Merge pull request kubernetes#115333 from aojea/automated-cherry-pick…

…-of-#115322-upstream-release-1.26

Automated cherry pick of kubernetes#115322: Fix panic on ClusterIP allocation for /28 subnets

pkg/registry/core/service/allocator/bitmap.go

@@ -68,6 +68,7 @@ func NewAllocationMap(max int, rangeSpec string) *AllocationBitmap {
 // allows to pass an offset that divides the allocation bitmap in two blocks.
 // The first block of values will not be used for random value assigned by the AllocateNext()
 // method until the second block of values has been exhausted.
+// The offset value must be always smaller than the bitmap size.
 func NewAllocationMapWithOffset(max int, rangeSpec string, offset int) *AllocationBitmap {
 	a := AllocationBitmap{
 		strategy: randomScanStrategyWithOffset{

pkg/registry/core/service/ipallocator/allocator.go

@@ -114,6 +114,11 @@ func New(cidr *net.IPNet, allocatorFactory allocator.AllocatorWithOffsetFactory)
 	base.Add(base, big.NewInt(1))
 	max--
 
+	// cidr with whole mask can be negative
+	if max < 0 {
+		max = 0
+	}
+
 	r := Range{
 		net:     cidr,
 		base:    base,
@@ -388,7 +393,10 @@ func calculateRangeOffset(cidr *net.IPNet) int {
 	)
 
 	cidrSize := netutils.RangeSize(cidr)
-	if cidrSize < min {
+	// available addresses are always less than the cidr size
+	// A /28 CIDR returns 16 addresses, but 2 of them, the network
+	// and broadcast addresses are not available.
+	if cidrSize <= min {
 		return 0
 	}
 

pkg/registry/core/service/ipallocator/allocator_test.go

@@ -786,8 +786,18 @@ func Test_calculateRangeOffset(t *testing.T) {
 		{
 			name: "small mask IPv4",
 			cidr: "192.168.1.1/28",
+			want: 0,
+		},
+		{
+			name: "small mask IPv4",
+			cidr: "192.168.1.1/27",
 			want: 16,
 		},
+		{
+			name: "small mask IPv6",
+			cidr: "fd00::1/124",
+			want: 0,
+		},
 		{
 			name: "small mask IPv6",
 			cidr: "fd00::1/122",

test/integration/network/services_test.go

@@ -128,3 +128,49 @@ func TestServicesFinalizersRepairLoop(t *testing.T) {
 	}
 	t.Logf("Created service: %s", svcNodePort.Name)
 }
+
+// Regresion test for https://issues.k8s.io/115316
+func TestServiceCIDR28bits(t *testing.T) {
+	serviceCIDR := "10.0.0.0/28"
+
+	client, _, tearDownFn := framework.StartTestServer(t, framework.TestServerSetup{
+		ModifyServerRunOptions: func(opts *options.ServerRunOptions) {
+			opts.ServiceClusterIPRanges = serviceCIDR
+		},
+	})
+	defer tearDownFn()
+
+	// Wait until the default "kubernetes" service is created.
+	if err := wait.Poll(250*time.Millisecond, time.Minute, func() (bool, error) {
+		_, err := client.CoreV1().Services(metav1.NamespaceDefault).Get(context.TODO(), "kubernetes", metav1.GetOptions{})
+		if err != nil {
+			return false, err
+		}
+		return true, nil
+	}); err != nil {
+		t.Fatalf("creating kubernetes service timed out")
+	}
+
+	ns := framework.CreateNamespaceOrDie(client, "test-regression", t)
+	defer framework.DeleteNamespaceOrDie(client, ns, t)
+
+	service := &v1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-1234",
+		},
+		Spec: v1.ServiceSpec{
+			Type: v1.ServiceTypeClusterIP,
+			Ports: []v1.ServicePort{{
+				Port: int32(80),
+			}},
+			Selector: map[string]string{
+				"foo": "bar",
+			},
+		},
+	}
+
+	_, err := client.CoreV1().Services(ns.Name).Create(context.TODO(), service, metav1.CreateOptions{})
+	if err != nil {
+		t.Fatalf("Error creating test service: %v", err)
+	}
+}