With tailscale --advertise-address passed to kube-apiserver shows both ipv4 as well as ipv6 address on a ipv6-only setup

[ShylajaDevadiga]

Environmental Info:
K3s Version:
k3s version v1.27.3+k3s-be442433

Node(s) CPU architecture, OS, and Version:
Ubuntu 22.04

Cluster Configuration:
Single node

Describe the bug:
--advertise-address flag passed to kube-apiserver and node-ip flag passed to the agent contains both ipv4 and ipv6 ip as tailscale ips

Steps To Reproduce:
On a ipv6 node
Install tailscale
Install k3s passing the authkey

Expected behavior:
We should pass ipv6 only address to --advertise-address to the kube-apiserver

Actual behavior:
Both ipv4 and ipv6 address is passed

Additional context / logs:

Jul 20 16:38:24 i-0754fbb40c58fae14 k3s[8802]: time="2023-07-20T16:38:24Z" level=info msg="Running kube-apiserver --advertise-address=100.77.219.2 --advertise-port=6443 --allow-privileged=true --anonymous-auth=false --api-audiences=https://kubernetes.default.svc.cluster.local,k3s

[manuelbuil]

flannel extension backend (the one used by flannel) does not support ipv6-only. We need to fix that in flannel first

[VestigeJ]

##Environment Details
VERSION=v1.27.4+k3s1
COMMIT=38a0b91c1a917d2866aee265bc7815424af3e701

Infrastructure

• Cloud

Node(s) CPU architecture, OS, and version:

ami-01f87c43e618bf8f0

Linux 5.11.0-1022-aws x86_64 GNU/Linux

PRETTY_NAME="Ubuntu 20.04.3 LTS"

Cluster Configuration:

NAME              STATUS   ROLES                       AGE    VERSION
ip-1-1-2-66       Ready    control-plane,etcd,master   4m5s   v1.27.4+k3s-38a0b91c 

Config.yaml:

=========== k3s config =========== 
write-kubeconfig-mode: 644
debug: true
token: YOUR_TOKEN_HERE
protect-kernel-defaults: true
cluster-init: true
cluster-cidr: 2001:cafe:42:0::/56
service-cidr: 2001:cafe:42:1::/112
vpn-auth: "name=tailscale,joinKey=tskey-auth-m0rt@l-W0m3b@t"
node-ip: 2600:cade:iced:eeee:b7a1:6e49:b389:2e60

Reproduction

$ curl https://get.k3s.io --output install-"k3s".sh
$ sudo chmod +x install-"k3s".sh
$ sudo groupadd --system etcd && sudo useradd -s /sbin/nologin --system -g etcd etcd
$ sudo modprobe ip_vs_rr
$ sudo modprobe ip_vs_wrr
$ sudo modprobe ip_vs_sh
$ sudo printf "on_oovm.panic_on_oom=0 \nvm.overcommit_memory=1 \nkernel.panic=10 \nkernel.panic_ps=1 \nkernel.panic_on_oops=1 \n" > ~/90-kubelet.conf
$ sudo cp 90-kubelet.conf /etc/sysctl.d/
$ sudo systemctl restart systemd-sysctl
$ get_tailscale //curl install tailscale binary
$ sudo INSTALL_K3S_VERSION=v1.27.4+k3s1 INSTALL_K3S_EXEC=server ./install-k3s.sh 
$ sudo journalctl -u k3s
$ ps -ef | grep k3s //k3s fails to have started correctly with this configuration

Results:

Validation

$ curl https://get.k3s.io --output install-"k3s".sh
$ sudo chmod +x install-"k3s".sh
$ sudo groupadd --system etcd && sudo useradd -s /sbin/nologin --system -g etcd etcd
$ sudo modprobe ip_vs_rr
$ sudo modprobe ip_vs_wrr
$ sudo modprobe ip_vs_sh
$ sudo printf "on_oovm.panic_on_oom=0 \nvm.overcommit_memory=1 \nkernel.panic=10 \nkernel.panic_ps=1 \nkernel.panic_on_oops=1 \n" > ~/90-kubelet.conf
$ sudo cp 90-kubelet.conf /etc/sysctl.d/
$ sudo systemctl restart systemd-sysctl
$ get_tailscale //curl install tailscale binary
$ sudo INSTALL_K3S_COMMIT=38a0b91c1a917d2866aee265bc7815424af3e701 INSTALL_K3S_EXEC=server ./install-k3s.sh 
$ sudo journalctl -u k3s | grep -i advertise
$ kgn -o wide
$ kgp -o wide -A //k3s running with all pods and nodes advertising ipv6 address

Results:

$ kgp -A

NAMESPACE     NAME                                     READY   STATUS      RESTARTS   AGE
kube-system   coredns-77ccd57875-wdcc9                 1/1     Running     0          36s
kube-system   helm-install-traefik-44jgf               0/1     Completed   1          37s
kube-system   helm-install-traefik-crd-98pbv           0/1     Completed   0          37s
kube-system   local-path-provisioner-957fdf8bc-ms7tp   1/1     Running     0          36s
kube-system   metrics-server-648b5df564-n7czh          1/1     Running     0          36s
kube-system   svclb-traefik-938d6ee1-bqj6r             2/2     Running     0          18s
kube-system   traefik-64f55bb67d-k978t                 1/1     Running     0          19s

$ kgn -o wide

NAME              STATUS   ROLES                       AGE   VERSION                INTERNAL-IP                               EXTERNAL-IP   OS-IMAGE             KERNEL-VERSION    CONTAINER-RUNTIME
ip-192-168-2-66   Ready    control-plane,etcd,master   55s   v1.27.4+k3s-38a0b91c   fd7a:iced:cafe:eeee:4843:cd96:6263:763b   <none>        Ubuntu 20.04.3 LTS   5.11.0-1022-aws   containerd://1.7.3-k3s1

$ kgp -o wide -A

NAMESPACE     NAME                                     READY   STATUS      RESTARTS   AGE   IP                NODE              NOMINATED NODE   READINESS GATES
kube-system   coredns-77ccd57875-wdcc9                 1/1     Running     0          53s   2001:cafe:42::3   ip-192-168-2-66   <none>           <none>
kube-system   helm-install-traefik-44jgf               0/1     Completed   1          54s   2001:cafe:42::6   ip-192-168-2-66   <none>           <none>
kube-system   helm-install-traefik-crd-98pbv           0/1     Completed   0          54s   2001:cafe:42::2   ip-192-168-2-66   <none>           <none>
kube-system   local-path-provisioner-957fdf8bc-ms7tp   1/1     Running     0          53s   2001:cafe:42::5   ip-192-168-2-66   <none>           <none>
kube-system   metrics-server-648b5df564-n7czh          1/1     Running     0          53s   2001:cafe:42::4   ip-192-168-2-66   <none>           <none>
kube-system   svclb-traefik-938d6ee1-bqj6r             2/2     Running     0          35s   2001:cafe:42::7   ip-192-168-2-66   <none>           <none>
kube-system   traefik-64f55bb67d-k978t                 1/1     Running     0          36s   2001:cafe:42::8   ip-192-168-2-66   <none>           <none>

Additional context / logs: