Improve htlc_maximum_msat in channel updates

eclair-core/src/main/resources/reference.conf

@@ -90,8 +90,12 @@ eclair {
     dust-limit-satoshis = 546
     max-remote-dust-limit-satoshis = 600
     htlc-minimum-msat = 1
-    // The following parameters apply to each HTLC direction (incoming or outgoing), which means that the total HTLC limits will be twice what is set here
+    // The following parameters apply to each HTLC direction (incoming or outgoing), which means that the maximum amount in flight will be at most twice what is set here.
+    // Note that our peer may use a lower value than ours, which would reduce the maximum amount in flight.
+    // The smallest value of max-htlc-value-in-flight-msat and max-htlc-value-in-flight-percent will be applied when opening channels.
+    // If for example you open a 60 mBTC channel, eclair will set max-htlc-value-in-flight to 27 mBTC.
     max-htlc-value-in-flight-msat = 5000000000 // 50 mBTC
+    max-htlc-value-in-flight-percent = 45 // 45% of the channel capacity
     max-accepted-htlcs = 30
 
     reserve-to-funding-ratio = 0.01 // recommended by BOLT #2

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

@@ -458,7 +458,8 @@ object NodeParams extends Logging {
         dustLimit = dustLimitSatoshis,
         maxRemoteDustLimit = Satoshi(config.getLong("channel.max-remote-dust-limit-satoshis")),
         htlcMinimum = htlcMinimum,
-        maxHtlcValueInFlightMsat = UInt64(config.getLong("channel.max-htlc-value-in-flight-msat")),
+        maxHtlcValueInFlightMsat = MilliSatoshi(config.getLong("channel.max-htlc-value-in-flight-msat")),
+        maxHtlcValueInFlightPercent = config.getInt("channel.max-htlc-value-in-flight-percent"),
         maxAcceptedHtlcs = maxAcceptedHtlcs,
         reserveToFundingRatio = config.getDouble("channel.reserve-to-funding-ratio"),
         maxReserveToFundingRatio = config.getDouble("channel.max-reserve-to-funding-ratio"),

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

@@ -557,7 +557,7 @@ final case class DATA_WAIT_FOR_REMOTE_PUBLISH_FUTURE_COMMITMENT(commitments: Com
 case class LocalParams(nodeId: PublicKey,
                        fundingKeyPath: DeterministicWallet.KeyPath,
                        dustLimit: Satoshi,
-                       maxHtlcValueInFlightMsat: UInt64, // this is not MilliSatoshi because it can exceed the total amount of MilliSatoshi
+                       maxHtlcValueInFlightMsat: MilliSatoshi,
                        requestedChannelReserve_opt: Option[Satoshi],
                        htlcMinimum: MilliSatoshi,
                        toSelfDelay: CltvExpiryDelta,

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

@@ -100,7 +100,7 @@ case class UnexpectedHtlcId                        (override val channelId: Byte
 case class ExpiryTooSmall                          (override val channelId: ByteVector32, minimum: CltvExpiry, actual: CltvExpiry, blockHeight: BlockHeight) extends ChannelException(channelId, s"expiry too small: minimum=$minimum actual=$actual blockHeight=$blockHeight")
 case class ExpiryTooBig                            (override val channelId: ByteVector32, maximum: CltvExpiry, actual: CltvExpiry, blockHeight: BlockHeight) extends ChannelException(channelId, s"expiry too big: maximum=$maximum actual=$actual blockHeight=$blockHeight")
 case class HtlcValueTooSmall                       (override val channelId: ByteVector32, minimum: MilliSatoshi, actual: MilliSatoshi) extends ChannelException(channelId, s"htlc value too small: minimum=$minimum actual=$actual")
-case class HtlcValueTooHighInFlight                (override val channelId: ByteVector32, maximum: UInt64, actual: MilliSatoshi) extends ChannelException(channelId, s"in-flight htlcs hold too much value: maximum=$maximum actual=$actual")
+case class HtlcValueTooHighInFlight                (override val channelId: ByteVector32, maximum: MilliSatoshi, actual: MilliSatoshi) extends ChannelException(channelId, s"in-flight htlcs hold too much value: maximum=$maximum actual=$actual")
 case class TooManyAcceptedHtlcs                    (override val channelId: ByteVector32, maximum: Long) extends ChannelException(channelId, s"too many accepted htlcs: maximum=$maximum")
 case class LocalDustHtlcExposureTooHigh            (override val channelId: ByteVector32, maximum: Satoshi, actual: MilliSatoshi) extends ChannelException(channelId, s"dust htlcs hold too much value: maximum=$maximum actual=$actual")
 case class RemoteDustHtlcExposureTooHigh           (override val channelId: ByteVector32, maximum: Satoshi, actual: MilliSatoshi) extends ChannelException(channelId, s"dust htlcs hold too much value: maximum=$maximum actual=$actual")

