feat(netxlite): add dialer factory, simplify resolver factory (#459)

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

internal/netxlite/dialer.go

@@ -15,6 +15,26 @@ type Dialer interface {
 	CloseIdleConnections()
 }
 
+// NewDialerWithResolver creates a dialer using the given resolver and logger.
+func NewDialerWithResolver(logger Logger, resolver Resolver) Dialer {
+	return &dialerLogger{
+		Dialer: &dialerResolver{
+			Dialer: &dialerLogger{
+				Dialer: &dialerSystem{},
+				Logger: logger,
+			},
+			Resolver: resolver,
+		},
+		Logger: logger,
+	}
+}
+
+// NewDialerWithoutResolver creates a dialer that uses the given
+// logger and fails with ErrNoResolver when it is passed a domain name.
+func NewDialerWithoutResolver(logger Logger) Dialer {
+	return NewDialerWithResolver(logger, &nullResolver{})
+}
+
 // underlyingDialer is the Dialer we use by default.
 var underlyingDialer = &net.Dialer{
 	Timeout:   15 * time.Second,

internal/netxlite/dialer_test.go

@@ -207,3 +207,31 @@ func TestUnderlyingDialerHasTimeout(t *testing.T) {
 		t.Fatal("unexpected timeout value")
 	}
 }
+
+func TestNewDialerWithoutResolverChain(t *testing.T) {
+	dlr := NewDialerWithoutResolver(log.Log)
+	dlog, okay := dlr.(*dialerLogger)
+	if !okay {
+		t.Fatal("invalid type")
+	}
+	if dlog.Logger != log.Log {
+		t.Fatal("invalid logger")
+	}
+	dreso, okay := dlog.Dialer.(*dialerResolver)
+	if !okay {
+		t.Fatal("invalid type")
+	}
+	if _, okay := dreso.Resolver.(*nullResolver); !okay {
+		t.Fatal("invalid Resolver type")
+	}
+	dlog, okay = dreso.Dialer.(*dialerLogger)
+	if !okay {
+		t.Fatal("invalid type")
+	}
+	if dlog.Logger != log.Log {
+		t.Fatal("invalid logger")
+	}
+	if _, okay := dlog.Dialer.(*dialerSystem); !okay {
+		t.Fatal("invalid type")
+	}
+}

internal/netxlite/http3_test.go

@@ -13,7 +13,7 @@ func TestHTTP3TransportWorks(t *testing.T) {
 		Dialer: &quicDialerQUICGo{
 			QUICListener: &quicListenerStdlib{},
 		},
-		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
+		Resolver: NewResolverSystem(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: NewResolver(&ResolverConfig{Logger: log.Log}),
+		Resolver: NewResolverSystem(log.Log),
 	}
 	th := &tlsHandshakerConfigurable{}
 	txp := NewHTTPTransport(d, &tls.Config{}, th)
@@ -134,7 +134,7 @@ func TestHTTPTransportWithFailingDialer(t *testing.T) {
 				return nil, expected
 			},
 		},
-		Resolver: NewResolver(&ResolverConfig{Logger: log.Log}),
+		Resolver: NewResolverSystem(log.Log),
 	}
 	th := &tlsHandshakerConfigurable{}
 	txp := NewHTTPTransport(d, &tls.Config{}, th)

internal/netxlite/quic_test.go

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

internal/netxlite/resolver.go

@@ -2,6 +2,7 @@ package netxlite
 
 import (
 	"context"
+	"errors"
 	"net"
 	"time"
 
@@ -23,20 +24,15 @@ type Resolver interface {
 	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 {
+// NewResolverSystem creates a new resolver using system
+// facilities for resolving domain names (e.g., getaddrinfo).
+func NewResolverSystem(logger Logger) Resolver {
 	return &resolverIDNA{
 		Resolver: &resolverLogger{
 			Resolver: &resolverShortCircuitIPAddr{
 				Resolver: &resolverSystem{},
 			},
-			Logger: config.Logger,
+			Logger: logger,
 		},
 	}
 }
@@ -159,3 +155,30 @@ func (r *resolverShortCircuitIPAddr) LookupHost(ctx context.Context, hostname st
 	}
 	return r.Resolver.LookupHost(ctx, hostname)
 }
+
+// ErrNoResolver indicates you are using a dialer without a resolver.
+var ErrNoResolver = errors.New("no configured resolver")
+
+// nullResolver is a resolver that is not capable of resolving
+// domain names to IP addresses and always returns ErrNoResolver.
+type nullResolver struct{}
+
+// LookupHost implements Resolver.LookupHost.
+func (r *nullResolver) LookupHost(ctx context.Context, hostname string) (addrs []string, err error) {
+	return nil, ErrNoResolver
+}
+
+// Network implements Resolver.Network.
+func (r *nullResolver) Network() string {
+	return "null"
+}
+
+// Address implements Resolver.Address.
+func (r *nullResolver) Address() string {
+	return ""
+}
+
+// CloseIdleConnections implements Resolver.CloseIdleConnections.
+func (r *nullResolver) CloseIdleConnections() {
+	// nothing
+}

internal/netxlite/resolver_test.go

@@ -180,9 +180,7 @@ func TestResolverIDNAWithInvalidPunycode(t *testing.T) {
 }
 
 func TestNewResolverTypeChain(t *testing.T) {
-	r := NewResolver(&ResolverConfig{
-		Logger: log.Log,
-	})
+	r := NewResolverSystem(log.Log)
 	ridna, ok := r.(*resolverIDNA)
 	if !ok {
 		t.Fatal("invalid resolver")
@@ -238,3 +236,22 @@ func TestResolverShortCircuitIPAddrWithDomain(t *testing.T) {
 		t.Fatal("invalid result")
 	}
 }
+
+func TestNullResolverWorksAsIntended(t *testing.T) {
+	r := &nullResolver{}
+	ctx := context.Background()
+	addrs, err := r.LookupHost(ctx, "dns.google")
+	if !errors.Is(err, ErrNoResolver) {
+		t.Fatal("not the error we expected", err)
+	}
+	if addrs != nil {
+		t.Fatal("expected nil addr")
+	}
+	if r.Network() != "null" {
+		t.Fatal("invalid network")
+	}
+	if r.Address() != "" {
+		t.Fatal("invalid address")
+	}
+	r.CloseIdleConnections() // should not crash
+}