loop: add support for the probe API

client.go

@@ -48,6 +48,9 @@ var (
 	// and pay for an LSAT token.
 	globalCallTimeout = serverRPCTimeout + lsat.PaymentTimeout
 
+	// probeTimeout is the maximum time until a probe is allowed to take.
+	probeTimeout = 3 * time.Minute
+
 	republishDelay = 10 * time.Second
 
 	// MinerFeeEstimationFailed is a magic number that is returned in a
@@ -560,7 +563,9 @@ func (s *Client) LoopInQuote(ctx context.Context,
 		return nil, ErrSwapAmountTooHigh
 	}
 
-	quote, err := s.Server.GetLoopInQuote(ctx, request.Amount)
+	quote, err := s.Server.GetLoopInQuote(
+		ctx, request.Amount, s.lndServices.NodePubkey, request.LastHop,
+	)
 	if err != nil {
 		return nil, err
 	}
@@ -625,3 +630,13 @@ func wrapGrpcError(message string, err error) error {
 			grpcStatus.Message()),
 	)
 }
+
+// Probe asks the server to probe a route to us given a requested amount and
+// last hop. The server is free to discard frequent request to avoid abuse or if
+// there's been a recent probe to us for the same amount.
+func (s *Client) Probe(ctx context.Context, req *ProbeRequest) error {
+	return s.Server.Probe(
+		ctx, req.Amount, s.lndServices.NodePubkey, req.LastHop,
+		req.RouteHints,
+	)
+}

interface.go

@@ -8,6 +8,7 @@ import (
 	"github.com/lightninglabs/loop/swap"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/routing/route"
+	"github.com/lightningnetwork/lnd/zpay32"
 )
 
 // OutRequest contains the required parameters for a loop out swap.
@@ -243,6 +244,11 @@ type LoopInQuoteRequest struct {
 	// ExternalHtlc specifies whether the htlc is published by an external
 	// source.
 	ExternalHtlc bool
+
+	// LastHop is an optional last hop to use. This last hop is used when
+	// the client has already requested a server probe for more accurate
+	// routing fee estimation.
+	LastHop *route.Vertex
 }
 
 // LoopInQuote contains estimates for the fees making up the total swap cost
@@ -340,3 +346,15 @@ func (s *In) LastUpdate() time.Time {
 func (s *In) SwapHash() lntypes.Hash {
 	return s.Hash
 }
+
+// ProbeRequest specifies probe parameters for the server probe.
+type ProbeRequest struct {
+	// Amount is the amount that will be probed.
+	Amount btcutil.Amount
+
+	// LastHop is the last hop along the route.
+	LastHop *route.Vertex
+
+	// Optional hop hints.
+	RouteHints [][]zpay32.HopHint
+}

loopd/macaroons.go

@@ -95,6 +95,13 @@ var (
 			Entity: "suggestions",
 			Action: "write",
 		}},
+		"/looprpc.SwapClient/Probe": {{
+			Entity: "swap",
+			Action: "execute",
+		}, {
+			Entity: "loop",
+			Action: "in",
+		}},
 	}
 
 	// allPermissions is the list of all existing permissions that exist

loopd/swapclient_server.go

@@ -2,12 +2,14 @@ package loopd
 
 import (
 	"context"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"sort"
 	"sync"
 	"time"
 
+	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/btcsuite/btcutil"
 	"github.com/lightninglabs/lndclient"
@@ -22,6 +24,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/queue"
 	"github.com/lightningnetwork/lnd/routing/route"
+	"github.com/lightningnetwork/lnd/zpay32"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
@@ -495,6 +498,85 @@ func (s *swapClientServer) GetLoopInQuote(ctx context.Context,
 	}, nil
 }
 
+// unmarshallRouteHints unmarshalls a list of route hints.
+func unmarshallRouteHints(rpcRouteHints []*looprpc.RouteHint) (
+	[][]zpay32.HopHint, error) {
+
+	routeHints := make([][]zpay32.HopHint, 0, len(rpcRouteHints))
+	for _, rpcRouteHint := range rpcRouteHints {
+		routeHint := make(
+			[]zpay32.HopHint, 0, len(rpcRouteHint.HopHints),
+		)
+		for _, rpcHint := range rpcRouteHint.HopHints {
+			hint, err := unmarshallHopHint(rpcHint)
+			if err != nil {
+				return nil, err
+			}
+
+			routeHint = append(routeHint, hint)
+		}
+		routeHints = append(routeHints, routeHint)
+	}
+
+	return routeHints, nil
+}
+
+// unmarshallHopHint unmarshalls a single hop hint.
+func unmarshallHopHint(rpcHint *looprpc.HopHint) (zpay32.HopHint, error) {
+	pubBytes, err := hex.DecodeString(rpcHint.NodeId)
+	if err != nil {
+		return zpay32.HopHint{}, err
+	}
+
+	pubkey, err := btcec.ParsePubKey(pubBytes, btcec.S256())
+	if err != nil {
+		return zpay32.HopHint{}, err
+	}
+
+	return zpay32.HopHint{
+		NodeID:                    pubkey,
+		ChannelID:                 rpcHint.ChanId,
+		FeeBaseMSat:               rpcHint.FeeBaseMsat,
+		FeeProportionalMillionths: rpcHint.FeeProportionalMillionths,
+		CLTVExpiryDelta:           uint16(rpcHint.CltvExpiryDelta),
+	}, nil
+}
+
+// Probe requests the server to probe the client's node to test inbound
+// liquidity.
+func (s *swapClientServer) Probe(ctx context.Context,
+	req *looprpc.ProbeRequest) (*looprpc.ProbeResponse, error) {
+
+	log.Infof("Probe request received")
+
+	var lastHop *route.Vertex
+	if req.LastHop != nil {
+		lastHopVertex, err := route.NewVertexFromBytes(req.LastHop)
+		if err != nil {
+			return nil, err
+		}
+
+		lastHop = &lastHopVertex
+	}
+
+	routeHints, err := unmarshallRouteHints(req.RouteHints)
+	if err != nil {
+		return nil, err
+	}
+
+	err = s.impl.Probe(ctx, &loop.ProbeRequest{
+		Amount:     btcutil.Amount(req.Amt),
+		LastHop:    lastHop,
+		RouteHints: routeHints,
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &looprpc.ProbeResponse{}, nil
+}
+
 func (s *swapClientServer) LoopIn(ctx context.Context,
 	in *looprpc.LoopInRequest) (
 	*looprpc.SwapResponse, error) {

loopdb/protocol_version.go

@@ -43,13 +43,17 @@ const (
 	// canceling loop out swaps.
 	ProtocolVersionLoopOutCancel = 7
 
