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