So I have a appVM that I use for torrenting. It’s based on debian-10-minimal (deb-min) and has the minimal amount of packages needed (torrenting software, RSS, Firefox, qubes-core-agent-networking) along with Tasket’s qubes-vm-hardening.
It worked fine for several months before its internet connectivity suddenly vanished, without any changes to the template, the firewall, or the appVM itself beforehand. This persisted across VM and Qubes OS restarts. All the while, network connectivity in other deb-min templates and whonix templates was fine.
This issue showed up again with a fresh appVM based on the same template, and also with fresh deb-min templates with the packages re-installed. Across my many attempts, internet connectivity was sometimes available at first, but then drops off and never returns even after restarting the appVM.
Switching to fedora-32-minimal (fed-min) gave inconsistent results, but was eventually fine. What bothers me is the inconsistent results at first, even for fed-min. I suspect this whole issue has something to do with how Xen/dom0 manages networks. By the way, I use Mirage firewalls.
The problem has been resolved, but is still cause for concern, which is why I’m posting this write-up here. I should mention that another user had a similar issue with fed-min (No internet in fedora-32-minimal) but didn’t specify whether he was using 4.1 or not.