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 __FBSDID("$FreeBSD: stable/12/sys/netinet/tcp_timer.c 365569 2020-09-10 12:54:46Z tuexen $");
36
37 #include "opt_inet.h"
38 #include "opt_inet6.h"
39 #include "opt_tcpdebug.h"
40 #include "opt_rss.h"
41
42 #include <sys/param.h>
43 #include <sys/kernel.h>
44 #include <sys/lock.h>
45 #include <sys/mbuf.h>
46 #include <sys/mutex.h>
47 #include <sys/protosw.h>
48 #include <sys/smp.h>
49 #include <sys/socket.h>
50 #include <sys/socketvar.h>
51 #include <sys/sysctl.h>
52 #include <sys/systm.h>
53
54 #include <net/if.h>
55 #include <net/route.h>
56 #include <net/rss_config.h>
57 #include <net/vnet.h>
58 #include <net/netisr.h>
59
60 #include <netinet/in.h>
61 #include <netinet/in_kdtrace.h>
62 #include <netinet/in_pcb.h>
63 #include <netinet/in_rss.h>
64 #include <netinet/in_systm.h>
65 #ifdef INET6
66 #include <netinet6/in6_pcb.h>
67 #endif
68 #include <netinet/ip_var.h>
69 #include <netinet/tcp.h>
70 #include <netinet/tcp_fsm.h>
71 #include <netinet/tcp_log_buf.h>
72 #include <netinet/tcp_timer.h>
73 #include <netinet/tcp_var.h>
74 #include <netinet/tcp_seq.h>
75 #include <netinet/cc/cc.h>
76 #ifdef INET6
77 #include <netinet6/tcp6_var.h>
78 #endif
79 #include <netinet/tcpip.h>
80 #ifdef TCPDEBUG
81 #include <netinet/tcp_debug.h>
82 #endif
83
84 int tcp_persmin;
85 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
86 &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
87
88 int tcp_persmax;
89 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
90 &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
91
92 int tcp_keepinit;
93 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
94 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
95
96 int tcp_keepidle;
97 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
98 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
99
100 int tcp_keepintvl;
101 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
102 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
103
104 int tcp_delacktime;
105 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
106 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
107 "Time before a delayed ACK is sent");
108
109 int tcp_msl;
110 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
111 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
112
113 int tcp_rexmit_initial;
114 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial, CTLTYPE_INT|CTLFLAG_RW,
115 &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
116 "Initial Retransmission Timeout");
117
118 int tcp_rexmit_min;
119 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
120 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
121 "Minimum Retransmission Timeout");
122
123 int tcp_rexmit_slop;
124 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
125 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
126 "Retransmission Timer Slop");
127
128 VNET_DEFINE(int, tcp_always_keepalive) = 1;
129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
130 &VNET_NAME(tcp_always_keepalive) , 0,
131 "Assume SO_KEEPALIVE on all TCP connections");
132
133 int tcp_fast_finwait2_recycle = 0;
134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
135 &tcp_fast_finwait2_recycle, 0,
136 "Recycle closed FIN_WAIT_2 connections faster");
137
138 int tcp_finwait2_timeout;
139 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
140 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
141
142 int tcp_keepcnt = TCPTV_KEEPCNT;
143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
144 "Number of keepalive probes to send");
145
146 /* max idle probes */
147 int tcp_maxpersistidle;
148
149 int tcp_rexmit_drop_options = 0;
150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
151 &tcp_rexmit_drop_options, 0,
152 "Drop TCP options from 3rd and later retransmitted SYN");
153
154 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
156 CTLFLAG_RW|CTLFLAG_VNET,
157 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
158 "Path MTU Discovery Black Hole Detection Enabled");
159
160 #ifdef INET
161 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
163 CTLFLAG_RW|CTLFLAG_VNET,
164 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
165 "Path MTU Discovery Black Hole Detection lowered MSS");
166 #endif
167
168 #ifdef INET6
169 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
171 CTLFLAG_RW|CTLFLAG_VNET,
172 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
173 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
174 #endif
175
176 #ifdef RSS
177 static int per_cpu_timers = 1;
178 #else
179 static int per_cpu_timers = 0;
180 #endif
181 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
182 &per_cpu_timers , 0, "run tcp timers on all cpus");
183
184 /*
185 * Map the given inp to a CPU id.
