| /* gprs_codel.h |
| * |
| * This is an implementation of the CoDel algorithm based on the reference |
| * pseudocode (see http://queue.acm.org/appendices/codel.html). |
| * Instead of abstracting the queue itself, the following implementation |
| * provides a time stamp based automaton. The main work is done by a single |
| * decision function which updates the state and tells whether to pass or to |
| * drop a packet after it has been taken from the queue. |
| * |
| * Copyright (C) 2015 by Sysmocom s.f.m.c. GmbH |
| * Author: Jacob Erlbeck <jerlbeck@sysmocom.de> |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License |
| * as published by the Free Software Foundation; either version 2 |
| * of the License, or (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| */ |
| |
| #pragma once |
| |
| #include <time.h> |
| |
| /* Spec default values */ |
| #define GPRS_CODEL_DEFAULT_INTERVAL_MS 100 |
| #define GPRS_CODEL_DEFAULT_MAXPACKET 512 |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| |
| struct gprs_codel { |
| int dropping; |
| unsigned count; |
| struct timespec first_above_time; |
| struct timespec drop_next; |
| struct timespec target; |
| struct timespec interval; |
| unsigned maxpacket; |
| }; |
| |
| /*! |
| * \brief Decide about packet drop and update CoDel state |
| * |
| * This function takes timing information and decides whether the packet in |
| * question should be dropped in order to keep related queue in a 'good' state. |
| * The function is meant to be called when the packet is dequeued. |
| * |
| * The CoDel state is updated by this function. |
| * |
| * \param state A pointer to the CoDel state of this queue |
| * \param recv The time when the packet has entered the queue, |
| * use NULL if dequeueing was not possible because the queue is |
| * empty |
| * \param now The current (dequeueing) time |
| * \param bytes The number of bytes currently stored in the queue (-1 if |
| * unknown) |
| * |
| * \return != 0 if the packet should be dropped, 0 otherwise |
| */ |
| int gprs_codel_control(struct gprs_codel *state, const struct timespec *recv, |
| const struct timespec *now, int bytes); |
| |
| /*! |
| * \brief Initialise CoDel state |
| * |
| * This function initialises the CoDel state object. It sets the interval time |
| * to the default value (GPRS_CODEL_DEFAULT_INTERVAL_MS). |
| * |
| * \param state A pointer to the CoDel state of this queue |
| */ |
| void gprs_codel_init(struct gprs_codel *state); |
| |
| /*! |
| * \brief Set interval time |
| * |
| * This function changes the interval time. |
| * The target time is derived from the interval time as proposed in the spec |
| * (5% of interval time). |
| * |
| * \param state A pointer to the CoDel state of this queue |
| * \param interval_ms The initial interval in ms to be used (<= 0 selects the |
| * default value) |
| */ |
| void gprs_codel_set_interval(struct gprs_codel *state, int interval_ms); |
| |
| /*! |
| * \brief Set max packet size |
| * |
| * This function changes the maxpacket value. If no more than this number of |
| * bytes are still stored in the queue, no dropping will be done. |
| * |
| * \param state A pointer to the CoDel state of this queue |
| * \param maxpacket The value in bytes |
| */ |
| void gprs_codel_set_maxpacket(struct gprs_codel *state, int maxpacket); |
| |
| #ifdef __cplusplus |
| } |
| #endif |