Osmocom Packet control Unit (PCU): Network-side GPRS (RLC/MAC); BTS- or BSC-colocated https://osmocom.org/projects/osmopcu
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
osmo-pcu/src/gprs_codel.h

108 lines
3.5 KiB

/* 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