2 * Copyright (c) 2001 McAfee, Inc.
3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG
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.
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
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.
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
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
37 #include "opt_inet6.h"
38 #include "opt_ipsec.h"
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>
46 #include <sys/mutex.h>
47 #include <sys/malloc.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>
60 #include <net/route.h>
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>
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>
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>
85 #include <netinet6/tcp6_var.h>
89 #include <netipsec/ipsec.h>
91 #include <netipsec/ipsec6.h>
93 #include <netipsec/key.h>
96 #include <machine/in_cksum.h>
98 #include <security/mac/mac_framework.h>
100 static VNET_DEFINE(int, tcp_syncookies) = 1;
101 #define V_tcp_syncookies VNET(tcp_syncookies)
102 SYSCTL_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");
106 static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
107 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
108 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW,
109 &VNET_NAME(tcp_syncookiesonly), 0,
110 "Use only TCP SYN cookies");
112 #ifdef TCP_OFFLOAD_DISABLE
113 #define TOEPCB_ISSET(sc) (0)
115 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL)
118 static void syncache_drop(struct syncache *, struct syncache_head *);
119 static void syncache_free(struct syncache *);
120 static void syncache_insert(struct syncache *, struct syncache_head *);
121 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
122 static int syncache_respond(struct syncache *);
123 static struct socket *syncache_socket(struct syncache *, struct socket *,
125 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
127 static void syncache_timer(void *);
128 static void syncookie_generate(struct syncache_head *, struct syncache *,
130 static struct syncache
131 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
132 struct syncache *, struct tcpopt *, struct tcphdr *,
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.
140 #define SYNCACHE_MAXREXMTS 3
142 /* Arbitrary values */
143 #define TCP_SYNCACHE_HASHSIZE 512
144 #define TCP_SYNCACHE_BUCKETLIMIT 30
146 static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
147 #define V_tcp_syncache VNET(tcp_syncache)
149 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
151 SYSCTL_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");
155 SYSCTL_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");
159 SYSCTL_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");
163 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
164 &VNET_NAME(tcp_syncache.hashsize), 0,
165 "Size of TCP syncache hashtable");
167 SYSCTL_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");
171 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
172 SYSCTL_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");
176 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
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)
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)
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 \
197 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
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)
204 * Requires the syncache entry to be already removed from the bucket list.
207 syncache_free(struct syncache *sc)
211 (void) m_free(sc->sc_ipopts);
215 mac_syncache_destroy(&sc->sc_label);
218 uma_zfree(V_tcp_syncache.zone, sc);
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();
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;
241 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
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);
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);
253 /* Initialize the hash buckets. */
254 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
256 V_tcp_syncache.hashbase[i].sch_vnet = curvnet;
258 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
259 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
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;
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);
274 syncache_destroy(void)
276 struct syncache_head *sch;
277 struct syncache *sc, *nsc;
280 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
281 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
283 sch = &V_tcp_syncache.hashbase[i];
284 callout_drain(&sch->sch_timer);
287 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
288 syncache_drop(sc, 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);
297 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0",
298 __func__, V_tcp_syncache.cache_count));
300 /* Free the allocated global resources. */
301 uma_zdestroy(V_tcp_syncache.zone);
302 free(V_tcp_syncache.hashbase, M_SYNCACHE);
307 * Inserts a syncache entry into the specified bucket row.
308 * Locks and unlocks the syncache_head autonomously.
311 syncache_insert(struct syncache *sc, struct syncache_head *sch)
313 struct syncache *sc2;
318 * Make sure that we don't overflow the per-bucket limit.
319 * If the bucket is full, toss the oldest element.
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);
329 /* Put it into the bucket. */
330 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
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);
340 V_tcp_syncache.cache_count++;
341 TCPSTAT_INC(tcps_sc_added);
345 * Remove and free entry from syncache bucket row.
346 * Expects locked syncache head.
349 syncache_drop(struct syncache *sc, struct syncache_head *sch)
352 SCH_LOCK_ASSERT(sch);
354 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
357 #ifndef TCP_OFFLOAD_DISABLE
359 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb);
362 V_tcp_syncache.cache_count--;
366 * Engage/reengage time on bucket row.
369 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
371 sc->sc_rxttime = ticks +
372 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
374 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
375 sch->sch_nextc = sc->sc_rxttime;
377 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
378 syncache_timer, (void *)sch);
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.
388 syncache_timer(void *xsch)
390 struct syncache_head *sch = (struct syncache_head *)xsch;
391 struct syncache *sc, *nsc;
395 CURVNET_SET(sch->sch_vnet);
397 /* NB: syncache_head has already been locked by the callout. */
398 SCH_LOCK_ASSERT(sch);
401 * In the following cycle we may remove some entries and/or
402 * advance some timeouts, so re-initialize the bucket timer.
404 sch->sch_nextc = tick + INT_MAX;
406 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
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.
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;
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",
427 syncache_drop(sc, sch);
428 TCPSTAT_INC(tcps_sc_stale);
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);
438 (void) syncache_respond(sc);
439 TCPSTAT_INC(tcps_sc_retransmitted);
440 syncache_timeout(sc, sch, 0);
442 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
443 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
444 syncache_timer, (void *)(sch));
449 * Find an entry in the syncache.
450 * Returns always with locked syncache_head plus a matching entry or NULL.
453 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
456 struct syncache_head *sch;
459 if (inc->inc_flags & INC_ISIPV6) {
460 sch = &V_tcp_syncache.hashbase[
461 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)];
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))
474 sch = &V_tcp_syncache.hashbase[
475 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)];
480 /* Circle through bucket row to find matching entry. */
481 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
483 if (sc->sc_inc.inc_flags & INC_ISIPV6)
486 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
490 SCH_LOCK_ASSERT(*schp);
491 return (NULL); /* always returns with locked sch */
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.
500 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
503 struct syncache_head *sch;
506 sc = syncache_lookup(inc, &sch); /* returns locked sch */
507 SCH_LOCK_ASSERT(sch);
510 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
511 * See RFC 793 page 65, section SEGMENT ARRIVES.
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);
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 RST was misdirected or spoofed.
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);
539 * If the RST bit is set, check the sequence number to see
540 * if this is a valid reset segment.
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.
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.
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",
558 TCPSTAT_INC(tcps_sc_reset);
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);
574 syncache_badack(struct in_conninfo *inc)
577 struct syncache_head *sch;
579 sc = syncache_lookup(inc, &sch); /* returns locked sch */
580 SCH_LOCK_ASSERT(sch);
582 syncache_drop(sc, sch);
583 TCPSTAT_INC(tcps_sc_badack);
589 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
592 struct syncache_head *sch;
594 sc = syncache_lookup(inc, &sch); /* returns locked sch */
595 SCH_LOCK_ASSERT(sch);
599 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
600 if (ntohl(th->th_seq) != sc->sc_iss)
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.
611 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
612 sc->sc_flags |= SCF_UNREACH;
615 syncache_drop(sc, sch);
616 TCPSTAT_INC(tcps_sc_unreach);
622 * Build a new TCP socket structure from a syncache entry.
624 static struct socket *
625 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
627 struct inpcb *inp = NULL;
633 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
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.
641 so = sonewconn(lso, SS_ISCONNECTED);
644 * Drop the connection; we will either send a RST or
645 * have the peer retransmit its SYN again after its
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",
658 mac_socketpeer_set_from_mbuf(m, so);
662 inp->inp_inc.inc_fibnum = so->so_fibnum;
664 INP_HASH_WLOCK(&V_tcbinfo);
666 /* Insert new socket into PCB hash list. */
667 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
669 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
670 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
672 inp->inp_vflag &= ~INP_IPV6;
673 inp->inp_vflag |= INP_IPV4;
675 inp->inp_laddr = sc->sc_inc.inc_laddr;
679 inp->inp_lport = sc->sc_inc.inc_lport;
680 if ((error = in_pcbinshash(inp)) != 0) {
682 * Undo the assignments above if we failed to
683 * put the PCB on the hash lists.
686 if (sc->sc_inc.inc_flags & INC_ISIPV6)
687 inp->in6p_laddr = in6addr_any;
690 inp->inp_laddr.s_addr = INADDR_ANY;
692 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
693 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
698 INP_HASH_WUNLOCK(&V_tcbinfo);
702 /* Copy old policy into new socket's. */
703 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
704 printf("syncache_socket: could not copy policy\n");
707 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
708 struct inpcb *oinp = sotoinpcb(lso);
709 struct in6_addr laddr6;
710 struct sockaddr_in6 sin6;
712 * Inherit socket options from the listening socket.
713 * Note that in6p_inputopts are not (and should not be)
714 * copied, since it stores previously received options and is
715 * used to detect if each new option is different than the
716 * previous one and hence should be passed to a user.
717 * If we copied in6p_inputopts, a user would not be able to
718 * receive options just after calling the accept system call.
