net/netns/generic.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 /*
0003  * generic net pointers
0004  */
0005
0006 #ifndef __NET_GENERIC_H__
0007 #define __NET_GENERIC_H__
0008
0009 #include <linux/bug.h>
0010 #include <linux/rcupdate.h>
0011 #include <net/net_namespace.h>
0012
0013 /*
0014  * Generic net pointers are to be used by modules to put some private
0015  * stuff on the struct net without explicit struct net modification
0016  *
0017  * The rules are simple:
0018  * 1. set pernet_operations->id.  After register_pernet_device you
0019  *    will have the id of your private pointer.
0020  * 2. set pernet_operations->size to have the code allocate and free
0021  *    a private structure pointed to from struct net.
0022  * 3. do not change this pointer while the net is alive;
0023  * 4. do not try to have any private reference on the net_generic object.
0024  *
0025  * After accomplishing all of the above, the private pointer can be
0026  * accessed with the net_generic() call.
0027  */
0028
0029 struct net_generic {
0030     union {
0031         struct {
0032             unsigned int len;
0033             struct rcu_head rcu;
0034         } s;
0035
0036         void *ptr[0];
0037     };
0038 };
0039
0040 static inline void *net_generic(const struct net *net, unsigned int id)
0041 {
0042     struct net_generic *ng;
0043     void *ptr;
0044
0045     rcu_read_lock();
0046     ng = rcu_dereference(net->gen);
0047     ptr = ng->ptr[id];
0048     rcu_read_unlock();
0049
0050     return ptr;
0051 }
0052 #endif