.\" Copyright (c) 2002 Mark Santcroos <marks@ripe.net>
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.\" $FreeBSD$
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.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