net/netfilter/nf_conntrack_pptp.c

   1 /*
   2  * Connection tracking support for PPTP (Point to Point Tunneling Protocol).
   3  * PPTP is a a protocol for creating virtual private networks.
   4  * It is a specification defined by Microsoft and some vendors
   5  * working with Microsoft.  PPTP is built on top of a modified
   6  * version of the Internet Generic Routing Encapsulation Protocol.
   7  * GRE is defined in RFC 1701 and RFC 1702.  Documentation of
   8  * PPTP can be found in RFC 2637
   9  *
  10  * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
  11  *
  12  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  13  *
  14  * Limitations:
  15  *       - We blindly assume that control connections are always
  16  *         established in PNS->PAC direction.  This is a violation
  17  *         of RFFC2673
  18  *       - We can only support one single call within each session
  19  * TODO:
  20  *       - testing of incoming PPTP calls
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/skbuff.h>
  25 #include <linux/in.h>
  26 #include <linux/tcp.h>
  27
  28 #include <net/netfilter/nf_conntrack.h>
  29 #include <net/netfilter/nf_conntrack_core.h>
  30 #include <net/netfilter/nf_conntrack_helper.h>
  31 #include <linux/netfilter/nf_conntrack_proto_gre.h>
  32 #include <linux/netfilter/nf_conntrack_pptp.h>
  33
  34 #define NF_CT_PPTP_VERSION "3.1"
  35
  36 MODULE_LICENSE("GPL");
  37 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  38 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
  39 MODULE_ALIAS("ip_conntrack_pptp");
  40
  41 static DEFINE_SPINLOCK(nf_pptp_lock);
  42
  43 int
  44 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
  45                              struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  46                              struct PptpControlHeader *ctlh,
  47                              union pptp_ctrl_union *pptpReq) __read_mostly;
  48 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
  49
  50 int
  51 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
  52                             struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  53                             struct PptpControlHeader *ctlh,
  54                             union pptp_ctrl_union *pptpReq) __read_mostly;
  55 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
  56
  57 void
  58 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
  59                             struct nf_conntrack_expect *expect_reply)
  60                             __read_mostly;
  61 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
  62
  63 void
  64 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
  65                              struct nf_conntrack_expect *exp) __read_mostly;
  66 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
  67
  68 #ifdef DEBUG
  69 /* PptpControlMessageType names */
  70 const char *const pptp_msg_name[] = {
  71         "UNKNOWN_MESSAGE",
  72         "START_SESSION_REQUEST",
  73         "START_SESSION_REPLY",
  74         "STOP_SESSION_REQUEST",
  75         "STOP_SESSION_REPLY",
  76         "ECHO_REQUEST",
  77         "ECHO_REPLY",
  78         "OUT_CALL_REQUEST",
  79         "OUT_CALL_REPLY",
  80         "IN_CALL_REQUEST",
  81         "IN_CALL_REPLY",
  82         "IN_CALL_CONNECT",
  83         "CALL_CLEAR_REQUEST",
  84         "CALL_DISCONNECT_NOTIFY",
  85         "WAN_ERROR_NOTIFY",
  86         "SET_LINK_INFO"
  87 };
  88 EXPORT_SYMBOL(pptp_msg_name);
  89 #endif
  90
  91 #define SECS *HZ
  92 #define MINS * 60 SECS
  93 #define HOURS * 60 MINS
  94
  95 #define PPTP_GRE_TIMEOUT                (10 MINS)
  96 #define PPTP_GRE_STREAM_TIMEOUT         (5 HOURS)
  97
  98 static void pptp_expectfn(struct nf_conn *ct,
  99                          struct nf_conntrack_expect *exp)
 100 {
 101         struct net *net = nf_ct_net(ct);
 102         typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
 103         pr_debug("increasing timeouts\n");
 104
 105         /* increase timeout of GRE data channel conntrack entry */
 106         ct->proto.gre.timeout        = PPTP_GRE_TIMEOUT;
 107         ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
 108
 109         /* Can you see how rusty this code is, compared with the pre-2.6.11
 110          * one? That's what happened to my shiny newnat of 2002 ;( -HW */
 111
 112         rcu_read_lock();
