multi: cap anchors feerate at configurable maximum

config.go

@@ -33,6 +33,7 @@ import (
 	"github.com/lightningnetwork/lnd/lncfg"
 	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
+	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/routing"
 	"github.com/lightningnetwork/lnd/tor"
 )
@@ -289,6 +290,8 @@ type Config struct {
 
 	MaxChannelFeeAllocation float64 `long:"max-channel-fee-allocation" description:"The maximum percentage of total funds that can be allocated to a channel's commitment fee. This only applies for the initiator of the channel. Valid values are within [0.1, 1]."`
 
+	MaxCommitFeeRateAnchors uint64 `long:"max-commit-fee-rate-anchors" description:"The maximum fee rate in sat/vbyte that will be used for commitments of channels of the anchors type. Must be large enough to ensure transaction propagation"`
+
 	DryRunMigration bool `long:"dry-run-migration" description:"If true, lnd will abort committing a migration if it would otherwise have been successful. This leaves the database unmodified, and still compatible with the previously active version of lnd."`
 
 	net tor.Net
@@ -475,6 +478,7 @@ func DefaultConfig() Config {
 		},
 		MaxOutgoingCltvExpiry:   htlcswitch.DefaultMaxOutgoingCltvExpiry,
 		MaxChannelFeeAllocation: htlcswitch.DefaultMaxLinkFeeAllocation,
+		MaxCommitFeeRateAnchors: lnwallet.DefaultAnchorsCommitMaxFeeRateSatPerVByte,
 		LogWriter:               build.NewRotatingLogWriter(),
 		DB:                      lncfg.DefaultDB(),
 		registeredChains:        chainreg.NewChainRegistry(),
@@ -735,6 +739,12 @@ func ValidateConfig(cfg Config, usageMessage string) (*Config, error) {
 			cfg.MaxChannelFeeAllocation)
 	}
 
+	if cfg.MaxCommitFeeRateAnchors < 1 {
+		return nil, fmt.Errorf("invalid max commit fee rate anchors: "+
+			"%v, must be at least 1 sat/vbyte",
+			cfg.MaxCommitFeeRateAnchors)
+	}
+
 	// Validate the Tor config parameters.
 	socks, err := lncfg.ParseAddressString(
 		cfg.Tor.SOCKS, strconv.Itoa(defaultTorSOCKSPort),

fundingmanager.go

@@ -366,6 +366,10 @@ type fundingConfig struct {
 	// RegisteredChains keeps track of all chains that have been registered
 	// with the daemon.
 	RegisteredChains *chainreg.ChainRegistry
+
+	// MaxAnchorsCommitFeeRate is the max commitment fee rate we'll use as
+	// the initiator for channels of the anchor type.
+	MaxAnchorsCommitFeeRate chainfee.SatPerKWeight
 }
 
 // fundingManager acts as an orchestrator/bridge between the wallet's
@@ -3122,16 +3126,6 @@ func (f *fundingManager) handleInitFundingMsg(msg *initFundingMsg) {
 		msg.pushAmt, msg.chainHash, peerKey.SerializeCompressed(),
 		ourDustLimit, msg.minConfs)
 
-	// First, we'll query the fee estimator for a fee that should get the
-	// commitment transaction confirmed by the next few blocks (conf target
-	// of 3). We target the near blocks here to ensure that we'll be able
-	// to execute a timely unilateral channel closure if needed.
-	commitFeePerKw, err := f.cfg.FeeEstimator.EstimateFeePerKW(3)
-	if err != nil {
-		msg.err <- err
-		return
-	}
-
 	// We set the channel flags to indicate whether we want this channel to
 	// be announced to the network.
 	var channelFlags lnwire.FundingFlag
@@ -3190,6 +3184,25 @@ func (f *fundingManager) handleInitFundingMsg(msg *initFundingMsg) {
 	commitType := commitmentType(
 		msg.peer.LocalFeatures(), msg.peer.RemoteFeatures(),
 	)
+
+	// First, we'll query the fee estimator for a fee that should get the
+	// commitment transaction confirmed by the next few blocks (conf target
+	// of 3). We target the near blocks here to ensure that we'll be able
+	// to execute a timely unilateral channel closure if needed.
+	commitFeePerKw, err := f.cfg.FeeEstimator.EstimateFeePerKW(3)
+	if err != nil {
+		msg.err <- err
+		return
+	}
+
+	// For anchor channels cap the initial commit fee rate at our defined
+	// maximum.
+	if commitType == lnwallet.CommitmentTypeAnchorsZeroFeeHtlcTx &&
+		commitFeePerKw > f.cfg.MaxAnchorsCommitFeeRate {
+
+		commitFeePerKw = f.cfg.MaxAnchorsCommitFeeRate
+	}
+
 	req := &lnwallet.InitFundingReserveMsg{
 		ChainHash:        &msg.chainHash,
 		PendingChanID:    chanID,

