linux-kernel - Re: [PATCH] net: atlantic: fix check for invalid ethernet addresses

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Date:   Wed, 30 Nov 2022 16:08:09 -0500
From:   Brian Masney <bmasney@...hat.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     irusskikh@...vell.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, cth451@...il.com
Subject: Re: [PATCH] net: atlantic: fix check for invalid ethernet addresses

On Wed, Nov 30, 2022 at 08:41:29PM +0100, Andrew Lunn wrote:
> On Wed, Nov 30, 2022 at 12:42:59PM -0500, Brian Masney wrote:
> > The Qualcomm sa8540p automotive development board (QDrive3) has an
> > Aquantia NIC wired over PCIe. The ethernet MAC address assigned to
> > all of the boards in our lab is 00:17:b6:00:00:00. The existing
> > check in aq_nic_is_valid_ether_addr() only checks for leading zeros
> > in the MAC address. Let's update the check to also check for trailing
> > zeros in the MAC address so that a random MAC address is assigned
> > in this case.
> > 
> > Signed-off-by: Brian Masney <bmasney@...hat.com>
> > ---
> >  drivers/net/ethernet/aquantia/atlantic/aq_nic.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
> > index 06508eebb585..c9c850bbc805 100644
> > --- a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
> > +++ b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
> > @@ -293,7 +293,8 @@ static bool aq_nic_is_valid_ether_addr(const u8 *addr)
> >  	/* Some engineering samples of Aquantia NICs are provisioned with a
> >  	 * partially populated MAC, which is still invalid.
> >  	 */
> > -	return !(addr[0] == 0 && addr[1] == 0 && addr[2] == 0);
> > +	return !(addr[0] == 0 && addr[1] == 0 && addr[2] == 0) &&
> > +		!(addr[3] == 0 && addr[4] == 0 && addr[5] == 0);
> 
> Hi Brian
> 
> is_valid_ether_addr()

aq_nic_ndev_register() already calls is_valid_ether_addr():

	if (is_valid_ether_addr(addr) &&
	    aq_nic_is_valid_ether_addr(addr)) {
		(self->ndev, addr);
	} else {
		...
	}

That won't work for this board since that function only checks that the
MAC "is not 00:00:00:00:00:00, is not a multicast address, and is not
FF:FF:FF:FF:FF:FF." The MAC address that we get on all of our boards is
00:17:b6:00:00:00.

Brian