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  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
  15  *
  16  * Limitations:
  17  *       - We blindly assume that control connections are always
  18  *         established in PNS->PAC direction.  This is a violation
  19  *         of RFC 2637
  20  *       - We can only support one single call within each session
  21  * TODO:
  22  *       - testing of incoming PPTP calls
  23  */
  24
  25 #include <linux/module.h>
  26 #include <linux/skbuff.h>
  27 #include <linux/in.h>
  28 #include <linux/tcp.h>
  29
  30 #include <net/netfilter/nf_conntrack.h>
  31 #include <net/netfilter/nf_conntrack_core.h>
  32 #include <net/netfilter/nf_conntrack_helper.h>
  33 #include <net/netfilter/nf_conntrack_zones.h>
  34 #include <linux/netfilter/nf_conntrack_proto_gre.h>
  35 #include <linux/netfilter/nf_conntrack_pptp.h>
  36
  37 #define NF_CT_PPTP_VERSION "3.1"
  38
  39 MODULE_LICENSE("GPL");
  40 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  41 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
  42 MODULE_ALIAS("ip_conntrack_pptp");
  43 MODULE_ALIAS_NFCT_HELPER("pptp");
  44
  45 static DEFINE_SPINLOCK(nf_pptp_lock);
  46
  47 int
  48 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
  49                              struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  50                              unsigned int protoff, struct PptpControlHeader *ctlh,
  51                              union pptp_ctrl_union *pptpReq) __read_mostly;
  52 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
  53
  54 int
  55 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
  56                             struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  57                             unsigned int protoff, struct PptpControlHeader *ctlh,
  58                             union pptp_ctrl_union *pptpReq) __read_mostly;
  59 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
  60
  61 void
  62 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
  63                             struct nf_conntrack_expect *expect_reply)
  64                             __read_mostly;
  65 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
  66
  67 void
  68 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
  69                              struct nf_conntrack_expect *exp) __read_mostly;
  70 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
  71
  72 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
  73 /* PptpControlMessageType names */
  74 static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = {
  75         [0]                             = "UNKNOWN_MESSAGE",
  76         [PPTP_START_SESSION_REQUEST]    = "START_SESSION_REQUEST",
  77         [PPTP_START_SESSION_REPLY]      = "START_SESSION_REPLY",
  78         [PPTP_STOP_SESSION_REQUEST]     = "STOP_SESSION_REQUEST",
  79         [PPTP_STOP_SESSION_REPLY]       = "STOP_SESSION_REPLY",
  80         [PPTP_ECHO_REQUEST]             = "ECHO_REQUEST",
  81         [PPTP_ECHO_REPLY]               = "ECHO_REPLY",
  82         [PPTP_OUT_CALL_REQUEST]         = "OUT_CALL_REQUEST",
  83         [PPTP_OUT_CALL_REPLY]           = "OUT_CALL_REPLY",
  84         [PPTP_IN_CALL_REQUEST]          = "IN_CALL_REQUEST",
  85         [PPTP_IN_CALL_REPLY]            = "IN_CALL_REPLY",
  86         [PPTP_IN_CALL_CONNECT]          = "IN_CALL_CONNECT",
  87         [PPTP_CALL_CLEAR_REQUEST]       = "CALL_CLEAR_REQUEST",
  88         [PPTP_CALL_DISCONNECT_NOTIFY]   = "CALL_DISCONNECT_NOTIFY",
  89         [PPTP_WAN_ERROR_NOTIFY]         = "WAN_ERROR_NOTIFY",
  90         [PPTP_SET_LINK_INFO]            = "SET_LINK_INFO"
  91 };
  92
  93 const char *pptp_msg_name(u_int16_t msg)
  94 {
  95         if (msg > PPTP_MSG_MAX)
  96                 return pptp_msg_name_array[0];
  97
  98         return pptp_msg_name_array[msg];
  99 }
 100 EXPORT_SYMBOL(pptp_msg_name);
 101 #endif
 102
 103 #define SECS *HZ
 104 #define MINS * 60 SECS
 105 #define HOURS * 60 MINS
 106
 107 #define PPTP_GRE_TIMEOUT                (10 MINS)
 108 #define PPTP_GRE_STREAM_TIMEOUT         (5 HOURS)
 109
 110 static void pptp_expectfn(struct nf_conn *ct,
 111                          struct nf_conntrack_expect *exp)
 112 {
 113         struct net *net = nf_ct_net(ct);
 114         typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
 115         pr_debug("increasing timeouts\n");
