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 const char *const pptp_msg_name[] = { 75 "UNKNOWN_MESSAGE", 76 "START_SESSION_REQUEST", 77 "START_SESSION_REPLY", 78 "STOP_SESSION_REQUEST", 79 "STOP_SESSION_REPLY", 80 "ECHO_REQUEST", 81 "ECHO_REPLY", 82 "OUT_CALL_REQUEST", 83 "OUT_CALL_REPLY", 84 "IN_CALL_REQUEST", 85 "IN_CALL_REPLY", 86 "IN_CALL_CONNECT", 87 "CALL_CLEAR_REQUEST", 88 "CALL_DISCONNECT_NOTIFY", 89 "WAN_ERROR_NOTIFY", 90 "SET_LINK_INFO" 91 }; 92 EXPORT_SYMBOL(pptp_msg_name); 93 #endif 94 95 #define SECS *HZ 96 #define MINS * 60 SECS 97 #define HOURS * 60 MINS 98 99 #define PPTP_GRE_TIMEOUT (10 MINS) 100 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS) 101 102 static void pptp_expectfn(struct nf_conn *ct, 103 struct nf_conntrack_expect *exp) 104 { 105 struct net *net = nf_ct_net(ct); 106 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn; 107 pr_debug("increasing timeouts\n"); 108 109 /* increase timeout of GRE data channel conntrack entry */ 110 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT; 111 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT; 112 113 /* Can you see how rusty this code is, compared with the pre-2.6.11 114 * one? That's what happened to my shiny newnat of 2002 ;( -HW */ 115 116 rcu_read_lock(); 117 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn); 118 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK) 119 nf_nat_pptp_expectfn(ct, exp); 120 else { 121 struct nf_conntrack_tuple inv_t; 122 struct nf_conntrack_expect *exp_other; 123 124 /* obviously this tuple inversion only works until you do NAT */ 125 nf_ct_invert_tuplepr(&inv_t, &exp->tuple); 126 pr_debug("trying to unexpect other dir: "); 127 nf_ct_dump_tuple(&inv_t); 128 129 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t); 130 if (exp_other) { 131 /* delete other expectation. */ 132 pr_debug("found\n"); 133 nf_ct_unexpect_related(exp_other); 134 nf_ct_expect_put(exp_other); 135 } else { 136 pr_debug("not found\n"); 137 } 138 } 139 rcu_read_unlock(); 140 } 141 142 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct, 143 const struct nf_conntrack_tuple *t) 144 { 145 const struct nf_conntrack_tuple_hash *h; 146 const struct nf_conntrack_zone *zone; 147 struct nf_conntrack_expect *exp; 148 struct nf_conn *sibling; 149 150 pr_debug("trying to timeout ct or exp for tuple "); 151 nf_ct_dump_tuple(t); 152 153 zone = nf_ct_zone(ct); 154 h = nf_conntrack_find_get(net, zone, t); 155 if (h) { 156 sibling = nf_ct_tuplehash_to_ctrack(h); 157 pr_debug("setting timeout of conntrack %p to 0\n", sibling); 158 sibling->proto.gre.timeout = 0; 159 sibling->proto.gre.stream_timeout = 0; 160 if (del_timer(&sibling->timeout)) 161 sibling->timeout.function((unsigned long)sibling); 162 nf_ct_put(sibling); 163 return 1; 164 } else { 165 exp = nf_ct_expect_find_get(net, zone, t); 166 if (exp) { 167 pr_debug("unexpect_related of expect %p\n", exp); 168 nf_ct_unexpect_related(exp); 169 nf_ct_expect_put(exp); 170 return 1; 171 } 172 } 173 return 0; 174 } 175 176 /* timeout GRE data connections */ 177 static void pptp_destroy_siblings(struct nf_conn *ct) 178 { 179 struct net *net = nf_ct_net(ct); 180 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 181 struct nf_conntrack_tuple t; 182 183 nf_ct_gre_keymap_destroy(ct); 184 185 /* try original (pns->pac) tuple */ 186 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t)); 187 t.dst.protonum = IPPROTO_GRE; 188 t.src.u.gre.key = ct_pptp_info->pns_call_id; 189 t.dst.u.gre.key = ct_pptp_info->pac_call_id; 190 if (!destroy_sibling_or_exp(net, ct, &t)) 191 pr_debug("failed to timeout original pns->pac ct/exp\n"); 192 193 /* try reply (pac->pns) tuple */ 194 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t)); 195 t.dst.protonum = IPPROTO_GRE; 196 t.src.u.gre.key = ct_pptp_info->pac_call_id; 197 t.dst.u.gre.key = ct_pptp_info->pns_call_id; 198 if (!destroy_sibling_or_exp(net, ct, &t)) 199 pr_debug("failed to timeout reply pac->pns ct/exp\n"); 200 } 201 202 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */ 203 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid) 204 { 205 struct nf_conntrack_expect *exp_orig, *exp_reply; 206 enum ip_conntrack_dir dir; 207 int ret = 1; 208 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre; 209 210 exp_orig = nf_ct_expect_alloc(ct); 211 if (exp_orig == NULL) 212 goto out; 213 214 exp_reply = nf_ct_expect_alloc(ct); 215 if (exp_reply == NULL) 216 goto out_put_orig; 217 218 /* original direction, PNS->PAC */ 219 dir = IP_CT_DIR_ORIGINAL; 220 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT, 221 nf_ct_l3num(ct), 222 &ct->tuplehash[dir].tuple.src.u3, 223 &ct->tuplehash[dir].tuple.dst.u3, 224 IPPROTO_GRE, &peer_callid, &callid); 225 exp_orig->expectfn = pptp_expectfn; 226 227 /* reply direction, PAC->PNS */ 228 dir = IP_CT_DIR_REPLY; 229 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT, 230 nf_ct_l3num(ct), 231 &ct->tuplehash[dir].tuple.src.u3, 232 &ct->tuplehash[dir].tuple.dst.u3, 233 IPPROTO_GRE, &callid, &peer_callid); 234 exp_reply->expectfn = pptp_expectfn; 235 236 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre); 237 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK) 238 nf_nat_pptp_exp_gre(exp_orig, exp_reply); 239 if (nf_ct_expect_related(exp_orig) != 0) 240 goto out_put_both; 241 if (nf_ct_expect_related(exp_reply) != 0) 242 goto out_unexpect_orig; 243 244 /* Add GRE keymap entries */ 245 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0) 246 goto out_unexpect_both; 247 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) { 248 nf_ct_gre_keymap_destroy(ct); 249 goto out_unexpect_both; 250 } 251 ret = 0; 252 253 out_put_both: 254 nf_ct_expect_put(exp_reply); 255 out_put_orig: 256 nf_ct_expect_put(exp_orig); 257 out: 258 return ret; 259 260 out_unexpect_both: 261 nf_ct_unexpect_related(exp_reply); 262 out_unexpect_orig: 263 nf_ct_unexpect_related(exp_orig); 264 goto out_put_both; 265 } 266 267 static inline int 268 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff, 269 struct PptpControlHeader *ctlh, 270 union pptp_ctrl_union *pptpReq, 271 unsigned int reqlen, 272 struct nf_conn *ct, 273 enum ip_conntrack_info ctinfo) 274 { 275 struct nf_ct_pptp_master *info = nfct_help_data(ct); 276 u_int16_t msg; 277 __be16 cid = 0, pcid = 0; 278 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound; 279 280 msg = ntohs(ctlh->messageType); 281 pr_debug("inbound control message %s\n", pptp_msg_name[msg]); 282 283 switch (msg) { 284 case PPTP_START_SESSION_REPLY: 285 /* server confirms new control session */ 286 if (info->sstate < PPTP_SESSION_REQUESTED) 287 goto invalid; 288 if (pptpReq->srep.resultCode == PPTP_START_OK) 289 info->sstate = PPTP_SESSION_CONFIRMED; 290 else 291 info->sstate = PPTP_SESSION_ERROR; 292 break; 293 294 case PPTP_STOP_SESSION_REPLY: 295 /* server confirms end of control session */ 296 if (info->sstate > PPTP_SESSION_STOPREQ) 297 goto invalid; 298 if (pptpReq->strep.resultCode == PPTP_STOP_OK) 299 info->sstate = PPTP_SESSION_NONE; 300 else 301 info->sstate = PPTP_SESSION_ERROR; 302 break; 303 304 case PPTP_OUT_CALL_REPLY: 305 /* server accepted call, we now expect GRE frames */ 306 if (info->sstate != PPTP_SESSION_CONFIRMED) 307 goto invalid; 308 if (info->cstate != PPTP_CALL_OUT_REQ && 309 info->cstate != PPTP_CALL_OUT_CONF) 310 goto invalid; 311 312 cid = pptpReq->ocack.callID; 313 pcid = pptpReq->ocack.peersCallID; 314 if (info->pns_call_id != pcid) 315 goto invalid; 316 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg], 317 ntohs(cid), ntohs(pcid)); 318 319 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) { 320 info->cstate = PPTP_CALL_OUT_CONF; 321 info->pac_call_id = cid; 322 exp_gre(ct, cid, pcid); 323 } else 324 info->cstate = PPTP_CALL_NONE; 325 break; 326 327 case PPTP_IN_CALL_REQUEST: 328 /* server tells us about incoming call request */ 329 if (info->sstate != PPTP_SESSION_CONFIRMED) 330 goto invalid; 331 332 cid = pptpReq->icreq.callID; 333 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 334 info->cstate = PPTP_CALL_IN_REQ; 335 info->pac_call_id = cid; 336 break; 337 338 case PPTP_IN_CALL_CONNECT: 339 /* server tells us about incoming call established */ 340 if (info->sstate != PPTP_SESSION_CONFIRMED) 341 goto invalid; 342 if (info->cstate != PPTP_CALL_IN_REP && 343 info->cstate != PPTP_CALL_IN_CONF) 344 goto invalid; 345 346 pcid = pptpReq->iccon.peersCallID; 347 cid = info->pac_call_id; 348 349 if (info->pns_call_id != pcid) 350 goto invalid; 351 352 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid)); 353 info->cstate = PPTP_CALL_IN_CONF; 354 355 /* we expect a GRE connection from PAC to PNS */ 356 exp_gre(ct, cid, pcid); 357 break; 358 359 case PPTP_CALL_DISCONNECT_NOTIFY: 360 /* server confirms disconnect */ 361 cid = pptpReq->disc.callID; 362 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 363 info->cstate = PPTP_CALL_NONE; 364 365 /* untrack this call id, unexpect GRE packets */ 366 pptp_destroy_siblings(ct); 367 break; 368 369 case PPTP_WAN_ERROR_NOTIFY: 370 case PPTP_SET_LINK_INFO: 371 case PPTP_ECHO_REQUEST: 372 case PPTP_ECHO_REPLY: 373 /* I don't have to explain these ;) */ 374 break; 375 376 default: 377 goto invalid; 378 } 379 380 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound); 381 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK) 382 return nf_nat_pptp_inbound(skb, ct, ctinfo, 383 protoff, ctlh, pptpReq); 384 return NF_ACCEPT; 385 386 invalid: 387 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 388 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 389 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 390 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 391 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 392 return NF_ACCEPT; 393 } 394 395 static inline int 396 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff, 397 struct PptpControlHeader *ctlh, 398 union pptp_ctrl_union *pptpReq, 399 unsigned int reqlen, 400 struct nf_conn *ct, 401 enum ip_conntrack_info ctinfo) 402 { 403 struct nf_ct_pptp_master *info = nfct_help_data(ct); 404 u_int16_t msg; 405 __be16 cid = 0, pcid = 0; 406 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound; 407 408 msg = ntohs(ctlh->messageType); 409 pr_debug("outbound control message %s\n", pptp_msg_name[msg]); 410 411 switch (msg) { 412 case PPTP_START_SESSION_REQUEST: 413 /* client requests for new control session */ 414 if (info->sstate != PPTP_SESSION_NONE) 415 goto invalid; 416 info->sstate = PPTP_SESSION_REQUESTED; 417 break; 418 419 case PPTP_STOP_SESSION_REQUEST: 420 /* client requests end of control session */ 421 info->sstate = PPTP_SESSION_STOPREQ; 422 break; 423 424 case PPTP_OUT_CALL_REQUEST: 425 /* client initiating connection to server */ 426 if (info->sstate != PPTP_SESSION_CONFIRMED) 427 goto invalid; 428 info->cstate = PPTP_CALL_OUT_REQ; 429 /* track PNS call id */ 430 cid = pptpReq->ocreq.callID; 431 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 432 info->pns_call_id = cid; 433 break; 434 435 case PPTP_IN_CALL_REPLY: 436 /* client answers incoming call */ 437 if (info->cstate != PPTP_CALL_IN_REQ && 438 info->cstate != PPTP_CALL_IN_REP) 439 goto invalid; 440 441 cid = pptpReq->icack.callID; 442 pcid = pptpReq->icack.peersCallID; 443 if (info->pac_call_id != pcid) 444 goto invalid; 445 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg], 446 ntohs(cid), ntohs(pcid)); 447 448 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) { 449 /* part two of the three-way handshake */ 450 info->cstate = PPTP_CALL_IN_REP; 451 info->pns_call_id = cid; 452 } else 453 info->cstate = PPTP_CALL_NONE; 454 break; 455 456 case PPTP_CALL_CLEAR_REQUEST: 457 /* client requests hangup of call */ 458 if (info->sstate != PPTP_SESSION_CONFIRMED) 459 goto invalid; 460 /* FUTURE: iterate over all calls and check if 461 * call ID is valid. We don't do this without newnat, 462 * because we only know about last call */ 463 info->cstate = PPTP_CALL_CLEAR_REQ; 464 break; 465 466 case PPTP_SET_LINK_INFO: 467 case PPTP_ECHO_REQUEST: 468 case PPTP_ECHO_REPLY: 469 /* I don't have to explain these ;) */ 470 break; 471 472 default: 473 goto invalid; 474 } 475 476 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound); 477 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK) 478 return nf_nat_pptp_outbound(skb, ct, ctinfo, 479 protoff, ctlh, pptpReq); 480 return NF_ACCEPT; 481 482 invalid: 483 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 484 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 485 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 486 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 487 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 488 return NF_ACCEPT; 489 } 490 491 static const unsigned int pptp_msg_size[] = { 492 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest), 493 