Add recommended_feerates optional message (#2860)

We send to our peers an optional message that tells them the feerates
we'd like to use for funding channels. This lets them know which values
are acceptable to us, in case we reject their funding requests.

This is using an odd type and will be automatically ignored by existing
nodes who don't support that feature.

Co-authored-by: Pierre-Marie Padiou <[email protected]>

Author: t-bast

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

@@ -381,9 +381,9 @@ class EclairImpl(appKit: Kit) extends Eclair with Logging {
   override def sendOnChain(address: String, amount: Satoshi, confirmationTargetOrFeerate: Either[Long, FeeratePerByte]): Future[TxId] = {
     val feeRate = confirmationTargetOrFeerate match {
       case Left(blocks) =>
-        if (blocks < 3) appKit.nodeParams.currentFeerates.fast
-        else if (blocks > 6) appKit.nodeParams.currentFeerates.slow
-        else appKit.nodeParams.currentFeerates.medium
+        if (blocks < 3) appKit.nodeParams.currentBitcoinCoreFeerates.fast
+        else if (blocks > 6) appKit.nodeParams.currentBitcoinCoreFeerates.slow
+        else appKit.nodeParams.currentBitcoinCoreFeerates.medium
       case Right(feeratePerByte) => FeeratePerKw(feeratePerByte)
     }
     appKit.wallet match {

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

@@ -21,9 +21,9 @@ import fr.acinq.bitcoin.scalacompat.Crypto.PublicKey
 import fr.acinq.bitcoin.scalacompat.{Block, BlockHash, Crypto, Satoshi, SatoshiLong}
 import fr.acinq.eclair.Setup.Seeds
 import fr.acinq.eclair.blockchain.fee._
-import fr.acinq.eclair.channel.ChannelFlags
 import fr.acinq.eclair.channel.fsm.Channel
 import fr.acinq.eclair.channel.fsm.Channel.{BalanceThreshold, ChannelConf, UnhandledExceptionStrategy}
+import fr.acinq.eclair.channel.{ChannelFlags, ChannelTypes}
 import fr.acinq.eclair.crypto.Noise.KeyPair
 import fr.acinq.eclair.crypto.keymanager.{ChannelKeyManager, NodeKeyManager, OnChainKeyManager}
 import fr.acinq.eclair.db._
@@ -36,6 +36,7 @@ import fr.acinq.eclair.router.Graph.{HeuristicsConstants, WeightRatios}
 import fr.acinq.eclair.router.Router._
 import fr.acinq.eclair.router.{Graph, PathFindingExperimentConf}
 import fr.acinq.eclair.tor.Socks5ProxyParams
+import fr.acinq.eclair.transactions.Transactions
 import fr.acinq.eclair.wire.protocol._
 import grizzled.slf4j.Logging
 import scodec.bits.ByteVector
@@ -57,7 +58,7 @@ case class NodeParams(nodeKeyManager: NodeKeyManager,
                       onChainKeyManager_opt: Option[OnChainKeyManager],
                       instanceId: UUID, // a unique instance ID regenerated after each restart
                       private val blockHeight: AtomicLong,
-                      private val feerates: AtomicReference[FeeratesPerKw],
+                      private val bitcoinCoreFeerates: AtomicReference[FeeratesPerKw],
                       alias: String,
                       color: Color,
                       publicAddresses: List[NodeAddress],
@@ -102,13 +103,34 @@ case class NodeParams(nodeKeyManager: NodeKeyManager,
 
   def currentBlockHeight: BlockHeight = BlockHeight(blockHeight.get)
 
-  def currentFeerates: FeeratesPerKw = feerates.get()
+  def currentBitcoinCoreFeerates: FeeratesPerKw = bitcoinCoreFeerates.get()
 
   /** Only to be used in tests. */
-  def setFeerates(value: FeeratesPerKw): Unit = feerates.set(value)
+  def setBitcoinCoreFeerates(value: FeeratesPerKw): Unit = bitcoinCoreFeerates.set(value)
 
