net/core/fib_notifier.c

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