1 /*-
2 * Copyright (c) 2001 Networks Associates Technology, Inc.
3 * All rights reserved.
4 *
5 * This software was developed for the FreeBSD Project by Jonathan Lemon
6 * and NAI Labs, the Security Research Division of Network Associates, Inc.
7 * under 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 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior written
20 * permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * $FreeBSD: releng/5.3/sys/netinet/tcp_syncache.c 136588 2004-10-16 08:43:07Z cvs2svn $
35 */
36
37 #include "opt_inet.h"
38 #include "opt_inet6.h"
39 #include "opt_ipsec.h"
40 #include "opt_mac.h"
41 #include "opt_tcpdebug.h"
42 #include "opt_tcp_sack.h"
43
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/kernel.h>
47 #include <sys/sysctl.h>
48 #include <sys/malloc.h>
49 #include <sys/mac.h>
50 #include <sys/mbuf.h>
51 #include <sys/md5.h>
52 #include <sys/proc.h> /* for proc0 declaration */
53 #include <sys/random.h>
54 #include <sys/socket.h>
55 #include <sys/socketvar.h>
56
57 #include <net/if.h>
58 #include <net/route.h>
59
60 #include <netinet/in.h>
61 #include <netinet/in_systm.h>
62 #include <netinet/ip.h>
63 #include <netinet/in_var.h>
64 #include <netinet/in_pcb.h>
65 #include <netinet/ip_var.h>
66 #ifdef INET6
67 #include <netinet/ip6.h>
68 #include <netinet/icmp6.h>
69 #include <netinet6/nd6.h>
70 #include <netinet6/ip6_var.h>
71 #include <netinet6/in6_pcb.h>
72 #endif
73 #include <netinet/tcp.h>
74 #ifdef TCPDEBUG
75 #include <netinet/tcpip.h>
76 #endif
77 #include <netinet/tcp_fsm.h>
78 #include <netinet/tcp_seq.h>
79 #include <netinet/tcp_timer.h>
80 #include <netinet/tcp_var.h>
81 #ifdef TCPDEBUG
82 #include <netinet/tcp_debug.h>
83 #endif
84 #ifdef INET6
85 #include <netinet6/tcp6_var.h>
86 #endif
87
88 #ifdef IPSEC
89 #include <netinet6/ipsec.h>
90 #ifdef INET6
91 #include <netinet6/ipsec6.h>
92 #endif
93 #endif /*IPSEC*/
94
95 #ifdef FAST_IPSEC
96 #include <netipsec/ipsec.h>
97 #ifdef INET6
98 #include <netipsec/ipsec6.h>
99 #endif
100 #include <netipsec/key.h>
101 #endif /*FAST_IPSEC*/
102
103 #include <machine/in_cksum.h>
104 #include <vm/uma.h>
105
106 static int tcp_syncookies = 1;
107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
108 &tcp_syncookies, 0,
109 "Use TCP SYN cookies if the syncache overflows");
110
111 static void syncache_drop(struct syncache *, struct syncache_head *);
112 static void syncache_free(struct syncache *);
113 static void syncache_insert(struct syncache *, struct syncache_head *);
114 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
115 #ifdef TCPDEBUG
116 static int syncache_respond(struct syncache *, struct mbuf *, struct socket *);
117 #else
118 static int syncache_respond(struct syncache *, struct mbuf *);
119 #endif
120 static struct socket *syncache_socket(struct syncache *, struct socket *,
121 struct mbuf *m);
122 static void syncache_timer(void *);
123 static u_int32_t syncookie_generate(struct syncache *, u_int32_t *);
124 static struct syncache *syncookie_lookup(struct in_conninfo *,
125 struct tcphdr *, struct socket *);
126
127 /*
128 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
129 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds,
130 * the odds are that the user has given up attempting to connect by then.
131 */
132 #define SYNCACHE_MAXREXMTS 3
133
134 /* Arbitrary values */
135 #define TCP_SYNCACHE_HASHSIZE 512
136 #define TCP_SYNCACHE_BUCKETLIMIT 30
137
138 struct tcp_syncache {
139 struct syncache_head *hashbase;
140 uma_zone_t zone;
141 u_int hashsize;
142 u_int hashmask;
143 u_int bucket_limit;
144 u_int cache_count;
145 u_int cache_limit;
146 u_int rexmt_limit;
147 u_int hash_secret;
148 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1];
149 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1];
150 };
151 static struct tcp_syncache tcp_syncache;
152
153 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
154
155 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
156 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
157
158 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
159 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
160
161 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
162 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
163
164 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
165 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
166
167 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
168 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
169
170 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
171
172 #define SYNCACHE_HASH(inc, mask) \
173 ((tcp_syncache.hash_secret ^ \
174 (inc)->inc_faddr.s_addr ^ \
175 ((inc)->inc_faddr.s_addr >> 16) ^ \
176 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
177
178 #define SYNCACHE_HASH6(inc, mask) \
179 ((tcp_syncache.hash_secret ^ \
180 (inc)->inc6_faddr.s6_addr32[0] ^ \
181 (inc)->inc6_faddr.s6_addr32[3] ^ \
182 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
183
184 #define ENDPTS_EQ(a, b) ( \
185 (a)->ie_fport == (b)->ie_fport && \
186 (a)->ie_lport == (b)->ie_lport && \
187 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
188 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
189 )
190
191 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
192
193 #define SYNCACHE_TIMEOUT(sc, slot) do { \
194 sc->sc_rxtslot = (slot); \
195 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \
196 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \
197 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \
198 callout_reset(&tcp_syncache.tt_timerq[(slot)], \
199 TCPTV_RTOBASE * tcp_backoff[(slot)], \
200 syncache_timer, (void *)((intptr_t)(slot))); \
201 } while (0)
202
203 static void
204 syncache_free(struct syncache *sc)
205 {
206 if (sc->sc_ipopts)
207 (void) m_free(sc->sc_ipopts);
208
209 uma_zfree(tcp_syncache.zone, sc);
210 }
211
212 void
213 syncache_init(void)
214 {
215 int i;
216
217 tcp_syncache.cache_count = 0;
218 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
219 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
220 tcp_syncache.cache_limit =
221 tcp_syncache.hashsize * tcp_syncache.bucket_limit;
222 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
223 tcp_syncache.hash_secret = arc4random();
224
225 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
226 &tcp_syncache.hashsize);
227 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
228 &tcp_syncache.cache_limit);
229 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
230 &tcp_syncache.bucket_limit);
231 if (!powerof2(tcp_syncache.hashsize)) {
232 printf("WARNING: syncache hash size is not a power of 2.\n");
233 tcp_syncache.hashsize = 512; /* safe default */
234 }
235 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
236
237 /* Allocate the hash table. */
238 MALLOC(tcp_syncache.hashbase, struct syncache_head *,
239 tcp_syncache.hashsize * sizeof(struct syncache_head),
240 M_SYNCACHE, M_WAITOK);
241
242 /* Initialize the hash buckets. */
243 for (i = 0; i < tcp_syncache.hashsize; i++) {
244 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket);
245 tcp_syncache.hashbase[i].sch_length = 0;
246 }
247
248 /* Initialize the timer queues. */
249 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) {
250 TAILQ_INIT(&tcp_syncache.timerq[i]);
251 callout_init(&tcp_syncache.tt_timerq[i],
252 debug_mpsafenet ? CALLOUT_MPSAFE : 0);
253 }
254
255 /*
256 * Allocate the syncache entries. Allow the zone to allocate one
257 * more entry than cache limit, so a new entry can bump out an
258 * older one.
