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: head/sys/netinet/tcp_syncache.c 217322 2011-01-12 19:53:50Z mdf $");
35
36#include "opt_inet.h"
37#include "opt_inet6.h"
38#include "opt_ipsec.h"
39
40#include <sys/param.h>
41#include <sys/systm.h>
42#include <sys/kernel.h>
43#include <sys/sysctl.h>
44#include <sys/limits.h>
45#include <sys/lock.h>
46#include <sys/mutex.h>
47#include <sys/malloc.h>
48#include <sys/mbuf.h>
49#include <sys/md5.h>
50#include <sys/proc.h> /* for proc0 declaration */
51#include <sys/random.h>
52#include <sys/socket.h>
53#include <sys/socketvar.h>
54#include <sys/syslog.h>
55#include <sys/ucred.h>
56
57#include <vm/uma.h>
58
59#include <net/if.h>
60#include <net/route.h>
61#include <net/vnet.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
100static VNET_DEFINE(int, tcp_syncookies) = 1;
101#define V_tcp_syncookies VNET(tcp_syncookies)
102SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
103 &VNET_NAME(tcp_syncookies), 0,
104 "Use TCP SYN cookies if the syncache overflows");
105
106static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
107#define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
108SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW,
109 &VNET_NAME(tcp_syncookiesonly), 0,
110 "Use only TCP SYN cookies");
111
112#ifdef TCP_OFFLOAD_DISABLE
113#define TOEPCB_ISSET(sc) (0)
114#else
115#define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL)
116#endif
117
118static void syncache_drop(struct syncache *, struct syncache_head *);
119static void syncache_free(struct syncache *);
120static void syncache_insert(struct syncache *, struct syncache_head *);
121struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
122static int syncache_respond(struct syncache *);
123static struct socket *syncache_socket(struct syncache *, struct socket *,
124 struct mbuf *m);
125static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
126 int docallout);
127static void syncache_timer(void *);
128static void syncookie_generate(struct syncache_head *, struct syncache *,
129 u_int32_t *);
130static struct syncache
131 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
132 struct syncache *, struct tcpopt *, struct tcphdr *,
133 struct socket *);
134
135/*
136 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
137 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
138 * the odds are that the user has given up attempting to connect by then.
139 */
140#define SYNCACHE_MAXREXMTS 3
141
142/* Arbitrary values */
143#define TCP_SYNCACHE_HASHSIZE 512
144#define TCP_SYNCACHE_BUCKETLIMIT 30
145
146static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
147#define V_tcp_syncache VNET(tcp_syncache)
148
149SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
150
151SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
152 &VNET_NAME(tcp_syncache.bucket_limit), 0,
153 "Per-bucket hash limit for syncache");
154
155SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
156 &VNET_NAME(tcp_syncache.cache_limit), 0,
157 "Overall entry limit for syncache");
158
159SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
160 &VNET_NAME(tcp_syncache.cache_count), 0,
161 "Current number of entries in syncache");
162
163SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
164 &VNET_NAME(tcp_syncache.hashsize), 0,
165 "Size of TCP syncache hashtable");
166
167SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
168 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
169 "Limit on SYN/ACK retransmissions");
170
171VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
172SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
173 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
174 "Send reset on socket allocation failure");
175
176static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
177
178#define SYNCACHE_HASH(inc, mask) \
179 ((V_tcp_syncache.hash_secret ^ \
180 (inc)->inc_faddr.s_addr ^ \
181 ((inc)->inc_faddr.s_addr >> 16) ^ \
182 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
183
184#define SYNCACHE_HASH6(inc, mask) \
185 ((V_tcp_syncache.hash_secret ^ \
186 (inc)->inc6_faddr.s6_addr32[0] ^ \
187 (inc)->inc6_faddr.s6_addr32[3] ^ \
188 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
189
190#define ENDPTS_EQ(a, b) ( \
191 (a)->ie_fport == (b)->ie_fport && \
192 (a)->ie_lport == (b)->ie_lport && \
193 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
194 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
195)
196
197#define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
198
199#define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
200#define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
201#define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
202
203/*
204 * Requires the syncache entry to be already removed from the bucket list.
205 */
206static void
207syncache_free(struct syncache *sc)
208{
209
210 if (sc->sc_ipopts)
211 (void) m_free(sc->sc_ipopts);
212 if (sc->sc_cred)
213 crfree(sc->sc_cred);
214#ifdef MAC
215 mac_syncache_destroy(&sc->sc_label);
216#endif
217
218 uma_zfree(V_tcp_syncache.zone, sc);
219}
220
221void
222syncache_init(void)
223{
224 int i;
225
226 V_tcp_syncache.cache_count = 0;
227 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
228 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
229 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
230 V_tcp_syncache.hash_secret = arc4random();
231
232 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
233 &V_tcp_syncache.hashsize);
234 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
235 &V_tcp_syncache.bucket_limit);
236 if (!powerof2(V_tcp_syncache.hashsize) ||
237 V_tcp_syncache.hashsize == 0) {
238 printf("WARNING: syncache hash size is not a power of 2.\n");
239 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
240 }
241 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
242
243 /* Set limits. */
244 V_tcp_syncache.cache_limit =
245 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
246 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
247 &V_tcp_syncache.cache_limit);
248
249 /* Allocate the hash table. */
250 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
251 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
252
253 /* Initialize the hash buckets. */
254 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
255#ifdef VIMAGE
256 V_tcp_syncache.hashbase[i].sch_vnet = curvnet;
257#endif
258 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
259 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
260 NULL, MTX_DEF);
261 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
262 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
263 V_tcp_syncache.hashbase[i].sch_length = 0;
264 }
265
266 /* Create the syncache entry zone. */
267 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
268 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
269 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit);
270}
271
272#ifdef VIMAGE
273void
274syncache_destroy(void)
275{
276 struct syncache_head *sch;
277 struct syncache *sc, *nsc;
278 int i;
279
280 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
281 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
282
283 sch = &V_tcp_syncache.hashbase[i];
284 callout_drain(&sch->sch_timer);
285
286 SCH_LOCK(sch);
287 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
288 syncache_drop(sc, sch);
289 SCH_UNLOCK(sch);
290 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
291 ("%s: sch->sch_bucket not empty", __func__));
292 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
293 __func__, sch->sch_length));
294 mtx_destroy(&sch->sch_mtx);
295 }
296
297 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0",
298 __func__, V_tcp_syncache.cache_count));
299
300 /* Free the allocated global resources. */
301 uma_zdestroy(V_tcp_syncache.zone);
302 free(V_tcp_syncache.hashbase, M_SYNCACHE);
303}
304#endif
305
306/*
307 * Inserts a syncache entry into the specified bucket row.
308 * Locks and unlocks the syncache_head autonomously.
309 */
310static void
311syncache_insert(struct syncache *sc, struct syncache_head *sch)
312{
313 struct syncache *sc2;
314
315 SCH_LOCK(sch);
316
317 /*
318 * Make sure that we don't overflow the per-bucket limit.
