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/list.h>
30 #include <linux/seq_file.h>
32 #include <linux/skbuff.h>
34 #include <net/netfilter/nf_conntrack_l4proto.h>
35 #include <net/netfilter/nf_conntrack_helper.h>
36 #include <net/netfilter/nf_conntrack_core.h>
37 #include <linux/netfilter/nf_conntrack_proto_gre.h>
38 #include <linux/netfilter/nf_conntrack_pptp.h>
40 #define GRE_TIMEOUT (30 * HZ)
41 #define GRE_STREAM_TIMEOUT (180 * HZ)
43 static DEFINE_RWLOCK(nf_ct_gre_lock
);
44 static LIST_HEAD(gre_keymap_list
);
46 void nf_ct_gre_keymap_flush(void)
48 struct nf_ct_gre_keymap
*km
, *tmp
;
50 write_lock_bh(&nf_ct_gre_lock
);
51 list_for_each_entry_safe(km
, tmp
, &gre_keymap_list
, list
) {
55 write_unlock_bh(&nf_ct_gre_lock
);
57 EXPORT_SYMBOL(nf_ct_gre_keymap_flush
);
59 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap
*km
,
60 const struct nf_conntrack_tuple
*t
)
62 return km
->tuple
.src
.l3num
== t
->src
.l3num
&&
63 !memcmp(&km
->tuple
.src
.u3
, &t
->src
.u3
, sizeof(t
->src
.u3
)) &&
64 !memcmp(&km
->tuple
.dst
.u3
, &t
->dst
.u3
, sizeof(t
->dst
.u3
)) &&
65 km
->tuple
.dst
.protonum
== t
->dst
.protonum
&&
66 km
->tuple
.dst
.u
.all
== t
->dst
.u
.all
;
69 /* look up the source key for a given tuple */
70 static __be16
gre_keymap_lookup(struct nf_conntrack_tuple
*t
)
72 struct nf_ct_gre_keymap
*km
;
75 read_lock_bh(&nf_ct_gre_lock
);
76 list_for_each_entry(km
, &gre_keymap_list
, list
) {
77 if (gre_key_cmpfn(km
, t
)) {
78 key
= km
->tuple
.src
.u
.gre
.key
;
82 read_unlock_bh(&nf_ct_gre_lock
);
84 pr_debug("lookup src key 0x%x for ", key
);
90 /* add a single keymap entry, associate with specified master ct */
91 int nf_ct_gre_keymap_add(struct nf_conn
*ct
, enum ip_conntrack_dir dir
,
92 struct nf_conntrack_tuple
*t
)
94 struct nf_conn_help
*help
= nfct_help(ct
);
95 struct nf_ct_gre_keymap
**kmp
, *km
;
97 kmp
= &help
->help
.ct_pptp_info
.keymap
[dir
];
99 /* check whether it's a retransmission */
100 read_lock_bh(&nf_ct_gre_lock
);
101 list_for_each_entry(km
, &gre_keymap_list
, list
) {
102 if (gre_key_cmpfn(km
, t
) && km
== *kmp
) {
103 read_unlock_bh(&nf_ct_gre_lock
);
107 read_unlock_bh(&nf_ct_gre_lock
);
108 pr_debug("trying to override keymap_%s for ct %p\n",
109 dir
== IP_CT_DIR_REPLY
? "reply" : "orig", ct
);
113 km
= kmalloc(sizeof(*km
), GFP_ATOMIC
);
116 memcpy(&km
->tuple
, t
, sizeof(*t
));
119 pr_debug("adding new entry %p: ", km
);
120 nf_ct_dump_tuple(&km
->tuple
);
122 write_lock_bh(&nf_ct_gre_lock
);
123 list_add_tail(&km
->list
, &gre_keymap_list
);
124 write_unlock_bh(&nf_ct_gre_lock
);
128 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add
);
130 /* destroy the keymap entries associated with specified master ct */
131 void nf_ct_gre_keymap_destroy(struct nf_conn
*ct
)
133 struct nf_conn_help
*help
= nfct_help(ct
);
134 enum ip_conntrack_dir dir
;
136 pr_debug("entering for ct %p\n", ct
);
138 write_lock_bh(&nf_ct_gre_lock
);
139 for (dir
= IP_CT_DIR_ORIGINAL
; dir
< IP_CT_DIR_MAX
; dir
++) {
140 if (help
->help
.ct_pptp_info
.keymap
[dir
]) {
141 pr_debug("removing %p from list\n",
142 help
->help
.ct_pptp_info
.keymap
[dir
]);
143 list_del(&help
->help
.ct_pptp_info
.keymap
[dir
]->list
);
144 kfree(help
->help
.ct_pptp_info
.keymap
[dir
]);
145 help
->help
.ct_pptp_info
.keymap
[dir
] = NULL
;
148 write_unlock_bh(&nf_ct_gre_lock
);
150 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy
);
152 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
154 /* invert gre part of tuple */
155 static bool gre_invert_tuple(struct nf_conntrack_tuple
*tuple
,
156 const struct nf_conntrack_tuple
*orig
)
158 tuple
->dst
.u
.gre
.key
= orig
->src
.u
.gre
.key
;
159 tuple
->src
.u
.gre
.key
= orig
->dst
.u
.gre
.key
;
163 /* gre hdr info to tuple */
164 static bool gre_pkt_to_tuple(const struct sk_buff
