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1 | /* |
2 | * Copyright (c) 1982, 1986, 1988, 1990, 1993 | |
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 8.1 (Berkeley) 6/10/93 | |
34 | * tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp | |
35 | */ | |
36 | ||
37 | #include <slirp.h> | |
38 | ||
f0cbd3ec FB |
39 | int tcp_keepidle = TCPTV_KEEP_IDLE; |
40 | int tcp_keepintvl = TCPTV_KEEPINTVL; | |
41 | int tcp_maxidle; | |
42 | int so_options = DO_KEEPALIVE; | |
43 | ||
44 | struct tcpstat tcpstat; /* tcp statistics */ | |
45 | u_int32_t tcp_now; /* for RFC 1323 timestamps */ | |
46 | ||
47 | /* | |
48 | * Fast timeout routine for processing delayed acks | |
49 | */ | |
50 | void | |
51 | tcp_fasttimo() | |
52 | { | |
53 | register struct socket *so; | |
54 | register struct tcpcb *tp; | |
55 | ||
56 | DEBUG_CALL("tcp_fasttimo"); | |
57 | ||
58 | so = tcb.so_next; | |
59 | if (so) | |
60 | for (; so != &tcb; so = so->so_next) | |
61 | if ((tp = (struct tcpcb *)so->so_tcpcb) && | |
62 | (tp->t_flags & TF_DELACK)) { | |
63 | tp->t_flags &= ~TF_DELACK; | |
64 | tp->t_flags |= TF_ACKNOW; | |
65 | tcpstat.tcps_delack++; | |
66 | (void) tcp_output(tp); | |
67 | } | |
68 | } | |
69 | ||
70 | /* | |
71 | * Tcp protocol timeout routine called every 500 ms. | |
72 | * Updates the timers in all active tcb's and | |
73 | * causes finite state machine actions if timers expire. | |
74 | */ | |
75 | void | |
76 | tcp_slowtimo() | |
77 | { | |
78 | register struct socket *ip, *ipnxt; | |
79 | register struct tcpcb *tp; | |
80 | register int i; | |
81 | ||
82 | DEBUG_CALL("tcp_slowtimo"); | |
83 | ||
84 | tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; | |
85 | /* | |
86 | * Search through tcb's and update active timers. | |
87 | */ | |
88 | ip = tcb.so_next; | |
89 | if (ip == 0) | |
90 | return; | |
91 | for (; ip != &tcb; ip = ipnxt) { | |
92 | ipnxt = ip->so_next; | |
93 | tp = sototcpcb(ip); | |
94 | if (tp == 0) | |
95 | continue; | |
96 | for (i = 0; i < TCPT_NTIMERS; i++) { | |
97 | if (tp->t_timer[i] && --tp->t_timer[i] == 0) { | |
98 | tcp_timers(tp,i); | |
99 | if (ipnxt->so_prev != ip) | |
100 | goto tpgone; | |
101 | } | |
102 | } | |
103 | tp->t_idle++; | |
104 | if (tp->t_rtt) | |
105 | tp->t_rtt++; | |
106 | tpgone: | |
107 | ; | |
108 | } | |
109 | tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ | |
110 | #ifdef TCP_COMPAT_42 | |
111 | if ((int)tcp_iss < 0) | |
112 | tcp_iss = 0; /* XXX */ | |
113 | #endif | |
114 | tcp_now++; /* for timestamps */ | |
115 | } | |
116 | ||
117 | /* | |
118 | * Cancel all timers for TCP tp. | |
119 | */ | |
120 | void | |
121 | tcp_canceltimers(tp) | |
122 | struct tcpcb *tp; | |
123 | { | |
124 | register int i; | |
125 | ||
126 | for (i = 0; i < TCPT_NTIMERS; i++) | |
127 | tp->t_timer[i] = 0; | |
128 | } | |
129 | ||
130 | int tcp_backoff[TCP_MAXRXTSHIFT + 1] = | |
131 | { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; | |
132 | ||
133 | /* | |
134 | * TCP timer processing. | |
135 | */ | |
136 | struct tcpcb * | |
137 | tcp_timers(tp, timer) | |
138 | register struct tcpcb *tp; | |
139 | int timer; | |
140 | { | |
141 | register int rexmt; | |
142 | ||
143 | DEBUG_CALL("tcp_timers"); | |
144 | ||
145 | switch (timer) { | |
146 | ||
147 | /* | |
148 | * 2 MSL timeout in shutdown went off. If we're closed but | |
149 | * still waiting for peer to close and connection has been idle | |