319 * If the bucket is full, toss the oldest element.
320 */
321 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
322 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
323 ("sch->sch_length incorrect"));
324 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
325 syncache_drop(sc2, sch);
326 TCPSTAT_INC(tcps_sc_bucketoverflow);
327 }
328
329 /* Put it into the bucket. */
330 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
331 sch->sch_length++;
332
333 /* Reinitialize the bucket row's timer. */
334 if (sch->sch_length == 1)
335 sch->sch_nextc = ticks + INT_MAX;
336 syncache_timeout(sc, sch, 1);
337
338 SCH_UNLOCK(sch);
339
340 V_tcp_syncache.cache_count++;
341 TCPSTAT_INC(tcps_sc_added);
342}
343
344/*
345 * Remove and free entry from syncache bucket row.
346 * Expects locked syncache head.
347 */
348static void
349syncache_drop(struct syncache *sc, struct syncache_head *sch)
350{
351
352 SCH_LOCK_ASSERT(sch);
353
354 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
355 sch->sch_length--;
356
357#ifndef TCP_OFFLOAD_DISABLE
358 if (sc->sc_tu)
359 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb);
360#endif
361 syncache_free(sc);
362 V_tcp_syncache.cache_count--;
363}
364
365/*
366 * Engage/reengage time on bucket row.
367 */
368static void
369syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
370{
371 sc->sc_rxttime = ticks +
372 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
373 sc->sc_rxmits++;
374 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
375 sch->sch_nextc = sc->sc_rxttime;
376 if (docallout)
377 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
378 syncache_timer, (void *)sch);
379 }
380}
381
382/*
383 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
384 * If we have retransmitted an entry the maximum number of times, expire it.
385 * One separate timer for each bucket row.
386 */
387static void
388syncache_timer(void *xsch)
389{
390 struct syncache_head *sch = (struct syncache_head *)xsch;
391 struct syncache *sc, *nsc;
392 int tick = ticks;
393 char *s;
394
395 CURVNET_SET(sch->sch_vnet);
396
397 /* NB: syncache_head has already been locked by the callout. */
398 SCH_LOCK_ASSERT(sch);
399
400 /*
401 * In the following cycle we may remove some entries and/or
402 * advance some timeouts, so re-initialize the bucket timer.
403 */
404 sch->sch_nextc = tick + INT_MAX;
405
406 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
407 /*
408 * We do not check if the listen socket still exists
409 * and accept the case where the listen socket may be
410 * gone by the time we resend the SYN/ACK. We do
411 * not expect this to happens often. If it does,
412 * then the RST will be sent by the time the remote
413 * host does the SYN/ACK->ACK.
414 */
415 if (TSTMP_GT(sc->sc_rxttime, tick)) {
416 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
417 sch->sch_nextc = sc->sc_rxttime;
418 continue;
419 }
420 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
421 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
422 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
423 "giving up and removing syncache entry\n",
424 s, __func__);
425 free(s, M_TCPLOG);
426 }
427 syncache_drop(sc, sch);
428 TCPSTAT_INC(tcps_sc_stale);
429 continue;
430 }
431 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
432 log(LOG_DEBUG, "%s; %s: Response timeout, "
433 "retransmitting (%u) SYN|ACK\n",
434 s, __func__, sc->sc_rxmits);
435 free(s, M_TCPLOG);
436 }
437
438 (void) syncache_respond(sc);
439 TCPSTAT_INC(tcps_sc_retransmitted);
440 syncache_timeout(sc, sch, 0);
441 }
442 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
443 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
444 syncache_timer, (void *)(sch));
445 CURVNET_RESTORE();
446}
447
448/*
449 * Find an entry in the syncache.
450 * Returns always with locked syncache_head plus a matching entry or NULL.
451 */
452struct syncache *
453syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
454{
455 struct syncache *sc;
456 struct syncache_head *sch;
457
458#ifdef INET6
459 if (inc->inc_flags & INC_ISIPV6) {
460 sch = &V_tcp_syncache.hashbase[
461 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)];
462 *schp = sch;
463
464 SCH_LOCK(sch);
465
466 /* Circle through bucket row to find matching entry. */
467 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
468 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
469 return (sc);
470 }
471 } else
472#endif
473 {
474 sch = &V_tcp_syncache.hashbase[
475 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)];
476 *schp = sch;
477
478 SCH_LOCK(sch);
479
480 /* Circle through bucket row to find matching entry. */
481 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
482#ifdef INET6
483 if (sc->sc_inc.inc_flags & INC_ISIPV6)
484 continue;
485#endif
486 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
487 return (sc);
488 }
489 }
490 SCH_LOCK_ASSERT(*schp);
491 return (NULL); /* always returns with locked sch */
492}
493
494/*
495 * This function is called when we get a RST for a
496 * non-existent connection, so that we can see if the
497 * connection is in the syn cache. If it is, zap it.
498 */
499void
500syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
501{
502 struct syncache *sc;
503 struct syncache_head *sch;
504 char *s = NULL;
505
506 sc = syncache_lookup(inc, &sch); /* returns locked sch */
507 SCH_LOCK_ASSERT(sch);
508
509 /*
510 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
511 * See RFC 793 page 65, section SEGMENT ARRIVES.
512 */
513 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
514 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
515 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
516 "FIN flag set, segment ignored\n", s, __func__);
517 TCPSTAT_INC(tcps_badrst);
518 goto done;
519 }
520
521 /*
522 * No corresponding connection was found in syncache.
523 * If syncookies are enabled and possibly exclusively
524 * used, or we are under memory pressure, a valid RST
525 * may not find a syncache entry. In that case we're
526 * done and no SYN|ACK retransmissions will happen.
527 * Otherwise the the RST was misdirected or spoofed.
528 */
529 if (sc == NULL) {
530 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
531 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
532 "syncache entry (possibly syncookie only), "
533 "segment ignored\n", s, __func__);
534 TCPSTAT_INC(tcps_badrst);
535 goto done;
536 }
537
538 /*
539 * If the RST bit is set, check the sequence number to see
540 * if this is a valid reset segment.
541 * RFC 793 page 37:
542 * In all states except SYN-SENT, all reset (RST) segments
543 * are validated by checking their SEQ-fields. A reset is
544 * valid if its sequence number is in the window.
545 *
546 * The sequence number in the reset segment is normally an
547 * echo of our outgoing acknowlegement numbers, but some hosts
548 * send a reset with the sequence number at the rightmost edge
549 * of our receive window, and we have to handle this case.
