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 && sk->sk_bound_dev_if != dif)) 65 goto found; 66 } 67 68 sk = NULL; 69 found: 70 return sk; 71 } 72 73 static inline struct sock *l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id) 74 { 75 struct sock *sk = __l2tp_ip_bind_lookup(net, laddr, dif, tunnel_id); 76 if (sk) 77 sock_hold(sk); 78 79 return sk; 80 } 81 82 /* When processing receive frames, there are two cases to 83 * consider. Data frames consist of a non-zero session-id and an 84 * optional cookie. Control frames consist of a regular L2TP header 85 * preceded by 32-bits of zeros. 86 * 87 * L2TPv3 Session Header Over IP 88 * 89 * 0 1 2 3 90 * 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 91 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 92 * | Session ID | 93 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 94 * | Cookie (optional, maximum 64 bits)... 95 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 96 * | 97 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 98 * 99 * L2TPv3 Control Message Header Over IP 100 * 101 * 0 1 2 3 102 * 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 1 103 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 104 * | (32 bits of zeros) | 105 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 106 * |T|L|x|x|S|x|x|x|x|x|x|x| Ver | Length | 107 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 108 * | Control Connection ID | 109 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 110 * | Ns | Nr | 111 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 112 * 113 * All control frames are passed to userspace. 114 */ 115 static int l2tp_ip_recv(struct sk_buff *skb) 116 { 117 struct net *net = dev_net(skb->dev); 118 struct sock *sk; 119 u32 session_id; 120 u32 tunnel_id; 121 unsigned char *ptr, *optr; 122 struct l2tp_session *session; 123 struct l2tp_tunnel *tunnel = NULL; 124 int length; 125 126 if (!pskb_may_pull(skb, 4)) 127 goto discard; 128 129 /* Point to L2TP header */ 130 optr = ptr = skb->data; 131 session_id = ntohl(*((__be32 *) ptr)); 132 ptr += 4; 133 134 /* RFC3931: L2TP/IP packets have the first 4 bytes containing 135 * the session_id. If it is 0, the packet is a L2TP control 136 * frame and the session_id value can be discarded. 137 */ 138 if (session_id == 0) { 139 __skb_pull(skb, 4); 140 goto pass_up; 141 } 142 143 /* Ok, this is a data packet. Lookup the session. */ 144 session = l2tp_session_find(net, NULL, session_id); 145 if (session == NULL) 146 goto discard; 147 148 tunnel = session->tunnel; 149 if (tunnel == NULL) 150 goto discard; 151 152 /* Trace packet contents, if enabled */ 153 if (tunnel->debug & L2TP_MSG_DATA) { 154 length = min(32u, skb->len); 155 if (!pskb_may_pull(skb, length)) 156 goto discard; 157 158 /* Point to L2TP header */ 159 optr = ptr = skb->data; 160 ptr += 4; 161 pr_debug("%s: ip recv\n", tunnel->name); 162 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length); 163 } 164 165 l2tp_recv_common(session, skb, ptr, optr, 0, skb->len, tunnel->recv_payload_hook); 166 167 return 0; 168 169 pass_up: 170 /* Get the tunnel_id from the L2TP header */ 171 if (!pskb_may_pull(skb, 12)) 172 goto discard; 173 174 if ((skb->data[0] & 0xc0) != 0xc0) 175 goto discard; 176 177 tunnel_id = ntohl(*(__be32 *) &skb->data[4]); 178 tunnel = l2tp_tunnel_find(net, tunnel_id); 179 if (tunnel != NULL) 180 sk = tunnel->sock; 181 else { 182 struct iphdr *iph = (struct iphdr *) skb_network_header(skb); 183 184 read_lock_bh(&l2tp_ip_lock); 185 sk = __l2tp_ip_bind_lookup(net, iph->daddr, 0, tunnel_id); 186 read_unlock_bh(&l2tp_ip_lock); 187 } 188 189 if (sk == NULL) 190 goto discard; 191 192 sock_hold(sk); 193 194 if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) 195 goto discard_put; 196 197 nf_reset(skb); 198 199 return sk_receive_skb(sk, skb, 1); 200 201 discard_put: 202 sock_put(sk); 203 204 