ClientEventChainedReceiveDatagram

ClientEventChainedReceiveDatagram

NTSTATUS
ClientEventChainedReceiveDatagram(
IN PVOID TdiEventContext,
IN LONG SourceAddressLength,
IN PVOID SourceAddress,
IN LONG OptionsLength,
IN PVOID Options,
IN ULONG ReceiveDatagramFlags,
IN ULONG ReceiveDatagramLength,
IN ULONG StartingOffset,
IN PMDL Tsdu,
IN PVOID TsduDescriptor
);

ClientEventChainedReceiveDatagram is an event handler that the underlying TDI transport calls in response to an incoming receive from a remote node that was directed to a local-node transport address opened by the client.

The transport calls this handler, rather than ClientEventReceiveDatagram, 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 ClientEventChainedReceiveDatagram was registered with the underlying transport.

SourceAddressLength

Specifies the size in bytes of the buffer at SourceAddress.

SourceAddress

Points to a buffer specifying the remote-node transport address from which the datagram was sent.

OptionsLength

Specifies the size in bytes of the buffer at Options. Zero implies no option string is available. Options is NULL if this parameter is zero.

Options

Points to a buffer specifying a string of transport-specific options sent with the datagram. This pointer is NULL if OptionsLength is zero.

ReceiveDatagramFlags

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

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 ClientEventChainedReceiveDatagram returns STATUS_PENDING. This flag is always set when ClientEventChainedReceiveDatagram is called.

TDI_RECEIVE_BROADCAST

The receive was broadcast.

TDI_RECEIVE_MULTICAST

The receive was multicast.

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 ClientEventChainedReceiveDatagram 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 ClientEventChainedReceiveDatagram returns STATUS_PENDING.

Return Value

ClientEventChainedReceiveDatagram 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 to the underlying driver 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.

Comments

When a datagram arrives from a remote node, the transport calls the registered ClientEvent(Chained)ReceiveDatagram handlers for each client with an open file object representing an address that matches the destination address of the datagram. Because a datagram is not associated with an established connection, the TDI driver passes the transport address of the remote-node sender at SourceAddress to the receiving client along with the datagram.

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

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

The underlying TDI transport does not call ClientEventChainedReceiveDatagram if the client has an outstanding receive or receive-datagram request on the local transport address that is the target of an incoming datagram.

To receive indications for broadcast datagrams that the TDI driver receives on the network, the client must open the broadcast address of its underlying transport and register its ClientEvent(Chained)ReceiveDatagram handler(s).

By default, ClientEventChainedReceiveDatagram runs at IRQL DISPATCH_LEVEL.