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. set pernet_operations->id.  After register_pernet_device you
  16  *    will have the id of your private pointer.
  17  * 2. Either set pernet_operations->size (to have the code allocate and
  18  *    free a private structure pointed to from struct net ) or
  19  *    call net_assign_generic() to put the private data on the struct
  20  *    net (most preferably this should be done in the ->init callback
  21  *    of the ops registered);
  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         unsigned int len;
  31         struct rcu_head rcu;
  32
  33         void *ptr[0];
  34 };
  35
  36 static inline void *net_generic(struct net *net, int id)
  37 {
  38         struct net_generic *ng;
  39         void *ptr;
  40
  41         rcu_read_lock();
  42         ng = rcu_dereference(net->gen);
  43         BUG_ON(id == 0 || id > ng->len);
  44         ptr = ng->ptr[id - 1];
  45         rcu_read_unlock();
  46
  47         return ptr;
  48 }
  49
  50 extern int net_assign_generic(struct net *net, int id, void *data);
  51 #endif