kernel/linux/net/ipv4/netfilter/ip_conntrack_pptp.c

   1 /*
   2  * ip_conntrack_pptp.c  - Version 1.9
   3  *
   4  * Connection tracking support for PPTP (Point to Point Tunneling Protocol).
   5  * PPTP is a a protocol for creating virtual private networks.
   6  * It is a specification defined by Microsoft and some vendors
   7  * working with Microsoft.  PPTP is built on top of a modified
   8  * version of the Internet Generic Routing Encapsulation Protocol.
   9  * GRE is defined in RFC 1701 and RFC 1702.  Documentation of
  10  * PPTP can be found in RFC 2637
  11  *
  12  * (C) 2000-2003 by Harald Welte <laforge@gnumonks.org>
  13  *
  14  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  15  *
  16  * Limitations:
  17  *       - We blindly assume that control connections are always
  18  *         established in PNS->PAC direction.  This is a violation
  19  *         of RFFC2673
  20  *
  21  * TODO: - finish support for multiple calls within one session
  22  *         (needs expect reservations in newnat)
  23  *       - testing of incoming PPTP calls
  24  *
  25  * Changes:
  26  *      2002-02-05 - Version 1.3
  27  *        - Call ip_conntrack_unexpect_related() from
  28  *          pptp_timeout_related() to destroy expectations in case
  29  *          CALL_DISCONNECT_NOTIFY or tcp fin packet was seen
  30  *          (Philip Craig <philipc@snapgear.com>)
  31  *        - Add Version information at module loadtime
  32  *      2002-02-10 - Version 1.6
  33  *        - move to C99 style initializers
  34  *        - remove second expectation if first arrives
  35  *
  36  */
  37
  38 #include <linux/config.h>
  39 #include <linux/module.h>
  40 #include <linux/netfilter.h>
  41 #include <linux/ip.h>
  42 #include <net/checksum.h>
  43 #include <net/tcp.h>
  44
  45 #include <linux/netfilter_ipv4/lockhelp.h>
  46 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  47 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
  48 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
  49
  50 #define IP_CT_PPTP_VERSION "1.9"
  51
  52 MODULE_LICENSE("GPL");
  53 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  54 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
  55
  56 DECLARE_LOCK(ip_pptp_lock);
  57
  58 #if 0
  59 #include "ip_conntrack_pptp_priv.h"
  60 #define DEBUGP(format, args...) printk(KERN_DEBUG __FILE__ ":" __FUNCTION__ \
  61                                         ": " format, ## args)
  62 #else
  63 #define DEBUGP(format, args...)
  64 #endif
  65
  66 #define SECS *HZ
  67 #define MINS * 60 SECS
  68 #define HOURS * 60 MINS
  69 #define DAYS * 24 HOURS
  70
  71 #define PPTP_GRE_TIMEOUT                (10 MINS)
  72 #define PPTP_GRE_STREAM_TIMEOUT         (5 DAYS)
  73
  74 static int pptp_expectfn(struct ip_conntrack *ct)
  75 {
  76         struct ip_conntrack *master;
  77         struct ip_conntrack_expect *exp;
  78
  79         DEBUGP("increasing timeouts\n");
  80         /* increase timeout of GRE data channel conntrack entry */
  81         ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
  82         ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
  83
  84         master = master_ct(ct);
  85         if (!master) {
  86                 DEBUGP(" no master!!!\n");
  87                 return 0;
  88         }
  89
  90         exp = ct->master;
  91         if (!exp) {
  92                 DEBUGP("no expectation!!\n");
  93                 return 0;
  94         }
  95
  96         DEBUGP("completing tuples with ct info\n");
  97         /* we can do this, since we're unconfirmed */
  98         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u.gre.key ==
  99                 htonl(master->help.ct_pptp_info.pac_call_id)) {
 100                 /* assume PNS->PAC */
 101                 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.gre.key =
 102                         htonl(master->help.ct_pptp_info.pns_call_id);
 103                 ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.gre.key =
 104                         htonl(master->help.ct_pptp_info.pns_call_id);
 105         } else {
 106                 /* assume PAC->PNS */
 107                 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.gre.key =
 108                         htonl(master->help.ct_pptp_info.pac_call_id);
 109                 ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.gre.key =
