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 <net/netfilter/nf_conntrack_zones.h>
  32 #include <linux/netfilter/nf_conntrack_proto_gre.h>
  33 #include <linux/netfilter/nf_conntrack_pptp.h>
  34
  35 #define NF_CT_PPTP_VERSION "3.1"
  36
  37 MODULE_LICENSE("GPL");
  38 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  39 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
  40 MODULE_ALIAS("ip_conntrack_pptp");
  41 MODULE_ALIAS_NFCT_HELPER("pptp");
  42
  43 static DEFINE_SPINLOCK(nf_pptp_lock);
  44
  45 int
  46 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
  47                              struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  48                              struct PptpControlHeader *ctlh,
  49                              union pptp_ctrl_union *pptpReq) __read_mostly;
  50 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
  51
  52 int
  53 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
  54                             struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  55                             struct PptpControlHeader *ctlh,
  56                             union pptp_ctrl_union *pptpReq) __read_mostly;
  57 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
  58
  59 void
  60 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
  61                             struct nf_conntrack_expect *expect_reply)
  62                             __read_mostly;
  63 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
  64
  65 void
  66 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
  67                              struct nf_conntrack_expect *exp) __read_mostly;
  68 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
  69
  70 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
  71 /* PptpControlMessageType names */
  72 const char *const pptp_msg_name[] = {
  73         "UNKNOWN_MESSAGE",
  74         "START_SESSION_REQUEST",
  75         "START_SESSION_REPLY",
  76         "STOP_SESSION_REQUEST",
  77         "STOP_SESSION_REPLY",
  78         "ECHO_REQUEST",
  79         "ECHO_REPLY",
  80         "OUT_CALL_REQUEST",
  81         "OUT_CALL_REPLY",
  82         "IN_CALL_REQUEST",
  83         "IN_CALL_REPLY",
  84         "IN_CALL_CONNECT",
  85         "CALL_CLEAR_REQUEST",
  86         "CALL_DISCONNECT_NOTIFY",
  87         "WAN_ERROR_NOTIFY",
  88         "SET_LINK_INFO"
  89 };
  90 EXPORT_SYMBOL(pptp_msg_name);
  91 #endif
  92
  93 #define SECS *HZ
  94 #define MINS * 60 SECS
  95 #define HOURS * 60 MINS
  96
  97 #define PPTP_GRE_TIMEOUT                (10 MINS)
  98 #define PPTP_GRE_STREAM_TIMEOUT         (5 HOURS)
  99
 100 static void pptp_expectfn(struct nf_conn *ct,
 101                          struct nf_conntrack_expect *exp)
 102 {
 103         struct net *net = nf_ct_net(ct);
 104         typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn;
 105         pr_debug("increasing timeouts\n");
 106
 107         /* increase timeout of GRE data channel conntrack entry */
 108         ct->proto.gre.timeout        = PPTP_GRE_TIMEOUT;
 109         ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
 110
 111         /* Can you see how rusty this code is, compared with the pre-2.6.11
 112          * one? That's what happened to my shiny newnat of 2002 ;( -HW */
 113
 114         rcu_read_lock();
 115         nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn);
 116         if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK)
 117                 nf_nat_pptp_expectfn(ct, exp);
 118         else {
 119                 struct nf_conntrack_tuple inv_t;
 120                 struct nf_conntrack_expect *exp_other;
 121
 122                 /* obviously this tuple inversion only works until you do NAT */
 123                 nf_ct_invert_tuplepr(&inv_t, &exp->tuple);
 124                 pr_debug("trying to unexpect other dir: ");
 125                 nf_ct_dump_tuple(&inv_t);
 126
 127                 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t);
 128                 if (exp_other) {
 129                         /* delete other expectation.  */
 130                         pr_debug("found\n");
 131                         nf_ct_unexpect_related(exp_other);
 132                         nf_ct_expect_put(exp_other);
 133                 } else {
 134                         pr_debug("not found\n");
 135                 }
 136         }
 137         rcu_read_unlock();
 138 }
 139
 140 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
 141                                   const struct nf_conntrack_tuple *t)
 142 {
 143         const struct nf_conntrack_tuple_hash *h;
 144         struct nf_conntrack_expect *exp;
 145         struct nf_conn *sibling;
 146         u16 zone = nf_ct_zone(ct);
 147
 148         pr_debug("trying to timeout ct or exp for tuple ");
 149         nf_ct_dump_tuple(t);
 150
 151         h = nf_conntrack_find_get(net, zone, t);
 152         if (h)  {
 153                 sibling = nf_ct_tuplehash_to_ctrack(h);
 154                 pr_debug("setting timeout of conntrack %p to 0\n", sibling);
