linux-kernel - Re: [PATCH net-next] sysfs: add entry to indicate network interfaces with random MAC address

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Message-ID: <4C469808.5060308@redhat.com>
Date:	Wed, 21 Jul 2010 08:47:36 +0200
From:	Harald Hoyer <harald@...hat.com>
To:	David Miller <davem@...emloft.net>
CC:	shemminger@...tta.com, bhutchings@...arflare.com,
	sassmann@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, gospo@...hat.com,
	gregory.v.rose@...el.com, alexander.h.duyck@...el.com,
	leedom@...lsio.com
Subject: Re: [PATCH net-next] sysfs: add entry to indicate network interfaces
 with random MAC address

On 07/21/2010 08:34 AM, David Miller wrote:
> From: Harald Hoyer<harald@...hat.com>
> Date: Wed, 21 Jul 2010 08:26:27 +0200
>
>> On 07/20/2010 11:20 PM, David Miller wrote:
>>> From: Stephen Hemminger<shemminger@...tta.com>
>>> Date: Tue, 20 Jul 2010 14:18:16 -0700
>>>
>>>> No one mentioned that the first octet of an Ethernet address already
>>>> indicates "software generated" Ethernet address. Per the standard,
>>>> if bit 1 is set it means address is locally assigned.
>>>>
>>>> static inline bool is_locally_assigned_ether(const u8 *addr)
>>>> {
>>>> 	return (addr[0]&   0x2) != 0;
>>>> }
>>>
>>> W00t!
>>>
>>> Indeed, can udev just use that?  :-)
>>
>> It already does:
>> see /lib/udev/rules.d/75-persistent-net-generator.rules
>
> So... why doesn't this work?

It works.. but the information, that the MAC is randomly generated would be 
valuable. So, for the non-random locally assigned MAC (with bit 1), we could 
easily make persistent rules based on the MAC, instead of completely ignoring 
them, like we do currently.
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