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25#include <linux/module.h>
26#include <linux/skbuff.h>
27#include <linux/in.h>
28#include <linux/tcp.h>
29
30#include <net/netfilter/nf_conntrack.h>
31#include <net/netfilter/nf_conntrack_core.h>
32#include <net/netfilter/nf_conntrack_helper.h>
33#include <net/netfilter/nf_conntrack_zones.h>
34#include <linux/netfilter/nf_conntrack_proto_gre.h>
35#include <linux/netfilter/nf_conntrack_pptp.h>
36
37#define NF_CT_PPTP_VERSION "3.1"
38
39MODULE_LICENSE("GPL");
40MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
41MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
42MODULE_ALIAS("ip_conntrack_pptp");
43MODULE_ALIAS_NFCT_HELPER("pptp");
44
45static DEFINE_SPINLOCK(nf_pptp_lock);
46
47int
48(*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
49 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
50 unsigned int protoff, struct PptpControlHeader *ctlh,
51 union pptp_ctrl_union *pptpReq) __read_mostly;
52EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
53
54int
55(*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
56 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
57 unsigned int protoff, struct PptpControlHeader *ctlh,
58 union pptp_ctrl_union *pptpReq) __read_mostly;
59EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
60
61void
62(*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
63 struct nf_conntrack_expect *expect_reply)
64 __read_mostly;
65EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
66
67void
68(*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
69 struct nf_conntrack_expect *exp) __read_mostly;
70EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
71
72#if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
73
74const char *const pptp_msg_name[] = {
75 "UNKNOWN_MESSAGE",
76 "START_SESSION_REQUEST",
77 "START_SESSION_REPLY",
78 "STOP_SESSION_REQUEST",
79 "STOP_SESSION_REPLY",
80 "ECHO_REQUEST",
81 "ECHO_REPLY",
82 "OUT_CALL_REQUEST",
83 "OUT_CALL_REPLY",
84 "IN_CALL_REQUEST",
85 "IN_CALL_REPLY",
86 "IN_CALL_CONNECT",
87 "CALL_CLEAR_REQUEST",
88 "CALL_DISCONNECT_NOTIFY",
89 "WAN_ERROR_NOTIFY",
90 "SET_LINK_INFO"
91};
92EXPORT_SYMBOL(pptp_msg_name);
93#endif
94
95#define SECS *HZ
96#define MINS * 60 SECS
97#define HOURS * 60 MINS
98
99#define PPTP_GRE_TIMEOUT (10 MINS)
100#define PPTP_GRE_STREAM_TIMEOUT (5 HOURS)
101
102static void pptp_expectfn(struct nf_conn *ct,
103 struct nf_conntrack_expect *exp)
104{
105 struct net *net = nf_ct_net(ct);
106 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
107 pr_debug("increasing timeouts\n");
108
109
110 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
111 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
112
113
114
115
116 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
117 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
118 nf_nat_pptp_expectfn(ct, exp);
119 else {
120 struct nf_conntrack_tuple inv_t;
121 struct nf_conntrack_expect *exp_other;
122
123
124 nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
125 pr_debug("trying to unexpect other dir: ");
126 nf_ct_dump_tuple(&inv_t);
127
128 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t);
129 if (exp_other) {
130
131 pr_debug("found\n");
132 nf_ct_unexpect_related(exp_other);
133 nf_ct_expect_put(exp_other);
134 } else {
135 pr_debug("not found\n");
136 }
137 }
138}
139
140static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
141 const struct nf_conntrack_tuple *t)
142{
143 const struct nf_conntrack_tuple_hash *h;
144 const struct nf_conntrack_zone *zone;
145 struct nf_conntrack_expect *exp;
146 struct nf_conn *sibling;
147
148 pr_debug("trying to timeout ct or exp for tuple ");
149 nf_ct_dump_tuple(t);
150
151 zone = nf_ct_zone(ct);
152 h = nf_conntrack_find_get(net, zone, t);
153 if (h) {
154 sibling = nf_ct_tuplehash_to_ctrack(h);
155 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
156 sibling->proto.gre.timeout = 0;
157 sibling->proto.gre.stream_timeout = 0;
158 nf_ct_kill(sibling);
159 nf_ct_put(sibling);
160 return 1;
161 } else {
162 exp = nf_ct_expect_find_get(net, zone, t);
163 if (exp) {
164 pr_debug("unexpect_related of expect %p\n", exp);
165 nf_ct_unexpect_related(exp);
166 nf_ct_expect_put(exp);
167 return 1;
168 }
