From f8e6854197cd337b652c1260999a8a397d0d4703 Mon Sep 17 00:00:00 2001
From: eugene <elzeigel@gmail.com>
Date: Mon, 16 Aug 2021 12:40:38 -0400
Subject: [PATCH] mempool: introduce GetDustThreshold to export dust limit
calculation
This commit modifies no behavior and would allow other projects to
retrieve the dust limit for a particular output type before the
amount of the output is known. This is particularly useful in the
Lightning Network for channel negotiation.
---
mempool/policy.go | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)
diff --git a/mempool/policy.go b/mempool/policy.go
index 74142bf6..1fe85079 100644
--- a/mempool/policy.go
+++ b/mempool/policy.go
@@ -172,17 +172,10 @@ func checkPkScriptStandard(pkScript []byte, scriptClass txscript.ScriptClass) er
return nil
}
-// IsDust returns whether or not the passed transaction output amount is
-// considered dust or not based on the passed minimum transaction relay fee.
-// Dust is defined in terms of the minimum transaction relay fee. In
-// particular, if the cost to the network to spend coins is more than 1/3 of the
-// minimum transaction relay fee, it is considered dust.
-func IsDust(txOut *wire.TxOut, minRelayTxFee btcutil.Amount) bool {
- // Unspendable outputs are considered dust.
- if txscript.IsUnspendable(txOut.PkScript) {
- return true
- }
-
+// GetDustThreshold calculates the dust limit for a *wire.TxOut by taking the
+// size of a typical spending transaction and multiplying it by 3 to account
+// for the minimum dust relay fee of 3000sat/kvb.
+func GetDustThreshold(txOut *wire.TxOut) int64 {
// The total serialized size consists of the output and the associated
// input script to redeem it. Since there is no input script
// to redeem it yet, use the minimum size of a typical input script.
@@ -253,6 +246,20 @@ func IsDust(txOut *wire.TxOut, minRelayTxFee btcutil.Amount) bool {
totalSize += 107
}
+ return 3 * int64(totalSize)
+}
+
+// IsDust returns whether or not the passed transaction output amount is
+// considered dust or not based on the passed minimum transaction relay fee.
+// Dust is defined in terms of the minimum transaction relay fee. In
+// particular, if the cost to the network to spend coins is more than 1/3 of the
+// minimum transaction relay fee, it is considered dust.
+func IsDust(txOut *wire.TxOut, minRelayTxFee btcutil.Amount) bool {
+ // Unspendable outputs are considered dust.
+ if txscript.IsUnspendable(txOut.PkScript) {
+ return true
+ }
+
// The output is considered dust if the cost to the network to spend the
// coins is more than 1/3 of the minimum free transaction relay fee.
// minFreeTxRelayFee is in Satoshi/KB, so multiply by 1000 to
@@ -265,7 +272,7 @@ func IsDust(txOut *wire.TxOut, minRelayTxFee btcutil.Amount) bool {
//
// The following is equivalent to (value/totalSize) * (1/3) * 1000
// without needing to do floating point math.
- return txOut.Value*1000/(3*int64(totalSize)) < int64(minRelayTxFee)
+ return txOut.Value*1000/GetDustThreshold(txOut) < int64(minRelayTxFee)
}
// checkTransactionStandard performs a series of checks on a transaction to