1 // SPDX-License-Identifier: GPL-2.0-only
2 /* L2TP core.
3  *
4  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
5  *
6  * This file contains some code of the original L2TPv2 pppol2tp
7  * driver, which has the following copyright:
8  *
9  * Authors:	Martijn van Oosterhout <kleptog@svana.org>
10  *		James Chapman (jchapman@katalix.com)
11  * Contributors:
12  *		Michal Ostrowski <mostrows@speakeasy.net>
13  *		Arnaldo Carvalho de Melo <acme@xconectiva.com.br>
14  *		David S. Miller (davem@redhat.com)
15  */
16 
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 
19 #include <linux/module.h>
20 #include <linux/string.h>
21 #include <linux/list.h>
22 #include <linux/rculist.h>
23 #include <linux/uaccess.h>
24 
25 #include <linux/kernel.h>
26 #include <linux/spinlock.h>
27 #include <linux/kthread.h>
28 #include <linux/sched.h>
29 #include <linux/slab.h>
30 #include <linux/errno.h>
31 #include <linux/jiffies.h>
32 
33 #include <linux/netdevice.h>
34 #include <linux/net.h>
35 #include <linux/inetdevice.h>
36 #include <linux/skbuff.h>
37 #include <linux/init.h>
38 #include <linux/in.h>
39 #include <linux/ip.h>
40 #include <linux/udp.h>
41 #include <linux/l2tp.h>
42 #include <linux/hash.h>
43 #include <linux/sort.h>
44 #include <linux/file.h>
45 #include <linux/nsproxy.h>
46 #include <net/net_namespace.h>
47 #include <net/netns/generic.h>
48 #include <net/dst.h>
49 #include <net/ip.h>
50 #include <net/udp.h>
51 #include <net/udp_tunnel.h>
52 #include <net/inet_common.h>
53 #include <net/xfrm.h>
54 #include <net/protocol.h>
55 #include <net/inet6_connection_sock.h>
56 #include <net/inet_ecn.h>
57 #include <net/ip6_route.h>
58 #include <net/ip6_checksum.h>
59 
60 #include <asm/byteorder.h>
61 #include <linux/atomic.h>
62 
63 #include "l2tp_core.h"
64 #include "trace.h"
65 
66 #define CREATE_TRACE_POINTS
67 #include "trace.h"
68 
69 #define L2TP_DRV_VERSION	"V2.0"
70 
71 /* L2TP header constants */
72 #define L2TP_HDRFLAG_T	   0x8000
73 #define L2TP_HDRFLAG_L	   0x4000
74 #define L2TP_HDRFLAG_S	   0x0800
75 #define L2TP_HDRFLAG_O	   0x0200
76 #define L2TP_HDRFLAG_P	   0x0100
77 
78 #define L2TP_HDR_VER_MASK  0x000F
79 #define L2TP_HDR_VER_2	   0x0002
80 #define L2TP_HDR_VER_3	   0x0003
81 
82 /* L2TPv3 default L2-specific sublayer */
83 #define L2TP_SLFLAG_S	   0x40000000
84 #define L2TP_SL_SEQ_MASK   0x00ffffff
85 
86 #define L2TP_HDR_SIZE_MAX		14
87 
88 /* Default trace flags */
89 #define L2TP_DEFAULT_DEBUG_FLAGS	0
90 
91 /* Private data stored for received packets in the skb.
92  */
93 struct l2tp_skb_cb {
94 	u32			ns;
95 	u16			has_seq;
96 	u16			length;
97 	unsigned long		expires;
98 };
99 
100 #define L2TP_SKB_CB(skb)	((struct l2tp_skb_cb *)&(skb)->cb[sizeof(struct inet_skb_parm)])
101 
102 static struct workqueue_struct *l2tp_wq;
103 
104 /* per-net private data for this module */
105 static unsigned int l2tp_net_id;
106 struct l2tp_net {
107 	struct list_head l2tp_tunnel_list;
108 	/* Lock for write access to l2tp_tunnel_list */
109 	spinlock_t l2tp_tunnel_list_lock;
110 	struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
111 	/* Lock for write access to l2tp_session_hlist */
112 	spinlock_t l2tp_session_hlist_lock;
113 };
114 
115 #if IS_ENABLED(CONFIG_IPV6)
l2tp_sk_is_v6(struct sock * sk)116 static bool l2tp_sk_is_v6(struct sock *sk)
117 {
118 	return sk->sk_family == PF_INET6 &&
119 	       !ipv6_addr_v4mapped(&sk->sk_v6_daddr);
120 }
121 #endif
122 
l2tp_pernet(const struct net * net)123 static inline struct l2tp_net *l2tp_pernet(const struct net *net)
124 {
125 	return net_generic(net, l2tp_net_id);
126 }
127 
128 /* Session hash global list for L2TPv3.
129  * The session_id SHOULD be random according to RFC3931, but several
130  * L2TP implementations use incrementing session_ids.  So we do a real
131  * hash on the session_id, rather than a simple bitmask.
132  */
133 static inline struct hlist_head *
l2tp_session_id_hash_2(struct l2tp_net * pn,u32 session_id)134 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
135 {
136 	return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
137 }
138 
139 /* Session hash list.
140  * The session_id SHOULD be random according to RFC2661, but several
141  * L2TP implementations (Cisco and Microsoft) use incrementing
142  * session_ids.  So we do a real hash on the session_id, rather than a
143  * simple bitmask.
