[NETFILTER]: nf_conntrack: introduce expectation classes and policies
[linux-2.6.git] / net / netfilter / nf_conntrack_pptp.c
1 /*
2  * Connection tracking support for PPTP (Point to Point Tunneling Protocol).
3  * PPTP is a a protocol for creating virtual private networks.
4  * It is a specification defined by Microsoft and some vendors
5  * working with Microsoft.  PPTP is built on top of a modified
6  * version of the Internet Generic Routing Encapsulation Protocol.
7  * GRE is defined in RFC 1701 and RFC 1702.  Documentation of
8  * PPTP can be found in RFC 2637
9  *
10  * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
11  *
12  * Development of this code funded by Astaro AG (http://www.astaro.com/)
13  *
14  * Limitations:
15  *       - We blindly assume that control connections are always
16  *         established in PNS->PAC direction.  This is a violation
17  *         of RFFC2673
18  *       - We can only support one single call within each session
19  * TODO:
20  *       - testing of incoming PPTP calls
21  */
22
23 #include <linux/module.h>
24 #include <linux/skbuff.h>
25 #include <linux/in.h>
26 #include <linux/tcp.h>
27
28 #include <net/netfilter/nf_conntrack.h>
29 #include <net/netfilter/nf_conntrack_core.h>
30 #include <net/netfilter/nf_conntrack_helper.h>
31 #include <linux/netfilter/nf_conntrack_proto_gre.h>
32 #include <linux/netfilter/nf_conntrack_pptp.h>
33
34 #define NF_CT_PPTP_VERSION "3.1"
35
36 MODULE_LICENSE("GPL");
37 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
38 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
39 MODULE_ALIAS("ip_conntrack_pptp");
40
41 static DEFINE_SPINLOCK(nf_pptp_lock);
42
43 int
44 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
45                              struct nf_conn *ct, enum ip_conntrack_info ctinfo,
46                              struct PptpControlHeader *ctlh,
47                              union pptp_ctrl_union *pptpReq) __read_mostly;
48 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
49
50 int
51 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
52                             struct nf_conn *ct, enum ip_conntrack_info ctinfo,
53                             struct PptpControlHeader *ctlh,
54                             union pptp_ctrl_union *pptpReq) __read_mostly;
55 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
56
57 void
58 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
59                             struct nf_conntrack_expect *expect_reply)
60                             __read_mostly;
61 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
62
63 void
64 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
65                              struct nf_conntrack_expect *exp) __read_mostly;
66 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
67
68 #ifdef DEBUG
69 /* PptpControlMessageType names */
70 const char *const pptp_msg_name[] = {
71         "UNKNOWN_MESSAGE",
72         "START_SESSION_REQUEST",
73         "START_SESSION_REPLY",
74         "STOP_SESSION_REQUEST",
75         "STOP_SESSION_REPLY",
76         "ECHO_REQUEST",
77         "ECHO_REPLY",
78         "OUT_CALL_REQUEST",
79         "OUT_CALL_REPLY",
80         "IN_CALL_REQUEST",
81         "IN_CALL_REPLY",
82         "IN_CALL_CONNECT",
83         "CALL_CLEAR_REQUEST",
84         "CALL_DISCONNECT_NOTIFY",
85         "WAN_ERROR_NOTIFY",
86         "SET_LINK_INFO"
87 };
88 EXPORT_SYMBOL(pptp_msg_name);
89 #endif
90
91 #define SECS *HZ
92 #define MINS * 60 SECS
93 #define HOURS * 60 MINS
94
95 #define PPTP_GRE_TIMEOUT                (10 MINS)
96 #define PPTP_GRE_STREAM_TIMEOUT         (5 HOURS)
97
98 static void pptp_expectfn(struct nf_conn *ct,
99                          struct nf_conntrack_expect *exp)
100 {
101         typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
102         pr_debug("increasing timeouts\n");
103
104         /* increase timeout of GRE data channel conntrack entry */
105         ct->proto.gre.timeout        = PPTP_GRE_TIMEOUT;
106         ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
107
108         /* Can you see how rusty this code is, compared with the pre-2.6.11
109          * one? That's what happened to my shiny newnat of 2002 ;( -HW */
110
111         rcu_read_lock();
112         nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
113         if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
114                 nf_nat_pptp_expectfn(ct, exp);
115         else {
116                 struct nf_conntrack_tuple inv_t;
117                 struct nf_conntrack_expect *exp_other;
118
119                 /* obviously this tuple inversion only works until you do NAT */
120                 nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
121                 pr_debug("trying to unexpect other dir: ");
122                 NF_CT_DUMP_TUPLE(&inv_t);
123
124                 exp_other = nf_ct_expect_find_get(&inv_t);
125                 if (exp_other) {
126                         /* delete other expectation.  */
127                         pr_debug("found\n");
