refactor: move quic dns dialing to netxlite (#408)

Part of https://github.com/ooni/probe/issues/1505

internal/netxlite/quic_test.go

@@ -133,3 +133,95 @@ func TestQUICDialerWorksAsIntended(t *testing.T) {
 		log.Fatal(err)
 	}
 }
+
+func TestQUICDialerResolverSuccess(t *testing.T) {
+	tlsConfig := &tls.Config{NextProtos: []string{"h3"}}
+	dialer := &QUICDialerResolver{
+		Resolver: &net.Resolver{}, Dialer: &QUICDialerQUICGo{
+			QUICListener: &QUICListenerStdlib{},
+		}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com:443",
+		tlsConfig, &quic.Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	<-sess.HandshakeComplete().Done()
+	if err := sess.CloseWithError(0, ""); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestQUICDialerResolverNoPort(t *testing.T) {
+	tlsConfig := &tls.Config{NextProtos: []string{"h3"}}
+	dialer := &QUICDialerResolver{
+		Resolver: new(net.Resolver), Dialer: &QUICDialerQUICGo{}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com",
+		tlsConfig, &quic.Config{})
+	if err == nil || !strings.HasSuffix(err.Error(), "missing port in address") {
+		t.Fatal("not the error we expected")
+	}
+	if sess != nil {
+		t.Fatal("expected a nil sess here")
+	}
+}
+
+func TestQUICDialerResolverLookupHostAddress(t *testing.T) {
+	dialer := &QUICDialerResolver{Resolver: &netxmocks.Resolver{
+		MockLookupHost: func(ctx context.Context, domain string) ([]string, error) {
+			// We should not arrive here and call this function but if we do then
+			// there is going to be an error that fails this test.
+			return nil, errors.New("mocked error")
+		},
+	}}
+	addrs, err := dialer.lookupHost(context.Background(), "1.1.1.1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(addrs) != 1 || addrs[0] != "1.1.1.1" {
+		t.Fatal("not the result we expected")
+	}
+}
+
+func TestQUICDialerResolverLookupHostFailure(t *testing.T) {
+	tlsConfig := &tls.Config{NextProtos: []string{"h3"}}
+	expected := errors.New("mocked error")
+	dialer := &QUICDialerResolver{Resolver: &netxmocks.Resolver{
+		MockLookupHost: func(ctx context.Context, domain string) ([]string, error) {
+			return nil, expected
+		},
+	}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "dns.google.com:853",
+		tlsConfig, &quic.Config{})
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+	if sess != nil {
+		t.Fatal("expected nil sess")
+	}
+}
+
+func TestQUICDialerResolverInvalidPort(t *testing.T) {
+	// This test allows us to check for the case where every attempt
+	// to establish a connection leads to a failure
+	tlsConf := &tls.Config{NextProtos: []string{"h3"}}
+	dialer := &QUICDialerResolver{
+		Resolver: new(net.Resolver), Dialer: &QUICDialerQUICGo{
+			QUICListener: &QUICListenerStdlib{},
+		}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com:0",
+		tlsConf, &quic.Config{})
+	if err == nil {
+		t.Fatal("expected an error here")
+	}
+	if !strings.HasSuffix(err.Error(), "sendto: invalid argument") &&
+		!strings.HasSuffix(err.Error(), "sendto: can't assign requested address") {
+		t.Fatal("not the error we expected", err)
+	}
+	if sess != nil {
+		t.Fatal("expected nil sess")
+	}
+}