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
| 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
|
72{
73 int error, s, tt;
74
75 tt = *(int *)oidp->oid_arg1;
76 s = tt * 1000 / hz;
77
78 error = sysctl_handle_int(oidp, &s, 0, req);
79 if (error || !req->newptr)
80 return (error);
81
82 tt = s * hz / 1000;
83 if (tt < 1)
84 return (EINVAL);
85
86 *(int *)oidp->oid_arg1 = tt;
87 return (0);
88}
89
90int tcp_keepinit;
91SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
92 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "");
93
94int tcp_keepidle;
95SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
96 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "");
97
98int tcp_keepintvl;
99SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
100 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "");
101
102int tcp_delacktime;
103SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
104 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
105 "Time before a delayed ACK is sent");
106
107int tcp_msl;
108SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
109 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
110
111static int always_keepalive = 0;
112SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
113 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
114
115static int tcp_keepcnt = TCPTV_KEEPCNT;
116 /* max idle probes */
117int tcp_maxpersistidle;
118 /* max idle time in persist */
119int tcp_maxidle;
120
121/*
122 * Tcp protocol timeout routine called every 500 ms.
123 * Updates timestamps used for TCP
124 * causes finite state machine actions if timers expire.
125 */
126void
127tcp_slowtimo()
128{
129 int s;
130
131 s = splnet();
132
133 tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
134
135 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
136#ifdef TCP_COMPAT_42
137 if ((int)tcp_iss < 0)
138 tcp_iss = TCP_ISSINCR; /* XXX */
139#endif
140 splx(s);
141}
142
143/*
144 * Cancel all timers for TCP tp.
145 */
146void
147tcp_canceltimers(tp)
148 struct tcpcb *tp;
149{
150 callout_stop(tp->tt_2msl);
151 callout_stop(tp->tt_persist);
152 callout_stop(tp->tt_keep);
153 callout_stop(tp->tt_rexmt);
154}
155
156int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
157 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
158
159static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
160
161/*
162 * TCP timer processing.
163 */
164void
165tcp_timer_delack(xtp)
166 void *xtp;
167{
168 struct tcpcb *tp = xtp;
169 int s;
170
171 s = splnet();
172 if (callout_pending(tp->tt_delack)) {
173 splx(s);
174 return;
175 }
176 callout_deactivate(tp->tt_delack);
177
178 tp->t_flags |= TF_ACKNOW;
179 tcpstat.tcps_delack++;
180 (void) tcp_output(tp);
181 splx(s);
182}
183
184void
185tcp_timer_2msl(xtp)
186 void *xtp;
187{
188 struct tcpcb *tp = xtp;
189 int s;
190#ifdef TCPDEBUG
191 int ostate;
192
193 ostate = tp->t_state;
194#endif
195 s = splnet();
196 if (callout_pending(tp->tt_2msl)) {
197 splx(s);
198 return;
199 }
200 callout_deactivate(tp->tt_2msl);
201 /*
202 * 2 MSL timeout in shutdown went off. If we're closed but
203 * still waiting for peer to close and connection has been idle
204 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
205 * control block. Otherwise, check again in a bit.
206 */
207 if (tp->t_state != TCPS_TIME_WAIT &&
208 (ticks - tp->t_rcvtime) <= tcp_maxidle)
209 callout_reset(tp->tt_2msl, tcp_keepintvl,
210 tcp_timer_2msl, tp);
211 else
212 tp = tcp_close(tp);
213
214#ifdef TCPDEBUG
215 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
216 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
217 PRU_SLOWTIMO);
218#endif
219 splx(s);
220}
221
222void
223tcp_timer_keep(xtp)
224 void *xtp;
225{
226 struct tcpcb *tp = xtp;
227 int s;
228#ifdef TCPDEBUG
229 int ostate;
230
231 ostate = tp->t_state;
232#endif
233 s = splnet();
234 if (callout_pending(tp->tt_keep)) {
235 splx(s);
236 return;
237 }
238 callout_deactivate(tp->tt_keep);
239 /*
240 * Keep-alive timer went off; send something
241 * or drop connection if idle for too long.
242 */
243 tcpstat.tcps_keeptimeo++;
244 if (tp->t_state < TCPS_ESTABLISHED)
245 goto dropit;
246 if ((always_keepalive ||
247 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&
248 tp->t_state <= TCPS_CLOSING) {
249 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle)
250 goto dropit;
251 /*
252 * Send a packet designed to force a response
253 * if the peer is up and reachable:
254 * either an ACK if the connection is still alive,
255 * or an RST if the peer has closed the connection
256 * due to timeout or reboot.
