all: on-chain oracle checkpoint syncing (#19543)

* all: implement simple checkpoint syncing cmd, les, node: remove callback mechanism cmd, node: remove callback definition les: simplify the registrar les: expose checkpoint rpc services in the light client les, light: don't store untrusted receipt cmd, contracts, les: discard stale checkpoint cmd, contracts/registrar: loose restriction of registeration cmd, contracts: add replay-protection all: off-chain multi-signature contract params: deploy checkpoint contract for rinkeby cmd/registrar: add raw signing mode for registrar cmd/registrar, contracts/registrar, les: fixed messages * cmd/registrar, contracts/registrar: fix lints * accounts/abi/bind, les: address comments * cmd, contracts, les, light, params: minor checkpoint sync cleanups * cmd, eth, les, light: move checkpoint config to config file * cmd, eth, les, params: address comments * eth, les, params: address comments * cmd: polish up the checkpoint admin CLI * cmd, contracts, params: deploy new version contract * cmd/checkpoint-admin: add another flag for clef mode signing * cmd, contracts, les: rename and regen checkpoint oracle with abigen
2019-06-28 15:34:02 +08:00
parent 702f52fb99
commit f7cdea2bdc
49 changed files with 2861 additions and 383 deletions
--- a/les/api.go
+++ b/les/api.go
@@ -34,6 +34,8 @@ var (
 	ErrMinCap               = errors.New("capacity too small")
 	ErrTotalCap             = errors.New("total capacity exceeded")
 	ErrUnknownBenchmarkType = errors.New("unknown benchmark type")
+	ErrNoCheckpoint         = errors.New("no local checkpoint provided")
+	ErrNotActivated         = errors.New("checkpoint registrar is not activated")

 	dropCapacityDelay = time.Second // delay applied to decreasing capacity changes
 )
@@ -470,3 +472,59 @@ func (api *PrivateLightServerAPI) Benchmark(setups []map[string]interface{}, pas
 	}
 	return result, nil
 }
+
+// PrivateLightAPI provides an API to access the LES light server or light client.
+type PrivateLightAPI struct {
+	backend *lesCommons
+	reg     *checkpointOracle
+}
+
+// NewPrivateLightAPI creates a new LES service API.
+func NewPrivateLightAPI(backend *lesCommons, reg *checkpointOracle) *PrivateLightAPI {
+	return &PrivateLightAPI{
+		backend: backend,
+		reg:     reg,
+	}
+}
+
+// LatestCheckpoint returns the latest local checkpoint package.
+//
+// The checkpoint package consists of 4 strings:
+//   result[0], hex encoded latest section index
+//   result[1], 32 bytes hex encoded latest section head hash
+//   result[2], 32 bytes hex encoded latest section canonical hash trie root hash
+//   result[3], 32 bytes hex encoded latest section bloom trie root hash
+func (api *PrivateLightAPI) LatestCheckpoint() ([4]string, error) {
+	var res [4]string
+	cp := api.backend.latestLocalCheckpoint()
+	if cp.Empty() {
+		return res, ErrNoCheckpoint
+	}
+	res[0] = hexutil.EncodeUint64(cp.SectionIndex)
+	res[1], res[2], res[3] = cp.SectionHead.Hex(), cp.CHTRoot.Hex(), cp.BloomRoot.Hex()
+	return res, nil
+}
+
+// GetLocalCheckpoint returns the specific local checkpoint package.
+//
+// The checkpoint package consists of 3 strings:
+//   result[0], 32 bytes hex encoded latest section head hash
+//   result[1], 32 bytes hex encoded latest section canonical hash trie root hash
+//   result[2], 32 bytes hex encoded latest section bloom trie root hash
+func (api *PrivateLightAPI) GetCheckpoint(index uint64) ([3]string, error) {
+	var res [3]string
+	cp := api.backend.getLocalCheckpoint(index)
+	if cp.Empty() {
+		return res, ErrNoCheckpoint
+	}
+	res[0], res[1], res[2] = cp.SectionHead.Hex(), cp.CHTRoot.Hex(), cp.BloomRoot.Hex()
+	return res, nil
+}
+
+// GetCheckpointContractAddress returns the contract contract address in hex format.
+func (api *PrivateLightAPI) GetCheckpointContractAddress() (string, error) {
+	if api.reg == nil {
+		return "", ErrNotActivated
+	}
+	return api.reg.config.Address.Hex(), nil
+}
--- a/les/backend.go
+++ b/les/backend.go
@@ -23,6 +23,7 @@ import (
 	"time"

 	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/common/mclock"
@@ -43,14 +44,13 @@ import (
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discv5"
 	"github.com/ethereum/go-ethereum/params"
-	rpc "github.com/ethereum/go-ethereum/rpc"
+	"github.com/ethereum/go-ethereum/rpc"
 )

 type LightEthereum struct {
 	lesCommons

 	odr         *LesOdr
-	relay       *LesTxRelay
 	chainConfig *params.ChainConfig
 	// Channel for shutting down the service
 	shutdownChan chan bool
@@ -62,6 +62,7 @@ type LightEthereum struct {
 	serverPool *serverPool
 	reqDist    *requestDistributor
 	retriever  *retrieveManager
+	relay      *lesTxRelay

 	bloomRequests chan chan *bloombits.Retrieval // Channel receiving bloom data retrieval requests
 	bloomIndexer  *core.ChainIndexer
@@ -116,16 +117,20 @@ func New(ctx *node.ServiceContext, config *eth.Config) (*LightEthereum, error) {
 	}
 	leth.serverPool = newServerPool(chainDb, quitSync, &leth.wg, trustedNodes)
 	leth.retriever = newRetrieveManager(peers, leth.reqDist, leth.serverPool)
-	leth.relay = NewLesTxRelay(peers, leth.retriever)
+	leth.relay = newLesTxRelay(peers, leth.retriever)

 	leth.odr = NewLesOdr(chainDb, light.DefaultClientIndexerConfig, leth.retriever)
 	leth.chtIndexer = light.NewChtIndexer(chainDb, leth.odr, params.CHTFrequency, params.HelperTrieConfirmations)
 	leth.bloomTrieIndexer = light.NewBloomTrieIndexer(chainDb, leth.odr, params.BloomBitsBlocksClient, params.BloomTrieFrequency)
 	leth.odr.SetIndexers(leth.chtIndexer, leth.bloomTrieIndexer, leth.bloomIndexer)

+	checkpoint := config.Checkpoint
+	if checkpoint == nil {
+		checkpoint = params.TrustedCheckpoints[genesisHash]
+	}
 	// Note: NewLightChain adds the trusted checkpoint so it needs an ODR with
 	// indexers already set but not started yet
-	if leth.blockchain, err = light.NewLightChain(leth.odr, leth.chainConfig, leth.engine); err != nil {
+	if leth.blockchain, err = light.NewLightChain(leth.odr, leth.chainConfig, leth.engine, checkpoint); err != nil {
 		return nil, err
 	}
 	// Note: AddChildIndexer starts the update process for the child
@@ -141,32 +146,6 @@ func New(ctx *node.ServiceContext, config *eth.Config) (*LightEthereum, error) {
 	}

 	leth.txPool = light.NewTxPool(leth.chainConfig, leth.blockchain, leth.relay)
-
-	if leth.protocolManager, err = NewProtocolManager(
-		leth.chainConfig,
-		light.DefaultClientIndexerConfig,
-		true,
-		config.NetworkId,
-		leth.eventMux,
-		leth.engine,
-		leth.peers,
-		leth.blockchain,
-		nil,
-		chainDb,
-		leth.odr,
-		leth.relay,
-		leth.serverPool,
-		quitSync,
-		&leth.wg,
-		config.ULC,
-		nil); err != nil {
-		return nil, err
-	}
-
-	if leth.protocolManager.isULCEnabled() {
-		log.Warn("Ultra light client is enabled", "trustedNodes", len(leth.protocolManager.ulc.trustedKeys), "minTrustedFraction", leth.protocolManager.ulc.minTrustedFraction)
-		leth.blockchain.DisableCheckFreq()
-	}
 	leth.ApiBackend = &LesApiBackend{ctx.ExtRPCEnabled(), leth, nil}

 	gpoParams := config.GPO
@@ -174,6 +153,19 @@ func New(ctx *node.ServiceContext, config *eth.Config) (*LightEthereum, error) {
 		gpoParams.Default = config.Miner.GasPrice
 	}
 	leth.ApiBackend.gpo = gasprice.NewOracle(leth.ApiBackend, gpoParams)
+
+	oracle := config.CheckpointOracle
+	if oracle == nil {
+		oracle = params.CheckpointOracles[genesisHash]
+	}
+	registrar := newCheckpointOracle(oracle, leth.getLocalCheckpoint)
+	if leth.protocolManager, err = NewProtocolManager(leth.chainConfig, checkpoint, light.DefaultClientIndexerConfig, config.ULC, true, config.NetworkId, leth.eventMux, leth.peers, leth.blockchain, nil, chainDb, leth.odr, leth.serverPool, registrar, quitSync, &leth.wg, nil); err != nil {
+		return nil, err
+	}
+	if leth.protocolManager.isULCEnabled() {
+		log.Warn("Ultra light client is enabled", "trustedNodes", len(leth.protocolManager.ulc.trustedKeys), "minTrustedFraction", leth.protocolManager.ulc.minTrustedFraction)
+		leth.blockchain.DisableCheckFreq()
+	}
 	return leth, nil
 }

@@ -234,6 +226,11 @@ func (s *LightEthereum) APIs() []rpc.API {
 			Version:   "1.0",
 			Service:   s.netRPCService,
 			Public:    true,
+		}, {
+			Namespace: "les",
+			Version:   "1.0",
+			Service:   NewPrivateLightAPI(&s.lesCommons, s.protocolManager.reg),
+			Public:    false,
 		},
 	}...)
 }
@@ -288,3 +285,12 @@ func (s *LightEthereum) Stop() error {

