tirdwr(7xti)
tirdwr --
Transport Interface read/write interface STREAMS module
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.
The tirdwr module must only be pushed [see I_PUSH in
streamio(7)]
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 Transport Interface functions can be used.
Subsequent calls to TI functions will cause an error on the stream.
Once the error is detected, subsequent system calls on the stream will 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(7)
off the stream, or when data passes through it.
push-
When the module is pushed onto a stream, it will check any existing
data destined for the user to ensure that only regular data messages
are present. It will ignore 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 will take the following actions on
data that originated from a write system call:
-
All messages with the exception of messages that contain
control portions (see the putmsg and getmsg
system calls) will be transparently passed onto the module's
downstream neighbor.
-
Any zero length data messages will be freed by the module and they
will not be passed onto the module's downstream neighbor.
-
Any messages with control portions will generate an error,
and any further system calls associated with the stream will fail with
errno set to EPROTO.
read-
The module will take 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)
will be transparently passed onto the module's upstream neighbor.
-
The action taken on messages with control portions will be as follows:
-
Messages that represent expedited data will generate an error.
All further system calls associated with the stream will fail with
errno set to EPROTO.
-
Any data messages with control portions will have the control portions
removed from the message prior to passing the message on to the
upstream neighbor.
-
Messages that represent an orderly release indication from the transport
provider will 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 will be freed by the module.
-
Messages that represent an abortive disconnect indication from the transport
provider will cause all further write and
putmsg system calls to fail with errno
set to ENXIO.
All further read and getmsg system
calls will return zero length data (indicating end of file)
once all previous data has been read.
-
With the exception of the above rules, all other messages with control
portions will generate an error and all further system calls
associated with the stream
will fail with errno set to EPROTO.
-
Any zero length data messages will be freed by the module and they will not
be passed onto the module's upstream neighbor.
pop-
When the module is popped off the stream or the stream is closed, the
module will take the following action:
-
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.
References
getmsg(2),
intro(2),
intro(3xti),
putmsg(2),
read(2),
streamio(7),
timod(7xti),
write(2)
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004