netdev - Re: [flamebait] xdp, well meaning but pointless

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Message-ID: <f1eef5a5-023e-4edb-ce9e-53a94821044c@stressinduktion.org>
Date:   Thu, 1 Dec 2016 18:20:36 +0100
From:   Hannes Frederic Sowa <hannes@...essinduktion.org>
To:     David Miller <davem@...emloft.net>, tgraf@...g.ch
Cc:     fw@...len.de, netdev@...r.kernel.org
Subject: Re: [flamebait] xdp, well meaning but pointless

On 01.12.2016 17:19, David Miller wrote:
> Saying that ntuple filters can handle the early drop use case doesn't
> take into consideration the nature of the tables (hundreds of
> thousands of "evil" IP addresses), whether hardware can actually
> handle that (it can't), and whether simple IP address matching is the
> full extent of it (it isn't).

Yes, that is why you certainly use ntuple filters in combination with
some kind of high level business logic in user space.

I have to check but am pretty sure you can't even do the simplest thing
in XDP, parsing the apexes of DNS packets and checking them against a
hash table, because the program won't pass the verifier.