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