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Technical Reference: Communications, Volume 2
Supports the Transport Interface
functions of the Network Services library.
The tirdwr module is a
STREAMS module that provides an alternate interface to a transport provider
that supports the Transport Interface (TI) functions of the Network Services
library. This alternate interface allows a user to communicate with the
transport protocol provider by using the read
and write subroutines. The putmsg and getmsg system calls can also be
used. However, the putmsg and getmsg system calls
can only transfer data messages between user and stream.
The tirdwr module must
only be pushed (see the I_PUSH operation)
onto a stream terminated by a transport protocol provider that 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
will cause an error on the stream. Once the error is detected,
subsequent system calls on the stream will return an error with the
errno global variable set to EPROTO.
The following list describes
actions taken by the tirdwr module when it is pushed or popped or
when data passes through it:
| push
| Checks any existing data to ensure that only regular data messages are
present. It ignores any messages on the stream that relate to process
management. If any other messages are present, the I_PUSH
operation returns an error and sets the errno global variable to
EPROTO.
|
| write
| Takes the following actions on data that originated from a
write subroutine:
- Messages with no control
portions
- Passes the message on downstream.
- Zero length data messages
- Frees the message and does not pass downstream.
- Messages with control
portions
- Generates an error, fails any further system calls, and sets the
errno global variable to EPROTO.
|
| read
| Takes the following actions on data that originated from the transport
protocol provider:
- Messages with no control
portions
- Passes the message on upstream.
- Zero length data messages
- Frees the message and does not pass upstream.
Messages with control portions
will produce the following actions:
- Messages that represent expedited data generate an
error. All further calls associated with the stream fail with the
errno global variable set to EPROTO.
- Any data messages with control portions have the control
portions removed from the message prior to passing the message to the upstream
neighbor.
- Messages that represent an orderly release indication from
the transport provider generate a zero length data message, indicating the end
of file, which is sent to the reader of the stream. The orderly release
message itself is freed by the module.
- Messages that represent an abortive disconnect indication
from the transport provider cause all further write and
putmsg calls to fail with the errno global variable set
to ENXIO. All further read and getmsg
calls 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 generate an error, and all further system calls
associated with the stream fail with the errno global variable set
to EPROTO.
|
| pop
| Sends an orderly release request to the remote side of the transport
connection if an orderly release indication has been previously
received.
|
This module is part of STREAMS
Kernel Extensions.
The timod module.
The streamio operations.
The read subroutine, write subroutine.
The getmsg system call, putmsg system call.
Benefits and
Features of STREAMS, Building STREAMS, Pushable Modules, STREAMS Overview, Understanding STREAMS Drivers and Modules, Understanding STREAMS Messages, Using
STREAMS in AIX 5L Version 5.1 Communications Programming
Concepts.
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