[Snort-devel] [Snort-users] inline mode works(seems) without compiling with --enable-inline option

Joel Ebrahimi joel.ebrahimi at ...2499...
Mon Sep 21 19:29:24 EDT 2009


Hey Russ,
I finally have a chance to revisit this. I have been looking through
inline.c for information on how dropping would work on the Bivio hardware.

You mentioned that there are no non-standard pcap calls in Snort and that
only global variables are shared. Im assuming this means you must be setting
global variable pcap_bvzcp_drop out of Bivios zero copy pcap.  I dont see
this variable in inline.c nor anywhere else in the code. Could you elaborate
on which global variable your setting, or what else you are doing to let
Bivios zero copy pcap know that the packet is to be dropped.

Thanks,

// Joel

On Fri, Aug 7, 2009 at 1:42 PM, Russ Combs <rcombs at ...402...> wrote:

> Comments below ...
>
> On Fri, Aug 7, 2009 at 4:08 PM, Joel Ebrahimi <joel.ebrahimi at ...2499...>wrote:
>
>> I have always been curious how this works. Working for Bivio Networks I
>> know that there is a Snort IPS that Sourcefire uses on our platform but I
>> was never sure how they integrated it. Since our performance relies on pcap
>> and since our pcap is modified to drop packets I had assumed it was all
>> handled through pcap.
>> So does --enable-inline need to be used at all to initialize any of the
>> drop structures or mechanisms?
>>
>
> That depends on what you are trying to do:
>
> * use --enable-inline for ipq.
> * use --enable-inline --enable-ipfw for ipfw.
> * otherwise, if you have a modified libpcap, the drop is handled there.
> * otherwise, the drop doesn't take place.
>
>
>> Would the keyword 'drop' still be able to be used from the rules just like
>> the -Q option is allowed ?
>>
>
> Using -Q and a drop action in a rule is perfectly fine without the use of
> --enable-inline with a modified
> libpcap.
>
>>
>> I don't actually see any of the Bivio specific API calls to drop packets.
>> I assuming this is not released in the general Snort release. Is this code
>> available or is it licensed differently then the available public Snort?
>>
>
> There are no calls to non-standard libpcap API functions in Snort.
> Everything to do this is there in the snort code base and the license is the
> same.  There are a few global variables that need to be shared between the
> pcap library and Snort.  Have a look at inline.c for details.
>
>
>> Thanks,
>>
>> // Joel
>>
>> On Wed, Aug 5, 2009 at 8:48 AM, Russ Combs <rcombs at ...402...> wrote:
>>
>>> Hey Justin,
>>>
>>> Thanks for the patch.  The -Q option, and the inline implementation in
>>> general, is a little confusing.  However, there is no warning without
>>> --enable-inline because it allows Snort to be deployed inline using 3rd
>>> party pcap implementations that don't require ipq or ipfw.
>>>
>>> Compounding that, the help for -Q is only output for ipq builds.  The
>>> help will be addressed in an upcoming release.
>>>
>>> Russ
>>>
>>> On Wed, Aug 5, 2009 at 8:11 AM, justin joseph <justinjoseph007 at ...2499...
>>> > wrote:
>>>
>>>> Hi
>>>>
>>>> Were trying to configure snort-inline on Ubuntu hardy (snort version
>>>> 2.7.0) for some days.
>>>> Today figured out by looking at the code that even if snort was not
>>>> compiled with --enable-inline
>>>> option, it was seemingly running with the -Q option(drop, sdrop,
>>>> reject won't work off course)
>>>>
>>>> IMHO this confuses a newbie user like me because if snort was not
>>>> compiled enabling
>>>> inline mode then it is supposed to print error and abort if user tries
>>>> to run with the -Q option.
>>>>
>>>> Attached patch against 2.8.4(changes in snort.c) or something like
>>>> that would be nice IMHO.
>>>>
>>>> thank you
>>>> Justin
>>>>
>>>>
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>>
>>
>
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