Merge pull request #8734 from hieblmi/cancel-estimateroutefee

routing: cancelable payment loop

cmd/lncli/cmd_payments.go

@@ -139,6 +139,17 @@ var (
 		Usage: "(blinded paths) the total cltv delay for the " +
 			"blinded portion of the route",
 	}
+
+	cancelableFlag = cli.BoolFlag{
+		Name: "cancelable",
+		Usage: "if set to true, the payment loop can be interrupted " +
+			"by manually canceling the payment context, even " +
+			"before the payment timeout is reached. Note that " +
+			"the payment may still succeed after cancellation, " +
+			"as in-flight attempts can still settle afterwards. " +
+			"Canceling will only prevent further attempts from " +
+			"being sent",
+	}
 )
 
 // paymentFlags returns common flags for sendpayment and payinvoice.
@@ -166,6 +177,7 @@ func paymentFlags() []cli.Flag {
 				"after the timeout has elapsed",
 			Value: paymentTimeout,
 		},
+		cancelableFlag,
 		cltvLimitFlag,
 		lastHopFlag,
 		cli.Int64SliceFlag{
@@ -329,6 +341,7 @@ func sendPayment(ctx *cli.Context) error {
 			Amt:               ctx.Int64("amt"),
 			DestCustomRecords: make(map[uint64][]byte),
 			Amp:               ctx.Bool(ampFlag.Name),
+			Cancelable:        ctx.Bool(cancelableFlag.Name),
 		}
 
 		// We'll attempt to parse a payment address as well, given that
@@ -387,6 +400,7 @@ func sendPayment(ctx *cli.Context) error {
 		Amt:               amount,
 		DestCustomRecords: make(map[uint64][]byte),
 		Amp:               ctx.Bool(ampFlag.Name),
+		Cancelable:        ctx.Bool(cancelableFlag.Name),
 	}
 
 	var rHash []byte
@@ -888,6 +902,7 @@ func payInvoice(ctx *cli.Context) error {
 		Amt:               ctx.Int64("amt"),
 		DestCustomRecords: make(map[uint64][]byte),
 		Amp:               ctx.Bool(ampFlag.Name),
+		Cancelable:        ctx.Bool(cancelableFlag.Name),
 	}
 
 	return sendPaymentRequest(ctx, req)

docs/release-notes/release-notes-0.18.1.md

@@ -22,15 +22,25 @@
 * `closedchannels` now [successfully reports](https://github.com/lightningnetwork/lnd/pull/8800)
   settled balances even if the delivery address is set to an address that
   LND does not control.
+ 
+* [SendPaymentV2](https://github.com/lightningnetwork/lnd/pull/8734) now cancels
+  the background payment loop if the user cancels the stream context.
 
 # New Features
 ## Functional Enhancements
 ## RPC Additions
+
+* The [SendPaymentRequest](https://github.com/lightningnetwork/lnd/pull/8734) 
+  message receives a new flag `cancelable` which indicates if the payment loop 
+  is cancelable. The cancellation can either occur manually by cancelling the 
+  send payment stream context, or automatically at the end of the timeout period 
+  if the user provided `timeout_seconds`.
+
 ## lncli Additions
 
 * [Added](https://github.com/lightningnetwork/lnd/pull/8491) the `cltv_expiry`
   argument to `addinvoice` and `addholdinvoice`, allowing users to set the
-  `min_final_cltv_expiry_delta`
+  `min_final_cltv_expiry_delta`.
 
 * The [`lncli wallet estimatefeerate`](https://github.com/lightningnetwork/lnd/pull/8730)
   command returns the fee rate estimate for on-chain transactions in sat/kw and
@@ -72,3 +82,4 @@
 
 * Andras Banki-Horvath
 * Bufo
+* Slyghtning

lnrpc/routerrpc/router.pb.go

@@ -492,6 +492,12 @@ type SendPaymentRequest struct {
 	// The time preference for this payment. Set to -1 to optimize for fees
 	// only, to 1 to optimize for reliability only or a value inbetween for a mix.
 	TimePref float64 `protobuf:"fixed64,23,opt,name=time_pref,json=timePref,proto3" json:"time_pref,omitempty"`
+	// If set, the payment loop can be interrupted by manually canceling the
+	// payment context, even before the payment timeout is reached. Note that the
+	// payment may still succeed after cancellation, as in-flight attempts can
+	// still settle afterwards. Canceling will only prevent further attempts from
+	// being sent.
+	Cancelable bool `protobuf:"varint,24,opt,name=cancelable,proto3" json:"cancelable,omitempty"`
 }
 
 func (x *SendPaymentRequest) Reset() {
@@ -688,6 +694,13 @@ func (x *SendPaymentRequest) GetTimePref() float64 {
 	return 0
 }
 
+func (x *SendPaymentRequest) GetCancelable() bool {
+	if x != nil {
+		return x.Cancelable
+	}
+	return false
+}
+
 type TrackPaymentRequest struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -3339,7 +3352,7 @@ var file_routerrpc_router_proto_rawDesc = []byte{
 	0x0a, 0x16, 0x72, 0x6f, 0x75, 0x74, 0x65, 0x72, 0x72, 0x70, 0x63, 0x2f, 0x72, 0x6f, 0x75, 0x74,
 	0x65, 0x72, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x12, 0x09, 0x72, 0x6f, 0x75, 0x74, 0x65, 0x72,
 	0x72, 0x70, 0x63, 0x1a, 0x0f, 0x6c, 0x69, 0x67, 0x68, 0x74, 0x6e, 0x69, 0x6e, 0x67, 0x2e, 0x70,
-	0x72, 0x6f, 0x74, 0x6f, 0x22, 0xf4, 0x07, 0x0a, 0x12, 0x53, 0x65, 0x6e, 0x64, 0x50, 0x61, 0x79,
+	0x72, 0x6f, 0x74, 0x6f, 0x22, 0x94, 0x08, 0x0a, 0x12, 0x53, 0x65, 0x6e, 0x64, 0x50, 0x61, 0x79,
 	0x6d, 0x65, 0x6e, 0x74, 0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x12, 0x12, 0x0a, 0x04, 0x64,
 	0x65, 0x73, 0x74, 0x18, 0x01, 0x20, 0x01, 0x28, 0x0c, 0x52, 0x04, 0x64, 0x65, 0x73, 0x74, 0x12,
 	0x10, 0x0a, 0x03, 0x61, 0x6d, 0x74, 0x18, 0x02, 0x20, 0x01, 0x28, 0x03, 0x52, 0x03, 0x61, 0x6d,
@@ -3398,7 +3411,9 @@ var file_routerrpc_router_proto_rawDesc = []byte{
 	0x7a, 0x65, 0x4d, 0x73, 0x61, 0x74, 0x12, 0x10, 0x0a, 0x03, 0x61, 0x6d, 0x70, 0x18, 0x16, 0x20,
 	0x01, 0x28, 0x08, 0x52, 0x03, 0x61, 0x6d, 0x70, 0x12, 0x1b, 0x0a, 0x09, 0x74, 0x69, 0x6d, 0x65,
 	0x5f, 0x70, 0x72, 0x65, 0x66, 0x18, 0x17, 0x20, 0x01, 0x28, 0x01, 0x52, 0x08, 0x74, 0x69, 0x6d,
-	0x65, 0x50, 0x72, 0x65, 0x66, 0x1a, 0x44, 0x0a, 0x16, 0x44, 0x65, 0x73, 0x74, 0x43, 0x75, 0x73,
+	0x65, 0x50, 0x72, 0x65, 0x66, 0x12, 0x1e, 0x0a, 0x0a, 0x63, 0x61, 0x6e, 0x63, 0x65, 0x6c, 0x61,
+	0x62, 0x6c, 0x65, 0x18, 0x18, 0x20, 0x01, 0x28, 0x08, 0x52, 0x0a, 0x63, 0x61, 0x6e, 0x63, 0x65,
+	0x6c, 0x61, 0x62, 0x6c, 0x65, 0x1a, 0x44, 0x0a, 0x16, 0x44, 0x65, 0x73, 0x74, 0x43, 0x75, 0x73,
 	0x74, 0x6f, 0x6d, 0x52, 0x65, 0x63, 0x6f, 0x72, 0x64, 0x73, 0x45, 0x6e, 0x74, 0x72, 0x79, 0x12,
 	0x10, 0x0a, 0x03, 0x6b, 0x65, 0x79, 0x18, 0x01, 0x20, 0x01, 0x28, 0x04, 0x52, 0x03, 0x6b, 0x65,
 	0x79, 0x12, 0x14, 0x0a, 0x05, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x18, 0x02, 0x20, 0x01, 0x28, 0x0c,

