[client] Redirect dns forwarder port 5353 to new listening port 22054 (#4707)

- Port dnat changes from https://github.com/netbirdio/netbird/pull/4015 (nftables/iptables/userspace)
  - For userspace: rewrite the original port to the target port
  - Remember original destination port in conntrack
  - Rewrite the source port back to the original port for replies
- Redirect incoming port 5353 to 22054 (tcp/udp)
- Revert port changes based on the network map received from management
- Adjust tracer to show NAT stages

client/internal/dnsfwd/manager.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"fmt"
 	"net"
-	"sync"
+	"net/netip"
+	"os"
+	"strconv"
 
 	"github.com/hashicorp/go-multierror"
 	log "github.com/sirupsen/logrus"
@@ -12,18 +14,14 @@ import (
 	nberrors "github.com/netbirdio/netbird/client/errors"
 	firewall "github.com/netbirdio/netbird/client/firewall/manager"
 	"github.com/netbirdio/netbird/client/internal/peer"
+	nbdns "github.com/netbirdio/netbird/dns"
 	"github.com/netbirdio/netbird/route"
 	"github.com/netbirdio/netbird/shared/management/domain"
 )
 
-var (
-	// ListenPort is the port that the DNS forwarder listens on. It has been used by the client peers also
-	listenPort   uint16 = 5353
-	listenPortMu sync.RWMutex
-)
-
 const (
-	dnsTTL = 60 //seconds
+	dnsTTL        = 60
+	envServerPort = "NB_DNS_FORWARDER_PORT"
 )
 
 // ForwarderEntry is a mapping from a domain to a resource ID and a hash of the parent domain list.
@@ -36,28 +34,30 @@ type ForwarderEntry struct {
 type Manager struct {
 	firewall       firewall.Manager
 	statusRecorder *peer.Status
+	localAddr      netip.Addr
+	serverPort     uint16
 
 	fwRules      []firewall.Rule
 	tcpRules     []firewall.Rule
 	dnsForwarder *DNSForwarder
 }
 
-func ListenPort() uint16 {
-	listenPortMu.RLock()
-	defer listenPortMu.RUnlock()
-	return listenPort
-}
+func NewManager(fw firewall.Manager, statusRecorder *peer.Status, localAddr netip.Addr) *Manager {
+	serverPort := nbdns.ForwarderServerPort
+	if envPort := os.Getenv(envServerPort); envPort != "" {
+		if port, err := strconv.ParseUint(envPort, 10, 16); err == nil && port > 0 {
+			serverPort = uint16(port)
+			log.Infof("using custom DNS forwarder port from %s: %d", envServerPort, serverPort)
+		} else {
+			log.Warnf("invalid %s value %q, using default %d", envServerPort, envPort, nbdns.ForwarderServerPort)
+		}
+	}
 
-func SetListenPort(port uint16) {
-	listenPortMu.Lock()
-	listenPort = port
-	listenPortMu.Unlock()
-}
-
-func NewManager(fw firewall.Manager, statusRecorder *peer.Status) *Manager {
 	return &Manager{
 		firewall:       fw,
 		statusRecorder: statusRecorder,
+		localAddr:      localAddr,
+		serverPort:     serverPort,
 	}
 }
 
@@ -71,7 +71,21 @@ func (m *Manager) Start(fwdEntries []*ForwarderEntry) error {
 		return err
 	}
 
-	m.dnsForwarder = NewDNSForwarder(fmt.Sprintf(":%d", ListenPort()), dnsTTL, m.firewall, m.statusRecorder)
+	if m.localAddr.IsValid() && m.firewall != nil {
+		if err := m.firewall.AddInboundDNAT(m.localAddr, firewall.ProtocolUDP, nbdns.ForwarderClientPort, m.serverPort); err != nil {
+			log.Warnf("failed to add DNS UDP DNAT rule: %v", err)
+		} else {
+			log.Infof("added DNS UDP DNAT rule: %s:%d -> %s:%d", m.localAddr, nbdns.ForwarderClientPort, m.localAddr, m.serverPort)
+		}
+
+		if err := m.firewall.AddInboundDNAT(m.localAddr, firewall.ProtocolTCP, nbdns.ForwarderClientPort, m.serverPort); err != nil {
+			log.Warnf("failed to add DNS TCP DNAT rule: %v", err)
+		} else {
+			log.Infof("added DNS TCP DNAT rule: %s:%d -> %s:%d", m.localAddr, nbdns.ForwarderClientPort, m.localAddr, m.serverPort)
+		}
+	}
+
+	m.dnsForwarder = NewDNSForwarder(fmt.Sprintf(":%d", m.serverPort), dnsTTL, m.firewall, m.statusRecorder)
 	go func() {
 		if err := m.dnsForwarder.Listen(fwdEntries); err != nil {
 			// todo handle close error if it is exists
@@ -96,6 +110,17 @@ func (m *Manager) Stop(ctx context.Context) error {
 	}
 
