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/7.4/sys/netinet/tcp_syncache.c 211601 2010-08-22 08:47:51Z andre $");
35
36 #include "opt_inet.h"
37 #include "opt_inet6.h"
38 #include "opt_ipsec.h"
39 #include "opt_mac.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
63 #include <netinet/in.h>
64 #include <netinet/in_systm.h>
65 #include <netinet/ip.h>
66 #include <netinet/in_var.h>
67 #include <netinet/in_pcb.h>
68 #include <netinet/ip_var.h>
69 #include <netinet/ip_options.h>
70 #ifdef INET6
71 #include <netinet/ip6.h>
72 #include <netinet/icmp6.h>
73 #include <netinet6/nd6.h>
74 #include <netinet6/ip6_var.h>
75 #include <netinet6/in6_pcb.h>
76 #endif
77 #include <netinet/tcp.h>
78 #include <netinet/tcp_fsm.h>
79 #include <netinet/tcp_seq.h>
80 #include <netinet/tcp_timer.h>
81 #include <netinet/tcp_var.h>
82 #include <netinet/tcp_syncache.h>
83 #include <netinet/tcp_offload.h>
84 #ifdef INET6
85 #include <netinet6/tcp6_var.h>
86 #endif
87
88 #ifdef IPSEC
89 #include <netipsec/ipsec.h>
90 #ifdef INET6
91 #include <netipsec/ipsec6.h>
92 #endif
93 #include <netipsec/key.h>
94 #endif /*IPSEC*/
95
96 #include <machine/in_cksum.h>
97
98 #include <security/mac/mac_framework.h>
99
100 static int tcp_syncookies = 1;
101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
102 &tcp_syncookies, 0,
103 "Use TCP SYN cookies if the syncache overflows");
104
105 static int tcp_syncookiesonly = 0;
106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW,
107 &tcp_syncookiesonly, 0,
108 "Use only TCP SYN cookies");
109
110 #define SYNCOOKIE_SECRET_SIZE 8 /* dwords */
111 #define SYNCOOKIE_LIFETIME 16 /* seconds */
112
113 struct syncache {
114 TAILQ_ENTRY(syncache) sc_hash;
115 struct in_conninfo sc_inc; /* addresses */
116 int sc_rxttime; /* retransmit time */
117 u_int16_t sc_rxmits; /* retransmit counter */
118 u_int32_t sc_tsreflect; /* timestamp to reflect */
119 u_int32_t sc_ts; /* our timestamp to send */
120 u_int32_t sc_tsoff; /* ts offset w/ syncookies */
121 u_int32_t sc_flowlabel; /* IPv6 flowlabel */
122 tcp_seq sc_irs; /* seq from peer */
123 tcp_seq sc_iss; /* our ISS */
124 struct mbuf *sc_ipopts; /* source route */
125 u_int16_t sc_peer_mss; /* peer's MSS */
126 u_int16_t sc_wnd; /* advertised window */
127 u_int8_t sc_ip_ttl; /* IPv4 TTL */
128 u_int8_t sc_ip_tos; /* IPv4 TOS */
129 u_int8_t sc_requested_s_scale:4,
130 sc_requested_r_scale:4;
131 u_int8_t sc_flags;
132 #ifndef TCP_OFFLOAD_DISABLE
133 struct toe_usrreqs *sc_tu; /* TOE operations */
134 void *sc_toepcb; /* TOE protocol block */
135 #endif
136 #ifdef MAC
137 struct label *sc_label; /* MAC label reference */
138 #endif
139 struct ucred *sc_cred; /* cred cache for jail checks */
140 };
141
142 /*
143 * Flags for the sc_flags field.
144 */
145 #define SCF_NOOPT 0x01 /* no TCP options */
146 #define SCF_WINSCALE 0x02 /* negotiated window scaling */
147 #define SCF_TIMESTAMP 0x04 /* negotiated timestamps */
148 /* MSS is implicit */
149 #define SCF_UNREACH 0x10 /* icmp unreachable received */
150 #define SCF_SIGNATURE 0x20 /* send MD5 digests */
151 #define SCF_SACK 0x80 /* send SACK option */
152
153 #ifdef TCP_OFFLOAD_DISABLE
154 #define TOEPCB_ISSET(sc) (0)
155 #else
156 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL)
157 #endif
158
159
160 struct syncache_head {
161 struct mtx sch_mtx;
162 TAILQ_HEAD(sch_head, syncache) sch_bucket;
163 struct callout sch_timer;
164 int sch_nextc;
165 u_int sch_length;
166 u_int sch_oddeven;
167 u_int32_t sch_secbits_odd[SYNCOOKIE_SECRET_SIZE];
168 u_int32_t sch_secbits_even[SYNCOOKIE_SECRET_SIZE];
169 u_int sch_reseed; /* time_uptime, seconds */
170 };
171
172 static void syncache_drop(struct syncache *, struct syncache_head *);
173 static void syncache_free(struct syncache *);
174 static void syncache_insert(struct syncache *, struct syncache_head *);
175 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
176 static int syncache_respond(struct syncache *);
177 static struct socket *syncache_socket(struct syncache *, struct socket *,
178 struct mbuf *m);
179 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
180 int docallout);
181 static void syncache_timer(void *);
182 static void syncookie_generate(struct syncache_head *, struct syncache *,
183 u_int32_t *);
184 static struct syncache
185 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
186 struct syncache *, struct tcpopt *, struct tcphdr *,
187 struct socket *);
188
189 /*
190 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
191 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
192 * the odds are that the user has given up attempting to connect by then.
193 */
194 #define SYNCACHE_MAXREXMTS 3
195
196 /* Arbitrary values */
197 #define TCP_SYNCACHE_HASHSIZE 512
198 #define TCP_SYNCACHE_BUCKETLIMIT 30
199
200 struct tcp_syncache {
201 struct syncache_head *hashbase;
202 uma_zone_t zone;
203 u_int hashsize;
204 u_int hashmask;
205 u_int bucket_limit;
206 u_int cache_count; /* XXX: unprotected */
207 u_int cache_limit;
208 u_int rexmt_limit;
209 u_int hash_secret;
210 };
211 static struct tcp_syncache tcp_syncache;
212
213 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
214
215 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
216 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
217
218 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
219 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
220
221 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
222 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
223
224 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
225 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
226
227 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
228 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
229
230 int tcp_sc_rst_sock_fail = 1;
231 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, CTLFLAG_RW,
232 &tcp_sc_rst_sock_fail, 0, "Send reset on socket allocation failure");
233
234 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
235
236 #define SYNCACHE_HASH(inc, mask) \
237 ((tcp_syncache.hash_secret ^ \
238 (inc)->inc_faddr.s_addr ^ \
239 ((inc)->inc_faddr.s_addr >> 16) ^ \
240 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
241
242 #define SYNCACHE_HASH6(inc, mask) \
243 ((tcp_syncache.hash_secret ^ \
244 (inc)->inc6_faddr.s6_addr32[0] ^ \
245 (inc)->inc6_faddr.s6_addr32[3] ^ \
246 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
247
248 #define ENDPTS_EQ(a, b) ( \
249 (a)->ie_fport == (b)->ie_fport && \
250 (a)->ie_lport == (b)->ie_lport && \
251 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
252 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
253 )
254
255 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
256
257 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
258 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
259 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
260
261 /*
262 * Requires the syncache entry to be already removed from the bucket list.
