op-program: Add server mode

op-e2e/system_fpp_test.go

@@ -108,7 +108,7 @@ func testVerifyL2OutputRoot(t *testing.T, detached bool) {
 
 	// Check the FPP confirms the expected output
 	t.Log("Running fault proof in fetching mode")
-	err = opp.FaultProofProgram(log, fppConfig)
+	err = opp.FaultProofProgram(ctx, log, fppConfig)
 	require.NoError(t, err)
 
 	t.Log("Shutting down network")
@@ -124,13 +124,13 @@ func testVerifyL2OutputRoot(t *testing.T, detached bool) {
 	// Should be able to rerun in offline mode using the pre-fetched images
 	fppConfig.L1URL = ""
 	fppConfig.L2URL = ""
-	err = opp.FaultProofProgram(log, fppConfig)
+	err = opp.FaultProofProgram(ctx, log, fppConfig)
 	require.NoError(t, err)
 
 	// Check that a fault is detected if we provide an incorrect claim
 	t.Log("Running fault proof with invalid claim")
 	fppConfig.L2Claim = common.Hash{0xaa}
-	err = opp.FaultProofProgram(log, fppConfig)
+	err = opp.FaultProofProgram(ctx, log, fppConfig)
 	if detached {
 		require.Error(t, err, "exit status 1")
 	} else {

op-program/host/cmd/main.go

 package main
 
 import (
-	"errors"
 	"fmt"
 	"os"
 
-	"github.com/ethereum-optimism/optimism/op-program/client/driver"
 	"github.com/ethereum-optimism/optimism/op-program/host"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
 	"github.com/ethereum-optimism/optimism/op-program/host/flags"
@@ -37,12 +35,8 @@ var VersionWithMeta = func() string {
 
 func main() {
 	args := os.Args
-	if err := run(args, host.FaultProofProgram); errors.Is(err, driver.ErrClaimNotValid) {
-		log.Crit("Claim is invalid", "err", err)
-	} else if err != nil {
+	if err := run(args, host.Main); err != nil {
 		log.Crit("Application failed", "err", err)
-	} else {
-		log.Info("Claim successfully verified")
 	}
 }
 

op-program/host/cmd/main_test.go

@@ -232,6 +232,28 @@ func TestExec(t *testing.T) {
 	})
 }
 
+func TestServerMode(t *testing.T) {
+	t.Run("DefaultFalse", func(t *testing.T) {
+		cfg := configForArgs(t, addRequiredArgs())
+		require.False(t, cfg.ServerMode)
+	})
+	t.Run("Enabled", func(t *testing.T) {
+		cfg := configForArgs(t, addRequiredArgs("--server"))
+		require.True(t, cfg.ServerMode)
+	})
+	t.Run("EnabledWithArg", func(t *testing.T) {
+		cfg := configForArgs(t, addRequiredArgs("--server=true"))
+		require.True(t, cfg.ServerMode)
+	})
+	t.Run("DisabledWithArg", func(t *testing.T) {
+		cfg := configForArgs(t, addRequiredArgs("--server=false"))
+		require.False(t, cfg.ServerMode)
+	})
+	t.Run("InvalidArg", func(t *testing.T) {
+		verifyArgsInvalid(t, "invalid boolean value \"foo\" for -server", addRequiredArgs("--server=foo"))
+	})
+}
+
 func verifyArgsInvalid(t *testing.T, messageContains string, cliArgs []string) {
 	_, _, err := runWithArgs(cliArgs)
 	require.ErrorContains(t, err, messageContains)

op-program/host/config/config.go

@@ -25,6 +25,7 @@ var (
 	ErrInvalidL2Claim      = errors.New("invalid l2 claim")
 	ErrInvalidL2ClaimBlock = errors.New("invalid l2 claim block number")
 	ErrDataDirRequired     = errors.New("datadir must be specified when in non-fetching mode")
+	ErrNoExecInServerMode  = errors.New("exec command must not be set when in server mode")
 )
 
