[client] Add bind activity listener to bypass udp sockets (#4646)

client/iface/device.go

@@ -23,4 +23,5 @@ type WGTunDevice interface {
 	FilteredDevice() *device.FilteredDevice
 	Device() *wgdevice.Device
 	GetNet() *netstack.Net
+	GetICEBind() device.EndpointManager
 }

client/iface/device/device_android.go

@@ -150,6 +150,11 @@ func (t *WGTunDevice) GetNet() *netstack.Net {
 	return nil
 }
 
+// GetICEBind returns the ICEBind instance
+func (t *WGTunDevice) GetICEBind() EndpointManager {
+	return t.iceBind
+}
+
 func routesToString(routes []string) string {
 	return strings.Join(routes, ";")
 }

client/iface/device/device_darwin.go

@@ -154,3 +154,8 @@ func (t *TunDevice) assignAddr() error {
 func (t *TunDevice) GetNet() *netstack.Net {
 	return nil
 }
+
+// GetICEBind returns the ICEBind instance
+func (t *TunDevice) GetICEBind() EndpointManager {
+	return t.iceBind
+}

client/iface/device/device_ios.go

@@ -144,3 +144,8 @@ func (t *TunDevice) FilteredDevice() *FilteredDevice {
 func (t *TunDevice) GetNet() *netstack.Net {
 	return nil
 }
+
+// GetICEBind returns the ICEBind instance
+func (t *TunDevice) GetICEBind() EndpointManager {
+	return t.iceBind
+}

client/iface/device/device_kernel_unix.go

@@ -179,3 +179,8 @@ func (t *TunKernelDevice) assignAddr() error {
 func (t *TunKernelDevice) GetNet() *netstack.Net {
 	return nil
 }
+
+// GetICEBind returns nil for kernel mode devices
+func (t *TunKernelDevice) GetICEBind() EndpointManager {
+	return nil
+}

client/iface/device/device_netstack.go

@@ -21,6 +21,7 @@ type Bind interface {
 	conn.Bind
 	GetICEMux() (*udpmux.UniversalUDPMuxDefault, error)
 	ActivityRecorder() *bind.ActivityRecorder
+	EndpointManager
 }
 
 type TunNetstackDevice struct {
@@ -155,3 +156,8 @@ func (t *TunNetstackDevice) Device() *device.Device {
 func (t *TunNetstackDevice) GetNet() *netstack.Net {
 	return t.net
 }
+
+// GetICEBind returns the bind instance
+func (t *TunNetstackDevice) GetICEBind() EndpointManager {
+	return t.bind
+}

client/iface/device/device_usp_unix.go

@@ -146,3 +146,8 @@ func (t *USPDevice) assignAddr() error {
 func (t *USPDevice) GetNet() *netstack.Net {
 	return nil
 }
+
+// GetICEBind returns the ICEBind instance
+func (t *USPDevice) GetICEBind() EndpointManager {
+	return t.iceBind
+}

client/iface/device/device_windows.go

@@ -185,3 +185,8 @@ func (t *TunDevice) assignAddr() error {
 func (t *TunDevice) GetNet() *netstack.Net {
 	return nil
 }
+
+// GetICEBind returns the ICEBind instance
+func (t *TunDevice) GetICEBind() EndpointManager {
+	return t.iceBind
+}

client/iface/device/endpoint_manager.go

@@ -0,0 +1,13 @@
+package device
+
+import (
+	"net"
+	"net/netip"
+)
+
+// EndpointManager manages fake IP to connection mappings for userspace bind implementations.
+// Implemented by bind.ICEBind and bind.RelayBindJS.
+type EndpointManager interface {
+	SetEndpoint(fakeIP netip.Addr, conn net.Conn)
+	RemoveEndpoint(fakeIP netip.Addr)
+}

client/iface/device_android.go

@@ -21,4 +21,5 @@ type WGTunDevice interface {
 	FilteredDevice() *device.FilteredDevice
 	Device() *wgdevice.Device
 	GetNet() *netstack.Net
+	GetICEBind() device.EndpointManager
 }

client/iface/iface.go

@@ -80,6 +80,17 @@ func (w *WGIface) GetProxy() wgproxy.Proxy {
 	return w.wgProxyFactory.GetProxy()
 }
 
