package lnwallet import ( "encoding/json" "github.com/btcsuite/btcd/blockchain" "github.com/btcsuite/btcd/rpcclient" "github.com/btcsuite/btcutil" ) // SatPerVByte represents a fee rate in satoshis per vbyte. type SatPerVByte btcutil.Amount // FeeForVSize calculates the fee resulting from this fee rate and // the given vsize in vbytes. func (s SatPerVByte) FeeForVSize(vbytes int64) btcutil.Amount { return btcutil.Amount(s) * btcutil.Amount(vbytes) } // FeePerKWeight converts the fee rate into SatPerKWeight. func (s SatPerVByte) FeePerKWeight() SatPerKWeight { return SatPerKWeight(s * 1000 / blockchain.WitnessScaleFactor) } // SatPerKWeight represents a fee rate in satoshis per kilo weight unit. type SatPerKWeight btcutil.Amount // FeeForWeight calculates the fee resulting from this fee rate and the // given weight in weight units (wu). func (s SatPerKWeight) FeeForWeight(wu int64) btcutil.Amount { // The resulting fee is rounded down, as specified in BOLT#03. return btcutil.Amount(s) * btcutil.Amount(wu) / 1000 } // FeeEstimator provides the ability to estimate on-chain transaction fees for // various combinations of transaction sizes and desired confirmation time // (measured by number of blocks). type FeeEstimator interface { // EstimateFeePerVSize takes in a target for the number of blocks until // an initial confirmation and returns the estimated fee expressed in // satoshis/vbyte. EstimateFeePerVSize(numBlocks uint32) (SatPerVByte, error) // Start signals the FeeEstimator to start any processes or goroutines // it needs to perform its duty. Start() error // Stop stops any spawned goroutines and cleans up the resources used // by the fee estimator. Stop() error } // StaticFeeEstimator will return a static value for all fee calculation // requests. It is designed to be replaced by a proper fee calculation // implementation. type StaticFeeEstimator struct { // FeeRate is the static fee rate in satoshis-per-vbyte that will be // returned by this fee estimator. FeeRate SatPerVByte } // EstimateFeePerVSize will return a static value for fee calculations. // // NOTE: This method is part of the FeeEstimator interface. func (e StaticFeeEstimator) EstimateFeePerVSize(numBlocks uint32) (SatPerVByte, error) { return e.FeeRate, nil } // Start signals the FeeEstimator to start any processes or goroutines // it needs to perform its duty. // // NOTE: This method is part of the FeeEstimator interface. func (e StaticFeeEstimator) Start() error { return nil } // Stop stops any spawned goroutines and cleans up the resources used // by the fee estimator. // // NOTE: This method is part of the FeeEstimator interface. func (e StaticFeeEstimator) Stop() error { return nil } // A compile-time assertion to ensure that StaticFeeEstimator implements the // FeeEstimator interface. var _ FeeEstimator = (*StaticFeeEstimator)(nil) // BtcdFeeEstimator is an implementation of the FeeEstimator interface backed // by the RPC interface of an active btcd node. This implementation will proxy // any fee estimation requests to btcd's RPC interface. type BtcdFeeEstimator struct { // fallBackFeeRate is the fall back fee rate in satoshis per vbyte that // is returned if the fee estimator does not yet have enough data to // actually produce fee estimates. fallBackFeeRate SatPerVByte // minFeeRate is the minimum relay fee, in sat/vbyte, of the backend // node. This will be used as the default fee rate of a transaction when // the estimated fee rate is too low to allow the transaction to // propagate through the network. minFeeRate SatPerVByte btcdConn *rpcclient.Client } // NewBtcdFeeEstimator creates a new BtcdFeeEstimator given a fully populated // rpc config that is able to successfully connect and authenticate with the // btcd node, and also a fall back fee rate. The fallback fee rate is used in // the occasion that the estimator has insufficient data, or returns zero for a // fee estimate. func NewBtcdFeeEstimator(rpcConfig rpcclient.ConnConfig, fallBackFeeRate SatPerVByte) (*BtcdFeeEstimator, error) { rpcConfig.DisableConnectOnNew = true rpcConfig.DisableAutoReconnect = false chainConn, err := rpcclient.New(&rpcConfig, nil) if err != nil { return nil, err } return &BtcdFeeEstimator{ fallBackFeeRate: fallBackFeeRate, btcdConn: chainConn, }, nil } // Start signals the FeeEstimator to start any processes or goroutines // it needs to perform its duty. // // NOTE: This method is part of the FeeEstimator interface. func (b *BtcdFeeEstimator) Start() error { if err := b.btcdConn.Connect(20); err != nil { return err } // Once the connection to the backend node has been established, we'll // query it for its minimum relay fee. info, err := b.btcdConn.GetInfo() if err != nil { return err } relayFee, err := btcutil.NewAmount(info.RelayFee) if err != nil { return err } // The fee rate is expressed in sat/KB, so we'll manually convert it to // our desired sat/vbyte rate. b.minFeeRate = SatPerVByte(relayFee / 1000) return nil } // Stop stops any spawned goroutines and cleans up the resources used // by the fee estimator. // // NOTE: This method is part of the FeeEstimator interface. func (b *BtcdFeeEstimator) Stop() error { b.btcdConn.Shutdown() return nil } // EstimateFeePerVSize takes in a target for the number of blocks until an // initial confirmation and returns the estimated fee expressed in // satoshis/vbyte. // // NOTE: This method is part of the FeeEstimator interface. func (b *BtcdFeeEstimator) EstimateFeePerVSize(numBlocks uint32) (SatPerVByte, error) { feeEstimate, err := b.fetchEstimatePerVSize(numBlocks) switch { // If the estimator doesn't have enough data, or returns an error, then // to return a proper value, then we'll return the default fall back // fee rate. case err != nil: walletLog.Errorf("unable to query estimator: %v", err) fallthrough case feeEstimate == 0: return b.fallBackFeeRate, nil } return feeEstimate, nil } // fetchEstimate returns a fee estimate for a transaction to be confirmed in // confTarget blocks. The estimate is returned in sat/vbyte. func (b *BtcdFeeEstimator) fetchEstimatePerVSize( confTarget uint32) (SatPerVByte, error) { // First, we'll fetch the estimate for our confirmation target. btcPerKB, err := b.btcdConn.EstimateFee(int64(confTarget)) if err != nil { return 0, err } // Next, we'll convert the returned value to satoshis, as it's // currently returned in BTC. satPerKB, err := btcutil.NewAmount(btcPerKB) if err != nil { return 0, err } // The value returned is expressed in fees per KB, while we want // fee-per-byte, so we'll divide by 1000 to map to satoshis-per-byte // before returning the estimate. satPerByte := SatPerVByte(satPerKB / 1000) // Before proceeding, we'll make sure that this fee rate respects the // minimum relay fee set on the backend node. if satPerByte < b.minFeeRate { walletLog.Debugf("Using backend node's minimum relay fee rate "+ "of %v sat/vbyte", b.minFeeRate) satPerByte = b.minFeeRate } walletLog.Debugf("Returning %v sat/vbyte for conf target of %v", int64(satPerByte), confTarget) return satPerByte, nil } // A compile-time assertion to ensure that BtcdFeeEstimator implements the // FeeEstimator interface. var _ FeeEstimator = (*BtcdFeeEstimator)(nil) // BitcoindFeeEstimator is an implementation of the FeeEstimator interface // backed by the RPC interface of an active bitcoind node. This implementation // will proxy any fee estimation requests to bitcoind's RPC interface. type BitcoindFeeEstimator struct { // fallBackFeeRate is the fall back fee rate in satoshis per vbyte that // is returned if the fee estimator does not yet have enough data to // actually produce fee estimates. fallBackFeeRate SatPerVByte // minFeeRate is the minimum relay fee, in sat/vbyte, of the backend // node. This will be used as the default fee rate of a transaction when // the estimated fee rate is too low to allow the transaction to // propagate through the network. minFeeRate SatPerVByte bitcoindConn *rpcclient.Client } // NewBitcoindFeeEstimator creates a new BitcoindFeeEstimator given a fully // populated rpc config that is able to successfully connect and authenticate // with the bitcoind node, and also a fall back fee rate. The fallback fee rate // is used in the occasion that the estimator has insufficient