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_rss.h"
38
39 #include <sys/param.h>
40 #include <sys/kernel.h>
41 #include <sys/lock.h>
42 #include <sys/mbuf.h>
43 #include <sys/mutex.h>
44 #include <sys/protosw.h>
45 #include <sys/smp.h>
46 #include <sys/socket.h>
47 #include <sys/socketvar.h>
48 #include <sys/sysctl.h>
49 #include <sys/systm.h>
50
51 #include <net/if.h>
52 #include <net/route.h>
53 #include <net/rss_config.h>
54 #include <net/vnet.h>
55 #include <net/netisr.h>
56
57 #include <netinet/in.h>
58 #include <netinet/in_kdtrace.h>
59 #include <netinet/in_pcb.h>
60 #include <netinet/in_rss.h>
61 #include <netinet/in_systm.h>
62 #ifdef INET6
63 #include <netinet6/in6_pcb.h>
64 #endif
65 #include <netinet/ip_var.h>
66 #include <netinet/tcp.h>
67 #include <netinet/tcp_fsm.h>
68 #include <netinet/tcp_timer.h>
69 #include <netinet/tcp_var.h>
70 #include <netinet/tcp_log_buf.h>
71 #include <netinet/tcp_seq.h>
72 #include <netinet/cc/cc.h>
73 #ifdef INET6
74 #include <netinet6/tcp6_var.h>
75 #endif
76 #include <netinet/tcpip.h>
77
78 int tcp_persmin;
79 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin,
80 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
81 &tcp_persmin, 0, sysctl_msec_to_ticks, "I",
82 "minimum persistence interval");
83
84 int tcp_persmax;
85 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax,
86 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
87 &tcp_persmax, 0, sysctl_msec_to_ticks, "I",
88 "maximum persistence interval");
89
90 int tcp_keepinit;
91 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
92 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
93 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I",
94 "time to establish connection");
95
96 int tcp_keepidle;
97 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
98 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
99 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I",
100 "time before keepalive probes begin");
101
102 int tcp_keepintvl;
103 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
104 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
105 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I",
106 "time between keepalive probes");
107
108 int tcp_delacktime;
109 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
110 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
111 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
112 "Time before a delayed ACK is sent");
113
114 VNET_DEFINE(int, tcp_msl);
115 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl,
116 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_VNET,
117 &VNET_NAME(tcp_msl), 0, sysctl_msec_to_ticks, "I",
118 "Maximum segment lifetime");
119
120 int tcp_rexmit_initial;
121 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial,
122 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
123 &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
124 "Initial Retransmission Timeout");
125
126 int tcp_rexmit_min;
127 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min,
128 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
129 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
130 "Minimum Retransmission Timeout");
131
132 int tcp_rexmit_slop;
133 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop,
134 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
135 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
136 "Retransmission Timer Slop");
137
138 VNET_DEFINE(int, tcp_always_keepalive) = 1;
139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW,
140 &VNET_NAME(tcp_always_keepalive) , 0,
141 "Assume SO_KEEPALIVE on all TCP connections");
142
143 int tcp_fast_finwait2_recycle = 0;
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
145 &tcp_fast_finwait2_recycle, 0,
146 "Recycle closed FIN_WAIT_2 connections faster");
147
148 int tcp_finwait2_timeout;
149 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout,
150 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
151 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I",
152 "FIN-WAIT2 timeout");
153
154 int tcp_keepcnt = TCPTV_KEEPCNT;
155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
156 "Number of keepalive probes to send");
157
158 /* max idle probes */
