1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * generic net pointers
4 */
5
6 #ifndef __NET_GENERIC_H__
7 #define __NET_GENERIC_H__
8
9 #include <linux/bug.h>
10 #include <linux/rcupdate.h>
11
12 /*
13 * Generic net pointers are to be used by modules to put some private
14 * stuff on the struct net without explicit struct net modification
15 *
16 * The rules are simple:
17 * 1. set pernet_operations->id. After register_pernet_device you
18 * will have the id of your private pointer.
19 * 2. set pernet_operations->size to have the code allocate and free
20 * a private structure pointed to from struct net.
21 * 3. do not change this pointer while the net is alive;
22 * 4. do not try to have any private reference on the net_generic object.
23 *
24 * After accomplishing all of the above, the private pointer can be
25 * accessed with the net_generic() call.
26 */
27
28 struct net_generic {
29 union {
30 struct {
31 unsigned int len;
32 struct rcu_head rcu;
33 } s;
34
35 void *ptr[0];
36 };
37 };
38
39 static inline void *net_generic(const struct net *net, unsigned int id)
40 {
41 struct net_generic *ng;
42 void *ptr;
43
44 rcu_read_lock();
45 ng = rcu_dereference(net->gen);
46 ptr = ng->ptr[id];
47 rcu_read_unlock();
48
49 return ptr;
50 }
51 #endif