99 lines
3.4 KiB
Go
99 lines
3.4 KiB
Go
// Copyright (c) 2016 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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// Package txrules provides transaction rules that should be followed by
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// transaction authors for wide mempool acceptance and quick mining.
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package txrules
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import (
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"errors"
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"github.com/btcsuite/btcd/txscript"
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"github.com/btcsuite/btcd/wire"
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"github.com/btcsuite/btcutil"
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)
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// DefaultRelayFeePerKb is the default minimum relay fee policy for a mempool.
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const DefaultRelayFeePerKb btcutil.Amount = 1e3
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// GetDustThreshold is used to define the amount below which output will be
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// determined as dust. Threshold is determined as 3 times the relay fee.
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func GetDustThreshold(scriptSize int, relayFeePerKb btcutil.Amount) btcutil.Amount {
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// Calculate the total (estimated) cost to the network. This is
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// calculated using the serialize size of the output plus the serial
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// size of a transaction input which redeems it. The output is assumed
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// to be compressed P2PKH as this is the most common script type. Use
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// the average size of a compressed P2PKH redeem input (148) rather than
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// the largest possible (txsizes.RedeemP2PKHInputSize).
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totalSize := 8 + wire.VarIntSerializeSize(uint64(scriptSize)) +
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scriptSize + 148
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byteFee := relayFeePerKb / 1000
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relayFee := btcutil.Amount(totalSize) * byteFee
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return 3 * relayFee
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}
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// IsDustAmount determines whether a transaction output value and script length would
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// cause the output to be considered dust. Transactions with dust outputs are
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// not standard and are rejected by mempools with default policies.
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func IsDustAmount(amount btcutil.Amount, scriptSize int, relayFeePerKb btcutil.Amount) bool {
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return amount < GetDustThreshold(scriptSize, relayFeePerKb)
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}
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// IsDustOutput determines whether a transaction output is considered dust.
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// Transactions with dust outputs are not standard and are rejected by mempools
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// with default policies.
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func IsDustOutput(output *wire.TxOut, relayFeePerKb btcutil.Amount) bool {
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// Unspendable outputs which solely carry data are not checked for dust.
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if txscript.GetScriptClass(output.PkScript) == txscript.NullDataTy {
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return false
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}
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// All other unspendable outputs are considered dust.
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if txscript.IsUnspendable(output.PkScript) {
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return true
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}
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return IsDustAmount(btcutil.Amount(output.Value), len(output.PkScript),
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relayFeePerKb)
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}
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// Transaction rule violations
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var (
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ErrAmountNegative = errors.New("transaction output amount is negative")
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ErrAmountExceedsMax = errors.New("transaction output amount exceeds maximum value")
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ErrOutputIsDust = errors.New("transaction output is dust")
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)
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// CheckOutput performs simple consensus and policy tests on a transaction
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// output.
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func CheckOutput(output *wire.TxOut, relayFeePerKb btcutil.Amount) error {
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if output.Value < 0 {
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return ErrAmountNegative
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}
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if output.Value > btcutil.MaxSatoshi {
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return ErrAmountExceedsMax
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}
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if IsDustOutput(output, relayFeePerKb) {
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return ErrOutputIsDust
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}
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return nil
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}
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// FeeForSerializeSize calculates the required fee for a transaction of some
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// arbitrary size given a mempool's relay fee policy.
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func FeeForSerializeSize(relayFeePerKb btcutil.Amount, txSerializeSize int) btcutil.Amount {
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fee := relayFeePerKb * btcutil.Amount(txSerializeSize) / 1000
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if fee == 0 && relayFeePerKb > 0 {
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fee = relayFeePerKb
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}
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if fee < 0 || fee > btcutil.MaxSatoshi {
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fee = btcutil.MaxSatoshi
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}
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return fee
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}
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