+// GetBind returns the EndpointManager userspace bind mode.
+func (w *WGIface) GetBind() device.EndpointManager {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+
+	if w.tun == nil {
+		return nil
+	}
+	return w.tun.GetICEBind()
+}
+
 // IsUserspaceBind indicates whether this interfaces is userspace with bind.ICEBind
 func (w *WGIface) IsUserspaceBind() bool {
 	return w.userspaceBind

client/internal/lazyconn/activity/lazy_conn.go

@@ -0,0 +1,82 @@
+package activity
+
+import (
+	"context"
+	"io"
+	"net"
+	"time"
+)
+
+// lazyConn detects activity when WireGuard attempts to send packets.
+// It does not deliver packets, only signals that activity occurred.
+type lazyConn struct {
+	activityCh chan struct{}
+	ctx        context.Context
+	cancel     context.CancelFunc
+}
+
+// newLazyConn creates a new lazyConn for activity detection.
+func newLazyConn() *lazyConn {
+	ctx, cancel := context.WithCancel(context.Background())
+	return &lazyConn{
+		activityCh: make(chan struct{}, 1),
+		ctx:        ctx,
+		cancel:     cancel,
+	}
+}
+
+// Read blocks until the connection is closed.
+func (c *lazyConn) Read(_ []byte) (n int, err error) {
+	<-c.ctx.Done()
+	return 0, io.EOF
+}
+
+// Write signals activity detection when ICEBind routes packets to this endpoint.
+func (c *lazyConn) Write(b []byte) (n int, err error) {
+	if c.ctx.Err() != nil {
+		return 0, io.EOF
+	}
+
+	select {
+	case c.activityCh <- struct{}{}:
+	default:
+	}
+
+	return len(b), nil
+}
+
+// ActivityChan returns the channel that signals when activity is detected.
+func (c *lazyConn) ActivityChan() <-chan struct{} {
+	return c.activityCh
+}
+
+// Close closes the connection.
+func (c *lazyConn) Close() error {
+	c.cancel()
+	return nil
+}
+
+// LocalAddr returns the local address.
+func (c *lazyConn) LocalAddr() net.Addr {
+	return &net.UDPAddr{IP: net.IP{127, 0, 0, 1}, Port: lazyBindPort}
+}
+
+// RemoteAddr returns the remote address.
+func (c *lazyConn) RemoteAddr() net.Addr {
+	return &net.UDPAddr{IP: net.IP{127, 0, 0, 1}, Port: lazyBindPort}
+}
+
+// SetDeadline sets the read and write deadlines.
+func (c *lazyConn) SetDeadline(_ time.Time) error {
+	return nil
+}
+
+// SetReadDeadline sets the deadline for future Read calls.
+func (c *lazyConn) SetReadDeadline(_ time.Time) error {
+	return nil
+}
+
+// SetWriteDeadline sets the deadline for future Write calls.
+func (c *lazyConn) SetWriteDeadline(_ time.Time) error {
+	return nil
+}