186 *
187 * This queries RSS if it's compiled in, else it defaults to the current
188 * CPU ID.
189 */
190 inline int
inp_to_cpuid(struct inpcb * inp)191 inp_to_cpuid(struct inpcb *inp)
192 {
193 u_int cpuid;
194
195 #ifdef RSS
196 if (per_cpu_timers) {
197 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
198 if (cpuid == NETISR_CPUID_NONE)
199 return (curcpu); /* XXX */
200 else
201 return (cpuid);
202 }
203 #else
204 /* Legacy, pre-RSS behaviour */
205 if (per_cpu_timers) {
206 /*
207 * We don't have a flowid -> cpuid mapping, so cheat and
208 * just map unknown cpuids to curcpu. Not the best, but
209 * apparently better than defaulting to swi 0.
210 */
211 cpuid = inp->inp_flowid % (mp_maxid + 1);
212 if (! CPU_ABSENT(cpuid))
213 return (cpuid);
214 return (curcpu);
215 }
216 #endif
217 /* Default for RSS and non-RSS - cpuid 0 */
218 else {
219 return (0);
220 }
221 }
222
223 /*
224 * Tcp protocol timeout routine called every 500 ms.
225 * Updates timestamps used for TCP
226 * causes finite state machine actions if timers expire.
227 */
228 void
tcp_slowtimo(void)229 tcp_slowtimo(void)
230 {
231 VNET_ITERATOR_DECL(vnet_iter);
232
233 VNET_LIST_RLOCK_NOSLEEP();
234 VNET_FOREACH(vnet_iter) {
235 CURVNET_SET(vnet_iter);
236 (void) tcp_tw_2msl_scan(0);
237 CURVNET_RESTORE();
238 }
239 VNET_LIST_RUNLOCK_NOSLEEP();
240 }
241
242 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
243 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
244
245 int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
246
247 /*
248 * TCP timer processing.
249 */
250
251 void
tcp_timer_delack(void * xtp)252 tcp_timer_delack(void *xtp)
253 {
254 struct tcpcb *tp = xtp;
255 struct inpcb *inp;
256 CURVNET_SET(tp->t_vnet);
257
258 inp = tp->t_inpcb;
259 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
260 INP_WLOCK(inp);
261 if (callout_pending(&tp->t_timers->tt_delack) ||
262 !callout_active(&tp->t_timers->tt_delack)) {
263 INP_WUNLOCK(inp);
264 CURVNET_RESTORE();
265 return;
266 }
267 callout_deactivate(&tp->t_timers->tt_delack);
268 if ((inp->inp_flags & INP_DROPPED) != 0) {
269 INP_WUNLOCK(inp);
270 CURVNET_RESTORE();
271 return;
272 }
273 tp->t_flags |= TF_ACKNOW;
274 TCPSTAT_INC(tcps_delack);
275 (void) tp->t_fb->tfb_tcp_output(tp);
276 INP_WUNLOCK(inp);
277 CURVNET_RESTORE();
278 }
279
280 void
tcp_inpinfo_lock_del(struct inpcb * inp,struct tcpcb * tp)281 tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
282 {
283 if (inp && tp != NULL)
284 INP_WUNLOCK(inp);
285 }
286
287 void
tcp_timer_2msl(void * xtp)288 tcp_timer_2msl(void *xtp)
289 {
290 struct tcpcb *tp = xtp;
291 struct inpcb *inp;
292 struct epoch_tracker et;
293 CURVNET_SET(tp->t_vnet);
294 #ifdef TCPDEBUG
295 int ostate;
296
297 ostate = tp->t_state;
298 #endif
299 inp = tp->t_inpcb;
300 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
301 INP_WLOCK(inp);
302 tcp_free_sackholes(tp);
303 if (callout_pending(&tp->t_timers->tt_2msl) ||
304 !callout_active(&tp->t_timers->tt_2msl)) {
305 INP_WUNLOCK(tp->t_inpcb);
306 CURVNET_RESTORE();
307 return;
308 }
309 callout_deactivate(&tp->t_timers->tt_2msl);
310 if ((inp->inp_flags & INP_DROPPED) != 0) {
311 INP_WUNLOCK(inp);
312 CURVNET_RESTORE();
313 return;
314 }
315 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
316 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
317 /*
318 * 2 MSL timeout in shutdown went off. If we're closed but
319 * still waiting for peer to close and connection has been idle
320 * too long delete connection control block. Otherwise, check
321 * again in a bit.