data, or returns // zero for a fee estimate. func NewBitcoindFeeEstimator(rpcConfig rpcclient.ConnConfig, fallBackFeeRate SatPerVByte) (*BitcoindFeeEstimator, error) { rpcConfig.DisableConnectOnNew = true rpcConfig.DisableAutoReconnect = false rpcConfig.DisableTLS = true rpcConfig.HTTPPostMode = true chainConn, err := rpcclient.New(&rpcConfig, nil) if err != nil { return nil, err } return &BitcoindFeeEstimator{ fallBackFeeRate: fallBackFeeRate, bitcoindConn: chainConn, }, nil } // Start signals the FeeEstimator to start any processes or goroutines // it needs to perform its duty. // // NOTE: This method is part of the FeeEstimator interface. func (b *BitcoindFeeEstimator) Start() error { // Once the connection to the backend node has been established, we'll // query it for its minimum relay fee. Since the `getinfo` RPC has been // deprecated for `bitcoind`, we'll need to send a `getnetworkinfo` // command as a raw request. resp, err := b.bitcoindConn.RawRequest("getnetworkinfo", nil) if err != nil { return err } // Parse the response to retrieve the relay fee in sat/KB. info := struct { RelayFee float64 `json:"relayfee"` }{} if err := json.Unmarshal(resp, &info); err != nil { return err } relayFee, err := btcutil.NewAmount(info.RelayFee) if err != nil { return err } // The fee rate is expressed in sat/KB, so we'll manually convert it to // our desired sat/vbyte rate. b.minFeeRate = SatPerVByte(relayFee / 1000) return nil } // Stop stops any spawned goroutines and cleans up the resources used // by the fee estimator. // // NOTE: This method is part of the FeeEstimator interface. func (b *BitcoindFeeEstimator) Stop() error { return nil } // EstimateFeePerVSize takes in a target for the number of blocks until an // initial confirmation and returns the estimated fee expressed in // satoshis/vbyte. // // NOTE: This method is part of the FeeEstimator interface. func (b *BitcoindFeeEstimator) EstimateFeePerVSize(numBlocks uint32) (SatPerVByte, error) { feeEstimate, err := b.fetchEstimatePerVSize(numBlocks) switch { // If the estimator doesn't have enough data, or returns an error, then // to return a proper value, then we'll return the default fall back // fee rate. case err != nil: walletLog.Errorf("unable to query estimator: %v", err) fallthrough case feeEstimate == 0: return b.fallBackFeeRate, nil } return feeEstimate, nil } // fetchEstimatePerVSize returns a fee estimate for a transaction to be confirmed in // confTarget blocks. The estimate is returned in sat/vbyte. func (b *BitcoindFeeEstimator) fetchEstimatePerVSize( confTarget uint32) (SatPerVByte, error) { // First, we'll send an "estimatesmartfee" command as a raw request, // since it isn't supported by btcd but is available in bitcoind. target, err := json.Marshal(uint64(confTarget)) if err != nil { return 0, err } // TODO: Allow selection of economical/conservative modifiers. resp, err := b.bitcoindConn.RawRequest("estimatesmartfee", []json.RawMessage{target}) if err != nil { return 0, err } // Next, we'll parse the response to get the BTC per KB. feeEstimate := struct { Feerate float64 `json:"feerate"` }{} err = json.Unmarshal(resp, &feeEstimate) if err != nil { return 0, err } // Next, we'll convert the returned value to satoshis, as it's // currently returned in BTC. satPerKB, err := btcutil.NewAmount(feeEstimate.Feerate) if err != nil { return 0, err } // The value returned is expressed in fees per KB, while we want // fee-per-byte, so we'll divide by 1000 to map to satoshis-per-byte // before returning the estimate. satPerByte := SatPerVByte(satPerKB / 1000) // Before proceeding, we'll make sure that this fee rate respects the // minimum relay fee set on the backend node. if satPerByte < b.minFeeRate { walletLog.Debugf("Using backend node's minimum relay fee rate "+ "of %v sat/vbyte", b.minFeeRate) satPerByte = b.minFeeRate } walletLog.Debugf("Returning %v sat/vbyte for conf target of %v", int64(satPerByte), confTarget) return satPerByte, nil } // A compile-time assertion to ensure that BitcoindFeeEstimator implements the // FeeEstimator interface. var _ FeeEstimator = (*BitcoindFeeEstimator)(nil)