[deliverable/linux.git] / net / ipv4 / gre_demux.c

/*
 *	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 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 (skb_checksum_simple_validate(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");
Commit	Line	Data
00959ade DK	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
afd46503 JP	13	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
afd46503 JP	14
00959ade	15	#include <linux/module.h>
bda7bb46 PS	16	#include <linux/if.h>
bda7bb46 PS	17	#include <linux/icmp.h>
00959ade DK	18	#include <linux/kernel.h>
	19	#include <linux/kmod.h>
	20	#include <linux/skbuff.h>
	21	#include <linux/in.h>
559fafb9	22	#include <linux/ip.h>
00959ade	23	#include <linux/netdevice.h>
68c33163	24	#include <linux/if_tunnel.h>
00959ade DK	25	#include <linux/spinlock.h>
	26	#include <net/protocol.h>
	27	#include <net/gre.h>
	28
bda7bb46 PS	29	#include <net/icmp.h>
	30	#include <net/route.h>
	31	#include <net/xfrm.h>
00959ade	32
6f0bcf15	33	static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
bda7bb46	34	static struct gre_cisco_protocol __rcu *gre_cisco_proto_list[GRE_IP_PROTO_MAX];
00959ade DK	35
	36	int gre_add_protocol(const struct gre_protocol *proto, u8 version)
	37	{
	38	if (version >= GREPROTO_MAX)
20fd4d1f	39	return -EINVAL;
00959ade	40
20fd4d1f PS	41	return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
20fd4d1f PS	42	0 : -EBUSY;
00959ade DK	43	}
	44	EXPORT_SYMBOL_GPL(gre_add_protocol);
	45
	46	int gre_del_protocol(const struct gre_protocol *proto, u8 version)
	47	{
20fd4d1f PS	48	int ret;
20fd4d1f PS	49
00959ade	50	if (version >= GREPROTO_MAX)
20fd4d1f PS	51	return -EINVAL;
	52
	53	ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
	54	0 : -EBUSY;
	55
	56	if (ret)
	57	return ret;
	58
00959ade DK	59	synchronize_rcu();
00959ade DK	60	return 0;
00959ade DK	61	}
	62	EXPORT_SYMBOL_GPL(gre_del_protocol);
	63
752f36da PS	64	void gre_build_header(struct sk_buff skb, const struct tnl_ptk_info tpi,
	65	int hdr_len)
	66	{
	67	struct gre_base_hdr *greh;
	68
	69	skb_push(skb, hdr_len);
	70
	71	greh = (struct gre_base_hdr *)skb->data;
	72	greh->flags = tnl_flags_to_gre_flags(tpi->flags);
	73	greh->protocol = tpi->proto;
	74
	75	if (tpi->flags&(TUNNEL_KEY\|TUNNEL_CSUM\|TUNNEL_SEQ)) {
	76	__be32 ptr = (__be32 )(((u8 *)greh) + hdr_len - 4);
	77
	78	if (tpi->flags&TUNNEL_SEQ) {
	79	*ptr = tpi->seq;
	80	ptr--;
	81	}
	82	if (tpi->flags&TUNNEL_KEY) {
	83	*ptr = tpi->key;
	84	ptr--;
	85	}
	86	if (tpi->flags&TUNNEL_CSUM &&
	87	!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) {
	88	*ptr = 0;
	89	(__sum16 )ptr = csum_fold(skb_checksum(skb, 0,
	90	skb->len, 0));
	91	}
	92	}
	93	}
	94	EXPORT_SYMBOL_GPL(gre_build_header);
	95
bda7bb46 PS	96	static int parse_gre_header(struct sk_buff skb, struct tnl_ptk_info tpi,
	97	bool *csum_err)
	98	{
	99	unsigned int ip_hlen = ip_hdrlen(skb);
	100	const struct gre_base_hdr *greh;
	101	__be32 *options;
	102	int hdr_len;
	103
	104	if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
	105	return -EINVAL;
	106
	107	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
	108	if (unlikely(greh->flags & (GRE_VERSION \| GRE_ROUTING)))
	109	return -EINVAL;
	110
	111	tpi->flags = gre_flags_to_tnl_flags(greh->flags);
	112	hdr_len = ip_gre_calc_hlen(tpi->flags);
	113
	114	if (!pskb_may_pull(skb, hdr_len))
	115	return -EINVAL;
	116
	117	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
	118	tpi->proto = greh->protocol;
	119
	120	options = (__be32 *)(greh + 1);
	121	if (greh->flags & GRE_CSUM) {
b1036c6a	122	if (skb_checksum_simple_validate(skb)) {
bda7bb46 PS	123	*csum_err = true;
	124	return -EINVAL;
	125	}
	126	options++;
	127	}
	128
	129	if (greh->flags & GRE_KEY) {
	130	tpi->key = *options;
	131	options++;
	132	} else
	133	tpi->key = 0;
	134
	135	if (unlikely(greh->flags & GRE_SEQ)) {
	136	tpi->seq = *options;
	137	options++;
	138	} else
	139	tpi->seq = 0;
	140
	141	/* WCCP version 1 and 2 protocol decoding.
