xref: /linux/net/ipv4/gre_demux.c (revision 95f5c64c3c13a609e137d35c4b452519e0b954df)
1c50cd357SDaniel Borkmann /*
2c50cd357SDaniel Borkmann  *	GRE over IPv4 demultiplexer driver
3c50cd357SDaniel Borkmann  *
4c50cd357SDaniel Borkmann  *	Authors: Dmitry Kozlov (xeb@mail.ru)
5c50cd357SDaniel Borkmann  *
6c50cd357SDaniel Borkmann  *	This program is free software; you can redistribute it and/or
7c50cd357SDaniel Borkmann  *	modify it under the terms of the GNU General Public License
8c50cd357SDaniel Borkmann  *	as published by the Free Software Foundation; either version
9c50cd357SDaniel Borkmann  *	2 of the License, or (at your option) any later version.
10c50cd357SDaniel Borkmann  *
11c50cd357SDaniel Borkmann  */
12c50cd357SDaniel Borkmann 
13c50cd357SDaniel Borkmann #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14c50cd357SDaniel Borkmann 
15c50cd357SDaniel Borkmann #include <linux/module.h>
16c50cd357SDaniel Borkmann #include <linux/if.h>
17c50cd357SDaniel Borkmann #include <linux/icmp.h>
18c50cd357SDaniel Borkmann #include <linux/kernel.h>
19c50cd357SDaniel Borkmann #include <linux/kmod.h>
20c50cd357SDaniel Borkmann #include <linux/skbuff.h>
21c50cd357SDaniel Borkmann #include <linux/in.h>
22c50cd357SDaniel Borkmann #include <linux/ip.h>
23c50cd357SDaniel Borkmann #include <linux/netdevice.h>
24c50cd357SDaniel Borkmann #include <linux/if_tunnel.h>
25c50cd357SDaniel Borkmann #include <linux/spinlock.h>
26c50cd357SDaniel Borkmann #include <net/protocol.h>
27c50cd357SDaniel Borkmann #include <net/gre.h>
28c50cd357SDaniel Borkmann 
29c50cd357SDaniel Borkmann #include <net/icmp.h>
30c50cd357SDaniel Borkmann #include <net/route.h>
31c50cd357SDaniel Borkmann #include <net/xfrm.h>
32c50cd357SDaniel Borkmann 
33c50cd357SDaniel Borkmann static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
34c50cd357SDaniel Borkmann 
35c50cd357SDaniel Borkmann int gre_add_protocol(const struct gre_protocol *proto, u8 version)
36c50cd357SDaniel Borkmann {
37c50cd357SDaniel Borkmann 	if (version >= GREPROTO_MAX)
38c50cd357SDaniel Borkmann 		return -EINVAL;
39c50cd357SDaniel Borkmann 
40c50cd357SDaniel Borkmann 	return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
41c50cd357SDaniel Borkmann 		0 : -EBUSY;
42c50cd357SDaniel Borkmann }
43c50cd357SDaniel Borkmann EXPORT_SYMBOL_GPL(gre_add_protocol);
44c50cd357SDaniel Borkmann 
45c50cd357SDaniel Borkmann int gre_del_protocol(const struct gre_protocol *proto, u8 version)
46c50cd357SDaniel Borkmann {
47c50cd357SDaniel Borkmann 	int ret;
48c50cd357SDaniel Borkmann 
49c50cd357SDaniel Borkmann 	if (version >= GREPROTO_MAX)
50c50cd357SDaniel Borkmann 		return -EINVAL;
51c50cd357SDaniel Borkmann 
52c50cd357SDaniel Borkmann 	ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
53c50cd357SDaniel Borkmann 		0 : -EBUSY;
54c50cd357SDaniel Borkmann 
55c50cd357SDaniel Borkmann 	if (ret)
56c50cd357SDaniel Borkmann 		return ret;
57c50cd357SDaniel Borkmann 
58c50cd357SDaniel Borkmann 	synchronize_rcu();
59c50cd357SDaniel Borkmann 	return 0;
60c50cd357SDaniel Borkmann }
61c50cd357SDaniel Borkmann EXPORT_SYMBOL_GPL(gre_del_protocol);
62c50cd357SDaniel Borkmann 
63*95f5c64cSTom Herbert int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
