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
10 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
12 * Development of this code funded by Astaro AG (http://www.astaro.com/)
14 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
17 * - We blindly assume that control connections are always
18 * established in PNS->PAC direction. This is a violation
20 * - We can only support one single call within each session
22 * - testing of incoming PPTP calls
25 #include <linux/module.h>
26 #include <linux/skbuff.h>
28 #include <linux/tcp.h>
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>
37 #define NF_CT_PPTP_VERSION "3.1"
39 MODULE_LICENSE("GPL");
40 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
41 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
42 MODULE_ALIAS("ip_conntrack_pptp");
43 MODULE_ALIAS_NFCT_HELPER("pptp");
45 static DEFINE_SPINLOCK(nf_pptp_lock);
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;
52 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
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;
59 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
62 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
63 struct nf_conntrack_expect *expect_reply)
65 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
68 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
69 struct nf_conntrack_expect *exp) __read_mostly;
70 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
72 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
73 /* PptpControlMessageType names */
74 static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = {
75 [0] = "UNKNOWN_MESSAGE",
76 [PPTP_START_SESSION_REQUEST] = "START_SESSION_REQUEST",
77 [PPTP_START_SESSION_REPLY] = "START_SESSION_REPLY",
78 [PPTP_STOP_SESSION_REQUEST] = "STOP_SESSION_REQUEST",
79 [PPTP_STOP_SESSION_REPLY] = "STOP_SESSION_REPLY",
80 [PPTP_ECHO_REQUEST] = "ECHO_REQUEST",
81 [PPTP_ECHO_REPLY] = "ECHO_REPLY",
82 [PPTP_OUT_CALL_REQUEST] = "OUT_CALL_REQUEST",
83 [PPTP_OUT_CALL_REPLY] = "OUT_CALL_REPLY",
84 [PPTP_IN_CALL_REQUEST] = "IN_CALL_REQUEST",
85 [PPTP_IN_CALL_REPLY] = "IN_CALL_REPLY",
86 [PPTP_IN_CALL_CONNECT] = "IN_CALL_CONNECT",
87 [PPTP_CALL_CLEAR_REQUEST] = "CALL_CLEAR_REQUEST",
88 [PPTP_CALL_DISCONNECT_NOTIFY] = "CALL_DISCONNECT_NOTIFY",
89 [PPTP_WAN_ERROR_NOTIFY] = "WAN_ERROR_NOTIFY",
90 [PPTP_SET_LINK_INFO] = "SET_LINK_INFO"
93 const char *pptp_msg_name(u_int16_t msg)
95 if (msg > PPTP_MSG_MAX)
96 return pptp_msg_name_array[0];
98 return pptp_msg_name_array[msg];
100 EXPORT_SYMBOL(pptp_msg_name);
104 #define MINS * 60 SECS
105 #define HOURS * 60 MINS
107 #define PPTP_GRE_TIMEOUT (10 MINS)
108 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS)
110 static void pptp_expectfn(struct nf_conn *ct,
111 struct nf_conntrack_expect *exp)
113 struct net *net = nf_ct_net(ct);
114 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
115 pr_debug("increasing timeouts\n");
117 /* increase timeout of GRE data channel conntrack entry */
118 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
119 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
121 /* Can you see how rusty this code is, compared with the pre-2.6.11
122 * one? That's what happened to my shiny newnat of 2002 ;( -HW */
125 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
126 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
127 nf_nat_pptp_expectfn(ct, exp);
129 struct nf_conntrack_tuple inv_t;
130 struct nf_conntrack_expect *exp_other;
132 /* obviously this tuple inversion only works until you do NAT */
133 nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
134 pr_debug("trying to unexpect other dir: ");
135 nf_ct_dump_tuple(&inv_t);
137 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t);
139 /* delete other expectation. */
141 nf_ct_unexpect_related(exp_other);
142 nf_ct_expect_put(exp_other);
144 pr_debug("not found\n");
150 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
151 const struct nf_conntrack_tuple *t)
153 const struct nf_conntrack_tuple_hash *h;
154 const struct nf_conntrack_zone *zone;
155 struct nf_conntrack_expect *exp;
156 struct nf_conn *sibling;
158 pr_debug("trying to timeout ct or exp for tuple ");
