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 /* Point to L2TP header */ 127 optr = ptr = skb->data; 128 129 if (!pskb_may_pull(skb, 4)) 130 goto discard; 131 132 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 pr_debug("%s: ip recv\n", tunnel->name); 160 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length); 161 } 162 163 l2tp_recv_common(session, skb, ptr, optr, 0, skb->len, tunnel->recv_payload_hook); 164 165 return 0; 166 167 pass_up: 168 /* Get the tunnel_id from the L2TP header */ 169 if (!pskb_may_pull(skb, 12)) 170 goto discard; 171 172 if ((skb->data[0] & 0xc0) != 0xc0) 173 goto discard; 174 175 tunnel_id = ntohl(*(__be32 *) &skb->data[4]); 176 tunnel = l2tp_tunnel_find(net, tunnel_id); 177 if (tunnel != NULL) 178 sk = tunnel->sock; 179 else { 180 struct iphdr *iph = (struct iphdr *) skb_network_header(skb); 181 182 read_lock_bh(&l2tp_ip_lock); 183 sk = __l2tp_ip_bind_lookup(net, iph->daddr, 0, tunnel_id); 184 read_unlock_bh(&l2tp_ip_lock); 185 } 186 187 if (sk == NULL) 188 goto discard; 189 190 sock_hold(sk); 191 192 if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb)) 193 goto discard_put; 194 195 nf_reset(skb); 196 197 return sk_receive_skb(sk, skb, 1); 198 199 discard_put: 200 sock_put(sk); 201 202 discard: 203 kfree_skb(skb); 204 return 0; 205 } 206 207 static int l2tp_ip_open(struct sock *sk) 208 { 209 /* Prevent autobind. We don't have ports. */ 210 inet_sk(sk)->inet_num = IPPROTO_L2TP; 211 212 write_lock_bh(&l2tp_ip_lock); 213 sk_add_node(sk, &l2tp_ip_table); 214 write_unlock_bh(&l2tp_ip_lock); 215 216 return 0; 217 } 218 219 static void l2tp_ip_close(struct sock *sk, long timeout) 220 { 221 write_lock_bh(&l2tp_ip_lock); 222 hlist_del_init(&sk->sk_bind_node); 223 sk_del_node_init(sk); 224 write_unlock_bh(&l2tp_ip_lock); 225 sk_common_release(sk); 226 } 227 228 static void l2tp_ip_destroy_sock(struct sock *sk) 229 { 230 struct sk_buff *skb; 231 struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk); 232 233 while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL) 234 kfree_skb(skb); 235 236 if (tunnel) { 237 l2tp_tunnel_closeall(tunnel); 238 sock_put(sk); 239 } 240 241 sk_refcnt_debug_dec(sk); 242 } 243 244 static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len) 245 { 246 struct inet_sock *inet = inet_sk(sk); 247 struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr; 248 struct net *net = sock_net(sk); 249 int ret; 250 int chk_addr_ret; 251 252 if (!sock_flag(sk, SOCK_ZAPPED)) 253 return -EINVAL; 254 if (addr_len < sizeof(struct sockaddr_l2tpip)) 255 return -EINVAL; 256 if (addr->l2tp_family != AF_INET) 257 return -EINVAL; 258 259 ret = -EADDRINUSE; 260 read_lock_bh(&l2tp_ip_lock); 261 if (__l2tp_ip_bind_lookup(net, addr->l2tp_addr.s_addr, 262 sk->sk_bound_dev_if, addr->l2tp_conn_id)) 263 goto out_in_use; 264 265 read_unlock_bh(&l2tp_ip_lock); 266 267 lock_sock(sk); 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 sk_dst_reset(sk); 282 283 l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id; 284 285 write_lock_bh(&l2tp_ip_lock); 286 sk_add_bind_node(sk, &l2tp_ip_bind_table); 287 sk_del_node_init(sk); 288 write_unlock_bh(&l2tp_ip_lock); 289 ret = 0; 290 sock_reset_flag(sk, SOCK_ZAPPED); 291 292 out: 293 release_sock(sk); 294 295 return ret; 296 297 out_in_use: 298 read_unlock_bh(&l2tp_ip_lock); 299 300 return ret; 301 } 302 303 static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) 304 { 305 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr; 306 int rc; 307 308 