linux-kernel - Re: [PATCH net] net: renesas: rswitch: fix forwarding offload statemachine

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ff475397-8894-46e9-858a-78714c5b4bd5@cogentembedded.com>
Date: Thu, 5 Feb 2026 16:03:43 +0100
From: Nikita Yushchenko <nikita.yoush@...entembedded.com>
To: Michael Dege <michael.dege@...esas.com>,
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: renesas: rswitch: fix forwarding offload
 statemachine

>>> The driver was originally designed to enable hardware forwarding when not less than two ports are in
>>> forwarding state. When only one port has hw forwarding, there is no destination to forward.
>>>
>>> Nikita
>>>
>>
>> The current driver allows Linux to use the bridge port as local port to the bridge. The offloading
>> Also supports switching traffic to Linux through the bridge port. Therefore, the offloading shouldn't
>> Be dropped if only one external port is up on the bridge.
> 
> "Offloading" means - forward a frame from one hw port to other hw port without inserting it into CPU 
> queue. Offloaded frame is never visible to software bridge.
> 
> There is code that allows offload only if the linux bridge device used to connect rswitch ports does not 
> have anything else.  If it has something else, offloading is disabled (because there is no way to know 
> when a frame can be processed within rswitch hw without sending it to cpu).

Ah I see the code that explicitly enabled l2 offload only when at least two ports are active is not in 
mainline.

Still, l2 offload requires at least two ports participating, by definition.
When there is only one port with hw forwarding enabled, it will get empty allowed forward destination mask.