Add CNAME test

x/smart/finder.go

@@ -36,7 +36,6 @@ import (
 )
 
 // TODO:
-// - Fix for China
 // - Add DNS caching
 // - Parallelize TLS
 // - Add debug logging to proxy handler
@@ -240,7 +239,7 @@ func evaluateNetResolver(ctx context.Context, resolver *net.Resolver, testDomain
 	if err != nil {
 		return nil, fmt.Errorf("could not get cname: %w", err)
 	}
-	ips, err := net.LookupIP(requestDomain)
+	ips, err := resolver.LookupIP(ctx, "ip", requestDomain)
 	if err != nil {
 		return nil, fmt.Errorf("failed to lookup IPs: %w", err)
 	}
@@ -256,7 +255,10 @@ func evaluateNetResolver(ctx context.Context, resolver *net.Resolver, testDomain
 	return ips, nil
 }
 
-func evaluateResponse(response *miekgdns.Msg, requestDomain string) ([]net.IP, error) {
+func evaluateAResponse(response *miekgdns.Msg, requestDomain string) ([]net.IP, error) {
+	if response.Rcode != miekgdns.RcodeSuccess {
+		return nil, fmt.Errorf("rcode is not success: %v", response.Rcode)
+	}
 	var ips []net.IP
 	if len(response.Answer) == 0 {
 		return ips, errors.New("no answers") // -1
@@ -287,6 +289,37 @@ func evaluateResponse(response *miekgdns.Msg, requestDomain string) ([]net.IP, e
 	return ips, nil
 }
 
+func evaluateCNAMEResponse(response *miekgdns.Msg, requestDomain string) error {
+	if response.Rcode != miekgdns.RcodeSuccess {
+		return fmt.Errorf("rcode is not success: %v", response.Rcode)
+	}
+	if len(response.Answer) == 0 {
+		var numSOA int
+		for _, answer := range response.Ns {
+			if _, ok := answer.(*miekgdns.SOA); ok {
+				numSOA++
+			}
+		}
+		if numSOA != 1 {
+			return fmt.Errorf("SOA records is %v, expected 1", numSOA)
+		}
+		return nil
+	}
+	var cname string
+	for _, answer := range response.Answer {
+		if rr, ok := answer.(*miekgdns.CNAME); ok {
+			if cname != "" {
+				return fmt.Errorf("found too many CNAMEs: %v %v", cname, rr.Target)
+			}
+			cname = rr.Target
+		}
+	}
+	if cname == "" {
+		return errors.New("no CNAME in answers")
+	}
+	return nil
+}
+
 type StrategyFinder struct {
 	TestTimeout  time.Duration
 	LogWriter    io.Writer
@@ -312,14 +345,28 @@ func (f *StrategyFinder) testDNSClient(ctx context.Context, dnsRT dns.RoundTripp
 		return evaluateNetResolver(ctx, new(net.Resolver), testDomain)
 	}
 
-	var request miekgdns.Msg
 	requestDomain := mixCase(testDomain)
+	var request miekgdns.Msg
+
+	request = miekgdns.Msg{}
 	request.SetQuestion(requestDomain, miekgdns.TypeA)
 	response, err := (&MiekgRoundTripper{dnsRT}).RoundTripMsg(ctx, &request)
 	if err != nil {
-		return nil, fmt.Errorf("request failed: %w", err)
+		return nil, fmt.Errorf("request for A query failed: %w", err)
+	}
+	ips, err := evaluateAResponse(response, requestDomain)
+	if err != nil {
+		return ips, err
+	}
+
+	request = miekgdns.Msg{}
+	request.SetQuestion(requestDomain, miekgdns.TypeCNAME)
+	response, err = (&MiekgRoundTripper{dnsRT}).RoundTripMsg(ctx, &request)
+	if err != nil {
+		return nil, fmt.Errorf("request for CNAME query failed: %w", err)
 	}
-	return evaluateResponse(response, requestDomain)
+	err = evaluateCNAMEResponse(response, requestDomain)
+	return ips, err
 }
 
 type httpsEntryJSON struct {