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: releng/9.1/sys/netinet/tcp_syncache.c 238247 2012-07-08 14:21:36Z bz $");
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 #include <netinet/tcp_offload.h>
85 #ifdef INET6
86 #include <netinet6/tcp6_var.h>
87 #endif
88
89 #ifdef IPSEC
90 #include <netipsec/ipsec.h>
91 #ifdef INET6
92 #include <netipsec/ipsec6.h>
93 #endif
94 #include <netipsec/key.h>
95 #endif /*IPSEC*/
96
97 #include <machine/in_cksum.h>
98
99 #include <security/mac/mac_framework.h>
100
101 static VNET_DEFINE(int, tcp_syncookies) = 1;
102 #define V_tcp_syncookies VNET(tcp_syncookies)
103 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
104 &VNET_NAME(tcp_syncookies), 0,
105 "Use TCP SYN cookies if the syncache overflows");
106
107 static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
108 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
109 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW,
110 &VNET_NAME(tcp_syncookiesonly), 0,
111 "Use only TCP SYN cookies");
112
113 #ifdef TCP_OFFLOAD_DISABLE
114 #define TOEPCB_ISSET(sc) (0)
115 #else
116 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != 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 void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
127 int docallout);
128 static void syncache_timer(void *);
129 static void syncookie_generate(struct syncache_head *, struct syncache *,
130 u_int32_t *);
131 static struct syncache
132 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
133 struct syncache *, struct tcpopt *, struct tcphdr *,
134 struct socket *);
135
136 /*
137 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
138 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
139 * the odds are that the user has given up attempting to connect by then.
140 */
141 #define SYNCACHE_MAXREXMTS 3
142
143 /* Arbitrary values */
144 #define TCP_SYNCACHE_HASHSIZE 512
145 #define TCP_SYNCACHE_BUCKETLIMIT 30
146
147 static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
148 #define V_tcp_syncache VNET(tcp_syncache)
149
150 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
151
152 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
153 &VNET_NAME(tcp_syncache.bucket_limit), 0,
154 "Per-bucket hash limit for syncache");
155
156 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
157 &VNET_NAME(tcp_syncache.cache_limit), 0,
158 "Overall entry limit for syncache");
159
160 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
161 &VNET_NAME(tcp_syncache.cache_count), 0,
162 "Current number of entries in syncache");
163
164 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
165 &VNET_NAME(tcp_syncache.hashsize), 0,
166 "Size of TCP syncache hashtable");
167
168 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
169 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
170 "Limit on SYN/ACK retransmissions");
171
172 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
173 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
174 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
175 "Send reset on socket allocation failure");
176
177 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
178
179 #define SYNCACHE_HASH(inc, mask) \
180 ((V_tcp_syncache.hash_secret ^ \
181 (inc)->inc_faddr.s_addr ^ \
182 ((inc)->inc_faddr.s_addr >> 16) ^ \
183 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
184
185 #define SYNCACHE_HASH6(inc, mask) \
186 ((V_tcp_syncache.hash_secret ^ \
187 (inc)->inc6_faddr.s6_addr32[0] ^ \
188 (inc)->inc6_faddr.s6_addr32[3] ^ \
189 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
190
191 #define ENDPTS_EQ(a, b) ( \
192 (a)->ie_fport == (b)->ie_fport && \
193 (a)->ie_lport == (b)->ie_lport && \
194 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
195 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
196 )
197
198 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
199
200 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
201 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
202 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
203
204 /*
205 * Requires the syncache entry to be already removed from the bucket list.
206 */
207 static void
208 syncache_free(struct syncache *sc)
209 {
210
211 if (sc->sc_ipopts)
212 (void) m_free(sc->sc_ipopts);
213 if (sc->sc_cred)
214 crfree(sc->sc_cred);
215 #ifdef MAC
216 mac_syncache_destroy(&sc->sc_label);
217 #endif
218
219 uma_zfree(V_tcp_syncache.zone, sc);
220 }
221
222 void
223 syncache_init(void)
224 {
225 int i;
226
227 V_tcp_syncache.cache_count = 0;
228 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
229 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
230 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
231 V_tcp_syncache.hash_secret = arc4random();
232
233 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
234 &V_tcp_syncache.hashsize);
235 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
236 &V_tcp_syncache.bucket_limit);
237 if (!powerof2(V_tcp_syncache.hashsize) ||
238 V_tcp_syncache.hashsize == 0) {
239 printf("WARNING: syncache hash size is not a power of 2.\n");
240 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
241 }
242 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
243
244 /* Set limits. */
245 V_tcp_syncache.cache_limit =
246 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
247 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
248 &V_tcp_syncache.cache_limit);
249
250 /* Allocate the hash table. */
251 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
252 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
253
254 /* Initialize the hash buckets. */
255 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
256 #ifdef VIMAGE
257 V_tcp_syncache.hashbase[i].sch_vnet = curvnet;
258 #endif
259 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
260 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
261 NULL, MTX_DEF);
262 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
263 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
264 V_tcp_syncache.hashbase[i].sch_length = 0;
265 }
266
267 /* Create the syncache entry zone. */
268 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
269 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
270 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit);
271 }
272
273 #ifdef VIMAGE
274 void
275 syncache_destroy(void)
276 {
277 struct syncache_head *sch;
278 struct syncache *sc, *nsc;
279 int i;
280
281 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
282 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
283
284 sch = &V_tcp_syncache.hashbase[i];
285 callout_drain(&sch->sch_timer);
286
287 SCH_LOCK(sch);
288 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
289 syncache_drop(sc, sch);
290 SCH_UNLOCK(sch);
291 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
292 ("%s: sch->sch_bucket not empty", __func__));
293 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
294 __func__, sch->sch_length));
295 mtx_destroy(&sch->sch_mtx);
296 }
297
298 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0",
299 __func__, V_tcp_syncache.cache_count));
300
301 /* Free the allocated global resources. */
302 uma_zdestroy(V_tcp_syncache.zone);
303 free(V_tcp_syncache.hashbase, M_SYNCACHE);
304 }
305 #endif
306
307 /*
308 * Inserts a syncache entry into the specified bucket row.
309 * Locks and unlocks the syncache_head autonomously.
310 */
311 static void
312 syncache_insert(struct syncache *sc, struct syncache_head *sch)
313 {
314 struct syncache *sc2;
315
316 SCH_LOCK(sch);
317
318 /*
319 * Make sure that we don't overflow the per-bucket limit.
320 * If the bucket is full, toss the oldest element.
321 */
322 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
323 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
324 ("sch->sch_length incorrect"));
325 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
326 syncache_drop(sc2, sch);
327 TCPSTAT_INC(tcps_sc_bucketoverflow);
328 }
329
330 /* Put it into the bucket. */
331 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
332 sch->sch_length++;
333
334 /* Reinitialize the bucket row's timer. */
335 if (sch->sch_length == 1)
336 sch->sch_nextc = ticks + INT_MAX;
337 syncache_timeout(sc, sch, 1);
338
339 SCH_UNLOCK(sch);
340
341 V_tcp_syncache.cache_count++;
342 TCPSTAT_INC(tcps_sc_added);
343 }
344
345 /*
346 * Remove and free entry from syncache bucket row.
