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>

Debian                                            July 31, 2020                                      NG_IFACE(4)