lnrpc/routerrpc/router.proto

@@ -330,6 +330,15 @@ message SendPaymentRequest {
     only, to 1 to optimize for reliability only or a value inbetween for a mix.
     */
     double time_pref = 23;
+
+    /*
+    If set, the payment loop can be interrupted by manually canceling the
+    payment context, even before the payment timeout is reached. Note that the
+    payment may still succeed after cancellation, as in-flight attempts can
+    still settle afterwards. Canceling will only prevent further attempts from
+    being sent.
+    */
+    bool cancelable = 24;
 }
 
 message TrackPaymentRequest {

lnrpc/routerrpc/router.swagger.json

@@ -1804,6 +1804,10 @@
           "type": "number",
           "format": "double",
           "description": "The time preference for this payment. Set to -1 to optimize for fees\nonly, to 1 to optimize for reliability only or a value inbetween for a mix."
+        },
+        "cancelable": {
+          "type": "boolean",
+          "description": "If set, the payment loop can be interrupted by manually canceling the\npayment context, even before the payment timeout is reached. Note that the\npayment may still succeed after cancellation, as in-flight attempts can\nstill settle afterwards. Canceling will only prevent further attempts from\nbeing sent."
         }
       }
     },

lnrpc/routerrpc/router_server.go

@@ -149,14 +149,14 @@ var (
 	DefaultRouterMacFilename = "router.macaroon"
 )
 
-// ServerShell a is shell struct holding a reference to the actual sub-server.
+// ServerShell is a shell struct holding a reference to the actual sub-server.
 // It is used to register the gRPC sub-server with the root server before we
 // have the necessary dependencies to populate the actual sub-server.
 type ServerShell struct {
 	RouterServer
 }
 
-// Server is a stand alone sub RPC server which exposes functionality that
+// 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.
@@ -181,7 +181,7 @@ var _ RouterServer = (*Server)(nil)
 // 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.
+// of this documentation, this is the same macaroon 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.
@@ -360,13 +360,25 @@ func (s *Server) SendPaymentV2(req *SendPaymentRequest,
 		return err
 	}
 
+	// The payment context is influenced by two user-provided parameters,
+	// the cancelable flag and the payment attempt timeout.
+	// If the payment is cancelable, we will use the stream context as the
+	// payment context. That way, if the user ends the stream, the payment
+	// loop will be canceled.
+	// The second context parameter is the timeout. If the user provides a
+	// timeout, we will additionally wrap the context in a deadline. If the
+	// user provided 'cancelable' and ends the stream before the timeout is
+	// reached the payment will be canceled.
+	ctx := context.Background()
+	if req.Cancelable {
+		ctx = stream.Context()
+	}
+
 	// Send the payment asynchronously.
-	s.cfg.Router.SendPaymentAsync(payment, paySession, shardTracker)
+	s.cfg.Router.SendPaymentAsync(ctx, payment, paySession, shardTracker)
 
 	// Track the payment and return.
-	return s.trackPayment(
-		sub, payHash, stream, req.NoInflightUpdates,
-	)
+	return s.trackPayment(sub, payHash, stream, req.NoInflightUpdates)
 }
 
 // EstimateRouteFee allows callers to obtain an expected value w.r.t how much it
@@ -986,9 +998,8 @@ func (s *Server) SetMissionControlConfig(ctx context.Context,
 				AprioriHopProbability: float64(
 					req.Config.HopProbability,
 				),
-				AprioriWeight: float64(req.Config.Weight),
-				CapacityFraction: float64(
-					routing.DefaultCapacityFraction),
+				AprioriWeight:    float64(req.Config.Weight),
+				CapacityFraction: routing.DefaultCapacityFraction, //nolint:lll
 			}
 		}
 
@@ -1032,8 +1043,8 @@ func (s *Server) SetMissionControlConfig(ctx context.Context,
 
 // 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) {
+func (s *Server) QueryMissionControl(_ context.Context,
+	_ *QueryMissionControlRequest) (*QueryMissionControlResponse, error) {
 
 	snapshot := s.cfg.RouterBackend.MissionControl.GetHistorySnapshot()
 
@@ -1080,7 +1091,7 @@ func toRPCPairData(data *routing.TimedPairResult) *PairData {
 
 // XImportMissionControl imports the state provided to our internal mission
 // control. Only entries that are fresher than our existing state will be used.
-func (s *Server) XImportMissionControl(ctx context.Context,
+func (s *Server) XImportMissionControl(_ context.Context,
 	req *XImportMissionControlRequest) (*XImportMissionControlResponse,
 	error) {
 
@@ -1273,8 +1284,9 @@ func (s *Server) subscribePayment(identifier lntypes.Hash) (
 	sub, err := router.Tower.SubscribePayment(identifier)
 
 	switch {
-	case err == channeldb.ErrPaymentNotInitiated:
+	case errors.Is(err, channeldb.ErrPaymentNotInitiated):
 		return nil, status.Error(codes.NotFound, err.Error())
+
 	case err != nil:
 		return nil, err
 	}
@@ -1385,7 +1397,7 @@ func (s *Server) trackPaymentStream(context context.Context,
 }
 
 // BuildRoute builds a route from a list of hop addresses.
-func (s *Server) BuildRoute(ctx context.Context,
+func (s *Server) BuildRoute(_ context.Context,
 	req *BuildRouteRequest) (*BuildRouteResponse, error) {
 
 	// Unmarshall hop list.
@@ -1446,7 +1458,7 @@ func (s *Server) BuildRoute(ctx context.Context,
 
