Subject: Re: [PATCH] netfilter: xtables: userspace notification target

From: Patrick McHardy <[email-masked]>
Date: Thu, 15 Jul 2010 11:05:49 +0200

Am 14.07.2010 18:34, schrieb Pablo Neira Ayuso:
> Hi Luciano,
> 
> On 14/07/10 14:22, Luciano Coelho wrote:
>> On Wed, 2010-07-14 at 13:48 +0200, ext Patrick McHardy wrote:
>>> If you're using connection tracking, you can use conntrack marks
>>> to avoid sending more than a single message:
>>>
>>> iptables ... -m connmark --mark 0x1/0x1 -j RETURN
>>> iptables ... -j NFLOG ...
>>> iptables ... -j CONNMARK --set-mark 0x1/0x1
>>
>> Cool, thanks.
>>
>> It seems that there are lots of possibilities to get this to work, but
>> this is starting to get quite complex.  I would still prefer having the
>> NFNOTIF module included, since we would be able to do what we want in a
>> very simple way.  It's also probably much more efficient that using
>> several rules, which would increase the CPU usage considerably (in our
>> device we are already reaching the limit of a reasonable CPU resource
>> usage with high throughput WLAN connections).

Its hard to believe that a connmark match filtering out notifications
would require more CPU time than doing the same in a new target module.

>> While I agree that it is possible to achieve the NFNOTIF functionality
>> with existing modules, I still think there is a "niche" for such module,
>> because it is very simple, has a very clear purpose and would make the
>> ruleset simpler and more efficient.
>>
>> Does this make any sense?
> 
> I don't think that the NFNOTIF infrastructure fulfill the policy for
> inclusion. It seems to me like something quite specific for your needs.
> It is simple, yes, but we already have this feature into the kernel. I
> don't think that this will reduce CPU usage considerably with regards to
> the NFLOG way.
> 
> I would still prefer adding the once-per-matching notification feature
> to NFLOG than these extra lines in the kernel, Patrick?

I agree with Pablo.