TUNNEL_ID field support in flow matching and actions

Change-Id: I886123a7c8d57dc4a3e12727ec8a9be4920da79e
diff --git a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
index e8101f1..0467a91 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
@@ -350,6 +350,17 @@
     }
 
     /**
+     * Creates a Tunnel ID modification.
+     *
+     * @param tunnelId the Tunnel ID to modify to
+     * @return a L2 modification
+     */
+    public static L2ModificationInstruction modTunnelId(long tunnelId) {
+        checkNotNull(tunnelId, "Tunnel id cannot be null");
+        return new L2ModificationInstruction.ModTunnelIdInstruction(tunnelId);
+    }
+
+    /**
      *  Drop instruction.
      */
     public static final class DropInstruction implements Instruction {