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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 | */ |
25 | |
26 | #include <linux/module.h> |
27 | #include <linux/types.h> |
28 | #include <linux/timer.h> |
29 | #include <linux/list.h> |
30 | #include <linux/seq_file.h> |
31 | #include <linux/in.h> |
32 | #include <linux/netdevice.h> |
33 | #include <linux/skbuff.h> |
34 | #include <linux/slab.h> |
35 | #include <net/dst.h> |
36 | #include <net/net_namespace.h> |
37 | #include <net/netns/generic.h> |
38 | #include <net/netfilter/nf_conntrack_l4proto.h> |
39 | #include <net/netfilter/nf_conntrack_helper.h> |
40 | #include <net/netfilter/nf_conntrack_core.h> |
41 | #include <linux/netfilter/nf_conntrack_proto_gre.h> |
42 | #include <linux/netfilter/nf_conntrack_pptp.h> |
43 | |
44 | #define GRE_TIMEOUT (30 * HZ) |
45 | #define GRE_STREAM_TIMEOUT (180 * HZ) |
46 | |
47 | static int proto_gre_net_id __read_mostly; |
48 | struct netns_proto_gre { |
49 | rwlock_t keymap_lock; |
50 | struct list_head keymap_list; |
51 | }; |
52 | |
53 | void nf_ct_gre_keymap_flush(struct net *net) |
54 | { |
55 | struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id); |
56 | struct nf_ct_gre_keymap *km, *tmp; |
57 | |
58 | write_lock_bh(&net_gre->keymap_lock); |
59 | list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) { |
60 | list_del(&km->list); |
61 | kfree(km); |
62 | } |
63 | write_unlock_bh(&net_gre->keymap_lock); |
64 | } |
65 | EXPORT_SYMBOL(nf_ct_gre_keymap_flush); |
66 | |
67 | static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km, |
68 | const struct nf_conntrack_tuple *t) |
69 | { |
70 | return km->tuple.src.l3num == t->src.l3num && |
71 | !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) && |
72 | !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) && |
73 | km->tuple.dst.protonum == t->dst.protonum && |
74 | km->tuple.dst.u.all == t->dst.u.all; |
75 | } |
76 | |
77 | /* look up the source key for a given tuple */ |
78 | static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t) |
79 | { |
80 | struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id); |
81 | struct nf_ct_gre_keymap *km; |
82 | __be16 key = 0; |
83 | |
84 | read_lock_bh(&net_gre->keymap_lock); |
85 | list_for_each_entry(km, &net_gre->keymap_list, list) { |
86 | if (gre_key_cmpfn(km, t)) { |
87 | key = km->tuple.src.u.gre.key; |
88 | break; |
89 | } |
90 | } |
91 | read_unlock_bh(&net_gre->keymap_lock); |
92 | |
93 | pr_debug("lookup src key 0x%x for ", key); |
94 | nf_ct_dump_tuple(t); |
95 | |
96 | return key; |
97 | } |
98 | |
99 | /* add a single keymap entry, associate with specified master ct */ |
100 | int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir, |
101 | struct nf_conntrack_tuple *t) |
102 | { |
103 | struct net *net = nf_ct_net(ct); |
104 | struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id); |
105 | struct nf_conn_help *help = nfct_help(ct); |
106 | struct nf_ct_gre_keymap **kmp, *km; |
107 | |
108 | kmp = &help->help.ct_pptp_info.keymap[dir]; |
109 | if (*kmp) { |
110 | /* check whether it's a retransmission */ |
111 | read_lock_bh(&net_gre->keymap_lock); |
112 | list_for_each_entry(km, &net_gre->keymap_list, list) { |
113 | if (gre_key_cmpfn(km, t) && km == *kmp) { |
114 | read_unlock_bh(&net_gre->keymap_lock); |
115 | return 0; |
116 | } |
117 | } |
118 | read_unlock_bh(&net_gre->keymap_lock); |
119 | pr_debug("trying to override keymap_%s for ct %p\n", |
120 | dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct); |
121 | return -EEXIST; |
122 | } |
123 | |
124 | km = kmalloc(sizeof(*km), GFP_ATOMIC); |
125 | if (!km) |
126 | return -ENOMEM; |
127 | memcpy(&km->tuple, t, sizeof(*t)); |
128 | *kmp = km; |
129 | |
130 | pr_debug("adding new entry %p: ", km); |
