cmd/geth: enable DNS discovery by default (ethereum#20660)

* node: expose config in service context

* eth: integrate p2p/dnsdisc

* cmd/geth: add some DNS flags

* eth: remove DNS URLs

* cmd/utils: configure DNS names for testnets

* params: update DNS URLs

* cmd/geth: configure mainnet DNS

* cmd/utils: rename DNS flag and fix flag processing

* cmd/utils: remove debug print

* node: fix test

cmd/geth/main.go

@@ -131,6 +131,7 @@ var (
 		utils.NetrestrictFlag,
 		utils.NodeKeyFileFlag,
 		utils.NodeKeyHexFlag,
+		utils.DNSDiscoveryFlag,
 		utils.DeveloperFlag,
 		utils.DeveloperPeriodFlag,
 		utils.TestnetFlag,

cmd/geth/usage.go

@@ -182,6 +182,7 @@ var AppHelpFlagGroups = []flagGroup{
 			utils.BootnodesFlag,
 			utils.BootnodesV4Flag,
 			utils.BootnodesV5Flag,
+			utils.DNSDiscoveryFlag,
 			utils.ListenPortFlag,
 			utils.MaxPeersFlag,
 			utils.MaxPendingPeersFlag,

cmd/utils/flags.go

@@ -658,6 +658,10 @@ var (
 		Name:  "netrestrict",
 		Usage: "Restricts network communication to the given IP networks (CIDR masks)",
 	}
+	DNSDiscoveryFlag = cli.StringFlag{
+		Name:  "discovery.dns",
+		Usage: "Sets DNS discovery entry points (use \"\" to disable DNS)",
+	}
 
 	// ATM the url is left to the user and deployment to
 	JSpathFlag = cli.StringFlag{
@@ -811,9 +815,9 @@ func setBootstrapNodes(ctx *cli.Context, cfg *p2p.Config) {
 	switch {
 	case ctx.GlobalIsSet(BootnodesFlag.Name) || ctx.GlobalIsSet(BootnodesV4Flag.Name):
 		if ctx.GlobalIsSet(BootnodesV4Flag.Name) {
-			urls = strings.Split(ctx.GlobalString(BootnodesV4Flag.Name), ",")
+			urls = splitAndTrim(ctx.GlobalString(BootnodesV4Flag.Name))
 		} else {
-			urls = strings.Split(ctx.GlobalString(BootnodesFlag.Name), ",")
+			urls = splitAndTrim(ctx.GlobalString(BootnodesFlag.Name))
 		}
 	case ctx.GlobalBool(TestnetFlag.Name):
 		urls = params.TestnetBootnodes
@@ -845,9 +849,9 @@ func setBootstrapNodesV5(ctx *cli.Context, cfg *p2p.Config) {
 	switch {
 	case ctx.GlobalIsSet(BootnodesFlag.Name) || ctx.GlobalIsSet(BootnodesV5Flag.Name):
 		if ctx.GlobalIsSet(BootnodesV5Flag.Name) {
-			urls = strings.Split(ctx.GlobalString(BootnodesV5Flag.Name), ",")
+			urls = splitAndTrim(ctx.GlobalString(BootnodesV5Flag.Name))
 		} else {
-			urls = strings.Split(ctx.GlobalString(BootnodesFlag.Name), ",")
+			urls = splitAndTrim(ctx.GlobalString(BootnodesFlag.Name))
 		}
 	case ctx.GlobalBool(RinkebyFlag.Name):
 		urls = params.RinkebyBootnodes
@@ -1477,6 +1481,14 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 	if ctx.GlobalIsSet(RPCGlobalGasCap.Name) {
 		cfg.RPCGasCap = new(big.Int).SetUint64(ctx.GlobalUint64(RPCGlobalGasCap.Name))
 	}
+	if ctx.GlobalIsSet(DNSDiscoveryFlag.Name) {
+		urls := ctx.GlobalString(DNSDiscoveryFlag.Name)
+		if urls == "" {
+			cfg.DiscoveryURLs = []string{}
+		} else {
+			cfg.DiscoveryURLs = splitAndTrim(urls)
+		}
+	}
 
