage\n",
674 s, __func__);
675 free(s, M_TCPLOG);
676 }
677 goto abort2;
678 }
679 #ifdef MAC
680 mac_socketpeer_set_from_mbuf(m, so);
681 #endif
682
683 inp = sotoinpcb(so);
684 inp->inp_inc.inc_fibnum = so->so_fibnum;
685 INP_WLOCK(inp);
686 INP_HASH_WLOCK(&V_tcbinfo);
687
688 /* Insert new socket into PCB hash list. */
689 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
690 #ifdef INET6
691 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
692 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
693 } else {
694 inp->inp_vflag &= ~INP_IPV6;
695 inp->inp_vflag |= INP_IPV4;
696 #endif
697 inp->inp_laddr = sc->sc_inc.inc_laddr;
698 #ifdef INET6
699 }
700 #endif
701
702 /*
703 * Install in the reservation hash table for now, but don't yet
704 * install a connection group since the full 4-tuple isn't yet
705 * configured.
706 */
707 inp->inp_lport = sc->sc_inc.inc_lport;
708 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) {
709 /*
710 * Undo the assignments above if we failed to
711 * put the PCB on the hash lists.
712 */
713 #ifdef INET6
714 if (sc->sc_inc.inc_flags & INC_ISIPV6)
715 inp->in6p_laddr = in6addr_any;
716 else
717 #endif
718 inp->inp_laddr.s_addr = INADDR_ANY;
719 inp->inp_lport = 0;
720 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
721 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
722 "with error %i\n",
723 s, __func__, error);
724 free(s, M_TCPLOG);
725 }
726 INP_HASH_WUNLOCK(&V_tcbinfo);
727 goto abort;
728 }
729 #ifdef IPSEC
730 /* Copy old policy into new socket's. */
731 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
732 printf("syncache_socket: could not copy policy\n");
733 #endif
734 #ifdef INET6
735 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
736 struct inpcb *oinp = sotoinpcb(lso);
737 struct in6_addr laddr6;
738 struct sockaddr_in6 sin6;
739 /*
740 * Inherit socket options from the listening socket.
741 * Note that in6p_inputopts are not (and should not be)
742 * copied, since it stores previously received options and is
743 * used to detect if each new option is different than the
744 * previous one and hence should be passed to a user.
745 * If we copied in6p_inputopts, a user would not be able to
746 * receive options just after calling the accept system call.
747 */
748 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
749 if (oinp->in6p_outputopts)
750 inp->in6p_outputopts =
751 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
752
753 sin6.sin6_family = AF_INET6;
754 sin6.sin6_len = sizeof(sin6);
755 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
756 sin6.sin6_port = sc->sc_inc.inc_fport;
757 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
758 laddr6 = inp->in6p_laddr;
759 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
760 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
761 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
762 thread0.td_ucred, m)) != 0) {
763 inp->in6p_laddr = laddr6;
764 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
765 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
766 "with error %i\n",
767 s, __func__, error);
768 free(s, M_TCPLOG);
769 }
770 INP_HASH_WUNLOCK(&V_tcbinfo);
771 goto abort;
772 }
773 /* Override flowlabel from in6_pcbconnect. */
774 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
775 inp->inp_flow |= sc->sc_flowlabel;
776 }
777 #endif /* INET6 */
778 #if defined(INET) && defined(INET6)
779 else
780 #endif
781 #ifdef INET
782 {
783 struct in_addr laddr;
784 struct sockaddr_in sin;
785
786 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
787
788 if (inp->inp_options == NULL) {
789 inp->inp_options = sc->sc_ipopts;
790 sc->sc_ipopts = NULL;
791 }
792
793 sin.sin_family = AF_INET;
794 sin.sin_len = sizeof(sin);
795 sin.sin_addr = sc->sc_inc.inc_faddr;
796 sin.sin_port = sc->sc_inc.inc_fport;
797 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
798 laddr = inp->inp_laddr;
799 if (inp->inp_laddr.s_addr == INADDR_ANY)
800 inp->inp_laddr = sc->sc_inc.inc_laddr;
801 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin,
802 thread0.td_ucred, m)) != 0) {
803 inp->inp_laddr = laddr;
804 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
805 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
806 "with error %i\n",
807 s, __func__, error);
808 free(s, M_TCPLOG);
809 }
810 INP_HASH_WUNLOCK(&V_tcbinfo);
811 goto abort;
812 }
813 }
814 #endif /* INET */
815 INP_HASH_WUNLOCK(&V_tcbinfo);
816 tp = intotcpcb(inp);
817 tp->t_state = TCPS_SYN_RECEIVED;
818 tp->iss = sc->sc_iss;
819 tp->irs = sc->sc_irs;
820 tcp_rcvseqinit(tp);
821 tcp_sendseqinit(tp);
822 tp->snd_wl1 = sc->sc_irs;
823 tp->snd_max = tp->iss + 1;
824 tp->snd_nxt = tp->iss + 1;
825 tp->rcv_up = sc->sc_irs + 1;
826 tp->rcv_wnd = sc->sc_wnd;
827 tp->rcv_adv += tp->rcv_wnd;
828 tp->last_ack_sent = tp->rcv_nxt;
829
830 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
831 if (sc->sc_flags & SCF_NOOPT)
832 tp->t_flags |= TF_NOOPT;
833 else {
834 if (sc->sc_flags & SCF_WINSCALE) {
835 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
836 tp->snd_scale = sc->sc_requested_s_scale;
837 tp->request_r_scale = sc->sc_requested_r_scale;
838 }
839 if (sc->sc_flags & SCF_TIMESTAMP) {
840 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
841 tp->ts_recent = sc->sc_tsreflect;
842 tp->ts_recent_age = tcp_ts_getticks();
843 tp->ts_offset = sc->sc_tsoff;
844 }
845 #ifdef TCP_SIGNATURE
846 if (sc->sc_flags & SCF_SIGNATURE)
847 tp->t_flags |= TF_SIGNATURE;
848 #endif
849 if (sc->sc_flags & SCF_SACK)
850 tp->t_flags |= TF_SACK_PERMIT;
851 }
852
853 if (sc->sc_flags & SCF_ECN)
854 tp->t_flags |= TF_ECN_PERMIT;
855
856 /*
857 * Set up MSS and get cached values from tcp_hostcache.
