1 /* 2 * L2TPv3 IP encapsulation support 3 * 4 * Copyright (c) 2008,2009,2010 Katalix Systems Ltd 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 13 14 #include <linux/icmp.h> 15 #include <linux/module.h> 16 #include <linux/skbuff.h> 17 #include <linux/random.h> 18 #include <linux/socket.h> 19 #include <linux/l2tp.h> 20 #include <linux/in.h> 21 #include <net/sock.h> 22 #include <net/ip.h> 23 #include <net/icmp.h> 24 #include <net/udp.h> 25 #include <net/inet_common.h> 26 #include <net/inet_hashtables.h> 27 #include <net/tcp_states.h> 28 #include <net/protocol.h> 29 #include <net/xfrm.h> 30 31 #include "l2tp_core.h" 32 33 struct l2tp_ip_sock { 34 /* inet_sock has to be the first member of l2tp_ip_sock */ 35 struct inet_sock inet; 36 37 u32 conn_id; 38 u32 peer_conn_id; 39 }; 40 41 static DEFINE_RWLOCK(l2tp_ip_lock); 42 static struct hlist_head l2tp_ip_table; 43 static struct hlist_head l2tp_ip_bind_table; 44 45 static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk) 46 { 47 return (struct l2tp_ip_sock *)sk; 48 } 49 50 static struct sock *__l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id) 51 { 52 struct sock *sk; 53 54 sk_for_each_bound(sk, &l2tp_ip_bind_table) { 55 struct inet_sock *inet = inet_sk(sk); 56 struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk); 57 58 if (l2tp == NULL) 59 continue; 60 61 if ((l2tp->conn_id == tunnel_id) && 62 net_eq(sock_net(sk), net) && 63 !(inet->inet_rcv_saddr && inet->inet_rcv_saddr != laddr) && 64 (!sk->sk_bound_dev_if || !dif || 65 sk->sk_bound_dev_if == dif)) 66 goto found; 67 } 68 69 sk = NULL; 70 found: 71 return sk; 72 } 73 74 static inline struct sock *l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id) 75 { 76 struct sock *sk = __l2tp_ip_bind_lookup(net, laddr, dif, tunnel_id); 77 if (sk) 78 sock_hold(sk); 79 80 return sk; 81 } 82 83 /* When processing receive frames, there are two cases to 84 * consider. Data frames consist of a non-zero session-id and an 85 * optional cookie. Control frames consist of a regular L2TP header 86 * preceded by 32-bits of zeros. 87 * 88 * L2TPv3 Session Header Over IP 89 * 90 * 0 1 2 3 91 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 92 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 93 * | Session ID | 94 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 95 * | Cookie (optional, maximum 64 bits)... 96 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 97 * | 98 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 99 * 100 * L2TPv3 Control Message Header Over IP 101 * 102 * 0 1 2 3 103 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 104 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 105 * | (32 bits of zeros) | 106 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 107 * |T|L|x|x|S|x|x|x|x|x|x|x| Ver | Length | 108 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 109 * | Control Connection ID | 110 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 111 * | Ns | Nr | 112 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 113 * 114 * All control frames are passed to userspace. 