freebsd/share/man/man4/ng_ether.4

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.\" Author: Archie Cobbs <archie@FreeBSD.org>
.\"
.\" $FreeBSD$
.\"
.Dd June 23, 2011
.Dt NG_ETHER 4
.Os
.Sh NAME
.Nm ng_ether
.Nd Ethernet netgraph node type
.Sh SYNOPSIS
.In netgraph/ng_ether.h
.Sh DESCRIPTION
The
.Nm ether
netgraph node type allows Ethernet interfaces to interact with
the
.Xr netgraph 4
networking subsystem.
Once the
.Nm
module is loaded into the kernel, a node is automatically created
for each Ethernet interface in the system.
Each node will attempt to name itself with the same name
as the associated interface.
.Pp
Three hooks are supported:
.Va lower , upper ,
and
.Va orphans .
The hook name
.Va divert
may be used as an alias for
.Va lower ,
and is provided for backward compatibility.
In reality, the two names represent the same hook.
.Pp
The
.Va lower
hook is a connection to the raw Ethernet device.
When connected, all incoming packets are forwarded to this hook,
instead of being passed to the kernel for upper layer processing.
Writing to this hook results in a raw Ethernet frame being transmitted
by the device.
Normal outgoing packets are not affected by
.Va lower
being connected.
.Pp
The
.Va upper
hook is a connection to the upper protocol layers.
When connected, all outgoing packets are forwarded to this hook,
instead of being transmitted by the device.
Writing to this hook results in a raw Ethernet frame being received by
the kernel just as if it had come in over the wire.
Normal incoming packets are not affected by
.Va upper
being connected.
.Pp
The
.Va orphans
hook is equivalent to
.Va lower ,
except that only unrecognized packets (that would otherwise be discarded)
are written to the hook, while other normal incoming traffic is unaffected.
Unrecognized packets written to
.Va upper
will be forwarded back out to
.Va orphans
if connected.
.Pp
In all cases, frames are raw Ethernet frames with the standard
14 byte Ethernet header (but no checksum).
.Pp
When no hooks are connected,
.Va upper
and
.Va lower
are in effect connected together,
so that packets flow normally upwards and downwards.
.Sh HOOKS
This node type supports the following hooks:
.Bl -tag -width ".Va orphans"
.It Va lower
Connection to the lower device link layer.
.It Va upper
Connection to the upper protocol layers.
.It Va orphans
Like
.Va lower ,
but only receives unrecognized packets.
.El
.Sh CONTROL MESSAGES
This node type supports the generic control messages, plus the following:
.Bl -tag -width foo
.It Dv NGM_ETHER_GET_IFNAME Pq Ic getifname
Returns the name of the associated interface as a
.Dv NUL Ns -terminated
.Tn ASCII
string.
Normally this is the same as the name of the node.
.It Dv NGM_ETHER_GET_IFINDEX Pq Ic getifindex
Returns the global index of the associated interface as a 32 bit integer.
.It Dv NGM_ETHER_GET_ENADDR Pq Ic getenaddr
Returns the device's unique six byte Ethernet address.
.It Dv NGM_ETHER_SET_ENADDR Pq Ic setenaddr
Sets the device's unique six byte Ethernet address.
This control message is equivalent to using the
.Dv SIOCSIFLLADDR
.Xr ioctl 2
system call.
.It Dv NGM_ETHER_SET_PROMISC Pq Ic setpromisc
Enable or disable promiscuous mode.
This message includes a single 32 bit integer flag that enables or
disables promiscuous mode on the interface.
Any non-zero value enables promiscuous mode.
.It Dv NGM_ETHER_GET_PROMISC Pq Ic getpromisc
Get the current value of the node's promiscuous flag.
The returned value is always either one or zero.
Note that this flag reflects the node's own promiscuous setting
and does not necessarily reflect the promiscuous state of the actual
interface, which can be affected by other means (e.g.,
.Xr bpf 4 ) .
.It Dv NGM_ETHER_SET_AUTOSRC Pq Ic setautosrc
Sets the automatic source address override flag.
This message includes a single 32 bit integer flag that causes
all outgoing packets to have their source Ethernet
address field overwritten with the device's unique Ethernet address.
If this flag is set to zero, the source address in outgoing packets
is not modified.
The default setting for this flag is disabled.
.It Dv NGM_ETHER_GET_AUTOSRC Pq Ic getautosrc
Get the current value of the node's source address override flag.
The returned value is always either one or zero.
.It Dv NGM_ETHER_ADD_MULTI Pq Ic addmulti
Join Ethernet multicast group.
This control message is equivalent to using the
.Dv SIOCADDMULTI
.Xr ioctl 2
system call.
.It Dv NGM_ETHER_DEL_MULTI Pq Ic delmulti
Leave Ethernet multicast group.
This control message is equivalent to using the
.Dv SIOCDELMULTI
.Xr ioctl 2
system call.
.It Dv NGM_ETHER_DETACH Pq Ic detach
Detach from underlying Ethernet interface and shut down node.
.El
.Sh SHUTDOWN
Upon receipt of the
.Dv NGM_SHUTDOWN
control message, all hooks are disconnected, promiscuous mode is disabled,
but the node is not removed.
Node can be shut down only using
.Dv NGM_ETHER_DETACH
control message.
If the interface itself is detached (e.g., because of PC Card removal), the
node disappears as well.
.Sh EXAMPLES
This command dumps all unrecognized packets received by the
.Dq Li fxp0
interface to standard output decoded in hex and
.Tn ASCII :
.Pp
.Dl "nghook -a fxp0: orphans"
.Pp
This command sends the contents of
.Pa sample.pkt
out the interface
.Dq Li fxp0 :
.Pp
.Dl "cat sample.pkt | nghook fxp0: orphans"
.Pp
These commands insert an
.Xr ng_tee 4
node between the
.Va lower
and
.Va upper
protocol layers, which can be used for
tracing packet flow, statistics, etc.:
.Bd -literal -offset indent
ngctl mkpeer fxp0: tee lower right
ngctl connect fxp0: lower upper left
.Ed
.Sh SEE ALSO
.Xr arp 4 ,
.Xr netgraph 4 ,
.Xr netintro 4 ,
.Xr ifconfig 8 ,
.Xr ngctl 8 ,
.Xr nghook 8
.Sh AUTHORS
.An Julian Elischer Aq Mt julian@FreeBSD.org
.An Archie Cobbs Aq Mt archie@FreeBSD.org
.Sh BUGS
The automatic KLD module loading mechanism that works for most
other Netgraph node types does not work for the
.Nm ether
node type,
because
.Nm ether
nodes are not created on demand; instead, they are created when
Ethernet interfaces are attached or when the KLD is first loaded.
Therefore, if the KLD is not statically compiled into the kernel,
it is necessary to load the KLD manually in order to bring the
.Nm ether
nodes into existence.