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f0cbd3ec FB |
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. | |
2f5f8996 | 13 | * 3. Neither the name of the University nor the names of its contributors |
f0cbd3ec FB |
14 | * may be used to endorse or promote products derived from this software |
15 | * without specific prior written permission. | |
16 | * | |
17 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
27 | * SUCH DAMAGE. | |
28 | * | |
29 | * @(#)tcp_timer.c 8.1 (Berkeley) 6/10/93 | |
30 | * tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp | |
31 | */ | |
32 | ||
33 | #include <slirp.h> | |
34 | ||
31a60e22 | 35 | #ifdef LOG_ENABLED |
f0cbd3ec | 36 | struct tcpstat tcpstat; /* tcp statistics */ |
31a60e22 BS |
37 | #endif |
38 | ||
f0cbd3ec FB |
39 | u_int32_t tcp_now; /* for RFC 1323 timestamps */ |
40 | ||
9634d903 BS |
41 | static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer); |
42 | ||
f0cbd3ec FB |
43 | /* |
44 | * Fast timeout routine for processing delayed acks | |
45 | */ | |
46 | void | |
aeed97c4 | 47 | tcp_fasttimo(void) |
f0cbd3ec FB |
48 | { |
49 | register struct socket *so; | |
50 | register struct tcpcb *tp; | |
51 | ||
52 | DEBUG_CALL("tcp_fasttimo"); | |
5fafdf24 | 53 | |
f0cbd3ec FB |
54 | so = tcb.so_next; |
55 | if (so) | |
56 | for (; so != &tcb; so = so->so_next) | |
57 | if ((tp = (struct tcpcb *)so->so_tcpcb) && | |
58 | (tp->t_flags & TF_DELACK)) { | |
59 | tp->t_flags &= ~TF_DELACK; | |
60 | tp->t_flags |= TF_ACKNOW; | |
31a60e22 | 61 | STAT(tcpstat.tcps_delack++); |
f0cbd3ec FB |
62 | (void) tcp_output(tp); |
63 | } | |
64 | } | |
65 | ||
66 | /* | |
67 | * Tcp protocol timeout routine called every 500 ms. | |
68 | * Updates the timers in all active tcb's and | |
69 | * causes finite state machine actions if timers expire. | |
70 | */ | |
71 | void | |
aeed97c4 | 72 | tcp_slowtimo(void) |
f0cbd3ec FB |
73 | { |
74 | register struct socket *ip, *ipnxt; | |
75 | register struct tcpcb *tp; | |
76 | register int i; | |
77 | ||
78 | DEBUG_CALL("tcp_slowtimo"); | |
5fafdf24 | 79 | |
f0cbd3ec FB |
80 | /* |
81 | * Search through tcb's and update active timers. | |
82 | */ | |
83 | ip = tcb.so_next; | |
84 | if (ip == 0) | |
85 | return; | |
86 | for (; ip != &tcb; ip = ipnxt) { | |
87 | ipnxt = ip->so_next; | |
88 | tp = sototcpcb(ip); | |
89 | if (tp == 0) | |
90 | continue; | |
91 | for (i = 0; i < TCPT_NTIMERS; i++) { | |
92 | if (tp->t_timer[i] && --tp->t_timer[i] == 0) { | |
93 | tcp_timers(tp,i); | |
94 | if (ipnxt->so_prev != ip) | |
95 | goto tpgone; | |
96 | } | |
97 | } | |
98 | tp->t_idle++; | |
99 | if (tp->t_rtt) | |
100 | tp->t_rtt++; | |
101 | tpgone: | |
102 | ; | |
103 | } | |
104 | tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ | |
105 | #ifdef TCP_COMPAT_42 | |
106 | if ((int)tcp_iss < 0) | |
107 | tcp_iss = 0; /* XXX */ | |
108 | #endif | |
109 | tcp_now++; /* for timestamps */ | |
110 | } | |
111 | ||
112 | /* | |
113 | * Cancel all timers for TCP tp. | |
114 | */ | |
115 | void | |
aeed97c4 | 116 | tcp_canceltimers(struct tcpcb *tp) |
f0cbd3ec FB |
117 | { |
118 | register int i; | |
119 | ||
120 | for (i = 0; i < TCPT_NTIMERS; i++) | |
121 | tp->t_timer[i] = 0; | |
122 | } | |
123 | ||
9634d903 | 124 | const int tcp_backoff[TCP_MAXRXTSHIFT + 1] = |
f0cbd3ec FB |
125 | { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; |
126 | ||
127 | /* | |
128 | * TCP timer processing. | |
129 | */ | |
9634d903 BS |
130 | static struct tcpcb * |
131 | tcp_timers(register struct tcpcb *tp, int timer) | |
f0cbd3ec FB |
132 | { |
133 | register int rexmt; | |
5fafdf24 | 134 | |
f0cbd3ec | 135 | DEBUG_CALL("tcp_timers"); |
5fafdf24 | 136 | |
f0cbd3ec FB |