+	// ProtocolVerionProbe indicates that the client is able to request
+	// the server to perform a probe to test inbound liquidty.
+	ProtocolVersionProbe ProtocolVersion = 8
+
 	// ProtocolVersionUnrecorded is set for swaps were created before we
 	// started saving protocol version with swaps.
 	ProtocolVersionUnrecorded ProtocolVersion = math.MaxUint32
 
 	// CurrentRPCProtocolVersion defines the version of the RPC protocol
 	// that is currently supported by the loop client.
-	CurrentRPCProtocolVersion = looprpc.ProtocolVersion_LOOP_OUT_CANCEL
+	CurrentRPCProtocolVersion = looprpc.ProtocolVersion_PROBE
 
 	// CurrentInternalProtocolVersion defines the RPC current protocol in
 	// the internal representation.
@@ -88,6 +92,9 @@ func (p ProtocolVersion) String() string {
 	case ProtocolVersionLoopOutCancel:
 		return "Loop Out Cancel"
 
+	case ProtocolVersionProbe:
+		return "Probe"
+
 	default:
 		return "Unknown"
 	}

loopdb/protocol_version_test.go

@@ -22,6 +22,7 @@ func TestProtocolVersionSanity(t *testing.T) {
 		ProtocolVersionHtlcV2,
 		ProtocolVersionMultiLoopIn,
 		ProtocolVersionLoopOutCancel,
+		ProtocolVersionProbe,
 	}
 
 	rpcVersions := [...]looprpc.ProtocolVersion{
@@ -33,6 +34,7 @@ func TestProtocolVersionSanity(t *testing.T) {
 		looprpc.ProtocolVersion_HTLC_V2,
 		looprpc.ProtocolVersion_MULTI_LOOP_IN,
 		looprpc.ProtocolVersion_LOOP_OUT_CANCEL,
+		looprpc.ProtocolVersion_PROBE,
 	}
 
 	require.Equal(t, len(versions), len(rpcVersions))

loopin.go

@@ -83,7 +83,9 @@ func newLoopInSwap(globalCtx context.Context, cfg *swapConfig,
 	// Request current server loop in terms and use these to calculate the
 	// swap fee that we should subtract from the swap amount in the payment
 	// request that we send to the server.
-	quote, err := cfg.server.GetLoopInQuote(globalCtx, request.Amount)
+	quote, err := cfg.server.GetLoopInQuote(
+		globalCtx, request.Amount, cfg.lnd.NodePubkey, request.LastHop,
+	)
 	if err != nil {
 		return nil, wrapGrpcError("loop in terms", err)
 	}

looprpc/client.pb.gw.go

@@ -345,6 +345,76 @@ func local_request_SwapClient_GetLoopInQuote_0(ctx context.Context, marshaler ru
 
 }
 
+var (
+	filter_SwapClient_Probe_0 = &utilities.DoubleArray{Encoding: map[string]int{"amt": 0}, Base: []int{1, 1, 0}, Check: []int{0, 1, 2}}
+)
+
+func request_SwapClient_Probe_0(ctx context.Context, marshaler runtime.Marshaler, client SwapClientClient, req *http.Request, pathParams map[string]string) (proto.Message, runtime.ServerMetadata, error) {
+	var protoReq ProbeRequest
+	var metadata runtime.ServerMetadata
+
+	var (
+		val string
+		ok  bool
+		err error
+		_   = err
+	)
+
+	val, ok = pathParams["amt"]
+	if !ok {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "missing parameter %s", "amt")
+	}
+
+	protoReq.Amt, err = runtime.Int64(val)
+	if err != nil {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "type mismatch, parameter: %s, error: %v", "amt", err)
+	}
+
+	if err := req.ParseForm(); err != nil {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "%v", err)
+	}
+	if err := runtime.PopulateQueryParameters(&protoReq, req.Form, filter_SwapClient_Probe_0); err != nil {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "%v", err)
+	}
+
+	msg, err := client.Probe(ctx, &protoReq, grpc.Header(&metadata.HeaderMD), grpc.Trailer(&metadata.TrailerMD))
+	return msg, metadata, err
+
+}
+
+func local_request_SwapClient_Probe_0(ctx context.Context, marshaler runtime.Marshaler, server SwapClientServer, req *http.Request, pathParams map[string]string) (proto.Message, runtime.ServerMetadata, error) {
+	var protoReq ProbeRequest
+	var metadata runtime.ServerMetadata
+
+	var (
+		val string
+		ok  bool
+		err error
+		_   = err
+	)
+
+	val, ok = pathParams["amt"]
+	if !ok {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "missing parameter %s", "amt")
+	}
+
+	protoReq.Amt, err = runtime.Int64(val)
+	if err != nil {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "type mismatch, parameter: %s, error: %v", "amt", err)
+	}
+
+	if err := req.ParseForm(); err != nil {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "%v", err)
+	}
+	if err := runtime.PopulateQueryParameters(&protoReq, req.Form, filter_SwapClient_Probe_0); err != nil {
+		return nil, metadata, status.Errorf(codes.InvalidArgument, "%v", err)
+	}
+
+	msg, err := server.Probe(ctx, &protoReq)
+	return msg, metadata, err
+
+}
+
 func request_SwapClient_GetLsatTokens_0(ctx context.Context, marshaler runtime.Marshaler, client SwapClientClient, req *http.Request, pathParams map[string]string) (proto.Message, runtime.ServerMetadata, error) {
 	var protoReq TokensRequest
 	var metadata runtime.ServerMetadata
@@ -623,6 +693,29 @@ func RegisterSwapClientHandlerServer(ctx context.Context, mux *runtime.ServeMux,
 
 	})
 
