tirdwr(7)         UNIX System V(Networking Support Utilities)         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 I_PUSH 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 I_POP 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 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:




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tirdwr(7)         UNIX System V(Networking Support Utilities)         tirdwr(7)


                -  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.

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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