720 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
721 if (oinp->in6p_outputopts)
722 inp->in6p_outputopts =
723 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
725 sin6.sin6_family = AF_INET6;
726 sin6.sin6_len = sizeof(sin6);
727 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
728 sin6.sin6_port = sc->sc_inc.inc_fport;
729 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
730 laddr6 = inp->in6p_laddr;
731 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
732 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
733 if ((error = in6_pcbconnect(inp, (struct sockaddr *)&sin6,
734 thread0.td_ucred)) != 0) {
735 inp->in6p_laddr = laddr6;
736 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
737 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
742 INP_HASH_WUNLOCK(&V_tcbinfo);
745 /* Override flowlabel from in6_pcbconnect. */
746 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
747 inp->inp_flow |= sc->sc_flowlabel;
750 #if defined(INET) && defined(INET6)
755 struct in_addr laddr;
756 struct sockaddr_in sin;
758 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
760 if (inp->inp_options == NULL) {
761 inp->inp_options = sc->sc_ipopts;
762 sc->sc_ipopts = NULL;
765 sin.sin_family = AF_INET;
766 sin.sin_len = sizeof(sin);
767 sin.sin_addr = sc->sc_inc.inc_faddr;
768 sin.sin_port = sc->sc_inc.inc_fport;
769 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
770 laddr = inp->inp_laddr;
771 if (inp->inp_laddr.s_addr == INADDR_ANY)
772 inp->inp_laddr = sc->sc_inc.inc_laddr;
773 if ((error = in_pcbconnect(inp, (struct sockaddr *)&sin,
774 thread0.td_ucred)) != 0) {
775 inp->inp_laddr = laddr;
776 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
777 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
782 INP_HASH_WUNLOCK(&V_tcbinfo);
787 INP_HASH_WUNLOCK(&V_tcbinfo);
789 tp->t_state = TCPS_SYN_RECEIVED;
790 tp->iss = sc->sc_iss;
791 tp->irs = sc->sc_irs;
794 tp->snd_wl1 = sc->sc_irs;
795 tp->snd_max = tp->iss + 1;
796 tp->snd_nxt = tp->iss + 1;
797 tp->rcv_up = sc->sc_irs + 1;
798 tp->rcv_wnd = sc->sc_wnd;
799 tp->rcv_adv += tp->rcv_wnd;
800 tp->last_ack_sent = tp->rcv_nxt;
802 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
803 if (sc->sc_flags & SCF_NOOPT)
804 tp->t_flags |= TF_NOOPT;
806 if (sc->sc_flags & SCF_WINSCALE) {
807 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
808 tp->snd_scale = sc->sc_requested_s_scale;
809 tp->request_r_scale = sc->sc_requested_r_scale;
811 if (sc->sc_flags & SCF_TIMESTAMP) {
812 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
813 tp->ts_recent = sc->sc_tsreflect;
814 tp->ts_recent_age = ticks;
815 tp->ts_offset = sc->sc_tsoff;
818 if (sc->sc_flags & SCF_SIGNATURE)
819 tp->t_flags |= TF_SIGNATURE;
821 if (sc->sc_flags & SCF_SACK)
822 tp->t_flags |= TF_SACK_PERMIT;
825 if (sc->sc_flags & SCF_ECN)
826 tp->t_flags |= TF_ECN_PERMIT;
829 * Set up MSS and get cached values from tcp_hostcache.
830 * This might overwrite some of the defaults we just set.
832 tcp_mss(tp, sc->sc_peer_mss);
835 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
836 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
838 if (sc->sc_rxmits > 1)
839 tp->snd_cwnd = tp->t_maxseg;
840 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit);
844 TCPSTAT_INC(tcps_accepts);
856 * This function gets called when we receive an ACK for a
857 * socket in the LISTEN state. We look up the connection
858 * in the syncache, and if its there, we pull it out of
859 * the cache and turn it into a full-blown connection in
860 * the SYN-RECEIVED state.
863 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
864 struct socket **lsop, struct mbuf *m)
867 struct syncache_head *sch;
872 * Global TCP locks are held because we manipulate the PCB lists
873 * and create a new socket.
875 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
876 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
877 ("%s: can handle only ACK", __func__));
879 sc = syncache_lookup(inc, &sch); /* returns locked sch */
880 SCH_LOCK_ASSERT(sch);
883 * There is no syncache entry, so see if this ACK is
884 * a returning syncookie. To do this, first:
885 * A. See if this socket has had a syncache entry dropped in
886 * the past. We don't want to accept a bogus syncookie
887 * if we've never received a SYN.
888 * B. check that the syncookie is valid. If it is, then
889 * cobble up a fake syncache entry, and return.
891 if (!V_tcp_syncookies) {
893 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
894 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
895 "segment rejected (syncookies disabled)\n",
899 bzero(&scs, sizeof(scs));
900 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop);
903 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
904 log(LOG_DEBUG, "%s; %s: Segment failed "
905 "SYNCOOKIE authentication, segment rejected "
906 "(probably spoofed)\n", s, __func__);
910 /* Pull out the entry to unlock the bucket row. */
911 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
913 V_tcp_syncache.cache_count--;
918 * Segment validation:
919 * ACK must match our initial sequence number + 1 (the SYN|ACK).
