--- a/src/pppoe.h
+++ b/src/pppoe.h
@@ -132,6 +132,9 @@ typedef unsigned long UINT32_t;
 #endif
 
 #include <netinet/in.h>
+/* avoid redefinitions if <linux/in.h> and <linux/in6.h> get included. */
+#define _LINUX_IN_H
+#define _LINUX_IN6_H
 
 #ifdef HAVE_NETINET_IF_ETHER_H
 #include <sys/types.h>
