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   1 /*
   2  * ip_conntrack_pptp.c  - Version 3.0
   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) 2000-2005 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  *       - We can only support one single call within each session
  21  *
  22  * TODO:
  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_destroy_siblings() 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  *      2004-10-22 - Version 2.0
  36  *        - merge Mandrake's 2.6.x port with recent 2.6.x API changes
  37  *        - fix lots of linear skb assumptions from Mandrake's port
  38  *      2005-06-10 - Version 2.1
  39  *        - use ip_conntrack_expect_free() instead of kfree() on the
  40  *          expect's (which are from the slab for quite some time)
  41  *      2005-06-10 - Version 3.0
  42  *        - port helper to post-2.6.11 API changes,
  43  *          funded by Oxcoda NetBox Blue (http://www.netboxblue.com/)
  44  *      2005-07-30 - Version 3.1
  45  *        - port helper to 2.6.13 API changes
  46  *
  47  */
  48
  49 #include <linux/config.h>
  50 #include <linux/module.h>
  51 #include <linux/netfilter.h>
  52 #include <linux/ip.h>
  53 #include <net/checksum.h>
  54 #include <net/tcp.h>
  55
  56 #include <linux/netfilter_ipv4/ip_conntrack.h>
  57 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
  58 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  59 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
  60 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
  61
  62 #define IP_CT_PPTP_VERSION "3.1"
  63
  64 MODULE_LICENSE("GPL");
  65 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  66 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
  67
  68 static DEFINE_SPINLOCK(ip_pptp_lock);
  69
  70 int
  71 (*ip_nat_pptp_hook_outbound)(struct sk_buff **pskb,
  72                           struct ip_conntrack *ct,
  73                           enum ip_conntrack_info ctinfo,
  74                           struct PptpControlHeader *ctlh,
  75                           union pptp_ctrl_union *pptpReq);
  76
  77 int
  78 (*ip_nat_pptp_hook_inbound)(struct sk_buff **pskb,
  79                           struct ip_conntrack *ct,
  80                           enum ip_conntrack_info ctinfo,
  81                           struct PptpControlHeader *ctlh,
  82                           union pptp_ctrl_union *pptpReq);
  83
  84 int
  85 (*ip_nat_pptp_hook_exp_gre)(struct ip_conntrack_expect *expect_orig,
  86                             struct ip_conntrack_expect *expect_reply);
  87
  88 void
  89 (*ip_nat_pptp_hook_expectfn)(struct ip_conntrack *ct,
  90                              struct ip_conntrack_expect *exp);
  91
  92 #if 0
  93 /* PptpControlMessageType names */
  94 const char *pptp_msg_name[] = {
  95         "UNKNOWN_MESSAGE",
  96         "START_SESSION_REQUEST",
  97         "START_SESSION_REPLY",
  98         "STOP_SESSION_REQUEST",
  99         "STOP_SESSION_REPLY",
 100         "ECHO_REQUEST",
 101         "ECHO_REPLY",
 102         "OUT_CALL_REQUEST",
 103         "OUT_CALL_REPLY",
 104         "IN_CALL_REQUEST",
 105         "IN_CALL_REPLY",
 106         "IN_CALL_CONNECT",
 107         "CALL_CLEAR_REQUEST",
 108         "CALL_DISCONNECT_NOTIFY",
 109         "WAN_ERROR_NOTIFY",
 110         "SET_LINK_INFO"
 111 };
 112 EXPORT_SYMBOL(pptp_msg_name);
 113 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
 114 #else
 115 #define DEBUGP(format, args...)
