tirdwr(7) DG/UX 5.4.2 tirdwr(7)
NAME
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 IPUSH 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 IPOP 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 IPUSH 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
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tirdwr(7) DG/UX 5.4.2 tirdwr(7)
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.
SEE ALSO
streamio(7), timod(7).
intro(2), getmsg(2), putmsg(2), read(2), write(2), intro(3).
Programmer's Guide: STREAMS.
Programmer's Guide: Networking Interfaces.
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