swarm: add CLI --ens-endpoint flag (#14386)

Implement a CLI flag that can be repeated to allow multiple ENS
resolvers for different TLDs.

5 files changed, 459 insertions, 63 deletions

diff --git a/cmd/swarm/main.go b/cmd/swarm/main.go
index 603fd9b94..98a0352dc 100644
--- a/cmd/swarm/main.go
+++ b/cmd/swarm/main.go
@@ -17,11 +17,9 @@
 package main
 
 import (
-	"context"
 	"crypto/ecdsa"
 	"fmt"
 	"io/ioutil"
-	"math/big"
 	"os"
 	"os/signal"
 	"runtime"
@@ -29,14 +27,13 @@ import (
 	"strconv"
 	"strings"
 	"syscall"
-	"time"
+	"unicode"
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/console"
-	"github.com/ethereum/go-ethereum/contracts/ens"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethclient"
 	"github.com/ethereum/go-ethereum/internal/debug"
@@ -45,7 +42,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/params"
-	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/ethereum/go-ethereum/swarm"
 	bzzapi "github.com/ethereum/go-ethereum/swarm/api"
 	"gopkg.in/urfave/cli.v1"
@@ -101,6 +97,10 @@ var (
 		Name:  "sync",
 		Usage: "Swarm Syncing enabled (default true)",
 	}
+	EnsEndpointsFlag = cli.StringSliceFlag{
+		Name:  "ens-endpoint",
+		Usage: "ENS API endpoint for a TLD and with contract address, can be repeated, format [tld:][contract-addr@]url",
+	}
 	EnsAPIFlag = cli.StringFlag{
 		Name:  "ens-api",
 		Usage: "URL of the Ethereum API provider to use for ENS record lookups",
@@ -323,6 +323,7 @@ DEPRECATED: use 'swarm db clean'.
 		utils.PasswordFileFlag,
 		// bzzd-specific flags
 		CorsStringFlag,
+		EnsEndpointsFlag,
 		EnsAPIFlag,
 		EnsAddrFlag,
 		SwarmConfigPathFlag,
@@ -416,38 +417,6 @@ func bzzd(ctx *cli.Context) error {
 	return nil
 }
 
-// detectEnsAddr determines the ENS contract address by getting both the
-// version and genesis hash using the client and matching them to either
-// mainnet or testnet addresses
-func detectEnsAddr(client *rpc.Client) (common.Address, error) {
-	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
-
-	var version string
-	if err := client.CallContext(ctx, &version, "net_version"); err != nil {
-		return common.Address{}, err
-	}
-
-	block, err := ethclient.NewClient(client).BlockByNumber(ctx, big.NewInt(0))
-	if err != nil {
-		return common.Address{}, err
-	}
-
-	switch {
-
-	case version == "1" && block.Hash() == params.MainnetGenesisHash:
-		log.Info("using Mainnet ENS contract address", "addr", ens.MainNetAddress)
-		return ens.MainNetAddress, nil
-
-	case version == "3" && block.Hash() == params.TestnetGenesisHash:
-		log.Info("using Testnet ENS contract address", "addr", ens.TestNetAddress)
-		return ens.TestNetAddress, nil
-
-	default:
-		return common.Address{}, fmt.Errorf("unknown version and genesis hash: %s %s", version, block.Hash())
-	}
-}
-
 func registerBzzService(ctx *cli.Context, stack *node.Node) {
 	prvkey := getAccount(ctx, stack)
 
@@ -476,6 +445,7 @@ func registerBzzService(ctx *cli.Context, stack *node.Node) {
 		utils.Fatalf("SWAP is enabled but --swap-api is not set")
 	}
 
+	ensEndpoints := ctx.GlobalStringSlice(EnsEndpointsFlag.Name)
 	ensapi := ctx.GlobalString(EnsAPIFlag.Name)
 	ensAddr := ctx.GlobalString(EnsAddrFlag.Name)
 
@@ -491,34 +461,59 @@ func registerBzzService(ctx *cli.Context, stack *node.Node) {
 			}
 		}
 
