regtest: add source-built Loop server

cmd/loopserver-regtest/main.go

@@ -0,0 +1,203 @@
+// loopserver-regtest is a disposable, source-available Loop server that moves
+// real regtest Bitcoin and pays real regtest Lightning invoices. It must never
+// be used on testnet, signet or mainnet.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/btcsuite/btcd/btcutil"
+	"github.com/btcsuite/btcd/rpcclient"
+	"github.com/lightninglabs/lndclient"
+	regtestserver "github.com/lightninglabs/loop/regtest/server"
+	"github.com/lightninglabs/loop/swapserverrpc"
+	"github.com/lightningnetwork/lnd/lnrpc/verrpc"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/health"
+	"google.golang.org/grpc/health/grpc_health_v1"
+)
+
+type config struct {
+	listen      string
+	tlsCertPath string
+	tlsKeyPath  string
+
+	lndHost         string
+	lndMacaroonPath string
+	lndTLSPath      string
+
+	bitcoinHost     string
+	bitcoinUser     string
+	bitcoinPassword string
+
+	minAmount int64
+	maxAmount int64
+	timeout   time.Duration
+}
+
+func parseConfig() config {
+	var cfg config
+
+	flag.StringVar(&cfg.listen, "listen", "0.0.0.0:11009",
+		"address for the regtest-only gRPC server")
+	flag.StringVar(&cfg.tlsCertPath, "tls.certpath", "",
+		"optional path to the server TLS certificate")
+	flag.StringVar(&cfg.tlsKeyPath, "tls.keypath", "",
+		"optional path to the server TLS private key")
+	flag.StringVar(&cfg.lndHost, "lnd.host", "localhost:10009",
+		"server-side lnd RPC address")
+	flag.StringVar(&cfg.lndMacaroonPath, "lnd.macaroonpath", "",
+		"path to the server-side lnd admin macaroon")
+	flag.StringVar(&cfg.lndTLSPath, "lnd.tlspath", "",
+		"path to the server-side lnd TLS certificate")
+	flag.StringVar(&cfg.bitcoinHost, "bitcoin.host", "localhost:18443",
+		"Bitcoin Core RPC address")
+	flag.StringVar(&cfg.bitcoinUser, "bitcoin.user", "lightning",
+		"Bitcoin Core RPC user")
+	flag.StringVar(&cfg.bitcoinPassword, "bitcoin.password", "lightning",
+		"Bitcoin Core RPC password")
+	flag.Int64Var(&cfg.minAmount, "minamt", 50_000,
+		"minimum swap amount in satoshis")
+	flag.Int64Var(&cfg.maxAmount, "maxamt", 5_000_000,
+		"maximum swap amount in satoshis")
+	flag.DurationVar(&cfg.timeout, "paymenttimeout", time.Minute,
+		"maximum time for a regtest Lightning payment")
+	flag.Parse()
+
+	return cfg
+}
+
+func run(ctx context.Context, cfg config) error {
+	// These are the oldest APIs needed by the regtest server: MuSig2 signer,
+	// wallet kit, chain notifier, router and invoices. Keeping the explicit
+	// floor also allows the repository's v0.18.5 regtest image to be used.
+	minLndVersion := &verrpc.Version{
+		AppMajor: 0,
+		AppMinor: 18,
+		AppPatch: 4,
+		BuildTags: []string{
+			"signrpc", "walletrpc", "chainrpc", "invoicesrpc",
+		},
+	}
+
+	lnd, err := lndclient.NewLndServices(&lndclient.LndServicesConfig{
+		LndAddress:         cfg.lndHost,
+		Network:            lndclient.NetworkRegtest,
+		CustomMacaroonPath: cfg.lndMacaroonPath,
+		TLSPath:            cfg.lndTLSPath,
+		CheckVersion:       minLndVersion,
+		CallerCtx:          ctx,
+		RPCTimeout:         30 * time.Second,
+
+		BlockUntilChainSynced:   true,
+		BlockUntilUnlocked:      true,
+		BlockUntilChainNotifier: true,
+	})
+	if err != nil {
+		return fmt.Errorf("connect to lnd: %w", err)
+	}
+	defer lnd.Close()
+
