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1.1 root 1: /*
2: * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California.
3: * All rights reserved.
4: *
5: * Redistribution is only permitted until one year after the first shipment
6: * of 4.4BSD by the Regents. Otherwise, redistribution and use in source and
7: * binary forms are permitted provided that: (1) source distributions retain
8: * this entire copyright notice and comment, and (2) distributions including
9: * binaries display the following acknowledgement: This product includes
10: * software developed by the University of California, Berkeley and its
11: * contributors'' in the documentation or other materials provided with the
12: * distribution and in all advertising materials mentioning features or use
13: * of this software. Neither the name of the University nor the names of
14: * its contributors may be used to endorse or promote products derived from
15: * this software without specific prior written permission.
16: * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
17: * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
18: * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19: *
20: * @(#)tcp_timer.c 7.18 (Berkeley) 6/28/90
21: */
22:
23: #include "param.h"
24: #include "systm.h"
25: #include "malloc.h"
26: #include "mbuf.h"
27: #include "socket.h"
28: #include "socketvar.h"
29: #include "protosw.h"
30: #include "errno.h"
31:
32: #include "../net/if.h"
33: #include "../net/route.h"
34:
35: #include "in.h"
36: #include "in_systm.h"
37: #include "ip.h"
38: #include "in_pcb.h"
39: #include "ip_var.h"
40: #include "tcp.h"
41: #include "tcp_fsm.h"
42: #include "tcp_seq.h"
43: #include "tcp_timer.h"
44: #include "tcp_var.h"
45: #include "tcpip.h"
46:
47: int tcp_keepidle = TCPTV_KEEP_IDLE;
48: int tcp_keepintvl = TCPTV_KEEPINTVL;
49: int tcp_maxidle;
50: /*
51: * Fast timeout routine for processing delayed acks
52: */
53: tcp_fasttimo()
54: {
55: register struct inpcb *inp;
56: register struct tcpcb *tp;
57: int s = splnet();
58:
59: inp = tcb.inp_next;
60: if (inp)
61: for (; inp != &tcb; inp = inp->inp_next)
62: if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
63: (tp->t_flags & TF_DELACK)) {
64: tp->t_flags &= ~TF_DELACK;
65: tp->t_flags |= TF_ACKNOW;
66: tcpstat.tcps_delack++;
67: (void) tcp_output(tp);
68: }
69: splx(s);
70: }
71:
72: /*
73: * Tcp protocol timeout routine called every 500 ms.
74: * Updates the timers in all active tcb's and
75: * causes finite state machine actions if timers expire.
76: */
77: tcp_slowtimo()
78: {
79: register struct inpcb *ip, *ipnxt;
80: register struct tcpcb *tp;
81: int s = splnet();
82: register int i;
83:
84: tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
85: /*
86: * Search through tcb's and update active timers.
87: */
88: ip = tcb.inp_next;
89: if (ip == 0) {
90: splx(s);
91: return;
92: }
93: for (; ip != &tcb; ip = ipnxt) {
94: ipnxt = ip->inp_next;
95: tp = intotcpcb(ip);
96: if (tp == 0)
97: continue;
98: for (i = 0; i < TCPT_NTIMERS; i++) {
99: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
100: (void) tcp_usrreq(tp->t_inpcb->inp_socket,
101: PRU_SLOWTIMO, (struct mbuf *)0,
102: (struct mbuf *)i, (struct mbuf *)0);
103: if (ipnxt->inp_prev != ip)
104: goto tpgone;
105: }
106: }
107: tp->t_idle++;
108: if (tp->t_rtt)
109: tp->t_rtt++;
110: tpgone:
111: ;
112: }
113: tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
114: #ifdef TCP_COMPAT_42
115: if ((int)tcp_iss < 0)
116: tcp_iss = 0; /* XXX */
117: #endif
118: splx(s);
119: }
120:
121: /*
122: * Cancel all timers for TCP tp.
123: */
124: tcp_canceltimers(tp)
125: struct tcpcb *tp;
126: {
127: register int i;
128:
129: for (i = 0; i < TCPT_NTIMERS; i++)
130: tp->t_timer[i] = 0;
131: }
132:
133: int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
134: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
135:
136: /*
137: * TCP timer processing.
138: */
139: struct tcpcb *
140: tcp_timers(tp, timer)
141: register struct tcpcb *tp;
142: int timer;
143: {
144: register int rexmt;
145:
146: switch (timer) {
147:
148: /*
149: * 2 MSL timeout in shutdown went off. If we're closed but
150: * still waiting for peer to close and connection has been idle
151: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
152: * control block. Otherwise, check again in a bit.
