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https://git.kernel.org/pub/scm/network/iproute2/iproute2.git
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abf70ef494
Using a 32 bit field to represent time in nanoseconds results in a maximum value of about 4.3 seconds, which is well below many observed delays in WiFi and LTE, and barely in the ballpark for a trip past the Earth's moon, Luna. Using 64 bit time fields in nanoseconds allows us to simulate network diameters of several hundred light-years. However, only conversions to and from ns, us, ms, and seconds are provided. The iproute2 64 bit api uses signed values for time. Being able to represent positive or negative time allows us to calculate +/- deltas between, for example, the CLOCK_TAI and CLOCK_REALTIME clocks. Time related utility functions in tc_util.c are moved to lib/utils.c. Signed-off-by: Yousuk Seung <ysseung@google.com> Signed-off-by: Dave Taht <dave.taht@gmail.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David Ahern <dsahern@gmail.com>
46 lines
1.1 KiB
C
46 lines
1.1 KiB
C
/*
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* tc_core.c TC core library.
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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 <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 "utils.h"
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#include "tc_core.h"
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int tc_setup_estimator(unsigned int A, unsigned int time_const, struct tc_estimator *est)
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{
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for (est->interval = 0; est->interval <= 5; est->interval++) {
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if (A <= (1<<est->interval)*(TIME_UNITS_PER_SEC/4))
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break;
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}
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if (est->interval > 5)
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return -1;
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est->interval -= 2;
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for (est->ewma_log = 1; est->ewma_log < 32; est->ewma_log++) {
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double w = 1.0 - 1.0/(1<<est->ewma_log);
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if (A/(-log(w)) > time_const)
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break;
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}
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est->ewma_log--;
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if (est->ewma_log == 0 || est->ewma_log >= 31)
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return -1;
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return 0;
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}
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