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1.1 root 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:
1.1.1.2 ! root 39: #ifdef LOG_ENABLED
1.1 root 40: struct tcpstat tcpstat; /* tcp statistics */
1.1.1.2 ! root 41: #endif
! 42:
1.1 root 43: u_int32_t tcp_now; /* for RFC 1323 timestamps */
44:
1.1.1.2 ! root 45: static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer);
! 46:
1.1 root 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");
1.1.1.2 ! root 57:
1.1 root 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;
1.1.1.2 ! root 65: STAT(tcpstat.tcps_delack++);
1.1 root 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");
1.1.1.2 ! root 83:
1.1 root 84: /*
85: * Search through tcb's and update active timers.
86: */
87: ip = tcb.so_next;
88: if (ip == 0)
89: return;
90: for (; ip != &tcb; ip = ipnxt) {
91: ipnxt = ip->so_next;
92: tp = sototcpcb(ip);
93: if (tp == 0)
94: continue;
95: for (i = 0; i < TCPT_NTIMERS; i++) {
96: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
97: tcp_timers(tp,i);
98: if (ipnxt->so_prev != ip)
99: goto tpgone;
100: }
101: }
102: tp->t_idle++;
103: if (tp->t_rtt)
104: tp->t_rtt++;
105: tpgone:
106: ;
107: }
108: tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
109: #ifdef TCP_COMPAT_42
110: if ((int)tcp_iss < 0)
111: tcp_iss = 0; /* XXX */
112: #endif
113: tcp_now++; /* for timestamps */
114: }
115:
116: /*
117: * Cancel all timers for TCP tp.
118: */
119: void
120: tcp_canceltimers(tp)
121: struct tcpcb *tp;
122: {
123: register int i;
124:
125: for (i = 0; i < TCPT_NTIMERS; i++)
126: tp->t_timer[i] = 0;
127: }
128:
1.1.1.2 ! root 129: const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
1.1 root 130: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
131:
132: /*
133: * TCP timer processing.
134: */
1.1.1.2 ! root 135: static struct tcpcb *
! 136: tcp_timers(register struct tcpcb *tp, int timer)
1.1 root 137: {
138: register int rexmt;
1.1.1.2 ! root 139:
1.1 root 140: DEBUG_CALL("tcp_timers");
1.1.1.2 ! root 141:
1.1 root 142: switch (timer) {
143:
144: /*
145: * 2 MSL timeout in shutdown went off. If we're closed but
146: * still waiting for peer to close and connection has been idle
147: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
148: * control block. Otherwise, check again in a bit.
149: */
150: case TCPT_2MSL:
151: if (tp->t_state != TCPS_TIME_WAIT &&
1.1.1.2 ! root 152: tp->t_idle <= TCP_MAXIDLE)
! 153: tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL;
1.1 root 154: else
155: tp = tcp_close(tp);
156: break;
157:
158: /*
159: * Retransmission timer went off. Message has not
160: * been acked within retransmit interval. Back off
161: * to a longer retransmit interval and retransmit one segment.
162: */
163: case TCPT_REXMT:
1.1.1.2 ! root 164:
1.1 root 165: /*
166: * XXXXX If a packet has timed out, then remove all the queued
167: * packets for that session.
168: */
1.1.1.2 ! root 169:
1.1 root 170: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
171: /*
172: * This is a hack to suit our terminal server here at the uni of canberra
173: * since they have trouble with zeroes... It usually lets them through
174: * unharmed, but under some conditions, it'll eat the zeros. If we
175: * keep retransmitting it, it'll keep eating the zeroes, so we keep
176: * retransmitting, and eventually the connection dies...
177: * (this only happens on incoming data)
1.1.1.2 ! root 178: *
1.1 root 179: * So, if we were gonna drop the connection from too many retransmits,
180: * don't... instead halve the t_maxseg, which might break up the NULLs and
181: * let them through
1.1.1.2 ! root 182: *
1.1 root 183: * *sigh*
184: */
1.1.1.2 ! root 185:
1.1 root 186: tp->t_maxseg >>= 1;
187: if (tp->t_maxseg < 32) {
188: /*
189: * We tried our best, now the connection must die!
