From: Gopikrishna [gkrishna@cswl.com]
Sent: Friday, April 14, 2000 6:47 AM
To: NT Developers Interest List
Subject: [ntdev] Filter driver on TCP/IP driver

I am new to writing Drivers. I have wriiten a hook driver over TCP/IP driver.  In my hook driver I am dispatching all the IRP's to the TCP/IP driver through IOCallDriver method ( I felt, after successfully dispatching all the IRP's, I can add fuctionality to my filter driver).

I am successfully able to attach to "\Device\Tcp". But after that My system is crashing. I am attaching the code below.
Please tell me if I am missing anything.

Regards,
Gopikrishna.

#include <ntddk.h>          // various NT definitions
#include <ntiologc.h>
#include <string.h>

#include "TCPEncryptor.h"
// pointer to the lower TCP/IP device
PDEVICE_OBJECT      TCPIPDevice;
// pointer to the local filter device
PDEVICE_OBJECT      TCPIPFilterDevice;
PDEVICE_OBJECT      ThisDevice;
NTSTATUS
DriverEntry(
    IN OUT PDRIVER_OBJECT   DriverObject,
    IN PUNICODE_STRING      RegistryPath
    )
{
 NTSTATUS ntStatus;

 KdPrint(("TCPIP Driver entry Filter Level Drv\n"));
 DriverObject->MajorFunction [IRP_MJ_CREATE] = 
    DriverObject->MajorFunction [IRP_MJ_CLOSE] = 
    DriverObject->MajorFunction [IRP_MJ_CLEANUP] =
    DriverObject->MajorFunction [IRP_MJ_INTERNAL_DEVICE_CONTROL] = 
    DriverObject->MajorFunction [IRP_MJ_DEVICE_CONTROL] = DrvDispatchGeneral;

 DriverObject->DriverUnload = DrvUnloadDriver;

    ntStatus = DrvInitialize(DriverObject);

 if ( !NT_SUCCESS( ntStatus ) )
    {
  KdPrint(("TCPIP Encrption Driver: DrvInitailize failed"));
  return ntStatus;
 }
 return ntStatus;
}

NTSTATUS 
DrvInitialize(
    IN PDRIVER_OBJECT       DriverObject
    )
{
 UNICODE_STRING      ntUnicodeString;    
 UNICODE_STRING      Win32NameString;            
    NTSTATUS            ntStatus;

    RtlInitUnicodeString( &ntUnicodeString, NT_DEVICE_NAME );
    
    ntStatus = IoCreateDevice(
        DriverObject,                   // Our Driver Object
        0,                        // We don't use a device extension
        &ntUnicodeString,               // Device name 
        FILE_DEVICE_UNKNOWN,         // Device type
        0,                              // Device characteristics
        FALSE,                          // Not an exclusive device
        &ThisDevice );                // Returned ptr to Device Object

    if ( !NT_SUCCESS( ntStatus ) )
    {
        KdPrint(("TCPIP Encrption Driver:: Couldn't create the device object\n"));
        goto InitializeExit;
    }

    //
    // Allocate and initialize a Unicode String containing the Win32 name
    // for our device.
    //

    RtlInitUnicodeString( &Win32NameString, DOS_DEVICE_NAME );

    ntStatus = IoCreateSymbolicLink(
                        &Win32NameString, &ntUnicodeString );

  if(!NT_SUCCESS(ntStatus)){
   goto InitializeExit;
  }

 ntStatus=DrvFilterInit(DriverObject);
  if(!NT_SUCCESS(ntStatus)){
        IoDeleteDevice (ThisDevice);
        IoDeleteSymbolicLink(&Win32NameString);
        return ntStatus;
    }
InitializeExit:

    if ( !NT_SUCCESS( ntStatus ) )
    {
        //
        // Delete everything that this routine has allocated.
        //
        if ( ThisDevice != NULL )
        {
            IoDeleteDevice( ThisDevice);
        }
    }

    return ntStatus;
}

NTSTATUS
DrvClose(
    IN PDEVICE_OBJECT       DeviceObject,
    IN PIRP                 Irp
    )
{
 KdPrint(("TCPIP Encrption Driver:: Close irp"));
 Irp->IoStatus.Status = STATUS_SUCCESS;
    Irp->IoStatus.Information = 0;
    
