beacon/blsync: remove cli dependencies (#30720)

This PR moves chain config related code (config file processing, fork
logic, network defaults) from `beacon/types` and `beacon/blsync` into
`beacon/params` while the command line flag logic of the chain config is
moved into `cmd/utils`, thereby removing the cli dependencies from
package `beacon` and its sub-packages.

beacon/blsync/client.go

@@ -17,25 +17,22 @@
 package blsync
 
 import (
-	"strings"
-
 	"github.com/ethereum/go-ethereum/beacon/light"
 	"github.com/ethereum/go-ethereum/beacon/light/api"
 	"github.com/ethereum/go-ethereum/beacon/light/request"
 	"github.com/ethereum/go-ethereum/beacon/light/sync"
+	"github.com/ethereum/go-ethereum/beacon/params"
 	"github.com/ethereum/go-ethereum/beacon/types"
-	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/common/mclock"
 	"github.com/ethereum/go-ethereum/ethdb/memorydb"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/rpc"
-	"github.com/urfave/cli/v2"
 )
 
 type Client struct {
 	urls         []string
 	customHeader map[string]string
-	chainConfig  *lightClientConfig
+	config       *params.ClientConfig
 	scheduler    *request.Scheduler
 	blockSync    *beaconBlockSync
 	engineRPC    *rpc.Client
@@ -44,34 +41,18 @@ type Client struct {
 	engineClient *engineClient
 }
 
-func NewClient(ctx *cli.Context) *Client {
+func NewClient(config params.ClientConfig) *Client {
-	if !ctx.IsSet(utils.BeaconApiFlag.Name) {
-		utils.Fatalf("Beacon node light client API URL not specified")
-	}
-	var (
-		chainConfig  = makeChainConfig(ctx)
-		customHeader = make(map[string]string)
-	)
-	for _, s := range ctx.StringSlice(utils.BeaconApiHeaderFlag.Name) {
-		kv := strings.Split(s, ":")
-		if len(kv) != 2 {
-			utils.Fatalf("Invalid custom API header entry: %s", s)
-		}
-		customHeader[strings.TrimSpace(kv[0])] = strings.TrimSpace(kv[1])
-	}
-
 	// create data structures
 	var (
 		db             = memorydb.New()
-		threshold      = ctx.Int(utils.BeaconThresholdFlag.Name)
+		committeeChain = light.NewCommitteeChain(db, &config.ChainConfig, config.Threshold, !config.NoFilter)
-		committeeChain = light.NewCommitteeChain(db, chainConfig.ChainConfig, threshold, !ctx.Bool(utils.BeaconNoFilterFlag.Name))
+		headTracker    = light.NewHeadTracker(committeeChain, config.Threshold)
-		headTracker    = light.NewHeadTracker(committeeChain, threshold)
 	)
 	headSync := sync.NewHeadSync(headTracker, committeeChain)
 
 	// set up scheduler and sync modules
 	scheduler := request.NewScheduler()
-	checkpointInit := sync.NewCheckpointInit(committeeChain, chainConfig.Checkpoint)
+	checkpointInit := sync.NewCheckpointInit(committeeChain, config.Checkpoint)
 	forwardSync := sync.NewForwardUpdateSync(committeeChain)
 	beaconBlockSync := newBeaconBlockSync(headTracker)
 	scheduler.RegisterTarget(headTracker)
@@ -83,9 +64,9 @@ func NewClient(ctx *cli.Context) *Client {
 
 	return &Client{
 		scheduler:    scheduler,
-		urls:         ctx.StringSlice(utils.BeaconApiFlag.Name),
+		urls:         config.Apis,
-		customHeader: customHeader,
+		customHeader: config.CustomHeader,
-		chainConfig:  &chainConfig,
+		config:       &config,
 		blockSync:    beaconBlockSync,
 	}
 }
@@ -97,7 +78,7 @@ func (c *Client) SetEngineRPC(engine *rpc.Client) {
 func (c *Client) Start() error {
 	headCh := make(chan types.ChainHeadEvent, 16)
 	c.chainHeadSub = c.blockSync.SubscribeChainHead(headCh)
-	c.engineClient = startEngineClient(c.chainConfig, c.engineRPC, headCh)
+	c.engineClient = startEngineClient(c.config, c.engineRPC, headCh)
 
