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/if.h>
17 #include <linux/icmp.h>
18 #include <linux/kernel.h>
19 #include <linux/kmod.h>
20 #include <linux/skbuff.h>
21 #include <linux/in.h>
22 #include <linux/ip.h>
23 #include <linux/netdevice.h>
24 #include <linux/if_tunnel.h>
25 #include <linux/spinlock.h>
26 #include <net/protocol.h>
27 #include <net/gre.h>
28 #include <net/erspan.h>
29
30 #include <net/icmp.h>
31 #include <net/route.h>
32 #include <net/xfrm.h>
33
34 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
35
gre_add_protocol(const struct gre_protocol * proto,u8 version)36 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
37 {
38 if (version >= GREPROTO_MAX)
39 return -EINVAL;
40
41 return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
42 0 : -EBUSY;
43 }
44 EXPORT_SYMBOL_GPL(gre_add_protocol);
45
gre_del_protocol(const struct gre_protocol * proto,u8 version)46 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
47 {
48 int ret;
49
50 if (version >= GREPROTO_MAX)
51 return -EINVAL;
52
53 ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
54 0 : -EBUSY;
55
56 if (ret)
57 return ret;
58
59 synchronize_rcu();
60 return 0;
61 }
62 EXPORT_SYMBOL_GPL(gre_del_protocol);
63
64 /* Fills in tpi and returns header length to be pulled.
65 * Note that caller must use pskb_may_pull() before pulling GRE header.
66 */
gre_parse_header(struct sk_buff * skb,struct tnl_ptk_info * tpi,bool * csum_err,__be16 proto,int nhs)67 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
68 bool *csum_err, __be16 proto, int nhs)
69 {
70 const struct gre_base_hdr *greh;
71 __be32 *options;
72 int hdr_len;
73
74 if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr))))
75 return -EINVAL;
76
77 greh = (struct gre_base_hdr *)(skb->data + nhs);
78 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
79 return -EINVAL;
80
81 tpi->flags = gre_flags_to_tnl_flags(greh->flags);
82 hdr_len = gre_calc_hlen(tpi->flags);
83
84 if (!pskb_may_pull(skb, nhs + hdr_len))
85 return -EINVAL;
86
87 greh = (struct gre_base_hdr *)(skb->data + nhs);
88 tpi->proto = greh->protocol;
89
90 options = (__be32 *)(greh + 1);
91 if (greh->flags & GRE_CSUM) {
92 if (!skb_checksum_simple_validate(skb)) {
93 skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
94 null_compute_pseudo);
95 } else if (csum_err) {
96 *csum_err = true;
97 return -EINVAL;
98 }
99
100 options++;
101 }
102
103 if (greh->flags & GRE_KEY) {
104 tpi->key = *options;
105 options++;
106 } else {
107 tpi->key = 0;
108 }
109 if (unlikely(greh->flags & GRE_SEQ)) {
110 tpi->seq = *options;
111 options++;
112 } else {
113 tpi->seq = 0;
114 }
115 /* WCCP version 1 and 2 protocol decoding.
116 * - Change protocol to IPv4/IPv6
117 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
118 */
119 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
120 u8 _val, *val;
121
122 val = skb_header_pointer(skb, nhs + hdr_len,
123 sizeof(_val), &_val);
124 if (!val)
125 return -EINVAL;
126 tpi->proto = proto;
127 if ((*val & 0xF0) != 0x40)
128 hdr_len += 4;
129 }
130 tpi->hdr_len = hdr_len;
131
132 /* ERSPAN ver 1 and 2 protocol sets GRE key field
133 * to 0 and sets the configured key in the
134 * inner erspan header field
135 */
136 if (greh->protocol == htons(ETH_P_ERSPAN) ||
137 greh->protocol == htons(ETH_P_ERSPAN2)) {
138 struct erspan_base_hdr *ershdr;
139
140 if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr)))
141 return -EINVAL;
142
143 ershdr = (struct erspan_base_hdr *)(skb->data + nhs + hdr_len);
144 tpi->key = cpu_to_be32(get_session_id(ershdr));
145 }
146
147 return hdr_len;
148 }
149 EXPORT_SYMBOL(gre_parse_header);
150
gre_rcv(struct sk_buff * skb)151 static int gre_rcv(struct sk_buff *skb)
152 {
153 const struct gre_protocol *proto;
154 u8 ver;
155 int ret;
156
157 if (!pskb_may_pull(skb, 12))
158 goto drop;
159
160 ver = skb->data[1]&0x7f;
161 if (ver >= GREPROTO_MAX)
162 goto drop;
163
164 rcu_read_lock();
165 proto = rcu_dereference(gre_proto[ver]);
166 if (!proto || !proto->handler)
167 goto drop_unlock;
168 ret = proto->handler(skb);
169 rcu_read_unlock();
170 return ret;
171
172 drop_unlock:
173 rcu_read_unlock();
174 drop:
175 kfree_skb(skb);
176 return NET_RX_DROP;
177 }
178
gre_err(struct sk_buff * skb,u32 info)179 static void gre_err(struct sk_buff *skb, u32 info)
180 {
181 const struct gre_protocol *proto;
182 const struct iphdr *iph = (const struct iphdr *)skb->data;
183 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
184
185 if (ver >= GREPROTO_MAX)
186 return;
187
188 rcu_read_lock();
189 proto = rcu_dereference(gre_proto[ver]);
190 if (proto && proto->err_handler)
191 proto->err_handler(skb, info);
192 rcu_read_unlock();
193 }
194
195 static const struct net_protocol net_gre_protocol = {
196 .handler = gre_rcv,
197 .err_handler = gre_err,
198 .netns_ok = 1,
199 };
200
gre_init(void)201 static int __init gre_init(void)
202 {
203 pr_info("GRE over IPv4 demultiplexor driver\n");
204
205 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
206 pr_err("can't add protocol\n");
207 return -EAGAIN;
208 }
209 return 0;
210 }
211
gre_exit(void)212 static void __exit gre_exit(void)
213 {
214 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
215 }
216
217 module_init(gre_init);
218 module_exit(gre_exit);
219
220 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
221 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
222 MODULE_LICENSE("GPL");
223