linux-kernel - Re: [PATCH] netfilter: add CHECKSUM target

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Message-ID: <20100709071814.GA27964@gondor.apana.org.au>
Date:	Fri, 9 Jul 2010 15:18:14 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	"Pekka Savola (ipv6)" <pekkas@...core.fi>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
	netfilter@...r.kernel.org, coreteam@...filter.org,
	netdev@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] netfilter: add CHECKSUM target

On Fri, Jul 09, 2010 at 01:29:13AM +0300, Michael S. Tsirkin wrote:
> This adds a `CHECKSUM' target, which can be used in the iptables mangle
> table.
> 
> You can use this target to compute and fill in the checksum in
> an IP packet that lacks a checksum.  This is particularly useful,
> if you need to work around old applications such as dhcp clients,
> that do not work well with checksum offloads, but don't want to
> disable checksum offload in your device.
> 
> The problem happens in the field with virtualized applications.
> For reference, see Red Hat bz 605555, as well as
> http://www.spinics.net/lists/kvm/msg37660.html
> 
> Typical expected use (helps old dhclient binary running in a VM):
> iptables -A POSTROUTING -t mangle -p udp --dport 68 -j CHECKSUM
> --checksum-fill
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

I'd think that this target would be protocol-agnostic, no?

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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