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
33 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
34
gre_add_protocol(const struct gre_protocol * proto,u8 version)35 int 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 }
43 EXPORT_SYMBOL_GPL(gre_add_protocol);
44
gre_del_protocol(const struct gre_protocol * proto,u8 version)45 int 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 }
61 EXPORT_SYMBOL_GPL(gre_del_protocol);
62
63 /* Fills in tpi and returns header length to be pulled.
64 * Note that caller must use pskb_may_pull() before pulling GRE header.
65 */
gre_parse_header(struct sk_buff * skb,struct tnl_ptk_info * tpi,bool * csum_err,__be16 proto,int nhs)66 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
67 bool *csum_err, __be16 proto, int nhs)
68 {
69 const struct gre_base_hdr *greh;
70 __be32 *options;
71 int hdr_len;
72
73 if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr))))
74 return -EINVAL;
75
76 greh = (struct gre_base_hdr *)(skb->data + nhs);
77 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
78 return -EINVAL;
79
80 tpi->flags = gre_flags_to_tnl_flags(greh->flags);
81 hdr_len = gre_calc_hlen(tpi->flags);
82
83 if (!pskb_may_pull(skb, nhs + hdr_len))
84 return -EINVAL;
85
86 greh = (struct gre_base_hdr *)(skb->data + nhs);
87 tpi->proto = greh->protocol;
88
89 options = (__be32 *)(greh + 1);
90 if (greh->flags & GRE_CSUM) {
91 if (!skb_checksum_simple_validate(skb)) {
92 skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
93 null_compute_pseudo);
94 } else if (csum_err) {
95 *csum_err = true;
96 return -EINVAL;
97 }
98
99 options++;
100 }
101
102 if (greh->flags & GRE_KEY) {
103 tpi->key = *options;
104 options++;
105 } else {
106 tpi->key = 0;
107 }
108 if (unlikely(greh->flags & GRE_SEQ)) {
109 tpi->seq = *options;
110 options++;
111 } else {
112 tpi->seq = 0;
113 }
114 /* WCCP version 1 and 2 protocol decoding.
115 * - Change protocol to IPv4/IPv6
116 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
117 */
118 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
119 u8 _val, *val;
120
121 val = skb_header_pointer(skb, nhs + hdr_len,
122 sizeof(_val), &_val);
123 if (!val)
124 return -EINVAL;
125 tpi->proto = proto;
126 if ((*val & 0xF0) != 0x40)
127 hdr_len += 4;
128 }
129 tpi->hdr_len = hdr_len;
130 return hdr_len;
131 }
132 EXPORT_SYMBOL(gre_parse_header);
133
gre_rcv(struct sk_buff * skb)134 static int gre_rcv(struct sk_buff *skb)
135 {
136 const struct gre_protocol *proto;
137 u8 ver;
138 int ret;
139
140 if (!pskb_may_pull(skb, 12))
141 goto drop;
142
143 ver = skb->data[1]&0x7f;
144 if (ver >= GREPROTO_MAX)
145 goto drop;
146
147 rcu_read_lock();
148 proto = rcu_dereference(gre_proto[ver]);
149 if (!proto || !proto->handler)
150 goto drop_unlock;
151 ret = proto->handler(skb);
152 rcu_read_unlock();
153 return ret;
154
155 drop_unlock:
156 rcu_read_unlock();
157 drop:
158 kfree_skb(skb);
159 return NET_RX_DROP;
160 }
161
gre_err(struct sk_buff * skb,u32 info)162 static void gre_err(struct sk_buff *skb, u32 info)
163 {
164 const struct gre_protocol *proto;
165 const struct iphdr *iph = (const struct iphdr *)skb->data;
166 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
167
168 if (ver >= GREPROTO_MAX)
169 return;
170
171 rcu_read_lock();
172 proto = rcu_dereference(gre_proto[ver]);
173 if (proto && proto->err_handler)
174 proto->err_handler(skb, info);
175 rcu_read_unlock();
176 }
177
178 static const struct net_protocol net_gre_protocol = {
179 .handler = gre_rcv,
180 .err_handler = gre_err,
181 .netns_ok = 1,
182 };
183
gre_init(void)184 static int __init gre_init(void)
185 {
186 pr_info("GRE over IPv4 demultiplexor driver\n");
187
188 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
189 pr_err("can't add protocol\n");
190 return -EAGAIN;
191 }
192 return 0;
193 }
194
gre_exit(void)195 static void __exit gre_exit(void)
196 {
197 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
198 }
199
200 module_init(gre_init);
201 module_exit(gre_exit);
202
203 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
204 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
205 MODULE_LICENSE("GPL");
206