 155                 sibling->proto.gre.timeout        = 0;
 156                 sibling->proto.gre.stream_timeout = 0;
 157                 if (del_timer(&sibling->timeout))
 158                         sibling->timeout.function((unsigned long)sibling);
 159                 nf_ct_put(sibling);
 160                 return 1;
 161         } else {
 162                 exp = nf_ct_expect_find_get(net, zone, t);
 163                 if (exp) {
 164                         pr_debug("unexpect_related of expect %p\n", exp);
 165                         nf_ct_unexpect_related(exp);
 166                         nf_ct_expect_put(exp);
 167                         return 1;
 168                 }
 169         }
 170         return 0;
 171 }
 172
 173 /* timeout GRE data connections */
 174 static void pptp_destroy_siblings(struct nf_conn *ct)
 175 {
 176         struct net *net = nf_ct_net(ct);
 177         const struct nf_conn_help *help = nfct_help(ct);
 178         struct nf_conntrack_tuple t;
 179
 180         nf_ct_gre_keymap_destroy(ct);
 181
 182         /* try original (pns->pac) tuple */
 183         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 184         t.dst.protonum = IPPROTO_GRE;
 185         t.src.u.gre.key = help->help.ct_pptp_info.pns_call_id;
 186         t.dst.u.gre.key = help->help.ct_pptp_info.pac_call_id;
 187         if (!destroy_sibling_or_exp(net, ct, &t))
 188                 pr_debug("failed to timeout original pns->pac ct/exp\n");
 189
 190         /* try reply (pac->pns) tuple */
 191         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 192         t.dst.protonum = IPPROTO_GRE;
 193         t.src.u.gre.key = help->help.ct_pptp_info.pac_call_id;
 194         t.dst.u.gre.key = help->help.ct_pptp_info.pns_call_id;
 195         if (!destroy_sibling_or_exp(net, ct, &t))
 196                 pr_debug("failed to timeout reply pac->pns ct/exp\n");
 197 }
 198
 199 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 200 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
 201 {
 202         struct nf_conntrack_expect *exp_orig, *exp_reply;
 203         enum ip_conntrack_dir dir;
 204         int ret = 1;
 205         typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
 206
 207         exp_orig = nf_ct_expect_alloc(ct);
 208         if (exp_orig == NULL)
 209                 goto out;
 210
 211         exp_reply = nf_ct_expect_alloc(ct);
 212         if (exp_reply == NULL)
 213                 goto out_put_orig;
 214
 215         /* original direction, PNS->PAC */
 216         dir = IP_CT_DIR_ORIGINAL;
 217         nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
 218                           nf_ct_l3num(ct),
 219                           &ct->tuplehash[dir].tuple.src.u3,
 220                           &ct->tuplehash[dir].tuple.dst.u3,
 221                           IPPROTO_GRE, &peer_callid, &callid);
 222         exp_orig->expectfn = pptp_expectfn;
 223
 224         /* reply direction, PAC->PNS */
 225         dir = IP_CT_DIR_REPLY;
 226         nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
 227                           nf_ct_l3num(ct),
 228                           &ct->tuplehash[dir].tuple.src.u3,
 229                           &ct->tuplehash[dir].tuple.dst.u3,
 230                           IPPROTO_GRE, &callid, &peer_callid);
 231         exp_reply->expectfn = pptp_expectfn;
 232
 233         nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
 234         if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
 235                 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
 236         if (nf_ct_expect_related(exp_orig) != 0)
 237                 goto out_put_both;
 238         if (nf_ct_expect_related(exp_reply) != 0)
 239                 goto out_unexpect_orig;
 240
 241         /* Add GRE keymap entries */
 242         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
 243                 goto out_unexpect_both;
 244         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
 245                 nf_ct_gre_keymap_destroy(ct);
 246                 goto out_unexpect_both;
 247         }
 248         ret = 0;
 249
 250 out_put_both:
 251         nf_ct_expect_put(exp_reply);
 252 out_put_orig:
 253         nf_ct_expect_put(exp_orig);
 254 out:
 255         return ret;
 256
 257 out_unexpect_both:
 258         nf_ct_unexpect_related(exp_reply);
 259 out_unexpect_orig:
 260         nf_ct_unexpect_related(exp_orig);
 261         goto out_put_both;
 262 }
 263
 264 static inline int
 265 pptp_inbound_pkt(struct sk_buff *skb,
 266                  struct PptpControlHeader *ctlh,
 267                  union pptp_ctrl_union *pptpReq,
 268                  unsigned int reqlen,
 269                  struct nf_conn *ct,
 270                  enum ip_conntrack_info ctinfo)
 271 {
 272         struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
 273         u_int16_t msg;
 274         __be16 cid = 0, pcid = 0;
 275         typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
 276
 277         msg = ntohs(ctlh->messageType);
