netdev - Re: [PATCH v2 net-next 02/16] net: dsa: allow drivers to request promiscuous mode on master

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Message-ID: <20200926174700.GB3883417@lunn.ch>
Date:   Sat, 26 Sep 2020 19:47:00 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, f.fainelli@...il.com,
        vivien.didelot@...il.com, kuba@...nel.org
Subject: Re: [PATCH v2 net-next 02/16] net: dsa: allow drivers to request
 promiscuous mode on master

On Sat, Sep 26, 2020 at 08:30:54PM +0300, Vladimir Oltean wrote:
> Currently DSA assumes that taggers don't mess with the destination MAC
> address of the frames on RX. That is not always the case. Some DSA
> headers are placed before the Ethernet header (ocelot), and others
> simply mangle random bytes from the destination MAC address (sja1105
> with its incl_srcpt option).

...

> So give drivers the possibility to signal that their tagging protocol
> will get randomly dropped otherwise, and let DSA deal with fixing that.

> @@ -317,6 +317,13 @@ struct dsa_switch {
>  	 */
>  	bool			mtu_enforcement_ingress;
>  
> +	/* Some tagging protocols either mangle or shift the destination MAC
> +	 * address, in which case the DSA master would drop packets on ingress
> +	 * if what it understands out of the destination MAC address is not in
> +	 * its RX filter.
> +	 */
> +	bool			promisc_on_master;
> +
>  	size_t num_ports;
>  };

Hi Vladimir

I actually think this is a property of the tagger, not the DSA
driver. In fact, DSA drivers never handle actual frames, they are all
about the control plane, not the data plane. So i think this bool
should be in the tagger structure, dsa_device_ops.

       Andrew