322 *
323 * If in TIME_WAIT state just ignore as this timeout is handled in
324 * tcp_tw_2msl_scan().
325 *
326 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
327 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
328 * Ignore fact that there were recent incoming segments.
329 */
330 if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
331 INP_WUNLOCK(inp);
332 CURVNET_RESTORE();
333 return;
334 }
335 if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
336 tp->t_inpcb && tp->t_inpcb->inp_socket &&
337 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
338 TCPSTAT_INC(tcps_finwait2_drops);
339 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
340 tcp_inpinfo_lock_del(inp, tp);
341 goto out;
342 }
343 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
344 tp = tcp_close(tp);
345 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
346 tcp_inpinfo_lock_del(inp, tp);
347 goto out;
348 } else {
349 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
350 callout_reset(&tp->t_timers->tt_2msl,
351 TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
352 } else {
353 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
354 tcp_inpinfo_lock_del(inp, tp);
355 goto out;
356 }
357 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
358 tp = tcp_close(tp);
359 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
360 tcp_inpinfo_lock_del(inp, tp);
361 goto out;
362 }
363 }
364
365 #ifdef TCPDEBUG
366 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
367 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
368 PRU_SLOWTIMO);
369 #endif
370 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
371
372 if (tp != NULL)
373 INP_WUNLOCK(inp);
374 out:
375 CURVNET_RESTORE();
376 }
377
378 void
tcp_timer_keep(void * xtp)379 tcp_timer_keep(void *xtp)
380 {
381 struct tcpcb *tp = xtp;
382 struct tcptemp *t_template;
383 struct inpcb *inp;
384 struct epoch_tracker et;
385 CURVNET_SET(tp->t_vnet);
386 #ifdef TCPDEBUG
387 int ostate;
388
389 ostate = tp->t_state;
390 #endif
391 inp = tp->t_inpcb;
392 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
393 INP_WLOCK(inp);
394 if (callout_pending(&tp->t_timers->tt_keep) ||
395 !callout_active(&tp->t_timers->tt_keep)) {
396 INP_WUNLOCK(inp);
397 CURVNET_RESTORE();
398 return;
399 }
400 callout_deactivate(&tp->t_timers->tt_keep);
401 if ((inp->inp_flags & INP_DROPPED) != 0) {
402 INP_WUNLOCK(inp);
403 CURVNET_RESTORE();
404 return;
405 }
406 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
407 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
408
409 /*
410 * Because we don't regularly reset the keepalive callout in
411 * the ESTABLISHED state, it may be that we don't actually need
412 * to send a keepalive yet. If that occurs, schedule another
413 * call for the next time the keepalive timer might expire.
414 */
415 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
416 u_int idletime;
417
418 idletime = ticks - tp->t_rcvtime;
419 if (idletime < TP_KEEPIDLE(tp)) {
420 callout_reset(&tp->t_timers->tt_keep,
421 TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
422 INP_WUNLOCK(inp);
423 CURVNET_RESTORE();
424 return;
425 }
426 }
427
428 /*
429 * Keep-alive timer went off; send something
430 * or drop connection if idle for too long.
431 */
432 TCPSTAT_INC(tcps_keeptimeo);
433 if (tp->t_state < TCPS_ESTABLISHED)
434 goto dropit;
435 if ((V_tcp_always_keepalive ||
436 inp->inp_socket->so_options & SO_KEEPALIVE) &&
437 tp->t_state <= TCPS_CLOSING) {
438 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
439 goto dropit;
440 /*
441 * Send a packet designed to force a response
442 * if the peer is up and reachable:
443 * either an ACK if the connection is still alive,
444 * or an RST if the peer has closed the connection
445 * due to timeout or reboot.
446 * Using sequence number tp->snd_una-1
447 * causes the transmitted zero-length segment
448 * to lie outside the receive window;
449 * by the protocol spec, this requires the
450 * correspondent TCP to respond.
