lib/connections: Fix local address priority

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4534
LGTM: imsodin, calmh

cmd/syncthing/main.go

@@ -87,13 +87,6 @@ const (
 	maxSystemLog         = 250
 )
 
-// The discovery results are sorted by their source priority.
-const (
-	ipv6LocalDiscoveryPriority = iota
-	ipv4LocalDiscoveryPriority
-	globalDiscoveryPriority
-)
-
 func init() {
 	if Version != "unknown-dev" {
 		// If not a generic dev build, version string should come from git describe
@@ -824,7 +817,7 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 			// Each global discovery server gets its results cached for five
 			// minutes, and is not asked again for a minute when it's returned
 			// unsuccessfully.
-			cachedDiscovery.Add(gd, 5*time.Minute, time.Minute, globalDiscoveryPriority)
+			cachedDiscovery.Add(gd, 5*time.Minute, time.Minute)
 		}
 	}
 
@@ -834,14 +827,14 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 		if err != nil {
 			l.Warnln("IPv4 local discovery:", err)
 		} else {
-			cachedDiscovery.Add(bcd, 0, 0, ipv4LocalDiscoveryPriority)
+			cachedDiscovery.Add(bcd, 0, 0)
 		}
 		// v6 multicasts
 		mcd, err := discover.NewLocal(myID, cfg.Options().LocalAnnMCAddr, connectionsService)
 		if err != nil {
 			l.Warnln("IPv6 local discovery:", err)
 		} else {
-			cachedDiscovery.Add(mcd, 0, 0, ipv6LocalDiscoveryPriority)
+			cachedDiscovery.Add(mcd, 0, 0)
 		}
 	}
 

cmd/syncthing/mocked_discovery_test.go

@@ -44,7 +44,7 @@ func (m *mockedCachingMux) Cache() map[protocol.DeviceID]discover.CacheEntry {
 
 // from events.CachingMux
 
-func (m *mockedCachingMux) Add(finder discover.Finder, cacheTime, negCacheTime time.Duration, priority int) {
+func (m *mockedCachingMux) Add(finder discover.Finder, cacheTime, negCacheTime time.Duration) {
 }
 
 func (m *mockedCachingMux) ChildErrors() map[string]error {

lib/connections/kcp_dial.go

@@ -100,6 +100,10 @@ func (kcpDialerFactory) Priority() int {
 	return kcpPriority
 }
 
+func (kcpDialerFactory) AlwaysWAN() bool {
+	return false
+}
+
 func (kcpDialerFactory) Enabled(cfg config.Configuration) bool {
 	return true
 }

lib/connections/relay_dial.go

@@ -64,10 +64,6 @@ func (d *relayDialer) Dial(id protocol.DeviceID, uri *url.URL) (internalConn, er
 	return internalConn{tc, connTypeRelayClient, relayPriority}, nil
 }
 
-func (relayDialer) Priority() int {
-	return relayPriority
-}
-
 func (d *relayDialer) RedialFrequency() time.Duration {
 	return time.Duration(d.cfg.Options().RelayReconnectIntervalM) * time.Minute
 }
@@ -85,6 +81,10 @@ func (relayDialerFactory) Priority() int {
 	return relayPriority
 }
 
+func (relayDialerFactory) AlwaysWAN() bool {
+	return true
+}
+
 func (relayDialerFactory) Enabled(cfg config.Configuration) bool {
 	return cfg.Options.RelaysEnabled
 }

lib/connections/service.go

@@ -336,6 +336,8 @@ func (s *Service) connect() {
 				}
 			}
 
+			addrs = util.UniqueStrings(addrs)
+
 			l.Debugln("Reconnect loop for", deviceID, addrs)
 
 			seen = append(seen, addrs...)
@@ -375,9 +377,9 @@ func (s *Service) connect() {
 					continue
 				}
 
-				prio := dialerFactory.Priority()
+				priority := dialerFactory.Priority()
 
-				if connected && prio >= ct.Priority() {
+				if connected && priority >= ct.Priority() {
 					l.Debugf("Not dialing using %s as priority is less than current connection (%d >= %d)", dialerFactory, dialerFactory.Priority(), ct.Priority())
 					continue
 				}
@@ -385,9 +387,18 @@ func (s *Service) connect() {
 				dialer := dialerFactory.New(s.cfg, s.tlsCfg)
 				nextDial[addr] = now.Add(dialer.RedialFrequency())
 
