1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 32 * $FreeBSD$ 33 */ 34 35 #ifndef _NETINET_TCP_TIMER_H_ 36 #define _NETINET_TCP_TIMER_H_ 37 38 /* 39 * The TCPT_REXMT timer is used to force retransmissions. 40 * The TCP has the TCPT_REXMT timer set whenever segments 41 * have been sent for which ACKs are expected but not yet 42 * received. If an ACK is received which advances tp->snd_una, 43 * then the retransmit timer is cleared (if there are no more 44 * outstanding segments) or reset to the base value (if there 45 * are more ACKs expected). Whenever the retransmit timer goes off, 46 * we retransmit one unacknowledged segment, and do a backoff 47 * on the retransmit timer. 48 * 49 * The TCPT_PERSIST timer is used to keep window size information 50 * flowing even if the window goes shut. If all previous transmissions 51 * have been acknowledged (so that there are no retransmissions in progress), 52 * and the window is too small to bother sending anything, then we start 53 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 54 * we go to transmit state. Otherwise, at intervals send a single byte 55 * into the peer's window to force him to update our window information. 56 * We do this at most as often as TCPT_PERSMIN time intervals, 57 * but no more frequently than the current estimate of round-trip 58 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 59 * a window update from the peer. 60 * 61 * The TCPT_KEEP timer is used to keep connections alive. If an 62 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 63 * but not yet established, then we drop the connection. Once the connection 64 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 65 * (and keepalives have been enabled on the socket), we begin to probe 66 * the connection. We force the peer to send us a segment by sending: 67 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 68 * This segment is (deliberately) outside the window, and should elicit 69 * an ack segment in response from the peer. If, despite the TCPT_KEEP 70 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 71 * amount of time probing, then we drop the connection. 72 */ 73 74 /* 75 * Time constants. 76 */ 77 #define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */ 78 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 79 if 0, no idea yet */ 80 #define TCPTV_RTOBASE ( 1*hz) /* assumed RTO if no info */ 81 82 #define TCPTV_PERSMIN ( 5*hz) /* minimum persist interval */ 83 #define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ 84 85 #define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ 86 #define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ 87 #define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ 88 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 89 #define TCPTV_MAXUNACKTIME 0 /* max time without making progress */ 90 91 #define TCPTV_FINWAIT2_TIMEOUT (60*hz) /* FIN_WAIT_2 timeout if no receiver */ 92 93 /* 94 * Minimum retransmit timer is 3 ticks, for algorithmic stability. 95 * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with 96 * the expected worst-case processing variances by the kernels 97 * representing the end points. Such variances do not always show 98 * up in the srtt because the timestamp is often calculated at 99 * the interface rather then at the TCP layer. This value is 100 * typically 50ms. However, it is also possible that delayed 101 * acks (typically 100ms) could create issues so we set the slop 102 * to 200ms to try to cover it. Note that, properly speaking, 103 * delayed-acks should not create a major issue for interactive 104 * environments which 'P'ush the last segment, at least as 105 * long as implementations do the required 'at least one ack 106 * for every two packets' for the non-interactive streaming case. 107 * (maybe the RTO calculation should use 2*RTT instead of RTT 108 * to handle the ack-every-other-packet case). 