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