1 /*-
2 * Copyright (c) 2001 McAfee, Inc.
3 * All rights reserved.
4 *
5 * This software was developed for the FreeBSD Project by Jonathan Lemon
6 * and McAfee Research, the Security Research Division of McAfee, Inc. under
7 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
8 * DARPA CHATS research program.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.66.2.5 2006/02/16 18:05:03 qingli Exp $
32 */
33
34 #include "opt_inet.h"
35 #include "opt_inet6.h"
36 #include "opt_ipsec.h"
37 #include "opt_mac.h"
38 #include "opt_tcpdebug.h"
39 #include "opt_tcp_sack.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/malloc.h>
46 #include <sys/mac.h>
47 #include <sys/mbuf.h>
48 #include <sys/md5.h>
49 #include <sys/proc.h> /* for proc0 declaration */
50 #include <sys/random.h>
51 #include <sys/socket.h>
52 #include <sys/socketvar.h>
53
54 #include <net/if.h>
55 #include <net/route.h>
56
57 #include <netinet/in.h>
58 #include <netinet/in_systm.h>
59 #include <netinet/ip.h>
60 #include <netinet/in_var.h>
61 #include <netinet/in_pcb.h>
62 #include <netinet/ip_var.h>
63 #ifdef INET6
64 #include <netinet/ip6.h>
65 #include <netinet/icmp6.h>
66 #include <netinet6/nd6.h>
67 #include <netinet6/ip6_var.h>
68 #include <netinet6/in6_pcb.h>
69 #endif
70 #include <netinet/tcp.h>
71 #ifdef TCPDEBUG
72 #include <netinet/tcpip.h>
73 #endif
74 #include <netinet/tcp_fsm.h>
75 #include <netinet/tcp_seq.h>
76 #include <netinet/tcp_timer.h>
77 #include <netinet/tcp_var.h>
78 #ifdef TCPDEBUG
79 #include <netinet/tcp_debug.h>
80 #endif
81 #ifdef INET6
82 #include <netinet6/tcp6_var.h>
83 #endif
84
85 #ifdef IPSEC
86 #include <netinet6/ipsec.h>
87 #ifdef INET6
88 #include <netinet6/ipsec6.h>
89 #endif
90 #endif /*IPSEC*/
91
92 #ifdef FAST_IPSEC
93 #include <netipsec/ipsec.h>
94 #ifdef INET6
95 #include <netipsec/ipsec6.h>
96 #endif
97 #include <netipsec/key.h>
98 #endif /*FAST_IPSEC*/
99
100 #include <machine/in_cksum.h>
101 #include <vm/uma.h>
102
103 static int tcp_syncookies = 1;
104 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
105 &tcp_syncookies, 0,
106 "Use TCP SYN cookies if the syncache overflows");
107
108 static void syncache_drop(struct syncache *, struct syncache_head *);
109 static void syncache_free(struct syncache *);
110 static void syncache_insert(struct syncache *, struct syncache_head *);
111 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
112 #ifdef TCPDEBUG
113 static int syncache_respond(struct syncache *, struct mbuf *, struct socket *);
114 #else
115 static int syncache_respond(struct syncache *, struct mbuf *);
116 #endif
117 static struct socket *syncache_socket(struct syncache *, struct socket *,
118 struct mbuf *m);
119 static void syncache_timer(void *);
120 static u_int32_t syncookie_generate(struct syncache *, u_int32_t *);
121 static struct syncache *syncookie_lookup(struct in_conninfo *,
122 struct tcphdr *, struct socket *);
123
124 /*
125 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
126 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds,
127 * the odds are that the user has given up attempting to connect by then.
128 */
129 #define SYNCACHE_MAXREXMTS 3
130
131 /* Arbitrary values */
132 #define TCP_SYNCACHE_HASHSIZE 512
133 #define TCP_SYNCACHE_BUCKETLIMIT 30
134
135 struct tcp_syncache {
136 struct syncache_head *hashbase;
137 uma_zone_t zone;
138 u_int hashsize;
139 u_int hashmask;
140 u_int bucket_limit;
141 u_int cache_count;
142 u_int cache_limit;
143 u_int rexmt_limit;
144 u_int hash_secret;
145 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1];
146 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1];
147 };
148 static struct tcp_syncache tcp_syncache;
149
150 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
151
152 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
153 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
154
155 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
156 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
157
158 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
159 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
160
161 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
162 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
163
164 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
165 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
166
167 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
168
169 #define SYNCACHE_HASH(inc, mask) \
170 ((tcp_syncache.hash_secret ^ \
171 (inc)->inc_faddr.s_addr ^ \
172 ((inc)->inc_faddr.s_addr >> 16) ^ \
173 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
174
175 #define SYNCACHE_HASH6(inc, mask) \
176 ((tcp_syncache.hash_secret ^ \
177 (inc)->inc6_faddr.s6_addr32[0] ^ \
178 (inc)->inc6_faddr.s6_addr32[3] ^ \
179 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
180
181 #define ENDPTS_EQ(a, b) ( \
182 (a)->ie_fport == (b)->ie_fport && \
183 (a)->ie_lport == (b)->ie_lport && \
184 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
185 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
186 )
187
188 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
189
190 #define SYNCACHE_TIMEOUT(sc, slot) do { \
191 sc->sc_rxtslot = (slot); \
192 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \
193 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \
194 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \
195 callout_reset(&tcp_syncache.tt_timerq[(slot)], \
196 TCPTV_RTOBASE * tcp_backoff[(slot)], \
197 syncache_timer, (void *)((intptr_t)(slot))); \
198 } while (0)
199
200 static void
201 syncache_free(struct syncache *sc)
202 {
203 if (sc->sc_ipopts)
204 (void) m_free(sc->sc_ipopts);
205
206 uma_zfree(tcp_syncache.zone, sc);
207 }
208
209 void
210 syncache_init(void)
211 {
212 int i;
213
214 tcp_syncache.cache_count = 0;
215 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
216 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
217 tcp_syncache.cache_limit =
218 tcp_syncache.hashsize * tcp_syncache.bucket_limit;
219 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
220 tcp_syncache.hash_secret = arc4random();
221
222 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
223 &tcp_syncache.hashsize);
224 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
225 &tcp_syncache.cache_limit);
226 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
227 &tcp_syncache.bucket_limit);
228 if (!powerof2(tcp_syncache.hashsize) || tcp_syncache.hashsize == 0) {
229 printf("WARNING: syncache hash size is not a power of 2.\n");
230 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
231 }
232 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
233
234 /* Allocate the hash table. */
235 MALLOC(tcp_syncache.hashbase, struct syncache_head *,
236 tcp_syncache.hashsize * sizeof(struct syncache_head),
237 M_SYNCACHE, M_WAITOK);
238
239 /* Initialize the hash buckets. */
240 for (i = 0; i < tcp_syncache.hashsize; i++) {
241 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket);
242 tcp_syncache.hashbase[i].sch_length = 0;
243 }
244
245 /* Initialize the timer queues. */
246 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) {
247 TAILQ_INIT(&tcp_syncache.timerq[i]);
248 callout_init(&tcp_syncache.tt_timerq[i],
249 debug_mpsafenet ? CALLOUT_MPSAFE : 0);
250 }
251
252 /*
253 * Allocate the syncache entries. Allow the zone to allocate one
254 * more entry than cache limit, so a new entry can bump out an
255 * older one.
