1 /*
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
34 * $FreeBSD$
35 */
36
37 #include "opt_compat.h"
38 #include "opt_inet6.h"
39 #include "opt_tcpdebug.h"
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/kernel.h>
44 #include <sys/mbuf.h>
45 #include <sys/sysctl.h>
46 #include <sys/socket.h>
47 #include <sys/socketvar.h>
48 #include <sys/protosw.h>
49
50 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
51
52 #include <net/route.h>
53
54 #include <netinet/in.h>
55 #include <netinet/in_systm.h>
56 #include <netinet/in_pcb.h>
57 #ifdef INET6
58 #include <netinet6/in6_pcb.h>
59 #endif
60 #include <netinet/ip_var.h>
61 #include <netinet/tcp.h>
62 #include <netinet/tcp_fsm.h>
63 #include <netinet/tcp_seq.h>
64 #include <netinet/tcp_timer.h>
65 #include <netinet/tcp_var.h>
66 #include <netinet/tcpip.h>
67 #ifdef TCPDEBUG
68 #include <netinet/tcp_debug.h>
69 #endif
70
71 static int
72 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS)
73 {
74 int error, s, tt;
75
76 tt = *(int *)oidp->oid_arg1;
77 s = (int)((int64_t)tt * 1000 / hz);
78
79 error = sysctl_handle_int(oidp, &s, 0, req);
80 if (error || !req->newptr)
81 return (error);
82
83 tt = (int)((int64_t)s * hz / 1000);
84 if (tt < 1)
85 return (EINVAL);
86
87 *(int *)oidp->oid_arg1 = tt;
88 return (0);
89 }
90
91 int tcp_keepinit;
92 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
93 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "");
94
95 int tcp_keepidle;
96 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
97 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "");
98
99 int tcp_keepintvl;
100 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
101 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "");
102
103 int tcp_delacktime;
104 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
105 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
106 "Time before a delayed ACK is sent");
107
108 int tcp_msl;
109 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
110 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
111
112 int tcp_rexmit_min;
113 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
114 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout");
115
116 int tcp_rexmit_slop;
117 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
118 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", "Retransmission Timer Slop");
119
120 static int always_keepalive = 0;
121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
122 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
123
124 static int tcp_keepcnt = TCPTV_KEEPCNT;
125 /* max idle probes */
126 int tcp_maxpersistidle;
127 /* max idle time in persist */
128 int tcp_maxidle;
129
130 /*
131 * Tcp protocol timeout routine called every 500 ms.
132 * Updates timestamps used for TCP
133 * causes finite state machine actions if timers expire.
134 */
135 void
136 tcp_slowtimo()
137 {
138 int s;
139
140 s = splnet();
141
142 tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
143
144 splx(s);
145 }
146
147 /*
148 * Cancel all timers for TCP tp.
149 */
150 void
151 tcp_canceltimers(tp)
152 struct tcpcb *tp;
153 {
154 callout_stop(tp->tt_2msl);
155 callout_stop(tp->tt_persist);
156 callout_stop(tp->tt_keep);
157 callout_stop(tp->tt_rexmt);
158 }
159
160 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
161 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
162
163 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
164 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
165
166 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
167
168 /*
169 * TCP timer processing.
170 */
171 void
172 tcp_timer_delack(xtp)
173 void *xtp;
174 {
175 struct tcpcb *tp = xtp;
176 int s;
177
178 s = splnet();
179 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) {
180 splx(s);
181 return;
182 }
183 callout_deactivate(tp->tt_delack);
184
185 tp->t_flags |= TF_ACKNOW;
186 tcpstat.tcps_delack++;
187 (void) tcp_output(tp);
188 splx(s);
189 }
190
191 void
192 tcp_timer_2msl(xtp)
193 void *xtp;
194 {
195 struct tcpcb *tp = xtp;
196 int s;
197 #ifdef TCPDEBUG
198 int ostate;
199
200 ostate = tp->t_state;
201 #endif
202 s = splnet();
203 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) {
204 splx(s);
205 return;
206 }
207 callout_deactivate(tp->tt_2msl);
208 /*
209 * 2 MSL timeout in shutdown went off. If we're closed but
210 * still waiting for peer to close and connection has been idle
211 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
212 * control block. Otherwise, check again in a bit.
