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 <linux/netfilter/nf_conntrack_proto_gre.h>
43 #include <linux/netfilter/nf_conntrack_pptp.h>
44
45 enum grep_conntrack {
46 GRE_CT_UNREPLIED,
47 GRE_CT_REPLIED,
48 GRE_CT_MAX
49 };
50
51 static unsigned int gre_timeouts[GRE_CT_MAX] = {
52 [GRE_CT_UNREPLIED] = 30*HZ,
53 [GRE_CT_REPLIED] = 180*HZ,
54 };
55
56 static int proto_gre_net_id __read_mostly;
57 struct netns_proto_gre {
58 struct nf_proto_net nf;
59 rwlock_t keymap_lock;
60 struct list_head keymap_list;
61 unsigned int gre_timeouts[GRE_CT_MAX];
62 };
63
64 static inline struct netns_proto_gre *gre_pernet(struct net *net)
65 {
66 return net_generic(net, proto_gre_net_id);
67 }
68
69 static void nf_ct_gre_keymap_flush(struct net *net)
70 {
71 struct netns_proto_gre *net_gre = gre_pernet(net);
72 struct nf_ct_gre_keymap *km, *tmp;
73
74 write_lock_bh(&net_gre->keymap_lock);
75 list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
76 list_del(&km->list);
77 kfree(km);
78 }
79 write_unlock_bh(&net_gre->keymap_lock);
80 }
81
82 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
83 const struct nf_conntrack_tuple *t)
84 {
85 return km->tuple.src.l3num == t->src.l3num &&
86 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
87 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
88 km->tuple.dst.protonum == t->dst.protonum &&
89 km->tuple.dst.u.all == t->dst.u.all;
90 }
91
92 /* look up the source key for a given tuple */
93 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
94 {
95 struct netns_proto_gre *net_gre = gre_pernet(net);
96 struct nf_ct_gre_keymap *km;
97 __be16 key = 0;
98
99 read_lock_bh(&net_gre->keymap_lock);
100 list_for_each_entry(km, &net_gre->keymap_list, list) {
101 if (gre_key_cmpfn(km, t)) {
102 key = km->tuple.src.u.gre.key;
103 break;
104 }
105 }
106 read_unlock_bh(&net_gre->keymap_lock);
107
108 pr_debug("lookup src key 0x%x for ", key);
109 nf_ct_dump_tuple(t);
110
111 return key;
112 }
113
114 /* add a single keymap entry, associate with specified master ct */
115 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
116 struct nf_conntrack_tuple *t)
117 {
118 struct net *net = nf_ct_net(ct);
119 struct netns_proto_gre *net_gre = gre_pernet(net);
120 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
121 struct nf_ct_gre_keymap **kmp, *km;
122
123 kmp = &ct_pptp_info->keymap[dir];
124 if (*kmp) {
125 /* check whether it's a retransmission */
126 read_lock_bh(&net_gre->keymap_lock);
127 list_for_each_entry(km, &net_gre->keymap_list, list) {
128 if (gre_key_cmpfn(km, t) && km == *kmp) {
129 read_unlock_bh(&net_gre->keymap_lock);
130 return 0;
131 }
132 }
133 read_unlock_bh(&net_gre->keymap_lock);
134 pr_debug("trying to override keymap_%s for ct %p\n",
135 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
136 return -EEXIST;
137 }
138
139 km = kmalloc(sizeof(*km), GFP_ATOMIC);
140 if (!km)
141 return -ENOMEM;
142 memcpy(&km->tuple, t, sizeof(*t));
143 *kmp = km;
144
145 pr_debug("adding new entry %p: ", km);
146 nf_ct_dump_tuple(&km->tuple);
147
148 write_lock_bh(&net_gre->keymap_lock);
149 list_add_tail(&km->list, &net_gre->keymap_list);
150 write_unlock_bh(&net_gre->keymap_lock);
151
152 return 0;
153 }
154 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
155
