[Winpcap-users] Monitoring multiple network interfaces

[Gianluca Varenni]

----- Original Message ----- 
From: "soulstone" <soulstone at gmx.de>
To: <winpcap-users at winpcap.org>
Sent: Friday, December 04, 2009 7:02 AM
Subject: Re: [Winpcap-users] Monitoring multiple network interfaces


> Gianluca Varenni wrote:
>> ----- Original Message ----- 
>> From: "soulstone" <soulstone at gmx.de>
>> To: <winpcap-users at winpcap.org>
>> Sent: Thursday, December 03, 2009 8:49 AM
>> Subject: [Winpcap-users] Monitoring multiple network interfaces
>>
>>
>>> Hi,
>>>
>>> I've tried to monitor multiple networ interfaces installed on
>>> a system.
>>> The reason is that I need to monitor network traffic to determine
>>> whether a user navigates to a given url.
>>>
>>> I'd rather capture only packages from the interface which is connected
>>> to the internet but I don't know how to find out which one I need.
>>>
>>> So I tried to monitor all interfaces.
>>> I did this by creating one thread per interface which calls pcap_loop.
>>> But this doesn't work.
>>
>> What do you mean by "it doesn't work"?
>
> 1. I use pcap_findalldevs to get all devices.
> 2. I open every interface by pcap_open_live.
> 3. I use a loop to itter through all interfaces and spawn
> a seperated thread for each call of pcap_loop(Desc, 0, @PacketHandler, 
> Err).
>
> Usually after that the method PacketHandler would be called
> if I only invoke pcap_look for the correct interface with internet access.
> But if I try to monitor multiple interfaces the function PacketHandler
> isn't called anymore.
>
> I also tried to reverse the loop (the first interface is coincidental
> the one with internet access) it works.

What's the name of the interface with real traffic? What OS are you running 
on?

GV


>
> Example code:
>   // doesn't work
>   for i := 0 to Length(Interfaces) - 1 do
>   begin
> // creates a thread which calls pcap_loop
> SpawnMonitor(Interfaces[i];
>   end;
>
>   // works, because our (now last) item is the correct NIC
>   for i := Length(ValidP) - 1 downto 0 do
>   begin
> SpawnMonitor(Interfaces[i];
>   end;
>
> So the problem is that PacketHandler isn't called for all devices.
>
> Kind regards,
>   dy
>
>>
>> GV
>>
>>> Specifying only one interface everything works fine.
>>> Can I only monitor one interface at once or do I miss something?
>>>
>>> Maybe someone can give me an advice.
>>>
>>>
>>> Kind regards,
>>>   dy
>>> _______________________________________________
>>> Winpcap-users mailing list
>>> Winpcap-users at winpcap.org
>>> https://www.winpcap.org/mailman/listinfo/winpcap-users
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