 // 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,
+func (s *Server) SubscribeHtlcEvents(_ *SubscribeHtlcEventsRequest,
 	stream Router_SubscribeHtlcEventsServer) error {
 
 	htlcClient, err := s.cfg.RouterBackend.SubscribeHtlcEvents()
@@ -1495,7 +1507,7 @@ func (s *Server) SubscribeHtlcEvents(req *SubscribeHtlcEventsRequest,
 
 // HtlcInterceptor is a bidirectional stream for streaming interception
 // requests to the caller.
-// Upon connection it does the following:
+// Upon connection, it does the following:
 // 1. Check if there is already a live stream, if yes it rejects the request.
 // 2. Registered a ForwardInterceptor
 // 3. Delivers to the caller every √√ and detect his answer.
@@ -1525,7 +1537,7 @@ func extractOutPoint(req *UpdateChanStatusRequest) (*wire.OutPoint, error) {
 }
 
 // UpdateChanStatus allows channel state to be set manually.
-func (s *Server) UpdateChanStatus(ctx context.Context,
+func (s *Server) UpdateChanStatus(_ context.Context,
 	req *UpdateChanStatusRequest) (*UpdateChanStatusResponse, error) {
 
 	outPoint, err := extractOutPoint(req)

routing/payment_lifecycle.go

@@ -1,6 +1,7 @@
 package routing
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"time"
@@ -29,7 +30,6 @@ type paymentLifecycle struct {
 	identifier    lntypes.Hash
 	paySession    PaymentSession
 	shardTracker  shards.ShardTracker
-	timeoutChan   <-chan time.Time
 	currentHeight int32
 
 	// quit is closed to signal the sub goroutines of the payment lifecycle
@@ -52,7 +52,7 @@ type paymentLifecycle struct {
 // newPaymentLifecycle initiates a new payment lifecycle and returns it.
 func newPaymentLifecycle(r *ChannelRouter, feeLimit lnwire.MilliSatoshi,
 	identifier lntypes.Hash, paySession PaymentSession,
-	shardTracker shards.ShardTracker, timeout time.Duration,
+	shardTracker shards.ShardTracker,
 	currentHeight int32) *paymentLifecycle {
 
 	p := &paymentLifecycle{
@@ -69,13 +69,6 @@ func newPaymentLifecycle(r *ChannelRouter, feeLimit lnwire.MilliSatoshi,
 	// Mount the result collector.
 	p.resultCollector = p.collectResultAsync
 
-	// If a timeout is specified, create a timeout channel. If no timeout is
-	// specified, the channel is left nil and will never abort the payment
-	// loop.
-	if timeout != 0 {
-		p.timeoutChan = time.After(timeout)
-	}
-
 	return p
 }
 
@@ -167,7 +160,9 @@ func (p *paymentLifecycle) decideNextStep(
 }
 
 // resumePayment resumes the paymentLifecycle from the current state.
-func (p *paymentLifecycle) resumePayment() ([32]byte, *route.Route, error) {
+func (p *paymentLifecycle) resumePayment(ctx context.Context) ([32]byte,
+	*route.Route, error) {
+
 	// When the payment lifecycle loop exits, we make sure to signal any
 	// sub goroutine of the HTLC attempt to exit, then wait for them to
 	// return.
@@ -221,18 +216,17 @@ lifecycle:
 
 		// We now proceed our lifecycle with the following tasks in
 		// order,
-		//   1. check timeout.
+		//   1. check context.
 		//   2. request route.
 		//   3. create HTLC attempt.
 		//   4. send HTLC attempt.
 		//   5. collect HTLC attempt result.
 		//
-		// Before we attempt any new shard, we'll check to see if
-		// either we've gone past the payment attempt timeout, or the
-		// router is exiting. In either case, we'll stop this payment
-		// attempt short. If a timeout is not applicable, timeoutChan
-		// will be nil.
-		if err := p.checkTimeout(); err != nil {
+		// Before we attempt any new shard, we'll check to see if we've
+		// gone past the payment attempt timeout, or if the context was
+		// cancelled, or the router is exiting. In any of these cases,
+		// we'll stop this payment attempt short.
+		if err := p.checkContext(ctx); err != nil {
 			return exitWithErr(err)
 		}
 
@@ -318,19 +312,30 @@ lifecycle:
 	return [32]byte{}, nil, *failure
 }
 
-// checkTimeout checks whether the payment has reached its timeout.
-func (p *paymentLifecycle) checkTimeout() error {
+// checkContext checks whether the payment context has been canceled.
+// Cancellation occurs manually or if the context times out.
+func (p *paymentLifecycle) checkContext(ctx context.Context) error {
 	select {
-	case <-p.timeoutChan:
-		log.Warnf("payment attempt not completed before timeout")
+	case <-ctx.Done():
+		// If the context was canceled, we'll mark the payment as
+		// failed. There are two cases to distinguish here: Either a
+		// user-provided timeout was reached, or the context was
+		// canceled, either to a manual cancellation or due to an
+		// unknown error.
+		if errors.Is(ctx.Err(), context.DeadlineExceeded) {
+			log.Warnf("Payment attempt not completed before "+
+				"timeout, id=%s", p.identifier.String())
+		} else {
+			log.Warnf("Payment attempt context canceled, id=%s",
+				p.identifier.String())
+		}
 
 		// By marking the payment failed, depending on whether it has
 		// inflight HTLCs or not, its status will now either be
 		// `StatusInflight` or `StatusFailed`. In either case, no more
 		// HTLCs will be attempted.
-		err := p.router.cfg.Control.FailPayment(
-			p.identifier, channeldb.FailureReasonTimeout,
-		)
+		reason := channeldb.FailureReasonTimeout
+		err := p.router.cfg.Control.FailPayment(p.identifier, reason)
 		if err != nil {
 			return fmt.Errorf("FailPayment got %w", err)
 		}
@@ -368,7 +373,7 @@ func (p *paymentLifecycle) requestRoute(
 	log.Warnf("Failed to find route for payment %v: %v", p.identifier, err)
 
 	// If the error belongs to `noRouteError` set, it means a non-critical
-	// error has happened during path finding and we will mark the payment
+	// error has happened during path finding, and we will mark the payment
 	// failed with this reason. Otherwise, we'll return the critical error
 	// found to abort the lifecycle.
 	var routeErr noRouteError
@@ -377,9 +382,9 @@ func (p *paymentLifecycle) requestRoute(
 	}
 
 	// It's the `paymentSession`'s responsibility to find a route for us
-	// with best effort. When it cannot find a path, we need to treat it as
-	// a terminal condition and fail the payment no matter it has inflight
-	// HTLCs or not.
+	// with the best effort. When it cannot find a path, we need to treat it
+	// as a terminal condition and fail the payment no matter it has
+	// inflight HTLCs or not.
 	failureCode := routeErr.FailureReason()
 	log.Warnf("Marking payment %v permanently failed with no route: %v",
 		p.identifier, failureCode)
@@ -415,7 +420,7 @@ type attemptResult struct {
 
