Feature/exit node Android (#1916)

Support exit node on Android.
With the protect socket function, we mark every connection that should be used out of VPN.

client/android/client.go

@@ -1,3 +1,5 @@
+//go:build android
+
 package android
 
 import (
@@ -14,6 +16,7 @@ import (
 	"github.com/netbirdio/netbird/client/system"
 	"github.com/netbirdio/netbird/formatter"
 	"github.com/netbirdio/netbird/iface"
+	"github.com/netbirdio/netbird/util/net"
 )
 
 // ConnectionListener export internal Listener for mobile
@@ -59,6 +62,7 @@ type Client struct {
 
 // NewClient instantiate a new Client
 func NewClient(cfgFile, deviceName string, tunAdapter TunAdapter, iFaceDiscover IFaceDiscover, networkChangeListener NetworkChangeListener) *Client {
+	net.SetAndroidProtectSocketFn(tunAdapter.ProtectSocket)
 	return &Client{
 		cfgFile:               cfgFile,
 		deviceName:            deviceName,

client/internal/dns/hosts_dns_holder.go

@@ -0,0 +1,63 @@
+package dns
+
+import (
+	"fmt"
+	"net/netip"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type hostsDNSHolder struct {
+	unprotectedDNSList map[string]struct{}
+	mutex              sync.RWMutex
+}
+
+func newHostsDNSHolder() *hostsDNSHolder {
+	return &hostsDNSHolder{
+		unprotectedDNSList: make(map[string]struct{}),
+	}
+}
+
+func (h *hostsDNSHolder) set(list []string) {
+	h.mutex.Lock()
+	h.unprotectedDNSList = make(map[string]struct{})
+	for _, dns := range list {
+		dnsAddr, err := h.normalizeAddress(dns)
+		if err != nil {
+			continue
+		}
+		h.unprotectedDNSList[dnsAddr] = struct{}{}
+	}
+	h.mutex.Unlock()
+}
+
+func (h *hostsDNSHolder) get() map[string]struct{} {
+	h.mutex.RLock()
+	l := h.unprotectedDNSList
+	h.mutex.RUnlock()
+	return l
+}
+
+//nolint:unused
+func (h *hostsDNSHolder) isContain(upstream string) bool {
+	h.mutex.RLock()
+	defer h.mutex.RUnlock()
+
+	_, ok := h.unprotectedDNSList[upstream]
+	return ok
+}
+
+func (h *hostsDNSHolder) normalizeAddress(addr string) (string, error) {
+	a, err := netip.ParseAddr(addr)
+	if err != nil {
+		log.Errorf("invalid upstream IP address: %s, error: %s", addr, err)
+		return "", err
+	}
+
+	if a.Is4() {
+		return fmt.Sprintf("%s:53", addr), nil
+	} else {
+		return fmt.Sprintf("[%s]:53", addr), nil
+	}
+}

client/internal/dns/server.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"net/netip"
+	"runtime"
 	"strings"
 	"sync"
 
@@ -54,9 +55,8 @@ type DefaultServer struct {
 	currentConfig      HostDNSConfig
 
 	// permanent related properties
-	permanent        bool
-	hostsDnsList     []string
-	hostsDnsListLock sync.Mutex
+	permanent      bool
+	hostsDNSHolder *hostsDNSHolder
 
 	// make sense on mobile only
 	searchDomainNotifier *notifier
@@ -113,8 +113,8 @@ func NewDefaultServerPermanentUpstream(
 ) *DefaultServer {
 	log.Debugf("host dns address list is: %v", hostsDnsList)
 	ds := newDefaultServer(ctx, wgInterface, newServiceViaMemory(wgInterface), statusRecorder)
+	ds.hostsDNSHolder.set(hostsDnsList)
 	ds.permanent = true
-	ds.hostsDnsList = hostsDnsList
 	ds.addHostRootZone()
 	ds.currentConfig = dnsConfigToHostDNSConfig(config, ds.service.RuntimeIP(), ds.service.RuntimePort())
 	ds.searchDomainNotifier = newNotifier(ds.SearchDomains())
@@ -147,6 +147,7 @@ func newDefaultServer(ctx context.Context, wgInterface WGIface, dnsService servi
 		},
 		wgInterface:    wgInterface,
 		statusRecorder: statusRecorder,
+		hostsDNSHolder: newHostsDNSHolder(),
 	}
 
 	return defaultServer
@@ -202,10 +203,8 @@ func (s *DefaultServer) Stop() {
 // OnUpdatedHostDNSServer update the DNS servers addresses for root zones
 // It will be applied if the mgm server do not enforce DNS settings for root zone
 func (s *DefaultServer) OnUpdatedHostDNSServer(hostsDnsList []string) {
-	s.hostsDnsListLock.Lock()
-	defer s.hostsDnsListLock.Unlock()
+	s.hostsDNSHolder.set(hostsDnsList)
 