client/internal/lazyconn/activity/listener_bind.go

@@ -0,0 +1,127 @@
+package activity
+
+import (
+	"fmt"
+	"net"
+	"net/netip"
+	"sync"
+
+	"github.com/netbirdio/netbird/client/iface/device"
+	"github.com/netbirdio/netbird/client/internal/lazyconn"
+)
+
+type bindProvider interface {
+	GetBind() device.EndpointManager
+}
+
+const (
+	// lazyBindPort is an obscure port used for lazy peer endpoints to avoid confusion with real peers.
+	// The actual routing is done via fakeIP in ICEBind, not by this port.
+	lazyBindPort = 17473
+)
+
+// BindListener uses lazyConn with bind implementations for direct data passing in userspace bind mode.
+type BindListener struct {
+	wgIface WgInterface
+	peerCfg lazyconn.PeerConfig
+	done    sync.WaitGroup
+
+	lazyConn *lazyConn
+	bind     device.EndpointManager
+	fakeIP   netip.Addr
+}
+
+// NewBindListener creates a listener that passes data directly through bind using LazyConn.
+// It automatically derives a unique fake IP from the peer's NetBird IP in the 127.2.x.x range.
+func NewBindListener(wgIface WgInterface, bind device.EndpointManager, cfg lazyconn.PeerConfig) (*BindListener, error) {
+	fakeIP, err := deriveFakeIP(wgIface, cfg.AllowedIPs)
+	if err != nil {
+		return nil, fmt.Errorf("derive fake IP: %w", err)
+	}
+
+	d := &BindListener{
+		wgIface: wgIface,
+		peerCfg: cfg,
+		bind:    bind,
+		fakeIP:  fakeIP,
+	}
+
+	if err := d.setupLazyConn(); err != nil {
+		return nil, fmt.Errorf("setup lazy connection: %v", err)
+	}
+
+	d.done.Add(1)
+	return d, nil
+}
+
+// deriveFakeIP creates a deterministic fake IP for bind mode based on peer's NetBird IP.
+// Maps peer IP 100.64.x.y to fake IP 127.2.x.y (similar to relay proxy using 127.1.x.y).
+// It finds the peer's actual NetBird IP by checking which allowedIP is in the same subnet as our WG interface.
+func deriveFakeIP(wgIface WgInterface, allowedIPs []netip.Prefix) (netip.Addr, error) {
+	if len(allowedIPs) == 0 {
+		return netip.Addr{}, fmt.Errorf("no allowed IPs for peer")
+	}
+
+	ourNetwork := wgIface.Address().Network
+
+	var peerIP netip.Addr
+	for _, allowedIP := range allowedIPs {
+		ip := allowedIP.Addr()
+		if !ip.Is4() {
+			continue
+		}
+		if ourNetwork.Contains(ip) {
+			peerIP = ip
+			break
+		}
+	}
+
+	if !peerIP.IsValid() {
+		return netip.Addr{}, fmt.Errorf("no peer NetBird IP found in allowed IPs")
+	}
+
+	octets := peerIP.As4()
+	fakeIP := netip.AddrFrom4([4]byte{127, 2, octets[2], octets[3]})
+	return fakeIP, nil
+}
+
+func (d *BindListener) setupLazyConn() error {
+	d.lazyConn = newLazyConn()
+	d.bind.SetEndpoint(d.fakeIP, d.lazyConn)
+
+	endpoint := &net.UDPAddr{
+		IP:   d.fakeIP.AsSlice(),
+		Port: lazyBindPort,
+	}
+	return d.wgIface.UpdatePeer(d.peerCfg.PublicKey, d.peerCfg.AllowedIPs, 0, endpoint, nil)
+}
+
+// ReadPackets blocks until activity is detected on the LazyConn or the listener is closed.
+func (d *BindListener) ReadPackets() {
+	select {
+	case <-d.lazyConn.ActivityChan():
+		d.peerCfg.Log.Infof("activity detected via LazyConn")
+	case <-d.lazyConn.ctx.Done():
+		d.peerCfg.Log.Infof("exit from activity listener")
+	}
+
+	d.peerCfg.Log.Debugf("removing lazy endpoint for peer %s", d.peerCfg.PublicKey)
+	if err := d.wgIface.RemovePeer(d.peerCfg.PublicKey); err != nil {
+		d.peerCfg.Log.Errorf("failed to remove endpoint: %s", err)
+	}
+
+	_ = d.lazyConn.Close()
+	d.bind.RemoveEndpoint(d.fakeIP)
+	d.done.Done()
+}
+
+// Close stops the listener and cleans up resources.
+func (d *BindListener) Close() {
+	d.peerCfg.Log.Infof("closing activity listener (LazyConn)")
+
+	if err := d.lazyConn.Close(); err != nil {
+		d.peerCfg.Log.Errorf("failed to close LazyConn: %s", err)
+	}
+
+	d.done.Wait()
+}

