cmd/loop: add session gRPC transport hook

cmd/loop/debug.go

@@ -43,12 +43,7 @@ func forceAutoloop(ctx context.Context, cmd *cli.Command) error {
 }
 
 func getDebugClient(ctx context.Context, cmd *cli.Command) (looprpc.DebugClient, func(), error) {
-	rpcServer := cmd.String("rpcserver")
-	tlsCertPath, macaroonPath, err := extractPathArgs(cmd)
-	if err != nil {
-		return nil, nil, err
-	}
-	conn, cleanup, err := getClientConn(rpcServer, tlsCertPath, macaroonPath)
+	conn, cleanup, err := sessionTransport.Dial(cmd)
 	if err != nil {
 		return nil, nil, err
 	}

cmd/loop/main.go

@@ -252,14 +252,9 @@ func getClient(cmd *cli.Command) (looprpc.SwapClientClient,
 // getClientWithConn returns both the SwapClient RPC client and the underlying
 // gRPC connection so callers can perform connection-aware actions.
 func getClientWithConn(cmd *cli.Command) (looprpc.SwapClientClient,
-	*grpc.ClientConn, func(), error) {
+	daemonConn, func(), error) {
 
-	rpcServer := cmd.String("rpcserver")
-	tlsCertPath, macaroonPath, err := extractPathArgs(cmd)
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	conn, cleanup, err := getClientConn(rpcServer, tlsCertPath, macaroonPath)
+	conn, cleanup, err := sessionTransport.Dial(cmd)
 	if err != nil {
 		return nil, nil, nil, err
 	}
@@ -481,7 +476,8 @@ func logSwap(swap *looprpc.SwapStatus) {
 	fmt.Println()
 }
 
-func getClientConn(address, tlsCertPath, macaroonPath string) (*grpc.ClientConn,
+// getClientConn dials the loopd gRPC server with TLS and macaroon auth.
+func getClientConn(address, tlsCertPath, macaroonPath string) (daemonConn,
 	func(), error) {
 
 	// We always need to send a macaroon.
@@ -495,6 +491,14 @@ func getClientConn(address, tlsCertPath, macaroonPath string) (*grpc.ClientConn,
 		macOption,
 	}
 
+	// Install gRPC interceptors for session recording if needed.
+	if unary := sessionTransport.UnaryInterceptor(); unary != nil {
+		opts = append(opts, grpc.WithChainUnaryInterceptor(unary))
+	}
+	if stream := sessionTransport.StreamInterceptor(); stream != nil {
+		opts = append(opts, grpc.WithChainStreamInterceptor(stream))
+	}
+
 	// Since TLS cannot be disabled, we'll always have a cert file to read.
 	creds, err := credentials.NewClientTLSFromFile(tlsCertPath, "")
 	if err != nil {

cmd/loop/session_transport.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"context"
+
+	"github.com/urfave/cli/v3"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/connectivity"
+)
+
+// grpcTransport customizes gRPC dialing and interceptors for sessions.
+type grpcTransport interface {
+	// Dial returns a gRPC connection for the CLI.
+	Dial(cmd *cli.Command) (daemonConn, func(), error)
+
+	// UnaryInterceptor returns the unary interceptor to apply for session
+	// flows.
+	UnaryInterceptor() grpc.UnaryClientInterceptor
+
+	// StreamInterceptor returns the stream interceptor to apply for session
+	// flows.
+	StreamInterceptor() grpc.StreamClientInterceptor
+}
+
+// daemonConn is the client connection interface required by stop/wait flows.
+type daemonConn interface {
+	grpc.ClientConnInterface
+
+	// GetState reports the current connectivity state of the client
+	// channel.
+	GetState() connectivity.State
+
+	// WaitForStateChange blocks until the state changes or the context
+	// expires.
+	WaitForStateChange(ctx context.Context,
+		sourceState connectivity.State) bool
+
+	// Connect forces the channel out of idle mode.
+	Connect()
+}
+
+// directGrpcTransport establishes real gRPC connections to loopd.
+type directGrpcTransport struct{}
+
+// Dial opens a direct gRPC connection.
+func (t *directGrpcTransport) Dial(
+	cmd *cli.Command) (daemonConn, func(), error) {
+
+	return dialDirectConn(cmd)
+}
+
+// UnaryInterceptor returns nil because direct connections do not need wrapping.
+func (t *directGrpcTransport) UnaryInterceptor() grpc.UnaryClientInterceptor {
+	return nil
+}
+
+// StreamInterceptor returns nil because direct connections do not need
+// wrapping.
+func (t *directGrpcTransport) StreamInterceptor() grpc.StreamClientInterceptor {
+	return nil
+}
+
+// sessionTransport defines the active gRPC transport for CLI commands.
+var sessionTransport grpcTransport = &directGrpcTransport{}
+
+// hookGrpc installs the active gRPC session transport hook.
+func hookGrpc(transport grpcTransport) func() {
+	prev := sessionTransport
+	sessionTransport = transport
+
+	return func() { sessionTransport = prev }
+}
+
+// dialDirectConn returns the standard CLI gRPC connection.
+func dialDirectConn(cmd *cli.Command) (daemonConn, func(), error) {
+	rpcServer := cmd.String("rpcserver")
+	tlsCertPath, macaroonPath, err := extractPathArgs(cmd)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return getClientConn(rpcServer, tlsCertPath, macaroonPath)
+}

cmd/loop/stop.go

@@ -6,7 +6,6 @@ import (
 
 	"github.com/lightninglabs/loop/looprpc"
 	"github.com/urfave/cli/v3"
-	"google.golang.org/grpc"
 	"google.golang.org/grpc/connectivity"
 )
 
@@ -63,7 +62,7 @@ func stopDaemon(ctx context.Context, cmd *cli.Command) error {
 // waitForDaemonShutdown monitors the gRPC connectivity state until the daemon
 // disappears. To avoid getting stuck in idle mode we nudge the connection to
 // reconnect when needed.
-func waitForDaemonShutdown(ctx context.Context, conn *grpc.ClientConn) error {
+func waitForDaemonShutdown(ctx context.Context, conn daemonConn) error {
 	for {
 		state := conn.GetState()