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(3),
although not necessarily precisely the same values. This function
enables a transport user to access this information during any
phase of communication.
Parameters
Before call
After call
fd
x
/
info->
addr
/
info->
options
/
info->
tsdu
/
info->
etsdu
/
info->
connect
/
info->
discon
/
info->
servtype
/
info->
flags
/
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 (see and ).
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(3) and t_rcvdis(3) 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_snddis(3) and t_rcvdis(3) 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. See for a discussion of the separate issue of
zero-length fragments within a TSDU.
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(3)
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(3) call has no effect on the values
returned by t_getinfo()). These values will only change from
the values presented to t_open(3) 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(3) will return T_INVALID (-2) for
etsdu, connect and discon.
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.