144  */
145 static inline struct hlist_head *
l2tp_session_id_hash(struct l2tp_tunnel * tunnel,u32 session_id)146 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
147 {
148 	return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
149 }
150 
l2tp_tunnel_free(struct l2tp_tunnel * tunnel)151 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
152 {
153 	trace_free_tunnel(tunnel);
154 	sock_put(tunnel->sock);
155 	/* the tunnel is freed in the socket destructor */
156 }
157 
l2tp_session_free(struct l2tp_session * session)158 static void l2tp_session_free(struct l2tp_session *session)
159 {
160 	trace_free_session(session);
161 	if (session->tunnel)
162 		l2tp_tunnel_dec_refcount(session->tunnel);
163 	kfree(session);
164 }
165 
l2tp_sk_to_tunnel(struct sock * sk)166 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk)
167 {
168 	struct l2tp_tunnel *tunnel = sk->sk_user_data;
169 
170 	if (tunnel)
171 		if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
172 			return NULL;
173 
174 	return tunnel;
175 }
176 EXPORT_SYMBOL_GPL(l2tp_sk_to_tunnel);
177 
l2tp_tunnel_inc_refcount(struct l2tp_tunnel * tunnel)178 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel)
179 {
180 	refcount_inc(&tunnel->ref_count);
181 }
182 EXPORT_SYMBOL_GPL(l2tp_tunnel_inc_refcount);
183 
l2tp_tunnel_dec_refcount(struct l2tp_tunnel * tunnel)184 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel)
185 {
186 	if (refcount_dec_and_test(&tunnel->ref_count))
187 		l2tp_tunnel_free(tunnel);
188 }
189 EXPORT_SYMBOL_GPL(l2tp_tunnel_dec_refcount);
190 
l2tp_session_inc_refcount(struct l2tp_session * session)191 void l2tp_session_inc_refcount(struct l2tp_session *session)
192 {
193 	refcount_inc(&session->ref_count);
194 }
195 EXPORT_SYMBOL_GPL(l2tp_session_inc_refcount);
196 
l2tp_session_dec_refcount(struct l2tp_session * session)197 void l2tp_session_dec_refcount(struct l2tp_session *session)
198 {
199 	if (refcount_dec_and_test(&session->ref_count))
200 		l2tp_session_free(session);
201 }
202 EXPORT_SYMBOL_GPL(l2tp_session_dec_refcount);
203 
204 /* Lookup a tunnel. A new reference is held on the returned tunnel. */
l2tp_tunnel_get(const struct net * net,u32 tunnel_id)205 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
206 {
207 	const struct l2tp_net *pn = l2tp_pernet(net);
208 	struct l2tp_tunnel *tunnel;
209 
210 	rcu_read_lock_bh();
211 	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
212 		if (tunnel->tunnel_id == tunnel_id &&
213 		    refcount_inc_not_zero(&tunnel->ref_count)) {
214 			rcu_read_unlock_bh();
215 
216 			return tunnel;
217 		}
218 	}
219 	rcu_read_unlock_bh();
220 
221 	return NULL;
222 }
223 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
224 
l2tp_tunnel_get_nth(const struct net * net,int nth)225 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
226 {
227 	const struct l2tp_net *pn = l2tp_pernet(net);
228 	struct l2tp_tunnel *tunnel;
229 	int count = 0;
230 
231 	rcu_read_lock_bh();
232 	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
233 		if (++count > nth &&
234 		    refcount_inc_not_zero(&tunnel->ref_count)) {
235 			rcu_read_unlock_bh();
236 			return tunnel;
237 		}
238 	}
239 	rcu_read_unlock_bh();
240 
241 	return NULL;
242 }
243 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
244 
l2tp_tunnel_get_session(struct l2tp_tunnel * tunnel,u32 session_id)245 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
246 					     u32 session_id)
247 {
248 	struct hlist_head *session_list;
249 	struct l2tp_session *session;
250 
251 	session_list = l2tp_session_id_hash(tunnel, session_id);
252 
253 	rcu_read_lock_bh();
254 	hlist_for_each_entry_rcu(session, session_list, hlist)
255 		if (session->session_id == session_id) {
256 			l2tp_session_inc_refcount(session);
257 			rcu_read_unlock_bh();
258 
259 			return session;
260 		}
261 	rcu_read_unlock_bh();
262 
263 	return NULL;
264 }
265 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
266 
l2tp_session_get(const struct net * net,u32 session_id)267 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
268 {
269 	struct hlist_head *session_list;
270 	struct l2tp_session *session;
271 
272 	session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
273 
274 	rcu_read_lock_bh();
275 	hlist_for_each_entry_rcu(session, session_list, global_hlist)
276 		if (session->session_id == session_id) {
277 			l2tp_session_inc_refcount(session);
278 			rcu_read_unlock_bh();
279 
280 			return session;
281 		}
282 	rcu_read_unlock_bh();
283 
284 	return NULL;
285 }
286 EXPORT_SYMBOL_GPL(l2tp_session_get);
287 
l2tp_session_get_nth(struct l2tp_tunnel * tunnel,int nth)288 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
289 {
290 	int hash;
291 	struct l2tp_session *session;
292 	int count = 0;
293 
294 	rcu_read_lock_bh();
295 	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
296 		hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
297 			if (++count > nth) {
298 				l2tp_session_inc_refcount(session);
299 				rcu_read_unlock_bh();
300 				return session;
301 			}
302 		}
303 	}
304 
305 	rcu_read_unlock_bh();
306 
307 	return NULL;
308 }
309 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
310 
311 /* Lookup a session by interface name.
312  * This is very inefficient but is only used by management interfaces.
313  */
l2tp_session_get_by_ifname(const struct net * net,const char * ifname)314 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
315 						const char *ifname)
316 {
317 	struct l2tp_net *pn = l2tp_pernet(net);
318 	int hash;
319 	struct l2tp_session *session;
320 
321 	rcu_read_lock_bh();
322 	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
323 		hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
324 			if (!strcmp(session->ifname, ifname)) {
325 				l2tp_session_inc_refcount(session);
326 				rcu_read_unlock_bh();
327 
328 				return session;
329 			}
330 		}
331 	}
332 
333 	rcu_read_unlock_bh();
334 
335 	return NULL;
336 }
337 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
338 
l2tp_session_register(struct l2tp_session * session,struct l2tp_tunnel * tunnel)339 int l2tp_session_register(struct l2tp_session *session,
340 			  struct l2tp_tunnel *tunnel)
341 {
342 	struct l2tp_session *session_walk;
343 	struct hlist_head *g_head;
344 	struct hlist_head *head;
345 	struct l2tp_net *pn;
346 	int err;
347 
348 	head = l2tp_session_id_hash(tunnel, session->session_id);
349 
350 	spin_lock_bh(&tunnel->hlist_lock);
351 	if (!tunnel->acpt_newsess) {
352 		err = -ENODEV;
353 		goto err_tlock;
354 	}
355 
356 	hlist_for_each_entry(session_walk, head, hlist)
357 		if (session_walk->session_id == session->session_id) {
358 			err = -EEXIST;
359 			goto err_tlock;
360 		}
361 
362 	if (tunnel->version == L2TP_HDR_VER_3) {
363 		pn = l2tp_pernet(tunnel->l2tp_net);
364 		g_head = l2tp_session_id_hash_2(pn, session->session_id);
365 
366 		spin_lock_bh(&pn->l2tp_session_hlist_lock);
367 
368 		/* IP encap expects session IDs to be globally unique, while
369 		 * UDP encap doesn't.
370 		 */
371 		hlist_for_each_entry(session_walk, g_head, global_hlist)
372 			if (session_walk->session_id == session->session_id &&
373 			    (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP ||
374 			     tunnel->encap == L2TP_ENCAPTYPE_IP)) {
375 				err = -EEXIST;
376 				goto err_tlock_pnlock;
377 			}
378 
379 		l2tp_tunnel_inc_refcount(tunnel);
380 		hlist_add_head_rcu(&session->global_hlist, g_head);
381 
382 		spin_unlock_bh(&pn->l2tp_session_hlist_lock);
383 	} else {
384 		l2tp_tunnel_inc_refcount(tunnel);
385 	}
386 
387 	hlist_add_head_rcu(&session->hlist, head);
388 	spin_unlock_bh(&tunnel->hlist_lock);
389 
390 	trace_register_session(session);
391 
392 	return 0;
393 
394 err_tlock_pnlock:
395 	spin_unlock_bh(&pn->l2tp_session_hlist_lock);
396 err_tlock:
397 	spin_unlock_bh(&tunnel->hlist_lock);
398 
399 	return err;
400 }
401 EXPORT_SYMBOL_GPL(l2tp_session_register);
402 
403 /*****************************************************************************
404  * Receive data handling
405  *****************************************************************************/
406 
407 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
408  * number.
