1 /*
2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved.
4 *
5 * This code is derived from software contributed to The DragonFly Project
6 * by Jeffrey M. Hsu.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 /*
35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
36 * The Regents of the University of California. All rights reserved.
37 *
38 * Redistribution and use in source and binary forms, with or without
39 * modification, are permitted provided that the following conditions
40 * are met:
41 * 1. Redistributions of source code must retain the above copyright
42 * notice, this list of conditions and the following disclaimer.
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice, this list of conditions and the following disclaimer in the
45 * documentation and/or other materials provided with the distribution.
46 * 3. Neither the name of the University nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
60 * SUCH DAMAGE.
61 *
62 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
63 * $FreeBSD: src/sys/netinet/tcp_timer.c,v 1.34.2.14 2003/02/03 02:33:41 hsu Exp $
64 */
65
66 #include "opt_inet6.h"
67 #include "opt_tcpdebug.h"
68
69 #include <sys/param.h>
70 #include <sys/systm.h>
71 #include <sys/kernel.h>
72 #include <sys/mbuf.h>
73 #include <sys/sysctl.h>
74 #include <sys/socket.h>
75 #include <sys/socketvar.h>
76 #include <sys/protosw.h>
77 #include <sys/thread.h>
78 #include <sys/globaldata.h>
79 #include <sys/thread2.h>
80 #include <sys/msgport2.h>
81
82 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
83
84 #include <net/route.h>
85 #include <net/netmsg2.h>
86
87 #include <netinet/in.h>
88 #include <netinet/in_systm.h>
89 #include <netinet/in_pcb.h>
90 #ifdef INET6
91 #include <netinet6/in6_pcb.h>
92 #endif
93 #include <netinet/ip_var.h>
94 #include <netinet/tcp.h>
95 #include <netinet/tcp_fsm.h>
96 #include <netinet/tcp_seq.h>
97 #include <netinet/tcp_timer.h>
98 #include <netinet/tcp_timer2.h>
99 #include <netinet/tcp_var.h>
100 #include <netinet/tcpip.h>
101 #ifdef TCPDEBUG
102 #include <netinet/tcp_debug.h>
103 #endif
104
105 #define TCP_TIMER_REXMT 0x01
106 #define TCP_TIMER_PERSIST 0x02
107 #define TCP_TIMER_KEEP 0x04
108 #define TCP_TIMER_2MSL 0x08
109 #define TCP_TIMER_DELACK 0x10
110
111 static struct tcpcb *tcp_timer_rexmt_handler(struct tcpcb *);
112 static struct tcpcb *tcp_timer_persist_handler(struct tcpcb *);
113 static struct tcpcb *tcp_timer_keep_handler(struct tcpcb *);
114 static struct tcpcb *tcp_timer_2msl_handler(struct tcpcb *);
115 static struct tcpcb *tcp_timer_delack_handler(struct tcpcb *);
116
117 static const struct tcp_timer {
118 uint32_t tt_task;
119 struct tcpcb *(*tt_handler)(struct tcpcb *);
120 } tcp_timer_handlers[] = {
121 { TCP_TIMER_DELACK, tcp_timer_delack_handler },
122 { TCP_TIMER_REXMT, tcp_timer_rexmt_handler },
123 { TCP_TIMER_PERSIST, tcp_timer_persist_handler },
124 { TCP_TIMER_KEEP, tcp_timer_keep_handler },
125 { TCP_TIMER_2MSL, tcp_timer_2msl_handler },
126 { 0, NULL }
127 };
128
129 static int
sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS)130 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS)
131 {
132 int error, s, tt;
133
134 tt = *(int *)oidp->oid_arg1;
135 s = (int)((int64_t)tt * 1000 / hz);
136
137 error = sysctl_handle_int(oidp, &s, 0, req);
138 if (error || !req->newptr)
139 return (error);
140
141 tt = (int)((int64_t)s * hz / 1000);
142 if (tt < 1)
143 return (EINVAL);
144
145 *(int *)oidp->oid_arg1 = tt;
146 return (0);
147 }
148
149 int tcp_keepinit;
150 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
151 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "Time to establish TCP connection");
152
153 int tcp_keepidle;
154 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
155 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "Time before TCP keepalive probes begin");
156
157 int tcp_keepintvl;
158 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
159 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "Time between TCP keepalive probes");
160
161 int tcp_delacktime;
162 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
163 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
164 "Time before a delayed ACK is sent");
165
166 int tcp_msl;
167 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
168 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
169
170 int tcp_rexmit_min;
171 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
172 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout");
173
174 int tcp_rexmit_slop;
175 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
176 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
177 "Retransmission Timer Slop");
178
179 static int always_keepalive = 1;
180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
181 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
182
183 /* max idle probes */
184 int tcp_keepcnt = TCPTV_KEEPCNT;
185 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW,
186 &tcp_keepcnt, 0, "Maximum number of keepalive probes to be sent");
187
188 static int tcp_do_eifel_response = 1;
189 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel_response, CTLFLAG_RW,
190 &tcp_do_eifel_response, 0, "Eifel response algorithm (RFC 4015)");
191
192 int tcp_eifel_rtoinc = 2;
193 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, eifel_rtoinc, CTLTYPE_INT|CTLFLAG_RW,
194 &tcp_eifel_rtoinc, 0, sysctl_msec_to_ticks, "I",
195 "Eifel response RTO increment");
196
197 /* max idle time in persist */
198 int tcp_maxpersistidle;
199
200 /*
201 * Cancel all timers for TCP tp.
