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/* SPDX-License-Identifier: BSD-3-Clause */
/*
* 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
* tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp
*/
#ifndef TCP_TIMER_H
#define 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 persistence */
#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.
*/
#define TCPTV_MSL ( 5*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 persistence */
#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 ( 12*PR_SLOWHZ) /* max allowable REXMT value */
#define TCP_LINGERTIME 120 /* linger at most 2 minutes */
#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
/*
* Force a time value to be in a certain range.
*/
#define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
(tv) = (value); \
if ((tv) < (tvmin)) \
(tv) = (tvmin); \
else if ((tv) > (tvmax)) \
(tv) = (tvmax); \
}
extern const int tcp_backoff[];
struct tcpcb;
void tcp_fasttimo(Slirp *);
void tcp_slowtimo(Slirp *);
void tcp_canceltimers(struct tcpcb *);
#endif
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