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/*-
* 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.
* 4. 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
* $FreeBSD$
*/
#ifndef _NETINET_TCP_TIMER_H_
#define _NETINET_TCP_TIMER_H_
/*
* 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 ( 30*hz) /* max seg lifetime (hah!) */
#define TCPTV_SRTTBASE 0 /* base roundtrip time;
if 0, no idea yet */
#define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */
#define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */
#define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */
#define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */
#define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */
#define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */
#define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */
#define TCPTV_KEEPCNT 8 /* max probes before drop */
/*
* Minimum retransmit timer is 3 ticks, for algorithmic stability.
* TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with
* the expected worst-case processing variances by the kernels
* representing the end points. Such variances do not always show
* up in the srtt because the timestamp is often calculated at
* the interface rather then at the TCP layer. This value is
* typically 50ms. However, it is also possible that delayed
* acks (typically 100ms) could create issues so we set the slop
* to 200ms to try to cover it. Note that, properly speaking,
* delayed-acks should not create a major issue for interactive
* environments which 'P'ush the last segment, at least as
* long as implementations do the required 'at least one ack
* for every two packets' for the non-interactive streaming case.
* (maybe the RTO calculation should use 2*RTT instead of RTT
* to handle the ack-every-other-packet case).
*
* The prior minimum of 1*hz (1 second) badly breaks throughput on any
* networks faster then a modem that has minor (e.g. 1%) packet loss.
*/
#define TCPTV_MIN ( 3 ) /* minimum allowable value */
#define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */
#define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */
#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */
#define TCP_LINGERTIME 120 /* linger at most 2 minutes */
#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
#define TCPTV_DELACK (hz / PR_FASTHZ / 2) /* 100ms timeout */
#ifdef TCPTIMERS
static const char *tcptimers[] =
{ "REXMT", "PERSIST", "KEEP", "2MSL" };
#endif
/*
* Force a time value to be in a certain range.
*/
#define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \
(tv) = (value) + tcp_rexmit_slop; \
if ((u_long)(tv) < (u_long)(tvmin)) \
(tv) = (tvmin); \
else if ((u_long)(tv) > (u_long)(tvmax)) \
(tv) = (tvmax); \
} while(0)
#ifdef _KERNEL
extern int tcp_keepinit; /* time to establish connection */
extern int tcp_keepidle; /* time before keepalive probes begin */
extern int tcp_keepintvl; /* time between keepalive probes */
extern int tcp_maxidle; /* time to drop after starting probes */
extern int tcp_delacktime; /* time before sending a delayed ACK */
extern int tcp_maxpersistidle;
extern int tcp_rexmit_min;
extern int tcp_rexmit_slop;
extern int tcp_msl;
extern int tcp_ttl; /* time to live for TCP segs */
extern int tcp_backoff[];
struct tcptw;
void tcp_timer_init(void);
void tcp_timer_2msl(void *xtp);
struct tcptw *
tcp_timer_2msl_tw(int _reuse); /* XXX temporary */
void tcp_timer_2msl_reset(struct tcptw *_tw, int _timeo);
void tcp_timer_2msl_stop(struct tcptw *_tw);
void tcp_timer_keep(void *xtp);
void tcp_timer_persist(void *xtp);
void tcp_timer_rexmt(void *xtp);
void tcp_timer_delack(void *xtp);
#endif /* _KERNEL */
#endif /* !_NETINET_TCP_TIMER_H_ */
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