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

NAME

t_rcvudata - receive a data unit

SYNOPSIS

#include <xti.h>


int t_rcvudata(int fd, struct t_unitdata *unitdata, int *flags);

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 is used in connectionless-mode to receive a data unit
from another transport user. The argument fd identifies the local
transport endpoint through which data will be received, unitdata
holds information associated with the received data unit, and flags
is set on return to indicate that the complete data unit was not
received. The argument unitdata points to a t_unitdata structure
containing the following members:

struct netbuf addr;
struct netbuf opt;
struct netbuf udata;


The maxlen field of addr, opt and udata must be set before calling
this function to indicate the maximum size of the buffer for each. If
the maxlen field of addr or opt is set to zero, no information is
returned in the buf field of this parameter.


On return from this call, addr specifies the protocol address of the
sending user, opt identifies options that were associated with this
data unit, and udata specifies the user data that was received.


By default, t_rcvudata() operates in synchronous mode and will wait
for a data unit to arrive if none is currently available. However, if
O_NONBLOCK is set by means of t_open(3NSL) or fcntl(2), t_rcvudata()
will execute in asynchronous mode and will fail if no data units are
available.


If the buffer defined in the udata field of unitdata is not large
enough to hold the current data unit, the buffer will be filled and
T_MORE will be set in flags on return to indicate that another
t_rcvudata() should be called to retrieve the rest of the data unit.
Subsequent calls to t_rcvudata() will return zero for the length of
the address and options until the full data unit has been received.


If the call is interrupted, t_rcvudata() will return EINTR and no
datagrams will have been removed from the endpoint.

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

T_IDLE.

ERRORS

On failure, t_errno is set to one of the following:

TBADF
The specified file descriptor does not refer to a
transport endpoint.


TBUFOVFLW
The number of bytes allocated for the incoming
protocol address or options (maxlen) is greater than
0 but not sufficient to store the information. The
unit data information to be returned in unitdata will
be discarded.


TLOOK
An asynchronous event has occurred on this transport
endpoint and requires immediate attention.


TNODATA
O_NONBLOCK was set, but no data units are currently
available from the transport provider.


TNOTSUPPORT
This function is not supported by the underlying
transport provider.


TOUTSTATE
The communications endpoint referenced by fd is not
in one of the states in which a call to this function
is valid.


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 values that can be set by the XTI interface and cannot be
set by the TLI interface are:
TPROTO
TOUTSTATE


A t_errno value that this routine can return under different
circumstances than its XTI counterpart is TBUFOVFLW. It can be
returned even when the maxlen field of the corresponding buffer has
been set to zero.

Option Buffers

The format of the options in an opt buffer is dictated by the
transport provider. Unlike the XTI interface, the TLI interface does
not fix the buffer format.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT Level | Safe |
+---------------+-----------------+

SEE ALSO

fcntl(2), t_alloc(3NSL), t_open(3NSL), t_rcvuderr(3NSL),
t_sndudata(3NSL), attributes(7)

October 22, 2014 T_RCVUDATA(3NSL)