 	return nil
 }
+
+// SetClient sets the rpc client and binds the registrar contract.
+func (s *LightEthereum) SetContractBackend(backend bind.ContractBackend) {
+	// Short circuit if registrar is nil
+	if s.protocolManager.reg == nil {
+		return
+	}
+	s.protocolManager.reg.start(backend)
+}
--- a/les/checkpointoracle.go
+++ b/les/checkpointoracle.go
@@ -0,0 +1,158 @@
+// Copyright 2019 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 les
+
+import (
+	"encoding/binary"
+	"sync/atomic"
+
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/contracts/checkpointoracle"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+// checkpointOracle is responsible for offering the latest stable checkpoint
+// generated and announced by the contract admins on-chain. The checkpoint is
+// verified by clients locally during the checkpoint syncing.
+type checkpointOracle struct {
+	config   *params.CheckpointOracleConfig
+	contract *checkpointoracle.CheckpointOracle
+
+	// Whether the contract backend is set.
+	running int32
+
+	getLocal     func(uint64) params.TrustedCheckpoint // Function used to retrieve local checkpoint
+	syncDoneHook func()                                // Function used to notify that light syncing has completed.
+}
+
+// newCheckpointOracle returns a checkpoint registrar handler.
+func newCheckpointOracle(config *params.CheckpointOracleConfig, getLocal func(uint64) params.TrustedCheckpoint) *checkpointOracle {
+	if config == nil {
+		log.Info("Checkpoint registrar is not enabled")
+		return nil
+	}
+	if config.Address == (common.Address{}) || uint64(len(config.Signers)) < config.Threshold {
+		log.Warn("Invalid checkpoint registrar config")
+		return nil
+	}
+	log.Info("Configured checkpoint registrar", "address", config.Address, "signers", len(config.Signers), "threshold", config.Threshold)
+
+	return &checkpointOracle{
+		config:   config,
+		getLocal: getLocal,
+	}
+}
+
+// start binds the registrar contract and start listening to the
+// newCheckpointEvent for the server side.
+func (reg *checkpointOracle) start(backend bind.ContractBackend) {
+	contract, err := checkpointoracle.NewCheckpointOracle(reg.config.Address, backend)
+	if err != nil {
+		log.Error("Oracle contract binding failed", "err", err)
+		return
+	}
+	if !atomic.CompareAndSwapInt32(&reg.running, 0, 1) {
+		log.Error("Already bound and listening to registrar")
+		return
+	}
+	reg.contract = contract
+}
+
+// isRunning returns an indicator whether the registrar is running.
+func (reg *checkpointOracle) isRunning() bool {
+	return atomic.LoadInt32(&reg.running) == 1
+}
+
+// stableCheckpoint returns the stable checkpoint which was generated by local
+// indexers and announced by trusted signers.
+func (reg *checkpointOracle) stableCheckpoint() (*params.TrustedCheckpoint, uint64) {
+	// Retrieve the latest checkpoint from the contract, abort if empty
+	latest, hash, height, err := reg.contract.Contract().GetLatestCheckpoint(nil)
+	if err != nil || (latest == 0 && hash == [32]byte{}) {
+		return nil, 0
+	}
+	local := reg.getLocal(latest)
+
+	// The following scenarios may occur:
+	//
+	// * local node is out of sync so that it doesn't have the
+	//   checkpoint which registered in the contract.
+	// * local checkpoint doesn't match with the registered one.
+	//
+	// In both cases, server won't send the **stable** checkpoint
+	// to the client(no worry, client can use hardcoded one instead).
+	if local.HashEqual(common.Hash(hash)) {
+		return &local, height.Uint64()
+	}
+	return nil, 0
+}
+
+// verifySigners recovers the signer addresses according to the signature and
+// checks whether there are enough approvals to finalize the checkpoint.
+func (reg *checkpointOracle) verifySigners(index uint64, hash [32]byte, signatures [][]byte) (bool, []common.Address) {
+	// Short circuit if the given signatures doesn't reach the threshold.
+	if len(signatures) < int(reg.config.Threshold) {
+		return false, nil
+	}
+	var (
+		signers []common.Address
+		checked = make(map[common.Address]struct{})
+	)
+	for i := 0; i < len(signatures); i++ {
+		if len(signatures[i]) != 65 {
+			continue
+		}
+		// EIP 191 style signatures
+		//
+		// Arguments when calculating hash to validate
+		// 1: byte(0x19) - the initial 0x19 byte
+		// 2: byte(0) - the version byte (data with intended validator)
+		// 3: this - the validator address
+		// --  Application specific data
+		// 4 : checkpoint section_index (uint64)
+		// 5 : checkpoint hash (bytes32)
+		//     hash = keccak256(checkpoint_index, section_head, cht_root, bloom_root)
+		buf := make([]byte, 8)
+		binary.BigEndian.PutUint64(buf, index)
+		data := append([]byte{0x19, 0x00}, append(reg.config.Address.Bytes(), append(buf, hash[:]...)...)...)
+		signatures[i][64] -= 27 // Transform V from 27/28 to 0/1 according to the yellow paper for verification.
+		pubkey, err := crypto.Ecrecover(crypto.Keccak256(data), signatures[i])
+		if err != nil {
+			return false, nil
+		}
+		var signer common.Address
+		copy(signer[:], crypto.Keccak256(pubkey[1:])[12:])
+		if _, exist := checked[signer]; exist {
+			continue
+		}
+		for _, s := range reg.config.Signers {
+			if s == signer {
+				signers = append(signers, signer)
+				checked[signer] = struct{}{}
+			}
+		}
+	}
+	threshold := reg.config.Threshold
+	if uint64(len(signers)) < threshold {
+		log.Warn("Not enough signers to approve checkpoint", "signers", len(signers), "threshold", threshold)
+		return false, nil
+	}
+	return true, signers
+}
--- a/les/commons.go
+++ b/les/commons.go
@@ -76,24 +76,6 @@ func (c *lesCommons) makeProtocols(versions []uint) []p2p.Protocol {

 // nodeInfo retrieves some protocol metadata about the running host node.
 func (c *lesCommons) nodeInfo() interface{} {
-	var cht params.TrustedCheckpoint
-	sections, _, _ := c.chtIndexer.Sections()
-	sections2, _, _ := c.bloomTrieIndexer.Sections()
-
-	if sections2 < sections {
-		sections = sections2
-	}
-	if sections > 0 {
-		sectionIndex := sections - 1
-		sectionHead := c.bloomTrieIndexer.SectionHead(sectionIndex)
-		cht = params.TrustedCheckpoint{
-			SectionIndex: sectionIndex,
-			SectionHead:  sectionHead,
-			CHTRoot:      light.GetChtRoot(c.chainDb, sectionIndex, sectionHead),
-			BloomRoot:    light.GetBloomTrieRoot(c.chainDb, sectionIndex, sectionHead),
-		}
-	}
-
 	chain := c.protocolManager.blockchain
 	head := chain.CurrentHeader()
 	hash := head.Hash()
@@ -103,6 +85,38 @@ func (c *lesCommons) nodeInfo() interface{} {
 		Genesis:    chain.Genesis().Hash(),
 		Config:     chain.Config(),
 		Head:       chain.CurrentHeader().Hash(),
-		CHT:        cht,
+		CHT:        c.latestLocalCheckpoint(),
+	}
+}
+
+// latestLocalCheckpoint finds the common stored section index and returns a set of
+// post-processed trie roots (CHT and BloomTrie) associated with
+// the appropriate section index and head hash as a local checkpoint package.
+func (c *lesCommons) latestLocalCheckpoint() params.TrustedCheckpoint {
+	sections, _, _ := c.chtIndexer.Sections()
+	sections2, _, _ := c.bloomTrieIndexer.Sections()
+	// Cap the section index if the two sections are not consistent.
+	if sections > sections2 {
+		sections = sections2
+	}
+	if sections == 0 {
+		// No checkpoint information can be provided.
+		return params.TrustedCheckpoint{}
+	}
+	return c.getLocalCheckpoint(sections - 1)
+}
+
+// getLocalCheckpoint returns a set of post-processed trie roots (CHT and BloomTrie)
+// associated with the appropriate head hash by specific section index.
+//
+// The returned checkpoint is only the checkpoint generated by the local indexers,
+// not the stable checkpoint registered in the registrar contract.
+func (c *lesCommons) getLocalCheckpoint(index uint64) params.TrustedCheckpoint {
+	sectionHead := c.chtIndexer.SectionHead(index)
+	return params.TrustedCheckpoint{
+		SectionIndex: index,
+		SectionHead:  sectionHead,
+		CHTRoot:      light.GetChtRoot(c.chainDb, index, sectionHead),
+		BloomRoot:    light.GetBloomTrieRoot(c.chainDb, index, sectionHead),
 	}
 }
--- a/les/handler.go
+++ b/les/handler.go
@@ -27,7 +27,6 @@ import (
 	"time"

 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/consensus"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state"
@@ -101,7 +100,7 @@ type ProtocolManager struct {
 	networkId uint64 // The identity of network.

 	txpool       txPool
-	txrelay      *LesTxRelay
+	txrelay      *lesTxRelay
 	blockchain   BlockChain
 	chainDb      ethdb.Database
 	odr          *LesOdr
@@ -115,6 +114,8 @@ type ProtocolManager struct {
 	fetcher      *lightFetcher
 	ulc          *ulc
 	peers        *peerSet
+	checkpoint   *params.TrustedCheckpoint
+	reg          *checkpointOracle // If reg == nil, it means the checkpoint registrar is not activated

 	// channels for fetcher, syncer, txsyncLoop
 	newPeerCh   chan *peer
@@ -131,23 +132,7 @@ type ProtocolManager struct {

 // NewProtocolManager returns a new ethereum sub protocol manager. The Ethereum sub protocol manages peers capable
 // with the ethereum network.
-func NewProtocolManager(
-	chainConfig *params.ChainConfig,
-	indexerConfig *light.IndexerConfig,
-	client bool,
-	networkId uint64,
-	mux *event.TypeMux,
-	engine consensus.Engine,
-	peers *peerSet,
-	blockchain BlockChain,
-	txpool txPool,
-	chainDb ethdb.Database,
-	odr *LesOdr,
-	txrelay *LesTxRelay,
-	serverPool *serverPool,
-	quitSync chan struct{},
-	wg *sync.WaitGroup,
-	ulcConfig *eth.ULCConfig, synced func() bool) (*ProtocolManager, error) {
+func NewProtocolManager(chainConfig *params.ChainConfig, checkpoint *params.TrustedCheckpoint, indexerConfig *light.IndexerConfig, ulcConfig *eth.ULCConfig, client bool, networkId uint64, mux *event.TypeMux, peers *peerSet, blockchain BlockChain, txpool txPool, chainDb ethdb.Database, odr *LesOdr, serverPool *serverPool, registrar *checkpointOracle, quitSync chan struct{}, wg *sync.WaitGroup, synced func() bool) (*ProtocolManager, error) {
 	// Create the protocol manager with the base fields
 	manager := &ProtocolManager{
 		client:      client,
@@ -159,13 +144,14 @@ func NewProtocolManager(
 		odr:         odr,
 		networkId:   networkId,
 		txpool:      txpool,
-		txrelay:     txrelay,
 		serverPool:  serverPool,
+		reg:         registrar,
 		peers:       peers,
 		newPeerCh:   make(chan *peer),
 		quitSync:    quitSync,
 		wg:          wg,
 		noMorePeers: make(chan struct{}),
+		checkpoint:  checkpoint,
 		synced:      synced,
 	}
 	if odr != nil {
@@ -182,11 +168,11 @@ func NewProtocolManager(
 		removePeer = func(id string) {}
 	}
 	if client {
-		var checkpoint uint64
-		if cht, ok := params.TrustedCheckpoints[blockchain.Genesis().Hash()]; ok {
-			checkpoint = (cht.SectionIndex+1)*params.CHTFrequency - 1
+		var checkpointNumber uint64
+		if checkpoint != nil {
+			checkpointNumber = (checkpoint.SectionIndex+1)*params.CHTFrequency - 1
 		}
-		manager.downloader = downloader.New(checkpoint, chainDb, nil, manager.eventMux, nil, blockchain, removePeer)
+		manager.downloader = downloader.New(checkpointNumber, chainDb, nil, manager.eventMux, nil, blockchain, removePeer)
 		manager.peers.notify((*downloaderPeerNotify)(manager))
 		manager.fetcher = newLightFetcher(manager)
 	}
--- a/les/handler_test.go
+++ b/les/handler_test.go
@@ -259,7 +259,6 @@ func testGetCode(t *testing.T, protocol int) {

 	var codereqs []*CodeReq
 	var codes [][]byte
-
 	for i := uint64(0); i <= bc.CurrentBlock().NumberU64(); i++ {
 		header := bc.GetHeaderByNumber(i)
 		req := &CodeReq{
@@ -342,11 +341,10 @@ func testGetProofs(t *testing.T, protocol int) {
 	var proofreqs []ProofReq
 	proofsV2 := light.NewNodeSet()

