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 void
  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         ip_ct_gre_keymap_destroy(ct);
 198         /* Since ct->sibling_list has literally rusted away in 2.6.11,
 199          * we now need another way to find out about our sibling
 200          * contrack and expects... -HW */
 201
 202         /* try original (pns->pac) tuple */
 203         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 204         t.dst.protonum = IPPROTO_GRE;
 205         t.src.u.gre.key = ct->help.ct_pptp_info.pns_call_id;
 206         t.dst.u.gre.key = ct->help.ct_pptp_info.pac_call_id;
 207
 208         if (!destroy_sibling_or_exp(&t))
 209                 DEBUGP("failed to timeout original pns->pac ct/exp\n");
 210
 211         /* try reply (pac->pns) tuple */
 212         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 213         t.dst.protonum = IPPROTO_GRE;
 214         t.src.u.gre.key = ct->help.ct_pptp_info.pac_call_id;
 215         t.dst.u.gre.key = ct->help.ct_pptp_info.pns_call_id;
 216
 217         if (!destroy_sibling_or_exp(&t))
 218                 DEBUGP("failed to timeout reply pac->pns ct/exp\n");
 219 }
 220
 221 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 222 static inline int
 223 exp_gre(struct ip_conntrack *ct,
 224         __be16 callid,
 225         __be16 peer_callid)
 226 {
 227         struct ip_conntrack_expect *exp_orig, *exp_reply;
 228         int ret = 1;
 229
 230         exp_orig = ip_conntrack_expect_alloc(ct);
 231         if (exp_orig == NULL)
 232                 goto out;
 233
 234         exp_reply = ip_conntrack_expect_alloc(ct);
 235         if (exp_reply == NULL)
 236                 goto out_put_orig;
 237
 238         /* original direction, PNS->PAC */
 239         exp_orig->tuple.src.ip = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip;
 240         exp_orig->tuple.src.u.gre.key = peer_callid;
 241         exp_orig->tuple.dst.ip = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip;
 242         exp_orig->tuple.dst.u.gre.key = callid;
 243         exp_orig->tuple.dst.protonum = IPPROTO_GRE;
 244
 245         exp_orig->mask.src.ip = 0xffffffff;
 246         exp_orig->mask.src.u.all = 0;
 247         exp_orig->mask.dst.u.gre.key = htons(0xffff);
 248         exp_orig->mask.dst.ip = 0xffffffff;
 249         exp_orig->mask.dst.protonum = 0xff;
 250
 251         exp_orig->master = ct;
 252         exp_orig->expectfn = pptp_expectfn;
 253         exp_orig->flags = 0;
 254
 255         /* both expectations are identical apart from tuple */
 256         memcpy(exp_reply, exp_orig, sizeof(*exp_reply));
 257
 258         /* reply direction, PAC->PNS */
 259         exp_reply->tuple.src.ip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip;
 260         exp_reply->tuple.src.u.gre.key = callid;
 261         exp_reply->tuple.dst.ip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip;
 262         exp_reply->tuple.dst.u.gre.key = peer_callid;
 263         exp_reply->tuple.dst.protonum = IPPROTO_GRE;
 264
 265         if (ip_nat_pptp_hook_exp_gre)
 266                 ip_nat_pptp_hook_exp_gre(exp_orig, exp_reply);
 267         if (ip_conntrack_expect_related(exp_orig) != 0)
 268                 goto out_put_both;
 269         if (ip_conntrack_expect_related(exp_reply) != 0)
 270                 goto out_unexpect_orig;
 271
 272         /* Add GRE keymap entries */
 273         if (ip_ct_gre_keymap_add(ct, &exp_orig->tuple, 0) != 0)
 274                 goto out_unexpect_both;
 275         if (ip_ct_gre_keymap_add(ct, &exp_reply->tuple, 1) != 0) {
 276                 ip_ct_gre_keymap_destroy(ct);
 277                 goto out_unexpect_both;
 278         }
 279         ret = 0;
 280
 281 out_put_both:
 282         ip_conntrack_expect_put(exp_reply);
 283 out_put_orig:
 284         ip_conntrack_expect_put(exp_orig);
 285 out:
 286         return ret;
 287
 288 out_unexpect_both:
 289         ip_conntrack_unexpect_related(exp_reply);
 290 out_unexpect_orig:
 291         ip_conntrack_unexpect_related(exp_orig);
 292         goto out_put_both;
 293 }
 294
 295 static inline int
