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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                 /* refresh_acct will not modify counters if skb == NULL */
 176                 if (del_timer(&sibling->timeout))
 177                         sibling->timeout.function((unsigned long)sibling);
 178                 ip_conntrack_put(sibling);
 179                 return 1;
 180         } else {
 181                 exp = ip_conntrack_expect_find(t);
 182                 if (exp) {
 183                         DEBUGP("unexpect_related of expect %p\n", exp);
 184                         ip_conntrack_unexpect_related(exp);
 185                         ip_conntrack_expect_put(exp);
 186                         return 1;
 187                 }
 188         }
 189
 190         return 0;
 191 }
 192
 193
 194 /* timeout GRE data connections */
 195 static void pptp_destroy_siblings(struct ip_conntrack *ct)
 196 {
 197         struct ip_conntrack_tuple t;
 198
 199         /* Since ct->sibling_list has literally rusted away in 2.6.11,
 200          * we now need another way to find out about our sibling
 201          * contrack and expects... -HW */
 202
 203         /* try original (pns->pac) tuple */
 204         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 205         t.dst.protonum = IPPROTO_GRE;
 206         t.src.u.gre.key = htons(ct->help.ct_pptp_info.pns_call_id);
 207         t.dst.u.gre.key = htons(ct->help.ct_pptp_info.pac_call_id);
 208
 209         if (!destroy_sibling_or_exp(&t))
 210                 DEBUGP("failed to timeout original pns->pac ct/exp\n");
 211
 212         /* try reply (pac->pns) tuple */
 213         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 214         t.dst.protonum = IPPROTO_GRE;
 215         t.src.u.gre.key = htons(ct->help.ct_pptp_info.pac_call_id);
 216         t.dst.u.gre.key = htons(ct->help.ct_pptp_info.pns_call_id);
 217
 218         if (!destroy_sibling_or_exp(&t))
 219                 DEBUGP("failed to timeout reply pac->pns ct/exp\n");
 220 }
 221
 222 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 223 static inline int
 224 exp_gre(struct ip_conntrack *master,
 225         u_int32_t seq,
 226         u_int16_t callid,
 227         u_int16_t peer_callid)
 228 {
 229         struct ip_conntrack_tuple inv_tuple;
 230         struct ip_conntrack_tuple exp_tuples[] = {
 231                 /* tuple in original direction, PNS->PAC */
 232                 { .src = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip,
 233                            .u = { .gre = { .key = peer_callid } }
 234                          },
 235                   .dst = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip,
 236                            .u = { .gre = { .key = callid } },
 237                            .protonum = IPPROTO_GRE
 238                          },
 239                  },
 240                 /* tuple in reply direction, PAC->PNS */
 241                 { .src = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip,
 242                            .u = { .gre = { .key = callid } }
 243                          },
 244                   .dst = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip,
 245                            .u = { .gre = { .key = peer_callid } },
 246                            .protonum = IPPROTO_GRE
 247                          },
 248                  }
 249         };
 250         struct ip_conntrack_expect *exp_orig, *exp_reply;
 251         int ret = 1;
 252
 253         exp_orig = ip_conntrack_expect_alloc(master);
 254         if (exp_orig == NULL)
 255                 goto out;
 256
 257         exp_reply = ip_conntrack_expect_alloc(master);
 258         if (exp_reply == NULL)
 259                 goto out_put_orig;
 260
 261         memcpy(&exp_orig->tuple, &exp_tuples[0], sizeof(exp_orig->tuple));
 262
 263         exp_orig->mask.src.ip = 0xffffffff;
 264         exp_orig->mask.src.u.all = 0;
 265         exp_orig->mask.dst.u.all = 0;
 266         exp_orig->mask.dst.u.gre.key = 0xffff;
 267         exp_orig->mask.dst.ip = 0xffffffff;
 268         exp_orig->mask.dst.protonum = 0xff;
 269
 270         exp_orig->master = master;
 271         exp_orig->expectfn = pptp_expectfn;
 272         exp_orig->flags = 0;
 273
 274         exp_orig->dir = IP_CT_DIR_ORIGINAL;
 275
 276         /* both expectations are identical apart from tuple */