451 */
452 TCPSTAT_INC(tcps_keepprobe);
453 t_template = tcpip_maketemplate(inp);
454 if (t_template) {
455 tcp_respond(tp, t_template->tt_ipgen,
456 &t_template->tt_t, (struct mbuf *)NULL,
457 tp->rcv_nxt, tp->snd_una - 1, 0);
458 free(t_template, M_TEMP);
459 }
460 callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
461 tcp_timer_keep, tp);
462 } else
463 callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
464 tcp_timer_keep, tp);
465
466 #ifdef TCPDEBUG
467 if (inp->inp_socket->so_options & SO_DEBUG)
468 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
469 PRU_SLOWTIMO);
470 #endif
471 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
472 INP_WUNLOCK(inp);
473 CURVNET_RESTORE();
474 return;
475
476 dropit:
477 TCPSTAT_INC(tcps_keepdrops);
478 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
479 tcp_inpinfo_lock_del(inp, tp);
480 goto out;
481 }
482 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
483 tp = tcp_drop(tp, ETIMEDOUT);
484
485 #ifdef TCPDEBUG
486 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
487 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
488 PRU_SLOWTIMO);
489 #endif
490 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
491 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
492 tcp_inpinfo_lock_del(inp, tp);
493 out:
494 CURVNET_RESTORE();
495 }
496
497 void
tcp_timer_persist(void * xtp)498 tcp_timer_persist(void *xtp)
499 {
500 struct tcpcb *tp = xtp;
501 struct inpcb *inp;
502 struct epoch_tracker et;
503 CURVNET_SET(tp->t_vnet);
504 #ifdef TCPDEBUG
505 int ostate;
506
507 ostate = tp->t_state;
508 #endif
509 inp = tp->t_inpcb;
510 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
511 INP_WLOCK(inp);
512 if (callout_pending(&tp->t_timers->tt_persist) ||
513 !callout_active(&tp->t_timers->tt_persist)) {
514 INP_WUNLOCK(inp);
515 CURVNET_RESTORE();
516 return;
517 }
518 callout_deactivate(&tp->t_timers->tt_persist);
519 if ((inp->inp_flags & INP_DROPPED) != 0) {
520 INP_WUNLOCK(inp);
521 CURVNET_RESTORE();
522 return;
523 }
524 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
525 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
526 /*
527 * Persistence timer into zero window.
528 * Force a byte to be output, if possible.
529 */
530 TCPSTAT_INC(tcps_persisttimeo);
531 /*
532 * Hack: if the peer is dead/unreachable, we do not
533 * time out if the window is closed. After a full
534 * backoff, drop the connection if the idle time
535 * (no responses to probes) reaches the maximum
536 * backoff that we would use if retransmitting.
537 */
538 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
539 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
540 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
541 TCPSTAT_INC(tcps_persistdrop);
542 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
543 tcp_inpinfo_lock_del(inp, tp);
544 goto out;
545 }
546 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
547 tp = tcp_drop(tp, ETIMEDOUT);
548 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
549 tcp_inpinfo_lock_del(inp, tp);
550 goto out;
551 }
552 /*
553 * If the user has closed the socket then drop a persisting
554 * connection after a much reduced timeout.
555 */
556 if (tp->t_state > TCPS_CLOSE_WAIT &&
557 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
558 TCPSTAT_INC(tcps_persistdrop);
559 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
560 tcp_inpinfo_lock_del(inp, tp);
561 goto out;
562 }
563 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
564 tp = tcp_drop(tp, ETIMEDOUT);
565 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
566 tcp_inpinfo_lock_del(inp, tp);
567 goto out;
568 }
569 tcp_setpersist(tp);
570 tp->t_flags |= TF_FORCEDATA;
571 (void) tp->t_fb->tfb_tcp_output(tp);
572 tp->t_flags &= ~TF_FORCEDATA;
573
574 #ifdef TCPDEBUG
575 if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
576 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
577 #endif
578 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
579 INP_WUNLOCK(inp);
580 out:
581 CURVNET_RESTORE();
582 }
583
584 void
tcp_timer_rexmt(void * xtp)585 tcp_timer_rexmt(void * xtp)
586 {
587 struct tcpcb *tp = xtp;
588 CURVNET_SET(tp->t_vnet);
589 int rexmt;
590 struct inpcb *inp;
591 struct epoch_tracker et;
592 bool isipv6;
593 #ifdef TCPDEBUG
594 int ostate;
595
596 ostate = tp->t_state;
597 #endif
598 inp = tp->t_inpcb;
599 KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
600 INP_WLOCK(inp);
601 if (callout_pending(&tp->t_timers->tt_rexmt) ||
602 !callout_active(&tp->t_timers->tt_rexmt)) {
603 INP_WUNLOCK(inp);
604 CURVNET_RESTORE();
605 return;
606 }
607 callout_deactivate(&tp->t_timers->tt_rexmt);
608 if ((inp->inp_flags & INP_DROPPED) != 0) {
609 INP_WUNLOCK(inp);
610 CURVNET_RESTORE();
611 return;
612 }
613 KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
614 ("%s: tp %p tcpcb can't be stopped here", __func__, tp));
615 tcp_free_sackholes(tp);
616 TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
617 if (tp->t_fb->tfb_tcp_rexmit_tmr) {
618 /* The stack has a timer action too. */
619 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
620 }
621 /*
622 * Retransmission timer went off. Message has not
623 * been acked within retransmit interval. Back off
624 * to a longer retransmit interval and retransmit one segment.
