Use official feature bit for option_simple_taproot

docs/release-notes/eclair-vnext.md

@@ -4,6 +4,28 @@
 
 ## Major changes
 
+### Taproot Channels (without announcements)
+
+This release adds support for taproot channels, as specified in [the BOLTs](https://github.com/lightning/bolts/pull/995).
+Taproot channels improve privacy and cost less on-chain fees by using musig2 for the channel output.
+This release is fully compatible with the `lnd` implementation of taproot channels.
+
+We don't support public taproot channels yet, as the gossip mechanism for this isn't finalized yet.
+It is thus only possible to open "private" (unannounced) taproot channels.
+You may follow progress on the specification for public taproot channels [here](https://github.com/lightning/bolts/pull/1059).
+
+This feature is active by default. To disable it, add the following to your `eclair.conf`:
+
+```conf
+eclair.features.option_simple_taproot = disabled
+```
+
+To open a taproot channel with a node that supports the `option_simple_taproot` feature, use the following command:
+
+```sh
+$ eclair-cli open --nodeId=<node_id> --fundingSatoshis=<funding_amount> --channelType=simple_taproot_channel --announceChannel=false
+```
+
 ### Remove support for non-anchor channels
 
 We remove the code used to support legacy channels that don't use anchor outputs or taproot.

eclair-core/src/main/resources/reference.conf

@@ -88,6 +88,7 @@ eclair {
     option_zeroconf = disabled
     keysend = disabled
     option_simple_close = optional
+    option_simple_taproot = optional
     trampoline_payment_prototype = disabled
     async_payment_prototype = disabled
     on_the_fly_funding = disabled

eclair-core/src/main/scala/fr/acinq/eclair/Features.scala

@@ -312,6 +312,11 @@ object Features {
     val mandatory = 60
   }
 
+  case object SimpleTaprootChannels extends Feature with InitFeature with NodeFeature with ChannelTypeFeature {
+    val rfcName = "option_simple_taproot"
+    val mandatory = 80
+  }
+
   case object PhoenixZeroReserve extends Feature with InitFeature with ChannelTypeFeature with PermanentChannelFeature {
     val rfcName = "phoenix_zero_reserve"
     val mandatory = 128
@@ -351,11 +356,6 @@ object Features {
     val mandatory = 564
   }
 
-  case object SimpleTaprootChannelsStaging extends Feature with InitFeature with NodeFeature with ChannelTypeFeature {
-    val rfcName = "option_simple_taproot_staging"
-    val mandatory = 180
-  }
-
   /**
    * Activate this feature to provide on-the-fly funding to remote nodes, as specified in bLIP 36: https://github.com/lightning/blips/blob/master/blip-0036.md.
    * TODO: add NodeFeature once bLIP is merged.
@@ -399,8 +399,8 @@ object Features {
     ZeroConf,
     KeySend,
     SimpleClose,
+    SimpleTaprootChannels,
     SimpleTaprootChannelsPhoenix,
-    SimpleTaprootChannelsStaging,
     WakeUpNotificationClient,
     TrampolinePaymentPrototype,
     AsyncPaymentPrototype,
@@ -421,6 +421,7 @@ object Features {
     TrampolinePaymentPrototype -> (PaymentSecret :: Nil),
     KeySend -> (VariableLengthOnion :: Nil),
     SimpleClose -> (ShutdownAnySegwit :: Nil),
+    SimpleTaprootChannels -> (ChannelType :: SimpleClose :: Nil),
     SimpleTaprootChannelsPhoenix -> (ChannelType :: SimpleClose :: Nil),
     AsyncPaymentPrototype -> (TrampolinePaymentPrototype :: Nil),
     OnTheFlyFunding -> (SplicePrototype :: Nil),

