1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
32 */
33
34 #include <sys/cdefs.h>
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_tcpdebug.h"
38 #include "opt_rss.h"
39
40 #include <sys/param.h>
41 #include <sys/kernel.h>
42 #include <sys/lock.h>
43 #include <sys/mbuf.h>
44 #include <sys/mutex.h>
45 #include <sys/protosw.h>
46 #include <sys/smp.h>
47 #include <sys/socket.h>
48 #include <sys/socketvar.h>
49 #include <sys/sysctl.h>
50 #include <sys/systm.h>
51
52 #include <net/if.h>
53 #include <net/route.h>
54 #include <net/rss_config.h>
55 #include <net/vnet.h>
56 #include <net/netisr.h>
57
58 #include <netinet/in.h>
59 #include <netinet/in_kdtrace.h>
60 #include <netinet/in_pcb.h>
61 #include <netinet/in_rss.h>
62 #include <netinet/in_systm.h>
63 #ifdef INET6
64 #include <netinet6/in6_pcb.h>
65 #endif
66 #include <netinet/ip_var.h>
67 #include <netinet/tcp.h>
68 #include <netinet/tcp_fsm.h>
69 #include <netinet/tcp_log_buf.h>
70 #include <netinet/tcp_timer.h>
71 #include <netinet/tcp_var.h>
72 #include <netinet/tcp_seq.h>
73 #include <netinet/cc/cc.h>
74 #ifdef INET6
75 #include <netinet6/tcp6_var.h>
76 #endif
77 #include <netinet/tcpip.h>
78 #ifdef TCPDEBUG
79 #include <netinet/tcp_debug.h>
80 #endif
81
82 int tcp_persmin;
83 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin,
84 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
85 &tcp_persmin, 0, sysctl_msec_to_ticks, "I",
86 "minimum persistence interval");
87
88 int tcp_persmax;
89 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax,
90 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
91 &tcp_persmax, 0, sysctl_msec_to_ticks, "I",
92 "maximum persistence interval");
93
94 int tcp_keepinit;
95 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
96 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
97 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I",
98 "time to establish connection");
99
100 int tcp_keepidle;
101 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
102 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
103 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I",
104 "time before keepalive probes begin");
105
106 int tcp_keepintvl;
107 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
108 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
109 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I",
110 "time between keepalive probes");
111
112 int tcp_delacktime;
113 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
114 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
115 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
116 "Time before a delayed ACK is sent");
117
118 VNET_DEFINE(int, tcp_msl);
119 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl,
120 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_VNET,
121 &VNET_NAME(tcp_msl), 0, sysctl_msec_to_ticks, "I",
122 "Maximum segment lifetime");
123
124 int tcp_rexmit_initial;
125 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial,
126 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
127 &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
128 "Initial Retransmission Timeout");
129
130 int tcp_rexmit_min;
131 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min,
132 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
133 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
134 "Minimum Retransmission Timeout");
135
136 int tcp_rexmit_slop;
137 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop,
138 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
139 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
140 "Retransmission Timer Slop");
141
142 VNET_DEFINE(int, tcp_always_keepalive) = 1;
143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
144 &VNET_NAME(tcp_always_keepalive) , 0,
145 "Assume SO_KEEPALIVE on all TCP connections");
146
147 int tcp_fast_finwait2_recycle = 0;
148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
149 &tcp_fast_finwait2_recycle, 0,
150 "Recycle closed FIN_WAIT_2 connections faster");
151
152 int tcp_finwait2_timeout;
153 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout,
154 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
155 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I",
156 "FIN-WAIT2 timeout");
157
158 int tcp_keepcnt = TCPTV_KEEPCNT;
159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
160 "Number of keepalive probes to send");
161
162 /* max idle probes */
163 int tcp_maxpersistidle;
164
165 int tcp_rexmit_drop_options = 0;
166 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
167 &tcp_rexmit_drop_options, 0,
168 "Drop TCP options from 3rd and later retransmitted SYN");
169
170 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
172 CTLFLAG_RW|CTLFLAG_VNET,
173 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
174 "Path MTU Discovery Black Hole Detection Enabled");
175
176 #ifdef INET
177 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
179 CTLFLAG_RW|CTLFLAG_VNET,
180 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
181 "Path MTU Discovery Black Hole Detection lowered MSS");
182 #endif
183
184 #ifdef INET6
185 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
186 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
187 CTLFLAG_RW|CTLFLAG_VNET,
188 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
189 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
190 #endif
191
192 #ifdef RSS
193 static int per_cpu_timers = 1;
194 #else
195 static int per_cpu_timers = 0;
196 #endif
197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
198 &per_cpu_timers , 0, "run tcp timers on all cpus");
199
200 /*
201 * Map the given inp to a CPU id.