128                         nf_ct_unexpect_related(exp_other);
129                         nf_ct_expect_put(exp_other);
130                 } else {
131                         pr_debug("not found\n");
132                 }
133         }
134         rcu_read_unlock();
135 }
136
137 static int destroy_sibling_or_exp(const struct nf_conntrack_tuple *t)
138 {
139         const struct nf_conntrack_tuple_hash *h;
140         struct nf_conntrack_expect *exp;
141         struct nf_conn *sibling;
142
143         pr_debug("trying to timeout ct or exp for tuple ");
144         NF_CT_DUMP_TUPLE(t);
145
146         h = nf_conntrack_find_get(t);
147         if (h)  {
148                 sibling = nf_ct_tuplehash_to_ctrack(h);
149                 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
150                 sibling->proto.gre.timeout        = 0;
151                 sibling->proto.gre.stream_timeout = 0;
152                 if (del_timer(&sibling->timeout))
153                         sibling->timeout.function((unsigned long)sibling);
154                 nf_ct_put(sibling);
155                 return 1;
156         } else {
157                 exp = nf_ct_expect_find_get(t);
158                 if (exp) {
159                         pr_debug("unexpect_related of expect %p\n", exp);
160                         nf_ct_unexpect_related(exp);
161                         nf_ct_expect_put(exp);
162                         return 1;
163                 }
164         }
165         return 0;
166 }
167
168 /* timeout GRE data connections */
169 static void pptp_destroy_siblings(struct nf_conn *ct)
170 {
171         const struct nf_conn_help *help = nfct_help(ct);
172         struct nf_conntrack_tuple t;
173
174         nf_ct_gre_keymap_destroy(ct);
175
176         /* try original (pns->pac) tuple */
177         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
178         t.dst.protonum = IPPROTO_GRE;
179         t.src.u.gre.key = help->help.ct_pptp_info.pns_call_id;
180         t.dst.u.gre.key = help->help.ct_pptp_info.pac_call_id;
181         if (!destroy_sibling_or_exp(&t))
182                 pr_debug("failed to timeout original pns->pac ct/exp\n");
183
184         /* try reply (pac->pns) tuple */
185         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
186         t.dst.protonum = IPPROTO_GRE;
187         t.src.u.gre.key = help->help.ct_pptp_info.pac_call_id;
188         t.dst.u.gre.key = help->help.ct_pptp_info.pns_call_id;
189         if (!destroy_sibling_or_exp(&t))
190                 pr_debug("failed to timeout reply pac->pns ct/exp\n");
191 }
192
193 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
194 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
195 {
196         struct nf_conntrack_expect *exp_orig, *exp_reply;
197         enum ip_conntrack_dir dir;
198         int ret = 1;
199         typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
200
201         exp_orig = nf_ct_expect_alloc(ct);
202         if (exp_orig == NULL)
203                 goto out;
204
205         exp_reply = nf_ct_expect_alloc(ct);
206         if (exp_reply == NULL)
207                 goto out_put_orig;
208
209         /* original direction, PNS->PAC */
210         dir = IP_CT_DIR_ORIGINAL;
211         nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
212                           ct->tuplehash[dir].tuple.src.l3num,
213                           &ct->tuplehash[dir].tuple.src.u3,
214                           &ct->tuplehash[dir].tuple.dst.u3,
215                           IPPROTO_GRE, &peer_callid, &callid);
216         exp_orig->expectfn = pptp_expectfn;
217
218         /* reply direction, PAC->PNS */
219         dir = IP_CT_DIR_REPLY;
220         nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
221                           ct->tuplehash[dir].tuple.src.l3num,
222                           &ct->tuplehash[dir].tuple.src.u3,
223                           &ct->tuplehash[dir].tuple.dst.u3,
224                           IPPROTO_GRE, &callid, &peer_callid);
225         exp_reply->expectfn = pptp_expectfn;
226
227         nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
228         if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
229                 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
230         if (nf_ct_expect_related(exp_orig) != 0)
231                 goto out_put_both;
232         if (nf_ct_expect_related(exp_reply) != 0)
233                 goto out_unexpect_orig;
234
235         /* Add GRE keymap entries */
236         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
237                 goto out_unexpect_both;
238         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
239                 nf_ct_gre_keymap_destroy(ct);
240                 goto out_unexpect_both;
241         }
242         ret = 0;
243
244 out_put_both:
245         nf_ct_expect_put(exp_reply);
246 out_put_orig:
247         nf_ct_expect_put(exp_orig);
248 out:
249         return ret;
250
251 out_unexpect_both:
