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 hlist_node *node; 53 struct sock *sk; 54 55 sk_for_each_bound(sk, node, &l2tp_ip_bind_table) { 56 struct inet_sock *inet = inet_sk(sk); 57 struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk); 58 59 if (l2tp == NULL) 60 continue; 61 62 if ((l2tp->conn_id == tunnel_id) && 63 net_eq(sock_net(sk), net) && 64 !(inet->inet_rcv_saddr && inet->inet_rcv_saddr != laddr) && 65 !(sk->sk_bound_dev_if && 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 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(&init_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(&init_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(&init_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; 231 232 while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL) 233 kfree_skb(skb); 234 235 sk_refcnt_debug_dec(sk); 236 } 237 238 static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len) 239 { 240 struct inet_sock *inet = inet_sk(sk); 241 struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr; 242 int ret; 243 int chk_addr_ret; 244 245 if (!sock_flag(sk, SOCK_ZAPPED)) 246 return -EINVAL; 247 if (addr_len < sizeof(struct sockaddr_l2tpip)) 248 return -EINVAL; 249 if (addr->l2tp_family != AF_INET) 250 return -EINVAL; 251 252 ret = -EADDRINUSE; 253 read_lock_bh(&l2tp_ip_lock); 254 if (__l2tp_ip_bind_lookup(&init_net, addr->l2tp_addr.s_addr, sk->sk_bound_dev_if, addr->l2tp_conn_id)) 255 goto out_in_use; 256 257 read_unlock_bh(&l2tp_ip_lock); 258 259 lock_sock(sk); 260 if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip)) 261 goto out; 262 263 chk_addr_ret = inet_addr_type(&init_net, addr->l2tp_addr.s_addr); 264 ret = -EADDRNOTAVAIL; 265 if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL && 266 chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST) 267 goto out; 268 269 if (addr->l2tp_addr.s_addr) 270 inet->inet_rcv_saddr = inet->inet_saddr = addr->l2tp_addr.s_addr; 271 if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST) 272 inet->inet_saddr = 0; /* Use device */ 273 sk_dst_reset(sk); 274 275 l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id; 276 277 write_lock_bh(&l2tp_ip_lock); 278 sk_add_bind_node(sk, &l2tp_ip_bind_table); 279 sk_del_node_init(sk); 280 write_unlock_bh(&l2tp_ip_lock); 281 ret = 0; 282 sock_reset_flag(sk, SOCK_ZAPPED); 283 284 out: 285 release_sock(sk); 286 287 return ret; 288 289 out_in_use: 290 read_unlock_bh(&l2tp_ip_lock); 291 292 return ret; 293 } 294 295 static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) 296 { 297 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr; 298 int rc; 299 300 if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */ 301 return -EINVAL; 302 303 if (addr_len < sizeof(*lsa)) 304 return -EINVAL; 305 306 if (ipv4_is_multicast(lsa->l2tp_addr.s_addr)) 307 return -EINVAL; 308 309 rc = ip4_datagram_connect(sk, uaddr, addr_len); 310 if (rc < 0) 311 return rc; 312 313 lock_sock(sk); 314 315 l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id; 316 317 write_lock_bh(&l2tp_ip_lock); 318 hlist_del_init(&sk->sk_bind_node); 319 sk_add_bind_node(sk, &l2tp_ip_bind_table); 320 write_unlock_bh(&l2tp_ip_lock); 321 322 release_sock(sk); 323 return rc; 324 } 325 326 static int l2tp_ip_disconnect(struct sock *sk, int flags) 327 { 328 if (sock_flag(sk, SOCK_ZAPPED)) 329 return 0; 330 331 return udp_disconnect(sk, flags); 332 } 333 334 static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr, 335 int *uaddr_len, int peer) 336 { 337 struct sock *sk = sock->sk; 338 struct inet_sock *inet = inet_sk(sk); 339 struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk); 340 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr; 341 342 memset(lsa, 0, sizeof(*lsa)); 343 lsa->l2tp_family = AF_INET; 344 if (peer) { 345 if (!inet->inet_dport) 346 return -ENOTCONN; 347 