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/netinet/tcp_timer.h

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    1 /*      $NetBSD: tcp_timer.h,v 1.26 2008/04/28 20:24:09 martin Exp $    */
    2 
    3 /*-
    4  * Copyright (c) 2001, 2005 The NetBSD Foundation, Inc.
    5  * All rights reserved.
    6  *
    7  * This code is derived from software contributed to The NetBSD Foundation
    8  * by Jason R. Thorpe of Wasabi Systems, Inc.
    9  * This code is derived from software contributed to The NetBSD Foundation
   10  * by Charles M. Hannum.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   23  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   24  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   25  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   26  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   27  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   28  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   29  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   30  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   31  * POSSIBILITY OF SUCH DAMAGE.
   32  */
   33 
   34 /*
   35  * Copyright (c) 1982, 1986, 1993
   36  *      The Regents of the University of California.  All rights reserved.
   37  *
   38  * Redistribution and use in source and binary forms, with or without
   39  * modification, are permitted provided that the following conditions
   40  * are met:
   41  * 1. Redistributions of source code must retain the above copyright
   42  *    notice, this list of conditions and the following disclaimer.
   43  * 2. Redistributions in binary form must reproduce the above copyright
   44  *    notice, this list of conditions and the following disclaimer in the
   45  *    documentation and/or other materials provided with the distribution.
   46  * 3. Neither the name of the University nor the names of its contributors
   47  *    may be used to endorse or promote products derived from this software
   48  *    without specific prior written permission.
   49  *
   50  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   51  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   53  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   54  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   55  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   56  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   57  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   58  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   59  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   60  * SUCH DAMAGE.
   61  *
   62  *      @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
   63  */
   64 
   65 #ifndef _NETINET_TCP_TIMER_H_
   66 #define _NETINET_TCP_TIMER_H_
   67 
   68 /*
   69  * Definitions of the TCP timers.  These timers are counted
   70  * down PR_SLOWHZ times a second.
   71  */
   72 #define TCPT_NTIMERS    4
   73 
   74 #define TCPT_REXMT      0               /* retransmit */
   75 #define TCPT_PERSIST    1               /* retransmit persistance */
   76 #define TCPT_KEEP       2               /* keep alive */
   77 #define TCPT_2MSL       3               /* 2*msl quiet time timer */
   78 
   79 /*
   80  * The TCPT_REXMT timer is used to force retransmissions.
   81  * The TCP has the TCPT_REXMT timer set whenever segments
   82  * have been sent for which ACKs are expected but not yet
   83  * received.  If an ACK is received which advances tp->snd_una,
   84  * then the retransmit timer is cleared (if there are no more
   85  * outstanding segments) or reset to the base value (if there
   86  * are more ACKs expected).  Whenever the retransmit timer goes off,
   87  * we retransmit one unacknowledged segment, and do a backoff
   88  * on the retransmit timer.
   89  *
   90  * The TCPT_PERSIST timer is used to keep window size information
   91  * flowing even if the window goes shut.  If all previous transmissions
   92  * have been acknowledged (so that there are no retransmissions in progress),
   93  * and the window is too small to bother sending anything, then we start
   94  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
   95  * we go to transmit state.  Otherwise, at intervals send a single byte
   96  * into the peer's window to force him to update our window information.
   97  * We do this at most as often as TCPT_PERSMIN time intervals,
   98  * but no more frequently than the current estimate of round-trip
   99  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  100  * a window update from the peer.
  101  *
  102  * The TCPT_KEEP timer is used to keep connections alive.  If an
  103  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  104  * but not yet established, then we drop the connection.  Once the connection
  105  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  106  * (and keepalives have been enabled on the socket), we begin to probe
  107  * the connection.  We force the peer to send us a segment by sending:
  108  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  109  * This segment is (deliberately) outside the window, and should elicit
  110  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
  111  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
  112  * amount of time probing, then we drop the connection.
  113  */
  114 
  115 /*
  116  * Time constants.
  117  */
  118 #define TCPTV_MSL       ( 30*PR_SLOWHZ)         /* max seg lifetime (hah!) */
  119 #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
  120                                                    if 0, no idea yet */
  121 #define TCPTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
  122 
  123 #define TCPTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistance */
  124 #define TCPTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
  125 
  126 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ)         /* initial connect keep alive */
  127 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)      /* dflt time before probing */
  128 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ)         /* default probe interval */
  129 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
  130 
  131 #define TCPTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
  132 #define TCPTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
  133 
  134 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
  135 
  136 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
  137 
  138 #define TCP_DELACK_TICKS (hz / PR_FASTHZ)       /* time to delay ACK */
  139 
  140 #ifdef  TCPTIMERS
  141 const char *tcptimers[] =
  142     { "REXMT", "PERSIST", "KEEP", "2MSL" };
  143 #endif
  144 
  145 /*
  146  * Init, arm, disarm, and test TCP timers.
  147  */
  148 #define TCP_TIMER_INIT(tp, timer)                                       \
  149         callout_setfunc(&(tp)->t_timer[(timer)],                        \
  150             tcp_timer_funcs[(timer)], (tp))
  151 
  152 #define TCP_TIMER_ARM(tp, timer, nticks)                                \
  153         callout_schedule(&(tp)->t_timer[(timer)],                       \
  154             (nticks) * (hz / PR_SLOWHZ))
  155 
  156 #define TCP_TIMER_DISARM(tp, timer)                                     \
  157         callout_stop(&(tp)->t_timer[(timer)])
  158 
  159 #define TCP_TIMER_ISARMED(tp, timer)                                    \
  160         callout_active(&(tp)->t_timer[(timer)])
  161 
  162 /*
  163  * Force a time value to be in a certain range.
  164  */
  165 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
  166         (tv) = (value); \
  167         if ((tv) < (tvmin)) \
  168                 (tv) = (tvmin); \
  169         if ((tv) > (tvmax)) \
  170                 (tv) = (tvmax); \
  171 }
  172 
  173 #ifdef _KERNEL
  174 typedef void (*tcp_timer_func_t)(void *);
  175 
  176 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
  177 
  178 extern u_int tcp_keepinit;              /* time before initial connection times out */
  179 extern u_int tcp_keepidle;              /* time before keepalive probes begin */
  180 extern u_int tcp_keepintvl;             /* time between keepalive probes */
  181 extern u_int tcp_keepcnt;               /* number of keepalives, 0=infty */
  182 extern int tcp_maxpersistidle;          /* max idle time in persist */
  183 extern int tcp_ttl;                     /* time to live for TCP segs */
  184 extern const int tcp_backoff[];
  185 
  186 void    tcp_timer_init(void);
  187 #endif
  188 
  189 #endif /* !_NETINET_TCP_TIMER_H_ */

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