netdev - Re: PROBLEM with summary: Re: [PATCH] netfilter: per netns nf_conntrack

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Date:	Tue, 02 Feb 2010 12:23:01 -0500
From:	Jon Masters <jonathan@...masters.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Patrick McHardy <kaber@...sh.net>,
	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	netfilter-devel <netfilter-devel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: PROBLEM with summary: Re: [PATCH] netfilter: per netns
 nf_conntrack_cachep

On Tue, 2010-02-02 at 18:16 +0100, Eric Dumazet wrote:
> Le mardi 02 février 2010 à 18:04 +0100, Patrick McHardy a écrit :
> 
> > Ah nice catch, that seems to be the problem. When the untracked
> > conntrack is already attached to an skb and thus has refcnt > 1
> > and we re-initalize the refcnt, it will get freed.
> > 
> > The question is whether the ct_net pointer of the untracked conntrack
> > is actually required. If so, we need one instance per namespace,
> > otherwise we can just move initialization and cleanup to the init_net
> > init/cleanup functions. Alexey, do you happen to know this?
> > 
> 
> One untracked per netns seems the way to go, and move it outside of
> read_mostly area too, we obviously can modify its refcount frequently...

Sure, that will work. Also, rather than just the NF_CT_ASSERT on the use
count, maybe worth catching the specific case of trying to free the
untracked ct, but that's only if it's not a horrible fast path.

Anyway, thanks. If you want to send me a patch, I'll try it.

Jon.


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