[netdevice] Refuse to create duplicate network device names

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/netdevice.c

 		goto err_duplicate;
 	}
 
+	/* Reject named network devices that already exist */
+	if ( netdev->name[0] && ( duplicate = find_netdev ( netdev->name ) ) ) {
+		DBGC ( netdev, "NETDEV rejecting duplicate name %s\n",
+		       duplicate->name );
+		rc = -EEXIST;
+		goto err_duplicate;
+	}
+
 	/* Record device index and create device name */
 	if ( netdev->name[0] == '\0' ) {
 		snprintf ( netdev->name, sizeof ( netdev->name ), "net%d",