host-local: fix allocation of last address in a /30

plugins/ipam/host-local/allocator.go

@@ -173,7 +173,7 @@ func (a *IPAllocator) Get(id string) (*types.IPConfig, error) {
 	}
 
 	startIP, endIP := a.getSearchRange()
-	for cur := startIP; !cur.Equal(endIP); cur = a.nextIP(cur) {
+	for cur := startIP; ; cur = a.nextIP(cur) {
 		// don't allocate gateway IP
 		if gw != nil && cur.Equal(gw) {
 			continue
@@ -190,6 +190,10 @@ func (a *IPAllocator) Get(id string) (*types.IPConfig, error) {
 				Routes:  a.conf.Routes,
 			}, nil
 		}
+		// break here to complete the loop
+		if cur.Equal(endIP) {
+			break
+		}
 	}
 	return nil, fmt.Errorf("no IP addresses available in network: %s", a.conf.Name)
 }

plugins/ipam/host-local/allocator_test.go

@@ -65,6 +65,12 @@ var _ = Describe("host-local ip allocator", func() {
 					expectResult: "10.0.0.2",
 					lastIP:       "",
 				},
+				{
+					subnet:       "10.0.0.0/30",
+					ipmap:        map[string]string{},
+					expectResult: "10.0.0.2",
+					lastIP:       "",
+				},
 				{
 					subnet: "10.0.0.0/29",
 					ipmap: map[string]string{
@@ -107,6 +113,18 @@ var _ = Describe("host-local ip allocator", func() {
 					expectResult: "10.0.0.3",
 					lastIP:       "10.0.0.128",
 				},
+				// wrap around and reserve lastIP
+				{
+					subnet: "10.0.0.0/29",
+					ipmap: map[string]string{
+						"10.0.0.2": "id",
+						"10.0.0.4": "id",
+						"10.0.0.5": "id",
+						"10.0.0.6": "id",
+					},
+					expectResult: "10.0.0.3",
+					lastIP:       "10.0.0.3",
+				},
 			}
 
 			for _, tc := range testCases {