if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */ 309 return -EINVAL; 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 rc = ip4_datagram_connect(sk, uaddr, addr_len); 318 if (rc < 0) 319 return rc; 320 321 lock_sock(sk); 322 323 l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id; 324 325 write_lock_bh(&l2tp_ip_lock); 326 hlist_del_init(&sk->sk_bind_node); 327 sk_add_bind_node(sk, &l2tp_ip_bind_table); 328 write_unlock_bh(&l2tp_ip_lock); 329 330 release_sock(sk); 331 return rc; 332 } 333 334 static int l2tp_ip_disconnect(struct sock *sk, int flags) 335 { 336 if (sock_flag(sk, SOCK_ZAPPED)) 337 return 0; 338 339 return udp_disconnect(sk, flags); 340 } 341 342 static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr, 343 int *uaddr_len, int peer) 344 { 345 struct sock *sk = sock->sk; 346 struct inet_sock *inet = inet_sk(sk); 347 struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk); 348 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr; 349 350 memset(lsa, 0, sizeof(*lsa)); 351 lsa->l2tp_family = AF_INET; 352 if (peer) { 353 if (!inet->inet_dport) 354 return -ENOTCONN; 355 lsa->l2tp_conn_id = lsk->peer_conn_id; 356 lsa->l2tp_addr.s_addr = inet->inet_daddr; 357 } else { 358 __be32 addr = inet->inet_rcv_saddr; 359 if (!addr) 360 addr = inet->inet_saddr; 361 lsa->l2tp_conn_id = lsk->conn_id; 362 lsa->l2tp_addr.s_addr = addr; 363 } 364 *uaddr_len = sizeof(*lsa); 365 return 0; 366 } 367 368 static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb) 369 { 370 int rc; 371 372 /* Charge it to the socket, dropping if the queue is full. */ 373 rc = sock_queue_rcv_skb(sk, skb); 374 if (rc < 0) 375 goto drop; 376 377 return 0; 378 379 drop: 380 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS); 381 kfree_skb(skb); 382 return -1; 383 } 384 385 /* Userspace will call sendmsg() on the tunnel socket to send L2TP 386 * control frames. 387 */ 388 static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, size_t len) 389 { 390 struct sk_buff *skb; 391 int rc; 392 struct inet_sock *inet = inet_sk(sk); 393 struct rtable *rt = NULL; 394 struct flowi4 *fl4; 395 int connected = 0; 396 __be32 daddr; 397 398 lock_sock(sk); 399 400 rc = -ENOTCONN; 401 if (sock_flag(sk, SOCK_DEAD)) 402 goto out; 403 404 /* Get and verify the address. */ 405 if (msg->msg_name) { 406 struct sockaddr_l2tpip *lip = (struct sockaddr_l2tpip *) msg->msg_name; 407 rc = -EINVAL; 408 if (msg->msg_namelen < sizeof(*lip)) 409 goto out; 410 411 if (lip->l2tp_family != AF_INET) { 412 rc = -EAFNOSUPPORT; 413 if (lip->l2tp_family != AF_UNSPEC) 414 goto out; 415 } 416 417 daddr = lip->l2tp_addr.s_addr; 418 } else { 419 rc = -EDESTADDRREQ; 420 if (sk->sk_state != TCP_ESTABLISHED) 421 goto out; 422 423 daddr = inet->inet_daddr; 424 connected = 1; 425 } 426 427 /* Allocate a socket buffer */ 428 rc = -ENOMEM; 429 skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) + 430 4 + len, 0, GFP_KERNEL); 431 if (!skb) 432 goto error; 433 434 /* Reserve space for headers, putting IP header on 4-byte boundary. */ 435 skb_reserve(skb, 2 + NET_SKB_PAD); 436 skb_reset_network_header(skb); 437 skb_reserve(skb, sizeof(struct iphdr)); 438 skb_reset_transport_header(skb); 439 440 /* Insert 0 session_id */ 441 *((__be32 *) skb_put(skb, 4)) = 0; 442 443 /* Copy user data into skb */ 444 rc = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len); 445 if (rc < 0) { 446 kfree_skb(skb); 447 goto error; 448 } 449 450 fl4 = &inet->cork.fl.u.ip4; 451 if (connected) 452 rt = (struct rtable *) __sk_dst_check(sk, 0); 453 454 