Allow node IP to be passed as optional config for kubelet

cmd/kubelet/app/server.go

@@ -158,6 +158,7 @@ type KubeletServer struct {
 	// Pull images one at a time.
 	SerializeImagePulls        bool
 	ExperimentalFlannelOverlay bool
+	NodeIP                     net.IP
 }
 
 // bootstrapping interface for kubelet, targets the initialization protocol
@@ -349,6 +350,7 @@ func (s *KubeletServer) AddFlags(fs *pflag.FlagSet) {
 	fs.IntVar(&s.KubeAPIBurst, "kube-api-burst", s.KubeAPIBurst, "Burst to use while talking with kubernetes apiserver")
 	fs.BoolVar(&s.SerializeImagePulls, "serialize-image-pulls", s.SerializeImagePulls, "Pull images one at a time. We recommend *not* changing the default value on nodes that run docker daemon with version < 1.9 or an Aufs storage backend. Issue #10959 has more details. [default=true]")
 	fs.BoolVar(&s.ExperimentalFlannelOverlay, "experimental-flannel-overlay", s.ExperimentalFlannelOverlay, "Experimental support for starting the kubelet with the default overlay network (flannel). Assumes flanneld is already running in client mode. [default=false]")
+	fs.IPVar(&s.NodeIP, "node-ip", s.NodeIP, "IP address of the node. If set, kubelet will use this IP address for the node")
 }
 
 // UnsecuredKubeletConfig returns a KubeletConfig suitable for being run, or an error if the server setup
@@ -488,6 +490,7 @@ func (s *KubeletServer) UnsecuredKubeletConfig() (*KubeletConfig, error) {
 		VolumePlugins:                  ProbeVolumePlugins(s.VolumePluginDir),
 
 		ExperimentalFlannelOverlay: s.ExperimentalFlannelOverlay,
+		NodeIP: s.NodeIP,
 	}, nil
 }
 
@@ -964,6 +967,7 @@ type KubeletConfig struct {
 	VolumePlugins                  []volume.VolumePlugin
 
 	ExperimentalFlannelOverlay bool
+	NodeIP                     net.IP
 }
 
 func CreateAndInitKubelet(kc *KubeletConfig) (k KubeletBootstrap, pc *config.PodConfig, err error) {
@@ -1047,6 +1051,7 @@ func CreateAndInitKubelet(kc *KubeletConfig) (k KubeletBootstrap, pc *config.Pod
 		kc.SerializeImagePulls,
 		kc.ContainerManager,
 		kc.ExperimentalFlannelOverlay,
+		kc.NodeIP,
 	)
 
 	if err != nil {

pkg/kubelet/kubelet.go

@@ -197,6 +197,7 @@ func NewMainKubelet(
 	serializeImagePulls bool,
 	containerManager cm.ContainerManager,
 	flannelExperimentalOverlay bool,
+	nodeIP net.IP,
 ) (*Kubelet, error) {
 
 	if rootDirectory == "" {
@@ -313,10 +314,17 @@ func NewMainKubelet(
 		containerManager:               containerManager,
 		flannelExperimentalOverlay:     flannelExperimentalOverlay,
 		flannelHelper:                  NewFlannelHelper(),
+		nodeIP:                         nodeIP,
 	}
 	if klet.flannelExperimentalOverlay {
 		glog.Infof("Flannel is in charge of podCIDR and overlay networking.")
 	}
+	if klet.nodeIP != nil {
+		if err := klet.validateNodeIP(); err != nil {
+			return nil, err
+		}
+		glog.Infof("Using node IP: %q", klet.nodeIP.String())
+	}
 	if plug, err := network.InitNetworkPlugin(networkPlugins, networkPluginName, &networkHost{klet}); err != nil {
 		return nil, err
 	} else {
@@ -643,6 +651,42 @@ type Kubelet struct {
 	// on the fly if we're confident the dbus connetions it opens doesn't
 	// put the system under duress.
 	flannelHelper *FlannelHelper
+
+	// If non-nil, use this IP address for the node
+	nodeIP net.IP
+}
+
+// Validate given node IP belongs to the current host
+func (kl *Kubelet) validateNodeIP() error {
+	if kl.nodeIP == nil {
+		return nil
+	}
+
+	// Honor IP limitations set in setNodeStatus()
+	if kl.nodeIP.IsLoopback() {
+		return fmt.Errorf("nodeIP can't be loopback address")
+	}
+	if kl.nodeIP.To4() == nil {
+		return fmt.Errorf("nodeIP must be IPv4 address")
+	}
+
+	addrs, err := net.InterfaceAddrs()
+	if err != nil {
+		return err
+	}
+	for _, addr := range addrs {
+		var ip net.IP
+		switch v := addr.(type) {
+		case *net.IPNet:
+			ip = v.IP
+		case *net.IPAddr:
+			ip = v.IP
+		}
+		if ip != nil && ip.Equal(kl.nodeIP) {
+			return nil
+		}
+	}
+	return fmt.Errorf("Node IP: %q not found in the host's network interfaces", kl.nodeIP.String())
 }
 
 func (kl *Kubelet) allSourcesReady() bool {
@@ -2663,8 +2707,12 @@ func (kl *Kubelet) setNodeAddress(node *api.Node) error {
 		}
 		node.Status.Addresses = nodeAddresses
 	} else {
-		addr := net.ParseIP(kl.hostname)
-		if addr != nil {
+		if kl.nodeIP != nil {
+			node.Status.Addresses = []api.NodeAddress{
+				{Type: api.NodeLegacyHostIP, Address: kl.nodeIP.String()},
+				{Type: api.NodeInternalIP, Address: kl.nodeIP.String()},
+			}
+		} else if addr := net.ParseIP(kl.hostname); addr != nil {
 			node.Status.Addresses = []api.NodeAddress{
 				{Type: api.NodeLegacyHostIP, Address: addr.String()},
 				{Type: api.NodeInternalIP, Address: addr.String()},

pkg/kubelet/kubelet_test.go

@@ -787,6 +787,46 @@ func TestGetContainerInfoWithNoContainers(t *testing.T) {
 	mockCadvisor.AssertExpectations(t)
 }
 
+func TestNodeIPParam(t *testing.T) {
+	testKubelet := newTestKubelet(t)
+	kubelet := testKubelet.kubelet
+	tests := []struct {
+		nodeIP   string
+		success  bool
+		testName string
+	}{
+		{
+			nodeIP:   "",
+			success:  true,
+			testName: "IP not set",
+		},
+		{
+			nodeIP:   "127.0.0.1",
+			success:  false,
+			testName: "loopback address",
+		},
+		{
+			nodeIP:   "FE80::0202:B3FF:FE1E:8329",
+			success:  false,
+			testName: "IPv6 address",
+		},
+		{
+			nodeIP:   "1.2.3.4",
+			success:  false,
+			testName: "IPv4 address that doesn't belong to host",
+		},
+	}
+	for _, test := range tests {
+		kubelet.nodeIP = net.ParseIP(test.nodeIP)
+		err := kubelet.validateNodeIP()
+		if err != nil && test.success {
+			t.Errorf("Test: %s, expected no error but got: %v", test.testName, err)
+		} else if err == nil && !test.success {
+			t.Errorf("Test: %s, expected an error", test.testName)
+		}
+	}
+}
+
 func TestGetContainerInfoWithNoMatchingContainers(t *testing.T) {
 	testKubelet := newTestKubelet(t)
 	fakeRuntime := testKubelet.fakeRuntime