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 = ct->help.ct_pptp_info.pns_call_id;
 205         t.dst.u.gre.key = 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 = ct->help.ct_pptp_info.pac_call_id;
 214         t.dst.u.gre.key = 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         __be16 callid,
 224         __be16 peer_callid)
 225 {
 226         struct ip_conntrack_tuple inv_tuple;
 227         struct ip_conntrack_tuple exp_tuples[] = {
 228                 /* tuple in original direction, PNS->PAC */
 229                 { .src = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip,
 230                            .u = { .gre = { .key = peer_callid } }
 231                          },
 232                   .dst = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip,
 233                            .u = { .gre = { .key = callid } },
 234                            .protonum = IPPROTO_GRE
 235                          },
 236                  },
 237                 /* tuple in reply direction, PAC->PNS */
 238                 { .src = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip,
 239                            .u = { .gre = { .key = callid } }
 240                          },
 241                   .dst = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip,
 242                            .u = { .gre = { .key = peer_callid } },
 243                            .protonum = IPPROTO_GRE
 244                          },
 245                  }
 246         };
 247         struct ip_conntrack_expect *exp_orig, *exp_reply;
 248         int ret = 1;
 249
 250         exp_orig = ip_conntrack_expect_alloc(master);
 251         if (exp_orig == NULL)
 252                 goto out;
 253
 254         exp_reply = ip_conntrack_expect_alloc(master);
 255         if (exp_reply == NULL)
 256                 goto out_put_orig;
 257
 258         memcpy(&exp_orig->tuple, &exp_tuples[0], sizeof(exp_orig->tuple));
 259
 260         exp_orig->mask.src.ip = 0xffffffff;
 261         exp_orig->mask.src.u.all = 0;
 262         exp_orig->mask.dst.u.all = 0;
 263         exp_orig->mask.dst.u.gre.key = htons(0xffff);
 264         exp_orig->mask.dst.ip = 0xffffffff;
 265         exp_orig->mask.dst.protonum = 0xff;
 266
 267         exp_orig->master = master;
 268         exp_orig->expectfn = pptp_expectfn;
 269         exp_orig->flags = 0;
 270
 271         /* both expectations are identical apart from tuple */
 272         memcpy(exp_reply, exp_orig, sizeof(*exp_reply));
 273         memcpy(&exp_reply->tuple, &exp_tuples[1], sizeof(exp_reply->tuple));
 274
 275         if (ip_nat_pptp_hook_exp_gre)
 276                 ret = ip_nat_pptp_hook_exp_gre(exp_orig, exp_reply);
 277         else {
 278
 279                 DEBUGP("calling expect_related PNS->PAC");
 280                 DUMP_TUPLE(&exp_orig->tuple);
 281
 282                 if (ip_conntrack_expect_related(exp_orig) != 0) {
 283                         DEBUGP("cannot expect_related()\n");
 284                         goto out_put_both;
 285                 }
 286
 287                 DEBUGP("calling expect_related PAC->PNS");
 288                 DUMP_TUPLE(&exp_reply->tuple);
 289
 290                 if (ip_conntrack_expect_related(exp_reply) != 0) {
 291                         DEBUGP("cannot expect_related()\n");
 292                         goto out_unexpect_orig;
 293                 }
 294
 295                 /* Add GRE keymap entries */
 296                 if (ip_ct_gre_keymap_add(master, &exp_reply->tuple, 0) != 0) {
 297                         DEBUGP("cannot keymap_add() exp\n");
 298                         goto out_unexpect_both;
 299                 }
 300
 301                 invert_tuplepr(&inv_tuple, &exp_reply->tuple);
 302                 if (ip_ct_gre_keymap_add(master, &inv_tuple, 1) != 0) {
 303                         ip_ct_gre_keymap_destroy(master);
 304                         DEBUGP("cannot keymap_add() exp_inv\n");
 305                         goto out_unexpect_both;
 306                 }
 307                 ret = 0;
 308         }
 309
 310 out_put_both:
 311         ip_conntrack_expect_put(exp_reply);
 312 out_put_orig:
 313         ip_conntrack_expect_put(exp_orig);
 314 out:
 315         return ret;
 316
 317 out_unexpect_both:
 318         ip_conntrack_unexpect_related(exp_reply);
 319 out_unexpect_orig:
 320         ip_conntrack_unexpect_related(exp_orig);
 321         goto out_put_both;
 322 }
 323
 324 static inline int
 325 pptp_inbound_pkt(struct sk_buff **pskb,
 326                  struct tcphdr *tcph,
 327                  unsigned int nexthdr_off,
 328                  unsigned int datalen,
 329                  struct ip_conntrack *ct,
 330                  enum ip_conntrack_info ctinfo)
