check microshift configured ip_family strategy

Signed-off-by: Evgeny Slutsky <[email protected]>

pkg/components/networking.go

@@ -8,6 +8,7 @@ import (
 	"github.com/openshift/microshift/pkg/assets"
 	"github.com/openshift/microshift/pkg/config"
 	"github.com/openshift/microshift/pkg/config/ovn"
+	"github.com/vishvananda/netlink"
 	"k8s.io/klog/v2"
 )
 
@@ -52,7 +53,16 @@ func startCNIPlugin(ctx context.Context, cfg *config.Config, kubeconfigPath stri
 		}
 	}
 
-	ovnConfig, err := ovn.NewOVNKubernetesConfigFromFileOrDefault(filepath.Dir(config.ConfigFile), cfg.MultiNode.Enabled)
+	ip_family := netlink.FAMILY_ALL
+	if cfg.IsIPv4() && !cfg.IsIPv6() {
+		ip_family = netlink.FAMILY_V4
+	}
+
+	if cfg.IsIPv6() && !cfg.IsIPv4() {
+		ip_family = netlink.FAMILY_V6
+	}
+
+	ovnConfig, err := ovn.NewOVNKubernetesConfigFromFileOrDefault(filepath.Dir(config.ConfigFile), cfg.MultiNode.Enabled, ip_family)
 	if err != nil {
 		return fmt.Errorf("failed to create OVN-K configuration from %q: %w", config.ConfigFile, err)
 	}

pkg/config/ovn/ovn.go

@@ -9,6 +9,7 @@ import (
 	"regexp"
 
 	"github.com/openshift/microshift/pkg/util"
+	"github.com/vishvananda/netlink"
 	"k8s.io/klog/v2"
 	"sigs.k8s.io/yaml"
 )
@@ -55,16 +56,29 @@ func (o *OVNKubernetesConfig) validateOVSBridge() error {
 
 // getClusterMTU retrieves MTU from the default route network interface,
 // and falls back to use 1500 when unable to get the mtu or less than 0.
-func (o *OVNKubernetesConfig) getClusterMTU(multinode bool) {
+func (o *OVNKubernetesConfig) getClusterMTU(multinode bool, ip_family int) {
 	klog.Infof("getClusterMTU: finding default route interface")
-	link, err := util.FindDefaultRouteIface()
+	o.MTU = defaultMTU
+
+	// if configure both IPV4 and IPV6 check the smallest
+	//nolint:nestif
+	if ip_family == netlink.FAMILY_ALL {
+		mtu, err := util.FindDefaultRouteMinMTU()
+		if err == nil {
+			o.MTU = mtu
+		} else {
+			klog.Infof("getClusterMTU: error %s.", err)
+		}
+		klog.Infof("getClusterMTU: using Dual stack MTU discovery found - %d", mtu)
 
-	if err == nil && link.MTU > 0 {
-		klog.Infof("getClusterMTU: Using Interface %s with MTU %d as source default route.", link.Name, link.MTU)
-		o.MTU = link.MTU
 	} else {
-		klog.Infof("getClusterMTU: Couldnt extract MTU from the default route interface , Using Default MTU.")
-		o.MTU = defaultMTU
+		mtu, err := util.FindDefaultRouteMTU(ip_family)
+		if err == nil {
+			o.MTU = mtu
+		} else {
+			klog.Infof("getClusterMTU: error %s.", err)
+		}
+		klog.Infof("getClusterMTU: using ip version: %d stack MTU discovery found - with MTU %d", ip_family, mtu)
 	}
 
 	if multinode {
@@ -73,12 +87,12 @@ func (o *OVNKubernetesConfig) getClusterMTU(multinode bool) {
 }
 
 // withDefaults returns the default values when ovn.yaml is not provided
-func (o *OVNKubernetesConfig) withDefaults(multinode bool) *OVNKubernetesConfig {
-	o.getClusterMTU(multinode)
+func (o *OVNKubernetesConfig) withDefaults(multinode bool, ip_family int) *OVNKubernetesConfig {
+	o.getClusterMTU(multinode, ip_family)
 	return o
 }
 
