server: add watchtower client

lnd.go

@@ -51,6 +51,7 @@ import (
 	"github.com/lightningnetwork/lnd/macaroons"
 	"github.com/lightningnetwork/lnd/signal"
 	"github.com/lightningnetwork/lnd/walletunlocker"
+	"github.com/lightningnetwork/lnd/watchtower/wtdb"
 )
 
 const (
@@ -313,11 +314,23 @@ func Main() error {
 			"is proxying over Tor as well", cfg.Tor.StreamIsolation)
 	}
 
+	// If the watchtower client should be active, open the client database.
+	// This is done here so that Close always executes when lndMain returns.
+	var towerClientDB *wtdb.ClientDB
+	if cfg.WtClient.IsActive() {
+		var err error
+		towerClientDB, err = wtdb.OpenClientDB(graphDir)
+		if err != nil {
+			ltndLog.Errorf("Unable to open watchtower client db: %v", err)
+		}
+		defer towerClientDB.Close()
+	}
+
 	// Set up the core server which will listen for incoming peer
 	// connections.
 	server, err := newServer(
-		cfg.Listeners, chanDB, activeChainControl, idPrivKey,
-		walletInitParams.ChansToRestore,
+		cfg.Listeners, chanDB, towerClientDB, activeChainControl,
+		idPrivKey, walletInitParams.ChansToRestore,
 	)
 	if err != nil {
 		srvrLog.Errorf("unable to create server: %v\n", err)

server.go

@@ -50,6 +50,9 @@ import (
 	"github.com/lightningnetwork/lnd/ticker"
 	"github.com/lightningnetwork/lnd/tor"
 	"github.com/lightningnetwork/lnd/walletunlocker"
+	"github.com/lightningnetwork/lnd/watchtower/wtclient"
+	"github.com/lightningnetwork/lnd/watchtower/wtdb"
+	"github.com/lightningnetwork/lnd/watchtower/wtpolicy"
 	"github.com/lightningnetwork/lnd/zpay32"
 )
 
@@ -204,6 +207,8 @@ type server struct {
 
 	sphinx *htlcswitch.OnionProcessor
 
+	towerClient wtclient.Client
+
 	connMgr *connmgr.ConnManager
 
 	sigPool *lnwallet.SigPool
@@ -282,7 +287,8 @@ func noiseDial(idPriv *btcec.PrivateKey) func(net.Addr) (net.Conn, error) {
 
 // newServer creates a new instance of the server which is to listen using the
 // passed listener address.
-func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB, cc *chainControl,
+func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
+	towerClientDB *wtdb.ClientDB, cc *chainControl,
 	privKey *btcec.PrivateKey,
 	chansToRestore walletunlocker.ChannelsToRecover) (*server, error) {
 
@@ -1056,6 +1062,39 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB, cc *chainControl,
 		return nil, err
 	}
 
+	if cfg.WtClient.IsActive() {
+		policy := wtpolicy.DefaultPolicy()
+
+		if cfg.WtClient.SweepFeeRate != 0 {
+			// We expose the sweep fee rate in sat/byte, but the
+			// tower protocol operations on sat/kw.
+			sweepRateSatPerByte := lnwallet.SatPerKVByte(
+				1000 * cfg.WtClient.SweepFeeRate,
+			)
+			policy.SweepFeeRate = sweepRateSatPerByte.FeePerKWeight()
+		}
+
+		s.towerClient, err = wtclient.New(&wtclient.Config{
+			Signer: cc.wallet.Cfg.Signer,
+			NewAddress: func() ([]byte, error) {
+				return newSweepPkScript(cc.wallet)
+			},
+			SecretKeyRing:  s.cc.keyRing,
+			Dial:           cfg.net.Dial,
+			AuthDial:       wtclient.AuthDial,
+			DB:             towerClientDB,
+			Policy:         wtpolicy.DefaultPolicy(),
+			PrivateTower:   cfg.WtClient.PrivateTowers[0],
+			ChainHash:      *activeNetParams.GenesisHash,
+			MinBackoff:     10 * time.Second,
+			MaxBackoff:     5 * time.Minute,
+			ForceQuitDelay: wtclient.DefaultForceQuitDelay,
+		})
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	// Create the connection manager which will be responsible for
 	// maintaining persistent outbound connections and also accepting new
 	// incoming connections
@@ -1128,6 +1167,12 @@ func (s *server) Start() error {
 			startErr = err
 			return
 		}
+		if s.towerClient != nil {
+			if err := s.towerClient.Start(); err != nil {
+				startErr = err
+				return
+			}
+		}
 		if err := s.htlcSwitch.Start(); err != nil {
 			startErr = err
 			return
@@ -1290,6 +1335,14 @@ func (s *server) Stop() error {
 			s.DisconnectPeer(peer.addr.IdentityKey)
 		}
 
+		// Now that all connections have been torn down, stop the tower
+		// client which will reliably flush all queued states to the
+		// tower. If this is halted for any reason, the force quit timer
+		// will kick in and abort to allow this method to return.
+		if s.towerClient != nil {
+			s.towerClient.Stop()
+		}
+
 		// Wait for all lingering goroutines to quit.
 		s.wg.Wait()
 

watchtower/wtclient/client.go

@@ -29,6 +29,11 @@ const (
 	// DefaultStatInterval specifies the default interval between logging
 	// metrics about the client's operation.
 	DefaultStatInterval = 30 * time.Second
+
+	// DefaultForceQuitDelay specifies the default duration after which the
+	// client should abandon any pending updates or session negotiations
+	// before terminating.
+	DefaultForceQuitDelay = 10 * time.Second
 )
 
 // Client is the primary interface used by the daemon to control a client's