259 */
260 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
261 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
262 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit);
263 tcp_syncache.cache_limit -= 1;
264 }
265
266 static void
267 syncache_insert(sc, sch)
268 struct syncache *sc;
269 struct syncache_head *sch;
270 {
271 struct syncache *sc2;
272 int i;
273
274 INP_INFO_WLOCK_ASSERT(&tcbinfo);
275
276 /*
277 * Make sure that we don't overflow the per-bucket
278 * limit or the total cache size limit.
279 */
280 if (sch->sch_length >= tcp_syncache.bucket_limit) {
281 /*
282 * The bucket is full, toss the oldest element.
283 */
284 sc2 = TAILQ_FIRST(&sch->sch_bucket);
285 sc2->sc_tp->ts_recent = ticks;
286 syncache_drop(sc2, sch);
287 tcpstat.tcps_sc_bucketoverflow++;
288 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) {
289 /*
290 * The cache is full. Toss the oldest entry in the
291 * entire cache. This is the front entry in the
292 * first non-empty timer queue with the largest
293 * timeout value.
294 */
295 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
296 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]);
297 if (sc2 != NULL)
298 break;
299 }
300 sc2->sc_tp->ts_recent = ticks;
301 syncache_drop(sc2, NULL);
302 tcpstat.tcps_sc_cacheoverflow++;
303 }
304
305 /* Initialize the entry's timer. */
306 SYNCACHE_TIMEOUT(sc, 0);
307
308 /* Put it into the bucket. */
309 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash);
310 sch->sch_length++;
311 tcp_syncache.cache_count++;
312 tcpstat.tcps_sc_added++;
313 }
314
315 static void
316 syncache_drop(sc, sch)
317 struct syncache *sc;
318 struct syncache_head *sch;
319 {
320 INP_INFO_WLOCK_ASSERT(&tcbinfo);
321
322 if (sch == NULL) {
323 #ifdef INET6
324 if (sc->sc_inc.inc_isipv6) {
325 sch = &tcp_syncache.hashbase[
326 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)];
327 } else
328 #endif
329 {
330 sch = &tcp_syncache.hashbase[
331 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)];
332 }
333 }
334
335 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
336 sch->sch_length--;
337 tcp_syncache.cache_count--;
338
339 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq);
340 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot]))
341 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]);
342
343 syncache_free(sc);
344 }
345
346 /*
347 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
348 * If we have retransmitted an entry the maximum number of times, expire it.
349 */
350 static void
351 syncache_timer(xslot)
352 void *xslot;
353 {
354 intptr_t slot = (intptr_t)xslot;
355 struct syncache *sc, *nsc;
356 struct inpcb *inp;
357
358 INP_INFO_WLOCK(&tcbinfo);
359 if (callout_pending(&tcp_syncache.tt_timerq[slot]) ||
360 !callout_active(&tcp_syncache.tt_timerq[slot])) {
361 /* XXX can this happen? */
362 INP_INFO_WUNLOCK(&tcbinfo);
363 return;
364 }
365 callout_deactivate(&tcp_syncache.tt_timerq[slot]);
366
367 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]);
368 while (nsc != NULL) {
369 if (ticks < nsc->sc_rxttime)
370 break;
371 sc = nsc;
372 inp = sc->sc_tp->t_inpcb;
373 if (slot == SYNCACHE_MAXREXMTS ||
374 slot >= tcp_syncache.rexmt_limit ||
375 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) {
376 nsc = TAILQ_NEXT(sc, sc_timerq);
377 syncache_drop(sc, NULL);
378 tcpstat.tcps_sc_stale++;
379 continue;
380 }
381 /*
382 * syncache_respond() may call back into the syncache to
383 * to modify another entry, so do not obtain the next
384 * entry on the timer chain until it has completed.
385 */
386 #ifdef TCPDEBUG
387 (void) syncache_respond(sc, NULL, NULL);
388 #else
389 (void) syncache_respond(sc, NULL);
390 #endif
391 nsc = TAILQ_NEXT(sc, sc_timerq);
392 tcpstat.tcps_sc_retransmitted++;
393 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq);
394 SYNCACHE_TIMEOUT(sc, slot + 1);
395 }
396 if (nsc != NULL)
397 callout_reset(&tcp_syncache.tt_timerq[slot],
398 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot));
399 INP_INFO_WUNLOCK(&tcbinfo);
400 }
401
402 /*
403 * Find an entry in the syncache.
