package routerrpc import ( "context" "errors" "fmt" "io/ioutil" "os" "path/filepath" "sync/atomic" "github.com/btcsuite/btcutil" "github.com/grpc-ecosystem/grpc-gateway/runtime" "github.com/lightningnetwork/lnd/channeldb" "github.com/lightningnetwork/lnd/lnrpc" "github.com/lightningnetwork/lnd/lntypes" "github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/macaroons" "github.com/lightningnetwork/lnd/routing" "github.com/lightningnetwork/lnd/routing/route" "google.golang.org/grpc" "google.golang.org/grpc/codes" "google.golang.org/grpc/status" "gopkg.in/macaroon-bakery.v2/bakery" ) const ( // subServerName is the name of the sub rpc server. We'll use this name // to register ourselves, and we also require that the main // SubServerConfigDispatcher instance recognize as the name of our subServerName = "RouterRPC" ) var ( errServerShuttingDown = errors.New("routerrpc server shutting down") // ErrInterceptorAlreadyExists is an error returned when the a new stream // is opened and there is already one active interceptor. // The user must disconnect prior to open another stream. ErrInterceptorAlreadyExists = errors.New("interceptor already exists") // macaroonOps are the set of capabilities that our minted macaroon (if // it doesn't already exist) will have. macaroonOps = []bakery.Op{ { Entity: "offchain", Action: "read", }, { Entity: "offchain", Action: "write", }, } // macPermissions maps RPC calls to the permissions they require. macPermissions = map[string][]bakery.Op{ "/routerrpc.Router/SendPaymentV2": {{ Entity: "offchain", Action: "write", }}, "/routerrpc.Router/SendToRouteV2": {{ Entity: "offchain", Action: "write", }}, "/routerrpc.Router/SendToRoute": {{ Entity: "offchain", Action: "write", }}, "/routerrpc.Router/TrackPaymentV2": {{ Entity: "offchain", Action: "read", }}, "/routerrpc.Router/EstimateRouteFee": {{ Entity: "offchain", Action: "read", }}, "/routerrpc.Router/QueryMissionControl": {{ Entity: "offchain", Action: "read", }}, "/routerrpc.Router/QueryProbability": {{ Entity: "offchain", Action: "read", }}, "/routerrpc.Router/ResetMissionControl": {{ Entity: "offchain", Action: "write", }}, "/routerrpc.Router/BuildRoute": {{ Entity: "offchain", Action: "read", }}, "/routerrpc.Router/SubscribeHtlcEvents": {{ Entity: "offchain", Action: "read", }}, "/routerrpc.Router/SendPayment": {{ Entity: "offchain", Action: "write", }}, "/routerrpc.Router/TrackPayment": {{ Entity: "offchain", Action: "read", }}, "/routerrpc.Router/HtlcInterceptor": {{ Entity: "offchain", Action: "write", }}, } // DefaultRouterMacFilename is the default name of the router macaroon // that we expect to find via a file handle within the main // configuration file in this package. DefaultRouterMacFilename = "router.macaroon" ) // Server is a stand alone sub RPC server which exposes functionality that // allows clients to route arbitrary payment through the Lightning Network. type Server struct { started int32 // To be used atomically. shutdown int32 // To be used atomically. forwardInterceptorActive int32 // To be used atomically. cfg *Config quit chan struct{} } // A compile time check to ensure that Server fully implements the RouterServer // gRPC service. var _ RouterServer = (*Server)(nil) // New creates a new instance of the RouterServer given a configuration struct // that contains all external dependencies. If the target macaroon exists, and // we're unable to create it, then an error will be returned. We also return // the set of permissions that we require as a server. At the time of writing // of this documentation, this is the same macaroon as as the admin macaroon. func New(cfg *Config) (*Server, lnrpc.MacaroonPerms, error) { // If the path of the router macaroon wasn't generated, then we'll // assume that it's found at the default network directory. if cfg.RouterMacPath == "" { cfg.RouterMacPath = filepath.Join( cfg.NetworkDir, DefaultRouterMacFilename, ) } // Now that we know the full path of the router macaroon, we can check // to see if we need to create it or not. If stateless_init is set // then we don't write the macaroons. macFilePath := cfg.RouterMacPath if cfg.MacService != nil && !cfg.MacService.StatelessInit && !lnrpc.FileExists(macFilePath) { log.Infof("Making macaroons for Router RPC Server at: %v", macFilePath) // At this point, we know that the router macaroon doesn't yet, // exist, so we need to create it with