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,