+	mux.Handle("GET", pattern_SwapClient_Probe_0, func(w http.ResponseWriter, req *http.Request, pathParams map[string]string) {
+		ctx, cancel := context.WithCancel(req.Context())
+		defer cancel()
+		var stream runtime.ServerTransportStream
+		ctx = grpc.NewContextWithServerTransportStream(ctx, &stream)
+		inboundMarshaler, outboundMarshaler := runtime.MarshalerForRequest(mux, req)
+		rctx, err := runtime.AnnotateIncomingContext(ctx, mux, req, "/looprpc.SwapClient/Probe", runtime.WithHTTPPathPattern("/v1/loop/in/probe/{amt}"))
+		if err != nil {
+			runtime.HTTPError(ctx, mux, outboundMarshaler, w, req, err)
+			return
+		}
+		resp, md, err := local_request_SwapClient_Probe_0(rctx, inboundMarshaler, server, req, pathParams)
+		md.HeaderMD, md.TrailerMD = metadata.Join(md.HeaderMD, stream.Header()), metadata.Join(md.TrailerMD, stream.Trailer())
+		ctx = runtime.NewServerMetadataContext(ctx, md)
+		if err != nil {
+			runtime.HTTPError(ctx, mux, outboundMarshaler, w, req, err)
+			return
+		}
+
+		forward_SwapClient_Probe_0(ctx, mux, outboundMarshaler, w, req, resp, mux.GetForwardResponseOptions()...)
+
+	})
+
 	mux.Handle("GET", pattern_SwapClient_GetLsatTokens_0, func(w http.ResponseWriter, req *http.Request, pathParams map[string]string) {
 		ctx, cancel := context.WithCancel(req.Context())
 		defer cancel()
@@ -916,6 +1009,26 @@ func RegisterSwapClientHandlerClient(ctx context.Context, mux *runtime.ServeMux,
 
 	})
 
+	mux.Handle("GET", pattern_SwapClient_Probe_0, func(w http.ResponseWriter, req *http.Request, pathParams map[string]string) {
+		ctx, cancel := context.WithCancel(req.Context())
+		defer cancel()
+		inboundMarshaler, outboundMarshaler := runtime.MarshalerForRequest(mux, req)
+		rctx, err := runtime.AnnotateContext(ctx, mux, req, "/looprpc.SwapClient/Probe", runtime.WithHTTPPathPattern("/v1/loop/in/probe/{amt}"))
+		if err != nil {
+			runtime.HTTPError(ctx, mux, outboundMarshaler, w, req, err)
+			return
+		}
+		resp, md, err := request_SwapClient_Probe_0(rctx, inboundMarshaler, client, req, pathParams)
+		ctx = runtime.NewServerMetadataContext(ctx, md)
+		if err != nil {
+			runtime.HTTPError(ctx, mux, outboundMarshaler, w, req, err)
+			return
+		}
+
+		forward_SwapClient_Probe_0(ctx, mux, outboundMarshaler, w, req, resp, mux.GetForwardResponseOptions()...)
+
+	})
+
 	mux.Handle("GET", pattern_SwapClient_GetLsatTokens_0, func(w http.ResponseWriter, req *http.Request, pathParams map[string]string) {
 		ctx, cancel := context.WithCancel(req.Context())
 		defer cancel()
@@ -1016,6 +1129,8 @@ var (
 
 	pattern_SwapClient_GetLoopInQuote_0 = runtime.MustPattern(runtime.NewPattern(1, []int{2, 0, 2, 1, 2, 2, 2, 3, 1, 0, 4, 1, 5, 4}, []string{"v1", "loop", "in", "quote", "amt"}, ""))
 
+	pattern_SwapClient_Probe_0 = runtime.MustPattern(runtime.NewPattern(1, []int{2, 0, 2, 1, 2, 2, 2, 3, 1, 0, 4, 1, 5, 4}, []string{"v1", "loop", "in", "probe", "amt"}, ""))
+
 	pattern_SwapClient_GetLsatTokens_0 = runtime.MustPattern(runtime.NewPattern(1, []int{2, 0, 2, 1, 2, 2}, []string{"v1", "lsat", "tokens"}, ""))
 
 	pattern_SwapClient_GetLiquidityParams_0 = runtime.MustPattern(runtime.NewPattern(1, []int{2, 0, 2, 1, 2, 2}, []string{"v1", "liquidity", "params"}, ""))
@@ -1042,6 +1157,8 @@ var (
 
 	forward_SwapClient_GetLoopInQuote_0 = runtime.ForwardResponseMessage
 
+	forward_SwapClient_Probe_0 = runtime.ForwardResponseMessage
+
 	forward_SwapClient_GetLsatTokens_0 = runtime.ForwardResponseMessage
 
 	forward_SwapClient_GetLiquidityParams_0 = runtime.ForwardResponseMessage

looprpc/client.proto

@@ -1,5 +1,7 @@
 syntax = "proto3";
 
+import "common.proto";
+
 package looprpc;
 
 option go_package = "github.com/lightninglabs/loop/looprpc";
@@ -62,6 +64,12 @@ service SwapClient {
     */
     rpc GetLoopInQuote (QuoteRequest) returns (InQuoteResponse);
 
+    /*
+    Probe asks he sever to probe the route to us to have a better upfront
+    estimate about routing fees when loopin-in.
+    */
+    rpc Probe (ProbeRequest) returns (ProbeResponse);
+
     /* loop: `listauth`
     GetLsatTokens returns all LSAT tokens the daemon ever paid for.
     */
@@ -560,6 +568,13 @@ message QuoteRequest {
     lower total swap fee. This only has an effect on loop out quotes.
     */
     uint64 swap_publication_deadline = 4;
+
+    /*
+    Optionally the client can specify the last hop pubkey when requesting a
+    loop-in quote. This is useful to get better off-chain routing fee from the
+    server.
+    */
+    bytes loop_in_last_hop = 5;
 }
 
 message InQuoteResponse {
@@ -625,6 +640,26 @@ message OutQuoteResponse {
     int32 conf_target = 6;
 }
 
