netdev - Re: [PATCH RFC v1 net-next 00/12] bridge-fastpath and related improvements

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Message-ID: <b5739f78-9cd5-4fd0-ae63-d80a5a37aaf0@nbd.name>
Date: Thu, 17 Oct 2024 11:17:09 +0200
From: Felix Fietkau <nbd@....name>
To: Eric Woudstra <ericwouds@...il.com>,
 Nikolay Aleksandrov <razor@...ckwall.org>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Pablo Neira Ayuso <pablo@...filter.org>,
 Jozsef Kadlecsik <kadlec@...filter.org>, Roopa Prabhu <roopa@...dia.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Jiri Pirko <jiri@...nulli.us>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Lorenzo Bianconi <lorenzo@...nel.org>,
 Frank Wunderlich <frank-w@...lic-files.de>,
 Daniel Golle <daniel@...rotopia.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 netfilter-devel@...r.kernel.org, coreteam@...filter.org,
 bridge@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH RFC v1 net-next 00/12] bridge-fastpath and related
 improvements

On 16.10.24 17:59, Eric Woudstra wrote:
> 
> 
> On 10/15/24 9:44 PM, Felix Fietkau wrote:
>> On 15.10.24 15:32, Eric Woudstra wrote:
>>>
>>>
>>> On 10/15/24 2:16 PM, Felix Fietkau wrote:
>>>> Hi Eric,
>>>>
>>>> On 14.10.24 20:29, Eric Woudstra wrote:
>>>>> It would be no problem for me to change the subject and body, if you
>>>>> think that is better.
>>>>>
>>>>> The thing is, these patches actually make it possible to set up a fully
>>>>> functional software fastpath between bridged interfaces. Only after the
>>>>> software fastpath is set up and functional, it can be offloaded, which
>>>>> happens to by my personal motivation to write this patch-set.
>>>>>
>>>>> If the offload flag is set in the flowtable, the software fastpath will
>>>>> be offloaded. But in this patch-set, there is nothing that changes
>>>>> anything there, the existing code is used unchanged.
>>>>
>>>> FWIW, a while back, I also wanted to add a software fast path for the
>>>> bridge layer to the kernel, also with the intention of using it for
>>>> hardware offload. It wasn't accepted back then, because (if I remember
>>>> correctly) people didn't want any extra complexity in the network stack
>>>> to make the bridge layer faster.
>>>
>>> Hello Felix,
>>>
>>> I think this patch-set is a clear showcase it is not very complex at
>>> all. The core of making it possible only consists a few patches. Half of
>>> this patch-set involves improvements that also apply to the
>>> forward-fastpath.
>> 
>> It's definitely an interesting approach. How does it deal with devices
>> roaming from one bridge port to another? I couldn't find that in the code.
> 
> It is handled in the same manner when dealing with the forward-fastpath,
> with the aid of conntrack. If roaming is problematic, then it would be
> for both the forward-fastpath and the bridge-fastpath. I have a topic on
> the banana-pi forum about this patch-set, so I think long discussions
> about additional details we could have there, keeping the mailing list
> more clean.

You forgot to include a link to the forum topic :)

By the way, based on some reports that I received, I do believe that the 
existing forwarding fastpath also doesn't handle roaming properly.
I just didn't have the time to properly look into that yet.

- Felix