Menggunakan Callout untuk Inspeksi Mendalam Data Aliran
Saat callout memeriksa data aliran, fungsi callout classifyFn-nya dapat memeriksa kombinasi bidang data tetap, bidang metadata, dan data aliran mentah yang diteruskan ke dalamnya, dan data relevan apa pun yang telah disimpan dalam konteks yang terkait dengan filter atau aliran data.
Contohnya:
// 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;
}
...
}
Nilai dalam filter-action.type> menentukan tindakan mana yang harus dikembalikan oleh fungsi callout classifyFn callout dalam anggota actionType struktur yang diacu oleh parameter classifyOut. Untuk informasi selengkapnya tentang tindakan ini, lihat struktur FWPS_ACTION0 .
Untuk informasi selengkapnya tentang pemeriksaan paket dan aliran data, lihat Memeriksa Paket dan Data Aliran.
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