les: implement ultralight client (#16904)

For more information about this light client mode, read
https://hackmd.io/s/HJy7jjZpm

cmd/geth/config.go

@@ -125,6 +125,7 @@ func makeConfigNode(ctx *cli.Context) (*node.Node, gethConfig) {
 	}
 
 	// Apply flags.
+	utils.SetULC(ctx, &cfg.Eth)
 	utils.SetNodeConfig(ctx, &cfg.Node)
 	stack, err := node.New(&cfg.Node)
 	if err != nil {

cmd/geth/main.go

@@ -82,6 +82,10 @@ var (
 		utils.TxPoolAccountQueueFlag,
 		utils.TxPoolGlobalQueueFlag,
 		utils.TxPoolLifetimeFlag,
+		utils.ULCModeConfigFlag,
+		utils.OnlyAnnounceModeFlag,
+		utils.ULCTrustedNodesFlag,
+		utils.ULCMinTrustedFractionFlag,
 		utils.SyncModeFlag,
 		utils.GCModeFlag,
 		utils.LightServFlag,

cmd/utils/flags.go

@@ -19,6 +19,7 @@ package utils
 
 import (
 	"crypto/ecdsa"
+	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"math/big"
@@ -161,6 +162,23 @@ var (
 		Usage: "Document Root for HTTPClient file scheme",
 		Value: DirectoryString{homeDir()},
 	}
+	ULCModeConfigFlag = cli.StringFlag{
+		Name:  "ulc.config",
+		Usage: "Config file to use for ultra light client mode",
+	}
+	OnlyAnnounceModeFlag = cli.BoolFlag{
+		Name:  "ulc.onlyannounce",
+		Usage: "ULC server sends announcements only",
+	}
+	ULCMinTrustedFractionFlag = cli.IntFlag{
+		Name:  "ulc.fraction",
+		Usage: "Minimum % of trusted ULC servers required to announce a new head",
+	}
+	ULCTrustedNodesFlag = cli.StringFlag{
+		Name:  "ulc.trusted",
+		Usage: "List of trusted ULC servers",
+	}
+
 	defaultSyncMode = eth.DefaultConfig.SyncMode
 	SyncModeFlag    = TextMarshalerFlag{
 		Name:  "syncmode",
@@ -871,6 +889,40 @@ func setIPC(ctx *cli.Context, cfg *node.Config) {
 	}
 }
 
+// SetULC setup ULC config from file if given.
+func SetULC(ctx *cli.Context, cfg *eth.Config) {
+	// ULC config isn't loaded from global config and ULC config and ULC trusted nodes are not defined.
+	if cfg.ULC == nil && !(ctx.GlobalIsSet(ULCModeConfigFlag.Name) || ctx.GlobalIsSet(ULCTrustedNodesFlag.Name)) {
+		return
+	}
+	cfg.ULC = &eth.ULCConfig{}
+
+	path := ctx.GlobalString(ULCModeConfigFlag.Name)
+	if path != "" {
+		cfgData, err := ioutil.ReadFile(path)
+		if err != nil {
+			Fatalf("Failed to unmarshal ULC configuration: %v", err)
+		}
+
+		err = json.Unmarshal(cfgData, &cfg.ULC)
+		if err != nil {
+			Fatalf("Failed to unmarshal ULC configuration: %s", err.Error())
+		}
+	}
+
+	if trustedNodes := ctx.GlobalString(ULCTrustedNodesFlag.Name); trustedNodes != "" {
+		cfg.ULC.TrustedServers = strings.Split(trustedNodes, ",")
+	}
+
+	if trustedFraction := ctx.GlobalInt(ULCMinTrustedFractionFlag.Name); trustedFraction > 0 {
+		cfg.ULC.MinTrustedFraction = trustedFraction
+	}
+	if cfg.ULC.MinTrustedFraction <= 0 && cfg.ULC.MinTrustedFraction > 100 {
+		log.Error("MinTrustedFraction is invalid", "MinTrustedFraction", cfg.ULC.MinTrustedFraction, "Changed to default", eth.DefaultULCMinTrustedFraction)
+		cfg.ULC.MinTrustedFraction = eth.DefaultULCMinTrustedFraction
+	}
+}
+
 // makeDatabaseHandles raises out the number of allowed file handles per process
 // for Geth and returns half of the allowance to assign to the database.
 func makeDatabaseHandles() int {
@@ -1222,6 +1274,9 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 	if ctx.GlobalIsSet(LightPeersFlag.Name) {
 		cfg.LightPeers = ctx.GlobalInt(LightPeersFlag.Name)
 	}
+	if ctx.GlobalIsSet(OnlyAnnounceModeFlag.Name) {
+		cfg.OnlyAnnounce = ctx.GlobalBool(OnlyAnnounceModeFlag.Name)
+	}
 	if ctx.GlobalIsSet(NetworkIdFlag.Name) {
 		cfg.NetworkId = ctx.GlobalUint64(NetworkIdFlag.Name)
 	}

core/headerchain.go

@@ -219,14 +219,18 @@ func (hc *HeaderChain) ValidateHeaderChain(chain []*types.Header, checkFreq int)
 
 	// Generate the list of seal verification requests, and start the parallel verifier
 	seals := make([]bool, len(chain))
-	for i := 0; i < len(seals)/checkFreq; i++ {
+	if checkFreq != 0 {
-		index := i*checkFreq + hc.rand.Intn(checkFreq)
+		// In case of checkFreq == 0 all seals are left false.
-		if index >= len(seals) {
+		for i := 0; i < len(seals)/checkFreq; i++ {
-			index = len(seals) - 1
+			index := i*checkFreq + hc.rand.Intn(checkFreq)
+			if index >= len(seals) {
+				index = len(seals) - 1
+			}
+			seals[index] = true
 		}
-		seals[index] = true
+		// Last should always be verified to avoid junk.
+		seals[len(seals)-1] = true
 	}
-	seals[len(seals)-1] = true // Last should always be verified to avoid junk
 
 	abort, results := hc.engine.VerifyHeaders(hc, chain, seals)
 	defer close(abort)

eth/config.go

@@ -91,8 +91,12 @@ type Config struct {
 	Whitelist map[uint64]common.Hash `toml:"-"`
 
 	// Light client options
-	LightServ  int `toml:",omitempty"` // Maximum percentage of time allowed for serving LES requests
+	LightServ    int  `toml:",omitempty"` // Maximum percentage of time allowed for serving LES requests
-	LightPeers int `toml:",omitempty"` // Maximum number of LES client peers
+	LightPeers   int  `toml:",omitempty"` // Maximum number of LES client peers
+	OnlyAnnounce bool // Maximum number of LES client peers
+
+	// Ultra Light client options
+	ULC *ULCConfig `toml:",omitempty"`
 
 	// Database options
 	SkipBcVersionCheck bool `toml:"-"`

eth/gen_config.go

@@ -23,10 +23,12 @@ func (c Config) MarshalTOML() (interface{}, error) {
 		NetworkId               uint64
 		SyncMode                downloader.SyncMode
 		NoPruning               bool
-		LightServ               int  `toml:",omitempty"`
+		LightServ               int `toml:",omitempty"`
-		LightPeers              int  `toml:",omitempty"`
+		LightPeers              int `toml:",omitempty"`
-		SkipBcVersionCheck      bool `toml:"-"`
+		OnlyAnnounce            bool
-		DatabaseHandles         int  `toml:"-"`
+		ULC                     *ULCConfig `toml:",omitempty"`
+		SkipBcVersionCheck      bool       `toml:"-"`
+		DatabaseHandles         int        `toml:"-"`
 		DatabaseCache           int
 		TrieCleanCache          int
 		TrieDirtyCache          int
@@ -54,6 +56,8 @@ func (c Config) MarshalTOML() (interface{}, error) {
 	enc.NoPruning = c.NoPruning
 	enc.LightServ = c.LightServ
 	enc.LightPeers = c.LightPeers
+	enc.OnlyAnnounce = c.OnlyAnnounce
+	enc.ULC = c.ULC
 	enc.SkipBcVersionCheck = c.SkipBcVersionCheck
 	enc.DatabaseHandles = c.DatabaseHandles
 	enc.DatabaseCache = c.DatabaseCache
@@ -71,6 +75,7 @@ func (c Config) MarshalTOML() (interface{}, error) {
 	enc.Ethash = c.Ethash
 	enc.TxPool = c.TxPool
 	enc.GPO = c.GPO
+
 	enc.EnablePreimageRecording = c.EnablePreimageRecording
 	enc.DocRoot = c.DocRoot
 	enc.EWASMInterpreter = c.EWASMInterpreter
@@ -85,10 +90,12 @@ func (c *Config) UnmarshalTOML(unmarshal func(interface{}) error) error {
 		NetworkId               *uint64
 		SyncMode                *downloader.SyncMode
 		NoPruning               *bool
-		LightServ               *int  `toml:",omitempty"`
+		LightServ               *int `toml:",omitempty"`
-		LightPeers              *int  `toml:",omitempty"`
+		LightPeers              *int `toml:",omitempty"`
-		SkipBcVersionCheck      *bool `toml:"-"`
+		OnlyAnnounce            *bool
-		DatabaseHandles         *int  `toml:"-"`
+		ULC                     *ULCConfig `toml:",omitempty"`
+		SkipBcVersionCheck      *bool      `toml:"-"`
+		DatabaseHandles         *int       `toml:"-"`
 		DatabaseCache           *int
 		TrieCleanCache          *int
 		TrieDirtyCache          *int
@@ -131,6 +138,12 @@ func (c *Config) UnmarshalTOML(unmarshal func(interface{}) error) error {
 	if dec.LightPeers != nil {
 		c.LightPeers = *dec.LightPeers
 	}
+	if dec.OnlyAnnounce != nil {
+		c.OnlyAnnounce = *dec.OnlyAnnounce
+	}
+	if dec.ULC != nil {
+		c.ULC = dec.ULC
+	}
 	if dec.SkipBcVersionCheck != nil {
 		c.SkipBcVersionCheck = *dec.SkipBcVersionCheck
 	}