 // collectResultAsync launches a goroutine that will wait for the result of the
 // given HTLC attempt to be available then handle its result. Once received, it
-// will send a nil error to channel `resultCollected` to indicate there's an
+// will send a nil error to channel `resultCollected` to indicate there's a
 // result.
 func (p *paymentLifecycle) collectResultAsync(attempt *channeldb.HTLCAttempt) {
 	log.Debugf("Collecting result for attempt %v in payment %v",
@@ -484,7 +489,7 @@ func (p *paymentLifecycle) collectResult(attempt *channeldb.HTLCAttempt) (
 		return p.failAttempt(attempt.AttemptID, err)
 	}
 
-	// Using the created circuit, initialize the error decrypter so we can
+	// Using the created circuit, initialize the error decrypter, so we can
 	// parse+decode any failures incurred by this payment within the
 	// switch.
 	errorDecryptor := &htlcswitch.SphinxErrorDecrypter{
@@ -786,7 +791,7 @@ func (p *paymentLifecycle) handleSwitchErr(attempt *channeldb.HTLCAttempt,
 		return p.failAttempt(attemptID, sendErr)
 	}
 
-	if sendErr == htlcswitch.ErrUnreadableFailureMessage {
+	if errors.Is(sendErr, htlcswitch.ErrUnreadableFailureMessage) {
 		log.Warn("Unreadable failure when sending htlc: id=%v, hash=%v",
 			attempt.AttemptID, attempt.Hash)
 
@@ -801,7 +806,8 @@ func (p *paymentLifecycle) handleSwitchErr(attempt *channeldb.HTLCAttempt,
 	// down the route. If the error is not related to the propagation of
 	// our payment, we can stop trying because an internal error has
 	// occurred.
-	rtErr, ok := sendErr.(htlcswitch.ClearTextError)
+	var rtErr htlcswitch.ClearTextError
+	ok := errors.As(sendErr, &rtErr)
 	if !ok {
 		return p.failPaymentAndAttempt(
 			attemptID, &internalErrorReason, sendErr,
@@ -815,7 +821,8 @@ func (p *paymentLifecycle) handleSwitchErr(attempt *channeldb.HTLCAttempt,
 	// ForwardingError, it did not originate at our node, so we set
 	// failureSourceIdx to the index of the node where the failure occurred.
 	failureSourceIdx := 0
-	source, ok := rtErr.(*htlcswitch.ForwardingError)
+	var source *htlcswitch.ForwardingError
+	ok = errors.As(rtErr, &source)
 	if ok {
 		failureSourceIdx = source.FailureSourceIdx
 	}
@@ -863,7 +870,7 @@ func (p *paymentLifecycle) handleFailureMessage(rt *route.Route,
 
 	// Parse pubkey to allow validation of the channel update. This should
 	// always succeed, otherwise there is something wrong in our
-	// implementation. Therefore return an error.
+	// implementation. Therefore, return an error.
 	errVertex := rt.Hops[errorSourceIdx-1].PubKeyBytes
 	errSource, err := btcec.ParsePubKey(errVertex[:])
 	if err != nil {
@@ -951,17 +958,18 @@ func marshallError(sendError error, time time.Time) *channeldb.HTLCFailInfo {
 		FailTime: time,
 	}
 
-	switch sendError {
-	case htlcswitch.ErrPaymentIDNotFound:
+	switch {
+	case errors.Is(sendError, htlcswitch.ErrPaymentIDNotFound):
 		response.Reason = channeldb.HTLCFailInternal
 		return response
 
-	case htlcswitch.ErrUnreadableFailureMessage:
+	case errors.Is(sendError, htlcswitch.ErrUnreadableFailureMessage):
 		response.Reason = channeldb.HTLCFailUnreadable
 		return response
 	}
 
-	rtErr, ok := sendError.(htlcswitch.ClearTextError)
+	var rtErr htlcswitch.ClearTextError
+	ok := errors.As(sendError, &rtErr)
 	if !ok {
 		response.Reason = channeldb.HTLCFailInternal
 		return response
@@ -981,7 +989,8 @@ func marshallError(sendError error, time time.Time) *channeldb.HTLCFailInfo {
 	// failure occurred. If the error is not a ForwardingError, the failure
 	// occurred at our node, so we leave the index as 0 to indicate that
 	// we failed locally.
-	fErr, ok := rtErr.(*htlcswitch.ForwardingError)
+	var fErr *htlcswitch.ForwardingError
+	ok = errors.As(rtErr, &fErr)
 	if ok {
 		response.FailureSourceIndex = uint32(fErr.FailureSourceIdx)
 	}

routing/payment_lifecycle_test.go

@@ -1,6 +1,7 @@
 package routing
 
 import (
+	"context"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -88,7 +89,7 @@ func newTestPaymentLifecycle(t *testing.T) (*paymentLifecycle, *mockers) {
 	// Create a test payment lifecycle with no fee limit and no timeout.
 	p := newPaymentLifecycle(
 		rt, noFeeLimit, paymentHash, mockPaymentSession,
-		mockShardTracker, 0, 0,
+		mockShardTracker, 0,
 	)
 
 	// Create a mock payment which is returned from mockControlTower.
@@ -151,9 +152,9 @@ type resumePaymentResult struct {
 	err      error
 }
 
-// sendPaymentAndAssertFailed calls `resumePayment` and asserts that an error
-// is returned.
-func sendPaymentAndAssertFailed(t *testing.T,
+// sendPaymentAndAssertError calls `resumePayment` and asserts that an error is
+// returned.
+func sendPaymentAndAssertError(t *testing.T, ctx context.Context,
 	p *paymentLifecycle, errExpected error) {
 
 	resultChan := make(chan *resumePaymentResult, 1)
@@ -161,7 +162,7 @@ func sendPaymentAndAssertFailed(t *testing.T,
 	// We now make a call to `resumePayment` and expect it to return the
 	// error.
 	go func() {
-		preimage, _, err := p.resumePayment()
+		preimage, _, err := p.resumePayment(ctx)
 		resultChan <- &resumePaymentResult{
 			preimage: preimage,
 			err:      err,
@@ -189,7 +190,7 @@ func sendPaymentAndAssertSucceeded(t *testing.T,
 	// We now make a call to `resumePayment` and expect it to return the
 	// preimage.
 	go func() {
-		preimage, _, err := p.resumePayment()
+		preimage, _, err := p.resumePayment(context.Background())
 		resultChan <- &resumePaymentResult{
 			preimage: preimage,
 			err:      err,
@@ -278,6 +279,10 @@ func makeAttemptInfo(t *testing.T, amt int) channeldb.HTLCAttemptInfo {
 func TestCheckTimeoutTimedOut(t *testing.T) {
 	t.Parallel()
 
+	deadline := time.Now().Add(time.Nanosecond)
+	ctx, cancel := context.WithDeadline(context.Background(), deadline)
+	defer cancel()
+
 	p := createTestPaymentLifecycle()
 
 	// Mock the control tower's `FailPayment` method.
@@ -288,14 +293,11 @@ func TestCheckTimeoutTimedOut(t *testing.T) {
 	// Mount the mocked control tower.
 	p.router.cfg.Control = ct
 
