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 enum grep_conntrack {
47 GRE_CT_UNREPLIED,
48 GRE_CT_REPLIED,
49 GRE_CT_MAX
50 };
51
52 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
53 [GRE_CT_UNREPLIED] = 30*HZ,
54 [GRE_CT_REPLIED] = 180*HZ,
55 };
56
57 static unsigned int proto_gre_net_id __read_mostly;
58 struct netns_proto_gre {
59 struct nf_proto_net nf;
60 rwlock_t keymap_lock;
61 struct list_head keymap_list;
62 unsigned int gre_timeouts[GRE_CT_MAX];
63 };
64
gre_pernet(struct net * net)65 static inline struct netns_proto_gre *gre_pernet(struct net *net)
66 {
67 return net_generic(net, proto_gre_net_id);
68 }
69
nf_ct_gre_keymap_flush(struct net * net)70 static void nf_ct_gre_keymap_flush(struct net *net)
71 {
72 struct netns_proto_gre *net_gre = gre_pernet(net);
73 struct nf_ct_gre_keymap *km, *tmp;
74
75 write_lock_bh(&net_gre->keymap_lock);
76 list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
77 list_del(&km->list);
78 kfree(km);
79 }
80 write_unlock_bh(&net_gre->keymap_lock);
81 }
82
gre_key_cmpfn(const struct nf_ct_gre_keymap * km,const struct nf_conntrack_tuple * t)83 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
84 const struct nf_conntrack_tuple *t)
85 {
86 return km->tuple.src.l3num == t->src.l3num &&
87 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
88 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
89 km->tuple.dst.protonum == t->dst.protonum &&
90 km->tuple.dst.u.all == t->dst.u.all;
91 }
92
93 /* look up the source key for a given tuple */
gre_keymap_lookup(struct net * net,struct nf_conntrack_tuple * t)94 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
95 {
96 struct netns_proto_gre *net_gre = gre_pernet(net);
97 struct nf_ct_gre_keymap *km;
98 __be16 key = 0;
99
100 read_lock_bh(&net_gre->keymap_lock);
101 list_for_each_entry(km, &net_gre->keymap_list, list) {
102 if (gre_key_cmpfn(km, t)) {
103 key = km->tuple.src.u.gre.key;
104 break;
105 }
106 }
107 read_unlock_bh(&net_gre->keymap_lock);
108
109 pr_debug("lookup src key 0x%x for ", key);
110 nf_ct_dump_tuple(t);
111
112 return key;
113 }
114
115 /* add a single keymap entry, associate with specified master ct */
nf_ct_gre_keymap_add(struct nf_conn * ct,enum ip_conntrack_dir dir,struct nf_conntrack_tuple * t)116 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
117 struct nf_conntrack_tuple *t)
118 {
119 struct net *net = nf_ct_net(ct);
120 struct netns_proto_gre *net_gre = gre_pernet(net);
121 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
122 struct nf_ct_gre_keymap **kmp, *km;
123
124 kmp = &ct_pptp_info->keymap[dir];
125 if (*kmp) {
126 /* check whether it's a retransmission */
127 read_lock_bh(&net_gre->keymap_lock);
128 list_for_each_entry(km, &net_gre->keymap_list, list) {
129 if (gre_key_cmpfn(km, t) && km == *kmp) {
130 read_unlock_bh(&net_gre->keymap_lock);
131 return 0;
132 }
133 }
134 read_unlock_bh(&net_gre->keymap_lock);
135 pr_debug("trying to override keymap_%s for ct %p\n",
136 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
137 return -EEXIST;
138 }
139
140 km = kmalloc(sizeof(*km), GFP_ATOMIC);
141 if (!km)
142 return -ENOMEM;
143 memcpy(&km->tuple, t, sizeof(*t));
144 *kmp = km;
145
146 pr_debug("adding new entry %p: ", km);
147 nf_ct_dump_tuple(&km->tuple);
148
149 write_lock_bh(&net_gre->keymap_lock);
150 list_add_tail(&km->list, &net_gre->keymap_list);
151 write_unlock_bh(&net_gre->keymap_lock);
152
153 return 0;
154 }
155 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
156
157 /* destroy the keymap entries associated with specified master ct */
nf_ct_gre_keymap_destroy(struct nf_conn * ct)158 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
159 {
160 struct net *net = nf_ct_net(ct);
161 struct netns_proto_gre *net_gre = gre_pernet(net);
162 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
163 enum ip_conntrack_dir dir;
164
165 pr_debug("entering for ct %p\n", ct);
166
167 write_lock_bh(&net_gre->keymap_lock);
168 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
169 if (ct_pptp_info->keymap[dir]) {
170 pr_debug("removing %p from list\n",
171 ct_pptp_info->keymap[dir]);
172 list_del(&ct_pptp_info->keymap[dir]->list);
173 kfree(ct_pptp_info->keymap[dir]);
174 ct_pptp_info->keymap[dir] = NULL;