256 */
257 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
258 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
259 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit);
260 tcp_syncache.cache_limit -= 1;
261 }
262
263 static void
264 syncache_insert(sc, sch)
265 struct syncache *sc;
266 struct syncache_head *sch;
267 {
268 struct syncache *sc2;
269 int i;
270
271 INP_INFO_WLOCK_ASSERT(&tcbinfo);
272
273 /*
274 * Make sure that we don't overflow the per-bucket
275 * limit or the total cache size limit.
276 */
277 if (sch->sch_length >= tcp_syncache.bucket_limit) {
278 /*
279 * The bucket is full, toss the oldest element.
280 */
281 sc2 = TAILQ_FIRST(&sch->sch_bucket);
282 sc2->sc_tp->ts_recent = ticks;
283 syncache_drop(sc2, sch);
284 tcpstat.tcps_sc_bucketoverflow++;
285 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) {
286 /*
287 * The cache is full. Toss the oldest entry in the
288 * entire cache. This is the front entry in the
289 * first non-empty timer queue with the largest
290 * timeout value.
291 */
292 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
293 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]);
294 if (sc2 != NULL)
295 break;
296 }
297 sc2->sc_tp->ts_recent = ticks;
298 syncache_drop(sc2, NULL);
299 tcpstat.tcps_sc_cacheoverflow++;
300 }
301
302 /* Initialize the entry's timer. */
303 SYNCACHE_TIMEOUT(sc, 0);
304
305 /* Put it into the bucket. */
306 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash);
307 sch->sch_length++;
308 tcp_syncache.cache_count++;
309 tcpstat.tcps_sc_added++;
310 }
311
312 static void
313 syncache_drop(sc, sch)
314 struct syncache *sc;
315 struct syncache_head *sch;
316 {
317 INP_INFO_WLOCK_ASSERT(&tcbinfo);
318
319 if (sch == NULL) {
320 #ifdef INET6
321 if (sc->sc_inc.inc_isipv6) {
322 sch = &tcp_syncache.hashbase[
323 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)];
324 } else
325 #endif
326 {
327 sch = &tcp_syncache.hashbase[
328 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)];
329 }
330 }
331
332 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
333 sch->sch_length--;
334 tcp_syncache.cache_count--;
335
336 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq);
337 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot]))
338 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]);
339
340 syncache_free(sc);
341 }
342
343 /*
344 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
345 * If we have retransmitted an entry the maximum number of times, expire it.
346 */
347 static void
348 syncache_timer(xslot)
349 void *xslot;
350 {
351 intptr_t slot = (intptr_t)xslot;
352 struct syncache *sc, *nsc;
353 struct inpcb *inp;
354
355 INP_INFO_WLOCK(&tcbinfo);
356 if (callout_pending(&tcp_syncache.tt_timerq[slot]) ||
357 !callout_active(&tcp_syncache.tt_timerq[slot])) {
358 /* XXX can this happen? */
359 INP_INFO_WUNLOCK(&tcbinfo);
360 return;
361 }
362 callout_deactivate(&tcp_syncache.tt_timerq[slot]);
363
364 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]);
365 while (nsc != NULL) {
366 if (ticks < nsc->sc_rxttime)
367 break;
368 sc = nsc;
369 inp = sc->sc_tp->t_inpcb;
370 if (slot == SYNCACHE_MAXREXMTS ||
371 slot >= tcp_syncache.rexmt_limit ||
372 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) {
373 nsc = TAILQ_NEXT(sc, sc_timerq);
374 syncache_drop(sc, NULL);
375 tcpstat.tcps_sc_stale++;
376 continue;
377 }
378 /*
379 * syncache_respond() may call back into the syncache to
380 * to modify another entry, so do not obtain the next
381 * entry on the timer chain until it has completed.
382 */
383 #ifdef TCPDEBUG
384 (void) syncache_respond(sc, NULL, NULL);
385 #else
386 (void) syncache_respond(sc, NULL);
387 #endif
388 nsc = TAILQ_NEXT(sc, sc_timerq);
389 tcpstat.tcps_sc_retransmitted++;
390 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq);
391 SYNCACHE_TIMEOUT(sc, slot + 1);
392 }
393 if (nsc != NULL)
394 callout_reset(&tcp_syncache.tt_timerq[slot],
395 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot));
396 INP_INFO_WUNLOCK(&tcbinfo);
397 }
398
399 /*
400 * Find an entry in the syncache.
