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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 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 7.18 (Berkeley) 6/28/90
34: */
35:
36: #include "param.h"
37: #include "systm.h"
38: #include "malloc.h"
39: #include "mbuf.h"
40: #include "socket.h"
41: #include "socketvar.h"
42: #include "protosw.h"
43: #include "errno.h"
44:
45: #include "../net/if.h"
46: #include "../net/route.h"
47:
48: #include "in.h"
49: #include "in_systm.h"
50: #include "ip.h"
51: #include "in_pcb.h"
52: #include "ip_var.h"
53: #include "tcp.h"
54: #include "tcp_fsm.h"
55: #include "tcp_seq.h"
56: #include "tcp_timer.h"
57: #include "tcp_var.h"
58: #include "tcpip.h"
59:
60: int tcp_keepidle = TCPTV_KEEP_IDLE;
61: int tcp_keepintvl = TCPTV_KEEPINTVL;
62: int tcp_maxidle;
63: /*
64: * Fast timeout routine for processing delayed acks
65: */
66: tcp_fasttimo()
67: {
68: register struct inpcb *inp;
69: register struct tcpcb *tp;
70: int s = splnet();
71:
72: inp = tcb.inp_next;
73: if (inp)
74: for (; inp != &tcb; inp = inp->inp_next)
75: if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
76: (tp->t_flags & TF_DELACK)) {
77: tp->t_flags &= ~TF_DELACK;
78: tp->t_flags |= TF_ACKNOW;
79: tcpstat.tcps_delack++;
80: (void) tcp_output(tp);
81: }
82: splx(s);
83: }
84:
85: /*
86: * Tcp protocol timeout routine called every 500 ms.
87: * Updates the timers in all active tcb's and
88: * causes finite state machine actions if timers expire.
89: */
90: tcp_slowtimo()
91: {
92: register struct inpcb *ip, *ipnxt;
93: register struct tcpcb *tp;
94: int s = splnet();
95: register int i;
96:
97: tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
98: /*
99: * Search through tcb's and update active timers.
100: */
101: ip = tcb.inp_next;
102: if (ip == 0) {
103: splx(s);
104: return;
105: }
106: for (; ip != &tcb; ip = ipnxt) {
107: ipnxt = ip->inp_next;
108: tp = intotcpcb(ip);
109: if (tp == 0)
110: continue;
111: for (i = 0; i < TCPT_NTIMERS; i++) {
112: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
113: (void) tcp_usrreq(tp->t_inpcb->inp_socket,
114: PRU_SLOWTIMO, (struct mbuf *)0,
115: (struct mbuf *)i, (struct mbuf *)0);
116: if (ipnxt->inp_prev != ip)
117: goto tpgone;
118: }
119: }
120: tp->t_idle++;
121: if (tp->t_rtt)
122: tp->t_rtt++;
123: tpgone:
124: ;
125: }
126: tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
127: #ifdef TCP_COMPAT_42
128: if ((int)tcp_iss < 0)
129: tcp_iss = 0; /* XXX */
130: #endif
131: splx(s);
132: }
133:
134: /*
135: * Cancel all timers for TCP tp.
136: */
137: tcp_canceltimers(tp)
138: struct tcpcb *tp;
139: {
140: register int i;
141:
142: for (i = 0; i < TCPT_NTIMERS; i++)
143: tp->t_timer[i] = 0;
144: }
145:
146: int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
147: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
148:
149: /*
150: * TCP timer processing.
151: */
152: struct tcpcb *
153: tcp_timers(tp, timer)
154: register struct tcpcb *tp;
155: int timer;
156: {
157: register int rexmt;
158:
159: switch (timer) {
160:
161: /*
162: * 2 MSL timeout in shutdown went off. If we're closed but
163: * still waiting for peer to close and connection has been idle
164: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
165: * control block. Otherwise, check again in a bit.
166: */
167: case TCPT_2MSL:
168: if (tp->t_state != TCPS_TIME_WAIT &&
169: tp->t_idle <= tcp_maxidle)
170: tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
171: else
172: tp = tcp_close(tp);
173: break;
174:
175: /*
176: * Retransmission timer went off. Message has not
177: * been acked within retransmit interval. Back off
178: * to a longer retransmit interval and retransmit one segment.