-	accounts := []common.Address{testBankAddress, acc1Addr, acc2Addr, {}}
+	accounts := []common.Address{bankAddr, userAddr1, userAddr2, {}}
 	for i := uint64(0); i <= bc.CurrentBlock().NumberU64(); i++ {
 		header := bc.GetHeaderByNumber(i)
-		root := header.Root
-		trie, _ := trie.New(root, trie.NewDatabase(server.db))
+		trie, _ := trie.New(header.Root, trie.NewDatabase(server.db))

 		for _, acc := range accounts {
 			req := ProofReq{
@@ -377,7 +375,7 @@ func testGetStaleProof(t *testing.T, protocol int) {
 	check := func(number uint64, wantOK bool) {
 		var (
 			header  = bc.GetHeaderByNumber(number)
-			account = crypto.Keccak256(testBankAddress.Bytes())
+			account = crypto.Keccak256(userAddr1.Bytes())
 		)
 		req := &ProofReq{
 			BHash: header.Hash(),
@@ -390,7 +388,7 @@ func testGetStaleProof(t *testing.T, protocol int) {
 		if wantOK {
 			proofsV2 := light.NewNodeSet()
 			t, _ := trie.New(header.Root, trie.NewDatabase(server.db))
-			t.Prove(crypto.Keccak256(account), 0, proofsV2)
+			t.Prove(account, 0, proofsV2)
 			expected = proofsV2.NodeList()
 		}
 		if err := expectResponse(server.tPeer.app, ProofsV2Msg, 42, testBufLimit, expected); err != nil {
@@ -496,14 +494,15 @@ func TestGetBloombitsProofs(t *testing.T) {
 }

 func TestTransactionStatusLes2(t *testing.T) {
-	db := rawdb.NewMemoryDatabase()
-	pm := newTestProtocolManagerMust(t, false, 0, nil, nil, nil, db, nil)
-	chain := pm.blockchain.(*core.BlockChain)
+	server, tearDown := newServerEnv(t, 0, 2, nil)
+	defer tearDown()
+
+	chain := server.pm.blockchain.(*core.BlockChain)
 	config := core.DefaultTxPoolConfig
 	config.Journal = ""
 	txpool := core.NewTxPool(config, params.TestChainConfig, chain)
-	pm.txpool = txpool
-	peer, _ := newTestPeer(t, "peer", 2, pm, true, 0)
+	server.pm.txpool = txpool
+	peer, _ := newTestPeer(t, "peer", 2, server.pm, true, 0)
 	defer peer.close()

 	var reqID uint64
@@ -511,13 +510,13 @@ func TestTransactionStatusLes2(t *testing.T) {
 	test := func(tx *types.Transaction, send bool, expStatus light.TxStatus) {
 		reqID++
 		if send {
-			cost := peer.GetRequestCost(SendTxV2Msg, 1)
-			sendRequest(peer.app, SendTxV2Msg, reqID, cost, types.Transactions{tx})
+			cost := server.tPeer.GetRequestCost(SendTxV2Msg, 1)
+			sendRequest(server.tPeer.app, SendTxV2Msg, reqID, cost, types.Transactions{tx})
 		} else {
-			cost := peer.GetRequestCost(GetTxStatusMsg, 1)
-			sendRequest(peer.app, GetTxStatusMsg, reqID, cost, []common.Hash{tx.Hash()})
+			cost := server.tPeer.GetRequestCost(GetTxStatusMsg, 1)
+			sendRequest(server.tPeer.app, GetTxStatusMsg, reqID, cost, []common.Hash{tx.Hash()})
 		}
-		if err := expectResponse(peer.app, TxStatusMsg, reqID, testBufLimit, []light.TxStatus{expStatus}); err != nil {
+		if err := expectResponse(server.tPeer.app, TxStatusMsg, reqID, testBufLimit, []light.TxStatus{expStatus}); err != nil {
 			t.Errorf("transaction status mismatch")
 		}
 	}
@@ -525,16 +524,16 @@ func TestTransactionStatusLes2(t *testing.T) {
 	signer := types.HomesteadSigner{}

 	// test error status by sending an underpriced transaction
-	tx0, _ := types.SignTx(types.NewTransaction(0, acc1Addr, big.NewInt(10000), params.TxGas, nil, nil), signer, testBankKey)
+	tx0, _ := types.SignTx(types.NewTransaction(0, userAddr1, big.NewInt(10000), params.TxGas, nil, nil), signer, bankKey)
 	test(tx0, true, light.TxStatus{Status: core.TxStatusUnknown, Error: core.ErrUnderpriced.Error()})

-	tx1, _ := types.SignTx(types.NewTransaction(0, acc1Addr, big.NewInt(10000), params.TxGas, big.NewInt(100000000000), nil), signer, testBankKey)
+	tx1, _ := types.SignTx(types.NewTransaction(0, userAddr1, big.NewInt(10000), params.TxGas, big.NewInt(100000000000), nil), signer, bankKey)
 	test(tx1, false, light.TxStatus{Status: core.TxStatusUnknown}) // query before sending, should be unknown
 	test(tx1, true, light.TxStatus{Status: core.TxStatusPending})  // send valid processable tx, should return pending
 	test(tx1, true, light.TxStatus{Status: core.TxStatusPending})  // adding it again should not return an error

-	tx2, _ := types.SignTx(types.NewTransaction(1, acc1Addr, big.NewInt(10000), params.TxGas, big.NewInt(100000000000), nil), signer, testBankKey)
-	tx3, _ := types.SignTx(types.NewTransaction(2, acc1Addr, big.NewInt(10000), params.TxGas, big.NewInt(100000000000), nil), signer, testBankKey)
+	tx2, _ := types.SignTx(types.NewTransaction(1, userAddr1, big.NewInt(10000), params.TxGas, big.NewInt(100000000000), nil), signer, bankKey)
+	tx3, _ := types.SignTx(types.NewTransaction(2, userAddr1, big.NewInt(10000), params.TxGas, big.NewInt(100000000000), nil), signer, bankKey)
 	// send transactions in the wrong order, tx3 should be queued
 	test(tx3, true, light.TxStatus{Status: core.TxStatusQueued})
 	test(tx2, true, light.TxStatus{Status: core.TxStatusPending})
@@ -542,7 +541,7 @@ func TestTransactionStatusLes2(t *testing.T) {
 	test(tx3, false, light.TxStatus{Status: core.TxStatusPending})

 	// generate and add a block with tx1 and tx2 included
-	gchain, _ := core.GenerateChain(params.TestChainConfig, chain.GetBlockByNumber(0), ethash.NewFaker(), db, 1, func(i int, block *core.BlockGen) {
+	gchain, _ := core.GenerateChain(params.TestChainConfig, chain.GetBlockByNumber(0), ethash.NewFaker(), server.db, 1, func(i int, block *core.BlockGen) {
 		block.AddTx(tx1)
 		block.AddTx(tx2)
 	})
@@ -561,12 +560,12 @@ func TestTransactionStatusLes2(t *testing.T) {
 	}

 	// check if their status is included now
-	block1hash := rawdb.ReadCanonicalHash(db, 1)
+	block1hash := rawdb.ReadCanonicalHash(server.db, 1)
 	test(tx1, false, light.TxStatus{Status: core.TxStatusIncluded, Lookup: &rawdb.LegacyTxLookupEntry{BlockHash: block1hash, BlockIndex: 1, Index: 0}})
 	test(tx2, false, light.TxStatus{Status: core.TxStatusIncluded, Lookup: &rawdb.LegacyTxLookupEntry{BlockHash: block1hash, BlockIndex: 1, Index: 1}})

 	// create a reorg that rolls them back
-	gchain, _ = core.GenerateChain(params.TestChainConfig, chain.GetBlockByNumber(0), ethash.NewFaker(), db, 2, func(i int, block *core.BlockGen) {})
+	gchain, _ = core.GenerateChain(params.TestChainConfig, chain.GetBlockByNumber(0), ethash.NewFaker(), server.db, 2, func(i int, block *core.BlockGen) {})
 	if _, err := chain.InsertChain(gchain); err != nil {
 		panic(err)
 	}
@@ -589,7 +588,7 @@ func TestStopResumeLes3(t *testing.T) {
 	db := rawdb.NewMemoryDatabase()
 	clock := &mclock.Simulated{}
 	testCost := testBufLimit / 10
-	pm, err := newTestProtocolManager(false, 0, nil, nil, nil, db, nil, testCost, clock)
+	pm, _, err := newTestProtocolManager(false, 0, nil, nil, nil, db, nil, testCost, clock)
 	if err != nil {
 		t.Fatalf("Failed to create protocol manager: %v", err)
 	}
--- a/les/helper_test.go
+++ b/les/helper_test.go
@@ -20,19 +20,22 @@
 package les

 import (
+	"context"
 	"crypto/rand"
 	"math/big"
 	"sync"
 	"testing"
 	"time"

+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/accounts/abi/bind/backends"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/mclock"
 	"github.com/ethereum/go-ethereum/consensus/ethash"
+	"github.com/ethereum/go-ethereum/contracts/checkpointoracle/contract"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -45,14 +48,14 @@ import (
 )

 var (
-	testBankKey, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-	testBankAddress = crypto.PubkeyToAddress(testBankKey.PublicKey)
-	testBankFunds   = big.NewInt(1000000000000000000)
+	bankKey, _ = crypto.GenerateKey()
+	bankAddr   = crypto.PubkeyToAddress(bankKey.PublicKey)
+	bankFunds  = big.NewInt(1000000000000000000)