161 zone = nf_ct_zone(ct);
162 h = nf_conntrack_find_get(net, zone, t);
164 sibling = nf_ct_tuplehash_to_ctrack(h);
165 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
166 sibling->proto.gre.timeout = 0;
167 sibling->proto.gre.stream_timeout = 0;
168 if (del_timer(&sibling->timeout))
169 sibling->timeout.function((unsigned long)sibling);
173 exp = nf_ct_expect_find_get(net, zone, t);
175 pr_debug("unexpect_related of expect %p\n", exp);
176 nf_ct_unexpect_related(exp);
177 nf_ct_expect_put(exp);
184 /* timeout GRE data connections */
185 static void pptp_destroy_siblings(struct nf_conn *ct)
187 struct net *net = nf_ct_net(ct);
188 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
189 struct nf_conntrack_tuple t;
191 nf_ct_gre_keymap_destroy(ct);
193 /* try original (pns->pac) tuple */
194 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
195 t.dst.protonum = IPPROTO_GRE;
196 t.src.u.gre.key = ct_pptp_info->pns_call_id;
197 t.dst.u.gre.key = ct_pptp_info->pac_call_id;
198 if (!destroy_sibling_or_exp(net, ct, &t))
199 pr_debug("failed to timeout original pns->pac ct/exp\n");
201 /* try reply (pac->pns) tuple */
202 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
203 t.dst.protonum = IPPROTO_GRE;
204 t.src.u.gre.key = ct_pptp_info->pac_call_id;
205 t.dst.u.gre.key = ct_pptp_info->pns_call_id;
206 if (!destroy_sibling_or_exp(net, ct, &t))
207 pr_debug("failed to timeout reply pac->pns ct/exp\n");
210 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
211 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
213 struct nf_conntrack_expect *exp_orig, *exp_reply;
214 enum ip_conntrack_dir dir;
216 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
218 exp_orig = nf_ct_expect_alloc(ct);
219 if (exp_orig == NULL)
222 exp_reply = nf_ct_expect_alloc(ct);
223 if (exp_reply == NULL)
226 /* original direction, PNS->PAC */
227 dir = IP_CT_DIR_ORIGINAL;
228 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
230 &ct->tuplehash[dir].tuple.src.u3,
231 &ct->tuplehash[dir].tuple.dst.u3,
232 IPPROTO_GRE, &peer_callid, &callid);
233 exp_orig->expectfn = pptp_expectfn;
235 /* reply direction, PAC->PNS */
236 dir = IP_CT_DIR_REPLY;
237 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
239 &ct->tuplehash[dir].tuple.src.u3,
240 &ct->tuplehash[dir].tuple.dst.u3,
241 IPPROTO_GRE, &callid, &peer_callid);
242 exp_reply->expectfn = pptp_expectfn;
244 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
245 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
246 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
247 if (nf_ct_expect_related(exp_orig) != 0)
249 if (nf_ct_expect_related(exp_reply) != 0)
250 goto out_unexpect_orig;
252 /* Add GRE keymap entries */
253 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
254 goto out_unexpect_both;
255 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
256 nf_ct_gre_keymap_destroy(ct);
257 goto out_unexpect_both;
262 nf_ct_expect_put(exp_reply);
264 nf_ct_expect_put(exp_orig);
269 nf_ct_unexpect_related(exp_reply);
271 nf_ct_unexpect_related(exp_orig);
276 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
277 struct PptpControlHeader *ctlh,
278 union pptp_ctrl_union *pptpReq,
281 enum ip_conntrack_info ctinfo)
283 struct nf_ct_pptp_master *info = nfct_help_data(ct);
285 __be16 cid = 0, pcid = 0;
286 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
288 msg = ntohs(ctlh->messageType);
289 pr_debug("inbound control message %s\n", pptp_msg_name(msg));
292 case PPTP_START_SESSION_REPLY:
293 /* server confirms new control session */
294 if (info->sstate < PPTP_SESSION_REQUESTED)
296 if (pptpReq->srep.resultCode == PPTP_START_OK)
297 info->sstate = PPTP_SESSION_CONFIRMED;
299 info->sstate = PPTP_SESSION_ERROR;
302 case PPTP_STOP_SESSION_REPLY:
303 /* server confirms end of control session */
304 if (info->sstate > PPTP_SESSION_STOPREQ)
306 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
307 info->sstate = PPTP_SESSION_NONE;
309 info->sstate = PPTP_SESSION_ERROR;
312 case PPTP_OUT_CALL_REPLY:
313 /* server accepted call, we now expect GRE frames */
314 if (info->sstate != PPTP_SESSION_CONFIRMED)
316 if (info->cstate != PPTP_CALL_OUT_REQ &&
