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 */ 33 34 #ifndef _NETINET_TCP_TIMER_H_ 35 #define _NETINET_TCP_TIMER_H_ 36 37 /* 38 * The TCPT_REXMT timer is used to force retransmissions. 39 * The TCP has the TCPT_REXMT timer set whenever segments 40 * have been sent for which ACKs are expected but not yet 41 * received. If an ACK is received which advances tp->snd_una, 42 * then the retransmit timer is cleared (if there are no more 43 * outstanding segments) or reset to the base value (if there 44 * are more ACKs expected). Whenever the retransmit timer goes off, 45 * we retransmit one unacknowledged segment, and do a backoff 46 * on the retransmit timer. 47 * 48 * The TCPT_PERSIST timer is used to keep window size information 49 * flowing even if the window goes shut. If all previous transmissions 50 * have been acknowledged (so that there are no retransmissions in progress), 51 * and the window is too small to bother sending anything, then we start 52 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 53 * we go to transmit state. Otherwise, at intervals send a single byte 54 * into the peer's window to force him to update our window information. 55 * We do this at most as often as TCPT_PERSMIN time intervals, 56 * but no more frequently than the current estimate of round-trip 57 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 58 * a window update from the peer. 59 * 60 * The TCPT_KEEP timer is used to keep connections alive. If an 61 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 62 * but not yet established, then we drop the connection. Once the connection 63 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 64 * (and keepalives have been enabled on the socket), we begin to probe 65 * the connection. We force the peer to send us a segment by sending: 66 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 67 * This segment is (deliberately) outside the window, and should elicit 68 * an ack segment in response from the peer. If, despite the TCPT_KEEP 69 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 70 * amount of time probing, then we drop the connection. 71 */ 72 73 /* 74 * Time constants. 75 */ 76 #define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */ 77 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 78 if 0, no idea yet */ 79 #define TCPTV_RTOBASE ( 1*hz) /* assumed RTO if no info */ 80 81 #define TCPTV_PERSMIN ( 5*hz) /* minimum persist interval */ 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 #define TCPTV_MAXUNACKTIME 0 /* max time without making progress */ 89 90 #define TCPTV_FINWAIT2_TIMEOUT (60*hz) /* FIN_WAIT_2 timeout if no receiver */ 91 92 /* 93 * Minimum retransmit timer is 3 ticks, for algorithmic stability. 94 * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with 95 * the expected worst-case processing variances by the kernels 96 * representing the end points. Such variances do not always show 97 * up in the srtt because the timestamp is often calculated at 98 * the interface rather then at the TCP layer. This value is 99 * typically 50ms. However, it is also possible that delayed 100 * acks (typically 100ms) could create issues so we set the slop 101 * to 200ms to try to cover it. Note that, properly speaking, 102 * delayed-acks should not create a major issue for interactive 103 * environments which 'P'ush the last segment, at least as 104 * long as implementations do the required 'at least one ack 105 * for every two packets' for the non-interactive streaming case. 106 * (maybe the RTO calculation should use 2*RTT instead of RTT 107 * to handle the ack-every-other-packet case). 108 * 109 * The prior minimum of 1*hz (1 second) badly breaks throughput on any 110 * networks faster then a modem that has minor (e.g. 1%) packet loss. 111 */ 112 #define TCPTV_MIN ( hz/33 ) /* minimum allowable value */ 113 #define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */ 114 #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 115 116 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 117 118 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 119 120 #define TCPTV_DELACK ( hz/25 ) /* 40ms timeout */ 121 122 /* 123 * If we exceed this number of retransmits for a single segment, we'll consider 124 * the current srtt measurement no longer valid and will recalculate from 125 * scratch starting with the next ACK. 126 */ 127 #define TCP_RTT_INVALIDATE (TCP_MAXRXTSHIFT / 4) 128 129 /* 130 * Force a time value to be in a certain range. 131 */ 132 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 133 (tv) = (value) + tcp_rexmit_slop; \ 134 if ((u_long)(tv) < (u_long)(tvmin)) \ 135 (tv) = (tvmin); \ 136 if ((u_long)(tv) > (u_long)(tvmax)) \ 137 (tv) = (tvmax); \ 138 } while(0) 139 140 #ifdef _KERNEL 141 142 #define TP_KEEPINIT(tp) ((tp)->t_keepinit ? (tp)->t_keepinit : tcp_keepinit) 143 #define TP_KEEPIDLE(tp) ((tp)->t_keepidle ? (tp)->t_keepidle : tcp_keepidle) 144 #define TP_KEEPINTVL(tp) ((tp)->t_keepintvl ? (tp)->t_keepintvl : tcp_keepintvl) 145 #define TP_KEEPCNT(tp) ((tp)->t_keepcnt ? (tp)->t_keepcnt : tcp_keepcnt) 146 #define TP_MAXIDLE(tp) (TP_KEEPCNT(tp) * TP_KEEPINTVL(tp)) 147 #define TP_MAXUNACKTIME(tp) \ 148 ((tp)->t_maxunacktime ? (tp)->t_maxunacktime : tcp_maxunacktime) 149 150 /* 151 * Obtain the time until the restransmit timer should fire. 152 * This macro ensures the restransmit timer fires at the earlier of the 153 * t_rxtcur value or the time the maxunacktime would be exceeded. 154 */ 155 #define TP_RXTCUR(tp) \ 156 ((TP_MAXUNACKTIME(tp) == 0 || tp->t_acktime == 0) ? tp->t_rxtcur : \ 157 max(1, min(tp->t_rxtcur, tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks))) 158 159 extern int tcp_persmin; /* minimum persist interval */ 160 extern int tcp_persmax; /* maximum persist interval */ 161 extern int tcp_keepinit; /* time to establish connection */ 162 extern int tcp_keepidle; /* time before keepalive probes begin */ 163 extern int tcp_keepintvl; /* time between keepalive probes */ 164 extern int tcp_keepcnt; /* number of keepalives */ 165 extern int tcp_delacktime; /* time before sending a delayed ACK */ 166 extern int tcp_maxunacktime; /* max time without making progress */ 167 extern int tcp_maxpersistidle; 168 extern int tcp_rexmit_initial; 169 extern int tcp_rexmit_min; 170 extern int tcp_rexmit_slop; 171 extern int tcp_ttl; /* time to live for TCP segs */ 172 extern int tcp_backoff[]; 173 extern int tcp_totbackoff; 174 extern int tcp_rexmit_drop_options; 175 176 extern int tcp_finwait2_timeout; 177 extern int tcp_fast_finwait2_recycle; 178 179 VNET_DECLARE(int, tcp_always_keepalive); 180 #define V_tcp_always_keepalive VNET(tcp_always_keepalive) 181 VNET_DECLARE(int, tcp_pmtud_blackhole_detect); 182 #define V_tcp_pmtud_blackhole_detect VNET(tcp_pmtud_blackhole_detect) 183 VNET_DECLARE(int, tcp_pmtud_blackhole_mss); 184 #define V_tcp_pmtud_blackhole_mss VNET(tcp_pmtud_blackhole_mss) 185 VNET_DECLARE(int, tcp_v6pmtud_blackhole_mss); 186 #define V_tcp_v6pmtud_blackhole_mss VNET(tcp_v6pmtud_blackhole_mss) 187 VNET_DECLARE(int, tcp_msl); 188 #define V_tcp_msl VNET(tcp_msl) 189 190 #endif /* _KERNEL */ 191 192 #endif /* !_NETINET_TCP_TIMER_H_ */ 193