all: Fix some linter errors (#5499)

I'm working through linter complaints, these are some fixes. Broad
categories:

1) Ignore errors where we can ignore errors: add "_ = ..." construct.
you can argue that this is annoying noise, but apart from silencing the
linter it *does* serve the purpose of highlighting that an error is
being ignored. I think this is OK, because the linter highlighted some
error cases I wasn't aware of (starting CPU profiles, for example).

2) Untyped constants where we though we had set the type.

3) A real bug where we ineffectually assigned to a shadowed err.

4) Some dead code removed.

There'll be more of these, because not all packages are fixed, but the
diff was already large enough.

cmd/syncthing/auditservice.go

@@ -44,7 +44,7 @@ func (s *auditService) Serve() {
 	for {
 		select {
 		case ev := <-sub.C():
-			enc.Encode(ev)
+			_ = enc.Encode(ev)
 		case <-s.stop:
 			return
 		}

cmd/syncthing/cpuusage_unix.go

@@ -13,6 +13,6 @@ import "time"
 
 func cpuUsage() time.Duration {
 	var rusage syscall.Rusage
-	syscall.Getrusage(syscall.RUSAGE_SELF, &rusage)
+	_ = syscall.Getrusage(syscall.RUSAGE_SELF, &rusage)
 	return time.Duration(rusage.Utime.Nano() + rusage.Stime.Nano())
 }

cmd/syncthing/gui.go

@@ -27,7 +27,7 @@ import (
 	"strings"
 	"time"
 
-	"github.com/rcrowley/go-metrics"
+	metrics "github.com/rcrowley/go-metrics"
 	"github.com/syncthing/syncthing/lib/config"
 	"github.com/syncthing/syncthing/lib/connections"
 	"github.com/syncthing/syncthing/lib/db"
@@ -966,7 +966,7 @@ func (s *apiService) postSystemShutdown(w http.ResponseWriter, r *http.Request)
 }
 
 func (s *apiService) flushResponse(resp string, w http.ResponseWriter) {
-	w.Write([]byte(resp + "\n"))
+	_, _ = w.Write([]byte(resp + "\n"))
 	f := w.(http.Flusher)
 	f.Flush()
 }
@@ -1121,15 +1121,17 @@ func (s *apiService) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	var heapBuffer, cpuBuffer bytes.Buffer
 	filename := fmt.Sprintf("syncthing-heap-%s-%s-%s-%s.pprof", runtime.GOOS, runtime.GOARCH, Version, time.Now().Format("150405")) // hhmmss
 	runtime.GC()
-	pprof.WriteHeapProfile(&heapBuffer)
-	files = append(files, fileEntry{name: filename, data: heapBuffer.Bytes()})
+	if err := pprof.WriteHeapProfile(&heapBuffer); err == nil {
+		files = append(files, fileEntry{name: filename, data: heapBuffer.Bytes()})
+	}
 
 	const duration = 4 * time.Second
 	filename = fmt.Sprintf("syncthing-cpu-%s-%s-%s-%s.pprof", runtime.GOOS, runtime.GOARCH, Version, time.Now().Format("150405")) // hhmmss
-	pprof.StartCPUProfile(&cpuBuffer)
-	time.Sleep(duration)
-	pprof.StopCPUProfile()
-	files = append(files, fileEntry{name: filename, data: cpuBuffer.Bytes()})
+	if err := pprof.StartCPUProfile(&cpuBuffer); err == nil {
+		time.Sleep(duration)
+		pprof.StopCPUProfile()
+		files = append(files, fileEntry{name: filename, data: cpuBuffer.Bytes()})
+	}
 
 	// Add buffer files to buffer zip
 	var zipFilesBuffer bytes.Buffer
@@ -1151,7 +1153,7 @@ func (s *apiService) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	// Serve the buffer zip to client for download
 	w.Header().Set("Content-Type", "application/zip")
 	w.Header().Set("Content-Disposition", "attachment; filename="+zipFileName)
-	io.Copy(w, &zipFilesBuffer)
+	_, _ = io.Copy(w, &zipFilesBuffer)
 }
 
 func (s *apiService) getSystemHTTPMetrics(w http.ResponseWriter, r *http.Request) {
@@ -1171,7 +1173,7 @@ func (s *apiService) getSystemHTTPMetrics(w http.ResponseWriter, r *http.Request
 		}
 	})
 	bs, _ := json.MarshalIndent(stats, "", "  ")
-	w.Write(bs)
+	_, _ = w.Write(bs)
 }
 
