linux/net/netfilter/nf_conntrack_pptp.c
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   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
  37MODULE_LICENSE("GPL");
  38MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  39MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
  40MODULE_ALIAS("ip_conntrack_pptp");
  41MODULE_ALIAS_NFCT_HELPER("pptp");
  42
  43static DEFINE_SPINLOCK(nf_pptp_lock);
  44
  45int
  46(*nf_nat_pptp_hook_outbound)(struct sk_buff *skb,
  47                             struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  48                             unsigned int protoff, struct PptpControlHeader *ctlh,
  49                             union pptp_ctrl_union *pptpReq) __read_mostly;
  50EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound);
  51
  52int
  53(*nf_nat_pptp_hook_inbound)(struct sk_buff *skb,
  54                            struct nf_conn *ct, enum ip_conntrack_info ctinfo,
  55                            unsigned int protoff, struct PptpControlHeader *ctlh,
  56                            union pptp_ctrl_union *pptpReq) __read_mostly;
  57EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound);
  58
  59void
  60(*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig,
  61                            struct nf_conntrack_expect *expect_reply)
  62                            __read_mostly;
  63EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre);
  64
  65void
  66(*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct,
  67                             struct nf_conntrack_expect *exp) __read_mostly;
  68EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn);
  69
  70#if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG)
  71/* PptpControlMessageType names */
  72const 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};
  90EXPORT_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
 100static 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
 140static 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 */
 174static void pptp_destroy_siblings(struct nf_conn *ct)
 175{
 176        struct net *net = nf_ct_net(ct);
 177        const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(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 = ct_pptp_info->pns_call_id;
 186        t.dst.u.gre.key = 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 = ct_pptp_info->pac_call_id;
 194        t.dst.u.gre.key = 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) */
 200static 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
 250out_put_both:
 251        nf_ct_expect_put(exp_reply);
 252out_put_orig:
 253        nf_ct_expect_put(exp_orig);
 254out:
 255        return ret;
 256
 257out_unexpect_both:
 258        nf_ct_unexpect_related(exp_reply);
 259out_unexpect_orig:
 260        nf_ct_unexpect_related(exp_orig);
 261        goto out_put_both;
 262}
 263
 264static inline int
 265pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 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_data(ct);
 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,
 380                                           protoff, ctlh, pptpReq);
 381        return NF_ACCEPT;
 382
 383invalid:
 384        pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 385                 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 386                 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 387                 msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 388                 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 389        return NF_ACCEPT;
 390}
 391
 392static inline int
 393pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 394                  struct PptpControlHeader *ctlh,
 395                  union pptp_ctrl_union *pptpReq,
 396                  unsigned int reqlen,
 397                  struct nf_conn *ct,
 398                  enum ip_conntrack_info ctinfo)
 399{
 400        struct nf_ct_pptp_master *info = nfct_help_data(ct);
 401        u_int16_t msg;
 402        __be16 cid = 0, pcid = 0;
 403        typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
 404
 405        msg = ntohs(ctlh->messageType);
 406        pr_debug("outbound control message %s\n", pptp_msg_name[msg]);
 407
 408        switch (msg) {
 409        case PPTP_START_SESSION_REQUEST:
 410                /* client requests for new control session */
 411                if (info->sstate != PPTP_SESSION_NONE)
 412                        goto invalid;
 413                info->sstate = PPTP_SESSION_REQUESTED;
 414                break;
 415
 416        case PPTP_STOP_SESSION_REQUEST:
