[mle] prioritize equivalent pending dataset update over MLE announce …

…(#10631)

Avoid processing announce messages with equivalent data that is stored
in a pending dataset update.

src/core/meshcop/dataset_manager.cpp

@@ -885,6 +885,35 @@ PendingDatasetManager::PendingDatasetManager(Instance &aInstance)
 {
 }
 
+Error PendingDatasetManager::ReadActiveTimestamp(Timestamp &aTimestamp) const
+{
+ Error error = kErrorNotFound;
+ Dataset dataset;
+
+ SuccessOrExit(Read(dataset));
+
+ SuccessOrExit(dataset.Read<ActiveTimestampTlv>(aTimestamp));
+ error = kErrorNone;
+
+exit:
+ return error;
+}
+
+Error PendingDatasetManager::ReadRemainingDelay(uint32_t &aRemainingDelay) const
+{
+ Error error = kErrorNone;
+ TimeMilli now = TimerMilli::GetNow();
+
+ aRemainingDelay = 0;
+
+ VerifyOrExit(mDelayTimer.IsRunning(), error = kErrorNotFound);
+ VerifyOrExit(mDelayTimer.GetFireTime() > now);
+ aRemainingDelay = mDelayTimer.GetFireTime() - now;
+
+exit:
+ return error;
+}
+
 void PendingDatasetManager::StartDelayTimer(void)
 {
  Dataset dataset;

src/core/meshcop/dataset_manager.hpp

@@ -441,6 +441,28 @@ class PendingDatasetManager : public DatasetManager, private NonCopyable
  */
  explicit PendingDatasetManager(Instance &aInstance);
 
+ /**
+ * Reads the Active Timestamp in the Pending Operational Dataset.
+ *
+ * @param[out] aTimestamp A reference to return the read timestamp.
+ *
+ * @retval kErrorNone The active timestamp was successfully fetched.
+ * @retval kErrorNotFound The pending dataset is not currently valid.
+ *
+ */
+ Error ReadActiveTimestamp(Timestamp &aTimestamp) const;
+
+ /**
+ * Reads the remaining delay time in ms.
+ *
+ * @param[out] aRemainingDelay A reference to return the remaining delay time.
+ *
+ * @retval kErrorNone The remaining delay time was successfully fetched.
+ * @retval kErrorNotFound The pending dataset is not currently valid.
+ *
+ */
+ Error ReadRemainingDelay(uint32_t &aRemainingDelay) const;
+
 #if OPENTHREAD_FTD
  /**
  * Starts the Leader functions for maintaining the Active Operational Dataset.

src/core/thread/mle.cpp

@@ -3663,6 +3663,7 @@ void Mle::HandleAnnounce(RxInfo &aRxInfo)
  Error error = kErrorNone;
  ChannelTlvValue channelTlvValue;
  MeshCoP::Timestamp timestamp;
+ MeshCoP::Timestamp pendingActiveTimestamp;
  uint8_t channel;
  uint16_t panId;
  bool isFromOrphan;
@@ -3707,6 +3708,24 @@ void Mle::HandleAnnounce(RxInfo &aRxInfo)
  VerifyOrExit(!channelAndPanIdMatch);
  }
 
+ if (Get<MeshCoP::PendingDatasetManager>().ReadActiveTimestamp(pendingActiveTimestamp) == kErrorNone)
+ {
+ // Ignore the Announce and take no action, if a pending
+ // dataset exists with an equal or more recent timestamp,
+ // and it will be applied soon.
+
+ if (pendingActiveTimestamp >= timestamp)
+ {
+ uint32_t remainingDelay;
+
+ if ((Get<MeshCoP::PendingDatasetManager>().ReadRemainingDelay(remainingDelay) == kErrorNone) &&
+ (remainingDelay < kAnnounceBackoffForPendingDataset))
+ {
+ ExitNow();
+ }
+ }
+ }
+
  if (mAttachState == kAttachStateProcessAnnounce)
  {
  VerifyOrExit(mAlternateTimestamp < timestamp.GetSeconds());

src/core/thread/mle.hpp

@@ -811,6 +811,7 @@ class Mle : public InstanceLocator, private NonCopyable
  static constexpr uint32_t kMulticastRetxDelay = 5000; // Base delay for MLE multicast retx
  static constexpr uint32_t kMulticastRetxDelayMin = kMulticastRetxDelay * 9 / 10; // 0.9 * base delay
  static constexpr uint32_t kMulticastRetxDelayMax = kMulticastRetxDelay * 11 / 10; // 1.1 * base delay
+ static constexpr uint32_t kAnnounceBackoffForPendingDataset = 60000; // Max delay left to block Announce processing.
 
  static constexpr uint8_t kMaxTxCount = 3; // Max tx count for MLE message
  static constexpr uint8_t kMaxCriticalTxCount = 6; // Max tx count for critical MLE message