eclair-core/src/main/scala/fr/acinq/eclair/NodeParams.scala

@@ -131,7 +131,7 @@ case class NodeParams(nodeKeyManager: NodeKeyManager,
     // We use the most likely commitment format, even though there is no guarantee that this is the one that will be used.
     val commitmentFormat = if (Features.canUseFeature(localFeatures, remoteFeatures, Features.SimpleTaprootChannelsPhoenix)) {
       PhoenixSimpleTaprootChannelCommitmentFormat
-    } else if (Features.canUseFeature(localFeatures, remoteFeatures, Features.SimpleTaprootChannelsStaging)) {
+    } else if (Features.canUseFeature(localFeatures, remoteFeatures, Features.SimpleTaprootChannels)) {
       ZeroFeeHtlcTxSimpleTaprootChannelCommitmentFormat
     } else {
       ZeroFeeHtlcTxAnchorOutputsCommitmentFormat

eclair-core/src/main/scala/fr/acinq/eclair/channel/ChannelFeatures.scala

@@ -95,14 +95,14 @@ object ChannelTypes {
     override def commitmentFormat: CommitmentFormat = ZeroFeeHtlcTxAnchorOutputsCommitmentFormat
     override def toString: String = s"anchor_outputs_zero_fee_htlc_tx${if (scidAlias) "+scid_alias" else ""}${if (zeroConf) "+zeroconf" else ""}"
   }
-  case class SimpleTaprootChannelsStaging(scidAlias: Boolean = false, zeroConf: Boolean = false) extends SupportedChannelType {
+  case class SimpleTaprootChannel(scidAlias: Boolean = false, zeroConf: Boolean = false) extends SupportedChannelType {
     override def features: Set[ChannelTypeFeature] = Set(
       if (scidAlias) Some(Features.ScidAlias) else None,
       if (zeroConf) Some(Features.ZeroConf) else None,
-      Some(Features.SimpleTaprootChannelsStaging),
+      Some(Features.SimpleTaprootChannels),
     ).flatten
     override def commitmentFormat: CommitmentFormat = ZeroFeeHtlcTxSimpleTaprootChannelCommitmentFormat
-    override def toString: String = s"simple_taproot_channel_staging${if (scidAlias) "+scid_alias" else ""}${if (zeroConf) "+zeroconf" else ""}"
+    override def toString: String = s"simple_taproot_channel${if (scidAlias) "+scid_alias" else ""}${if (zeroConf) "+zeroconf" else ""}"
   }
 
   case class UnsupportedChannelType(featureBits: Features[InitFeature]) extends ChannelType {
@@ -127,10 +127,10 @@ object ChannelTypes {
     AnchorOutputsZeroFeeHtlcTx(zeroConf = true),
     AnchorOutputsZeroFeeHtlcTx(scidAlias = true),
     AnchorOutputsZeroFeeHtlcTx(scidAlias = true, zeroConf = true),
-    SimpleTaprootChannelsStaging(),
-    SimpleTaprootChannelsStaging(zeroConf = true),
-    SimpleTaprootChannelsStaging(scidAlias = true),
-    SimpleTaprootChannelsStaging(scidAlias = true, zeroConf = true),
+    SimpleTaprootChannel(),
+    SimpleTaprootChannel(zeroConf = true),
+    SimpleTaprootChannel(scidAlias = true),
+    SimpleTaprootChannel(scidAlias = true, zeroConf = true),
     SimpleTaprootChannelsPhoenix,
   ).map {
     channelType => Features(channelType.features.map(_ -> FeatureSupport.Mandatory).toMap) -> channelType
@@ -150,7 +150,9 @@ object ChannelTypes {
 
   /** Returns our preferred channel type for public channels, if supported by our peer. */
   def preferredForPublicChannels(localFeatures: Features[InitFeature], remoteFeatures: Features[InitFeature]): Option[SupportedChannelType] = {
-    if (Features.canUseFeature(localFeatures, remoteFeatures, Features.AnchorOutputsZeroFeeHtlcTx)) {
+    if (Features.canUseFeature(localFeatures, remoteFeatures, Features.SimpleTaprootChannels)) {
+      Some(SimpleTaprootChannel(scidAlias = Features.canUseFeature(localFeatures, remoteFeatures, Features.ScidAlias)))
+    } else if (Features.canUseFeature(localFeatures, remoteFeatures, Features.AnchorOutputsZeroFeeHtlcTx)) {
       Some(AnchorOutputsZeroFeeHtlcTx(scidAlias = Features.canUseFeature(localFeatures, remoteFeatures, Features.ScidAlias)))
     } else {
       None