linux-kernel - Re: [PATCH RFC net 0/2] net: dsa: felix: fix VLAN-unaware reception

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Message-ID: <20241215170921.5qlundy4jzutvze7@skbuf>
Date: Sun, 15 Dec 2024 19:09:21 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: Robert Hodaszi <robert.hodaszi@...i.com>
Cc: netdev@...r.kernel.org, claudiu.manoil@....com,
	alexandre.belloni@...tlin.com, UNGLinuxDriver@...rochip.com,
	andrew@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC net 0/2] net: dsa: felix: fix VLAN-unaware reception

On Sun, Dec 15, 2024 at 05:33:32PM +0100, Robert Hodaszi wrote:
> Hello,
> 
> This patchset supposed to fix the currently non-working ocelot-8021q
> mode of the Felix driver if bridge is VLAN-unaware.
> 
> As can see in the commit messages, the driver enables
> 'untag_vlan_aware_bridge_pvid' to software VLAN untag all packets, but
> tagging is only enabled if VLAN-filtering is enabled
> (push_inner_tag=1).
> 
> Untagging packets from VLAN-unaware bridge ports is wrong, and corrupts
> the packets.
> 
> It was tempting to simply restore dsa_software_vlan_untag()'s checking
> as it was before:
> 
>   /* Move VLAN tag from data to hwaccel **
>   if (!skb_vlan_tag_present(skb) && skb->protocol == htons(proto)) {
>     skb = skb_vlan_untag(skb);
>     if (!skb)
>       return NULL;
>   }
> 
> And so untagging only VLAN packets, but that's not really a solution,
> VLAN-tagged packets may arrive on VLAN-unaware ports, and those would
> get untagged incorrectly.
> 
> So I added a way to mark ports as untagged when untagging is enabled,
> and return without altering the packet.

Give me an example traffic pattern, Linux configuration and corruption,
please. I spent a lot of time trying to make sure I am not introducing
regressions, and I have no idea what you are seeing that is wrong.
Please don't try to make assumptions, just let me see what you see.