1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Connection tracking support for PPTP (Point to Point Tunneling Protocol). 4 * PPTP is a protocol for creating virtual private networks. 5 * It is a specification defined by Microsoft and some vendors 6 * working with Microsoft. PPTP is built on top of a modified 7 * version of the Internet Generic Routing Encapsulation Protocol. 8 * GRE is defined in RFC 1701 and RFC 1702. Documentation of 9 * PPTP can be found in RFC 2637 10 * 11 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org> 12 * 13 * Development of this code funded by Astaro AG (http://www.astaro.com/) 14 * 15 * (C) 2006-2012 Patrick McHardy <kaber@trash.net> 16 * 17 * Limitations: 18 * - We blindly assume that control connections are always 19 * established in PNS->PAC direction. This is a violation 20 * of RFC 2637 21 * - We can only support one single call within each session 22 * TODO: 23 * - testing of incoming PPTP calls 24 */ 25 26 #include <linux/module.h> 27 #include <linux/skbuff.h> 28 #include <linux/in.h> 29 #include <linux/tcp.h> 30 31 #include <net/netfilter/nf_conntrack.h> 32 #include <net/netfilter/nf_conntrack_core.h> 33 #include <net/netfilter/nf_conntrack_helper.h> 34 #include <net/netfilter/nf_conntrack_zones.h> 35 #include <linux/netfilter/nf_conntrack_proto_gre.h> 36 #include <linux/netfilter/nf_conntrack_pptp.h> 37 38 #define NF_CT_PPTP_VERSION "3.1" 39 40 MODULE_LICENSE("GPL"); 41 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); 42 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP"); 43 MODULE_ALIAS("ip_conntrack_pptp"); 44 MODULE_ALIAS_NFCT_HELPER("pptp"); 45 46 static DEFINE_SPINLOCK(nf_pptp_lock); 47 48 const struct nf_nat_pptp_hook *nf_nat_pptp_hook; 49 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook); 50 51 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG) 52 /* PptpControlMessageType names */ 53 static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = { 54 [0] = "UNKNOWN_MESSAGE", 55 [PPTP_START_SESSION_REQUEST] = "START_SESSION_REQUEST", 56 [PPTP_START_SESSION_REPLY] = "START_SESSION_REPLY", 57 [PPTP_STOP_SESSION_REQUEST] = "STOP_SESSION_REQUEST", 58 [PPTP_STOP_SESSION_REPLY] = "STOP_SESSION_REPLY", 59 [PPTP_ECHO_REQUEST] = "ECHO_REQUEST", 60 [PPTP_ECHO_REPLY] = "ECHO_REPLY", 61 [PPTP_OUT_CALL_REQUEST] = "OUT_CALL_REQUEST", 62 [PPTP_OUT_CALL_REPLY] = "OUT_CALL_REPLY", 63 [PPTP_IN_CALL_REQUEST] = "IN_CALL_REQUEST", 64 [PPTP_IN_CALL_REPLY] = "IN_CALL_REPLY", 65 [PPTP_IN_CALL_CONNECT] = "IN_CALL_CONNECT", 66 [PPTP_CALL_CLEAR_REQUEST] = "CALL_CLEAR_REQUEST", 67 [PPTP_CALL_DISCONNECT_NOTIFY] = "CALL_DISCONNECT_NOTIFY", 68 [PPTP_WAN_ERROR_NOTIFY] = "WAN_ERROR_NOTIFY", 69 [PPTP_SET_LINK_INFO] = "SET_LINK_INFO" 70 }; 71 72 const char *pptp_msg_name(u_int16_t msg) 73 { 74 if (msg > PPTP_MSG_MAX) 75 return pptp_msg_name_array[0]; 76 77 return pptp_msg_name_array[msg]; 78 } 79 EXPORT_SYMBOL(pptp_msg_name); 80 #endif 81 82 #define SECS *HZ 83 #define MINS * 60 SECS 84 #define HOURS * 60 MINS 85 86 #define PPTP_GRE_TIMEOUT (10 MINS) 87 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS) 88 89 static void pptp_expectfn(struct nf_conn *ct, 90 struct nf_conntrack_expect *exp) 91 { 92 const struct nf_nat_pptp_hook *hook; 93 struct net *net = nf_ct_net(ct); 94 pr_debug("increasing timeouts\n"); 95 96 /* increase timeout of GRE data channel conntrack entry */ 97 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT; 98 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT; 99 100 /* Can you see how rusty this code is, compared with the pre-2.6.11 101 * one? That's what happened to my shiny newnat of 2002 ;( -HW */ 102 103 hook = rcu_dereference(nf_nat_pptp_hook); 104 if (hook && ct->master->status & IPS_NAT_MASK) 105 hook->expectfn(ct, exp); 106 else { 107 struct nf_conntrack_tuple inv_t; 108 struct nf_conntrack_expect *exp_other; 109 110 /* obviously this