625 */
626 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
627 tp->t_rxtshift = TCP_MAXRXTSHIFT;
628 TCPSTAT_INC(tcps_timeoutdrop);
629 if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
630 tcp_inpinfo_lock_del(inp, tp);
631 goto out;
632 }
633 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
634 tp = tcp_drop(tp, ETIMEDOUT);
635 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
636 tcp_inpinfo_lock_del(inp, tp);
637 goto out;
638 }
639 if (tp->t_state == TCPS_SYN_SENT) {
640 /*
641 * If the SYN was retransmitted, indicate CWND to be
642 * limited to 1 segment in cc_conn_init().
643 */
644 tp->snd_cwnd = 1;
645 } else if (tp->t_rxtshift == 1) {
646 /*
647 * first retransmit; record ssthresh and cwnd so they can
648 * be recovered if this turns out to be a "bad" retransmit.
649 * A retransmit is considered "bad" if an ACK for this
650 * segment is received within RTT/2 interval; the assumption
651 * here is that the ACK was already in flight. See
652 * "On Estimating End-to-End Network Path Properties" by
653 * Allman and Paxson for more details.
654 */
655 tp->snd_cwnd_prev = tp->snd_cwnd;
656 tp->snd_ssthresh_prev = tp->snd_ssthresh;
657 tp->snd_recover_prev = tp->snd_recover;
658 if (IN_FASTRECOVERY(tp->t_flags))
659 tp->t_flags |= TF_WASFRECOVERY;
660 else
661 tp->t_flags &= ~TF_WASFRECOVERY;
662 if (IN_CONGRECOVERY(tp->t_flags))
663 tp->t_flags |= TF_WASCRECOVERY;
664 else
665 tp->t_flags &= ~TF_WASCRECOVERY;
666 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
667 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
668 /* In the event that we've negotiated timestamps
669 * badrxtwin will be set to the value that we set
670 * the retransmitted packet's to_tsval to by tcp_output
671 */
672 tp->t_flags |= TF_PREVVALID;
673 } else
674 tp->t_flags &= ~TF_PREVVALID;
675 TCPSTAT_INC(tcps_rexmttimeo);
676 if ((tp->t_state == TCPS_SYN_SENT) ||
677 (tp->t_state == TCPS_SYN_RECEIVED))
678 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
679 else
680 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
681 TCPT_RANGESET(tp->t_rxtcur, rexmt,
682 tp->t_rttmin, TCPTV_REXMTMAX);
683
684 /*
685 * We enter the path for PLMTUD if connection is established or, if
686 * connection is FIN_WAIT_1 status, reason for the last is that if
687 * amount of data we send is very small, we could send it in couple of
688 * packets and process straight to FIN. In that case we won't catch
689 * ESTABLISHED state.
690 */
691 #ifdef INET6
692 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? true : false;
693 #else
694 isipv6 = false;
695 #endif
696 if (((V_tcp_pmtud_blackhole_detect == 1) ||
697 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
698 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
699 ((tp->t_state == TCPS_ESTABLISHED) ||
700 (tp->t_state == TCPS_FIN_WAIT_1))) {
701 if (tp->t_rxtshift == 1) {
702 /*
703 * We enter blackhole detection after the first
704 * unsuccessful timer based retransmission.
705 * Then we reduce up to two times the MSS, each
706 * candidate giving two tries of retransmissions.
707 * But we give a candidate only two tries, if it
708 * actually reduces the MSS.
