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The original was posted on /r/selfhosted by /u/yuuuuuuuut on 2025-03-21 22:01:17+00:00.
TLDR: If you are using ddclient for dynamic DNS and you have it configured to use dynamicdns.park-your-domain.com for fetching your IP address, it will incorrectly set the IP address for your configured domains to 1.0.1.1. whois says this server is owned by China Telecom.
Just ran into a very strange bug. All my web services were unreachable. I checked my DNS records and found they had all been changed to 1.0.1.1. After some digging, it turns out that requests to dynamicdns.park-your-domain.com are now returning a header with 1.0.1.1 in it.
For whatever reason, ddclient parses the entire response (not just the body) and takes the first thing that looks like an IP address and uses that when it updates your DNS records. park-your-domain.com is now returning a Cookie header with 1.0.1.1 in it and ddclient is interpreting this as your IP address.
There is a github issue tracking this:
And it appears this functionality has been patched in the latest version of ddclient but it is not available on my distro's repos yet.
My solution is to use a different service for fetching my IP address and I have this in my ddclient.conf:
usev4=webv4, webv4=https://api.ipify.org/
I'm not sure how many requests were made from my devices to the wrong IP address but it's definitely possible that this could be a method of hijacking session tokens. I'm rotating all my passwords and expiring active sessions for all my services.