-	// Make the timeout happens instantly.
-	p.timeoutChan = time.After(1 * time.Nanosecond)
-
 	// Sleep one millisecond to make sure it timed out.
 	time.Sleep(1 * time.Millisecond)
 
 	// Call the function and expect no error.
-	err := p.checkTimeout()
+	err := p.checkContext(ctx)
 	require.NoError(t, err)
 
 	// Assert that `FailPayment` is called as expected.
@@ -313,13 +315,15 @@ func TestCheckTimeoutTimedOut(t *testing.T) {
 	p.router.cfg.Control = ct
 
 	// Make the timeout happens instantly.
-	p.timeoutChan = time.After(1 * time.Nanosecond)
+	deadline = time.Now().Add(time.Nanosecond)
+	ctx, cancel = context.WithDeadline(context.Background(), deadline)
+	defer cancel()
 
 	// Sleep one millisecond to make sure it timed out.
 	time.Sleep(1 * time.Millisecond)
 
 	// Call the function and expect an error.
-	err = p.checkTimeout()
+	err = p.checkContext(ctx)
 	require.ErrorIs(t, err, errDummy)
 
 	// Assert that `FailPayment` is called as expected.
@@ -331,10 +335,13 @@ func TestCheckTimeoutTimedOut(t *testing.T) {
 func TestCheckTimeoutOnRouterQuit(t *testing.T) {
 	t.Parallel()
 
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
 	p := createTestPaymentLifecycle()
 
 	close(p.router.quit)
-	err := p.checkTimeout()
+	err := p.checkContext(ctx)
 	require.ErrorIs(t, err, ErrRouterShuttingDown)
 }
 
@@ -627,7 +634,7 @@ func TestResumePaymentFailOnFetchPayment(t *testing.T) {
 	m.control.On("FetchPayment", p.identifier).Return(nil, errDummy)
 
 	// Send the payment and assert it failed.
-	sendPaymentAndAssertFailed(t, p, errDummy)
+	sendPaymentAndAssertError(t, context.Background(), p, errDummy)
 
 	// Expected collectResultAsync to not be called.
 	require.Zero(t, m.collectResultsCount)
@@ -656,14 +663,15 @@ func TestResumePaymentFailOnTimeout(t *testing.T) {
 	}
 	m.payment.On("GetState").Return(ps).Once()
 
-	// NOTE: GetStatus is only used to populate the logs which is
-	// not critical so we loosen the checks on how many times it's
-	// been called.
+	// NOTE: GetStatus is only used to populate the logs which is not
+	// critical, so we loosen the checks on how many times it's been called.
 	m.payment.On("GetStatus").Return(channeldb.StatusInFlight)
 
 	// 3. make the timeout happens instantly and sleep one millisecond to
 	// make sure it timed out.
-	p.timeoutChan = time.After(1 * time.Nanosecond)
+	deadline := time.Now().Add(time.Nanosecond)
+	ctx, cancel := context.WithDeadline(context.Background(), deadline)
+	defer cancel()
 	time.Sleep(1 * time.Millisecond)
 
 	// 4. the payment should be failed with reason timeout.
@@ -683,7 +691,7 @@ func TestResumePaymentFailOnTimeout(t *testing.T) {
 	m.payment.On("TerminalInfo").Return(nil, &reason)
 
 	// Send the payment and assert it failed with the timeout reason.
-	sendPaymentAndAssertFailed(t, p, reason)
+	sendPaymentAndAssertError(t, ctx, p, reason)
 
 	// Expected collectResultAsync to not be called.
 	require.Zero(t, m.collectResultsCount)
@@ -721,7 +729,65 @@ func TestResumePaymentFailOnTimeoutErr(t *testing.T) {
 	close(p.router.quit)
 
 	// Send the payment and assert it failed when router is shutting down.
-	sendPaymentAndAssertFailed(t, p, ErrRouterShuttingDown)
+	sendPaymentAndAssertError(
+		t, context.Background(), p, ErrRouterShuttingDown,
+	)
+
+	// Expected collectResultAsync to not be called.
+	require.Zero(t, m.collectResultsCount)
+}
+
+// TestResumePaymentFailContextCancel checks that the lifecycle fails when the
+// context is canceled.
+//
+// NOTE: No parallel test because it overwrites global variables.
+//
+//nolint:paralleltest
+func TestResumePaymentFailContextCancel(t *testing.T) {
+	// Create a test paymentLifecycle with the initial two calls mocked.
+	p, m := setupTestPaymentLifecycle(t)
+
+	// Create the cancelable payment context.
+	ctx, cancel := context.WithCancel(context.Background())
+
+	paymentAmt := lnwire.MilliSatoshi(10000)
+
+	// We now enter the payment lifecycle loop.
+	//
+	// 1. calls `FetchPayment` and return the payment.
+	m.control.On("FetchPayment", p.identifier).Return(m.payment, nil).Once()
+
+	// 2. calls `GetState` and return the state.
+	ps := &channeldb.MPPaymentState{
+		RemainingAmt: paymentAmt,
+	}
+	m.payment.On("GetState").Return(ps).Once()
+
+	// NOTE: GetStatus is only used to populate the logs which is not
+	// critical, so we loosen the checks on how many times it's been called.
+	m.payment.On("GetStatus").Return(channeldb.StatusInFlight)
+
+	// 3. Cancel the context and skip the FailPayment error to trigger the
+	// context cancellation of the payment.
+	cancel()
+
+	m.control.On(
+		"FailPayment", p.identifier, channeldb.FailureReasonTimeout,
+	).Return(nil).Once()
+
+	// 5. decideNextStep now returns stepExit.
+	m.payment.On("AllowMoreAttempts").Return(false, nil).Once().
+		On("NeedWaitAttempts").Return(false, nil).Once()
+
+	// 6. Control tower deletes failed attempts.
+	m.control.On("DeleteFailedAttempts", p.identifier).Return(nil).Once()
+
+	// 7. We will observe FailureReasonError if the context was cancelled.
+	reason := channeldb.FailureReasonError
+	m.payment.On("TerminalInfo").Return(nil, &reason)
+
+	// Send the payment and assert it failed with the timeout reason.
+	sendPaymentAndAssertError(t, ctx, p, reason)
 
 	// Expected collectResultAsync to not be called.
 	require.Zero(t, m.collectResultsCount)
@@ -759,7 +825,7 @@ func TestResumePaymentFailOnStepErr(t *testing.T) {
 	m.payment.On("AllowMoreAttempts").Return(false, errDummy).Once()
 
 	// Send the payment and assert it failed.
-	sendPaymentAndAssertFailed(t, p, errDummy)
+	sendPaymentAndAssertError(t, context.Background(), p, errDummy)
 
 	// Expected collectResultAsync to not be called.
 	require.Zero(t, m.collectResultsCount)
@@ -803,7 +869,7 @@ func TestResumePaymentFailOnRequestRouteErr(t *testing.T) {
 	).Return(nil, errDummy).Once()
 
 	// Send the payment and assert it failed.
-	sendPaymentAndAssertFailed(t, p, errDummy)
+	sendPaymentAndAssertError(t, context.Background(), p, errDummy)
 