263 */
264 static void
265 syncache_free(struct syncache *sc)
266 {
267 if (sc->sc_ipopts)
268 (void) m_free(sc->sc_ipopts);
269 if (sc->sc_cred)
270 crfree(sc->sc_cred);
271 #ifdef MAC
272 mac_destroy_syncache(&sc->sc_label);
273 #endif
274
275 uma_zfree(tcp_syncache.zone, sc);
276 }
277
278 void
279 syncache_init(void)
280 {
281 int i;
282
283 tcp_syncache.cache_count = 0;
284 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
285 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
286 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
287 tcp_syncache.hash_secret = arc4random();
288
289 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
290 &tcp_syncache.hashsize);
291 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
292 &tcp_syncache.bucket_limit);
293 if (!powerof2(tcp_syncache.hashsize) || tcp_syncache.hashsize == 0) {
294 printf("WARNING: syncache hash size is not a power of 2.\n");
295 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
296 }
297 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
298
299 /* Set limits. */
300 tcp_syncache.cache_limit =
301 tcp_syncache.hashsize * tcp_syncache.bucket_limit;
302 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
303 &tcp_syncache.cache_limit);
304
305 /* Allocate the hash table. */
306 MALLOC(tcp_syncache.hashbase, struct syncache_head *,
307 tcp_syncache.hashsize * sizeof(struct syncache_head),
308 M_SYNCACHE, M_WAITOK | M_ZERO);
309
310 /* Initialize the hash buckets. */
311 for (i = 0; i < tcp_syncache.hashsize; i++) {
312 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket);
313 mtx_init(&tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
314 NULL, MTX_DEF);
315 callout_init_mtx(&tcp_syncache.hashbase[i].sch_timer,
316 &tcp_syncache.hashbase[i].sch_mtx, 0);
317 tcp_syncache.hashbase[i].sch_length = 0;
318 }
319
320 /* Create the syncache entry zone. */
321 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
322 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
323 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit);
324 }
325
326 /*
327 * Inserts a syncache entry into the specified bucket row.
328 * Locks and unlocks the syncache_head autonomously.
329 */
330 static void
331 syncache_insert(struct syncache *sc, struct syncache_head *sch)
332 {
333 struct syncache *sc2;
334
335 SCH_LOCK(sch);
336
337 /*
338 * Make sure that we don't overflow the per-bucket limit.
339 * If the bucket is full, toss the oldest element.
340 */
341 if (sch->sch_length >= tcp_syncache.bucket_limit) {
342 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
343 ("sch->sch_length incorrect"));
344 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
345 syncache_drop(sc2, sch);
346 tcpstat.tcps_sc_bucketoverflow++;
347 }
348
349 /* Put it into the bucket. */
350 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
351 sch->sch_length++;
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 tcp_syncache.cache_count++;
361 tcpstat.tcps_sc_added++;
362 }
363
364 /*
365 * Remove and free entry from syncache bucket row.
366 * Expects locked syncache head.
367 */
368 static void
369 syncache_drop(struct syncache *sc, struct syncache_head *sch)
370 {
371
372 SCH_LOCK_ASSERT(sch);
373
374 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
375 sch->sch_length--;
376
377 #ifndef TCP_OFFLOAD_DISABLE
378 if (sc->sc_tu)
379 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb);
380 #endif
381 syncache_free(sc);
382 tcp_syncache.cache_count--;
383 }
384
385 /*
386 * Engage/reengage time on bucket row.
387 */
388 static void
389 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
390 {
391 sc->sc_rxttime = ticks +
392 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
393 sc->sc_rxmits++;
394 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
395 sch->sch_nextc = sc->sc_rxttime;
396 if (docallout)
397 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
398 syncache_timer, (void *)sch);
399 }
400 }
401
402 /*
403 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
404 * If we have retransmitted an entry the maximum number of times, expire it.
405 * One separate timer for each bucket row.
406 */
407 static void
408 syncache_timer(void *xsch)
409 {
410 struct syncache_head *sch = (struct syncache_head *)xsch;
411 struct syncache *sc, *nsc;
412 int tick = ticks;
413 char *s;
414
415 /* NB: syncache_head has already been locked by the callout. */
416 SCH_LOCK_ASSERT(sch);
417
418 /*
419 * In the following cycle we may remove some entries and/or
420 * advance some timeouts, so re-initialize the bucket timer.
421 */
422 sch->sch_nextc = tick + INT_MAX;
423
424 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
425 /*
426 * We do not check if the listen socket still exists
427 * and accept the case where the listen socket may be
428 * gone by the time we resend the SYN/ACK. We do
429 * not expect this to happens often. If it does,
430 * then the RST will be sent by the time the remote
431 * host does the SYN/ACK->ACK.
432 */
433 if (TSTMP_GT(sc->sc_rxttime, tick)) {
434 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
435 sch->sch_nextc = sc->sc_rxttime;
436 continue;
437 }
438
439 if (sc->sc_rxmits > tcp_syncache.rexmt_limit) {
440 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
441 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
442 "giving up and removing syncache entry\n",
443 s, __func__);
444 free(s, M_TCPLOG);
445 }
446 syncache_drop(sc, sch);
447 tcpstat.tcps_sc_stale++;
448 continue;
449 }
450 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
451 log(LOG_DEBUG, "%s; %s: Response timeout, "
452 "retransmitting (%u) SYN|ACK\n",
453 s, __func__, sc->sc_rxmits);
454 free(s, M_TCPLOG);
455 }
456
457 (void) syncache_respond(sc);
458 tcpstat.tcps_sc_retransmitted++;
459 syncache_timeout(sc, sch, 0);
460 }
461 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
462 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
463 syncache_timer, (void *)(sch));
464 }
465
466 /*
467 * Find an entry in the syncache.
468 * Returns always with locked syncache_head plus a matching entry or NULL.
469 */
470 struct syncache *
471 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
472 {
473 struct syncache *sc;
474 struct syncache_head *sch;
475
476 #ifdef INET6
477 if (inc->inc_flags & INC_ISIPV6) {
478 sch = &tcp_syncache.hashbase[
479 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
480 *schp = sch;
481
482 SCH_LOCK(sch);
483
484 /* Circle through bucket row to find matching entry. */
485 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
486 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
487 return (sc);
488 }
489 } else
490 #endif
491 {
492 sch = &tcp_syncache.hashbase[
493 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
494 *schp = sch;
495
496 SCH_LOCK(sch);
497
498 /* Circle through bucket row to find matching entry. */
499 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
500 #ifdef INET6
501 if (sc->sc_inc.inc_flags & INC_ISIPV6)
502 continue;
503 #endif
504 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
505 return (sc);
506 }
507 }
508 SCH_LOCK_ASSERT(*schp);
509 return (NULL); /* always returns with locked sch */
510 }
511
512 /*
513 * This function is called when we get a RST for a
514 * non-existent connection, so that we can see if the
515 * connection is in the syn cache. If it is, zap it.
516 */
517 void
518 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
519 {
520 struct syncache *sc;
521 struct syncache_head *sch;
522 char *s = NULL;
523
524 sc = syncache_lookup(inc, &sch); /* returns locked sch */
525 SCH_LOCK_ASSERT(sch);
526
527 /*
528 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
529 * See RFC 793 page 65, section SEGMENT ARRIVES.