 116 #endif
 117
 118 #define SECS *HZ
 119 #define MINS * 60 SECS
 120 #define HOURS * 60 MINS
 121
 122 #define PPTP_GRE_TIMEOUT                (10 MINS)
 123 #define PPTP_GRE_STREAM_TIMEOUT         (5 HOURS)
 124
 125 static void pptp_expectfn(struct ip_conntrack *ct,
 126                          struct ip_conntrack_expect *exp)
 127 {
 128         DEBUGP("increasing timeouts\n");
 129
 130         /* increase timeout of GRE data channel conntrack entry */
 131         ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
 132         ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
 133
 134         /* Can you see how rusty this code is, compared with the pre-2.6.11
 135          * one? That's what happened to my shiny newnat of 2002 ;( -HW */
 136
 137         if (!ip_nat_pptp_hook_expectfn) {
 138                 struct ip_conntrack_tuple inv_t;
 139                 struct ip_conntrack_expect *exp_other;
 140
 141                 /* obviously this tuple inversion only works until you do NAT */
 142                 invert_tuplepr(&inv_t, &exp->tuple);
 143                 DEBUGP("trying to unexpect other dir: ");
 144                 DUMP_TUPLE(&inv_t);
 145
 146                 exp_other = ip_conntrack_expect_find(&inv_t);
 147                 if (exp_other) {
 148                         /* delete other expectation.  */
 149                         DEBUGP("found\n");
 150                         ip_conntrack_unexpect_related(exp_other);
 151                         ip_conntrack_expect_put(exp_other);
 152                 } else {
 153                         DEBUGP("not found\n");
 154                 }
 155         } else {
 156                 /* we need more than simple inversion */
 157                 ip_nat_pptp_hook_expectfn(ct, exp);
 158         }
 159 }
 160
 161 static int destroy_sibling_or_exp(const struct ip_conntrack_tuple *t)
 162 {
 163         struct ip_conntrack_tuple_hash *h;
 164         struct ip_conntrack_expect *exp;
 165
 166         DEBUGP("trying to timeout ct or exp for tuple ");
 167         DUMP_TUPLE(t);
 168
 169         h = ip_conntrack_find_get(t, NULL);
 170         if (h)  {
 171                 struct ip_conntrack *sibling = tuplehash_to_ctrack(h);
 172                 DEBUGP("setting timeout of conntrack %p to 0\n", sibling);
 173                 sibling->proto.gre.timeout = 0;
 174                 sibling->proto.gre.stream_timeout = 0;
 175                 if (del_timer(&sibling->timeout))
 176                         sibling->timeout.function((unsigned long)sibling);
 177                 ip_conntrack_put(sibling);
 178                 return 1;
 179         } else {
 180                 exp = ip_conntrack_expect_find(t);
 181                 if (exp) {
 182                         DEBUGP("unexpect_related of expect %p\n", exp);
 183                         ip_conntrack_unexpect_related(exp);
 184                         ip_conntrack_expect_put(exp);
 185                         return 1;
 186                 }
 187         }
 188
 189         return 0;
 190 }
 191
 192
 193 /* timeout GRE data connections */
 194 static void pptp_destroy_siblings(struct ip_conntrack *ct)
 195 {
 196         struct ip_conntrack_tuple t;
 197
 198         /* Since ct->sibling_list has literally rusted away in 2.6.11,
 199          * we now need another way to find out about our sibling
 200          * contrack and expects... -HW */
 201
 202         /* try original (pns->pac) tuple */
 203         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 204         t.dst.protonum = IPPROTO_GRE;
 205         t.src.u.gre.key = htons(ct->help.ct_pptp_info.pns_call_id);
 206         t.dst.u.gre.key = htons(ct->help.ct_pptp_info.pac_call_id);
 207
 208         if (!destroy_sibling_or_exp(&t))
 209                 DEBUGP("failed to timeout original pns->pac ct/exp\n");
 210
 211         /* try reply (pac->pns) tuple */
 212         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 213         t.dst.protonum = IPPROTO_GRE;
 214         t.src.u.gre.key = htons(ct->help.ct_pptp_info.pac_call_id);
 215         t.dst.u.gre.key = htons(ct->help.ct_pptp_info.pns_call_id);
 216
 217         if (!destroy_sibling_or_exp(&t))
 218                 DEBUGP("failed to timeout reply pac->pns ct/exp\n");
 219 }
 220
 221 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 222 static inline int
 223 exp_gre(struct ip_conntrack *master,
 224         u_int32_t seq,
 225         __be16 callid,
 226         __be16 peer_callid)
 227 {
 228         struct ip_conntrack_tuple inv_tuple;
 229         struct ip_conntrack_tuple exp_tuples[] = {
 230                 /* tuple in original direction, PNS->PAC */
 231                 { .src = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip,
