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
gre_pernet(struct net * net)64 static inline struct netns_proto_gre *gre_pernet(struct net *net)
65 {
66 return net_generic(net, proto_gre_net_id);
67 }
68
nf_ct_gre_keymap_flush(struct net * net)69 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 EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
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 /* invert gre part of tuple */
gre_invert_tuple(struct nf_conntrack_tuple * tuple,const struct nf_conntrack_tuple * orig)184 static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple,
185 const struct nf_conntrack_tuple *orig)
186 {
187 tuple->dst.u.gre.key = orig->src.u.gre.key;
188 tuple->src.u.gre.key = orig->dst.u.gre.key;
189 return true;
190 }
191
192 /* gre hdr info to tuple */
gre_pkt_to_tuple(const struct sk_buff * skb,unsigned int dataoff,struct nf_conntrack_tuple * tuple)193 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
194 struct nf_conntrack_tuple *tuple)
195 {
196 struct net *net = dev_net(skb->dev ? skb->dev : skb_dst(skb)->dev);
197 const struct gre_hdr_pptp *pgrehdr;
198 struct gre_hdr_pptp _pgrehdr;
199 __be16 srckey;
200 const struct gre_hdr *grehdr;
201 struct gre_hdr _grehdr;
202
203 /* first only delinearize old RFC1701 GRE header */
204 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
205 if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
206 /* try to behave like "nf_conntrack_proto_generic" */
207 tuple->src.u.all = 0;
208 tuple->dst.u.all = 0;
209 return true;
210 }
211
212 /* PPTP header is variable length, only need up to the call_id field */
213 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
214 if (!pgrehdr)
215 return true;
216
217 if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
218 pr_debug("GRE_VERSION_PPTP but unknown proto\n");
219 return false;
220 }
221
222 tuple->dst.u.gre.key = pgrehdr->call_id;
223 srckey = gre_keymap_lookup(net, tuple);
224 tuple->src.u.gre.key = srckey;
225
226 return true;
227 }
228
229 /* print gre part of tuple */
gre_print_tuple(struct seq_file * s,const struct nf_conntrack_tuple * tuple)230 static int gre_print_tuple(struct seq_file *s,
231 const struct nf_conntrack_tuple *tuple)
232 {
233 return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
234 ntohs(tuple->src.u.gre.key),
235 ntohs(tuple->dst.u.gre.key));
236 }
237
238 /* print private data for conntrack */
gre_print_conntrack(struct seq_file * s,struct nf_conn * ct)239 static int gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
240 {
241 return seq_printf(s, "timeout=%u, stream_timeout=%u ",
242 (ct->proto.gre.timeout / HZ),
243 (ct->proto.gre.stream_timeout / HZ));
244 }
245
gre_get_timeouts(struct net * net)246 static unsigned int *gre_get_timeouts(struct net *net)
247 {
248 return gre_pernet(net)->gre_timeouts;
249 }
250
251 /* 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,u_int8_t pf,unsigned int hooknum,unsigned int * timeouts)252 static int gre_packet(struct nf_conn *ct,
253 const struct sk_buff *skb,
254 unsigned int dataoff,
255 enum ip_conntrack_info ctinfo,
256 u_int8_t pf,
257 unsigned int hooknum,
258 unsigned int *timeouts)
259 {
260 /* If we've seen traffic both ways, this is a GRE connection.