-	acc1Key, _ = crypto.HexToECDSA("8a1f9a8f95be41cd7ccb6168179afb4504aefe388d1e14474d32c45c72ce7b7a")
-	acc2Key, _ = crypto.HexToECDSA("49a7b37aa6f6645917e7b807e9d1c00d4fa71f18343b0d4122a4d2df64dd6fee")
-	acc1Addr   = crypto.PubkeyToAddress(acc1Key.PublicKey)
-	acc2Addr   = crypto.PubkeyToAddress(acc2Key.PublicKey)
+	userKey1, _ = crypto.GenerateKey()
+	userKey2, _ = crypto.GenerateKey()
+	userAddr1   = crypto.PubkeyToAddress(userKey1.PublicKey)
+	userAddr2   = crypto.PubkeyToAddress(userKey2.PublicKey)

 	testContractCode         = common.Hex2Bytes("606060405260cc8060106000396000f360606040526000357c01000000000000000000000000000000000000000000000000000000009004806360cd2685146041578063c16431b914606b57603f565b005b6055600480803590602001909190505060a9565b6040518082815260200191505060405180910390f35b60886004808035906020019091908035906020019091905050608a565b005b80600060005083606481101560025790900160005b50819055505b5050565b6000600060005082606481101560025790900160005b5054905060c7565b91905056")
 	testContractAddr         common.Address
@@ -60,8 +63,21 @@ var (
 	testContractDeployed     = uint64(2)

 	testEventEmitterCode = common.Hex2Bytes("60606040523415600e57600080fd5b7f57050ab73f6b9ebdd9f76b8d4997793f48cf956e965ee070551b9ca0bb71584e60405160405180910390a160358060476000396000f3006060604052600080fd00a165627a7a723058203f727efcad8b5811f8cb1fc2620ce5e8c63570d697aef968172de296ea3994140029")
-	testEventEmitterAddr common.Address

+	// Checkpoint registrar relative
+	registrarAddr common.Address
+	signerKey, _  = crypto.GenerateKey()
+	signerAddr    = crypto.PubkeyToAddress(signerKey.PublicKey)
+)
+
+var (
+	// The block frequency for creating checkpoint(only used in test)
+	sectionSize = big.NewInt(512)
+
+	// The number of confirmations needed to generate a checkpoint(only used in test).
+	processConfirms = big.NewInt(4)
+
+	//
 	testBufLimit    = uint64(1000000)
 	testBufRecharge = uint64(1000)
 )
@@ -81,102 +97,139 @@ contract test {
 }
 */

-func testChainGen(i int, block *core.BlockGen) {
-	signer := types.HomesteadSigner{}
+// prepareTestchain pre-commits specified number customized blocks into chain.
+func prepareTestchain(n int, backend *backends.SimulatedBackend) {
+	var (
+		ctx    = context.Background()
+		signer = types.HomesteadSigner{}
+	)
+	for i := 0; i < n; i++ {
+		switch i {
+		case 0:
+			// deploy checkpoint contract
+			registrarAddr, _, _, _ = contract.DeployCheckpointOracle(bind.NewKeyedTransactor(bankKey), backend, []common.Address{signerAddr}, sectionSize, processConfirms, big.NewInt(1))
+			// bankUser transfers some ether to user1
+			nonce, _ := backend.PendingNonceAt(ctx, bankAddr)
+			tx, _ := types.SignTx(types.NewTransaction(nonce, userAddr1, big.NewInt(10000), params.TxGas, nil, nil), signer, bankKey)
+			backend.SendTransaction(ctx, tx)
+		case 1:
+			bankNonce, _ := backend.PendingNonceAt(ctx, bankAddr)
+			userNonce1, _ := backend.PendingNonceAt(ctx, userAddr1)

-	switch i {
-	case 0:
-		// In block 1, the test bank sends account #1 some ether.
-		tx, _ := types.SignTx(types.NewTransaction(block.TxNonce(testBankAddress), acc1Addr, big.NewInt(10000), params.TxGas, nil, nil), signer, testBankKey)
-		block.AddTx(tx)
-	case 1:
-		// In block 2, the test bank sends some more ether to account #1.
-		// acc1Addr passes it on to account #2.
-		// acc1Addr creates a test contract.
-		// acc1Addr creates a test event.
-		nonce := block.TxNonce(acc1Addr)
+			// bankUser transfers more ether to user1
+			tx1, _ := types.SignTx(types.NewTransaction(bankNonce, userAddr1, big.NewInt(1000), params.TxGas, nil, nil), signer, bankKey)
+			backend.SendTransaction(ctx, tx1)

-		tx1, _ := types.SignTx(types.NewTransaction(block.TxNonce(testBankAddress), acc1Addr, big.NewInt(1000), params.TxGas, nil, nil), signer, testBankKey)
-		tx2, _ := types.SignTx(types.NewTransaction(nonce, acc2Addr, big.NewInt(1000), params.TxGas, nil, nil), signer, acc1Key)
-		tx3, _ := types.SignTx(types.NewContractCreation(nonce+1, big.NewInt(0), 200000, big.NewInt(0), testContractCode), signer, acc1Key)
-		testContractAddr = crypto.CreateAddress(acc1Addr, nonce+1)
-		tx4, _ := types.SignTx(types.NewContractCreation(nonce+2, big.NewInt(0), 200000, big.NewInt(0), testEventEmitterCode), signer, acc1Key)
-		testEventEmitterAddr = crypto.CreateAddress(acc1Addr, nonce+2)
-		block.AddTx(tx1)
-		block.AddTx(tx2)
-		block.AddTx(tx3)
-		block.AddTx(tx4)
-	case 2:
-		// Block 3 is empty but was mined by account #2.
-		block.SetCoinbase(acc2Addr)
-		block.SetExtra([]byte("yeehaw"))
-		data := common.Hex2Bytes("C16431B900000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000001")
-		tx, _ := types.SignTx(types.NewTransaction(block.TxNonce(testBankAddress), testContractAddr, big.NewInt(0), 100000, nil, data), signer, testBankKey)
-		block.AddTx(tx)
-	case 3:
-		// Block 4 includes blocks 2 and 3 as uncle headers (with modified extra data).
-		b2 := block.PrevBlock(1).Header()
-		b2.Extra = []byte("foo")
-		block.AddUncle(b2)
-		b3 := block.PrevBlock(2).Header()
-		b3.Extra = []byte("foo")
-		block.AddUncle(b3)
-		data := common.Hex2Bytes("C16431B900000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000002")
-		tx, _ := types.SignTx(types.NewTransaction(block.TxNonce(testBankAddress), testContractAddr, big.NewInt(0), 100000, nil, data), signer, testBankKey)
-		block.AddTx(tx)
+			// user1 relays ether to user2
+			tx2, _ := types.SignTx(types.NewTransaction(userNonce1, userAddr2, big.NewInt(1000), params.TxGas, nil, nil), signer, userKey1)
+			backend.SendTransaction(ctx, tx2)
+
+			// user1 deploys a test contract
+			tx3, _ := types.SignTx(types.NewContractCreation(userNonce1+1, big.NewInt(0), 200000, big.NewInt(0), testContractCode), signer, userKey1)
+			backend.SendTransaction(ctx, tx3)
+			testContractAddr = crypto.CreateAddress(userAddr1, userNonce1+1)
+
+			// user1 deploys a event contract
+			tx4, _ := types.SignTx(types.NewContractCreation(userNonce1+2, big.NewInt(0), 200000, big.NewInt(0), testEventEmitterCode), signer, userKey1)
+			backend.SendTransaction(ctx, tx4)
+		case 2:
+			// bankUser transfer some ether to signer
+			bankNonce, _ := backend.PendingNonceAt(ctx, bankAddr)
+			tx1, _ := types.SignTx(types.NewTransaction(bankNonce, signerAddr, big.NewInt(1000000000), params.TxGas, nil, nil), signer, bankKey)
+			backend.SendTransaction(ctx, tx1)
+
+			// invoke test contract
+			data := common.Hex2Bytes("C16431B900000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000001")
+			tx2, _ := types.SignTx(types.NewTransaction(bankNonce+1, testContractAddr, big.NewInt(0), 100000, nil, data), signer, bankKey)
+			backend.SendTransaction(ctx, tx2)
+		case 3:
+			// invoke test contract
+			bankNonce, _ := backend.PendingNonceAt(ctx, bankAddr)
+			data := common.Hex2Bytes("C16431B900000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000002")
+			tx, _ := types.SignTx(types.NewTransaction(bankNonce, testContractAddr, big.NewInt(0), 100000, nil, data), signer, bankKey)
+			backend.SendTransaction(ctx, tx)
+		}
+		backend.Commit()
 	}
 }

 // testIndexers creates a set of indexers with specified params for testing purpose.
-func testIndexers(db ethdb.Database, odr light.OdrBackend, iConfig *light.IndexerConfig) (*core.ChainIndexer, *core.ChainIndexer, *core.ChainIndexer) {
-	chtIndexer := light.NewChtIndexer(db, odr, iConfig.ChtSize, iConfig.ChtConfirms)
-	bloomIndexer := eth.NewBloomIndexer(db, iConfig.BloomSize, iConfig.BloomConfirms)
-	bloomTrieIndexer := light.NewBloomTrieIndexer(db, odr, iConfig.BloomSize, iConfig.BloomTrieSize)
-	bloomIndexer.AddChildIndexer(bloomTrieIndexer)
-	return chtIndexer, bloomIndexer, bloomTrieIndexer
+func testIndexers(db ethdb.Database, odr light.OdrBackend, config *light.IndexerConfig) []*core.ChainIndexer {
+	var indexers [3]*core.ChainIndexer
+	indexers[0] = light.NewChtIndexer(db, odr, config.ChtSize, config.ChtConfirms)
+	indexers[1] = eth.NewBloomIndexer(db, config.BloomSize, config.BloomConfirms)
+	indexers[2] = light.NewBloomTrieIndexer(db, odr, config.BloomSize, config.BloomTrieSize)
+	// make bloomTrieIndexer as a child indexer of bloom indexer.
+	indexers[1].AddChildIndexer(indexers[2])
+	return indexers[:]
 }

 // newTestProtocolManager creates a new protocol manager for testing purposes,
 // with the given number of blocks already known, potential notification
 // channels for different events and relative chain indexers array.
-func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *core.BlockGen), odr *LesOdr, peers *peerSet, db ethdb.Database, ulcConfig *eth.ULCConfig, testCost uint64, clock mclock.Clock) (*ProtocolManager, error) {
+func newTestProtocolManager(lightSync bool, blocks int, odr *LesOdr, indexers []*core.ChainIndexer, peers *peerSet, db ethdb.Database, ulcConfig *eth.ULCConfig, testCost uint64, clock mclock.Clock) (*ProtocolManager, *backends.SimulatedBackend, error) {
 	var (
 		evmux  = new(event.TypeMux)
 		engine = ethash.NewFaker()
 		gspec  = core.Genesis{
-			Config: params.TestChainConfig,
-			Alloc:  core.GenesisAlloc{testBankAddress: {Balance: testBankFunds}},
+			Config: params.AllEthashProtocolChanges,
+			Alloc:  core.GenesisAlloc{bankAddr: {Balance: bankFunds}},
 		}
-		genesis = gspec.MustCommit(db)
-		chain   BlockChain
-		pool    txPool
+		pool   txPool
+		chain  BlockChain
+		exitCh = make(chan struct{})
 	)
+	gspec.MustCommit(db)
 	if peers == nil {
 		peers = newPeerSet()
 	}
+	// create a simulation backend and pre-commit several customized block to the database.
+	simulation := backends.NewSimulatedBackendWithDatabase(db, gspec.Alloc, 100000000)
+	prepareTestchain(blocks, simulation)

