1 /* $OpenBSD: tcp_timer.h,v 1.12 2008/11/08 12:54:58 dlg Exp $ */ 2 /* $NetBSD: tcp_timer.h,v 1.6 1995/03/26 20:32:37 jtc Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 33 */ 34 35 #ifndef _NETINET_TCP_TIMER_H_ 36 #define _NETINET_TCP_TIMER_H_ 37 38 /* 39 * Definitions of the TCP timers. These timers are counted 40 * down PR_SLOWHZ times a second. 41 */ 42 #define TCPT_NTIMERS 4 43 44 #define TCPT_REXMT 0 /* retransmit */ 45 #define TCPT_PERSIST 1 /* retransmit persistence */ 46 #define TCPT_KEEP 2 /* keep alive */ 47 #define TCPT_2MSL 3 /* 2*msl quiet time timer */ 48 49 /* 50 * The TCPT_REXMT timer is used to force retransmissions. 51 * The TCP has the TCPT_REXMT timer set whenever segments 52 * have been sent for which ACKs are expected but not yet 53 * received. If an ACK is received which advances tp->snd_una, 54 * then the retransmit timer is cleared (if there are no more 55 * outstanding segments) or reset to the base value (if there 56 * are more ACKs expected). Whenever the retransmit timer goes off, 57 * we retransmit one unacknowledged segment, and do a backoff 58 * on the retransmit timer. 59 * 60 * The TCPT_PERSIST timer is used to keep window size information 61 * flowing even if the window goes shut. If all previous transmissions 62 * have been acknowledged (so that there are no retransmissions in progress), 63 * and the window is too small to bother sending anything, then we start 64 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 65 * we go to transmit state. Otherwise, at intervals send a single byte 66 * into the peer's window to force him to update our window information. 67 * We do this at most as often as TCPT_PERSMIN time intervals, 68 * but no more frequently than the current estimate of round-trip 69 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 70 * a window update from the peer. 71 * 72 * The TCPT_KEEP timer is used to keep connections alive. If an 73 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 74 * but not yet established, then we drop the connection. Once the connection 75 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 76 * (and keepalives have been enabled on the socket), we begin to probe 77 * the connection. We force the peer to send us a segment by sending: 78 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 79 * This segment is (deliberately) outside the window, and should elicit 80 * an ack segment in response from the peer. If, despite the TCPT_KEEP 81 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 82 * amount of time probing, then we drop the connection. 83 */ 84 85 /* 86 * Time constants. 87 */ 88 #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */ 89 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 90 if 0, no idea yet */ 91 #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 92 93 #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistence */ 94 #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ 95 96 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */ 97 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */ 98 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */ 99 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 100 101 #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ 102 #define TCPTV_REXMTMAX ( 64*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 #define TCP_DELACK_TICKS (hz / PR_FASTHZ) /* time to delay ACK */ 109 110 #ifdef TCPTIMERS 111 const char *tcptimers[] = 112 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 113 #endif /* TCPTIMERS */ 114 115 /* 116 * Init, arm, disarm, and test TCP timers. 117 */ 118 #define TCP_TIMER_INIT(tp, timer) \ 119 timeout_set(&(tp)->t_timer[(timer)], tcp_timer_funcs[(timer)], tp) 120 121 #define TCP_TIMER_ARM(tp, timer, nticks) \ 122 timeout_add(&(tp)->t_timer[(timer)], (nticks) * (hz / PR_SLOWHZ)) 123 124 #define TCP_TIMER_DISARM(tp, timer) \ 125 timeout_del(&(tp)->t_timer[(timer)]) 126 127 #define TCP_TIMER_ISARMED(tp, timer) \ 128 timeout_pending(&(tp)->t_timer[(timer)]) 129 130 /* 131 * Force a time value to be in a certain range. 132 */ 133 #define TCPT_RANGESET(tv, value, tvmin, tvmax) \ 134 do { \ 135 (tv) = (value); \ 136 if ((tv) < (tvmin)) \ 137 (tv) = (tvmin); \ 138 else if ((tv) > (tvmax)) \ 139 (tv) = (tvmax); \ 140 } while (/* CONSTCOND */ 0) 141 142 #ifdef _KERNEL 143 typedef void (*tcp_timer_func_t)(void *); 144 145 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS]; 146 147 extern int tcptv_keep_init; 148 extern int tcp_keepidle; /* time before keepalive probes begin */ 149 extern int tcp_keepintvl; /* time between keepalive probes */ 150 extern int tcp_maxidle; /* time to drop after starting probes */ 151 extern int tcp_ttl; /* time to live for TCP segs */ 152 extern int tcp_backoff[]; 153 154 void tcp_timer_init(void); 155 #endif /* _KERNEL */ 156 #endif /* _NETINET_TCP_TIMER_H_ */ 157