--- a/Port-linux/interface.c
+++ b/Port-linux/interface.c
@@ -43,6 +43,9 @@
 #include <linux/sockios.h>
 #include <linux/if_ether.h>
 
+int interface_auto_up;
+int interface_do_message;
+
 void daemon_log(int loglevel, const char *fmt,...)
 {
     char buf[255];
--- a/Port-linux/interface.h
+++ b/Port-linux/interface.h
@@ -23,8 +23,8 @@
 extern "C" {
 #endif
 
-int interface_auto_up;
-int interface_do_message;
+extern int interface_auto_up;
+extern int interface_do_message;
 
 typedef enum { IFSTATUS_UP, IFSTATUS_DOWN, IFSTATUS_ERR } interface_status_t;