202 */
203 void
tcp_canceltimers(struct tcpcb * tp)204 tcp_canceltimers(struct tcpcb *tp)
205 {
206 tcp_callout_stop(tp, tp->tt_2msl);
207 tcp_callout_stop(tp, tp->tt_persist);
208 tcp_callout_stop(tp, tp->tt_keep);
209 tcp_callout_stop(tp, tp->tt_rexmt);
210 }
211
212 /*
213 * Caller should be in critical section
214 */
215 static void
tcp_send_timermsg(struct tcpcb * tp,uint32_t task)216 tcp_send_timermsg(struct tcpcb *tp, uint32_t task)
217 {
218 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
219
220 KKASSERT(tmsg != NULL && tmsg->tt_cpuid == mycpuid &&
221 tmsg->tt_tcb != NULL);
222
223 tmsg->tt_tasks |= task;
224 if (tmsg->tt_msg.lmsg.ms_flags & MSGF_DONE)
225 lwkt_sendmsg_oncpu(tmsg->tt_msgport, &tmsg->tt_msg.lmsg);
226 }
227
228 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
229 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
230
231 int tcp_syn_backoff_low[TCP_MAXRXTSHIFT + 1] =
232 { 1, 1, 2, 4, 8, 8, 16, 16, 32, 64, 64, 64, 64 };
233
234 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
235 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
236
237 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
238
239 /* Caller should be in critical section */
240 static struct tcpcb *
tcp_timer_delack_handler(struct tcpcb * tp)241 tcp_timer_delack_handler(struct tcpcb *tp)
242 {
243 tp->t_flags |= TF_ACKNOW;
244 tcpstat.tcps_delack++;
245 tcp_output(tp);
246 return tp;
247 }
248
249 /*
250 * TCP timer processing.
251 */
252 void
tcp_timer_delack(void * xtp)253 tcp_timer_delack(void *xtp)
254 {
255 struct tcpcb *tp = xtp;
256 struct callout *co = &tp->tt_delack->tc_callout;
257
258 crit_enter();
259 if (callout_pending(co) || !callout_active(co)) {
260 crit_exit();
261 return;
262 }
263 callout_deactivate(co);
264 tcp_send_timermsg(tp, TCP_TIMER_DELACK);
265 crit_exit();
266 }
267
268 /* Caller should be in critical section */
269 static struct tcpcb *
tcp_timer_2msl_handler(struct tcpcb * tp)270 tcp_timer_2msl_handler(struct tcpcb *tp)
271 {
272 #ifdef TCPDEBUG
273 int ostate;
274 #endif
275
276 #ifdef TCPDEBUG
277 ostate = tp->t_state;
278 #endif
279 /*
280 * 2 MSL timeout in shutdown went off. If we're closed but
281 * still waiting for peer to close and connection has been idle
282 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
283 * control block. Otherwise, check again in a bit.
