Accept remote's closing fee when we have nothing at stake (#1633)

If we have nothing at stake there is no need to negotiate and we accept their fee right away.
ACINQ · Dec 15, 2020 · bbbd229 · bbbd229
1 parent ade17ec
commit bbbd229
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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
@@ -1180,9 +1180,14 @@ class Channel(val nodeParams: NodeParams, val wallet: EclairWallet, remoteNodeId
         case Right(signedClosingTx) =>
           // if we are fundee and we were waiting for them to send their first closing_signed, we don't have a lastLocalClosingFee, so we compute a firstClosingFee
           val lastLocalClosingFee = d.closingTxProposed.last.lastOption.map(_.localClosingSigned.feeSatoshis)
-          val nextClosingFee = Closing.nextClosingFee(
-            localClosingFee = lastLocalClosingFee.getOrElse(Closing.firstClosingFee(d.commitments, d.localShutdown.scriptPubKey, d.remoteShutdown.scriptPubKey, nodeParams.onChainFeeConf.feeEstimator, nodeParams.onChainFeeConf.feeTargets)),
-            remoteClosingFee = remoteClosingFee)
+          val nextClosingFee = if (d.commitments.localCommit.spec.toLocal == 0.msat) {
+            // if we have nothing at stake there is no need to negotiate and we accept their fee right away
+            remoteClosingFee
+          } else {
+            Closing.nextClosingFee(
+              localClosingFee = lastLocalClosingFee.getOrElse(Closing.firstClosingFee(d.commitments, d.localShutdown.scriptPubKey, d.remoteShutdown.scriptPubKey, nodeParams.onChainFeeConf.feeEstimator, nodeParams.onChainFeeConf.feeTargets)),
+              remoteClosingFee = remoteClosingFee)
+          }
           val (closingTx, closingSigned) = Closing.makeClosingTx(keyManager, d.commitments, d.localShutdown.scriptPubKey, d.remoteShutdown.scriptPubKey, nextClosingFee)
           if (lastLocalClosingFee.contains(nextClosingFee)) {
             // next computed fee is the same than the one we previously sent (probably because of rounding), let's close now

diff --git a/eclair-core/src/test/scala/fr/acinq/eclair/channel/states/g/NegotiatingStateSpec.scala b/eclair-core/src/test/scala/fr/acinq/eclair/channel/states/g/NegotiatingStateSpec.scala
@@ -137,6 +137,22 @@ class NegotiatingStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLike
     testFeeConverge(f)
   }
 
+  test("recv ClosingSigned (nothing at stake)", Tag("no_push_msat")) { f =>
+    import f._
+    val aliceCloseFee = alice2bob.expectMsgType[ClosingSigned].feeSatoshis
+    alice2bob.forward(bob)
+    val bobCloseFee = bob2alice.expectMsgType[ClosingSigned].feeSatoshis
+    assert(aliceCloseFee === bobCloseFee)
+    bob2alice.forward(alice)
+    val mutualCloseTxAlice = alice2blockchain.expectMsgType[PublishAsap].tx
+    val mutualCloseTxBob = bob2blockchain.expectMsgType[PublishAsap].tx
+    assert(mutualCloseTxAlice === mutualCloseTxBob)
+    assert(alice2blockchain.expectMsgType[WatchConfirmed].event === BITCOIN_TX_CONFIRMED(mutualCloseTxAlice))
+    assert(bob2blockchain.expectMsgType[WatchConfirmed].event === BITCOIN_TX_CONFIRMED(mutualCloseTxBob))
+    assert(alice.stateData.asInstanceOf[DATA_CLOSING].mutualClosePublished == List(mutualCloseTxAlice))
+    assert(bob.stateData.asInstanceOf[DATA_CLOSING].mutualClosePublished == List(mutualCloseTxBob))
+  }
+
   test("recv ClosingSigned (fee too high)") { f =>
     import f._
     val aliceCloseSig = alice2bob.expectMsgType[ClosingSigned]