 	c.scheduler.Start()
 	for _, url := range c.urls {

beacon/blsync/config.go

@@ -1,129 +0,0 @@
-// Copyright 2022 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package blsync
-
-import (
-	"github.com/ethereum/go-ethereum/beacon/types"
-	"github.com/ethereum/go-ethereum/cmd/utils"
-	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/hexutil"
-	"github.com/urfave/cli/v2"
-)
-
-// lightClientConfig contains beacon light client configuration
-type lightClientConfig struct {
-	*types.ChainConfig
-	Checkpoint common.Hash
-}
-
-var (
-	MainnetConfig = lightClientConfig{
-		ChainConfig: (&types.ChainConfig{
-			GenesisValidatorsRoot: common.HexToHash("0x4b363db94e286120d76eb905340fdd4e54bfe9f06bf33ff6cf5ad27f511bfe95"),
-			GenesisTime:           1606824023,
-		}).
-			AddFork("GENESIS", 0, []byte{0, 0, 0, 0}).
-			AddFork("ALTAIR", 74240, []byte{1, 0, 0, 0}).
-			AddFork("BELLATRIX", 144896, []byte{2, 0, 0, 0}).
-			AddFork("CAPELLA", 194048, []byte{3, 0, 0, 0}).
-			AddFork("DENEB", 269568, []byte{4, 0, 0, 0}),
-		Checkpoint: common.HexToHash("0x6509b691f4de4f7b083f2784938fd52f0e131675432b3fd85ea549af9aebd3d0"),
-	}
-
-	SepoliaConfig = lightClientConfig{
-		ChainConfig: (&types.ChainConfig{
-			GenesisValidatorsRoot: common.HexToHash("0xd8ea171f3c94aea21ebc42a1ed61052acf3f9209c00e4efbaaddac09ed9b8078"),
-			GenesisTime:           1655733600,
-		}).
-			AddFork("GENESIS", 0, []byte{144, 0, 0, 105}).
-			AddFork("ALTAIR", 50, []byte{144, 0, 0, 112}).
-			AddFork("BELLATRIX", 100, []byte{144, 0, 0, 113}).
-			AddFork("CAPELLA", 56832, []byte{144, 0, 0, 114}).
-			AddFork("DENEB", 132608, []byte{144, 0, 0, 115}),
-		Checkpoint: common.HexToHash("0x456e85f5608afab3465a0580bff8572255f6d97af0c5f939e3f7536b5edb2d3f"),
-	}
-
-	HoleskyConfig = lightClientConfig{
-		ChainConfig: (&types.ChainConfig{
-			GenesisValidatorsRoot: common.HexToHash("0x9143aa7c615a7f7115e2b6aac319c03529df8242ae705fba9df39b79c59fa8b1"),
-			GenesisTime:           1695902400,
-		}).
-			AddFork("GENESIS", 0, []byte{1, 1, 112, 0}).
-			AddFork("ALTAIR", 0, []byte{2, 1, 112, 0}).
-			AddFork("BELLATRIX", 0, []byte{3, 1, 112, 0}).
-			AddFork("CAPELLA", 256, []byte{4, 1, 112, 0}).
-			AddFork("DENEB", 29696, []byte{5, 1, 112, 0}),
-		Checkpoint: common.HexToHash("0x6456a1317f54d4b4f2cb5bc9d153b5af0988fe767ef0609f0236cf29030bcff7"),
-	}
-)
-
-func makeChainConfig(ctx *cli.Context) lightClientConfig {
-	var config lightClientConfig
-	customConfig := ctx.IsSet(utils.BeaconConfigFlag.Name)
-	utils.CheckExclusive(ctx, utils.MainnetFlag, utils.SepoliaFlag, utils.HoleskyFlag, utils.BeaconConfigFlag)
-	switch {
-	case ctx.Bool(utils.MainnetFlag.Name):
-		config = MainnetConfig
-	case ctx.Bool(utils.SepoliaFlag.Name):
-		config = SepoliaConfig
-	case ctx.Bool(utils.HoleskyFlag.Name):
-		config = HoleskyConfig
-	default:
-		if !customConfig {
-			config = MainnetConfig
-		}
-	}
-	// Genesis root and time should always be specified together with custom chain config
-	if customConfig {
-		if !ctx.IsSet(utils.BeaconGenesisRootFlag.Name) {
-			utils.Fatalf("Custom beacon chain config is specified but genesis root is missing")
-		}
-		if !ctx.IsSet(utils.BeaconGenesisTimeFlag.Name) {
-			utils.Fatalf("Custom beacon chain config is specified but genesis time is missing")
-		}
-		if !ctx.IsSet(utils.BeaconCheckpointFlag.Name) {
-			utils.Fatalf("Custom beacon chain config is specified but checkpoint is missing")
-		}
-		config.ChainConfig = &types.ChainConfig{
-			GenesisTime: ctx.Uint64(utils.BeaconGenesisTimeFlag.Name),
-		}
-		if c, err := hexutil.Decode(ctx.String(utils.BeaconGenesisRootFlag.Name)); err == nil && len(c) <= 32 {
-			copy(config.GenesisValidatorsRoot[:len(c)], c)
-		} else {
-			utils.Fatalf("Invalid hex string", "beacon.genesis.gvroot", ctx.String(utils.BeaconGenesisRootFlag.Name), "error", err)
-		}
-		if err := config.ChainConfig.LoadForks(ctx.String(utils.BeaconConfigFlag.Name)); err != nil {
-			utils.Fatalf("Could not load beacon chain config file", "file name", ctx.String(utils.BeaconConfigFlag.Name), "error", err)
-		}
-	} else {
-		if ctx.IsSet(utils.BeaconGenesisRootFlag.Name) {
-			utils.Fatalf("Genesis root is specified but custom beacon chain config is missing")
-		}
-		if ctx.IsSet(utils.BeaconGenesisTimeFlag.Name) {
-			utils.Fatalf("Genesis time is specified but custom beacon chain config is missing")
-		}
-	}
-	// Checkpoint is required with custom chain config and is optional with pre-defined config
-	if ctx.IsSet(utils.BeaconCheckpointFlag.Name) {
-		if c, err := hexutil.Decode(ctx.String(utils.BeaconCheckpointFlag.Name)); err == nil && len(c) <= 32 {
-			copy(config.Checkpoint[:len(c)], c)
-		} else {
-			utils.Fatalf("Invalid hex string", "beacon.checkpoint", ctx.String(utils.BeaconCheckpointFlag.Name), "error", err)
-		}
-	}
-	return config
-}

