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/config.h>
27 #include <linux/module.h>
28 #include <linux/types.h>
29 #include <linux/timer.h>
30 #include <linux/netfilter.h>
33 #include <linux/list.h>
34 #include <linux/seq_file.h>
35 #include <linux/interrupt.h>
37 static DEFINE_RWLOCK(ip_ct_gre_lock
);
38 #define ASSERT_READ_LOCK(x)
39 #define ASSERT_WRITE_LOCK(x)
41 #include <linux/netfilter_ipv4/listhelp.h>
42 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
43 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
44 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
46 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
47 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
49 MODULE_LICENSE("GPL");
50 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
51 MODULE_DESCRIPTION("netfilter connection tracking protocol helper for GRE");
53 /* shamelessly stolen from ip_conntrack_proto_udp.c */
54 #define GRE_TIMEOUT (30*HZ)
55 #define GRE_STREAM_TIMEOUT (180*HZ)
58 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
59 #define DUMP_TUPLE_GRE(x) printk("%u.%u.%u.%u:0x%x -> %u.%u.%u.%u:0x%x\n", \
60 NIPQUAD((x)->src.ip), ntohs((x)->src.u.gre.key), \
61 NIPQUAD((x)->dst.ip), ntohs((x)->dst.u.gre.key))
63 #define DEBUGP(x, args...)
64 #define DUMP_TUPLE_GRE(x)
67 /* GRE KEYMAP HANDLING FUNCTIONS */
68 static LIST_HEAD(gre_keymap_list
);
70 static inline int gre_key_cmpfn(const struct ip_ct_gre_keymap
*km
,
71 const struct ip_conntrack_tuple
*t
)
73 return ((km
->tuple
.src
.ip
== t
->src
.ip
) &&
74 (km
->tuple
.dst
.ip
== t
->dst
.ip
) &&
75 (km
->tuple
.dst
.protonum
== t
->dst
.protonum
) &&
76 (km
->tuple
.dst
.u
.all
== t
->dst
.u
.all
));
79 /* look up the source key for a given tuple */
80 static u_int32_t
gre_keymap_lookup(struct ip_conntrack_tuple
*t
)
82 struct ip_ct_gre_keymap
*km
;
85 read_lock_bh(&ip_ct_gre_lock
);
86 km
= LIST_FIND(&gre_keymap_list
, gre_key_cmpfn
,
87 struct ip_ct_gre_keymap
*, t
);
89 key
= km
->tuple
.src
.u
.gre
.key
;
90 read_unlock_bh(&ip_ct_gre_lock
);
92 DEBUGP("lookup src key 0x%x up key for ", key
);
98 /* add a single keymap entry, associate with specified master ct */
100 ip_ct_gre_keymap_add(struct ip_conntrack
*ct
,
101 struct ip_conntrack_tuple
*t
, int reply
)
103 struct ip_ct_gre_keymap
**exist_km
, *km
, *old
;
105 if (!ct
->helper
|| strcmp(ct
->helper
->name
, "pptp")) {
106 DEBUGP("refusing to add GRE keymap to non-pptp session\n");
111 exist_km
= &ct
->help
.ct_pptp_info
.keymap_orig
;
113 exist_km
= &ct
->help
.ct_pptp_info
.keymap_reply
;
116 /* check whether it's a retransmission */
117 old
= LIST_FIND(&gre_keymap_list
, gre_key_cmpfn
,
118 struct ip_ct_gre_keymap
*, t
);
119 if (old
== *exist_km
) {
120 DEBUGP("retransmission\n");
124 DEBUGP("trying to override keymap_%s for ct %p\n",
125 reply
? "reply":"orig", ct
);
129 km
= kmalloc(sizeof(*km
), GFP_ATOMIC
);
133 memcpy(&km
->tuple
, t
, sizeof(*t
));
136 DEBUGP("adding new entry %p: ", km
);
137 DUMP_TUPLE_GRE(&km
->tuple
);
139 write_lock_bh(&ip_ct_gre_lock
);
140 list_append(&gre_keymap_list
, km
);
141 write_unlock_bh(&ip_ct_gre_lock
);
146 /* destroy the keymap entries associated with specified master ct */
147 void ip_ct_gre_keymap_destroy(struct ip_conntrack
*ct
)
149 DEBUGP("entering for ct %p\n", ct
);
151 if (!ct
->helper
|| strcmp(ct
->helper
->name
, "pptp")) {
152 DEBUGP("refusing to destroy GRE keymap to non-pptp session\n");
156 write_lock_bh(&ip_ct_gre_lock
);
157 if (ct
->help
.ct_pptp_info
.keymap_orig
) {
158 DEBUGP("removing %p from list\n",
159 ct
->help
.ct_pptp_info
.keymap_orig
);
160 list_del(&ct
->help
.ct_pptp_info
.keymap_orig
->list
);
161 kfree(ct
->help
.ct_pptp_info
.keymap_orig
);
162 ct
->help
.ct_pptp_info
.keymap_orig
= NULL
;
164 if (ct
->help
.ct_pptp_info
.keymap_reply
) {
165 DEBUGP("removing %p from list\n",
166 ct
->help
.ct_pptp_info
.keymap_reply
);
167 list_del(&ct
->help
.ct_pptp_info
.keymap_reply
->list
);
168 kfree(ct
->help
.ct_pptp_info
.keymap_reply
);
169 ct
->help
.ct_pptp_info
.keymap_reply
= NULL
;
171 write_unlock_bh(&ip_ct_gre_lock
);
175 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
177 /* invert gre part of tuple */
178 static int gre_invert_tuple(struct ip_conntrack_tuple
*tuple
