Merge pull request #15748 from janos/multiple-ens-endpoints

swarm: repeated --ens-api CLI flag (#14386)

cmd/swarm/config.go

@@ -23,6 +23,7 @@ import (
 	"os"
 	"reflect"
 	"strconv"
+	"strings"
 	"unicode"
 
 	cli "gopkg.in/urfave/cli.v1"
@@ -97,10 +98,15 @@ func buildConfig(ctx *cli.Context) (config *bzzapi.Config, err error) {
 	config = bzzapi.NewDefaultConfig()
 	//first load settings from config file (if provided)
 	config, err = configFileOverride(config, ctx)
+	if err != nil {
+		return nil, err
+	}
 	//override settings provided by environment variables
 	config = envVarsOverride(config)
 	//override settings provided by command line
 	config = cmdLineOverride(config, ctx)
+	//validate configuration parameters
+	err = validateConfig(config)
 
 	return
 }
@@ -194,12 +200,16 @@ func cmdLineOverride(currentConfig *bzzapi.Config, ctx *cli.Context) *bzzapi.Con
 		utils.Fatalf(SWARM_ERR_SWAP_SET_NO_API)
 	}
 
-	//EnsApi can be set to "", so can't check for empty string, as it is allowed!
 	if ctx.GlobalIsSet(EnsAPIFlag.Name) {
-		currentConfig.EnsApi = ctx.GlobalString(EnsAPIFlag.Name)
+		ensAPIs := ctx.GlobalStringSlice(EnsAPIFlag.Name)
+		// preserve backward compatibility to disable ENS with --ens-api=""
+		if len(ensAPIs) == 1 && ensAPIs[0] == "" {
+			ensAPIs = nil
+		}
+		currentConfig.EnsAPIs = ensAPIs
 	}
 
-	if ensaddr := ctx.GlobalString(EnsAddrFlag.Name); ensaddr != "" {
+	if ensaddr := ctx.GlobalString(DeprecatedEnsAddrFlag.Name); ensaddr != "" {
 		currentConfig.EnsRoot = common.HexToAddress(ensaddr)
 	}
 
@@ -266,9 +276,8 @@ func envVarsOverride(currentConfig *bzzapi.Config) (config *bzzapi.Config) {
 		utils.Fatalf(SWARM_ERR_SWAP_SET_NO_API)
 	}
 
-	//EnsApi can be set to "", so can't check for empty string, as it is allowed
-	if ensapi, exists := os.LookupEnv(SWARM_ENV_ENS_API); exists {
-		currentConfig.EnsApi = ensapi
+	if ensapi := os.Getenv(SWARM_ENV_ENS_API); ensapi != "" {
+		currentConfig.EnsAPIs = strings.Split(ensapi, ",")
 	}
 
 	if ensaddr := os.Getenv(SWARM_ENV_ENS_ADDR); ensaddr != "" {
@@ -309,6 +318,43 @@ func checkDeprecated(ctx *cli.Context) {
 	if ctx.GlobalString(DeprecatedEthAPIFlag.Name) != "" {
 		utils.Fatalf("--ethapi is no longer a valid command line flag, please use --ens-api and/or --swap-api.")
 	}
+	// warn if --ens-api flag is set
+	if ctx.GlobalString(DeprecatedEnsAddrFlag.Name) != "" {
+		log.Warn("--ens-addr is no longer a valid command line flag, please use --ens-api to specify contract address.")
+	}
+}
+
+//validate configuration parameters
+func validateConfig(cfg *bzzapi.Config) (err error) {
+	for _, ensAPI := range cfg.EnsAPIs {
+		if ensAPI != "" {
+			if err := validateEnsAPIs(ensAPI); err != nil {
+				return fmt.Errorf("invalid format [tld:][contract-addr@]url for ENS API endpoint configuration %q: %v", ensAPI, err)
+			}
+		}
+	}
+	return nil
+}
+
+//validate EnsAPIs configuration parameter
+func validateEnsAPIs(s string) (err error) {
+	// missing contract address
+	if strings.HasPrefix(s, "@") {
+		return errors.New("missing contract address")
+	}
+	// missing url
+	if strings.HasSuffix(s, "@") {
+		return errors.New("missing url")
+	}
+	// missing tld
+	if strings.HasPrefix(s, ":") {
+		return errors.New("missing tld")
+	}
+	// missing url
+	if strings.HasSuffix(s, ":") {
+		return errors.New("missing url")
+	}
+	return nil
 }
 
