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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.
1.1.1.3 ! root 13: * 3. Neither the name of the University nor the names of its contributors
1.1 root 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:
1.1.1.2 root 35: #ifdef LOG_ENABLED
1.1 root 36: struct tcpstat tcpstat; /* tcp statistics */
1.1.1.2 root 37: #endif
38:
1.1 root 39: u_int32_t tcp_now; /* for RFC 1323 timestamps */
40:
1.1.1.2 root 41: static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer);
42:
1.1 root 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");
1.1.1.2 root 53:
1.1 root 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;
1.1.1.2 root 61: STAT(tcpstat.tcps_delack++);
1.1 root 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");
1.1.1.2 root 79:
1.1 root 80: /*
81: * Search through tcb's and update active timers.
82: */
83: ip = tcb.so_next;
84: if (ip == 0)
85: return;
86: for (; ip != &tcb; ip = ipnxt) {
87: ipnxt = ip->so_next;
88: tp = sototcpcb(ip);
89: if (tp == 0)
90: continue;
91: for (i = 0; i < TCPT_NTIMERS; i++) {
92: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
93: tcp_timers(tp,i);
94: if (ipnxt->so_prev != ip)
95: goto tpgone;
96: }
97: }
98: tp->t_idle++;
99: if (tp->t_rtt)
100: tp->t_rtt++;
101: tpgone:
102: ;
103: }
104: tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
105: #ifdef TCP_COMPAT_42
106: if ((int)tcp_iss < 0)
107: tcp_iss = 0; /* XXX */
108: #endif
109: tcp_now++; /* for timestamps */
110: }
111:
112: /*
113: * Cancel all timers for TCP tp.
114: */
115: void
116: tcp_canceltimers(tp)
117: struct tcpcb *tp;
118: {
119: register int i;
120:
121: for (i = 0; i < TCPT_NTIMERS; i++)
122: tp->t_timer[i] = 0;
123: }
124:
1.1.1.2 root 125: const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
1.1 root 126: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
127:
128: /*
129: * TCP timer processing.
130: */
1.1.1.2 root 131: static struct tcpcb *
132: tcp_timers(register struct tcpcb *tp, int timer)
1.1 root 133: {
134: register int rexmt;
1.1.1.2 root 135:
1.1 root 136: DEBUG_CALL("tcp_timers");
1.1.1.2 root 137:
1.1 root 138: switch (timer) {
139:
140: /*
141: * 2 MSL timeout in shutdown went off. If we're closed but
142: * still waiting for peer to close and connection has been idle
143: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
144: * control block. Otherwise, check again in a bit.
145: */
146: case TCPT_2MSL:
147: if (tp->t_state != TCPS_TIME_WAIT &&
1.1.1.2 root 148: tp->t_idle <= TCP_MAXIDLE)
149: tp->t_timer[TCPT_2MSL] = TCPTV_KEEPINTVL;
1.1 root 150: else
151: tp = tcp_close(tp);
152: break;
153:
154: /*
155: * Retransmission timer went off. Message has not
156: * been acked within retransmit interval. Back off
157: * to a longer retransmit interval and retransmit one segment.
158: */
159: case TCPT_REXMT:
1.1.1.2 root 160:
1.1 root 161: /*
162: * XXXXX If a packet has timed out, then remove all the queued
163: * packets for that session.
164: */
1.1.1.2 root 165:
1.1 root 166: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
167: /*
168: * This is a hack to suit our terminal server here at the uni of canberra
169: * since they have trouble with zeroes... It usually lets them through
170: * unharmed, but under some conditions, it'll eat the zeros. If we
171: * keep retransmitting it, it'll keep eating the zeroes, so we keep
172: * retransmitting, and eventually the connection dies...
173: * (this only happens on incoming data)
1.1.1.2 root 174: *
1.1 root 175: * So, if we were gonna drop the connection from too many retransmits,
176: * don't... instead halve the t_maxseg, which might break up the NULLs and
177: * let them through
1.1.1.2 root 178: *
1.1 root 179: * *sigh*
180: */
1.1.1.2 root 181:
1.1 root 182: tp->t_maxseg >>= 1;
183: if (tp->t_maxseg < 32) {
184: /*
185: * We tried our best, now the connection must die!
