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Handle aggregated anchor outputs htlc txs (#1738)
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An interesting side-effect of anchor outputs is that htlc txs can be merged
when they have the same lockTime (thanks to sighash flags).

We're not currently doing that, but our peers may do it, so we need to handle
it in the revoked commit tx case and correctly claim multiple outputs if
necessary.
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t-bast authored Mar 25, 2021
1 parent f202587 commit c37eb1a
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Showing 6 changed files with 155 additions and 53 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -134,7 +134,7 @@ class BitcoinCoreWallet(rpcClient: BitcoinJsonRPCClient)(implicit ec: ExecutionC
// now let's sign the funding tx
SignTransactionResponse(fundingTx, true) <- signTransactionOrUnlock(fundTxResponse.tx)
// there will probably be a change output, so we need to find which output is ours
outputIndex <- Transactions.findPubKeyScriptIndex(fundingTx, pubkeyScript, amount_opt = None) match {
outputIndex <- Transactions.findPubKeyScriptIndex(fundingTx, pubkeyScript) match {
case Right(outputIndex) => Future.successful(outputIndex)
case Left(skipped) => Future.failed(new RuntimeException(skipped.toString))
}
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Original file line number Diff line number Diff line change
Expand Up @@ -1340,9 +1340,9 @@ class Channel(val nodeParams: NodeParams, val wallet: EclairWallet, remoteNodeId
}
}
val revokedCommitPublished1 = d.revokedCommitPublished.map { rev =>
val (rev1, tx_opt) = Closing.claimRevokedHtlcTxOutputs(keyManager, d.commitments, rev, tx, nodeParams.onChainFeeConf.feeEstimator)
tx_opt.foreach(claimTx => blockchain ! PublishAsap(claimTx.tx, PublishStrategy.JustPublish))
tx_opt.foreach(claimTx => blockchain ! WatchSpent(self, tx, claimTx.input.outPoint.index.toInt, BITCOIN_OUTPUT_SPENT, hints = Set(claimTx.tx.txid)))
val (rev1, penaltyTxs) = Closing.claimRevokedHtlcTxOutputs(keyManager, d.commitments, rev, tx, nodeParams.onChainFeeConf.feeEstimator)
penaltyTxs.foreach(claimTx => blockchain ! PublishAsap(claimTx.tx, PublishStrategy.JustPublish))
penaltyTxs.foreach(claimTx => blockchain ! WatchSpent(self, tx, claimTx.input.outPoint.index.toInt, BITCOIN_OUTPUT_SPENT, hints = Set(claimTx.tx.txid)))
rev1
}
stay using d.copy(revokedCommitPublished = revokedCommitPublished1) storing()
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39 changes: 20 additions & 19 deletions eclair-core/src/main/scala/fr/acinq/eclair/channel/Helpers.scala
Original file line number Diff line number Diff line change
Expand Up @@ -850,8 +850,11 @@ object Helpers {
* - by spending the delayed output of [[HtlcSuccessTx]] and [[HtlcTimeoutTx]] if those get confirmed; because the output of these txs is protected by
* an OP_CSV delay, we will have time to spend them with a revocation key. In that case, we generate the spending transactions "on demand",
* this is the purpose of this method.
*
* NB: when anchor outputs is used, htlc transactions can be aggregated in a single transaction if they share the same
* lockTime (thanks to the use of sighash_single | sighash_anyonecanpay), so we may need to claim multiple outputs.
*/
def claimRevokedHtlcTxOutputs(keyManager: ChannelKeyManager, commitments: Commitments, revokedCommitPublished: RevokedCommitPublished, htlcTx: Transaction, feeEstimator: FeeEstimator)(implicit log: LoggingAdapter): (RevokedCommitPublished, Option[ClaimHtlcDelayedOutputPenaltyTx]) = {
def claimRevokedHtlcTxOutputs(keyManager: ChannelKeyManager, commitments: Commitments, revokedCommitPublished: RevokedCommitPublished, htlcTx: Transaction, feeEstimator: FeeEstimator)(implicit log: LoggingAdapter): (RevokedCommitPublished, Seq[ClaimHtlcDelayedOutputPenaltyTx]) = {
val isHtlcTx = htlcTx.txIn.map(_.outPoint.txid).contains(revokedCommitPublished.commitTx.txid) &&
htlcTx.txIn.map(_.witness).collect(Scripts.extractPreimageFromHtlcSuccess.orElse(Scripts.extractPaymentHashFromHtlcTimeout)).nonEmpty
if (isHtlcTx) {
Expand All @@ -867,32 +870,30 @@ object Helpers {
// now we know what commit number this tx is referring to, we can derive the commitment point from the shachain
remotePerCommitmentSecrets.getHash(0xFFFFFFFFFFFFL - txNumber)
.map(d => PrivateKey(d))
.flatMap(remotePerCommitmentSecret => {
.map(remotePerCommitmentSecret => {
val remotePerCommitmentPoint = remotePerCommitmentSecret.publicKey
val remoteDelayedPaymentPubkey = Generators.derivePubKey(remoteParams.delayedPaymentBasepoint, remotePerCommitmentPoint)
val remoteRevocationPubkey = Generators.revocationPubKey(keyManager.revocationPoint(channelKeyPath).publicKey, remotePerCommitmentPoint)

