/* * 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