 232                            .u = { .gre = { .key = peer_callid } }
 233                          },
 234                   .dst = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip,
 235                            .u = { .gre = { .key = callid } },
 236                            .protonum = IPPROTO_GRE
 237                          },
 238                  },
 239                 /* tuple in reply direction, PAC->PNS */
 240                 { .src = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip,
 241                            .u = { .gre = { .key = callid } }
 242                          },
 243                   .dst = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip,
 244                            .u = { .gre = { .key = peer_callid } },
 245                            .protonum = IPPROTO_GRE
 246                          },
 247                  }
 248         };
 249         struct ip_conntrack_expect *exp_orig, *exp_reply;
 250         int ret = 1;
 251
 252         exp_orig = ip_conntrack_expect_alloc(master);
 253         if (exp_orig == NULL)
 254                 goto out;
 255
 256         exp_reply = ip_conntrack_expect_alloc(master);
 257         if (exp_reply == NULL)
 258                 goto out_put_orig;
 259
 260         memcpy(&exp_orig->tuple, &exp_tuples[0], sizeof(exp_orig->tuple));
 261
 262         exp_orig->mask.src.ip = 0xffffffff;
 263         exp_orig->mask.src.u.all = 0;
 264         exp_orig->mask.dst.u.all = 0;
 265         exp_orig->mask.dst.u.gre.key = htons(0xffff);
 266         exp_orig->mask.dst.ip = 0xffffffff;
 267         exp_orig->mask.dst.protonum = 0xff;
 268
 269         exp_orig->master = master;
 270         exp_orig->expectfn = pptp_expectfn;
 271         exp_orig->flags = 0;
 272
 273         /* both expectations are identical apart from tuple */
 274         memcpy(exp_reply, exp_orig, sizeof(*exp_reply));
 275         memcpy(&exp_reply->tuple, &exp_tuples[1], sizeof(exp_reply->tuple));
 276
 277         if (ip_nat_pptp_hook_exp_gre)
 278                 ret = ip_nat_pptp_hook_exp_gre(exp_orig, exp_reply);
 279         else {
 280
 281                 DEBUGP("calling expect_related PNS->PAC");
 282                 DUMP_TUPLE(&exp_orig->tuple);
 283
 284                 if (ip_conntrack_expect_related(exp_orig) != 0) {
 285                         DEBUGP("cannot expect_related()\n");
 286                         goto out_put_both;
 287                 }
 288
 289                 DEBUGP("calling expect_related PAC->PNS");
 290                 DUMP_TUPLE(&exp_reply->tuple);
 291
 292                 if (ip_conntrack_expect_related(exp_reply) != 0) {
 293                         DEBUGP("cannot expect_related()\n");
 294                         goto out_unexpect_orig;
 295                 }
 296
 297                 /* Add GRE keymap entries */
 298                 if (ip_ct_gre_keymap_add(master, &exp_reply->tuple, 0) != 0) {
 299                         DEBUGP("cannot keymap_add() exp\n");
 300                         goto out_unexpect_both;
 301                 }
 302
 303                 invert_tuplepr(&inv_tuple, &exp_reply->tuple);
 304                 if (ip_ct_gre_keymap_add(master, &inv_tuple, 1) != 0) {
 305                         ip_ct_gre_keymap_destroy(master);
 306                         DEBUGP("cannot keymap_add() exp_inv\n");
 307                         goto out_unexpect_both;
 308                 }
 309                 ret = 0;
 310         }
 311
 312 out_put_both:
 313         ip_conntrack_expect_put(exp_reply);
 314 out_put_orig:
 315         ip_conntrack_expect_put(exp_orig);
 316 out:
 317         return ret;
 318
 319 out_unexpect_both:
 320         ip_conntrack_unexpect_related(exp_reply);
 321 out_unexpect_orig:
 322         ip_conntrack_unexpect_related(exp_orig);
 323         goto out_put_both;
 324 }
 325
 326 static inline int
 327 pptp_inbound_pkt(struct sk_buff **pskb,
 328                  struct tcphdr *tcph,
 329                  unsigned int nexthdr_off,
 330                  unsigned int datalen,
 331                  struct ip_conntrack *ct,
 332                  enum ip_conntrack_info ctinfo)
 333 {
 334         struct PptpControlHeader _ctlh, *ctlh;
 335         unsigned int reqlen;
 336         union pptp_ctrl_union _pptpReq, *pptpReq;
 337         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 338         u_int16_t msg;
 339         __be16 *cid, *pcid;
 340         u_int32_t seq;
 341
 342         ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 343         if (!ctlh) {
 344                 DEBUGP("error during skb_header_pointer\n");
 345                 return NF_ACCEPT;
 346         }
 347         nexthdr_off += sizeof(_ctlh);
 348         datalen -= sizeof(_ctlh);
 349
 350         reqlen = datalen;
 351         if (reqlen > sizeof(*pptpReq))