*skb
, unsigned int dataoff
,
165 struct nf_conntrack_tuple
*tuple
)
167 const struct gre_hdr_pptp
*pgrehdr
;
168 struct gre_hdr_pptp _pgrehdr
;
170 const struct gre_hdr
*grehdr
;
171 struct gre_hdr _grehdr
;
173 /* first only delinearize old RFC1701 GRE header */
174 grehdr
= skb_header_pointer(skb
, dataoff
, sizeof(_grehdr
), &_grehdr
);
175 if (!grehdr
|| grehdr
->version
!= GRE_VERSION_PPTP
) {
176 /* try to behave like "nf_conntrack_proto_generic" */
177 tuple
->src
.u
.all
= 0;
178 tuple
->dst
.u
.all
= 0;
182 /* PPTP header is variable length, only need up to the call_id field */
183 pgrehdr
= skb_header_pointer(skb
, dataoff
, 8, &_pgrehdr
);
187 if (ntohs(grehdr
->protocol
) != GRE_PROTOCOL_PPTP
) {
188 pr_debug("GRE_VERSION_PPTP but unknown proto\n");
192 tuple
->dst
.u
.gre
.key
= pgrehdr
->call_id
;
193 srckey
= gre_keymap_lookup(tuple
);
194 tuple
->src
.u
.gre
.key
= srckey
;
199 /* print gre part of tuple */
200 static int gre_print_tuple(struct seq_file
*s
,
201 const struct nf_conntrack_tuple
*tuple
)
203 return seq_printf(s
, "srckey=0x%x dstkey=0x%x ",
204 ntohs(tuple
->src
.u
.gre
.key
),
205 ntohs(tuple
->dst
.u
.gre
.key
));
208 /* print private data for conntrack */
209 static int gre_print_conntrack(struct seq_file
*s
,
210 const struct nf_conn
*ct
)
212 return seq_printf(s
, "timeout=%u, stream_timeout=%u ",
213 (ct
->proto
.gre
.timeout
/ HZ
),
214 (ct
->proto
.gre
.stream_timeout
/ HZ
));
217 /* Returns verdict for packet, and may modify conntrack */
218 static int gre_packet(struct nf_conn
*ct
,
219 const struct sk_buff
*skb
,
220 unsigned int dataoff
,
221 enum ip_conntrack_info ctinfo
,
223 unsigned int hooknum
)
225 /* If we've seen traffic both ways, this is a GRE connection.
227 if (ct
->status
& IPS_SEEN_REPLY
) {
228 nf_ct_refresh_acct(ct
, ctinfo
, skb
,
229 ct
->proto
.gre
.stream_timeout
);
230 /* Also, more likely to be important, and not a probe. */
231 set_bit(IPS_ASSURED_BIT
, &ct
->status
);
232 nf_conntrack_event_cache(IPCT_STATUS
, skb
);
234 nf_ct_refresh_acct(ct
, ctinfo
, skb
,
235 ct
->proto
.gre
.timeout
);
240 /* Called when a new connection for this protocol found. */
241 static bool gre_new(struct nf_conn
*ct
, const struct sk_buff
*skb
,
242 unsigned int dataoff
)
245 nf_ct_dump_tuple(&ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
);
247 /* initialize to sane value. Ideally a conntrack helper
248 * (e.g. in case of pptp) is increasing them */
249 ct
->proto
.gre
.stream_timeout
= GRE_STREAM_TIMEOUT
;
250 ct
->proto
.gre
.timeout
= GRE_TIMEOUT
;
255 /* Called when a conntrack entry has already been removed from the hashes
256 * and is about to be deleted from memory */
257 static void gre_destroy(struct nf_conn
*ct
)
259 struct nf_conn
*master
= ct
->master
;
260 pr_debug(" entering\n");
263 pr_debug("no master !?!\n");
265 nf_ct_gre_keymap_destroy(master
);
268 /* protocol helper struct */
269 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly
= {
271 .l4proto
= IPPROTO_GRE
,
273 .pkt_to_tuple
= gre_pkt_to_tuple
,
274 .invert_tuple
= gre_invert_tuple
,
275 .print_tuple
= gre_print_tuple
,
276 .print_conntrack
= gre_print_conntrack
,
277 .packet
= gre_packet
,
279 .destroy
= gre_destroy
,
281 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
282 .tuple_to_nlattr
= nf_ct_port_tuple_to_nlattr
,
283 .nlattr_to_tuple
= nf_ct_port_nlattr_to_tuple
,
284 .nla_policy
= nf_ct_port_nla_policy
,
288 static int __init
nf_ct_proto_gre_init(void)
290 return nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4
);
293 static void nf_ct_proto_gre_fini(void)
295 nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4
);
296 nf_ct_gre_keymap_flush();
299 module_init(nf_ct_proto_gre_init
);
300 module_exit(nf_ct_proto_gre_fini
);
302 MODULE_LICENSE("GPL");