tcp_timer.c revision 1.43 1 /* $NetBSD: tcp_timer.c,v 1.43 1998/09/10 10:47:00 mouse Exp $ */
2
3 /*-
4 * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation
9 * Facility, NASA Ames Research Center.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by the NetBSD
22 * Foundation, Inc. and its contributors.
23 * 4. Neither the name of The NetBSD Foundation nor the names of its
24 * contributors may be used to endorse or promote products derived
25 * from this software without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
37 * POSSIBILITY OF SUCH DAMAGE.
38 */
39
40 /*
41 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
42 * The Regents of the University of California. All rights reserved.
43 *
44 * Redistribution and use in source and binary forms, with or without
45 * modification, are permitted provided that the following conditions
46 * are met:
47 * 1. Redistributions of source code must retain the above copyright
48 * notice, this list of conditions and the following disclaimer.
49 * 2. Redistributions in binary form must reproduce the above copyright
50 * notice, this list of conditions and the following disclaimer in the
51 * documentation and/or other materials provided with the distribution.
52 * 3. All advertising materials mentioning features or use of this software
53 * must display the following acknowledgement:
54 * This product includes software developed by the University of
55 * California, Berkeley and its contributors.
56 * 4. Neither the name of the University nor the names of its contributors
57 * may be used to endorse or promote products derived from this software
58 * without specific prior written permission.
59 *
60 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
61 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
62 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
63 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
64 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
65 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
66 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
67 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
68 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
69 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
70 * SUCH DAMAGE.
71 *
72 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
73 */
74
75 #include <sys/param.h>
76 #include <sys/systm.h>
77 #include <sys/malloc.h>
78 #include <sys/mbuf.h>
79 #include <sys/socket.h>
80 #include <sys/socketvar.h>
81 #include <sys/protosw.h>
82 #include <sys/errno.h>
83
84 #include <net/if.h>
85 #include <net/route.h>
86
87 #include <netinet/in.h>
88 #include <netinet/in_systm.h>
89 #include <netinet/ip.h>
90 #include <netinet/in_pcb.h>
91 #include <netinet/ip_var.h>
92 #include <netinet/tcp.h>
93 #include <netinet/tcp_fsm.h>
94 #include <netinet/tcp_seq.h>
95 #include <netinet/tcp_timer.h>
96 #include <netinet/tcp_var.h>
97 #include <netinet/tcpip.h>
98
99 int tcp_keepidle = TCPTV_KEEP_IDLE;
100 int tcp_keepintvl = TCPTV_KEEPINTVL;
101 int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */
102 int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */
103 int tcp_maxidle;
104
105 struct tcp_delack_head tcp_delacks;
106
107 /*
108 * Fast timeout routine for processing delayed acks
109 */
110 void
111 tcp_fasttimo()
112 {
113 register struct tcpcb *tp, *ntp;
114 int s;
115
116 s = splsoftnet();
117 for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) {
118 /*
119 * If tcp_output() can't transmit the ACK for whatever
120 * reason, it will remain on the queue for the next
121 * time the heartbeat ticks.
122 */
123 ntp = tp->t_delack.le_next;
124 tp->t_flags |= TF_ACKNOW;
125 (void) tcp_output(tp);
126 }
127 splx(s);
128 }
129
130 /*
131 * Tcp protocol timeout routine called every 500 ms.
132 * Updates the timers in all active tcb's and
133 * causes finite state machine actions if timers expire.
134 */
135 void
136 tcp_slowtimo()
137 {
138 register struct inpcb *inp, *ninp;
139 register struct tcpcb *tp;
140 int s;
141 register long i;
142 static int syn_cache_last = 0;
143
144 s = splsoftnet();
145 tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
146 /*
147 * Search through tcb's and update active timers.