317 info->cstate != PPTP_CALL_OUT_CONF)
320 cid = pptpReq->ocack.callID;
321 pcid = pptpReq->ocack.peersCallID;
322 if (info->pns_call_id != pcid)
324 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg),
325 ntohs(cid), ntohs(pcid));
327 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
328 info->cstate = PPTP_CALL_OUT_CONF;
329 info->pac_call_id = cid;
330 exp_gre(ct, cid, pcid);
332 info->cstate = PPTP_CALL_NONE;
335 case PPTP_IN_CALL_REQUEST:
336 /* server tells us about incoming call request */
337 if (info->sstate != PPTP_SESSION_CONFIRMED)
340 cid = pptpReq->icreq.callID;
341 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
342 info->cstate = PPTP_CALL_IN_REQ;
343 info->pac_call_id = cid;
346 case PPTP_IN_CALL_CONNECT:
347 /* server tells us about incoming call established */
348 if (info->sstate != PPTP_SESSION_CONFIRMED)
350 if (info->cstate != PPTP_CALL_IN_REP &&
351 info->cstate != PPTP_CALL_IN_CONF)
354 pcid = pptpReq->iccon.peersCallID;
355 cid = info->pac_call_id;
357 if (info->pns_call_id != pcid)
360 pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid));
361 info->cstate = PPTP_CALL_IN_CONF;
363 /* we expect a GRE connection from PAC to PNS */
364 exp_gre(ct, cid, pcid);
367 case PPTP_CALL_DISCONNECT_NOTIFY:
368 /* server confirms disconnect */
369 cid = pptpReq->disc.callID;
370 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
371 info->cstate = PPTP_CALL_NONE;
373 /* untrack this call id, unexpect GRE packets */
374 pptp_destroy_siblings(ct);
377 case PPTP_WAN_ERROR_NOTIFY:
378 case PPTP_SET_LINK_INFO:
379 case PPTP_ECHO_REQUEST:
380 case PPTP_ECHO_REPLY:
381 /* I don't have to explain these ;) */
388 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
389 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
390 return nf_nat_pptp_inbound(skb, ct, ctinfo,
391 protoff, ctlh, pptpReq);
395 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
396 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
398 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
399 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
404 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
405 struct PptpControlHeader *ctlh,
406 union pptp_ctrl_union *pptpReq,
409 enum ip_conntrack_info ctinfo)
411 struct nf_ct_pptp_master *info = nfct_help_data(ct);
413 __be16 cid = 0, pcid = 0;
414 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
416 msg = ntohs(ctlh->messageType);
417 pr_debug("outbound control message %s\n", pptp_msg_name(msg));
420 case PPTP_START_SESSION_REQUEST:
421 /* client requests for new control session */
422 if (info->sstate != PPTP_SESSION_NONE)
424 info->sstate = PPTP_SESSION_REQUESTED;
427 case PPTP_STOP_SESSION_REQUEST:
428 /* client requests end of control session */
429 info->sstate = PPTP_SESSION_STOPREQ;
432 case PPTP_OUT_CALL_REQUEST:
433 /* client initiating connection to server */
434 if (info->sstate != PPTP_SESSION_CONFIRMED)
436 info->cstate = PPTP_CALL_OUT_REQ;
437 /* track PNS call id */
438 cid = pptpReq->ocreq.callID;
439 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
440 info->pns_call_id = cid;
443 case PPTP_IN_CALL_REPLY:
444 /* client answers incoming call */
445 if (info->cstate != PPTP_CALL_IN_REQ &&
446 info->cstate != PPTP_CALL_IN_REP)
449 cid = pptpReq->icack.callID;
450 pcid = pptpReq->icack.peersCallID;
451 if (info->pac_call_id != pcid)
453 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg),
454 ntohs(cid), ntohs(pcid));
456 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
457 /* part two of the three-way handshake */
458 info->cstate = PPTP_CALL_IN_REP;
459 info->pns_call_id = cid;
461 info->cstate = PPTP_CALL_NONE;
464 case PPTP_CALL_CLEAR_REQUEST:
465 /* client requests hangup of call */
466 if (info->sstate != PPTP_SESSION_CONFIRMED)
468 /* FUTURE: iterate over all calls and check if
469 * call ID is valid. We don't do this without newnat,
470 * because we only know about last call */
471 info->cstate = PPTP_CALL_CLEAR_REQ;
474 case PPTP_SET_LINK_INFO:
475 case PPTP_ECHO_REQUEST:
476 case PPTP_ECHO_REPLY:
477 /* I don't have to explain these ;) */
484 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
