lib/connections: Refactor

1. Removes separate relay lists and relay clients/services, just makes it a listen address
2. Easier plugging-in of other transports
3. Allows "hot" disabling and enabling NAT services
4. Allows "hot" listen address changes
5. Changes listen address list with a preferable "default" value just like for discovery
6. Debounces global discovery announcements as external addresses change (which it might alot upon starting)
7. Stops this whole "pick other peers relay by latency". This information is no longer available,
   but I don't think it matters as most of the time other peer only has one relay.
8. Rename ListenAddress to ListenAddresses, as well as in javascript land.
9. Stop serializing deprecated values to JSON

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/2982

cmd/syncthing/gui.go

@@ -35,7 +35,6 @@ import (
 	"github.com/syncthing/syncthing/lib/model"
 	"github.com/syncthing/syncthing/lib/osutil"
 	"github.com/syncthing/syncthing/lib/protocol"
-	"github.com/syncthing/syncthing/lib/relay"
 	"github.com/syncthing/syncthing/lib/stats"
 	"github.com/syncthing/syncthing/lib/sync"
 	"github.com/syncthing/syncthing/lib/tlsutil"
@@ -51,21 +50,21 @@ var (
 )
 
 type apiService struct {
-	id              protocol.DeviceID
-	cfg             configIntf
-	httpsCertFile   string
-	httpsKeyFile    string
-	assetDir        string
-	themes          []string
-	model           modelIntf
-	eventSub        events.BufferedSubscription
-	discoverer      discover.CachingMux
-	relayService    relay.Service
-	fss             *folderSummaryService
-	systemConfigMut sync.Mutex    // serializes posts to /rest/system/config
-	stop            chan struct{} // signals intentional stop
-	configChanged   chan struct{} // signals intentional listener close due to config change
-	started         chan struct{} // signals startup complete, for testing only
+	id                 protocol.DeviceID
+	cfg                configIntf
+	httpsCertFile      string
+	httpsKeyFile       string
+	assetDir           string
+	themes             []string
+	model              modelIntf
+	eventSub           events.BufferedSubscription
+	discoverer         discover.CachingMux
+	connectionsService connectionsIntf
+	fss                *folderSummaryService
+	systemConfigMut    sync.Mutex    // serializes posts to /rest/system/config
+	stop               chan struct{} // signals intentional stop
+	configChanged      chan struct{} // signals intentional listener close due to config change
+	started            chan struct{} // signals startup complete, for testing only
 
 	listener    net.Listener
 	listenerMut sync.Mutex
@@ -113,25 +112,30 @@ type configIntf interface {
 	Folders() map[string]config.FolderConfiguration
 	Devices() map[protocol.DeviceID]config.DeviceConfiguration
 	Save() error
+	ListenAddresses() []string
 }
 
-func newAPIService(id protocol.DeviceID, cfg configIntf, httpsCertFile, httpsKeyFile, assetDir string, m modelIntf, eventSub events.BufferedSubscription, discoverer discover.CachingMux, relayService relay.Service, errors, systemLog logger.Recorder) (*apiService, error) {
+type connectionsIntf interface {
+	Status() map[string]interface{}
+}
+
+func newAPIService(id protocol.DeviceID, cfg configIntf, httpsCertFile, httpsKeyFile, assetDir string, m modelIntf, eventSub events.BufferedSubscription, discoverer discover.CachingMux, connectionsService connectionsIntf, errors, systemLog logger.Recorder) (*apiService, error) {
 	service := &apiService{
-		id:              id,
-		cfg:             cfg,
-		httpsCertFile:   httpsCertFile,
-		httpsKeyFile:    httpsKeyFile,
-		assetDir:        assetDir,
-		model:           m,
-		eventSub:        eventSub,
-		discoverer:      discoverer,
-		relayService:    relayService,
-		systemConfigMut: sync.NewMutex(),
-		stop:            make(chan struct{}),
-		configChanged:   make(chan struct{}),
-		listenerMut:     sync.NewMutex(),
-		guiErrors:       errors,
-		systemLog:       systemLog,
+		id:                 id,
+		cfg:                cfg,
+		httpsCertFile:      httpsCertFile,
+		httpsKeyFile:       httpsKeyFile,
+		assetDir:           assetDir,
+		model:              m,
+		eventSub:           eventSub,
+		discoverer:         discoverer,
+		connectionsService: connectionsService,
+		systemConfigMut:    sync.NewMutex(),
+		stop:               make(chan struct{}),
+		configChanged:      make(chan struct{}),
+		listenerMut:        sync.NewMutex(),
+		guiErrors:          errors,
+		systemLog:          systemLog,
 	}
 
 	seen := make(map[string]struct{})
@@ -825,18 +829,9 @@ func (s *apiService) getSystemStatus(w http.ResponseWriter, r *http.Request) {
 		res["discoveryMethods"] = discoMethods
 		res["discoveryErrors"] = discoErrors
 	}
-	if s.relayService != nil {
-		res["relaysEnabled"] = true
-		relayClientStatus := make(map[string]bool)
-		relayClientLatency := make(map[string]int)
-		for _, relay := range s.relayService.Relays() {
-			latency, ok := s.relayService.RelayStatus(relay)
-			relayClientStatus[relay] = ok
-			relayClientLatency[relay] = int(latency / time.Millisecond)
-		}
-		res["relayClientStatus"] = relayClientStatus
-		res["relayClientLatency"] = relayClientLatency
-	}
+
+	res["connectionServiceStatus"] = s.connectionsService.Status()
+
 	cpuUsageLock.RLock()
 	var cpusum float64
 	for _, p := range cpuUsagePercent {