131 | nf_ct_dump_tuple(&km->tuple); |
132 | |
133 | write_lock_bh(&net_gre->keymap_lock); |
134 | list_add_tail(&km->list, &net_gre->keymap_list); |
135 | write_unlock_bh(&net_gre->keymap_lock); |
136 | |
137 | return 0; |
138 | } |
139 | EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add); |
140 | |
141 | /* destroy the keymap entries associated with specified master ct */ |
142 | void nf_ct_gre_keymap_destroy(struct nf_conn *ct) |
143 | { |
144 | struct net *net = nf_ct_net(ct); |
145 | struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id); |
146 | struct nf_conn_help *help = nfct_help(ct); |
147 | enum ip_conntrack_dir dir; |
148 | |
149 | pr_debug("entering for ct %p\n", ct); |
150 | |
151 | write_lock_bh(&net_gre->keymap_lock); |
152 | for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) { |
153 | if (help->help.ct_pptp_info.keymap[dir]) { |
154 | pr_debug("removing %p from list\n", |
155 | help->help.ct_pptp_info.keymap[dir]); |
156 | list_del(&help->help.ct_pptp_info.keymap[dir]->list); |
157 | kfree(help->help.ct_pptp_info.keymap[dir]); |
158 | help->help.ct_pptp_info.keymap[dir] = NULL; |
159 | } |
160 | } |
161 | write_unlock_bh(&net_gre->keymap_lock); |
162 | } |
163 | EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy); |
164 | |
165 | /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */ |
166 | |
167 | /* invert gre part of tuple */ |
168 | static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple, |
169 | const struct nf_conntrack_tuple *orig) |
170 | { |
171 | tuple->dst.u.gre.key = orig->src.u.gre.key; |
172 | tuple->src.u.gre.key = orig->dst.u.gre.key; |
173 | return true; |
174 | } |
175 | |
176 | /* gre hdr info to tuple */ |
177 | static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff, |
178 | struct nf_conntrack_tuple *tuple) |
179 | { |
180 | struct net *net = dev_net(skb->dev ? skb->dev : skb_dst(skb)->dev); |
181 | const struct gre_hdr_pptp *pgrehdr; |
182 | struct gre_hdr_pptp _pgrehdr; |
183 | __be16 srckey; |
184 | const struct gre_hdr *grehdr; |
185 | struct gre_hdr _grehdr; |
186 | |
187 | /* first only delinearize old RFC1701 GRE header */ |
188 | grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr); |
189 | if (!grehdr || grehdr->version != GRE_VERSION_PPTP) { |
190 | /* try to behave like "nf_conntrack_proto_generic" */ |
191 | tuple->src.u.all = 0; |
192 | tuple->dst.u.all = 0; |
193 | return true; |
194 | } |
195 | |
196 | /* PPTP header is variable length, only need up to the call_id field */ |
197 | pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr); |
198 | if (!pgrehdr) |
199 | return true; |
200 | |
201 | if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) { |
202 | pr_debug("GRE_VERSION_PPTP but unknown proto\n"); |
203 | return false; |
204 | } |
205 | |
206 | tuple->dst.u.gre.key = pgrehdr->call_id; |
207 | srckey = gre_keymap_lookup(net, tuple); |
208 | tuple->src.u.gre.key = srckey; |
209 | |
210 | return true; |
211 | } |
212 | |
213 | /* print gre part of tuple */ |
214 | static int gre_print_tuple(struct seq_file *s, |
215 | const struct nf_conntrack_tuple *tuple) |
216 | { |
217 | return seq_printf(s, "srckey=0x%x dstkey=0x%x ", |
218 | ntohs(tuple->src.u.gre.key), |
219 | ntohs(tuple->dst.u.gre.key)); |
220 | } |
221 | |
222 | /* print private data for conntrack */ |
223 | static int gre_print_conntrack(struct seq_file *s, struct nf_conn *ct) |
224 | { |
225 | return seq_printf(s, "timeout=%u, stream_timeout=%u ", |
226 | (ct->proto.gre.timeout / HZ), |
227 | (ct->proto.gre.stream_timeout / HZ)); |
228 | } |
229 | |
230 | /* Returns verdict for packet, and may modify conntrack */ |
231 | static int gre_packet(struct nf_conn *ct, |
232 | const struct sk_buff *skb, |
233 | unsigned int dataoff, |
234 | enum ip_conntrack_info ctinfo, |
