multi: add initial implementation of simple taproot chans spec proposal

channeldb/channel.go

@@ -278,6 +278,10 @@ const (
 	// ScidAliasFeatureBit indicates that the scid-alias feature bit was
 	// negotiated during the lifetime of this channel.
 	ScidAliasFeatureBit ChannelType = 1 << 9
+
+	// SimpleTaprootFeatureBit indicates that the simple-taproot-channels
+	// feature bit was negotiated during the lifetime of the channel.
+	SimpleTaprootFeatureBit ChannelType = 1 << 10
 )
 
 // IsSingleFunder returns true if the channel type if one of the known single
@@ -343,6 +347,11 @@ func (c ChannelType) HasScidAliasFeature() bool {
 	return c&ScidAliasFeatureBit == ScidAliasFeatureBit
 }
 
+// IsTaproot returns true if the channel is using taproot features.
+func (c ChannelType) IsTaproot() bool {
+	return c&SimpleTaprootFeatureBit == SimpleTaprootFeatureBit
+}
+
 // ChannelConstraints represents a set of constraints meant to allow a node to
 // limit their exposure, enact flow control and ensure that all HTLCs are
 // economically relevant. This struct will be mirrored for both sides of the
@@ -1315,11 +1324,11 @@ func (c *OpenChannel) SecondCommitmentPoint() (*btcec.PublicKey, error) {
 // commitment chains in the case of a last or only partially processed message.
 // When the remote party receives this message one of three things may happen:
 //
-//   1. We're fully synced and no messages need to be sent.
-//   2. We didn't get the last CommitSig message they sent, so they'll re-send
-//      it.
-//   3. We didn't get the last RevokeAndAck message they sent, so they'll
-//      re-send it.
+//  1. We're fully synced and no messages need to be sent.
+//  2. We didn't get the last CommitSig message they sent, so they'll re-send
+//     it.
+//  3. We didn't get the last RevokeAndAck message they sent, so they'll
+//     re-send it.
 //
 // If this is a restored channel, having status ChanStatusRestored, then we'll
 // modify our typical chan sync message to ensure they force close even if

feature/default_sets.go

@@ -83,4 +83,8 @@ var defaultSetDesc = setDesc{
 		SetInit:    {}, // I
 		SetNodeAnn: {}, // N
 	},
+	lnwire.SimpleTaprootChannelsOptional: {
+		SetInit:    {}, // I
+		SetNodeAnn: {}, // N
+	},
 }

feature/deps.go

@@ -75,6 +75,9 @@ var deps = depDesc{
 	lnwire.ZeroConfOptional: {
 		lnwire.ScidAliasOptional: {},
 	},
+	lnwire.SimpleTaprootChannelsOptional: {
+		lnwire.ExplicitChannelTypeOptional: {},
+	},
 }
 
 // ValidateDeps asserts that a feature vector sets all features and their

funding/commitment_type_negotiation.go

@@ -220,6 +220,51 @@ func explicitNegotiateCommitmentType(channelType lnwire.ChannelType, local,
 		}
 		return lnwallet.CommitmentTypeTweakless, nil
 
+	// Simple taproot channels only.
+	case channelFeatures.OnlyContains(lnwire.SimpleTaprootChannelsRequired):
+
+		if !hasFeatures(
+			local, remote, lnwire.SimpleTaprootChannelsOptional,
+		) {
+			return 0, errUnsupportedChannelType
+		}
+
+		return lnwallet.CommitmentTypeSimpleTaproot, nil
+
+	// Simple taproot channels with scid only.
+	case channelFeatures.OnlyContains(
+		lnwire.SimpleTaprootChannelsRequired,
+		lnwire.ScidAliasRequired,
+	):
+
+		if !hasFeatures(
+			local, remote,
+			lnwire.SimpleTaprootChannelsOptional,
+			lnwire.ScidAliasOptional,
+		) {
+			return 0, errUnsupportedChannelType
+		}
+
+		return lnwallet.CommitmentTypeSimpleTaproot, nil
+
+	// Simple taproot channels with zero conf only.
+	case channelFeatures.OnlyContains(
+		lnwire.SimpleTaprootChannelsRequired,
+		lnwire.ScidAliasRequired,
+		lnwire.ZeroConfRequired,
+	):
+
+		if !hasFeatures(
+			local, remote,
+			lnwire.SimpleTaprootChannelsOptional,
+			lnwire.ScidAliasOptional,
+			lnwire.ZeroConfOptional,
+		) {
+			return 0, errUnsupportedChannelType
+		}
+
+		return lnwallet.CommitmentTypeSimpleTaproot, nil
+
 	// No features, use legacy commitment type.
 	case channelFeatures.IsEmpty():
 		return lnwallet.CommitmentTypeLegacy, nil

funding/manager.go

@@ -1659,6 +1659,21 @@ func (f *Manager) handleFundingOpen(peer lnpeer.Peer,
 	log.Debugf("Remote party accepted commitment constraints: %v",
 		spew.Sdump(remoteContribution.ChannelConfig.ChannelConstraints))
 