202 *
203 * This queries RSS if it's compiled in, else it defaults to the current
204 * CPU ID.
205 */
206 inline int
inp_to_cpuid(struct inpcb * inp)207 inp_to_cpuid(struct inpcb *inp)
208 {
209 u_int cpuid;
210
211 if (per_cpu_timers) {
212 #ifdef RSS
213 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
214 if (cpuid == NETISR_CPUID_NONE)
215 return (curcpu); /* XXX */
216 else
217 return (cpuid);
218 #endif
219 /*
220 * We don't have a flowid -> cpuid mapping, so cheat and
221 * just map unknown cpuids to curcpu. Not the best, but
222 * apparently better than defaulting to swi 0.
223 */
224 cpuid = inp->inp_flowid % (mp_maxid + 1);
225 if (! CPU_ABSENT(cpuid))
226 return (cpuid);
227 return (curcpu);
228 } else {
229 return (0);
230 }
231 }
232
233 /*
234 * Tcp protocol timeout routine called every 500 ms.
235 * Updates timestamps used for TCP
236 * causes finite state machine actions if timers expire.
237 */
238 void
tcp_slowtimo(void)239 tcp_slowtimo(void)
240 {
241 VNET_ITERATOR_DECL(vnet_iter);
242
243 VNET_LIST_RLOCK_NOSLEEP();
244 VNET_FOREACH(vnet_iter) {
245 CURVNET_SET(vnet_iter);
246 (void) tcp_tw_2msl_scan(0);
247 CURVNET_RESTORE();
248 }
249 VNET_LIST_RUNLOCK_NOSLEEP();
250 }
251
252 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
253 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
254
255 int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
256
257 /*
258 * TCP timer processing.
259 */
260
261 void
tcp_timer_delack(void * xtp)262 tcp_timer_delack(void *xtp)
263 {
264 struct epoch_tracker et;
265 struct tcpcb *tp = xtp;
266 struct inpcb *inp;
267 #ifdef TCPDEBUG
268 int ostate;
269
270 ostate = tp->t_state;
271 #endif
272 CURVNET_SET(tp->t_vnet);
273 inp = tp->t_inpcb;
274 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
275 INP_WLOCK(inp);
276 if (callout_pending(&tp->t_timers->tt_delack) ||
277 !callout_active(&tp->t_timers->tt_delack)) {
278 INP_WUNLOCK(inp);
279 CURVNET_RESTORE();
280 return;
281 }
282 callout_deactivate(&tp->t_timers->tt_delack);
283 if ((inp->inp_flags & INP_DROPPED) != 0) {
284 INP_WUNLOCK(inp);
285 CURVNET_RESTORE();
286 return;
287 }
288 tp->t_flags |= TF_ACKNOW;
289 TCPSTAT_INC(tcps_delack);
290 NET_EPOCH_ENTER(et);
291 (void) tp->t_fb->tfb_tcp_output(tp);
292 #ifdef TCPDEBUG
293 if (inp->inp_socket->so_options & SO_DEBUG)
294 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
295 (TCPT_DELACK << 8) | PRU_FASTTIMO);
296 #endif
297 INP_WUNLOCK(inp);
298 NET_EPOCH_EXIT(et);
299 CURVNET_RESTORE();
300 }
301
302 void
tcp_inpinfo_lock_del(struct inpcb * inp,struct tcpcb * tp)303 tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
304 {
305 if (inp && tp != NULL)
306 INP_WUNLOCK(inp);
307 }
308
309 void
tcp_timer_2msl(void * xtp)310 tcp_timer_2msl(void *xtp)
311 {
312 struct tcpcb *tp = xtp;
313 struct inpcb *inp;
314 struct epoch_tracker et;
315 CURVNET_SET(tp->t_vnet);
316 #ifdef TCPDEBUG
317 int ostate;
318
319 ostate = tp->t_state;
320 #endif
321 inp = tp->t_inpcb;
322 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
323 INP_WLOCK(inp);
324 tcp_free_sackholes(tp);
325 if (callout_pending(&tp->t_timers->tt_2msl) ||
326 !callout_active(&tp->t_timers->tt_2msl)) {
327 INP_WUNLOCK(tp->t_inpcb);
328 CURVNET_RESTORE();
329 return;
330 }
331 callout_deactivate(&tp->t_timers->tt_2msl);
332 if ((inp->inp_flags & INP_DROPPED) != 0) {
333 INP_WUNLOCK(inp);
334 CURVNET_RESTORE();
335 return;
336 }
337 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
338 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
339 /*
340 * 2 MSL timeout in shutdown went off. If we're closed but
341 * still waiting for peer to close and connection has been idle
342 * too long delete connection control block. Otherwise, check
343 * again in a bit.
