funding+lnwallet: support funding new script enforced leased channels

funding/commitment_type_negotiation.go

@@ -50,6 +50,23 @@ func explicitNegotiateCommitmentType(channelType lnwire.ChannelType,
 	channelFeatures := lnwire.RawFeatureVector(channelType)
 
 	switch {
+	// Lease script enforcement + anchors zero fee + static remote key
+	// features only.
+	case channelFeatures.OnlyContains(
+		lnwire.ScriptEnforcedLeaseRequired,
+		lnwire.AnchorsZeroFeeHtlcTxRequired,
+		lnwire.StaticRemoteKeyRequired,
+	):
+		if !hasFeatures(
+			local, remote,
+			lnwire.ScriptEnforcedLeaseOptional,
+			lnwire.AnchorsZeroFeeHtlcTxOptional,
+			lnwire.StaticRemoteKeyOptional,
+		) {
+			return 0, errUnsupportedChannelType
+		}
+		return lnwallet.CommitmentTypeScriptEnforcedLease, nil
+
 	// Anchors zero fee + static remote key features only.
 	case channelFeatures.OnlyContains(
 		lnwire.AnchorsZeroFeeHtlcTxRequired,

funding/manager.go

@@ -1364,6 +1364,28 @@ func (f *Manager) handleFundingOpen(peer lnpeer.Peer,
 	}
 	reservation.SetOurUpfrontShutdown(shutdown)
 
+	// If a script enforced channel lease is being proposed, we'll need to
+	// validate its custom TLV records.
+	if commitType == lnwallet.CommitmentTypeScriptEnforcedLease {
+		if msg.LeaseExpiry == nil {
+			err := errors.New("missing lease expiry")
+			f.failFundingFlow(peer, msg.PendingChannelID, err)
+			return
+		}
+
+		// If we had a shim registered for this channel prior to
+		// receiving its corresponding OpenChannel message, then we'll
+		// validate the proposed LeaseExpiry against what was registered
+		// in our shim.
+		if reservation.LeaseExpiry() != 0 {
+			if uint32(*msg.LeaseExpiry) != reservation.LeaseExpiry() {
+				err := errors.New("lease expiry mismatch")
+				f.failFundingFlow(peer, msg.PendingChannelID, err)
+				return
+			}
+		}
+	}
+
 	log.Infof("Requiring %v confirmations for pendingChan(%x): "+
 		"amt=%v, push_amt=%v, committype=%v, upfrontShutdown=%x", numConfsReq,
 		msg.PendingChannelID, amt, msg.PushAmount,
@@ -1499,6 +1521,7 @@ func (f *Manager) handleFundingOpen(peer lnpeer.Peer,
 		FirstCommitmentPoint:  ourContribution.FirstCommitmentPoint,
 		UpfrontShutdownScript: ourContribution.UpfrontShutdown,
 		ChannelType:           msg.ChannelType,
+		LeaseExpiry:           msg.LeaseExpiry,
 	}
 
 	if err := peer.SendMessage(true, &fundingAccept); err != nil {
@@ -1530,11 +1553,12 @@ func (f *Manager) handleFundingAccept(peer lnpeer.Peer,
 	log.Infof("Recv'd fundingResponse for pending_id(%x)",
 		pendingChanID[:])
 
