[spinel] drop received frames between RCP disable and reset (#9793)

Signed-off-by: Ashishkumar Vara <[email protected]>

src/lib/spinel/multi_frame_buffer.hpp

@@ -371,7 +371,7 @@ public:
 
         aFrame = (aFrame == nullptr) ? mBuffer : aFrame + aLength;
 
-        if (aFrame != mWriteFrameStart)
+        if (HasSavedFrame() && (aFrame != mWriteFrameStart))
         {
             uint16_t totalLength = LittleEndian::ReadUint16(aFrame + kHeaderTotalLengthOffset);
             uint16_t skipLength  = LittleEndian::ReadUint16(aFrame + kHeaderSkipLengthOffset);

src/lib/spinel/radio_spinel.cpp

@@ -670,6 +670,9 @@ void RadioSpinel::HandleValueIs(spinel_prop_key_t aKey, const uint8_t *aBuffer,
                 ExitNow();
             }
 
+            // this clear is necessary in case the RCP has sent messages between disable and reset
+            mRxFrameBuffer.Clear();
+
             LogInfo("RCP reset: %s", spinel_status_to_cstr(status));
             sIsReady = true;
         }

src/lib/spinel/spinel_encoder.cpp

@@ -291,5 +291,7 @@ exit:
     return error;
 }
 
+void Encoder::ClearNcpBuffer(void) { mNcpBuffer.Clear(); }
+
 } // namespace Spinel
 } // namespace ot

src/lib/spinel/spinel_encoder.hpp

@@ -676,6 +676,12 @@ public:
      */
     otError ResetToSaved(void);
 
+    /**
+     * Clear NCP buffer on reset command.
+     *
+     */
+    void ClearNcpBuffer(void);
+
 private:
     enum
     {

src/ncp/ncp_base.cpp

@@ -1285,6 +1285,8 @@ otError NcpBase::CommandHandler_RESET(uint8_t aHeader)
 
         ResetCounters();
 
+        mEncoder.ClearNcpBuffer();
+
         SuccessOrAssert(error = WriteLastStatusFrame(SPINEL_HEADER_FLAG | SPINEL_HEADER_TX_NOTIFICATION_IID,
                                                      SPINEL_STATUS_RESET_POWER_ON));
     }