179: */
180: case TCPT_REXMT:
181: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
182: tp->t_rxtshift = TCP_MAXRXTSHIFT;
183: tcpstat.tcps_timeoutdrop++;
184: tp = tcp_drop(tp, tp->t_softerror ?
185: tp->t_softerror : ETIMEDOUT);
186: break;
187: }
188: tcpstat.tcps_rexmttimeo++;
189: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
190: TCPT_RANGESET(tp->t_rxtcur, rexmt,
191: tp->t_rttmin, TCPTV_REXMTMAX);
192: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
193: /*
194: * If losing, let the lower level know and try for
195: * a better route. Also, if we backed off this far,
196: * our srtt estimate is probably bogus. Clobber it
197: * so we'll take the next rtt measurement as our srtt;
198: * move the current srtt into rttvar to keep the current
199: * retransmit times until then.
200: */
201: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
202: in_losing(tp->t_inpcb);
203: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
204: tp->t_srtt = 0;
205: }
206: tp->snd_nxt = tp->snd_una;
207: /*
208: * If timing a segment in this window, stop the timer.
209: */
210: tp->t_rtt = 0;
211: /*
212: * Close the congestion window down to one segment
213: * (we'll open it by one segment for each ack we get).
214: * Since we probably have a window's worth of unacked
215: * data accumulated, this "slow start" keeps us from
216: * dumping all that data as back-to-back packets (which
217: * might overwhelm an intermediate gateway).
218: *
219: * There are two phases to the opening: Initially we
220: * open by one mss on each ack. This makes the window
221: * size increase exponentially with time. If the
222: * window is larger than the path can handle, this
223: * exponential growth results in dropped packet(s)
224: * almost immediately. To get more time between
225: * drops but still "push" the network to take advantage
226: * of improving conditions, we switch from exponential
227: * to linear window opening at some threshhold size.
228: * For a threshhold, we use half the current window
229: * size, truncated to a multiple of the mss.
230: *
231: * (the minimum cwnd that will give us exponential
232: * growth is 2 mss. We don't allow the threshhold
233: * to go below this.)
234: */
235: {
236: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
237: if (win < 2)
238: win = 2;
239: tp->snd_cwnd = tp->t_maxseg;
240: tp->snd_ssthresh = win * tp->t_maxseg;
241: tp->t_dupacks = 0;
242: }
243: (void) tcp_output(tp);
244: break;
245:
246: /*
247: * Persistance timer into zero window.
248: * Force a byte to be output, if possible.
249: */
250: case TCPT_PERSIST:
251: tcpstat.tcps_persisttimeo++;
252: tcp_setpersist(tp);
253: tp->t_force = 1;
254: (void) tcp_output(tp);
255: tp->t_force = 0;
256: break;
257:
258: /*
259: * Keep-alive timer went off; send something
260: * or drop connection if idle for too long.
261: */
262: case TCPT_KEEP:
263: tcpstat.tcps_keeptimeo++;
264: if (tp->t_state < TCPS_ESTABLISHED)
265: goto dropit;
266: if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
267: tp->t_state <= TCPS_CLOSE_WAIT) {
268: if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
269: goto dropit;
270: /*
271: * Send a packet designed to force a response
272: * if the peer is up and reachable:
273: * either an ACK if the connection is still alive,
274: * or an RST if the peer has closed the connection
275: * due to timeout or reboot.
276: * Using sequence number tp->snd_una-1
277: * causes the transmitted zero-length segment
278: * to lie outside the receive window;
279: * by the protocol spec, this requires the
280: * correspondent TCP to respond.
281: */
282: tcpstat.tcps_keepprobe++;
283: #ifdef TCP_COMPAT_42
284: /*
285: * The keepalive packet must have nonzero length
286: * to get a 4.2 host to respond.
287: */
288: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
289: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
290: #else
291: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
292: tp->rcv_nxt, tp->snd_una - 1, 0);
293: #endif
294: tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
295: } else
296: tp->t_timer[TCPT_KEEP] = tcp_keepidle;
297: break;
298: dropit:
299: tcpstat.tcps_keepdrops++;
300: tp = tcp_drop(tp, ETIMEDOUT);
301: break;
302: }
303: return (tp);
304: }
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