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 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 34 * $FreeBSD: src/sys/netinet/tcp_timer.h,v 1.18.2.1 2002/08/16 22:16:39 dillon Exp $ 35 * $DragonFly: src/sys/netinet/tcp_timer.h,v 1.3 2003/08/23 11:18:00 rob Exp $ 36 */ 37 38 #ifndef _NETINET_TCP_TIMER_H_ 39 #define _NETINET_TCP_TIMER_H_ 40 41 /* 42 * The TCPT_REXMT timer is used to force retransmissions. 43 * The TCP has the TCPT_REXMT timer set whenever segments 44 * have been sent for which ACKs are expected but not yet 45 * received. If an ACK is received which advances tp->snd_una, 46 * then the retransmit timer is cleared (if there are no more 47 * outstanding segments) or reset to the base value (if there 48 * are more ACKs expected). Whenever the retransmit timer goes off, 49 * we retransmit one unacknowledged segment, and do a backoff 50 * on the retransmit timer. 51 * 52 * The TCPT_PERSIST timer is used to keep window size information 53 * flowing even if the window goes shut. If all previous transmissions 54 * have been acknowledged (so that there are no retransmissions in progress), 55 * and the window is too small to bother sending anything, then we start 56 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 57 * we go to transmit state. Otherwise, at intervals send a single byte 58 * into the peer's window to force him to update our window information. 59 * We do this at most as often as TCPT_PERSMIN time intervals, 60 * but no more frequently than the current estimate of round-trip 61 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 62 * a window update from the peer. 63 * 64 * The TCPT_KEEP timer is used to keep connections alive. If an 65 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 66 * but not yet established, then we drop the connection. Once the connection 67 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 68 * (and keepalives have been enabled on the socket), we begin to probe 69 * the connection. We force the peer to send us a segment by sending: 70 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 71 * This segment is (deliberately) outside the window, and should elicit 72 * an ack segment in response from the peer. If, despite the TCPT_KEEP 73 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 74 * amount of time probing, then we drop the connection. 75 */ 76 77 /* 78 * Time constants. 79 */ 80 #define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */ 81 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 82 if 0, no idea yet */ 83 #define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */ 84 #define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */ 85 86 #define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */ 87 #define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ 88 89 #define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ 90 #define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ 91 #define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ 92 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 93 94 /* 95 * TCPTV_MIN represents the minimum allowed retransmit interval. It 96 * is currently one second but will ultimately be reduced to 3 ticks 97 * for algorithmic stability, leaving the 200ms variance to deal with 98 * delayed-acks, protocol overheads. A 1 second minimum badly breaks 99 * throughput on any network faster then a modem that has minor but 100 * continuous packet loss unrelated to congestion, such as on a wireless 101 * network. 102 */ 103 #define TCPTV_MIN ( hz ) /* minimum allowable value */ 104 #define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance (200ms) */ 105 #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 106 107 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 108 109 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 110 111 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 112 113 #define TCPTV_DELACK (hz / PR_FASTHZ / 2) /* 100ms timeout */ 114 115 #ifdef TCPTIMERS 116 static char *tcptimers[] = 117 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 118 #endif 119 120 /* 121 * Force a time value to be in a certain range. 122 */ 123 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 124 (tv) = (value) + tcp_rexmit_slop; \ 125 if ((u_long)(tv) < (u_long)(tvmin)) \ 126 (tv) = (tvmin); \ 127 else if ((u_long)(tv) > (u_long)(tvmax)) \ 128 (tv) = (tvmax); \ 129 } while(0) 130 131 #ifdef _KERNEL 132 133 struct tcpcb; 134 struct netmsg_tcp_timer { 135 struct netmsg tt_nmsg; 136 struct tcpcb *tt_tcb; 137 int tt_cpuid; /* owner cpuid */ 138 uint32_t tt_tasks; /* pending tasks */ 139 uint32_t tt_running_tasks; /* running tasks */ 140 uint32_t tt_prev_tasks; /* prev pending tasks (debug) */ 141 }; 142 143 struct tcp_callout { 144 struct callout tc_callout; 145 uint32_t tc_task; /* callout's task id */ 146 }; 147 148 extern int tcp_keepinit; /* time to establish connection */ 149 extern int tcp_keepidle; /* time before keepalive probes begin */ 150 extern int tcp_keepintvl; /* time between keepalive probes */ 151 extern int tcp_maxidle; /* time to drop after starting probes */ 152 extern int tcp_delacktime; /* time before sending a delayed ACK */ 153 extern int tcp_maxpersistidle; 154 extern int tcp_rexmit_min; 155 extern int tcp_rexmit_slop; 156 extern int tcp_msl; 157 extern int tcp_ttl; /* time to live for TCP segs */ 158 extern int tcp_backoff[]; 159 160 void tcp_timer_2msl(void *xtp); 161 void tcp_timer_keep(void *xtp); 162 void tcp_timer_persist(void *xtp); 163 void tcp_timer_rexmt(void *xtp); 164 void tcp_timer_delack(void *xtp); 165 void tcp_inittimers(struct tcpcb *); 166 167 void tcp_create_timermsg(struct tcpcb *); 168 void tcp_destroy_timermsg(struct tcpcb *); 169 170 #endif /* _KERNEL */ 171 172 #endif /* !_NETINET_TCP_TIMER_H_ */ 173