NG_IFACE(4)            FreeBSD Kernel Interfaces Manual            NG_IFACE(4)

NAME
     ng_iface - interface netgraph node type

SYNOPSIS
     #include <netgraph/ng_iface.h>

DESCRIPTION
     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-point.

     Iface nodes support the Berkeley Packet Filter (BPF).

HOOKS
     This node type supports the following hooks:

     inet       Transmission and reception of IP packets.

     inet6      Transmission and reception of IPv6 packets.

CONTROL MESSAGES
     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.

SHUTDOWN
     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.

Nesting
     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 nesting.

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

HISTORY
     The iface node type was implemented in FreeBSD 4.0.

AUTHORS
     Archie Cobbs <archie@FreeBSD.org>

FreeBSD 13.1-RELEASE-p6          July 31, 2020         FreeBSD 13.1-RELEASE-p6