refactor(netxlite): add more functions to resolver (#455)

We would like to refactor the code so that a DoH resolver owns the
connections of its underlying HTTP client.

To do that, we need first to incorporate CloseIdleConnections
into the Resolver model. Then, we need to add the same function
to all netxlite types that wrap a Resolver type.

At the same time, we want the rest of the code for now to continue
with the simpler definition of a Resolver, now called ResolverLegacy.

We will eventually propagate this change to the rest of the tree
and simplify the way in which we manage Resolvers.

To make this possible, we introduce a new factory function that
adapts a ResolverLegacy to become a Resolver.

See https://github.com/ooni/probe/issues/1591.

internal/cmd/oohelperd/internal/websteps/explore.go

@@ -27,7 +27,7 @@ type Explorer interface {
 
 // DefaultExplorer is the default Explorer.
 type DefaultExplorer struct {
-	resolver netxlite.Resolver
+	resolver netxlite.ResolverLegacy
 }
 
 // Explore returns a list of round trips sorted so that the first

internal/cmd/oohelperd/internal/websteps/generate.go

@@ -24,7 +24,7 @@ type Generator interface {
 type DefaultGenerator struct {
 	dialer     netxlite.Dialer
 	quicDialer netxlite.QUICContextDialer
-	resolver   netxlite.Resolver
+	resolver   netxlite.ResolverLegacy
 	transport  http.RoundTripper
 }
 

internal/cmd/oohelperd/internal/websteps/initialchecks.go

@@ -31,7 +31,7 @@ type InitChecker interface {
 
 // DefaultInitChecker is the default InitChecker.
 type DefaultInitChecker struct {
-	resolver netxlite.Resolver
+	resolver netxlite.ResolverLegacy
 }
 
 // InitialChecks checks whether the URL is valid and whether the

internal/cmd/oohelperd/internal/websteps/measure.go

@@ -24,7 +24,7 @@ type Config struct {
 	checker   InitChecker
 	explorer  Explorer
 	generator Generator
-	resolver  netxlite.Resolver
+	resolver  netxlite.ResolverLegacy
 }
 
 // Measure performs the three consecutive steps of the testhelper algorithm:
@@ -87,10 +87,12 @@ func newDNSFailedResponse(err error, URL string) *ControlResponse {
 }
 
 // newResolver creates a new DNS resolver instance
-func newResolver() netxlite.Resolver {
+func newResolver() netxlite.ResolverLegacy {
 	childResolver, err := netx.NewDNSClient(netx.Config{Logger: log.Log}, "doh://google")
 	runtimex.PanicOnError(err, "NewDNSClient failed")
-	var r netxlite.Resolver = childResolver
-	r = &netxlite.ResolverIDNA{Resolver: r}
+	var r netxlite.ResolverLegacy = childResolver
+	r = &netxlite.ResolverIDNA{
+		Resolver: netxlite.NewResolverLegacyAdapter(r),
+	}
 	return r
 }

internal/engine/experiment/ndt7/dial.go

@@ -35,7 +35,10 @@ func newDialManager(ndt7URL string, logger model.Logger, userAgent string) dialM
 
 func (mgr dialManager) dialWithTestName(ctx context.Context, testName string) (*websocket.Conn, error) {
 	var reso resolver.Resolver = &netxlite.ResolverSystem{}
-	reso = &netxlite.ResolverLogger{Resolver: reso, Logger: mgr.logger}
+	reso = &netxlite.ResolverLogger{
+		Resolver: netxlite.NewResolverLegacyAdapter(reso),
+		Logger:   mgr.logger,
+	}
 	dlr := dialer.New(&dialer.Config{
 		ContextByteCounting: true,
 		Logger:              mgr.logger,

internal/engine/experiment/websteps/dns.go

@@ -11,7 +11,7 @@ import (
 
 type DNSConfig struct {
 	Domain   string
-	Resolver netxlite.Resolver
+	Resolver netxlite.ResolverLegacy
 }
 
 // DNSDo performs the DNS check.
@@ -21,7 +21,9 @@ func DNSDo(ctx context.Context, config DNSConfig) ([]string, error) {
 		childResolver, err := netx.NewDNSClient(netx.Config{Logger: log.Log}, "doh://google")
 		runtimex.PanicOnError(err, "NewDNSClient failed")
 		resolver = childResolver
-		resolver = &netxlite.ResolverIDNA{Resolver: resolver}
+		resolver = &netxlite.ResolverIDNA{
+			Resolver: netxlite.NewResolverLegacyAdapter(resolver),
+		}
 	}
 	return resolver.LookupHost(ctx, config.Domain)
 }

internal/engine/experiment/websteps/factory.go

@@ -33,23 +33,29 @@ func NewRequest(ctx context.Context, URL *url.URL, headers http.Header) *http.Re
 
 // NewDialerResolver contructs a new dialer for TCP connections,
 // with default, errorwrapping and resolve functionalities
-func NewDialerResolver(resolver netxlite.Resolver) netxlite.Dialer {
+func NewDialerResolver(resolver netxlite.ResolverLegacy) netxlite.Dialer {
 	var d netxlite.Dialer = netxlite.DefaultDialer
 	d = &errorsx.ErrorWrapperDialer{Dialer: d}
-	d = &netxlite.DialerResolver{Resolver: resolver, Dialer: d}
+	d = &netxlite.DialerResolver{
+		Resolver: netxlite.NewResolverLegacyAdapter(resolver),
+		Dialer:   d,
+	}
 	return d
 }
 
 // NewQUICDialerResolver creates a new QUICDialerResolver
 // with default, errorwrapping and resolve functionalities
-func NewQUICDialerResolver(resolver netxlite.Resolver) netxlite.QUICContextDialer {
+func NewQUICDialerResolver(resolver netxlite.ResolverLegacy) netxlite.QUICContextDialer {
 	var ql quicdialer.QUICListener = &netxlite.QUICListenerStdlib{}
 	ql = &errorsx.ErrorWrapperQUICListener{QUICListener: ql}
 	var dialer netxlite.QUICContextDialer = &netxlite.QUICDialerQUICGo{
 		QUICListener: ql,
 	}
 	dialer = &errorsx.ErrorWrapperQUICDialer{Dialer: dialer}
-	dialer = &netxlite.QUICDialerResolver{Resolver: resolver, Dialer: dialer}
+	dialer = &netxlite.QUICDialerResolver{
+		Resolver: netxlite.NewResolverLegacyAdapter(resolver),
+		Dialer:   dialer,
+	}
 	return dialer
 }
 

internal/engine/experiment/websteps/quic.go

@@ -11,7 +11,7 @@ import (
 type QUICConfig struct {
 	Endpoint   string
 	QUICDialer netxlite.QUICContextDialer
-	Resolver   netxlite.Resolver
+	Resolver   netxlite.ResolverLegacy
 	TLSConf    *tls.Config
 }
 

internal/engine/experiment/websteps/tcp.go

@@ -10,7 +10,7 @@ import (
 type TCPConfig struct {
 	Dialer   netxlite.Dialer
 	Endpoint string
-	Resolver netxlite.Resolver
+	Resolver netxlite.ResolverLegacy
 }
 
 // TCPDo performs the TCP check.

internal/engine/netx/dialer/dialer.go

@@ -80,7 +80,10 @@ func New(config *Config, resolver Resolver) Dialer {
 	if config.ReadWriteSaver != nil {
 		d = &saverConnDialer{Dialer: d, Saver: config.ReadWriteSaver}
 	}
-	d = &netxlite.DialerResolver{Resolver: resolver, Dialer: d}
+	d = &netxlite.DialerResolver{
+		Resolver: netxlite.NewResolverLegacyAdapter(resolver),
+		Dialer:   d,
+	}
 	d = &proxyDialer{ProxyURL: config.ProxyURL, Dialer: d}
 	if config.ContextByteCounting {
 		d = &byteCounterDialer{Dialer: d}