159 int tcp_maxpersistidle;
160
161 int tcp_rexmit_drop_options = 0;
162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
163 &tcp_rexmit_drop_options, 0,
164 "Drop TCP options from 3rd and later retransmitted SYN");
165
166 int tcp_maxunacktime = TCPTV_MAXUNACKTIME;
167 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxunacktime,
168 CTLTYPE_INT|CTLFLAG_RW | CTLFLAG_NEEDGIANT,
169 &tcp_maxunacktime, 0, sysctl_msec_to_ticks, "I",
170 "Maximum time (in ms) that a session can linger without making progress");
171
172 VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
174 CTLFLAG_RW|CTLFLAG_VNET,
175 &VNET_NAME(tcp_pmtud_blackhole_detect), 0,
176 "Path MTU Discovery Black Hole Detection Enabled");
177
178 #ifdef INET
179 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
181 CTLFLAG_RW|CTLFLAG_VNET,
182 &VNET_NAME(tcp_pmtud_blackhole_mss), 0,
183 "Path MTU Discovery Black Hole Detection lowered MSS");
184 #endif
185
186 #ifdef INET6
187 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
189 CTLFLAG_RW|CTLFLAG_VNET,
190 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
191 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
192 #endif
193
194 #ifdef RSS
195 static int per_cpu_timers = 1;
196 #else
197 static int per_cpu_timers = 0;
198 #endif
199 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
200 &per_cpu_timers , 0, "run tcp timers on all cpus");
201
202 static int
sysctl_net_inet_tcp_retries(SYSCTL_HANDLER_ARGS)203 sysctl_net_inet_tcp_retries(SYSCTL_HANDLER_ARGS)
204 {
205 int error, new;
206
207 new = V_tcp_retries;
208 error = sysctl_handle_int(oidp, &new, 0, req);
209 if (error == 0 && req->newptr) {
210 if ((new < 1) || (new > TCP_MAXRXTSHIFT))
211 error = EINVAL;
212 else
213 V_tcp_retries = new;
214 }
215 return (error);
216 }
217
218 VNET_DEFINE(int, tcp_retries) = TCP_MAXRXTSHIFT;
219 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, retries,
220 CTLTYPE_INT | CTLFLAG_VNET | CTLFLAG_RW,
221 &VNET_NAME(tcp_retries), 0, sysctl_net_inet_tcp_retries, "I",
222 "maximum number of consecutive timer based retransmissions");
223
224 /*
225 * Map the given inp to a CPU id.
226 *
227 * This queries RSS if it's compiled in, else it defaults to the current
228 * CPU ID.
229 */
230 inline int
inp_to_cpuid(struct inpcb * inp)231 inp_to_cpuid(struct inpcb *inp)
232 {
233 u_int cpuid;
234
235 if (per_cpu_timers) {
236 #ifdef RSS
237 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
238 if (cpuid == NETISR_CPUID_NONE)
239 return (curcpu); /* XXX */
240 else
241 return (cpuid);
242 #endif
243 /*
244 * We don't have a flowid -> cpuid mapping, so cheat and
245 * just map unknown cpuids to curcpu. Not the best, but
246 * apparently better than defaulting to swi 0.
247 */
248 cpuid = inp->inp_flowid % (mp_maxid + 1);
249 if (! CPU_ABSENT(cpuid))
250 return (cpuid);
251 return (curcpu);
252 } else {
253 return (0);
254 }
255 }
256
257 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
258 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
259
260 int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
261
262 /*
263 * TCP timer processing.
264 *
265 * Each connection has 5 timers associated with it, which can be scheduled
266 * simultaneously. They all are serviced by one callout tcp_timer_enter().
267 * This function executes the next timer via tcp_timersw[] vector. Each
268 * timer is supposed to return 'true' unless the connection was destroyed.
269 * In the former case tcp_timer_enter() will schedule callout for next timer.
270 */
271
272 typedef bool tcp_timer_t(struct tcpcb *);
273 static tcp_timer_t tcp_timer_delack;
274 static tcp_timer_t tcp_timer_2msl;
275 static tcp_timer_t tcp_timer_keep;
276 static tcp_timer_t tcp_timer_persist;
277 static tcp_timer_t tcp_timer_rexmt;
278
279 static tcp_timer_t * const tcp_timersw[TT_N] = {
280 [TT_DELACK] = tcp_timer_delack,
281 [TT_REXMT] = tcp_timer_rexmt,
282 [TT_PERSIST] = tcp_timer_persist,
283 [TT_KEEP] = tcp_timer_keep,
284 [TT_2MSL] = tcp_timer_2msl,
285 };
286
287 /*
288 * tcp_output_locked() s a timer specific variation of call to tcp_output(),
289 * see tcp_var.h for the rest. It handles drop request from advanced stacks,
290 * but keeps tcpcb locked unless tcp_drop() destroyed it.
291 * Returns true if tcpcb is valid and locked.
292 */
293 static inline bool
tcp_output_locked(struct tcpcb * tp)294 tcp_output_locked(struct tcpcb *tp)
295 {
296 int rv;
297
298 INP_WLOCK_ASSERT(tptoinpcb(tp));
299
300 if ((rv = tp->t_fb->tfb_tcp_output(tp)) < 0) {
301 KASSERT(tp->t_fb->tfb_flags & TCP_FUNC_OUTPUT_CANDROP,
302 ("TCP stack %s requested tcp_drop(%p)",
303 tp->t_fb->tfb_tcp_block_name, tp));
304 tp = tcp_drop(tp, rv);
305 }
306
307 return (tp != NULL);
308 }
309
310 static bool
tcp_timer_delack(struct tcpcb * tp)311 tcp_timer_delack(struct tcpcb *tp)
312 {
313 struct epoch_tracker et;
314 #if defined(INVARIANTS) || defined(VIMAGE)
315 struct inpcb *inp = tptoinpcb(tp);
316 #endif
317 bool rv;
318
319 INP_WLOCK_ASSERT(inp);
320
321 CURVNET_SET(inp->inp_vnet);
322 tp->t_flags |= TF_ACKNOW;
323 TCPSTAT_INC(tcps_delack);
324 NET_EPOCH_ENTER(et);
325 rv = tcp_output_locked(tp);
326 NET_EPOCH_EXIT(et);
327 CURVNET_RESTORE();
328
329 return (rv);
330 }
331
332 static bool
tcp_timer_2msl(struct tcpcb * tp)333 tcp_timer_2msl(struct tcpcb *tp)
334 {
335 struct inpcb *inp = tptoinpcb(tp);
336 bool close = false;
337
338 INP_WLOCK_ASSERT(inp);
339
340 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
341 CURVNET_SET(inp->inp_vnet);
342 tcp_log_end_status(tp, TCP_EI_STATUS_2MSL);
343 tcp_free_sackholes(tp);
344 /*
345 * 2 MSL timeout in shutdown went off. If we're closed but
346 * still waiting for peer to close and connection has been idle
347 * too long delete connection control block. Otherwise, check
348 * again in a bit.
349 *
350 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
351 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
352 * Ignore fact that there were recent incoming segments.
353 *
354 * XXXGL: check if inp_socket shall always be !NULL here?
355 */
356 if (tp->t_state == TCPS_TIME_WAIT) {
357 close = true;
358 } else if (tp->t_state == TCPS_FIN_WAIT_2 &&
359 tcp_fast_finwait2_recycle && inp->inp_socket &&
360 (inp->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
361 TCPSTAT_INC(tcps_finwait2_drops);
362 close = true;
363 } else {
364 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp))
365 tcp_timer_activate(tp, TT_2MSL, TP_KEEPINTVL(tp));
366 else
367 close = true;
368 }
369 if (close) {
370 struct epoch_tracker et;
371
372 NET_EPOCH_ENTER(et);
373 tp = tcp_close(tp);
374 NET_EPOCH_EXIT(et);
375 }
376 CURVNET_RESTORE();
377
378 return (tp != NULL);
379 }
380
381 static bool
tcp_timer_keep(struct tcpcb * tp)382 tcp_timer_keep(struct tcpcb *tp)
383 {
384 struct epoch_tracker et;
385 struct inpcb *inp = tptoinpcb(tp);
386 struct tcptemp *t_template;
387
388 INP_WLOCK_ASSERT(inp);
389
390 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
391 CURVNET_SET(inp->inp_vnet);
392 /*
393 * Because we don't regularly reset the keepalive callout in
394 * the ESTABLISHED state, it may be that we don't actually need
395 * to send a keepalive yet. If that occurs, schedule another
396 * call for the next time the keepalive timer might expire.
