Support attaching instances to a "physical" network that's using a bridge as parent

[mweinelt]

The host system provides a bridge interface that is connected to a physical interface.

When integrating that bridge via the physical nic type and passing the bridge interface as the parentI get the following error when starting the VM.

Failed to start device "eth-1": Failed to get PCI device info for "br-lan": open /sys/class/net/br-lan/device/uevent: no such file or directory

This is because the bridge does not have a device directory, but the code requires it for looking up PCIe information.

incus/internal/server/device/nic_physical.go

Line 211 in 36701b9

return nil, fmt.Errorf("Failed to get PCI device info for %q: %w", saveData["host_name"], err)

The documentation claims I can pass a bridge:

The physical network type connects to an existing physical network, which can be a network interface or a bridge, and serves as an uplink network for OVN.

https://linuxcontainers.org/incus/docs/main/reference/network_physical/

This issue is reproducible on incus 6.10.1.

[stgraber]

and serves as an uplink network for OVN

You're not trying to use it as an uplink for an OVN network but directly as a physical NIC on an instance, so that's probably why this is failing. I very commonly use a "physical" network with a bridge as parent for OVN uplinks and that works just fine.

[stgraber]

That said, I think it'd make sense to support attaching instances to such a "physical" type network, just using the normal bridge handling logic if we see it's a bridge.

I updated the issue title accordingly.