109 * 110 * The prior minimum of 1*hz (1 second) badly breaks throughput on any 111 * networks faster then a modem that has minor (e.g. 1%) packet loss. 112 */ 113 #define TCPTV_MIN ( hz/33 ) /* minimum allowable value */ 114 #define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */ 115 #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 116 117 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 118 119 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 120 121 #define TCPTV_DELACK ( hz/25 ) /* 40ms timeout */ 122 123 /* 124 * If we exceed this number of retransmits for a single segment, we'll consider 125 * the current srtt measurement no longer valid and will recalculate from 126 * scratch starting with the next ACK. 127 */ 128 #define TCP_RTT_INVALIDATE (TCP_MAXRXTSHIFT / 4) 129 130 #ifdef TCPTIMERS 131 static const char *tcptimers[] = 132 { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" }; 133 #endif 134 135 /* 136 * Force a time value to be in a certain range. 137 */ 138 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 139 (tv) = (value) + tcp_rexmit_slop; \ 140 if ((u_long)(tv) < (u_long)(tvmin)) \ 141 (tv) = (tvmin); \ 142 if ((u_long)(tv) > (u_long)(tvmax)) \ 143 (tv) = (tvmax); \ 144 } while(0) 145 146 #ifdef _KERNEL 147 148 #define TP_KEEPINIT(tp) ((tp)->t_keepinit ? (tp)->t_keepinit : tcp_keepinit) 149 #define TP_KEEPIDLE(tp) ((tp)->t_keepidle ? (tp)->t_keepidle : tcp_keepidle) 150 #define TP_KEEPINTVL(tp) ((tp)->t_keepintvl ? (tp)->t_keepintvl : tcp_keepintvl) 151 #define TP_KEEPCNT(tp) ((tp)->t_keepcnt ? (tp)->t_keepcnt : tcp_keepcnt) 152 #define TP_MAXIDLE(tp) (TP_KEEPCNT(tp) * TP_KEEPINTVL(tp)) 153 #define TP_MAXUNACKTIME(tp) \ 154 ((tp)->t_maxunacktime ? (tp)->t_maxunacktime : tcp_maxunacktime) 155 156 /* 157 * Obtain the time until the restransmit timer should fire. 158 * This macro ensures the restransmit timer fires at the earlier of the 159 * t_rxtcur value or the time the maxunacktime would be exceeded. 160 */ 161 #define TP_RXTCUR(tp) \ 162 ((TP_MAXUNACKTIME(tp) == 0 || tp->t_acktime == 0) ? tp->t_rxtcur : \ 163 max(1, min(tp->t_rxtcur, tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks))) 164 165 extern int tcp_persmin; /* minimum persist interval */ 166 extern int tcp_persmax; /* maximum persist interval */ 167 extern int tcp_keepinit; /* time to establish connection */ 168 extern int tcp_keepidle; /* time before keepalive probes begin */ 169 extern int tcp_keepintvl; /* time between keepalive probes */ 170 extern int tcp_keepcnt; /* number of keepalives */ 171 extern int tcp_delacktime; /* time before sending a delayed ACK */ 172 extern int tcp_maxunacktime; /* max time without making progress */ 173 extern int tcp_maxpersistidle; 174 extern int tcp_rexmit_initial; 175 extern int tcp_rexmit_min; 176 extern int tcp_rexmit_slop; 177 extern int tcp_ttl; /* time to live for TCP segs */ 178 extern int tcp_backoff[]; 179 extern int tcp_totbackoff; 180 extern int tcp_rexmit_drop_options; 181 182 extern int tcp_finwait2_timeout; 183 extern int tcp_fast_finwait2_recycle; 184 185 VNET_DECLARE(int, tcp_always_keepalive); 186 #define V_tcp_always_keepalive VNET(tcp_always_keepalive) 187 VNET_DECLARE(int, tcp_pmtud_blackhole_detect); 188 #define V_tcp_pmtud_blackhole_detect VNET(tcp_pmtud_blackhole_detect) 189 VNET_DECLARE(int, tcp_pmtud_blackhole_mss); 190 #define V_tcp_pmtud_blackhole_mss VNET(tcp_pmtud_blackhole_mss) 191 VNET_DECLARE(int, tcp_v6pmtud_blackhole_mss); 192 #define V_tcp_v6pmtud_blackhole_mss VNET(tcp_v6pmtud_blackhole_mss) 193 VNET_DECLARE(int, tcp_msl); 194 #define V_tcp_msl VNET(tcp_msl) 195 196 #endif /* _KERNEL */ 197 198 #endif /* !_NETINET_TCP_TIMER_H_ */ 199