Restore dns on unclean shutdown (netbirdio#1494)

client/cmd/service_controller.go

@@ -11,11 +11,12 @@ import (
 	"github.com/kardianos/service"
 	log "github.com/sirupsen/logrus"
 
+	"github.com/spf13/cobra"
+	"google.golang.org/grpc"
+
 	"github.com/netbirdio/netbird/client/proto"
 	"github.com/netbirdio/netbird/client/server"
 	"github.com/netbirdio/netbird/util"
-	"github.com/spf13/cobra"
-	"google.golang.org/grpc"
 )
 
 func (p *program) Start(svc service.Service) error {
@@ -109,7 +110,6 @@ var runCmd = &cobra.Command{
 		if err != nil {
 			return err
 		}
-		cmd.Printf("Netbird service is running")
 		return nil
 	},
 }

client/internal/connect.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -93,6 +94,12 @@ func runClient(
 ) error {
 	log.Infof("starting NetBird client version %s", version.NetbirdVersion())
 
+	// Check if client was not shut down in a clean way and restore DNS config if required.
+	// Otherwise, we might not be able to connect to the management server to retrieve new config.
+	if err := dns.CheckUncleanShutdown(config.WgIface); err != nil {
+		log.Errorf("checking unclean shutdown error: %s", err)
+	}
+
 	backOff := &backoff.ExponentialBackOff{
 		InitialInterval:     time.Second,
 		RandomizationFactor: 1,
@@ -244,7 +251,7 @@ func runClient(
 
 		log.Info("stopped NetBird client")
 
-		if _, err := state.Status(); err == ErrResetConnection {
+		if _, err := state.Status(); errors.Is(err, ErrResetConnection) {
 			return err
 		}
 

client/internal/dns/dbus_linux.go

@@ -4,31 +4,38 @@ package dns
 
 import (
 	"context"
+	"fmt"
+	"time"
+
 	"github.com/godbus/dbus/v5"
 	log "github.com/sirupsen/logrus"
-	"time"
 )
 
 const dbusDefaultFlag = 0
 
 func isDbusListenerRunning(dest string, path dbus.ObjectPath) bool {
 	obj, closeConn, err := getDbusObject(dest, path)
 	if err != nil {
+		log.Tracef("error getting dbus object: %s", err)
 		return false
 	}
 	defer closeConn()
 
 	ctx, cancel := context.WithTimeout(context.TODO(), 5*time.Second)
 	defer cancel()
 
-	err = obj.CallWithContext(ctx, "org.freedesktop.DBus.Peer.Ping", 0).Store()
-	return err == nil
+	if err = obj.CallWithContext(ctx, "org.freedesktop.DBus.Peer.Ping", 0).Store(); err != nil {
+		log.Tracef("error calling dbus: %s", err)
+		return false
+	}
+
+	return true
 }
 
 func getDbusObject(dest string, path dbus.ObjectPath) (dbus.BusObject, func(), error) {
 	conn, err := dbus.SystemBus()
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, fmt.Errorf("get dbus: %w", err)
 	}
 	obj := conn.Object(dest, path)
 

client/internal/dns/file_linux.go

@@ -5,6 +5,7 @@ package dns
 import (
 	"bytes"
 	"fmt"
+	"net/netip"
 	"os"
 	"strings"
 
@@ -49,7 +50,7 @@ func (f *fileConfigurator) applyDNSConfig(config HostDNSConfig) error {
 		if backupFileExist {
 			err = f.restore()
 			if err != nil {
-				return fmt.Errorf("unable to configure DNS for this peer using file manager without a Primary nameserver group. Restoring the original file return err: %s", err)
+				return fmt.Errorf("unable to configure DNS for this peer using file manager without a Primary nameserver group. Restoring the original file return err: %w", err)
 			}
 		}
 		return fmt.Errorf("unable to configure DNS for this peer using file manager without a nameserver group with all domains configured")
@@ -58,7 +59,7 @@ func (f *fileConfigurator) applyDNSConfig(config HostDNSConfig) error {
 	if !backupFileExist {
 		err = f.backup()
 		if err != nil {
-			return fmt.Errorf("unable to backup the resolv.conf file")
+			return fmt.Errorf("unable to backup the resolv.conf file: %w", err)
 		}
 	}
 
@@ -67,7 +68,7 @@ func (f *fileConfigurator) applyDNSConfig(config HostDNSConfig) error {
 
 	resolvConf, err := parseBackupResolvConf()
 	if err != nil {
-		log.Error(err)
+		log.Errorf("could not read original search domains from %s: %s", fileDefaultResolvConfBackupLocation, err)
 	}
 
 	f.repair.stopWatchFileChanges()
@@ -96,10 +97,16 @@ func (f *fileConfigurator) updateConfig(nbSearchDomains []string, nbNameserverIP
 		if restoreErr != nil {
 			log.Errorf("attempt to restore default file failed with error: %s", err)
 		}
-		return fmt.Errorf("got an creating resolver file %s. Error: %s", defaultResolvConfPath, err)
+		return fmt.Errorf("creating resolver file %s. Error: %w", defaultResolvConfPath, err)
+	}
+
+	log.Infof("created a NetBird managed %s file with the DNS settings. Added %d search domains. Search list: %s", defaultResolvConfPath, len(searchDomainList), searchDomainList)
+
+	// create another backup for unclean shutdown detection right after overwriting the original resolv.conf
+	if err := createUncleanShutdownIndicator(fileDefaultResolvConfBackupLocation, fileManager, nbNameserverIP); err != nil {
+		log.Errorf("failed to create unclean shutdown resolv.conf backup: %s", err)
 	}
 
-	log.Infof("created a NetBird managed %s file with your DNS settings. Added %d search domains. Search list: %s", defaultResolvConfPath, len(searchDomainList), searchDomainList)
 	return nil
 }
 
@@ -111,27 +118,73 @@ func (f *fileConfigurator) restoreHostDNS() error {
 func (f *fileConfigurator) backup() error {
 	stats, err := os.Stat(defaultResolvConfPath)
 	if err != nil {
-		return fmt.Errorf("got an error while checking stats for %s file. Error: %s", defaultResolvConfPath, err)
+		return fmt.Errorf("checking stats for %s file. Error: %w", defaultResolvConfPath, err)
 	}
 
 	f.originalPerms = stats.Mode()
 
 	err = copyFile(defaultResolvConfPath, fileDefaultResolvConfBackupLocation)
 	if err != nil {
-		return fmt.Errorf("got error while backing up the %s file. Error: %s", defaultResolvConfPath, err)
+		return fmt.Errorf("backing up %s: %w", defaultResolvConfPath, err)
 	}
 	return nil
 }
 
 func (f *fileConfigurator) restore() error {
 	err := copyFile(fileDefaultResolvConfBackupLocation, defaultResolvConfPath)
 	if err != nil {
-		return fmt.Errorf("got error while restoring the %s file from %s. Error: %s", defaultResolvConfPath, fileDefaultResolvConfBackupLocation, err)
+		return fmt.Errorf("restoring %s from %s: %w", defaultResolvConfPath, fileDefaultResolvConfBackupLocation, err)
+	}
+
+	if err := removeUncleanShutdownIndicator(); err != nil {
+		log.Errorf("failed to remove unclean shutdown resolv.conf backup: %s", err)
 	}
 
 	return os.RemoveAll(fileDefaultResolvConfBackupLocation)
 }
 
+func (f *fileConfigurator) restoreUncleanShutdownDNS(storedDNSAddress *netip.Addr) error {
+	resolvConf, err := parseDefaultResolvConf()
+	if err != nil {
+		return fmt.Errorf("parse current resolv.conf: %w", err)
+	}
+
+	// no current nameservers set -> restore
+	if len(resolvConf.nameServers) == 0 {
+		return restoreResolvConfFile()
+	}
+
+	currentDNSAddress, err := netip.ParseAddr(resolvConf.nameServers[0])
+	// not a valid first nameserver -> restore
+	if err != nil {
+		log.Errorf("restoring unclean shutdown: parse dns address %s failed: %s", resolvConf.nameServers[1], err)
+		return restoreResolvConfFile()
+	}
+
+	// current address is still netbird's non-available dns address -> restore
+	// comparing parsed addresses only, to remove ambiguity
+	if currentDNSAddress.String() == storedDNSAddress.String() {
+		return restoreResolvConfFile()
+	}
+
+	log.Info("restoring unclean shutdown: first current nameserver differs from saved nameserver pre-netbird: not restoring")
+	return nil
+}
+
+func restoreResolvConfFile() error {
+	log.Debugf("restoring unclean shutdown: restoring %s from %s", defaultResolvConfPath, fileUncleanShutdownResolvConfLocation)
+
+	if err := copyFile(fileUncleanShutdownResolvConfLocation, defaultResolvConfPath); err != nil {
+		return fmt.Errorf("restoring %s from %s: %w", defaultResolvConfPath, fileUncleanShutdownResolvConfLocation, err)
+	}
+
+	if err := removeUncleanShutdownIndicator(); err != nil {
+		log.Errorf("failed to remove unclean shutdown resolv.conf file: %s", err)
+	}
+
+	return nil
+}
+
 // generateNsList generates a list of nameservers from the config and adds the primary nameserver to the beginning of the list
 func generateNsList(nbNameserverIP string, cfg *resolvConf) []string {
 	ns := make([]string, 1, len(cfg.nameServers)+1)
@@ -231,17 +284,17 @@ func validateAndFillSearchDomains(initialLineChars int, s *[]string, vs []string
 func copyFile(src, dest string) error {
 	stats, err := os.Stat(src)
 	if err != nil {
-		return fmt.Errorf("got an error while checking stats for %s file when copying it. Error: %s", src, err)
+		return fmt.Errorf("checking stats for %s file when copying it. Error: %s", src, err)
 	}
 