 278         pr_debug("inbound control message %s\n", pptp_msg_name[msg]);
 279
 280         switch (msg) {
 281         case PPTP_START_SESSION_REPLY:
 282                 /* server confirms new control session */
 283                 if (info->sstate < PPTP_SESSION_REQUESTED)
 284                         goto invalid;
 285                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 286                         info->sstate = PPTP_SESSION_CONFIRMED;
 287                 else
 288                         info->sstate = PPTP_SESSION_ERROR;
 289                 break;
 290
 291         case PPTP_STOP_SESSION_REPLY:
 292                 /* server confirms end of control session */
 293                 if (info->sstate > PPTP_SESSION_STOPREQ)
 294                         goto invalid;
 295                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 296                         info->sstate = PPTP_SESSION_NONE;
 297                 else
 298                         info->sstate = PPTP_SESSION_ERROR;
 299                 break;
 300
 301         case PPTP_OUT_CALL_REPLY:
 302                 /* server accepted call, we now expect GRE frames */
 303                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 304                         goto invalid;
 305                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 306                     info->cstate != PPTP_CALL_OUT_CONF)
 307                         goto invalid;
 308
 309                 cid = pptpReq->ocack.callID;
 310                 pcid = pptpReq->ocack.peersCallID;
 311                 if (info->pns_call_id != pcid)
 312                         goto invalid;
 313                 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg],
 314                          ntohs(cid), ntohs(pcid));
 315
 316                 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
 317                         info->cstate = PPTP_CALL_OUT_CONF;
 318                         info->pac_call_id = cid;
 319                         exp_gre(ct, cid, pcid);
 320                 } else
 321                         info->cstate = PPTP_CALL_NONE;
 322                 break;
 323
 324         case PPTP_IN_CALL_REQUEST:
 325                 /* server tells us about incoming call request */
 326                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 327                         goto invalid;
 328
 329                 cid = pptpReq->icreq.callID;
 330                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 331                 info->cstate = PPTP_CALL_IN_REQ;
 332                 info->pac_call_id = cid;
 333                 break;
 334
 335         case PPTP_IN_CALL_CONNECT:
 336                 /* server tells us about incoming call established */
 337                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 338                         goto invalid;
 339                 if (info->cstate != PPTP_CALL_IN_REP &&
 340                     info->cstate != PPTP_CALL_IN_CONF)
 341                         goto invalid;
 342
 343                 pcid = pptpReq->iccon.peersCallID;
 344                 cid = info->pac_call_id;
 345
 346                 if (info->pns_call_id != pcid)
 347                         goto invalid;
 348
 349                 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid));
 350                 info->cstate = PPTP_CALL_IN_CONF;
 351
 352                 /* we expect a GRE connection from PAC to PNS */
 353                 exp_gre(ct, cid, pcid);
 354                 break;
 355
 356         case PPTP_CALL_DISCONNECT_NOTIFY:
 357                 /* server confirms disconnect */
 358                 cid = pptpReq->disc.callID;
 359                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 360                 info->cstate = PPTP_CALL_NONE;
 361
 362                 /* untrack this call id, unexpect GRE packets */
 363                 pptp_destroy_siblings(ct);
 364                 break;
 365
 366         case PPTP_WAN_ERROR_NOTIFY:
 367         case PPTP_SET_LINK_INFO:
 368         case PPTP_ECHO_REQUEST:
 369         case PPTP_ECHO_REPLY:
 370                 /* I don't have to explain these ;) */
 371                 break;
 372
 373         default:
 374                 goto invalid;
 375         }
 376
 377         nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
 378         if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
 379                 return nf_nat_pptp_inbound(skb, ct, ctinfo, ctlh, pptpReq);
 380         return NF_ACCEPT;
 381
 382 invalid:
 383         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 384                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 385                  msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 386                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 387                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 388         return NF_ACCEPT;
 389 }
 390
 391 static inline int
 392 pptp_outbound_pkt(struct sk_buff *skb,
 393                   struct PptpControlHeader *ctlh,
 394                   union pptp_ctrl_union *pptpReq,
 395                   unsigned int reqlen,
 396                   struct nf_conn *ct,
 397                   enum ip_conntrack_info ctinfo)
 398 {
 399         struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
 400         u_int16_t msg;
 401         __be16 cid = 0, pcid = 0;
 402         typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
 403
 404         msg = ntohs(ctlh->messageType);
 405         pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
 406
 407         switch (msg) {
 408         case PPTP_START_SESSION_REQUEST:
 409                 /* client requests for new control session */
 410                 if (info->sstate != PPTP_SESSION_NONE)
 411                         goto invalid;
 412                 info->sstate = PPTP_SESSION_REQUESTED;
 413                 break;
 414
 415         case PPTP_STOP_SESSION_REQUEST:
 416                 /* client requests end of control session */
 417                 info->sstate = PPTP_SESSION_STOPREQ;
 418                 break;
 419
 420         case PPTP_OUT_CALL_REQUEST:
 421                 /* client initiating connection to server */
 422                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 423                         goto invalid;
 424                 info->cstate = PPTP_CALL_OUT_REQ;
 425                 /* track PNS call id */
 426                 cid = pptpReq->ocreq.callID;
 427                 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 428                 info->pns_call_id = cid;
 429                 break;
 430
 431         case PPTP_IN_CALL_REPLY:
 432                 /* client answers incoming call */
 433                 if (info->cstate != PPTP_CALL_IN_REQ &&
 434                     info->cstate != PPTP_CALL_IN_REP)
 435                         goto invalid;
 436
 437                 cid = pptpReq->icack.callID;
 438                 pcid = pptpReq->icack.peersCallID;
 439                 if (info->pac_call_id != pcid)
 440                         goto invalid;
 441                 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
 442                          ntohs(cid), ntohs(pcid));
 443
 444                 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
 445                         /* part two of the three-way handshake */
 446                         info->cstate = PPTP_CALL_IN_REP;
 447                         info->pns_call_id = cid;
 448                 } else
 449                         info->cstate = PPTP_CALL_NONE;
 450                 break;
 451
 452         case PPTP_CALL_CLEAR_REQUEST:
 453                 /* client requests hangup of call */
 454                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 455                         goto invalid;
 456                 /* FUTURE: iterate over all calls and check if
 457                  * call ID is valid.  We don't do this without newnat,
 458                  * because we only know about last call */
 459                 info->cstate = PPTP_CALL_CLEAR_REQ;
 460                 break;
 461
 462         case PPTP_SET_LINK_INFO:
 463         case PPTP_ECHO_REQUEST:
 464         case PPTP_ECHO_REPLY:
 465                 /* I don't have to explain these ;) */
 466                 break;
 467
 468         default:
 469                 goto invalid;
 470         }
 471
 472         nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
 473         if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
 474                 return nf_nat_pptp_outbound(skb, ct, ctinfo, ctlh, pptpReq);
 475         return NF_ACCEPT;
 476
 477 invalid:
 478         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 479                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 480                  msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 481                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 482                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 483         return NF_ACCEPT;
 484 }
 485
 486 static const unsigned int pptp_msg_size[] = {
 487         [PPTP_START_SESSION_REQUEST]  = sizeof(struct PptpStartSessionRequest),
 488         [PPTP_START_SESSION_REPLY]    = sizeof(struct PptpStartSessionReply),
 489         [PPTP_STOP_SESSION_REQUEST]   = sizeof(struct PptpStopSessionRequest),
 490         [PPTP_STOP_SESSION_REPLY]     = sizeof(struct PptpStopSessionReply),
 491         [PPTP_OUT_CALL_REQUEST]       = sizeof(struct PptpOutCallRequest),
 492         [PPTP_OUT_CALL_REPLY]         = sizeof(struct PptpOutCallReply),
 493         [PPTP_IN_CALL_REQUEST]        = sizeof(struct PptpInCallRequest),
 494         [PPTP_IN_CALL_REPLY]          = sizeof(struct PptpInCallReply),
 495         [PPTP_IN_CALL_CONNECT]        = sizeof(struct PptpInCallConnected),
 496         [PPTP_CALL_CLEAR_REQUEST]     = sizeof(struct PptpClearCallRequest),
 497         [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
 498         [PPTP_WAN_ERROR_NOTIFY]       = sizeof(struct PptpWanErrorNotify),
 499         [PPTP_SET_LINK_INFO]          = sizeof(struct PptpSetLinkInfo),
