2 * ip_nat_proto_gre.c - Version 2.0
4 * NAT protocol helper module for GRE.
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.
9 * It has an optional key field, which may help us distinguishing two
10 * connections between the same two hosts.
12 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
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
18 * Documentation about PPTP can be found in RFC 2637
20 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
22 * Development of this code funded by Astaro AG (http://www.astaro.com/)
26 #include <linux/config.h>
27 #include <linux/module.h>
29 #include <linux/netfilter_ipv4/ip_nat.h>
30 #include <linux/netfilter_ipv4/ip_nat_rule.h>
31 #include <linux/netfilter_ipv4/ip_nat_protocol.h>
32 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
34 MODULE_LICENSE("GPL");
35 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
36 MODULE_DESCRIPTION("Netfilter NAT protocol helper module for GRE");
39 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \
40 __FUNCTION__, ## args)
42 #define DEBUGP(x, args...)
45 /* is key in given range between min and max */
47 gre_in_range(const struct ip_conntrack_tuple
*tuple
,
48 enum ip_nat_manip_type maniptype
,
49 const union ip_conntrack_manip_proto
*min
,
50 const union ip_conntrack_manip_proto
*max
)
54 if (maniptype
== IP_NAT_MANIP_SRC
)
55 key
= tuple
->src
.u
.gre
.key
;
57 key
= tuple
->dst
.u
.gre
.key
;
59 return ntohl(key
) >= ntohl(min
->gre
.key
)
60 && ntohl(key
) <= ntohl(max
->gre
.key
);
63 /* generate unique tuple ... */
65 gre_unique_tuple(struct ip_conntrack_tuple
*tuple
,
66 const struct ip_nat_range
*range
,
67 enum ip_nat_manip_type maniptype
,
68 const struct ip_conntrack
*conntrack
)
72 unsigned int min
, i
, range_size
;
74 if (maniptype
== IP_NAT_MANIP_SRC
)
75 keyptr
= &tuple
->src
.u
.gre
.key
;
77 keyptr
= &tuple
->dst
.u
.gre
.key
;
79 if (!(range
->flags
& IP_NAT_RANGE_PROTO_SPECIFIED
)) {
80 DEBUGP("%p: NATing GRE PPTP\n", conntrack
);
84 min
= ntohl(range
->min
.gre
.key
);
85 range_size
= ntohl(range
->max
.gre
.key
) - min
+ 1;
88 DEBUGP("min = %u, range_size = %u\n", min
, range_size
);
90 for (i
= 0; i
< range_size
; i
++, key
++) {
91 *keyptr
= htonl(min
+ key
% range_size
);
92 if (!ip_nat_used_tuple(tuple
, conntrack
))
96 DEBUGP("%p: no NAT mapping\n", conntrack
);
101 /* manipulate a GRE packet according to maniptype */
103 gre_manip_pkt(struct sk_buff
**pskb
,
104 unsigned int iphdroff
,
105 const struct ip_conntrack_tuple
*tuple
,
106 enum ip_nat_manip_type maniptype
)
108 struct gre_hdr
*greh
;
109 struct gre_hdr_pptp
*pgreh
;
110 struct iphdr
*iph
= (struct iphdr
*)((*pskb
)->data
+ iphdroff
);
111 unsigned int hdroff
= iphdroff
+ iph
->ihl
*4;
113 /* pgreh includes two optional 32bit fields which are not required
114 * to be there. That's where the magic '8' comes from */
115 if (!skb_make_writable(pskb
, hdroff
+ sizeof(*pgreh
)-8))
118 greh
= (void *)(*pskb
)->data
+ hdroff
;
119 pgreh
= (struct gre_hdr_pptp
*) greh
;
121 /* we only have destination manip of a packet, since 'source key'
122 * is not present in the packet itself */
123 if (maniptype
== IP_NAT_MANIP_DST
) {
124 /* key manipulation is always dest */
125 switch (greh
->version
) {
128 DEBUGP("can't nat GRE w/o key\n");
132 /* FIXME: Never tested this code... */
134 ip_nat_cheat_check(~*(gre_key(greh
)),
135 tuple
->dst
.u
.gre
.key
,
138 *(gre_key(greh
)) = tuple
->dst
.u
.gre
.key
;
140 case GRE_VERSION_PPTP
:
141 DEBUGP("call_id -> 0x%04x\n",
142 ntohs(tuple
->dst
.u
.gre
.key
));
143 pgreh
->call_id
= tuple
->dst
.u
.gre
.key
;
146 DEBUGP("can't nat unknown GRE version\n");
154 /* nat helper struct */
155 static struct ip_nat_protocol gre
= {
157 .protonum
= IPPROTO_GRE
,
158 .manip_pkt
= gre_manip_pkt
,
159 .in_range
= gre_in_range
,
160 .unique_tuple
= gre_unique_tuple
,
161 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
162 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
163 .range_to_nfattr
= ip_nat_port_range_to_nfattr
,
164 .nfattr_to_range
= ip_nat_port_nfattr_to_range
,
168 int __init
ip_nat_proto_gre_init(void)
170 return ip_nat_protocol_register(&gre
);
173 void __exit
ip_nat_proto_gre_fini(void)
175 ip_nat_protocol_unregister(&gre
);