aboutsummaryrefslogtreecommitdiff
path: root/net/ipv4/gre_demux.c
blob: 250be7421ab36c50ce00a25dcd3c659ca1c97f18 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
/*
 *	GRE over IPv4 demultiplexer driver
 *
 *	Authors: Dmitry Kozlov (xeb@mail.ru)
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/if.h>
#include <linux/icmp.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netdevice.h>
#include <linux/if_tunnel.h>
#include <linux/spinlock.h>
#include <net/protocol.h>
#include <net/gre.h>

#include <net/icmp.h>
#include <net/route.h>
#include <net/xfrm.h>

static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
static struct gre_cisco_protocol __rcu *gre_cisco_proto_list[GRE_IP_PROTO_MAX];

int gre_add_protocol(const struct gre_protocol *proto, u8 version)
{
	if (version >= GREPROTO_MAX)
		return -EINVAL;

	return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
		0 : -EBUSY;
}
EXPORT_SYMBOL_GPL(gre_add_protocol);

int gre_del_protocol(const struct gre_protocol *proto, u8 version)
{
	int ret;

	if (version >= GREPROTO_MAX)
		return -EINVAL;

	ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
		0 : -EBUSY;

	if (ret)
		return ret;

	synchronize_rcu();
	return 0;
}
EXPORT_SYMBOL_GPL(gre_del_protocol);

void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
		      int hdr_len)
{
	struct gre_base_hdr *greh;

	skb_push(skb, hdr_len);

	greh = (struct gre_base_hdr *)skb->data;
	greh->flags = tnl_flags_to_gre_flags(tpi->flags);
	greh->protocol = tpi->proto;

	if (tpi->flags&(TUNNEL_KEY|TUNNEL_CSUM|TUNNEL_SEQ)) {
		__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);

		if (tpi->flags&TUNNEL_SEQ) {
			*ptr = tpi->seq;
			ptr--;
		}
		if (tpi->flags&TUNNEL_KEY) {
			*ptr = tpi->key;
			ptr--;
		}
		if (tpi->flags&TUNNEL_CSUM &&
		    !(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) {
			*ptr = 0;
			*(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
								 skb->len, 0));
		}
	}
}
EXPORT_SYMBOL_GPL(gre_build_header);

static __sum16 check_checksum(struct sk_buff *skb)
{
	__sum16 csum = 0;

	switch (skb->ip_summed) {
	case CHECKSUM_COMPLETE:
		csum = csum_fold(skb->csum);

		if (!csum)
			break;
		/* Fall through. */

	case CHECKSUM_NONE:
		skb->csum = 0;
		csum = __skb_checksum_complete(skb);
		skb->ip_summed = CHECKSUM_COMPLETE;
		break;
	}

	return csum;
}

static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
			    bool *csum_err)
{
	unsigned int ip_hlen = ip_hdrlen(skb);
	const struct gre_base_hdr *greh;
	__be32 *options;
	int hdr_len;

	if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
		return -EINVAL;

	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
	if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
		return -EINVAL;

	tpi->flags = gre_flags_to_tnl_flags(greh->flags);
	hdr_len = ip_gre_calc_hlen(tpi->flags);

	if (!pskb_may_pull(skb, hdr_len))
		return -EINVAL;

	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
	tpi->proto = greh->protocol;

	options = (__be32 *)(greh + 1);
	if (greh->flags & GRE_CSUM) {
		if (check_checksum(skb)) {
			*csum_err = true;
			return -EINVAL;
		}
		options++;
	}

	if (greh->flags & GRE_KEY) {
		tpi->key = *options;
		options++;
	} else
		tpi->key = 0;

	if (unlikely(greh->flags & GRE_SEQ)) {
		tpi->seq = *options;
		options++;
	} else
		tpi->seq = 0;

	/* WCCP version 1 and 2 protocol decoding.
	 * - Change protocol to IP
	 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
	 */
	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
		tpi->proto = htons(ETH_P_IP);
		if ((*(u8 *)options & 0xF0) != 0x40) {
			hdr_len += 4;
			if (!pskb_may_pull(skb, hdr_len))
				return -EINVAL;
		}
	}

	return iptunnel_pull_header(skb, hdr_len, tpi->proto);
}

static int gre_cisco_rcv(struct sk_buff *skb)
{
	struct tnl_ptk_info tpi;
	int i;
	bool csum_err = false;