397 */
398 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
399 u_int idletime;
400
401 idletime = ticks - tp->t_rcvtime;
402 if (idletime < TP_KEEPIDLE(tp)) {
403 tcp_timer_activate(tp, TT_KEEP,
404 TP_KEEPIDLE(tp) - idletime);
405 CURVNET_RESTORE();
406 return (true);
407 }
408 }
409
410 /*
411 * Keep-alive timer went off; send something
412 * or drop connection if idle for too long.
413 */
414 TCPSTAT_INC(tcps_keeptimeo);
415 if (tp->t_state < TCPS_ESTABLISHED)
416 goto dropit;
417 if ((V_tcp_always_keepalive ||
418 inp->inp_socket->so_options & SO_KEEPALIVE) &&
419 tp->t_state <= TCPS_CLOSING) {
420 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
421 goto dropit;
422 /*
423 * Send a packet designed to force a response
424 * if the peer is up and reachable:
425 * either an ACK if the connection is still alive,
426 * or an RST if the peer has closed the connection
427 * due to timeout or reboot.
428 * Using sequence number tp->snd_una-1
429 * causes the transmitted zero-length segment
430 * to lie outside the receive window;
431 * by the protocol spec, this requires the
432 * correspondent TCP to respond.
433 */
434 TCPSTAT_INC(tcps_keepprobe);
435 t_template = tcpip_maketemplate(inp);
436 if (t_template) {
437 NET_EPOCH_ENTER(et);
438 tcp_respond(tp, t_template->tt_ipgen,
439 &t_template->tt_t, (struct mbuf *)NULL,
440 tp->rcv_nxt, tp->snd_una - 1, 0);
441 NET_EPOCH_EXIT(et);
442 free(t_template, M_TEMP);
443 }
444 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINTVL(tp));
445 } else
446 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
447
448 CURVNET_RESTORE();
449 return (true);
450
451 dropit:
452 TCPSTAT_INC(tcps_keepdrops);
453 NET_EPOCH_ENTER(et);
454 tcp_log_end_status(tp, TCP_EI_STATUS_KEEP_MAX);
455 tp = tcp_drop(tp, ETIMEDOUT);
456 NET_EPOCH_EXIT(et);
457 CURVNET_RESTORE();
458
459 return (tp != NULL);
460 }
461
462 /*
463 * Has this session exceeded the maximum time without seeing a substantive
464 * acknowledgement? If so, return true; otherwise false.
465 */
466 static bool
tcp_maxunacktime_check(struct tcpcb * tp)467 tcp_maxunacktime_check(struct tcpcb *tp)
468 {
469
470 /* Are we tracking this timer for this session? */
471 if (TP_MAXUNACKTIME(tp) == 0)
472 return false;
473
474 /* Do we have a current measurement. */
475 if (tp->t_acktime == 0)
476 return false;
477
478 /* Are we within the acceptable range? */
479 if (TSTMP_GT(TP_MAXUNACKTIME(tp) + tp->t_acktime, (u_int)ticks))
480 return false;
481
482 /* We exceeded the timer. */
483 TCPSTAT_INC(tcps_progdrops);
484 return true;
485 }
486
487 static bool
tcp_timer_persist(struct tcpcb * tp)488 tcp_timer_persist(struct tcpcb *tp)
489 {
490 struct epoch_tracker et;
491 #if defined(INVARIANTS) || defined(VIMAGE)
492 struct inpcb *inp = tptoinpcb(tp);
493 #endif
494 bool progdrop, rv;
495
496 INP_WLOCK_ASSERT(inp);
497
498 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
499 CURVNET_SET(inp->inp_vnet);
500 /*
501 * Persistence timer into zero window.
502 * Force a byte to be output, if possible.
503 */
504 TCPSTAT_INC(tcps_persisttimeo);
505 /*
506 * Hack: if the peer is dead/unreachable, we do not
507 * time out if the window is closed. After a full
508 * backoff, drop the connection if the idle time
509 * (no responses to probes) reaches the maximum
510 * backoff that we would use if retransmitting.
511 * Also, drop the connection if we haven't been making
512 * progress.
513 */
514 progdrop = tcp_maxunacktime_check(tp);
515 if (progdrop || (tp->t_rxtshift >= V_tcp_retries &&
516 (ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
517 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff))) {
518 if (!progdrop)
519 TCPSTAT_INC(tcps_persistdrop);
520 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX);
521 goto dropit;
522 }
523 /*
524 * If the user has closed the socket then drop a persisting
525 * connection after a much reduced timeout.