   /** Returns the features that should be used in our init message with the given peer. */
   def initFeaturesFor(nodeId: PublicKey): Features[InitFeature] = overrideInitFeatures.getOrElse(nodeId, features).initFeatures()
+
+  /** Returns the feerates we'd like our peer to use when funding channels. */
+  def recommendedFeerates(remoteNodeId: PublicKey, localFeatures: Features[InitFeature], remoteFeatures: Features[InitFeature]): RecommendedFeerates = {
+    val feerateTolerance = onChainFeeConf.feerateToleranceFor(remoteNodeId)
+    val fundingFeerate = onChainFeeConf.getFundingFeerate(currentBitcoinCoreFeerates)
+    val fundingRange = RecommendedFeeratesTlv.FundingFeerateRange(
+      min = fundingFeerate * feerateTolerance.ratioLow,
+      max = fundingFeerate * feerateTolerance.ratioHigh,
+    )
+    // We use the most likely commitment format, even though there is no guarantee that this is the one that will be used.
+    val commitmentFormat = ChannelTypes.defaultFromFeatures(localFeatures, remoteFeatures, announceChannel = false).commitmentFormat
+    val commitmentFeerate = onChainFeeConf.getCommitmentFeerate(currentBitcoinCoreFeerates, remoteNodeId, commitmentFormat, channelConf.minFundingPrivateSatoshis)
+    val commitmentRange = RecommendedFeeratesTlv.CommitmentFeerateRange(
+      min = commitmentFeerate * feerateTolerance.ratioLow,
+      max = commitmentFormat match {
+        case Transactions.DefaultCommitmentFormat => commitmentFeerate * feerateTolerance.ratioHigh
+        case _: Transactions.AnchorOutputsCommitmentFormat => (commitmentFeerate * feerateTolerance.ratioHigh).max(feerateTolerance.anchorOutputMaxCommitFeerate)
+      },
+    )
+    RecommendedFeerates(chainHash, fundingFeerate, commitmentFeerate, TlvStream(fundingRange, commitmentRange))
+  }
 }
 
 case class PaymentFinalExpiryConf(min: CltvExpiryDelta, max: CltvExpiryDelta) {
@@ -219,7 +241,7 @@ object NodeParams extends Logging {
 
   def makeNodeParams(config: Config, instanceId: UUID,
                      nodeKeyManager: NodeKeyManager, channelKeyManager: ChannelKeyManager, onChainKeyManager_opt: Option[OnChainKeyManager],
-                     torAddress_opt: Option[NodeAddress], database: Databases, blockHeight: AtomicLong, feerates: AtomicReference[FeeratesPerKw],
+                     torAddress_opt: Option[NodeAddress], database: Databases, blockHeight: AtomicLong, bitcoinCoreFeerates: AtomicReference[FeeratesPerKw],
                      pluginParams: Seq[PluginParams] = Nil): NodeParams = {
     // check configuration for keys that have been renamed
     val deprecatedKeyPaths = Map(
@@ -513,7 +535,7 @@ object NodeParams extends Logging {
       onChainKeyManager_opt = onChainKeyManager_opt,
       instanceId = instanceId,
       blockHeight = blockHeight,
-      feerates = feerates,
+      bitcoinCoreFeerates = bitcoinCoreFeerates,
       alias = nodeAlias,
       color = Color(color(0), color(1), color(2)),
       publicAddresses = addresses,