409  */
l2tp_recv_queue_skb(struct l2tp_session * session,struct sk_buff * skb)410 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
411 {
412 	struct sk_buff *skbp;
413 	struct sk_buff *tmp;
414 	u32 ns = L2TP_SKB_CB(skb)->ns;
415 
416 	spin_lock_bh(&session->reorder_q.lock);
417 	skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
418 		if (L2TP_SKB_CB(skbp)->ns > ns) {
419 			__skb_queue_before(&session->reorder_q, skbp, skb);
420 			atomic_long_inc(&session->stats.rx_oos_packets);
421 			goto out;
422 		}
423 	}
424 
425 	__skb_queue_tail(&session->reorder_q, skb);
426 
427 out:
428 	spin_unlock_bh(&session->reorder_q.lock);
429 }
430 
431 /* Dequeue a single skb.
432  */
l2tp_recv_dequeue_skb(struct l2tp_session * session,struct sk_buff * skb)433 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
434 {
435 	struct l2tp_tunnel *tunnel = session->tunnel;
436 	int length = L2TP_SKB_CB(skb)->length;
437 
438 	/* We're about to requeue the skb, so return resources
439 	 * to its current owner (a socket receive buffer).
440 	 */
441 	skb_orphan(skb);
442 
443 	atomic_long_inc(&tunnel->stats.rx_packets);
444 	atomic_long_add(length, &tunnel->stats.rx_bytes);
445 	atomic_long_inc(&session->stats.rx_packets);
446 	atomic_long_add(length, &session->stats.rx_bytes);
447 
448 	if (L2TP_SKB_CB(skb)->has_seq) {
449 		/* Bump our Nr */
450 		session->nr++;
451 		session->nr &= session->nr_max;
452 		trace_session_seqnum_update(session);
453 	}
454 
455 	/* call private receive handler */
456 	if (session->recv_skb)
457 		(*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
458 	else
459 		kfree_skb(skb);
460 }
461 
462 /* Dequeue skbs from the session's reorder_q, subject to packet order.
463  * Skbs that have been in the queue for too long are simply discarded.
464  */
l2tp_recv_dequeue(struct l2tp_session * session)465 static void l2tp_recv_dequeue(struct l2tp_session *session)
466 {
467 	struct sk_buff *skb;
468 	struct sk_buff *tmp;
469 
470 	/* If the pkt at the head of the queue has the nr that we
471 	 * expect to send up next, dequeue it and any other
472 	 * in-sequence packets behind it.
473 	 */
474 start:
475 	spin_lock_bh(&session->reorder_q.lock);
476 	skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
477 		struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
478 
479 		/* If the packet has been pending on the queue for too long, discard it */
480 		if (time_after(jiffies, cb->expires)) {
481 			atomic_long_inc(&session->stats.rx_seq_discards);
482 			atomic_long_inc(&session->stats.rx_errors);
483 			trace_session_pkt_expired(session, cb->ns);
484 			session->reorder_skip = 1;
485 			__skb_unlink(skb, &session->reorder_q);
486 			kfree_skb(skb);
487 			continue;
488 		}
489 
490 		if (cb->has_seq) {
491 			if (session->reorder_skip) {
492 				session->reorder_skip = 0;
493 				session->nr = cb->ns;
494 				trace_session_seqnum_reset(session);
495 			}
496 			if (cb->ns != session->nr)
497 				goto out;
498 		}
499 		__skb_unlink(skb, &session->reorder_q);
500 
501 		/* Process the skb. We release the queue lock while we
502 		 * do so to let other contexts process the queue.
503 		 */
504 		spin_unlock_bh(&session->reorder_q.lock);
505 		l2tp_recv_dequeue_skb(session, skb);
506 		goto start;
507 	}
508 
509 out:
510 	spin_unlock_bh(&session->reorder_q.lock);
511 }
512 
l2tp_seq_check_rx_window(struct l2tp_session * session,u32 nr)513 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
514 {
515 	u32 nws;
516 
517 	if (nr >= session->nr)
518 		nws = nr - session->nr;
519 	else
520 		nws = (session->nr_max + 1) - (session->nr - nr);
521 
522 	return nws < session->nr_window_size;
523 }
524 
525 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
526  * acceptable, else non-zero.
527  */
l2tp_recv_data_seq(struct l2tp_session * session,struct sk_buff * skb)528 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
529 {
530 	struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
531 
532 	if (!l2tp_seq_check_rx_window(session, cb->ns)) {
533 		/* Packet sequence number is outside allowed window.
534 		 * Discard it.
535 		 */
536 		trace_session_pkt_outside_rx_window(session, cb->ns);
537 		goto discard;
538 	}
539 
540 	if (session->reorder_timeout != 0) {
541 		/* Packet reordering enabled. Add skb to session's
542 		 * reorder queue, in order of ns.
543 		 */
544 		l2tp_recv_queue_skb(session, skb);
545 		goto out;
546 	}
547 
548 	/* Packet reordering disabled. Discard out-of-sequence packets, while
549 	 * tracking the number if in-sequence packets after the first OOS packet
550 	 * is seen. After nr_oos_count_max in-sequence packets, reset the
551 	 * sequence number to re-enable packet reception.
552 	 */
553 	if (cb->ns == session->nr) {
554 		skb_queue_tail(&session->reorder_q, skb);
555 	} else {
556 		u32 nr_oos = cb->ns;
557 		u32 nr_next = (session->nr_oos + 1) & session->nr_max;
558 
559 		if (nr_oos == nr_next)
560 			session->nr_oos_count++;
561 		else
562 			session->nr_oos_count = 0;
563 
564 		session->nr_oos = nr_oos;
565 		if (session->nr_oos_count > session->nr_oos_count_max) {
566 			session->reorder_skip = 1;
567 		}
568 		if (!session->reorder_skip) {
569 			atomic_long_inc(&session->stats.rx_seq_discards);
570 			trace_session_pkt_oos(session, cb->ns);
571 			goto discard;
572 		}
573 		skb_queue_tail(&session->reorder_q, skb);
574 	}
575 
576 out:
577 	return 0;
578 
579 discard:
580 	return 1;
581 }
582 
583 /* Do receive processing of L2TP data frames. We handle both L2TPv2
584  * and L2TPv3 data frames here.
585  *
586  * L2TPv2 Data Message Header
587  *
588  *  0                   1                   2                   3
589  *  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
590  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
591  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
592  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
593  * |           Tunnel ID           |           Session ID          |
594  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
595  * |             Ns (opt)          |             Nr (opt)          |
596  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
597  * |      Offset Size (opt)        |    Offset pad... (opt)
598  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
599  *
600  * Data frames are marked by T=0. All other fields are the same as
601  * those in L2TP control frames.
602  *
603  * L2TPv3 Data Message Header
604  *
605  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
606  * |                      L2TP Session Header                      |
607  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
608  * |                      L2-Specific Sublayer                     |
609  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
610  * |                        Tunnel Payload                      ...
611  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
612  *
613  * L2TPv3 Session Header Over IP
614  *
615  *  0                   1                   2                   3
616  *  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
617  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
618  * |                           Session ID                          |
619  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
620  * |               Cookie (optional, maximum 64 bits)...
