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1 /*
2 * ip_conntrack_proto_gre.c - Version 3.0
3 *
4 * Connection tracking protocol helper module for GRE.
5 *
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.
8 *
9 * It has an optional key field, which may help us distinguishing two
10 * connections between the same two hosts.
11 *
12 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
13 *
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
16 * field in plain GRE.
17 *
18 * Documentation about PPTP can be found in RFC 2637
19 *
20 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
21 *
22 * Development of this code funded by Astaro AG (http://www.astaro.com/)
23 *
24 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
25 */
26
27 #include <linux/module.h>
28 #include <linux/types.h>
29 #include <linux/timer.h>
30 #include <linux/list.h>
31 #include <linux/seq_file.h>
32 #include <linux/in.h>
33 #include <linux/netdevice.h>
34 #include <linux/skbuff.h>
35 #include <linux/slab.h>
36 #include <net/dst.h>
37 #include <net/net_namespace.h>
38 #include <net/netns/generic.h>
39 #include <net/netfilter/nf_conntrack_l4proto.h>
40 #include <net/netfilter/nf_conntrack_helper.h>
41 #include <net/netfilter/nf_conntrack_core.h>
42 #include <net/netfilter/nf_conntrack_timeout.h>
43 #include <linux/netfilter/nf_conntrack_proto_gre.h>
44 #include <linux/netfilter/nf_conntrack_pptp.h>
45
46 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
47 [GRE_CT_UNREPLIED] = 30*HZ,
48 [GRE_CT_REPLIED] = 180*HZ,
49 };
50
51 static unsigned int proto_gre_net_id __read_mostly;
52
53 static inline struct netns_proto_gre *gre_pernet(struct net *net)
54 {
55 return net_generic(net, proto_gre_net_id);
56 }
57
58 static void nf_ct_gre_keymap_flush(struct net *net)
59 {
60 struct netns_proto_gre *net_gre = gre_pernet(net);
61 struct nf_ct_gre_keymap *km, *tmp;
62
63 write_lock_bh(&net_gre->keymap_lock);
64 list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
65 list_del(&km->list);
66 kfree(km);
67 }
68 write_unlock_bh(&net_gre->keymap_lock);
69 }
70
71 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
72 const struct nf_conntrack_tuple *t)
73 {
74 return km->tuple.src.l3num == t->src.l3num &&
75 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
76 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
77 km->tuple.dst.protonum == t->dst.protonum &&
78 km->tuple.dst.u.all == t->dst.u.all;
79 }
80
81 /* look up the source key for a given tuple */
82 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
83 {
84 struct netns_proto_gre *net_gre = gre_pernet(net);
85 struct nf_ct_gre_keymap *km;
86 __be16 key = 0;
87
88 read_lock_bh(&net_gre->keymap_lock);
89 list_for_each_entry(km, &net_gre->keymap_list, list) {
90 if (gre_key_cmpfn(km, t)) {
91 key = km->tuple.src.u.gre.key;
92 break;
93 }
94 }
95 read_unlock_bh(&net_gre->keymap_lock);
96
97 pr_debug("lookup src key 0x%x for ", key);
98 nf_ct_dump_tuple(t);
99
100 return key;
101 }
102
103 /* add a single keymap entry, associate with specified master ct */
104 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
105 struct nf_conntrack_tuple *t)
106 {
107 struct net *net = nf_ct_net(ct);
108 struct netns_proto_gre *net_gre = gre_pernet(net);
109 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
110 struct nf_ct_gre_keymap **kmp, *km;
111
112 kmp = &ct_pptp_info->keymap[dir];
113 if (*kmp) {
114 /* check whether it's a retransmission */
115 read_lock_bh(&net_gre->keymap_lock);
116 list_for_each_entry(km, &net_gre->keymap_list, list) {
117 if (gre_key_cmpfn(km, t) && km == *kmp) {
118 read_unlock_bh(&net_gre->keymap_lock);
119 return 0;
120 }
121 }
122 read_unlock_bh(&net_gre->keymap_lock);
