Re: [PATCH 0/3] netfilter: add connlabel conntrack extension

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Fri, Nov 16, 2012 at 12:31:09PM +0100, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > On Thu, Nov 15, 2012 at 04:55:12PM +0100, Florian Westphal wrote:
> > > Changes since RFCv2:
> > > - make it a variable-size extension and remove dynamic
> > >   reallocation of the label array
> > > - add ctnetlink support for receiving/setting labels
> > > - limit to 128 instead of 1k labels due to limited extension
> > >   space (128 is more than enough for now, so this is no problem).
> > 
> > At a quick glance I like this round, you got this simplified :-).
> > 
> > My only concern is that (if I'm not missing anything) it
> > inconditionally add the extension even if we don't need it.
> 
> Its conditional:
> 
> words = ACCESS_ONCE(net->ct.label_words);
> if (words == 0 || WARN_ON_ONCE(words > 8))
> 	return NULL;
> cl_ext = nf_ct_ext_add_length(ct, NF_CT_EXT_LABELS, words * sizeof(long),..
> 
> xt_connlabel increases "label_words" to a non-zero
> value based on the highest bit it saw so far.  So e.g. when bit 32 is
> requested, a 32-bit machine kernel will set words to 2, and
> a 64 bit kernel to 1, thus turning the extension on for new connections.
> 
> The only drawback is that when you add a connlabel rule for bits 127,
> then for bit 1, then delete the first rule again words will be larger
> than one.
> 
> But i think this ok (I don't want to add per-bit refcountr :-) )

I see. Let me give a more look in-depth, in any case this version
seems reasonable to be included mainstream :-).

Regards.