401 */
402 struct syncache *
403 syncache_lookup(inc, schp)
404 struct in_conninfo *inc;
405 struct syncache_head **schp;
406 {
407 struct syncache *sc;
408 struct syncache_head *sch;
409
410 INP_INFO_WLOCK_ASSERT(&tcbinfo);
411
412 #ifdef INET6
413 if (inc->inc_isipv6) {
414 sch = &tcp_syncache.hashbase[
415 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
416 *schp = sch;
417 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
418 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
419 return (sc);
420 }
421 } else
422 #endif
423 {
424 sch = &tcp_syncache.hashbase[
425 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
426 *schp = sch;
427 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
428 #ifdef INET6
429 if (sc->sc_inc.inc_isipv6)
430 continue;
431 #endif
432 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
433 return (sc);
434 }
435 }
436 return (NULL);
437 }
438
439 /*
440 * This function is called when we get a RST for a
441 * non-existent connection, so that we can see if the
442 * connection is in the syn cache. If it is, zap it.
443 */
444 void
445 syncache_chkrst(inc, th)
446 struct in_conninfo *inc;
447 struct tcphdr *th;
448 {
449 struct syncache *sc;
450 struct syncache_head *sch;
451
452 INP_INFO_WLOCK_ASSERT(&tcbinfo);
453
454 sc = syncache_lookup(inc, &sch);
455 if (sc == NULL)
456 return;
457 /*
458 * If the RST bit is set, check the sequence number to see
459 * if this is a valid reset segment.
460 * RFC 793 page 37:
461 * In all states except SYN-SENT, all reset (RST) segments
462 * are validated by checking their SEQ-fields. A reset is
463 * valid if its sequence number is in the window.
464 *
465 * The sequence number in the reset segment is normally an
466 * echo of our outgoing acknowlegement numbers, but some hosts
467 * send a reset with the sequence number at the rightmost edge
468 * of our receive window, and we have to handle this case.
469 */
470 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
471 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
472 syncache_drop(sc, sch);
473 tcpstat.tcps_sc_reset++;
474 }
475 }
476
477 void
478 syncache_badack(inc)
479 struct in_conninfo *inc;
480 {
481 struct syncache *sc;
482 struct syncache_head *sch;
483
484 INP_INFO_WLOCK_ASSERT(&tcbinfo);
485
486 sc = syncache_lookup(inc, &sch);
487 if (sc != NULL) {
488 syncache_drop(sc, sch);
489 tcpstat.tcps_sc_badack++;
490 }
491 }
492
493 void
494 syncache_unreach(inc, th)
495 struct in_conninfo *inc;
496 struct tcphdr *th;
497 {
498 struct syncache *sc;
499 struct syncache_head *sch;
500
501 INP_INFO_WLOCK_ASSERT(&tcbinfo);
502
503 /* we are called at splnet() here */
504 sc = syncache_lookup(inc, &sch);
505 if (sc == NULL)
506 return;
507
508 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
509 if (ntohl(th->th_seq) != sc->sc_iss)
510 return;
511
512 /*
513 * If we've rertransmitted 3 times and this is our second error,
514 * we remove the entry. Otherwise, we allow it to continue on.
515 * This prevents us from incorrectly nuking an entry during a
516 * spurious network outage.
517 *
518 * See tcp_notify().
519 */
520 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) {
521 sc->sc_flags |= SCF_UNREACH;
522 return;
523 }
524 syncache_drop(sc, sch);
525 tcpstat.tcps_sc_unreach++;
526 }
527
528 /*
529 * Build a new TCP socket structure from a syncache entry.
530 */
531 static struct socket *
532 syncache_socket(sc, lso, m)
533 struct syncache *sc;
534 struct socket *lso;
535 struct mbuf *m;
536 {
537 struct inpcb *inp = NULL;
538 struct socket *so;
539 struct tcpcb *tp;
540
541 NET_ASSERT_GIANT();
542 INP_INFO_WLOCK_ASSERT(&tcbinfo);
543
544 /*
545 * Ok, create the full blown connection, and set things up
546 * as they would have been set up if we had created the
547 * connection when the SYN arrived. If we can't create
548 * the connection, abort it.
549 */
550 so = sonewconn(lso, SS_ISCONNECTED);
551 if (so == NULL) {
552 /*
553 * Drop the connection; we will send a RST if the peer
554 * retransmits the ACK,
555 */
556 tcpstat.tcps_listendrop++;
557 goto abort2;
558 }
559 #ifdef MAC
560 SOCK_LOCK(so);
561 mac_set_socket_peer_from_mbuf(m, so);
562 SOCK_UNLOCK(so);
563 #endif
564
565 inp = sotoinpcb(so);
566 INP_LOCK(inp);
567
568 /*
569 * Insert new socket into hash list.
570 */
571 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
572 #ifdef INET6
573 if (sc->sc_inc.inc_isipv6) {
574 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
575 } else {
576 inp->inp_vflag &= ~INP_IPV6;
577 inp->inp_vflag |= INP_IPV4;
578 #endif
579 inp->inp_laddr = sc->sc_inc.inc_laddr;
580 #ifdef INET6
581 }
582 #endif
583 inp->inp_lport = sc->sc_inc.inc_lport;
584 if (in_pcbinshash(inp) != 0) {
585 /*
586 * Undo the assignments above if we failed to
587 * put the PCB on the hash lists.
588 */
589 #ifdef INET6
590 if (sc->sc_inc.inc_isipv6)
591 inp->in6p_laddr = in6addr_any;
592 else
593 #endif
594 inp->inp_laddr.s_addr = INADDR_ANY;
595 inp->inp_lport = 0;
596 goto abort;
597 }
598 #ifdef IPSEC
599 /* copy old policy into new socket's */
600 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
601 printf("syncache_expand: could not copy policy\n");
602 #endif
603 #ifdef FAST_IPSEC
604 /* copy old policy into new socket's */
605 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
606 printf("syncache_expand: could not copy policy\n");
607 #endif
608 #ifdef INET6
609 if (sc->sc_inc.inc_isipv6) {
610 struct inpcb *oinp = sotoinpcb(lso);
611 struct in6_addr laddr6;
612 struct sockaddr_in6 sin6;
613 /*
614 * Inherit socket options from the listening socket.