 type Config struct {
@@ -52,6 +53,10 @@ type Config struct {
 	// ExecCmd specifies the client program to execute in a separate process.
 	// If unset, the fault proof client is run in the same process.
 	ExecCmd string
+
+	// ServerMode indicates that the program should run in pre-image server mode and wait for requests.
+	// No client program is run.
+	ServerMode bool
 }
 
 func (c *Config) Check() error {
@@ -82,6 +87,9 @@ func (c *Config) Check() error {
 	if !c.FetchingEnabled() && c.DataDir == "" {
 		return ErrDataDirRequired
 	}
+	if c.ServerMode && c.ExecCmd != "" {
+		return ErrNoExecInServerMode
+	}
 	return nil
 }
 
@@ -149,7 +157,8 @@ func NewConfigFromCLI(ctx *cli.Context) (*Config, error) {
 		L1URL:              ctx.GlobalString(flags.L1NodeAddr.Name),
 		L1TrustRPC:         ctx.GlobalBool(flags.L1TrustRPC.Name),
 		L1RPCKind:          sources.RPCProviderKind(ctx.GlobalString(flags.L1RPCProviderKind.Name)),
-		ExecCmd:            ctx.String(flags.Exec.Name),
+		ExecCmd:            ctx.GlobalString(flags.Exec.Name),
+		ServerMode:         ctx.GlobalBool(flags.Server.Name),
 	}, nil
 }
 

op-program/host/config/config_test.go

@@ -142,6 +142,14 @@ func TestRequireDataDirInNonFetchingMode(t *testing.T) {
 	require.ErrorIs(t, err, ErrDataDirRequired)
 }
 
+func TestRejectExecAndServerMode(t *testing.T) {
+	cfg := validConfig()
+	cfg.ServerMode = true
+	cfg.ExecCmd = "echo"
+	err := cfg.Check()
+	require.ErrorIs(t, err, ErrNoExecInServerMode)
+}
+
 func validConfig() *Config {
 	cfg := NewConfig(validRollupConfig, validL2Genesis, validL1Head, validL2Head, validL2Claim, validL2ClaimBlockNum)
 	cfg.DataDir = "/tmp/configTest"

op-program/host/flags/flags.go

@@ -86,6 +86,11 @@ var (
 		Usage:  "Run the specified client program as a separate process detached from the host. Default is to run the client program in the host process.",
 		EnvVar: service.PrefixEnvVar(envVarPrefix, "EXEC"),
 	}
+	Server = cli.BoolFlag{
+		Name:   "server",
+		Usage:  "Run in pre-image server mode without executing any client program.",
+		EnvVar: service.PrefixEnvVar(envVarPrefix, "SERVER"),
+	}
 )
 
 // Flags contains the list of configuration options available to the binary.
@@ -107,6 +112,7 @@ var programFlags = []cli.Flag{
 	L1TrustRPC,
 	L1RPCProviderKind,
 	Exec,
+	Server,
 }
 
 func init() {

op-program/host/host.go

@@ -13,6 +13,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-node/client"
 	"github.com/ethereum-optimism/optimism/op-node/sources"
 	cl "github.com/ethereum-optimism/optimism/op-program/client"
+	"github.com/ethereum-optimism/optimism/op-program/client/driver"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
 	"github.com/ethereum-optimism/optimism/op-program/host/kvstore"
 	"github.com/ethereum-optimism/optimism/op-program/host/prefetcher"
@@ -27,56 +28,36 @@ type L2Source struct {
 	*sources.DebugClient
 }
 
