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 
net_generic(const struct net * net,unsigned int id)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
52