T_GETINFO(3NSL)T_GETINFO(3NSL)NAMEt_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 informa‐
tion 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 pre‐
served 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 con‐
nection 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 maxi‐
mum 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) 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 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 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(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 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 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), 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 ALSOt_alloc(3NSL), t_open(3NSL), t_optmgmt(3NSL), t_rcvdis(3NSL), t_snd‐
dis(3NSL), attributes(5)
May 7, 1998 T_GETINFO(3NSL)
