linux-kernel - Re: [PATCH net v3 1/1] net: dsa: microchip: implement multi-bridge support

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Message-ID: <20211126114336.05fd7ebd@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Fri, 26 Nov 2021 11:43:36 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>, kernel@...gutronix.de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3 1/1] net: dsa: microchip: implement multi-bridge
 support

On Fri, 26 Nov 2021 13:39:26 +0100 Oleksij Rempel wrote:
> Current driver version is able to handle only one bridge at time.
> Configuring two bridges on two different ports would end up shorting this
> bridges by HW. To reproduce it:
> 
> 	ip l a name br0 type bridge
> 	ip l a name br1 type bridge
> 	ip l s dev br0 up
> 	ip l s dev br1 up
> 	ip l s lan1 master br0
> 	ip l s dev lan1 up
> 	ip l s lan2 master br1
> 	ip l s dev lan2 up
> 
> 	Ping on lan1 and get response on lan2, which should not happen.
> 
> This happened, because current driver version is storing one global "Port VLAN
> Membership" and applying it to all ports which are members of any
> bridge.
> To solve this issue, we need to handle each port separately.
> 
> This patch is dropping the global port member storage and calculating
> membership dynamically depending on STP state and bridge participation.
> 
> Note: STP support was broken before this patch and should be fixed
> separately.
> 
> Fixes: c2e866911e25 ("net: dsa: microchip: break KSZ9477 DSA driver into two files")

Suspicious, this sounds like a code reshuffling commit. Where was the
bad code introduced? The fixes tag should point at the earliest point 
in the git history where the problem exists.