return error if conf missing, add test

Signed-off-by: Michael Zappa <[email protected]>

cni.go

@@ -227,6 +227,8 @@ func (c *libcni) BuildMultiNetwork(networkNames []*NetworkInterface) ([]*Network
 			} 
 
 			ifs[name] = net
+		} else {
+			return nil, fmt.Errorf("the network config: %v does not exist", v.NetworkName)
 		}
 	}
 

cni_test.go

@@ -382,6 +382,34 @@ func TestBuildNetworksDuplicateIfName(t *testing.T) {
 	assert.EqualError(t, err, "the interface: net10 already exists and must be unique")
 }
 
+func TestBuildNetworksMissingNetworkConfig(t *testing.T) {
+	// Get the default CNI config
+	l := defaultCNIConfig()
+	// Create a fake cni config directory and file
+	cniDir, confDir := makeFakeCNIConfig(t)
+	defer tearDownCNIConfig(t, cniDir)
+	l.pluginConfDir = confDir
+	// Set the minimum network count as 2 for this test
+	l.networkCount = 2
+	err := l.Load(WithLoNetwork, WithAllConf)
+	assert.NoError(t, err)
+
+	err = l.Status()
+	assert.NoError(t, err)
+
+	net := []*NetworkInterface{
+		{
+			NetworkName:   "thisdoesnotexist",
+			InterfaceName: "net10",
+		},
+	}
+
+	_, err = l.BuildMultiNetwork(net)
+
+	assert.Error(t, err)
+	assert.EqualError(t, err, "the network config: thisdoesnotexist does not exist")
+}
+
 type MockCNI struct {
 	mock.Mock
 }