client/internal/lazyconn/activity/listener_bind_test.go

@@ -0,0 +1,291 @@
+package activity
+
+import (
+	"net"
+	"net/netip"
+	"runtime"
+	"testing"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+
+	"github.com/netbirdio/netbird/client/iface/device"
+	"github.com/netbirdio/netbird/client/iface/wgaddr"
+	"github.com/netbirdio/netbird/client/internal/lazyconn"
+	peerid "github.com/netbirdio/netbird/client/internal/peer/id"
+)
+
+func isBindListenerPlatform() bool {
+	return runtime.GOOS == "windows" || runtime.GOOS == "js"
+}
+
+// mockEndpointManager implements device.EndpointManager for testing
+type mockEndpointManager struct {
+	endpoints map[netip.Addr]net.Conn
+}
+
+func newMockEndpointManager() *mockEndpointManager {
+	return &mockEndpointManager{
+		endpoints: make(map[netip.Addr]net.Conn),
+	}
+}
+
+func (m *mockEndpointManager) SetEndpoint(fakeIP netip.Addr, conn net.Conn) {
+	m.endpoints[fakeIP] = conn
+}
+
+func (m *mockEndpointManager) RemoveEndpoint(fakeIP netip.Addr) {
+	delete(m.endpoints, fakeIP)
+}
+
+func (m *mockEndpointManager) GetEndpoint(fakeIP netip.Addr) net.Conn {
+	return m.endpoints[fakeIP]
+}
+
+// MockWGIfaceBind mocks WgInterface with bind support
+type MockWGIfaceBind struct {
+	endpointMgr *mockEndpointManager
+}
+
+func (m *MockWGIfaceBind) RemovePeer(string) error {
+	return nil
+}
+
+func (m *MockWGIfaceBind) UpdatePeer(string, []netip.Prefix, time.Duration, *net.UDPAddr, *wgtypes.Key) error {
+	return nil
+}
+
+func (m *MockWGIfaceBind) IsUserspaceBind() bool {
+	return true
+}
+
+func (m *MockWGIfaceBind) Address() wgaddr.Address {
+	return wgaddr.Address{
+		IP:      netip.MustParseAddr("100.64.0.1"),
+		Network: netip.MustParsePrefix("100.64.0.0/16"),
+	}
+}
+
+func (m *MockWGIfaceBind) GetBind() device.EndpointManager {
+	return m.endpointMgr
+}
+
+func TestBindListener_Creation(t *testing.T) {
+	mockEndpointMgr := newMockEndpointManager()
+	mockIface := &MockWGIfaceBind{endpointMgr: mockEndpointMgr}
+
+	peer := &MocPeer{PeerID: "testPeer1"}
+	cfg := lazyconn.PeerConfig{
+		PublicKey:  peer.PeerID,
+		PeerConnID: peer.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	listener, err := NewBindListener(mockIface, mockEndpointMgr, cfg)
+	require.NoError(t, err)
+
+	expectedFakeIP := netip.MustParseAddr("127.2.0.2")
+	conn := mockEndpointMgr.GetEndpoint(expectedFakeIP)
+	require.NotNil(t, conn, "Endpoint should be registered in mock endpoint manager")
+
+	_, ok := conn.(*lazyConn)
+	assert.True(t, ok, "Registered endpoint should be a lazyConn")
+
+	readPacketsDone := make(chan struct{})
+	go func() {
+		listener.ReadPackets()
+		close(readPacketsDone)
+	}()
+
+	listener.Close()
+
+	select {
+	case <-readPacketsDone:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for ReadPackets to exit after Close")
+	}
+}
+
+func TestBindListener_ActivityDetection(t *testing.T) {
+	mockEndpointMgr := newMockEndpointManager()
+	mockIface := &MockWGIfaceBind{endpointMgr: mockEndpointMgr}
+
+	peer := &MocPeer{PeerID: "testPeer1"}
+	cfg := lazyconn.PeerConfig{
+		PublicKey:  peer.PeerID,
+		PeerConnID: peer.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	listener, err := NewBindListener(mockIface, mockEndpointMgr, cfg)
+	require.NoError(t, err)
+
+	activityDetected := make(chan struct{})
+	go func() {
+		listener.ReadPackets()
+		close(activityDetected)
+	}()
+
+	fakeIP := listener.fakeIP
+	conn := mockEndpointMgr.GetEndpoint(fakeIP)
+	require.NotNil(t, conn, "Endpoint should be registered")
+
+	_, err = conn.Write([]byte{0x01, 0x02, 0x03})
+	require.NoError(t, err)
+
+	select {
+	case <-activityDetected:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for activity detection")
+	}
+
+	assert.Nil(t, mockEndpointMgr.GetEndpoint(fakeIP), "Endpoint should be removed after activity detection")
+}
+
+func TestBindListener_Close(t *testing.T) {
+	mockEndpointMgr := newMockEndpointManager()
+	mockIface := &MockWGIfaceBind{endpointMgr: mockEndpointMgr}
+
+	peer := &MocPeer{PeerID: "testPeer1"}
+	cfg := lazyconn.PeerConfig{
+		PublicKey:  peer.PeerID,
+		PeerConnID: peer.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	listener, err := NewBindListener(mockIface, mockEndpointMgr, cfg)
+	require.NoError(t, err)
+
+	readPacketsDone := make(chan struct{})
+	go func() {
+		listener.ReadPackets()
+		close(readPacketsDone)
+	}()
+
+	fakeIP := listener.fakeIP
+	listener.Close()
+
+	select {
+	case <-readPacketsDone:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for ReadPackets to exit after Close")
+	}
+
+	assert.Nil(t, mockEndpointMgr.GetEndpoint(fakeIP), "Endpoint should be removed after Close")
+}
+
+func TestManager_BindMode(t *testing.T) {
+	if !isBindListenerPlatform() {
+		t.Skip("BindListener only used on Windows/JS platforms")
+	}
+
+	mockEndpointMgr := newMockEndpointManager()
+	mockIface := &MockWGIfaceBind{endpointMgr: mockEndpointMgr}
+
+	peer := &MocPeer{PeerID: "testPeer1"}
+	mgr := NewManager(mockIface)
+	defer mgr.Close()
+
+	cfg := lazyconn.PeerConfig{
+		PublicKey:  peer.PeerID,
+		PeerConnID: peer.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	err := mgr.MonitorPeerActivity(cfg)
+	require.NoError(t, err)
+
+	listener, exists := mgr.GetPeerListener(cfg.PeerConnID)
+	require.True(t, exists, "Peer listener should be found")
+
+	bindListener, ok := listener.(*BindListener)
+	require.True(t, ok, "Listener should be BindListener, got %T", listener)
+
+	fakeIP := bindListener.fakeIP
+	conn := mockEndpointMgr.GetEndpoint(fakeIP)
+	require.NotNil(t, conn, "Endpoint should be registered")
+
+	_, err = conn.Write([]byte{0x01, 0x02, 0x03})
+	require.NoError(t, err)
+
+	select {
+	case peerConnID := <-mgr.OnActivityChan:
+		assert.Equal(t, cfg.PeerConnID, peerConnID, "Received peer connection ID should match")
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for activity notification")
+	}
+
+	assert.Nil(t, mockEndpointMgr.GetEndpoint(fakeIP), "Endpoint should be removed after activity")
+}
+
+func TestManager_BindMode_MultiplePeers(t *testing.T) {
+	if !isBindListenerPlatform() {
+		t.Skip("BindListener only used on Windows/JS platforms")
+	}
+
+	mockEndpointMgr := newMockEndpointManager()
+	mockIface := &MockWGIfaceBind{endpointMgr: mockEndpointMgr}
+
+	peer1 := &MocPeer{PeerID: "testPeer1"}
+	peer2 := &MocPeer{PeerID: "testPeer2"}
+	mgr := NewManager(mockIface)
+	defer mgr.Close()
+
+	cfg1 := lazyconn.PeerConfig{
+		PublicKey:  peer1.PeerID,
+		PeerConnID: peer1.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	cfg2 := lazyconn.PeerConfig{
+		PublicKey:  peer2.PeerID,
+		PeerConnID: peer2.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.3/32")},
+		Log:        log.WithField("peer", "testPeer2"),
+	}
+
+	err := mgr.MonitorPeerActivity(cfg1)
+	require.NoError(t, err)
+
+	err = mgr.MonitorPeerActivity(cfg2)
+	require.NoError(t, err)
+
+	listener1, exists := mgr.GetPeerListener(cfg1.PeerConnID)
+	require.True(t, exists, "Peer1 listener should be found")
+	bindListener1 := listener1.(*BindListener)
+
+	listener2, exists := mgr.GetPeerListener(cfg2.PeerConnID)
+	require.True(t, exists, "Peer2 listener should be found")
+	bindListener2 := listener2.(*BindListener)
+
+	conn1 := mockEndpointMgr.GetEndpoint(bindListener1.fakeIP)
+	require.NotNil(t, conn1, "Peer1 endpoint should be registered")
+	_, err = conn1.Write([]byte{0x01})
+	require.NoError(t, err)
+
+	conn2 := mockEndpointMgr.GetEndpoint(bindListener2.fakeIP)
+	require.NotNil(t, conn2, "Peer2 endpoint should be registered")
+	_, err = conn2.Write([]byte{0x02})
+	require.NoError(t, err)
+
+	receivedPeers := make(map[peerid.ConnID]bool)
+	for i := 0; i < 2; i++ {
+		select {
+		case peerConnID := <-mgr.OnActivityChan:
+			receivedPeers[peerConnID] = true
+		case <-time.After(2 * time.Second):
+			t.Fatal("timeout waiting for activity notifications")
+		}
+	}
+
+	assert.True(t, receivedPeers[cfg1.PeerConnID], "Peer1 activity should be received")
+	assert.True(t, receivedPeers[cfg2.PeerConnID], "Peer2 activity should be received")
+}

