Remove please_open_channel

It is usually the wallet that decides that it needs a channel, but we
want the LSP to pay the commit fees to allow the wallet user to empty
its wallet over lightning. We previously used a `please_open_channel`
message that was sent by the wallet to the LSP, but it doesn't work
well with liquidity ads.

We remove that message and instead send `open_channel` from the wallet
but with a custom channel flag that tells the LSP that they should be
paying the commit fees. This only works if the LSP adds funds on their
side of the channel, so we couple that with liquidity ads to request
funds from the LSP.

We also add a `recommended_feerates` message from the LSP which lets
the wallet know the on-chain feerates that the LSP will accept for
on-chain funding operations, since those feerates are set in the
`open_channel` message that is now sent by the wallet.

Author: t-bast

src/commonMain/kotlin/fr/acinq/lightning/NodeEvents.kt

@@ -2,7 +2,10 @@ package fr.acinq.lightning
 
 import fr.acinq.bitcoin.ByteVector32
 import fr.acinq.bitcoin.PublicKey
+import fr.acinq.bitcoin.OutPoint
 import fr.acinq.bitcoin.Satoshi
+import fr.acinq.lightning.blockchain.electrum.WalletState
+import fr.acinq.lightning.channel.ChannelManagementFees
 import fr.acinq.lightning.channel.InteractiveTxParams
 import fr.acinq.lightning.channel.SharedFundingInput
 import fr.acinq.lightning.channel.states.ChannelStateWithCommitments
@@ -11,16 +14,18 @@ import fr.acinq.lightning.channel.states.WaitForFundingCreated
 import fr.acinq.lightning.db.IncomingPayment
 import fr.acinq.lightning.utils.sum
 import fr.acinq.lightning.wire.Init
-import fr.acinq.lightning.wire.PleaseOpenChannel
-import kotlinx.coroutines.CompletableDeferred
 
 sealed interface NodeEvents
 
 data class PeerConnected(val remoteNodeId: PublicKey, val theirInit: Init) : NodeEvents
 
 sealed interface SwapInEvents : NodeEvents {
-    data class Requested(val req: PleaseOpenChannel) : SwapInEvents
-    data class Accepted(val requestId: ByteVector32, val serviceFee: MilliSatoshi, val miningFee: Satoshi) : SwapInEvents
+    data class Requested(val walletInputs: List<WalletState.Utxo>) : SwapInEvents {
+        val totalAmount: Satoshi = walletInputs.map { it.amount }.sum()
+    }
+    data class Accepted(val inputs: Set<OutPoint>, val amount: Satoshi, val fees: ChannelManagementFees) : SwapInEvents {
+        val receivedAmount: Satoshi = amount - fees.total
+    }
 }
 
 sealed interface ChannelEvents : NodeEvents {
@@ -30,6 +35,7 @@ sealed interface ChannelEvents : NodeEvents {
 }
 
 sealed interface LiquidityEvents : NodeEvents {
+    /** Amount of the liquidity event, before fees are paid. */
     val amount: MilliSatoshi
     val fee: MilliSatoshi
     val source: Source
@@ -45,8 +51,7 @@ sealed interface LiquidityEvents : NodeEvents {
             data object ChannelInitializing : Reason()
         }
     }
-
-    data class ApprovalRequested(override val amount: MilliSatoshi, override val fee: MilliSatoshi, override val source: Source, val replyTo: CompletableDeferred<Boolean>) : LiquidityEvents
+    data class Accepted(override val amount: MilliSatoshi, override val fee: MilliSatoshi, override val source: Source) : LiquidityEvents
 }
 
 /** This is useful on iOS to ask the OS for time to finish some sensitive tasks. */
@@ -59,7 +64,6 @@ sealed interface SensitiveTaskEvents : NodeEvents {
     }
     data class TaskStarted(val id: TaskIdentifier) : SensitiveTaskEvents
     data class TaskEnded(val id: TaskIdentifier) : SensitiveTaskEvents
-
 }
 
