mgmt: Add UP and DOWN kinds to FaceEventNotification

refs #3794

Change-Id: I3676841c004e0861c45c2cb9e0669f2091b5b372
diff --git a/src/mgmt/nfd/face-event-notification.hpp b/src/mgmt/nfd/face-event-notification.hpp
index a4d1ea7..7d3121e 100644
--- a/src/mgmt/nfd/face-event-notification.hpp
+++ b/src/mgmt/nfd/face-event-notification.hpp
@@ -32,8 +32,10 @@
  * \ingroup management
  */
 enum FaceEventKind {
-  FACE_EVENT_CREATED = 1,
-  FACE_EVENT_DESTROYED = 2
+  FACE_EVENT_CREATED = 1, ///< face created
+  FACE_EVENT_DESTROYED = 2, ///< face destroyed
+  FACE_EVENT_UP = 3, ///< face went UP (from DOWN state)
+  FACE_EVENT_DOWN = 4 ///< face went DOWN (from UP state)
 };
 
 /**