From: Arnd Bergmann <arnd@arndb.de>
To: andy.green@linaro.org
Cc: linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org,
patches@linaro.org, nicolas.pitre@linaro.org, x0132446@ti.com,
s-jan@ti.com, tony@atomide.com
Subject: Re: [RFC PATCH 1/2] OMAP2+: add cpu id register to MAC address helper
Date: Fri, 25 Mar 2011 15:50:25 +0100 [thread overview]
Message-ID: <201103251550.26117.arnd@arndb.de> (raw)
In-Reply-To: <4D8C99CC.5020103@linaro.org>
On Friday 25 March 2011, Andy Green wrote:
> I see. It would work OK then. They probably wouldn't want to blow
> their $1750 just on Panda though, so maybe they set 4 bits or whatever
> and let 20 be computed.
Well, if the algorithm is defined well, it could be used for any device
based on OMAP. The marketing department could turn this into a win by
declaring "does not require external EEPROM for ethernet mac address" ;-)
> However, the only practical advantage is that it would show up as a TI
> MAC in an OUI database. The "locally administered" address as used at
> the moment is otherwise legal in every respect AFAIK.
It should work almost always, except in very special corner cases:
* If you have a netboot setup, you want the boot loader to use the
same mac address for requesting the kernel image that you use later,
otherwise the switch might consider it a MAC spoofing attach and disable
the port. The obvious workaround is to put your code into the boot loader
as well.
* Some environments might be configured to disallow locally administered
MAC addresses for "security" reasons. A bit bogus, but not unheard of.
* Some places try to keep a database of all used machines and their MAC
addresses to monitor who connects to the network. This requires the address
to be stable. It also prevents the use of virtualization, so it's becoming
less common.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH 1/2] OMAP2+: add cpu id register to MAC address helper
Date: Fri, 25 Mar 2011 15:50:25 +0100 [thread overview]
Message-ID: <201103251550.26117.arnd@arndb.de> (raw)
In-Reply-To: <4D8C99CC.5020103@linaro.org>
On Friday 25 March 2011, Andy Green wrote:
> I see. It would work OK then. They probably wouldn't want to blow
> their $1750 just on Panda though, so maybe they set 4 bits or whatever
> and let 20 be computed.
Well, if the algorithm is defined well, it could be used for any device
based on OMAP. The marketing department could turn this into a win by
declaring "does not require external EEPROM for ethernet mac address" ;-)
> However, the only practical advantage is that it would show up as a TI
> MAC in an OUI database. The "locally administered" address as used at
> the moment is otherwise legal in every respect AFAIK.
It should work almost always, except in very special corner cases:
* If you have a netboot setup, you want the boot loader to use the
same mac address for requesting the kernel image that you use later,
otherwise the switch might consider it a MAC spoofing attach and disable
the port. The obvious workaround is to put your code into the boot loader
as well.
* Some environments might be configured to disallow locally administered
MAC addresses for "security" reasons. A bit bogus, but not unheard of.
* Some places try to keep a database of all used machines and their MAC
addresses to monitor who connects to the network. This requires the address
to be stable. It also prevents the use of virtualization, so it's becoming
less common.
Arnd
next prev parent reply other threads:[~2011-03-25 14:50 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-24 21:27 [RFC PATCH 0/2] OMAP2+: PANDA: Provide unique-ish MAC addresses for Ethernet and WLAN interfaces Andy Green
2011-03-24 21:27 ` Andy Green
2011-03-24 21:27 ` [RFC PATCH 1/2] OMAP2+: add cpu id register to MAC address helper Andy Green
2011-03-24 21:27 ` Andy Green
2011-03-25 11:49 ` Arnd Bergmann
2011-03-25 11:49 ` Arnd Bergmann
2011-03-25 12:08 ` Andy Green
2011-03-25 12:08 ` Andy Green
2011-03-25 13:24 ` Arnd Bergmann
2011-03-25 13:24 ` Arnd Bergmann
2011-03-25 13:34 ` Andy Green
2011-03-25 13:34 ` Andy Green
2011-03-25 14:50 ` Arnd Bergmann [this message]
2011-03-25 14:50 ` Arnd Bergmann
2011-03-25 15:00 ` Andy Green
2011-03-25 15:00 ` Andy Green
2011-03-24 21:27 ` [RFC PATCH 2/2] OMAP2+: PANDA: Fix up random or missing MAC addresses for eth0 and wlan0 Andy Green
2011-03-24 21:27 ` Andy Green
2011-03-25 7:39 ` Hema Kalliguddi
2011-03-25 7:39 ` Hema Kalliguddi
2011-03-25 20:13 ` Jason Kridner
2011-03-25 20:13 ` Jason Kridner
2011-03-25 20:20 ` Arnd Bergmann
2011-03-25 20:20 ` Arnd Bergmann
2011-03-25 20:23 ` Nicolas Pitre
2011-03-25 20:23 ` Nicolas Pitre
2011-03-28 12:54 ` Jason Kridner
2011-03-28 12:54 ` Jason Kridner
2011-03-25 20:30 ` Andy Green
2011-03-25 20:30 ` Andy Green
2011-03-25 11:39 ` Arnd Bergmann
2011-03-25 11:39 ` Arnd Bergmann
2012-06-28 14:18 ` [RFC PATCH 0/2] OMAP2+: PANDA: Provide unique-ish MAC addresses for Ethernet and WLAN interfaces Arnd Bergmann
2012-06-28 14:18 ` Arnd Bergmann
2012-06-28 14:45 ` Steven Rostedt
2012-06-28 14:45 ` Steven Rostedt
2012-06-28 14:49 ` "Andy Green (林安廸)"
2012-06-28 14:49 ` "Andy Green (林安廸)"
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