530 */
531 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
532 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
533 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
534 "FIN flag set, segment ignored\n", s, __func__);
535 tcpstat.tcps_badrst++;
536 goto done;
537 }
538
539 /*
540 * No corresponding connection was found in syncache.
541 * If syncookies are enabled and possibly exclusively
542 * used, or we are under memory pressure, a valid RST
543 * may not find a syncache entry. In that case we're
544 * done and no SYN|ACK retransmissions will happen.
545 * Otherwise the the RST was misdirected or spoofed.
546 */
547 if (sc == NULL) {
548 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
549 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
550 "syncache entry (possibly syncookie only), "
551 "segment ignored\n", s, __func__);
552 tcpstat.tcps_badrst++;
553 goto done;
554 }
555
556 /*
557 * If the RST bit is set, check the sequence number to see
558 * if this is a valid reset segment.
559 * RFC 793 page 37:
560 * In all states except SYN-SENT, all reset (RST) segments
561 * are validated by checking their SEQ-fields. A reset is
562 * valid if its sequence number is in the window.
563 *
564 * The sequence number in the reset segment is normally an
565 * echo of our outgoing acknowlegement numbers, but some hosts
566 * send a reset with the sequence number at the rightmost edge
567 * of our receive window, and we have to handle this case.
568 */
569 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
570 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
571 syncache_drop(sc, sch);
572 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
573 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
574 "connection attempt aborted by remote endpoint\n",
575 s, __func__);
576 tcpstat.tcps_sc_reset++;
577 } else {
578 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
579 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
580 "IRS %u (+WND %u), segment ignored\n",
581 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
582 tcpstat.tcps_badrst++;
583 }
584
585 done:
586 if (s != NULL)
587 free(s, M_TCPLOG);
588 SCH_UNLOCK(sch);
589 }
590
591 void
592 syncache_badack(struct in_conninfo *inc)
593 {
594 struct syncache *sc;
595 struct syncache_head *sch;
596
597 sc = syncache_lookup(inc, &sch); /* returns locked sch */
598 SCH_LOCK_ASSERT(sch);
599 if (sc != NULL) {
600 syncache_drop(sc, sch);
601 tcpstat.tcps_sc_badack++;
602 }
603 SCH_UNLOCK(sch);
604 }
605
606 void
607 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
608 {
609 struct syncache *sc;
610 struct syncache_head *sch;
611
612 sc = syncache_lookup(inc, &sch); /* returns locked sch */
613 SCH_LOCK_ASSERT(sch);
614 if (sc == NULL)
615 goto done;
616
617 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
618 if (ntohl(th->th_seq) != sc->sc_iss)
619 goto done;
620
621 /*
622 * If we've rertransmitted 3 times and this is our second error,
623 * we remove the entry. Otherwise, we allow it to continue on.
624 * This prevents us from incorrectly nuking an entry during a
625 * spurious network outage.
626 *
627 * See tcp_notify().
628 */
629 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
630 sc->sc_flags |= SCF_UNREACH;
631 goto done;
632 }
633 syncache_drop(sc, sch);
634 tcpstat.tcps_sc_unreach++;
635 done:
636 SCH_UNLOCK(sch);
637 }
638
639 /*
640 * Build a new TCP socket structure from a syncache entry.
641 */
642 static struct socket *
643 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
644 {
645 struct inpcb *inp = NULL;
646 struct socket *so;
647 struct tcpcb *tp;
648 int error = 0;
649 char *s;
650
651 INP_INFO_WLOCK_ASSERT(&tcbinfo);
652
653 /*
654 * Ok, create the full blown connection, and set things up
655 * as they would have been set up if we had created the
656 * connection when the SYN arrived. If we can't create
657 * the connection, abort it.
658 */
659 so = sonewconn(lso, SS_ISCONNECTED);
660 if (so == NULL) {
661 /*
662 * Drop the connection; we will either send a RST or
663 * have the peer retransmit its SYN again after its
664 * RTO and try again.
665 */
666 tcpstat.tcps_listendrop++;
667 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
668 log(LOG_DEBUG, "%s; %s: Socket create failed "
669 "due to limits or memory shortage\n",
670 s, __func__);
671 free(s, M_TCPLOG);
672 }
673 goto abort2;
674 }
675 #ifdef MAC
676 SOCK_LOCK(so);
677 mac_set_socket_peer_from_mbuf(m, so);
678 SOCK_UNLOCK(so);
679 #endif
680
681 inp = sotoinpcb(so);
682 inp->inp_inc.inc_fibnum = so->so_fibnum;
683 INP_WLOCK(inp);
684
685 /* Insert new socket into PCB hash list. */
686 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
687 #ifdef INET6
688 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
689 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
690 } else {
691 inp->inp_vflag &= ~INP_IPV6;
692 inp->inp_vflag |= INP_IPV4;
693 #endif
694 inp->inp_laddr = sc->sc_inc.inc_laddr;
695 #ifdef INET6
696 }
697 #endif
698 inp->inp_lport = sc->sc_inc.inc_lport;
699 if ((error = in_pcbinshash(inp)) != 0) {
700 /*
701 * Undo the assignments above if we failed to
702 * put the PCB on the hash lists.
703 */
704 #ifdef INET6
705 if (sc->sc_inc.inc_flags & INC_ISIPV6)
706 inp->in6p_laddr = in6addr_any;
707 else
708 #endif
709 inp->inp_laddr.s_addr = INADDR_ANY;
710 inp->inp_lport = 0;
711 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
712 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
713 "with error %i\n",
714 s, __func__, error);
715 free(s, M_TCPLOG);
716 }
717 goto abort;
718 }
719 #ifdef IPSEC
720 /* Copy old policy into new socket's. */
721 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
722 printf("syncache_socket: could not copy policy\n");
723 #endif
724 #ifdef INET6
725 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
726 struct inpcb *oinp = sotoinpcb(lso);
727 struct in6_addr laddr6;
728 struct sockaddr_in6 sin6;
729 /*
730 * Inherit socket options from the listening socket.
731 * Note that in6p_inputopts are not (and should not be)
732 * copied, since it stores previously received options and is
733 * used to detect if each new option is different than the
734 * previous one and hence should be passed to a user.
735 * If we copied in6p_inputopts, a user would not be able to
736 * receive options just after calling the accept system call.
