linux-kernel - Re: [PATCH] af_unix: implement socket filter

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Message-ID: <20110118175143.3a164669@chocolatine.cbg.collabora.co.uk>
Date:	Tue, 18 Jan 2011 17:51:43 +0000
From:	Alban Crequy <alban.crequy@...labora.co.uk>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Ian Molton <ian.molton@...labora.co.uk>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	davem@...emloft.net, ebiederm@...ssion.com, xemul@...nvz.org,
	davidel@...ilserver.org
Subject: Re: [PATCH] af_unix: implement socket filter

Le Tue, 18 Jan 2011 18:22:41 +0100,
Eric Dumazet <eric.dumazet@...il.com> a écrit :

> Le mardi 18 janvier 2011 à 16:39 +0000, Ian Molton a écrit :
> > From: Alban Crequy <alban.crequy@...labora.co.uk>
> > 
> > Linux Socket Filters can already be successfully attached and
> > detached on unix sockets with setsockopt(sockfd, SOL_SOCKET,
> > SO_{ATTACH,DETACH}_FILTER, ....). See:
> > Documentation/networking/filter.txt
> > 
> > But the filter was never used in the unix socket code so it did not
> > work. This patch uses sk_filter() to filter buffers before delivery.
> > 
> > This short program demonstrates the problem on SOCK_DGRAM.

By the way, the patch implements socket filters on SOCK_DGRAM and
SOCK_SEQPACKET but not SOCK_STREAM. Socket filters does not make sense
to me when there is no packet boundaries. But if there is a need for
it, the code for SOCK_STREAM could be added easily.

> Any idea on performance cost adding sk_filter() call ?

Ian will write a performance test and repost the patch with some stats.
I don't know about the performance cost.

> Hmm, looking at it, I have no idea why sk_filter() needs to block BH.

I don't know neither.

> I'll send a patch to relax this requirement.

Thanks for your review!

Alban
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