[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);

	skb_reset_transport_header(skb);
	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|SKB_GSO_GRE_CSUM))) {
			*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
d0a7ebbc	71	skb_reset_transport_header(skb);
752f36da PS	72	greh = (struct gre_base_hdr *)skb->data;
	73	greh->flags = tnl_flags_to_gre_flags(tpi->flags);
	74	greh->protocol = tpi->proto;
	75
	76	if (tpi->flags&(TUNNEL_KEY\|TUNNEL_CSUM\|TUNNEL_SEQ)) {
	77	__be32 ptr = (__be32 )(((u8 *)greh) + hdr_len - 4);
	78
	79	if (tpi->flags&TUNNEL_SEQ) {
	80	*ptr = tpi->seq;
	81	ptr--;
	82	}
	83	if (tpi->flags&TUNNEL_KEY) {
	84	*ptr = tpi->key;
	85	ptr--;
	86	}
	87	if (tpi->flags&TUNNEL_CSUM &&
4749c09c TH	88	!(skb_shinfo(skb)->gso_type &
4749c09c TH	89	(SKB_GSO_GRE\|SKB_GSO_GRE_CSUM))) {
752f36da PS	90	*ptr = 0;
	91	(__sum16 )ptr = csum_fold(skb_checksum(skb, 0,
	92	skb->len, 0));
	93	}
	94	}
	95	}
	96	EXPORT_SYMBOL_GPL(gre_build_header);
	97
bda7bb46 PS	98	static int parse_gre_header(struct sk_buff skb, struct tnl_ptk_info tpi,
	99	bool *csum_err)
	100	{
	101	unsigned int ip_hlen = ip_hdrlen(skb);
	102	const struct gre_base_hdr *greh;
	103	__be32 *options;
	104	int hdr_len;
	105
	106	if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
	107	return -EINVAL;
	108
	109	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
	110	if (unlikely(greh->flags & (GRE_VERSION \| GRE_ROUTING)))
	111	return -EINVAL;
	112
	113	tpi->flags = gre_flags_to_tnl_flags(greh->flags);
	114	hdr_len = ip_gre_calc_hlen(tpi->flags);
	115
	116	if (!pskb_may_pull(skb, hdr_len))
	117	return -EINVAL;
	118
	119	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
	120	tpi->proto = greh->protocol;
	121
	122	options = (__be32 *)(greh + 1);
	123	if (greh->flags & GRE_CSUM) {
b1036c6a	124	if (skb_checksum_simple_validate(skb)) {
bda7bb46 PS	125	*csum_err = true;
	126	return -EINVAL;
	127	}
	128	options++;
	129	}
	130
	131	if (greh->flags & GRE_KEY) {
	132	tpi->key = *options;
	133	options++;
	134	} else
	135	tpi->key = 0;
	136
	137	if (unlikely(greh->flags & GRE_SEQ)) {
	138	tpi->seq = *options;
	139	options++;
	140	} else
	141	tpi->seq = 0;
	142
	143	/* WCCP version 1 and 2 protocol decoding.
	144	* - Change protocol to IP
	145	* - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
	146	*/
	147	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
	148	tpi->proto = htons(ETH_P_IP);
	149	if (((u8 )options & 0xF0) != 0x40) {
	150	hdr_len += 4;
	151	if (!pskb_may_pull(skb, hdr_len))
	152	return -EINVAL;
	153	}
	154	}
3d7b46cd PS	155
3d7b46cd PS	156	return iptunnel_pull_header(skb, hdr_len, tpi->proto);
bda7bb46 PS	157	}
	158
	159	static int gre_cisco_rcv(struct sk_buff *skb)
	160	{
	161	struct tnl_ptk_info tpi;
	162	int i;
	163	bool csum_err = false;
	164
fbd02dd4 PS	165	#ifdef CONFIG_NET_IPGRE_BROADCAST
	166	if (ipv4_is_multicast(ip_hdr(skb)->daddr)) {
	167	/* Looped back packet, drop it! */
	168	if (rt_is_output_route(skb_rtable(skb)))
	169	goto drop;
	170	}
	171	#endif
	172
bda7bb46 PS	173	if (parse_gre_header(skb, &tpi, &csum_err) < 0)
	174	goto drop;
	175
	176	rcu_read_lock();
	177	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
	178	struct gre_cisco_protocol *proto;
	179	int ret;
	180
	181	proto = rcu_dereference(gre_cisco_proto_list[i]);
	182	if (!proto)
	183	continue;
	184	ret = proto->handler(skb, &tpi);
	185	if (ret == PACKET_RCVD) {
	186	rcu_read_unlock();
	187	return 0;
	188	}
	189	}
	190	rcu_read_unlock();
	191
	192	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
	193	drop:
	194	kfree_skb(skb);
	195	return 0;
	196	}
	197
	198	static void gre_cisco_err(struct sk_buff *skb, u32 info)
	199	{
	200	/* All the routers (except for Linux) return only
	201	* 8 bytes of packet payload. It means, that precise relaying of
	202	* ICMP in the real Internet is absolutely infeasible.
