108 lines
3.6 KiB
C
108 lines
3.6 KiB
C
/*
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* util/rtt.h - UDP round trip time estimator for resend timeouts.
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*
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* Copyright (c) 2007, NLnet Labs. All rights reserved.
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*
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* This software is open source.
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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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*
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* Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* Neither the name of the NLNET LABS nor the names of its contributors may
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* be used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* \file
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*
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* This file contains a data type and functions to help estimate good
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* round trip times for UDP resend timeout values.
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*/
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#ifndef UTIL_RTT_H
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#define UTIL_RTT_H
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/**
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* RTT information. Keeps packet Round Trip Time.
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*/
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struct rtt_info {
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/** smoothed rtt estimator, in milliseconds */
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int srtt;
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/** smoothed mean deviation, in milliseconds */
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int rttvar;
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/** current RTO in use, in milliseconds */
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int rto;
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};
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/** min retransmit timeout value, in milliseconds */
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extern int RTT_MIN_TIMEOUT;
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/** max retransmit timeout value, in milliseconds */
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#define RTT_MAX_TIMEOUT 120000
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/**
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* Initialize RTT estimators.
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* @param rtt: The structure. Caller is responsible for allocation of it.
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*/
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void rtt_init(struct rtt_info* rtt);
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/**
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* Get timeout to use for sending a UDP packet.
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* @param rtt: round trip statistics structure.
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* @return: timeout to use in milliseconds. Relative time value.
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*/
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int rtt_timeout(const struct rtt_info* rtt);
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/**
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* Get unclamped timeout to use for server selection.
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* Recent timeouts are reflected in the returned value.
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* @param rtt: round trip statistics structure.
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* @return: value to use in milliseconds.
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*/
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int rtt_unclamped(const struct rtt_info* rtt);
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/**
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* RTT for valid responses. Without timeouts.
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* @param rtt: round trip statistics structure.
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* @return: value in msec.
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*/
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int rtt_notimeout(const struct rtt_info* rtt);
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/**
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* Update the statistics with a new roundtrip estimate observation.
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* @param rtt: round trip statistics structure.
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* @param ms: estimate of roundtrip time in milliseconds.
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*/
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void rtt_update(struct rtt_info* rtt, int ms);
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/**
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* Update the statistics with a new timeout expired observation.
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* @param rtt: round trip statistics structure.
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* @param orig: original rtt time given for the query that timed out.
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* Used to calculate the maximum responsible backed off time that
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* can reasonably be applied.
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*/
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void rtt_lost(struct rtt_info* rtt, int orig);
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#endif /* UTIL_RTT_H */
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