 331 {
 332         struct PptpControlHeader _ctlh, *ctlh;
 333         unsigned int reqlen;
 334         union pptp_ctrl_union _pptpReq, *pptpReq;
 335         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 336         u_int16_t msg;
 337         __be16 cid, pcid;
 338
 339         ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 340         if (!ctlh) {
 341                 DEBUGP("error during skb_header_pointer\n");
 342                 return NF_ACCEPT;
 343         }
 344         nexthdr_off += sizeof(_ctlh);
 345         datalen -= sizeof(_ctlh);
 346
 347         reqlen = datalen;
 348         if (reqlen > sizeof(*pptpReq))
 349                 reqlen = sizeof(*pptpReq);
 350         pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
 351         if (!pptpReq) {
 352                 DEBUGP("error during skb_header_pointer\n");
 353                 return NF_ACCEPT;
 354         }
 355
 356         msg = ntohs(ctlh->messageType);
 357         DEBUGP("inbound control message %s\n", pptp_msg_name[msg]);
 358
 359         switch (msg) {
 360         case PPTP_START_SESSION_REPLY:
 361                 if (reqlen < sizeof(_pptpReq.srep)) {
 362                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 363                         break;
 364                 }
 365
 366                 /* server confirms new control session */
 367                 if (info->sstate < PPTP_SESSION_REQUESTED) {
 368                         DEBUGP("%s without START_SESS_REQUEST\n",
 369                                 pptp_msg_name[msg]);
 370                         break;
 371                 }
 372                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 373                         info->sstate = PPTP_SESSION_CONFIRMED;
 374                 else
 375                         info->sstate = PPTP_SESSION_ERROR;
 376                 break;
 377
 378         case PPTP_STOP_SESSION_REPLY:
 379                 if (reqlen < sizeof(_pptpReq.strep)) {
 380                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 381                         break;
 382                 }
 383
 384                 /* server confirms end of control session */
 385                 if (info->sstate > PPTP_SESSION_STOPREQ) {
 386                         DEBUGP("%s without STOP_SESS_REQUEST\n",
 387                                 pptp_msg_name[msg]);
 388                         break;
 389                 }
 390                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 391                         info->sstate = PPTP_SESSION_NONE;
 392                 else
 393                         info->sstate = PPTP_SESSION_ERROR;
 394                 break;
 395
 396         case PPTP_OUT_CALL_REPLY:
 397                 if (reqlen < sizeof(_pptpReq.ocack)) {
 398                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 399                         break;
 400                 }
 401
 402                 /* server accepted call, we now expect GRE frames */
 403                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 404                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 405                         break;
 406                 }
 407                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 408                     info->cstate != PPTP_CALL_OUT_CONF) {
 409                         DEBUGP("%s without OUTCALL_REQ\n", pptp_msg_name[msg]);
 410                         break;
 411                 }
 412                 if (pptpReq->ocack.resultCode != PPTP_OUTCALL_CONNECT) {
 413                         info->cstate = PPTP_CALL_NONE;
 414                         break;
 415                 }
 416
 417                 cid = pptpReq->ocack.callID;
 418                 pcid = pptpReq->ocack.peersCallID;
 419
 420                 info->pac_call_id = cid;
 421
 422                 if (info->pns_call_id != pcid) {
 423                         DEBUGP("%s for unknown callid %u\n",
 424                                 pptp_msg_name[msg], ntohs(pcid));
 425                         break;
 426                 }
 427
 428                 DEBUGP("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
 429                         ntohs(cid), ntohs(pcid));
 430
 431                 info->cstate = PPTP_CALL_OUT_CONF;
 432
 433                 exp_gre(ct, cid, pcid);
 434                 break;
 435
 436         case PPTP_IN_CALL_REQUEST:
 437                 if (reqlen < sizeof(_pptpReq.icack)) {
 438                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 439                         break;
 440                 }
 441
 442                 /* server tells us about incoming call request */