 /** This will be emitted in a corner case where the user restores a wallet on an older version of the app, which is unable to read the channel data. */

src/commonMain/kotlin/fr/acinq/lightning/NodeParams.kt

@@ -12,6 +12,7 @@ import fr.acinq.lightning.payment.LiquidityPolicy
 import fr.acinq.lightning.utils.msat
 import fr.acinq.lightning.utils.sat
 import fr.acinq.lightning.utils.toMilliSatoshi
+import fr.acinq.lightning.wire.LiquidityAds
 import fr.acinq.lightning.wire.OfferTypes
 import io.ktor.utils.io.charsets.*
 import io.ktor.utils.io.core.*
@@ -69,12 +70,14 @@ object DefaultSwapInParams {
  * @param trampolineFees ordered list of trampoline fees to try when making an outgoing payment.
  * @param invoiceDefaultRoutingFees default routing fees set in invoices when we don't have any channel.
  * @param swapInParams parameters for swap-in transactions.
+ * @param leaseRate rate at which our peer sells their liquidity.
  */
 data class WalletParams(
     val trampolineNode: NodeUri,
     val trampolineFees: List<TrampolineFees>,
     val invoiceDefaultRoutingFees: InvoiceDefaultRoutingFees,
     val swapInParams: SwapInParams,
+    val leaseRate: LiquidityAds.LeaseRate,
 )
 
 /**
@@ -229,7 +232,7 @@ data class NodeParams(
         maxPaymentAttempts = 5,
         zeroConfPeers = emptySet(),
         paymentRecipientExpiryParams = RecipientCltvExpiryParams(CltvExpiryDelta(75), CltvExpiryDelta(200)),
-        liquidityPolicy = MutableStateFlow<LiquidityPolicy>(LiquidityPolicy.Auto(maxAbsoluteFee = 2_000.sat, maxRelativeFeeBasisPoints = 3_000 /* 3000 = 30 % */, skipAbsoluteFeeCheck = false)),
+        liquidityPolicy = MutableStateFlow<LiquidityPolicy>(LiquidityPolicy.Auto(inboundLiquidityTarget = null, maxAbsoluteFee = 2_000.sat, maxRelativeFeeBasisPoints = 3_000 /* 3000 = 30 % */, skipAbsoluteFeeCheck = false)),
         minFinalCltvExpiryDelta = Bolt11Invoice.DEFAULT_MIN_FINAL_EXPIRY_DELTA,
         maxFinalCltvExpiryDelta = CltvExpiryDelta(360),
         bolt12invoiceExpiry = 60.seconds,

src/commonMain/kotlin/fr/acinq/lightning/blockchain/electrum/SwapInManager.kt

@@ -2,21 +2,18 @@ package fr.acinq.lightning.blockchain.electrum
 
 import fr.acinq.bitcoin.OutPoint
 import fr.acinq.bitcoin.Transaction
-import fr.acinq.bitcoin.TxId
-import fr.acinq.lightning.Lightning
 import fr.acinq.lightning.SwapInParams
 import fr.acinq.lightning.channel.FundingContributions.Companion.stripInputWitnesses
 import fr.acinq.lightning.channel.LocalFundingStatus
 import fr.acinq.lightning.channel.RbfStatus
-import fr.acinq.lightning.channel.SignedSharedTransaction
 import fr.acinq.lightning.channel.SpliceStatus
 import fr.acinq.lightning.channel.states.*
-import fr.acinq.lightning.io.RequestChannelOpen
+import fr.acinq.lightning.io.AddWalletInputsToChannel
 import fr.acinq.lightning.logging.MDCLogger
 import fr.acinq.lightning.utils.sat
 
 internal sealed class SwapInCommand {
-    data class TrySwapIn(val currentBlockHeight: Int, val wallet: WalletState, val swapInParams: SwapInParams, val trustedTxs: Set<TxId>) : SwapInCommand()
+    data class TrySwapIn(val currentBlockHeight: Int, val wallet: WalletState, val swapInParams: SwapInParams) : SwapInCommand()
     data class UnlockWalletInputs(val inputs: Set<OutPoint>) : SwapInCommand()
 }
 
@@ -33,20 +30,15 @@ internal sealed class SwapInCommand {
 class SwapInManager(private var reservedUtxos: Set<OutPoint>, private val logger: MDCLogger) {
     constructor(bootChannels: List<PersistedChannelState>, logger: MDCLogger) : this(reservedWalletInputs(bootChannels), logger)
 
