[client] Fix netstack dns forwarder

client/firewall/uspfilter/filter.go

@@ -50,6 +50,12 @@ const (
 
 var errNatNotSupported = errors.New("nat not supported with userspace firewall")
 
+// serviceKey represents a protocol/port combination for netstack service registry
+type serviceKey struct {
+	protocol gopacket.LayerType
+	port     uint16
+}
+
 // RuleSet is a set of rules grouped by a string key
 type RuleSet map[string]PeerRule
 
@@ -113,6 +119,9 @@ type Manager struct {
 	portDNATEnabled atomic.Bool
 	portDNATRules   []portDNATRule
 	portDNATMutex   sync.RWMutex
+
+	netstackServices     map[serviceKey]struct{}
+	netstackServiceMutex sync.RWMutex
 }
 
 // decoder for packages
@@ -203,6 +212,7 @@ func create(iface common.IFaceMapper, nativeFirewall firewall.Manager, disableSe
 		localForwarding:     enableLocalForwarding,
 		dnatMappings:        make(map[netip.Addr]netip.Addr),
 		portDNATRules:       []portDNATRule{},
+		netstackServices:    make(map[serviceKey]struct{}),
 	}
 	m.routingEnabled.Store(false)
 
@@ -838,9 +848,7 @@ func (m *Manager) handleLocalTraffic(d *decoder, srcIP, dstIP netip.Addr, packet
 		return true
 	}
 
-	// If requested we pass local traffic to internal interfaces to the forwarder.
-	// netstack doesn't have an interface to forward packets to the native stack so we always need to use the forwarder.
-	if m.localForwarding && (m.netstack || dstIP != m.wgIface.Address().IP) {
+	if m.shouldForward(d, dstIP) {
 		return m.handleForwardedLocalTraffic(packetData)
 	}
 
@@ -1274,3 +1282,86 @@ func (m *Manager) DisableRouting() error {
 
 	return nil
 }
+
+// RegisterNetstackService registers a service as listening on the netstack for the given protocol and port
+func (m *Manager) RegisterNetstackService(protocol nftypes.Protocol, port uint16) {
+	m.netstackServiceMutex.Lock()
+	defer m.netstackServiceMutex.Unlock()
+	layerType := m.protocolToLayerType(protocol)
+	key := serviceKey{protocol: layerType, port: port}
+	m.netstackServices[key] = struct{}{}
+	m.logger.Debug3("RegisterNetstackService: registered %s:%d (layerType=%s)", protocol, port, layerType)
+	m.logger.Debug1("RegisterNetstackService: current registry size: %d", len(m.netstackServices))
+}
+
+// UnregisterNetstackService removes a service from the netstack registry
+func (m *Manager) UnregisterNetstackService(protocol nftypes.Protocol, port uint16) {
+	m.netstackServiceMutex.Lock()
+	defer m.netstackServiceMutex.Unlock()
+	layerType := m.protocolToLayerType(protocol)
+	key := serviceKey{protocol: layerType, port: port}
+	delete(m.netstackServices, key)
+	m.logger.Debug2("Unregistered netstack service on protocol %s port %d", protocol, port)
+}
+
+// protocolToLayerType converts nftypes.Protocol to gopacket.LayerType for internal use
+func (m *Manager) protocolToLayerType(protocol nftypes.Protocol) gopacket.LayerType {
+	switch protocol {
+	case nftypes.TCP:
+		return layers.LayerTypeTCP
+	case nftypes.UDP:
+		return layers.LayerTypeUDP
+	case nftypes.ICMP:
+		return layers.LayerTypeICMPv4
+	default:
+		return gopacket.LayerType(0) // Invalid/unknown
+	}
+}
+
+// shouldForward determines if a packet should be forwarded to the forwarder.
+// The forwarder handles routing packets to the native OS network stack.
+// Returns true if packet should go to the forwarder, false if it should go to netstack listeners or the native stack directly.
+func (m *Manager) shouldForward(d *decoder, dstIP netip.Addr) bool {
+	// not enabled, never forward
+	if !m.localForwarding {
+		return false
+	}
+
+	// netstack always needs to forward because it's lacking a native interface
+	// exception for registered netstack services, those should go to netstack listeners
+	if m.netstack {
+		return !m.hasMatchingNetstackService(d)
+	}
+
+	// traffic to our other local interfaces (not NetBird IP) - always forward
+	if dstIP != m.wgIface.Address().IP {
+		return true
+	}
+
+	// traffic to our NetBird IP, not netstack mode - send to netstack listeners
+	return false
+}
+
+// hasMatchingNetstackService checks if there's a registered netstack service for this packet
+func (m *Manager) hasMatchingNetstackService(d *decoder) bool {
+	if len(d.decoded) < 2 {
+		return false
+	}
+
+	var dstPort uint16
+	switch d.decoded[1] {
+	case layers.LayerTypeTCP:
+		dstPort = uint16(d.tcp.DstPort)
+	case layers.LayerTypeUDP:
+		dstPort = uint16(d.udp.DstPort)
+	default:
+		return false
+	}
+
+	key := serviceKey{protocol: d.decoded[1], port: dstPort}
+	m.netstackServiceMutex.RLock()
+	_, exists := m.netstackServices[key]
+	m.netstackServiceMutex.RUnlock()
+
+	return exists
+}

