Merge pull request #1639 from gabrielstedman/feat/allow-iface-not-up

Add an opt-in flag/env var to allow kube-vip to start when interface exists but is not up

cmd/kube-vip.go

@@ -60,6 +60,7 @@ func init() {
 	// Basic flags
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.Interface, "interface", "", "Name of the interface to bind to")
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.ServicesInterface, "serviceInterface", "", "Name of the interface to bind to (for services)")
+	kubeVipCmd.PersistentFlags().BoolVar(&initConfig.AllowInterfaceNotUp, "allowInterfaceNotUp", false, "Allow kube-vip to start even if the interface is not up")
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.VIP, "vip", "", "The Virtual IP address")
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.VIPSubnet, "vipSubnet", "", "The Virtual IP address subnet e.g. /32 /24 /8 etc.. (Default to 32 for IPv4 and 128 for IPv6)")
 	kubeVipCmd.PersistentFlags().StringVar(&initConfig.NodeName, "nodeName", "", "Name to be used for lease holder. Must be unique for each node/instance")

pkg/kubevip/config_environment.go

@@ -77,6 +77,16 @@ func ParseEnvironment(c *Config) error {
 		c.ServicesInterface = env
 	}
 
+	// Tolerate a down interface
+	env = os.Getenv(vipAllowInterfaceNotUp)
+	if env != "" {
+		b, err := strconv.ParseBool(env)
+		if err != nil {
+			return err
+		}
+		c.AllowInterfaceNotUp = b
+	}
+
 	// Find Kubernetes Leader Election configuration
 	env = os.Getenv(vipLeaderElection)
 	if env != "" {

pkg/kubevip/config_envvar.go

@@ -51,6 +51,9 @@ const (
 	// vipServicesInterface - defines the interface that the service vips should bind too
 	vipServicesInterface = "vip_servicesinterface"
 
+	// vipAllowInterfaceNotUp - defines if kube-vip should tolerate a down interface
+	vipAllowInterfaceNotUp = "vip_allow_interface_not_up"
+
 	// vipSubnet - defines the subnet that the vip will use
 	vipSubnet = "vip_subnet"
 

pkg/kubevip/config_generator.go

@@ -239,6 +239,17 @@ func generatePodSpec(c *Config, image, imageVersion string, inCluster bool) (*co
 		newEnvironment = append(newEnvironment, svcInterface...)
 	}
 
+	// Tolerate a down interface
+	if c.AllowInterfaceNotUp {
+		allowIface := []corev1.EnvVar{
+			{
+				Name:  vipAllowInterfaceNotUp,
+				Value: strconv.FormatBool(c.AllowInterfaceNotUp),
+			},
+		}
+		newEnvironment = append(newEnvironment, allowIface...)
+	}
+
 	// If a subnet is required for the VIP
 	if c.VIPSubnet != "" {
 		// build environment variables

pkg/kubevip/config_manager.go

@@ -1,6 +1,7 @@
 package kubevip
 
 import (
+	"errors"
 	"fmt"
 
 	log "log/slog"
@@ -12,6 +13,8 @@ const (
 	Auto = "auto"
 )
 
+var ErrInterfaceNotUp = errors.New("interface is not up")
+
 func (c *Config) CheckSubnetExists() error {
 	if c.VIPSubnet == "" && c.VIP != "" && c.Address == "" {
 		return fmt.Errorf("vip_subnet must be set if using vip_address instead of address environment variable")
@@ -23,15 +26,23 @@ func (c *Config) CheckSubnetExists() error {
 func (c *Config) CheckInterface() error {
 	if c.Interface != "" {
 		if err := isValidInterface(c.Interface); err != nil {
+			if errors.Is(err, ErrInterfaceNotUp) && c.AllowInterfaceNotUp {
+				log.Warn("interface is not up, continuing as allowInterfaceNotUp is set", "interface", c.Interface)
+			} else {
 				return fmt.Errorf("%s is not valid interface, reason: %w", c.Interface, err)
 			}
 		}
+	}
 
 	if c.ServicesInterface != "" {
 		if err := isValidInterface(c.ServicesInterface); err != nil {
+			if errors.Is(err, ErrInterfaceNotUp) && c.AllowInterfaceNotUp {
+				log.Warn("interface is not up, continuing as allowInterfaceNotUp is set", "interface", c.ServicesInterface)
+			} else {
 				return fmt.Errorf("%s is not valid interface, reason: %w", c.ServicesInterface, err)
 			}
 		}
+	}
 
 	return nil
 }
@@ -58,7 +69,7 @@ func isValidInterface(iface string) error {
 			iface,
 		)
 	} else if attrs.OperState != netlink.OperUp {
-		return fmt.Errorf("%s is not up", iface)
+		return fmt.Errorf("%s %w", iface, ErrInterfaceNotUp)
 	}
 
 	return nil

pkg/kubevip/config_types.go

@@ -115,6 +115,9 @@ type Config struct {
 	// ServicesInterface is the network interface to bind to for services (optional)
 	ServicesInterface string `yaml:"servicesInterface,omitempty"`
 
+	// AllowInterfaceNotUp allows kube-vip to start even when the interface is not up
+	AllowInterfaceNotUp bool `yaml:"allowInterfaceNotUp,omitempty"`
+
 	// EnableLoadBalancer, provides the flexibility to make the load-balancer optional
 	EnableLoadBalancer bool `yaml:"enableLoadBalancer"`