Monitor network changes and restart engine on detection (#1904)

client/internal/engine.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"math/rand"
 	"net"
@@ -21,6 +22,7 @@ import (
 	"github.com/netbirdio/netbird/client/firewall/manager"
 	"github.com/netbirdio/netbird/client/internal/acl"
 	"github.com/netbirdio/netbird/client/internal/dns"
+	"github.com/netbirdio/netbird/client/internal/networkmonitor"
 	"github.com/netbirdio/netbird/client/internal/peer"
 	"github.com/netbirdio/netbird/client/internal/relay"
 	"github.com/netbirdio/netbird/client/internal/rosenpass"
@@ -60,6 +62,9 @@ type EngineConfig struct {
 	// WgPrivateKey is a Wireguard private key of our peer (it MUST never leave the machine)
 	WgPrivateKey wgtypes.Key
 
+	// NetworkMonitor is a flag to enable network monitoring
+	NetworkMonitor bool
+
 	// IFaceBlackList is a list of network interfaces to ignore when discovering connection candidates (ICE related)
 	IFaceBlackList       []string
 	DisableIPv6Discovery bool
@@ -114,9 +119,11 @@ type Engine struct {
 	// clientRoutes is the most recent list of clientRoutes received from the Management Service
 	clientRoutes route.HAMap
 
-	cancel context.CancelFunc
+	clientCtx    context.Context
+	clientCancel context.CancelFunc
 
-	ctx context.Context
+	ctx    context.Context
+	cancel context.CancelFunc
 
 	wgInterface    *iface.WGIface
 	wgProxyFactory *wgproxy.Factory
@@ -126,6 +133,8 @@ type Engine struct {
 	// networkSerial is the latest CurrentSerial (state ID) of the network sent by the Management service
 	networkSerial uint64
 
+	networkWatcher *networkmonitor.NetworkWatcher
+
 	sshServerFunc func(hostKeyPEM []byte, addr string) (nbssh.Server, error)
 	sshServer     nbssh.Server
 
@@ -151,8 +160,8 @@ type Peer struct {
 
 // NewEngine creates a new Connection Engine
 func NewEngine(
-	ctx context.Context,
-	cancel context.CancelFunc,
+	clientCtx context.Context,
+	clientCancel context.CancelFunc,
 	signalClient signal.Client,
 	mgmClient mgm.Client,
 	config *EngineConfig,
@@ -160,8 +169,8 @@ func NewEngine(
 	statusRecorder *peer.Status,
 ) *Engine {
 	return NewEngineWithProbes(
-		ctx,
-		cancel,
+		clientCtx,
+		clientCancel,
 		signalClient,
 		mgmClient,
 		config,
@@ -176,8 +185,8 @@ func NewEngine(
 
 // NewEngineWithProbes creates a new Connection Engine with probes attached
 func NewEngineWithProbes(
-	ctx context.Context,
-	cancel context.CancelFunc,
+	clientCtx context.Context,
+	clientCancel context.CancelFunc,
 	signalClient signal.Client,
 	mgmClient mgm.Client,
 	config *EngineConfig,
@@ -188,9 +197,10 @@ func NewEngineWithProbes(
 	relayProbe *Probe,
 	wgProbe *Probe,
 ) *Engine {
+
 	return &Engine{
-		ctx:            ctx,
-		cancel:         cancel,
+		clientCtx:      clientCtx,
+		clientCancel:   clientCancel,
 		signal:         signalClient,
 		mgmClient:      mgmClient,
 		peerConns:      make(map[string]*peer.Conn),
@@ -202,7 +212,7 @@ func NewEngineWithProbes(
 		networkSerial:  0,
 		sshServerFunc:  nbssh.DefaultSSHServer,
 		statusRecorder: statusRecorder,
-		wgProxyFactory: wgproxy.NewFactory(config.WgPort),
+		networkWatcher: networkmonitor.New(),
 		mgmProbe:       mgmProbe,
 		signalProbe:    signalProbe,
 		relayProbe:     relayProbe,
@@ -214,6 +224,13 @@ func (e *Engine) Stop() error {
 	e.syncMsgMux.Lock()
 	defer e.syncMsgMux.Unlock()
 
+	if e.cancel != nil {
+		e.cancel()
+	}
+
+	// stopping network monitor first to avoid starting the engine again
+	e.networkWatcher.Stop()
+
 	err := e.removeAllPeers()
 	if err != nil {
 		return err
@@ -222,7 +239,7 @@ func (e *Engine) Stop() error {
 	e.clientRoutes = nil
 