	142	* - Change protocol to IP
	143	* - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
	144	*/
	145	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
	146	tpi->proto = htons(ETH_P_IP);
	147	if (((u8 )options & 0xF0) != 0x40) {
	148	hdr_len += 4;
	149	if (!pskb_may_pull(skb, hdr_len))
	150	return -EINVAL;
	151	}
	152	}
3d7b46cd PS	153
3d7b46cd PS	154	return iptunnel_pull_header(skb, hdr_len, tpi->proto);
bda7bb46 PS	155	}
	156
	157	static int gre_cisco_rcv(struct sk_buff *skb)
	158	{
	159	struct tnl_ptk_info tpi;
	160	int i;
	161	bool csum_err = false;
	162
fbd02dd4 PS	163	#ifdef CONFIG_NET_IPGRE_BROADCAST
	164	if (ipv4_is_multicast(ip_hdr(skb)->daddr)) {
	165	/* Looped back packet, drop it! */
	166	if (rt_is_output_route(skb_rtable(skb)))
	167	goto drop;
	168	}
	169	#endif
	170
bda7bb46 PS	171	if (parse_gre_header(skb, &tpi, &csum_err) < 0)
	172	goto drop;
	173
	174	rcu_read_lock();
	175	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
	176	struct gre_cisco_protocol *proto;
	177	int ret;
	178
	179	proto = rcu_dereference(gre_cisco_proto_list[i]);
	180	if (!proto)
	181	continue;
	182	ret = proto->handler(skb, &tpi);
	183	if (ret == PACKET_RCVD) {
	184	rcu_read_unlock();
	185	return 0;
	186	}
	187	}
	188	rcu_read_unlock();
	189
	190	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
	191	drop:
	192	kfree_skb(skb);
	193	return 0;
	194	}
	195
	196	static void gre_cisco_err(struct sk_buff *skb, u32 info)
	197	{
	198	/* All the routers (except for Linux) return only
	199	* 8 bytes of packet payload. It means, that precise relaying of
	200	* ICMP in the real Internet is absolutely infeasible.
	201	*
	202	* Moreover, Cisco "wise men" put GRE key to the third word
	203	* in GRE header. It makes impossible maintaining even soft
	204	* state for keyed
	205	* GRE tunnels with enabled checksum. Tell them "thank you".
	206	*
	207	* Well, I wonder, rfc1812 was written by Cisco employee,
	208	* what the hell these idiots break standards established
	209	* by themselves???
