package btcdnotify import ( "errors" "fmt" "sync" "sync/atomic" "time" "github.com/lightningnetwork/lnd/chainntnfs" "github.com/roasbeef/btcd/btcjson" "github.com/roasbeef/btcd/chaincfg/chainhash" "github.com/roasbeef/btcd/rpcclient" "github.com/roasbeef/btcd/wire" "github.com/roasbeef/btcutil" ) const ( // notifierType uniquely identifies this concrete implementation of the // ChainNotifier interface. notifierType = "btcd" // reorgSafetyLimit is assumed maximum depth of a chain reorganization. // After this many confirmation, transaction confirmation info will be // pruned. reorgSafetyLimit = 100 ) var ( // ErrChainNotifierShuttingDown is used when we are trying to // measure a spend notification when notifier is already stopped. ErrChainNotifierShuttingDown = errors.New("chainntnfs: system interrupt " + "while attempting to register for spend notification.") ) // chainUpdate encapsulates an update to the current main chain. This struct is // used as an element within an unbounded queue in order to avoid blocking the // main rpc dispatch rule. type chainUpdate struct { blockHash *chainhash.Hash blockHeight int32 // connected is true if this update is a new block and false if it is a // disconnected block. connect bool } // txUpdate encapsulates a transaction related notification sent from btcd to // the registered RPC client. This struct is used as an element within an // unbounded queue in order to avoid blocking the main rpc dispatch rule. type txUpdate struct { tx *btcutil.Tx details *btcjson.BlockDetails } // TODO(roasbeef): generalize struct below: // * move chans to config, allow outside callers to handle send conditions // BtcdNotifier implements the ChainNotifier interface using btcd's websockets // notifications. Multiple concurrent clients are supported. All notifications // are achieved via non-blocking sends on client channels. type BtcdNotifier struct { spendClientCounter uint64 // To be used atomically. epochClientCounter uint64 // To be used atomically. started int32 // To be used atomically. stopped int32 // To be used atomically. chainConn *rpcclient.Client notificationCancels chan interface{} notificationRegistry chan interface{} spendNotifications map[wire.OutPoint]map[uint64]*spendNotification txConfNotifier *chainntnfs.TxConfNotifier blockEpochClients map[uint64]*blockEpochRegistration chainUpdates *chainntnfs.ConcurrentQueue txUpdates *chainntnfs.ConcurrentQueue wg sync.WaitGroup quit chan struct{} } // Ensure BtcdNotifier implements the ChainNotifier interface at compile time. var _ chainntnfs.ChainNotifier = (*BtcdNotifier)(nil) // New returns a new BtcdNotifier instance. This function assumes the btcd node // detailed in the passed configuration is already running, and willing to // accept new websockets clients. func New(config *rpcclient.ConnConfig) (*BtcdNotifier, error) { notifier := &BtcdNotifier{ notificationCancels: make(chan interface{}), notificationRegistry: make(chan interface{}), blockEpochClients: make(map[uint64]*blockEpochRegistration), spendNotifications: make(map[wire.OutPoint]map[uint64]*spendNotification), chainUpdates: chainntnfs.NewConcurrentQueue(10), txUpdates: chainntnfs.NewConcurrentQueue(10), quit: make(chan struct{}), } ntfnCallbacks := &rpcclient.NotificationHandlers{ OnBlockConnected: notifier.onBlockConnected, OnBlockDisconnected: notifier.onBlockDisconnected, OnRedeemingTx: notifier.onRedeemingTx, } // Disable connecting to btcd within the rpcclient.New method. We // defer establishing the connection to our .Start() method. config.DisableConnectOnNew = true config.DisableAutoReconnect = false chainConn, err := rpcclient.New(config, ntfnCallbacks) if err != nil { return nil, err } notifier.chainConn = chainConn return notifier, nil } // Start connects to the running btcd node over websockets, registers for block // notifications, and finally launches all related helper goroutines. func (b *BtcdNotifier) Start() error { // Already started? if atomic.AddInt32(&b.started, 1) != 1 { return nil } // Connect to btcd, and register for notifications on connected, and // disconnected blocks. if err := b.chainConn.Connect(20); err != nil { return err } if err := b.chainConn.NotifyBlocks(); err != nil { return err } _, currentHeight, err := b.chainConn.GetBestBlock() if err != nil { return err } b.txConfNotifier = chainntnfs.NewTxConfNotifier( uint32(currentHeight), reorgSafetyLimit) b.chainUpdates.Start() b.txUpdates.Start() b.wg.Add(1) go b.notificationDispatcher(currentHeight) return nil } // Stop shutsdown the BtcdNotifier. func (b *BtcdNotifier) Stop() error { // Already shutting down? if atomic.AddInt32(&b.stopped, 1) != 1 { return nil } // Shutdown the rpc client, this gracefully disconnects from btcd, and // cleans up all related resources. b.chainConn.Shutdown() close(b.quit) b.wg.Wait() b.chainUpdates.Stop() b.txUpdates.Stop() // Notify all pending clients of our shutdown by closing the related // notification channels. for _, spendClients := range b.spendNotifications { for _, spendClient := range spendClients { close(spendClient.spendChan) } } for _, epochClient := range b.blockEpochClients { close(epochClient.cancelChan) epochClient.wg.Wait() close(epochClient.epochChan) } b.txConfNotifier.TearDown() return nil } // onBlockConnected implements on OnBlockConnected callback for rpcclient. // Ingesting a block updates the wallet's internal utxo state based on the // outputs created and destroyed within each block. func (b *BtcdNotifier) onBlockConnected(hash *chainhash.Hash, height int32, t time.Time) { // Append this new chain update to the end of the queue of new chain // updates. b.chainUpdates.ChanIn() <- &chainUpdate{ blockHash: hash, blockHeight: height, connect: true, } } // onBlockDisconnected implements on OnBlockDisconnected callback for rpcclient. func (b *BtcdNotifier) onBlockDisconnected(hash *chainhash.Hash, height int32, t time.Time) { // Append this new chain update to the end of the queue of new chain // updates. b.chainUpdates.ChanIn() <- &chainUpdate{ blockHash: hash, blockHeight: height, connect: false, } } // onRedeemingTx implements on OnRedeemingTx callback for rpcclient. func (b *BtcdNotifier) onRedeemingTx(tx *btcutil.Tx, details *btcjson.BlockDetails) { // Append this new transaction update to the end of the queue of new // chain updates. b.txUpdates.ChanIn() <- &txUpdate{tx, details} } // notificationDispatcher is the primary goroutine which handles client // notification registrations, as well as notification dispatches. func (b *BtcdNotifier) notificationDispatcher(currentHeight int32) { out: for { select { case cancelMsg := <-b.notificationCancels: switch msg := cancelMsg.(type) { case *spendCancel: chainntnfs.Log.Infof("Cancelling spend "+ "notification for out_point=%v, "+ "spend_id=%v", msg.op, msg.spendID) // Before we attempt to close the spendChan, // ensure that the notification hasn't already // yet been dispatched. if outPointClients, ok := b.spendNotifications[msg.op]; ok { close(outPointClients[msg.spendID].spendChan) delete(b.spendNotifications[msg.op], msg.spendID) } case *epochCancel: chainntnfs.Log.Infof("Cancelling epoch "+ "notification, epoch_id=%v", msg.epochID) // First, we'll lookup the original // registration in order to stop the active // queue goroutine. reg := b.blockEpochClients[msg.epochID] reg.epochQueue.Stop() // Next, close the cancel channel for this // specific client, and wait for the client to // exit. close(b.blockEpochClients[msg.epochID].cancelChan) b.blockEpochClients[msg.epochID].wg.Wait() // Once the client has exited, we can then // safely close the channel used to send epoch // notifications, in order to notify any // listeners that the intent has been // cancelled. close(b.blockEpochClients[msg.epochID].epochChan) delete(b.blockEpochClients, msg.epochID) } case registerMsg := <-b.notificationRegistry: switch msg := registerMsg.(type) { case *spendNotification: chainntnfs.Log.Infof("New spend subscription: "+ "utxo=%v", msg.targetOutpoint) op := *msg.targetOutpoint if _, ok := b.spendNotifications[op]; !ok { b.spendNotifications[op] = make(map[uint64]*spendNotification) } b.spendNotifications[op][msg.spendID] = msg case *confirmationsNotification: chainntnfs.Log.Infof("New confirmations "+ "subscription: txid=%v, numconfs=%v", msg.TxID, msg.NumConfirmations) // Lookup whether the transaction is already included in the // active chain. txConf, err := b.historicalConfDetails(msg.TxID) if err != nil { chainntnfs.Log.Error(err) } err = b.txConfNotifier.Register(&msg.ConfNtfn, txConf) if err != nil { chainntnfs.Log.Error(err) } case *blockEpochRegistration: chainntnfs.Log.Infof("New block epoch subscription") b.blockEpochClients[msg.epochID] = msg } case item := <-b.chainUpdates.ChanOut(): update := item.(*chainUpdate) if update.connect { if update.blockHeight != currentHeight+1 { chainntnfs.Log.Warnf("Received blocks out of order: "+ "current height=%d, new height=%d", currentHeight, update.blockHeight) continue } currentHeight = update.blockHeight rawBlock, err := b.chainConn.GetBlock(update.blockHash) if err != nil { chainntnfs.Log.Errorf("Unable to get block: %v", err) continue } chainntnfs.Log.Infof("New block: height=%v, sha=%v", update.blockHeight, update.blockHash) b.notifyBlockEpochs(update.blockHeight, update.blockHash) txns := btcutil.NewBlock(rawBlock).Transactions() err = b.txConfNotifier.ConnectTip(update.blockHash, uint32(update.blockHeight), txns) if err != nil { chainntnfs.Log.Error(err) } continue } if update.blockHeight != currentHeight { chainntnfs.Log.Warnf("Received blocks out of order: "+ "current height=%d, disconnected height=%d", currentHeight, update.blockHeight) continue } currentHeight = update.blockHeight - 1 chainntnfs.Log.Infof("Block disconnected from main chain: "+ "height=%v, sha=%v", update.blockHeight, update.blockHash) err := b.txConfNotifier.DisconnectTip(uint32(update.blockHeight)) if err != nil { chainntnfs.Log.Error(err) } case item := <-b.txUpdates.ChanOut(): newSpend := item.(*txUpdate) spendingTx := newSpend.tx // First, check if this transaction spends an output // that has an existing spend notification for it. for i, txIn := range spendingTx.MsgTx().TxIn { prevOut := txIn.PreviousOutPoint // If this transaction indeed does spend an // output which we have a registered // notification for, then create a spend // summary, finally sending off the details to // the notification subscriber. if clients, ok := b.spendNotifications[prevOut]; ok { spenderSha := newSpend.tx.Hash() spendDetails := &chainntnfs.SpendDetail{ SpentOutPoint: &prevOut, SpenderTxHash: spenderSha, SpendingTx: spendingTx.MsgTx(), SpenderInputIndex: uint32(i), } // TODO(roasbeef): after change to // loadfilter, only notify on block // inclusion? if newSpend.details != nil { spendDetails.SpendingHeight = newSpend.details.Height } else { spendDetails.SpendingHeight = currentHeight + 1 } for _, ntfn := range clients { chainntnfs.Log.Infof("Dispatching "+ "spend notification for "+ "outpoint=%v", ntfn.targetOutpoint) ntfn.spendChan <- spendDetails // Close spendChan to ensure that any calls to Cancel will not // block. This is safe to do since the channel is buffered, and the // message can still be read by the receiver. close(ntfn.spendChan) } delete(b.spendNotifications, prevOut) } } case <-b.quit: break out } } b.wg.Done() } // historicalConfDetails looks up whether a transaction is already included in a // block in the active chain and, if so, returns details about the confirmation. func (b *BtcdNotifier) historicalConfDetails(txid *chainhash.Hash, ) (*chainntnfs.TxConfirmation, error) { // If the transaction already has some or all of the confirmations, // then we may be able to dispatch it immediately. tx, err := b.chainConn.GetRawTransactionVerbose(txid) if err != nil || tx == nil || tx.BlockHash == "" { if err == nil { return nil, nil } // Do not return an error if the transaction was not found. if jsonErr, ok := err.