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

@@ -216,6 +216,9 @@ case class Commitments(channelId: ByteVector32,
 
   val capacity: Satoshi = commitInput.txOut.amount
 
+  // We can safely cast to millisatoshis since we verify that it's less than a valid millisatoshi amount.
+  val maxHtlcAmount: MilliSatoshi = remoteParams.maxHtlcValueInFlightMsat.toBigInt.min(localParams.maxHtlcValueInFlightMsat.toLong).toLong.msat
+
   /** Channel reserve that applies to our funds. */
   val localChannelReserve: Satoshi = if (channelFeatures.hasFeature(Features.DualFunding)) {
     (capacity / 100).max(remoteParams.dustLimit)
@@ -406,9 +409,9 @@ object Commitments {
     // We apply local *and* remote restrictions, to ensure both peers are happy with the resulting number of HTLCs.
     // NB: we need the `toSeq` because otherwise duplicate amountMsat would be removed (since outgoingHtlcs is a Set).
     val htlcValueInFlight = outgoingHtlcs.toSeq.map(_.amountMsat).sum
-    if (Seq(commitments1.localParams.maxHtlcValueInFlightMsat, commitments1.remoteParams.maxHtlcValueInFlightMsat).min < htlcValueInFlight) {
-      // TODO: this should be a specific UPDATE error (but it would require a spec change)
-      return Left(HtlcValueTooHighInFlight(commitments.channelId, maximum = Seq(commitments1.localParams.maxHtlcValueInFlightMsat, commitments1.remoteParams.maxHtlcValueInFlightMsat).min, actual = htlcValueInFlight))
+    val allowedHtlcValueInFlight = commitments1.maxHtlcAmount
+    if (allowedHtlcValueInFlight < htlcValueInFlight) {
+      return Left(HtlcValueTooHighInFlight(commitments.channelId, maximum = allowedHtlcValueInFlight, actual = htlcValueInFlight))
     }
     if (Seq(commitments1.localParams.maxAcceptedHtlcs, commitments1.remoteParams.maxAcceptedHtlcs).min < outgoingHtlcs.size) {
       return Left(TooManyAcceptedHtlcs(commitments.channelId, maximum = Seq(commitments1.localParams.maxAcceptedHtlcs, commitments1.remoteParams.maxAcceptedHtlcs).min))

eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/Channel.scala

@@ -63,7 +63,8 @@ object Channel {
                          dustLimit: Satoshi,
                          maxRemoteDustLimit: Satoshi,
                          htlcMinimum: MilliSatoshi,
-                         maxHtlcValueInFlightMsat: UInt64,
+                         maxHtlcValueInFlightMsat: MilliSatoshi,
+                         maxHtlcValueInFlightPercent: Int,
                          maxAcceptedHtlcs: Int,
                          reserveToFundingRatio: Double,
                          maxReserveToFundingRatio: Double,
@@ -81,6 +82,8 @@ object Channel {
                          unhandledExceptionStrategy: UnhandledExceptionStrategy,
                          revocationTimeout: FiniteDuration,
                          requireConfirmedInputsForDualFunding: Boolean) {
+    require(0 <= maxHtlcValueInFlightPercent && maxHtlcValueInFlightPercent <= 100, "max-htlc-value-in-flight-percent must be between 0 and 100")
+
     def minFundingSatoshis(announceChannel: Boolean): Satoshi = if (announceChannel) minFundingPublicSatoshis else minFundingPrivateSatoshis
   }
 