client/internal/dnsfwd/cache_test.go

@@ -83,4 +83,3 @@ func TestCacheMiss(t *testing.T) {
 		t.Fatalf("expected cache miss, got=%v ok=%v", got, ok)
 	}
 }
-

client/internal/dnsfwd/forwarder.go

@@ -14,6 +14,7 @@ import (
 	"github.com/hashicorp/go-multierror"
 	"github.com/miekg/dns"
 	log "github.com/sirupsen/logrus"
+	"golang.zx2c4.com/wireguard/tun/netstack"
 
 	nberrors "github.com/netbirdio/netbird/client/errors"
 	firewall "github.com/netbirdio/netbird/client/firewall/manager"
@@ -33,7 +34,7 @@ type firewaller interface {
 }
 
 type DNSForwarder struct {
-	listenAddress  string
+	listenAddress  netip.AddrPort
 	ttl            uint32
 	statusRecorder *peer.Status
 
@@ -47,9 +48,11 @@ type DNSForwarder struct {
 	firewall   firewaller
 	resolver   resolver
 	cache      *cache
+
+	wgIface wgIface
 }
 
-func NewDNSForwarder(listenAddress string, ttl uint32, firewall firewaller, statusRecorder *peer.Status) *DNSForwarder {
+func NewDNSForwarder(listenAddress netip.AddrPort, ttl uint32, firewall firewaller, statusRecorder *peer.Status, wgIface wgIface) *DNSForwarder {
 	log.Debugf("creating DNS forwarder with listen_address=%s ttl=%d", listenAddress, ttl)
 	return &DNSForwarder{
 		listenAddress:  listenAddress,
@@ -58,49 +61,80 @@ func NewDNSForwarder(listenAddress string, ttl uint32, firewall firewaller, stat
 		statusRecorder: statusRecorder,
 		resolver:       net.DefaultResolver,
 		cache:          newCache(),
+		wgIface:        wgIface,
 	}
 }
 
 func (f *DNSForwarder) Listen(entries []*ForwarderEntry) error {
-	log.Infof("starting DNS forwarder on address=%s", f.listenAddress)
+	var netstackNet *netstack.Net
+	if f.wgIface != nil {
+		netstackNet = f.wgIface.GetNet()
+	}
+
+	addrDesc := f.listenAddress.String()
+	if netstackNet != nil {
+		addrDesc = fmt.Sprintf("netstack %s", f.listenAddress)
+	}
+	log.Infof("starting DNS forwarder on address=%s", addrDesc)
+
+	udpLn, err := f.createUDPListener(netstackNet)
+	if err != nil {
+		return fmt.Errorf("create UDP listener: %w", err)
+	}
+
+	tcpLn, err := f.createTCPListener(netstackNet)
+	if err != nil {
+		return fmt.Errorf("create TCP listener: %w", err)
+	}
 
