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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
33struct 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
41static DEFINE_RWLOCK(l2tp_ip_lock);
42static struct hlist_head l2tp_ip_table;
43static struct hlist_head l2tp_ip_bind_table;
44
45static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk)
46{
47 return (struct l2tp_ip_sock *)sk;
48}
49
50static 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;
69found:
70 return sk;
71}
72
73static 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 */
115static 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
169pass_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
201discard_put:
202 sock_put(sk);
203
204discard:
205 kfree_skb(skb);
206 return 0;
207}
208
209static 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
221static 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
230static 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
246static 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
294out:
295 release_sock(sk);
296
297 return ret;
298
299out_in_use:
300 read_unlock_bh(&l2tp_ip_lock);
301
302 return ret;
303}
304
305static 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
336static 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
344static 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
370static 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
381drop:
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 */
390static 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
490xmit:
491 /* Queue the packet to IP for output */
492 rc = ip_queue_xmit(sk, skb, &inet->cork.fl);
493 rcu_read_unlock();
494
495error:
496 if (rc >= 0)
497 rc = len;
498
499out:
500 release_sock(sk);
501 return rc;
502
503no_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
511static 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;
551done:
552 skb_free_datagram(sk, skb);
553out:
554 return err ? err : copied;
555}
556
557static 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
581static 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
606static 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
613static struct net_protocol l2tp_ip_protocol __read_mostly = {
614 .handler = l2tp_ip_recv,
615 .netns_ok = 1,
616};
617
618static 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
635out1:
636 proto_unregister(&l2tp_ip_prot);
637out:
638 return err;
639}
640
641static 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
648module_init(l2tp_ip_init);
649module_exit(l2tp_ip_exit);
650
651MODULE_LICENSE("GPL");
652MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
653MODULE_DESCRIPTION("L2TP over IP");
654MODULE_VERSION("1.0");
655
656/* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
657 * enums
658 */
659MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP);
660MODULE_ALIAS_NET_PF_PROTO(PF_INET, IPPROTO_L2TP);
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
33struct 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
41static DEFINE_RWLOCK(l2tp_ip_lock);
42static struct hlist_head l2tp_ip_table;
43static struct hlist_head l2tp_ip_bind_table;
44
45static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk)
46{
47 return (struct l2tp_ip_sock *)sk;
48}
49
50static 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;
70found:
71 return sk;
72}
73
74static 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 */
116static 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
167pass_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
199discard_put:
200 sock_put(sk);
201
202discard:
203 kfree_skb(skb);
204 return 0;
205}
206
207static 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
219static 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
228static 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
238static 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
284out:
285 release_sock(sk);
286
287 return ret;
288
289out_in_use:
290 read_unlock_bh(&l2tp_ip_lock);
291
292 return ret;
293}
294
295static 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
326static 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
334static 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
360static 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
371drop:
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 */
380static 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
480xmit:
481 /* Queue the packet to IP for output */
482 rc = ip_queue_xmit(skb, &inet->cork.fl);
483 rcu_read_unlock();
484
485error:
486 if (rc >= 0)
487 rc = len;
488
489out:
490 release_sock(sk);
491 return rc;
492
493no_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
501static 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;
543done:
544 skb_free_datagram(sk, skb);
545out:
546 return err ? err : copied;
547}
548
549static 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
573static 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
598static 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
606static struct net_protocol l2tp_ip_protocol __read_mostly = {
607 .handler = l2tp_ip_recv,
608};
609
610static 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
627out1:
628 proto_unregister(&l2tp_ip_prot);
629out:
630 return err;
631}
632
633static 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
640module_init(l2tp_ip_init);
641module_exit(l2tp_ip_exit);
642
643MODULE_LICENSE("GPL");
644MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
645MODULE_DESCRIPTION("L2TP over IP");
646MODULE_VERSION("1.0");
647
648/* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
649 * enums
650 */
651MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP);