linux-kernel - Re: [PATCH net-next v1 1/9] net: dsa: add rcv

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Date:   Sat, 3 Apr 2021 17:05:34 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org
Subject: Re: [PATCH net-next v1 1/9] net: dsa: add rcv_post call back

On Sat, Apr 03, 2021 at 01:48:40PM +0200, Oleksij Rempel wrote:
> Some switches (for example ar9331) do not provide enough information
> about forwarded packets. If the switch decision was made based on IPv4
> or IPv6 header, we need to analyze it and set proper flag.
> 
> Potentially we can do it in existing rcv path, on other hand we can
> avoid part of duplicated work and let the dsa framework set skb header
> pointers and then use preprocessed skb one step later withing the rcv_post
> call back.
> 
> This patch is needed for ar9331 switch.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---

I don't necessarily disagree with this, perhaps we can even move
Florian's dsa_untag_bridge_pvid() call inside a rcv_post() method
implemented by the DSA_TAG_PROTO_BRCM_LEGACY, DSA_TAG_PROTO_BRCM_PREPEND
and DSA_TAG_PROTO_BRCM taggers. Or even better, because Oleksij's
rcv_post is already prototype-compatible with dsa_untag_bridge_pvid, we
can already do:

	.rcv_post = dsa_untag_bridge_pvid,

This should be generally useful for stuff that DSA taggers need to do
which is easiest done after eth_type_trans() was called.