284 */
285 if (tp->t_state != TCPS_TIME_WAIT &&
286 (ticks - tp->t_rcvtime) <= tp->t_maxidle) {
287 tcp_callout_reset(tp, tp->tt_2msl, tp->t_keepintvl,
288 tcp_timer_2msl);
289 } else {
290 tp = tcp_close(tp);
291 }
292
293 #ifdef TCPDEBUG
294 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
295 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
296 #endif
297 return tp;
298 }
299
300 void
tcp_timer_2msl(void * xtp)301 tcp_timer_2msl(void *xtp)
302 {
303 struct tcpcb *tp = xtp;
304 struct callout *co = &tp->tt_2msl->tc_callout;
305
306 crit_enter();
307 if (callout_pending(co) || !callout_active(co)) {
308 crit_exit();
309 return;
310 }
311 callout_deactivate(co);
312 tcp_send_timermsg(tp, TCP_TIMER_2MSL);
313 crit_exit();
314 }
315
316 /* Caller should be in critical section */
317 static struct tcpcb *
tcp_timer_keep_handler(struct tcpcb * tp)318 tcp_timer_keep_handler(struct tcpcb *tp)
319 {
320 struct tcptemp *t_template;
321 #ifdef TCPDEBUG
322 int ostate = tp->t_state;
323 #endif
324
325 /*
326 * Keep-alive timer went off; send something
327 * or drop connection if idle for too long.
328 */
329 tcpstat.tcps_keeptimeo++;
330 if (tp->t_state < TCPS_ESTABLISHED)
331 goto dropit;
332 if ((always_keepalive || (tp->t_flags & TF_KEEPALIVE) ||
333 (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE)) &&
334 tp->t_state <= TCPS_CLOSING) {
335 if ((ticks - tp->t_rcvtime) >= tp->t_keepidle + tp->t_maxidle)
336 goto dropit;
337 /*
338 * Send a packet designed to force a response
339 * if the peer is up and reachable:
340 * either an ACK if the connection is still alive,
341 * or an RST if the peer has closed the connection
342 * due to timeout or reboot.
343 * Using sequence number tp->snd_una-1
344 * causes the transmitted zero-length segment
345 * to lie outside the receive window;
346 * by the protocol spec, this requires the
347 * correspondent TCP to respond.
348 */
349 tcpstat.tcps_keepprobe++;
350 t_template = tcp_maketemplate(tp);
351 if (t_template) {
352 tcp_respond(tp, t_template->tt_ipgen,
353 &t_template->tt_t, NULL,
354 tp->rcv_nxt, tp->snd_una - 1, 0);
355 tcp_freetemplate(t_template);
356 }
357 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepintvl,
358 tcp_timer_keep);
359 } else {
360 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle,
361 tcp_timer_keep);
362 }
363
364 #ifdef TCPDEBUG
365 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
366 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
367 #endif
368 return tp;
369
370 dropit:
371 tcpstat.tcps_keepdrops++;
372 tp = tcp_drop(tp, ETIMEDOUT);
373
374 #ifdef TCPDEBUG
375 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
376 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
377 #endif
378 return tp;
379 }
380
381 void
tcp_timer_keep(void * xtp)382 tcp_timer_keep(void *xtp)
383 {
384 struct tcpcb *tp = xtp;
385 struct callout *co = &tp->tt_keep->tc_callout;
386
387 crit_enter();
388 if (callout_pending(co) || !callout_active(co)) {
389 crit_exit();
390 return;
391 }
392 callout_deactivate(co);
393 tcp_send_timermsg(tp, TCP_TIMER_KEEP);
394 crit_exit();
395 }
396
397 /* Caller should be in critical section */
398 static struct tcpcb *
tcp_timer_persist_handler(struct tcpcb * tp)399 tcp_timer_persist_handler(struct tcpcb *tp)
400 {
401 #ifdef TCPDEBUG
402 int ostate;
403 #endif
404
405 #ifdef TCPDEBUG
406 ostate = tp->t_state;
407 #endif
408 /*
409 * Persistance timer into zero window.
410 * Force a byte to be output, if possible.
411 */
412 tcpstat.tcps_persisttimeo++;
413 /*
414 * Hack: if the peer is dead/unreachable, we do not
415 * time out if the window is closed. After a full
416 * backoff, drop the connection if the idle time
417 * (no responses to probes) reaches the maximum
418 * backoff that we would use if retransmitting.
