2.11BSD#431 - /usr/src/sys/netinet/tcp_timer.h

   1: /*
   2:  * Copyright (c) 1982, 1986 Regents of the University of California.
   3:  * All rights reserved.
   4:  *
   5:  * Redistribution and use in source and binary forms are permitted
   6:  * provided that this notice is preserved and that due credit is given
   7:  * to the University of California at Berkeley. The name of the University
   8:  * may not be used to endorse or promote products derived from this
   9:  * software without specific prior written permission. This software
  10:  * is provided ``as is'' without express or implied warranty.
  11:  *
  12:  *	@(#)tcp_timer.h	7.5.1 (2.11BSD) 1995/10/10
  13:  */
  14: 
  15: /*
  16:  * Definitions of the TCP timers.  These timers are counted
  17:  * down PR_SLOWHZ times a second.
  18:  */
  19: #define TCPT_NTIMERS    4
  20: 
  21: #define TCPT_REXMT  0       /* retransmit */
  22: #define TCPT_PERSIST    1       /* retransmit persistance */
  23: #define TCPT_KEEP   2       /* keep alive */
  24: #define TCPT_2MSL   3       /* 2*msl quiet time timer */
  25: 
  26: /*
  27:  * The TCPT_REXMT timer is used to force retransmissions.
  28:  * The TCP has the TCPT_REXMT timer set whenever segments
  29:  * have been sent for which ACKs are expected but not yet
  30:  * received.  If an ACK is received which advances tp->snd_una,
  31:  * then the retransmit timer is cleared (if there are no more
  32:  * outstanding segments) or reset to the base value (if there
  33:  * are more ACKs expected).  Whenever the retransmit timer goes off,
  34:  * we retransmit one unacknowledged segment, and do a backoff
  35:  * on the retransmit timer.
  36:  *
  37:  * The TCPT_PERSIST timer is used to keep window size information
  38:  * flowing even if the window goes shut.  If all previous transmissions
  39:  * have been acknowledged (so that there are no retransmissions in progress),
  40:  * and the window is too small to bother sending anything, then we start
  41:  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
  42:  * we go to transmit state.  Otherwise, at intervals send a single byte
  43:  * into the peer's window to force him to update our window information.
  44:  * We do this at most as often as TCPT_PERSMIN time intervals,
  45:  * but no more frequently than the current estimate of round-trip
  46:  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  47:  * a window update from the peer.
  48:  *
  49:  * The TCPT_KEEP timer is used to keep connections alive.  If an
  50:  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  51:  * but not yet established, then we drop the connection.  Once the connection
  52:  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  53:  * (and keepalives have been enabled on the socket), we begin to probe
  54:  * the connection.  We force the peer to send us a segment by sending:
  55:  *	<SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  56:  * This segment is (deliberately) outside the window, and should elicit
  57:  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
  58:  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
  59:  * amount of time probing, then we drop the connection.
  60:  */
  61: 
  62: /*
  63:  * Time constants.
  64:  */
  65: #define TCPTV_MSL   ( 30*PR_SLOWHZ)     /* max seg lifetime (hah!) */
  66: #define TCPTV_SRTTBASE  0           /* base roundtrip time;
  67: 						   if 0, no idea yet */
  68: #define TCPTV_SRTTDFLT  (  3*PR_SLOWHZ)     /* assumed RTT if no info */
  69: 
  70: #define TCPTV_PERSMIN   (  5*PR_SLOWHZ)     /* retransmit persistance */
  71: #define TCPTV_PERSMAX   ( 60*PR_SLOWHZ)     /* maximum persist interval */
  72: 
  73: #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ)     /* initial connect keep alive */
  74: #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)  /* dflt time before probing */
  75: #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ)     /* default probe interval */
  76: #define TCPTV_KEEPCNT   8           /* max probes before drop */
  77: 
  78: #define TCPTV_MIN   (  1*PR_SLOWHZ)     /* minimum allowable value */
  79: #define TCPTV_REXMTMAX  ( 64*PR_SLOWHZ)     /* max allowable REXMT value */
  80: 
  81: #define TCP_LINGERTIME  120         /* linger at most 2 minutes */
  82: 
  83: #define TCP_MAXRXTSHIFT 12          /* maximum retransmits */
  84: 
  85: #ifdef  TCPTIMERS
  86: char *tcptimers[] =
  87:     { "REXMT", "PERSIST", "KEEP", "2MSL" };
  88: #endif
  89: 
  90: /*
  91:  * Force a time value to be in a certain range.
  92:  */
  93: #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
  94:     (tv) = (value); \
  95:     if ((tv) < (tvmin)) \
  96:         (tv) = (tvmin); \
  97:     else if ((tv) > (tvmax)) \
  98:         (tv) = (tvmax); \
  99: }
 100: 
 101: #ifdef SUPERVISOR
 102: #define tcp_keepidle tcp_kdle
 103: #define tcp_keepintvl tcp_kntv
 104: extern int tcp_keepidle;        /* time before keepalive probes begin */
 105: extern int tcp_keepintvl;       /* time between keepalive probes */
 106: extern int tcp_maxidle;         /* time to drop after starting probes */
 107: extern int tcp_backoff[];
 108: #endif

Defined variables

Defined macros

Usage of this include