netdev - Re: What makes a good fake MAC address?

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Message-Id: <200904221428.03539.inaky@linux.intel.com>
Date:	Wed, 22 Apr 2009 14:28:03 -0700
From:	Inaky Perez-Gonzalez <inaky@...ux.intel.com>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	netdev@...r.kernel.org
Subject: Re: What makes a good fake MAC address?

On Wednesday 22 April 2009, Eric Dumazet wrote:
> Inaky Perez-Gonzalez a écrit :
> > Hi All
> >
> > The Intel i2400m WiMAX driver behaves as an ethernet device, and
> > currently when sending packets to the netdev stack, it fakes an ethernet
> > header, sets the "from" mac address to zeroes and the "to" to it's own
> > MAC address.
> >
> > The WiMAX network can be considered to be a point-to-point (up to the
> > gateway) connection, all IP based, so there are not MAC addresses from
> > our gateway (not to mention that it can change behind us).
> >
> > The problem with using a zero mac address is that it confuses the
> > bridging software (and maybe others). I was wondering, what would be a
> > fake mac address we could put in there that is legal for this kind of
> > "faking"? [or the closest thing to legal?]
> >
> > Thanks!
>
> We have random_ether_addr(), it should be self explained :)

(Also in reply to Stephen's comment) the device has its own local address; 
what we are faking is the address the packet comes from.

According to random_ether_addr(), it sets the local bits; will this work to 
fake the "other end of the connection"? (for which there is an IP address but 
no MAC address, it being a pure IP link).

Thanks,

-- 
Inaky
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