526 */
527 if (tp->t_state > TCPS_CLOSE_WAIT &&
528 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
529 TCPSTAT_INC(tcps_persistdrop);
530 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX);
531 goto dropit;
532 }
533 tcp_setpersist(tp);
534 tp->t_flags |= TF_FORCEDATA;
535 NET_EPOCH_ENTER(et);
536 if ((rv = tcp_output_locked(tp)))
537 tp->t_flags &= ~TF_FORCEDATA;
538 NET_EPOCH_EXIT(et);
539 CURVNET_RESTORE();
540
541 return (rv);
542
543 dropit:
544 NET_EPOCH_ENTER(et);
545 tp = tcp_drop(tp, ETIMEDOUT);
546 NET_EPOCH_EXIT(et);
547 CURVNET_RESTORE();
548
549 return (tp != NULL);
550 }
551
552 static bool
tcp_timer_rexmt(struct tcpcb * tp)553 tcp_timer_rexmt(struct tcpcb *tp)
554 {
555 struct epoch_tracker et;
556 struct inpcb *inp = tptoinpcb(tp);
557 int rexmt;
558 bool isipv6, rv;
559
560 INP_WLOCK_ASSERT(inp);
561
562 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
563 CURVNET_SET(inp->inp_vnet);
564 tcp_free_sackholes(tp);
565 if (tp->t_fb->tfb_tcp_rexmit_tmr) {
566 /* The stack has a timer action too. */
567 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
568 }
569 /*
570 * Retransmission timer went off. Message has not
571 * been acked within retransmit interval. Back off
572 * to a longer retransmit interval and retransmit one segment.
573 *
574 * If we've either exceeded the maximum number of retransmissions,
575 * or we've gone long enough without making progress, then drop
576 * the session.
577 */
578 if (++tp->t_rxtshift > V_tcp_retries || tcp_maxunacktime_check(tp)) {
579 if (tp->t_rxtshift > V_tcp_retries)
580 TCPSTAT_INC(tcps_timeoutdrop);
581 tp->t_rxtshift = V_tcp_retries;
582 tcp_log_end_status(tp, TCP_EI_STATUS_RETRAN);
583 NET_EPOCH_ENTER(et);
584 tp = tcp_drop(tp, ETIMEDOUT);
585 NET_EPOCH_EXIT(et);
586 CURVNET_RESTORE();
587
588 return (tp != NULL);
589 }
590 if (tp->t_state == TCPS_SYN_SENT) {
591 /*
592 * If the SYN was retransmitted, indicate CWND to be
593 * limited to 1 segment in cc_conn_init().
594 */
595 tp->snd_cwnd = 1;
596 } else if (tp->t_rxtshift == 1) {
597 /*
598 * first retransmit; record ssthresh and cwnd so they can
599 * be recovered if this turns out to be a "bad" retransmit.
600 * A retransmit is considered "bad" if an ACK for this
601 * segment is received within RTT/2 interval; the assumption
602 * here is that the ACK was already in flight. See
603 * "On Estimating End-to-End Network Path Properties" by
604 * Allman and Paxson for more details.
605 */
606 tp->snd_cwnd_prev = tp->snd_cwnd;
607 tp->snd_ssthresh_prev = tp->snd_ssthresh;
608 tp->snd_recover_prev = tp->snd_recover;
609 if (IN_FASTRECOVERY(tp->t_flags))
610 tp->t_flags |= TF_WASFRECOVERY;
611 else
612 tp->t_flags &= ~TF_WASFRECOVERY;
613 if (IN_CONGRECOVERY(tp->t_flags))
614 tp->t_flags |= TF_WASCRECOVERY;
615 else
616 tp->t_flags &= ~TF_WASCRECOVERY;
617 if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
618 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
619 /* In the event that we've negotiated timestamps
620 * badrxtwin will be set to the value that we set
621 * the retransmitted packet's to_tsval to by tcp_output
622 */
623 tp->t_flags |= TF_PREVVALID;
624 } else
625 tp->t_flags &= ~TF_PREVVALID;
626 TCPSTAT_INC(tcps_rexmttimeo);
627 if ((tp->t_state == TCPS_SYN_SENT) ||
628 (tp->t_state == TCPS_SYN_RECEIVED))
629 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
630 else
631 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
632 TCPT_RANGESET(tp->t_rxtcur, rexmt,
633 tp->t_rttmin, TCPTV_REXMTMAX);
634
635 /*
636 * We enter the path for PLMTUD if connection is established or, if
637 * connection is FIN_WAIT_1 status, reason for the last is that if
638 * amount of data we send is very small, we could send it in couple of
639 * packets and process straight to FIN. In that case we won't catch
640 * ESTABLISHED state.
