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We create a new `SwapInManager` that checks the wallet state and decides whether to initiate a channel funding attempt, while keeping track of utxos that are currently being used. We allow unlocking those utxos once a channel funding attempt fails, which ensures that if we retry later (because another input is confirmed) we will reuse the previously failed inputs (instead of waiting for a restart to use them).
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src/commonMain/kotlin/fr/acinq/lightning/blockchain/electrum/SwapInManager.kt
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| package fr.acinq.lightning.blockchain.electrum | ||
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| import fr.acinq.bitcoin.OutPoint | ||
| import fr.acinq.lightning.Lightning | ||
| import fr.acinq.lightning.channel.LocalFundingStatus | ||
| import fr.acinq.lightning.channel.RbfStatus | ||
| import fr.acinq.lightning.channel.SignedSharedTransaction | ||
| import fr.acinq.lightning.channel.SpliceStatus | ||
| import fr.acinq.lightning.channel.states.* | ||
| import fr.acinq.lightning.io.RequestChannelOpen | ||
| import fr.acinq.lightning.utils.MDCLogger | ||
| import fr.acinq.lightning.utils.sat | ||
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| internal sealed class SwapInCommand { | ||
| data class TrySwapIn(val currentBlockHeight: Int, val wallet: WalletState, val swapInConfirmations: Int, val isMigrationFromLegacyApp: Boolean) : SwapInCommand() | ||
| data class UnlockWalletInputs(val inputs: Set<OutPoint>) : SwapInCommand() | ||
| } | ||
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| /** | ||
| * This object selects inputs that are ready to be used for swaps and keeps track of those that are currently used in channel funding attempts. | ||
| * Those inputs should not be reused, otherwise we would double-spend ourselves. | ||
| * If the electrum server we connect to has our channel funding attempts in their mempool, those inputs wouldn't be added to our wallet at all. | ||
| * But we cannot rely only on that, since we may connect to a different electrum server after a restart, or transactions may be evicted from their mempool. | ||
| * Since we don't have an easy way of asking electrum to check for double-spends, we would end up with channels that are stuck waiting for confirmations. | ||
| * This generally wouldn't be a security issue (only one of the funding attempts would succeed), unless 0-conf is used and our LSP is malicious. | ||
| * | ||
| * Note: this object is *not* thread-safe and should be used in a dedicated coroutine. | ||
| */ | ||
| class SwapInManager(private var reservedUtxos: Set<OutPoint>, private val logger: MDCLogger) { | ||
| constructor(bootChannels: List<PersistedChannelState>, logger: MDCLogger) : this(reservedWalletInputs(bootChannels), logger) | ||
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| internal fun process(cmd: SwapInCommand): RequestChannelOpen? = when (cmd) { | ||
| is SwapInCommand.TrySwapIn -> { | ||
| val availableWallet = cmd.wallet.withoutReservedUtxos(reservedUtxos).withConfirmations(cmd.currentBlockHeight, cmd.swapInConfirmations) | ||
| logger.info { "swap-in wallet balance (migration=${cmd.isMigrationFromLegacyApp}): deeplyConfirmed=${availableWallet.deeplyConfirmed.balance}, weaklyConfirmed=${availableWallet.weaklyConfirmed.balance}, unconfirmed=${availableWallet.unconfirmed.balance}" } | ||
| val utxos = when { | ||
| // When migrating from the legacy android app, we use all utxos, even unconfirmed ones. | ||
| cmd.isMigrationFromLegacyApp -> availableWallet.all | ||
| else -> availableWallet.deeplyConfirmed | ||
| } | ||
| if (utxos.balance > 0.sat) { | ||
| logger.info { "swap-in wallet: requesting channel using ${utxos.size} utxos with balance=${utxos.balance}" } | ||
| reservedUtxos = reservedUtxos.union(utxos.map { it.outPoint }) | ||
| RequestChannelOpen(Lightning.randomBytes32(), utxos) | ||
| } else { | ||
| null | ||
| } | ||
| } | ||
| is SwapInCommand.UnlockWalletInputs -> { | ||
| logger.debug { "releasing ${cmd.inputs.size} utxos" } | ||
| reservedUtxos = reservedUtxos - cmd.inputs | ||
| null | ||
| } | ||
| } | ||
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| companion object { | ||
| /** | ||
| * Return the list of wallet inputs used in pending unconfirmed channel funding attempts. | ||
| * These inputs should not be reused in other funding attempts, otherwise we would double-spend ourselves. | ||
| */ | ||
| fun reservedWalletInputs(channels: List<PersistedChannelState>): Set<OutPoint> { | ||
| val unconfirmedFundingTxs: List<SignedSharedTransaction> = buildList { | ||
| for (channel in channels) { | ||
| // Add all unsigned inputs currently used to build a funding tx that isn't broadcast yet (creation, rbf, splice). | ||
| when { | ||
| channel is WaitForFundingSigned -> add(channel.signingSession.fundingTx) | ||
| channel is WaitForFundingConfirmed && channel.rbfStatus is RbfStatus.WaitingForSigs -> add(channel.rbfStatus.session.fundingTx) | ||
| channel is Normal && channel.spliceStatus is SpliceStatus.WaitingForSigs -> add(channel.spliceStatus.session.fundingTx) | ||
| else -> {} | ||
| } | ||
| // Add all inputs in unconfirmed funding txs (utxos spent by confirmed transactions will never appear in our wallet). | ||
| when (channel) { | ||
| is ChannelStateWithCommitments -> channel.commitments.all | ||
| .map { it.localFundingStatus } | ||
| .filterIsInstance<LocalFundingStatus.UnconfirmedFundingTx>() | ||
| .forEach { add(it.sharedTx) } | ||
| else -> {} | ||
| } | ||
| } | ||
| } | ||
| val localInputs = unconfirmedFundingTxs.flatMap { fundingTx -> fundingTx.tx.localInputs.map { it.outPoint } } | ||
| return localInputs.toSet() | ||
| } | ||
| } | ||
| } |
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