Use min fee instead of tx propagation check

ACINQ · Sep 6, 2021 · 4ce2dde · 4ce2dde
1 parent ed8ada9
commit 4ce2dde
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Showing 2 changed files with 9 additions and 8 deletions.
diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/channel/Channel.scala b/eclair-core/src/main/scala/fr/acinq/eclair/channel/Channel.scala
@@ -1289,14 +1289,12 @@ class Channel(val nodeParams: NodeParams, val wallet: EclairWallet, remoteNodeId
               case Some(ClosingSignedTlv.FeeRange(minFee, maxFee)) if !d.commitments.localParams.isFunder =>
                 // if we are fundee and they proposed a fee range, we pick a value in that range and they should accept it without further negotiation
                 // we don't care much about the closing fee since they're paying it (not us) and we can use CPFP if we want to speed up confirmation
-                // but we need to ensure it's high enough to at least propagate across the network
-                val txPropagationFeerate = nodeParams.onChainFeeConf.feeEstimator.getFeeratePerKw(1008)
-                val txPropagationMinFee = Transactions.weight2fee(txPropagationFeerate, signedClosingTx.tx.weight())
-                if (maxFee < txPropagationMinFee) {
-                  log.warning("their highest closing fee is below our tx propagation threshold (feerate={}): {} < {}", txPropagationFeerate, maxFee, txPropagationMinFee)
-                  stay() sending Warning(d.channelId, s"closing fee range must not be below $txPropagationMinFee ($txPropagationFeerate)")
+                val localClosingFees = Closing.firstClosingFee(d.commitments, d.localShutdown.scriptPubKey, d.remoteShutdown.scriptPubKey, nodeParams.onChainFeeConf.feeEstimator, nodeParams.onChainFeeConf.feeTargets)
+                if (maxFee < localClosingFees.min) {
+                  log.warning("their highest closing fee is below our minimum fee: {} < {}", maxFee, localClosingFees.min)
+                  stay() sending Warning(d.channelId, s"closing fee range must not be below ${localClosingFees.min}")
                 } else {
-                  val closingFee = Closing.firstClosingFee(d.commitments, d.localShutdown.scriptPubKey, d.remoteShutdown.scriptPubKey, nodeParams.onChainFeeConf.feeEstimator, nodeParams.onChainFeeConf.feeTargets) match {
+                  val closingFee = localClosingFees match {
                     case ClosingFees(preferred, _, _) if preferred > maxFee => maxFee
                     // if we underestimate the fee, then we're happy with whatever they propose (it will confirm more quickly and we're not paying it)
                     case ClosingFees(preferred, _, _) if preferred < remoteClosingFee => remoteClosingFee

diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/channel/Helpers.scala b/eclair-core/src/main/scala/fr/acinq/eclair/channel/Helpers.scala
@@ -478,7 +478,10 @@ object Helpers {
         // we "MUST set fee_satoshis less than or equal to the base fee of the final commitment transaction"
         requestedFeerate.min(commitments.localCommit.spec.feeratePerKw)
       }
-      firstClosingFee(commitments, localScriptPubkey, remoteScriptPubkey, ClosingFeerates(preferredFeerate, preferredFeerate / 2, preferredFeerate * 2))
+      // NB: we choose a minimum fee that ensures the tx will easily propagate while allowing low fees since we can
+      // always use CPFP to speed up confirmation if necessary.
+      val closingFeerates = ClosingFeerates(preferredFeerate, preferredFeerate.min(feeEstimator.getFeeratePerKw(1008)), preferredFeerate * 2)
+      firstClosingFee(commitments, localScriptPubkey, remoteScriptPubkey, closingFeerates)
     }
 
     def nextClosingFee(localClosingFee: Satoshi, remoteClosingFee: Satoshi): Satoshi = ((localClosingFee + remoteClosingFee) / 4) * 2