Issue(#74): Drop frames with a downlink counter difference greater or equal to MAX_FCNT_GAP.

Author: Daniel Jäckle

src/mac/LoRaMac.c

@@ -369,7 +369,6 @@ static ChannelParams_t Channels[LORA_MAX_NB_CHANNELS];
  * Contains the channels which remain to be applied.
  */
 static uint16_t ChannelsMaskRemaining[6];
-
 #else
     #error "Please define a frequency band in the compiler options."
 #endif
@@ -1102,6 +1101,15 @@ static void OnRadioRxDone( uint8_t *payload, uint16_t size, int16_t rssi, int8_t
                     }
                 }
 
+                // Check for a the maximum allowed counter difference
+                if( sequenceCounterDiff >= MAX_FCNT_GAP )
+                {
+                    McpsIndication.Status = LORAMAC_EVENT_INFO_STATUS_DOWNLINK_TOO_MANY_FRAMES_LOSS;
+                    McpsIndication.DownLinkCounter = downLinkCounter;
+                    PrepareRxDoneAbort( );
+                    return;
+                }
+
                 if( isMicOk == true )
                 {
                     McpsIndication.Status = LORAMAC_EVENT_INFO_STATUS_OK;

src/mac/LoRaMac.h

@@ -540,6 +540,10 @@ typedef enum eLoRaMacEventInfoStatus
      * of the downlink counter of the node.
      */
     LORAMAC_EVENT_INFO_STATUS_DOWNLINK_REPEATED,
+    /*!
+     * The node has lost MAX_FCNT_GAP or more frames.
+     */
+    LORAMAC_EVENT_INFO_STATUS_DOWNLINK_TOO_MANY_FRAMES_LOSS,
     /*!
      * An address error occured
      */