sensors: introduce SensorIface interface

current code use a struct Sensor, which makes testing the sensor manager
code hard. This patch introduces a sensor interface.

Subsequent patches will use the interface for testing.

Signed-off-by: Kornilios Kourtis <kornilios@isovalent.com>

pkg/bench/bench.go

@@ -138,7 +138,7 @@ func runTetragon(ctx context.Context, configFile string, args *Arguments, summar
 	}
 
 	<-ctx.Done()
-	sensors.UnloadSensors([]*sensors.Sensor{benchSensors, baseSensors})
+	sensors.UnloadSensors([]sensors.SensorIface{benchSensors, baseSensors})
 }
 
 func sigHandler(ctx context.Context, cancel context.CancelFunc) {

pkg/observer/observertesthelper/observer_test_helper.go

@@ -344,7 +344,7 @@ func GetDefaultSensorsWithFile(tb testing.TB, file, lib string, opts ...TestOpti
 		}
 	}
 
-	var sens []*sensors.Sensor
+	var sens []sensors.SensorIface
 
 	if tp != nil {
 		sens, err = sensors.SensorsFromPolicy(tp, policyfilter.NoFilterID)
@@ -360,7 +360,13 @@ func GetDefaultSensorsWithFile(tb testing.TB, file, lib string, opts ...TestOpti
 	}
 
 	sens = append(sens, base)
-	return sens, nil
+	ret := make([]*sensors.Sensor, 0, len(sens))
+	for _, si := range sens {
+		if s, ok := si.(*sensors.Sensor); ok {
+			ret = append(ret, s)
+		}
+	}
+	return ret, nil
 }
 
 func loadExporter(tb testing.TB, ctx context.Context, obs *observer.Observer, opts *testExporterOptions, oo *testObserverOptions) error {
@@ -458,7 +464,7 @@ func loadObserver(tb testing.TB, ctx context.Context, base *sensors.Sensor,
 	return nil
 }
 
-func loadSensors(tb testing.TB, base *sensors.Sensor, sens []*sensors.Sensor) error {
+func loadSensors(tb testing.TB, base sensors.SensorIface, sens []sensors.SensorIface) error {
 	if err := base.Load(option.Config.BpfDir); err != nil {
 		tb.Fatalf("Load base error: %s\n", err)
 	}

pkg/sensors/collection.go

@@ -60,7 +60,7 @@ func (ck *collectionKey) String() string {
 // This can either be creating from a tracing policy, or by loading sensors indepenently for sensors
 // that are not loaded via a tracing policy (e.g., base sensor) and testing.
 type collection struct {
-	sensors []*Sensor
+	sensors []SensorIface
 	name    string
 	err     error
 	// fields below are only set for tracing policies
@@ -97,21 +97,21 @@ func (c *collection) load(bpfDir string) error {
 
 	var err error
 	for _, sensor := range c.sensors {
-		if sensor.Loaded {
+		if sensor.IsLoaded() {
 			// NB: For now, we don't treat a sensor already loaded as an error
 			// because that would complicate things.
 			continue
 		}
 		if err = sensor.Load(bpfDir); err != nil {
-			err = fmt.Errorf("sensor %s from collection %s failed to load: %s", sensor.Name, c.name, err)
+			err = fmt.Errorf("sensor %s from collection %s failed to load: %s", sensor.GetName(), c.name, err)
 			break
 		}
 	}
 
