XDP_EXTENSION structure

A structure defining an XDP data path extension.

Syntax

//
// Structure defining an XDP data path extension.
//
typedef struct _XDP_EXTENSION {
    //
    // This field is reserved for XDP platform use.
    //
    UINT16 Reserved;
} XDP_EXTENSION;

Members

Reserved

A 16-bit field reserved for XDP platform use. This field contains the byte offset from the descriptor base to the extension data. Applications and drivers should not access this field directly; instead use the XdpGetExtensionData helper function or extension-specific getter functions.

Remarks

The XDP_EXTENSION structure serves as an opaque handle to an XDP descriptor extension. It is obtained by querying for a specific extension using XDP_EXTENSION_INFO via socket options (for AF_XDP applications) or driver APIs (for XDP drivers).

Usage Pattern

1. Initialize extension info: Use XdpInitializeExtensionInfo to create an XDP_EXTENSION_INFO structure describing the desired extension
2. Query for extension: Register the extension with XskSetSockopt (AF_XDP) or driver APIs
3. Retrieve extension handle: After binding/queue creation, query to get the populated XDP_EXTENSION structure
4. Access extension data: Use XdpGetExtensionData() or extension-specific helper functions like XdpGetFragmentExtension() to access extension data for each descriptor

Thread Safety

Once obtained, an XDP_EXTENSION handle can be safely accessed from multiple threads concurrently as long as the associated queue/socket remains active. The extension offset is immutable after initialization.

Performance Considerations

Extension handles should be cached during initialization rather than queried per-packet. The small size (2 bytes) makes extension handles suitable for stack allocation or embedding in context structures.

For more information about the extension model, see Descriptor Extensions.

See Also

XDP_EXTENSION_INFO