[systemd-devel] systemd-networkd: setting the MAC address for a .netdev unit?

[Tom Gundersen]

On Mon, May 12, 2014 at 10:43 AM, Matthias Schiffer
<mschiffer at universe-factory.net> wrote:
>>>> This should really be added as AFAICT there is currently no way to match
>>>> on virtual devices like briges, TAP devices, batman-adv devices, etc...
>>>> which have neither a persistent MAC address nor an ID_PATH to match on.
>>>
>>> So I think what we should do here is to allow MAC address (and other
>>> things) to be set when creating the netdevs. I made an attempt at this
>>> by generating a "predictable" one based on the interface name and the
>>> machine-id. Would that do it for you, or are you after a _specific_
>>> mac address, rather than just one that is always the same? I had to
>>> revert the code doing this for now as there was a kernel bug, however
>>> we'll hopefully get that sorted soon and then get back to this.
>>>
>>> Cheers,
>>>
>>> Tom
>>>
>>
>> For my usecase, a predictable, but otherwise random MAC address would
>> do. But I also see that setting an arbitrary MAC address (or any other
>> link parameter) for a specific virtual device is useful as well
>> (especially as it is possible to do so with real devices). As virtual
>> devices are almost always created with specific names, a Name= match for
>> .link units would make the most sense in my opinion.
>>
>> As a workaround, I've added the following udev rule to
>> 80-net-setup-link.rules for now to allow matching for virtual devices
>> with Path= matches:
>>
>> ENV{DEVPATH}=="/devices/virtual/net/*", ENV{ID_PATH}=="",
>> ENV{ID_PATH}="virtual-$kernel"
>>
>> Thanks,
>> Matthias
>>
>
> Ping. There is still no way to match for virtual devices in .link units
> without my workaround. Is it planned to add something similar? Would a
> facility allowing to configure the MAC address of a virtual device be in
> the scope of the TODO point "add reduced [Link] support to .network files"?

Yes. What we will do is that by default we will generate a MAC address
that will be stable between reboots and use that, but we will also
allow the MAC address to be set manually in the [NetDev] section (in
the same way as in the .link files).

The kernel interface for doing this is currently broken, but a patch
has been submitted to fix it, and once that hits the stable kernels I
guess we can start using it (otherwise we are just going to get heaps
of weird bug reports).

Cheers,

Tom