 277         memcpy(exp_reply, exp_orig, sizeof(*exp_reply));
 278         memcpy(&exp_reply->tuple, &exp_tuples[1], sizeof(exp_reply->tuple));
 279
 280         exp_reply->dir = !exp_orig->dir;
 281
 282         if (ip_nat_pptp_hook_exp_gre)
 283                 ret = ip_nat_pptp_hook_exp_gre(exp_orig, exp_reply);
 284         else {
 285
 286                 DEBUGP("calling expect_related PNS->PAC");
 287                 DUMP_TUPLE(&exp_orig->tuple);
 288
 289                 if (ip_conntrack_expect_related(exp_orig) != 0) {
 290                         DEBUGP("cannot expect_related()\n");
 291                         goto out_put_both;
 292                 }
 293
 294                 DEBUGP("calling expect_related PAC->PNS");
 295                 DUMP_TUPLE(&exp_reply->tuple);
 296
 297                 if (ip_conntrack_expect_related(exp_reply) != 0) {
 298                         DEBUGP("cannot expect_related()\n");
 299                         goto out_unexpect_orig;
 300                 }
 301
 302                 /* Add GRE keymap entries */
 303                 if (ip_ct_gre_keymap_add(master, &exp_reply->tuple, 0) != 0) {
 304                         DEBUGP("cannot keymap_add() exp\n");
 305                         goto out_unexpect_both;
 306                 }
 307
 308                 invert_tuplepr(&inv_tuple, &exp_reply->tuple);
 309                 if (ip_ct_gre_keymap_add(master, &inv_tuple, 1) != 0) {
 310                         ip_ct_gre_keymap_destroy(master);
 311                         DEBUGP("cannot keymap_add() exp_inv\n");
 312                         goto out_unexpect_both;
 313                 }
 314                 ret = 0;
 315         }
 316
 317 out_put_both:
 318         ip_conntrack_expect_put(exp_reply);
 319 out_put_orig:
 320         ip_conntrack_expect_put(exp_orig);
 321 out:
 322         return ret;
 323
 324 out_unexpect_both:
 325         ip_conntrack_unexpect_related(exp_reply);
 326 out_unexpect_orig:
 327         ip_conntrack_unexpect_related(exp_orig);
 328         goto out_put_both;
 329 }
 330
 331 static inline int
 332 pptp_inbound_pkt(struct sk_buff **pskb,
 333                  struct tcphdr *tcph,
 334                  unsigned int nexthdr_off,
 335                  unsigned int datalen,
 336                  struct ip_conntrack *ct,
 337                  enum ip_conntrack_info ctinfo)
 338 {
 339         struct PptpControlHeader _ctlh, *ctlh;
 340         unsigned int reqlen;
 341         union pptp_ctrl_union _pptpReq, *pptpReq;
 342         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 343         u_int16_t msg, *cid, *pcid;
 344         u_int32_t seq;
 345
 346         ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 347         if (!ctlh) {
 348                 DEBUGP("error during skb_header_pointer\n");
 349                 return NF_ACCEPT;
 350         }
 351         nexthdr_off += sizeof(_ctlh);
 352         datalen -= sizeof(_ctlh);
 353
 354         reqlen = datalen;
 355         if (reqlen > sizeof(*pptpReq))
 356                 reqlen = sizeof(*pptpReq);
 357         pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
 358         if (!pptpReq) {
 359                 DEBUGP("error during skb_header_pointer\n");
 360                 return NF_ACCEPT;
 361         }
 362
 363         msg = ntohs(ctlh->messageType);
 364         DEBUGP("inbound control message %s\n", pptp_msg_name[msg]);
 365
 366         switch (msg) {
 367         case PPTP_START_SESSION_REPLY:
 368                 if (reqlen < sizeof(_pptpReq.srep)) {
 369                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 370                         break;
 371                 }
 372
 373                 /* server confirms new control session */
 374                 if (info->sstate < PPTP_SESSION_REQUESTED) {
 375                         DEBUGP("%s without START_SESS_REQUEST\n",
 376                                 pptp_msg_name[msg]);
 377                         break;
 378                 }
 379                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 380                         info->sstate = PPTP_SESSION_CONFIRMED;
 381                 else
 382                         info->sstate = PPTP_SESSION_ERROR;
 383                 break;
 384
 385         case PPTP_STOP_SESSION_REPLY:
 386                 if (reqlen < sizeof(_pptpReq.strep)) {