 110                         htonl(master->help.ct_pptp_info.pac_call_id);
 111         }
 112
 113         /* delete other expectation */
 114         if (exp->expected_list.next != &exp->expected_list) {
 115                 struct ip_conntrack_expect *other_exp;
 116                 struct list_head *cur_item, *next;
 117
 118                 for (cur_item = master->sibling_list.next;
 119                      cur_item != &master->sibling_list; cur_item = next) {
 120                         next = cur_item->next;
 121                         other_exp = list_entry(cur_item,
 122                                                struct ip_conntrack_expect,
 123                                                expected_list);
 124                         /* remove only if occurred at same sequence number */
 125                         if (other_exp != exp && other_exp->seq == exp->seq) {
 126                                 DEBUGP("unexpecting other direction\n");
 127                                 ip_ct_gre_keymap_destroy(other_exp);
 128                                 ip_conntrack_unexpect_related(other_exp);
 129                         }
 130                 }
 131         }
 132
 133         return 0;
 134 }
 135
 136 /* timeout GRE data connections */
 137 static int pptp_timeout_related(struct ip_conntrack *ct)
 138 {
 139         struct list_head *cur_item, *next;
 140         struct ip_conntrack_expect *exp;
 141
 142         /* FIXME: do we have to lock something ? */
 143         for (cur_item = ct->sibling_list.next;
 144             cur_item != &ct->sibling_list; cur_item = next) {
 145                 next = cur_item->next;
 146                 exp = list_entry(cur_item, struct ip_conntrack_expect,
 147                                  expected_list);
 148
 149                 ip_ct_gre_keymap_destroy(exp);
 150                 if (!exp->sibling) {
 151                         ip_conntrack_unexpect_related(exp);
 152                         continue;
 153                 }
 154
 155                 DEBUGP("setting timeout of conntrack %p to 0\n",
 156                         exp->sibling);
 157                 exp->sibling->proto.gre.timeout = 0;
 158                 exp->sibling->proto.gre.stream_timeout = 0;
 159                 ip_ct_refresh(exp->sibling, 0);
 160         }
 161
 162         return 0;
 163 }
 164
 165 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 166 static inline int
 167 exp_gre(struct ip_conntrack *master,
 168         u_int32_t seq,
 169         u_int16_t callid,
 170         u_int16_t peer_callid)
 171 {
 172         struct ip_conntrack_expect exp;
 173         struct ip_conntrack_tuple inv_tuple;
 174
 175         memset(&exp, 0, sizeof(exp));
 176         /* tuple in original direction, PNS->PAC */
 177         exp.tuple.src.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
 178         exp.tuple.src.u.gre.key = htonl(ntohs(peer_callid));
 179         exp.tuple.dst.ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip;
 180         exp.tuple.dst.u.gre.key = htonl(ntohs(callid));
 181         exp.tuple.dst.u.gre.protocol = __constant_htons(GRE_PROTOCOL_PPTP);
 182         exp.tuple.dst.u.gre.version = GRE_VERSION_PPTP;
 183         exp.tuple.dst.protonum = IPPROTO_GRE;
 184
 185         exp.mask.src.ip = 0xffffffff;
 186         exp.mask.src.u.all = 0;
 187         exp.mask.dst.u.all = 0;
 188         exp.mask.dst.u.gre.key = 0xffffffff;
 189         exp.mask.dst.u.gre.version = 0xff;
 190         exp.mask.dst.u.gre.protocol = 0xffff;
 191         exp.mask.dst.ip = 0xffffffff;
 192         exp.mask.dst.protonum = 0xffff;
 193
 194         exp.seq = seq;
 195         exp.expectfn = pptp_expectfn;
 196
 197         exp.help.exp_pptp_info.pac_call_id = ntohs(callid);
 198         exp.help.exp_pptp_info.pns_call_id = ntohs(peer_callid);
 199
 200         DEBUGP("calling expect_related ");
 201         DUMP_TUPLE_RAW(&exp.tuple);
 202
 203         /* Add GRE keymap entries */
 204         if (ip_ct_gre_keymap_add(&exp, &exp.tuple, 0) != 0)
 205                 return 1;
 206
 207         invert_tuplepr(&inv_tuple, &exp.tuple);
 208         if (ip_ct_gre_keymap_add(&exp, &inv_tuple, 1) != 0) {
 209                 ip_ct_gre_keymap_destroy(&exp);
 210                 return 1;
 211         }
 212
 213         if (ip_conntrack_expect_related(&exp, master) != 0) {
 214                 ip_ct_gre_keymap_destroy(&exp);
 215                 DEBUGP("cannot expect_related()\n");
