7.4 KiB
IPv6 only kubernetes clusters
This project is testing, deploying and using IPv6 only k8s clusters.
Docs
Working
- networking (calico)
- ceph with rook (cephfs, rbd)
- letsencrypt (nginx, certbot, homemade)
- k8s test on arm64
Not (yet) working or tested
- virtualisation (VMs, kubevirt)
- network policies
- prometheus in the cluster
- argocd (?) for CI and upgrades
- Maybe LoadBalancer support (our ClusterIP already does that though)
- (Other) DNS entrys for services
Cluster setup
- Calico CNI with BGP peering to our upstream infrastructure
- Rook for RBD and CephFS support
The following steps are a full walk through on setting up the IPv6 only kubernetes cluster "c2.k8s.ooo".
Initialise the master with kubeadm
We are using a custom kubeadm.conf to
- configure the cgroupdriver (for alpine)
- configure the IP addresses
- configure the DNS domain (c2.k8s.ooo)
kubeadm init --config k8s/c2/kubeadm.yaml
Adding worker nodes
kubeadm join [2a0a:e5c0:13:0:225:b3ff:fe20:38cc]:6443 --token cfrita.. \
--discovery-token-ca-cert-hash sha256:...
Verifying that all nodes joined:
% kubectl get nodes
NAME STATUS ROLES AGE VERSION
server47 Ready control-plane,master 2m25s v1.21.1
server48 Ready <none> 66s v1.21.1
server49 Ready <none> 24s v1.21.1
server50 Ready <none> 19s v1.21.1
Configuring networking
- This customised calico.yaml enables IPv6
kubectl apply -f cni-calico/calico.yaml
After applying, check that all calico pods are up and running:
% kubectl -n kube-system get pods
NAME READY STATUS RESTARTS AGE
calico-kube-controllers-b656ddcfc-5kfg6 0/1 Running 4 3m27s
calico-node-975vh 1/1 Running 3 3m28s
calico-node-gbnvj 1/1 Running 2 3m28s
calico-node-qjm5v 0/1 Running 4 113s
calico-node-xxxmk 1/1 Running 4 3m28s
coredns-558bd4d5db-56dv9 1/1 Running 0 8m51s
coredns-558bd4d5db-hsspb 1/1 Running 0 8m51s
etcd-server47 1/1 Running 0 9m9s
kube-apiserver-server47 1/1 Running 0 9m4s
kube-controller-manager-server47 1/1 Running 0 9m4s
kube-proxy-5g5qm 1/1 Running 0 8m51s
kube-proxy-85mck 1/1 Running 0 7m8s
kube-proxy-b95sv 1/1 Running 0 7m13s
kube-proxy-mpjkm 1/1 Running 0 7m55s
kube-scheduler-server47 1/1 Running 0 9m10s
Often you will have some pods crashing in the beginning and you might need to make mounts shared (if they are not) like this:
mount --make-shared /sys
mount --make-shared /run
(above mounts are necessary for Alpine Linux)
Getting calicoctl
To configure calico, we need calicoctl, which we can run in yet-another-pod as following:
kubectl apply -f https://docs.projectcalico.org/manifests/calicoctl.yaml
And we alias it for easier usage:
alias calicoctl="kubectl exec -i -n kube-system calicoctl -- /calicoctl"
Adding BGP peering
We need to tell calico with which BGP peers to peer with. For this we use the bgp-c2.yaml file, which has configurations fitting for our cluster:
calicoctl create -f - < cni-calico/bgp-c2.yaml
At this point all nodes should be peering with our upstream infrastructure. We can confirm this on the upstream side, where we also run bird:
% birdc show route
BIRD 2.0.7 ready.
Table master6:
2a0a:e5c0:13:e1:f4c5:ab65:a67f:53c0/122 unicast [place7-server1 20:04:14.222] * (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:3554 on eth0
unicast [place7-server3 20:04:14.224] (100) [AS65534i]
via 2a0a:e5c0:13:0:224:81ff:fee0:db7a on eth0
unicast [place7-server2 20:04:14.222] (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:38cc on eth0
unicast [place7-server4 20:04:14.221] (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:3564 on eth0
2a0a:e5c0:13:e2::/108 unicast [place7-server1 20:04:14.222] * (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:3554 on eth0
unicast [place7-server2 20:04:14.222] (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:38cc on eth0
unicast [place7-server3 20:04:14.113] (100) [AS65534i]
via 2a0a:e5c0:13:0:224:81ff:fee0:db7a on eth0
unicast [place7-server4 20:04:14.221] (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:3564 on eth0
2a0a:e5c0:13:e1:176b:eaa6:6d47:1c40/122 unicast [place7-server1 20:04:14.222] * (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:3554 on eth0
unicast [place7-server2 20:04:14.222] (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:38cc on eth0
unicast [place7-server3 20:04:14.221] (100) [AS65534i]
via 2a0a:e5c0:13:0:224:81ff:fee0:db7a on eth0
unicast [place7-server4 20:04:14.221] (100) [AS65534i]
via 2a0a:e5c0:13:0:225:b3ff:fe20:3564 on eth0
2a0a:e5c0:13::/48 unreachable [v6 2021-05-16] * (200)
Testing the cluster
At this point we should have a functioning k8s cluster, now we should test whether it works using a simple nginx deployment:
Do NOT use https://k8s.io/examples/application/deployment.yaml. It contains an outdated nginx container that has no IPv6 listener. You will get results such as
% curl http://[2a0a:e5c0:13:bbb:176b:eaa6:6d47:1c41]
curl: (7) Failed to connect to 2a0a:e5c0:13:bbb:176b:eaa6:6d47:1c41 port 80: Connection refused
if you use that deployment. Instead use something on the line of the included nginx-test-deployment.yaml:
kubectl apply -f generic/nginx-test-deployment.yaml
Let's see whether the pods are coming up:
% kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deployment-95d596f7b-484mz 1/1 Running 0 13s
nginx-deployment-95d596f7b-4wfkp 1/1 Running 0 13s
And the associated service:
% kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 2a0a:e5c0:13:e2::1 <none> 443/TCP 16m
nginx-service ClusterIP 2a0a:e5c0:13:e2::4412 <none> 80/TCP 34s
It is up and running, let's curl it!
% curl -I http://[2a0a:e5c0:13:e2::4412]
HTTP/1.1 200 OK
Server: nginx/1.20.0
Date: Mon, 14 Jun 2021 18:08:29 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 20 Apr 2021 16:11:05 GMT
Connection: keep-alive
ETag: "607efd19-264"
Accept-Ranges: bytes
Perfect. Let's delete it again:
kubectl delete -f generic/nginx-test-deployment.yaml
Next steps
While above is already a fully running k8s cluster, we do want to have support for PersistentVolumeclaims. See the rook documentation on how to achieve the next step.
The IPv4 "problem"
- Clusters are IPv6 only
- Need to have one or more services to map IPv4
- Maybe outside haproxy w/ generic ssl/sni/host mapping
- Could even be inside haproxy service