    IoCompleteRequest( Irp, IO_NO_INCREMENT );
    
    return STATUS_SUCCESS;
}

NTSTATUS
DrvDispatchGeneral(
    IN PDEVICE_OBJECT       DeviceObject,
    IN PIRP                 Irp
    )
{
 NTSTATUS ntstatus;
    PIO_STACK_LOCATION currentIrpStack = IoGetCurrentIrpStackLocation(Irp);
    PIO_STACK_LOCATION nextIrpStack    = IoGetNextIrpStackLocation(Irp);

 KdPrint(("TCPIP Encryption Driver: DrvDispatch General CHECKING MAJOR FUNCTION CODE !\n"));

    //
    // Default to success.
    //

 KdPrint(("TCPIP Encryption Driver: DrvDispatch General!\n"));
    if( DeviceObject == TCPIPFilterDevice) {
        //
        // It's for Ltf
        //
        KdPrint(("TCPIP Encrypter Driver: Calling Lower driver!\n"));
        *nextIrpStack = *currentIrpStack;
  IoCallDriver( TCPIPDevice, Irp );
  ntstatus= IoCallDriver( TCPIPDevice, Irp );
  if (ntstatus== STATUS_SUCCESS ){
   KdPrint(("TCPIP Encrypter Driver: Returned from Lower driver Successfully!\n"));
   return ntstatus;
  }
  else
  {
   KdPrint(("TCPIP Encrypter Driver: Return from Lower driver failed!\n"));
   return ntstatus;
  }

    } else {
        //
        // Nothing to do here, so just..
        //
      KdPrint(("TCPIP Encryption Driver: Doing Noting in dispatch!\n"));
  Irp->IoStatus.Status      = STATUS_SUCCESS;
  Irp->IoStatus.Information = 0;  
        return STATUS_SUCCESS;
    }
}

NTSTATUS
DrvFilterInit(
    IN PDRIVER_OBJECT DriverObject 
    )
/*++

Routine Description:

   Create a device object and attaches it to the
   first Ltf device

Arguments:

   DeviceObject - pointer to a device object.

Return Value:

   NT Status code

--*/

{
    UNICODE_STRING          ntUnicodeString;
    NTSTATUS                ntStatus;
   PDEVICE_OBJECT          DeviceObject        = NULL;


    //
    // Only hook onto the first Ltf chain. BUGBUG
    //
    RtlInitUnicodeString( &ntUnicodeString, L"\\Device\\Tcp");
    //
    // Create device object for the Ltf
    //
    ntStatus = IoCreateDevice( DriverObject,
                 0,
                 NULL,
                 FILE_DEVICE_UNKNOWN,
                 0,
                 FALSE,
                 &TCPIPFilterDevice);

    if( !NT_SUCCESS(ntStatus) ) {
        KdPrint(("TCPIP Encrption Driver: failed to create filter device for TCPIP!\n"));
        return ntStatus;
    }

    //
    // Attach to the Ltf chain.
    //
    ntStatus = IoAttachDevice( TCPIPFilterDevice, &ntUnicodeString, &TCPIPDevice );
    if( !NT_SUCCESS(ntStatus) ) {
        KdPrint(("TCPIP Encryption driver: Connect with TCPIP failed!\n"));
        IoDeleteDevice( TCPIPFilterDevice );
        return ntStatus;
    }

    return STATUS_SUCCESS;

}
VOID
DrvUnloadDriver(
    IN PDRIVER_OBJECT       DriverObject
    )
{
    UNICODE_STRING uniWin32NameString;
 KdPrint(("TopLevel Driver : Unload driver\n"));
 RtlInitUnicodeString( &uniWin32NameString, DOS_DEVICE_NAME );

    //
    // Delete the link from our device name to a name in the Win32 namespace.
    //
 IoDetachDevice(TCPIPDevice);

 IoDeleteDevice(TCPIPFilterDevice);

    IoDeleteSymbolicLink( &uniWin32NameString );
 IoDeleteDevice( ThisDevice);
    //
    // Create counted string version of our Win32 device name.
    //
}