eth/ulc_config.go

@@ -0,0 +1,9 @@
+package eth
+
+const DefaultULCMinTrustedFraction = 75
+
+// ULCConfig is a Ultra Light client options.
+type ULCConfig struct {
+	TrustedServers     []string `toml:",omitempty"` // A list of trusted servers
+	MinTrustedFraction int      `toml:",omitempty"` // Minimum percentage of connected trusted servers to validate trusted (1-100)
+}

les/backend.go

@@ -109,8 +109,12 @@ func New(ctx *node.ServiceContext, config *eth.Config) (*LightEthereum, error) {
 		bloomIndexer:   eth.NewBloomIndexer(chainDb, params.BloomBitsBlocksClient, params.HelperTrieConfirmations),
 	}
 
+	var trustedNodes []string
+	if leth.config.ULC != nil {
+		trustedNodes = leth.config.ULC.TrustedServers
+	}
 	leth.relay = NewLesTxRelay(peers, leth.reqDist)
-	leth.serverPool = newServerPool(chainDb, quitSync, &leth.wg)
+	leth.serverPool = newServerPool(chainDb, quitSync, &leth.wg, trustedNodes)
 	leth.retriever = newRetrieveManager(peers, leth.reqDist, leth.serverPool)
 
 	leth.odr = NewLesOdr(chainDb, light.DefaultClientIndexerConfig, leth.retriever)
@@ -136,10 +140,33 @@ 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); err != nil {
+
+	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); 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{leth, nil}
+
 	gpoParams := config.GPO
 	if gpoParams.Default == nil {
 		gpoParams.Default = config.MinerGasPrice

les/fetcher.go

@@ -43,7 +43,7 @@ const (
 type lightFetcher struct {
 	pm    *ProtocolManager
 	odr   *LesOdr
-	chain *light.LightChain
+	chain lightChain
 
 	lock            sync.Mutex // lock protects access to the fetcher's internal state variables except sent requests
 	maxConfirmedTd  *big.Int
@@ -52,11 +52,19 @@ type lightFetcher struct {
 	syncing         bool
 	syncDone        chan *peer
 
-	reqMu      sync.RWMutex // reqMu protects access to sent header fetch requests
+	reqMu             sync.RWMutex // reqMu protects access to sent header fetch requests
-	requested  map[uint64]fetchRequest
+	requested         map[uint64]fetchRequest
-	deliverChn chan fetchResponse
+	deliverChn        chan fetchResponse
-	timeoutChn chan uint64
+	timeoutChn        chan uint64
-	requestChn chan bool // true if initiated from outside
+	requestChn        chan bool // true if initiated from outside
+	lastTrustedHeader *types.Header
+}
+
+// lightChain extends the BlockChain interface by locking.
+type lightChain interface {
+	BlockChain
+	LockChain()
+	UnlockChain()
 }
 
 // fetcherPeerInfo holds fetcher-specific information about each active peer
@@ -145,6 +153,7 @@ func (f *lightFetcher) syncLoop() {
 				reqID   uint64
 				syncing bool
 			)
+
 			if !f.syncing && !(newAnnounce && s) {
 				rq, reqID, syncing = f.nextRequest()
 			}
@@ -227,7 +236,6 @@ func (f *lightFetcher) registerPeer(p *peer) {
 
 	f.lock.Lock()
 	defer f.lock.Unlock()
-
 	f.peers[p] = &fetcherPeerInfo{nodeByHash: make(map[common.Hash]*fetcherTreeNode)}
 }
 
@@ -280,8 +288,10 @@ func (f *lightFetcher) announce(p *peer, head *announceData) {
 		fp.nodeCnt = 0
 		fp.nodeByHash = make(map[common.Hash]*fetcherTreeNode)
 	}
+	// check if the node count is too high to add new nodes, discard oldest ones if necessary
 	if n != nil {
-		// check if the node count is too high to add new nodes, discard oldest ones if necessary
+		// n is now the reorg common ancestor, add a new branch of nodes
+		// check if the node count is too high to add new nodes
 		locked := false
 		for uint64(fp.nodeCnt)+head.Number-n.number > maxNodeCount && fp.root != nil {
 			if !locked {
@@ -325,6 +335,7 @@ func (f *lightFetcher) announce(p *peer, head *announceData) {
 			fp.nodeByHash[n.hash] = n
 		}
 	}
+
 	if n == nil {
 		// could not find reorg common ancestor or had to delete entire tree, a new root and a resync is needed
 		if fp.root != nil {
@@ -411,25 +422,13 @@ func (f *lightFetcher) requestedID(reqID uint64) bool {
 // to be downloaded starting from the head backwards is also returned
 func (f *lightFetcher) nextRequest() (*distReq, uint64, bool) {
 	var (
-		bestHash   common.Hash
+		bestHash    common.Hash
-		bestAmount uint64
+		bestAmount  uint64
+		bestTd      *big.Int
+		bestSyncing bool
 	)
-	bestTd := f.maxConfirmedTd
+	bestHash, bestAmount, bestTd, bestSyncing = f.findBestRequest()
-	bestSyncing := false
 
-	for p, fp := range f.peers {
-		for hash, n := range fp.nodeByHash {
-			if !f.checkKnownNode(p, n) && !n.requested && (bestTd == nil || n.td.Cmp(bestTd) >= 0) {
-				amount := f.requestAmount(p, n)
-				if bestTd == nil || n.td.Cmp(bestTd) > 0 || amount < bestAmount {
-					bestHash = hash
-					bestAmount = amount
-					bestTd = n.td
-					bestSyncing = fp.bestConfirmed == nil || fp.root == nil || !f.checkKnownNode(p, fp.root)
-				}
-			}
-		}
-	}
 	if bestTd == f.maxConfirmedTd {
 		return nil, 0, false
 	}
@@ -437,74 +436,142 @@ func (f *lightFetcher) nextRequest() (*distReq, uint64, bool) {
 	var rq *distReq
 	reqID := genReqID()
 	if bestSyncing {
-		rq = &distReq{
+		rq = f.newFetcherDistReqForSync(bestHash)
-			getCost: func(dp distPeer) uint64 {
-				return 0
-			},
-			canSend: func(dp distPeer) bool {
-				p := dp.(*peer)
-				f.lock.Lock()
-				defer f.lock.Unlock()
-
-				fp := f.peers[p]
-				return fp != nil && fp.nodeByHash[bestHash] != nil
-			},
-			request: func(dp distPeer) func() {
-				go func() {
-					p := dp.(*peer)
-					p.Log().Debug("Synchronisation started")
-					f.pm.synchronise(p)
-					f.syncDone <- p
-				}()
-				return nil
-			},
-		}
 	} else {
-		rq = &distReq{
+		rq = f.newFetcherDistReq(bestHash, reqID, bestAmount)
-			getCost: func(dp distPeer) uint64 {
-				p := dp.(*peer)
-				return p.GetRequestCost(GetBlockHeadersMsg, int(bestAmount))
-			},
-			canSend: func(dp distPeer) bool {
-				p := dp.(*peer)
-				f.lock.Lock()
-				defer f.lock.Unlock()
-
-				fp := f.peers[p]
-				if fp == nil {
-					return false
-				}
-				n := fp.nodeByHash[bestHash]
-				return n != nil && !n.requested
-			},
-			request: func(dp distPeer) func() {
-				p := dp.(*peer)
-				f.lock.Lock()
-				fp := f.peers[p]
-				if fp != nil {
-					n := fp.nodeByHash[bestHash]
-					if n != nil {
-						n.requested = true
-					}
-				}
-				f.lock.Unlock()
-
-				cost := p.GetRequestCost(GetBlockHeadersMsg, int(bestAmount))
-				p.fcServer.QueueRequest(reqID, cost)
-				f.reqMu.Lock()
-				f.requested[reqID] = fetchRequest{hash: bestHash, amount: bestAmount, peer: p, sent: mclock.Now()}
-				f.reqMu.Unlock()
-				go func() {
-					time.Sleep(hardRequestTimeout)
-					f.timeoutChn <- reqID
-				}()
-				return func() { p.RequestHeadersByHash(reqID, cost, bestHash, int(bestAmount), 0, true) }
-			},
-		}
 	}
 	return rq, reqID, bestSyncing
 }
 