150 | * too long, or if 2MSL time is up from TIME_WAIT, delete connection | |
151 | * control block. Otherwise, check again in a bit. | |
152 | */ | |
153 | case TCPT_2MSL: | |
154 | if (tp->t_state != TCPS_TIME_WAIT && | |
155 | tp->t_idle <= tcp_maxidle) | |
156 | tp->t_timer[TCPT_2MSL] = tcp_keepintvl; | |
157 | else | |
158 | tp = tcp_close(tp); | |
159 | break; | |
160 | ||
161 | /* | |
162 | * Retransmission timer went off. Message has not | |
163 | * been acked within retransmit interval. Back off | |
164 | * to a longer retransmit interval and retransmit one segment. | |
165 | */ | |
166 | case TCPT_REXMT: | |
167 | ||
168 | /* | |
169 | * XXXXX If a packet has timed out, then remove all the queued | |
170 | * packets for that session. | |
171 | */ | |
172 | ||
173 | if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { | |
174 | /* | |
175 | * This is a hack to suit our terminal server here at the uni of canberra | |
176 | * since they have trouble with zeroes... It usually lets them through | |
177 | * unharmed, but under some conditions, it'll eat the zeros. If we | |
178 | * keep retransmitting it, it'll keep eating the zeroes, so we keep | |
179 | * retransmitting, and eventually the connection dies... | |
180 | * (this only happens on incoming data) | |
181 | * | |
182 | * So, if we were gonna drop the connection from too many retransmits, | |
183 | * don't... instead halve the t_maxseg, which might break up the NULLs and | |
184 | * let them through | |
185 | * | |
186 | * *sigh* | |
187 | */ | |
188 | ||
189 | tp->t_maxseg >>= 1; | |
190 | if (tp->t_maxseg < 32) { | |
191 | /* | |
192 | * We tried our best, now the connection must die! | |
193 | */ | |
194 | tp->t_rxtshift = TCP_MAXRXTSHIFT; | |
195 | tcpstat.tcps_timeoutdrop++; | |
196 | tp = tcp_drop(tp, tp->t_softerror); | |
197 | /* tp->t_softerror : ETIMEDOUT); */ /* XXX */ | |
198 | return (tp); /* XXX */ | |
199 | } | |
200 | ||
201 | /* | |
202 | * Set rxtshift to 6, which is still at the maximum | |
203 | * backoff time | |
204 | */ | |
205 | tp->t_rxtshift = 6; | |
206 | } | |
207 | tcpstat.tcps_rexmttimeo++; | |
208 | rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; | |
209 | TCPT_RANGESET(tp->t_rxtcur, rexmt, | |
210 | (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */ | |
211 | tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; | |
212 | /* | |
213 | * If losing, let the lower level know and try for | |
214 | * a better route. Also, if we backed off this far, | |
215 | * our srtt estimate is probably bogus. Clobber it | |
216 | * so we'll take the next rtt measurement as our srtt; | |
217 | * move the current srtt into rttvar to keep the current | |
218 | * retransmit times until then. | |
219 | */ | |
220 | if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { | |
221 | /* in_losing(tp->t_inpcb); */ | |
222 | tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); | |
223 | tp->t_srtt = 0; | |
224 | } | |
225 | tp->snd_nxt = tp->snd_una; | |
226 | /* | |
227 | * If timing a segment in this window, stop the timer. | |
228 | */ | |
229 | tp->t_rtt = 0; | |
230 | /* | |
231 | * Close the congestion window down to one segment | |
232 | * (we'll open it by one segment for each ack we get). | |
233 | * Since we probably have a window's worth of unacked | |
234 | * data accumulated, this "slow start" keeps us from | |