921 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) {
922 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
923 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
924 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
929 * The SEQ must fall in the window starting at the received
930 * initial receive sequence number + 1 (the SYN).
932 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) ||
933 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) &&
935 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
936 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
937 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
941 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
942 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
943 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
944 "segment rejected\n", s, __func__);
948 * If timestamps were negotiated the reflected timestamp
949 * must be equal to what we actually sent in the SYN|ACK.
951 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts &&
953 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
954 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
955 "segment rejected\n",
956 s, __func__, to->to_tsecr, sc->sc_ts);
960 *lsop = syncache_socket(sc, *lsop, m);
963 TCPSTAT_INC(tcps_sc_aborted);
965 TCPSTAT_INC(tcps_sc_completed);
967 /* how do we find the inp for the new socket? */
972 if (sc != NULL && sc != &scs)
981 tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo,
982 struct tcphdr *th, struct socket **lsop, struct mbuf *m)
987 bzero(&to, sizeof(struct tcpopt));
988 to.to_mss = toeo->to_mss;
989 to.to_wscale = toeo->to_wscale;
990 to.to_flags = toeo->to_flags;
992 INP_INFO_WLOCK(&V_tcbinfo);
993 rc = syncache_expand(inc, &to, th, lsop, m);
994 INP_INFO_WUNLOCK(&V_tcbinfo);
1000 * Given a LISTEN socket and an inbound SYN request, add
1001 * this to the syn cache, and send back a segment:
1002 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1005 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1006 * Doing so would require that we hold onto the data and deliver it
1007 * to the application. However, if we are the target of a SYN-flood
1008 * DoS attack, an attacker could send data which would eventually
1009 * consume all available buffer space if it were ACKed. By not ACKing
1010 * the data, we avoid this DoS scenario.
1013 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1014 struct inpcb *inp, struct socket **lsop, struct mbuf *m,
1015 struct toe_usrreqs *tu, void *toepcb)
1019 struct syncache *sc = NULL;
1020 struct syncache_head *sch;
1021 struct mbuf *ipopts = NULL;
1024 int win, sb_hiwat, ip_ttl, ip_tos;
1027 int autoflowlabel = 0;
1030 struct label *maclabel;
1032 struct syncache scs;
1035 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1036 INP_WLOCK_ASSERT(inp); /* listen socket */
1037 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1038 ("%s: unexpected tcp flags", __func__));
1041 * Combine all so/tp operations very early to drop the INP lock as
1046 cred = crhold(so->so_cred);
1049 if ((inc->inc_flags & INC_ISIPV6) &&
1050 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1053 ip_ttl = inp->inp_ip_ttl;
1054 ip_tos = inp->inp_ip_tos;
1055 win = sbspace(&so->so_rcv);
1056 sb_hiwat = so->so_rcv.sb_hiwat;
1057 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1059 /* By the time we drop the lock these should no longer be used. */
1064 if (mac_syncache_init(&maclabel) != 0) {
1066 INP_INFO_WUNLOCK(&V_tcbinfo);
1069 mac_syncache_create(maclabel, inp);
1072 INP_INFO_WUNLOCK(&V_tcbinfo);
1075 * Remember the IP options, if any.
1078 if (!(inc->inc_flags & INC_ISIPV6))
1081 ipopts = (m) ? ip_srcroute(m) : NULL;
1087 * See if we already have an entry for this connection.
1088 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1090 * XXX: should the syncache be re-initialized with the contents
1091 * of the new SYN here (which may have different options?)
1093 * XXX: We do not check the sequence number to see if this is a
1094 * real retransmit or a new connection attempt. The question is
1095 * how to handle such a case; either ignore it as spoofed, or
1096 * drop the current entry and create a new one?
1098 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1099 SCH_LOCK_ASSERT(sch);
1101 #ifndef TCP_OFFLOAD_DISABLE
1103 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT,
1106 TCPSTAT_INC(tcps_sc_dupsyn);
1109 * If we were remembering a previous source route,
1110 * forget it and use the new one we've been given.
1113 (void) m_free(sc->sc_ipopts);
1114 sc->sc_ipopts = ipopts;
1117 * Update timestamp if present.
1119 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1120 sc->sc_tsreflect = to->to_tsval;
1122 sc->sc_flags &= ~SCF_TIMESTAMP;
1125 * Since we have already unconditionally allocated label
1126 * storage, free it up. The syncache entry will already
1127 * have an initialized label we can use.
1129 mac_syncache_destroy(&maclabel);
1131 /* Retransmit SYN|ACK and reset retransmit count. */
1132 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1133 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1134 "resetting timer and retransmitting SYN|ACK\n",
1138 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) {
1140 syncache_timeout(sc, sch, 1);
1141 TCPSTAT_INC(tcps_sndacks);
1142 TCPSTAT_INC(tcps_sndtotal);
1148 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1151 * The zone allocator couldn't provide more entries.