550 */
551 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
552 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
553 syncache_drop(sc, sch);
554 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
555 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
556 "connection attempt aborted by remote endpoint\n",
557 s, __func__);
558 TCPSTAT_INC(tcps_sc_reset);
559 } else {
560 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
561 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
562 "IRS %u (+WND %u), segment ignored\n",
563 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
564 TCPSTAT_INC(tcps_badrst);
565 }
566
567done:
568 if (s != NULL)
569 free(s, M_TCPLOG);
570 SCH_UNLOCK(sch);
571}
572
573void
574syncache_badack(struct in_conninfo *inc)
575{
576 struct syncache *sc;
577 struct syncache_head *sch;
578
579 sc = syncache_lookup(inc, &sch); /* returns locked sch */
580 SCH_LOCK_ASSERT(sch);
581 if (sc != NULL) {
582 syncache_drop(sc, sch);
583 TCPSTAT_INC(tcps_sc_badack);
584 }
585 SCH_UNLOCK(sch);
586}
587
588void
589syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
590{
591 struct syncache *sc;
592 struct syncache_head *sch;
593
594 sc = syncache_lookup(inc, &sch); /* returns locked sch */
595 SCH_LOCK_ASSERT(sch);
596 if (sc == NULL)
597 goto done;
598
599 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
600 if (ntohl(th->th_seq) != sc->sc_iss)
601 goto done;
602
603 /*
604 * If we've rertransmitted 3 times and this is our second error,
605 * we remove the entry. Otherwise, we allow it to continue on.
606 * This prevents us from incorrectly nuking an entry during a
607 * spurious network outage.
608 *
609 * See tcp_notify().
610 */
611 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
612 sc->sc_flags |= SCF_UNREACH;
613 goto done;
614 }
615 syncache_drop(sc, sch);
616 TCPSTAT_INC(tcps_sc_unreach);
617done:
618 SCH_UNLOCK(sch);
619}
620
621/*
622 * Build a new TCP socket structure from a syncache entry.
623 */
624static struct socket *
625syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
626{
627 struct inpcb *inp = NULL;
628 struct socket *so;
629 struct tcpcb *tp;
630 int error;
631 char *s;
632
633 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
634
635 /*
636 * Ok, create the full blown connection, and set things up
637 * as they would have been set up if we had created the
638 * connection when the SYN arrived. If we can't create
639 * the connection, abort it.
640 */
641 so = sonewconn(lso, SS_ISCONNECTED);
642 if (so == NULL) {
643 /*
644 * Drop the connection; we will either send a RST or
645 * have the peer retransmit its SYN again after its
646 * RTO and try again.
647 */
648 TCPSTAT_INC(tcps_listendrop);
649 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
650 log(LOG_DEBUG, "%s; %s: Socket create failed "
651 "due to limits or memory shortage\n",
652 s, __func__);
653 free(s, M_TCPLOG);
654 }
655 goto abort2;
656 }
657#ifdef MAC
658 mac_socketpeer_set_from_mbuf(m, so);
659#endif
660
661 inp = sotoinpcb(so);
662 inp->inp_inc.inc_fibnum = so->so_fibnum;
663 INP_WLOCK(inp);
664
665 /* Insert new socket into PCB hash list. */
666 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
667#ifdef INET6
668 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
669 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
670 } else {
671 inp->inp_vflag &= ~INP_IPV6;
672 inp->inp_vflag |= INP_IPV4;
673#endif
674 inp->inp_laddr = sc->sc_inc.inc_laddr;
675#ifdef INET6
676 }
677#endif
678 inp->inp_lport = sc->sc_inc.inc_lport;
679 if ((error = in_pcbinshash(inp)) != 0) {
680 /*
681 * Undo the assignments above if we failed to
682 * put the PCB on the hash lists.
683 */
684#ifdef INET6
685 if (sc->sc_inc.inc_flags & INC_ISIPV6)
686 inp->in6p_laddr = in6addr_any;
687 else
688#endif
689 inp->inp_laddr.s_addr = INADDR_ANY;
690 inp->inp_lport = 0;
691 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
692 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
693 "with error %i\n",
694 s, __func__, error);
695 free(s, M_TCPLOG);
696 }
697 goto abort;
698 }
699#ifdef IPSEC
700 /* Copy old policy into new socket's. */
701 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
702 printf("syncache_socket: could not copy policy\n");
703#endif
704#ifdef INET6
705 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
706 struct inpcb *oinp = sotoinpcb(lso);
707 struct in6_addr laddr6;
708 struct sockaddr_in6 sin6;
709 /*
710 * Inherit socket options from the listening socket.
711 * Note that in6p_inputopts are not (and should not be)
712 * copied, since it stores previously received options and is
713 * used to detect if each new option is different than the
714 * previous one and hence should be passed to a user.
715 * If we copied in6p_inputopts, a user would not be able to
716 * receive options just after calling the accept system call.
717 */
718 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
719 if (oinp->in6p_outputopts)
720 inp->in6p_outputopts =
721 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
722
723 sin6.sin6_family = AF_INET6;
724 sin6.sin6_len = sizeof(sin6);
725 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
726 sin6.sin6_port = sc->sc_inc.inc_fport;
727 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
728 laddr6 = inp->in6p_laddr;
729 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
730 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
731 if ((error = in6_pcbconnect(inp, (struct sockaddr *)&sin6,
732 thread0.td_ucred)) != 0) {
733 inp->in6p_laddr = laddr6;
734 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
735 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
736 "with error %i\n",
737 s, __func__, error);
738 free(s, M_TCPLOG);
739 }
740 goto abort;
741 }
742 /* Override flowlabel from in6_pcbconnect. */
743 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
744 inp->inp_flow |= sc->sc_flowlabel;
745 } else
746#endif
747 {
748 struct in_addr laddr;
749 struct sockaddr_in sin;
750
751 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
752
753 if (inp->inp_options == NULL) {
754 inp->inp_options = sc->sc_ipopts;
755 sc->sc_ipopts = NULL;
756 }
757
758 sin.sin_family = AF_INET;
759 sin.sin_len = sizeof(sin);
760 sin.sin_addr = sc->sc_inc.inc_faddr;
761 sin.sin_port = sc->sc_inc.inc_fport;
762 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
763 laddr = inp->inp_laddr;
764 if (inp->inp_laddr.s_addr == INADDR_ANY)
765 inp->inp_laddr = sc->sc_inc.inc_laddr;
766 if ((error = in_pcbconnect(inp, (struct sockaddr *)&sin,
767 thread0.td_ucred)) != 0) {
768 inp->inp_laddr = laddr;
769 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
770 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
771 "with error %i\n",
772 s, __func__, error);
773 free(s, M_TCPLOG);
774 }
775 goto abort;
776 }
777 }
778 tp = intotcpcb(inp);
779 tp->t_state = TCPS_SYN_RECEIVED;
780 tp->iss = sc->sc_iss;
781 tp->irs = sc->sc_irs;
782 tcp_rcvseqinit(tp);
783 tcp_sendseqinit(tp);
784 tp->snd_wl1 = sc->sc_irs;
785 tp->snd_max = tp->iss + 1;
786 tp->snd_nxt = tp->iss + 1;
787 tp->rcv_up = sc->sc_irs + 1;
788 tp->rcv_wnd = sc->sc_wnd;
789 tp->rcv_adv += tp->rcv_wnd;
790 tp->last_ack_sent = tp->rcv_nxt;
791
792 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
793 if (sc->sc_flags & SCF_NOOPT)
794 tp->t_flags |= TF_NOOPT;
795 else {
796 if (sc->sc_flags & SCF_WINSCALE) {
797 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
798 tp->snd_scale = sc->sc_requested_s_scale;
799 tp->request_r_scale = sc->sc_requested_r_scale;
800 }
801 if (sc->sc_flags & SCF_TIMESTAMP) {
802 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
803 tp->ts_recent = sc->sc_tsreflect;
804 tp->ts_recent_age = ticks;
805 tp->ts_offset = sc->sc_tsoff;
806 }
807#ifdef TCP_SIGNATURE
808 if (sc->sc_flags & SCF_SIGNATURE)
809 tp->t_flags |= TF_SIGNATURE;
810#endif
811 if (sc->sc_flags & SCF_SACK)
812 tp->t_flags |= TF_SACK_PERMIT;
813 }
814
815 if (sc->sc_flags & SCF_ECN)
816 tp->t_flags |= TF_ECN_PERMIT;
817
818 /*
819 * Set up MSS and get cached values from tcp_hostcache.
