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ng_sppp - sppp netgraph node type
An sppp node is a netgraph(4) interface to the original sppp(4) network
module for synchronous lines. Currently, sppp(4) supports PPP and Cisco
HDLC protocols. An sppp node could be considered as an alternative
kernel mode PPP implementation to net/mpd port + ng_ppp(4), and as an
alternative to ng_cisco(4) node. While having less features than net/mpd
+ ng_ppp(4), it is significantly easier to use in the majority of simple
configurations, and allows the administrator to not install the net/mpd
port. With sppp you do not need any other nodes, not even an ng_iface(4)
node. When an sppp node is created, a new interface appears which is
accessible via ifconfig(8). Network interfaces corresponding to sppp
nodes are named sppp0, sppp1, etc. When a node is shut down, the
corresponding interface is removed, and the interface name becomes
available for reuse by future sppp 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. The sppp node allows drivers written to the old sppp(4)
interface to be rewritten using the newer more powerful netgraph(4)
interface, and still behave in a compatible manner without supporting
both network modules.
An sppp node has a single hook named downstream. Usually it is connected
directly to a device driver hook.
The sppp nodes support the Berkeley Packet Filter, bpf(4).
This node type supports the following hooks:
downstream The connection to the synchronous line.
This node type supports the generic control messages, plus the following:
Returns the name of the associated interface as a NUL-terminated
ASCII string. Normally this is the same as the name of the node.
This node shuts down upon receipt of a NGM_SHUTDOWN control message. The
associated interface is removed and becomes available for use by future
Unlike most other node types and like ng_iface(4) does, an sppp node does
not go away when all hooks have been disconnected; rather, an explicit
NGM_SHUTDOWN control message is required.
For example, if you have the cx(4) device, you could run PPP over it with
just one command:
ngctl mkpeer cx0: sppp rawdata downstream
Now you have the sppp0 interface (if this was the first sppp node) which
can be accessed via ifconfig(8) as a normal network interface, or via
spppcontrol(8) as an sppp(4) interface.
bpf(4), cx(4), netgraph(4), ng_cisco(4), ng_iface(4), ng_ppp(4), sppp(4),
ifconfig(8), ngctl(8), spppcontrol(8)
For complex networking topologies you may want to look at net/mpd port.
The sppp node type was implemented for FreeBSD 5.0. It was included to
the system since FreeBSD 5.3.
Copyright (C) 2003-2004 Roman Kurakin 〈email@example.com〉.