htlcswitch/link.go

@@ -269,6 +269,10 @@ type ChannelLinkConfig struct {
 	// initiator of the channel.
 	MaxFeeAllocation float64
 
+	// MaxAnchorsCommitFeeRate is the max commitment fee rate we'll use as
+	// the initiator for channels of the anchor type.
+	MaxAnchorsCommitFeeRate chainfee.SatPerKWeight
+
 	// NotifyActiveLink allows the link to tell the ChannelNotifier when a
 	// link is first started.
 	NotifyActiveLink func(wire.OutPoint)
@@ -1090,7 +1094,10 @@ func (l *channelLink) htlcManager() {
 			// based on our current set fee rate. We'll cap the new
 			// fee rate to our max fee allocation.
 			commitFee := l.channel.CommitFeeRate()
-			maxFee := l.channel.MaxFeeRate(l.cfg.MaxFeeAllocation)
+			maxFee := l.channel.MaxFeeRate(
+				l.cfg.MaxFeeAllocation,
+				l.cfg.MaxAnchorsCommitFeeRate,
+			)
 			newCommitFee := chainfee.SatPerKWeight(
 				math.Min(float64(netFee), float64(maxFee)),
 			)

htlcswitch/test_utils.go

@@ -1185,6 +1185,7 @@ func (h *hopNetwork) createChannelLink(server, peer *mockServer,
 			OutgoingCltvRejectDelta: 3,
 			MaxOutgoingCltvExpiry:   DefaultMaxOutgoingCltvExpiry,
 			MaxFeeAllocation:        DefaultMaxLinkFeeAllocation,
+			MaxAnchorsCommitFeeRate: chainfee.SatPerKVByte(10 * 1000).FeePerKWeight(),
 			NotifyActiveLink:        func(wire.OutPoint) {},
 			NotifyActiveChannel:     func(wire.OutPoint) {},
 			NotifyInactiveChannel:   func(wire.OutPoint) {},

lntest/itest/lnd_test.go

@@ -1166,8 +1166,12 @@ func (c commitType) calcStaticFee(numHTLCs int) btcutil.Amount {
 
 	// The anchor commitment type is slightly heavier, and we must also add
 	// the value of the two anchors to the resulting fee the initiator
-	// pays.
+	// pays. In addition the fee rate is capped at 10 sat/vbyte for anchor
+	// channels.
 	if c == commitTypeAnchors {
+		feePerKw = chainfee.SatPerKVByte(
+			lnwallet.DefaultAnchorsCommitMaxFeeRateSatPerVByte * 1000,
+		).FeePerKWeight()
 		commitWeight = input.AnchorCommitWeight
 		anchors = 2 * anchorSize
 	}

lnwallet/channel.go

@@ -6809,11 +6809,14 @@ func (lc *LightningChannel) CalcFee(feeRate chainfee.SatPerKWeight) btcutil.Amou
 
 // MaxFeeRate returns the maximum fee rate given an allocation of the channel
 // initiator's spendable balance. This can be useful to determine when we should
-// stop proposing fee updates that exceed our maximum allocation.
+// stop proposing fee updates that exceed our maximum allocation. We also take
+// a fee rate cap that should be used for anchor type channels.
 //
 // NOTE: This should only be used for channels in which the local commitment is
 // the initiator.
-func (lc *LightningChannel) MaxFeeRate(maxAllocation float64) chainfee.SatPerKWeight {
+func (lc *LightningChannel) MaxFeeRate(maxAllocation float64,
+	maxAnchorFeeRate chainfee.SatPerKWeight) chainfee.SatPerKWeight {
+
 	lc.RLock()
 	defer lc.RUnlock()
 