beacon/blsync/engineclient.go

@@ -23,6 +23,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/beacon/engine"
+	"github.com/ethereum/go-ethereum/beacon/params"
 	"github.com/ethereum/go-ethereum/beacon/types"
 	"github.com/ethereum/go-ethereum/common"
 	ctypes "github.com/ethereum/go-ethereum/core/types"
@@ -31,14 +32,14 @@ import (
 )
 
 type engineClient struct {
-	config     *lightClientConfig
+	config     *params.ClientConfig
 	rpc        *rpc.Client
 	rootCtx    context.Context
 	cancelRoot context.CancelFunc
 	wg         sync.WaitGroup
 }
 
-func startEngineClient(config *lightClientConfig, rpc *rpc.Client, headCh <-chan types.ChainHeadEvent) *engineClient {
+func startEngineClient(config *params.ClientConfig, rpc *rpc.Client, headCh <-chan types.ChainHeadEvent) *engineClient {
 	ctx, cancel := context.WithCancel(context.Background())
 	ec := &engineClient{
 		config:     config,

beacon/light/committee_chain.go

@@ -76,24 +76,24 @@ type CommitteeChain struct {
 	unixNano    func() int64         // system clock (simulated clock in tests)
 	sigVerifier committeeSigVerifier // BLS sig verifier (dummy verifier in tests)
 
-	config             *types.ChainConfig
+	config             *params.ChainConfig
 	minimumUpdateScore types.UpdateScore
 	enforceTime        bool // enforceTime specifies whether the age of a signed header should be checked
 }
 
 // NewCommitteeChain creates a new CommitteeChain.
-func NewCommitteeChain(db ethdb.KeyValueStore, config *types.ChainConfig, signerThreshold int, enforceTime bool) *CommitteeChain {
+func NewCommitteeChain(db ethdb.KeyValueStore, config *params.ChainConfig, signerThreshold int, enforceTime bool) *CommitteeChain {
 	return newCommitteeChain(db, config, signerThreshold, enforceTime, blsVerifier{}, &mclock.System{}, func() int64 { return time.Now().UnixNano() })
 }
 
