netdev - Re: [RFC net-next v2 5/5] net: phy: nxp-c45-tja11xx: implement mdo_insert_tx

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Date: Fri, 1 Sep 2023 15:56:20 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Radu Pirea <radu-nicolae.pirea@....com>,
	"atenart@...nel.org" <atenart@...nel.org>,
	"Radu-nicolae Pirea (OSS)" <radu-nicolae.pirea@....nxp.com>,
	"andrew@...n.ch" <andrew@...n.ch>,
	"hkallweit1@...il.com" <hkallweit1@...il.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	Sebastian Tobuschat <sebastian.tobuschat@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>,
	"richardcochran@...il.com" <richardcochran@...il.com>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC net-next v2 5/5] net: phy: nxp-c45-tja11xx: implement
 mdo_insert_tx_tag

2023-09-01, 11:32:19 +0100, Russell King (Oracle) wrote:
> On Fri, Sep 01, 2023 at 12:07:32PM +0200, Sabrina Dubroca wrote:
> > 2023-09-01, 09:09:06 +0000, Radu Pirea wrote:
> > > We can do a flush very simple, but to restore the configuration maybe
> > > we should to save the key in the macsec_key structure. I am not sure if
> > > the key can be extracted from crypto_aead structure.
> > 
> > Either that or in the driver. I have a small preference for driver,
> > because then cases that don't need this restore won't have to keep the
> > key in memory, reducing the likelihood of accidentally sharing it.
> > OTOH, if we centralize that code, it's easier to make sure everything
> > is cleared from kernel memory when we delete the SA.
> 
> Maybe consider about doing it as a library function, so drivers that
> need this don't have to reimplement the functionality in randomly
> buggy ways?

But then the driver would depend on the macsec module, right? It's not
a large module, but that seems a bit undesirable.

I think I'd rather add the key to macsec_key, and only copy it there
in case we're offloading (we currently don't allow enabling offloading
after installing some SAs/keys so that would be fine). Maybe add a
driver flag to request keeping the keys in memory (I don't know if all
drivers will require that -- seems like all PHY drivers would, but what
about the MAC ones?).

-- 
Sabrina