[deliverable/linux.git] / net / ipv4 / netfilter / nf_nat_proto_gre.c

/*
 * nf_nat_proto_gre.c
 *
 * NAT protocol helper module for GRE.
 *
 * GRE is a generic encapsulation protocol, which is generally not very
 * suited for NAT, as it has no protocol-specific part as port numbers.
 *
 * It has an optional key field, which may help us distinguishing two
 * connections between the same two hosts.
 *
 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
 *
 * PPTP is built on top of a modified version of GRE, and has a mandatory
 * field called "CallID", which serves us for the same purpose as the key
 * field in plain GRE.
 *
 * Documentation about PPTP can be found in RFC 2637
 *
 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 *
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>

#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_rule.h>
#include <net/netfilter/nf_nat_protocol.h>
#include <linux/netfilter/nf_conntrack_proto_gre.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
MODULE_DESCRIPTION("Netfilter NAT protocol helper module for GRE");

#if 0
#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
				       __FUNCTION__, ## args)
#else
#define DEBUGP(x, args...)
#endif

/* is key in given range between min and max */
static int
gre_in_range(const struct nf_conntrack_tuple *tuple,
	     enum nf_nat_manip_type maniptype,
	     const union nf_conntrack_man_proto *min,
	     const union nf_conntrack_man_proto *max)
{
	__be16 key;

	if (maniptype == IP_NAT_MANIP_SRC)
		key = tuple->src.u.gre.key;
	else
		key = tuple->dst.u.gre.key;

	return ntohs(key) >= ntohs(min->gre.key) &&
	       ntohs(key) <= ntohs(max->gre.key);
}

/* generate unique tuple ... */
static int
gre_unique_tuple(struct nf_conntrack_tuple *tuple,
		 const struct nf_nat_range *range,
		 enum nf_nat_manip_type maniptype,
		 const struct nf_conn *conntrack)
{
	static u_int16_t key;
	__be16 *keyptr;
	unsigned int min, i, range_size;

	/* If there is no master conntrack we are not PPTP,
	   do not change tuples */
	if (!conntrack->master)
		return 0;

	if (maniptype == IP_NAT_MANIP_SRC)
		keyptr = &tuple->src.u.gre.key;
	else
		keyptr = &tuple->dst.u.gre.key;

	if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
		DEBUGP("%p: NATing GRE PPTP\n", conntrack);
		min = 1;
		range_size = 0xffff;
	} else {
		min = ntohs(range->min.gre.key);
		range_size = ntohs(range->max.gre.key) - min + 1;
	}

	DEBUGP("min = %u, range_size = %u\n", min, range_size);

	for (i = 0; i < range_size; i++, key++) {
		*keyptr = htons(min + key % range_size);
		if (!nf_nat_used_tuple(tuple, conntrack))
			return 1;
	}

	DEBUGP("%p: no NAT mapping\n", conntrack);
	return 0;
}

/* manipulate a GRE packet according to maniptype */
static int
gre_manip_pkt(struct sk_buff **pskb, unsigned int iphdroff,
	      const struct nf_conntrack_tuple *tuple,
	      enum nf_nat_manip_type maniptype)
{
	struct gre_hdr *greh;
	struct gre_hdr_pptp *pgreh;
	struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff);
	unsigned int hdroff = iphdroff + iph->ihl * 4;

	/* pgreh includes two optional 32bit fields which are not required
	 * to be there.  That's where the magic '8' comes from */
	if (!skb_make_writable(pskb, hdroff + sizeof(*pgreh) - 8))
		return 0;

	greh = (void *)(*pskb)->data + hdroff;
	pgreh = (struct gre_hdr_pptp *)greh;

