Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: David S. Miller <davem@davemloft.net>
175 lines
4.6 KiB
C
175 lines
4.6 KiB
C
/*
|
|
* ip_nat_proto_gre.c - Version 2.0
|
|
*
|
|
* 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/ip.h>
|
|
#include <linux/netfilter_ipv4/ip_nat.h>
|
|
#include <linux/netfilter_ipv4/ip_nat_rule.h>
|
|
#include <linux/netfilter_ipv4/ip_nat_protocol.h>
|
|
#include <linux/netfilter_ipv4/ip_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 ip_conntrack_tuple *tuple,
|
|
enum ip_nat_manip_type maniptype,
|
|
const union ip_conntrack_manip_proto *min,
|
|
const union ip_conntrack_manip_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 ip_conntrack_tuple *tuple,
|
|
const struct ip_nat_range *range,
|
|
enum ip_nat_manip_type maniptype,
|
|
const struct ip_conntrack *conntrack)
|
|
{
|
|
static u_int16_t key;
|
|
__be16 *keyptr;
|
|
unsigned int min, i, range_size;
|
|
|
|
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 (!ip_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 ip_conntrack_tuple *tuple,
|
|
enum ip_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) {
|
|
/* key manipulation is always dest */
|
|
switch (greh->version) {
|
|
case 0:
|
|
if (!greh->key) {
|
|
DEBUGP("can't nat GRE w/o key\n");
|
|
break;
|
|
}
|
|
if (greh->csum) {
|
|
/* FIXME: Never tested this code... */
|
|
nf_proto_csum_replace4(gre_csum(greh), *pskb,
|
|
*(gre_key(greh)),
|
|
tuple->dst.u.gre.key, 0);
|
|
}
|
|
*(gre_key(greh)) = tuple->dst.u.gre.key;
|
|
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;
|
|
break;
|
|
}
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
/* nat helper struct */
|
|
static struct ip_nat_protocol gre = {
|
|
.name = "GRE",
|
|
.protonum = IPPROTO_GRE,
|
|
.manip_pkt = gre_manip_pkt,
|
|
.in_range = gre_in_range,
|
|
.unique_tuple = gre_unique_tuple,
|
|
#if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
|
|
defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
|
|
.range_to_nfattr = ip_nat_port_range_to_nfattr,
|
|
.nfattr_to_range = ip_nat_port_nfattr_to_range,
|
|
#endif
|
|
};
|
|
|
|
int __init ip_nat_proto_gre_init(void)
|
|
{
|
|
return ip_nat_protocol_register(&gre);
|
|
}
|
|
|
|
void __exit ip_nat_proto_gre_fini(void)
|
|
{
|
|
ip_nat_protocol_unregister(&gre);
|
|
}
|