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