NG_IFACE(4) MidnightBSD 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, IPv6, AppleTalk, IPX, 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.

atalk

Transmission and reception of AppleTalk packets.

ipx

Transmission and reception of IPX 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

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

Returns the global index of the associated interface as a 32 bit integer.

NGM_IFACE_POINT2POINT

Set the interface to point-to-point mode. The interface must not currently be up.

NGM_IFACE_BROADCAST

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

NGM_CISCO_GET_IPADDR

This message is defined by the ng_cisco(4) node type; see ng_cisco(4) for a description.

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, then 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〉

MidnightBSD 0.3 October 28, 2005 MidnightBSD 0.3