 387                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 388                         break;
 389                 }
 390
 391                 /* server confirms end of control session */
 392                 if (info->sstate > PPTP_SESSION_STOPREQ) {
 393                         DEBUGP("%s without STOP_SESS_REQUEST\n",
 394                                 pptp_msg_name[msg]);
 395                         break;
 396                 }
 397                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 398                         info->sstate = PPTP_SESSION_NONE;
 399                 else
 400                         info->sstate = PPTP_SESSION_ERROR;
 401                 break;
 402
 403         case PPTP_OUT_CALL_REPLY:
 404                 if (reqlen < sizeof(_pptpReq.ocack)) {
 405                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 406                         break;
 407                 }
 408
 409                 /* server accepted call, we now expect GRE frames */
 410                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 411                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 412                         break;
 413                 }
 414                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 415                     info->cstate != PPTP_CALL_OUT_CONF) {
 416                         DEBUGP("%s without OUTCALL_REQ\n", pptp_msg_name[msg]);
 417                         break;
 418                 }
 419                 if (pptpReq->ocack.resultCode != PPTP_OUTCALL_CONNECT) {
 420                         info->cstate = PPTP_CALL_NONE;
 421                         break;
 422                 }
 423
 424                 cid = &pptpReq->ocack.callID;
 425                 pcid = &pptpReq->ocack.peersCallID;
 426
 427                 info->pac_call_id = ntohs(*cid);
 428
 429                 if (htons(info->pns_call_id) != *pcid) {
 430                         DEBUGP("%s for unknown callid %u\n",
 431                                 pptp_msg_name[msg], ntohs(*pcid));
 432                         break;
 433                 }
 434
 435                 DEBUGP("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
 436                         ntohs(*cid), ntohs(*pcid));
 437
 438                 info->cstate = PPTP_CALL_OUT_CONF;
 439
 440                 seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
 441                                        + sizeof(struct PptpControlHeader)
 442                                        + ((void *)pcid - (void *)pptpReq);
 443
 444                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 445                         printk("ip_conntrack_pptp: error during exp_gre\n");
 446                 break;
 447
 448         case PPTP_IN_CALL_REQUEST:
 449                 if (reqlen < sizeof(_pptpReq.icack)) {
 450                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 451                         break;
 452                 }
 453
 454                 /* server tells us about incoming call request */
 455                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 456                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 457                         break;
 458                 }
 459                 pcid = &pptpReq->icack.peersCallID;
 460                 DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
 461                 info->cstate = PPTP_CALL_IN_REQ;
 462                 info->pac_call_id = ntohs(*pcid);
 463                 break;
 464
 465         case PPTP_IN_CALL_CONNECT:
 466                 if (reqlen < sizeof(_pptpReq.iccon)) {
 467                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 468                         break;
 469                 }
 470
 471                 /* server tells us about incoming call established */
 472                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 473                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 474                         break;
 475                 }
 476                 if (info->sstate != PPTP_CALL_IN_REP
 477                     && info->sstate != PPTP_CALL_IN_CONF) {
 478                         DEBUGP("%s but never sent IN_CALL_REPLY\n",
 479                                 pptp_msg_name[msg]);
 480                         break;
 481                 }
 482
 483                 pcid = &pptpReq->iccon.peersCallID;