 func (s *apiService) getSystemDiscovery(w http.ResponseWriter, r *http.Request) {
@@ -1463,7 +1465,7 @@ func (s *apiService) getQR(w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.Header().Set("Content-Type", "image/png")
-	w.Write(code.PNG())
+	_, _ = w.Write(code.PNG())
 }
 
 func (s *apiService) getPeerCompletion(w http.ResponseWriter, r *http.Request) {
@@ -1561,7 +1563,7 @@ func (s *apiService) getSystemBrowse(w http.ResponseWriter, r *http.Request) {
 
 	// Default value or in case of error unmarshalling ends up being basic fs.
 	var fsType fs.FilesystemType
-	fsType.UnmarshalText([]byte(qs.Get("filesystem")))
+	_ = fsType.UnmarshalText([]byte(qs.Get("filesystem")))
 
 	sendJSON(w, browseFiles(current, fsType))
 }
@@ -1645,9 +1647,10 @@ func (s *apiService) getCPUProf(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/octet-stream")
 	w.Header().Set("Content-Disposition", "attachment; filename="+filename)
 
-	pprof.StartCPUProfile(w)
-	time.Sleep(duration)
-	pprof.StopCPUProfile()
+	if err := pprof.StartCPUProfile(w); err == nil {
+		time.Sleep(duration)
+		pprof.StopCPUProfile()
+	}
 }
 
 func (s *apiService) getHeapProf(w http.ResponseWriter, r *http.Request) {
@@ -1657,7 +1660,7 @@ func (s *apiService) getHeapProf(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Disposition", "attachment; filename="+filename)
 
 	runtime.GC()
-	pprof.WriteHeapProfile(w)
+	_ = pprof.WriteHeapProfile(w)
 }
 
 func toJsonFileInfoSlice(fs []db.FileInfoTruncated) []jsonDBFileInfo {

cmd/syncthing/gui_auth.go

@@ -20,7 +20,7 @@ import (
 	"github.com/syncthing/syncthing/lib/rand"
 	"github.com/syncthing/syncthing/lib/sync"
 	"golang.org/x/crypto/bcrypt"
-	"gopkg.in/ldap.v2"
+	ldap "gopkg.in/ldap.v2"
 )
 
 var (
@@ -80,11 +80,10 @@ func basicAuthAndSessionMiddleware(cookieName string, guiCfg config.GUIConfigura
 			return
 		}
 
-		authOk := false
 		username := string(fields[0])
 		password := string(fields[1])
 
-		authOk = auth(username, password, guiCfg, ldapCfg)
+		authOk := auth(username, password, guiCfg, ldapCfg)
 		if !authOk {
 			usernameIso := string(iso88591ToUTF8([]byte(username)))
 			passwordIso := string(iso88591ToUTF8([]byte(password)))

cmd/syncthing/gui_statics.go

@@ -160,7 +160,7 @@ func (s *staticsServer) serveAsset(w http.ResponseWriter, r *http.Request) {
 	}
 	w.Header().Set("Content-Length", fmt.Sprintf("%d", len(bs)))
 
-	w.Write(bs)
+	_, _ = w.Write(bs)
 }
 
 func (s *staticsServer) serveThemes(w http.ResponseWriter, r *http.Request) {

cmd/syncthing/gui_test.go

@@ -114,13 +114,13 @@ func TestAssetsDir(t *testing.T) {
 	// The asset map contains compressed assets, so create a couple of gzip compressed assets here.
 	buf := new(bytes.Buffer)
 	gw := gzip.NewWriter(buf)
-	gw.Write([]byte("default"))
+	_, _ = gw.Write([]byte("default"))
 	gw.Close()
 	def := buf.Bytes()
 
 	buf = new(bytes.Buffer)
 	gw = gzip.NewWriter(buf)
-	gw.Write([]byte("foo"))
+	_, _ = gw.Write([]byte("foo"))
 	gw.Close()
 	foo := buf.Bytes()
 

cmd/syncthing/main.go

@@ -127,7 +127,6 @@ func setBuildMetadata() {
 var (
 	myID protocol.DeviceID
 	stop = make(chan int)
-	lans []*net.IPNet
 )
 
 const (
@@ -436,7 +435,9 @@ func main() {
 	}
 
 	if options.resetDatabase {
-		resetDB()
+		if err := resetDB(); err != nil {
+			l.Fatalln("Resetting database:", err)
+		}
 		return
 	}
 
