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1.1 root 1: /*
2: * Copyright (c) 1982, 1986 Regents of the University of California.
3: * All rights reserved.
4: *
5: * Redistribution and use in source and binary forms are permitted
6: * provided that the above copyright notice and this paragraph are
7: * duplicated in all such forms and that any documentation,
8: * advertising materials, and other materials related to such
9: * distribution and use acknowledge that the software was developed
10: * by the University of California, Berkeley. The name of the
11: * University may not be used to endorse or promote products derived
12: * from this software without specific prior written permission.
13: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
15: * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
16: *
17: * @(#)tcp_timer.c 7.14 (Berkeley) 6/29/88
18: */
19:
20: #include "param.h"
21: #include "systm.h"
22: #include "mbuf.h"
23: #include "socket.h"
24: #include "socketvar.h"
25: #include "protosw.h"
26: #include "errno.h"
27:
28: #include "../net/if.h"
29: #include "../net/route.h"
30:
31: #include "in.h"
32: #include "in_pcb.h"
33: #include "in_systm.h"
34: #include "ip.h"
35: #include "ip_var.h"
36: #include "tcp.h"
37: #include "tcp_fsm.h"
38: #include "tcp_seq.h"
39: #include "tcp_timer.h"
40: #include "tcp_var.h"
41: #include "tcpip.h"
42:
43: int tcp_keepidle = TCPTV_KEEP_IDLE;
44: int tcp_keepintvl = TCPTV_KEEPINTVL;
45: int tcp_maxidle;
46: /*
47: * Fast timeout routine for processing delayed acks
48: */
49: tcp_fasttimo()
50: {
51: register struct inpcb *inp;
52: register struct tcpcb *tp;
53: int s = splnet();
54:
55: inp = tcb.inp_next;
56: if (inp)
57: for (; inp != &tcb; inp = inp->inp_next)
58: if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
59: (tp->t_flags & TF_DELACK)) {
60: tp->t_flags &= ~TF_DELACK;
61: tp->t_flags |= TF_ACKNOW;
62: tcpstat.tcps_delack++;
63: (void) tcp_output(tp);
64: }
65: splx(s);
66: }
67:
68: /*
69: * Tcp protocol timeout routine called every 500 ms.
70: * Updates the timers in all active tcb's and
71: * causes finite state machine actions if timers expire.
72: */
73: tcp_slowtimo()
74: {
75: register struct inpcb *ip, *ipnxt;
76: register struct tcpcb *tp;
77: int s = splnet();
78: register int i;
79:
80: tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
81: /*
82: * Search through tcb's and update active timers.
83: */
84: ip = tcb.inp_next;
85: if (ip == 0) {
86: splx(s);
87: return;
88: }
89: for (; ip != &tcb; ip = ipnxt) {
90: ipnxt = ip->inp_next;
91: tp = intotcpcb(ip);
92: if (tp == 0)
93: continue;
94: for (i = 0; i < TCPT_NTIMERS; i++) {
95: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
96: (void) tcp_usrreq(tp->t_inpcb->inp_socket,
97: PRU_SLOWTIMO, (struct mbuf *)0,
98: (struct mbuf *)i, (struct mbuf *)0);
99: if (ipnxt->inp_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: splx(s);
115: }
116:
117: /*
118: * Cancel all timers for TCP tp.
119: */
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:
129: int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
130: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
131:
132: /*
133: * TCP timer processing.
134: */
135: struct tcpcb *
136: tcp_timers(tp, timer)
137: register struct tcpcb *tp;
138: int timer;
139: {
140: register int rexmt;
141:
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 &&
152: tp->t_idle <= tcp_maxidle)
153: tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
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:
164: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
165: tp->t_rxtshift = TCP_MAXRXTSHIFT;
166: tcpstat.tcps_timeoutdrop++;
167: tp = tcp_drop(tp, ETIMEDOUT);
168: break;
169: }
170: tcpstat.tcps_rexmttimeo++;
171: rexmt = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
172: rexmt *= tcp_backoff[tp->t_rxtshift];
173: TCPT_RANGESET(tp->t_rxtcur, rexmt, TCPTV_MIN, TCPTV_REXMTMAX);
174: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
175: /*
176: * If losing, let the lower level know and try for
177: * a better route. Also, if we backed off this far,
178: * our srtt estimate is probably bogus. Clobber it
179: * so we'll take the next rtt measurement as our srtt;
180: * move the current srtt into rttvar to keep the current
181: * retransmit times until then.