 484                 cid = &info->pac_call_id;
 485
 486                 if (info->pns_call_id != ntohs(*pcid)) {
 487                         DEBUGP("%s for unknown CallID %u\n",
 488                                 pptp_msg_name[msg], ntohs(*cid));
 489                         break;
 490                 }
 491
 492                 DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
 493                 info->cstate = PPTP_CALL_IN_CONF;
 494
 495                 /* we expect a GRE connection from PAC to PNS */
 496                 seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
 497                                        + sizeof(struct PptpControlHeader)
 498                                        + ((void *)pcid - (void *)pptpReq);
 499
 500                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 501                         printk("ip_conntrack_pptp: error during exp_gre\n");
 502
 503                 break;
 504
 505         case PPTP_CALL_DISCONNECT_NOTIFY:
 506                 if (reqlen < sizeof(_pptpReq.disc)) {
 507                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 508                         break;
 509                 }
 510
 511                 /* server confirms disconnect */
 512                 cid = &pptpReq->disc.callID;
 513                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*cid));
 514                 info->cstate = PPTP_CALL_NONE;
 515
 516                 /* untrack this call id, unexpect GRE packets */
 517                 pptp_destroy_siblings(ct);
 518                 break;
 519
 520         case PPTP_WAN_ERROR_NOTIFY:
 521                 break;
 522
 523         case PPTP_ECHO_REQUEST:
 524         case PPTP_ECHO_REPLY:
 525                 /* I don't have to explain these ;) */
 526                 break;
 527         default:
 528                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)
 529                         ? pptp_msg_name[msg]:pptp_msg_name[0], msg);
 530                 break;
 531         }
 532
 533
 534         if (ip_nat_pptp_hook_inbound)
 535                 return ip_nat_pptp_hook_inbound(pskb, ct, ctinfo, ctlh,
 536                                                 pptpReq);
 537
 538         return NF_ACCEPT;
 539
 540 }
 541
 542 static inline int
 543 pptp_outbound_pkt(struct sk_buff **pskb,
 544                   struct tcphdr *tcph,
 545                   unsigned int nexthdr_off,
 546                   unsigned int datalen,
 547                   struct ip_conntrack *ct,
 548                   enum ip_conntrack_info ctinfo)
 549 {
 550         struct PptpControlHeader _ctlh, *ctlh;
 551         unsigned int reqlen;
 552         union pptp_ctrl_union _pptpReq, *pptpReq;
 553         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 554         u_int16_t msg, *cid, *pcid;
 555
 556         ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 557         if (!ctlh)
 558                 return NF_ACCEPT;
 559         nexthdr_off += sizeof(_ctlh);
 560         datalen -= sizeof(_ctlh);
 561
 562         reqlen = datalen;
 563         if (reqlen > sizeof(*pptpReq))
 564                 reqlen = sizeof(*pptpReq);
 565         pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
 566         if (!pptpReq)
 567                 return NF_ACCEPT;
 568
 569         msg = ntohs(ctlh->messageType);
 570         DEBUGP("outbound control message %s\n", pptp_msg_name[msg]);
 571
 572         switch (msg) {
 573         case PPTP_START_SESSION_REQUEST:
 574                 /* client requests for new control session */
 575                 if (info->sstate != PPTP_SESSION_NONE) {
 576                         DEBUGP("%s but we already have one",
 577                                 pptp_msg_name[msg]);
 578                 }
 579                 info->sstate = PPTP_SESSION_REQUESTED;
 580                 break;
 581         case PPTP_STOP_SESSION_REQUEST:
 582                 /* client requests end of control session */
 583                 info->sstate = PPTP_SESSION_STOPREQ;
 584                 break;
 585
 586         case PPTP_OUT_CALL_REQUEST:
 587                 if (reqlen < sizeof(_pptpReq.ocreq)) {
 588                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 589                         /* FIXME: break; */
 590                 }
 591
 592                 /* client initiating connection to server */