737 */
738 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
739 if (oinp->in6p_outputopts)
740 inp->in6p_outputopts =
741 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
742
743 sin6.sin6_family = AF_INET6;
744 sin6.sin6_len = sizeof(sin6);
745 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
746 sin6.sin6_port = sc->sc_inc.inc_fport;
747 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
748 laddr6 = inp->in6p_laddr;
749 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
750 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
751 if ((error = in6_pcbconnect(inp, (struct sockaddr *)&sin6,
752 thread0.td_ucred)) != 0) {
753 inp->in6p_laddr = laddr6;
754 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
755 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
756 "with error %i\n",
757 s, __func__, error);
758 free(s, M_TCPLOG);
759 }
760 goto abort;
761 }
762 /* Override flowlabel from in6_pcbconnect. */
763 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
764 inp->inp_flow |= sc->sc_flowlabel;
765 } else
766 #endif
767 {
768 struct in_addr laddr;
769 struct sockaddr_in sin;
770
771 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
772
773 if (inp->inp_options == NULL) {
774 inp->inp_options = sc->sc_ipopts;
775 sc->sc_ipopts = NULL;
776 }
777
778 sin.sin_family = AF_INET;
779 sin.sin_len = sizeof(sin);
780 sin.sin_addr = sc->sc_inc.inc_faddr;
781 sin.sin_port = sc->sc_inc.inc_fport;
782 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
783 laddr = inp->inp_laddr;
784 if (inp->inp_laddr.s_addr == INADDR_ANY)
785 inp->inp_laddr = sc->sc_inc.inc_laddr;
786 if ((error = in_pcbconnect(inp, (struct sockaddr *)&sin,
787 thread0.td_ucred)) != 0) {
788 inp->inp_laddr = laddr;
789 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
790 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
791 "with error %i\n",
792 s, __func__, error);
793 free(s, M_TCPLOG);
794 }
795 goto abort;
796 }
797 }
798 tp = intotcpcb(inp);
799 tp->t_state = TCPS_SYN_RECEIVED;
800 tp->iss = sc->sc_iss;
801 tp->irs = sc->sc_irs;
802 tcp_rcvseqinit(tp);
803 tcp_sendseqinit(tp);
804 tp->snd_wl1 = sc->sc_irs;
805 tp->snd_max = tp->iss + 1;
806 tp->snd_nxt = tp->iss + 1;
807 tp->rcv_up = sc->sc_irs + 1;
808 tp->rcv_wnd = sc->sc_wnd;
809 tp->rcv_adv += tp->rcv_wnd;
810 tp->last_ack_sent = tp->rcv_nxt;
811
812 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
813 if (sc->sc_flags & SCF_NOOPT)
814 tp->t_flags |= TF_NOOPT;
815 else {
816 if (sc->sc_flags & SCF_WINSCALE) {
817 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
818 tp->snd_scale = sc->sc_requested_s_scale;
819 tp->request_r_scale = sc->sc_requested_r_scale;
820 }
821 if (sc->sc_flags & SCF_TIMESTAMP) {
822 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
823 tp->ts_recent = sc->sc_tsreflect;
824 tp->ts_recent_age = ticks;
825 tp->ts_offset = sc->sc_tsoff;
826 }
827 #ifdef TCP_SIGNATURE
828 if (sc->sc_flags & SCF_SIGNATURE)
829 tp->t_flags |= TF_SIGNATURE;
830 #endif
831 if (sc->sc_flags & SCF_SACK)
832 tp->t_flags |= TF_SACK_PERMIT;
833 }
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 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit);
848
849 INP_WUNLOCK(inp);
850
851 tcpstat.tcps_accepts++;
852 return (so);
853
854 abort:
855 INP_WUNLOCK(inp);
856 abort2:
857 if (so != NULL)
858 soabort(so);
859 return (NULL);
860 }
861
862 /*
863 * This function gets called when we receive an ACK for a
864 * socket in the LISTEN state. We look up the connection
865 * in the syncache, and if its there, we pull it out of
866 * the cache and turn it into a full-blown connection in
867 * the SYN-RECEIVED state.
868 */
869 int
870 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
871 struct socket **lsop, struct mbuf *m)
872 {
873 struct syncache *sc;
874 struct syncache_head *sch;
875 struct syncache scs;
876 char *s;
877
878 /*
879 * Global TCP locks are held because we manipulate the PCB lists
880 * and create a new socket.
881 */
882 INP_INFO_WLOCK_ASSERT(&tcbinfo);
883 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
884 ("%s: can handle only ACK", __func__));
885
886 sc = syncache_lookup(inc, &sch); /* returns locked sch */
887 SCH_LOCK_ASSERT(sch);
888 if (sc == NULL) {
889 /*
890 * There is no syncache entry, so see if this ACK is
891 * a returning syncookie. To do this, first:
892 * A. See if this socket has had a syncache entry dropped in
893 * the past. We don't want to accept a bogus syncookie
894 * if we've never received a SYN.
895 * B. check that the syncookie is valid. If it is, then
896 * cobble up a fake syncache entry, and return.
897 */
898 if (!tcp_syncookies) {
899 SCH_UNLOCK(sch);
900 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
901 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
902 "segment rejected (syncookies disabled)\n",
903 s, __func__);
904 goto failed;
905 }
906 bzero(&scs, sizeof(scs));
907 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop);
908 SCH_UNLOCK(sch);
909 if (sc == NULL) {
910 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
911 log(LOG_DEBUG, "%s; %s: Segment failed "
912 "SYNCOOKIE authentication, segment rejected "
913 "(probably spoofed)\n", s, __func__);
914 goto failed;
915 }
916 } else {
917 /* Pull out the entry to unlock the bucket row. */
918 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
919 sch->sch_length--;
920 tcp_syncache.cache_count--;
921 SCH_UNLOCK(sch);
922 }
923
924 /*
925 * Segment validation:
926 * ACK must match our initial sequence number + 1 (the SYN|ACK).
927 */
928 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) {
929 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
930 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
931 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
932 goto failed;
933 }
934
935 /*
936 * The SEQ must fall in the window starting at the received
937 * initial receive sequence number + 1 (the SYN).
938 */
939 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) ||
940 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) &&
941 !TOEPCB_ISSET(sc)) {
942 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
943 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
944 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
945 goto failed;
946 }
947 #if 0
948 /*
949 * If timestamps were present in the SYN and we accepted
950 * them in our SYN|ACK we require them to be present from
951 * now on. And vice versa.
952 *
953 * Unfortunately, during testing of 7.0 some users found
954 * network devices that violate this constraint, so it must
955 * be disabled.
956 */
957 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) {
958 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
959 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
960 "segment rejected\n", s, __func__);
961 goto failed;
962 }
963 #endif
964 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
965 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
966 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
967 "segment rejected\n", s, __func__);
968 goto failed;
969 }
970 /*
971 * If timestamps were negotiated the reflected timestamp
972 * must be equal to what we actually sent in the SYN|ACK.
973 */
974 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts &&
975 !TOEPCB_ISSET(sc)) {
976 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
977 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
978 "segment rejected\n",
979 s, __func__, to->to_tsecr, sc->sc_ts);
980 goto failed;
981 }
982
983 *lsop = syncache_socket(sc, *lsop, m);
984
985 if (*lsop == NULL)
986 tcpstat.tcps_sc_aborted++;
987 else
988 tcpstat.tcps_sc_completed++;
989
990 /* how do we find the inp for the new socket? */
991 if (sc != &scs)
992 syncache_free(sc);
993 return (1);
994 failed:
995 if (sc != NULL && sc != &scs)
996 syncache_free(sc);
997 if (s != NULL)
998 free(s, M_TCPLOG);
999 *lsop = NULL;
1000 return (0);
1001 }
1002
1003 int
1004 tcp_offload_syncache_expand(struct in_conninfo *inc, struct tcpopt *to,
1005 struct tcphdr *th, struct socket **lsop, struct mbuf *m)
1006 {
1007 int rc;
1008
1009 INP_INFO_WLOCK(&tcbinfo);
1010 rc = syncache_expand(inc, to, th, lsop, m);
1011 INP_INFO_WUNLOCK(&tcbinfo);
1012
1013 return (rc);
1014 }
1015
1016 /*
1017 * Given a LISTEN socket and an inbound SYN request, add
1018 * this to the syn cache, and send back a segment:
1019 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1020 * to the source.