 // NewTestCommitteeChain creates a new CommitteeChain for testing.
-func NewTestCommitteeChain(db ethdb.KeyValueStore, config *types.ChainConfig, signerThreshold int, enforceTime bool, clock *mclock.Simulated) *CommitteeChain {
+func NewTestCommitteeChain(db ethdb.KeyValueStore, config *params.ChainConfig, signerThreshold int, enforceTime bool, clock *mclock.Simulated) *CommitteeChain {
 	return newCommitteeChain(db, config, signerThreshold, enforceTime, dummyVerifier{}, clock, func() int64 { return int64(clock.Now()) })
 }
 
 // newCommitteeChain creates a new CommitteeChain with the option of replacing the
 // clock source and signature verification for testing purposes.
-func newCommitteeChain(db ethdb.KeyValueStore, config *types.ChainConfig, signerThreshold int, enforceTime bool, sigVerifier committeeSigVerifier, clock mclock.Clock, unixNano func() int64) *CommitteeChain {
+func newCommitteeChain(db ethdb.KeyValueStore, config *params.ChainConfig, signerThreshold int, enforceTime bool, sigVerifier committeeSigVerifier, clock mclock.Clock, unixNano func() int64) *CommitteeChain {
 	s := &CommitteeChain{
 		committeeCache: lru.NewCache[uint64, syncCommittee](10),
 		db:             db,
@@ -505,7 +505,7 @@ func (s *CommitteeChain) verifySignedHeader(head types.SignedHeader) (bool, time
 	if committee == nil {
 		return false, age, nil
 	}
-	if signingRoot, err := s.config.Forks.SigningRoot(head.Header); err == nil {
+	if signingRoot, err := s.config.Forks.SigningRoot(head.Header.Epoch(), head.Header.Hash()); err == nil {
 		return s.sigVerifier.verifySignature(committee, signingRoot, &head.Signature), age, nil
 	}
 	return false, age, nil

beacon/light/committee_chain_test.go

@@ -31,15 +31,15 @@ var (
 	testGenesis  = newTestGenesis()
 	testGenesis2 = newTestGenesis()
 
-	tfBase = newTestForks(testGenesis, types.Forks{
+	tfBase = newTestForks(testGenesis, params.Forks{
-		&types.Fork{Epoch: 0, Version: []byte{0}},
+		&params.Fork{Epoch: 0, Version: []byte{0}},
 	})
-	tfAlternative = newTestForks(testGenesis, types.Forks{
+	tfAlternative = newTestForks(testGenesis, params.Forks{
-		&types.Fork{Epoch: 0, Version: []byte{0}},
+		&params.Fork{Epoch: 0, Version: []byte{0}},
-		&types.Fork{Epoch: 0x700, Version: []byte{1}},
+		&params.Fork{Epoch: 0x700, Version: []byte{1}},
 	})
-	tfAnotherGenesis = newTestForks(testGenesis2, types.Forks{
+	tfAnotherGenesis = newTestForks(testGenesis2, params.Forks{
-		&types.Fork{Epoch: 0, Version: []byte{0}},
+		&params.Fork{Epoch: 0, Version: []byte{0}},
 	})
 
 	tcBase                      = newTestCommitteeChain(nil, tfBase, true, 0, 10, 400, false)
@@ -226,13 +226,13 @@ type committeeChainTest struct {
 	t               *testing.T
 	db              *memorydb.Database
 	clock           *mclock.Simulated
-	config          types.ChainConfig
+	config          params.ChainConfig
 	signerThreshold int
 	enforceTime     bool
 	chain           *CommitteeChain
 }
 
-func newCommitteeChainTest(t *testing.T, config types.ChainConfig, signerThreshold int, enforceTime bool) *committeeChainTest {
+func newCommitteeChainTest(t *testing.T, config params.ChainConfig, signerThreshold int, enforceTime bool) *committeeChainTest {
 	c := &committeeChainTest{
 		t:               t,
 		db:              memorydb.New(),
@@ -298,20 +298,20 @@ func (c *committeeChainTest) verifyRange(tc *testCommitteeChain, begin, end uint
 	c.verifySignedHeader(tc, float64(end)+1.5, false)
 }
 
-func newTestGenesis() types.ChainConfig {
+func newTestGenesis() params.ChainConfig {
-	var config types.ChainConfig
+	var config params.ChainConfig
 	rand.Read(config.GenesisValidatorsRoot[:])
 	return config
 }
 
