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