 116
 117         /* increase timeout of GRE data channel conntrack entry */
 118         ct->proto.gre.timeout        = PPTP_GRE_TIMEOUT;
 119         ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
 120
 121         /* Can you see how rusty this code is, compared with the pre-2.6.11
 122          * one? That's what happened to my shiny newnat of 2002 ;( -HW */
 123
 124         rcu_read_lock();
 125         nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
 126         if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
 127                 nf_nat_pptp_expectfn(ct, exp);
 128         else {
 129                 struct nf_conntrack_tuple inv_t;
 130                 struct nf_conntrack_expect *exp_other;
 131
 132                 /* obviously this tuple inversion only works until you do NAT */
 133                 nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
 134                 pr_debug("trying to unexpect other dir: ");
 135                 nf_ct_dump_tuple(&inv_t);
 136
 137                 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t);
 138                 if (exp_other) {
 139                         /* delete other expectation.  */
 140                         pr_debug("found\n");
 141                         nf_ct_unexpect_related(exp_other);
 142                         nf_ct_expect_put(exp_other);
 143                 } else {
 144                         pr_debug("not found\n");
 145                 }
 146         }
 147         rcu_read_unlock();
 148 }
 149
 150 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
 151                                   const struct nf_conntrack_tuple *t)
 152 {
 153         const struct nf_conntrack_tuple_hash *h;
 154         const struct nf_conntrack_zone *zone;
 155         struct nf_conntrack_expect *exp;
 156         struct nf_conn *sibling;
 157
 158         pr_debug("trying to timeout ct or exp for tuple ");
 159         nf_ct_dump_tuple(t);
 160
 161         zone = nf_ct_zone(ct);
 162         h = nf_conntrack_find_get(net, zone, t);
 163         if (h)  {
 164                 sibling = nf_ct_tuplehash_to_ctrack(h);
 165                 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
 166                 sibling->proto.gre.timeout        = 0;
 167                 sibling->proto.gre.stream_timeout = 0;
 168                 if (del_timer(&sibling->timeout))
 169                         sibling->timeout.function((unsigned long)sibling);
 170                 nf_ct_put(sibling);
 171                 return 1;
 172         } else {
 173                 exp = nf_ct_expect_find_get(net, zone, t);
 174                 if (exp) {
 175                         pr_debug("unexpect_related of expect %p\n", exp);
 176                         nf_ct_unexpect_related(exp);
 177                         nf_ct_expect_put(exp);
 178                         return 1;
 179                 }
 180         }
 181         return 0;
 182 }
 183
 184 /* timeout GRE data connections */
 185 static void pptp_destroy_siblings(struct nf_conn *ct)
 186 {
 187         struct net *net = nf_ct_net(ct);
 188         const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 189         struct nf_conntrack_tuple t;
 190
 191         nf_ct_gre_keymap_destroy(ct);
 192
 193         /* try original (pns->pac) tuple */
 194         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 195         t.dst.protonum = IPPROTO_GRE;
 196         t.src.u.gre.key = ct_pptp_info->pns_call_id;
 197         t.dst.u.gre.key = ct_pptp_info->pac_call_id;
 198         if (!destroy_sibling_or_exp(net, ct, &t))
 199                 pr_debug("failed to timeout original pns->pac ct/exp\n");
 200
 201         /* try reply (pac->pns) tuple */
 202         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 203         t.dst.protonum = IPPROTO_GRE;
 204         t.src.u.gre.key = ct_pptp_info->pac_call_id;
 205         t.dst.u.gre.key = ct_pptp_info->pns_call_id;
 206         if (!destroy_sibling_or_exp(net, ct, &t))
 207                 pr_debug("failed to timeout reply pac->pns ct/exp\n");
 208 }
 209
 210 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 211 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
 212 {
 213         struct nf_conntrack_expect *exp_orig, *exp_reply;
 214         enum ip_conntrack_dir dir;
 215         int ret = 1;
 216         typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