 216                 return 1;
 217         }
 218
 219         /* tuple in reply direction, PAC->PNS */
 220         exp.tuple.src.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip;
 221         exp.tuple.src.u.gre.key = htonl(ntohs(callid));
 222         exp.tuple.dst.ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
 223         exp.tuple.dst.u.gre.key = htonl(ntohs(peer_callid));
 224
 225         DEBUGP("calling expect_related ");
 226         DUMP_TUPLE_RAW(&exp.tuple);
 227
 228         /* Add GRE keymap entries */
 229         ip_ct_gre_keymap_add(&exp, &exp.tuple, 0);
 230         invert_tuplepr(&inv_tuple, &exp.tuple);
 231         ip_ct_gre_keymap_add(&exp, &inv_tuple, 1);
 232         /* FIXME: cannot handle error correctly, since we need to free
 233          * the above keymap :( */
 234
 235         if (ip_conntrack_expect_related(&exp, master) != 0) {
 236                 /* free the second pair of keypmaps */
 237                 ip_ct_gre_keymap_destroy(&exp);
 238                 DEBUGP("cannot expect_related():\n");
 239                 return 1;
 240         }
 241
 242         return 0;
 243 }
 244
 245 static inline int
 246 pptp_inbound_pkt(struct tcphdr *tcph,
 247                  struct pptp_pkt_hdr *pptph,
 248                  size_t datalen,
 249                  struct ip_conntrack *ct,
 250                  enum ip_conntrack_info ctinfo)
 251 {
 252         struct PptpControlHeader *ctlh;
 253         union pptp_ctrl_union pptpReq;
 254
 255         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 256         u_int16_t msg, *cid, *pcid;
 257         u_int32_t seq;
 258
 259         ctlh = (struct PptpControlHeader *)
 260                 ((char *) pptph + sizeof(struct pptp_pkt_hdr));
 261         pptpReq.rawreq = (void *)
 262                 ((char *) ctlh + sizeof(struct PptpControlHeader));
 263
 264         msg = ntohs(ctlh->messageType);
 265         DEBUGP("inbound control message %s\n", strMName[msg]);
 266
 267         switch (msg) {
 268         case PPTP_START_SESSION_REPLY:
 269                 /* server confirms new control session */
 270                 if (info->sstate < PPTP_SESSION_REQUESTED) {
 271                         DEBUGP("%s without START_SESS_REQUEST\n",
 272                                 strMName[msg]);
 273                         break;
 274                 }
 275                 if (pptpReq.srep->resultCode == PPTP_START_OK)
 276                         info->sstate = PPTP_SESSION_CONFIRMED;
 277                 else
 278                         info->sstate = PPTP_SESSION_ERROR;
 279                 break;
 280
 281         case PPTP_STOP_SESSION_REPLY:
 282                 /* server confirms end of control session */
 283                 if (info->sstate > PPTP_SESSION_STOPREQ) {
 284                         DEBUGP("%s without STOP_SESS_REQUEST\n",
 285                                 strMName[msg]);
 286                         break;
 287                 }
 288                 if (pptpReq.strep->resultCode == PPTP_STOP_OK)
 289                         info->sstate = PPTP_SESSION_NONE;
 290                 else
 291                         info->sstate = PPTP_SESSION_ERROR;
 292                 break;
 293
 294         case PPTP_OUT_CALL_REPLY:
 295                 /* server accepted call, we now expect GRE frames */
 296                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 297                         DEBUGP("%s but no session\n", strMName[msg]);
 298                         break;
 299                 }
 300                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 301                     info->cstate != PPTP_CALL_OUT_CONF) {
 302                         DEBUGP("%s without OUTCALL_REQ\n", strMName[msg]);
 303                         break;
 304                 }
 305                 if (pptpReq.ocack->resultCode != PPTP_OUTCALL_CONNECT) {
 306                         info->cstate = PPTP_CALL_NONE;
 307                         break;
 308                 }
 309
 310                 cid = &pptpReq.ocack->callID;
 311                 pcid = &pptpReq.ocack->peersCallID;
 312
 313                 info->pac_call_id = ntohs(*cid);
 314
 315                 if (htons(info->pns_call_id) != *pcid) {
 316                         DEBUGP("%s for unknown callid %u\n",
 317                                 strMName[msg], ntohs(*pcid));
 318                         break;