404 */
405 struct syncache *
406 syncache_lookup(inc, schp)
407 struct in_conninfo *inc;
408 struct syncache_head **schp;
409 {
410 struct syncache *sc;
411 struct syncache_head *sch;
412
413 INP_INFO_WLOCK_ASSERT(&tcbinfo);
414
415 #ifdef INET6
416 if (inc->inc_isipv6) {
417 sch = &tcp_syncache.hashbase[
418 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
419 *schp = sch;
420 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
421 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
422 return (sc);
423 }
424 } else
425 #endif
426 {
427 sch = &tcp_syncache.hashbase[
428 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
429 *schp = sch;
430 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
431 #ifdef INET6
432 if (sc->sc_inc.inc_isipv6)
433 continue;
434 #endif
435 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
436 return (sc);
437 }
438 }
439 return (NULL);
440 }
441
442 /*
443 * This function is called when we get a RST for a
444 * non-existent connection, so that we can see if the
445 * connection is in the syn cache. If it is, zap it.
446 */
447 void
448 syncache_chkrst(inc, th)
449 struct in_conninfo *inc;
450 struct tcphdr *th;
451 {
452 struct syncache *sc;
453 struct syncache_head *sch;
454
455 INP_INFO_WLOCK_ASSERT(&tcbinfo);
456
457 sc = syncache_lookup(inc, &sch);
458 if (sc == NULL)
459 return;
460 /*
461 * If the RST bit is set, check the sequence number to see
462 * if this is a valid reset segment.
463 * RFC 793 page 37:
464 * In all states except SYN-SENT, all reset (RST) segments
465 * are validated by checking their SEQ-fields. A reset is
466 * valid if its sequence number is in the window.
467 *
468 * The sequence number in the reset segment is normally an
469 * echo of our outgoing acknowlegement numbers, but some hosts
470 * send a reset with the sequence number at the rightmost edge
471 * of our receive window, and we have to handle this case.
472 */
473 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
474 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
475 syncache_drop(sc, sch);
476 tcpstat.tcps_sc_reset++;
477 }
478 }
479
480 void
481 syncache_badack(inc)
482 struct in_conninfo *inc;
483 {
484 struct syncache *sc;
485 struct syncache_head *sch;
486
487 INP_INFO_WLOCK_ASSERT(&tcbinfo);
488
489 sc = syncache_lookup(inc, &sch);
490 if (sc != NULL) {
491 syncache_drop(sc, sch);
492 tcpstat.tcps_sc_badack++;
493 }
494 }
495
496 void
497 syncache_unreach(inc, th)
498 struct in_conninfo *inc;
499 struct tcphdr *th;
500 {
501 struct syncache *sc;
502 struct syncache_head *sch;
503
504 INP_INFO_WLOCK_ASSERT(&tcbinfo);
505
506 /* we are called at splnet() here */
507 sc = syncache_lookup(inc, &sch);
508 if (sc == NULL)
509 return;
510
511 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
512 if (ntohl(th->th_seq) != sc->sc_iss)
513 return;
514
515 /*
516 * If we've rertransmitted 3 times and this is our second error,
517 * we remove the entry. Otherwise, we allow it to continue on.
518 * This prevents us from incorrectly nuking an entry during a
519 * spurious network outage.
520 *
521 * See tcp_notify().
522 */
523 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) {
524 sc->sc_flags |= SCF_UNREACH;
525 return;
526 }
527 syncache_drop(sc, sch);
528 tcpstat.tcps_sc_unreach++;
529 }
530
531 /*
532 * Build a new TCP socket structure from a syncache entry.
533 */
534 static struct socket *
535 syncache_socket(sc, lso, m)
536 struct syncache *sc;
537 struct socket *lso;
538 struct mbuf *m;
539 {
540 struct inpcb *inp = NULL;
541 struct socket *so;
542 struct tcpcb *tp;
543
544 NET_ASSERT_GIANT();
545 INP_INFO_WLOCK_ASSERT(&tcbinfo);
546
547 /*
548 * Ok, create the full blown connection, and set things up
549 * as they would have been set up if we had created the
550 * connection when the SYN arrived. If we can't create
551 * the connection, abort it.
552 */
553 so = sonewconn(lso, SS_ISCONNECTED);
554 if (so == NULL) {
555 /*
556 * Drop the connection; we will send a RST if the peer
557 * retransmits the ACK,
558 */
559 tcpstat.tcps_listendrop++;
560 goto abort2;
561 }
562 #ifdef MAC
563 SOCK_LOCK(so);
564 mac_set_socket_peer_from_mbuf(m, so);
565 SOCK_UNLOCK(so);
566 #endif
567
568 inp = sotoinpcb(so);
569 INP_LOCK(inp);
570
571 /*
572 * Insert new socket into hash list.
573 */
574 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
575 #ifdef INET6
576 if (sc->sc_inc.inc_isipv6) {
577 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
578 } else {
579 inp->inp_vflag &= ~INP_IPV6;
580 inp->inp_vflag |= INP_IPV4;
581 #endif
582 inp->inp_laddr = sc->sc_inc.inc_laddr;
583 #ifdef INET6
584 }
585 #endif
586 inp->inp_lport = sc->sc_inc.inc_lport;
587 if (in_pcbinshash(inp) != 0) {
588 /*
589 * Undo the assignments above if we failed to
590 * put the PCB on the hash lists.
591 */
592 #ifdef INET6
593 if (sc->sc_inc.inc_isipv6)
594 inp->in6p_laddr = in6addr_any;
595 else
596 #endif
597 inp->inp_laddr.s_addr = INADDR_ANY;
598 inp->inp_lport = 0;
599 goto abort;
600 }
601 #ifdef IPSEC
602 /* copy old policy into new socket's */
603 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
604 printf("syncache_expand: could not copy policy\n");
605 #endif
606 #ifdef FAST_IPSEC
607 /* copy old policy into new socket's */
608 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
609 printf("syncache_expand: could not copy policy\n");
610 #endif
611 #ifdef INET6
612 if (sc->sc_inc.inc_isipv6) {
613 struct inpcb *oinp = sotoinpcb(lso);
614 struct in6_addr laddr6;
615 struct sockaddr_in6 sin6;
616 /*
617 * Inherit socket options from the listening socket.
