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
11static unsigned int fib_notifier_net_id;
12
13struct fib_notifier_net {
14	struct list_head fib_notifier_ops;
15	struct atomic_notifier_head fib_chain;
16};
17
18int 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}
27EXPORT_SYMBOL(call_fib_notifier);
28
29int 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}
38EXPORT_SYMBOL(call_fib_notifiers);
39
40static 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
60static 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
77unlock:
78	rcu_read_unlock();
79
80	return err;
81}
82
83static 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
99int 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}
119EXPORT_SYMBOL(register_fib_notifier);
120
121int 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}
127EXPORT_SYMBOL(unregister_fib_notifier);
128
129static 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
142struct fib_notifier_ops *
143fib_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
158err_register:
159	kfree(ops);
160	return ERR_PTR(err);
161}
162EXPORT_SYMBOL(fib_notifier_ops_register);
163
164void fib_notifier_ops_unregister(struct fib_notifier_ops *ops)
165{
166	list_del_rcu(&ops->list);
167	kfree_rcu(ops, rcu);
168}
169EXPORT_SYMBOL(fib_notifier_ops_unregister);
170
171static 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
180static 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
187static 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
194static int __init fib_notifier_init(void)
195{
196	return register_pernet_subsys(&fib_notifier_net_ops);
197}
198
199subsys_initcall(fib_notifier_init);
200