 319                 }
 320
 321                 DEBUGP("%s, CID=%X, PCID=%X\n", strMName[msg],
 322                         ntohs(*cid), ntohs(*pcid));
 323
 324                 info->cstate = PPTP_CALL_OUT_CONF;
 325
 326                 seq = ntohl(tcph->seq) + ((void *)pcid - (void *)pptph);
 327                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 328                         printk("ip_conntrack_pptp: error during exp_gre\n");
 329                 break;
 330
 331         case PPTP_IN_CALL_REQUEST:
 332                 /* server tells us about incoming call request */
 333                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 334                         DEBUGP("%s but no session\n", strMName[msg]);
 335                         break;
 336                 }
 337                 pcid = &pptpReq.icack->peersCallID;
 338                 DEBUGP("%s, PCID=%X\n", strMName[msg], ntohs(*pcid));
 339                 info->cstate = PPTP_CALL_IN_REQ;
 340                 info->pac_call_id= ntohs(*pcid);
 341                 break;
 342
 343         case PPTP_IN_CALL_CONNECT:
 344                 /* server tells us about incoming call established */
 345                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 346                         DEBUGP("%s but no session\n", strMName[msg]);
 347                         break;
 348                 }
 349                 if (info->sstate != PPTP_CALL_IN_REP
 350                     && info->sstate != PPTP_CALL_IN_CONF) {
 351                         DEBUGP("%s but never sent IN_CALL_REPLY\n",
 352                                 strMName[msg]);
 353                         break;
 354                 }
 355
 356                 pcid = &pptpReq.iccon->peersCallID;
 357                 cid = &info->pac_call_id;
 358
 359                 if (info->pns_call_id != ntohs(*pcid)) {
 360                         DEBUGP("%s for unknown CallID %u\n",
 361                                 strMName[msg], ntohs(*cid));
 362                         break;
 363                 }
 364
 365                 DEBUGP("%s, PCID=%X\n", strMName[msg], ntohs(*pcid));
 366                 info->cstate = PPTP_CALL_IN_CONF;
 367
 368                 /* we expect a GRE connection from PAC to PNS */
 369                 seq = ntohl(tcph->seq) + ((void *)pcid - (void *)pptph);
 370                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 371                         printk("ip_conntrack_pptp: error during exp_gre\n");
 372
 373                 break;
 374
 375         case PPTP_CALL_DISCONNECT_NOTIFY:
 376                 /* server confirms disconnect */
 377                 cid = &pptpReq.disc->callID;
 378                 DEBUGP("%s, CID=%X\n", strMName[msg], ntohs(*cid));
 379                 info->cstate = PPTP_CALL_NONE;
 380
 381                 /* untrack this call id, unexpect GRE packets */
 382                 pptp_timeout_related(ct);
 383                 break;
 384
 385         case PPTP_WAN_ERROR_NOTIFY:
 386                 break;
 387
 388         case PPTP_ECHO_REQUEST:
 389         case PPTP_ECHO_REPLY:
 390                 /* I don't have to explain these ;) */
 391                 break;
 392         default:
 393                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)
 394                         ? strMName[msg]:strMName[0], msg);
 395                 break;
 396         }
 397
 398         return NF_ACCEPT;
 399
 400 }
 401
 402 static inline int
 403 pptp_outbound_pkt(struct tcphdr *tcph,
 404                   struct pptp_pkt_hdr *pptph,
 405                   size_t datalen,
 406                   struct ip_conntrack *ct,
 407                   enum ip_conntrack_info ctinfo)
 408 {
 409         struct PptpControlHeader *ctlh;
 410         union pptp_ctrl_union pptpReq;
 411         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 412         u_int16_t msg, *cid, *pcid;
 413
 414         ctlh = (struct PptpControlHeader *) ((void *) pptph + sizeof(*pptph));
 415         pptpReq.rawreq = (void *) ((void *) ctlh + sizeof(*ctlh));
 416
 417         msg = ntohs(ctlh->messageType);
 418         DEBUGP("outbound control message %s\n", strMName[msg]);
 419
 420         switch (msg) {
 421         case PPTP_START_SESSION_REQUEST:
 422                 /* client requests for new control session */
 423                 if (info->sstate != PPTP_SESSION_NONE) {
 424                         DEBUGP("%s but we already have one",