137 | switch (timer) { |
138 | ||
139 | /* | |
140 | * 2 MSL timeout in shutdown went off. If we're closed but | |
141 | * still waiting for peer to close and connection has been idle | |
142 | * too long, or if 2MSL time is up from TIME_WAIT, delete connection | |
143 | * control block. Otherwise, check again in a bit. | |
144 | */ | |
145 | case TCPT_2MSL: | |
146 | if (tp->t_state != TCPS_TIME_WAIT && | |
9634d903 BS |
147 | tp->t_idle <= TCP_MAXIDLE) |
148 | tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL; | |
f0cbd3ec FB |
149 | else |
150 | tp = tcp_close(tp); | |
151 | break; | |
152 | ||
153 | /* | |
154 | * Retransmission timer went off. Message has not | |
155 | * been acked within retransmit interval. Back off | |
156 | * to a longer retransmit interval and retransmit one segment. | |
157 | */ | |
158 | case TCPT_REXMT: | |
3b46e624 | 159 | |
f0cbd3ec FB |
160 | /* |
161 | * XXXXX If a packet has timed out, then remove all the queued | |
162 | * packets for that session. | |
163 | */ | |
3b46e624 | 164 | |
f0cbd3ec FB |
165 | if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { |
166 | /* | |
167 | * This is a hack to suit our terminal server here at the uni of canberra | |
168 | * since they have trouble with zeroes... It usually lets them through | |
169 | * unharmed, but under some conditions, it'll eat the zeros. If we | |
170 | * keep retransmitting it, it'll keep eating the zeroes, so we keep | |
171 | * retransmitting, and eventually the connection dies... | |
172 | * (this only happens on incoming data) | |
5fafdf24 | 173 | * |
f0cbd3ec FB |
174 | * So, if we were gonna drop the connection from too many retransmits, |
175 | * don't... instead halve the t_maxseg, which might break up the NULLs and | |
176 | * let them through | |
5fafdf24 | 177 | * |
f0cbd3ec FB |
178 | * *sigh* |
179 | */ | |
3b46e624 | 180 | |
f0cbd3ec FB |
181 | tp->t_maxseg >>= 1; |
182 | if (tp->t_maxseg < 32) { | |
183 | /* | |
184 | * We tried our best, now the connection must die! | |
185 | */ | |
186 | tp->t_rxtshift = TCP_MAXRXTSHIFT; | |
31a60e22 | 187 | STAT(tcpstat.tcps_timeoutdrop++); |
f0cbd3ec FB |
188 | tp = tcp_drop(tp, tp->t_softerror); |
189 | /* tp->t_softerror : ETIMEDOUT); */ /* XXX */ | |
190 | return (tp); /* XXX */ | |
191 | } | |
3b46e624 | 192 | |
f0cbd3ec FB |
193 | /* |
194 | * Set rxtshift to 6, which is still at the maximum | |
195 | * backoff time | |
196 | */ | |
197 | tp->t_rxtshift = 6; | |
198 | } | |
31a60e22 | 199 | STAT(tcpstat.tcps_rexmttimeo++); |
f0cbd3ec FB |
200 | rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; |
201 | TCPT_RANGESET(tp->t_rxtcur, rexmt, | |
202 | (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */ | |
203 | tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; | |
204 | /* | |
205 | * If losing, let the lower level know and try for | |
206 | * a better route. Also, if we backed off this far, | |
207 | * our srtt estimate is probably bogus. Clobber it | |
208 | * so we'll take the next rtt measurement as our srtt; | |
209 | * move the current srtt into rttvar to keep the current | |
210 | * retransmit times until then. | |
211 | */ | |
212 | if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { | |
213 | /* in_losing(tp->t_inpcb); */ | |
214 | tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); | |
215 | tp->t_srtt = 0; | |
216 | } | |
217 | tp->snd_nxt = tp->snd_una; | |
218 | /* | |
219 | * If timing a segment in this window, stop the timer. | |
220 | */ | |
221 | tp->t_rtt = 0; | |
222 | /* | |
223 | * Close the congestion window down to one segment | |
224 | * (we'll open it by one segment for each ack we get). | |
225 | * Since we probably have a window's worth of unacked | |