858 * This might overwrite some of the defaults we just set.
859 */
860 tcp_mss(tp, sc->sc_peer_mss);
861
862 /*
863 * If the SYN,ACK was retransmitted, indicate that CWND to be
864 * limited to one segment in cc_conn_init().
865 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
866 */
867 if (sc->sc_rxmits > 1)
868 tp->snd_cwnd = 1;
869
870 #ifdef TCP_OFFLOAD
871 /*
872 * Allow a TOE driver to install its hooks. Note that we hold the
873 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a
874 * new connection before the TOE driver has done its thing.
875 */
876 if (ADDED_BY_TOE(sc)) {
877 struct toedev *tod = sc->sc_tod;
878
879 tod->tod_offload_socket(tod, sc->sc_todctx, so);
880 }
881 #endif
882 /*
883 * Copy and activate timers.
884 */
885 tp->t_keepinit = sototcpcb(lso)->t_keepinit;
886 tp->t_keepidle = sototcpcb(lso)->t_keepidle;
887 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
888 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
889 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
890
891 INP_WUNLOCK(inp);
892
893 TCPSTAT_INC(tcps_accepts);
894 return (so);
895
896 abort:
897 INP_WUNLOCK(inp);
898 abort2:
899 if (so != NULL)
900 soabort(so);
901 return (NULL);
902 }
903
904 /*
905 * This function gets called when we receive an ACK for a
906 * socket in the LISTEN state. We look up the connection
907 * in the syncache, and if its there, we pull it out of
908 * the cache and turn it into a full-blown connection in
909 * the SYN-RECEIVED state.
910 */
911 int
912 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
913 struct socket **lsop, struct mbuf *m)
914 {
915 struct syncache *sc;
916 struct syncache_head *sch;
917 struct syncache scs;
918 char *s;
919
920 /*
921 * Global TCP locks are held because we manipulate the PCB lists
922 * and create a new socket.
923 */
924 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
925 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
926 ("%s: can handle only ACK", __func__));
927
928 sc = syncache_lookup(inc, &sch); /* returns locked sch */
929 SCH_LOCK_ASSERT(sch);
930 if (sc == NULL) {
931 /*
932 * There is no syncache entry, so see if this ACK is
933 * a returning syncookie. To do this, first:
934 * A. See if this socket has had a syncache entry dropped in
935 * the past. We don't want to accept a bogus syncookie
936 * if we've never received a SYN.
937 * B. check that the syncookie is valid. If it is, then
938 * cobble up a fake syncache entry, and return.
939 */
940 if (!V_tcp_syncookies) {
941 SCH_UNLOCK(sch);
942 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
943 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
944 "segment rejected (syncookies disabled)\n",
945 s, __func__);
946 goto failed;
947 }
948 bzero(&scs, sizeof(scs));
949 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop);
950 SCH_UNLOCK(sch);
951 if (sc == NULL) {
952 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
953 log(LOG_DEBUG, "%s; %s: Segment failed "
954 "SYNCOOKIE authentication, segment rejected "
955 "(probably spoofed)\n", s, __func__);
956 goto failed;
957 }
958 } else {
959 /* Pull out the entry to unlock the bucket row. */
960 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
961 sch->sch_length--;
962 #ifdef TCP_OFFLOAD
963 if (ADDED_BY_TOE(sc)) {
964 struct toedev *tod = sc->sc_tod;
965
966 tod->tod_syncache_removed(tod, sc->sc_todctx);
967 }
968 #endif
969 SCH_UNLOCK(sch);
970 }
971
972 /*
973 * Segment validation:
974 * ACK must match our initial sequence number + 1 (the SYN|ACK).
975 */
976 if (th->th_ack != sc->sc_iss + 1) {
977 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
978 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
979 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
980 goto failed;
981 }
982
983 /*
984 * The SEQ must fall in the window starting at the received
985 * initial receive sequence number + 1 (the SYN).
