How to setup hotplug to do dynamic DNS

Installing and Using OpenWrt
1

After looking at the docs for hotplug (https://openwrt.org/docs/guide-user/base-system/hotplug) and the forum I am still not sure how to do this.

My public IPv4 is dynamic and my WAN interface is set to DHCP client. What I want to do is when the DHCP lease is renewed then a script is executed with a hit on my DNS server's API with the new IPv4 that has been assigned.

From what I understand it's a matter of adding a shell script in the corresponding folder in /etc/hotplug.d. But my first question is what is the corresponding folder for the DHCP client, which I believe is udhcpc? And how can I know what that folder should be?

Then I understand I need to match an action that would trigger a command. So in this case I guess the action would be renew but I'm not sure and again, I don't know how I can find this information.
And last, the command that I want to execute needs the new IPv4 address that has been assigned. I guess this is something I can find in the environment variables that are passed to the script but what is this variable called?

Thanks a lot for any help!

1 Like
2

Are you aware of ddns package?
https://openwrt.org/docs/guide-user/base-system/ddns

2 Likes
3

More specifically, the update_script configuration option for ddns-scripts.

Here is a sample script: https://github.com/openwrt/packages/blob/master/net/ddns-scripts/samples/update_sample.sh

1 Like
4

Thanks for the suggestions.
I am aware of the ddns package. But I'm really interested in the hotplug framework, I only lack a tiny bit of information to get it to work.

I could spot some reference to hotplug in the link but it is not very clear how it is used.

I'll keep looking.

5

So, if you want to script this from the ground up, why not just drop a script into /etc/hotplug.d/iface/ with content like this:

/usr/bin/env > /tmp/envs_${INTERFACE}_${DEVICE}_${ACTION}.log

Then you see, which variables you get, and can write a script to react accordingly

6

that's interesting! thanks.

So the right folder to catch the dhcp client actions should be iface?

I'll try and see what I can get from it. I'll also try to artificially trigger a dhcp renew without triggering other actions.