tcp_timer.c revision 1.6 1 /*
2 * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California.
3 * 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 * from: @(#)tcp_timer.c 7.18 (Berkeley) 6/28/90
34 * $Id: tcp_timer.c,v 1.6 1994/01/08 23:07:22 mycroft Exp $
35 */
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/malloc.h>
40 #include <sys/mbuf.h>
41 #include <sys/socket.h>
42 #include <sys/socketvar.h>
43 #include <sys/protosw.h>
44 #include <sys/errno.h>
45
46 #include <net/if.h>
47 #include <net/route.h>
48
49 #include <netinet/in.h>
50 #include <netinet/in_systm.h>
51 #include <netinet/ip.h>
52 #include <netinet/in_pcb.h>
53 #include <netinet/ip_var.h>
54 #include <netinet/tcp.h>
55 #include <netinet/tcp_fsm.h>
56 #include <netinet/tcp_seq.h>
57 #include <netinet/tcp_timer.h>
58 #include <netinet/tcp_var.h>
59 #include <netinet/tcpip.h>
60
61 int tcp_keepidle = TCPTV_KEEP_IDLE;
62 int tcp_keepintvl = TCPTV_KEEPINTVL;
63 int tcp_maxidle;
64
65 /*
66 * Fast timeout routine for processing delayed acks
67 */
68 void
69 tcp_fasttimo()
70 {
71 register struct inpcb *inp;
72 register struct tcpcb *tp;
73 int s = splnet();
74
75 inp = tcb.inp_next;
76 if (inp)
77 for (; inp != &tcb; inp = inp->inp_next)
78 if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
79 (tp->t_flags & TF_DELACK)) {
80 tp->t_flags &= ~TF_DELACK;
81 tp->t_flags |= TF_ACKNOW;
82 tcpstat.tcps_delack++;
83 (void) tcp_output(tp);
84 }
85 splx(s);
86 }
87
88 /*
89 * Tcp protocol timeout routine called every 500 ms.
90 * Updates the timers in all active tcb's and
91 * causes finite state machine actions if timers expire.
92 */
93 void
94 tcp_slowtimo()
95 {
96 register struct inpcb *ip, *ipnxt;
97 register struct tcpcb *tp;
98 int s = splnet();
99 register int i;
100
101 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
102 /*
103 * Search through tcb's and update active timers.
104 */
105 ip = tcb.inp_next;
106 if (ip == 0) {
107 splx(s);
108 return;
109 }
110 for (; ip != &tcb; ip = ipnxt) {
111 ipnxt = ip->inp_next;
112 tp = intotcpcb(ip);
113 if (tp == 0)
114 continue;
115 for (i = 0; i < TCPT_NTIMERS; i++) {
116 if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
117 (void) tcp_usrreq(tp->t_inpcb->inp_socket,
118 PRU_SLOWTIMO, (struct mbuf *)0,
119 (struct mbuf *)i, (struct mbuf *)0);
120 if (ipnxt->inp_prev != ip)
121 goto tpgone;
122 }
123 }
124 tp->t_idle++;
125 if (tp->t_rtt)
126 tp->t_rtt++;
127 tpgone:
128 ;
129 }
130 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
131 #ifdef TCP_COMPAT_42
132 if ((int)tcp_iss < 0)
133 tcp_iss = 0; /* XXX */
134 #endif
135 splx(s);
136 }
137
138 /*
139 * Cancel all timers for TCP tp.
140 */
141 void
142 tcp_canceltimers(tp)
143 struct tcpcb *tp;
144 {
145 register int i;
146
147 for (i = 0; i < TCPT_NTIMERS; i++)
148 tp->t_timer[i] = 0;
149 }
150
151 int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
152 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
153
154 /*
155 * TCP timer processing.
156 */
157 struct tcpcb *
158 tcp_timers(tp, timer)
159 register struct tcpcb *tp;
160 int timer;
161 {
162 register int rexmt;
163
164 switch (timer) {
165
166 /*
167 * 2 MSL timeout in shutdown went off. If we're closed but
168 * still waiting for peer to close and connection has been idle
169 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
170 * control block. Otherwise, check again in a bit.
171 */
172 case TCPT_2MSL:
173 if (tp->t_state != TCPS_TIME_WAIT &&
174 tp->t_idle <= tcp_maxidle)
175 tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
176 else
177 tp = tcp_close(tp);
178 break;
179
180 /*
181 * Retransmission timer went off. Message has not
182 * been acked within retransmit interval. Back off
183 * to a longer retransmit interval and retransmit one segment.