 593                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 594                         DEBUGP("%s but no session\n",
 595                                 pptp_msg_name[msg]);
 596                         break;
 597                 }
 598                 info->cstate = PPTP_CALL_OUT_REQ;
 599                 /* track PNS call id */
 600                 cid = &pptpReq->ocreq.callID;
 601                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*cid));
 602                 info->pns_call_id = ntohs(*cid);
 603                 break;
 604         case PPTP_IN_CALL_REPLY:
 605                 if (reqlen < sizeof(_pptpReq.icack)) {
 606                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 607                         break;
 608                 }
 609
 610                 /* client answers incoming call */
 611                 if (info->cstate != PPTP_CALL_IN_REQ
 612                     && info->cstate != PPTP_CALL_IN_REP) {
 613                         DEBUGP("%s without incall_req\n",
 614                                 pptp_msg_name[msg]);
 615                         break;
 616                 }
 617                 if (pptpReq->icack.resultCode != PPTP_INCALL_ACCEPT) {
 618                         info->cstate = PPTP_CALL_NONE;
 619                         break;
 620                 }
 621                 pcid = &pptpReq->icack.peersCallID;
 622                 if (info->pac_call_id != ntohs(*pcid)) {
 623                         DEBUGP("%s for unknown call %u\n",
 624                                 pptp_msg_name[msg], ntohs(*pcid));
 625                         break;
 626                 }
 627                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(*pcid));
 628                 /* part two of the three-way handshake */
 629                 info->cstate = PPTP_CALL_IN_REP;
 630                 info->pns_call_id = ntohs(pptpReq->icack.callID);
 631                 break;
 632
 633         case PPTP_CALL_CLEAR_REQUEST:
 634                 /* client requests hangup of call */
 635                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 636                         DEBUGP("CLEAR_CALL but no session\n");
 637                         break;
 638                 }
 639                 /* FUTURE: iterate over all calls and check if
 640                  * call ID is valid.  We don't do this without newnat,
 641                  * because we only know about last call */
 642                 info->cstate = PPTP_CALL_CLEAR_REQ;
 643                 break;
 644         case PPTP_SET_LINK_INFO:
 645                 break;
 646         case PPTP_ECHO_REQUEST:
 647         case PPTP_ECHO_REPLY:
 648                 /* I don't have to explain these ;) */
 649                 break;
 650         default:
 651                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)?
 652                         pptp_msg_name[msg]:pptp_msg_name[0], msg);
 653                 /* unknown: no need to create GRE masq table entry */
 654                 break;
 655         }
 656
 657         if (ip_nat_pptp_hook_outbound)
 658                 return ip_nat_pptp_hook_outbound(pskb, ct, ctinfo, ctlh,
 659                                                  pptpReq);
 660
 661         return NF_ACCEPT;
 662 }
 663
 664
 665 /* track caller id inside control connection, call expect_related */
 666 static int
 667 conntrack_pptp_help(struct sk_buff **pskb,
 668                     struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 669
 670 {
 671         struct pptp_pkt_hdr _pptph, *pptph;
 672         struct tcphdr _tcph, *tcph;
 673         u_int32_t tcplen = (*pskb)->len - (*pskb)->nh.iph->ihl * 4;
 674         u_int32_t datalen;
 675         int dir = CTINFO2DIR(ctinfo);
 676         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 677         unsigned int nexthdr_off;
 678
 679         int oldsstate, oldcstate;
 680         int ret;
 681
 682         /* don't do any tracking before tcp handshake complete */
 683         if (ctinfo != IP_CT_ESTABLISHED
 684             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
 685                 DEBUGP("ctinfo = %u, skipping\n", ctinfo);
 686                 return NF_ACCEPT;
 687         }
 688
 689         nexthdr_off = (*pskb)->nh.iph->ihl*4;
 690         tcph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_tcph), &_tcph);
 691         BUG_ON(!tcph);
