Add detailed error message when splice feerate is incorrect (#2920)

This can be helpful when troubleshooting cross-compatibility issues.

Replaces #2911.

Author: t-bast

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

@@ -83,6 +83,7 @@ case class UnexpectedFundingSignatures             (override val channelId: Byte
 case class InvalidFundingFeerate                   (override val channelId: ByteVector32, targetFeerate: FeeratePerKw, actualFeerate: FeeratePerKw) extends ChannelException(channelId, s"invalid funding feerate: target=$targetFeerate actual=$actualFeerate")
 case class InvalidFundingSignature                 (override val channelId: ByteVector32, txId_opt: Option[TxId]) extends ChannelException(channelId, s"invalid funding signature: txId=${txId_opt.map(_.toString()).getOrElse("n/a")}")
 case class InvalidRbfFeerate                       (override val channelId: ByteVector32, proposed: FeeratePerKw, expected: FeeratePerKw) extends ChannelException(channelId, s"invalid rbf attempt: the feerate must be at least $expected, you proposed $proposed")
+case class InvalidSpliceFeerate                    (override val channelId: ByteVector32, proposed: FeeratePerKw, expected: FeeratePerKw) extends ChannelException(channelId, s"invalid splice request: the feerate must be at least $expected, you proposed $proposed")
 case class InvalidSpliceRequest                    (override val channelId: ByteVector32) extends ChannelException(channelId, "invalid splice request")
 case class InvalidRbfAlreadyInProgress             (override val channelId: ByteVector32) extends ChannelException(channelId, "invalid rbf attempt: the current rbf attempt must be completed or aborted first")
 case class InvalidSpliceAlreadyInProgress          (override val channelId: ByteVector32) extends ChannelException(channelId, "invalid splice attempt: the current splice attempt must be completed or aborted first")

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

@@ -986,8 +986,8 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder with
             log.info("rejecting splice request: channel not quiescent")
             stay() using d.copy(spliceStatus = SpliceStatus.SpliceAborted) sending TxAbort(d.channelId, InvalidSpliceNotQuiescent(d.channelId).getMessage)
           } else if (msg.feerate < nodeParams.currentBitcoinCoreFeerates.minimum) {
-            log.info("rejecting splice request: feerate too low")
-            stay() using d.copy(spliceStatus = SpliceStatus.SpliceAborted) sending TxAbort(d.channelId, InvalidSpliceRequest(d.channelId).getMessage)
+            log.info("rejecting splice request: feerate too low ({} < {})", msg.feerate, nodeParams.currentBitcoinCoreFeerates.minimum)
+            stay() using d.copy(spliceStatus = SpliceStatus.SpliceAborted) sending TxAbort(d.channelId, InvalidSpliceFeerate(d.channelId, msg.feerate, nodeParams.currentBitcoinCoreFeerates.minimum).getMessage)
           } else if (d.commitments.active.count(_.fundingTxIndex == d.commitments.latest.fundingTxIndex) > 1) {
             val previousTxs = d.commitments.active.filter(_.fundingTxIndex == d.commitments.latest.fundingTxIndex).map(_.fundingTxId)
             log.info("rejecting splice request: the previous splice has unconfirmed rbf attempts (txIds={})", previousTxs.mkString(", "))

eclair-core/src/main/scala/fr/acinq/eclair/channel/fund/InteractiveTxBuilder.scala

@@ -795,7 +795,7 @@ private class InteractiveTxBuilder(replyTo: ActorRef[InteractiveTxBuilder.Respon
         val nextFeerate = Transactions.fee2rate(sharedTx.fees, tx.weight())
         if (nextFeerate <= previousFeerate) {
           log.warn("invalid interactive tx: next feerate isn't greater than previous feerate (previous={}, next={})", previousFeerate, nextFeerate)
-          return Left(InvalidCompleteInteractiveTx(fundingParams.channelId))
+          return Left(InvalidRbfFeerate(fundingParams.channelId, nextFeerate, previousFeerate))
         }
       case None =>
         val feeWithoutWitness = Transactions.weight2fee(fundingParams.targetFeerate, tx.weight())
@@ -811,7 +811,7 @@ private class InteractiveTxBuilder(replyTo: ActorRef[InteractiveTxBuilder.Respon
         }
         if (sharedTx.fees < minimumFee) {
           log.warn("invalid interactive tx: below the target feerate (target={}, actual={})", fundingParams.targetFeerate, Transactions.fee2rate(sharedTx.fees, tx.weight()))
-          return Left(InvalidCompleteInteractiveTx(fundingParams.channelId))
+          return Left(InvalidSpliceFeerate(fundingParams.channelId, Transactions.fee2rate(sharedTx.fees, tx.weight()), fundingParams.targetFeerate))
         }
     }
 

eclair-core/src/test/scala/fr/acinq/eclair/channel/InteractiveTxBuilderSpec.scala

@@ -2669,7 +2669,7 @@ class InteractiveTxBuilderSpec extends TestKitBaseClass with AnyFunSuiteLike wit
     probe.expectMsgType[SendMessage]
     // Alice --- tx_complete --> Bob
     bob ! ReceiveMessage(TxComplete(params.channelId))
-    assert(probe.expectMsgType[RemoteFailure].cause == InvalidCompleteInteractiveTx(params.channelId))
+    assert(probe.expectMsgType[RemoteFailure].cause.isInstanceOf[InvalidSpliceFeerate])
   }
 
   test("previous attempts not double-spent") {