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

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Date:   Tue, 8 Jan 2019 15:09:38 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ian Kumlien <ian.kumlien@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>
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 1/8/19 3:00 PM, Ian Kumlien wrote:
> On Tue, Jan 8, 2019 at 11:51 PM Stephen Hemminger
> <stephen@...workplumber.org> wrote:
>> 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.
> 
> Yeah, I'm not running any VF:s and it just seems like the responses
> are dropped somewhere
> 
> when looking at "git log v4.19...v4.20
> drivers/net/ethernet/intel/ixgbe/" nothing else really stands out...
> The machine is also running NAT for my home network and all of that
> works just fine...
> 
> I started with tcpdump, prooving that packets reached all the way
> outside but replies never made it, reboorting
> with 4.19.13 resulted in replies appearing in the tcpdump.
> 
> I don't quite know where to look - and what can i do to test - i tried
> disabling all offloading (due to the UDP
> offloading changes) but nothing helped...
> 
> Ideas? Patches? ;)

Running a bisection would certainly help find the offending commit if
that is something that you can do?
-- 
Florian