ng_etf man page on FreeBSD

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NG_ETF(4)		 BSD Kernel Interfaces Manual		     NG_ETF(4)

NAME
     ng_etf — Ethertype filtering netgraph node type

SYNOPSIS
     #include <netgraph.h>
     #include <netgraph/ng_etf.h>

DESCRIPTION
     The etf node type multiplexes and filters data between hooks on the basis
     of the ethertype found in an Ethernet header, presumed to be in the first
     14 bytes of the data.  Incoming Ethernet frames are accepted on the
     downstream hook and if the ethertype matches a value which the node has
     been configured to filter, the packet is forwarded out the hook which was
     identified at the time that value was configured.	If it does not match a
     configured value, it is passed to the nomatch hook.  If the nomatch hook
     is not connected, the packet is dropped.

     Packets travelling in the other direction (towards the downstream hook)
     are also examined and filtered.  If a packet has an ethertype that
     matches one of the values configured into the node, it must have arrived
     in on the hook for which that value was configured, otherwise it will be
     discarded.	 Ethertypes of values other than those configured by the con‐
     trol messages must have arrived via the nomatch hook.

HOOKS
     This node type supports the following hooks:

     downstream	 Typically this hook would be connected to a ng_ether(4) node,
		 using the lower hook.

     nomatch	 Typically this hook would also be connected to an ng_ether(4)
		 type node using the upper hook.

     ⟨any legal name⟩
		 Any other hook name will be accepted and can be used as the
		 match target of an ethertype.	Typically this hook would be
		 attached to a protocol handling node that requires and gener‐
		 ates packets with a particular set of ethertypes.

CONTROL MESSAGES
     This node type supports the generic control messages, plus the following:

     NGM_ETF_GET_STATUS
	   This command returns a struct ng_etfstat containing node statistics
	   for packet counts.

     NGM_ETF_SET_FILTER
	   Sets the a new ethertype filter into the node and specifies the
	   hook to and from which packets of that type should use.  The hook
	   and ethertype are specified in a structure of type struct
	   ng_etffilter:

	       struct ng_etffilter {
		       char	  matchhook[NG_HOOKSIZ];     /* hook name */
		       u_int16_t  ethertype;		     /* catch these */
	       };

EXAMPLES
     Using ngctl(8) it is possible to set a filter in place from the command
     line as follows:

	 #!/bin/sh
	 ETHER_IF=fxp0
	 MATCH1=0x834
	 MATCH2=0x835
	 cat <<DONE >/tmp/xwert
	 # Make a new ethertype filter and attach to the Ethernet lower hook.
	 # first remove left over bits from last time.
	 shutdown ${ETHER_IF}:lower
	 mkpeer ${ETHER_IF}: etf lower downstream
	 # Give it a name to easily refer to it.
	 name ${ETHER_IF}:lower etf
	 # Connect the nomatch hook to the upper part of the same interface.
	 # All unmatched packets will act as if the filter is not present.
	 connect ${ETHER_IF}: etf: upper nomatch
	 DONE
	 ngctl -f /tmp/xwert

	 # something to set a hook to catch packets and show them.
	 echo "Unrecognised packets:"
	 nghook -a etf: newproto &
	 # Filter two random ethertypes to that hook.
	 ngctl 'msg etf: setfilter { matchhook="newproto" ethertype=${MATCH1} }
	 ngctl 'msg etf: setfilter { matchhook="newproto" ethertype=${MATCH2} }
	 DONE

SHUTDOWN
     This node shuts down upon receipt of a NGM_SHUTDOWN control message, or
     when all hooks have been disconnected.

SEE ALSO
     netgraph(4), ng_ether(4), ngctl(8), nghook(8)

HISTORY
     The ng_etf node type was implemented in FreeBSD 5.0.

AUTHORS
     Julian Elischer ⟨julian@FreeBSD.org⟩

BSD				 May 16, 2006				   BSD
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