include/net/netns/generic.h

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