	210	*/
	211
	212	const int type = icmp_hdr(skb)->type;
	213	const int code = icmp_hdr(skb)->code;
	214	struct tnl_ptk_info tpi;
	215	bool csum_err = false;
	216	int i;
	217
	218	if (parse_gre_header(skb, &tpi, &csum_err)) {
	219	if (!csum_err) /* ignore csum errors. */
	220	return;
	221	}
	222
	223	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
	224	ipv4_update_pmtu(skb, dev_net(skb->dev), info,
	225	skb->dev->ifindex, 0, IPPROTO_GRE, 0);
	226	return;
	227	}
	228	if (type == ICMP_REDIRECT) {
	229	ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0,
	230	IPPROTO_GRE, 0);
	231	return;
	232	}
	233
	234	rcu_read_lock();
235	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
236	struct gre_cisco_protocol *proto;
237
238	proto = rcu_dereference(gre_cisco_proto_list[i]);
239	if (!proto)
240	continue;
241
242	if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD)
243	goto out;
244
245	}
246	out:
247	rcu_read_unlock();
248	}
249
00959ade DK	250	static int gre_rcv(struct sk_buff *skb)
	251	{
	252	const struct gre_protocol *proto;
	253	u8 ver;
	254	int ret;
	255
	256	if (!pskb_may_pull(skb, 12))
	257	goto drop;
	258
	259	ver = skb->data[1]&0x7f;
	260	if (ver >= GREPROTO_MAX)
	261	goto drop;
	262
	263	rcu_read_lock();
	264	proto = rcu_dereference(gre_proto[ver]);
	265	if (!proto \|\| !proto->handler)
	266	goto drop_unlock;
	267	ret = proto->handler(skb);
	268	rcu_read_unlock();
	269	return ret;
	270
	271	drop_unlock:
	272	rcu_read_unlock();
	273	drop:
	274	kfree_skb(skb);
	275	return NET_RX_DROP;
	276	}
	277
	278	static void gre_err(struct sk_buff *skb, u32 info)
	279	{
	280	const struct gre_protocol *proto;
559fafb9	281	const struct iphdr iph = (const struct iphdr )skb->data;
559fafb9	282	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
00959ade	283
00959ade	284	if (ver >= GREPROTO_MAX)
559fafb9	285	return;
00959ade DK	286
	287	rcu_read_lock();
	288	proto = rcu_dereference(gre_proto[ver]);
559fafb9	289	if (proto && proto->err_handler)
559fafb9	290	proto->err_handler(skb, info);
00959ade	291	rcu_read_unlock();
00959ade DK	292	}
	293
	294	static const struct net_protocol net_gre_protocol = {
	295	.handler = gre_rcv,
	296	.err_handler = gre_err,
	297	.netns_ok = 1,
	298	};
	299
bda7bb46 PS	300	static const struct gre_protocol ipgre_protocol = {
	301	.handler = gre_cisco_rcv,
	302	.err_handler = gre_cisco_err,
	303	};
	304
	305	int gre_cisco_register(struct gre_cisco_protocol *newp)
	306	{
	307	struct gre_cisco_protocol proto = (struct gre_cisco_protocol )
	308	&gre_cisco_proto_list[newp->priority];
	309
	310	return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY;
	311	}
	312	EXPORT_SYMBOL_GPL(gre_cisco_register);
	313
	314	int gre_cisco_unregister(struct gre_cisco_protocol *del_proto)
	315	{
	316	struct gre_cisco_protocol proto = (struct gre_cisco_protocol )
	317	&gre_cisco_proto_list[del_proto->priority];
	318	int ret;
	319
	320	ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL;
	321
	322	if (ret)
	323	return ret;
	324
	325	synchronize_net();
	326	return 0;
	327	}
	328	EXPORT_SYMBOL_GPL(gre_cisco_unregister);
	329
00959ade DK	330	static int __init gre_init(void)
00959ade DK	331	{
afd46503	332	pr_info("GRE over IPv4 demultiplexor driver\n");
00959ade DK	333
00959ade DK	334	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
afd46503	335	pr_err("can't add protocol\n");
bda7bb46 PS	336	goto err;
	337	}
	338
	339	if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) {
	340	pr_info("%s: can't add ipgre handler\n", __func__);
	341	goto err_gre;
00959ade DK	342	}
	343
	344	return 0;
bda7bb46 PS	345	err_gre:
	346	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
	347	err:
	348	return -EAGAIN;
00959ade DK	349	}
	350
	351	static void __exit gre_exit(void)
	352	{
bda7bb46	353	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
00959ade DK	354	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
	355	}
	356
	357	module_init(gre_init);
	358	module_exit(gre_exit);
	359
	360	MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
	361	MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
	362	MODULE_LICENSE("GPL");