netdev - Re: RFC: New BGF 'LOOP' instruction

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Message-ID: <6809423e656a160df11216ea5acc3d8b@localhost>
Date:	Tue, 03 Aug 2010 11:10:28 +0200
From:	Hagen Paul Pfeifer <hagen@...u.net>
To:	David Miller <davem@...emloft.net>
Cc:	<leonerd@...nerd.org.uk>, <netdev@...r.kernel.org>
Subject: Re: RFC: New BGF 'LOOP' instruction


On Tue, 03 Aug 2010 00:19:04 -0700 (PDT), David Miller wrote:
> From: Paul LeoNerd Evans <leonerd@...nerd.org.uk>

>> Rightnow, BPF is all but useless for parsing, say, IPv6. I only pick
>> IPv6 as one example, I'm sure there must exist a great number more
>> packet-based protocols that use a "linked-list" style approach to
>> headers. None of those are currently filterable on the current set of
>> instructions. LOOP would allow these.
> 
> It's not meant for detailed packet protocol header analysis,
> it's for stateless straight line matching of masked values
> in packet headers.

David is right, BPF cannot - and will not - keep with any high level
connection tracking packet filter. There is an processing trade-off between
packet classification and packet storage with post processing analysis.

Hagen
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