Merge branch 'main' into feature/client-metrics

client/internal/acl/manager_test.go

@@ -189,6 +189,212 @@ func TestDefaultManagerStateless(t *testing.T) {
 	})
 }
 
+// TestDenyRulesNotAccumulatedOnRepeatedApply verifies that applying the same
+// deny rules repeatedly does not accumulate duplicate rules in the uspfilter.
+// This tests the full ACL manager -> uspfilter integration.
+func TestDenyRulesNotAccumulatedOnRepeatedApply(t *testing.T) {
+	t.Setenv("NB_WG_KERNEL_DISABLED", "true")
+
+	networkMap := &mgmProto.NetworkMap{
+		FirewallRules: []*mgmProto.FirewallRule{
+			{
+				PeerIP:    "10.93.0.1",
+				Direction: mgmProto.RuleDirection_IN,
+				Action:    mgmProto.RuleAction_DROP,
+				Protocol:  mgmProto.RuleProtocol_TCP,
+				Port:      "22",
+			},
+			{
+				PeerIP:    "10.93.0.2",
+				Direction: mgmProto.RuleDirection_IN,
+				Action:    mgmProto.RuleAction_DROP,
+				Protocol:  mgmProto.RuleProtocol_TCP,
+				Port:      "80",
+			},
+			{
+				PeerIP:    "10.93.0.3",
+				Direction: mgmProto.RuleDirection_IN,
+				Action:    mgmProto.RuleAction_ACCEPT,
+				Protocol:  mgmProto.RuleProtocol_TCP,
+				Port:      "443",
+			},
+		},
+		FirewallRulesIsEmpty: false,
+	}
+
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	ifaceMock := mocks.NewMockIFaceMapper(ctrl)
+	ifaceMock.EXPECT().IsUserspaceBind().Return(true).AnyTimes()
+	ifaceMock.EXPECT().SetFilter(gomock.Any())
+	network := netip.MustParsePrefix("172.0.0.1/32")
+	ifaceMock.EXPECT().Name().Return("lo").AnyTimes()
+	ifaceMock.EXPECT().Address().Return(wgaddr.Address{
+		IP:      network.Addr(),
+		Network: network,
+	}).AnyTimes()
+	ifaceMock.EXPECT().GetWGDevice().Return(nil).AnyTimes()
+
+	fw, err := firewall.NewFirewall(ifaceMock, nil, flowLogger, false, iface.DefaultMTU)
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, fw.Close(nil))
+	}()
+
+	acl := NewDefaultManager(fw)
+
+	// Apply the same rules 5 times (simulating repeated network map updates)
+	for i := 0; i < 5; i++ {
+		acl.ApplyFiltering(networkMap, false)
+	}
+
+	// The ACL manager should track exactly 3 rule pairs (2 deny + 1 accept inbound)
+	assert.Equal(t, 3, len(acl.peerRulesPairs),
+		"Should have exactly 3 rule pairs after 5 identical updates")
+}
+
+// TestDenyRulesCleanedUpOnRemoval verifies that deny rules are properly cleaned
+// up when they're removed from the network map in a subsequent update.
+func TestDenyRulesCleanedUpOnRemoval(t *testing.T) {
+	t.Setenv("NB_WG_KERNEL_DISABLED", "true")
+
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	ifaceMock := mocks.NewMockIFaceMapper(ctrl)
+	ifaceMock.EXPECT().IsUserspaceBind().Return(true).AnyTimes()
+	ifaceMock.EXPECT().SetFilter(gomock.Any())
+	network := netip.MustParsePrefix("172.0.0.1/32")
+	ifaceMock.EXPECT().Name().Return("lo").AnyTimes()
+	ifaceMock.EXPECT().Address().Return(wgaddr.Address{
+		IP:      network.Addr(),
+		Network: network,
+	}).AnyTimes()
+	ifaceMock.EXPECT().GetWGDevice().Return(nil).AnyTimes()
+
+	fw, err := firewall.NewFirewall(ifaceMock, nil, flowLogger, false, iface.DefaultMTU)
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, fw.Close(nil))
+	}()
+
+	acl := NewDefaultManager(fw)
+
+	// First update: add deny and accept rules
+	networkMap1 := &mgmProto.NetworkMap{
+		FirewallRules: []*mgmProto.FirewallRule{
+			{
+				PeerIP:    "10.93.0.1",
+				Direction: mgmProto.RuleDirection_IN,
+				Action:    mgmProto.RuleAction_DROP,
+				Protocol:  mgmProto.RuleProtocol_TCP,
+				Port:      "22",
+			},
+			{
+				PeerIP:    "10.93.0.2",
+				Direction: mgmProto.RuleDirection_IN,
+				Action:    mgmProto.RuleAction_ACCEPT,
+				Protocol:  mgmProto.RuleProtocol_TCP,
+				Port:      "443",
+			},
+		},
+		FirewallRulesIsEmpty: false,
+	}
+
+	acl.ApplyFiltering(networkMap1, false)
+	assert.Equal(t, 2, len(acl.peerRulesPairs), "Should have 2 rules after first update")
+
+	// Second update: remove the deny rule, keep only accept
+	networkMap2 := &mgmProto.NetworkMap{
+		FirewallRules: []*mgmProto.FirewallRule{
+			{
+				PeerIP:    "10.93.0.2",
+				Direction: mgmProto.RuleDirection_IN,
+				Action:    mgmProto.RuleAction_ACCEPT,
+				Protocol:  mgmProto.RuleProtocol_TCP,
+				Port:      "443",
+			},
+		},
+		FirewallRulesIsEmpty: false,
+	}
+
+	acl.ApplyFiltering(networkMap2, false)
+	assert.Equal(t, 1, len(acl.peerRulesPairs),
+		"Should have 1 rule after removing deny rule")
+
+	// Third update: remove all rules
+	networkMap3 := &mgmProto.NetworkMap{
+		FirewallRules:        []*mgmProto.FirewallRule{},
+		FirewallRulesIsEmpty: true,
+	}
+
+	acl.ApplyFiltering(networkMap3, false)
+	assert.Equal(t, 0, len(acl.peerRulesPairs),
+		"Should have 0 rules after removing all rules")
+}
+
+// TestRuleUpdateChangingAction verifies that when a rule's action changes from
+// accept to deny (or vice versa), the old rule is properly removed and the new
+// one added without leaking.
+func TestRuleUpdateChangingAction(t *testing.T) {
+	t.Setenv("NB_WG_KERNEL_DISABLED", "true")
+
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	ifaceMock := mocks.NewMockIFaceMapper(ctrl)
+	ifaceMock.EXPECT().IsUserspaceBind().Return(true).AnyTimes()
+	ifaceMock.EXPECT().SetFilter(gomock.Any())
+	network := netip.MustParsePrefix("172.0.0.1/32")
+	ifaceMock.EXPECT().Name().Return("lo").AnyTimes()
+	ifaceMock.EXPECT().Address().Return(wgaddr.Address{
+		IP:      network.Addr(),
+		Network: network,
+	}).AnyTimes()
+	ifaceMock.EXPECT().GetWGDevice().Return(nil).AnyTimes()
+
+	fw, err := firewall.NewFirewall(ifaceMock, nil, flowLogger, false, iface.DefaultMTU)
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, fw.Close(nil))
+	}()
+
+	acl := NewDefaultManager(fw)
+
+	// First update: accept rule
+	networkMap := &mgmProto.NetworkMap{
+		FirewallRules: []*mgmProto.FirewallRule{
+			{
+				PeerIP:    "10.93.0.1",
+				Direction: mgmProto.RuleDirection_IN,
+				Action:    mgmProto.RuleAction_ACCEPT,
+				Protocol:  mgmProto.RuleProtocol_TCP,
+				Port:      "22",
+			},
+		},
+		FirewallRulesIsEmpty: false,
+	}
+	acl.ApplyFiltering(networkMap, false)
+	assert.Equal(t, 1, len(acl.peerRulesPairs))
+
+	// Second update: change to deny (same IP/port/proto, different action)
+	networkMap.FirewallRules = []*mgmProto.FirewallRule{
+		{
+			PeerIP:    "10.93.0.1",
+			Direction: mgmProto.RuleDirection_IN,
+			Action:    mgmProto.RuleAction_DROP,
+			Protocol:  mgmProto.RuleProtocol_TCP,
+			Port:      "22",
+		},
+	}
+	acl.ApplyFiltering(networkMap, false)
+
+	// Should still have exactly 1 rule (the old accept removed, new deny added)
+	assert.Equal(t, 1, len(acl.peerRulesPairs),
+		"Changing action should result in exactly 1 rule, not 2")
+}
+
 func TestPortInfoEmpty(t *testing.T) {
 	tests := []struct {
 		name     string

