tirdwr(M)

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(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(HW)] 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(HW) 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(S), intro(S), intro(NET), putmsg(S), read(S), streamio(HW), timod(M), write(S)