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Date: Mon, 25 Aug 2008 21:02:07 +0200
From: John Hay <jhay@meraka.org.za>
To: gnn@FreeBSD.org
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Cc: Luigi Rizzo <rizzo@iet.unipi.it>, "Bruce M. Simpson" <bms@FreeBSD.org>,
	net@FreeBSD.org
Subject: Re: Small patch to multicast code...
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On Fri, Aug 22, 2008 at 03:03:30PM -0700, gnn@FreeBSD.org wrote:
> At Fri, 22 Aug 2008 22:43:39 +0100,
> Bruce M. Simpson wrote:
> > 
> > gnn@FreeBSD.org wrote:
> > > Somehow the data that the device needs to do the proper checksum
> > > offload is getting trashed here.  Now, since it's clear we need a
> > > writable packet structure so that we don't trash the original, I'm
> > > wondering if the m_pullup() will be sufficient.
> > >   
> > 
> > If it's serious enough to break UDP checksumming on the wire, perhaps we 
> > should just swallow the mbuf allocator heap churn and do the m_dup() for 
> > now, but slap in a big comment about why it's there.
> 
> I think if none of us finds a better way before early next week that's
> what I'll do so that this at least works in 7.1.

I think we and others have been hitting this problem:

kern/119635: [em] Bad UDP packet checksum with em(4) and rxcsum/txcsum enabled
http://www.freebsd.org/cgi/query-pr.cgi?pr=119635

I'll try out your patch.

John
-- 
John Hay -- John.Hay@meraka.csir.co.za / jhay@FreeBSD.org