FwpsPendOperation0 function (fwpsk.h)

The FwpsPendOperation0 function is called by a callout to suspend packet processing pending completion of another operation.

Note  FwpsPendOperation0 is a specific version of FwpsPendOperation. See WFP Version-Independent Names and Targeting Specific Versions of Windows for more information.


NTSTATUS FwpsPendOperation0(
  HANDLE completionHandle,
  HANDLE *completionContext



[in] A completion handle that is required to pend the current filtering operation. This parameter is obtained from the completionHandle member of the FWPS_INCOMING_METADATA_VALUES0 structure passed into the callout driver's classifyFn function.


[out] The handle to the completion context of this pend operation. When the callout is ready to resume packet processing, it calls the FwpsCompleteOperation0 function with the value of this parameter as the input completionContext parameter.

Return value

The FwpsPendOperation0 function returns one of the following NTSTATUS codes.

Return code Description
Packet processing was successfully pended.
A call was made to FwpsPendOperation0 in a reauthorization classify operation. For more information, see Remarks.
One or more of the parameters is invalid.
The TCP/IP network stack is not ready to allow this operation.
Other status codes
An error occurred.


The callout should retain the completionContext parameter value until it resumes packet processing. When the operation that prompted the call to this function has completed, the callout should call the FwpsCompleteOperation0 function, passing it the completionContext parameter value.

A callout can call this function only to pend a packet that originates from the FWPM_LAYER_ALE_RESOURCE_ASSIGNMENT_ Xxx, FWPM_LAYER_ALE_AUTH_LISTEN_ Xxx, or FWPM_LAYER_ALE_AUTH_CONNECT_ Xxx filtering layers. A callout can pend the current processing operation on a packet when the callout must perform processing on one of these layers that may take a long interval to complete or that should occur at IRQL = PASSIVE_LEVEL if the current IRQL > PASSIVE_LEVEL.

To complete a connection that was previously pended at the FWPS_LAYER_ALE_AUTH_RECV_ACCEPT_ Xxx layer, the callout driver must reinject the packet that was cloned at that layer as well as call the FwpsCompleteOperation0 function.

To be able to pend packet processing, the callout driver's classifyFn function should set the actionType member of the FWPS_CLASSIFY_OUT0 structure to FWP_ACTION_BLOCK and the Flags member to FWPS_CLASSIFY_OUT_FLAG_ABSORB.

Pended connections are reauthenticated after the FwpsCompleteOperation0 function executes. TCP connections, if allowed, are created by completing the handshake operation, but non-TCP connections only create state entries. Any pended packet data is flushed from memory when the FwpsPendOperation0 function completes, so applications must retransmit those packets after FwpsCompleteOperation0 runs. Callouts could buffer such data and reinject the data on their behalf.

Only an initial Application Layer Enforcement (ALE) flow authorization can be postponed by calling FwpsPendOperation0 and FwpsCompleteOperation0. If an ALE flow is reauthorized, the FWP_CONDITION_FLAG_IS_REAUTHORIZE flag is set. A call to FwpsPendOperation0 from the FWPM_LAYER_ALE_AUTH_CONNECT_ Xxx or FWPM_LAYER_ALE_AUTH_RECV_ACCEPT_ Xxx filtering layers will fail if the FWP_CONDITION_FLAG_IS_REAUTHORIZE flag is set, and the STATUS_FWP_CANNOT_PEND status code will be returned. For more information, see ALE Reauthorization in the Windows SDK.


Minimum supported client Available starting with Windows Vista.
Target Platform Universal
Header fwpsk.h (include Fwpsk.h)
Library Fwpkclnt.lib

See also