344 *
345 * If in TIME_WAIT state just ignore as this timeout is handled in
346 * tcp_tw_2msl_scan().
347 *
348 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
349 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
350 * Ignore fact that there were recent incoming segments.
351 */
352 if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
353 INP_WUNLOCK(inp);
354 CURVNET_RESTORE();
355 return;
356 }
357 if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
358 tp->t_inpcb && tp->t_inpcb->inp_socket &&
359 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
360 TCPSTAT_INC(tcps_finwait2_drops);
361 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
362 tcp_inpinfo_lock_del(inp, tp);
363 goto out;
364 }
365 NET_EPOCH_ENTER(et);
366 tp = tcp_close(tp);
367 NET_EPOCH_EXIT(et);
368 tcp_inpinfo_lock_del(inp, tp);
369 goto out;
370 } else {
371 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
372 callout_reset(&tp->t_timers->tt_2msl,
373 TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
374 } else {
375 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
376 tcp_inpinfo_lock_del(inp, tp);
377 goto out;
378 }
379 NET_EPOCH_ENTER(et);
380 tp = tcp_close(tp);
381 NET_EPOCH_EXIT(et);
382 tcp_inpinfo_lock_del(inp, tp);
383 goto out;
384 }
385 }
386
387 #ifdef TCPDEBUG
388 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
389 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
390 (TCPT_2MSL << 8) | PRU_SLOWTIMO);
391 #endif
392 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
393
394 if (tp != NULL)
395 INP_WUNLOCK(inp);
396 out:
397 CURVNET_RESTORE();
398 }
399
400 void
tcp_timer_keep(void * xtp)401 tcp_timer_keep(void *xtp)
402 {
403 struct tcpcb *tp = xtp;
404 struct tcptemp *t_template;
405 struct inpcb *inp;
406 struct epoch_tracker et;
407 CURVNET_SET(tp->t_vnet);
408 #ifdef TCPDEBUG
409 int ostate;
410
411 ostate = tp->t_state;
412 #endif
413 inp = tp->t_inpcb;
414 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
415 INP_WLOCK(inp);
416 if (callout_pending(&tp->t_timers->tt_keep) ||
417 !callout_active(&tp->t_timers->tt_keep)) {
418 INP_WUNLOCK(inp);
419 CURVNET_RESTORE();
420 return;
421 }
422 callout_deactivate(&tp->t_timers->tt_keep);
423 if ((inp->inp_flags & INP_DROPPED) != 0) {
424 INP_WUNLOCK(inp);
425 CURVNET_RESTORE();
426 return;
427 }
428 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
429 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
430
431 /*
432 * Because we don't regularly reset the keepalive callout in
433 * the ESTABLISHED state, it may be that we don't actually need
434 * to send a keepalive yet. If that occurs, schedule another
435 * call for the next time the keepalive timer might expire.
436 */
437 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
438 u_int idletime;
439
440 idletime = ticks - tp->t_rcvtime;
441 if (idletime < TP_KEEPIDLE(tp)) {
442 callout_reset(&tp->t_timers->tt_keep,
443 TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
444 INP_WUNLOCK(inp);
445 CURVNET_RESTORE();
446 return;
447 }
448 }
449
450 /*
451 * Keep-alive timer went off; send something
452 * or drop connection if idle for too long.
453 */
454 TCPSTAT_INC(tcps_keeptimeo);
455 if (tp->t_state < TCPS_ESTABLISHED)
456 goto dropit;
457 if ((V_tcp_always_keepalive ||
458 inp->inp_socket->so_options & SO_KEEPALIVE) &&
459 tp->t_state <= TCPS_CLOSING) {
460 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
461 goto dropit;
462 /*
463 * Send a packet designed to force a response
464 * if the peer is up and reachable:
465 * either an ACK if the connection is still alive,
466 * or an RST if the peer has closed the connection
467 * due to timeout or reboot.
468 * Using sequence number tp->snd_una-1
469 * causes the transmitted zero-length segment
470 * to lie outside the receive window;
471 * by the protocol spec, this requires the
472 * correspondent TCP to respond.