internal/engine/netx/netx.go

@@ -134,12 +134,15 @@ func NewResolver(config Config) Resolver {
 	}
 	r = &errorsx.ErrorWrapperResolver{Resolver: r}
 	if config.Logger != nil {
-		r = &netxlite.ResolverLogger{Logger: config.Logger, Resolver: r}
+		r = &netxlite.ResolverLogger{
+			Logger:   config.Logger,
+			Resolver: netxlite.NewResolverLegacyAdapter(r),
+		}
 	}
 	if config.ResolveSaver != nil {
 		r = resolver.SaverResolver{Resolver: r, Saver: config.ResolveSaver}
 	}
-	return &resolver.IDNAResolver{Resolver: r}
+	return &resolver.IDNAResolver{Resolver: netxlite.NewResolverLegacyAdapter(r)}
 }
 
 // NewDialer creates a new Dialer from the specified config
@@ -176,7 +179,10 @@ func NewQUICDialer(config Config) QUICDialer {
 	if config.TLSSaver != nil {
 		d = quicdialer.HandshakeSaver{Saver: config.TLSSaver, Dialer: d}
 	}
-	d = &netxlite.QUICDialerResolver{Resolver: config.FullResolver, Dialer: d}
+	d = &netxlite.QUICDialerResolver{
+		Resolver: netxlite.NewResolverLegacyAdapter(config.FullResolver),
+		Dialer:   d,
+	}
 	return d
 }
 

internal/engine/netx/netx_test.go

@@ -24,7 +24,11 @@ func TestNewResolverVanilla(t *testing.T) {
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
-	ewr, ok := ir.Resolver.(*errorsx.ErrorWrapperResolver)
+	rla, ok := ir.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	ewr, ok := rla.ResolverLegacy.(*errorsx.ErrorWrapperResolver)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
@@ -48,7 +52,11 @@ func TestNewResolverSpecificResolver(t *testing.T) {
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
-	ewr, ok := ir.Resolver.(*errorsx.ErrorWrapperResolver)
+	rla, ok := ir.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	ewr, ok := rla.ResolverLegacy.(*errorsx.ErrorWrapperResolver)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
@@ -70,7 +78,11 @@ func TestNewResolverWithBogonFilter(t *testing.T) {
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
-	ewr, ok := ir.Resolver.(*errorsx.ErrorWrapperResolver)
+	rla, ok := ir.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	ewr, ok := rla.ResolverLegacy.(*errorsx.ErrorWrapperResolver)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
@@ -96,17 +108,33 @@ func TestNewResolverWithLogging(t *testing.T) {
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
-	lr, ok := ir.Resolver.(*netxlite.ResolverLogger)
+	rla, ok := ir.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	lr, ok := rla.ResolverLegacy.(*netxlite.ResolverLogger)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
 	if lr.Logger != log.Log {
 		t.Fatal("not the logger we expected")
 	}
-	ewr, ok := lr.Resolver.(*errorsx.ErrorWrapperResolver)
+	rla, ok = ir.Resolver.(*netxlite.ResolverLegacyAdapter)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
+	lr, ok = rla.ResolverLegacy.(*netxlite.ResolverLogger)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	rla, ok = lr.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	ewr, ok := rla.ResolverLegacy.(*errorsx.ErrorWrapperResolver)
+	if !ok {
+		t.Fatalf("not the resolver we expected %T", rla.ResolverLegacy)
+	}
 	ar, ok := ewr.Resolver.(resolver.AddressResolver)
 	if !ok {
 		t.Fatal("not the resolver we expected")
@@ -126,7 +154,11 @@ func TestNewResolverWithSaver(t *testing.T) {
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
-	sr, ok := ir.Resolver.(resolver.SaverResolver)
+	rla, ok := ir.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	sr, ok := rla.ResolverLegacy.(resolver.SaverResolver)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
@@ -155,7 +187,11 @@ func TestNewResolverWithReadWriteCache(t *testing.T) {
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
-	ewr, ok := ir.Resolver.(*errorsx.ErrorWrapperResolver)
+	rla, ok := ir.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	ewr, ok := rla.ResolverLegacy.(*errorsx.ErrorWrapperResolver)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
@@ -186,7 +222,11 @@ func TestNewResolverWithPrefilledReadonlyCache(t *testing.T) {
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}
-	ewr, ok := ir.Resolver.(*errorsx.ErrorWrapperResolver)
+	rla, ok := ir.Resolver.(*netxlite.ResolverLegacyAdapter)
+	if !ok {
+		t.Fatal("not the resolver we expected")
+	}
+	ewr, ok := rla.ResolverLegacy.(*errorsx.ErrorWrapperResolver)
 	if !ok {
 		t.Fatal("not the resolver we expected")
 	}