client/internal/connect.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/netbirdio/netbird/client/iface"
 	"github.com/netbirdio/netbird/client/iface/device"
+	"github.com/netbirdio/netbird/client/iface/netstack"
 	"github.com/netbirdio/netbird/client/internal/dns"
 	"github.com/netbirdio/netbird/client/internal/listener"
 	"github.com/netbirdio/netbird/client/internal/peer"
@@ -244,7 +245,7 @@ func (c *ConnectClient) run(mobileDependency MobileDependency, runningChan chan
 		localPeerState := peer.LocalPeerState{
 			IP:              loginResp.GetPeerConfig().GetAddress(),
 			PubKey:          myPrivateKey.PublicKey().String(),
-			KernelInterface: device.WireGuardModuleIsLoaded(),
+			KernelInterface: device.WireGuardModuleIsLoaded() && !netstack.IsEnabled(),
 			FQDN:            loginResp.GetPeerConfig().GetFqdn(),
 		}
 		c.statusRecorder.UpdateLocalPeerState(localPeerState)

client/internal/dns/handler_chain_test.go

@@ -112,6 +112,54 @@ func TestHandlerChain_ServeDNS_DomainMatching(t *testing.T) {
 			matchSubdomains: false,
 			shouldMatch:     false,
 		},
+		{
+			name:            "single letter TLD exact match",
+			handlerDomain:   "example.x.",
+			queryDomain:     "example.x.",
+			isWildcard:      false,
+			matchSubdomains: false,
+			shouldMatch:     true,
+		},
+		{
+			name:            "single letter TLD subdomain match",
+			handlerDomain:   "example.x.",
+			queryDomain:     "sub.example.x.",
+			isWildcard:      false,
+			matchSubdomains: true,
+			shouldMatch:     true,
+		},
+		{
+			name:            "single letter TLD wildcard match",
+			handlerDomain:   "*.example.x.",
+			queryDomain:     "sub.example.x.",
+			isWildcard:      true,
+			matchSubdomains: false,
+			shouldMatch:     true,
+		},
+		{
+			name:            "two letter domain labels",
+			handlerDomain:   "a.b.",
+			queryDomain:     "a.b.",
+			isWildcard:      false,
+			matchSubdomains: false,
+			shouldMatch:     true,
+		},
+		{
+			name:            "single character domain",
+			handlerDomain:   "x.",
+			queryDomain:     "x.",
+			isWildcard:      false,
+			matchSubdomains: false,
+			shouldMatch:     true,
+		},
+		{
+			name:            "single character domain with subdomain match",
+			handlerDomain:   "x.",
+			queryDomain:     "sub.x.",
+			isWildcard:      false,
+			matchSubdomains: true,
+			shouldMatch:     true,
+		},
 	}
 
 	for _, tt := range tests {

client/internal/dns/host_darwin.go

@@ -9,8 +9,10 @@ import (
 	"io"
 	"net/netip"
 	"os/exec"
+	"slices"
 	"strconv"
 	"strings"
+	"sync"
 
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/exp/maps"
@@ -38,6 +40,9 @@ const (
 type systemConfigurator struct {
 	createdKeys       map[string]struct{}
 	systemDNSSettings SystemDNSSettings
+
+	mu              sync.RWMutex
+	origNameservers []netip.Addr
 }
 
 func newHostManager() (*systemConfigurator, error) {
@@ -218,6 +223,7 @@ func (s *systemConfigurator) getSystemDNSSettings() (SystemDNSSettings, error) {
 	}
 
 	var dnsSettings SystemDNSSettings
+	var serverAddresses []netip.Addr
 	inSearchDomainsArray := false
 	inServerAddressesArray := false
 
@@ -244,9 +250,12 @@ func (s *systemConfigurator) getSystemDNSSettings() (SystemDNSSettings, error) {
 			dnsSettings.Domains = append(dnsSettings.Domains, searchDomain)
 		} else if inServerAddressesArray {
 			address := strings.Split(line, " : ")[1]
-			if ip, err := netip.ParseAddr(address); err == nil && ip.Is4() {
-				dnsSettings.ServerIP = ip.Unmap()
-				inServerAddressesArray = false // Stop reading after finding the first IPv4 address
+			if ip, err := netip.ParseAddr(address); err == nil && !ip.IsUnspecified() {
+				ip = ip.Unmap()
+				serverAddresses = append(serverAddresses, ip)
+				if !dnsSettings.ServerIP.IsValid() && ip.Is4() {
+					dnsSettings.ServerIP = ip
+				}
 			}
 		}
 	}
@@ -258,9 +267,19 @@ func (s *systemConfigurator) getSystemDNSSettings() (SystemDNSSettings, error) {
 	// default to 53 port
 	dnsSettings.ServerPort = DefaultPort
 
+	s.mu.Lock()
+	s.origNameservers = serverAddresses
+	s.mu.Unlock()
+
 	return dnsSettings, nil
 }
 
+func (s *systemConfigurator) getOriginalNameservers() []netip.Addr {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return slices.Clone(s.origNameservers)
+}
+
 func (s *systemConfigurator) addSearchDomains(key, domains string, ip netip.Addr, port int) error {
 	err := s.addDNSState(key, domains, ip, port, true)
 	if err != nil {

