netdev - removing bridge in vlan_filtering mode requests delete of attached ports main MAC address

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Message-ID: <02874ECE860811409154E81DA85FBB5882ACC90F@ORSMSX115.amr.corp.intel.com>
Date:   Fri, 20 Oct 2017 17:23:22 +0000
From:   "Keller, Jacob E" <jacob.e.keller@...el.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "Malek, Patryk" <patryk.malek@...el.com>,
        Vlad Yasevich <vyasevic@...hat.com>
Subject: removing bridge in vlan_filtering mode requests delete of attached
 ports main MAC address

Hi,

We've run into an issue with bridges set in vlan_filtering mode. Basically, if we attach a device to a bridge which has enabled vlan_filtering, and then remove the bridge, we end up requesting the driver of the attached device to remove its own MAC HW address.

In i40e, at least, this causes the driver to actually delete such an address and then it will no longer receive any traffic.

To reproduce this:

a) brctl addbr br0
b) brctl addif br0 enp<n>
# enable vlan filtering
c) echo 1 >/sys/class/net/br0/bridge/vlan_filtering
d) brctl delbr br0

Specifically this appears to happen because of how we automatically enter static configuration for routes when vlan_filtering is enabled, and we call br_fdb_unsync_static which will clear all the routes from the fdb table for the device. See commit 2796d0c648c9 ("bridge: Automatically manage port promiscuous mode.", 2014-05-16) for more details.

This happens to include the devices own default address, which results in the bug.

I'm not sure if this is a driver bug, or if it's a bug in the bridging code.

Who would know more about this and what to do about this?

One obvious solution is to hard code the i40e device driver so that it does not actually delete the HW address from the unicast filter list. This could work, but seems to me like its papering over the problem. Is this just a known thing that drivers should be aware of? I don't really know...

An alternative solution would be to possibly ignore any fdb addresses which specifically target that port?

Any ideas?

Regards,
Jake