xtables: extend matches and targets with .usersize

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>

path: root/rnd.h

#ifndef RND_H
#define RND_H

#define HIG_ENTROPY_SOURCE	"/dev/random"
#define LOW_ENTROPY_SOURCE	"/dev/urandom"

/* secrand is not really secure, but the name only suggests it's better to use
 * than rand(3) when transferring bytes over the network in non-security
 * critical structure members. secrand() is only used to fill up salts actually.
 */
extern int secrand(void);
extern void gen_key_bytes(unsigned char *area, size_t len);

#endif /* RND_H */