kubernetes: Kubelet service cannot bind port 10250 on both the ipv4 and ipv6 network ips in Dual stack k8s setup.

What happened?

The parameter address in the kubelet /var/lib/kubelet/config.yaml enables to bind the kubelet to a node ip .
It’s the parameter which accepts single value, that means only one IP could be provided. In case of dual stack environment kubelet cannot listen on both the ipv4 and ipv6 network ips.

Following output is from the case where kubelet listens on ipv6 node’s ip in a dualstack environment.

kubectl logs node-cert-exporter-h74s2 -n monitoring
Error from server: Get "[https://<ipv4NodeIp>:10250/containerLogs/monitoring/node-cert-exporter-h74s2/node-cert-exporter":](https://<ipv4NodeIp>:10250/containerLogs/monitoring/node-cert-exporter-h74s2/node-cert-exporter%22:) dial tcp <ipv4NodeIp>:10250: connect: connection refused

What did you expect to happen?

kubelet should listen to both the network node ips in case of dual stack. This will enable communication to the kubelet on both the networks.

How can we reproduce it (as minimally and precisely as possible)?

1. Update the address: <node ip> in the /var/lib/kubelet/config.yaml
2. Restart the kubelet service.
3. ss -anlp | grep 10250

Anything else we need to know?

Kubeapiserver with the configuration --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname always tries to contact the kubelet on the ipv4 network ip ( ipv4, dualstack deployment) with the exception in ipv6 deployment. Kubeapiserver is unable to make calls to the kubelet where the kubelet listens on the ipv6 node ip in the dual stack environment.

Kubernetes version

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"23", GitVersion:"v1.23.0", GitCommit:"6abac1505370282a9583329dd35622792b60e449", GitTreeState:"clean", BuildDate:"2022-01-10T12:53:58Z", GoVersion:"go1.17.3", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"23", GitVersion:"v1.23.0", GitCommit:"6abac1505370282a9583329dd35622792b60e449", GitTreeState:"clean", BuildDate:"2022-01-10T12:44:17Z", GoVersion:"go1.17.3", Compiler:"gc", Platform:"linux/amd64"}

Cloud provider

OS version

# On Linux:
$ cat /etc/os-release
NAME="SLES"
VERSION="15-SP2"
VERSION_ID="15.2"
PRETTY_NAME="SUSE Linux Enterprise Server 15 SP2"
ID="sles"
ID_LIKE="suse"
ANSI_COLOR="0;32"
CPE_NAME="cpe:/o:suse:sles:15:sp2"

Install tools

Container runtime (CRI) and and version (if applicable)

Related plugins (CNI, CSI, …) and versions (if applicable)