[Winpcap-users] While testing Gianlucas winpcap3.1[prerelease]...

[Marc Wetzel]

I wrote a little test application

First version just calls ThreadProc() (without using threads),
the second version uses BeginThread() to use this function as the 
threadproc.

Please see my findings:

Winpcap (prerelease) using Windows XP/latest SP

SingleThreaded version:
- Works with and without using COINIT_APARTMENTTHREADED
- mulitple calls to pcap_open() are successful (not tested if they 
actually receive packets)


MultiThreaded version:
- Works only with using COINIT_MULTITHREADED !!
- it only works if I init COM _outside_ the thread.
- mulitple calls (say multiple threads) to pcap_open() are NOT 
successful, the second call to pcap_open blocks until the first 
pcap_handle is closed


Greetings
/Marc

--
PS:
snippet of my testcode:
I only used it to test, while single-stepping through the code, so 
checking some resultcodes was omitted!

FUNCTION ThreadProc(Thread: TThread): Integer;
VAR
    ErrBuf          : ARRAY[0..PCAP_ERRBUF_SIZE - 1] OF Char;
    FPcap           : PPcap;
    FError          : STRING;
BEGIN
    FPcap := pcap_open('\Device\NPF_GenericDialupAdapter', 1600, 0, 30, 
NIL, ErrBuf);
    //FPcap := pcap_open('\Device\NPF_GenericNdisWanAdapter', 1600, 0, 
30, NIL, ErrBuf);
    IF FPcap = NIL THEN
    BEGIN
        FError := ErrBuf;
        exit;
    END;
    IF assigned(Thread) THEN
        WHILE (true) DO
            sleep(1000);

END;

PROCEDURE TForm1.Button1Click(Sender: TObject);
VAR
    FHandle         : THandle;
    FThreadID       : THandle;
    FHandle2        : THandle;
    FThreadID2      : THandle;
    res             : LongInt;
BEGIN
    InitPCAP; // Loadlibrary and function binding...
    CoUninitialize;
    //res:=CoInitializeEx(NIL, COINIT_APARTMENTTHREADED);
    res := CoInitializeEx(NIL, COINIT_MULTITHREADED);
    // Test-1 SingleThreaded
    //    ThreadProc(nil);
    //    ThreadProc(nil);
    // Test-2 MultiThreaded
    FHandle := BeginThread(NIL, 0, @ThreadProc, Pointer(Self), 
CREATE_SUSPENDED, FThreadID);
    ResumeThread(FHandle);
    Sleep(5000);
    FHandle2 := BeginThread(NIL, 0, @ThreadProc, Pointer(Self), 
CREATE_SUSPENDED, FThreadID2);
    ResumeThread(FHandle2);
END;



Gianluca Varenni wrote:

>
> ----- Original Message ----- From: "Marc Wetzel" <mwse at gmx.de>
> To: <winpcap-users at winpcap.org>
> Sent: Monday, August 01, 2005 12:43 PM
> Subject: Re: [Winpcap-users] While testing Gianlucas winpcap3.1 
> [prerelease]...
>
>
>>
>>>>
>>>> But you might remember, that I had trouble using winpcap3.1.b4/WAN 
>>>> devices with Delphi,
>>>> because of some kind of COM initialization problems.
>>>> It only worked if I do a CoInitializeEx(NIL, COINIT_MULTITHREADED) 
>>>> at the very start of the code.
>>>
>>>
>>>
>>> I know. This is one of the biggest headaches I had with WinPcap and 
>>> NdisWan.
>>>
>> It really really only works if I set it to COINIT_MULTITHREADED (not 
>> the other way around).
>
>
> Uhm, are you using Windows XP? If you are using the test dlls on my 
> web pages (i.e. the latest build of the dlls, in practice) every 
> attempt to open/list the wan adapters fails if COM has been 
> initialized as COINIT_MULTITHREADED *on the same thread*.
>
>
>>
>> I use winpcap the following way... maybe there is a problem with my 
>> code?
>>
>> in the main process I fetch the devices (pcap_findalldevs) to look if 
>> there is a WAN device.
>> I such device is found I create a new thread and tell it to open the 
>> specific device (I found out in the main process)
>> inside the thread I use pcap_open to open this device...
>
>
> That's ok.
>
>>
>> And I really have to initialize to COINIT_MULTITHREADED, get it going 
>> (in beta4)
>> In beta4 this had nothing to do with pcap_findalldevs(). This just 
>> ever worked, regardless which
>> ComThreadModel I choosed.
>> The failure just happened on pcap_open()
>
>
> In beta4, there were a series of bugs related to COM initialization 
> (coupled to a series of bugs in the MS NetMon
> COM component for which I've put some patches only after 3.1beta4, 
> i.e. in the test DLLs on my web). These bugs caused a whole series of 
> random effects: application crashes, Wan adapters not listed....
>
>
>>
>> I just tested it again (this time I tried to use multiple threads 
>> opening NdisWanBh)
>> And I found out, that my second call to pcap_open blocks until I 
>> close the first winpcap handle.
>
>
> Wait, wait. NdisWanBh should NOT be listed by WinPcap. If it's listed, 
> it probably means that your WinPcap installation has something really 
> weird. Are you sure it's NdisWanBh??
>
>>
>>
>>
>>>>
>>>> #2:
>>>> With the prerelease I have now other problems...
>>>> If I use CoInitializeEx(NIL, COINIT_MULTITHREADED) I only see my 
>>>> Ethernet-Device (using pcap_findalldevs).
>>>
>>>
>>>
>>> This is correct. Basically, the NetMon COM component used by WinPcap 
>>> to capture from PPP does NOT work in the MULTITHREADED threading 
>>> model on Windows XP. As a consequence, that device is not listed 
>>> *if* COM has already been initialized with that threading model.
>>>
>>>
>> Is there any official documentation to this? I didnt found anything 
>> on MSDN on this subject.
>
>
> Nope. The MSDN documentation says almost *nothing* about the NetMon 
> component (and all its issues/bugs).
>
>>
>>>
>>>> And if I comment the CoInitializeEx call out, I see all devices as 
>>>> expected, but then it fails
>>>> in the call to  pcap_open() with the error message "The system 
>>>> cannot find the device" (just as before).
>>>
>>>
>>>
>>> Uhm, are you sure? I've thoroughly tested it without any problem on 
>>> my machine. Have you tried building a small C app (or one in the 
>>> devpack) and see if it works?
>>>
>>> If you don't initialize COM, winpcap initializes it with 
>>> CoInitialize(NULL) before opening the GenericDialupAdapter.
>>>
>> Delphi normally does not initialize COM. Only if needed (by using 
>> certain libraries, I dont use).
>>
>>>>
>>>>
>>>> Just an addendum:
>>>> #3:
>>>> Using CoInitializeEx(NIL, COINIT_MULTITHREADED) in a 
>>>> Com-Application is not possible,
>>>> e.g. embedding the IE-ActiveX object will always fail. This means 
>>>> that having an application which uses
>>>> both the IE-ActiveX and winpcap (sniffing on WAN devices) is not 
>>>> possible.
>>>>
>>>> Sniffing ethernet devices is not touched by this problem.
>>>>
>>>> Maybe I am completely wrong?
>>>> Does anybody have a clue, or is this a bug?
>>>
>>>
>>>
>>> I think that's what I explained before. On Windows XP the MS NetMon 
>>> COM component does NOT support the MULTITHREADED threading model. At 
>>> the moment I haven't found an easy solution to this issue.
>>>
>>
>> Gianluca,
>> Is there maybe a newer release I can test against?
>
>
> No. No further patches have been added to the dialup/NdisWan code. The 
> test dlls on my web area are the latest ones from that point of view.
>
> Have a nice day
> GV
>
>>
>>
>> TIA
>> /Marc
>> _______________________________________________
>> Winpcap-users mailing list
>> Winpcap-users at winpcap.org
>> https://www.winpcap.org/mailman/listinfo/winpcap-users 
>
>
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