+	// initialize empty chain for light client or pre-committed chain for server.
 	if lightSync {
-		chain, _ = light.NewLightChain(odr, gspec.Config, engine)
+		chain, _ = light.NewLightChain(odr, gspec.Config, engine, nil)
 	} else {
-		blockchain, _ := core.NewBlockChain(db, nil, gspec.Config, engine, vm.Config{}, nil)
-		gchain, _ := core.GenerateChain(gspec.Config, genesis, ethash.NewFaker(), db, blocks, generator)
-		if _, err := blockchain.InsertChain(gchain); err != nil {
-			panic(err)
-		}
-		chain = blockchain
-		pool = core.NewTxPool(core.DefaultTxPoolConfig, gspec.Config, blockchain)
+		chain = simulation.Blockchain()
+		pool = core.NewTxPool(core.DefaultTxPoolConfig, gspec.Config, simulation.Blockchain())
 	}

+	// Create contract registrar
 	indexConfig := light.TestServerIndexerConfig
 	if lightSync {
 		indexConfig = light.TestClientIndexerConfig
 	}
-	pm, err := NewProtocolManager(gspec.Config, indexConfig, lightSync, NetworkId, evmux, engine, peers, chain, pool, db, odr, nil, nil, make(chan struct{}), new(sync.WaitGroup), ulcConfig, func() bool { return true })
-	if err != nil {
-		return nil, err
+	config := &params.CheckpointOracleConfig{
+		Address:   crypto.CreateAddress(bankAddr, 0),
+		Signers:   []common.Address{signerAddr},
+		Threshold: 1,
 	}
+	var reg *checkpointOracle
+	if indexers != nil {
+		getLocal := func(index uint64) params.TrustedCheckpoint {
+			chtIndexer := indexers[0]
+			sectionHead := chtIndexer.SectionHead(index)
+			return params.TrustedCheckpoint{
+				SectionIndex: index,
+				SectionHead:  sectionHead,
+				CHTRoot:      light.GetChtRoot(db, index, sectionHead),
+				BloomRoot:    light.GetBloomTrieRoot(db, index, sectionHead),
+			}
+		}
+		reg = newCheckpointOracle(config, getLocal)
+	}
+	pm, err := NewProtocolManager(gspec.Config, nil, indexConfig, ulcConfig, lightSync, NetworkId, evmux, peers, chain, pool, db, odr, nil, reg, exitCh, new(sync.WaitGroup), func() bool { return true })
+	if err != nil {
+		return nil, nil, err
+	}
+	// Registrar initialization could failed if checkpoint contract is not specified.
+	if pm.reg != nil {
+		pm.reg.start(simulation)
+	}
+	// Set up les server stuff.
 	if !lightSync {
-		srv := &LesServer{lesCommons: lesCommons{protocolManager: pm}}
+		srv := &LesServer{lesCommons: lesCommons{protocolManager: pm, chainDb: db}}
 		pm.server = srv
 		pm.servingQueue = newServingQueue(int64(time.Millisecond*10), 1, nil)
 		pm.servingQueue.setThreads(4)
@@ -189,19 +242,19 @@ func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *cor
 		srv.fcManager = flowcontrol.NewClientManager(nil, clock)
 	}
 	pm.Start(1000)
-	return pm, nil
+	return pm, simulation, nil
 }

 // newTestProtocolManagerMust creates a new protocol manager for testing purposes,
-// with the given number of blocks already known, potential notification
-// channels for different events and relative chain indexers array. In case of an error, the constructor force-
-// fails the test.
-func newTestProtocolManagerMust(t *testing.T, lightSync bool, blocks int, generator func(int, *core.BlockGen), odr *LesOdr, peers *peerSet, db ethdb.Database, ulcConfig *eth.ULCConfig) *ProtocolManager {
-	pm, err := newTestProtocolManager(lightSync, blocks, generator, odr, peers, db, ulcConfig, 0, &mclock.System{})
+// with the given number of blocks already known, potential notification channels
+// for different events and relative chain indexers array. In case of an error, the
+// constructor force-fails the test.
+func newTestProtocolManagerMust(t *testing.T, lightSync bool, blocks int, odr *LesOdr, indexers []*core.ChainIndexer, peers *peerSet, db ethdb.Database, ulcConfig *eth.ULCConfig) (*ProtocolManager, *backends.SimulatedBackend) {
+	pm, backend, err := newTestProtocolManager(lightSync, blocks, odr, indexers, peers, db, ulcConfig, 0, &mclock.System{})
 	if err != nil {
 		t.Fatalf("Failed to create protocol manager: %v", err)
 	}
-	return pm
+	return pm, backend
 }

 // testPeer is a simulated peer to allow testing direct network calls.
@@ -324,11 +377,13 @@ func (p *testPeer) close() {

 // TestEntity represents a network entity for testing with necessary auxiliary fields.
 type TestEntity struct {
-	db    ethdb.Database
-	rPeer *peer
-	tPeer *testPeer
-	peers *peerSet
-	pm    *ProtocolManager
+	db      ethdb.Database
+	rPeer   *peer
+	tPeer   *testPeer
+	peers   *peerSet
+	pm      *ProtocolManager
+	backend *backends.SimulatedBackend
+
 	// Indexers
 	chtIndexer       *core.ChainIndexer
 	bloomIndexer     *core.ChainIndexer
@@ -338,11 +393,12 @@ type TestEntity struct {
 // newServerEnv creates a server testing environment with a connected test peer for testing purpose.
 func newServerEnv(t *testing.T, blocks int, protocol int, waitIndexers func(*core.ChainIndexer, *core.ChainIndexer, *core.ChainIndexer)) (*TestEntity, func()) {
 	db := rawdb.NewMemoryDatabase()
-	cIndexer, bIndexer, btIndexer := testIndexers(db, nil, light.TestServerIndexerConfig)
+	indexers := testIndexers(db, nil, light.TestServerIndexerConfig)

-	pm := newTestProtocolManagerMust(t, false, blocks, testChainGen, nil, nil, db, nil)
+	pm, b := newTestProtocolManagerMust(t, false, blocks, nil, indexers, nil, db, nil)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true, 0)

+	cIndexer, bIndexer, btIndexer := indexers[0], indexers[1], indexers[2]
 	cIndexer.Start(pm.blockchain.(*core.BlockChain))
 	bIndexer.Start(pm.blockchain.(*core.BlockChain))

@@ -355,6 +411,7 @@ func newServerEnv(t *testing.T, blocks int, protocol int, waitIndexers func(*cor
 			db:               db,
 			tPeer:            peer,
 			pm:               pm,
+			backend:          b,
 			chtIndexer:       cIndexer,
 			bloomIndexer:     bIndexer,
 			bloomTrieIndexer: btIndexer,
@@ -376,12 +433,16 @@ func newClientServerEnv(t *testing.T, blocks int, protocol int, waitIndexers fun
 	rm := newRetrieveManager(lPeers, dist, nil)
 	odr := NewLesOdr(ldb, light.TestClientIndexerConfig, rm)

-	cIndexer, bIndexer, btIndexer := testIndexers(db, nil, light.TestServerIndexerConfig)
-	lcIndexer, lbIndexer, lbtIndexer := testIndexers(ldb, odr, light.TestClientIndexerConfig)
+	indexers := testIndexers(db, nil, light.TestServerIndexerConfig)
+	lIndexers := testIndexers(ldb, odr, light.TestClientIndexerConfig)
+
+	cIndexer, bIndexer, btIndexer := indexers[0], indexers[1], indexers[2]
+	lcIndexer, lbIndexer, lbtIndexer := lIndexers[0], lIndexers[1], lIndexers[2]
+
 	odr.SetIndexers(lcIndexer, lbtIndexer, lbIndexer)

-	pm := newTestProtocolManagerMust(t, false, blocks, testChainGen, nil, peers, db, nil)
-	lpm := newTestProtocolManagerMust(t, true, 0, nil, odr, lPeers, ldb, nil)
+	pm, b := newTestProtocolManagerMust(t, false, blocks, nil, indexers, peers, db, nil)
+	lpm, lb := newTestProtocolManagerMust(t, true, 0, odr, lIndexers, lPeers, ldb, nil)

 	startIndexers := func(clientMode bool, pm *ProtocolManager) {
 		if clientMode {
@@ -421,6 +482,7 @@ func newClientServerEnv(t *testing.T, blocks int, protocol int, waitIndexers fun
 			pm:               pm,
 			rPeer:            peer,
 			peers:            peers,
+			backend:          b,
 			chtIndexer:       cIndexer,
 			bloomIndexer:     bIndexer,
 			bloomTrieIndexer: btIndexer,
@@ -429,6 +491,7 @@ func newClientServerEnv(t *testing.T, blocks int, protocol int, waitIndexers fun
 			pm:               lpm,
 			rPeer:            lPeer,
 			peers:            lPeers,
+			backend:          lb,
 			chtIndexer:       lcIndexer,
 			bloomIndexer:     lbIndexer,
 			bloomTrieIndexer: lbtIndexer,
--- a/les/odr_requests.go
+++ b/les/odr_requests.go
@@ -166,11 +166,13 @@ func (r *ReceiptsRequest) Validate(db ethdb.Database, msg *Msg) error {
 	receipt := receipts[0]

 	// Retrieve our stored header and validate receipt content against it
-	header := rawdb.ReadHeader(db, r.Hash, r.Number)
-	if header == nil {
+	if r.Header == nil {
+		r.Header = rawdb.ReadHeader(db, r.Hash, r.Number)
+	}
+	if r.Header == nil {
 		return errHeaderUnavailable
 	}
-	if header.ReceiptHash != types.DeriveSha(receipt) {
+	if r.Header.ReceiptHash != types.DeriveSha(receipt) {
 		return errReceiptHashMismatch
 	}
 	// Validations passed, store and return
@@ -323,7 +325,11 @@ func (r *ChtRequest) CanSend(peer *peer) bool {
 	peer.lock.RLock()
 	defer peer.lock.RUnlock()

-	return peer.headInfo.Number >= r.Config.ChtConfirms && r.ChtNum <= (peer.headInfo.Number-r.Config.ChtConfirms)/r.Config.ChtSize
+	if r.Untrusted {
+		return peer.headInfo.Number >= r.BlockNum && peer.id == r.PeerId
+	} else {
+		return peer.headInfo.Number >= r.Config.ChtConfirms && r.ChtNum <= (peer.headInfo.Number-r.Config.ChtConfirms)/r.Config.ChtSize
+	}
 }

 // Request sends an ODR request to the LES network (implementation of LesOdrRequest)
@@ -364,32 +370,37 @@ func (r *ChtRequest) Validate(db ethdb.Database, msg *Msg) error {
 	}