// we need to use a high fee here for punishment txs because after a delay they can be spent by the counterparty
val feeratePerKwPenalty = feeEstimator.getFeeratePerKw(target = 1)

generateTx("claim-htlc-delayed-penalty") {
Transactions.makeClaimHtlcDelayedOutputPenaltyTx(htlcTx, localParams.dustLimit, remoteRevocationPubkey, localParams.toSelfDelay, remoteDelayedPaymentPubkey, localParams.defaultFinalScriptPubKey, feeratePerKwPenalty).map(htlcDelayedPenalty => {
val sig = keyManager.sign(htlcDelayedPenalty, keyManager.revocationPoint(channelKeyPath), remotePerCommitmentSecret, TxOwner.Local, commitmentFormat)
val signedTx = Transactions.addSigs(htlcDelayedPenalty, sig)
// we need to make sure that the tx is indeed valid
Transaction.correctlySpends(signedTx.tx, Seq(htlcTx), ScriptFlags.STANDARD_SCRIPT_VERIFY_FLAGS)
signedTx
})
}
}) match {
case Some(tx) =>
val revokedCommitPublished1 = revokedCommitPublished.copy(claimHtlcDelayedPenaltyTxs = revokedCommitPublished.claimHtlcDelayedPenaltyTxs :+ tx)
(revokedCommitPublished1, Some(tx))
case None =>
(revokedCommitPublished, None)
}
val penaltyTxs = Transactions.makeClaimHtlcDelayedOutputPenaltyTxs(htlcTx, localParams.dustLimit, remoteRevocationPubkey, localParams.toSelfDelay, remoteDelayedPaymentPubkey, localParams.defaultFinalScriptPubKey, feeratePerKwPenalty).flatMap(claimHtlcDelayedOutputPenaltyTx => {
generateTx("claim-htlc-delayed-penalty") {
claimHtlcDelayedOutputPenaltyTx.map(htlcDelayedPenalty => {
val sig = keyManager.sign(htlcDelayedPenalty, keyManager.revocationPoint(channelKeyPath), remotePerCommitmentSecret, TxOwner.Local, commitmentFormat)
val signedTx = Transactions.addSigs(htlcDelayedPenalty, sig)
// we need to make sure that the tx is indeed valid
Transaction.correctlySpends(signedTx.tx, Seq(htlcTx), ScriptFlags.STANDARD_SCRIPT_VERIFY_FLAGS)
signedTx
})
}
})
val revokedCommitPublished1 = revokedCommitPublished.copy(claimHtlcDelayedPenaltyTxs = revokedCommitPublished.claimHtlcDelayedPenaltyTxs ++ penaltyTxs)
(revokedCommitPublished1, penaltyTxs)
}).getOrElse((revokedCommitPublished, Nil))
} else {
(revokedCommitPublished, None)
(revokedCommitPublished, Nil)
}
}

