Statistics
| Branch: | Revision:

root / slirp / tcp_timer.c @ 5fafdf24

History | View | Annotate | Download (9.4 kB)

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
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
}