ClientEventChainedReceive

NTSTATUS
ClientEventChainedReceive(
IN PVOID TdiEventContext,
IN CONNECTION_CONTEXT ConnectionContext,
IN ULONG ReceiveFlags,
IN ULONG ReceiveLength,
IN ULONG StartingOffset,
IN PMDL Tsdu,
IN PVOID TsduDescriptor
);

ClientEventChainedReceive is an event handler that the underlying TDI transport calls in response to an incoming receive from a remote node with which the client has an established endpoint-to-endpoint connection.

The transport calls this handler, rather than ClientEventReceive, when it is indicating a full TSDU and the client can be given direct read-only access to the buffered TSDU until the client has consumed the data.

Parameters

TdiEventContext

Points to the client-supplied context provided in the IRP that was set up with TdiBuildSetEventHandler when ClientEventChainedReceive was registered with the underlying transport.

ConnectionContext

Points to the client's context area for this connection endpoint. The client previously supplied this value to its underlying transport when its ClientEventConnect handler accepted a connection offer from the remote-node peer and/or when it opened the connection endpoint with ZwCreateFile.

ReceiveFlags

Specifies the nature of the receive indication as a combination (ORed) of the following flags:

TDI_RECEIVE_NORMAL: The buffer mapped at Tsdu contains normal data received from the client's remote-node peer. This flag and TDI_RECEIVE_EXPEDITED are mutually exclusive.
TDI_RECEIVE_EXPEDITED: The buffer mapped at Tsdu contains expedited data received from the client's remote-node peer. This flag can be set only if the client did not register either or both ClientEventChainedReceiveExpedited and/or ClientEventReceiveExpedited handler(s) and if the underlying transports support expedited transfers.
TDI_RECEIVE_ENTIRE_MESSAGE: The buffer mapped at Tsdu contains a full TSDU, and the client retains read-only access to this buffer until the client consumes the indicated data if ClientEventChainedReceive returns STATUS_PENDING. This flag is always set when ClientEventChainedReceive is called.
TDI_RECEIVE_AT_DISPATCH_LEVEL: The receive is being indicated at IRQL DISPATCH_LEVEL. This flag restricts the set of support routines that the client can call in processing this indication. Some transports never set this flag, whatever the current IRQL, when making receive-event notifications.

ReceiveLength

Specifies the number of bytes of client data in the buffer mapped at Tsdu.

StartingOffset

Specifies the byte offset at which the client data starts within the buffer mapped at Tsdu.

Tsdu

Points to an MDL, possibly the initial MDL in a chain, mapping the buffer containing the received TSDU.

TsduDescriptor

Points to a descriptor for the received TSDU. The client must call TdiReturnChainedReceives with this pointer subsequently if it returns STATUS_PENDING for this receive indication. This pointer should be treated as a handle to an opaque variable, to be used by the client only as a parameter to TdiReturnChainedReceives if ClientEventChainedReceive returns STATUS_PENDING.

Return Value

ClientEventChainedReceive can return one of the following:

STATUS_SUCCESS: Indicates the client consumed all the data in the given TSDU and is returning ownership of the buffer (and TsduDescriptor) immediately.
STATUS_PENDING: Indicates the client is retaining ownership of the buffer containing the given TSDU until it calls TdiReturnChainedPackets with the given TsduDescriptor.
STATUS_DATA_NOT_ACCEPTED: Indicates the client is not interested in the TSDU.
If the underlying transport buffers receives internally, the client might retrieve the data with a TDI_RECEIVE request, unless the transport discards buffered data indicated to ClientEventChainedReceive(Xxx) handlers.

Comments

A call to ClientEventChainedReceive gives the client read-only access to the indicated TSDU for the range within the buffer specified by the input StartingOffset and ReceiveLength. If the indicated data is of interest to the client, ClientEventChainedReceive either copies the indicated range of TSDU data into a client-allocated internal buffer and returns STATUS_SUCCESS immediately or retains control of the buffer by returning STATUS_PENDING. If it returns STATUS_PENDING, the client must call TdiReturnChainedReceives subsequently with the input TsduDescriptor to relinquish control of the buffer after the client has consumed the data.

In general, such a call to TdiReturnChainedReceives should occur as quickly as possible. Holding on to a buffer passed to ClientEventChainedReceive for any extended period constrains I/O throughput in underlying driver(s), because the driver that allocated the buffer cannot reuse this resource for subsequent receive indications until TdiReturnChainedReceives is called.

Because calls to ClientEventChainedReceive always indicate the availability of a full TSDU, the client never has to set up TDI_RECEIVE requests for such an indication, as the corresponding ClientEventReceive handler sometimes must to obtain a full TSDU. Consequently, receive indications made to ClientEventChainedReceive increase network I/O throughput and performance by decreasing call overhead for the client, for its underlying transport, and for the system overall.

If the client has registered only ClientEventChainedReceive and ClientEventReceive handlers for the endpoint-to-endpoint connection, ClientEventChainedReceive can determine whether the TSDU is normal or expedited data by checking the ReceiveFlags, assuming both transports support expedited sends and receives. A transport never calls the corresponding ClientEventReceive handler with the same indication it makes to ClientEventChainedReceive.

The transport does not call ClientEvent(Chained)Receive while the client has an outstanding normal receive request or has rejected previously indicated data for a particular incoming normal receive until that receive is done. However, a transport that supports expedited data can call ClientEvent(Chained)Receive(Expedited) in the process of indicating a normal TSDU if an expedited TSDU comes in from the remote-node peer.

When ClientEventChainedReceive returns control with either STATUS_SUCCESS or STATUS_DATA_NOT_ACCEPTED, the underlying transport assumes the client is done with this receive indication.

By default, ClientEventChainedReceive runs at IRQL DISPATCH_LEVEL.