FltIsIoRedirectionAllowedForOperation function (fltkernel.h)

Article
02/22/2024

The FltIsIoRedirectionAllowedForOperation routine determines whether I/O can be redirected from the filter instance associated with the specified FLT_CALLBACK_DATA structure to the specified filter instance.

Syntax

NTSTATUS FLTAPI FltIsIoRedirectionAllowedForOperation(
  [in]            PFLT_CALLBACK_DATA Data,
  [in]            PFLT_INSTANCE      TargetInstance,
  [out]           PBOOLEAN           RedirectionAllowedThisIo,
  [out, optional] PBOOLEAN           RedirectionAllowedAllIo
);

Parameters

[in] Data

An FLT_CALLBACK_DATA structure representing the I/O operation.

[in] TargetInstance

A filter instance on the target device stack.

[out] RedirectionAllowedThisIo

A value of TRUE if this I/O can be redirected to the target device stack by changing the filter instance referenced.

[out, optional] RedirectionAllowedAllIo

This optional parameter has a value of TRUE if all I/O to the device stack to which the I/O operation is issued can be redirected to the target device by changing the filter instance referenced, otherwise FALSE.

Return value

An NTSTATUS value of STATUS_SUCCESS for success or STATUS_NOT_SUPPORTED if the redirection is not supported.

Remarks

An I/O operation is associated with a FLT_CALLBACK_DATA structure. That structure contains a reference to a PFLT_IO_PARAMETER_BLOCK object, which contains a reference to the FLT_INSTANCE of the minifilter associated with the I/O operation.

If RedirectionAllowed is TRUE, the minifilter can redirect I/O by changing that instance to a new target instance.

If RedirectionAllowed is FALSE, the minifilter needs to allocate a new callback data object to issue I/O on the target stack or call FltAdjustDeviceStackSizeForIoRedirection to increase the size of the source device stack.

Note Minifilters should not modify the reference to the FLT_INSTANCE before verifying that redirection can be done this way. Use FltIsIoRedirectionAllowedForOperation or FltIsIoRedirectionAllowed.

Requirements

Requirement	Value
Minimum supported client	Available in Windows 7 and later versions of the Windows operating system.
Target Platform	Universal
Header	fltkernel.h (include FltKernel.h)
Library	FltMgr.lib
DLL	Fltmgr.sys
IRQL	<=DISPATCH_LEVEL