621  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
622  *                                                                 |
623  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
624  *
625  * L2TPv3 L2-Specific Sublayer Format
626  *
627  *  0                   1                   2                   3
628  *  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
629  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
630  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
631  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
632  *
633  * Cookie value and sublayer format are negotiated with the peer when
634  * the session is set up. Unlike L2TPv2, we do not need to parse the
635  * packet header to determine if optional fields are present.
636  *
637  * Caller must already have parsed the frame and determined that it is
638  * a data (not control) frame before coming here. Fields up to the
639  * session-id have already been parsed and ptr points to the data
640  * after the session-id.
641  */
l2tp_recv_common(struct l2tp_session * session,struct sk_buff * skb,unsigned char * ptr,unsigned char * optr,u16 hdrflags,int length)642 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
643 		      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
644 		      int length)
645 {
646 	struct l2tp_tunnel *tunnel = session->tunnel;
647 	int offset;
648 
649 	/* Parse and check optional cookie */
650 	if (session->peer_cookie_len > 0) {
651 		if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
652 			pr_debug_ratelimited("%s: cookie mismatch (%u/%u). Discarding.\n",
653 					     tunnel->name, tunnel->tunnel_id,
654 					     session->session_id);
655 			atomic_long_inc(&session->stats.rx_cookie_discards);
656 			goto discard;
657 		}
658 		ptr += session->peer_cookie_len;
659 	}
660 
661 	/* Handle the optional sequence numbers. Sequence numbers are
662 	 * in different places for L2TPv2 and L2TPv3.
663 	 *
664 	 * If we are the LAC, enable/disable sequence numbers under
665 	 * the control of the LNS.  If no sequence numbers present but
666 	 * we were expecting them, discard frame.
667 	 */
668 	L2TP_SKB_CB(skb)->has_seq = 0;
669 	if (tunnel->version == L2TP_HDR_VER_2) {
670 		if (hdrflags & L2TP_HDRFLAG_S) {
671 			/* Store L2TP info in the skb */
672 			L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr);
673 			L2TP_SKB_CB(skb)->has_seq = 1;
674 			ptr += 2;
675 			/* Skip past nr in the header */
676 			ptr += 2;
677 
678 		}
679 	} else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
680 		u32 l2h = ntohl(*(__be32 *)ptr);
681 
682 		if (l2h & 0x40000000) {
683 			/* Store L2TP info in the skb */
684 			L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff;
685 			L2TP_SKB_CB(skb)->has_seq = 1;
686 		}
687 		ptr += 4;
688 	}
689 
690 	if (L2TP_SKB_CB(skb)->has_seq) {
691 		/* Received a packet with sequence numbers. If we're the LAC,
692 		 * check if we sre sending sequence numbers and if not,
693 		 * configure it so.
694 		 */
695 		if (!session->lns_mode && !session->send_seq) {
696 			trace_session_seqnum_lns_enable(session);
697 			session->send_seq = 1;
698 			l2tp_session_set_header_len(session, tunnel->version);
699 		}
700 	} else {
701 		/* No sequence numbers.
702 		 * If user has configured mandatory sequence numbers, discard.
703 		 */
704 		if (session->recv_seq) {
705 			pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
706 					     session->name);
707 			atomic_long_inc(&session->stats.rx_seq_discards);
708 			goto discard;
709 		}
710 
711 		/* If we're the LAC and we're sending sequence numbers, the
712 		 * LNS has requested that we no longer send sequence numbers.
713 		 * If we're the LNS and we're sending sequence numbers, the
714 		 * LAC is broken. Discard the frame.
715 		 */
716 		if (!session->lns_mode && session->send_seq) {
717 			trace_session_seqnum_lns_disable(session);
718 			session->send_seq = 0;
719 			l2tp_session_set_header_len(session, tunnel->version);
720 		} else if (session->send_seq) {
721 			pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
722 					     session->name);
723 			atomic_long_inc(&session->stats.rx_seq_discards);
724 			goto discard;
725 		}
726 	}
727 
728 	/* Session data offset is defined only for L2TPv2 and is
729 	 * indicated by an optional 16-bit value in the header.
730 	 */
731 	if (tunnel->version == L2TP_HDR_VER_2) {
732 		/* If offset bit set, skip it. */
733 		if (hdrflags & L2TP_HDRFLAG_O) {
734 			offset = ntohs(*(__be16 *)ptr);
735 			ptr += 2 + offset;
736 		}
737 	}
738 
739 	offset = ptr - optr;
740 	if (!pskb_may_pull(skb, offset))
741 		goto discard;
742 
743 	__skb_pull(skb, offset);
744 
745 	/* Prepare skb for adding to the session's reorder_q.  Hold
746 	 * packets for max reorder_timeout or 1 second if not
747 	 * reordering.
748 	 */
749 	L2TP_SKB_CB(skb)->length = length;
750 	L2TP_SKB_CB(skb)->expires = jiffies +
751 		(session->reorder_timeout ? session->reorder_timeout : HZ);
752 
753 	/* Add packet to the session's receive queue. Reordering is done here, if
754 	 * enabled. Saved L2TP protocol info is stored in skb->sb[].
755 	 */
756 	if (L2TP_SKB_CB(skb)->has_seq) {
757 		if (l2tp_recv_data_seq(session, skb))
758 			goto discard;
759 	} else {
760 		/* No sequence numbers. Add the skb to the tail of the
761 		 * reorder queue. This ensures that it will be
762 		 * delivered after all previous sequenced skbs.
763 		 */
764 		skb_queue_tail(&session->reorder_q, skb);
765 	}
766 
767 	/* Try to dequeue as many skbs from reorder_q as we can. */
768 	l2tp_recv_dequeue(session);
769 
770 	return;
771 
772 discard:
773 	atomic_long_inc(&session->stats.rx_errors);
774 	kfree_skb(skb);
775 }
776 EXPORT_SYMBOL_GPL(l2tp_recv_common);
777 
778 /* Drop skbs from the session's reorder_q
779  */
l2tp_session_queue_purge(struct l2tp_session * session)780 static void l2tp_session_queue_purge(struct l2tp_session *session)
781 {
782 	struct sk_buff *skb = NULL;
783 
784 	while ((skb = skb_dequeue(&session->reorder_q))) {
785 		atomic_long_inc(&session->stats.rx_errors);
786 		kfree_skb(skb);
787 	}
788 }
789 
790 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
791  * here. The skb is not on a list when we get here.
792  * Returns 0 if the packet was a data packet and was successfully passed on.
793  * Returns 1 if the packet was not a good data packet and could not be
794  * forwarded.  All such packets are passed up to userspace to deal with.
795  */
l2tp_udp_recv_core(struct l2tp_tunnel * tunnel,struct sk_buff * skb)796 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
797 {
798 	struct l2tp_session *session = NULL;
799 	unsigned char *ptr, *optr;
800 	u16 hdrflags;
801 	u32 tunnel_id, session_id;
802 	u16 version;
803 	int length;
804 
805 	/* UDP has verified checksum */
806 
807 	/* UDP always verifies the packet length. */
808 	__skb_pull(skb, sizeof(struct udphdr));
809 
810 	/* Short packet? */
811 	if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
812 		pr_debug_ratelimited("%s: recv short packet (len=%d)\n",
813 				     tunnel->name, skb->len);
814 		goto invalid;
815 	}
816 
817 	/* Point to L2TP header */
818 	optr = skb->data;
819 	ptr = skb->data;
820 
821 	/* Get L2TP header flags */
822 	hdrflags = ntohs(*(__be16 *)ptr);
823 
824 	/* Check protocol version */
825 	version = hdrflags & L2TP_HDR_VER_MASK;
826 	if (version != tunnel->version) {
827 		pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n",
828 				     tunnel->name, version, tunnel->version);
829 		goto invalid;
830 	}
831 
832 	/* Get length of L2TP packet */
833 	length = skb->len;
834 
835 	/* If type is control packet, it is handled by userspace. */
836 	if (hdrflags & L2TP_HDRFLAG_T)
837 		goto pass;
838 
839 	/* Skip flags */
840 	ptr += 2;
841 
842 	if (tunnel->version == L2TP_HDR_VER_2) {
843 		/* If length is present, skip it */
844 		if (hdrflags & L2TP_HDRFLAG_L)
845 			ptr += 2;
846 
847 		/* Extract tunnel and session ID */
848 		tunnel_id = ntohs(*(__be16 *)ptr);
849 		ptr += 2;
850 		session_id = ntohs(*(__be16 *)ptr);
851 		ptr += 2;
852 	} else {
853 		ptr += 2;	/* skip reserved bits */
854 		tunnel_id = tunnel->tunnel_id;
855 		session_id = ntohl(*(__be32 *)ptr);
856 		ptr += 4;
857 	}
858 
859 	/* Find the session context */
860 	session = l2tp_tunnel_get_session(tunnel, session_id);
861 	if (!session || !session->recv_skb) {
862 		if (session)
863 			l2tp_session_dec_refcount(session);
864 
865 		/* Not found? Pass to userspace to deal with */
866 		pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n",
867 				     tunnel->name, tunnel_id, session_id);
868 		goto pass;
869 	}
870 
871 	if (tunnel->version == L2TP_HDR_VER_3 &&
872 	    l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
873 		l2tp_session_dec_refcount(session);
874 		goto invalid;
875 	}
876 
877 	l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
878 	l2tp_session_dec_refcount(session);
879 
880 	return 0;
881 
882 invalid:
883 	atomic_long_inc(&tunnel->stats.rx_invalid);
884 
885 pass:
886 	/* Put UDP header back */
887 	__skb_push(skb, sizeof(struct udphdr));
888 
889 	return 1;
890 }
891 
892 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
893  * Return codes:
894  * 0 : success.
895  * <0: error
896  * >0: skb should be passed up to userspace as UDP.
897  */
l2tp_udp_encap_recv(struct sock * sk,struct sk_buff * skb)898 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
899 {
900 	struct l2tp_tunnel *tunnel;
901 
902 	/* Note that this is called from the encap_rcv hook inside an
903 	 * RCU-protected region, but without the socket being locked.
904 	 * Hence we use rcu_dereference_sk_user_data to access the
905 	 * tunnel data structure rather the usual l2tp_sk_to_tunnel
906 	 * accessor function.
907 	 */
908 	tunnel = rcu_dereference_sk_user_data(sk);
909 	if (!tunnel)
910 		goto pass_up;
911 	if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
912 		goto pass_up;
913 
914 	if (l2tp_udp_recv_core(tunnel, skb))
915 		goto pass_up;
916 
917 	return 0;
918 
919 pass_up:
920 	return 1;
921 }
922 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
923 
924 /************************************************************************
925  * Transmit handling
926  ***********************************************************************/
927 
928 /* Build an L2TP header for the session into the buffer provided.
929  */
l2tp_build_l2tpv2_header(struct l2tp_session * session,void * buf)930 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
931 {
932 	struct l2tp_tunnel *tunnel = session->tunnel;
933 	__be16 *bufp = buf;
934 	__be16 *optr = buf;
935 	u16 flags = L2TP_HDR_VER_2;
936 	u32 tunnel_id = tunnel->peer_tunnel_id;
937 	u32 session_id = session->peer_session_id;
938 
939 	if (session->send_seq)
940 		flags |= L2TP_HDRFLAG_S;
941 
942 	/* Setup L2TP header. */
943 	*bufp++ = htons(flags);
944 	*bufp++ = htons(tunnel_id);
945 	*bufp++ = htons(session_id);
946 	if (session->send_seq) {
947 		*bufp++ = htons(session->ns);
948 		*bufp++ = 0;
949 		session->ns++;
950 		session->ns &= 0xffff;
951 		trace_session_seqnum_update(session);
952 	}
953 
954 	return bufp - optr;
955 }
956 
l2tp_build_l2tpv3_header(struct l2tp_session * session,void * buf)957 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
958 {
959 	struct l2tp_tunnel *tunnel = session->tunnel;
960 	char *bufp = buf;
961 	char *optr = bufp;
962 
963 	/* Setup L2TP header. The header differs slightly for UDP and
964 	 * IP encapsulations. For UDP, there is 4 bytes of flags.
965 	 */
966 	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
967 		u16 flags = L2TP_HDR_VER_3;
968 		*((__be16 *)bufp) = htons(flags);
969 		bufp += 2;
970 		*((__be16 *)bufp) = 0;
971 		bufp += 2;
972 	}
973 
974 	*((__be32 *)bufp) = htonl(session->peer_session_id);
975 	bufp += 4;
976 	if (session->cookie_len) {
977 		memcpy(bufp, &session->cookie[0], session->cookie_len);
978 		bufp += session->cookie_len;
979 	}
980 	if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
981 		u32 l2h = 0;
982 
983 		if (session->send_seq) {
984 			l2h = 0x40000000 | session->ns;
985 			session->ns++;
986 			session->ns &= 0xffffff;
987 			trace_session_seqnum_update(session);
988 		}
989 
990 		*((__be32 *)bufp) = htonl(l2h);
991 		bufp += 4;
992 	}
993 
994 	return bufp - optr;
995 }
996 
997 /* Queue the packet to IP for output: tunnel socket lock must be held */
l2tp_xmit_queue(struct l2tp_tunnel * tunnel,struct sk_buff * skb,struct flowi * fl)998 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
999 {
1000 	int err;
1001 
1002 	skb->ignore_df = 1;
1003 	skb_dst_drop(skb);
1004 #if IS_ENABLED(CONFIG_IPV6)
1005 	if (l2tp_sk_is_v6(tunnel->sock))
1006 		err = inet6_csk_xmit(tunnel->sock, skb, NULL);
1007 	else
1008 #endif
1009 		err = ip_queue_xmit(tunnel->sock, skb, fl);
1010 
1011 	return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
1012 }
1013 
l2tp_xmit_core(struct l2tp_session * session,struct sk_buff * skb,unsigned int * len)1014 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len)
1015 {
1016 	struct l2tp_tunnel *tunnel = session->tunnel;
1017 	unsigned int data_len = skb->len;
1018 	struct sock *sk = tunnel->sock;
1019 	int headroom, uhlen, udp_len;
1020 	int ret = NET_XMIT_SUCCESS;
1021 	struct inet_sock *inet;
1022 	struct udphdr *uh;
1023 
1024 	/* Check that there's enough headroom in the skb to insert IP,
1025 	 * UDP and L2TP headers. If not enough, expand it to
1026 	 * make room. Adjust truesize.
