ProtocolSendComplete

VOID
ProtocolSendComplete(
IN NDIS_HANDLE ProtocolBindingContext,
IN PNDIS_PACKET Packet,
IN NDIS_STATUS Status
);

ProtocolSendComplete is a required driver function that completes the processing of a protocol-initiated send previously passed to NdisSendPackets or NdisSend, which returned NDIS_STATUS_PENDING.

Parameters

ProtocolBindingContext: Specifies the handle to a protocol-allocated context area in which the protocol driver maintains per-binding runtime state. The driver supplied this handle when it called NdisOpenAdapter.
Packet: Points to the protocol-supplied packet descriptor for the completed send.
Status: Specifies the final status of the send operation.

Comments

ProtocolSendComplete performs whatever postprocessing is necessary for a completed transmit operation, such as notifying the client that originally requested the protocol to send data over the network.

Completion of a send operation usually implies that the underlying NIC driver actually has transmitted the given packet over the network. However, the driver of a so-called intelligent NIC can consider a send complete as soon as it downloads the net packet to its NIC. The underlying driver’s call to NdisMSendComplete or NdisMWanSendComplete causes NDIS to call the ProtocolSendComplete function.

When ProtocolSendComplete is called, the driver regains ownership of the following protocol-allocated resources:

The packet descriptor at Packet
All buffer descriptors chained to the packet descriptor that map buffers containing the net packet data and any protocol-allocated buffers mapped by these descriptors
Any out-of-band block associated with the packet descriptor
Any protocol-allocated buffer specified in the out-of-band block at MediaSpecificInformation

Consequently, ProtocolSendComplete can either release these resources or prepare them for reuse in a subsequent call to NdisSendPackets or NdisSend. As a general rule, reusing such resources yields better performance than releasing them except, possibly, in periods of low network traffic if the protocol previously allocated a surplus of these resources to handle a period of heavy I/O demand.

To prepare the buffer and packet descriptors for reuse, ProtocolSendComplete should follow these guidelines:

Always call an NdisUnchainBufferAtXxx function as many times as necessary to save the buffer descriptor pointers before ProtocolSendComplete calls NdisReinitializePacket with the descriptor at Packet.
Otherwise, NdisReinitializePacket sets the head of the buffer chain to NULL so the protocol cannot recover pointers to the buffer descriptors chained to the packet descriptor. Either the protocol loses MDL(s) mapping client-supplied buffer(s) or it loses a set of buffer descriptors the protocol allocated with NdisAllocateBuffer.
Always pass the pointer returned by NDIS_OOB_DATA_FROM_PACKET to NdisZeroMemory to clear an associated out-of-band data block, never the Packet pointer.
Otherwise, NdisZeroMemory destroys the packet descriptor the protocol allocated with NdisAllocatePacket, rendering it unusable for specifying subsequent sends.
As an alternative to clearing the out-of-band block, the protocol can reinitialize only those members that the protocol normally sets up for sends with the appropriate NDIS_SET_PACKET_XXX macros.

Until ProtocolSendComplete is called, the current status of a protocol-initiated send is volatile. A protocol temporarily releases ownership of all resources it allocated for a send when it calls NdisSendPackets or NdisSend, even if the protocol supplies out-of-band information with the packet descriptors it allocates for sends. In particular, a protocol should never attempt to examine the Status member of the associated out-of-band data block when NdisSendPackets or NdisSend returns control.

Although NDIS always submits protocol-supplied packet arrays to the underlying miniport in the protocol-determined order passed in calls to NdisSendPackets, the underlying driver can complete the given packets in random order. That is, every bound protocol can rely on NDIS to submit the packets the protocol passes to NdisSendPackets or NdisSend in FIFO order to the underlying driver, but no protocol can rely on that underlying driver to call NdisMSendComplete with those packets in the same order.

The ProtocolSendComplete function of an NDIS intermediate driver cannot simply forward completion indications to still higher-level protocols. Such an attempt can cause a deadlock. Instead, such a driver must call NdisIMSwitchToMiniport to forward the indication from the appropriate context. If NdisIMSwitchToMiniport returns FALSE, the driver must call NdisIMQueueMiniportCallback and forward the indication from the protocol-supplied MiniportCallback function.

By default, ProtocolSendComplete runs at IRQL DISPATCH_LEVEL in an arbitrary thread context.