[Bro] High cpu when calling lookup_hostname

[Chris Chiaverini]

It is probably in IO wait on the lookup.  Could you run a local caching 
nameserver?  nscd is the easiest to setup but there are others.

Regards,

Chris Chiaverini

On 05/06/2016 06:16 AM, Pasqualino Paladino wrote:
>
> Hello everybody,
>
> I’m using Bro 2.4.1 stable and I developed a script in order to add 
> some information to http.log.
>
> This code snippet attempts to lookup each external hostname that is 
> being contacted by an internal IP.
>
> *if(c?$http && c$http?$host && c$http$host != ""){*
>
> *when (local h = lookup_hostname(c$http$host)){*
>
> *if (|h|>0 && (0.0.0.0 !in h))*
>
> *{*
>
> *c$http$host_ip = h;*
>
> *Log::write(HTTP::LOG, c$http);*
>
> *}*
>
> *return;*
>
> *}*
>
> *timeout 2 sec {*
>
> *return;*
>
> *}*
>
> *}*
>
> **
>
> My problem is that the cores that have been assigned for Bro are using 
> the 100% of the cpu and I guess the problem is caused by *when* call.
>
> I have tried to install an internal dns cache (Bind9) in order to 
> increase the performance, but, having a 300 mb/s of throughput and 
> setting 2 sec of timeout doesn’t work .
>
> By disabling the script bro has the expected behavior (around 50%-60% 
> of cpu usage).
>
> Is anyone able to help me?
>
> Thanks in advance,
>
> Pasquale
>
>
>
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