419 */
420 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
421 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
422 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
423 tcpstat.tcps_persistdrop++;
424 tp = tcp_drop(tp, ETIMEDOUT);
425 goto out;
426 }
427 tcp_setpersist(tp);
428 tp->t_flags |= TF_FORCE;
429 tcp_output(tp);
430 tp->t_flags &= ~TF_FORCE;
431
432 out:
433 #ifdef TCPDEBUG
434 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
435 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
436 #endif
437 return tp;
438 }
439
440 void
tcp_timer_persist(void * xtp)441 tcp_timer_persist(void *xtp)
442 {
443 struct tcpcb *tp = xtp;
444 struct callout *co = &tp->tt_persist->tc_callout;
445
446 crit_enter();
447 if (callout_pending(co) || !callout_active(co)){
448 crit_exit();
449 return;
450 }
451 callout_deactivate(co);
452 tcp_send_timermsg(tp, TCP_TIMER_PERSIST);
453 crit_exit();
454 }
455
456 void
tcp_save_congestion_state(struct tcpcb * tp)457 tcp_save_congestion_state(struct tcpcb *tp)
458 {
459 /*
460 * Record connection's current states so that they could be
461 * recovered, if this turns out to be a spurious retransmit.
462 */
463 tp->snd_cwnd_prev = tp->snd_cwnd;
464 tp->snd_wacked_prev = tp->snd_wacked;
465 tp->snd_ssthresh_prev = tp->snd_ssthresh;
466 tp->snd_recover_prev = tp->snd_recover;
467
468 /*
469 * State for Eifel response after spurious timeout retransmit
470 * is detected. We save the current value of snd_max even if
471 * we are called from fast retransmit code, so if RTO needs
472 * rebase, it will be rebased using the RTT of segment that
473 * is not sent during possible congestion.
474 */
475 tp->snd_max_prev = tp->snd_max;
476
477 if (IN_FASTRECOVERY(tp))
478 tp->rxt_flags |= TRXT_F_WASFRECOVERY;
479 else
480 tp->rxt_flags &= ~TRXT_F_WASFRECOVERY;
481 if (tp->t_flags & TF_RCVD_TSTMP) {
482 /* States for Eifel detection */
483 tp->t_rexmtTS = ticks;
484 tp->rxt_flags |= TRXT_F_FIRSTACCACK;
485 }
486 #ifdef later
487 tcp_sack_save_scoreboard(&tp->scb);
488 #endif
489 }
490
491 void
tcp_revert_congestion_state(struct tcpcb * tp)492 tcp_revert_congestion_state(struct tcpcb *tp)
493 {
494 tp->snd_cwnd = tp->snd_cwnd_prev;
495 tp->snd_wacked = tp->snd_wacked_prev;
496 tp->snd_ssthresh = tp->snd_ssthresh_prev;
497 tp->snd_recover = tp->snd_recover_prev;
498 if (tp->rxt_flags & TRXT_F_WASFRECOVERY)
499 ENTER_FASTRECOVERY(tp);
500 if (tp->rxt_flags & TRXT_F_FASTREXMT) {
501 ++tcpstat.tcps_sndfastrexmitbad;
502 if (tp->rxt_flags & TRXT_F_EARLYREXMT)
503 ++tcpstat.tcps_sndearlyrexmitbad;
504 } else {
505 ++tcpstat.tcps_sndrtobad;
506 tp->snd_last = ticks;
507 if (tcp_do_eifel_response)
508 tp->rxt_flags |= TRXT_F_REBASERTO;
509 }
510 tp->t_badrxtwin = 0;
511 tp->t_rxtshift = 0;
512 tp->snd_nxt = tp->snd_max;
513 #ifdef later
514 tcp_sack_revert_scoreboard(&tp->scb, tp->snd_una);
515 #endif
516 }
517
518 /* Caller should be in critical section */
519 static struct tcpcb *
tcp_timer_rexmt_handler(struct tcpcb * tp)520 tcp_timer_rexmt_handler(struct tcpcb *tp)
521 {
522 int rexmt;
523 #ifdef TCPDEBUG
524 int ostate;
525 #endif
526
527 #ifdef TCPDEBUG
528 ostate = tp->t_state;
529 #endif
530 /*
531 * Retransmission timer went off. Message has not
532 * been acked within retransmit interval. Back off
533 * to a longer retransmit interval and retransmit one segment.
534 */
535 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
536 tp->t_rxtshift = TCP_MAXRXTSHIFT;
537 tcpstat.tcps_timeoutdrop++;
538 tp = tcp_drop(tp, tp->t_softerror ?
539 tp->t_softerror : ETIMEDOUT);
540 goto out;
541 }
542 if (tp->t_rxtshift == 1) {
543 /*
544 * First retransmit.