 113         nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
 114         if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
 115                 nf_nat_pptp_expectfn(ct, exp);
 116         else {
 117                 struct nf_conntrack_tuple inv_t;
 118                 struct nf_conntrack_expect *exp_other;
 119
 120                 /* obviously this tuple inversion only works until you do NAT */
 121                 nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
 122                 pr_debug("trying to unexpect other dir: ");
 123                 nf_ct_dump_tuple(&inv_t);
 124
 125                 exp_other = nf_ct_expect_find_get(net, &inv_t);
 126                 if (exp_other) {
 127                         /* delete other expectation.  */
 128                         pr_debug("found\n");
 129                         nf_ct_unexpect_related(exp_other);
 130                         nf_ct_expect_put(exp_other);
 131                 } else {
 132                         pr_debug("not found\n");
 133                 }
 134         }
 135         rcu_read_unlock();
 136 }
 137
 138 static int destroy_sibling_or_exp(struct net *net,
 139                                   const struct nf_conntrack_tuple *t)
 140 {
 141         const struct nf_conntrack_tuple_hash *h;
 142         struct nf_conntrack_expect *exp;
 143         struct nf_conn *sibling;
 144
 145         pr_debug("trying to timeout ct or exp for tuple ");
 146         nf_ct_dump_tuple(t);
 147
 148         h = nf_conntrack_find_get(net, t);
 149         if (h)  {
 150                 sibling = nf_ct_tuplehash_to_ctrack(h);
 151                 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
 152                 sibling->proto.gre.timeout        = 0;
 153                 sibling->proto.gre.stream_timeout = 0;
 154                 if (del_timer(&sibling->timeout))
 155                         sibling->timeout.function((unsigned long)sibling);
 156                 nf_ct_put(sibling);
 157                 return 1;
 158         } else {
 159                 exp = nf_ct_expect_find_get(net, t);
 160                 if (exp) {
 161                         pr_debug("unexpect_related of expect %p\n", exp);
 162                         nf_ct_unexpect_related(exp);
 163                         nf_ct_expect_put(exp);
 164                         return 1;
 165                 }
 166         }
 167         return 0;
 168 }
 169
 170 /* timeout GRE data connections */
 171 static void pptp_destroy_siblings(struct nf_conn *ct)
 172 {
 173         struct net *net = nf_ct_net(ct);
 174         const struct nf_conn_help *help = nfct_help(ct);
 175         struct nf_conntrack_tuple t;
 176
 177         nf_ct_gre_keymap_destroy(ct);
 178
 179         /* try original (pns->pac) tuple */
 180         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 181         t.dst.protonum = IPPROTO_GRE;
 182         t.src.u.gre.key = help->help.ct_pptp_info.pns_call_id;
 183         t.dst.u.gre.key = help->help.ct_pptp_info.pac_call_id;
 184         if (!destroy_sibling_or_exp(net, &t))
 185                 pr_debug("failed to timeout original pns->pac ct/exp\n");
 186
 187         /* try reply (pac->pns) tuple */
 188         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 189         t.dst.protonum = IPPROTO_GRE;
 190         t.src.u.gre.key = help->help.ct_pptp_info.pac_call_id;
 191         t.dst.u.gre.key = help->help.ct_pptp_info.pns_call_id;
 192         if (!destroy_sibling_or_exp(net, &t))
 193                 pr_debug("failed to timeout reply pac->pns ct/exp\n");
 194 }
 195
 196 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 197 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
 198 {
 199         struct nf_conntrack_expect *exp_orig, *exp_reply;
 200         enum ip_conntrack_dir dir;
 201         int ret = 1;
 202         typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
 203
 204         exp_orig = nf_ct_expect_alloc(ct);
 205         if (exp_orig == NULL)
 206                 goto out;
 207
 208         exp_reply = nf_ct_expect_alloc(ct);
 209         if (exp_reply == NULL)
 210                 goto out_put_orig;
 211
 212         /* original direction, PNS->PAC */
 213         dir = IP_CT_DIR_ORIGINAL;
 214         nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
 215                           nf_ct_l3num(ct),
 216                           &ct->tuplehash[dir].tuple.src.u3,
