Tribblix: manual page: t

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

NAME

t_open - establish a transport endpoint

SYNOPSIS

#include <xti.h>
#include <fcntl.h>

int t_open(const char *name, int oflag, 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.

The t_open() function must be called as the first step in the
initialization of a transport endpoint. This function establishes a
transport endpoint by supplying a transport provider identifier that
indicates a particular transport provider, that is, transport
protocol, and returning a file descriptor that identifies that
endpoint.

The argument name points to a transport provider identifier and oflag
identifies any open flags, as in open(2). The argument oflag is
constructed from O_RDWR optionally bitwise inclusive-OR'ed with
O_NONBLOCK. These flags are defined by the header <fcntl.h>. The file
descriptor returned by t_open() will be used by all subsequent
functions to identify the particular local transport endpoint.

This function also returns various default characteristics of the
underlying transport protocol by setting fields in the t_info
structure. This argument points to a t_info which contains the
following members:

t_scalar_t addr; /* max size of the transport protocol address */
t_scalar_t options; /* max number of bytes of */
/* protocol-specific options */
t_scalar_t tsdu; /* max size of a transport service data */
/* unit (TSDU) */
t_scalar_t etsdu; /* max size of an expedited transport */
/* service data unit (ETSDU) */
t_scalar_t connect; /* max amount of data allowed on */
/* connection establishment functions */
t_scalar_t discon; /* max amount 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 (T_NULL) indicates the maximum
size of a transport protocol address and a value of -2
(T_INVALID) specifies that the transport provider does
not provide user access to transport protocol addresses.

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

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

etsdu
A value greater than zero (T_NULL) specifies the maximum
size of an expedited transport service data unit (ETSDU);
a value of zero (T_NULL) 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 -1 (T_INFINITE) specifies that there is no
limit on the size of an ETSDU; and a value of -2
(T_INVALID) 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 (T_NULL) specifies the maximum
amount of data that may be associated with connection
establishment functions, and a value of -2 (T_INVALID)
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 (T_NULL) specifies the maximum amount
of data that may be associated with the t_snddis(3NSL)
and t_rcvdis(3NSL) functions, and a value of -2
(T_INVALID) 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 (T_NULL) 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 user
data to be sent with an orderly release. If the
T_SENDZERO bit is set in flags, this indicates 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 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() will return
-2 (T_INVALID) for etsdu, connect and discon.

A single transport endpoint may support only one of the above
services at one time.

If info is set to a null pointer by the transport user, no protocol
information is returned by t_open().

RETURN VALUES

A valid file descriptor is returned upon successful completion.
Otherwise, a value of -1 is returned and t_errno is set to indicate
an error.

VALID STATES

T_UNINIT.

ERRORS

On failure, t_errno is set to the following:

TBADFLAG
An invalid flag is specified.

TBADNAME
Invalid transport provider name.

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 xti.h. TLI interfaces should not use this
header. They should use the header:
#include <tiuser.h>

Error Description Values

The t_errno values TPROTO and TBADNAME can be set by the XTI
interface but cannot be set by the TLI interface.

Notes

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