internal/engine/netx/resolver/integration_test.go

@@ -19,7 +19,10 @@ func testresolverquick(t *testing.T, reso resolver.Resolver) {
 	if testing.Short() {
 		t.Skip("skip test in short mode")
 	}
-	reso = &netxlite.ResolverLogger{Logger: log.Log, Resolver: reso}
+	reso = &netxlite.ResolverLogger{
+		Logger:   log.Log,
+		Resolver: netxlite.NewResolverLegacyAdapter(reso),
+	}
 	addrs, err := reso.LookupHost(context.Background(), "dns.google.com")
 	if err != nil {
 		t.Fatal(err)
@@ -45,7 +48,10 @@ func testresolverquickidna(t *testing.T, reso resolver.Resolver) {
 		t.Skip("skip test in short mode")
 	}
 	reso = &resolver.IDNAResolver{
-		Resolver: &netxlite.ResolverLogger{Logger: log.Log, Resolver: reso},
+		Resolver: &netxlite.ResolverLogger{
+			Logger:   log.Log,
+			Resolver: netxlite.NewResolverLegacyAdapter(reso),
+		},
 	}
 	addrs, err := reso.LookupHost(context.Background(), "яндекс.рф")
 	if err != nil {

internal/netxlite/http3_test.go

@@ -2,9 +2,10 @@ package netxlite
 
 import (
 	"crypto/tls"
-	"net"
 	"net/http"
 	"testing"
+
+	"github.com/apex/log"
 )
 
 func TestHTTP3TransportWorks(t *testing.T) {
@@ -12,7 +13,7 @@ func TestHTTP3TransportWorks(t *testing.T) {
 		Dialer: &quicDialerQUICGo{
 			QUICListener: &quicListenerStdlib{},
 		},
-		Resolver: &net.Resolver{},
+		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
 	}
 	txp := NewHTTP3Transport(d, &tls.Config{})
 	client := &http.Client{Transport: txp}

internal/netxlite/http_test.go

@@ -112,7 +112,7 @@ func TestHTTPTransportLoggerCloseIdleConnections(t *testing.T) {
 func TestHTTPTransportWorks(t *testing.T) {
 	d := &dialerResolver{
 		Dialer:   defaultDialer,
-		Resolver: &net.Resolver{},
+		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
 	}
 	th := &tlsHandshakerConfigurable{}
 	txp := NewHTTPTransport(d, &tls.Config{}, th)
@@ -134,7 +134,7 @@ func TestHTTPTransportWithFailingDialer(t *testing.T) {
 				return nil, expected
 			},
 		},
-		Resolver: &net.Resolver{},
+		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
 	}
 	th := &tlsHandshakerConfigurable{}
 	txp := NewHTTPTransport(d, &tls.Config{}, th)

internal/netxlite/legacy.go

@@ -1,6 +1,7 @@
 package netxlite
 
 import (
+	"context"
 	"errors"
 	"strings"
 
