Minor tweak to IPv6 service IP allocation

The service allocator skips the "broadcast address" in the service
CIDR, but that concept only applies to IPv4 addressing.

Author: danwinship

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

@@ -91,12 +91,19 @@ func NewAllocatorCIDRRange(cidr *net.IPNet, allocatorFactory allocator.Allocator
 		if max > 65536 {
 			max = 65536
 		}
+	} else {
+		// Don't use the IPv4 network's broadcast address.
+		max--
 	}
 
+	// Don't use the network's ".0" address.
+	base.Add(base, big.NewInt(1))
+	max--
+
 	r := Range{
 		net:  cidr,
-		base: base.Add(base, big.NewInt(1)), // don't use the network base
-		max:  maximum(0, int(max-2)),        // don't use the network broadcast,
+		base: base,
+		max:  maximum(0, int(max)),
 	}
 	var err error
 	r.alloc, err = allocatorFactory(r.max, rangeSpec)

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

@@ -49,14 +49,13 @@ func TestAllocate(t *testing.T) {
 		{
 			name:     "IPv6",
 			cidr:     "2001:db8:1::/48",
-			free:     65534,
+			free:     65535,
 			released: "2001:db8:1::5",
 			outOfRange: []string{
-				"2001:db8::1",      // not in 2001:db8:1::/48
-				"2001:db8:1::",     // reserved (base address)
-				"2001:db8:1::ffff", // reserved (broadcast address)
-				"2001:db8:1::1:0",  // not in the low 16 bits of 2001:db8:1::/48
-				"2001:db8:2::2",    // not in 2001:db8:1::/48
+				"2001:db8::1",     // not in 2001:db8:1::/48
+				"2001:db8:1::",    // reserved (base address)
+				"2001:db8:1::1:0", // not in the low 16 bits of 2001:db8:1::/48
+				"2001:db8:2::2",   // not in 2001:db8:1::/48
 			},
 			alreadyAllocated: "2001:db8:1::1",
 		},

pkg/registry/core/service/ipallocator/controller/repair_test.go

@@ -529,7 +529,7 @@ func TestRepairWithExistingDualStack(t *testing.T) {
 	if !secondaryAfter.Has(net.ParseIP("2000::1")) || !secondaryAfter.Has(net.ParseIP("2000::2")) {
 		t.Errorf("unexpected ipallocator state: %#v", secondaryAfter)
 	}
-	if free := secondaryAfter.Free(); free != 65532 {
+	if free := secondaryAfter.Free(); free != 65533 {
 		t.Errorf("unexpected ipallocator state: %d free (number of free ips is not 65532)", free)
 	}