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. 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: src/sys/netinet/tcp_timer.h,v 1.18.2.1 2002/08/16 22:16:39 dillon Exp $ 31 * $DragonFly: src/sys/netinet/tcp_timer.h,v 1.3 2003/08/23 11:18:00 rob Exp $ 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_RTOBASE3 ( 3*hz) /* assumed RTO if no info */ 80 #define TCPTV_RTOBASE1 ( 1*hz) /* assumed RTO (RFC 6298) */ 81 #define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */ 82 83 #define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */ 84 #define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ 85 86 #define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ 87 #define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ 88 #define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ 89 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 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 ~160ms 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 * 106 * The prior minimum of 1*hz (1 second) badly breaks throughput 107 * on any networks faster then a modem that has minor (e.g. 1%) 108 * packet loss. 109 */ 110 #define TCPTV_MIN ( hz/33 ) /* minimum allowable value */ 111 #define TCPTV_CPU_VAR ( hz/6 ) /* cpu variance (~160ms) */ 112 #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 113 114 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 115 116 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 117 118 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 119 120 #define TCPTV_DELACK ( hz/10) /* 100ms timeout */ 121 122 #ifdef TCPTIMERS 123 static const char *tcptimers[] = 124 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 125 #endif 126 127 /* 128 * Force a time value to be in a certain range. 129 */ 130 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 131 (tv) = (value) + tcp_rexmit_slop; \ 132 if ((u_long)(tv) < (u_long)(tvmin)) \ 133 (tv) = (tvmin); \ 134 else if ((u_long)(tv) > (u_long)(tvmax)) \ 135 (tv) = (tvmax); \ 136 } while(0) 137 138 #ifdef _KERNEL 139 140 #define TCPTV_RTOBASE \ 141 (tcp_low_rtobase ? TCPTV_RTOBASE1 : TCPTV_RTOBASE3) 142 143 struct tcpcb; 144 struct netmsg_tcp_timer { 145 struct netmsg_base tt_msg; 146 struct tcpcb *tt_tcb; 147 int tt_cpuid; /* owner cpuid */ 148 lwkt_port_t tt_msgport; /* owner msgport */ 149 uint32_t tt_tasks; /* pending tasks */ 150 uint32_t tt_running_tasks; /* running tasks */ 151 uint32_t tt_prev_tasks; /* prev pending tasks (debug) */ 152 }; 153 154 struct tcp_callout { 155 struct callout tc_callout; 156 uint32_t tc_task; /* callout's task id */ 157 }; 158 159 extern int tcp_keepinit; /* time to establish connection */ 160 extern int tcp_keepidle; /* time before keepalive probes begin */ 161 extern int tcp_keepintvl; /* time between keepalive probes */ 162 extern int tcp_keepcnt; /* maximum number of keepalive probes */ 163 extern int tcp_delacktime; /* time before sending a delayed ACK */ 164 extern int tcp_maxpersistidle; 165 extern int tcp_rexmit_min; 166 extern int tcp_rexmit_slop; 167 extern int tcp_msl; 168 extern int tcp_ttl; /* time to live for TCP segs */ 169 extern int tcp_backoff[]; /* rxt backoff for data */ 170 extern int tcp_syn_backoff[]; /* rxt backoff for SYN */ 171 extern int tcp_syn_backoff_low[]; /* rxt backoff for SYN w/ RFC6298 */ 172 173 void tcp_timer_2msl(void *xtp); 174 void tcp_timer_keep(void *xtp); 175 void tcp_timer_persist(void *xtp); 176 void tcp_timer_rexmt(void *xtp); 177 void tcp_timer_delack(void *xtp); 178 void tcp_inittimers(struct tcpcb *); 179 180 struct lwkt_port; 181 void tcp_create_timermsg(struct tcpcb *, struct lwkt_port *); 182 void tcp_destroy_timermsg(struct tcpcb *); 183 184 #endif /* _KERNEL */ 185 186 #endif /* !_NETINET_TCP_TIMER_H_ */ 187