client/internal/lazyconn/activity/listener_test.go

@@ -1,41 +0,0 @@
-package activity
-
-import (
-	"testing"
-	"time"
-
-	log "github.com/sirupsen/logrus"
-
-	"github.com/netbirdio/netbird/client/internal/lazyconn"
-)
-
-func TestNewListener(t *testing.T) {
-	peer := &MocPeer{
-		PeerID: "examplePublicKey1",
-	}
-
-	cfg := lazyconn.PeerConfig{
-		PublicKey:  peer.PeerID,
-		PeerConnID: peer.ConnID(),
-		Log:        log.WithField("peer", "examplePublicKey1"),
-	}
-
-	l, err := NewListener(MocWGIface{}, cfg)
-	if err != nil {
-		t.Fatalf("failed to create listener: %v", err)
-	}
-
-	chanClosed := make(chan struct{})
-	go func() {
-		defer close(chanClosed)
-		l.ReadPackets()
-	}()
-
-	time.Sleep(1 * time.Second)
-	l.Close()
-
-	select {
-	case <-chanClosed:
-	case <-time.After(time.Second):
-	}
-}

client/internal/lazyconn/activity/listener_udp.go

@@ -11,26 +11,27 @@ import (
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
 )
 
-// Listener it is not a thread safe implementation, do not call Close before ReadPackets. It will cause blocking
-type Listener struct {
+// UDPListener uses UDP sockets for activity detection in kernel mode.
+type UDPListener struct {
 	wgIface  WgInterface
 	peerCfg  lazyconn.PeerConfig
 	conn     *net.UDPConn
 	endpoint *net.UDPAddr
 	done     sync.Mutex
 
