diff -up rp-pppoe-3.12/src/configure.in.than rp-pppoe-3.12/src/configure.in
--- rp-pppoe-3.12/src/configure.in.than	2015-12-11 16:19:38.700092797 +0100
+++ rp-pppoe-3.12/src/configure.in	2015-12-11 16:20:15.670875690 +0100
@@ -26,6 +26,7 @@ AC_CHECK_HEADERS(linux/if_pppox.h, [], [
 #include<net/ethernet.h>
 #include<linux/if.h>
 #include<linux/in.h>
+#include<linux/in6.h>
 ])
 
 dnl Checks for typedefs, structures, and compiler characteristics.
diff -up rp-pppoe-3.12/src/configure.than rp-pppoe-3.12/src/configure