debian drivers ethernet usb-device mac-address – Debian 12: USB3 LAN Adapter Gets Assigned Random MAC Address at Each Reboot

debiandriversethernetmac addressusb device

I have various small NUCs with attached on each one some of this USB3 LAN adapters (because the NUCs have only one Ethernet,
so I added extra ones with USB3 adapters).

You can see an image of the product here.

All of a sudden, probably due to an unattended automatic upgrade,
these devices started getting random MAC addresses.

Before:

Each USB3 attached device had an address in the form:

00:0E:C6:XX:XX:XX

Each one was distinct and always the same (stable), surviving reboots.

Now they have address like:

eth1 - be:7d:ee:6a:26:ab  
eth2 - be:7d:ee:6a:26:ab  
eth3 - be:7d:ee:6a:26:ab  
eth4 - be:7d:ee:6a:26:ab  
eth5 - be:7d:ee:6a:26:ab

all sharing the same randomly picked address.

In short, troubles:

  • Each time the machine reboots, this random MAC address changes.
  • They all share the same random MAC address. 
    Previously each one had a different and clearly distinct one.

The devices are identified in lsusb as:

   ASIX Electronics Corp. AX88179 Gigabit Ethernet

I have no idea what happened since latest automatic update, it's matter of the latest 2 days, 1h ago everything was working OK, after all these devices started to have this weird behaviour.

Could it be a problematic update? 
Could it be a new driver been released
that randomizes the MAC address each time? 
Could it be a feature from the Linux kernel or the distro or GRUB setting where USB LAN devices now get random MAC address each time? 
But in this case, why all of them share the same? 
They should be totally random….

I am seeking help and willing to do tests…

Regarding the OS:

Debian Version: 12.5

Linux 6.1.0-20-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.85-1 (2024-04-11) x86_64 GNU/Linux

Workarounds suggested so far, including the final one always working thanks to @A.B:

Best Answer

This 6.8 kernel commit, backported to 6.1.x:

net: usb: ax88179_178a: avoid two consecutive device resets

intended to avoid a double reset on the AX88179-based NIC had as side effect to get a random MAC address for the NIC.

There's a fix in the works for future 6.9 kernel, already backported to kernel 6.1.85+ which acknowledges the previous issue (and is supposed to fix it). Here's the acknowledge part:

net: usb: ax88179_178a: avoid the interface always configured as random address

After the commit d2689b6a86b9 ("net: usb: ax88179_178a: avoid two consecutive device resets"), reset is not executed from bind operation and mac address is not read from the device registers or the devicetree at that moment. Since the check to configure if the assigned mac address is random or not for the interface, happens after the bind operation from usbnet_probe, the interface keeps configured as random address, although the address is correctly read and set during open operation (the only reset now).

The problem is that Debian's kernel 6.1.0-20-amd64 already uses upstream kernel 6.1.85 which includes the fix. From OP's comment this doesn't appear to work correctly, since OP is using kernel 6.1.0-20-amd64.

What is guaranteed to work is to revert to the previous state: before the patch backported to 6.1.x on 2024-02-05. It appears that currently that means reverting TWO patches:

to be guaranteed to get it working as before (and getting the double-reset behavior back which didn't appear to be a problem then).

I could verify in the past weeks that reverting net: usb: ax88179_178a: avoid two consecutive device resets made it work, I didn't verify how the newer state (eg: kernel 6.1.85 or Debian 6.1.0-20-amd64) behaves. OP's Q/A suggests that maybe the 2nd patch intended to fix the behavior caused after the 1st patch is not enough and possibly yet-an-other-fix has to be provided.

To summarize, possible options today:

Related Question