client/internal/dns/host_darwin_test.go

@@ -109,3 +109,169 @@ func removeTestDNSKey(key string) error {
 	_, err := cmd.CombinedOutput()
 	return err
 }
+
+func TestGetOriginalNameservers(t *testing.T) {
+	configurator := &systemConfigurator{
+		createdKeys: make(map[string]struct{}),
+		origNameservers: []netip.Addr{
+			netip.MustParseAddr("8.8.8.8"),
+			netip.MustParseAddr("1.1.1.1"),
+		},
+	}
+
+	servers := configurator.getOriginalNameservers()
+	assert.Len(t, servers, 2)
+	assert.Equal(t, netip.MustParseAddr("8.8.8.8"), servers[0])
+	assert.Equal(t, netip.MustParseAddr("1.1.1.1"), servers[1])
+}
+
+func TestGetOriginalNameserversFromSystem(t *testing.T) {
+	configurator := &systemConfigurator{
+		createdKeys: make(map[string]struct{}),
+	}
+
+	_, err := configurator.getSystemDNSSettings()
+	require.NoError(t, err)
+
+	servers := configurator.getOriginalNameservers()
+
+	require.NotEmpty(t, servers, "expected at least one DNS server from system configuration")
+
+	for _, server := range servers {
+		assert.True(t, server.IsValid(), "server address should be valid")
+		assert.False(t, server.IsUnspecified(), "server address should not be unspecified")
+	}
+
+	t.Logf("found %d original nameservers: %v", len(servers), servers)
+}
+
+func setupTestConfigurator(t *testing.T) (*systemConfigurator, *statemanager.Manager, func()) {
+	t.Helper()
+
+	tmpDir := t.TempDir()
+	stateFile := filepath.Join(tmpDir, "state.json")
+	sm := statemanager.New(stateFile)
+	sm.RegisterState(&ShutdownState{})
+	sm.Start()
+
+	configurator := &systemConfigurator{
+		createdKeys: make(map[string]struct{}),
+	}
+
+	searchKey := getKeyWithInput(netbirdDNSStateKeyFormat, searchSuffix)
+	matchKey := getKeyWithInput(netbirdDNSStateKeyFormat, matchSuffix)
+	localKey := getKeyWithInput(netbirdDNSStateKeyFormat, localSuffix)
+
+	cleanup := func() {
+		_ = sm.Stop(context.Background())
+		for _, key := range []string{searchKey, matchKey, localKey} {
+			_ = removeTestDNSKey(key)
+		}
+	}
+
+	return configurator, sm, cleanup
+}
+
+func TestOriginalNameserversNoTransition(t *testing.T) {
+	netbirdIP := netip.MustParseAddr("100.64.0.1")
+
+	testCases := []struct {
+		name     string
+		routeAll bool
+	}{
+		{"routeall_false", false},
+		{"routeall_true", true},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			configurator, sm, cleanup := setupTestConfigurator(t)
+			defer cleanup()
+
+			_, err := configurator.getSystemDNSSettings()
+			require.NoError(t, err)
+			initialServers := configurator.getOriginalNameservers()
+			t.Logf("Initial servers: %v", initialServers)
+			require.NotEmpty(t, initialServers)
+
+			for _, srv := range initialServers {
+				require.NotEqual(t, netbirdIP, srv, "initial servers should not contain NetBird IP")
+			}
+
+			config := HostDNSConfig{
+				ServerIP:   netbirdIP,
+				ServerPort: 53,
+				RouteAll:   tc.routeAll,
+				Domains:    []DomainConfig{{Domain: "example.com", MatchOnly: true}},
+			}
+
+			for i := 1; i <= 2; i++ {
+				err = configurator.applyDNSConfig(config, sm)
+				require.NoError(t, err)
+
+				servers := configurator.getOriginalNameservers()
+				t.Logf("After apply %d (RouteAll=%v): %v", i, tc.routeAll, servers)
+				assert.Equal(t, initialServers, servers)
+			}
+		})
+	}
+}
+
+func TestOriginalNameserversRouteAllTransition(t *testing.T) {
+	netbirdIP := netip.MustParseAddr("100.64.0.1")
+
+	testCases := []struct {
+		name         string
+		initialRoute bool
+	}{
+		{"start_with_routeall_false", false},
+		{"start_with_routeall_true", true},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			configurator, sm, cleanup := setupTestConfigurator(t)
+			defer cleanup()
+
+			_, err := configurator.getSystemDNSSettings()
+			require.NoError(t, err)
+			initialServers := configurator.getOriginalNameservers()
+			t.Logf("Initial servers: %v", initialServers)
+			require.NotEmpty(t, initialServers)
+
+			config := HostDNSConfig{
+				ServerIP:   netbirdIP,
+				ServerPort: 53,
+				RouteAll:   tc.initialRoute,
+				Domains:    []DomainConfig{{Domain: "example.com", MatchOnly: true}},
+			}
+
+			// First apply
+			err = configurator.applyDNSConfig(config, sm)
+			require.NoError(t, err)
+			servers := configurator.getOriginalNameservers()
+			t.Logf("After first apply (RouteAll=%v): %v", tc.initialRoute, servers)
+			assert.Equal(t, initialServers, servers)
+
+			// Toggle RouteAll
+			config.RouteAll = !tc.initialRoute
+			err = configurator.applyDNSConfig(config, sm)
+			require.NoError(t, err)
+			servers = configurator.getOriginalNameservers()
+			t.Logf("After toggle (RouteAll=%v): %v", config.RouteAll, servers)
+			assert.Equal(t, initialServers, servers)
+
+			// Toggle back
+			config.RouteAll = tc.initialRoute
+			err = configurator.applyDNSConfig(config, sm)
+			require.NoError(t, err)
+			servers = configurator.getOriginalNameservers()
+			t.Logf("After toggle back (RouteAll=%v): %v", config.RouteAll, servers)
+			assert.Equal(t, initialServers, servers)
+
+			for _, srv := range servers {
+				assert.NotEqual(t, netbirdIP, srv, "servers should not contain NetBird IP")
+			}
+		})
+	}
+}

client/internal/dns/server.go

@@ -6,7 +6,9 @@ import (
 	"fmt"
 	"net/netip"
 	"net/url"
+	"os"
 	"runtime"
+	"strconv"
 	"strings"
 	"sync"
 
@@ -27,6 +29,8 @@ import (
 	"github.com/netbirdio/netbird/shared/management/domain"
 )
 
+const envSkipDNSProbe = "NB_SKIP_DNS_PROBE"
+
 // ReadyListener is a notification mechanism what indicate the server is ready to handle host dns address changes
 type ReadyListener interface {
 	OnReady()
@@ -439,6 +443,17 @@ func (s *DefaultServer) SearchDomains() []string {
 // ProbeAvailability tests each upstream group's servers for availability
 // and deactivates the group if no server responds
 func (s *DefaultServer) ProbeAvailability() {
+	if val := os.Getenv(envSkipDNSProbe); val != "" {
+		skipProbe, err := strconv.ParseBool(val)
+		if err != nil {
+			log.Warnf("failed to parse %s: %v", envSkipDNSProbe, err)
+		}
+		if skipProbe {
+			log.Infof("skipping DNS probe due to %s", envSkipDNSProbe)
+			return
+		}
+	}
+
 	var wg sync.WaitGroup
 	for _, mux := range s.dnsMuxMap {
 		wg.Add(1)
@@ -615,7 +630,7 @@ func (s *DefaultServer) applyHostConfig() {
 	s.registerFallback(config)
 }
 
-// registerFallback registers original nameservers as low-priority fallback handlers
+// registerFallback registers original nameservers as low-priority fallback handlers.
 func (s *DefaultServer) registerFallback(config HostDNSConfig) {
 	hostMgrWithNS, ok := s.hostManager.(hostManagerWithOriginalNS)
 	if !ok {
@@ -624,6 +639,7 @@ func (s *DefaultServer) registerFallback(config HostDNSConfig) {
 
 	originalNameservers := hostMgrWithNS.getOriginalNameservers()
 	if len(originalNameservers) == 0 {
+		s.deregisterHandler([]string{nbdns.RootZone}, PriorityFallback)
 		return
 	}
 

client/internal/dns/test/mock.go

@@ -8,15 +8,21 @@ import (
 
 type MockResponseWriter struct {
 	WriteMsgFunc func(m *dns.Msg) error
+	lastResponse *dns.Msg
 }
 
 func (rw *MockResponseWriter) WriteMsg(m *dns.Msg) error {
+	rw.lastResponse = m
 	if rw.WriteMsgFunc != nil {
 		return rw.WriteMsgFunc(m)
 	}
 	return nil
 }
 
+func (rw *MockResponseWriter) GetLastResponse() *dns.Msg {
+	return rw.lastResponse
+}
+
 func (rw *MockResponseWriter) LocalAddr() net.Addr       { return nil }
 func (rw *MockResponseWriter) RemoteAddr() net.Addr      { return nil }
 func (rw *MockResponseWriter) Write([]byte) (int, error) { return 0, nil }

client/internal/dnsfwd/forwarder.go

@@ -190,50 +190,75 @@ func (f *DNSForwarder) Close(ctx context.Context) error {
 	return nberrors.FormatErrorOrNil(result)
 }
 
