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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* L2TPv3 IP encapsulation support
3 *
4 * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
5 */
6
7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9#include <asm/ioctls.h>
10#include <linux/icmp.h>
11#include <linux/module.h>
12#include <linux/skbuff.h>
13#include <linux/random.h>
14#include <linux/socket.h>
15#include <linux/l2tp.h>
16#include <linux/in.h>
17#include <net/sock.h>
18#include <net/ip.h>
19#include <net/icmp.h>
20#include <net/udp.h>
21#include <net/inet_common.h>
22#include <net/tcp_states.h>
23#include <net/protocol.h>
24#include <net/xfrm.h>
25
26#include "l2tp_core.h"
27
28struct l2tp_ip_sock {
29 /* inet_sock has to be the first member of l2tp_ip_sock */
30 struct inet_sock inet;
31
32 u32 conn_id;
33 u32 peer_conn_id;
34};
35
36static DEFINE_RWLOCK(l2tp_ip_lock);
37static struct hlist_head l2tp_ip_table;
38static struct hlist_head l2tp_ip_bind_table;
39
40static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk)
41{
42 return (struct l2tp_ip_sock *)sk;
43}
44
45static struct sock *__l2tp_ip_bind_lookup(const struct net *net, __be32 laddr,
46 __be32 raddr, int dif, u32 tunnel_id)
47{
48 struct sock *sk;
49
50 sk_for_each_bound(sk, &l2tp_ip_bind_table) {
51 const struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk);
52 const struct inet_sock *inet = inet_sk(sk);
53 int bound_dev_if;
54
55 if (!net_eq(sock_net(sk), net))
56 continue;
57
58 bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
59 if (bound_dev_if && dif && bound_dev_if != dif)
60 continue;
61
62 if (inet->inet_rcv_saddr && laddr &&
63 inet->inet_rcv_saddr != laddr)
64 continue;
65
66 if (inet->inet_daddr && raddr && inet->inet_daddr != raddr)
67 continue;
68
69 if (l2tp->conn_id != tunnel_id)
70 continue;
71
72 goto found;
73 }
74
75 sk = NULL;
76found:
77 return sk;
78}
79
80/* When processing receive frames, there are two cases to
81 * consider. Data frames consist of a non-zero session-id and an
82 * optional cookie. Control frames consist of a regular L2TP header
83 * preceded by 32-bits of zeros.
84 *
85 * L2TPv3 Session Header Over IP
86 *
87 * 0 1 2 3
88 * 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
89 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
90 * | Session ID |
91 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
92 * | Cookie (optional, maximum 64 bits)...
93 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
94 * |
95 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
96 *
97 * L2TPv3 Control Message Header Over IP
98 *
99 * 0 1 2 3
100 * 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
101 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
102 * | (32 bits of zeros) |
103 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
104 * |T|L|x|x|S|x|x|x|x|x|x|x| Ver | Length |
105 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
106 * | Control Connection ID |
107 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
108 * | Ns | Nr |
109 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
110 *
111 * All control frames are passed to userspace.
112 */
113static int l2tp_ip_recv(struct sk_buff *skb)
114{
115 struct net *net = dev_net(skb->dev);
116 struct sock *sk;
117 u32 session_id;
118 u32 tunnel_id;
119 unsigned char *ptr, *optr;
120 struct l2tp_session *session;
121 struct l2tp_tunnel *tunnel = NULL;
122 struct iphdr *iph;
123
124 if (!pskb_may_pull(skb, 4))
125 goto discard;
126
127 /* Point to L2TP header */
128 optr = skb->data;
129 ptr = skb->data;
130 session_id = ntohl(*((__be32 *)ptr));
131 ptr += 4;
132
133 /* RFC3931: L2TP/IP packets have the first 4 bytes containing
134 * the session_id. If it is 0, the packet is a L2TP control
135 * frame and the session_id value can be discarded.
