FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_timer.h

     /*      $NetBSD: tcp_timer.h,v 1.30 2019/08/06 15:48:18 riastradh Exp $ */
     
     /*-
      * Copyright (c) 2001, 2005 The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * This code is derived from software contributed to The NetBSD Foundation
      * by Jason R. Thorpe of Wasabi Systems, Inc.
      * This code is derived from software contributed to The NetBSD Foundation
     * by Charles M. Hannum.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     * POSSIBILITY OF SUCH DAMAGE.
     */
    
    /*
     * Copyright (c) 1982, 1986, 1993
     *      The Regents of the University of California.  All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
     */
    
    #ifndef _NETINET_TCP_TIMER_H_
    #define _NETINET_TCP_TIMER_H_
    
    /*
     * Definitions of the TCP timers.  These timers are counted
     * down PR_SLOWHZ times a second.
     */
    #define TCPT_NTIMERS    4
    
    #define TCPT_REXMT      0               /* retransmit */
    #define TCPT_PERSIST    1               /* retransmit persistance */
    #define TCPT_KEEP       2               /* keep alive */
    #define TCPT_2MSL       3               /* 2*msl quiet time timer */
    
    /*
     * The TCPT_REXMT timer is used to force retransmissions.
     * The TCP has the TCPT_REXMT timer set whenever segments
     * have been sent for which ACKs are expected but not yet
     * received.  If an ACK is received which advances tp->snd_una,
     * then the retransmit timer is cleared (if there are no more
     * outstanding segments) or reset to the base value (if there
     * are more ACKs expected).  Whenever the retransmit timer goes off,
     * we retransmit one unacknowledged segment, and do a backoff
     * on the retransmit timer.
     *
     * The TCPT_PERSIST timer is used to keep window size information
     * flowing even if the window goes shut.  If all previous transmissions
     * have been acknowledged (so that there are no retransmissions in progress),
     * and the window is too small to bother sending anything, then we start
     * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
     * we go to transmit state.  Otherwise, at intervals send a single byte
     * into the peer's window to force him to update our window information.
     * We do this at most as often as TCPT_PERSMIN time intervals,
     * but no more frequently than the current estimate of round-trip
     * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
    * a window update from the peer.
    *
    * The TCPT_KEEP timer is used to keep connections alive.  If an
    * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
    * but not yet established, then we drop the connection.  Once the connection
    * is established, if the connection is idle for TCPTV_KEEP_IDLE time
    * (and keepalives have been enabled on the socket), we begin to probe
    * the connection.  We force the peer to send us a segment by sending:
    *      <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
    * This segment is (deliberately) outside the window, and should elicit
    * an ack segment in response from the peer.  If, despite the TCPT_KEEP
    * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
    * amount of time probing, then we drop the connection.
    */
   
   /*
    * Time constants.
    * All TCPTV_* constants are in units of slow ticks (typically 500 ms).
    */
   #define TCPTV_MSL       ( 30*PR_SLOWHZ)         /* max seg lifetime (hah!) */
   #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
                                                      if 0, no idea yet */
   #define TCPTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
   
   #define TCPTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistance */
   #define TCPTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
   
   #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ)         /* initial connect keep alive */
   #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)      /* dflt time before probing */
   #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ)         /* default probe interval */
   #define TCPTV_KEEPCNT   8                       /* max probes before drop */
   
   #define TCPTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
   #define TCPTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
   
   #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
   
   #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
   
   /* Acks are delayed for 1 second; constant is in fast ticks. */
   #define TCP_DELACK_TICKS (hz / PR_FASTHZ)       /* time to delay ACK */
   
   #ifdef  TCPTIMERS
   const char *tcptimers[] =
       { "REXMT", "PERSIST", "KEEP", "2MSL" };
   #endif
   
   /*
    * Init, arm, disarm, and test TCP timers.
    */
   #define TCP_TIMER_INIT(tp, timer)                                       \
           callout_setfunc(&(tp)->t_timer[(timer)],                        \
               tcp_timer_funcs[(timer)], (tp))
   
   /*
    * nticks is given in units of slow timeouts,
    * typically 500 ms (with PR_SLOWHZ at 2).
    */
   #define TCP_TIMER_ARM(tp, timer, nticks)                                \
           callout_schedule(&(tp)->t_timer[(timer)],                       \
               (nticks) * (hz / PR_SLOWHZ))
   
   #define TCP_TIMER_DISARM(tp, timer)                                     \
           callout_stop(&(tp)->t_timer[(timer)])
   
   #define TCP_TIMER_ISARMED(tp, timer)                                    \
           callout_active(&(tp)->t_timer[(timer)])
   
   #define TCP_TIMER_MAXTICKS                                                    \
           (INT_MAX / (hz / PR_SLOWHZ))
   
   #define TCP_MAXMSL                                                            \
           (TCP_TIMER_MAXTICKS / 2)
   
   /*
    * Force a time value to be in a certain range.
    */
   #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
           (tv) = (value); \
           if ((tv) < (tvmin)) \
                   (tv) = (tvmin); \
           if ((tv) > (tvmax)) \
                   (tv) = (tvmax); \
   }
   
   #ifdef _KERNEL
   typedef void (*tcp_timer_func_t)(void *);
   
   extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
   
   extern u_int tcp_keepinit;              /* time before initial connection times out */
   extern u_int tcp_keepidle;              /* time before keepalive probes begin */
   extern u_int tcp_keepintvl;             /* time between keepalive probes */
   extern u_int tcp_keepcnt;               /* number of keepalives, 0=infty */
   extern int tcp_maxpersistidle;          /* max idle time in persist */
   extern int tcp_ttl;                     /* time to live for TCP segs */
   extern const int tcp_backoff[];
   
   void    tcp_timer_init(void);
   void    tcp_slowtimo_init(void);
   #endif
   
   #endif /* !_NETINET_TCP_TIMER_H_ */

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