 352                 reqlen = sizeof(*pptpReq);
 353         pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
 354         if (!pptpReq) {
 355                 DEBUGP("error during skb_header_pointer\n");
 356                 return NF_ACCEPT;
 357         }
 358
 359         msg = ntohs(ctlh->messageType);
 360         DEBUGP("inbound control message %s\n", pptp_msg_name[msg]);
 361
 362         switch (msg) {
 363         case PPTP_START_SESSION_REPLY:
 364                 if (reqlen < sizeof(_pptpReq.srep)) {
 365                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 366                         break;
 367                 }
 368
 369                 /* server confirms new control session */
 370                 if (info->sstate < PPTP_SESSION_REQUESTED) {
 371                         DEBUGP("%s without START_SESS_REQUEST\n",
 372                                 pptp_msg_name[msg]);
 373                         break;
 374                 }
 375                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 376                         info->sstate = PPTP_SESSION_CONFIRMED;
 377                 else
 378                         info->sstate = PPTP_SESSION_ERROR;
 379                 break;
 380
 381         case PPTP_STOP_SESSION_REPLY:
 382                 if (reqlen < sizeof(_pptpReq.strep)) {
 383                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 384                         break;
 385                 }
 386
 387                 /* server confirms end of control session */
 388                 if (info->sstate > PPTP_SESSION_STOPREQ) {
 389                         DEBUGP("%s without STOP_SESS_REQUEST\n",
 390                                 pptp_msg_name[msg]);
 391                         break;
 392                 }
 393                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 394                         info->sstate = PPTP_SESSION_NONE;
 395                 else
 396                         info->sstate = PPTP_SESSION_ERROR;
 397                 break;
 398
 399         case PPTP_OUT_CALL_REPLY:
 400                 if (reqlen < sizeof(_pptpReq.ocack)) {
 401                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 402                         break;
 403                 }
 404
 405                 /* server accepted call, we now expect GRE frames */
 406                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 407                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 408                         break;
 409                 }
 410                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 411                     info->cstate != PPTP_CALL_OUT_CONF) {
 412                         DEBUGP("%s without OUTCALL_REQ\n", pptp_msg_name[msg]);
 413                         break;
 414                 }
 415                 if (pptpReq->ocack.resultCode != PPTP_OUTCALL_CONNECT) {
 416                         info->cstate = PPTP_CALL_NONE;
 417                         break;
 418                 }
 419
 420                 cid = &pptpReq->ocack.callID;
 421                 pcid = &pptpReq->ocack.peersCallID;
 422
 423                 info->pac_call_id = ntohs(*cid);
 424
 425                 if (htons(info->pns_call_id) != *pcid) {
 426                         DEBUGP("%s for unknown callid %u\n",
 427                                 pptp_msg_name[msg], ntohs(*pcid));
 428                         break;
 429                 }
 430
 431                 DEBUGP("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
 432                         ntohs(*cid), ntohs(*pcid));
 433
 434                 info->cstate = PPTP_CALL_OUT_CONF;
 435
 436                 seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
 437                                        + sizeof(struct PptpControlHeader)
 438                                        + ((void *)pcid - (void *)pptpReq);
 439
 440                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 441                         printk("ip_conntrack_pptp: error during exp_gre\n");
 442                 break;
 443
 444         case PPTP_IN_CALL_REQUEST:
 445                 if (reqlen < sizeof(_pptpReq.icack)) {
 446                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 447                         break;
 448                 }
 449
 450                 /* server tells us about incoming call request */
 451                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 452                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 453                         break;
 454                 }
 455                 pcid = &pptpReq->icack.peersCallID;
 456                 DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
