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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:
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: }
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