986 */
987 if (SEQ_LEQ(th->th_seq, sc->sc_irs) ||
988 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
989 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
990 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
991 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
992 goto failed;
993 }
994
995 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
996 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
997 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
998 "segment rejected\n", s, __func__);
999 goto failed;
1000 }
1001 /*
1002 * If timestamps were negotiated the reflected timestamp
1003 * must be equal to what we actually sent in the SYN|ACK.
1004 */
1005 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts) {
1006 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1007 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
1008 "segment rejected\n",
1009 s, __func__, to->to_tsecr, sc->sc_ts);
1010 goto failed;
1011 }
1012
1013 *lsop = syncache_socket(sc, *lsop, m);
1014
1015 if (*lsop == NULL)
1016 TCPSTAT_INC(tcps_sc_aborted);
1017 else
1018 TCPSTAT_INC(tcps_sc_completed);
1019
1020 /* how do we find the inp for the new socket? */
1021 if (sc != &scs)
1022 syncache_free(sc);
1023 return (1);
1024 failed:
1025 if (sc != NULL && sc != &scs)
1026 syncache_free(sc);
1027 if (s != NULL)
1028 free(s, M_TCPLOG);
1029 *lsop = NULL;
1030 return (0);
1031 }
1032
1033 /*
1034 * Given a LISTEN socket and an inbound SYN request, add
1035 * this to the syn cache, and send back a segment:
1036 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1037 * to the source.
1038 *
1039 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1040 * Doing so would require that we hold onto the data and deliver it
1041 * to the application. However, if we are the target of a SYN-flood
1042 * DoS attack, an attacker could send data which would eventually
1043 * consume all available buffer space if it were ACKed. By not ACKing
1044 * the data, we avoid this DoS scenario.
1045 */
1046 static void
1047 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1048 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod,
1049 void *todctx)
1050 {
1051 struct tcpcb *tp;
1052 struct socket *so;
1053 struct syncache *sc = NULL;
1054 struct syncache_head *sch;
1055 struct mbuf *ipopts = NULL;
1056 u_int32_t flowtmp;
1057 u_int ltflags;
1058 int win, sb_hiwat, ip_ttl, ip_tos;
1059 char *s;
1060 #ifdef INET6
1061 int autoflowlabel = 0;
1062 #endif
1063 #ifdef MAC
1064 struct label *maclabel;
1065 #endif
1066 struct syncache scs;
1067 struct ucred *cred;
1068
1069 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1070 INP_WLOCK_ASSERT(inp); /* listen socket */
1071 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1072 ("%s: unexpected tcp flags", __func__));
1073
1074 /*
1075 * Combine all so/tp operations very early to drop the INP lock as
1076 * soon as possible.
1077 */
1078 so = *lsop;
1079 tp = sototcpcb(so);
1080 cred = crhold(so->so_cred);
1081
1082 #ifdef INET6
1083 if ((inc->inc_flags & INC_ISIPV6) &&
1084 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1085 autoflowlabel = 1;
1086 #endif
1087 ip_ttl = inp->inp_ip_ttl;
1088 ip_tos = inp->inp_ip_tos;
1089 win = sbspace(&so->so_rcv);
1090 sb_hiwat = so->so_rcv.sb_hiwat;
1091 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1092
1093 /* By the time we drop the lock these should no longer be used. */
1094 so = NULL;
1095 tp = NULL;
1096
1097 #ifdef MAC
1098 if (mac_syncache_init(&maclabel) != 0) {
1099 INP_WUNLOCK(inp);
1100 INP_INFO_WUNLOCK(&V_tcbinfo);
1101 goto done;
1102 } else
1103 mac_syncache_create(maclabel, inp);
1104 #endif
1105 INP_WUNLOCK(inp);
1106 INP_INFO_WUNLOCK(&V_tcbinfo);
1107
1108 /*
1109 * Remember the IP options, if any.
1110 */
1111 #ifdef INET6
1112 if (!(inc->inc_flags & INC_ISIPV6))
1113 #endif
1114 #ifdef INET
1115 ipopts = (m) ? ip_srcroute(m) : NULL;
1116 #else
1117 ipopts = NULL;
1118 #endif
1119
1120 /*
1121 * See if we already have an entry for this connection.
1122 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1123 *
1124 * XXX: should the syncache be re-initialized with the contents
1125 * of the new SYN here (which may have different options?)
1126 *
1127 * XXX: We do not check the sequence number to see if this is a
1128 * real retransmit or a new connection attempt. The question is
1129 * how to handle such a case; either ignore it as spoofed, or
1130 * drop the current entry and create a new one?
1131 */
1132 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1133 SCH_LOCK_ASSERT(sch);
1134 if (sc != NULL) {
1135 TCPSTAT_INC(tcps_sc_dupsyn);
1136 if (ipopts) {
1137 /*
1138 * If we were remembering a previous source route,
1139 * forget it and use the new one we've been given.
1140 */
1141 if (sc->sc_ipopts)
1142 (void) m_free(sc->sc_ipopts);
1143 sc->sc_ipopts = ipopts;
1144 }
1145 /*
1146 * Update timestamp if present.
