Should we tell Exits to reject all traffic if DNS fails?
Tor Exits with broken DNS still allow Exit traffic.
But this slows down initial connections for clients, because the Exit will refuse all DNS requests. (Clients no longer cache DNS.)
Perhaps we should make Exits refuse traffic until their DNS is working? (Unless a non-default option is set?)
This would also fix #21900 (moved), where a broken DNS config really does stop all Exit traffic.