eth: dial nodes from discv5

eth/backend.go

@@ -23,6 +23,7 @@ import (
 	"math/big"
 	"runtime"
 	"sync"
+	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
@@ -64,15 +65,13 @@ type Config = ethconfig.Config
 
 // Ethereum implements the Ethereum full node service.
 type Ethereum struct {
-	config *ethconfig.Config
+	// core protocol objects
+	config     *ethconfig.Config
+	txPool     *txpool.TxPool
+	blockchain *core.BlockChain
 
-	// Handlers
-	txPool *txpool.TxPool
-
-	blockchain         *core.BlockChain
-	handler            *handler
-	ethDialCandidates  enode.Iterator
-	snapDialCandidates enode.Iterator
+	handler *handler
+	discmix *enode.FairMix
 
 	// DB interfaces
 	chainDb ethdb.Database // Block chain database
@@ -162,6 +161,7 @@ func New(stack *node.Node, config *ethconfig.Config) (*Ethereum, error) {
 		bloomRequests:     make(chan chan *bloombits.Retrieval),
 		bloomIndexer:      core.NewBloomIndexer(chainDb, params.BloomBitsBlocks, params.BloomConfirms),
 		p2pServer:         stack.Server(),
+		discmix:           enode.NewFairMix(2 * time.Second),
 		shutdownTracker:   shutdowncheck.NewShutdownTracker(chainDb),
 	}
 	bcVersion := rawdb.ReadDatabaseVersion(chainDb)
@@ -266,17 +266,6 @@ func New(stack *node.Node, config *ethconfig.Config) (*Ethereum, error) {
 	}
 	eth.APIBackend.gpo = gasprice.NewOracle(eth.APIBackend, config.GPO, config.Miner.GasPrice)
 
-	// Setup DNS discovery iterators.
-	dnsclient := dnsdisc.NewClient(dnsdisc.Config{})
-	eth.ethDialCandidates, err = dnsclient.NewIterator(eth.config.EthDiscoveryURLs...)
-	if err != nil {
-		return nil, err
-	}
-	eth.snapDialCandidates, err = dnsclient.NewIterator(eth.config.SnapDiscoveryURLs...)
-	if err != nil {
-		return nil, err
-	}
-
 	// Start the RPC service
 	eth.netRPCService = ethapi.NewNetAPI(eth.p2pServer, networkID)
 
@@ -359,17 +348,17 @@ func (s *Ethereum) BloomIndexer() *core.ChainIndexer   { return s.bloomIndexer }
 // Protocols returns all the currently configured
 // network protocols to start.
 func (s *Ethereum) Protocols() []p2p.Protocol {
-	protos := eth.MakeProtocols((*ethHandler)(s.handler), s.networkID, s.ethDialCandidates)
+	protos := eth.MakeProtocols((*ethHandler)(s.handler), s.networkID, s.discmix)
 	if s.config.SnapshotCache > 0 {
-		protos = append(protos, snap.MakeProtocols((*snapHandler)(s.handler), s.snapDialCandidates)...)
+		protos = append(protos, snap.MakeProtocols((*snapHandler)(s.handler))...)
 	}
 	return protos
 }
 
 // Start implements node.Lifecycle, starting all internal goroutines needed by the
 // Ethereum protocol implementation.
 func (s *Ethereum) Start() error {
-	eth.StartENRUpdater(s.blockchain, s.p2pServer.LocalNode())
+	s.setupDiscovery()
 
 	// Start the bloom bits servicing goroutines
 	s.startBloomHandlers(params.BloomBitsBlocks)
@@ -382,12 +371,40 @@ func (s *Ethereum) Start() error {
 	return nil
 }
 
+func (s *Ethereum) setupDiscovery() error {
+	eth.StartENRUpdater(s.blockchain, s.p2pServer.LocalNode())
+
+	dnsclient := dnsdisc.NewClient(dnsdisc.Config{})
+	if len(s.config.EthDiscoveryURLs) > 0 {
+		iter, err := dnsclient.NewIterator(s.config.EthDiscoveryURLs...)
+		if err != nil {
+			return err
+		}
+		s.discmix.AddSource(iter)
+	}
+
+	if len(s.config.SnapDiscoveryURLs) > 0 {
+		iter, err := dnsclient.NewIterator(s.config.SnapDiscoveryURLs...)
+		if err != nil {
+			return err
+		}
+		s.discmix.AddSource(iter)
+	}
+
+	if s.p2pServer.DiscoveryV5() != nil {
+		filter := eth.NewNodeFilter(s.blockchain)
+		iter := enode.Filter(s.p2pServer.DiscoveryV5().RandomNodes(), filter)
+		s.discmix.AddSource(iter)
+	}
+
+	return nil
+}
+
 // Stop implements node.Lifecycle, terminating all internal goroutines used by the
 // Ethereum protocol.
 func (s *Ethereum) Stop() error {
 	// Stop all the peer-related stuff first.
-	s.ethDialCandidates.Close()
-	s.snapDialCandidates.Close()
+	s.discmix.Close()
 	s.handler.Stop()
 
 	// Then stop everything else.

eth/protocols/eth/discovery.go

@@ -64,3 +64,17 @@ func currentENREntry(chain *core.BlockChain) *enrEntry {
 		ForkID: forkid.NewID(chain.Config(), chain.Genesis(), head.Number.Uint64(), head.Time),
 	}
 }
+
+// NewNodeFilter returns a filtering function that returns whether the provided
+// enode advertises a forkid compatible with the current chain.
+func NewNodeFilter(chain *core.BlockChain) func(*enode.Node) bool {
+	filter := forkid.NewFilter(chain)
+	return func(n *enode.Node) bool {
+		var entry enrEntry
+		if err := n.Load(entry); err != nil {
+			return false
+		}
+		err := filter(entry.ForkID)
+		return err == nil
+	}
+}

eth/protocols/eth/handler.go

@@ -113,8 +113,7 @@ func MakeProtocols(backend Backend, network uint64, dnsdisc enode.Iterator) []p2
 			PeerInfo: func(id enode.ID) interface{} {
 				return backend.PeerInfo(id)
 			},
-			Attributes:     []enr.Entry{currentENREntry(backend.Chain())},
-			DialCandidates: dnsdisc,
+			Attributes: []enr.Entry{currentENREntry(backend.Chain())},
 		})
 	}
 	return protocols

eth/protocols/snap/handler.go

@@ -82,13 +82,7 @@ type Backend interface {
 }
 
 // MakeProtocols constructs the P2P protocol definitions for `snap`.
-func MakeProtocols(backend Backend, dnsdisc enode.Iterator) []p2p.Protocol {
-	// Filter the discovery iterator for nodes advertising snap support.
-	dnsdisc = enode.Filter(dnsdisc, func(n *enode.Node) bool {
-		var snap enrEntry
-		return n.Load(&snap) == nil
-	})
-
+func MakeProtocols(backend Backend) []p2p.Protocol {
 	protocols := make([]p2p.Protocol, len(ProtocolVersions))
 	for i, version := range ProtocolVersions {
 		version := version // Closure
@@ -108,8 +102,7 @@ func MakeProtocols(backend Backend, dnsdisc enode.Iterator) []p2p.Protocol {
 			PeerInfo: func(id enode.ID) interface{} {
 				return backend.PeerInfo(id)
 			},
-			Attributes:     []enr.Entry{&enrEntry{}},
-			DialCandidates: dnsdisc,
+			Attributes: []enr.Entry{&enrEntry{}},
 		}
 	}
 	return protocols