618 * Note that in6p_inputopts are not (and should not be)
619 * copied, since it stores previously received options and is
620 * used to detect if each new option is different than the
621 * previous one and hence should be passed to a user.
622 * If we copied in6p_inputopts, a user would not be able to
623 * receive options just after calling the accept system call.
624 */
625 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
626 if (oinp->in6p_outputopts)
627 inp->in6p_outputopts =
628 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
629
630 sin6.sin6_family = AF_INET6;
631 sin6.sin6_len = sizeof(sin6);
632 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
633 sin6.sin6_port = sc->sc_inc.inc_fport;
634 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
635 laddr6 = inp->in6p_laddr;
636 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
637 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
638 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6,
639 thread0.td_ucred)) {
640 inp->in6p_laddr = laddr6;
641 goto abort;
642 }
643 /* Override flowlabel from in6_pcbconnect. */
644 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK;
645 inp->in6p_flowinfo |= sc->sc_flowlabel;
646 } else
647 #endif
648 {
649 struct in_addr laddr;
650 struct sockaddr_in sin;
651
652 inp->inp_options = ip_srcroute(m);
653 if (inp->inp_options == NULL) {
654 inp->inp_options = sc->sc_ipopts;
655 sc->sc_ipopts = NULL;
656 }
657
658 sin.sin_family = AF_INET;
659 sin.sin_len = sizeof(sin);
660 sin.sin_addr = sc->sc_inc.inc_faddr;
661 sin.sin_port = sc->sc_inc.inc_fport;
662 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
663 laddr = inp->inp_laddr;
664 if (inp->inp_laddr.s_addr == INADDR_ANY)
665 inp->inp_laddr = sc->sc_inc.inc_laddr;
666 if (in_pcbconnect(inp, (struct sockaddr *)&sin,
667 thread0.td_ucred)) {
668 inp->inp_laddr = laddr;
669 goto abort;
670 }
671 }
672
673 tp = intotcpcb(inp);
674 tp->t_state = TCPS_SYN_RECEIVED;
675 tp->iss = sc->sc_iss;
676 tp->irs = sc->sc_irs;
677 tcp_rcvseqinit(tp);
678 tcp_sendseqinit(tp);
679 tp->snd_wl1 = sc->sc_irs;
680 tp->rcv_up = sc->sc_irs + 1;
681 tp->rcv_wnd = sc->sc_wnd;
682 tp->rcv_adv += tp->rcv_wnd;
683
684 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
685 if (sc->sc_flags & SCF_NOOPT)
686 tp->t_flags |= TF_NOOPT;
687 if (sc->sc_flags & SCF_WINSCALE) {
688 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
689 tp->requested_s_scale = sc->sc_requested_s_scale;
690 tp->request_r_scale = sc->sc_request_r_scale;
691 }
692 if (sc->sc_flags & SCF_TIMESTAMP) {
693 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
694 tp->ts_recent = sc->sc_tsrecent;
695 tp->ts_recent_age = ticks;
696 }
697 if (sc->sc_flags & SCF_CC) {
698 /*
699 * Initialization of the tcpcb for transaction;
700 * set SND.WND = SEG.WND,
701 * initialize CCsend and CCrecv.
702 */
703 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC;
704 tp->cc_send = sc->sc_cc_send;
705 tp->cc_recv = sc->sc_cc_recv;
706 }
707 #ifdef TCP_SIGNATURE
708 if (sc->sc_flags & SCF_SIGNATURE)
709 tp->t_flags |= TF_SIGNATURE;
710 #endif
711 if (sc->sc_flags & SCF_SACK) {
712 tp->sack_enable = 1;
713 tp->t_flags |= TF_SACK_PERMIT;
714 }
715 /*
716 * Set up MSS and get cached values from tcp_hostcache.
717 * This might overwrite some of the defaults we just set.
718 */
719 tcp_mss(tp, sc->sc_peer_mss);
720
721 /*
722 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
723 */
724 if (sc->sc_rxtslot != 0)
725 tp->snd_cwnd = tp->t_maxseg;
726 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
727
728 INP_UNLOCK(inp);
729
730 tcpstat.tcps_accepts++;
731 return (so);
732
733 abort:
734 INP_UNLOCK(inp);
735 abort2:
736 if (so != NULL)
737 (void) soabort(so);
738 return (NULL);
739 }
740
741 /*
742 * This function gets called when we receive an ACK for a
743 * socket in the LISTEN state. We look up the connection
744 * in the syncache, and if its there, we pull it out of
745 * the cache and turn it into a full-blown connection in
746 * the SYN-RECEIVED state.
747 */
748 int
749 syncache_expand(inc, th, sop, m)
750 struct in_conninfo *inc;
751 struct tcphdr *th;
752 struct socket **sop;
753 struct mbuf *m;
754 {
755 struct syncache *sc;
756 struct syncache_head *sch;
757 struct socket *so;
758
759 INP_INFO_WLOCK_ASSERT(&tcbinfo);
760
761 sc = syncache_lookup(inc, &sch);
762 if (sc == NULL) {
763 /*
764 * There is no syncache entry, so see if this ACK is
765 * a returning syncookie. To do this, first:
766 * A. See if this socket has had a syncache entry dropped in
767 * the past. We don't want to accept a bogus syncookie
768 * if we've never received a SYN.
769 * B. check that the syncookie is valid. If it is, then
770 * cobble up a fake syncache entry, and return.
771 */
772 if (!tcp_syncookies)
773 return (0);
774 sc = syncookie_lookup(inc, th, *sop);
775 if (sc == NULL)
776 return (0);
777 sch = NULL;
778 tcpstat.tcps_sc_recvcookie++;
779 }
780
781 /*
782 * If seg contains an ACK, but not for our SYN/ACK, send a RST.