 443                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 444                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 445                         break;
 446                 }
 447                 pcid = pptpReq->icack.peersCallID;
 448                 DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
 449                 info->cstate = PPTP_CALL_IN_REQ;
 450                 info->pac_call_id = pcid;
 451                 break;
 452
 453         case PPTP_IN_CALL_CONNECT:
 454                 if (reqlen < sizeof(_pptpReq.iccon)) {
 455                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 456                         break;
 457                 }
 458
 459                 /* server tells us about incoming call established */
 460                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 461                         DEBUGP("%s but no session\n", pptp_msg_name[msg]);
 462                         break;
 463                 }
 464                 if (info->cstate != PPTP_CALL_IN_REP
 465                     && info->cstate != PPTP_CALL_IN_CONF) {
 466                         DEBUGP("%s but never sent IN_CALL_REPLY\n",
 467                                 pptp_msg_name[msg]);
 468                         break;
 469                 }
 470
 471                 pcid = pptpReq->iccon.peersCallID;
 472                 cid = info->pac_call_id;
 473
 474                 if (info->pns_call_id != pcid) {
 475                         DEBUGP("%s for unknown CallID %u\n",
 476                                 pptp_msg_name[msg], ntohs(pcid));
 477                         break;
 478                 }
 479
 480                 DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
 481                 info->cstate = PPTP_CALL_IN_CONF;
 482
 483                 /* we expect a GRE connection from PAC to PNS */
 484                 exp_gre(ct, cid, pcid);
 485                 break;
 486
 487         case PPTP_CALL_DISCONNECT_NOTIFY:
 488                 if (reqlen < sizeof(_pptpReq.disc)) {
 489                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 490                         break;
 491                 }
 492
 493                 /* server confirms disconnect */
 494                 cid = pptpReq->disc.callID;
 495                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 496                 info->cstate = PPTP_CALL_NONE;
 497
 498                 /* untrack this call id, unexpect GRE packets */
 499                 pptp_destroy_siblings(ct);
 500                 break;
 501
 502         case PPTP_WAN_ERROR_NOTIFY:
 503                 break;
 504
 505         case PPTP_ECHO_REQUEST:
 506         case PPTP_ECHO_REPLY:
 507                 /* I don't have to explain these ;) */
 508                 break;
 509         default:
 510                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)
 511                         ? pptp_msg_name[msg]:pptp_msg_name[0], msg);
 512                 break;
 513         }
 514
 515
 516         if (ip_nat_pptp_hook_inbound)
 517                 return ip_nat_pptp_hook_inbound(pskb, ct, ctinfo, ctlh,
 518                                                 pptpReq);
 519
 520         return NF_ACCEPT;
 521
 522 }
 523
 524 static inline int
 525 pptp_outbound_pkt(struct sk_buff **pskb,
 526                   struct tcphdr *tcph,
 527                   unsigned int nexthdr_off,
 528                   unsigned int datalen,
 529                   struct ip_conntrack *ct,
 530                   enum ip_conntrack_info ctinfo)
 531 {
 532         struct PptpControlHeader _ctlh, *ctlh;
 533         unsigned int reqlen;
 534         union pptp_ctrl_union _pptpReq, *pptpReq;
 535         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 536         u_int16_t msg;
 537         __be16 cid, pcid;
 538
 539         ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 540         if (!ctlh)
 541                 return NF_ACCEPT;
 542         nexthdr_off += sizeof(_ctlh);
 543         datalen -= sizeof(_ctlh);
 544
 545         reqlen = datalen;
 546         if (reqlen > sizeof(*pptpReq))
 547                 reqlen = sizeof(*pptpReq);
 548         pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
 549         if (!pptpReq)
 550                 return NF_ACCEPT;
 551
 552         msg = ntohs(ctlh->messageType);
 553         DEBUGP("outbound control message %s\n", pptp_msg_name[msg]);
 554
 555         switch (msg) {
 556         case PPTP_START_SESSION_REQUEST:
 557                 /* client requests for new control session */
 558                 if (info->sstate != PPTP_SESSION_NONE) {
 559                         DEBUGP("%s but we already have one",
 560                                 pptp_msg_name[msg]);
 561                 }
