163 lines
7.1 KiB
C
163 lines
7.1 KiB
C
/*
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* Copyright (c) 1982, 1986, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
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* $FreeBSD$
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*/
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#ifndef _NETINET_TCP_TIMER_H_
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#define _NETINET_TCP_TIMER_H_
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/*
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* The TCPT_REXMT timer is used to force retransmissions.
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* The TCP has the TCPT_REXMT timer set whenever segments
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* have been sent for which ACKs are expected but not yet
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* received. If an ACK is received which advances tp->snd_una,
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* then the retransmit timer is cleared (if there are no more
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* outstanding segments) or reset to the base value (if there
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* are more ACKs expected). Whenever the retransmit timer goes off,
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* we retransmit one unacknowledged segment, and do a backoff
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* on the retransmit timer.
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*
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* The TCPT_PERSIST timer is used to keep window size information
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* flowing even if the window goes shut. If all previous transmissions
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* have been acknowledged (so that there are no retransmissions in progress),
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* and the window is too small to bother sending anything, then we start
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* the TCPT_PERSIST timer. When it expires, if the window is nonzero,
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* we go to transmit state. Otherwise, at intervals send a single byte
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* into the peer's window to force him to update our window information.
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* We do this at most as often as TCPT_PERSMIN time intervals,
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* but no more frequently than the current estimate of round-trip
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* packet time. The TCPT_PERSIST timer is cleared whenever we receive
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* a window update from the peer.
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*
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* The TCPT_KEEP timer is used to keep connections alive. If an
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* connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
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* but not yet established, then we drop the connection. Once the connection
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* is established, if the connection is idle for TCPTV_KEEP_IDLE time
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* (and keepalives have been enabled on the socket), we begin to probe
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* the connection. We force the peer to send us a segment by sending:
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* <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
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* This segment is (deliberately) outside the window, and should elicit
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* an ack segment in response from the peer. If, despite the TCPT_KEEP
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* initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
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* amount of time probing, then we drop the connection.
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*/
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/*
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* Time constants.
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*/
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#define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */
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#define TCPTV_SRTTBASE 0 /* base roundtrip time;
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if 0, no idea yet */
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#define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */
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#define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */
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#define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */
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#define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */
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#define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */
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#define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */
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#define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */
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#define TCPTV_KEEPCNT 8 /* max probes before drop */
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/*
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* Minimum retransmit timer is 3 ticks, for algorithmic stability.
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* TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with
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* the expected worst-case processing variances by the kernels
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* representing the end points. Such variances do not always show
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* up in the srtt because the timestamp is often calculated at
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* the interface rather then at the TCP layer. This value is
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* typically 50ms. However, it is also possible that delayed
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* acks (typically 100ms) could create issues so we set the slop
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* to 200ms to try to cover it. Note that, properly speaking,
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* delayed-acks should not create a major issue for interactive
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* environments which 'P'ush the last segment, at least as
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* long as implementations do the required 'at least one ack
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* for every two packets' for the non-interactive streaming case.
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* (maybe the RTO calculation should use 2*RTT instead of RTT
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* to handle the ack-every-other-packet case).
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*
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* The prior minimum of 1*hz (1 second) badly breaks throughput on any
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* networks faster then a modem that has minor (e.g. 1%) packet loss.
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*/
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#define TCPTV_MIN ( 3 ) /* minimum allowable value */
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#define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */
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#define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */
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#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */
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#define TCP_LINGERTIME 120 /* linger at most 2 minutes */
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#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
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#define TCPTV_DELACK (hz / PR_FASTHZ / 2) /* 100ms timeout */
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#ifdef TCPTIMERS
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static const char *tcptimers[] =
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{ "REXMT", "PERSIST", "KEEP", "2MSL" };
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#endif
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/*
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* Force a time value to be in a certain range.
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*/
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#define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \
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(tv) = (value) + tcp_rexmit_slop; \
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if ((u_long)(tv) < (u_long)(tvmin)) \
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(tv) = (tvmin); \
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else if ((u_long)(tv) > (u_long)(tvmax)) \
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(tv) = (tvmax); \
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} while(0)
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#ifdef _KERNEL
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extern int tcp_keepinit; /* time to establish connection */
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extern int tcp_keepidle; /* time before keepalive probes begin */
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extern int tcp_keepintvl; /* time between keepalive probes */
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extern int tcp_maxidle; /* time to drop after starting probes */
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extern int tcp_delacktime; /* time before sending a delayed ACK */
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extern int tcp_maxpersistidle;
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extern int tcp_rexmit_min;
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extern int tcp_rexmit_slop;
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extern int tcp_msl;
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extern int tcp_ttl; /* time to live for TCP segs */
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extern int tcp_backoff[];
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void tcp_timer_2msl(void *xtp);
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void tcp_timer_keep(void *xtp);
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void tcp_timer_persist(void *xtp);
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void tcp_timer_rexmt(void *xtp);
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void tcp_timer_delack(void *xtp);
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#endif /* _KERNEL */
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#endif /* !_NETINET_TCP_TIMER_H_ */
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