[client] Use management-provided dns forwarder port on the client side (#4712)

Author: lixmal

client/internal/engine.go

@@ -1059,10 +1059,14 @@ func (e *Engine) updateNetworkMap(networkMap *mgmProto.NetworkMap) error {
 		protoDNSConfig = &mgmProto.DNSConfig{}
 	}
 
-	if err := e.dnsServer.UpdateDNSServer(serial, toDNSConfig(protoDNSConfig, e.wgInterface.Address().Network)); err != nil {
+	dnsConfig := toDNSConfig(protoDNSConfig, e.wgInterface.Address().Network)
+
+	if err := e.dnsServer.UpdateDNSServer(serial, dnsConfig); err != nil {
 		log.Errorf("failed to update dns server, err: %v", err)
 	}
 
+	e.routeManager.SetDNSForwarderPort(dnsConfig.ForwarderPort)
+
 	// apply routes first, route related actions might depend on routing being enabled
 	routes := toRoutes(networkMap.GetRoutes())
 	serverRoutes, clientRoutes := e.routeManager.ClassifyRoutes(routes)
@@ -1207,10 +1211,16 @@ func toRouteDomains(myPubKey string, routes []*route.Route) []*dnsfwd.ForwarderE
 }
 
 func toDNSConfig(protoDNSConfig *mgmProto.DNSConfig, network netip.Prefix) nbdns.Config {
+	forwarderPort := uint16(protoDNSConfig.GetForwarderPort())
+	if forwarderPort == 0 {
+		forwarderPort = nbdns.ForwarderClientPort
+	}
+
 	dnsUpdate := nbdns.Config{
 		ServiceEnable:    protoDNSConfig.GetServiceEnable(),
 		CustomZones:      make([]nbdns.CustomZone, 0),
 		NameServerGroups: make([]*nbdns.NameServerGroup, 0),
+		ForwarderPort:    forwarderPort,
 	}
 
 	for _, zone := range protoDNSConfig.GetCustomZones() {

client/internal/routemanager/common/params.go

@@ -1,6 +1,7 @@
 package common
 
 import (
+	"sync/atomic"
 	"time"
 
 	"github.com/netbirdio/netbird/client/firewall/manager"
@@ -25,4 +26,5 @@ type HandlerParams struct {
 	UseNewDNSRoute       bool
 	Firewall             manager.Manager
 	FakeIPManager        *fakeip.Manager
+	ForwarderPort        *atomic.Uint32
 }

client/internal/routemanager/dnsinterceptor/handler.go

@@ -8,6 +8,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/hashicorp/go-multierror"
@@ -20,7 +21,6 @@ import (
 	nbdns "github.com/netbirdio/netbird/client/internal/dns"
 	"github.com/netbirdio/netbird/client/internal/peer"
 	"github.com/netbirdio/netbird/client/internal/peerstore"
-	pkgdns "github.com/netbirdio/netbird/dns"
 	"github.com/netbirdio/netbird/client/internal/routemanager/common"
 	"github.com/netbirdio/netbird/client/internal/routemanager/fakeip"
 	"github.com/netbirdio/netbird/client/internal/routemanager/refcounter"
@@ -55,6 +55,7 @@ type DnsInterceptor struct {
 	peerStore            *peerstore.Store
 	firewall             firewall.Manager
 	fakeIPManager        *fakeip.Manager
+	forwarderPort        *atomic.Uint32
 }
 
 func New(params common.HandlerParams) *DnsInterceptor {
@@ -69,6 +70,7 @@ func New(params common.HandlerParams) *DnsInterceptor {
 		firewall:             params.Firewall,
 		fakeIPManager:        params.FakeIPManager,
 		interceptedDomains:   make(domainMap),
+		forwarderPort:        params.ForwarderPort,
 	}
 }
 
@@ -257,7 +259,7 @@ func (d *DnsInterceptor) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
 		r.MsgHdr.AuthenticatedData = true
 	}
 
