FWPS_CALLOUT_NOTIFY_FN0 callback function (fwpsk.h)

Article
10/21/2021

The filter engine calls a callout's notifyFn0 callout function to notify the callout driver about events that are associated with the callout.

Note notifyFn0 is the specific version of notifyFn used in Windows Vista and later. See WFP Version-Independent Names and Targeting Specific Versions of Windows for more information. For Windows 8, notifyFn2 is available. For Windows 7, notifyFn1 is available.

Syntax

FWPS_CALLOUT_NOTIFY_FN0 FwpsCalloutNotifyFn0;

NTSTATUS FwpsCalloutNotifyFn0(
  [in] FWPS_CALLOUT_NOTIFY_TYPE notifyType,
  [in] const GUID *filterKey,
  [in] FWPS_FILTER0 *filter
)
{...}

Parameters

[in] notifyType

A value that indicates the type of notification that the filter engine is sending to the callout. Valid values for this parameter are:

FWPS_CALLOUT_NOTIFY_ADD_FILTER

A filter is being added to the filter engine that specifies the callout for the filter's action.

FWPS_CALLOUT_NOTIFY_DELETE_FILTER

A filter is being deleted from the filter engine that specifies the callout for the filter's action.

FWPS_CALLOUT_NOTIFY_TYPE_MAX

A maximum value for testing purposes.

[in] filterKey

A pointer to the management identifier for the filter, as specified by the application or driver that is adding or deleting the filter. Must be NULL if the notifyType parameter is set to FWPS_CALLOUT_NOTIFY_DELETE_FILTER. For more information, see Remarks.

[in] filter

A pointer to an FWPS_FILTER0 structure. This structure describes the filter that is being added to or deleted from the filter engine.

A callout's notifyFn0 callout function can set the Context member of this structure to point to a callout driver-supplied context structure when the filter is added to the filter engine. This context structure is opaque to the filter engine, and can be used by the callout driver's classifyFn0 callout function to preserve any driver-specific data or state information between calls by the filter engine to the callout driver's
classifyFn0 callout function.

A callout's notifyFn0 callout function can clean up any context associated with the filter when the filter is deleted from the filter engine.

Return value

A callout's notifyFn0 function returns one of the following NTSTATUS codes.

Return code	Description
STATUS_SUCCESS	The callout driver accepts the notification from the filter engine.
Other status codes	An error occurred. If the notifyType parameter is FWPS_CALLOUT_NOTIFY_ADD_FILTER, the filter will not be added to the filter engine. If the notifyType parameter is FWPS_CALLOUT_NOTIFY_DELETE_FILTER, the filter will still be deleted from the filter engine.

Remarks

A callout driver registers a callout's callout functions with the filter engine by calling the FwpsCalloutRegister0 function.

The filter engine calls a callout's notifyFn0 callout function to notify the callout driver about events that are associated with the callout. If the callout driver's notifyFn0 callout function does not recognize the type of notification that is passed in the notifyType parameter, it ignores the notification and return STATUS_SUCCESS.

If a callout driver registers a callout with the filter engine after filters that specify the callout for the filter's action have already been added to the filter engine, the filter engine does not call the callout driver's notifyFn0 callout function to notify the callout about any of the existing filters. The filter engine calls the callout driver's notifyFn0 callout function to notify the callout when new filters that specify the callout for the filter's action are added to the filter engine. In this situation, a callout's notifyFn0 callout function might not get called for every filter in the filter engine that specifies the callout for the filter's action. If a callout driver registers a callout after the filter engine is started and the callout needs to know about every filter in the filter engine that specifies the callout for the filter's action, the callout driver must call the appropriate management functions to enumerate all the filters in the filter engine and sort through the resulting list of filters to find those that specify the callout for the filter's action. See Calling Other Windows Filtering Platform Functions for more information about calling these functions.

When a filter that specifies a callout for the filter's action is deleted from the filter engine, the filter engine calls the callout driver's notifyFn0 callout function and passes FWP_CALLOUT_NOTIFY_DELETE_FILTER in the notifyType parameter and NULL in the filterKey parameter. For more information, see Processing Notify Callouts.

Requirements

Requirement	Value
Minimum supported client	Available starting with Windows Vista.
Target Platform	Windows
Header	fwpsk.h (include Fwpsk.h)
IRQL	<= DISPATCH_LEVEL

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