FILTER_STATUS callback function (ndis.h)

Article
10/21/2021

The FilterStatus function indicates status changes that are reported by NDIS or an underlying driver.

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

Syntax

FILTER_STATUS FilterStatus;

void FilterStatus(
  [in] NDIS_HANDLE FilterModuleContext,
  [in] PNDIS_STATUS_INDICATION StatusIndication
)
{...}

Parameters

[in] FilterModuleContext

A handle to the context area for the filter module. The filter driver created and initialized this context area in the FilterAttach function.

[in] StatusIndication

A pointer to an NDIS_STATUS_INDICATION structure that contains the status information.

Return value

None

Remarks

FilterStatus is an optional function. If a filter driver does not use status indications, it can set the entry point for this function to NULL when it calls the NdisFRegisterFilterDriver function.

To determine link status, use the status indications from underlying drivers instead of OID queries. These status indications will improve system performance and avoid possible race conditions.

A filter driver usually calls the NdisFIndicateStatus function at the end of its FilterStatus function to pass on the status indication to overlying drivers.

A filter driver can filter out certain status indications or modify the indicated status. To filter out a status indication, the driver simply does not call NdisFIndicateStatus.

NDIS calls FilterStatus at IRQL <= DISPATCH_LEVEL.

Examples

To define a FilterStatus 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 FilterStatus function that is named "MyStatus", use the FILTER_STATUS type as shown in this code example:

FILTER_STATUS MyStatus;

Then, implement your function as follows:

_Use_decl_annotations_
VOID
 MyStatus(
    NDIS_HANDLE  FilterModuleContext,
    PNDIS_STATUS_INDICATION  StatusIndication
    )
  {...}

The FILTER_STATUS 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_STATUS 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	<= DISPATCH_LEVEL

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