discard: 205 kfree_skb(skb); 206 return 0; 207 } 208 209 static int l2tp_ip_open(struct sock *sk) 210 { 211 /* Prevent autobind. We don't have ports. */ 212 inet_sk(sk)->inet_num = IPPROTO_L2TP; 213 214 write_lock_bh(&l2tp_ip_lock); 215 sk_add_node(sk, &l2tp_ip_table); 216 write_unlock_bh(&l2tp_ip_lock); 217 218 return 0; 219 } 220 221 static void l2tp_ip_close(struct sock *sk, long timeout) 222 { 223 write_lock_bh(&l2tp_ip_lock); 224 hlist_del_init(&sk->sk_bind_node); 225 sk_del_node_init(sk); 226 write_unlock_bh(&l2tp_ip_lock); 227 sk_common_release(sk); 228 } 229 230 static void l2tp_ip_destroy_sock(struct sock *sk) 231 { 232 struct sk_buff *skb; 233 struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk); 234 235 while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL) 236 kfree_skb(skb); 237 238 if (tunnel) { 239 l2tp_tunnel_closeall(tunnel); 240 sock_put(sk); 241 } 242 243 sk_refcnt_debug_dec(sk); 244 } 245 246 static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len) 247 { 248 struct inet_sock *inet = inet_sk(sk); 249 struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr; 250 struct net *net = sock_net(sk); 251 int ret; 252 int chk_addr_ret; 253 254 if (!sock_flag(sk, SOCK_ZAPPED)) 255 return -EINVAL; 256 if (addr_len < sizeof(struct sockaddr_l2tpip)) 257 return -EINVAL; 258 if (addr->l2tp_family != AF_INET) 259 return -EINVAL; 260 261 ret = -EADDRINUSE; 262 read_lock_bh(&l2tp_ip_lock); 263 if (__l2tp_ip_bind_lookup(net, addr->l2tp_addr.s_addr, 264 sk->sk_bound_dev_if, addr->l2tp_conn_id)) 265 goto out_in_use; 266 267 read_unlock_bh(&l2tp_ip_lock); 268 269 lock_sock(sk); 270 if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip)) 271 goto out; 272 273 chk_addr_ret = inet_addr_type(net, addr->l2tp_addr.s_addr); 274 ret = -EADDRNOTAVAIL; 275 if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL && 276 chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST) 277 goto out; 278 279 if (addr->l2tp_addr.s_addr) 280 inet->inet_rcv_saddr = inet->inet_saddr = addr->l2tp_addr.s_addr; 281 if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST) 282 inet->inet_saddr = 0; /* Use device */ 283 sk_dst_reset(sk); 284 285 l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id; 286 287 write_lock_bh(&l2tp_ip_lock); 288 sk_add_bind_node(sk, &l2tp_ip_bind_table); 289 sk_del_node_init(sk); 290 write_unlock_bh(&l2tp_ip_lock); 291 ret = 0; 292 sock_reset_flag(sk, SOCK_ZAPPED); 293 294 out: 295 release_sock(sk); 296 297 return ret; 298 299 out_in_use: 300 read_unlock_bh(&l2tp_ip_lock); 301 302 return ret; 303 } 304 305 static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) 306 { 307 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr; 308 int rc; 309 310 if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */ 311 return -EINVAL; 312 313 if (addr_len < sizeof(*lsa)) 314 return -EINVAL; 315 316 if (ipv4_is_multicast(lsa->l2tp_addr.s_addr)) 317 return -EINVAL; 318 319 rc = ip4_datagram_connect(sk, uaddr, addr_len); 320 if (rc < 0) 321 return rc; 322 323 lock_sock(sk); 324 325 l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id; 326 327 write_lock_bh(&l2tp_ip_lock); 328 hlist_del_init(&sk->sk_bind_node); 329 sk_add_bind_node(sk, &l2tp_ip_bind_table); 330 write_unlock_bh(&l2tp_ip_lock); 331 332 release_sock(sk); 333 return rc; 334 } 335 336 static int l2tp_ip_disconnect(struct sock *sk, int flags) 337 { 338 if (sock_flag(sk, SOCK_ZAPPED)) 339 return 0; 340 341 return __udp_disconnect(sk, flags); 342 } 343 344 static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr, 345 int *uaddr_len, int peer) 346 { 347 struct sock *sk = sock->sk; 348 struct inet_sock *inet = inet_sk(sk); 349 struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk); 350 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr; 351 352 memset(lsa, 0, sizeof(*lsa)); 353 lsa->l2tp_family = AF_INET; 354 if (peer) { 355 