/*
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* tc_red.c RED maintanance routines.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <syslog.h>
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#include <fcntl.h>
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#include <math.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <string.h>
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#include "tc_core.h"
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#include "tc_red.h"
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/*
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Plog = log(prob/(qmax - qmin))
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*/
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int tc_red_eval_P(unsigned int qmin, unsigned int qmax, double prob)
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{
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int i = qmax - qmin;
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if (i <= 0)
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return -1;
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prob /= i;
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for (i = 0; i < 32; i++) {
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if (prob > 1.0)
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break;
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prob *= 2;
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}
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if (i >= 32)
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return -1;
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return i;
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}
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/*
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burst + 1 - qmin/avpkt < (1-(1-W)^burst)/W
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*/
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int tc_red_eval_ewma(unsigned int qmin, unsigned int burst, unsigned int avpkt)
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{
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int wlog = 1;
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double W = 0.5;
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double a = (double)burst + 1 - (double)qmin/avpkt;
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if (a < 1.0) {
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fprintf(stderr, "tc_red_eval_ewma() burst %u is too small ? Try burst %u\n",
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burst, 1 + qmin/avpkt);
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return -1;
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}
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for (wlog = 1; wlog < 32; wlog++, W /= 2) {
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if (a <= (1 - pow(1-W, burst))/W)
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return wlog;
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}
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return -1;
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}
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/*
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Stab[t>>Scell_log] = -log(1-W) * t/xmit_time
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*/
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int tc_red_eval_idle_damping(int Wlog, unsigned int avpkt, unsigned int bps, __u8 *sbuf)
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{
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double xmit_time = tc_calc_xmittime(bps, avpkt);
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double lW = -log(1.0 - 1.0/(1<<Wlog))/xmit_time;
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double maxtime = 31/lW;
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int clog;
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int i;
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for (clog = 0; clog < 32; clog++) {
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if (maxtime/(1<<clog) < 512)
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break;
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}
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if (clog >= 32)
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return -1;
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sbuf[0] = 0;
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for (i = 1; i < 255; i++) {
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sbuf[i] = (i<<clog)*lW;
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if (sbuf[i] > 31)
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sbuf[i] = 31;
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}
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sbuf[255] = 31;
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return clog;
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}
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