 457                 info->cstate = PPTP_CALL_IN_REQ;
 458                 info->pac_call_id = ntohs(*pcid);
 459                 break;
 460
 461         case PPTP_IN_CALL_CONNECT:
 462                 if (reqlen < sizeof(_pptpReq.iccon)) {
 463                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 464                         break;
 465                 }
 466
 467                 /* server tells us about incoming call established */
 468                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 469                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 470                         break;
 471                 }
 472                 if (info->cstate != PPTP_CALL_IN_REP
 473                     && info->cstate != PPTP_CALL_IN_CONF) {
 474                         DEBUGP("%s but never sent IN_CALL_REPLY\n",
 475                                 pptp_msg_name[msg]);
 476                         break;
 477                 }
 478
 479                 pcid = &pptpReq->iccon.peersCallID;
 480                 cid = &info->pac_call_id;
 481
 482                 if (info->pns_call_id != ntohs(*pcid)) {
 483                         DEBUGP("%s for unknown CallID %u\n",
 484                                 pptp_msg_name[msg], ntohs(*pcid));
 485                         break;
 486                 }
 487
 488                 DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
 489                 info->cstate = PPTP_CALL_IN_CONF;
 490
 491                 /* we expect a GRE connection from PAC to PNS */
 492                 seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
 493                                        + sizeof(struct PptpControlHeader)
 494                                        + ((void *)pcid - (void *)pptpReq);
 495
 496                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 497                         printk("ip_conntrack_pptp: error during exp_gre\n");
 498
 499                 break;
 500
 501         case PPTP_CALL_DISCONNECT_NOTIFY:
 502                 if (reqlen < sizeof(_pptpReq.disc)) {
 503                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 504                         break;
 505                 }
 506
 507                 /* server confirms disconnect */
 508                 cid = &pptpReq->disc.callID;
 509                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*cid));
 510                 info->cstate = PPTP_CALL_NONE;
 511
 512                 /* untrack this call id, unexpect GRE packets */
 513                 pptp_destroy_siblings(ct);
 514                 break;
 515
 516         case PPTP_WAN_ERROR_NOTIFY:
 517                 break;
 518
 519         case PPTP_ECHO_REQUEST:
 520         case PPTP_ECHO_REPLY:
 521                 /* I don't have to explain these ;) */
 522                 break;
 523         default:
 524                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)
 525                         ? pptp_msg_name[msg]:pptp_msg_name[0], msg);
 526                 break;
 527         }
 528
 529
 530         if (ip_nat_pptp_hook_inbound)
 531                 return ip_nat_pptp_hook_inbound(pskb, ct, ctinfo, ctlh,
 532                                                 pptpReq);
 533
 534         return NF_ACCEPT;
 535
 536 }
 537
 538 static inline int
 539 pptp_outbound_pkt(struct sk_buff **pskb,
 540                   struct tcphdr *tcph,
 541                   unsigned int nexthdr_off,
 542                   unsigned int datalen,
 543                   struct ip_conntrack *ct,
 544                   enum ip_conntrack_info ctinfo)
 545 {
 546         struct PptpControlHeader _ctlh, *ctlh;
 547         unsigned int reqlen;
 548         union pptp_ctrl_union _pptpReq, *pptpReq;
 549         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 550         u_int16_t msg;
 551         __be16 *cid, *pcid;
 552
 553         ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 554         if (!ctlh)
 555                 return NF_ACCEPT;
 556         nexthdr_off += sizeof(_ctlh);
 557         datalen -= sizeof(_ctlh);
 558
 559         reqlen = datalen;
 560         if (reqlen > sizeof(*pptpReq))
 561                 reqlen = sizeof(*pptpReq);
 562         pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
 563         if (!pptpReq)
 564                 return NF_ACCEPT;
 565
 566         msg = ntohs(ctlh->messageType);
 567         DEBUGP("outbound control message %s\n", pptp_msg_name[msg]);
 568
 569         switch (msg) {
 570         case PPTP_START_SESSION_REQUEST:
 571                 /* client requests for new control session */
 572                 if (info->sstate != PPTP_SESSION_NONE) {
 573                         DEBUGP("%s but we already have one",
 574                                 pptp_msg_name[msg]);
