netdev - Re: [PATCH] net: usb: r8152: Check used MAC passthrough address

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Message-ID: <20220105083238.4278d331@md1za8fc.ad001.siemens.net>
Date:   Wed, 5 Jan 2022 08:32:38 +0100
From:   Henning Schild <henning.schild@...mens.com>
To:     Aaron Ma <aaron.ma@...onical.com>
CC:     <kuba@...nel.org>, <linux-usb@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <davem@...emloft.net>, <hayeswang@...ltek.com>, <tiwai@...e.de>
Subject: Re: [PATCH] net: usb: r8152: Check used MAC passthrough address

Am Wed, 5 Jan 2022 08:23:55 +0100
schrieb Henning Schild <henning.schild@...mens.com>:

> 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@...onical.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@...onical.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.

That is wrong, need to know that MAC so can not move up too much. But
maybe above the is_valid_ether_addr

Henning

> > +		}
> > +	}
> > +	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);
> >  
>