replace maxAbsoluteFee by maxMiningFee

It makes much more sense to consider only the mining fee for absolute
fee check, as it is volatile and amount-independent. The service fee is
in % and predictable.

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

@@ -41,14 +41,16 @@ sealed interface LiquidityEvents : NodeEvents {
             sealed class Reason {
                 data object PolicySetToDisabled : Reason()
                 sealed class TooExpensive : Reason() {
-                    data class OverAbsoluteFee(val maxAbsoluteFee: Satoshi) : TooExpensive()
+                    data class OverMaxMiningFee(val maxMiningFee: Satoshi) : TooExpensive()
                     data class OverRelativeFee(val maxRelativeFeeBasisPoints: Int) : TooExpensive()
                 }
+
                 data class OverMaxCredit(val maxAllowedCredit: Satoshi) : TooExpensive()
 
                 data object ChannelInitializing : Reason()
             }
         }
+
         data class AddedToFeeCredit(override val amount: MilliSatoshi, override val fee: MilliSatoshi, override val source: Source) : Decision
         data class Accepted(override val amount: MilliSatoshi, override val fee: MilliSatoshi, override val source: Source) : Decision
     }
@@ -62,8 +64,10 @@ sealed interface SensitiveTaskEvents : NodeEvents {
         data class InteractiveTx(val channelId: ByteVector32, val fundingTxIndex: Long) : TaskIdentifier() {
             constructor(fundingParams: InteractiveTxParams) : this(fundingParams.channelId, (fundingParams.sharedInput as? SharedFundingInput.Multisig2of2)?.fundingTxIndex?.let { it + 1 } ?: 0)
         }
+
         data class IncomingMultiPartPayment(val paymentHash: ByteVector32) : TaskIdentifier()
     }
+
     data class TaskStarted(val id: TaskIdentifier) : SensitiveTaskEvents
     data class TaskEnded(val id: TaskIdentifier) : SensitiveTaskEvents
 

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

@@ -231,9 +231,9 @@ data class NodeParams(
         paymentRecipientExpiryParams = RecipientCltvExpiryParams(CltvExpiryDelta(75), CltvExpiryDelta(200)),
         liquidityPolicy = MutableStateFlow<LiquidityPolicy>(
             LiquidityPolicy.Auto(
-                maxAbsoluteFee = 2_000.sat,
+                maxMiningFee = 2_000.sat,
                 maxRelativeFeeBasisPoints = 3_000 /* 3000 = 30 % */,
-                skipAbsoluteFeeCheck = false,
+                skipMiningFeeCheck = false,
                 maxAllowedCredit = 0.sat
             )
         ),

src/commonMain/kotlin/fr/acinq/lightning/io/Peer.kt

@@ -1037,7 +1037,7 @@ class Peer(
                                 is Origin.PleaseOpenChannelOrigin -> when (val request = channelRequests[origin.requestId]) {
                                     is RequestChannelOpen -> {
                                         val totalFee = origin.serviceFee + origin.miningFee.toMilliSatoshi() - msg.pushAmount
-                                        val decision = nodeParams.liquidityPolicy.value.maybeReject(request.walletInputs.balance.toMilliSatoshi(), totalFee, LiquidityEvents.Source.OnChainWallet, logger, nodeParams.feeCredit.value)
+                                        val decision = nodeParams.liquidityPolicy.value.maybeReject(request.walletInputs.balance.toMilliSatoshi(), totalFee, LiquidityEvents.Source.OnChainWallet, logger, currentFeeCredit = nodeParams.feeCredit.value)
                                         when (decision) {
                                             is LiquidityEvents.Decision.Rejected -> {
                                                 logger.info { "rejecting open_channel2: reason=${decision.reason}" }
@@ -1249,7 +1249,7 @@ class Peer(
                         val (feerate, fee) = client.computeSpliceCpfpFeerate(available.channel.commitments, targetFeerate, spliceWeight = weight, logger)
 
