The reverse proxy in Undertow fails on OpenShift since it doesn't support a binding address for its sockets. Without the binding address, it will default to using localhost, which is not allowed on OpenShift gears.

See: https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/client/http/HttpClientProvider.java#L77

Here the XnioIoThread.openStreamConnection uses the method without the binding address option (which internally default to 'localhost'). If this method is changed to use the one which uses a binding address, and is bound to the ip address for the openshift gear, then the reverse proxy works in openshift.

Being able to specify this IP address needs to be a configurable option.