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Linux/net/netfilter/nf_conntrack_proto_gre.c

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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 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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