tuple inversion only works until you do NAT */ 111 nf_ct_invert_tuple(&inv_t, &exp->tuple); 112 pr_debug("trying to unexpect other dir: "); 113 nf_ct_dump_tuple(&inv_t); 114 115 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t); 116 if (exp_other) { 117 /* delete other expectation. */ 118 pr_debug("found\n"); 119 nf_ct_unexpect_related(exp_other); 120 nf_ct_expect_put(exp_other); 121 } else { 122 pr_debug("not found\n"); 123 } 124 } 125 } 126 127 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct, 128 const struct nf_conntrack_tuple *t) 129 { 130 const struct nf_conntrack_tuple_hash *h; 131 const struct nf_conntrack_zone *zone; 132 struct nf_conntrack_expect *exp; 133 struct nf_conn *sibling; 134 135 pr_debug("trying to timeout ct or exp for tuple "); 136 nf_ct_dump_tuple(t); 137 138 zone = nf_ct_zone(ct); 139 h = nf_conntrack_find_get(net, zone, t); 140 if (h) { 141 sibling = nf_ct_tuplehash_to_ctrack(h); 142 pr_debug("setting timeout of conntrack %p to 0\n", sibling); 143 sibling->proto.gre.timeout = 0; 144 sibling->proto.gre.stream_timeout = 0; 145 nf_ct_kill(sibling); 146 nf_ct_put(sibling); 147 return 1; 148 } else { 149 exp = nf_ct_expect_find_get(net, zone, t); 150 if (exp) { 151 pr_debug("unexpect_related of expect %p\n", exp); 152 nf_ct_unexpect_related(exp); 153 nf_ct_expect_put(exp); 154 return 1; 155 } 156 } 157 return 0; 158 } 159 160 /* timeout GRE data connections */ 161 static void pptp_destroy_siblings(struct nf_conn *ct) 162 { 163 struct net *net = nf_ct_net(ct); 164 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 165 struct nf_conntrack_tuple t; 166 167 nf_ct_gre_keymap_destroy(ct); 168 169 /* try original (pns->pac) tuple */ 170 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t)); 171 t.dst.protonum = IPPROTO_GRE; 172 t.src.u.gre.key = ct_pptp_info->pns_call_id; 173 t.dst.u.gre.key = ct_pptp_info->pac_call_id; 174 if (!destroy_sibling_or_exp(net, ct, &t)) 175 pr_debug("failed to timeout original pns->pac ct/exp\n"); 176 177 /* try reply (pac->pns) tuple */ 178 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t)); 179 t.dst.protonum = IPPROTO_GRE; 180 t.src.u.gre.key = ct_pptp_info->pac_call_id; 181 t.dst.u.gre.key = ct_pptp_info->pns_call_id; 182 if (!destroy_sibling_or_exp(net, ct, &t)) 183 pr_debug("failed to timeout reply pac->pns ct/exp\n"); 184 } 185 186 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */ 187 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid) 188 { 189 struct nf_conntrack_expect *exp_orig, *exp_reply; 190 const struct nf_nat_pptp_hook *hook; 191 enum ip_conntrack_dir dir; 192 int ret = 1; 193 194 exp_orig = nf_ct_expect_alloc(ct); 195 if (exp_orig == NULL) 196 goto out; 197 198 exp_reply = nf_ct_expect_alloc(ct); 199 if (exp_reply == NULL) 200 goto out_put_orig; 201 202 /* original direction, PNS->PAC */ 203 dir = IP_CT_DIR_ORIGINAL; 204 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT, 205 nf_ct_l3num(ct), 206 &ct->tuplehash[dir].tuple.src.u3, 207 &ct->tuplehash[dir].tuple.dst.u3, 208 IPPROTO_GRE, &peer_callid, &callid); 209 exp_orig->expectfn = pptp_expectfn; 210 211 /* reply direction, PAC->PNS */ 212 dir = IP_CT_DIR_REPLY; 213 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT, 214 nf_ct_l3num(ct), 215 &ct->tuplehash[dir].tuple.src.u3, 216 &ct->tuplehash[dir].tuple.dst.u3, 217 IPPROTO_GRE, &callid, &peer_callid); 218 exp_reply->expectfn = pptp_expectfn; 219 220 hook = rcu_dereference(nf_nat_pptp_hook); 221 if (hook && ct->status & IPS_NAT_MASK) 222 hook->exp_gre(exp_orig, exp_reply); 223 if (nf_ct_expect_related(exp_orig, 0) != 0) 224 goto out_put_both; 225 if (nf_ct_expect_related(exp_reply, 0) != 0) 226 goto out_unexpect_orig; 227 228 /* Add GRE keymap entries */ 229 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0) 230 goto out_unexpect_both; 231 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) { 232 nf_ct_gre_keymap_destroy(ct); 