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 * $FreeBSD$ 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_FINWAIT2_TIMEOUT (60*hz) /* FIN_WAIT_2 timeout if no receiver */ 90 91 /* 92 * Minimum retransmit timer is 3 ticks, for algorithmic stability. 93 * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with 94 * the expected worst-case processing variances by the kernels 95 * representing the end points. Such variances do not always show 96 * up in the srtt because the timestamp is often calculated at 97 * the interface rather then at the TCP layer. This value is 98 * typically 50ms. However, it is also possible that delayed 99 * acks (typically 100ms) could create issues so we set the slop 100 * to 200ms to try to cover it. Note that, properly speaking, 101 * delayed-acks should not create a major issue for interactive 102 * environments which 'P'ush the last segment, at least as 103 * long as implementations do the required 'at least one ack 104 * for every two packets' for the non-interactive streaming case. 105 * (maybe the RTO calculation should use 2*RTT instead of RTT 106 * to handle the ack-every-other-packet case). 107 * 108 * The prior minimum of 1*hz (1 second) badly breaks throughput on any 109 * networks faster then a modem that has minor (e.g. 1%) packet loss. 110 */ 111 #define TCPTV_MIN ( hz/33 ) /* minimum allowable value */ 112 #define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */ 113 #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 114 115 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 116 117 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 118 119 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 120 121 #define TCPTV_DELACK ( hz/10 ) /* 100ms timeout */ 122 123 #ifdef TCPTIMERS 124 static const char *tcptimers[] = 125 { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" }; 126 #endif 127 128 /* 129 * Force a time value to be in a certain range. 130 */ 131 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 132 (tv) = (value) + tcp_rexmit_slop; \ 133 if ((u_long)(tv) < (u_long)(tvmin)) \ 134 (tv) = (tvmin); \ 135 if ((u_long)(tv) > (u_long)(tvmax)) \ 136 (tv) = (tvmax); \ 137 } while(0) 138 139 #ifdef _KERNEL 140 141 struct xtcp_timer; 142 143 struct tcp_timer { 144 struct callout tt_rexmt; /* retransmit timer */ 145 struct callout tt_persist; /* retransmit persistence */ 146 struct callout tt_keep; /* keepalive */ 147 struct callout tt_2msl; /* 2*msl TIME_WAIT timer */ 148 struct callout tt_delack; /* delayed ACK timer */ 149 }; 150 #define TT_DELACK 0x01 151 #define TT_REXMT 0x02 152 #define TT_PERSIST 0x04 153 #define TT_KEEP 0x08 154 #define TT_2MSL 0x10 155 156 #define TP_KEEPINIT(tp) ((tp)->t_keepinit ? (tp)->t_keepinit : tcp_keepinit) 157 #define TP_KEEPIDLE(tp) ((tp)->t_keepidle ? (tp)->t_keepidle : tcp_keepidle) 158 #define TP_KEEPINTVL(tp) ((tp)->t_keepintvl ? (tp)->t_keepintvl : tcp_keepintvl) 159 #define TP_KEEPCNT(tp) ((tp)->t_keepcnt ? (tp)->t_keepcnt : tcp_keepcnt) 160 #define TP_MAXIDLE(tp) (TP_KEEPCNT(tp) * TP_KEEPINTVL(tp)) 161 162 extern int tcp_keepinit; /* time to establish connection */ 163 extern int tcp_keepidle; /* time before keepalive probes begin */ 164 extern int tcp_keepintvl; /* time between keepalive probes */ 165 extern int tcp_keepcnt; /* number of keepalives */ 166 extern int tcp_delacktime; /* time before sending a delayed ACK */ 167 extern int tcp_maxpersistidle; 168 extern int tcp_rexmit_min; 169 extern int tcp_rexmit_slop; 170 extern int tcp_msl; 171 extern int tcp_ttl; /* time to live for TCP segs */ 172 extern int tcp_backoff[]; 173 extern int tcp_syn_backoff[]; 174 175 extern int tcp_finwait2_timeout; 176 extern int tcp_fast_finwait2_recycle; 177 178 void tcp_timer_init(void); 179 void tcp_timer_2msl(void *xtp); 180 struct tcptw * 181 tcp_tw_2msl_scan(int reuse); /* XXX temporary? */ 182 void tcp_timer_keep(void *xtp); 183 void tcp_timer_persist(void *xtp); 184 void tcp_timer_rexmt(void *xtp); 185 void tcp_timer_delack(void *xtp); 186 void tcp_timer_to_xtimer(struct tcpcb *tp, struct tcp_timer *timer, 187 struct xtcp_timer *xtimer); 188 189 #endif /* _KERNEL */ 190 191 #endif /* !_NETINET_TCP_TIMER_H_ */ 192