-	s.hostsDnsList = hostsDnsList
 	_, ok := s.dnsMuxMap[nbdns.RootZone]
 	if ok {
 		log.Debugf("on new host DNS config but skip to apply it")
@@ -374,6 +373,7 @@ func (s *DefaultServer) buildUpstreamHandlerUpdate(nameServerGroups []*nbdns.Nam
 			s.wgInterface.Address().IP,
 			s.wgInterface.Address().Network,
 			s.statusRecorder,
+			s.hostsDNSHolder,
 		)
 		if err != nil {
 			return nil, fmt.Errorf("unable to create a new upstream resolver, error: %v", err)
@@ -452,9 +452,7 @@ func (s *DefaultServer) updateMux(muxUpdates []muxUpdate) {
 		_, found := muxUpdateMap[key]
 		if !found {
 			if !isContainRootUpdate && key == nbdns.RootZone {
-				s.hostsDnsListLock.Lock()
 				s.addHostRootZone()
-				s.hostsDnsListLock.Unlock()
 				existingHandler.stop()
 			} else {
 				existingHandler.stop()
@@ -512,6 +510,7 @@ func (s *DefaultServer) upstreamCallbacks(
 		if nsGroup.Primary {
 			removeIndex[nbdns.RootZone] = -1
 			s.currentConfig.RouteAll = false
+			s.service.DeregisterMux(nbdns.RootZone)
 		}
 
 		for i, item := range s.currentConfig.Domains {
@@ -521,10 +520,15 @@ func (s *DefaultServer) upstreamCallbacks(
 				removeIndex[item.Domain] = i
 			}
 		}
+
 		if err := s.hostManager.applyDNSConfig(s.currentConfig); err != nil {
 			l.Errorf("Failed to apply nameserver deactivation on the host: %v", err)
 		}
 
+		if runtime.GOOS == "android" && nsGroup.Primary && len(s.hostsDNSHolder.get()) > 0 {
+			s.addHostRootZone()
+		}
+
 		s.updateNSState(nsGroup, err, false)
 
 	}
@@ -545,6 +549,9 @@ func (s *DefaultServer) upstreamCallbacks(
 
 		if nsGroup.Primary {
 			s.currentConfig.RouteAll = true
+			if runtime.GOOS == "android" {
+				s.service.RegisterMux(nbdns.RootZone, handler)
+			}
 		}
 		if err := s.hostManager.applyDNSConfig(s.currentConfig); err != nil {
 			l.WithError(err).Error("reactivate temporary disabled nameserver group, DNS update apply")
@@ -562,25 +569,16 @@ func (s *DefaultServer) addHostRootZone() {
 		s.wgInterface.Address().IP,
 		s.wgInterface.Address().Network,
 		s.statusRecorder,
+		s.hostsDNSHolder,
 	)
 	if err != nil {
 		log.Errorf("unable to create a new upstream resolver, error: %v", err)
 		return
 	}
-	handler.upstreamServers = make([]string, len(s.hostsDnsList))
-	for n, ua := range s.hostsDnsList {
-		a, err := netip.ParseAddr(ua)
-		if err != nil {
-			log.Errorf("invalid upstream IP address: %s, error: %s", ua, err)
-			continue
-		}
 