-func newTestForks(config types.ChainConfig, forks types.Forks) types.ChainConfig {
+func newTestForks(config params.ChainConfig, forks params.Forks) params.ChainConfig {
 	for _, fork := range forks {
 		config.AddFork(fork.Name, fork.Epoch, fork.Version)
 	}
 	return config
 }
 
-func newTestCommitteeChain(parent *testCommitteeChain, config types.ChainConfig, newCommittees bool, begin, end int, signerCount int, finalizedHeader bool) *testCommitteeChain {
+func newTestCommitteeChain(parent *testCommitteeChain, config params.ChainConfig, newCommittees bool, begin, end int, signerCount int, finalizedHeader bool) *testCommitteeChain {
 	tc := &testCommitteeChain{
 		config: config,
 	}
@@ -337,7 +337,7 @@ type testPeriod struct {
 
 type testCommitteeChain struct {
 	periods []testPeriod
-	config  types.ChainConfig
+	config  params.ChainConfig
 }
 
 func (tc *testCommitteeChain) fillCommittees(begin, end int) {

beacon/light/test_helpers.go

@@ -33,7 +33,7 @@ func GenerateTestCommittee() *types.SerializedSyncCommittee {
 	return s
 }
 
-func GenerateTestUpdate(config *types.ChainConfig, period uint64, committee, nextCommittee *types.SerializedSyncCommittee, signerCount int, finalizedHeader bool) *types.LightClientUpdate {
+func GenerateTestUpdate(config *params.ChainConfig, period uint64, committee, nextCommittee *types.SerializedSyncCommittee, signerCount int, finalizedHeader bool) *types.LightClientUpdate {
 	update := new(types.LightClientUpdate)
 	update.NextSyncCommitteeRoot = nextCommittee.Root()
 	var attestedHeader types.Header
@@ -48,9 +48,9 @@ func GenerateTestUpdate(config *types.ChainConfig, period uint64, committee, nex
 	return update
 }
 
-func GenerateTestSignedHeader(header types.Header, config *types.ChainConfig, committee *types.SerializedSyncCommittee, signatureSlot uint64, signerCount int) types.SignedHeader {
+func GenerateTestSignedHeader(header types.Header, config *params.ChainConfig, committee *types.SerializedSyncCommittee, signatureSlot uint64, signerCount int) types.SignedHeader {
 	bitmask := makeBitmask(signerCount)
-	signingRoot, _ := config.Forks.SigningRoot(header)
+	signingRoot, _ := config.Forks.SigningRoot(header.Epoch(), header.Hash())
 	c, _ := dummyVerifier{}.deserializeSyncCommittee(committee)
 	return types.SignedHeader{
 		Header: header,

beacon/params/config.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package types
+package params
 
