Hey everyone,
I've set up a DaemonSet as a remedy for the nginx CVE issue mentioned in a blog post I found. However, I'm confused about how it manages to alter iptables rules within the containers of that DaemonSet while still affecting the entire cluster. I even SSH'ed into the Kubernetes nodes thinking the changes were made there, but I couldn't find the deny rule. Can someone please clarify how this works and what would happen if I removed the DaemonSet? Thanks!
4 Answers
The DaemonSet modifies iptables in the node's network namespace rather than the host's directly, which is why you can't see the changes by SSHing in. If you decide to remove the DaemonSet, the changes it made would be rolled back. Just be cautious, as some of your services might rely on those custom iptables rules!
The reason the DaemonSet can change iptables rules throughout the cluster is that it has host network privileges, meaning any changes it makes apply to the host node as well. That's likely why you're seeing the impact across the entire cluster instead of just within the DaemonSet containers.
Thanks for the clarity! I think I get it now.
In Kubernetes, each Pod typically has its own network namespace, so changes made here typically impact just that Pod. However, when you set spec.hostNetwork to true in your Pod's configuration, it shares the host's network namespace, causing iptables modifications from your Pod to affect the entire node. This is also why your Pod's IP matches the node's IP—everything operates within the same network namespace. Pretty nifty how it all works!
Thanks, that's a really clear explanation!