@@ -635,7 +638,7 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder, val
       val channelUpdate1 = if (d.channelUpdate.shortChannelId != scidForChannelUpdate) {
         log.info(s"using new scid in channel_update: old=${d.channelUpdate.shortChannelId} new=$scidForChannelUpdate")
         // we re-announce the channelUpdate for the same reason
-        Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate, d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.capacity.toMilliSatoshi, isPrivate = !d.commitments.announceChannel, enable = Helpers.aboveReserve(d.commitments))
+        Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate, d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.maxHtlcAmount, isPrivate = !d.commitments.announceChannel, enable = Helpers.aboveReserve(d.commitments))
       } else {
         d.channelUpdate
       }
@@ -668,7 +671,7 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder, val
               } else {
                 // we generate a new channel_update because the scid used may change if we were previously using an alias
                 val scidForChannelUpdate = Helpers.scidForChannelUpdate(Some(channelAnn), d.shortIds.localAlias)
-                val channelUpdate = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate, d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.capacity.toMilliSatoshi, isPrivate = false, enable = Helpers.aboveReserve(d.commitments))
+                val channelUpdate = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate, d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.maxHtlcAmount, isPrivate = false, enable = Helpers.aboveReserve(d.commitments))
                 // we use goto() instead of stay() because we want to fire transitions
                 goto(NORMAL) using d.copy(channelAnnouncement = Some(channelAnn), channelUpdate = channelUpdate) storing()
               }
@@ -690,7 +693,7 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder, val
       }
 
     case Event(c: CMD_UPDATE_RELAY_FEE, d: DATA_NORMAL) =>
-      val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), c.cltvExpiryDelta_opt.getOrElse(d.channelUpdate.cltvExpiryDelta), d.channelUpdate.htlcMinimumMsat, c.feeBase, c.feeProportionalMillionths, d.commitments.capacity.toMilliSatoshi, isPrivate = !d.commitments.announceChannel, enable = Helpers.aboveReserve(d.commitments))
+      val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), c.cltvExpiryDelta_opt.getOrElse(d.channelUpdate.cltvExpiryDelta), d.channelUpdate.htlcMinimumMsat, c.feeBase, c.feeProportionalMillionths, d.commitments.maxHtlcAmount, isPrivate = !d.commitments.announceChannel, enable = Helpers.aboveReserve(d.commitments))
       log.info(s"updating relay fees: prev={} next={}", d.channelUpdate.toStringShort, channelUpdate1.toStringShort)
       val replyTo = if (c.replyTo == ActorRef.noSender) sender() else c.replyTo
       replyTo ! RES_SUCCESS(c, d.channelId)
@@ -699,7 +702,7 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder, val
 