148 */
149 inp = tcbtable.inpt_queue.cqh_first;
150 if (inp == (struct inpcb *)0) { /* XXX */
151 splx(s);
152 return;
153 }
154 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) {
155 ninp = inp->inp_queue.cqe_next;
156 tp = intotcpcb(inp);
157 if (tp == 0 || tp->t_state == TCPS_LISTEN)
158 continue;
159 for (i = 0; i < TCPT_NTIMERS; i++) {
160 if (TCP_TIMER_ISEXPIRED(tp, i)) {
161 TCP_TIMER_DISARM(tp, i);
162 (void) tcp_usrreq(tp->t_inpcb->inp_socket,
163 PRU_SLOWTIMO, (struct mbuf *)0,
164 (struct mbuf *)i, (struct mbuf *)0,
165 (struct proc *)0);
166 /* XXX NOT MP SAFE */
167 if ((ninp == (void *)&tcbtable.inpt_queue &&
168 tcbtable.inpt_queue.cqh_last != inp) ||
169 ninp->inp_queue.cqe_prev != inp)
170 goto tpgone;
171 }
172 }
173 tp->t_idle++;
174 if (tp->t_rtt)
175 tp->t_rtt++;
176 tpgone:
177 ;
178 }
179 tcp_iss_seq += TCP_ISSINCR; /* increment iss */
180 tcp_now++; /* for timestamps */
181 if (++syn_cache_last >= tcp_syn_cache_interval) {
182 syn_cache_timer();
183 syn_cache_last = 0;
184 }
185 splx(s);
186 }
187
188 /*
189 * Cancel all timers for TCP tp.
190 */
191 void
192 tcp_canceltimers(tp)
193 struct tcpcb *tp;
194 {
195 register int i;
196
197 for (i = 0; i < TCPT_NTIMERS; i++)
198 TCP_TIMER_DISARM(tp, i);
199 }
200
201 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
202 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
203
204 int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
205
206 /*
207 * TCP timer processing.
208 */
209 struct tcpcb *
210 tcp_timers(tp, timer)
211 register struct tcpcb *tp;
212 int timer;
213 {
214 short rto;
215
216 switch (timer) {
217
218 /*
219 * 2 MSL timeout in shutdown went off. If we're closed but
220 * still waiting for peer to close and connection has been idle
221 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
222 * control block. Otherwise, check again in a bit.
223 */
224 case TCPT_2MSL:
225 if (tp->t_state != TCPS_TIME_WAIT &&
226 ((tcp_maxidle == 0) || (tp->t_idle <= tcp_maxidle)))
227 TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl);
228 else
229 tp = tcp_close(tp);
230 break;
231
232 /*
233 * Retransmission timer went off. Message has not
234 * been acked within retransmit interval. Back off
235 * to a longer retransmit interval and retransmit one segment.
236 */
237 case TCPT_REXMT:
238 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
239 tp->t_rxtshift = TCP_MAXRXTSHIFT;
240 tcpstat.tcps_timeoutdrop++;
241 tp = tcp_drop(tp, tp->t_softerror ?
242 tp->t_softerror : ETIMEDOUT);
243 break;
244 }
245 tcpstat.tcps_rexmttimeo++;
246 rto = TCP_REXMTVAL(tp);
247 if (rto < tp->t_rttmin)
248 rto = tp->t_rttmin;
249 TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift],
250 tp->t_rttmin, TCPTV_REXMTMAX);
251 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
252 #if 0
253 /*
254 * If we are losing and we are trying path MTU discovery,
255 * try turning it off. This will avoid black holes in
256 * the network which suppress or fail to send "packet
257 * too big" ICMP messages. We should ideally do
258 * lots more sophisticated searching to find the right
259 * value here...
260 */
261 if (ip_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) {
262 struct inpcb *inp = tp->t_inpcb;
263 struct rtentry *rt = in_pcbrtentry(inp);
264
265 /* XXX: Black hole recovery code goes here */
266 }
267 #endif
268 /*
269 * If losing, let the lower level know and try for
270 * a better route. Also, if we backed off this far,
271 * our srtt estimate is probably bogus. Clobber it
272 * so we'll take the next rtt measurement as our srtt;
273 * move the current srtt into rttvar to keep the current
274 * retransmit times until then.
275 */
276 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
277 in_losing(tp->t_inpcb);
278 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
279 tp->t_srtt = 0;
280 }
281 tp->snd_nxt = tp->snd_una;
282 /*
283 * If timing a segment in this window, stop the timer.
284 */
285 tp->t_rtt = 0;
286 /*
287 * Remember if we are retransmitting a SYN, because if
288 * we do, set the initial congestion window must be set
289 * to 1 segment.
