Impl addinvoice minroutinghints

lnrpc/invoicesrpc/addinvoice.go

@@ -136,6 +136,10 @@ type AddInvoiceData struct {
 	// RouteHints are optional route hints that can each be individually
 	// used to assist in reaching the invoice's destination.
 	RouteHints [][]zpay32.HopHint
+
+	// The minimum number of routing hints that will be included in an
+	// invoice.
+	MinHopHints int32
 }
 
 // paymentHashAndPreimage returns the payment hash and preimage for this invoice
@@ -400,7 +404,11 @@ func AddInvoice(ctx context.Context, cfg *AddInvoiceConfig,
 			totalHopHints = maxHopHints
 		}
 
-		hopHintsCfg := newSelectHopHintsCfg(cfg, totalHopHints)
+		hopHintsCfg := newSelectHopHintsCfg(
+			cfg,
+			totalHopHints,
+			int(invoice.MinHopHints),
+		)
 		hopHints, err := PopulateHopHints(
 			hopHintsCfg, amtMSat, invoice.RouteHints,
 		)
@@ -645,10 +653,13 @@ type SelectHopHintsCfg struct {
 
 	// MaxHopHints is the maximum number of hop hints we are interested in.
 	MaxHopHints int
+
+	// MinHopHints is the minimum number of hop hints we are interested in.
+	MinHopHints int
 }
 
 func newSelectHopHintsCfg(invoicesCfg *AddInvoiceConfig,
-	maxHopHints int) *SelectHopHintsCfg {
+	maxHopHints int, minHopHints int) *SelectHopHintsCfg {
 
 	return &SelectHopHintsCfg{
 		FetchAllChannels:      invoicesCfg.ChanDB.FetchAllChannels,
@@ -657,21 +668,27 @@ func newSelectHopHintsCfg(invoicesCfg *AddInvoiceConfig,
 		FetchChannelEdgesByID: invoicesCfg.Graph.FetchChannelEdgesByID,
 		GetAlias:              invoicesCfg.GetAlias,
 		MaxHopHints:           maxHopHints,
+		MinHopHints:           minHopHints,
 	}
 }
 
 // sufficientHints checks whether we have sufficient hop hints, based on the
 // any of the following criteria:
+//   - Min hop hints: the minimum of hints to include.
 //   - Hop hint count: the number of hints have reach our max target.
 //   - Total incoming capacity (for non-zero invoice amounts): the sum of the
 //     remote balance amount in the hints is bigger of equal than our target
 //     (currently twice the invoice amount)
 //
 // We limit our number of hop hints like this to keep our invoice size down,
 // and to avoid leaking all our private channels when we don't need to.
-func sufficientHints(nHintsLeft int, currentAmount,
+func sufficientHints(nCurrentHints, nHintsLeft, nMinHopHints int, currentAmount,
 	targetAmount lnwire.MilliSatoshi) bool {
 
+	if nCurrentHints < nMinHopHints {
+		return false
+	}
+
 	if nHintsLeft <= 0 {
 		log.Debugf("Reached targeted number of hop hints")
 		return true
@@ -765,16 +782,21 @@ func shouldIncludeChannel(cfg *SelectHopHintsCfg,
 //
 // NOTE: selectHopHints expects potentialHints to be already sorted in
 // descending priority.
-func selectHopHints(cfg *SelectHopHintsCfg, nHintsLeft int,
+func selectHopHints(cfg *SelectHopHintsCfg, nHintsLeft, nMinHopHints int,
 	targetBandwidth lnwire.MilliSatoshi,
 	potentialHints []*channeldb.OpenChannel,
 	alreadyIncluded map[uint64]bool) [][]zpay32.HopHint {
 
 	currentBandwidth := lnwire.MilliSatoshi(0)
 	hopHints := make([][]zpay32.HopHint, 0, nHintsLeft)
+	nCurrentHints := len(hopHints)
 	for _, channel := range potentialHints {
 		enoughHopHints := sufficientHints(
-			nHintsLeft, currentBandwidth, targetBandwidth,
+			nCurrentHints,
+			nHintsLeft,
+			nMinHopHints,
+			currentBandwidth,
+			targetBandwidth,
 		)
 		if enoughHopHints {
 			return hopHints
@@ -832,8 +854,8 @@ func PopulateHopHints(cfg *SelectHopHintsCfg, amtMSat lnwire.MilliSatoshi,
 
 	targetBandwidth := amtMSat * hopHintFactor
 	selectedHints := selectHopHints(
-		cfg, nHintsLeft, targetBandwidth, potentialHints,
-		alreadyIncluded,
+		cfg, nHintsLeft, cfg.MinHopHints, targetBandwidth,
+		potentialHints, alreadyIncluded,
 	)
 
 	hopHints = append(hopHints, selectedHints...)

lnrpc/invoicesrpc/addinvoice_test.go

@@ -458,7 +458,9 @@ func TestShouldIncludeChannel(t *testing.T) {
 
 var sufficientHintsTestCases = []struct {
 	name          string
+	nCurrentHints int
 	nHintsLeft    int
+	nMinHopHints  int
 	currentAmount lnwire.MilliSatoshi
 	targetAmount  lnwire.MilliSatoshi
 	done          bool
@@ -472,6 +474,23 @@ var sufficientHintsTestCases = []struct {
 	name:       "enough hints",
 	nHintsLeft: 0,
 	done:       true,
+}, {
+	name:          "not enough hints (minimum)",
+	nCurrentHints: 1,
+	nHintsLeft:    0,
+	nMinHopHints:  2,
+	done:          false,
+}, {
+	name:          "enough hints (minimum)",
+	nCurrentHints: 2,
+	nHintsLeft:    0,
+	nMinHopHints:  2,
+	done:          true,
+}, {
+	name:          "current hints",
+	nCurrentHints: 20,
+	nHintsLeft:    0,
+	done:          true,
 }, {
 	name:          "enough bandwidth",
 	nHintsLeft:    1,
@@ -494,7 +513,10 @@ func TestSufficientHints(t *testing.T) {
 			t.Parallel()
 
 			enoughHints := sufficientHints(
-				tc.nHintsLeft, tc.currentAmount,
+				tc.nCurrentHints,
+				tc.nHintsLeft,
+				tc.nMinHopHints,
+				tc.currentAmount,
 				tc.targetAmount,
 			)
 			require.Equal(t, tc.done, enoughHints)

lnrpc/invoicesrpc/invoices.swagger.json

@@ -578,6 +578,11 @@
           },
           "description": "Maps a 32-byte hex-encoded set ID to the sub-invoice AMP state for the\ngiven set ID. This field is always populated for AMP invoices, and can be\nused along side LookupInvoice to obtain the HTLC information related to a\ngiven sub-invoice.\nNote: Output only, don't specify for creating an invoice.",
           "title": "[EXPERIMENTAL]:"
+        },
+        "min_hop_hints": {
+          "type": "integer",
+          "format": "int32",
+          "description": "The minimum number of hop hints to include in this invoice."
         }
       }
     },