@@ -6828,9 +6831,16 @@ func (lc *LightningChannel) MaxFeeRate(maxAllocation float64) chainfee.SatPerKWe
 	// Ensure the fee rate doesn't dip below the fee floor.
 	_, weight := lc.availableBalance()
 	maxFeeRate := maxFee / (float64(weight) / 1000)
-	return chainfee.SatPerKWeight(
+	feeRate := chainfee.SatPerKWeight(
 		math.Max(maxFeeRate, float64(chainfee.FeePerKwFloor)),
 	)
+
+	// Cap anchor fee rates.
+	if lc.channelState.ChanType.HasAnchors() && feeRate > maxAnchorFeeRate {
+		return maxAnchorFeeRate
+	}
+
+	return feeRate
 }
 
 // RemoteNextRevocation returns the channelState's RemoteNextRevocation.

lnwallet/channel_test.go

@@ -7996,6 +7996,19 @@ func TestForceCloseBorkedState(t *testing.T) {
 func TestChannelMaxFeeRate(t *testing.T) {
 	t.Parallel()
 
+	assertMaxFeeRate := func(c *LightningChannel,
+		maxAlloc float64, anchorMax, expFeeRate chainfee.SatPerKWeight) {
+
+		t.Helper()
+
+		maxFeeRate := c.MaxFeeRate(maxAlloc, anchorMax)
+		if maxFeeRate != expFeeRate {
+			t.Fatalf("expected max fee rate of %v with max "+
+				"allocation of %v, got %v", expFeeRate,
+				maxAlloc, maxFeeRate)
+		}
+	}
+
 	aliceChannel, _, cleanUp, err := CreateTestChannels(
 		channeldb.SingleFunderTweaklessBit,
 	)
@@ -8004,21 +8017,32 @@ func TestChannelMaxFeeRate(t *testing.T) {
 	}
 	defer cleanUp()
 
-	assertMaxFeeRate := func(maxAlloc float64,
-		expFeeRate chainfee.SatPerKWeight) {
+	assertMaxFeeRate(aliceChannel, 1.0, 0, 690607734)
+	assertMaxFeeRate(aliceChannel, 0.001, 0, 690607)
+	assertMaxFeeRate(aliceChannel, 0.000001, 0, 690)
+	assertMaxFeeRate(aliceChannel, 0.0000001, 0, chainfee.FeePerKwFloor)
 
-		maxFeeRate := aliceChannel.MaxFeeRate(maxAlloc)
-		if maxFeeRate != expFeeRate {
-			t.Fatalf("expected max fee rate of %v with max "+
-				"allocation of %v, got %v", expFeeRate,
-				maxAlloc, maxFeeRate)
-		}
+	// Check that anchor channels are capped at their max fee rate.
+	anchorChannel, _, cleanUp, err := CreateTestChannels(
+		channeldb.SingleFunderTweaklessBit | channeldb.AnchorOutputsBit,
+	)
+	if err != nil {
+		t.Fatalf("unable to create test channels: %v", err)
 	}
+	defer cleanUp()
 
-	assertMaxFeeRate(1.0, 690607734)
-	assertMaxFeeRate(0.001, 690607)
-	assertMaxFeeRate(0.000001, 690)
-	assertMaxFeeRate(0.0000001, chainfee.FeePerKwFloor)
+	// Anchor commitments are heavier, hence will the same allocation lead
+	// to slightly lower fee rates.
+	assertMaxFeeRate(
+		anchorChannel, 1.0, chainfee.FeePerKwFloor,
+		chainfee.FeePerKwFloor,
+	)
+	assertMaxFeeRate(anchorChannel, 0.001, 1000000, 444839)
+	assertMaxFeeRate(anchorChannel, 0.001, 300000, 300000)
+	assertMaxFeeRate(anchorChannel, 0.000001, 700, 444)
+	assertMaxFeeRate(
+		anchorChannel, 0.0000001, 1000000, chainfee.FeePerKwFloor,
+	)
 }
 
