LXR linux/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
  27struct net_generic {
  28        unsigned int len;
  29        struct rcu_head rcu;
  30
  31        void *ptr[0];
  32};
  33
  34static 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
  48extern int net_assign_generic(struct net *net, int id, void *data);
  49#endif
  50