ipfw rule processing performances

[Julian Elischer]

On 10/26/11 11:28 AM, Karim wrote:
> On 11-10-25 11:30 PM, Michael Sierchio wrote:
>> On Tue, Oct 25, 2011 at 6:43 PM, Julian 
>> Elischer<julian at freebsd.org>  wrote:
>>
>>> I find that the structure of teh ruleset has a huge affect on the 
>>> cpu usage.
>>>
>>> for example I immediately split incoming and outgoing packets 
>>> apart and send
>>> them to different groups of rules.
>>> I also have different groups of rules for internal and external 
>>> rules.
>>> so my rulesets usually start with:
>>>
>>> skipto 1000  all from any to any in recv ${OUTSIDE_INTERFACE}
>>> skipto 2000 all from any to any in recv ${INSIDE_INTERFACE}
>>> skipto 3000 all from any to any out xmit ${OUTSIDE_INTERFACE}
>>> skipto 4000 all from any to any out xmit ${INSIDE_INTERFACE}
>>> allow all from any to any via lo0
>>> drop all from any to any
>>>
>>> I also try use tables whenever possible.
>> I've found the same to be true, and use a scheme similar to what
>> Julian describes - I have rules grouped based on interface and
>> direction.  Having larger tables and fewer table lookups is faster, in
>> my experience - such that I have a big block list (~20,000 nets) and a
>> small whitelist (~20 nets) ...
>>
>> - M
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> Hi,
>
> Thanks to everyone who contributed I will try to digest all the 
> information and see how I can improve my ruleset. Couple of points 
> I've identified so far:
>
> 1) As Luigi's article points out route lookups are expensive due to 
> locking (I am using verrervpath ...)
> 2) ipfw_nat performance impact is an unknown at the moment (?)
> 3) Using mbuf tags (IPFW_TAG) is costly (so is ALTQ due to pf_tags 
> and FORWARD_IP due to m_tag). In other words policy based routing is 
> costly.
> 4) Its preferable to split incoming and outgoing packets apart as 
> early as possible in the ruleset
>
> Anything else I'm missing?

read up on all the things you can do with tablearg.. sometimes a 
single table can replace dozens of rules.

>
> Regards,
>
> Karim.
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