	/* we only have destination manip of a packet, since 'source key'
	 * is not present in the packet itself */
	if (maniptype != IP_NAT_MANIP_DST)
		return 1;
	switch (greh->version) {
	case GRE_VERSION_1701:
		/* We do not currently NAT any GREv0 packets.
		 * Try to behave like "nf_nat_proto_unknown" */
		break;
	case GRE_VERSION_PPTP:
		DEBUGP("call_id -> 0x%04x\n", ntohs(tuple->dst.u.gre.key));
		pgreh->call_id = tuple->dst.u.gre.key;
		break;
	default:
		DEBUGP("can't nat unknown GRE version\n");
		return 0;
	}
	return 1;
}

static struct nf_nat_protocol gre __read_mostly = {
	.name			= "GRE",
	.protonum		= IPPROTO_GRE,
	.manip_pkt		= gre_manip_pkt,
	.in_range		= gre_in_range,
	.unique_tuple		= gre_unique_tuple,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
	.range_to_nfattr	= nf_nat_port_range_to_nfattr,
	.nfattr_to_range	= nf_nat_port_nfattr_to_range,
#endif
};

int __init nf_nat_proto_gre_init(void)
{
	return nf_nat_protocol_register(&gre);
}

void __exit nf_nat_proto_gre_fini(void)
{
	nf_nat_protocol_unregister(&gre);
}

module_init(nf_nat_proto_gre_init);
module_exit(nf_nat_proto_gre_fini);