1147 */
1148 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1149 sc->sc_tsreflect = to->to_tsval;
1150 else
1151 sc->sc_flags &= ~SCF_TIMESTAMP;
1152 #ifdef MAC
1153 /*
1154 * Since we have already unconditionally allocated label
1155 * storage, free it up. The syncache entry will already
1156 * have an initialized label we can use.
1157 */
1158 mac_syncache_destroy(&maclabel);
1159 #endif
1160 /* Retransmit SYN|ACK and reset retransmit count. */
1161 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1162 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1163 "resetting timer and retransmitting SYN|ACK\n",
1164 s, __func__);
1165 free(s, M_TCPLOG);
1166 }
1167 if (syncache_respond(sc) == 0) {
1168 sc->sc_rxmits = 0;
1169 syncache_timeout(sc, sch, 1);
1170 TCPSTAT_INC(tcps_sndacks);
1171 TCPSTAT_INC(tcps_sndtotal);
1172 }
1173 SCH_UNLOCK(sch);
1174 goto done;
1175 }
1176
1177 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1178 if (sc == NULL) {
1179 /*
1180 * The zone allocator couldn't provide more entries.
1181 * Treat this as if the cache was full; drop the oldest
1182 * entry and insert the new one.
1183 */
1184 TCPSTAT_INC(tcps_sc_zonefail);
1185 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1186 syncache_drop(sc, sch);
1187 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1188 if (sc == NULL) {
1189 if (V_tcp_syncookies) {
1190 bzero(&scs, sizeof(scs));
1191 sc = &scs;
1192 } else {
1193 SCH_UNLOCK(sch);
1194 if (ipopts)
1195 (void) m_free(ipopts);
1196 goto done;
1197 }
1198 }
1199 }
1200
1201 /*
1202 * Fill in the syncache values.
1203 */
1204 #ifdef MAC
1205 sc->sc_label = maclabel;
1206 #endif
1207 sc->sc_cred = cred;
1208 cred = NULL;
1209 sc->sc_ipopts = ipopts;
1210 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1211 #ifdef INET6
1212 if (!(inc->inc_flags & INC_ISIPV6))
1213 #endif
1214 {
1215 sc->sc_ip_tos = ip_tos;
1216 sc->sc_ip_ttl = ip_ttl;
1217 }
1218 #ifdef TCP_OFFLOAD
1219 sc->sc_tod = tod;
1220 sc->sc_todctx = todctx;
1221 #endif
1222 sc->sc_irs = th->th_seq;
1223 sc->sc_iss = arc4random();
1224 sc->sc_flags = 0;
1225 sc->sc_flowlabel = 0;
1226
1227 /*
1228 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1229 * win was derived from socket earlier in the function.
1230 */
1231 win = imax(win, 0);
1232 win = imin(win, TCP_MAXWIN);
1233 sc->sc_wnd = win;
1234
1235 if (V_tcp_do_rfc1323) {
1236 /*
1237 * A timestamp received in a SYN makes
1238 * it ok to send timestamp requests and replies.
1239 */
1240 if (to->to_flags & TOF_TS) {
1241 sc->sc_tsreflect = to->to_tsval;
1242 sc->sc_ts = tcp_ts_getticks();
1243 sc->sc_flags |= SCF_TIMESTAMP;
1244 }
1245 if (to->to_flags & TOF_SCALE) {
1246 int wscale = 0;
1247
1248 /*
1249 * Pick the smallest possible scaling factor that
1250 * will still allow us to scale up to sb_max, aka
1251 * kern.ipc.maxsockbuf.
1252 *
1253 * We do this because there are broken firewalls that
1254 * will corrupt the window scale option, leading to
1255 * the other endpoint believing that our advertised
1256 * window is unscaled. At scale factors larger than
1257 * 5 the unscaled window will drop below 1500 bytes,
1258 * leading to serious problems when traversing these
1259 * broken firewalls.
1260 *
1261 * With the default maxsockbuf of 256K, a scale factor
1262 * of 3 will be chosen by this algorithm. Those who
1263 * choose a larger maxsockbuf should watch out
1264 * for the compatiblity problems mentioned above.
1265 *
1266 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1267 * or <SYN,ACK>) segment itself is never scaled.
1268 */
1269 while (wscale < TCP_MAX_WINSHIFT &&
1270 (TCP_MAXWIN << wscale) < sb_max)
1271 wscale++;
1272 sc->sc_requested_r_scale = wscale;
1273 sc->sc_requested_s_scale = to->to_wscale;
1274 sc->sc_flags |= SCF_WINSCALE;
1275 }
1276 }
1277 #ifdef TCP_SIGNATURE
1278 /*
1279 * If listening socket requested TCP digests, and received SYN
1280 * contains the option, flag this in the syncache so that
1281 * syncache_respond() will do the right thing with the SYN+ACK.
1282 * XXX: Currently we always record the option by default and will
1283 * attempt to use it in syncache_respond().
