Merge pull request #2177 from ARMmbed/IOTTHD-3530

MAC: Do not update framecounter for fhss channel retry

Author: Jarkko Paso

source/MAC/IEEE802_15_4/mac_mcps_sap.c

@@ -1199,6 +1199,7 @@ mac_pre_build_frame_t *mcps_sap_prebuild_frame_buffer_get(uint16_t payload_size)
         return NULL;
     }
     memset(buffer, 0, sizeof(mac_pre_build_frame_t));
+    buffer->aux_header.frameCounter = 0xffffffff;
     if (payload_size) {
         //Mac interlnal payload allocate
         buffer->mac_payload = ns_dyn_mem_temporary_alloc(payload_size);
@@ -1519,14 +1520,20 @@ static int8_t mcps_generic_packet_build(protocol_interface_rf_mac_setup_s *rf_pt
     mcps_generic_sequence_number_allocate(rf_ptr, buffer);
 
     if (buffer->fcf_dsn.securityEnabled) {
+        bool increment_framecounter = false;
         //Remember to update security counter here!
-        buffer->aux_header.frameCounter = mac_mlme_framecounter_get(rf_ptr);
+        uint32_t new_frameCounter = mac_mlme_framecounter_get(rf_ptr);
+        // If buffer frame counter is set, this is FHSS channel retry, update frame counter only if something was sent after failure
+        if ((buffer->aux_header.frameCounter == 0xffffffff) || ((new_frameCounter - buffer->aux_header.frameCounter) > 1)) {
+            buffer->aux_header.frameCounter = new_frameCounter;
+            increment_framecounter = true;
+        }
         if (!mac_frame_security_parameters_init(&ccm_ptr, rf_ptr, buffer)) {
             return -2;
         }
-        //Increment security counter
-        mac_mlme_framecounter_increment(rf_ptr);
-
+        if (increment_framecounter) {
+            mac_mlme_framecounter_increment(rf_ptr);
+        }
     }
 
     //Calculate Payload length here with IE extension