+	ourContribution := reservation.OurContribution()
+
+	var (
+		localNonce  *lnwire.LocalMusig2Nonce
+		remoteNonce *lnwire.RemoteMusig2Nonce
+	)
+	if commitType == lnwallet.CommitmentTypeSimpleTaproot {
+		localNonce = &lnwire.LocalMusig2Nonce{
+			Musig2Nonce: ourContribution.LocalNonce.PubNonce,
+		}
+		remoteNonce = &lnwire.RemoteMusig2Nonce{
+			Musig2Nonce: ourContribution.RemoteNonce.PubNonce,
+		}
+	}
+
 	// With the initiator's contribution recorded, respond with our
 	// contribution in the next message of the workflow.
 	ourContribution := reservation.OurContribution()
@@ -1680,6 +1695,8 @@ func (f *Manager) handleFundingOpen(peer lnpeer.Peer,
 		UpfrontShutdownScript: ourContribution.UpfrontShutdown,
 		ChannelType:           chanTypeFeatureBits,
 		LeaseExpiry:           msg.LeaseExpiry,
+		LocalNonce:            localNonce,
+		RemoteNonce:           remoteNonce,
 	}
 
 	if err := peer.SendMessage(true, &fundingAccept); err != nil {
@@ -4037,6 +4054,19 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 	log.Infof("Starting funding workflow with %v for pending_id(%x), "+
 		"committype=%v", msg.Peer.Address(), chanID, commitType)
 
+	var (
+		localNonce  *lnwire.LocalMusig2Nonce
+		remoteNonce *lnwire.RemoteMusig2Nonce
+	)
+	if commitType == lnwallet.CommitmentTypeSimpleTaproot {
+		localNonce = &lnwire.LocalMusig2Nonce{
+			Musig2Nonce: ourContribution.LocalNonce.PubNonce,
+		}
+		remoteNonce = &lnwire.RemoteMusig2Nonce{
+			Musig2Nonce: ourContribution.RemoteNonce.PubNonce,
+		}
+	}
+
 	fundingOpen := lnwire.OpenChannel{
 		ChainHash:             *f.cfg.Wallet.Cfg.NetParams.GenesisHash,
 		PendingChannelID:      chanID,
@@ -4059,6 +4089,8 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 		UpfrontShutdownScript: shutdown,
 		ChannelType:           chanType,
 		LeaseExpiry:           leaseExpiry,
+		LocalNonce:            localNonce,
+		RemoteNonce:           remoteNonce,
 	}
 	if err := msg.Peer.SendMessage(true, &fundingOpen); err != nil {
 		e := fmt.Errorf("unable to send funding request message: %v",

input/musig2.go

@@ -31,9 +31,16 @@ type MuSig2Signer interface {
 	// public key of the local signing key. If nonces of other parties are
 	// already known, they can be submitted as well to reduce the number of
 	// method calls necessary later on.
+	//
+	// The set of sessionOpts are _optional_ and allow a caller to modify the
+	// generated sessions. As an example the local nonce might already be generated
+	// ahead of time.
 	MuSig2CreateSession(keychain.KeyLocator, []*btcec.PublicKey,
-		*MuSig2Tweaks, [][musig2.PubNonceSize]byte) (*MuSig2SessionInfo,
-		error)
+		*MuSig2Tweaks, [][musig2.PubNonceSize]byte,
+		...musig2.SessionOption) (*MuSig2SessionInfo, error)
+
+	// TODO(roasbeef): need to make the sparse one here?
+	//  * don't have any info but want a session
 
 	// MuSig2RegisterNonces registers one or more public nonces of other
 	// signing participants for a session identified by its ID. This method
@@ -76,6 +83,8 @@ type MuSig2SessionInfo struct {
 	// CombinedKey is the combined public key with all tweaks applied to it.
 	CombinedKey *btcec.PublicKey
 
+	// TODO(roasbeef): also add combined nonce
+
 	// TaprootTweak indicates whether a taproot tweak (BIP-0086 or script
 	// path) was used. The TaprootInternalKey will only be set if this is
 	// set to true.