347 * Expects locked syncache head.
348 */
349 static void
350 syncache_drop(struct syncache *sc, struct syncache_head *sch)
351 {
352
353 SCH_LOCK_ASSERT(sch);
354
355 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
356 sch->sch_length--;
357
358 #ifndef TCP_OFFLOAD_DISABLE
359 if (sc->sc_tu)
360 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb);
361 #endif
362 syncache_free(sc);
363 V_tcp_syncache.cache_count--;
364 }
365
366 /*
367 * Engage/reengage time on bucket row.
368 */
369 static void
370 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
371 {
372 sc->sc_rxttime = ticks +
373 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
374 sc->sc_rxmits++;
375 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
376 sch->sch_nextc = sc->sc_rxttime;
377 if (docallout)
378 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
379 syncache_timer, (void *)sch);
380 }
381 }
382
383 /*
384 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
385 * If we have retransmitted an entry the maximum number of times, expire it.
386 * One separate timer for each bucket row.
387 */
388 static void
389 syncache_timer(void *xsch)
390 {
391 struct syncache_head *sch = (struct syncache_head *)xsch;
392 struct syncache *sc, *nsc;
393 int tick = ticks;
394 char *s;
395
396 CURVNET_SET(sch->sch_vnet);
397
398 /* NB: syncache_head has already been locked by the callout. */
399 SCH_LOCK_ASSERT(sch);
400
401 /*
402 * In the following cycle we may remove some entries and/or
403 * advance some timeouts, so re-initialize the bucket timer.
404 */
405 sch->sch_nextc = tick + INT_MAX;
406
407 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
408 /*
409 * We do not check if the listen socket still exists
410 * and accept the case where the listen socket may be
411 * gone by the time we resend the SYN/ACK. We do
412 * not expect this to happens often. If it does,
413 * then the RST will be sent by the time the remote
414 * host does the SYN/ACK->ACK.
415 */
416 if (TSTMP_GT(sc->sc_rxttime, tick)) {
417 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
418 sch->sch_nextc = sc->sc_rxttime;
419 continue;
420 }
421 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
422 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
423 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
424 "giving up and removing syncache entry\n",
425 s, __func__);
426 free(s, M_TCPLOG);
427 }
428 syncache_drop(sc, sch);
429 TCPSTAT_INC(tcps_sc_stale);
430 continue;
431 }
432 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
433 log(LOG_DEBUG, "%s; %s: Response timeout, "
434 "retransmitting (%u) SYN|ACK\n",
435 s, __func__, sc->sc_rxmits);
436 free(s, M_TCPLOG);
437 }
438
439 (void) syncache_respond(sc);
440 TCPSTAT_INC(tcps_sc_retransmitted);
441 syncache_timeout(sc, sch, 0);
442 }
443 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
444 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
445 syncache_timer, (void *)(sch));
446 CURVNET_RESTORE();
447 }
448
449 /*
450 * Find an entry in the syncache.
451 * Returns always with locked syncache_head plus a matching entry or NULL.
452 */
453 struct syncache *
454 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
455 {
456 struct syncache *sc;
457 struct syncache_head *sch;
458
459 #ifdef INET6
460 if (inc->inc_flags & INC_ISIPV6) {
461 sch = &V_tcp_syncache.hashbase[
462 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)];
463 *schp = sch;
464
465 SCH_LOCK(sch);
466
467 /* Circle through bucket row to find matching entry. */
468 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
469 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
470 return (sc);
471 }
472 } else
473 #endif
474 {
475 sch = &V_tcp_syncache.hashbase[
476 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)];
477 *schp = sch;
478
479 SCH_LOCK(sch);
480
481 /* Circle through bucket row to find matching entry. */
482 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
483 #ifdef INET6
484 if (sc->sc_inc.inc_flags & INC_ISIPV6)
485 continue;
486 #endif
487 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
488 return (sc);
489 }
490 }
491 SCH_LOCK_ASSERT(*schp);
492 return (NULL); /* always returns with locked sch */
493 }
494
495 /*
496 * This function is called when we get a RST for a
497 * non-existent connection, so that we can see if the
498 * connection is in the syn cache. If it is, zap it.
499 */
500 void
501 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
502 {
503 struct syncache *sc;
504 struct syncache_head *sch;
505 char *s = NULL;
506
507 sc = syncache_lookup(inc, &sch); /* returns locked sch */
508 SCH_LOCK_ASSERT(sch);
509
510 /*
511 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
512 * See RFC 793 page 65, section SEGMENT ARRIVES.
513 */
514 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
515 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
516 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
517 "FIN flag set, segment ignored\n", s, __func__);
518 TCPSTAT_INC(tcps_badrst);
519 goto done;
520 }
521
522 /*
523 * No corresponding connection was found in syncache.
524 * If syncookies are enabled and possibly exclusively
525 * used, or we are under memory pressure, a valid RST
526 * may not find a syncache entry. In that case we're
527 * done and no SYN|ACK retransmissions will happen.
528 * Otherwise the RST was misdirected or spoofed.
529 */
530 if (sc == NULL) {
531 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
532 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
533 "syncache entry (possibly syncookie only), "
534 "segment ignored\n", s, __func__);
535 TCPSTAT_INC(tcps_badrst);
536 goto done;
537 }
538
539 /*
540 * If the RST bit is set, check the sequence number to see
541 * if this is a valid reset segment.
542 * RFC 793 page 37:
543 * In all states except SYN-SENT, all reset (RST) segments
544 * are validated by checking their SEQ-fields. A reset is
545 * valid if its sequence number is in the window.
546 *
547 * The sequence number in the reset segment is normally an
548 * echo of our outgoing acknowlegement numbers, but some hosts
549 * send a reset with the sequence number at the rightmost edge
550 * of our receive window, and we have to handle this case.
551 */
552 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
553 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
554 syncache_drop(sc, sch);
555 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
556 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
557 "connection attempt aborted by remote endpoint\n",
558 s, __func__);
559 TCPSTAT_INC(tcps_sc_reset);
560 } else {
561 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
562 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
563 "IRS %u (+WND %u), segment ignored\n",
564 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
565 TCPSTAT_INC(tcps_badrst);
566 }
567
568 done:
569 if (s != NULL)
570 free(s, M_TCPLOG);
571 SCH_UNLOCK(sch);
572 }
573
574 void
575 syncache_badack(struct in_conninfo *inc)
576 {
577 struct syncache *sc;
578 struct syncache_head *sch;
579
580 sc = syncache_lookup(inc, &sch); /* returns locked sch */
581 SCH_LOCK_ASSERT(sch);
582 if (sc != NULL) {
583 syncache_drop(sc, sch);
584 TCPSTAT_INC(tcps_sc_badack);
585 }
586 SCH_UNLOCK(sch);
587 }
588
589 void
590 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
591 {
592 struct syncache *sc;
593 struct syncache_head *sch;
594
595 sc = syncache_lookup(inc, &sch); /* returns locked sch */
596 SCH_LOCK_ASSERT(sch);
597 if (sc == NULL)
598 goto done;
599
600 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
601 if (ntohl(th->th_seq) != sc->sc_iss)
602 goto done;
603
604 /*
605 * If we've rertransmitted 3 times and this is our second error,
606 * we remove the entry. Otherwise, we allow it to continue on.
