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 1.24 2006/09/26 06:39:22 jeremy 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  * 3. All advertising materials mentioning features or use of this software
   21  *    must display the following acknowledgement:
   22  *      This product includes software developed by the NetBSD
   23  *      Foundation, Inc. and its contributors.
   24  * 4. Neither the name of The NetBSD Foundation nor the names of its
   25  *    contributors may be used to endorse or promote products derived
   26  *    from this software without specific prior written permission.
   27  *
   28  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   29  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   30  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   31  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   32  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   33  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   34  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   35  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   36  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   37  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   38  * POSSIBILITY OF SUCH DAMAGE.
   39  */
   40 
   41 /*
   42  * Copyright (c) 1982, 1986, 1993
   43  *      The Regents of the University of California.  All rights reserved.
   44  *
   45  * Redistribution and use in source and binary forms, with or without
   46  * modification, are permitted provided that the following conditions
   47  * are met:
   48  * 1. Redistributions of source code must retain the above copyright
   49  *    notice, this list of conditions and the following disclaimer.
   50  * 2. Redistributions in binary form must reproduce the above copyright
   51  *    notice, this list of conditions and the following disclaimer in the
   52  *    documentation and/or other materials provided with the distribution.
   53  * 3. Neither the name of the University nor the names of its contributors
   54  *    may be used to endorse or promote products derived from this software
   55  *    without specific prior written permission.
   56  *
   57  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   58  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   59  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   60  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   61  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   62  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   63  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   64  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   65  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   66  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   67  * SUCH DAMAGE.
   68  *
   69  *      @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
   70  */
   71 
   72 #ifndef _NETINET_TCP_TIMER_H_
   73 #define _NETINET_TCP_TIMER_H_
   74 
   75 /*
   76  * Definitions of the TCP timers.  These timers are counted
   77  * down PR_SLOWHZ times a second.
   78  */
   79 #define TCPT_NTIMERS    4
   80 
   81 #define TCPT_REXMT      0               /* retransmit */
   82 #define TCPT_PERSIST    1               /* retransmit persistance */
   83 #define TCPT_KEEP       2               /* keep alive */
   84 #define TCPT_2MSL       3               /* 2*msl quiet time timer */
   85 
   86 /*
   87  * The TCPT_REXMT timer is used to force retransmissions.
   88  * The TCP has the TCPT_REXMT timer set whenever segments
   89  * have been sent for which ACKs are expected but not yet
   90  * received.  If an ACK is received which advances tp->snd_una,
   91  * then the retransmit timer is cleared (if there are no more
   92  * outstanding segments) or reset to the base value (if there
   93  * are more ACKs expected).  Whenever the retransmit timer goes off,
   94  * we retransmit one unacknowledged segment, and do a backoff
   95  * on the retransmit timer.
   96  *
   97  * The TCPT_PERSIST timer is used to keep window size information
   98  * flowing even if the window goes shut.  If all previous transmissions
   99  * have been acknowledged (so that there are no retransmissions in progress),
  100  * and the window is too small to bother sending anything, then we start
  101  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
  102  * we go to transmit state.  Otherwise, at intervals send a single byte
  103  * into the peer's window to force him to update our window information.
  104  * We do this at most as often as TCPT_PERSMIN time intervals,
  105  * but no more frequently than the current estimate of round-trip
  106  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
  107  * a window update from the peer.
  108  *
  109  * The TCPT_KEEP timer is used to keep connections alive.  If an
  110  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
  111  * but not yet established, then we drop the connection.  Once the connection
  112  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
  113  * (and keepalives have been enabled on the socket), we begin to probe
  114  * the connection.  We force the peer to send us a segment by sending:
  115  *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
  116  * This segment is (deliberately) outside the window, and should elicit
  117  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
  118  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
  119  * amount of time probing, then we drop the connection.
  120  */
  121 
  122 /*
  123  * Time constants.
  124  */
  125 #define TCPTV_MSL       ( 30*PR_SLOWHZ)         /* max seg lifetime (hah!) */
  126 #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
  127                                                    if 0, no idea yet */
  128 #define TCPTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
  129 
  130 #define TCPTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistance */
  131 #define TCPTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
  132 
  133 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ)         /* initial connect keep alive */
  134 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)      /* dflt time before probing */
  135 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ)         /* default probe interval */
  136 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
  137 
  138 #define TCPTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
  139 #define TCPTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
  140 
  141 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
  142 
  143 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
  144 
  145 #define TCP_DELACK_TICKS (hz / PR_FASTHZ)       /* time to delay ACK */
  146 
  147 #ifdef  TCPTIMERS
  148 const char *tcptimers[] =
  149     { "REXMT", "PERSIST", "KEEP", "2MSL" };
  150 #endif
  151 
  152 /*
  153  * Init, arm, disarm, and test TCP timers.
  154  */
  155 #define TCP_TIMER_INIT(tp, timer)                                       \
  156         callout_setfunc(&(tp)->t_timer[(timer)],                        \
  157             tcp_timer_funcs[(timer)], (tp))
  158 
  159 #define TCP_TIMER_ARM(tp, timer, nticks)                                \
  160         callout_schedule(&(tp)->t_timer[(timer)],                       \
  161             (nticks) * (hz / PR_SLOWHZ))
  162 
  163 #define TCP_TIMER_DISARM(tp, timer)                                     \
  164         callout_stop(&(tp)->t_timer[(timer)])
  165 
  166 #define TCP_TIMER_ISARMED(tp, timer)                                    \
  167         callout_active(&(tp)->t_timer[(timer)])
  168 
  169 /*
  170  * Force a time value to be in a certain range.
  171  */
  172 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
  173         (tv) = (value); \
  174         if ((tv) < (tvmin)) \
  175                 (tv) = (tvmin); \
  176         if ((tv) > (tvmax)) \
  177                 (tv) = (tvmax); \
  178 }
  179 
  180 #ifdef _KERNEL
  181 typedef void (*tcp_timer_func_t)(void *);
  182 
  183 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
  184 
  185 extern int tcp_keepidle;                /* time before keepalive probes begin */
  186 extern int tcp_keepintvl;               /* time between keepalive probes */
  187 extern int tcp_keepcnt;                 /* number of keepalives, 0=infty */
  188 extern int tcp_maxpersistidle;          /* max idle time in persist */
  189 extern int tcp_maxidle;                 /* time to drop after starting probes */
  190 extern int tcp_ttl;                     /* time to live for TCP segs */
  191 extern const int tcp_backoff[];
  192 
  193 void    tcp_timer_init(void);
  194 #endif
  195 
  196 #endif /* !_NETINET_TCP_TIMER_H_ */

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