1238106Sdes/* 2238106Sdes * util/rtt.h - UDP round trip time estimator for resend timeouts. 3238106Sdes * 4238106Sdes * Copyright (c) 2007, NLnet Labs. All rights reserved. 5238106Sdes * 6238106Sdes * This software is open source. 7238106Sdes * 8238106Sdes * Redistribution and use in source and binary forms, with or without 9238106Sdes * modification, are permitted provided that the following conditions 10238106Sdes * are met: 11238106Sdes * 12238106Sdes * Redistributions of source code must retain the above copyright notice, 13238106Sdes * this list of conditions and the following disclaimer. 14238106Sdes * 15238106Sdes * Redistributions in binary form must reproduce the above copyright notice, 16238106Sdes * this list of conditions and the following disclaimer in the documentation 17238106Sdes * and/or other materials provided with the distribution. 18238106Sdes * 19238106Sdes * Neither the name of the NLNET LABS nor the names of its contributors may 20238106Sdes * be used to endorse or promote products derived from this software without 21238106Sdes * specific prior written permission. 22238106Sdes * 23238106Sdes * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 24269257Sdes * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 25269257Sdes * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 26269257Sdes * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 27269257Sdes * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28269257Sdes * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED 29269257Sdes * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 30269257Sdes * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 31269257Sdes * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 32269257Sdes * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 33269257Sdes * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34238106Sdes */ 35238106Sdes 36238106Sdes/** 37238106Sdes * \file 38238106Sdes * 39238106Sdes * This file contains a data type and functions to help estimate good 40238106Sdes * round trip times for UDP resend timeout values. 41238106Sdes */ 42238106Sdes 43238106Sdes#ifndef UTIL_RTT_H 44238106Sdes#define UTIL_RTT_H 45238106Sdes 46238106Sdes/** 47238106Sdes * RTT information. Keeps packet Round Trip Time. 48238106Sdes */ 49238106Sdesstruct rtt_info { 50238106Sdes /** smoothed rtt estimator, in milliseconds */ 51238106Sdes int srtt; 52238106Sdes /** smoothed mean deviation, in milliseconds */ 53238106Sdes int rttvar; 54238106Sdes /** current RTO in use, in milliseconds */ 55238106Sdes int rto; 56238106Sdes}; 57238106Sdes 58238106Sdes/** min retransmit timeout value, in milliseconds */ 59285206Sdesextern int RTT_MIN_TIMEOUT; 60238106Sdes/** max retransmit timeout value, in milliseconds */ 61238106Sdes#define RTT_MAX_TIMEOUT 120000 62238106Sdes 63238106Sdes/** 64238106Sdes * Initialize RTT estimators. 65238106Sdes * @param rtt: The structure. Caller is responsible for allocation of it. 66238106Sdes */ 67238106Sdesvoid rtt_init(struct rtt_info* rtt); 68238106Sdes 69238106Sdes/** 70238106Sdes * Get timeout to use for sending a UDP packet. 71238106Sdes * @param rtt: round trip statistics structure. 72238106Sdes * @return: timeout to use in milliseconds. Relative time value. 73238106Sdes */ 74238106Sdesint rtt_timeout(const struct rtt_info* rtt); 75238106Sdes 76238106Sdes/** 77238106Sdes * Get unclamped timeout to use for server selection. 78238106Sdes * Recent timeouts are reflected in the returned value. 79238106Sdes * @param rtt: round trip statistics structure. 80238106Sdes * @return: value to use in milliseconds. 81238106Sdes */ 82238106Sdesint rtt_unclamped(const struct rtt_info* rtt); 83238106Sdes 84238106Sdes/** 85238106Sdes * RTT for valid responses. Without timeouts. 86238106Sdes * @param rtt: round trip statistics structure. 87238106Sdes * @return: value in msec. 88238106Sdes */ 89238106Sdesint rtt_notimeout(const struct rtt_info* rtt); 90238106Sdes 91238106Sdes/** 92238106Sdes * Update the statistics with a new roundtrip estimate observation. 93238106Sdes * @param rtt: round trip statistics structure. 94238106Sdes * @param ms: estimate of roundtrip time in milliseconds. 95238106Sdes */ 96238106Sdesvoid rtt_update(struct rtt_info* rtt, int ms); 97238106Sdes 98238106Sdes/** 99238106Sdes * Update the statistics with a new timout expired observation. 100238106Sdes * @param rtt: round trip statistics structure. 101238106Sdes * @param orig: original rtt time given for the query that timed out. 102238106Sdes * Used to calculate the maximum responsible backed off time that 103238106Sdes * can reasonably be applied. 104238106Sdes */ 105238106Sdesvoid rtt_lost(struct rtt_info* rtt, int orig); 106238106Sdes 107238106Sdes#endif /* UTIL_RTT_H */ 108