+// findBestRequest finds the best head to request that has been announced by but not yet requested from a known peer.
+// It also returns the announced Td (which should be verified after fetching the head),
+// the necessary amount to request and whether a downloader sync is necessary instead of a normal header request.
+func (f *lightFetcher) findBestRequest() (bestHash common.Hash, bestAmount uint64, bestTd *big.Int, bestSyncing bool) {
+	bestTd = f.maxConfirmedTd
+	bestSyncing = false
+
+	for p, fp := range f.peers {
+		for hash, n := range fp.nodeByHash {
+			if f.checkKnownNode(p, n) || n.requested {
+				continue
+			}
+
+			//if ulc mode is disabled, isTrustedHash returns true
+			amount := f.requestAmount(p, n)
+			if (bestTd == nil || n.td.Cmp(bestTd) > 0 || amount < bestAmount) && (f.isTrustedHash(hash) || f.maxConfirmedTd.Int64() == 0) {
+				bestHash = hash
+				bestTd = n.td
+				bestAmount = amount
+				bestSyncing = fp.bestConfirmed == nil || fp.root == nil || !f.checkKnownNode(p, fp.root)
+			}
+		}
+	}
+	return
+}
+
+// isTrustedHash checks if the block can be trusted by the minimum trusted fraction.
+func (f *lightFetcher) isTrustedHash(hash common.Hash) bool {
+	if !f.pm.isULCEnabled() {
+		return true
+	}
+
+	var numAgreed int
+	for p, fp := range f.peers {
+		if !p.isTrusted {
+			continue
+		}
+		if _, ok := fp.nodeByHash[hash]; !ok {
+			continue
+		}
+
+		numAgreed++
+	}
+
+	return 100*numAgreed/len(f.pm.ulc.trustedKeys) >= f.pm.ulc.minTrustedFraction
+}
+
+func (f *lightFetcher) newFetcherDistReqForSync(bestHash common.Hash) *distReq {
+	return &distReq{
+		getCost: func(dp distPeer) uint64 {
+			return 0
+		},
+		canSend: func(dp distPeer) bool {
+			p := dp.(*peer)
+			f.lock.Lock()
+			defer f.lock.Unlock()
+
+			if p.isOnlyAnnounce {
+				return false
+			}
+
+			fp := f.peers[p]
+			return fp != nil && fp.nodeByHash[bestHash] != nil
+		},
+		request: func(dp distPeer) func() {
+			if f.pm.isULCEnabled() {
+				//keep last trusted header before sync
+				f.setLastTrustedHeader(f.chain.CurrentHeader())
+			}
+			go func() {
+				p := dp.(*peer)
+				p.Log().Debug("Synchronisation started")
+				f.pm.synchronise(p)
+				f.syncDone <- p
+			}()
+			return nil
+		},
+	}
+}
+
+// newFetcherDistReq creates a new request for the distributor.
+func (f *lightFetcher) newFetcherDistReq(bestHash common.Hash, reqID uint64, bestAmount uint64) *distReq {
+	return &distReq{
+		getCost: func(dp distPeer) uint64 {
+			p := dp.(*peer)
+			return p.GetRequestCost(GetBlockHeadersMsg, int(bestAmount))
+		},
+		canSend: func(dp distPeer) bool {
+			p := dp.(*peer)
+			f.lock.Lock()
+			defer f.lock.Unlock()
+
+			if p.isOnlyAnnounce {
+				return false
+			}
+
+			fp := f.peers[p]
+			if fp == nil {
+				return false
+			}
+			n := fp.nodeByHash[bestHash]
+			return n != nil && !n.requested
+		},
+		request: func(dp distPeer) func() {
+			p := dp.(*peer)
+			f.lock.Lock()
+			fp := f.peers[p]
+			if fp != nil {
+				n := fp.nodeByHash[bestHash]
+				if n != nil {
+					n.requested = true
+				}
+			}
+			f.lock.Unlock()
+
+			cost := p.GetRequestCost(GetBlockHeadersMsg, int(bestAmount))
+			p.fcServer.QueueRequest(reqID, cost)
+			f.reqMu.Lock()
+			f.requested[reqID] = fetchRequest{hash: bestHash, amount: bestAmount, peer: p, sent: mclock.Now()}
+			f.reqMu.Unlock()
+			go func() {
+				time.Sleep(hardRequestTimeout)
+				f.timeoutChn <- reqID
+			}()
+			return func() { p.RequestHeadersByHash(reqID, cost, bestHash, int(bestAmount), 0, true) }
+		},
+	}
+}
+
 // deliverHeaders delivers header download request responses for processing
 func (f *lightFetcher) deliverHeaders(peer *peer, reqID uint64, headers []*types.Header) {
 	f.deliverChn <- fetchResponse{reqID: reqID, headers: headers, peer: peer}
@@ -520,6 +587,7 @@ func (f *lightFetcher) processResponse(req fetchRequest, resp fetchResponse) boo
 	for i, header := range resp.headers {
 		headers[int(req.amount)-1-i] = header
 	}
+
 	if _, err := f.chain.InsertHeaderChain(headers, 1); err != nil {
 		if err == consensus.ErrFutureBlock {
 			return true
@@ -544,6 +612,7 @@ func (f *lightFetcher) processResponse(req fetchRequest, resp fetchResponse) boo
 // downloaded and validated batch or headers
 func (f *lightFetcher) newHeaders(headers []*types.Header, tds []*big.Int) {
 	var maxTd *big.Int
+
 	for p, fp := range f.peers {
 		if !f.checkAnnouncedHeaders(fp, headers, tds) {
 			p.Log().Debug("Inconsistent announcement")
@@ -553,6 +622,7 @@ func (f *lightFetcher) newHeaders(headers []*types.Header, tds []*big.Int) {
 			maxTd = fp.confirmedTd
 		}
 	}
+
 	if maxTd != nil {
 		f.updateMaxConfirmedTd(maxTd)
 	}
@@ -640,22 +710,72 @@ func (f *lightFetcher) checkSyncedHeaders(p *peer) {
 		p.Log().Debug("Unknown peer to check sync headers")
 		return
 	}
+
 	n := fp.lastAnnounced
 	var td *big.Int
+
+	var h *types.Header
+	if f.pm.isULCEnabled() {
+		var unapprovedHashes []common.Hash
+		// Overwrite last announced for ULC mode
+		h, unapprovedHashes = f.lastTrustedTreeNode(p)
+		//rollback untrusted blocks
+		f.chain.Rollback(unapprovedHashes)
+		//overwrite to last trusted
+		n = fp.nodeByHash[h.Hash()]
+	}
+
+	//find last valid block
 	for n != nil {
 		if td = f.chain.GetTd(n.hash, n.number); td != nil {
 			break
 		}
 		n = n.parent
 	}
-	// now n is the latest downloaded header after syncing
+
+	// Now n is the latest downloaded/approved header after syncing
 	if n == nil {
 		p.Log().Debug("Synchronisation failed")
 		go f.pm.removePeer(p.id)
-	} else {
+		return
-		header := f.chain.GetHeader(n.hash, n.number)
-		f.newHeaders([]*types.Header{header}, []*big.Int{td})
 	}
+	header := f.chain.GetHeader(n.hash, n.number)
+	f.newHeaders([]*types.Header{header}, []*big.Int{td})
+}
+
+// lastTrustedTreeNode return last approved treeNode and a list of unapproved hashes
+func (f *lightFetcher) lastTrustedTreeNode(p *peer) (*types.Header, []common.Hash) {
+	unapprovedHashes := make([]common.Hash, 0)
+	current := f.chain.CurrentHeader()
+
+	if f.lastTrustedHeader == nil {
+		return current, unapprovedHashes
+	}
+
+	canonical := f.chain.CurrentHeader()
+	if canonical.Number.Uint64() > f.lastTrustedHeader.Number.Uint64() {
+		canonical = f.chain.GetHeaderByNumber(f.lastTrustedHeader.Number.Uint64())
+	}
+	commonAncestor := rawdb.FindCommonAncestor(f.pm.chainDb, canonical, f.lastTrustedHeader)
+	if commonAncestor == nil {
+		log.Error("Common ancestor of last trusted header and canonical header is nil", "canonical hash", canonical.Hash(), "trusted hash", f.lastTrustedHeader.Hash())
+		return current, unapprovedHashes
+	}
+
+	for current.Hash() == commonAncestor.Hash() {
+		if f.isTrustedHash(current.Hash()) {
+			break
+		}
+		unapprovedHashes = append(unapprovedHashes, current.Hash())
+		current = f.chain.GetHeader(current.ParentHash, current.Number.Uint64()-1)
+	}
+	return current, unapprovedHashes
+}
+
+func (f *lightFetcher) setLastTrustedHeader(h *types.Header) {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	f.lastTrustedHeader = h
 }
 
