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/bug.h>
   9#include <linux/rcupdate.h>
  10
  11/*
  12 * Generic net pointers are to be used by modules to put some private
  13 * stuff on the struct net without explicit struct net modification
  14 *
  15 * The rules are simple:
  16 * 1. set pernet_operations->id.  After register_pernet_device you
  17 *    will have the id of your private pointer.
  18 * 2. set pernet_operations->size to have the code allocate and free
  19 *    a private structure pointed to from struct net.
  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(const 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        BUG_ON(!ptr);
  46        return ptr;
  47}
  48#endif
  49