the help of the main // macaroon service. routerMac, err := cfg.MacService.NewMacaroon( context.Background(), macaroons.DefaultRootKeyID, macaroonOps..., ) if err != nil { return nil, nil, err } routerMacBytes, err := routerMac.M().MarshalBinary() if err != nil { return nil, nil, err } err = ioutil.WriteFile(macFilePath, routerMacBytes, 0644) if err != nil { _ = os.Remove(macFilePath) return nil, nil, err } } routerServer := &Server{ cfg: cfg, quit: make(chan struct{}), } return routerServer, macPermissions, nil } // Start launches any helper goroutines required for the rpcServer to function. // // NOTE: This is part of the lnrpc.SubServer interface. func (s *Server) Start() error { if atomic.AddInt32(&s.started, 1) != 1 { return nil } return nil } // Stop signals any active goroutines for a graceful closure. // // NOTE: This is part of the lnrpc.SubServer interface. func (s *Server) Stop() error { if atomic.AddInt32(&s.shutdown, 1) != 1 { return nil } close(s.quit) return nil } // Name returns a unique string representation of the sub-server. This can be // used to identify the sub-server and also de-duplicate them. // // NOTE: This is part of the lnrpc.SubServer interface. func (s *Server) Name() string { return subServerName } // RegisterWithRootServer will be called by the root gRPC server to direct a // sub RPC server to register itself with the main gRPC root server. Until this // is called, each sub-server won't be able to have requests routed towards it. // // NOTE: This is part of the lnrpc.SubServer interface. func (s *Server) RegisterWithRootServer(grpcServer *grpc.Server) error { // We make sure that we register it with the main gRPC server to ensure // all our methods are routed properly. RegisterRouterServer(grpcServer, s) log.Debugf("Router RPC server successfully register with root gRPC " + "server") return nil } // RegisterWithRestServer will be called by the root REST mux to direct a sub // RPC server to register itself with the main REST mux server. Until this is // called, each sub-server won't be able to have requests routed towards it. // // NOTE: This is part of the lnrpc.SubServer interface. func (s *Server) RegisterWithRestServer(ctx context.Context, mux *runtime.ServeMux, dest string, opts []grpc.DialOption) error { // We make sure that we register it with the main REST server to ensure // all our methods are routed properly. err := RegisterRouterHandlerFromEndpoint(ctx, mux, dest, opts) if err != nil { log.Errorf("Could not register Router REST server "+ "with root REST server: %v", err) return err } log.Debugf("Router REST server successfully registered with " + "root REST server") return nil } // SendPaymentV2 attempts to route a payment described by the passed // PaymentRequest to the final destination. If we are unable to route the // payment, or cannot find a route that satisfies the constraints in the // PaymentRequest, then an error will be returned. Otherwise, the payment // pre-image, along with the final route will be returned. func (s *Server) SendPaymentV2(req *SendPaymentRequest, stream Router_SendPaymentV2Server) error { payment, err := s.cfg.RouterBackend.extractIntentFromSendRequest(req) if err != nil { return err } err = s.cfg.Router.SendPaymentAsync(payment) if err != nil { // Transform user errors to grpc code. if err == channeldb.ErrPaymentInFlight || err == channeldb.ErrAlreadyPaid { log.Debugf("SendPayment async result for hash %x: %v", payment.PaymentHash, err) return status.Error( codes.AlreadyExists, err.Error(), ) } log.Errorf("SendPayment async error for hash %x: %v", payment.PaymentHash, err) return err } return s.trackPayment(payment.PaymentHash, stream, req.NoInflightUpdates) } // EstimateRouteFee allows callers to obtain a lower bound w.r.t how much it // may cost to send an HTLC to the target end destination. func (s *Server) EstimateRouteFee(ctx context.Context, req *RouteFeeRequest) (*RouteFeeResponse, error) { if len(req.Dest) != 33 { return nil, errors.New("invalid length destination key") } var destNode route.Vertex copy(destNode[:], req.Dest) // Next, we'll convert the amount in satoshis to mSAT, which are the // native unit of LN. amtMsat := lnwire.NewMSatFromSatoshis(btcutil.Amount(req.AmtSat)) // Pick a fee limit // // TODO: Change this into behaviour that makes more sense. feeLimit := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin) // Finally, we'll