 //print a Config as string

cmd/swarm/config_test.go

@@ -457,3 +457,98 @@ func TestCmdLineOverridesFile(t *testing.T) {
 
 	node.Shutdown()
 }
+
+func TestValidateConfig(t *testing.T) {
+	for _, c := range []struct {
+		cfg *api.Config
+		err string
+	}{
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"/data/testnet/geth.ipc",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"http://127.0.0.1:1234",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"ws://127.0.0.1:1234",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"test:/data/testnet/geth.ipc",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"test:ws://127.0.0.1:1234",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"314159265dD8dbb310642f98f50C066173C1259b@/data/testnet/geth.ipc",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"314159265dD8dbb310642f98f50C066173C1259b@http://127.0.0.1:1234",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"314159265dD8dbb310642f98f50C066173C1259b@ws://127.0.0.1:1234",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"test:314159265dD8dbb310642f98f50C066173C1259b@/data/testnet/geth.ipc",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"eth:314159265dD8dbb310642f98f50C066173C1259b@http://127.0.0.1:1234",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"eth:314159265dD8dbb310642f98f50C066173C1259b@ws://127.0.0.1:12344",
+			}},
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"eth:",
+			}},
+			err: "invalid format [tld:][contract-addr@]url for ENS API endpoint configuration \"eth:\": missing url",
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"314159265dD8dbb310642f98f50C066173C1259b@",
+			}},
+			err: "invalid format [tld:][contract-addr@]url for ENS API endpoint configuration \"314159265dD8dbb310642f98f50C066173C1259b@\": missing url",
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				":314159265dD8dbb310642f98f50C066173C1259",
+			}},
+			err: "invalid format [tld:][contract-addr@]url for ENS API endpoint configuration \":314159265dD8dbb310642f98f50C066173C1259\": missing tld",
+		},
+		{
+			cfg: &api.Config{EnsAPIs: []string{
+				"@/data/testnet/geth.ipc",
+			}},
+			err: "invalid format [tld:][contract-addr@]url for ENS API endpoint configuration \"@/data/testnet/geth.ipc\": missing contract address",
+		},
+	} {
+		err := validateConfig(c.cfg)
+		if c.err != "" && err.Error() != c.err {
+			t.Errorf("expected error %q, got %q", c.err, err)
+		}
+		if c.err == "" && err != nil {
+			t.Errorf("unexpected error %q", err)
+		}
+	}
+}

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 +27,12 @@ import (
 	"strconv"
 	"strings"
 	"syscall"
-	"time"
 
 	"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 +41,6 @@ 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"
 
@@ -110,16 +105,11 @@ var (
 		Usage:  "Swarm Syncing enabled (default true)",
 		EnvVar: SWARM_ENV_SYNC_ENABLE,
 	}
-	EnsAPIFlag = cli.StringFlag{
+	EnsAPIFlag = cli.StringSliceFlag{
 		Name:   "ens-api",
-		Usage:  "URL of the Ethereum API provider to use for ENS record lookups",
+		Usage:  "ENS API endpoint for a TLD and with contract address, can be repeated, format [tld:][contract-addr@]url",
 		EnvVar: SWARM_ENV_ENS_API,
 	}
-	EnsAddrFlag = cli.StringFlag{
-		Name:   "ens-addr",
-		Usage:  "ENS contract address (default is detected as testnet or mainnet using --ens-api)",
-		EnvVar: SWARM_ENV_ENS_ADDR,
-	}
 	SwarmApiFlag = cli.StringFlag{
 		Name:  "bzzapi",
 		Usage: "Swarm HTTP endpoint",
@@ -156,6 +146,10 @@ var (
 		Name:  "ethapi",
 		Usage: "DEPRECATED: please use --ens-api and --swap-api",
 	}
+	DeprecatedEnsAddrFlag = cli.StringFlag{
+		Name:  "ens-addr",
+		Usage: "DEPRECATED: ENS contract address, please use --ens-api with contract address according to its format",
+	}
 )
 