64*95f5c64cSTom Herbert 		     bool *csum_err, int *ret_hdr_len)
65*95f5c64cSTom Herbert {
66*95f5c64cSTom Herbert 	const struct gre_base_hdr *greh;
67*95f5c64cSTom Herbert 	__be32 *options;
68*95f5c64cSTom Herbert 	int hdr_len;
69*95f5c64cSTom Herbert 
70*95f5c64cSTom Herbert 	if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
71*95f5c64cSTom Herbert 		return -EINVAL;
72*95f5c64cSTom Herbert 
73*95f5c64cSTom Herbert 	greh = (struct gre_base_hdr *)skb_transport_header(skb);
74*95f5c64cSTom Herbert 	if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
75*95f5c64cSTom Herbert 		return -EINVAL;
76*95f5c64cSTom Herbert 
77*95f5c64cSTom Herbert 	tpi->flags = gre_flags_to_tnl_flags(greh->flags);
78*95f5c64cSTom Herbert 	hdr_len = gre_calc_hlen(tpi->flags);
79*95f5c64cSTom Herbert 
80*95f5c64cSTom Herbert 	if (!pskb_may_pull(skb, hdr_len))
81*95f5c64cSTom Herbert 		return -EINVAL;
82*95f5c64cSTom Herbert 
83*95f5c64cSTom Herbert 	greh = (struct gre_base_hdr *)skb_transport_header(skb);
84*95f5c64cSTom Herbert 	tpi->proto = greh->protocol;
85*95f5c64cSTom Herbert 
86*95f5c64cSTom Herbert 	options = (__be32 *)(greh + 1);
87*95f5c64cSTom Herbert 	if (greh->flags & GRE_CSUM) {
88*95f5c64cSTom Herbert 		if (skb_checksum_simple_validate(skb)) {
89*95f5c64cSTom Herbert 			*csum_err = true;
90*95f5c64cSTom Herbert 			return -EINVAL;
91*95f5c64cSTom Herbert 		}
92*95f5c64cSTom Herbert 
93*95f5c64cSTom Herbert 		skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
94*95f5c64cSTom Herbert 					 null_compute_pseudo);
95*95f5c64cSTom Herbert 		options++;
96*95f5c64cSTom Herbert 	}
97*95f5c64cSTom Herbert 
98*95f5c64cSTom Herbert 	if (greh->flags & GRE_KEY) {
99*95f5c64cSTom Herbert 		tpi->key = *options;
100*95f5c64cSTom Herbert 		options++;
101*95f5c64cSTom Herbert 	} else {
102*95f5c64cSTom Herbert 		tpi->key = 0;
103*95f5c64cSTom Herbert 	}
104*95f5c64cSTom Herbert 	if (unlikely(greh->flags & GRE_SEQ)) {
105*95f5c64cSTom Herbert 		tpi->seq = *options;
106*95f5c64cSTom Herbert 		options++;
107*95f5c64cSTom Herbert 	} else {
108*95f5c64cSTom Herbert 		tpi->seq = 0;
109*95f5c64cSTom Herbert 	}
110*95f5c64cSTom Herbert 	/* WCCP version 1 and 2 protocol decoding.
111*95f5c64cSTom Herbert 	 * - Change protocol to IP
112*95f5c64cSTom Herbert 	 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
113*95f5c64cSTom Herbert 	 */
114*95f5c64cSTom Herbert 	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
115*95f5c64cSTom Herbert 		tpi->proto = htons(ETH_P_IP);
116*95f5c64cSTom Herbert 		if ((*(u8 *)options & 0xF0) != 0x40) {
117*95f5c64cSTom Herbert 			hdr_len += 4;
118*95f5c64cSTom Herbert 			if (!pskb_may_pull(skb, hdr_len))
119*95f5c64cSTom Herbert 				return -EINVAL;
120*95f5c64cSTom Herbert 		}
121*95f5c64cSTom Herbert 	}
122*95f5c64cSTom Herbert 	*ret_hdr_len = hdr_len;
123*95f5c64cSTom Herbert 	return 0;
124*95f5c64cSTom Herbert }
125*95f5c64cSTom Herbert EXPORT_SYMBOL(gre_parse_header);
126*95f5c64cSTom Herbert 
127c50cd357SDaniel Borkmann static int gre_rcv(struct sk_buff *skb)
128c50cd357SDaniel Borkmann {
129c50cd357SDaniel Borkmann 	const struct gre_protocol *proto;
130c50cd357SDaniel Borkmann 	u8 ver;
131c50cd357SDaniel Borkmann 	int ret;
132c50cd357SDaniel Borkmann 
