1 /*
2 * GRE over IPv4 demultiplexer driver
3 *
4 * Authors: Dmitry Kozlov (xeb@mail.ru)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 */
12
13 #include <linux/module.h>
14 #include <linux/kernel.h>
15 #include <linux/kmod.h>
16 #include <linux/skbuff.h>
17 #include <linux/in.h>
18 #include <linux/ip.h>
19 #include <linux/netdevice.h>
20 #include <linux/spinlock.h>
21 #include <net/protocol.h>
22 #include <net/gre.h>
23
24
25 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
26 static DEFINE_SPINLOCK(gre_proto_lock);
27
gre_add_protocol(const struct gre_protocol * proto,u8 version)28 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
29 {
30 if (version >= GREPROTO_MAX)
31 goto err_out;
32
33 spin_lock(&gre_proto_lock);
34 if (gre_proto[version])
35 goto err_out_unlock;
36
37 RCU_INIT_POINTER(gre_proto[version], proto);
38 spin_unlock(&gre_proto_lock);
39 return 0;
40
41 err_out_unlock:
42 spin_unlock(&gre_proto_lock);
43 err_out:
44 return -1;
45 }
46 EXPORT_SYMBOL_GPL(gre_add_protocol);
47
gre_del_protocol(const struct gre_protocol * proto,u8 version)48 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
49 {
50 if (version >= GREPROTO_MAX)
51 goto err_out;
52
53 spin_lock(&gre_proto_lock);
54 if (rcu_dereference_protected(gre_proto[version],
55 lockdep_is_held(&gre_proto_lock)) != proto)
56 goto err_out_unlock;
57 RCU_INIT_POINTER(gre_proto[version], NULL);
58 spin_unlock(&gre_proto_lock);
59 synchronize_rcu();
60 return 0;
61
62 err_out_unlock:
63 spin_unlock(&gre_proto_lock);
64 err_out:
65 return -1;
66 }
67 EXPORT_SYMBOL_GPL(gre_del_protocol);
68
gre_rcv(struct sk_buff * skb)69 static int gre_rcv(struct sk_buff *skb)
70 {
71 const struct gre_protocol *proto;
72 u8 ver;
73 int ret;
74
75 if (!pskb_may_pull(skb, 12))
76 goto drop;
77
78 ver = skb->data[1]&0x7f;
79 if (ver >= GREPROTO_MAX)
80 goto drop;
81
82 rcu_read_lock();
83 proto = rcu_dereference(gre_proto[ver]);
84 if (!proto || !proto->handler)
85 goto drop_unlock;
86 ret = proto->handler(skb);
87 rcu_read_unlock();
88 return ret;
89
90 drop_unlock:
91 rcu_read_unlock();
92 drop:
93 kfree_skb(skb);
94 return NET_RX_DROP;
95 }
96
gre_err(struct sk_buff * skb,u32 info)97 static void gre_err(struct sk_buff *skb, u32 info)
98 {
99 const struct gre_protocol *proto;
100 const struct iphdr *iph = (const struct iphdr *)skb->data;
101 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
102
103 if (ver >= GREPROTO_MAX)
104 return;
105
106 rcu_read_lock();
107 proto = rcu_dereference(gre_proto[ver]);
108 if (proto && proto->err_handler)
109 proto->err_handler(skb, info);
110 rcu_read_unlock();
111 }
112
113 static const struct net_protocol net_gre_protocol = {
114 .handler = gre_rcv,
115 .err_handler = gre_err,
116 .netns_ok = 1,
117 };
118
gre_init(void)119 static int __init gre_init(void)
120 {
121 pr_info("GRE over IPv4 demultiplexor driver");
122
123 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
124 pr_err("gre: can't add protocol\n");
125 return -EAGAIN;
126 }
127
128 return 0;
129 }
130
gre_exit(void)131 static void __exit gre_exit(void)
132 {
133 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
134 }
135
136 module_init(gre_init);
137 module_exit(gre_exit);
138
139 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
140 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
141 MODULE_LICENSE("GPL");
142
143