Auto-generate an intg-bridge ID if it is not specified via net-cfg

Change-Id: I31601f87b1cb26fdb0379d2c711ff8da5de24d31
diff --git a/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/util/OpenstackNodeUtil.java b/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/util/OpenstackNodeUtil.java
index fac184e..e970b2b 100644
--- a/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/util/OpenstackNodeUtil.java
+++ b/apps/openstacknode/app/src/main/java/org/onosproject/openstacknode/util/OpenstackNodeUtil.java
@@ -58,6 +58,10 @@
     private static final String IDENTITY_PATH = "identity/";
     private static final String SSL_TYPE = "SSL";
 
+    private static final int HEX_LENGTH = 16;
+    private static final String OF_PREFIX = "of:";
+    private static final String ZERO = "0";
+
     /**
      * Prevents object installation from external.
      */
@@ -175,6 +179,27 @@
     }
 
     /**
+     * Generates a DPID (of:0000000000000001) from an index value.
+     *
+     * @param index index value
+     * @return generated DPID
+     */
+    public static String genDpid(long index) {
+        if (index < 0) {
+            return null;
+        }
+
+        String hexStr = Long.toHexString(index);
+
+        StringBuilder zeroPadding = new StringBuilder();
+        for (int i = 0; i < HEX_LENGTH - hexStr.length(); i++) {
+            zeroPadding.append(ZERO);
+        }
+
+        return OF_PREFIX + zeroPadding.toString() + hexStr;
+    }
+
+    /**
      * Builds up and a complete endpoint URL from gateway node.
      *
      * @param node gateway node