[1570] added doc for processDSAtChild()

src/bin/auth/query.h

@@ -178,7 +178,21 @@ private:
     /// data for the query are to be found.
     void addAuthAdditional(isc::datasrc::ZoneFinder& finder);
 
-    /// TBD
+    /// \brief Process a DS query possible at the child side of zone cut.
+    ///
+    /// This private method is a subroutine of process(), and is called
+    /// there's a possibility that this server has authority for the child
+    /// side of the DS's owner name (and it's detected that the server at
+    /// least doesn't have authority at the parent side).  This method
+    /// first checks if it has authority for the child, and if does,
+    /// just build a "no data" response with SOA for the zone origin
+    /// (possibly with a proof for the no data) as specified in Section
+    /// 2.2.1.1 of RFC3658.
+    ///
+    /// It returns true if this server has authority of the child; otherwise
+    /// it returns false.  In the former case, the caller is expected to
+    /// terminate the query processing, because it should have been completed
+    /// within this method.
     bool processDSAtChild();
 
 public: