multi: allow user defined psbt max fee ratio

This commit allows the user to set their own value for the maximum
allowed fees to total output amount ratio that is used by the wallet
when funding PSBTs.

Author: GeorgeTsagk

lndservices/wallet_anchor.go

@@ -21,17 +21,59 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 )
 
+// defaultPsbtMaxFeeRatio is the maximum ratio between fees paid and total
+// output amount produced. Since taproot assets can be anchored to outpoints
+// that may carry relatively small bitcoin amounts, we want to bump the allowed
+// ratio between fees paid and total produced output amount. This can prove
+// useful in high fee environments where we'd otherwise fail to fund the psbt.
+const defaultPsbtMaxFeeRatio = 0.75
+
 // LndRpcWalletAnchor is an implementation of the tapgarden.WalletAnchor
 // interfaced backed by an active remote lnd node.
 type LndRpcWalletAnchor struct {
 	lnd *lndclient.LndServices
+	cfg *WalletAnchorConfig
+}
+
+// WalletAnchorConfig is a configuration for the wallet anchor.
+type WalletAnchorConfig struct {
+	psbtMaxFeeRatio float64
+}
+
+// defaultWalletAnchorConfig returns the default configuration for the wallet
+// anchor.
+func defaultWalletAnchorConfig() *WalletAnchorConfig {
+	return &WalletAnchorConfig{
+		psbtMaxFeeRatio: defaultPsbtMaxFeeRatio,
+	}
+}
+
+// WalletAnchorOption is an optional argument that modifies the wallet anchor
+// configuration.
+type WalletAnchorOption func(cfg *WalletAnchorConfig)
+
+// WithPsbtMaxFeeRatio is an optional argument that provides a custom psbt
+// max fee ratio.
+func WithPsbtMaxFeeRatio(val float64) WalletAnchorOption {
+	return func(cfg *WalletAnchorConfig) {
+		cfg.psbtMaxFeeRatio = val
+	}
 }
 
 // NewLndRpcWalletAnchor returns a new wallet anchor instance using the passed
 // lnd node.
-func NewLndRpcWalletAnchor(lnd *lndclient.LndServices) *LndRpcWalletAnchor {
+func NewLndRpcWalletAnchor(lnd *lndclient.LndServices,
+	opts ...WalletAnchorOption) *LndRpcWalletAnchor {
+
+	cfg := defaultWalletAnchorConfig()
+
+	for _, opt := range opts {
+		opt(cfg)
+	}
+
 	return &LndRpcWalletAnchor{
 		lnd: lnd,
+		cfg: cfg,
 	}
 }
 
@@ -82,8 +124,9 @@ func (l *LndRpcWalletAnchor) FundPsbt(ctx context.Context, packet *psbt.Packet,
 			Fees: &walletrpc.FundPsbtRequest_SatPerKw{
 				SatPerKw: uint64(feeRate),
 			},
-			MinConfs:   int32(minConfs),
-			ChangeType: defaultChangeType,
+			MinConfs:    int32(minConfs),
+			ChangeType:  defaultChangeType,
+			MaxFeeRatio: l.cfg.psbtMaxFeeRatio,
 		},
 	)
 	if err != nil {

tapcfg/config.go

@@ -143,6 +143,10 @@ const (
 	// defaultMailboxAuthTimeout is the default timeout we'll use for
 	// mailbox message retrieval client authentication.
 	defaultMailboxAuthTimeout = 10 * time.Second
+
+	// defaultPsbtMaxFeeRatio is the default maximum for fees to total
+	// output amount ratio to use when funding PSBTs.
+	defaultPsbtMaxFeeRatio = 0.75
 )
 
 var (
@@ -276,6 +280,17 @@ type LndConfig struct {
 	RPCTimeout time.Duration `long:"rpctimeout" description:"The timeout to use for RPC requests to lnd; a sufficiently long duration should be chosen to avoid issues with slow responses. Valid time units are {s, m, h}."`
 }
 
+// WalletConfig is the config that contains wallet related configurations.
+type WalletConfig struct {
+	// PsbtMaxFeeRatio is the maximum fees to total output amount ratio to
+	// use when funding PSBTs for asset transfers. Since taproot assets can
+	// be anchored to outpoints that may carry relatively small bitcoin
+	// amounts it is useful to pick a high value for this argument as in
+	// high fee environments the total fees paid may outweight the anchor
+	// amount. The allowed values for this argument range from 0.00 to 1.00.
+	PsbtMaxFeeRatio float64 `long:"psbt-max-fee-ratio" description:"The maximum fees to total output amount ratio to use when funding PSBTs for asset transfers. Value must be between 0.00 and 1.00"`
+}
+
 // UniverseConfig is the config that houses any Universe related config
 // values.
 type UniverseConfig struct {
@@ -355,6 +370,8 @@ type Config struct {
 
 	Universe *UniverseConfig `group:"universe" namespace:"universe"`
 
+	Wallet *WalletConfig `group:"wallet" namespace:"wallet"`
+
 	AddrBook *AddrBookConfig `group:"address" namespace:"address"`
 
 	Prometheus monitoring.PrometheusConfig `group:"prometheus" namespace:"prometheus"`
@@ -461,6 +478,9 @@ func DefaultConfig() Config {
 			),
 			MboxAuthTimeout: defaultMailboxAuthTimeout,
 		},
+		Wallet: &WalletConfig{
+			PsbtMaxFeeRatio: defaultPsbtMaxFeeRatio,
+		},
 		AddrBook: &AddrBookConfig{
 			DisableSyncer: false,
 		},

tapcfg/server.go

@@ -106,7 +106,10 @@ func genServerConfig(cfg *Config, cfgLogger btclog.Logger,
 	assetStore := tapdb.NewAssetStore(assetDB, metaDB, defaultClock, dbType)
 
 	keyRing := lndservices.NewLndRpcKeyRing(lndServices)
-	walletAnchor := lndservices.NewLndRpcWalletAnchor(lndServices)
+	walletAnchor := lndservices.NewLndRpcWalletAnchor(
+		lndServices,
+		lndservices.WithPsbtMaxFeeRatio(cfg.Wallet.PsbtMaxFeeRatio),
+	)
 	chainBridge := lndservices.NewLndRpcChainBridge(lndServices, assetStore)
 	msgTransportClient := lndservices.NewLndMsgTransportClient(lndServices)
 	lndRouterClient := lndservices.NewLndRouterClient(lndServices)