Интерактивная система просмотра системных руководств (man-ов)
ng_ether (4)
>> ng_ether (4) ( FreeBSD man: Специальные файлы /dev/* )
BSD mandoc
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
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,
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
lower
being connected.
The
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
upper
being 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.
Unrecognized packets written to
upper
will be forwarded back out to
orphans
if connected.
In all cases, frames are raw Ethernet frames with the standard
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 downwards.
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 -terminatedASCII
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 address.
NGM_ETHER_SET_ENADDR (setenaddr
)
Sets the device's unique six byte Ethernet address.
This control message is equivalent to using the
SIOCSIFLLADDRioctl(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 disabled.
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
SIOCADDMULTIioctl(2)
system call.
NGM_ETHER_DEL_MULTI (delmulti
)
Leave Ethernet multicast group.
This control message is equivalent to using the
SIOCDELMULTIioctl(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 interface itself is detached (e.g., because of PC Card removal), the
node disappears 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 interface
``fxp0
''
"cat sample.pkt | nghook fxp0: orphans"
These commands insert an
ng_tee4
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
The automatic KLD module loading mechanism that works for most
other Netgraph node types does not work for the
ether
node type,
because
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.
