| 1 | /* Modified for gcc/os2 by bird 2003
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| 2 | *
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| 3 | * Copyright (c) 1982, 1986, 1993
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| 4 | * The Regents of the University of California. All rights reserved.
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| 5 | *
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| 6 | * Redistribution and use in source and binary forms, with or without
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| 7 | * modification, are permitted provided that the following conditions
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| 8 | * are met:
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| 9 | * 1. Redistributions of source code must retain the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer.
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| 11 | * 2. Redistributions in binary form must reproduce the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer in the
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| 13 | * documentation and/or other materials provided with the distribution.
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| 14 | * 3. All advertising materials mentioning features or use of this software
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| 15 | * must display the following acknowledgement:
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| 16 | * This product includes software developed by the University of
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| 17 | * California, Berkeley and its contributors.
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| 18 | * 4. Neither the name of the University nor the names of its contributors
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| 19 | * may be used to endorse or promote products derived from this software
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| 20 | * without specific prior written permission.
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| 21 | *
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| 22 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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| 23 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 24 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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| 25 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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| 26 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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| 27 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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| 28 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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| 29 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 30 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 31 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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| 32 | * SUCH DAMAGE.
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| 33 | *
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| 34 | * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
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| 35 | * $FreeBSD: src/sys/netinet/tcp_timer.h,v 1.18.2.1 2002/08/16 22:16:39 dillon Exp $
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| 36 | */
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| 37 |
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| 38 | #ifndef _NETINET_TCP_TIMER_H_
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| 39 | #define _NETINET_TCP_TIMER_H_
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| 40 | #ifndef TCPV40HDRS
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| 41 |
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| 42 | /*
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| 43 | * The TCPT_REXMT timer is used to force retransmissions.
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| 44 | * The TCP has the TCPT_REXMT timer set whenever segments
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| 45 | * have been sent for which ACKs are expected but not yet
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| 46 | * received. If an ACK is received which advances tp->snd_una,
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| 47 | * then the retransmit timer is cleared (if there are no more
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| 48 | * outstanding segments) or reset to the base value (if there
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| 49 | * are more ACKs expected). Whenever the retransmit timer goes off,
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| 50 | * we retransmit one unacknowledged segment, and do a backoff
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| 51 | * on the retransmit timer.
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| 52 | *
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| 53 | * The TCPT_PERSIST timer is used to keep window size information
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| 54 | * flowing even if the window goes shut. If all previous transmissions
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| 55 | * have been acknowledged (so that there are no retransmissions in progress),
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| 56 | * and the window is too small to bother sending anything, then we start
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| 57 | * the TCPT_PERSIST timer. When it expires, if the window is nonzero,
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| 58 | * we go to transmit state. Otherwise, at intervals send a single byte
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| 59 | * into the peer's window to force him to update our window information.
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| 60 | * We do this at most as often as TCPT_PERSMIN time intervals,
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| 61 | * but no more frequently than the current estimate of round-trip
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| 62 | * packet time. The TCPT_PERSIST timer is cleared whenever we receive
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| 63 | * a window update from the peer.
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| 64 | *
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| 65 | * The TCPT_KEEP timer is used to keep connections alive. If an
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| 66 | * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
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| 67 | * but not yet established, then we drop the connection. Once the connection
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| 68 | * is established, if the connection is idle for TCPTV_KEEP_IDLE time
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| 69 | * (and keepalives have been enabled on the socket), we begin to probe
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| 70 | * the connection. We force the peer to send us a segment by sending:
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| 71 | * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
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| 72 | * This segment is (deliberately) outside the window, and should elicit
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| 73 | * an ack segment in response from the peer. If, despite the TCPT_KEEP
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| 74 | * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
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| 75 | * amount of time probing, then we drop the connection.
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| 76 | */
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| 77 |
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| 78 | /*
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| 79 | * Time constants.
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| 80 | */
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| 81 | #define hz PR_SLOWHZ /* OS2 mapping */
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| 82 | #if 0 /* not on OS/2 */
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| 83 | #define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */
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| 84 | #endif
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| 85 | #define TCPTV_SRTTBASE 0 /* base roundtrip time;
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| 86 | if 0, no idea yet */
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| 87 | #if 0 /* not on OS/2 */
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| 88 | #define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */
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| 89 | #endif
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| 90 | #define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */
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| 91 |
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| 92 | #define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */
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| 93 | #define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */
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| 94 |
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| 95 | #define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */
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| 96 | #define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */
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| 97 | #define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */
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| 98 | #if 0 /* not on OS/2 */
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| 99 | #define TCPTV_KEEPCNT 8 /* max probes before drop */
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| 100 | #endif
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| 101 |
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| 102 | /*
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| 103 | * TCPTV_MIN represents the minimum allowed retransmit interval. It
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| 104 | * is currently one second but will ultimately be reduced to 3 ticks
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| 105 | * for algorithmic stability, leaving the 200ms variance to deal with
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| 106 | * delayed-acks, protocol overheads. A 1 second minimum badly breaks
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| 107 | * throughput on any network faster then a modem that has minor but
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| 108 | * continuous packet loss unrelated to congestion, such as on a wireless
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| 109 | * network.
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