-    internal fun process(cmd: SwapInCommand): RequestChannelOpen? = when (cmd) {
+    internal fun process(cmd: SwapInCommand): AddWalletInputsToChannel? = when (cmd) {
         is SwapInCommand.TrySwapIn -> {
             val availableWallet = cmd.wallet.withoutReservedUtxos(reservedUtxos).withConfirmations(cmd.currentBlockHeight, cmd.swapInParams)
             logger.info { "swap-in wallet balance: deeplyConfirmed=${availableWallet.deeplyConfirmed.balance}, weaklyConfirmed=${availableWallet.weaklyConfirmed.balance}, unconfirmed=${availableWallet.unconfirmed.balance}" }
-            val utxos = buildSet {
-                // some utxos may be used for swap-in even if they are not confirmed, for example when migrating from the legacy phoenix android app
-                addAll(availableWallet.unconfirmed.filter { cmd.trustedTxs.contains(it.outPoint.txid) })
-                addAll(availableWallet.weaklyConfirmed.filter { cmd.trustedTxs.contains(it.outPoint.txid) })
-                addAll(availableWallet.deeplyConfirmed.filter { Transaction.write(it.previousTx.stripInputWitnesses()).size < 65_000 })
-            }.toList()
+            val utxos = availableWallet.deeplyConfirmed.filter { Transaction.write(it.previousTx.stripInputWitnesses()).size < 65_000 }
             if (utxos.balance > 0.sat) {
                 logger.info { "swap-in wallet: requesting channel using ${utxos.size} utxos with balance=${utxos.balance}" }
                 reservedUtxos = reservedUtxos.union(utxos.map { it.outPoint })
-                RequestChannelOpen(Lightning.randomBytes32(), utxos)
+                AddWalletInputsToChannel(utxos)
             } else {
                 null
             }

src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelAction.kt

@@ -1,9 +1,9 @@
 package fr.acinq.lightning.channel
 
 import fr.acinq.bitcoin.*
-import fr.acinq.lightning.ChannelEvents
 import fr.acinq.lightning.CltvExpiry
 import fr.acinq.lightning.MilliSatoshi
+import fr.acinq.lightning.NodeEvents
 import fr.acinq.lightning.blockchain.Watch
 import fr.acinq.lightning.channel.states.PersistedChannelState
 import fr.acinq.lightning.db.ChannelClosingType
@@ -79,7 +79,7 @@ sealed class ChannelAction {
             abstract val txId: TxId
             abstract val localInputs: Set<OutPoint>
             data class ViaNewChannel(val amount: MilliSatoshi, val serviceFee: MilliSatoshi, val miningFee: Satoshi, override val localInputs: Set<OutPoint>, override val txId: TxId, override val origin: Origin?) : StoreIncomingPayment()
-            data class ViaSpliceIn(val amount: MilliSatoshi, val serviceFee: MilliSatoshi, val miningFee: Satoshi, override val localInputs: Set<OutPoint>, override val txId: TxId, override val origin: Origin.PayToOpenOrigin?) : StoreIncomingPayment()
+            data class ViaSpliceIn(val amount: MilliSatoshi, val serviceFee: MilliSatoshi, val miningFee: Satoshi, override val localInputs: Set<OutPoint>, override val txId: TxId, override val origin: Origin?) : StoreIncomingPayment()
         }
         /** Payment sent through on-chain operations (channel close or splice-out) */
         sealed class StoreOutgoingPayment : Storage() {
@@ -128,8 +128,8 @@ sealed class ChannelAction {
         }
     }
 
-    data class EmitEvent(val event: ChannelEvents) : ChannelAction()
+    data class EmitEvent(val event: NodeEvents) : ChannelAction()
 
-    object Disconnect : ChannelAction()
+    data object Disconnect : ChannelAction()
     // @formatter:on
 }

src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelCommand.kt

@@ -32,10 +32,11 @@ sealed class ChannelCommand {
             val fundingTxFeerate: FeeratePerKw,
             val localParams: LocalParams,
             val remoteInit: InitMessage,
-            val channelFlags: Byte,
+            val channelFlags: ChannelFlags,
             val channelConfig: ChannelConfig,
             val channelType: ChannelType.SupportedChannelType,
-            val channelOrigin: Origin? = null
+            val requestRemoteFunding: LiquidityAds.RequestRemoteFunding?,
+            val channelOrigin: Origin?,
         ) : Init() {
             fun temporaryChannelId(keyManager: KeyManager): ByteVector32 = keyManager.channelKeys(localParams.fundingKeyPath).temporaryChannelId
         }
@@ -85,7 +86,7 @@ sealed class ChannelCommand {
         data class UpdateFee(val feerate: FeeratePerKw, val commit: Boolean = false) : Commitment(), ForbiddenDuringSplice, ForbiddenDuringQuiescence
         data object CheckHtlcTimeout : Commitment()
         sealed class Splice : Commitment() {
-            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() {
+            data class Request(val replyTo: CompletableDeferred<Response>, val spliceIn: SpliceIn?, val spliceOut: SpliceOut?, val requestRemoteFunding: LiquidityAds.RequestRemoteFunding?, val feerate: FeeratePerKw, val origins: List<Origin>) : Splice() {
                 val pushAmount: MilliSatoshi = spliceIn?.pushAmount ?: 0.msat
                 val spliceOutputs: List<TxOut> = spliceOut?.let { listOf(TxOut(it.amount, it.scriptPubKey)) } ?: emptyList()
 