 217
 218         exp_orig = nf_ct_expect_alloc(ct);
 219         if (exp_orig == NULL)
 220                 goto out;
 221
 222         exp_reply = nf_ct_expect_alloc(ct);
 223         if (exp_reply == NULL)
 224                 goto out_put_orig;
 225
 226         /* original direction, PNS->PAC */
 227         dir = IP_CT_DIR_ORIGINAL;
 228         nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
 229                           nf_ct_l3num(ct),
 230                           &ct->tuplehash[dir].tuple.src.u3,
 231                           &ct->tuplehash[dir].tuple.dst.u3,
 232                           IPPROTO_GRE, &peer_callid, &callid);
 233         exp_orig->expectfn = pptp_expectfn;
 234
 235         /* reply direction, PAC->PNS */
 236         dir = IP_CT_DIR_REPLY;
 237         nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
 238                           nf_ct_l3num(ct),
 239                           &ct->tuplehash[dir].tuple.src.u3,
 240                           &ct->tuplehash[dir].tuple.dst.u3,
 241                           IPPROTO_GRE, &callid, &peer_callid);
 242         exp_reply->expectfn = pptp_expectfn;
 243
 244         nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
 245         if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
 246                 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
 247         if (nf_ct_expect_related(exp_orig) != 0)
 248                 goto out_put_both;
 249         if (nf_ct_expect_related(exp_reply) != 0)
 250                 goto out_unexpect_orig;
 251
 252         /* Add GRE keymap entries */
 253         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
 254                 goto out_unexpect_both;
 255         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
 256                 nf_ct_gre_keymap_destroy(ct);
 257                 goto out_unexpect_both;
 258         }
 259         ret = 0;
 260
 261 out_put_both:
 262         nf_ct_expect_put(exp_reply);
 263 out_put_orig:
 264         nf_ct_expect_put(exp_orig);
 265 out:
 266         return ret;
 267
 268 out_unexpect_both:
 269         nf_ct_unexpect_related(exp_reply);
 270 out_unexpect_orig:
 271         nf_ct_unexpect_related(exp_orig);
 272         goto out_put_both;
 273 }
 274
 275 static inline int
 276 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 277                  struct PptpControlHeader *ctlh,
 278                  union pptp_ctrl_union *pptpReq,
 279                  unsigned int reqlen,
 280                  struct nf_conn *ct,
 281                  enum ip_conntrack_info ctinfo)
 282 {
 283         struct nf_ct_pptp_master *info = nfct_help_data(ct);
 284         u_int16_t msg;
 285         __be16 cid = 0, pcid = 0;
 286         typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
 287
 288         msg = ntohs(ctlh->messageType);
 289         pr_debug("inbound control message %s\n", pptp_msg_name(msg));
 290
 291         switch (msg) {
 292         case PPTP_START_SESSION_REPLY:
 293                 /* server confirms new control session */
 294                 if (info->sstate < PPTP_SESSION_REQUESTED)
 295                         goto invalid;
 296                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 297                         info->sstate = PPTP_SESSION_CONFIRMED;
 298                 else
 299                         info->sstate = PPTP_SESSION_ERROR;
 300                 break;
 301
 302         case PPTP_STOP_SESSION_REPLY:
 303                 /* server confirms end of control session */
 304                 if (info->sstate > PPTP_SESSION_STOPREQ)
 305                         goto invalid;
 306                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 307                         info->sstate = PPTP_SESSION_NONE;
 308                 else
 309                         info->sstate = PPTP_SESSION_ERROR;
 310                 break;
 311
 312         case PPTP_OUT_CALL_REPLY:
 313                 /* server accepted call, we now expect GRE frames */
 314                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 315                         goto invalid;
 316                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 317                     info->cstate != PPTP_CALL_OUT_CONF)
 318                         goto invalid;
 319
 320                 cid = pptpReq->ocack.callID;
 321                 pcid = pptpReq->ocack.peersCallID;
