TIRDWR(4M) STREAMS Modules TIRDWR(4M)

NAME

tirdwr - Transport Interface read/write interface STREAMS module

SYNOPSIS

int ioctl( fd, I_PUSH, "tirdwr");

DESCRIPTION

tirdwr is a STREAMS module that provides an alternate interface to a
transport provider which supports the Transport Interface ("TI")
functions of the Network Services library (see Section 3N). This
alternate interface allows a user to communicate with the transport
protocol provider using the read(2) and write(2) system calls. The
putmsg(2) and getmsg(2) system calls may also be used. However,
putmsg and getmsg can only transfer data messages between user and
stream; control portions are disallowed.


The tirdwr module must only be pushed (see I_PUSH in streamio(4I))
onto a stream terminated by a transport protocol provider which
supports the TI. After the tirdwr module has been pushed onto a
stream, none of the TI functions can be used. Subsequent calls to TI
functions cause an error on the stream. Once the error is detected,
subsequent system calls on the stream return an error with errno set
to EPROTO.


The following are the actions taken by the tirdwr module when pushed
on the stream, popped (see I_POP in streamio(4I)) off the stream,
or when data passes through it.

push
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 I_PUSH will return an error with errno set to
EPROTO.


write
The module takes the following actions on data that
originated from a write system call:

o All messages with the exception of messages that
contain control portions (see the putmsg and
getmsg system calls) are transparently passed
onto the module's downstream neighbor.

o Any zero length data messages are freed by the
module and they will not be passed onto the
module's downstream neighbor.

o Any messages with control portions generate an
error, and any further system calls associated
with the stream fails with errno set to EPROTO.


read
The module takes the following actions on data that
originated from the transport protocol provider.

All messages with the exception of those that contain
control portions (see the putmsg and getmsg system calls)
are transparently passed onto the module's upstream
neighbor. The action taken on messages with control portions
will be as follows:

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.

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.

o Messages that represent an abortive disconnect
indication from the transport provider cause all
further write and putmsg system calls to fail
with errno set to ENXIO. All further read and
getmsg system calls return zero length data
(indicating end of file) once all previous data
has been read.

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 errno set to EPROTO.
Any zero length data messages are freed by the module and
they are not passed onto the module's upstream neighbor.


pop
When the module is popped off the stream or the stream is
closed, the module takes the following action:

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.

SEE ALSO

getmsg(2), putmsg(2), read(2), write(2), Intro(3), streamio(4I),
timod(4M)


STREAMS Programming Guide

February 21, 2023 TIRDWR(4M)