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Original file line number Diff line number Diff line change
Expand Up @@ -568,7 +568,7 @@ object Transactions {
def makeClaimP2WPKHOutputTx(commitTx: Transaction, localDustLimit: Satoshi, localPaymentPubkey: PublicKey, localFinalScriptPubKey: ByteVector, feeratePerKw: FeeratePerKw): Either[TxGenerationSkipped, ClaimP2WPKHOutputTx] = {
val redeemScript = Script.pay2pkh(localPaymentPubkey)
val pubkeyScript = write(pay2wpkh(localPaymentPubkey))
findPubKeyScriptIndex(commitTx, pubkeyScript, amount_opt = None) match {
findPubKeyScriptIndex(commitTx, pubkeyScript) match {
case Left(skip) => Left(skip)
case Right(outputIndex) =>
val input = InputInfo(OutPoint(commitTx, outputIndex), commitTx.txOut(outputIndex), write(redeemScript))
Expand All @@ -594,7 +594,7 @@ object Transactions {
def makeClaimRemoteDelayedOutputTx(commitTx: Transaction, localDustLimit: Satoshi, localPaymentPubkey: PublicKey, localFinalScriptPubKey: ByteVector, feeratePerKw: FeeratePerKw): Either[TxGenerationSkipped, ClaimRemoteDelayedOutputTx] = {
val redeemScript = toRemoteDelayed(localPaymentPubkey)
val pubkeyScript = write(pay2wsh(redeemScript))
findPubKeyScriptIndex(commitTx, pubkeyScript, amount_opt = None) match {
findPubKeyScriptIndex(commitTx, pubkeyScript) match {
case Left(skip) => Left(skip)
case Right(outputIndex) =>
val input = InputInfo(OutPoint(commitTx, outputIndex), commitTx.txOut(outputIndex), write(redeemScript))
Expand All @@ -620,7 +620,7 @@ object Transactions {
def makeClaimLocalDelayedOutputTx(commitTx: Transaction, localDustLimit: Satoshi, localRevocationPubkey: PublicKey, toLocalDelay: CltvExpiryDelta, localDelayedPaymentPubkey: PublicKey, localFinalScriptPubKey: ByteVector, feeratePerKw: FeeratePerKw): Either[TxGenerationSkipped, ClaimLocalDelayedOutputTx] = {
val redeemScript = toLocalDelayed(localRevocationPubkey, toLocalDelay, localDelayedPaymentPubkey)
val pubkeyScript = write(pay2wsh(redeemScript))
findPubKeyScriptIndex(commitTx, pubkeyScript, amount_opt = None) match {
findPubKeyScriptIndex(commitTx, pubkeyScript) match {
case Left(skip) => Left(skip)
case Right(outputIndex) =>
val input = InputInfo(OutPoint(commitTx, outputIndex), commitTx.txOut(outputIndex), write(redeemScript))
Expand All @@ -646,7 +646,7 @@ object Transactions {
private def makeClaimAnchorOutputTx(commitTx: Transaction, fundingPubkey: PublicKey): Either[TxGenerationSkipped, (InputInfo, Transaction)] = {
val redeemScript = anchor(fundingPubkey)
val pubkeyScript = write(pay2wsh(redeemScript))
findPubKeyScriptIndex(commitTx, pubkeyScript, amount_opt = None) match {
findPubKeyScriptIndex(commitTx, pubkeyScript) match {
case Left(skip) => Left(skip)
case Right(outputIndex) =>
val input = InputInfo(OutPoint(commitTx, outputIndex), commitTx.txOut(outputIndex), write(redeemScript))
Expand All @@ -668,12 +668,12 @@ object Transactions {
makeClaimAnchorOutputTx(commitTx, remoteFundingPubkey).map { case (input, tx) => ClaimRemoteAnchorOutputTx(input, tx) }
}