156 /* destroy the keymap entries associated with specified master ct */
157 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
158 {
159 struct net *net = nf_ct_net(ct);
160 struct netns_proto_gre *net_gre = gre_pernet(net);
161 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
162 enum ip_conntrack_dir dir;
163
164 pr_debug("entering for ct %p\n", ct);
165
166 write_lock_bh(&net_gre->keymap_lock);
167 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
168 if (ct_pptp_info->keymap[dir]) {
169 pr_debug("removing %p from list\n",
170 ct_pptp_info->keymap[dir]);
171 list_del(&ct_pptp_info->keymap[dir]->list);
172 kfree(ct_pptp_info->keymap[dir]);
173 ct_pptp_info->keymap[dir] = NULL;
174 }
175 }
176 write_unlock_bh(&net_gre->keymap_lock);
177 }
178 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
179
180 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
181
182 /* invert gre part of tuple */
183 static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple,
184 const struct nf_conntrack_tuple *orig)
185 {
186 tuple->dst.u.gre.key = orig->src.u.gre.key;
187 tuple->src.u.gre.key = orig->dst.u.gre.key;
188 return true;
189 }
190
191 /* gre hdr info to tuple */
192 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
193 struct nf_conntrack_tuple *tuple)
194 {
195 struct net *net = dev_net(skb->dev ? skb->dev : skb_dst(skb)->dev);
196 const struct gre_hdr_pptp *pgrehdr;
197 struct gre_hdr_pptp _pgrehdr;
198 __be16 srckey;
199 const struct gre_hdr *grehdr;
200 struct gre_hdr _grehdr;
201
202 /* first only delinearize old RFC1701 GRE header */
203 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
204 if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
205 /* try to behave like "nf_conntrack_proto_generic" */
206 tuple->src.u.all = 0;
207 tuple->dst.u.all = 0;
208 return true;
209 }
210
211 /* PPTP header is variable length, only need up to the call_id field */
212 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
213 if (!pgrehdr)
214 return true;
215
216 if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
217 pr_debug("GRE_VERSION_PPTP but unknown proto\n");
218 return false;
219 }
220
221 tuple->dst.u.gre.key = pgrehdr->call_id;
222 srckey = gre_keymap_lookup(net, tuple);
223 tuple->src.u.gre.key = srckey;
224
225 return true;
226 }
227
228 /* print gre part of tuple */
229 static void gre_print_tuple(struct seq_file *s,
230 const struct nf_conntrack_tuple *tuple)
231 {
232 seq_printf(s, "srckey=0x%x dstkey=0x%x ",
233 ntohs(tuple->src.u.gre.key),
234 ntohs(tuple->dst.u.gre.key));
235 }
236
237 /* print private data for conntrack */
238 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
239 {
240 seq_printf(s, "timeout=%u, stream_timeout=%u ",
241 (ct->proto.gre.timeout / HZ),
242 (ct->proto.gre.stream_timeout / HZ));
243 }
244
245 static unsigned int *gre_get_timeouts(struct net *net)
246 {
247 return gre_pernet(net)->gre_timeouts;
248 }
249
250 /* Returns verdict for packet, and may modify conntrack */
251 static int gre_packet(struct nf_conn *ct,
252 const struct sk_buff *skb,
253 unsigned int dataoff,
254 enum ip_conntrack_info ctinfo,
255 u_int8_t pf,
256 unsigned int hooknum,
257 unsigned int *timeouts)
258 {
259 /* If we've seen traffic both ways, this is a GRE connection.