615 * Note that in6p_inputopts are not (and should not be)
616 * copied, since it stores previously received options and is
617 * used to detect if each new option is different than the
618 * previous one and hence should be passed to a user.
619 * If we copied in6p_inputopts, a user would not be able to
620 * receive options just after calling the accept system call.
621 */
622 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
623 if (oinp->in6p_outputopts)
624 inp->in6p_outputopts =
625 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
626
627 sin6.sin6_family = AF_INET6;
628 sin6.sin6_len = sizeof(sin6);
629 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
630 sin6.sin6_port = sc->sc_inc.inc_fport;
631 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
632 laddr6 = inp->in6p_laddr;
633 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
634 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
635 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6,
636 thread0.td_ucred)) {
637 inp->in6p_laddr = laddr6;
638 goto abort;
639 }
640 /* Override flowlabel from in6_pcbconnect. */
641 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK;
642 inp->in6p_flowinfo |= sc->sc_flowlabel;
643 } else
644 #endif
645 {
646 struct in_addr laddr;
647 struct sockaddr_in sin;
648
649 inp->inp_options = ip_srcroute(m);
650 if (inp->inp_options == NULL) {
651 inp->inp_options = sc->sc_ipopts;
652 sc->sc_ipopts = NULL;
653 }
654
655 sin.sin_family = AF_INET;
656 sin.sin_len = sizeof(sin);
657 sin.sin_addr = sc->sc_inc.inc_faddr;
658 sin.sin_port = sc->sc_inc.inc_fport;
659 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
660 laddr = inp->inp_laddr;
661 if (inp->inp_laddr.s_addr == INADDR_ANY)
662 inp->inp_laddr = sc->sc_inc.inc_laddr;
663 if (in_pcbconnect(inp, (struct sockaddr *)&sin,
664 thread0.td_ucred)) {
665 inp->inp_laddr = laddr;
666 goto abort;
667 }
668 }
669
670 tp = intotcpcb(inp);
671 tp->t_state = TCPS_SYN_RECEIVED;
672 tp->iss = sc->sc_iss;
673 tp->irs = sc->sc_irs;
674 tcp_rcvseqinit(tp);
675 tcp_sendseqinit(tp);
676 tp->snd_wl1 = sc->sc_irs;
677 tp->rcv_up = sc->sc_irs + 1;
678 tp->rcv_wnd = sc->sc_wnd;
679 tp->rcv_adv += tp->rcv_wnd;
680
681 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
682 if (sc->sc_flags & SCF_NOOPT)
683 tp->t_flags |= TF_NOOPT;
684 if (sc->sc_flags & SCF_WINSCALE) {
685 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
686 tp->requested_s_scale = sc->sc_requested_s_scale;
687 tp->request_r_scale = sc->sc_request_r_scale;
688 }
689 if (sc->sc_flags & SCF_TIMESTAMP) {
690 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
691 tp->ts_recent = sc->sc_tsrecent;
692 tp->ts_recent_age = ticks;
693 }
694 if (sc->sc_flags & SCF_CC) {
695 /*
696 * Initialization of the tcpcb for transaction;
697 * set SND.WND = SEG.WND,
698 * initialize CCsend and CCrecv.
699 */
700 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC;
701 tp->cc_send = sc->sc_cc_send;
702 tp->cc_recv = sc->sc_cc_recv;
703 }
704 #ifdef TCP_SIGNATURE
705 if (sc->sc_flags & SCF_SIGNATURE)
706 tp->t_flags |= TF_SIGNATURE;
707 #endif
708 if (sc->sc_flags & SCF_SACK) {
709 tp->sack_enable = 1;
710 tp->t_flags |= TF_SACK_PERMIT;
711 }
712 /*
713 * Set up MSS and get cached values from tcp_hostcache.
714 * This might overwrite some of the defaults we just set.
715 */
716 tcp_mss(tp, sc->sc_peer_mss);
717
718 /*
719 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
720 */
721 if (sc->sc_rxtslot != 0)
722 tp->snd_cwnd = tp->t_maxseg;
723 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
724
725 INP_UNLOCK(inp);
726
727 tcpstat.tcps_accepts++;
728 return (so);
729
730 abort:
731 INP_UNLOCK(inp);
732 abort2:
733 if (so != NULL)
734 (void) soabort(so);
735 return (NULL);
736 }
737
738 /*
739 * This function gets called when we receive an ACK for a
740 * socket in the LISTEN state. We look up the connection
741 * in the syncache, and if its there, we pull it out of
742 * the cache and turn it into a full-blown connection in
743 * the SYN-RECEIVED state.
744 */
745 int
746 syncache_expand(inc, th, sop, m)
747 struct in_conninfo *inc;
748 struct tcphdr *th;
749 struct socket **sop;
750 struct mbuf *m;
751 {
752 struct syncache *sc;
753 struct syncache_head *sch;
754 struct socket *so;
755
756 INP_INFO_WLOCK_ASSERT(&tcbinfo);
757
758 sc = syncache_lookup(inc, &sch);
759 if (sc == NULL) {
760 /*
761 * There is no syncache entry, so see if this ACK is
762 * a returning syncookie. To do this, first:
763 * A. See if this socket has had a syncache entry dropped in
764 * the past. We don't want to accept a bogus syncookie
765 * if we've never received a SYN.
766 * B. check that the syncookie is valid. If it is, then
767 * cobble up a fake syncache entry, and return.
768 */
769 if (!tcp_syncookies)
770 return (0);
771 sc = syncookie_lookup(inc, th, *sop);
772 if (sc == NULL)
773 return (0);
774 sch = NULL;
775 tcpstat.tcps_sc_recvcookie++;
776 }
777
778 /*
779 * If seg contains an ACK, but not for our SYN/ACK, send a RST.
