FltTagFile function (fltkernel.h)

Article
10/21/2021

FltTagFile sets a reparse tag on a file or directory.

Syntax

NTSTATUS FLTAPI FltTagFile(
  [in]           PFLT_INSTANCE InitiatingInstance,
  [in]           PFILE_OBJECT  FileObject,
  [in]           ULONG         FileTag,
  [in, optional] GUID          *Guid,
  [in]           PVOID         DataBuffer,
  [in]           USHORT        DataBufferLength
);

Parameters

[in] InitiatingInstance

Opaque instance pointer for the minifilter driver instance that initiated this I/O request. This parameter is required and cannot be NULL.

[in] FileObject

Pointer to a file object for the file or directory on which to set a reparse point. The file object must be opened for FILE_WRITE_DATA access. This parameter is required and cannot be NULL.

[in] FileTag

Reparse point tag. If an existing reparse tag is being modified, the tag specified in this parameter must match the tag of the reparse point to be modified.

[in, optional] Guid

GUID that uniquely identifies the type of reparse point. If FileTag is not a Microsoft tag, this parameter is required and cannot be NULL. If an existing reparse tag is being modified, the GUID specified in this parameter must match the GUID of the reparse point to be modified.

[in] DataBuffer

Pointer to a buffer that contains user-defined data for the reparse point.

[in] DataBufferLength

Size, in bytes, of the buffer that DataBuffer points to.

Return value

FltTagFile returns STATUS_SUCCESS or an appropriate NTSTATUS value such as one of the following:

Return code	Description
STATUS_INSUFFICIENT_RESOURCES	FltTagFileEx encountered a pool allocation failure. This is an error code.
STATUS_INVALID_DEVICE_REQUEST	The file system does not support reparse points. This is an error code.
STATUS_INVALID_PARAMETER	FileTag is not a Microsoft tag, and NULL was specified for Guid. This is an error code.
STATUS_IO_REPARSE_TAG_MISMATCH	The reparse tag specified by the caller did not match the tag of the reparse point to be modified. This is an error code.
STATUS_REPARSE_ATTRIBUTE_CONFLICT	The reparse GUID specified by the caller did not match the GUID of the reparse point to be modified. This is an error code.

Remarks

Minifilter drivers should use FltTagFile instead of FSCTL_SET_REPARSE_POINT to set a reparse point.

Not all file systems support reparse points. The NTFS file system supports them; the FAT file system does not. Minifilter drivers can determine whether a file system supports reparse points by calling FltQueryVolumeInformation, specifying FileFsAttributeInformation for the FsInformation parameter, and examining the FILE_SUPPORTS_REPARSE_POINTS bit flag in the returned FILE_FS_ATTRIBUTE_INFORMATION structure.

To remove an existing reparse point, call FltUntagFile.

For more information about reparse points, see the Microsoft Windows SDK documentation.

Requirements

Requirement	Value
Target Platform	Universal
Header	fltkernel.h (include Fltkernel.h)
Library	FltMgr.lib
DLL	Fltmgr.sys
IRQL	PASSIVE_LEVEL