blob: e9b2f0ee3baa5db935e235895262f932aea587be [file] [log] [blame]
/*
* tc_red.c RED maintanance routines.
*
* 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.
*
* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include <fcntl.h>
#include <math.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include "tc_core.h"
#include "tc_red.h"
/*
Plog = log(prob/(qmax - qmin))
*/
int tc_red_eval_P(unsigned int qmin, unsigned int qmax, double prob)
{
int i = qmax - qmin;
if (i <= 0)
return -1;
prob /= i;
for (i = 0; i < 32; i++) {
if (prob > 1.0)
break;
prob *= 2;
}
if (i >= 32)
return -1;
return i;
}
/*
burst + 1 - qmin/avpkt < (1-(1-W)^burst)/W
*/
int tc_red_eval_ewma(unsigned int qmin, unsigned int burst, unsigned int avpkt)
{
int wlog = 1;
double W = 0.5;
double a = (double)burst + 1 - (double)qmin/avpkt;
if (a < 1.0) {
fprintf(stderr, "tc_red_eval_ewma() burst %u is too small ? Try burst %u\n",
burst, 1 + qmin/avpkt);
return -1;
}
for (wlog = 1; wlog < 32; wlog++, W /= 2) {
if (a <= (1 - pow(1-W, burst))/W)
return wlog;
}
return -1;
}
/*
Stab[t>>Scell_log] = -log(1-W) * t/xmit_time
*/
int tc_red_eval_idle_damping(int Wlog, unsigned int avpkt, unsigned int bps, __u8 *sbuf)
{
double xmit_time = tc_calc_xmittime(bps, avpkt);
double lW = -log(1.0 - 1.0/(1<<Wlog))/xmit_time;
double maxtime = 31/lW;
int clog;
int i;
for (clog = 0; clog < 32; clog++) {
if (maxtime/(1<<clog) < 512)
break;
}
if (clog >= 32)
return -1;
sbuf[0] = 0;
for (i = 1; i < 255; i++) {
sbuf[i] = (i<<clog)*lW;
if (sbuf[i] > 31)
sbuf[i] = 31;
}
sbuf[255] = 31;
return clog;
}