-	isClosed atomic.Bool // use to avoid error log when closing the listener
+	isClosed atomic.Bool
 }
 
-func NewListener(wgIface WgInterface, cfg lazyconn.PeerConfig) (*Listener, error) {
-	d := &Listener{
+// NewUDPListener creates a listener that detects activity via UDP socket reads.
+func NewUDPListener(wgIface WgInterface, cfg lazyconn.PeerConfig) (*UDPListener, error) {
+	d := &UDPListener{
 		wgIface: wgIface,
 		peerCfg: cfg,
 	}
 
 	conn, err := d.newConn()
 	if err != nil {
-		return nil, fmt.Errorf("failed to creating activity listener: %v", err)
+		return nil, fmt.Errorf("create UDP connection: %v", err)
 	}
 	d.conn = conn
 	d.endpoint = conn.LocalAddr().(*net.UDPAddr)
@@ -38,12 +39,14 @@ func NewListener(wgIface WgInterface, cfg lazyconn.PeerConfig) (*Listener, error
 	if err := d.createEndpoint(); err != nil {
 		return nil, err
 	}
+
 	d.done.Lock()
-	cfg.Log.Infof("created activity listener: %s", conn.LocalAddr().(*net.UDPAddr).String())
+	cfg.Log.Infof("created activity listener: %s", d.conn.LocalAddr().(*net.UDPAddr).String())
 	return d, nil
 }
 
-func (d *Listener) ReadPackets() {
+// ReadPackets blocks reading from the UDP socket until activity is detected or the listener is closed.
+func (d *UDPListener) ReadPackets() {
 	for {
 		n, remoteAddr, err := d.conn.ReadFromUDP(make([]byte, 1))
 		if err != nil {
@@ -64,15 +67,17 @@ func (d *Listener) ReadPackets() {
 	}
 
 	d.peerCfg.Log.Debugf("removing lazy endpoint: %s", d.endpoint.String())
-	if err := d.removeEndpoint(); err != nil {
+	if err := d.wgIface.RemovePeer(d.peerCfg.PublicKey); err != nil {
 		d.peerCfg.Log.Errorf("failed to remove endpoint: %s", err)
 	}
 
-	_ = d.conn.Close() // do not care err because some cases it will return "use of closed network connection"
+	// Ignore close error as it may return "use of closed network connection" if already closed.
+	_ = d.conn.Close()
 	d.done.Unlock()
 }
 
-func (d *Listener) Close() {
+// Close stops the listener and cleans up resources.
+func (d *UDPListener) Close() {
 	d.peerCfg.Log.Infof("closing activity listener: %s", d.conn.LocalAddr().String())
 	d.isClosed.Store(true)
 
@@ -82,16 +87,12 @@ func (d *Listener) Close() {
 	d.done.Lock()
 }
 
-func (d *Listener) removeEndpoint() error {
-	return d.wgIface.RemovePeer(d.peerCfg.PublicKey)
-}
-
-func (d *Listener) createEndpoint() error {
+func (d *UDPListener) createEndpoint() error {
 	d.peerCfg.Log.Debugf("creating lazy endpoint: %s", d.endpoint.String())
 	return d.wgIface.UpdatePeer(d.peerCfg.PublicKey, d.peerCfg.AllowedIPs, 0, d.endpoint, nil)
 }
 
-func (d *Listener) newConn() (*net.UDPConn, error) {
+func (d *UDPListener) newConn() (*net.UDPConn, error) {
 	addr := &net.UDPAddr{
 		Port: 0,
 		IP:   listenIP,