257 * Using sequence number tp->snd_una-1
258 * causes the transmitted zero-length segment
259 * to lie outside the receive window;
260 * by the protocol spec, this requires the
261 * correspondent TCP to respond.
262 */
263 tcpstat.tcps_keepprobe++;
264#ifdef TCP_COMPAT_42
265 /*
266 * The keepalive packet must have nonzero length
267 * to get a 4.2 host to respond.
268 */
269 tcp_respond(tp, tp->t_template->tt_ipgen,
270 &tp->t_template->tt_t, (struct mbuf *)NULL,
271 tp->rcv_nxt - 1, tp->snd_una - 1, 0);
272#else
273 tcp_respond(tp, tp->t_template->tt_ipgen,
274 &tp->t_template->tt_t, (struct mbuf *)NULL,
275 tp->rcv_nxt, tp->snd_una - 1, 0);
276#endif
277 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp);
278 } else
279 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
280
281#ifdef TCPDEBUG
282 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
283 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
284 PRU_SLOWTIMO);
285#endif
286 splx(s);
287 return;
288
289dropit:
290 tcpstat.tcps_keepdrops++;
291 tp = tcp_drop(tp, ETIMEDOUT);
292
293#ifdef TCPDEBUG
294 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
295 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
296 PRU_SLOWTIMO);
297#endif
298 splx(s);
299}
300
301void
302tcp_timer_persist(xtp)
303 void *xtp;
304{
305 struct tcpcb *tp = xtp;
306 int s;
307#ifdef TCPDEBUG
308 int ostate;
309
310 ostate = tp->t_state;
311#endif
312 s = splnet();
313 if (callout_pending(tp->tt_persist)) {
314 splx(s);
315 return;
316 }
317 callout_deactivate(tp->tt_persist);
318 /*
319 * Persistance timer into zero window.
320 * Force a byte to be output, if possible.
321 */
322 tcpstat.tcps_persisttimeo++;
323 /*
324 * Hack: if the peer is dead/unreachable, we do not
325 * time out if the window is closed. After a full
326 * backoff, drop the connection if the idle time
327 * (no responses to probes) reaches the maximum
328 * backoff that we would use if retransmitting.
329 */
330 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
331 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
332 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
333 tcpstat.tcps_persistdrop++;
334 tp = tcp_drop(tp, ETIMEDOUT);
335 goto out;
336 }
337 tcp_setpersist(tp);
338 tp->t_force = 1;
339 (void) tcp_output(tp);
340 tp->t_force = 0;
341
342out:
343#ifdef TCPDEBUG
344 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
345 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
346 PRU_SLOWTIMO);
347#endif
348 splx(s);
349}
350
351void
352tcp_timer_rexmt(xtp)
353 void *xtp;
354{
355 struct tcpcb *tp = xtp;
356 int s;
357 int rexmt;
358#ifdef TCPDEBUG
359 int ostate;
360
361 ostate = tp->t_state;
362#endif
363 s = splnet();
364 if (callout_pending(tp->tt_rexmt)) {
365 splx(s);
366 return;
367 }
368 callout_deactivate(tp->tt_rexmt);
369 /*
370 * Retransmission timer went off. Message has not
371 * been acked within retransmit interval. Back off
372 * to a longer retransmit interval and retransmit one segment.
373 */
374 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
375 tp->t_rxtshift = TCP_MAXRXTSHIFT;
376 tcpstat.tcps_timeoutdrop++;
377 tp = tcp_drop(tp, tp->t_softerror ?
378 tp->t_softerror : ETIMEDOUT);
379 goto out;
380 }
381 if (tp->t_rxtshift == 1) {
382 /*
383 * first retransmit; record ssthresh and cwnd so they can
384 * be recovered if this turns out to be a "bad" retransmit.
385 * A retransmit is considered "bad" if an ACK for this
386 * segment is received within RTT/2 interval; the assumption
387 * here is that the ACK was already in flight. See
388 * "On Estimating End-to-End Network Path Properties" by
389 * Allman and Paxson for more details.
390 */
391 tp->snd_cwnd_prev = tp->snd_cwnd;
392 tp->snd_ssthresh_prev = tp->snd_ssthresh;
393 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
394 }
395 tcpstat.tcps_rexmttimeo++;
396 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
397 TCPT_RANGESET(tp->t_rxtcur, rexmt,
398 tp->t_rttmin, TCPTV_REXMTMAX);
399 /*
400 * If losing, let the lower level know and try for
401 * a better route. Also, if we backed off this far,
402 * our srtt estimate is probably bogus. Clobber it
403 * so we'll take the next rtt measurement as our srtt;
404 * move the current srtt into rttvar to keep the current
405 * retransmit times until then.