641 */
642 #ifdef INET6
643 isipv6 = (inp->inp_vflag & INP_IPV6) ? true : false;
644 #else
645 isipv6 = false;
646 #endif
647 if (((V_tcp_pmtud_blackhole_detect == 1) ||
648 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) ||
649 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) &&
650 ((tp->t_state == TCPS_ESTABLISHED) ||
651 (tp->t_state == TCPS_FIN_WAIT_1))) {
652 if (tp->t_rxtshift == 1) {
653 /*
654 * We enter blackhole detection after the first
655 * unsuccessful timer based retransmission.
656 * Then we reduce up to two times the MSS, each
657 * candidate giving two tries of retransmissions.
658 * But we give a candidate only two tries, if it
659 * actually reduces the MSS.
660 */
661 tp->t_blackhole_enter = 2;
662 tp->t_blackhole_exit = tp->t_blackhole_enter;
663 if (isipv6) {
664 #ifdef INET6
665 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss)
666 tp->t_blackhole_exit += 2;
667 if (tp->t_maxseg > V_tcp_v6mssdflt &&
668 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt)
669 tp->t_blackhole_exit += 2;
670 #endif
671 } else {
672 #ifdef INET
673 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss)
674 tp->t_blackhole_exit += 2;
675 if (tp->t_maxseg > V_tcp_mssdflt &&
676 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt)
677 tp->t_blackhole_exit += 2;
678 #endif
679 }
680 }
681 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
682 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
683 (tp->t_rxtshift >= tp->t_blackhole_enter &&
684 tp->t_rxtshift < tp->t_blackhole_exit &&
685 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) {
686 /*
687 * Enter Path MTU Black-hole Detection mechanism:
688 * - Disable Path MTU Discovery (IP "DF" bit).
689 * - Reduce MTU to lower value than what we
690 * negotiated with peer.
691 */
692 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
693 /* Record that we may have found a black hole. */
694 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
695 /* Keep track of previous MSS. */
696 tp->t_pmtud_saved_maxseg = tp->t_maxseg;
697 }
698
699 /*
700 * Reduce the MSS to blackhole value or to the default
701 * in an attempt to retransmit.
702 */
703 #ifdef INET6
704 if (isipv6 &&
705 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss &&
706 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) {
707 /* Use the sysctl tuneable blackhole MSS. */
708 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
709 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
710 } else if (isipv6) {
711 /* Use the default MSS. */
712 tp->t_maxseg = V_tcp_v6mssdflt;
713 /*
714 * Disable Path MTU Discovery when we switch to
715 * minmss.
716 */
717 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
718 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
719 }
720 #endif
721 #if defined(INET6) && defined(INET)
722 else
723 #endif
724 #ifdef INET
725 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss &&
726 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) {
727 /* Use the sysctl tuneable blackhole MSS. */
728 tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
729 TCPSTAT_INC(tcps_pmtud_blackhole_activated);
730 } else {
731 /* Use the default MSS. */
732 tp->t_maxseg = V_tcp_mssdflt;
733 /*
734 * Disable Path MTU Discovery when we switch to
735 * minmss.
736 */
737 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
738 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
739 }
740 #endif
741 /*
742 * Reset the slow-start flight size
743 * as it may depend on the new MSS.
