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 Layer Interface (TLI) functions of the Network
Services library (see Section NSL). This alternate
interface allows a user to communicate with the transport
protocol provider using the read(S) and write(S) system
calls. The putmsg(S) and getmsg(S) 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(STR)] onto a stream terminated by a transport
protocol provider which supports the TLI. After the tirdwr
module has been pushed onto a stream, none of the Transport
Layer Interface functions can be used. Subsequent calls to
TLI 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(STR)] 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 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(STR), timod(STR).
intro(S), getmsg(S), putmsg(S), read(S), write(S) in the
UNIX Reference.
intro(NSL) in Appendix D of the Network Programmer's Guide.
STREAMS Primer.
STREAMS Programmer's Guide.
(printed 6/18/89)