820 * This might overwrite some of the defaults we just set.
821 */
822 tcp_mss(tp, sc->sc_peer_mss);
823
824 /*
825 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
826 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
827 */
828 if (sc->sc_rxmits > 1)
829 tp->snd_cwnd = tp->t_maxseg;
830 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit);
831
832 INP_WUNLOCK(inp);
833
834 TCPSTAT_INC(tcps_accepts);
835 return (so);
836
837abort:
838 INP_WUNLOCK(inp);
839abort2:
840 if (so != NULL)
841 soabort(so);
842 return (NULL);
843}
844
845/*
846 * This function gets called when we receive an ACK for a
847 * socket in the LISTEN state. We look up the connection
848 * in the syncache, and if its there, we pull it out of
849 * the cache and turn it into a full-blown connection in
850 * the SYN-RECEIVED state.
851 */
852int
853syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
854 struct socket **lsop, struct mbuf *m)
855{
856 struct syncache *sc;
857 struct syncache_head *sch;
858 struct syncache scs;
859 char *s;
860
861 /*
862 * Global TCP locks are held because we manipulate the PCB lists
863 * and create a new socket.
864 */
865 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
866 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
867 ("%s: can handle only ACK", __func__));
868
869 sc = syncache_lookup(inc, &sch); /* returns locked sch */
870 SCH_LOCK_ASSERT(sch);
871 if (sc == NULL) {
872 /*
873 * There is no syncache entry, so see if this ACK is
874 * a returning syncookie. To do this, first:
875 * A. See if this socket has had a syncache entry dropped in
876 * the past. We don't want to accept a bogus syncookie
877 * if we've never received a SYN.
878 * B. check that the syncookie is valid. If it is, then
879 * cobble up a fake syncache entry, and return.
880 */
881 if (!V_tcp_syncookies) {
882 SCH_UNLOCK(sch);
883 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
884 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
885 "segment rejected (syncookies disabled)\n",
886 s, __func__);
887 goto failed;
888 }
889 bzero(&scs, sizeof(scs));
890 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop);
891 SCH_UNLOCK(sch);
892 if (sc == NULL) {
893 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
894 log(LOG_DEBUG, "%s; %s: Segment failed "
895 "SYNCOOKIE authentication, segment rejected "
896 "(probably spoofed)\n", s, __func__);
897 goto failed;
898 }
899 } else {
900 /* Pull out the entry to unlock the bucket row. */
901 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
902 sch->sch_length--;
903 V_tcp_syncache.cache_count--;
904 SCH_UNLOCK(sch);
905 }
906
907 /*
908 * Segment validation:
909 * ACK must match our initial sequence number + 1 (the SYN|ACK).
910 */
911 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) {
912 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
913 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
914 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
915 goto failed;
916 }
917
918 /*
919 * The SEQ must fall in the window starting at the received
920 * initial receive sequence number + 1 (the SYN).
921 */
922 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) ||
923 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) &&
924 !TOEPCB_ISSET(sc)) {
925 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
926 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
927 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
928 goto failed;
929 }
930
931 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
932 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
933 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
934 "segment rejected\n", s, __func__);
935 goto failed;
936 }
937 /*
938 * If timestamps were negotiated the reflected timestamp
939 * must be equal to what we actually sent in the SYN|ACK.
940 */
941 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts &&
942 !TOEPCB_ISSET(sc)) {
943 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
944 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
945 "segment rejected\n",
946 s, __func__, to->to_tsecr, sc->sc_ts);
947 goto failed;
948 }
949
950 *lsop = syncache_socket(sc, *lsop, m);
951
952 if (*lsop == NULL)
953 TCPSTAT_INC(tcps_sc_aborted);
954 else
955 TCPSTAT_INC(tcps_sc_completed);
956
957/* how do we find the inp for the new socket? */
958 if (sc != &scs)
959 syncache_free(sc);
960 return (1);
961failed:
962 if (sc != NULL && sc != &scs)
963 syncache_free(sc);
964 if (s != NULL)
965 free(s, M_TCPLOG);
966 *lsop = NULL;
967 return (0);
968}
969
970int
971tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo,
972 struct tcphdr *th, struct socket **lsop, struct mbuf *m)
973{
974 struct tcpopt to;
975 int rc;
976
977 bzero(&to, sizeof(struct tcpopt));
978 to.to_mss = toeo->to_mss;
979 to.to_wscale = toeo->to_wscale;
980 to.to_flags = toeo->to_flags;
981
982 INP_INFO_WLOCK(&V_tcbinfo);
983 rc = syncache_expand(inc, &to, th, lsop, m);
984 INP_INFO_WUNLOCK(&V_tcbinfo);
985
986 return (rc);
987}
988
989/*
990 * Given a LISTEN socket and an inbound SYN request, add
991 * this to the syn cache, and send back a segment:
992 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
993 * to the source.
994 *
995 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
996 * Doing so would require that we hold onto the data and deliver it
997 * to the application. However, if we are the target of a SYN-flood
998 * DoS attack, an attacker could send data which would eventually
999 * consume all available buffer space if it were ACKed. By not ACKing
1000 * the data, we avoid this DoS scenario.
1001 */
1002static void
1003_syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1004 struct inpcb *inp, struct socket **lsop, struct mbuf *m,
1005 struct toe_usrreqs *tu, void *toepcb)
1006{
1007 struct tcpcb *tp;
1008 struct socket *so;
1009 struct syncache *sc = NULL;
1010 struct syncache_head *sch;
1011 struct mbuf *ipopts = NULL;
1012 u_int32_t flowtmp;
1013 int win, sb_hiwat, ip_ttl, ip_tos, noopt;
1014 char *s;
1015#ifdef INET6
1016 int autoflowlabel = 0;
1017#endif
1018#ifdef MAC
1019 struct label *maclabel;
1020#endif
1021 struct syncache scs;
1022 struct ucred *cred;
1023
1024 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1025 INP_WLOCK_ASSERT(inp); /* listen socket */
1026 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1027 ("%s: unexpected tcp flags", __func__));
1028
1029 /*
1030 * Combine all so/tp operations very early to drop the INP lock as
1031 * soon as possible.
