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tcp_timer.h revision 1.11 
      1 /*	$NetBSD: tcp_timer.h,v 1.11 2001/09/10 04:24:25 thorpej Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1982, 1986, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  *
     35  *	@(#)tcp_timer.h	8.1 (Berkeley) 6/10/93
     36  */
     37 
     38 #ifndef _NETINET_TCP_TIMER_H_
     39 #define _NETINET_TCP_TIMER_H_
     40 
     41 /*
     42  * Definitions of the TCP timers.  These timers are counted
     43  * down PR_SLOWHZ times a second.
     44  */
     45 #define	TCPT_NTIMERS	4
     46 
     47 #define	TCPT_REXMT	0		/* retransmit */
     48 #define	TCPT_PERSIST	1		/* retransmit persistance */
     49 #define	TCPT_KEEP	2		/* keep alive */
     50 #define	TCPT_2MSL	3		/* 2*msl quiet time timer */
     51 
     52 /*
     53  * The TCPT_REXMT timer is used to force retransmissions.
     54  * The TCP has the TCPT_REXMT timer set whenever segments
     55  * have been sent for which ACKs are expected but not yet
     56  * received.  If an ACK is received which advances tp->snd_una,
     57  * then the retransmit timer is cleared (if there are no more
     58  * outstanding segments) or reset to the base value (if there
     59  * are more ACKs expected).  Whenever the retransmit timer goes off,
     60  * we retransmit one unacknowledged segment, and do a backoff
     61  * on the retransmit timer.
     62  *
     63  * The TCPT_PERSIST timer is used to keep window size information
     64  * flowing even if the window goes shut.  If all previous transmissions
     65  * have been acknowledged (so that there are no retransmissions in progress),
     66  * and the window is too small to bother sending anything, then we start
     67  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
     68  * we go to transmit state.  Otherwise, at intervals send a single byte
     69  * into the peer's window to force him to update our window information.
     70  * We do this at most as often as TCPT_PERSMIN time intervals,
     71  * but no more frequently than the current estimate of round-trip
     72  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
     73  * a window update from the peer.
     74  *
     75  * The TCPT_KEEP timer is used to keep connections alive.  If an
     76  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
     77  * but not yet established, then we drop the connection.  Once the connection
     78  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
     79  * (and keepalives have been enabled on the socket), we begin to probe
     80  * the connection.  We force the peer to send us a segment by sending:
     81  *	<SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
     82  * This segment is (deliberately) outside the window, and should elicit
     83  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
     84  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
     85  * amount of time probing, then we drop the connection.
     86  */
     87 
     88 /*
     89  * Time constants.
     90  */
     91 #define	TCPTV_MSL	( 30*PR_SLOWHZ)		/* max seg lifetime (hah!) */
     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 persistance */
     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 
    107 #define	TCP_LINGERTIME	120			/* linger at most 2 minutes */
    108 
    109 #define	TCP_MAXRXTSHIFT	12			/* maximum retransmits */
    110 
    111 #define	TCP_DELACK_TICKS (hz / PR_FASTHZ)	/* time to delay ACK */
    112 
    113 #ifdef	TCPTIMERS
    114 char *tcptimers[] =
    115     { "REXMT", "PERSIST", "KEEP", "2MSL" };
    116 #endif
    117 
    118 /*
    119  * Arm, disarm, and test TCP timers.
    120  */
    121 #define	TCP_TIMER_ARM(tp, timer, nticks) \
    122 	PRT_SLOW_ARM((tp)->t_timer[(timer)], (nticks))
    123 
    124 #define	TCP_TIMER_DISARM(tp, timer) \
    125 	PRT_SLOW_DISARM((tp)->t_timer[(timer)])
    126 
    127 #define	TCP_TIMER_ISARMED(tp, timer) \
    128 	PRT_SLOW_ISARMED((tp)->t_timer[(timer)])
    129 
    130 #define	TCP_TIMER_ISEXPIRED(tp, timer) \
    131 	PRT_SLOW_ISEXPIRED((tp)->t_timer[(timer)])
    132 
    133 /*
    134  * Force a time value to be in a certain range.
    135  */
    136 #define	TCPT_RANGESET(tv, value, tvmin, tvmax) { \
    137 	(tv) = (value); \
    138 	if ((tv) < (tvmin)) \
    139 		(tv) = (tvmin); \
    140 	else if ((tv) > (tvmax)) \
    141 		(tv) = (tvmax); \
    142 }
    143 
    144 #ifdef _KERNEL
    145 extern int tcp_keepidle;		/* time before keepalive probes begin */
    146 extern int tcp_keepintvl;		/* time between keepalive probes */
    147 extern int tcp_keepcnt;			/* number of keepalives, 0=infty */
    148 extern int tcp_maxidle;			/* time to drop after starting probes */
    149 extern int tcp_ttl;			/* time to live for TCP segs */
    150 extern int tcp_backoff[];
    151 #endif
    152 
    153 #endif /* _NETINET_TCP_TIMER_H_ */
    154