-func (f *DNSForwarder) handleDNSQuery(logger *log.Entry, w dns.ResponseWriter, query *dns.Msg) *dns.Msg {
+func (f *DNSForwarder) handleDNSQuery(logger *log.Entry, w dns.ResponseWriter, query *dns.Msg, startTime time.Time) {
 	if len(query.Question) == 0 {
-		return nil
+		return
 	}
 	question := query.Question[0]
-	logger.Tracef("received DNS request for DNS forwarder: domain=%s type=%s class=%s",
-		question.Name, dns.TypeToString[question.Qtype], dns.ClassToString[question.Qclass])
+	qname := strings.ToLower(question.Name)
 
-	domain := strings.ToLower(question.Name)
+	logger.Tracef("question: domain=%s type=%s class=%s",
+		qname, dns.TypeToString[question.Qtype], dns.ClassToString[question.Qclass])
 
 	resp := query.SetReply(query)
 	network := resutil.NetworkForQtype(question.Qtype)
 	if network == "" {
 		resp.Rcode = dns.RcodeNotImplemented
-		if err := w.WriteMsg(resp); err != nil {
-			logger.Errorf("failed to write DNS response: %v", err)
-		}
-		return nil
+		f.writeResponse(logger, w, resp, qname, startTime)
+		return
 	}
 
-	mostSpecificResId, matchingEntries := f.getMatchingEntries(strings.TrimSuffix(domain, "."))
-	// query doesn't match any configured domain
+	mostSpecificResId, matchingEntries := f.getMatchingEntries(strings.TrimSuffix(qname, "."))
 	if mostSpecificResId == "" {
 		resp.Rcode = dns.RcodeRefused
-		if err := w.WriteMsg(resp); err != nil {
-			logger.Errorf("failed to write DNS response: %v", err)
-		}
-		return nil
+		f.writeResponse(logger, w, resp, qname, startTime)
+		return
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), upstreamTimeout)
 	defer cancel()
 
-	result := resutil.LookupIP(ctx, f.resolver, network, domain, question.Qtype)
+	result := resutil.LookupIP(ctx, f.resolver, network, qname, question.Qtype)
 	if result.Err != nil {
-		f.handleDNSError(ctx, logger, w, question, resp, domain, result)
-		return nil
+		f.handleDNSError(ctx, logger, w, question, resp, qname, result, startTime)
+		return
 	}
 
 	f.updateInternalState(result.IPs, mostSpecificResId, matchingEntries)
-	resp.Answer = append(resp.Answer, resutil.IPsToRRs(domain, result.IPs, f.ttl)...)
-	f.cache.set(domain, question.Qtype, result.IPs)
+	resp.Answer = append(resp.Answer, resutil.IPsToRRs(qname, result.IPs, f.ttl)...)
+	f.cache.set(qname, question.Qtype, result.IPs)
 
-	return resp
+	f.writeResponse(logger, w, resp, qname, startTime)
+}
+
+func (f *DNSForwarder) writeResponse(logger *log.Entry, w dns.ResponseWriter, resp *dns.Msg, qname string, startTime time.Time) {
+	if err := w.WriteMsg(resp); err != nil {
+		logger.Errorf("failed to write DNS response: %v", err)
+		return
+	}
+
+	logger.Tracef("response: domain=%s rcode=%s answers=%s took=%s",
+		qname, dns.RcodeToString[resp.Rcode], resutil.FormatAnswers(resp.Answer), time.Since(startTime))
+}
+
+// udpResponseWriter wraps a dns.ResponseWriter to handle UDP-specific truncation.
+type udpResponseWriter struct {
+	dns.ResponseWriter
+	query *dns.Msg
+}
+
+func (u *udpResponseWriter) WriteMsg(resp *dns.Msg) error {
+	opt := u.query.IsEdns0()
+	maxSize := dns.MinMsgSize
+	if opt != nil {
+		maxSize = int(opt.UDPSize())
+	}
+
+	if resp.Len() > maxSize {
+		resp.Truncate(maxSize)
+	}
+
+	return u.ResponseWriter.WriteMsg(resp)
 }
 
 func (f *DNSForwarder) handleDNSQueryUDP(w dns.ResponseWriter, query *dns.Msg) {
@@ -243,30 +268,7 @@ func (f *DNSForwarder) handleDNSQueryUDP(w dns.ResponseWriter, query *dns.Msg) {
 		"dns_id":     fmt.Sprintf("%04x", query.Id),
 	})
 
-	resp := f.handleDNSQuery(logger, w, query)
-	if resp == nil {
-		return
-	}
-
-	opt := query.IsEdns0()
-	maxSize := dns.MinMsgSize
-	if opt != nil {
-		// client advertised a larger EDNS0 buffer
-		maxSize = int(opt.UDPSize())
-	}
-
-	// if our response is too big, truncate and set the TC bit
-	if resp.Len() > maxSize {
-		resp.Truncate(maxSize)
-	}
-
-	if err := w.WriteMsg(resp); err != nil {
-		logger.Errorf("failed to write DNS response: %v", err)
-		return
-	}
-
-	logger.Tracef("response: domain=%s rcode=%s answers=%s took=%s",
-		query.Question[0].Name, dns.RcodeToString[resp.Rcode], resutil.FormatAnswers(resp.Answer), time.Since(startTime))
+	f.handleDNSQuery(logger, &udpResponseWriter{ResponseWriter: w, query: query}, query, startTime)
 }
 
 func (f *DNSForwarder) handleDNSQueryTCP(w dns.ResponseWriter, query *dns.Msg) {
@@ -276,18 +278,7 @@ func (f *DNSForwarder) handleDNSQueryTCP(w dns.ResponseWriter, query *dns.Msg) {
 		"dns_id":     fmt.Sprintf("%04x", query.Id),
 	})
 
-	resp := f.handleDNSQuery(logger, w, query)
-	if resp == nil {
-		return
-	}
-
-	if err := w.WriteMsg(resp); err != nil {
-		logger.Errorf("failed to write DNS response: %v", err)
-		return
-	}
-
-	logger.Tracef("response: domain=%s rcode=%s answers=%s took=%s",
-		query.Question[0].Name, dns.RcodeToString[resp.Rcode], resutil.FormatAnswers(resp.Answer), time.Since(startTime))
+	f.handleDNSQuery(logger, w, query, startTime)
 }
 
 func (f *DNSForwarder) updateInternalState(ips []netip.Addr, mostSpecificResId route.ResID, matchingEntries []*ForwarderEntry) {
@@ -334,6 +325,7 @@ func (f *DNSForwarder) handleDNSError(
 	resp *dns.Msg,
 	domain string,
 	result resutil.LookupResult,
+	startTime time.Time,
 ) {
 	qType := question.Qtype
 	qTypeName := dns.TypeToString[qType]
@@ -343,9 +335,7 @@ func (f *DNSForwarder) handleDNSError(
 	// NotFound: cache negative result and respond
 	if result.Rcode == dns.RcodeNameError || result.Rcode == dns.RcodeSuccess {
 		f.cache.set(domain, question.Qtype, nil)
-		if writeErr := w.WriteMsg(resp); writeErr != nil {
-			logger.Errorf("failed to write failure DNS response: %v", writeErr)
-		}
+		f.writeResponse(logger, w, resp, domain, startTime)
 		return
 	}
 