 425                                 strMName[msg]);
 426                 }
 427                 info->sstate = PPTP_SESSION_REQUESTED;
 428                 break;
 429         case PPTP_STOP_SESSION_REQUEST:
 430                 /* client requests end of control session */
 431                 info->sstate = PPTP_SESSION_STOPREQ;
 432                 break;
 433
 434         case PPTP_OUT_CALL_REQUEST:
 435                 /* client initiating connection to server */
 436                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 437                         DEBUGP("%s but no session\n",
 438                                 strMName[msg]);
 439                         break;
 440                 }
 441                 info->cstate = PPTP_CALL_OUT_REQ;
 442                 /* track PNS call id */
 443                 cid = &pptpReq.ocreq->callID;
 444                 DEBUGP("%s, CID=%X\n", strMName[msg], ntohs(*cid));
 445                 info->pns_call_id = ntohs(*cid);
 446                 break;
 447         case PPTP_IN_CALL_REPLY:
 448                 /* client answers incoming call */
 449                 if (info->cstate != PPTP_CALL_IN_REQ
 450                     && info->cstate != PPTP_CALL_IN_REP) {
 451                         DEBUGP("%s without incall_req\n",
 452                                 strMName[msg]);
 453                         break;
 454                 }
 455                 if (pptpReq.icack->resultCode != PPTP_INCALL_ACCEPT) {
 456                         info->cstate = PPTP_CALL_NONE;
 457                         break;
 458                 }
 459                 pcid = &pptpReq.icack->peersCallID;
 460                 if (info->pac_call_id != ntohs(*pcid)) {
 461                         DEBUGP("%s for unknown call %u\n",
 462                                 strMName[msg], ntohs(*pcid));
 463                         break;
 464                 }
 465                 DEBUGP("%s, CID=%X\n", strMName[msg], ntohs(*pcid));
 466                 /* part two of the three-way handshake */
 467                 info->cstate = PPTP_CALL_IN_REP;
 468                 info->pns_call_id = ntohs(pptpReq.icack->callID);
 469                 break;
 470
 471         case PPTP_CALL_CLEAR_REQUEST:
 472                 /* client requests hangup of call */
 473                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 474                         DEBUGP("CLEAR_CALL but no session\n");
 475                         break;
 476                 }
 477                 /* FUTURE: iterate over all calls and check if
 478                  * call ID is valid.  We don't do this without newnat,
 479                  * because we only know about last call */
 480                 info->cstate = PPTP_CALL_CLEAR_REQ;
 481                 break;
 482         case PPTP_SET_LINK_INFO:
 483                 break;
 484         case PPTP_ECHO_REQUEST:
 485         case PPTP_ECHO_REPLY:
 486                 /* I don't have to explain these ;) */
 487                 break;
 488         default:
 489                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)?
 490                         strMName[msg]:strMName[0], msg);
 491                 /* unknown: no need to create GRE masq table entry */
 492                 break;
 493         }
 494
 495         return NF_ACCEPT;
 496 }
 497
 498
 499 /* track caller id inside control connection, call expect_related */
 500 static int
 501 conntrack_pptp_help(struct sk_buff *skb,
 502                     struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 503
 504 {
 505         struct pptp_pkt_hdr *pptph;
 506
 507         struct tcphdr *tcph = (void *) skb->nh.iph + skb->nh.iph->ihl * 4;
 508         u_int32_t tcplen = skb->len - skb->nh.iph->ihl * 4;
 509         u_int32_t datalen = tcplen - tcph->doff * 4;
 510         void *datalimit;
 511         int dir = CTINFO2DIR(ctinfo);
 512         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 513
 514         int oldsstate, oldcstate;
 515         int ret;
 516
 517         /* don't do any tracking before tcp handshake complete */
 518         if (ctinfo != IP_CT_ESTABLISHED
 519             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
 520                 DEBUGP("ctinfo = %u, skipping\n", ctinfo);
 521                 return NF_ACCEPT;
 522         }
 523
 524         /* not a complete TCP header? */
