+
+/* Note that LOOPBACK_IFINDEX is currently not exported by the
+ * kernel/glibc, but hardcoded internally by the kernel. However, as
+ * it is exported to userspace indirectly via rtnetlink and the
+ * ioctls, and made use of widely we define it here too, in a way that
+ * is compatible with the kernel's internal definition. */
+#ifndef LOOPBACK_IFINDEX
+#define LOOPBACK_IFINDEX 1
+#endif