+message ProbeRequest {
+    /*
+    The amount to probe.
+    */
+    int64 amt = 1;
+
+    /*
+    Optional last hop of the route to probe.
+    */
+    bytes last_hop = 2;
+
+    /*
+    Optional route hints to reach the destination through private channels.
+    */
+    repeated RouteHint route_hints = 3;
+}
+
+message ProbeResponse {
+}
+
 message TokensRequest {
 }
 

looprpc/client.swagger.json

@@ -126,6 +126,47 @@
         ]
       }
     },
+    "/v1/loop/in/probe/{amt}": {
+      "get": {
+        "summary": "Probe asks he sever to probe the route to us to have a better upfront\nestimate about routing fees when loopin-in.",
+        "operationId": "SwapClient_Probe",
+        "responses": {
+          "200": {
+            "description": "A successful response.",
+            "schema": {
+              "$ref": "#/definitions/looprpcProbeResponse"
+            }
+          },
+          "default": {
+            "description": "An unexpected error response.",
+            "schema": {
+              "$ref": "#/definitions/rpcStatus"
+            }
+          }
+        },
+        "parameters": [
+          {
+            "name": "amt",
+            "description": "The amount to probe.",
+            "in": "path",
+            "required": true,
+            "type": "string",
+            "format": "int64"
+          },
+          {
+            "name": "last_hop",
+            "description": "Optional last hop of the route to probe.",
+            "in": "query",
+            "required": false,
+            "type": "string",
+            "format": "byte"
+          }
+        ],
+        "tags": [
+          "SwapClient"
+        ]
+      }
+    },
     "/v1/loop/in/quote/{amt}": {
       "get": {
         "summary": "loop: `quote`\nGetQuote returns a quote for a swap with the provided parameters.",
@@ -175,6 +216,14 @@
             "required": false,
             "type": "string",
             "format": "uint64"
+          },
+          {
+            "name": "loop_in_last_hop",
+            "description": "Optionally the client can specify the last hop pubkey when requesting a\nloop-in quote. This is useful to get better off-chain routing fee from the\nserver.",
+            "in": "query",
+            "required": false,
+            "type": "string",
+            "format": "byte"
           }
         ],
         "tags": [
@@ -287,6 +336,14 @@
             "required": false,
             "type": "string",
             "format": "uint64"
+          },
+          {
+            "name": "loop_in_last_hop",
+            "description": "Optionally the client can specify the last hop pubkey when requesting a\nloop-in quote. This is useful to get better off-chain routing fee from the\nserver.",
+            "in": "query",
+            "required": false,
+            "type": "string",
+            "format": "byte"
           }
         ],
         "tags": [
@@ -452,6 +509,35 @@
       "default": "FAILURE_REASON_NONE",
       "description": " - FAILURE_REASON_NONE: FAILURE_REASON_NONE is set when the swap did not fail, it is either in\nprogress or succeeded.\n - FAILURE_REASON_OFFCHAIN: FAILURE_REASON_OFFCHAIN indicates that a loop out failed because it wasn't\npossible to find a route for one or both off chain payments that met the fee\nand timelock limits required.\n - FAILURE_REASON_TIMEOUT: FAILURE_REASON_TIMEOUT indicates that the swap failed because on chain htlc\ndid not confirm before its expiry, or it confirmed too late for us to reveal\nour preimage and claim.\n - FAILURE_REASON_SWEEP_TIMEOUT: FAILURE_REASON_SWEEP_TIMEOUT indicates that a loop out permanently failed\nbecause the on chain htlc wasn't swept before the server revoked the\nhtlc.\n - FAILURE_REASON_INSUFFICIENT_VALUE: FAILURE_REASON_INSUFFICIENT_VALUE indicates that a loop out has failed\nbecause the on chain htlc had a lower value than requested.\n - FAILURE_REASON_TEMPORARY: FAILURE_REASON_TEMPORARY indicates that a swap cannot continue due to an\ninternal error. Manual intervention such as a restart is required.\n - FAILURE_REASON_INCORRECT_AMOUNT: FAILURE_REASON_INCORRECT_AMOUNT indicates that a loop in permanently failed\nbecause the amount extended by an external loop in htlc is insufficient."
     },
+    "looprpcHopHint": {
+      "type": "object",
+      "properties": {
+        "node_id": {
+          "type": "string",
+          "description": "The public key of the node at the start of the channel."
+        },
+        "chan_id": {
+          "type": "string",
+          "format": "uint64",
+          "description": "The unique identifier of the channel."
+        },
+        "fee_base_msat": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The base fee of the channel denominated in millisatoshis."
+        },
+        "fee_proportional_millionths": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The fee rate of the channel for sending one satoshi across it denominated in\nmillionths of a satoshi."
+        },
+        "cltv_expiry_delta": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The time-lock delta of the channel."
+        }
+      }
+    },
     "looprpcInQuoteResponse": {
       "type": "object",
       "properties": {
@@ -847,6 +933,21 @@
         }
       }
     },
+    "looprpcProbeResponse": {
+      "type": "object"
+    },
+    "looprpcRouteHint": {
+      "type": "object",
+      "properties": {
+        "hop_hints": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/looprpcHopHint"
+          },
+          "description": "A list of hop hints that when chained together can assist in reaching a\nspecific destination."
+        }
+      }
+    },
     "looprpcSetLiquidityParamsRequest": {
       "type": "object",
       "properties": {

looprpc/client.yaml

@@ -22,6 +22,8 @@ http:
       get: "/v1/loop/in/terms"
     - selector: looprpc.SwapClient.GetLoopInQuote
       get: "/v1/loop/in/quote/{amt}"
+    - selector: looprpc.SwapClient.Probe
+      get: "/v1/loop/in/probe/{amt}"
     - selector: looprpc.SwapClient.GetLsatTokens
       get: "/v1/lsat/tokens"
     - selector: looprpc.SwapClient.GetLiquidityParams

looprpc/client_grpc.pb.go

@@ -53,6 +53,10 @@ type SwapClientClient interface {
 	// loop: `quote`
 	//GetQuote returns a quote for a swap with the provided parameters.
 	GetLoopInQuote(ctx context.Context, in *QuoteRequest, opts ...grpc.CallOption) (*InQuoteResponse, error)
+	//
+	//Probe asks he sever to probe the route to us to have a better upfront
+	//estimate about routing fees when loopin-in.
+	Probe(ctx context.Context, in *ProbeRequest, opts ...grpc.CallOption) (*ProbeResponse, error)
 	// loop: `listauth`
 	//GetLsatTokens returns all LSAT tokens the daemon ever paid for.
 	GetLsatTokens(ctx context.Context, in *TokensRequest, opts ...grpc.CallOption) (*TokensResponse, error)
@@ -187,6 +191,15 @@ func (c *swapClientClient) GetLoopInQuote(ctx context.Context, in *QuoteRequest,
 	return out, nil
 }
 
