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                 nf_ct_kill(sibling);
 169                 nf_ct_put(sibling);
 170                 return 1;
 171         } else {
 172                 exp = nf_ct_expect_find_get(net, zone, t);
 173                 if (exp) {
 174                         pr_debug("unexpect_related of expect %p\n", exp);
 175                         nf_ct_unexpect_related(exp);
 176                         nf_ct_expect_put(exp);
 177                         return 1;
 178                 }
 179         }
 180         return 0;
 181 }
 182
 183 /* timeout GRE data connections */
 184 static void pptp_destroy_siblings(struct nf_conn *ct)
 185 {
 186         struct net *net = nf_ct_net(ct);
 187         const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 188         struct nf_conntrack_tuple t;
 189
 190         nf_ct_gre_keymap_destroy(ct);
 191
 192         /* try original (pns->pac) tuple */
 193         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 194         t.dst.protonum = IPPROTO_GRE;
 195         t.src.u.gre.key = ct_pptp_info->pns_call_id;
 196         t.dst.u.gre.key = ct_pptp_info->pac_call_id;
 197         if (!destroy_sibling_or_exp(net, ct, &t))
 198                 pr_debug("failed to timeout original pns->pac ct/exp\n");
 199
 200         /* try reply (pac->pns) tuple */
 201         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 202         t.dst.protonum = IPPROTO_GRE;
 203         t.src.u.gre.key = ct_pptp_info->pac_call_id;
 204         t.dst.u.gre.key = ct_pptp_info->pns_call_id;
 205         if (!destroy_sibling_or_exp(net, ct, &t))
 206                 pr_debug("failed to timeout reply pac->pns ct/exp\n");
 207 }
 208
 209 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 210 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid)
 211 {
 212         struct nf_conntrack_expect *exp_orig, *exp_reply;
 213         enum ip_conntrack_dir dir;
 214         int ret = 1;
 215         typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre;
 216
 217         exp_orig = nf_ct_expect_alloc(ct);
 218         if (exp_orig == NULL)
 219                 goto out;
 220
 221         exp_reply = nf_ct_expect_alloc(ct);
 222         if (exp_reply == NULL)
 223                 goto out_put_orig;
 224
 225         /* original direction, PNS->PAC */
 226         dir = IP_CT_DIR_ORIGINAL;
 227         nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT,
 228                           nf_ct_l3num(ct),
 229                           &ct->tuplehash[dir].tuple.src.u3,
 230                           &ct->tuplehash[dir].tuple.dst.u3,
 231                           IPPROTO_GRE, &peer_callid, &callid);
 232         exp_orig->expectfn = pptp_expectfn;
 233
 234         /* reply direction, PAC->PNS */
 235         dir = IP_CT_DIR_REPLY;
 236         nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT,
 237                           nf_ct_l3num(ct),
 238                           &ct->tuplehash[dir].tuple.src.u3,
 239                           &ct->tuplehash[dir].tuple.dst.u3,
 240                           IPPROTO_GRE, &callid, &peer_callid);
 241         exp_reply->expectfn = pptp_expectfn;
 242
 243         nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre);
 244         if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK)
 245                 nf_nat_pptp_exp_gre(exp_orig, exp_reply);
 246         if (nf_ct_expect_related(exp_orig) != 0)
 247                 goto out_put_both;
 248         if (nf_ct_expect_related(exp_reply) != 0)
 249                 goto out_unexpect_orig;
 250
 251         /* Add GRE keymap entries */
 252         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0)
 253                 goto out_unexpect_both;
 254         if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) {
 255                 nf_ct_gre_keymap_destroy(ct);
 256                 goto out_unexpect_both;
 257         }
 258         ret = 0;
 259
 260 out_put_both:
 261         nf_ct_expect_put(exp_reply);
 262 out_put_orig:
 263         nf_ct_expect_put(exp_orig);
 264 out:
 265         return ret;
 266
 267 out_unexpect_both:
 268         nf_ct_unexpect_related(exp_reply);
 269 out_unexpect_orig:
 270         nf_ct_unexpect_related(exp_orig);
 271         goto out_put_both;
 272 }
 273
 274 static inline int
 275 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 276                  struct PptpControlHeader *ctlh,
 277                  union pptp_ctrl_union *pptpReq,
 278                  unsigned int reqlen,
 279                  struct nf_conn *ct,
 280                  enum ip_conntrack_info ctinfo)
 281 {
 282         struct nf_ct_pptp_master *info = nfct_help_data(ct);
 283         u_int16_t msg;
 284         __be16 cid = 0, pcid = 0;
 285         typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
 286
 287         msg = ntohs(ctlh->messageType);