@@ -450,7 +451,9 @@ func main() {
 func openGUI() {
 	cfg, _ := loadOrDefaultConfig()
 	if cfg.GUI().Enabled {
-		openURL(cfg.GUI().URL())
+		if err := openURL(cfg.GUI().URL()); err != nil {
+			l.Fatalln("Open URL:", err)
+		}
 	} else {
 		l.Warnln("Browser: GUI is currently disabled")
 	}
@@ -631,7 +634,7 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 	// Attempt to increase the limit on number of open files to the maximum
 	// allowed, in case we have many peers. We don't really care enough to
 	// report the error if there is one.
-	osutil.MaximizeOpenFileLimit()
+	_, _ = osutil.MaximizeOpenFileLimit()
 
 	// Ensure that we have a certificate and key.
 	cert, err := tls.LoadX509KeyPair(locations[locCertFile], locations[locKeyFile])
@@ -754,7 +757,7 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 	// Add and start folders
 	for _, folderCfg := range cfg.Folders() {
 		if folderCfg.Paused {
-			folderCfg.CreateRoot()
+			_ = folderCfg.CreateRoot()
 			continue
 		}
 		m.AddFolder(folderCfg)
@@ -823,9 +826,11 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 	if runtimeOptions.cpuProfile {
 		f, err := os.Create(fmt.Sprintf("cpu-%d.pprof", os.Getpid()))
 		if err != nil {
-			log.Fatal(err)
+			l.Fatalln("Creating profile:", err)
+		}
+		if err := pprof.StartCPUProfile(f); err != nil {
+			l.Fatalln("Starting profile:", err)
 		}
-		pprof.StartCPUProfile(f)
 	}
 
 	myDev, _ := cfg.Device(myID)
@@ -842,8 +847,8 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 		l.Infoln("Anonymous usage reporting is always enabled for candidate releases.")
 		if opts.URAccepted != usageReportVersion {
 			opts.URAccepted = usageReportVersion
-			cfg.SetOptions(opts)
-			cfg.Save()
+			_, _ = cfg.SetOptions(opts)
+			_ = cfg.Save()
 			// Unique ID will be set and config saved below if necessary.
 		}
 	}
@@ -851,8 +856,8 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 	// If we are going to do usage reporting, ensure we have a valid unique ID.
 	if opts := cfg.Options(); opts.URAccepted > 0 && opts.URUniqueID == "" {
 		opts.URUniqueID = rand.String(8)
-		cfg.SetOptions(opts)
-		cfg.Save()
+		_, _ = cfg.SetOptions(opts)
+		_ = cfg.Save()
 	}
 
 	usageReportingSvc := newUsageReportingService(cfg, m, connectionsService)
@@ -872,8 +877,8 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 			opts.AutoUpgradeIntervalH = 12
 			// Set the option into the config as well, as the auto upgrade
 			// loop expects to read a valid interval from there.
-			cfg.SetOptions(opts)
-			cfg.Save()
+			_, _ = cfg.SetOptions(opts)
+			_ = cfg.Save()
 		}
 		// We don't tweak the user's choice of upgrading to pre-releases or
 		// not, as otherwise they cannot step off the candidate channel.
@@ -954,7 +959,7 @@ func loadConfigAtStartup() *config.Wrapper {
 	cfg, err := config.Load(cfgFile, myID)
 	if os.IsNotExist(err) {
 		cfg = defaultConfig(cfgFile)
-		cfg.Save()
+		_ = cfg.Save()
 		l.Infof("Default config saved. Edit %s to taste or use the GUI\n", cfg.ConfigPath())
 	} else if err == io.EOF {
 		l.Fatalln("Failed to load config: unexpected end of file. Truncated or empty configuration?")
@@ -1058,7 +1063,7 @@ func setupGUI(mainService *suture.Supervisor, cfg *config.Wrapper, m *model.Mode
 		// Can potentially block if the utility we are invoking doesn't
 		// fork, and just execs, hence keep it in its own routine.
 		<-api.startedOnce
-		go openURL(guiCfg.URL())
+		go func() { _ = openURL(guiCfg.URL()) }()
 	}
 }
 