+func (c *swapClientClient) Probe(ctx context.Context, in *ProbeRequest, opts ...grpc.CallOption) (*ProbeResponse, error) {
+	out := new(ProbeResponse)
+	err := c.cc.Invoke(ctx, "/looprpc.SwapClient/Probe", in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 func (c *swapClientClient) GetLsatTokens(ctx context.Context, in *TokensRequest, opts ...grpc.CallOption) (*TokensResponse, error) {
 	out := new(TokensResponse)
 	err := c.cc.Invoke(ctx, "/looprpc.SwapClient/GetLsatTokens", in, out, opts...)
@@ -262,6 +275,10 @@ type SwapClientServer interface {
 	// loop: `quote`
 	//GetQuote returns a quote for a swap with the provided parameters.
 	GetLoopInQuote(context.Context, *QuoteRequest) (*InQuoteResponse, error)
+	//
+	//Probe asks he sever to probe the route to us to have a better upfront
+	//estimate about routing fees when loopin-in.
+	Probe(context.Context, *ProbeRequest) (*ProbeResponse, error)
 	// loop: `listauth`
 	//GetLsatTokens returns all LSAT tokens the daemon ever paid for.
 	GetLsatTokens(context.Context, *TokensRequest) (*TokensResponse, error)
@@ -316,6 +333,9 @@ func (UnimplementedSwapClientServer) GetLoopInTerms(context.Context, *TermsReque
 func (UnimplementedSwapClientServer) GetLoopInQuote(context.Context, *QuoteRequest) (*InQuoteResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method GetLoopInQuote not implemented")
 }
+func (UnimplementedSwapClientServer) Probe(context.Context, *ProbeRequest) (*ProbeResponse, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method Probe not implemented")
+}
 func (UnimplementedSwapClientServer) GetLsatTokens(context.Context, *TokensRequest) (*TokensResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method GetLsatTokens not implemented")
 }
@@ -506,6 +526,24 @@ func _SwapClient_GetLoopInQuote_Handler(srv interface{}, ctx context.Context, de
 	return interceptor(ctx, in, info, handler)
 }
 
+func _SwapClient_Probe_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(ProbeRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SwapClientServer).Probe(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: "/looprpc.SwapClient/Probe",
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SwapClientServer).Probe(ctx, req.(*ProbeRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 func _SwapClient_GetLsatTokens_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
 	in := new(TokensRequest)
 	if err := dec(in); err != nil {
@@ -617,6 +655,10 @@ var SwapClient_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "GetLoopInQuote",
 			Handler:    _SwapClient_GetLoopInQuote_Handler,
 		},
+		{
+			MethodName: "Probe",
+			Handler:    _SwapClient_Probe_Handler,
+		},
 		{
 			MethodName: "GetLsatTokens",
 			Handler:    _SwapClient_GetLsatTokens_Handler,

