fix(udps): publish the producer's HRT frequency so timestamps survive the hop
DATA packets timestamp with the raw value of the producer's high-resolution counter, and the wire never said how fast that counter runs. The hub divided by its own timer's frequency instead, which is only the same number while producer and hub share a machine — on x86 it is the TSC frequency and differs from model to model. Off-box, every accumulated batch was therefore laid out over the wrong span of time: the samples in it drift away from where they belong and start colliding with the next packet's, which is the "same" symptom as a stale time base even though nothing is out of order. CONFIG now carries the rate as a trailing uint64, alongside the publish-mode byte and read the same tolerant way: absent or zero means the producer did not say, and the hub falls back to its own timer as before. Anything below 1 kHz is not a high-resolution timer and is refused, so a mis-parsed payload cannot stretch a millisecond batch across seconds. The Accumulate DATA payload is unchanged, so this costs nothing per packet and the period *within* a batch is still estimated from the gap between packets. The Go, C and browser parsers already ignore trailer bytes they do not know, so they read the new CONFIG unchanged; none of them uses the HRT timestamp. Also corrects the Accumulate DATA layout in all three protocol documents: they described it as one snapshot per array signal, where it has always been one per accumulated cycle. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Martino Ferrari
co-authored by
Claude Opus 4.6
Claude Opus 4.6
parent
092fd3c775
commit
5562877c99
@@ -0,0 +1,151 @@
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/**
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* @file ConfigHrtFreqGTest.cpp
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* @brief Tests UDPSConfigHrtFrequency, which picks the tick rate used to turn
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* a producer's DATA timestamps into seconds.
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*
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* DATA packets carry the raw value of the producer's high-resolution counter.
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* Until the rate was published in CONFIG the hub divided by its own timer's
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* frequency, which is only right while the producer runs on the same host —
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* on x86 that number is the TSC frequency and differs from model to model, so
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* off-box every accumulated batch was laid out over the wrong span of time.
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*
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* The field is a trailer, so these tests pin both directions: a payload that
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* carries it must be believed, and one that stops early — an older producer —
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* must still decode against the local fallback rather than against zero.
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*
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* @copyright Copyright 2015 F4E | European Joint Undertaking for ITER and
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* the Development of Fusion Energy ('Fusion for Energy').
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* Licensed under the EUPL, Version 1.1 or - as soon they will be approved
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* by the European Commission - subsequent versions of the EUPL (the "Licence")
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* You may not use this work except in compliance with the Licence.
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* You may obtain a copy of the Licence at: http://ec.europa.eu/idabc/eupl
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*
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* @warning Unless required by applicable law or agreed to in writing,
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* software distributed under the Licence is distributed on an "AS IS"
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* basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the Licence permissions and limitations under the Licence.
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*/
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#include <gtest/gtest.h>
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#include <string.h>
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#include "UDPSourceSession.h"
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using MARTe::uint8;
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using MARTe::uint32;
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using MARTe::uint64;
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using MARTe::float64;
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using MARTe::UDPS_SIGNAL_DESC_SIZE;
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using StreamHub::UDPSConfigHrtFrequency;
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namespace {
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/** This hub's own timer rate, i.e. what the code must fall back to. */
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const float64 kLocalFreq = 1.0e9;
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/** A plausible producer rate that is deliberately not kLocalFreq. */
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const uint64 kWireFreq = 2400000000ULL;
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const uint32 kNumSigs = 2u;
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/** Offset of the CONFIG trailer that follows the publish-mode byte. */
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uint32 TrailerOffset(uint32 numSigs) {
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return 4u + (numSigs * UDPS_SIGNAL_DESC_SIZE) + 1u;
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}
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/**
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* Builds a CONFIG payload for kNumSigs signals.
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* @param withFreq Append the 8-byte HRT frequency trailer.
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* @param freq Value to append when @p withFreq.
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* @param[out] size Bytes written.