175 }
176 }
177 write_unlock_bh(&net_gre->keymap_lock);
178 }
179 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
180
181 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
182
183 /* gre hdr info to tuple */
gre_pkt_to_tuple(const struct sk_buff * skb,unsigned int dataoff,struct net * net,struct nf_conntrack_tuple * tuple)184 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
185 struct net *net, struct nf_conntrack_tuple *tuple)
186 {
187 const struct pptp_gre_header *pgrehdr;
188 struct pptp_gre_header _pgrehdr;
189 __be16 srckey;
190 const struct gre_base_hdr *grehdr;
191 struct gre_base_hdr _grehdr;
192
193 /* first only delinearize old RFC1701 GRE header */
194 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
195 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
196 /* try to behave like "nf_conntrack_proto_generic" */
197 tuple->src.u.all = 0;
198 tuple->dst.u.all = 0;
199 return true;
200 }
201
202 /* PPTP header is variable length, only need up to the call_id field */
203 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
204 if (!pgrehdr)
205 return true;
206
207 if (grehdr->protocol != GRE_PROTO_PPP) {
208 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
209 return false;
210 }
211
212 tuple->dst.u.gre.key = pgrehdr->call_id;
213 srckey = gre_keymap_lookup(net, tuple);
214 tuple->src.u.gre.key = srckey;
215
216 return true;
217 }
218
219 #ifdef CONFIG_NF_CONNTRACK_PROCFS
220 /* print private data for conntrack */
gre_print_conntrack(struct seq_file * s,struct nf_conn * ct)221 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
222 {
223 seq_printf(s, "timeout=%u, stream_timeout=%u ",
224 (ct->proto.gre.timeout / HZ),
225 (ct->proto.gre.stream_timeout / HZ));
226 }
227 #endif
228
gre_get_timeouts(struct net * net)229 static unsigned int *gre_get_timeouts(struct net *net)
230 {
231 return gre_pernet(net)->gre_timeouts;
232 }
233
234 /* Returns verdict for packet, and may modify conntrack */
gre_packet(struct nf_conn * ct,const struct sk_buff * skb,unsigned int dataoff,enum ip_conntrack_info ctinfo)235 static int gre_packet(struct nf_conn *ct,
236 const struct sk_buff *skb,
237 unsigned int dataoff,
238 enum ip_conntrack_info ctinfo)
239 {
240 /* If we've seen traffic both ways, this is a GRE connection.
241 * Extend timeout. */
242 if (ct->status & IPS_SEEN_REPLY) {
243 nf_ct_refresh_acct(ct, ctinfo, skb,
244 ct->proto.gre.stream_timeout);
245 /* Also, more likely to be important, and not a probe. */
246 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
247 nf_conntrack_event_cache(IPCT_ASSURED, ct);
248 } else
249 nf_ct_refresh_acct(ct, ctinfo, skb,
250 ct->proto.gre.timeout);
251
252 return NF_ACCEPT;
253 }
254
255 /* Called when a new connection for this protocol found. */
gre_new(struct nf_conn * ct,const struct sk_buff * skb,unsigned int dataoff)256 static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
257 unsigned int dataoff)
258 {
259 unsigned int *timeouts = nf_ct_timeout_lookup(ct);
260
261 if (!timeouts)
262 timeouts = gre_get_timeouts(nf_ct_net(ct));
263
264 pr_debug(": ");
265 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
266
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 = timeouts[GRE_CT_REPLIED];
270 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
271
272 return true;
273 }
274
275 /* Called when a conntrack entry has already been removed from the hashes
276 * and is about to be deleted from memory */
gre_destroy(struct nf_conn * ct)277 static void gre_destroy(struct nf_conn *ct)
278 {
279 struct nf_conn *master = ct->master;
280 pr_debug(" entering\n");
281
282 if (!master)
283 pr_debug("no master !?!\n");
284 else
285 nf_ct_gre_keymap_destroy(master);
286 }
287
288 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
289
290 #include <linux/netfilter/nfnetlink.h>
291 #include <linux/netfilter/nfnetlink_cttimeout.h>
292
gre_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)293 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
294 struct net *net, void *data)
295 {
296 unsigned int *timeouts = data;
297 struct netns_proto_gre *net_gre = gre_pernet(net);
298
299 if (!timeouts)
300 timeouts = gre_get_timeouts(net);
301 /* set default timeouts for GRE. */
