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/*
* util/rtt.h - UDP round trip time estimator for resend timeouts.
*
* Copyright (c) 2007, NLnet Labs. All rights reserved.
*
* This software is open source.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the NLNET LABS nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* \file
*
* This file contains a data type and functions to help estimate good
* round trip times for UDP resend timeout values.
*/
#ifndef UTIL_RTT_H
#define UTIL_RTT_H
/**
* RTT information. Keeps packet Round Trip Time.
*/
struct rtt_info {
/** smoothed rtt estimator, in milliseconds */
int srtt;
/** smoothed mean deviation, in milliseconds */
int rttvar;
/** current RTO in use, in milliseconds */
int rto;
};
/** min retransmit timeout value, in milliseconds */
#define RTT_MIN_TIMEOUT 50
/** max retransmit timeout value, in milliseconds */
#define RTT_MAX_TIMEOUT 120000
/**
* Initialize RTT estimators.
* @param rtt: The structure. Caller is responsible for allocation of it.
*/
void rtt_init(struct rtt_info* rtt);
/**
* Get timeout to use for sending a UDP packet.
* @param rtt: round trip statistics structure.
* @return: timeout to use in milliseconds. Relative time value.
*/
int rtt_timeout(const struct rtt_info* rtt);
/**
* Get unclamped timeout to use for server selection.
* Recent timeouts are reflected in the returned value.
* @param rtt: round trip statistics structure.
* @return: value to use in milliseconds.
*/
int rtt_unclamped(const struct rtt_info* rtt);
/**
* RTT for valid responses. Without timeouts.
* @param rtt: round trip statistics structure.
* @return: value in msec.
*/
int rtt_notimeout(const struct rtt_info* rtt);
/**
* Update the statistics with a new roundtrip estimate observation.
* @param rtt: round trip statistics structure.
* @param ms: estimate of roundtrip time in milliseconds.
*/
void rtt_update(struct rtt_info* rtt, int ms);
/**
* Update the statistics with a new timout expired observation.
* @param rtt: round trip statistics structure.
* @param orig: original rtt time given for the query that timed out.
* Used to calculate the maximum responsible backed off time that
* can reasonably be applied.
*/
void rtt_lost(struct rtt_info* rtt, int orig);
#endif /* UTIL_RTT_H */
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