-// FaultProofProgram is the programmatic entry-point for the fault proof program
-func FaultProofProgram(logger log.Logger, cfg *config.Config) error {
+func Main(logger log.Logger, cfg *config.Config) error {
 	if err := cfg.Check(); err != nil {
 		return fmt.Errorf("invalid config: %w", err)
 	}
 	cfg.Rollup.LogDescription(logger, chaincfg.L2ChainIDToNetworkName)
 
 	ctx := context.Background()
-	var kv kvstore.KV
-	if cfg.DataDir == "" {
-		logger.Info("Using in-memory storage")
-		kv = kvstore.NewMemKV()
-	} else {
-		logger.Info("Creating disk storage", "datadir", cfg.DataDir)
-		if err := os.MkdirAll(cfg.DataDir, 0755); err != nil {
-			return fmt.Errorf("creating datadir: %w", err)
-		}
-		kv = kvstore.NewDiskKV(cfg.DataDir)
+	if cfg.ServerMode {
+		preimageChan := cl.CreatePreimageChannel()
+		hinterChan := cl.CreateHinterChannel()
+		return PreimageServer(ctx, logger, cfg, preimageChan, hinterChan)
 	}
 
-	var (
-		getPreimage func(key common.Hash) ([]byte, error)
-		hinter      func(hint string) error
-	)
-	if cfg.FetchingEnabled() {
-		prefetch, err := makePrefetcher(ctx, logger, kv, cfg)
-		if err != nil {
-			return fmt.Errorf("failed to create prefetcher: %w", err)
-		}
-		getPreimage = func(key common.Hash) ([]byte, error) { return prefetch.GetPreimage(ctx, key) }
-		hinter = prefetch.Hint
+	if err := FaultProofProgram(ctx, logger, cfg); errors.Is(err, driver.ErrClaimNotValid) {
+		log.Crit("Claim is invalid", "err", err)
+	} else if err != nil {
+		return err
 	} else {
-		logger.Info("Using offline mode. All required pre-images must be pre-populated.")
-		getPreimage = kv.Get
-		hinter = func(hint string) error {
-			logger.Debug("ignoring prefetch hint", "hint", hint)
-			return nil
-		}
+		log.Info("Claim successfully verified")
 	}
+	return nil
+}
 
-	localPreimageSource := kvstore.NewLocalPreimageSource(cfg)
-	splitter := kvstore.NewPreimageSourceSplitter(localPreimageSource.Get, getPreimage)
-
+// FaultProofProgram is the programmatic entry-point for the fault proof program
+func FaultProofProgram(ctx context.Context, logger log.Logger, cfg *config.Config) error {
 	// Setup client I/O for preimage oracle interaction
 	pClientRW, pHostRW, err := oppio.CreateBidirectionalChannel()
 	if err != nil {
 		return fmt.Errorf("failed to create preimage pipe: %w", err)
 	}
-	oracleServer := preimage.NewOracleServer(pHostRW)
-	launchOracleServer(logger, oracleServer, splitter.Get)
 	defer pHostRW.Close()
 
 	// Setup client I/O for hint comms
@@ -84,9 +65,15 @@ func FaultProofProgram(logger log.Logger, cfg *config.Config) error {
 	if err != nil {
 		return fmt.Errorf("failed to create hints pipe: %w", err)
 	}
-	defer hHostRW.Close()
-	hHost := preimage.NewHintReader(hHostRW)
-	routeHints(logger, hHost, hinter)
+
+	go func() {
+		defer hHostRW.Close()
+		err := PreimageServer(ctx, logger, cfg, pHostRW, hHostRW)
+		if err != nil {
+			logger.Error("preimage server failed", "err", err)
+		}
+		logger.Debug("Preimage server stopped")
+	}()
 
 	var cmd *exec.Cmd
 	if cfg.ExecCmd != "" {
@@ -106,12 +93,61 @@ func FaultProofProgram(logger log.Logger, cfg *config.Config) error {
 		if err := cmd.Wait(); err != nil {
 			return fmt.Errorf("failed to wait for child program: %w", err)
 		}
+		logger.Debug("Client program completed successfully")
 		return nil
 	} else {
 		return cl.RunProgram(logger, pClientRW, hClientRW)
 	}
 }
 