void nf_nat_need_gre(void)
{
	return;
}
EXPORT_SYMBOL_GPL(nf_nat_need_gre);
Commit	Line	Data
f09943fe PM	1	/*
	2	* nf_nat_proto_gre.c
	3	*
	4	* NAT protocol helper module for GRE.
	5	*
	6	* GRE is a generic encapsulation protocol, which is generally not very
	7	* suited for NAT, as it has no protocol-specific part as port numbers.
	8	*
	9	* It has an optional key field, which may help us distinguishing two
	10	* connections between the same two hosts.
	11	*
	12	* GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
	13	*
	14	* PPTP is built on top of a modified version of GRE, and has a mandatory
	15	* field called "CallID", which serves us for the same purpose as the key
	16	* field in plain GRE.
	17	*
	18	* Documentation about PPTP can be found in RFC 2637
	19	*
	20	* (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
	21	*
	22	* Development of this code funded by Astaro AG (http://www.astaro.com/)
	23	*
	24	*/
	25
	26	#include <linux/module.h>
	27	#include <linux/skbuff.h>
	28	#include <linux/ip.h>
	29
	30	#include <net/netfilter/nf_nat.h>
	31	#include <net/netfilter/nf_nat_rule.h>
	32	#include <net/netfilter/nf_nat_protocol.h>
	33	#include <linux/netfilter/nf_conntrack_proto_gre.h>
	34
	35	MODULE_LICENSE("GPL");
	36	MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
	37	MODULE_DESCRIPTION("Netfilter NAT protocol helper module for GRE");
	38
	39	#if 0
	40	#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
	41	__FUNCTION__, ## args)
	42	#else
	43	#define DEBUGP(x, args...)
	44	#endif
	45
	46	/* is key in given range between min and max */
	47	static int
	48	gre_in_range(const struct nf_conntrack_tuple *tuple,
	49	enum nf_nat_manip_type maniptype,
	50	const union nf_conntrack_man_proto *min,
	51	const union nf_conntrack_man_proto *max)
	52	{
	53	__be16 key;
	54
	55	if (maniptype == IP_NAT_MANIP_SRC)
	56	key = tuple->src.u.gre.key;
	57	else
	58	key = tuple->dst.u.gre.key;
	59
	60	return ntohs(key) >= ntohs(min->gre.key) &&
	61	ntohs(key) <= ntohs(max->gre.key);
	62	}
	63
	64	/* generate unique tuple ... */
65	static int
66	gre_unique_tuple(struct nf_conntrack_tuple *tuple,
67	const struct nf_nat_range *range,
68	enum nf_nat_manip_type maniptype,
69	const struct nf_conn *conntrack)
70	{
71	static u_int16_t key;
72	__be16 *keyptr;
73	unsigned int min, i, range_size;
74
c2a1910b JB	75	/* If there is no master conntrack we are not PPTP,
	76	do not change tuples */
	77	if (!conntrack->master)
	78	return 0;
	79
f09943fe PM	80	if (maniptype == IP_NAT_MANIP_SRC)
	81	keyptr = &tuple->src.u.gre.key;
	82	else
	83	keyptr = &tuple->dst.u.gre.key;
	84
	85	if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) {
	86	DEBUGP("%p: NATing GRE PPTP\n", conntrack);
	87	min = 1;
	88	range_size = 0xffff;
	89	} else {
	90	min = ntohs(range->min.gre.key);
	91	range_size = ntohs(range->max.gre.key) - min + 1;
	92	}
	93
	94	DEBUGP("min = %u, range_size = %u\n", min, range_size);
	95
	96	for (i = 0; i < range_size; i++, key++) {
	97	*keyptr = htons(min + key % range_size);
	98	if (!nf_nat_used_tuple(tuple, conntrack))
	99	return 1;
	100	}
	101
	102	DEBUGP("%p: no NAT mapping\n", conntrack);
	103	return 0;
	104	}
	105
	106	/* manipulate a GRE packet according to maniptype */
	107	static int
	108	gre_manip_pkt(struct sk_buff **pskb, unsigned int iphdroff,
	109	const struct nf_conntrack_tuple *tuple,
	110	enum nf_nat_manip_type maniptype)
	111	{
	112	struct gre_hdr *greh;
	113	struct gre_hdr_pptp *pgreh;
	114	struct iphdr iph = (struct iphdr )((*pskb)->data + iphdroff);
	115	unsigned int hdroff = iphdroff + iph->ihl * 4;
	116
	117	/* pgreh includes two optional 32bit fields which are not required
	118	* to be there. That's where the magic '8' comes from */
	119	if (!skb_make_writable(pskb, hdroff + sizeof(*pgreh) - 8))
	120	return 0;
	121
	122	greh = (void )(pskb)->data + hdroff;
	123	pgreh = (struct gre_hdr_pptp *)greh;
	124
	125	/* we only have destination manip of a packet, since 'source key'
	126	* is not present in the packet itself */
	127	if (maniptype != IP_NAT_MANIP_DST)
	128	return 1;
	129	switch (greh->version) {
c2a1910b JB	130	case GRE_VERSION_1701:
	131	/* We do not currently NAT any GREv0 packets.
	132	* Try to behave like "nf_nat_proto_unknown" */
f09943fe PM	133	break;
	134	case GRE_VERSION_PPTP:
	135	DEBUGP("call_id -> 0x%04x\n", ntohs(tuple->dst.u.gre.key));
	136	pgreh->call_id = tuple->dst.u.gre.key;
	137	break;
	138	default:
	139	DEBUGP("can't nat unknown GRE version\n");
	140	return 0;
	141	}
	142	return 1;
	143	}
	144
	145	static struct nf_nat_protocol gre __read_mostly = {
	146	.name = "GRE",
	147	.protonum = IPPROTO_GRE,
	148	.manip_pkt = gre_manip_pkt,
	149	.in_range = gre_in_range,
	150	.unique_tuple = gre_unique_tuple,
e281db5c	151	#if defined(CONFIG_NF_CT_NETLINK) \|\| defined(CONFIG_NF_CT_NETLINK_MODULE)
f09943fe PM	152	.range_to_nfattr = nf_nat_port_range_to_nfattr,
	153	.nfattr_to_range = nf_nat_port_nfattr_to_range,
	154	#endif
	155	};
	156
	157	int __init nf_nat_proto_gre_init(void)
	158	{
	159	return nf_nat_protocol_register(&gre);
	160	}
	161
	162	void __exit nf_nat_proto_gre_fini(void)
	163	{
	164	nf_nat_protocol_unregister(&gre);
	165	}
	166
	167	module_init(nf_nat_proto_gre_init);
	168	module_exit(nf_nat_proto_gre_fini);
	169
	170	void nf_nat_need_gre(void)
	171	{
	172	return;
	173	}
	174	EXPORT_SYMBOL_GPL(nf_nat_need_gre);