Daemonset for CNI DHCP process

README.md

Multus + DHCP IPAM example

Prerequisites: Multus + NetworkAttachmentDefinition CRD installed.

In order to have DHCP working as an IPAM plugin -- you'll need to have the DHCP CNI binary running.

In this example, we'll run this (as a daemonset) from the dougbtv/dhcp image, which is based on Tomo's dockerfile.

About my setup: In this setup, I use a macvlan plugin as the secondary interface for Multus. In my setup, I used an upstream Kubernetes running on KVM guests. The master device for macvlan is eth0 and that device is connected to a bridge in the 192.168.122.0/24 network space, and has an already running DHCP server available.

Run the DHCP CNI binary (as a daemonset)

Create this daemonset, as a file and apply it:

---
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: kube-dhcp-ds-amd64
  namespace: kube-system
  labels:
    tier: node
    app: dhcp
spec:
  template:
    metadata:
      labels:
        tier: node
        app: dhcp
    spec:
      hostNetwork: true
      nodeSelector:
        beta.kubernetes.io/arch: amd64
      tolerations:
      - operator: Exists
        effect: NoSchedule
      initContainers:
      - name: dhcp-daemon-initialization
        image: dougbtv/dhcp:latest
        command: ["/bin/sh"]
        args: ["-c", "rm -f /var/run/cni/dhcp.sock"]
        volumeMounts:
        - name: socketpath
          mountPath: /var/run/cni
      containers:
      - name: kube-dhcp
        # Based on: https://github.com/s1061123/cni-dhcp-daemon/blob/master/Dockerfile
        image: dougbtv/dhcp:latest
        resources:
          requests:
            cpu: "100m"
            memory: "50Mi"
          limits:
            cpu: "100m"
            memory: "50Mi"
        command: ["./dhcp"]
        args:
          - "daemon"
          - "-hostprefix"
          - "/host"
        securityContext:
          privileged: true
        volumeMounts:
          - name: socketpath
            mountPath: /run/cni
          - name: procpath
            mountPath: /host/proc
      volumes:
        - name: socketpath
          hostPath:
            path: /run/cni
        - name: procpath
          hostPath:
            path: /proc

Apply it, wait for it to come up:

[centos@kube-nonetwork-master ~]$ kubectl create -f dhcp.yml 
daemonset.extensions/kube-dhcp-ds-amd64 created
[centos@kube-nonetwork-master ~]$ kubectl get pods --namespace=kube-system -o wide | grep -P "NAME|dhcp"
NAME                                            READY   STATUS    RESTARTS   AGE    IP                NODE                    NOMINATED NODE
kube-dhcp-ds-amd64-66rsf                        1/1     Running   0          57s    192.168.122.233   kube-nonetwork-master   <none>
kube-dhcp-ds-amd64-6kxv7                        1/1     Running   0          57s    192.168.122.46    kube-nonetwork-node-1   <none>

Create a custom resource with a configuration referencing DHCP IPAM

I created mine like so:

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: dhcppod
  annotations:
    k8s.v1.cni.cncf.io/networks: dhcp-conf
spec:
  containers:
  - name: dhcppod
    command: ["/bin/bash", "-c", "trap : TERM INT; sleep infinity & wait"]
    image: dougbtv/centos-network
EOF

Create a pod with an annotation referencing that configuration

And the pod I created was:

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: dhcppod
  annotations:
    k8s.v1.cni.cncf.io/networks: dhcp-conf
spec:
  containers:
  - name: dhcppod
    command: ["/bin/bash", "-c", "sleep 2000000000000"]
    image: dougbtv/centos-network
EOF

Verify the results

I then verified that a DHCP address was assigned to the secondary interface:

[centos@kube-nonetwork-master ~]$ kubectl exec -it dhcppod -- ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth0@if12: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UP 
    link/ether 0a:58:0a:f4:01:08 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.244.1.8/24 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::f003:cff:fe19:1cb5/64 scope link tentative dadfailed 
       valid_lft forever preferred_lft forever
4: net1@if2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN 
    link/ether 9e:a7:91:3f:d2:65 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 192.168.122.74/24 scope global net1
       valid_lft forever preferred_lft forever
    inet6 fe80::9ca7:91ff:fe3f:d265/64 scope link 
       valid_lft forever preferred_lft forever