136 */
137 if (session_id == 0) {
138 __skb_pull(skb, 4);
139 goto pass_up;
140 }
141
142 /* Ok, this is a data packet. Lookup the session. */
143 session = l2tp_session_get(net, session_id);
144 if (!session)
145 goto discard;
146
147 tunnel = session->tunnel;
148 if (!tunnel)
149 goto discard_sess;
150
151 if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
152 goto discard_sess;
153
154 l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
155 l2tp_session_dec_refcount(session);
156
157 return 0;
158
159pass_up:
160 /* Get the tunnel_id from the L2TP header */
161 if (!pskb_may_pull(skb, 12))
162 goto discard;
163
164 if ((skb->data[0] & 0xc0) != 0xc0)
165 goto discard;
166
167 tunnel_id = ntohl(*(__be32 *)&skb->data[4]);
168 iph = (struct iphdr *)skb_network_header(skb);
169
170 read_lock_bh(&l2tp_ip_lock);
171 sk = __l2tp_ip_bind_lookup(net, iph->daddr, iph->saddr, inet_iif(skb),
172 tunnel_id);
173 if (!sk) {
174 read_unlock_bh(&l2tp_ip_lock);
175 goto discard;
176 }
177 sock_hold(sk);
178 read_unlock_bh(&l2tp_ip_lock);
179
180 if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
181 goto discard_put;
182
183 nf_reset_ct(skb);
184
185 return sk_receive_skb(sk, skb, 1);
186
187discard_sess:
188 l2tp_session_dec_refcount(session);
189 goto discard;
190
191discard_put:
192 sock_put(sk);
193
194discard:
195 kfree_skb(skb);
196 return 0;
197}
198
199static int l2tp_ip_hash(struct sock *sk)
200{
201 if (sk_unhashed(sk)) {
202 write_lock_bh(&l2tp_ip_lock);
203 sk_add_node(sk, &l2tp_ip_table);
204 write_unlock_bh(&l2tp_ip_lock);
205 }
206 return 0;
207}
208
209static void l2tp_ip_unhash(struct sock *sk)
210{
211 if (sk_unhashed(sk))
212 return;
213 write_lock_bh(&l2tp_ip_lock);
214 sk_del_node_init(sk);
215 write_unlock_bh(&l2tp_ip_lock);
216}
217
218static int l2tp_ip_open(struct sock *sk)
219{
220 /* Prevent autobind. We don't have ports. */
221 inet_sk(sk)->inet_num = IPPROTO_L2TP;
222
223 l2tp_ip_hash(sk);
224 return 0;
225}
226
227static void l2tp_ip_close(struct sock *sk, long timeout)
228{
229 write_lock_bh(&l2tp_ip_lock);
230 hlist_del_init(&sk->sk_bind_node);
231 sk_del_node_init(sk);
232 write_unlock_bh(&l2tp_ip_lock);
233 sk_common_release(sk);
234}
235
236static void l2tp_ip_destroy_sock(struct sock *sk)
237{
238 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
239 struct sk_buff *skb;
240
241 while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
242 kfree_skb(skb);
243
244 if (tunnel)
245 l2tp_tunnel_delete(tunnel);
246}
247
248static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
249{
250 struct inet_sock *inet = inet_sk(sk);
251 struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *)uaddr;
252 struct net *net = sock_net(sk);
253 int ret;
254 int chk_addr_ret;
255
256 if (addr_len < sizeof(struct sockaddr_l2tpip))
257 return -EINVAL;
258 if (addr->l2tp_family != AF_INET)
259 return -EINVAL;
260
261 lock_sock(sk);
262
263 ret = -EINVAL;
264 if (!sock_flag(sk, SOCK_ZAPPED))
265 goto out;
266
267 if (sk->sk_state != TCP_CLOSE)
268 goto out;
269
270 chk_addr_ret = inet_addr_type(net, addr->l2tp_addr.s_addr);
271 ret = -EADDRNOTAVAIL;
272 if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL &&
273 chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST)
274 goto out;
275
276 if (addr->l2tp_addr.s_addr) {
277 inet->inet_rcv_saddr = addr->l2tp_addr.s_addr;
278 inet->inet_saddr = addr->l2tp_addr.s_addr;
279 }
280 if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST)
281 inet->inet_saddr = 0; /* Use device */
282
283 write_lock_bh(&l2tp_ip_lock);
284 if (__l2tp_ip_bind_lookup(net, addr->l2tp_addr.s_addr, 0,
285 sk->sk_bound_dev_if, addr->l2tp_conn_id)) {
286 write_unlock_bh(&l2tp_ip_lock);
287 ret = -EADDRINUSE;
288 goto out;
289 }
290
291 sk_dst_reset(sk);
292 l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id;
293
294 sk_add_bind_node(sk, &l2tp_ip_bind_table);
295 sk_del_node_init(sk);
296 write_unlock_bh(&l2tp_ip_lock);
297
298 ret = 0;
299 sock_reset_flag(sk, SOCK_ZAPPED);
300
301out:
302 release_sock(sk);
303
304 return ret;
305}
306
307static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
308{
309 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr;
310 int rc;
311
312 if (addr_len < sizeof(*lsa))
313 return -EINVAL;
314
315 if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
316 return -EINVAL;
317
318 lock_sock(sk);
319
320 /* Must bind first - autobinding does not work */
321 if (sock_flag(sk, SOCK_ZAPPED)) {
322 rc = -EINVAL;
323 goto out_sk;
324 }
325
326 rc = __ip4_datagram_connect(sk, uaddr, addr_len);
327 if (rc < 0)
328 goto out_sk;
329
330 l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
331
332 write_lock_bh(&l2tp_ip_lock);
333 hlist_del_init(&sk->sk_bind_node);
334 sk_add_bind_node(sk, &l2tp_ip_bind_table);
335 write_unlock_bh(&l2tp_ip_lock);
336
337out_sk:
338 release_sock(sk);
339
340 return rc;
341}
342
343static int l2tp_ip_disconnect(struct sock *sk, int flags)
344{
345 if (sock_flag(sk, SOCK_ZAPPED))
346 return 0;
347
348 return __udp_disconnect(sk, flags);
349}
350
351static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr,
352 int peer)
353{
354 struct sock *sk = sock->sk;
355 struct inet_sock *inet = inet_sk(sk);
356 struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk);
357 struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr;
358
359 memset(lsa, 0, sizeof(*lsa));
360 lsa->l2tp_family = AF_INET;
361 if (peer) {
362 if (!inet->inet_dport)
363 return -ENOTCONN;
364 lsa->l2tp_conn_id = lsk->peer_conn_id;
365 lsa->l2tp_addr.s_addr = inet->inet_daddr;
366 } else {
367 __be32 addr = inet->inet_rcv_saddr;
368
369 if (!addr)
370 addr = inet->inet_saddr;
371 lsa->l2tp_conn_id = lsk->conn_id;
372 lsa->l2tp_addr.s_addr = addr;
373 }
374 return sizeof(*lsa);
375}
376
377static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb)
378{
379 int rc;
380
381 /* Charge it to the socket, dropping if the queue is full. */
382 rc = sock_queue_rcv_skb(sk, skb);
383 if (rc < 0)
384 goto drop;
385
386 return 0;
387
388drop:
389 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS);
390 kfree_skb(skb);
391 return 0;
392}
393
394/* Userspace will call sendmsg() on the tunnel socket to send L2TP
395 * control frames.