if (!inet->inet_dport) 356 return -ENOTCONN; 357 lsa->l2tp_conn_id = lsk->peer_conn_id; 358 lsa->l2tp_addr.s_addr = inet->inet_daddr; 359 } else { 360 __be32 addr = inet->inet_rcv_saddr; 361 if (!addr) 362 addr = inet->inet_saddr; 363 lsa->l2tp_conn_id = lsk->conn_id; 364 lsa->l2tp_addr.s_addr = addr; 365 } 366 *uaddr_len = sizeof(*lsa); 367 return 0; 368 } 369 370 static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb) 371 { 372 int rc; 373 374 /* Charge it to the socket, dropping if the queue is full. */ 375 rc = sock_queue_rcv_skb(sk, skb); 376 if (rc < 0) 377 goto drop; 378 379 return 0; 380 381 drop: 382 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS); 383 kfree_skb(skb); 384 return -1; 385 } 386 387 /* Userspace will call sendmsg() on the tunnel socket to send L2TP 388 * control frames. 389 */ 390 static int l2tp_ip_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 391 { 392 struct sk_buff *skb; 393 int rc; 394 struct inet_sock *inet = inet_sk(sk); 395 struct rtable *rt = NULL; 396 struct flowi4 *fl4; 397 int connected = 0; 398 __be32 daddr; 399 400 lock_sock(sk); 401 402 rc = -ENOTCONN; 403 if (sock_flag(sk, SOCK_DEAD)) 404 goto out; 405 406 /* Get and verify the address. */ 407 if (msg->msg_name) { 408 DECLARE_SOCKADDR(struct sockaddr_l2tpip *, lip, msg->msg_name); 409 rc = -EINVAL; 410 if (msg->msg_namelen < sizeof(*lip)) 411 goto out; 412 413 if (lip->l2tp_family != AF_INET) { 414 rc = -EAFNOSUPPORT; 415 if (lip->l2tp_family != AF_UNSPEC) 416 goto out; 417 } 418 419 daddr = lip->l2tp_addr.s_addr; 420 } else { 421 rc = -EDESTADDRREQ; 422 if (sk->sk_state != TCP_ESTABLISHED) 423 goto out; 424 425 daddr = inet->inet_daddr; 426 connected = 1; 427 } 428 429 /* Allocate a socket buffer */ 430 rc = -ENOMEM; 431 skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) + 432 4 + len, 0, GFP_KERNEL); 433 if (!skb) 434 goto error; 435 436 /* Reserve space for headers, putting IP header on 4-byte boundary. */ 437 skb_reserve(skb, 2 + NET_SKB_PAD); 438 skb_reset_network_header(skb); 439 skb_reserve(skb, sizeof(struct iphdr)); 440 skb_reset_transport_header(skb); 441 442 /* Insert 0 session_id */ 443 *((__be32 *) skb_put(skb, 4)) = 0; 444 445 /* Copy user data into skb */ 446 rc = memcpy_from_msg(skb_put(skb, len), msg, len); 447 if (rc < 0) { 448 kfree_skb(skb); 449 goto error; 450 } 451 452 fl4 = &inet->cork.fl.u.ip4; 453 if (connected) 454 rt = (struct rtable *) __sk_dst_check(sk, 0); 455 456 rcu_read_lock(); 457 if (rt == NULL) { 458 const struct ip_options_rcu *inet_opt; 459 460 inet_opt = rcu_dereference(inet->inet_opt); 461 462 /* Use correct destination address if we have options. */ 463 if (inet_opt && inet_opt->opt.srr) 464 daddr = inet_opt->opt.faddr; 465 466 /* If this fails, retransmit mechanism of transport layer will 467 * keep trying until route appears or the connection times 468 * itself out. 469 */ 470 rt = ip_route_output_ports(sock_net(sk), fl4, sk, 471 daddr, inet->inet_saddr, 472 inet->inet_dport, inet->inet_sport, 473 sk->sk_protocol, RT_CONN_FLAGS(sk), 474 sk->sk_bound_dev_if); 475 if (IS_ERR(rt)) 476 goto no_route; 477 if (connected) { 478 sk_setup_caps(sk, &rt->dst); 479 } else { 480 skb_dst_set(skb, &rt->dst); 481 goto xmit; 482 } 483 } 484 485 /* We dont need to clone dst here, it is guaranteed to not disappear. 486 * __dev_xmit_skb() might force a refcount if needed. 