406 */
407 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
408#ifdef INET6
409 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
410 in6_losing(tp->t_inpcb);
411 else
412#endif
413 in_losing(tp->t_inpcb);
414 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
415 tp->t_srtt = 0;
416 }
417 tp->snd_nxt = tp->snd_una;
418 /*
419 * Note: We overload snd_recover to function also as the
420 * snd_last variable described in RFC 2582
421 */
422 tp->snd_recover = tp->snd_max;
423 /*
424 * Force a segment to be sent.
425 */
426 tp->t_flags |= TF_ACKNOW;
427 /*
428 * If timing a segment in this window, stop the timer.
429 */
430 tp->t_rtttime = 0;
431 /*
432 * Close the congestion window down to one segment
433 * (we'll open it by one segment for each ack we get).
434 * Since we probably have a window's worth of unacked
435 * data accumulated, this "slow start" keeps us from
436 * dumping all that data as back-to-back packets (which
437 * might overwhelm an intermediate gateway).
438 *
439 * There are two phases to the opening: Initially we
440 * open by one mss on each ack. This makes the window
441 * size increase exponentially with time. If the
442 * window is larger than the path can handle, this
443 * exponential growth results in dropped packet(s)
444 * almost immediately. To get more time between
445 * drops but still "push" the network to take advantage
446 * of improving conditions, we switch from exponential
447 * to linear window opening at some threshhold size.
448 * For a threshhold, we use half the current window
449 * size, truncated to a multiple of the mss.
450 *
451 * (the minimum cwnd that will give us exponential
452 * growth is 2 mss. We don't allow the threshhold
453 * to go below this.)
454 */
455 {
456 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
457 if (win < 2)
458 win = 2;
459 tp->snd_cwnd = tp->t_maxseg;
460 tp->snd_ssthresh = win * tp->t_maxseg;
461 tp->t_dupacks = 0;
462 }
463 (void) tcp_output(tp);
464
465out:
466#ifdef TCPDEBUG
467 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
468 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
469 PRU_SLOWTIMO);
470#endif
471 splx(s);
472}
| 72{
73 int error, s, tt;
74
75 tt = *(int *)oidp->oid_arg1;
76 s = tt * 1000 / hz;
77
78 error = sysctl_handle_int(oidp, &s, 0, req);
79 if (error || !req->newptr)
80 return (error);
81
82 tt = s * hz / 1000;
83 if (tt < 1)
84 return (EINVAL);
85
86 *(int *)oidp->oid_arg1 = tt;
87 return (0);
88}
89
90int tcp_keepinit;
91SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
92 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "");
93
94int tcp_keepidle;
95SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
96 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "");
97
98int tcp_keepintvl;
99SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
100 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "");
101
102int tcp_delacktime;
103SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime,
104 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
105 "Time before a delayed ACK is sent");
106
107int tcp_msl;
108SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
109 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
110
111static int always_keepalive = 0;
112SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
113 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
114
115static int tcp_keepcnt = TCPTV_KEEPCNT;
116 /* max idle probes */
117int tcp_maxpersistidle;
118 /* max idle time in persist */
119int tcp_maxidle;
120
121/*
122 * Tcp protocol timeout routine called every 500 ms.
123 * Updates timestamps used for TCP
124 * causes finite state machine actions if timers expire.
125 */
126void
127tcp_slowtimo()
128{
129 int s;
130
131 s = splnet();
132
133 tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
134
135 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
136#ifdef TCP_COMPAT_42
137 if ((int)tcp_iss < 0)
138 tcp_iss = TCP_ISSINCR; /* XXX */
139#endif
140 splx(s);
141}
142
143/*
144 * Cancel all timers for TCP tp.
145 */
146void
147tcp_canceltimers(tp)
148 struct tcpcb *tp;
149{
150 callout_stop(tp->tt_2msl);
151 callout_stop(tp->tt_persist);
152 callout_stop(tp->tt_keep);
153 callout_stop(tp->tt_rexmt);
154}
155
156int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
157 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
158
159static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
160
161/*
162 * TCP timer processing.
