NdisReturnPackets

NdisReturnPackets

VOID
NdisReturnPackets(
       IN PNDIS_PACKET *PacketsToReturn,
      IN UINT NumberOfPackets
       );

NdisReturnPackets releases ownership of one or more packets after a protocol has consumed the received data.

Parameters

PacketsToReturn

Points to an array of pointers to packet descriptors to be returned to the underlying driver that allocated them for a receive indication.

NumberOfPackets

Specifies the number of pointers in the array.

Comments

An NDIS intermediate driver should call NdisReturnPackets as soon as possible after its ProtocolReceivePacket function has returned control. Otherwise, both the underlying driver that supports multipacket receive indications and the bound protocol driver that processes them suffer a performance degradation.

When an underlying NIC driver runs low on available packet pool for receive indications or its NIC runs low on empty receive buffers, the miniport can force the NDIS library to call every bound protocol driver’s ProtocolReceive function with a single packet descriptor at a time until the miniport has regained ownership of its packet descriptors and the NIC has receive buffers available for incoming net packets. A ProtocolReceive function cannot begin postprocessing a packet of received data and forwarding the processed data to clients until the driver’s ProtocolReceiveComplete function is called.

For a packet descriptor passed in to its ProtocolReceivePacket function, a highest level protocol driver can process its copy of received data and forward the processed data to clients immediately because the protocol can control how long it retains ownership of the resources allocated by the indicating driver. Assuming a highest level protocol driver does not massage the data it indicates to its clients, the protocol can even set up the range of data within the receive buffer of interest to its client, and make a receive indication to its client(s) by forwarding the input packet descriptor to those clients.

If an intermediate protocol driver’s ProtocolReceivePacket function returns a nonzero reference count to an input packet descriptor, that driver must call NdisReturnPackets one or more times. When it has called NdisReturnPackets with a particular packet descriptor as many times as the value returned by ProtocolReceivePacket, the NDIS library returns the packet descriptor to the driver that made the indication. For a highest level protocol that forwards an input packet descriptor to its clients, those clients return the packet descriptor to the NDIS driver that allocated it by making calls to TdiReturnChainedReceives.

A protocol driver can rely on NDIS to manage the reference count for every receive packet passed to the ProtocolReceivePacket function. When the reference count for a packet descriptor originally set to the return from ProtocolReceivePacket goes to zero, the NDIS library calls the indicating driver’s MiniportReturnPacket function with the released packet descriptor.

NdisReturnPackets cannot be called from a ProtocolReceivePacket function.

Callers of NdisReturnPackets run at IRQL <= DISPATCH_LEVEL.