+				// For LAN addresses, increase the priority so that we
+				// try these first.
+				switch {
+				case dialerFactory.AlwaysWAN():
+					// Do nothing.
+				case s.isLANHost(uri.Host):
+					priority -= 1
+				}
+
 				dialTargets = append(dialTargets, dialTarget{
 					dialer:   dialer,
-					priority: prio,
+					priority: priority,
 					deviceID: deviceID,
 					uri:      uri,
 				})
@@ -412,6 +423,17 @@ func (s *Service) connect() {
 	}
 }
 
+func (s *Service) isLANHost(host string) bool {
+	if noPort, _, err := net.SplitHostPort(host); err == nil && noPort != "" {
+		host = noPort
+	}
+	addr, err := net.ResolveIPAddr("ip", host)
+	if err != nil {
+		return false
+	}
+	return s.isLAN(addr)
+}
+
 func (s *Service) isLAN(addr net.Addr) bool {
 	tcpaddr, ok := addr.(*net.TCPAddr)
 	if !ok {

lib/connections/structs.go

@@ -120,6 +120,7 @@ func (c internalConn) String() string {
 type dialerFactory interface {
 	New(*config.Wrapper, *tls.Config) genericDialer
 	Priority() int
+	AlwaysWAN() bool
 	Enabled(config.Configuration) bool
 	String() string
 }

lib/connections/tcp_dial.go

@@ -73,6 +73,10 @@ func (tcpDialerFactory) Priority() int {
 	return tcpPriority
 }
 
+func (tcpDialerFactory) AlwaysWAN() bool {
+	return false
+}
+
 func (tcpDialerFactory) Enabled(cfg config.Configuration) bool {
 	return true
 }

lib/discover/cache.go

@@ -7,7 +7,6 @@
 package discover
 
 import (
-	"sort"
 	stdsync "sync"
 	"time"
 
@@ -25,7 +24,7 @@ import (
 // or negative).
 type CachingMux interface {
 	FinderService
-	Add(finder Finder, cacheTime, negCacheTime time.Duration, priority int)
+	Add(finder Finder, cacheTime, negCacheTime time.Duration)
 	ChildErrors() map[string]error
 }
 
@@ -41,14 +40,6 @@ type cachedFinder struct {
 	Finder
 	cacheTime    time.Duration
 	negCacheTime time.Duration
-	priority     int
-}
-
-// A prioritizedAddress is what we use to sort addresses returned from
-// different sources with different priorities.
-type prioritizedAddress struct {
-	priority int
-	addr     string
 }
 
 // An error may implement cachedError, in which case it will be interrogated
@@ -66,9 +57,9 @@ func NewCachingMux() CachingMux {
 }
 
 // Add registers a new Finder, with associated cache timeouts.
-func (m *cachingMux) Add(finder Finder, cacheTime, negCacheTime time.Duration, priority int) {
+func (m *cachingMux) Add(finder Finder, cacheTime, negCacheTime time.Duration) {
 	m.mut.Lock()
-	m.finders = append(m.finders, cachedFinder{finder, cacheTime, negCacheTime, priority})
+	m.finders = append(m.finders, cachedFinder{finder, cacheTime, negCacheTime})
 	m.caches = append(m.caches, newCache())
 	m.mut.Unlock()
 
@@ -80,8 +71,6 @@ func (m *cachingMux) Add(finder Finder, cacheTime, negCacheTime time.Duration, p
 // Lookup attempts to resolve the device ID using any of the added Finders,
 // while obeying the cache settings.
 func (m *cachingMux) Lookup(deviceID protocol.DeviceID) (addresses []string, err error) {
-	var paddresses []prioritizedAddress
-
 	m.mut.RLock()
 	for i, finder := range m.finders {
 		if cacheEntry, ok := m.caches[i].Get(deviceID); ok {
@@ -91,9 +80,7 @@ func (m *cachingMux) Lookup(deviceID protocol.DeviceID) (addresses []string, err
 				// It's a positive, valid entry. Use it.
 				l.Debugln("cached discovery entry for", deviceID, "at", finder)
 				l.Debugln("  cache:", cacheEntry)
-				for _, addr := range cacheEntry.Addresses {
-					paddresses = append(paddresses, prioritizedAddress{finder.priority, addr})
-				}
+				addresses = append(addresses, cacheEntry.Addresses...)
 				continue
 			}
 