looprpc/common.pb.go

@@ -0,0 +1,261 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.26.0
+// 	protoc        v3.6.1
+// source: common.proto
+
+package looprpc
+
+import (
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	reflect "reflect"
+	sync "sync"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+type HopHint struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// The public key of the node at the start of the channel.
+	NodeId string `protobuf:"bytes,1,opt,name=node_id,json=nodeId,proto3" json:"node_id,omitempty"`
+	// The unique identifier of the channel.
+	ChanId uint64 `protobuf:"varint,2,opt,name=chan_id,json=chanId,proto3" json:"chan_id,omitempty"`
+	// The base fee of the channel denominated in millisatoshis.
+	FeeBaseMsat uint32 `protobuf:"varint,3,opt,name=fee_base_msat,json=feeBaseMsat,proto3" json:"fee_base_msat,omitempty"`
+	//
+	//The fee rate of the channel for sending one satoshi across it denominated in
+	//millionths of a satoshi.
+	FeeProportionalMillionths uint32 `protobuf:"varint,4,opt,name=fee_proportional_millionths,json=feeProportionalMillionths,proto3" json:"fee_proportional_millionths,omitempty"`
+	// The time-lock delta of the channel.
+	CltvExpiryDelta uint32 `protobuf:"varint,5,opt,name=cltv_expiry_delta,json=cltvExpiryDelta,proto3" json:"cltv_expiry_delta,omitempty"`
+}
+
+func (x *HopHint) Reset() {
+	*x = HopHint{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_common_proto_msgTypes[0]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *HopHint) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*HopHint) ProtoMessage() {}
+
+func (x *HopHint) ProtoReflect() protoreflect.Message {
+	mi := &file_common_proto_msgTypes[0]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use HopHint.ProtoReflect.Descriptor instead.
+func (*HopHint) Descriptor() ([]byte, []int) {
+	return file_common_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *HopHint) GetNodeId() string {
+	if x != nil {
+		return x.NodeId
+	}
+	return ""
+}
+
+func (x *HopHint) GetChanId() uint64 {
+	if x != nil {
+		return x.ChanId
+	}
+	return 0
+}
+
+func (x *HopHint) GetFeeBaseMsat() uint32 {
+	if x != nil {
+		return x.FeeBaseMsat
+	}
+	return 0
+}
+
+func (x *HopHint) GetFeeProportionalMillionths() uint32 {
+	if x != nil {
+		return x.FeeProportionalMillionths
+	}
+	return 0
+}
+
+func (x *HopHint) GetCltvExpiryDelta() uint32 {
+	if x != nil {
+		return x.CltvExpiryDelta
+	}
+	return 0
+}
+
+type RouteHint struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	//
+	//A list of hop hints that when chained together can assist in reaching a
+	//specific destination.
+	HopHints []*HopHint `protobuf:"bytes,1,rep,name=hop_hints,json=hopHints,proto3" json:"hop_hints,omitempty"`
+}
+
+func (x *RouteHint) Reset() {
+	*x = RouteHint{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_common_proto_msgTypes[1]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *RouteHint) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*RouteHint) ProtoMessage() {}
+
+func (x *RouteHint) ProtoReflect() protoreflect.Message {
+	mi := &file_common_proto_msgTypes[1]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use RouteHint.ProtoReflect.Descriptor instead.
+func (*RouteHint) Descriptor() ([]byte, []int) {
+	return file_common_proto_rawDescGZIP(), []int{1}
+}
+
+func (x *RouteHint) GetHopHints() []*HopHint {
+	if x != nil {
+		return x.HopHints
+	}
+	return nil
+}
+
+var File_common_proto protoreflect.FileDescriptor
+
+var file_common_proto_rawDesc = []byte{
+	0x0a, 0x0c, 0x63, 0x6f, 0x6d, 0x6d, 0x6f, 0x6e, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x12, 0x07,
+	0x6c, 0x6f, 0x6f, 0x70, 0x72, 0x70, 0x63, 0x22, 0xcb, 0x01, 0x0a, 0x07, 0x48, 0x6f, 0x70, 0x48,
+	0x69, 0x6e, 0x74, 0x12, 0x17, 0x0a, 0x07, 0x6e, 0x6f, 0x64, 0x65, 0x5f, 0x69, 0x64, 0x18, 0x01,
+	0x20, 0x01, 0x28, 0x09, 0x52, 0x06, 0x6e, 0x6f, 0x64, 0x65, 0x49, 0x64, 0x12, 0x17, 0x0a, 0x07,
+	0x63, 0x68, 0x61, 0x6e, 0x5f, 0x69, 0x64, 0x18, 0x02, 0x20, 0x01, 0x28, 0x04, 0x52, 0x06, 0x63,
+	0x68, 0x61, 0x6e, 0x49, 0x64, 0x12, 0x22, 0x0a, 0x0d, 0x66, 0x65, 0x65, 0x5f, 0x62, 0x61, 0x73,
+	0x65, 0x5f, 0x6d, 0x73, 0x61, 0x74, 0x18, 0x03, 0x20, 0x01, 0x28, 0x0d, 0x52, 0x0b, 0x66, 0x65,
+	0x65, 0x42, 0x61, 0x73, 0x65, 0x4d, 0x73, 0x61, 0x74, 0x12, 0x3e, 0x0a, 0x1b, 0x66, 0x65, 0x65,
+	0x5f, 0x70, 0x72, 0x6f, 0x70, 0x6f, 0x72, 0x74, 0x69, 0x6f, 0x6e, 0x61, 0x6c, 0x5f, 0x6d, 0x69,
+	0x6c, 0x6c, 0x69, 0x6f, 0x6e, 0x74, 0x68, 0x73, 0x18, 0x04, 0x20, 0x01, 0x28, 0x0d, 0x52, 0x19,
+	0x66, 0x65, 0x65, 0x50, 0x72, 0x6f, 0x70, 0x6f, 0x72, 0x74, 0x69, 0x6f, 0x6e, 0x61, 0x6c, 0x4d,
+	0x69, 0x6c, 0x6c, 0x69, 0x6f, 0x6e, 0x74, 0x68, 0x73, 0x12, 0x2a, 0x0a, 0x11, 0x63, 0x6c, 0x74,
+	0x76, 0x5f, 0x65, 0x78, 0x70, 0x69, 0x72, 0x79, 0x5f, 0x64, 0x65, 0x6c, 0x74, 0x61, 0x18, 0x05,
+	0x20, 0x01, 0x28, 0x0d, 0x52, 0x0f, 0x63, 0x6c, 0x74, 0x76, 0x45, 0x78, 0x70, 0x69, 0x72, 0x79,
+	0x44, 0x65, 0x6c, 0x74, 0x61, 0x22, 0x3a, 0x0a, 0x09, 0x52, 0x6f, 0x75, 0x74, 0x65, 0x48, 0x69,
+	0x6e, 0x74, 0x12, 0x2d, 0x0a, 0x09, 0x68, 0x6f, 0x70, 0x5f, 0x68, 0x69, 0x6e, 0x74, 0x73, 0x18,
+	0x01, 0x20, 0x03, 0x28, 0x0b, 0x32, 0x10, 0x2e, 0x6c, 0x6f, 0x6f, 0x70, 0x72, 0x70, 0x63, 0x2e,
+	0x48, 0x6f, 0x70, 0x48, 0x69, 0x6e, 0x74, 0x52, 0x08, 0x68, 0x6f, 0x70, 0x48, 0x69, 0x6e, 0x74,
+	0x73, 0x42, 0x27, 0x5a, 0x25, 0x67, 0x69, 0x74, 0x68, 0x75, 0x62, 0x2e, 0x63, 0x6f, 0x6d, 0x2f,
+	0x6c, 0x69, 0x67, 0x68, 0x74, 0x6e, 0x69, 0x6e, 0x67, 0x6c, 0x61, 0x62, 0x73, 0x2f, 0x6c, 0x6f,
+	0x6f, 0x70, 0x2f, 0x6c, 0x6f, 0x6f, 0x70, 0x72, 0x70, 0x63, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74,
+	0x6f, 0x33,
+}
+
+var (
+	file_common_proto_rawDescOnce sync.Once
+	file_common_proto_rawDescData = file_common_proto_rawDesc
+)
+
+func file_common_proto_rawDescGZIP() []byte {
+	file_common_proto_rawDescOnce.Do(func() {
+		file_common_proto_rawDescData = protoimpl.X.CompressGZIP(file_common_proto_rawDescData)
+	})
+	return file_common_proto_rawDescData
+}
+
+var file_common_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
+var file_common_proto_goTypes = []interface{}{
+	(*HopHint)(nil),   // 0: looprpc.HopHint
+	(*RouteHint)(nil), // 1: looprpc.RouteHint
+}
+var file_common_proto_depIdxs = []int32{
+	0, // 0: looprpc.RouteHint.hop_hints:type_name -> looprpc.HopHint
+	1, // [1:1] is the sub-list for method output_type
+	1, // [1:1] is the sub-list for method input_type
+	1, // [1:1] is the sub-list for extension type_name
+	1, // [1:1] is the sub-list for extension extendee
+	0, // [0:1] is the sub-list for field type_name
+}
+
+func init() { file_common_proto_init() }
+func file_common_proto_init() {
+	if File_common_proto != nil {
+		return
+	}
+	if !protoimpl.UnsafeEnabled {
+		file_common_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*HopHint); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_common_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*RouteHint); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: file_common_proto_rawDesc,
+			NumEnums:      0,
+			NumMessages:   2,
+			NumExtensions: 0,
+			NumServices:   0,
+		},
+		GoTypes:           file_common_proto_goTypes,
+		DependencyIndexes: file_common_proto_depIdxs,
+		MessageInfos:      file_common_proto_msgTypes,
+	}.Build()
+	File_common_proto = out.File
+	file_common_proto_rawDesc = nil
+	file_common_proto_goTypes = nil
+	file_common_proto_depIdxs = nil
+}

looprpc/common.proto

@@ -0,0 +1,33 @@
+syntax = "proto3";
+
+package looprpc;
+
+option go_package = "github.com/lightninglabs/loop/looprpc";
+
+message HopHint {
+    // The public key of the node at the start of the channel.
+    string node_id = 1;
+
+    // The unique identifier of the channel.
+    uint64 chan_id = 2;
+
+    // The base fee of the channel denominated in millisatoshis.
+    uint32 fee_base_msat = 3;
+
+    /*
+    The fee rate of the channel for sending one satoshi across it denominated in
+    millionths of a satoshi.
+    */
+    uint32 fee_proportional_millionths = 4;
+
+    // The time-lock delta of the channel.
+    uint32 cltv_expiry_delta = 5;
+}
+
+message RouteHint {
+    /*
+    A list of hop hints that when chained together can assist in reaching a
+    specific destination.
+    */
+    repeated HopHint hop_hints = 1;
+}

looprpc/server.proto

@@ -1,5 +1,7 @@
 syntax = "proto3";
 
