1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* GRE over IPv4 demultiplexer driver
*
* Authors: Dmitry Kozlov (xeb@mail.ru)
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/if.h>
#include <linux/icmp.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netdevice.h>
#include <linux/if_tunnel.h>
#include <linux/spinlock.h>
#include <net/protocol.h>
#include <net/gre.h>
#include <net/erspan.h>
#include <net/icmp.h>
#include <net/route.h>
#include <net/xfrm.h>
static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
int gre_add_protocol(const struct gre_protocol *proto, u8 version)
{
if (version >= GREPROTO_MAX)
return -EINVAL;
return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
0 : -EBUSY;
}
EXPORT_SYMBOL_GPL(gre_add_protocol);
int gre_del_protocol(const struct gre_protocol *proto, u8 version)
{
int ret;
if (version >= GREPROTO_MAX)
return -EINVAL;
ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
0 : -EBUSY;
if (ret)
return ret;
synchronize_rcu();
return 0;
}
EXPORT_SYMBOL_GPL(gre_del_protocol);
/* Fills in tpi and returns header length to be pulled.
* Note that caller must use pskb_may_pull() before pulling GRE header.
*/
int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
bool *csum_err, __be16 proto, int nhs)
{
const struct gre_base_hdr *greh;
__be32 *options;
int hdr_len;
if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr))))
return -EINVAL;
greh = (struct gre_base_hdr *)(skb->data + nhs);
if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
return -EINVAL;
tpi->flags = gre_flags_to_tnl_flags(greh->flags);
hdr_len = gre_calc_hlen(tpi->flags);
if (!pskb_may_pull(skb, nhs + hdr_len))
return -EINVAL;
greh = (struct gre_base_hdr *)(skb->data + nhs);
tpi->proto = greh->protocol;
options = (__be32 *)(greh + 1);
if (greh->flags & GRE_CSUM) {
if (!skb_checksum_simple_validate(skb)) {
skb_checksum_try_convert(skb, IPPROTO_GRE,
null_compute_pseudo);
} else if (csum_err) {
*csum_err = true;
return -EINVAL;
}
options++;
}
if (greh->flags & GRE_KEY) {
tpi->key = *options;
options++;
} else {
tpi->key = 0;
}
if (unlikely(greh->flags & GRE_SEQ)) {
tpi->seq = *options;
options++;
} else {
tpi->seq = 0;
}
/* WCCP version 1 and 2 protocol decoding.
* - Change protocol to IPv4/IPv6
* - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
*/
if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
u8 _val, *val;
val = skb_header_pointer(skb, nhs + hdr_len,
sizeof(_val), &_val);
if (!val)
return -EINVAL;
tpi->proto = proto;
if ((*val & 0xF0) != 0x40)
hdr_len += 4;
}
tpi->hdr_len = hdr_len;
/* ERSPAN ver 1 and 2 protocol sets GRE key field
* to 0 and sets the configured key in the
* inner erspan header field
*/
if ((greh->protocol == htons(ETH_P_ERSPAN) && hdr_len != 4) ||
greh->protocol == htons(ETH_P_ERSPAN2)) {
struct erspan_base_hdr *ershdr;
if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr)))
return -EINVAL;
ershdr = (struct erspan_base_hdr *)(skb->data + nhs + hdr_len);
tpi->key = cpu_to_be32(get_session_id(ershdr));
}
return hdr_len;
}
EXPORT_SYMBOL(gre_parse_header);
static int gre_rcv(struct sk_buff *skb)
{
const struct gre_protocol *proto;
u8 ver;
int ret;
if (!pskb_may_pull(skb, 12))
goto drop;
ver = skb->data[1]&0x7f;
if (ver >= GREPROTO_MAX)
goto drop;
rcu_read_lock();
proto = rcu_dereference(gre_proto[ver]);
if (!proto || !proto->handler)
goto drop_unlock;
ret = proto->handler(skb);
rcu_read_unlock();
return ret;
drop_unlock:
rcu_read_unlock();
drop:
kfree_skb(skb);
return NET_RX_DROP;
}
static int gre_err(struct sk_buff *skb, u32 info)
{
const struct gre_protocol *proto;
const struct iphdr *iph = (const struct iphdr *)skb->data;
u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
int err = 0;
if (ver >= GREPROTO_MAX)
return -EINVAL;
rcu_read_lock();
proto = rcu_dereference(gre_proto[ver]);
if (proto && proto->err_handler)
proto->err_handler(skb, info);
else
err = -EPROTONOSUPPORT;
rcu_read_unlock();
return err;
}
static const struct net_protocol net_gre_protocol = {
.handler = gre_rcv,
.err_handler = gre_err,
};
static int __init gre_init(void)
{
pr_info("GRE over IPv4 demultiplexor driver\n");
if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
pr_err("can't add protocol\n");
return -EAGAIN;
}
return 0;
}
static void __exit gre_exit(void)
{
inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
}
module_init(gre_init);
module_exit(gre_exit);
MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
MODULE_AUTHOR("D. Kozlov <xeb@mail.ru>");
MODULE_LICENSE("GPL");
|
