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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.


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?


Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc

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