fact(GetMTUFromNodeIP): move up a layer of abstraction

This function is useful for more than just the NRC, move it up a layer
into the global utils so it can be used from multiple controllers.

Author: aauren

pkg/controllers/routing/network_routes_controller.go

@@ -215,7 +215,7 @@ func (nrc *NetworkRoutingController) Run(healthChan chan<- *healthcheck.Controll
 	}
 
 	if nrc.autoMTU {
-		mtu, err := getMTUFromNodeIP(nrc.nodeIP, nrc.enableOverlays)
+		mtu, err := utils.GetMTUFromNodeIP(nrc.nodeIP, nrc.enableOverlays)
 		if err != nil {
 			klog.Errorf("Failed to find MTU for node IP: %s for intelligently setting the kube-bridge MTU due to %s.", nrc.nodeIP, err.Error())
 		}
@@ -373,7 +373,7 @@ func (nrc *NetworkRoutingController) updateCNIConfig() {
 }
 
 func (nrc *NetworkRoutingController) autoConfigureMTU() error {
-	mtu, err := getMTUFromNodeIP(nrc.nodeIP, nrc.enableOverlays)
+	mtu, err := utils.GetMTUFromNodeIP(nrc.nodeIP, nrc.enableOverlays)
 	if err != nil {
 		return fmt.Errorf("failed to generate MTU: %s", err.Error())
 	}

pkg/controllers/routing/utils.go

@@ -109,29 +109,6 @@ func getNodeSubnet(nodeIP net.IP) (net.IPNet, string, error) {
 	return net.IPNet{}, "", errors.New("failed to find interface with specified node ip")
 }
 
-func getMTUFromNodeIP(nodeIP net.IP, overlayEnabled bool) (int, error) {
-	links, err := netlink.LinkList()
-	if err != nil {
-		return 0, errors.New("failed to get list of links")
-	}
-	for _, link := range links {
-		addresses, err := netlink.AddrList(link, netlink.FAMILY_ALL)
-		if err != nil {
-			return 0, errors.New("failed to get list of addr")
-		}
-		for _, addr := range addresses {
-			if addr.IPNet.IP.Equal(nodeIP) {
-				linkMTU := link.Attrs().MTU
-				if overlayEnabled {
-					return linkMTU - 20, nil // -20 to accommodate IPIP header
-				}
-				return linkMTU, nil
-			}
-		}
-	}
-	return 0, errors.New("failed to find interface with specified node ip")
-}
-
 // generateTunnelName will generate a name for a tunnel interface given a node IP
 // for example, if the node IP is 10.0.0.1 the tunnel interface will be named tun-10001
 // Since linux restricts interface names to 15 characters, if length of a node IP

pkg/utils/node.go

@@ -7,6 +7,8 @@ import (
 	"net"
 	"os"
 
+	"github.com/vishvananda/netlink"
+
 	apiv1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes"
@@ -59,3 +61,27 @@ func GetNodeIP(node *apiv1.Node) (net.IP, error) {
 	}
 	return nil, errors.New("host IP unknown")
 }
+
+// GetMTUFromNodeIP returns the MTU by detecting it from the IP on the node and figuring in tunneling configurations
+func GetMTUFromNodeIP(nodeIP net.IP, overlayEnabled bool) (int, error) {
+	links, err := netlink.LinkList()
+	if err != nil {
+		return 0, errors.New("failed to get list of links")
+	}
+	for _, link := range links {
+		addresses, err := netlink.AddrList(link, netlink.FAMILY_ALL)
+		if err != nil {
+			return 0, errors.New("failed to get list of addr")
+		}
+		for _, addr := range addresses {
+			if addr.IPNet.IP.Equal(nodeIP) {
+				linkMTU := link.Attrs().MTU
+				if overlayEnabled {
+					return linkMTU - 20, nil // -20 to accommodate IPIP header
+				}
+				return linkMTU, nil
+			}
+		}
+	}
+	return 0, errors.New("failed to find interface with specified node IP")
+}