netdev - Re: [BUG] v4.20 - bridge not getting DHCP responses? (works in 4.19.13)

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Date:   Tue, 8 Jan 2019 14:51:12 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Ian Kumlien <ian.kumlien@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        jeffrey.t.kirsher@...el.com,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        nikolay@...ulusnetworks.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] v4.20 - bridge not getting DHCP responses? (works in
 4.19.13)

On Tue, 8 Jan 2019 23:10:04 +0100
Ian Kumlien <ian.kumlien@...il.com> wrote:

> On Sun, Jan 6, 2019 at 11:21 PM Ian Kumlien <ian.kumlien@...il.com> wrote:
> >
> > [Sorry for the repost, screwed up the netdev address...]
> >
> > Hi,
> >
> > Switching from 4.19.x -> 4.20 resulted in DHCP not working for my VM:s.
> >
> > My firewall (which also runs the dhcpd) runs VM:s and it does this by
> > having physical
> > interfaces attached to bridges - which the VM:s in turn attach to.
> >
> > Since 4.20 the VM:s can't use DHCP, it's odd since the requests are
> > seen - a response is sent but
> > it never enters the interface attached to the bridge.
> >
> > Basically:
> > VM vnet2: -> br0 -> eno2 -> switch -> eno1 (dhcpd)
> > dhcpd eno1 -> siwtch and... gone.
> >
> > Any clues?
> >
> > All the nics are handled by ixgbe  
> 
> So, doing similar tests at work with other drivers works - could it be
> related to the mac address filter that was added?
> I don't *really* use VF:s though... (can't really find anything else atm)
> 
> Will try to test, but the VM:s on this machine is in use.

The default MAC address of the bridge device is the first device assigned
to the bridge.  Remember most VF interfaces will only allow single MAC address
and no promiscious mode.