783 */
784 if (th->th_ack != sc->sc_iss + 1)
785 return (0);
786
787 so = syncache_socket(sc, *sop, m);
788 if (so == NULL) {
789 #if 0
790 resetandabort:
791 /* XXXjlemon check this - is this correct? */
792 (void) tcp_respond(NULL, m, m, th,
793 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK);
794 #endif
795 m_freem(m); /* XXX only needed for above */
796 tcpstat.tcps_sc_aborted++;
797 } else
798 tcpstat.tcps_sc_completed++;
799
800 if (sch == NULL)
801 syncache_free(sc);
802 else
803 syncache_drop(sc, sch);
804 *sop = so;
805 return (1);
806 }
807
808 /*
809 * Given a LISTEN socket and an inbound SYN request, add
810 * this to the syn cache, and send back a segment:
811 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
812 * to the source.
813 *
814 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
815 * Doing so would require that we hold onto the data and deliver it
816 * to the application. However, if we are the target of a SYN-flood
817 * DoS attack, an attacker could send data which would eventually
818 * consume all available buffer space if it were ACKed. By not ACKing
819 * the data, we avoid this DoS scenario.
820 */
821 int
822 syncache_add(inc, to, th, sop, m)
823 struct in_conninfo *inc;
824 struct tcpopt *to;
825 struct tcphdr *th;
826 struct socket **sop;
827 struct mbuf *m;
828 {
829 struct tcpcb *tp;
830 struct socket *so;
831 struct syncache *sc = NULL;
832 struct syncache_head *sch;
833 struct mbuf *ipopts = NULL;
834 struct rmxp_tao tao;
835 u_int32_t flowtmp;
836 int i, win;
837
838 INP_INFO_WLOCK_ASSERT(&tcbinfo);
839
840 so = *sop;
841 tp = sototcpcb(so);
842 bzero(&tao, sizeof(tao));
843
844 /*
845 * Remember the IP options, if any.
846 */
847 #ifdef INET6
848 if (!inc->inc_isipv6)
849 #endif
850 ipopts = ip_srcroute(m);
851
852 /*
853 * See if we already have an entry for this connection.
854 * If we do, resend the SYN,ACK, and reset the retransmit timer.
855 *
856 * XXX
857 * should the syncache be re-initialized with the contents
858 * of the new SYN here (which may have different options?)
859 */
860 sc = syncache_lookup(inc, &sch);
861 if (sc != NULL) {
862 tcpstat.tcps_sc_dupsyn++;
863 if (ipopts) {
864 /*
865 * If we were remembering a previous source route,
866 * forget it and use the new one we've been given.
867 */
868 if (sc->sc_ipopts)
869 (void) m_free(sc->sc_ipopts);
870 sc->sc_ipopts = ipopts;
871 }
872 /*
873 * Update timestamp if present.
874 */
875 if (sc->sc_flags & SCF_TIMESTAMP)
876 sc->sc_tsrecent = to->to_tsval;
877 /*
878 * PCB may have changed, pick up new values.
879 */
880 sc->sc_tp = tp;
881 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
882 #ifdef TCPDEBUG
883 if (syncache_respond(sc, m, so) == 0) {
884 #else
885 if (syncache_respond(sc, m) == 0) {
886 #endif
887 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */
888 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot],
889 sc, sc_timerq);
890 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot);
891 tcpstat.tcps_sndacks++;
892 tcpstat.tcps_sndtotal++;
893 }
894 *sop = NULL;
895 return (1);
896 }
897
898 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT);
899 if (sc == NULL) {
900 /*
901 * The zone allocator couldn't provide more entries.
902 * Treat this as if the cache was full; drop the oldest
903 * entry and insert the new one.
904 */
905 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */
906 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
907 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]);
908 if (sc != NULL)
909 break;
910 }
911 sc->sc_tp->ts_recent = ticks;
912 syncache_drop(sc, NULL);
913 tcpstat.tcps_sc_zonefail++;
914 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT);
915 if (sc == NULL) {
916 if (ipopts)
917 (void) m_free(ipopts);
918 return (0);
919 }
920 }
921
922 /*
923 * Fill in the syncache values.
924 */
925 bzero(sc, sizeof(*sc));
926 sc->sc_tp = tp;
927 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
928 sc->sc_ipopts = ipopts;
929 sc->sc_inc.inc_fport = inc->inc_fport;
930 sc->sc_inc.inc_lport = inc->inc_lport;
931 #ifdef INET6
932 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
933 if (inc->inc_isipv6) {
934 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
935 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
936 } else
937 #endif
938 {
939 sc->sc_inc.inc_faddr = inc->inc_faddr;
940 sc->sc_inc.inc_laddr = inc->inc_laddr;
941 }
942 sc->sc_irs = th->th_seq;
943 sc->sc_flags = 0;
944 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0;
945 sc->sc_flowlabel = 0;
946 if (tcp_syncookies) {
947 sc->sc_iss = syncookie_generate(sc, &flowtmp);
948 #ifdef INET6
949 if (inc->inc_isipv6 &&
950 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) {
951 sc->sc_flowlabel = flowtmp & IPV6_FLOWLABEL_MASK;
952 }
953 #endif
954 } else {
955 sc->sc_iss = arc4random();
956 #ifdef INET6
957 if (inc->inc_isipv6 &&
958 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) {
959 sc->sc_flowlabel =
960 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
961 }
962 #endif
963 }
964
965 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */
966 win = sbspace(&so->so_rcv);
967 win = imax(win, 0);
968 win = imin(win, TCP_MAXWIN);
969 sc->sc_wnd = win;
970
971 if (tcp_do_rfc1323) {
972 /*
973 * A timestamp received in a SYN makes
974 * it ok to send timestamp requests and replies.