 288         pr_debug("inbound control message %s\n", pptp_msg_name(msg));
 289
 290         switch (msg) {
 291         case PPTP_START_SESSION_REPLY:
 292                 /* server confirms new control session */
 293                 if (info->sstate < PPTP_SESSION_REQUESTED)
 294                         goto invalid;
 295                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 296                         info->sstate = PPTP_SESSION_CONFIRMED;
 297                 else
 298                         info->sstate = PPTP_SESSION_ERROR;
 299                 break;
 300
 301         case PPTP_STOP_SESSION_REPLY:
 302                 /* server confirms end of control session */
 303                 if (info->sstate > PPTP_SESSION_STOPREQ)
 304                         goto invalid;
 305                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 306                         info->sstate = PPTP_SESSION_NONE;
 307                 else
 308                         info->sstate = PPTP_SESSION_ERROR;
 309                 break;
 310
 311         case PPTP_OUT_CALL_REPLY:
 312                 /* server accepted call, we now expect GRE frames */
 313                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 314                         goto invalid;
 315                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 316                     info->cstate != PPTP_CALL_OUT_CONF)
 317                         goto invalid;
 318
 319                 cid = pptpReq->ocack.callID;
 320                 pcid = pptpReq->ocack.peersCallID;
 321                 if (info->pns_call_id != pcid)
 322                         goto invalid;
 323                 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg),
 324                          ntohs(cid), ntohs(pcid));
 325
 326                 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) {
 327                         info->cstate = PPTP_CALL_OUT_CONF;
 328                         info->pac_call_id = cid;
 329                         exp_gre(ct, cid, pcid);
 330                 } else
 331                         info->cstate = PPTP_CALL_NONE;
 332                 break;
 333
 334         case PPTP_IN_CALL_REQUEST:
 335                 /* server tells us about incoming call request */
 336                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 337                         goto invalid;
 338
 339                 cid = pptpReq->icreq.callID;
 340                 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 341                 info->cstate = PPTP_CALL_IN_REQ;
 342                 info->pac_call_id = cid;
 343                 break;
 344
 345         case PPTP_IN_CALL_CONNECT:
 346                 /* server tells us about incoming call established */
 347                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 348                         goto invalid;
 349                 if (info->cstate != PPTP_CALL_IN_REP &&
 350                     info->cstate != PPTP_CALL_IN_CONF)
 351                         goto invalid;
 352
 353                 pcid = pptpReq->iccon.peersCallID;
 354                 cid = info->pac_call_id;
 355
 356                 if (info->pns_call_id != pcid)
 357                         goto invalid;
 358
 359                 pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid));
 360                 info->cstate = PPTP_CALL_IN_CONF;
 361
 362                 /* we expect a GRE connection from PAC to PNS */
 363                 exp_gre(ct, cid, pcid);
 364                 break;
 365
 366         case PPTP_CALL_DISCONNECT_NOTIFY:
 367                 /* server confirms disconnect */
 368                 cid = pptpReq->disc.callID;
 369                 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 370                 info->cstate = PPTP_CALL_NONE;
 371
 372                 /* untrack this call id, unexpect GRE packets */
 373                 pptp_destroy_siblings(ct);
 374                 break;
 375
 376         case PPTP_WAN_ERROR_NOTIFY:
 377         case PPTP_SET_LINK_INFO:
 378         case PPTP_ECHO_REQUEST:
 379         case PPTP_ECHO_REPLY:
 380                 /* I don't have to explain these ;) */
 381                 break;
 382
 383         default:
 384                 goto invalid;
 385         }
 386
 387         nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound);
 388         if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK)
 389                 return nf_nat_pptp_inbound(skb, ct, ctinfo,
 390                                            protoff, ctlh, pptpReq);
 391         return NF_ACCEPT;
 392
 393 invalid:
 394         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 395                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 396                  pptp_msg_name(msg),
 397                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 398                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 399         return NF_ACCEPT;