252         nf_ct_unexpect_related(exp_reply);
253 out_unexpect_orig:
254         nf_ct_unexpect_related(exp_orig);
255         goto out_put_both;
256 }
257
258 static inline int
259 pptp_inbound_pkt(struct sk_buff *skb,
260                  struct PptpControlHeader *ctlh,
261                  union pptp_ctrl_union *pptpReq,
262                  unsigned int reqlen,
263                  struct nf_conn *ct,
264                  enum ip_conntrack_info ctinfo)
265 {
266         struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
267         u_int16_t msg;
268         __be16 cid = 0, pcid = 0;
269         typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
270
271         msg = ntohs(ctlh->messageType);
272         pr_debug("inbound control message %s\n", pptp_msg_name[msg]);
273
274         switch (msg) {
275         case PPTP_START_SESSION_REPLY:
276                 /* server confirms new control session */
277                 if (info->sstate < PPTP_SESSION_REQUESTED)
278                         goto invalid;
279                 if (pptpReq->srep.resultCode == PPTP_START_OK)
280                         info->sstate = PPTP_SESSION_CONFIRMED;
281                 else
282                         info->sstate = PPTP_SESSION_ERROR;
283                 break;
284
285         case PPTP_STOP_SESSION_REPLY:
286                 /* server confirms end of control session */
287                 if (info->sstate > PPTP_SESSION_STOPREQ)
288                         goto invalid;
289                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
290                         info->sstate = PPTP_SESSION_NONE;
291                 else
292                         info->sstate = PPTP_SESSION_ERROR;
293                 break;
294
295         case PPTP_OUT_CALL_REPLY:
296                 /* server accepted call, we now expect GRE frames */
297                 if (info->sstate != PPTP_SESSION_CONFIRMED)
298                         goto invalid;
299                 if (info->cstate != PPTP_CALL_OUT_REQ &&
300                     info->cstate != PPTP_CALL_OUT_CONF)
301                         goto invalid;
302
303                 cid = pptpReq->ocack.callID;
304                 pcid = pptpReq->ocack.peersCallID;
305                 if (info->pns_call_id != pcid)
306                         goto invalid;
307                 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
308                          ntohs(cid), ntohs(pcid));
309
310                 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
311                         info->cstate = PPTP_CALL_OUT_CONF;
312                         info->pac_call_id = cid;
313                         exp_gre(ct, cid, pcid);
314                 } else
315                         info->cstate = PPTP_CALL_NONE;
316                 break;
317
318         case PPTP_IN_CALL_REQUEST:
319                 /* server tells us about incoming call request */
320                 if (info->sstate != PPTP_SESSION_CONFIRMED)
321                         goto invalid;
322
323                 cid = pptpReq->icreq.callID;
324                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
325                 info->cstate = PPTP_CALL_IN_REQ;
326                 info->pac_call_id = cid;
327                 break;
328
329         case PPTP_IN_CALL_CONNECT:
330                 /* server tells us about incoming call established */
331                 if (info->sstate != PPTP_SESSION_CONFIRMED)
332                         goto invalid;
333                 if (info->cstate != PPTP_CALL_IN_REP &&
334                     info->cstate != PPTP_CALL_IN_CONF)
335                         goto invalid;
336
337                 pcid = pptpReq->iccon.peersCallID;
338                 cid = info->pac_call_id;
339
340                 if (info->pns_call_id != pcid)
341                         goto invalid;
342
343                 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
344                 info->cstate = PPTP_CALL_IN_CONF;
345
346                 /* we expect a GRE connection from PAC to PNS */
347                 exp_gre(ct, cid, pcid);
348                 break;
349
350         case PPTP_CALL_DISCONNECT_NOTIFY:
351                 /* server confirms disconnect */
352                 cid = pptpReq->disc.callID;
353                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
354                 info->cstate = PPTP_CALL_NONE;
355
356                 /* untrack this call id, unexpect GRE packets */
357                 pptp_destroy_siblings(ct);
358                 break;
359
360         case PPTP_WAN_ERROR_NOTIFY:
361         case PPTP_ECHO_REQUEST:
362         case PPTP_ECHO_REPLY:
363                 /* I don't have to explain these ;) */
364                 break;
365
366         default:
367                 goto invalid;
368         }
369
370         nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
371         if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
372                 return nf_nat_pptp_inbound(skb, ct, ctinfo, ctlh, pptpReq);
