VirtualBox

source: vbox/trunk/src/VBox/Devices/Network/slirp/tcp_timer.c@ 9114

Last change on this file since 9114 was 1076, checked in by vboxsync, 18 years ago

Removed tons of ifdef VBOX conditionals to make slirp readable again

  • Property svn:eol-style set to native
File size: 9.2 KB
Line 
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
39
40/*
41 * Fast timeout routine for processing delayed acks
42 */
43void
44tcp_fasttimo(PNATState pData)
45{
46 register struct socket *so;
47 register struct tcpcb *tp;
48
49 DEBUG_CALL("tcp_fasttimo");
50
51 so = tcb.so_next;
52 if (so)
53 for (; so != &tcb; so = so->so_next)
54 if ((tp = (struct tcpcb *)so->so_tcpcb) &&
55 (tp->t_flags & TF_DELACK)) {
56 tp->t_flags &= ~TF_DELACK;
57 tp->t_flags |= TF_ACKNOW;
58 tcpstat.tcps_delack++;
59 (void) tcp_output(pData, tp);
60 }
61}
62
63/*
64 * Tcp protocol timeout routine called every 500 ms.
65 * Updates the timers in all active tcb's and
66 * causes finite state machine actions if timers expire.
67 */
68void
69tcp_slowtimo(PNATState pData)
70{
71 register struct socket *ip, *ipnxt;
72 register struct tcpcb *tp;
73 register int i;
74
75 DEBUG_CALL("tcp_slowtimo");
76
77 /*
78 * Search through tcb's and update active timers.
79 */
80 ip = tcb.so_next;
81 if (ip == 0)
82 return;
83 for (; ip != &tcb; ip = ipnxt) {
84 ipnxt = ip->so_next;
85 tp = sototcpcb(ip);
86 if (tp == 0)
87 continue;
88 for (i = 0; i < TCPT_NTIMERS; i++) {
89 if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
90 tcp_timers(pData, tp,i);
91 if (ipnxt->so_prev != ip)
92 goto tpgone;
93 }
94 }
95 tp->t_idle++;
96 if (tp->t_rtt)
97 tp->t_rtt++;
98tpgone:
99 ;
100 }
101 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
102#ifdef TCP_COMPAT_42
103 if ((int)tcp_iss < 0)
104 tcp_iss = 0; /* XXX */
105#endif
106 tcp_now++; /* for timestamps */
107}
108
109/*
110 * Cancel all timers for TCP tp.
111 */
112void
113tcp_canceltimers(tp)
114 struct tcpcb *tp;
115{
116 register int i;
117
118 for (i = 0; i < TCPT_NTIMERS; i++)
119 tp->t_timer[i] = 0;
120}
121
122const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
123 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
124
125/*
126 * TCP timer processing.
127 */
128struct tcpcb *
129tcp_timers(PNATState pData, register struct tcpcb *tp, int timer)
130{
131 register int rexmt;
132
133 DEBUG_CALL("tcp_timers");
134
135 switch (timer) {
136
137 /*
138 * 2 MSL timeout in shutdown went off. If we're closed but
139 * still waiting for peer to close and connection has been idle
140 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
141 * control block. Otherwise, check again in a bit.
142 */
143 case TCPT_2MSL:
144 if (tp->t_state != TCPS_TIME_WAIT &&
145 tp->t_idle <= tcp_maxidle)
146 tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
147 else
148 tp = tcp_close(pData, tp);
149 break;
150
151 /*
152 * Retransmission timer went off. Message has not
153 * been acked within retransmit interval. Back off
154 * to a longer retransmit interval and retransmit one segment.
155 */
156 case TCPT_REXMT:
157
158 /*
159 * XXXXX If a packet has timed out, then remove all the queued
160 * packets for that session.
161 */
162
163 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
164 /*
165 * This is a hack to suit our terminal server here at the uni of canberra
166 * since they have trouble with zeroes... It usually lets them through
167 * unharmed, but under some conditions, it'll eat the zeros. If we
168 * keep retransmitting it, it'll keep eating the zeroes, so we keep
169 * retransmitting, and eventually the connection dies...
170 * (this only happens on incoming data)
171 *
172 * So, if we were gonna drop the connection from too many retransmits,
173 * don't... instead halve the t_maxseg, which might break up the NULLs and
174 * let them through
175 *
176 * *sigh*
177 */
178
179 tp->t_maxseg >>= 1;
180 if (tp->t_maxseg < 32) {
181 /*
182 * We tried our best, now the connection must die!
183 */
184 tp->t_rxtshift = TCP_MAXRXTSHIFT;
185 tcpstat.tcps_timeoutdrop++;
186 tp = tcp_drop(pData, tp, tp->t_softerror);
187 /* tp->t_softerror : ETIMEDOUT); */ /* XXX */
188 return (tp); /* XXX */