1284 */
1285 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE)
1286 sc->sc_flags |= SCF_SIGNATURE;
1287 #endif
1288 if (to->to_flags & TOF_SACKPERM)
1289 sc->sc_flags |= SCF_SACK;
1290 if (to->to_flags & TOF_MSS)
1291 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1292 if (ltflags & TF_NOOPT)
1293 sc->sc_flags |= SCF_NOOPT;
1294 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1295 sc->sc_flags |= SCF_ECN;
1296
1297 if (V_tcp_syncookies) {
1298 syncookie_generate(sch, sc, &flowtmp);
1299 #ifdef INET6
1300 if (autoflowlabel)
1301 sc->sc_flowlabel = flowtmp;
1302 #endif
1303 } else {
1304 #ifdef INET6
1305 if (autoflowlabel)
1306 sc->sc_flowlabel =
1307 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
1308 #endif
1309 }
1310 SCH_UNLOCK(sch);
1311
1312 /*
1313 * Do a standard 3-way handshake.
1314 */
1315 if (syncache_respond(sc) == 0) {
1316 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1317 syncache_free(sc);
1318 else if (sc != &scs)
1319 syncache_insert(sc, sch); /* locks and unlocks sch */
1320 TCPSTAT_INC(tcps_sndacks);
1321 TCPSTAT_INC(tcps_sndtotal);
1322 } else {
1323 if (sc != &scs)
1324 syncache_free(sc);
1325 TCPSTAT_INC(tcps_sc_dropped);
1326 }
1327
1328 done:
1329 if (cred != NULL)
1330 crfree(cred);
1331 #ifdef MAC
1332 if (sc == &scs)
1333 mac_syncache_destroy(&maclabel);
1334 #endif
1335 if (m) {
1336
1337 *lsop = NULL;
1338 m_freem(m);
1339 }
1340 }
1341
1342 static int
1343 syncache_respond(struct syncache *sc)
1344 {
1345 struct ip *ip = NULL;
1346 struct mbuf *m;
1347 struct tcphdr *th = NULL;
1348 int optlen, error = 0; /* Make compiler happy */
1349 u_int16_t hlen, tlen, mssopt;
1350 struct tcpopt to;
1351 #ifdef INET6
1352 struct ip6_hdr *ip6 = NULL;
1353 #endif
1354
1355 hlen =
1356 #ifdef INET6
1357 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1358 #endif
1359 sizeof(struct ip);
1360 tlen = hlen + sizeof(struct tcphdr);
1361
1362 /* Determine MSS we advertize to other end of connection. */
1363 mssopt = tcp_mssopt(&sc->sc_inc);
1364 if (sc->sc_peer_mss)
1365 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss);
1366
1367 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1368 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1369 ("syncache: mbuf too small"));
1370
1371 /* Create the IP+TCP header from scratch. */
1372 m = m_gethdr(M_DONTWAIT, MT_DATA);
1373 if (m == NULL)
1374 return (ENOBUFS);
1375 #ifdef MAC
1376 mac_syncache_create_mbuf(sc->sc_label, m);
1377 #endif
1378 m->m_data += max_linkhdr;
1379 m->m_len = tlen;
1380 m->m_pkthdr.len = tlen;
1381 m->m_pkthdr.rcvif = NULL;
1382
1383 #ifdef INET6
1384 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1385 ip6 = mtod(m, struct ip6_hdr *);
1386 ip6->ip6_vfc = IPV6_VERSION;
1387 ip6->ip6_nxt = IPPROTO_TCP;
1388 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1389 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1390 ip6->ip6_plen = htons(tlen - hlen);
1391 /* ip6_hlim is set after checksum */
1392 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1393 ip6->ip6_flow |= sc->sc_flowlabel;
1394
1395 th = (struct tcphdr *)(ip6 + 1);
1396 }
1397 #endif
1398 #if defined(INET6) && defined(INET)
1399 else
1400 #endif
1401 #ifdef INET
1402 {
1403 ip = mtod(m, struct ip *);
1404 ip->ip_v = IPVERSION;
1405 ip->ip_hl = sizeof(struct ip) >> 2;
1406 ip->ip_len = tlen;
1407 ip->ip_id = 0;
1408 ip->ip_off = 0;
1409 ip->ip_sum = 0;
1410 ip->ip_p = IPPROTO_TCP;
1411 ip->ip_src = sc->sc_inc.inc_laddr;
1412 ip->ip_dst = sc->sc_inc.inc_faddr;
1413 ip->ip_ttl = sc->sc_ip_ttl;
1414 ip->ip_tos = sc->sc_ip_tos;
1415
1416 /*
1417 * See if we should do MTU discovery. Route lookups are
1418 * expensive, so we will only unset the DF bit if:
1419 *
1420 * 1) path_mtu_discovery is disabled
1421 * 2) the SCF_UNREACH flag has been set
1422 */
1423 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1424 ip->ip_off |= IP_DF;
1425
1426 th = (struct tcphdr *)(ip + 1);
1427 }
1428 #endif /* INET */
1429 th->th_sport = sc->sc_inc.inc_lport;
1430 th->th_dport = sc->sc_inc.inc_fport;
1431
1432 th->th_seq = htonl(sc->sc_iss);
1433 th->th_ack = htonl(sc->sc_irs + 1);
1434 th->th_off = sizeof(struct tcphdr) >> 2;
1435 th->th_x2 = 0;
1436 th->th_flags = TH_SYN|TH_ACK;
1437 th->th_win = htons(sc->sc_wnd);
1438 th->th_urp = 0;
1439
1440 if (sc->sc_flags & SCF_ECN) {
1441 th->th_flags |= TH_ECE;
1442 TCPSTAT_INC(tcps_ecn_shs);
1443 }
1444
1445 /* Tack on the TCP options. */