#ifdef CONFIG_NET_IPGRE_BROADCAST
	if (ipv4_is_multicast(ip_hdr(skb)->daddr)) {
		/* Looped back packet, drop it! */
		if (rt_is_output_route(skb_rtable(skb)))
			goto drop;
	}
#endif

	if (parse_gre_header(skb, &tpi, &csum_err) < 0)
		goto drop;

	rcu_read_lock();
	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
		struct gre_cisco_protocol *proto;
		int ret;

		proto = rcu_dereference(gre_cisco_proto_list[i]);
		if (!proto)
			continue;
		ret = proto->handler(skb, &tpi);
		if (ret == PACKET_RCVD) {
			rcu_read_unlock();
			return 0;
		}
	}
	rcu_read_unlock();

	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
drop:
	kfree_skb(skb);
	return 0;
}

static void gre_cisco_err(struct sk_buff *skb, u32 info)
{
	/* All the routers (except for Linux) return only
	 * 8 bytes of packet payload. It means, that precise relaying of
	 * ICMP in the real Internet is absolutely infeasible.
	 *
	 * Moreover, Cisco "wise men" put GRE key to the third word
	 * in GRE header. It makes impossible maintaining even soft
	 * state for keyed
	 * GRE tunnels with enabled checksum. Tell them "thank you".
	 *
	 * Well, I wonder, rfc1812 was written by Cisco employee,
	 * what the hell these idiots break standards established
	 * by themselves???
	 */

	const int type = icmp_hdr(skb)->type;
	const int code = icmp_hdr(skb)->code;
	struct tnl_ptk_info tpi;
	bool csum_err = false;
	int i;

	if (parse_gre_header(skb, &tpi, &csum_err)) {
		if (!csum_err)		/* ignore csum errors. */
			return;
	}

	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
		ipv4_update_pmtu(skb, dev_net(skb->dev), info,
				skb->dev->ifindex, 0, IPPROTO_GRE, 0);
		return;
	}
	if (type == ICMP_REDIRECT) {
		ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0,
				IPPROTO_GRE, 0);
		return;
	}

	rcu_read_lock();
	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
		struct gre_cisco_protocol *proto;

		proto = rcu_dereference(gre_cisco_proto_list[i]);
		if (!proto)
			continue;

		if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD)
			goto out;

	}
out:
	rcu_read_unlock();
}

static int gre_rcv(struct sk_buff *skb)
{
	const struct gre_protocol *proto;
	u8 ver;
	int ret;

	if (!pskb_may_pull(skb, 12))
		goto drop;

	ver = skb->data[1]&0x7f;
	if (ver >= GREPROTO_MAX)
		goto drop;

	rcu_read_lock();
	proto = rcu_dereference(gre_proto[ver]);
	if (!proto || !proto->handler)
		goto drop_unlock;
	ret = proto->handler(skb);
	rcu_read_unlock();
	return ret;

drop_unlock:
	rcu_read_unlock();
drop:
	kfree_skb(skb);
	return NET_RX_DROP;
}

static void gre_err(struct sk_buff *skb, u32 info)
{
	const struct gre_protocol *proto;
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;

	if (ver >= GREPROTO_MAX)
		return;

	rcu_read_lock();
	proto = rcu_dereference(gre_proto[ver]);
	if (proto && proto->err_handler)
		proto->err_handler(skb, info);
	rcu_read_unlock();
}

static const struct net_protocol net_gre_protocol = {
	.handler     = gre_rcv,
	.err_handler = gre_err,
	.netns_ok    = 1,
};

static const struct gre_protocol ipgre_protocol = {
	.handler     = gre_cisco_rcv,
	.err_handler = gre_cisco_err,
};

int gre_cisco_register(struct gre_cisco_protocol *newp)
{
	struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
					    &gre_cisco_proto_list[newp->priority];

	return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY;
}
EXPORT_SYMBOL_GPL(gre_cisco_register);

int gre_cisco_unregister(struct gre_cisco_protocol *del_proto)
{
	struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
					    &gre_cisco_proto_list[del_proto->priority];
	int ret;

	ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL;

	if (ret)
		return ret;

	synchronize_net();
	return 0;
}
EXPORT_SYMBOL_GPL(gre_cisco_unregister);

static int __init gre_init(void)
{
	pr_info("GRE over IPv4 demultiplexor driver\n");

	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
		pr_err("can't add protocol\n");
		goto err;
	}

	if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) {
		pr_info("%s: can't add ipgre handler\n", __func__);
		goto err_gre;
	}

	return 0;
err_gre:
	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
err:
	return -EAGAIN;
}

static void __exit gre_exit(void)
{
	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
}

module_init(gre_init);
module_exit(gre_exit);

MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
MODULE_LICENSE("GPL");