 322                 if (info->pns_call_id != pcid)
 323                         goto invalid;
 324                 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg),
 325                          ntohs(cid), ntohs(pcid));
 326
 327                 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
 328                         info->cstate = PPTP_CALL_OUT_CONF;
 329                         info->pac_call_id = cid;
 330                         exp_gre(ct, cid, pcid);
 331                 } else
 332                         info->cstate = PPTP_CALL_NONE;
 333                 break;
 334
 335         case PPTP_IN_CALL_REQUEST:
 336                 /* server tells us about incoming call request */
 337                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 338                         goto invalid;
 339
 340                 cid = pptpReq->icreq.callID;
 341                 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 342                 info->cstate = PPTP_CALL_IN_REQ;
 343                 info->pac_call_id = cid;
 344                 break;
 345
 346         case PPTP_IN_CALL_CONNECT:
 347                 /* server tells us about incoming call established */
 348                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 349                         goto invalid;
 350                 if (info->cstate != PPTP_CALL_IN_REP &&
 351                     info->cstate != PPTP_CALL_IN_CONF)
 352                         goto invalid;
 353
 354                 pcid = pptpReq->iccon.peersCallID;
 355                 cid = info->pac_call_id;
 356
 357                 if (info->pns_call_id != pcid)
 358                         goto invalid;
 359
 360                 pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid));
 361                 info->cstate = PPTP_CALL_IN_CONF;
 362
 363                 /* we expect a GRE connection from PAC to PNS */
 364                 exp_gre(ct, cid, pcid);
 365                 break;
 366
 367         case PPTP_CALL_DISCONNECT_NOTIFY:
 368                 /* server confirms disconnect */
 369                 cid = pptpReq->disc.callID;
 370                 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 371                 info->cstate = PPTP_CALL_NONE;
 372
 373                 /* untrack this call id, unexpect GRE packets */
 374                 pptp_destroy_siblings(ct);
 375                 break;
 376
 377         case PPTP_WAN_ERROR_NOTIFY:
 378         case PPTP_SET_LINK_INFO:
 379         case PPTP_ECHO_REQUEST:
 380         case PPTP_ECHO_REPLY:
 381                 /* I don't have to explain these ;) */
 382                 break;
 383
 384         default:
 385                 goto invalid;
 386         }
 387
 388         nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
 389         if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
 390                 return nf_nat_pptp_inbound(skb, ct, ctinfo,
 391                                            protoff, ctlh, pptpReq);
 392         return NF_ACCEPT;
 393
 394 invalid:
 395         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 396                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 397                  pptp_msg_name(msg),
 398                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 399                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 400         return NF_ACCEPT;
 401 }
 402
 403 static inline int
 404 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 405                   struct PptpControlHeader *ctlh,
 406                   union pptp_ctrl_union *pptpReq,
 407                   unsigned int reqlen,
 408                   struct nf_conn *ct,
 409                   enum ip_conntrack_info ctinfo)
 410 {
 411         struct nf_ct_pptp_master *info = nfct_help_data(ct);
 412         u_int16_t msg;
 413         __be16 cid = 0, pcid = 0;
 414         typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
 415
 416         msg = ntohs(ctlh->messageType);
 417         pr_debug("outbound control message %s\n", pptp_msg_name(msg));
 418
 419         switch (msg) {
 420         case PPTP_START_SESSION_REQUEST:
 421                 /* client requests for new control session */
 422                 if (info->sstate != PPTP_SESSION_NONE)
 423                         goto invalid;
 424                 info->sstate = PPTP_SESSION_REQUESTED;
 425                 break;