169 }
170 return 0;
171}
172
173
174static void pptp_destroy_siblings(struct nf_conn *ct)
175{
176 struct net *net = nf_ct_net(ct);
177 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
178 struct nf_conntrack_tuple t;
179
180 nf_ct_gre_keymap_destroy(ct);
181
182
183 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
184 t.dst.protonum = IPPROTO_GRE;
185 t.src.u.gre.key = ct_pptp_info->pns_call_id;
186 t.dst.u.gre.key = ct_pptp_info->pac_call_id;
187 if (!destroy_sibling_or_exp(net, ct, &t))
188 pr_debug("failed to timeout original pns->pac ct/exp\n");
189
190
191 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
192 t.dst.protonum = IPPROTO_GRE;
193 t.src.u.gre.key = ct_pptp_info->pac_call_id;
194 t.dst.u.gre.key = ct_pptp_info->pns_call_id;
195 if (!destroy_sibling_or_exp(net, ct, &t))
196 pr_debug("failed to timeout reply pac->pns ct/exp\n");
197}
198
199
200static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
201{
202 struct nf_conntrack_expect *exp_orig, *exp_reply;
203 enum ip_conntrack_dir dir;
204 int ret = 1;
205 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
206
207 exp_orig = nf_ct_expect_alloc(ct);
208 if (exp_orig == NULL)
209 goto out;
210
211 exp_reply = nf_ct_expect_alloc(ct);
212 if (exp_reply == NULL)
213 goto out_put_orig;
214
215
216 dir = IP_CT_DIR_ORIGINAL;
217 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
218 nf_ct_l3num(ct),
219 &ct->tuplehash[dir].tuple.src.u3,
220 &ct->tuplehash[dir].tuple.dst.u3,
221 IPPROTO_GRE, &peer_callid, &callid);
222 exp_orig->expectfn = pptp_expectfn;
223
224
225 dir = IP_CT_DIR_REPLY;
226 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
227 nf_ct_l3num(ct),
228 &ct->tuplehash[dir].tuple.src.u3,
229 &ct->tuplehash[dir].tuple.dst.u3,
230 IPPROTO_GRE, &callid, &peer_callid);
231 exp_reply->expectfn = pptp_expectfn;
232
233 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
234 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
235 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
236 if (nf_ct_expect_related(exp_orig) != 0)
237 goto out_put_both;
238 if (nf_ct_expect_related(exp_reply) != 0)
239 goto out_unexpect_orig;
240
241
242 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
243 goto out_unexpect_both;
244 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
245 nf_ct_gre_keymap_destroy(ct);
246 goto out_unexpect_both;
247 }
248 ret = 0;
249
250out_put_both:
251 nf_ct_expect_put(exp_reply);
252out_put_orig:
253 nf_ct_expect_put(exp_orig);
254out:
255 return ret;
256
257out_unexpect_both:
258 nf_ct_unexpect_related(exp_reply);
259out_unexpect_orig:
260 nf_ct_unexpect_related(exp_orig);
261 goto out_put_both;
262}
263
264static int
265pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
266 struct PptpControlHeader *ctlh,
267 union pptp_ctrl_union *pptpReq,
268 unsigned int reqlen,
269 struct nf_conn *ct,
270 enum ip_conntrack_info ctinfo)
271{
272 struct nf_ct_pptp_master *info = nfct_help_data(ct);
273 u_int16_t msg;
274 __be16 cid = 0, pcid = 0;
275 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
276
277 msg = ntohs(ctlh->messageType);
278 pr_debug("inbound control message %s\n", pptp_msg_name[msg]);
279
280 switch (msg) {
281 case PPTP_START_SESSION_REPLY:
282
283 if (info->sstate < PPTP_SESSION_REQUESTED)
284 goto invalid;
285 if (pptpReq->srep.resultCode == PPTP_START_OK)
286 info->sstate = PPTP_SESSION_CONFIRMED;
287 else
288 info->sstate = PPTP_SESSION_ERROR;
289 break;
290
291 case PPTP_STOP_SESSION_REPLY:
292
293 if (info->sstate > PPTP_SESSION_STOPREQ)
294 goto invalid;
295 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
296 info->sstate = PPTP_SESSION_NONE;
297 else
298 info->sstate = PPTP_SESSION_ERROR;
299 break;
300
301 case PPTP_OUT_CALL_REPLY:
302
303 if (info->sstate != PPTP_SESSION_CONFIRMED)
304 goto invalid;
305 if (info->cstate != PPTP_CALL_OUT_REQ &&
306 info->cstate != PPTP_CALL_OUT_CONF)
307 goto invalid;
308
309 cid = pptpReq->ocack.callID;
310 pcid = pptpReq->ocack.peersCallID;
311 if (info->pns_call_id != pcid)
312 goto invalid;
313 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
314 ntohs(cid), ntohs(pcid));
315
316 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
317 info->cstate = PPTP_CALL_OUT_CONF;
318 info->pac_call_id = cid;
