usm: file registery: Introduce already activated callback

To support the go-tls unique use-case, in which we need to run a callback everytime
a path id needs to be re-registered, we introduce a new callback option.

Currently, using a nop callback

pkg/network/usm/ebpf_gotls.go

@@ -338,7 +338,9 @@ func (p *goTLSProgram) AttachPID(pid uint32) error {
 
 	// Check go process
 	probeList := make([]manager.ProbeIdentificationPair, 0)
-	return p.registry.Register(binPath, pid, registerCBCreator(p.manager, p.offsetsDataMap, &probeList, p.binAnalysisMetric, p.binNoSymbolsMetric), unregisterCBCreator(p.manager, &probeList, p.offsetsDataMap))
+	return p.registry.Register(binPath, pid, registerCBCreator(p.manager, p.offsetsDataMap, &probeList, p.binAnalysisMetric, p.binNoSymbolsMetric),
+		unregisterCBCreator(p.manager, &probeList, p.offsetsDataMap),
+		utils.NopCallback)
 }
 
 func registerCBCreator(mgr *manager.Manager, offsetsDataMap *ebpf.Map, probeIDs *[]manager.ProbeIdentificationPair, binAnalysisMetric, binNoSymbolsMetric *libtelemetry.Counter) func(path utils.FilePath) error {
@@ -383,6 +385,21 @@ func registerCBCreator(mgr *manager.Manager, offsetsDataMap *ebpf.Map, probeIDs
 	}
 }
 
+// alreadyCBCreator handles the case where a binary is already registered. In such a case the registry callback won't
+// be called, so we need to add a mapping from the PID to the device/inode of the binary.
+func alreadyCBCreator(pidToDeviceInodeMap *ebpf.Map) func(utils.FilePath) error {
+	return func(filePath utils.FilePath) error {
+		if filePath.PID == 0 {
+			return nil
+		}
+		return pidToDeviceInodeMap.Put(unsafe.Pointer(&filePath.PID), unsafe.Pointer(&gotls.TlsBinaryId{
+			Id_major: unix.Major(filePath.ID.Dev),
+			Id_minor: unix.Minor(filePath.ID.Dev),
+			Ino:      filePath.ID.Inode,
+		}))
+	}
+}
+
 func (p *goTLSProgram) handleProcessExit(pid pid) {
 	_ = p.DetachPID(pid)
 }

pkg/network/usm/istio.go

@@ -136,6 +136,7 @@ func (m *istioMonitor) AttachPID(pid uint32) error {
 		pid,
 		m.registerCB,
 		m.unregisterCB,
+		utils.NopCallback,
 	)
 }
 

pkg/network/usm/nodejs.go

@@ -228,6 +228,7 @@ func (m *nodeJSMonitor) AttachPID(pid uint32) error {
 		pid,
 		m.registerCB,
 		m.unregisterCB,
+		utils.NopCallback,
 	)
 }
 

pkg/network/usm/sharedlibraries/watcher.go

@@ -156,7 +156,7 @@ func (w *Watcher) AttachPID(pid uint32) error {
 		// Iterate over the rule, and look for a match.
 		for _, r := range w.rules {
 			if r.Re.MatchString(path) {
-				if err := w.registry.Register(path, pid, r.RegisterCB, r.UnregisterCB); err != nil {
+				if err := w.registry.Register(path, pid, r.RegisterCB, r.UnregisterCB, utils.NopCallback); err != nil {
 					registerErrors = append(registerErrors, err)
 				} else {
 					successfulMatches = append(successfulMatches, path)
@@ -210,7 +210,7 @@ func (w *Watcher) Start() {
 			// Iterate over the rule, and look for a match.
 			for _, r := range w.rules {
 				if r.Re.MatchString(path) {
-					_ = w.registry.Register(path, uint32(pid), r.RegisterCB, r.UnregisterCB)
+					_ = w.registry.Register(path, uint32(pid), r.RegisterCB, r.UnregisterCB, utils.NopCallback)
 					break
 				}
 			}
@@ -267,7 +267,7 @@ func (w *Watcher) Start() {
 				for _, r := range w.rules {
 					if r.Re.Match(path) {
 						w.libMatches.Add(1)
-						_ = w.registry.Register(string(path), lib.Pid, r.RegisterCB, r.UnregisterCB)
+						_ = w.registry.Register(string(path), lib.Pid, r.RegisterCB, r.UnregisterCB, utils.NopCallback)
 						break
 					}
 				}

pkg/network/usm/utils/file_registry.go

@@ -80,6 +80,11 @@ func NewFilePath(procRoot, namespacedPath string, pid uint32) (FilePath, error)
 
 type callback func(FilePath) error
 
+var (
+	// NopCallback is an empty callback implementation, useful for testing and code paths the does not need all callbacks.
+	NopCallback = callback(nil)
+)
+
 // NewFileRegistry creates a new `FileRegistry` instance
 func NewFileRegistry(programName string) *FileRegistry {
 	blocklistByID, err := simplelru.NewLRU[PathIdentifier, string](2000, nil)
@@ -118,7 +123,7 @@ var (
 // If no current registration exists for the given `PathIdentifier`, we execute
 // its *activation* callback. Otherwise, we increment the reference counter for
 // the existing registration if and only if `pid` is new;
-func (r *FileRegistry) Register(namespacedPath string, pid uint32, activationCB, deactivationCB callback) error {
+func (r *FileRegistry) Register(namespacedPath string, pid uint32, activationCB, deactivationCB, alreadyRegistered callback) error {
 	if activationCB == nil || deactivationCB == nil {
 		return errCallbackIsMissing
 	}
@@ -152,6 +157,9 @@ func (r *FileRegistry) Register(namespacedPath string, pid uint32, activationCB,
 			r.byPID[pid][pathID] = struct{}{}
 		}
 		r.telemetry.fileAlreadyRegistered.Add(1)
+		if alreadyRegistered != nil {
+			_ = alreadyRegistered(path)
+		}
 		return ErrPathIsAlreadyRegistered
 	}
 

