VPN allows network access to other connected clients

If you connect to the VPN with a client, you can make direct network connections to the other connected clients.

We must block in shorewall clients from talking to each other over the VPN network (currently 10.42.0.0 and 10.42.1.0)

(from redmine: created on 2016-07-26, closed on 2016-08-08)