connld - line discipline for unique stream connections




     connld is a STREAMS-based module that provides  unique  con-
     nections between server and client processes. It can only be
     pushed (see  streamio(7I)) onto one end of  a  STREAMS-based
     pipe that may subsequently be attached to a name in the file
     system name space with
      fattach(3C). After the pipe end is attached, a new pipe  is
     created  internally when an  originating process attempts to
     open(2) or  creat(2) the file system name. A file descriptor
     for  one  end  of  the  new  pipe is packaged into a message
     identical   to   that   for   the   ioctl    I_SENDFD   (see
     streamio(7I))  and  is  transmitted  along the stream to the
     server process on the  other end. The originating process is
     blocked until the server responds.

     The server responds to the  I_SENDFD  request  by  accepting
     the  file  descriptor  through  the  I_RECVFD ioctl message.
     When this happens, the file descriptor associated  with  the
     other  end of the new pipe is transmitted to the originating
     process as the file descriptor  returned   from  open(2)  or

     If the server does not respond to the  I_SENDFD request, the
     stream  that  the  connld  module  is pushed on becomes uni-
     directional because the server  will not be able to retrieve
     any  data  off  the  stream  until  the  I_RECVFD request is
     issued. If the  server  process  exits  before  issuing  the
     I_RECVFD  request,  the  open(2) or the  creat(2) invocation
     will fail and return -1 to the originating process.

     When the connld module is pushed onto  a  pipe,  it  ignores
     messages going back and forth  through the pipe.


     On success, an open of connld returns 0. On  failure,  errno
     is set to the following values:

           A stream onto which connld is being pushed  is  not  a
           pipe  or  the pipe does not have a write queue pointer
           pointing to a stream head read queue.

           The other end of the pipe onto which connld  is  being
           pushed is linked under a multiplexor.

     EPIPE connld is being pushed onto a pipe end whose other end
           is no longer there.

           An internal pipe could not be created.

     ENXIO An  M_HANGUP message is at the stream head of the pipe
           onto which connld is being pushed.

           Internal data structures could not be allocated.

           A file table entry could not be allocated.


     creat(2), open(2), fattach(3C), streamio(7I)

     STREAMS Programming Guide

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