illumos: manual page: t

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