netdev - Re: [PATCH net] net: dsa: refuse cross-chip mirroring operations

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Message-ID: <1abbbea3-0eb8-42c4-b4d5-c06c36676a4c@lunn.ch>
Date: Tue, 8 Oct 2024 14:19:16 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Tobias Waldekranz <tobias@...dekranz.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: dsa: refuse cross-chip mirroring operations

On Tue, Oct 08, 2024 at 12:43:20PM +0300, Vladimir Oltean wrote:
> In case of a tc mirred action from one switch to another, the behavior
> is not correct. We simply tell the source switch driver to program a
> mirroring entry towards mirror->to_local_port = to_dp->index, but it is
> not even guaranteed that the to_dp belongs to the same switch as dp.
> 
> For proper cross-chip support, we would need to go through the
> cross-chip notifier layer in switch.c, program the entry on cascade
> ports, and introduce new, explicit API for cross-chip mirroring, given
> that intermediary switches should have introspection into the DSA tags
> passed through the cascade port (and not just program a port mirror on
> the entire cascade port). None of that exists today.
> 
> Reject what is not implemented so that user space is not misled into
> thinking it works.
> 
> Fixes: f50f212749e8 ("net: dsa: Add plumbing for port mirroring")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

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

    Andrew