/*

 * Copyright (c) 1982, 1986, 1993

 *	The Regents of the University of California.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *	This product includes software developed by the University of

 *	California, Berkeley and its contributors.

 * 4. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 *

 *	@(#)tcp_timer.h	8.1 (Berkeley) 6/10/93

 * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp

 */

#ifndef _TCP_TIMER_H_

#define _TCP_TIMER_H_

/*

 * Definitions of the TCP timers.  These timers are counted

 * down PR_SLOWHZ times a second.

 */

#define	TCPT_NTIMERS	4

#define	TCPT_REXMT	0		/* retransmit */

#define	TCPT_PERSIST	1		/* retransmit persistence */

#define	TCPT_KEEP	2		/* keep alive */

#define	TCPT_2MSL	3		/* 2*msl quiet time timer */

/*

 * The TCPT_REXMT timer is used to force retransmissions.

 * The TCP has the TCPT_REXMT timer set whenever segments

 * have been sent for which ACKs are expected but not yet

 * received.  If an ACK is received which advances tp->snd_una,

 * then the retransmit timer is cleared (if there are no more

 * outstanding segments) or reset to the base value (if there

 * are more ACKs expected).  Whenever the retransmit timer goes off,

 * we retransmit one unacknowledged segment, and do a backoff

 * on the retransmit timer.

 *

 * The TCPT_PERSIST timer is used to keep window size information

 * flowing even if the window goes shut.  If all previous transmissions

 * have been acknowledged (so that there are no retransmissions in progress),

 * and the window is too small to bother sending anything, then we start

 * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,

 * we go to transmit state.  Otherwise, at intervals send a single byte

 * into the peer's window to force him to update our window information.

 * We do this at most as often as TCPT_PERSMIN time intervals,

 * but no more frequently than the current estimate of round-trip

 * packet time.  The TCPT_PERSIST timer is cleared whenever we receive

 * a window update from the peer.

 *

 * The TCPT_KEEP timer is used to keep connections alive.  If an

 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,

 * but not yet established, then we drop the connection.  Once the connection

 * is established, if the connection is idle for TCPTV_KEEP_IDLE time

 * (and keepalives have been enabled on the socket), we begin to probe

 * the connection.  We force the peer to send us a segment by sending:

 *	<SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>

 * This segment is (deliberately) outside the window, and should elicit

 * an ack segment in response from the peer.  If, despite the TCPT_KEEP

 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE

 * amount of time probing, then we drop the connection.

 */

/*

 * Time constants.

 */

#define TCPTV_MSL       ( 5*PR_SLOWHZ)          /* max seg lifetime (hah!) */

#define	TCPTV_SRTTBASE	0			/* base roundtrip time;

						   if 0, no idea yet */

#define	TCPTV_SRTTDFLT	(  3*PR_SLOWHZ)		/* assumed RTT if no info */

#define	TCPTV_PERSMIN	(  5*PR_SLOWHZ)		/* retransmit persistence */

#define	TCPTV_PERSMAX	( 60*PR_SLOWHZ)		/* maximum persist interval */

#define	TCPTV_KEEP_INIT	( 75*PR_SLOWHZ)		/* initial connect keep alive */

#define	TCPTV_KEEP_IDLE	(120*60*PR_SLOWHZ)	/* dflt time before probing */

#define	TCPTV_KEEPINTVL	( 75*PR_SLOWHZ)		/* default probe interval */

#define	TCPTV_KEEPCNT	8			/* max probes before drop */

#define	TCPTV_MIN	(  1*PR_SLOWHZ)		/* minimum allowable value */

/* #define	TCPTV_REXMTMAX	( 64*PR_SLOWHZ)	*/	/* max allowable REXMT value */

#define TCPTV_REXMTMAX  ( 12*PR_SLOWHZ)		/* max allowable REXMT value */

#define	TCP_LINGERTIME	120			/* linger at most 2 minutes */

#define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */

#ifdef	TCPTIMERS

char *tcptimers[] =

    { "REXMT", "PERSIST", "KEEP", "2MSL" };

#endif

/*

 * Force a time value to be in a certain range.

 */

#define	TCPT_RANGESET(tv, value, tvmin, tvmax) { \

	(tv) = (value); \

	if ((tv) < (tvmin)) \

		(tv) = (tvmin); \

	else if ((tv) > (tvmax)) \

		(tv) = (tvmax); \

}

extern const int tcp_backoff[];

struct tcpcb;

void tcp_fasttimo _P((void));

void tcp_slowtimo _P((void));

void tcp_canceltimers _P((struct tcpcb *));

#endif