Add unit tests for createHostNCApipaNetwork() function and apply changes from PR #3693

cns/hnsclient/hnsclient_windows.go

@@ -1,3 +1,6 @@
+//go:build windows
+// +build windows
+
 package hnsclient
 
 import (
@@ -53,6 +56,9 @@ const (
 	// Name of the loopback adapter needed to create Host NC apipa network
 	hostNCLoopbackAdapterName = "LoopbackAdapterHostNCConnectivity"
 
+	// Name of the loopback adapter created by HNS for Host NC apipa network
+	vEthernethostNCLoopbackAdapterName = "vEthernet (" + hostNCLoopbackAdapterName + ")"
+
 	// HNS rehydration issue requires this GW to be different than the loopback adapter ip, so we set it to .2
 	defaultHnsGwIPAddress       = "169.254.128.2"
 	hnsLoopbackAdapterIPAddress = "169.254.128.1"
@@ -301,7 +307,12 @@ func createHostNCApipaNetwork(
 		}
 
 		// Create loopback adapter needed for this HNS network
-		if interfaceExists, _ := networkcontainers.InterfaceExists(hostNCLoopbackAdapterName); !interfaceExists {
+		// We need to first check the existence of either "LoopbackAdapterHostNCConnectivity" or the vEthernet(LoopbackAdapterHostNCConnectivity) interfaces
+		// If neither exists, we create the loopback adapter with the specified IP configuration.
+		shouldCreate, logMessage := shouldCreateLoopbackAdapter(networkcontainers.InterfaceExists)
+		logger.Printf(logMessage)
+
+		if shouldCreate {
 			ipconfig := cns.IPConfiguration{
 				IPSubnet: cns.IPSubnet{
 					IPAddress:    hnsLoopbackAdapterIPAddress,
@@ -339,6 +350,24 @@ func createHostNCApipaNetwork(
 	return network, err
 }
 
+// shouldCreateLoopbackAdapter determines whether a loopback adapter should be created
+// based on the existence of either the hostNCLoopbackAdapterName or vEthernethostNCLoopbackAdapterName interfaces
+func shouldCreateLoopbackAdapter(
+	interfaceExistsFunc func(string) (bool, error)) (bool, string) {
+	loopbackInterfaceExists, _ := interfaceExistsFunc(hostNCLoopbackAdapterName)
+	vethernetLoopbackInterfaceExists, _ := interfaceExistsFunc(vEthernethostNCLoopbackAdapterName)
+
+	if loopbackInterfaceExists {
+		return false, hostNCLoopbackAdapterName + " already created, skipping loopback interface creation"
+	}
+	if vethernetLoopbackInterfaceExists {
+		return false, vEthernethostNCLoopbackAdapterName + " already created, skipping loopback interface creation"
+	}
+
+	// Neither interface exists, so we should create the loopback adapter
+	return true, "Creating loopback adapter"
+}
+
 // LogNetworkInterfaces logs the host's network interfaces in the default namespace.
 func LogNetworkInterfaces() {
 	interfaces, err := net.Interfaces()

cns/hnsclient/hnsclient_windows_test.go

@@ -1,3 +1,6 @@
+//go:build windows
+// +build windows
+
 package hnsclient
 
 import (
@@ -33,3 +36,73 @@ func TestAdhocAdjustIPConfig(t *testing.T) {
 		})
 	}
 }
+
+func TestShouldCreateLoopbackAdapter(t *testing.T) {
+	tests := []struct {
+		name                     string
+		hostNCExists             bool
+		vEthernetHostNCExists    bool
+		expectedShouldCreate     bool
+		expectedLogMessagePrefix string
+	}{
+		{
+			name:                     "should create when neither interface exists",
+			hostNCExists:             false,
+			vEthernetHostNCExists:    false,
+			expectedShouldCreate:     true,
+			expectedLogMessagePrefix: "Creating loopback adapter",
+		},
+		{
+			name:                     "should not create when hostNCLoopbackAdapterName exists",
+			hostNCExists:             true,
+			vEthernetHostNCExists:    false,
+			expectedShouldCreate:     false,
+			expectedLogMessagePrefix: "LoopbackAdapterHostNCConnectivity already created",
+		},
+		{
+			name:                     "should not create when vEthernethostNCLoopbackAdapterName exists",
+			hostNCExists:             false,
+			vEthernetHostNCExists:    true,
+			expectedShouldCreate:     false,
+			expectedLogMessagePrefix: "vEthernet (LoopbackAdapterHostNCConnectivity) already created",
+		},
+		{
+			name:                     "should not create when both interfaces exist - prioritizes hostNCLoopbackAdapterName",
+			hostNCExists:             true,
+			vEthernetHostNCExists:    true,
+			expectedShouldCreate:     false,
+			expectedLogMessagePrefix: "LoopbackAdapterHostNCConnectivity already created",
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			// Create mock interface exists function
+			mockInterfaceExists := func(interfaceName string) (bool, error) {
+				switch interfaceName {
+				case hostNCLoopbackAdapterName:
+					return tt.hostNCExists, nil
+				case vEthernethostNCLoopbackAdapterName:
+					return tt.vEthernetHostNCExists, nil
+				default:
+					return false, nil
+				}
+			}
+
+			shouldCreate, logMessage := shouldCreateLoopbackAdapter(mockInterfaceExists)
+
+			assert.Equal(t, tt.expectedShouldCreate, shouldCreate)
+			assert.Contains(t, logMessage, tt.expectedLogMessagePrefix)
+		})
+	}
+}
+
+func TestConstants(t *testing.T) {
+	// Test that the vEthernet constant is constructed correctly
+	expectedVEthernetName := "vEthernet (LoopbackAdapterHostNCConnectivity)"
+	assert.Equal(t, expectedVEthernetName, vEthernethostNCLoopbackAdapterName)
+
+	// Test that the hostNCLoopbackAdapterName constant is as expected
+	assert.Equal(t, "LoopbackAdapterHostNCConnectivity", hostNCLoopbackAdapterName)
+}