487 */ 488 skb_dst_set_noref(skb, &rt->dst); 489 490 xmit: 491 /* Queue the packet to IP for output */ 492 rc = ip_queue_xmit(sk, skb, &inet->cork.fl); 493 rcu_read_unlock(); 494 495 error: 496 if (rc >= 0) 497 rc = len; 498 499 out: 500 release_sock(sk); 501 return rc; 502 503 no_route: 504 rcu_read_unlock(); 505 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES); 506 kfree_skb(skb); 507 rc = -EHOSTUNREACH; 508 goto out; 509 } 510 511 static int l2tp_ip_recvmsg(struct sock *sk, struct msghdr *msg, 512 size_t len, int noblock, int flags, int *addr_len) 513 { 514 struct inet_sock *inet = inet_sk(sk); 515 size_t copied = 0; 516 int err = -EOPNOTSUPP; 517 DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name); 518 struct sk_buff *skb; 519 520 if (flags & MSG_OOB) 521 goto out; 522 523 skb = skb_recv_datagram(sk, flags, noblock, &err); 524 if (!skb) 525 goto out; 526 527 copied = skb->len; 528 if (len < copied) { 529 msg->msg_flags |= MSG_TRUNC; 530 copied = len; 531 } 532 533 err = skb_copy_datagram_msg(skb, 0, msg, copied); 534 if (err) 535 goto done; 536 537 sock_recv_timestamp(msg, sk, skb); 538 539 /* Copy the address. */ 540 if (sin) { 541 sin->sin_family = AF_INET; 542 sin->sin_addr.s_addr = ip_hdr(skb)->saddr; 543 sin->sin_port = 0; 544 memset(&sin->sin_zero, 0, sizeof(sin->sin_zero)); 545 *addr_len = sizeof(*sin); 546 } 547 if (inet->cmsg_flags) 548 ip_cmsg_recv(msg, skb); 549 if (flags & MSG_TRUNC) 550 copied = skb->len; 551 done: 552 skb_free_datagram(sk, skb); 553 out: 554 return err ? err : copied; 555 } 556 557 static struct proto l2tp_ip_prot = { 558 .name = "L2TP/IP", 559 .owner = THIS_MODULE, 560 .init = l2tp_ip_open, 561 .close = l2tp_ip_close, 562 .bind = l2tp_ip_bind, 563 .connect = l2tp_ip_connect, 564 .disconnect = l2tp_ip_disconnect, 565 .ioctl = udp_ioctl, 566 .destroy = l2tp_ip_destroy_sock, 567 .setsockopt = ip_setsockopt, 568 .getsockopt = ip_getsockopt, 569 .sendmsg = l2tp_ip_sendmsg, 570 .recvmsg = l2tp_ip_recvmsg, 571 .backlog_rcv = l2tp_ip_backlog_recv, 572 .hash = inet_hash, 573 .unhash = inet_unhash, 574 .obj_size = sizeof(struct l2tp_ip_sock), 575 #ifdef CONFIG_COMPAT 576 .compat_setsockopt = compat_ip_setsockopt, 577 .compat_getsockopt = compat_ip_getsockopt, 578 #endif 579 }; 580 581 static const struct proto_ops l2tp_ip_ops = { 582 .family = PF_INET, 583 .owner = THIS_MODULE, 584 .release = inet_release, 585 .bind = inet_bind, 586 .connect = inet_dgram_connect, 587 .socketpair = sock_no_socketpair, 588 .accept = sock_no_accept, 589 .getname = l2tp_ip_getname, 590 .poll = datagram_poll, 591 .ioctl = inet_ioctl, 592 .listen = sock_no_listen, 593 .shutdown = inet_shutdown, 594 .setsockopt = sock_common_setsockopt, 595 .getsockopt = sock_common_getsockopt, 596 .sendmsg = inet_sendmsg, 597 .recvmsg = sock_common_recvmsg, 598 .mmap = sock_no_mmap, 599 .sendpage = sock_no_sendpage, 600 #ifdef CONFIG_COMPAT 601 .compat_setsockopt = compat_sock_common_setsockopt, 602 .compat_getsockopt = compat_sock_common_getsockopt, 603 #endif 604 }; 605 606 static struct inet_protosw l2tp_ip_protosw = { 607 .type = SOCK_DGRAM, 608 .protocol = IPPROTO_L2TP, 609 .prot = &l2tp_ip_prot, 610 .ops = &l2tp_ip_ops, 611 }; 612 613 static struct net_protocol l2tp_ip_protocol __read_mostly = { 614 .handler = l2tp_ip_recv, 615 .netns_ok = 1, 616 }; 617 618 static int __init l2tp_ip_init(void) 619 { 620 int err; 621 622 pr_info("L2TP IP encapsulation support (L2TPv3)\n"); 623 624 err = proto_register(&l2tp_ip_prot, 1); 625 if (err != 0) 626 goto out; 627 628 err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 629 if (err) 630 goto out1; 631 632 inet_register_protosw(&l2tp_ip_protosw); 633 return 0; 634 635 out1: 636 proto_unregister(&l2tp_ip_prot); 637 out: 638 return err; 639 } 640 641 static void __exit l2tp_ip_exit(void) 642 { 643 inet_unregister_protosw(&l2tp_ip_protosw); 644 inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 645 proto_unregister(&l2tp_ip_prot); 646 } 647 648 module_init(l2tp_ip_init); 649 module_exit(l2tp_ip_exit); 650 651 MODULE_LICENSE("GPL"); 652 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>"); 653 MODULE_DESCRIPTION("L2TP over IP"); 654 MODULE_VERSION("1.0"); 655 656 /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like 657 * enums 658 */ 659 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP); 660 MODULE_ALIAS_NET_PF_PROTO(PF_INET, IPPROTO_L2TP); 661