| 1 | /*␊ |
| 2 | * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.␊ |
| 3 | *␊ |
| 4 | * @APPLE_OSREFERENCE_LICENSE_HEADER_START@␊ |
| 5 | * ␊ |
| 6 | * This file contains Original Code and/or Modifications of Original Code␊ |
| 7 | * as defined in and that are subject to the Apple Public Source License␊ |
| 8 | * Version 2.0 (the 'License'). You may not use this file except in␊ |
| 9 | * compliance with the License. The rights granted to you under the License␊ |
| 10 | * may not be used to create, or enable the creation or redistribution of,␊ |
| 11 | * unlawful or unlicensed copies of an Apple operating system, or to␊ |
| 12 | * circumvent, violate, or enable the circumvention or violation of, any␊ |
| 13 | * terms of an Apple operating system software license agreement.␊ |
| 14 | * ␊ |
| 15 | * Please obtain a copy of the License at␊ |
| 16 | * http://www.opensource.apple.com/apsl/ and read it before using this file.␊ |
| 17 | * ␊ |
| 18 | * The Original Code and all software distributed under the License are␊ |
| 19 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER␊ |
| 20 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,␊ |
| 21 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,␊ |
| 22 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.␊ |
| 23 | * Please see the License for the specific language governing rights and␊ |
| 24 | * limitations under the License.␊ |
| 25 | * ␊ |
| 26 | * @APPLE_OSREFERENCE_LICENSE_HEADER_END@␊ |
| 27 | */␊ |
| 28 | /*␊ |
| 29 | * Copyright (c) 1982, 1986, 1993␊ |
| 30 | *␉The Regents of the University of California. All rights reserved.␊ |
| 31 | *␊ |
| 32 | * Redistribution and use in source and binary forms, with or without␊ |
| 33 | * modification, are permitted provided that the following conditions␊ |
| 34 | * are met:␊ |
| 35 | * 1. Redistributions of source code must retain the above copyright␊ |
| 36 | * notice, this list of conditions and the following disclaimer.␊ |
| 37 | * 2. Redistributions in binary form must reproduce the above copyright␊ |
| 38 | * notice, this list of conditions and the following disclaimer in the␊ |
| 39 | * documentation and/or other materials provided with the distribution.␊ |
| 40 | * 3. All advertising materials mentioning features or use of this software␊ |
| 41 | * must display the following acknowledgement:␊ |
| 42 | *␉This product includes software developed by the University of␊ |
| 43 | *␉California, Berkeley and its contributors.␊ |
| 44 | * 4. Neither the name of the University nor the names of its contributors␊ |
| 45 | * may be used to endorse or promote products derived from this software␊ |
| 46 | * without specific prior written permission.␊ |
| 47 | *␊ |
| 48 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND␊ |
| 49 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE␊ |
| 50 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE␊ |
| 51 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE␊ |
| 52 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL␊ |
| 53 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS␊ |
| 54 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)␊ |
| 55 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT␊ |
| 56 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY␊ |
| 57 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF␊ |
| 58 | * SUCH DAMAGE.␊ |
| 59 | *␊ |
| 60 | *␉@(#)tcp_timer.h␉8.1 (Berkeley) 6/10/93␊ |
| 61 | * $FreeBSD: src/sys/netinet/tcp_timer.h,v 1.18 1999/12/29 04:41:03 peter Exp $␊ |
| 62 | */␊ |
| 63 | ␊ |
| 64 | #ifndef _NETINET_TCP_TIMER_H_␊ |
| 65 | #define _NETINET_TCP_TIMER_H_␊ |
| 66 | #include <sys/appleapiopts.h>␊ |
| 67 | ␊ |
| 68 | /*␊ |
| 69 | * Definitions of the TCP timers. These timers are counted␊ |
| 70 | * down PR_SLOWHZ times a second.␊ |
| 71 | */␊ |
| 72 | #define␉TCPT_NTIMERS␉4␊ |
| 73 | ␊ |
| 74 | #define␉TCPT_REXMT␉0␉␉/* retransmit */␊ |
| 75 | #define␉TCPT_PERSIST␉1␉␉/* retransmit persistence */␊ |
| 76 | #define␉TCPT_KEEP␉2␉␉/* keep alive */␊ |
| 77 | #define␉TCPT_2MSL␉3␉␉/* 2*msl quiet time timer */␊ |
| 78 | ␊ |
| 79 | /*␊ |
| 80 | * The TCPT_REXMT timer is used to force retransmissions.␊ |
| 81 | * The TCP has the TCPT_REXMT timer set whenever segments␊ |
| 82 | * have been sent for which ACKs are expected but not yet␊ |
| 83 | * received. If an ACK is received which advances tp->snd_una,␊ |
| 84 | * then the retransmit timer is cleared (if there are no more␊ |
| 85 | * outstanding segments) or reset to the base value (if there␊ |
| 86 | * are more ACKs expected). Whenever the retransmit timer goes off,␊ |
| 87 | * we retransmit one unacknowledged segment, and do a backoff␊ |
| 88 | * on the retransmit timer.␊ |
| 89 | *␊ |
| 90 | * The TCPT_PERSIST timer is used to keep window size information␊ |
| 91 | * flowing even if the window goes shut. If all previous transmissions␊ |
| 92 | * have been acknowledged (so that there are no retransmissions in progress),␊ |
| 93 | * and the window is too small to bother sending anything, then we start␊ |
| 94 | * the TCPT_PERSIST timer. When it expires, if the window is nonzero,␊ |
| 95 | * we go to transmit state. Otherwise, at intervals send a single byte␊ |
| 96 | * into the peer's window to force him to update our window information.␊ |
| 97 | * We do this at most as often as TCPT_PERSMIN time intervals,␊ |
| 98 | * but no more frequently than the current estimate of round-trip␊ |
| 99 | * packet time. The TCPT_PERSIST timer is cleared whenever we receive␊ |
| 100 | * a window update from the peer.␊ |
| 101 | *␊ |
| 102 | * The TCPT_KEEP timer is used to keep connections alive. If an␊ |
| 103 | * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,␊ |
| 104 | * but not yet established, then we drop the connection. Once the connection␊ |
| 105 | * is established, if the connection is idle for TCPTV_KEEP_IDLE time␊ |
| 106 | * (and keepalives have been enabled on the socket), we begin to probe␊ |
| 107 | * the connection. We force the peer to send us a segment by sending:␊ |
| 108 | *␉<SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>␊ |
| 109 | * This segment is (deliberately) outside the window, and should elicit␊ |
| 110 | * an ack segment in response from the peer. If, despite the TCPT_KEEP␊ |
| 111 | * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE␊ |
| 112 | * amount of time probing, then we drop the connection.␊ |
| 113 | */␊ |
| 114 | ␊ |
| 115 | #endif /* !_NETINET_TCP_TIMER_H_ */␊ |
| 116 | ␊ |
| 117 | |