 575                 }
 576                 info->sstate = PPTP_SESSION_REQUESTED;
 577                 break;
 578         case PPTP_STOP_SESSION_REQUEST:
 579                 /* client requests end of control session */
 580                 info->sstate = PPTP_SESSION_STOPREQ;
 581                 break;
 582
 583         case PPTP_OUT_CALL_REQUEST:
 584                 if (reqlen < sizeof(_pptpReq.ocreq)) {
 585                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 586                         /* FIXME: break; */
 587                 }
 588
 589                 /* client initiating connection to server */
 590                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 591                         DEBUGP("%s but no session\n",
 592                                 pptp_msg_name[msg]);
 593                         break;
 594                 }
 595                 info->cstate = PPTP_CALL_OUT_REQ;
 596                 /* track PNS call id */
 597                 cid = &pptpReq->ocreq.callID;
 598                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*cid));
 599                 info->pns_call_id = ntohs(*cid);
 600                 break;
 601         case PPTP_IN_CALL_REPLY:
 602                 if (reqlen < sizeof(_pptpReq.icack)) {
 603                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 604                         break;
 605                 }
 606
 607                 /* client answers incoming call */
 608                 if (info->cstate != PPTP_CALL_IN_REQ
 609                     && info->cstate != PPTP_CALL_IN_REP) {
 610                         DEBUGP("%s without incall_req\n",
 611                                 pptp_msg_name[msg]);
 612                         break;
 613                 }
 614                 if (pptpReq->icack.resultCode != PPTP_INCALL_ACCEPT) {
 615                         info->cstate = PPTP_CALL_NONE;
 616                         break;
 617                 }
 618                 pcid = &pptpReq->icack.peersCallID;
 619                 if (info->pac_call_id != ntohs(*pcid)) {
 620                         DEBUGP("%s for unknown call %u\n",
 621                                 pptp_msg_name[msg], ntohs(*pcid));
 622                         break;
 623                 }
 624                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
 625                 /* part two of the three-way handshake */
 626                 info->cstate = PPTP_CALL_IN_REP;
 627                 info->pns_call_id = ntohs(pptpReq->icack.callID);
 628                 break;
 629
 630         case PPTP_CALL_CLEAR_REQUEST:
 631                 /* client requests hangup of call */
 632                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 633                         DEBUGP("CLEAR_CALL but no session\n");
 634                         break;
 635                 }
 636                 /* FUTURE: iterate over all calls and check if
 637                  * call ID is valid.  We don't do this without newnat,
 638                  * because we only know about last call */
 639                 info->cstate = PPTP_CALL_CLEAR_REQ;
 640                 break;
 641         case PPTP_SET_LINK_INFO:
 642                 break;
 643         case PPTP_ECHO_REQUEST:
 644         case PPTP_ECHO_REPLY:
 645                 /* I don't have to explain these ;) */
 646                 break;
 647         default:
 648                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)?
 649                         pptp_msg_name[msg]:pptp_msg_name[0], msg);
 650                 /* unknown: no need to create GRE masq table entry */
 651                 break;
 652         }
 653
 654         if (ip_nat_pptp_hook_outbound)
 655                 return ip_nat_pptp_hook_outbound(pskb, ct, ctinfo, ctlh,
 656                                                  pptpReq);
 657
 658         return NF_ACCEPT;
 659 }
 660
 661
 662 /* track caller id inside control connection, call expect_related */
 663 static int
 664 conntrack_pptp_help(struct sk_buff **pskb,
 665                     struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 666
 667 {
 668         struct pptp_pkt_hdr _pptph, *pptph;
 669         struct tcphdr _tcph, *tcph;
 670         u_int32_t tcplen = (*pskb)->len - (*pskb)->nh.iph->ihl * 4;
 671         u_int32_t datalen;
 672         int dir = CTINFO2DIR(ctinfo);
 673         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 674         unsigned int nexthdr_off;
 675
 676         int oldsstate, oldcstate;
 677         int ret;
 678
 679         /* don't do any tracking before tcp handshake complete */
 680         if (ctinfo != IP_CT_ESTABLISHED
 681             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
