config+rpcserver: allow configurable defualt-remote-max-htlcs

config.go

@@ -27,6 +27,7 @@ import (
 	"github.com/lightningnetwork/lnd/discovery"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/htlcswitch/hodl"
+	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lncfg"
 	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
@@ -101,6 +102,11 @@ const (
 	defaultDiskTimeout  = time.Second * 5
 	defaultDiskBackoff  = time.Minute
 	defaultDiskAttempts = 2
+
+	// defaultRemoteMaxHtlcs specifies the default limit for maximum
+	// concurrent HTLCs the remote party may add to commitment transactions.
+	// This value can be overridden with --default-remote-max-htlcs.
+	defaultRemoteMaxHtlcs = 483
 )
 
 var (
@@ -235,6 +241,8 @@ type Config struct {
 	Color                         string        `long:"color" description:"The color of the node in hex format (i.e. '#3399FF'). Used to customize node appearance in intelligence services"`
 	MinChanSize                   int64         `long:"minchansize" description:"The smallest channel size (in satoshis) that we should accept. Incoming channels smaller than this will be rejected"`
 
+	DefaultRemoteMaxHtlcs uint16 `long:"default-remote-max-htlcs" description:"The default max_htlc applied when opening or accepting channels. This value limits the number of concurrent HTLCs that the remote party can add to the commitment. The maximum possible value is 483."`
+
 	NumGraphSyncPeers      int           `long:"numgraphsyncpeers" description:"The number of peers that we should receive new graph updates from. This option can be tuned to save bandwidth for light clients or routing nodes."`
 	HistoricalSyncInterval time.Duration `long:"historicalsyncinterval" description:"The polling interval between historical graph sync attempts. Each historical graph sync attempt ensures we reconcile with the remote peer's graph from the genesis block."`
 
@@ -379,6 +387,7 @@ func DefaultConfig() Config {
 		Alias:                         defaultAlias,
 		Color:                         defaultColor,
 		MinChanSize:                   int64(minChanFundingSize),
+		DefaultRemoteMaxHtlcs:         defaultRemoteMaxHtlcs,
 		NumGraphSyncPeers:             defaultMinPeers,
 		HistoricalSyncInterval:        discovery.DefaultHistoricalSyncInterval,
 		Tor: &lncfg.Tor{
@@ -1152,6 +1161,15 @@ func ValidateConfig(cfg Config, usageMessage string) (*Config, error) {
 		cfg.DB.Bolt.SyncFreelist = cfg.SyncFreelist
 	}
 
+	// Ensure that the user hasn't chosen a remote-max-htlc value greater
+	// than the protocol maximum.
+	maxRemoteHtlcs := uint16(input.MaxHTLCNumber / 2)
+	if cfg.DefaultRemoteMaxHtlcs > maxRemoteHtlcs {
+		return nil, fmt.Errorf("default-remote-max-htlcs (%v) must be "+
+			"less than %v", cfg.DefaultRemoteMaxHtlcs,
+			maxRemoteHtlcs)
+	}
+
 	// Validate the subconfigs for workers, caches, and the tower client.
 	err = lncfg.Validate(
 		cfg.Workers,

lntest/itest/lnd_test.go

@@ -4844,14 +4844,21 @@ func assertChannelConstraintsEqual(
 func testListChannels(net *lntest.NetworkHarness, t *harnessTest) {
 	ctxb := context.Background()
 
+	const aliceRemoteMaxHtlcs = 50
+	const bobRemoteMaxHtlcs = 100
+
 	// Create two fresh nodes and open a channel between them.
-	alice, err := net.NewNode("Alice", nil)
+	alice, err := net.NewNode("Alice", []string{
+		fmt.Sprintf("--default-remote-max-htlcs=%v", aliceRemoteMaxHtlcs),
+	})
 	if err != nil {
 		t.Fatalf("unable to create new node: %v", err)
 	}
 	defer shutdownAndAssert(net, t, alice)
 
-	bob, err := net.NewNode("Bob", nil)
+	bob, err := net.NewNode("Bob", []string{
+		fmt.Sprintf("--default-remote-max-htlcs=%v", bobRemoteMaxHtlcs),
+	})
 	if err != nil {
 		t.Fatalf("unable to create new node: %v", err)
 	}
@@ -4927,7 +4934,7 @@ func testListChannels(net *lntest.NetworkHarness, t *harnessTest) {
 		DustLimitSat:      uint64(lnwallet.DefaultDustLimit()),
 		MaxPendingAmtMsat: 99000000,
 		MinHtlcMsat:       1,
-		MaxAcceptedHtlcs:  input.MaxHTLCNumber / 2,
+		MaxAcceptedHtlcs:  bobRemoteMaxHtlcs,
 	}
 	assertChannelConstraintsEqual(
 		t, defaultConstraints, aliceChannel.LocalConstraints,
@@ -4943,7 +4950,7 @@ func testListChannels(net *lntest.NetworkHarness, t *harnessTest) {
 		DustLimitSat:      uint64(lnwallet.DefaultDustLimit()),
 		MaxPendingAmtMsat: 99000000,
 		MinHtlcMsat:       customizedMinHtlc,
-		MaxAcceptedHtlcs:  input.MaxHTLCNumber / 2,
+		MaxAcceptedHtlcs:  aliceRemoteMaxHtlcs,
 	}
 	assertChannelConstraintsEqual(
 		t, customizedConstraints, aliceChannel.RemoteConstraints,
@@ -14452,7 +14459,10 @@ func TestLightningNetworkDaemon(t *testing.T) {
 	// initialization of the network. args - list of lnd arguments,
 	// example: "--debuglevel=debug"
 	// TODO(roasbeef): create master balanced channel with all the monies?
-	if err = lndHarness.SetUp(nil); err != nil {
+	aliceBobArgs := []string{
+		"--default-remote-max-htlcs=483",
+	}
+	if err = lndHarness.SetUp(aliceBobArgs); err != nil {
 		ht.Fatalf("unable to set up test lightning network: %v", err)
 	}
 

server.go

@@ -1156,6 +1156,10 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 			return lnwire.NewMSatFromSatoshis(chanAmt) - reserve
 		},
 		RequiredRemoteMaxHTLCs: func(chanAmt btcutil.Amount) uint16 {
+			if cfg.DefaultRemoteMaxHtlcs > 0 {
+				return cfg.DefaultRemoteMaxHtlcs
+			}
+
 			// By default, we'll permit them to utilize the full
 			// channel bandwidth.
 			return uint16(input.MaxHTLCNumber / 2)