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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. 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: int tcp_keepidle = TCPTV_KEEP_IDLE;
36: int tcp_keepintvl = TCPTV_KEEPINTVL;
37: int tcp_maxidle;
38: int so_options = DO_KEEPALIVE;
39:
40: struct tcpstat tcpstat; /* tcp statistics */
41: u_int32_t tcp_now; /* for RFC 1323 timestamps */
42:
43: /*
44: * Fast timeout routine for processing delayed acks
45: */
46: void
47: tcp_fasttimo()
48: {
49: register struct socket *so;
50: register struct tcpcb *tp;
51:
52: DEBUG_CALL("tcp_fasttimo");
53:
54: so = tcb.so_next;
55: if (so)
56: for (; so != &tcb; so = so->so_next)
57: if ((tp = (struct tcpcb *)so->so_tcpcb) &&
58: (tp->t_flags & TF_DELACK)) {
59: tp->t_flags &= ~TF_DELACK;
60: tp->t_flags |= TF_ACKNOW;
61: tcpstat.tcps_delack++;
62: (void) tcp_output(tp);
63: }
64: }
65:
66: /*
67: * Tcp protocol timeout routine called every 500 ms.
68: * Updates the timers in all active tcb's and
69: * causes finite state machine actions if timers expire.
70: */
71: void
72: tcp_slowtimo()
73: {
74: register struct socket *ip, *ipnxt;
75: register struct tcpcb *tp;
76: register int i;
77:
78: DEBUG_CALL("tcp_slowtimo");
79:
80: tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
81: /*
82: * Search through tcb's and update active timers.
83: */
84: ip = tcb.so_next;
85: if (ip == 0)
86: return;
87: for (; ip != &tcb; ip = ipnxt) {
88: ipnxt = ip->so_next;
89: tp = sototcpcb(ip);
90: if (tp == 0)
91: continue;
92: for (i = 0; i < TCPT_NTIMERS; i++) {
93: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
94: tcp_timers(tp,i);
95: if (ipnxt->so_prev != ip)
96: goto tpgone;
97: }
98: }
99: tp->t_idle++;
100: if (tp->t_rtt)
101: tp->t_rtt++;
102: tpgone:
103: ;
104: }
105: tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
106: #ifdef TCP_COMPAT_42
107: if ((int)tcp_iss < 0)
108: tcp_iss = 0; /* XXX */
109: #endif
110: tcp_now++; /* for timestamps */
111: }
112:
113: /*
114: * Cancel all timers for TCP tp.
115: */
116: void
117: tcp_canceltimers(tp)
118: struct tcpcb *tp;
119: {
120: register int i;
121:
122: for (i = 0; i < TCPT_NTIMERS; i++)
123: tp->t_timer[i] = 0;
124: }
125:
126: int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
127: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
128:
129: /*
130: * TCP timer processing.
131: */
132: struct tcpcb *
133: tcp_timers(tp, timer)
134: register struct tcpcb *tp;
135: int timer;
136: {
137: register int rexmt;
138:
139: DEBUG_CALL("tcp_timers");
140:
141: switch (timer) {
142:
143: /*
144: * 2 MSL timeout in shutdown went off. If we're closed but
145: * still waiting for peer to close and connection has been idle
146: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
147: * control block. Otherwise, check again in a bit.
148: */
149: case TCPT_2MSL:
150: if (tp->t_state != TCPS_TIME_WAIT &&
151: tp->t_idle <= tcp_maxidle)
152: tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
153: else
154: tp = tcp_close(tp);
155: break;
156:
157: /*
158: * Retransmission timer went off. Message has not
159: * been acked within retransmit interval. Back off
160: * to a longer retransmit interval and retransmit one segment.
161: */
162: case TCPT_REXMT:
163:
164: /*
165: * XXXXX If a packet has timed out, then remove all the queued
166: * packets for that session.
167: */
168:
169: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
170: /*
171: * This is a hack to suit our terminal server here at the uni of canberra
172: * since they have trouble with zeroes... It usually lets them through
173: * unharmed, but under some conditions, it'll eat the zeros. If we
174: * keep retransmitting it, it'll keep eating the zeroes, so we keep
175: * retransmitting, and eventually the connection dies...
176: * (this only happens on incoming data)
177: *
178: * So, if we were gonna drop the connection from too many retransmits,
179: * don't... instead halve the t_maxseg, which might break up the NULLs and
180: * let them through
181: *
182: * *sigh*
183: */
184:
185: tp->t_maxseg >>= 1;
186: if (tp->t_maxseg < 32) {
187: /*
188: * We tried our best, now the connection must die!
