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//      include/netinet_tcp_timer.h

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//      

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// Portions of this software may have been derived from OpenBSD or other sources,

// and are covered by the appropriate copyright disclaimers included herein.

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//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):    gthomas

// Contributors: gthomas

// Date:         2000-01-10

// Purpose:      

// Description:  

//              

//

//####DESCRIPTIONEND####

//

//==========================================================================

/*      $OpenBSD: tcp_timer.h,v 1.3 1997/02/24 14:06:46 niklas Exp $    */

/*      $NetBSD: tcp_timer.h,v 1.6 1995/03/26 20:32:37 jtc Exp $        */

/*

 * 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

 */

#ifndef _NETINET_TCP_TIMER_H_

#define _NETINET_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 persistance */

#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       ( 30*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 persistance */

#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 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); \

}

#ifdef _KERNEL

extern int tcptv_keep_init;

extern int tcp_keepidle;                /* time before keepalive probes begin */

extern int tcp_keepintvl;               /* time between keepalive probes */

extern int tcp_maxidle;                 /* time to drop after starting probes */

extern int tcp_ttl;                     /* time to live for TCP segs */

extern int tcp_backoff[];

#endif

#endif  // _NETINET_TCP_TIMER_H_