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Message-ID: <20241017134413.GL1697@kernel.org>
Date: Thu, 17 Oct 2024 14:44:13 +0100
From: Simon Horman <horms@...nel.org>
To: Oliver Neukum <oneukum@...e.com>
Cc: edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
netdev@...r.kernel.org, Greg Thelen <gthelen@...gle.com>,
John Sperbeck <jsperbeck@...gle.com>
Subject: Re: [RFC] net: usb: usbnet: fix name regression
On Tue, Oct 15, 2024 at 04:03:32PM +0200, Oliver Neukum wrote:
> The fix for MAC addresses broke detection of the naming convention
> because it gave network devices no random MAC before bind()
> was called. This means that the check for the local assignment bit
> was always negative as the address was zeroed from allocation,
> instead of from overwriting the MAC with a unique hardware address.
>
> The correct check for whether bind() has altered the MAC is
> done with is_zero_ether_addr
>
> Signed-off-by: Oliver Neukum <oneukum@...e.com>
> Reported-by: Greg Thelen <gthelen@...gle.com>
> Diagnosed-by: John Sperbeck <jsperbeck@...gle.com>
> Fixes: bab8eb0dd4cb9 ("usbnet: modern method to get random MAC")
> ---
> drivers/net/usb/usbnet.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index ee1b5fd7b491..44179f4e807f 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -1767,7 +1767,8 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
> // can rename the link if it knows better.
> if ((dev->driver_info->flags & FLAG_ETHER) != 0 &&
> ((dev->driver_info->flags & FLAG_POINTTOPOINT) == 0 ||
> - (net->dev_addr [0] & 0x02) == 0))
> + /* somebody touched it*/
> + !is_zero_ether_addr(net->dev_addr)))
Hi Oliver,
I think works for the case where a random address will be assigned
as per the cited commit. But I'm unsure that is correct wrt
to the case where ->bind assigns an address with 0x2 set in the 0th octet.
Can that occur in practice? Perhaps not because the driver would
rely on usbnet_probe() to set a random address. But if so then
it would previously have hit the "eth%d" logic, but does not anymore.
> strscpy(net->name, "eth%d", sizeof(net->name));
> /* WLAN devices should always be named "wlan%d" */
> if ((dev->driver_info->flags & FLAG_WLAN) != 0)
> --
> 2.47.0
>
>
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