Kubelet should be able to manage changes to iptables
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Description
Allow Kubelet to manage iptables.
Rationale
Kubelets can automatically manage the required changes to iptables based on how you choose your networking options for the pods. It is recommended to let kubelets manage the changes to iptables. This ensures that the iptables configuration remains in sync with pods networking configuration. Manually configuring iptables with dynamic pod network configuration changes might hamper the communication between pods/containers and to the outside world. You might have iptables rules too restrictive or too open.
Audit
Run the following command on each node: ps -ef | grep kubelet. Verify that if the --make-iptables-util-chains argument exists then it is set to true. If the --make-iptables-util-chains argument does not exist, and there is a Kubelet config file specified by --config, verify that the file does not set makeIPTablesUtilChains to false.
If using a kubelet config file, edit the file to set makeIPTablesUtilChains: true. If using command line arguments, edit the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubeadm.conf on each worker node and remove the --make-iptables-util-chains argument from the KUBELET_SYSTEM_PODS_ARGS variable. Based on your system, restart the kubelet service. For example: systemctl daemon-reload systemctl restart kubelet.service
Impact
Kubelet would manage the iptables on the system and keep it in sync. If you are using any other iptables management solution, then there might be some conflicts.
Default value
By default, --make-iptables-util-chains argument is set to true.
References
- https://kubernetes.io/docs/admin/kubelet/
CIS controls
Version 6.9 Limitation and Control of Network Ports, Protocols, and Services
