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Linux/net/core/fib_notifier.c

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  1 #include <linux/rtnetlink.h>
  2 #include <linux/notifier.h>
  3 #include <linux/rcupdate.h>
  4 #include <linux/kernel.h>
  5 #include <linux/module.h>
  6 #include <linux/init.h>
  7 #include <net/net_namespace.h>
  8 #include <net/netns/generic.h>
  9 #include <net/fib_notifier.h>
 10 
 11 static unsigned int fib_notifier_net_id;
 12 
 13 struct fib_notifier_net {
 14         struct list_head fib_notifier_ops;
 15         struct atomic_notifier_head fib_chain;
 16 };
 17 
 18 int call_fib_notifier(struct notifier_block *nb,
 19                       enum fib_event_type event_type,
 20                       struct fib_notifier_info *info)
 21 {
 22         int err;
 23 
 24         err = nb->notifier_call(nb, event_type, info);
 25         return notifier_to_errno(err);
 26 }
 27 EXPORT_SYMBOL(call_fib_notifier);
 28 
 29 int call_fib_notifiers(struct net *net, enum fib_event_type event_type,
 30                        struct fib_notifier_info *info)
 31 {
 32         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
 33         int err;
 34 
 35         err = atomic_notifier_call_chain(&fn_net->fib_chain, event_type, info);
 36         return notifier_to_errno(err);
 37 }
 38 EXPORT_SYMBOL(call_fib_notifiers);
 39 
 40 static unsigned int fib_seq_sum(struct net *net)
 41 {
 42         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
 43         struct fib_notifier_ops *ops;
 44         unsigned int fib_seq = 0;
 45 
 46         rtnl_lock();
 47         rcu_read_lock();
 48         list_for_each_entry_rcu(ops, &fn_net->fib_notifier_ops, list) {
 49                 if (!try_module_get(ops->owner))
 50                         continue;
 51                 fib_seq += ops->fib_seq_read(net);
 52                 module_put(ops->owner);
 53         }
 54         rcu_read_unlock();
 55         rtnl_unlock();
 56 
 57         return fib_seq;
 58 }
 59 
 60 static int fib_net_dump(struct net *net, struct notifier_block *nb,
 61                         struct netlink_ext_ack *extack)
 62 {
 63         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
 64         struct fib_notifier_ops *ops;
 65         int err = 0;
 66 
 67         rcu_read_lock();
 68         list_for_each_entry_rcu(ops, &fn_net->fib_notifier_ops, list) {
 69                 if (!try_module_get(ops->owner))
 70                         continue;
 71                 err = ops->fib_dump(net, nb, extack);
 72                 module_put(ops->owner);
 73                 if (err)
 74                         goto unlock;
 75         }
 76 
 77 unlock:
 78         rcu_read_unlock();
 79 
 80         return err;
 81 }
 82 
 83 static bool fib_dump_is_consistent(struct net *net, struct notifier_block *nb,
 84                                    void (*cb)(struct notifier_block *nb),
 85                                    unsigned int fib_seq)
 86 {
 87         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
 88 
 89         atomic_notifier_chain_register(&fn_net->fib_chain, nb);
 90         if (fib_seq == fib_seq_sum(net))
 91                 return true;
 92         atomic_notifier_chain_unregister(&fn_net->fib_chain, nb);
 93         if (cb)
 94                 cb(nb);
 95         return false;
 96 }
 97 
 98 #define FIB_DUMP_MAX_RETRIES 5
 99 int register_fib_notifier(struct net *net, struct notifier_block *nb,
100                           void (*cb)(struct notifier_block *nb),
101                           struct netlink_ext_ack *extack)
102 {
103         int retries = 0;
104         int err;
105 
106         do {
107                 unsigned int fib_seq = fib_seq_sum(net);
108 
109                 err = fib_net_dump(net, nb, extack);
110                 if (err)
111                         return err;
112 
113                 if (fib_dump_is_consistent(net, nb, cb, fib_seq))
114                         return 0;
115         } while (++retries < FIB_DUMP_MAX_RETRIES);
116 
117         return -EBUSY;
118 }
119 EXPORT_SYMBOL(register_fib_notifier);
120 
121 int unregister_fib_notifier(struct net *net, struct notifier_block *nb)
122 {
123         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
124 
125         return atomic_notifier_chain_unregister(&fn_net->fib_chain, nb);
126 }
127 EXPORT_SYMBOL(unregister_fib_notifier);
128 
129 static int __fib_notifier_ops_register(struct fib_notifier_ops *ops,
130                                        struct net *net)
131 {
132         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
133         struct fib_notifier_ops *o;
134 
135         list_for_each_entry(o, &fn_net->fib_notifier_ops, list)
136                 if (ops->family == o->family)
137                         return -EEXIST;
138         list_add_tail_rcu(&ops->list, &fn_net->fib_notifier_ops);
139         return 0;
140 }
141 
142 struct fib_notifier_ops *
143 fib_notifier_ops_register(const struct fib_notifier_ops *tmpl, struct net *net)
144 {
145         struct fib_notifier_ops *ops;
146         int err;
147 
148         ops = kmemdup(tmpl, sizeof(*ops), GFP_KERNEL);
149         if (!ops)
150                 return ERR_PTR(-ENOMEM);
151 
152         err = __fib_notifier_ops_register(ops, net);
153         if (err)
154                 goto err_register;
155 
156         return ops;
157 
158 err_register:
159         kfree(ops);
160         return ERR_PTR(err);
161 }
162 EXPORT_SYMBOL(fib_notifier_ops_register);
163 
164 void fib_notifier_ops_unregister(struct fib_notifier_ops *ops)
165 {
166         list_del_rcu(&ops->list);
167         kfree_rcu(ops, rcu);
168 }
169 EXPORT_SYMBOL(fib_notifier_ops_unregister);
170 
171 static int __net_init fib_notifier_net_init(struct net *net)
172 {
173         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
174 
175         INIT_LIST_HEAD(&fn_net->fib_notifier_ops);
176         ATOMIC_INIT_NOTIFIER_HEAD(&fn_net->fib_chain);
177         return 0;
178 }
179 
180 static void __net_exit fib_notifier_net_exit(struct net *net)
181 {
182         struct fib_notifier_net *fn_net = net_generic(net, fib_notifier_net_id);
183 
184         WARN_ON_ONCE(!list_empty(&fn_net->fib_notifier_ops));
185 }
186 
187 static struct pernet_operations fib_notifier_net_ops = {
188         .init = fib_notifier_net_init,
189         .exit = fib_notifier_net_exit,
190         .id = &fib_notifier_net_id,
191         .size = sizeof(struct fib_notifier_net),
192 };
193 
194 static int __init fib_notifier_init(void)
195 {
196         return register_pernet_subsys(&fib_notifier_net_ops);
197 }
198 
199 subsys_initcall(fib_notifier_init);
200 

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