 217                           &ct->tuplehash[dir].tuple.dst.u3,
 218                           IPPROTO_GRE, &peer_callid, &callid);
 219         exp_orig->expectfn = pptp_expectfn;
 220
 221         /* reply direction, PAC->PNS */
 222         dir = IP_CT_DIR_REPLY;
 223         nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
 224                           nf_ct_l3num(ct),
 225                           &ct->tuplehash[dir].tuple.src.u3,
 226                           &ct->tuplehash[dir].tuple.dst.u3,
 227                           IPPROTO_GRE, &callid, &peer_callid);
 228         exp_reply->expectfn = pptp_expectfn;
 229
 230         nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
 231         if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
 232                 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
 233         if (nf_ct_expect_related(exp_orig) != 0)
 234                 goto out_put_both;
 235         if (nf_ct_expect_related(exp_reply) != 0)
 236                 goto out_unexpect_orig;
 237
 238         /* Add GRE keymap entries */
 239         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
 240                 goto out_unexpect_both;
 241         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
 242                 nf_ct_gre_keymap_destroy(ct);
 243                 goto out_unexpect_both;
 244         }
 245         ret = 0;
 246
 247 out_put_both:
 248         nf_ct_expect_put(exp_reply);
 249 out_put_orig:
 250         nf_ct_expect_put(exp_orig);
 251 out:
 252         return ret;
 253
 254 out_unexpect_both:
 255         nf_ct_unexpect_related(exp_reply);
 256 out_unexpect_orig:
 257         nf_ct_unexpect_related(exp_orig);
 258         goto out_put_both;
 259 }
 260
 261 static inline int
 262 pptp_inbound_pkt(struct sk_buff *skb,
 263                  struct PptpControlHeader *ctlh,
 264                  union pptp_ctrl_union *pptpReq,
 265                  unsigned int reqlen,
 266                  struct nf_conn *ct,
 267                  enum ip_conntrack_info ctinfo)
 268 {
 269         struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
 270         u_int16_t msg;
 271         __be16 cid = 0, pcid = 0;
 272         typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
 273
 274         msg = ntohs(ctlh->messageType);
 275         pr_debug("inbound control message %s\n", pptp_msg_name[msg]);
 276
 277         switch (msg) {
 278         case PPTP_START_SESSION_REPLY:
 279                 /* server confirms new control session */
 280                 if (info->sstate < PPTP_SESSION_REQUESTED)
 281                         goto invalid;
 282                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 283                         info->sstate = PPTP_SESSION_CONFIRMED;
 284                 else
 285                         info->sstate = PPTP_SESSION_ERROR;
 286                 break;
 287
 288         case PPTP_STOP_SESSION_REPLY:
 289                 /* server confirms end of control session */
 290                 if (info->sstate > PPTP_SESSION_STOPREQ)
 291                         goto invalid;
 292                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 293                         info->sstate = PPTP_SESSION_NONE;
 294                 else
 295                         info->sstate = PPTP_SESSION_ERROR;
 296                 break;
 297
 298         case PPTP_OUT_CALL_REPLY:
 299                 /* server accepted call, we now expect GRE frames */
 300                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 301                         goto invalid;
 302                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 303                     info->cstate != PPTP_CALL_OUT_CONF)
 304                         goto invalid;
 305
 306                 cid = pptpReq->ocack.callID;
 307                 pcid = pptpReq->ocack.peersCallID;
 308                 if (info->pns_call_id != pcid)
 309                         goto invalid;
 310                 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
 311                          ntohs(cid), ntohs(pcid));
 312
 313                 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
 314                         info->cstate = PPTP_CALL_OUT_CONF;
 315                         info->pac_call_id = cid;
 316                         exp_gre(ct, cid, pcid);
 317                 } else