184 */
185 case TCPT_REXMT:
186 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
187 tp->t_rxtshift = TCP_MAXRXTSHIFT;
188 tcpstat.tcps_timeoutdrop++;
189 tp = tcp_drop(tp, tp->t_softerror ?
190 tp->t_softerror : ETIMEDOUT);
191 break;
192 }
193 tcpstat.tcps_rexmttimeo++;
194 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
195 TCPT_RANGESET(tp->t_rxtcur, rexmt,
196 tp->t_rttmin, TCPTV_REXMTMAX);
197 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
198 /*
199 * If losing, let the lower level know and try for
200 * a better route. Also, if we backed off this far,
201 * our srtt estimate is probably bogus. Clobber it
202 * so we'll take the next rtt measurement as our srtt;
203 * move the current srtt into rttvar to keep the current
204 * retransmit times until then.
205 */
206 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
207 in_losing(tp->t_inpcb);
208 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
209 tp->t_srtt = 0;
210 }
211 tp->snd_nxt = tp->snd_una;
212 /*
213 * If timing a segment in this window, stop the timer.
214 */
215 tp->t_rtt = 0;
216 /*
217 * Close the congestion window down to one segment
218 * (we'll open it by one segment for each ack we get).
219 * Since we probably have a window's worth of unacked
220 * data accumulated, this "slow start" keeps us from
221 * dumping all that data as back-to-back packets (which
222 * might overwhelm an intermediate gateway).
223 *
224 * There are two phases to the opening: Initially we
225 * open by one mss on each ack. This makes the window
226 * size increase exponentially with time. If the
227 * window is larger than the path can handle, this
228 * exponential growth results in dropped packet(s)
229 * almost immediately. To get more time between
230 * drops but still "push" the network to take advantage
231 * of improving conditions, we switch from exponential
232 * to linear window opening at some threshhold size.
233 * For a threshhold, we use half the current window
234 * size, truncated to a multiple of the mss.
235 *
236 * (the minimum cwnd that will give us exponential
237 * growth is 2 mss. We don't allow the threshhold
238 * to go below this.)
239 */
240 {
241 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
242 if (win < 2)
243 win = 2;
244 tp->snd_cwnd = tp->t_maxseg;
245 tp->snd_ssthresh = win * tp->t_maxseg;
246 tp->t_dupacks = 0;
247 }
248 (void) tcp_output(tp);
249 break;
250
251 /*
252 * Persistance timer into zero window.
253 * Force a byte to be output, if possible.
254 */
255 case TCPT_PERSIST:
256 tcpstat.tcps_persisttimeo++;
257 tcp_setpersist(tp);
258 tp->t_force = 1;
259 (void) tcp_output(tp);
260 tp->t_force = 0;
261 break;
262
263 /*
264 * Keep-alive timer went off; send something
265 * or drop connection if idle for too long.
266 */
267 case TCPT_KEEP:
268 tcpstat.tcps_keeptimeo++;
269 if (tp->t_state < TCPS_ESTABLISHED)
270 goto dropit;
271 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
272 tp->t_state <= TCPS_CLOSE_WAIT) {
273 if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
274 goto dropit;
275 /*
276 * Send a packet designed to force a response
277 * if the peer is up and reachable:
278 * either an ACK if the connection is still alive,
279 * or an RST if the peer has closed the connection
280 * due to timeout or reboot.
281 * Using sequence number tp->snd_una-1
282 * causes the transmitted zero-length segment
283 * to lie outside the receive window;
284 * by the protocol spec, this requires the
285 * correspondent TCP to respond.
286 */
287 tcpstat.tcps_keepprobe++;
288 #ifdef TCP_COMPAT_42
289 /*
290 * The keepalive packet must have nonzero length
291 * to get a 4.2 host to respond.
292 */
293 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
294 tp->rcv_nxt - 1, tp->snd_una - 1, 0);
295 #else
296 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
297 tp->rcv_nxt, tp->snd_una - 1, 0);
298 #endif
299 tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
300 } else
301 tp->t_timer[TCPT_KEEP] = tcp_keepidle;
302 break;
303 dropit:
304 tcpstat.tcps_keepdrops++;
305 tp = tcp_drop(tp, ETIMEDOUT);
306 break;
307 }
308 return (tp);
309 }
310