Disallow chains of unconfirmed splice transactions

When 0-conf isn't used, we reject `splice_init` while the previous
splice transaction hasn't confirmed. Our peer should either use RBF
instead of creating a new splice, or they should wait for our node
to receive the block that confirmed the previous transaction. This
protects against chains of unconfirmed transactions.

Author: t-bast

docs/release-notes/eclair-vnext.md

@@ -40,6 +40,9 @@ eclair-cli spliceout --channelId=<channel_id> --amountOut=<amount_satoshis> --sc
 
 That operation can also be RBF-ed with the `rbfsplice` API to speed up confirmation if necessary.
 
+Note that when 0-conf is used for the channel, it is not possible to RBF splice transactions.
+Node operators should instead create a new splice transaction (with `splicein` or `spliceout`) to CPFP the previous transaction.
+
 Note that eclair had already introduced support for a splicing prototype in v0.9.0, which helped improve the BOLT proposal.
 We're removing support for the previous splicing prototype feature: users that depended on this protocol must upgrade to create official splice transactions.
 

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

@@ -91,6 +91,7 @@ case class InvalidRbfAttemptTooSoon                (override val channelId: Byte
 case class InvalidSpliceTxAbortNotAcked            (override val channelId: ByteVector32) extends ChannelException(channelId, "invalid splice attempt: our previous tx_abort has not been acked")
 case class InvalidSpliceNotQuiescent               (override val channelId: ByteVector32) extends ChannelException(channelId, "invalid splice attempt: the channel is not quiescent")
 case class InvalidSpliceWithUnconfirmedRbf         (override val channelId: ByteVector32, previousTxs: Seq[TxId]) extends ChannelException(channelId, s"invalid splice attempt: the previous splice was rbf-ed and is still unconfirmed (txIds=${previousTxs.mkString(", ")})")
+case class InvalidSpliceWithUnconfirmedTx          (override val channelId: ByteVector32, fundingTx: TxId) extends ChannelException(channelId, s"invalid splice attempt: the current funding transaction is still unconfirmed (txId=$fundingTx), you should use tx_init_rbf instead")
 case class InvalidRbfTxConfirmed                   (override val channelId: ByteVector32) extends ChannelException(channelId, "no need to rbf, transaction is already confirmed")
 case class InvalidRbfNonInitiator                  (override val channelId: ByteVector32) extends ChannelException(channelId, "cannot initiate rbf: we're not the initiator of this interactive-tx attempt")
 case class InvalidRbfZeroConf                      (override val channelId: ByteVector32) extends ChannelException(channelId, "cannot initiate rbf: we're using zero-conf for this interactive-tx attempt")

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

@@ -986,6 +986,9 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder with
             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 ({})", previousTxs.mkString(", "))
             stay() using d.copy(spliceStatus = SpliceStatus.SpliceAborted) sending TxAbort(d.channelId, InvalidSpliceWithUnconfirmedRbf(d.channelId, previousTxs).getMessage)
+          } else if (d.commitments.latest.localFundingStatus.isInstanceOf[LocalFundingStatus.DualFundedUnconfirmedFundingTx]) {
+            log.info("rejecting splice request: the previous funding transaction is unconfirmed ({})", d.commitments.latest.fundingTxId)
+            stay() using d.copy(spliceStatus = SpliceStatus.SpliceAborted) sending TxAbort(d.channelId, InvalidSpliceWithUnconfirmedTx(d.channelId, d.commitments.latest.fundingTxId).getMessage)
           } else {
             val parentCommitment = d.commitments.latest.commitment
             val localFundingPubKey = nodeParams.channelKeyManager.fundingPublicKey(d.commitments.params.localParams.fundingKeyPath, parentCommitment.fundingTxIndex + 1).publicKey

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

@@ -706,7 +706,7 @@ trait ChannelOpenDualFunded extends DualFundingHandlers with ErrorHandlers {
           }
         case _ =>
           // This can happen if we received a tx_abort right before receiving the interactive-tx result.
-          log.warning("ignoring interactive-tx result with rbfStatus={}", d.status.getClass.getSimpleName)
+          log.warning("ignoring interactive-tx result with funding status={}", d.status.getClass.getSimpleName)
           stay()
       }