190: */
191: tp->t_rxtshift = TCP_MAXRXTSHIFT;
1.1.1.2 ! root 192: STAT(tcpstat.tcps_timeoutdrop++);
1.1 root 193: tp = tcp_drop(tp, tp->t_softerror);
194: /* tp->t_softerror : ETIMEDOUT); */ /* XXX */
195: return (tp); /* XXX */
196: }
1.1.1.2 ! root 197:
1.1 root 198: /*
199: * Set rxtshift to 6, which is still at the maximum
200: * backoff time
201: */
202: tp->t_rxtshift = 6;
203: }
1.1.1.2 ! root 204: STAT(tcpstat.tcps_rexmttimeo++);
1.1 root 205: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
206: TCPT_RANGESET(tp->t_rxtcur, rexmt,
207: (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
208: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
209: /*
210: * If losing, let the lower level know and try for
211: * a better route. Also, if we backed off this far,
212: * our srtt estimate is probably bogus. Clobber it
213: * so we'll take the next rtt measurement as our srtt;
214: * move the current srtt into rttvar to keep the current
215: * retransmit times until then.
216: */
217: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
218: /* in_losing(tp->t_inpcb); */
219: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
220: tp->t_srtt = 0;
221: }
222: tp->snd_nxt = tp->snd_una;
223: /*
224: * If timing a segment in this window, stop the timer.
225: */
226: tp->t_rtt = 0;
227: /*
228: * Close the congestion window down to one segment
229: * (we'll open it by one segment for each ack we get).
230: * Since we probably have a window's worth of unacked
231: * data accumulated, this "slow start" keeps us from
232: * dumping all that data as back-to-back packets (which
233: * might overwhelm an intermediate gateway).
234: *
235: * There are two phases to the opening: Initially we
236: * open by one mss on each ack. This makes the window
237: * size increase exponentially with time. If the
238: * window is larger than the path can handle, this
239: * exponential growth results in dropped packet(s)
1.1.1.2 ! root 240: * almost immediately. To get more time between
1.1 root 241: * drops but still "push" the network to take advantage
242: * of improving conditions, we switch from exponential
243: * to linear window opening at some threshold size.
244: * For a threshold, we use half the current window
245: * size, truncated to a multiple of the mss.
246: *
247: * (the minimum cwnd that will give us exponential
248: * growth is 2 mss. We don't allow the threshold
249: * to go below this.)
250: */
251: {
252: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
253: if (win < 2)
254: win = 2;
255: tp->snd_cwnd = tp->t_maxseg;
256: tp->snd_ssthresh = win * tp->t_maxseg;
257: tp->t_dupacks = 0;
258: }
259: (void) tcp_output(tp);
260: break;
261:
262: /*
263: * Persistence timer into zero window.
264: * Force a byte to be output, if possible.
265: */
266: case TCPT_PERSIST:
1.1.1.2 ! root 267: STAT(tcpstat.tcps_persisttimeo++);
1.1 root 268: tcp_setpersist(tp);
269: tp->t_force = 1;
270: (void) tcp_output(tp);
271: tp->t_force = 0;
272: break;
273:
274: /*
275: * Keep-alive timer went off; send something
276: * or drop connection if idle for too long.
277: */
278: case TCPT_KEEP:
1.1.1.2 ! root 279: STAT(tcpstat.tcps_keeptimeo++);
1.1 root 280: if (tp->t_state < TCPS_ESTABLISHED)
281: goto dropit;
282:
283: /* if (tp->t_socket->so_options & SO_KEEPALIVE && */
1.1.1.2 ! root 284: if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
! 285: if (tp->t_idle >= TCPTV_KEEP_IDLE + TCP_MAXIDLE)
1.1 root 286: goto dropit;
287: /*
288: * Send a packet designed to force a response
289: * if the peer is up and reachable:
290: * either an ACK if the connection is still alive,
291: * or an RST if the peer has closed the connection
292: * due to timeout or reboot.
293: * Using sequence number tp->snd_una-1
294: * causes the transmitted zero-length segment
295: * to lie outside the receive window;
296: * by the protocol spec, this requires the
297: * correspondent TCP to respond.
298: */
1.1.1.2 ! root 299: STAT(tcpstat.tcps_keepprobe++);
1.1 root 300: #ifdef TCP_COMPAT_42
301: /*
302: * The keepalive packet must have nonzero length
303: * to get a 4.2 host to respond.
304: */
305: tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
306: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
307: #else
308: tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
309: tp->rcv_nxt, tp->snd_una - 1, 0);
310: #endif
1.1.1.2 ! root 311: tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
1.1 root 312: } else
1.1.1.2 ! root 313: tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
1.1 root 314: break;
315:
316: dropit:
1.1.1.2 ! root 317: STAT(tcpstat.tcps_keepdrops++);
1.1 root 318: tp = tcp_drop(tp, 0); /* ETIMEDOUT); */
319: break;
320: }
321:
322: return (tp);
323: }
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