FltIsIoRedirectionAllowed function (fltkernel.h)

Article
10/21/2021

The FltIsIoRedirectionAllowed routine determines whether I/O can be redirected from the specified source filter instance to another specified filter instance.

Syntax

NTSTATUS FLTAPI FltIsIoRedirectionAllowed(
  [in]  PFLT_INSTANCE SourceInstance,
  [in]  PFLT_INSTANCE TargetInstance,
  [out] PBOOLEAN      RedirectionAllowed
);

Parameters

[in] SourceInstance

The filter instance on the source device stack.

[in] TargetInstance

The filter instance on the target device stack.

[out] RedirectionAllowed

A value of TRUE if all I/O to the source device stack can be redirected to the target device stack by changing the filter instance referenced, otherwise FALSE.

Return value

An NTSTATUS value of STATUS_SUCCESS for success or STATUS_NOT_SUPPORTED if 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