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