src/commonMain/kotlin/fr/acinq/lightning/channel/ChannelData.kt

@@ -350,23 +350,29 @@ data class LocalParams(
     val htlcMinimum: MilliSatoshi,
     val toSelfDelay: CltvExpiryDelta,
     val maxAcceptedHtlcs: Int,
-    val isInitiator: Boolean,
+    val isChannelOpener: Boolean,
+    val paysCommitTxFees: Boolean,
     val defaultFinalScriptPubKey: ByteVector,
     val features: Features
 ) {
-    constructor(nodeParams: NodeParams, isInitiator: Boolean) : this(
+    constructor(nodeParams: NodeParams, isChannelOpener: Boolean, payCommitTxFees: Boolean) : this(
         nodeId = nodeParams.nodeId,
-        fundingKeyPath = nodeParams.keyManager.newFundingKeyPath(isInitiator), // we make sure that initiator and non-initiator key path end differently
+        fundingKeyPath = nodeParams.keyManager.newFundingKeyPath(isChannelOpener), // we make sure that initiator and non-initiator key path end differently
         dustLimit = nodeParams.dustLimit,
         maxHtlcValueInFlightMsat = nodeParams.maxHtlcValueInFlightMsat,
         htlcMinimum = nodeParams.htlcMinimum,
         toSelfDelay = nodeParams.toRemoteDelayBlocks, // we choose their delay
         maxAcceptedHtlcs = nodeParams.maxAcceptedHtlcs,
-        isInitiator = isInitiator,
+        isChannelOpener = isChannelOpener,
+        paysCommitTxFees = payCommitTxFees,
         defaultFinalScriptPubKey = nodeParams.keyManager.finalOnChainWallet.pubkeyScript(addressIndex = 0), // the default closing address is the same for all channels
         features = nodeParams.features.initFeatures()
     )
 
+    // The node responsible for the commit tx fees is also the node paying the mutual close fees.
+    // The other node's balance may be empty, which wouldn't allow them to pay the closing fees.
+    val paysClosingFees: Boolean = paysCommitTxFees
+
     fun channelKeys(keyManager: KeyManager) = keyManager.channelKeys(fundingKeyPath)
 }
 
@@ -384,10 +390,11 @@ data class RemoteParams(
     val features: Features
 )
 
-object ChannelFlags {
-    const val AnnounceChannel = 0x01.toByte()
-    const val Empty = 0x00.toByte()
-}
+/**
+ * The [nonInitiatorPaysCommitFees] parameter can be set to true when the sender wants the receiver to pay the commitment transaction fees.
+ * This is not part of the BOLTs and won't be needed anymore once commitment transactions don't pay any on-chain fees.
+ */
+data class ChannelFlags(val announceChannel: Boolean, val nonInitiatorPaysCommitFees: Boolean)
 
 data class ClosingTxProposed(val unsignedTx: ClosingTx, val localClosingSigned: ClosingSigned)
 
@@ -399,13 +406,17 @@ data class ChannelManagementFees(val miningFee: Satoshi, val serviceFee: Satoshi
     val total: Satoshi = miningFee + serviceFee
 }
 
-/** Reason for creating a new channel or a splice. */
+/** Reason for creating a new channel or splicing into an existing channel. */
 // @formatter:off
 sealed class Origin {
+    /** Amount of the origin payment, before fees are paid. */
     abstract val amount: MilliSatoshi
-    abstract val serviceFee: MilliSatoshi
-    abstract val miningFee: Satoshi
-    data class PayToOpenOrigin(val paymentHash: ByteVector32, override val serviceFee: MilliSatoshi, override val miningFee: Satoshi, override val amount: MilliSatoshi) : Origin()
-    data class PleaseOpenChannelOrigin(val requestId: ByteVector32, override val serviceFee: MilliSatoshi, override val miningFee: Satoshi, override val amount: MilliSatoshi) : Origin()
+    /** Fees applied for the channel funding transaction. */
+    abstract val fees: ChannelManagementFees
+
+    data class OnChainWallet(val inputs: Set<OutPoint>, override val amount: MilliSatoshi, override val fees: ChannelManagementFees) : Origin()
+    data class OffChainPayment(val paymentPreimage: ByteVector32, override val amount: MilliSatoshi, override val fees: ChannelManagementFees) : Origin() {
+        val paymentHash: ByteVector32 = Crypto.sha256(paymentPreimage).byteVector32()
+    }
 }
 // @formatter:on