115 */ 116 static int l2tp_ip_recv(struct sk_buff *skb) 117 { 118 struct net *net = dev_net(skb->dev); 119 struct sock *sk; 120 u32 session_id; 121 u32 tunnel_id; 122 unsigned char *ptr, *optr; 123 struct l2tp_session *session; 124 struct l2tp_tunnel *tunnel = NULL; 125 int length; 126 127 if (!pskb_may_pull(skb, 4)) 128 goto discard; 129 130 /* Point to L2TP header */ 131 optr = ptr = skb->data; 132 session_id = ntohl(*((__be32 *) ptr)); 133 ptr += 4; 134 135 /* RFC3931: L2TP/IP packets have the first 4 bytes containing 136 * the session_id. If it is 0, the packet is a L2TP control 137 * frame and the session_id value can be discarded. 138 */ 139 if (session_id == 0) { 140 __skb_pull(skb, 4); 141 goto pass_up; 142 } 143 144 /* Ok, this is a data packet. Lookup the session. */ 145 session = l2tp_session_find(net, NULL, session_id); 146 if (session == NULL) 147 goto discard; 148 149 tunnel = session->tunnel; 150 if (tunnel == NULL) 151 goto discard; 152 153 /* Trace packet contents, if enabled */ 154 if (tunnel->debug & L2TP_MSG_DATA) { 155 length = min(32u, skb->len); 156 if (!pskb_may_pull(skb, length)) 157 goto discard; 158 159 /* Point to L2TP header */ 160 optr = ptr = skb->data; 161 ptr += 4; 162 pr_debug("%s: ip recv\n", tunnel->name); 163 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length); 164 } 165 166 l2tp_recv_common(session, skb, ptr, optr, 0, skb->len, tunnel->recv_payload_hook); 167 168 return 0; 169 170 pass_up: 171 /* Get the tunnel_id from the L2TP header */ 172 if (!pskb_may_pull(skb, 12)) 173 goto discard; 174 175 if ((skb->data[0] & 0xc0) != 0xc0) 176 goto discard; 177 178 tunnel_id = ntohl(*(__be32 *) &skb->data[4]); 179 tunnel = l2tp_tunnel_find(net, tunnel_id); 180 if (tunnel != NULL) 181 sk = tunnel->sock; 182 else { 183 struct iphdr *iph = (struct iphdr *) skb_network_header(skb); 184 185 read_lock_bh(&l2tp_ip_lock); 186 sk = __l2tp_ip_bind_lookup(net, iph->daddr, inet_iif(skb), 187 tunnel_id); 188 if (!sk) { 189 read_unlock_bh(&l2tp_ip_lock); 190 goto discard; 191 } 192 193 sock_hold(sk); 194 read_unlock_bh(&l2tp_ip_lock); 195 } 196 197 if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) 198 goto discard_put; 199 200 nf_reset(skb); 201 202 return sk_receive_skb(sk, skb, 1); 203 204 discard_put: 205 sock_put(sk); 206 207 discard: 208 kfree_skb(skb); 209 return 0; 210 } 211 212 static int l2tp_ip_open(struct sock *sk) 213 { 214 /* Prevent autobind. We don't have ports. */ 215 inet_sk(sk)->inet_num = IPPROTO_L2TP; 216 217 write_lock_bh(&l2tp_ip_lock); 218 sk_add_node(sk, &l2tp_ip_table); 219 write_unlock_bh(&l2tp_ip_lock); 220 221 return 0; 222 } 223 224 static void l2tp_ip_close(struct sock *sk, long timeout) 225 { 226 write_lock_bh(&l2tp_ip_lock); 227 hlist_del_init(&sk->sk_bind_node); 228 sk_del_node_init(sk); 229 write_unlock_bh(&l2tp_ip_lock); 230 sk_common_release(sk); 231 } 232 233 static void l2tp_ip_destroy_sock(struct sock *sk) 234 { 235 struct sk_buff *skb; 236 struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk); 237 238 while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL) 239 kfree_skb(skb); 240 241 if (tunnel) { 242 l2tp_tunnel_closeall(tunnel); 243 sock_put(sk); 244 } 245 246 sk_refcnt_debug_dec(sk); 247 } 248 249 static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len) 250 { 251 struct inet_sock *inet = inet_sk(sk); 252 struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr; 253 struct net *net = sock_net(sk); 254 int ret; 255 int chk_addr_ret; 256 257 if (addr_len < sizeof(struct sockaddr_l2tpip)) 258 return -EINVAL; 259 if (addr->l2tp_family != AF_INET) 260 return -EINVAL; 261 262 lock_sock(sk); 263 264 ret = -EINVAL; 265 if (!sock_flag(sk, SOCK_ZAPPED)) 266 goto out; 267 268 