cmd/syncthing/mocked_config_test.go

@@ -30,7 +30,7 @@ func (c *mockedConfig) LDAP() config.LDAPConfiguration {
 
 func (c *mockedConfig) RawCopy() config.Configuration {
 	cfg := config.Configuration{}
-	util.SetDefaults(&cfg.Options)
+	_ = util.SetDefaults(&cfg.Options)
 	return cfg
 }
 

cmd/syncthing/monitor.go

@@ -127,13 +127,13 @@ func monitorMain(runtimeOptions RuntimeOptions) {
 		select {
 		case s := <-stopSign:
 			l.Infof("Signal %d received; exiting", s)
-			cmd.Process.Signal(sigTerm)
+			_ = cmd.Process.Signal(sigTerm)
 			<-exit
 			return
 
 		case s := <-restartSign:
 			l.Infof("Signal %d received; restarting", s)
-			cmd.Process.Signal(sigHup)
+			_ = cmd.Process.Signal(sigHup)
 			err = <-exit
 
 		case err = <-exit:
@@ -179,7 +179,7 @@ func copyStderr(stderr io.Reader, dst io.Writer) {
 		}
 
 		if panicFd == nil {
-			dst.Write([]byte(line))
+			_, _ = dst.Write([]byte(line))
 
 			if strings.Contains(line, "SIGILL") {
 				l.Warnln(`
@@ -226,20 +226,20 @@ func copyStderr(stderr io.Reader, dst io.Writer) {
 
 				stdoutMut.Lock()
 				for _, line := range stdoutFirstLines {
-					panicFd.WriteString(line)
+					_, _ = panicFd.WriteString(line)
 				}
-				panicFd.WriteString("...\n")
+				_, _ = panicFd.WriteString("...\n")
 				for _, line := range stdoutLastLines {
-					panicFd.WriteString(line)
+					_, _ = panicFd.WriteString(line)
 				}
 				stdoutMut.Unlock()
 			}
 
-			panicFd.WriteString("Panic at " + time.Now().Format(time.RFC3339) + "\n")
+			_, _ = panicFd.WriteString("Panic at " + time.Now().Format(time.RFC3339) + "\n")
 		}
 
 		if panicFd != nil {
-			panicFd.WriteString(line)
+			_, _ = panicFd.WriteString(line)
 		}
 	}
 }
@@ -263,7 +263,7 @@ func copyStdout(stdout io.Reader, dst io.Writer) {
 		}
 		stdoutMut.Unlock()
 
-		dst.Write([]byte(line))
+		_, _ = dst.Write([]byte(line))
 	}
 }
 

cmd/syncthing/monitor_test.go

@@ -17,7 +17,7 @@ import (
 func TestAutoClosedFile(t *testing.T) {
 	os.RemoveAll("_autoclose")
 	defer os.RemoveAll("_autoclose")
-	os.Mkdir("_autoclose", 0755)
+	_ = os.Mkdir("_autoclose", 0755)
 	file := filepath.FromSlash("_autoclose/tmp")
 	data := []byte("hello, world\n")
 

cmd/syncthing/perfstats_unix.go

@@ -38,7 +38,10 @@ func savePerfStats(file string) {
 
 	t0 := time.Now()
 	for t := range time.NewTicker(250 * time.Millisecond).C {
-		syscall.Getrusage(syscall.RUSAGE_SELF, &rusage)
+		if err := syscall.Getrusage(syscall.RUSAGE_SELF, &rusage); err != nil {
+			continue
+		}
+
 		curTime := time.Now().UnixNano()
 		timeDiff := curTime - prevTime
 		curUsage := rusage.Utime.Nano() + rusage.Stime.Nano()

cmd/syncthing/usage.go

@@ -19,11 +19,11 @@ func optionTable(w io.Writer, rows [][]string) {
 	for _, row := range rows {
 		for i, cell := range row {
 			if i > 0 {
-				tw.Write([]byte("\t"))
+				_, _ = tw.Write([]byte("\t"))
 			}
-			tw.Write([]byte(cell))
+			_, _ = tw.Write([]byte(cell))
 		}
-		tw.Write([]byte("\n"))
+		_, _ = tw.Write([]byte("\n"))
 	}
 	tw.Flush()
 }

