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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: *
1.1.1.2 ! root 33: * from: @(#)tcp_timer.c 7.18 (Berkeley) 6/28/90
! 34: * tcp_timer.c,v 1.3 1993/05/22 11:42:47 cgd Exp
1.1 root 35: */
36:
37: #include "param.h"
38: #include "systm.h"
39: #include "malloc.h"
40: #include "mbuf.h"
41: #include "socket.h"
42: #include "socketvar.h"
43: #include "protosw.h"
44: #include "errno.h"
45:
46: #include "../net/if.h"
47: #include "../net/route.h"
48:
49: #include "in.h"
50: #include "in_systm.h"
51: #include "ip.h"
52: #include "in_pcb.h"
53: #include "ip_var.h"
54: #include "tcp.h"
55: #include "tcp_fsm.h"
56: #include "tcp_seq.h"
57: #include "tcp_timer.h"
58: #include "tcp_var.h"
59: #include "tcpip.h"
60:
61: int tcp_keepidle = TCPTV_KEEP_IDLE;
62: int tcp_keepintvl = TCPTV_KEEPINTVL;
63: int tcp_maxidle;
64: /*
65: * Fast timeout routine for processing delayed acks
66: */
67: tcp_fasttimo()
68: {
69: register struct inpcb *inp;
70: register struct tcpcb *tp;
71: int s = splnet();
72:
73: inp = tcb.inp_next;
74: if (inp)
75: for (; inp != &tcb; inp = inp->inp_next)
76: if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
77: (tp->t_flags & TF_DELACK)) {
78: tp->t_flags &= ~TF_DELACK;
79: tp->t_flags |= TF_ACKNOW;
80: tcpstat.tcps_delack++;
81: (void) tcp_output(tp);
82: }
83: splx(s);
84: }
85:
86: /*
87: * Tcp protocol timeout routine called every 500 ms.
88: * Updates the timers in all active tcb's and
89: * causes finite state machine actions if timers expire.
90: */
91: tcp_slowtimo()
92: {
93: register struct inpcb *ip, *ipnxt;
94: register struct tcpcb *tp;
95: int s = splnet();
96: register int i;
97:
98: tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
99: /*
100: * Search through tcb's and update active timers.
101: */
102: ip = tcb.inp_next;
103: if (ip == 0) {
104: splx(s);
105: return;
106: }
107: for (; ip != &tcb; ip = ipnxt) {
108: ipnxt = ip->inp_next;
109: tp = intotcpcb(ip);
110: if (tp == 0)
111: continue;
112: for (i = 0; i < TCPT_NTIMERS; i++) {
113: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
114: (void) tcp_usrreq(tp->t_inpcb->inp_socket,
115: PRU_SLOWTIMO, (struct mbuf *)0,
116: (struct mbuf *)i, (struct mbuf *)0);
117: if (ipnxt->inp_prev != ip)
118: goto tpgone;
119: }
120: }
121: tp->t_idle++;
122: if (tp->t_rtt)
123: tp->t_rtt++;
124: tpgone:
125: ;
126: }
127: tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
128: #ifdef TCP_COMPAT_42
129: if ((int)tcp_iss < 0)
130: tcp_iss = 0; /* XXX */
131: #endif
132: splx(s);
133: }
134:
135: /*
136: * Cancel all timers for TCP tp.
137: */
138: tcp_canceltimers(tp)
139: struct tcpcb *tp;
140: {
141: register int i;
142:
143: for (i = 0; i < TCPT_NTIMERS; i++)
144: tp->t_timer[i] = 0;
145: }
146:
147: int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
148: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
149:
150: /*
151: * TCP timer processing.
152: */
153: struct tcpcb *
154: tcp_timers(tp, timer)
155: register struct tcpcb *tp;
156: int timer;
157: {
158: register int rexmt;
159:
160: switch (timer) {
161:
162: /*
163: * 2 MSL timeout in shutdown went off. If we're closed but
164: * still waiting for peer to close and connection has been idle
165: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
166: * control block. Otherwise, check again in a bit.
167: */
168: case TCPT_2MSL:
169: if (tp->t_state != TCPS_TIME_WAIT &&
170: tp->t_idle <= tcp_maxidle)
171: tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
172: else
173: tp = tcp_close(tp);
174: break;
175:
176: /*
177: * Retransmission timer went off. Message has not
178: * been acked within retransmit interval. Back off
179: * to a longer retransmit interval and retransmit one segment.