 import (
 	"crypto/sha256"
@@ -39,81 +39,13 @@ const syncCommitteeDomain = 7
 
 var knownForks = []string{"GENESIS", "ALTAIR", "BELLATRIX", "CAPELLA", "DENEB"}
 
-// Fork describes a single beacon chain fork and also stores the calculated
+// ClientConfig contains beacon light client configuration.
-// signature domain used after this fork.
+type ClientConfig struct {
-type Fork struct {
+	ChainConfig
-	// Name of the fork in the chain config (config.yaml) file
+	Apis         []string
-	Name string
+	CustomHeader map[string]string
-
+	Threshold    int
-	// Epoch when given fork version is activated
+	NoFilter     bool
-	Epoch uint64
-
-	// Fork version, see https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/beacon-chain.md#custom-types
-	Version []byte
-
-	// index in list of known forks or MaxInt if unknown
-	knownIndex int
-
-	// calculated by computeDomain, based on fork version and genesis validators root
-	domain merkle.Value
-}
-
-// computeDomain returns the signature domain based on the given fork version
-// and genesis validator set root.
-func (f *Fork) computeDomain(genesisValidatorsRoot common.Hash) {
-	var (
-		hasher        = sha256.New()
-		forkVersion32 merkle.Value
-		forkDataRoot  merkle.Value
-	)
-	copy(forkVersion32[:], f.Version)
-	hasher.Write(forkVersion32[:])
-	hasher.Write(genesisValidatorsRoot[:])
-	hasher.Sum(forkDataRoot[:0])
-
-	f.domain[0] = syncCommitteeDomain
-	copy(f.domain[4:], forkDataRoot[:28])
-}
-
-// Forks is the list of all beacon chain forks in the chain configuration.
-type Forks []*Fork
-
-// domain returns the signature domain for the given epoch (assumes that domains
-// have already been calculated).
-func (f Forks) domain(epoch uint64) (merkle.Value, error) {
-	for i := len(f) - 1; i >= 0; i-- {
-		if epoch >= f[i].Epoch {
-			return f[i].domain, nil
-		}
-	}
-	return merkle.Value{}, fmt.Errorf("unknown fork for epoch %d", epoch)
-}
-
-// SigningRoot calculates the signing root of the given header.
-func (f Forks) SigningRoot(header Header) (common.Hash, error) {
-	domain, err := f.domain(header.Epoch())
-	if err != nil {
-		return common.Hash{}, err
-	}
-	var (
-		signingRoot common.Hash
-		headerHash  = header.Hash()
-		hasher      = sha256.New()
-	)
-	hasher.Write(headerHash[:])
-	hasher.Write(domain[:])
-	hasher.Sum(signingRoot[:0])
-
-	return signingRoot, nil
-}
-
-func (f Forks) Len() int      { return len(f) }
-func (f Forks) Swap(i, j int) { f[i], f[j] = f[j], f[i] }
-func (f Forks) Less(i, j int) bool {
-	if f[i].Epoch != f[j].Epoch {
-		return f[i].Epoch < f[j].Epoch
-	}
-	return f[i].knownIndex < f[j].knownIndex
 }
 
 // ChainConfig contains the beacon chain configuration.
@@ -121,6 +53,7 @@ type ChainConfig struct {
 	GenesisTime           uint64      // Unix timestamp of slot 0
 	GenesisValidatorsRoot common.Hash // Root hash of the genesis validator set, used for signature domain calculation
 	Forks                 Forks
+	Checkpoint            common.Hash
 }
 
 // ForkAtEpoch returns the latest active fork at the given epoch.
@@ -202,3 +135,79 @@ func (c *ChainConfig) LoadForks(path string) error {
 	}
 	return nil
 }
+
+// Fork describes a single beacon chain fork and also stores the calculated
+// signature domain used after this fork.
+type Fork struct {
+	// Name of the fork in the chain config (config.yaml) file
+	Name string
+
+	// Epoch when given fork version is activated
+	Epoch uint64
+
+	// Fork version, see https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/beacon-chain.md#custom-types
+	Version []byte
+
+	// index in list of known forks or MaxInt if unknown
+	knownIndex int
+
+	// calculated by computeDomain, based on fork version and genesis validators root
+	domain merkle.Value
+}
+
+// computeDomain returns the signature domain based on the given fork version
+// and genesis validator set root.
+func (f *Fork) computeDomain(genesisValidatorsRoot common.Hash) {
+	var (
+		hasher        = sha256.New()
+		forkVersion32 merkle.Value
+		forkDataRoot  merkle.Value
+	)
+	copy(forkVersion32[:], f.Version)
+	hasher.Write(forkVersion32[:])
+	hasher.Write(genesisValidatorsRoot[:])
+	hasher.Sum(forkDataRoot[:0])
+
+	f.domain[0] = syncCommitteeDomain
+	copy(f.domain[4:], forkDataRoot[:28])
+}
+
+// Forks is the list of all beacon chain forks in the chain configuration.
+type Forks []*Fork
+
+// domain returns the signature domain for the given epoch (assumes that domains
+// have already been calculated).
+func (f Forks) domain(epoch uint64) (merkle.Value, error) {
+	for i := len(f) - 1; i >= 0; i-- {
+		if epoch >= f[i].Epoch {
+			return f[i].domain, nil
+		}
+	}
+	return merkle.Value{}, fmt.Errorf("unknown fork for epoch %d", epoch)
+}
+
+// SigningRoot calculates the signing root of the given header.
+func (f Forks) SigningRoot(epoch uint64, root common.Hash) (common.Hash, error) {
+	domain, err := f.domain(epoch)
+	if err != nil {
+		return common.Hash{}, err
+	}
+	var (
+		signingRoot common.Hash
+		hasher      = sha256.New()
+	)
+	hasher.Write(root[:])
+	hasher.Write(domain[:])
+	hasher.Sum(signingRoot[:0])
+
+	return signingRoot, nil
+}
+
+func (f Forks) Len() int      { return len(f) }
+func (f Forks) Swap(i, j int) { f[i], f[j] = f[j], f[i] }
+func (f Forks) Less(i, j int) bool {
+	if f[i].Epoch != f[j].Epoch {
+		return f[i].Epoch < f[j].Epoch
+	}
+	return f[i].knownIndex < f[j].knownIndex
+}