373         return NF_ACCEPT;
374
375 invalid:
376         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
377                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
378                  msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
379                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
380                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
381         return NF_ACCEPT;
382 }
383
384 static inline int
385 pptp_outbound_pkt(struct sk_buff *skb,
386                   struct PptpControlHeader *ctlh,
387                   union pptp_ctrl_union *pptpReq,
388                   unsigned int reqlen,
389                   struct nf_conn *ct,
390                   enum ip_conntrack_info ctinfo)
391 {
392         struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
393         u_int16_t msg;
394         __be16 cid = 0, pcid = 0;
395         typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
396
397         msg = ntohs(ctlh->messageType);
398         pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
399
400         switch (msg) {
401         case PPTP_START_SESSION_REQUEST:
402                 /* client requests for new control session */
403                 if (info->sstate != PPTP_SESSION_NONE)
404                         goto invalid;
405                 info->sstate = PPTP_SESSION_REQUESTED;
406                 break;
407
408         case PPTP_STOP_SESSION_REQUEST:
409                 /* client requests end of control session */
410                 info->sstate = PPTP_SESSION_STOPREQ;
411                 break;
412
413         case PPTP_OUT_CALL_REQUEST:
414                 /* client initiating connection to server */
415                 if (info->sstate != PPTP_SESSION_CONFIRMED)
416                         goto invalid;
417                 info->cstate = PPTP_CALL_OUT_REQ;
418                 /* track PNS call id */
419                 cid = pptpReq->ocreq.callID;
420                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
421                 info->pns_call_id = cid;
422                 break;
423
424         case PPTP_IN_CALL_REPLY:
425                 /* client answers incoming call */
426                 if (info->cstate != PPTP_CALL_IN_REQ &&
427                     info->cstate != PPTP_CALL_IN_REP)
428                         goto invalid;
429
430                 cid = pptpReq->icack.callID;
431                 pcid = pptpReq->icack.peersCallID;
432                 if (info->pac_call_id != pcid)
433                         goto invalid;
434                 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
435                          ntohs(cid), ntohs(pcid));
436
437                 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
438                         /* part two of the three-way handshake */
439                         info->cstate = PPTP_CALL_IN_REP;
440                         info->pns_call_id = cid;
441                 } else
442                         info->cstate = PPTP_CALL_NONE;
443                 break;
444
445         case PPTP_CALL_CLEAR_REQUEST:
446                 /* client requests hangup of call */
447                 if (info->sstate != PPTP_SESSION_CONFIRMED)
448                         goto invalid;
449                 /* FUTURE: iterate over all calls and check if
450                  * call ID is valid.  We don't do this without newnat,
451                  * because we only know about last call */
452                 info->cstate = PPTP_CALL_CLEAR_REQ;
453                 break;
454
455         case PPTP_SET_LINK_INFO:
456         case PPTP_ECHO_REQUEST:
457         case PPTP_ECHO_REPLY:
458                 /* I don't have to explain these ;) */
459                 break;
460
461         default:
462                 goto invalid;
463         }
464
465         nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
466         if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
467                 return nf_nat_pptp_outbound(skb, ct, ctinfo, ctlh, pptpReq);
468         return NF_ACCEPT;
469
470 invalid:
471         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
472                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
473                  msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
474                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
475                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
476         return NF_ACCEPT;
477 }
478
479 static const unsigned int pptp_msg_size[] = {
480         [PPTP_START_SESSION_REQUEST]  = sizeof(struct PptpStartSessionRequest),
481         [PPTP_START_SESSION_REPLY]    = sizeof(struct PptpStartSessionReply),
482         [PPTP_STOP_SESSION_REQUEST]   = sizeof(struct PptpStopSessionRequest),
483         [PPTP_STOP_SESSION_REPLY]     = sizeof(struct PptpStopSessionReply),
484         [PPTP_OUT_CALL_REQUEST]       = sizeof(struct PptpOutCallRequest),
485         [PPTP_OUT_CALL_REPLY]         = sizeof(struct PptpOutCallReply),
