netdev - Re: [Bugme-new] [Bug 11316] New: severe performance regression for iptables nat routing

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Date:	Thu, 14 Aug 2008 23:49:33 -0600
From:	Alex Williamson <alex.williamson@...com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	kaber@...sh.net, davem@...emloft.net, akpm@...ux-foundation.org,
	buytenh@...vell.com, netdev@...r.kernel.org,
	bugme-daemon@...zilla.kernel.org
Subject: Re: [Bugme-new] [Bug 11316] New: severe performance regression
	for	iptables nat routing

On Fri, 2008-08-15 at 15:35 +1000, Herbert Xu wrote:
> On Fri, Aug 15, 2008 at 02:44:26PM +1000, Herbert Xu wrote:
> > 
> > Actually, I think know what's going on but a raw packet dump should
> > confirm whether we're getting a partial checksum.
> 
> Nevermind, I think I've found the problem.
> 
> loopback: Drop obsolete ip_summed setting
> 
> Now that the network stack can handle inbound packets with partial
> checksums, we should no longer clobber the ip_summed field in the
> loopback driver.  This is because CHECKSUM_UNNECESSARY implies that
> the checksum field is actually valid which is not true for loopback
> packets since it's only partial (and thus complemented).
> 
> This allows packets from lo to then be SNATed to an external source
> while still preserving the checksum's validity.

Nope, that doesn't fix it.  NAT'd throughput remains about the same.
Thanks,

	Alex

-- 
Alex Williamson                             HP Open Source & Linux Org.

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