     case Event(BroadcastChannelUpdate(reason), d: DATA_NORMAL) =>
       val age = TimestampSecond.now() - d.channelUpdate.timestamp
-      val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.capacity.toMilliSatoshi, isPrivate = !d.commitments.announceChannel, enable = Helpers.aboveReserve(d.commitments))
+      val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.maxHtlcAmount, isPrivate = !d.commitments.announceChannel, enable = Helpers.aboveReserve(d.commitments))
       reason match {
         case Reconnected if d.commitments.announceChannel && Announcements.areSame(channelUpdate1, d.channelUpdate) && age < REFRESH_CHANNEL_UPDATE_INTERVAL =>
           // we already sent an identical channel_update not long ago (flapping protection in case we keep being disconnected/reconnected)
@@ -723,7 +726,7 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder, val
       // if we have pending unsigned htlcs, then we cancel them and generate an update with the disabled flag set, that will be returned to the sender in a temporary channel failure
       if (d.commitments.localChanges.proposed.collectFirst { case add: UpdateAddHtlc => add }.isDefined) {
         log.debug("updating channel_update announcement (reason=disabled)")
-        val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.capacity.toMilliSatoshi, isPrivate = !d.commitments.announceChannel, enable = false)
+        val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.maxHtlcAmount, isPrivate = !d.commitments.announceChannel, enable = false)
         // NB: the htlcs stay() in the commitments.localChange, they will be cleaned up after reconnection
         d.commitments.localChanges.proposed.collect {
           case add: UpdateAddHtlc => relayer ! RES_ADD_SETTLED(d.commitments.originChannels(add.id), add, HtlcResult.DisconnectedBeforeSigned(channelUpdate1))
@@ -1865,7 +1868,7 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder, val
     if (d.channelUpdate.channelFlags.isEnabled) {
       // if the channel isn't disabled we generate a new channel_update
       log.info("updating channel_update announcement (reason=disabled)")
-      val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.capacity.toMilliSatoshi, isPrivate = !d.commitments.announceChannel, enable = false)
+      val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), d.channelUpdate.cltvExpiryDelta, d.channelUpdate.htlcMinimumMsat, d.channelUpdate.feeBaseMsat, d.channelUpdate.feeProportionalMillionths, d.commitments.maxHtlcAmount, isPrivate = !d.commitments.announceChannel, enable = false)
       // then we update the state and replay the request
       self forward c
       // we use goto() to fire transitions
@@ -1878,7 +1881,7 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder, val
   }
 
   private def handleUpdateRelayFeeDisconnected(c: CMD_UPDATE_RELAY_FEE, d: DATA_NORMAL) = {
-    val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), c.cltvExpiryDelta_opt.getOrElse(d.channelUpdate.cltvExpiryDelta), d.channelUpdate.htlcMinimumMsat, c.feeBase, c.feeProportionalMillionths, d.commitments.capacity.toMilliSatoshi, isPrivate = !d.commitments.announceChannel, enable = false)
+    val channelUpdate1 = Announcements.makeChannelUpdate(nodeParams.chainHash, nodeParams.privateKey, remoteNodeId, scidForChannelUpdate(d), c.cltvExpiryDelta_opt.getOrElse(d.channelUpdate.cltvExpiryDelta), d.channelUpdate.htlcMinimumMsat, c.feeBase, c.feeProportionalMillionths, d.commitments.maxHtlcAmount, isPrivate = !d.commitments.announceChannel, enable = false)
     log.info(s"updating relay fees: prev={} next={}", d.channelUpdate.toStringShort, channelUpdate1.toStringShort)
     val replyTo = if (c.replyTo == ActorRef.noSender) sender() else c.replyTo
     replyTo ! RES_SUCCESS(c, d.channelId)

eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/ChannelOpenDualFunded.scala

@@ -27,7 +27,7 @@ import fr.acinq.eclair.channel.fsm.Channel._
 import fr.acinq.eclair.channel.publish.TxPublisher.SetChannelId
 import fr.acinq.eclair.transactions.Scripts
 import fr.acinq.eclair.wire.protocol._
-import fr.acinq.eclair.{Features, RealShortChannelId, ToMilliSatoshiConversion}
+import fr.acinq.eclair.{Features, RealShortChannelId, ToMilliSatoshiConversion, UInt64}
 
