shared: introduce dnssd_srv_type_is_valid() function

src/shared/dns-domain.c

@@ -959,6 +959,12 @@ bool dns_srv_type_is_valid(const char *name) {
         return c == 2; /* exactly two labels */
 }
 
+bool dnssd_srv_type_is_valid(const char *name) {
+        return dns_srv_type_is_valid(name) &&
+                ((dns_name_endswith(name, "_tcp") > 0) ||
+                 (dns_name_endswith(name, "_udp") > 0)); /* Specific to DNS-SD. RFC 6763, Section 7 */
+}
+
 bool dns_service_name_is_valid(const char *name) {
         size_t l;
 

src/shared/dns-domain.h

@@ -96,6 +96,7 @@ bool dns_name_is_single_label(const char *name);
 int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len, bool canonical);
 
 bool dns_srv_type_is_valid(const char *name);
+bool dnssd_srv_type_is_valid(const char *name);
 bool dns_service_name_is_valid(const char *name);
 
 int dns_service_join(const char *name, const char *type, const char *domain, char **ret);