AMPAK/Broadcom BCM43455 changing its MAC address on boot

[disneysw]

I manage several Gentoo machines and I recently noticed that some units were changing their MAC address over time when using Wi-Fi. This can cause random network issues with firewalls and DHCP servers and I think is the reason we see a large number of "random" issues when using Wi-Fi based systems.


All the units in question use the AMPAK/Broadcom SDIO BCM43455 (Device 0x02d0 Vendor 0x434).

The systems run connman as the network manager which creates separate Wi-Fi profiles based on the MAC address (so it knows which network interface to associate the profile with). From that I can see connman has over time created two Wi-Fi profiles. Since there has only ever been one physical Wi-Fi interface I know this should never have happened.

One of the MAC address of consistently B8:27:EB:74:F2:6C across all of the machines (registered to the Raspberry Pi foundation) and another is what I believe to be the correct MAC address CC:4B:73:xx:xx:xx (registered to AMPAK Technology, Inc).

Searching the firmware directory I can see the MAC address B8:27:EB:74:F2:6C is listed in a number of Broadcom files and a quick google search shows this MAC address is also being used on other people machines.

While duplicate MAC addresses is typical not a big deal it is a problem when they happen on the same subnet - which has happened to me due to this issue.


I know I can change the MAC address by running the following commands:

Code: Select all

ip link set dev wlan0 down
ip link set dev wlan0 address cc:4b:73:xx:xx:xx
ip link set dev wlan0 up

But what I don't understand is what causes the MAC address to change especially since it sometimes seem to switch back to the correct one again at a later time!

Have I incorrectly set a flag in the kernel or is this just a driver bug?