tails-blocked-network-detector for wired connections

Currently we can only detect “blocked” (due to MAC address white-listing) wireless networks in tails-blocked-network-detector. What about wired networks? Compared to wireless networks, wired ones do not have a strong concept of being associated (perhaps there is in 802.1x security, but that seems very edge case:y so we can probably ignore it) so how does it work if practice? Probably it’s something like:

1. Block all non-HDCP request traffic from hosts without a DHCP lease
2. DHCP leases are only given to hosts with a MAC address on the whitelist

Any way, we may want to check how this works in practice, and if we can easily detect it (e.g. by checking the NetworkManager logs, like for the wireless case).

Original created by @anonym on 6526 (Redmine)