Add getDpid() to Port interface

Change-Id: Ibb40d8af9eb5ff0003f7d7205d0fdb59c48d9632
diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/PortImpl.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/PortImpl.java
index eb411f0..ca7cd25 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/PortImpl.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/PortImpl.java
@@ -30,6 +30,11 @@
 	}
 
 	@Override
+	public Long getDpid() {
+	    return sw.getDpid();
+	}
+
+	@Override
 	public Long getNumber() {
 		return number;
 	}