net/ipv4/netfilter/ip_conntrack_helper_pptp.c

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