 417                /* client requests end of control session */
 418                info->sstate = PPTP_SESSION_STOPREQ;
 419                break;
 420
 421        case PPTP_OUT_CALL_REQUEST:
 422                /* client initiating connection to server */
 423                if (info->sstate != PPTP_SESSION_CONFIRMED)
 424                        goto invalid;
 425                info->cstate = PPTP_CALL_OUT_REQ;
 426                /* track PNS call id */
 427                cid = pptpReq->ocreq.callID;
 428                pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid));
 429                info->pns_call_id = cid;
 430                break;
 431
 432        case PPTP_IN_CALL_REPLY:
 433                /* client answers incoming call */
 434                if (info->cstate != PPTP_CALL_IN_REQ &&
 435                    info->cstate != PPTP_CALL_IN_REP)
 436                        goto invalid;
 437
 438                cid = pptpReq->icack.callID;
 439                pcid = pptpReq->icack.peersCallID;
 440                if (info->pac_call_id != pcid)
 441                        goto invalid;
 442                pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg],
 443                         ntohs(cid), ntohs(pcid));
 444
 445                if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) {
 446                        /* part two of the three-way handshake */
 447                        info->cstate = PPTP_CALL_IN_REP;
 448                        info->pns_call_id = cid;
 449                } else
 450                        info->cstate = PPTP_CALL_NONE;
 451                break;
 452
 453        case PPTP_CALL_CLEAR_REQUEST:
 454                /* client requests hangup of call */
 455                if (info->sstate != PPTP_SESSION_CONFIRMED)
 456                        goto invalid;
 457                /* FUTURE: iterate over all calls and check if
 458                 * call ID is valid.  We don't do this without newnat,
 459                 * because we only know about last call */
 460                info->cstate = PPTP_CALL_CLEAR_REQ;
 461                break;
 462
 463        case PPTP_SET_LINK_INFO:
 464        case PPTP_ECHO_REQUEST:
 465        case PPTP_ECHO_REPLY:
 466                /* I don't have to explain these ;) */
 467                break;
 468
 469        default:
 470                goto invalid;
 471        }
 472
 473        nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound);
 474        if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK)
 475                return nf_nat_pptp_outbound(skb, ct, ctinfo,
 476                                            protoff, ctlh, pptpReq);
 477        return NF_ACCEPT;
 478
 479invalid:
 480        pr_debug("invalid %s: type=%d cid=%u pcid=%u "
 481                 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n",
 482                 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0],
 483                 msg, ntohs(cid), ntohs(pcid),  info->cstate, info->sstate,
 484                 ntohs(info->pns_call_id), ntohs(info->pac_call_id));
 485        return NF_ACCEPT;
 486}
 487
 488static const unsigned int pptp_msg_size[] = {
 489        [PPTP_START_SESSION_REQUEST]  = sizeof(struct PptpStartSessionRequest),
 490        [PPTP_START_SESSION_REPLY]    = sizeof(struct PptpStartSessionReply),
 491        [PPTP_STOP_SESSION_REQUEST]   = sizeof(struct PptpStopSessionRequest),
 492        [PPTP_STOP_SESSION_REPLY]     = sizeof(struct PptpStopSessionReply),
 493        [PPTP_OUT_CALL_REQUEST]       = sizeof(struct PptpOutCallRequest),
 494        [PPTP_OUT_CALL_REPLY]         = sizeof(struct PptpOutCallReply),
 495        [PPTP_IN_CALL_REQUEST]        = sizeof(struct PptpInCallRequest),
 496        [PPTP_IN_CALL_REPLY]          = sizeof(struct PptpInCallReply),
 497        [PPTP_IN_CALL_CONNECT]        = sizeof(struct PptpInCallConnected),
 498        [PPTP_CALL_CLEAR_REQUEST]     = sizeof(struct PptpClearCallRequest),
 499        [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify),
 500        [PPTP_WAN_ERROR_NOTIFY]       = sizeof(struct PptpWanErrorNotify),
 501        [PPTP_SET_LINK_INFO]          = sizeof(struct PptpSetLinkInfo),
 502};
 503
 504/* track caller id inside control connection, call expect_related */
 505static int
 506conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 507                    struct nf_conn *ct, enum ip_conntrack_info ctinfo)
 508
 509{
 510        int dir = CTINFO2DIR(ctinfo);
 511        const struct nf_ct_pptp_master *info = nfct_help_data(ct);
 512        const struct tcphdr *tcph;
 513        struct tcphdr _tcph;