 296 pptp_inbound_pkt(struct sk_buff **pskb,
 297                  struct PptpControlHeader *ctlh,
 298                  union pptp_ctrl_union *pptpReq,
 299                  unsigned int reqlen,
 300                  struct ip_conntrack *ct,
 301                  enum ip_conntrack_info ctinfo)
 302 {
 303         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 304         u_int16_t msg;
 305         __be16 cid = 0, pcid = 0;
 306
 307         msg = ntohs(ctlh->messageType);
 308         DEBUGP("inbound control message %s\n", pptp_msg_name[msg]);
 309
 310         switch (msg) {
 311         case PPTP_START_SESSION_REPLY:
 312                 /* server confirms new control session */
 313                 if (info->sstate < PPTP_SESSION_REQUESTED)
 314                         goto invalid;
 315                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 316                         info->sstate = PPTP_SESSION_CONFIRMED;
 317                 else
 318                         info->sstate = PPTP_SESSION_ERROR;
 319                 break;
 320
 321         case PPTP_STOP_SESSION_REPLY:
 322                 /* server confirms end of control session */
 323                 if (info->sstate > PPTP_SESSION_STOPREQ)
 324                         goto invalid;
 325                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 326                         info->sstate = PPTP_SESSION_NONE;
 327                 else
 328                         info->sstate = PPTP_SESSION_ERROR;
 329                 break;
 330
 331         case PPTP_OUT_CALL_REPLY:
 332                 /* server accepted call, we now expect GRE frames */
 333                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 334                         goto invalid;
 335                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 336                     info->cstate != PPTP_CALL_OUT_CONF)
 337                         goto invalid;
 338
 339                 cid = pptpReq->ocack.callID;
 340                 pcid = pptpReq->ocack.peersCallID;
 341                 if (info->pns_call_id != pcid)
 342                         goto invalid;
 343                 DEBUGP("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
 344                         ntohs(cid), ntohs(pcid));
 345
 346                 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
 347                         info->cstate = PPTP_CALL_OUT_CONF;
 348                         info->pac_call_id = cid;
 349                         exp_gre(ct, cid, pcid);
 350                 } else
 351                         info->cstate = PPTP_CALL_NONE;
 352                 break;
 353
 354         case PPTP_IN_CALL_REQUEST:
 355                 /* server tells us about incoming call request */
 356                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 357                         goto invalid;
 358
 359                 cid = pptpReq->icreq.callID;
 360                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 361                 info->cstate = PPTP_CALL_IN_REQ;
 362                 info->pac_call_id = cid;
 363                 break;
 364
 365         case PPTP_IN_CALL_CONNECT:
 366                 /* server tells us about incoming call established */
 367                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 368                         goto invalid;
 369                 if (info->cstate != PPTP_CALL_IN_REP &&
 370                     info->cstate != PPTP_CALL_IN_CONF)
 371                         goto invalid;
 372
 373                 pcid = pptpReq->iccon.peersCallID;
 374                 cid = info->pac_call_id;
 375
 376                 if (info->pns_call_id != pcid)
 377                         goto invalid;
 378
 379                 DEBUGP("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
 380                 info->cstate = PPTP_CALL_IN_CONF;
 381
 382                 /* we expect a GRE connection from PAC to PNS */
 383                 exp_gre(ct, cid, pcid);
 384                 break;
 385
 386         case PPTP_CALL_DISCONNECT_NOTIFY:
 387                 /* server confirms disconnect */
 388                 cid = pptpReq->disc.callID;