,
179 const struct ip_conntrack_tuple
*orig
)
181 tuple
->dst
.u
.gre
.key
= orig
->src
.u
.gre
.key
;
182 tuple
->src
.u
.gre
.key
= orig
->dst
.u
.gre
.key
;
187 /* gre hdr info to tuple */
188 static int gre_pkt_to_tuple(const struct sk_buff
*skb
,
189 unsigned int dataoff
,
190 struct ip_conntrack_tuple
*tuple
)
192 struct gre_hdr_pptp _pgrehdr
, *pgrehdr
;
194 struct gre_hdr _grehdr
, *grehdr
;
196 /* first only delinearize old RFC1701 GRE header */
197 grehdr
= skb_header_pointer(skb
, dataoff
, sizeof(_grehdr
), &_grehdr
);
198 if (!grehdr
|| grehdr
->version
!= GRE_VERSION_PPTP
) {
199 /* try to behave like "ip_conntrack_proto_generic" */
200 tuple
->src
.u
.all
= 0;
201 tuple
->dst
.u
.all
= 0;
205 /* PPTP header is variable length, only need up to the call_id field */
206 pgrehdr
= skb_header_pointer(skb
, dataoff
, 8, &_pgrehdr
);
210 if (ntohs(grehdr
->protocol
) != GRE_PROTOCOL_PPTP
) {
211 DEBUGP("GRE_VERSION_PPTP but unknown proto\n");
215 tuple
->dst
.u
.gre
.key
= pgrehdr
->call_id
;
216 srckey
= gre_keymap_lookup(tuple
);
217 tuple
->src
.u
.gre
.key
= srckey
;
222 /* print gre part of tuple */
223 static int gre_print_tuple(struct seq_file
*s
,
224 const struct ip_conntrack_tuple
*tuple
)
226 return seq_printf(s
, "srckey=0x%x dstkey=0x%x ",
227 ntohs(tuple
->src
.u
.gre
.key
),
228 ntohs(tuple
->dst
.u
.gre
.key
));
231 /* print private data for conntrack */
232 static int gre_print_conntrack(struct seq_file
*s
,
233 const struct ip_conntrack
*ct
)
235 return seq_printf(s
, "timeout=%u, stream_timeout=%u ",
236 (ct
->proto
.gre
.timeout
/ HZ
),
237 (ct
->proto
.gre
.stream_timeout
/ HZ
));
240 /* Returns verdict for packet, and may modify conntrack */
241 static int gre_packet(struct ip_conntrack
*ct
,
242 const struct sk_buff
*skb
,
243 enum ip_conntrack_info conntrackinfo
)
245 /* If we've seen traffic both ways, this is a GRE connection.
247 if (ct
->status
& IPS_SEEN_REPLY
) {
248 ip_ct_refresh_acct(ct
, conntrackinfo
, skb
,
249 ct
->proto
.gre
.stream_timeout
);
250 /* Also, more likely to be important, and not a probe. */
251 set_bit(IPS_ASSURED_BIT
, &ct
->status
);
252 ip_conntrack_event_cache(IPCT_STATUS
, skb
);
254 ip_ct_refresh_acct(ct
, conntrackinfo
, skb
,
255 ct
->proto
.gre
.timeout
);
260 /* Called when a new connection for this protocol found. */
261 static int gre_new(struct ip_conntrack
*ct
,
262 const struct sk_buff
*skb
)
265 DUMP_TUPLE_GRE(&ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
);
267 /* initialize to sane value. Ideally a conntrack helper
268 * (e.g. in case of pptp) is increasing them */
269 ct
->proto
.gre
.stream_timeout
= GRE_STREAM_TIMEOUT
;
270 ct
->proto
.gre
.timeout
= GRE_TIMEOUT
;
275 /* Called when a conntrack entry has already been removed from the hashes
276 * and is about to be deleted from memory */
277 static void gre_destroy(struct ip_conntrack
*ct
)
279 struct ip_conntrack
*master
= ct
->master
;
280 DEBUGP(" entering\n");
283 DEBUGP("no master !?!\n");
285 ip_ct_gre_keymap_destroy(master
);
288 /* protocol helper struct */
289 static struct ip_conntrack_protocol gre
= {
290 .proto
= IPPROTO_GRE
,
292 .pkt_to_tuple
= gre_pkt_to_tuple
,
293 .invert_tuple
= gre_invert_tuple
,
294 .print_tuple
= gre_print_tuple
,
295 .print_conntrack
= gre_print_conntrack
,
296 .packet
= gre_packet
,
298 .destroy
= gre_destroy
,
300 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
301 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
302 .tuple_to_nfattr
= ip_ct_port_tuple_to_nfattr
,
303 .nfattr_to_tuple
= ip_ct_port_nfattr_to_tuple
,
307 /* ip_conntrack_proto_gre initialization */
308 int __init
ip_ct_proto_gre_init(void)
310 return ip_conntrack_protocol_register(&gre
);
313 /* This cannot be __exit, as it is invoked from ip_conntrack_helper_pptp.c's
314 * init() code on errors.
316 void ip_ct_proto_gre_fini(void)
318 struct list_head
*pos
, *n
;
320 /* delete all keymap entries */
321 write_lock_bh(&ip_ct_gre_lock
);
322 list_for_each_safe(pos
, n
, &gre_keymap_list
) {
323 DEBUGP("deleting keymap %p at module unload time\n", pos
);
327 write_unlock_bh(&ip_ct_gre_lock
);
329 ip_conntrack_protocol_unregister(&gre
);
332 EXPORT_SYMBOL(ip_ct_gre_keymap_add
);
333 EXPORT_SYMBOL(ip_ct_gre_keymap_destroy
);