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Re: RFC: Enabling ethernet drivers to return FCS in the skb?

To: Rask Ingemann Lambertsen <rask@xxxxxxxxxx>
Subject: Re: RFC: Enabling ethernet drivers to return FCS in the skb?
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Wed, 19 Nov 2003 07:33:53 -0800
Cc: "'netdev@xxxxxxxxxxx'" <netdev@xxxxxxxxxxx>
In-reply-to: <20031119123556.A7622@xxxxxxxxxx>
Organization: Candela Technologies
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Rask Ingemann Lambertsen wrote:
On Mon, Nov 17, 2003 at 01:52:17PM -0800, Ben Greear wrote:

Is there any interest in adding an Ethtool command to tell the driver to
push the extra 4 bytes of CSUM into the skb?

When enabling this feature, I'd also like to allow drivers to receive
frames with bad FCS as well.

[cut]

At least some hardware appears
to support receiving bad FCS frames (e1000, evidently), but I am not sure
how wide-spread this feature is...


The Intel i82586 and i82596 and can be told to receive frames with a bad FCS.
They can also be told to send a precomputed FCS rather than computing it on
the fly. The i82596 and tulip can also transfer the FCS to memory when
receiving frames. I guess all of this is also supported on the i82557/8/9.

If you have a patch or example code that shows how to do this, I'd love to
see it.  I have code that should RX bad CSUM from the Intel folks, but I can't
get it to generate bad CRC (it does framing errors instead with my attempt),
so I can't test the RX code properly!

I have the path from user-space to the NIC written, so just need to tweak the
drivers a bit...

Do you know if tulip can be told to accept bad FCS and/or if it can generate
a frame with bad FCS somehow?

Thanks!
Ben




--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com



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