-	upstream := fmt.Sprintf("%s:%d", upstreamIP.String(), pkgdns.ForwarderClientPort)
+	upstream := fmt.Sprintf("%s:%d", upstreamIP.String(), uint16(d.forwarderPort.Load()))
 	ctx, cancel := context.WithTimeout(context.Background(), dnsTimeout)
 	defer cancel()
 

client/internal/routemanager/manager.go

@@ -10,6 +10,7 @@ import (
 	"runtime"
 	"slices"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/google/uuid"
@@ -23,6 +24,7 @@ import (
 	"github.com/netbirdio/netbird/client/iface/netstack"
 	"github.com/netbirdio/netbird/client/internal/dns"
 	"github.com/netbirdio/netbird/client/internal/listener"
+	nbdns "github.com/netbirdio/netbird/dns"
 	"github.com/netbirdio/netbird/client/internal/peer"
 	"github.com/netbirdio/netbird/client/internal/peerstore"
 	"github.com/netbirdio/netbird/client/internal/routemanager/client"
@@ -54,6 +56,7 @@ type Manager interface {
 	SetRouteChangeListener(listener listener.NetworkChangeListener)
 	InitialRouteRange() []string
 	SetFirewall(firewall.Manager) error
+	SetDNSForwarderPort(port uint16)
 	Stop(stateManager *statemanager.Manager)
 }
 
@@ -101,6 +104,7 @@ type DefaultManager struct {
 	disableServerRoutes bool
 	activeRoutes        map[route.HAUniqueID]client.RouteHandler
 	fakeIPManager       *fakeip.Manager
+	dnsForwarderPort    atomic.Uint32
 }
 
 func NewManager(config ManagerConfig) *DefaultManager {
@@ -130,6 +134,7 @@ func NewManager(config ManagerConfig) *DefaultManager {
 		disableServerRoutes: config.DisableServerRoutes,
 		activeRoutes:        make(map[route.HAUniqueID]client.RouteHandler),
 	}
+	dm.dnsForwarderPort.Store(uint32(nbdns.ForwarderClientPort))
 
 	useNoop := netstack.IsEnabled() || config.DisableClientRoutes
 	dm.setupRefCounters(useNoop)
@@ -270,6 +275,11 @@ func (m *DefaultManager) SetFirewall(firewall firewall.Manager) error {
 	return nil
 }
 
+// SetDNSForwarderPort sets the DNS forwarder port for route handlers
+func (m *DefaultManager) SetDNSForwarderPort(port uint16) {
+	m.dnsForwarderPort.Store(uint32(port))
+}
+
 // Stop stops the manager watchers and clean firewall rules
 func (m *DefaultManager) Stop(stateManager *statemanager.Manager) {
 	m.stop()
@@ -345,6 +355,7 @@ func (m *DefaultManager) updateSystemRoutes(newRoutes route.HAMap) error {
 			UseNewDNSRoute:       m.useNewDNSRoute,
 			Firewall:             m.firewall,
 			FakeIPManager:        m.fakeIPManager,
+			ForwarderPort:        &m.dnsForwarderPort,
 		}
 		handler := client.HandlerFromRoute(params)
 		if err := handler.AddRoute(m.ctx); err != nil {

client/internal/routemanager/mock.go

@@ -90,6 +90,10 @@ func (m *MockManager) SetFirewall(firewall.Manager) error {
 	panic("implement me")
 }
 
+// SetDNSForwarderPort mock implementation of SetDNSForwarderPort from Manager interface
+func (m *MockManager) SetDNSForwarderPort(port uint16) {
+}
+
 // Stop mock implementation of Stop from Manager interface
 func (m *MockManager) Stop(stateManager *statemanager.Manager) {
 	if m.StopFunc != nil {

dns/dns.go

@@ -35,6 +35,8 @@ type Config struct {
 	NameServerGroups []*NameServerGroup
 	// CustomZones contains a list of custom zone
 	CustomZones []CustomZone
+	// ForwarderPort is the port clients should connect to on routing peers for DNS forwarding
+	ForwarderPort uint16
 }
 
 // CustomZone represents a custom zone to be resolved by the dns server