 525         if (tcplen < sizeof(struct tcphdr) || tcplen < tcph->doff * 4) {
 526                 DEBUGP("tcplen = %u\n", tcplen);
 527                 return NF_ACCEPT;
 528         }
 529
 530         /* checksum invalid? */
 531         if (tcp_v4_check(tcph, tcplen, skb->nh.iph->saddr, skb->nh.iph->daddr,
 532                         csum_partial((char *) tcph, tcplen, 0))) {
 533                 printk(KERN_NOTICE __FILE__ ": bad csum\n");
 534                 /* W2K PPTP server sends TCP packets with wrong checksum :(( */
 535                 //return NF_ACCEPT;
 536         }
 537
 538         if (tcph->fin || tcph->rst) {
 539                 DEBUGP("RST/FIN received, timeouting GRE\n");
 540                 /* can't do this after real newnat */
 541                 info->cstate = PPTP_CALL_NONE;
 542
 543                 /* untrack this call id, unexpect GRE packets */
 544                 pptp_timeout_related(ct);
 545         }
 546
 547
 548         pptph = (struct pptp_pkt_hdr *) ((void *) tcph + tcph->doff * 4);
 549         datalimit = (void *) pptph + datalen;
 550
 551         /* not a full pptp packet header? */
 552         if ((void *) pptph+sizeof(*pptph) >= datalimit) {
 553                 DEBUGP("no full PPTP header, can't track\n");
 554                 return NF_ACCEPT;
 555         }
 556
 557         /* if it's not a control message we can't do anything with it */
 558         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 559             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 560                 DEBUGP("not a control packet\n");
 561                 return NF_ACCEPT;
 562         }
 563
 564         oldsstate = info->sstate;
 565         oldcstate = info->cstate;
 566
 567         LOCK_BH(&ip_pptp_lock);
 568
 569         /* FIXME: We just blindly assume that the control connection is always
 570          * established from PNS->PAC.  However, RFC makes no guarantee */
 571         if (dir == IP_CT_DIR_ORIGINAL)
 572                 /* client -> server (PNS -> PAC) */
 573                 ret = pptp_outbound_pkt(tcph, pptph, datalen, ct, ctinfo);
 574         else
 575                 /* server -> client (PAC -> PNS) */
 576                 ret = pptp_inbound_pkt(tcph, pptph, datalen, ct, ctinfo);
 577         DEBUGP("sstate: %d->%d, cstate: %d->%d\n",
 578                 oldsstate, info->sstate, oldcstate, info->cstate);
 579         UNLOCK_BH(&ip_pptp_lock);
 580
 581         return ret;
 582 }
 583
 584 /* control protocol helper */
 585 static struct ip_conntrack_helper pptp = {
 586         .list = { NULL, NULL },
 587         .name = "pptp",
 588         .flags = IP_CT_HELPER_F_REUSE_EXPECT,
 589         .me = THIS_MODULE,
 590         .max_expected = 2,
 591         .timeout = 0,
 592         .tuple = { .src = { .ip = 0,
 593                             .u = { .tcp = { .port =
 594                                     __constant_htons(PPTP_CONTROL_PORT) } }
 595                           },
 596                    .dst = { .ip = 0,
 597                             .u = { .all = 0 },
 598                             .protonum = IPPROTO_TCP
 599                           }
 600                  },
 601         .mask = { .src = { .ip = 0,
 602                            .u = { .tcp = { .port = 0xffff } }
 603                          },
 604                   .dst = { .ip = 0,
 605                            .u = { .all = 0 },
 606                            .protonum = 0xffff
 607                          }
 608                 },
 609         .help = conntrack_pptp_help
 610 };
 611
 612 /* ip_conntrack_pptp initialization */
 613 static int __init init(void)
 614 {
 615         int retcode;
 616
 617         DEBUGP(__FILE__ ": registering helper\n");
 618         return 0;
 619         if ((retcode = ip_conntrack_helper_register(&pptp))) {
 620                 printk(KERN_ERR "Unable to register conntrack application "
 621                                 "helper for pptp: %d\n", retcode);
 622                 return -EIO;
 623         }
 624
 625         printk("ip_conntrack_pptp version %s loaded\n", IP_CT_PPTP_VERSION);
 626         return 0;
 627 }
 628
 629 static void __exit fini(void)
 630 {
 631         return 0;
 632         ip_conntrack_helper_unregister(&pptp);
 633         printk("ip_conntrack_pptp version %s unloaded\n", IP_CT_PPTP_VERSION);
 634 }
 635
 636 module_init(init);
 637 module_exit(fini);
 638
 639 EXPORT_SYMBOL(ip_pptp_lock);