 682                 DEBUGP("ctinfo = %u, skipping\n", ctinfo);
 683                 return NF_ACCEPT;
 684         }
 685
 686         nexthdr_off = (*pskb)->nh.iph->ihl*4;
 687         tcph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_tcph), &_tcph);
 688         BUG_ON(!tcph);
 689         nexthdr_off += tcph->doff * 4;
 690         datalen = tcplen - tcph->doff * 4;
 691
 692         if (tcph->fin || tcph->rst) {
 693                 DEBUGP("RST/FIN received, timeouting GRE\n");
 694                 /* can't do this after real newnat */
 695                 info->cstate = PPTP_CALL_NONE;
 696
 697                 /* untrack this call id, unexpect GRE packets */
 698                 pptp_destroy_siblings(ct);
 699         }
 700
 701         pptph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_pptph), &_pptph);
 702         if (!pptph) {
 703                 DEBUGP("no full PPTP header, can't track\n");
 704                 return NF_ACCEPT;
 705         }
 706         nexthdr_off += sizeof(_pptph);
 707         datalen -= sizeof(_pptph);
 708
 709         /* if it's not a control message we can't do anything with it */
 710         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 711             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 712                 DEBUGP("not a control packet\n");
 713                 return NF_ACCEPT;
 714         }
 715
 716         oldsstate = info->sstate;
 717         oldcstate = info->cstate;
 718
 719         spin_lock_bh(&ip_pptp_lock);
 720
 721         /* FIXME: We just blindly assume that the control connection is always
 722          * established from PNS->PAC.  However, RFC makes no guarantee */
 723         if (dir == IP_CT_DIR_ORIGINAL)
 724                 /* client -> server (PNS -> PAC) */
 725                 ret = pptp_outbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 726                                         ctinfo);
 727         else
 728                 /* server -> client (PAC -> PNS) */
 729                 ret = pptp_inbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 730                                        ctinfo);
 731         DEBUGP("sstate: %d->%d, cstate: %d->%d\n",
 732                 oldsstate, info->sstate, oldcstate, info->cstate);
 733         spin_unlock_bh(&ip_pptp_lock);
 734
 735         return ret;
 736 }
 737
 738 /* control protocol helper */
 739 static struct ip_conntrack_helper pptp = {
 740         .list = { NULL, NULL },
 741         .name = "pptp",
 742         .me = THIS_MODULE,
 743         .max_expected = 2,
 744         .timeout = 5 * 60,
 745         .tuple = { .src = { .ip = 0,
 746                             .u = { .tcp = { .port =
 747                                     __constant_htons(PPTP_CONTROL_PORT) } }
 748                           },
 749                    .dst = { .ip = 0,
 750                             .u = { .all = 0 },
 751                             .protonum = IPPROTO_TCP
 752                           }
 753                  },
 754         .mask = { .src = { .ip = 0,
 755                            .u = { .tcp = { .port = __constant_htons(0xffff) } }
 756                          },
 757                   .dst = { .ip = 0,
 758                            .u = { .all = 0 },
 759                            .protonum = 0xff
 760                          }
 761                 },
 762         .help = conntrack_pptp_help
 763 };
 764
 765 extern void ip_ct_proto_gre_fini(void);
 766 extern int __init ip_ct_proto_gre_init(void);
 767
 768 /* ip_conntrack_pptp initialization */
 769 static int __init ip_conntrack_helper_pptp_init(void)
 770 {
 771         int retcode;
 772
 773         retcode = ip_ct_proto_gre_init();
 774         if (retcode < 0)
 775                 return retcode;
 776
 777         DEBUGP(" registering helper\n");
 778         if ((retcode = ip_conntrack_helper_register(&pptp))) {
 779                 printk(KERN_ERR "Unable to register conntrack application "
 780                                 "helper for pptp: %d\n", retcode);
 781                 ip_ct_proto_gre_fini();
 782                 return retcode;
 783         }
 784
 785         printk("ip_conntrack_pptp version %s loaded\n", IP_CT_PPTP_VERSION);
 786         return 0;
 787 }
 788
 789 static void __exit ip_conntrack_helper_pptp_fini(void)
 790 {
 791         ip_conntrack_helper_unregister(&pptp);
 792         ip_ct_proto_gre_fini();
 793         printk("ip_conntrack_pptp version %s unloaded\n", IP_CT_PPTP_VERSION);
 794 }
 795
 796 module_init(ip_conntrack_helper_pptp_init);
 797 module_exit(ip_conntrack_helper_pptp_fini);
 798
 799 EXPORT_SYMBOL(ip_nat_pptp_hook_outbound);
 800 EXPORT_SYMBOL(ip_nat_pptp_hook_inbound);
 801 EXPORT_SYMBOL(ip_nat_pptp_hook_exp_gre);
 802 EXPORT_SYMBOL(ip_nat_pptp_hook_expectfn);