client/internal/lazyconn/activity/listener_udp_test.go

@@ -0,0 +1,110 @@
+package activity
+
+import (
+	"net"
+	"net/netip"
+	"testing"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/client/internal/lazyconn"
+)
+
+func TestUDPListener_Creation(t *testing.T) {
+	mockIface := &MocWGIface{}
+
+	peer := &MocPeer{PeerID: "testPeer1"}
+	cfg := lazyconn.PeerConfig{
+		PublicKey:  peer.PeerID,
+		PeerConnID: peer.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	listener, err := NewUDPListener(mockIface, cfg)
+	require.NoError(t, err)
+	require.NotNil(t, listener.conn)
+	require.NotNil(t, listener.endpoint)
+
+	readPacketsDone := make(chan struct{})
+	go func() {
+		listener.ReadPackets()
+		close(readPacketsDone)
+	}()
+
+	listener.Close()
+
+	select {
+	case <-readPacketsDone:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for ReadPackets to exit after Close")
+	}
+}
+
+func TestUDPListener_ActivityDetection(t *testing.T) {
+	mockIface := &MocWGIface{}
+
+	peer := &MocPeer{PeerID: "testPeer1"}
+	cfg := lazyconn.PeerConfig{
+		PublicKey:  peer.PeerID,
+		PeerConnID: peer.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	listener, err := NewUDPListener(mockIface, cfg)
+	require.NoError(t, err)
+
+	activityDetected := make(chan struct{})
+	go func() {
+		listener.ReadPackets()
+		close(activityDetected)
+	}()
+
+	conn, err := net.Dial("udp", listener.conn.LocalAddr().String())
+	require.NoError(t, err)
+	defer conn.Close()
+
+	_, err = conn.Write([]byte{0x01, 0x02, 0x03})
+	require.NoError(t, err)
+
+	select {
+	case <-activityDetected:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for activity detection")
+	}
+}
+
+func TestUDPListener_Close(t *testing.T) {
+	mockIface := &MocWGIface{}
+
+	peer := &MocPeer{PeerID: "testPeer1"}
+	cfg := lazyconn.PeerConfig{
+		PublicKey:  peer.PeerID,
+		PeerConnID: peer.ConnID(),
+		AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.64.0.2/32")},
+		Log:        log.WithField("peer", "testPeer1"),
+	}
+
+	listener, err := NewUDPListener(mockIface, cfg)
+	require.NoError(t, err)
+
+	readPacketsDone := make(chan struct{})
+	go func() {
+		listener.ReadPackets()
+		close(readPacketsDone)
+	}()
+
+	listener.Close()
+
+	select {
+	case <-readPacketsDone:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for ReadPackets to exit after Close")
+	}
+
+	assert.True(t, listener.isClosed.Load(), "Listener should be marked as closed")
+}

client/internal/lazyconn/activity/manager.go

@@ -1,21 +1,32 @@
 package activity
 
 import (
+	"errors"
 	"net"
 	"net/netip"
+	"runtime"
 	"sync"
 	"time"
 
 	log "github.com/sirupsen/logrus"
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
+	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
 	peerid "github.com/netbirdio/netbird/client/internal/peer/id"
 )
 
+// listener defines the contract for activity detection listeners.
+type listener interface {
+	ReadPackets()
+	Close()
+}
+
 type WgInterface interface {
 	RemovePeer(peerKey string) error
 	UpdatePeer(peerKey string, allowedIps []netip.Prefix, keepAlive time.Duration, endpoint *net.UDPAddr, preSharedKey *wgtypes.Key) error
+	IsUserspaceBind() bool
+	Address() wgaddr.Address
 }
 
 type Manager struct {
@@ -23,7 +34,7 @@ type Manager struct {
 
 	wgIface WgInterface
 
-	peers map[peerid.ConnID]*Listener
+	peers map[peerid.ConnID]listener
 	done  chan struct{}
 
 	mu sync.Mutex
@@ -33,7 +44,7 @@ func NewManager(wgIface WgInterface) *Manager {
 	m := &Manager{
 		OnActivityChan: make(chan peerid.ConnID, 1),
 		wgIface:        wgIface,
-		peers:          make(map[peerid.ConnID]*Listener),
+		peers:          make(map[peerid.ConnID]listener),
 		done:           make(chan struct{}),
 	}
 	return m
@@ -48,16 +59,38 @@ func (m *Manager) MonitorPeerActivity(peerCfg lazyconn.PeerConfig) error {
 		return nil
 	}
 
-	listener, err := NewListener(m.wgIface, peerCfg)
+	listener, err := m.createListener(peerCfg)
 	if err != nil {
 		return err
 	}
-	m.peers[peerCfg.PeerConnID] = listener
 
+	m.peers[peerCfg.PeerConnID] = listener
 	go m.waitForTraffic(listener, peerCfg.PeerConnID)
 	return nil
 }
 
+func (m *Manager) createListener(peerCfg lazyconn.PeerConfig) (listener, error) {
+	if !m.wgIface.IsUserspaceBind() {
+		return NewUDPListener(m.wgIface, peerCfg)
+	}
+
+	// BindListener is only used on Windows and JS platforms:
+	// - JS: Cannot listen to UDP sockets
+	// - Windows: IP_UNICAST_IF socket option forces packets out the interface the default
+	//   gateway points to, preventing them from reaching the loopback interface.
+	//   BindListener bypasses this by passing data directly through the bind.
+	if runtime.GOOS != "windows" && runtime.GOOS != "js" {
+		return NewUDPListener(m.wgIface, peerCfg)
+	}
+
+	provider, ok := m.wgIface.(bindProvider)
+	if !ok {
+		return nil, errors.New("interface claims userspace bind but doesn't implement bindProvider")
+	}
+
+	return NewBindListener(m.wgIface, provider.GetBind(), peerCfg)
+}
+
 func (m *Manager) RemovePeer(log *log.Entry, peerConnID peerid.ConnID) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -82,8 +115,8 @@ func (m *Manager) Close() {
 	}
 }
 