607 * This prevents us from incorrectly nuking an entry during a
608 * spurious network outage.
609 *
610 * See tcp_notify().
611 */
612 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
613 sc->sc_flags |= SCF_UNREACH;
614 goto done;
615 }
616 syncache_drop(sc, sch);
617 TCPSTAT_INC(tcps_sc_unreach);
618 done:
619 SCH_UNLOCK(sch);
620 }
621
622 /*
623 * Build a new TCP socket structure from a syncache entry.
624 */
625 static struct socket *
626 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
627 {
628 struct inpcb *inp = NULL;
629 struct socket *so;
630 struct tcpcb *tp;
631 int error;
632 char *s;
633
634 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
635
636 /*
637 * Ok, create the full blown connection, and set things up
638 * as they would have been set up if we had created the
639 * connection when the SYN arrived. If we can't create
640 * the connection, abort it.
641 */
642 so = sonewconn(lso, SS_ISCONNECTED);
643 if (so == NULL) {
644 /*
645 * Drop the connection; we will either send a RST or
646 * have the peer retransmit its SYN again after its
647 * RTO and try again.
648 */
649 TCPSTAT_INC(tcps_listendrop);
650 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
651 log(LOG_DEBUG, "%s; %s: Socket create failed "
652 "due to limits or memory shortage\n",
653 s, __func__);
654 free(s, M_TCPLOG);
655 }
656 goto abort2;
657 }
658 #ifdef MAC
659 mac_socketpeer_set_from_mbuf(m, so);
660 #endif
661
662 inp = sotoinpcb(so);
663 inp->inp_inc.inc_fibnum = so->so_fibnum;
664 INP_WLOCK(inp);
665 INP_HASH_WLOCK(&V_tcbinfo);
666
667 /* Insert new socket into PCB hash list. */
668 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
669 #ifdef INET6
670 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
671 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
672 } else {
673 inp->inp_vflag &= ~INP_IPV6;
674 inp->inp_vflag |= INP_IPV4;
675 #endif
676 inp->inp_laddr = sc->sc_inc.inc_laddr;
677 #ifdef INET6
678 }
679 #endif
680
681 /*
682 * Install in the reservation hash table for now, but don't yet
683 * install a connection group since the full 4-tuple isn't yet
684 * configured.
685 */
686 inp->inp_lport = sc->sc_inc.inc_lport;
687 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) {
688 /*
689 * Undo the assignments above if we failed to
690 * put the PCB on the hash lists.
691 */
692 #ifdef INET6
693 if (sc->sc_inc.inc_flags & INC_ISIPV6)
694 inp->in6p_laddr = in6addr_any;
695 else
696 #endif
697 inp->inp_laddr.s_addr = INADDR_ANY;
698 inp->inp_lport = 0;
699 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
700 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
701 "with error %i\n",
702 s, __func__, error);
703 free(s, M_TCPLOG);
704 }
705 INP_HASH_WUNLOCK(&V_tcbinfo);
706 goto abort;
707 }
708 #ifdef IPSEC
709 /* Copy old policy into new socket's. */
710 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
711 printf("syncache_socket: could not copy policy\n");
712 #endif
713 #ifdef INET6
714 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
715 struct inpcb *oinp = sotoinpcb(lso);
716 struct in6_addr laddr6;
717 struct sockaddr_in6 sin6;
718 /*
719 * Inherit socket options from the listening socket.
720 * Note that in6p_inputopts are not (and should not be)
721 * copied, since it stores previously received options and is
722 * used to detect if each new option is different than the
723 * previous one and hence should be passed to a user.
724 * If we copied in6p_inputopts, a user would not be able to
725 * receive options just after calling the accept system call.
726 */
727 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
728 if (oinp->in6p_outputopts)
729 inp->in6p_outputopts =
730 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
731
732 sin6.sin6_family = AF_INET6;
733 sin6.sin6_len = sizeof(sin6);
734 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
735 sin6.sin6_port = sc->sc_inc.inc_fport;
736 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
737 laddr6 = inp->in6p_laddr;
738 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
739 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
740 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
741 thread0.td_ucred, m)) != 0) {
742 inp->in6p_laddr = laddr6;
743 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
744 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
745 "with error %i\n",
746 s, __func__, error);
747 free(s, M_TCPLOG);
748 }
749 INP_HASH_WUNLOCK(&V_tcbinfo);
750 goto abort;
751 }
752 /* Override flowlabel from in6_pcbconnect. */
753 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
754 inp->inp_flow |= sc->sc_flowlabel;
755 }
756 #endif /* INET6 */
757 #if defined(INET) && defined(INET6)
758 else
759 #endif
760 #ifdef INET
761 {
762 struct in_addr laddr;
763 struct sockaddr_in sin;
764
765 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
766
767 if (inp->inp_options == NULL) {
768 inp->inp_options = sc->sc_ipopts;
769 sc->sc_ipopts = NULL;
770 }
771
772 sin.sin_family = AF_INET;
773 sin.sin_len = sizeof(sin);
774 sin.sin_addr = sc->sc_inc.inc_faddr;
775 sin.sin_port = sc->sc_inc.inc_fport;
776 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
777 laddr = inp->inp_laddr;
778 if (inp->inp_laddr.s_addr == INADDR_ANY)
779 inp->inp_laddr = sc->sc_inc.inc_laddr;
780 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin,
781 thread0.td_ucred, m)) != 0) {
782 inp->inp_laddr = laddr;
783 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
784 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
785 "with error %i\n",
786 s, __func__, error);
787 free(s, M_TCPLOG);
788 }
789 INP_HASH_WUNLOCK(&V_tcbinfo);
790 goto abort;
791 }
792 }
793 #endif /* INET */
794 INP_HASH_WUNLOCK(&V_tcbinfo);
795 tp = intotcpcb(inp);
796 tp->t_state = TCPS_SYN_RECEIVED;
797 tp->iss = sc->sc_iss;
798 tp->irs = sc->sc_irs;
799 tcp_rcvseqinit(tp);
800 tcp_sendseqinit(tp);
801 tp->snd_wl1 = sc->sc_irs;
802 tp->snd_max = tp->iss + 1;
803 tp->snd_nxt = tp->iss + 1;
804 tp->rcv_up = sc->sc_irs + 1;
805 tp->rcv_wnd = sc->sc_wnd;
806 tp->rcv_adv += tp->rcv_wnd;
807 tp->last_ack_sent = tp->rcv_nxt;
808
809 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
810 if (sc->sc_flags & SCF_NOOPT)
811 tp->t_flags |= TF_NOOPT;
812 else {
813 if (sc->sc_flags & SCF_WINSCALE) {
814 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
815 tp->snd_scale = sc->sc_requested_s_scale;
816 tp->request_r_scale = sc->sc_requested_r_scale;
817 }
818 if (sc->sc_flags & SCF_TIMESTAMP) {
819 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
820 tp->ts_recent = sc->sc_tsreflect;
821 tp->ts_recent_age = tcp_ts_getticks();
822 tp->ts_offset = sc->sc_tsoff;
823 }
824 #ifdef TCP_SIGNATURE
825 if (sc->sc_flags & SCF_SIGNATURE)
826 tp->t_flags |= TF_SIGNATURE;
827 #endif
828 if (sc->sc_flags & SCF_SACK)
829 tp->t_flags |= TF_SACK_PERMIT;
830 }
831
832 if (sc->sc_flags & SCF_ECN)
833 tp->t_flags |= TF_ECN_PERMIT;
834
835 /*
836 * Set up MSS and get cached values from tcp_hostcache.
