File:
[Qemu by Fabrice Bellard] /
qemu /
slirp /
tcp_timer.c
Revision
1.1.1.4 (vendor branch):
download - view:
text,
annotated -
select for diffs
Tue Apr 24 17:25:33 2018 UTC (2 years, 11 months ago) by
root
Branches:
qemu,
MAIN
CVS tags:
qemu1101,
qemu1001,
qemu1000,
qemu0151,
qemu0150,
qemu0141,
qemu0140,
qemu0130,
qemu0125,
qemu0124,
qemu0123,
qemu0122,
qemu0121,
qemu0120,
qemu0111,
qemu0110,
HEAD
qemu 0.11.0
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 <slirp.h>
34:
35: static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer);
36:
37: /*
38: * Fast timeout routine for processing delayed acks
39: */
40: void
41: tcp_fasttimo(Slirp *slirp)
42: {
43: register struct socket *so;
44: register struct tcpcb *tp;
45:
46: DEBUG_CALL("tcp_fasttimo");
47:
48: so = slirp->tcb.so_next;
49: if (so)
50: for (; so != &slirp->tcb; so = so->so_next)
51: if ((tp = (struct tcpcb *)so->so_tcpcb) &&
52: (tp->t_flags & TF_DELACK)) {
53: tp->t_flags &= ~TF_DELACK;
54: tp->t_flags |= TF_ACKNOW;
55: (void) tcp_output(tp);
56: }
57: }
58:
59: /*
60: * Tcp protocol timeout routine called every 500 ms.
61: * Updates the timers in all active tcb's and
62: * causes finite state machine actions if timers expire.
63: */
64: void
65: tcp_slowtimo(Slirp *slirp)
66: {
67: register struct socket *ip, *ipnxt;
68: register struct tcpcb *tp;
69: register int i;
70:
71: DEBUG_CALL("tcp_slowtimo");
72:
73: /*
74: * Search through tcb's and update active timers.
75: */
76: ip = slirp->tcb.so_next;
77: if (ip == NULL) {
78: return;
79: }
80: for (; ip != &slirp->tcb; ip = ipnxt) {
81: ipnxt = ip->so_next;
82: tp = sototcpcb(ip);
83: if (tp == NULL) {
84: continue;
85: }
86: for (i = 0; i < TCPT_NTIMERS; i++) {
87: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
88: tcp_timers(tp,i);
89: if (ipnxt->so_prev != ip)
90: goto tpgone;
91: }
92: }
93: tp->t_idle++;
94: if (tp->t_rtt)
95: tp->t_rtt++;
96: tpgone:
97: ;
98: }
99: slirp->tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
100: slirp->tcp_now++; /* for timestamps */
101: }
102:
103: /*
104: * Cancel all timers for TCP tp.
105: */
106: void
107: tcp_canceltimers(struct tcpcb *tp)
108: {
109: register int i;
110:
111: for (i = 0; i < TCPT_NTIMERS; i++)
112: tp->t_timer[i] = 0;
113: }
114:
115: const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
116: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
117:
118: /*
119: * TCP timer processing.
120: */
121: static struct tcpcb *
122: tcp_timers(register struct tcpcb *tp, int timer)
123: {
124: register int rexmt;
125:
126: DEBUG_CALL("tcp_timers");
127:
128: switch (timer) {
129:
130: /*
131: * 2 MSL timeout in shutdown went off. If we're closed but
132: * still waiting for peer to close and connection has been idle
133: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
134: * control block. Otherwise, check again in a bit.
135: */
136: case TCPT_2MSL:
137: if (tp->t_state != TCPS_TIME_WAIT &&
138: tp->t_idle <= TCP_MAXIDLE)
139: tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL;
140: else
141: tp = tcp_close(tp);
142: break;
143:
144: /*
145: * Retransmission timer went off. Message has not
146: * been acked within retransmit interval. Back off
147: * to a longer retransmit interval and retransmit one segment.
148: */
149: case TCPT_REXMT:
150:
151: /*
152: * XXXXX If a packet has timed out, then remove all the queued
153: * packets for that session.
154: */
155:
156: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
157: /*
158: * This is a hack to suit our terminal server here at the uni of canberra
159: * since they have trouble with zeroes... It usually lets them through
160: * unharmed, but under some conditions, it'll eat the zeros. If we
161: * keep retransmitting it, it'll keep eating the zeroes, so we keep
162: * retransmitting, and eventually the connection dies...