-		ipString := ua
-		if !a.Is4() {
-			ipString = fmt.Sprintf("[%s]", ua)
-		}
-
-		handler.upstreamServers[n] = fmt.Sprintf("%s:53", ipString)
+	handler.upstreamServers = make([]string, 0)
+	for k := range s.hostsDNSHolder.get() {
+		handler.upstreamServers = append(handler.upstreamServers, k)
 	}
 	handler.deactivate = func(error) {}
 	handler.reactivate = func() {}

client/internal/dns/upstream_android.go

@@ -0,0 +1,84 @@
+package dns
+
+import (
+	"context"
+	"net"
+	"syscall"
+	"time"
+
+	"github.com/miekg/dns"
+
+	"github.com/netbirdio/netbird/client/internal/peer"
+	nbnet "github.com/netbirdio/netbird/util/net"
+)
+
+type upstreamResolver struct {
+	*upstreamResolverBase
+	hostsDNSHolder *hostsDNSHolder
+}
+
+// newUpstreamResolver in Android we need to distinguish the DNS servers to available through VPN or outside of VPN
+// In case if the assigned DNS address is available only in the protected network then the resolver will time out at the
+// first time, and we need to wait for a while to start to use again the proper DNS resolver.
+func newUpstreamResolver(
+	ctx context.Context,
+	_ string,
+	_ net.IP,
+	_ *net.IPNet,
+	statusRecorder *peer.Status,
+	hostsDNSHolder *hostsDNSHolder,
+) (*upstreamResolver, error) {
+	upstreamResolverBase := newUpstreamResolverBase(ctx, statusRecorder)
+	c := &upstreamResolver{
+		upstreamResolverBase: upstreamResolverBase,
+		hostsDNSHolder:       hostsDNSHolder,
+	}
+	upstreamResolverBase.upstreamClient = c
+	return c, nil
+}
+
+// exchange in case of Android if the upstream is a local resolver then we do not need to mark the socket as protected.
+// In other case the DNS resolvation goes through the VPN, so we need to force to use the
+func (u *upstreamResolver) exchange(ctx context.Context, upstream string, r *dns.Msg) (rm *dns.Msg, t time.Duration, err error) {
+	if u.isLocalResolver(upstream) {
+		return u.exchangeWithoutVPN(ctx, upstream, r)
+	} else {
+		return u.exchangeWithinVPN(ctx, upstream, r)
+	}
+}
+
+func (u *upstreamResolver) exchangeWithinVPN(ctx context.Context, upstream string, r *dns.Msg) (rm *dns.Msg, t time.Duration, err error) {
+	upstreamExchangeClient := &dns.Client{}
+	return upstreamExchangeClient.ExchangeContext(ctx, r, upstream)
+}
+
+// exchangeWithoutVPN protect the UDP socket by Android SDK to avoid to goes through the VPN
+func (u *upstreamResolver) exchangeWithoutVPN(ctx context.Context, upstream string, r *dns.Msg) (rm *dns.Msg, t time.Duration, err error) {
+	timeout := upstreamTimeout
+	if deadline, ok := ctx.Deadline(); ok {
+		timeout = time.Until(deadline)
+	}
+	dialTimeout := timeout
+
+	nbDialer := nbnet.NewDialer()
+
+	dialer := &net.Dialer{
+		Control: func(network, address string, c syscall.RawConn) error {
+			return nbDialer.Control(network, address, c)
+		},
+		Timeout: dialTimeout,
+	}
+
+	upstreamExchangeClient := &dns.Client{
+		Dialer: dialer,
+	}
+
+	return upstreamExchangeClient.Exchange(r, upstream)
+}
+
+func (u *upstreamResolver) isLocalResolver(upstream string) bool {
+	if u.hostsDNSHolder.isContain(upstream) {
+		return true
+	}
+	return false
+}

client/internal/dns/upstream_general.go

@@ -1,4 +1,4 @@
-//go:build !ios
+//go:build !android && !ios
 
 package dns
 
@@ -12,7 +12,7 @@ import (
 	"github.com/netbirdio/netbird/client/internal/peer"
 )
 
-type upstreamResolverNonIOS struct {
+type upstreamResolver struct {
 	*upstreamResolverBase
 }
 
@@ -22,16 +22,17 @@ func newUpstreamResolver(
 	_ net.IP,
 	_ *net.IPNet,
 	statusRecorder *peer.Status,
-) (*upstreamResolverNonIOS, error) {
+	_ *hostsDNSHolder,
+) (*upstreamResolver, error) {
 	upstreamResolverBase := newUpstreamResolverBase(ctx, statusRecorder)
-	nonIOS := &upstreamResolverNonIOS{
+	nonIOS := &upstreamResolver{
 		upstreamResolverBase: upstreamResolverBase,
 	}
 	upstreamResolverBase.upstreamClient = nonIOS
 	return nonIOS, nil
 }
 