-		var ensClient *ethclient.Client
+		ensClientConfigs := []swarm.ENSClientConfig{}
 		if ensapi != "" {
-			log.Info("connecting to ENS API", "url", ensapi)
-			client, err := rpc.Dial(ensapi)
-			if err != nil {
-				return nil, fmt.Errorf("error connecting to ENS API %s: %s", ensapi, err)
-			}
-			ensClient = ethclient.NewClient(client)
-
-			if ensAddr != "" {
-				bzzconfig.EnsRoot = common.HexToAddress(ensAddr)
-			} else {
-				ensAddr, err := detectEnsAddr(client)
-				if err == nil {
-					bzzconfig.EnsRoot = ensAddr
-				} else {
-					log.Warn(fmt.Sprintf("could not determine ENS contract address, using default %s", bzzconfig.EnsRoot), "err", err)
+			ensClientConfigs = append(ensClientConfigs, swarm.ENSClientConfig{
+				Endpoint:        ensapi,
+				ContractAddress: ensAddr,
+			})
+		}
+		if ensEndpoints != nil {
+			for _, s := range ensEndpoints {
+				if s != "" {
+					ensClientConfigs = append(ensClientConfigs, parseFlagEnsEndpoint(s))
 				}
 			}
 		}
+		if len(ensClientConfigs) == 0 {
+			log.Warn("No ENS, please specify non-empty --ens-api or --ens-endpoint to use domain name resolution")
+		}
 
-		return swarm.NewSwarm(ctx, swapClient, ensClient, bzzconfig, swapEnabled, syncEnabled, cors)
+		return swarm.NewSwarm(ctx, swapClient, ensClientConfigs, bzzconfig, swapEnabled, syncEnabled, cors)
 	}
 	if err := stack.Register(boot); err != nil {
 		utils.Fatalf("Failed to register the Swarm service: %v", err)
 	}
 }
 
+func parseFlagEnsEndpoint(s string) swarm.ENSClientConfig {
+	isAllLetterString := func(s string) bool {
+		for _, r := range s {
+			if !unicode.IsLetter(r) {
+				return false
+			}
+		}
+		return true
+	}
+	endpoint := s
+	var addr, tld string
+	if i := strings.Index(endpoint, ":"); i > 0 {
+		if isAllLetterString(endpoint[:i]) && len(endpoint) > i+2 && endpoint[i+1:i+3] != "//" {
+			tld = endpoint[:i]
+			endpoint = endpoint[i+1:]
+		}
+	}
+	if i := strings.Index(endpoint, "@"); i > 0 {
+		addr = endpoint[:i]
+		endpoint = endpoint[i+1:]
+	}
+	return swarm.ENSClientConfig{
+		Endpoint:        endpoint,
+		ContractAddress: addr,
+		TLD:             tld,
+	}
+}
+
 func getAccount(ctx *cli.Context, stack *node.Node) *ecdsa.PrivateKey {
 	keyid := ctx.GlobalString(SwarmAccountFlag.Name)
 
