Comment by jonesetc

I have also yet to see a reasonable solution for connecting out of a container back to the host with Docker.app.

On linux and OSX with docker-machine this is easy with:

    docker run --add-host host:ip.for.docker.interface foo

But there is no equivalent to the docker0 interface or the vboxnet interface for Docker.app.

EDIT: I don't use this for any production environments, but it is very useful for debugging and testing.