 400 }
 401
 402 static inline int
 403 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 404                   struct PptpControlHeader *ctlh,
 405                   union pptp_ctrl_union *pptpReq,
 406                   unsigned int reqlen,
 407                   struct nf_conn *ct,
 408                   enum ip_conntrack_info ctinfo)
 409 {
 410         struct nf_ct_pptp_master *info = nfct_help_data(ct);
 411         u_int16_t msg;
 412         __be16 cid = 0, pcid = 0;
 413         typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
 414
 415         msg = ntohs(ctlh->messageType);
 416         pr_debug("outbound control message %s\n", pptp_msg_name(msg));
 417
 418         switch (msg) {
 419         case PPTP_START_SESSION_REQUEST:
 420                 /* client requests for new control session */
 421                 if (info->sstate != PPTP_SESSION_NONE)
 422                         goto invalid;
 423                 info->sstate = PPTP_SESSION_REQUESTED;
 424                 break;
 425
 426         case PPTP_STOP_SESSION_REQUEST:
 427                 /* client requests end of control session */
 428                 info->sstate = PPTP_SESSION_STOPREQ;
 429                 break;
 430
 431         case PPTP_OUT_CALL_REQUEST:
 432                 /* client initiating connection to server */
 433                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 434                         goto invalid;
 435                 info->cstate = PPTP_CALL_OUT_REQ;
 436                 /* track PNS call id */
 437                 cid = pptpReq->ocreq.callID;
 438                 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid));
 439                 info->pns_call_id = cid;
 440                 break;
 441
 442         case PPTP_IN_CALL_REPLY:
 443                 /* client answers incoming call */
 444                 if (info->cstate != PPTP_CALL_IN_REQ &&
 445                     info->cstate != PPTP_CALL_IN_REP)
 446                         goto invalid;
 447
 448                 cid = pptpReq->icack.callID;
 449                 pcid = pptpReq->icack.peersCallID;
 450                 if (info->pac_call_id != pcid)
 451                         goto invalid;
 452                 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg),
 453                          ntohs(cid), ntohs(pcid));
 454
 455                 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
 456                         /* part two of the three-way handshake */
 457                         info->cstate = PPTP_CALL_IN_REP;
 458                         info->pns_call_id = cid;
 459                 } else
 460                         info->cstate = PPTP_CALL_NONE;
 461                 break;
 462
 463         case PPTP_CALL_CLEAR_REQUEST:
 464                 /* client requests hangup of call */
 465                 if (info->sstate != PPTP_SESSION_CONFIRMED)
 466                         goto invalid;
 467                 /* FUTURE: iterate over all calls and check if
 468                  * call ID is valid.  We don't do this without newnat,
 469                  * because we only know about last call */
 470                 info->cstate = PPTP_CALL_CLEAR_REQ;
 471                 break;
 472
 473         case PPTP_SET_LINK_INFO:
 474         case PPTP_ECHO_REQUEST:
 475         case PPTP_ECHO_REPLY:
 476                 /* I don't have to explain these ;) */
 477                 break;
 478
 479         default:
 480                 goto invalid;
 481         }
 482
 483         nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
 484         if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
 485                 return nf_nat_pptp_outbound(skb, ct, ctinfo,
 486                                             protoff, ctlh, pptpReq);
 487         return NF_ACCEPT;
 488
 489 invalid:
 490         pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 491                  "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 492                  pptp_msg_name(msg),
 493                  msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 494                  ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 495         return NF_ACCEPT;
 496 }
 497
 498 static const unsigned int pptp_msg_size[] = {
 499         [PPTP_START_SESSION_REQUEST]  = sizeof(struct PptpStartSessionRequest),
 500         [PPTP_START_SESSION_REPLY]    = sizeof(struct PptpStartSessionReply),
 501         [PPTP_STOP_SESSION_REQUEST]   = sizeof(struct PptpStopSessionRequest),
 502         [PPTP_STOP_SESSION_REPLY]     = sizeof(struct PptpStopSessionReply),
 503         [PPTP_OUT_CALL_REQUEST]       = sizeof(struct PptpOutCallRequest),
 504         [PPTP_OUT_CALL_REPLY]         = sizeof(struct PptpOutCallReply),
 505         [PPTP_IN_CALL_REQUEST]        = sizeof(struct PptpInCallRequest),
 506         [PPTP_IN_CALL_REPLY]          = sizeof(struct PptpInCallReply),
