Purchase liquidity using a splice

We allow purchasing inbound liquidity by initiating an empty splice, similar to what we do for CPFP. If the remote doesn't fund, or its rates are too expensive, we immediately abort the splice attempt.
ACINQ · Nov 29, 2023 · d698cd9 · d698cd9
1 parent c1f0b1b
commit d698cd9
Show file tree

Hide file tree

Showing 8 changed files with 187 additions and 60 deletions.
diff --git a/src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelCommand.kt b/src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelCommand.kt
@@ -13,6 +13,7 @@ import fr.acinq.lightning.utils.UUID
 import fr.acinq.lightning.utils.msat
 import fr.acinq.lightning.wire.FailureMessage
 import fr.acinq.lightning.wire.LightningMessage
+import fr.acinq.lightning.wire.LiquidityAds
 import fr.acinq.lightning.wire.OnionRoutingPacket
 import kotlinx.coroutines.CompletableDeferred
 import fr.acinq.lightning.wire.Init as InitMessage
@@ -83,7 +84,7 @@ sealed class ChannelCommand {
         data class UpdateFee(val feerate: FeeratePerKw, val commit: Boolean = false) : Commitment(), ForbiddenDuringSplice
         object CheckHtlcTimeout : Commitment()
         sealed class Splice : Commitment() {
-            data class Request(val replyTo: CompletableDeferred<Response>, val spliceIn: SpliceIn?, val spliceOut: SpliceOut?, val feerate: FeeratePerKw, val origins: List<Origin.PayToOpenOrigin> = emptyList()) : Splice() {
+            data class Request(val replyTo: CompletableDeferred<Response>, val spliceIn: SpliceIn?, val spliceOut: SpliceOut?, val requestRemoteFunding: LiquidityAds.RequestRemoteFunding?, val feerate: FeeratePerKw, val origins: List<Origin.PayToOpenOrigin> = emptyList()) : Splice() {
                 val pushAmount: MilliSatoshi = spliceIn?.pushAmount ?: 0.msat
                 val spliceOutputs: List<TxOut> = spliceOut?.let { listOf(TxOut(it.amount, it.scriptPubKey)) } ?: emptyList()
 
@@ -101,14 +102,16 @@ sealed class ChannelCommand {
                     val fundingTxIndex: Long,
                     val fundingTxId: TxId,
                     val capacity: Satoshi,
-                    val balance: MilliSatoshi
+                    val balance: MilliSatoshi,
+                    val liquidityPurchased: LiquidityAds.Lease?,
                 ) : Response()
 
                 sealed class Failure : Response() {
                     object InsufficientFunds : Failure()
                     object InvalidSpliceOutPubKeyScript : Failure()
                     object SpliceAlreadyInProgress : Failure()
                     object ChannelNotIdle : Failure()
+                    data class InvalidLiquidityAds(val reason: ChannelException) : Failure()
                     data class FundingFailure(val reason: FundingContributionFailure) : Failure()
                     object CannotStartSession : Failure()
                     data class InteractiveTxSessionFailed(val reason: InteractiveTxSessionAction.RemoteFailure) : Failure()

diff --git a/src/commonMain/kotlin/fr/acinq/lightning/channel/InteractiveTx.kt b/src/commonMain/kotlin/fr/acinq/lightning/channel/InteractiveTx.kt
@@ -826,6 +826,7 @@ data class InteractiveTxSigningSession(
             sharedTx: SharedTransaction,
             localPushAmount: MilliSatoshi,
             remotePushAmount: MilliSatoshi,
+            liquidityPurchased: LiquidityAds.Lease?,
             localCommitmentIndex: Long,
             remoteCommitmentIndex: Long,
             commitTxFeerate: FeeratePerKw,
@@ -834,13 +835,14 @@ data class InteractiveTxSigningSession(
             val channelKeys = channelParams.localParams.channelKeys(keyManager)
             val unsignedTx = sharedTx.buildUnsignedTx()
             val sharedOutputIndex = unsignedTx.txOut.indexOfFirst { it.publicKeyScript == fundingParams.fundingPubkeyScript(channelKeys) }
+            val liquidityFees = liquidityPurchased?.fees?.toMilliSatoshi() ?: 0.msat
             return Helpers.Funding.makeCommitTxsWithoutHtlcs(
                 channelKeys,
                 channelParams.channelId,
                 channelParams.localParams, channelParams.remoteParams,
                 fundingAmount = sharedTx.sharedOutput.amount,
-                toLocal = sharedTx.sharedOutput.localAmount - localPushAmount + remotePushAmount,
-                toRemote = sharedTx.sharedOutput.remoteAmount - remotePushAmount + localPushAmount,
+                toLocal = sharedTx.sharedOutput.localAmount - localPushAmount + remotePushAmount - liquidityFees,
+                toRemote = sharedTx.sharedOutput.remoteAmount - remotePushAmount + localPushAmount + liquidityFees,
                 localCommitmentIndex = localCommitmentIndex,
                 remoteCommitmentIndex = remoteCommitmentIndex,
                 commitTxFeerate,
@@ -900,7 +902,14 @@ sealed class RbfStatus {
 sealed class SpliceStatus {
     object None : SpliceStatus()
     data class Requested(val command: ChannelCommand.Commitment.Splice.Request, val spliceInit: SpliceInit) : SpliceStatus()
-    data class InProgress(val replyTo: CompletableDeferred<ChannelCommand.Commitment.Splice.Response>?, val spliceSession: InteractiveTxSession, val localPushAmount: MilliSatoshi, val remotePushAmount: MilliSatoshi, val origins: List<Origin.PayToOpenOrigin>) : SpliceStatus()
+    data class InProgress(
+        val replyTo: CompletableDeferred<ChannelCommand.Commitment.Splice.Response>?,
+        val spliceSession: InteractiveTxSession,
+        val localPushAmount: MilliSatoshi,
+        val remotePushAmount: MilliSatoshi,
+        val liquidityPurchased: LiquidityAds.Lease?,
+        val origins: List<Origin.PayToOpenOrigin>
+    ) : SpliceStatus()
     data class WaitingForSigs(val session: InteractiveTxSigningSession, val origins: List<Origin.PayToOpenOrigin>) : SpliceStatus()
     object Aborted : SpliceStatus()
 }