when i started searching for OpenDns i started by reverse engeniering...that's the wrong approach...if your a MIM you need a to access the VPN by a frame on the docker..and so it is what's the post is about

if you want to access the Docker API from the containers, you can setup Docker to listen on the IP address of the Docker bridge.

To do that, you would:

• create a bridge
  ip link add docker0 type bridge
• assign an IP address to it
  ip link set docker0 up
ip addr add 172.17.0.1/16 dev docker0
• start docker and bind the API to the bridge
  docker -d -H 172.17.0.1:4242

Now you can access the Docker API from your containers.

https://github.com/moby/moby/issues/1143