multi: introduce config-level DustThreshold for defining threshold

config.go

@@ -355,6 +355,8 @@ type Config struct {
 
 	GcCanceledInvoicesOnTheFly bool `long:"gc-canceled-invoices-on-the-fly" description:"If true, we'll delete newly canceled invoices on the fly."`
 
+	DustThreshold uint64 `long:"dust-threshold" description:"Sets the dust sum threshold in satoshis for a channel after which dust HTLC's will be failed."`
+
 	Invoices *lncfg.Invoices `group:"invoices" namespace:"invoices"`
 
 	Routing *lncfg.Routing `group:"routing" namespace:"routing"`
@@ -550,6 +552,7 @@ func DefaultConfig() Config {
 		MaxOutgoingCltvExpiry:   htlcswitch.DefaultMaxOutgoingCltvExpiry,
 		MaxChannelFeeAllocation: htlcswitch.DefaultMaxLinkFeeAllocation,
 		MaxCommitFeeRateAnchors: lnwallet.DefaultAnchorsCommitMaxFeeRateSatPerVByte,
+		DustThreshold:           uint64(htlcswitch.DefaultDustThreshold.ToSatoshis()),
 		LogWriter:               build.NewRotatingLogWriter(),
 		DB:                      lncfg.DefaultDB(),
 		Cluster:                 lncfg.DefaultCluster(),

htlcswitch/mock.go

@@ -189,6 +189,7 @@ func initSwitchWithDB(startingHeight uint32, db *channeldb.DB) (*Switch, error)
 		HtlcNotifier:   &mockHTLCNotifier{},
 		Clock:          clock.NewDefaultClock(),
 		HTLCExpiry:     time.Hour,
+		DustThreshold:  DefaultDustThreshold,
 	}
 
 	return New(cfg, startingHeight)

htlcswitch/switch.go

@@ -77,9 +77,9 @@ var (
 	// threshold.
 	errDustThresholdExceeded = errors.New("dust threshold exceeded")
 
-	// defaultDustThreshold is the default threshold after which we'll fail
+	// DefaultDustThreshold is the default threshold after which we'll fail
-	// payments if they are dust. This is currently set to 500k sats.
+	// payments if they are dust. This is currently set to 500m msats.
-	defaultDustThreshold = lnwire.MilliSatoshi(500_000_000)
+	DefaultDustThreshold = lnwire.MilliSatoshi(500_000_000)
 )
 
 // plexPacket encapsulates switch packet and adds error channel to receive
@@ -187,6 +187,10 @@ type Config struct {
 	// will expiry this long after the Adds are added to a mailbox via
 	// AddPacket.
 	HTLCExpiry time.Duration
+
+	// DustThreshold is the threshold in milli-satoshis after which we'll
+	// fail incoming or outgoing dust payments for a particular channel.
+	DustThreshold lnwire.MilliSatoshi
 }
 
 // Switch is the central messaging bus for all incoming/outgoing HTLCs.
@@ -2375,7 +2379,7 @@ func (s *Switch) evaluateDustThreshold(link ChannelLink,
 		}
 
 		// Finally check against the defined dust threshold.
-		if localSum > defaultDustThreshold {
+		if localSum > s.cfg.DustThreshold {
 			return true
 		}
 	}
@@ -2393,7 +2397,7 @@ func (s *Switch) evaluateDustThreshold(link ChannelLink,
 		}
 
 		// Finally check against the defined dust threshold.
-		if remoteSum > defaultDustThreshold {
+		if remoteSum > s.cfg.DustThreshold {
 			return true
 		}
 	}

lntest/itest/lnd_test.go

@@ -203,6 +203,7 @@ func TestLightningNetworkDaemon(t *testing.T) {
 	// TODO(roasbeef): create master balanced channel with all the monies?
 	aliceBobArgs := []string{
 		"--default-remote-max-htlcs=483",
+		"--dust-threshold=5000000",
 	}
 
 	// Run the subset of the test cases selected in this tranche.

sample-lnd.conf

@@ -365,6 +365,11 @@
 ; propagation (default: 10)
 ; max-commit-fee-rate-anchors=5
 
+; A threshold defining the maximum amount of dust a given channel can have
+; after which forwarding and sending dust HTLC's to and from the channel will
+; fail. This amount is expressed in satoshis. (default: 500000)
+; dust-threshold=1000000
+
 ; If true, lnd will abort committing a migration if it would otherwise have been
 ; successful. This leaves the database unmodified, and still compatible with the
 ; previously active version of lnd.

server.go

@@ -490,6 +490,9 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 
 	s.htlcNotifier = htlcswitch.NewHtlcNotifier(time.Now)
 
+	thresholdSats := btcutil.Amount(cfg.DustThreshold)
+	thresholdMSats := lnwire.NewMSatFromSatoshis(thresholdSats)
+
 	s.htlcSwitch, err = htlcswitch.New(htlcswitch.Config{
 		DB: dbs.chanStateDB,
 		LocalChannelClose: func(pubKey []byte,
@@ -519,6 +522,7 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 		RejectHTLC:             cfg.RejectHTLC,
 		Clock:                  clock.NewDefaultClock(),
 		HTLCExpiry:             htlcswitch.DefaultHTLCExpiry,
+		DustThreshold:          thresholdMSats,
 	}, uint32(currentHeight))
 	if err != nil {
 		return nil, err