 	var mErr *multierror.Error
+
+	if m.localAddr.IsValid() && m.firewall != nil {
+		if err := m.firewall.RemoveInboundDNAT(m.localAddr, firewall.ProtocolUDP, nbdns.ForwarderClientPort, m.serverPort); err != nil {
+			mErr = multierror.Append(mErr, fmt.Errorf("remove DNS UDP DNAT rule: %w", err))
+		}
+
+		if err := m.firewall.RemoveInboundDNAT(m.localAddr, firewall.ProtocolTCP, nbdns.ForwarderClientPort, m.serverPort); err != nil {
+			mErr = multierror.Append(mErr, fmt.Errorf("remove DNS TCP DNAT rule: %w", err))
+		}
+	}
+
 	if err := m.dropDNSFirewall(); err != nil {
 		mErr = multierror.Append(mErr, err)
 	}
@@ -111,7 +136,7 @@ func (m *Manager) Stop(ctx context.Context) error {
 func (m *Manager) allowDNSFirewall() error {
 	dport := &firewall.Port{
 		IsRange: false,
-		Values:  []uint16{ListenPort()},
+		Values:  []uint16{m.serverPort},
 	}
 
 	if m.firewall == nil {

client/internal/engine.go

@@ -202,9 +202,6 @@ type Engine struct {
 	// WireGuard interface monitor
 	wgIfaceMonitor   *WGIfaceMonitor
 	wgIfaceMonitorWg sync.WaitGroup
-
-	// dns forwarder port
-	dnsFwdPort uint16
 }
 
 // Peer is an instance of the Connection Peer
@@ -247,7 +244,6 @@ func NewEngine(
 		statusRecorder: statusRecorder,
 		checks:         checks,
 		connSemaphore:  semaphoregroup.NewSemaphoreGroup(connInitLimit),
-		dnsFwdPort:     dnsfwd.ListenPort(),
 	}
 
 	sm := profilemanager.NewServiceManager("")
@@ -1084,7 +1080,7 @@ func (e *Engine) updateNetworkMap(networkMap *mgmProto.NetworkMap) error {
 	}
 
 	fwdEntries := toRouteDomains(e.config.WgPrivateKey.PublicKey().String(), routes)
-	e.updateDNSForwarder(dnsRouteFeatureFlag, fwdEntries, uint16(protoDNSConfig.ForwarderPort))
+	e.updateDNSForwarder(dnsRouteFeatureFlag, fwdEntries)
 
 	// Ingress forward rules
 	forwardingRules, err := e.updateForwardRules(networkMap.GetForwardingRules())
@@ -1843,16 +1839,11 @@ func (e *Engine) GetWgAddr() netip.Addr {
 func (e *Engine) updateDNSForwarder(
 	enabled bool,
 	fwdEntries []*dnsfwd.ForwarderEntry,
-	forwarderPort uint16,
 ) {
 	if e.config.DisableServerRoutes {
 		return
 	}
 
