From: Nathan Nesbit [nathann@Exchange.Microsoft.com]
Sent: Thursday, March 23, 2000 12:53 PM
To: NT Developers Interest List
Subject: [ntdev] RE: problems using CreateFile -- followup

Why do you do a DefineDosDevice?

Wouldn't it be better to do a IoCreateSymbolicLink in the driver after
creating your device?

something like this

IoCreateDevice(DriverObject,                              
			sizeof(DEVICE_EXTENSION),
               &UnicodeDeviceName,
               FILE_DEVICE_TRANSPORT,
               0, FALSE, &DeviceObject);

 RtlInitUnicodeString(&SymLinkName,
                      L"\\??\\MyDeviceName");

IoCreateSymbolicLink(&SymLinkName,
			   &UnicodeDeviceName);

then in your user mode code do a:

HANDLE PacketOpenAdapter(PCTSTR AdapterName)
{
	TCHAR strName[MAX_PATH];

	_stprintf(strName,
			_T("\\\\.\\MyDeviceName"));

	return CreateFile(strName,
				GENERIC_READ | GENERIC_WRITE,
				FILE_SHARE_READ | FILE_SHARE_WRITE,
				NULL,
				OPEN_ALWAYS,
				0,
				NULL);	
}

This is the way I've always done it and never had a problem.  If this
doesn't work you would also want to check the Create entry point of your
driver to make sure it isn't interferring with the second open.

-----Original Message-----
From: Barak Mandelovich [mailto:barak@conduct.com]
Sent: Thursday, March 23, 2000 5:26 AM
To: NT Developers Interest List
Subject: [ntdev] problems using CreateFile -- followup


Hi everybody!

I've read the answers here, but according to them, I guess
I did not explain myself clearly...

I have an NDIS driver, which I start using StartService(), and
connect to it from my application using DefineDosDevice() and 
then CreateFile().

It worked fine till now, but now - I have been asked to support
"multiple clients", i.e.: multiple threads/processes can issue
a CreateFile() and connect to the driver.

The IoCreateDevice in the DriverEntry is:
IoCreateDevice(DriverObject,                              
sizeof(DEVICE_EXTENSION),
               &UnicodeDeviceName,
               FILE_DEVICE_TRANSPORT,
               0, FALSE, &DeviceObject);

(as you can see - non exclusive).


I'm trying to run the SAME CODE that works now twice.
In both - the same lines are being called, the same symbolic
link name is used etc.

The 1st process succeeds in the CreateFile(), and the other does not.

Now, I tried to run them both with debuggers - I set a breakpoint
before the CreateFile() in both debuggers, and ran it.

When they both reached the CreateFile() line,
I stepped over it (f-10 in VC++), and then stepped over in the over
debugger - and it was successful in both cases!

BUT..  When I put a breakpoint before the function the does
the CreateFile(), and steps over one, and then steps over
in the other debugger - it fails!

Another interesting thing, is that although the Symbolic Link name
is in the system (I checked with WinObj),
I must issue a DefineDosDevice() (that defines the already defined
symbolic link), and only then the CreateFile succeeds... otherwise - 
it fails.

Please note that I tried all of the 4 combinations:
  a. DefineDosDevice() in both processes
  b. DefineDosDevice() in the 1st only
  c. DefineDosDevice() in the 2nd only
  d. DefineDosDevice() in no process

options c, d failed because the 1st process did not
succeed in the CreateFile()

options a,b - only the 1st process succeeded...


I'm desperate... I've been working on this stuff for a few
days - and nothing!!!!



following is the function that does the CreateFile...
(You may recognize it as the Packet.sys sample from the NT-DDK...   ;-) 
)

Any ideas?

PVOID
PacketOpenAdapter(LPTSTR AdapterName)
{
	LPADAPTER  lpAdapter;
	BOOLEAN    Result;
	c_debug (DEBUG_INFO, "Packet32: PacketOpenAdapter started");
	
	lpAdapter=(LPADAPTER)GlobalAllocPtr(
		GMEM_MOVEABLE | GMEM_ZEROINIT,
		sizeof(ADAPTER)
		);

	
	if (lpAdapter==NULL) {
		c_error (0, "Packet32: PacketOpenAdapter GlobalAlloc
Failed");
		return NULL;
    }
	wsprintf(
		lpAdapter->SymbolicLink,
		TEXT("\\\\.\\%s%s"),
		DOSNAMEPREFIX,
		&AdapterName[8]
		);
	
	Result=DefineDosDevice(
		DDD_RAW_TARGET_PATH,
		&lpAdapter->SymbolicLink[4],
		AdapterName);
	
	
	if (Result) {
		lpAdapter->hFile=CreateFile(lpAdapter->SymbolicLink,
			GENERIC_WRITE | GENERIC_READ,
			FILE_SHARE_READ | FILE_SHARE_WRITE,
			NULL,
			OPEN_ALWAYS,
			FILE_FLAG_OVERLAPPED,
			0);
		
		if (lpAdapter->hFile != INVALID_HANDLE_VALUE) {
			return lpAdapter;
		}
		else {
			int x=GetLastError();
			c_error (x, "Packet32: PacketOpenAdapter Could not
open adapter");
		}
	}
	
	GlobalFreePtr(lpAdapter);
	return NULL;
}


Note: c_debug and c_error are my macros for debugging.. u may ignore
them...



	thanks in advance,

		- Barak



> -----Original Message-----
> From: Barak Mandelovich [mailto:barak@conduct.com]
> Sent: Tuesday, March 21, 2000 4:44 AM
> To: NT Developers Interest List
> Subject: [ntdev] problems using CreateFile
> 
> Hi everybody, and sorry for troubling you with
> newbies questions, but I have a problem with CreateFile
> that I just can't figure out:
> 
> I have a driver, to which I want to connect from my application,
> using CreateFile(), and I have 2 processes that try to
> attach to the driver.
> 
> The first succeeds, and the second fails with error code #2
> (ERROR_FILE_NOT_FOUND).
> 
> The CreateFile line is this:
> CreateFile(SymbolicLinkName,
>            GENERIC_WRITE | GENERIC_READ,
>            0,
>            NULL,
>            CREATE_ALWAYS,
>            FILE_FLAG_OVERLAPPED,0);
> 

----------------------------------------------------
Barak Mandelovich           Mercury Interactive ltd.
Barak@conduct.com           19 Shabazi st.      
Tel: +972 3 539 9286        Yehud, 56100
Fax: +972 3 533 1617        Israel
----------------------------------------------------


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