les: implement ultralight client (ethereum#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++ {
-		index := i*checkFreq + hc.rand.Intn(checkFreq)
-		if index >= len(seals) {
-			index = len(seals) - 1
+	if checkFreq != 0 {
+		// In case of checkFreq == 0 all seals are left false.
+		for i := 0; i < len(seals)/checkFreq; i++ {
+			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
-	LightPeers int `toml:",omitempty"` // Maximum number of LES client peers
+	LightServ    int  `toml:",omitempty"` // Maximum percentage of time allowed for serving LES requests
+	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/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