226 | * data accumulated, this "slow start" keeps us from | |
227 | * dumping all that data as back-to-back packets (which | |
228 | * might overwhelm an intermediate gateway). | |
229 | * | |
230 | * There are two phases to the opening: Initially we | |
231 | * open by one mss on each ack. This makes the window | |
232 | * size increase exponentially with time. If the | |
233 | * window is larger than the path can handle, this | |
234 | * exponential growth results in dropped packet(s) | |
5fafdf24 | 235 | * almost immediately. To get more time between |
f0cbd3ec FB |
236 | * drops but still "push" the network to take advantage |
237 | * of improving conditions, we switch from exponential | |
238 | * to linear window opening at some threshold size. | |
239 | * For a threshold, we use half the current window | |
240 | * size, truncated to a multiple of the mss. | |
241 | * | |
242 | * (the minimum cwnd that will give us exponential | |
243 | * growth is 2 mss. We don't allow the threshold | |
244 | * to go below this.) | |
245 | */ | |
246 | { | |
247 | u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; | |
248 | if (win < 2) | |
249 | win = 2; | |
250 | tp->snd_cwnd = tp->t_maxseg; | |
251 | tp->snd_ssthresh = win * tp->t_maxseg; | |
252 | tp->t_dupacks = 0; | |
253 | } | |
254 | (void) tcp_output(tp); | |
255 | break; | |
256 | ||
257 | /* | |
258 | * Persistence timer into zero window. | |
259 | * Force a byte to be output, if possible. | |
260 | */ | |
261 | case TCPT_PERSIST: | |
31a60e22 | 262 | STAT(tcpstat.tcps_persisttimeo++); |
f0cbd3ec FB |
263 | tcp_setpersist(tp); |
264 | tp->t_force = 1; | |
265 | (void) tcp_output(tp); | |
266 | tp->t_force = 0; | |
267 | break; | |
268 | ||
269 | /* | |
270 | * Keep-alive timer went off; send something | |
271 | * or drop connection if idle for too long. | |
272 | */ | |
273 | case TCPT_KEEP: | |
31a60e22 | 274 | STAT(tcpstat.tcps_keeptimeo++); |
f0cbd3ec FB |
275 | if (tp->t_state < TCPS_ESTABLISHED) |
276 | goto dropit; | |
277 | ||
278 | /* if (tp->t_socket->so_options & SO_KEEPALIVE && */ | |
9634d903 BS |
279 | if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) { |
280 | if (tp->t_idle >= TCPTV_KEEP_IDLE + TCP_MAXIDLE) | |
f0cbd3ec FB |
281 | goto dropit; |
282 | /* | |
283 | * Send a packet designed to force a response | |
284 | * if the peer is up and reachable: | |
285 | * either an ACK if the connection is still alive, | |
286 | * or an RST if the peer has closed the connection | |
287 | * due to timeout or reboot. | |
288 | * Using sequence number tp->snd_una-1 | |
289 | * causes the transmitted zero-length segment | |
290 | * to lie outside the receive window; | |
291 | * by the protocol spec, this requires the | |
292 | * correspondent TCP to respond. | |
293 | */ | |
31a60e22 | 294 | STAT(tcpstat.tcps_keepprobe++); |
f0cbd3ec FB |
295 | #ifdef TCP_COMPAT_42 |
296 | /* | |
297 | * The keepalive packet must have nonzero length | |
298 | * to get a 4.2 host to respond. | |
299 | */ | |
300 | tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL, | |
301 | tp->rcv_nxt - 1, tp->snd_una - 1, 0); | |
302 | #else | |
303 | tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL, | |
304 | tp->rcv_nxt, tp->snd_una - 1, 0); | |
305 | #endif | |
9634d903 | 306 | tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL; |
f0cbd3ec | 307 | } else |
9634d903 | 308 | tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE; |
f0cbd3ec FB |
309 | break; |
310 | ||
311 | dropit: | |
31a60e22 | 312 | STAT(tcpstat.tcps_keepdrops++); |
f0cbd3ec FB |
313 | tp = tcp_drop(tp, 0); /* ETIMEDOUT); */ |
314 | break; | |
315 | } | |
316 | ||
317 | return (tp); | |
318 | } |