233 goto out_unexpect_both; 234 } 235 ret = 0; 236 237 out_put_both: 238 nf_ct_expect_put(exp_reply); 239 out_put_orig: 240 nf_ct_expect_put(exp_orig); 241 out: 242 return ret; 243 244 out_unexpect_both: 245 nf_ct_unexpect_related(exp_reply); 246 out_unexpect_orig: 247 nf_ct_unexpect_related(exp_orig); 248 goto out_put_both; 249 } 250 251 static int 252 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff, 253 struct PptpControlHeader *ctlh, 254 union pptp_ctrl_union *pptpReq, 255 unsigned int reqlen, 256 struct nf_conn *ct, 257 enum ip_conntrack_info ctinfo) 258 { 259 struct nf_ct_pptp_master *info = nfct_help_data(ct); 260 const struct nf_nat_pptp_hook *hook; 261 u_int16_t msg; 262 __be16 cid = 0, pcid = 0; 263 264 msg = ntohs(ctlh->messageType); 265 pr_debug("inbound control message %s\n", pptp_msg_name(msg)); 266 267 switch (msg) { 268 case PPTP_START_SESSION_REPLY: 269 /* server confirms new control session */ 270 if (info->sstate < PPTP_SESSION_REQUESTED) 271 goto invalid; 272 if (pptpReq->srep.resultCode == PPTP_START_OK) 273 info->sstate = PPTP_SESSION_CONFIRMED; 274 else 275 info->sstate = PPTP_SESSION_ERROR; 276 break; 277 278 case PPTP_STOP_SESSION_REPLY: 279 /* server confirms end of control session */ 280 if (info->sstate > PPTP_SESSION_STOPREQ) 281 goto invalid; 282 if (pptpReq->strep.resultCode == PPTP_STOP_OK) 283 info->sstate = PPTP_SESSION_NONE; 284 else 285 info->sstate = PPTP_SESSION_ERROR; 286 break; 287 288 case PPTP_OUT_CALL_REPLY: 289 /* server accepted call, we now expect GRE frames */ 290 if (info->sstate != PPTP_SESSION_CONFIRMED) 291 goto invalid; 292 if (info->cstate != PPTP_CALL_OUT_REQ && 293 info->cstate != PPTP_CALL_OUT_CONF) 294 goto invalid; 295 296 cid = pptpReq->ocack.callID; 297 pcid = pptpReq->ocack.peersCallID; 298 if (info->pns_call_id != pcid) 299 goto invalid; 300 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg), 301 ntohs(cid), ntohs(pcid)); 302 303 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) { 304 info->cstate = PPTP_CALL_OUT_CONF; 305 info->pac_call_id = cid; 306 exp_gre(ct, cid, pcid); 307 } else 308 info->cstate = PPTP_CALL_NONE; 309 break; 310 311 case PPTP_IN_CALL_REQUEST: 312 /* server tells us about incoming call request */ 313 if (info->sstate != PPTP_SESSION_CONFIRMED) 314 goto invalid; 315 316 cid = pptpReq->icreq.callID; 317 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid)); 318 info->cstate = PPTP_CALL_IN_REQ; 319 info->pac_call_id = cid; 320 break; 321 322 case PPTP_IN_CALL_CONNECT: 323 /* server tells us about incoming call established */ 324 if (info->sstate != PPTP_SESSION_CONFIRMED) 325 goto invalid; 326 if (info->cstate != PPTP_CALL_IN_REP && 327 info->cstate != PPTP_CALL_IN_CONF) 328 goto invalid; 329 330 pcid = pptpReq->iccon.peersCallID; 331 cid = info->pac_call_id; 332 333 if (info->pns_call_id != pcid) 334 goto invalid; 335 336 pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid)); 337 info->cstate = PPTP_CALL_IN_CONF; 338 339 /* we expect a GRE connection from PAC to PNS */ 340 exp_gre(ct, cid, pcid); 341 break; 342 343 case PPTP_CALL_DISCONNECT_NOTIFY: 344 /* server confirms disconnect */ 345 cid = pptpReq->disc.callID; 346 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid)); 347 info->cstate = PPTP_CALL_NONE; 348 349 /* untrack this call id, unexpect GRE packets */ 350 pptp_destroy_siblings(ct); 351 break; 352 353 case PPTP_WAN_ERROR_NOTIFY: 354 case PPTP_SET_LINK_INFO: 355 case PPTP_ECHO_REQUEST: 356 case PPTP_ECHO_REPLY: 357 /* I don't have to explain these ;) */ 358 break; 359 360 default: 361 goto invalid; 362 } 363 364 hook = rcu_dereference(nf_nat_pptp_hook); 365 if (hook && ct->status & IPS_NAT_MASK) 366 return hook->inbound(skb, ct, ctinfo, protoff, ctlh, pptpReq); 367 return NF_ACCEPT; 368 369 invalid: 370 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 371 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 