if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip)) 269 goto out; 270 271 chk_addr_ret = inet_addr_type(net, addr->l2tp_addr.s_addr); 272 ret = -EADDRNOTAVAIL; 273 if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL && 274 chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST) 275 goto out; 276 277 if (addr->l2tp_addr.s_addr) 278 inet->inet_rcv_saddr = inet->inet_saddr = addr->l2tp_addr.s_addr; 279 if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST) 280 inet->inet_saddr = 0; /* Use device */ 281 282 write_lock_bh(&l2tp_ip_lock); 283 if (__l2tp_ip_bind_lookup(net, addr->l2tp_addr.s_addr, 284 sk->sk_bound_dev_if, addr->l2tp_conn_id)) { 285 write_unlock_bh(&l2tp_ip_lock); 286 ret = -EADDRINUSE; 287 goto out; 288 } 289 290 sk_dst_reset(sk); 291 l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id; 292 293 sk_add_bind_node(sk, &l2tp_ip_bind_table); 294 sk_del_node_init(sk); 295 write_unlock_bh(&l2tp_ip_lock); 296 297 ret = 0; 298 sock_reset_flag(sk, SOCK_ZAPPED); 299 300 out: 301 release_sock(sk); 302 303 return ret; 304 } 305 306 static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) 307 { 308 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr; 309 int rc; 310 311 if (addr_len < sizeof(*lsa)) 312 return -EINVAL; 313 314 if (ipv4_is_multicast(lsa->l2tp_addr.s_addr)) 315 return -EINVAL; 316 317 lock_sock(sk); 318 319 /* Must bind first - autobinding does not work */ 320 if (sock_flag(sk, SOCK_ZAPPED)) { 321 rc = -EINVAL; 322 goto out_sk; 323 } 324 325 rc = __ip4_datagram_connect(sk, uaddr, addr_len); 326 if (rc < 0) 327 goto out_sk; 328 329 l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id; 330 331 write_lock_bh(&l2tp_ip_lock); 332 hlist_del_init(&sk->sk_bind_node); 333 sk_add_bind_node(sk, &l2tp_ip_bind_table); 334 write_unlock_bh(&l2tp_ip_lock); 335 336 out_sk: 337 release_sock(sk); 338 339 return rc; 340 } 341 342 static int l2tp_ip_disconnect(struct sock *sk, int flags) 343 { 344 if (sock_flag(sk, SOCK_ZAPPED)) 345 return 0; 346 347 return __udp_disconnect(sk, flags); 348 } 349 350 static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr, 351 int *uaddr_len, int peer) 352 { 353 struct sock *sk = sock->sk; 354 struct inet_sock *inet = inet_sk(sk); 355 struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk); 356 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr; 357 358 memset(lsa, 0, sizeof(*lsa)); 359 lsa->l2tp_family = AF_INET; 360 if (peer) { 361 if (!inet->inet_dport) 362 return -ENOTCONN; 363 lsa->l2tp_conn_id = lsk->peer_conn_id; 364 lsa->l2tp_addr.s_addr = inet->inet_daddr; 365 } else { 366 __be32 addr = inet->inet_rcv_saddr; 367 if (!addr) 368 addr = inet->inet_saddr; 369 lsa->l2tp_conn_id = lsk->conn_id; 370 lsa->l2tp_addr.s_addr = addr; 371 } 372 *uaddr_len = sizeof(*lsa); 373 return 0; 374 } 375 376 static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb) 377 { 378 int rc; 379 380 /* Charge it to the socket, dropping if the queue is full. */ 381 rc = sock_queue_rcv_skb(sk, skb); 382 if (rc < 0) 383 goto drop; 384 385 return 0; 386 387 drop: 388 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS); 389 kfree_skb(skb); 390 return -1; 391 } 392 393 /* Userspace will call sendmsg() on the tunnel socket to send L2TP 394 * control frames. 