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Date:      Mon, 29 Oct 2012 13:41:04 -0700
From:      YongHyeon PYUN <pyunyh@gmail.com>
To:        Gleb Smirnoff <glebius@freebsd.org>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Andre Oppermann <andre@freebsd.org>
Subject:   Re: svn commit: r242161 - in head/sys: net netinet netpfil/pf
Message-ID:  <20121029204104.GA1431@michelle.cdnetworks.com>
In-Reply-To: <20121027220137.GJ70741@FreeBSD.org>
References:  <201210262106.q9QL6YgY000943@svn.freebsd.org> <508BBE6C.7010409@freebsd.org> <20121027220137.GJ70741@FreeBSD.org>

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On Sun, Oct 28, 2012 at 02:01:37AM +0400, Gleb Smirnoff wrote:
> On Sat, Oct 27, 2012 at 12:58:52PM +0200, Andre Oppermann wrote:
> A> On 26.10.2012 23:06, Gleb Smirnoff wrote:
> A> > Author: glebius
> A> > Date: Fri Oct 26 21:06:33 2012
> A> > New Revision: 242161
> A> > URL: http://svn.freebsd.org/changeset/base/242161
> A> >
> A> > Log:
> A> >    o Remove last argument to ip_fragment(), and obtain all needed information
> A> >      on checksums directly from mbuf flags. This simplifies code.
> A> >    o Clear CSUM_IP from the mbuf in ip_fragment() if we did checksums in

I'm not sure whether ti(4)'s checksum offloading for IP fragmented
packets(CSUM_IP_FRAGS) still works after this change.  ti(4)
requires CSUM_IP should be set for IP fragmented packets. Not sure
whether it's a bug or not. I have a ti(4) controller but I don't
remember where I can find it and don't have a link
parter(1000baseSX) to test it. :-(

> A> >      hardware. Some driver may not announce CSUM_IP in theur if_hwassist,
> A> >      although try to do checksums if CSUM_IP set on mbuf. Example is em(4).

em(4) had TX IP checksum offloading support but it was removed
without justification. There could be some reason on that decision
but I don't see any compelling reason.

> A> 
> A> I'm not getting your description here?  Why work around a bug in a driver
> A> in ip_fragment() when we can fix the bug in the driver?
> 
> Well, that was actually bug in the stack and a very special driver that
> demonstrates it. I may even agree that driver is incorrect, but the stack was
> incorrect, too.
> 
> -- 
> Totus tuus, Glebius.



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