                         logger.info { "requesting splice-in using balance=${cmd.walletInputs.balance} feerate=$feerate fee=$fee" }
-                        val decision = nodeParams.liquidityPolicy.value.maybeReject(cmd.walletInputs.balance.toMilliSatoshi(), fee.toMilliSatoshi(), LiquidityEvents.Source.OnChainWallet, logger, nodeParams.feeCredit.value)
+                        val decision = nodeParams.liquidityPolicy.value.maybeReject(cmd.walletInputs.balance.toMilliSatoshi(), fee.toMilliSatoshi(), LiquidityEvents.Source.OnChainWallet, logger, currentFeeCredit = nodeParams.feeCredit.value)
                         nodeParams._nodeEvents.emit(decision)
                         when (decision) {
                             is LiquidityEvents.Decision.Rejected -> {

src/commonMain/kotlin/fr/acinq/lightning/payment/IncomingPaymentHandler.kt

@@ -258,7 +258,8 @@ class IncomingPaymentHandler(val nodeParams: NodeParams, val db: IncomingPayment
                             val liquidityDecision = if (payment.parts.filterIsInstance<PayToOpenPart>().isNotEmpty()) {
                                 // We consider the total amount received (not only the pay-to-open parts) to evaluate whether or not to accept the payment
                                 val payToOpenFee = payment.parts.filterIsInstance<PayToOpenPart>().map { it.payToOpenRequest.payToOpenFeeSatoshis }.sum()
-                                val decision = nodeParams.liquidityPolicy.value.maybeReject(payment.amountReceived, payToOpenFee.toMilliSatoshi(), LiquidityEvents.Source.OffChainPayment, logger, nodeParams.feeCredit.value)
+                                val liquidity = payment.parts.filterIsInstance<PayToOpenPart>().map { it.payToOpenRequest.liquidity }.sum()
+                                val decision = nodeParams.liquidityPolicy.value.maybeReject(payment.amountReceived, payToOpenFee.toMilliSatoshi(), LiquidityEvents.Source.OffChainPayment, logger, currentFeeCredit = nodeParams.feeCredit.value, liquidity = liquidity)
                                 logger.info { "pay-to-open decision: $decision" }
                                 nodeParams._nodeEvents.emit(decision)
                                 when (decision) {

src/commonMain/kotlin/fr/acinq/lightning/payment/LiquidityPolicy.kt

@@ -15,32 +15,37 @@ sealed class LiquidityPolicy {
 
     /**
      * Allow automated liquidity managements, within relative and absolute fee limits. Both conditions must be met.
-     * @param maxAbsoluteFee max absolute fee
+     * @param maxMiningFee max mining fee
      * @param maxRelativeFeeBasisPoints max relative fee (all included: service fee and mining fee) (1_000 bips = 10 %)
-     * @param skipAbsoluteFeeCheck only applies for off-chain payments, being more lax may make sense when the sender doesn't retry payments
+     * @param skipMiningFeeCheck only applies for off-chain payments, being more lax may make sense when the sender doesn't retry payments
      * @param maxAllowedCredit if other checks fail, accept the payment and add the corresponding amount to fee credit up to this max value (only applies to offline payments, 0 sat to disable)
      */
-    data class Auto(val maxAbsoluteFee: Satoshi, val maxRelativeFeeBasisPoints: Int, val skipAbsoluteFeeCheck: Boolean, val maxAllowedCredit: Satoshi) : LiquidityPolicy()
+    data class Auto(val maxMiningFee: Satoshi, val maxRelativeFeeBasisPoints: Int, val skipMiningFeeCheck: Boolean, val maxAllowedCredit: Satoshi) : LiquidityPolicy()
 
