T_UNITDATA_REQ(D7tpi)

T_UNITDATA_REQ -- Unitdata Request

Synopsis

This message consists of one M_PROTO message block followed by zero or more M_DATA message blocks where each M_DATA message block contains zero or more bytes of data. The format of the M_PROTO message block is as follows:

   struct T_unitdata_req {
   	long 	PRIM_type; 	/* always T_UNITDATA_REQ */
   	long	DEST_length;	/* dest addr length */
   	long	DEST_offset;	/* dest addr offset */
   	long	OPT_length;	/* options length */
   	long	OPT_offset;	/* options offset */
   }

Description

This primitive requests that the transport provider send the specified datagram to the specified destination.

Parameters

PRIM_type: identifies the primitive type.
DEST_length: is the length of the destination address
DEST_offset: is the offset (from the beginning of the M_PROTO message block) where the destination address begins.
OPT_length: is the length of the requested options associated with the primitive.
OPT_offset: is the offset (from the beginning of the M_PROTO message block) of the requested options associated with the primitive.

The proper alignment of the destination address and options in the M_PROTO message block is not guaranteed. The destination address and options in the M_PROTO message block are, however, aligned the same as they were received from the transport user.

This primitive does not require any acknowledgment. If a non-fatal error occurs, it is the responsibility of the transport provider to report it via the T_UDERROR_IND indication. Fatal errors are indicated via a M_ERROR message type which results in the failure of all operating system service routines on the stream.

Errors

The allowable fatal errors are as follows:

EPROTO

This indicates one of the following unrecoverable protocol conditions:

The transport service interface was found to be in an incorrect state.
The amount of transport user data associated with the primitive defines an transport service data unit larger than that allowed by the transport provider.

Modes

Only connectionless-mode.

Originator

Transport user.

Notices

Hardware constraints

None

Applicability

N/A

Backward compatibility

UnixWare-specific TPI Message Formats

Forward compatibility

N/A