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 /** 34 * samkumar: The FreeBSD Operating System uses its callout subsystem to 35 * implement TCP timers. I've removed the relevant definitions/declarations 36 * below, since TCPlp relies on the host system to implement TCP timers. To 37 * save memory, I've removed some configurability (e.g., per-TCB keepalive 38 * parameters) and global statistics (e.g. tcp_keepcnt). 39 */ 40 41 #ifndef TCPLP_NETINET_TCP_TIMER_H_ 42 #define TCPLP_NETINET_TCP_TIMER_H_ 43 44 #include "tcp_var.h" 45 46 /* 47 * The TCPT_REXMT timer is used to force retransmissions. 48 * The TCP has the TCPT_REXMT timer set whenever segments 49 * have been sent for which ACKs are expected but not yet 50 * received. If an ACK is received which advances tp->snd_una, 51 * then the retransmit timer is cleared (if there are no more 52 * outstanding segments) or reset to the base value (if there 53 * are more ACKs expected). Whenever the retransmit timer goes off, 54 * we retransmit one unacknowledged segment, and do a backoff 55 * on the retransmit timer. 56 * 57 * The TCPT_PERSIST timer is used to keep window size information 58 * flowing even if the window goes shut. If all previous transmissions 59 * have been acknowledged (so that there are no retransmissions in progress), 60 * and the window is too small to bother sending anything, then we start 61 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 62 * we go to transmit state. Otherwise, at intervals send a single byte 63 * into the peer's window to force him to update our window information. 64 * We do this at most as often as TCPT_PERSMIN time intervals, 65 * but no more frequently than the current estimate of round-trip 66 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 67 * a window update from the peer. 68 * 69 * The TCPT_KEEP timer is used to keep connections alive. If an 70 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 71 * but not yet established, then we drop the connection. Once the connection 72 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 73 * (and keepalives have been enabled on the socket), we begin to probe 74 * the connection. We force the peer to send us a segment by sending: 75 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 76 * This segment is (deliberately) outside the window, and should elicit 77 * an ack segment in response from the peer. If, despite the TCPT_KEEP 78 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 79 * amount of time probing, then we drop the connection. 80 */ 81 82 #define TT_DELACK 0x0001 83 #define TT_REXMT 0x0002 84 #define TT_PERSIST 0x0004 85 #define TT_KEEP 0x0008 86 #define TT_2MSL 0x0010 87 88 /* 89 * Time constants. 90 */ 91 #define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */ 92 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 93 if 0, no idea yet */ 94 #define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */ 95 96 #define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */ 97 #define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ 98 99 #define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ 100 #define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ 101 #define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ 102 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 103 104 #define TCPTV_FINWAIT2_TIMEOUT (60*hz) /* FIN_WAIT_2 timeout if no receiver */ 105 106 /* 107 * Minimum retransmit timer is 3 ticks, for algorithmic stability. 108 * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with 109 * the expected worst-case processing variances by the kernels 110 * representing the end points. Such variances do not always show 111 * up in the srtt because the timestamp is often calculated at 112 * the interface rather then at the TCP layer. This value is 113 * typically 50ms. However, it is also possible that delayed 114 * acks (typically 100ms) could create issues so we set the slop 115 * to 200ms to try to cover it. Note that, properly speaking, 116 * delayed-acks should not create a major issue for interactive 117 * environments which 'P'ush the last segment, at least as 118 * long as implementations do the required 'at least one ack 119 * for every two packets' for the non-interactive streaming case. 120 * (maybe the RTO calculation should use 2*RTT instead of RTT 121 * to handle the ack-every-other-packet case). 122 * 123 * The prior minimum of 1*hz (1 second) badly breaks throughput on any 124 * networks faster then a modem that has minor (e.g. 1%) packet loss. 125 */ 126 #define TCPTV_MIN ( hz/33 ) /* minimum allowable value */ 127 #define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */ 128 #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 129 130 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 131 132 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 133 134 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 135 136 #define TCPTV_DELACK ( hz/10 ) /* 100ms timeout */ 137 138 #ifdef TCPTIMERS 139 static const char *tcptimers[] = 140 { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" }; 141 #endif 142 143 int tcp_timer_active(struct tcpcb *tp, uint32_t timer_type); 144 void tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, uint32_t delta); 145 void tcp_cancel_timers(struct tcpcb* tp); 146 147 /* I moved the definition of TCPT_RANGESET to tcp_const.h. */ 148 149 static const int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 150 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 151 152 static const int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 153 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 }; 154 155 static const int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */ 156 157 /* 158 * samkumar: Changed return value to int to indicate whether connection was 159 * dropped or not. 160 */ 161 int tcp_timer_delack(struct tcpcb* tp); 162 int tcp_timer_keep(struct tcpcb* tp); 163 int tcp_timer_persist(struct tcpcb* tp); 164 int tcp_timer_2msl(struct tcpcb* tp); 165 int tcp_timer_rexmt(struct tcpcb *tp); 166 int tcp_timer_active(struct tcpcb *tp, uint32_t timer_type); 167 168 /* 169 * samkumar: Modified to use default keepalive parameters, since we removed 170 * the fields from tcpcb that allow them to be set on a per-connection basis. 171 */ 172 #define TP_KEEPINIT(tp) (/*(tp)->t_keepinit ? (tp)->t_keepinit :*/ tcp_keepinit) 173 #define TP_KEEPIDLE(tp) (/*(tp)->t_keepidle ? (tp)->t_keepidle :*/ tcp_keepidle) 174 #define TP_KEEPINTVL(tp) (/*(tp)->t_keepintvl ? (tp)->t_keepintvl :*/ tcp_keepintvl) 175 #define TP_KEEPCNT(tp) (/*(tp)->t_keepcnt ? (tp)->t_keepcnt :*/ tcp_keepcnt) 176 #define TP_MAXIDLE(tp) (TP_KEEPCNT(tp) * TP_KEEPINTVL(tp)) 177 178 /* 179 * samkumar: MOVED NECESSARY EXTERN DECLARATIONS TO TCP_SUBR.C 180 * Removed timer declarations that aren't needed since timers are handled 181 * by the host system (in this case, OpenThread), in TCPlp. 182 */ 183 184 #endif /* !_NETINET_TCP_TIMER_H_ */ 185