 	// Expected collectResultAsync to not be called.
 	require.Zero(t, m.collectResultsCount)
@@ -863,7 +929,7 @@ func TestResumePaymentFailOnRegisterAttemptErr(t *testing.T) {
 	).Return(nil, errDummy).Once()
 
 	// Send the payment and assert it failed.
-	sendPaymentAndAssertFailed(t, p, errDummy)
+	sendPaymentAndAssertError(t, context.Background(), p, errDummy)
 
 	// Expected collectResultAsync to not be called.
 	require.Zero(t, m.collectResultsCount)
@@ -955,7 +1021,7 @@ func TestResumePaymentFailOnSendAttemptErr(t *testing.T) {
 	).Return(nil, errDummy).Once()
 
 	// Send the payment and assert it failed.
-	sendPaymentAndAssertFailed(t, p, errDummy)
+	sendPaymentAndAssertError(t, context.Background(), p, errDummy)
 
 	// Expected collectResultAsync to not be called.
 	require.Zero(t, m.collectResultsCount)

routing/router.go

@@ -2,6 +2,7 @@ package routing
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"math"
 	"runtime"
@@ -45,11 +46,11 @@ const (
 	// DefaultPayAttemptTimeout is the default payment attempt timeout. The
 	// payment attempt timeout defines the duration after which we stop
 	// trying more routes for a payment.
-	DefaultPayAttemptTimeout = time.Duration(time.Second * 60)
+	DefaultPayAttemptTimeout = time.Second * 60
 
 	// DefaultChannelPruneExpiry is the default duration used to determine
 	// if a channel should be pruned or not.
-	DefaultChannelPruneExpiry = time.Duration(time.Hour * 24 * 14)
+	DefaultChannelPruneExpiry = time.Hour * 24 * 14
 
 	// DefaultFirstTimePruneDelay is the time we'll wait after startup
 	// before attempting to prune the graph for zombie channels. We don't
@@ -376,9 +377,9 @@ type Config struct {
 	FirstTimePruneDelay time.Duration
 
 	// QueryBandwidth is a method that allows the router to query the lower
-	// link layer to determine the up to date available bandwidth at a
+	// link layer to determine the up-to-date available bandwidth at a
 	// prospective link to be traversed. If the  link isn't available, then
-	// a value of zero should be returned. Otherwise, the current up to
+	// a value of zero should be returned. Otherwise, the current up-to-
 	// date knowledge of the available bandwidth of the link should be
 	// returned.
 	GetLink getLinkQuery
@@ -389,7 +390,7 @@ type Config struct {
 	// the switch can properly handle the HTLC.
 	NextPaymentID func() (uint64, error)
 
-	// AssumeChannelValid toggles whether or not the router will check for
+	// AssumeChannelValid toggles whether the router will check for
 	// spentness of channel outpoints. For neutrino, this saves long rescans
 	// from blocking initial usage of the daemon.
 	AssumeChannelValid bool
@@ -423,7 +424,7 @@ type EdgeLocator struct {
 	Direction uint8
 }
 
-// String returns a human readable version of the edgeLocator values.
+// String returns a human-readable version of the edgeLocator values.
 func (e *EdgeLocator) String() string {
 	return fmt.Sprintf("%v:%v", e.ChannelID, e.Direction)
 }
@@ -551,9 +552,10 @@ func (r *ChannelRouter) Start() error {
 	// then we don't treat this as an explicit error.
 	if _, _, err := r.cfg.Graph.PruneTip(); err != nil {
 		switch {
-		case err == channeldb.ErrGraphNeverPruned:
+		case errors.Is(err, channeldb.ErrGraphNeverPruned):
 			fallthrough
-		case err == channeldb.ErrGraphNotFound:
+
+		case errors.Is(err, channeldb.ErrGraphNotFound):
 			// If the graph has never been pruned, then we'll set
 			// the prune height to the current best height of the
 			// chain backend.
@@ -563,6 +565,7 @@ func (r *ChannelRouter) Start() error {
 			if err != nil {
 				return err
 			}
+
 		default:
 			return err
 		}
@@ -603,7 +606,10 @@ func (r *ChannelRouter) Start() error {
 		// we may miss on-chain events as the filter hasn't properly
 		// been applied.
 		channelView, err := r.cfg.Graph.ChannelView()
-		if err != nil && err != channeldb.ErrGraphNoEdgesFound {
+		if err != nil && !errors.Is(
+			err, channeldb.ErrGraphNoEdgesFound,
+		) {
+
 			return err
 		}
 
@@ -638,7 +644,10 @@ func (r *ChannelRouter) Start() error {
 		// from the graph in order to ensure we maintain a tight graph
 		// of "useful" nodes.
 		err = r.cfg.Graph.PruneGraphNodes()
-		if err != nil && err != channeldb.ErrGraphNodesNotFound {
+		if err != nil && !errors.Is(
+			err, channeldb.ErrGraphNodesNotFound,
+		) {
+
 			return err
 		}
 	}
@@ -707,13 +716,15 @@ func (r *ChannelRouter) Start() error {
 			// result for the in-flight attempt is received.
 			paySession := r.cfg.SessionSource.NewPaymentSessionEmpty()
 
-			// We pass in a zero timeout value, to indicate we
+			// We pass in a non-timeout context, to indicate we
 			// don't need it to timeout. It will stop immediately
 			// after the existing attempt has finished anyway. We
 			// also set a zero fee limit, as no more routes should
 			// be tried.
+			noTimeout := time.Duration(0)
 			_, _, err := r.sendPayment(
-				0, payment.Info.PaymentIdentifier, 0,
+				context.Background(), 0,
+				payment.Info.PaymentIdentifier, noTimeout,
 				paySession, shardTracker,
 			)
 			if err != nil {
@@ -776,8 +787,8 @@ func (r *ChannelRouter) syncGraphWithChain() error {
 		switch {
 		// If the graph has never been pruned, or hasn't fully been
 		// created yet, then we don't treat this as an explicit error.
-		case err == channeldb.ErrGraphNeverPruned:
-		case err == channeldb.ErrGraphNotFound:
+		case errors.Is(err, channeldb.ErrGraphNeverPruned):
+		case errors.Is(err, channeldb.ErrGraphNotFound):
 		default:
 			return err
 		}
@@ -826,10 +837,12 @@ func (r *ChannelRouter) syncGraphWithChain() error {
 			// can exit as this entails we are back to the point
 			// where it hasn't seen any block or created channels,
 			// alas there's nothing left to prune.
-			case err == channeldb.ErrGraphNeverPruned:
+			case errors.Is(err, channeldb.ErrGraphNeverPruned):
 				return nil
-			case err == channeldb.ErrGraphNotFound:
+
+			case errors.Is(err, channeldb.ErrGraphNotFound):
 				return nil
+
 			default:
 				return err
 			}
@@ -1047,7 +1060,10 @@ func (r *ChannelRouter) pruneZombieChans() error {
 	}
 
 	for _, u := range oldEdges {
-		filterPruneChans(u.Info, u.Policy1, u.Policy2)
+		err = filterPruneChans(u.Info, u.Policy1, u.Policy2)
+		if err != nil {
+			log.Warnf("Filter pruning channels: %w\n", err)
+		}
 	}
 
 	log.Infof("Pruning %v zombie channels", len(chansToPrune))
@@ -1072,7 +1088,7 @@ func (r *ChannelRouter) pruneZombieChans() error {
 	// With the channels pruned, we'll also attempt to prune any nodes that
 	// were a part of them.
 	err = r.cfg.Graph.PruneGraphNodes()
-	if err != nil && err != channeldb.ErrGraphNodesNotFound {
+	if err != nil && !errors.Is(err, channeldb.ErrGraphNodesNotFound) {
 		return fmt.Errorf("unable to prune graph nodes: %w", err)
 	}
 