189: */
190: tp->t_rxtshift = TCP_MAXRXTSHIFT;
191: tcpstat.tcps_timeoutdrop++;
192: tp = tcp_drop(tp, tp->t_softerror);
193: /* tp->t_softerror : ETIMEDOUT); */ /* XXX */
194: return (tp); /* XXX */
195: }
196:
197: /*
198: * Set rxtshift to 6, which is still at the maximum
199: * backoff time
200: */
201: tp->t_rxtshift = 6;
202: }
203: tcpstat.tcps_rexmttimeo++;
204: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
205: TCPT_RANGESET(tp->t_rxtcur, rexmt,
206: (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
207: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
208: /*
209: * If losing, let the lower level know and try for
210: * a better route. Also, if we backed off this far,
211: * our srtt estimate is probably bogus. Clobber it
212: * so we'll take the next rtt measurement as our srtt;
213: * move the current srtt into rttvar to keep the current
214: * retransmit times until then.
215: */
216: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
217: /* in_losing(tp->t_inpcb); */
218: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
219: tp->t_srtt = 0;
220: }
221: tp->snd_nxt = tp->snd_una;
222: /*
223: * If timing a segment in this window, stop the timer.
224: */
225: tp->t_rtt = 0;
226: /*
227: * Close the congestion window down to one segment
228: * (we'll open it by one segment for each ack we get).
229: * Since we probably have a window's worth of unacked
230: * data accumulated, this "slow start" keeps us from
231: * dumping all that data as back-to-back packets (which
232: * might overwhelm an intermediate gateway).
233: *
234: * There are two phases to the opening: Initially we
235: * open by one mss on each ack. This makes the window
236: * size increase exponentially with time. If the
237: * window is larger than the path can handle, this
238: * exponential growth results in dropped packet(s)
239: * almost immediately. To get more time between
240: * drops but still "push" the network to take advantage
241: * of improving conditions, we switch from exponential
242: * to linear window opening at some threshold size.
243: * For a threshold, we use half the current window
244: * size, truncated to a multiple of the mss.
245: *
246: * (the minimum cwnd that will give us exponential
247: * growth is 2 mss. We don't allow the threshold
248: * to go below this.)
249: */
250: {
251: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
252: if (win < 2)
253: win = 2;
254: tp->snd_cwnd = tp->t_maxseg;
255: tp->snd_ssthresh = win * tp->t_maxseg;
256: tp->t_dupacks = 0;
257: }
258: (void) tcp_output(tp);
259: break;
260:
261: /*
262: * Persistence timer into zero window.
263: * Force a byte to be output, if possible.
264: */
265: case TCPT_PERSIST:
266: tcpstat.tcps_persisttimeo++;
267: tcp_setpersist(tp);
268: tp->t_force = 1;
269: (void) tcp_output(tp);
270: tp->t_force = 0;
271: break;
272:
273: /*
274: * Keep-alive timer went off; send something
275: * or drop connection if idle for too long.
276: */
277: case TCPT_KEEP:
278: tcpstat.tcps_keeptimeo++;
279: if (tp->t_state < TCPS_ESTABLISHED)
280: goto dropit;
281:
282: /* if (tp->t_socket->so_options & SO_KEEPALIVE && */
283: if ((so_options) && tp->t_state <= TCPS_CLOSE_WAIT) {
284: if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
285: goto dropit;
286: /*
287: * Send a packet designed to force a response
288: * if the peer is up and reachable:
289: * either an ACK if the connection is still alive,
290: * or an RST if the peer has closed the connection
291: * due to timeout or reboot.
292: * Using sequence number tp->snd_una-1
293: * causes the transmitted zero-length segment
294: * to lie outside the receive window;
295: * by the protocol spec, this requires the
296: * correspondent TCP to respond.
297: */
298: tcpstat.tcps_keepprobe++;
299: #ifdef TCP_COMPAT_42
300: /*
301: * The keepalive packet must have nonzero length
302: * to get a 4.2 host to respond.
303: */
304: tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
305: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
306: #else
307: tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
308: tp->rcv_nxt, tp->snd_una - 1, 0);
309: #endif
310: tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
311: } else
312: tp->t_timer[TCPT_KEEP] = tcp_keepidle;
313: break;
314:
315: dropit:
316: tcpstat.tcps_keepdrops++;
317: tp = tcp_drop(tp, 0); /* ETIMEDOUT); */
318: break;
319: }
320:
321: return (tp);
322: }
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