 318                         info->cstate = PPTP_CALL_NONE;
 319                 break;
 320
 321         case PPTP_IN_CALL_REQUEST:
 322                 /* server tells us about incoming call request */
 323                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 324                         goto invalid;
 325
 326                 cid = pptpReq->icreq.callID;
 327                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 328                 info->cstate = PPTP_CALL_IN_REQ;
 329                 info->pac_call_id = cid;
 330                 break;
 331
 332         case PPTP_IN_CALL_CONNECT:
 333                 /* server tells us about incoming call established */
 334                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 335                         goto invalid;
 336                 if (info->cstate != PPTP_CALL_IN_REP &&
 337                     info->cstate != PPTP_CALL_IN_CONF)
 338                         goto invalid;
 339
 340                 pcid = pptpReq->iccon.peersCallID;
 341                 cid = info->pac_call_id;
 342
 343                 if (info->pns_call_id != pcid)
 344                         goto invalid;
 345
 346                 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
 347                 info->cstate = PPTP_CALL_IN_CONF;
 348
 349                 /* we expect a GRE connection from PAC to PNS */
 350                 exp_gre(ct, cid, pcid);
 351                 break;
 352
 353         case PPTP_CALL_DISCONNECT_NOTIFY:
 354                 /* server confirms disconnect */
 355                 cid = pptpReq->disc.callID;
 356                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 357                 info->cstate = PPTP_CALL_NONE;
 358
 359                 /* untrack this call id, unexpect GRE packets */
 360                 pptp_destroy_siblings(ct);
 361                 break;
 362
 363         case PPTP_WAN_ERROR_NOTIFY:
 364         case PPTP_ECHO_REQUEST:
 365         case PPTP_ECHO_REPLY:
 366                 /* I don't have to explain these ;) */
 367                 break;
 368
 369         default:
 370                 goto invalid;
 371         }
 372
 373         nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
 374         if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
 375                 return nf_nat_pptp_inbound(skb, ct, ctinfo, ctlh, pptpReq);
 376         return NF_ACCEPT;
 377
 378 invalid:
 379         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 380                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 381                  msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 382                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 383                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 384         return NF_ACCEPT;
 385 }
 386
 387 static inline int
 388 pptp_outbound_pkt(struct sk_buff *skb,
 389                   struct PptpControlHeader *ctlh,
 390                   union pptp_ctrl_union *pptpReq,
 391                   unsigned int reqlen,
 392                   struct nf_conn *ct,
 393                   enum ip_conntrack_info ctinfo)
 394 {
 395         struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
 396         u_int16_t msg;
 397         __be16 cid = 0, pcid = 0;
 398         typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
 399
 400         msg = ntohs(ctlh->messageType);
 401         pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
 402
 403         switch (msg) {
 404         case PPTP_START_SESSION_REQUEST:
 405                 /* client requests for new control session */
 406                 if (info->sstate != PPTP_SESSION_NONE)
 407                         goto invalid;
 408                 info->sstate = PPTP_SESSION_REQUESTED;
 409                 break;
 410
 411         case PPTP_STOP_SESSION_REQUEST:
 412                 /* client requests end of control session */
 413                 info->sstate = PPTP_SESSION_STOPREQ;
 414                 break;
 415
 416         case PPTP_OUT_CALL_REQUEST:
 417                 /* client initiating connection to server */
 418                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 419                         goto invalid;
 420                 info->cstate = PPTP_CALL_OUT_REQ;
 421                 /* track PNS call id */
 422                 cid = pptpReq->ocreq.callID;
