| 1 | /* $Id: tcp_timer.h 98103 2023-01-17 14:15:46Z vboxsync $ */
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| 2 | /** @file
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| 3 | * NAT - TCP timer (declarations/defines).
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2006-2023 Oracle and/or its affiliates.
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| 8 | *
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| 9 | * This file is part of VirtualBox base platform packages, as
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| 10 | * available from https://www.virtualbox.org.
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| 11 | *
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| 12 | * This program is free software; you can redistribute it and/or
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| 13 | * modify it under the terms of the GNU General Public License
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| 14 | * as published by the Free Software Foundation, in version 3 of the
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| 15 | * License.
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| 16 | *
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| 17 | * This program is distributed in the hope that it will be useful, but
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| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 20 | * General Public License for more details.
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| 21 | *
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| 22 | * You should have received a copy of the GNU General Public License
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| 23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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| 24 | *
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| 25 | * SPDX-License-Identifier: GPL-3.0-only
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| 26 | */
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| 27 |
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| 28 | /*
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| 29 | * This code is based on:
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| 30 | *
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| 31 | * Copyright (c) 1982, 1986, 1993
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| 32 | * The Regents of the University of California. All rights reserved.
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| 33 | *
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| 34 | * Redistribution and use in source and binary forms, with or without
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| 35 | * modification, are permitted provided that the following conditions
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| 36 | * are met:
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| 37 | * 1. Redistributions of source code must retain the above copyright
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| 38 | * notice, this list of conditions and the following disclaimer.
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| 39 | * 2. Redistributions in binary form must reproduce the above copyright
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| 40 | * notice, this list of conditions and the following disclaimer in the
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| 41 | * documentation and/or other materials provided with the distribution.
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| 42 | * 3. Neither the name of the University nor the names of its contributors
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| 43 | * may be used to endorse or promote products derived from this software
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| 44 | * without specific prior written permission.
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| 45 | *
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| 46 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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| 47 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 48 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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| 49 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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| 50 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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| 51 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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| 52 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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| 53 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 54 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 55 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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| 56 | * SUCH DAMAGE.
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| 57 | *
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| 58 | * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
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| 59 | * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp
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| 60 | */
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| 61 |
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| 62 | #ifndef _TCP_TIMER_H_
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| 63 | #define _TCP_TIMER_H_
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| 64 |
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| 65 | /*
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| 66 | * Definitions of the TCP timers. These timers are counted
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| 67 | * down PR_SLOWHZ times a second.
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| 68 | */
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| 69 | #define TCPT_NTIMERS 4
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| 70 |
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| 71 | #define TCPT_REXMT 0 /* retransmit */
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| 72 | #define TCPT_PERSIST 1 /* retransmit persistence */
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| 73 | #define TCPT_KEEP 2 /* keep alive */
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| 74 | #define TCPT_2MSL 3 /* 2*msl quiet time timer */
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| 75 |
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| 76 | /*
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| 77 | * The TCPT_REXMT timer is used to force retransmissions.
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| 78 | * The TCP has the TCPT_REXMT timer set whenever segments
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| 79 | * have been sent for which ACKs are expected but not yet
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| 80 | * received. If an ACK is received which advances tp->snd_una,
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| 81 | * then the retransmit timer is cleared (if there are no more
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| 82 | * outstanding segments) or reset to the base value (if there
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| 83 | * are more ACKs expected). Whenever the retransmit timer goes off,
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| 84 | * we retransmit one unacknowledged segment, and do a backoff
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| 85 | * on the retransmit timer.
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| 86 | *
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| 87 | * The TCPT_PERSIST timer is used to keep window size information
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| 88 | * flowing even if the window goes shut. If all previous transmissions
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| 89 | * have been acknowledged (so that there are no retransmissions in progress),
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| 90 | * and the window is too small to bother sending anything, then we start
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| 91 | * the TCPT_PERSIST timer. When it expires, if the window is nonzero,
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| 92 | * we go to transmit state. Otherwise, at intervals send a single byte
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| 93 | * into the peer's window to force him to update our window information.
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| 94 | * We do this at most as often as TCPT_PERSMIN time intervals,
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| 95 | * but no more frequently than the current estimate of round-trip
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| 96 | * packet time. The TCPT_PERSIST timer is cleared whenever we receive
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| 97 | * a window update from the peer.
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| 98 | *
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| 99 | * The TCPT_KEEP timer is used to keep connections alive. If an
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| 100 | * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
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| 101 | * but not yet established, then we drop the connection. Once the connection
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| 102 | * is established, if the connection is idle for TCPTV_KEEP_IDLE time
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| 103 | * (and keepalives have been enabled on the socket), we begin to probe
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| 104 | * the connection. We force the peer to send us a segment by sending:
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| 105 | * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
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| 106 | * This segment is (deliberately) outside the window, and should elicit
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| 107 | * an ack segment in response from the peer. If, despite the TCPT_KEEP
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| 108 | * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
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| 109 | * amount of time probing, then we drop the connection.
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| 110 | */
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| 111 |
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| 112 | /*
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| 113 | * Time constants.
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| 114 | */
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| 115 | #define TCPTV_MSL ( 5*PR_SLOWHZ) /* max seg lifetime (hah!) */
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| 116 |
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| 117 | #define TCPTV_SRTTBASE 0 /* base roundtrip time;
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| 118 | if 0, no idea yet */
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| 119 | #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */
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| 120 |
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| 121 | #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistence */
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| 122 | #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */
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| 123 |
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| 124 | #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */
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| 125 | #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */
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| 126 | #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */
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| 127 | #define TCPTV_KEEPCNT 8 /* max probes before drop */
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| 128 |
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| 129 | #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */
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| 130 | #define TCPTV_REXMTMAX ( 12*PR_SLOWHZ) /* max allowable REXMT value */
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| 131 |
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| 132 | #define TCP_LINGERTIME 120 /* linger at most 2 minutes */
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| 133 |
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| 134 | #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
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| 135 |
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| 136 |
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| 137 | #ifdef TCPTIMERS
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| 138 | char *tcptimers[] =
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| 139 | { "REXMT", "PERSIST", "KEEP", "2MSL" };
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| 140 | #endif
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| 141 |
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| 142 | /*
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| 143 | * Force a time value to be in a certain range.
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| 144 | */
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| 145 | #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
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| 146 | (tv) = (value); \
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| 147 | if ((tv) < (tvmin)) \
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| 148 | (tv) = (tvmin); \
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| 149 | else if ((tv) > (tvmax)) \
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| 150 | (tv) = (tvmax); \
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| 151 | }
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| 152 |
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| 153 | extern const int tcp_backoff[];
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| 154 |
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| 155 | struct tcpcb;
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| 156 |
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| 157 | void tcp_fasttimo (PNATState);
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| 158 | void tcp_slowtimo (PNATState);
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| 159 | void tcp_canceltimers (struct tcpcb *);
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| 160 | #endif
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