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

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 {