The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/netipx/spx_timer.h

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    1 /*
    2  * Copyright (c) 1995, Mike Mitchell
    3  * Copyright (c) 1982, 1986, 1988, 1993
    4  *      The Regents of the University of California.  All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. All advertising materials mentioning features or use of this software
   15  *    must display the following acknowledgement:
   16  *      This product includes software developed by the University of
   17  *      California, Berkeley and its contributors.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)spx_timer.h
   35  *
   36  * $FreeBSD: releng/5.0/sys/netipx/spx_timer.h 50477 1999-08-28 01:08:13Z peter $
   37  */
   38 
   39 #ifndef _NETIPX_SPX_TIMER_H_
   40 #define _NETIPX_SPX_TIMER_H_
   41 
   42 /*
   43  * Definitions of the SPX timers.  These timers are counted
   44  * down PR_SLOWHZ times a second.
   45  */
   46 #define SPXT_REXMT      0               /* retransmit */
   47 #define SPXT_PERSIST    1               /* retransmit persistence */
   48 #define SPXT_KEEP       2               /* keep alive */
   49 #define SPXT_2MSL       3               /* 2*msl quiet time timer */
   50 
   51 /*
   52  * The SPXT_REXMT timer is used to force retransmissions.
   53  * The SPX has the SPXT_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 SPXT_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 SPXT_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 SPXT_PERSMIN time intervals,
   70  * but no more frequently than the current estimate of round-trip
   71  * packet time.  The SPXT_PERSIST timer is cleared whenever we receive
   72  * a window update from the peer.
   73  *
   74  * The SPXT_KEEP timer is used to keep connections alive.  If an
   75  * connection is idle (no segments received) for SPXTV_KEEP amount of time,
   76  * but not yet established, then we drop the connection.  If the connection
   77  * is established, then we force the peer to send us a segment by sending:
   78  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
   79  * This segment is (deliberately) outside the window, and should elicit
   80  * an ack segment in response from the peer.  If, despite the SPXT_KEEP
   81  * initiated segments we cannot elicit a response from a peer in SPXT_MAXIDLE
   82  * amount of time, then we drop the connection.
   83  */
   84 
   85 #define SPX_TTL         30              /* default time to live for SPX segs */
   86 /*
   87  * Time constants.
   88  */
   89 #define SPXTV_MSL       ( 15*PR_SLOWHZ)         /* max seg lifetime */
   90 #define SPXTV_SRTTBASE  0                       /* base roundtrip time;
   91                                                    if 0, no idea yet */
   92 #define SPXTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
   93 
   94 #define SPXTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistence */
   95 #define SPXTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
   96 
   97 #define SPXTV_KEEP      ( 75*PR_SLOWHZ)         /* keep alive - 75 secs */
   98 #define SPXTV_MAXIDLE   (  8*SPXTV_KEEP)        /* maximum allowable idle
   99                                                    time before drop conn */
  100 
  101 #define SPXTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
  102 #define SPXTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
  103 
  104 #define SPX_LINGERTIME  120                     /* linger at most 2 minutes */
  105 
  106 #define SPX_MAXRXTSHIFT 12                      /* maximum retransmits */
  107 
  108 #ifdef  SPXTIMERS
  109 char *spxtimers[] =
  110     { "REXMT", "PERSIST", "KEEP", "2MSL" };
  111 #endif
  112 
  113 /*
  114  * Force a time value to be in a certain range.
  115  */
  116 #define SPXT_RANGESET(tv, value, tvmin, tvmax) { \
  117         (tv) = (value); \
  118         if ((tv) < (tvmin)) \
  119                 (tv) = (tvmin); \
  120         else if ((tv) > (tvmax)) \
  121                 (tv) = (tvmax); \
  122 }
  123 
  124 #endif /* !_NETIPX_SPX_TIMER_H_ */

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