It's my first look at the code, but AFAICT cockpit-machines doesn't do anything with the information it gathers from 'ListInterfaces', and subsequent 'GetXMLDesc' for each interface. It gets stored, but not updated or retrieved. Did I overlook the use of this information? Can someone describe how it is used?

IMO, cockpit-machines should remove the use of libvirt's virInterface* APIs. virt-manager long ago dropped their use. The libvirt community would like to deprecate them

https://listman.redhat.com/archives/libvir-list/2020-December/msg00183.html

The only interface backend common among all distros is the udev backend, which only implements read operations and likely returns inconsistent results across distros (and even distro versions).

At SUSE, we'd like to take advantage of libvirt's modularization efforts and provide a minimal installation that does not include the virtinterfaced daemon. Removing the use of these APIs in cockpit-machines, or making their use configurable, would make it more friendly with minimal (but sufficient) libvirt installations.

BTW, the virInterface* APIs are all about managing network interface devices on the host. As Claudio mentioned, distro tools (NetworkManager, netplan, etc) are better suited for that. Does cockpit already support the creation and management of host eth, vlan, bond, bridge, etc devices? If so, that's where libvirt's virInterface* APIs should be used. But again, I'd suggest dropping their use altogether since they provide no practical value.

Thanks @hw-claudio for pointing out! I remember that I already tried to remove it once, back then it was unsuccessful. PR #1779 just landed which removes the central bit (thanks @Lunarequest !). I'll work on a PR to clean it up some more.

See PR #1782 , that should get rid of everything.

I'm not 100% certain, but a libvirt without a udev driver might also not return devices that were not defined manually from the nodedev api. Can someone with a libvirt compiled without udev confirm? I don't have one handy. ( https://libvirt.org/hvsupport.html#virNodeDeviceDriver implies it is all provided by udev, but @jfehlig said that the SR-IOV support still works without udev, so perhaps the function call would still succeed, but without any system devices that were not manually defined in libvirt. )

I see various references to that outside of what #1782 touches. Some of those might not be affected, but some look like they are relied on to enumerate all devices on a host.

I'm not 100% certain, but a libvirt without a udev driver might also not return devices that were not defined manually from the nodedev api.

There is no udev driver in libvirt.

Can someone with a libvirt compiled without udev confirm?

There is no proposal to build libvirt without udev support.

Sorry, no idea why I though that was also disabled in Micro 6.0, after checking again, yes the udev driver is enabled (meson argument -Dudev=enabled).

Forget what I said before.