def makeClaimHtlcDelayedOutputPenaltyTx(htlcTx: Transaction, localDustLimit: Satoshi, localRevocationPubkey: PublicKey, toLocalDelay: CltvExpiryDelta, localDelayedPaymentPubkey: PublicKey, localFinalScriptPubKey: ByteVector, feeratePerKw: FeeratePerKw): Either[TxGenerationSkipped, ClaimHtlcDelayedOutputPenaltyTx] = {
def makeClaimHtlcDelayedOutputPenaltyTxs(htlcTx: Transaction, localDustLimit: Satoshi, localRevocationPubkey: PublicKey, toLocalDelay: CltvExpiryDelta, localDelayedPaymentPubkey: PublicKey, localFinalScriptPubKey: ByteVector, feeratePerKw: FeeratePerKw): Seq[Either[TxGenerationSkipped, ClaimHtlcDelayedOutputPenaltyTx]] = {
val redeemScript = toLocalDelayed(localRevocationPubkey, toLocalDelay, localDelayedPaymentPubkey)
val pubkeyScript = write(pay2wsh(redeemScript))
findPubKeyScriptIndex(htlcTx, pubkeyScript, amount_opt = None) match {
case Left(skip) => Left(skip)
case Right(outputIndex) =>
findPubKeyScriptIndexes(htlcTx, pubkeyScript) match {
case Left(skip) => Seq(Left(skip))
case Right(outputIndexes) => outputIndexes.map(outputIndex => {
val input = InputInfo(OutPoint(htlcTx, outputIndex), htlcTx.txOut(outputIndex), write(redeemScript))
// unsigned transaction
val tx = Transaction(
Expand All @@ -691,13 +691,14 @@ object Transactions {
val tx1 = tx.copy(txOut = tx.txOut.head.copy(amount = amount) :: Nil)
Right(ClaimHtlcDelayedOutputPenaltyTx(input, tx1))
}
})
}
}

def makeMainPenaltyTx(commitTx: Transaction, localDustLimit: Satoshi, remoteRevocationPubkey: PublicKey, localFinalScriptPubKey: ByteVector, toRemoteDelay: CltvExpiryDelta, remoteDelayedPaymentPubkey: PublicKey, feeratePerKw: FeeratePerKw): Either[TxGenerationSkipped, MainPenaltyTx] = {
val redeemScript = toLocalDelayed(remoteRevocationPubkey, toRemoteDelay, remoteDelayedPaymentPubkey)
val pubkeyScript = write(pay2wsh(redeemScript))
findPubKeyScriptIndex(commitTx, pubkeyScript, amount_opt = None) match {
findPubKeyScriptIndex(commitTx, pubkeyScript) match {
case Left(skip) => Left(skip)
case Right(outputIndex) =>
val input = InputInfo(OutPoint(commitTx, outputIndex), commitTx.txOut(outputIndex), write(redeemScript))
Expand Down Expand Up @@ -760,21 +761,30 @@ object Transactions {
txIn = TxIn(commitTxInput.outPoint, ByteVector.empty, sequence = 0xffffffffL) :: Nil,
txOut = toLocalOutput_opt.toSeq ++ toRemoteOutput_opt.toSeq ++ Nil,
lockTime = 0))
val toLocalOutput = findPubKeyScriptIndex(tx, localScriptPubKey, None).map(index => OutputInfo(index, toLocalAmount, localScriptPubKey)).toOption
val toLocalOutput = findPubKeyScriptIndex(tx, localScriptPubKey).map(index => OutputInfo(index, toLocalAmount, localScriptPubKey)).toOption
ClosingTx(commitTxInput, tx, toLocalOutput)
}

def findPubKeyScriptIndex(tx: Transaction, pubkeyScript: ByteVector, amount_opt: Option[Satoshi]): Either[TxGenerationSkipped, Int] = {
val outputIndex = tx.txOut
.zipWithIndex
.indexWhere { case (txOut, _) => amount_opt.forall(_ == txOut.amount) && txOut.publicKeyScript == pubkeyScript }
def findPubKeyScriptIndex(tx: Transaction, pubkeyScript: ByteVector): Either[TxGenerationSkipped, Int] = {
val outputIndex = tx.txOut.indexWhere(_.publicKeyScript == pubkeyScript)
if (outputIndex >= 0) {
Right(outputIndex)
} else {
Left(OutputNotFound)
}
}

def findPubKeyScriptIndexes(tx: Transaction, pubkeyScript: ByteVector): Either[TxGenerationSkipped, Seq[Int]] = {
val outputIndexes = tx.txOut.zipWithIndex.collect {
case (txOut, index) if txOut.publicKeyScript == pubkeyScript => index
}
if (outputIndexes.nonEmpty) {
Right(outputIndexes)
} else {
Left(OutputNotFound)
}
}

