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

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

[Hans Schillstrom]

>
>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.

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

[Patrick McHardy]

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.