545 */
546
547 /*
548 * State for "RTT based spurious timeout retransmit detection"
549 *
550 * RTT based spurious timeout retransmit detection:
551 * A retransmit is considered spurious if an ACK for this
552 * segment is received within RTT/2 interval; the assumption
553 * here is that the ACK was already in flight. See
554 * "On Estimating End-to-End Network Path Properties" by
555 * Allman and Paxson for more details.
556 */
557 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
558
559 /*
560 * States for Eifel response after spurious timeout retransmit
561 * is detected.
562 */
563 tp->t_rxtcur_prev = tp->t_rxtcur;
564 tp->t_srtt_prev = tp->t_srtt +
565 (tcp_eifel_rtoinc << TCP_RTT_SHIFT);
566 tp->t_rttvar_prev = tp->t_rttvar;
567
568 tcp_save_congestion_state(tp);
569 tp->rxt_flags &= ~(TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT |
570 TRXT_F_REBASERTO);
571 }
572 if (tp->t_state == TCPS_SYN_SENT || tp->t_state == TCPS_SYN_RECEIVED) {
573 /*
574 * Record the time that we spent in SYN or SYN|ACK
575 * retransmition.
576 *
577 * Needed by RFC3390 and RFC6298.
578 */
579 tp->t_rxtsyn += tp->t_rxtcur;
580 }
581 /* Throw away SACK blocks on a RTO, as specified by RFC2018. */
582 tcp_sack_discard(tp);
583 tcpstat.tcps_rexmttimeo++;
584 if (tp->t_state == TCPS_SYN_SENT) {
585 if (tcp_low_rtobase) {
586 rexmt = TCP_REXMTVAL(tp) *
587 tcp_syn_backoff_low[tp->t_rxtshift];
588 } else {
589 rexmt = TCP_REXMTVAL(tp) *
590 tcp_syn_backoff[tp->t_rxtshift];
591 }
592 } else {
593 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
594 }
595 TCPT_RANGESET(tp->t_rxtcur, rexmt,
596 tp->t_rttmin, TCPTV_REXMTMAX);
597 /*
598 * If losing, let the lower level know and try for
599 * a better route. Also, if we backed off this far,
600 * our srtt estimate is probably bogus. Clobber it
601 * so we'll take the next rtt measurement as our srtt;
602 * move the current srtt into rttvar to keep the current
603 * retransmit times until then.
604 */
605 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
606 #ifdef INET6
607 if (INP_ISIPV6(tp->t_inpcb))
608 in6_losing(tp->t_inpcb);
609 else
610 #endif
611 in_losing(tp->t_inpcb);
612 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
613 tp->t_srtt = 0;
614 }
615 tp->snd_nxt = tp->snd_una;
616 tp->snd_recover = tp->snd_max;
617 /*
618 * Force a segment to be sent.
619 */
620 tp->t_flags |= TF_ACKNOW;
621 /*
622 * If timing a segment in this window, stop the timer.
623 */
624 tp->t_rtttime = 0;
625 /*
626 * Close the congestion window down to one segment
627 * (we'll open it by one segment for each ack we get).
628 * Since we probably have a window's worth of unacked
629 * data accumulated, this "slow start" keeps us from
630 * dumping all that data as back-to-back packets (which
631 * might overwhelm an intermediate gateway).
632 *
633 * There are two phases to the opening: Initially we
634 * open by one mss on each ack. This makes the window
635 * size increase exponentially with time. If the
636 * window is larger than the path can handle, this
637 * exponential growth results in dropped packet(s)
638 * almost immediately. To get more time between
639 * drops but still "push" the network to take advantage
640 * of improving conditions, we switch from exponential
641 * to linear window opening at some threshhold size.
642 * For a threshhold, we use half the current window
643 * size, truncated to a multiple of the mss.
644 *
645 * (the minimum cwnd that will give us exponential
646 * growth is 2 mss. We don't allow the threshhold
647 * to go below this.)