 // checkKnownNode checks if a block tree node is known (downloaded and validated)
@@ -747,6 +867,7 @@ func (f *lightFetcher) updateMaxConfirmedTd(td *big.Int) {
 		if f.lastUpdateStats != nil {
 			f.lastUpdateStats.next = newEntry
 		}
+
 		f.lastUpdateStats = newEntry
 		for p := range f.peers {
 			f.checkUpdateStats(p, newEntry)
@@ -769,6 +890,7 @@ func (f *lightFetcher) checkUpdateStats(p *peer, newEntry *updateStatsEntry) {
 		p.Log().Debug("Unknown peer to check update stats")
 		return
 	}
+
 	if newEntry != nil && fp.firstUpdateStats == nil {
 		fp.firstUpdateStats = newEntry
 	}

les/fetcher_test.go

@@ -0,0 +1,155 @@
+package les
+
+import (
+	"math/big"
+	"testing"
+
+	"net"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+)
+
+func TestFetcherULCPeerSelector(t *testing.T) {
+
+	var (
+		id1 enode.ID = newNodeID(t).ID()
+		id2 enode.ID = newNodeID(t).ID()
+		id3 enode.ID = newNodeID(t).ID()
+		id4 enode.ID = newNodeID(t).ID()
+	)
+
+	ftn1 := &fetcherTreeNode{
+		hash: common.HexToHash("1"),
+		td:   big.NewInt(1),
+	}
+	ftn2 := &fetcherTreeNode{
+		hash:   common.HexToHash("2"),
+		td:     big.NewInt(2),
+		parent: ftn1,
+	}
+	ftn3 := &fetcherTreeNode{
+		hash:   common.HexToHash("3"),
+		td:     big.NewInt(3),
+		parent: ftn2,
+	}
+	lf := lightFetcher{
+		pm: &ProtocolManager{
+			ulc: &ulc{
+				trustedKeys: map[string]struct{}{
+					id1.String(): {},
+					id2.String(): {},
+					id3.String(): {},
+					id4.String(): {},
+				},
+				minTrustedFraction: 70,
+			},
+		},
+		maxConfirmedTd: ftn1.td,
+
+		peers: map[*peer]*fetcherPeerInfo{
+			{
+				id:        "peer1",
+				Peer:      p2p.NewPeer(id1, "peer1", []p2p.Cap{}),
+				isTrusted: true,
+			}: {
+				nodeByHash: map[common.Hash]*fetcherTreeNode{
+					ftn1.hash: ftn1,
+					ftn2.hash: ftn2,
+				},
+			},
+			{
+				Peer:      p2p.NewPeer(id2, "peer2", []p2p.Cap{}),
+				id:        "peer2",
+				isTrusted: true,
+			}: {
+				nodeByHash: map[common.Hash]*fetcherTreeNode{
+					ftn1.hash: ftn1,
+					ftn2.hash: ftn2,
+				},
+			},
+			{
+				id:        "peer3",
+				Peer:      p2p.NewPeer(id3, "peer3", []p2p.Cap{}),
+				isTrusted: true,
+			}: {
+				nodeByHash: map[common.Hash]*fetcherTreeNode{
+					ftn1.hash: ftn1,
+					ftn2.hash: ftn2,
+					ftn3.hash: ftn3,
+				},
+			},
+			{
+				id:        "peer4",
+				Peer:      p2p.NewPeer(id4, "peer4", []p2p.Cap{}),
+				isTrusted: true,
+			}: {
+				nodeByHash: map[common.Hash]*fetcherTreeNode{
+					ftn1.hash: ftn1,
+				},
+			},
+		},
+		chain: &lightChainStub{
+			tds: map[common.Hash]*big.Int{},
+			headers: map[common.Hash]*types.Header{
+				ftn1.hash: {},
+				ftn2.hash: {},
+				ftn3.hash: {},
+			},
+		},
+	}
+	bestHash, bestAmount, bestTD, sync := lf.findBestRequest()
+
+	if bestTD == nil {
+		t.Fatal("Empty result")
+	}
+
+	if bestTD.Cmp(ftn2.td) != 0 {
+		t.Fatal("bad td", bestTD)
+	}
+	if bestHash != ftn2.hash {
+		t.Fatal("bad hash", bestTD)
+	}
+
+	_, _ = bestAmount, sync
+}
+
+type lightChainStub struct {
+	BlockChain
+	tds                         map[common.Hash]*big.Int
+	headers                     map[common.Hash]*types.Header
+	insertHeaderChainAssertFunc func(chain []*types.Header, checkFreq int) (int, error)
+}
+
+func (l *lightChainStub) GetHeader(hash common.Hash, number uint64) *types.Header {
+	if h, ok := l.headers[hash]; ok {
+		return h
+	}
+
+	return nil
+}
+
+func (l *lightChainStub) LockChain()   {}
+func (l *lightChainStub) UnlockChain() {}
+
+func (l *lightChainStub) GetTd(hash common.Hash, number uint64) *big.Int {
+	if td, ok := l.tds[hash]; ok {
+		return td
+	}
+	return nil
+}
+
+func (l *lightChainStub) InsertHeaderChain(chain []*types.Header, checkFreq int) (int, error) {
+	return l.insertHeaderChainAssertFunc(chain, checkFreq)
+}
+
+func newNodeID(t *testing.T) *enode.Node {
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		t.Fatal("generate key err:", err)
+	}
+	return enode.NewV4(&key.PublicKey, net.IP{}, 35000, 35000)
+}

les/handler.go

@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/eth/downloader"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/event"
@@ -119,12 +120,29 @@ type ProtocolManager struct {
 
 	// wait group is used for graceful shutdowns during downloading
 	// and processing
-	wg *sync.WaitGroup
+	wg  *sync.WaitGroup
+	ulc *ulc
 }
 
 // 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, lightSync 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) (*ProtocolManager, error) {
+func NewProtocolManager(
+	chainConfig *params.ChainConfig,
+	indexerConfig *light.IndexerConfig,
+	lightSync 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) (*ProtocolManager, error) {
 	// Create the protocol manager with the base fields
 	manager := &ProtocolManager{
 		lightSync:   lightSync,
@@ -149,6 +167,10 @@ func NewProtocolManager(chainConfig *params.ChainConfig, indexerConfig *light.In
 		manager.reqDist = odr.retriever.dist
 	}
 
+	if ulcConfig != nil {
+		manager.ulc = newULC(ulcConfig)
+	}
+
 	removePeer := manager.removePeer
 	if disableClientRemovePeer {
 		removePeer = func(id string) {}
@@ -234,7 +256,11 @@ func (pm *ProtocolManager) runPeer(version uint, p *p2p.Peer, rw p2p.MsgReadWrit
 }
 
 func (pm *ProtocolManager) newPeer(pv int, nv uint64, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
-	return newPeer(pv, nv, p, newMeteredMsgWriter(rw))
+	var isTrusted bool
+	if pm.isULCEnabled() {
+		isTrusted = pm.ulc.isTrusted(p.ID())
+	}
+	return newPeer(pv, nv, isTrusted, p, newMeteredMsgWriter(rw))
 }
 
 // handle is the callback invoked to manage the life cycle of a les peer. When
@@ -276,6 +302,7 @@ func (pm *ProtocolManager) handle(p *peer) error {
 	if rw, ok := p.rw.(*meteredMsgReadWriter); ok {
 		rw.Init(p.version)
 	}
+
 	// Register the peer locally
 	if err := pm.peers.Register(p); err != nil {
 		p.Log().Error("Light Ethereum peer registration failed", "err", err)
@@ -287,6 +314,7 @@ func (pm *ProtocolManager) handle(p *peer) error {
 		}
 		pm.removePeer(p.id)
 	}()
+
 	// Register the peer in the downloader. If the downloader considers it banned, we disconnect
 	if pm.lightSync {
 		p.lock.Lock()
@@ -371,16 +399,15 @@ func (pm *ProtocolManager) handleMsg(p *peer) error {
 	// Block header query, collect the requested headers and reply
 	case AnnounceMsg:
 		p.Log().Trace("Received announce message")
-		if p.requestAnnounceType == announceTypeNone {
+		if p.announceType == announceTypeNone {
 			return errResp(ErrUnexpectedResponse, "")
 		}
-
 		var req announceData
 		if err := msg.Decode(&req); err != nil {
 			return errResp(ErrDecode, "%v: %v", msg, err)
 		}
 
-		if p.requestAnnounceType == announceTypeSigned {
+		if p.announceType == announceTypeSigned {
 			if err := req.checkSignature(p.ID()); err != nil {
 				p.Log().Trace("Invalid announcement signature", "err", err)
 				return err
@@ -1175,6 +1202,14 @@ func (pm *ProtocolManager) txStatus(hashes []common.Hash) []txStatus {
 	return stats
 }
 
+// isULCEnabled returns true if we can use ULC
+func (pm *ProtocolManager) isULCEnabled() bool {
+	if pm.ulc == nil || len(pm.ulc.trustedKeys) == 0 {
+		return false
+	}
+	return true
+}
+
 // downloaderPeerNotify implements peerSetNotify
 type downloaderPeerNotify ProtocolManager
 

les/handler_test.go

@@ -494,7 +494,7 @@ func TestGetBloombitsProofs(t *testing.T) {
 
 func TestTransactionStatusLes2(t *testing.T) {
 	db := ethdb.NewMemDatabase()
-	pm := newTestProtocolManagerMust(t, false, 0, nil, nil, nil, db)
+	pm := newTestProtocolManagerMust(t, false, 0, nil, nil, nil, db, nil)
 	chain := pm.blockchain.(*core.BlockChain)
 	config := core.DefaultTxPoolConfig
 	config.Journal = ""

les/helper_test.go

@@ -146,7 +146,7 @@ func testRCL() RequestCostList {
 // 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) (*ProtocolManager, error) {
+func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *core.BlockGen), odr *LesOdr, peers *peerSet, db ethdb.Database, ulcConfig *eth.ULCConfig) (*ProtocolManager, error) {
 	var (
 		evmux  = new(event.TypeMux)
 		engine = ethash.NewFaker()
@@ -176,7 +176,7 @@ func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *cor
 	if lightSync {
 		indexConfig = light.TestClientIndexerConfig
 	}
-	pm, err := NewProtocolManager(gspec.Config, indexConfig, lightSync, NetworkId, evmux, engine, peers, chain, nil, db, odr, nil, nil, make(chan struct{}), new(sync.WaitGroup))
+	pm, err := NewProtocolManager(gspec.Config, indexConfig, lightSync, NetworkId, evmux, engine, peers, chain, nil, db, odr, nil, nil, make(chan struct{}), new(sync.WaitGroup), ulcConfig)
 	if err != nil {
 		return nil, err
 	}
@@ -200,8 +200,8 @@ func newTestProtocolManager(lightSync bool, blocks int, generator func(int, *cor
 // 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) *ProtocolManager {
+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)
+	pm, err := newTestProtocolManager(lightSync, blocks, generator, odr, peers, db, ulcConfig)
 	if err != nil {
 		t.Fatalf("Failed to create protocol manager: %v", err)
 	}
@@ -343,7 +343,7 @@ func newServerEnv(t *testing.T, blocks int, protocol int, waitIndexers func(*cor
 	db := ethdb.NewMemDatabase()
 	cIndexer, bIndexer, btIndexer := testIndexers(db, nil, light.TestServerIndexerConfig)
 
