Re: systemd-networkd MAC address randomization stops working when iwd restarts

On Mon, Feb 23, 2026 at 5:57 PM James Prestwood <[email protected]> wrote:
> On 2/23/26 8:43 AM, Roman Žilka wrote:
> > On Mon, Feb 23, 2026 at 2:36 PM James Prestwood <[email protected]> wrote:
> >> Looks like the issue is in the configuration. IWD removes/creates a new
> >> fresh interface on startup, which conflicts with how you want to use
> >> randomization with systemd. If you want systemd to manage the interface
> >> you need to tell IWD to use the interface systemd/udev creates by using
> >> this option in main.conf:
> >>
> >> [DriverQuirks]
> >> DefaultInterface=<driver>
> > thank you, that fixed it. It has no bad side effects, does it?
> >
> > I have to say, the situation still looks like a bug. Having systemd
> > manage the interface and using iwd for 802.11 is a supported
> > configuration, I assume, so iwd shouldn't collide with systemd
> > components then. Also, I would never think of looking at
> > DefaultInterface: there is no driver quirk, the name sounds unrelated
> > to the issue and I actually don't understand the terse description
> > (what is a default interface?).
>
> Having IWD manage the interface was a design decision made since IWD's
> inception. But there has always been a way to use the interface the
> system creates via "default interface" options. So yes this is a
> supported configuration.

Oh...

> I'll admit, the use of [DriverQuirks].DefaultInterface in this context
> isn't typical. The reason for this option in the first place was because
> some drivers didn't support removing the default interface, or at the
> very least would cause issues. brcmfmac is one example. In you're case
> the driver itself supports interface removal/addition but you're trying
> to also have systemd manage the interface when IWD expects to manage it.
> There's no other way to tell IWD this situation except this DriveQuirks
> option.
>
> In case I wasn't clear a "default interface" is the network interface
> that the kernel/driver creates during initialization.

It would never have crossed my mind that iwd might remove and
re-create an interface in the first place.

Anyway, I'm off the mailinglist. Thanks again,
Roman