@@ -1125,7 +1141,7 @@ func (r *ChannelRouter) handleNetworkUpdate(vb *ValidationBarrier,
 	if err != nil {
 		// We now decide to log an error or not. If allowDependents is
 		// false, it means there is an error and the error is neither
-		// ErrIgnored or ErrOutdated. In this case, we'll log an error.
+		// ErrIgnored nor ErrOutdated. In this case, we'll log an error.
 		// Otherwise, we'll add debug log only.
 		if allowDependents {
 			log.Debugf("process network updates got: %v", err)
@@ -1225,7 +1241,7 @@ func (r *ChannelRouter) networkHandler() {
 
 			// Since this block is stale, we update our best height
 			// to the previous block.
-			blockHeight := uint32(chainUpdate.Height)
+			blockHeight := chainUpdate.Height
 			atomic.StoreUint32(&r.bestHeight, blockHeight-1)
 
 			// Update the channel graph to reflect that this block
@@ -1485,9 +1501,9 @@ func (r *ChannelRouter) assertNodeAnnFreshness(node route.Vertex,
 }
 
 // addZombieEdge adds a channel that failed complete validation into the zombie
-// index so we can avoid having to re-validate it in the future.
+// index, so we can avoid having to re-validate it in the future.
 func (r *ChannelRouter) addZombieEdge(chanID uint64) error {
-	// If the edge fails validation we'll mark the edge itself as a zombie
+	// If the edge fails validation we'll mark the edge itself as a zombie,
 	// so we don't continue to request it. We use the "zero key" for both
 	// node pubkeys so this edge can't be resurrected.
 	var zeroKey [33]byte
@@ -1598,7 +1614,10 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 		_, _, exists, isZombie, err := r.cfg.Graph.HasChannelEdge(
 			msg.ChannelID,
 		)
-		if err != nil && err != channeldb.ErrGraphNoEdgesFound {
+		if err != nil && !errors.Is(
+			err, channeldb.ErrGraphNoEdgesFound,
+		) {
+
 			return errors.Errorf("unable to check for edge "+
 				"existence: %v", err)
 		}
@@ -1655,7 +1674,7 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 			case strings.Contains(err.Error(), "out of range"):
 				// If the funding transaction isn't found at
 				// all, then we'll mark the edge itself as a
-				// zombie so we don't continue to request it.
+				// zombie, so we don't continue to request it.
 				// We use the "zero key" for both node pubkeys
 				// so this edge can't be resurrected.
 				zErr := r.addZombieEdge(msg.ChannelID)
@@ -1681,8 +1700,8 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 			return err
 		}
 
-		// Next we'll validate that this channel is actually well
-		// formed. If this check fails, then this channel either
+		// Next we'll validate that this channel is actually
+		// well-formed. If this check fails, then this channel either
 		// doesn't exist, or isn't the one that was meant to be created
 		// according to the passed channel proofs.
 		fundingPoint, err := chanvalidate.Validate(&chanvalidate.Context{
@@ -1693,7 +1712,7 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 			FundingTx:        fundingTx,
 		})
 		if err != nil {
-			// Mark the edge as a zombie so we won't try to
+			// Mark the edge as a zombie, so we won't try to
 			// re-validate it on start up.
 			if err := r.addZombieEdge(msg.ChannelID); err != nil {
 				return err
@@ -1705,7 +1724,7 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 
 		// Now that we have the funding outpoint of the channel, ensure
 		// that it hasn't yet been spent. If so, then this channel has
-		// been closed so we'll ignore it.
+		// been closed, so we'll ignore it.
 		chanUtxo, err := r.cfg.Chain.GetUtxo(
 			fundingPoint, fundingPkScript, channelID.BlockHeight,
 			r.quit,
@@ -1740,7 +1759,7 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 
 		// As a new edge has been added to the channel graph, we'll
 		// update the current UTXO filter within our active
-		// FilteredChainView so we are notified if/when this channel is
+		// FilteredChainView, so we are notified if/when this channel is
 		// closed.
 		filterUpdate := []channeldb.EdgePoint{
 			{
@@ -1768,7 +1787,10 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 
 		edge1Timestamp, edge2Timestamp, exists, isZombie, err :=
 			r.cfg.Graph.HasChannelEdge(msg.ChannelID)
-		if err != nil && err != channeldb.ErrGraphNoEdgesFound {
+		if err != nil && !errors.Is(
+			err, channeldb.ErrGraphNoEdgesFound,
+		) {
+
 			return errors.Errorf("unable to check for edge "+
 				"existence: %v", err)
 
@@ -1795,8 +1817,8 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 		}
 
 		// As edges are directional edge node has a unique policy for
-		// the direction of the edge they control. Therefore we first
-		// check if we already have the most up to date information for
+		// the direction of the edge they control. Therefore, we first
+		// check if we already have the most up-to-date information for
 		// that edge. If this message has a timestamp not strictly
 		// newer than what we already know of we can exit early.
 		switch {
@@ -2099,8 +2121,8 @@ func (r *ChannelRouter) FindRoute(req *RouteRequest) (*route.Route, float64,
 		return nil, 0, err
 	}
 
-	// We'll fetch the current block height so we can properly calculate the
-	// required HTLC time locks within the route.
+	// We'll fetch the current block height, so we can properly calculate
+	// the required HTLC time locks within the route.
 	_, currentHeight, err := r.cfg.Chain.GetBestBlock()
 	if err != nil {
 		return nil, 0, err
@@ -2172,7 +2194,7 @@ func generateSphinxPacket(rt *route.Route, paymentHash []byte,
 	// Now that we know we have an actual route, we'll map the route into a
 	// sphinx payment path which includes per-hop payloads for each hop
 	// that give each node within the route the necessary information
-	// (fees, CLTV value, etc) to properly forward the payment.
+	// (fees, CLTV value, etc.) to properly forward the payment.
 	sphinxPath, err := rt.ToSphinxPath()
 	if err != nil {
 		return nil, nil, err
@@ -2285,11 +2307,11 @@ type LightningPayment struct {
 	LastHop *route.Vertex
 
 	// DestFeatures specifies the set of features we assume the final node
-	// has for pathfinding. Typically these will be taken directly from an
+	// has for pathfinding. Typically, these will be taken directly from an
 	// invoice, but they can also be manually supplied or assumed by the
 	// sender. If a nil feature vector is provided, the router will try to
-	// fallback to the graph in order to load a feature vector for a node in
-	// the public graph.
+	// fall back to the graph in order to load a feature vector for a node
+	// in the public graph.
 	DestFeatures *lnwire.FeatureVector
 