-	pm := newTestProtocolManagerMust(t, false, blocks, testChainGen, nil, nil, db)
+	pm := newTestProtocolManagerMust(t, false, blocks, testChainGen, nil, nil, db, nil)
 	peer, _ := newTestPeer(t, "peer", protocol, pm, true)
 
 	cIndexer.Start(pm.blockchain.(*core.BlockChain))
@@ -383,8 +383,8 @@ func newClientServerEnv(t *testing.T, blocks int, protocol int, waitIndexers fun
 	lcIndexer, lbIndexer, lbtIndexer := testIndexers(ldb, odr, light.TestClientIndexerConfig)
 	odr.SetIndexers(lcIndexer, lbtIndexer, lbIndexer)
 
-	pm := newTestProtocolManagerMust(t, false, blocks, testChainGen, nil, peers, db)
+	pm := newTestProtocolManagerMust(t, false, blocks, testChainGen, nil, peers, db, nil)
-	lpm := newTestProtocolManagerMust(t, true, 0, nil, odr, lPeers, ldb)
+	lpm := newTestProtocolManagerMust(t, true, 0, nil, odr, lPeers, ldb, nil)
 
 	startIndexers := func(clientMode bool, pm *ProtocolManager) {
 		if clientMode {

les/odr.go

@@ -109,7 +109,10 @@ func (odr *LesOdr) Retrieve(ctx context.Context, req light.OdrRequest) (err erro
 		},
 		canSend: func(dp distPeer) bool {
 			p := dp.(*peer)
-			return lreq.CanSend(p)
+			if !p.isOnlyAnnounce {
+				return lreq.CanSend(p)
+			}
+			return false
 		},
 		request: func(dp distPeer) func() {
 			p := dp.(*peer)

les/peer.go

@@ -56,7 +56,7 @@ type peer struct {
 	version int    // Protocol version negotiated
 	network uint64 // Network ID being on
 
-	announceType, requestAnnounceType uint64
+	announceType uint64
 
 	id string
 
@@ -74,9 +74,12 @@ type peer struct {
 	fcServer       *flowcontrol.ServerNode // nil if the peer is client only
 	fcServerParams *flowcontrol.ServerParams
 	fcCosts        requestCostTable
+
+	isTrusted      bool
+	isOnlyAnnounce bool
 }
 
-func newPeer(version int, network uint64, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
+func newPeer(version int, network uint64, isTrusted bool, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
 	id := p.ID()
 
 	return &peer{
@@ -86,6 +89,7 @@ func newPeer(version int, network uint64, p *p2p.Peer, rw p2p.MsgReadWriter) *pe
 		network:     network,
 		id:          fmt.Sprintf("%x", id[:8]),
 		announceChn: make(chan announceData, 20),
+		isTrusted:   isTrusted,
 	}
 }
 
@@ -401,23 +405,32 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, headNum uint64, genesis
 	send = send.add("headNum", headNum)
 	send = send.add("genesisHash", genesis)
 	if server != nil {
-		send = send.add("serveHeaders", nil)
+		if !server.onlyAnnounce {
-		send = send.add("serveChainSince", uint64(0))
+			//only announce server. It sends only announse requests
-		send = send.add("serveStateSince", uint64(0))
+			send = send.add("serveHeaders", nil)
-		send = send.add("txRelay", nil)
+			send = send.add("serveChainSince", uint64(0))
+			send = send.add("serveStateSince", uint64(0))
+			send = send.add("txRelay", nil)
+		}
 		send = send.add("flowControl/BL", server.defParams.BufLimit)
 		send = send.add("flowControl/MRR", server.defParams.MinRecharge)
 		list := server.fcCostStats.getCurrentList()
 		send = send.add("flowControl/MRC", list)
 		p.fcCosts = list.decode()
 	} else {
-		p.requestAnnounceType = announceTypeSimple // set to default until "very light" client mode is implemented
+		//on client node
-		send = send.add("announceType", p.requestAnnounceType)
+		p.announceType = announceTypeSimple
+		if p.isTrusted {
+			p.announceType = announceTypeSigned
+		}
+		send = send.add("announceType", p.announceType)
 	}
+
 	recvList, err := p.sendReceiveHandshake(send)
 	if err != nil {
 		return err
 	}
+
 	recv := recvList.decode()
 
 	var rGenesis, rHash common.Hash
@@ -452,25 +465,33 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, headNum uint64, genesis
 	if int(rVersion) != p.version {
 		return errResp(ErrProtocolVersionMismatch, "%d (!= %d)", rVersion, p.version)
 	}
+
 	if server != nil {
 		// until we have a proper peer connectivity API, allow LES connection to other servers
 		/*if recv.get("serveStateSince", nil) == nil {
 			return errResp(ErrUselessPeer, "wanted client, got server")
 		}*/
 		if recv.get("announceType", &p.announceType) != nil {
+			//set default announceType on server side
 			p.announceType = announceTypeSimple
 		}
 		p.fcClient = flowcontrol.NewClientNode(server.fcManager, server.defParams)
 	} else {
+		//mark OnlyAnnounce server if "serveHeaders", "serveChainSince", "serveStateSince" or "txRelay" fields don't exist
 		if recv.get("serveChainSince", nil) != nil {
-			return errResp(ErrUselessPeer, "peer cannot serve chain")
+			p.isOnlyAnnounce = true
 		}
 		if recv.get("serveStateSince", nil) != nil {
-			return errResp(ErrUselessPeer, "peer cannot serve state")
+			p.isOnlyAnnounce = true
 		}
 		if recv.get("txRelay", nil) != nil {
-			return errResp(ErrUselessPeer, "peer cannot relay transactions")
+			p.isOnlyAnnounce = true
 		}
+
+		if p.isOnlyAnnounce && !p.isTrusted {
+			return errResp(ErrUselessPeer, "peer cannot serve requests")
+		}
+
 		params := &flowcontrol.ServerParams{}
 		if err := recv.get("flowControl/BL", &params.BufLimit); err != nil {
 			return err
@@ -486,7 +507,6 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, headNum uint64, genesis
 		p.fcServer = flowcontrol.NewServerNode(params)
 		p.fcCosts = MRC.decode()
 	}
-
 	p.headInfo = &announceData{Td: rTd, Hash: rHash, Number: rNum}
 	return nil
 }
@@ -576,8 +596,10 @@ func (ps *peerSet) Unregister(id string) error {
 		for _, n := range peers {
 			n.unregisterPeer(p)
 		}
+
 		p.sendQueue.quit()
 		p.Peer.Disconnect(p2p.DiscUselessPeer)
+
 		return nil
 	}
 }