396 */
397static int l2tp_ip_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
398{
399 struct sk_buff *skb;
400 int rc;
401 struct inet_sock *inet = inet_sk(sk);
402 struct rtable *rt = NULL;
403 struct flowi4 *fl4;
404 int connected = 0;
405 __be32 daddr;
406
407 lock_sock(sk);
408
409 rc = -ENOTCONN;
410 if (sock_flag(sk, SOCK_DEAD))
411 goto out;
412
413 /* Get and verify the address. */
414 if (msg->msg_name) {
415 DECLARE_SOCKADDR(struct sockaddr_l2tpip *, lip, msg->msg_name);
416
417 rc = -EINVAL;
418 if (msg->msg_namelen < sizeof(*lip))
419 goto out;
420
421 if (lip->l2tp_family != AF_INET) {
422 rc = -EAFNOSUPPORT;
423 if (lip->l2tp_family != AF_UNSPEC)
424 goto out;
425 }
426
427 daddr = lip->l2tp_addr.s_addr;
428 } else {
429 rc = -EDESTADDRREQ;
430 if (sk->sk_state != TCP_ESTABLISHED)
431 goto out;
432
433 daddr = inet->inet_daddr;
434 connected = 1;
435 }
436
437 /* Allocate a socket buffer */
438 rc = -ENOMEM;
439 skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) +
440 4 + len, 0, GFP_KERNEL);
441 if (!skb)
442 goto error;
443
444 /* Reserve space for headers, putting IP header on 4-byte boundary. */
445 skb_reserve(skb, 2 + NET_SKB_PAD);
446 skb_reset_network_header(skb);
447 skb_reserve(skb, sizeof(struct iphdr));
448 skb_reset_transport_header(skb);
449
450 /* Insert 0 session_id */
451 *((__be32 *)skb_put(skb, 4)) = 0;
452
453 /* Copy user data into skb */
454 rc = memcpy_from_msg(skb_put(skb, len), msg, len);
455 if (rc < 0) {
456 kfree_skb(skb);
457 goto error;
458 }
459
460 fl4 = &inet->cork.fl.u.ip4;
461 if (connected)
462 rt = (struct rtable *)__sk_dst_check(sk, 0);
463
464 rcu_read_lock();
465 if (!rt) {
466 const struct ip_options_rcu *inet_opt;
467
468 inet_opt = rcu_dereference(inet->inet_opt);
469
470 /* Use correct destination address if we have options. */
471 if (inet_opt && inet_opt->opt.srr)
472 daddr = inet_opt->opt.faddr;
473
474 /* If this fails, retransmit mechanism of transport layer will
475 * keep trying until route appears or the connection times
476 * itself out.
477 */
478 rt = ip_route_output_ports(sock_net(sk), fl4, sk,
479 daddr, inet->inet_saddr,
480 inet->inet_dport, inet->inet_sport,
481 sk->sk_protocol, RT_CONN_FLAGS(sk),
482 sk->sk_bound_dev_if);
483 if (IS_ERR(rt))
484 goto no_route;
485 if (connected) {
486 sk_setup_caps(sk, &rt->dst);
487 } else {
488 skb_dst_set(skb, &rt->dst);
489 goto xmit;
490 }
491 }
492
493 /* We don't need to clone dst here, it is guaranteed to not disappear.
494 * __dev_xmit_skb() might force a refcount if needed.
495 */
496 skb_dst_set_noref(skb, &rt->dst);
497
498xmit:
499 /* Queue the packet to IP for output */
500 rc = ip_queue_xmit(sk, skb, &inet->cork.fl);
501 rcu_read_unlock();
502
503error:
504 if (rc >= 0)
505 rc = len;
506
507out:
508 release_sock(sk);
509 return rc;
510
511no_route:
512 rcu_read_unlock();
513 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
514 kfree_skb(skb);
515 rc = -EHOSTUNREACH;
516 goto out;
517}
518
519static int l2tp_ip_recvmsg(struct sock *sk, struct msghdr *msg,
520 size_t len, int flags, int *addr_len)
521{
522 struct inet_sock *inet = inet_sk(sk);
523 size_t copied = 0;
524 int err = -EOPNOTSUPP;
525 DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
526 struct sk_buff *skb;
527
528 if (flags & MSG_OOB)
529 goto out;
530
531 skb = skb_recv_datagram(sk, flags, &err);
532 if (!skb)
533 goto out;
534
535 copied = skb->len;
536 if (len < copied) {
537 msg->msg_flags |= MSG_TRUNC;
538 copied = len;
539 }
540
541 err = skb_copy_datagram_msg(skb, 0, msg, copied);
542 if (err)
543 goto done;
544
545 sock_recv_timestamp(msg, sk, skb);
546
547 /* Copy the address. */
548 if (sin) {
549 sin->sin_family = AF_INET;
550 sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
551 sin->sin_port = 0;
552 memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
553 *addr_len = sizeof(*sin);
554 }
555 if (inet_cmsg_flags(inet))
556 ip_cmsg_recv(msg, skb);
557 if (flags & MSG_TRUNC)
558 copied = skb->len;
559done:
560 skb_free_datagram(sk, skb);
561out:
562 return err ? err : copied;
563}
564
565int l2tp_ioctl(struct sock *sk, int cmd, int *karg)
566{
567 struct sk_buff *skb;
568
569 switch (cmd) {
570 case SIOCOUTQ:
571 *karg = sk_wmem_alloc_get(sk);
572 break;
573 case SIOCINQ:
574 spin_lock_bh(&sk->sk_receive_queue.lock);
575 skb = skb_peek(&sk->sk_receive_queue);
576 *karg = skb ? skb->len : 0;
577 spin_unlock_bh(&sk->sk_receive_queue.lock);
578 break;
579
580 default:
581 return -ENOIOCTLCMD;
582 }
583
584 return 0;
585}
586EXPORT_SYMBOL_GPL(l2tp_ioctl);
587
588static struct proto l2tp_ip_prot = {
589 .name = "L2TP/IP",
590 .owner = THIS_MODULE,
591 .init = l2tp_ip_open,
592 .close = l2tp_ip_close,
593 .bind = l2tp_ip_bind,
594 .connect = l2tp_ip_connect,
595 .disconnect = l2tp_ip_disconnect,
596 .ioctl = l2tp_ioctl,
597 .destroy = l2tp_ip_destroy_sock,
598 .setsockopt = ip_setsockopt,
599 .getsockopt = ip_getsockopt,
600 .sendmsg = l2tp_ip_sendmsg,
601 .recvmsg = l2tp_ip_recvmsg,
602 .backlog_rcv = l2tp_ip_backlog_recv,
603 .hash = l2tp_ip_hash,
604 .unhash = l2tp_ip_unhash,
605 .obj_size = sizeof(struct l2tp_ip_sock),
606};
607
608static const struct proto_ops l2tp_ip_ops = {
609 .family = PF_INET,
610 .owner = THIS_MODULE,
611 .release = inet_release,
612 .bind = inet_bind,
613 .connect = inet_dgram_connect,
614 .socketpair = sock_no_socketpair,
615 .accept = sock_no_accept,
616 .getname = l2tp_ip_getname,
617 .poll = datagram_poll,
618 .ioctl = inet_ioctl,
619 .gettstamp = sock_gettstamp,
620 .listen = sock_no_listen,
621 .shutdown = inet_shutdown,
622 .setsockopt = sock_common_setsockopt,
623 .getsockopt = sock_common_getsockopt,
624 .sendmsg = inet_sendmsg,
625 .recvmsg = sock_common_recvmsg,
626 .mmap = sock_no_mmap,
627};
628
629static struct inet_protosw l2tp_ip_protosw = {
630 .type = SOCK_DGRAM,
631 .protocol = IPPROTO_L2TP,
632 .prot = &l2tp_ip_prot,
633 .ops = &l2tp_ip_ops,
634};
635
636static struct net_protocol l2tp_ip_protocol __read_mostly = {
637 .handler = l2tp_ip_recv,
638};
639
640static int __init l2tp_ip_init(void)
641{
642 int err;
643
644 pr_info("L2TP IP encapsulation support (L2TPv3)\n");
645
646 err = proto_register(&l2tp_ip_prot, 1);
647 if (err != 0)
648 goto out;
649
650 err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
651 if (err)
652 goto out1;
653
654 inet_register_protosw(&l2tp_ip_protosw);
655 return 0;
656
657out1:
658 proto_unregister(&l2tp_ip_prot);
659out:
660 return err;
661}
662
663static void __exit l2tp_ip_exit(void)
664{
665 inet_unregister_protosw(&l2tp_ip_protosw);
666 inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
667 proto_unregister(&l2tp_ip_prot);
668}
669
670module_init(l2tp_ip_init);
671module_exit(l2tp_ip_exit);
672
673MODULE_LICENSE("GPL");
674MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
675MODULE_DESCRIPTION("L2TP over IP");
676MODULE_VERSION("1.0");
677
678/* Use the values of SOCK_DGRAM (2) as type and IPPROTO_L2TP (115) as protocol,
679 * because __stringify doesn't like enums
680 */
681MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 115, 2);
682MODULE_ALIAS_NET_PF_PROTO(PF_INET, 115);
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);