-func (m *Manager) waitForTraffic(listener *Listener, peerConnID peerid.ConnID) {
-	listener.ReadPackets()
+func (m *Manager) waitForTraffic(l listener, peerConnID peerid.ConnID) {
+	l.ReadPackets()
 
 	m.mu.Lock()
 	if _, ok := m.peers[peerConnID]; !ok {

client/internal/lazyconn/activity/manager_test.go

@@ -9,6 +9,7 @@ import (
 	log "github.com/sirupsen/logrus"
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
+	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
 	peerid "github.com/netbirdio/netbird/client/internal/peer/id"
 )
@@ -30,16 +31,26 @@ func (m MocWGIface) RemovePeer(string) error {
 
 func (m MocWGIface) UpdatePeer(string, []netip.Prefix, time.Duration, *net.UDPAddr, *wgtypes.Key) error {
 	return nil
-
 }
 
-// Add this method to the Manager struct
-func (m *Manager) GetPeerListener(peerConnID peerid.ConnID) (*Listener, bool) {
+func (m MocWGIface) IsUserspaceBind() bool {
+	return false
+}
+
+func (m MocWGIface) Address() wgaddr.Address {
+	return wgaddr.Address{
+		IP:      netip.MustParseAddr("100.64.0.1"),
+		Network: netip.MustParsePrefix("100.64.0.0/16"),
+	}
+}
+
+// GetPeerListener is a test helper to access listeners
+func (m *Manager) GetPeerListener(peerConnID peerid.ConnID) (listener, bool) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
-	listener, exists := m.peers[peerConnID]
-	return listener, exists
+	l, exists := m.peers[peerConnID]
+	return l, exists
 }
 
 func TestManager_MonitorPeerActivity(t *testing.T) {
@@ -65,7 +76,12 @@ func TestManager_MonitorPeerActivity(t *testing.T) {
 		t.Fatalf("peer listener not found")
 	}
 
-	if err := trigger(listener.conn.LocalAddr().String()); err != nil {
+	// Get the UDP listener's address for triggering
+	udpListener, ok := listener.(*UDPListener)
+	if !ok {
+		t.Fatalf("expected UDPListener")
+	}
+	if err := trigger(udpListener.conn.LocalAddr().String()); err != nil {
 		t.Fatalf("failed to trigger activity: %v", err)
 	}
 
@@ -97,7 +113,9 @@ func TestManager_RemovePeerActivity(t *testing.T) {
 		t.Fatalf("failed to monitor peer activity: %v", err)
 	}
 
-	addr := mgr.peers[peerCfg1.PeerConnID].conn.LocalAddr().String()
+	listener, _ := mgr.GetPeerListener(peerCfg1.PeerConnID)
+	udpListener, _ := listener.(*UDPListener)
+	addr := udpListener.conn.LocalAddr().String()
 
 	mgr.RemovePeer(peerCfg1.Log, peerCfg1.PeerConnID)
 
@@ -147,7 +165,8 @@ func TestManager_MultiPeerActivity(t *testing.T) {
 		t.Fatalf("peer listener for peer1 not found")
 	}
 
-	if err := trigger(listener.conn.LocalAddr().String()); err != nil {
+	udpListener1, _ := listener.(*UDPListener)
+	if err := trigger(udpListener1.conn.LocalAddr().String()); err != nil {
 		t.Fatalf("failed to trigger activity: %v", err)
 	}
 
@@ -156,7 +175,8 @@ func TestManager_MultiPeerActivity(t *testing.T) {
 		t.Fatalf("peer listener for peer2 not found")
 	}
 
-	if err := trigger(listener.conn.LocalAddr().String()); err != nil {
+	udpListener2, _ := listener.(*UDPListener)
+	if err := trigger(udpListener2.conn.LocalAddr().String()); err != nil {
 		t.Fatalf("failed to trigger activity: %v", err)
 	}
 

client/internal/lazyconn/wgiface.go

@@ -7,6 +7,7 @@ import (
 
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
+	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/monotime"
 )
 
@@ -14,5 +15,6 @@ type WGIface interface {
 	RemovePeer(peerKey string) error
 	UpdatePeer(peerKey string, allowedIps []netip.Prefix, keepAlive time.Duration, endpoint *net.UDPAddr, preSharedKey *wgtypes.Key) error
 	IsUserspaceBind() bool
+	Address() wgaddr.Address
 	LastActivities() map[string]monotime.Time
 }