@@ -355,9 +345,7 @@ func (f *DNSForwarder) handleDNSError(
 			logger.Debugf("serving cached DNS response after upstream failure: domain=%s type=%s", domain, qTypeName)
 			resp.Answer = append(resp.Answer, resutil.IPsToRRs(domain, ips, f.ttl)...)
 			resp.Rcode = dns.RcodeSuccess
-			if writeErr := w.WriteMsg(resp); writeErr != nil {
-				logger.Errorf("failed to write cached DNS response: %v", writeErr)
-			}
+			f.writeResponse(logger, w, resp, domain, startTime)
 			return
 		}
 
@@ -365,9 +353,7 @@ func (f *DNSForwarder) handleDNSError(
 		verifyResult := resutil.LookupIP(ctx, f.resolver, resutil.NetworkForQtype(qType), domain, qType)
 		if verifyResult.Rcode == dns.RcodeNameError || verifyResult.Rcode == dns.RcodeSuccess {
 			resp.Rcode = verifyResult.Rcode
-			if writeErr := w.WriteMsg(resp); writeErr != nil {
-				logger.Errorf("failed to write failure DNS response: %v", writeErr)
-			}
+			f.writeResponse(logger, w, resp, domain, startTime)
 			return
 		}
 	}
@@ -375,15 +361,12 @@ func (f *DNSForwarder) handleDNSError(
 	// No cache or verification failed. Log with or without the server field for more context.
 	var dnsErr *net.DNSError
 	if errors.As(result.Err, &dnsErr) && dnsErr.Server != "" {
-		logger.Warnf("failed to resolve: type=%s domain=%s server=%s: %v", qTypeName, domain, dnsErr.Server, result.Err)
+		logger.Warnf("upstream failure: type=%s domain=%s server=%s: %v", qTypeName, domain, dnsErr.Server, result.Err)
 	} else {
 		logger.Warnf(errResolveFailed, domain, result.Err)
 	}
 
-	// Write final failure response.
-	if writeErr := w.WriteMsg(resp); writeErr != nil {
-		logger.Errorf("failed to write failure DNS response: %v", writeErr)
-	}
+	f.writeResponse(logger, w, resp, domain, startTime)
 }
 
 // getMatchingEntries retrieves the resource IDs for a given domain.

client/internal/dnsfwd/forwarder_test.go

@@ -318,8 +318,9 @@ func TestDNSForwarder_UnauthorizedDomainAccess(t *testing.T) {
 			query.SetQuestion(dns.Fqdn(tt.queryDomain), dns.TypeA)
 
 			mockWriter := &test.MockResponseWriter{}
-			resp := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query)
+			forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query, time.Now())
 
+			resp := mockWriter.GetLastResponse()
 			if tt.shouldResolve {
 				require.NotNil(t, resp, "Expected response for authorized domain")
 				require.Equal(t, dns.RcodeSuccess, resp.Rcode, "Expected successful response")
@@ -329,10 +330,9 @@ func TestDNSForwarder_UnauthorizedDomainAccess(t *testing.T) {
 				mockFirewall.AssertExpectations(t)
 				mockResolver.AssertExpectations(t)
 			} else {
-				if resp != nil {
-					assert.True(t, len(resp.Answer) == 0 || resp.Rcode != dns.RcodeSuccess,
-						"Unauthorized domain should not return successful answers")
-				}
+				require.NotNil(t, resp, "Expected response")
+				assert.True(t, len(resp.Answer) == 0 || resp.Rcode != dns.RcodeSuccess,
+					"Unauthorized domain should not return successful answers")
 				mockFirewall.AssertNotCalled(t, "UpdateSet")
 				mockResolver.AssertNotCalled(t, "LookupNetIP")
 			}
@@ -466,14 +466,16 @@ func TestDNSForwarder_FirewallSetUpdates(t *testing.T) {
 			dnsQuery.SetQuestion(dns.Fqdn(tt.query), dns.TypeA)
 
 			mockWriter := &test.MockResponseWriter{}
-			resp := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, dnsQuery)
+			forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, dnsQuery, time.Now())
 
 			// Verify response
+			resp := mockWriter.GetLastResponse()
 			if tt.shouldResolve {
 				require.NotNil(t, resp, "Expected response for authorized domain")
 				require.Equal(t, dns.RcodeSuccess, resp.Rcode)
 				require.NotEmpty(t, resp.Answer)
-			} else if resp != nil {
+			} else {
+				require.NotNil(t, resp, "Expected response")
 				assert.True(t, resp.Rcode == dns.RcodeRefused || len(resp.Answer) == 0,
 					"Unauthorized domain should be refused or have no answers")
 			}
@@ -528,9 +530,10 @@ func TestDNSForwarder_MultipleIPsInSingleUpdate(t *testing.T) {
 	query.SetQuestion("example.com.", dns.TypeA)
 
 	mockWriter := &test.MockResponseWriter{}
-	resp := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query)
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query, time.Now())
 
 	// Verify response contains all IPs
+	resp := mockWriter.GetLastResponse()
 	require.NotNil(t, resp)
 	require.Equal(t, dns.RcodeSuccess, resp.Rcode)
 	require.Len(t, resp.Answer, 3, "Should have 3 answer records")
@@ -605,7 +608,7 @@ func TestDNSForwarder_ResponseCodes(t *testing.T) {
 				},
 			}
 
-			_ = forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query)
+			forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query, time.Now())
 
 			// Check the response written to the writer
 			require.NotNil(t, writtenResp, "Expected response to be written")
@@ -675,7 +678,8 @@ func TestDNSForwarder_ServeFromCacheOnUpstreamFailure(t *testing.T) {
 	q1 := &dns.Msg{}
 	q1.SetQuestion(dns.Fqdn("example.com"), dns.TypeA)
 	w1 := &test.MockResponseWriter{}
-	resp1 := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w1, q1)
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w1, q1, time.Now())
+	resp1 := w1.GetLastResponse()
 	require.NotNil(t, resp1)
 	require.Equal(t, dns.RcodeSuccess, resp1.Rcode)
 	require.Len(t, resp1.Answer, 1)
@@ -683,13 +687,13 @@ func TestDNSForwarder_ServeFromCacheOnUpstreamFailure(t *testing.T) {
 	// Second query: serve from cache after upstream failure
 	q2 := &dns.Msg{}
 	q2.SetQuestion(dns.Fqdn("example.com"), dns.TypeA)
-	var writtenResp *dns.Msg
-	w2 := &test.MockResponseWriter{WriteMsgFunc: func(m *dns.Msg) error { writtenResp = m; return nil }}
-	_ = forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w2, q2)
+	w2 := &test.MockResponseWriter{}
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w2, q2, time.Now())
 
-	require.NotNil(t, writtenResp, "expected response to be written")
-	require.Equal(t, dns.RcodeSuccess, writtenResp.Rcode)
-	require.Len(t, writtenResp.Answer, 1)
+	resp2 := w2.GetLastResponse()
+	require.NotNil(t, resp2, "expected response to be written")
+	require.Equal(t, dns.RcodeSuccess, resp2.Rcode)
+	require.Len(t, resp2.Answer, 1)
 
 	mockResolver.AssertExpectations(t)
 }
@@ -715,7 +719,8 @@ func TestDNSForwarder_CacheNormalizationCasingAndDot(t *testing.T) {
 	q1 := &dns.Msg{}
 	q1.SetQuestion(mixedQuery+".", dns.TypeA)
 	w1 := &test.MockResponseWriter{}
-	resp1 := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w1, q1)
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w1, q1, time.Now())
+	resp1 := w1.GetLastResponse()
 	require.NotNil(t, resp1)
 	require.Equal(t, dns.RcodeSuccess, resp1.Rcode)
 	require.Len(t, resp1.Answer, 1)
@@ -727,13 +732,13 @@ func TestDNSForwarder_CacheNormalizationCasingAndDot(t *testing.T) {
 
 	q2 := &dns.Msg{}
 	q2.SetQuestion("EXAMPLE.COM", dns.TypeA)
-	var writtenResp *dns.Msg
-	w2 := &test.MockResponseWriter{WriteMsgFunc: func(m *dns.Msg) error { writtenResp = m; return nil }}
-	_ = forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w2, q2)
+	w2 := &test.MockResponseWriter{}
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), w2, q2, time.Now())
 