 	// if there was an error, try to unload all the sensors
 	if err != nil {
 		// NB: we could try to unload sensors going back from the one that failed, but since
-		// unload() checks s.Loaded, is easier to just to use unload().
+		// unload() checks s.IsLoaded, is easier to just to use unload().
 		if unloadErr := c.unload(); unloadErr != nil {
 			err = multierr.Append(err, fmt.Errorf("unloading after loading failure failed: %w", unloadErr))
 		}
@@ -124,7 +124,7 @@ func (c *collection) load(bpfDir string) error {
 func (c *collection) unload() error {
 	var err error
 	for _, s := range c.sensors {
-		if !s.Loaded {
+		if !s.IsLoaded() {
 			continue
 		}
 		unloadErr := s.Unload()
@@ -173,7 +173,7 @@ func (cm *collectionMap) listPolicies() []*tetragon.TracingPolicyStatus {
 		}
 
 		for _, sens := range col.sensors {
-			pol.Sensors = append(pol.Sensors, sens.Name)
+			pol.Sensors = append(pol.Sensors, sens.GetName())
 		}
 
 		ret = append(ret, &pol)

pkg/sensors/handler.go

@@ -43,7 +43,7 @@ func (h *handler) allocPolicyID() uint64 {
 }
 
 // revive:disable:exported
-func SensorsFromPolicy(tp tracingpolicy.TracingPolicy, filterID policyfilter.PolicyID) ([]*Sensor, error) {
+func SensorsFromPolicy(tp tracingpolicy.TracingPolicy, filterID policyfilter.PolicyID) ([]SensorIface, error) {
 	return sensorsFromPolicyHandlers(tp, filterID)
 }
 
@@ -133,7 +133,8 @@ func (h *handler) addTracingPolicy(op *tracingPolicyAdd) error {
 		col.state = LoadErrorState
 		return err
 	}
-	col.sensors = sensors
+	col.sensors = make([]SensorIface, 0, len(sensors))
+	col.sensors = append(col.sensors, sensors...)
 	col.state = LoadingState
 
 	// unlock so that policyLister can access the collections (read-only) while we are loading.
@@ -244,7 +245,7 @@ func (h *handler) addSensor(op *sensorAdd) error {
 		return fmt.Errorf("sensor %s already exists", ck)
 	}
 	collections[ck] = &collection{
-		sensors: []*Sensor{op.sensor},
+		sensors: []SensorIface{op.sensor},
 		name:    op.name,
 	}
 	return nil
@@ -322,8 +323,8 @@ func (h *handler) listSensors(op *sensorList) error {
 		colInfo := col.info()
 		for _, s := range col.sensors {
 			ret = append(ret, SensorStatus{
-				Name:       s.Name,
-				Enabled:    s.Loaded,
+				Name:       s.GetName(),
+				Enabled:    s.IsLoaded(),
 				Collection: colInfo,
 			})
 		}
@@ -332,10 +333,9 @@ func (h *handler) listSensors(op *sensorList) error {
 	return nil
 }
 
-func sensorsFromPolicyHandlers(tp tracingpolicy.TracingPolicy, filterID policyfilter.PolicyID) ([]*Sensor, error) {
-	var sensors []*Sensor
+func sensorsFromPolicyHandlers(tp tracingpolicy.TracingPolicy, filterID policyfilter.PolicyID) ([]SensorIface, error) {
+	var sensors []SensorIface
 	for n, s := range registeredPolicyHandlers {
-		var sensor *Sensor
 		sensor, err := s.PolicyHandler(tp, filterID)
 		if err != nil {
 			return nil, fmt.Errorf("policy handler '%s' failed loading policy '%s': %w", n, tp.TpName(), err)

pkg/sensors/load.go

@@ -374,7 +374,7 @@ func unloadProgram(prog *program.Program) {
 	log.Info("BPF prog was unloaded")
 }
 
-func UnloadSensors(sens []*Sensor) {
+func UnloadSensors(sens []SensorIface) {
 	for i := range sens {
 		if err := sens[i].Unload(); err != nil {
 			logger.GetLogger().Warnf("Failed to unload sensor: %s", err)

pkg/sensors/manager_test.go

@@ -21,11 +21,11 @@ import (
 )
 
 type dummyHandler struct {
-	s *Sensor
+	s SensorIface
 	e error
 }
 
-func (d *dummyHandler) PolicyHandler(_ tracingpolicy.TracingPolicy, _ policyfilter.PolicyID) (*Sensor, error) {
+func (d *dummyHandler) PolicyHandler(_ tracingpolicy.TracingPolicy, _ policyfilter.PolicyID) (SensorIface, error) {
 	return d.s, d.e
 }
 

