bionic (4) ng_iface.4freebsd.gz

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, IPv6, ATM, NATM, and NS.

     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.

     atm    Transmission and reception of ATM packets.

     natm   Transmission and reception of NATM packets.

     ns     Transmission and reception of NS 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.

SEE ALSO

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

HISTORY

     The iface node type was implemented in FreeBSD 4.0.

AUTHORS

     Archie Cobbs <archie@FreeBSD.org>