netdev - Re: [PATCH net-next 2/2] net: dsa: mt7530: add support for bridge port isolation

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Message-ID: <0dcdf71c-8b47-4490-bee2-8551c75f19e0@lunn.ch>
Date: Sun, 16 Jun 2024 17:35:48 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Matthias Schiffer <mschiffer@...verse-factory.net>
Cc: Arınç ÜNAL <arinc.unal@...nc9.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	Daniel Golle <daniel@...rotopia.org>,
	DENG Qingfang <dqfext@...il.com>,
	Sean Wang <sean.wang@...iatek.com>
Subject: Re: [PATCH net-next 2/2] net: dsa: mt7530: add support for bridge
 port isolation

> As far as I can tell, the rules are:
> 
> - non-isolated ports can communicate with every port
> - isolated ports can't communicate with other isolated ports
> - communication is symmetric

It is a bit more subtle than that.

By default, all ports should be isolated. They can exchange packets
with the CPU port, but nothing else. This goes back to the model of
switches just look like a bunch of netdev interfaces. By default,
linux netdev interfaces are standalone. You need to add a bridge
before packets can flow between ports.

Once you add a bridge, ports within that bridge can exchange
packets. However, there can be multiple bridges. So a port needs to be
isolated from ports in another bridge, but non-isolated to ports
within the same bridge.

       Andrew