473 */
474 TCPSTAT_INC(tcps_keepprobe);
475 t_template = tcpip_maketemplate(inp);
476 if (t_template) {
477 NET_EPOCH_ENTER(et);
478 tcp_respond(tp, t_template->tt_ipgen,
479 &t_template->tt_t, (struct mbuf *)NULL,
480 tp->rcv_nxt, tp->snd_una - 1, 0);
481 NET_EPOCH_EXIT(et);
482 free(t_template, M_TEMP);
483 }
484 callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
485 tcp_timer_keep, tp);
486 } else
487 callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
488 tcp_timer_keep, tp);
489
490 #ifdef TCPDEBUG
491 if (inp->inp_socket->so_options & SO_DEBUG)
492 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
493 PRU_SLOWTIMO);
494 #endif
495 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
496 INP_WUNLOCK(inp);
497 CURVNET_RESTORE();
498 return;
499
500 dropit:
501 TCPSTAT_INC(tcps_keepdrops);
502 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
503 tcp_inpinfo_lock_del(inp, tp);
504 goto out;
505 }
506 NET_EPOCH_ENTER(et);
507 tp = tcp_drop(tp, ETIMEDOUT);
508
509 #ifdef TCPDEBUG
510 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
511 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
512 (TCPT_KEEP << 8) | PRU_SLOWTIMO);
513 #endif
514 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
515 NET_EPOCH_EXIT(et);
516 tcp_inpinfo_lock_del(inp, tp);
517 out:
518 CURVNET_RESTORE();
519 }
520
521 void
tcp_timer_persist(void * xtp)522 tcp_timer_persist(void *xtp)
523 {
524 struct tcpcb *tp = xtp;
525 struct inpcb *inp;
526 struct epoch_tracker et;
527 CURVNET_SET(tp->t_vnet);
528 #ifdef TCPDEBUG
529 int ostate;
530
531 ostate = tp->t_state;
532 #endif
533 inp = tp->t_inpcb;
534 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
535 INP_WLOCK(inp);
536 if (callout_pending(&tp->t_timers->tt_persist) ||
537 !callout_active(&tp->t_timers->tt_persist)) {
538 INP_WUNLOCK(inp);
539 CURVNET_RESTORE();
540 return;
541 }
542 callout_deactivate(&tp->t_timers->tt_persist);
543 if ((inp->inp_flags & INP_DROPPED) != 0) {
544 INP_WUNLOCK(inp);
545 CURVNET_RESTORE();
546 return;
547 }
548 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
549 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
550 /*
551 * Persistence timer into zero window.
552 * Force a byte to be output, if possible.
553 */
554 TCPSTAT_INC(tcps_persisttimeo);
555 /*
556 * Hack: if the peer is dead/unreachable, we do not
557 * time out if the window is closed. After a full
558 * backoff, drop the connection if the idle time
559 * (no responses to probes) reaches the maximum
560 * backoff that we would use if retransmitting.
561 */
562 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
563 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
564 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
565 TCPSTAT_INC(tcps_persistdrop);
566 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
567 tcp_inpinfo_lock_del(inp, tp);
568 goto out;
569 }
570 NET_EPOCH_ENTER(et);
571 tp = tcp_drop(tp, ETIMEDOUT);
572 NET_EPOCH_EXIT(et);
573 tcp_inpinfo_lock_del(inp, tp);
574 goto out;
575 }
576 /*
577 * If the user has closed the socket then drop a persisting
578 * connection after a much reduced timeout.