133c50cd357SDaniel Borkmann 	if (!pskb_may_pull(skb, 12))
134c50cd357SDaniel Borkmann 		goto drop;
135c50cd357SDaniel Borkmann 
136c50cd357SDaniel Borkmann 	ver = skb->data[1]&0x7f;
137c50cd357SDaniel Borkmann 	if (ver >= GREPROTO_MAX)
138c50cd357SDaniel Borkmann 		goto drop;
139c50cd357SDaniel Borkmann 
140c50cd357SDaniel Borkmann 	rcu_read_lock();
141c50cd357SDaniel Borkmann 	proto = rcu_dereference(gre_proto[ver]);
142c50cd357SDaniel Borkmann 	if (!proto || !proto->handler)
143c50cd357SDaniel Borkmann 		goto drop_unlock;
144c50cd357SDaniel Borkmann 	ret = proto->handler(skb);
145c50cd357SDaniel Borkmann 	rcu_read_unlock();
146c50cd357SDaniel Borkmann 	return ret;
147c50cd357SDaniel Borkmann 
148c50cd357SDaniel Borkmann drop_unlock:
149c50cd357SDaniel Borkmann 	rcu_read_unlock();
150c50cd357SDaniel Borkmann drop:
151c50cd357SDaniel Borkmann 	kfree_skb(skb);
152c50cd357SDaniel Borkmann 	return NET_RX_DROP;
153c50cd357SDaniel Borkmann }
154c50cd357SDaniel Borkmann 
155c50cd357SDaniel Borkmann static void gre_err(struct sk_buff *skb, u32 info)
156c50cd357SDaniel Borkmann {
157c50cd357SDaniel Borkmann 	const struct gre_protocol *proto;
158c50cd357SDaniel Borkmann 	const struct iphdr *iph = (const struct iphdr *)skb->data;
159c50cd357SDaniel Borkmann 	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
160c50cd357SDaniel Borkmann 
161c50cd357SDaniel Borkmann 	if (ver >= GREPROTO_MAX)
162c50cd357SDaniel Borkmann 		return;
163c50cd357SDaniel Borkmann 
164c50cd357SDaniel Borkmann 	rcu_read_lock();
165c50cd357SDaniel Borkmann 	proto = rcu_dereference(gre_proto[ver]);
166c50cd357SDaniel Borkmann 	if (proto && proto->err_handler)
167c50cd357SDaniel Borkmann 		proto->err_handler(skb, info);
168c50cd357SDaniel Borkmann 	rcu_read_unlock();
169c50cd357SDaniel Borkmann }
170c50cd357SDaniel Borkmann 
171c50cd357SDaniel Borkmann static const struct net_protocol net_gre_protocol = {
172c50cd357SDaniel Borkmann 	.handler     = gre_rcv,
173c50cd357SDaniel Borkmann 	.err_handler = gre_err,
174c50cd357SDaniel Borkmann 	.netns_ok    = 1,
175c50cd357SDaniel Borkmann };
176c50cd357SDaniel Borkmann 
177c50cd357SDaniel Borkmann static int __init gre_init(void)
178c50cd357SDaniel Borkmann {
179c50cd357SDaniel Borkmann 	pr_info("GRE over IPv4 demultiplexor driver\n");
180c50cd357SDaniel Borkmann 
181c50cd357SDaniel Borkmann 	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
182c50cd357SDaniel Borkmann 		pr_err("can't add protocol\n");
183c50cd357SDaniel Borkmann 		return -EAGAIN;
184c50cd357SDaniel Borkmann 	}
1859f57c67cSPravin B Shelar 	return 0;
1869f57c67cSPravin B Shelar }
187c50cd357SDaniel Borkmann 
188c50cd357SDaniel Borkmann static void __exit gre_exit(void)
189c50cd357SDaniel Borkmann {
190c50cd357SDaniel Borkmann 	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
191c50cd357SDaniel Borkmann }
192c50cd357SDaniel Borkmann 
193c50cd357SDaniel Borkmann module_init(gre_init);
194c50cd357SDaniel Borkmann module_exit(gre_exit);
195c50cd357SDaniel Borkmann 
196c50cd357SDaniel Borkmann MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
197c50cd357SDaniel Borkmann MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
198c50cd357SDaniel Borkmann MODULE_LICENSE("GPL");
199