1021 *
1022 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1023 * Doing so would require that we hold onto the data and deliver it
1024 * to the application. However, if we are the target of a SYN-flood
1025 * DoS attack, an attacker could send data which would eventually
1026 * consume all available buffer space if it were ACKed. By not ACKing
1027 * the data, we avoid this DoS scenario.
1028 */
1029 static void
1030 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1031 struct inpcb *inp, struct socket **lsop, struct mbuf *m,
1032 struct toe_usrreqs *tu, void *toepcb)
1033 {
1034 struct tcpcb *tp;
1035 struct socket *so;
1036 struct syncache *sc = NULL;
1037 struct syncache_head *sch;
1038 struct mbuf *ipopts = NULL;
1039 u_int32_t flowtmp;
1040 int win, sb_hiwat, ip_ttl, ip_tos, noopt;
1041 char *s;
1042 #ifdef INET6
1043 int autoflowlabel = 0;
1044 #endif
1045 #ifdef MAC
1046 struct label *maclabel;
1047 #endif
1048 struct syncache scs;
1049 struct ucred *cred;
1050
1051 INP_INFO_WLOCK_ASSERT(&tcbinfo);
1052 INP_WLOCK_ASSERT(inp); /* listen socket */
1053 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1054 ("%s: unexpected tcp flags", __func__));
1055
1056 /*
1057 * Combine all so/tp operations very early to drop the INP lock as
1058 * soon as possible.
1059 */
1060 so = *lsop;
1061 tp = sototcpcb(so);
1062 cred = crhold(so->so_cred);
1063
1064 #ifdef INET6
1065 if ((inc->inc_flags & INC_ISIPV6) &&
1066 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1067 autoflowlabel = 1;
1068 #endif
1069 ip_ttl = inp->inp_ip_ttl;
1070 ip_tos = inp->inp_ip_tos;
1071 win = sbspace(&so->so_rcv);
1072 sb_hiwat = so->so_rcv.sb_hiwat;
1073 noopt = (tp->t_flags & TF_NOOPT);
1074
1075 /* By the time we drop the lock these should no longer be used. */
1076 so = NULL;
1077 tp = NULL;
1078
1079 #ifdef MAC
1080 if (mac_init_syncache(&maclabel) != 0) {
1081 INP_WUNLOCK(inp);
1082 INP_INFO_WUNLOCK(&tcbinfo);
1083 goto done;
1084 } else
1085 mac_init_syncache_from_inpcb(maclabel, inp);
1086 #endif
1087 INP_WUNLOCK(inp);
1088 INP_INFO_WUNLOCK(&tcbinfo);
1089
1090 /*
1091 * Remember the IP options, if any.
1092 */
1093 #ifdef INET6
1094 if (!(inc->inc_flags & INC_ISIPV6))
1095 #endif
1096 ipopts = (m) ? ip_srcroute(m) : NULL;
1097
1098 /*
1099 * See if we already have an entry for this connection.
1100 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1101 *
1102 * XXX: should the syncache be re-initialized with the contents
1103 * of the new SYN here (which may have different options?)
1104 *
1105 * XXX: We do not check the sequence number to see if this is a
1106 * real retransmit or a new connection attempt. The question is
1107 * how to handle such a case; either ignore it as spoofed, or
1108 * drop the current entry and create a new one?
1109 */
1110 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1111 SCH_LOCK_ASSERT(sch);
1112 if (sc != NULL) {
1113 #ifndef TCP_OFFLOAD_DISABLE
1114 if (sc->sc_tu)
1115 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT,
1116 sc->sc_toepcb);
1117 #endif
1118 tcpstat.tcps_sc_dupsyn++;
1119 if (ipopts) {
1120 /*
1121 * If we were remembering a previous source route,
1122 * forget it and use the new one we've been given.
1123 */
1124 if (sc->sc_ipopts)
1125 (void) m_free(sc->sc_ipopts);
1126 sc->sc_ipopts = ipopts;
1127 }
1128 /*
1129 * Update timestamp if present.
1130 */
1131 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1132 sc->sc_tsreflect = to->to_tsval;
1133 else
1134 sc->sc_flags &= ~SCF_TIMESTAMP;
1135 #ifdef MAC
1136 /*
1137 * Since we have already unconditionally allocated label
1138 * storage, free it up. The syncache entry will already
1139 * have an initialized label we can use.
1140 */
1141 mac_destroy_syncache(&maclabel);
1142 KASSERT(sc->sc_label != NULL,
1143 ("%s: label not initialized", __func__));
1144 #endif
1145 /* Retransmit SYN|ACK and reset retransmit count. */
1146 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1147 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1148 "resetting timer and retransmitting SYN|ACK\n",
1149 s, __func__);
1150 free(s, M_TCPLOG);
1151 }
1152 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) {
1153 sc->sc_rxmits = 0;
1154 syncache_timeout(sc, sch, 1);
1155 tcpstat.tcps_sndacks++;
1156 tcpstat.tcps_sndtotal++;
1157 }
1158 SCH_UNLOCK(sch);
1159 goto done;
1160 }
1161
1162 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO);
1163 if (sc == NULL) {
1164 /*
1165 * The zone allocator couldn't provide more entries.
1166 * Treat this as if the cache was full; drop the oldest
1167 * entry and insert the new one.
1168 */
1169 tcpstat.tcps_sc_zonefail++;
1170 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1171 syncache_drop(sc, sch);
1172 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO);
1173 if (sc == NULL) {
1174 if (tcp_syncookies) {
1175 bzero(&scs, sizeof(scs));
1176 sc = &scs;
1177 } else {
1178 SCH_UNLOCK(sch);
1179 if (ipopts)
1180 (void) m_free(ipopts);
1181 goto done;
1182 }
1183 }
1184 }
1185
1186 /*
1187 * Fill in the syncache values.
1188 */
1189 #ifdef MAC
1190 sc->sc_label = maclabel;
1191 #endif
1192 sc->sc_cred = cred;
1193 cred = NULL;
1194 sc->sc_ipopts = ipopts;
1195 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1196 #ifdef INET6
1197 if (!(inc->inc_flags & INC_ISIPV6))
1198 #endif
1199 {
1200 sc->sc_ip_tos = ip_tos;
1201 sc->sc_ip_ttl = ip_ttl;
1202 }
1203 #ifndef TCP_OFFLOAD_DISABLE
1204 sc->sc_tu = tu;
1205 sc->sc_toepcb = toepcb;
1206 #endif
1207 sc->sc_irs = th->th_seq;
1208 sc->sc_iss = arc4random();
1209 sc->sc_flags = 0;
1210 sc->sc_flowlabel = 0;
1211
1212 /*
1213 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1214 * win was derived from socket earlier in the function.
1215 */
1216 win = imax(win, 0);
1217 win = imin(win, TCP_MAXWIN);
1218 sc->sc_wnd = win;
1219
1220 if (tcp_do_rfc1323) {
1221 /*
1222 * A timestamp received in a SYN makes
1223 * it ok to send timestamp requests and replies.
