netdev - Re[2]: [PATCH 2/3] ipvs: Fix faulty IPv6 extension header handling in IPVS

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Message-ID: <Pine.GSO.4.63.1208271308282.11224@stinky-local.trash.net>
Date:	Mon, 27 Aug 2012 13:13:44 +0200 (MEST)
From:	Patrick McHardy <kaber@...sh.net>
To:	Hans Schillstrom <hans@...illstrom.com>
cc:	Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
	lvs-devel@...r.kernel.org, Julian Anastasov <ja@....bg>,
	Simon Horman <horms@...ge.net.au>,
	Wensong Zhang <wensong@...ux-vs.org>,
	netfilter-devel@...r.kernel.org
Subject: Re[2]:  [PATCH 2/3] ipvs: Fix faulty IPv6 extension header  handling
 in IPVS

On Mon, 27 Aug 2012, Hans Schillstrom wrote:

>>
>> On Mon, 20 Aug 2012, Jesper Dangaard Brouer wrote:
>>
>>> Based on patch from: Hans Schillstrom
>>>
>>> IPv6 headers must be processed in order of appearance,
>>> neither can it be assumed that Upper layer headers is first.
>>> If anything else than L4 is the first header IPVS will throw it.
>>>
>>> IPVS will write SNAT & DNAT modifications at a fixed pos which
>>> will corrupt the message. Proper header position must be found
>>> before writing modifying packet.
>>>
>>> This patch contains a lot of API changes.  This is done, to avoid
>>> the costly scan of finding the IPv6 headers, via ipv6_find_hdr().
>>> Finding the IPv6 headers is done as early as possible, and passed
>>> on as a pointer "struct ip_vs_iphdr *" to the affected functions.
>>
>> How about we change netfilter to set up the skb's transport header
>> at an early time so we can avoid all (most of) these header scans
>> in netfilter?
>
> I think that would be great, maybe it should be global i.e. not only a netfilter issue.

I think in most other cases the headers are supposed to be processed 
sequentially. One problem though - to be useful for netfilter/IPVS
we'd also need to store the transport layer protocol somewhere.
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