* Implement some logging.
* Watch dhcp leases by polling the dhcp server's leases file.
* Watch dhcp leases by some sort of IPC with the dhcp server.
* Watch public ip address changes by IPC with the dhcp client.
* Implement some kind of a relay for multilayer NAT.
* Mapped ports are bindable by local applications, optionally bind to
  mapped ports to prevent this. The benefit from this would be, that
  these applications always get a reachable port.