 //declare a few constant error messages, useful for later error check comparisons in test
@@ -343,7 +337,6 @@ DEPRECATED: use 'swarm db clean'.
 		// bzzd-specific flags
 		CorsStringFlag,
 		EnsAPIFlag,
-		EnsAddrFlag,
 		SwarmTomlConfigPathFlag,
 		SwarmConfigPathFlag,
 		SwarmSwapEnabledFlag,
@@ -363,6 +356,7 @@ DEPRECATED: use 'swarm db clean'.
 		SwarmUploadMimeType,
 		//deprecated flags
 		DeprecatedEthAPIFlag,
+		DeprecatedEnsAddrFlag,
 	}
 	app.Flags = append(app.Flags, debug.Flags...)
 	app.Before = func(ctx *cli.Context) error {
@@ -448,38 +442,6 @@ 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(bzzconfig *bzzapi.Config, ctx *cli.Context, stack *node.Node) {
 
 	//define the swarm service boot function
@@ -494,27 +456,7 @@ func registerBzzService(bzzconfig *bzzapi.Config, ctx *cli.Context, stack *node.
 			}
 		}
 
-		var ensClient *ethclient.Client
-		if bzzconfig.EnsApi != "" {
-			log.Info("connecting to ENS API", "url", bzzconfig.EnsApi)
-			client, err := rpc.Dial(bzzconfig.EnsApi)
-			if err != nil {
-				return nil, fmt.Errorf("error connecting to ENS API %s: %s", bzzconfig.EnsApi, err)
-			}
-			ensClient = ethclient.NewClient(client)
-
-			//no ENS root address set yet
-			if bzzconfig.EnsRoot == (common.Address{}) {
-				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)
-				}
-			}
-		}
-
-		return swarm.NewSwarm(ctx, swapClient, ensClient, bzzconfig, bzzconfig.SwapEnabled, bzzconfig.SyncEnabled, bzzconfig.Cors)
+		return swarm.NewSwarm(ctx, swapClient, bzzconfig)
 	}
 	//register within the ethereum node
 	if err := stack.Register(boot); err != nil {

swarm/api/api.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"path"
 	"regexp"
 	"strings"
 	"sync"
@@ -40,6 +41,81 @@ type Resolver interface {
 	Resolve(string) (common.Hash, error)
 }
 
+// NoResolverError is returned by MultiResolver.Resolve if no resolver
+// can be found for the address.
+type NoResolverError struct {
+	TLD string
+}
+
+func NewNoResolverError(tld string) *NoResolverError {
+	return &NoResolverError{TLD: tld}
+}
+
+func (e *NoResolverError) Error() string {
+	if e.TLD == "" {
+		return "no ENS resolver"
+	}
+	return fmt.Sprintf("no ENS endpoint configured to resolve .%s TLD names", e.TLD)
+}
+
+// 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) {
+		m.resolvers[tld] = append(m.resolvers[tld], r)
+	}
+}
+
+// NewMultiResolver creates a new instance of MultiResolver.
+func NewMultiResolver(opts ...MultiResolverOption) (m *MultiResolver) {
+	m = &MultiResolver{
+		resolvers: make(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[""]
+	tld := path.Ext(addr)
+	if tld != "" {
+		tld = tld[1:]
+		rstld, ok := m.resolvers[tld]
+		if ok {
+			rs = rstld
+		}
+	}
+	if rs == nil {
+		return h, NewNoResolverError(tld)
+	}
+	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

swarm/api/api_test.go

@@ -237,3 +237,128 @@ 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:  NewNoResolverError(""),
+		},
+		{
+			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,
+		},
+		{
+			desc: "One TLD resolver, no default resolver, returns error for different TLD",
+			r: NewMultiResolver(
+				MultiResolverOptionWithResolver(ethResolve, "eth"),
+			),
+			addr: testAddr,
+			err:  NewNoResolverError("test"),
+		},
+	}
+	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)
+				}
+			}
+		})
+	}
+}