 426
 427         case PPTP_STOP_SESSION_REQUEST:
 428                 /* client requests end of control session */
 429                 info->sstate = PPTP_SESSION_STOPREQ;
 430                 break;
 431
 432         case PPTP_OUT_CALL_REQUEST:
 433                 /* client initiating connection to server */
 434                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 435                         goto invalid;
 436                 info->cstate = PPTP_CALL_OUT_REQ;
 437                 /* track PNS call id */
 438                 cid = pptpReq->ocreq.callID;
 439                 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 440                 info->pns_call_id = cid;
 441                 break;
 442
 443         case PPTP_IN_CALL_REPLY:
 444                 /* client answers incoming call */
 445                 if (info->cstate != PPTP_CALL_IN_REQ &&
 446                     info->cstate != PPTP_CALL_IN_REP)
 447                         goto invalid;
 448
 449                 cid = pptpReq->icack.callID;
 450                 pcid = pptpReq->icack.peersCallID;
 451                 if (info->pac_call_id != pcid)
 452                         goto invalid;
 453                 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg),
 454                          ntohs(cid), ntohs(pcid));
 455
 456                 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
 457                         /* part two of the three-way handshake */
 458                         info->cstate = PPTP_CALL_IN_REP;
 459                         info->pns_call_id = cid;
 460                 } else
 461                         info->cstate = PPTP_CALL_NONE;
 462                 break;
 463
 464         case PPTP_CALL_CLEAR_REQUEST:
 465                 /* client requests hangup of call */
 466                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 467                         goto invalid;
 468                 /* FUTURE: iterate over all calls and check if
 469                  * call ID is valid.  We don't do this without newnat,
 470                  * because we only know about last call */
 471                 info->cstate = PPTP_CALL_CLEAR_REQ;
 472                 break;
 473
 474         case PPTP_SET_LINK_INFO:
 475         case PPTP_ECHO_REQUEST:
 476         case PPTP_ECHO_REPLY:
 477                 /* I don't have to explain these ;) */
 478                 break;
 479
 480         default:
 481                 goto invalid;
 482         }
 483
 484         nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
 485         if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
 486                 return nf_nat_pptp_outbound(skb, ct, ctinfo,
 487                                             protoff, ctlh, pptpReq);
 488         return NF_ACCEPT;
 489
 490 invalid:
 491         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 492                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 493                  pptp_msg_name(msg),
 494                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 495                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 496         return NF_ACCEPT;
 497 }
 498
 499 static const unsigned int pptp_msg_size[] = {
 500         [PPTP_START_SESSION_REQUEST]  = sizeof(struct PptpStartSessionRequest),
 501         [PPTP_START_SESSION_REPLY]    = sizeof(struct PptpStartSessionReply),
 502         [PPTP_STOP_SESSION_REQUEST]   = sizeof(struct PptpStopSessionRequest),
 503         [PPTP_STOP_SESSION_REPLY]     = sizeof(struct PptpStopSessionReply),
 504         [PPTP_OUT_CALL_REQUEST]       = sizeof(struct PptpOutCallRequest),
 505         [PPTP_OUT_CALL_REPLY]         = sizeof(struct PptpOutCallReply),
 506         [PPTP_IN_CALL_REQUEST]        = sizeof(struct PptpInCallRequest),
 507         [PPTP_IN_CALL_REPLY]          = sizeof(struct PptpInCallReply),
 508         [PPTP_IN_CALL_CONNECT]        = sizeof(struct PptpInCallConnected),
 509         [PPTP_CALL_CLEAR_REQUEST]     = sizeof(struct PptpClearCallRequest),
 510         [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
 511         [PPTP_WAN_ERROR_NOTIFY]       = sizeof(struct PptpWanErrorNotify),
 512         [PPTP_SET_LINK_INFO]          = sizeof(struct PptpSetLinkInfo),
 513 };
 514
 515 /* track caller id inside control connection, call expect_related */
 516 static int