-	require.NotNil(t, writtenResp)
-	require.Equal(t, dns.RcodeSuccess, writtenResp.Rcode)
-	require.Len(t, writtenResp.Answer, 1)
+	resp2 := w2.GetLastResponse()
+	require.NotNil(t, resp2)
+	require.Equal(t, dns.RcodeSuccess, resp2.Rcode)
+	require.Len(t, resp2.Answer, 1)
 
 	mockResolver.AssertExpectations(t)
 }
@@ -784,8 +789,9 @@ func TestDNSForwarder_MultipleOverlappingPatterns(t *testing.T) {
 	query.SetQuestion("smtp.mail.example.com.", dns.TypeA)
 
 	mockWriter := &test.MockResponseWriter{}
-	resp := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query)
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query, time.Now())
 
+	resp := mockWriter.GetLastResponse()
 	require.NotNil(t, resp)
 	assert.Equal(t, dns.RcodeSuccess, resp.Rcode)
 
@@ -897,26 +903,15 @@ func TestDNSForwarder_NodataVsNxdomain(t *testing.T) {
 			query := &dns.Msg{}
 			query.SetQuestion(dns.Fqdn("example.com"), tt.queryType)
 
-			var writtenResp *dns.Msg
-			mockWriter := &test.MockResponseWriter{
-				WriteMsgFunc: func(m *dns.Msg) error {
-					writtenResp = m
-					return nil
-				},
-			}
+			mockWriter := &test.MockResponseWriter{}
+			forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query, time.Now())
 
-			resp := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query)
-
-			// If a response was returned, it means it should be written (happens in wrapper functions)
-			if resp != nil && writtenResp == nil {
-				writtenResp = resp
-			}
-
-			require.NotNil(t, writtenResp, "Expected response to be written")
-			assert.Equal(t, tt.expectedCode, writtenResp.Rcode, tt.description)
+			resp := mockWriter.GetLastResponse()
+			require.NotNil(t, resp, "Expected response to be written")
+			assert.Equal(t, tt.expectedCode, resp.Rcode, tt.description)
 
 			if tt.expectNoAnswer {
-				assert.Empty(t, writtenResp.Answer, "Response should have no answer records")
+				assert.Empty(t, resp.Answer, "Response should have no answer records")
 			}
 
 			mockResolver.AssertExpectations(t)
@@ -931,15 +926,8 @@ func TestDNSForwarder_EmptyQuery(t *testing.T) {
 	query := &dns.Msg{}
 	// Don't set any question
 
-	writeCalled := false
-	mockWriter := &test.MockResponseWriter{
-		WriteMsgFunc: func(m *dns.Msg) error {
-			writeCalled = true
-			return nil
-		},
-	}
-	resp := forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query)
+	mockWriter := &test.MockResponseWriter{}
+	forwarder.handleDNSQuery(log.NewEntry(log.StandardLogger()), mockWriter, query, time.Now())
 
-	assert.Nil(t, resp, "Should return nil for empty query")
-	assert.False(t, writeCalled, "Should not write response for empty query")
+	assert.Nil(t, mockWriter.GetLastResponse(), "Should not write response for empty query")
 }

client/internal/engine.go

@@ -584,9 +584,11 @@ func (e *Engine) createFirewall() error {
 
 	var err error
 	e.firewall, err = firewall.NewFirewall(e.wgInterface, e.stateManager, e.flowManager.GetLogger(), e.config.DisableServerRoutes, e.config.MTU)
-	if err != nil || e.firewall == nil {
-		log.Errorf("failed creating firewall manager: %s", err)
-		return nil
+	if err != nil {
+		return fmt.Errorf("create firewall manager: %w", err)
+	}
+	if e.firewall == nil {
+		return fmt.Errorf("create firewall manager: received nil manager")
 	}
 
 	if err := e.initFirewall(); err != nil {
@@ -837,6 +839,10 @@ func (e *Engine) handleAutoUpdateVersion(autoUpdateSettings *mgmProto.AutoUpdate
 }
 
 func (e *Engine) handleSync(update *mgmProto.SyncResponse) error {
+	started := time.Now()
+	defer func() {
+		log.Infof("sync finished in %s", time.Since(started))
+	}()
 	e.syncMsgMux.Lock()
 	defer e.syncMsgMux.Unlock()
 
@@ -1026,7 +1032,7 @@ func (e *Engine) updateConfig(conf *mgmProto.PeerConfig) error {
 	state := e.statusRecorder.GetLocalPeerState()
 	state.IP = e.wgInterface.Address().String()
 	state.PubKey = e.config.WgPrivateKey.PublicKey().String()
-	state.KernelInterface = device.WireGuardModuleIsLoaded()
+	state.KernelInterface = !e.wgInterface.IsUserspaceBind()
 	state.FQDN = conf.GetFqdn()
 
 	e.statusRecorder.UpdateLocalPeerState(state)

client/internal/engine_ssh.go

@@ -10,6 +10,7 @@ import (
 	log "github.com/sirupsen/logrus"
 
 	firewallManager "github.com/netbirdio/netbird/client/firewall/manager"
+	"github.com/netbirdio/netbird/client/iface/netstack"
 	nftypes "github.com/netbirdio/netbird/client/internal/netflow/types"
 	sshauth "github.com/netbirdio/netbird/client/ssh/auth"
 	sshconfig "github.com/netbirdio/netbird/client/ssh/config"
@@ -94,6 +95,10 @@ func (e *Engine) updateSSH(sshConf *mgmProto.SSHConfig) error {
 
 // updateSSHClientConfig updates the SSH client configuration with peer information
 func (e *Engine) updateSSHClientConfig(remotePeers []*mgmProto.RemotePeerConfig) error {
+	if netstack.IsEnabled() {
+		return nil
+	}
+
 	peerInfo := e.extractPeerSSHInfo(remotePeers)
 	if len(peerInfo) == 0 {
 		log.Debug("no SSH-enabled peers found, skipping SSH config update")
@@ -216,6 +221,10 @@ func (e *Engine) GetPeerSSHKey(peerAddress string) ([]byte, bool) {
 
 // cleanupSSHConfig removes NetBird SSH client configuration on shutdown
 func (e *Engine) cleanupSSHConfig() {
+	if netstack.IsEnabled() {
+		return
+	}
+
 	configMgr := sshconfig.New()
 
 	if err := configMgr.RemoveSSHClientConfig(); err != nil {

client/internal/lazyconn/activity/manager.go

@@ -11,6 +11,7 @@ import (
 	log "github.com/sirupsen/logrus"
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
+	"github.com/netbirdio/netbird/client/iface/netstack"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
 	peerid "github.com/netbirdio/netbird/client/internal/peer/id"
@@ -74,12 +75,13 @@ func (m *Manager) createListener(peerCfg lazyconn.PeerConfig) (listener, error)
 		return NewUDPListener(m.wgIface, peerCfg)
 	}
 
-	// BindListener is only used on Windows and JS platforms:
+	// BindListener is used on Windows, JS, and netstack 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" {
+	// - Netstack: Allows multiple instances on the same host without port conflicts.
+	// BindListener bypasses these issues by passing data directly through the bind.
+	if runtime.GOOS != "windows" && runtime.GOOS != "js" && !netstack.IsEnabled() {
 		return NewUDPListener(m.wgIface, peerCfg)
 	}
 

client/internal/networkmonitor/monitor.go

@@ -14,6 +14,7 @@ import (
 	"github.com/cenkalti/backoff/v4"
 	log "github.com/sirupsen/logrus"
 