les/peer_test.go

@@ -0,0 +1,297 @@
+package les
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/les/flowcontrol"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+const (
+	test_networkid   = 10
+	protocol_version = 2123
+)
+
+var (
+	hash    = common.HexToHash("some string")
+	genesis = common.HexToHash("genesis hash")
+	headNum = uint64(1234)
+	td      = big.NewInt(123)
+)
+
+//ulc connects to trusted peer and send announceType=announceTypeSigned
+func TestPeerHandshakeSetAnnounceTypeToAnnounceTypeSignedForTrustedPeer(t *testing.T) {
+
+	var id enode.ID = newNodeID(t).ID()
+
+	//peer to connect(on ulc side)
+	p := peer{
+		Peer:      p2p.NewPeer(id, "test peer", []p2p.Cap{}),
+		version:   protocol_version,
+		isTrusted: true,
+		rw: &rwStub{
+			WriteHook: func(recvList keyValueList) {
+				//checking that ulc sends to peer allowedRequests=onlyAnnounceRequests and announceType = announceTypeSigned
+				recv := recvList.decode()
+				var reqType uint64
+
+				err := recv.get("announceType", &reqType)
+				if err != nil {
+					t.Fatal(err)
+				}
+
+				if reqType != announceTypeSigned {
+					t.Fatal("Expected announceTypeSigned")
+				}
+			},
+			ReadHook: func(l keyValueList) keyValueList {
+				l = l.add("serveHeaders", nil)
+				l = l.add("serveChainSince", uint64(0))
+				l = l.add("serveStateSince", uint64(0))
+				l = l.add("txRelay", nil)
+				l = l.add("flowControl/BL", uint64(0))
+				l = l.add("flowControl/MRR", uint64(0))
+				l = l.add("flowControl/MRC", RequestCostList{})
+
+				return l
+			},
+		},
+		network: test_networkid,
+	}
+
+	err := p.Handshake(td, hash, headNum, genesis, nil)
+	if err != nil {
+		t.Fatalf("Handshake error: %s", err)
+	}
+
+	if p.announceType != announceTypeSigned {
+		t.Fatal("Incorrect announceType")
+	}
+}
+
+func TestPeerHandshakeAnnounceTypeSignedForTrustedPeersPeerNotInTrusted(t *testing.T) {
+	var id enode.ID = newNodeID(t).ID()
+	p := peer{
+		Peer:    p2p.NewPeer(id, "test peer", []p2p.Cap{}),
+		version: protocol_version,
+		rw: &rwStub{
+			WriteHook: func(recvList keyValueList) {
+				//checking that ulc sends to peer allowedRequests=noRequests and announceType != announceTypeSigned
+				recv := recvList.decode()
+				var reqType uint64
+
+				err := recv.get("announceType", &reqType)
+				if err != nil {
+					t.Fatal(err)
+				}
+
+				if reqType == announceTypeSigned {
+					t.Fatal("Expected not announceTypeSigned")
+				}
+			},
+			ReadHook: func(l keyValueList) keyValueList {
+				l = l.add("serveHeaders", nil)
+				l = l.add("serveChainSince", uint64(0))
+				l = l.add("serveStateSince", uint64(0))
+				l = l.add("txRelay", nil)
+				l = l.add("flowControl/BL", uint64(0))
+				l = l.add("flowControl/MRR", uint64(0))
+				l = l.add("flowControl/MRC", RequestCostList{})
+
+				return l
+			},
+		},
+		network: test_networkid,
+	}
+
+	err := p.Handshake(td, hash, headNum, genesis, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.announceType == announceTypeSigned {
+		t.Fatal("Incorrect announceType")
+	}
+}
+
+func TestPeerHandshakeDefaultAllRequests(t *testing.T) {
+	var id enode.ID = newNodeID(t).ID()
+
+	s := generateLesServer()
+
+	p := peer{
+		Peer:    p2p.NewPeer(id, "test peer", []p2p.Cap{}),
+		version: protocol_version,
+		rw: &rwStub{
+			ReadHook: func(l keyValueList) keyValueList {
+				l = l.add("announceType", uint64(announceTypeSigned))
+				l = l.add("allowedRequests", uint64(0))
+
+				return l
+			},
+		},
+		network: test_networkid,
+	}
+
+	err := p.Handshake(td, hash, headNum, genesis, s)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if p.isOnlyAnnounce {
+		t.Fatal("Incorrect announceType")
+	}
+}
+
+func TestPeerHandshakeServerSendOnlyAnnounceRequestsHeaders(t *testing.T) {
+	var id enode.ID = newNodeID(t).ID()
+
+	s := generateLesServer()
+	s.onlyAnnounce = true
+
+	p := peer{
+		Peer:    p2p.NewPeer(id, "test peer", []p2p.Cap{}),
+		version: protocol_version,
+		rw: &rwStub{
+			ReadHook: func(l keyValueList) keyValueList {
+				l = l.add("announceType", uint64(announceTypeSigned))
+
+				return l
+			},
+			WriteHook: func(l keyValueList) {
+				for _, v := range l {
+					if v.Key == "serveHeaders" ||
+						v.Key == "serveChainSince" ||
+						v.Key == "serveStateSince" ||
+						v.Key == "txRelay" {
+						t.Fatalf("%v exists", v.Key)
+					}
+				}
+			},
+		},
+		network: test_networkid,
+	}
+
+	err := p.Handshake(td, hash, headNum, genesis, s)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+func TestPeerHandshakeClientReceiveOnlyAnnounceRequestsHeaders(t *testing.T) {
+	var id enode.ID = newNodeID(t).ID()
+
+	p := peer{
+		Peer:    p2p.NewPeer(id, "test peer", []p2p.Cap{}),
+		version: protocol_version,
+		rw: &rwStub{
+			ReadHook: func(l keyValueList) keyValueList {
+				l = l.add("flowControl/BL", uint64(0))
+				l = l.add("flowControl/MRR", uint64(0))
+				l = l.add("flowControl/MRC", RequestCostList{})
+
+				l = l.add("announceType", uint64(announceTypeSigned))
+
+				return l
+			},
+		},
+		network:   test_networkid,
+		isTrusted: true,
+	}
+
+	err := p.Handshake(td, hash, headNum, genesis, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !p.isOnlyAnnounce {
+		t.Fatal("isOnlyAnnounce must be true")
+	}
+}
+
+func TestPeerHandshakeClientReturnErrorOnUselessPeer(t *testing.T) {
+	var id enode.ID = newNodeID(t).ID()
+
+	p := peer{
+		Peer:    p2p.NewPeer(id, "test peer", []p2p.Cap{}),
+		version: protocol_version,
+		rw: &rwStub{
+			ReadHook: func(l keyValueList) keyValueList {
+				l = l.add("flowControl/BL", uint64(0))
+				l = l.add("flowControl/MRR", uint64(0))
+				l = l.add("flowControl/MRC", RequestCostList{})
+
+				l = l.add("announceType", uint64(announceTypeSigned))
+
+				return l
+			},
+		},
+		network: test_networkid,
+	}
+
+	err := p.Handshake(td, hash, headNum, genesis, nil)
+	if err == nil {
+		t.FailNow()
+	}
+}
+
+func generateLesServer() *LesServer {
+	s := &LesServer{
+		defParams: &flowcontrol.ServerParams{
+			BufLimit:    uint64(300000000),
+			MinRecharge: uint64(50000),
+		},
+		fcManager: flowcontrol.NewClientManager(1, 2, 3),
+		fcCostStats: &requestCostStats{
+			stats: make(map[uint64]*linReg, len(reqList)),
+		},
+	}
+	for _, code := range reqList {
+		s.fcCostStats.stats[code] = &linReg{cnt: 100}
+	}
+	return s
+}
+
+type rwStub struct {
+	ReadHook  func(l keyValueList) keyValueList
+	WriteHook func(l keyValueList)
+}
+
+func (s *rwStub) ReadMsg() (p2p.Msg, error) {
+	payload := keyValueList{}
+	payload = payload.add("protocolVersion", uint64(protocol_version))
+	payload = payload.add("networkId", uint64(test_networkid))
+	payload = payload.add("headTd", td)
+	payload = payload.add("headHash", hash)
+	payload = payload.add("headNum", headNum)
+	payload = payload.add("genesisHash", genesis)
+
+	if s.ReadHook != nil {
+		payload = s.ReadHook(payload)
+	}
+
+	size, p, err := rlp.EncodeToReader(payload)
+	if err != nil {
+		return p2p.Msg{}, err
+	}
+
+	return p2p.Msg{
+		Size:    uint32(size),
+		Payload: p,
+	}, nil
+}
+
+func (s *rwStub) WriteMsg(m p2p.Msg) error {
+	recvList := keyValueList{}
+	if err := m.Decode(&recvList); err != nil {
+		return err
+	}
+
+	if s.WriteHook != nil {
+		s.WriteHook(recvList)
+	}
+
+	return nil
+}

les/server.go

@@ -41,17 +41,34 @@ import (
 type LesServer struct {
 	lesCommons
 
-	fcManager   *flowcontrol.ClientManager // nil if our node is client only
+	fcManager    *flowcontrol.ClientManager // nil if our node is client only
-	fcCostStats *requestCostStats
+	fcCostStats  *requestCostStats
-	defParams   *flowcontrol.ServerParams
+	defParams    *flowcontrol.ServerParams
-	lesTopics   []discv5.Topic
+	lesTopics    []discv5.Topic
-	privateKey  *ecdsa.PrivateKey
+	privateKey   *ecdsa.PrivateKey
-	quitSync    chan struct{}
+	quitSync     chan struct{}
+	onlyAnnounce bool
 }
 
 func NewLesServer(eth *eth.Ethereum, config *eth.Config) (*LesServer, error) {
 	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))
+	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)
 	if err != nil {
 		return nil, err
 	}
@@ -70,8 +87,9 @@ func NewLesServer(eth *eth.Ethereum, config *eth.Config) (*LesServer, error) {
 			bloomTrieIndexer: light.NewBloomTrieIndexer(eth.ChainDb(), nil, params.BloomBitsBlocks, params.BloomTrieFrequency),
 			protocolManager:  pm,
 		},
-		quitSync:  quitSync,
+		quitSync:     quitSync,
-		lesTopics: lesTopics,
+		lesTopics:    lesTopics,
+		onlyAnnounce: config.OnlyAnnounce,
 	}
 
 	logger := log.New()
@@ -289,10 +307,8 @@ func (s *requestCostStats) getCurrentList() RequestCostList {
 	defer s.lock.Unlock()
 
 	list := make(RequestCostList, len(reqList))
-	//fmt.Println("RequestCostList")
 	for idx, code := range reqList {
 		b, m := s.stats[code].calc()
-		//fmt.Println(code, s.stats[code].cnt, b/1000000, m/1000000)
 		if m < 0 {
 			b += m
 			m = 0

les/serverpool.go

@@ -126,22 +126,22 @@ type serverPool struct {
 	discNodes     chan *enode.Node
 	discLookups   chan bool
 
