ng_ether(4)

NAME

ng_ether - Ethernet netgraph node type

SYNOPSIS

#include <netgraph/ng_ether.h>

DESCRIPTION

The ether netgraph node type allows Ethernet interfaces to

interact with
the netgraph(4) networking subsystem. Once the ng_ether

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.

Three hooks are supported: lower, upper, and orphans. The

hook name
divert may be used as an alias for lower, and is provided

for backward
compatibility. In reality, the two names represent the same

hook.

The lower hook is a connection to the raw Ethernet device.

When connected, all incoming packets are forwarded to this hook, in

stead of being
passed to the kernel for upper layer processing. Writing to

this hook
results in a raw Ethernet frame being transmitted by the de

vice. Normal
outgoing packets are not affected by lower being connected.

The upper hook is a connection to the upper protocol layers.

When connected, all outgoing packets are forwarded to this hook, in

stead 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 upper be

ing connected.

The orphans hook is equivalent to lower, except that only

unrecognized
packets (that would otherwise be discarded) are written to

the hook,
while other normal incoming traffic is unaffected. Unrecog

nized packets
written to upper will be forwarded back out to orphans if

connected.

In all cases, frames are raw Ethernet frames with the stan

dard 14 byte
Ethernet header (but no checksum).

When no hooks are connected, upper and lower are in effect

connected
together, so that packets flow normally upwards and down

wards.

HOOKS

This node type supports the following hooks:

lower Connection to the lower device link layer.

upper Connection to the upper protocol layers.

orphans Like lower, but only receives unrecognized

packets.

CONTROL MESSAGES

This node type supports the generic control messages, plus

the following:

NGM_ETHER_GET_IFNAME (getifname)

Returns the name of the associated interface as a

NUL-terminated
ASCII string. Normally this is the same as the name

of the node.

NGM_ETHER_GET_IFINDEX (getifindex)

Returns the global index of the associated interface

as a 32 bit
integer.

NGM_ETHER_GET_ENADDR (getenaddr)

Returns the device's unique six byte Ethernet ad

dress.

NGM_ETHER_SET_ENADDR (setenaddr)

Sets the device's unique six byte Ethernet address.

This control
message is equivalent to using the SIOCSIFLLADDR

ioctl(2) system
call.

NGM_ETHER_SET_PROMISC (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.

NGM_ETHER_GET_PROMISC (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., bpf(4)).

NGM_ETHER_SET_AUTOSRC (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 enabled.

NGM_ETHER_GET_AUTOSRC (getautosrc)

Get the current value of the node's source address

override flag.
The returned value is always either one or zero.

NGM_ETHER_ADD_MULTI (addmulti)

Join Ethernet multicast group. This control message

is equivalent to using the SIOCADDMULTI ioctl(2) system call.

NGM_ETHER_DEL_MULTI (delmulti)

Leave Ethernet multicast group. This control mes

sage is equivalent to using the SIOCDELMULTI ioctl(2) system call.

NGM_ETHER_DETACH (detach)

Detach from underlying Ethernet interface and shut

down node.

SHUTDOWN

Upon receipt of the NGM_SHUTDOWN control message, all hooks

are disconnected, promiscuous mode is disabled, and the source address

override
flag is re-enabled, but the node is not removed. Node can

be shut down
only using NGM_ETHER_DETACH control message. If the inter

face itself is
detached (e.g., because of PC Card removal), the node disap

pears as well.

EXAMPLES

This command dumps all unrecognized packets received by the

``fxp0''
interface to standard output decoded in hex and ASCII:

nghook -a fxp0: orphans

This command sends the contents of sample.pkt out the inter

face ``fxp0'':

cat sample.pkt | nghook fxp0: orphans

These commands insert an ng_tee(4) node between the lower

and upper protocol layers, which can be used for tracing packet flow,

statistics,
etc.:

ngctl mkpeer fxp0: tee lower right
ngctl connect fxp0: lower upper left

SEE ALSO

arp(4), netgraph(4), netintro(4), ifconfig(8), ngctl(8),

nghook(8)

AUTHORS

Julian Elischer <julian@FreeBSD.org>
Archie Cobbs <archie@FreeBSD.org>

BUGS

The automatic KLD module loading mechanism that works for

most other Netgraph node types does not work for the ether node type, be

cause 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 ether nodes into

existence.

BSD February 14, 2005

BSD