OpenVPN tap issue (br0 changes MAC address)

[henrikk]

There seems to be a known issue with OpenVPN 'tap' interfaces where if a 'tap' interface is created, the bridge (br0) MAC address changes to the 'tap' MAC address. This causes issues with Windows which believes the computer has changed locations (e.g. this is a new router!) and Windows starts asking you (every time the the router MAC address changes when a 'tap' interface is created) to set the "Network Location" (home/work/public).

The problem has been solved on some Tomato based firmware, but it appears it still is present on the Merlin firmware.

After there plans on fixing this issue?

I believe the command:

ifconfig `nvram get lan_ifname` hw ether `nvram get lan_hwaddr`

when issued after the tap interface is created, fixes the problem (it resets the br0 MAC address back to what it was). I may be able to implement this fix using the new "openvpn-event" script, but it seems strange this bug is not fixed in the code itself.

For the record, I usually use a 'tun' interface. Routed VPN is much better in most cases, but sometimes it helps to have a 'tap' interface available -- especially when trying to diagnose a remote network issue.

- Henrik

 

[RMerlin]

By default the bridge will try to inherit the smallest MAC address in the bridge.

Kernel.org commit 92c0574f11598c8036f81e27d2e8bdd6eed7d76d takes care of solving that by ensuring that if the MAC gets explicitely set on the bridge, then it won't be automatically overriden (which is what is currently happening when the tap interface gets added).

The patch will be included in the next build - thanks for the report!

 

[henrikk]

By default the bridge will try to inherit the smallest MAC address in the bridge.

Kernel.org commit 92c0574f11598c8036f81e27d2e8bdd6eed7d76d takes care of solving that by ensuring that if the MAC gets explicitely set on the bridge, then it won't be automatically overriden (which is what is currently happening when the tap interface gets added).

The patch will be included in the next build - thanks for the report!

Thank you Merlin for taking care of this.

- Henrik