1032 */
1033 so = *lsop;
1034 tp = sototcpcb(so);
1035 cred = crhold(so->so_cred);
1036
1037#ifdef INET6
1038 if ((inc->inc_flags & INC_ISIPV6) &&
1039 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1040 autoflowlabel = 1;
1041#endif
1042 ip_ttl = inp->inp_ip_ttl;
1043 ip_tos = inp->inp_ip_tos;
1044 win = sbspace(&so->so_rcv);
1045 sb_hiwat = so->so_rcv.sb_hiwat;
1046 noopt = (tp->t_flags & TF_NOOPT);
1047
1048 /* By the time we drop the lock these should no longer be used. */
1049 so = NULL;
1050 tp = NULL;
1051
1052#ifdef MAC
1053 if (mac_syncache_init(&maclabel) != 0) {
1054 INP_WUNLOCK(inp);
1055 INP_INFO_WUNLOCK(&V_tcbinfo);
1056 goto done;
1057 } else
1058 mac_syncache_create(maclabel, inp);
1059#endif
1060 INP_WUNLOCK(inp);
1061 INP_INFO_WUNLOCK(&V_tcbinfo);
1062
1063 /*
1064 * Remember the IP options, if any.
1065 */
1066#ifdef INET6
1067 if (!(inc->inc_flags & INC_ISIPV6))
1068#endif
1069 ipopts = (m) ? ip_srcroute(m) : NULL;
1070
1071 /*
1072 * See if we already have an entry for this connection.
1073 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1074 *
1075 * XXX: should the syncache be re-initialized with the contents
1076 * of the new SYN here (which may have different options?)
1077 *
1078 * XXX: We do not check the sequence number to see if this is a
1079 * real retransmit or a new connection attempt. The question is
1080 * how to handle such a case; either ignore it as spoofed, or
1081 * drop the current entry and create a new one?
1082 */
1083 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1084 SCH_LOCK_ASSERT(sch);
1085 if (sc != NULL) {
1086#ifndef TCP_OFFLOAD_DISABLE
1087 if (sc->sc_tu)
1088 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT,
1089 sc->sc_toepcb);
1090#endif
1091 TCPSTAT_INC(tcps_sc_dupsyn);
1092 if (ipopts) {
1093 /*
1094 * If we were remembering a previous source route,
1095 * forget it and use the new one we've been given.
1096 */
1097 if (sc->sc_ipopts)
1098 (void) m_free(sc->sc_ipopts);
1099 sc->sc_ipopts = ipopts;
1100 }
1101 /*
1102 * Update timestamp if present.
1103 */
1104 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1105 sc->sc_tsreflect = to->to_tsval;
1106 else
1107 sc->sc_flags &= ~SCF_TIMESTAMP;
1108#ifdef MAC
1109 /*
1110 * Since we have already unconditionally allocated label
1111 * storage, free it up. The syncache entry will already
1112 * have an initialized label we can use.
1113 */
1114 mac_syncache_destroy(&maclabel);
1115#endif
1116 /* Retransmit SYN|ACK and reset retransmit count. */
1117 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1118 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1119 "resetting timer and retransmitting SYN|ACK\n",
1120 s, __func__);
1121 free(s, M_TCPLOG);
1122 }
1123 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) {
1124 sc->sc_rxmits = 0;
1125 syncache_timeout(sc, sch, 1);
1126 TCPSTAT_INC(tcps_sndacks);
1127 TCPSTAT_INC(tcps_sndtotal);
1128 }
1129 SCH_UNLOCK(sch);
1130 goto done;
1131 }
1132
1133 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1134 if (sc == NULL) {
1135 /*
1136 * The zone allocator couldn't provide more entries.
1137 * Treat this as if the cache was full; drop the oldest
1138 * entry and insert the new one.
1139 */
1140 TCPSTAT_INC(tcps_sc_zonefail);
1141 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1142 syncache_drop(sc, sch);
1143 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1144 if (sc == NULL) {
1145 if (V_tcp_syncookies) {
1146 bzero(&scs, sizeof(scs));
1147 sc = &scs;
1148 } else {
1149 SCH_UNLOCK(sch);
1150 if (ipopts)
1151 (void) m_free(ipopts);
1152 goto done;
1153 }
1154 }
1155 }
1156
1157 /*
1158 * Fill in the syncache values.
1159 */
1160#ifdef MAC
1161 sc->sc_label = maclabel;
1162#endif
1163 sc->sc_cred = cred;
1164 cred = NULL;
1165 sc->sc_ipopts = ipopts;
1166 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1167#ifdef INET6
1168 if (!(inc->inc_flags & INC_ISIPV6))
1169#endif
1170 {
1171 sc->sc_ip_tos = ip_tos;
1172 sc->sc_ip_ttl = ip_ttl;
1173 }
1174#ifndef TCP_OFFLOAD_DISABLE
1175 sc->sc_tu = tu;
1176 sc->sc_toepcb = toepcb;
1177#endif
1178 sc->sc_irs = th->th_seq;
1179 sc->sc_iss = arc4random();
1180 sc->sc_flags = 0;
1181 sc->sc_flowlabel = 0;
1182
1183 /*
1184 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1185 * win was derived from socket earlier in the function.
1186 */
1187 win = imax(win, 0);
1188 win = imin(win, TCP_MAXWIN);
1189 sc->sc_wnd = win;
1190
1191 if (V_tcp_do_rfc1323) {
1192 /*
1193 * A timestamp received in a SYN makes
1194 * it ok to send timestamp requests and replies.
1195 */
1196 if (to->to_flags & TOF_TS) {
1197 sc->sc_tsreflect = to->to_tsval;
1198 sc->sc_ts = ticks;
1199 sc->sc_flags |= SCF_TIMESTAMP;
1200 }
1201 if (to->to_flags & TOF_SCALE) {
1202 int wscale = 0;
1203
1204 /*
1205 * Pick the smallest possible scaling factor that
1206 * will still allow us to scale up to sb_max, aka
1207 * kern.ipc.maxsockbuf.
1208 *
1209 * We do this because there are broken firewalls that
1210 * will corrupt the window scale option, leading to
1211 * the other endpoint believing that our advertised
1212 * window is unscaled. At scale factors larger than
1213 * 5 the unscaled window will drop below 1500 bytes,
1214 * leading to serious problems when traversing these
1215 * broken firewalls.
1216 *
1217 * With the default maxsockbuf of 256K, a scale factor
1218 * of 3 will be chosen by this algorithm. Those who
1219 * choose a larger maxsockbuf should watch out
1220 * for the compatiblity problems mentioned above.
1221 *
1222 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1223 * or <SYN,ACK>) segment itself is never scaled.