diff --git a/cmd/swarm/main_test.go b/cmd/swarm/main_test.go
new file mode 100644
index 000000000..054034434
--- /dev/null
+++ b/cmd/swarm/main_test.go
@@ -0,0 +1,141 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/swarm"
+)
+
+func TestParseFlagEnsEndpoint(t *testing.T) {
+	for _, x := range []struct {
+		description string
+		value       string
+		config      swarm.ENSClientConfig
+	}{
+		{
+			description: "IPC endpoint",
+			value:       "/data/testnet/geth.ipc",
+			config: swarm.ENSClientConfig{
+				Endpoint: "/data/testnet/geth.ipc",
+			},
+		},
+		{
+			description: "HTTP endpoint",
+			value:       "http://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint: "http://127.0.0.1:1234",
+			},
+		},
+		{
+			description: "WS endpoint",
+			value:       "ws://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint: "ws://127.0.0.1:1234",
+			},
+		},
+		{
+			description: "IPC Endpoint and TLD",
+			value:       "test:/data/testnet/geth.ipc",
+			config: swarm.ENSClientConfig{
+				Endpoint: "/data/testnet/geth.ipc",
+				TLD:      "test",
+			},
+		},
+		{
+			description: "HTTP endpoint and TLD",
+			value:       "test:http://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint: "http://127.0.0.1:1234",
+				TLD:      "test",
+			},
+		},
+		{
+			description: "WS endpoint and TLD",
+			value:       "test:ws://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint: "ws://127.0.0.1:1234",
+				TLD:      "test",
+			},
+		},
+		{
+			description: "IPC Endpoint and contract address",
+			value:       "314159265dD8dbb310642f98f50C066173C1259b@/data/testnet/geth.ipc",
+			config: swarm.ENSClientConfig{
+				Endpoint:        "/data/testnet/geth.ipc",
+				ContractAddress: "314159265dD8dbb310642f98f50C066173C1259b",
+			},
+		},
+		{
+			description: "HTTP endpoint and contract address",
+			value:       "314159265dD8dbb310642f98f50C066173C1259b@http://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint:        "http://127.0.0.1:1234",
+				ContractAddress: "314159265dD8dbb310642f98f50C066173C1259b",
+			},
+		},
+		{
+			description: "WS endpoint and contract address",
+			value:       "314159265dD8dbb310642f98f50C066173C1259b@ws://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint:        "ws://127.0.0.1:1234",
+				ContractAddress: "314159265dD8dbb310642f98f50C066173C1259b",
+			},
+		},
+		{
+			description: "IPC Endpoint, TLD and contract address",
+			value:       "test:314159265dD8dbb310642f98f50C066173C1259b@/data/testnet/geth.ipc",
+			config: swarm.ENSClientConfig{
+				Endpoint:        "/data/testnet/geth.ipc",
+				ContractAddress: "314159265dD8dbb310642f98f50C066173C1259b",
+				TLD:             "test",
+			},
+		},
+		{
+			description: "HTTP endpoint, TLD and contract address",
+			value:       "eth:314159265dD8dbb310642f98f50C066173C1259b@http://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint:        "http://127.0.0.1:1234",
+				ContractAddress: "314159265dD8dbb310642f98f50C066173C1259b",
+				TLD:             "eth",
+			},
+		},
+		{
+			description: "WS endpoint, TLD and contract address",
+			value:       "eth:314159265dD8dbb310642f98f50C066173C1259b@ws://127.0.0.1:1234",
+			config: swarm.ENSClientConfig{
+				Endpoint:        "ws://127.0.0.1:1234",
+				ContractAddress: "314159265dD8dbb310642f98f50C066173C1259b",
+				TLD:             "eth",
+			},
+		},
+	} {
+		t.Run(x.description, func(t *testing.T) {
+			config := parseFlagEnsEndpoint(x.value)
+			if config.Endpoint != x.config.Endpoint {
+				t.Errorf("expected Endpoint %q, got %q", x.config.Endpoint, config.Endpoint)
+			}
+			if config.ContractAddress != x.config.ContractAddress {
+				t.Errorf("expected ContractAddress %q, got %q", x.config.ContractAddress, config.ContractAddress)
+			}
+			if config.TLD != x.config.TLD {
+				t.Errorf("expected TLD %q, got %q", x.config.TLD, config.TLD)
+			}
+		})
+	}
+}
diff --git a/swarm/api/api.go b/swarm/api/api.go
index 79de29a1c..d0c3754e0 100644
--- a/swarm/api/api.go
+++ b/swarm/api/api.go
@@ -17,6 +17,7 @@
 package api
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -40,6 +41,69 @@ type Resolver interface {
 	Resolve(string) (common.Hash, error)
 }
 