     /** Make decision for a particular liquidity event */
-    fun maybeReject(amount: MilliSatoshi, fee: MilliSatoshi, source: LiquidityEvents.Source, logger: MDCLogger, currentFeeCredit: Satoshi): LiquidityEvents.Decision {
+    fun maybeReject(amount: MilliSatoshi, fee: MilliSatoshi, source: LiquidityEvents.Source, logger: MDCLogger, currentFeeCredit: Satoshi, liquidity: Satoshi = 0.sat): LiquidityEvents.Decision {
+        val serviceFee = when (source) {
+            LiquidityEvents.Source.OnChainWallet -> 0.msat // no service fee for swap-ins
+            LiquidityEvents.Source.OffChainPayment -> (amount + liquidity.toMilliSatoshi()) * 0.01 // 1% service fee
+        }
+        val miningFee = fee - serviceFee
         return when (this) {
             is Disable -> LiquidityEvents.Decision.Rejected(amount, fee, source, LiquidityEvents.Decision.Rejected.Reason.PolicySetToDisabled)
             is Auto -> {
-                val maxAbsoluteFee = if (skipAbsoluteFeeCheck && source == LiquidityEvents.Source.OffChainPayment) Long.MAX_VALUE.msat else this.maxAbsoluteFee.toMilliSatoshi()
+                val maxMiningFee = if (skipMiningFeeCheck && source == LiquidityEvents.Source.OffChainPayment) Long.MAX_VALUE.msat else this.maxMiningFee.toMilliSatoshi()
                 if (maxAllowedCredit == 0.sat || source == LiquidityEvents.Source.OnChainWallet) {
                     val maxRelativeFee = amount * maxRelativeFeeBasisPoints / 10_000
-                    logger.info { "auto liquidity policy check: amount=$amount fee=$fee maxAbsoluteFee=$maxAbsoluteFee maxRelativeFee=$maxRelativeFee policy=$this" }
+                    logger.info { "auto liquidity policy check: amount=$amount fee=$fee (miningFee=$miningFee serviceFee=$serviceFee) maxMiningFee=$maxMiningFee maxRelativeFee=$maxRelativeFee policy=$this" }
                     if (fee > maxRelativeFee) {
                         LiquidityEvents.Decision.Rejected(amount, fee, source, LiquidityEvents.Decision.Rejected.Reason.TooExpensive.OverRelativeFee(maxRelativeFeeBasisPoints))
-                    } else if (fee > maxAbsoluteFee) {
-                        LiquidityEvents.Decision.Rejected(amount, fee, source, LiquidityEvents.Decision.Rejected.Reason.TooExpensive.OverAbsoluteFee(this.maxAbsoluteFee))
+                    } else if (miningFee > maxMiningFee) {
+                        LiquidityEvents.Decision.Rejected(amount, fee, source, LiquidityEvents.Decision.Rejected.Reason.TooExpensive.OverMaxMiningFee(this.maxMiningFee))
                     } else LiquidityEvents.Decision.Accepted(amount, fee, source)
                 } else {
-                    logger.info { "fee-credit liquidity policy check: amount=$amount fee=$fee maxAbsoluteFee=$maxAbsoluteFee currentFeeCredit=$currentFeeCredit maxAllowedCredit=$maxAllowedCredit policy=$this" }
-                    // NB: we do check the max absolute fee, but will never raise an explicit error for it, because the payment will either be added to fee credit or rejected due to exceeding the
+                    logger.info { "fee-credit liquidity policy check: amount=$amount fee=$fee (miningFee=$miningFee serviceFee=$serviceFee) maxMiningFee=$maxMiningFee currentFeeCredit=$currentFeeCredit maxAllowedCredit=$maxAllowedCredit policy=$this" }
+                    // NB: we do check the max mining fee, but will never raise an explicit error for it, because the payment will either be added to fee credit or rejected due to exceeding the
                     // max allowed credit
-                    if (fee <= maxAbsoluteFee && fee < (amount + currentFeeCredit.toMilliSatoshi())) {
+                    if (miningFee <= maxMiningFee && fee < (amount + currentFeeCredit.toMilliSatoshi())) {
                         LiquidityEvents.Decision.Accepted(amount, fee, source)
                     } else if ((amount + currentFeeCredit.toMilliSatoshi()) > maxAllowedCredit.toMilliSatoshi()) {
                         LiquidityEvents.Decision.Rejected(amount, fee, source, LiquidityEvents.Decision.Rejected.Reason.OverMaxCredit(maxAllowedCredit))

src/commonMain/kotlin/fr/acinq/lightning/wire/LightningMessages.kt

@@ -1619,7 +1619,7 @@ data class PayToOpenRequest(
     val paymentHash: ByteVector32,
     val expireAt: Long,
     val finalPacket: OnionRoutingPacket,
-    val liquidity: Satoshi = 0.sat,
+    val liquidity: Satoshi,
     val tlvStream: TlvStream<PayToOpenRequestTlv> = TlvStream.empty(),
 ) : LightningMessage, HasChainHash {
     override val type: Long get() = PayToOpenRequest.type

src/commonTest/kotlin/fr/acinq/lightning/payment/IncomingPaymentHandlerTestsCommon.kt

@@ -248,7 +248,8 @@ class IncomingPaymentHandlerTestsCommon : LightningTestSuite() {
                 hops = channelHops(paymentHandler.nodeParams.nodeId),
                 finalPayload = makeMppPayload(defaultAmount, defaultAmount, randomBytes32()),
                 payloadLength = OnionRoutingPacket.PaymentPacketLength
-            ).third.packet
+            ).third.packet,
+            liquidity = 0.sat
         )
         val result = paymentHandler.process(payToOpenRequest, TestConstants.defaultBlockHeight)
 