163: * (this only happens on incoming data)
164: *
165: * So, if we were gonna drop the connection from too many retransmits,
166: * don't... instead halve the t_maxseg, which might break up the NULLs and
167: * let them through
168: *
169: * *sigh*
170: */
171:
172: tp->t_maxseg >>= 1;
173: if (tp->t_maxseg < 32) {
174: /*
175: * We tried our best, now the connection must die!
176: */
177: tp->t_rxtshift = TCP_MAXRXTSHIFT;
178: tp = tcp_drop(tp, tp->t_softerror);
179: /* tp->t_softerror : ETIMEDOUT); */ /* XXX */
180: return (tp); /* XXX */
181: }
182:
183: /*
184: * Set rxtshift to 6, which is still at the maximum
185: * backoff time
186: */
187: tp->t_rxtshift = 6;
188: }
189: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
190: TCPT_RANGESET(tp->t_rxtcur, rexmt,
191: (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
192: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
193: /*
194: * If losing, let the lower level know and try for
195: * a better route. Also, if we backed off this far,
196: * our srtt estimate is probably bogus. Clobber it
197: * so we'll take the next rtt measurement as our srtt;
198: * move the current srtt into rttvar to keep the current
199: * retransmit times until then.
200: */
201: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
202: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
203: tp->t_srtt = 0;
204: }
205: tp->snd_nxt = tp->snd_una;
206: /*
207: * If timing a segment in this window, stop the timer.
208: */
209: tp->t_rtt = 0;
210: /*
211: * Close the congestion window down to one segment
212: * (we'll open it by one segment for each ack we get).
213: * Since we probably have a window's worth of unacked
214: * data accumulated, this "slow start" keeps us from
215: * dumping all that data as back-to-back packets (which
216: * might overwhelm an intermediate gateway).
217: *
218: * There are two phases to the opening: Initially we
219: * open by one mss on each ack. This makes the window
220: * size increase exponentially with time. If the
221: * window is larger than the path can handle, this
222: * exponential growth results in dropped packet(s)
223: * almost immediately. To get more time between
224: * drops but still "push" the network to take advantage
225: * of improving conditions, we switch from exponential
226: * to linear window opening at some threshold size.
227: * For a threshold, we use half the current window
228: * size, truncated to a multiple of the mss.
229: *
230: * (the minimum cwnd that will give us exponential
231: * growth is 2 mss. We don't allow the threshold
232: * to go below this.)
233: */
234: {
235: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
236: if (win < 2)
237: win = 2;
238: tp->snd_cwnd = tp->t_maxseg;
239: tp->snd_ssthresh = win * tp->t_maxseg;
240: tp->t_dupacks = 0;
241: }
242: (void) tcp_output(tp);
243: break;
244:
245: /*
246: * Persistence timer into zero window.
247: * Force a byte to be output, if possible.
248: */
249: case TCPT_PERSIST:
250: tcp_setpersist(tp);
251: tp->t_force = 1;
252: (void) tcp_output(tp);
253: tp->t_force = 0;
254: break;
255:
256: /*
257: * Keep-alive timer went off; send something
258: * or drop connection if idle for too long.
259: */
260: case TCPT_KEEP:
261: if (tp->t_state < TCPS_ESTABLISHED)
262: goto dropit;
263:
264: if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
265: if (tp->t_idle >= TCPTV_KEEP_IDLE + TCP_MAXIDLE)
266: goto dropit;
267: /*
268: * Send a packet designed to force a response
269: * if the peer is up and reachable:
270: * either an ACK if the connection is still alive,
271: * or an RST if the peer has closed the connection
272: * due to timeout or reboot.
273: * Using sequence number tp->snd_una-1
274: * causes the transmitted zero-length segment
275: * to lie outside the receive window;
276: * by the protocol spec, this requires the
277: * correspondent TCP to respond.
278: */
279: tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
280: tp->rcv_nxt, tp->snd_una - 1, 0);
281: tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
282: } else
283: tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
284: break;
285:
286: dropit:
287: tp = tcp_drop(tp, 0);
288: break;
289: }
290:
291: return (tp);
292: }
unix.superglobalmegacorp.com