Message-ID: <d7d48102-4c52-4161-a21c-4d5b42539fbb@gmail.com>
Date: Wed, 16 Oct 2024 17:59:50 +0200
From: Eric Woudstra <ericwouds@...il.com>
To: Felix Fietkau <nbd@....name>, 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 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.

>>> 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

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