query for a route to the destination that can carry // that target amount, we'll only request a single route. Set a // restriction for the default CLTV limit, otherwise we can find a route // that exceeds it and is useless to us. mc := s.cfg.RouterBackend.MissionControl route, err := s.cfg.Router.FindRoute( s.cfg.RouterBackend.SelfNode, destNode, amtMsat, &routing.RestrictParams{ FeeLimit: feeLimit, CltvLimit: s.cfg.RouterBackend.MaxTotalTimelock, ProbabilitySource: mc.GetProbability, }, nil, nil, s.cfg.RouterBackend.DefaultFinalCltvDelta, ) if err != nil { return nil, err } return &RouteFeeResponse{ RoutingFeeMsat: int64(route.TotalFees()), TimeLockDelay: int64(route.TotalTimeLock), }, nil } // SendToRouteV2 sends a payment through a predefined route. The response of this // call contains structured error information. func (s *Server) SendToRouteV2(ctx context.Context, req *SendToRouteRequest) (*lnrpc.HTLCAttempt, error) { if req.Route == nil { return nil, fmt.Errorf("unable to send, no routes provided") } route, err := s.cfg.RouterBackend.UnmarshallRoute(req.Route) if err != nil { return nil, err } hash, err := lntypes.MakeHash(req.PaymentHash) if err != nil { return nil, err } // Pass route to the router. This call returns the full htlc attempt // information as it is stored in the database. It is possible that both // the attempt return value and err are non-nil. This can happen when // the attempt was already initiated before the error happened. In that // case, we give precedence to the attempt information as stored in the // db. attempt, err := s.cfg.Router.SendToRoute(hash, route) if attempt != nil { rpcAttempt, err := s.cfg.RouterBackend.MarshalHTLCAttempt( *attempt, ) if err != nil { return nil, err } return rpcAttempt, nil } // Transform user errors to grpc code. if err == channeldb.ErrPaymentInFlight || err == channeldb.ErrAlreadyPaid { return nil, status.Error(codes.AlreadyExists, err.Error()) } return nil, err } // ResetMissionControl clears all mission control state and starts with a clean // slate. func (s *Server) ResetMissionControl(ctx context.Context, req *ResetMissionControlRequest) (*ResetMissionControlResponse, error) { err := s.cfg.RouterBackend.MissionControl.ResetHistory() if err != nil { return nil, err } return &ResetMissionControlResponse{}, nil } // QueryMissionControl exposes the internal mission control state to callers. It // is a development feature. func (s *Server) QueryMissionControl(ctx context.Context, req *QueryMissionControlRequest) (*QueryMissionControlResponse, error) { snapshot := s.cfg.RouterBackend.MissionControl.GetHistorySnapshot() rpcPairs := make([]*PairHistory, 0, len(snapshot.Pairs)) for _, p := range snapshot.Pairs { // Prevent binding to loop variable. pair := p rpcPair := PairHistory{ NodeFrom: pair.Pair.From[:], NodeTo: pair.Pair.To[:], History: toRPCPairData(&pair.TimedPairResult), } rpcPairs = append(rpcPairs, &rpcPair) } response := QueryMissionControlResponse{ Pairs: rpcPairs, } return &response, nil } // toRPCPairData marshalls mission control pair data to the rpc struct. func toRPCPairData(data *routing.TimedPairResult) *PairData { rpcData := PairData{ FailAmtSat: int64(data.FailAmt.ToSatoshis()), FailAmtMsat: int64(data.FailAmt), SuccessAmtSat: int64(data.SuccessAmt.ToSatoshis()), SuccessAmtMsat: int64(data.SuccessAmt), } if !data.FailTime.IsZero() { rpcData.FailTime = data.FailTime.Unix() } if !data.SuccessTime.IsZero() { rpcData.SuccessTime = data.SuccessTime.Unix() } return &rpcData } // QueryProbability returns the current success probability estimate for a // given node pair and amount. func (s *Server) QueryProbability(ctx context.Context, req *QueryProbabilityRequest) (*QueryProbabilityResponse, error) { fromNode, err := route.NewVertexFromBytes(req.FromNode) if err != nil { return nil, err } toNode, err := route.NewVertexFromBytes(req.ToNode) if err != nil { return nil, err } amt := lnwire.MilliSatoshi(req.AmtMsat) mc := s.cfg.RouterBackend.MissionControl prob := mc.GetProbability(fromNode, toNode, amt) history := mc.GetPairHistorySnapshot(fromNode, toNode) return &QueryProbabilityResponse{ Probability: prob, History: toRPCPairData(&history), }, nil } // TrackPaymentV2 returns a stream of payment state updates. The stream is // closed when the payment completes. func (s *Server) TrackPaymentV2(request *TrackPaymentRequest, stream