t_getinfo Subroutine for Transport Layer Interface

Communications Technical Reference, Volume 2

t_getinfo Subroutine for Transport Layer Interface

Purpose

Gets protocol-specific service information.

Library

Transport Layer Interface Library (libtli.a)

Syntax

#include <tiuser.h>

int t_getinfo(fd, info)
int fd;
struct t_info *info;

Description

The t_getinfo subroutine returns the current characteristics of the underlying transport protocol associated with fd file descriptor. The t_info structure is used to return the same information returned by the t_open subroutine. This function enables a transport user to access this information during any phase of communication.

Parameters

Specifies the file descriptor.

info

Points to a t_info structure that contains the following members:

long addr;
long options;
long tsdu;
long etsdu;
long connect;
long discon;
long servtype;

The values of the fields have the following meanings:

`addr`	A value greater than or equal to 0 indicates the maximum size of a transport protocol address; a value of -1 specifies that there is no limit on the address size; and a value of -2 specifies that the transport provider does not provide user access to transport protocol addresses.
`options`	A value greater than or equal to 0 indicates the maximum number of bytes of protocol-specific options supported by the provider; a value of -1 specifies that there is no limit on the option size; and a value of -2 specifies that the transport provider does not support user-settable options.
`tsdu`	A value greater than 0 specifies the maximum size of a transport service data unit (TSDU); a value of 0 specifies that the transport provider does not support the concept of TSDU, although it does support the sending of a data stream having no logical boundaries preserved across a connection; a value of -1 specifies that there is no limit on the size of a TSDU; and a value of -2 specifies that the transfer of normal data is not supported by the transport provider.
`etsdu`	A value greater than 0 specifies the maximum size of an expedited transport service data unit (ETSDU); a value of 0 specifies that the transport provider does not support the concept of ETSDU, although it does support the sending of an expedited data stream having no logical boundaries preserved across a connection; a value of -1 specifies that there is no limit on the size of an ETSDU; and a value of -2 specifies that the transfer of expedited data is not supported by the transport provider.
`connect`	A value greater than or equal to 0 specifies the maximum amount of data that may be associated with connection establishment functions; a value of -1 specifies that there is no limit on the amount of data sent during connection establishment; and a value of -2 specifies that the transport provider does not allow data to be sent with connection establishment functions.
`discon`	A value greater than or equal to 0 specifies the maximum amount of data that may be associated with the t_snddis and t_rcvdis subroutines; a value of -1 specifies that there is no limit on the amount of data sent with these abortive release functions; and a value of -2 specifies that the transport provider does not allow data to be sent with the abortive release functions.
`servtype`	This field specifies the service type supported by the transport provider.

If a transport user is concerned with protocol independence, the sizes may be accessed to determine how large the buffers must be to hold each piece of information. Alternatively, the t_alloc subroutine may be used to allocate these buffers. An error will result if a transport user exceeds the allowed data size on any function. The value of each field can change as a result of option negotiation; the t_getinfo subroutine enables a user to retrieve the current characteristics.

Return Values

On successful completion, the t_getinfo subroutine returns a value of 0. Otherwise, it returns a value of -1, and the t_errno variable is set to indicate the error.

The servtype field of the info parameter may specify one of the following values on return:

T_COTS	The transport provider supports a connection-mode service, but does not support the optional orderly release facility.
T_COTS_ORD	The transport provider supports a connection-mode service with the optional orderly release facility.
T_CLTS	The transport provider supports a connectionless-mode service. For this service type, the t_open subroutine returns -2 for the values in the `etsdu`, `connect`, and `discon` fields.

Error Codes

In unsuccessful, the t_errno variable is set to one of the following:

TBADF	The specified file descriptor does not refer to a transport end point.
TSYSERR	A system error has occurred during execution of this function.

Implementation Specifics

This subroutine is part of Base Operating System (BOS) Runtime.

Related Information

The t_alloc subroutine, t_open subroutine, t_rcvdis subroutine and t_snddis subroutine.

List of Streams Programming Reference and STREAMS Overview in AIX Version 4.3 Communications Programming Concepts.