Improve SRV name parsing

Author: rtpt-erikgeiser

dns.go

@@ -154,7 +154,7 @@ func createDNSReplyFromRequest(
 				continue
 			}
 
-			target := removeServiceAndPort(answerName)
+			target := removeServiceAndProtocol(answerName)
 
 			reply.Answer = append(reply.Answer, &dns.SRV{
 				Hdr:    rrHeader(target, dns.TypeSRV, config.TTL),
@@ -487,14 +487,14 @@ func delegateToDNSServer(dnsServer string, timeout time.Duration) delegateQuesti
 	}
 }
 
-func removeServiceAndPort(host string) string {
-	var parts []string
+func removeServiceAndProtocol(host string) string {
+	parts := strings.Split(host, ".")
 
-	for _, part := range strings.Split(host, ".") {
+	for i, part := range parts {
 		if !strings.HasPrefix(part, "_") {
-			parts = append(parts, part)
+			return strings.Join(parts[i:], ".")
 		}
 	}
 
-	return strings.Join(parts, ".")
+	return ""
 }

dns_test.go

@@ -451,12 +451,12 @@ func testSRVQuery(tb testing.TB, matcher string, port uint16) {
 		tb.Fatalf("port is %d instead of 389", srvRecord.Port)
 	}
 
-	if srvRecord.Hdr.Name != removeServiceAndPort(serviceName) {
-		tb.Fatalf("reply name is %q instead of %q", srvRecord.Hdr.Name, removeServiceAndPort(serviceName))
+	if srvRecord.Hdr.Name != removeServiceAndProtocol(serviceName) {
+		tb.Fatalf("reply name is %q instead of %q", srvRecord.Hdr.Name, removeServiceAndProtocol(serviceName))
 	}
 
-	if srvRecord.Target != removeServiceAndPort(serviceName) {
-		tb.Fatalf("target name is %q instead of %q", srvRecord.Target, removeServiceAndPort(serviceName))
+	if srvRecord.Target != removeServiceAndProtocol(serviceName) {
+		tb.Fatalf("target name is %q instead of %q", srvRecord.Target, removeServiceAndProtocol(serviceName))
 	}
 
 	if len(reply.Extra) != 2 {
@@ -470,8 +470,8 @@ func testSRVQuery(tb testing.TB, matcher string, port uint16) {
 		case *dns.A:
 			checkedA = true
 
-			if e.Hdr.Name != removeServiceAndPort(serviceName) {
-				tb.Fatalf("A extra record name is %s instead of %s", e.Hdr.Name, removeServiceAndPort(serviceName))
+			if e.Hdr.Name != removeServiceAndProtocol(serviceName) {
+				tb.Fatalf("A extra record name is %s instead of %s", e.Hdr.Name, removeServiceAndProtocol(serviceName))
 			}
 
 			if !e.A.Equal(relayIPv4) {
@@ -480,8 +480,8 @@ func testSRVQuery(tb testing.TB, matcher string, port uint16) {
 		case *dns.AAAA:
 			checkedAAAA = true
 
-			if e.Hdr.Name != removeServiceAndPort(serviceName) {
-				tb.Fatalf("AAAA extra record name is %s instead of %s", e.Hdr.Name, removeServiceAndPort(serviceName))
+			if e.Hdr.Name != removeServiceAndProtocol(serviceName) {
+				tb.Fatalf("AAAA extra record name is %s instead of %s", e.Hdr.Name, removeServiceAndProtocol(serviceName))
 			}
 
 			if !e.AAAA.Equal(relayIPv6) {

filter.go

@@ -24,7 +24,7 @@ func shouldRespondToNameResolutionQuery(config *Config, host string, queryType u
 
 	if queryType == dns.TypeSRV {
 		hostWithService = host
-		host = removeServiceAndPort(host)
+		host = removeServiceAndProtocol(host)
 	}
 
 	if config.spoofingTemporarilyDisabled {