+func PreimageServer(ctx context.Context, logger log.Logger, cfg *config.Config, preimageChannel oppio.FileChannel, hintChannel oppio.FileChannel) error {
+	logger.Info("Starting preimage server")
+	var kv kvstore.KV
+	if cfg.DataDir == "" {
+		logger.Info("Using in-memory storage")
+		kv = kvstore.NewMemKV()
+	} else {
+		logger.Info("Creating disk storage", "datadir", cfg.DataDir)
+		if err := os.MkdirAll(cfg.DataDir, 0755); err != nil {
+			return fmt.Errorf("creating datadir: %w", err)
+		}
+		kv = kvstore.NewDiskKV(cfg.DataDir)
+	}
+
+	var (
+		getPreimage kvstore.PreimageSource
+		hinter      preimage.HintHandler
+	)
+	if cfg.FetchingEnabled() {
+		prefetch, err := makePrefetcher(ctx, logger, kv, cfg)
+		if err != nil {
+			return fmt.Errorf("failed to create prefetcher: %w", err)
+		}
+		getPreimage = func(key common.Hash) ([]byte, error) { return prefetch.GetPreimage(ctx, key) }
+		hinter = prefetch.Hint
+	} else {
+		logger.Info("Using offline mode. All required pre-images must be pre-populated.")
+		getPreimage = kv.Get
+		hinter = func(hint string) error {
+			logger.Debug("ignoring prefetch hint", "hint", hint)
+			return nil
+		}
+	}
+
+	localPreimageSource := kvstore.NewLocalPreimageSource(cfg)
+	splitter := kvstore.NewPreimageSourceSplitter(localPreimageSource.Get, getPreimage)
+	preimageGetter := splitter.Get
+
+	serverDone := launchOracleServer(logger, preimageChannel, preimageGetter)
+	hinterDone := routeHints(logger, hintChannel, hinter)
+	select {
+	case err := <-serverDone:
+		return err
+	case err := <-hinterDone:
+		return err
+	}
+}
+
 func makePrefetcher(ctx context.Context, logger log.Logger, kv kvstore.KV, cfg *config.Config) (*prefetcher.Prefetcher, error) {
 	logger.Info("Connecting to L1 node", "l1", cfg.L1URL)
 	l1RPC, err := client.NewRPC(ctx, logger, cfg.L1URL)
@@ -139,8 +175,11 @@ func makePrefetcher(ctx context.Context, logger log.Logger, kv kvstore.KV, cfg *
 	return prefetcher.NewPrefetcher(logger, l1Cl, l2DebugCl, kv), nil
 }
 
-func routeHints(logger log.Logger, hintReader *preimage.HintReader, hinter func(hint string) error) {
+func routeHints(logger log.Logger, hHostRW io.ReadWriter, hinter preimage.HintHandler) chan error {
+	chErr := make(chan error)
+	hintReader := preimage.NewHintReader(hHostRW)
 	go func() {
+		defer close(chErr)
 		for {
 			if err := hintReader.NextHint(hinter); err != nil {
 				if err == io.EOF || errors.Is(err, fs.ErrClosed) {
@@ -148,14 +187,19 @@ func routeHints(logger log.Logger, hintReader *preimage.HintReader, hinter func(
 					return
 				}
 				logger.Error("pre-image hint router error", "err", err)
+				chErr <- err
 				return
 			}
 		}
 	}()
+	return chErr
 }
 
