Re: How to handle USB CDC driver randomly assigned MAC

[test name <tuksgig gmail com>]

On Mon, Mar 18, 2013 at 5:45 PM, Dan Williams <dcbw redhat com> wrote:
> On Sun, 2013-03-17 at 13:39 +0200, test name wrote:
> > Hi,
> >
> > I'm busy with a new embedded design, and I'd really like to use the
> > USB gadget CDC EEM driver for connectivity to the device. On the PC
> > side I get a random MAC address for the usb0 interface each time the
> > usbnet and cdc_eem driver is reloaded.
>
> That's probably because your device doesn't have an assigned MAC stored
> anywhere right?  EEM/usbnet do have the ability to retrieve the
> permanent MAC address if the device has one, but of course that requires
> support on the embedded device side, and some memory to store the MAC,
> and the ability of your organization to assign MAC addresses to devices
> with your vendor OUI.
>
> > What would be the best way to handle this in NM? I want to use ipv4
> > link local addressing on the usb0 interface, but NM forgets this each
> > time the MAC is reset.
> >
> > Teach usbnet/cdc_eem to give the same MAC every time?
> > Use udev/systemd to rename device based on USB VID/PID?
> > Handle locally assigned MACs differently in NM?
>
> At the moment, the best solution is to use udev rules to assign the same
> MAC to the interface every time it's connected, either based on
> interface name or based on USB serial number or other characteristics.
> We just merged a feature (targeted to NM 0.9.10) that will allow you to
> "lock" a connection to an interface based on name, where previously you
> could only do this on MAC address.
>
> In any case, if you do use udev rules to assign a stable MAC to the
> device, then you'll create a new connection that's "locked" to that MAC
> address and set the IPv4 addressing method to "link-local".  That would
> be represented by a 'keyfile'-type connection like this, which you'd
> drop into /etc/NetworkManager/system-connections/ :
>
> [connection]
> id=Embedded Link-Local
> uuid=4e80a56d-c99f-4aad-a6dd-b449bc398c57
> type=802-3-ethernet
> autoconnect=true
>
> [802-3-ethernet]
> mac-address=00:11:22:33:44:55
>
> [ipv4]
> method=link-local
>
> Dan

Thanks, got it working with this udev rule:

SUBSYSTEM=="net", ACTION=="add", ENV{ID_BUS}=="usb",
ENV{ID_VENDOR_ID}=="xxxx", RUN="/sbin/ip link set %k address
02:11:22:33:44:%n"


where xxxx is my USB VID.