connld - line discipline for unique stream connections
int ioctl(fd, I_PUSH, "connld");
connld is a STREAMS-based module that provides unique connections 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 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
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.
connld is being pushed onto a pipe end whose other
end is no longer there.
An internal pipe could not be created.
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.