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