cmd/syncthing/usage_report.go

@@ -348,7 +348,9 @@ func newUsageReportingService(cfg *config.Wrapper, model *model.Model, connectio
 func (s *usageReportingService) sendUsageReport() error {
 	d := reportData(s.cfg, s.model, s.connectionsService, s.cfg.Options().URAccepted, false)
 	var b bytes.Buffer
-	json.NewEncoder(&b).Encode(d)
+	if err := json.NewEncoder(&b).Encode(d); err != nil {
+		return err
+	}
 
 	client := &http.Client{
 		Transport: &http.Transport{
@@ -417,7 +419,7 @@ func (s *usageReportingService) Stop() {
 	s.stopMut.RUnlock()
 }
 
-func (usageReportingService) String() string {
+func (*usageReportingService) String() string {
 	return "usageReportingService"
 }
 
@@ -425,7 +427,7 @@ func (usageReportingService) String() string {
 func cpuBench(iterations int, duration time.Duration, useWeakHash bool) float64 {
 	dataSize := 16 * protocol.MinBlockSize
 	bs := make([]byte, dataSize)
-	rand.Reader.Read(bs)
+	_, _ = rand.Reader.Read(bs)
 
 	var perf float64
 	for i := 0; i < iterations; i++ {

lib/model/folder_sendrecv.go

@@ -60,14 +60,13 @@ type copyBlocksState struct {
 const retainBits = fs.ModeSetgid | fs.ModeSetuid | fs.ModeSticky
 
 var (
-	activity               = newDeviceActivity()
-	errNoDevice            = errors.New("peers who had this file went away, or the file has changed while syncing. will retry later")
-	errSymlinksUnsupported = errors.New("symlinks not supported")
-	errDirHasToBeScanned   = errors.New("directory contains unexpected files, scheduling scan")
-	errDirHasIgnored       = errors.New("directory contains ignored files (see ignore documentation for (?d) prefix)")
-	errDirNotEmpty         = errors.New("directory is not empty; files within are probably ignored on connected devices only")
-	errNotAvailable        = errors.New("no connected device has the required version of this file")
-	errModified            = errors.New("file modified but not rescanned; will try again later")
+	activity             = newDeviceActivity()
+	errNoDevice          = errors.New("peers who had this file went away, or the file has changed while syncing. will retry later")
+	errDirHasToBeScanned = errors.New("directory contains unexpected files, scheduling scan")
+	errDirHasIgnored     = errors.New("directory contains ignored files (see ignore documentation for (?d) prefix)")
+	errDirNotEmpty       = errors.New("directory is not empty; files within are probably ignored on connected devices only")
+	errNotAvailable      = errors.New("no connected device has the required version of this file")
+	errModified          = errors.New("file modified but not rescanned; will try again later")
 )
 
 const (
@@ -882,7 +881,8 @@ func (f *sendReceiveFolder) renameFile(cur, source, target protocol.FileInfo, ig
 		scanChan <- target.Name
 		err = errModified
 	default:
-		if fi, err := scanner.CreateFileInfo(stat, target.Name, f.fs); err == nil {
+		var fi protocol.FileInfo
+		if fi, err = scanner.CreateFileInfo(stat, target.Name, f.fs); err == nil {
 			if !fi.IsEquivalentOptional(curTarget, f.IgnorePerms, true, protocol.LocalAllFlags) {
 				// Target changed
 				scanChan <- target.Name
@@ -1016,7 +1016,7 @@ func (f *sendReceiveFolder) handleFile(file protocol.FileInfo, copyChan chan<- c
 			// Otherwise, discard the file ourselves in order for the
 			// sharedpuller not to panic when it fails to exclusively create a
 			// file which already exists
-			osutil.InWritableDir(f.fs.Remove, f.fs, tempName)
+			_ = osutil.InWritableDir(f.fs.Remove, f.fs, tempName)
 		}
 	} else {
 		// Copy the blocks, as we don't want to shuffle them on the FileInfo
@@ -1142,7 +1142,7 @@ func (f *sendReceiveFolder) shortcutFile(file, curFile protocol.FileInfo, dbUpda
 		}
 	}
 
-	f.fs.Chtimes(file.Name, file.ModTime(), file.ModTime()) // never fails
+	_ = f.fs.Chtimes(file.Name, file.ModTime(), file.ModTime()) // never fails
 
 	// This may have been a conflict. We should merge the version vectors so
 	// that our clock doesn't move backwards.
@@ -1536,7 +1536,7 @@ func (f *sendReceiveFolder) performFinish(ignores *ignore.Matcher, file, curFile
 	}
 
 	// Set the correct timestamp on the new file
-	f.fs.Chtimes(file.Name, file.ModTime(), file.ModTime()) // never fails
+	_ = f.fs.Chtimes(file.Name, file.ModTime(), file.ModTime()) // never fails
 
 	// Record the updated file in the index
 	dbUpdateChan <- dbUpdateJob{file, dbUpdateHandleFile}
@@ -1706,7 +1706,7 @@ func (f *sendReceiveFolder) pullScannerRoutine(scanChan <-chan string) {
 			l.Debugln(f, "scheduling scan after pulling for", path)
 			scanList = append(scanList, path)
 		}
-		f.Scan(scanList)
+		_ = f.Scan(scanList)
 	}
 }
 
@@ -1858,7 +1858,7 @@ func (f *sendReceiveFolder) deleteDir(dir string, ignores *ignore.Matcher, scanC
 	}
 
 	for _, del := range toBeDeleted {
-		f.fs.RemoveAll(del)
+		_ = f.fs.RemoveAll(del)
 	}
 
 	err := osutil.InWritableDir(f.fs.Remove, f.fs, dir)

lib/model/model.go

@@ -258,9 +258,9 @@ func (m *Model) startFolderLocked(folder string) config.FolderType {
 	ffs := fs.MtimeFS()
 
 	// These are our metadata files, and they should always be hidden.
-	ffs.Hide(config.DefaultMarkerName)
-	ffs.Hide(".stversions")
-	ffs.Hide(".stignore")
+	_ = ffs.Hide(config.DefaultMarkerName)
+	_ = ffs.Hide(".stversions")
+	_ = ffs.Hide(".stignore")
 
 	p := folderFactory(m, cfg, ver, ffs)
 
@@ -338,7 +338,7 @@ func (m *Model) RemoveFolder(cfg config.FolderConfiguration) {
 	m.fmut.Lock()
 	m.pmut.Lock()
 	// Delete syncthing specific files
-	cfg.Filesystem().RemoveAll(config.DefaultMarkerName)
+	_ = cfg.Filesystem().RemoveAll(config.DefaultMarkerName)
 
 	m.tearDownFolderLocked(cfg, fmt.Errorf("removing folder %v", cfg.Description()))
 	// Remove it from the database
@@ -362,7 +362,7 @@ func (m *Model) tearDownFolderLocked(cfg config.FolderConfiguration, err error)
 	m.pmut.Unlock()
 	m.fmut.Unlock()
 	for _, id := range tokens {
-		m.RemoveAndWait(id, 0)
+		_ = m.RemoveAndWait(id, 0)
 	}
 	m.fmut.Lock()
 	m.pmut.Lock()
@@ -1189,7 +1189,7 @@ func (m *Model) handleIntroductions(introducerCfg config.DeviceConfiguration, cm
 		}
 
 		if changed {
-			m.cfg.SetFolder(fcfg)
+			_, _ = m.cfg.SetFolder(fcfg)
 		}
 	}
 
@@ -1246,7 +1246,7 @@ func (m *Model) handleDeintroductions(introducerCfg config.DeviceConfiguration,
 		cfg := m.cfg.RawCopy()
 		cfg.Folders = folders
 		cfg.Devices = devices
-		m.cfg.Replace(cfg)
+		_, _ = m.cfg.Replace(cfg)
 	}
 
 	return changed
@@ -1325,7 +1325,7 @@ func (m *Model) introduceDevice(device protocol.Device, introducerCfg config.Dev
 		newDeviceCfg.SkipIntroductionRemovals = device.SkipIntroductionRemovals
 	}
 
-	m.cfg.SetDevice(newDeviceCfg)
+	_, _ = m.cfg.SetDevice(newDeviceCfg)
 }
 
 // Closed is called when a connection has been closed
@@ -1776,8 +1776,8 @@ func (m *Model) AddConnection(conn connections.Connection, hello protocol.HelloR
 
 	if (device.Name == "" || m.cfg.Options().OverwriteRemoteDevNames) && hello.DeviceName != "" {
 		device.Name = hello.DeviceName
-		m.cfg.SetDevice(device)
-		m.cfg.Save()
+		_, _ = m.cfg.SetDevice(device)
+		_ = m.cfg.Save()
 	}
 
 	m.deviceWasSeen(deviceID)
@@ -1864,7 +1864,7 @@ func sendIndexes(conn protocol.Connection, folder string, fs *db.FileSet, ignore
 		// local index may update for other folders than the one we are
 		// sending for.
 		if fs.Sequence(protocol.LocalDeviceID) <= prevSequence {
-			sub.Poll(time.Minute)
+			_, _ = sub.Poll(time.Minute)
 			continue
 		}
 
@@ -2484,7 +2484,7 @@ func (m *Model) RestoreFolderVersions(folder string, versions map[string]time.Ti
 			}
 		}
 
-		filesystem.MkdirAll(filepath.Dir(target), 0755)
+		_ = filesystem.MkdirAll(filepath.Dir(target), 0755)
 		if err == nil {
 			err = osutil.Copy(filesystem, source, target)
 		}
@@ -2734,17 +2734,6 @@ func getChunk(data []string, skip, get int) ([]string, int, int) {
 	return data[skip : skip+get], 0, 0
 }
 
-func stringSliceWithout(ss []string, s string) []string {
-	for i := range ss {
-		if ss[i] == s {
-			copy(ss[i:], ss[i+1:])
-			ss = ss[:len(ss)-1]
-			return ss
-		}
-	}
-	return ss
-}
-
 func readOffsetIntoBuf(fs fs.Filesystem, file string, offset int64, buf []byte) error {
 	fd, err := fs.Open(file)
 	if err != nil {

lib/nat/interface.go

@@ -15,7 +15,7 @@ type Protocol string
 
 const (
 	TCP Protocol = "TCP"
-	UDP          = "UDP"
+	UDP Protocol = "UDP"
 )
 
 type Device interface {

lib/nat/service.go

@@ -92,7 +92,7 @@ func (s *Service) process() int {
 			toRenew = append(toRenew, mapping)
 		} else {
 			toUpdate = append(toUpdate, mapping)
-			mappingRenewIn := mapping.expires.Sub(time.Now())
+			mappingRenewIn := time.Until(mapping.expires)
 			if mappingRenewIn < renewIn {
 				renewIn = mappingRenewIn
 			}
@@ -328,6 +328,6 @@ findIP:
 
 func hash(input string) int64 {
 	h := fnv.New64a()
-	h.Write([]byte(input))
+	_, _ = h.Write([]byte(input))
 	return int64(h.Sum64())
 }

lib/protocol/hello.go

@@ -77,12 +77,7 @@ func readHello(c io.Reader) (HelloResult, error) {
 		if err := hello.Unmarshal(buf); err != nil {
 			return HelloResult{}, err
 		}
-		res := HelloResult{
-			DeviceName:    hello.DeviceName,
-			ClientName:    hello.ClientName,
-			ClientVersion: hello.ClientVersion,
-		}
-		return res, nil
+		return HelloResult(hello), nil
 
 	case 0x00010001, 0x00010000, Version13HelloMagic:
 		// This is the first word of an older cluster config message or an

lib/upgrade/upgrade_common.go

@@ -83,10 +83,10 @@ type Relation int
 
 const (
 	MajorOlder Relation = -2 // Older by a major version (x in x.y.z or 0.x.y).
-	Older               = -1 // Older by a minor version (y or z in x.y.z, or y in 0.x.y)
-	Equal               = 0  // Versions are semantically equal
-	Newer               = 1  // Newer by a minor version (y or z in x.y.z, or y in 0.x.y)
-	MajorNewer          = 2  // Newer by a major version (x in x.y.z or 0.x.y).
+	Older      Relation = -1 // Older by a minor version (y or z in x.y.z, or y in 0.x.y)
+	Equal      Relation = 0  // Versions are semantically equal
+	Newer      Relation = 1  // Newer by a minor version (y or z in x.y.z, or y in 0.x.y)
+	MajorNewer Relation = 2  // Newer by a major version (x in x.y.z or 0.x.y).
 )
 
 // CompareVersions returns a relation describing how a compares to b.