2 * ip_conntrack_proto_gre.c - Version 3.0
4 * Connection tracking 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/module.h>
27 #include <linux/types.h>
28 #include <linux/timer.h>
29 #include <linux/netfilter.h>
32 #include <linux/list.h>
33 #include <linux/seq_file.h>
34 #include <linux/interrupt.h>
36 static DEFINE_RWLOCK(ip_ct_gre_lock
);
38 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
39 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
40 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
42 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
43 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
45 MODULE_LICENSE("GPL");
46 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
47 MODULE_DESCRIPTION("netfilter connection tracking protocol helper for GRE");
49 /* shamelessly stolen from ip_conntrack_proto_udp.c */
50 #define GRE_TIMEOUT (30*HZ)
51 #define GRE_STREAM_TIMEOUT (180*HZ)
54 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
55 #define DUMP_TUPLE_GRE(x) printk("%u.%u.%u.%u:0x%x -> %u.%u.%u.%u:0x%x\n", \
56 NIPQUAD((x)->src.ip), ntohs((x)->src.u.gre.key), \
57 NIPQUAD((x)->dst.ip), ntohs((x)->dst.u.gre.key))
59 #define DEBUGP(x, args...)
60 #define DUMP_TUPLE_GRE(x)
63 /* GRE KEYMAP HANDLING FUNCTIONS */
64 static LIST_HEAD(gre_keymap_list
);
66 static inline int gre_key_cmpfn(const struct ip_ct_gre_keymap
*km
,
67 const struct ip_conntrack_tuple
*t
)
69 return ((km
->tuple
.src
.ip
== t
->src
.ip
) &&
70 (km
->tuple
.dst
.ip
== t
->dst
.ip
) &&
71 (km
->tuple
.dst
.protonum
== t
->dst
.protonum
) &&
72 (km
->tuple
.dst
.u
.all
== t
->dst
.u
.all
));
75 /* look up the source key for a given tuple */
76 static __be16
gre_keymap_lookup(struct ip_conntrack_tuple
*t
)
78 struct ip_ct_gre_keymap
*km
;
81 read_lock_bh(&ip_ct_gre_lock
);
82 list_for_each_entry(km
, &gre_keymap_list
, list
) {
83 if (gre_key_cmpfn(km
, t
)) {
84 key
= km
->tuple
.src
.u
.gre
.key
;
88 read_unlock_bh(&ip_ct_gre_lock
);
90 DEBUGP("lookup src key 0x%x up key for ", key
);
96 /* add a single keymap entry, associate with specified master ct */
98 ip_ct_gre_keymap_add(struct ip_conntrack
*ct
,
99 struct ip_conntrack_tuple
*t
, int reply
)
101 struct ip_ct_gre_keymap
**exist_km
, *km
;
103 if (!ct
->helper
|| strcmp(ct
->helper
->name
, "pptp")) {
104 DEBUGP("refusing to add GRE keymap to non-pptp session\n");
109 exist_km
= &ct
->help
.ct_pptp_info
.keymap_orig
;
111 exist_km
= &ct
->help
.ct_pptp_info
.keymap_reply
;
114 /* check whether it's a retransmission */
115 list_for_each_entry(km
, &gre_keymap_list
, list
) {
116 if (gre_key_cmpfn(km
, t
) && km
== *exist_km
)
119 DEBUGP("trying to override keymap_%s for ct %p\n",
120 reply
? "reply":"orig", ct
);
124 km
= kmalloc(sizeof(*km
), GFP_ATOMIC
);
128 memcpy(&km
->tuple
, t
, sizeof(*t
));
131 DEBUGP("adding new entry %p: ", km
);
132 DUMP_TUPLE_GRE(&km
->tuple
);
134 write_lock_bh(&ip_ct_gre_lock
);
135 list_add_tail(&km
->list
, &gre_keymap_list
);
136 write_unlock_bh(&ip_ct_gre_lock
);
141 /* destroy the keymap entries associated with specified master ct */
142 void ip_ct_gre_keymap_destroy(struct ip_conntrack
*ct
)
144 DEBUGP("entering for ct %p\n", ct
);
146 if (!ct
->helper
|| strcmp(ct
->helper
->name
, "pptp")) {
147 DEBUGP("refusing to destroy GRE keymap to non-pptp session\n");
151 write_lock_bh(&ip_ct_gre_lock
);
152 if (ct
->help
.ct_pptp_info
.keymap_orig
) {
153 DEBUGP("removing %p from list\n",
154 ct
->help
.ct_pptp_info
.keymap_orig
);
155 list_del(&ct
->help
.ct_pptp_info
.keymap_orig
->list
);
156 kfree(ct
->help
.ct_pptp_info
.keymap_orig
);
157 ct
->help
.ct_pptp_info
.keymap_orig
= NULL
;
159 if (ct
->help
.ct_pptp_info
.keymap_reply
) {
160 DEBUGP("removing %p from list\n",
161 ct
->help
.ct_pptp_info
.keymap_reply
);
162 list_del(&ct
->help
.ct_pptp_info
.keymap_reply
->list
);
163 kfree(ct
->help
.ct_pptp_info
.keymap_reply
);
164 ct
->help
.ct_pptp_info
.keymap_reply
= NULL
;
166 write_unlock_bh(&ip_ct_gre_lock
);
170 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
172 /* invert gre part of tuple */
173 static int gre_invert_tuple(struct ip_conntrack_tuple
*tuple
,
174 const struct ip_conntrack_tuple
*orig
)
176 tuple