372 pptp_msg_name(msg), 373 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 374 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 375 return NF_ACCEPT; 376 } 377 378 static int 379 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff, 380 struct PptpControlHeader *ctlh, 381 union pptp_ctrl_union *pptpReq, 382 unsigned int reqlen, 383 struct nf_conn *ct, 384 enum ip_conntrack_info ctinfo) 385 { 386 struct nf_ct_pptp_master *info = nfct_help_data(ct); 387 const struct nf_nat_pptp_hook *hook; 388 u_int16_t msg; 389 __be16 cid = 0, pcid = 0; 390 391 msg = ntohs(ctlh->messageType); 392 pr_debug("outbound control message %s\n", pptp_msg_name(msg)); 393 394 switch (msg) { 395 case PPTP_START_SESSION_REQUEST: 396 /* client requests for new control session */ 397 if (info->sstate != PPTP_SESSION_NONE) 398 goto invalid; 399 info->sstate = PPTP_SESSION_REQUESTED; 400 break; 401 402 case PPTP_STOP_SESSION_REQUEST: 403 /* client requests end of control session */ 404 info->sstate = PPTP_SESSION_STOPREQ; 405 break; 406 407 case PPTP_OUT_CALL_REQUEST: 408 /* client initiating connection to server */ 409 if (info->sstate != PPTP_SESSION_CONFIRMED) 410 goto invalid; 411 info->cstate = PPTP_CALL_OUT_REQ; 412 /* track PNS call id */ 413 cid = pptpReq->ocreq.callID; 414 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid)); 415 info->pns_call_id = cid; 416 break; 417 418 case PPTP_IN_CALL_REPLY: 419 /* client answers incoming call */ 420 if (info->cstate != PPTP_CALL_IN_REQ && 421 info->cstate != PPTP_CALL_IN_REP) 422 goto invalid; 423 424 cid = pptpReq->icack.callID; 425 pcid = pptpReq->icack.peersCallID; 426 if (info->pac_call_id != pcid) 427 goto invalid; 428 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg), 429 ntohs(cid), ntohs(pcid)); 430 431 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) { 432 /* part two of the three-way handshake */ 433 info->cstate = PPTP_CALL_IN_REP; 434 info->pns_call_id = cid; 435 } else 436 info->cstate = PPTP_CALL_NONE; 437 break; 438 439 case PPTP_CALL_CLEAR_REQUEST: 440 /* client requests hangup of call */ 441 if (info->sstate != PPTP_SESSION_CONFIRMED) 442 goto invalid; 443 /* FUTURE: iterate over all calls and check if 444 * call ID is valid. We don't do this without newnat, 445 * because we only know about last call */ 446 info->cstate = PPTP_CALL_CLEAR_REQ; 447 break; 448 449 case PPTP_SET_LINK_INFO: 450 case PPTP_ECHO_REQUEST: 451 case PPTP_ECHO_REPLY: 452 /* I don't have to explain these ;) */ 453 break; 454 455 default: 456 goto invalid; 457 } 458 459 hook = rcu_dereference(nf_nat_pptp_hook); 460 if (hook && ct->status & IPS_NAT_MASK) 461 return hook->outbound(skb, ct, ctinfo, protoff, ctlh, pptpReq); 462 return NF_ACCEPT; 463 464 invalid: 465 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 466 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 467 pptp_msg_name(msg), 468 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 469 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 470 return NF_ACCEPT; 471 } 472 473 static const unsigned int pptp_msg_size[] = { 474 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest), 475 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply), 476 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest), 477 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply), 478 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest), 479 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply), 480 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest), 481 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply), 482 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected), 483 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest), 484 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify), 485 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify), 486 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo), 