180: */
181: case TCPT_REXMT:
182: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
183: tp->t_rxtshift = TCP_MAXRXTSHIFT;
184: tcpstat.tcps_timeoutdrop++;
185: tp = tcp_drop(tp, tp->t_softerror ?
186: tp->t_softerror : ETIMEDOUT);
187: break;
188: }
189: tcpstat.tcps_rexmttimeo++;
190: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
191: TCPT_RANGESET(tp->t_rxtcur, rexmt,
192: tp->t_rttmin, TCPTV_REXMTMAX);
193: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
194: /*
195: * If losing, let the lower level know and try for
196: * a better route. Also, if we backed off this far,
197: * our srtt estimate is probably bogus. Clobber it
198: * so we'll take the next rtt measurement as our srtt;
199: * move the current srtt into rttvar to keep the current
200: * retransmit times until then.
201: */
202: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
203: in_losing(tp->t_inpcb);
204: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
205: tp->t_srtt = 0;
206: }
207: tp->snd_nxt = tp->snd_una;
208: /*
209: * If timing a segment in this window, stop the timer.
210: */
211: tp->t_rtt = 0;
212: /*
213: * Close the congestion window down to one segment
214: * (we'll open it by one segment for each ack we get).
215: * Since we probably have a window's worth of unacked
216: * data accumulated, this "slow start" keeps us from
217: * dumping all that data as back-to-back packets (which
218: * might overwhelm an intermediate gateway).
219: *
220: * There are two phases to the opening: Initially we
221: * open by one mss on each ack. This makes the window
222: * size increase exponentially with time. If the
223: * window is larger than the path can handle, this
224: * exponential growth results in dropped packet(s)
225: * almost immediately. To get more time between
226: * drops but still "push" the network to take advantage
227: * of improving conditions, we switch from exponential
228: * to linear window opening at some threshhold size.
229: * For a threshhold, we use half the current window
230: * size, truncated to a multiple of the mss.
231: *
232: * (the minimum cwnd that will give us exponential
233: * growth is 2 mss. We don't allow the threshhold
234: * to go below this.)
235: */
236: {
237: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
238: if (win < 2)
239: win = 2;
240: tp->snd_cwnd = tp->t_maxseg;
241: tp->snd_ssthresh = win * tp->t_maxseg;
242: tp->t_dupacks = 0;
243: }
244: (void) tcp_output(tp);
245: break;
246:
247: /*
248: * Persistance timer into zero window.
249: * Force a byte to be output, if possible.
250: */
251: case TCPT_PERSIST:
252: tcpstat.tcps_persisttimeo++;
253: tcp_setpersist(tp);
254: tp->t_force = 1;
255: (void) tcp_output(tp);
256: tp->t_force = 0;
257: break;
258:
259: /*
260: * Keep-alive timer went off; send something
261: * or drop connection if idle for too long.
262: */
263: case TCPT_KEEP:
264: tcpstat.tcps_keeptimeo++;
265: if (tp->t_state < TCPS_ESTABLISHED)
266: goto dropit;
267: if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
268: tp->t_state <= TCPS_CLOSE_WAIT) {
269: if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
270: goto dropit;
271: /*
272: * Send a packet designed to force a response
273: * if the peer is up and reachable:
274: * either an ACK if the connection is still alive,
275: * or an RST if the peer has closed the connection
276: * due to timeout or reboot.
277: * Using sequence number tp->snd_una-1
278: * causes the transmitted zero-length segment
279: * to lie outside the receive window;
280: * by the protocol spec, this requires the
281: * correspondent TCP to respond.
282: */
283: tcpstat.tcps_keepprobe++;
284: #ifdef TCP_COMPAT_42
285: /*
286: * The keepalive packet must have nonzero length
287: * to get a 4.2 host to respond.
288: */
289: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
290: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
291: #else
292: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
293: tp->rcv_nxt, tp->snd_una - 1, 0);
294: #endif
295: tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
296: } else
297: tp->t_timer[TCPT_KEEP] = tcp_keepidle;
298: break;
299: dropit:
300: tcpstat.tcps_keepdrops++;
301: tp = tcp_drop(tp, ETIMEDOUT);
302: break;
303: }
304: return (tp);
305: }
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