I would like to know, inside my container:

1. host address of my container (docker0 link, eg 172.16.42.1). I know that I can pass this value at runtime of the container already, but the next value I cannot pass yet, thus I think it makes sense to have a uniform solution:
2. the external value of the mapped port. Eg. I configured Docker to use port 8000 internally, but want to figure out which external port that is.

root@thijs:~# docker ps
ID                  IMAGE                         COMMAND             CREATED             STATUS              PORTS
1a4994c874f6        thijsterlouw/erlang3:latest   /usr/sbin/sshd -D   18 hours ago        Up 18 hours         49161->22, 49162->8000               
a63ec666e1e5        thijsterlouw/erlang2:latest   /usr/sbin/sshd -D   26 hours ago        Up 26 hours         49159->22, 49160->8000               
ab0a3e84fd1e        thijsterlouw/erlang2:latest   /usr/sbin/sshd -D   7 days ago          Up 27 hours         4369->4369, 49153->22, 49154->8000   

So Inside container ab0a3e84fd1e I want to be able to lookup value 49154 for port 8000.

Usecase for both of these values: Erlang distribution where the container should register with a port-mapper daemon the public (and not the private 8000) port.

This could be implemented nicely with a special environment variable. I think there is no harm in transparently making these values available, but I am also fine if it is possible to pass these values via the -e option of 'docker run'.