186: */
187: tp->t_rxtshift = TCP_MAXRXTSHIFT;
1.1.1.2 root 188: STAT(tcpstat.tcps_timeoutdrop++);
1.1 root 189: tp = tcp_drop(tp, tp->t_softerror);
190: /* tp->t_softerror : ETIMEDOUT); */ /* XXX */
191: return (tp); /* XXX */
192: }
1.1.1.2 root 193:
1.1 root 194: /*
195: * Set rxtshift to 6, which is still at the maximum
196: * backoff time
197: */
198: tp->t_rxtshift = 6;
199: }
1.1.1.2 root 200: STAT(tcpstat.tcps_rexmttimeo++);
1.1 root 201: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
202: TCPT_RANGESET(tp->t_rxtcur, rexmt,
203: (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
204: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
205: /*
206: * If losing, let the lower level know and try for
207: * a better route. Also, if we backed off this far,
208: * our srtt estimate is probably bogus. Clobber it
209: * so we'll take the next rtt measurement as our srtt;
210: * move the current srtt into rttvar to keep the current
211: * retransmit times until then.
212: */
213: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
214: /* in_losing(tp->t_inpcb); */
215: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
216: tp->t_srtt = 0;
217: }
218: tp->snd_nxt = tp->snd_una;
219: /*
220: * If timing a segment in this window, stop the timer.
221: */
222: tp->t_rtt = 0;
223: /*
224: * Close the congestion window down to one segment
225: * (we'll open it by one segment for each ack we get).
226: * Since we probably have a window's worth of unacked
227: * data accumulated, this "slow start" keeps us from
228: * dumping all that data as back-to-back packets (which
229: * might overwhelm an intermediate gateway).
230: *
231: * There are two phases to the opening: Initially we
232: * open by one mss on each ack. This makes the window
233: * size increase exponentially with time. If the
234: * window is larger than the path can handle, this
235: * exponential growth results in dropped packet(s)
1.1.1.2 root 236: * almost immediately. To get more time between
1.1 root 237: * drops but still "push" the network to take advantage
238: * of improving conditions, we switch from exponential
239: * to linear window opening at some threshold size.
240: * For a threshold, we use half the current window
241: * size, truncated to a multiple of the mss.
242: *
243: * (the minimum cwnd that will give us exponential
244: * growth is 2 mss. We don't allow the threshold
245: * to go below this.)
246: */
247: {
248: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
249: if (win < 2)
250: win = 2;
251: tp->snd_cwnd = tp->t_maxseg;
252: tp->snd_ssthresh = win * tp->t_maxseg;
253: tp->t_dupacks = 0;
254: }
255: (void) tcp_output(tp);
256: break;
257:
258: /*
259: * Persistence timer into zero window.
260: * Force a byte to be output, if possible.
261: */
262: case TCPT_PERSIST:
1.1.1.2 root 263: STAT(tcpstat.tcps_persisttimeo++);
1.1 root 264: tcp_setpersist(tp);
265: tp->t_force = 1;
266: (void) tcp_output(tp);
267: tp->t_force = 0;
268: break;
269:
270: /*
271: * Keep-alive timer went off; send something
272: * or drop connection if idle for too long.
273: */
274: case TCPT_KEEP:
1.1.1.2 root 275: STAT(tcpstat.tcps_keeptimeo++);
1.1 root 276: if (tp->t_state < TCPS_ESTABLISHED)
277: goto dropit;
278:
279: /* if (tp->t_socket->so_options & SO_KEEPALIVE && */
1.1.1.2 root 280: if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
281: if (tp->t_idle >= TCPTV_KEEP_IDLE + TCP_MAXIDLE)
1.1 root 282: goto dropit;
283: /*
284: * Send a packet designed to force a response
285: * if the peer is up and reachable:
286: * either an ACK if the connection is still alive,
287: * or an RST if the peer has closed the connection
288: * due to timeout or reboot.
289: * Using sequence number tp->snd_una-1
290: * causes the transmitted zero-length segment
291: * to lie outside the receive window;
292: * by the protocol spec, this requires the
293: * correspondent TCP to respond.
294: */
1.1.1.2 root 295: STAT(tcpstat.tcps_keepprobe++);
1.1 root 296: #ifdef TCP_COMPAT_42
297: /*
298: * The keepalive packet must have nonzero length
299: * to get a 4.2 host to respond.
300: */
301: tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
302: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
303: #else
304: tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
305: tp->rcv_nxt, tp->snd_una - 1, 0);
306: #endif
1.1.1.2 root 307: tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
1.1 root 308: } else
1.1.1.2 root 309: tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
1.1 root 310: break;
311:
312: dropit:
1.1.1.2 root 313: STAT(tcpstat.tcps_keepdrops++);
1.1 root 314: tp = tcp_drop(tp, 0); /* ETIMEDOUT); */
315: break;
316: }
317:
318: return (tp);
319: }
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