 /**
  * Created by t-bast on 19/04/2022.
@@ -123,7 +123,7 @@ trait ChannelOpenDualFunded extends DualFundingHandlers with ErrorHandlers {
         commitmentFeerate = input.commitTxFeerate,
         fundingAmount = input.fundingAmount,
         dustLimit = input.localParams.dustLimit,
-        maxHtlcValueInFlightMsat = input.localParams.maxHtlcValueInFlightMsat,
+        maxHtlcValueInFlightMsat = UInt64(input.localParams.maxHtlcValueInFlightMsat.toLong),
         htlcMinimum = input.localParams.htlcMinimum,
         toSelfDelay = input.localParams.toSelfDelay,
         maxAcceptedHtlcs = input.localParams.maxAcceptedHtlcs,
@@ -165,7 +165,7 @@ trait ChannelOpenDualFunded extends DualFundingHandlers with ErrorHandlers {
             temporaryChannelId = open.temporaryChannelId,
             fundingAmount = d.init.fundingContribution_opt.getOrElse(0 sat),
             dustLimit = localParams.dustLimit,
-            maxHtlcValueInFlightMsat = localParams.maxHtlcValueInFlightMsat,
+            maxHtlcValueInFlightMsat = UInt64(localParams.maxHtlcValueInFlightMsat.toLong),
             htlcMinimum = localParams.htlcMinimum,
             minimumDepth = minimumDepth.getOrElse(0),
             toSelfDelay = localParams.toSelfDelay,

eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/ChannelOpenSingleFunded.scala

@@ -31,7 +31,7 @@ import fr.acinq.eclair.crypto.ShaChain
 import fr.acinq.eclair.transactions.Transactions.TxOwner
 import fr.acinq.eclair.transactions.{Scripts, Transactions}
 import fr.acinq.eclair.wire.protocol.{AcceptChannel, AnnouncementSignatures, ChannelReady, ChannelTlv, Error, FundingCreated, FundingSigned, OpenChannel, TlvStream}
-import fr.acinq.eclair.{Features, MilliSatoshiLong, RealShortChannelId, randomKey, toLongId}
+import fr.acinq.eclair.{Features, MilliSatoshiLong, RealShortChannelId, UInt64, randomKey, toLongId}
 import scodec.bits.ByteVector
 
 import scala.util.{Failure, Success, Try}
@@ -87,7 +87,7 @@ trait ChannelOpenSingleFunded extends SingleFundingHandlers with ErrorHandlers {
         fundingSatoshis = input.fundingAmount,
         pushMsat = input.pushAmount_opt.getOrElse(0 msat),
         dustLimitSatoshis = input.localParams.dustLimit,
-        maxHtlcValueInFlightMsat = input.localParams.maxHtlcValueInFlightMsat,
+        maxHtlcValueInFlightMsat = UInt64(input.localParams.maxHtlcValueInFlightMsat.toLong),
         channelReserveSatoshis = input.localParams.requestedChannelReserve_opt.get,
         htlcMinimumMsat = input.localParams.htlcMinimum,
         feeratePerKw = input.commitTxFeerate,
@@ -122,7 +122,7 @@ trait ChannelOpenSingleFunded extends SingleFundingHandlers with ErrorHandlers {
           val localShutdownScript = if (Features.canUseFeature(d.initFundee.localParams.initFeatures, d.initFundee.remoteInit.features, Features.UpfrontShutdownScript)) d.initFundee.localParams.defaultFinalScriptPubKey else ByteVector.empty
           val accept = AcceptChannel(temporaryChannelId = open.temporaryChannelId,
             dustLimitSatoshis = d.initFundee.localParams.dustLimit,
-            maxHtlcValueInFlightMsat = d.initFundee.localParams.maxHtlcValueInFlightMsat,
+            maxHtlcValueInFlightMsat = UInt64(d.initFundee.localParams.maxHtlcValueInFlightMsat.toLong),
             channelReserveSatoshis = d.initFundee.localParams.requestedChannelReserve_opt.get,
             minimumDepth = minimumDepth.getOrElse(0),
             htlcMinimumMsat = d.initFundee.localParams.htlcMinimum,