/**
* Default public key used for fee estimation
*/
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ package fr.acinq.eclair.channel.states.h

import akka.testkit.{TestFSMRef, TestProbe}
import fr.acinq.bitcoin.Crypto.PrivateKey
import fr.acinq.bitcoin.{ByteVector32, OutPoint, SatoshiLong, ScriptFlags, Transaction, TxIn}
import fr.acinq.bitcoin.{ByteVector32, Crypto, OutPoint, SatoshiLong, Script, ScriptFlags, Transaction, TxIn, TxOut}
import fr.acinq.eclair.TestConstants.{Alice, Bob}
import fr.acinq.eclair.blockchain._
import fr.acinq.eclair.blockchain.fee.{FeeratePerKw, FeeratesPerKw}
Expand All @@ -27,10 +27,10 @@ import fr.acinq.eclair.channel._
import fr.acinq.eclair.channel.states.{StateTestsBase, StateTestsTags}
import fr.acinq.eclair.payment._
import fr.acinq.eclair.payment.relay.Relayer._
import fr.acinq.eclair.transactions.Transactions.{HtlcSuccessTx, HtlcTimeoutTx}
import fr.acinq.eclair.transactions.Transactions.{AnchorOutputsCommitmentFormat, HtlcSuccessTx, HtlcTimeoutTx}
import fr.acinq.eclair.transactions.{Scripts, Transactions}
import fr.acinq.eclair.wire.protocol._
import fr.acinq.eclair.{CltvExpiry, MilliSatoshiLong, TestConstants, TestKitBaseClass, randomBytes32}
import fr.acinq.eclair.{CltvExpiry, MilliSatoshiLong, TestConstants, TestKitBaseClass, randomBytes32, randomKey}
import org.scalatest.funsuite.FixtureAnyFunSuiteLike
import org.scalatest.{Outcome, Tag}
import scodec.bits.ByteVector
Expand Down Expand Up @@ -1442,6 +1442,83 @@ class ClosingStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLike with
testOutputSpentRevokedTx(f, ChannelVersion.ANCHOR_OUTPUTS)
}

test("recv BITCOIN_OUTPUT_SPENT (one revoked tx, counterparty published aggregated htlc tx)", Tag(StateTestsTags.AnchorOutputs)) { f =>
import f._

// bob publishes one of his revoked txs
val revokedCloseFixture = prepareRevokedClose(f, ChannelVersion.ANCHOR_OUTPUTS)
val bobRevokedTxs = revokedCloseFixture.bobRevokedTxs(2)
alice ! WatchEventSpent(BITCOIN_FUNDING_SPENT, bobRevokedTxs.commitTx.tx)
awaitCond(alice.stateData.isInstanceOf[DATA_CLOSING])
assert(alice.stateData.asInstanceOf[DATA_CLOSING].commitments.commitmentFormat === AnchorOutputsCommitmentFormat)
awaitCond(alice.stateData.asInstanceOf[DATA_CLOSING].revokedCommitPublished.size == 1)
val rvk = alice.stateData.asInstanceOf[DATA_CLOSING].revokedCommitPublished.head
assert(rvk.commitTx === bobRevokedTxs.commitTx.tx)
assert(rvk.htlcPenaltyTxs.size === 4)
assert(rvk.claimHtlcDelayedPenaltyTxs.isEmpty)

// alice publishes the penalty txs and watches outputs
(1 to 6).foreach(_ => alice2blockchain.expectMsgType[PublishAsap]) // 2 main outputs and 4 htlcs
assert(alice2blockchain.expectMsgType[WatchConfirmed].txId === rvk.commitTx.txid)
assert(alice2blockchain.expectMsgType[WatchConfirmed].txId === rvk.claimMainOutputTx.get.tx.txid)
(1 to 5).foreach(_ => alice2blockchain.expectMsgType[WatchSpent]) // main output penalty and 4 htlc penalties
alice2blockchain.expectNoMsg(1 second)

