Add VirtletForceDHCPNetworkConfig annotation

docs/docs/reference/cloud-init.md

@@ -344,6 +344,21 @@ use the following construct in the pod annotations:
 VirtletCloudInitUserDataScript: "@virtlet-mount-script@"
 ```
 
+# Disabling cloud-init based network configuration
+
+As the network configuration is applied only upon the first startup,
+it's not used when
+[persistent root filesystem](../volumes/#persistent-root-filesystem)
+is used, so new network configuration can be passed using DHCP to a
+new pod with the same rootfs. Moreover, in some cases it may be
+desirable to force Virtlet to use DHCP instead of cloud-init based
+network config. To do so, you need to add the following annotation
+to the pod:
+
+```yaml
+VirtletForceDHCPNetworkConfig: "true"
+```
+
 # Additional links
 
 These links may help to understand some basics about cloud-init:

pkg/libvirttools/TestCloudInitGenerator__pod_with_forced_dhcp_network_config.out.yaml

@@ -0,0 +1,5 @@
+meta-data:
+  instance-id: foo.default
+  local-hostname: foo
+network-config: null
+user-data: null

pkg/libvirttools/TestContainerLifecycle.out.yaml

@@ -115,6 +115,7 @@
         CPUModel: ""
         CPUSetting: null
         DiskDriver: scsi
+        ForceDHCPNetworkConfig: false
         InjectedFiles: null
         MetaData: null
         RootVolumeSize: 0
@@ -173,6 +174,7 @@
         CPUModel: ""
         CPUSetting: null
         DiskDriver: scsi
+        ForceDHCPNetworkConfig: false
         InjectedFiles: null
         MetaData: null
         RootVolumeSize: 0
@@ -226,6 +228,7 @@
         CPUModel: ""
         CPUSetting: null
         DiskDriver: scsi
+        ForceDHCPNetworkConfig: false
         InjectedFiles: null
         MetaData: null
         RootVolumeSize: 0

pkg/libvirttools/TestDomainForcedShutdown.out.yaml

@@ -131,6 +131,7 @@
         CPUModel: ""
         CPUSetting: null
         DiskDriver: scsi
+        ForceDHCPNetworkConfig: false
         InjectedFiles: null
         MetaData: null
         RootVolumeSize: 0

pkg/libvirttools/cloudinit.go

@@ -177,9 +177,11 @@ func (g *CloudInitGenerator) generateUserData(volumeMap diskPathMap) ([]byte, er
 }
 
 func (g *CloudInitGenerator) generateNetworkConfiguration() ([]byte, error) {
-	if g.config.RootVolumeDevice() != nil {
-		// We don't use network config with persistent rootfs
-		// for now because with some cloud-init
+	if g.config.ParsedAnnotations.ForceDHCPNetworkConfig || g.config.RootVolumeDevice() != nil {
+		// Don't use cloud-init network config if asked not
+		// to do so.
+		// Also, we don't use network config with persistent
+		// rootfs for now because with some cloud-init
 		// implementations it's applied only once
 		return nil, nil
 	}

pkg/libvirttools/cloudinit_test.go

@@ -388,6 +388,18 @@ func TestCloudInitGenerator(t *testing.T) {
 			// make sure network config is null for the persistent rootfs case
 			verifyNetworkConfig: true,
 		},
+		{
+			name: "pod with forced dhcp network config",
+			config: &types.VMConfig{
+				PodName:           "foo",
+				PodNamespace:      "default",
+				ParsedAnnotations: &types.VirtletAnnotations{ForceDHCPNetworkConfig: true},
+			},
+			verifyMetaData: true,
+			verifyUserData: true,
+			// make sure network config is null
+			verifyNetworkConfig: true,
+		},
 		{
 			name: "injecting mount script into user data script",
 			config: &types.VMConfig{

pkg/metadata/types/annotations.go

@@ -45,6 +45,7 @@ const (
 	sshKeysKeyName                    = "VirtletSSHKeys"
 	chown9pfsMountsKeyName            = "VirtletChown9pfsMounts"
 	systemUUIDKeyName                 = "VirtletSystemUUID"
+	forceDHCPNetworkConfigKeyName     = "VirtletForceDHCPNetworkConfig"
 	// CloudInitUserDataSourceKeyName is the name of user data source key in the pod annotations.
 	CloudInitUserDataSourceKeyName = "VirtletCloudInitUserDataSource"
 	// SSHKeySourceKeyName is the name of ssh key source key in the pod annotations.
@@ -119,6 +120,10 @@ type VirtletAnnotations struct {
 	// SystemUUID specifies fixed SMBIOS UUID to be used for the domain.
 	// If not set, the SMBIOS UUID will be automatically generated from the Pod ID.
 	SystemUUID *uuid.UUID
+	// ForceDHCPNetworkConfig prevents Virtlet from using Cloud-Init based network
+	// configuration and makes it only provide DHCP. Note that this will
+	// not work for multi-CNI configuration.
+	ForceDHCPNetworkConfig bool
 }
 
 // ExternalDataLoader is used to load extra pod data from
@@ -318,5 +323,13 @@ func (va *VirtletAnnotations) parsePodAnnotations(ns string, podAnnotations map[
 		}
 	}
 
+	if podAnnotations[chown9pfsMountsKeyName] == "true" {
+		va.VirtletChown9pfsMounts = true
+	}
+
+	if podAnnotations[forceDHCPNetworkConfigKeyName] == "true" {
+		va.ForceDHCPNetworkConfig = true
+	}
+
 	return nil
 }

pkg/metadata/types/annotations_test.go

@@ -163,6 +163,18 @@ func TestVirtletAnnotations(t *testing.T) {
 				CDImageType: "nocloud",
 			},
 		},
+		{
+			name: "force DHCP network config",
+			annotations: map[string]string{
+				"VirtletForceDHCPNetworkConfig": "true",
+			},
+			va: &VirtletAnnotations{
+				VCPUCount:              1,
+				DiskDriver:             "scsi",
+				CDImageType:            "nocloud",
+				ForceDHCPNetworkConfig: true,
+			},
+		},
 		// bad metadata items follow
 		{
 			name:        "bad vcpu count",