-func (u *upstreamResolverNonIOS) exchange(ctx context.Context, upstream string, r *dns.Msg) (rm *dns.Msg, t time.Duration, err error) {
+func (u *upstreamResolver) exchange(ctx context.Context, upstream string, r *dns.Msg) (rm *dns.Msg, t time.Duration, err error) {
 	upstreamExchangeClient := &dns.Client{}
 	return upstreamExchangeClient.ExchangeContext(ctx, r, upstream)
 }

client/internal/dns/upstream_ios.go

@@ -28,6 +28,7 @@ func newUpstreamResolver(
 	ip net.IP,
 	net *net.IPNet,
 	statusRecorder *peer.Status,
+	_ *hostsDNSHolder,
 ) (*upstreamResolverIOS, error) {
 	upstreamResolverBase := newUpstreamResolverBase(ctx, statusRecorder)
 

client/internal/dns/upstream_test.go

@@ -58,7 +58,7 @@ func TestUpstreamResolver_ServeDNS(t *testing.T) {
 	for _, testCase := range testCases {
 		t.Run(testCase.name, func(t *testing.T) {
 			ctx, cancel := context.WithCancel(context.TODO())
-			resolver, _ := newUpstreamResolver(ctx, "", net.IP{}, &net.IPNet{}, nil)
+			resolver, _ := newUpstreamResolver(ctx, "", net.IP{}, &net.IPNet{}, nil, nil)
 			resolver.upstreamServers = testCase.InputServers
 			resolver.upstreamTimeout = testCase.timeout
 			if testCase.cancelCTX {

client/internal/routemanager/manager.go

@@ -155,7 +155,7 @@ func (m *DefaultManager) SetRouteChangeListener(listener listener.NetworkChangeL
 
 // InitialRouteRange return the list of initial routes. It used by mobile systems
 func (m *DefaultManager) InitialRouteRange() []string {
-	return m.notifier.initialRouteRanges()
+	return m.notifier.getInitialRouteRanges()
 }
 
 // GetRouteSelector returns the route selector
@@ -261,10 +261,7 @@ func (m *DefaultManager) clientRoutes(initialRoutes []*route.Route) []*route.Rou
 
 func isPrefixSupported(prefix netip.Prefix) bool {
 	if !nbnet.CustomRoutingDisabled() {
-		switch runtime.GOOS {
-		case "linux", "windows", "darwin", "ios":
-			return true
-		}
+		return true
 	}
 
 	// If prefix is too small, lets assume it is a possible default prefix which is not yet supported

client/internal/routemanager/notifier.go

@@ -10,8 +10,8 @@ import (
 )
 
 type notifier struct {
-	initialRouteRangers []string
-	routeRangers        []string
+	initialRouteRanges []string
+	routeRanges        []string
 
 	listener    listener.NetworkChangeListener
 	listenerMux sync.Mutex
@@ -33,7 +33,7 @@ func (n *notifier) setInitialClientRoutes(clientRoutes []*route.Route) {
 		nets = append(nets, r.Network.String())
 	}
 	sort.Strings(nets)
-	n.initialRouteRangers = nets
+	n.initialRouteRanges = nets
 }
 
 func (n *notifier) onNewRoutes(idMap route.HAMap) {
@@ -45,11 +45,11 @@ func (n *notifier) onNewRoutes(idMap route.HAMap) {
 	}
 
 	sort.Strings(newNets)
-	if !n.hasDiff(n.initialRouteRangers, newNets) {
+	if !n.hasDiff(n.initialRouteRanges, newNets) {
 		return
 	}
 
-	n.routeRangers = newNets
+	n.routeRanges = newNets
 
 	n.notify()
 }
@@ -62,7 +62,7 @@ func (n *notifier) notify() {
 	}
 
 	go func(l listener.NetworkChangeListener) {
-		l.OnNetworkChanged(strings.Join(n.routeRangers, ","))
+		l.OnNetworkChanged(strings.Join(addIPv6RangeIfNeeded(n.routeRanges), ","))
 	}(n.listener)
 }
 