rcu_read_lock(); 455 if (rt == NULL) { 456 const struct ip_options_rcu *inet_opt; 457 458 inet_opt = rcu_dereference(inet->inet_opt); 459 460 /* Use correct destination address if we have options. */ 461 if (inet_opt && inet_opt->opt.srr) 462 daddr = inet_opt->opt.faddr; 463 464 /* If this fails, retransmit mechanism of transport layer will 465 * keep trying until route appears or the connection times 466 * itself out. 467 */ 468 rt = ip_route_output_ports(sock_net(sk), fl4, sk, 469 daddr, inet->inet_saddr, 470 inet->inet_dport, inet->inet_sport, 471 sk->sk_protocol, RT_CONN_FLAGS(sk), 472 sk->sk_bound_dev_if); 473 if (IS_ERR(rt)) 474 goto no_route; 475 if (connected) { 476 sk_setup_caps(sk, &rt->dst); 477 } else { 478 skb_dst_set(skb, &rt->dst); 479 goto xmit; 480 } 481 } 482 483 /* We dont need to clone dst here, it is guaranteed to not disappear. 484 * __dev_xmit_skb() might force a refcount if needed. 485 */ 486 skb_dst_set_noref(skb, &rt->dst); 487 488 xmit: 489 /* Queue the packet to IP for output */ 490 rc = ip_queue_xmit(skb, &inet->cork.fl); 491 rcu_read_unlock(); 492 493 error: 494 if (rc >= 0) 495 rc = len; 496 497 out: 498 release_sock(sk); 499 return rc; 500 501 no_route: 502 rcu_read_unlock(); 503 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES); 504 kfree_skb(skb); 505 rc = -EHOSTUNREACH; 506 goto out; 507 } 508 509 static int l2tp_ip_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, 510 size_t len, int noblock, int flags, int *addr_len) 511 { 512 struct inet_sock *inet = inet_sk(sk); 513 size_t copied = 0; 514 int err = -EOPNOTSUPP; 515 struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name; 516 struct sk_buff *skb; 517 518 if (flags & MSG_OOB) 519 goto out; 520 521 if (addr_len) 522 *addr_len = sizeof(*sin); 523 524 skb = skb_recv_datagram(sk, flags, noblock, &err); 525 if (!skb) 526 goto out; 527 528 copied = skb->len; 529 if (len < copied) { 530 msg->msg_flags |= MSG_TRUNC; 531 copied = len; 532 } 533 534 err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied); 535 if (err) 536 goto done; 537 538 sock_recv_timestamp(msg, sk, skb); 539 540 /* Copy the address. */ 541 if (sin) { 542 sin->sin_family = AF_INET; 543 sin->sin_addr.s_addr = ip_hdr(skb)->saddr; 544 sin->sin_port = 0; 545 memset(&sin->sin_zero, 0, sizeof(sin->sin_zero)); 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 .no_check = 0, 612 }; 613 614 static struct net_protocol l2tp_ip_protocol __read_mostly = { 615 .handler = l2tp_ip_recv, 616 .netns_ok = 1, 617 }; 618 619 static int __init l2tp_ip_init(void) 620 { 621 int err; 622 623 pr_info("L2TP IP encapsulation support (L2TPv3)\n"); 624 625 err = proto_register(&l2tp_ip_prot, 1); 626 if (err != 0) 627 goto out; 628 629 err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 630 if (err) 631 goto out1; 632 633 inet_register_protosw(&l2tp_ip_protosw); 634 return 0; 635 636 out1: 637 proto_unregister(&l2tp_ip_prot); 638 out: 639 return err; 640 } 641 642 static void __exit l2tp_ip_exit(void) 643 { 644 inet_unregister_protosw(&l2tp_ip_protosw); 645 inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 646 proto_unregister(&l2tp_ip_prot); 647 } 648 649 module_init(l2tp_ip_init); 650 module_exit(l2tp_ip_exit); 651 652 MODULE_LICENSE("GPL"); 653 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>"); 654 MODULE_DESCRIPTION("L2TP over IP"); 655 MODULE_VERSION("1.0"); 656 657 /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like 658 * enums 659 */ 660 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP); 661