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Technical Reference: Communications, 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
fd |
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:
Value |
Description |
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:
Value |
Description |
TBADF |
The specified file descriptor does not refer to a transport end point. |
TSYSERR |
A system error has occurred during execution of this function. |
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 5L Version 5.2 Communications Programming Concepts.
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