123 pr_debug("trying to override keymap_%s for ct %p\n",
124 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
125 return -EEXIST;
126 }
127
128 km = kmalloc(sizeof(*km), GFP_ATOMIC);
129 if (!km)
130 return -ENOMEM;
131 memcpy(&km->tuple, t, sizeof(*t));
132 *kmp = km;
133
134 pr_debug("adding new entry %p: ", km);
135 nf_ct_dump_tuple(&km->tuple);
136
137 write_lock_bh(&net_gre->keymap_lock);
138 list_add_tail(&km->list, &net_gre->keymap_list);
139 write_unlock_bh(&net_gre->keymap_lock);
140
141 return 0;
142 }
143 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
144
145 /* destroy the keymap entries associated with specified master ct */
146 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
147 {
148 struct net *net = nf_ct_net(ct);
149 struct netns_proto_gre *net_gre = gre_pernet(net);
150 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
151 enum ip_conntrack_dir dir;
152
153 pr_debug("entering for ct %p\n", ct);
154
155 write_lock_bh(&net_gre->keymap_lock);
156 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
157 if (ct_pptp_info->keymap[dir]) {
158 pr_debug("removing %p from list\n",
159 ct_pptp_info->keymap[dir]);
160 list_del(&ct_pptp_info->keymap[dir]->list);
161 kfree(ct_pptp_info->keymap[dir]);
162 ct_pptp_info->keymap[dir] = NULL;
163 }
164 }
165 write_unlock_bh(&net_gre->keymap_lock);
166 }
167 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
168
169 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
170
171 /* gre hdr info to tuple */
172 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
173 struct net *net, struct nf_conntrack_tuple *tuple)
174 {
175 const struct pptp_gre_header *pgrehdr;
176 struct pptp_gre_header _pgrehdr;
177 __be16 srckey;
178 const struct gre_base_hdr *grehdr;
179 struct gre_base_hdr _grehdr;
180
181 /* first only delinearize old RFC1701 GRE header */
182 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
183 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
184 /* try to behave like "nf_conntrack_proto_generic" */
185 tuple->src.u.all = 0;
186 tuple->dst.u.all = 0;
187 return true;
188 }
189
190 /* PPTP header is variable length, only need up to the call_id field */
191 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
192 if (!pgrehdr)
193 return true;
194
195 if (grehdr->protocol != GRE_PROTO_PPP) {
196 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
197 return false;
198 }
199
200 tuple->dst.u.gre.key = pgrehdr->call_id;
201 srckey = gre_keymap_lookup(net, tuple);
202 tuple->src.u.gre.key = srckey;
203
204 return true;
205 }
206
207 #ifdef CONFIG_NF_CONNTRACK_PROCFS
208 /* print private data for conntrack */
209 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
210 {
211 seq_printf(s, "timeout=%u, stream_timeout=%u ",
212 (ct->proto.gre.timeout / HZ),
213 (ct->proto.gre.stream_timeout / HZ));
214 }
215 #endif
216
217 static unsigned int *gre_get_timeouts(struct net *net)
218 {
219 return gre_pernet(net)->gre_timeouts;
220 }
221
222 /* Returns verdict for packet, and may modify conntrack */
223 static int gre_packet(struct nf_conn *ct,
224 struct sk_buff *skb,
225 unsigned int dataoff,
226 enum ip_conntrack_info ctinfo,
227 const struct nf_hook_state *state)
228 {
229 if (state->pf != NFPROTO_IPV4)
230 return -NF_ACCEPT;
231
232 if (!nf_ct_is_confirmed(ct)) {
233 unsigned int *timeouts = nf_ct_timeout_lookup(ct);
234
235 if (!timeouts)
236 timeouts = gre_get_timeouts(nf_ct_net(ct));
237
238 /* initialize to sane value. Ideally a conntrack helper
239 * (e.g. in case of pptp) is increasing them */
240 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
241 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
242 }
243
244 /* If we've seen traffic both ways, this is a GRE connection.