@@ -338,7 +339,8 @@ class IncomingPaymentHandlerTestsCommon : LightningTestSuite() {
                 hops = trampolineHops,
                 finalPayload = makeMppPayload(defaultAmount, defaultAmount, paymentSecret.reversed()), // <-- wrong secret
                 payloadLength = 400
-            ).third.packet
+            ).third.packet,
+            liquidity = 0.sat
         )
         val result = paymentHandler.process(payToOpenRequest, TestConstants.defaultBlockHeight)
 
@@ -1405,7 +1407,8 @@ class IncomingPaymentHandlerTestsCommon : LightningTestSuite() {
                     hops = channelHops(TestConstants.Bob.nodeParams.nodeId),
                     finalPayload = finalPayload,
                     payloadLength = OnionRoutingPacket.PaymentPacketLength
-                ).third.packet
+                ).third.packet,
+                liquidity = 0.sat
             )
         }
 

src/commonTest/kotlin/fr/acinq/lightning/payment/LiquidityPolicyTestsCommon.kt

@@ -7,7 +7,6 @@ import fr.acinq.lightning.utils.msat
 import fr.acinq.lightning.utils.sat
 import kotlin.test.Test
 import kotlin.test.assertEquals
-import kotlin.test.assertNull
 
 class LiquidityPolicyTestsCommon : LightningTestSuite() {
 
@@ -16,7 +15,7 @@ class LiquidityPolicyTestsCommon : LightningTestSuite() {
     @Test
     fun `policy rejection`() {
 
-        val policy = LiquidityPolicy.Auto(maxAbsoluteFee = 2_000.sat, maxRelativeFeeBasisPoints = 3_000 /* 3000 = 30 % */, skipAbsoluteFeeCheck = false, maxAllowedCredit = 0.sat)
+        val policy = LiquidityPolicy.Auto(maxMiningFee = 2_000.sat, maxRelativeFeeBasisPoints = 3_000 /* 3000 = 30 % */, skipMiningFeeCheck = false, maxAllowedCredit = 0.sat)
 
         // fee over both absolute and relative
         assertEquals(
@@ -26,7 +25,7 @@ class LiquidityPolicyTestsCommon : LightningTestSuite() {
 
         // fee over absolute
         assertEquals(
-            expected = LiquidityEvents.Decision.Rejected.Reason.TooExpensive.OverAbsoluteFee(policy.maxAbsoluteFee),
+            expected = LiquidityEvents.Decision.Rejected.Reason.TooExpensive.OverMaxMiningFee(policy.maxMiningFee),
             actual = (policy.maybeReject(amount = 15_000_000.msat, fee = 3_000_000.msat, source = LiquidityEvents.Source.OffChainPayment, logger, currentFeeCredit = 0.sat) as? LiquidityEvents.Decision.Rejected)?.reason
         )
 
@@ -45,7 +44,7 @@ class LiquidityPolicyTestsCommon : LightningTestSuite() {
     @Test
     fun `policy rejection skip absolute check`() {
 
-        val policy = LiquidityPolicy.Auto(maxAbsoluteFee = 1_000.sat, maxRelativeFeeBasisPoints = 5_000 /* 3000 = 30 % */, skipAbsoluteFeeCheck = true, maxAllowedCredit = 0.sat)
+        val policy = LiquidityPolicy.Auto(maxMiningFee = 1_000.sat, maxRelativeFeeBasisPoints = 5_000 /* 3000 = 30 % */, skipMiningFeeCheck = true, maxAllowedCredit = 0.sat)
 
         // fee is over absolute, and it's an offchain payment so the check passes
         assertEquals(
@@ -54,7 +53,7 @@ class LiquidityPolicyTestsCommon : LightningTestSuite() {
 
         // fee is over absolute, but it's an on-chain payment so the check fails
         assertEquals(
-            expected = LiquidityEvents.Decision.Rejected.Reason.TooExpensive.OverAbsoluteFee(policy.maxAbsoluteFee),
+            expected = LiquidityEvents.Decision.Rejected.Reason.TooExpensive.OverMaxMiningFee(policy.maxMiningFee),
             actual = (policy.maybeReject(amount = 4_000_000.msat, fee = 2_000_000.msat, source = LiquidityEvents.Source.OnChainWallet, logger, currentFeeCredit = 0.sat) as? LiquidityEvents.Decision.Rejected)?.reason
         )