837 * This might overwrite some of the defaults we just set.
838 */
839 tcp_mss(tp, sc->sc_peer_mss);
840
841 /*
842 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
843 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
844 */
845 if (sc->sc_rxmits > 1)
846 tp->snd_cwnd = tp->t_maxseg;
847
848 /*
849 * Copy and activate timers.
850 */
851 tp->t_keepinit = sototcpcb(lso)->t_keepinit;
852 tp->t_keepidle = sototcpcb(lso)->t_keepidle;
853 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
854 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
855 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
856
857 INP_WUNLOCK(inp);
858
859 TCPSTAT_INC(tcps_accepts);
860 return (so);
861
862 abort:
863 INP_WUNLOCK(inp);
864 abort2:
865 if (so != NULL)
866 soabort(so);
867 return (NULL);
868 }
869
870 /*
871 * This function gets called when we receive an ACK for a
872 * socket in the LISTEN state. We look up the connection
873 * in the syncache, and if its there, we pull it out of
874 * the cache and turn it into a full-blown connection in
875 * the SYN-RECEIVED state.
876 */
877 int
878 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
879 struct socket **lsop, struct mbuf *m)
880 {
881 struct syncache *sc;
882 struct syncache_head *sch;
883 struct syncache scs;
884 char *s;
885
886 /*
887 * Global TCP locks are held because we manipulate the PCB lists
888 * and create a new socket.
889 */
890 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
891 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
892 ("%s: can handle only ACK", __func__));
893
894 sc = syncache_lookup(inc, &sch); /* returns locked sch */
895 SCH_LOCK_ASSERT(sch);
896 if (sc == NULL) {
897 /*
898 * There is no syncache entry, so see if this ACK is
899 * a returning syncookie. To do this, first:
900 * A. See if this socket has had a syncache entry dropped in
901 * the past. We don't want to accept a bogus syncookie
902 * if we've never received a SYN.
903 * B. check that the syncookie is valid. If it is, then
904 * cobble up a fake syncache entry, and return.
905 */
906 if (!V_tcp_syncookies) {
907 SCH_UNLOCK(sch);
908 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
909 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
910 "segment rejected (syncookies disabled)\n",
911 s, __func__);
912 goto failed;
913 }
914 bzero(&scs, sizeof(scs));
915 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop);
916 SCH_UNLOCK(sch);
917 if (sc == NULL) {
918 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
919 log(LOG_DEBUG, "%s; %s: Segment failed "
920 "SYNCOOKIE authentication, segment rejected "
921 "(probably spoofed)\n", s, __func__);
922 goto failed;
923 }
924 } else {
925 /* Pull out the entry to unlock the bucket row. */
926 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
927 sch->sch_length--;
928 V_tcp_syncache.cache_count--;
929 SCH_UNLOCK(sch);
930 }
931
932 /*
933 * Segment validation:
934 * ACK must match our initial sequence number + 1 (the SYN|ACK).
935 */
936 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) {
937 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
938 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
939 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
940 goto failed;
941 }
942
943 /*
944 * The SEQ must fall in the window starting at the received
945 * initial receive sequence number + 1 (the SYN).
946 */
947 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) ||
948 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) &&
949 !TOEPCB_ISSET(sc)) {
950 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
951 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
952 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
953 goto failed;
954 }
955
956 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
957 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
958 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
959 "segment rejected\n", s, __func__);
960 goto failed;
961 }
962 /*
963 * If timestamps were negotiated the reflected timestamp
964 * must be equal to what we actually sent in the SYN|ACK.
965 */
966 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts &&
967 !TOEPCB_ISSET(sc)) {
968 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
969 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
970 "segment rejected\n",
971 s, __func__, to->to_tsecr, sc->sc_ts);
972 goto failed;
973 }
974
975 *lsop = syncache_socket(sc, *lsop, m);
976
977 if (*lsop == NULL)
978 TCPSTAT_INC(tcps_sc_aborted);
979 else
980 TCPSTAT_INC(tcps_sc_completed);
981
982 /* how do we find the inp for the new socket? */
983 if (sc != &scs)
984 syncache_free(sc);
985 return (1);
986 failed:
987 if (sc != NULL && sc != &scs)
988 syncache_free(sc);
989 if (s != NULL)
990 free(s, M_TCPLOG);
991 *lsop = NULL;
992 return (0);
993 }
994
995 int
996 tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo,
997 struct tcphdr *th, struct socket **lsop, struct mbuf *m)
998 {
999 struct tcpopt to;
1000 int rc;
1001
1002 bzero(&to, sizeof(struct tcpopt));
1003 to.to_mss = toeo->to_mss;
1004 to.to_wscale = toeo->to_wscale;
1005 to.to_flags = toeo->to_flags;
1006
1007 INP_INFO_WLOCK(&V_tcbinfo);
1008 rc = syncache_expand(inc, &to, th, lsop, m);
1009 INP_INFO_WUNLOCK(&V_tcbinfo);
1010
1011 return (rc);
1012 }
1013
1014 /*
1015 * Given a LISTEN socket and an inbound SYN request, add
1016 * this to the syn cache, and send back a segment:
1017 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1018 * to the source.
1019 *
1020 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1021 * Doing so would require that we hold onto the data and deliver it
1022 * to the application. However, if we are the target of a SYN-flood
1023 * DoS attack, an attacker could send data which would eventually
1024 * consume all available buffer space if it were ACKed. By not ACKing
1025 * the data, we avoid this DoS scenario.
1026 */
1027 static void
1028 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1029 struct inpcb *inp, struct socket **lsop, struct mbuf *m,
1030 struct toe_usrreqs *tu, void *toepcb)
1031 {
1032 struct tcpcb *tp;
1033 struct socket *so;
1034 struct syncache *sc = NULL;
1035 struct syncache_head *sch;
1036 struct mbuf *ipopts = NULL;
1037 u_int32_t flowtmp;
1038 u_int ltflags;
1039 int win, sb_hiwat, ip_ttl, ip_tos;
1040 char *s;
1041 #ifdef INET6
1042 int autoflowlabel = 0;
1043 #endif
1044 #ifdef MAC
1045 struct label *maclabel;
1046 #endif
1047 struct syncache scs;
1048 struct ucred *cred;
1049
1050 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1051 INP_WLOCK_ASSERT(inp); /* listen socket */
1052 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1053 ("%s: unexpected tcp flags", __func__));
1054
1055 /*
1056 * Combine all so/tp operations very early to drop the INP lock as
1057 * soon as possible.