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

@@ -255,7 +255,7 @@ class Setup(val datadir: File,
           blockchain.Monitoring.Metrics.FeeratesPerByte.withTag(blockchain.Monitoring.Tags.Priority, blockchain.Monitoring.Tags.Priorities.Medium).update(feeratesPerKw.get.medium.toLong.toDouble)
           blockchain.Monitoring.Metrics.FeeratesPerByte.withTag(blockchain.Monitoring.Tags.Priority, blockchain.Monitoring.Tags.Priorities.Fast).update(feeratesPerKw.get.fast.toLong.toDouble)
           blockchain.Monitoring.Metrics.FeeratesPerByte.withTag(blockchain.Monitoring.Tags.Priority, blockchain.Monitoring.Tags.Priorities.Fastest).update(feeratesPerKw.get.fastest.toLong.toDouble)
-          system.eventStream.publish(CurrentFeerates(feeratesPerKw.get))
+          system.eventStream.publish(CurrentFeerates.BitcoinCore(feeratesPerKw.get))
           logger.info(s"current feeratesPerKB=$feeratesPerKB feeratesPerKw=${feeratesPerKw.get}")
           feeratesRetrieved.trySuccess(Done)
         case Failure(exception) =>

eclair-core/src/main/scala/fr/acinq/eclair/blockchain/BlockchainEvents.scala

@@ -32,4 +32,14 @@ case class NewTransaction(tx: Transaction) extends BlockchainEvent
 
 case class CurrentBlockHeight(blockHeight: BlockHeight) extends BlockchainEvent
 
-case class CurrentFeerates(feeratesPerKw: FeeratesPerKw) extends BlockchainEvent
+sealed trait CurrentFeerates extends BlockchainEvent {
+  val feeratesPerKw: FeeratesPerKw
+}
+
+object CurrentFeerates {
+  //@formatter:off
+  case class BitcoinCore(feeratesPerKw: FeeratesPerKw) extends CurrentFeerates
+  //@formatter:on
+}
+
+

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

@@ -119,7 +119,7 @@ object Helpers {
     val channelFeatures = ChannelFeatures(channelType, localFeatures, remoteFeatures, open.channelFlags.announceChannel)
 
     // BOLT #2: The receiving node MUST fail the channel if: it considers feerate_per_kw too small for timely processing or unreasonably large.
-    val localFeeratePerKw = nodeParams.onChainFeeConf.getCommitmentFeerate(nodeParams.currentFeerates, remoteNodeId, channelFeatures.commitmentFormat, open.fundingSatoshis)
+    val localFeeratePerKw = nodeParams.onChainFeeConf.getCommitmentFeerate(nodeParams.currentBitcoinCoreFeerates, remoteNodeId, channelFeatures.commitmentFormat, open.fundingSatoshis)
     if (nodeParams.onChainFeeConf.feerateToleranceFor(remoteNodeId).isFeeDiffTooHigh(channelFeatures.commitmentFormat, localFeeratePerKw, open.feeratePerKw)) return Left(FeerateTooDifferent(open.temporaryChannelId, localFeeratePerKw, open.feeratePerKw))
 
     // we don't check that the funder's amount for the initial commitment transaction is sufficient for full fee payment
@@ -166,7 +166,7 @@ object Helpers {
     val channelFeatures = ChannelFeatures(channelType, localFeatures, remoteFeatures, open.channelFlags.announceChannel)
 
     // BOLT #2: The receiving node MUST fail the channel if: it considers feerate_per_kw too small for timely processing or unreasonably large.
-    val localFeeratePerKw = nodeParams.onChainFeeConf.getCommitmentFeerate(nodeParams.currentFeerates, remoteNodeId, channelFeatures.commitmentFormat, open.fundingAmount)
+    val localFeeratePerKw = nodeParams.onChainFeeConf.getCommitmentFeerate(nodeParams.currentBitcoinCoreFeerates, remoteNodeId, channelFeatures.commitmentFormat, open.fundingAmount)
     if (nodeParams.onChainFeeConf.feerateToleranceFor(remoteNodeId).isFeeDiffTooHigh(channelFeatures.commitmentFormat, localFeeratePerKw, open.commitmentFeerate)) return Left(FeerateTooDifferent(open.temporaryChannelId, localFeeratePerKw, open.commitmentFeerate))
 
     for {