 423                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 424                 info->pns_call_id = cid;
 425                 break;
 426
 427         case PPTP_IN_CALL_REPLY:
 428                 /* client answers incoming call */
 429                 if (info->cstate != PPTP_CALL_IN_REQ &&
 430                     info->cstate != PPTP_CALL_IN_REP)
 431                         goto invalid;
 432
 433                 cid = pptpReq->icack.callID;
 434                 pcid = pptpReq->icack.peersCallID;
 435                 if (info->pac_call_id != pcid)
 436                         goto invalid;
 437                 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
 438                          ntohs(cid), ntohs(pcid));
 439
 440                 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
 441                         /* part two of the three-way handshake */
 442                         info->cstate = PPTP_CALL_IN_REP;
 443                         info->pns_call_id = cid;
 444                 } else
 445                         info->cstate = PPTP_CALL_NONE;
 446                 break;
 447
 448         case PPTP_CALL_CLEAR_REQUEST:
 449                 /* client requests hangup of call */
 450                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 451                         goto invalid;
 452                 /* FUTURE: iterate over all calls and check if
 453                  * call ID is valid.  We don't do this without newnat,
 454                  * because we only know about last call */
 455                 info->cstate = PPTP_CALL_CLEAR_REQ;
 456                 break;
 457
 458         case PPTP_SET_LINK_INFO:
 459         case PPTP_ECHO_REQUEST:
 460         case PPTP_ECHO_REPLY:
 461                 /* I don't have to explain these ;) */
 462                 break;
 463
 464         default:
 465                 goto invalid;
 466         }
 467
 468         nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
 469         if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
 470                 return nf_nat_pptp_outbound(skb, ct, ctinfo, ctlh, pptpReq);
 471         return NF_ACCEPT;
 472
 473 invalid:
 474         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 475                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 476                  msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 477                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 478                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 479         return NF_ACCEPT;
 480 }
 481
 482 static const unsigned int pptp_msg_size[] = {
 483         [PPTP_START_SESSION_REQUEST]  = sizeof(struct PptpStartSessionRequest),
 484         [PPTP_START_SESSION_REPLY]    = sizeof(struct PptpStartSessionReply),
 485         [PPTP_STOP_SESSION_REQUEST]   = sizeof(struct PptpStopSessionRequest),
 486         [PPTP_STOP_SESSION_REPLY]     = sizeof(struct PptpStopSessionReply),
 487         [PPTP_OUT_CALL_REQUEST]       = sizeof(struct PptpOutCallRequest),
 488         [PPTP_OUT_CALL_REPLY]         = sizeof(struct PptpOutCallReply),
 489         [PPTP_IN_CALL_REQUEST]        = sizeof(struct PptpInCallRequest),
 490         [PPTP_IN_CALL_REPLY]          = sizeof(struct PptpInCallReply),
 491         [PPTP_IN_CALL_CONNECT]        = sizeof(struct PptpInCallConnected),
 492         [PPTP_CALL_CLEAR_REQUEST]     = sizeof(struct PptpClearCallRequest),
 493         [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
 494         [PPTP_WAN_ERROR_NOTIFY]       = sizeof(struct PptpWanErrorNotify),
 495         [PPTP_SET_LINK_INFO]          = sizeof(struct PptpSetLinkInfo),
 496 };
 497
 498 /* track caller id inside control connection, call expect_related */
 499 static int
 500 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 501                     struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 502
 503 {
 504         int dir = CTINFO2DIR(ctinfo);
 505         const struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
 506         const struct tcphdr *tcph;
 507         struct tcphdr _tcph;
 508         const struct pptp_pkt_hdr *pptph;
 509         struct pptp_pkt_hdr _pptph;
 510         struct PptpControlHeader _ctlh, *ctlh;
 511         union pptp_ctrl_union _pptpReq, *pptpReq;
 512         unsigned int tcplen = skb->len - protoff;
 513         unsigned int datalen, reqlen, nexthdr_off;
