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 27 struct net_generic { 28 union { 29 struct { 30 unsigned int len; 31 struct rcu_head rcu; 32 } s; 33 34 void *ptr[0]; 35 }; 36 }; 37 38 static inline void *net_generic(const struct net *net, unsigned int id) 39 { 40 struct net_generic *ng; 41 void *ptr; 42 43 rcu_read_lock(); 44 ng = rcu_dereference(net->gen); 45 ptr = ng->ptr[id]; 46 rcu_read_unlock(); 47 48 return ptr; 49 } 50 #endif 51