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