connld(7M) manual page
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connld - line discipline for unique stream connections
/dev/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 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:
- 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.
creat(2)
, open(2)
, fattach(3C)
,
streamio(7I)
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