213 */
214 if (tp->t_state != TCPS_TIME_WAIT &&
215 (ticks - tp->t_rcvtime) <= tcp_maxidle)
216 callout_reset(tp->tt_2msl, tcp_keepintvl,
217 tcp_timer_2msl, tp);
218 else
219 tp = tcp_close(tp);
220
221 #ifdef TCPDEBUG
222 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
223 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
224 PRU_SLOWTIMO);
225 #endif
226 splx(s);
227 }
228
229 void
230 tcp_timer_keep(xtp)
231 void *xtp;
232 {
233 struct tcpcb *tp = xtp;
234 struct tcptemp *t_template;
235 int s;
236 #ifdef TCPDEBUG
237 int ostate;
238
239 ostate = tp->t_state;
240 #endif
241 s = splnet();
242 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) {
243 splx(s);
244 return;
245 }
246 callout_deactivate(tp->tt_keep);
247 /*
248 * Keep-alive timer went off; send something
249 * or drop connection if idle for too long.
250 */
251 tcpstat.tcps_keeptimeo++;
252 if (tp->t_state < TCPS_ESTABLISHED)
253 goto dropit;
254 if ((always_keepalive ||
255 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&
256 tp->t_state <= TCPS_CLOSING) {
257 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle)
258 goto dropit;
259 /*
260 * Send a packet designed to force a response
261 * if the peer is up and reachable:
262 * either an ACK if the connection is still alive,
263 * or an RST if the peer has closed the connection
264 * due to timeout or reboot.
265 * Using sequence number tp->snd_una-1
266 * causes the transmitted zero-length segment
267 * to lie outside the receive window;
268 * by the protocol spec, this requires the
269 * correspondent TCP to respond.
270 */
271 tcpstat.tcps_keepprobe++;
272 t_template = tcp_maketemplate(tp);
273 if (t_template) {
274 tcp_respond(tp, t_template->tt_ipgen,
275 &t_template->tt_t, (struct mbuf *)NULL,
276 tp->rcv_nxt, tp->snd_una - 1, 0);
277 (void) m_free(dtom(t_template));
278 }
279 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp);
280 } else
281 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
282
283 #ifdef TCPDEBUG
284 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
285 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
286 PRU_SLOWTIMO);
287 #endif
288 splx(s);
289 return;
290
291 dropit:
292 tcpstat.tcps_keepdrops++;
293 tp = tcp_drop(tp, ETIMEDOUT);
294
295 #ifdef TCPDEBUG
296 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
297 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
298 PRU_SLOWTIMO);
299 #endif
300 splx(s);
301 }
302
303 void
304 tcp_timer_persist(xtp)
305 void *xtp;
306 {
307 struct tcpcb *tp = xtp;
308 int s;
309 #ifdef TCPDEBUG
310 int ostate;
311
312 ostate = tp->t_state;
313 #endif
314 s = splnet();
315 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){
316 splx(s);
317 return;
318 }
319 callout_deactivate(tp->tt_persist);
320 /*
321 * Persistance timer into zero window.
322 * Force a byte to be output, if possible.
323 */
324 tcpstat.tcps_persisttimeo++;
325 /*
326 * Hack: if the peer is dead/unreachable, we do not
327 * time out if the window is closed. After a full
328 * backoff, drop the connection if the idle time
329 * (no responses to probes) reaches the maximum
330 * backoff that we would use if retransmitting.
331 */
332 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
333 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
334 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
335 tcpstat.tcps_persistdrop++;
336 tp = tcp_drop(tp, ETIMEDOUT);
337 goto out;
338 }
339 tcp_setpersist(tp);
340 tp->t_force = 1;
341 (void) tcp_output(tp);
342 tp->t_force = 0;
343
344 out:
345 #ifdef TCPDEBUG
346 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
347 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
348 PRU_SLOWTIMO);
349 #endif
350 splx(s);
351 }
352
353 void
354 tcp_timer_rexmt(xtp)
355 void *xtp;
356 {
357 struct tcpcb *tp = xtp;
358 int s;
359 int rexmt;
360 #ifdef TCPDEBUG
361 int ostate;
362
363 ostate = tp->t_state;
364 #endif
365 s = splnet();
366 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) {
367 splx(s);
368 return;
369 }
370 callout_deactivate(tp->tt_rexmt);
371 /*
372 * Retransmission timer went off. Message has not
373 * been acked within retransmit interval. Back off
374 * to a longer retransmit interval and retransmit one segment.