+	bitcoin, err := rpcclient.New(&rpcclient.ConnConfig{
+		Host:         cfg.bitcoinHost,
+		User:         cfg.bitcoinUser,
+		Pass:         cfg.bitcoinPassword,
+		Params:       "regtest",
+		DisableTLS:   true,
+		HTTPPostMode: true,
+	}, nil)
+	if err != nil {
+		return fmt.Errorf("connect to bitcoind: %w", err)
+	}
+	defer bitcoin.Shutdown()
+
+	chainInfo, err := bitcoin.GetBlockChainInfo()
+	if err != nil {
+		return fmt.Errorf("query bitcoind: %w", err)
+	}
+	if chainInfo.Chain != "regtest" {
+		return fmt.Errorf("refusing Bitcoin network %q", chainInfo.Chain)
+	}
+
+	serverCfg := regtestserver.Config{
+		Lnd:            &lnd.LndServices,
+		Bitcoin:        bitcoin,
+		MinSwapAmount:  btcutil.Amount(cfg.minAmount),
+		MaxSwapAmount:  btcutil.Amount(cfg.maxAmount),
+		PaymentTimeout: cfg.timeout,
+	}
+	loopServer, err := regtestserver.New(ctx, serverCfg)
+	if err != nil {
+		return err
+	}
+	defer loopServer.Stop()
+
+	listener, err := net.Listen("tcp", cfg.listen)
+	if err != nil {
+		return fmt.Errorf("listen on %s: %w", cfg.listen, err)
+	}
+
+	var serverOpts []grpc.ServerOption
+	switch {
+	case cfg.tlsCertPath == "" && cfg.tlsKeyPath == "":
+
+	case cfg.tlsCertPath == "" || cfg.tlsKeyPath == "":
+		return fmt.Errorf("both TLS certificate and key paths are required")
+
+	default:
+		creds, err := credentials.NewServerTLSFromFile(
+			cfg.tlsCertPath, cfg.tlsKeyPath,
+		)
+		if err != nil {
+			return fmt.Errorf("load server TLS credentials: %w", err)
+		}
+
+		serverOpts = append(serverOpts, grpc.Creds(creds))
+	}
+
+	grpcServer := grpc.NewServer(serverOpts...)
+	swapserverrpc.RegisterSwapServerServer(grpcServer, loopServer)
+	swapserverrpc.RegisterStaticAddressServerServer(grpcServer, loopServer)
+
+	healthServer := health.NewServer()
+	healthServer.SetServingStatus("", grpc_health_v1.HealthCheckResponse_SERVING)
+	grpc_health_v1.RegisterHealthServer(grpcServer, healthServer)
+
+	errChan := make(chan error, 1)
+	go func() {
+		errChan <- grpcServer.Serve(listener)
+	}()
+
+	log.Printf("regtest Loop server listening on %s", cfg.listen)
+	select {
+	case err := <-errChan:
+		return err
+
+	case <-ctx.Done():
+		healthServer.Shutdown()
+		grpcServer.GracefulStop()
+		return nil
+	}
+}
+
+func main() {
+	cfg := parseConfig()
+	ctx, cancel := signal.NotifyContext(
+		context.Background(), os.Interrupt, syscall.SIGTERM,
+	)
+
+	err := run(ctx, cfg)
+	cancel()
+	if err != nil {
+		log.Fatalf("loopserver-regtest: %v", err)
+	}
+}

docs/release-notes/release-notes-next.md

@@ -2,6 +2,10 @@
 
 #### New Features
 
+* Added a source-built, regtest-only Loop server and Docker environment that
+  completes real Loop Out, standard Loop In, and static-address deposit Loop In
+  swaps without the proprietary server image.
+
 #### Breaking Changes
 
 #### Bug Fixes

regtest/Dockerfile

@@ -0,0 +1,19 @@
+FROM --platform=${BUILDPLATFORM} golang:1.26-alpine AS builder
+
+ARG TARGETOS
+ARG TARGETARCH
+
+RUN apk add --no-cache alpine-sdk git
+
+WORKDIR /src
+COPY . .
+RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -trimpath \
+    -o /bin/loopserver-regtest ./cmd/loopserver-regtest
+
+FROM --platform=${TARGETPLATFORM} alpine:3.22
+
+RUN apk add --no-cache ca-certificates
+COPY --from=builder /bin/loopserver-regtest /bin/loopserver-regtest
+
+EXPOSE 11009
+ENTRYPOINT ["/bin/loopserver-regtest"]