1224 */
1225 if (to->to_flags & TOF_TS) {
1226 sc->sc_tsreflect = to->to_tsval;
1227 sc->sc_ts = ticks;
1228 sc->sc_flags |= SCF_TIMESTAMP;
1229 }
1230 if (to->to_flags & TOF_SCALE) {
1231 int wscale = 0;
1232
1233 /*
1234 * Pick the smallest possible scaling factor that
1235 * will still allow us to scale up to sb_max, aka
1236 * kern.ipc.maxsockbuf.
1237 *
1238 * We do this because there are broken firewalls that
1239 * will corrupt the window scale option, leading to
1240 * the other endpoint believing that our advertised
1241 * window is unscaled. At scale factors larger than
1242 * 5 the unscaled window will drop below 1500 bytes,
1243 * leading to serious problems when traversing these
1244 * broken firewalls.
1245 *
1246 * With the default maxsockbuf of 256K, a scale factor
1247 * of 3 will be chosen by this algorithm. Those who
1248 * choose a larger maxsockbuf should watch out
1249 * for the compatiblity problems mentioned above.
1250 *
1251 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1252 * or <SYN,ACK>) segment itself is never scaled.
1253 */
1254 while (wscale < TCP_MAX_WINSHIFT &&
1255 (TCP_MAXWIN << wscale) < sb_max)
1256 wscale++;
1257 sc->sc_requested_r_scale = wscale;
1258 sc->sc_requested_s_scale = to->to_wscale;
1259 sc->sc_flags |= SCF_WINSCALE;
1260 }
1261 }
1262 #ifdef TCP_SIGNATURE
1263 /*
1264 * If listening socket requested TCP digests, and received SYN
1265 * contains the option, flag this in the syncache so that
1266 * syncache_respond() will do the right thing with the SYN+ACK.
1267 * XXX: Currently we always record the option by default and will
1268 * attempt to use it in syncache_respond().
1269 */
1270 if (to->to_flags & TOF_SIGNATURE)
1271 sc->sc_flags |= SCF_SIGNATURE;
1272 #endif
1273 if (to->to_flags & TOF_SACKPERM)
1274 sc->sc_flags |= SCF_SACK;
1275 if (to->to_flags & TOF_MSS)
1276 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1277 if (noopt)
1278 sc->sc_flags |= SCF_NOOPT;
1279
1280 if (tcp_syncookies) {
1281 syncookie_generate(sch, sc, &flowtmp);
1282 #ifdef INET6
1283 if (autoflowlabel)
1284 sc->sc_flowlabel = flowtmp;
1285 #endif
1286 } else {
1287 #ifdef INET6
1288 if (autoflowlabel)
1289 sc->sc_flowlabel =
1290 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
1291 #endif
1292 }
1293 SCH_UNLOCK(sch);
1294
1295 /*
1296 * Do a standard 3-way handshake.
1297 */
1298 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) {
1299 if (tcp_syncookies && tcp_syncookiesonly && sc != &scs)
1300 syncache_free(sc);
1301 else if (sc != &scs)
1302 syncache_insert(sc, sch); /* locks and unlocks sch */
1303 tcpstat.tcps_sndacks++;
1304 tcpstat.tcps_sndtotal++;
1305 } else {
1306 if (sc != &scs)
1307 syncache_free(sc);
1308 tcpstat.tcps_sc_dropped++;
1309 }
1310
1311 done:
1312 if (cred != NULL)
1313 crfree(cred);
1314 #ifdef MAC
1315 if (sc == &scs)
1316 mac_destroy_syncache(&maclabel);
1317 #endif
1318 *lsop = NULL;
1319 m_freem(m);
1320 }
1321
1322 static int
1323 syncache_respond(struct syncache *sc)
1324 {
1325 struct ip *ip = NULL;
1326 struct mbuf *m;
1327 struct tcphdr *th;
1328 int optlen, error;
1329 u_int16_t hlen, tlen, mssopt;
1330 struct tcpopt to;
1331 #ifdef INET6
1332 struct ip6_hdr *ip6 = NULL;
1333 #endif
1334
1335 hlen =
1336 #ifdef INET6
1337 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1338 #endif
1339 sizeof(struct ip);
1340 tlen = hlen + sizeof(struct tcphdr);
1341
1342 /* Determine MSS we advertize to other end of connection. */
1343 mssopt = tcp_mssopt(&sc->sc_inc);
1344 if (sc->sc_peer_mss)
1345 mssopt = max( min(sc->sc_peer_mss, mssopt), tcp_minmss);
1346
1347 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1348 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1349 ("syncache: mbuf too small"));
1350
1351 /* Create the IP+TCP header from scratch. */
1352 m = m_gethdr(M_DONTWAIT, MT_DATA);
1353 if (m == NULL)
1354 return (ENOBUFS);
1355 #ifdef MAC
1356 mac_create_mbuf_from_syncache(sc->sc_label, m);
1357 #endif
1358 m->m_data += max_linkhdr;
1359 m->m_len = tlen;
1360 m->m_pkthdr.len = tlen;
1361 m->m_pkthdr.rcvif = NULL;
1362
1363 #ifdef INET6
1364 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1365 ip6 = mtod(m, struct ip6_hdr *);
1366 ip6->ip6_vfc = IPV6_VERSION;
1367 ip6->ip6_nxt = IPPROTO_TCP;
1368 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1369 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1370 ip6->ip6_plen = htons(tlen - hlen);
1371 /* ip6_hlim is set after checksum */
1372 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1373 ip6->ip6_flow |= sc->sc_flowlabel;
1374
1375 th = (struct tcphdr *)(ip6 + 1);
1376 } else
1377 #endif
1378 {
1379 ip = mtod(m, struct ip *);
1380 ip->ip_v = IPVERSION;
1381 ip->ip_hl = sizeof(struct ip) >> 2;
1382 ip->ip_len = tlen;
1383 ip->ip_id = 0;
1384 ip->ip_off = 0;
1385 ip->ip_sum = 0;
1386 ip->ip_p = IPPROTO_TCP;
1387 ip->ip_src = sc->sc_inc.inc_laddr;
1388 ip->ip_dst = sc->sc_inc.inc_faddr;
1389 ip->ip_ttl = sc->sc_ip_ttl;
1390 ip->ip_tos = sc->sc_ip_tos;
1391
1392 /*
1393 * See if we should do MTU discovery. Route lookups are
1394 * expensive, so we will only unset the DF bit if:
1395 *
1396 * 1) path_mtu_discovery is disabled
1397 * 2) the SCF_UNREACH flag has been set
1398 */
1399 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1400 ip->ip_off |= IP_DF;
1401
1402 th = (struct tcphdr *)(ip + 1);
1403 }
1404 th->th_sport = sc->sc_inc.inc_lport;
1405 th->th_dport = sc->sc_inc.inc_fport;
1406
1407 th->th_seq = htonl(sc->sc_iss);
1408 th->th_ack = htonl(sc->sc_irs + 1);
1409 th->th_off = sizeof(struct tcphdr) >> 2;
1410 th->th_x2 = 0;
1411 th->th_flags = TH_SYN|TH_ACK;
1412 th->th_win = htons(sc->sc_wnd);
1413 th->th_urp = 0;
1414
1415 /* Tack on the TCP options. */
1416 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1417 to.to_flags = 0;
1418
1419 to.to_mss = mssopt;
1420 to.to_flags = TOF_MSS;
1421 if (sc->sc_flags & SCF_WINSCALE) {
1422 to.to_wscale = sc->sc_requested_r_scale;
1423 to.to_flags |= TOF_SCALE;
1424 }
1425 if (sc->sc_flags & SCF_TIMESTAMP) {
1426 /* Virgin timestamp or TCP cookie enhanced one. */
1427 to.to_tsval = sc->sc_ts;
1428 to.to_tsecr = sc->sc_tsreflect;
1429 to.to_flags |= TOF_TS;
1430 }
1431 if (sc->sc_flags & SCF_SACK)
1432 to.to_flags |= TOF_SACKPERM;
1433 #ifdef TCP_SIGNATURE
1434 if (sc->sc_flags & SCF_SIGNATURE)
1435 to.to_flags |= TOF_SIGNATURE;
1436 #endif
1437 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1438
1439 /* Adjust headers by option size. */
1440 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1441 m->m_len += optlen;
1442 m->m_pkthdr.len += optlen;
1443
1444 #ifdef TCP_SIGNATURE
1445 if (sc->sc_flags & SCF_SIGNATURE)
1446 tcp_signature_compute(m, 0, 0, optlen,
1447 to.to_signature, IPSEC_DIR_OUTBOUND);
1448 #endif
1449 #ifdef INET6
1450 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1451 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1452 else
1453 #endif
1454 ip->ip_len += optlen;
1455 } else
1456 optlen = 0;
1457
1458 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1459 #ifdef INET6
1460 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1461 th->th_sum = 0;
1462 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen,
1463 tlen + optlen - hlen);
1464 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1465 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1466 } else
1467 #endif
1468 {
1469 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1470 htons(tlen + optlen - hlen + IPPROTO_TCP));
1471 m->m_pkthdr.csum_flags = CSUM_TCP;
1472 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1473 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1474 }
1475 return (error);
1476 }
1477
1478 void
1479 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1480 struct inpcb *inp, struct socket **lsop, struct mbuf *m)
1481 {
1482
1483 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL);
1484 }
1485
1486 void
1487 tcp_offload_syncache_add(struct in_conninfo *inc, struct tcpopt *to,
1488 struct tcphdr *th, struct inpcb *inp, struct socket **lsop,
1489 struct toe_usrreqs *tu, void *toepcb)
1490 {
1491
1492
1493 INP_INFO_WLOCK(&tcbinfo);
1494 INP_WLOCK(inp);
1495 _syncache_add(inc, to, th, inp, lsop, NULL, tu, toepcb);
1496
1497 }
1498
1499 /*
1500 * The purpose of SYN cookies is to avoid keeping track of all SYN's we
1501 * receive and to be able to handle SYN floods from bogus source addresses
1502 * (where we will never receive any reply). SYN floods try to exhaust all
1503 * our memory and available slots in the SYN cache table to cause a denial
1504 * of service to legitimate users of the local host.
1505 *
1506 * The idea of SYN cookies is to encode and include all necessary information
1507 * about the connection setup state within the SYN-ACK we send back and thus
1508 * to get along without keeping any local state until the ACK to the SYN-ACK
1509 * arrives (if ever). Everything we need to know should be available from
1510 * the information we encoded in the SYN-ACK.
1511 *
1512 * More information about the theory behind SYN cookies and its first
1513 * discussion and specification can be found at:
1514 * http://cr.yp.to/syncookies.html (overview)
1515 * http://cr.yp.to/syncookies/archive (gory details)
1516 *
1517 * This implementation extends the orginal idea and first implementation
1518 * of FreeBSD by using not only the initial sequence number field to store
1519 * information but also the timestamp field if present. This way we can
1520 * keep track of the entire state we need to know to recreate the session in
1521 * its original form. Almost all TCP speakers implement RFC1323 timestamps
1522 * these days. For those that do not we still have to live with the known
1523 * shortcomings of the ISN only SYN cookies.
1524 *
1525 * Cookie layers:
1526 *
1527 * Initial sequence number we send:
1528 * 31|................................|0
1529 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP
1530 * D = MD5 Digest (first dword)
1531 * M = MSS index
1532 * R = Rotation of secret
1533 * P = Odd or Even secret
1534 *
1535 * The MD5 Digest is computed with over following parameters:
1536 * a) randomly rotated secret
1537 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6)
1538 * c) the received initial sequence number from remote host
1539 * d) the rotation offset and odd/even bit
1540 *
1541 * Timestamp we send:
1542 * 31|................................|0
1543 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5
1544 * D = MD5 Digest (third dword) (only as filler)
1545 * S = Requested send window scale
1546 * R = Requested receive window scale
1547 * A = SACK allowed
1548 * 5 = TCP-MD5 enabled (not implemented yet)
1549 * XORed with MD5 Digest (forth dword)
1550 *
1551 * The timestamp isn't cryptographically secure and doesn't need to be.
1552 * The double use of the MD5 digest dwords ties it to a specific remote/
1553 * local host/port, remote initial sequence number and our local time
1554 * limited secret. A received timestamp is reverted (XORed) and then
1555 * the contained MD5 dword is compared to the computed one to ensure the
1556 * timestamp belongs to the SYN-ACK we sent. The other parameters may
1557 * have been tampered with but this isn't different from supplying bogus
1558 * values in the SYN in the first place.
1559 *
1560 * Some problems with SYN cookies remain however:
1561 * Consider the problem of a recreated (and retransmitted) cookie. If the
1562 * original SYN was accepted, the connection is established. The second
1563 * SYN is inflight, and if it arrives with an ISN that falls within the
1564 * receive window, the connection is killed.
1565 *
1566 * Notes:
1567 * A heuristic to determine when to accept syn cookies is not necessary.
1568 * An ACK flood would cause the syncookie verification to be attempted,
1569 * but a SYN flood causes syncookies to be generated. Both are of equal
1570 * cost, so there's no point in trying to optimize the ACK flood case.
1571 * Also, if you don't process certain ACKs for some reason, then all someone
1572 * would have to do is launch a SYN and ACK flood at the same time, which
1573 * would stop cookie verification and defeat the entire purpose of syncookies.
1574 */
1575 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 };
1576
1577 static void
1578 syncookie_generate(struct syncache_head *sch, struct syncache *sc,
1579 u_int32_t *flowlabel)
1580 {
1581 MD5_CTX ctx;
1582 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1583 u_int32_t data;
1584 u_int32_t *secbits;
1585 u_int off, pmss, mss;
1586 int i;
1587
1588 SCH_LOCK_ASSERT(sch);
1589
1590 /* Which of the two secrets to use. */
1591 secbits = sch->sch_oddeven ?
1592 sch->sch_secbits_odd : sch->sch_secbits_even;
1593
1594 /* Reseed secret if too old. */
1595 if (sch->sch_reseed < time_uptime) {
1596 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */
1597 secbits = sch->sch_oddeven ?