1058 */
1059 so = *lsop;
1060 tp = sototcpcb(so);
1061 cred = crhold(so->so_cred);
1062
1063 #ifdef INET6
1064 if ((inc->inc_flags & INC_ISIPV6) &&
1065 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1066 autoflowlabel = 1;
1067 #endif
1068 ip_ttl = inp->inp_ip_ttl;
1069 ip_tos = inp->inp_ip_tos;
1070 win = sbspace(&so->so_rcv);
1071 sb_hiwat = so->so_rcv.sb_hiwat;
1072 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1073
1074 /* By the time we drop the lock these should no longer be used. */
1075 so = NULL;
1076 tp = NULL;
1077
1078 #ifdef MAC
1079 if (mac_syncache_init(&maclabel) != 0) {
1080 INP_WUNLOCK(inp);
1081 INP_INFO_WUNLOCK(&V_tcbinfo);
1082 goto done;
1083 } else
1084 mac_syncache_create(maclabel, inp);
1085 #endif
1086 INP_WUNLOCK(inp);
1087 INP_INFO_WUNLOCK(&V_tcbinfo);
1088
1089 /*
1090 * Remember the IP options, if any.
1091 */
1092 #ifdef INET6
1093 if (!(inc->inc_flags & INC_ISIPV6))
1094 #endif
1095 #ifdef INET
1096 ipopts = (m) ? ip_srcroute(m) : NULL;
1097 #else
1098 ipopts = NULL;
1099 #endif
1100
1101 /*
1102 * See if we already have an entry for this connection.
1103 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1104 *
1105 * XXX: should the syncache be re-initialized with the contents
1106 * of the new SYN here (which may have different options?)
1107 *
1108 * XXX: We do not check the sequence number to see if this is a
1109 * real retransmit or a new connection attempt. The question is
1110 * how to handle such a case; either ignore it as spoofed, or
1111 * drop the current entry and create a new one?
1112 */
1113 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1114 SCH_LOCK_ASSERT(sch);
1115 if (sc != NULL) {
1116 #ifndef TCP_OFFLOAD_DISABLE
1117 if (sc->sc_tu)
1118 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT,
1119 sc->sc_toepcb);
1120 #endif
1121 TCPSTAT_INC(tcps_sc_dupsyn);
1122 if (ipopts) {
1123 /*
1124 * If we were remembering a previous source route,
1125 * forget it and use the new one we've been given.
1126 */
1127 if (sc->sc_ipopts)
1128 (void) m_free(sc->sc_ipopts);
1129 sc->sc_ipopts = ipopts;
1130 }
1131 /*
1132 * Update timestamp if present.
1133 */
1134 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1135 sc->sc_tsreflect = to->to_tsval;
1136 else
1137 sc->sc_flags &= ~SCF_TIMESTAMP;
1138 #ifdef MAC
1139 /*
1140 * Since we have already unconditionally allocated label
1141 * storage, free it up. The syncache entry will already
1142 * have an initialized label we can use.
1143 */
1144 mac_syncache_destroy(&maclabel);
1145 #endif
1146 /* Retransmit SYN|ACK and reset retransmit count. */
1147 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1148 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1149 "resetting timer and retransmitting SYN|ACK\n",
1150 s, __func__);
1151 free(s, M_TCPLOG);
1152 }
1153 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) {
1154 sc->sc_rxmits = 0;
1155 syncache_timeout(sc, sch, 1);
1156 TCPSTAT_INC(tcps_sndacks);
1157 TCPSTAT_INC(tcps_sndtotal);
1158 }
1159 SCH_UNLOCK(sch);
1160 goto done;
1161 }
1162
1163 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1164 if (sc == NULL) {
1165 /*
1166 * The zone allocator couldn't provide more entries.
1167 * Treat this as if the cache was full; drop the oldest
1168 * entry and insert the new one.
1169 */
1170 TCPSTAT_INC(tcps_sc_zonefail);
1171 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1172 syncache_drop(sc, sch);
1173 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1174 if (sc == NULL) {
1175 if (V_tcp_syncookies) {
1176 bzero(&scs, sizeof(scs));
1177 sc = &scs;
1178 } else {
1179 SCH_UNLOCK(sch);
1180 if (ipopts)
1181 (void) m_free(ipopts);
1182 goto done;
1183 }
1184 }
1185 }
1186
1187 /*
1188 * Fill in the syncache values.
1189 */
1190 #ifdef MAC
1191 sc->sc_label = maclabel;
1192 #endif
1193 sc->sc_cred = cred;
1194 cred = NULL;
1195 sc->sc_ipopts = ipopts;
1196 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1197 #ifdef INET6
1198 if (!(inc->inc_flags & INC_ISIPV6))
1199 #endif
1200 {
1201 sc->sc_ip_tos = ip_tos;
1202 sc->sc_ip_ttl = ip_ttl;
1203 }
1204 #ifndef TCP_OFFLOAD_DISABLE
1205 sc->sc_tu = tu;
1206 sc->sc_toepcb = toepcb;
1207 #endif
1208 sc->sc_irs = th->th_seq;
1209 sc->sc_iss = arc4random();
1210 sc->sc_flags = 0;
1211 sc->sc_flowlabel = 0;
1212
1213 /*
1214 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1215 * win was derived from socket earlier in the function.
1216 */
1217 win = imax(win, 0);
1218 win = imin(win, TCP_MAXWIN);
1219 sc->sc_wnd = win;
1220
1221 if (V_tcp_do_rfc1323) {
1222 /*
1223 * A timestamp received in a SYN makes
1224 * it ok to send timestamp requests and replies.
1225 */
1226 if (to->to_flags & TOF_TS) {
1227 sc->sc_tsreflect = to->to_tsval;
1228 sc->sc_ts = tcp_ts_getticks();
1229 sc->sc_flags |= SCF_TIMESTAMP;
1230 }
1231 if (to->to_flags & TOF_SCALE) {
1232 int wscale = 0;
1233
1234 /*
1235 * Pick the smallest possible scaling factor that
1236 * will still allow us to scale up to sb_max, aka
1237 * kern.ipc.maxsockbuf.
1238 *
1239 * We do this because there are broken firewalls that
1240 * will corrupt the window scale option, leading to
1241 * the other endpoint believing that our advertised
1242 * window is unscaled. At scale factors larger than
1243 * 5 the unscaled window will drop below 1500 bytes,
1244 * leading to serious problems when traversing these
1245 * broken firewalls.
1246 *
1247 * With the default maxsockbuf of 256K, a scale factor
1248 * of 3 will be chosen by this algorithm. Those who
1249 * choose a larger maxsockbuf should watch out
1250 * for the compatiblity problems mentioned above.
1251 *
1252 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1253 * or <SYN,ACK>) segment itself is never scaled.