 514        const struct pptp_pkt_hdr *pptph;
 515        struct pptp_pkt_hdr _pptph;
 516        struct PptpControlHeader _ctlh, *ctlh;
 517        union pptp_ctrl_union _pptpReq, *pptpReq;
 518        unsigned int tcplen = skb->len - protoff;
 519        unsigned int datalen, reqlen, nexthdr_off;
 520        int oldsstate, oldcstate;
 521        int ret;
 522        u_int16_t msg;
 523
 524        /* don't do any tracking before tcp handshake complete */
 525        if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
 526                return NF_ACCEPT;
 527
 528        nexthdr_off = protoff;
 529        tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph);
 530        BUG_ON(!tcph);
 531        nexthdr_off += tcph->doff * 4;
 532        datalen = tcplen - tcph->doff * 4;
 533
 534        pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
 535        if (!pptph) {
 536                pr_debug("no full PPTP header, can't track\n");
 537                return NF_ACCEPT;
 538        }
 539        nexthdr_off += sizeof(_pptph);
 540        datalen -= sizeof(_pptph);
 541
 542        /* if it's not a control message we can't do anything with it */
 543        if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 544            ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 545                pr_debug("not a control packet\n");
 546                return NF_ACCEPT;
 547        }
 548
 549        ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 550        if (!ctlh)
 551                return NF_ACCEPT;
 552        nexthdr_off += sizeof(_ctlh);
 553        datalen -= sizeof(_ctlh);
 554
 555        reqlen = datalen;
 556        msg = ntohs(ctlh->messageType);
 557        if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
 558                return NF_ACCEPT;
 559        if (reqlen > sizeof(*pptpReq))
 560                reqlen = sizeof(*pptpReq);
 561
 562        pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
 563        if (!pptpReq)
 564                return NF_ACCEPT;
 565
 566        oldsstate = info->sstate;
 567        oldcstate = info->cstate;
 568
 569        spin_lock_bh(&nf_pptp_lock);
 570
 571        /* FIXME: We just blindly assume that the control connection is always
 572         * established from PNS->PAC.  However, RFC makes no guarantee */
 573        if (dir == IP_CT_DIR_ORIGINAL)
 574                /* client -> server (PNS -> PAC) */
 575                ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 576                                        ctinfo);
 577        else
 578                /* server -> client (PAC -> PNS) */
 579                ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 580                                       ctinfo);
 581        pr_debug("sstate: %d->%d, cstate: %d->%d\n",
 582                 oldsstate, info->sstate, oldcstate, info->cstate);
 583        spin_unlock_bh(&nf_pptp_lock);
 584
 585        return ret;
 586}
 587
 588static const struct nf_conntrack_expect_policy pptp_exp_policy = {
 589        .max_expected   = 2,
 590        .timeout        = 5 * 60,
 591};
 592
 593/* control protocol helper */
 594static struct nf_conntrack_helper pptp __read_mostly = {
 595        .name                   = "pptp",
 596        .me                     = THIS_MODULE,
 597        .data_len               = sizeof(struct nf_ct_pptp_master),
 598        .tuple.src.l3num        = AF_INET,
 599        .tuple.src.u.tcp.port   = cpu_to_be16(PPTP_CONTROL_PORT),
 600        .tuple.dst.protonum     = IPPROTO_TCP,
 601        .help                   = conntrack_pptp_help,
 602        .destroy                = pptp_destroy_siblings,
 603        .expect_policy          = &pptp_exp_policy,
 604};
 605
 606static void nf_conntrack_pptp_net_exit(struct net *net)
 607{
 608        nf_ct_gre_keymap_flush(net);
 609}
 610
 611static struct pernet_operations nf_conntrack_pptp_net_ops = {
 612        .exit = nf_conntrack_pptp_net_exit,
 613};
 614
 615static int __init nf_conntrack_pptp_init(void)
 616{
 617        int rv;
 618
 619        rv = nf_conntrack_helper_register(&pptp);
 620        if (rv < 0)
 621                return rv;
 622        rv = register_pernet_subsys(&nf_conntrack_pptp_net_ops);
 623        if (rv < 0)
 624                nf_conntrack_helper_unregister(&pptp);
 625        return rv;
 626}
 627
 628static void __exit nf_conntrack_pptp_fini(void)
 629{
 630        nf_conntrack_helper_unregister(&pptp);
 631        unregister_pernet_subsys(&nf_conntrack_pptp_net_ops);
 632}
 633
 634module_init(nf_conntrack_pptp_init);
 635module_exit(nf_conntrack_pptp_fini);
 636
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