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/netns/spp_timer.h

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    1 /*      $NetBSD: spp_timer.h,v 1.8 2003/08/07 16:33:48 agc Exp $        */
    2 
    3 /*
    4  * Copyright (c) 1982, 1986, 1988, 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. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      @(#)spp_timer.h 8.1 (Berkeley) 6/10/93
   32  */
   33 
   34 /*
   35  * Definitions of the SPP timers.  These timers are counted
   36  * down PR_SLOWHZ times a second.
   37  */
   38 #define SPPT_NTIMERS    4
   39 
   40 #define SPPT_REXMT      0               /* retransmit */
   41 #define SPPT_PERSIST    1               /* retransmit persistance */
   42 #define SPPT_KEEP       2               /* keep alive */
   43 #define SPPT_2MSL       3               /* 2*msl quiet time timer */
   44 
   45 /*
   46  * The SPPT_REXMT timer is used to force retransmissions.
   47  * The SPP has the SPPT_REXMT timer set whenever segments
   48  * have been sent for which ACKs are expected but not yet
   49  * received.  If an ACK is received which advances tp->snd_una,
   50  * then the retransmit timer is cleared (if there are no more
   51  * outstanding segments) or reset to the base value (if there
   52  * are more ACKs expected).  Whenever the retransmit timer goes off,
   53  * we retransmit one unacknowledged segment, and do a backoff
   54  * on the retransmit timer.
   55  *
   56  * The SPPT_PERSIST timer is used to keep window size information
   57  * flowing even if the window goes shut.  If all previous transmissions
   58  * have been acknowledged (so that there are no retransmissions in progress),
   59  * and the window is too small to bother sending anything, then we start
   60  * the SPPT_PERSIST timer.  When it expires, if the window is nonzero,
   61  * we go to transmit state.  Otherwise, at intervals send a single byte
   62  * into the peer's window to force him to update our window information.
   63  * We do this at most as often as SPPT_PERSMIN time intervals,
   64  * but no more frequently than the current estimate of round-trip
   65  * packet time.  The SPPT_PERSIST timer is cleared whenever we receive
   66  * a window update from the peer.
   67  *
   68  * The SPPT_KEEP timer is used to keep connections alive.  If an
   69  * connection is idle (no segments received) for SPPTV_KEEP amount of time,
   70  * but not yet established, then we drop the connection.  If the connection
   71  * is established, then we force the peer to send us a segment by sending:
   72  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
   73  * This segment is (deliberately) outside the window, and should elicit
   74  * an ack segment in response from the peer.  If, despite the SPPT_KEEP
   75  * initiated segments we cannot elicit a response from a peer in SPPT_MAXIDLE
   76  * amount of time, then we drop the connection.
   77  */
   78 
   79 #define SPP_TTL         30              /* default time to live for SPP segs */
   80 /*
   81  * Time constants.
   82  */
   83 #define SPPTV_MSL       ( 15*PR_SLOWHZ)         /* max seg lifetime */
   84 #define SPPTV_SRTTBASE  0                       /* base roundtrip time;
   85                                                    if 0, no idea yet */
   86 #define SPPTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
   87 
   88 #define SPPTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistance */
   89 #define SPPTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
   90 
   91 #define SPPTV_KEEP      ( 75*PR_SLOWHZ)         /* keep alive - 75 secs */
   92 #define SPPTV_MAXIDLE   (  8*SPPTV_KEEP)        /* maximum allowable idle
   93                                                    time before drop conn */
   94 
   95 #define SPPTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
   96 #define SPPTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
   97 
   98 #define SPP_LINGERTIME  120                     /* linger at most 2 minutes */
   99 
  100 #define SPP_MAXRXTSHIFT 12                      /* maximum retransmits */
  101 
  102 #ifdef  SPPTIMERS
  103 const char * const spptimers[] =
  104     { "REXMT", "PERSIST", "KEEP", "2MSL" };
  105 #endif
  106 
  107 /*
  108  * Force a time value to be in a certain range.
  109  */
  110 #define SPPT_RANGESET(tv, value, tvmin, tvmax) { \
  111         (tv) = (value); \
  112         if ((tv) < (tvmin)) \
  113                 (tv) = (tvmin); \
  114         else if ((tv) > (tvmax)) \
  115                 (tv) = (tvmax); \
  116 }
  117 
  118 #ifdef _KERNEL
  119 extern int spp_backoff[];
  120 #endif

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