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

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Message-ID: <a7ab80d5-ff49-4277-ba73-db46547a8a8e@nbd.name>
Date: Tue, 15 Oct 2024 21:44:52 +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 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.

>> Because of that, I created this piece of software:
>> https://github.com/nbd168/bridger
>> 
>> It uses an eBPF TC classifier for discovering flows and handling the
>> software fast path, and also creates hardware offload rules for flows.
>> With that, hardware offloading for bridged LAN->WLAN flows is fully
>> supported on MediaTek hardware with upstream kernels.
>> 
>> - Felix
> 
> Thanks, I've seen that already. Nice piece of software, but I'm not
> running openwrt. I would like to see a solution implemented in the
> kernel, so any operating system can use it.

Makes sense. By the way, bridger can easily be built for non-OpenWrt 
systems too. The only library that's actually needed is libubox - that 
one is small and can be linked in statically. ubus support is fully 
optional and not necessary for standard cases.

- Felix