That's strange; I checked my changes and there wasn't a frontend configuration before. I also grepped for net user and netdev and nothing in installer tests comes up. So - how did it work before?

Adding more context:

• https://logs.nix.samueldr.com/nixos-dev/2019-07-21#2408864;

@cleverca22 bisected to 81d35a9 for the first commit making tests fail for tested. The failures happen for non-PXE tests.

Thanks, I'm testing it now! I'll also investigate how did it break things, I feel I misunderstand something about qemu options.

how did it work before?

The Qemu wiki has a page on Networking which explains things better than I can, but the super short version is: the old command line used the legacy option -net nic,... to configure both frontend and backend. Specifying just -device TYPE,netdev=net0 is defining a frontend for a non-existent backend net0. The netboot tests passed by defining the corresponding backend with -netdev user,id=net0,....

nix-build nixos/release.nix -A tests.bittorrent.x86_64-linux

this is one of the tests that involves multiple network devices in qemu, to setup a full router with upnp, and then test torrents going thru it

the test fails on my end, on rev 771985dd3091fdd216060ec154b8094ac31a497b
cause not clear yet

That test is passing for me, I've uploaded my log to a gist.

@thefloweringash I see, -net nic automatically creates a hub and that's why it only issues a warning when no backend is specified. I assumed the same behavior happens with new options but it turns out they require a backend.

I also misunderstood how tests work - Machine.pm default arguments aren't usually used, instead NixOS testing harness passes a script built by qemu-vm.nix which has its own set of qemu arguments. That's why other random tests that I tried succeeded - I needed to explicitly test ones that use createMachine.

Ran the same tests (installer and netboot), they succeed for me.

@cleverca22 BitTorrent test succeeds for me on this revision, there may be test flakiness in motion. Can you post your log?

Let's merge; this blocks master.