sys/netinet/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  * $FreeBSD: src/sys/netinet/tcp_timer.h,v 1.18.2.1 2002/08/16 22:16:39 dillon Exp $
  35  * $DragonFly: src/sys/netinet/tcp_timer.h,v 1.3 2003/08/23 11:18:00 rob Exp $
  36  */
  37
  38 #ifndef _NETINET_TCP_TIMER_H_
  39 #define _NETINET_TCP_TIMER_H_
  40
  41 /*
  42  * The TCPT_REXMT timer is used to force retransmissions.
  43  * The TCP has the TCPT_REXMT timer set whenever segments
  44  * have been sent for which ACKs are expected but not yet
  45  * received.  If an ACK is received which advances tp->snd_una,
  46  * then the retransmit timer is cleared (if there are no more
  47  * outstanding segments) or reset to the base value (if there
  48  * are more ACKs expected).  Whenever the retransmit timer goes off,
  49  * we retransmit one unacknowledged segment, and do a backoff
  50  * on the retransmit timer.
  51  *
  52  * The TCPT_PERSIST timer is used to keep window size information
  53  * flowing even if the window goes shut.  If all previous transmissions
  54  * have been acknowledged (so that there are no retransmissions in progress),
  55  * and the window is too small to bother sending anything, then we start
  56  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
  57  * we go to transmit state.  Otherwise, at intervals send a single byte
  58  * into the peer's window to force him to update our window information.
  59  * We do this at most as often as TCPT_PERSMIN time intervals,
  60  * but no more frequently than the current estimate of round-trip
  61  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  62  * a window update from the peer.
  63  *
  64  * The TCPT_KEEP timer is used to keep connections alive.  If an
  65  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  66  * but not yet established, then we drop the connection.  Once the connection
  67  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  68  * (and keepalives have been enabled on the socket), we begin to probe
  69  * the connection.  We force the peer to send us a segment by sending:
  70  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  71  * This segment is (deliberately) outside the window, and should elicit
  72  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
  73  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
  74  * amount of time probing, then we drop the connection.
  75  */
  76
  77 /*
  78  * Time constants.
  79  */
  80 #define TCPTV_MSL       ( 30*hz)                /* max seg lifetime (hah!) */
  81 #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
  82                                                    if 0, no idea yet */
  83 #define TCPTV_RTOBASE   (  3*hz)                /* assumed RTO if no info */
  84 #define TCPTV_SRTTDFLT  (  3*hz)                /* assumed RTT if no info */
  85
  86 #define TCPTV_PERSMIN   (  5*hz)                /* retransmit persistence */
  87 #define TCPTV_PERSMAX   ( 60*hz)                /* maximum persist interval */
  88
  89 #define TCPTV_KEEP_INIT ( 75*hz)                /* initial connect keepalive */
  90 #define TCPTV_KEEP_IDLE (120*60*hz)             /* dflt time before probing */
  91 #define TCPTV_KEEPINTVL ( 75*hz)                /* default probe interval */
  92 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
  93
  94 /*
  95  * TCPTV_MIN represents the minimum allowed retransmit interval.  It
  96  * is currently one second but will ultimately be reduced to 3 ticks
  97  * for algorithmic stability, leaving the 200ms variance to deal with
  98  * delayed-acks, protocol overheads.  A 1 second minimum badly breaks
  99  * throughput on any network faster then a modem that has minor but
 100  * continuous packet loss unrelated to congestion, such as on a wireless
 101  * network.
 102  */
 103 #define TCPTV_MIN       ( hz )                  /* minimum allowable value */
 104 #define TCPTV_CPU_VAR   ( hz/5 )                /* cpu variance (200ms) */
 105 #define TCPTV_REXMTMAX  ( 64*hz)                /* max allowable REXMT value */
 106
 107 #define TCPTV_TWTRUNC   8                       /* RTO factor to truncate TW */
 108
 109 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
 110
 111 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
 112
 113 #define TCPTV_DELACK    (hz / PR_FASTHZ / 2)    /* 100ms timeout */
 114
 115 #ifdef  TCPTIMERS
 116 static char *tcptimers[] =
 117     { "REXMT", "PERSIST", "KEEP", "2MSL" };
 118 #endif
 119
 120 /*
 121  * Force a time value to be in a certain range.
 122  */
 123 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \
 124         (tv) = (value) + tcp_rexmit_slop; \
 125         if ((u_long)(tv) < (u_long)(tvmin)) \
 126                 (tv) = (tvmin); \
 127         else if ((u_long)(tv) > (u_long)(tvmax)) \
 128                 (tv) = (tvmax); \
 129 } while(0)
 130
 131 #ifdef _KERNEL
 132 extern int tcp_keepinit;                /* time to establish connection */
 133 extern int tcp_keepidle;                /* time before keepalive probes begin */
 134 extern int tcp_keepintvl;               /* time between keepalive probes */
 135 extern int tcp_maxidle;                 /* time to drop after starting probes */
 136 extern int tcp_delacktime;              /* time before sending a delayed ACK */
 137 extern int tcp_maxpersistidle;
 138 extern int tcp_rexmit_min;
 139 extern int tcp_rexmit_slop;
 140 extern int tcp_msl;
 141 extern int tcp_ttl;                     /* time to live for TCP segs */
 142 extern int tcp_backoff[];
 143
 144 void    tcp_timer_2msl (void *xtp);
 145 void    tcp_timer_keep (void *xtp);
 146 void    tcp_timer_persist (void *xtp);
 147 void    tcp_timer_rexmt (void *xtp);
 148 void    tcp_timer_delack (void *xtp);
 149
 150 #endif /* _KERNEL */
 151
 152 #endif /* !_NETINET_TCP_TIMER_H_ */