netdev - Re: [PATCH] smsc75xx: only set mac address once on bind

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Message-ID: <CAKh2mn4i0uwfLeO4yvujJn3nvu3MbsTmrOJp_6uk1ezQMF6V+g@mail.gmail.com>
Date:	Tue, 11 Dec 2012 14:35:43 +0000
From:	Steve Glendinning <steve@...well.net>
To:	Dan Williams <dcbw@...hat.com>
Cc:	Steve Glendinning <steve.glendinning@...well.net>,
	netdev <netdev@...r.kernel.org>, Bjorn Mork <bjorn@...k.no>
Subject: Re: [PATCH] smsc75xx: only set mac address once on bind

Hi Dan,

On 10 December 2012 23:00, Dan Williams <dcbw@...hat.com> wrote:
> On Mon, 2012-12-10 at 11:01 +0000, Steve Glendinning wrote:
>> This patch changes when we decide what the device's MAC address
>> is from per ifconfig up to once when the device is connected.
>>
>> Without this patch, a manually forced device MAC is overwritten
>> on ifconfig down/up.  Also devices that have no EEPROM are
>> assigned a new random address on ifconfig down/up instead of
>> persisting the same one.
>
> Does this mean that on devices without EEPROM, ifconfig XXX
> down/ifconfig XXX up will generate a *new* random address?  That seems a
> bit odd; why wouldn't the first random address generated for the device
> persist until either (a) changed by ifconfig or (b) device was
> disconnected?

Sorry if my commit message wasn't clear enough.  That is indeed a bit
odd, and it describes the (buggy) behaviour BEFORE this patch was
applied.

With this patch applied, devices without EEPROM (and without a
manually specified MAC address) will get a randomly generated address
assigned once at bind time, so this MAC will persist for the lifetime
the USB device is connected.  We also now won't trash a manually
specified MAC, for cases where userland sets the MAC before bringing
up the interface.

-- 
Steve Glendinning
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