+	"github.com/netbirdio/netbird/client/iface/netstack"
 	"github.com/netbirdio/netbird/client/internal/routemanager/systemops"
 )
 
@@ -37,6 +38,11 @@ func New() *NetworkMonitor {
 
 // Listen begins monitoring network changes. When a change is detected, this function will return without error.
 func (nw *NetworkMonitor) Listen(ctx context.Context) (err error) {
+	if netstack.IsEnabled() {
+		log.Debugf("Network monitor: skipping in netstack mode")
+		return nil
+	}
+
 	nw.mu.Lock()
 	if nw.cancel != nil {
 		nw.mu.Unlock()

client/internal/peer/conn.go

@@ -425,15 +425,14 @@ func (conn *Conn) onICEConnectionIsReady(priority conntype.ConnPriority, iceConn
 	}
 
 	conn.Log.Infof("configure WireGuard endpoint to: %s", ep.String())
-	presharedKey := conn.presharedKey(iceConnInfo.RosenpassPubKey)
 	updateTime := time.Now()
+	conn.enableWgWatcherIfNeeded(updateTime)
+
+	presharedKey := conn.presharedKey(iceConnInfo.RosenpassPubKey)
 	if err = conn.endpointUpdater.ConfigureWGEndpoint(ep, presharedKey); err != nil {
 		conn.handleConfigurationFailure(err, wgProxy)
 		return
 	}
-
-	conn.enableWgWatcherIfNeeded(updateTime)
-
 	wgConfigWorkaround()
 
 	if conn.wgProxyRelay != nil {
@@ -542,7 +541,10 @@ func (conn *Conn) onRelayConnectionIsReady(rci RelayConnInfo) {
 
 	wgProxy.Work()
 	presharedKey := conn.presharedKey(rci.rosenpassPubKey)
+
 	updateTime := time.Now()
+	conn.enableWgWatcherIfNeeded(updateTime)
+
 	if err := conn.endpointUpdater.ConfigureWGEndpoint(wgProxy.EndpointAddr(), presharedKey); err != nil {
 		if err := wgProxy.CloseConn(); err != nil {
 			conn.Log.Warnf("Failed to close relay connection: %v", err)
@@ -551,8 +553,6 @@ func (conn *Conn) onRelayConnectionIsReady(rci RelayConnInfo) {
 		return
 	}
 
-	conn.enableWgWatcherIfNeeded(updateTime)
-
 	wgConfigWorkaround()
 
 	conn.rosenpassRemoteKey = rci.rosenpassPubKey

client/internal/peer/ice/agent.go

@@ -2,6 +2,7 @@ package ice
 
 import (
 	"context"
+	"fmt"
 	"sync"
 	"time"
 
@@ -32,24 +33,6 @@ type ThreadSafeAgent struct {
 	once sync.Once
 }
 
-func (a *ThreadSafeAgent) Close() error {
-	var err error
-	a.once.Do(func() {
-		done := make(chan error, 1)
-		go func() {
-			done <- a.Agent.Close()
-		}()
-
-		select {
-		case err = <-done:
-		case <-time.After(iceAgentCloseTimeout):
-			log.Warnf("ICE agent close timed out after %v, proceeding with cleanup", iceAgentCloseTimeout)
-			err = nil
-		}
-	})
-	return err
-}
-
 func NewAgent(ctx context.Context, iFaceDiscover stdnet.ExternalIFaceDiscover, config Config, candidateTypes []ice.CandidateType, ufrag string, pwd string) (*ThreadSafeAgent, error) {
 	iceKeepAlive := iceKeepAlive()
 	iceDisconnectedTimeout := iceDisconnectedTimeout()
@@ -93,9 +76,41 @@ func NewAgent(ctx context.Context, iFaceDiscover stdnet.ExternalIFaceDiscover, c
 		return nil, err
 	}
 
+	if agent == nil {
+		return nil, fmt.Errorf("ice.NewAgent returned nil agent without error")
+	}
+
 	return &ThreadSafeAgent{Agent: agent}, nil
 }
 
+func (a *ThreadSafeAgent) Close() error {
+	var err error
+	a.once.Do(func() {
+		// Defensive check to prevent nil pointer dereference
+		// This can happen during sleep/wake transitions or memory corruption scenarios
+		// github.com/netbirdio/netbird/client/internal/peer/ice.(*ThreadSafeAgent).Close(0x40006883f0?)
+		//  [signal 0xc0000005 code=0x0 addr=0x0 pc=0x7ff7e73af83c]
+		agent := a.Agent
+		if agent == nil {
+			log.Warnf("ICE agent is nil during close, skipping")
+			return
+		}
+
+		done := make(chan error, 1)
+		go func() {
+			done <- agent.Close()
+		}()
+
+		select {
+		case err = <-done:
+		case <-time.After(iceAgentCloseTimeout):
+			log.Warnf("ICE agent close timed out after %v, proceeding with cleanup", iceAgentCloseTimeout)
+			err = nil
+		}
+	})
+	return err
+}
+
 func GenerateICECredentials() (string, string, error) {
 	ufrag, err := randutil.GenerateCryptoRandomString(lenUFrag, runesAlpha)
 	if err != nil {

client/internal/peer/worker_ice.go

@@ -107,8 +107,10 @@ func (w *WorkerICE) OnNewOffer(remoteOfferAnswer *OfferAnswer) {
 		}
 		w.log.Debugf("agent already exists, recreate the connection")
 		w.agentDialerCancel()
-		if err := w.agent.Close(); err != nil {
-			w.log.Warnf("failed to close ICE agent: %s", err)
+		if w.agent != nil {
+			if err := w.agent.Close(); err != nil {
+				w.log.Warnf("failed to close ICE agent: %s", err)
+			}
 		}
 
 		sessionID, err := NewICESessionID()

client/internal/profilemanager/config.go

@@ -252,7 +252,7 @@ func (config *Config) apply(input ConfigInput) (updated bool, err error) {
 	}
 
 	if config.AdminURL == nil {
-		log.Infof("using default Admin URL %s", DefaultManagementURL)
+		log.Infof("using default Admin URL %s", DefaultAdminURL)
 		config.AdminURL, err = parseURL("Admin URL", DefaultAdminURL)
 		if err != nil {
 			return false, err

client/internal/routemanager/manager.go

@@ -173,12 +173,21 @@ func (m *DefaultManager) setupAndroidRoutes(config ManagerConfig) {
 }
 
 func (m *DefaultManager) setupRefCounters(useNoop bool) {
+	var once sync.Once
+	var wgIface *net.Interface
+	toInterface := func() *net.Interface {
+		once.Do(func() {
+			wgIface = m.wgInterface.ToInterface()
+		})
+		return wgIface
+	}
+
 	m.routeRefCounter = refcounter.New(
 		func(prefix netip.Prefix, _ struct{}) (struct{}, error) {
-			return struct{}{}, m.sysOps.AddVPNRoute(prefix, m.wgInterface.ToInterface())
+			return struct{}{}, m.sysOps.AddVPNRoute(prefix, toInterface())
 		},
 		func(prefix netip.Prefix, _ struct{}) error {
-			return m.sysOps.RemoveVPNRoute(prefix, m.wgInterface.ToInterface())
+			return m.sysOps.RemoveVPNRoute(prefix, toInterface())
 		},
 	)
 

client/internal/routemanager/systemops/routeflags_bsd.go

@@ -4,16 +4,17 @@ package systemops
 
 import (
 	"strings"
-	"syscall"
+
+	"golang.org/x/sys/unix"
 )
 