395 */ 396 static int l2tp_ip_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 397 { 398 struct sk_buff *skb; 399 int rc; 400 struct inet_sock *inet = inet_sk(sk); 401 struct rtable *rt = NULL; 402 struct flowi4 *fl4; 403 int connected = 0; 404 __be32 daddr; 405 406 lock_sock(sk); 407 408 rc = -ENOTCONN; 409 if (sock_flag(sk, SOCK_DEAD)) 410 goto out; 411 412 /* Get and verify the address. */ 413 if (msg->msg_name) { 414 DECLARE_SOCKADDR(struct sockaddr_l2tpip *, lip, msg->msg_name); 415 rc = -EINVAL; 416 if (msg->msg_namelen < sizeof(*lip)) 417 goto out; 418 419 if (lip->l2tp_family != AF_INET) { 420 rc = -EAFNOSUPPORT; 421 if (lip->l2tp_family != AF_UNSPEC) 422 goto out; 423 } 424 425 daddr = lip->l2tp_addr.s_addr; 426 } else { 427 rc = -EDESTADDRREQ; 428 if (sk->sk_state != TCP_ESTABLISHED) 429 goto out; 430 431 daddr = inet->inet_daddr; 432 connected = 1; 433 } 434 435 /* Allocate a socket buffer */ 436 rc = -ENOMEM; 437 skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) + 438 4 + len, 0, GFP_KERNEL); 439 if (!skb) 440 goto error; 441 442 /* Reserve space for headers, putting IP header on 4-byte boundary. */ 443 skb_reserve(skb, 2 + NET_SKB_PAD); 444 skb_reset_network_header(skb); 445 skb_reserve(skb, sizeof(struct iphdr)); 446 skb_reset_transport_header(skb); 447 448 /* Insert 0 session_id */ 449 *((__be32 *) skb_put(skb, 4)) = 0; 450 451 /* Copy user data into skb */ 452 rc = memcpy_from_msg(skb_put(skb, len), msg, len); 453 if (rc < 0) { 454 kfree_skb(skb); 455 goto error; 456 } 457 458 fl4 = &inet->cork.fl.u.ip4; 459 if (connected) 460 rt = (struct rtable *) __sk_dst_check(sk, 0); 461 462 rcu_read_lock(); 463 if (rt == NULL) { 464 const struct ip_options_rcu *inet_opt; 465 466 inet_opt = rcu_dereference(inet->inet_opt); 467 468 /* Use correct destination address if we have options. */ 469 if (inet_opt && inet_opt->opt.srr) 470 daddr = inet_opt->opt.faddr; 471 472 /* If this fails, retransmit mechanism of transport layer will 473 * keep trying until route appears or the connection times 474 * itself out. 475 */ 476 rt = ip_route_output_ports(sock_net(sk), fl4, sk, 477 daddr, inet->inet_saddr, 478 inet->inet_dport, inet->inet_sport, 479 sk->sk_protocol, RT_CONN_FLAGS(sk), 480 sk->sk_bound_dev_if); 481 if (IS_ERR(rt)) 482 goto no_route; 483 if (connected) { 484 sk_setup_caps(sk, &rt->dst); 485 } else { 486 skb_dst_set(skb, &rt->dst); 487 goto xmit; 488 } 489 } 490 491 /* We dont need to clone dst here, it is guaranteed to not disappear. 492 * __dev_xmit_skb() might force a refcount if needed. 493 */ 494 skb_dst_set_noref(skb, &rt->dst); 495 496 xmit: 497 /* Queue the packet to IP for output */ 498 rc = ip_queue_xmit(sk, skb, &inet->cork.fl); 499 rcu_read_unlock(); 500 501 error: 502 if (rc >= 0) 503 rc = len; 504 505 out: 506 release_sock(sk); 507 return rc; 508 509 no_route: 510 rcu_read_unlock(); 511 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES); 512 kfree_skb(skb); 513 rc = -EHOSTUNREACH; 514 goto out; 515 } 516 517 static int l2tp_ip_recvmsg(struct sock *sk, struct msghdr *msg, 518 size_t len, int noblock, int flags, int *addr_len) 519 { 520 struct inet_sock *inet = inet_sk(sk); 521 size_t copied = 0; 522 int err = -EOPNOTSUPP; 523 DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name); 524 struct sk_buff *skb; 525 526 if (flags & MSG_OOB) 527 goto out; 528 529 skb = skb_recv_datagram(sk, flags, noblock, &err); 530 if (!skb) 531 goto out; 532 533 copied = skb->len; 534 if (len < copied) { 535 msg->msg_flags |= MSG_TRUNC; 536 copied = len; 537 } 538 539 err = skb_copy_datagram_msg(skb, 0, msg, copied); 540 if (err) 541 goto done; 542 543 sock_recv_timestamp(msg, sk, skb); 544 545 /* Copy the address. */ 546 if (sin) { 547 sin->sin_family = AF_INET; 548 sin->sin_addr.s_addr = ip_hdr(skb)->saddr; 549 sin->sin_port = 0; 550 memset(&sin->sin_zero, 0, sizeof(sin->sin_zero)); 551 *addr_len = sizeof(*sin); 552 } 553 if (inet->cmsg_flags) 554 ip_cmsg_recv(msg, skb); 555 if (flags & MSG_TRUNC) 556 copied = skb->len; 557 done: 558 skb_free_datagram(sk, skb); 559 out: 560 return err ? err : copied; 561 } 562 563 static struct proto l2tp_ip_prot = { 564 .name = "L2TP/IP", 565 .owner = THIS_MODULE, 566 .init = l2tp_ip_open, 567 .close = l2tp_ip_close, 568 .bind = l2tp_ip_bind, 569 .connect = l2tp_ip_connect, 570 .disconnect = l2tp_ip_disconnect, 571 .ioctl = udp_ioctl, 572 .destroy = l2tp_ip_destroy_sock, 573 .setsockopt = ip_setsockopt, 574 .getsockopt = ip_getsockopt, 575 .sendmsg = l2tp_ip_sendmsg, 576 .recvmsg = l2tp_ip_recvmsg, 577 .backlog_rcv = l2tp_ip_backlog_recv, 578 .hash = inet_hash, 579 .unhash = inet_unhash, 580 .obj_size = sizeof(struct l2tp_ip_sock), 581 #ifdef CONFIG_COMPAT 582 .compat_setsockopt = compat_ip_setsockopt, 583 .compat_getsockopt = compat_ip_getsockopt, 584 #endif 585 }; 586 587 static const struct proto_ops l2tp_ip_ops = { 588 .family = PF_INET, 589 .owner = THIS_MODULE, 590 .release = inet_release, 591 .bind = inet_bind, 592 .connect = inet_dgram_connect, 593 .socketpair = sock_no_socketpair, 594 .accept = sock_no_accept, 595 .getname = l2tp_ip_getname, 596 .poll = datagram_poll, 597 .ioctl = inet_ioctl, 598 .listen = sock_no_listen, 599 .shutdown = inet_shutdown, 600 .setsockopt = sock_common_setsockopt, 601 .getsockopt = sock_common_getsockopt, 602 .sendmsg = inet_sendmsg, 603 .recvmsg = sock_common_recvmsg, 604 .mmap = sock_no_mmap, 605 .sendpage = sock_no_sendpage, 606 #ifdef CONFIG_COMPAT 607 .compat_setsockopt = compat_sock_common_setsockopt, 608 .compat_getsockopt = compat_sock_common_getsockopt, 609 #endif 610 }; 611 612 static struct inet_protosw l2tp_ip_protosw = { 613 .type = SOCK_DGRAM, 614 .protocol = IPPROTO_L2TP, 615 .prot = &l2tp_ip_prot, 616 .ops = &l2tp_ip_ops, 617 }; 618 619 static struct net_protocol l2tp_ip_protocol __read_mostly = { 620 .handler = l2tp_ip_recv, 621 .netns_ok = 1, 622 }; 623 624 static int __init l2tp_ip_init(void) 625 { 626 int err; 627 628 pr_info("L2TP IP encapsulation support (L2TPv3)\n"); 629 630 err = proto_register(&l2tp_ip_prot, 1); 631 if (err != 0) 632 goto out; 633 634 err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 635 if (err) 636 goto out1; 637 638 inet_register_protosw(&l2tp_ip_protosw); 639 return 0; 640 641 out1: 642 proto_unregister(&l2tp_ip_prot); 643 out: 644 return err; 645 } 646 647 static void __exit l2tp_ip_exit(void) 648 { 649 inet_unregister_protosw(&l2tp_ip_protosw); 650 inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 651 proto_unregister(&l2tp_ip_prot); 652 } 653 654 module_init(l2tp_ip_init); 655 module_exit(l2tp_ip_exit); 656 657 MODULE_LICENSE("GPL"); 658 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>"); 659 MODULE_DESCRIPTION("L2TP over IP"); 660 MODULE_VERSION("1.0"); 661 662 /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like 663 * enums 664 */ 665 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP); 666 MODULE_ALIAS_NET_PF_PROTO(PF_INET, IPPROTO_L2TP); 667