Added back-pipe for role assertion issues.

 package org.onlab.onos.net.device;
 
 import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.MastershipRole;
 import org.onlab.onos.net.provider.ProviderService;
 
 import java.util.List;
@@ -45,4 +46,13 @@ public interface DeviceProviderService extends ProviderService<DeviceProvider> {
      */
     void portStatusChanged(DeviceId deviceId, PortDescription portDescription);
 
+    /**
+     * Notifies the core about the providers inability to assert the specified
+     * mastership role on the device.
+     *
+     * @param deviceId identity of the device
+     * @param role mastership role being asserted
+     */
+    void unableToAssertRole(DeviceId deviceId, MastershipRole role);
+
 }

@@ -224,6 +224,11 @@ public class DeviceManager
                 post(event);
             }
         }
+
+        @Override
+        public void unableToAssertRole(DeviceId deviceId, MastershipRole role) {
+            // FIXME: implement response to this notification
+        }
     }
 
     // Posts the specified event to the local event dispatcher.

@@ -20,6 +20,7 @@ import org.junit.Test;
 import org.onlab.onos.net.DefaultDevice;
 import org.onlab.onos.net.Device;
 import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.MastershipRole;
 import org.onlab.onos.net.device.DeviceDescription;
 import org.onlab.onos.net.device.DeviceProvider;
 import org.onlab.onos.net.device.DeviceProviderRegistry;
@@ -181,6 +182,11 @@ public class OpenFlowDeviceProviderTest {
                 descr = portDescription;
             }
 
+            @Override
+            public void unableToAssertRole(DeviceId deviceId, MastershipRole role) {
+                // FIXME: add fixture core when tests are done on this
+            }
+
         }
     }