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. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 *	@(#)tcp_timer.h	8.1 (Berkeley) 6/10/93
30 * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp
31 */
32
33#ifndef _TCP_TIMER_H_
34#define _TCP_TIMER_H_
35
36/*
37 * Definitions of the TCP timers.  These timers are counted
38 * down PR_SLOWHZ times a second.
39 */
40#define	TCPT_NTIMERS	4
41
42#define	TCPT_REXMT	0		/* retransmit */
43#define	TCPT_PERSIST	1		/* retransmit persistence */
44#define	TCPT_KEEP	2		/* keep alive */
45#define	TCPT_2MSL	3		/* 2*msl quiet time timer */
46
47/*
48 * The TCPT_REXMT timer is used to force retransmissions.
49 * The TCP has the TCPT_REXMT timer set whenever segments
50 * have been sent for which ACKs are expected but not yet
51 * received.  If an ACK is received which advances tp->snd_una,
52 * then the retransmit timer is cleared (if there are no more
53 * outstanding segments) or reset to the base value (if there
54 * are more ACKs expected).  Whenever the retransmit timer goes off,
55 * we retransmit one unacknowledged segment, and do a backoff
56 * on the retransmit timer.
57 *
58 * The TCPT_PERSIST timer is used to keep window size information
59 * flowing even if the window goes shut.  If all previous transmissions
60 * have been acknowledged (so that there are no retransmissions in progress),
61 * and the window is too small to bother sending anything, then we start
62 * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
63 * we go to transmit state.  Otherwise, at intervals send a single byte
64 * into the peer's window to force him to update our window information.
65 * We do this at most as often as TCPT_PERSMIN time intervals,
66 * but no more frequently than the current estimate of round-trip
67 * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
68 * a window update from the peer.
69 *
70 * The TCPT_KEEP timer is used to keep connections alive.  If an
71 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
72 * but not yet established, then we drop the connection.  Once the connection
73 * is established, if the connection is idle for TCPTV_KEEP_IDLE time
74 * (and keepalives have been enabled on the socket), we begin to probe
75 * the connection.  We force the peer to send us a segment by sending:
76 *	<SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
77 * This segment is (deliberately) outside the window, and should elicit
78 * an ack segment in response from the peer.  If, despite the TCPT_KEEP
79 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
80 * amount of time probing, then we drop the connection.
81 */
82
83/*
84 * Time constants.
85 */
86#define TCPTV_MSL       ( 5*PR_SLOWHZ)          /* max seg lifetime (hah!) */
87
88#define	TCPTV_SRTTBASE	0			/* base roundtrip time;
89						   if 0, no idea yet */
90#define	TCPTV_SRTTDFLT	(  3*PR_SLOWHZ)		/* assumed RTT if no info */
91
92#define	TCPTV_PERSMIN	(  5*PR_SLOWHZ)		/* retransmit persistence */
93#define	TCPTV_PERSMAX	( 60*PR_SLOWHZ)		/* maximum persist interval */
94
95#define	TCPTV_KEEP_INIT	( 75*PR_SLOWHZ)		/* initial connect keep alive */
96#define	TCPTV_KEEP_IDLE	(120*60*PR_SLOWHZ)	/* dflt time before probing */
97#define	TCPTV_KEEPINTVL	( 75*PR_SLOWHZ)		/* default probe interval */
98#define	TCPTV_KEEPCNT	8			/* max probes before drop */
99
100#define	TCPTV_MIN	(  1*PR_SLOWHZ)		/* minimum allowable value */
101/* #define	TCPTV_REXMTMAX	( 64*PR_SLOWHZ)	*/	/* max allowable REXMT value */
102#define TCPTV_REXMTMAX  ( 12*PR_SLOWHZ)		/* max allowable REXMT value */
103
104#define	TCP_LINGERTIME	120			/* linger at most 2 minutes */
105
106#define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
107
108
109#ifdef	TCPTIMERS
110char *tcptimers[] =
111    { "REXMT", "PERSIST", "KEEP", "2MSL" };
112#endif
113
114/*
115 * Force a time value to be in a certain range.
116 */
117#define	TCPT_RANGESET(tv, value, tvmin, tvmax) { \
118	(tv) = (value); \
119	if ((tv) < (tvmin)) \
120		(tv) = (tvmin); \
121	else if ((tv) > (tvmax)) \
122		(tv) = (tvmax); \
123}
124
125extern const int tcp_backoff[];
126
127struct tcpcb;
128
129void tcp_fasttimo _P((void));
130void tcp_slowtimo _P((void));
131void tcp_canceltimers _P((struct tcpcb *));
132
133#endif
134