+ return NULL;
+
+ /* Subtype name */
+
+ if (!(avahi_unescape_label(&t, label, sizeof(label))))
+ return NULL;
+
+ if (strlen(label) <= 2 || label[0] != '_')
+ return NULL;
+
+ if (!*t)
+ return NULL;
+
+ /* String "_sub" */
+
+ if (!(avahi_unescape_label(&t, label, sizeof(label))))
+ return NULL;
+
+ if (strcasecmp(label, "_sub"))
+ return NULL;
+
+ if (!*t)
+ return NULL;
+
+ ret = t;
+
+ /* Application name */
+
+ if (!(avahi_unescape_label(&t, label, sizeof(label))))
+ return NULL;
+
+ if (strlen(label) <= 2 || label[0] != '_')
+ return NULL;
+
+ if (!*t)
+ return NULL;
+
+ /* _tcp or _udp boilerplate */
+
+ if (!(avahi_unescape_label(&t, label, sizeof(label))))
+ return NULL;
+
+ if (strcasecmp(label, "_tcp") && strcasecmp(label, "_udp"))
+ return NULL;
+
+ if (*t)
+ return NULL;
+
+ return ret;
+}
+
+int avahi_is_valid_service_subtype(const char *t) {
+ assert(t);
+
+ return !!avahi_get_type_from_subtype(t);
+}
+
+int avahi_is_valid_domain_name(const char *t) {
+ int is_first = 1;
+ assert(t);
+
+ if (strlen(t) >= AVAHI_DOMAIN_NAME_MAX)