net/ipv4/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 <net/net_namespace.h>
   6 #include <net/netns/ipv4.h>
   7 #include <net/ip_fib.h>
   8
   9 static ATOMIC_NOTIFIER_HEAD(fib_chain);
  10
  11 int call_fib_notifier(struct notifier_block *nb, struct net *net,
  12                       enum fib_event_type event_type,
  13                       struct fib_notifier_info *info)
  14 {
  15         info->net = net;
  16         return nb->notifier_call(nb, event_type, info);
  17 }
  18
  19 int call_fib_notifiers(struct net *net, enum fib_event_type event_type,
  20                        struct fib_notifier_info *info)
  21 {
  22         net->ipv4.fib_seq++;
  23         info->net = net;
  24         return atomic_notifier_call_chain(&fib_chain, event_type, info);
  25 }
  26
  27 static unsigned int fib_seq_sum(void)
  28 {
  29         unsigned int fib_seq = 0;
  30         struct net *net;
  31
  32         rtnl_lock();
  33         for_each_net(net)
  34                 fib_seq += net->ipv4.fib_seq;
  35         rtnl_unlock();
  36
  37         return fib_seq;
  38 }
  39
  40 static bool fib_dump_is_consistent(struct notifier_block *nb,
  41                                    void (*cb)(struct notifier_block *nb),
  42                                    unsigned int fib_seq)
  43 {
  44         atomic_notifier_chain_register(&fib_chain, nb);
  45         if (fib_seq == fib_seq_sum())
  46                 return true;
  47         atomic_notifier_chain_unregister(&fib_chain, nb);
  48         if (cb)
  49                 cb(nb);
  50         return false;
  51 }
  52
  53 #define FIB_DUMP_MAX_RETRIES 5
  54 int register_fib_notifier(struct notifier_block *nb,
  55                           void (*cb)(struct notifier_block *nb))
  56 {
  57         int retries = 0;
  58
  59         do {
  60                 unsigned int fib_seq = fib_seq_sum();
  61                 struct net *net;
  62
  63                 /* Mutex semantics guarantee that every change done to
  64                  * FIB tries before we read the change sequence counter
  65                  * is now visible to us.
  66                  */
  67                 rcu_read_lock();
  68                 for_each_net_rcu(net) {
  69                         fib_rules_notify(net, nb);
  70                         fib_notify(net, nb);
  71                 }
  72                 rcu_read_unlock();
  73
  74                 if (fib_dump_is_consistent(nb, cb, fib_seq))
  75                         return 0;
  76         } while (++retries < FIB_DUMP_MAX_RETRIES);
  77
  78         return -EBUSY;
  79 }
  80 EXPORT_SYMBOL(register_fib_notifier);
  81
  82 int unregister_fib_notifier(struct notifier_block *nb)
  83 {
  84         return atomic_notifier_chain_unregister(&fib_chain, nb);
  85 }
  86 EXPORT_SYMBOL(unregister_fib_notifier);