1027 	 */
1028 	uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
1029 	headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
1030 	if (skb_cow_head(skb, headroom)) {
1031 		kfree_skb(skb);
1032 		return NET_XMIT_DROP;
1033 	}
1034 
1035 	/* Setup L2TP header */
1036 	if (tunnel->version == L2TP_HDR_VER_2)
1037 		l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len));
1038 	else
1039 		l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len));
1040 
1041 	/* Reset skb netfilter state */
1042 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1043 	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);
1044 	nf_reset_ct(skb);
1045 
1046 	bh_lock_sock(sk);
1047 	if (sock_owned_by_user(sk)) {
1048 		kfree_skb(skb);
1049 		ret = NET_XMIT_DROP;
1050 		goto out_unlock;
1051 	}
1052 
1053 	/* The user-space may change the connection status for the user-space
1054 	 * provided socket at run time: we must check it under the socket lock
1055 	 */
1056 	if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1057 		kfree_skb(skb);
1058 		ret = NET_XMIT_DROP;
1059 		goto out_unlock;
1060 	}
1061 
1062 	/* Report transmitted length before we add encap header, which keeps
1063 	 * statistics consistent for both UDP and IP encap tx/rx paths.
1064 	 */
1065 	*len = skb->len;
1066 
1067 	inet = inet_sk(sk);
1068 	switch (tunnel->encap) {
1069 	case L2TP_ENCAPTYPE_UDP:
1070 		/* Setup UDP header */
1071 		__skb_push(skb, sizeof(*uh));
1072 		skb_reset_transport_header(skb);
1073 		uh = udp_hdr(skb);
1074 		uh->source = inet->inet_sport;
1075 		uh->dest = inet->inet_dport;
1076 		udp_len = uhlen + session->hdr_len + data_len;
1077 		uh->len = htons(udp_len);
1078 
1079 		/* Calculate UDP checksum if configured to do so */
1080 #if IS_ENABLED(CONFIG_IPV6)
1081 		if (l2tp_sk_is_v6(sk))
1082 			udp6_set_csum(udp_get_no_check6_tx(sk),
1083 				      skb, &inet6_sk(sk)->saddr,
1084 				      &sk->sk_v6_daddr, udp_len);
1085 		else
1086 #endif
1087 			udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1088 				     inet->inet_daddr, udp_len);
1089 		break;
1090 
1091 	case L2TP_ENCAPTYPE_IP:
1092 		break;
1093 	}
1094 
1095 	ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
1096 
1097 out_unlock:
1098 	bh_unlock_sock(sk);
1099 
1100 	return ret;
1101 }
1102 
1103 /* If caller requires the skb to have a ppp header, the header must be
1104  * inserted in the skb data before calling this function.
1105  */
l2tp_xmit_skb(struct l2tp_session * session,struct sk_buff * skb)1106 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
1107 {
1108 	unsigned int len = 0;
1109 	int ret;
1110 
1111 	ret = l2tp_xmit_core(session, skb, &len);
1112 	if (ret == NET_XMIT_SUCCESS) {
1113 		atomic_long_inc(&session->tunnel->stats.tx_packets);
1114 		atomic_long_add(len, &session->tunnel->stats.tx_bytes);
1115 		atomic_long_inc(&session->stats.tx_packets);
1116 		atomic_long_add(len, &session->stats.tx_bytes);
1117 	} else {
1118 		atomic_long_inc(&session->tunnel->stats.tx_errors);
1119 		atomic_long_inc(&session->stats.tx_errors);
1120 	}
1121 	return ret;
1122 }
1123 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1124 
1125 /*****************************************************************************
1126  * Tinnel and session create/destroy.
1127  *****************************************************************************/
1128 
1129 /* Tunnel socket destruct hook.
1130  * The tunnel context is deleted only when all session sockets have been
1131  * closed.
1132  */
l2tp_tunnel_destruct(struct sock * sk)1133 static void l2tp_tunnel_destruct(struct sock *sk)
1134 {
1135 	struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1136 
1137 	if (!tunnel)
1138 		goto end;
1139 
1140 	/* Disable udp encapsulation */
1141 	switch (tunnel->encap) {
1142 	case L2TP_ENCAPTYPE_UDP:
1143 		/* No longer an encapsulation socket. See net/ipv4/udp.c */
1144 		(udp_sk(sk))->encap_type = 0;
1145 		(udp_sk(sk))->encap_rcv = NULL;
1146 		(udp_sk(sk))->encap_destroy = NULL;
1147 		break;
1148 	case L2TP_ENCAPTYPE_IP:
1149 		break;
1150 	}
1151 
1152 	/* Remove hooks into tunnel socket */
1153 	sk->sk_destruct = tunnel->old_sk_destruct;
1154 	sk->sk_user_data = NULL;
1155 
1156 	/* Call the original destructor */
1157 	if (sk->sk_destruct)
1158 		(*sk->sk_destruct)(sk);
1159 
1160 	kfree_rcu(tunnel, rcu);
1161 end:
1162 	return;
1163 }
1164 
1165 /* Remove an l2tp session from l2tp_core's hash lists. */
l2tp_session_unhash(struct l2tp_session * session)1166 static void l2tp_session_unhash(struct l2tp_session *session)
1167 {
1168 	struct l2tp_tunnel *tunnel = session->tunnel;
1169 
1170 	/* Remove the session from core hashes */
1171 	if (tunnel) {
1172 		/* Remove from the per-tunnel hash */
1173 		spin_lock_bh(&tunnel->hlist_lock);
1174 		hlist_del_init_rcu(&session->hlist);
1175 		spin_unlock_bh(&tunnel->hlist_lock);
1176 
1177 		/* For L2TPv3 we have a per-net hash: remove from there, too */
1178 		if (tunnel->version != L2TP_HDR_VER_2) {
1179 			struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1180 
1181 			spin_lock_bh(&pn->l2tp_session_hlist_lock);
1182 			hlist_del_init_rcu(&session->global_hlist);
1183 			spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1184 		}
1185 
1186 		synchronize_rcu();
1187 	}
1188 }
1189 
1190 /* When the tunnel is closed, all the attached sessions need to go too.
1191  */
l2tp_tunnel_closeall(struct l2tp_tunnel * tunnel)1192 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1193 {
1194 	struct l2tp_session *session;
1195 	int hash;
1196 
1197 	spin_lock_bh(&tunnel->hlist_lock);
1198 	tunnel->acpt_newsess = false;
1199 	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1200 again:
1201 		hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
1202 			hlist_del_init_rcu(&session->hlist);
1203 
1204 			spin_unlock_bh(&tunnel->hlist_lock);
1205 			l2tp_session_delete(session);
1206 			spin_lock_bh(&tunnel->hlist_lock);
1207 
1208 			/* Now restart from the beginning of this hash
1209 			 * chain.  We always remove a session from the
1210 			 * list so we are guaranteed to make forward
1211 			 * progress.
1212 			 */
1213 			goto again;
1214 		}
1215 	}
1216 	spin_unlock_bh(&tunnel->hlist_lock);
1217 }
1218 
1219 /* Tunnel socket destroy hook for UDP encapsulation */
l2tp_udp_encap_destroy(struct sock * sk)1220 static void l2tp_udp_encap_destroy(struct sock *sk)
1221 {
1222 	struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1223 
1224 	if (tunnel)
1225 		l2tp_tunnel_delete(tunnel);
1226 }
1227 
1228 /* Workqueue tunnel deletion function */
l2tp_tunnel_del_work(struct work_struct * work)1229 static void l2tp_tunnel_del_work(struct work_struct *work)
1230 {
1231 	struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1232 						  del_work);
1233 	struct sock *sk = tunnel->sock;
1234 	struct socket *sock = sk->sk_socket;
1235 	struct l2tp_net *pn;
1236 
1237 	l2tp_tunnel_closeall(tunnel);
1238 
1239 	/* If the tunnel socket was created within the kernel, use
1240 	 * the sk API to release it here.
1241 	 */
1242 	if (tunnel->fd < 0) {
1243 		if (sock) {
1244 			kernel_sock_shutdown(sock, SHUT_RDWR);
1245 			sock_release(sock);
1246 		}
1247 	}
1248 
1249 	/* Remove the tunnel struct from the tunnel list */
1250 	pn = l2tp_pernet(tunnel->l2tp_net);
1251 	spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1252 	list_del_rcu(&tunnel->list);
1253 	spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1254 
1255 	/* drop initial ref */
1256 	l2tp_tunnel_dec_refcount(tunnel);
1257 
1258 	/* drop workqueue ref */
1259 	l2tp_tunnel_dec_refcount(tunnel);
1260 }
1261 
1262 /* Create a socket for the tunnel, if one isn't set up by
1263  * userspace. This is used for static tunnels where there is no
1264  * managing L2TP daemon.
1265  *
1266  * Since we don't want these sockets to keep a namespace alive by
1267  * themselves, we drop the socket's namespace refcount after creation.
1268  * These sockets are freed when the namespace exits using the pernet
1269  * exit hook.
1270  */
l2tp_tunnel_sock_create(struct net * net,u32 tunnel_id,u32 peer_tunnel_id,struct l2tp_tunnel_cfg * cfg,struct socket ** sockp)1271 static int l2tp_tunnel_sock_create(struct net *net,
1272 				   u32 tunnel_id,
1273 				   u32 peer_tunnel_id,
1274 				   struct l2tp_tunnel_cfg *cfg,
1275 				   struct socket **sockp)
1276 {
1277 	int err = -EINVAL;
1278 	struct socket *sock = NULL;
1279 	struct udp_port_cfg udp_conf;
1280 
1281 	switch (cfg->encap) {
1282 	case L2TP_ENCAPTYPE_UDP:
1283 		memset(&udp_conf, 0, sizeof(udp_conf));
1284 
1285 #if IS_ENABLED(CONFIG_IPV6)
1286 		if (cfg->local_ip6 && cfg->peer_ip6) {
1287 			udp_conf.family = AF_INET6;
1288 			memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1289 			       sizeof(udp_conf.local_ip6));
1290 			memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1291 			       sizeof(udp_conf.peer_ip6));
1292 			udp_conf.use_udp6_tx_checksums =
1293 			  !cfg->udp6_zero_tx_checksums;
1294 			udp_conf.use_udp6_rx_checksums =
1295 			  !cfg->udp6_zero_rx_checksums;
1296 		} else
1297 #endif
1298 		{
1299 			udp_conf.family = AF_INET;
1300 			udp_conf.local_ip = cfg->local_ip;
1301 			udp_conf.peer_ip = cfg->peer_ip;
1302 			udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1303 		}
1304 
1305 		udp_conf.local_udp_port = htons(cfg->local_udp_port);
1306 		udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1307 
1308 		err = udp_sock_create(net, &udp_conf, &sock);
1309 		if (err < 0)
1310 			goto out;
1311 
1312 		break;
1313 
1314 	case L2TP_ENCAPTYPE_IP:
1315 #if IS_ENABLED(CONFIG_IPV6)
1316 		if (cfg->local_ip6 && cfg->peer_ip6) {
1317 			struct sockaddr_l2tpip6 ip6_addr = {0};
1318 
1319 			err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1320 					       IPPROTO_L2TP, &sock);
1321 			if (err < 0)
1322 				goto out;
1323 
1324 			ip6_addr.l2tp_family = AF_INET6;
1325 			memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1326 			       sizeof(ip6_addr.l2tp_addr));
1327 			ip6_addr.l2tp_conn_id = tunnel_id;
1328 			err = kernel_bind(sock, (struct sockaddr *)&ip6_addr,
1329 					  sizeof(ip6_addr));
1330 			if (err < 0)
1331 				goto out;
1332 
1333 			ip6_addr.l2tp_family = AF_INET6;
1334 			memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1335 			       sizeof(ip6_addr.l2tp_addr));
1336 			ip6_addr.l2tp_conn_id = peer_tunnel_id;
1337 			err = kernel_connect(sock,
1338 					     (struct sockaddr *)&ip6_addr,
1339 					     sizeof(ip6_addr), 0);
1340 			if (err < 0)
1341 				goto out;
1342 		} else
1343 #endif
1344 		{
1345 			struct sockaddr_l2tpip ip_addr = {0};
1346 
1347 			err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1348 					       IPPROTO_L2TP, &sock);
1349 			if (err < 0)
1350 				goto out;
1351 
1352 			ip_addr.l2tp_family = AF_INET;
1353 			ip_addr.l2tp_addr = cfg->local_ip;
1354 			ip_addr.l2tp_conn_id = tunnel_id;
1355 			err = kernel_bind(sock, (struct sockaddr *)&ip_addr,
1356 					  sizeof(ip_addr));
1357 			if (err < 0)
1358 				goto out;
1359 
1360 			ip_addr.l2tp_family = AF_INET;
1361 			ip_addr.l2tp_addr = cfg->peer_ip;
1362 			ip_addr.l2tp_conn_id = peer_tunnel_id;
1363 			err = kernel_connect(sock, (struct sockaddr *)&ip_addr,
1364 					     sizeof(ip_addr), 0);
1365 			if (err < 0)
1366 				goto out;
1367 		}
1368 		break;
1369 
1370 	default:
1371 		goto out;
1372 	}
1373 
1374 out:
1375 	*sockp = sock;
1376 	if (err < 0 && sock) {
1377 		kernel_sock_shutdown(sock, SHUT_RDWR);
1378 		sock_release(sock);
1379 		*sockp = NULL;
1380 	}
1381 
1382 	return err;
1383 }
1384 
1385 static struct lock_class_key l2tp_socket_class;
1386 
l2tp_tunnel_create(int fd,int version,u32 tunnel_id,u32 peer_tunnel_id,struct l2tp_tunnel_cfg * cfg,struct l2tp_tunnel ** tunnelp)1387 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id,
1388 		       struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
1389 {
1390 	struct l2tp_tunnel *tunnel = NULL;
1391 	int err;
1392 	enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1393 
1394 	if (cfg)
1395 		encap = cfg->encap;
1396 
1397 	tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
1398 	if (!tunnel) {
1399 		err = -ENOMEM;
1400 		goto err;
1401 	}
1402 
1403 	tunnel->version = version;
1404 	tunnel->tunnel_id = tunnel_id;
1405 	tunnel->peer_tunnel_id = peer_tunnel_id;