744 */
745 if (CC_ALGO(tp)->conn_init != NULL)
746 CC_ALGO(tp)->conn_init(&tp->t_ccv);
747 } else {
748 /*
749 * If further retransmissions are still unsuccessful
750 * with a lowered MTU, maybe this isn't a blackhole and
751 * we restore the previous MSS and blackhole detection
752 * flags.
753 */
754 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
755 (tp->t_rxtshift >= tp->t_blackhole_exit)) {
756 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
757 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
758 tp->t_maxseg = tp->t_pmtud_saved_maxseg;
759 TCPSTAT_INC(tcps_pmtud_blackhole_failed);
760 /*
761 * Reset the slow-start flight size as it
762 * may depend on the new MSS.
763 */
764 if (CC_ALGO(tp)->conn_init != NULL)
765 CC_ALGO(tp)->conn_init(&tp->t_ccv);
766 }
767 }
768 }
769
770 /*
771 * Disable RFC1323 and SACK if we haven't got any response to
772 * our third SYN to work-around some broken terminal servers
773 * (most of which have hopefully been retired) that have bad VJ
774 * header compression code which trashes TCP segments containing
775 * unknown-to-them TCP options.
776 */
777 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
778 (tp->t_rxtshift == 3))
779 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
780 /*
781 * If we backed off this far, notify the L3 protocol that we're having
782 * connection problems.
783 */
784 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
785 #ifdef INET6
786 if ((inp->inp_vflag & INP_IPV6) != 0)
787 in6_losing(inp);
788 else
789 #endif
790 in_losing(inp);
791 }
792 tp->snd_nxt = tp->snd_una;
793 tp->snd_recover = tp->snd_max;
794 /*
795 * Force a segment to be sent.
796 */
797 tp->t_flags |= TF_ACKNOW;
798 /*
799 * If timing a segment in this window, stop the timer.
800 */
801 tp->t_rtttime = 0;
802
803 cc_cong_signal(tp, NULL, CC_RTO);
804 NET_EPOCH_ENTER(et);
805 rv = tcp_output_locked(tp);
806 NET_EPOCH_EXIT(et);
807 CURVNET_RESTORE();
808
809 return (rv);
810 }
811
812 static void
tcp_bblog_timer(struct tcpcb * tp,tt_which which,tt_what what,uint32_t ticks)813 tcp_bblog_timer(struct tcpcb *tp, tt_which which, tt_what what, uint32_t ticks)
814 {
815 struct tcp_log_buffer *lgb;
816 uint64_t ms;
817
818 INP_WLOCK_ASSERT(tptoinpcb(tp));
819 if (tcp_bblogging_on(tp))
820 lgb = tcp_log_event(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0,
821 NULL, false, NULL, NULL, 0, NULL);
822 else
823 lgb = NULL;
824 if (lgb != NULL) {
825 lgb->tlb_flex1 = (what << 8) | which;
826 if (what == TT_STARTING) {
827 /* Convert ticks to ms and store it in tlb_flex2. */
828 if (hz == 1000)
829 lgb->tlb_flex2 = ticks;
830 else {
831 ms = (((uint64_t)ticks * 1000) + (hz - 1)) / hz;
832 if (ms > UINT32_MAX)
833 lgb->tlb_flex2 = UINT32_MAX;
834 else
835 lgb->tlb_flex2 = (uint32_t)ms;
836 }
837 }
838 }
839 }
840
841 static inline tt_which
tcp_timer_next(struct tcpcb * tp,sbintime_t * precision)842 tcp_timer_next(struct tcpcb *tp, sbintime_t *precision)
843 {
844 tt_which i, rv;
845 sbintime_t after, before;
846
847 for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) {
848 if (tp->t_timers[i] < after) {
849 after = tp->t_timers[i];
850 rv = i;
851 }
852 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]);
853 }
854 if (precision != NULL)
855 *precision = before - after;
856
857 return (rv);
858 }
859
860 static void
tcp_timer_enter(void * xtp)861 tcp_timer_enter(void *xtp)
862 {
863 struct tcpcb *tp = xtp;
864 struct inpcb *inp = tptoinpcb(tp);
865 sbintime_t precision;
866 tt_which which;
867 bool tp_valid;
868
869 INP_WLOCK_ASSERT(inp);
870 MPASS((curthread->td_pflags & TDP_INTCPCALLOUT) == 0);
871
872 curthread->td_pflags |= TDP_INTCPCALLOUT;
873
874 which = tcp_timer_next(tp, NULL);
875 MPASS(which < TT_N);
876 tp->t_timers[which] = SBT_MAX;
877 tp->t_precisions[which] = 0;
878
879 tcp_bblog_timer(tp, which, TT_PROCESSING, 0);
880 tp_valid = tcp_timersw[which](tp);
881 if (tp_valid) {
882 tcp_bblog_timer(tp, which, TT_PROCESSED, 0);
883 if ((which = tcp_timer_next(tp, &precision)) != TT_N) {
884 callout_reset_sbt_on(&tp->t_callout,
885 tp->t_timers[which], precision, tcp_timer_enter,
886 tp, inp_to_cpuid(inp), C_ABSOLUTE);
887 }
888 INP_WUNLOCK(inp);
889 }
890
891 curthread->td_pflags &= ~TDP_INTCPCALLOUT;
892 }
893
894 /*
895 * Activate or stop (delta == 0) a TCP timer.