709 */
710 tp->t_blackhole_enter = 2;
711 tp->t_blackhole_exit = tp->t_blackhole_enter;
712 if (isipv6) {
713 #ifdef INET6
714 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss)
715 tp->t_blackhole_exit += 2;
716 if (tp->t_maxseg > V_tcp_v6mssdflt &&
717 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt)
718 tp->t_blackhole_exit += 2;
719 #endif
720 } else {
721 #ifdef INET
722 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss)
723 tp->t_blackhole_exit += 2;
724 if (tp->t_maxseg > V_tcp_mssdflt &&
725 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt)
726 tp->t_blackhole_exit += 2;
727 #endif
728 }
729 }
730 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
731 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
732 (tp->t_rxtshift >= tp->t_blackhole_enter &&
733 tp->t_rxtshift < tp->t_blackhole_exit &&
734 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) {
735 /*
736 * Enter Path MTU Black-hole Detection mechanism:
737 * - Disable Path MTU Discovery (IP "DF" bit).
738 * - Reduce MTU to lower value than what we
739 * negotiated with peer.
740 */
741 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
742 /* Record that we may have found a black hole. */
743 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
744 /* Keep track of previous MSS. */
745 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
746 }
747
748 /*
749 * Reduce the MSS to blackhole value or to the default
750 * in an attempt to retransmit.
751 */
752 #ifdef INET6
753 if (isipv6 &&
754 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss &&
755 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) {
756 /* Use the sysctl tuneable blackhole MSS. */
757 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
758 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
759 } else if (isipv6) {
760 /* Use the default MSS. */
761 tp->t_maxseg = V_tcp_v6mssdflt;
762 /*
763 * Disable Path MTU Discovery when we switch to
764 * minmss.
765 */
766 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
767 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
768 }
769 #endif
770 #if defined(INET6) && defined(INET)
771 else
772 #endif
773 #ifdef INET
774 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss &&
775 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) {
776 /* Use the sysctl tuneable blackhole MSS. */
777 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
778 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
779 } else {
780 /* Use the default MSS. */
781 tp->t_maxseg = V_tcp_mssdflt;
782 /*
783 * Disable Path MTU Discovery when we switch to
784 * minmss.
785 */
786 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
787 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
788 }
789 #endif
790 /*
791 * Reset the slow-start flight size
792 * as it may depend on the new MSS.
793 */
794 if (CC_ALGO(tp)->conn_init != NULL)
795 CC_ALGO(tp)->conn_init(tp->ccv);
796 } else {
797 /*
798 * If further retransmissions are still unsuccessful
799 * with a lowered MTU, maybe this isn't a blackhole and
800 * we restore the previous MSS and blackhole detection
801 * flags.
802 */
803 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
804 (tp->t_rxtshift >= tp->t_blackhole_exit)) {
805 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
806 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
807 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
808 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
809 /*
810 * Reset the slow-start flight size as it
811 * may depend on the new MSS.
812 */
813 if (CC_ALGO(tp)->conn_init != NULL)
814 CC_ALGO(tp)->conn_init(tp->ccv);
815 }
816 }
817 }
818
819 /*
820 * Disable RFC1323 and SACK if we haven't got any response to
821 * our third SYN to work-around some broken terminal servers
822 * (most of which have hopefully been retired) that have bad VJ
823 * header compression code which trashes TCP segments containing
824 * unknown-to-them TCP options.
825 */
826 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
827 (tp->t_rxtshift == 3))
828 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
829 /*
830 * If we backed off this far, notify the L3 protocol that we're having
831 * connection problems.
832 */
833 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
834 #ifdef INET6
835 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
836 in6_losing(tp->t_inpcb);
837 else
838 #endif
839 in_losing(tp->t_inpcb);
840 }
841 tp->snd_nxt = tp->snd_una;
842 tp->snd_recover = tp->snd_max;
843 /*
844 * Force a segment to be sent.
845 */
846 tp->t_flags |= TF_ACKNOW;
847 /*
848 * If timing a segment in this window, stop the timer.