 517 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 518                     struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 519
 520 {
 521         int dir = CTINFO2DIR(ctinfo);
 522         const struct nf_ct_pptp_master *info = nfct_help_data(ct);
 523         const struct tcphdr *tcph;
 524         struct tcphdr _tcph;
 525         const struct pptp_pkt_hdr *pptph;
 526         struct pptp_pkt_hdr _pptph;
 527         struct PptpControlHeader _ctlh, *ctlh;
 528         union pptp_ctrl_union _pptpReq, *pptpReq;
 529         unsigned int tcplen = skb->len - protoff;
 530         unsigned int datalen, reqlen, nexthdr_off;
 531         int oldsstate, oldcstate;
 532         int ret;
 533         u_int16_t msg;
 534
 535         /* don't do any tracking before tcp handshake complete */
 536         if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
 537                 return NF_ACCEPT;
 538
 539         nexthdr_off = protoff;
 540         tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
 541         BUG_ON(!tcph);
 542         nexthdr_off += tcph->doff * 4;
 543         datalen = tcplen - tcph->doff * 4;
 544
 545         pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
 546         if (!pptph) {
 547                 pr_debug("no full PPTP header, can't track\n");
 548                 return NF_ACCEPT;
 549         }
 550         nexthdr_off += sizeof(_pptph);
 551         datalen -= sizeof(_pptph);
 552
 553         /* if it's not a control message we can't do anything with it */
 554         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 555             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 556                 pr_debug("not a control packet\n");
 557                 return NF_ACCEPT;
 558         }
 559
 560         ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 561         if (!ctlh)
 562                 return NF_ACCEPT;
 563         nexthdr_off += sizeof(_ctlh);
 564         datalen -= sizeof(_ctlh);
 565
 566         reqlen = datalen;
 567         msg = ntohs(ctlh->messageType);
 568         if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
 569                 return NF_ACCEPT;
 570         if (reqlen > sizeof(*pptpReq))
 571                 reqlen = sizeof(*pptpReq);
 572
 573         pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
 574         if (!pptpReq)
 575                 return NF_ACCEPT;
 576
 577         oldsstate = info->sstate;
 578         oldcstate = info->cstate;
 579
 580         spin_lock_bh(&nf_pptp_lock);
 581
 582         /* FIXME: We just blindly assume that the control connection is always
 583          * established from PNS->PAC.  However, RFC makes no guarantee */
 584         if (dir == IP_CT_DIR_ORIGINAL)
 585                 /* client -> server (PNS -> PAC) */
 586                 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 587                                         ctinfo);
 588         else
 589                 /* server -> client (PAC -> PNS) */
 590                 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 591                                        ctinfo);
 592         pr_debug("sstate: %d->%d, cstate: %d->%d\n",
 593                  oldsstate, info->sstate, oldcstate, info->cstate);
 594         spin_unlock_bh(&nf_pptp_lock);
 595
 596         return ret;
 597 }
 598
 599 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
 600         .max_expected   = 2,
 601         .timeout        = 5 * 60,
 602 };
 603
 604 /* control protocol helper */
 605 static struct nf_conntrack_helper pptp __read_mostly = {
 606         .name                   = "pptp",
 607         .me                     = THIS_MODULE,
 608         .data_len               = sizeof(struct nf_ct_pptp_master),
 609         .tuple.src.l3num        = AF_INET,
 610         .tuple.src.u.tcp.port   = cpu_to_be16(PPTP_CONTROL_PORT),
 611         .tuple.dst.protonum     = IPPROTO_TCP,
 612         .help                   = conntrack_pptp_help,
 613         .destroy                = pptp_destroy_siblings,
 614         .expect_policy          = &pptp_exp_policy,
 615 };
 616
 617 static int __init nf_conntrack_pptp_init(void)
 618 {
 619         return nf_conntrack_helper_register(&pptp);
 620 }
 621
 622 static void __exit nf_conntrack_pptp_fini(void)
 623 {
 624         nf_conntrack_helper_unregister(&pptp);
 625 }
 626
 627 module_init(nf_conntrack_pptp_init);
 628 module_exit(nf_conntrack_pptp_fini);