780 */
781 if (th->th_ack != sc->sc_iss + 1)
782 return (0);
783
784 so = syncache_socket(sc, *sop, m);
785 if (so == NULL) {
786 #if 0
787 resetandabort:
788 /* XXXjlemon check this - is this correct? */
789 (void) tcp_respond(NULL, m, m, th,
790 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK);
791 #endif
792 m_freem(m); /* XXX only needed for above */
793 tcpstat.tcps_sc_aborted++;
794 } else
795 tcpstat.tcps_sc_completed++;
796
797 if (sch == NULL)
798 syncache_free(sc);
799 else
800 syncache_drop(sc, sch);
801 *sop = so;
802 return (1);
803 }
804
805 /*
806 * Given a LISTEN socket and an inbound SYN request, add
807 * this to the syn cache, and send back a segment:
808 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
809 * to the source.
810 *
811 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
812 * Doing so would require that we hold onto the data and deliver it
813 * to the application. However, if we are the target of a SYN-flood
814 * DoS attack, an attacker could send data which would eventually
815 * consume all available buffer space if it were ACKed. By not ACKing
816 * the data, we avoid this DoS scenario.
817 */
818 int
819 syncache_add(inc, to, th, sop, m)
820 struct in_conninfo *inc;
821 struct tcpopt *to;
822 struct tcphdr *th;
823 struct socket **sop;
824 struct mbuf *m;
825 {
826 struct tcpcb *tp;
827 struct socket *so;
828 struct syncache *sc = NULL;
829 struct syncache_head *sch;
830 struct mbuf *ipopts = NULL;
831 struct rmxp_tao tao;
832 u_int32_t flowtmp;
833 int i, win;
834
835 INP_INFO_WLOCK_ASSERT(&tcbinfo);
836
837 so = *sop;
838 tp = sototcpcb(so);
839 bzero(&tao, sizeof(tao));
840
841 /*
842 * Remember the IP options, if any.
843 */
844 #ifdef INET6
845 if (!inc->inc_isipv6)
846 #endif
847 ipopts = ip_srcroute(m);
848
849 /*
850 * See if we already have an entry for this connection.
851 * If we do, resend the SYN,ACK, and reset the retransmit timer.
852 *
853 * XXX
854 * should the syncache be re-initialized with the contents
855 * of the new SYN here (which may have different options?)
856 */
857 sc = syncache_lookup(inc, &sch);
858 if (sc != NULL) {
859 tcpstat.tcps_sc_dupsyn++;
860 if (ipopts) {
861 /*
862 * If we were remembering a previous source route,
863 * forget it and use the new one we've been given.
864 */
865 if (sc->sc_ipopts)
866 (void) m_free(sc->sc_ipopts);
867 sc->sc_ipopts = ipopts;
868 }
869 /*
870 * Update timestamp if present.
871 */
872 if (sc->sc_flags & SCF_TIMESTAMP)
873 sc->sc_tsrecent = to->to_tsval;
874 /*
875 * PCB may have changed, pick up new values.
876 */
877 sc->sc_tp = tp;
878 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
879 #ifdef TCPDEBUG
880 if (syncache_respond(sc, m, so) == 0) {
881 #else
882 if (syncache_respond(sc, m) == 0) {
883 #endif
884 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */
885 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot],
886 sc, sc_timerq);
887 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot);
888 tcpstat.tcps_sndacks++;
889 tcpstat.tcps_sndtotal++;
890 }
891 *sop = NULL;
892 return (1);
893 }
894
895 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO);
896 if (sc == NULL) {
897 /*
898 * The zone allocator couldn't provide more entries.
899 * Treat this as if the cache was full; drop the oldest
900 * entry and insert the new one.
901 */
902 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */
903 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
904 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]);
905 if (sc != NULL)
906 break;
907 }
908 sc->sc_tp->ts_recent = ticks;
909 syncache_drop(sc, NULL);
910 tcpstat.tcps_sc_zonefail++;
911 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO);
912 if (sc == NULL) {
913 if (ipopts)
914 (void) m_free(ipopts);
915 return (0);
916 }
917 }
918
919 /*
920 * Fill in the syncache values.
921 */
922 sc->sc_tp = tp;
923 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
924 sc->sc_ipopts = ipopts;
925 sc->sc_inc.inc_fport = inc->inc_fport;
926 sc->sc_inc.inc_lport = inc->inc_lport;
927 #ifdef INET6
928 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
929 if (inc->inc_isipv6) {
930 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
931 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
932 } else
933 #endif
934 {
935 sc->sc_inc.inc_faddr = inc->inc_faddr;
936 sc->sc_inc.inc_laddr = inc->inc_laddr;
937 }
938 sc->sc_irs = th->th_seq;
939 sc->sc_flags = 0;
940 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0;
941 sc->sc_flowlabel = 0;
942 if (tcp_syncookies) {
943 sc->sc_iss = syncookie_generate(sc, &flowtmp);
944 #ifdef INET6
945 if (inc->inc_isipv6 &&
946 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) {
947 sc->sc_flowlabel = flowtmp & IPV6_FLOWLABEL_MASK;
948 }
949 #endif
950 } else {
951 sc->sc_iss = arc4random();
952 #ifdef INET6
953 if (inc->inc_isipv6 &&
954 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) {
955 sc->sc_flowlabel =
956 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
957 }
958 #endif
959 }
960
961 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */
962 win = sbspace(&so->so_rcv);
963 win = imax(win, 0);
964 win = imin(win, TCP_MAXWIN);
965 sc->sc_wnd = win;
966
967 if (tcp_do_rfc1323) {
968 /*
969 * A timestamp received in a SYN makes
970 * it ok to send timestamp requests and replies.
971 */
972 if (to->to_flags & TOF_TS) {
973 sc->sc_tsrecent = to->to_tsval;
974 sc->sc_flags |= SCF_TIMESTAMP;
975 }
976 if (to->to_flags & TOF_SCALE) {
977 int wscale = 0;
978
979 /* Compute proper scaling value from buffer space */
980 while (wscale < TCP_MAX_WINSHIFT &&
981 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat)
982 wscale++;
983 sc->sc_request_r_scale = wscale;
984 sc->sc_requested_s_scale = to->to_requested_s_scale;
985 sc->sc_flags |= SCF_WINSCALE;
986 }
987 }
988 if (tcp_do_rfc1644) {
989 /*
990 * A CC or CC.new option received in a SYN makes
991 * it ok to send CC in subsequent segments.