153: */
154: case TCPT_2MSL:
155: if (tp->t_state != TCPS_TIME_WAIT &&
156: tp->t_idle <= tcp_maxidle)
157: tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
158: else
159: tp = tcp_close(tp);
160: break;
161:
162: /*
163: * Retransmission timer went off. Message has not
164: * been acked within retransmit interval. Back off
165: * to a longer retransmit interval and retransmit one segment.
166: */
167: case TCPT_REXMT:
168: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
169: tp->t_rxtshift = TCP_MAXRXTSHIFT;
170: tcpstat.tcps_timeoutdrop++;
171: tp = tcp_drop(tp, tp->t_softerror ?
172: tp->t_softerror : ETIMEDOUT);
173: break;
174: }
175: tcpstat.tcps_rexmttimeo++;
176: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
177: TCPT_RANGESET(tp->t_rxtcur, rexmt,
178: tp->t_rttmin, TCPTV_REXMTMAX);
179: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
180: /*
181: * If losing, let the lower level know and try for
182: * a better route. Also, if we backed off this far,
183: * our srtt estimate is probably bogus. Clobber it
184: * so we'll take the next rtt measurement as our srtt;
185: * move the current srtt into rttvar to keep the current
186: * retransmit times until then.
187: */
188: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
189: in_losing(tp->t_inpcb);
190: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
191: tp->t_srtt = 0;
192: }
193: tp->snd_nxt = tp->snd_una;
194: /*
195: * If timing a segment in this window, stop the timer.
196: */
197: tp->t_rtt = 0;
198: /*
199: * Close the congestion window down to one segment
200: * (we'll open it by one segment for each ack we get).
201: * Since we probably have a window's worth of unacked
202: * data accumulated, this "slow start" keeps us from
203: * dumping all that data as back-to-back packets (which
204: * might overwhelm an intermediate gateway).
205: *
206: * There are two phases to the opening: Initially we
207: * open by one mss on each ack. This makes the window
208: * size increase exponentially with time. If the
209: * window is larger than the path can handle, this
210: * exponential growth results in dropped packet(s)
211: * almost immediately. To get more time between
212: * drops but still "push" the network to take advantage
213: * of improving conditions, we switch from exponential
214: * to linear window opening at some threshhold size.
215: * For a threshhold, we use half the current window
216: * size, truncated to a multiple of the mss.
217: *
218: * (the minimum cwnd that will give us exponential
219: * growth is 2 mss. We don't allow the threshhold
220: * to go below this.)
221: */
222: {
223: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
224: if (win < 2)
225: win = 2;
226: tp->snd_cwnd = tp->t_maxseg;
227: tp->snd_ssthresh = win * tp->t_maxseg;
228: tp->t_dupacks = 0;
229: }
230: (void) tcp_output(tp);
231: break;
232:
233: /*
234: * Persistance timer into zero window.
235: * Force a byte to be output, if possible.
236: */
237: case TCPT_PERSIST:
238: tcpstat.tcps_persisttimeo++;
239: tcp_setpersist(tp);
240: tp->t_force = 1;
241: (void) tcp_output(tp);
242: tp->t_force = 0;
243: break;
244:
245: /*
246: * Keep-alive timer went off; send something
247: * or drop connection if idle for too long.
248: */
249: case TCPT_KEEP:
250: tcpstat.tcps_keeptimeo++;
251: if (tp->t_state < TCPS_ESTABLISHED)
252: goto dropit;
253: if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
254: tp->t_state <= TCPS_CLOSE_WAIT) {
255: if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
256: goto dropit;
257: /*
258: * Send a packet designed to force a response
259: * if the peer is up and reachable:
260: * either an ACK if the connection is still alive,
261: * or an RST if the peer has closed the connection
262: * due to timeout or reboot.
263: * Using sequence number tp->snd_una-1
264: * causes the transmitted zero-length segment
265: * to lie outside the receive window;
266: * by the protocol spec, this requires the
267: * correspondent TCP to respond.
268: */
269: tcpstat.tcps_keepprobe++;
270: #ifdef TCP_COMPAT_42
271: /*
272: * The keepalive packet must have nonzero length
273: * to get a 4.2 host to respond.
274: */
275: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
276: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
277: #else
278: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
279: tp->rcv_nxt, tp->snd_una - 1, 0);
280: #endif
281: tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
282: } else
283: tp->t_timer[TCPT_KEEP] = tcp_keepidle;
284: break;
285: dropit:
286: tcpstat.tcps_keepdrops++;
287: tp = tcp_drop(tp, ETIMEDOUT);
288: break;
289: }
290: return (tp);
291: }
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