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