163 */
164void
165tcp_timer_delack(xtp)
166 void *xtp;
167{
168 struct tcpcb *tp = xtp;
169 int s;
170
171 s = splnet();
172 if (callout_pending(tp->tt_delack)) {
173 splx(s);
174 return;
175 }
176 callout_deactivate(tp->tt_delack);
177
178 tp->t_flags |= TF_ACKNOW;
179 tcpstat.tcps_delack++;
180 (void) tcp_output(tp);
181 splx(s);
182}
183
184void
185tcp_timer_2msl(xtp)
186 void *xtp;
187{
188 struct tcpcb *tp = xtp;
189 int s;
190#ifdef TCPDEBUG
191 int ostate;
192
193 ostate = tp->t_state;
194#endif
195 s = splnet();
196 if (callout_pending(tp->tt_2msl)) {
197 splx(s);
198 return;
199 }
200 callout_deactivate(tp->tt_2msl);
201 /*
202 * 2 MSL timeout in shutdown went off. If we're closed but
203 * still waiting for peer to close and connection has been idle
204 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
205 * control block. Otherwise, check again in a bit.
206 */
207 if (tp->t_state != TCPS_TIME_WAIT &&
208 (ticks - tp->t_rcvtime) <= tcp_maxidle)
209 callout_reset(tp->tt_2msl, tcp_keepintvl,
210 tcp_timer_2msl, tp);
211 else
212 tp = tcp_close(tp);
213
214#ifdef TCPDEBUG
215 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
216 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
217 PRU_SLOWTIMO);
218#endif
219 splx(s);
220}
221
222void
223tcp_timer_keep(xtp)
224 void *xtp;
225{
226 struct tcpcb *tp = xtp;
227 int s;
228#ifdef TCPDEBUG
229 int ostate;
230
231 ostate = tp->t_state;
232#endif
233 s = splnet();
234 if (callout_pending(tp->tt_keep)) {
235 splx(s);
236 return;
237 }
238 callout_deactivate(tp->tt_keep);
239 /*
240 * Keep-alive timer went off; send something
241 * or drop connection if idle for too long.
242 */
243 tcpstat.tcps_keeptimeo++;
244 if (tp->t_state < TCPS_ESTABLISHED)
245 goto dropit;
246 if ((always_keepalive ||
247 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&
248 tp->t_state <= TCPS_CLOSING) {
249 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle)
250 goto dropit;
251 /*
252 * Send a packet designed to force a response
253 * if the peer is up and reachable:
254 * either an ACK if the connection is still alive,
255 * or an RST if the peer has closed the connection
256 * due to timeout or reboot.
257 * Using sequence number tp->snd_una-1
258 * causes the transmitted zero-length segment
259 * to lie outside the receive window;
260 * by the protocol spec, this requires the
261 * correspondent TCP to respond.
262 */
263 tcpstat.tcps_keepprobe++;
264#ifdef TCP_COMPAT_42
265 /*
266 * The keepalive packet must have nonzero length
267 * to get a 4.2 host to respond.
268 */
269 tcp_respond(tp, tp->t_template->tt_ipgen,
270 &tp->t_template->tt_t, (struct mbuf *)NULL,
271 tp->rcv_nxt - 1, tp->snd_una - 1, 0);
272#else
273 tcp_respond(tp, tp->t_template->tt_ipgen,
274 &tp->t_template->tt_t, (struct mbuf *)NULL,
275 tp->rcv_nxt, tp->snd_una - 1, 0);
276#endif
277 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp);
278 } else
279 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
280
281#ifdef TCPDEBUG
282 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
283 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
284 PRU_SLOWTIMO);
285#endif
286 splx(s);
287 return;
288
289dropit:
290 tcpstat.tcps_keepdrops++;
291 tp = tcp_drop(tp, ETIMEDOUT);
292
293#ifdef TCPDEBUG
294 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
295 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
296 PRU_SLOWTIMO);
297#endif
298 splx(s);
299}
300
301void
302tcp_timer_persist(xtp)
303 void *xtp;
304{
305 struct tcpcb *tp = xtp;
306 int s;
307#ifdef TCPDEBUG
308 int ostate;
309
310 ostate = tp->t_state;
311#endif
312 s = splnet();
313 if (callout_pending(tp->tt_persist)) {
314 splx(s);
315 return;
316 }
317 callout_deactivate(tp->tt_persist);
318 /*
319 * Persistance timer into zero window.
320 * Force a byte to be output, if possible.
321 */
322 tcpstat.tcps_persisttimeo++;
323 /*
324 * Hack: if the peer is dead/unreachable, we do not
325 * time out if the window is closed. After a full
326 * backoff, drop the connection if the idle time
327 * (no responses to probes) reaches the maximum
328 * backoff that we would use if retransmitting.
