[mac] enable broadcast message retransmission in MAC layer (#2815)

src/core/mac/mac.cpp

@@ -179,6 +179,7 @@ Mac::Mac(Instance &aInstance)
     , mDataSequence(Random::GetUint8())
     , mCsmaAttempts(0)
     , mTransmitAttempts(0)
+    , mBroadcastTransmitCount(0)
     , mScanChannelMask()
     , mScanDuration(0)
     , mScanChannel(OT_RADIO_CHANNEL_MIN)
@@ -1154,7 +1155,7 @@ void Mac::BeginTransmit(void)
         sendFrame.SetCsmaCaEnabled(true);
     }
 
-    if (mCsmaAttempts == 0 && mTransmitAttempts == 0)
+    if (mCsmaAttempts == 0 && mTransmitAttempts == 0 && mBroadcastTransmitCount == 0)
     {
         switch (mOperation)
         {
@@ -1418,15 +1419,6 @@ void Mac::HandleTransmitDone(otRadioFrame *aFrame, otRadioFrame *aAckFrame, otEr
         mCounters.mTxErrBusyChannel++;
     }
 
-    if (dstAddr.IsBroadcast())
-    {
-        mCounters.mTxBroadcast++;
-    }
-    else
-    {
-        mCounters.mTxUnicast++;
-    }
-
     if (ackRequested)
     {
         mCounters.mTxAckRequested++;
@@ -1441,6 +1433,25 @@ void Mac::HandleTransmitDone(otRadioFrame *aFrame, otRadioFrame *aAckFrame, otEr
         mCounters.mTxNoAckRequested++;
     }
 
+    if (dstAddr.IsBroadcast())
+    {
+        mCounters.mTxBroadcast++;
+
+        // Determine whether to re-transmit the broadcast frame.
+        mBroadcastTransmitCount++;
+        if (mBroadcastTransmitCount < kTxNumBcast)
+        {
+            StartCsmaBackoff();
+            ExitNow();
+        }
+
+        mBroadcastTransmitCount = 0;
+    }
+    else
+    {
+        mCounters.mTxUnicast++;
+    }
+
     // Determine next action based on current operation.
 
     switch (mOperation)

src/core/mac/mac.hpp

@@ -96,6 +96,12 @@ enum
      *
      */
     kIndirectFrameMacTxAttempts = OPENTHREAD_CONFIG_MAX_TX_ATTEMPTS_INDIRECT_PER_POLL,
+
+    /**
+     * The transmit number of a broadcast frame in MAC layer.
+     *
+     */
+    kTxNumBcast = OPENTHREAD_CONFIG_TX_NUM_BCAST,
 };
 
 /**
@@ -1055,6 +1061,7 @@ private:
     uint8_t mDataSequence;
     uint8_t mCsmaAttempts;
     uint8_t mTransmitAttempts;
+    uint8_t mBroadcastTransmitCount;
 
     ChannelMask mScanChannelMask;
     uint16_t    mScanDuration;

src/core/openthread-core-default-config.h

@@ -159,6 +159,19 @@
 #define OPENTHREAD_CONFIG_MAX_TX_ATTEMPTS_INDIRECT_POLLS 4
 #endif
 
+/**
+ * @def OPENTHREAD_CONFIG_TX_NUM_BCAST
+ *
+ * The number of times each IEEE 802.15.4 broadcast frame is transmitted.
+ *
+ * The minimum value is 1. Values larger than 1 may improve broadcast reliability by increasing redundancy, but may also
+ * increase congestion.
+ *
+ */
+#ifndef OPENTHREAD_CONFIG_TX_NUM_BCAST
+#define OPENTHREAD_CONFIG_TX_NUM_BCAST 1
+#endif
+
 /**
  * @def OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE
  *

src/core/thread/mle_router.cpp

@@ -1637,6 +1637,10 @@ otError MleRouter::HandleParentRequest(const Message &aMessage, const Ip6::Messa
         }
 #endif
     }
+    else if ((TimerMilli::GetNow() - child->GetLastHeard()) < kParentRequestRouterTimeout)
+    {
+        ExitNow(error = OT_ERROR_DUPLICATED);
+    }
 
     if (!child->IsStateValidOrRestoring())
     {