+import "common.proto";
+
 package looprpc;
 
 option go_package = "github.com/lightninglabs/loop/looprpc";
@@ -29,6 +31,8 @@ service SwapServer {
 
     rpc CancelLoopOutSwap (CancelLoopOutSwapRequest)
         returns (CancelLoopOutSwapResponse);
+
+    rpc Probe (ServerProbeRequest) returns (ServerProbeResponse);
 }
 
 /**
@@ -70,6 +74,10 @@ enum ProtocolVersion {
 
     // The client supports loop out swap cancelation.
     LOOP_OUT_CANCEL = 7;
+
+    // The client is able to ask the server to probe to test inbound
+    // liquidity.
+    PROBE = 8;
 }
 
 message ServerLoopOutRequest {
@@ -201,6 +209,16 @@ message ServerLoopInQuoteRequest {
     /// The swap amount. If zero, a quote for a maximum amt swap will be given.
     uint64 amt = 1;
 
+    // The destination pubkey. Will be used to retrieve cached probed routing
+    // fee.
+    bytes pubkey = 3;
+
+    // The last hop to use. Will be used to retrieve cached probed routing fee.
+    bytes last_hop = 4;
+
+    // Optional route hints to reach the destination through private channels.
+    repeated RouteHint route_hints = 5;
+
     /// The protocol version that the client adheres to.
     ProtocolVersion protocol_version = 2;
 }
@@ -414,3 +432,25 @@ message CancelLoopOutSwapRequest {
 
 message CancelLoopOutSwapResponse {
 }
+
+message ServerProbeRequest {
+    /// The protocol version that the client adheres to.
+    ProtocolVersion protocol_version = 1;
+
+    // The probe amount.
+    uint64 amt = 2;
+
+    // The target node for the probe.
+    bytes target = 3;
+
+    // Optional last hop to use when probing the client.
+    bytes last_hop = 4;
+
+    /*
+    Optional route hints to reach the destination through private channels.
+    */
+    repeated RouteHint route_hints = 5;
+}
+
+message ServerProbeResponse {
+}

looprpc/server_grpc.pb.go

@@ -28,6 +28,7 @@ type SwapServerClient interface {
 	SubscribeLoopOutUpdates(ctx context.Context, in *SubscribeUpdatesRequest, opts ...grpc.CallOption) (SwapServer_SubscribeLoopOutUpdatesClient, error)
 	SubscribeLoopInUpdates(ctx context.Context, in *SubscribeUpdatesRequest, opts ...grpc.CallOption) (SwapServer_SubscribeLoopInUpdatesClient, error)
 	CancelLoopOutSwap(ctx context.Context, in *CancelLoopOutSwapRequest, opts ...grpc.CallOption) (*CancelLoopOutSwapResponse, error)
+	Probe(ctx context.Context, in *ServerProbeRequest, opts ...grpc.CallOption) (*ServerProbeResponse, error)
 }
 
 type swapServerClient struct {
@@ -174,6 +175,15 @@ func (c *swapServerClient) CancelLoopOutSwap(ctx context.Context, in *CancelLoop
 	return out, nil
 }
 
+func (c *swapServerClient) Probe(ctx context.Context, in *ServerProbeRequest, opts ...grpc.CallOption) (*ServerProbeResponse, error) {
+	out := new(ServerProbeResponse)
+	err := c.cc.Invoke(ctx, "/looprpc.SwapServer/Probe", in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // SwapServerServer is the server API for SwapServer service.
 // All implementations must embed UnimplementedSwapServerServer
 // for forward compatibility
@@ -188,6 +198,7 @@ type SwapServerServer interface {
 	SubscribeLoopOutUpdates(*SubscribeUpdatesRequest, SwapServer_SubscribeLoopOutUpdatesServer) error
 	SubscribeLoopInUpdates(*SubscribeUpdatesRequest, SwapServer_SubscribeLoopInUpdatesServer) error
 	CancelLoopOutSwap(context.Context, *CancelLoopOutSwapRequest) (*CancelLoopOutSwapResponse, error)
+	Probe(context.Context, *ServerProbeRequest) (*ServerProbeResponse, error)
 	mustEmbedUnimplementedSwapServerServer()
 }
 
@@ -225,6 +236,9 @@ func (UnimplementedSwapServerServer) SubscribeLoopInUpdates(*SubscribeUpdatesReq
 func (UnimplementedSwapServerServer) CancelLoopOutSwap(context.Context, *CancelLoopOutSwapRequest) (*CancelLoopOutSwapResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method CancelLoopOutSwap not implemented")
 }
+func (UnimplementedSwapServerServer) Probe(context.Context, *ServerProbeRequest) (*ServerProbeResponse, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method Probe not implemented")
+}
 func (UnimplementedSwapServerServer) mustEmbedUnimplementedSwapServerServer() {}
 
 // UnsafeSwapServerServer may be embedded to opt out of forward compatibility for this service.
@@ -424,6 +438,24 @@ func _SwapServer_CancelLoopOutSwap_Handler(srv interface{}, ctx context.Context,
 	return interceptor(ctx, in, info, handler)
 }
 