lsa->l2tp_conn_id = lsk->peer_conn_id; 348 lsa->l2tp_addr.s_addr = inet->inet_daddr; 349 } else { 350 __be32 addr = inet->inet_rcv_saddr; 351 if (!addr) 352 addr = inet->inet_saddr; 353 lsa->l2tp_conn_id = lsk->conn_id; 354 lsa->l2tp_addr.s_addr = addr; 355 } 356 *uaddr_len = sizeof(*lsa); 357 return 0; 358 } 359 360 static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb) 361 { 362 int rc; 363 364 /* Charge it to the socket, dropping if the queue is full. */ 365 rc = sock_queue_rcv_skb(sk, skb); 366 if (rc < 0) 367 goto drop; 368 369 return 0; 370 371 drop: 372 IP_INC_STATS(&init_net, IPSTATS_MIB_INDISCARDS); 373 kfree_skb(skb); 374 return -1; 375 } 376 377 /* Userspace will call sendmsg() on the tunnel socket to send L2TP 378 * control frames. 379 */ 380 static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, size_t len) 381 { 382 struct sk_buff *skb; 383 int rc; 384 struct inet_sock *inet = inet_sk(sk); 385 struct rtable *rt = NULL; 386 struct flowi4 *fl4; 387 int connected = 0; 388 __be32 daddr; 389 390 lock_sock(sk); 391 392 rc = -ENOTCONN; 393 if (sock_flag(sk, SOCK_DEAD)) 394 goto out; 395 396 /* Get and verify the address. */ 397 if (msg->msg_name) { 398 struct sockaddr_l2tpip *lip = (struct sockaddr_l2tpip *) msg->msg_name; 399 rc = -EINVAL; 400 if (msg->msg_namelen < sizeof(*lip)) 401 goto out; 402 403 if (lip->l2tp_family != AF_INET) { 404 rc = -EAFNOSUPPORT; 405 if (lip->l2tp_family != AF_UNSPEC) 406 goto out; 407 } 408 409 daddr = lip->l2tp_addr.s_addr; 410 } else { 411 rc = -EDESTADDRREQ; 412 if (sk->sk_state != TCP_ESTABLISHED) 413 goto out; 414 415 daddr = inet->inet_daddr; 416 connected = 1; 417 } 418 419 /* Allocate a socket buffer */ 420 rc = -ENOMEM; 421 skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) + 422 4 + len, 0, GFP_KERNEL); 423 if (!skb) 424 goto error; 425 426 /* Reserve space for headers, putting IP header on 4-byte boundary. */ 427 skb_reserve(skb, 2 + NET_SKB_PAD); 428 skb_reset_network_header(skb); 429 skb_reserve(skb, sizeof(struct iphdr)); 430 skb_reset_transport_header(skb); 431 432 /* Insert 0 session_id */ 433 *((__be32 *) skb_put(skb, 4)) = 0; 434 435 /* Copy user data into skb */ 436 rc = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len); 437 if (rc < 0) { 438 kfree_skb(skb); 439 goto error; 440 } 441 442 fl4 = &inet->cork.fl.u.ip4; 443 if (connected) 444 rt = (struct rtable *) __sk_dst_check(sk, 0); 445 446 rcu_read_lock(); 447 if (rt == NULL) { 448 const struct ip_options_rcu *inet_opt; 449 450 inet_opt = rcu_dereference(inet->inet_opt); 451 452 /* Use correct destination address if we have options. */ 453 if (inet_opt && inet_opt->opt.srr) 454 daddr = inet_opt->opt.faddr; 455 456 /* If this fails, retransmit mechanism of transport layer will 457 * keep trying until route appears or the connection times 458 * itself out. 459 */ 460 rt = ip_route_output_ports(sock_net(sk), fl4, sk, 461 daddr, inet->inet_saddr, 462 inet->inet_dport, inet->inet_sport, 463 sk->sk_protocol, RT_CONN_FLAGS(sk), 464 sk->sk_bound_dev_if); 465 if (IS_ERR(rt)) 466 goto no_route; 467 if (connected) { 468 sk_setup_caps(sk, &rt->dst); 469 } else { 470 skb_dst_set(skb, &rt->dst); 471 goto xmit; 472 } 473 } 474 475 /* We dont need to clone dst here, it is guaranteed to not disappear. 476 * __dev_xmit_skb() might force a refcount if needed. 