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T_GETINFO(3NSL) Networking Services Library Functions T_GETINFO(3NSL)

NAME

t_getinfo - get protocol-specific service information

SYNOPSIS

#include <xti.h>

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

DESCRIPTION

This routine is part of the XTI interfaces which evolved from the TLI
interfaces. XTI represents the future evolution of these interfaces.
However, TLI interfaces are supported for compatibility. When using a
TLI routine that has the same name as an XTI routine, the tiuser.h
header file must be used. Refer to the TLI COMPATIBILITY section
for a description of differences between the two interfaces.

This function returns the current characteristics of the underlying
transport protocol and/or transport connection associated with file
descriptor fd. The info pointer is used to return the same
information returned by t_open(3NSL), although not necessarily
precisely the same values. This function enables a transport user to
access this information during any phase of communication.

This argument points to a t_info structure which contains the
following members:

t_scalar_t addr; /*max size in octets of the transport protocol address*/
t_scalar_t options; /*max number of bytes of protocol-specific options */
t_scalar_t tsdu; /*max size in octets of a transport service data unit */
t_scalar_t etsdu; /*max size in octets of an expedited transport service*/
/*data unit (ETSDU) */
t_scalar_t connect; /*max number of octets allowed on connection */
/*establishment functions */
t_scalar_t discon; /*max number of octets of data allowed on t_snddis() */
/*and t_rcvdis() functions */
t_scalar_t servtype; /*service type supported by the transport provider */
t_scalar_t flags; /*other info about the transport provider */

The values of the fields have the following meanings:

addr
A value greater than zero indicates the maximum size of a
transport protocol address and a value of T_INVALID (-2)
specifies that the transport provider does not provide
user access to transport protocol addresses.

options
A value greater than zero indicates the maximum number of
bytes of protocol-specific options supported by the
provider, and a value of T_INVALID (-2) specifies that
the transport provider does not support user-settable
options.

tsdu
A value greater than zero specifies the maximum size in
octets of a transport service data unit (TSDU); a value
of T_NULL (zero) specifies that the transport provider
does not support the concept of TSDU, although it does
support the sending of a datastream with no logical
boundaries preserved across a connection; a value of
T_INFINITE (-1) specifies that there is no limit on the
size in octets of a TSDU; and a value of T_INVALID (-2)
specifies that the transfer of normal data is not
supported by the transport provider.

etsdu
A value greater than zero specifies the maximum size in
octets of an expedited transport service data unit
(ETSDU); a value of T_NULL (zero) specifies that the
transport provider does not support the concept of ETSDU,
although it does support the sending of an expedited data
stream with no logical boundaries preserved across a
connection; a value of T_INFINITE (-1) specifies that
there is no limit on the size (in octets) of an ETSDU;
and a value of T_INVALID (-2) specifies that the transfer
of expedited data is not supported by the transport
provider. Note that the semantics of expedited data may
be quite different for different transport providers.

connect
A value greater than zero specifies the maximum number of
octets that may be associated with connection
establishment functions and a value of T_INVALID (-2)
specifies that the transport provider does not allow
data to be sent with connection establishment functions.

discon
If the T_ORDRELDATA bit in flags is clear, a value
greater than zero specifies the maximum number of octets
that may be associated with the t_snddis(3NSL) and
t_rcvdis(3NSL) functions, and a value of T_INVALID (-2)
specifies that the transport provider does not allow
data to be sent with the abortive release functions. If
the T_ORDRELDATA bit is set in flags, a value greater
than zero specifies the maximum number of octets that may
be associated with the t_sndreldata(), t_rcvreldata(),
t_snddis(3NSL) and t_rcvdis(3NSL) functions.

servtype
This field specifies the service type supported by the
transport provider, as described below.

flags
This is a bit field used to specify other information
about the communications provider. If the T_ORDRELDATA
bit is set, the communications provider supports sending
user data with an orderly release. If the T_SENDZERO bit
is set in flags, this indicates that the underlying
transport provider supports the sending of zero-length
TSDUs.

If a transport user is concerned with protocol independence, the
above sizes may be accessed to determine how large the buffers must
be to hold each piece of information. Alternatively, the
t_alloc(3NSL) function 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 may change as a result of
protocol option negotiation during connection establishment (the
t_optmgmt(3NSL) call has no effect on the values returned by
t_getinfo()). These values will only change from the values presented
to t_open(3NSL) after the endpoint enters the T_DATAXFER state.

The servtype field of info specifies 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, t_open(3NSL) will
return T_INVALID (-1) for etsdu, connect and discon.

RETURN VALUES

Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and t_errno is set to indicate an error.

VALID STATES

ALL - apart from T_UNINIT.

ERRORS

On failure, t_errno is set to one of the following:

TBADF
The specified file descriptor does not refer to a
transport endpoint.

TPROTO
This error indicates that a communication problem has been
detected between XTI and the transport provider for which
there is no other suitable XTI error (t_errno).

TSYSERR
A system error has occurred during execution of this
function.

TLI COMPATIBILITY

The XTI and TLI interface definitions have common names but use
different header files. This, and other semantic differences between
the two interfaces are described in the subsections below.

Interface Header

The XTI interfaces use the header file, xti.h. TLI interfaces should
not use this header. They should use the header:

#include <tiuser.h>

Error Description Values

The t_errno value TPROTO can be set by the XTI interface but not by
the TLI interface.

The t_info Structure
For TLI, the t_info structure referenced by info lacks the following
structure member:

t_scalar_t flags; /* other info about the transport provider */

This member was added to struct t_info in the XTI interfaces.

When a value of -1 is observed as the return value in various t_info
structure members, it signifies that the transport provider can
handle an infinite length buffer for a corresponding attribute, such
as address data, option data, TSDU (octet size), ETSDU (octet size),
connection data, and disconnection data. The corresponding structure
members are addr, options, tsdu, estdu, connect, and discon,
respectively.

ATTRIBUTES