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