485 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
486 return nf_nat_pptp_outbound(skb, ct, ctinfo,
487 protoff, ctlh, pptpReq);
491 pr_debug("invalid %s: type=%d cid=%u pcid=%u "
492 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
494 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate,
495 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
499 static const unsigned int pptp_msg_size[] = {
500 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest),
501 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply),
502 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest),
503 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply),
504 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest),
505 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply),
506 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest),
507 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply),
508 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected),
509 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest),
510 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
511 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify),
512 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo),
515 /* track caller id inside control connection, call expect_related */
517 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
518 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
521 int dir = CTINFO2DIR(ctinfo);
522 const struct nf_ct_pptp_master *info = nfct_help_data(ct);
523 const struct tcphdr *tcph;
525 const struct pptp_pkt_hdr *pptph;
526 struct pptp_pkt_hdr _pptph;
527 struct PptpControlHeader _ctlh, *ctlh;
528 union pptp_ctrl_union _pptpReq, *pptpReq;
529 unsigned int tcplen = skb->len - protoff;
530 unsigned int datalen, reqlen, nexthdr_off;
531 int oldsstate, oldcstate;
535 /* don't do any tracking before tcp handshake complete */
536 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
539 nexthdr_off = protoff;
540 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
542 nexthdr_off += tcph->doff * 4;
543 datalen = tcplen - tcph->doff * 4;
545 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
547 pr_debug("no full PPTP header, can't track\n");
550 nexthdr_off += sizeof(_pptph);
551 datalen -= sizeof(_pptph);
553 /* if it's not a control message we can't do anything with it */
554 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
555 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
556 pr_debug("not a control packet\n");
560 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
563 nexthdr_off += sizeof(_ctlh);
564 datalen -= sizeof(_ctlh);
567 msg = ntohs(ctlh->messageType);
568 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
570 if (reqlen > sizeof(*pptpReq))
571 reqlen = sizeof(*pptpReq);
573 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
577 oldsstate = info->sstate;
578 oldcstate = info->cstate;
580 spin_lock_bh(&nf_pptp_lock);
582 /* FIXME: We just blindly assume that the control connection is always
583 * established from PNS->PAC. However, RFC makes no guarantee */
584 if (dir == IP_CT_DIR_ORIGINAL)
585 /* client -> server (PNS -> PAC) */
586 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
589 /* server -> client (PAC -> PNS) */
590 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
592 pr_debug("sstate: %d->%d, cstate: %d->%d\n",
593 oldsstate, info->sstate, oldcstate, info->cstate);
594 spin_unlock_bh(&nf_pptp_lock);
599 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
604 /* control protocol helper */
605 static struct nf_conntrack_helper pptp __read_mostly = {
608 .data_len = sizeof(struct nf_ct_pptp_master),
609 .tuple.src.l3num = AF_INET,
610 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT),
611 .tuple.dst.protonum = IPPROTO_TCP,
612 .help = conntrack_pptp_help,
613 .destroy = pptp_destroy_siblings,
614 .expect_policy = &pptp_exp_policy,
617 static int __init nf_conntrack_pptp_init(void)
619 return nf_conntrack_helper_register(&pptp);
622 static void __exit nf_conntrack_pptp_fini(void)
624 nf_conntrack_helper_unregister(&pptp);
627 module_init(nf_conntrack_pptp_init);
628 module_exit(nf_conntrack_pptp_fini);