235 | * dumping all that data as back-to-back packets (which | |
236 | * might overwhelm an intermediate gateway). | |
237 | * | |
238 | * There are two phases to the opening: Initially we | |
239 | * open by one mss on each ack. This makes the window | |
240 | * size increase exponentially with time. If the | |
241 | * window is larger than the path can handle, this | |
242 | * exponential growth results in dropped packet(s) | |
243 | * almost immediately. To get more time between | |
244 | * drops but still "push" the network to take advantage | |
245 | * of improving conditions, we switch from exponential | |
246 | * to linear window opening at some threshold size. | |
247 | * For a threshold, we use half the current window | |
248 | * size, truncated to a multiple of the mss. | |
249 | * | |
250 | * (the minimum cwnd that will give us exponential | |
251 | * growth is 2 mss. We don't allow the threshold | |
252 | * to go below this.) | |
253 | */ | |
254 | { | |
255 | u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; | |
256 | if (win < 2) | |
257 | win = 2; | |
258 | tp->snd_cwnd = tp->t_maxseg; | |
259 | tp->snd_ssthresh = win * tp->t_maxseg; | |
260 | tp->t_dupacks = 0; | |
261 | } | |
262 | (void) tcp_output(tp); | |
263 | break; | |
264 | ||
265 | /* | |
266 | * Persistence timer into zero window. | |
267 | * Force a byte to be output, if possible. | |
268 | */ | |
269 | case TCPT_PERSIST: | |
270 | tcpstat.tcps_persisttimeo++; | |
271 | tcp_setpersist(tp); | |
272 | tp->t_force = 1; | |
273 | (void) tcp_output(tp); | |
274 | tp->t_force = 0; | |
275 | break; | |
276 | ||
277 | /* | |
278 | * Keep-alive timer went off; send something | |
279 | * or drop connection if idle for too long. | |
280 | */ | |
281 | case TCPT_KEEP: | |
282 | tcpstat.tcps_keeptimeo++; | |
283 | if (tp->t_state < TCPS_ESTABLISHED) | |
284 | goto dropit; | |
285 | ||
286 | /* if (tp->t_socket->so_options & SO_KEEPALIVE && */ | |
287 | if ((so_options) && tp->t_state <= TCPS_CLOSE_WAIT) { | |
288 | if (tp->t_idle >= tcp_keepidle + tcp_maxidle) | |
289 | goto dropit; | |
290 | /* | |
291 | * Send a packet designed to force a response | |
292 | * if the peer is up and reachable: | |
293 | * either an ACK if the connection is still alive, | |
294 | * or an RST if the peer has closed the connection | |
295 | * due to timeout or reboot. | |
296 | * Using sequence number tp->snd_una-1 | |
297 | * causes the transmitted zero-length segment | |
298 | * to lie outside the receive window; | |
299 | * by the protocol spec, this requires the | |
300 | * correspondent TCP to respond. | |
301 | */ | |
302 | tcpstat.tcps_keepprobe++; | |
303 | #ifdef TCP_COMPAT_42 | |
304 | /* | |
305 | * The keepalive packet must have nonzero length | |
306 | * to get a 4.2 host to respond. | |
307 | */ | |
308 | tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL, | |
309 | tp->rcv_nxt - 1, tp->snd_una - 1, 0); | |
310 | #else | |
311 | tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL, | |
312 | tp->rcv_nxt, tp->snd_una - 1, 0); | |
313 | #endif | |
314 | tp->t_timer[TCPT_KEEP] = tcp_keepintvl; | |
315 | } else | |
316 | tp->t_timer[TCPT_KEEP] = tcp_keepidle; | |
317 | break; | |
318 | ||
319 | dropit: | |
320 | tcpstat.tcps_keepdrops++; | |
321 | tp = tcp_drop(tp, 0); /* ETIMEDOUT); */ | |
322 | break; | |
323 | } | |
324 | ||
325 | return (tp); | |
326 | } |