sys/netinet/tcp_timer.h

   1 /*      $NetBSD: tcp_timer.h,v 1.28 2011/05/24 18:37:52 gdt 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  * All TCPTV_* constants are in units of slow ticks (typically 500 ms).
 118  */
 119 #define TCPTV_MSL       ( 30*PR_SLOWHZ)         /* max seg lifetime (hah!) */
 120 #define TCPTV_SRTTBASE  0                       /* base roundtrip time;
 121                                                    if 0, no idea yet */
 122 #define TCPTV_SRTTDFLT  (  3*PR_SLOWHZ)         /* assumed RTT if no info */
 123
 124 #define TCPTV_PERSMIN   (  5*PR_SLOWHZ)         /* retransmit persistance */
 125 #define TCPTV_PERSMAX   ( 60*PR_SLOWHZ)         /* maximum persist interval */
 126
 127 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ)         /* initial connect keep alive */
 128 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ)      /* dflt time before probing */
 129 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ)         /* default probe interval */
 130 #define TCPTV_KEEPCNT   8                       /* max probes before drop */
 131
 132 #define TCPTV_MIN       (  1*PR_SLOWHZ)         /* minimum allowable value */
 133 #define TCPTV_REXMTMAX  ( 64*PR_SLOWHZ)         /* max allowable REXMT value */
 134
 135 #define TCP_LINGERTIME  120                     /* linger at most 2 minutes */
 136
 137 #define TCP_MAXRXTSHIFT 12                      /* maximum retransmits */
 138
 139 /* Acks are delayed for 1 second; constant is in fast ticks. */
 140 #define TCP_DELACK_TICKS (hz / PR_FASTHZ)       /* time to delay ACK */
 141
 142 #ifdef  TCPTIMERS
 143 const char *tcptimers[] =
 144     { "REXMT", "PERSIST", "KEEP", "2MSL" };
 145 #endif
 146
 147 /*
 148  * Init, arm, disarm, and test TCP timers.
 149  */
 150 #define TCP_TIMER_INIT(tp, timer)                                       \
 151         callout_setfunc(&(tp)->t_timer[(timer)],                        \
 152             tcp_timer_funcs[(timer)], (tp))
 153
 154 /*
 155  * nticks is given in units of slow timeouts,
 156  * typically 500 ms (with PR_SLOWHZ at 2).
 157  */
 158 #define TCP_TIMER_ARM(tp, timer, nticks)                                \
 159         callout_schedule(&(tp)->t_timer[(timer)],                       \
 160             (nticks) * (hz / PR_SLOWHZ))
 161
 162 #define TCP_TIMER_DISARM(tp, timer)                                     \
 163         callout_stop(&(tp)->t_timer[(timer)])
 164
 165 #define TCP_TIMER_ISARMED(tp, timer)                                    \
 166         callout_active(&(tp)->t_timer[(timer)])
 167
 168 /*
 169  * Force a time value to be in a certain range.
 170  */
 171 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
 172         (tv) = (value); \
 173         if ((tv) < (tvmin)) \
 174                 (tv) = (tvmin); \
 175         if ((tv) > (tvmax)) \
 176                 (tv) = (tvmax); \
 177 }
 178
 179 #ifdef _KERNEL
 180 typedef void (*tcp_timer_func_t)(void *);
 181
 182 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
 183
 184 extern u_int tcp_keepinit;              /* time before initial connection times out */
 185 extern u_int tcp_keepidle;              /* time before keepalive probes begin */
 186 extern u_int tcp_keepintvl;             /* time between keepalive probes */
 187 extern u_int tcp_keepcnt;               /* number of keepalives, 0=infty */
 188 extern int tcp_maxpersistidle;          /* max idle time in persist */
 189 extern int tcp_ttl;                     /* time to live for TCP segs */
 190 extern const int tcp_backoff[];
 191
 192 void    tcp_timer_init(void);
 193 #endif
 194
 195 #endif /* !_NETINET_TCP_TIMER_H_ */