1254 */
1255 while (wscale < TCP_MAX_WINSHIFT &&
1256 (TCP_MAXWIN << wscale) < sb_max)
1257 wscale++;
1258 sc->sc_requested_r_scale = wscale;
1259 sc->sc_requested_s_scale = to->to_wscale;
1260 sc->sc_flags |= SCF_WINSCALE;
1261 }
1262 }
1263 #ifdef TCP_SIGNATURE
1264 /*
1265 * If listening socket requested TCP digests, and received SYN
1266 * contains the option, flag this in the syncache so that
1267 * syncache_respond() will do the right thing with the SYN+ACK.
1268 * XXX: Currently we always record the option by default and will
1269 * attempt to use it in syncache_respond().
1270 */
1271 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE)
1272 sc->sc_flags |= SCF_SIGNATURE;
1273 #endif
1274 if (to->to_flags & TOF_SACKPERM)
1275 sc->sc_flags |= SCF_SACK;
1276 if (to->to_flags & TOF_MSS)
1277 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1278 if (ltflags & TF_NOOPT)
1279 sc->sc_flags |= SCF_NOOPT;
1280 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1281 sc->sc_flags |= SCF_ECN;
1282
1283 if (V_tcp_syncookies) {
1284 syncookie_generate(sch, sc, &flowtmp);
1285 #ifdef INET6
1286 if (autoflowlabel)
1287 sc->sc_flowlabel = flowtmp;
1288 #endif
1289 } else {
1290 #ifdef INET6
1291 if (autoflowlabel)
1292 sc->sc_flowlabel =
1293 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
1294 #endif
1295 }
1296 SCH_UNLOCK(sch);
1297
1298 /*
1299 * Do a standard 3-way handshake.
1300 */
1301 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) {
1302 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1303 syncache_free(sc);
1304 else if (sc != &scs)
1305 syncache_insert(sc, sch); /* locks and unlocks sch */
1306 TCPSTAT_INC(tcps_sndacks);
1307 TCPSTAT_INC(tcps_sndtotal);
1308 } else {
1309 if (sc != &scs)
1310 syncache_free(sc);
1311 TCPSTAT_INC(tcps_sc_dropped);
1312 }
1313
1314 done:
1315 if (cred != NULL)
1316 crfree(cred);
1317 #ifdef MAC
1318 if (sc == &scs)
1319 mac_syncache_destroy(&maclabel);
1320 #endif
1321 if (m) {
1322
1323 *lsop = NULL;
1324 m_freem(m);
1325 }
1326 }
1327
1328 static int
1329 syncache_respond(struct syncache *sc)
1330 {
1331 struct ip *ip = NULL;
1332 struct mbuf *m;
1333 struct tcphdr *th = NULL;
1334 int optlen, error = 0; /* Make compiler happy */
1335 u_int16_t hlen, tlen, mssopt;
1336 struct tcpopt to;
1337 #ifdef INET6
1338 struct ip6_hdr *ip6 = NULL;
1339 #endif
1340
1341 hlen =
1342 #ifdef INET6
1343 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1344 #endif
1345 sizeof(struct ip);
1346 tlen = hlen + sizeof(struct tcphdr);
1347
1348 /* Determine MSS we advertize to other end of connection. */
1349 mssopt = tcp_mssopt(&sc->sc_inc);
1350 if (sc->sc_peer_mss)
1351 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss);
1352
1353 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1354 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1355 ("syncache: mbuf too small"));
1356
1357 /* Create the IP+TCP header from scratch. */
1358 m = m_gethdr(M_DONTWAIT, MT_DATA);
1359 if (m == NULL)
1360 return (ENOBUFS);
1361 #ifdef MAC
1362 mac_syncache_create_mbuf(sc->sc_label, m);
1363 #endif
1364 m->m_data += max_linkhdr;
1365 m->m_len = tlen;
1366 m->m_pkthdr.len = tlen;
1367 m->m_pkthdr.rcvif = NULL;
1368
1369 #ifdef INET6
1370 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1371 ip6 = mtod(m, struct ip6_hdr *);
1372 ip6->ip6_vfc = IPV6_VERSION;
1373 ip6->ip6_nxt = IPPROTO_TCP;
1374 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1375 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1376 ip6->ip6_plen = htons(tlen - hlen);
1377 /* ip6_hlim is set after checksum */
1378 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1379 ip6->ip6_flow |= sc->sc_flowlabel;
1380
1381 th = (struct tcphdr *)(ip6 + 1);
1382 }
1383 #endif
1384 #if defined(INET6) && defined(INET)
1385 else
1386 #endif
1387 #ifdef INET
1388 {
1389 ip = mtod(m, struct ip *);
1390 ip->ip_v = IPVERSION;
1391 ip->ip_hl = sizeof(struct ip) >> 2;
1392 ip->ip_len = tlen;
1393 ip->ip_id = 0;
1394 ip->ip_off = 0;
1395 ip->ip_sum = 0;
1396 ip->ip_p = IPPROTO_TCP;
1397 ip->ip_src = sc->sc_inc.inc_laddr;
1398 ip->ip_dst = sc->sc_inc.inc_faddr;
1399 ip->ip_ttl = sc->sc_ip_ttl;
1400 ip->ip_tos = sc->sc_ip_tos;
1401
1402 /*
1403 * See if we should do MTU discovery. Route lookups are
1404 * expensive, so we will only unset the DF bit if:
1405 *
1406 * 1) path_mtu_discovery is disabled
1407 * 2) the SCF_UNREACH flag has been set
1408 */
1409 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1410 ip->ip_off |= IP_DF;
1411
1412 th = (struct tcphdr *)(ip + 1);
1413 }
1414 #endif /* INET */
1415 th->th_sport = sc->sc_inc.inc_lport;
1416 th->th_dport = sc->sc_inc.inc_fport;
1417
1418 th->th_seq = htonl(sc->sc_iss);
1419 th->th_ack = htonl(sc->sc_irs + 1);
1420 th->th_off = sizeof(struct tcphdr) >> 2;
1421 th->th_x2 = 0;
1422 th->th_flags = TH_SYN|TH_ACK;
1423 th->th_win = htons(sc->sc_wnd);
1424 th->th_urp = 0;
1425
1426 if (sc->sc_flags & SCF_ECN) {
1427 th->th_flags |= TH_ECE;
1428 TCPSTAT_INC(tcps_ecn_shs);
1429 }
1430
1431 /* Tack on the TCP options. */
1432 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1433 to.to_flags = 0;
1434
1435 to.to_mss = mssopt;
1436 to.to_flags = TOF_MSS;
1437 if (sc->sc_flags & SCF_WINSCALE) {
1438 to.to_wscale = sc->sc_requested_r_scale;
1439 to.to_flags |= TOF_SCALE;
1440 }
1441 if (sc->sc_flags & SCF_TIMESTAMP) {
1442 /* Virgin timestamp or TCP cookie enhanced one. */
1443 to.to_tsval = sc->sc_ts;
1444 to.to_tsecr = sc->sc_tsreflect;
1445 to.to_flags |= TOF_TS;
1446 }
1447 if (sc->sc_flags & SCF_SACK)
1448 to.to_flags |= TOF_SACKPERM;
1449 #ifdef TCP_SIGNATURE
1450 if (sc->sc_flags & SCF_SIGNATURE)
1451 to.to_flags |= TOF_SIGNATURE;
1452 #endif
1453 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1454
1455 /* Adjust headers by option size. */
1456 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1457 m->m_len += optlen;
1458 m->m_pkthdr.len += optlen;
1459
1460 #ifdef TCP_SIGNATURE
1461 if (sc->sc_flags & SCF_SIGNATURE)
1462 tcp_signature_compute(m, 0, 0, optlen,
1463 to.to_signature, IPSEC_DIR_OUTBOUND);
1464 #endif
1465 #ifdef INET6
1466 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1467 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1468 else
1469 #endif
