--- services/listen_dnsport.c.orig	2024-10-17 02:23:14
+++ services/listen_dnsport.c	2025-04-03 14:13:48
@@ -103,6 +103,10 @@
 
 #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() */