992 */
993 if (to->to_flags & (TOF_CC|TOF_CCNEW)) {
994 sc->sc_cc_recv = to->to_cc;
995 sc->sc_cc_send = CC_INC(tcp_ccgen);
996 sc->sc_flags |= SCF_CC;
997 }
998 }
999 if (tp->t_flags & TF_NOOPT)
1000 sc->sc_flags = SCF_NOOPT;
1001 #ifdef TCP_SIGNATURE
1002 /*
1003 * If listening socket requested TCP digests, and received SYN
1004 * contains the option, flag this in the syncache so that
1005 * syncache_respond() will do the right thing with the SYN+ACK.
1006 * XXX Currently we always record the option by default and will
1007 * attempt to use it in syncache_respond().
1008 */
1009 if (to->to_flags & TOF_SIGNATURE)
1010 sc->sc_flags |= SCF_SIGNATURE;
1011 #endif
1012
1013 if (to->to_flags & TOF_SACK)
1014 sc->sc_flags |= SCF_SACK;
1015
1016 /*
1017 * XXX
1018 * We have the option here of not doing TAO (even if the segment
1019 * qualifies) and instead fall back to a normal 3WHS via the syncache.
1020 * This allows us to apply synflood protection to TAO-qualifying SYNs
1021 * also. However, there should be a hueristic to determine when to
1022 * do this, and is not present at the moment.
1023 */
1024
1025 /*
1026 * Perform TAO test on incoming CC (SEG.CC) option, if any.
1027 * - compare SEG.CC against cached CC from the same host, if any.
1028 * - if SEG.CC > chached value, SYN must be new and is accepted
1029 * immediately: save new CC in the cache, mark the socket
1030 * connected, enter ESTABLISHED state, turn on flag to
1031 * send a SYN in the next segment.
1032 * A virtual advertised window is set in rcv_adv to
1033 * initialize SWS prevention. Then enter normal segment
1034 * processing: drop SYN, process data and FIN.
1035 * - otherwise do a normal 3-way handshake.
1036 */
1037 if (tcp_do_rfc1644)
1038 tcp_hc_gettao(&sc->sc_inc, &tao);
1039
1040 if ((to->to_flags & TOF_CC) != 0) {
1041 if (((tp->t_flags & TF_NOPUSH) != 0) &&
1042 sc->sc_flags & SCF_CC && tao.tao_cc != 0 &&
1043 CC_GT(to->to_cc, tao.tao_cc)) {
1044 sc->sc_rxtslot = 0;
1045 so = syncache_socket(sc, *sop, m);
1046 if (so != NULL) {
1047 tao.tao_cc = to->to_cc;
1048 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC,
1049 tao.tao_cc, 0);
1050 *sop = so;
1051 }
1052 syncache_free(sc);
1053 return (so != NULL);
1054 }
1055 } else {
1056 /*
1057 * No CC option, but maybe CC.NEW: invalidate cached value.
1058 */
1059 if (tcp_do_rfc1644) {
1060 tao.tao_cc = 0;
1061 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC,
1062 tao.tao_cc, 0);
1063 }
1064 }
1065
1066 /*
1067 * TAO test failed or there was no CC option,
1068 * do a standard 3-way handshake.
1069 */
1070 #ifdef TCPDEBUG
1071 if (syncache_respond(sc, m, so) == 0) {
1072 #else
1073 if (syncache_respond(sc, m) == 0) {
1074 #endif
1075 syncache_insert(sc, sch);
1076 tcpstat.tcps_sndacks++;
1077 tcpstat.tcps_sndtotal++;
1078 } else {
1079 syncache_free(sc);
1080 tcpstat.tcps_sc_dropped++;
1081 }
1082 *sop = NULL;
1083 return (1);
1084 }
1085
1086 #ifdef TCPDEBUG
1087 static int
1088 syncache_respond(sc, m, so)
1089 struct syncache *sc;
1090 struct mbuf *m;
1091 struct socket *so;
1092 #else
1093 static int
1094 syncache_respond(sc, m)
1095 struct syncache *sc;
1096 struct mbuf *m;
1097 #endif
1098 {
1099 u_int8_t *optp;
1100 int optlen, error;
1101 u_int16_t tlen, hlen, mssopt;
1102 struct ip *ip = NULL;
1103 struct tcphdr *th;
1104 struct inpcb *inp;
1105 #ifdef INET6
1106 struct ip6_hdr *ip6 = NULL;
1107 #endif
1108
1109 hlen =
1110 #ifdef INET6
1111 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) :
1112 #endif
1113 sizeof(struct ip);
1114
1115 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer"));
1116
1117 /* Determine MSS we advertize to other end of connection */
1118 mssopt = tcp_mssopt(&sc->sc_inc);
1119
1120 /* Compute the size of the TCP options. */
1121 if (sc->sc_flags & SCF_NOOPT) {
1122 optlen = 0;
1123 } else {
1124 optlen = TCPOLEN_MAXSEG +
1125 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
1126 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
1127 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0);
1128 #ifdef TCP_SIGNATURE
1129 optlen += (sc->sc_flags & SCF_SIGNATURE) ?
1130 TCPOLEN_SIGNATURE + 2 : 0;
1131 #endif
1132 optlen += ((sc->sc_flags & SCF_SACK) ? 4 : 0);
1133 }
1134 tlen = hlen + sizeof(struct tcphdr) + optlen;
1135
1136 /*
1137 * XXX
1138 * assume that the entire packet will fit in a header mbuf
1139 */
1140 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small"));
1141
1142 /*
1143 * XXX shouldn't this reuse the mbuf if possible ?
1144 * Create the IP+TCP header from scratch.
