The filter engine calls the vSwitchFilterEngineReorderNotifyRn (FWPS_VSWITCH_FILTER_ENGINE_REORDER_CALLBACK0) callout function to notify the callout driver about events that are associated the virtual switch filter engine reordering.

Note  FWPS_VSWITCH_FILTER_ENGINE_REORDER_CALLBACK0 is a specific version of FWPS_VSWITCH_FILTER_ENGINE_REORDER_CALLBACK. See WFP Version-Independent Names and Targeting Specific Versions of Windows for more information.



NTSTATUS FwpsVswitchFilterEngineReorderCallback0(
  void *notifyContext,
  void *completionContext,
  BOOLEAN isInRequiredPosition,
  const NDIS_ENUM_FILTERS *vSwitchExtensionLwfList



A pointer to a context provided by the callout driver. The driver passed this pointer to the notifyContext parameter of the FwpsvSwitchEventsSubscribe0 function. This parameter is optional and can be NULL.


A pointer to a completion context provided by the callout driver. This parameter is optional and can be NULL.


A BOOLEAN value that is set to TRUE if the filter is in the required position in the filter stack or FALSE if it is not.


An NDIS_ENUM_FILTERS structure that specifies a list of the virtual switch extension NDIS filter drivers.

Return Value

A callout's

FWPS_VSWITCH_FILTER_ENGINE_REORDER_CALLBACK0 function returns one of the following NTSTATUS codes.

Return code Description
The callout driver accepts the notification from the filter engine.
Other status codes
An error occurred.


A callout driver registers a

vSwitchFilterEngineReorderNotifyRn function by calling
the FwpsvSwitchEventsSubscribe0 function.

By default, the WFP virtual switch extension is positioned as the first filtering extension at virtual switch ingress. (Therefore, it is also the last extension at virtual switch egress). This is usually the best position, because the WFP extension can intercept packets before any other extensions can modify them at ingress. Also, the WFP extension can intercept packets after all packet modifications are done at egress.

However, because an administrator can reorder any virtual switch extensions of the same class, the WFP extension can be reordered out of the default position. After a reorder occurs, a WFP client’s filters could be bypassed and might need to be adjusted.

If the vSwitchFilterEngineReorderNotifyRn callback is registered, the callout driver is notified when a virtual switch reorder is occurring. The callout driver receives an NDIS_ENUM_FILTERS structure with an ordered list of current virtual switch extensions in the vSwitchExtensionLwfList parameter.

If the virtual switch extensions are reordered, the WFP extension is paused (see FilterPause) and restarted (see FilterRestart). From the WFP filter FilterRestart call, the WFP filter driver calls the NdisEnumerateFilterModules function to obtain an ordered list of virtual switch extension filters. If the WFP extension is not in the default position, then the filter driver notifies the callout drivers.

A callout driver cannot return STATUS_PENDING from vSwitchFilterEngineReorderNotifyRn.


Minimum supported client Available starting with Windows 8.
Target Platform Windows
Header fwpsk.h (include Fwpsk.h)

See Also

Callout Driver Callout Functions