include/net/netns/generic.h

   1 /*
   2  * generic net pointers
   3  */
   4
   5 #ifndef __NET_GENERIC_H__
   6 #define __NET_GENERIC_H__
   7
   8 #include <linux/rcupdate.h>
   9
  10 /*
  11  * Generic net pointers are to be used by modules to put some private
  12  * stuff on the struct net without explicit struct net modification
  13  *
  14  * The rules are simple:
  15  * 1. register the ops with register_pernet_gen_device to get the id
  16  *    of your private pointer;
  17  * 2. call net_assign_generic() to put the private data on the struct
  18  *    net (most preferably this should be done in the ->init callback
  19  *    of the ops registered);
  20  * 3. do not change this pointer while the net is alive;
  21  * 4. do not try to have any private reference on the net_generic object.
  22  *
  23  * After accomplishing all of the above, the private pointer can be
  24  * accessed with the net_generic() call.
  25  */
  26
  27 struct net_generic {
  28         unsigned int len;
  29         struct rcu_head rcu;
  30
  31         void *ptr[0];
  32 };
  33
  34 static inline void *net_generic(struct net *net, int id)
  35 {
  36         struct net_generic *ng;
  37         void *ptr;
  38
  39         rcu_read_lock();
  40         ng = rcu_dereference(net->gen);
  41         BUG_ON(id == 0 || id > ng->len);
  42         ptr = ng->ptr[id - 1];
  43         rcu_read_unlock();
  44
  45         return ptr;
  46 }
  47
  48 extern int net_assign_generic(struct net *net, int id, void *data);
  49 #endif