tcp_timer.h revision 413f05aaf54fa08c0ae7e997327a4f4a473c0a8d 
1/*
2 * Copyright (c) 1982, 1986, 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.
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.h	8.1 (Berkeley) 6/10/93
34 * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp
35 */
36
37#ifndef _TCP_TIMER_H_
38#define _TCP_TIMER_H_
39
40/*
41 * Definitions of the TCP timers.  These timers are counted
42 * down PR_SLOWHZ times a second.
43 */
44#define	TCPT_NTIMERS	4
45
46#define	TCPT_REXMT	0		/* retransmit */
47#define	TCPT_PERSIST	1		/* retransmit persistence */
48#define	TCPT_KEEP	2		/* keep alive */
49#define	TCPT_2MSL	3		/* 2*msl quiet time timer */
50
51/*
52 * The TCPT_REXMT timer is used to force retransmissions.
53 * The TCP has the TCPT_REXMT timer set whenever segments
54 * have been sent for which ACKs are expected but not yet
55 * received.  If an ACK is received which advances tp->snd_una,
56 * then the retransmit timer is cleared (if there are no more
57 * outstanding segments) or reset to the base value (if there
58 * are more ACKs expected).  Whenever the retransmit timer goes off,
59 * we retransmit one unacknowledged segment, and do a backoff
60 * on the retransmit timer.
61 *
62 * The TCPT_PERSIST timer is used to keep window size information
63 * flowing even if the window goes shut.  If all previous transmissions
64 * have been acknowledged (so that there are no retransmissions in progress),
65 * and the window is too small to bother sending anything, then we start
66 * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
67 * we go to transmit state.  Otherwise, at intervals send a single byte
68 * into the peer's window to force him to update our window information.
69 * We do this at most as often as TCPT_PERSMIN time intervals,
70 * but no more frequently than the current estimate of round-trip
71 * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
72 * a window update from the peer.
73 *
74 * The TCPT_KEEP timer is used to keep connections alive.  If an
75 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
76 * but not yet established, then we drop the connection.  Once the connection
77 * is established, if the connection is idle for TCPTV_KEEP_IDLE time
78 * (and keepalives have been enabled on the socket), we begin to probe
79 * the connection.  We force the peer to send us a segment by sending:
80 *	<SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
81 * This segment is (deliberately) outside the window, and should elicit
82 * an ack segment in response from the peer.  If, despite the TCPT_KEEP
83 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
84 * amount of time probing, then we drop the connection.
85 */
86
87/*
88 * Time constants.
89 */
90#define TCPTV_MSL       ( 5*PR_SLOWHZ)          /* max seg lifetime (hah!) */
91
92#define	TCPTV_SRTTBASE	0			/* base roundtrip time;
93						   if 0, no idea yet */
94#define	TCPTV_SRTTDFLT	(  3*PR_SLOWHZ)		/* assumed RTT if no info */
95
96#define	TCPTV_PERSMIN	(  5*PR_SLOWHZ)		/* retransmit persistence */
97#define	TCPTV_PERSMAX	( 60*PR_SLOWHZ)		/* maximum persist interval */
98
99#define	TCPTV_KEEP_INIT	( 75*PR_SLOWHZ)		/* initial connect keep alive */
100#define	TCPTV_KEEP_IDLE	(120*60*PR_SLOWHZ)	/* dflt time before probing */
101#define	TCPTV_KEEPINTVL	( 75*PR_SLOWHZ)		/* default probe interval */
102#define	TCPTV_KEEPCNT	8			/* max probes before drop */
103
104#define	TCPTV_MIN	(  1*PR_SLOWHZ)		/* minimum allowable value */
105/* #define	TCPTV_REXMTMAX	( 64*PR_SLOWHZ)	*/	/* max allowable REXMT value */
106#define TCPTV_REXMTMAX  ( 12*PR_SLOWHZ)		/* max allowable REXMT value */
107
108#define	TCP_LINGERTIME	120			/* linger at most 2 minutes */
109
110#define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
111
112
113#ifdef	TCPTIMERS
114char *tcptimers[] =
115    { "REXMT", "PERSIST", "KEEP", "2MSL" };
116#endif
117
118/*
119 * Force a time value to be in a certain range.
120 */
121#define	TCPT_RANGESET(tv, value, tvmin, tvmax) { \
122	(tv) = (value); \
123	if ((tv) < (tvmin)) \
124		(tv) = (tvmin); \
125	else if ((tv) > (tvmax)) \
126		(tv) = (tvmax); \
127}
128
129extern int tcp_keepidle;		/* time before keepalive probes begin */
130extern int tcp_keepintvl;		/* time between keepalive probes */
131extern int tcp_maxidle;			/* time to drop after starting probes */
132extern int tcp_ttl;			/* time to live for TCP segs */
133extern int tcp_backoff[];
134
135struct tcpcb;
136
137void tcp_fasttimo _P((void));
138void tcp_slowtimo _P((void));
139void tcp_canceltimers _P((struct tcpcb *));
140struct tcpcb * tcp_timers _P((register struct tcpcb *, int));
141
142#endif
143