235 | u_int8_t pf, |
236 | unsigned int hooknum) |
237 | { |
238 | /* If we've seen traffic both ways, this is a GRE connection. |
239 | * Extend timeout. */ |
240 | if (ct->status & IPS_SEEN_REPLY) { |
241 | nf_ct_refresh_acct(ct, ctinfo, skb, |
242 | ct->proto.gre.stream_timeout); |
243 | /* Also, more likely to be important, and not a probe. */ |
244 | set_bit(IPS_ASSURED_BIT, &ct->status); |
245 | nf_conntrack_event_cache(IPCT_ASSURED, ct); |
246 | } else |
247 | nf_ct_refresh_acct(ct, ctinfo, skb, |
248 | ct->proto.gre.timeout); |
249 | |
250 | return NF_ACCEPT; |
251 | } |
252 | |
253 | /* Called when a new connection for this protocol found. */ |
254 | static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb, |
255 | unsigned int dataoff) |
256 | { |
257 | pr_debug(": "); |
258 | nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); |
259 | |
260 | /* initialize to sane value. Ideally a conntrack helper |
261 | * (e.g. in case of pptp) is increasing them */ |
262 | ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT; |
263 | ct->proto.gre.timeout = GRE_TIMEOUT; |
264 | |
265 | return true; |
266 | } |
267 | |
268 | /* Called when a conntrack entry has already been removed from the hashes |
269 | * and is about to be deleted from memory */ |
270 | static void gre_destroy(struct nf_conn *ct) |
271 | { |
272 | struct nf_conn *master = ct->master; |
273 | pr_debug(" entering\n"); |
274 | |
275 | if (!master) |
276 | pr_debug("no master !?!\n"); |
277 | else |
278 | nf_ct_gre_keymap_destroy(master); |
279 | } |
280 | |
281 | /* protocol helper struct */ |
282 | static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = { |
283 | .l3proto = AF_INET, |
284 | .l4proto = IPPROTO_GRE, |
285 | .name = "gre", |
286 | .pkt_to_tuple = gre_pkt_to_tuple, |
287 | .invert_tuple = gre_invert_tuple, |
288 | .print_tuple = gre_print_tuple, |
289 | .print_conntrack = gre_print_conntrack, |
290 | .packet = gre_packet, |
291 | .new = gre_new, |
292 | .destroy = gre_destroy, |
293 | .me = THIS_MODULE, |
294 | #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE) |
295 | .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr, |
296 | .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size, |
297 | .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple, |
298 | .nla_policy = nf_ct_port_nla_policy, |
299 | #endif |
300 | }; |
301 | |
302 | static int proto_gre_net_init(struct net *net) |
303 | { |
304 | struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id); |
305 | |
306 | rwlock_init(&net_gre->keymap_lock); |
307 | INIT_LIST_HEAD(&net_gre->keymap_list); |
308 | |
309 | return 0; |
310 | } |
311 | |
312 | static void proto_gre_net_exit(struct net *net) |
313 | { |
314 | nf_ct_gre_keymap_flush(net); |
315 | } |
316 | |
317 | static struct pernet_operations proto_gre_net_ops = { |
318 | .init = proto_gre_net_init, |
319 | .exit = proto_gre_net_exit, |
320 | .id = &proto_gre_net_id, |
321 | .size = sizeof(struct netns_proto_gre), |
322 | }; |
323 | |
324 | static int __init nf_ct_proto_gre_init(void) |
325 | { |
326 | int rv; |
327 | |
328 | rv = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4); |
329 | if (rv < 0) |
330 | return rv; |
331 | rv = register_pernet_subsys(&proto_gre_net_ops); |
332 | if (rv < 0) |
333 | nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4); |
334 | return rv; |
335 | } |
336 | |
337 | static void __exit nf_ct_proto_gre_fini(void) |
338 | { |
339 | nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4); |
340 | unregister_pernet_subsys(&proto_gre_net_ops); |
341 | } |
342 | |
343 | module_init(nf_ct_proto_gre_init); |
344 | module_exit(nf_ct_proto_gre_fini); |
345 | |
346 | MODULE_LICENSE("GPL"); |
347 |
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