[Snort-devel] snort inline mode and bridge

Russ rucombs at ...3461...
Thu Oct 27 06:51:36 EDT 2016



On 10/26/16 5:02 PM, Vincent Li wrote:
> it is not a problem, but some optimal improvement I would like to see.
> I have a lower end PC with two NIC running snort IPS bridge mode
> between my ISP modem and my  router at home.  I use pulledpork to
> update signatures every day and I scripted snort to restart to take
> the updated signatures after new signatures finishing downloading. the
> snort restart takes about 5  minutes to finish and during these 5
> minutes period, my home Internet is down since snort start the DAQ
> bridge after  SnortInit which take most of the time I think. btw I
> have not tried snort reload
You should try reload, that is exactly what it is for.  Snort will keep 
running during the reload so you don't have that downtime.
>
> my question is : can the DAQ bridge be started earlier in the snort
> startup process, maybe before SnortInit , so that traffic can be
> passed through early to reduce the network connectivity downtime to
> minimum.
Snort has "fail open" support during startup because some initialization 
must be done after opening the DAQ interfaces. During that time, which 
is typically very brief, it will pass packets so your network remains 
functional.  However, most of the startup time is prior to the fail open 
state.  The change you suggest is possible but reload should make it 
unnecessary.
>
> let me know if I made myself clear :)
>
>
>
> Thanks
>
> Vincent
>
> On Tue, Oct 25, 2016 at 11:31 AM, Russ <rucombs at ...3461...> wrote:
>> Please restate the original problem.  I don't think fail open is what
>> you are after.
>>
>> On 10/25/16 2:03 PM, Vincent Li wrote:
>>> On Thu, Oct 13, 2016 at 8:26 PM, Y M <snort at ...3347...> wrote:
>>>> Hello Vincent,
>>>>
>>>>
>>>> I haven't tried this before, but when building Snort, there is this build
>>>> option:
>>>>
>>>>
>>>> "--enable-inline-init-failopen  Enable Fail Open during initialization for
>>>> Inline Mode (adds pthread support implicitly)"
>>>>
>>>>
>>>> Have you tried this? I would be interested to know if this achieves what you
>>>> need.
>>>>
>>> so I tried to build snort with --enable-inline-init-failopen, it did
>>> not sovle the problem I have.  it looks to me the InlineFailOpen is
>>> called near to the end of  SnortMain after SnortInit (which take most
>>> of the time during snort restart) and before PacketLoop();
>>>
>>> I tried to hack the code to call InlineFailOpen before SnortInit, but
>>> I had memory segment fault after starting up snort and pass traffic
>>> through it, I assume some memory has to be allocated before starting
>>> up the DAQ bridge, any further clue?
>>>
>>> maybe some improvement needed in line with the idea of InlineFailOpen ?
>>>
>>> Thanks
>>>
>>> Vincent
>>>
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