975 */
976 if (to->to_flags & TOF_TS) {
977 sc->sc_tsrecent = to->to_tsval;
978 sc->sc_flags |= SCF_TIMESTAMP;
979 }
980 if (to->to_flags & TOF_SCALE) {
981 int wscale = 0;
982
983 /* Compute proper scaling value from buffer space */
984 while (wscale < TCP_MAX_WINSHIFT &&
985 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat)
986 wscale++;
987 sc->sc_request_r_scale = wscale;
988 sc->sc_requested_s_scale = to->to_requested_s_scale;
989 sc->sc_flags |= SCF_WINSCALE;
990 }
991 }
992 if (tcp_do_rfc1644) {
993 /*
994 * A CC or CC.new option received in a SYN makes
995 * it ok to send CC in subsequent segments.
996 */
997 if (to->to_flags & (TOF_CC|TOF_CCNEW)) {
998 sc->sc_cc_recv = to->to_cc;
999 sc->sc_cc_send = CC_INC(tcp_ccgen);
1000 sc->sc_flags |= SCF_CC;
1001 }
1002 }
1003 if (tp->t_flags & TF_NOOPT)
1004 sc->sc_flags = SCF_NOOPT;
1005 #ifdef TCP_SIGNATURE
1006 /*
1007 * If listening socket requested TCP digests, and received SYN
1008 * contains the option, flag this in the syncache so that
1009 * syncache_respond() will do the right thing with the SYN+ACK.
1010 * XXX Currently we always record the option by default and will
1011 * attempt to use it in syncache_respond().
1012 */
1013 if (to->to_flags & TOF_SIGNATURE)
1014 sc->sc_flags = SCF_SIGNATURE;
1015 #endif
1016
1017 if (to->to_flags & TOF_SACK)
1018 sc->sc_flags |= SCF_SACK;
1019
1020 /*
1021 * XXX
1022 * We have the option here of not doing TAO (even if the segment
1023 * qualifies) and instead fall back to a normal 3WHS via the syncache.
1024 * This allows us to apply synflood protection to TAO-qualifying SYNs
1025 * also. However, there should be a hueristic to determine when to
1026 * do this, and is not present at the moment.
1027 */
1028
1029 /*
1030 * Perform TAO test on incoming CC (SEG.CC) option, if any.
1031 * - compare SEG.CC against cached CC from the same host, if any.
1032 * - if SEG.CC > chached value, SYN must be new and is accepted
1033 * immediately: save new CC in the cache, mark the socket
1034 * connected, enter ESTABLISHED state, turn on flag to
1035 * send a SYN in the next segment.
1036 * A virtual advertised window is set in rcv_adv to
1037 * initialize SWS prevention. Then enter normal segment
1038 * processing: drop SYN, process data and FIN.
1039 * - otherwise do a normal 3-way handshake.
1040 */
1041 if (tcp_do_rfc1644)
1042 tcp_hc_gettao(&sc->sc_inc, &tao);
1043
1044 if ((to->to_flags & TOF_CC) != 0) {
1045 if (((tp->t_flags & TF_NOPUSH) != 0) &&
1046 sc->sc_flags & SCF_CC && tao.tao_cc != 0 &&
1047 CC_GT(to->to_cc, tao.tao_cc)) {
1048 sc->sc_rxtslot = 0;
1049 so = syncache_socket(sc, *sop, m);
1050 if (so != NULL) {
1051 tao.tao_cc = to->to_cc;
1052 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC,
1053 tao.tao_cc, 0);
1054 *sop = so;
1055 }
1056 syncache_free(sc);
1057 return (so != NULL);
1058 }
1059 } else {
1060 /*
1061 * No CC option, but maybe CC.NEW: invalidate cached value.
1062 */
1063 if (tcp_do_rfc1644) {
1064 tao.tao_cc = 0;
1065 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC,
1066 tao.tao_cc, 0);
1067 }
1068 }
1069
1070 /*
1071 * TAO test failed or there was no CC option,
1072 * do a standard 3-way handshake.
1073 */
1074 #ifdef TCPDEBUG
1075 if (syncache_respond(sc, m, so) == 0) {
1076 #else
1077 if (syncache_respond(sc, m) == 0) {
1078 #endif
1079 syncache_insert(sc, sch);
1080 tcpstat.tcps_sndacks++;
1081 tcpstat.tcps_sndtotal++;
1082 } else {
1083 syncache_free(sc);
1084 tcpstat.tcps_sc_dropped++;
1085 }
1086 *sop = NULL;
1087 return (1);
1088 }
1089
1090 #ifdef TCPDEBUG
1091 static int
1092 syncache_respond(sc, m, so)
1093 struct syncache *sc;
1094 struct mbuf *m;
1095 struct socket *so;
1096 #else
1097 static int
1098 syncache_respond(sc, m)
1099 struct syncache *sc;
1100 struct mbuf *m;
1101 #endif
1102 {
1103 u_int8_t *optp;
1104 int optlen, error;
1105 u_int16_t tlen, hlen, mssopt;
1106 struct ip *ip = NULL;
1107 struct tcphdr *th;
1108 struct inpcb *inp;
1109 #ifdef INET6
1110 struct ip6_hdr *ip6 = NULL;
1111 #endif
1112
1113 hlen =
1114 #ifdef INET6
1115 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) :
1116 #endif
1117 sizeof(struct ip);
1118
1119 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer"));
1120
1121 /* Determine MSS we advertize to other end of connection */
1122 mssopt = tcp_mssopt(&sc->sc_inc);
1123
1124 /* Compute the size of the TCP options. */
1125 if (sc->sc_flags & SCF_NOOPT) {
1126 optlen = 0;
1127 } else {
1128 optlen = TCPOLEN_MAXSEG +
1129 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
1130 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
1131 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0);
1132 #ifdef TCP_SIGNATURE
1133 optlen += (sc->sc_flags & SCF_SIGNATURE) ?
1134 TCPOLEN_SIGNATURE + 2 : 0;
1135 #endif
1136 optlen += ((sc->sc_flags & SCF_SACK) ? 4 : 0);
1137 }
1138 tlen = hlen + sizeof(struct tcphdr) + optlen;
1139
1140 /*
1141 * XXX
1142 * assume that the entire packet will fit in a header mbuf
1143 */
1144 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small"));
1145
1146 /*
1147 * XXX shouldn't this reuse the mbuf if possible ?
1148 * Create the IP+TCP header from scratch.