 	// Override any default configs for hard coded networks.
 	switch {
@@ -1485,16 +1497,19 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 			cfg.NetworkId = 3
 		}
 		cfg.Genesis = core.DefaultTestnetGenesisBlock()
+		setDNSDiscoveryDefaults(cfg, params.KnownDNSNetworks[params.TestnetGenesisHash])
 	case ctx.GlobalBool(RinkebyFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 4
 		}
 		cfg.Genesis = core.DefaultRinkebyGenesisBlock()
+		setDNSDiscoveryDefaults(cfg, params.KnownDNSNetworks[params.RinkebyGenesisHash])
 	case ctx.GlobalBool(GoerliFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 5
 		}
 		cfg.Genesis = core.DefaultGoerliGenesisBlock()
+		setDNSDiscoveryDefaults(cfg, params.KnownDNSNetworks[params.GoerliGenesisHash])
 	case ctx.GlobalBool(DeveloperFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 1337
@@ -1521,7 +1536,20 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 		if !ctx.GlobalIsSet(MinerGasPriceFlag.Name) && !ctx.GlobalIsSet(MinerLegacyGasPriceFlag.Name) {
 			cfg.Miner.GasPrice = big.NewInt(1)
 		}
+	default:
+		if cfg.NetworkId == 1 {
+			setDNSDiscoveryDefaults(cfg, params.KnownDNSNetworks[params.MainnetGenesisHash])
+		}
+	}
+}
+
+// setDNSDiscoveryDefaults configures DNS discovery with the given URL if
+// no URLs are set.
+func setDNSDiscoveryDefaults(cfg *eth.Config, url string) {
+	if cfg.DiscoveryURLs != nil {
+		return
 	}
+	cfg.DiscoveryURLs = []string{url}
 }
 
 // RegisterEthService adds an Ethereum client to the stack.

eth/backend.go

@@ -47,6 +47,7 @@ import (
 	"github.com/ethereum/go-ethereum/miner"
 	"github.com/ethereum/go-ethereum/node"
 	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/enr"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
@@ -74,6 +75,7 @@ type Ethereum struct {
 	blockchain      *core.BlockChain
 	protocolManager *ProtocolManager
 	lesServer       LesServer
+	dialCandiates   enode.Iterator
 
 	// DB interfaces
 	chainDb ethdb.Database // Block chain database
@@ -220,6 +222,11 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 	}
 	eth.APIBackend.gpo = gasprice.NewOracle(eth.APIBackend, gpoParams)
 
+	eth.dialCandiates, err = eth.setupDiscovery(&ctx.Config.P2P)
+	if err != nil {
+		return nil, err
+	}
+
 	return eth, nil
 }
 
@@ -510,6 +517,7 @@ func (s *Ethereum) Protocols() []p2p.Protocol {
 	for i, vsn := range ProtocolVersions {
 		protos[i] = s.protocolManager.makeProtocol(vsn)
 		protos[i].Attributes = []enr.Entry{s.currentEthEntry()}
+		protos[i].DialCandidates = s.dialCandiates
 	}
 	if s.lesServer != nil {
 		protos = append(protos, s.lesServer.Protocols()...)

eth/config.go

@@ -95,6 +95,10 @@ type Config struct {
 	NetworkId uint64 // Network ID to use for selecting peers to connect to
 	SyncMode  downloader.SyncMode
 
+	// This can be set to list of enrtree:// URLs which will be queried for
+	// for nodes to connect to.
+	DiscoveryURLs []string
+
 	NoPruning  bool // Whether to disable pruning and flush everything to disk
 	NoPrefetch bool // Whether to disable prefetching and only load state on demand
 
@@ -156,8 +160,8 @@ type Config struct {
 	CheckpointOracle *params.CheckpointOracleConfig `toml:",omitempty"`
 
 	// Istanbul block override (TODO: remove after the fork)
-	OverrideIstanbul *big.Int
+	OverrideIstanbul *big.Int `toml:",omitempty"`
 
