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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 <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 int gre_print_tuple(struct seq_file *s, |
230 | const struct nf_conntrack_tuple *tuple) |
231 | { |
232 | return 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 int gre_print_conntrack(struct seq_file *s, struct nf_conn *ct) |
239 | { |
240 | return 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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