9pfs: fix crash when fsdev is missing
[qemu.git] / slirp / tcp_timer.c
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. Neither the name of the University nor the names of its contributors
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 "qemu/osdep.h"
34 #include "slirp.h"
35
36 static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer);
37
38 /*
39 * Fast timeout routine for processing delayed acks
40 */
41 void
42 tcp_fasttimo(Slirp *slirp)
43 {
44 register struct socket *so;
45 register struct tcpcb *tp;
46
47 DEBUG_CALL("tcp_fasttimo");
48
49 so = slirp->tcb.so_next;
50 if (so)
51 for (; so != &slirp->tcb; so = so->so_next)
52 if ((tp = (struct tcpcb *)so->so_tcpcb) &&
53 (tp->t_flags & TF_DELACK)) {
54 tp->t_flags &= ~TF_DELACK;
55 tp->t_flags |= TF_ACKNOW;
56 (void) tcp_output(tp);
57 }
58 }
59
60 /*
61 * Tcp protocol timeout routine called every 500 ms.
62 * Updates the timers in all active tcb's and
63 * causes finite state machine actions if timers expire.
64 */
65 void
66 tcp_slowtimo(Slirp *slirp)
67 {
68 register struct socket *ip, *ipnxt;
69 register struct tcpcb *tp;
70 register int i;
71
72 DEBUG_CALL("tcp_slowtimo");
73
74 /*
75 * Search through tcb's and update active timers.
76 */
77 ip = slirp->tcb.so_next;
78 if (ip == NULL) {
79 return;
80 }
81 for (; ip != &slirp->tcb; ip = ipnxt) {
82 ipnxt = ip->so_next;
83 tp = sototcpcb(ip);
84 if (tp == NULL) {
85 continue;
86 }
87 for (i = 0; i < TCPT_NTIMERS; i++) {
88 if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
89 tcp_timers(tp,i);
90 if (ipnxt->so_prev != ip)
91 goto tpgone;
92 }
93 }
94 tp->t_idle++;
95 if (tp->t_rtt)
96 tp->t_rtt++;
97 tpgone:
98 ;
99 }
100 slirp->tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
101 slirp->tcp_now++; /* for timestamps */
102 }
103
104 /*
105 * Cancel all timers for TCP tp.
106 */
107 void
108 tcp_canceltimers(struct tcpcb *tp)
109 {
110 register int i;
111
112 for (i = 0; i < TCPT_NTIMERS; i++)
113 tp->t_timer[i] = 0;
114 }
115
116 const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
117 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
118
119 /*
120 * TCP timer processing.
121 */
122 static struct tcpcb *
123 tcp_timers(register struct tcpcb *tp, int timer)
124 {
125 register int rexmt;
126
127 DEBUG_CALL("tcp_timers");
128
129 switch (timer) {
130
131 /*
132 * 2 MSL timeout in shutdown went off. If we're closed but
133 * still waiting for peer to close and connection has been idle
134 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
135 * control block. Otherwise, check again in a bit.
136 */
137 case TCPT_2MSL:
138 if (tp->t_state != TCPS_TIME_WAIT &&
139 tp->t_idle <= TCP_MAXIDLE)
140 tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL;
141 else
142 tp = tcp_close(tp);
143 break;
144
145 /*
146 * Retransmission timer went off. Message has not
147 * been acked within retransmit interval. Back off
148 * to a longer retransmit interval and retransmit one segment.
149 */
150 case TCPT_REXMT:
151
152 /*
153 * XXXXX If a packet has timed out, then remove all the queued
154 * packets for that session.
155 */
156
157 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
158 /*
159 * This is a hack to suit our terminal server here at the uni of canberra
160 * since they have trouble with zeroes... It usually lets them through
161 * unharmed, but under some conditions, it'll eat the zeros. If we
162 * keep retransmitting it, it'll keep eating the zeroes, so we keep
163 * retransmitting, and eventually the connection dies...
