connld - line discipline for unique stream connections
connld is a STREAMS-based module that provides unique connections between
server and client processes. It can only be pushed (see streamio(7))
onto one end of a STREAMS-based pipe that may subsequently be attached to
a name in the filesystem name space. After the pipe end is attached, a
new pipe is created internally when an originating process attempts to
open(2) or creat(2) the filesystem 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(7)) 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
can not 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) system calls will fail and return -1 to the
When the connld module is pushed onto a pipe, messages going back and
forth through the pipe are ignored by connld.
On success, an open of connld returns 0. On failure, errno is set to the
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
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.
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