849 */
850 tp->t_rtttime = 0;
851
852 cc_cong_signal(tp, NULL, CC_RTO);
853
854 (void) tp->t_fb->tfb_tcp_output(tp);
855
856 #ifdef TCPDEBUG
857 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
858 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
859 PRU_SLOWTIMO);
860 #endif
861 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
862 INP_WUNLOCK(inp);
863 out:
864 CURVNET_RESTORE();
865 }
866
867 void
tcp_timer_activate(struct tcpcb * tp,uint32_t timer_type,u_int delta)868 tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
869 {
870 struct callout *t_callout;
871 timeout_t *f_callout;
872 struct inpcb *inp = tp->t_inpcb;
873 int cpu = inp_to_cpuid(inp);
874
875 #ifdef TCP_OFFLOAD
876 if (tp->t_flags & TF_TOE)
877 return;
878 #endif
879
880 if (tp->t_timers->tt_flags & TT_STOPPED)
881 return;
882
883 switch (timer_type) {
884 case TT_DELACK:
885 t_callout = &tp->t_timers->tt_delack;
886 f_callout = tcp_timer_delack;
887 break;
888 case TT_REXMT:
889 t_callout = &tp->t_timers->tt_rexmt;
890 f_callout = tcp_timer_rexmt;
891 break;
892 case TT_PERSIST:
893 t_callout = &tp->t_timers->tt_persist;
894 f_callout = tcp_timer_persist;
895 break;
896 case TT_KEEP:
897 t_callout = &tp->t_timers->tt_keep;
898 f_callout = tcp_timer_keep;
899 break;
900 case TT_2MSL:
901 t_callout = &tp->t_timers->tt_2msl;
902 f_callout = tcp_timer_2msl;
903 break;
904 default:
905 if (tp->t_fb->tfb_tcp_timer_activate) {
906 tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
907 return;
908 }
909 panic("tp %p bad timer_type %#x", tp, timer_type);
910 }
911 if (delta == 0) {
912 callout_stop(t_callout);
913 } else {
914 callout_reset_on(t_callout, delta, f_callout, tp, cpu);
915 }
916 }
917
918 int
tcp_timer_active(struct tcpcb * tp,uint32_t timer_type)919 tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
920 {
921 struct callout *t_callout;
922
923 switch (timer_type) {
924 case TT_DELACK:
925 t_callout = &tp->t_timers->tt_delack;
926 break;
927 case TT_REXMT:
928 t_callout = &tp->t_timers->tt_rexmt;
929 break;
930 case TT_PERSIST:
931 t_callout = &tp->t_timers->tt_persist;
932 break;
933 case TT_KEEP:
934 t_callout = &tp->t_timers->tt_keep;
935 break;
936 case TT_2MSL:
937 t_callout = &tp->t_timers->tt_2msl;
938 break;
939 default:
940 if (tp->t_fb->tfb_tcp_timer_active) {
941 return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
942 }
943 panic("tp %p bad timer_type %#x", tp, timer_type);
944 }
945 return callout_active(t_callout);
946 }
947
948 /*
949 * Stop the timer from running, and apply a flag
950 * against the timer_flags that will force the
951 * timer never to run. The flag is needed to assure
952 * a race does not leave it running and cause
953 * the timer to possibly restart itself (keep and persist
954 * especially do this).
