Auto detect default interface for VIP

cmd/kube-vip-manifests.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/kube-vip/kube-vip/pkg/kubevip"
+	"github.com/kube-vip/kube-vip/pkg/vip"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
@@ -43,6 +44,15 @@ var kubeManifestPod = &cobra.Command{
 		// TODO - A load of text detailing what's actually happening
 		kubevip.ParseEnvironment(&initConfig)
 		// TODO - check for certain things VIP/interfaces
+
+		if initConfig.AutoInterface {
+			defaultIF, err := vip.GetDefaultGatewayInterface()
+			if err != nil {
+				log.Fatalf("unable to set default interface -> [%v]", err)
+			}
+			initConfig.Interface = defaultIF.Name
+		}
+
 		if initConfig.Interface == "" {
 			cmd.Help()
 			log.Fatalln("No interface is specified for kube-vip to bind to")
@@ -69,6 +79,15 @@ var kubeManifestDaemon = &cobra.Command{
 		// TODO - A load of text detailing what's actually happening
 		kubevip.ParseEnvironment(&initConfig)
 		// TODO - check for certain things VIP/interfaces
+
+		if initConfig.AutoInterface {
+			defaultIF, err := vip.GetDefaultGatewayInterface()
+			if err != nil {
+				log.Fatalf("unable to set default interface -> [%v]", err)
+			}
+			initConfig.Interface = defaultIF.Name
+		}
+
 		if initConfig.Interface == "" {
 			cmd.Help()
 			log.Fatalln("No interface is specified for kube-vip to bind to")

cmd/kube-vip.go

@@ -10,6 +10,7 @@ import (
 	"github.com/kube-vip/kube-vip/pkg/kubevip"
 	"github.com/kube-vip/kube-vip/pkg/manager"
 	"github.com/kube-vip/kube-vip/pkg/packet"
+	"github.com/kube-vip/kube-vip/pkg/vip"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	log "github.com/sirupsen/logrus"
@@ -67,6 +68,8 @@ func init() {
 	initConfig.LocalPeer = *localpeer
 	//initConfig.Peers = append(initConfig.Peers, *localpeer)
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.Interface, "interface", "", "Name of the interface to bind to")
+	kubeVipCmd.PersistentFlags().BoolVar(&initConfig.AutoInterface, "autoInterface", false, "Name of the interface to bind to")
+
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.ServicesInterface, "serviceInterface", "", "Name of the interface to bind to (for services)")
 
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.VIP, "vip", "", "The Virtual IP address")
@@ -209,6 +212,19 @@ var kubeVipManager = &cobra.Command{
 		// Set the logging level for all subsequent functions
 		log.SetLevel(log.Level(logLevel))
 
+		if initConfig.AutoInterface {
+			defaultIF, err := vip.GetDefaultGatewayInterface()
+			if err != nil {
+				log.Fatalf("unable to set default interface -> [%v]", err)
+			}
+			initConfig.Interface = defaultIF.Name
+		}
+
+		if initConfig.Interface == "" {
+			cmd.Help()
+			log.Fatalln("No interface is specified for kube-vip to bind to")
+		}
+
 		go servePrometheusHTTPServer(cmd.Context(), PrometheusHTTPServerConfig{
 			Addr: initConfig.PrometheusHTTPServer,
 		})
@@ -240,7 +256,7 @@ var kubeVipManager = &cobra.Command{
 		// Define the new service manager
 		mgr, err := manager.New(configMap, &initConfig)
 		if err != nil {
-			log.Fatalf("%v", err)
+			log.Fatalf("configuring new Manager error -> %v", err)
 		}
 
 		prometheus.MustRegister(mgr.PrometheusCollector()...)
@@ -248,7 +264,7 @@ var kubeVipManager = &cobra.Command{
 		// Start the service manager, this will watch the config Map and construct kube-vip services for it
 		err = mgr.Start()
 		if err != nil {
-			log.Fatalf("%v", err)
+			log.Fatalf("starting new Manager error -> %v", err)
 		}
 	},
 }

pkg/kubevip/config_envvar.go

@@ -24,6 +24,9 @@ const (
 	//vipInterface - defines the interface that the vip should bind too
 	vipInterface = "vip_interface"
 
