Subject: Re: [PATCH net-next 2/4] net: dev: don't set the same mac address for netdev

From: Ding Tianhong <[email-masked]>
Date: Thu, 5 Jun 2014 17:50:18 +0800

On 2014/6/5 17:09, Toshiaki Makita wrote:
> (2014/06/05 15:50), Ding Tianhong wrote:
>> Most of netdev just like bond, team, vlan will set the mac address
>> and propagate to the upperdev or lowerdev regardless the mac address
>> is  same or not, I could not find that the same mac address could
>> make affect, so add equal check when set mac address.
>>
>> Signed-off-by: Ding Tianhong <[email-masked]>
>> ---
>>  net/core/dev.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 5367bfb..4008a51 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -5570,6 +5570,8 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa)
>>  		return -EINVAL;
>>  	if (!netif_device_present(dev))
>>  		return -ENODEV;
>> +	if (ether_addr_equal_64bits(dev->dev_addr, sa->sa_data))
>> +		return 0;
>>  	err = ops->ndo_set_mac_address(dev, sa);
>>  	if (err)
>>  		return err;
>>
> 
> Bridge uses addr_assign_type to check if bridge_id can be propageted by
> bridge ports. If user set mac address, and even if it is the same as
> current one, bridge uses the fact that the mac address is set by user.
> 

OK

> Although I'm not aware of a driver that needs calling of
> ndo_set_mac_address() for the same mac address, this change looks a bit
> risky to me.
> (For example, old bridge code needed this call because it managed
> BR_SET_MAC_ADDR in bridge flags.)
> 
Except the old bridge, I still don't think any other driver need to call ndo_set_mac_address()
for the same mac address, if the dev_set_mac_address() don't do anything for the same address,
I think some drivers should ignore the same mac address themselves just like bonding, macvlan, vlan and so on.

Ding 

> Thanks,
> Toshiaki Makita