FltTagFileEx function (fltkernel.h)

Article
04/01/2021

FltTagFileEx sets a reparse point on a file or directory.

Syntax

NTSTATUS FLTAPI FltTagFileEx(
  PFLT_INSTANCE InitiatingInstance,
  PFILE_OBJECT  FileObject,
  ULONG         FileTag,
  GUID          *Guid,
  PVOID         DataBuffer,
  USHORT        DataBufferLength,
  ULONG         ExistingFileTag,
  GUID          *ExistingGuid,
  ULONG         Flags
);

Parameters

InitiatingInstance

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

FileObject

Pointer to the 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.

FileTag

Reparse point tag. Can be one of the IO_REPARSE_TAG_XXX values defined in ntifs.h.

Guid

GUID that uniquely identifies the reparse point. If FileTag is a non-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.

DataBuffer

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

DataBufferLength

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

ExistingFileTag

Existing tag on the file if the tag has to be replaced. This parameter must be set to zero to set a reparse tag on a file that doesn't already have one.

ExistingGuid

GUID that uniquely identifies an existing reparse point. If ExistingFileTag is a non-Microsoft tag and is non-zero, this parameter must not be NULL.

Flags

Specifies the REPARSE_DATA_BUFFER_EX_XXX flags defined in ntifs.h.

Return value

This function returns STATUS_SUCCESS or an appropriate NTSTATUS value such as the following:

Return Code	Description
STATUS_IO_REPARSE_TAG_MISMATCH	The tag value specified in ExistingFileTag does not match that of the existing tag value.
STATUS_REPARSE_ATTRIBUTE_CONFLICT	For an existing reparse point with a non-Microsoft tag, ExistingFileTag matches the existing tag value, but the Guid does not match the existing Guid.

Remarks

Minifilter drivers should use FltTagFileEx instead of FSCTL_SET_REPARSE_POINT_EX to set a reparse point.

Not all file systems support reparse points; for example, the NTFS and ReFS file systems supports them, but 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
Header	fltkernel.h