579 */
580 if (tp->t_state > TCPS_CLOSE_WAIT &&
581 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
582 TCPSTAT_INC(tcps_persistdrop);
583 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
584 tcp_inpinfo_lock_del(inp, tp);
585 goto out;
586 }
587 NET_EPOCH_ENTER(et);
588 tp = tcp_drop(tp, ETIMEDOUT);
589 NET_EPOCH_EXIT(et);
590 tcp_inpinfo_lock_del(inp, tp);
591 goto out;
592 }
593 tcp_setpersist(tp);
594 tp->t_flags |= TF_FORCEDATA;
595 NET_EPOCH_ENTER(et);
596 (void) tp->t_fb->tfb_tcp_output(tp);
597 NET_EPOCH_EXIT(et);
598 tp->t_flags &= ~TF_FORCEDATA;
599
600 #ifdef TCPDEBUG
601 if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
602 tcp_trace(TA_USER, ostate, tp, NULL, NULL,
603 (TCPT_PERSIST << 8) | PRU_SLOWTIMO);
604 #endif
605 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
606 INP_WUNLOCK(inp);
607 out:
608 CURVNET_RESTORE();
609 }
610
611 void
tcp_timer_rexmt(void * xtp)612 tcp_timer_rexmt(void * xtp)
613 {
614 struct tcpcb *tp = xtp;
615 CURVNET_SET(tp->t_vnet);
616 int rexmt;
617 struct inpcb *inp;
618 struct epoch_tracker et;
619 bool isipv6;
620 #ifdef TCPDEBUG
621 int ostate;
622
623 ostate = tp->t_state;
624 #endif
625 inp = tp->t_inpcb;
626 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
627 INP_WLOCK(inp);
628 if (callout_pending(&tp->t_timers->tt_rexmt) ||
629 !callout_active(&tp->t_timers->tt_rexmt)) {
630 INP_WUNLOCK(inp);
631 CURVNET_RESTORE();
632 return;
633 }
634 callout_deactivate(&tp->t_timers->tt_rexmt);
635 if ((inp->inp_flags & INP_DROPPED) != 0) {
636 INP_WUNLOCK(inp);
637 CURVNET_RESTORE();
638 return;
639 }
640 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
641 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
642 tcp_free_sackholes(tp);
643 TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
644 if (tp->t_fb->tfb_tcp_rexmit_tmr) {
645 /* The stack has a timer action too. */
646 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
647 }
648 /*
649 * Retransmission timer went off. Message has not
650 * been acked within retransmit interval. Back off
651 * to a longer retransmit interval and retransmit one segment.
652 */
653 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
654 tp->t_rxtshift = TCP_MAXRXTSHIFT;
655 TCPSTAT_INC(tcps_timeoutdrop);
656 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
657 tcp_inpinfo_lock_del(inp, tp);
658 goto out;
659 }
660 NET_EPOCH_ENTER(et);
661 tp = tcp_drop(tp, ETIMEDOUT);
662 NET_EPOCH_EXIT(et);
663 tcp_inpinfo_lock_del(inp, tp);
664 goto out;
665 }
666 if (tp->t_state == TCPS_SYN_SENT) {
667 /*
668 * If the SYN was retransmitted, indicate CWND to be
669 * limited to 1 segment in cc_conn_init().
670 */
671 tp->snd_cwnd = 1;
672 } else if (tp->t_rxtshift == 1) {
673 /*
674 * first retransmit; record ssthresh and cwnd so they can
675 * be recovered if this turns out to be a "bad" retransmit.
676 * A retransmit is considered "bad" if an ACK for this
677 * segment is received within RTT/2 interval; the assumption
678 * here is that the ACK was already in flight. See
679 * "On Estimating End-to-End Network Path Properties" by
680 * Allman and Paxson for more details.
681 */
682 tp->snd_cwnd_prev = tp->snd_cwnd;
683 tp->snd_ssthresh_prev = tp->snd_ssthresh;
684 tp->snd_recover_prev = tp->snd_recover;
685 if (IN_FASTRECOVERY(tp->t_flags))
686 tp->t_flags |= TF_WASFRECOVERY;
687 else
688 tp->t_flags &= ~TF_WASFRECOVERY;
689 if (IN_CONGRECOVERY(tp->t_flags))
690 tp->t_flags |= TF_WASCRECOVERY;
691 else
692 tp->t_flags &= ~TF_WASCRECOVERY;
693 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
694 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
695 /* In the event that we've negotiated timestamps
696 * badrxtwin will be set to the value that we set
697 * the retransmitted packet's to_tsval to by tcp_output
698 */
699 tp->t_flags |= TF_PREVVALID;
700 } else
701 tp->t_flags &= ~TF_PREVVALID;
702 TCPSTAT_INC(tcps_rexmttimeo);
703 if ((tp->t_state == TCPS_SYN_SENT) ||
704 (tp->t_state == TCPS_SYN_RECEIVED))
705 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
706 else
707 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
708 TCPT_RANGESET(tp->t_rxtcur, rexmt,
709 tp->t_rttmin, TCPTV_REXMTMAX);
710
711 /*
712 * We enter the path for PLMTUD if connection is established or, if
713 * connection is FIN_WAIT_1 status, reason for the last is that if
714 * amount of data we send is very small, we could send it in couple of
715 * packets and process straight to FIN. In that case we won't catch
716 * ESTABLISHED state.