 	// MuirGlacier block override (TODO: remove after the fork)
-	OverrideMuirGlacier *big.Int
+	OverrideMuirGlacier *big.Int `toml:",omitempty"`
 }

eth/enr_entry.go → eth/discovery.go

@@ -19,6 +19,8 @@ package eth
 import (
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/forkid"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/dnsdisc"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/rlp"
 )
@@ -37,6 +39,7 @@ func (e ethEntry) ENRKey() string {
 	return "eth"
 }
 
+// startEthEntryUpdate starts the ENR updater loop.
 func (eth *Ethereum) startEthEntryUpdate(ln *enode.LocalNode) {
 	var newHead = make(chan core.ChainHeadEvent, 10)
 	sub := eth.blockchain.SubscribeChainHeadEvent(newHead)
@@ -59,3 +62,12 @@ func (eth *Ethereum) startEthEntryUpdate(ln *enode.LocalNode) {
 func (eth *Ethereum) currentEthEntry() *ethEntry {
 	return &ethEntry{ForkID: forkid.NewID(eth.blockchain)}
 }
+
+// setupDiscovery creates the node discovery source for the eth protocol.
+func (eth *Ethereum) setupDiscovery(cfg *p2p.Config) (enode.Iterator, error) {
+	if cfg.NoDiscovery || len(eth.config.DiscoveryURLs) == 0 {
+		return nil, nil
+	}
+	client := dnsdisc.NewClient(dnsdisc.Config{})
+	return client.NewIterator(eth.config.DiscoveryURLs...)
+}

node/node.go

@@ -194,7 +194,7 @@ func (n *Node) Start() error {
 	for _, constructor := range n.serviceFuncs {
 		// Create a new context for the particular service
 		ctx := &ServiceContext{
-			config:         n.config,
+			Config:         *n.config,
 			services:       make(map[reflect.Type]Service),
 			EventMux:       n.eventmux,
 			AccountManager: n.accman,

node/service.go

@@ -32,20 +32,20 @@ import (
 // the protocol stack, that is passed to all constructors to be optionally used;
 // as well as utility methods to operate on the service environment.
 type ServiceContext struct {
-	config         *Config
 	services       map[reflect.Type]Service // Index of the already constructed services
-	EventMux       *event.TypeMux           // Event multiplexer used for decoupled notifications
-	AccountManager *accounts.Manager        // Account manager created by the node.
+	Config         Config
+	EventMux       *event.TypeMux    // Event multiplexer used for decoupled notifications
+	AccountManager *accounts.Manager // Account manager created by the node.
 }
 
 // OpenDatabase opens an existing database with the given name (or creates one
 // if no previous can be found) from within the node's data directory. If the
 // node is an ephemeral one, a memory database is returned.
 func (ctx *ServiceContext) OpenDatabase(name string, cache int, handles int, namespace string) (ethdb.Database, error) {
-	if ctx.config.DataDir == "" {
+	if ctx.Config.DataDir == "" {
 		return rawdb.NewMemoryDatabase(), nil
 	}
-	return rawdb.NewLevelDBDatabase(ctx.config.ResolvePath(name), cache, handles, namespace)
+	return rawdb.NewLevelDBDatabase(ctx.Config.ResolvePath(name), cache, handles, namespace)
 }
 
 // OpenDatabaseWithFreezer opens an existing database with the given name (or
@@ -54,16 +54,16 @@ func (ctx *ServiceContext) OpenDatabase(name string, cache int, handles int, nam
 // database to immutable append-only files. If the node is an ephemeral one, a
 // memory database is returned.
 func (ctx *ServiceContext) OpenDatabaseWithFreezer(name string, cache int, handles int, freezer string, namespace string) (ethdb.Database, error) {
-	if ctx.config.DataDir == "" {
+	if ctx.Config.DataDir == "" {
 		return rawdb.NewMemoryDatabase(), nil
 	}
-	root := ctx.config.ResolvePath(name)
+	root := ctx.Config.ResolvePath(name)
 
