NAME

ng_device —

device netgraph node type

SYNOPSIS

#include <netgraph/ng_device.h>

DESCRIPTION

A device node is both a netgraph node and a system device interface. When a device node is created, a new device entry appears which is accessible via the regular file operators such as open(2), close(2), read(2), write(2), etc.

The first node is created as /dev/ngd0, subsequent nodes are /dev/ngd1, /dev/ngd2, etc.

HOOKS

A device node has a single hook with an arbitrary name. All data coming in over the hook will be presented to the device for read(2). All data coming in from the device entry by write(2) will be forwarded to the hook.

CONTROL MESSAGES

The device node supports the generic control messages, plus the following:

NGM_DEVICE_GET_DEVNAME: Returns the device name corresponding to the node.
NGM_DEVICE_ETHERALIGN: Apply the system ETHER_ALIGN offset to mbufs sent out the node's hook, if running on an architecture that requires strict alignment. Use this option when the data being injected via the device node ultimately ends up being fed into the protocol stack as ethernet packets (e.g., via an ng_eiface(4) node).

SHUTDOWN

This node shuts down upon receipt of a NGM_SHUTDOWN control message, or upon hook disconnection. The associated device entry is removed and becomes available for use by future device nodes.

HISTORY

The device node type was first implemented in FreeBSD 5.0.

AUTHORS

Mark Santcroos <marks@ripe.net>
Gleb Smirnoff <glebius@FreeBSD.org>