261 * Extend timeout. */
262 if (ct->status & IPS_SEEN_REPLY) {
263 nf_ct_refresh_acct(ct, ctinfo, skb,
264 ct->proto.gre.stream_timeout);
265 /* Also, more likely to be important, and not a probe. */
266 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
267 nf_conntrack_event_cache(IPCT_ASSURED, ct);
268 } else
269 nf_ct_refresh_acct(ct, ctinfo, skb,
270 ct->proto.gre.timeout);
271
272 return NF_ACCEPT;
273 }
274
275 /* Called when a new connection for this protocol found. */
gre_new(struct nf_conn * ct,const struct sk_buff * skb,unsigned int dataoff,unsigned int * timeouts)276 static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
277 unsigned int dataoff, unsigned int *timeouts)
278 {
279 pr_debug(": ");
280 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
281
282 /* initialize to sane value. Ideally a conntrack helper
283 * (e.g. in case of pptp) is increasing them */
284 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
285 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
286
287 return true;
288 }
289
290 /* Called when a conntrack entry has already been removed from the hashes
291 * and is about to be deleted from memory */
gre_destroy(struct nf_conn * ct)292 static void gre_destroy(struct nf_conn *ct)
293 {
294 struct nf_conn *master = ct->master;
295 pr_debug(" entering\n");
296
297 if (!master)
298 pr_debug("no master !?!\n");
299 else
300 nf_ct_gre_keymap_destroy(master);
301 }
302
303 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
304
305 #include <linux/netfilter/nfnetlink.h>
306 #include <linux/netfilter/nfnetlink_cttimeout.h>
307
gre_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)308 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
309 struct net *net, void *data)
310 {
311 unsigned int *timeouts = data;
312 struct netns_proto_gre *net_gre = gre_pernet(net);
313
314 /* set default timeouts for GRE. */
315 timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED];
316 timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED];
317
318 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
319 timeouts[GRE_CT_UNREPLIED] =
320 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
321 }
322 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
323 timeouts[GRE_CT_REPLIED] =
324 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
325 }
326 return 0;
327 }
328
329 static int
gre_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)330 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
331 {
332 const unsigned int *timeouts = data;
333
334 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
335 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
336 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
337 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
338 goto nla_put_failure;
339 return 0;
340
341 nla_put_failure:
342 return -ENOSPC;
343 }
344
345 static const struct nla_policy
346 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
347 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
348 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
349 };
350 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
351
gre_init_net(struct net * net,u_int16_t proto)352 static int gre_init_net(struct net *net, u_int16_t proto)
353 {
354 struct netns_proto_gre *net_gre = gre_pernet(net);
355 int i;
356
357 rwlock_init(&net_gre->keymap_lock);
358 INIT_LIST_HEAD(&net_gre->keymap_list);
359 for (i = 0; i < GRE_CT_MAX; i++)
360 net_gre->gre_timeouts[i] = gre_timeouts[i];
361
362 return 0;
363 }
364
365 /* protocol helper struct */
366 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
367 .l3proto = AF_INET,
368 .l4proto = IPPROTO_GRE,
369 .name = "gre",
370 .pkt_to_tuple = gre_pkt_to_tuple,
371 .invert_tuple = gre_invert_tuple,
372 .print_tuple = gre_print_tuple,
373 .print_conntrack = gre_print_conntrack,
374 .get_timeouts = gre_get_timeouts,
375 .packet = gre_packet,
376 .new = gre_new,
377 .destroy = gre_destroy,
378 .me = THIS_MODULE,
379 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
380 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
381 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
382 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
383 .nla_policy = nf_ct_port_nla_policy,
384 #endif
385 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
386 .ctnl_timeout = {
387 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
388 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
389 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
390 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
391 .nla_policy = gre_timeout_nla_policy,
392 },
393 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
394 .net_id = &proto_gre_net_id,
395 .init_net = gre_init_net,
396 };
397
proto_gre_net_init(struct net * net)398 static int proto_gre_net_init(struct net *net)
399 {
400 int ret = 0;
401 ret = nf_ct_l4proto_pernet_register(net, &nf_conntrack_l4proto_gre4);
402 if (ret < 0)
403 pr_err("nf_conntrack_gre4: pernet registration failed.\n");
404 return ret;
405 }
406
proto_gre_net_exit(struct net * net)407 static void proto_gre_net_exit(struct net *net)
408 {
409 nf_ct_l4proto_pernet_unregister(net, &nf_conntrack_l4proto_gre4);
410 nf_ct_gre_keymap_flush(net);
411 }
412
413 static struct pernet_operations proto_gre_net_ops = {
414 .init = proto_gre_net_init,
415 .exit = proto_gre_net_exit,
416 .id = &proto_gre_net_id,
417 .size = sizeof(struct netns_proto_gre),
418 };
419
nf_ct_proto_gre_init(void)420 static int __init nf_ct_proto_gre_init(void)
421 {
422 int ret;
423
424 ret = register_pernet_subsys(&proto_gre_net_ops);
425 if (ret < 0)
426 goto out_pernet;
427
428 ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_gre4);
429 if (ret < 0)
430 goto out_gre4;
431
432 return 0;
433 out_gre4:
434 unregister_pernet_subsys(&proto_gre_net_ops);
435 out_pernet:
436 return ret;
437 }
438
nf_ct_proto_gre_fini(void)439 static void __exit nf_ct_proto_gre_fini(void)
440 {
441 nf_ct_l4proto_unregister(&nf_conntrack_l4proto_gre4);
442 unregister_pernet_subsys(&proto_gre_net_ops);
443 }
444
445 module_init(nf_ct_proto_gre_init);
446 module_exit(nf_ct_proto_gre_fini);
447
448 MODULE_LICENSE("GPL");
449