lnwallet: Only perform account discovery once

This adds a new record in the database that tracks whether account
discovery is needed on the wallet. By default, dcrlnd will perform an
account discovery process and will only mark as account discovery not
needed once the wallet is fully synced at least once.

This is only applicable to the embedded wallet, given that remote
wallets are controlled externally.

channeldb/wallet.go

@@ -0,0 +1,44 @@
+package channeldb
+
+import (
+	"github.com/decred/dcrlnd/channeldb/kvdb"
+)
+
+const accountDiscoveryDisabled byte = 1
+
+var (
+	walletBucket              = []byte("wallet")
+	disableDiscoverAcctBucket = []byte("discoverAccounts")
+)
+
+func (d *DB) AccountDiscoveryDisabled() (bool, error) {
+	var res bool
+	err := kvdb.Update(d, func(tx kvdb.RwTx) error {
+		wallet, err := tx.CreateTopLevelBucket(walletBucket)
+		if err != nil {
+			return err
+		}
+
+		disableDiscoverAcct := wallet.Get(disableDiscoverAcctBucket)
+		if len(disableDiscoverAcct) == 0 {
+			return nil
+		}
+
+		res = disableDiscoverAcct[0] == accountDiscoveryDisabled
+		return nil
+	})
+	return res, err
+}
+
+func (d *DB) DisableAccountDiscovery() error {
+	return kvdb.Update(d, func(tx kvdb.RwTx) error {
+		wallet, err := tx.CreateTopLevelBucket(walletBucket)
+		if err != nil {
+			return err
+		}
+
+		v := []byte{accountDiscoveryDisabled}
+		wallet.Put(disableDiscoverAcctBucket, v)
+		return nil
+	})
+}

lnwallet/dcrwallet/rpcsync.go

@@ -46,6 +46,11 @@ func (s *RPCSyncer) start(w *DcrWallet) error {
 		CA:      s.rpcConfig.Certificates,
 	}
 
+	disableDiscoverAccts, err := w.cfg.DB.AccountDiscoveryDisabled()
+	if err != nil {
+		return err
+	}
+
 	s.wg.Add(1)
 	go func() {
 		defer s.wg.Done()
@@ -62,6 +67,10 @@ func (s *RPCSyncer) start(w *DcrWallet) error {
 				Synced: w.onSyncerSynced,
 			})
 
+			if disableDiscoverAccts {
+				syncer.DisableDiscoverAccounts()
+			}
+
 			dcrwLog.Debugf("Starting rpc syncer")
 			err := syncer.Run(ctx)
 			w.rpcSyncerFinished()

lnwallet/dcrwallet/spvsync.go

@@ -46,6 +46,11 @@ func (s *SPVSyncer) start(w *DcrWallet) error {
 
 	lookup := net.LookupIP
 
+	disableDiscoverAccts, err := w.cfg.DB.AccountDiscoveryDisabled()
+	if err != nil {
+		return err
+	}
+
 	addr := &net.TCPAddr{IP: net.ParseIP("::1"), Port: 0}
 	amgrDir := filepath.Join(s.cfg.AppDataDir, s.cfg.Net.Name)
 	amgr := addrmgr.New(amgrDir, lookup)
@@ -56,6 +61,10 @@ func (s *SPVSyncer) start(w *DcrWallet) error {
 	}
 	w.wallet.SetNetworkBackend(syncer)
 
+	if disableDiscoverAccts {
+		syncer.DisableDiscoverAccounts()
+	}
+
 	syncer.SetNotifications(&spv.Notifications{
 		Synced: w.onSyncerSynced,
 	})

lnwallet/dcrwallet/wallet.go

@@ -906,11 +906,17 @@ func (b *DcrWallet) onSyncerSynced(synced bool) {
 		return
 	}
 
+	// Record in the DB that the wallet doesn't need account discovery
+	// anymore.
+	err := b.cfg.DB.DisableAccountDiscovery()
+	if err != nil {
+		dcrwLog.Errorf("Unable to disable future account discoveries: %v", err)
+	}
+
 	// Now that the wallet is synced and address discovery has ended, we
 	// can create the keyring. We can only do this here (after sync)
 	// because address discovery might upgrade the underlying dcrwallet
 	// coin type.
-	var err error
 	b.walletKeyRing, err = newWalletKeyRing(b.wallet, b.cfg.DB)
 	if err != nil {
 		// Sign operations will fail, so signal the error and prevent