From db705bb45db2c3b698ea90fe3d0060170a47f87d Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Thu, 6 Feb 2020 22:14:13 +0100
Subject: [PATCH] eth: integrate p2p/dnsdisc

---
 eth/backend.go                     |  8 ++++++++
 eth/config.go                      |  4 ++++
 eth/{enr_entry.go => discovery.go} | 29 +++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+)
 rename eth/{enr_entry.go => discovery.go} (59%)

diff --git a/eth/backend.go b/eth/backend.go
index adde609de0..bda307d95b 100644
--- a/eth/backend.go
+++ b/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()...)
diff --git a/eth/config.go b/eth/config.go
index 8240391114..aff2b170cc 100644
--- a/eth/config.go
+++ b/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
 
+	// Discovery options
+	DisableDNSDiscovery bool
+	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
 
diff --git a/eth/enr_entry.go b/eth/discovery.go
similarity index 59%
rename from eth/enr_entry.go
rename to eth/discovery.go
index d9e7b95784..e0e539b7d8 100644
--- a/eth/enr_entry.go
+++ b/eth/discovery.go
@@ -17,12 +17,23 @@
 package eth
 
 import (
+	"github.com/ethereum/go-ethereum/common"
 	"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/params"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
+var knownDNSNetworks = map[common.Hash]string{
+	params.MainnetGenesisHash: "enrtree://AMBMWDM3J6UY3M32TMMROUNLX6Y3YTLVC3DC6HN2AVG5NHNSAXDW6@all.mainnet.nodes.ethflare.xyz",
+	params.TestnetGenesisHash: "enrtree://AMBMWDM3J6UY3M32TMMROUNLX6Y3YTLVC3DC6HN2AVG5NHNSAXDW6@all.ropsten.nodes.ethflare.xyz",
+	params.RinkebyGenesisHash: "enrtree://AMBMWDM3J6UY3M32TMMROUNLX6Y3YTLVC3DC6HN2AVG5NHNSAXDW6@all.rinkeby.nodes.ethflare.xyz",
+	params.GoerliGenesisHash:  "enrtree://AMBMWDM3J6UY3M32TMMROUNLX6Y3YTLVC3DC6HN2AVG5NHNSAXDW6@all.goerli.nodes.ethflare.xyz",
+}
+
 // ethEntry is the "eth" ENR entry which advertises eth protocol
 // on the discovery network.
 type ethEntry struct {
@@ -37,6 +48,7 @@ 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 +71,20 @@ 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 || eth.config.DisableDNSDiscovery {
+		return nil, nil
+	}
+	known := knownDNSNetworks[eth.blockchain.Genesis().Hash()]
+	urls := eth.config.DiscoveryURLs
+	if len(urls) == 0 {
+		if known == "" {
+			return nil, nil
+		}
+		urls = []string{known}
+	}
+	client := dnsdisc.NewClient(dnsdisc.Config{})
+	return client.NewIterator(urls...)
+}