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Date:   Wed, 5 Jan 2022 08:23:55 +0100
From:   Henning Schild <henning.schild@siemens.com>
To:     Aaron Ma <aaron.ma@canonical.com>
CC:     <kuba@kernel.org>, <linux-usb@vger.kernel.org>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
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Subject: Re: [PATCH] net: usb: r8152: Check used MAC passthrough address
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Hi Aaron,

if this or something similar goes in, please add another patch to
remove the left-over defines.

Am Wed,  5 Jan 2022 14:17:47 +0800
schrieb Aaron Ma <aaron.ma@canonical.com>:

> When plugin multiple r8152 ethernet dongles to Lenovo Docks
> or USB hub, MAC passthrough address from BIOS should be
> checked if it had been used to avoid using on other dongles.
> 
> Currently builtin r8152 on Dock still can't be identified.
> First detected r8152 will use the MAC passthrough address.
> 
> Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
> ---
>  drivers/net/usb/r8152.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index f9877a3e83ac..77f11b3f847b 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -1605,6 +1605,7 @@ static int vendor_mac_passthru_addr_read(struct
> r8152 *tp, struct sockaddr *sa) char *mac_obj_name;
>  	acpi_object_type mac_obj_type;
>  	int mac_strlen;
> +	struct net_device *ndev;
>  
>  	if (tp->lenovo_macpassthru) {
>  		mac_obj_name = "\\MACA";
> @@ -1662,6 +1663,15 @@ static int
> vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
> ret = -EINVAL; goto amacout;
>  	}
> +	rcu_read_lock();
> +	for_each_netdev_rcu(&init_net, ndev) {
> +		if (strncmp(buf, ndev->dev_addr, 6) == 0) {
> +			rcu_read_unlock();
> +			goto amacout;

Since the original PCI netdev will always be there, that would disable
inheritance would it not?
I guess a strncmp(MODULE_NAME, info->driver, strlen(MODULE_NAME)) is
needed as well.

Maybe leave here with
netif_info()

And move the whole block up, we can skip the whole ACPI story if we
find the MAC busy.

> +		}
> +	}
> +	rcu_read_unlock();

Not sure if this function is guaranteed to only run once at a time,
otherwise i think that is a race. Multiple instances could make it to
this very point at the same time.

Henning

>  	memcpy(sa->sa_data, buf, 6);
>  	netif_info(tp, probe, tp->netdev,
>  		   "Using pass-thru MAC addr %pM\n", sa->sa_data);