Utilisation d’une légende pour l’inspection approfondie des données de flux

Lorsqu’une légende inspecte les données de flux, sa fonction de légende classFn peut inspecter n’importe quelle combinaison des champs de données fixes, des champs de métadonnées et des données de flux brutes qui lui sont transmises, ainsi que toutes les données pertinentes qui ont été stockées dans un contexte associé au filtre ou au flux de données.

Par exemple :

// classifyFn callout function
VOID NTAPI
 ClassifyFn(
    IN const FWPS_INCOMING_VALUES0  *inFixedValues,
    IN const FWPS_INCOMING_METADATA_VALUES0  *inMetaValues,
    IN OUT VOID  *layerData,
    IN const FWPS_FILTER0  *filter,
    IN UINT64  flowContext,
    IN OUT FWPS_CLASSIFY_OUT  *classifyOut
    )
{
  FWPS_STREAM_CALLOUT_IO_PACKET0 *ioPacket;
  FWPS_STREAM_BUFFER0 *dataStream;
  UINT32 bytesRequired;
  SIZE_T bytesToPermit;
  SIZE_T bytesToBlock;
  ...

  // Get a pointer to the stream callout I/O packet
 ioPacket = (FWPS_STREAM_CALLOUT_IO_PACKET0 *)layerData;

  // Get the data fields from inFixedValues
  ...

  // Get any metadata fields from inMetaValues
  ...

  // Get the pointer to the data stream
 dataStream = ioPacket->dataStream;

  // Get any filter context data from filter->context
  ...

  // Get any flow context data from flowContext
  ...

  // Inspect the various data sources to determine
  // the action to be taken on the data
  ...

  // If more stream data is required to make a determination...
 if (...) {

    // Let the filter engine know how many more bytes are needed
 ioPacket->streamAction = FWPS_STREAM_ACTION_NEED_MORE_DATA;
 ioPacket->countBytesRequired = bytesRequired;
 ioPacket->countBytesEnforced = 0;

    // Set the action to continue to the next filter
 classifyOut->actionType = FWP_ACTION_CONTINUE;

 return;
  }
  ...

  // If some or all of the data should be permitted...
 if (...) {

    // No stream-specific action is required
 ioPacket->streamAction = FWPS_STREAM_ACTION_NONE;

    // Let the filter engine know how many of the leading bytes
    // in the stream should be permitted
 ioPacket->countBytesRequired = 0;
 ioPacket->countBytesEnforced = bytesToPermit;

    // Set the action to permit the data
 classifyOut->actionType = FWP_ACTION_PERMIT;

 return;
  }

  ...

  // If some or all of the data should be blocked...
 if (...) {

    // No stream-specific action is required
 ioPacket->streamAction = FWPS_STREAM_ACTION_NONE;

    // Let the filter engine know how many of the leading bytes
    // in the stream should be blocked
 ioPacket->countBytesRequired = 0;
 ioPacket->countBytesEnforced = bytesToBlock;

    // Set the action to block the data
 classifyOut->actionType = FWP_ACTION_BLOCK;

 return;
  }

  ...

  // If the decision to permit or block should be passed
  // to the next filter in the filter engine...
 if (...) {

    // No stream-specific action is required
 ioPacket->streamAction = FWPS_STREAM_ACTION_NONE;

    // No bytes are affected by this callout
 ioPacket->countBytesRequired = 0;
 ioPacket->countBytesEnforced = 0;

 return;
  }

  ...
}

La valeur dans filter-action.type> détermine les actions que la fonction de légende classifiable de la légende doit retourner dans le membre actionType de la structure vers laquelle pointe le paramètre classout. Pour plus d’informations sur ces actions, consultez la structure FWPS_ACTION0 .

Pour plus d’informations sur l’inspection des données de paquets et de flux, consultez Inspection des données de paquets et de flux.