pkg/network/usm/utils/file_registry_test.go

@@ -30,7 +30,7 @@ func TestRegister(t *testing.T) {
 	pid := uint32(cmd.Process.Pid)
 
 	r := newFileRegistry()
-	require.NoError(t, r.Register(path, pid, registerRecorder.Callback(), IgnoreCB))
+	require.NoError(t, r.Register(path, pid, registerRecorder.Callback(), IgnoreCB, NopCallback))
 
 	assert.Equal(t, 1, registerRecorder.CallsForPathID(pathID))
 	assert.Contains(t, r.GetRegisteredProcesses(), pid)
@@ -44,6 +44,9 @@ func TestMultiplePIDsSharingSameFile(t *testing.T) {
 	unregisterRecorder := new(CallbackRecorder)
 	unregisterCallback := unregisterRecorder.Callback()
 
+	alreadyRegisteredRecorder := new(CallbackRecorder)
+	alreadyRegisteredCallback := alreadyRegisteredRecorder.Callback()
+
 	r := newFileRegistry()
 	path, pathID := createTempTestFile(t, "foobar")
 
@@ -56,8 +59,8 @@ func TestMultiplePIDsSharingSameFile(t *testing.T) {
 	pid2 := uint32(cmd2.Process.Pid)
 
 	// Trying to register the same file twice from different PIDs
-	require.NoError(t, r.Register(path, pid1, registerCallback, unregisterCallback))
-	require.Equal(t, ErrPathIsAlreadyRegistered, r.Register(path, pid2, registerCallback, unregisterCallback))
+	require.NoError(t, r.Register(path, pid1, registerCallback, unregisterCallback, alreadyRegisteredCallback))
+	require.Equal(t, ErrPathIsAlreadyRegistered, r.Register(path, pid2, registerCallback, unregisterCallback, alreadyRegisteredCallback))
 
 	// Assert that the callback should execute only *once*
 	assert.Equal(t, 1, registerRecorder.CallsForPathID(pathID))
@@ -66,6 +69,9 @@ func TestMultiplePIDsSharingSameFile(t *testing.T) {
 	assert.Contains(t, r.GetRegisteredProcesses(), pid1)
 	assert.Contains(t, r.GetRegisteredProcesses(), pid2)
 
+	// Assert that the callback should execute only *once*
+	assert.Equal(t, 1, alreadyRegisteredRecorder.CallsForPathID(pathID))
+
 	// Assert that the first call to `Unregister` (from pid1) doesn't trigger
 	// the callback but removes pid1 from the list
 	require.NoError(t, r.Unregister(pid1))
@@ -99,8 +105,8 @@ func TestRepeatedRegistrationsFromSamePID(t *testing.T) {
 	require.NoError(t, err)
 	pid := uint32(cmd.Process.Pid)
 
-	require.NoError(t, r.Register(path, pid, registerCallback, unregisterCallback))
-	require.Equal(t, ErrPathIsAlreadyRegistered, r.Register(path, pid, registerCallback, unregisterCallback))
+	require.NoError(t, r.Register(path, pid, registerCallback, unregisterCallback, NopCallback))
+	require.Equal(t, ErrPathIsAlreadyRegistered, r.Register(path, pid, registerCallback, unregisterCallback, NopCallback))
 	require.NoError(t, r.Unregister(pid))
 
 	// Assert that despite multiple calls to `Register` from the same PID we
@@ -122,15 +128,15 @@ func TestFailedRegistration(t *testing.T) {
 	require.NoError(t, err)
 	pid := uint32(cmd.Process.Pid)
 
-	require.NoError(t, r.Register(path, pid, registerCallback, IgnoreCB))
+	require.NoError(t, r.Register(path, pid, registerCallback, IgnoreCB, NopCallback))
 
 	// First let's assert that the callback was executed once, but there are no
 	// registered processes because the registration should have failed
 	assert.Equal(t, 1, registerRecorder.CallsForPathID(pathID))
 	assert.Empty(t, r.GetRegisteredProcesses())
 
 	// Now let's try to register the same process again
-	require.Equal(t, errPathIsBlocked, r.Register(path, pid, registerCallback, IgnoreCB))
+	require.Equal(t, errPathIsBlocked, r.Register(path, pid, registerCallback, IgnoreCB, NopCallback))
 
 	// Assert that the number of callback executions hasn't changed for this pathID
 	// This is because we have block-listed this file
@@ -150,7 +156,7 @@ func TestFilePathInCallbackArgument(t *testing.T) {
 	pid := cmd.Process.Pid
 
 	r := newFileRegistry()
-	require.NoError(t, r.Register(path, uint32(pid), callback, callback))
+	require.NoError(t, r.Register(path, uint32(pid), callback, callback, NopCallback))
 
 	// Assert that the callback paths match the pattern <proc_root>/<pid>/root/<path>
 	expectedPath := filepath.Join(r.procRoot, strconv.Itoa(pid), "root", path)
@@ -182,7 +188,7 @@ func TestRelativeFilePathInCallbackArgument(t *testing.T) {
 	pid := cmd.Process.Pid
 
 	r := newFileRegistry()
-	require.NoError(t, r.Register(relpath, uint32(pid), callback, callback))
+	require.NoError(t, r.Register(relpath, uint32(pid), callback, callback, NopCallback))
 
 	// Assert that the callback paths match the pattern <proc_root>/<pid>/cwd/<path>.
 	// We need to avoid `filepath.Join` for the last component since using