+	trustedNodes         map[enode.ID]*enode.Node
 	entries              map[enode.ID]*poolEntry
 	timeout, enableRetry chan *poolEntry
 	adjustStats          chan poolStatAdjust
 
-	connCh     chan *connReq
-	disconnCh  chan *disconnReq
-	registerCh chan *registerReq
-
 	knownQueue, newQueue       poolEntryQueue
 	knownSelect, newSelect     *weightedRandomSelect
 	knownSelected, newSelected int
 	fastDiscover               bool
+	connCh                     chan *connReq
+	disconnCh                  chan *disconnReq
+	registerCh                 chan *registerReq
 }
 
 // newServerPool creates a new serverPool instance
-func newServerPool(db ethdb.Database, quit chan struct{}, wg *sync.WaitGroup) *serverPool {
+func newServerPool(db ethdb.Database, quit chan struct{}, wg *sync.WaitGroup, trustedNodes []string) *serverPool {
 	pool := &serverPool{
 		db:           db,
 		quit:         quit,
@@ -156,7 +156,9 @@ func newServerPool(db ethdb.Database, quit chan struct{}, wg *sync.WaitGroup) *s
 		knownSelect:  newWeightedRandomSelect(),
 		newSelect:    newWeightedRandomSelect(),
 		fastDiscover: true,
+		trustedNodes: parseTrustedNodes(trustedNodes),
 	}
+
 	pool.knownQueue = newPoolEntryQueue(maxKnownEntries, pool.removeEntry)
 	pool.newQueue = newPoolEntryQueue(maxNewEntries, pool.removeEntry)
 	return pool
@@ -168,6 +170,7 @@ func (pool *serverPool) start(server *p2p.Server, topic discv5.Topic) {
 	pool.dbKey = append([]byte("serverPool/"), []byte(topic)...)
 	pool.wg.Add(1)
 	pool.loadNodes()
+	pool.connectToTrustedNodes()
 
 	if pool.server.DiscV5 != nil {
 		pool.discSetPeriod = make(chan time.Duration, 1)
@@ -337,8 +340,10 @@ func (pool *serverPool) eventLoop() {
 			}
 
 		case node := <-pool.discNodes:
-			entry := pool.findOrNewNode(node)
+			if pool.trustedNodes[node.ID()] == nil {
-			pool.updateCheckDial(entry)
+				entry := pool.findOrNewNode(node)
+				pool.updateCheckDial(entry)
+			}
 
 		case conv := <-pool.discLookups:
 			if conv {
@@ -355,29 +360,34 @@ func (pool *serverPool) eventLoop() {
 			}
 
 		case req := <-pool.connCh:
-			// Handle peer connection requests.
+			if pool.trustedNodes[req.p.ID()] != nil {
-			entry := pool.entries[req.p.ID()]
+				// ignore trusted nodes
-			if entry == nil {
-				entry = pool.findOrNewNode(req.node)
-			}
-			if entry.state == psConnected || entry.state == psRegistered {
 				req.result <- nil
-				continue
+			} else {
+				// Handle peer connection requests.
+				entry := pool.entries[req.p.ID()]
+				if entry == nil {
+					entry = pool.findOrNewNode(req.node)
+				}
+				if entry.state == psConnected || entry.state == psRegistered {
+					req.result <- nil
+					continue
+				}
+				pool.connWg.Add(1)
+				entry.peer = req.p
+				entry.state = psConnected
+				addr := &poolEntryAddress{
+					ip:       req.node.IP(),
+					port:     uint16(req.node.TCP()),
+					lastSeen: mclock.Now(),
+				}
+				entry.lastConnected = addr
+				entry.addr = make(map[string]*poolEntryAddress)
+				entry.addr[addr.strKey()] = addr
+				entry.addrSelect = *newWeightedRandomSelect()
+				entry.addrSelect.update(addr)
+				req.result <- entry
 			}
-			pool.connWg.Add(1)
-			entry.peer = req.p
-			entry.state = psConnected
-			addr := &poolEntryAddress{
-				ip:       req.node.IP(),
-				port:     uint16(req.node.TCP()),
-				lastSeen: mclock.Now(),
-			}
-			entry.lastConnected = addr
-			entry.addr = make(map[string]*poolEntryAddress)
-			entry.addr[addr.strKey()] = addr
-			entry.addrSelect = *newWeightedRandomSelect()
-			entry.addrSelect.update(addr)
-			req.result <- entry
 
 		case req := <-pool.registerCh:
 			// Handle peer registration requests.
@@ -470,11 +480,42 @@ func (pool *serverPool) loadNodes() {
 			"response", fmt.Sprintf("%v/%v", time.Duration(e.responseStats.avg), e.responseStats.weight),
 			"timeout", fmt.Sprintf("%v/%v", e.timeoutStats.avg, e.timeoutStats.weight))
 		pool.entries[e.node.ID()] = e
-		pool.knownQueue.setLatest(e)
+		if pool.trustedNodes[e.node.ID()] == nil {
-		pool.knownSelect.update((*knownEntry)(e))
+			pool.knownQueue.setLatest(e)
+			pool.knownSelect.update((*knownEntry)(e))
+		}
 	}
 }
 
+// connectToTrustedNodes adds trusted server nodes as static trusted peers.
+//
+// Note: trusted nodes are not handled by the server pool logic, they are not
+// added to either the known or new selection pools. They are connected/reconnected
+// by p2p.Server whenever possible.
+func (pool *serverPool) connectToTrustedNodes() {
+	//connect to trusted nodes
+	for _, node := range pool.trustedNodes {
+		pool.server.AddTrustedPeer(node)
+		pool.server.AddPeer(node)
+		log.Debug("Added trusted node", "id", node.ID().String())
+	}
+}
+
+// parseTrustedNodes returns valid and parsed enodes
+func parseTrustedNodes(trustedNodes []string) map[enode.ID]*enode.Node {
+	nodes := make(map[enode.ID]*enode.Node)
+
+	for _, node := range trustedNodes {
+		node, err := enode.ParseV4(node)
+		if err != nil {
+			log.Warn("Trusted node URL invalid", "enode", node, "err", err)
+			continue
+		}
+		nodes[node.ID()] = node
+	}
+	return nodes
+}
+
 // saveNodes saves known nodes and their statistics into the database. Nodes are
 // ordered from least to most recently connected.
 func (pool *serverPool) saveNodes() {

les/txrelay.go

@@ -121,7 +121,7 @@ func (self *LesTxRelay) send(txs types.Transactions, count int) {
 				return peer.GetRequestCost(SendTxMsg, len(ll))
 			},
 			canSend: func(dp distPeer) bool {
-				return dp.(*peer) == pp
+				return !dp.(*peer).isOnlyAnnounce && dp.(*peer) == pp
 			},
 			request: func(dp distPeer) func() {
 				peer := dp.(*peer)

les/ulc.go

@@ -0,0 +1,39 @@
+package les
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/eth"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+)
+
+type ulc struct {
+	trustedKeys        map[string]struct{}
+	minTrustedFraction int
+}
+
+func newULC(ulcConfig *eth.ULCConfig) *ulc {
+	if ulcConfig == nil {
+		return nil
+	}
+
+	m := make(map[string]struct{}, len(ulcConfig.TrustedServers))
+	for _, id := range ulcConfig.TrustedServers {
+		node, err := enode.ParseV4(id)
+		if err != nil {
+			fmt.Println("node:", id, " err:", err)
+			continue
+		}
+		m[node.ID().String()] = struct{}{}
+	}
+
+	return &ulc{m, ulcConfig.MinTrustedFraction}
+}
+
+func (u *ulc) isTrusted(p enode.ID) bool {
+	if u.trustedKeys == nil {
+		return false
+	}
+	_, ok := u.trustedKeys[p.String()]
+	return ok
+}