 	// PaymentAddr is the payment address specified by the receiver. This
@@ -2387,18 +2409,16 @@ func (r *ChannelRouter) SendPayment(payment *LightningPayment) ([32]byte,
 	log.Tracef("Dispatching SendPayment for lightning payment: %v",
 		spewPayment(payment))
 
-	// Since this is the first time this payment is being made, we pass nil
-	// for the existing attempt.
 	return r.sendPayment(
-		payment.FeeLimit, payment.Identifier(),
+		context.Background(), payment.FeeLimit, payment.Identifier(),
 		payment.PayAttemptTimeout, paySession, shardTracker,
 	)
 }
 
 // SendPaymentAsync is the non-blocking version of SendPayment. The payment
 // result needs to be retrieved via the control tower.
-func (r *ChannelRouter) SendPaymentAsync(payment *LightningPayment,
-	ps PaymentSession, st shards.ShardTracker) {
+func (r *ChannelRouter) SendPaymentAsync(ctx context.Context,
+	payment *LightningPayment, ps PaymentSession, st shards.ShardTracker) {
 
 	// Since this is the first time this payment is being made, we pass nil
 	// for the existing attempt.
@@ -2410,7 +2430,7 @@ func (r *ChannelRouter) SendPaymentAsync(payment *LightningPayment,
 			spewPayment(payment))
 
 		_, _, err := r.sendPayment(
-			payment.FeeLimit, payment.Identifier(),
+			ctx, payment.FeeLimit, payment.Identifier(),
 			payment.PayAttemptTimeout, ps, st,
 		)
 		if err != nil {
@@ -2520,8 +2540,8 @@ func (r *ChannelRouter) sendToRoute(htlcHash lntypes.Hash, rt *route.Route,
 	// Calculate amount paid to receiver.
 	amt := rt.ReceiverAmt()
 
-	// If this is meant as a MP payment shard, we set the amount
-	// for the creating info to the total amount of the payment.
+	// If this is meant as an MP payment shard, we set the amount for the
+	// creating info to the total amount of the payment.
 	finalHop := rt.Hops[len(rt.Hops)-1]
 	mpp := finalHop.MPP
 	if mpp != nil {
@@ -2575,7 +2595,7 @@ func (r *ChannelRouter) sendToRoute(htlcHash lntypes.Hash, rt *route.Route,
 
 	// Since the HTLC hashes and preimages are specified manually over the
 	// RPC for SendToRoute requests, we don't have to worry about creating
-	// a ShardTracker that can generate hashes for AMP payments. Instead we
+	// a ShardTracker that can generate hashes for AMP payments. Instead, we
 	// create a simple tracker that can just return the hash for the single
 	// shard we'll now launch.
 	shardTracker := shards.NewSimpleShardTracker(htlcHash, nil)
@@ -2585,9 +2605,7 @@ func (r *ChannelRouter) sendToRoute(htlcHash lntypes.Hash, rt *route.Route,
 	// - nil payment session (since we already have a route).
 	// - no payment timeout.
 	// - no current block height.
-	p := newPaymentLifecycle(
-		r, 0, paymentIdentifier, nil, shardTracker, 0, 0,
-	)
+	p := newPaymentLifecycle(r, 0, paymentIdentifier, nil, shardTracker, 0)
 
 	// We found a route to try, create a new HTLC attempt to try.
 	//
@@ -2608,7 +2626,7 @@ func (r *ChannelRouter) sendToRoute(htlcHash lntypes.Hash, rt *route.Route,
 		return nil, err
 	}
 
-	// We now lookup the payment to see if it's already failed.
+	// We now look up the payment to see if it's already failed.
 	payment, err := p.router.cfg.Control.FetchPayment(p.identifier)
 	if err != nil {
 		return result.attempt, err
@@ -2677,15 +2695,27 @@ func (r *ChannelRouter) sendToRoute(htlcHash lntypes.Hash, rt *route.Route,
 // returned.
 //
 // This method relies on the ControlTower's internal payment state machine to
-// carry out its execution. After restarts it is safe, and assumed, that the
+// carry out its execution. After restarts, it is safe, and assumed, that the
 // router will call this method for every payment still in-flight according to
 // the ControlTower.
-func (r *ChannelRouter) sendPayment(feeLimit lnwire.MilliSatoshi,
-	identifier lntypes.Hash, timeout time.Duration,
-	paySession PaymentSession,
+func (r *ChannelRouter) sendPayment(ctx context.Context,
+	feeLimit lnwire.MilliSatoshi, identifier lntypes.Hash,
+	paymentAttemptTimeout time.Duration, paySession PaymentSession,
 	shardTracker shards.ShardTracker) ([32]byte, *route.Route, error) {
 
-	// We'll also fetch the current block height so we can properly
+	// If the user provides a timeout, we will additionally wrap the context
+	// in a deadline.
+	cancel := func() {}
+	if paymentAttemptTimeout > 0 {
+		ctx, cancel = context.WithTimeout(ctx, paymentAttemptTimeout)
+	}
+
+	// Since resumePayment is a blocking call, we'll cancel this
+	// context if the payment completes before the optional
+	// deadline.
+	defer cancel()
+
+	// We'll also fetch the current block height, so we can properly
 	// calculate the required HTLC time locks within the route.
 	_, currentHeight, err := r.cfg.Chain.GetBestBlock()
 	if err != nil {
@@ -2695,11 +2725,11 @@ func (r *ChannelRouter) sendPayment(feeLimit lnwire.MilliSatoshi,
 	// Now set up a paymentLifecycle struct with these params, such that we
 	// can resume the payment from the current state.
 	p := newPaymentLifecycle(
-		r, feeLimit, identifier, paySession,
-		shardTracker, timeout, currentHeight,
+		r, feeLimit, identifier, paySession, shardTracker,
+		currentHeight,
 	)
 
-	return p.resumePayment()
+	return p.resumePayment(ctx)
 }
 
 // extractChannelUpdate examines the error and extracts the channel update.
@@ -3022,8 +3052,8 @@ func (r *ChannelRouter) IsStaleEdgePolicy(chanID lnwire.ShortChannelID,
 	}
 
 	// As edges are directional edge node has a unique policy for the
-	// direction of the edge they control. Therefore we first check if we
-	// already have the most up to date information for that edge. If so,
+	// direction of the edge they control. Therefore, we first check if we
+	// already have the most up-to-date information for that edge. If so,
 	// then we can exit early.
 	switch {
 	// A flag set of 0 indicates this is an announcement for the "first"
@@ -3054,7 +3084,7 @@ type ErrNoChannel struct {
 	fromNode route.Vertex
 }
 
-// Error returns a human readable string describing the error.
+// Error returns a human-readable string describing the error.
 func (e ErrNoChannel) Error() string {
 	return fmt.Sprintf("no matching outgoing channel available for "+
 		"node %v (%v)", e.position, e.fromNode)