955 */
956 int
tcp_timer_suspend(struct tcpcb * tp,uint32_t timer_type)957 tcp_timer_suspend(struct tcpcb *tp, uint32_t timer_type)
958 {
959 struct callout *t_callout;
960 uint32_t t_flags;
961
962 switch (timer_type) {
963 case TT_DELACK:
964 t_flags = TT_DELACK_SUS;
965 t_callout = &tp->t_timers->tt_delack;
966 break;
967 case TT_REXMT:
968 t_flags = TT_REXMT_SUS;
969 t_callout = &tp->t_timers->tt_rexmt;
970 break;
971 case TT_PERSIST:
972 t_flags = TT_PERSIST_SUS;
973 t_callout = &tp->t_timers->tt_persist;
974 break;
975 case TT_KEEP:
976 t_flags = TT_KEEP_SUS;
977 t_callout = &tp->t_timers->tt_keep;
978 break;
979 case TT_2MSL:
980 t_flags = TT_2MSL_SUS;
981 t_callout = &tp->t_timers->tt_2msl;
982 break;
983 default:
984 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
985 }
986 tp->t_timers->tt_flags |= t_flags;
987 return (callout_stop(t_callout));
988 }
989
990 void
tcp_timers_unsuspend(struct tcpcb * tp,uint32_t timer_type)991 tcp_timers_unsuspend(struct tcpcb *tp, uint32_t timer_type)
992 {
993 switch (timer_type) {
994 case TT_DELACK:
995 if (tp->t_timers->tt_flags & TT_DELACK_SUS) {
996 tp->t_timers->tt_flags &= ~TT_DELACK_SUS;
997 if (tp->t_flags & TF_DELACK) {
998 /* Delayed ack timer should be up activate a timer */
999 tp->t_flags &= ~TF_DELACK;
1000 tcp_timer_activate(tp, TT_DELACK,
1001 tcp_delacktime);
1002 }
1003 }
1004 break;
1005 case TT_REXMT:
1006 if (tp->t_timers->tt_flags & TT_REXMT_SUS) {
1007 tp->t_timers->tt_flags &= ~TT_REXMT_SUS;
1008 if (SEQ_GT(tp->snd_max, tp->snd_una) &&
1009 (tcp_timer_active((tp), TT_PERSIST) == 0) &&
1010 tp->snd_wnd) {
1011 /* We have outstanding data activate a timer */
1012 tcp_timer_activate(tp, TT_REXMT,
1013 tp->t_rxtcur);
1014 }
1015 }
1016 break;
1017 case TT_PERSIST:
1018 if (tp->t_timers->tt_flags & TT_PERSIST_SUS) {
1019 tp->t_timers->tt_flags &= ~TT_PERSIST_SUS;
1020 if (tp->snd_wnd == 0) {
1021 /* Activate the persists timer */
1022 tp->t_rxtshift = 0;
1023 tcp_setpersist(tp);
1024 }
1025 }
1026 break;
1027 case TT_KEEP:
1028 if (tp->t_timers->tt_flags & TT_KEEP_SUS) {
1029 tp->t_timers->tt_flags &= ~TT_KEEP_SUS;
1030 tcp_timer_activate(tp, TT_KEEP,
1031 TCPS_HAVEESTABLISHED(tp->t_state) ?
1032 TP_KEEPIDLE(tp) : TP_KEEPINIT(tp));
1033 }
1034 break;
1035 case TT_2MSL:
1036 if (tp->t_timers->tt_flags &= TT_2MSL_SUS) {
1037 tp->t_timers->tt_flags &= ~TT_2MSL_SUS;
1038 if ((tp->t_state == TCPS_FIN_WAIT_2) &&
1039 ((tp->t_inpcb->inp_socket == NULL) ||
1040 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE))) {
1041 /* Star the 2MSL timer */
1042 tcp_timer_activate(tp, TT_2MSL,
1043 (tcp_fast_finwait2_recycle) ?
1044 tcp_finwait2_timeout : TP_MAXIDLE(tp));
1045 }
1046 }
1047 break;
1048 default:
1049 panic("tp:%p bad timer_type 0x%x", tp, timer_type);
1050 }
1051 }
1052
1053 void
tcp_timer_stop(struct tcpcb * tp,uint32_t timer_type)1054 tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
1055 {
1056 struct callout *t_callout;
1057
1058 tp->t_timers->tt_flags |= TT_STOPPED;
1059 switch (timer_type) {
1060 case TT_DELACK:
1061 t_callout = &tp->t_timers->tt_delack;
1062 break;
1063 case TT_REXMT:
1064 t_callout = &tp->t_timers->tt_rexmt;
1065 break;
1066 case TT_PERSIST:
1067 t_callout = &tp->t_timers->tt_persist;
1068 break;
1069 case TT_KEEP:
1070 t_callout = &tp->t_timers->tt_keep;
1071 break;
1072 case TT_2MSL:
1073 t_callout = &tp->t_timers->tt_2msl;
1074 break;
1075 default:
1076 if (tp->t_fb->tfb_tcp_timer_stop) {
1077 /*
1078 * XXXrrs we need to look at this with the
1079 * stop case below (flags).
1080 */
1081 tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
1082 return;
1083 }
1084 panic("tp %p bad timer_type %#x", tp, timer_type);
1085 }
1086
1087 if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
1088 /*
1089 * Can't stop the callout, defer tcpcb actual deletion
1090 * to the last one. We do this using the async drain
1091 * function and incrementing the count in
1092 */
1093 tp->t_timers->tt_draincnt++;
1094 }
1095 }
1096