->dst
.u
.gre
.key
= orig
->src
.u
.gre
.key
;
177 tuple
->src
.u
.gre
.key
= orig
->dst
.u
.gre
.key
;
182 /* gre hdr info to tuple */
183 static int gre_pkt_to_tuple(const struct sk_buff
*skb
,
184 unsigned int dataoff
,
185 struct ip_conntrack_tuple
*tuple
)
187 struct gre_hdr_pptp _pgrehdr
, *pgrehdr
;
189 struct gre_hdr _grehdr
, *grehdr
;
191 /* first only delinearize old RFC1701 GRE header */
192 grehdr
= skb_header_pointer(skb
, dataoff
, sizeof(_grehdr
), &_grehdr
);
193 if (!grehdr
|| grehdr
->version
!= GRE_VERSION_PPTP
) {
194 /* try to behave like "ip_conntrack_proto_generic" */
195 tuple
->src
.u
.all
= 0;
196 tuple
->dst
.u
.all
= 0;
200 /* PPTP header is variable length, only need up to the call_id field */
201 pgrehdr
= skb_header_pointer(skb
, dataoff
, 8, &_pgrehdr
);
205 if (ntohs(grehdr
->protocol
) != GRE_PROTOCOL_PPTP
) {
206 DEBUGP("GRE_VERSION_PPTP but unknown proto\n");
210 tuple
->dst
.u
.gre
.key
= pgrehdr
->call_id
;
211 srckey
= gre_keymap_lookup(tuple
);
212 tuple
->src
.u
.gre
.key
= srckey
;
217 /* print gre part of tuple */
218 static int gre_print_tuple(struct seq_file
*s
,
219 const struct ip_conntrack_tuple
*tuple
)
221 return seq_printf(s
, "srckey=0x%x dstkey=0x%x ",
222 ntohs(tuple
->src
.u
.gre
.key
),
223 ntohs(tuple
->dst
.u
.gre
.key
));
226 /* print private data for conntrack */
227 static int gre_print_conntrack(struct seq_file
*s
,
228 const struct ip_conntrack
*ct
)
230 return seq_printf(s
, "timeout=%u, stream_timeout=%u ",
231 (ct
->proto
.gre
.timeout
/ HZ
),
232 (ct
->proto
.gre
.stream_timeout
/ HZ
));
235 /* Returns verdict for packet, and may modify conntrack */
236 static int gre_packet(struct ip_conntrack
*ct
,
237 const struct sk_buff
*skb
,
238 enum ip_conntrack_info conntrackinfo
)
240 /* If we've seen traffic both ways, this is a GRE connection.
242 if (ct
->status
& IPS_SEEN_REPLY
) {
243 ip_ct_refresh_acct(ct
, conntrackinfo
, skb
,
244 ct
->proto
.gre
.stream_timeout
);
245 /* Also, more likely to be important, and not a probe. */
246 set_bit(IPS_ASSURED_BIT
, &ct
->status
);
247 ip_conntrack_event_cache(IPCT_STATUS
, skb
);
249 ip_ct_refresh_acct(ct
, conntrackinfo
, skb
,
250 ct
->proto
.gre
.timeout
);
255 /* Called when a new connection for this protocol found. */
256 static int gre_new(struct ip_conntrack
*ct
,
257 const struct sk_buff
*skb
)
260 DUMP_TUPLE_GRE(&ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
);
262 /* initialize to sane value. Ideally a conntrack helper
263 * (e.g. in case of pptp) is increasing them */
264 ct
->proto
.gre
.stream_timeout
= GRE_STREAM_TIMEOUT
;
265 ct
->proto
.gre
.timeout
= GRE_TIMEOUT
;
270 /* Called when a conntrack entry has already been removed from the hashes
271 * and is about to be deleted from memory */
272 static void gre_destroy(struct ip_conntrack
*ct
)
274 struct ip_conntrack
*master
= ct
->master
;
275 DEBUGP(" entering\n");
278 DEBUGP("no master !?!\n");
280 ip_ct_gre_keymap_destroy(master
);
283 /* protocol helper struct */
284 static struct ip_conntrack_protocol gre
= {
285 .proto
= IPPROTO_GRE
,
287 .pkt_to_tuple
= gre_pkt_to_tuple
,
288 .invert_tuple
= gre_invert_tuple
,
289 .print_tuple
= gre_print_tuple
,
290 .print_conntrack
= gre_print_conntrack
,
291 .packet
= gre_packet
,
293 .destroy
= gre_destroy
,
295 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
296 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
297 .tuple_to_nfattr
= ip_ct_port_tuple_to_nfattr
,
298 .nfattr_to_tuple
= ip_ct_port_nfattr_to_tuple
,
302 /* ip_conntrack_proto_gre initialization */
303 int __init
ip_ct_proto_gre_init(void)
305 return ip_conntrack_protocol_register(&gre
);
308 /* This cannot be __exit, as it is invoked from ip_conntrack_helper_pptp.c's
309 * init() code on errors.
311 void ip_ct_proto_gre_fini(void)
313 struct list_head
*pos
, *n
;
315 /* delete all keymap entries */
316 write_lock_bh(&ip_ct_gre_lock
);
317 list_for_each_safe(pos
, n
, &gre_keymap_list
) {
318 DEBUGP("deleting keymap %p at module unload time\n", pos
);
322 write_unlock_bh(&ip_ct_gre_lock
);
324 ip_conntrack_protocol_unregister(&gre
);
327 EXPORT_SYMBOL(ip_ct_gre_keymap_add
);
328 EXPORT_SYMBOL(ip_ct_gre_keymap_destroy
);