1446 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1447 to.to_flags = 0;
1448
1449 to.to_mss = mssopt;
1450 to.to_flags = TOF_MSS;
1451 if (sc->sc_flags & SCF_WINSCALE) {
1452 to.to_wscale = sc->sc_requested_r_scale;
1453 to.to_flags |= TOF_SCALE;
1454 }
1455 if (sc->sc_flags & SCF_TIMESTAMP) {
1456 /* Virgin timestamp or TCP cookie enhanced one. */
1457 to.to_tsval = sc->sc_ts;
1458 to.to_tsecr = sc->sc_tsreflect;
1459 to.to_flags |= TOF_TS;
1460 }
1461 if (sc->sc_flags & SCF_SACK)
1462 to.to_flags |= TOF_SACKPERM;
1463 #ifdef TCP_SIGNATURE
1464 if (sc->sc_flags & SCF_SIGNATURE)
1465 to.to_flags |= TOF_SIGNATURE;
1466 #endif
1467 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1468
1469 /* Adjust headers by option size. */
1470 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1471 m->m_len += optlen;
1472 m->m_pkthdr.len += optlen;
1473
1474 #ifdef TCP_SIGNATURE
1475 if (sc->sc_flags & SCF_SIGNATURE)
1476 tcp_signature_compute(m, 0, 0, optlen,
1477 to.to_signature, IPSEC_DIR_OUTBOUND);
1478 #endif
1479 #ifdef INET6
1480 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1481 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1482 else
1483 #endif
1484 ip->ip_len += optlen;
1485 } else
1486 optlen = 0;
1487
1488 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1489 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1490 #ifdef INET6
1491 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1492 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1493 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
1494 IPPROTO_TCP, 0);
1495 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1496 #ifdef TCP_OFFLOAD
1497 if (ADDED_BY_TOE(sc)) {
1498 struct toedev *tod = sc->sc_tod;
1499
1500 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1501
1502 return (error);
1503 }
1504 #endif
1505 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1506 }
1507 #endif
1508 #if defined(INET6) && defined(INET)
1509 else
1510 #endif
1511 #ifdef INET
1512 {
1513 m->m_pkthdr.csum_flags = CSUM_TCP;
1514 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1515 htons(tlen + optlen - hlen + IPPROTO_TCP));
1516 #ifdef TCP_OFFLOAD
1517 if (ADDED_BY_TOE(sc)) {
1518 struct toedev *tod = sc->sc_tod;
1519
1520 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1521
1522 return (error);
1523 }
1524 #endif
1525 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1526 }
1527 #endif
1528 return (error);
1529 }
1530
1531 void
1532 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1533 struct inpcb *inp, struct socket **lsop, struct mbuf *m)
1534 {
1535 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL);
1536 }
1537
1538 void
1539 tcp_offload_syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1540 struct inpcb *inp, struct socket **lsop, void *tod, void *todctx)
1541 {
1542
1543 _syncache_add(inc, to, th, inp, lsop, NULL, tod, todctx);
1544 }
1545 /*
1546 * The purpose of SYN cookies is to avoid keeping track of all SYN's we
1547 * receive and to be able to handle SYN floods from bogus source addresses
1548 * (where we will never receive any reply). SYN floods try to exhaust all
1549 * our memory and available slots in the SYN cache table to cause a denial
1550 * of service to legitimate users of the local host.
1551 *
1552 * The idea of SYN cookies is to encode and include all necessary information
1553 * about the connection setup state within the SYN-ACK we send back and thus
1554 * to get along without keeping any local state until the ACK to the SYN-ACK
1555 * arrives (if ever). Everything we need to know should be available from
1556 * the information we encoded in the SYN-ACK.
1557 *
1558 * More information about the theory behind SYN cookies and its first
1559 * discussion and specification can be found at:
1560 * http://cr.yp.to/syncookies.html (overview)
1561 * http://cr.yp.to/syncookies/archive (gory details)
1562 *
1563 * This implementation extends the orginal idea and first implementation
1564 * of FreeBSD by using not only the initial sequence number field to store
1565 * information but also the timestamp field if present. This way we can
1566 * keep track of the entire state we need to know to recreate the session in
1567 * its original form. Almost all TCP speakers implement RFC1323 timestamps
1568 * these days. For those that do not we still have to live with the known
1569 * shortcomings of the ISN only SYN cookies.
