detect: (m)dns keywords even with "alert udp"

Ticket: 8501

(m)dns.*.rrname keywords required the rules to start with
alert (m)dns
and refused to load if the rule started with generic alert ip or
alert udp, with error message
Error: detect-parse: invalid alproto 0

(cherry picked from commit 7e326f291a)

src/detect-dns-name.c

@@ -51,12 +51,24 @@ static int mdns_answer_buffer_id = 0;
 static int mdns_authority_buffer_id = 0;
 static int mdns_additional_buffer_id = 0;
 
-static int DetectSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str, int id)
+static int DetectSetupDNS(DetectEngineCtx *de_ctx, Signature *s, const char *str, int id)
 {
     if (SCDetectBufferSetActiveList(de_ctx, s, id) < 0) {
         return -1;
     }
-    if (SCDetectSignatureSetAppProto(s, s->alproto) < 0) {
+    if (SCDetectSignatureSetAppProto(s, ALPROTO_DNS) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static int DetectSetupMDNS(DetectEngineCtx *de_ctx, Signature *s, const char *str, int id)
+{
+    if (SCDetectBufferSetActiveList(de_ctx, s, id) < 0) {
+        return -1;
+    }
+    if (SCDetectSignatureSetAppProto(s, ALPROTO_MDNS) < 0) {
         return -1;
     }
 
@@ -65,42 +77,42 @@ static int DetectSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str, i
 
 static int SetupQueryBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, query_buffer_id);
+    return DetectSetupDNS(de_ctx, s, str, query_buffer_id);
 }
 
 static int SetupAnswerBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, answer_buffer_id);
+    return DetectSetupDNS(de_ctx, s, str, answer_buffer_id);
 }
 
 static int SetupAdditionalsBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, additional_buffer_id);
+    return DetectSetupDNS(de_ctx, s, str, additional_buffer_id);
 }
 
 static int SetupAuthoritiesBuffer(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, authority_buffer_id);
+    return DetectSetupDNS(de_ctx, s, str, authority_buffer_id);
 }
 
 static int SetupQueryBufferMdns(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, mdns_query_buffer_id);
+    return DetectSetupMDNS(de_ctx, s, str, mdns_query_buffer_id);
 }
 
 static int SetupAnswerBufferMdns(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, mdns_answer_buffer_id);
+    return DetectSetupMDNS(de_ctx, s, str, mdns_answer_buffer_id);
 }
 
 static int SetupAdditionalsBufferMdns(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, mdns_additional_buffer_id);
+    return DetectSetupMDNS(de_ctx, s, str, mdns_additional_buffer_id);
 }
 
 static int SetupAuthoritiesBufferMdns(DetectEngineCtx *de_ctx, Signature *s, const char *str)
 {
-    return DetectSetup(de_ctx, s, str, mdns_authority_buffer_id);
+    return DetectSetupMDNS(de_ctx, s, str, mdns_authority_buffer_id);
 }
 
 static int Register(const char *keyword, const char *desc, const char *doc,