 	// very ugly but we want to remove peers from the WireGuard interface first before removing interface.
-	// Removing peers happens in the conn.CLose() asynchronously
+	// Removing peers happens in the conn.Close() asynchronously
 	time.Sleep(500 * time.Millisecond)
 
 	e.close()
@@ -237,6 +254,13 @@ func (e *Engine) Start() error {
 	e.syncMsgMux.Lock()
 	defer e.syncMsgMux.Unlock()
 
+	if e.cancel != nil {
+		e.cancel()
+	}
+	e.ctx, e.cancel = context.WithCancel(e.clientCtx)
+
+	e.wgProxyFactory = wgproxy.NewFactory(e.clientCtx, e.config.WgPort)
+
 	wgIface, err := e.newWgIface()
 	if err != nil {
 		log.Errorf("failed creating wireguard interface instance %s: [%s]", e.config.WgIfaceName, err)
@@ -320,6 +344,21 @@ func (e *Engine) Start() error {
 	e.receiveManagementEvents()
 	e.receiveProbeEvents()
 
+	if e.config.NetworkMonitor {
+		// starting network monitor at the very last to avoid disruptions
+		go e.networkWatcher.Start(e.ctx, func() {
+			log.Infof("Network monitor detected network change, restarting engine")
+			if err := e.Stop(); err != nil {
+				log.Errorf("Failed to stop engine: %v", err)
+			}
+			if err := e.Start(); err != nil {
+				log.Errorf("Failed to start engine: %v", err)
+			}
+		})
+	} else {
+		log.Infof("Network monitor is disabled, not starting")
+	}
+
 	return nil
 }
 
@@ -588,12 +627,12 @@ func (e *Engine) updateConfig(conf *mgmProto.PeerConfig) error {
 // E.g. when a new peer has been registered and we are allowed to connect to it.
 func (e *Engine) receiveManagementEvents() {
 	go func() {
-		err := e.mgmClient.Sync(e.handleSync)
+		err := e.mgmClient.Sync(e.ctx, e.handleSync)
 		if err != nil {
 			// happens if management is unavailable for a long time.
 			// We want to cancel the operation of the whole client
 			_ = CtxGetState(e.ctx).Wrap(ErrResetConnection)
-			e.cancel()
+			e.clientCancel()
 			return
 		}
 		log.Debugf("stopped receiving updates from Management Service")
@@ -869,11 +908,12 @@ func (e *Engine) connWorker(conn *peer.Conn, peerKey string) {
 		conn.UpdateStunTurn(append(e.STUNs, e.TURNs...))
 		e.syncMsgMux.Unlock()
 
-		err := conn.Open()
+		err := conn.Open(e.ctx)
 		if err != nil {
 			log.Debugf("connection to peer %s failed: %v", peerKey, err)
-			switch err.(type) {
-			case *peer.ConnectionClosedError:
+			var connectionClosedError *peer.ConnectionClosedError
+			switch {
+			case errors.As(err, &connectionClosedError):
 				// conn has been forced to close, so we exit the loop
 				return
 			default:
@@ -984,7 +1024,7 @@ func (e *Engine) createPeerConn(pubKey string, allowedIPs string) (*peer.Conn, e
 func (e *Engine) receiveSignalEvents() {
 	go func() {
 		// connect to a stream of messages coming from the signal server
-		err := e.signal.Receive(func(msg *sProto.Message) error {
+		err := e.signal.Receive(e.ctx, func(msg *sProto.Message) error {
 			e.syncMsgMux.Lock()
 			defer e.syncMsgMux.Unlock()
 
@@ -1058,7 +1098,7 @@ func (e *Engine) receiveSignalEvents() {
 			// happens if signal is unavailable for a long time.
 			// We want to cancel the operation of the whole client
 			_ = CtxGetState(e.ctx).Wrap(ErrResetConnection)
-			e.cancel()
+			e.clientCancel()
 			return
 		}
 	}()
@@ -1119,13 +1159,16 @@ func (e *Engine) parseNATExternalIPMappings() []string {
 }
 
 func (e *Engine) close() {
-	if err := e.wgProxyFactory.Free(); err != nil {
-		log.Errorf("failed closing ebpf proxy: %s", err)
+	if e.wgProxyFactory != nil {
+		if err := e.wgProxyFactory.Free(); err != nil {
+			log.Errorf("failed closing ebpf proxy: %s", err)
+		}
 	}
 
 	// stop/restore DNS first so dbus and friends don't complain because of a missing interface
 	if e.dnsServer != nil {
 		e.dnsServer.Stop()
+		e.dnsServer = nil
 	}
 
 	if e.routeManager != nil {