Session Traversal Utilities for NAT (STUN) is a standardized set of method to reach the CPE devices that are connected behind NAT, the CWMP protocol introduces alternative method of executing Connection Request via NAT based on STUN. The stunc is an implementation of STUN client functionality that performs this feature.

Project Components

Project consists of following components:

Application itself written in C programming language
Documentation in a Markdown format

Build Instructions

stunc is written using C programming language and depends on a number of components found in OpenWrt for building and running.

UCI Config

The stunc requires a configuration file to get the required input parameters which is located in '/etc/config/stunc' and contains only one section stunc:

config stunc 'stunc'
	option enabled '0'
	option username 'stun'
	option password 'stun'
	option server_address 'stun.l.google.com'
	option server_port '19302'
	option min_keepalive '30'
	option max_keepalive '3600'
	option client_port 7547
	option log_level '0'

For more info on the stunc UCI configuration see link

Concepts and Workflow

stunc is developed according to RFC-3489 to detect if CPE is behind a NAT network, when enabled. This package is specifically designed to provide stun client functionality for a CWMP client.

stunc monitors and calls below ubus method to inform CWMP client of incoming connection requests.

ubus call tr069 inform '{"event": "6 connection request"}'

Public IP/UDP connection request details along with nat-detection status is available in below path:

root@iopsys:~# cat /var/state/stunc
stunc.stunc.nat_detected='1'
stunc.stunc.crudp_address='157.37.187.219:48942'

Dependencies

Build-Time Dependencies

To successfully build stunc, the following libraries are needed:

Dependency	Link	License
libuci	https://git.openwrt.org/project/uci.git	LGPL 2.1
libubox	https://git.openwrt.org/project/libubox.git	BSD
libubus	https://git.openwrt.org/project/ubus.git	LGPL 2.1
libjson-c	https://s3.amazonaws.com/json-c_releases	MIT

Run-Time Dependencies

In order to run the stunc, following dependencies are needed to be running/available before stunc.

Dependency	Link	License
ubusd	https://git.openwrt.org/project/ubus.git	LGPL 2.1