164 * (this only happens on incoming data)
165 *
166 * So, if we were gonna drop the connection from too many retransmits,
167 * don't... instead halve the t_maxseg, which might break up the NULLs and
168 * let them through
169 *
170 * *sigh*
171 */
172
173 tp->t_maxseg >>= 1;
174 if (tp->t_maxseg < 32) {
175 /*
176 * We tried our best, now the connection must die!
177 */
178 tp->t_rxtshift = TCP_MAXRXTSHIFT;
179 tp = tcp_drop(tp, tp->t_softerror);
180 /* tp->t_softerror : ETIMEDOUT); */ /* XXX */
181 return (tp); /* XXX */
182 }
183
184 /*
185 * Set rxtshift to 6, which is still at the maximum
186 * backoff time
187 */
188 tp->t_rxtshift = 6;
189 }
190 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
191 TCPT_RANGESET(tp->t_rxtcur, rexmt,
192 (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
193 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
194 /*
195 * If losing, let the lower level know and try for
196 * a better route. Also, if we backed off this far,
197 * our srtt estimate is probably bogus. Clobber it
198 * so we'll take the next rtt measurement as our srtt;
199 * move the current srtt into rttvar to keep the current
200 * retransmit times until then.
201 */
202 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
203 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
204 tp->t_srtt = 0;
205 }
206 tp->snd_nxt = tp->snd_una;
207 /*
208 * If timing a segment in this window, stop the timer.
209 */
210 tp->t_rtt = 0;
211 /*
212 * Close the congestion window down to one segment
213 * (we'll open it by one segment for each ack we get).
214 * Since we probably have a window's worth of unacked
215 * data accumulated, this "slow start" keeps us from
216 * dumping all that data as back-to-back packets (which
217 * might overwhelm an intermediate gateway).
218 *
219 * There are two phases to the opening: Initially we
220 * open by one mss on each ack. This makes the window
221 * size increase exponentially with time. If the
222 * window is larger than the path can handle, this
223 * exponential growth results in dropped packet(s)
224 * almost immediately. To get more time between
225 * drops but still "push" the network to take advantage
226 * of improving conditions, we switch from exponential
227 * to linear window opening at some threshold size.
228 * For a threshold, we use half the current window
229 * size, truncated to a multiple of the mss.
230 *
231 * (the minimum cwnd that will give us exponential
232 * growth is 2 mss. We don't allow the threshold
233 * to go below this.)
234 */
235 {
236 u_int win = MIN(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
237 if (win < 2)
238 win = 2;
239 tp->snd_cwnd = tp->t_maxseg;
240 tp->snd_ssthresh = win * tp->t_maxseg;
241 tp->t_dupacks = 0;
242 }
243 (void) tcp_output(tp);
244 break;
245
246 /*
247 * Persistence timer into zero window.
248 * Force a byte to be output, if possible.
249 */
250 case TCPT_PERSIST:
251 tcp_setpersist(tp);
252 tp->t_force = 1;
253 (void) tcp_output(tp);
254 tp->t_force = 0;
255 break;
256
257 /*
258 * Keep-alive timer went off; send something
259 * or drop connection if idle for too long.
260 */
261 case TCPT_KEEP:
262 if (tp->t_state < TCPS_ESTABLISHED)
263 goto dropit;
264
265 if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
266 if (tp->t_idle >= TCPTV_KEEP_IDLE + TCP_MAXIDLE)
267 goto dropit;
268 /*
269 * Send a packet designed to force a response
270 * if the peer is up and reachable:
271 * either an ACK if the connection is still alive,
272 * or an RST if the peer has closed the connection
273 * due to timeout or reboot.
274 * Using sequence number tp->snd_una-1
275 * causes the transmitted zero-length segment
276 * to lie outside the receive window;
277 * by the protocol spec, this requires the
278 * correspondent TCP to respond.
279 */
280 tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
281 tp->rcv_nxt, tp->snd_una - 1, 0,
282 tp->t_socket->so_ffamily);
283 tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
284 } else
285 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
286 break;
287
288 dropit:
289 tp = tcp_drop(tp, 0);
290 break;
291 }
292
293 return (tp);
294 }