 389                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 390                 info->cstate = PPTP_CALL_NONE;
 391
 392                 /* untrack this call id, unexpect GRE packets */
 393                 pptp_destroy_siblings(ct);
 394                 break;
 395
 396         case PPTP_WAN_ERROR_NOTIFY:
 397         case PPTP_ECHO_REQUEST:
 398         case PPTP_ECHO_REPLY:
 399                 /* I don't have to explain these ;) */
 400                 break;
 401         default:
 402                 goto invalid;
 403         }
 404
 405         if (ip_nat_pptp_hook_inbound)
 406                 return ip_nat_pptp_hook_inbound(pskb, ct, ctinfo, ctlh,
 407                                                 pptpReq);
 408         return NF_ACCEPT;
 409
 410 invalid:
 411         DEBUGP("invalid %s: type=%d cid=%u pcid=%u "
 412                "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 413                msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 414                msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 415                ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 416         return NF_ACCEPT;
 417 }
 418
 419 static inline int
 420 pptp_outbound_pkt(struct sk_buff **pskb,
 421                   struct PptpControlHeader *ctlh,
 422                   union pptp_ctrl_union *pptpReq,
 423                   unsigned int reqlen,
 424                   struct ip_conntrack *ct,
 425                   enum ip_conntrack_info ctinfo)
 426 {
 427         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 428         u_int16_t msg;
 429         __be16 cid = 0, pcid = 0;
 430
 431         msg = ntohs(ctlh->messageType);
 432         DEBUGP("outbound control message %s\n", pptp_msg_name[msg]);
 433
 434         switch (msg) {
 435         case PPTP_START_SESSION_REQUEST:
 436                 /* client requests for new control session */
 437                 if (info->sstate != PPTP_SESSION_NONE)
 438                         goto invalid;
 439                 info->sstate = PPTP_SESSION_REQUESTED;
 440                 break;
 441         case PPTP_STOP_SESSION_REQUEST:
 442                 /* client requests end of control session */
 443                 info->sstate = PPTP_SESSION_STOPREQ;
 444                 break;
 445
 446         case PPTP_OUT_CALL_REQUEST:
 447                 /* client initiating connection to server */
 448                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 449                         goto invalid;
 450                 info->cstate = PPTP_CALL_OUT_REQ;
 451                 /* track PNS call id */
 452                 cid = pptpReq->ocreq.callID;
 453                 DEBUGP("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 454                 info->pns_call_id = cid;
 455                 break;
 456         case PPTP_IN_CALL_REPLY:
 457                 /* client answers incoming call */
 458                 if (info->cstate != PPTP_CALL_IN_REQ &&
 459                     info->cstate != PPTP_CALL_IN_REP)
 460                         goto invalid;
 461
 462                 cid = pptpReq->icack.callID;
 463                 pcid = pptpReq->icack.peersCallID;
 464                 if (info->pac_call_id != pcid)
 465                         goto invalid;
 466                 DEBUGP("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
 467                        ntohs(cid), ntohs(pcid));
 468
 469                 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
 470                         /* part two of the three-way handshake */
 471                         info->cstate = PPTP_CALL_IN_REP;
 472                         info->pns_call_id = cid;
 473                 } else
 474                         info->cstate = PPTP_CALL_NONE;
 475                 break;
 476
 477         case PPTP_CALL_CLEAR_REQUEST:
 478                 /* client requests hangup of call */
 479                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 480                         goto invalid;
 481                 /* FUTURE: iterate over all calls and check if
 482                  * call ID is valid.  We don't do this without newnat,
 483                  * because we only know about last call */
 484                 info->cstate = PPTP_CALL_CLEAR_REQ;
 485                 break;
 486         case PPTP_SET_LINK_INFO:
 487         case PPTP_ECHO_REQUEST:
 488         case PPTP_ECHO_REPLY:
 489                 /* I don't have to explain these ;) */
 490                 break;
 491         default:
 492                 goto invalid;
 493         }
 494
 495         if (ip_nat_pptp_hook_outbound)
 496                 return ip_nat_pptp_hook_outbound(pskb, ct, ctinfo, ctlh,
 497                                                  pptpReq);
 498         return NF_ACCEPT;
 499
 500 invalid:
 501         DEBUGP("invalid %s: type=%d cid=%u pcid=%u "
 502                "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 503                msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 504                msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 505                ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 506         return NF_ACCEPT;
 507 }
 508
 509 static const unsigned int pptp_msg_size[] = {
 510         [PPTP_START_SESSION_REQUEST]  = sizeof(struct PptpStartSessionRequest),
 511         [PPTP_START_SESSION_REPLY]    = sizeof(struct PptpStartSessionReply),
 512         [PPTP_STOP_SESSION_REQUEST]   = sizeof(struct PptpStopSessionRequest),
 513         [PPTP_STOP_SESSION_REPLY]     = sizeof(struct PptpStopSessionReply),
 514         [PPTP_OUT_CALL_REQUEST]       = sizeof(struct PptpOutCallRequest),
 515         [PPTP_OUT_CALL_REPLY]         = sizeof(struct PptpOutCallReply),
 516         [PPTP_IN_CALL_REQUEST]        = sizeof(struct PptpInCallRequest),
 517         [PPTP_IN_CALL_REPLY]          = sizeof(struct PptpInCallReply),
 518         [PPTP_IN_CALL_CONNECT]        = sizeof(struct PptpInCallConnected),
 519         [PPTP_CALL_CLEAR_REQUEST]     = sizeof(struct PptpClearCallRequest),
 520         [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
 521         [PPTP_WAN_ERROR_NOTIFY]       = sizeof(struct PptpWanErrorNotify),
 522         [PPTP_SET_LINK_INFO]          = sizeof(struct PptpSetLinkInfo),
 523 };
 524
 525 /* track caller id inside control connection, call expect_related */
 526 static int
 527 conntrack_pptp_help(struct sk_buff **pskb,
 528                     struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 529
 530 {
 531         int dir = CTINFO2DIR(ctinfo);
 532         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 533         struct tcphdr _tcph, *tcph;
 534         struct pptp_pkt_hdr _pptph, *pptph;
 535         struct PptpControlHeader _ctlh, *ctlh;
 536         union pptp_ctrl_union _pptpReq, *pptpReq;
 537         unsigned int tcplen = (*pskb)->len - (*pskb)->nh.iph->ihl * 4;
 538         unsigned int datalen, reqlen, nexthdr_off;
 539         int oldsstate, oldcstate;
 540         int ret;
 541         u_int16_t msg;
 542
 543         /* don't do any tracking before tcp handshake complete */
 544         if (ctinfo != IP_CT_ESTABLISHED
 545             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
 546                 DEBUGP("ctinfo = %u, skipping\n", ctinfo);
 547                 return NF_ACCEPT;
 548         }
 549
 550         nexthdr_off = (*pskb)->nh.iph->ihl*4;
 551         tcph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_tcph), &_tcph);
 552         BUG_ON(!tcph);
 553         nexthdr_off += tcph->doff * 4;
 554         datalen = tcplen - tcph->doff * 4;
 555
 556         pptph = skb_header_pointer(*pskb, nexthdr_off, sizeof(_pptph), &_pptph);
 557         if (!pptph) {
 558                 DEBUGP("no full PPTP header, can't track\n");
 559                 return NF_ACCEPT;
 560         }
 561         nexthdr_off += sizeof(_pptph);
 562         datalen -= sizeof(_pptph);
 563
 564         /* if it's not a control message we can't do anything with it */
 565         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 566             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 567                 DEBUGP("not a control packet\n");
 568                 return NF_ACCEPT;
 569         }
 570
 571         ctlh = skb_header_pointer(*pskb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 572         if (!ctlh)
 573                 return NF_ACCEPT;
 574         nexthdr_off += sizeof(_ctlh);
 575         datalen -= sizeof(_ctlh);
 576
 577         reqlen = datalen;
 578         msg = ntohs(ctlh->messageType);
 579         if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
 580                 return NF_ACCEPT;
 581         if (reqlen > sizeof(*pptpReq))
 582                 reqlen = sizeof(*pptpReq);
 583
 584         pptpReq = skb_header_pointer(*pskb, nexthdr_off, reqlen, &_pptpReq);
 585         if (!pptpReq)
 586                 return NF_ACCEPT;
 587
 588         oldsstate = info->sstate;
 589         oldcstate = info->cstate;
 590
 591         spin_lock_bh(&ip_pptp_lock);
 592
 593         /* FIXME: We just blindly assume that the control connection is always
 594          * established from PNS->PAC.  However, RFC makes no guarantee */
 595         if (dir == IP_CT_DIR_ORIGINAL)
 596                 /* client -> server (PNS -> PAC) */
 597                 ret = pptp_outbound_pkt(pskb, ctlh, pptpReq, reqlen, ct,
 598                                         ctinfo);
 599         else
 600                 /* server -> client (PAC -> PNS) */
 601                 ret = pptp_inbound_pkt(pskb, ctlh, pptpReq, reqlen, ct,
 602                                        ctinfo);
 603         DEBUGP("sstate: %d->%d, cstate: %d->%d\n",
 604                 oldsstate, info->sstate, oldcstate, info->cstate);
 605         spin_unlock_bh(&ip_pptp_lock);
 606
 607         return ret;
 608 }
 609
 610 /* control protocol helper */
 611 static struct ip_conntrack_helper pptp = {
 612         .list = { NULL, NULL },
 613         .name = "pptp",
 614         .me = THIS_MODULE,
 615         .max_expected = 2,
 616         .timeout = 5 * 60,
 617         .tuple = { .src = { .ip = 0,
 618                             .u = { .tcp = { .port =
 619                                     __constant_htons(PPTP_CONTROL_PORT) } }
 620                           },
 621                    .dst = { .ip = 0,
 622                             .u = { .all = 0 },
 623                             .protonum = IPPROTO_TCP
 624                           }
 625                  },
 626         .mask = { .src = { .ip = 0,
 627                            .u = { .tcp = { .port = __constant_htons(0xffff) } }
 628                          },
 629                   .dst = { .ip = 0,
 630                            .u = { .all = 0 },
 631                            .protonum = 0xff
 632                          }
 633                 },
 634         .help = conntrack_pptp_help,
 635         .destroy = pptp_destroy_siblings,
 636 };
 637
 638 extern void ip_ct_proto_gre_fini(void);
 639 extern int __init ip_ct_proto_gre_init(void);
 640
 641 /* ip_conntrack_pptp initialization */
 642 static int __init ip_conntrack_helper_pptp_init(void)
 643 {
 644         int retcode;
 645
 646         retcode = ip_ct_proto_gre_init();
 647         if (retcode < 0)
 648                 return retcode;
 649
 650         DEBUGP(" registering helper\n");
 651         if ((retcode = ip_conntrack_helper_register(&pptp))) {
 652                 printk(KERN_ERR "Unable to register conntrack application "
 653                                 "helper for pptp: %d\n", retcode);
 654                 ip_ct_proto_gre_fini();
 655                 return retcode;
 656         }
 657
 658         printk("ip_conntrack_pptp version %s loaded\n", IP_CT_PPTP_VERSION);
 659         return 0;
 660 }
 661
 662 static void __exit ip_conntrack_helper_pptp_fini(void)
 663 {
 664         ip_conntrack_helper_unregister(&pptp);
 665         ip_ct_proto_gre_fini();
 666         printk("ip_conntrack_pptp version %s unloaded\n", IP_CT_PPTP_VERSION);
 667 }
 668
 669 module_init(ip_conntrack_helper_pptp_init);
 670 module_exit(ip_conntrack_helper_pptp_fini);
 671
 672 EXPORT_SYMBOL(ip_nat_pptp_hook_outbound);
 673 EXPORT_SYMBOL(ip_nat_pptp_hook_inbound);
 674 EXPORT_SYMBOL(ip_nat_pptp_hook_exp_gre);
 675 EXPORT_SYMBOL(ip_nat_pptp_hook_expectfn);