enable relay by default in New

config/config.go

@@ -44,8 +44,9 @@ type Config struct {
 	Insecure           bool
 	Protector          pnet.Protector
 
-	Relay     bool
-	RelayOpts []circuit.RelayOpt
+	RelayCustom bool
+	Relay       bool
+	RelayOpts   []circuit.RelayOpt
 
 	ListenAddrs  []ma.Multiaddr
 	AddrsFactory bhost.AddrsFactory

defaults.go

@@ -70,6 +70,11 @@ var DefaultListenAddrs = func(cfg *Config) error {
 	))
 }
 
+// DefaultEnableRelay enables relay dialing and listening by default
+var DefaultEnableRelay = func(cfg *Config) error {
+	return cfg.Apply(EnableRelay())
+}
+
 // Complete list of default options and when to fallback on them.
 //
 // Please *DON'T* specify default options any other way. Putting this all here
@@ -102,6 +107,10 @@ var defaults = []struct {
 		fallback: func(cfg *Config) bool { return cfg.Peerstore == nil },
 		opt:      DefaultPeerstore,
 	},
+	{
+		fallback: func(cfg *Config) bool { return !cfg.RelayCustom },
+		opt:      DefaultEnableRelay,
+	},
 }
 
 // Defaults configures libp2p to use the default options. Can be combined with

libp2p_test.go

@@ -81,6 +81,7 @@ func TestDefaultListenAddrs(t *testing.T) {
 	ctx := context.Background()
 
 	re := regexp.MustCompile("/(ip)[4|6]/((0.0.0.0)|(::))/tcp/")
+	re2 := regexp.MustCompile("/p2p-circuit")
 
 	// Test 1: Setting the correct listen addresses if userDefined.Transport == nil && userDefined.ListenAddrs == nil
 	h, err := New(ctx)
@@ -88,14 +89,15 @@ func TestDefaultListenAddrs(t *testing.T) {
 		t.Fatal(err)
 	}
 	for _, addr := range h.Network().ListenAddresses() {
-		if re.FindStringSubmatchIndex(addr.String()) == nil {
-			t.Error("expected ip4 or ip6 interface")
+		if re.FindStringSubmatchIndex(addr.String()) == nil &&
+			re2.FindStringSubmatchIndex(addr.String()) == nil {
+			t.Error("expected ip4 or ip6 or relay interface")
 		}
 	}
 
 	h.Close()
 
-	// Test 2: Listen addr should not set if user defined transport is passed.
+	// Test 2: Listen addr only include relay if user defined transport is passed.
 	h, err = New(
 		ctx,
 		Transport(tcp.NewTCPTransport),
@@ -104,8 +106,11 @@ func TestDefaultListenAddrs(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if len(h.Network().ListenAddresses()) != 0 {
-		t.Error("expected zero listen addrs as none is set with user defined transport")
+	if len(h.Network().ListenAddresses()) != 1 {
+		t.Error("expected one listen addr with user defined transport")
+	}
+	if re2.FindStringSubmatchIndex(h.Network().ListenAddresses()[0].String()) == nil {
+		t.Error("expected relay address")
 	}
 	h.Close()
 }

options.go

@@ -201,15 +201,25 @@ func AddrsFactory(factory config.AddrsFactory) Option {
 	}
 }
 
-// EnableRelay configures libp2p to enable the relay transport.
+// EnableRelay configures libp2p to enable the relay transport with configuration options.
 func EnableRelay(options ...circuit.RelayOpt) Option {
 	return func(cfg *Config) error {
+		cfg.RelayCustom = true
 		cfg.Relay = true
 		cfg.RelayOpts = options
 		return nil
 	}
 }
 
+// DisableRelay configures libp2p to disable the relay transport
+func DisableRelay() Option {
+	return func(cfg *Config) error {
+		cfg.RelayCustom = true
+		cfg.Relay = false
+		return nil
+	}
+}
+
 // FilterAddresses configures libp2p to never dial nor accept connections from
 // the given addresses.
 func FilterAddresses(addrs ...*net.IPNet) Option {
@@ -245,9 +255,15 @@ func NATManager(nm config.NATManagerC) Option {
 // NoListenAddrs will configure libp2p to not listen by default.
 //
 // This will both clear any configured listen addrs and prevent libp2p from
-// applying the default listen address option.
+// applying the default listen address option. It also disables relay, unless the
+// user explicitly specifies with an option, as the transport creates an implicit
+// listen address that would make the node diable through any relay it was connected to.
 var NoListenAddrs = func(cfg *Config) error {
 	cfg.ListenAddrs = []ma.Multiaddr{}
+	if !cfg.RelayCustom {
+		cfg.RelayCustom = true
+		cfg.Relay = false
+	}
 	return nil
 }