calmsacibis995
131 lines
5.4 KiB
C
131 lines
5.4 KiB
C
/*
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* Copyright (c) 1982, 1986 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution is only permitted until one year after the first shipment
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* of 4.4BSD by the Regents. Otherwise, redistribution and use in source and
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* binary forms are permitted provided that: (1) source distributions retain
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* this entire copyright notice and comment, and (2) distributions including
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* binaries display the following acknowledgement: This product includes
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* software developed by the University of California, Berkeley and its
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* contributors'' in the documentation or other materials provided with the
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* distribution and in all advertising materials mentioning features or use
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* of this software. Neither the name of the University nor the names of
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* its contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*
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* @(#)tcp_timer.h 7.8 (Berkeley) 6/28/90
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*/
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* Definitions of the TCP timers. These timers are counted
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* down PR_SLOWHZ times a second.
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*/
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#define TCPT_NTIMERS 5
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#define TCPT_REXMT 0 /* retransmit */
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#define TCPT_PERSIST 1 /* retransmit persistance */
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#define TCPT_KEEP 2 /* keep alive */
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#define TCPT_2MSL 3 /* 2*msl quiet time timer */
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#define TCPT_MTUEXP 4 /* expire mtu (mtu discovery) */
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/*
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* The TCPT_REXMT timer is used to force retransmissions.
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* The TCP has the TCPT_REXMT timer set whenever segments
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* have been sent for which ACKs are expected but not yet
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* received. If an ACK is received which advances tp->snd_una,
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* then the retransmit timer is cleared (if there are no more
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* outstanding segments) or reset to the base value (if there
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* are more ACKs expected). Whenever the retransmit timer goes off,
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* we retransmit one unacknowledged segment, and do a backoff
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* on the retransmit timer.
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*
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* The TCPT_PERSIST timer is used to keep window size information
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* flowing even if the window goes shut. If all previous transmissions
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* have been acknowledged (so that there are no retransmissions in progress),
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* and the window is too small to bother sending anything, then we start
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* the TCPT_PERSIST timer. When it expires, if the window is nonzero,
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* we go to transmit state. Otherwise, at intervals send a single byte
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* into the peer's window to force him to update our window information.
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* We do this at most as often as TCPT_PERSMIN time intervals,
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* but no more frequently than the current estimate of round-trip
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* packet time. The TCPT_PERSIST timer is cleared whenever we receive
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* a window update from the peer.
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*
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* The TCPT_KEEP timer is used to keep connections alive. If an
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* connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
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* but not yet established, then we drop the connection. Once the connection
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* is established, if the connection is idle for TCPTV_KEEP_IDLE time
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* (and keepalives have been enabled on the socket), we begin to probe
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* the connection. We force the peer to send us a segment by sending:
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* <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
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* This segment is (deliberately) outside the window, and should elicit
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* an ack segment in response from the peer. If, despite the TCPT_KEEP
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* initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
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* amount of time probing, then we drop the connection.
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*
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* The TCPT_MTUEXP timer is used to expire path MTU values that were obtained
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* using RFC 1191 MTU discovery with TCP. This timer is only set when an
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* MTU smaller than the originally chosen value is being used.
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*/
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#define TCP_TTL 60 /* default time to live for TCP segs */
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/*
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* Time constants.
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*/
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#define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */
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#define TCPTV_SRTTBASE 0 /* base roundtrip time;
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if 0, no idea yet */
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#define TCPTV_SRTTDFLT ( 3*PR_FASTHZ) /* assumed RTT if no info */
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#define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */
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#define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */
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#define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */
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#define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */
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#define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */
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#define TCPTV_KEEPCNT 8 /* max probes before drop */
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#define TCPTV_MIN ( 1) /* minimum allowable value */
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#define TCPTV_REXMTMAX ( 64*PR_FASTHZ) /* max allowable REXMT value */
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#define TCP_LINGERTIME 120 /* linger at most 2 minutes */
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#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
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#define TCPTV_MTUEXP ( 300 * PR_SLOWHZ ) /* after 5 minutes, expire
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* the smaller mtu.
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*/
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#ifdef TCPTIMERS
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char *tcptimers[] =
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{ "REXMT", "PERSIST", "KEEP", "2MSL", "MTUEXP" };
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#endif
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/*
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* Force a time value to be in a certain range.
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*/
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#define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
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(tv) = (value); \
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if ((tv) < (tvmin)) \
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(tv) = (tvmin); \
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else if ((tv) > (tvmax)) \
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(tv) = (tvmax); \
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}
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#ifdef _KERNEL
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extern int tcp_keepidle; /* time before keepalive probes begin */
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extern int tcp_keepintvl; /* time between keepalive probes */
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extern int tcp_maxidle; /* time to drop after starting probes */
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extern int tcp_ttl; /* time to live for TCP segs */
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extern int tcp_backoff[];
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#endif
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#ifdef __cplusplus
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}
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#endif
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