 	// Verify the CHT
-	var encNumber [8]byte
-	binary.BigEndian.PutUint64(encNumber[:], r.BlockNum)
-
-	reads := &readTraceDB{db: nodeSet}
-	value, _, err := trie.VerifyProof(r.ChtRoot, encNumber[:], reads)
-	if err != nil {
-		return fmt.Errorf("merkle proof verification failed: %v", err)
-	}
-	if len(reads.reads) != nodeSet.KeyCount() {
-		return errUselessNodes
-	}
-
+	// Note: For untrusted CHT request, there is no proof response but
+	// header data.
 	var node light.ChtNode
-	if err := rlp.DecodeBytes(value, &node); err != nil {
-		return err
-	}
-	if node.Hash != header.Hash() {
-		return errCHTHashMismatch
-	}
-	if r.BlockNum != header.Number.Uint64() {
-		return errCHTNumberMismatch
+	if !r.Untrusted {
+		var encNumber [8]byte
+		binary.BigEndian.PutUint64(encNumber[:], r.BlockNum)
+
+		reads := &readTraceDB{db: nodeSet}
+		value, _, err := trie.VerifyProof(r.ChtRoot, encNumber[:], reads)
+		if err != nil {
+			return fmt.Errorf("merkle proof verification failed: %v", err)
+		}
+		if len(reads.reads) != nodeSet.KeyCount() {
+			return errUselessNodes
+		}
+
+		if err := rlp.DecodeBytes(value, &node); err != nil {
+			return err
+		}
+		if node.Hash != header.Hash() {
+			return errCHTHashMismatch
+		}
+		if r.BlockNum != header.Number.Uint64() {
+			return errCHTNumberMismatch
+		}
 	}
 	// Verifications passed, store and return
 	r.Header = header
 	r.Proof = nodeSet
-	r.Td = node.Td
+	r.Td = node.Td // For untrusted request, td here is nil, todo improve the les/2 protocol
+
 	return nil
 }

--- a/les/odr_test.go
+++ b/les/odr_test.go
@@ -78,7 +78,7 @@ func TestOdrAccountsLes2(t *testing.T) { testOdr(t, 2, 1, true, odrAccounts) }

 func odrAccounts(ctx context.Context, db ethdb.Database, config *params.ChainConfig, bc *core.BlockChain, lc *light.LightChain, bhash common.Hash) []byte {
 	dummyAddr := common.HexToAddress("1234567812345678123456781234567812345678")
-	acc := []common.Address{testBankAddress, acc1Addr, acc2Addr, dummyAddr}
+	acc := []common.Address{bankAddr, userAddr1, userAddr2, dummyAddr}

 	var (
 		res []byte
@@ -121,7 +121,7 @@ func odrContractCall(ctx context.Context, db ethdb.Database, config *params.Chai
 			statedb, err := state.New(header.Root, state.NewDatabase(db))

 			if err == nil {
-				from := statedb.GetOrNewStateObject(testBankAddress)
+				from := statedb.GetOrNewStateObject(bankAddr)
 				from.SetBalance(math.MaxBig256)

 				msg := callmsg{types.NewMessage(from.Address(), &testContractAddr, 0, new(big.Int), 100000, new(big.Int), data, false)}
@@ -137,8 +137,8 @@ func odrContractCall(ctx context.Context, db ethdb.Database, config *params.Chai
 		} else {
 			header := lc.GetHeaderByHash(bhash)
 			state := light.NewState(ctx, header, lc.Odr())
-			state.SetBalance(testBankAddress, math.MaxBig256)
-			msg := callmsg{types.NewMessage(testBankAddress, &testContractAddr, 0, new(big.Int), 100000, new(big.Int), data, false)}
+			state.SetBalance(bankAddr, math.MaxBig256)
+			msg := callmsg{types.NewMessage(bankAddr, &testContractAddr, 0, new(big.Int), 100000, new(big.Int), data, false)}
 			context := core.NewEVMContext(msg, header, lc, nil)
 			vmenv := vm.NewEVM(context, state, config, vm.Config{})
 			gp := new(core.GasPool).AddGas(math.MaxUint64)
--- a/les/peer.go
+++ b/les/peer.go
@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/les/flowcontrol"
 	"github.com/ethereum/go-ethereum/light"
 	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 )

@@ -79,6 +80,10 @@ type peer struct {

 	announceType uint64

+	// Checkpoint relative fields
+	checkpoint       params.TrustedCheckpoint
+	checkpointNumber uint64
+
 	id string

 	headInfo *announceData
@@ -575,6 +580,14 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, headNum uint64, genesis
 		send = send.add("flowControl/MRC", costList)
 		p.fcCosts = costList.decode(ProtocolLengths[uint(p.version)])
 		p.fcParams = server.defParams
+
+		if server.protocolManager != nil && server.protocolManager.reg != nil && server.protocolManager.reg.isRunning() {
+			cp, height := server.protocolManager.reg.stableCheckpoint()
+			if cp != nil {
+				send = send.add("checkpoint/value", cp)
+				send = send.add("checkpoint/registerHeight", height)
+			}
+		}
 	} else {
 		//on client node
 		p.announceType = announceTypeSimple
@@ -658,20 +671,24 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, headNum uint64, genesis
 			return errResp(ErrUselessPeer, "peer cannot serve requests")
 		}

-		var params flowcontrol.ServerParams
-		if err := recv.get("flowControl/BL", &params.BufLimit); err != nil {
+		var sParams flowcontrol.ServerParams
+		if err := recv.get("flowControl/BL", &sParams.BufLimit); err != nil {
 			return err
 		}
-		if err := recv.get("flowControl/MRR", &params.MinRecharge); err != nil {
+		if err := recv.get("flowControl/MRR", &sParams.MinRecharge); err != nil {
 			return err
 		}
 		var MRC RequestCostList
 		if err := recv.get("flowControl/MRC", &MRC); err != nil {
 			return err
 		}
-		p.fcParams = params
-		p.fcServer = flowcontrol.NewServerNode(params, &mclock.System{})
+		p.fcParams = sParams
+		p.fcServer = flowcontrol.NewServerNode(sParams, &mclock.System{})
 		p.fcCosts = MRC.decode(ProtocolLengths[uint(p.version)])
+
+		recv.get("checkpoint/value", &p.checkpoint)
+		recv.get("checkpoint/registerHeight", &p.checkpointNumber)
+
 		if !p.isOnlyAnnounce {
 			for msgCode := range reqAvgTimeCost {
 				if p.fcCosts[msgCode] == nil {
--- a/les/request_test.go
+++ b/les/request_test.go
@@ -28,7 +28,7 @@ import (
 	"github.com/ethereum/go-ethereum/light"
 )

-var testBankSecureTrieKey = secAddr(testBankAddress)
+var testBankSecureTrieKey = secAddr(bankAddr)

 func secAddr(addr common.Address) []byte {
 	return crypto.Keccak256(addr[:])
--- a/les/server.go
+++ b/les/server.go
@@ -21,6 +21,7 @@ import (
 	"sync"
 	"time"

+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/mclock"
 	"github.com/ethereum/go-ethereum/core"
@@ -72,68 +73,38 @@ type LesServer struct {
 	priorityClientPool         *priorityClientPool
 }

-func NewLesServer(eth *eth.Ethereum, config *eth.Config) (*LesServer, error) {
+func NewLesServer(e *eth.Ethereum, config *eth.Config) (*LesServer, error) {
 	var csvLogger *csvlogger.Logger
 	if logFileName != "" {
 		csvLogger = csvlogger.NewLogger(logFileName, time.Second*10, "event, peerId")
 	}
-
-	quitSync := make(chan struct{})
-	pm, err := NewProtocolManager(
-		eth.BlockChain().Config(),
-		light.DefaultServerIndexerConfig,
-		false,
-		config.NetworkId,
-		eth.EventMux(),
-		eth.Engine(),
-		newPeerSet(),
-		eth.BlockChain(),
-		eth.TxPool(),
-		eth.ChainDb(),
-		nil,
-		nil,
-		nil,
-		quitSync,
-		new(sync.WaitGroup),
-		config.ULC,
-		eth.Synced)
-	if err != nil {
-		return nil, err
-	}
-	if logProtocolHandler {
-		pm.logger = csvLogger
-	}
 	requestLogger := csvLogger
 	if !logRequestServing {
 		requestLogger = nil
 	}
-	pm.servingQueue = newServingQueue(int64(time.Millisecond*10), float64(config.LightServ)/100, requestLogger)
-
 	lesTopics := make([]discv5.Topic, len(AdvertiseProtocolVersions))
 	for i, pv := range AdvertiseProtocolVersions {
-		lesTopics[i] = lesTopic(eth.BlockChain().Genesis().Hash(), pv)
+		lesTopics[i] = lesTopic(e.BlockChain().Genesis().Hash(), pv)
 	}
-
+	quitSync := make(chan struct{})
 	srv := &LesServer{
 		lesCommons: lesCommons{
 			config:           config,
-			chainDb:          eth.ChainDb(),
 			iConfig:          light.DefaultServerIndexerConfig,
-			chtIndexer:       light.NewChtIndexer(eth.ChainDb(), nil, params.CHTFrequency, params.HelperTrieProcessConfirmations),
-			bloomTrieIndexer: light.NewBloomTrieIndexer(eth.ChainDb(), nil, params.BloomBitsBlocks, params.BloomTrieFrequency),
-			protocolManager:  pm,
+			chainDb:          e.ChainDb(),
+			chtIndexer:       light.NewChtIndexer(e.ChainDb(), nil, params.CHTFrequency, params.HelperTrieProcessConfirmations),
+			bloomTrieIndexer: light.NewBloomTrieIndexer(e.ChainDb(), nil, params.BloomBitsBlocks, params.BloomTrieFrequency),
 		},
-		archiveMode:  eth.ArchiveMode(),
+		archiveMode:  e.ArchiveMode(),
 		quitSync:     quitSync,
 		lesTopics:    lesTopics,
 		onlyAnnounce: config.OnlyAnnounce,
 		csvLogger:    csvLogger,
 		logTotalCap:  requestLogger.NewChannel("totalCapacity", 0.01),
 	}
-	srv.costTracker, srv.minCapacity = newCostTracker(eth.ChainDb(), config, requestLogger)
+	srv.costTracker, srv.minCapacity = newCostTracker(e.ChainDb(), config, requestLogger)

 	logger := log.New()
-	pm.server = srv
 	srv.thcNormal = config.LightServ * 4 / 100
 	if srv.thcNormal < 4 {
 		srv.thcNormal = 4
@@ -141,22 +112,31 @@ func NewLesServer(eth *eth.Ethereum, config *eth.Config) (*LesServer, error) {
 	srv.thcBlockProcessing = config.LightServ/100 + 1
 	srv.fcManager = flowcontrol.NewClientManager(nil, &mclock.System{})

-	chtSectionCount, _, _ := srv.chtIndexer.Sections()
-	if chtSectionCount != 0 {
-		chtLastSection := chtSectionCount - 1
-		chtSectionHead := srv.chtIndexer.SectionHead(chtLastSection)
-		chtRoot := light.GetChtRoot(pm.chainDb, chtLastSection, chtSectionHead)
-		logger.Info("Loaded CHT", "section", chtLastSection, "head", chtSectionHead, "root", chtRoot)
-	}
-	bloomTrieSectionCount, _, _ := srv.bloomTrieIndexer.Sections()
-	if bloomTrieSectionCount != 0 {
-		bloomTrieLastSection := bloomTrieSectionCount - 1
-		bloomTrieSectionHead := srv.bloomTrieIndexer.SectionHead(bloomTrieLastSection)
-		bloomTrieRoot := light.GetBloomTrieRoot(pm.chainDb, bloomTrieLastSection, bloomTrieSectionHead)
-		logger.Info("Loaded bloom trie", "section", bloomTrieLastSection, "head", bloomTrieSectionHead, "root", bloomTrieRoot)
+	checkpoint := srv.latestLocalCheckpoint()
+	if !checkpoint.Empty() {
+		logger.Info("Loaded latest checkpoint", "section", checkpoint.SectionIndex, "head", checkpoint.SectionHead,
+			"chtroot", checkpoint.CHTRoot, "bloomroot", checkpoint.BloomRoot)
 	}

