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. set pernet_operations->id. After register_pernet_device you 16 * will have the id of your private pointer. 17 * 2. Either set pernet_operations->size (to have the code allocate and 18 * free a private structure pointed to from struct net ) or 19 * call net_assign_generic() to put the private data on the struct 20 * net (most preferably this should be done in the ->init callback 21 * of the ops registered); 22 * 3. do not change this pointer while the net is alive; 23 * 4. do not try to have any private reference on the net_generic object. 24 * 25 * After accomplishing all of the above, the private pointer can be 26 * accessed with the net_generic() call. 27 */ 28 29 struct net_generic { 30 unsigned int len; 31 struct rcu_head rcu; 32 33 void *ptr[0]; 34 }; 35 36 static inline void *net_generic(struct net *net, int id) 37 { 38 struct net_generic *ng; 39 void *ptr; 40 41 rcu_read_lock(); 42 ng = rcu_dereference(net->gen); 43 BUG_ON(id == 0 || id > ng->len); 44 ptr = ng->ptr[id - 1]; 45 rcu_read_unlock(); 46 47 return ptr; 48 } 49 50 extern int net_assign_generic(struct net *net, int id, void *data); 51 #endif 52