-	// UDP server
 	mux := dns.NewServeMux()
 	f.mux = mux
 	mux.HandleFunc(".", f.handleDNSQueryUDP)
 	f.dnsServer = &dns.Server{
-		Addr:    f.listenAddress,
-		Net:     "udp",
-		Handler: mux,
+		PacketConn: udpLn,
+		Handler:    mux,
 	}
 
-	// TCP server
 	tcpMux := dns.NewServeMux()
 	f.tcpMux = tcpMux
 	tcpMux.HandleFunc(".", f.handleDNSQueryTCP)
 	f.tcpServer = &dns.Server{
-		Addr:    f.listenAddress,
-		Net:     "tcp",
-		Handler: tcpMux,
+		Listener: tcpLn,
+		Handler:  tcpMux,
 	}
 
 	f.UpdateDomains(entries)
 
 	errCh := make(chan error, 2)
 
 	go func() {
-		log.Infof("DNS UDP listener running on %s", f.listenAddress)
-		errCh <- f.dnsServer.ListenAndServe()
+		log.Infof("DNS UDP listener running on %s", addrDesc)
+		errCh <- f.dnsServer.ActivateAndServe()
 	}()
 	go func() {
-		log.Infof("DNS TCP listener running on %s", f.listenAddress)
-		errCh <- f.tcpServer.ListenAndServe()
+		log.Infof("DNS TCP listener running on %s", addrDesc)
+		errCh <- f.tcpServer.ActivateAndServe()
 	}()
 
-	// return the first error we get (e.g. bind failure or shutdown)
 	return <-errCh
 }
 
+func (f *DNSForwarder) createUDPListener(netstackNet *netstack.Net) (net.PacketConn, error) {
+	if netstackNet != nil {
+		return netstackNet.ListenUDPAddrPort(f.listenAddress)
+	}
+
+	return net.ListenUDP("udp", net.UDPAddrFromAddrPort(f.listenAddress))
+}
+
+func (f *DNSForwarder) createTCPListener(netstackNet *netstack.Net) (net.Listener, error) {
+	if netstackNet != nil {
+		return netstackNet.ListenTCPAddrPort(f.listenAddress)
+	}
+
+	return net.ListenTCP("tcp", net.TCPAddrFromAddrPort(f.listenAddress))
+}
+
 func (f *DNSForwarder) UpdateDomains(entries []*ForwarderEntry) {
 	f.mutex.Lock()
 	defer f.mutex.Unlock()

client/internal/dnsfwd/forwarder_test.go

@@ -297,7 +297,7 @@ func TestDNSForwarder_UnauthorizedDomainAccess(t *testing.T) {
 				mockResolver.On("LookupNetIP", mock.Anything, "ip4", dns.Fqdn(tt.queryDomain)).Return([]netip.Addr{fakeIP}, nil)
 			}
 
-			forwarder := NewDNSForwarder("127.0.0.1:0", 300, mockFirewall, &peer.Status{})
+			forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, mockFirewall, &peer.Status{}, nil)
 			forwarder.resolver = mockResolver
 
 			d, err := domain.FromString(tt.configuredDomain)
@@ -402,7 +402,7 @@ func TestDNSForwarder_FirewallSetUpdates(t *testing.T) {
 			mockResolver := &MockResolver{}
 
 			// Set up forwarder
-			forwarder := NewDNSForwarder("127.0.0.1:0", 300, mockFirewall, &peer.Status{})
+			forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, mockFirewall, &peer.Status{}, nil)
 			forwarder.resolver = mockResolver
 
