T_OPEN(3NSL)T_OPEN(3NSL)NAMEt_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 initial‐
ization 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 return‐
ing 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 con‐
structed from O_RDWR optionally bitwise inclusive-OR'ed with O_NON‐
BLOCK. These flags are defined by the header <fcntl.h>. The file
descriptor returned by t_open() will be used by all subsequent func‐
tions 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 struc‐
ture. 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 sup‐
ported 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_snd‐
dis(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) func‐
tion 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 ser‐
vice but does not support the optional orderly release
facility.
T_COTS_ORD
The transport provider supports a connection-mode ser‐
vice 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. Other‐
wise, 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 func‐
tion.
TLI COMPATIBILITY
The XTI and TLI interface definitions have common names but use differ‐
ent 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), con‐
nection data, and disconnection data. The corresponding structure mem‐
bers are addr, options, tsdu, estdu, connect, and discon, respectively.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT Level │ Safe │
└───────────────┴─────────────────┘
SEE ALSOopen(2), attributes(5)
May 7, 1998 T_OPEN(3NSL)
