--- services/listen_dnsport.c.orig	2023-09-11 16:59:19
+++ services/listen_dnsport.c	2023-09-11 16:59:37
@@ -82,6 +82,11 @@
 #ifdef HAVE_LINUX_NET_TSTAMP_H
 #include <linux/net_tstamp.h>
 #endif
+
+#ifndef IPV6_TCLASS
+#define IPV6_TCLASS             36
+#endif
+
 /** number of queued TCP connections for listen() */
 #define TCP_BACKLOG 256