 			// Create entries and track sets
@@ -489,7 +489,7 @@ func TestDNSForwarder_MultipleIPsInSingleUpdate(t *testing.T) {
 	mockFirewall := &MockFirewall{}
 	mockResolver := &MockResolver{}
 
-	forwarder := NewDNSForwarder("127.0.0.1:0", 300, mockFirewall, &peer.Status{})
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, mockFirewall, &peer.Status{}, nil)
 	forwarder.resolver = mockResolver
 
 	// Configure a single domain
@@ -584,7 +584,7 @@ func TestDNSForwarder_ResponseCodes(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			forwarder := NewDNSForwarder("127.0.0.1:0", 300, nil, &peer.Status{})
+			forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, nil, &peer.Status{}, nil)
 
 			d, err := domain.FromString(tt.configured)
 			require.NoError(t, err)
@@ -616,7 +616,7 @@ func TestDNSForwarder_ResponseCodes(t *testing.T) {
 func TestDNSForwarder_TCPTruncation(t *testing.T) {
 	// Test that large UDP responses are truncated with TC bit set
 	mockResolver := &MockResolver{}
-	forwarder := NewDNSForwarder("127.0.0.1:0", 300, nil, &peer.Status{})
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, nil, &peer.Status{}, nil)
 	forwarder.resolver = mockResolver
 
 	d, _ := domain.FromString("example.com")
@@ -652,7 +652,7 @@ func TestDNSForwarder_TCPTruncation(t *testing.T) {
 // a subsequent upstream failure still returns a successful response from cache.
 func TestDNSForwarder_ServeFromCacheOnUpstreamFailure(t *testing.T) {
 	mockResolver := &MockResolver{}
-	forwarder := NewDNSForwarder("127.0.0.1:0", 300, nil, &peer.Status{})
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, nil, &peer.Status{}, nil)
 	forwarder.resolver = mockResolver
 
 	d, err := domain.FromString("example.com")
@@ -696,7 +696,7 @@ func TestDNSForwarder_ServeFromCacheOnUpstreamFailure(t *testing.T) {
 // Verifies that cache normalization works across casing and trailing dot variations.
 func TestDNSForwarder_CacheNormalizationCasingAndDot(t *testing.T) {
 	mockResolver := &MockResolver{}
-	forwarder := NewDNSForwarder("127.0.0.1:0", 300, nil, &peer.Status{})
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, nil, &peer.Status{}, nil)
 	forwarder.resolver = mockResolver
 
 	d, err := domain.FromString("ExAmPlE.CoM")
@@ -742,7 +742,7 @@ func TestDNSForwarder_MultipleOverlappingPatterns(t *testing.T) {
 	mockFirewall := &MockFirewall{}
 	mockResolver := &MockResolver{}
 
-	forwarder := NewDNSForwarder("127.0.0.1:0", 300, mockFirewall, &peer.Status{})
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, mockFirewall, &peer.Status{}, nil)
 	forwarder.resolver = mockResolver
 
 	// Set up complex overlapping patterns
@@ -804,7 +804,7 @@ func TestDNSForwarder_NodataVsNxdomain(t *testing.T) {
 	mockFirewall := &MockFirewall{}
 	mockResolver := &MockResolver{}
 
-	forwarder := NewDNSForwarder("127.0.0.1:0", 300, mockFirewall, &peer.Status{})
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, mockFirewall, &peer.Status{}, nil)
 	forwarder.resolver = mockResolver
 
 	d, err := domain.FromString("example.com")
@@ -925,7 +925,7 @@ func TestDNSForwarder_NodataVsNxdomain(t *testing.T) {
 
 func TestDNSForwarder_EmptyQuery(t *testing.T) {
 	// Test handling of malformed query with no questions
-	forwarder := NewDNSForwarder("127.0.0.1:0", 300, nil, &peer.Status{})
+	forwarder := NewDNSForwarder(netip.MustParseAddrPort("127.0.0.1:0"), 300, nil, &peer.Status{}, nil)
 
 	query := &dns.Msg{}
 	// Don't set any question