aboutsummaryrefslogtreecommitdiff
path: root/include/net/netns/generic.h
blob: 0931618c0f7ff6d41f72db1103b2aa0dc474e21f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
/*
 * 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