linux-kernel - Re: [PATCH v4 net-next 05/12] ether: Add dedicated Ethertype for pseudo-802.1Q DSA tagging

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Message-ID: <20190429221858.GR12333@lunn.ch>
Date:   Tue, 30 Apr 2019 00:18:58 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     f.fainelli@...il.com, vivien.didelot@...il.com,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 net-next 05/12] ether: Add dedicated Ethertype for
 pseudo-802.1Q DSA tagging

On Mon, Apr 29, 2019 at 03:16:59AM +0300, Vladimir Oltean wrote:
> There are two possible utilizations so far:
> 
> - Switch devices that don't support a native insertion/extraction header
>   on the CPU port may still enjoy the benefits of port isolation with a
>   custom VLAN tag.
> 
>   For this, they need to have a customizable TPID in hardware and a new
>   Ethertype to distinguish between real 802.1Q traffic and the private
>   tags used for port separation.
> 
> - Switches that don't support the deactivation of VLAN awareness, but
>   still want to have a mode in which they accept all traffic, including
>   frames that are tagged with a VLAN not configured on their ports, may
>   use this as a fake to trick the hardware into thinking that the TPID
>   for VLAN is something other than 0x8100.
> 
> What follows after the ETH_P_DSA_8021Q EtherType is a regular VLAN
> header (TCI), however there is no other EtherType that can be used for
> this purpose and doesn't already have a well-defined meaning.
> ETH_P_8021AD, ETH_P_QINQ1, ETH_P_QINQ2 and ETH_P_QINQ3 expect that
> another follow-up VLAN tag is present, which is not the case here.
> 
> Signed-off-by: Vladimir Oltean <olteanv@...il.com>
> Suggested-by: Andrew Lunn <andrew@...n.ch>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew