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