1152 * Treat this as if the cache was full; drop the oldest
1153 * entry and insert the new one.
1155 TCPSTAT_INC(tcps_sc_zonefail);
1156 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1157 syncache_drop(sc, sch);
1158 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1160 if (V_tcp_syncookies) {
1161 bzero(&scs, sizeof(scs));
1166 (void) m_free(ipopts);
1173 * Fill in the syncache values.
1176 sc->sc_label = maclabel;
1180 sc->sc_ipopts = ipopts;
1181 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1183 if (!(inc->inc_flags & INC_ISIPV6))
1186 sc->sc_ip_tos = ip_tos;
1187 sc->sc_ip_ttl = ip_ttl;
1189 #ifndef TCP_OFFLOAD_DISABLE
1191 sc->sc_toepcb = toepcb;
1193 sc->sc_irs = th->th_seq;
1194 sc->sc_iss = arc4random();
1196 sc->sc_flowlabel = 0;
1199 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1200 * win was derived from socket earlier in the function.
1203 win = imin(win, TCP_MAXWIN);
1206 if (V_tcp_do_rfc1323) {
1208 * A timestamp received in a SYN makes
1209 * it ok to send timestamp requests and replies.
1211 if (to->to_flags & TOF_TS) {
1212 sc->sc_tsreflect = to->to_tsval;
1214 sc->sc_flags |= SCF_TIMESTAMP;
1216 if (to->to_flags & TOF_SCALE) {
1220 * Pick the smallest possible scaling factor that
1221 * will still allow us to scale up to sb_max, aka
1222 * kern.ipc.maxsockbuf.
1224 * We do this because there are broken firewalls that
1225 * will corrupt the window scale option, leading to
1226 * the other endpoint believing that our advertised
1227 * window is unscaled. At scale factors larger than
1228 * 5 the unscaled window will drop below 1500 bytes,
1229 * leading to serious problems when traversing these
1232 * With the default maxsockbuf of 256K, a scale factor
1233 * of 3 will be chosen by this algorithm. Those who
1234 * choose a larger maxsockbuf should watch out
1235 * for the compatiblity problems mentioned above.
1237 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1238 * or <SYN,ACK>) segment itself is never scaled.
1240 while (wscale < TCP_MAX_WINSHIFT &&
1241 (TCP_MAXWIN << wscale) < sb_max)
1243 sc->sc_requested_r_scale = wscale;
1244 sc->sc_requested_s_scale = to->to_wscale;
1245 sc->sc_flags |= SCF_WINSCALE;
1248 #ifdef TCP_SIGNATURE
1250 * If listening socket requested TCP digests, and received SYN
1251 * contains the option, flag this in the syncache so that
1252 * syncache_respond() will do the right thing with the SYN+ACK.
1253 * XXX: Currently we always record the option by default and will
1254 * attempt to use it in syncache_respond().
1256 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE)
1257 sc->sc_flags |= SCF_SIGNATURE;
1259 if (to->to_flags & TOF_SACKPERM)
1260 sc->sc_flags |= SCF_SACK;
1261 if (to->to_flags & TOF_MSS)
1262 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1263 if (ltflags & TF_NOOPT)
1264 sc->sc_flags |= SCF_NOOPT;
1265 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1266 sc->sc_flags |= SCF_ECN;
1268 if (V_tcp_syncookies) {
1269 syncookie_generate(sch, sc, &flowtmp);
1272 sc->sc_flowlabel = flowtmp;
1278 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
1284 * Do a standard 3-way handshake.