+// errNoResolver is returned by MultiResolver.Resolve if no resolver
+// can be found for the address.
+var errNoResolver = errors.New("no resolver")
+
+// MultiResolver is used to resolve URL addresses based on their TLDs.
+// Each TLD can have multiple resolvers, and the resoluton from the
+// first one in the sequence will be returned.
+type MultiResolver struct {
+	resolvers map[string][]Resolver
+}
+
+// MultiResolverOption sets options for MultiResolver and is used as
+// arguments for its constructor.
+type MultiResolverOption func(*MultiResolver)
+
+// MultiResolverOptionWithResolver adds a Resolver to a list of resolvers
+// for a specific TLD. If TLD is an empty string, the resolver will be added
+// to the list of default resolver, the ones that will be used for resolution
+// of addresses which do not have their TLD resolver specified.
+func MultiResolverOptionWithResolver(r Resolver, tld string) MultiResolverOption {
+	return func(m *MultiResolver) {
+		if _, ok := m.resolvers[tld]; !ok {
+			m.resolvers[tld] = []Resolver{}
+		}
+		m.resolvers[tld] = append(m.resolvers[tld], r)
+	}
+}
+
+// NewMultiResolver creates a new instance of MultiResolver.
+func NewMultiResolver(opts ...MultiResolverOption) (m *MultiResolver) {
+	m = &MultiResolver{
+		resolvers: map[string][]Resolver{},
+	}
+	for _, o := range opts {
+		o(m)
+	}
+	return m
+}
+
+// Resolve resolves address by choosing a Resolver by TLD.
+// If there are more default Resolvers, or for a specific TLD,
+// the Hash from the the first one which does not return error
+// will be returned.
+func (m MultiResolver) Resolve(addr string) (h common.Hash, err error) {
+	rs, _ := m.resolvers[""]
+	if i := strings.LastIndex(addr, "."); i >= 0 {
+		rstld, ok := m.resolvers[addr[i+1:]]
+		if ok {
+			rs = rstld
+		}
+	}
+	if rs == nil {
+		return h, errNoResolver
+	}
+	for _, r := range rs {
+		h, err = r.Resolve(addr)
+		if err == nil {
+			return
+		}
+	}
+	return
+}
+
 /*
 Api implements webserver/file system related content storage and retrieval
 on top of the dpa
diff --git a/swarm/api/api_test.go b/swarm/api/api_test.go
index f9caed27f..36cbdb83c 100644
--- a/swarm/api/api_test.go
+++ b/swarm/api/api_test.go
@@ -237,3 +237,120 @@ func TestAPIResolve(t *testing.T) {
 		})
 	}
 }
+
+func TestMultiResolver(t *testing.T) {
+	doesntResolve := newTestResolver("")
+
+	ethAddr := "swarm.eth"
+	ethHash := "0x2222222222222222222222222222222222222222222222222222222222222222"
+	ethResolve := newTestResolver(ethHash)
+
+	testAddr := "swarm.test"
+	testHash := "0x1111111111111111111111111111111111111111111111111111111111111111"
+	testResolve := newTestResolver(testHash)
+
+	tests := []struct {
+		desc   string
+		r      Resolver
+		addr   string
+		result string
+		err    error
+	}{
+		{
+			desc: "No resolvers, returns error",
+			r:    NewMultiResolver(),
+			err:  errNoResolver,
+		},
+		{
+			desc:   "One default resolver, returns resolved address",
+			r:      NewMultiResolver(MultiResolverOptionWithResolver(ethResolve, "")),
+			addr:   ethAddr,
+			result: ethHash,
+		},
+		{
+			desc: "Two default resolvers, returns resolved address",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(ethResolve, ""),
+				MultiResolverOptionWithResolver(ethResolve, ""),
+			),
+			addr:   ethAddr,
+			result: ethHash,
+		},
+		{
+			desc: "Two default resolvers, first doesn't resolve, returns resolved address",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(doesntResolve, ""),
+				MultiResolverOptionWithResolver(ethResolve, ""),
+			),
+			addr:   ethAddr,
+			result: ethHash,
+		},
+		{
+			desc: "Default resolver doesn't resolve, tld resolver resolve, returns resolved address",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(doesntResolve, ""),
+				MultiResolverOptionWithResolver(ethResolve, "eth"),
+			),
+			addr:   ethAddr,
+			result: ethHash,
+		},
+		{
+			desc: "Three TLD resolvers, third resolves, returns resolved address",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(doesntResolve, "eth"),
+				MultiResolverOptionWithResolver(doesntResolve, "eth"),
+				MultiResolverOptionWithResolver(ethResolve, "eth"),
+			),
+			addr:   ethAddr,
+			result: ethHash,
+		},
+		{
+			desc: "One TLD resolver doesn't resolve, returns error",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(doesntResolve, ""),
+				MultiResolverOptionWithResolver(ethResolve, "eth"),
+			),
+			addr:   ethAddr,
+			result: ethHash,
+		},
+		{
+			desc: "One defautl and one TLD resolver, all doesn't resolve, returns error",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(doesntResolve, ""),
+				MultiResolverOptionWithResolver(doesntResolve, "eth"),
+			),
+			addr:   ethAddr,
+			result: ethHash,
+			err:    errors.New(`DNS name not found: "swarm.eth"`),
+		},
+		{
+			desc: "Two TLD resolvers, both resolve, returns resolved address",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(ethResolve, "eth"),
+				MultiResolverOptionWithResolver(testResolve, "test"),
+			),
+			addr:   testAddr,
+			result: testHash,
+		},
+	}
+	for _, x := range tests {
+		t.Run(x.desc, func(t *testing.T) {
+			res, err := x.r.Resolve(x.addr)
+			if err == nil {
+				if x.err != nil {
+					t.Fatalf("expected error %q, got result %q", x.err, res.Hex())
+				}
+				if res.Hex() != x.result {
+					t.Fatalf("expected result %q, got %q", x.result, res.Hex())
+				}
+			} else {
+				if x.err == nil {
+					t.Fatalf("expected no error, got %q", err)
+				}
+				if err.Error() != x.err.Error() {
+					t.Fatalf("expected error %q, got %q", x.err, err)
+				}
+			}
+		})
+	}
+}
diff --git a/swarm/swarm.go b/swarm/swarm.go
index 9db15325a..9b6abc5b9 100644
--- a/swarm/swarm.go
+++ b/swarm/swarm.go
@@ -21,7 +21,9 @@ import (
 	"context"
 	"crypto/ecdsa"
 	"fmt"
+	"math/big"
 	"net"
+	"time"
 
