Enable Platform9 DHCP

Platform9 DHCP is the recommended DHCP (vs whereabouts ) for KubeVirt installations. When leveraging whereabouts there is an issue that occurs during Live Migrations where the Virtual Machine IP address will change when migrated to the target host.

What is Platform9 DHCP

Platform9 created an alternative to whereabouts for the KubeVirt use case by having a DHCP server running inside the pod/vm to cater to the DHCP requests from the virtual machine instance (not the pod in the case of Kubevirt). Multus Network Attachment Definition will use the DHCP server, and there is no need to specify the IPAM plugin. The client/consumer VM will need the dhclient for sending DHCP requests.

Prerequisites

Kubevirt
Advanced Networking Operator (Luigi)
Kubemacpool

Enabling the Platform9 DHCP Addon:

Using the Advanced Networking Operator (Luigi) add-on, enable dhcpController addon by creating a Network Plugin resource as shown:

YAML
    
 
apiVersion: plumber.k8s.pf9.io/v1kind: NetworkPluginsmetadata:  name: networkplugins-sample-nosriovspec:  plugins:    ...    dhcpController: {}
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This creates the dhcp-controller-system namespace with the controller for the dnsmasq. This also installs Kubemacpool in dhcp-controller-system namespace.
Create HostNetoworkTemplate & NetworkAttachmentDefinition .

YAML
    
 
apiVersion: plumber.k8s.pf9.io/v1kind: HostNetworkTemplatemetadata:  name: ovs-br03-configspec:  # Add fields here  ovsConfig:    - bridgeName: "ovs-br03"      nodeInterface: "ens5"
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YAML
    
 
---apiVersion: "k8s.cni.cncf.io/v1"kind: NetworkAttachmentDefinitionmetadata:  name: ovs-dnsmasq-test-woipam  annotations:    k8s.v1.cni.cncf.io/resourceName: ovs-cni.network.kubevirt.io/ovs-br03spec:  config: '{      "cniVersion": "0.3.1",      "type": "ovs",      "name": "ovs-dnsmasq-test-woipam",      "bridge": "ovs-br03"    }'
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NetworkAttachmentDefinition used with Platform9 IPAM omits the ipam section in the config, which is present when whereabouts is used as IPAM. Platform9 IPAM also supports OVS-DPDK networks.
Create a DHCP Server

YAML
    
 
apiVersion: dhcp.plumber.k8s.pf9.io/v1alpha1 kind: DHCPServermetadata:  name: dhcpserver-samplespec:  networks:    - networkName: ovs-dnsmasq-test-woipam      interfaceIp: 192.168.15.14/24      leaseDuration: 10m      vlanId: vlan1      cidr:        range: 192.168.15.0/24        range_start: 192.168.15.30        range_end: 192.168.15.100        gateway: 192.168.15.1
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About the fields

a . Name: Name of the DHCPServer. Configurations of dnsmasq will be generated in a Configmap with the same name

b. networks: list of all networks that this pod will serve

networkName: Name of NetworkAttachmentDefinition. Should not have dhcp plugin enabled.
interfaceIp: IP address that the pod will be allocated. Must have prefix to ensure proper routes are added.
leaseDuration: Duration the leases offered should be valid for. Provide in valid formats for dnsmasq (eg: 10m, 5h, etc). Defaults to 1h
vlanId: Dnsmasq network identifier. Used as an identifier while restoring IPs.
cidr:range_start, range_end, gateway are optional. range is compulsory. If range start and end are provided, they will be used in place of the default start and end.

A configmap is generated based on the DHCPServer. This is a conf file for dnsmasq. It can be overridden by creating a valid configmap with the same name as that of the DHCPServer.

For any specific configurations, you can provide your own configmap. Create a configmap with valid dnsmasq.conf parameters. Along with this, dhcp-range must be in one of these two formats

dhcp-range=<start_IP>,<end_ip>,<netmask>,<leasetime>
dhcp-range=<vlanID>,<start_ip>,<end_ip>,<netmask>,<leasetime>

Sample VM yaml to apply

YAML
    
 
apiVersion: kubevirt.io/v1kind: VirtualMachinemetadata:  name: test-ovs-interface-1spec:  running: true  template:    metadata:      labels:        kubevirt.io/size: small        kubevirt.io/domain: testvm    spec:      domain:        devices:          disks:            - name: containerdisk              disk:                bus: virtio            - name: cloudinitdisk              disk:                bus: virtio          interfaces:          - name: default            masquerade: {}          - bridge: {}            name: ovs-br03        resources:          requests:            memory: 1024M      hostname: myhostname1      networks:      - name: default        pod: {}      - name: ovs-br03        multus:          networkName: ovs-dnsmasq-test-woipam      volumes:        - name: containerdisk          containerDisk:            image: quay.io/kubevirt/fedora-cloud-container-disk-demo:latest        - name: cloudinitdisk          cloudInitNoCloud:            userData: |-              #cloud-config              password: fedora              chpasswd: { expire: False }
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Sample StatefulSet YAML to apply.

YAML
    
 
---apiVersion: v1kind: Servicemetadata:  name: headlessspec:  ports:  - port: 80    name: web  selector:    app: test  clusterIP: None---apiVersion: apps/v1kind: StatefulSetmetadata:  name: test2spec:  replicas: 1  selector:    matchLabels:      app: test2  serviceName: headless  template:    metadata:      labels:        app: test2      annotations:        k8s.v1.cni.cncf.io/networks: '[       { "name" : "ovs-dnsmasq-test-woipam"}      ]'    spec:      securityContext:        runAsUser: 1000        runAsGroup: 3000      containers:      - name: test2        image: alpine        ports:        - containerPort: 80          name: web        command: ["/bin/sh"]        args:          - -c          - >-              udhcpc -i net1              tail -f /dev/null        securityContext:          runAsUser: 0          #allowPrivilegeEscalation: false          capabilities:            add: ["NET_ADMIN"]
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An IPAllocation is made for every lease stored in the server. It is used to restore leases back to the DHCPServer. Leases are only restored to the vlanID mentioned. Lease will expire at leaseExpiry. Sample of how an IPAllocation looks

YAML
    
 
apiVersion: dhcp.plumber.k8s.pf9.io/v1alpha1kind: IPAllocationmetadata:  creationTimestamp: "2022-11-09T12:18:58Z"  generation: 1  name: 192.168.15.90  namespace: default  resourceVersion: "189858"  uid: 70ee31e1-d3b4-47f0-be92-0eb03cd33d57spec:  entityRef: test-ovs-interface-1  leaseExpiry: "1667998138"  macAddr: 1e:8d:f0:c4:6c:8e  vlanId: vlan3
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Last updated on May 3, 2023

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