1570 *
1571 * Cookie layers:
1572 *
1573 * Initial sequence number we send:
1574 * 31|................................|0
1575 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP
1576 * D = MD5 Digest (first dword)
1577 * M = MSS index
1578 * R = Rotation of secret
1579 * P = Odd or Even secret
1580 *
1581 * The MD5 Digest is computed with over following parameters:
1582 * a) randomly rotated secret
1583 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6)
1584 * c) the received initial sequence number from remote host
1585 * d) the rotation offset and odd/even bit
1586 *
1587 * Timestamp we send:
1588 * 31|................................|0
1589 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5
1590 * D = MD5 Digest (third dword) (only as filler)
1591 * S = Requested send window scale
1592 * R = Requested receive window scale
1593 * A = SACK allowed
1594 * 5 = TCP-MD5 enabled (not implemented yet)
1595 * XORed with MD5 Digest (forth dword)
1596 *
1597 * The timestamp isn't cryptographically secure and doesn't need to be.
1598 * The double use of the MD5 digest dwords ties it to a specific remote/
1599 * local host/port, remote initial sequence number and our local time
1600 * limited secret. A received timestamp is reverted (XORed) and then
1601 * the contained MD5 dword is compared to the computed one to ensure the
1602 * timestamp belongs to the SYN-ACK we sent. The other parameters may
1603 * have been tampered with but this isn't different from supplying bogus
1604 * values in the SYN in the first place.
1605 *
1606 * Some problems with SYN cookies remain however:
1607 * Consider the problem of a recreated (and retransmitted) cookie. If the
1608 * original SYN was accepted, the connection is established. The second
1609 * SYN is inflight, and if it arrives with an ISN that falls within the
1610 * receive window, the connection is killed.
1611 *
1612 * Notes:
1613 * A heuristic to determine when to accept syn cookies is not necessary.
1614 * An ACK flood would cause the syncookie verification to be attempted,
1615 * but a SYN flood causes syncookies to be generated. Both are of equal
1616 * cost, so there's no point in trying to optimize the ACK flood case.
1617 * Also, if you don't process certain ACKs for some reason, then all someone
1618 * would have to do is launch a SYN and ACK flood at the same time, which
1619 * would stop cookie verification and defeat the entire purpose of syncookies.
1620 */
1621 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 };
1622
1623 static void
1624 syncookie_generate(struct syncache_head *sch, struct syncache *sc,
1625 u_int32_t *flowlabel)
1626 {
1627 MD5_CTX ctx;
1628 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1629 u_int32_t data;
1630 u_int32_t *secbits;
1631 u_int off, pmss, mss;
1632 int i;
1633
1634 SCH_LOCK_ASSERT(sch);
1635
1636 /* Which of the two secrets to use. */
1637 secbits = sch->sch_oddeven ?
1638 sch->sch_secbits_odd : sch->sch_secbits_even;
1639
1640 /* Reseed secret if too old. */
1641 if (sch->sch_reseed < time_uptime) {
1642 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */
1643 secbits = sch->sch_oddeven ?
1644 sch->sch_secbits_odd : sch->sch_secbits_even;
1645 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++)
1646 secbits[i] = arc4random();
1647 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME;
1648 }
1649
1650 /* Secret rotation offset. */
1651 off = sc->sc_iss & 0x7; /* iss was randomized before */
1652
1653 /* Maximum segment size calculation. */
1654 pmss =
1655 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss);
1656 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--)
1657 if (tcp_sc_msstab[mss] <= pmss)
1658 break;
1659
1660 /* Fold parameters and MD5 digest into the ISN we will send. */
1661 data = sch->sch_oddeven;/* odd or even secret, 1 bit */
1662 data |= off << 1; /* secret offset, derived from iss, 3 bits */
1663 data |= mss << 4; /* mss, 3 bits */
1664
1665 MD5Init(&ctx);
1666 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1667 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1668 MD5Update(&ctx, secbits, off);
1669 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc));
1670 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs));
1671 MD5Update(&ctx, &data, sizeof(data));
1672 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1673
1674 data |= (md5_buffer[0] << 7);
1675 sc->sc_iss = data;
1676
1677 #ifdef INET6
1678 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1679 #endif
1680
1681 /* Additional parameters are stored in the timestamp if present. */
1682 if (sc->sc_flags & SCF_TIMESTAMP) {
1683 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */
1684 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */
1685 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */
1686 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */
1687 data |= md5_buffer[2] << 10; /* more digest bits */
1688 data ^= md5_buffer[3];
1689 sc->sc_ts = data;
1690 sc->sc_tsoff = data - tcp_ts_getticks(); /* after XOR */
1691 }
1692
1693 TCPSTAT_INC(tcps_sc_sendcookie);
1694 }
1695
1696 static struct syncache *
1697 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
1698 struct syncache *sc, struct tcpopt *to, struct tcphdr *th,
1699 struct socket *so)
1700 {
1701 MD5_CTX ctx;
1702 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1703 u_int32_t data = 0;
1704 u_int32_t *secbits;
1705 tcp_seq ack, seq;
1706 int off, mss, wnd, flags;
1707
1708 SCH_LOCK_ASSERT(sch);
1709
1710 /*
1711 * Pull information out of SYN-ACK/ACK and
1712 * revert sequence number advances.
1713 */
1714 ack = th->th_ack - 1;
1715 seq = th->th_seq - 1;
1716 off = (ack >> 1) & 0x7;
1717 mss = (ack >> 4) & 0x7;
1718 flags = ack & 0x7f;
1719
1720 /* Which of the two secrets to use. */
1721 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even;
1722
1723 /*
1724 * The secret wasn't updated for the lifetime of a syncookie,
1725 * so this SYN-ACK/ACK is either too old (replay) or totally bogus.