290 */
291 if (tp->t_state == TCPS_SYN_SENT)
292 tp->t_flags |= TF_SYN_REXMT;
293 /*
294 * Close the congestion window down to one segment
295 * (we'll open it by one segment for each ack we get).
296 * Since we probably have a window's worth of unacked
297 * data accumulated, this "slow start" keeps us from
298 * dumping all that data as back-to-back packets (which
299 * might overwhelm an intermediate gateway).
300 *
301 * There are two phases to the opening: Initially we
302 * open by one mss on each ack. This makes the window
303 * size increase exponentially with time. If the
304 * window is larger than the path can handle, this
305 * exponential growth results in dropped packet(s)
306 * almost immediately. To get more time between
307 * drops but still "push" the network to take advantage
308 * of improving conditions, we switch from exponential
309 * to linear window opening at some threshhold size.
310 * For a threshhold, we use half the current window
311 * size, truncated to a multiple of the mss.
312 *
313 * (the minimum cwnd that will give us exponential
314 * growth is 2 mss. We don't allow the threshhold
315 * to go below this.)
316 */
317 {
318 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz;
319 if (win < 2)
320 win = 2;
321 /* Loss Window MUST be one segment. */
322 tp->snd_cwnd = tp->t_segsz;
323 tp->snd_ssthresh = win * tp->t_segsz;
324 tp->t_dupacks = 0;
325 }
326 (void) tcp_output(tp);
327 break;
328
329 /*
330 * Persistance timer into zero window.
331 * Force a byte to be output, if possible.
332 */
333 case TCPT_PERSIST:
334 /*
335 * Hack: if the peer is dead/unreachable, we do not
336 * time out if the window is closed. After a full
337 * backoff, drop the connection if the idle time
338 * (no responses to probes) reaches the maximum
339 * backoff that we would use if retransmitting.
340 */
341 rto = TCP_REXMTVAL(tp);
342 if (rto < tp->t_rttmin)
343 rto = tp->t_rttmin;
344 if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
345 (tp->t_idle >= tcp_maxpersistidle ||
346 tp->t_idle >= rto * tcp_totbackoff)) {
347 tcpstat.tcps_persistdrops++;
348 tp = tcp_drop(tp, ETIMEDOUT);
349 break;
350 }
351 tcpstat.tcps_persisttimeo++;
352 tcp_setpersist(tp);
353 tp->t_force = 1;
354 (void) tcp_output(tp);
355 tp->t_force = 0;
356 break;
357
358 /*
359 * Keep-alive timer went off; send something
360 * or drop connection if idle for too long.
361 */
362 case TCPT_KEEP:
363 tcpstat.tcps_keeptimeo++;
364 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)
365 goto dropit;
366 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
367 tp->t_state <= TCPS_CLOSE_WAIT) {
368 if ((tcp_maxidle > 0) &&
369 (tp->t_idle >= tcp_keepidle + tcp_maxidle))
370 goto dropit;
371 /*
372 * Send a packet designed to force a response
373 * if the peer is up and reachable:
374 * either an ACK if the connection is still alive,
375 * or an RST if the peer has closed the connection
376 * due to timeout or reboot.
377 * Using sequence number tp->snd_una-1
378 * causes the transmitted zero-length segment
379 * to lie outside the receive window;
380 * by the protocol spec, this requires the
381 * correspondent TCP to respond.
382 */
383 tcpstat.tcps_keepprobe++;
384 if (tcp_compat_42) {
385 /*
386 * The keepalive packet must have nonzero
387 * length to get a 4.2 host to respond.
388 */
389 (void)tcp_respond(tp, tp->t_template,
390 (struct mbuf *)NULL, tp->rcv_nxt - 1,
391 tp->snd_una - 1, 0);
392 } else {
393 (void)tcp_respond(tp, tp->t_template,
394 (struct mbuf *)NULL, tp->rcv_nxt,
395 tp->snd_una - 1, 0);
396 }
397 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl);
398 } else
399 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle);
400 break;
401 dropit:
402 tcpstat.tcps_keepdrops++;
403 tp = tcp_drop(tp, ETIMEDOUT);
404 break;
405 }
406 return (tp);
407 }
408