NDIS_GET_PACKET_MEDIA_SPECIFIC

NDIS_GET_PACKET_MEDIA_SPECIFIC_INFO

VOID
NDIS_GET_PACKET_MEDIA_SPECIFIC_INFO(
IN PNDIS_PACKET Packet,
IN PPVOID pMediaSpecificInfo,
IN PUINT pSizeMediaSpecificInfo
);

NDIS_GET_PACKET_MEDIA_SPECIFIC_INFO returns the MediaSpecificInformation pointer and the SizeMediaSpecificInfo value from the out-of-band data block associated with a given packet descriptor.

Parameters

Packet: Points to a packet descriptor.
pMediaSpecificInfo: Points to a caller supplied variable that this macro sets to the MediaSpecificInformation pointer. The returned address gives the caller access to any buffered out-of-band information, such as packet priority, associated with the specified net packet indicated or to be transmitted.
pSizeMediaSpecificInfo: Points to a caller-supplied variable that this macro sets to the SizeMediaSpecificInfo value, which specifies the size in bytes of the buffer at MediaSpecificInformation.

Comments

NDIS_GET_PACKET_MEDIA_SPECIFIC_INFO returns a NULL pointer at pMediaSpecificInfo and zero at pSizeMediaSpecificInfo if there is no media-specific information in the NDIS_PACKET_OOB_DATA block associated with the given packet descriptor.

Depending on the medium, a NIC miniport might set these members with NDIS_SET_PACKET_MEDIA_SPECIFIC_INFO in the out-of-band data blocks associated with the packet descriptors it allocates for receive indications.

Depending on the medium of the underlying driver to which it is bound, a protocol might set MediaSpecificInformation and SizeMediaSpecificInfo in the out-of-band blocks associated with the packet descriptors it allocates for sends.

In either case, while a higher-level protocol is consuming a receive indication or a lower-level miniport is processing a send, that driver must have exclusive access to the buffer at MediaSpecificInformation. This restriction implies the following:

A miniport cannot access the buffer it set up with media-specific information when NdisMIndicateReceivePacket returns control if NDIS_STATUS_PENDING is set in the Status member of the associated out-of-band block. The driver can use NDIS_GET_PACKET_STATUS to determine whether each packet in the packet array it just indicated has this status set or has been returned with NDIS_STATUS_SUCCESS.
A protocol driver cannot access the media-specific information buffer it set up for a send, nor anything else in the out-of-band data block associated with a packet descriptor it passes to NdisSendPackets or NdisSend, until the packet descriptor is returned to its ProtocolSendComplete function.
Because NDIS queues send packets and resubmits them if the MiniportSend function returns NDIS_STATUS_RESOURCES or if the MiniportSendPackets function sets NDIS_STATUS_RESOURCES for the Status of a packet in a submitted array, the final status of each packet in a send (array) is volatile until that packet has been returned to ProtocolSendComplete.

A protocol driver can call NdisQueryReceiveInformation to obtain this information from the NDIS_PACKET_OOB_DATA block associated with a packet descriptor when its ProtocolReceive function is given an indication. However, this call is superfluous if the protocol is bound to an underlying driver that does not supply out-of-band information with its indications.

Callers of NDIS_GET_PACKET_MEDIA_SPECIFIC_INFO run at IRQL <= DISPATCH_LEVEL.