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     ng_iface — interface netgraph node type


     #include <netgraph/ng_iface.h>


     An iface node is both a netgraph node and a system networking interface.  When an iface node
     is created, a new interface appears which is accessible via ifconfig(8).  Iface node
     interfaces are named ng0, ng1, etc.  When a node is shutdown, the corresponding interface is
     removed and the interface name becomes available for reuse by future iface nodes; new nodes
     always take the first unused interface.  The node itself is assigned the same name as its
     interface, unless the name already exists, in which case the node remains unnamed.

     An iface node has a single hook corresponding to each supported protocol.  Packets
     transmitted via the interface flow out the corresponding protocol-specific hook.  Similarly,
     packets received on a hook appear on the interface as packets received into the
     corresponding protocol stack.  The currently supported protocols are IP and IPv6.

     An iface node can be configured as a point-to-point interface or a broadcast interface.  The
     configuration can only be changed when the interface is down.  The default mode is point-to-

     Iface nodes support the Berkeley Packet Filter (BPF).


     This node type supports the following hooks:

     inet   Transmission and reception of IP packets.

     inet6  Transmission and reception of IPv6 packets.


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

     NGM_IFACE_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_IFACE_GET_IFINDEX (getifindex)
          Returns the global index of the associated interface as a 32 bit integer.

     NGM_IFACE_POINT2POINT (point2point)
          Set the interface to point-to-point mode.  The interface must not currently be up.

     NGM_IFACE_BROADCAST (broadcast)
          Set the interface to broadcast mode.  The interface must not currently be up.


     This node shuts down upon receipt of a NGM_SHUTDOWN control message.  The associated
     interface is removed and becomes available for use by future iface nodes.

     Unlike most other node types, an iface node does not go away when all hooks have been
     disconnected; rather, and explicit NGM_SHUTDOWN control message is required.

ALTQ Support

     The ng_iface interface supports ALTQ bandwidth management feature.  However, ng_iface is a
     special case, since it is not a physical interface with limited bandwidth.  One should not
     turn ALTQ on ng_iface if the latter corresponds to some tunneled connection, e.g. PPPoE or
     PPTP.  In this case, ALTQ should be configured on the interface that is used to transmit the
     encapsulated packets.  In case when your graph ends up with some kind of serial line, either
     synchronous or modem, the ng_iface is the right place to turn ALTQ on.


     ng_iface supports nesting, a configuration when traffic of one ng_iface interface flows
     through the other.  The default maximum allowed nesting level is 2.  It can be changed at
     runtime setting sysctl(8) variable net.graph.iface.max_nesting to the desired level of


     altq(4), bpf(4), netgraph(4), ng_cisco(4), ifconfig(8), ngctl(8) sysctl


     The iface node type was implemented in FreeBSD 4.0.


     Archie Cobbs <>