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
@@ -33,6 +35,7 @@ import (
 	"github.com/ethereum/go-ethereum/node"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/ethereum/go-ethereum/swarm/api"
 	httpapi "github.com/ethereum/go-ethereum/swarm/api/http"
@@ -76,7 +79,7 @@ func (self *Swarm) API() *SwarmAPI {
 
 // creates a new swarm service instance
 // implements node.Service
-func NewSwarm(ctx *node.ServiceContext, backend chequebook.Backend, ensClient *ethclient.Client, config *api.Config, swapEnabled, syncEnabled bool, cors string) (self *Swarm, err error) {
+func NewSwarm(ctx *node.ServiceContext, backend chequebook.Backend, ensClientConfigs []ENSClientConfig, config *api.Config, swapEnabled, syncEnabled bool, cors string) (self *Swarm, err error) {
 	if bytes.Equal(common.FromHex(config.PublicKey), storage.ZeroKey) {
 		return nil, fmt.Errorf("empty public key")
 	}
@@ -133,18 +136,22 @@ func NewSwarm(ctx *node.ServiceContext, backend chequebook.Backend, ensClient *e
 	self.dpa = storage.NewDPA(dpaChunkStore, self.config.ChunkerParams)
 	log.Debug(fmt.Sprintf("-> Content Store API"))
 