Router_TrackPaymentV2Server) error { paymentHash, err := lntypes.MakeHash(request.PaymentHash) if err != nil { return err } log.Debugf("TrackPayment called for payment %v", paymentHash) return s.trackPayment(paymentHash, stream, request.NoInflightUpdates) } // trackPayment writes payment status updates to the provided stream. func (s *Server) trackPayment(paymentHash lntypes.Hash, stream Router_TrackPaymentV2Server, noInflightUpdates bool) error { router := s.cfg.RouterBackend // Subscribe to the outcome of this payment. subscription, err := router.Tower.SubscribePayment( paymentHash, ) switch { case err == channeldb.ErrPaymentNotInitiated: return status.Error(codes.NotFound, err.Error()) case err != nil: return err } defer subscription.Close() // Stream updates back to the client. The first update is always the // current state of the payment. for { select { case item, ok := <-subscription.Updates: if !ok { // No more payment updates. return nil } result := item.(*channeldb.MPPayment) // Skip in-flight updates unless requested. if noInflightUpdates && result.Status == channeldb.StatusInFlight { continue } rpcPayment, err := router.MarshallPayment(result) if err != nil { return err } // Send event to the client. err = stream.Send(rpcPayment) if err != nil { return err } case <-s.quit: return errServerShuttingDown case <-stream.Context().Done(): log.Debugf("Payment status stream %v canceled", paymentHash) return stream.Context().Err() } } } // BuildRoute builds a route from a list of hop addresses. func (s *Server) BuildRoute(ctx context.Context, req *BuildRouteRequest) (*BuildRouteResponse, error) { // Unmarshall hop list. hops := make([]route.Vertex, len(req.HopPubkeys)) for i, pubkeyBytes := range req.HopPubkeys { pubkey, err := route.NewVertexFromBytes(pubkeyBytes) if err != nil { return nil, err } hops[i] = pubkey } // Prepare BuildRoute call parameters from rpc request. var amt *lnwire.MilliSatoshi if req.AmtMsat != 0 { rpcAmt := lnwire.MilliSatoshi(req.AmtMsat) amt = &rpcAmt } var outgoingChan *uint64 if req.OutgoingChanId != 0 { outgoingChan = &req.OutgoingChanId } var payAddr *[32]byte if len(req.PaymentAddr) != 0 { var backingPayAddr [32]byte copy(backingPayAddr[:], req.PaymentAddr) payAddr = &backingPayAddr } // Build the route and return it to the caller. route, err := s.cfg.Router.BuildRoute( amt, hops, outgoingChan, req.FinalCltvDelta, payAddr, ) if err != nil { return nil, err } rpcRoute, err := s.cfg.RouterBackend.MarshallRoute(route) if err != nil { return nil, err } routeResp := &BuildRouteResponse{ Route: rpcRoute, } return routeResp, nil } // SubscribeHtlcEvents creates a uni-directional stream from the server to // the client which delivers a stream of htlc events. func (s *Server) SubscribeHtlcEvents(req *SubscribeHtlcEventsRequest, stream Router_SubscribeHtlcEventsServer) error { htlcClient, err := s.cfg.RouterBackend.SubscribeHtlcEvents() if err != nil { return err } defer htlcClient.Cancel() for { select { case event := <-htlcClient.Updates(): rpcEvent, err := rpcHtlcEvent(event) if err != nil { return err } if err := stream.Send(rpcEvent); err != nil { return err } // If the stream's context is cancelled, return an error. case <-stream.Context().Done(): log.Debugf("htlc event stream cancelled") return stream.Context().Err() // If the subscribe client terminates, exit with an error. case <-htlcClient.Quit(): return errors.New("htlc event subscription terminated") // If the server has been signalled to shut down, exit. case <-s.quit: return errServerShuttingDown } } } // HtlcInterceptor is a bidirectional stream for streaming interception // requests to the caller. // Upon connection it does the following: // 1. Check if there is already a live stream, if yes it rejects the request. // 2. Regsitered a ForwardInterceptor // 3. Delivers to the caller every √√ and detect his answer. // It uses a local implementation of holdForwardsStore to keep all the hold // forwards and find them when manual resolution is later needed. func (s *Server) HtlcInterceptor(stream Router_HtlcInterceptorServer) error { // We ensure there is only one interceptor at a time. if !atomic.CompareAndSwapInt32(&s.forwardInterceptorActive, 0, 1) { return ErrInterceptorAlreadyExists } defer atomic.CompareAndSwapInt32(&s.forwardInterceptorActive, 1, 0) // run the forward interceptor. return newForwardInterceptor(s, stream).run() }