I guess the advantage of corridor is that is makes violations known in logs while using Qubes firewall simply blocks it if it ever was to happen.
I would be careful about this in context of Qubes. → Verify Changed Firewall Rules
qvm-firewall sys-firewall del --rule-no 0
If this is really useful, that seems at least like a usability issue. Please check that this has been reported anywhere and if not I suggest a to write a report to make sure you’re on the right track here.
Yes, only one (see above). I named the VM sys-firewall but you can name it whatever you want (e.g., sys-whonix-firewall). The thing is to put a firewall VM (clone or create a new one) before sys-whonix and configure the above firewall rules in that firewall VM.
Ok. So no corridor involved here.
otherwise DNS / ICMP would still be generally allowed.
How about blocking all UDP?
What about IPv6?
related: add IPv6 support