From owner-freebsd-hackers@FreeBSD.ORG  Sat Sep 17 20:57:33 2011
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From: YongHyeon PYUN <pyunyh@gmail.com>
Date: Sat, 17 Sep 2011 13:32:18 -0700
To: Hooman Fazaeli <fazaeli@sepehrs.com>
Message-ID: <20110917203218.GC13993@michelle.cdnetworks.com>
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Cc: jfv@FreeBSD.org, freebsd-hackers@freebsd.org
Subject: Re: intel checksum offload
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On Sat, Sep 17, 2011 at 11:57:10AM +0430, Hooman Fazaeli wrote:
> Hi list,
> 
> The data sheet for intel 82576 advertises IP TX/RX checksum offload
> but the driver does not set CSUM_IP in ifp->if_hwassist. Does this mean that
> driver (and chip) do not support IP TX checksum offload or the support for
> TX is not yet included in the driver?

After reading this mail, I checked em(4)/lem(4) code and noticed
these drivers removed CSUM_IP capability as well. igb(4) didn't
support CSUM_IP from day 1 but em(4)/lem(4) used to take advantage
of IP checksum offloading capability.
Given that these drivers share many code with Linux, Jack may know
the details and why IP checksum offloading code was removed. Note,
Linux does not use IP checksum offloading so I guess this could be
oversight in shared code.

BTW, hackers may not be right ML to post this kind of post.
CCed to jfv@, the driver maintainer.