-	srv.chtIndexer.Start(eth.BlockChain())
+	srv.chtIndexer.Start(e.BlockChain())
+
+	oracle := config.CheckpointOracle
+	if oracle == nil {
+		oracle = params.CheckpointOracles[e.BlockChain().Genesis().Hash()]
+	}
+	registrar := newCheckpointOracle(oracle, srv.getLocalCheckpoint)
+	// TODO(rjl493456442) Checkpoint is useless for les server, separate handler for client and server.
+	pm, err := NewProtocolManager(e.BlockChain().Config(), nil, light.DefaultServerIndexerConfig, config.ULC, false, config.NetworkId, e.EventMux(), newPeerSet(), e.BlockChain(), e.TxPool(), e.ChainDb(), nil, nil, registrar, quitSync, new(sync.WaitGroup), e.Synced)
+	if err != nil {
+		return nil, err
+	}
+	srv.protocolManager = pm
+	if logProtocolHandler {
+		pm.logger = csvLogger
+	}
+	pm.servingQueue = newServingQueue(int64(time.Millisecond*10), float64(config.LightServ)/100, requestLogger)
+	pm.server = srv
+
 	return srv, nil
 }

@@ -168,6 +148,12 @@ func (s *LesServer) APIs() []rpc.API {
 			Service:   NewPrivateLightServerAPI(s),
 			Public:    false,
 		},
+		{
+			Namespace: "les",
+			Version:   "1.0",
+			Service:   NewPrivateLightAPI(&s.lesCommons, s.protocolManager.reg),
+			Public:    false,
+		},
 	}
 }

@@ -292,6 +278,13 @@ func (s *LesServer) SetBloomBitsIndexer(bloomIndexer *core.ChainIndexer) {
 	bloomIndexer.AddChildIndexer(s.bloomTrieIndexer)
 }

+// SetClient sets the rpc client and starts running checkpoint contract if it is not yet watched.
+func (s *LesServer) SetContractBackend(backend bind.ContractBackend) {
+	if s.protocolManager.reg != nil {
+		s.protocolManager.reg.start(backend)
+	}
+}
+
 // Stop stops the LES service
 func (s *LesServer) Stop() {
 	s.fcManager.Stop()
--- a/les/sync.go
+++ b/les/sync.go
@@ -18,11 +18,29 @@ package les

 import (
 	"context"
+	"errors"
 	"time"

+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/eth/downloader"
 	"github.com/ethereum/go-ethereum/light"
+	"github.com/ethereum/go-ethereum/log"
+)
+
+var errInvalidCheckpoint = errors.New("invalid advertised checkpoint")
+
+const (
+	// lightSync starts syncing from the current highest block.
+	// If the chain is empty, syncing the entire header chain.
+	lightSync = iota
+
+	// legacyCheckpointSync starts syncing from a hardcoded checkpoint.
+	legacyCheckpointSync
+
+	// checkpointSync starts syncing from a checkpoint signed by trusted
+	// signer or hardcoded checkpoint for compatibility.
+	checkpointSync
 )

 // syncer is responsible for periodically synchronising with the network, both
@@ -54,26 +72,141 @@ func (pm *ProtocolManager) syncer() {
 	}
 }

-func (pm *ProtocolManager) needToSync(peerHead blockInfo) bool {
-	head := pm.blockchain.CurrentHeader()
-	currentTd := rawdb.ReadTd(pm.chainDb, head.Hash(), head.Number.Uint64())
-	return currentTd != nil && peerHead.Td.Cmp(currentTd) > 0
+// validateCheckpoint verifies the advertised checkpoint by peer is valid or not.
+//
+// Each network has several hard-coded checkpoint signer addresses. Only the
+// checkpoint issued by the specified signer is considered valid.
+//
+// In addition to the checkpoint registered in the registrar contract, there are
+// several legacy hardcoded checkpoints in our codebase. These checkpoints are
+// also considered as valid.
+func (pm *ProtocolManager) validateCheckpoint(peer *peer) error {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+	defer cancel()
+
+	// Fetch the block header corresponding to the checkpoint registration.
+	cp := peer.checkpoint
+	header, err := light.GetUntrustedHeaderByNumber(ctx, pm.odr, peer.checkpointNumber, peer.id)
+	if err != nil {
+		return err
+	}
+	// Fetch block logs associated with the block header.
+	logs, err := light.GetUntrustedBlockLogs(ctx, pm.odr, header)
+	if err != nil {
+		return err
+	}
+	events := pm.reg.contract.LookupCheckpointEvents(logs, cp.SectionIndex, cp.Hash())
+	if len(events) == 0 {
+		return errInvalidCheckpoint
+	}
+	var (
+		index      = events[0].Index
+		hash       = events[0].CheckpointHash
+		signatures [][]byte
+	)
+	for _, event := range events {
+		signatures = append(signatures, append(event.R[:], append(event.S[:], event.V)...))
+	}
+	valid, signers := pm.reg.verifySigners(index, hash, signatures)
+	if !valid {
+		return errInvalidCheckpoint
+	}
+	log.Warn("Verified advertised checkpoint", "peer", peer.id, "signers", len(signers))
+	return nil
 }

-// synchronise tries to sync up our local block chain with a remote peer.
+// synchronise tries to sync up our local chain with a remote peer.
 func (pm *ProtocolManager) synchronise(peer *peer) {
-	// Short circuit if no peers are available
+	// Short circuit if the peer is nil.
 	if peer == nil {
 		return
 	}
-
 	// Make sure the peer's TD is higher than our own.
-	if !pm.needToSync(peer.headBlockInfo()) {
+	latest := pm.blockchain.CurrentHeader()
+	currentTd := rawdb.ReadTd(pm.chainDb, latest.Hash(), latest.Number.Uint64())
+	if currentTd != nil && peer.headBlockInfo().Td.Cmp(currentTd) < 0 {
 		return
 	}
+	// Recap the checkpoint.
+	//
+	// The light client may be connected to several different versions of the server.
+	// (1) Old version server which can not provide stable checkpoint in the handshake packet.
+	//     => Use hardcoded checkpoint or empty checkpoint
+	// (2) New version server but simple checkpoint syncing is not enabled(e.g. mainnet, new testnet or private network)
+	//     => Use hardcoded checkpoint or empty checkpoint
+	// (3) New version server but the provided stable checkpoint is even lower than the hardcoded one.
+	//     => Use hardcoded checkpoint
+	// (4) New version server with valid and higher stable checkpoint
+	//     => Use provided checkpoint
+	var checkpoint = &peer.checkpoint
+	var hardcoded bool
+	if pm.checkpoint != nil && pm.checkpoint.SectionIndex >= peer.checkpoint.SectionIndex {
+		checkpoint = pm.checkpoint // Use the hardcoded one.
+		hardcoded = true
+	}
+	// Determine whether we should run checkpoint syncing or normal light syncing.
+	//
+	// Here has four situations that we will disable the checkpoint syncing:
+	//
+	// 1. The checkpoint is empty
+	// 2. The latest head block of the local chain is above the checkpoint.
+	// 3. The checkpoint is hardcoded(recap with local hardcoded checkpoint)
+	// 4. For some networks the checkpoint syncing is not activated.
+	mode := checkpointSync
+	switch {
+	case checkpoint.Empty():
+		mode = lightSync
+		log.Debug("Disable checkpoint syncing", "reason", "empty checkpoint")
+	case latest.Number.Uint64() >= (checkpoint.SectionIndex+1)*pm.iConfig.ChtSize-1:
+		mode = lightSync
+		log.Debug("Disable checkpoint syncing", "reason", "local chain beyond the checkpoint")
+	case hardcoded:
+		mode = legacyCheckpointSync
+		log.Debug("Disable checkpoint syncing", "reason", "checkpoint is hardcoded")
+	case pm.reg == nil || !pm.reg.isRunning():
+		mode = legacyCheckpointSync
+		log.Debug("Disable checkpoint syncing", "reason", "checkpoint syncing is not activated")
+	}
+	// Notify testing framework if syncing has completed(for testing purpose).
+	defer func() {
+		if pm.reg != nil && pm.reg.syncDoneHook != nil {
+			pm.reg.syncDoneHook()
+		}
+	}()
+	start := time.Now()
+	if mode == checkpointSync || mode == legacyCheckpointSync {
+		// Validate the advertised checkpoint
+		if mode == legacyCheckpointSync {
+			checkpoint = pm.checkpoint
+		} else if mode == checkpointSync {
+			if err := pm.validateCheckpoint(peer); err != nil {
+				log.Debug("Failed to validate checkpoint", "reason", err)
+				pm.removePeer(peer.id)
+				return
+			}
+			pm.blockchain.(*light.LightChain).AddTrustedCheckpoint(checkpoint)
+		}
+		log.Debug("Checkpoint syncing start", "peer", peer.id, "checkpoint", checkpoint.SectionIndex)

