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

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Message-ID: <02874ECE860811409154E81DA85FBB5882ACC9A4@ORSMSX115.amr.corp.intel.com>
Date:   Fri, 20 Oct 2017 18:06:39 +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>,
        "Keller, Jacob E" <jacob.e.keller@...el.com>
Subject: RE: removing bridge in vlan_filtering mode requests delete of
 attached ports main MAC address

> -----Original Message-----
> From: Keller, Jacob E
> Sent: Friday, October 20, 2017 10:23 AM
> To: 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?

For the record, adding a check to prevent unsync_static from removing addresses which are targetting the specific port does work to resolve this specific issue, but I'm sure it's not the correct solution as I expect that would cause other problems.

Thanks,
Jake

> 
> Regards,
> Jake