[Winpcap-users] winpcap and McAfee

tamagawa at skygroup.jp tamagawa at skygroup.jp
Wed Jun 25 01:32:41 GMT 2008


Thank you GV, for your very kind explanation!

Gianluca Varenni ????????:
> ----- Original Message ----- From: <tamagawa at skygroup.jp>
> To: <winpcap-users at winpcap.org>
> Sent: Monday, June 23, 2008 7:03 PM
> Subject: Re: [Winpcap-users] winpcap and McAfee
>> Hello,
>> I'm just curious:
>> What would happen if we call Winpcap API before notifying the SCM?
>> Or, why we need to notify before calling any Winpcap API?
> It all boils down to how the SCM works internally.
> First of all, when you call a WinPcap API, for example to list the 
> adapters, WinPcap makes sure that both the WinPcap driver and the 
> Microsoft NetMon driver (NM) are loaded into memory. Non-pnp drivers 
> (like winpcap and netmon) are managed as normal services by the OS and 
> started on demand, usually. The SCM uses a lock to protect the service 
> database, and that lock is held when you run your own service before 
> notifying the SCM. When the SCM database lock is held, no other services 
> can start (and basically times out). If in your service calls a WinPcap 
> API, WinPcap will try to load the winpcap driver and the netmon one (if 
> needed), the SCM will try to acquire the SCM database lock again and 
> wait for a certain timeout (I think it's one minute). The lock request 
> will eventually timeout, and the WinPcap and the NM drivers might not be 
> loaded into memory.
> Hope this explains a bit how the SCM works.
> Have a nice day
> GV
>> Cound be a stupid question but glad to hear any hints.
>> Thanks in advance,
>> -- 
>> tamagawa
>> Gianluca Varenni ????????:
>>> If you use WinPcap from within a service, I suggest you to have a 
>>> look at these slides
>>> http://www.cacetech.com/SHARKFEST.08/BoF_Varenni_%20WinPcap%20Do's%20and%20Don'ts.zip 
>>> in particular slide #9.
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