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) 1982, 1986, 1988, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  * Copyright (c) 1995, Mike Mitchell
   30  *
   31  * Redistribution and use in source and binary forms, with or without
   32  * modification, are permitted provided that the following conditions
   33  * are met:
   34  * 1. Redistributions of source code must retain the above copyright
   35  *    notice, this list of conditions and the following disclaimer.
   36  * 2. Redistributions in binary form must reproduce the above copyright
   37  *    notice, this list of conditions and the following disclaimer in the
   38  *    documentation and/or other materials provided with the distribution.
   39  * 3. All advertising materials mentioning features or use of this software
   40  *    must display the following acknowledgement:
   41  *      This product includes software developed by the University of
   42  *      California, Berkeley and its contributors.
   43  * 4. Neither the name of the University nor the names of its contributors
   44  *    may be used to endorse or promote products derived from this software
   45  *    without specific prior written permission.
   46  *
   47  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   48  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   49  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   50  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   51  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   52  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   53  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   54  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   55  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   56  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   57  * SUCH DAMAGE.
   58  *
   59  *      @(#)spx_timer.h
   60  *
   61  * $FreeBSD: releng/8.4/sys/netipx/spx_timer.h 199583 2009-11-20 15:27:52Z jhb $
   62  */
   63 
   64 #ifndef _NETIPX_SPX_TIMER_H_
   65 #define _NETIPX_SPX_TIMER_H_
   66 
   67 /*
   68  * Definitions of the SPX timers.  These timers are counted
   69  * down PR_SLOWHZ times a second.
   70  */
   71 #define SPXT_REXMT      0               /* retransmit */
   72 #define SPXT_PERSIST    1               /* retransmit persistence */
   73 #define SPXT_KEEP       2               /* keep alive */
   74 #define SPXT_2MSL       3               /* 2*msl quiet time timer */
   75 
   76 /*
   77  * The SPXT_REXMT timer is used to force retransmissions.
   78  * The SPX has the SPXT_REXMT timer set whenever segments
   79  * have been sent for which ACKs are expected but not yet
   80  * received.  If an ACK is received which advances tp->snd_una,
   81  * then the retransmit timer is cleared (if there are no more
   82  * outstanding segments) or reset to the base value (if there
   83  * are more ACKs expected).  Whenever the retransmit timer goes off,
   84  * we retransmit one unacknowledged segment, and do a backoff
   85  * on the retransmit timer.
   86  *
   87  * The SPXT_PERSIST timer is used to keep window size information
   88  * flowing even if the window goes shut.  If all previous transmissions
   89  * have been acknowledged (so that there are no retransmissions in progress),
   90  * and the window is too small to bother sending anything, then we start
   91  * the SPXT_PERSIST timer.  When it expires, if the window is nonzero,
   92  * we go to transmit state.  Otherwise, at intervals send a single byte
   93  * into the peer's window to force him to update our window information.
   94  * We do this at most as often as SPXT_PERSMIN time intervals,
   95  * but no more frequently than the current estimate of round-trip
   96  * packet time.  The SPXT_PERSIST timer is cleared whenever we receive
   97  * a window update from the peer.
   98  *
   99  * The SPXT_KEEP timer is used to keep connections alive.  If an
  100  * connection is idle (no segments received) for SPXTV_KEEP amount of time,
  101  * but not yet established, then we drop the connection.  If the connection
  102  * is established, then we force the peer to send us a segment by sending:
  103  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  104  * This segment is (deliberately) outside the window, and should elicit
  105  * an ack segment in response from the peer.  If, despite the SPXT_KEEP
  106  * initiated segments we cannot elicit a response from a peer in SPXT_MAXIDLE
  107  * amount of time, then we drop the connection.
  108  */
  109 
  110 #define SPX_TTL         30              /* default time to live for SPX segs */
  111 /*
  112  * Time constants.
  113  */
  114 #define SPXTV_MSL       ( 15*PR_SLOWHZ)         /* max seg lifetime */
  115 #define SPXTV_SRTTBASE  0                       /* base roundtrip time;
  116                                                    if 0, no idea yet */
  117 #define SPXTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
  118 
  119 #define SPXTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistence */
  120 #define SPXTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
  121 
  122 #define SPXTV_KEEP      ( 75*PR_SLOWHZ)         /* keep alive - 75 secs */
  123 #define SPXTV_MAXIDLE   (  8*SPXTV_KEEP)        /* maximum allowable idle
  124                                                    time before drop conn */
  125 
  126 #define SPXTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
  127 #define SPXTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
  128 
  129 #define SPX_LINGERTIME  120                     /* linger at most 2 minutes */
  130 
  131 #define SPX_MAXRXTSHIFT 12                      /* maximum retransmits */
  132 
  133 #ifdef  SPXTIMERS
  134 char *spxtimers[] =
  135     { "REXMT", "PERSIST", "KEEP", "2MSL" };
  136 #endif
  137 
  138 /*
  139  * Force a time value to be in a certain range.
  140  */
  141 #define SPXT_RANGESET(tv, value, tvmin, tvmax) { \
  142         (tv) = (value); \
  143         if ((tv) < (tvmin)) \
  144                 (tv) = (tvmin); \
  145         else if ((tv) > (tvmax)) \
  146                 (tv) = (tvmax); \
  147 }
  148 
  149 #endif /* !_NETIPX_SPX_TIMER_H_ */

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