@@ -59,3 +60,65 @@ type (
 	TLSHandshakerConfigurable = tlsHandshakerConfigurable
 	TLSHandshakerLogger       = tlsHandshakerLogger
 )
+
+// ResolverLegacy performs domain name resolutions.
+//
+// This definition of Resolver is DEPRECATED. New code should use
+// the more complete definition in the new Resolver interface.
+//
+// Existing code in ooni/probe-cli is still using this definition.
+type ResolverLegacy interface {
+	// LookupHost behaves like net.Resolver.LookupHost.
+	LookupHost(ctx context.Context, hostname string) (addrs []string, err error)
+}
+
+// NewResolverLegacyAdapter adapts a ResolverLegacy to
+// become compatible with the Resolver definition.
+func NewResolverLegacyAdapter(reso ResolverLegacy) Resolver {
+	return &ResolverLegacyAdapter{reso}
+}
+
+// ResolverLegacyAdapter makes a ResolverLegacy behave like
+// it was a Resolver type. If ResolverLegacy is actually also
+// a Resolver, this adapter will just forward missing calls,
+// otherwise it will implement a sensible default action.
+type ResolverLegacyAdapter struct {
+	ResolverLegacy
+}
+
+var _ Resolver = &ResolverLegacyAdapter{}
+
+type resolverLegacyNetworker interface {
+	Network() string
+}
+
+// Network implements Resolver.Network.
+func (r *ResolverLegacyAdapter) Network() string {
+	if rn, ok := r.ResolverLegacy.(resolverLegacyNetworker); ok {
+		return rn.Network()
+	}
+	return "adapter"
+}
+
+type resolverLegacyAddresser interface {
+	Address() string
+}
+
+// Address implements Resolver.Address.
+func (r *ResolverLegacyAdapter) Address() string {
+	if ra, ok := r.ResolverLegacy.(resolverLegacyAddresser); ok {
+		return ra.Address()
+	}
+	return ""
+}
+
+type resolverLegacyIdleConnectionsCloser interface {
+	CloseIdleConnections()
+}
+
+// CloseIdleConnections implements Resolver.CloseIdleConnections.
+func (r *ResolverLegacyAdapter) CloseIdleConnections() {
+	if ra, ok := r.ResolverLegacy.(resolverLegacyIdleConnectionsCloser); ok {
+		ra.CloseIdleConnections()
+	}
+}

internal/netxlite/legacy_test.go

@@ -2,9 +2,11 @@ package netxlite
 
 import (
 	"errors"
+	"net"
 	"testing"
 
 	"github.com/ooni/probe-cli/v3/internal/errorsx"
+	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
 )
 
 func TestReduceErrors(t *testing.T) {
@@ -44,3 +46,39 @@ func TestReduceErrors(t *testing.T) {
 		}
 	})
 }
+
+func TestResolverLegacyAdapterWithCompatibleType(t *testing.T) {
+	var called bool
+	r := NewResolverLegacyAdapter(&mocks.Resolver{
+		MockNetwork: func() string {
+			return "network"
+		},
+		MockAddress: func() string {
+			return "address"
+		},
+		MockCloseIdleConnections: func() {
+			called = true
+		},
+	})
+	if r.Network() != "network" {
+		t.Fatal("invalid Network")
+	}
+	if r.Address() != "address" {
+		t.Fatal("invalid Address")
+	}
+	r.CloseIdleConnections()
+	if !called {
+		t.Fatal("not called")
+	}
+}
+
+func TestResolverLegacyAdapterDefaults(t *testing.T) {
+	r := NewResolverLegacyAdapter(&net.Resolver{})
+	if r.Network() != "adapter" {
+		t.Fatal("invalid Network")
+	}
+	if r.Address() != "" {
+		t.Fatal("invalid Address")
+	}
+	r.CloseIdleConnections() // does not crash
+}

internal/netxlite/mocks/resolver.go

@@ -4,9 +4,10 @@ import "context"
 
 // Resolver is a mockable Resolver.
 type Resolver struct {
-	MockLookupHost func(ctx context.Context, domain string) ([]string, error)
-	MockNetwork    func() string
-	MockAddress    func() string
+	MockLookupHost           func(ctx context.Context, domain string) ([]string, error)
+	MockNetwork              func() string
+	MockAddress              func() string
+	MockCloseIdleConnections func()
 }
 
