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

lib/discover/local.go

@@ -9,7 +9,6 @@ package discover
 import (
 	"bytes"
 	"encoding/hex"
-	"errors"
 	"io"
 	"net"
 	"net/url"
@@ -24,10 +23,9 @@ import (
 
 type localClient struct {
 	*suture.Supervisor
-	myID      protocol.DeviceID
-	addrList  AddressLister
-	relayStat RelayStatusProvider
-	name      string
+	myID     protocol.DeviceID
+	addrList AddressLister
+	name     string
 
 	beacon          beacon.Interface
 	localBcastStart time.Time
@@ -42,16 +40,11 @@ const (
 	CacheLifeTime     = 3 * BroadcastInterval
 )
 
-var (
-	ErrIncorrectMagic = errors.New("incorrect magic number")
-)
-
-func NewLocal(id protocol.DeviceID, addr string, addrList AddressLister, relayStat RelayStatusProvider) (FinderService, error) {
+func NewLocal(id protocol.DeviceID, addr string, addrList AddressLister) (FinderService, error) {
 	c := &localClient{
 		Supervisor:      suture.NewSimple("local"),
 		myID:            id,
 		addrList:        addrList,
-		relayStat:       relayStat,
 		localBcastTick:  time.Tick(BroadcastInterval),
 		forcedBcastTick: make(chan time.Time),
 		localBcastStart: time.Now(),
@@ -94,13 +87,11 @@ func (c *localClient) startLocalIPv6Multicasts(localMCAddr string) {
 	go c.recvAnnouncements(c.beacon)
 }
 
-// Lookup returns a list of addresses the device is available at. Local
-// discovery never returns relays.
-func (c *localClient) Lookup(device protocol.DeviceID) (direct []string, relays []Relay, err error) {
+// Lookup returns a list of addresses the device is available at.
+func (c *localClient) Lookup(device protocol.DeviceID) (addresses []string, err error) {
 	if cache, ok := c.Get(device); ok {
 		if time.Since(cache.when) < CacheLifeTime {
-			direct = cache.Direct
-			relays = cache.Relays
+			addresses = cache.Addresses
 		}
 	}
 
@@ -123,25 +114,11 @@ func (c *localClient) announcementPkt() Announce {
 		})
 	}
 
-	var relays []Relay
-	if c.relayStat != nil {
-		for _, relay := range c.relayStat.Relays() {
-			latency, ok := c.relayStat.RelayStatus(relay)
-			if ok {
-				relays = append(relays, Relay{
-					URL:     relay,
-					Latency: int32(latency / time.Millisecond),
-				})
-			}
-		}
-	}
-
 	return Announce{
 		Magic: AnnouncementMagic,
 		This: Device{
 			ID:        c.myID[:],
 			Addresses: addrs,
-			Relays:    relays,
 		},
 	}
 }
@@ -171,6 +148,11 @@ func (c *localClient) recvAnnouncements(b beacon.Interface) {
 			continue
 		}
 
+		if pkt.Magic != AnnouncementMagic {
+			l.Debugf("discover: Incorrect magic from %s: %s != %s", addr, pkt.Magic, AnnouncementMagic)
+			continue
+		}
+
 		l.Debugf("discover: Received local announcement from %s for %s", addr, protocol.DeviceIDFromBytes(pkt.This.ID))
 
 		var newDevice bool
@@ -230,17 +212,15 @@ func (c *localClient) registerDevice(src net.Addr, device Device) bool {
 	}
 
 	c.Set(id, CacheEntry{
-		Direct: validAddresses,
-		Relays: device.Relays,
-		when:   time.Now(),
-		found:  true,
+		Addresses: validAddresses,
+		when:      time.Now(),
+		found:     true,
 	})
 
 	if isNewDevice {
 		events.Default.Log(events.DeviceDiscovered, map[string]interface{}{
 			"device": id.String(),
 			"addrs":  validAddresses,
-			"relays": device.Relays,
 		})
 	}