329 */
330 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
331 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle ||
332 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
333 tcpstat.tcps_persistdrop++;
334 tp = tcp_drop(tp, ETIMEDOUT);
335 goto out;
336 }
337 tcp_setpersist(tp);
338 tp->t_force = 1;
339 (void) tcp_output(tp);
340 tp->t_force = 0;
341
342out:
343#ifdef TCPDEBUG
344 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
345 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
346 PRU_SLOWTIMO);
347#endif
348 splx(s);
349}
350
351void
352tcp_timer_rexmt(xtp)
353 void *xtp;
354{
355 struct tcpcb *tp = xtp;
356 int s;
357 int rexmt;
358#ifdef TCPDEBUG
359 int ostate;
360
361 ostate = tp->t_state;
362#endif
363 s = splnet();
364 if (callout_pending(tp->tt_rexmt)) {
365 splx(s);
366 return;
367 }
368 callout_deactivate(tp->tt_rexmt);
369 /*
370 * Retransmission timer went off. Message has not
371 * been acked within retransmit interval. Back off
372 * to a longer retransmit interval and retransmit one segment.
373 */
374 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
375 tp->t_rxtshift = TCP_MAXRXTSHIFT;
376 tcpstat.tcps_timeoutdrop++;
377 tp = tcp_drop(tp, tp->t_softerror ?
378 tp->t_softerror : ETIMEDOUT);
379 goto out;
380 }
381 if (tp->t_rxtshift == 1) {
382 /*
383 * first retransmit; record ssthresh and cwnd so they can
384 * be recovered if this turns out to be a "bad" retransmit.
385 * A retransmit is considered "bad" if an ACK for this
386 * segment is received within RTT/2 interval; the assumption
387 * here is that the ACK was already in flight. See
388 * "On Estimating End-to-End Network Path Properties" by
389 * Allman and Paxson for more details.
390 */
391 tp->snd_cwnd_prev = tp->snd_cwnd;
392 tp->snd_ssthresh_prev = tp->snd_ssthresh;
393 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
394 }
395 tcpstat.tcps_rexmttimeo++;
396 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
397 TCPT_RANGESET(tp->t_rxtcur, rexmt,
398 tp->t_rttmin, TCPTV_REXMTMAX);
399 /*
400 * If losing, let the lower level know and try for
401 * a better route. Also, if we backed off this far,
402 * our srtt estimate is probably bogus. Clobber it
403 * so we'll take the next rtt measurement as our srtt;
404 * move the current srtt into rttvar to keep the current
405 * retransmit times until then.
406 */
407 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
408#ifdef INET6
409 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
410 in6_losing(tp->t_inpcb);
411 else
412#endif
413 in_losing(tp->t_inpcb);
414 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
415 tp->t_srtt = 0;
416 }
417 tp->snd_nxt = tp->snd_una;
418 /*
419 * Note: We overload snd_recover to function also as the
420 * snd_last variable described in RFC 2582
421 */
422 tp->snd_recover = tp->snd_max;
423 /*
424 * Force a segment to be sent.
425 */
426 tp->t_flags |= TF_ACKNOW;
427 /*
428 * If timing a segment in this window, stop the timer.
429 */
430 tp->t_rtttime = 0;
431 /*
432 * Close the congestion window down to one segment
433 * (we'll open it by one segment for each ack we get).
434 * Since we probably have a window's worth of unacked
435 * data accumulated, this "slow start" keeps us from
436 * dumping all that data as back-to-back packets (which
437 * might overwhelm an intermediate gateway).
438 *
439 * There are two phases to the opening: Initially we
440 * open by one mss on each ack. This makes the window
441 * size increase exponentially with time. If the
442 * window is larger than the path can handle, this
443 * exponential growth results in dropped packet(s)
444 * almost immediately. To get more time between
445 * drops but still "push" the network to take advantage
446 * of improving conditions, we switch from exponential
447 * to linear window opening at some threshhold size.
448 * For a threshhold, we use half the current window
449 * size, truncated to a multiple of the mss.
450 *
451 * (the minimum cwnd that will give us exponential
452 * growth is 2 mss. We don't allow the threshhold
453 * to go below this.)
454 */
455 {
456 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
457 if (win < 2)
458 win = 2;
459 tp->snd_cwnd = tp->t_maxseg;
460 tp->snd_ssthresh = win * tp->t_maxseg;
461 tp->t_dupacks = 0;
462 }
463 (void) tcp_output(tp);
464
465out:
466#ifdef TCPDEBUG
467 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
468 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
469 PRU_SLOWTIMO);
470#endif
471 splx(s);
472}
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