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply), 494 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest), 495 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply), 496 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest), 497 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply), 498 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest), 499 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply), 500 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected), 501 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest), 502 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify), 503 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify), 504 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo), 505 }; 506 507 /* track caller id inside control connection, call expect_related */ 508 static int 509 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff, 510 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 511 512 { 513 int dir = CTINFO2DIR(ctinfo); 514 const struct nf_ct_pptp_master *info = nfct_help_data(ct); 515 const struct tcphdr *tcph; 516 struct tcphdr _tcph; 517 const struct pptp_pkt_hdr *pptph; 518 struct pptp_pkt_hdr _pptph; 519 struct PptpControlHeader _ctlh, *ctlh; 520 union pptp_ctrl_union _pptpReq, *pptpReq; 521 unsigned int tcplen = skb->len - protoff; 522 unsigned int datalen, reqlen, nexthdr_off; 523 int oldsstate, oldcstate; 524 int ret; 525 u_int16_t msg; 526 527 /* don't do any tracking before tcp handshake complete */ 528 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 529 return NF_ACCEPT; 530 531 nexthdr_off = protoff; 532 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph); 533 BUG_ON(!tcph); 534 nexthdr_off += tcph->doff * 4; 535 datalen = tcplen - tcph->doff * 4; 536 537 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph); 538 if (!pptph) { 539 pr_debug("no full PPTP header, can't track\n"); 540 return NF_ACCEPT; 541 } 542 nexthdr_off += sizeof(_pptph); 543 datalen -= sizeof(_pptph); 544 545 /* if it's not a control message we can't do anything with it */ 546 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL || 547 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) { 548 pr_debug("not a control packet\n"); 549 return NF_ACCEPT; 550 } 551 552 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh); 553 if (!ctlh) 554 return NF_ACCEPT; 555 nexthdr_off += sizeof(_ctlh); 556 datalen -= sizeof(_ctlh); 557 558 reqlen = datalen; 559 msg = ntohs(ctlh->messageType); 560 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg]) 561 return NF_ACCEPT; 562 if (reqlen > sizeof(*pptpReq)) 563 reqlen = sizeof(*pptpReq); 564 565 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq); 566 if (!pptpReq) 567 return NF_ACCEPT; 568 569 oldsstate = info->sstate; 570 oldcstate = info->cstate; 571 572 spin_lock_bh(&nf_pptp_lock); 573 574 /* FIXME: We just blindly assume that the control connection is always 575 * established from PNS->PAC. However, RFC makes no guarantee */ 576 if (dir == IP_CT_DIR_ORIGINAL) 577 /* client -> server (PNS -> PAC) */ 578 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 579 ctinfo); 580 else 581 /* server -> client (PAC -> PNS) */ 582 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 583 ctinfo); 584 pr_debug("sstate: %d->%d, cstate: %d->%d\n", 585 oldsstate, info->sstate, oldcstate, info->cstate); 586 spin_unlock_bh(&nf_pptp_lock); 587 588 return ret; 589 } 590 591 static const struct nf_conntrack_expect_policy pptp_exp_policy = { 592 .max_expected = 2, 593 .timeout = 5 * 60, 594 }; 595 596 /* control protocol helper */ 597 static struct nf_conntrack_helper pptp __read_mostly = { 598 .name = "pptp", 599 .me = THIS_MODULE, 600 .data_len = sizeof(struct nf_ct_pptp_master), 601 .tuple.src.l3num = AF_INET, 602 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT), 603 .tuple.dst.protonum = IPPROTO_TCP, 604 .help = conntrack_pptp_help, 605 .destroy = pptp_destroy_siblings, 606 .expect_policy = &pptp_exp_policy, 607 }; 608 609 static int __init nf_conntrack_pptp_init(void) 610 { 611 return nf_conntrack_helper_register(&pptp); 612 } 613 614 static void __exit nf_conntrack_pptp_fini(void) 615 { 616 nf_conntrack_helper_unregister(&pptp); 617 } 618 619 module_init(nf_conntrack_pptp_init); 620 module_exit(nf_conntrack_pptp_fini); 621