(*btcjson.RPCError); ok { if jsonErr.Code == btcjson.ErrRPCNoTxInfo { return nil, nil } } return nil, fmt.Errorf("unable to query for txid(%v): %v", txid, err) } // As we need to fully populate the returned TxConfirmation struct, // grab the block in which the transaction was confirmed so we can // locate its exact index within the block. blockHash, err := chainhash.NewHashFromStr(tx.BlockHash) if err != nil { return nil, fmt.Errorf("unable to get block hash %v for historical "+ "dispatch: %v", tx.BlockHash, err) } block, err := b.chainConn.GetBlockVerbose(blockHash) if err != nil { return nil, fmt.Errorf("unable to get block hash: %v", err) } // If the block obtained, locate the transaction's index within the // block so we can give the subscriber full confirmation details. txIndex := -1 targetTxidStr := txid.String() for i, txHash := range block.Tx { if txHash == targetTxidStr { txIndex = i break } } if txIndex == -1 { return nil, fmt.Errorf("unable to locate tx %v in block %v", txid, blockHash) } txConf := chainntnfs.TxConfirmation{ BlockHash: blockHash, BlockHeight: uint32(block.Height), TxIndex: uint32(txIndex), } return &txConf, nil } // notifyBlockEpochs notifies all registered block epoch clients of the newly // connected block to the main chain. func (b *BtcdNotifier) notifyBlockEpochs(newHeight int32, newSha *chainhash.Hash) { epoch := &chainntnfs.BlockEpoch{ Height: newHeight, Hash: newSha, } for _, epochClient := range b.blockEpochClients { select { case epochClient.epochQueue.ChanIn() <- epoch: case <-epochClient.cancelChan: case <-b.quit: } } } // spendNotification couples a target outpoint along with the channel used for // notifications once a spend of the outpoint has been detected. type spendNotification struct { targetOutpoint *wire.OutPoint spendChan chan *chainntnfs.SpendDetail spendID uint64 } // spendCancel is a message sent to the BtcdNotifier when a client wishes to // cancel an outstanding spend notification that has yet to be dispatched. type spendCancel struct { // op is the target outpoint of the notification to be cancelled. op wire.OutPoint // spendID the ID of the notification to cancel. spendID uint64 } // RegisterSpendNtfn registers an intent to be notified once the target // outpoint has been spent by a transaction on-chain. Once a spend of the target // outpoint has been detected, the details of the spending event will be sent // across the 'Spend' channel. func (b *BtcdNotifier) RegisterSpendNtfn(outpoint *wire.OutPoint, _ uint32) (*chainntnfs.SpendEvent, error) { ntfn := &spendNotification{ targetOutpoint: outpoint, spendChan: make(chan *chainntnfs.SpendDetail, 1), spendID: atomic.AddUint64(&b.spendClientCounter, 1), } select { case <-b.quit: return nil, ErrChainNotifierShuttingDown case b.notificationRegistry <- ntfn: } if err := b.chainConn.NotifySpent([]*wire.OutPoint{outpoint}); err != nil { return nil, err } // The following conditional checks to ensure that when a spend notification // is registered, the output hasn't already been spent. If the output // is no longer in the UTXO set, the chain will be rescanned from the point // where the output was added. The rescan will dispatch the notification. txout, err := b.chainConn.GetTxOut(&outpoint.Hash, outpoint.Index, true) if err != nil { return nil, err } if txout == nil { transaction, err := b.chainConn.GetRawTransactionVerbose(&outpoint.Hash) if err != nil { jsonErr, ok := err.