les/ulc_test.go

@@ -0,0 +1,239 @@
+package les
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+	"time"
+
+	"net"
+
+	"crypto/ecdsa"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/eth"
+	"github.com/ethereum/go-ethereum/ethdb"
+	"github.com/ethereum/go-ethereum/light"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/enode"
+)
+
+func TestULCSyncWithOnePeer(t *testing.T) {
+	f := newFullPeerPair(t, 1, 4, testChainGen)
+	ulcConfig := &eth.ULCConfig{
+		MinTrustedFraction: 100,
+		TrustedServers:     []string{f.Node.String()},
+	}
+
+	l := newLightPeer(t, ulcConfig)
+
+	if reflect.DeepEqual(f.PM.blockchain.CurrentHeader().Hash(), l.PM.blockchain.CurrentHeader().Hash()) {
+		t.Fatal("blocks are equal")
+	}
+
+	_, _, err := connectPeers(f, l, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	l.PM.fetcher.lock.Lock()
+	l.PM.fetcher.nextRequest()
+	l.PM.fetcher.lock.Unlock()
+
+	if !reflect.DeepEqual(f.PM.blockchain.CurrentHeader().Hash(), l.PM.blockchain.CurrentHeader().Hash()) {
+		t.Fatal("sync doesn't work")
+	}
+}
+
+func TestULCReceiveAnnounce(t *testing.T) {
+	f := newFullPeerPair(t, 1, 4, testChainGen)
+	ulcConfig := &eth.ULCConfig{
+		MinTrustedFraction: 100,
+		TrustedServers:     []string{f.Node.String()},
+	}
+
+	l := newLightPeer(t, ulcConfig)
+	fPeer, lPeer, err := connectPeers(f, l, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	l.PM.synchronise(fPeer)
+
+	//check that the sync is finished correctly
+	if !reflect.DeepEqual(f.PM.blockchain.CurrentHeader().Hash(), l.PM.blockchain.CurrentHeader().Hash()) {
+		t.Fatal("sync doesn't work")
+	}
+
+	l.PM.peers.lock.Lock()
+	if len(l.PM.peers.peers) == 0 {
+		t.Fatal("peer list should not be empty")
+	}
+	l.PM.peers.lock.Unlock()
+
+	time.Sleep(time.Second)
+	//send a signed announce message(payload doesn't matter)
+	td := f.PM.blockchain.GetTd(l.PM.blockchain.CurrentHeader().Hash(), l.PM.blockchain.CurrentHeader().Number.Uint64())
+	announce := announceData{
+		Number: l.PM.blockchain.CurrentHeader().Number.Uint64() + 1,
+		Td:     td.Add(td, big.NewInt(1)),
+	}
+	announce.sign(f.Key)
+	lPeer.SendAnnounce(announce)
+}
+
+func TestULCShouldNotSyncWithTwoPeersOneHaveEmptyChain(t *testing.T) {
+	f1 := newFullPeerPair(t, 1, 4, testChainGen)
+	f2 := newFullPeerPair(t, 2, 0, nil)
+	ulcConf := &ulc{minTrustedFraction: 100, trustedKeys: make(map[string]struct{})}
+	ulcConf.trustedKeys[f1.Node.ID().String()] = struct{}{}
+	ulcConf.trustedKeys[f2.Node.ID().String()] = struct{}{}
+	ulcConfig := &eth.ULCConfig{
+		MinTrustedFraction: 100,
+		TrustedServers:     []string{f1.Node.String(), f2.Node.String()},
+	}
+	l := newLightPeer(t, ulcConfig)
+	l.PM.ulc.minTrustedFraction = 100
+
+	_, _, err := connectPeers(f1, l, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, _, err = connectPeers(f2, l, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	l.PM.fetcher.lock.Lock()
+	l.PM.fetcher.nextRequest()
+	l.PM.fetcher.lock.Unlock()
+
+	if reflect.DeepEqual(f2.PM.blockchain.CurrentHeader().Hash(), l.PM.blockchain.CurrentHeader().Hash()) {
+		t.Fatal("Incorrect hash: second peer has empty chain")
+	}
+}
+
+func TestULCShouldNotSyncWithThreePeersOneHaveEmptyChain(t *testing.T) {
+	f1 := newFullPeerPair(t, 1, 3, testChainGen)
+	f2 := newFullPeerPair(t, 2, 4, testChainGen)
+	f3 := newFullPeerPair(t, 3, 0, nil)
+
+	ulcConfig := &eth.ULCConfig{
+		MinTrustedFraction: 60,
+		TrustedServers:     []string{f1.Node.String(), f2.Node.String(), f3.Node.String()},
+	}
+
+	l := newLightPeer(t, ulcConfig)
+	_, _, err := connectPeers(f1, l, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, _, err = connectPeers(f2, l, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, _, err = connectPeers(f3, l, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	l.PM.fetcher.lock.Lock()
+	l.PM.fetcher.nextRequest()
+	l.PM.fetcher.lock.Unlock()
+
+	if !reflect.DeepEqual(f1.PM.blockchain.CurrentHeader().Hash(), l.PM.blockchain.CurrentHeader().Hash()) {
+		t.Fatal("Incorrect hash")
+	}
+}
+
+type pairPeer struct {
+	Name string
+	Node *enode.Node
+	PM   *ProtocolManager
+	Key  *ecdsa.PrivateKey
+}
+
+func connectPeers(full, light pairPeer, version int) (*peer, *peer, error) {
+	// Create a message pipe to communicate through
+	app, net := p2p.MsgPipe()
+
+	peerLight := full.PM.newPeer(version, NetworkId, p2p.NewPeer(light.Node.ID(), light.Name, nil), net)
+	peerFull := light.PM.newPeer(version, NetworkId, p2p.NewPeer(full.Node.ID(), full.Name, nil), app)
+
+	// Start the peerLight on a new thread
+	errc1 := make(chan error, 1)
+	errc2 := make(chan error, 1)
+	go func() {
+		select {
+		case light.PM.newPeerCh <- peerFull:
+			errc1 <- light.PM.handle(peerFull)
+		case <-light.PM.quitSync:
+			errc1 <- p2p.DiscQuitting
+		}
+	}()
+	go func() {
+		select {
+		case full.PM.newPeerCh <- peerLight:
+			errc2 <- full.PM.handle(peerLight)
+		case <-full.PM.quitSync:
+			errc2 <- p2p.DiscQuitting
+		}
+	}()
+
+	select {
+	case <-time.After(time.Millisecond * 100):
+	case err := <-errc1:
+		return nil, nil, fmt.Errorf("peerLight handshake error: %v", err)
+	case err := <-errc2:
+		return nil, nil, fmt.Errorf("peerFull handshake error: %v", err)
+	}
+
+	return peerFull, peerLight, nil
+}
+
+// newFullPeerPair creates node with full sync mode
+func newFullPeerPair(t *testing.T, index int, numberOfblocks int, chainGen func(int, *core.BlockGen)) pairPeer {
+	db := ethdb.NewMemDatabase()
+
+	pmFull := newTestProtocolManagerMust(t, false, numberOfblocks, chainGen, nil, nil, db, nil)
+
+	peerPairFull := pairPeer{
+		Name: "full node",
+		PM:   pmFull,
+	}
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		t.Fatal("generate key err:", err)
+	}
+	peerPairFull.Key = key
+	peerPairFull.Node = enode.NewV4(&key.PublicKey, net.ParseIP("127.0.0.1"), 35000, 35000)
+	return peerPairFull
+}
+
+// newLightPeer creates node with light sync mode
+func newLightPeer(t *testing.T, ulcConfig *eth.ULCConfig) pairPeer {
+	peers := newPeerSet()
+	dist := newRequestDistributor(peers, make(chan struct{}))
+	rm := newRetrieveManager(peers, dist, nil)
+	ldb := ethdb.NewMemDatabase()
+
+	odr := NewLesOdr(ldb, light.DefaultClientIndexerConfig, rm)
+
+	pmLight := newTestProtocolManagerMust(t, true, 0, nil, odr, peers, ldb, ulcConfig)
+	peerPairLight := pairPeer{
+		Name: "ulc node",
+		PM:   pmLight,
+	}
+
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		t.Fatal("generate key err:", err)
+	}
+	peerPairLight.Key = key
+	peerPairLight.Node = enode.NewV4(&key.PublicKey, net.IP{}, 35000, 35000)
+	return peerPairLight
+}

light/lightchain.go

@@ -70,6 +70,8 @@ type LightChain struct {
 	wg            sync.WaitGroup
 
 	engine consensus.Engine
+
+	disableCheckFreq bool
 }
 
 // NewLightChain returns a fully initialised light chain using information
@@ -354,6 +356,9 @@ func (self *LightChain) postChainEvents(events []interface{}) {
 // In the case of a light chain, InsertHeaderChain also creates and posts light
 // chain events when necessary.
 func (self *LightChain) InsertHeaderChain(chain []*types.Header, checkFreq int) (int, error) {
+	if self.disableCheckFreq {
+		checkFreq = 0
+	}
 	start := time.Now()
 	if i, err := self.hc.ValidateHeaderChain(chain, checkFreq); err != nil {
 		return i, err
@@ -526,3 +531,17 @@ func (self *LightChain) SubscribeLogsEvent(ch chan<- []*types.Log) event.Subscri
 func (self *LightChain) SubscribeRemovedLogsEvent(ch chan<- core.RemovedLogsEvent) event.Subscription {
 	return self.scope.Track(new(event.Feed).Subscribe(ch))
 }
+
+//DisableCheckFreq disables header validation. It needs for ULC
+func (self *LightChain) DisableCheckFreq() {
+	self.mu.Lock()
+	defer self.mu.Unlock()
+	self.disableCheckFreq = true
+}
+
+//EnableCheckFreq enables header validation
+func (self *LightChain) EnableCheckFreq() {
+	self.mu.Lock()
+	defer self.mu.Unlock()
+	self.disableCheckFreq = false
+}

mobile/geth.go

@@ -76,6 +76,9 @@ type NodeConfig struct {
 
 	// Listening address of pprof server.
 	PprofAddress string
+
+	// Ultra Light client options
+	ULC *eth.ULCConfig
 }
 
 // defaultNodeConfig contains the default node configuration values to use if all
@@ -131,6 +134,7 @@ func NewNode(datadir string, config *NodeConfig) (stack *Node, _ error) {
 			MaxPeers:         config.MaxPeers,
 		},
 	}
+
 	rawStack, err := node.New(nodeConf)
 	if err != nil {
 		return nil, err