@@ -78,6 +78,20 @@ func (n *notifier) hasDiff(a []string, b []string) bool {
 	return false
 }
 
-func (n *notifier) initialRouteRanges() []string {
-	return n.initialRouteRangers
+func (n *notifier) getInitialRouteRanges() []string {
+	return addIPv6RangeIfNeeded(n.initialRouteRanges)
+}
+
+// addIPv6RangeIfNeeded returns the input ranges with the default IPv6 range when there is an IPv4 default route.
+func addIPv6RangeIfNeeded(inputRanges []string) []string {
+	ranges := inputRanges
+	for _, r := range inputRanges {
+		// we are intentionally adding the ipv6 default range in case of ipv4 default range
+		// to ensure that all traffic is managed by the tunnel interface on android
+		if r == "0.0.0.0/0" {
+			ranges = append(ranges, "::/0")
+			break
+		}
+	}
+	return ranges
 }

iface/tun_adapter.go

@@ -4,4 +4,5 @@ package iface
 type TunAdapter interface {
 	ConfigureInterface(address string, mtu int, dns string, searchDomains string, routes string) (int, error)
 	UpdateAddr(address string) error
+	ProtectSocket(fd int32) bool
 }

util/net/dialer_android.go

@@ -0,0 +1,25 @@
+package net
+
+import (
+	"syscall"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func (d *Dialer) init() {
+	d.Dialer.Control = func(_, _ string, c syscall.RawConn) error {
+		err := c.Control(func(fd uintptr) {
+			androidProtectSocketLock.Lock()
+			f := androidProtectSocket
+			androidProtectSocketLock.Unlock()
+			if f == nil {
+				return
+			}
+			ok := f(int32(fd))
+			if !ok {
+				log.Errorf("failed to protect socket: %d", fd)
+			}
+		})
+		return err
+	}
+}

util/net/dialer_ios.go

@@ -1,5 +1,3 @@
-//go:build android || ios
-
 package net
 
 import (

util/net/dialer_nonios.go

@@ -1,4 +1,4 @@
-//go:build !android && !ios
+//go:build !ios
 
 package net
 
@@ -36,7 +36,7 @@ func AddDialerCloseHook(hook DialerCloseHookFunc) {
 	dialerCloseHooks = append(dialerCloseHooks, hook)
 }
 
-// RemoveDialerHook removes all dialer hooks.
+// RemoveDialerHooks removes all dialer hooks.
 func RemoveDialerHooks() {
 	dialerDialHooksMutex.Lock()
 	defer dialerDialHooksMutex.Unlock()

util/net/dialer_nonlinux.go

@@ -1,4 +1,4 @@
-//go:build !linux || android
+//go:build !linux
 
 package net
 

util/net/listener_android.go

@@ -0,0 +1,26 @@
+package net
+
+import (
+	"syscall"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// init configures the net.ListenerConfig Control function to set the fwmark on the socket
+func (l *ListenerConfig) init() {
+	l.ListenConfig.Control = func(_, _ string, c syscall.RawConn) error {
+		err := c.Control(func(fd uintptr) {
+			androidProtectSocketLock.Lock()
+			f := androidProtectSocket
+			androidProtectSocketLock.Unlock()
+			if f == nil {
+				return
+			}
+			ok := f(int32(fd))
+			if !ok {
+				log.Errorf("failed to protect listener socket: %d", fd)
+			}
+		})
+		return err
+	}
+}

util/net/listener_ios.go

@@ -1,4 +1,4 @@
-//go:build android || ios
+//go:build ios
 
 package net
 

util/net/listener_nonios.go

@@ -1,4 +1,4 @@
-//go:build !android && !ios
+//go:build !ios
 
 package net
 

util/net/listener_nonlinux.go

@@ -1,4 +1,4 @@
-//go:build !linux || android
+//go:build !linux
 
 package net
 

util/net/protectsocket_android.go

@@ -0,0 +1,14 @@
+package net
+
+import "sync"
+
+var (
+	androidProtectSocketLock sync.Mutex
+	androidProtectSocket     func(fd int32) bool
+)
+
+func SetAndroidProtectSocketFn(f func(fd int32) bool) {
+	androidProtectSocketLock.Lock()
+	androidProtectSocket = f
+	androidProtectSocketLock.Unlock()
+}