1149 */
1150 if (m)
1151 m_freem(m);
1152
1153 m = m_gethdr(M_DONTWAIT, MT_HEADER);
1154 if (m == NULL)
1155 return (ENOBUFS);
1156 m->m_data += max_linkhdr;
1157 m->m_len = tlen;
1158 m->m_pkthdr.len = tlen;
1159 m->m_pkthdr.rcvif = NULL;
1160 inp = sc->sc_tp->t_inpcb;
1161 INP_LOCK(inp);
1162 #ifdef MAC
1163 mac_create_mbuf_from_inpcb(inp, m);
1164 #endif
1165
1166 #ifdef INET6
1167 if (sc->sc_inc.inc_isipv6) {
1168 ip6 = mtod(m, struct ip6_hdr *);
1169 ip6->ip6_vfc = IPV6_VERSION;
1170 ip6->ip6_nxt = IPPROTO_TCP;
1171 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1172 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1173 ip6->ip6_plen = htons(tlen - hlen);
1174 /* ip6_hlim is set after checksum */
1175 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1176 ip6->ip6_flow |= sc->sc_flowlabel;
1177
1178 th = (struct tcphdr *)(ip6 + 1);
1179 } else
1180 #endif
1181 {
1182 ip = mtod(m, struct ip *);
1183 ip->ip_v = IPVERSION;
1184 ip->ip_hl = sizeof(struct ip) >> 2;
1185 ip->ip_len = tlen;
1186 ip->ip_id = 0;
1187 ip->ip_off = 0;
1188 ip->ip_sum = 0;
1189 ip->ip_p = IPPROTO_TCP;
1190 ip->ip_src = sc->sc_inc.inc_laddr;
1191 ip->ip_dst = sc->sc_inc.inc_faddr;
1192 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */
1193 ip->ip_tos = inp->inp_ip_tos; /* XXX */
1194
1195 /*
1196 * See if we should do MTU discovery. Route lookups are
1197 * expensive, so we will only unset the DF bit if:
1198 *
1199 * 1) path_mtu_discovery is disabled
1200 * 2) the SCF_UNREACH flag has been set
1201 */
1202 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1203 ip->ip_off |= IP_DF;
1204
1205 th = (struct tcphdr *)(ip + 1);
1206 }
1207 th->th_sport = sc->sc_inc.inc_lport;
1208 th->th_dport = sc->sc_inc.inc_fport;
1209
1210 th->th_seq = htonl(sc->sc_iss);
1211 th->th_ack = htonl(sc->sc_irs + 1);
1212 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1213 th->th_x2 = 0;
1214 th->th_flags = TH_SYN|TH_ACK;
1215 th->th_win = htons(sc->sc_wnd);
1216 th->th_urp = 0;
1217
1218 /* Tack on the TCP options. */
1219 if (optlen != 0) {
1220 optp = (u_int8_t *)(th + 1);
1221 *optp++ = TCPOPT_MAXSEG;
1222 *optp++ = TCPOLEN_MAXSEG;
1223 *optp++ = (mssopt >> 8) & 0xff;
1224 *optp++ = mssopt & 0xff;
1225
1226 if (sc->sc_flags & SCF_WINSCALE) {
1227 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
1228 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
1229 sc->sc_request_r_scale);
1230 optp += 4;
1231 }
1232
1233 if (sc->sc_flags & SCF_TIMESTAMP) {
1234 u_int32_t *lp = (u_int32_t *)(optp);
1235
1236 /* Form timestamp option per appendix A of RFC 1323. */
1237 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
1238 *lp++ = htonl(ticks);
1239 *lp = htonl(sc->sc_tsrecent);
1240 optp += TCPOLEN_TSTAMP_APPA;
1241 }
1242
1243 /*
1244 * Send CC and CC.echo if we received CC from our peer.
1245 */
1246 if (sc->sc_flags & SCF_CC) {
1247 u_int32_t *lp = (u_int32_t *)(optp);
1248
1249 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
1250 *lp++ = htonl(sc->sc_cc_send);
1251 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO));
1252 *lp = htonl(sc->sc_cc_recv);
1253 optp += TCPOLEN_CC_APPA * 2;
1254 }
1255
1256 #ifdef TCP_SIGNATURE
1257 /*
1258 * Handle TCP-MD5 passive opener response.
1259 */
1260 if (sc->sc_flags & SCF_SIGNATURE) {
1261 u_int8_t *bp = optp;
1262 int i;
1263
1264 *bp++ = TCPOPT_SIGNATURE;
1265 *bp++ = TCPOLEN_SIGNATURE;
1266 for (i = 0; i < TCP_SIGLEN; i++)
1267 *bp++ = 0;
1268 tcp_signature_compute(m, sizeof(struct ip), 0, optlen,
1269 optp + 2, IPSEC_DIR_OUTBOUND);
1270 *bp++ = TCPOPT_NOP;
1271 *bp++ = TCPOPT_EOL;
1272 optp += TCPOLEN_SIGNATURE + 2;
1273 }
1274 #endif /* TCP_SIGNATURE */
1275
1276 if (sc->sc_flags & SCF_SACK) {
1277 *(u_int32_t *)optp = htonl(TCPOPT_SACK_PERMIT_HDR);
1278 optp += 4;
1279 }
1280 }
1281
1282 #ifdef INET6
1283 if (sc->sc_inc.inc_isipv6) {
1284 th->th_sum = 0;
1285 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
1286 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1287 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp);
1288 } else
1289 #endif
1290 {
1291 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1292 htons(tlen - hlen + IPPROTO_TCP));
1293 m->m_pkthdr.csum_flags = CSUM_TCP;
1294 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1295 #ifdef TCPDEBUG
1296 /*
1297 * Trace.