-	if forwarderPort > 0 {
-		dnsfwd.SetListenPort(forwarderPort)
-	}
-
 	if !enabled {
 		if e.dnsForwardMgr == nil {
 			return
@@ -1864,20 +1855,17 @@ func (e *Engine) updateDNSForwarder(
 	}
 
 	if len(fwdEntries) > 0 {
-		switch {
-		case e.dnsForwardMgr == nil:
-			e.dnsForwardMgr = dnsfwd.NewManager(e.firewall, e.statusRecorder)
+		if e.dnsForwardMgr == nil {
+			localAddr := e.wgInterface.Address().IP
+			e.dnsForwardMgr = dnsfwd.NewManager(e.firewall, e.statusRecorder, localAddr)
+
 			if err := e.dnsForwardMgr.Start(fwdEntries); err != nil {
 				log.Errorf("failed to start DNS forward: %v", err)
 				e.dnsForwardMgr = nil
 			}
-			log.Infof("started domain router service with %d entries", len(fwdEntries))
-		case e.dnsFwdPort != forwarderPort:
-			log.Infof("updating domain router service port from %d to %d", e.dnsFwdPort, forwarderPort)
-			e.restartDnsFwd(fwdEntries, forwarderPort)
-			e.dnsFwdPort = forwarderPort
 
-		default:
+			log.Infof("started domain router service with %d entries", len(fwdEntries))
+		} else {
 			e.dnsForwardMgr.UpdateDomains(fwdEntries)
 		}
 	} else if e.dnsForwardMgr != nil {
@@ -1887,20 +1875,6 @@ func (e *Engine) updateDNSForwarder(
 		}
 		e.dnsForwardMgr = nil
 	}
-
-}
-
-func (e *Engine) restartDnsFwd(fwdEntries []*dnsfwd.ForwarderEntry, forwarderPort uint16) {
-	log.Infof("updating domain router service port from %d to %d", e.dnsFwdPort, forwarderPort)
-	// stop and start the forwarder to apply the new port
-	if err := e.dnsForwardMgr.Stop(context.Background()); err != nil {
-		log.Errorf("failed to stop DNS forward: %v", err)
-	}
-	e.dnsForwardMgr = dnsfwd.NewManager(e.firewall, e.statusRecorder)
-	if err := e.dnsForwardMgr.Start(fwdEntries); err != nil {
-		log.Errorf("failed to start DNS forward: %v", err)
-		e.dnsForwardMgr = nil
-	}
 }
 
 func (e *Engine) GetNet() (*netstack.Net, error) {

client/internal/netflow/logger/logger.go

@@ -10,10 +10,10 @@ import (
 	"github.com/google/uuid"
 	log "github.com/sirupsen/logrus"
 
-	"github.com/netbirdio/netbird/client/internal/dnsfwd"
 	"github.com/netbirdio/netbird/client/internal/netflow/store"
 	"github.com/netbirdio/netbird/client/internal/netflow/types"
 	"github.com/netbirdio/netbird/client/internal/peer"
+	"github.com/netbirdio/netbird/dns"
 )
 
 type rcvChan chan *types.EventFields
@@ -138,7 +138,8 @@ func (l *Logger) UpdateConfig(dnsCollection, exitNodeCollection bool) {
 
 func (l *Logger) shouldStore(event *types.EventFields, isExitNode bool) bool {
 	// check dns collection
-	if !l.dnsCollection.Load() && event.Protocol == types.UDP && (event.DestPort == 53 || event.DestPort == uint16(dnsfwd.ListenPort())) {
+	if !l.dnsCollection.Load() && event.Protocol == types.UDP &&
+		(event.DestPort == 53 || event.DestPort == dns.ForwarderClientPort || event.DestPort == dns.ForwarderServerPort) {
 		return false
 	}
 

client/internal/routemanager/dnsinterceptor/handler.go

@@ -18,9 +18,9 @@ import (
 	firewall "github.com/netbirdio/netbird/client/firewall/manager"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	nbdns "github.com/netbirdio/netbird/client/internal/dns"
-	"github.com/netbirdio/netbird/client/internal/dnsfwd"
 	"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"
@@ -257,7 +257,7 @@ func (d *DnsInterceptor) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
 		r.MsgHdr.AuthenticatedData = true
 	}
 
-	upstream := fmt.Sprintf("%s:%d", upstreamIP.String(), dnsfwd.ListenPort())
+	upstream := fmt.Sprintf("%s:%d", upstreamIP.String(), pkgdns.ForwarderClientPort)
 	ctx, cancel := context.WithTimeout(context.Background(), dnsTimeout)
 	defer cancel()