487 }; 488 489 /* track caller id inside control connection, call expect_related */ 490 static int 491 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff, 492 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 493 494 { 495 int dir = CTINFO2DIR(ctinfo); 496 const struct nf_ct_pptp_master *info = nfct_help_data(ct); 497 const struct tcphdr *tcph; 498 struct tcphdr _tcph; 499 const struct pptp_pkt_hdr *pptph; 500 struct pptp_pkt_hdr _pptph; 501 struct PptpControlHeader _ctlh, *ctlh; 502 union pptp_ctrl_union _pptpReq, *pptpReq; 503 unsigned int tcplen = skb->len - protoff; 504 unsigned int datalen, reqlen, nexthdr_off; 505 int oldsstate, oldcstate; 506 int ret; 507 u_int16_t msg; 508 509 #if IS_ENABLED(CONFIG_NF_NAT) 510 if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) { 511 struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT); 512 513 if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC)) 514 return NF_DROP; 515 } 516 #endif 517 /* don't do any tracking before tcp handshake complete */ 518 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 519 return NF_ACCEPT; 520 521 nexthdr_off = protoff; 522 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph); 523 if (!tcph) 524 return NF_ACCEPT; 525 526 nexthdr_off += tcph->doff * 4; 527 datalen = tcplen - tcph->doff * 4; 528 529 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph); 530 if (!pptph) { 531 pr_debug("no full PPTP header, can't track\n"); 532 return NF_ACCEPT; 533 } 534 nexthdr_off += sizeof(_pptph); 535 datalen -= sizeof(_pptph); 536 537 /* if it's not a control message we can't do anything with it */ 538 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL || 539 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) { 540 pr_debug("not a control packet\n"); 541 return NF_ACCEPT; 542 } 543 544 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh); 545 if (!ctlh) 546 return NF_ACCEPT; 547 nexthdr_off += sizeof(_ctlh); 548 datalen -= sizeof(_ctlh); 549 550 reqlen = datalen; 551 msg = ntohs(ctlh->messageType); 552 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg]) 553 return NF_ACCEPT; 554 if (reqlen > sizeof(*pptpReq)) 555 reqlen = sizeof(*pptpReq); 556 557 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq); 558 if (!pptpReq) 559 return NF_ACCEPT; 560 561 oldsstate = info->sstate; 562 oldcstate = info->cstate; 563 564 spin_lock_bh(&nf_pptp_lock); 565 566 /* FIXME: We just blindly assume that the control connection is always 567 * established from PNS->PAC. However, RFC makes no guarantee */ 568 if (dir == IP_CT_DIR_ORIGINAL) 569 /* client -> server (PNS -> PAC) */ 570 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 571 ctinfo); 572 else 573 /* server -> client (PAC -> PNS) */ 574 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 575 ctinfo); 576 pr_debug("sstate: %d->%d, cstate: %d->%d\n", 577 oldsstate, info->sstate, oldcstate, info->cstate); 578 spin_unlock_bh(&nf_pptp_lock); 579 580 return ret; 581 } 582 583 static const struct nf_conntrack_expect_policy pptp_exp_policy = { 584 .max_expected = 2, 585 .timeout = 5 * 60, 586 }; 587 588 /* control protocol helper */ 589 static struct nf_conntrack_helper pptp __read_mostly = { 590 .name = "pptp", 591 .me = THIS_MODULE, 592 .tuple.src.l3num = AF_INET, 593 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT), 594 .tuple.dst.protonum = IPPROTO_TCP, 595 .help = conntrack_pptp_help, 596 .destroy = pptp_destroy_siblings, 597 .expect_policy = &pptp_exp_policy, 598 }; 599 600 static int __init nf_conntrack_pptp_init(void) 601 { 602 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master)); 603 604 return nf_conntrack_helper_register(&pptp); 605 } 606 607 static void __exit nf_conntrack_pptp_fini(void) 608 { 609 nf_conntrack_helper_unregister(&pptp); 610 } 611 612 module_init(nf_conntrack_pptp_init); 613 module_exit(nf_conntrack_pptp_fini); 614