260 * Extend timeout. */
261 if (ct->status & IPS_SEEN_REPLY) {
262 nf_ct_refresh_acct(ct, ctinfo, skb,
263 ct->proto.gre.stream_timeout);
264 /* Also, more likely to be important, and not a probe. */
265 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
266 nf_conntrack_event_cache(IPCT_ASSURED, ct);
267 } else
268 nf_ct_refresh_acct(ct, ctinfo, skb,
269 ct->proto.gre.timeout);
270
271 return NF_ACCEPT;
272 }
273
274 /* Called when a new connection for this protocol found. */
275 static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
276 unsigned int dataoff, unsigned int *timeouts)
277 {
278 pr_debug(": ");
279 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
280
281 /* initialize to sane value. Ideally a conntrack helper
282 * (e.g. in case of pptp) is increasing them */
283 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
284 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
285
286 return true;
287 }
288
289 /* Called when a conntrack entry has already been removed from the hashes
290 * and is about to be deleted from memory */
291 static void gre_destroy(struct nf_conn *ct)
292 {
293 struct nf_conn *master = ct->master;
294 pr_debug(" entering\n");
295
296 if (!master)
297 pr_debug("no master !?!\n");
298 else
299 nf_ct_gre_keymap_destroy(master);
300 }
301
302 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
303
304 #include <linux/netfilter/nfnetlink.h>
305 #include <linux/netfilter/nfnetlink_cttimeout.h>
306
307 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
308 struct net *net, void *data)
309 {
310 unsigned int *timeouts = data;
311 struct netns_proto_gre *net_gre = gre_pernet(net);
312
313 /* set default timeouts for GRE. */
314 timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED];
315 timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED];
316
317 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
318 timeouts[GRE_CT_UNREPLIED] =
319 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
320 }
321 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
322 timeouts[GRE_CT_REPLIED] =
323 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
324 }
325 return 0;
326 }
327
328 static int
329 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
330 {
331 const unsigned int *timeouts = data;
332
333 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
334 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
335 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
336 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
337 goto nla_put_failure;
338 return 0;
339
340 nla_put_failure:
341 return -ENOSPC;
342 }
343
344 static const struct nla_policy
345 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
346 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
347 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
348 };
349 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
350
351 static int gre_init_net(struct net *net, u_int16_t proto)
352 {
353 struct netns_proto_gre *net_gre = gre_pernet(net);
354 int i;
355
356 rwlock_init(&net_gre->keymap_lock);
357 INIT_LIST_HEAD(&net_gre->keymap_list);
358 for (i = 0; i < GRE_CT_MAX; i++)
359 net_gre->gre_timeouts[i] = gre_timeouts[i];
360
361 return 0;
362 }
363
364 /* protocol helper struct */
365 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
366 .l3proto = AF_INET,
367 .l4proto = IPPROTO_GRE,
368 .name = "gre",
369 .pkt_to_tuple = gre_pkt_to_tuple,
370 .invert_tuple = gre_invert_tuple,
371 .print_tuple = gre_print_tuple,
372 .print_conntrack = gre_print_conntrack,
373 .get_timeouts = gre_get_timeouts,
374 .packet = gre_packet,
375 .new = gre_new,
376 .destroy = gre_destroy,
377 .me = THIS_MODULE,
378 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
379 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
380 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
381 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
382 .nla_policy = nf_ct_port_nla_policy,
383 #endif
384 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
385 .ctnl_timeout = {
386 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
387 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
388 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
389 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
390 .nla_policy = gre_timeout_nla_policy,
391 },
392 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
393 .net_id = &proto_gre_net_id,
394 .init_net = gre_init_net,
395 };
396
397 static int proto_gre_net_init(struct net *net)
398 {
399 int ret = 0;
400 ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_gre4);
401 if (ret < 0)
402 pr_err("nf_conntrack_gre4: pernet registration failed.\n");
403 return ret;
404 }
405
406 static void proto_gre_net_exit(struct net *net)
407 {
408 nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_gre4);
409 nf_ct_gre_keymap_flush(net);
410 }
411
412 static struct pernet_operations proto_gre_net_ops = {
413 .init = proto_gre_net_init,
414 .exit = proto_gre_net_exit,
415 .id = &proto_gre_net_id,
416 .size = sizeof(struct netns_proto_gre),
417 };
418
419 static int __init nf_ct_proto_gre_init(void)
420 {
421 int ret;
422
423 ret = register_pernet_subsys(&proto_gre_net_ops);
424 if (ret < 0)
425 goto out_pernet;
426
427 ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_gre4);
428 if (ret < 0)
429 goto out_gre4;
430
431 return 0;
432 out_gre4:
433 unregister_pernet_subsys(&proto_gre_net_ops);
434 out_pernet:
435 return ret;
436 }
437
438 static void __exit nf_ct_proto_gre_fini(void)
439 {
440 nf_ct_l4proto_unregister(&nf_conntrack_l4proto_gre4);
441 unregister_pernet_subsys(&proto_gre_net_ops);
442 }
443
444 module_init(nf_ct_proto_gre_init);
445 module_exit(nf_ct_proto_gre_fini);
446
447 MODULE_LICENSE("GPL");
448
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