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. */
gre_parse_header(struct sk_buff * skb,struct tnl_ptk_info * tpi,bool * csum_err,__be16 proto,int nhs)64 int 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 }
123 EXPORT_SYMBOL(gre_parse_header);
124
gre_rcv(struct sk_buff * skb)125 static 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
146 drop_unlock:
147 rcu_read_unlock();
148 drop:
149 kfree_skb(skb);
150 return NET_RX_DROP;
151 }
152
gre_err(struct sk_buff * skb,u32 info)153 static 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
169 static const struct net_protocol net_gre_protocol = {
170 .handler = gre_rcv,
171 .err_handler = gre_err,
172 .netns_ok = 1,
173 };
174
gre_init(void)175 static 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
gre_exit(void)186 static void __exit gre_exit(void)
187 {
188 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
189 }
190
191 module_init(gre_init);
192 module_exit(gre_exit);
193
194 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
195 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
196 MODULE_LICENSE("GPL");
197
