TIRDWR(4M) 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), Intro(3),
streamio(4I), timod(4M)


STREAMS Programming Guide


July 3, 1990 TIRDWR(4M)