swarm/api/config.go

@@ -48,7 +48,7 @@ type Config struct {
 	*network.SyncParams
 	Contract    common.Address
 	EnsRoot     common.Address
-	EnsApi      string
+	EnsAPIs     []string
 	Path        string
 	ListenAddr  string
 	Port        string
@@ -75,7 +75,7 @@ func NewDefaultConfig() (self *Config) {
 		ListenAddr:    DefaultHTTPListenAddr,
 		Port:          DefaultHTTPPort,
 		Path:          node.DefaultDataDir(),
-		EnsApi:        node.DefaultIPCEndpoint("geth"),
+		EnsAPIs:       nil,
 		EnsRoot:       ens.TestNetAddress,
 		NetworkId:     network.NetworkId,
 		SwapEnabled:   false,

swarm/swarm.go

@@ -21,7 +21,11 @@ import (
 	"context"
 	"crypto/ecdsa"
 	"fmt"
+	"math/big"
 	"net"
+	"strings"
+	"time"
+	"unicode"
 
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
@@ -33,6 +37,7 @@ 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 +81,7 @@ 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, config *api.Config) (self *Swarm, err error) {
 	if bytes.Equal(common.FromHex(config.PublicKey), storage.ZeroKey) {
 		return nil, fmt.Errorf("empty public key")
 	}
@@ -86,10 +91,10 @@ func NewSwarm(ctx *node.ServiceContext, backend chequebook.Backend, ensClient *e
 
 	self = &Swarm{
 		config:      config,
-		swapEnabled: swapEnabled,
+		swapEnabled: config.SwapEnabled,
 		backend:     backend,
 		privateKey:  config.Swap.PrivateKey(),
-		corsString:  cors,
+		corsString:  config.Cors,
 	}
 	log.Debug(fmt.Sprintf("Setting up Swarm service components"))
 
@@ -109,8 +114,8 @@ func NewSwarm(ctx *node.ServiceContext, backend chequebook.Backend, ensClient *e
 	self.hive = network.NewHive(
 		common.HexToHash(self.config.BzzKey), // key to hive (kademlia base address)
 		config.HiveParams,                    // configuration parameters
-		swapEnabled,                          // SWAP enabled
-		syncEnabled,                          // syncronisation enabled
+		config.SwapEnabled,                   // SWAP enabled
+		config.SyncEnabled,                   // syncronisation enabled
 	)
 	log.Debug(fmt.Sprintf("Set up swarm network with Kademlia hive"))
 
@@ -133,18 +138,18 @@ 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 err != nil {
-			return nil, err
+	if len(config.EnsAPIs) > 0 {
+		opts := []api.MultiResolverOption{}
+		for _, c := range config.EnsAPIs {
+			tld, endpoint, addr := parseEnsAPIAddress(c)
+			r, err := newEnsClient(endpoint, addr, config)
+			if err != nil {
+				return nil, err
+			}
+			opts = append(opts, api.MultiResolverOptionWithResolver(r, 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 +161,95 @@ func NewSwarm(ctx *node.ServiceContext, backend chequebook.Backend, ensClient *e
 	return self, nil
 }
 
+// parseEnsAPIAddress parses string according to format
+// [tld:][contract-addr@]url and returns ENSClientConfig structure
+// with endpoint, contract address and TLD.
+func parseEnsAPIAddress(s string) (tld, endpoint string, addr common.Address) {
+	isAllLetterString := func(s string) bool {
+		for _, r := range s {
+			if !unicode.IsLetter(r) {
+				return false
+			}
+		}
+		return true
+	}
+	endpoint = s
+	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 = common.HexToAddress(endpoint[:i])
+		endpoint = endpoint[i+1:]
+	}
+	return
+}
+
+// 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 string, addr common.Address, 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 != (common.Address{}) {
+		ensRoot = 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

