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/*
* Copyright (c) 1982, 1986 Regents of the University of California.
* All rights reserved.
* Copyright (c) 2016 by Delphix. All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley. The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
*/
/*
* Definitions of the TCP timers. These timers are counted
* down PR_SLOWHZ times a second.
*/
#ifndef _NETINET_TCP_TIMER_H
#define _NETINET_TCP_TIMER_H
/* tcp_timer.h 1.13 89/06/16 SMI; from UCB 7.6 6/29/88 */
#ifdef __cplusplus
extern "C" {
#endif
#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 it 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 a
* 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.
*/
#define TCP_TTL 60 /* default time to live for TCP segs */
/*
* Time constants.
*/
#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 */
#ifdef TCPTIMERS
char *tcptimers[] =
{ "REXMT", "PERSIST", "KEEP", "2MSL" };
#endif
/*
* 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); \
}
#ifdef __cplusplus
}
#endif
#endif /* _NETINET_TCP_TIMER_H */
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