00001 /* 00002 * Copyright (c) 1982, 1986, 1993 00003 * The Regents of the University of California. All rights reserved. 00004 * 00005 * Redistribution and use in source and binary forms, with or without 00006 * modification, are permitted provided that the following conditions 00007 * are met: 00008 * 1. Redistributions of source code must retain the above copyright 00009 * notice, this list of conditions and the following disclaimer. 00010 * 2. Redistributions in binary form must reproduce the above copyright 00011 * notice, this list of conditions and the following disclaimer in the 00012 * documentation and/or other materials provided with the distribution. 00013 * 3. Neither the name of the University nor the names of its contributors 00014 * may be used to endorse or promote products derived from this software 00015 * without specific prior written permission. 00016 * 00017 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 00018 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 00019 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 00020 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 00021 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 00022 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 00023 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 00024 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 00025 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 00026 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 00027 * SUCH DAMAGE. 00028 * 00029 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 00030 * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp 00031 */ 00032 00033 #ifndef _TCP_TIMER_H_ 00034 #define _TCP_TIMER_H_ 00035 00036 /* 00037 * Definitions of the TCP timers. These timers are counted 00038 * down PR_SLOWHZ times a second. 00039 */ 00040 #define TCPT_NTIMERS 4 00041 00042 #define TCPT_REXMT 0 /* retransmit */ 00043 #define TCPT_PERSIST 1 /* retransmit persistence */ 00044 #define TCPT_KEEP 2 /* keep alive */ 00045 #define TCPT_2MSL 3 /* 2*msl quiet time timer */ 00046 00047 /* 00048 * The TCPT_REXMT timer is used to force retransmissions. 00049 * The TCP has the TCPT_REXMT timer set whenever segments 00050 * have been sent for which ACKs are expected but not yet 00051 * received. If an ACK is received which advances tp->snd_una, 00052 * then the retransmit timer is cleared (if there are no more 00053 * outstanding segments) or reset to the base value (if there 00054 * are more ACKs expected). Whenever the retransmit timer goes off, 00055 * we retransmit one unacknowledged segment, and do a backoff 00056 * on the retransmit timer. 00057 * 00058 * The TCPT_PERSIST timer is used to keep window size information 00059 * flowing even if the window goes shut. If all previous transmissions 00060 * have been acknowledged (so that there are no retransmissions in progress), 00061 * and the window is too small to bother sending anything, then we start 00062 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 00063 * we go to transmit state. Otherwise, at intervals send a single byte 00064 * into the peer's window to force him to update our window information. 00065 * We do this at most as often as TCPT_PERSMIN time intervals, 00066 * but no more frequently than the current estimate of round-trip 00067 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 00068 * a window update from the peer. 00069 * 00070 * The TCPT_KEEP timer is used to keep connections alive. If an 00071 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 00072 * but not yet established, then we drop the connection. Once the connection 00073 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 00074 * (and keepalives have been enabled on the socket), we begin to probe 00075 * the connection. We force the peer to send us a segment by sending: 00076 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 00077 * This segment is (deliberately) outside the window, and should elicit 00078 * an ack segment in response from the peer. If, despite the TCPT_KEEP 00079 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 00080 * amount of time probing, then we drop the connection. 00081 */ 00082 00083 /* 00084 * Time constants. 00085 */ 00086 #define TCPTV_MSL ( 5*PR_SLOWHZ) /* max seg lifetime (hah!) */ 00087 00088 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 00089 if 0, no idea yet */ 00090 #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 00091 00092 #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistence */ 00093 #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ 00094 00095 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */ 00096 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */ 00097 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */ 00098 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 00099 00100 #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ 00101 /* #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) */ /* max allowable REXMT value */ 00102 #define TCPTV_REXMTMAX ( 12*PR_SLOWHZ) /* max allowable REXMT value */ 00103 00104 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 00105 00106 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 00107 00108 00109 #ifdef TCPTIMERS 00110 char *tcptimers[] = 00111 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 00112 #endif 00113 00114 /* 00115 * Force a time value to be in a certain range. 00116 */ 00117 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ 00118 (tv) = (value); \ 00119 if ((tv) < (tvmin)) \ 00120 (tv) = (tvmin); \ 00121 else if ((tv) > (tvmax)) \ 00122 (tv) = (tvmax); \ 00123 } 00124 00125 extern const int tcp_backoff[]; 00126 00127 struct tcpcb; 00128 00129 void tcp_fasttimo _P((void)); 00130 void tcp_slowtimo _P((void)); 00131 void tcp_canceltimers _P((struct tcpcb *)); 00132 00133 #endif