Implement simple taproot channels

This matches changes done on Eclair, and adds support for taproot channels (including splices) with the same TLV extensions.
Support for signing commit tx with alternative feerates is not implemented.

Author: sstone

modules/core/src/commonMain/kotlin/fr/acinq/lightning/Features.kt

@@ -217,6 +217,13 @@ sealed class Feature {
         override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
+    // README: this is not the feature bit specified in the BOLT, this one is specific to Phoenix
+    @Serializable
+    object SimpleTaprootChannels : Feature() {
+        override val rfcName get() = "simple_taproot_channels"
+        override val mandatory get() = 564
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
+    }
 }
 
 @Serializable
@@ -294,7 +301,8 @@ data class Features(val activated: Map<Feature, FeatureSupport>, val unknown: Se
             Feature.WakeUpNotificationProvider,
             Feature.ExperimentalSplice,
             Feature.OnTheFlyFunding,
-            Feature.FundingFeeCredit
+            Feature.FundingFeeCredit,
+            Feature.SimpleTaprootChannels
         )
 
         operator fun invoke(bytes: ByteVector): Features = invoke(bytes.toByteArray())

modules/core/src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelException.kt

@@ -92,4 +92,9 @@ data class PleasePublishYourCommitment             (override val channelId: Byte
 data class CommandUnavailableInThisState           (override val channelId: ByteVector32, val state: String) : ChannelException(channelId, "cannot execute command in state=$state")
 data class ForbiddenDuringSplice                   (override val channelId: ByteVector32, val command: String?) : ChannelException(channelId, "cannot process $command while splicing")
 data class InvalidSpliceRequest                    (override val channelId: ByteVector32) : ChannelException(channelId, "invalid splice request")
+data class MissingCommitNonce                      (override val channelId: ByteVector32, val fundingTxId: TxId, val commitmentNumber: Long) : ChannelException(channelId, "missing commit nonce for funding tx $fundingTxId commitmentNumber $commitmentNumber")
+data class InvalidCommitNonce                      (override val channelId: ByteVector32, val fundingTxId: TxId, val commitmentNumber: Long) : ChannelException(channelId, "invalid commit nonce for funding tx $fundingTxId commitmentNumber $commitmentNumber")
+data class MissingFundingNonce                     (override val channelId: ByteVector32, val fundingTxId: TxId) : ChannelException(channelId, "missing funding nonce for funding tx $fundingTxId")
+data class InvalidFundingNonce                     (override val channelId: ByteVector32, val fundingTxId: TxId) : ChannelException(channelId, "invalid funding nonce for funding tx $fundingTxId")
+data class MissingClosingNonce                     (override val channelId: ByteVector32) : ChannelException(channelId, "missing closing nonce")
 // @formatter:on

modules/core/src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelFeatures.kt

@@ -32,7 +32,7 @@ data class ChannelFeatures(val features: Set<Feature>) {
          * In addition to channel types features, the following features will be added to the permanent channel features if they
          * are supported by both peers.
          */
-        private val permanentChannelFeatures = setOf(Feature.DualFunding)
+        private val permanentChannelFeatures: Set<Feature> = setOf(Feature.DualFunding)
     }
 
 }
@@ -65,6 +65,12 @@ sealed class ChannelType {
             override val commitmentFormat: Transactions.CommitmentFormat get() = Transactions.CommitmentFormat.AnchorOutputs
         }
 
+        object SimpleTaprootChannels : SupportedChannelType() {
+            override val name: String get() = "simple_taproot_channel"
+            override val features: Set<Feature> get() = setOf(Feature.SimpleTaprootChannels, Feature.ZeroReserveChannels)
+            override val permanentChannelFeatures: Set<Feature> get() = setOf(Feature.ZeroReserveChannels)
+            override val commitmentFormat: Transactions.CommitmentFormat get() = Transactions.CommitmentFormat.SimpleTaprootChannels
+        }
     }
 
     data class UnsupportedChannelType(val featureBits: Features) : ChannelType() {
@@ -79,6 +85,7 @@ sealed class ChannelType {
         // NB: Bolt 2: features must exactly match in order to identify a channel type.
         fun fromFeatures(features: Features): ChannelType = when (features) {
             // @formatter:off
+            Features(Feature.SimpleTaprootChannels to FeatureSupport.Mandatory, Feature.ZeroReserveChannels to FeatureSupport.Mandatory) -> SupportedChannelType.SimpleTaprootChannels
             Features(Feature.StaticRemoteKey to FeatureSupport.Mandatory, Feature.AnchorOutputs to FeatureSupport.Mandatory, Feature.ZeroReserveChannels to FeatureSupport.Mandatory) -> SupportedChannelType.AnchorOutputsZeroReserve
             Features(Feature.StaticRemoteKey to FeatureSupport.Mandatory, Feature.AnchorOutputs to FeatureSupport.Mandatory) -> SupportedChannelType.AnchorOutputs
             else -> UnsupportedChannelType(features)