pkg/sensors/sensors.go

@@ -58,6 +58,23 @@ type Sensor struct {
 	DestroyHook SensorHook
 }
 
+// SensorIface is an interface for sensors.Sensor that allows implementing sensors for testing.
+type SensorIface interface {
+	GetName() string
+	IsLoaded() bool
+	Load(bpfDir string) error
+	Unload() error
+	Destroy()
+}
+
+func (s *Sensor) GetName() string {
+	return s.Name
+}
+
+func (s *Sensor) IsLoaded() bool {
+	return s.Loaded
+}
+
 // SensorHook is the function signature for an optional function
 // that can be called during sensor unloading and removing.
 type SensorHook func() error
@@ -84,7 +101,7 @@ type policyHandler interface {
 	// PolicyHandler returns a Sensor for a given policy
 	// sensors that support policyfilter can use the filterID to implement filtering.
 	// sensors that do not support policyfilter need to return an error if filterID != policyfilter.NoFilterID
-	PolicyHandler(policy tracingpolicy.TracingPolicy, filterID policyfilter.PolicyID) (*Sensor, error)
+	PolicyHandler(policy tracingpolicy.TracingPolicy, filterID policyfilter.PolicyID) (SensorIface, error)
 }
 
 type probeLoader interface {
@@ -132,11 +149,20 @@ type LoadProbeArgs struct {
 	Version, Verbose int
 }
 
-func GetMergedSensorFromParserPolicy(tp tracingpolicy.TracingPolicy) (*Sensor, error) {
+func GetMergedSensorFromParserPolicy(tp tracingpolicy.TracingPolicy) (SensorIface, error) {
 	// NB: use a filter id of 0, so no filtering will happen
-	sensors, err := SensorsFromPolicy(tp, policyfilter.NoFilterID)
+	sis, err := SensorsFromPolicy(tp, policyfilter.NoFilterID)
 	if err != nil {
 		return nil, err
 	}
+	sensors := make([]*Sensor, 0, len(sis))
+	for _, si := range sis {
+		s, ok := si.(*Sensor)
+		if !ok {
+			return nil, fmt.Errorf("cannot merge sensor of type %T", si)
+		}
+		sensors = append(sensors, s)
+	}
+
 	return SensorCombine(tp.TpName(), sensors...), nil
 }

pkg/sensors/tracing/enforcer.go

@@ -85,7 +85,7 @@ func (kp *enforcerPolicy) enforcerDel(name string) bool {
 func (kp *enforcerPolicy) PolicyHandler(
 	policy tracingpolicy.TracingPolicy,
 	_ policyfilter.PolicyID,
-) (*sensors.Sensor, error) {
+) (sensors.SensorIface, error) {
 
 	spec := policy.TpSpec()
 

pkg/sensors/tracing/genericuprobe.go

@@ -481,7 +481,7 @@ func createUprobeSensorFromEntry(uprobeEntry *genericUprobe,
 func (k *observerUprobeSensor) PolicyHandler(
 	p tracingpolicy.TracingPolicy,
 	fid policyfilter.PolicyID,
-) (*sensors.Sensor, error) {
+) (sensors.SensorIface, error) {
 	spec := p.TpSpec()
 
 	if len(spec.UProbes) == 0 {

pkg/sensors/tracing/kprobe_test.go

@@ -4314,22 +4314,24 @@ spec:
       type: "size_t"
 `
 
-	var sens []*sensors.Sensor
 	var err error
-
 	readConfigHook := []byte(readHook)
 	err = os.WriteFile(testConfigFile, readConfigHook, 0644)
 	if err != nil {
 		t.Fatalf("writeFile(%s): err %s", testConfigFile, err)
 	}
-	sens, err = observertesthelper.GetDefaultSensorsWithFile(t, testConfigFile, tus.Conf().TetragonLib, observertesthelper.WithMyPid())
+	sens, err := observertesthelper.GetDefaultSensorsWithFile(t, testConfigFile, tus.Conf().TetragonLib, observertesthelper.WithMyPid())
 	if err != nil {
 		t.Fatalf("GetDefaultObserverWithFile error: %s", err)
 	}
 
 	tus.CheckSensorLoad(sens, sensorMaps, sensorProgs, t)
 
