Support VPN via macvlan networking

[samip5]

Use case: I want to be able to have my router handle the VPN itself, but setup iptables in a way, that it wouldn't leak to other interfaces on container.

My idea of implementation: Setup the container in a macvlan, and have the network router do the VPN. Make sure with iptables that outgoing traffic to internet is only allowed via that said macvlan and not via other interfaces. Probably check periodly from a public service that IP address is not your connection's but the VPN's.