'\" te
.\"  Copyright 1989 AT&T
.\" Copyright (C) 1999, Sun Microsystems, Inc. All Rights Reserved
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.TH tirdwr 7M "3 Jul 1990" "SunOS 5.11" "STREAMS Modules"
.SH NAME
tirdwr \- Transport Interface read/write interface STREAMS module
.SH SYNOPSIS
.LP
.nf
\fBint ioctl( \fR\fIfd, \fR\fBI_PUSH\fR\fI, \fR\fB"tirdwr");\fR
.fi

.SH DESCRIPTION
.sp
.LP
\fBtirdwr\fR is a STREAMS module  that provides an alternate interface to a
transport provider which supports the  Transport Interface ("\fBTI\fR")
functions of the Network Services library (see Section 3N). This alternate
interface allows a user to communicate with the transport protocol  provider
using the  \fBread\fR(2) and  \fBwrite\fR(2) system calls. The  \fBputmsg\fR(2)
and  \fBgetmsg\fR(2) system calls may also be used. However, \fBputmsg\fR and
\fBgetmsg\fR can only transfer data messages between  user and stream; control
portions are disallowed.
.sp
.LP
The \fBtirdwr\fR module must only be pushed (see \fBI_PUSH\fR in
\fBstreamio\fR(7I)) onto a stream terminated by a transport protocol provider
which supports the \fBTI\fR. After the \fBtirdwr\fR module has been pushed onto
a stream, none of the \fBTI\fR functions can be used. Subsequent calls to
\fBTI\fR functions cause an error on the stream. Once the error is detected,
subsequent system calls on the stream return an error with \fBerrno\fR set to
\fBEPROTO\fR.
.sp
.LP
The following are the actions taken by the \fBtirdwr\fR module when pushed on
the stream, popped (see \fBI_POP\fR in  \fBstreamio\fR(7I)) off  the stream, or
when data passes through it.
.sp
.ne 2
.mk
.na
\fB\fBpush\fR\fR
.ad
.RS 9n
.rt  
When the module is pushed onto a stream, it checks any existing data destined
for the user to ensure that only regular data messages are present. It ignores
any messages on the stream that relate to process management, such as messages
that generate signals to the user processes associated with the stream. If any
other messages are present, the \fBI_PUSH\fR will return an error with
\fBerrno\fR set to \fBEPROTO\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBwrite\fR\fR
.ad
.RS 9n
.rt  
The module takes the following actions on data that originated from a
\fBwrite\fR system call:
.RS +4
.TP
.ie t \(bu
.el o
All messages with the exception of messages that contain control portions (see
the \fBputmsg\fR and \fBgetmsg\fR system calls) are transparently passed onto
the module's downstream neighbor.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Any zero length data messages are freed by the module and they will not be
passed onto the module's downstream neighbor.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Any messages with control portions generate an error, and any further system
calls associated with the stream fails with \fBerrno\fR set to \fBEPROTO\fR.
.RE
.RE

.sp
.ne 2
.mk
.na
\fB\fBread\fR\fR
.ad
.RS 9n
.rt  
The module takes the following actions on data that originated from the
transport protocol provider.
.sp
All messages with the exception of those that contain control portions (see the
\fBputmsg\fR and \fBgetmsg\fR system calls) are transparently passed onto the
module's upstream neighbor. The action taken on messages with control portions
will be as follows:
.RS +4
.TP
.ie t \(bu
.el o
Any data messages with control portions have the control portions removed from
the message before to passing the message on to the upstream neighbor.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Messages that represent an orderly release indication from the transport
provider generate a zero length data message, indicating the end of file, which
will be sent to the reader of the stream. The orderly release message itself is
freed by the module.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Messages that represent an abortive disconnect indication from the transport
provider cause all further \fBwrite\fR and \fBputmsg\fR system calls to fail
with \fBerrno\fR set to \fBENXIO\fR. All further \fBread\fR and \fBgetmsg\fR
system calls return zero length data (indicating end of file) once all previous
data has been read.
.RE
.RS +4
.TP
.ie t \(bu
.el o
With the exception of the above rules, all other messages with control portions
generate an error and all further system calls associated with the stream will
fail with \fBerrno\fR set to \fBEPROTO\fR.
.RE
Any zero length data messages are freed by the module and they are not passed
onto the module's upstream neighbor.
.RE

.sp
.ne 2
.mk
.na
\fB\fBpop\fR\fR
.ad
.RS 9n
.rt  
When the module is popped off the stream or the stream is closed, the module
takes the following action:
.RS +4
.TP
.ie t \(bu
.el o
If an orderly release indication has been previously received, then an orderly
release request will be sent to the remote side of the transport connection.
.RE
.RE

.SH SEE ALSO
.sp
.LP
\fBIntro\fR(3), \fBgetmsg\fR(2), \fBputmsg\fR(2), \fBread\fR(2),
\fBwrite\fR(2), \fBIntro\fR(3), \fBstreamio\fR(7I), \fBtimod\fR(7M)
.sp
.LP
\fISTREAMS Programming Guide\fR