-func launchOracleServer(logger log.Logger, server *preimage.OracleServer, getter func(key common.Hash) ([]byte, error)) {
+func launchOracleServer(logger log.Logger, pHostRW io.ReadWriteCloser, getter preimage.PreimageGetter) chan error {
+	chErr := make(chan error)
+	server := preimage.NewOracleServer(pHostRW)
 	go func() {
+		defer close(chErr)
 		for {
 			if err := server.NextPreimageRequest(getter); err != nil {
 				if err == io.EOF || errors.Is(err, fs.ErrClosed) {
@@ -163,8 +207,10 @@ func launchOracleServer(logger log.Logger, server *preimage.OracleServer, getter
 					return
 				}
 				logger.Error("pre-image server error", "error", err)
+				chErr <- err
 				return
 			}
 		}
 	}()
+	return chErr
 }

op-program/host/host_test.go

+package host
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/ethereum-optimism/optimism/op-node/chaincfg"
+	"github.com/ethereum-optimism/optimism/op-node/testlog"
+	"github.com/ethereum-optimism/optimism/op-program/client"
+	"github.com/ethereum-optimism/optimism/op-program/client/l1"
+	"github.com/ethereum-optimism/optimism/op-program/host/config"
+	"github.com/ethereum-optimism/optimism/op-program/host/kvstore"
+	"github.com/ethereum-optimism/optimism/op-program/io"
+	"github.com/ethereum-optimism/optimism/op-program/preimage"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/stretchr/testify/require"
+)
+
+func TestServerMode(t *testing.T) {
+	dir := t.TempDir()
+
+	l1Head := common.Hash{0x11}
+	cfg := config.NewConfig(&chaincfg.Goerli, config.OPGoerliChainConfig, l1Head, common.Hash{0x22}, common.Hash{0x33}, 1000)
+	cfg.DataDir = dir
+	cfg.ServerMode = true
+
+	preimageServer, preimageClient, err := io.CreateBidirectionalChannel()
+	require.NoError(t, err)
+	defer preimageClient.Close()
+	hintServer, hintClient, err := io.CreateBidirectionalChannel()
+	require.NoError(t, err)
+	defer hintClient.Close()
+	logger := testlog.Logger(t, log.LvlTrace)
+	result := make(chan error)
+	go func() {
+		result <- PreimageServer(context.Background(), logger, cfg, preimageServer, hintServer)
+	}()
+
+	pClient := preimage.NewOracleClient(preimageClient)
+	hClient := preimage.NewHintWriter(hintClient)
+	l1PreimageOracle := l1.NewPreimageOracle(pClient, hClient)
+
+	require.Equal(t, l1Head.Bytes(), pClient.Get(client.L1HeadLocalIndex), "Should get preimages")
+
+	// Should exit when a preimage is unavailable
+	require.Panics(t, func() {
+		l1PreimageOracle.HeaderByBlockHash(common.HexToHash("0x1234"))
+	}, "Preimage should not be available")
+	require.ErrorIs(t, waitFor(result), kvstore.ErrNotFound)
+}
+
+func waitFor(ch chan error) error {
+	timeout := time.After(30 * time.Second)
+	select {
+	case err := <-ch:
+		return err
+	case <-timeout:
+		return errors.New("timed out")
+	}
+}

op-program/preimage/hints.go

@@ -43,7 +43,9 @@ func NewHintReader(rw io.ReadWriter) *HintReader {
 	return &HintReader{rw: rw}
 }
 
-func (hr *HintReader) NextHint(router func(hint string) error) error {
+type HintHandler func(hint string) error
+
+func (hr *HintReader) NextHint(router HintHandler) error {
 	var length uint32
 	if err := binary.Read(hr.rw, binary.BigEndian, &length); err != nil {
 		if err == io.EOF {

op-program/preimage/oracle.go

@@ -47,7 +47,9 @@ func NewOracleServer(rw io.ReadWriter) *OracleServer {
 	return &OracleServer{rw: rw}
 }
 
-func (o *OracleServer) NextPreimageRequest(getPreimage func(key common.Hash) ([]byte, error)) error {
+type PreimageGetter func(key common.Hash) ([]byte, error)
+
+func (o *OracleServer) NextPreimageRequest(getPreimage PreimageGetter) error {
 	var key common.Hash
 	if _, err := io.ReadFull(o.rw, key[:]); err != nil {
 		if err == io.EOF {