tirdwr - Transport Interface read/write interface STREAMS
module
int ioctl( fd, I_PUSH, "tirdwr");
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.