 514         int oldsstate, oldcstate;
 515         int ret;
 516         u_int16_t msg;
 517
 518         /* don't do any tracking before tcp handshake complete */
 519         if (ctinfo != IP_CT_ESTABLISHED &&
 520             ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY)
 521                 return NF_ACCEPT;
 522
 523         nexthdr_off = protoff;
 524         tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
 525         BUG_ON(!tcph);
 526         nexthdr_off += tcph->doff * 4;
 527         datalen = tcplen - tcph->doff * 4;
 528
 529         pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
 530         if (!pptph) {
 531                 pr_debug("no full PPTP header, can't track\n");
 532                 return NF_ACCEPT;
 533         }
 534         nexthdr_off += sizeof(_pptph);
 535         datalen -= sizeof(_pptph);
 536
 537         /* if it's not a control message we can't do anything with it */
 538         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 539             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 540                 pr_debug("not a control packet\n");
 541                 return NF_ACCEPT;
 542         }
 543
 544         ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 545         if (!ctlh)
 546                 return NF_ACCEPT;
 547         nexthdr_off += sizeof(_ctlh);
 548         datalen -= sizeof(_ctlh);
 549
 550         reqlen = datalen;
 551         msg = ntohs(ctlh->messageType);
 552         if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
 553                 return NF_ACCEPT;
 554         if (reqlen > sizeof(*pptpReq))
 555                 reqlen = sizeof(*pptpReq);
 556
 557         pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
 558         if (!pptpReq)
 559                 return NF_ACCEPT;
 560
 561         oldsstate = info->sstate;
 562         oldcstate = info->cstate;
 563
 564         spin_lock_bh(&nf_pptp_lock);
 565
 566         /* FIXME: We just blindly assume that the control connection is always
 567          * established from PNS->PAC.  However, RFC makes no guarantee */
 568         if (dir == IP_CT_DIR_ORIGINAL)
 569                 /* client -> server (PNS -> PAC) */
 570                 ret = pptp_outbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
 571                                         ctinfo);
 572         else
 573                 /* server -> client (PAC -> PNS) */
 574                 ret = pptp_inbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
 575                                        ctinfo);
 576         pr_debug("sstate: %d->%d, cstate: %d->%d\n",
 577                  oldsstate, info->sstate, oldcstate, info->cstate);
 578         spin_unlock_bh(&nf_pptp_lock);
 579
 580         return ret;
 581 }
 582
 583 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
 584         .max_expected   = 2,
 585         .timeout        = 5 * 60,
 586 };
 587
 588 /* control protocol helper */
 589 static struct nf_conntrack_helper pptp __read_mostly = {
 590         .name                   = "pptp",
 591         .me                     = THIS_MODULE,
 592         .tuple.src.l3num        = AF_INET,
 593         .tuple.src.u.tcp.port   = __constant_htons(PPTP_CONTROL_PORT),
 594         .tuple.dst.protonum     = IPPROTO_TCP,
 595         .help                   = conntrack_pptp_help,
 596         .destroy                = pptp_destroy_siblings,
 597         .expect_policy          = &pptp_exp_policy,
 598 };
 599
 600 static void nf_conntrack_pptp_net_exit(struct net *net)
 601 {
 602         nf_ct_gre_keymap_flush(net);
 603 }
 604
 605 static struct pernet_operations nf_conntrack_pptp_net_ops = {
 606         .exit = nf_conntrack_pptp_net_exit,
 607 };
 608
 609 static int __init nf_conntrack_pptp_init(void)
 610 {
 611         int rv;
 612
 613         rv = nf_conntrack_helper_register(&pptp);
 614         if (rv < 0)
 615                 return rv;
 616         rv = register_pernet_subsys(&nf_conntrack_pptp_net_ops);
 617         if (rv < 0)
 618                 nf_conntrack_helper_unregister(&pptp);
 619         return rv;
 620 }
 621
 622 static void __exit nf_conntrack_pptp_fini(void)
 623 {
 624         nf_conntrack_helper_unregister(&pptp);
 625         unregister_pernet_subsys(&nf_conntrack_pptp_net_ops);
 626 }
 627
 628 module_init(nf_conntrack_pptp_init);
 629 module_exit(nf_conntrack_pptp_fini);