319 exp_gre(ct, cid, pcid);
320 } else
321 info->cstate = PPTP_CALL_NONE;
322 break;
323
324 case PPTP_IN_CALL_REQUEST:
325
326 if (info->sstate != PPTP_SESSION_CONFIRMED)
327 goto invalid;
328
329 cid = pptpReq->icreq.callID;
330 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
331 info->cstate = PPTP_CALL_IN_REQ;
332 info->pac_call_id = cid;
333 break;
334
335 case PPTP_IN_CALL_CONNECT:
336
337 if (info->sstate != PPTP_SESSION_CONFIRMED)
338 goto invalid;
339 if (info->cstate != PPTP_CALL_IN_REP &&
340 info->cstate != PPTP_CALL_IN_CONF)
341 goto invalid;
342
343 pcid = pptpReq->iccon.peersCallID;
344 cid = info->pac_call_id;
345
346 if (info->pns_call_id != pcid)
347 goto invalid;
348
349 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
350 info->cstate = PPTP_CALL_IN_CONF;
351
352
353 exp_gre(ct, cid, pcid);
354 break;
355
356 case PPTP_CALL_DISCONNECT_NOTIFY:
357
358 cid = pptpReq->disc.callID;
359 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
360 info->cstate = PPTP_CALL_NONE;
361
362
363 pptp_destroy_siblings(ct);
364 break;
365
366 case PPTP_WAN_ERROR_NOTIFY:
367 case PPTP_SET_LINK_INFO:
368 case PPTP_ECHO_REQUEST:
369 case PPTP_ECHO_REPLY:
370
371 break;
372
373 default:
374 goto invalid;
375 }
376
377 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
378 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
379 return nf_nat_pptp_inbound(skb, ct, ctinfo,
380 protoff, ctlh, pptpReq);
381 return NF_ACCEPT;
382
383invalid:
384 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
385 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
386 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
387 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
388 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
389 return NF_ACCEPT;
390}
391
392static int
393pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
394 struct PptpControlHeader *ctlh,
395 union pptp_ctrl_union *pptpReq,
396 unsigned int reqlen,
397 struct nf_conn *ct,
398 enum ip_conntrack_info ctinfo)
399{
400 struct nf_ct_pptp_master *info = nfct_help_data(ct);
401 u_int16_t msg;
402 __be16 cid = 0, pcid = 0;
403 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
404
405 msg = ntohs(ctlh->messageType);
406 pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
407
408 switch (msg) {
409 case PPTP_START_SESSION_REQUEST:
410
411 if (info->sstate != PPTP_SESSION_NONE)
412 goto invalid;
413 info->sstate = PPTP_SESSION_REQUESTED;
414 break;
415
416 case PPTP_STOP_SESSION_REQUEST:
417
418 info->sstate = PPTP_SESSION_STOPREQ;
419 break;
420
421 case PPTP_OUT_CALL_REQUEST:
422
423 if (info->sstate != PPTP_SESSION_CONFIRMED)
424 goto invalid;
425 info->cstate = PPTP_CALL_OUT_REQ;
426
427 cid = pptpReq->ocreq.callID;
428 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
429 info->pns_call_id = cid;
430 break;
431
432 case PPTP_IN_CALL_REPLY:
433
434 if (info->cstate != PPTP_CALL_IN_REQ &&
435 info->cstate != PPTP_CALL_IN_REP)
436 goto invalid;
437
438 cid = pptpReq->icack.callID;
439 pcid = pptpReq->icack.peersCallID;
440 if (info->pac_call_id != pcid)
441 goto invalid;
442 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
443 ntohs(cid), ntohs(pcid));
444
445 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
446
447 info->cstate = PPTP_CALL_IN_REP;
448 info->pns_call_id = cid;
449 } else
450 info->cstate = PPTP_CALL_NONE;
451 break;
452
453 case PPTP_CALL_CLEAR_REQUEST:
454
455 if (info->sstate != PPTP_SESSION_CONFIRMED)
456 goto invalid;
457
458
459
460 info->cstate = PPTP_CALL_CLEAR_REQ;
461 break;
462
463 case PPTP_SET_LINK_INFO:
464 case PPTP_ECHO_REQUEST:
465 case PPTP_ECHO_REPLY:
466
467 break;
468
469 default:
470 goto invalid;
471 }
472
473 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
474 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
475 return nf_nat_pptp_outbound(skb, ct, ctinfo,
476 protoff, ctlh, pptpReq);
477 return NF_ACCEPT;
478
479invalid:
480 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
481 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
482 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
483 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
484 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
485 return NF_ACCEPT;