 507         [PPTP_IN_CALL_CONNECT]        = sizeof(struct PptpInCallConnected),
 508         [PPTP_CALL_CLEAR_REQUEST]     = sizeof(struct PptpClearCallRequest),
 509         [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
 510         [PPTP_WAN_ERROR_NOTIFY]       = sizeof(struct PptpWanErrorNotify),
 511         [PPTP_SET_LINK_INFO]          = sizeof(struct PptpSetLinkInfo),
 512 };
 513
 514 /* track caller id inside control connection, call expect_related */
 515 static int
 516 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 517                     struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 518
 519 {
 520         int dir = CTINFO2DIR(ctinfo);
 521         const struct nf_ct_pptp_master *info = nfct_help_data(ct);
 522         const struct tcphdr *tcph;
 523         struct tcphdr _tcph;
 524         const struct pptp_pkt_hdr *pptph;
 525         struct pptp_pkt_hdr _pptph;
 526         struct PptpControlHeader _ctlh, *ctlh;
 527         union pptp_ctrl_union _pptpReq, *pptpReq;
 528         unsigned int tcplen = skb->len - protoff;
 529         unsigned int datalen, reqlen, nexthdr_off;
 530         int oldsstate, oldcstate;
 531         int ret;
 532         u_int16_t msg;
 533
 534         /* don't do any tracking before tcp handshake complete */
 535         if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
 536                 return NF_ACCEPT;
 537
 538         nexthdr_off = protoff;
 539         tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
 540         BUG_ON(!tcph);
 541         nexthdr_off += tcph->doff * 4;
 542         datalen = tcplen - tcph->doff * 4;
 543
 544         pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
 545         if (!pptph) {
 546                 pr_debug("no full PPTP header, can't track\n");
 547                 return NF_ACCEPT;
 548         }
 549         nexthdr_off += sizeof(_pptph);
 550         datalen -= sizeof(_pptph);
 551
 552         /* if it's not a control message we can't do anything with it */
 553         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 554             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 555                 pr_debug("not a control packet\n");
 556                 return NF_ACCEPT;
 557         }
 558
 559         ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 560         if (!ctlh)
 561                 return NF_ACCEPT;
 562         nexthdr_off += sizeof(_ctlh);
 563         datalen -= sizeof(_ctlh);
 564
 565         reqlen = datalen;
 566         msg = ntohs(ctlh->messageType);
 567         if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
 568                 return NF_ACCEPT;
 569         if (reqlen > sizeof(*pptpReq))
 570                 reqlen = sizeof(*pptpReq);
 571
 572         pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
 573         if (!pptpReq)
 574                 return NF_ACCEPT;
 575
 576         oldsstate = info->sstate;
 577         oldcstate = info->cstate;
 578
 579         spin_lock_bh(&nf_pptp_lock);
 580
 581         /* FIXME: We just blindly assume that the control connection is always
 582          * established from PNS->PAC.  However, RFC makes no guarantee */
 583         if (dir == IP_CT_DIR_ORIGINAL)
 584                 /* client -> server (PNS -> PAC) */
 585                 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 586                                         ctinfo);
 587         else
 588                 /* server -> client (PAC -> PNS) */
 589                 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 590                                        ctinfo);
 591         pr_debug("sstate: %d->%d, cstate: %d->%d\n",
 592                  oldsstate, info->sstate, oldcstate, info->cstate);
 593         spin_unlock_bh(&nf_pptp_lock);
 594
 595         return ret;
 596 }
 597
 598 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
 599         .max_expected   = 2,
 600         .timeout        = 5 * 60,
 601 };
 602
 603 /* control protocol helper */
 604 static struct nf_conntrack_helper pptp __read_mostly = {
 605         .name                   = "pptp",
 606         .me                     = THIS_MODULE,
 607         .data_len               = sizeof(struct nf_ct_pptp_master),
 608         .tuple.src.l3num        = AF_INET,
 609         .tuple.src.u.tcp.port   = cpu_to_be16(PPTP_CONTROL_PORT),
 610         .tuple.dst.protonum     = IPPROTO_TCP,
 611         .help                   = conntrack_pptp_help,
 612         .destroy                = pptp_destroy_siblings,
 613         .expect_policy          = &pptp_exp_policy,
 614 };
 615
 616 static int __init nf_conntrack_pptp_init(void)
 617 {
 618         return nf_conntrack_helper_register(&pptp);
 619 }
 620
 621 static void __exit nf_conntrack_pptp_fini(void)
 622 {
 623         nf_conntrack_helper_unregister(&pptp);
 624 }
 625
 626 module_init(nf_conntrack_pptp_init);
 627 module_exit(nf_conntrack_pptp_fini);