--- a/packet/utils.h
+++ b/packet/utils.h
@@ -0,0 +1,14 @@
+#ifndef _UTILS_H
+#define _UTILS_H
+
+// Fend off -Wunused-parameter
+#if defined(__GNUC__)
+# define UNUSED __attribute__((__unused__))
+#else
+# define UNUSED
+#endif
+
+// Number of entries in a fixed-length array
+#define N_ENTRIES(x) (sizeof(x) / sizeof(*x))
+
+#endif