	203	*
	204	* Moreover, Cisco "wise men" put GRE key to the third word
	205	* in GRE header. It makes impossible maintaining even soft
	206	* state for keyed
	207	* GRE tunnels with enabled checksum. Tell them "thank you".
	208	*
	209	* Well, I wonder, rfc1812 was written by Cisco employee,
	210	* what the hell these idiots break standards established
	211	* by themselves???
	212	*/
	213
	214	const int type = icmp_hdr(skb)->type;
	215	const int code = icmp_hdr(skb)->code;
	216	struct tnl_ptk_info tpi;
	217	bool csum_err = false;
	218	int i;
	219
	220	if (parse_gre_header(skb, &tpi, &csum_err)) {
	221	if (!csum_err) /* ignore csum errors. */
	222	return;
	223	}
	224
	225	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
	226	ipv4_update_pmtu(skb, dev_net(skb->dev), info,
	227	skb->dev->ifindex, 0, IPPROTO_GRE, 0);
	228	return;
	229	}
	230	if (type == ICMP_REDIRECT) {
	231	ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0,
	232	IPPROTO_GRE, 0);
	233	return;
	234	}
	235
	236	rcu_read_lock();
237	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
238	struct gre_cisco_protocol *proto;
239
240	proto = rcu_dereference(gre_cisco_proto_list[i]);
241	if (!proto)
242	continue;
243
244	if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD)
245	goto out;
246
247	}
248	out:
249	rcu_read_unlock();
250	}
251
00959ade DK	252	static int gre_rcv(struct sk_buff *skb)
	253	{
	254	const struct gre_protocol *proto;
	255	u8 ver;
	256	int ret;
	257
	258	if (!pskb_may_pull(skb, 12))
	259	goto drop;
	260
	261	ver = skb->data[1]&0x7f;
	262	if (ver >= GREPROTO_MAX)
	263	goto drop;
	264
	265	rcu_read_lock();
	266	proto = rcu_dereference(gre_proto[ver]);
	267	if (!proto \|\| !proto->handler)
	268	goto drop_unlock;
	269	ret = proto->handler(skb);
	270	rcu_read_unlock();
	271	return ret;
	272
	273	drop_unlock:
	274	rcu_read_unlock();
	275	drop:
	276	kfree_skb(skb);
	277	return NET_RX_DROP;
	278	}
	279
	280	static void gre_err(struct sk_buff *skb, u32 info)
	281	{
	282	const struct gre_protocol *proto;
559fafb9	283	const struct iphdr iph = (const struct iphdr )skb->data;
559fafb9	284	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
00959ade	285
00959ade	286	if (ver >= GREPROTO_MAX)
559fafb9	287	return;
00959ade DK	288
	289	rcu_read_lock();
	290	proto = rcu_dereference(gre_proto[ver]);
559fafb9	291	if (proto && proto->err_handler)
559fafb9	292	proto->err_handler(skb, info);
00959ade	293	rcu_read_unlock();
00959ade DK	294	}
	295
	296	static const struct net_protocol net_gre_protocol = {
	297	.handler = gre_rcv,
	298	.err_handler = gre_err,
	299	.netns_ok = 1,
	300	};
	301
bda7bb46 PS	302	static const struct gre_protocol ipgre_protocol = {
	303	.handler = gre_cisco_rcv,
	304	.err_handler = gre_cisco_err,
	305	};
	306
	307	int gre_cisco_register(struct gre_cisco_protocol *newp)
	308	{
	309	struct gre_cisco_protocol proto = (struct gre_cisco_protocol )
	310	&gre_cisco_proto_list[newp->priority];
	311
	312	return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY;
	313	}
	314	EXPORT_SYMBOL_GPL(gre_cisco_register);
	315
	316	int gre_cisco_unregister(struct gre_cisco_protocol *del_proto)
	317	{
	318	struct gre_cisco_protocol proto = (struct gre_cisco_protocol )
	319	&gre_cisco_proto_list[del_proto->priority];
	320	int ret;
	321
	322	ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL;
	323
	324	if (ret)
	325	return ret;
	326
	327	synchronize_net();
	328	return 0;
	329	}
	330	EXPORT_SYMBOL_GPL(gre_cisco_unregister);
	331
00959ade DK	332	static int __init gre_init(void)
00959ade DK	333	{
afd46503	334	pr_info("GRE over IPv4 demultiplexor driver\n");
00959ade DK	335
00959ade DK	336	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
afd46503	337	pr_err("can't add protocol\n");
bda7bb46 PS	338	goto err;
	339	}
	340
	341	if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) {
	342	pr_info("%s: can't add ipgre handler\n", __func__);
	343	goto err_gre;
00959ade DK	344	}
	345
	346	return 0;
bda7bb46 PS	347	err_gre:
	348	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
	349	err:
	350	return -EAGAIN;
00959ade DK	351	}
	352
	353	static void __exit gre_exit(void)
	354	{
bda7bb46	355	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
00959ade DK	356	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
	357	}
	358
	359	module_init(gre_init);
	360	module_exit(gre_exit);
	361
	362	MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
	363	MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
	364	MODULE_LICENSE("GPL");