*review* fix synced semantics

chain/sync.go

@@ -112,10 +112,11 @@ func (s *Syncer) DisableDiscoverAccounts() {
 // the target height it is attempting to sync to.
 func (s *Syncer) Synced(ctx context.Context) (bool, int32) {
 	synced := s.atomicWalletSynced.Load() == 1
-	targetHeight := s.atomicTargetSyncHeight.Load()
-	_, tipHeight := s.wallet.MainChainTip(ctx)
-	if tipHeight > targetHeight {
-		targetHeight = tipHeight
+	var targetHeight int32
+	if !synced {
+		targetHeight = s.atomicTargetSyncHeight.Load()
+	} else {
+		_, targetHeight = s.wallet.MainChainTip(ctx)
 	}
 	return synced, targetHeight
 }
@@ -129,6 +130,15 @@ func (s *Syncer) synced() {
 	}
 }
 
+// unsynced checks the atomic that controls wallet syncness and if previously
+// synced, updates to unsynced and notifies the callback, if set.
+func (s *Syncer) unsynced() {
+	swapped := s.atomicWalletSynced.CompareAndSwap(1, 0)
+	if swapped && s.cb != nil && s.cb.Synced != nil {
+		s.cb.Synced(false)
+	}
+}
+
 func (s *Syncer) fetchMissingCfiltersStart() {
 	if s.cb != nil && s.cb.FetchMissingCFiltersStarted != nil {
 		s.cb.FetchMissingCFiltersStarted()
@@ -203,18 +213,23 @@ func (s *Syncer) getHeaders(ctx context.Context) error {
 		return err
 	}
 
+	startedSynced := s.atomicWalletSynced.Load() == 1
+
 	cnet := s.wallet.ChainParams().Net
 	s.fetchHeadersStart()
 	for {
 		if err := ctx.Err(); err != nil {
 			return err
 		}
 
-		info, err := s.rpc.GetBlockchainInfo(ctx)
-		if err != nil {
-			return err
+		// If unsynced, update the target sync height.
+		if !startedSynced {
+			info, err := s.rpc.GetBlockchainInfo(ctx)
+			if err != nil {
+				return err
+			}
+			s.atomicTargetSyncHeight.Store(int32(info.Headers))
 		}
-		s.atomicTargetSyncHeight.Store(int32(info.Headers))
 
 		headers, err := s.rpc.Headers(ctx, locators, &hashStop)
 		if err != nil {
@@ -528,6 +543,7 @@ func (s *Syncer) Run(ctx context.Context) (err error) {
 	if err != nil {
 		return err
 	}
+	defer s.unsynced()
 
 	// Request notifications for connected and disconnected blocks.
 	err = s.rpc.Call(ctx, "notifyblocks", nil)

spv/sync.go

@@ -156,16 +156,31 @@ func (s *Syncer) synced() {
 	}
 }
 
-// Synced returns whether this wallet is completely synced to the network.
+// unsynced checks the atomic that controls wallet syncness and if previously
+// synced, updates to unsynced and notifies the callback, if set.
+func (s *Syncer) unsynced() {
+	if s.atomicWalletSynced.CompareAndSwap(1, 0) &&
+		s.notifications != nil &&
+		s.notifications.Synced != nil {
+		s.notifications.Synced(false)
+	}
+}
+
+// Synced returns whether this wallet is completely synced to the network and
+// the target height it is attempting to sync to.
 func (s *Syncer) Synced(ctx context.Context) (bool, int32) {
 	synced := s.atomicWalletSynced.Load() == 1
-	_, targetHeight := s.wallet.MainChainTip(ctx)
-	s.forRemotes(func(rp *p2p.RemotePeer) error {
-		if rp.InitialHeight() > targetHeight {
-			targetHeight = rp.InitialHeight()
-		}
-		return nil
-	})
+	var targetHeight int32
+	if !synced {
+		s.forRemotes(func(rp *p2p.RemotePeer) error {
+			if rp.InitialHeight() > targetHeight {
+				targetHeight = rp.InitialHeight()
+			}
+			return nil
+		})
+	} else {
+		_, targetHeight = s.wallet.MainChainTip(ctx)
+	}
 
 	return synced, targetHeight
 }
@@ -462,6 +477,9 @@ func (s *Syncer) connectAndRunPeer(ctx context.Context, raddr string) {
 		n = len(s.remotes)
 		s.remotesMu.Unlock()
 		s.peerDisconnected(n, raddr)
+		if n == 0 {
+			s.unsynced()
+		}
 	}()
 
 	// Perform peer startup.