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*/
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const uint8 *BuildConfig(bool withFreq, uint64 freq, uint32 &size) {
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static uint8 buf[4u + (kNumSigs * UDPS_SIGNAL_DESC_SIZE) + 1u + 8u];
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(void) memset(buf, 0, sizeof(buf));
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(void) memcpy(buf, &kNumSigs, 4u);
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size = TrailerOffset(kNumSigs);
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if (withFreq) {
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(void) memcpy(buf + size, &freq, 8u);
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size += 8u;
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}
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return buf;
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}
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} // namespace
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/* The whole point of the field: a producer that publishes its rate is believed
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* even when the hub's own timer runs at a different one. */
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TEST(ConfigHrtFreqGTest, AdoptsThePublishedRate) {
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uint32 size = 0u;
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const uint8 *cfg = BuildConfig(true, kWireFreq, size);
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EXPECT_DOUBLE_EQ(static_cast<float64>(kWireFreq),
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UDPSConfigHrtFrequency(cfg, size, kNumSigs, kLocalFreq));
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}
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/* A producer older than the field stops after the publish-mode byte. Reading
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* past it would take whatever follows in the receive buffer as a frequency. */
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TEST(ConfigHrtFreqGTest, FallsBackWhenTheTrailerIsAbsent) {
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uint32 size = 0u;
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const uint8 *cfg = BuildConfig(false, 0u, size);
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EXPECT_DOUBLE_EQ(kLocalFreq,
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UDPSConfigHrtFrequency(cfg, size, kNumSigs, kLocalFreq));
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}
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/* A trailer cut short mid-field is not a frequency either; taking the bytes
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* that are there would assemble one out of whatever the rest of the buffer
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* holds. */
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TEST(ConfigHrtFreqGTest, FallsBackOnATruncatedTrailer) {
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uint32 size = 0u;
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const uint8 *cfg = BuildConfig(true, kWireFreq, size);
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EXPECT_DOUBLE_EQ(kLocalFreq,
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UDPSConfigHrtFrequency(cfg, size - 1u, kNumSigs,
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kLocalFreq));
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}
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/* Zero is the protocol's "I do not know my own rate". Dividing by it yields
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* infinities that propagate into every timestamp. */
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TEST(ConfigHrtFreqGTest, FallsBackOnTheUnknownSentinel) {
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uint32 size = 0u;
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const uint8 *cfg = BuildConfig(true, MARTe::UDPS_HRT_FREQUENCY_UNKNOWN,
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size);
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EXPECT_DOUBLE_EQ(kLocalFreq,
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UDPSConfigHrtFrequency(cfg, size, kNumSigs, kLocalFreq));
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}
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/* No high-resolution timer ticks slower than 1 kHz, so a value that low means
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* the payload was misread. Adopting it would stretch a millisecond batch
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* across whole seconds. */
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TEST(ConfigHrtFreqGTest, FallsBackOnAnImplausiblyLowRate) {
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uint32 size = 0u;
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const uint8 *cfg = BuildConfig(true, 999u, size);
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EXPECT_DOUBLE_EQ(kLocalFreq,
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UDPSConfigHrtFrequency(cfg, size, kNumSigs, kLocalFreq));
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}
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/* The trailer sits after the descriptors, so its offset moves with the signal
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* count; a fixed offset would read descriptor bytes on any other config. */
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TEST(ConfigHrtFreqGTest, LocatesTheTrailerAfterTheDescriptors) {
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const uint32 numSigs = 7u;
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const uint32 size = TrailerOffset(numSigs) + 8u;
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uint8 buf[4u + (7u * UDPS_SIGNAL_DESC_SIZE) + 1u + 8u];
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/* Fill the descriptor area with a byte pattern that would decode as a
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* plausible frequency if the offset were wrong. */
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(void) memset(buf, 0x11, sizeof(buf));
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(void) memcpy(buf, &numSigs, 4u);
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(void) memcpy(buf + TrailerOffset(numSigs), &kWireFreq, 8u);
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EXPECT_DOUBLE_EQ(static_cast<float64>(kWireFreq),
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UDPSConfigHrtFrequency(buf, size, numSigs, kLocalFreq));
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}
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/* A null payload must not be dereferenced: CONFIG arrives from the network. */
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TEST(ConfigHrtFreqGTest, FallsBackOnANullPayload) {
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EXPECT_DOUBLE_EQ(kLocalFreq,
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UDPSConfigHrtFrequency(NULL_PTR(const uint8 *), 1024u,
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kNumSigs, kLocalFreq));
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}
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@@ -22,7 +22,7 @@
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#
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#############################################################
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OBJSX = TriggerEngineSrc.x BinaryRecorderSrc.x SignalRingBufferGTest.x TriggerEngineGTest.x LTTBGTest.x BinaryRecorderGTest.x BoundsCheckTest.x WSServerBufferTest.x AccumDtGTest.x
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OBJSX = TriggerEngineSrc.x BinaryRecorderSrc.x SignalRingBufferGTest.x TriggerEngineGTest.x LTTBGTest.x BinaryRecorderGTest.x BoundsCheckTest.x WSServerBufferTest.x AccumDtGTest.x ConfigHrtFreqGTest.x
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PACKAGE=Applications
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ROOT_DIR=../../..
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