1726 */
1727 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) {
1728 return (NULL);
1729 }
1730
1731 /* Recompute the digest so we can compare it. */
1732 MD5Init(&ctx);
1733 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1734 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1735 MD5Update(&ctx, secbits, off);
1736 MD5Update(&ctx, inc, sizeof(*inc));
1737 MD5Update(&ctx, &seq, sizeof(seq));
1738 MD5Update(&ctx, &flags, sizeof(flags));
1739 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1740
1741 /* Does the digest part of or ACK'ed ISS match? */
1742 if ((ack & (~0x7f)) != (md5_buffer[0] << 7))
1743 return (NULL);
1744
1745 /* Does the digest part of our reflected timestamp match? */
1746 if (to->to_flags & TOF_TS) {
1747 data = md5_buffer[3] ^ to->to_tsecr;
1748 if ((data & (~0x3ff)) != (md5_buffer[2] << 10))
1749 return (NULL);
1750 }
1751
1752 /* Fill in the syncache values. */
1753 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1754 sc->sc_ipopts = NULL;
1755
1756 sc->sc_irs = seq;
1757 sc->sc_iss = ack;
1758
1759 #ifdef INET6
1760 if (inc->inc_flags & INC_ISIPV6) {
1761 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL)
1762 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1763 } else
1764 #endif
1765 {
1766 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl;
1767 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos;
1768 }
1769
1770 /* Additional parameters that were encoded in the timestamp. */
1771 if (data) {
1772 sc->sc_flags |= SCF_TIMESTAMP;
1773 sc->sc_tsreflect = to->to_tsval;
1774 sc->sc_ts = to->to_tsecr;
1775 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
1776 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0;
1777 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0;
1778 sc->sc_requested_s_scale = min((data >> 2) & 0xf,
1779 TCP_MAX_WINSHIFT);
1780 sc->sc_requested_r_scale = min((data >> 6) & 0xf,
1781 TCP_MAX_WINSHIFT);
1782 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale)
1783 sc->sc_flags |= SCF_WINSCALE;
1784 } else
1785 sc->sc_flags |= SCF_NOOPT;
1786
1787 wnd = sbspace(&so->so_rcv);
1788 wnd = imax(wnd, 0);
1789 wnd = imin(wnd, TCP_MAXWIN);
1790 sc->sc_wnd = wnd;
1791
1792 sc->sc_rxmits = 0;
1793 sc->sc_peer_mss = tcp_sc_msstab[mss];
1794
1795 TCPSTAT_INC(tcps_sc_recvcookie);
1796 return (sc);
1797 }
1798
1799 /*
1800 * Returns the current number of syncache entries. This number
1801 * will probably change before you get around to calling
1802 * syncache_pcblist.
1803 */
1804
1805 int
1806 syncache_pcbcount(void)
1807 {
1808 struct syncache_head *sch;
1809 int count, i;
1810
1811 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1812 /* No need to lock for a read. */
1813 sch = &V_tcp_syncache.hashbase[i];
1814 count += sch->sch_length;
1815 }
1816 return count;
1817 }
1818
1819 /*
1820 * Exports the syncache entries to userland so that netstat can display
1821 * them alongside the other sockets. This function is intended to be
1822 * called only from tcp_pcblist.
1823 *
1824 * Due to concurrency on an active system, the number of pcbs exported
1825 * may have no relation to max_pcbs. max_pcbs merely indicates the
1826 * amount of space the caller allocated for this function to use.
1827 */
1828 int
1829 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
1830 {
1831 struct xtcpcb xt;
1832 struct syncache *sc;
1833 struct syncache_head *sch;
1834 int count, error, i;
1835
1836 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1837 sch = &V_tcp_syncache.hashbase[i];
1838 SCH_LOCK(sch);
1839 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
1840 if (count >= max_pcbs) {
1841 SCH_UNLOCK(sch);
1842 goto exit;
1843 }
1844 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
1845 continue;
1846 bzero(&xt, sizeof(xt));
1847 xt.xt_len = sizeof(xt);
1848 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1849 xt.xt_inp.inp_vflag = INP_IPV6;
1850 else
1851 xt.xt_inp.inp_vflag = INP_IPV4;
1852 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
1853 xt.xt_tp.t_inpcb = &xt.xt_inp;
1854 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
1855 xt.xt_socket.xso_protocol = IPPROTO_TCP;
1856 xt.xt_socket.xso_len = sizeof (struct xsocket);
1857 xt.xt_socket.so_type = SOCK_STREAM;
1858 xt.xt_socket.so_state = SS_ISCONNECTING;
1859 error = SYSCTL_OUT(req, &xt, sizeof xt);
1860 if (error) {
1861 SCH_UNLOCK(sch);
1862 goto exit;
1863 }
1864 count++;
1865 }
1866 SCH_UNLOCK(sch);
1867 }
1868 exit:
1869 *pcbs_exported = count;
1870 return error;
1871 }
Cache object: b0ad70e022c6c3437ff9d2da10a89f95
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