CONNLD(4M) STREAMS Modules CONNLD(4M)

NAME

connld - line discipline for unique stream connections

SYNOPSIS

int ioctl(fd, I_PUSH, "connld");

DESCRIPTION

connld is a STREAMS-based module that provides unique connections
between server and client processes. It can only be pushed (see
streamio(4I)) 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(4I)) 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 creat(2).


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.

ERRORS

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

EINVAL
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.


EINVAL
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.


ENOMEM
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.


EAGAIN
Internal data structures could not be allocated.


ENFILE
A file table entry could not be allocated.

SEE ALSO

creat(2), open(2), fattach(3C), streamio(4I)


STREAMS Programming Guide

June 19, 2021 CONNLD(4M)