486}
487
488static const unsigned int pptp_msg_size[] = {
489 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest),
490 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply),
491 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest),
492 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply),
493 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest),
494 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply),
495 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest),
496 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply),
497 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected),
498 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest),
499 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
500 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify),
501 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo),
502};
503
504
505static int
506conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
507 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
508
509{
510 int dir = CTINFO2DIR(ctinfo);
511 const struct nf_ct_pptp_master *info = nfct_help_data(ct);
512 const struct tcphdr *tcph;
513 struct tcphdr _tcph;
514 const struct pptp_pkt_hdr *pptph;
515 struct pptp_pkt_hdr _pptph;
516 struct PptpControlHeader _ctlh, *ctlh;
517 union pptp_ctrl_union _pptpReq, *pptpReq;
518 unsigned int tcplen = skb->len - protoff;
519 unsigned int datalen, reqlen, nexthdr_off;
520 int oldsstate, oldcstate;
521 int ret;
522 u_int16_t msg;
523
524#if IS_ENABLED(CONFIG_NF_NAT)
525 if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) {
526 struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);
527
528 if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC))
529 return NF_DROP;
530 }
531#endif
532
533 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
534 return NF_ACCEPT;
535
536 nexthdr_off = protoff;
537 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
538 BUG_ON(!tcph);
539 nexthdr_off += tcph->doff * 4;
540 datalen = tcplen - tcph->doff * 4;
541
542 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
543 if (!pptph) {
544 pr_debug("no full PPTP header, can't track\n");
545 return NF_ACCEPT;
546 }
547 nexthdr_off += sizeof(_pptph);
548 datalen -= sizeof(_pptph);
549
550
551 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
552 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
553 pr_debug("not a control packet\n");
554 return NF_ACCEPT;
555 }
556
557 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
558 if (!ctlh)
559 return NF_ACCEPT;
560 nexthdr_off += sizeof(_ctlh);
561 datalen -= sizeof(_ctlh);
562
563 reqlen = datalen;
564 msg = ntohs(ctlh->messageType);
565 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
566 return NF_ACCEPT;
567 if (reqlen > sizeof(*pptpReq))
568 reqlen = sizeof(*pptpReq);
569
570 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
571 if (!pptpReq)
572 return NF_ACCEPT;
573
574 oldsstate = info->sstate;
575 oldcstate = info->cstate;
576
577 spin_lock_bh(&nf_pptp_lock);
578
579
580
581 if (dir == IP_CT_DIR_ORIGINAL)
582
583 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
584 ctinfo);
585 else
586
587 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
588 ctinfo);
589 pr_debug("sstate: %d->%d, cstate: %d->%d\n",
590 oldsstate, info->sstate, oldcstate, info->cstate);
591 spin_unlock_bh(&nf_pptp_lock);
592
593 return ret;
594}
595
596static const struct nf_conntrack_expect_policy pptp_exp_policy = {
597 .max_expected = 2,
598 .timeout = 5 * 60,
599};
600
601
602static struct nf_conntrack_helper pptp __read_mostly = {
603 .name = "pptp",
604 .me = THIS_MODULE,
605 .tuple.src.l3num = AF_INET,
606 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT),
607 .tuple.dst.protonum = IPPROTO_TCP,
608 .help = conntrack_pptp_help,
609 .destroy = pptp_destroy_siblings,
610 .expect_policy = &pptp_exp_policy,
611};
612
613static int __init nf_conntrack_pptp_init(void)
614{
615 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master));
616
617 return nf_conntrack_helper_register(&pptp);
618}
619
620static void __exit nf_conntrack_pptp_fini(void)
621{
622 nf_conntrack_helper_unregister(&pptp);
623}
624
625module_init(nf_conntrack_pptp_init);
626module_exit(nf_conntrack_pptp_fini);
627
