Thread key ID change during attach (#1627)

Child ID response saves link layer frame counters that were learned
when parent response was received. If key ID is changed between parent
response and child id response then link layer frame counter should be
cleared.

Author: Arto Kinnunen

source/6LoWPAN/Thread/thread_host_bootstrap.c

@@ -832,6 +832,13 @@ static void thread_mle_child_request_receive_cb(int8_t interface_id, mle_message
 
             mac_helper_coordinator_address_set(cur, ADDR_802_15_4_SHORT, shortAddress);
             mle_entry_timeout_update(entry_temp, thread_info(cur)->host_link_timeout);
+
+            if (scan_result->security_key_index != security_headers->KeyIndex) {
+                // KeyIndex has been changed between parent_response and child_id_response, reset link layer frame counter
+                scan_result->linLayerFrameCounter = 0;
+                scan_result->security_key_index = security_headers->KeyIndex;
+            }
+
             mac_helper_devicetable_set(entry_temp, cur, scan_result->linLayerFrameCounter, security_headers->KeyIndex, new_entry_created);
 
             thread_info(cur)->thread_attached_state = THREAD_STATE_CONNECTED;