245 * Extend timeout. */
246 if (ct->status & IPS_SEEN_REPLY) {
247 nf_ct_refresh_acct(ct, ctinfo, skb,
248 ct->proto.gre.stream_timeout);
249 /* Also, more likely to be important, and not a probe. */
250 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
251 nf_conntrack_event_cache(IPCT_ASSURED, ct);
252 } else
253 nf_ct_refresh_acct(ct, ctinfo, skb,
254 ct->proto.gre.timeout);
255
256 return NF_ACCEPT;
257 }
258
259 /* Called when a conntrack entry has already been removed from the hashes
260 * and is about to be deleted from memory */
261 static void gre_destroy(struct nf_conn *ct)
262 {
263 struct nf_conn *master = ct->master;
264 pr_debug(" entering\n");
265
266 if (!master)
267 pr_debug("no master !?!\n");
268 else
269 nf_ct_gre_keymap_destroy(master);
270 }
271
272 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
273
274 #include <linux/netfilter/nfnetlink.h>
275 #include <linux/netfilter/nfnetlink_cttimeout.h>
276
277 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
278 struct net *net, void *data)
279 {
280 unsigned int *timeouts = data;
281 struct netns_proto_gre *net_gre = gre_pernet(net);
282
283 if (!timeouts)
284 timeouts = gre_get_timeouts(net);
285 /* set default timeouts for GRE. */
286 timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED];
287 timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED];
288
289 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
290 timeouts[GRE_CT_UNREPLIED] =
291 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
292 }
293 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
294 timeouts[GRE_CT_REPLIED] =
295 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
296 }
297 return 0;
298 }
299
300 static int
301 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
302 {
303 const unsigned int *timeouts = data;
304
305 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
306 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
307 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
308 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
309 goto nla_put_failure;
310 return 0;
311
312 nla_put_failure:
313 return -ENOSPC;
314 }
315
316 static const struct nla_policy
317 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
318 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
319 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
320 };
321 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
322
323 static int gre_init_net(struct net *net)
324 {
325 struct netns_proto_gre *net_gre = gre_pernet(net);
326 int i;
327
328 rwlock_init(&net_gre->keymap_lock);
329 INIT_LIST_HEAD(&net_gre->keymap_list);
330 for (i = 0; i < GRE_CT_MAX; i++)
331 net_gre->gre_timeouts[i] = gre_timeouts[i];
332
333 return 0;
334 }
335
336 /* protocol helper struct */
337 static const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 = {
338 .l4proto = IPPROTO_GRE,
339 .pkt_to_tuple = gre_pkt_to_tuple,
340 #ifdef CONFIG_NF_CONNTRACK_PROCFS
341 .print_conntrack = gre_print_conntrack,
342 #endif
343 .packet = gre_packet,
344 .destroy = gre_destroy,
345 .me = THIS_MODULE,
346 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
347 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
348 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
349 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
350 .nla_policy = nf_ct_port_nla_policy,
351 #endif
352 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
353 .ctnl_timeout = {
354 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
355 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
356 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
357 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
358 .nla_policy = gre_timeout_nla_policy,
359 },
360 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
361 .net_id = &proto_gre_net_id,
362 .init_net = gre_init_net,
363 };
364
365 static int proto_gre_net_init(struct net *net)
366 {
367 int ret = 0;
368
369 ret = nf_ct_l4proto_pernet_register_one(net,
370 &nf_conntrack_l4proto_gre4);
371 if (ret < 0)
372 pr_err("nf_conntrack_gre4: pernet registration failed.\n");
373 return ret;
374 }
375
376 static void proto_gre_net_exit(struct net *net)
377 {
378 nf_ct_l4proto_pernet_unregister_one(net, &nf_conntrack_l4proto_gre4);
379 nf_ct_gre_keymap_flush(net);
380 }
381
382 static struct pernet_operations proto_gre_net_ops = {
383 .init = proto_gre_net_init,
384 .exit = proto_gre_net_exit,
385 .id = &proto_gre_net_id,
386 .size = sizeof(struct netns_proto_gre),
387 };
388
389 static int __init nf_ct_proto_gre_init(void)
390 {
391 int ret;
392
393 BUILD_BUG_ON(offsetof(struct netns_proto_gre, nf) != 0);
394
395 ret = register_pernet_subsys(&proto_gre_net_ops);
396 if (ret < 0)
397 goto out_pernet;
398 ret = nf_ct_l4proto_register_one(&nf_conntrack_l4proto_gre4);
399 if (ret < 0)
400 goto out_gre4;
401
402 return 0;
403 out_gre4:
404 unregister_pernet_subsys(&proto_gre_net_ops);
405 out_pernet:
406 return ret;
407 }
408
409 static void __exit nf_ct_proto_gre_fini(void)
410 {
411 nf_ct_l4proto_unregister_one(&nf_conntrack_l4proto_gre4);
412 unregister_pernet_subsys(&proto_gre_net_ops);
413 }
414
415 module_init(nf_ct_proto_gre_init);
416 module_exit(nf_ct_proto_gre_fini);
417
418 MODULE_LICENSE("GPL");