1 /* 2 * Copyright (c) 1982, 1986, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * from: @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 34 * $Id: tcp_timer.h,v 1.4 1994/05/13 06:06:48 mycroft Exp $ 35 */ 36 37 /* 38 * Definitions of the TCP timers. These timers are counted 39 * down PR_SLOWHZ times a second. 40 */ 41 #define TCPT_NTIMERS 4 42 43 #define TCPT_REXMT 0 /* retransmit */ 44 #define TCPT_PERSIST 1 /* retransmit persistance */ 45 #define TCPT_KEEP 2 /* keep alive */ 46 #define TCPT_2MSL 3 /* 2*msl quiet time timer */ 47 48 /* 49 * The TCPT_REXMT timer is used to force retransmissions. 50 * The TCP has the TCPT_REXMT timer set whenever segments 51 * have been sent for which ACKs are expected but not yet 52 * received. If an ACK is received which advances tp->snd_una, 53 * then the retransmit timer is cleared (if there are no more 54 * outstanding segments) or reset to the base value (if there 55 * are more ACKs expected). Whenever the retransmit timer goes off, 56 * we retransmit one unacknowledged segment, and do a backoff 57 * on the retransmit timer. 58 * 59 * The TCPT_PERSIST timer is used to keep window size information 60 * flowing even if the window goes shut. If all previous transmissions 61 * have been acknowledged (so that there are no retransmissions in progress), 62 * and the window is too small to bother sending anything, then we start 63 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 64 * we go to transmit state. Otherwise, at intervals send a single byte 65 * into the peer's window to force him to update our window information. 66 * We do this at most as often as TCPT_PERSMIN time intervals, 67 * but no more frequently than the current estimate of round-trip 68 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 69 * a window update from the peer. 70 * 71 * The TCPT_KEEP timer is used to keep connections alive. If an 72 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 73 * but not yet established, then we drop the connection. Once the connection 74 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 75 * (and keepalives have been enabled on the socket), we begin to probe 76 * the connection. We force the peer to send us a segment by sending: 77 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 78 * This segment is (deliberately) outside the window, and should elicit 79 * an ack segment in response from the peer. If, despite the TCPT_KEEP 80 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 81 * amount of time probing, then we drop the connection. 82 */ 83 84 /* 85 * Time constants. 86 */ 87 #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */ 88 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 89 if 0, no idea yet */ 90 #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 91 92 #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */ 93 #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ 94 95 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */ 96 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */ 97 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */ 98 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 99 100 #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ 101 #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */ 102 103 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 104 105 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 106 107 #ifdef TCPTIMERS 108 char *tcptimers[] = 109 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 110 #endif 111 112 /* 113 * Force a time value to be in a certain range. 114 */ 115 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ 116 (tv) = (value); \ 117 if ((tv) < (tvmin)) \ 118 (tv) = (tvmin); \ 119 else if ((tv) > (tvmax)) \ 120 (tv) = (tvmax); \ 121 } 122 123 #ifdef KERNEL 124 extern int tcp_keepidle; /* time before keepalive probes begin */ 125 extern int tcp_keepintvl; /* time between keepalive probes */ 126 extern int tcp_maxidle; /* time to drop after starting probes */ 127 extern int tcp_ttl; /* time to live for TCP segs */ 128 extern int tcp_backoff[]; 129 #endif 130