tcp_timer.h revision 169608
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 * 4. 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 * $FreeBSD: head/sys/netinet/tcp_timer.h 169608 2007-05-16 17:14:25Z andre $ 31 */ 32 33#ifndef _NETINET_TCP_TIMER_H_ 34#define _NETINET_TCP_TIMER_H_ 35 36/* 37 * The TCPT_REXMT timer is used to force retransmissions. 38 * The TCP has the TCPT_REXMT timer set whenever segments 39 * have been sent for which ACKs are expected but not yet 40 * received. If an ACK is received which advances tp->snd_una, 41 * then the retransmit timer is cleared (if there are no more 42 * outstanding segments) or reset to the base value (if there 43 * are more ACKs expected). Whenever the retransmit timer goes off, 44 * we retransmit one unacknowledged segment, and do a backoff 45 * on the retransmit timer. 46 * 47 * The TCPT_PERSIST timer is used to keep window size information 48 * flowing even if the window goes shut. If all previous transmissions 49 * have been acknowledged (so that there are no retransmissions in progress), 50 * and the window is too small to bother sending anything, then we start 51 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 52 * we go to transmit state. Otherwise, at intervals send a single byte 53 * into the peer's window to force him to update our window information. 54 * We do this at most as often as TCPT_PERSMIN time intervals, 55 * but no more frequently than the current estimate of round-trip 56 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 57 * a window update from the peer. 58 * 59 * The TCPT_KEEP timer is used to keep connections alive. If an 60 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 61 * but not yet established, then we drop the connection. Once the connection 62 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 63 * (and keepalives have been enabled on the socket), we begin to probe 64 * the connection. We force the peer to send us a segment by sending: 65 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 66 * This segment is (deliberately) outside the window, and should elicit 67 * an ack segment in response from the peer. If, despite the TCPT_KEEP 68 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 69 * amount of time probing, then we drop the connection. 70 */ 71 72/* 73 * Time constants. 74 */ 75#define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */ 76#define TCPTV_SRTTBASE 0 /* base roundtrip time; 77 if 0, no idea yet */ 78#define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */ 79#define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */ 80 81#define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */ 82#define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ 83 84#define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ 85#define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ 86#define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ 87#define TCPTV_KEEPCNT 8 /* max probes before drop */ 88 89#define TCPTV_INFLIGHT_RTTTHRESH (10*hz/1000) /* below which inflight 90 disengages, in msec */ 91 92#define TCPTV_FINWAIT2_TIMEOUT (60*hz) /* FIN_WAIT_2 timeout if no receiver */ 93 94/* 95 * Minimum retransmit timer is 3 ticks, for algorithmic stability. 96 * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with 97 * the expected worst-case processing variances by the kernels 98 * representing the end points. Such variances do not always show 99 * up in the srtt because the timestamp is often calculated at 100 * the interface rather then at the TCP layer. This value is 101 * typically 50ms. However, it is also possible that delayed 102 * acks (typically 100ms) could create issues so we set the slop 103 * to 200ms to try to cover it. Note that, properly speaking, 104 * delayed-acks should not create a major issue for interactive 105 * environments which 'P'ush the last segment, at least as 106 * long as implementations do the required 'at least one ack 107 * for every two packets' for the non-interactive streaming case. 108 * (maybe the RTO calculation should use 2*RTT instead of RTT 109 * to handle the ack-every-other-packet case). 110 * 111 * The prior minimum of 1*hz (1 second) badly breaks throughput on any 112 * networks faster then a modem that has minor (e.g. 1%) packet loss. 113 */ 114#define TCPTV_MIN ( 3 ) /* minimum allowable value */ 115#define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */ 116#define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 117 118#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 119 120#define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 121 122#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 123 124#define TCPTV_DELACK (hz / PR_FASTHZ / 2) /* 100ms timeout */ 125 126#ifdef TCPTIMERS 127static const char *tcptimers[] = 128 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 129#endif 130 131/* 132 * Force a time value to be in a certain range. 133 */ 134#define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 135 (tv) = (value) + tcp_rexmit_slop; \ 136 if ((u_long)(tv) < (u_long)(tvmin)) \ 137 (tv) = (tvmin); \ 138 if ((u_long)(tv) > (u_long)(tvmax)) \ 139 (tv) = (tvmax); \ 140} while(0) 141 142#ifdef _KERNEL 143 144struct tcp_timer { 145 struct callout tt_timer; 146 int tt_nextc; /* next callout time in time_uptime */ 147 int tt_active; /* engaged callouts */ 148#define TT_DELACK 0x01 149#define TT_REXMT 0x02 150#define TT_PERSIST 0x04 151#define TT_KEEP 0x08 152#define TT_2MSL 0x10 153 int tt_delack; 154 int tt_rexmt; 155 int tt_persist; 156 int tt_keep; 157 int tt_2msl; 158}; 159 160extern int tcp_keepinit; /* time to establish connection */ 161extern int tcp_keepidle; /* time before keepalive probes begin */ 162extern int tcp_keepintvl; /* time between keepalive probes */ 163extern int tcp_maxidle; /* time to drop after starting probes */ 164extern int tcp_delacktime; /* time before sending a delayed ACK */ 165extern int tcp_maxpersistidle; 166extern int tcp_rexmit_min; 167extern int tcp_rexmit_slop; 168extern int tcp_msl; 169extern int tcp_ttl; /* time to live for TCP segs */ 170extern int tcp_backoff[]; 171 172struct tcptw; 173 174extern int tcp_finwait2_timeout; 175extern int tcp_fast_finwait2_recycle; 176 177void tcp_timer_init(void); 178void tcp_timer_2msl_reset(struct tcptw *_tw, int rearm); 179void tcp_timer_2msl_stop(struct tcptw *_tw); 180struct tcptw * 181 tcp_tw_2msl_scan(int _reuse); /* XXX temporary */ 182 183#endif /* _KERNEL */ 184 185#endif /* !_NETINET_TCP_TIMER_H_ */ 186