(*btcjson.RPCError) if !ok || jsonErr.Code != btcjson.ErrRPCNoTxInfo { return nil, err } } // We'll only request a rescan if the transaction has actually // been included within a block. Otherwise, we'll encounter an // error when scanning for blocks. This can happens in the case // of a race condition, wherein the output itself is unspent, // and only arrives in the mempool after the getxout call. if transaction != nil && transaction.BlockHash != "" { blockhash, err := chainhash.NewHashFromStr(transaction.BlockHash) if err != nil { return nil, err } ops := []*wire.OutPoint{outpoint} if err := b.chainConn.Rescan(blockhash, nil, ops); err != nil { chainntnfs.Log.Errorf("Rescan for spend "+ "notification txout failed: %v", err) return nil, err } } } return &chainntnfs.SpendEvent{ Spend: ntfn.spendChan, Cancel: func() { cancel := &spendCancel{ op: *outpoint, spendID: ntfn.spendID, } // Submit spend cancellation to notification dispatcher. select { case b.notificationCancels <- cancel: // Cancellation is being handled, drain the spend chan until it is // closed before yielding to the caller. for { select { case _, ok := <-ntfn.spendChan: if !ok { return } case <-b.quit: return } } case <-b.quit: } }, }, nil } // confirmationNotification represents a client's intent to receive a // notification once the target txid reaches numConfirmations confirmations. type confirmationsNotification struct { chainntnfs.ConfNtfn } // RegisterConfirmationsNtfn registers a notification with BtcdNotifier // which will be triggered once the txid reaches numConfs number of // confirmations. func (b *BtcdNotifier) RegisterConfirmationsNtfn(txid *chainhash.Hash, numConfs, _ uint32) (*chainntnfs.ConfirmationEvent, error) { ntfn := &confirmationsNotification{ chainntnfs.ConfNtfn{ TxID: txid, NumConfirmations: numConfs, Event: chainntnfs.NewConfirmationEvent(), }, } select { case <-b.quit: return nil, ErrChainNotifierShuttingDown case b.notificationRegistry <- ntfn: return ntfn.Event, nil } } // blockEpochRegistration represents a client's intent to receive a // notification with each newly connected block. type blockEpochRegistration struct { epochID uint64 epochChan chan *chainntnfs.BlockEpoch epochQueue *chainntnfs.ConcurrentQueue cancelChan chan struct{} wg sync.WaitGroup } // epochCancel is a message sent to the BtcdNotifier when a client wishes to // cancel an outstanding epoch notification that has yet to be dispatched. type epochCancel struct { epochID uint64 } // RegisterBlockEpochNtfn returns a BlockEpochEvent which subscribes the // caller to receive notifications, of each new block connected to the main // chain. func (b *BtcdNotifier) RegisterBlockEpochNtfn() (*chainntnfs.BlockEpochEvent, error) { reg := &blockEpochRegistration{ epochQueue: chainntnfs.NewConcurrentQueue(20), epochChan: make(chan *chainntnfs.BlockEpoch, 20), cancelChan: make(chan struct{}), epochID: atomic.AddUint64(&b.epochClientCounter, 1), } reg.epochQueue.Start() // Before we send the request to the main goroutine, we'll launch a new // goroutine to proxy items added to our queue to the client itself. // This ensures that all notifications are received *in order*. reg.wg.Add(1) go func() { defer reg.wg.Done() for { select { case ntfn := <-reg.epochQueue.ChanOut(): blockNtfn := ntfn.(*chainntnfs.BlockEpoch) select { case reg.epochChan <- blockNtfn: case <-reg.cancelChan: return case <-b.quit: return } case <-reg.cancelChan: return case <-b.quit: return } } }() select { case <-b.quit: // As we're exiting before the registration could be sent, // we'll stop the queue now ourselves. reg.epochQueue.Stop() return nil, errors.New("chainntnfs: system interrupt while " + "attempting to register for block epoch notification.") case b.notificationRegistry <- reg: return &chainntnfs.BlockEpochEvent{ Epochs: reg.epochChan, Cancel: func() { cancel := &epochCancel{ epochID: reg.epochID, } // Submit epoch cancellation to notification dispatcher. select { case b.notificationCancels <- cancel: // Cancellation is being handled, drain // the epoch channel until it is closed // before yielding to caller. for { select { case _, ok := <-reg.epochChan: if !ok { return } case <-b.quit: return } } case <-b.quit: } }, }, nil } }