648 */
649 {
650 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
651
652 if (win < 2)
653 win = 2;
654 tp->snd_cwnd = tp->t_maxseg;
655 tp->snd_wacked = 0;
656 tp->snd_ssthresh = win * tp->t_maxseg;
657 tp->t_dupacks = 0;
658 }
659 EXIT_FASTRECOVERY(tp);
660 tcp_output(tp);
661
662 out:
663 #ifdef TCPDEBUG
664 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
665 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
666 #endif
667 return tp;
668 }
669
670 void
tcp_timer_rexmt(void * xtp)671 tcp_timer_rexmt(void *xtp)
672 {
673 struct tcpcb *tp = xtp;
674 struct callout *co = &tp->tt_rexmt->tc_callout;
675
676 crit_enter();
677 if (callout_pending(co) || !callout_active(co)) {
678 crit_exit();
679 return;
680 }
681 callout_deactivate(co);
682 tcp_send_timermsg(tp, TCP_TIMER_REXMT);
683 crit_exit();
684 }
685
686 static void
tcp_timer_handler(netmsg_t msg)687 tcp_timer_handler(netmsg_t msg)
688 {
689 struct netmsg_tcp_timer *tmsg = (struct netmsg_tcp_timer *)msg;
690 const struct tcp_timer *tt;
691 struct tcpcb *tp;
692
693 crit_enter();
694
695 KKASSERT(tmsg->tt_cpuid == mycpuid && tmsg->tt_tcb != NULL);
696 tp = tmsg->tt_tcb;
697
698 /* Save pending tasks and reset the tasks in message */
699 tmsg->tt_running_tasks = tmsg->tt_tasks;
700 tmsg->tt_prev_tasks = tmsg->tt_tasks;
701 tmsg->tt_tasks = 0;
702
703 /* Reply ASAP */
704 lwkt_replymsg(&tmsg->tt_msg.lmsg, 0);
705
706 if (tmsg->tt_running_tasks == 0) {
707 /*
708 * All of the timers are cancelled when the message
709 * is pending; bail out.
710 */
711 crit_exit();
712 return;
713 }
714
715 for (tt = tcp_timer_handlers; tt->tt_handler != NULL; ++tt) {
716 if ((tmsg->tt_running_tasks & tt->tt_task) == 0)
717 continue;
718
719 tmsg->tt_running_tasks &= ~tt->tt_task;
720 tp = tt->tt_handler(tp);
721 if (tp == NULL)
722 break;
723
724 if (tmsg->tt_running_tasks == 0) /* nothing left to do */
725 break;
726 }
727
728 crit_exit();
729 }
730
731 void
tcp_create_timermsg(struct tcpcb * tp,struct lwkt_port * msgport)732 tcp_create_timermsg(struct tcpcb *tp, struct lwkt_port *msgport)
733 {
734 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
735
736 netmsg_init(&tmsg->tt_msg, NULL, &netisr_adone_rport,
737 MSGF_DROPABLE | MSGF_PRIORITY, tcp_timer_handler);
738 tmsg->tt_cpuid = mycpuid;
739 tmsg->tt_msgport = msgport;
740 tmsg->tt_tcb = tp;
741 tmsg->tt_tasks = 0;
742 }
743
744 void
tcp_destroy_timermsg(struct tcpcb * tp)745 tcp_destroy_timermsg(struct tcpcb *tp)
746 {
747 struct netmsg_tcp_timer *tmsg = tp->tt_msg;
748
749 if (tmsg == NULL || /* listen socket */
750 tmsg->tt_tcb == NULL) /* only tcp_attach() is called */
751 return;
752
753 KKASSERT(tmsg->tt_cpuid == mycpuid);
754
755 /*
756 * This message is still pending to be processed;
757 * drop it. Optimized.
758 */
759 crit_enter();
760 if ((tmsg->tt_msg.lmsg.ms_flags & MSGF_DONE) == 0) {
761 lwkt_dropmsg(&tmsg->tt_msg.lmsg);
762 }
763 crit_exit();
764 }
765
766 static __inline void
tcp_callout_init(struct tcp_callout * tc,uint32_t task)767 tcp_callout_init(struct tcp_callout *tc, uint32_t task)
768 {
769 callout_init_mp(&tc->tc_callout);
770 tc->tc_task = task;
771 }
772
773 void
tcp_inittimers(struct tcpcb * tp)774 tcp_inittimers(struct tcpcb *tp)
775 {
776 tcp_callout_init(tp->tt_rexmt, TCP_TIMER_REXMT);
777 tcp_callout_init(tp->tt_persist, TCP_TIMER_PERSIST);
778 tcp_callout_init(tp->tt_keep, TCP_TIMER_KEEP);
779 tcp_callout_init(tp->tt_2msl, TCP_TIMER_2MSL);
780 tcp_callout_init(tp->tt_delack, TCP_TIMER_DELACK);
781 }
782