Merge pull request #568 from GeorgeTsagk/fee-percentage-fix

liquidity: exclude prepay from total swap fees

Author: bhandras

liquidity/fees.go

@@ -329,13 +329,6 @@ func (f *FeePortion) loopOutLimits(swapAmt btcutil.Amount,
 		return newReasonError(ReasonSwapFee)
 	}
 
-	if quote.PrepayAmount > feeLimit {
-		log.Debugf("prepay amount: %v greater than fee limit: %v, at "+
-			"%v ppm", quote.PrepayAmount, feeLimit, f.PartsPerMillion)
-
-		return newReasonError(ReasonPrepay)
-	}
-
 	// If our miner and swap fee equal our limit, we will have nothing left
 	// for off-chain fees, so we fail out early.
 	if minerFee+quote.SwapFee >= feeLimit {
@@ -351,7 +344,7 @@ func (f *FeePortion) loopOutLimits(swapAmt btcutil.Amount,
 	// Calculate the worst case fees that we could pay for this swap,
 	// ensuring that we are within our fee limit even if the swap fails.
 	fees := worstCaseOutFees(
-		prepay, route, quote.SwapFee, miner, quote.PrepayAmount,
+		prepay, route, quote.SwapFee, miner,
 	)
 
 	if fees > feeLimit {

liquidity/liquidity.go

@@ -845,19 +845,10 @@ func (m *Manager) getSwapRestrictions(ctx context.Context, swapType swap.Type) (
 // the prepay because they failed to sweep the on chain htlc. This is unlikely,
 // because we expect clients to be online to sweep, but we want to account for
 // every outcome so we include it.
-func worstCaseOutFees(prepayRouting, swapRouting, swapFee, minerFee,
-	prepayAmount btcutil.Amount) btcutil.Amount {
+func worstCaseOutFees(prepayRouting, swapRouting, swapFee,
+	minerFee btcutil.Amount) btcutil.Amount {
 
-	var (
-		successFees = prepayRouting + minerFee + swapFee + swapRouting
-		noShowFees  = prepayRouting + prepayAmount
-	)
-
-	if noShowFees > successFees {
-		return noShowFees
-	}
-
-	return successFees
+	return prepayRouting + minerFee + swapFee + swapRouting
 }
 
 // existingAutoLoopSummary provides a summary of the existing autoloops which
@@ -910,19 +901,11 @@ func (m *Manager) checkExistingAutoLoops(ctx context.Context,
 		if out.State().State.Type() == loopdb.StateTypePending {
 			summary.inFlightCount++
 
-			prepay, err := m.cfg.Lnd.Client.DecodePaymentRequest(
-				ctx, out.Contract.PrepayInvoice,
-			)
-			if err != nil {
-				return nil, err
-			}
-
 			summary.pendingFees += worstCaseOutFees(
 				out.Contract.MaxPrepayRoutingFee,
 				out.Contract.MaxSwapRoutingFee,
 				out.Contract.MaxSwapFee,
 				out.Contract.MaxMinerFee,
-				mSatToSatoshis(prepay.Value),
 			)
 		} else if out.LastUpdateTime().After(
 			m.params.AutoloopBudgetLastRefresh,

liquidity/liquidity_test.go

@@ -1564,21 +1564,6 @@ func TestFeePercentage(t *testing.T) {
 				DisqualifiedPeers: noPeersDisqualified,
 			},
 		},
-		{
-			name:   "prepay too high",
-			feePPM: 30000,
-			quote: &loop.LoopOutQuote{
-				SwapFee:      75,
-				PrepayAmount: 300,
-				MinerFee:     1,
-			},
-			suggestions: &Suggestions{
-				DisqualifiedChans: map[lnwire.ShortChannelID]Reason{
-					chanID1: ReasonPrepay,
-				},
-				DisqualifiedPeers: noPeersDisqualified,
-			},
-		},
 	}
 
 	for _, testCase := range tests {

liquidity/loopout.go

@@ -28,7 +28,6 @@ func (l *loopOutSwapSuggestion) fees() btcutil.Amount {
 	return worstCaseOutFees(
 		l.OutRequest.MaxPrepayRoutingFee, l.OutRequest.MaxSwapRoutingFee,
 		l.OutRequest.MaxSwapFee, l.OutRequest.MaxMinerFee,
-		l.OutRequest.MaxPrepayAmount,
 	)
 }