IN  PFILE_OBJECT FileObject,
  OUT PVOID *FsContext,
  OUT PVOID *FsContext2

Routine Description:

    This procedure takes a pointer to a file object, that has already been
    opened by the MUP and figures out what it really is opened.


    FileObject - Supplies the file object pointer being interrogated

    FsContext - Receive the file object FsContext pointer

    FsContext2 - Receive the file object FsContext2 pointer

Return Value:

    BlockType - Returns the node type code for a Vcb or Fcb.

        Vcb - indicates that file object opens the mup driver.

        Ccb - indicates that the file object is for a broadcast mailslot file.

        Zero - indicates that the file object has been closed.