Using the HttpTunnelingServlet inside a WAR's web.xml is not possible (e.g. to tunnel HornetQ), because the module 'netty' cannot access the module 'servlet-api / javaee'

Fix is simple. Adjust modules/org/jboss/netty/main/module.xml with the following dependency:
<dependencies>
..
<module name="javax.servlet.api" />
</dependencies>