717 */
718 #ifdef INET6
719 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? true : false;
720 #else
721 isipv6 = false;
722 #endif
723 if (((V_tcp_pmtud_blackhole_detect == 1) ||
724 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
725 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
726 ((tp->t_state == TCPS_ESTABLISHED) ||
727 (tp->t_state == TCPS_FIN_WAIT_1))) {
728 if (tp->t_rxtshift == 1) {
729 /*
730 * We enter blackhole detection after the first
731 * unsuccessful timer based retransmission.
732 * Then we reduce up to two times the MSS, each
733 * candidate giving two tries of retransmissions.
734 * But we give a candidate only two tries, if it
735 * actually reduces the MSS.
736 */
737 tp->t_blackhole_enter = 2;
738 tp->t_blackhole_exit = tp->t_blackhole_enter;
739 if (isipv6) {
740 #ifdef INET6
741 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss)
742 tp->t_blackhole_exit += 2;
743 if (tp->t_maxseg > V_tcp_v6mssdflt &&
744 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt)
745 tp->t_blackhole_exit += 2;
746 #endif
747 } else {
748 #ifdef INET
749 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss)
750 tp->t_blackhole_exit += 2;
751 if (tp->t_maxseg > V_tcp_mssdflt &&
752 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt)
753 tp->t_blackhole_exit += 2;
754 #endif
755 }
756 }
757 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
758 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
759 (tp->t_rxtshift >= tp->t_blackhole_enter &&
760 tp->t_rxtshift < tp->t_blackhole_exit &&
761 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) {
762 /*
763 * Enter Path MTU Black-hole Detection mechanism:
764 * - Disable Path MTU Discovery (IP "DF" bit).
765 * - Reduce MTU to lower value than what we
766 * negotiated with peer.
767 */
768 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
769 /* Record that we may have found a black hole. */
770 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
771 /* Keep track of previous MSS. */
772 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
773 }
774
775 /*
776 * Reduce the MSS to blackhole value or to the default
777 * in an attempt to retransmit.
778 */
779 #ifdef INET6
780 if (isipv6 &&
781 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss &&
782 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) {
783 /* Use the sysctl tuneable blackhole MSS. */
784 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
785 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
786 } else if (isipv6) {
787 /* Use the default MSS. */
788 tp->t_maxseg = V_tcp_v6mssdflt;
789 /*
790 * Disable Path MTU Discovery when we switch to
791 * minmss.
792 */
793 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
794 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
795 }
796 #endif
797 #if defined(INET6) && defined(INET)
798 else
799 #endif
800 #ifdef INET
801 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss &&
802 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) {
803 /* Use the sysctl tuneable blackhole MSS. */
804 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
805 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
806 } else {
807 /* Use the default MSS. */
808 tp->t_maxseg = V_tcp_mssdflt;
809 /*
810 * Disable Path MTU Discovery when we switch to
811 * minmss.
812 */
813 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
814 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
815 }
816 #endif
817 /*
818 * Reset the slow-start flight size
819 * as it may depend on the new MSS.
820 */
821 if (CC_ALGO(tp)->conn_init != NULL)
822 CC_ALGO(tp)->conn_init(tp->ccv);
823 } else {
824 /*
825 * If further retransmissions are still unsuccessful
826 * with a lowered MTU, maybe this isn't a blackhole and
827 * we restore the previous MSS and blackhole detection
828 * flags.
829 */
830 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
831 (tp->t_rxtshift >= tp->t_blackhole_exit)) {
832 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
833 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
834 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
835 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
836 /*
837 * Reset the slow-start flight size as it
838 * may depend on the new MSS.
839 */
840 if (CC_ALGO(tp)->conn_init != NULL)
841 CC_ALGO(tp)->conn_init(tp->ccv);
842 }
843 }
844 }
845
846 /*
847 * Disable RFC1323 and SACK if we haven't got any response to
848 * our third SYN to work-around some broken terminal servers
849 * (most of which have hopefully been retired) that have bad VJ
850 * header compression code which trashes TCP segments containing
851 * unknown-to-them TCP options.
852 */
853 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
854 (tp->t_rxtshift == 3))
855 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
856 /*
857 * If we backed off this far, notify the L3 protocol that we're having
858 * connection problems.
859 */
860 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
861 #ifdef INET6
862 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
863 in6_losing(tp->t_inpcb);
864 else
865 #endif
866 in_losing(tp->t_inpcb);
867 }
868 tp->snd_nxt = tp->snd_una;
869 tp->snd_recover = tp->snd_max;
870 /*
871 * Force a segment to be sent.
872 */
873 tp->t_flags |= TF_ACKNOW;
874 /*
875 * If timing a segment in this window, stop the timer.