 	bytesRead, err := os.ReadFile(src)
 	if err != nil {
-		return fmt.Errorf("got an error while reading the file %s file for copy. Error: %s", src, err)
+		return fmt.Errorf("reading the file %s file for copy. Error: %s", src, err)
 	}
 
 	err = os.WriteFile(dest, bytesRead, stats.Mode())
 	if err != nil {
-		return fmt.Errorf("got an writing the destination file %s for copy. Error: %s", dest, err)
+		return fmt.Errorf("writing the destination file %s for copy. Error: %s", dest, err)
 	}
 	return nil
 }

client/internal/dns/host.go

@@ -2,6 +2,7 @@ package dns
 
 import (
 	"fmt"
+	"net/netip"
 	"strings"
 
 	nbdns "github.com/netbirdio/netbird/dns"
@@ -11,6 +12,7 @@ type hostManager interface {
 	applyDNSConfig(config HostDNSConfig) error
 	restoreHostDNS() error
 	supportCustomPort() bool
+	restoreUncleanShutdownDNS(storedDNSAddress *netip.Addr) error
 }
 
 type HostDNSConfig struct {
@@ -27,9 +29,10 @@ type DomainConfig struct {
 }
 
 type mockHostConfigurator struct {
-	applyDNSConfigFunc    func(config HostDNSConfig) error
-	restoreHostDNSFunc    func() error
-	supportCustomPortFunc func() bool
+	applyDNSConfigFunc            func(config HostDNSConfig) error
+	restoreHostDNSFunc            func() error
+	supportCustomPortFunc         func() bool
+	restoreUncleanShutdownDNSFunc func(*netip.Addr) error
 }
 
 func (m *mockHostConfigurator) applyDNSConfig(config HostDNSConfig) error {
@@ -53,11 +56,19 @@ func (m *mockHostConfigurator) supportCustomPort() bool {
 	return false
 }
 
+func (m *mockHostConfigurator) restoreUncleanShutdownDNS(storedDNSAddress *netip.Addr) error {
+	if m.restoreUncleanShutdownDNSFunc != nil {
+		return m.restoreUncleanShutdownDNSFunc(storedDNSAddress)
+	}
+	return fmt.Errorf("method restoreUncleanShutdownDNS is not implemented")
+}
+
 func newNoopHostMocker() hostManager {
 	return &mockHostConfigurator{
-		applyDNSConfigFunc:    func(config HostDNSConfig) error { return nil },
-		restoreHostDNSFunc:    func() error { return nil },
-		supportCustomPortFunc: func() bool { return true },
+		applyDNSConfigFunc:            func(config HostDNSConfig) error { return nil },
+		restoreHostDNSFunc:            func() error { return nil },
+		supportCustomPortFunc:         func() bool { return true },
+		restoreUncleanShutdownDNSFunc: func(*netip.Addr) error { return nil },
 	}
 }
 

client/internal/dns/host_android.go

@@ -1,9 +1,11 @@
 package dns
 
+import "net/netip"
+
 type androidHostManager struct {
 }
 
-func newHostManager(wgInterface WGIface) (hostManager, error) {
+func newHostManager() (hostManager, error) {
 	return &androidHostManager{}, nil
 }
 
@@ -18,3 +20,7 @@ func (a androidHostManager) restoreHostDNS() error {
 func (a androidHostManager) supportCustomPort() bool {
 	return false
 }
+
+func (a androidHostManager) restoreUncleanShutdownDNS(*netip.Addr) error {
+	return nil
+}