openwrt/docs/network-scripts.txt

	Structure of the network scripts in buildroot-ng


1) Usage

To be able to access the network functions, you need to include
the necessary shell scripts by running:

. /etc/functions.sh      # common functions
include /lib/network     # include /lib/network/*.sh
scan_interfaces          # read and parse the network config

Some protocols, such as PPP might change the configured interface names
at run time (e.g. eth0 => ppp0 for PPPoE). That's why you have to run
scan_interfaces instead of reading the values from the config directly.
After running scan_interfaces, the 'ifname' option will always contain
the effective interface name (which is used for IP traffic) and if the
physical device name differs from it, it will be stored in the 'device'
option.
That means that running 'config_get lan ifname' after scan_interfaces
might not return the same result as running it before.

After running scan_interfaces, the following functions are available:

- find_config <interface> looks for a network configuration that includes
  the specified network interface.

- setup_interface <interface> [<config>] [<protocol>] will set up the
  specified interface, optionally overriding the network configuration
  name or the protocol that it uses.



2) Writing protocol handlers

You can add custom protocol handlers by adding shell scripts to
/lib/network. They provide the following two shell functions:

scan_<protocolname>() {
	local config="$1"
	# change the interface names if necessary
}

setup_interface_<protocolname>() {
	local interface="$1"
	local config="$2"
	# set up the interface
}

scan_<protocolname> is optional and only necessary if your protocol
uses a custom device, e.g. a tunnel or a PPP device.