 // LookupHost calls MockLookupHost.
@@ -23,3 +24,8 @@ func (r *Resolver) Address() string {
 func (r *Resolver) Network() string {
 	return r.MockNetwork()
 }
+
+// CloseIdleConnections calls MockCloseIdleConnections.
+func (r *Resolver) CloseIdleConnections() {
+	r.MockCloseIdleConnections()
+}

internal/netxlite/mocks/resolver_test.go

@@ -44,3 +44,16 @@ func TestResolverAddress(t *testing.T) {
 		t.Fatal("unexpected address", v)
 	}
 }
+
+func TestResolverCloseIdleConnections(t *testing.T) {
+	var called bool
+	r := &Resolver{
+		MockCloseIdleConnections: func() {
+			called = true
+		},
+	}
+	r.CloseIdleConnections()
+	if !called {
+		t.Fatal("not called")
+	}
+}

internal/netxlite/quic_test.go

@@ -215,7 +215,8 @@ func TestQUICDialerQUICGoTLSDefaultsForDoQ(t *testing.T) {
 func TestQUICDialerResolverSuccess(t *testing.T) {
 	tlsConfig := &tls.Config{}
 	dialer := &quicDialerResolver{
-		Resolver: &net.Resolver{}, Dialer: &quicDialerQUICGo{
+		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
+		Dialer: &quicDialerQUICGo{
 			QUICListener: &quicListenerStdlib{},
 		}}
 	sess, err := dialer.DialContext(
@@ -233,7 +234,8 @@ func TestQUICDialerResolverSuccess(t *testing.T) {
 func TestQUICDialerResolverNoPort(t *testing.T) {
 	tlsConfig := &tls.Config{}
 	dialer := &quicDialerResolver{
-		Resolver: new(net.Resolver), Dialer: &quicDialerQUICGo{}}
+		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
+		Dialer:   &quicDialerQUICGo{}}
 	sess, err := dialer.DialContext(
 		context.Background(), "udp", "www.google.com",
 		tlsConfig, &quic.Config{})
@@ -286,7 +288,8 @@ func TestQUICDialerResolverInvalidPort(t *testing.T) {
 	// to establish a connection leads to a failure
 	tlsConf := &tls.Config{}
 	dialer := &quicDialerResolver{
-		Resolver: new(net.Resolver), Dialer: &quicDialerQUICGo{
+		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
+		Dialer: &quicDialerQUICGo{
 			QUICListener: &quicListenerStdlib{},
 		}}
 	sess, err := dialer.DialContext(
@@ -309,7 +312,8 @@ func TestQUICDialerResolverApplyTLSDefaults(t *testing.T) {
 	var gotTLSConfig *tls.Config
 	tlsConfig := &tls.Config{}
 	dialer := &quicDialerResolver{
-		Resolver: new(net.Resolver), Dialer: &mocks.QUICContextDialer{
+		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
+		Dialer: &mocks.QUICContextDialer{
 			MockDialContext: func(ctx context.Context, network, address string,
 				tlsConfig *tls.Config, quicConfig *quic.Config) (quic.EarlySession, error) {
 				gotTLSConfig = tlsConfig

internal/netxlite/resolver.go

@@ -12,6 +12,31 @@ import (
 type Resolver interface {
 	// LookupHost behaves like net.Resolver.LookupHost.
 	LookupHost(ctx context.Context, hostname string) (addrs []string, err error)
+
+	// Network returns the resolver type (e.g., system, dot, doh).
+	Network() string
+
+	// Address returns the resolver address (e.g., 8.8.8.8:53).
+	Address() string
+
+	// CloseIdleConnections closes idle connections, if any.
+	CloseIdleConnections()
+}
+
+// ResolverConfig contains config for creating a resolver.
+type ResolverConfig struct {
+	// Logger is the MANDATORY logger to use.
+	Logger Logger
+}
+
+// NewResolver creates a new resolver.
+func NewResolver(config *ResolverConfig) Resolver {
+	return &resolverIDNA{
+		Resolver: &resolverLogger{
+			Resolver: &resolverSystem{},
+			Logger:   config.Logger,
+		},
+	}
 }
 
 // resolverSystem is the system resolver.
@@ -34,6 +59,11 @@ func (r *resolverSystem) Address() string {
 	return ""
 }
 
+// CloseIdleConnections implements Resolver.CloseIdleConnections.
+func (r *resolverSystem) CloseIdleConnections() {
+	// nothing
+}
+
 // DefaultResolver is the resolver we use by default.
 var DefaultResolver = &resolverSystem{}
 