beacon/params/networks.go

@@ -0,0 +1,56 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package params
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+)
+
+var (
+	MainnetLightConfig = (&ChainConfig{
+		GenesisValidatorsRoot: common.HexToHash("0x4b363db94e286120d76eb905340fdd4e54bfe9f06bf33ff6cf5ad27f511bfe95"),
+		GenesisTime:           1606824023,
+		Checkpoint:            common.HexToHash("0x6509b691f4de4f7b083f2784938fd52f0e131675432b3fd85ea549af9aebd3d0"),
+	}).
+		AddFork("GENESIS", 0, []byte{0, 0, 0, 0}).
+		AddFork("ALTAIR", 74240, []byte{1, 0, 0, 0}).
+		AddFork("BELLATRIX", 144896, []byte{2, 0, 0, 0}).
+		AddFork("CAPELLA", 194048, []byte{3, 0, 0, 0}).
+		AddFork("DENEB", 269568, []byte{4, 0, 0, 0})
+
+	SepoliaLightConfig = (&ChainConfig{
+		GenesisValidatorsRoot: common.HexToHash("0xd8ea171f3c94aea21ebc42a1ed61052acf3f9209c00e4efbaaddac09ed9b8078"),
+		GenesisTime:           1655733600,
+		Checkpoint:            common.HexToHash("0x456e85f5608afab3465a0580bff8572255f6d97af0c5f939e3f7536b5edb2d3f"),
+	}).
+		AddFork("GENESIS", 0, []byte{144, 0, 0, 105}).
+		AddFork("ALTAIR", 50, []byte{144, 0, 0, 112}).
+		AddFork("BELLATRIX", 100, []byte{144, 0, 0, 113}).
+		AddFork("CAPELLA", 56832, []byte{144, 0, 0, 114}).
+		AddFork("DENEB", 132608, []byte{144, 0, 0, 115})
+
+	HoleskyLightConfig = (&ChainConfig{
+		GenesisValidatorsRoot: common.HexToHash("0x9143aa7c615a7f7115e2b6aac319c03529df8242ae705fba9df39b79c59fa8b1"),
+		GenesisTime:           1695902400,
+		Checkpoint:            common.HexToHash("0x6456a1317f54d4b4f2cb5bc9d153b5af0988fe767ef0609f0236cf29030bcff7"),
+	}).
+		AddFork("GENESIS", 0, []byte{1, 1, 112, 0}).
+		AddFork("ALTAIR", 0, []byte{2, 1, 112, 0}).
+		AddFork("BELLATRIX", 0, []byte{3, 1, 112, 0}).
+		AddFork("CAPELLA", 256, []byte{4, 1, 112, 0}).
+		AddFork("DENEB", 29696, []byte{5, 1, 112, 0})
+)

cmd/blsync/main.go

@@ -70,7 +70,7 @@ func main() {
 
 func sync(ctx *cli.Context) error {
 	// set up blsync
-	client := blsync.NewClient(ctx)
+	client := blsync.NewClient(utils.MakeBeaconLightConfig(ctx))
 	client.SetEngineRPC(makeRPCClient(ctx))
 	client.Start()
 

cmd/geth/config.go

@@ -240,7 +240,7 @@ func makeFullNode(ctx *cli.Context) *node.Node {
 		// Start blsync mode.
 		srv := rpc.NewServer()
 		srv.RegisterName("engine", catalyst.NewConsensusAPI(eth))
-		blsyncer := blsync.NewClient(ctx)
+		blsyncer := blsync.NewClient(utils.MakeBeaconLightConfig(ctx))
 		blsyncer.SetEngineRPC(rpc.DialInProc(srv))
 		stack.RegisterLifecycle(blsyncer)
 	} else {

cmd/utils/flags.go

@@ -40,6 +40,7 @@ import (
 	bparams "github.com/ethereum/go-ethereum/beacon/params"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/fdlimit"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/txpool/blobpool"
@@ -1889,6 +1890,81 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 	}
 }
 
