/*      $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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