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. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 30 * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp 31 */ 32 33 #ifndef _TCP_TIMER_H_ 34 #define _TCP_TIMER_H_ 35 36 /* 37 * Definitions of the TCP timers. These timers are counted 38 * down PR_SLOWHZ times a second. 39 */ 40 #define TCPT_NTIMERS 4 41 42 #define TCPT_REXMT 0 /* retransmit */ 43 #define TCPT_PERSIST 1 /* retransmit persistence */ 44 #define TCPT_KEEP 2 /* keep alive */ 45 #define TCPT_2MSL 3 /* 2*msl quiet time timer */ 46 47 /* 48 * The TCPT_REXMT timer is used to force retransmissions. 49 * The TCP has the TCPT_REXMT timer set whenever segments 50 * have been sent for which ACKs are expected but not yet 51 * received. If an ACK is received which advances tp->snd_una, 52 * then the retransmit timer is cleared (if there are no more 53 * outstanding segments) or reset to the base value (if there 54 * are more ACKs expected). Whenever the retransmit timer goes off, 55 * we retransmit one unacknowledged segment, and do a backoff 56 * on the retransmit timer. 57 * 58 * The TCPT_PERSIST timer is used to keep window size information 59 * flowing even if the window goes shut. If all previous transmissions 60 * have been acknowledged (so that there are no retransmissions in progress), 61 * and the window is too small to bother sending anything, then we start 62 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 63 * we go to transmit state. Otherwise, at intervals send a single byte 64 * into the peer's window to force him to update our window information. 65 * We do this at most as often as TCPT_PERSMIN time intervals, 66 * but no more frequently than the current estimate of round-trip 67 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 68 * a window update from the peer. 69 * 70 * The TCPT_KEEP timer is used to keep connections alive. If an 71 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 72 * but not yet established, then we drop the connection. Once the connection 73 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 74 * (and keepalives have been enabled on the socket), we begin to probe 75 * the connection. We force the peer to send us a segment by sending: 76 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 77 * This segment is (deliberately) outside the window, and should elicit 78 * an ack segment in response from the peer. If, despite the TCPT_KEEP 79 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 80 * amount of time probing, then we drop the connection. 81 */ 82 83 /* 84 * Time constants. 85 */ 86 #define TCPTV_MSL ( 5*PR_SLOWHZ) /* max seg lifetime (hah!) */ 87 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 persistence */ 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 #define TCPTV_REXMTMAX ( 12*PR_SLOWHZ) /* max allowable REXMT value */ 103 104 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 105 106 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 107 108 109 #ifdef TCPTIMERS 110 char *tcptimers[] = 111 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 112 #endif 113 114 /* 115 * Force a time value to be in a certain range. 116 */ 117 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ 118 (tv) = (value); \ 119 if ((tv) < (tvmin)) \ 120 (tv) = (tvmin); \ 121 else if ((tv) > (tvmax)) \ 122 (tv) = (tvmax); \ 123 } 124 125 extern const int tcp_backoff[]; 126 127 struct tcpcb; 128 129 void tcp_fasttimo _P((void)); 130 void tcp_slowtimo _P((void)); 131 void tcp_canceltimers _P((struct tcpcb *)); 132 133 #endif 134