+// MakeBeaconLightConfig constructs a beacon light client config based on the
+// related command line flags.
+func MakeBeaconLightConfig(ctx *cli.Context) bparams.ClientConfig {
+	var config bparams.ClientConfig
+	customConfig := ctx.IsSet(BeaconConfigFlag.Name)
+	CheckExclusive(ctx, MainnetFlag, SepoliaFlag, HoleskyFlag, BeaconConfigFlag)
+	switch {
+	case ctx.Bool(MainnetFlag.Name):
+		config.ChainConfig = *bparams.MainnetLightConfig
+	case ctx.Bool(SepoliaFlag.Name):
+		config.ChainConfig = *bparams.SepoliaLightConfig
+	case ctx.Bool(HoleskyFlag.Name):
+		config.ChainConfig = *bparams.HoleskyLightConfig
+	default:
+		if !customConfig {
+			config.ChainConfig = *bparams.MainnetLightConfig
+		}
+	}
+	// Genesis root and time should always be specified together with custom chain config
+	if customConfig {
+		if !ctx.IsSet(BeaconGenesisRootFlag.Name) {
+			Fatalf("Custom beacon chain config is specified but genesis root is missing")
+		}
+		if !ctx.IsSet(BeaconGenesisTimeFlag.Name) {
+			Fatalf("Custom beacon chain config is specified but genesis time is missing")
+		}
+		if !ctx.IsSet(BeaconCheckpointFlag.Name) {
+			Fatalf("Custom beacon chain config is specified but checkpoint is missing")
+		}
+		config.ChainConfig = bparams.ChainConfig{
+			GenesisTime: ctx.Uint64(BeaconGenesisTimeFlag.Name),
+		}
+		if c, err := hexutil.Decode(ctx.String(BeaconGenesisRootFlag.Name)); err == nil && len(c) <= 32 {
+			copy(config.GenesisValidatorsRoot[:len(c)], c)
+		} else {
+			Fatalf("Invalid hex string", "beacon.genesis.gvroot", ctx.String(BeaconGenesisRootFlag.Name), "error", err)
+		}
+		configFile := ctx.String(BeaconConfigFlag.Name)
+		if err := config.ChainConfig.LoadForks(configFile); err != nil {
+			Fatalf("Could not load beacon chain config", "file", configFile, "error", err)
+		}
+		log.Info("Using custom beacon chain config", "file", configFile)
+	} else {
+		if ctx.IsSet(BeaconGenesisRootFlag.Name) {
+			Fatalf("Genesis root is specified but custom beacon chain config is missing")
+		}
+		if ctx.IsSet(BeaconGenesisTimeFlag.Name) {
+			Fatalf("Genesis time is specified but custom beacon chain config is missing")
+		}
+	}
+	// Checkpoint is required with custom chain config and is optional with pre-defined config
+	if ctx.IsSet(BeaconCheckpointFlag.Name) {
+		if c, err := hexutil.Decode(ctx.String(BeaconCheckpointFlag.Name)); err == nil && len(c) <= 32 {
+			copy(config.Checkpoint[:len(c)], c)
+		} else {
+			Fatalf("Invalid hex string", "beacon.checkpoint", ctx.String(BeaconCheckpointFlag.Name), "error", err)
+		}
+	}
+	config.Apis = ctx.StringSlice(BeaconApiFlag.Name)
+	if config.Apis == nil {
+		Fatalf("Beacon node light client API URL not specified")
+	}
+	config.CustomHeader = make(map[string]string)
+	for _, s := range ctx.StringSlice(BeaconApiHeaderFlag.Name) {
+		kv := strings.Split(s, ":")
+		if len(kv) != 2 {
+			Fatalf("Invalid custom API header entry: %s", s)
+		}
+		config.CustomHeader[strings.TrimSpace(kv[0])] = strings.TrimSpace(kv[1])
+	}
+	config.Threshold = ctx.Int(BeaconThresholdFlag.Name)
+	config.NoFilter = ctx.Bool(BeaconNoFilterFlag.Name)
+	return config
+}
+
 // SetDNSDiscoveryDefaults configures DNS discovery with the given URL if
 // no URLs are set.
 func SetDNSDiscoveryDefaults(cfg *ethconfig.Config, genesis common.Hash) {