bumpfee: check LND>=0.18.5 if target_conf is used

The conf-target only reflects this behaviour for the 0.18.5 release, before
the conf target had a different meaning:
lightningnetwork/lnd#9470

This commit can be undone after minimalCompatibleVersion is bumbed to 0.18.5.

lnd_services.go

@@ -372,6 +372,7 @@ func NewLndServices(cfg *LndServicesConfig) (*GrpcLndServices, error) {
 	)
 	walletKitClient := newWalletKitClient(
 		conn, macaroons[WalletKitServiceMac], timeout, chainParams,
+		version,
 	)
 	invoicesClient := newInvoicesClient(
 		conn, macaroons[InvoiceServiceMac], timeout,

walletkit_client.go

@@ -20,6 +20,7 @@ import (
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
+	"github.com/lightningnetwork/lnd/lnrpc/verrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
@@ -219,6 +220,7 @@ type walletKitClient struct {
 	walletKitMac serializedMacaroon
 	timeout      time.Duration
 	params       *chaincfg.Params
+	version      *verrpc.Version
 }
 
 // A compile time check to ensure that  walletKitClient implements the
@@ -227,13 +229,15 @@ var _ WalletKitClient = (*walletKitClient)(nil)
 
 func newWalletKitClient(conn grpc.ClientConnInterface,
 	walletKitMac serializedMacaroon, timeout time.Duration,
-	chainParams *chaincfg.Params) *walletKitClient {
+	chainParams *chaincfg.Params,
+	version *verrpc.Version) *walletKitClient {
 
 	return &walletKitClient{
 		client:       walletrpc.NewWalletKitClient(conn),
 		walletKitMac: walletKitMac,
 		timeout:      timeout,
 		params:       chainParams,
+		version:      version,
 	}
 }
 
@@ -775,6 +779,15 @@ func WithBudget(budget btcutil.Amount) BumpFeeOption {
 	}
 }
 
+// targetConfFixed is the minimum version in which bug #9470 is merged and new
+// meaning of TargetConf is enabled. In versions prior to this version the field
+// had a different meaning.
+var targetConfFixed = &verrpc.Version{
+	AppMajor: 0,
+	AppMinor: 18,
+	AppPatch: 5,
+}
+
 // BumpFee attempts to bump the fee of a transaction by spending one of its
 // outputs at the given fee rate. This essentially results in a
 // child-pays-for-parent (CPFP) scenario. If the given output has been used in a
@@ -799,6 +812,20 @@ func (m *walletKitClient) BumpFee(ctx context.Context, op wire.OutPoint,
 		opt(req)
 	}
 
+	// Make sure that the version of LND is at least targetConfFixed,
+	// because before it the meaning of TargetConf was different. See
+	// https://github.com/lightningnetwork/lnd/pull/9470
+	// TODO(Boris): remove this check when minimalCompatibleVersion
+	// is bumped to targetConfFixed.
+	if req.TargetConf != 0 {
+		err := AssertVersionCompatible(m.version, targetConfFixed)
+		if err != nil {
+			return fmt.Errorf("can't use target_conf before "+
+				"version %s, current LND version is %s, "+
+				"see #9470", targetConfFixed, m.version)
+		}
+	}
+
 	_, err := m.client.BumpFee(m.walletKitMac.WithMacaroonAuth(rpcCtx), req)
 
 	return err