1470 ip->ip_len += optlen;
1471 } else
1472 optlen = 0;
1473
1474 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1475 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1476 #ifdef INET6
1477 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1478 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1479 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
1480 IPPROTO_TCP, 0);
1481 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1482 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1483 }
1484 #endif
1485 #if defined(INET6) && defined(INET)
1486 else
1487 #endif
1488 #ifdef INET
1489 {
1490 m->m_pkthdr.csum_flags = CSUM_TCP;
1491 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1492 htons(tlen + optlen - hlen + IPPROTO_TCP));
1493 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1494 }
1495 #endif
1496 return (error);
1497 }
1498
1499 void
1500 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1501 struct inpcb *inp, struct socket **lsop, struct mbuf *m)
1502 {
1503 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL);
1504 }
1505
1506 void
1507 tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo,
1508 struct tcphdr *th, struct inpcb *inp, struct socket **lsop,
1509 struct toe_usrreqs *tu, void *toepcb)
1510 {
1511 struct tcpopt to;
1512
1513 bzero(&to, sizeof(struct tcpopt));
1514 to.to_mss = toeo->to_mss;
1515 to.to_wscale = toeo->to_wscale;
1516 to.to_flags = toeo->to_flags;
1517
1518 INP_INFO_WLOCK(&V_tcbinfo);
1519 INP_WLOCK(inp);
1520
1521 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb);
1522 }
1523
1524 /*
1525 * The purpose of SYN cookies is to avoid keeping track of all SYN's we
1526 * receive and to be able to handle SYN floods from bogus source addresses
1527 * (where we will never receive any reply). SYN floods try to exhaust all
1528 * our memory and available slots in the SYN cache table to cause a denial
1529 * of service to legitimate users of the local host.
1530 *
1531 * The idea of SYN cookies is to encode and include all necessary information
1532 * about the connection setup state within the SYN-ACK we send back and thus
1533 * to get along without keeping any local state until the ACK to the SYN-ACK
1534 * arrives (if ever). Everything we need to know should be available from
1535 * the information we encoded in the SYN-ACK.
1536 *
1537 * More information about the theory behind SYN cookies and its first
1538 * discussion and specification can be found at:
1539 * http://cr.yp.to/syncookies.html (overview)
1540 * http://cr.yp.to/syncookies/archive (gory details)
1541 *
1542 * This implementation extends the orginal idea and first implementation
1543 * of FreeBSD by using not only the initial sequence number field to store
1544 * information but also the timestamp field if present. This way we can
1545 * keep track of the entire state we need to know to recreate the session in
1546 * its original form. Almost all TCP speakers implement RFC1323 timestamps
1547 * these days. For those that do not we still have to live with the known
1548 * shortcomings of the ISN only SYN cookies.
1549 *
1550 * Cookie layers:
1551 *
1552 * Initial sequence number we send:
1553 * 31|................................|0
1554 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP
1555 * D = MD5 Digest (first dword)
1556 * M = MSS index
1557 * R = Rotation of secret
1558 * P = Odd or Even secret
1559 *
1560 * The MD5 Digest is computed with over following parameters:
1561 * a) randomly rotated secret
1562 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6)
1563 * c) the received initial sequence number from remote host
1564 * d) the rotation offset and odd/even bit
1565 *
1566 * Timestamp we send:
1567 * 31|................................|0
1568 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5
1569 * D = MD5 Digest (third dword) (only as filler)
1570 * S = Requested send window scale
1571 * R = Requested receive window scale
1572 * A = SACK allowed
1573 * 5 = TCP-MD5 enabled (not implemented yet)
1574 * XORed with MD5 Digest (forth dword)
1575 *
1576 * The timestamp isn't cryptographically secure and doesn't need to be.
1577 * The double use of the MD5 digest dwords ties it to a specific remote/
1578 * local host/port, remote initial sequence number and our local time
1579 * limited secret. A received timestamp is reverted (XORed) and then
1580 * the contained MD5 dword is compared to the computed one to ensure the
1581 * timestamp belongs to the SYN-ACK we sent. The other parameters may
1582 * have been tampered with but this isn't different from supplying bogus
1583 * values in the SYN in the first place.
1584 *
1585 * Some problems with SYN cookies remain however:
1586 * Consider the problem of a recreated (and retransmitted) cookie. If the
1587 * original SYN was accepted, the connection is established. The second
1588 * SYN is inflight, and if it arrives with an ISN that falls within the
1589 * receive window, the connection is killed.
1590 *
1591 * Notes:
1592 * A heuristic to determine when to accept syn cookies is not necessary.
1593 * An ACK flood would cause the syncookie verification to be attempted,
1594 * but a SYN flood causes syncookies to be generated. Both are of equal
1595 * cost, so there's no point in trying to optimize the ACK flood case.
1596 * Also, if you don't process certain ACKs for some reason, then all someone
1597 * would have to do is launch a SYN and ACK flood at the same time, which
1598 * would stop cookie verification and defeat the entire purpose of syncookies.
1599 */
1600 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 };
1601
1602 static void
1603 syncookie_generate(struct syncache_head *sch, struct syncache *sc,
1604 u_int32_t *flowlabel)
1605 {
1606 MD5_CTX ctx;
1607 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1608 u_int32_t data;
1609 u_int32_t *secbits;
1610 u_int off, pmss, mss;
1611 int i;
1612
1613 SCH_LOCK_ASSERT(sch);
1614
1615 /* Which of the two secrets to use. */
1616 secbits = sch->sch_oddeven ?
1617 sch->sch_secbits_odd : sch->sch_secbits_even;
1618
1619 /* Reseed secret if too old. */
1620 if (sch->sch_reseed < time_uptime) {
1621 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */
1622 secbits = sch->sch_oddeven ?