1298 */
1299 if (so != NULL && so->so_options & SO_DEBUG) {
1300 struct tcpcb *tp = sototcpcb(so);
1301 tcp_trace(TA_OUTPUT, tp->t_state, tp,
1302 mtod(m, void *), th, 0);
1303 }
1304 #endif
1305 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp);
1306 }
1307 INP_UNLOCK(inp);
1308 return (error);
1309 }
1310
1311 /*
1312 * cookie layers:
1313 *
1314 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|
1315 * | peer iss |
1316 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .|
1317 * | 0 |(A)| |
1318 * (A): peer mss index
1319 */
1320
1321 /*
1322 * The values below are chosen to minimize the size of the tcp_secret
1323 * table, as well as providing roughly a 16 second lifetime for the cookie.
1324 */
1325
1326 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */
1327 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */
1328
1329 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1)
1330 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS)
1331 #define SYNCOOKIE_TIMEOUT \
1332 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT))
1333 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
1334
1335 static struct {
1336 u_int32_t ts_secbits[4];
1337 u_int ts_expire;
1338 } tcp_secret[SYNCOOKIE_NSECRETS];
1339
1340 static int tcp_msstab[] = { 0, 536, 1460, 8960 };
1341
1342 static MD5_CTX syn_ctx;
1343
1344 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v))
1345
1346 struct md5_add {
1347 u_int32_t laddr, faddr;
1348 u_int32_t secbits[4];
1349 u_int16_t lport, fport;
1350 };
1351
1352 #ifdef CTASSERT
1353 CTASSERT(sizeof(struct md5_add) == 28);
1354 #endif
1355
1356 /*
1357 * Consider the problem of a recreated (and retransmitted) cookie. If the
1358 * original SYN was accepted, the connection is established. The second
1359 * SYN is inflight, and if it arrives with an ISN that falls within the
1360 * receive window, the connection is killed.
1361 *
1362 * However, since cookies have other problems, this may not be worth
1363 * worrying about.
1364 */
1365
1366 static u_int32_t
1367 syncookie_generate(struct syncache *sc, u_int32_t *flowid)
1368 {
1369 u_int32_t md5_buffer[4];
1370 u_int32_t data;
1371 int idx, i;
1372 struct md5_add add;
1373
1374 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */
1375
1376 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
1377 if (tcp_secret[idx].ts_expire < ticks) {
1378 for (i = 0; i < 4; i++)
1379 tcp_secret[idx].ts_secbits[i] = arc4random();
1380 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT;
1381 }
1382 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--)
1383 if (tcp_msstab[data] <= sc->sc_peer_mss)
1384 break;
1385 data = (data << SYNCOOKIE_WNDBITS) | idx;
1386 data ^= sc->sc_irs; /* peer's iss */
1387 MD5Init(&syn_ctx);
1388 #ifdef INET6
1389 if (sc->sc_inc.inc_isipv6) {
1390 MD5Add(sc->sc_inc.inc6_laddr);
1391 MD5Add(sc->sc_inc.inc6_faddr);
1392 add.laddr = 0;
1393 add.faddr = 0;
1394 } else
1395 #endif
1396 {
1397 add.laddr = sc->sc_inc.inc_laddr.s_addr;
1398 add.faddr = sc->sc_inc.inc_faddr.s_addr;
1399 }
1400 add.lport = sc->sc_inc.inc_lport;
1401 add.fport = sc->sc_inc.inc_fport;
1402 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1403 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1404 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1405 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1406 MD5Add(add);
1407 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1408 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
1409 *flowid = md5_buffer[1];
1410 return (data);
1411 }
1412
1413 static struct syncache *
1414 syncookie_lookup(inc, th, so)
1415 struct in_conninfo *inc;
1416 struct tcphdr *th;
1417 struct socket *so;
1418 {
1419 u_int32_t md5_buffer[4];
1420 struct syncache *sc;
1421 u_int32_t data;
1422 int wnd, idx;
1423 struct md5_add add;
1424
1425 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */
1426
1427 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */
1428 idx = data & SYNCOOKIE_WNDMASK;
1429 if (tcp_secret[idx].ts_expire < ticks ||
1430 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks)
1431 return (NULL);
1432 MD5Init(&syn_ctx);
1433 #ifdef INET6
1434 if (inc->inc_isipv6) {
1435 MD5Add(inc->inc6_laddr);
1436 MD5Add(inc->inc6_faddr);
1437 add.laddr = 0;
1438 add.faddr = 0;
1439 } else
1440 #endif
1441 {
1442 add.laddr = inc->inc_laddr.s_addr;
1443 add.faddr = inc->inc_faddr.s_addr;
1444 }
1445 add.lport = inc->inc_lport;
1446 add.fport = inc->inc_fport;
1447 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1448 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1449 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1450 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1451 MD5Add(add);
1452 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1453 data ^= md5_buffer[0];
1454 if ((data & ~SYNCOOKIE_DATAMASK) != 0)
1455 return (NULL);
1456 data = data >> SYNCOOKIE_WNDBITS;
1457
1458 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT);
1459 if (sc == NULL)
1460 return (NULL);
1461 /*
1462 * Fill in the syncache values.
1463 * XXX duplicate code from syncache_add
1464 */
1465 sc->sc_ipopts = NULL;
1466 sc->sc_inc.inc_fport = inc->inc_fport;
1467 sc->sc_inc.inc_lport = inc->inc_lport;
1468 sc->sc_tp = sototcpcb(so);
1469 #ifdef INET6
1470 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1471 if (inc->inc_isipv6) {
1472 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1473 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1474 if (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)
1475 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1476 } else
1477 #endif
1478 {
1479 sc->sc_inc.inc_faddr = inc->inc_faddr;
1480 sc->sc_inc.inc_laddr = inc->inc_laddr;
1481 }
1482 sc->sc_irs = th->th_seq - 1;
1483 sc->sc_iss = th->th_ack - 1;
1484 wnd = sbspace(&so->so_rcv);
1485 wnd = imax(wnd, 0);
1486 wnd = imin(wnd, TCP_MAXWIN);
1487 sc->sc_wnd = wnd;
1488 sc->sc_flags = 0;
1489 sc->sc_rxtslot = 0;
1490 sc->sc_peer_mss = tcp_msstab[data];
1491 return (sc);
1492 }
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