 500 };
 501
 502 /* track caller id inside control connection, call expect_related */
 503 static int
 504 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 505                     struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 506
 507 {
 508         int dir = CTINFO2DIR(ctinfo);
 509         const struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
 510         const struct tcphdr *tcph;
 511         struct tcphdr _tcph;
 512         const struct pptp_pkt_hdr *pptph;
 513         struct pptp_pkt_hdr _pptph;
 514         struct PptpControlHeader _ctlh, *ctlh;
 515         union pptp_ctrl_union _pptpReq, *pptpReq;
 516         unsigned int tcplen = skb->len - protoff;
 517         unsigned int datalen, reqlen, nexthdr_off;
 518         int oldsstate, oldcstate;
 519         int ret;
 520         u_int16_t msg;
 521
 522         /* don't do any tracking before tcp handshake complete */
 523         if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
 524                 return NF_ACCEPT;
 525
 526         nexthdr_off = protoff;
 527         tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
 528         BUG_ON(!tcph);
 529         nexthdr_off += tcph->doff * 4;
 530         datalen = tcplen - tcph->doff * 4;
 531
 532         pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
 533         if (!pptph) {
 534                 pr_debug("no full PPTP header, can't track\n");
 535                 return NF_ACCEPT;
 536         }
 537         nexthdr_off += sizeof(_pptph);
 538         datalen -= sizeof(_pptph);
 539
 540         /* if it's not a control message we can't do anything with it */
 541         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 542             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 543                 pr_debug("not a control packet\n");
 544                 return NF_ACCEPT;
 545         }
 546
 547         ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 548         if (!ctlh)
 549                 return NF_ACCEPT;
 550         nexthdr_off += sizeof(_ctlh);
 551         datalen -= sizeof(_ctlh);
 552
 553         reqlen = datalen;
 554         msg = ntohs(ctlh->messageType);
 555         if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
 556                 return NF_ACCEPT;
 557         if (reqlen > sizeof(*pptpReq))
 558                 reqlen = sizeof(*pptpReq);
 559
 560         pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
 561         if (!pptpReq)
 562                 return NF_ACCEPT;
 563
 564         oldsstate = info->sstate;
 565         oldcstate = info->cstate;
 566
 567         spin_lock_bh(&nf_pptp_lock);
 568
 569         /* FIXME: We just blindly assume that the control connection is always
 570          * established from PNS->PAC.  However, RFC makes no guarantee */
 571         if (dir == IP_CT_DIR_ORIGINAL)
 572                 /* client -> server (PNS -> PAC) */
 573                 ret = pptp_outbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
 574                                         ctinfo);
 575         else
 576                 /* server -> client (PAC -> PNS) */
 577                 ret = pptp_inbound_pkt(skb, ctlh, pptpReq, reqlen, ct,
 578                                        ctinfo);
 579         pr_debug("sstate: %d->%d, cstate: %d->%d\n",
 580                  oldsstate, info->sstate, oldcstate, info->cstate);
 581         spin_unlock_bh(&nf_pptp_lock);
 582
 583         return ret;
 584 }
 585
 586 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
 587         .max_expected   = 2,
 588         .timeout        = 5 * 60,
 589 };
 590
 591 /* control protocol helper */
 592 static struct nf_conntrack_helper pptp __read_mostly = {
 593         .name                   = "pptp",
 594         .me                     = THIS_MODULE,
 595         .tuple.src.l3num        = AF_INET,
 596         .tuple.src.u.tcp.port   = cpu_to_be16(PPTP_CONTROL_PORT),
 597         .tuple.dst.protonum     = IPPROTO_TCP,
 598         .help                   = conntrack_pptp_help,
 599         .destroy                = pptp_destroy_siblings,
 600         .expect_policy          = &pptp_exp_policy,
 601 };
 602
 603 static void nf_conntrack_pptp_net_exit(struct net *net)
 604 {
 605         nf_ct_gre_keymap_flush(net);
 606 }
 607
 608 static struct pernet_operations nf_conntrack_pptp_net_ops = {
 609         .exit = nf_conntrack_pptp_net_exit,
 610 };
 611
 612 static int __init nf_conntrack_pptp_init(void)
 613 {
 614         int rv;
 615
 616         rv = nf_conntrack_helper_register(&pptp);
 617         if (rv < 0)
 618                 return rv;
 619         rv = register_pernet_subsys(&nf_conntrack_pptp_net_ops);
 620         if (rv < 0)
 621                 nf_conntrack_helper_unregister(&pptp);
 622         return rv;
 623 }
 624
 625 static void __exit nf_conntrack_pptp_fini(void)
 626 {
 627         nf_conntrack_helper_unregister(&pptp);
 628         unregister_pernet_subsys(&nf_conntrack_pptp_net_ops);
 629 }
 630
 631 module_init(nf_conntrack_pptp_init);
 632 module_exit(nf_conntrack_pptp_fini);