 // filterRoutesByFlags returns true if the route message should be ignored based on its flags.
 func filterRoutesByFlags(routeMessageFlags int) bool {
-	if routeMessageFlags&syscall.RTF_UP == 0 {
+	if routeMessageFlags&unix.RTF_UP == 0 {
 		return true
 	}
 
-	if routeMessageFlags&(syscall.RTF_REJECT|syscall.RTF_BLACKHOLE|syscall.RTF_WASCLONED) != 0 {
+	if routeMessageFlags&(unix.RTF_REJECT|unix.RTF_BLACKHOLE|unix.RTF_WASCLONED) != 0 {
 		return true
 	}
 
@@ -24,42 +25,51 @@ func filterRoutesByFlags(routeMessageFlags int) bool {
 func formatBSDFlags(flags int) string {
 	var flagStrs []string
 
-	if flags&syscall.RTF_UP != 0 {
+	if flags&unix.RTF_UP != 0 {
 		flagStrs = append(flagStrs, "U")
 	}
-	if flags&syscall.RTF_GATEWAY != 0 {
+	if flags&unix.RTF_GATEWAY != 0 {
 		flagStrs = append(flagStrs, "G")
 	}
-	if flags&syscall.RTF_HOST != 0 {
+	if flags&unix.RTF_HOST != 0 {
 		flagStrs = append(flagStrs, "H")
 	}
-	if flags&syscall.RTF_REJECT != 0 {
+	if flags&unix.RTF_REJECT != 0 {
 		flagStrs = append(flagStrs, "R")
 	}
-	if flags&syscall.RTF_DYNAMIC != 0 {
+	if flags&unix.RTF_DYNAMIC != 0 {
 		flagStrs = append(flagStrs, "D")
 	}
-	if flags&syscall.RTF_MODIFIED != 0 {
+	if flags&unix.RTF_MODIFIED != 0 {
 		flagStrs = append(flagStrs, "M")
 	}
-	if flags&syscall.RTF_STATIC != 0 {
+	if flags&unix.RTF_STATIC != 0 {
 		flagStrs = append(flagStrs, "S")
 	}
-	if flags&syscall.RTF_LLINFO != 0 {
+	if flags&unix.RTF_LLINFO != 0 {
 		flagStrs = append(flagStrs, "L")
 	}
-	if flags&syscall.RTF_LOCAL != 0 {
+	if flags&unix.RTF_LOCAL != 0 {
 		flagStrs = append(flagStrs, "l")
 	}
-	if flags&syscall.RTF_BLACKHOLE != 0 {
+	if flags&unix.RTF_BLACKHOLE != 0 {
 		flagStrs = append(flagStrs, "B")
 	}
-	if flags&syscall.RTF_CLONING != 0 {
+	if flags&unix.RTF_CLONING != 0 {
 		flagStrs = append(flagStrs, "C")
 	}
-	if flags&syscall.RTF_WASCLONED != 0 {
+	if flags&unix.RTF_WASCLONED != 0 {
 		flagStrs = append(flagStrs, "W")
 	}
+	if flags&unix.RTF_PROTO1 != 0 {
+		flagStrs = append(flagStrs, "1")
+	}
+	if flags&unix.RTF_PROTO2 != 0 {
+		flagStrs = append(flagStrs, "2")
+	}
+	if flags&unix.RTF_PROTO3 != 0 {
+		flagStrs = append(flagStrs, "3")
+	}
 
 	if len(flagStrs) == 0 {
 		return "-"

client/internal/routemanager/systemops/routeflags_freebsd.go

@@ -4,17 +4,18 @@ package systemops
 
 import (
 	"strings"
-	"syscall"
+
+	"golang.org/x/sys/unix"
 )
 
 // filterRoutesByFlags returns true if the route message should be ignored based on its flags.
 func filterRoutesByFlags(routeMessageFlags int) bool {
-	if routeMessageFlags&syscall.RTF_UP == 0 {
+	if routeMessageFlags&unix.RTF_UP == 0 {
 		return true
 	}
 
-	// NOTE: syscall.RTF_WASCLONED deprecated in FreeBSD 8.0
-	if routeMessageFlags&(syscall.RTF_REJECT|syscall.RTF_BLACKHOLE) != 0 {
+	// NOTE: RTF_WASCLONED deprecated in FreeBSD 8.0
+	if routeMessageFlags&(unix.RTF_REJECT|unix.RTF_BLACKHOLE) != 0 {
 		return true
 	}
 
@@ -25,37 +26,46 @@ func filterRoutesByFlags(routeMessageFlags int) bool {
 func formatBSDFlags(flags int) string {
 	var flagStrs []string
 
-	if flags&syscall.RTF_UP != 0 {
+	if flags&unix.RTF_UP != 0 {
 		flagStrs = append(flagStrs, "U")
 	}
-	if flags&syscall.RTF_GATEWAY != 0 {
+	if flags&unix.RTF_GATEWAY != 0 {
 		flagStrs = append(flagStrs, "G")
 	}
-	if flags&syscall.RTF_HOST != 0 {
+	if flags&unix.RTF_HOST != 0 {
 		flagStrs = append(flagStrs, "H")
 	}
-	if flags&syscall.RTF_REJECT != 0 {
+	if flags&unix.RTF_REJECT != 0 {
 		flagStrs = append(flagStrs, "R")
 	}
-	if flags&syscall.RTF_DYNAMIC != 0 {
+	if flags&unix.RTF_DYNAMIC != 0 {
 		flagStrs = append(flagStrs, "D")
 	}
-	if flags&syscall.RTF_MODIFIED != 0 {
+	if flags&unix.RTF_MODIFIED != 0 {
 		flagStrs = append(flagStrs, "M")
 	}
-	if flags&syscall.RTF_STATIC != 0 {
+	if flags&unix.RTF_STATIC != 0 {
 		flagStrs = append(flagStrs, "S")
 	}
-	if flags&syscall.RTF_LLINFO != 0 {
+	if flags&unix.RTF_LLINFO != 0 {
 		flagStrs = append(flagStrs, "L")
 	}
-	if flags&syscall.RTF_LOCAL != 0 {
+	if flags&unix.RTF_LOCAL != 0 {
 		flagStrs = append(flagStrs, "l")
 	}
-	if flags&syscall.RTF_BLACKHOLE != 0 {
+	if flags&unix.RTF_BLACKHOLE != 0 {
 		flagStrs = append(flagStrs, "B")
 	}
 	// Note: RTF_CLONING and RTF_WASCLONED deprecated in FreeBSD 8.0
+	if flags&unix.RTF_PROTO1 != 0 {
+		flagStrs = append(flagStrs, "1")
+	}
+	if flags&unix.RTF_PROTO2 != 0 {
+		flagStrs = append(flagStrs, "2")
+	}
+	if flags&unix.RTF_PROTO3 != 0 {
+		flagStrs = append(flagStrs, "3")
+	}
 
 	if len(flagStrs) == 0 {
 		return "-"

client/internal/wg_iface_monitor.go

@@ -9,6 +9,8 @@ import (
 	"time"
 
 	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/iface/netstack"
 )
 
 // WGIfaceMonitor monitors the WireGuard interface lifecycle and restarts the engine
@@ -35,6 +37,11 @@ func (m *WGIfaceMonitor) Start(ctx context.Context, ifaceName string) (shouldRes
 		return false, errors.New("not supported on mobile platforms")
 	}
 
+	if netstack.IsEnabled() {
+		log.Debugf("Interface monitor: skipped in netstack mode")
+		return false, nil
+	}
+
 	if ifaceName == "" {
 		log.Debugf("Interface monitor: empty interface name, skipping monitor")
 		return false, errors.New("empty interface name")