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kernel/linux-imx6_3.14.28/include/net/netns/generic.h 1.12 KB
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  /*
   * generic net pointers
   */
  
  #ifndef __NET_GENERIC_H__
  #define __NET_GENERIC_H__
  
  #include <linux/bug.h>
  #include <linux/rcupdate.h>
  
  /*
   * Generic net pointers are to be used by modules to put some private
   * stuff on the struct net without explicit struct net modification
   *
   * The rules are simple:
   * 1. set pernet_operations->id.  After register_pernet_device you
   *    will have the id of your private pointer.
   * 2. set pernet_operations->size to have the code allocate and free
   *    a private structure pointed to from struct net.
   * 3. do not change this pointer while the net is alive;
   * 4. do not try to have any private reference on the net_generic object.
   *
   * After accomplishing all of the above, the private pointer can be
   * accessed with the net_generic() call.
   */
  
  struct net_generic {
  	unsigned int len;
  	struct rcu_head rcu;
  
  	void *ptr[0];
  };
  
  static inline void *net_generic(const struct net *net, int id)
  {
  	struct net_generic *ng;
  	void *ptr;
  
  	rcu_read_lock();
  	ng = rcu_dereference(net->gen);
  	BUG_ON(id == 0 || id > ng->len);
  	ptr = ng->ptr[id - 1];
  	rcu_read_unlock();
  
  	BUG_ON(!ptr);
  	return ptr;
  }
  #endif