-	// We'll want to quickly check that ChannelType echoed by the channel
-	// request recipient matches what we proposed.
+	// Perform some basic validation of any custom TLV records included.
 	//
 	// TODO: Return errors as funding.Error to give context to remote peer?
 	if resCtx.channelType != nil {
+		// We'll want to quickly check that the ChannelType echoed by
+		// the channel request recipient matches what we proposed.
 		if msg.ChannelType == nil {
 			err := errors.New("explicit channel type not echoed back")
 			f.failFundingFlow(peer, msg.PendingChannelID, err)
@@ -1547,6 +1571,21 @@ func (f *Manager) handleFundingAccept(peer lnpeer.Peer,
 			f.failFundingFlow(peer, msg.PendingChannelID, err)
 			return
 		}
+
+		// We'll want to do the same with the LeaseExpiry if one should
+		// be set.
+		if resCtx.reservation.LeaseExpiry() != 0 {
+			if msg.LeaseExpiry == nil {
+				err := errors.New("lease expiry not echoed back")
+				f.failFundingFlow(peer, msg.PendingChannelID, err)
+				return
+			}
+			if uint32(*msg.LeaseExpiry) != resCtx.reservation.LeaseExpiry() {
+				err := errors.New("lease expiry mismatch")
+				f.failFundingFlow(peer, msg.PendingChannelID, err)
+				return
+			}
+		}
 	} else if msg.ChannelType != nil {
 		err := errors.New("received unexpected channel type")
 		f.failFundingFlow(peer, msg.PendingChannelID, err)
@@ -3206,9 +3245,8 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 
 	// For anchor channels cap the initial commit fee rate at our defined
 	// maximum.
-	if commitType == lnwallet.CommitmentTypeAnchorsZeroFeeHtlcTx &&
+	if commitType.HasAnchors() &&
 		commitFeePerKw > f.cfg.MaxAnchorsCommitFeeRate {
-
 		commitFeePerKw = f.cfg.MaxAnchorsCommitFeeRate
 	}
 
@@ -3311,6 +3349,14 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 	// remote party.
 	chanReserve := f.cfg.RequiredRemoteChanReserve(capacity, ourDustLimit)
 
+	// When opening a script enforced channel lease, include the required
+	// expiry TLV record in our proposal.
+	var leaseExpiry *lnwire.LeaseExpiry
+	if commitType == lnwallet.CommitmentTypeScriptEnforcedLease {
+		leaseExpiry = new(lnwire.LeaseExpiry)
+		*leaseExpiry = lnwire.LeaseExpiry(reservation.LeaseExpiry())
+	}
+
 	log.Infof("Starting funding workflow with %v for pending_id(%x), "+
 		"committype=%v", msg.Peer.Address(), chanID, commitType)
 
@@ -3335,6 +3381,7 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 		ChannelFlags:          channelFlags,
 		UpfrontShutdownScript: shutdown,
 		ChannelType:           msg.ChannelType,
+		LeaseExpiry:           leaseExpiry,
 	}
 	if err := msg.Peer.SendMessage(true, &fundingOpen); err != nil {
 		e := fmt.Errorf("unable to send funding request message: %v",

lnwallet/reservation.go

@@ -1,6 +1,7 @@
 package lnwallet
 
 import (
+	"errors"
 	"net"
 	"sync"
 
@@ -34,8 +35,40 @@ const (
 	// requires second-level HTLC transactions to be signed using a
 	// zero-fee.
 	CommitmentTypeAnchorsZeroFeeHtlcTx
+
+	// CommitmentTypeScriptEnforcedLease is a commitment type that builds
+	// upon CommitmentTypeTweakless and CommitmentTypeAnchorsZeroFeeHtlcTx,
+	// which in addition requires a CLTV clause to spend outputs paying to
+	// the channel initiator. This is intended for use on leased channels to
+	// guarantee that the channel initiator has no incentives to close a
+	// leased channel before its maturity date.
+	CommitmentTypeScriptEnforcedLease
 )
 
+// HasStaticRemoteKey returns whether the commitment type supports remote
+// outputs backed by static keys.
+func (c CommitmentType) HasStaticRemoteKey() bool {
+	switch c {
+	case CommitmentTypeTweakless,
+		CommitmentTypeAnchorsZeroFeeHtlcTx,
+		CommitmentTypeScriptEnforcedLease:
+		return true
+	default:
+		return false
+	}
+}
+
+// HasAnchors returns whether the commitment type supports anchor outputs.
+func (c CommitmentType) HasAnchors() bool {
+	switch c {
+	case CommitmentTypeAnchorsZeroFeeHtlcTx,
+		CommitmentTypeScriptEnforcedLease:
+		return true
+	default:
+		return false
+	}
+}
+
 // String returns the name of the CommitmentType.
 func (c CommitmentType) String() string {
 	switch c {
@@ -45,6 +78,8 @@ func (c CommitmentType) String() string {
 		return "tweakless"
 	case CommitmentTypeAnchorsZeroFeeHtlcTx:
 		return "anchors-zero-fee-second-level"
+	case CommitmentTypeScriptEnforcedLease:
+		return "script-enforced-lease"
 	default:
 		return "invalid"
 	}
@@ -188,8 +223,8 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 	// Based on the channel type, we determine the initial commit weight
 	// and fee.
 	commitWeight := int64(input.CommitWeight)
-	if commitType == CommitmentTypeAnchorsZeroFeeHtlcTx {
-		commitWeight = input.AnchorCommitWeight
+	if commitType.HasAnchors() {
+		commitWeight = int64(input.AnchorCommitWeight)
 	}
 	commitFee := commitFeePerKw.FeeForWeight(commitWeight)
 