477 */ 478 skb_dst_set_noref(skb, &rt->dst); 479 480 xmit: 481 /* Queue the packet to IP for output */ 482 rc = ip_queue_xmit(skb, &inet->cork.fl); 483 rcu_read_unlock(); 484 485 error: 486 if (rc >= 0) 487 rc = len; 488 489 out: 490 release_sock(sk); 491 return rc; 492 493 no_route: 494 rcu_read_unlock(); 495 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES); 496 kfree_skb(skb); 497 rc = -EHOSTUNREACH; 498 goto out; 499 } 500 501 static int l2tp_ip_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, 502 size_t len, int noblock, int flags, int *addr_len) 503 { 504 struct inet_sock *inet = inet_sk(sk); 505 size_t copied = 0; 506 int err = -EOPNOTSUPP; 507 struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name; 508 struct sk_buff *skb; 509 510 if (flags & MSG_OOB) 511 goto out; 512 513 if (addr_len) 514 *addr_len = sizeof(*sin); 515 516 skb = skb_recv_datagram(sk, flags, noblock, &err); 517 if (!skb) 518 goto out; 519 520 copied = skb->len; 521 if (len < copied) { 522 msg->msg_flags |= MSG_TRUNC; 523 copied = len; 524 } 525 526 err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied); 527 if (err) 528 goto done; 529 530 sock_recv_timestamp(msg, sk, skb); 531 532 /* Copy the address. */ 533 if (sin) { 534 sin->sin_family = AF_INET; 535 sin->sin_addr.s_addr = ip_hdr(skb)->saddr; 536 sin->sin_port = 0; 537 memset(&sin->sin_zero, 0, sizeof(sin->sin_zero)); 538 } 539 if (inet->cmsg_flags) 540 ip_cmsg_recv(msg, skb); 541 if (flags & MSG_TRUNC) 542 copied = skb->len; 543 done: 544 skb_free_datagram(sk, skb); 545 out: 546 return err ? err : copied; 547 } 548 549 static struct proto l2tp_ip_prot = { 550 .name = "L2TP/IP", 551 .owner = THIS_MODULE, 552 .init = l2tp_ip_open, 553 .close = l2tp_ip_close, 554 .bind = l2tp_ip_bind, 555 .connect = l2tp_ip_connect, 556 .disconnect = l2tp_ip_disconnect, 557 .ioctl = udp_ioctl, 558 .destroy = l2tp_ip_destroy_sock, 559 .setsockopt = ip_setsockopt, 560 .getsockopt = ip_getsockopt, 561 .sendmsg = l2tp_ip_sendmsg, 562 .recvmsg = l2tp_ip_recvmsg, 563 .backlog_rcv = l2tp_ip_backlog_recv, 564 .hash = inet_hash, 565 .unhash = inet_unhash, 566 .obj_size = sizeof(struct l2tp_ip_sock), 567 #ifdef CONFIG_COMPAT 568 .compat_setsockopt = compat_ip_setsockopt, 569 .compat_getsockopt = compat_ip_getsockopt, 570 #endif 571 }; 572 573 static const struct proto_ops l2tp_ip_ops = { 574 .family = PF_INET, 575 .owner = THIS_MODULE, 576 .release = inet_release, 577 .bind = inet_bind, 578 .connect = inet_dgram_connect, 579 .socketpair = sock_no_socketpair, 580 .accept = sock_no_accept, 581 .getname = l2tp_ip_getname, 582 .poll = datagram_poll, 583 .ioctl = inet_ioctl, 584 .listen = sock_no_listen, 585 .shutdown = inet_shutdown, 586 .setsockopt = sock_common_setsockopt, 587 .getsockopt = sock_common_getsockopt, 588 .sendmsg = inet_sendmsg, 589 .recvmsg = sock_common_recvmsg, 590 .mmap = sock_no_mmap, 591 .sendpage = sock_no_sendpage, 592 #ifdef CONFIG_COMPAT 593 .compat_setsockopt = compat_sock_common_setsockopt, 594 .compat_getsockopt = compat_sock_common_getsockopt, 595 #endif 596 }; 597 598 static struct inet_protosw l2tp_ip_protosw = { 599 .type = SOCK_DGRAM, 600 .protocol = IPPROTO_L2TP, 601 .prot = &l2tp_ip_prot, 602 .ops = &l2tp_ip_ops, 603 .no_check = 0, 604 }; 605 606 static struct net_protocol l2tp_ip_protocol __read_mostly = { 607 .handler = l2tp_ip_recv, 608 }; 609 610 static int __init l2tp_ip_init(void) 611 { 612 int err; 613 614 pr_info("L2TP IP encapsulation support (L2TPv3)\n"); 615 616 err = proto_register(&l2tp_ip_prot, 1); 617 if (err != 0) 618 goto out; 619 620 err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 621 if (err) 622 goto out1; 623 624 inet_register_protosw(&l2tp_ip_protosw); 625 return 0; 626 627 out1: 628 proto_unregister(&l2tp_ip_prot); 629 out: 630 return err; 631 } 632 633 static void __exit l2tp_ip_exit(void) 634 { 635 inet_unregister_protosw(&l2tp_ip_protosw); 636 inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP); 637 proto_unregister(&l2tp_ip_prot); 638 } 639 640 module_init(l2tp_ip_init); 641 module_exit(l2tp_ip_exit); 642 643 MODULE_LICENSE("GPL"); 644 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>"); 645 MODULE_DESCRIPTION("L2TP over IP"); 646 MODULE_VERSION("1.0"); 647 648 /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like 649 * enums 650 */ 651 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP); 652