1224 */
1225 while (wscale < TCP_MAX_WINSHIFT &&
1226 (TCP_MAXWIN << wscale) < sb_max)
1227 wscale++;
1228 sc->sc_requested_r_scale = wscale;
1229 sc->sc_requested_s_scale = to->to_wscale;
1230 sc->sc_flags |= SCF_WINSCALE;
1231 }
1232 }
1233#ifdef TCP_SIGNATURE
1234 /*
1235 * If listening socket requested TCP digests, and received SYN
1236 * contains the option, flag this in the syncache so that
1237 * syncache_respond() will do the right thing with the SYN+ACK.
1238 * XXX: Currently we always record the option by default and will
1239 * attempt to use it in syncache_respond().
1240 */
1241 if (to->to_flags & TOF_SIGNATURE)
1242 sc->sc_flags |= SCF_SIGNATURE;
1243#endif
1244 if (to->to_flags & TOF_SACKPERM)
1245 sc->sc_flags |= SCF_SACK;
1246 if (to->to_flags & TOF_MSS)
1247 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1248 if (noopt)
1249 sc->sc_flags |= SCF_NOOPT;
1250 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1251 sc->sc_flags |= SCF_ECN;
1252
1253 if (V_tcp_syncookies) {
1254 syncookie_generate(sch, sc, &flowtmp);
1255#ifdef INET6
1256 if (autoflowlabel)
1257 sc->sc_flowlabel = flowtmp;
1258#endif
1259 } else {
1260#ifdef INET6
1261 if (autoflowlabel)
1262 sc->sc_flowlabel =
1263 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
1264#endif
1265 }
1266 SCH_UNLOCK(sch);
1267
1268 /*
1269 * Do a standard 3-way handshake.
1270 */
1271 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) {
1272 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1273 syncache_free(sc);
1274 else if (sc != &scs)
1275 syncache_insert(sc, sch); /* locks and unlocks sch */
1276 TCPSTAT_INC(tcps_sndacks);
1277 TCPSTAT_INC(tcps_sndtotal);
1278 } else {
1279 if (sc != &scs)
1280 syncache_free(sc);
1281 TCPSTAT_INC(tcps_sc_dropped);
1282 }
1283
1284done:
1285 if (cred != NULL)
1286 crfree(cred);
1287#ifdef MAC
1288 if (sc == &scs)
1289 mac_syncache_destroy(&maclabel);
1290#endif
1291 if (m) {
1292
1293 *lsop = NULL;
1294 m_freem(m);
1295 }
1296}
1297
1298static int
1299syncache_respond(struct syncache *sc)
1300{
1301 struct ip *ip = NULL;
1302 struct mbuf *m;
1303 struct tcphdr *th;
1304 int optlen, error;
1305 u_int16_t hlen, tlen, mssopt;
1306 struct tcpopt to;
1307#ifdef INET6
1308 struct ip6_hdr *ip6 = NULL;
1309#endif
1310
1311 hlen =
1312#ifdef INET6
1313 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1314#endif
1315 sizeof(struct ip);
1316 tlen = hlen + sizeof(struct tcphdr);
1317
1318 /* Determine MSS we advertize to other end of connection. */
1319 mssopt = tcp_mssopt(&sc->sc_inc);
1320 if (sc->sc_peer_mss)
1321 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss);
1322
1323 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1324 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1325 ("syncache: mbuf too small"));
1326
1327 /* Create the IP+TCP header from scratch. */
1328 m = m_gethdr(M_DONTWAIT, MT_DATA);
1329 if (m == NULL)
1330 return (ENOBUFS);
1331#ifdef MAC
1332 mac_syncache_create_mbuf(sc->sc_label, m);
1333#endif
1334 m->m_data += max_linkhdr;
1335 m->m_len = tlen;
1336 m->m_pkthdr.len = tlen;
1337 m->m_pkthdr.rcvif = NULL;
1338
1339#ifdef INET6
1340 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1341 ip6 = mtod(m, struct ip6_hdr *);
1342 ip6->ip6_vfc = IPV6_VERSION;
1343 ip6->ip6_nxt = IPPROTO_TCP;
1344 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1345 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1346 ip6->ip6_plen = htons(tlen - hlen);
1347 /* ip6_hlim is set after checksum */
1348 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1349 ip6->ip6_flow |= sc->sc_flowlabel;
1350
1351 th = (struct tcphdr *)(ip6 + 1);
1352 } else
1353#endif
1354 {
1355 ip = mtod(m, struct ip *);
1356 ip->ip_v = IPVERSION;
1357 ip->ip_hl = sizeof(struct ip) >> 2;
1358 ip->ip_len = tlen;
1359 ip->ip_id = 0;
1360 ip->ip_off = 0;
1361 ip->ip_sum = 0;
1362 ip->ip_p = IPPROTO_TCP;
1363 ip->ip_src = sc->sc_inc.inc_laddr;
1364 ip->ip_dst = sc->sc_inc.inc_faddr;
1365 ip->ip_ttl = sc->sc_ip_ttl;
1366 ip->ip_tos = sc->sc_ip_tos;
1367
1368 /*
1369 * See if we should do MTU discovery. Route lookups are
1370 * expensive, so we will only unset the DF bit if:
1371 *
1372 * 1) path_mtu_discovery is disabled
1373 * 2) the SCF_UNREACH flag has been set
1374 */
1375 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1376 ip->ip_off |= IP_DF;
1377
1378 th = (struct tcphdr *)(ip + 1);
1379 }
1380 th->th_sport = sc->sc_inc.inc_lport;
1381 th->th_dport = sc->sc_inc.inc_fport;
1382
1383 th->th_seq = htonl(sc->sc_iss);
1384 th->th_ack = htonl(sc->sc_irs + 1);
1385 th->th_off = sizeof(struct tcphdr) >> 2;
1386 th->th_x2 = 0;
1387 th->th_flags = TH_SYN|TH_ACK;
1388 th->th_win = htons(sc->sc_wnd);
1389 th->th_urp = 0;
1390
1391 if (sc->sc_flags & SCF_ECN) {
1392 th->th_flags |= TH_ECE;
1393 TCPSTAT_INC(tcps_ecn_shs);
1394 }
1395
1396 /* Tack on the TCP options. */
1397 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1398 to.to_flags = 0;
1399
1400 to.to_mss = mssopt;
1401 to.to_flags = TOF_MSS;
1402 if (sc->sc_flags & SCF_WINSCALE) {
1403 to.to_wscale = sc->sc_requested_r_scale;
1404 to.to_flags |= TOF_SCALE;
1405 }
1406 if (sc->sc_flags & SCF_TIMESTAMP) {
1407 /* Virgin timestamp or TCP cookie enhanced one. */
1408 to.to_tsval = sc->sc_ts;
1409 to.to_tsecr = sc->sc_tsreflect;
1410 to.to_flags |= TOF_TS;
1411 }
1412 if (sc->sc_flags & SCF_SACK)
1413 to.to_flags |= TOF_SACKPERM;
1414#ifdef TCP_SIGNATURE
1415 if (sc->sc_flags & SCF_SIGNATURE)
1416 to.to_flags |= TOF_SIGNATURE;
1417#endif
1418 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1419
1420 /* Adjust headers by option size. */
1421 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1422 m->m_len += optlen;
1423 m->m_pkthdr.len += optlen;
1424
1425#ifdef TCP_SIGNATURE
1426 if (sc->sc_flags & SCF_SIGNATURE)
1427 tcp_signature_compute(m, 0, 0, optlen,
1428 to.to_signature, IPSEC_DIR_OUTBOUND);
1429#endif
1430#ifdef INET6
1431 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1432 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1433 else
1434#endif
1435 ip->ip_len += optlen;
1436 } else