-func newOVNKubernetesConfigFromFile(path string, multinode bool) (*OVNKubernetesConfig, error) {
+func newOVNKubernetesConfigFromFile(path string, multinode bool, ip_family int) (*OVNKubernetesConfig, error) {
 	o := new(OVNKubernetesConfig)
 	buf, err := os.ReadFile(path)
 	if err != nil {
@@ -91,24 +105,24 @@ func newOVNKubernetesConfigFromFile(path string, multinode bool) (*OVNKubernetes
 	}
 	// in case mtu is not defined
 	if o.MTU == 0 {
-		o.getClusterMTU(multinode)
+		o.getClusterMTU(multinode, ip_family)
 	}
 	klog.Infof("parsed OVNKubernetes config from file %q: %+v", path, o)
 
 	return o, nil
 }
 
-func NewOVNKubernetesConfigFromFileOrDefault(dir string, multinode bool) (*OVNKubernetesConfig, error) {
+func NewOVNKubernetesConfigFromFileOrDefault(dir string, multinode bool, ip_family int) (*OVNKubernetesConfig, error) {
 	path := filepath.Join(dir, ovnConfigFileName)
 	if _, err := os.Stat(path); err != nil {
 		if errors.Is(err, os.ErrNotExist) {
 			klog.Infof("OVNKubernetes config file not found, assuming default values")
-			return new(OVNKubernetesConfig).withDefaults(multinode), nil
+			return new(OVNKubernetesConfig).withDefaults(multinode, ip_family), nil
 		}
 		return nil, fmt.Errorf("failed to get OVNKubernetes config file: %v", err)
 	}
 
-	o, err := newOVNKubernetesConfigFromFile(path, multinode)
+	o, err := newOVNKubernetesConfigFromFile(path, multinode, ip_family)
 	if err == nil {
 		return o, nil
 	}

pkg/config/ovn/ovn_test.go

@@ -2,6 +2,8 @@ package ovn
 
 import (
 	"testing"
+
+	"github.com/vishvananda/netlink"
 )
 
 // tests to make sure that the config file is parsed correctly
@@ -15,7 +17,7 @@ func TestNewOVNKubernetesConfigFromFileOrDefault(t *testing.T) {
 	}
 
 	for _, tt := range ttests {
-		_, err := NewOVNKubernetesConfigFromFileOrDefault(tt.configFile, false)
+		_, err := NewOVNKubernetesConfigFromFileOrDefault(tt.configFile, false, netlink.FAMILY_V4)
 		if (err != nil) != (tt.err != nil) {
 			t.Errorf("NewOVNKubernetesConfigFromFileOrDefault() error = %v, wantErr %v", err, tt.err)
 		}

pkg/util/net.go

@@ -22,6 +22,7 @@ import (
 	tcpnet "net"
 	"net/http"
 	"os"
+	"slices"
 	"sort"
 	"strings"
 	"time"
@@ -275,16 +276,40 @@ func GetHostIPv6(ipHint string) (string, error) {
 	return "", fmt.Errorf("unable to find host IPv6 address")
 }
 
-// Find the Default route Interface based on ipv4 or ipv6 routes.
-func FindDefaultRouteIface() (iface *tcpnet.Interface, err error) {
-	// first try IPv4
-	parsedStruct, err := findDefaultRouteForFamily(netlink.FAMILY_V4)
-	if err != nil {
-		// then try IPv6
-		parsedStruct, err = findDefaultRouteForFamily(netlink.FAMILY_V6)
+func FindDefaultRouteMinMTU() (mtu int, err error) {
+	ip_families := []int{netlink.FAMILY_V4, netlink.FAMILY_V6}
+
+	mtu_slice := []int{}
+
+	for _, ip_family := range ip_families {
+		new_mtu, err := FindDefaultRouteMTU(ip_family)
 		if err != nil {
-			return nil, err
+			continue
 		}
+		mtu_slice = append(mtu_slice, new_mtu)
+	}
+	if len(mtu_slice) > 0 {
+		return slices.Min(mtu_slice), nil
+	}
+	return 0, fmt.Errorf("could not find minimal MTU")
+}
+
+func FindDefaultRouteMTU(ip_family int) (mtu int, err error) {
+	link, err := FindDefaultRouteIface(ip_family)
+	if err != nil && link.MTU == 0 {
+		return 0, err
+	}
+
+	klog.Infof("using IP %d on Interface %s with MTU %d ", ip_family, link.Name, link.MTU)
+
+	return link.MTU, nil
+}
+
+// Find the Default route Interface based on ipv4 or ipv6 routes.
+func FindDefaultRouteIface(ip_family int) (iface *tcpnet.Interface, err error) {
+	parsedStruct, err := findDefaultRouteForFamily(ip_family)
+	if err != nil {
+		return nil, err
 	}
 
 	iface, err = tcpnet.InterfaceByName(parsedStruct.Iface)