1598 sch->sch_secbits_odd : sch->sch_secbits_even;
1599 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++)
1600 secbits[i] = arc4random();
1601 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME;
1602 }
1603
1604 /* Secret rotation offset. */
1605 off = sc->sc_iss & 0x7; /* iss was randomized before */
1606
1607 /* Maximum segment size calculation. */
1608 pmss = max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), tcp_minmss);
1609 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--)
1610 if (tcp_sc_msstab[mss] <= pmss)
1611 break;
1612
1613 /* Fold parameters and MD5 digest into the ISN we will send. */
1614 data = sch->sch_oddeven;/* odd or even secret, 1 bit */
1615 data |= off << 1; /* secret offset, derived from iss, 3 bits */
1616 data |= mss << 4; /* mss, 3 bits */
1617
1618 MD5Init(&ctx);
1619 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1620 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1621 MD5Update(&ctx, secbits, off);
1622 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc));
1623 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs));
1624 MD5Update(&ctx, &data, sizeof(data));
1625 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1626
1627 data |= (md5_buffer[0] << 7);
1628 sc->sc_iss = data;
1629
1630 #ifdef INET6
1631 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1632 #endif
1633
1634 /* Additional parameters are stored in the timestamp if present. */
1635 if (sc->sc_flags & SCF_TIMESTAMP) {
1636 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */
1637 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */
1638 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */
1639 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */
1640 data |= md5_buffer[2] << 10; /* more digest bits */
1641 data ^= md5_buffer[3];
1642 sc->sc_ts = data;
1643 sc->sc_tsoff = data - ticks; /* after XOR */
1644 }
1645
1646 tcpstat.tcps_sc_sendcookie++;
1647 }
1648
1649 static struct syncache *
1650 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
1651 struct syncache *sc, struct tcpopt *to, struct tcphdr *th,
1652 struct socket *so)
1653 {
1654 MD5_CTX ctx;
1655 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1656 u_int32_t data = 0;
1657 u_int32_t *secbits;
1658 tcp_seq ack, seq;
1659 int off, mss, wnd, flags;
1660
1661 SCH_LOCK_ASSERT(sch);
1662
1663 /*
1664 * Pull information out of SYN-ACK/ACK and
1665 * revert sequence number advances.
1666 */
1667 ack = th->th_ack - 1;
1668 seq = th->th_seq - 1;
1669 off = (ack >> 1) & 0x7;
1670 mss = (ack >> 4) & 0x7;
1671 flags = ack & 0x7f;
1672
1673 /* Which of the two secrets to use. */
1674 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even;
1675
1676 /*
1677 * The secret wasn't updated for the lifetime of a syncookie,
1678 * so this SYN-ACK/ACK is either too old (replay) or totally bogus.
1679 */
1680 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) {
1681 return (NULL);
1682 }
1683
1684 /* Recompute the digest so we can compare it. */
1685 MD5Init(&ctx);
1686 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1687 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1688 MD5Update(&ctx, secbits, off);
1689 MD5Update(&ctx, inc, sizeof(*inc));
1690 MD5Update(&ctx, &seq, sizeof(seq));
1691 MD5Update(&ctx, &flags, sizeof(flags));
1692 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1693
1694 /* Does the digest part of or ACK'ed ISS match? */
1695 if ((ack & (~0x7f)) != (md5_buffer[0] << 7))
1696 return (NULL);
1697
1698 /* Does the digest part of our reflected timestamp match? */
1699 if (to->to_flags & TOF_TS) {
1700 data = md5_buffer[3] ^ to->to_tsecr;
1701 if ((data & (~0x3ff)) != (md5_buffer[2] << 10))
1702 return (NULL);
1703 }
1704
1705 /* Fill in the syncache values. */
1706 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1707 sc->sc_ipopts = NULL;
1708
1709 sc->sc_irs = seq;
1710 sc->sc_iss = ack;
1711
1712 #ifdef INET6
1713 if (inc->inc_flags & INC_ISIPV6) {
1714 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL)
1715 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1716 } else
1717 #endif
1718 {
1719 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl;
1720 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos;
1721 }
1722
1723 /* Additional parameters that were encoded in the timestamp. */
1724 if (data) {
1725 sc->sc_flags |= SCF_TIMESTAMP;
1726 sc->sc_tsreflect = to->to_tsval;
1727 sc->sc_ts = to->to_tsecr;
1728 sc->sc_tsoff = to->to_tsecr - ticks;
1729 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0;
1730 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0;
1731 sc->sc_requested_s_scale = min((data >> 2) & 0xf,
1732 TCP_MAX_WINSHIFT);
1733 sc->sc_requested_r_scale = min((data >> 6) & 0xf,
1734 TCP_MAX_WINSHIFT);
1735 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale)
1736 sc->sc_flags |= SCF_WINSCALE;
1737 } else
1738 sc->sc_flags |= SCF_NOOPT;
1739
1740 wnd = sbspace(&so->so_rcv);
1741 wnd = imax(wnd, 0);
1742 wnd = imin(wnd, TCP_MAXWIN);
1743 sc->sc_wnd = wnd;
1744
1745 sc->sc_rxmits = 0;
1746 sc->sc_peer_mss = tcp_sc_msstab[mss];
1747
1748 tcpstat.tcps_sc_recvcookie++;
1749 return (sc);
1750 }
1751
1752 /*
1753 * Returns the current number of syncache entries. This number
1754 * will probably change before you get around to calling
1755 * syncache_pcblist.
1756 */
1757
1758 int
1759 syncache_pcbcount(void)
1760 {
1761 struct syncache_head *sch;
1762 int count, i;
1763
1764 for (count = 0, i = 0; i < tcp_syncache.hashsize; i++) {
1765 /* No need to lock for a read. */
1766 sch = &tcp_syncache.hashbase[i];
1767 count += sch->sch_length;
1768 }
1769 return count;
1770 }
1771
1772 /*
1773 * Exports the syncache entries to userland so that netstat can display
1774 * them alongside the other sockets. This function is intended to be
1775 * called only from tcp_pcblist.
1776 *
1777 * Due to concurrency on an active system, the number of pcbs exported
1778 * may have no relation to max_pcbs. max_pcbs merely indicates the
1779 * amount of space the caller allocated for this function to use.
1780 */
1781 int
1782 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
1783 {
1784 struct xtcpcb xt;
1785 struct syncache *sc;
1786 struct syncache_head *sch;
1787 int count, error, i;
1788
1789 for (count = 0, error = 0, i = 0; i < tcp_syncache.hashsize; i++) {
1790 sch = &tcp_syncache.hashbase[i];
1791 SCH_LOCK(sch);
1792 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
1793 if (count >= max_pcbs) {
1794 SCH_UNLOCK(sch);
1795 goto exit;
1796 }
1797 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
1798 continue;
1799 bzero(&xt, sizeof(xt));
1800 xt.xt_len = sizeof(xt);
1801 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1802 xt.xt_inp.inp_vflag = INP_IPV6;
1803 else
1804 xt.xt_inp.inp_vflag = INP_IPV4;
1805 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
1806 xt.xt_tp.t_inpcb = &xt.xt_inp;
1807 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
1808 xt.xt_socket.xso_protocol = IPPROTO_TCP;
1809 xt.xt_socket.xso_len = sizeof (struct xsocket);
1810 xt.xt_socket.so_type = SOCK_STREAM;
1811 xt.xt_socket.so_state = SS_ISCONNECTING;
1812 error = SYSCTL_OUT(req, &xt, sizeof xt);
1813 if (error) {
1814 SCH_UNLOCK(sch);
1815 goto exit;
1816 }
1817 count++;
1818 }
1819 SCH_UNLOCK(sch);
1820 }
1821 exit:
1822 *pcbs_exported = count;
1823 return error;
1824 }
1825
Cache object: 3b0a849ef4bc0d76671283571ebe35fb
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