1437 optlen = 0;
1438
1439 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1440#ifdef INET6
1441 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1442 th->th_sum = 0;
1443 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen,
1444 tlen + optlen - hlen);
1445 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1446 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1447 } else
1448#endif
1449 {
1450 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1451 htons(tlen + optlen - hlen + IPPROTO_TCP));
1452 m->m_pkthdr.csum_flags = CSUM_TCP;
1453 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1454 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1455 }
1456 return (error);
1457}
1458
1459void
1460syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1461 struct inpcb *inp, struct socket **lsop, struct mbuf *m)
1462{
1463 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL);
1464}
1465
1466void
1467tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo,
1468 struct tcphdr *th, struct inpcb *inp, struct socket **lsop,
1469 struct toe_usrreqs *tu, void *toepcb)
1470{
1471 struct tcpopt to;
1472
1473 bzero(&to, sizeof(struct tcpopt));
1474 to.to_mss = toeo->to_mss;
1475 to.to_wscale = toeo->to_wscale;
1476 to.to_flags = toeo->to_flags;
1477
1478 INP_INFO_WLOCK(&V_tcbinfo);
1479 INP_WLOCK(inp);
1480
1481 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb);
1482}
1483
1484/*
1485 * The purpose of SYN cookies is to avoid keeping track of all SYN's we
1486 * receive and to be able to handle SYN floods from bogus source addresses
1487 * (where we will never receive any reply). SYN floods try to exhaust all
1488 * our memory and available slots in the SYN cache table to cause a denial
1489 * of service to legitimate users of the local host.
1490 *
1491 * The idea of SYN cookies is to encode and include all necessary information
1492 * about the connection setup state within the SYN-ACK we send back and thus
1493 * to get along without keeping any local state until the ACK to the SYN-ACK
1494 * arrives (if ever). Everything we need to know should be available from
1495 * the information we encoded in the SYN-ACK.
1496 *
1497 * More information about the theory behind SYN cookies and its first
1498 * discussion and specification can be found at:
1499 * http://cr.yp.to/syncookies.html (overview)
1500 * http://cr.yp.to/syncookies/archive (gory details)
1501 *
1502 * This implementation extends the orginal idea and first implementation
1503 * of FreeBSD by using not only the initial sequence number field to store
1504 * information but also the timestamp field if present. This way we can
1505 * keep track of the entire state we need to know to recreate the session in
1506 * its original form. Almost all TCP speakers implement RFC1323 timestamps
1507 * these days. For those that do not we still have to live with the known
1508 * shortcomings of the ISN only SYN cookies.
1509 *
1510 * Cookie layers:
1511 *
1512 * Initial sequence number we send:
1513 * 31|................................|0
1514 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP
1515 * D = MD5 Digest (first dword)
1516 * M = MSS index
1517 * R = Rotation of secret
1518 * P = Odd or Even secret
1519 *
1520 * The MD5 Digest is computed with over following parameters:
1521 * a) randomly rotated secret
1522 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6)
1523 * c) the received initial sequence number from remote host
1524 * d) the rotation offset and odd/even bit
1525 *
1526 * Timestamp we send:
1527 * 31|................................|0
1528 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5
1529 * D = MD5 Digest (third dword) (only as filler)
1530 * S = Requested send window scale
1531 * R = Requested receive window scale
1532 * A = SACK allowed
1533 * 5 = TCP-MD5 enabled (not implemented yet)
1534 * XORed with MD5 Digest (forth dword)
1535 *
1536 * The timestamp isn't cryptographically secure and doesn't need to be.
1537 * The double use of the MD5 digest dwords ties it to a specific remote/
1538 * local host/port, remote initial sequence number and our local time
1539 * limited secret. A received timestamp is reverted (XORed) and then
1540 * the contained MD5 dword is compared to the computed one to ensure the
1541 * timestamp belongs to the SYN-ACK we sent. The other parameters may
1542 * have been tampered with but this isn't different from supplying bogus
1543 * values in the SYN in the first place.
1544 *
1545 * Some problems with SYN cookies remain however:
1546 * Consider the problem of a recreated (and retransmitted) cookie. If the
1547 * original SYN was accepted, the connection is established. The second
1548 * SYN is inflight, and if it arrives with an ISN that falls within the
1549 * receive window, the connection is killed.
1550 *
1551 * Notes:
1552 * A heuristic to determine when to accept syn cookies is not necessary.
1553 * An ACK flood would cause the syncookie verification to be attempted,
1554 * but a SYN flood causes syncookies to be generated. Both are of equal
1555 * cost, so there's no point in trying to optimize the ACK flood case.
1556 * Also, if you don't process certain ACKs for some reason, then all someone
1557 * would have to do is launch a SYN and ACK flood at the same time, which
1558 * would stop cookie verification and defeat the entire purpose of syncookies.
1559 */
1560static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 };
1561
1562static void
1563syncookie_generate(struct syncache_head *sch, struct syncache *sc,
1564 u_int32_t *flowlabel)
1565{
1566 MD5_CTX ctx;
1567 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1568 u_int32_t data;
1569 u_int32_t *secbits;
1570 u_int off, pmss, mss;
1571 int i;
1572
1573 SCH_LOCK_ASSERT(sch);
1574
1575 /* Which of the two secrets to use. */
1576 secbits = sch->sch_oddeven ?
1577 sch->sch_secbits_odd : sch->sch_secbits_even;
1578
1579 /* Reseed secret if too old. */
1580 if (sch->sch_reseed < time_uptime) {
1581 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */
1582 secbits = sch->sch_oddeven ?