189 }
190
191 /*
192 * Set rxtshift to 6, which is still at the maximum
193 * backoff time
194 */
195 tp->t_rxtshift = 6;
196 }
197 tcpstat.tcps_rexmttimeo++;
198 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
199 TCPT_RANGESET(tp->t_rxtcur, rexmt,
200 (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
201 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
202 /*
203 * If losing, let the lower level know and try for
204 * a better route. Also, if we backed off this far,
205 * our srtt estimate is probably bogus. Clobber it
206 * so we'll take the next rtt measurement as our srtt;
207 * move the current srtt into rttvar to keep the current
208 * retransmit times until then.
209 */
210 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
211/* in_losing(tp->t_inpcb); */
212 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
213 tp->t_srtt = 0;
214 }
215 tp->snd_nxt = tp->snd_una;
216 /*
217 * If timing a segment in this window, stop the timer.
218 */
219 tp->t_rtt = 0;
220 /*
221 * Close the congestion window down to one segment
222 * (we'll open it by one segment for each ack we get).
223 * Since we probably have a window's worth of unacked
224 * data accumulated, this "slow start" keeps us from
225 * dumping all that data as back-to-back packets (which
226 * might overwhelm an intermediate gateway).
227 *
228 * There are two phases to the opening: Initially we
229 * open by one mss on each ack. This makes the window
230 * size increase exponentially with time. If the
231 * window is larger than the path can handle, this
232 * exponential growth results in dropped packet(s)
233 * almost immediately. To get more time between
234 * drops but still "push" the network to take advantage
235 * of improving conditions, we switch from exponential
236 * to linear window opening at some threshold size.
237 * For a threshold, we use half the current window
238 * size, truncated to a multiple of the mss.
239 *
240 * (the minimum cwnd that will give us exponential
241 * growth is 2 mss. We don't allow the threshold
242 * to go below this.)
243 */
244 {
245 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
246 if (win < 2)
247 win = 2;
248 tp->snd_cwnd = tp->t_maxseg;
249 tp->snd_ssthresh = win * tp->t_maxseg;
250 tp->t_dupacks = 0;
251 }
252 (void) tcp_output(pData, tp);
253 break;
254
255 /*
256 * Persistence timer into zero window.
257 * Force a byte to be output, if possible.
258 */
259 case TCPT_PERSIST:
260 tcpstat.tcps_persisttimeo++;
261 tcp_setpersist(tp);
262 tp->t_force = 1;
263 (void) tcp_output(pData, tp);
264 tp->t_force = 0;
265 break;
266
267 /*
268 * Keep-alive timer went off; send something
269 * or drop connection if idle for too long.
270 */
271 case TCPT_KEEP:
272 tcpstat.tcps_keeptimeo++;
273 if (tp->t_state < TCPS_ESTABLISHED)
274 goto dropit;
275
276/* if (tp->t_socket->so_options & SO_KEEPALIVE && */
277 if ((so_options) && tp->t_state <= TCPS_CLOSE_WAIT) {
278 if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
279 goto dropit;
280 /*
281 * Send a packet designed to force a response
282 * if the peer is up and reachable:
283 * either an ACK if the connection is still alive,
284 * or an RST if the peer has closed the connection
285 * due to timeout or reboot.
286 * Using sequence number tp->snd_una-1
287 * causes the transmitted zero-length segment
288 * to lie outside the receive window;
289 * by the protocol spec, this requires the
290 * correspondent TCP to respond.
291 */
292 tcpstat.tcps_keepprobe++;
293#ifdef TCP_COMPAT_42
294 /*
295 * The keepalive packet must have nonzero length
296 * to get a 4.2 host to respond.
297 */
298 tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
299 tp->rcv_nxt - 1, tp->snd_una - 1, 0);
300#else
301 tcp_respond(pData, tp, &tp->t_template, (struct mbuf *)NULL,
302 tp->rcv_nxt, tp->snd_una - 1, 0);
303#endif
304 tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
305 } else
306 tp->t_timer[TCPT_KEEP] = tcp_keepidle;
307 break;
308
309 dropit:
310 tcpstat.tcps_keepdrops++;
311 tp = tcp_drop(pData, tp, 0); /* ETIMEDOUT); */
312 break;
313 }
314
315 return (tp);
316}
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