1286 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) {
1287 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1289 else if (sc != &scs)
1290 syncache_insert(sc, sch); /* locks and unlocks sch */
1291 TCPSTAT_INC(tcps_sndacks);
1292 TCPSTAT_INC(tcps_sndtotal);
1296 TCPSTAT_INC(tcps_sc_dropped);
1304 mac_syncache_destroy(&maclabel);
1314 syncache_respond(struct syncache *sc)
1316 struct ip *ip = NULL;
1318 struct tcphdr *th = NULL;
1319 int optlen, error = 0; /* Make compiler happy */
1320 u_int16_t hlen, tlen, mssopt;
1323 struct ip6_hdr *ip6 = NULL;
1328 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1331 tlen = hlen + sizeof(struct tcphdr);
1333 /* Determine MSS we advertize to other end of connection. */
1334 mssopt = tcp_mssopt(&sc->sc_inc);
1335 if (sc->sc_peer_mss)
1336 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss);
1338 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1339 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1340 ("syncache: mbuf too small"));
1342 /* Create the IP+TCP header from scratch. */
1343 m = m_gethdr(M_DONTWAIT, MT_DATA);
1347 mac_syncache_create_mbuf(sc->sc_label, m);
1349 m->m_data += max_linkhdr;
1351 m->m_pkthdr.len = tlen;
1352 m->m_pkthdr.rcvif = NULL;
1355 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1356 ip6 = mtod(m, struct ip6_hdr *);
1357 ip6->ip6_vfc = IPV6_VERSION;
1358 ip6->ip6_nxt = IPPROTO_TCP;
1359 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1360 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1361 ip6->ip6_plen = htons(tlen - hlen);
1362 /* ip6_hlim is set after checksum */
1363 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1364 ip6->ip6_flow |= sc->sc_flowlabel;
1366 th = (struct tcphdr *)(ip6 + 1);
1369 #if defined(INET6) && defined(INET)
1374 ip = mtod(m, struct ip *);
1375 ip->ip_v = IPVERSION;
1376 ip->ip_hl = sizeof(struct ip) >> 2;
1381 ip->ip_p = IPPROTO_TCP;
1382 ip->ip_src = sc->sc_inc.inc_laddr;
1383 ip->ip_dst = sc->sc_inc.inc_faddr;
1384 ip->ip_ttl = sc->sc_ip_ttl;
1385 ip->ip_tos = sc->sc_ip_tos;
1388 * See if we should do MTU discovery. Route lookups are
1389 * expensive, so we will only unset the DF bit if:
1391 * 1) path_mtu_discovery is disabled
1392 * 2) the SCF_UNREACH flag has been set
1394 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1395 ip->ip_off |= IP_DF;
1397 th = (struct tcphdr *)(ip + 1);
1400 th->th_sport = sc->sc_inc.inc_lport;
1401 th->th_dport = sc->sc_inc.inc_fport;
1403 th->th_seq = htonl(sc->sc_iss);
1404 th->th_ack = htonl(sc->sc_irs + 1);
1405 th->th_off = sizeof(struct tcphdr) >> 2;
1407 th->th_flags = TH_SYN|TH_ACK;
1408 th->th_win = htons(sc->sc_wnd);
1411 if (sc->sc_flags & SCF_ECN) {
1412 th->th_flags |= TH_ECE;
1413 TCPSTAT_INC(tcps_ecn_shs);
1416 /* Tack on the TCP options. */
1417 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1421 to.to_flags = TOF_MSS;
1422 if (sc->sc_flags & SCF_WINSCALE) {
1423 to.to_wscale = sc->sc_requested_r_scale;
1424 to.to_flags |= TOF_SCALE;
1426 if (sc->sc_flags & SCF_TIMESTAMP) {
1427 /* Virgin timestamp or TCP cookie enhanced one. */
1428 to.to_tsval = sc->sc_ts;
1429 to.to_tsecr = sc->sc_tsreflect;
1430 to.to_flags |= TOF_TS;
1432 if (sc->sc_flags & SCF_SACK)
1433 to.to_flags |= TOF_SACKPERM;
1434 #ifdef TCP_SIGNATURE
1435 if (sc->sc_flags & SCF_SIGNATURE)
1436 to.to_flags |= TOF_SIGNATURE;
1438 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1440 /* Adjust headers by option size. */
1441 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1443 m->m_pkthdr.len += optlen;
1445 #ifdef TCP_SIGNATURE
1446 if (sc->sc_flags & SCF_SIGNATURE)
1447 tcp_signature_compute(m, 0, 0, optlen,
1448 to.to_signature, IPSEC_DIR_OUTBOUND);
1451 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1452 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1455 ip->ip_len += optlen;
1459 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1461 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1463 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen,
1464 tlen + optlen - hlen);
1465 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1466 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1469 #if defined(INET6) && defined(INET)
1474 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1475 htons(tlen + optlen - hlen + IPPROTO_TCP));
1476 m->m_pkthdr.csum_flags = CSUM_TCP;
1477 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1478 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1485 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1486 struct inpcb *inp, struct socket **lsop, struct mbuf *m)
1488 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL);
1492 tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo,
1493 struct tcphdr *th, struct inpcb *inp, struct socket **lsop,
1494 struct toe_usrreqs *tu, void *toepcb)
1498 bzero(&to, sizeof(struct tcpopt));
1499 to.to_mss = toeo->to_mss;
1500 to.to_wscale = toeo->to_wscale;
1501 to.to_flags = toeo->to_flags;
1503 INP_INFO_WLOCK(&V_tcbinfo);
1506 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb);
1510 * The purpose of SYN cookies is to avoid keeping track of all SYN's we
1511 * receive and to be able to handle SYN floods from bogus source addresses
1512 * (where we will never receive any reply). SYN floods try to exhaust all
1513 * our memory and available slots in the SYN cache table to cause a denial
1514 * of service to legitimate users of the local host.
