A node that creates a device entry in /dev (yay devfs)

so that /dev/mumble can be the entrypoint to some networking graph,
e.g. a tunnel or a remote tape drive or whatever...

Not fully tested (by me) yet.

Submitted by:	Mark Santcroos <marks@ripe.net>
MFC after:	3 weeks

1 files changed, 109 insertions, 0 deletions

diff --git a/share/man/man4/ng_device.4 b/share/man/man4/ng_device.4
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+.\" Copyright (c) 2002 Mark Santcroos <marks@ripe.net>
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. The name of the author may not be used to endorse or promote products
+.\"    derived from this software without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd June 15, 2002
+.Dt NG_DEVICE 4
+.Os
+.Sh NAME
+.Nm ng_device
+.Nd device netgraph node type
+.Sh SYNOPSIS
+.In netgraph/ng_device.h
+.Sh DESCRIPTION
+A
+.Nm device
+node is both a netgraph node and a system device interface.  When an
+.Nm device
+node is created, a new device entry appears which is accessible via the
+regular file operators such as
+.Xr open 2 ,
+.Xr close 2 ,
+.Xr read 2 ,
+.Xr write 2 , etc.
+.Pp
+The first node is created as /dev/ngd0, all subsequent nodes /dev/ngd1, 
+/dev/ngd2, etc. The only way a
+.Nm device 
+node can be created is by a connection to the main
+.Nm device
+node by another type of
+.Xr netgraph 4
+node.
+.Pp
+When a node is shut down, the corresponding device is removed
+and the device name becomes available for reuse by future
+.Nm device
+nodes.
+.Pp
+A
+.Nm device
+node has a single hook to which it connects to the requesting
+.Xr netgraph 4
+node. All data coming in over the hook will be presented to the device
+for
+.Xr read 2 .
+All data coming in from the device entry by
+.Xr write 2
+will be forwarded to the hook.
+.Sh HOOKS
+The
+.Nm device
+node has no named hooks. There is one hook which is used for all
+interactions. This is the hook created by the calling node.
+.Sh CONTROL MESSAGES
+The
+.Nm device
+node supports no special control messages. All incoming messages from the
+hook will be returned to the sender.
+Additionally the node accepts
+.Xr ioctl 2 's from the device entry. These will be encapsulated into
+.Xr netgraph 4
+messages and send out to the hook.
+.Sh SHUTDOWN
+This node shuts down upon receipt of a
+.Dv NGM_SHUTDOWN
+control message.  The associated interface is removed and becomes available
+for use by future
+.Nm device
+nodes.
+.Pp
+Unlike most other node types, a
+.Nm iface
+node does
+.Em not
+go away when all hooks have been disconnected; rather, and explicit
+.Dv NGM_SHUTDOWN
+control message is required.
+.Sh SEE ALSO
+.Xr netgraph 4 ,
+.Xr ngctl 8
+.Sh HISTORY
+The
+.Nm device
+node type was first implemented in
+.Fx 5.0 .
+.Sh AUTHORS
+.An Mark Santcroos Aq marks@ripe.net