+func _SwapServer_Probe_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(ServerProbeRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SwapServerServer).Probe(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: "/looprpc.SwapServer/Probe",
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SwapServerServer).Probe(ctx, req.(*ServerProbeRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 // SwapServer_ServiceDesc is the grpc.ServiceDesc for SwapServer service.
 // It's only intended for direct use with grpc.RegisterService,
 // and not to be introspected or modified (even as a copy)
@@ -463,6 +495,10 @@ var SwapServer_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "CancelLoopOutSwap",
 			Handler:    _SwapServer_CancelLoopOutSwap_Handler,
 		},
+		{
+			MethodName: "Probe",
+			Handler:    _SwapServer_Probe_Handler,
+		},
 	},
 	Streams: []grpc.StreamDesc{
 		{

server_mock_test.go

@@ -212,8 +212,8 @@ func (s *serverMock) GetLoopInTerms(ctx context.Context) (
 	}, nil
 }
 
-func (s *serverMock) GetLoopInQuote(ctx context.Context, amt btcutil.Amount) (
-	*LoopInQuote, error) {
+func (s *serverMock) GetLoopInQuote(context.Context, btcutil.Amount,
+	route.Vertex, *route.Vertex) (*LoopInQuote, error) {
 
 	return &LoopInQuote{
 		SwapFee:   testSwapFee,
@@ -235,3 +235,10 @@ func (s *serverMock) SubscribeLoopInUpdates(_ context.Context,
 
 	return nil, nil, nil
 }
+
+func (s *serverMock) Probe(ctx context.Context, amt btcutil.Amount,
+	pubKey route.Vertex, lastHop *route.Vertex,
+	routeHints [][]zpay32.HopHint) error {
+
+	return nil
+}

swap_server_client.go

@@ -21,6 +21,7 @@ import (
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/lightningnetwork/lnd/tor"
+	"github.com/lightningnetwork/lnd/zpay32"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
 )
@@ -51,8 +52,11 @@ type swapServerClient interface {
 	GetLoopInTerms(ctx context.Context) (
 		*LoopInTerms, error)
 
-	GetLoopInQuote(ctx context.Context, amt btcutil.Amount) (
-		*LoopInQuote, error)
+	GetLoopInQuote(ctx context.Context, amt btcutil.Amount,
+		pubKey route.Vertex, lastHop *route.Vertex) (*LoopInQuote, error)
+
+	Probe(ctx context.Context, amt btcutil.Amount, target route.Vertex,
+		lastHop *route.Vertex, routeHints [][]zpay32.HopHint) error
 
 	NewLoopOutSwap(ctx context.Context,
 		swapHash lntypes.Hash, amount btcutil.Amount, expiry int32,
@@ -203,16 +207,23 @@ func (s *grpcSwapServerClient) GetLoopInTerms(ctx context.Context) (
 }
 
 func (s *grpcSwapServerClient) GetLoopInQuote(ctx context.Context,
-	amt btcutil.Amount) (*LoopInQuote, error) {
+	amt btcutil.Amount, pubKey route.Vertex, lastHop *route.Vertex) (
+	*LoopInQuote, error) {
 
 	rpcCtx, rpcCancel := context.WithTimeout(ctx, globalCallTimeout)
 	defer rpcCancel()
-	quoteResp, err := s.server.LoopInQuote(rpcCtx,
-		&looprpc.ServerLoopInQuoteRequest{
-			Amt:             uint64(amt),
-			ProtocolVersion: loopdb.CurrentRPCProtocolVersion,
-		},
-	)
+
+	req := &looprpc.ServerLoopInQuoteRequest{
+		Amt:             uint64(amt),
+		ProtocolVersion: loopdb.CurrentRPCProtocolVersion,
+		Pubkey:          pubKey[:],
+	}
+
+	if lastHop != nil {
+		req.LastHop = lastHop[:]
+	}
+
+	quoteResp, err := s.server.LoopInQuote(rpcCtx, req)
 	if err != nil {
 		return nil, err
 	}
@@ -223,6 +234,76 @@ func (s *grpcSwapServerClient) GetLoopInQuote(ctx context.Context,
 	}, nil
 }
 
+// marshallRouteHints marshalls a list of route hints.
+func marshallRouteHints(routeHints [][]zpay32.HopHint) (
+	[]*looprpc.RouteHint, error) {
+
+	rpcRouteHints := make([]*looprpc.RouteHint, 0, len(routeHints))
+	for _, routeHint := range routeHints {
+		rpcRouteHint := make(
+			[]*looprpc.HopHint, 0, len(routeHint),
+		)
+		for _, hint := range routeHint {
+			rpcHint, err := marshallHopHint(hint)
+			if err != nil {
+				return nil, err
+			}
+
+			rpcRouteHint = append(rpcRouteHint, rpcHint)
+		}
+		rpcRouteHints = append(rpcRouteHints, &looprpc.RouteHint{
+			HopHints: rpcRouteHint,
+		})
+	}
+
+	return rpcRouteHints, nil
+}
+
+// marshallHopHint marshalls a single hop hint.
+func marshallHopHint(hint zpay32.HopHint) (*looprpc.HopHint, error) {
+	nodeID, err := route.NewVertexFromBytes(
+		hint.NodeID.SerializeCompressed(),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return &looprpc.HopHint{
+		ChanId:                    hint.ChannelID,
+		CltvExpiryDelta:           uint32(hint.CLTVExpiryDelta),
+		FeeBaseMsat:               hint.FeeBaseMSat,
+		FeeProportionalMillionths: hint.FeeProportionalMillionths,
+		NodeId:                    nodeID.String(),
+	}, nil
+}
+
+func (s *grpcSwapServerClient) Probe(ctx context.Context, amt btcutil.Amount,
+	target route.Vertex, lastHop *route.Vertex,
+	routeHints [][]zpay32.HopHint) error {
+
+	rpcCtx, rpcCancel := context.WithTimeout(ctx, probeTimeout)
+	defer rpcCancel()
+
+	rpcRouteHints, err := marshallRouteHints(routeHints)
+	if err != nil {
+		return err
+	}
+
+	req := &looprpc.ServerProbeRequest{
+		Amt:             uint64(amt),
+		Target:          target[:],
+		ProtocolVersion: loopdb.CurrentRPCProtocolVersion,
+		RouteHints:      rpcRouteHints,
+	}
+
+	if lastHop != nil {
+		req.LastHop = lastHop[:]
+	}
+
+	_, err = s.server.Probe(rpcCtx, req)
+	return err
+}
+
 func (s *grpcSwapServerClient) NewLoopOutSwap(ctx context.Context,
 	swapHash lntypes.Hash, amount btcutil.Amount, expiry int32,
 	receiverKey [33]byte, swapPublicationDeadline time.Time,