1516 * The idea of SYN cookies is to encode and include all necessary information
1517 * about the connection setup state within the SYN-ACK we send back and thus
1518 * to get along without keeping any local state until the ACK to the SYN-ACK
1519 * arrives (if ever). Everything we need to know should be available from
1520 * the information we encoded in the SYN-ACK.
1522 * More information about the theory behind SYN cookies and its first
1523 * discussion and specification can be found at:
1524 * http://cr.yp.to/syncookies.html (overview)
1525 * http://cr.yp.to/syncookies/archive (gory details)
1527 * This implementation extends the orginal idea and first implementation
1528 * of FreeBSD by using not only the initial sequence number field to store
1529 * information but also the timestamp field if present. This way we can
1530 * keep track of the entire state we need to know to recreate the session in
1531 * its original form. Almost all TCP speakers implement RFC1323 timestamps
1532 * these days. For those that do not we still have to live with the known
1533 * shortcomings of the ISN only SYN cookies.
1537 * Initial sequence number we send:
1538 * 31|................................|0
1539 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP
1540 * D = MD5 Digest (first dword)
1542 * R = Rotation of secret
1543 * P = Odd or Even secret
1545 * The MD5 Digest is computed with over following parameters:
1546 * a) randomly rotated secret
1547 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6)
1548 * c) the received initial sequence number from remote host
1549 * d) the rotation offset and odd/even bit
1551 * Timestamp we send:
1552 * 31|................................|0
1553 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5
1554 * D = MD5 Digest (third dword) (only as filler)
1555 * S = Requested send window scale
1556 * R = Requested receive window scale
1558 * 5 = TCP-MD5 enabled (not implemented yet)
1559 * XORed with MD5 Digest (forth dword)
1561 * The timestamp isn't cryptographically secure and doesn't need to be.
1562 * The double use of the MD5 digest dwords ties it to a specific remote/
1563 * local host/port, remote initial sequence number and our local time
1564 * limited secret. A received timestamp is reverted (XORed) and then
1565 * the contained MD5 dword is compared to the computed one to ensure the
1566 * timestamp belongs to the SYN-ACK we sent. The other parameters may
1567 * have been tampered with but this isn't different from supplying bogus
1568 * values in the SYN in the first place.
1570 * Some problems with SYN cookies remain however:
1571 * Consider the problem of a recreated (and retransmitted) cookie. If the
1572 * original SYN was accepted, the connection is established. The second
1573 * SYN is inflight, and if it arrives with an ISN that falls within the
1574 * receive window, the connection is killed.
1577 * A heuristic to determine when to accept syn cookies is not necessary.
1578 * An ACK flood would cause the syncookie verification to be attempted,
1579 * but a SYN flood causes syncookies to be generated. Both are of equal
1580 * cost, so there's no point in trying to optimize the ACK flood case.
1581 * Also, if you don't process certain ACKs for some reason, then all someone
1582 * would have to do is launch a SYN and ACK flood at the same time, which
1583 * would stop cookie verification and defeat the entire purpose of syncookies.
1585 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 };
1588 syncookie_generate(struct syncache_head *sch, struct syncache *sc,
1589 u_int32_t *flowlabel)
1592 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1595 u_int off, pmss, mss;
1598 SCH_LOCK_ASSERT(sch);
1600 /* Which of the two secrets to use. */
1601 secbits = sch->sch_oddeven ?
1602 sch->sch_secbits_odd : sch->sch_secbits_even;
1604 /* Reseed secret if too old. */
1605 if (sch->sch_reseed < time_uptime) {
1606 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */
1607 secbits = sch->sch_oddeven ?
1608 sch->sch_secbits_odd : sch->sch_secbits_even;
1609 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++)
1610 secbits[i] = arc4random();
1611 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME;
1614 /* Secret rotation offset. */
1615 off = sc->sc_iss & 0x7; /* iss was randomized before */
1617 /* Maximum segment size calculation. */
1619 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss);
1620 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--)
1621 if (tcp_sc_msstab[mss] <= pmss)
1624 /* Fold parameters and MD5 digest into the ISN we will send. */
1625 data = sch->sch_oddeven;/* odd or even secret, 1 bit */
1626 data |= off << 1; /* secret offset, derived from iss, 3 bits */
1627 data |= mss << 4; /* mss, 3 bits */
1630 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1631 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1632 MD5Update(&ctx, secbits, off);
1633 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc));
1634 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs));
1635 MD5Update(&ctx, &data, sizeof(data));
1636 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1638 data |= (md5_buffer[0] << 7);
1642 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1645 /* Additional parameters are stored in the timestamp if present. */
1646 if (sc->sc_flags & SCF_TIMESTAMP) {
1647 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */
1648 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */
1649 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */
1650 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */
1651 data |= md5_buffer[2] << 10; /* more digest bits */
1652 data ^= md5_buffer[3];
1654 sc->sc_tsoff = data - ticks; /* after XOR */
1657 TCPSTAT_INC(tcps_sc_sendcookie);
1660 static struct syncache *
1661 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
1662 struct syncache *sc, struct tcpopt *to, struct tcphdr *th,
1666 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1670 int off, mss, wnd, flags;
1672 SCH_LOCK_ASSERT(sch);
1675 * Pull information out of SYN-ACK/ACK and
1676 * revert sequence number advances.
