netdev - Re: [net-next,rfc] net: bridge: mdb: Extend with multicast LLADDR

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Date:   Thu, 1 Aug 2019 18:25:19 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>, idosch@...lanox.com,
        andrew@...n.ch, allan.nielsen@...rochip.com
Cc:     davem@...emloft.net, roopa@...ulusnetworks.com, petrm@...lanox.com,
        tglx@...utronix.de, fw@...len.de, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org
Subject: Re: [net-next,rfc] net: bridge: mdb: Extend with multicast LLADDR

On 01/08/2019 17:15, Nikolay Aleksandrov wrote:
> On 01/08/2019 17:11, Nikolay Aleksandrov wrote:
>> On 01/08/2019 17:07, Nikolay Aleksandrov wrote:
>>> Hi Horatiu,
>>> Overall I think MDB is the right way, we'd like to contain the multicast code.
>>> A few comments below.
>>>
>>> On 01/08/2019 15:50, Horatiu Vultur wrote:
>> [snip]
>>>>
>>>> Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
>>>> Co-developed-by: Allan W. Nielsen <allan.nielsen@...rochip.com>
>>>> Signed-off-by: Allan W. Nielsen <allan.nielsen@...rochip.com>
>>>> ---
>>>>  include/linux/if_bridge.h      |  1 +
>>>>  include/uapi/linux/if_bridge.h |  1 +
>>>>  net/bridge/br_device.c         |  7 +++++--
>>>>  net/bridge/br_forward.c        |  3 ++-
>>>>  net/bridge/br_input.c          | 13 ++++++++++--
>>>>  net/bridge/br_mdb.c            | 47 +++++++++++++++++++++++++++++++++++-------
>>>>  net/bridge/br_multicast.c      |  4 +++-
>>>>  net/bridge/br_private.h        |  3 ++-
>>>>  8 files changed, 64 insertions(+), 15 deletions(-)
>>>>
>>>
>>> Overall I don't think we need this BR_PKT_MULTICAST_L2, we could do the below much
>>> easier and without the checks if you use a per-mdb flag that says it's to be treated
>>> as a MULTICAST_L2 entry. Then you remove all of the BR_PKT_MULTICAST_L2 code (see the
>>> attached patch based on this one for example). and continue processing it as it is processed today.
>>> We'll keep the fast-path with minimal number of new conditionals.
>>>
>>> Something like the patch I've attached to this reply, note that it is not complete
>>> just to show the intent, you'll have to re-work br_mdb_notify() to make it proper
>>> and there're most probably other details I've missed. If you find even better/less
>>> complex way to do it then please do.
>>>
>>> Cheers,
>>>  Nik
>>
>> Oops, I sent back your original patch. Here's the actually changed version
>> I was talking about.
>>
>> Thanks,
>>  Nik
>>
>>
>>
> 
> The querier exists change is a hack just to get the point, I'd prefer
> to re-write that portion in a better way which makes more sense, i.e.
> get that check out of there since it doesn't mean that an actual querier
> exists. :)
> 

TBH, I'm inclined to just use proto == 0 *internally* as this even though it's reserved,
we're not putting it on the wire or using it to construct packets, it's just internal
use which can change into a flag if some day that value needs to be used. Obviously
to user-space we need it to be a flag, we can't expose or configure it as a proto value
without making it permanent uapi. I haven't looked into detail how feasible this is,
just a thought that might make it simpler.