DDNS Manager

DDNS manager is a lightweight program to manage Device.DynamicDNS. TR069 datamodel as per 2.16 version. This package is dependent on openwrt ddns-script package for the backend job of managing dynamic DNS updation. We need to create this separate because there is a limitation in ddns-script package that it supports only one host in every DNS client section in the UCI. Where as datamodel definition allows multiple host under one DNS client object. So to achieve the datamodel specification there was one option to patch the openwrt ddns-script package.

We found it not good enough to patch the ddns-script package in openwrt and hence decided to create this 'ddnsmngr' package to achive the datamodel specification.

Package details

1. In this package we have used bbfdm micro-service mechanism to register the Device.DynamicDNS. datamodel tree.
2. We have created separate UCI and init script namely "/etc/config/ddnsmngr" and "/etc/init.d/ddnsmngr" respecively. Datamodel interaction will be with these files rather than the standard ddns-script UCI and init script.
3. We have added a shell script in this package namely "ddnsmngr_updater.sh" which will spawn one ddns process for each configured hosts as it is now being done from the standard "dynamic_dns_updater.sh" in the ddns-script package. We avoided the patch work in "ddns-script" package by introducing this script. This script uses apis from the "dynamic_dns_functions.sh" script in ddns-script package and does the ddns work.

UCI format

Below is the format of the UCI:

config ddnsmngr 'global'
	option configfile '/var/run/ddnsmngr/ddnsmngr.json'
	option ddns_dateformat '%F %R'
	option ddns_rundir '/var/run/ddnsmngr'
	option ddns_logdir '/var/log/ddnsmngr'
	option ddns_loglines '250'
	option upd_privateip '0'
	option use_curl '1'

config client 'client_1'
	option enabled '1'
	option service_name 'dynu.com'
	option interface 'wan'
	option ip_network 'wan'
	option username 'xxxxxx'
	option password 'xxxxxx'
	option use_ipv6 '0'
	option force_ipversion '0'
	option use_https '0'
	option force_dnstcp '0'

config host 'client_1_host_1'
	option enabled '1'
	option dm_parent 'client_1'
	option lookup_host 'device1.loseyourip.com'

config host 'client_1_host_2'
	option enabled '1'
	option dm_parent 'client_1'
	option lookup_host 'device2.loseyourip.com'

How it works

1. The init script of 'ddnsmngr' package parses each host section in the UCI and creates a 1:1 client-host json configuration in the file mentioned in 'configfile' option of UCI. The default file is "/var/run/ddnsmngr/ddnsmngr.json".
2. For above UCI config the json configuration would be like:

{
  "services": [
    {
      "interface": "wan",
      "service_name": "dynu.com",
      "username": "xxxxxx",
      "password": "xxxxxx",
      "lookup_host": "device1.loseyourip.com",
      "ip_network": "wan",
      "proc_info_file": "client_1_host_1",
      "use_ipv6": "0",
      "force_ipversion": "0",
      "use_https": "0",
      "force_dnstcp": "0"
    },
    {
      "interface": "wan",
      "service_name": "dynu.com",
      "username": "xxxxxx",
      "password": "xxxxxx",
      "lookup_host": "device2.loseyourip.com",
      "ip_network": "wan",
      "proc_info_file": "client_1_host_2",
      "use_ipv6": "0",
      "force_ipversion": "0",
      "use_https": "0",
      "force_dnstcp": "0"
    }
  ]
}

3. Init script then calls the "ddnsmngr_updater.sh" script with this json object as an argument.
4. "ddnsmngr_updater.sh" script then validates each object in the "services" array and starts process for every valid object.

ddnsmngr_updater.sh VS dynamic_dns_updater.sh

In ddns-script package "dynamic_dns_updater.sh" script spawn processes for every DDNS client object and every process can take care of a single host.

"ddnsmngr_updater.sh" spawn a separate process for each host and hence every hostname is being updated by a dedicated process.

Backend Support

We have analysed several dynamic DNS client packages for the purpose of using as a backend of this ddnsmngr package, out of which "ddns-script" and "inadyn" are the two packages we have found suitable for the implementation. Below are the details of the packages which were analysed