-	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
-	defer cancel()
-	pm.blockchain.(*light.LightChain).SyncCht(ctx)
-	pm.downloader.Synchronise(peer.id, peer.Head(), peer.Td(), downloader.LightSync)
+		// Fetch the start point block header.
+		//
+		// For the ethash consensus engine, the start header is the block header
+		// of the checkpoint.
+		//
+		// For the clique consensus engine, the start header is the block header
+		// of the latest epoch covered by checkpoint.
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+		defer cancel()
+		if !checkpoint.Empty() && !pm.blockchain.(*light.LightChain).SyncCheckpoint(ctx, checkpoint) {
+			log.Debug("Sync checkpoint failed")
+			pm.removePeer(peer.id)
+			return
+		}
+	}
+	// Fetch the remaining block headers based on the current chain header.
+	if err := pm.downloader.Synchronise(peer.id, peer.Head(), peer.Td(), downloader.LightSync); err != nil {
+		log.Debug("Synchronise failed", "reason", err)
+		return
+	}
+	log.Debug("Synchronise finished", "elapsed", common.PrettyDuration(time.Since(start)))
 }
--- a/les/sync_test.go
+++ b/les/sync_test.go
@@ -0,0 +1,133 @@
+// Copyright 2018 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 les
+
+import (
+	"fmt"
+	"math/big"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/light"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+// Test light syncing which will download all headers from genesis.
+func TestLightSyncingLes2(t *testing.T) { testCheckpointSyncing(t, 2, 0) }
+func TestLightSyncingLes3(t *testing.T) { testCheckpointSyncing(t, 3, 0) }
+
+// Test legacy checkpoint syncing which will download tail headers
+// based on a hardcoded checkpoint.
+func TestLegacyCheckpointSyncingLes2(t *testing.T) { testCheckpointSyncing(t, 2, 1) }
+func TestLegacyCheckpointSyncingLes3(t *testing.T) { testCheckpointSyncing(t, 3, 1) }
+
+// Test checkpoint syncing which will download tail headers based
+// on a verified checkpoint.
+func TestCheckpointSyncingLes2(t *testing.T) { testCheckpointSyncing(t, 2, 2) }
+func TestCheckpointSyncingLes3(t *testing.T) { testCheckpointSyncing(t, 3, 2) }
+
+func testCheckpointSyncing(t *testing.T, protocol int, syncMode int) {
+	config := light.TestServerIndexerConfig
+
+	waitIndexers := func(cIndexer, bIndexer, btIndexer *core.ChainIndexer) {
+		for {
+			cs, _, _ := cIndexer.Sections()
+			bts, _, _ := btIndexer.Sections()
+			if cs >= 1 && bts >= 1 {
+				break
+			}
+			time.Sleep(10 * time.Millisecond)
+		}
+	}
+	// Generate 512+4 blocks (totally 1 CHT sections)
+	server, client, tearDown := newClientServerEnv(t, int(config.ChtSize+config.ChtConfirms), protocol, waitIndexers, false)
+	defer tearDown()
+
+	expected := config.ChtSize + config.ChtConfirms
+
+	// Checkpoint syncing or legacy checkpoint syncing.
+	if syncMode == 1 || syncMode == 2 {
+		// Assemble checkpoint 0
+		s, _, head := server.chtIndexer.Sections()
+		cp := &params.TrustedCheckpoint{
+			SectionIndex: 0,
+			SectionHead:  head,
+			CHTRoot:      light.GetChtRoot(server.db, s-1, head),
+			BloomRoot:    light.GetBloomTrieRoot(server.db, s-1, head),
+		}
+		if syncMode == 1 {
+			// Register the assembled checkpoint as hardcoded one.
+			client.pm.checkpoint = cp
+			client.pm.blockchain.(*light.LightChain).AddTrustedCheckpoint(cp)
+		} else {
+			// Register the assembled checkpoint into oracle.
+			header := server.backend.Blockchain().CurrentHeader()
+
+			data := append([]byte{0x19, 0x00}, append(registrarAddr.Bytes(), append([]byte{0, 0, 0, 0, 0, 0, 0, 0}, cp.Hash().Bytes()...)...)...)
+			sig, _ := crypto.Sign(crypto.Keccak256(data), signerKey)
+			sig[64] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
+			if _, err := server.pm.reg.contract.RegisterCheckpoint(signerKey, cp.SectionIndex, cp.Hash().Bytes(), new(big.Int).Sub(header.Number, big.NewInt(1)), header.ParentHash, [][]byte{sig}); err != nil {
+				t.Error("register checkpoint failed", err)
+			}
+			server.backend.Commit()
+
+			// Wait for the checkpoint registration
+			for {
+				_, hash, _, err := server.pm.reg.contract.Contract().GetLatestCheckpoint(nil)
+				if err != nil || hash == [32]byte{} {
+					time.Sleep(100 * time.Millisecond)
+					continue
+				}
+				break
+			}
+			expected += 1
+		}
+	}
+
+	done := make(chan error)
+	client.pm.reg.syncDoneHook = func() {
+		header := client.pm.blockchain.CurrentHeader()
+		if header.Number.Uint64() == expected {
+			done <- nil
+		} else {
+			done <- fmt.Errorf("blockchain length mismatch, want %d, got %d", expected, header.Number)
+		}
+	}
+
+	// Create connected peer pair.
+	peer, err1, lPeer, err2 := newTestPeerPair("peer", protocol, server.pm, client.pm)
+	select {
+	case <-time.After(time.Millisecond * 100):
+	case err := <-err1:
+		t.Fatalf("peer 1 handshake error: %v", err)
+	case err := <-err2:
+		t.Fatalf("peer 2 handshake error: %v", err)
+	}
+	server.rPeer, client.rPeer = peer, lPeer
+
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Error("sync failed", err)
+		}
+		return
+	case <-time.NewTimer(10 * time.Second).C:
+		t.Error("checkpoint syncing timeout")
+	}
+}
--- a/les/transactions.rlp
+++ b/les/transactions.rlp
--- a/les/txrelay.go
+++ b/les/txrelay.go
@@ -30,7 +30,7 @@ type ltrInfo struct {
 	sentTo map[*peer]struct{}
 }

-type LesTxRelay struct {
+type lesTxRelay struct {
 	txSent       map[common.Hash]*ltrInfo
 	txPending    map[common.Hash]struct{}
 	ps           *peerSet
@@ -42,8 +42,8 @@ type LesTxRelay struct {
 	retriever *retrieveManager
 }

-func NewLesTxRelay(ps *peerSet, retriever *retrieveManager) *LesTxRelay {
-	r := &LesTxRelay{
+func newLesTxRelay(ps *peerSet, retriever *retrieveManager) *lesTxRelay {
+	r := &lesTxRelay{
 		txSent:    make(map[common.Hash]*ltrInfo),
 		txPending: make(map[common.Hash]struct{}),
 		ps:        ps,
@@ -54,18 +54,18 @@ func NewLesTxRelay(ps *peerSet, retriever *retrieveManager) *LesTxRelay {
 	return r
 }

-func (self *LesTxRelay) Stop() {
+func (self *lesTxRelay) Stop() {
 	close(self.stop)
 }

-func (self *LesTxRelay) registerPeer(p *peer) {
+func (self *lesTxRelay) registerPeer(p *peer) {
 	self.lock.Lock()
 	defer self.lock.Unlock()

 	self.peerList = self.ps.AllPeers()
 }

-func (self *LesTxRelay) unregisterPeer(p *peer) {
+func (self *lesTxRelay) unregisterPeer(p *peer) {
 	self.lock.Lock()
 	defer self.lock.Unlock()

@@ -74,7 +74,7 @@ func (self *LesTxRelay) unregisterPeer(p *peer) {

 // send sends a list of transactions to at most a given number of peers at
 // once, never resending any particular transaction to the same peer twice
-func (self *LesTxRelay) send(txs types.Transactions, count int) {
+func (self *lesTxRelay) send(txs types.Transactions, count int) {
 	sendTo := make(map[*peer]types.Transactions)

 	self.peerStartPos++ // rotate the starting position of the peer list
@@ -143,14 +143,14 @@ func (self *LesTxRelay) send(txs types.Transactions, count int) {
 	}
 }

-func (self *LesTxRelay) Send(txs types.Transactions) {
+func (self *lesTxRelay) Send(txs types.Transactions) {
 	self.lock.Lock()
 	defer self.lock.Unlock()

 	self.send(txs, 3)
 }

-func (self *LesTxRelay) NewHead(head common.Hash, mined []common.Hash, rollback []common.Hash) {
+func (self *lesTxRelay) NewHead(head common.Hash, mined []common.Hash, rollback []common.Hash) {
 	self.lock.Lock()
 	defer self.lock.Unlock()

@@ -173,7 +173,7 @@ func (self *LesTxRelay) NewHead(head common.Hash, mined []common.Hash, rollback
 	}
 }

-func (self *LesTxRelay) Discard(hashes []common.Hash) {
+func (self *lesTxRelay) Discard(hashes []common.Hash) {
 	self.lock.Lock()
 	defer self.lock.Unlock()

--- a/les/ulc_test.go
+++ b/les/ulc_test.go
@@ -26,7 +26,6 @@ import (
 	"time"

 	"github.com/ethereum/go-ethereum/common/mclock"
-	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth"
@@ -36,7 +35,7 @@ import (
 )

 func TestULCSyncWithOnePeer(t *testing.T) {
-	f := newFullPeerPair(t, 1, 4, testChainGen)
+	f := newFullPeerPair(t, 1, 4)
 	ulcConfig := &eth.ULCConfig{
 		MinTrustedFraction: 100,
 		TrustedServers:     []string{f.Node.String()},
@@ -63,7 +62,7 @@ func TestULCSyncWithOnePeer(t *testing.T) {
 }

 func TestULCReceiveAnnounce(t *testing.T) {
-	f := newFullPeerPair(t, 1, 4, testChainGen)
+	f := newFullPeerPair(t, 1, 4)
 	ulcConfig := &eth.ULCConfig{
 		MinTrustedFraction: 100,
 		TrustedServers:     []string{f.Node.String()},
@@ -100,8 +99,8 @@ func TestULCReceiveAnnounce(t *testing.T) {
 }

 func TestULCShouldNotSyncWithTwoPeersOneHaveEmptyChain(t *testing.T) {
-	f1 := newFullPeerPair(t, 1, 4, testChainGen)
-	f2 := newFullPeerPair(t, 2, 0, nil)
+	f1 := newFullPeerPair(t, 1, 4)
+	f2 := newFullPeerPair(t, 2, 0)
 	ulcConf := &ulc{minTrustedFraction: 100, trustedKeys: make(map[string]struct{})}
 	ulcConf.trustedKeys[f1.Node.ID().String()] = struct{}{}
 	ulcConf.trustedKeys[f2.Node.ID().String()] = struct{}{}
@@ -131,9 +130,9 @@ func TestULCShouldNotSyncWithTwoPeersOneHaveEmptyChain(t *testing.T) {
 }

 func TestULCShouldNotSyncWithThreePeersOneHaveEmptyChain(t *testing.T) {
-	f1 := newFullPeerPair(t, 1, 3, testChainGen)
-	f2 := newFullPeerPair(t, 2, 4, testChainGen)
-	f3 := newFullPeerPair(t, 3, 0, nil)
+	f1 := newFullPeerPair(t, 1, 3)
+	f2 := newFullPeerPair(t, 2, 4)
+	f3 := newFullPeerPair(t, 3, 0)

 	ulcConfig := &eth.ULCConfig{
 		MinTrustedFraction: 60,
@@ -211,10 +210,10 @@ func connectPeers(full, light pairPeer, version int) (*peer, *peer, error) {
 }

 // newFullPeerPair creates node with full sync mode
-func newFullPeerPair(t *testing.T, index int, numberOfblocks int, chainGen func(int, *core.BlockGen)) pairPeer {
+func newFullPeerPair(t *testing.T, index int, numberOfblocks int) pairPeer {
 	db := rawdb.NewMemoryDatabase()

-	pmFull := newTestProtocolManagerMust(t, false, numberOfblocks, chainGen, nil, nil, db, nil)
+	pmFull, _ := newTestProtocolManagerMust(t, false, numberOfblocks, nil, nil, nil, db, nil)

 	peerPairFull := pairPeer{
 		Name: "full node",
@@ -238,7 +237,7 @@ func newLightPeer(t *testing.T, ulcConfig *eth.ULCConfig) pairPeer {

 	odr := NewLesOdr(ldb, light.DefaultClientIndexerConfig, rm)

-	pmLight := newTestProtocolManagerMust(t, true, 0, nil, odr, peers, ldb, ulcConfig)
+	pmLight, _ := newTestProtocolManagerMust(t, true, 0, odr, nil, peers, ldb, ulcConfig)
 	peerPairLight := pairPeer{
 		Name: "ulc node",
 		PM:   pmLight,