1583 sch->sch_secbits_odd : sch->sch_secbits_even;
1584 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++)
1585 secbits[i] = arc4random();
1586 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME;
1587 }
1588
1589 /* Secret rotation offset. */
1590 off = sc->sc_iss & 0x7; /* iss was randomized before */
1591
1592 /* Maximum segment size calculation. */
1593 pmss =
1594 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss);
1595 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--)
1596 if (tcp_sc_msstab[mss] <= pmss)
1597 break;
1598
1599 /* Fold parameters and MD5 digest into the ISN we will send. */
1600 data = sch->sch_oddeven;/* odd or even secret, 1 bit */
1601 data |= off << 1; /* secret offset, derived from iss, 3 bits */
1602 data |= mss << 4; /* mss, 3 bits */
1603
1604 MD5Init(&ctx);
1605 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1606 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1607 MD5Update(&ctx, secbits, off);
1608 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc));
1609 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs));
1610 MD5Update(&ctx, &data, sizeof(data));
1611 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1612
1613 data |= (md5_buffer[0] << 7);
1614 sc->sc_iss = data;
1615
1616#ifdef INET6
1617 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1618#endif
1619
1620 /* Additional parameters are stored in the timestamp if present. */
1621 if (sc->sc_flags & SCF_TIMESTAMP) {
1622 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */
1623 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */
1624 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */
1625 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */
1626 data |= md5_buffer[2] << 10; /* more digest bits */
1627 data ^= md5_buffer[3];
1628 sc->sc_ts = data;
1629 sc->sc_tsoff = data - ticks; /* after XOR */
1630 }
1631
1632 TCPSTAT_INC(tcps_sc_sendcookie);
1633}
1634
1635static struct syncache *
1636syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
1637 struct syncache *sc, struct tcpopt *to, struct tcphdr *th,
1638 struct socket *so)
1639{
1640 MD5_CTX ctx;
1641 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1642 u_int32_t data = 0;
1643 u_int32_t *secbits;
1644 tcp_seq ack, seq;
1645 int off, mss, wnd, flags;
1646
1647 SCH_LOCK_ASSERT(sch);
1648
1649 /*
1650 * Pull information out of SYN-ACK/ACK and
1651 * revert sequence number advances.
1652 */
1653 ack = th->th_ack - 1;
1654 seq = th->th_seq - 1;
1655 off = (ack >> 1) & 0x7;
1656 mss = (ack >> 4) & 0x7;
1657 flags = ack & 0x7f;
1658
1659 /* Which of the two secrets to use. */
1660 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even;
1661
1662 /*
1663 * The secret wasn't updated for the lifetime of a syncookie,
1664 * so this SYN-ACK/ACK is either too old (replay) or totally bogus.
1665 */
1666 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) {
1667 return (NULL);
1668 }
1669
1670 /* Recompute the digest so we can compare it. */
1671 MD5Init(&ctx);
1672 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1673 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1674 MD5Update(&ctx, secbits, off);
1675 MD5Update(&ctx, inc, sizeof(*inc));
1676 MD5Update(&ctx, &seq, sizeof(seq));
1677 MD5Update(&ctx, &flags, sizeof(flags));
1678 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1679
1680 /* Does the digest part of or ACK'ed ISS match? */
1681 if ((ack & (~0x7f)) != (md5_buffer[0] << 7))
1682 return (NULL);
1683
1684 /* Does the digest part of our reflected timestamp match? */
1685 if (to->to_flags & TOF_TS) {
1686 data = md5_buffer[3] ^ to->to_tsecr;
1687 if ((data & (~0x3ff)) != (md5_buffer[2] << 10))
1688 return (NULL);
1689 }
1690
1691 /* Fill in the syncache values. */
1692 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1693 sc->sc_ipopts = NULL;
1694
1695 sc->sc_irs = seq;
1696 sc->sc_iss = ack;
1697
1698#ifdef INET6
1699 if (inc->inc_flags & INC_ISIPV6) {
1700 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL)
1701 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1702 } else
1703#endif
1704 {
1705 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl;
1706 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos;
1707 }
1708
1709 /* Additional parameters that were encoded in the timestamp. */
1710 if (data) {
1711 sc->sc_flags |= SCF_TIMESTAMP;
1712 sc->sc_tsreflect = to->to_tsval;
1713 sc->sc_ts = to->to_tsecr;
1714 sc->sc_tsoff = to->to_tsecr - ticks;
1715 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0;
1716 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0;
1717 sc->sc_requested_s_scale = min((data >> 2) & 0xf,
1718 TCP_MAX_WINSHIFT);
1719 sc->sc_requested_r_scale = min((data >> 6) & 0xf,
1720 TCP_MAX_WINSHIFT);
1721 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale)
1722 sc->sc_flags |= SCF_WINSCALE;
1723 } else
1724 sc->sc_flags |= SCF_NOOPT;
1725
1726 wnd = sbspace(&so->so_rcv);
1727 wnd = imax(wnd, 0);
1728 wnd = imin(wnd, TCP_MAXWIN);
1729 sc->sc_wnd = wnd;
1730
1731 sc->sc_rxmits = 0;
1732 sc->sc_peer_mss = tcp_sc_msstab[mss];
1733
1734 TCPSTAT_INC(tcps_sc_recvcookie);
1735 return (sc);
1736}
1737
1738/*
1739 * Returns the current number of syncache entries. This number
1740 * will probably change before you get around to calling
1741 * syncache_pcblist.
1742 */
1743
1744int
1745syncache_pcbcount(void)
1746{
1747 struct syncache_head *sch;
1748 int count, i;
1749
1750 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1751 /* No need to lock for a read. */
1752 sch = &V_tcp_syncache.hashbase[i];
1753 count += sch->sch_length;
1754 }
1755 return count;
1756}
1757
1758/*
1759 * Exports the syncache entries to userland so that netstat can display
1760 * them alongside the other sockets. This function is intended to be
1761 * called only from tcp_pcblist.
1762 *
1763 * Due to concurrency on an active system, the number of pcbs exported
1764 * may have no relation to max_pcbs. max_pcbs merely indicates the
1765 * amount of space the caller allocated for this function to use.
1766 */
1767int
1768syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
1769{
1770 struct xtcpcb xt;
1771 struct syncache *sc;
1772 struct syncache_head *sch;
1773 int count, error, i;
1774
1775 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1776 sch = &V_tcp_syncache.hashbase[i];
1777 SCH_LOCK(sch);
1778 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
1779 if (count >= max_pcbs) {
1780 SCH_UNLOCK(sch);
1781 goto exit;
1782 }
1783 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
1784 continue;
1785 bzero(&xt, sizeof(xt));
1786 xt.xt_len = sizeof(xt);
1787 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1788 xt.xt_inp.inp_vflag = INP_IPV6;
1789 else
1790 xt.xt_inp.inp_vflag = INP_IPV4;
1791 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
1792 xt.xt_tp.t_inpcb = &xt.xt_inp;
1793 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
1794 xt.xt_socket.xso_protocol = IPPROTO_TCP;
1795 xt.xt_socket.xso_len = sizeof (struct xsocket);
1796 xt.xt_socket.so_type = SOCK_STREAM;
1797 xt.xt_socket.so_state = SS_ISCONNECTING;
1798 error = SYSCTL_OUT(req, &xt, sizeof xt);
1799 if (error) {
1800 SCH_UNLOCK(sch);
1801 goto exit;
1802 }
1803 count++;
1804 }
1805 SCH_UNLOCK(sch);
1806 }
1807exit:
1808 *pcbs_exported = count;
1809 return error;
1810}