FILTER_DETACH callback function (ndis.h)

Article
02/22/2024

NDIS calls a filter driver's FilterDetach function to release all the resources that are associated with a filter module.

Note You must declare the function by using the FILTER_DETACH type. For more information, see the following Examples section.

Syntax

FILTER_DETACH FilterDetach;

void FilterDetach(
  [in] NDIS_HANDLE FilterModuleContext
)
{...}

Parameters

[in] FilterModuleContext

A handle to the context area for the filter module that NDIS will remove from the driver stack. The filter driver created and initialized this context area in the FilterAttach function.

Return value

None

Remarks

FilterDetach is a required function. NDIS calls FilterDetach to remove a filter module from a driver stack. NDIS calls FilterDetach when the filter module is in the Paused state.

FilterDetach frees the driver's context areas and other resources (such as buffer pools) for the affected filter module.

After the filter driver returns from FilterDetach, the filter module is in the Detached state.

NDIS calls FilterDetach at IRQL = PASSIVE_LEVEL.

Examples

To define a FilterDetach function, you must first provide a function declaration that identifies the type of function you're defining. Windows provides a set of function types for drivers. Declaring a function using the function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it's a requirement for writing drivers for the Windows operating system.

For example, to define a FilterDetach function that is named "MyDetach", use the FILTER_DETACH type as shown in this code example:

FILTER_DETACH MyDetach;

Then, implement your function as follows:

_Use_decl_annotations_
VOID
 MyDetach(
    NDIS_HANDLE  FilterModuleContext
    )
  {...}

The FILTER_DETACH function type is defined in the Ndis.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the Use_decl_annotations annotation to your function definition. The Use_decl_annotations annotation ensures that the annotations that are applied to the FILTER_DETACH function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for NDIS Drivers.

For information about Use_decl_annotations, see Annotating Function Behavior.

Requirements

Requirement	Value
Minimum supported client	Supported in NDIS 6.0 and later.
Target Platform	Windows
Header	ndis.h (include Ndis.h)
IRQL	PASSIVE_LEVEL

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