1678 ack = th->th_ack - 1;
1679 seq = th->th_seq - 1;
1680 off = (ack >> 1) & 0x7;
1681 mss = (ack >> 4) & 0x7;
1684 /* Which of the two secrets to use. */
1685 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even;
1688 * The secret wasn't updated for the lifetime of a syncookie,
1689 * so this SYN-ACK/ACK is either too old (replay) or totally bogus.
1691 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) {
1695 /* Recompute the digest so we can compare it. */
1697 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1698 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1699 MD5Update(&ctx, secbits, off);
1700 MD5Update(&ctx, inc, sizeof(*inc));
1701 MD5Update(&ctx, &seq, sizeof(seq));
1702 MD5Update(&ctx, &flags, sizeof(flags));
1703 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1705 /* Does the digest part of or ACK'ed ISS match? */
1706 if ((ack & (~0x7f)) != (md5_buffer[0] << 7))
1709 /* Does the digest part of our reflected timestamp match? */
1710 if (to->to_flags & TOF_TS) {
1711 data = md5_buffer[3] ^ to->to_tsecr;
1712 if ((data & (~0x3ff)) != (md5_buffer[2] << 10))
1716 /* Fill in the syncache values. */
1717 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1718 sc->sc_ipopts = NULL;
1724 if (inc->inc_flags & INC_ISIPV6) {
1725 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL)
1726 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1730 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl;
1731 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos;
1734 /* Additional parameters that were encoded in the timestamp. */
1736 sc->sc_flags |= SCF_TIMESTAMP;
1737 sc->sc_tsreflect = to->to_tsval;
1738 sc->sc_ts = to->to_tsecr;
1739 sc->sc_tsoff = to->to_tsecr - ticks;
1740 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0;
1741 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0;
1742 sc->sc_requested_s_scale = min((data >> 2) & 0xf,
1744 sc->sc_requested_r_scale = min((data >> 6) & 0xf,
1746 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale)
1747 sc->sc_flags |= SCF_WINSCALE;
1749 sc->sc_flags |= SCF_NOOPT;
1751 wnd = sbspace(&so->so_rcv);
1753 wnd = imin(wnd, TCP_MAXWIN);
1757 sc->sc_peer_mss = tcp_sc_msstab[mss];
1759 TCPSTAT_INC(tcps_sc_recvcookie);
1764 * Returns the current number of syncache entries. This number
1765 * will probably change before you get around to calling
1770 syncache_pcbcount(void)
1772 struct syncache_head *sch;
1775 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1776 /* No need to lock for a read. */
1777 sch = &V_tcp_syncache.hashbase[i];
1778 count += sch->sch_length;
1784 * Exports the syncache entries to userland so that netstat can display
1785 * them alongside the other sockets. This function is intended to be
1786 * called only from tcp_pcblist.
1788 * Due to concurrency on an active system, the number of pcbs exported
1789 * may have no relation to max_pcbs. max_pcbs merely indicates the
1790 * amount of space the caller allocated for this function to use.
1793 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
1796 struct syncache *sc;
1797 struct syncache_head *sch;
1798 int count, error, i;
1800 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
1801 sch = &V_tcp_syncache.hashbase[i];
1803 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
1804 if (count >= max_pcbs) {
1808 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
1810 bzero(&xt, sizeof(xt));
1811 xt.xt_len = sizeof(xt);
1812 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1813 xt.xt_inp.inp_vflag = INP_IPV6;
1815 xt.xt_inp.inp_vflag = INP_IPV4;
1816 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
1817 xt.xt_tp.t_inpcb = &xt.xt_inp;
1818 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
1819 xt.xt_socket.xso_protocol = IPPROTO_TCP;
1820 xt.xt_socket.xso_len = sizeof (struct xsocket);
1821 xt.xt_socket.so_type = SOCK_STREAM;
1822 xt.xt_socket.so_state = SS_ISCONNECTING;
1823 error = SYSCTL_OUT(req, &xt, sizeof xt);
1833 *pcbs_exported = count;