 692         nexthdr_off += tcph->doff * 4;
 693         datalen = tcplen - tcph->doff * 4;
 694
 695         if (tcph->fin || tcph->rst) {
 696                 DEBUGP("RST/FIN received, timeouting GRE\n");
 697                 /* can't do this after real newnat */
 698                 info->cstate = PPTP_CALL_NONE;
 699
 700                 /* untrack this call id, unexpect GRE packets */
 701                 pptp_destroy_siblings(ct);
 702         }
 703
 704         pptph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_pptph), &_pptph);
 705         if (!pptph) {
 706                 DEBUGP("no full PPTP header, can't track\n");
 707                 return NF_ACCEPT;
 708         }
 709         nexthdr_off += sizeof(_pptph);
 710         datalen -= sizeof(_pptph);
 711
 712         /* if it's not a control message we can't do anything with it */
 713         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 714             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 715                 DEBUGP("not a control packet\n");
 716                 return NF_ACCEPT;
 717         }
 718
 719         oldsstate = info->sstate;
 720         oldcstate = info->cstate;
 721
 722         spin_lock_bh(&ip_pptp_lock);
 723
 724         /* FIXME: We just blindly assume that the control connection is always
 725          * established from PNS->PAC.  However, RFC makes no guarantee */
 726         if (dir == IP_CT_DIR_ORIGINAL)
 727                 /* client -> server (PNS -> PAC) */
 728                 ret = pptp_outbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 729                                         ctinfo);
 730         else
 731                 /* server -> client (PAC -> PNS) */
 732                 ret = pptp_inbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 733                                        ctinfo);
 734         DEBUGP("sstate: %d->%d, cstate: %d->%d\n",
 735                 oldsstate, info->sstate, oldcstate, info->cstate);
 736         spin_unlock_bh(&ip_pptp_lock);
 737
 738         return ret;
 739 }
 740
 741 /* control protocol helper */
 742 static struct ip_conntrack_helper pptp = {
 743         .list = { NULL, NULL },
 744         .name = "pptp",
 745         .me = THIS_MODULE,
 746         .max_expected = 2,
 747         .timeout = 5 * 60,
 748         .tuple = { .src = { .ip = 0,
 749                             .u = { .tcp = { .port =
 750                                     __constant_htons(PPTP_CONTROL_PORT) } }
 751                           },
 752                    .dst = { .ip = 0,
 753                             .u = { .all = 0 },
 754                             .protonum = IPPROTO_TCP
 755                           }
 756                  },
 757         .mask = { .src = { .ip = 0,
 758                            .u = { .tcp = { .port = 0xffff } }
 759                          },
 760                   .dst = { .ip = 0,
 761                            .u = { .all = 0 },
 762                            .protonum = 0xff
 763                          }
 764                 },
 765         .help = conntrack_pptp_help
 766 };
 767
 768 extern void __exit ip_ct_proto_gre_fini(void);
 769 extern int __init ip_ct_proto_gre_init(void);
 770
 771 /* ip_conntrack_pptp initialization */
 772 static int __init init(void)
 773 {
 774         int retcode;
 775
 776         retcode = ip_ct_proto_gre_init();
 777         if (retcode < 0)
 778                 return retcode;
 779
 780         DEBUGP(" registering helper\n");
 781         if ((retcode = ip_conntrack_helper_register(&pptp))) {
 782                 printk(KERN_ERR "Unable to register conntrack application "
 783                                 "helper for pptp: %d\n", retcode);
 784                 ip_ct_proto_gre_fini();
 785                 return retcode;
 786         }
 787
 788         printk("ip_conntrack_pptp version %s loaded\n", IP_CT_PPTP_VERSION);
 789         return 0;
 790 }
 791
 792 static void __exit fini(void)
 793 {
 794         ip_conntrack_helper_unregister(&pptp);
 795         ip_ct_proto_gre_fini();
 796         printk("ip_conntrack_pptp version %s unloaded\n", IP_CT_PPTP_VERSION);
 797 }
 798
 799 module_init(init);
 800 module_exit(fini);
 801
 802 EXPORT_SYMBOL(ip_nat_pptp_hook_outbound);
 803 EXPORT_SYMBOL(ip_nat_pptp_hook_inbound);
 804 EXPORT_SYMBOL(ip_nat_pptp_hook_exp_gre);
 805 EXPORT_SYMBOL(ip_nat_pptp_hook_expectfn);