-	// set up high level api
-	transactOpts := bind.NewKeyedTransactor(self.privateKey)
-
-	if ensClient == nil {
-		log.Warn("No ENS, please specify non-empty --ens-api to use domain name resolution")
-	} else {
-		self.dns, err = ens.NewENS(transactOpts, config.EnsRoot, ensClient)
+	if len(ensClientConfigs) == 1 {
+		self.dns, err = newEnsClient(ensClientConfigs[0].Endpoint, ensClientConfigs[0].ContractAddress, config)
 		if err != nil {
 			return nil, err
 		}
+	} else if len(ensClientConfigs) > 1 {
+		opts := []api.MultiResolverOption{}
+		for _, c := range ensClientConfigs {
+			r, err := newEnsClient(c.Endpoint, c.ContractAddress, config)
+			if err != nil {
+				return nil, err
+			}
+			opts = append(opts, api.MultiResolverOptionWithResolver(r, c.TLD))
+		}
+		self.dns = api.NewMultiResolver(opts...)
 	}
-	log.Debug(fmt.Sprintf("-> Swarm Domain Name Registrar @ address %v", config.EnsRoot.Hex()))
 
 	self.api = api.NewApi(self.dpa, self.dns)
 	// Manifests for Smart Hosting
@@ -156,6 +163,78 @@ func NewSwarm(ctx *node.ServiceContext, backend chequebook.Backend, ensClient *e
 	return self, nil
 }
 
+// ENSClientConfig holds information to construct ENS resolver. If TLD is non-empty,
+// the resolver will be used only for that TLD. If ContractAddress is empty,
+// it will be discovered by the client, or used one from the configuration.
+type ENSClientConfig struct {
+	Endpoint        string
+	ContractAddress string
+	TLD             string
+}
+
+// newEnsClient creates a new ENS client for that is a consumer of
+// a ENS API on a specific endpoint. It is used as a helper function
+// for creating multiple resolvers in NewSwarm function.
+func newEnsClient(endpoint, addr string, config *api.Config) (*ens.ENS, error) {
+	log.Info("connecting to ENS API", "url", endpoint)
+	client, err := rpc.Dial(endpoint)
+	if err != nil {
+		return nil, fmt.Errorf("error connecting to ENS API %s: %s", endpoint, err)
+	}
+	ensClient := ethclient.NewClient(client)
+
+	ensRoot := config.EnsRoot
+	if addr != "" {
+		ensRoot = common.HexToAddress(addr)
+	} else {
+		a, err := detectEnsAddr(client)
+		if err == nil {
+			ensRoot = a
+		} else {
+			log.Warn(fmt.Sprintf("could not determine ENS contract address, using default %s", ensRoot), "err", err)
+		}
+	}
+	transactOpts := bind.NewKeyedTransactor(config.Swap.PrivateKey())
+	dns, err := ens.NewENS(transactOpts, ensRoot, ensClient)
+	if err != nil {
+		return nil, err
+	}
+	log.Debug(fmt.Sprintf("-> Swarm Domain Name Registrar %v @ address %v", endpoint, ensRoot.Hex()))
+	return dns, err
+}
+
+// detectEnsAddr determines the ENS contract address by getting both the
+// version and genesis hash using the client and matching them to either
+// mainnet or testnet addresses
+func detectEnsAddr(client *rpc.Client) (common.Address, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	var version string
+	if err := client.CallContext(ctx, &version, "net_version"); err != nil {
+		return common.Address{}, err
+	}
+
+	block, err := ethclient.NewClient(client).BlockByNumber(ctx, big.NewInt(0))
+	if err != nil {
+		return common.Address{}, err
+	}
+
+	switch {
+
+	case version == "1" && block.Hash() == params.MainnetGenesisHash:
+		log.Info("using Mainnet ENS contract address", "addr", ens.MainNetAddress)
+		return ens.MainNetAddress, nil
+
+	case version == "3" && block.Hash() == params.TestnetGenesisHash:
+		log.Info("using Testnet ENS contract address", "addr", ens.TestNetAddress)
+		return ens.TestNetAddress, nil
+
+	default:
+		return common.Address{}, fmt.Errorf("unknown version and genesis hash: %s %s", version, block.Hash())
+	}
+}
+
 /*
 Start is called when the stack is started
 * starts the network kademlia hive peer management