 	switch {
 	case freezer == "":
 		freezer = filepath.Join(root, "ancient")
 	case !filepath.IsAbs(freezer):
-		freezer = ctx.config.ResolvePath(freezer)
+		freezer = ctx.Config.ResolvePath(freezer)
 	}
 	return rawdb.NewLevelDBDatabaseWithFreezer(root, cache, handles, freezer, namespace)
 }
@@ -72,7 +72,7 @@ func (ctx *ServiceContext) OpenDatabaseWithFreezer(name string, cache int, handl
 // and if the user actually uses persistent storage. It will return an empty string
 // for emphemeral storage and the user's own input for absolute paths.
 func (ctx *ServiceContext) ResolvePath(path string) string {
-	return ctx.config.ResolvePath(path)
+	return ctx.Config.ResolvePath(path)
 }
 
 // Service retrieves a currently running service registered of a specific type.
@@ -88,7 +88,7 @@ func (ctx *ServiceContext) Service(service interface{}) error {
 // ExtRPCEnabled returns the indicator whether node enables the external
 // RPC(http, ws or graphql).
 func (ctx *ServiceContext) ExtRPCEnabled() bool {
-	return ctx.config.ExtRPCEnabled()
+	return ctx.Config.ExtRPCEnabled()
 }
 
 // ServiceConstructor is the function signature of the constructors needed to be

node/service_test.go

@@ -38,7 +38,7 @@ func TestContextDatabases(t *testing.T) {
 		t.Fatalf("non-created database already exists")
 	}
 	// Request the opening/creation of a database and ensure it persists to disk
-	ctx := &ServiceContext{config: &Config{Name: "unit-test", DataDir: dir}}
+	ctx := &ServiceContext{Config: Config{Name: "unit-test", DataDir: dir}}
 	db, err := ctx.OpenDatabase("persistent", 0, 0, "")
 	if err != nil {
 		t.Fatalf("failed to open persistent database: %v", err)
@@ -49,7 +49,7 @@ func TestContextDatabases(t *testing.T) {
 		t.Fatalf("persistent database doesn't exists: %v", err)
 	}
 	// Request th opening/creation of an ephemeral database and ensure it's not persisted
-	ctx = &ServiceContext{config: &Config{DataDir: ""}}
+	ctx = &ServiceContext{Config: Config{DataDir: ""}}
 	db, err = ctx.OpenDatabase("ephemeral", 0, 0, "")
 	if err != nil {
 		t.Fatalf("failed to open ephemeral database: %v", err)

params/bootnodes.go

@@ -16,6 +16,8 @@
 
 package params
 
+import "github.com/ethereum/go-ethereum/common"
+
 // MainnetBootnodes are the enode URLs of the P2P bootstrap nodes running on
 // the main Ethereum network.
 var MainnetBootnodes = []string{
@@ -69,3 +71,14 @@ var DiscoveryV5Bootnodes = []string{
 	"enode://1c7a64d76c0334b0418c004af2f67c50e36a3be60b5e4790bdac0439d21603469a85fad36f2473c9a80eb043ae60936df905fa28f1ff614c3e5dc34f15dcd2dc@40.118.3.223:30306",
 	"enode://85c85d7143ae8bb96924f2b54f1b3e70d8c4d367af305325d30a61385a432f247d2c75c45c6b4a60335060d072d7f5b35dd1d4c45f76941f62a4f83b6e75daaf@40.118.3.223:30307",
 }
+
+const dnsPrefix = "enrtree://AKA3AM6LPBYEUDMVNU3BSVQJ5AD45Y7YPOHJLEF6W26QOE4VTUDPE@"
+
+// These DNS names provide bootstrap connectivity for public testnets and the mainnet.
+// See https://github.com/ethereum/discv4-dns-lists for more information.
+var KnownDNSNetworks = map[common.Hash]string{
+	MainnetGenesisHash: dnsPrefix + "all.mainnet.ethdisco.net",
+	TestnetGenesisHash: dnsPrefix + "all.ropsten.ethdisco.net",
+	RinkebyGenesisHash: dnsPrefix + "all.rinkeby.ethdisco.net",
+	GoerliGenesisHash:  dnsPrefix + "all.goerli.ethdisco.net",
+}