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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, 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-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 address.

     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 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 SIOCADDMULTI ioctl(2) system call.

     NGM_ETHER_DEL_MULTI (delmulti)
             Leave Ethernet multicast group.  This control message 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 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_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, 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.