+	//vipAutoInterface - defines the interface that the vip should bind too
+	vipAutoInterface = "vip_autointerface"
+
 	//vipServicesInterface - defines the interface that the service vips should bind too
 	vipServicesInterface = "vip_servicesinterface"
 

pkg/kubevip/config_generator.go

@@ -34,6 +34,16 @@ func ParseEnvironment(c *Config) error {
 		c.Interface = env
 	}
 
+	// Find interface
+	env = os.Getenv(vipAutoInterface)
+	if env != "" {
+		b, err := strconv.ParseBool(env)
+		if err != nil {
+			return err
+		}
+		c.AutoInterface = b
+	}
+
 	// Find (services) interface
 	env = os.Getenv(vipServicesInterface)
 	if env != "" {
@@ -449,22 +459,37 @@ func parseEnvironmentLoadBalancer(c *Config) error {
 // generatePodSpec will take a kube-vip config and generate a Pod spec
 func generatePodSpec(c *Config, imageVersion string, inCluster bool) *corev1.Pod {
 	command := "manager"
+
 	// build environment variables
 	newEnvironment := []corev1.EnvVar{
 		{
 			Name:  vipArp,
 			Value: strconv.FormatBool(c.EnableARP),
 		},
-		{
-			Name:  vipInterface,
-			Value: c.Interface,
-		},
 		{
 			Name:  port,
 			Value: fmt.Sprintf("%d", c.Port),
 		},
 	}
 
+	if c.AutoInterface {
+		// build environment variables
+		autoInterface := []corev1.EnvVar{
+			{
+				Name:  vipAutoInterface,
+				Value: strconv.FormatBool(c.AutoInterface),
+			},
+		}
+		newEnvironment = append(newEnvironment, autoInterface...)
+	} else {
+		iface := []corev1.EnvVar{
+			{
+				Name:  vipInterface,
+				Value: c.Interface,
+			},
+		}
+		newEnvironment = append(newEnvironment, iface...)
+	}
 	// Detect if we should be using a seperate interface for sercices
 	if c.ServicesInterface != "" {
 		// build environment variables

pkg/kubevip/config_types.go

@@ -63,6 +63,9 @@ type Config struct {
 	// Interface is the network interface to bind to (default: First Adapter)
 	Interface string `yaml:"interface,omitempty"`
 
+	// AutoInterface is the network interface to bind to (Adapter is determined from Default Gateway)
+	AutoInterface bool `yaml:"interface,omitempty"`
+
 	// ServicesInterface is the network interface to bind to for services (optional)
 	ServicesInterface string `yaml:"servicesInterface,omitempty"`
 

pkg/manager/manager.go

@@ -93,7 +93,7 @@ func New(configMap string, config *kubevip.Config) (*Manager, error) {
 		// Second check in home directory for kube config
 		configPath = filepath.Join(os.Getenv("HOME"), ".kube", "config")
 		if fileExists(configPath) {
-			log.Debugf("Using external Kubernetes configuration from file [%s]", configPath)
+			log.Debugf("Using external Kubernetes configuration from home file [%s]", configPath)
 			cfg, err = clientcmd.BuildConfigFromFlags("", configPath)
 			if err != nil {
 				return nil, err

pkg/vip/util.go

@@ -4,8 +4,10 @@ import (
 	"fmt"
 	"net"
 	"strings"
+	"syscall"
 
 	"github.com/pkg/errors"
+	"github.com/vishvananda/netlink"
 )
 
 // LookupHost resolves dnsName and return an IP or an error
@@ -64,3 +66,22 @@ func GetFullMask(address string) (string, error) {
 	}
 	return "", fmt.Errorf("failed to parse %s as either IPv4 or IPv6", address)
 }
+
+// GetDefaultGatewayInterface return default gateway interface link
+func GetDefaultGatewayInterface() (*net.Interface, error) {
+	routes, err := netlink.RouteList(nil, syscall.AF_INET)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, route := range routes {
+		if route.Dst == nil || route.Dst.String() == "0.0.0.0/0" {
+			if route.LinkIndex <= 0 {
+				return nil, errors.New("Found default route but could not determine interface")
+			}
+			return net.InterfaceByIndex(route.LinkIndex)
+		}
+	}
+
+	return nil, errors.New("Unable to find default route")
+}