@@ -201,7 +236,7 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 	// The total fee paid by the initiator will be the commitment fee in
 	// addition to the two anchor outputs.
 	feeMSat := lnwire.NewMSatFromSatoshis(commitFee)
-	if commitType == CommitmentTypeAnchorsZeroFeeHtlcTx {
+	if commitType.HasAnchors() {
 		feeMSat += 2 * lnwire.NewMSatFromSatoshis(anchorSize)
 	}
 
@@ -288,8 +323,7 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 	if ourBalance == 0 || theirBalance == 0 || pushMSat != 0 {
 		// Both the tweakless type and the anchor type is tweakless,
 		// hence set the bit.
-		if commitType == CommitmentTypeTweakless ||
-			commitType == CommitmentTypeAnchorsZeroFeeHtlcTx {
+		if commitType.HasStaticRemoteKey() {
 			chanType |= channeldb.SingleFunderTweaklessBit
 		} else {
 			chanType |= channeldb.SingleFunderBit
@@ -325,14 +359,20 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 
 	// We are adding anchor outputs to our commitment. We only support this
 	// in combination with zero-fee second-levels HTLCs.
-	if commitType == CommitmentTypeAnchorsZeroFeeHtlcTx {
+	if commitType.HasAnchors() {
 		chanType |= channeldb.AnchorOutputsBit
 		chanType |= channeldb.ZeroHtlcTxFeeBit
 	}
 
-	// If the channel is meant to be frozen, then we'll set the frozen bit
-	// now so once the channel is open, it can be interpreted properly.
-	if thawHeight != 0 {
+	// Set the appropriate LeaseExpiration/Frozen bit based on the
+	// reservation parameters.
+	if commitType == CommitmentTypeScriptEnforcedLease {
+		if thawHeight == 0 {
+			return nil, errors.New("missing absolute expiration " +
+				"for script enforced lease commitment type")
+		}
+		chanType |= channeldb.LeaseExpirationBit
+	} else if thawHeight > 0 {
 		chanType |= channeldb.FrozenBit
 	}
 
@@ -719,6 +759,16 @@ func (r *ChannelReservation) Capacity() btcutil.Amount {
 	return r.partialState.Capacity
 }
 
+// LeaseExpiry returns the absolute expiration height for a leased channel using
+// the script enforced commitment type. A zero value is returned when the
+// channel is not using a script enforced lease commitment type.
+func (r *ChannelReservation) LeaseExpiry() uint32 {
+	if !r.partialState.ChanType.HasLeaseExpiration() {
+		return 0
+	}
+	return r.partialState.ThawHeight
+}
+
 // Cancel abandons this channel reservation. This method should be called in
 // the scenario that communications with the counterparty break down. Upon
 // cancellation, all resources previously reserved for this pending payment

lnwallet/wallet.go

@@ -818,7 +818,7 @@ func (l *LightningWallet) handleFundingReserveRequest(req *InitFundingReserveMsg
 	// funding tx ready, so this will always pass.  We'll do another check
 	// when the PSBT has been verified.
 	isPublic := req.Flags&lnwire.FFAnnounceChannel != 0
-	hasAnchors := req.CommitType == CommitmentTypeAnchorsZeroFeeHtlcTx
+	hasAnchors := req.CommitType.HasAnchors()
 	err = l.enforceNewReservedValue(fundingIntent, isPublic, hasAnchors)
 	if err != nil {
 		fundingIntent.Cancel()