896 */
897 void
tcp_timer_activate(struct tcpcb * tp,tt_which which,u_int delta)898 tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta)
899 {
900 struct inpcb *inp = tptoinpcb(tp);
901 sbintime_t precision;
902 tt_what what;
903
904 #ifdef TCP_OFFLOAD
905 if (tp->t_flags & TF_TOE)
906 return;
907 #endif
908
909 INP_WLOCK_ASSERT(inp);
910
911 if (delta > 0) {
912 what = TT_STARTING;
913 callout_when(tick_sbt * delta, 0, C_HARDCLOCK,
914 &tp->t_timers[which], &tp->t_precisions[which]);
915 } else {
916 what = TT_STOPPING;
917 tp->t_timers[which] = SBT_MAX;
918 }
919 tcp_bblog_timer(tp, which, what, delta);
920
921 if ((which = tcp_timer_next(tp, &precision)) != TT_N)
922 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which],
923 precision, tcp_timer_enter, tp, inp_to_cpuid(inp),
924 C_ABSOLUTE);
925 else
926 callout_stop(&tp->t_callout);
927 }
928
929 bool
tcp_timer_active(struct tcpcb * tp,tt_which which)930 tcp_timer_active(struct tcpcb *tp, tt_which which)
931 {
932
933 INP_WLOCK_ASSERT(tptoinpcb(tp));
934
935 return (tp->t_timers[which] != SBT_MAX);
936 }
937
938 /*
939 * Stop all timers associated with tcpcb.
940 *
941 * Called only on tcpcb destruction. The tcpcb shall already be dropped from
942 * the pcb lookup database and socket is not losing the last reference.
943 *
944 * XXXGL: unfortunately our callout(9) is not able to fully stop a locked
945 * callout even when only two threads are involved: the callout itself and the
946 * thread that does callout_stop(). See where softclock_call_cc() swaps the
947 * callwheel lock to callout lock and then checks cc_exec_cancel(). This is
948 * the race window. If it happens, the tcp_timer_enter() won't be executed,
949 * however pcb lock will be locked and released, hence we can't free memory.
950 * Until callout(9) is improved, just keep retrying. In my profiling I've seen
951 * such event happening less than 1 time per hour with 20-30 Gbit/s of traffic.
952 */
953 void
tcp_timer_stop(struct tcpcb * tp)954 tcp_timer_stop(struct tcpcb *tp)
955 {
956 struct inpcb *inp = tptoinpcb(tp);
957
958 INP_WLOCK_ASSERT(inp);
959
960 if (curthread->td_pflags & TDP_INTCPCALLOUT) {
961 int stopped __diagused;
962
963 stopped = callout_stop(&tp->t_callout);
964 MPASS(stopped == 0);
965 } else while(__predict_false(callout_stop(&tp->t_callout) == 0)) {
966 INP_WUNLOCK(inp);
967 kern_yield(PRI_UNCHANGED);
968 INP_WLOCK(inp);
969 }
970 }
971