tapchannel: assert proof courier connection

To make sure the universe proof courier address configured isn't only
formally valid but can also be connected to, we do a quick connection
check before requesting or accepting a channel funding action.

Author: guggero

tapchannel/aux_funding_controller.go

@@ -53,6 +53,11 @@ const (
 	// level ACK from the remote party before timing out.
 	ackTimeout = time.Second * 30
 
+	// proofCourierCheckTimeout is the amount of time we'll wait before we
+	// time out an attempt to connect to a proof courier when checking the
+	// configured address.
+	proofCourierCheckTimeout = time.Second * 5
+
 	// maxNumAssetIDs is the maximum number of fungible asset pieces (asset
 	// IDs) that can be committed to a single channel. The number needs to
 	// be limited to prevent the number of required HTLC signatures to be
@@ -1373,7 +1378,7 @@ func (f *FundingController) processFundingMsg(ctx context.Context,
 	// We can only support asset channels if we have the correct proof
 	// courier type configured, so we're ready to receive the channel funds
 	// once the channel is (force) closed.
-	if err := f.validateLocalProofCourier(); err != nil {
+	if err := f.validateLocalProofCourier(ctx); err != nil {
 		return tempPID, fmt.Errorf("unable to accept channel funding "+
 			"request, local proof courier is invalid: %w", err)
 	}
@@ -1542,7 +1547,7 @@ func (f *FundingController) processFundingReq(fundingFlows fundingFlowIndex,
 
 	// We need to make sure we're ready to receive the channel funds once
 	// the channel is (force) closed.
-	if err := f.validateLocalProofCourier(); err != nil {
+	if err := f.validateLocalProofCourier(fundReq.ctx); err != nil {
 		return fmt.Errorf("unable to fund channel, local proof "+
 			"courier is invalid: %w", err)
 	}
@@ -2070,7 +2075,9 @@ func (f *FundingController) validateWitness(outAsset asset.Asset,
 // universe based proof courier configured. A hashmail based courier can't deal
 // with the OP_TRUE funding output script key, as that's the same for asset
 // channels out there. So the single mailbox would always be occupied.
-func (f *FundingController) validateLocalProofCourier() error {
+func (f *FundingController) validateLocalProofCourier(
+	ctx context.Context) error {
+
 	courierURL := f.cfg.DefaultCourierAddr
 
 	flagHelp := "please set a universe based (universerpc://) proof " +
@@ -2090,7 +2097,9 @@ func (f *FundingController) validateLocalProofCourier() error {
 			courierURL.Scheme, flagHelp)
 	}
 
-	return nil
+	return proof.CheckUniverseRpcCourierConnection(
+		ctx, proofCourierCheckTimeout, courierURL,
+	)
 }
 
 // FundReq is a message that's sent to the funding controller to request a new

tapchannel/aux_funding_controller_test.go

@@ -1,16 +1,35 @@
 package tapchannel
 
 import (
+	"context"
 	"net/url"
 	"testing"
 
+	"github.com/lightninglabs/taproot-assets/internal/test"
 	"github.com/lightninglabs/taproot-assets/proof"
+	"github.com/lightninglabs/taproot-assets/taprpc/universerpc"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
 )
 
 // TestValidateLocalProofCourier tests that the local proof courier is
 // validated correctly.
 func TestValidateLocalProofCourier(t *testing.T) {
+	serverOpts := []grpc.ServerOption{
+		grpc.Creds(insecure.NewCredentials()),
+	}
+	grpcServer := grpc.NewServer(serverOpts...)
+
+	server := proof.MockUniverseServer{}
+	universerpc.RegisterUniverseServer(grpcServer, &server)
+
+	mockServerAddr, cleanup, err := test.StartMockGRPCServer(
+		t, grpcServer, true,
+	)
+	require.NoError(t, err)
+	t.Cleanup(cleanup)
+
 	tests := []struct {
 		name        string
 		courierAddr *url.URL
@@ -19,13 +38,13 @@ func TestValidateLocalProofCourier(t *testing.T) {
 		{
 			name: "valid universe rpc courier",
 			courierAddr: proof.MockCourierURL(
-				t, proof.UniverseRpcCourierType, ":1234",
+				t, proof.UniverseRpcCourierType, mockServerAddr,
 			),
 		},
 		{
 			name: "invalid courier type",
 			courierAddr: proof.MockCourierURL(
-				t, proof.HashmailCourierType, ":1234",
+				t, proof.HashmailCourierType, mockServerAddr,
 			),
 			expectErr: "unsupported proof courier type " +
 				"'hashmail'",
@@ -49,7 +68,16 @@ func TestValidateLocalProofCourier(t *testing.T) {
 				},
 			}
 
-			err := fc.validateLocalProofCourier()
+			// We use a short timeout here, since we don't want to
+			// wait for the full default timeout of the funding
+			// controller
+			ctxb := context.Background()
+			ctxb, cancel := context.WithTimeout(
+				ctxb, test.StartupWaitTime*2,
+			)
+			defer cancel()
+
+			err := fc.validateLocalProofCourier(ctxb)
 			if tt.expectErr != "" {
 				require.ErrorContains(t, err, tt.expectErr)