Re[2]: Re[3]: [PATCH 2/3] ipvs: Fix faulty IPv6 extension header handl

To: "Jesper Dangaard Brouer" <brouer@xxxxxxxxxx>
Subject: Re[2]: Re[3]: [PATCH 2/3] ipvs: Fix faulty IPv6 extension header handling in IPVS
Cc: "Patrick McHardy" <kaber@xxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, "Julian Anastasov" <ja@xxxxxx>, "Simon Horman" <horms@xxxxxxxxxxxx>, "Wensong Zhang" <wensong@xxxxxxxxxxxx>, netfilter-devel@xxxxxxxxxxxxxxx
From: "Hans Schillstrom" <hans@xxxxxxxxxxxxxxx>
Date: Wed, 29 Aug 2012 11:47:16 +0200 (CEST)
>To Hans and Patrick,
>On Mon, 2012-08-27 at 14:02 +0200, Patrick McHardy wrote:
>> 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.
>> >
>> > I guess that's the problem, adding it to the skb will not be popular ....
>> > Right now I don't have a good solution, maybe a more generic netfilter ptr 
>> > in the skb ...
>> I guess inet6_skb_parm will be at least slightly more popular than
>> adding it to the skb itself. The netfilter pointers are all used for
>> optional things, so we can't really add it to any of those.
>Okay, but how do we go from here?
>Hans, should this hold back the patch ("ipvs: Fix faulty IPv6 extension
>header handling in IPVS").  Or should we pursue our patch, and circle
>back later once e.g. Patrick have found a generic solution for IPv6
>transport header handling?

Should we give it a try to put it in inet6_skb_parm 
and minimize what we put there ?
I think it could be worth it.

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