lnwallet: add new helper functions to scale confirmations based on amt

lnwallet/confscale.go

@@ -0,0 +1,58 @@
+package lnwallet
+
+import (
+	"github.com/btcsuite/btcd/btcutil"
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+const (
+	// minRequiredConfs is the minimum number of confirmations we'll
+	// require for channel operations.
+	minRequiredConfs = 1
+
+	// maxRequiredConfs is the maximum number of confirmations we'll
+	// require for channel operations.
+	maxRequiredConfs = 6
+
+	// maxChannelSize is the maximum expected channel size in satoshis.
+	// This matches MaxBtcFundingAmount (0.16777215 BTC).
+	maxChannelSize = 16777215
+)
+
+// ScaleNumConfs returns a linearly scaled number of confirmations based on the
+// provided channel amount and push amount (for funding transactions). The push
+// amount represents additional risk when receiving funds.
+func ScaleNumConfs(chanAmt btcutil.Amount, pushAmt lnwire.MilliSatoshi) uint16 {
+	// For wumbo channels, always require maximum confirmations.
+	if chanAmt > maxChannelSize {
+		return maxRequiredConfs
+	}
+
+	// Calculate total stake: channel amount + push amount. The push amount
+	// represents value at risk for the receiver.
+	maxChannelSizeMsat := lnwire.NewMSatFromSatoshis(maxChannelSize)
+	stake := lnwire.NewMSatFromSatoshis(chanAmt) + pushAmt
+
+	// Scale confirmations linearly based on stake.
+	conf := uint64(maxRequiredConfs) * uint64(stake) /
+		uint64(maxChannelSizeMsat)
+
+	// Bound the result between minRequiredConfs and maxRequiredConfs.
+	if conf < minRequiredConfs {
+		conf = minRequiredConfs
+	}
+	if conf > maxRequiredConfs {
+		conf = maxRequiredConfs
+	}
+
+	return uint16(conf)
+}
+
+// FundingConfsForAmounts returns the number of confirmations to wait for a
+// funding transaction, taking into account both the channel amount and any
+// pushed amount (which represents additional risk).
+func FundingConfsForAmounts(chanAmt btcutil.Amount,
+	pushAmt lnwire.MilliSatoshi) uint16 {
+
+	return ScaleNumConfs(chanAmt, pushAmt)
+}