// bob claims multiple htlc outputs in a single transaction (this is possible with anchor outputs because signatures
// use sighash_single | sighash_anyonecanpay)
val bobHtlcTxs = bobRevokedTxs.htlcTxsAndSigs.collect {
case HtlcTxAndSigs(txInfo: HtlcSuccessTx, localSig, remoteSig) =>
val preimage = revokedCloseFixture.htlcsAlice.collectFirst { case (add, preimage) if add.id == txInfo.htlcId => preimage }.get
assert(Crypto.sha256(preimage) === txInfo.paymentHash)
Transactions.addSigs(txInfo, localSig, remoteSig, preimage, AnchorOutputsCommitmentFormat)
case HtlcTxAndSigs(txInfo: HtlcTimeoutTx, localSig, remoteSig) =>
Transactions.addSigs(txInfo, localSig, remoteSig, AnchorOutputsCommitmentFormat)
}
assert(bobHtlcTxs.map(_.input.outPoint).size === 4)
val bobHtlcTx = Transaction(
2,
Seq(
TxIn(OutPoint(randomBytes32, 4), Nil, 1), // utxo used for fee bumping
bobHtlcTxs(0).tx.txIn.head,
bobHtlcTxs(1).tx.txIn.head,
bobHtlcTxs(2).tx.txIn.head,
bobHtlcTxs(3).tx.txIn.head
),
Seq(
TxOut(10000 sat, Script.pay2wpkh(randomKey.publicKey)), // change output
bobHtlcTxs(0).tx.txOut.head,
bobHtlcTxs(1).tx.txOut.head,
bobHtlcTxs(2).tx.txOut.head,
bobHtlcTxs(3).tx.txOut.head
),
0
)

// alice reacts by publishing penalty txs that spend bob's htlc transaction
alice ! WatchEventSpent(BITCOIN_OUTPUT_SPENT, bobHtlcTx)
awaitCond(alice.stateData.asInstanceOf[DATA_CLOSING].revokedCommitPublished.head.claimHtlcDelayedPenaltyTxs.size == 4)
val claimHtlcDelayedPenaltyTxs = alice.stateData.asInstanceOf[DATA_CLOSING].revokedCommitPublished.head.claimHtlcDelayedPenaltyTxs
val spentOutpoints = Set(OutPoint(bobHtlcTx, 1), OutPoint(bobHtlcTx, 2), OutPoint(bobHtlcTx, 3), OutPoint(bobHtlcTx, 4))
assert(claimHtlcDelayedPenaltyTxs.map(_.input.outPoint).toSet === spentOutpoints)
claimHtlcDelayedPenaltyTxs.foreach(claimHtlcPenalty => Transaction.correctlySpends(claimHtlcPenalty.tx, bobHtlcTx :: Nil, ScriptFlags.STANDARD_SCRIPT_VERIFY_FLAGS))
assert(alice2blockchain.expectMsgType[WatchConfirmed].txId === bobHtlcTx.txid)
val publishedPenaltyTxs = Set(
alice2blockchain.expectMsgType[PublishAsap],
alice2blockchain.expectMsgType[PublishAsap],
alice2blockchain.expectMsgType[PublishAsap],
alice2blockchain.expectMsgType[PublishAsap]
)
assert(publishedPenaltyTxs.map(_.tx) === claimHtlcDelayedPenaltyTxs.map(_.tx).toSet)
val watchedOutpoints = Seq(
alice2blockchain.expectMsgType[WatchSpent],
alice2blockchain.expectMsgType[WatchSpent],
alice2blockchain.expectMsgType[WatchSpent],
alice2blockchain.expectMsgType[WatchSpent]
).map(w => OutPoint(w.txId.reverse, w.outputIndex)).toSet
assert(watchedOutpoints === spentOutpoints)
alice2blockchain.expectNoMsg(1 second)
}

private def testRevokedTxConfirmed(f: FixtureParam, channelVersion: ChannelVersion): Unit = {
import f._
assert(alice.stateData.asInstanceOf[DATA_NORMAL].commitments.channelVersion === channelVersion)
Expand Down
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