486         [PPTP_IN_CALL_REQUEST]        = sizeof(struct PptpInCallRequest),
487         [PPTP_IN_CALL_REPLY]          = sizeof(struct PptpInCallReply),
488         [PPTP_IN_CALL_CONNECT]        = sizeof(struct PptpInCallConnected),
489         [PPTP_CALL_CLEAR_REQUEST]     = sizeof(struct PptpClearCallRequest),
490         [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
491         [PPTP_WAN_ERROR_NOTIFY]       = sizeof(struct PptpWanErrorNotify),
492         [PPTP_SET_LINK_INFO]          = sizeof(struct PptpSetLinkInfo),
493 };
494
495 /* track caller id inside control connection, call expect_related */
496 static int
497 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
498                     struct nf_conn *ct, enum ip_conntrack_info ctinfo)
499
500 {
501         int dir = CTINFO2DIR(ctinfo);
502         const struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
503         const struct tcphdr *tcph;
504         struct tcphdr _tcph;
505         const struct pptp_pkt_hdr *pptph;
506         struct pptp_pkt_hdr _pptph;
507         struct PptpControlHeader _ctlh, *ctlh;
508         union pptp_ctrl_union _pptpReq, *pptpReq;
509         unsigned int tcplen = skb->len - protoff;
510         unsigned int datalen, reqlen, nexthdr_off;
511         int oldsstate, oldcstate;
512         int ret;
513         u_int16_t msg;
514
515         /* don't do any tracking before tcp handshake complete */
516         if (ctinfo != IP_CT_ESTABLISHED &&
517             ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
518                 return NF_ACCEPT;
519
520         nexthdr_off = protoff;
521         tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
522         BUG_ON(!tcph);
523         nexthdr_off += tcph->doff * 4;
524         datalen = tcplen - tcph->doff * 4;
525
526         pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
527         if (!pptph) {
528                 pr_debug("no full PPTP header, can't track\n");
529                 return NF_ACCEPT;
530         }
531         nexthdr_off += sizeof(_pptph);
532         datalen -= sizeof(_pptph);
533
534         /* if it's not a control message we can't do anything with it */
535         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
536             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
537                 pr_debug("not a control packet\n");
538                 return NF_ACCEPT;
539         }
540
541         ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
542         if (!ctlh)
543                 return NF_ACCEPT;
544         nexthdr_off += sizeof(_ctlh);
545         datalen -= sizeof(_ctlh);
546
547         reqlen = datalen;
548         msg = ntohs(ctlh->messageType);
549         if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
550                 return NF_ACCEPT;
551         if (reqlen > sizeof(*pptpReq))
552                 reqlen = sizeof(*pptpReq);
553
554         pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
555         if (!pptpReq)
556                 return NF_ACCEPT;
557
558         oldsstate = info->sstate;
559         oldcstate = info->cstate;
560
561         spin_lock_bh(&nf_pptp_lock);
562
563         /* FIXME: We just blindly assume that the control connection is always
564          * established from PNS->PAC.  However, RFC makes no guarantee */
565         if (dir == IP_CT_DIR_ORIGINAL)
566                 /* client -> server (PNS -> PAC) */
567                 ret = pptp_outbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
568                                         ctinfo);
569         else
570                 /* server -> client (PAC -> PNS) */
571                 ret = pptp_inbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
572                                        ctinfo);
573         pr_debug("sstate: %d->%d, cstate: %d->%d\n",
574                  oldsstate, info->sstate, oldcstate, info->cstate);
575         spin_unlock_bh(&nf_pptp_lock);
576
577         return ret;
578 }
579
580 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
581         .max_expected   = 2,
582         .timeout        = 5 * 60,
583 };
584
585 /* control protocol helper */
586 static struct nf_conntrack_helper pptp __read_mostly = {
587         .name                   = "pptp",
588         .me                     = THIS_MODULE,
589         .tuple.src.l3num        = AF_INET,
590         .tuple.src.u.tcp.port   = __constant_htons(PPTP_CONTROL_PORT),
591         .tuple.dst.protonum     = IPPROTO_TCP,
592         .help                   = conntrack_pptp_help,
593         .destroy                = pptp_destroy_siblings,
594         .expect_policy          = &pptp_exp_policy,
595 };
596
597 static int __init nf_conntrack_pptp_init(void)
598 {
599         return nf_conntrack_helper_register(&pptp);
600 }
601
602 static void __exit nf_conntrack_pptp_fini(void)
603 {
604         nf_conntrack_helper_unregister(&pptp);
605         nf_ct_gre_keymap_flush();
606 }
607
608 module_init(nf_conntrack_pptp_init);
609 module_exit(nf_conntrack_pptp_fini);