 562                 info->sstate = PPTP_SESSION_REQUESTED;
 563                 break;
 564         case PPTP_STOP_SESSION_REQUEST:
 565                 /* client requests end of control session */
 566                 info->sstate = PPTP_SESSION_STOPREQ;
 567                 break;
 568
 569         case PPTP_OUT_CALL_REQUEST:
 570                 if (reqlen < sizeof(_pptpReq.ocreq)) {
 571                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 572                         break;
 573                 }
 574
 575                 /* client initiating connection to server */
 576                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 577                         DEBUGP("%s but no session\n",
 578                                 pptp_msg_name[msg]);
 579                         break;
 580                 }
 581                 info->cstate = PPTP_CALL_OUT_REQ;
 582                 /* track PNS call id */
 583                 cid = pptpReq->ocreq.callID;
 584                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 585                 info->pns_call_id = cid;
 586                 break;
 587         case PPTP_IN_CALL_REPLY:
 588                 if (reqlen < sizeof(_pptpReq.icack)) {
 589                         DEBUGP("%s: short packet\n", pptp_msg_name[msg]);
 590                         break;
 591                 }
 592
 593                 /* client answers incoming call */
 594                 if (info->cstate != PPTP_CALL_IN_REQ
 595                     && info->cstate != PPTP_CALL_IN_REP) {
 596                         DEBUGP("%s without incall_req\n",
 597                                 pptp_msg_name[msg]);
 598                         break;
 599                 }
 600                 if (pptpReq->icack.resultCode != PPTP_INCALL_ACCEPT) {
 601                         info->cstate = PPTP_CALL_NONE;
 602                         break;
 603                 }
 604                 pcid = pptpReq->icack.peersCallID;
 605                 if (info->pac_call_id != pcid) {
 606                         DEBUGP("%s for unknown call %u\n",
 607                                 pptp_msg_name[msg], ntohs(pcid));
 608                         break;
 609                 }
 610                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(pcid));
 611                 /* part two of the three-way handshake */
 612                 info->cstate = PPTP_CALL_IN_REP;
 613                 info->pns_call_id = pcid;
 614                 break;
 615
 616         case PPTP_CALL_CLEAR_REQUEST:
 617                 /* client requests hangup of call */
 618                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 619                         DEBUGP("CLEAR_CALL but no session\n");
 620                         break;
 621                 }
 622                 /* FUTURE: iterate over all calls and check if
 623                  * call ID is valid.  We don't do this without newnat,
 624                  * because we only know about last call */
 625                 info->cstate = PPTP_CALL_CLEAR_REQ;
 626                 break;
 627         case PPTP_SET_LINK_INFO:
 628                 break;
 629         case PPTP_ECHO_REQUEST:
 630         case PPTP_ECHO_REPLY:
 631                 /* I don't have to explain these ;) */
 632                 break;
 633         default:
 634                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)?
 635                         pptp_msg_name[msg]:pptp_msg_name[0], msg);
 636                 /* unknown: no need to create GRE masq table entry */
 637                 break;
 638         }
 639
 640         if (ip_nat_pptp_hook_outbound)
 641                 return ip_nat_pptp_hook_outbound(pskb, ct, ctinfo, ctlh,
 642                                                  pptpReq);
 643
 644         return NF_ACCEPT;
 645 }
 646
 647
 648 /* track caller id inside control connection, call expect_related */
 649 static int
 650 conntrack_pptp_help(struct sk_buff **pskb,
 651                     struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 652
 653 {
 654         struct pptp_pkt_hdr _pptph, *pptph;
 655         struct tcphdr _tcph, *tcph;
 656         u_int32_t tcplen = (*pskb)->len - (*pskb)->nh.iph->ihl * 4;
 657         u_int32_t datalen;
 658         int dir = CTINFO2DIR(ctinfo);
 659         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 660         unsigned int nexthdr_off;
 661
 662         int oldsstate, oldcstate;
 663         int ret;
 664
 665         /* don't do any tracking before tcp handshake complete */
 666         if (ctinfo != IP_CT_ESTABLISHED
 667             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
 668                 DEBUGP("ctinfo = %u, skipping\n", ctinfo);
 669                 return NF_ACCEPT;
 670         }
 671
 672         nexthdr_off = (*pskb)->nh.iph->ihl*4;
 673         tcph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_tcph), &_tcph);
 674         BUG_ON(!tcph);
 675         nexthdr_off += tcph->doff * 4;
 676         datalen = tcplen - tcph->doff * 4;
 677
 678         if (tcph->fin || tcph->rst) {
 679                 DEBUGP("RST/FIN received, timeouting GRE\n");
 680                 /* can't do this after real newnat */
 681                 info->cstate = PPTP_CALL_NONE;
 682
 683                 /* untrack this call id, unexpect GRE packets */
 684                 pptp_destroy_siblings(ct);
 685         }
 686
 687         pptph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_pptph), &_pptph);
 688         if (!pptph) {
 689                 DEBUGP("no full PPTP header, can't track\n");
 690                 return NF_ACCEPT;
 691         }
 692         nexthdr_off += sizeof(_pptph);
 693         datalen -= sizeof(_pptph);
 694
 695         /* if it's not a control message we can't do anything with it */
 696         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 697             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 698                 DEBUGP("not a control packet\n");
 699                 return NF_ACCEPT;
 700         }
 701
 702         oldsstate = info->sstate;
 703         oldcstate = info->cstate;
 704
 705         spin_lock_bh(&ip_pptp_lock);
 706
 707         /* FIXME: We just blindly assume that the control connection is always
 708          * established from PNS->PAC.  However, RFC makes no guarantee */
 709         if (dir == IP_CT_DIR_ORIGINAL)
 710                 /* client -> server (PNS -> PAC) */
 711                 ret = pptp_outbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 712                                         ctinfo);
 713         else
 714                 /* server -> client (PAC -> PNS) */
 715                 ret = pptp_inbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 716                                        ctinfo);
 717         DEBUGP("sstate: %d->%d, cstate: %d->%d\n",
 718                 oldsstate, info->sstate, oldcstate, info->cstate);
 719         spin_unlock_bh(&ip_pptp_lock);
 720
 721         return ret;
 722 }
 723
 724 /* control protocol helper */
 725 static struct ip_conntrack_helper pptp = {
 726         .list = { NULL, NULL },
 727         .name = "pptp",
 728         .me = THIS_MODULE,
 729         .max_expected = 2,
 730         .timeout = 5 * 60,
 731         .tuple = { .src = { .ip = 0,
 732                             .u = { .tcp = { .port =
 733                                     __constant_htons(PPTP_CONTROL_PORT) } }
 734                           },
 735                    .dst = { .ip = 0,
 736                             .u = { .all = 0 },
 737                             .protonum = IPPROTO_TCP
 738                           }
 739                  },
 740         .mask = { .src = { .ip = 0,
 741                            .u = { .tcp = { .port = __constant_htons(0xffff) } }
 742                          },
 743                   .dst = { .ip = 0,
 744                            .u = { .all = 0 },
 745                            .protonum = 0xff
 746                          }
 747                 },
 748         .help = conntrack_pptp_help
 749 };
 750
 751 extern void ip_ct_proto_gre_fini(void);
 752 extern int __init ip_ct_proto_gre_init(void);
 753
 754 /* ip_conntrack_pptp initialization */
 755 static int __init ip_conntrack_helper_pptp_init(void)
 756 {
 757         int retcode;
 758
 759         retcode = ip_ct_proto_gre_init();
 760         if (retcode < 0)
 761                 return retcode;
 762
 763         DEBUGP(" registering helper\n");
 764         if ((retcode = ip_conntrack_helper_register(&pptp))) {
 765                 printk(KERN_ERR "Unable to register conntrack application "
 766                                 "helper for pptp: %d\n", retcode);
 767                 ip_ct_proto_gre_fini();
 768                 return retcode;
 769         }
 770
 771         printk("ip_conntrack_pptp version %s loaded\n", IP_CT_PPTP_VERSION);
 772         return 0;
 773 }
 774
 775 static void __exit ip_conntrack_helper_pptp_fini(void)
 776 {
 777         ip_conntrack_helper_unregister(&pptp);
 778         ip_ct_proto_gre_fini();
 779         printk("ip_conntrack_pptp version %s unloaded\n", IP_CT_PPTP_VERSION);
 780 }
 781
 782 module_init(ip_conntrack_helper_pptp_init);
 783 module_exit(ip_conntrack_helper_pptp_fini);
 784
 785 EXPORT_SYMBOL(ip_nat_pptp_hook_outbound);
 786 EXPORT_SYMBOL(ip_nat_pptp_hook_inbound);
 787 EXPORT_SYMBOL(ip_nat_pptp_hook_exp_gre);
 788 EXPORT_SYMBOL(ip_nat_pptp_hook_expectfn);