/*
* generic net pointers
*/

#ifndef __NET_GENERIC_H__
#define __NET_GENERIC_H__

#include <linux/bug.h>
#include <linux/rcupdate.h>

/*
* Generic net pointers are to be used by modules to put some private
* stuff on the struct net without explicit struct net modification
*
* The rules are simple:
* 1. set pernet_operations->id. After register_pernet_device you
* will have the id of your private pointer.
* 2. set pernet_operations->size to have the code allocate and free
* a private structure pointed to from struct net.
* 3. do not change this pointer while the net is alive;
* 4. do not try to have any private reference on the net_generic object.
*
* After accomplishing all of the above, the private pointer can be
* accessed with the net_generic() call.
*/

struct net_generic {
unsigned int len;
struct rcu_head rcu;

void *ptr[0];
};

static inline void *net_generic(const struct net *net, int id)
{
struct net_generic *ng;
void *ptr;

rcu_read_lock();
ng = rcu_dereference(net->gen);
BUG_ON(id == 0 || id > ng->len);
ptr = ng->ptr[id - 1];
rcu_read_unlock();

BUG_ON(!ptr);
return ptr;
}
#endif