swarm/swarm_test.go

+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library 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 Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package swarm
+
+import (
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+func TestParseEnsAPIAddress(t *testing.T) {
+	for _, x := range []struct {
+		description string
+		value       string
+		tld         string
+		endpoint    string
+		addr        common.Address
+	}{
+		{
+			description: "IPC endpoint",
+			value:       "/data/testnet/geth.ipc",
+			endpoint:    "/data/testnet/geth.ipc",
+		},
+		{
+			description: "HTTP endpoint",
+			value:       "http://127.0.0.1:1234",
+			endpoint:    "http://127.0.0.1:1234",
+		},
+		{
+			description: "WS endpoint",
+			value:       "ws://127.0.0.1:1234",
+			endpoint:    "ws://127.0.0.1:1234",
+		},
+		{
+			description: "IPC Endpoint and TLD",
+			value:       "test:/data/testnet/geth.ipc",
+			endpoint:    "/data/testnet/geth.ipc",
+			tld:         "test",
+		},
+		{
+			description: "HTTP endpoint and TLD",
+			value:       "test:http://127.0.0.1:1234",
+			endpoint:    "http://127.0.0.1:1234",
+			tld:         "test",
+		},
+		{
+			description: "WS endpoint and TLD",
+			value:       "test:ws://127.0.0.1:1234",
+			endpoint:    "ws://127.0.0.1:1234",
+			tld:         "test",
+		},
+		{
+			description: "IPC Endpoint and contract address",
+			value:       "314159265dD8dbb310642f98f50C066173C1259b@/data/testnet/geth.ipc",
+			endpoint:    "/data/testnet/geth.ipc",
+			addr:        common.HexToAddress("314159265dD8dbb310642f98f50C066173C1259b"),
+		},
+		{
+			description: "HTTP endpoint and contract address",
+			value:       "314159265dD8dbb310642f98f50C066173C1259b@http://127.0.0.1:1234",
+			endpoint:    "http://127.0.0.1:1234",
+			addr:        common.HexToAddress("314159265dD8dbb310642f98f50C066173C1259b"),
+		},
+		{
+			description: "WS endpoint and contract address",
+			value:       "314159265dD8dbb310642f98f50C066173C1259b@ws://127.0.0.1:1234",
+			endpoint:    "ws://127.0.0.1:1234",
+			addr:        common.HexToAddress("314159265dD8dbb310642f98f50C066173C1259b"),
+		},
+		{
+			description: "IPC Endpoint, TLD and contract address",
+			value:       "test:314159265dD8dbb310642f98f50C066173C1259b@/data/testnet/geth.ipc",
+			endpoint:    "/data/testnet/geth.ipc",
+			addr:        common.HexToAddress("314159265dD8dbb310642f98f50C066173C1259b"),
+			tld:         "test",
+		},
+		{
+			description: "HTTP endpoint, TLD and contract address",
+			value:       "eth:314159265dD8dbb310642f98f50C066173C1259b@http://127.0.0.1:1234",
+			endpoint:    "http://127.0.0.1:1234",
+			addr:        common.HexToAddress("314159265dD8dbb310642f98f50C066173C1259b"),
+			tld:         "eth",
+		},
+		{
+			description: "WS endpoint, TLD and contract address",
+			value:       "eth:314159265dD8dbb310642f98f50C066173C1259b@ws://127.0.0.1:1234",
+			endpoint:    "ws://127.0.0.1:1234",
+			addr:        common.HexToAddress("314159265dD8dbb310642f98f50C066173C1259b"),
+			tld:         "eth",
+		},
+	} {
+		t.Run(x.description, func(t *testing.T) {
+			tld, endpoint, addr := parseEnsAPIAddress(x.value)
+			if endpoint != x.endpoint {
+				t.Errorf("expected Endpoint %q, got %q", x.endpoint, endpoint)
+			}
+			if addr != x.addr {
+				t.Errorf("expected ContractAddress %q, got %q", x.addr.String(), addr.String())
+			}
+			if tld != x.tld {
+				t.Errorf("expected TLD %q, got %q", x.tld, tld)
+			}
+		})
+	}
+}