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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.