302 timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED];
303 timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED];
304
305 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
306 timeouts[GRE_CT_UNREPLIED] =
307 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
308 }
309 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
310 timeouts[GRE_CT_REPLIED] =
311 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
312 }
313 return 0;
314 }
315
316 static int
gre_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)317 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
318 {
319 const unsigned int *timeouts = data;
320
321 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
322 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
323 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
324 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
325 goto nla_put_failure;
326 return 0;
327
328 nla_put_failure:
329 return -ENOSPC;
330 }
331
332 static const struct nla_policy
333 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
334 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
335 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
336 };
337 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
338
gre_init_net(struct net * net,u_int16_t proto)339 static int gre_init_net(struct net *net, u_int16_t proto)
340 {
341 struct netns_proto_gre *net_gre = gre_pernet(net);
342 int i;
343
344 rwlock_init(&net_gre->keymap_lock);
345 INIT_LIST_HEAD(&net_gre->keymap_list);
346 for (i = 0; i < GRE_CT_MAX; i++)
347 net_gre->gre_timeouts[i] = gre_timeouts[i];
348
349 return 0;
350 }
351
352 /* protocol helper struct */
353 static const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 = {
354 .l3proto = AF_INET,
355 .l4proto = IPPROTO_GRE,
356 .pkt_to_tuple = gre_pkt_to_tuple,
357 #ifdef CONFIG_NF_CONNTRACK_PROCFS
358 .print_conntrack = gre_print_conntrack,
359 #endif
360 .packet = gre_packet,
361 .new = gre_new,
362 .destroy = gre_destroy,
363 .me = THIS_MODULE,
364 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
365 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
366 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
367 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
368 .nla_policy = nf_ct_port_nla_policy,
369 #endif
370 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
371 .ctnl_timeout = {
372 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
373 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
374 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
375 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
376 .nla_policy = gre_timeout_nla_policy,
377 },
378 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
379 .net_id = &proto_gre_net_id,
380 .init_net = gre_init_net,
381 };
382
proto_gre_net_init(struct net * net)383 static int proto_gre_net_init(struct net *net)
384 {
385 int ret = 0;
386
387 ret = nf_ct_l4proto_pernet_register_one(net,
388 &nf_conntrack_l4proto_gre4);
389 if (ret < 0)
390 pr_err("nf_conntrack_gre4: pernet registration failed.\n");
391 return ret;
392 }
393
proto_gre_net_exit(struct net * net)394 static void proto_gre_net_exit(struct net *net)
395 {
396 nf_ct_l4proto_pernet_unregister_one(net, &nf_conntrack_l4proto_gre4);
397 nf_ct_gre_keymap_flush(net);
398 }
399
400 static struct pernet_operations proto_gre_net_ops = {
401 .init = proto_gre_net_init,
402 .exit = proto_gre_net_exit,
403 .id = &proto_gre_net_id,
404 .size = sizeof(struct netns_proto_gre),
405 };
406
nf_ct_proto_gre_init(void)407 static int __init nf_ct_proto_gre_init(void)
408 {
409 int ret;
410
411 ret = register_pernet_subsys(&proto_gre_net_ops);
412 if (ret < 0)
413 goto out_pernet;
414 ret = nf_ct_l4proto_register_one(&nf_conntrack_l4proto_gre4);
415 if (ret < 0)
416 goto out_gre4;
417
418 return 0;
419 out_gre4:
420 unregister_pernet_subsys(&proto_gre_net_ops);
421 out_pernet:
422 return ret;
423 }
424
nf_ct_proto_gre_fini(void)425 static void __exit nf_ct_proto_gre_fini(void)
426 {
427 nf_ct_l4proto_unregister_one(&nf_conntrack_l4proto_gre4);
428 unregister_pernet_subsys(&proto_gre_net_ops);
429 }
430
431 module_init(nf_ct_proto_gre_init);
432 module_exit(nf_ct_proto_gre_fini);
433
434 MODULE_LICENSE("GPL");
435