1145 */
1146 if (m)
1147 m_freem(m);
1148
1149 m = m_gethdr(M_DONTWAIT, MT_HEADER);
1150 if (m == NULL)
1151 return (ENOBUFS);
1152 m->m_data += max_linkhdr;
1153 m->m_len = tlen;
1154 m->m_pkthdr.len = tlen;
1155 m->m_pkthdr.rcvif = NULL;
1156 inp = sc->sc_tp->t_inpcb;
1157 INP_LOCK(inp);
1158 #ifdef MAC
1159 mac_create_mbuf_from_inpcb(inp, m);
1160 #endif
1161
1162 #ifdef INET6
1163 if (sc->sc_inc.inc_isipv6) {
1164 ip6 = mtod(m, struct ip6_hdr *);
1165 ip6->ip6_vfc = IPV6_VERSION;
1166 ip6->ip6_nxt = IPPROTO_TCP;
1167 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1168 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1169 ip6->ip6_plen = htons(tlen - hlen);
1170 /* ip6_hlim is set after checksum */
1171 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1172 ip6->ip6_flow |= sc->sc_flowlabel;
1173
1174 th = (struct tcphdr *)(ip6 + 1);
1175 } else
1176 #endif
1177 {
1178 ip = mtod(m, struct ip *);
1179 ip->ip_v = IPVERSION;
1180 ip->ip_hl = sizeof(struct ip) >> 2;
1181 ip->ip_len = tlen;
1182 ip->ip_id = 0;
1183 ip->ip_off = 0;
1184 ip->ip_sum = 0;
1185 ip->ip_p = IPPROTO_TCP;
1186 ip->ip_src = sc->sc_inc.inc_laddr;
1187 ip->ip_dst = sc->sc_inc.inc_faddr;
1188 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */
1189 ip->ip_tos = inp->inp_ip_tos; /* XXX */
1190
1191 /*
1192 * See if we should do MTU discovery. Route lookups are
1193 * expensive, so we will only unset the DF bit if:
1194 *
1195 * 1) path_mtu_discovery is disabled
1196 * 2) the SCF_UNREACH flag has been set
1197 */
1198 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1199 ip->ip_off |= IP_DF;
1200
1201 th = (struct tcphdr *)(ip + 1);
1202 }
1203 th->th_sport = sc->sc_inc.inc_lport;
1204 th->th_dport = sc->sc_inc.inc_fport;
1205
1206 th->th_seq = htonl(sc->sc_iss);
1207 th->th_ack = htonl(sc->sc_irs + 1);
1208 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1209 th->th_x2 = 0;
1210 th->th_flags = TH_SYN|TH_ACK;
1211 th->th_win = htons(sc->sc_wnd);
1212 th->th_urp = 0;
1213
1214 /* Tack on the TCP options. */
1215 if (optlen != 0) {
1216 optp = (u_int8_t *)(th + 1);
1217 *optp++ = TCPOPT_MAXSEG;
1218 *optp++ = TCPOLEN_MAXSEG;
1219 *optp++ = (mssopt >> 8) & 0xff;
1220 *optp++ = mssopt & 0xff;
1221
1222 if (sc->sc_flags & SCF_WINSCALE) {
1223 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
1224 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
1225 sc->sc_request_r_scale);
1226 optp += 4;
1227 }
1228
1229 if (sc->sc_flags & SCF_TIMESTAMP) {
1230 u_int32_t *lp = (u_int32_t *)(optp);
1231
1232 /* Form timestamp option per appendix A of RFC 1323. */
1233 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
1234 *lp++ = htonl(ticks);
1235 *lp = htonl(sc->sc_tsrecent);
1236 optp += TCPOLEN_TSTAMP_APPA;
1237 }
1238
1239 /*
1240 * Send CC and CC.echo if we received CC from our peer.
1241 */
1242 if (sc->sc_flags & SCF_CC) {
1243 u_int32_t *lp = (u_int32_t *)(optp);
1244
1245 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
1246 *lp++ = htonl(sc->sc_cc_send);
1247 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO));
1248 *lp = htonl(sc->sc_cc_recv);
1249 optp += TCPOLEN_CC_APPA * 2;
1250 }
1251
1252 #ifdef TCP_SIGNATURE
1253 /*
1254 * Handle TCP-MD5 passive opener response.
1255 */
1256 if (sc->sc_flags & SCF_SIGNATURE) {
1257 u_int8_t *bp = optp;
1258 int i;
1259
1260 *bp++ = TCPOPT_SIGNATURE;
1261 *bp++ = TCPOLEN_SIGNATURE;
1262 for (i = 0; i < TCP_SIGLEN; i++)
1263 *bp++ = 0;
1264 tcp_signature_compute(m, sizeof(struct ip), 0, optlen,
1265 optp + 2, IPSEC_DIR_OUTBOUND);
1266 *bp++ = TCPOPT_NOP;
1267 *bp++ = TCPOPT_EOL;
1268 optp += TCPOLEN_SIGNATURE + 2;
1269 }
1270 #endif /* TCP_SIGNATURE */
1271
1272 if (sc->sc_flags & SCF_SACK) {
1273 *(u_int32_t *)optp = htonl(TCPOPT_SACK_PERMIT_HDR);
1274 optp += 4;
1275 }
1276 }
1277
1278 #ifdef INET6
1279 if (sc->sc_inc.inc_isipv6) {
1280 th->th_sum = 0;
1281 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
1282 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1283 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp);
1284 } else
1285 #endif
1286 {
1287 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1288 htons(tlen - hlen + IPPROTO_TCP));
1289 m->m_pkthdr.csum_flags = CSUM_TCP;
1290 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1291 #ifdef TCPDEBUG
1292 /*
1293 * Trace.
