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extras/timekeeping -- provide POSIX-like interface (#578)

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Jeff Kletsky 2018-02-28 16:01:40 -08:00 • committed by Ruslan V. Uss
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commit 33082ba2c9
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extras/timekeeping/tests/sntp-run/sntp_impl.c Normal file
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/*
* Test implementation of callback for LWIP SNTP
*
* Production code would likely decide how to handle
* various magnitude changes, be robust to outliers,
* and be brisk about it all
*/
/*-
* Copyright (c) 2018, Jeff Kletsky
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of the copyright holder nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/time.h>
#include <stdlib.h>
#include "sntp_impl.h"
/**********************************************************
* IMPORTANT: THIS IS A TEST HARNESS, NOT PRODUCTION CODE *
**********************************************************
*
* Spikes in delay of over 200 ms have been observed in testing.
* Such spikes would likely cause both a forward and a backward jump
* in time using this simplistic approach. Increasing the threshold to,
* for example, 250 ms would require 2000 * 250 ms = 500 sec ~ 10 min
* for the time to slew back after a "bad set" or series of "bad" packets.
*
* PRODUCTION CODE SHOULD USE AN APPLICATION-APPROPRIATE CLOCK DISCIPLINE
*/
#ifndef SNTP_IMPL_STEP_THRESHOLD
#define SNTP_IMPL_STEP_THRESHOLD 125000
#endif
#define TV2LD(TV) ((long double)TV.tv_sec + (long double)TV.tv_usec * 1.e-6)
#include <stdio.h>
/*
* Called by lwip/apps/sntp.c through
* #define SNTP_SET_SYSTEM_TIME_US(S, F) sntp_impl_set_system_time_us(S, F)
* u32_t matches lwip/apps/sntp.c
*/
void
sntp_impl_set_system_time_us(uint32_t secs, uint32_t us) {
struct timeval new;
struct timeval old;
struct timeval dt;
#ifdef TIMEKEEPING_SET_AND_MEASURE_ONLY
static long double time_has_been_set_at;
#endif
gettimeofday(&old, NULL);
new.tv_sec = secs;
new.tv_usec = us;
timersub(&new, &old, &dt);
#ifdef TIMEKEEPING_SET_AND_MEASURE_ONLY
if (time_has_been_set_at == 0) {
settimeofday(&new, NULL);
time_has_been_set_at = TV2LD(new);
}
printf("SNTP: %20.6Lf delta: %10.3Lf ms %3.1Lf ppm\n",
TV2LD(new), TV2LD(dt)*1e3, (TV2LD(dt) / (TV2LD(new) - time_has_been_set_at))*1e6);
#else /* Normal operation */
if (secs || abs(us) > SNTP_IMPL_STEP_THRESHOLD) {
settimeofday(&new, NULL);
} else {
adjtime(&dt, NULL);
}
printf("SNTP: %20.6Lf delta: %7.3Lf ms\n",
TV2LD(new), TV2LD(dt)*1e3);
#endif
}