slirp/tcp_timer.h

   1 /*
   2  * Copyright (c) 1982, 1986, 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  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
  34  * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp
  35  */
  36
  37 #ifndef _TCP_TIMER_H_
  38 #define _TCP_TIMER_H_
  39
  40 /*
  41  * Definitions of the TCP timers.  These timers are counted
  42  * down PR_SLOWHZ times a second.
  43  */
  44 #define TCPT_NTIMERS    4
  45
  46 #define TCPT_REXMT      0               /* retransmit */
  47 #define TCPT_PERSIST    1               /* retransmit persistence */
  48 #define TCPT_KEEP       2               /* keep alive */
  49 #define TCPT_2MSL       3               /* 2*msl quiet time timer */
  50
  51 /*
  52  * The TCPT_REXMT timer is used to force retransmissions.
  53  * The TCP has the TCPT_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 TCPT_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 TCPT_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 TCPT_PERSMIN time intervals,
  70  * but no more frequently than the current estimate of round-trip
  71  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  72  * a window update from the peer.
  73  *
  74  * The TCPT_KEEP timer is used to keep connections alive.  If an
  75  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  76  * but not yet established, then we drop the connection.  Once the connection
  77  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  78  * (and keepalives have been enabled on the socket), we begin to probe
  79  * the connection.  We force the peer to send us a segment by sending:
  80  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  81  * This segment is (deliberately) outside the window, and should elicit
  82  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
  83  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
  84  * amount of time probing, then we drop the connection.
  85  */
  86
  87 /*
  88  * Time constants.
  89  */
  90 #define TCPTV_MSL       ( 5*PR_SLOWHZ)          /* max seg lifetime (hah!) */
  91
  92 #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
  93                                                    if 0, no idea yet */
  94 #define TCPTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
  95
  96 #define TCPTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistence */
  97 #define TCPTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
  98
  99 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ)         /* initial connect keep alive */
 100 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)      /* dflt time before probing */
 101 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ)         /* default probe interval */
 102 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
 103
 104 #define TCPTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
 105 /* #define      TCPTV_REXMTMAX  ( 64*PR_SLOWHZ) */      /* max allowable REXMT value */
 106 #define TCPTV_REXMTMAX  ( 12*PR_SLOWHZ)         /* max allowable REXMT value */
 107
 108 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
 109
 110 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
 111
 112
 113 #ifdef  TCPTIMERS
 114 char *tcptimers[] =
 115     { "REXMT", "PERSIST", "KEEP", "2MSL" };
 116 #endif
 117
 118 /*
 119  * Force a time value to be in a certain range.
 120  */
 121 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
 122         (tv) = (value); \
 123         if ((tv) < (tvmin)) \
 124                 (tv) = (tvmin); \
 125         else if ((tv) > (tvmax)) \
 126                 (tv) = (tvmax); \
 127 }
 128
 129 extern int tcp_keepidle;                /* time before keepalive probes begin */
 130 extern int tcp_keepintvl;               /* time between keepalive probes */
 131 extern int tcp_maxidle;                 /* time to drop after starting probes */
 132 extern int tcp_ttl;                     /* time to live for TCP segs */
 133 extern int tcp_backoff[];
 134
 135 struct tcpcb;
 136
 137 void tcp_fasttimo _P((void));
 138 void tcp_slowtimo _P((void));
 139 void tcp_canceltimers _P((struct tcpcb *));
 140 struct tcpcb * tcp_timers _P((register struct tcpcb *, int));
 141
 142 #endif