linux-kernel - Re: [PATCH net-next] bridge: Make the FDB consider inner tag for Q-in-Q

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Message-ID: <20241130160815.4n5hnr44v6ea3m44@skbuf>
Date: Sat, 30 Nov 2024 18:08:15 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: Andy Strohman <andrew@...rewstrohman.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.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>,
	Ido Schimmel <idosch@...dia.com>, Petr Machata <petrm@...dia.com>,
	Claudiu Manoil <claudiu.manoil@....com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	UNGLinuxDriver@...rochip.com, Shahed Shaikh <shshaikh@...vell.com>,
	Manish Chopra <manishc@...vell.com>, GR-Linux-NIC-Dev@...vell.com,
	Simon Horman <horms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Roopa Prabhu <roopa@...dia.com>, intel-wired-lan@...ts.osuosl.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, bridge@...ts.linux.dev
Subject: Re: [PATCH net-next] bridge: Make the FDB consider inner tag for
 Q-in-Q

On Sat, Nov 30, 2024 at 06:04:52PM +0200, Nikolay Aleksandrov wrote:
> Hi,
> This patch makes fdb lookups slower for everybody, ruins the nice key alignment,
> increases the key memory usage and adds more complexity for a corner case, especially
> having 2 different hosts with identical macs sounds weird. Fdb matching on both tags
> isn't a feature I've heard of, I don't know if there are switches that support it.
> Could you point to anywhere in the specs that such support is mentioned?
> Also could you please give more details about the use case? Maybe we can help you solve
> your problem without impacting everyone. Perhaps we can mix vlan-aware bridge and tc
> to solve it. As it stands I'm against adding such matching, but I'd love to hear what
> other people think.
> 
> Cheers,
>  Nik

Correct, I was also going to plan asking Andy what is his plan on making
switchdev digest this. The switch ASICs I'm most familiar with can learn
on inner VID or outer VID, but not both. Like you, I'm also not sure
what 802.1Q says about FDB entries with 2 associated VIDs.