375 */
376 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
377 tp->t_rxtshift = TCP_MAXRXTSHIFT;
378 tcpstat.tcps_timeoutdrop++;
379 tp = tcp_drop(tp, tp->t_softerror ?
380 tp->t_softerror : ETIMEDOUT);
381 goto out;
382 }
383 if (tp->t_rxtshift == 1) {
384 /*
385 * first retransmit; record ssthresh and cwnd so they can
386 * be recovered if this turns out to be a "bad" retransmit.
387 * A retransmit is considered "bad" if an ACK for this
388 * segment is received within RTT/2 interval; the assumption
389 * here is that the ACK was already in flight. See
390 * "On Estimating End-to-End Network Path Properties" by
391 * Allman and Paxson for more details.
392 */
393 tp->snd_cwnd_prev = tp->snd_cwnd;
394 tp->snd_ssthresh_prev = tp->snd_ssthresh;
395 tp->snd_high_prev = tp->snd_high;
396 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
397 }
398 tcpstat.tcps_rexmttimeo++;
399 if (tp->t_state == TCPS_SYN_SENT)
400 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift];
401 else
402 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
403 TCPT_RANGESET(tp->t_rxtcur, rexmt,
404 tp->t_rttmin, TCPTV_REXMTMAX);
405 /*
406 * Disable rfc1323 and rfc1644 if we havn't got any response to
407 * our third SYN to work-around some broken terminal servers
408 * (most of which have hopefully been retired) that have bad VJ
409 * header compression code which trashes TCP segments containing
410 * unknown-to-them TCP options.
411 */
412 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3))
413 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC);
414 /*
415 * If losing, let the lower level know and try for
416 * a better route. Also, if we backed off this far,
417 * our srtt estimate is probably bogus. Clobber it
418 * so we'll take the next rtt measurement as our srtt;
419 * move the current srtt into rttvar to keep the current
420 * retransmit times until then.
421 */
422 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
423 #ifdef INET6
424 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
425 in6_losing(tp->t_inpcb);
426 else
427 #endif
428 in_losing(tp->t_inpcb);
429 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
430 tp->t_srtt = 0;
431 }
432 tp->snd_nxt = tp->snd_una;
433 tp->snd_high = tp->snd_max;
434 /*
435 * Force a segment to be sent.
436 */
437 tp->t_flags |= TF_ACKNOW;
438 /*
439 * If timing a segment in this window, stop the timer.
440 */
441 tp->t_rtttime = 0;
442 /*
443 * Close the congestion window down to one segment
444 * (we'll open it by one segment for each ack we get).
445 * Since we probably have a window's worth of unacked
446 * data accumulated, this "slow start" keeps us from
447 * dumping all that data as back-to-back packets (which
448 * might overwhelm an intermediate gateway).
449 *
450 * There are two phases to the opening: Initially we
451 * open by one mss on each ack. This makes the window
452 * size increase exponentially with time. If the
453 * window is larger than the path can handle, this
454 * exponential growth results in dropped packet(s)
455 * almost immediately. To get more time between
456 * drops but still "push" the network to take advantage
457 * of improving conditions, we switch from exponential
458 * to linear window opening at some threshhold size.
459 * For a threshhold, we use half the current window
460 * size, truncated to a multiple of the mss.
461 *
462 * (the minimum cwnd that will give us exponential
463 * growth is 2 mss. We don't allow the threshhold
464 * to go below this.)
465 */
466 {
467 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
468 if (win < 2)
469 win = 2;
470 tp->snd_cwnd = tp->t_maxseg;
471 tp->snd_ssthresh = win * tp->t_maxseg;
472 tp->t_dupacks = 0;
473 }
474 (void) tcp_output(tp);
475
476 out:
477 #ifdef TCPDEBUG
478 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
479 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
480 PRU_SLOWTIMO);
481 #endif
482 splx(s);
483 }
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