 // TestChannelFeeRateFloor asserts that valid commitments can be proposed and

lnwallet/commitment.go

@@ -17,6 +17,11 @@ import (
 // anchorSize is the constant anchor output size.
 const anchorSize = btcutil.Amount(330)
 
+// DefaultAnchorsCommitMaxFeeRateSatPerVByte is the default max fee rate in
+// sat/vbyte the initiator will use for anchor channels. This should be enough
+// to ensure propagation before anchoring down the commitment transaction.
+const DefaultAnchorsCommitMaxFeeRateSatPerVByte = 10
+
 // CommitmentKeyRing holds all derived keys needed to construct commitment and
 // HTLC transactions. The keys are derived differently depending whether the
 // commitment transaction is ours or the remote peer's. Private keys associated

peer/brontide.go

@@ -294,6 +294,10 @@ type Config struct {
 	// commitment fee. This only applies for the initiator of the channel.
 	MaxChannelFeeAllocation float64
 
+	// MaxAnchorsCommitFeeRate is the maximum fee rate we'll use as an
+	// initiator for anchor channel commitments.
+	MaxAnchorsCommitFeeRate chainfee.SatPerKWeight
+
 	// ServerPubKey is the serialized, compressed public key of our lnd node.
 	// It is used to determine which policy (channel edge) to pass to the
 	// ChannelLink.
@@ -815,6 +819,7 @@ func (p *Brontide) addLink(chanPoint *wire.OutPoint,
 		TowerClient:             towerClient,
 		MaxOutgoingCltvExpiry:   p.cfg.MaxOutgoingCltvExpiry,
 		MaxFeeAllocation:        p.cfg.MaxChannelFeeAllocation,
+		MaxAnchorsCommitFeeRate: p.cfg.MaxAnchorsCommitFeeRate,
 		NotifyActiveLink:        p.cfg.ChannelNotifier.NotifyActiveLinkEvent,
 		NotifyActiveChannel:     p.cfg.ChannelNotifier.NotifyActiveChannelEvent,
 		NotifyInactiveChannel:   p.cfg.ChannelNotifier.NotifyInactiveChannelEvent,

sample-lnd.conf

@@ -307,6 +307,11 @@
 ; values are within [0.1, 1]. (default: 0.5)
 ; max-channel-fee-allocation=0.9
 
+; The maximum fee rate in sat/vbyte that will be used for commitments of
+; channels of the anchors type. Must be large enough to ensure transaction
+; propagation (default: 10)
+; max-commit-fee-rate-anchors=5
+
 ; If true, lnd will abort committing a migration if it would otherwise have been
 ; successful. This leaves the database unmodified, and still compatible with the
 ; previously active version of lnd.

server.go

@@ -1185,6 +1185,8 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 		NotifyPendingOpenChannelEvent: s.channelNotifier.NotifyPendingOpenChannelEvent,
 		EnableUpfrontShutdown:         cfg.EnableUpfrontShutdown,
 		RegisteredChains:              cfg.registeredChains,
+		MaxAnchorsCommitFeeRate: chainfee.SatPerKVByte(
+			s.cfg.MaxCommitFeeRateAnchors * 1000).FeePerKWeight(),
 	})
 	if err != nil {
 		return nil, err
@@ -3119,7 +3121,9 @@ func (s *server) peerConnected(conn net.Conn, connReq *connmgr.ConnReq,
 		UnsafeReplay:            s.cfg.UnsafeReplay,
 		MaxOutgoingCltvExpiry:   s.cfg.MaxOutgoingCltvExpiry,
 		MaxChannelFeeAllocation: s.cfg.MaxChannelFeeAllocation,
-		Quit:                    s.quit,
+		MaxAnchorsCommitFeeRate: chainfee.SatPerKVByte(
+			s.cfg.MaxCommitFeeRateAnchors * 1000).FeePerKWeight(),
+		Quit: s.quit,
 	}
 
 	copy(pCfg.PubKeyBytes[:], peerAddr.IdentityKey.SerializeCompressed())