182: */
183: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
184: in_losing(tp->t_inpcb);
185: tp->t_rttvar += (tp->t_srtt >> 2);
186: tp->t_srtt = 0;
187: }
188: tp->snd_nxt = tp->snd_una;
189: /*
190: * If timing a segment in this window, stop the timer.
191: */
192: tp->t_rtt = 0;
193: /*
194: * Close the congestion window down to one segment
195: * (we'll open it by one segment for each ack we get).
196: * Since we probably have a window's worth of unacked
197: * data accumulated, this "slow start" keeps us from
198: * dumping all that data as back-to-back packets (which
199: * might overwhelm an intermediate gateway).
200: *
201: * There are two phases to the opening: Initially we
202: * open by one mss on each ack. This makes the window
203: * size increase exponentially with time. If the
204: * window is larger than the path can handle, this
205: * exponential growth results in dropped packet(s)
206: * almost immediately. To get more time between
207: * drops but still "push" the network to take advantage
208: * of improving conditions, we switch from exponential
209: * to linear window opening at some threshhold size.
210: * For a threshhold, we use half the current window
211: * size, truncated to a multiple of the mss.
212: *
213: * (the minimum cwnd that will give us exponential
214: * growth is 2 mss. We don't allow the threshhold
215: * to go below this.)
216: */
217: {
218: u_int win = MIN(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
219: if (win < 2)
220: win = 2;
221: tp->snd_cwnd = tp->t_maxseg;
222: tp->snd_ssthresh = win * tp->t_maxseg;
223: }
224: (void) tcp_output(tp);
225: break;
226:
227: /*
228: * Persistance timer into zero window.
229: * Force a byte to be output, if possible.
230: */
231: case TCPT_PERSIST:
232: tcpstat.tcps_persisttimeo++;
233: tcp_setpersist(tp);
234: tp->t_force = 1;
235: (void) tcp_output(tp);
236: tp->t_force = 0;
237: break;
238:
239: /*
240: * Keep-alive timer went off; send something
241: * or drop connection if idle for too long.
242: */
243: case TCPT_KEEP:
244: tcpstat.tcps_keeptimeo++;
245: if (tp->t_state < TCPS_ESTABLISHED)
246: goto dropit;
247: if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
248: tp->t_state <= TCPS_CLOSE_WAIT) {
249: if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
250: goto dropit;
251: /*
252: * Send a packet designed to force a response
253: * if the peer is up and reachable:
254: * either an ACK if the connection is still alive,
255: * or an RST if the peer has closed the connection
256: * due to timeout or reboot.
257: * Using sequence number tp->snd_una-1
258: * causes the transmitted zero-length segment
259: * to lie outside the receive window;
260: * by the protocol spec, this requires the
261: * correspondent TCP to respond.
262: */
263: tcpstat.tcps_keepprobe++;
264: #ifdef TCP_COMPAT_42
265: /*
266: * The keepalive packet must have nonzero length
267: * to get a 4.2 host to respond.
268: */
269: tcp_respond(tp, tp->t_template,
270: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
271: #else
272: tcp_respond(tp, tp->t_template,
273: tp->rcv_nxt, tp->snd_una - 1, 0);
274: #endif
275: tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
276: } else
277: tp->t_timer[TCPT_KEEP] = tcp_keepidle;
278: break;
279: dropit:
280: tcpstat.tcps_keepdrops++;
281: tp = tcp_drop(tp, ETIMEDOUT);
282: break;
283: }
284: return (tp);
285: }
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