In matches and targets that define a kernel-only tail to their xt_match and xt_target data structs, add a field .usersize that specifies up to where data is to be shared with userspace. Performed a search for comment "Used internally by the kernel" to find relevant matches and targets. Manually inspected the structs to derive a valid offsetof. Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>