1623 sch->sch_secbits_odd : sch->sch_secbits_even;
1624 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++)
1625 secbits[i] = arc4random();
1626 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME;
1627 }
1628
1629 /* Secret rotation offset. */
1630 off = sc->sc_iss & 0x7; /* iss was randomized before */
1631
1632 /* Maximum segment size calculation. */
1633 pmss =
1634 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss);
1635 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--)
1636 if (tcp_sc_msstab[mss] <= pmss)
1637 break;
1638
1639 /* Fold parameters and MD5 digest into the ISN we will send. */
1640 data = sch->sch_oddeven;/* odd or even secret, 1 bit */
1641 data |= off << 1; /* secret offset, derived from iss, 3 bits */
1642 data |= mss << 4; /* mss, 3 bits */
1643
1644 MD5Init(&ctx);
1645 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1646 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1647 MD5Update(&ctx, secbits, off);
1648 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc));
1649 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs));
1650 MD5Update(&ctx, &data, sizeof(data));
1651 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1652
1653 data |= (md5_buffer[0] << 7);
1654 sc->sc_iss = data;
1655
1656 #ifdef INET6
1657 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1658 #endif
1659
1660 /* Additional parameters are stored in the timestamp if present. */
1661 if (sc->sc_flags & SCF_TIMESTAMP) {
1662 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */
1663 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */
1664 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */
1665 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */
1666 data |= md5_buffer[2] << 10; /* more digest bits */
1667 data ^= md5_buffer[3];
1668 sc->sc_ts = data;
1669 sc->sc_tsoff = data - tcp_ts_getticks(); /* after XOR */
1670 }
1671
1672 TCPSTAT_INC(tcps_sc_sendcookie);
1673 }
1674
1675 static struct syncache *
1676 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
1677 struct syncache *sc, struct tcpopt *to, struct tcphdr *th,
1678 struct socket *so)
1679 {
1680 MD5_CTX ctx;
1681 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1682 u_int32_t data = 0;
1683 u_int32_t *secbits;
1684 tcp_seq ack, seq;
1685 int off, mss, wnd, flags;
1686
1687 SCH_LOCK_ASSERT(sch);
1688
1689 /*
1690 * Pull information out of SYN-ACK/ACK and
1691 * revert sequence number advances.
1692 */
1693 ack = th->th_ack - 1;
1694 seq = th->th_seq - 1;
1695 off = (ack >> 1) & 0x7;
1696 mss = (ack >> 4) & 0x7;
1697 flags = ack & 0x7f;
1698
1699 /* Which of the two secrets to use. */
1700 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even;
1701
1702 /*
1703 * The secret wasn't updated for the lifetime of a syncookie,
1704 * so this SYN-ACK/ACK is either too old (replay) or totally bogus.
1705 */
1706 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) {
1707 return (NULL);
1708 }
1709
1710 /* Recompute the digest so we can compare it. */
1711 MD5Init(&ctx);
1712 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1713 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1714 MD5Update(&ctx, secbits, off);
1715 MD5Update(&ctx, inc, sizeof(*inc));
1716 MD5Update(&ctx, &seq, sizeof(seq));
1717 MD5Update(&ctx, &flags, sizeof(flags));
1718 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1719
1720 /* Does the digest part of or ACK'ed ISS match? */
1721 if ((ack & (~0x7f)) != (md5_buffer[0] << 7))
1722 return (NULL);
1723
1724 /* Does the digest part of our reflected timestamp match? */
1725 if (to->to_flags & TOF_TS) {
1726 data = md5_buffer[3] ^ to->to_tsecr;
1727 if ((data & (~0x3ff)) != (md5_buffer[2] << 10))
1728 return (NULL);
1729 }
1730
1731 /* Fill in the syncache values. */
1732 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1733 sc->sc_ipopts = NULL;
1734
1735 sc->sc_irs = seq;
1736 sc->sc_iss = ack;
1737
1738 #ifdef INET6
1739 if (inc->inc_flags & INC_ISIPV6) {
1740 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL)
1741 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1742 } else
1743 #endif
1744 {
1745 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl;
1746 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos;
1747 }
1748
1749 /* Additional parameters that were encoded in the timestamp. */
1750 if (data) {
1751 sc->sc_flags |= SCF_TIMESTAMP;
1752 sc->sc_tsreflect = to->to_tsval;
1753 sc->sc_ts = to->to_tsecr;
1754 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
1755 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0;
1756 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0;
1757 sc->sc_requested_s_scale = min((data >> 2) & 0xf,
1758 TCP_MAX_WINSHIFT);
1759 sc->sc_requested_r_scale = min((data >> 6) & 0xf,
1760 TCP_MAX_WINSHIFT);
1761 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale)
1762 sc->sc_flags |= SCF_WINSCALE;
1763 } else
1764 sc->sc_flags |= SCF_NOOPT;
1765
1766 wnd = sbspace(&so->so_rcv);
1767 wnd = imax(wnd, 0);
1768 wnd = imin(wnd, TCP_MAXWIN);
1769 sc->sc_wnd = wnd;
1770
1771 sc->sc_rxmits = 0;
1772 sc->sc_peer_mss = tcp_sc_msstab[mss];
1773
1774 TCPSTAT_INC(tcps_sc_recvcookie);
1775 return (sc);
1776 }
1777
1778 /*
1779 * Returns the current number of syncache entries. This number
1780 * will probably change before you get around to calling
1781 * syncache_pcblist.
1782 */
1783
1784 int
1785 syncache_pcbcount(void)
1786 {
1787 struct syncache_head *sch;
1788 int count, i;
1789
1790 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1791 /* No need to lock for a read. */
1792 sch = &V_tcp_syncache.hashbase[i];
1793 count += sch->sch_length;
1794 }
1795 return count;
1796 }
1797
1798 /*
1799 * Exports the syncache entries to userland so that netstat can display
1800 * them alongside the other sockets. This function is intended to be
1801 * called only from tcp_pcblist.
1802 *
1803 * Due to concurrency on an active system, the number of pcbs exported
1804 * may have no relation to max_pcbs. max_pcbs merely indicates the
1805 * amount of space the caller allocated for this function to use.
1806 */
1807 int
1808 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
1809 {
1810 struct xtcpcb xt;
1811 struct syncache *sc;
1812 struct syncache_head *sch;
1813 int count, error, i;
1814
1815 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1816 sch = &V_tcp_syncache.hashbase[i];
1817 SCH_LOCK(sch);
1818 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
1819 if (count >= max_pcbs) {
1820 SCH_UNLOCK(sch);
1821 goto exit;
1822 }
1823 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
1824 continue;
1825 bzero(&xt, sizeof(xt));
1826 xt.xt_len = sizeof(xt);
1827 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1828 xt.xt_inp.inp_vflag = INP_IPV6;
1829 else
1830 xt.xt_inp.inp_vflag = INP_IPV4;
1831 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
1832 xt.xt_tp.t_inpcb = &xt.xt_inp;
1833 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
1834 xt.xt_socket.xso_protocol = IPPROTO_TCP;
1835 xt.xt_socket.xso_len = sizeof (struct xsocket);
1836 xt.xt_socket.so_type = SOCK_STREAM;
1837 xt.xt_socket.so_state = SS_ISCONNECTING;
1838 error = SYSCTL_OUT(req, &xt, sizeof xt);
1839 if (error) {
1840 SCH_UNLOCK(sch);
1841 goto exit;
1842 }
1843 count++;
1844 }
1845 SCH_UNLOCK(sch);
1846 }
1847 exit:
1848 *pcbs_exported = count;
1849 return error;
1850 }
Cache object: d57d24de09db51ab1a86358e0a047786
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