876 */
877 tp->t_rtttime = 0;
878
879 /* Do not overwrite the snd_cwnd on SYN retransmissions. */
880 if (tp->t_state != TCPS_SYN_SENT)
881 cc_cong_signal(tp, NULL, CC_RTO);
882 NET_EPOCH_ENTER(et);
883 (void) tp->t_fb->tfb_tcp_output(tp);
884 NET_EPOCH_EXIT(et);
885 #ifdef TCPDEBUG
886 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
887 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
888 (TCPT_REXMT << 8) | PRU_SLOWTIMO);
889 #endif
890 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
891 INP_WUNLOCK(inp);
892 out:
893 CURVNET_RESTORE();
894 }
895
896 void
tcp_timer_activate(struct tcpcb * tp,uint32_t timer_type,u_int delta)897 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
898 {
899 struct callout *t_callout;
900 callout_func_t *f_callout;
901 struct inpcb *inp = tp->t_inpcb;
902 int cpu = inp_to_cpuid(inp);
903
904 #ifdef TCP_OFFLOAD
905 if (tp->t_flags & TF_TOE)
906 return;
907 #endif
908
909 if (tp->t_timers->tt_flags & TT_STOPPED)
910 return;
911
912 switch (timer_type) {
913 case TT_DELACK:
914 t_callout = &tp->t_timers->tt_delack;
915 f_callout = tcp_timer_delack;
916 break;
917 case TT_REXMT:
918 t_callout = &tp->t_timers->tt_rexmt;
919 f_callout = tcp_timer_rexmt;
920 break;
921 case TT_PERSIST:
922 t_callout = &tp->t_timers->tt_persist;
923 f_callout = tcp_timer_persist;
924 break;
925 case TT_KEEP:
926 t_callout = &tp->t_timers->tt_keep;
927 f_callout = tcp_timer_keep;
928 break;
929 case TT_2MSL:
930 t_callout = &tp->t_timers->tt_2msl;
931 f_callout = tcp_timer_2msl;
932 break;
933 default:
934 if (tp->t_fb->tfb_tcp_timer_activate) {
935 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
936 return;
937 }
938 panic("tp %p bad timer_type %#x", tp, timer_type);
939 }
940 if (delta == 0) {
941 callout_stop(t_callout);
942 } else {
943 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
944 }
945 }
946
947 int
tcp_timer_active(struct tcpcb * tp,uint32_t timer_type)948 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
949 {
950 struct callout *t_callout;
951
952 switch (timer_type) {
953 case TT_DELACK:
954 t_callout = &tp->t_timers->tt_delack;
955 break;
956 case TT_REXMT:
957 t_callout = &tp->t_timers->tt_rexmt;
958 break;
959 case TT_PERSIST:
960 t_callout = &tp->t_timers->tt_persist;
961 break;
962 case TT_KEEP:
963 t_callout = &tp->t_timers->tt_keep;
964 break;
965 case TT_2MSL:
966 t_callout = &tp->t_timers->tt_2msl;
967 break;
968 default:
969 if (tp->t_fb->tfb_tcp_timer_active) {
970 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
971 }
972 panic("tp %p bad timer_type %#x", tp, timer_type);
973 }
974 return callout_active(t_callout);
975 }
976
977 /*
978 * Stop the timer from running, and apply a flag
979 * against the timer_flags that will force the
980 * timer never to run. The flag is needed to assure
981 * a race does not leave it running and cause
982 * the timer to possibly restart itself (keep and persist
983 * especially do this).
