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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15 #include <linux/module.h>
16 #include <linux/kernel.h>
17 #include <linux/kmod.h>
18 #include <linux/skbuff.h>
19 #include <linux/in.h>
20 #include <linux/ip.h>
21 #include <linux/netdevice.h>
22 #include <linux/spinlock.h>
23 #include <net/protocol.h>
24 #include <net/gre.h>
25
26
27 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
28 static DEFINE_SPINLOCK(gre_proto_lock);
29
gre_add_protocol(const struct gre_protocol * proto,u8 version)30 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
31 {
32 if (version >= GREPROTO_MAX)
33 goto err_out;
34
35 spin_lock(&gre_proto_lock);
36 if (gre_proto[version])
37 goto err_out_unlock;
38
39 RCU_INIT_POINTER(gre_proto[version], proto);
40 spin_unlock(&gre_proto_lock);
41 return 0;
42
43 err_out_unlock:
44 spin_unlock(&gre_proto_lock);
45 err_out:
46 return -1;
47 }
48 EXPORT_SYMBOL_GPL(gre_add_protocol);
49
gre_del_protocol(const struct gre_protocol * proto,u8 version)50 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
51 {
52 if (version >= GREPROTO_MAX)
53 goto err_out;
54
55 spin_lock(&gre_proto_lock);
56 if (rcu_dereference_protected(gre_proto[version],
57 lockdep_is_held(&gre_proto_lock)) != proto)
58 goto err_out_unlock;
59 RCU_INIT_POINTER(gre_proto[version], NULL);
60 spin_unlock(&gre_proto_lock);
61 synchronize_rcu();
62 return 0;
63
64 err_out_unlock:
65 spin_unlock(&gre_proto_lock);
66 err_out:
67 return -1;
68 }
69 EXPORT_SYMBOL_GPL(gre_del_protocol);
70
gre_rcv(struct sk_buff * skb)71 static int gre_rcv(struct sk_buff *skb)
72 {
73 const struct gre_protocol *proto;
74 u8 ver;
75 int ret;
76
77 if (!pskb_may_pull(skb, 12))
78 goto drop;
79
80 ver = skb->data[1]&0x7f;
81 if (ver >= GREPROTO_MAX)
82 goto drop;
83
84 rcu_read_lock();
85 proto = rcu_dereference(gre_proto[ver]);
86 if (!proto || !proto->handler)
87 goto drop_unlock;
88 ret = proto->handler(skb);
89 rcu_read_unlock();
90 return ret;
91
92 drop_unlock:
93 rcu_read_unlock();
94 drop:
95 kfree_skb(skb);
96 return NET_RX_DROP;
97 }
98
gre_err(struct sk_buff * skb,u32 info)99 static void gre_err(struct sk_buff *skb, u32 info)
100 {
101 const struct gre_protocol *proto;
102 const struct iphdr *iph = (const struct iphdr *)skb->data;
103 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
104
105 if (ver >= GREPROTO_MAX)
106 return;
107
108 rcu_read_lock();
109 proto = rcu_dereference(gre_proto[ver]);
110 if (proto && proto->err_handler)
111 proto->err_handler(skb, info);
112 rcu_read_unlock();
113 }
114
115 static const struct net_protocol net_gre_protocol = {
116 .handler = gre_rcv,
117 .err_handler = gre_err,
118 .netns_ok = 1,
119 };
120
gre_init(void)121 static int __init gre_init(void)
122 {
123 pr_info("GRE over IPv4 demultiplexor driver\n");
124
125 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
126 pr_err("can't add protocol\n");
127 return -EAGAIN;
128 }
129
130 return 0;
131 }
132
gre_exit(void)133 static void __exit gre_exit(void)
134 {
135 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
136 }
137
138 module_init(gre_init);
139 module_exit(gre_exit);
140
141 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
142 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
143 MODULE_LICENSE("GPL");
144
145