feat(wireguard): add debug logs for IPv6 detection

- To debug issue #998
- Enable with `LOG_LEVEL=debug`

internal/wireguard/ipv6.go

@@ -12,16 +12,23 @@ func (w *Wireguard) isIPv6Supported() (supported bool, err error) {
 		return false, fmt.Errorf("cannot list links: %w", err)
 	}
 
+	w.logger.Debug("Checking for IPv6 support...")
 	for _, link := range links {
+		linkName := link.Attrs().Name
 		routes, err := w.netlink.RouteList(link, netlink.FAMILY_V6)
 		if err != nil {
-			return false, fmt.Errorf("cannot list routes: %w", err)
+			return false, fmt.Errorf("cannot list routes for link %s: %w", linkName, err)
 		}
 
-		if len(routes) > 0 {
-			return true, nil
-		}
+		if len(routes) == 0 {
+			w.logger.Debugf("Link %s has no IPv6 route", linkName)
+			continue
 		}
 
-	return false, nil
+		w.logger.Debugf("Link %s has IPv6 routes: %#v",
+			linkName, routes)
+		supported = true
+	}
+
+	return supported, nil
 }

internal/wireguard/log.go

@@ -1,8 +1,6 @@
 package wireguard
 
 import (
-	"fmt"
-
 	"golang.zx2c4.com/wireguard/device"
 )
 
@@ -10,17 +8,15 @@ import (
 
 type Logger interface {
 	Debug(s string)
+	Debugf(format string, args ...interface{})
 	Info(s string)
 	Error(s string)
+	Errorf(format string, args ...interface{})
 }
 
 func makeDeviceLogger(logger Logger) (deviceLogger *device.Logger) {
 	return &device.Logger{
-		Verbosef: func(format string, args ...interface{}) {
-			logger.Debug(fmt.Sprintf(format, args...))
-		},
-		Errorf: func(format string, args ...interface{}) {
-			logger.Error(fmt.Sprintf(format, args...))
-		},
+		Verbosef: logger.Debugf,
+		Errorf:   logger.Errorf,
 	}
 }

internal/wireguard/log_mock_test.go

@@ -45,6 +45,23 @@ func (mr *MockLoggerMockRecorder) Debug(arg0 interface{}) *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debug", reflect.TypeOf((*MockLogger)(nil).Debug), arg0)
 }
 
+// Debugf mocks base method.
+func (m *MockLogger) Debugf(arg0 string, arg1 ...interface{}) {
+	m.ctrl.T.Helper()
+	varargs := []interface{}{arg0}
+	for _, a := range arg1 {
+		varargs = append(varargs, a)
+	}
+	m.ctrl.Call(m, "Debugf", varargs...)
+}
+
+// Debugf indicates an expected call of Debugf.
+func (mr *MockLoggerMockRecorder) Debugf(arg0 interface{}, arg1 ...interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	varargs := append([]interface{}{arg0}, arg1...)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debugf", reflect.TypeOf((*MockLogger)(nil).Debugf), varargs...)
+}
+
 // Error mocks base method.
 func (m *MockLogger) Error(arg0 string) {
 	m.ctrl.T.Helper()
@@ -57,6 +74,23 @@ func (mr *MockLoggerMockRecorder) Error(arg0 interface{}) *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Error", reflect.TypeOf((*MockLogger)(nil).Error), arg0)
 }
 
+// Errorf mocks base method.
+func (m *MockLogger) Errorf(arg0 string, arg1 ...interface{}) {
+	m.ctrl.T.Helper()
+	varargs := []interface{}{arg0}
+	for _, a := range arg1 {
+		varargs = append(varargs, a)
+	}
+	m.ctrl.Call(m, "Errorf", varargs...)
+}
+
+// Errorf indicates an expected call of Errorf.
+func (mr *MockLoggerMockRecorder) Errorf(arg0 interface{}, arg1 ...interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	varargs := append([]interface{}{arg0}, arg1...)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Errorf", reflect.TypeOf((*MockLogger)(nil).Errorf), varargs...)
+}
+
 // Info mocks base method.
 func (m *MockLogger) Info(arg0 string) {
 	m.ctrl.T.Helper()

internal/wireguard/log_test.go

@@ -15,9 +15,9 @@ func Test_makeDeviceLogger(t *testing.T) {
 
 	deviceLogger := makeDeviceLogger(logger)
 
-	logger.EXPECT().Debug("test 1")
+	logger.EXPECT().Debugf("test %d", 1)
 	deviceLogger.Verbosef("test %d", 1)
 
-	logger.EXPECT().Error("test 2")
+	logger.EXPECT().Errorf("test %d", 2)
 	deviceLogger.Errorf("test %d", 2)
 }

internal/wireguard/route.go

@@ -19,7 +19,9 @@ func (w *Wireguard) addRoute(link netlink.Link, dst *net.IPNet,
 
 	err = w.netlink.RouteAdd(route)
 	if err != nil {
-		return fmt.Errorf("cannot add route %s: %w", route, err)
+		return fmt.Errorf(
+			"cannot add route for link %s, destination %s and table %d: %w",
+			link.Attrs().Name, dst, firewallMark, err)
 	}
 
 	return err

internal/wireguard/route_test.go

@@ -53,7 +53,7 @@ func Test_Wireguard_addRoute(t *testing.T) {
 				Table:     firewallMark,
 			},
 			routeAddErr: errDummy,
-			err:         errors.New("cannot add route {Ifindex: 88 Dst: 1.2.3.4/32 Src: <nil> Gw: <nil> Flags: [] Table: 51820 Realm: 0}: dummy"), //nolint:lll
+			err:         errors.New("cannot add route for link a_bridge, destination 1.2.3.4/32 and table 51820: dummy"), //nolint:lll
 		},
 	}