984 */
985 int
tcp_timer_suspend(struct tcpcb * tp,uint32_t timer_type)986 tcp_timer_suspend(struct tcpcb *tp, uint32_t timer_type)
987 {
988 struct callout *t_callout;
989 uint32_t t_flags;
990
991 switch (timer_type) {
992 case TT_DELACK:
993 t_flags = TT_DELACK_SUS;
994 t_callout = &tp->t_timers->tt_delack;
995 break;
996 case TT_REXMT:
997 t_flags = TT_REXMT_SUS;
998 t_callout = &tp->t_timers->tt_rexmt;
999 break;
1000 case TT_PERSIST:
1001 t_flags = TT_PERSIST_SUS;
1002 t_callout = &tp->t_timers->tt_persist;
1003 break;
1004 case TT_KEEP:
1005 t_flags = TT_KEEP_SUS;
1006 t_callout = &tp->t_timers->tt_keep;
1007 break;
1008 case TT_2MSL:
1009 t_flags = TT_2MSL_SUS;
1010 t_callout = &tp->t_timers->tt_2msl;
1011 break;
1012 default:
1013 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
1014 }
1015 tp->t_timers->tt_flags |= t_flags;
1016 return (callout_stop(t_callout));
1017 }
1018
1019 void
tcp_timers_unsuspend(struct tcpcb * tp,uint32_t timer_type)1020 tcp_timers_unsuspend(struct tcpcb *tp, uint32_t timer_type)
1021 {
1022 switch (timer_type) {
1023 case TT_DELACK:
1024 if (tp->t_timers->tt_flags & TT_DELACK_SUS) {
1025 tp->t_timers->tt_flags &= ~TT_DELACK_SUS;
1026 if (tp->t_flags & TF_DELACK) {
1027 /* Delayed ack timer should be up activate a timer */
1028 tp->t_flags &= ~TF_DELACK;
1029 tcp_timer_activate(tp, TT_DELACK,
1030 tcp_delacktime);
1031 }
1032 }
1033 break;
1034 case TT_REXMT:
1035 if (tp->t_timers->tt_flags & TT_REXMT_SUS) {
1036 tp->t_timers->tt_flags &= ~TT_REXMT_SUS;
1037 if (SEQ_GT(tp->snd_max, tp->snd_una) &&
1038 (tcp_timer_active((tp), TT_PERSIST) == 0) &&
1039 tp->snd_wnd) {
1040 /* We have outstanding data activate a timer */
1041 tcp_timer_activate(tp, TT_REXMT,
1042 tp->t_rxtcur);
1043 }
1044 }
1045 break;
1046 case TT_PERSIST:
1047 if (tp->t_timers->tt_flags & TT_PERSIST_SUS) {
1048 tp->t_timers->tt_flags &= ~TT_PERSIST_SUS;
1049 if (tp->snd_wnd == 0) {
1050 /* Activate the persists timer */
1051 tp->t_rxtshift = 0;
1052 tcp_setpersist(tp);
1053 }
1054 }
1055 break;
1056 case TT_KEEP:
1057 if (tp->t_timers->tt_flags & TT_KEEP_SUS) {
1058 tp->t_timers->tt_flags &= ~TT_KEEP_SUS;
1059 tcp_timer_activate(tp, TT_KEEP,
1060 TCPS_HAVEESTABLISHED(tp->t_state) ?
1061 TP_KEEPIDLE(tp) : TP_KEEPINIT(tp));
1062 }
1063 break;
1064 case TT_2MSL:
1065 if (tp->t_timers->tt_flags &= TT_2MSL_SUS) {
1066 tp->t_timers->tt_flags &= ~TT_2MSL_SUS;
1067 if ((tp->t_state == TCPS_FIN_WAIT_2) &&
1068 ((tp->t_inpcb->inp_socket == NULL) ||
1069 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE))) {
1070 /* Star the 2MSL timer */
1071 tcp_timer_activate(tp, TT_2MSL,
1072 (tcp_fast_finwait2_recycle) ?
1073 tcp_finwait2_timeout : TP_MAXIDLE(tp));
1074 }
1075 }
1076 break;
1077 default:
1078 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
1079 }
1080 }
1081
1082 void
tcp_timer_stop(struct tcpcb * tp,uint32_t timer_type)1083 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
1084 {
1085 struct callout *t_callout;
1086
1087 tp->t_timers->tt_flags |= TT_STOPPED;
1088 switch (timer_type) {
1089 case TT_DELACK:
1090 t_callout = &tp->t_timers->tt_delack;
1091 break;
1092 case TT_REXMT:
1093 t_callout = &tp->t_timers->tt_rexmt;
1094 break;
1095 case TT_PERSIST:
1096 t_callout = &tp->t_timers->tt_persist;
1097 break;
1098 case TT_KEEP:
1099 t_callout = &tp->t_timers->tt_keep;
1100 break;
1101 case TT_2MSL:
1102 t_callout = &tp->t_timers->tt_2msl;
1103 break;
1104 default:
1105 if (tp->t_fb->tfb_tcp_timer_stop) {
1106 /*
1107 * XXXrrs we need to look at this with the
1108 * stop case below (flags).
1109 */
1110 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
1111 return;
1112 }
1113 panic("tp %p bad timer_type %#x", tp, timer_type);
1114 }
1115
1116 if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
1117 /*
1118 * Can't stop the callout, defer tcpcb actual deletion
1119 * to the last one. We do this using the async drain
1120 * function and incrementing the count in
1121 */
1122 tp->t_timers->tt_draincnt++;
1123 }
1124 }
1125