-	sensors.UnloadSensors(sens)
+	sensi := make([]sensors.SensorIface, 0, len(sens))
+	for _, s := range sens {
+		sensi = append(sensi, s)
+	}
+	sensors.UnloadSensors(sensi)
 }
 
 func TestFakeSyscallError(t *testing.T) {

pkg/sensors/tracing/loader.go

@@ -112,7 +112,7 @@ func hasLoaderEvents() bool {
 	return bpf.HasBuildId() && kernels.MinKernelVersion("5.19.0")
 }
 
-func (k *loaderSensor) PolicyHandler(p tracingpolicy.TracingPolicy, fid policyfilter.PolicyID) (*sensors.Sensor, error) {
+func (k *loaderSensor) PolicyHandler(p tracingpolicy.TracingPolicy, fid policyfilter.PolicyID) (sensors.SensorIface, error) {
 	spec := p.TpSpec()
 	// NB: no loader section is the spec, so nothing to do
 	if !spec.Loader {

pkg/sensors/tracing/policyhandler.go

@@ -23,7 +23,7 @@ func init() {
 func (h policyHandler) PolicyHandler(
 	policy tracingpolicy.TracingPolicy,
 	policyID policyfilter.PolicyID,
-) (*sensors.Sensor, error) {
+) (sensors.SensorIface, error) {
 
 	policyName := policy.TpName()
 	spec := policy.TpSpec()

pkg/sensors/tracing/selectors_test.go

@@ -57,7 +57,7 @@ func loadGenericSensorTest(t *testing.T, spec *v1alpha1.TracingPolicySpec) *sens
 	tus.LoadSensor(t, base.GetInitialSensor())
 	tus.LoadSensor(t, testsensor.GetTestSensor())
 	tus.LoadSensor(t, tpSensor)
-	return tpSensor
+	return tpSensor.(*sensors.Sensor)
 }
 
 // lseekTestOps retruns a function to perform test lseek operations using the

pkg/sensors/tracing/tracepoint_test.go

@@ -488,7 +488,11 @@ spec:
 
 	tus.CheckSensorLoad(sens, sensorMaps, sensorProgs, t)
 
-	sensors.UnloadSensors(sens)
+	sensi := make([]sensors.SensorIface, 0, len(sens))
+	for _, s := range sens {
+		sensi = append(sensi, s)
+	}
+	sensors.UnloadSensors(sensi)
 }
 
 func TestTracepointCloneThreads(t *testing.T) {

pkg/sensors/tracing/uprobe_test.go

@@ -87,7 +87,11 @@ spec:
 
 	tus.CheckSensorLoad(sens, sensorMaps, sensorProgs, t)
 
-	sensors.UnloadSensors(sens)
+	sensi := make([]sensors.SensorIface, 0, len(sens))
+	for _, s := range sens {
+		sensi = append(sensi, s)
+	}
+	sensors.UnloadSensors(sensi)
 }
 
 func TestUprobeGeneric(t *testing.T) {

pkg/testutils/sensors/sensors.go

@@ -13,7 +13,11 @@ import (
 )
 
 // LoadSensor is a helper for loading a sensor in tests
-func LoadSensor(t *testing.T, sensor *sensors.Sensor) {
+func LoadSensor(t *testing.T, sensori sensors.SensorIface) {
+	sensor, ok := sensori.(*sensors.Sensor)
+	if !ok {
+		t.Fatalf("Cannot call LoadSensor on type %T", sensori)
+	}
 
 	if err := sensor.FindPrograms(); err != nil {
 		t.Fatalf("ObserverFindProgs error: %s", err)