1294 */
1295 if (so != NULL && so->so_options & SO_DEBUG) {
1296 struct tcpcb *tp = sototcpcb(so);
1297 tcp_trace(TA_OUTPUT, tp->t_state, tp,
1298 mtod(m, void *), th, 0);
1299 }
1300 #endif
1301 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp);
1302 }
1303 INP_UNLOCK(inp);
1304 return (error);
1305 }
1306
1307 /*
1308 * cookie layers:
1309 *
1310 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|
1311 * | peer iss |
1312 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .|
1313 * | 0 |(A)| |
1314 * (A): peer mss index
1315 */
1316
1317 /*
1318 * The values below are chosen to minimize the size of the tcp_secret
1319 * table, as well as providing roughly a 16 second lifetime for the cookie.
1320 */
1321
1322 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */
1323 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */
1324
1325 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1)
1326 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS)
1327 #define SYNCOOKIE_TIMEOUT \
1328 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT))
1329 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
1330
1331 static struct {
1332 u_int32_t ts_secbits[4];
1333 u_int ts_expire;
1334 } tcp_secret[SYNCOOKIE_NSECRETS];
1335
1336 static int tcp_msstab[] = { 0, 536, 1460, 8960 };
1337
1338 static MD5_CTX syn_ctx;
1339
1340 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v))
1341
1342 struct md5_add {
1343 u_int32_t laddr, faddr;
1344 u_int32_t secbits[4];
1345 u_int16_t lport, fport;
1346 };
1347
1348 #ifdef CTASSERT
1349 CTASSERT(sizeof(struct md5_add) == 28);
1350 #endif
1351
1352 /*
1353 * Consider the problem of a recreated (and retransmitted) cookie. If the
1354 * original SYN was accepted, the connection is established. The second
1355 * SYN is inflight, and if it arrives with an ISN that falls within the
1356 * receive window, the connection is killed.
1357 *
1358 * However, since cookies have other problems, this may not be worth
1359 * worrying about.
1360 */
1361
1362 static u_int32_t
1363 syncookie_generate(struct syncache *sc, u_int32_t *flowid)
1364 {
1365 u_int32_t md5_buffer[4];
1366 u_int32_t data;
1367 int idx, i;
1368 struct md5_add add;
1369
1370 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */
1371
1372 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
1373 if (tcp_secret[idx].ts_expire < ticks) {
1374 for (i = 0; i < 4; i++)
1375 tcp_secret[idx].ts_secbits[i] = arc4random();
1376 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT;
1377 }
1378 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--)
1379 if (tcp_msstab[data] <= sc->sc_peer_mss)
1380 break;
1381 data = (data << SYNCOOKIE_WNDBITS) | idx;
1382 data ^= sc->sc_irs; /* peer's iss */
1383 MD5Init(&syn_ctx);
1384 #ifdef INET6
1385 if (sc->sc_inc.inc_isipv6) {
1386 MD5Add(sc->sc_inc.inc6_laddr);
1387 MD5Add(sc->sc_inc.inc6_faddr);
1388 add.laddr = 0;
1389 add.faddr = 0;
1390 } else
1391 #endif
1392 {
1393 add.laddr = sc->sc_inc.inc_laddr.s_addr;
1394 add.faddr = sc->sc_inc.inc_faddr.s_addr;
1395 }
1396 add.lport = sc->sc_inc.inc_lport;
1397 add.fport = sc->sc_inc.inc_fport;
1398 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1399 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1400 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1401 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1402 MD5Add(add);
1403 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1404 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
1405 *flowid = md5_buffer[1];
1406 return (data);
1407 }
1408
1409 static struct syncache *
1410 syncookie_lookup(inc, th, so)
1411 struct in_conninfo *inc;
1412 struct tcphdr *th;
1413 struct socket *so;
1414 {
1415 u_int32_t md5_buffer[4];
1416 struct syncache *sc;
1417 u_int32_t data;
1418 int wnd, idx;
1419 struct md5_add add;
1420
1421 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */
1422
1423 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */
1424 idx = data & SYNCOOKIE_WNDMASK;
1425 if (tcp_secret[idx].ts_expire < ticks ||
1426 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks)
1427 return (NULL);
1428 MD5Init(&syn_ctx);
1429 #ifdef INET6
1430 if (inc->inc_isipv6) {
1431 MD5Add(inc->inc6_laddr);
1432 MD5Add(inc->inc6_faddr);
1433 add.laddr = 0;
1434 add.faddr = 0;
1435 } else
1436 #endif
1437 {
1438 add.laddr = inc->inc_laddr.s_addr;
1439 add.faddr = inc->inc_faddr.s_addr;
1440 }
1441 add.lport = inc->inc_lport;
1442 add.fport = inc->inc_fport;
1443 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1444 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1445 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1446 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1447 MD5Add(add);
1448 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1449 data ^= md5_buffer[0];
1450 if ((data & ~SYNCOOKIE_DATAMASK) != 0)
1451 return (NULL);
1452 data = data >> SYNCOOKIE_WNDBITS;
1453
1454 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO);
1455 if (sc == NULL)
1456 return (NULL);
1457 /*
1458 * Fill in the syncache values.
1459 * XXX duplicate code from syncache_add
1460 */
1461 sc->sc_ipopts = NULL;
1462 sc->sc_inc.inc_fport = inc->inc_fport;
1463 sc->sc_inc.inc_lport = inc->inc_lport;
1464 sc->sc_tp = sototcpcb(so);
1465 #ifdef INET6
1466 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1467 if (inc->inc_isipv6) {
1468 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1469 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1470 if (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)
1471 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1472 } else
1473 #endif
1474 {
1475 sc->sc_inc.inc_faddr = inc->inc_faddr;
1476 sc->sc_inc.inc_laddr = inc->inc_laddr;
1477 }
1478 sc->sc_irs = th->th_seq - 1;
1479 sc->sc_iss = th->th_ack - 1;
1480 wnd = sbspace(&so->so_rcv);
1481 wnd = imax(wnd, 0);
1482 wnd = imin(wnd, TCP_MAXWIN);
1483 sc->sc_wnd = wnd;
1484 sc->sc_flags = 0;
1485 sc->sc_rxtslot = 0;
1486 sc->sc_peer_mss = tcp_msstab[data];
1487 return (sc);
1488 }
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