@@ -59,30 +89,6 @@ func (r *resolverLogger) LookupHost(ctx context.Context, hostname string) ([]str
 	return addrs, nil
 }
 
-type resolverNetworker interface {
-	Network() string
-}
-
-// Network implements Resolver.Network.
-func (r *resolverLogger) Network() string {
-	if rn, ok := r.Resolver.(resolverNetworker); ok {
-		return rn.Network()
-	}
-	return "logger"
-}
-
-type resolverAddresser interface {
-	Address() string
-}
-
-// Address implements Resolver.Address.
-func (r *resolverLogger) Address() string {
-	if ra, ok := r.Resolver.(resolverAddresser); ok {
-		return ra.Address()
-	}
-	return ""
-}
-
 // resolverIDNA supports resolving Internationalized Domain Names.
 //
 // See RFC3492 for more information.
@@ -98,19 +104,3 @@ func (r *resolverIDNA) LookupHost(ctx context.Context, hostname string) ([]strin
 	}
 	return r.Resolver.LookupHost(ctx, host)
 }
-
-// Network implements Resolver.Network.
-func (r *resolverIDNA) Network() string {
-	if rn, ok := r.Resolver.(resolverNetworker); ok {
-		return rn.Network()
-	}
-	return "idna"
-}
-
-// Address implements Resolver.Address.
-func (r *resolverIDNA) Address() string {
-	if ra, ok := r.Resolver.(resolverAddresser); ok {
-		return ra.Address()
-	}
-	return ""
-}

internal/netxlite/resolver_test.go

@@ -3,7 +3,6 @@ package netxlite
 import (
 	"context"
 	"errors"
-	"net"
 	"strings"
 	"testing"
 
@@ -71,26 +70,6 @@ func TestResolverLoggerWithFailure(t *testing.T) {
 	}
 }
 
-func TestResolverLoggerChildNetworkAddress(t *testing.T) {
-	r := &resolverLogger{Logger: log.Log, Resolver: DefaultResolver}
-	if r.Network() != "system" {
-		t.Fatal("invalid Network")
-	}
-	if r.Address() != "" {
-		t.Fatal("invalid Address")
-	}
-}
-
-func TestResolverLoggerNoChildNetworkAddress(t *testing.T) {
-	r := &resolverLogger{Logger: log.Log, Resolver: &net.Resolver{}}
-	if r.Network() != "logger" {
-		t.Fatal("invalid Network")
-	}
-	if r.Address() != "" {
-		t.Fatal("invalid Address")
-	}
-}
-
 func TestResolverIDNAWorksAsIntended(t *testing.T) {
 	expectedIPs := []string{"77.88.55.66"}
 	r := &resolverIDNA{
@@ -130,24 +109,22 @@ func TestResolverIDNAWithInvalidPunycode(t *testing.T) {
 	}
 }
 
-func TestResolverIDNAChildNetworkAddress(t *testing.T) {
-	r := &resolverIDNA{
-		Resolver: DefaultResolver,
+func TestNewResolverTypeChain(t *testing.T) {
+	r := NewResolver(&ResolverConfig{
+		Logger: log.Log,
+	})
+	ridna, ok := r.(*resolverIDNA)
+	if !ok {
+		t.Fatal("invalid resolver")
 	}
-	if v := r.Network(); v != "system" {
-		t.Fatal("invalid network", v)
+	rl, ok := ridna.Resolver.(*resolverLogger)
+	if !ok {
+		t.Fatal("invalid resolver")
 	}
-	if v := r.Address(); v != "" {
-		t.Fatal("invalid address", v)
-	}
-}
-
-func TestResolverIDNANoChildNetworkAddress(t *testing.T) {
-	r := &resolverIDNA{}
-	if v := r.Network(); v != "idna" {
-		t.Fatal("invalid network", v)
-	}
-	if v := r.Address(); v != "" {
-		t.Fatal("invalid address", v)
+	if rl.Logger != log.Log {
+		t.Fatal("invalid logger")
+	}
+	if _, ok := rl.Resolver.(*resolverSystem); !ok {
+		t.Fatal("invalid resolver")
 	}
 }