netdev - Re: [RFC PATCH net-next 5/5] net: dsa: add explicit support for host bridge VLANs

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Date:   Thu, 10 Feb 2022 15:30:54 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        Rafael Richter <rafael.richter@....de>,
        Daniel Klauer <daniel.klauer@....de>,
        Tobias Waldekranz <tobias@...dekranz.com>
Subject: Re: [RFC PATCH net-next 5/5] net: dsa: add explicit support for host
 bridge VLANs

On Wed, Feb 09, 2022 at 11:30:43PM +0200, Vladimir Oltean wrote:
> - It is possible to artificially fill the VLAN table of a switch, by
>   walking through the entire VLAN space, adding and deleting them.
>   For each VLAN added on a user port, DSA will add it on shared ports
>   too, but for each VLAN deletion on a user port, it will remain
>   installed on shared ports, since DSA has no good indication of whether
>   the VLAN is still in use or not. If the hardware has a limited number
>   of VLAN table entries, this may uselessly consume that space.

There's another, more important angle to this which I forgot while I was
writing the commit message. If you don't have a way to delete VLANs on
CPU ports, you have no way of removing yourself from a VLAN with noisy
stations, once you've entered it. I'll make sure to update the commit
message for v2.