@@ -112,9 +99,7 @@ func (m *cachingMux) Lookup(deviceID protocol.DeviceID) (addresses []string, err
 		if addrs, err := finder.Lookup(deviceID); err == nil {
 			l.Debugln("lookup for", deviceID, "at", finder)
 			l.Debugln("  addresses:", addrs)
-			for _, addr := range addrs {
-				paddresses = append(paddresses, prioritizedAddress{finder.priority, addr})
-			}
+			addresses = append(addresses, addrs...)
 			m.caches[i].Set(deviceID, CacheEntry{
 				Addresses: addrs,
 				when:      time.Now(),
@@ -134,10 +119,11 @@ func (m *cachingMux) Lookup(deviceID protocol.DeviceID) (addresses []string, err
 	}
 	m.mut.RUnlock()
 
-	addresses = uniqueSortedAddrs(paddresses)
 	l.Debugln("lookup results for", deviceID)
 	l.Debugln("  addresses: ", addresses)
 
+	addresses = util.UniqueStrings(addresses)
+
 	return addresses, nil
 }
 
@@ -239,35 +225,3 @@ func (c *cache) Cache() map[protocol.DeviceID]CacheEntry {
 	c.mut.Unlock()
 	return m
 }
-
-func uniqueSortedAddrs(ss []prioritizedAddress) []string {
-	// We sort the addresses by priority, then filter them based on seen
-	// (first time seen is the on kept, so we retain priority).
-	sort.Sort(prioritizedAddressList(ss))
-	filtered := make([]string, 0, len(ss))
-	seen := make(map[string]struct{}, len(ss))
-	for _, s := range ss {
-		if _, ok := seen[s.addr]; !ok {
-			filtered = append(filtered, s.addr)
-			seen[s.addr] = struct{}{}
-		}
-	}
-	return filtered
-}
-
-type prioritizedAddressList []prioritizedAddress
-
-func (l prioritizedAddressList) Len() int {
-	return len(l)
-}
-
-func (l prioritizedAddressList) Swap(a, b int) {
-	l[a], l[b] = l[b], l[a]
-}
-
-func (l prioritizedAddressList) Less(a, b int) bool {
-	if l[a].priority != l[b].priority {
-		return l[a].priority < l[b].priority
-	}
-	return l[a].addr < l[b].addr
-}

lib/discover/cache_test.go

@@ -15,19 +15,18 @@ import (
 )
 
 func TestCacheUnique(t *testing.T) {
-	addresses0 := []string{"tcp://192.0.2.44:22000", "tcp://192.0.2.42:22000"} // prio 0
-	addresses1 := []string{"tcp://192.0.2.43:22000", "tcp://192.0.2.42:22000"} // prio 1
+	addresses0 := []string{"tcp://192.0.2.44:22000", "tcp://192.0.2.42:22000"}
+	addresses1 := []string{"tcp://192.0.2.43:22000", "tcp://192.0.2.42:22000"}
 
 	// what we expect from just addresses0
 	addresses0Sorted := []string{"tcp://192.0.2.42:22000", "tcp://192.0.2.44:22000"}
 
 	// what we expect from addresses0+addresses1
 	totalSorted := []string{
-		// first prio 0, sorted
-		"tcp://192.0.2.42:22000", "tcp://192.0.2.44:22000",
-		// then prio 1
-		"tcp://192.0.2.43:22000",
+		"tcp://192.0.2.42:22000",
 		// no duplicate .42
+		"tcp://192.0.2.43:22000",
+		"tcp://192.0.2.44:22000",
 	}
 
 	c := NewCachingMux()
@@ -38,7 +37,7 @@ func TestCacheUnique(t *testing.T) {
 	// cache.
 
 	f1 := &fakeDiscovery{addresses0}
-	c.Add(f1, time.Minute, 0, 0)
+	c.Add(f1, time.Minute, 0)
 
 	addr, err := c.Lookup(protocol.LocalDeviceID)
 	if err != nil {
@@ -52,7 +51,7 @@ func TestCacheUnique(t *testing.T) {
 	// duplicate or otherwise mess up the responses now.
 
 	f2 := &fakeDiscovery{addresses1}
-	c.Add(f2, time.Minute, 0, 1)
+	c.Add(f2, time.Minute, 0)
 
 	addr, err = c.Lookup(protocol.LocalDeviceID)
 	if err != nil {
@@ -92,7 +91,7 @@ func TestCacheSlowLookup(t *testing.T) {
 
 	started := make(chan struct{})
 	f1 := &slowDiscovery{time.Second, started}
-	c.Add(f1, time.Minute, 0, 0)
+	c.Add(f1, time.Minute, 0)
 
 	// Start a lookup, which will take at least a second