bsd/netinet/tcp_timer.h

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1982, 1986, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * Redistribution and use in source and binary forms, with or without
  27  * modification, are permitted provided that the following conditions
  28  * are met:
  29  * 1. Redistributions of source code must retain the above copyright
  30  *    notice, this list of conditions and the following disclaimer.
  31  * 2. Redistributions in binary form must reproduce the above copyright
  32  *    notice, this list of conditions and the following disclaimer in the
  33  *    documentation and/or other materials provided with the distribution.
  34  * 3. All advertising materials mentioning features or use of this software
  35  *    must display the following acknowledgement:
  36  *      This product includes software developed by the University of
  37  *      California, Berkeley and its contributors.
  38  * 4. Neither the name of the University nor the names of its contributors
  39  *    may be used to endorse or promote products derived from this software
  40  *    without specific prior written permission.
  41  *
  42  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  43  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  44  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  45  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  46  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  47  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  48  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  49  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  50  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  51  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  52  * SUCH DAMAGE.
  53  *
  54  *      @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
  55  */
  56
  57 #ifndef _NETINET_TCP_TIMER_H_
  58 #define _NETINET_TCP_TIMER_H_
  59
  60 /*
  61  * Definitions of the TCP timers.  These timers are counted
  62  * down PR_SLOWHZ times a second.
  63  */
  64 #define TCPT_NTIMERS    4
  65
  66 #define TCPT_REXMT      0               /* retransmit */
  67 #define TCPT_PERSIST    1               /* retransmit persistence */
  68 #define TCPT_KEEP       2               /* keep alive */
  69 #define TCPT_2MSL       3               /* 2*msl quiet time timer */
  70
  71 /*
  72  * The TCPT_REXMT timer is used to force retransmissions.
  73  * The TCP has the TCPT_REXMT timer set whenever segments
  74  * have been sent for which ACKs are expected but not yet
  75  * received.  If an ACK is received which advances tp->snd_una,
  76  * then the retransmit timer is cleared (if there are no more
  77  * outstanding segments) or reset to the base value (if there
  78  * are more ACKs expected).  Whenever the retransmit timer goes off,
  79  * we retransmit one unacknowledged segment, and do a backoff
  80  * on the retransmit timer.
  81  *
  82  * The TCPT_PERSIST timer is used to keep window size information
  83  * flowing even if the window goes shut.  If all previous transmissions
  84  * have been acknowledged (so that there are no retransmissions in progress),
  85  * and the window is too small to bother sending anything, then we start
  86  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
  87  * we go to transmit state.  Otherwise, at intervals send a single byte
  88  * into the peer's window to force him to update our window information.
  89  * We do this at most as often as TCPT_PERSMIN time intervals,
  90  * but no more frequently than the current estimate of round-trip
  91  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  92  * a window update from the peer.
  93  *
  94  * The TCPT_KEEP timer is used to keep connections alive.  If an
  95  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  96  * but not yet established, then we drop the connection.  Once the connection
  97  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  98  * (and keepalives have been enabled on the socket), we begin to probe
  99  * the connection.  We force the peer to send us a segment by sending:
 100  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
 101  * This segment is (deliberately) outside the window, and should elicit
 102  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
 103  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
 104  * amount of time probing, then we drop the connection.
 105  */
 106
 107 /*
 108  * Time constants.
 109  */
 110 #define TCPTV_MSL       ( 30*PR_SLOWHZ)         /* max seg lifetime (hah!) */
 111 #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
 112                                                    if 0, no idea yet */
 113 #define TCPTV_RTOBASE   (  3*PR_SLOWHZ)         /* assumed RTO if no info */
 114 #define TCPTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
 115
 116 #define TCPTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistence */
 117 #define TCPTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
 118
 119 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ)         /* initial connect keep alive */
 120 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)      /* dflt time before probing */
 121 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ)         /* default probe interval */
 122 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
 123
 124 #define TCPTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
 125 #define TCPTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
 126
 127 #define TCPTV_TWTRUNC   8                       /* RTO factor to truncate TW */
 128
 129 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
 130
 131 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
 132
 133 #ifdef  TCPTIMERS
 134 static char *tcptimers[] =
 135     { "REXMT", "PERSIST", "KEEP", "2MSL" };
 136 #endif
 137
 138 /*
 139  * Force a time value to be in a certain range.
 140  */
 141 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
 142         (tv) = (value); \
 143         if ((u_long)(tv) < (u_long)(tvmin)) \
 144                 (tv) = (tvmin); \
 145         else if ((u_long)(tv) > (u_long)(tvmax)) \
 146                 (tv) = (tvmax); \
 147 }
 148
 149 #ifdef KERNEL
 150 extern int tcp_keepinit;                /* time to establish connection */
 151 extern int tcp_keepidle;                /* time before keepalive probes begin */
 152 extern int tcp_maxidle;                 /* time to drop after starting probes */
 153 extern int tcp_ttl;                     /* time to live for TCP segs */
 154 extern int tcp_backoff[];
 155 #endif
 156
 157 #endif