always select non link-local interface, fixes #11961

The API server will refuse to start if a link-local IP address is selected, however, ChooseNetworkInterface can still select link-local network routes. This causes a startup failure on platforms like DigitalOcean that use a link-local route to fetch metadata.

Signed-off-by: Christian Stewart <christian@paral.in>

pkg/util/util.go

@@ -321,7 +321,7 @@ func isInterfaceUp(intf *net.Interface) bool {
 }
 
 //getFinalIP method receives all the IP addrs of a Interface
-//and returns a nil if the address is Loopback , Ipv6  or nil.
+//and returns a nil if the address is Loopback, Ipv6, link-local or nil.
 //It returns a valid IPv4 if an Ipv4 address is found in the array.
 func getFinalIP(addrs []net.Addr) (net.IP, error) {
 	if len(addrs) > 0 {
@@ -334,11 +334,11 @@ func getFinalIP(addrs []net.Addr) (net.IP, error) {
 			//Only IPv4
 			//TODO : add IPv6 support
 			if ip.To4() != nil {
-				if !ip.IsLoopback() {
+				if !ip.IsLoopback() && !ip.IsLinkLocalMulticast() && !ip.IsLinkLocalUnicast() {
 					glog.V(4).Infof("IP found %v", ip)
 					return ip, nil
 				} else {
-					glog.V(4).Infof("Loopback found %v", ip)
+					glog.V(4).Infof("Loopback/link-local found %v", ip)
 				}
 			} else {
 				glog.V(4).Infof("%v is not a valid IPv4 address", ip)
@@ -399,7 +399,9 @@ func chooseHostInterfaceNativeGo() (net.IP, error) {
 					if addrIP, _, err := net.ParseCIDR(addr.String()); err == nil {
 						if addrIP.To4() != nil {
 							ip = addrIP.To4()
-							break
+							if !ip.IsLinkLocalMulticast() && !ip.IsLinkLocalUnicast() {
+								break
+							}
 						}
 					}
 				}

pkg/util/util_test.go

@@ -379,6 +379,12 @@ docker0	000011AC	00000000	0001	0	0	0	0000FFFF	0	0	0
 virbr0	007AA8C0	00000000	0001	0	0	0	00FFFFFF	0	0	0
 `
 
+// Based on DigitalOcean COREOS
+const gatewayfirstLinkLocal = `Iface   Destination     Gateway         Flags   RefCnt  Use     Metric  Mask            MTU     Window  IRTT                                                       
+eth0    00000000        0120372D        0001    0       0       0       00000000        0       0       0                                                                               
+eth0    00000000        00000000        0001    0       0       2048    00000000        0       0       0                                                                            
+`
+
 func TestGetRoutes(t *testing.T) {
 	testCases := []struct {
 		tcase    string
@@ -499,6 +505,19 @@ func (_ validNetworkInterface) Addrs(intf *net.Interface) ([]net.Addr, error) {
 	return ifat, nil
 }
 
+type validNetworkInterfaceWithLinkLocal struct {
+}
+
+func (_ validNetworkInterfaceWithLinkLocal) InterfaceByName(intfName string) (*net.Interface, error) {
+	c := net.Interface{Index: 0, MTU: 0, Name: "eth0", HardwareAddr: nil, Flags: net.FlagUp}
+	return &c, nil
+}
+func (_ validNetworkInterfaceWithLinkLocal) Addrs(intf *net.Interface) ([]net.Addr, error) {
+	var ifat []net.Addr
+	ifat = []net.Addr{addrStruct{val: "169.254.162.166/16"}, addrStruct{val: "45.55.47.146/19"}}
+	return ifat, nil
+}
+
 type validNetworkInterfacewithIpv6Only struct {
 }
 
@@ -577,6 +596,7 @@ func TestChooseHostInterfaceFromRoute(t *testing.T) {
 		{"valid_routemiddle", strings.NewReader(gatewaymiddle), validNetworkInterface{}, net.ParseIP("10.254.71.145")},
 		{"valid_routemiddle_ipv6", strings.NewReader(gatewaymiddle), validNetworkInterfacewithIpv6Only{}, nil},
 		{"no internet connection", strings.NewReader(noInternetConnection), validNetworkInterface{}, nil},
+		{"no non-link-local ip", strings.NewReader(gatewayfirstLinkLocal), validNetworkInterfaceWithLinkLocal{}, net.ParseIP("45.55.47.146")},
 		{"no route", strings.NewReader(nothing), validNetworkInterface{}, nil},
 		{"no route file", nil, validNetworkInterface{}, nil},
 		{"no interfaces", nil, noNetworkInterface{}, nil},