netdev - Re: [PATCH 20/38] netns ct: NOTRACK in netns

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Date:	Fri, 22 Aug 2008 15:30:28 +0400
From:	adobriyan@...il.com
To:	Jan Engelhardt <jengelh@...ozas.de>
Cc:	kaber@...sh.net, netfilter-devel@...r.kernel.org,
	netdev@...r.kernel.org, containers@...ts.linux-foundation.org
Subject: Re: [PATCH 20/38] netns ct: NOTRACK in netns

On Thu, Aug 21, 2008 at 07:06:37PM -0400, Jan Engelhardt wrote:
> On Thursday 2008-08-21 18:04, adobriyan@...il.com wrote:
> 
> >Make untracked conntrack per-netns.
> 
> Why? It does not store any useful information per se, it is
> merely used to add a third type of ct, iow:
> 
> (a) ct==NULL
> (b) ct!=NULL
> (c) ct==&untracked
> 
> mmap(2)'s return value for example has something similar:
> 
> (a) mmap(...)==NULL
> (b) mmap(...)==MMAP_FAILED
> (c) otherwise
> 
> The untracked ct is a singleton, and should stay one, unless
> there are further reasons not to do so.

We wait for untracked ct refcount to drop to 1 back:

	/* wait until all references to nf_conntrack_untracked are dropped */
	while (atomic_read(&nf_conntrack_untracked.ct_general.use) > 1)
		schedule();

Consequently it should be one per netns, otherwise netns A can prevent
netns B from stopping.

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