1406 
1407 	tunnel->magic = L2TP_TUNNEL_MAGIC;
1408 	sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1409 	spin_lock_init(&tunnel->hlist_lock);
1410 	tunnel->acpt_newsess = true;
1411 
1412 	tunnel->encap = encap;
1413 
1414 	refcount_set(&tunnel->ref_count, 1);
1415 	tunnel->fd = fd;
1416 
1417 	/* Init delete workqueue struct */
1418 	INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1419 
1420 	INIT_LIST_HEAD(&tunnel->list);
1421 
1422 	err = 0;
1423 err:
1424 	if (tunnelp)
1425 		*tunnelp = tunnel;
1426 
1427 	return err;
1428 }
1429 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1430 
l2tp_validate_socket(const struct sock * sk,const struct net * net,enum l2tp_encap_type encap)1431 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1432 				enum l2tp_encap_type encap)
1433 {
1434 	if (!net_eq(sock_net(sk), net))
1435 		return -EINVAL;
1436 
1437 	if (sk->sk_type != SOCK_DGRAM)
1438 		return -EPROTONOSUPPORT;
1439 
1440 	if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
1441 		return -EPROTONOSUPPORT;
1442 
1443 	if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1444 	    (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1445 		return -EPROTONOSUPPORT;
1446 
1447 	if (sk->sk_user_data)
1448 		return -EBUSY;
1449 
1450 	return 0;
1451 }
1452 
l2tp_tunnel_register(struct l2tp_tunnel * tunnel,struct net * net,struct l2tp_tunnel_cfg * cfg)1453 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1454 			 struct l2tp_tunnel_cfg *cfg)
1455 {
1456 	struct l2tp_tunnel *tunnel_walk;
1457 	struct l2tp_net *pn;
1458 	struct socket *sock;
1459 	struct sock *sk;
1460 	int ret;
1461 
1462 	if (tunnel->fd < 0) {
1463 		ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1464 					      tunnel->peer_tunnel_id, cfg,
1465 					      &sock);
1466 		if (ret < 0)
1467 			goto err;
1468 	} else {
1469 		sock = sockfd_lookup(tunnel->fd, &ret);
1470 		if (!sock)
1471 			goto err;
1472 
1473 		ret = l2tp_validate_socket(sock->sk, net, tunnel->encap);
1474 		if (ret < 0)
1475 			goto err_sock;
1476 	}
1477 
1478 	tunnel->l2tp_net = net;
1479 	pn = l2tp_pernet(net);
1480 
1481 	sk = sock->sk;
1482 	sock_hold(sk);
1483 	tunnel->sock = sk;
1484 
1485 	spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1486 	list_for_each_entry(tunnel_walk, &pn->l2tp_tunnel_list, list) {
1487 		if (tunnel_walk->tunnel_id == tunnel->tunnel_id) {
1488 			spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1489 			sock_put(sk);
1490 			ret = -EEXIST;
1491 			goto err_sock;
1492 		}
1493 	}
1494 	list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1495 	spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1496 
1497 	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1498 		struct udp_tunnel_sock_cfg udp_cfg = {
1499 			.sk_user_data = tunnel,
1500 			.encap_type = UDP_ENCAP_L2TPINUDP,
1501 			.encap_rcv = l2tp_udp_encap_recv,
1502 			.encap_destroy = l2tp_udp_encap_destroy,
1503 		};
1504 
1505 		setup_udp_tunnel_sock(net, sock, &udp_cfg);
1506 	} else {
1507 		sk->sk_user_data = tunnel;
1508 	}
1509 
1510 	tunnel->old_sk_destruct = sk->sk_destruct;
1511 	sk->sk_destruct = &l2tp_tunnel_destruct;
1512 	lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class,
1513 				   "l2tp_sock");
1514 	sk->sk_allocation = GFP_ATOMIC;
1515 
1516 	trace_register_tunnel(tunnel);
1517 
1518 	if (tunnel->fd >= 0)
1519 		sockfd_put(sock);
1520 
1521 	return 0;
1522 
1523 err_sock:
1524 	if (tunnel->fd < 0)
1525 		sock_release(sock);
1526 	else
1527 		sockfd_put(sock);
1528 err:
1529 	return ret;
1530 }
1531 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1532 
1533 /* This function is used by the netlink TUNNEL_DELETE command.
1534  */
l2tp_tunnel_delete(struct l2tp_tunnel * tunnel)1535 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1536 {
1537 	if (!test_and_set_bit(0, &tunnel->dead)) {
1538 		trace_delete_tunnel(tunnel);
1539 		l2tp_tunnel_inc_refcount(tunnel);
1540 		queue_work(l2tp_wq, &tunnel->del_work);
1541 	}
1542 }
1543 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1544 
l2tp_session_delete(struct l2tp_session * session)1545 void l2tp_session_delete(struct l2tp_session *session)
1546 {
1547 	if (test_and_set_bit(0, &session->dead))
1548 		return;
1549 
1550 	trace_delete_session(session);
1551 	l2tp_session_unhash(session);
1552 	l2tp_session_queue_purge(session);
1553 	if (session->session_close)
1554 		(*session->session_close)(session);
1555 
1556 	l2tp_session_dec_refcount(session);
1557 }
1558 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1559 
1560 /* We come here whenever a session's send_seq, cookie_len or
1561  * l2specific_type parameters are set.
1562  */
l2tp_session_set_header_len(struct l2tp_session * session,int version)1563 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1564 {
1565 	if (version == L2TP_HDR_VER_2) {
1566 		session->hdr_len = 6;
1567 		if (session->send_seq)
1568 			session->hdr_len += 4;
1569 	} else {
1570 		session->hdr_len = 4 + session->cookie_len;
1571 		session->hdr_len += l2tp_get_l2specific_len(session);
1572 		if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1573 			session->hdr_len += 4;
1574 	}
1575 }
1576 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1577 
l2tp_session_create(int priv_size,struct l2tp_tunnel * tunnel,u32 session_id,u32 peer_session_id,struct l2tp_session_cfg * cfg)1578 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id,
1579 					 u32 peer_session_id, struct l2tp_session_cfg *cfg)
1580 {
1581 	struct l2tp_session *session;
1582 
1583 	session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
1584 	if (session) {
1585 		session->magic = L2TP_SESSION_MAGIC;
1586 		session->tunnel = tunnel;
1587 
1588 		session->session_id = session_id;
1589 		session->peer_session_id = peer_session_id;
1590 		session->nr = 0;
1591 		if (tunnel->version == L2TP_HDR_VER_2)
1592 			session->nr_max = 0xffff;
1593 		else
1594 			session->nr_max = 0xffffff;
1595 		session->nr_window_size = session->nr_max / 2;
1596 		session->nr_oos_count_max = 4;
1597 
1598 		/* Use NR of first received packet */
1599 		session->reorder_skip = 1;
1600 
1601 		sprintf(&session->name[0], "sess %u/%u",
1602 			tunnel->tunnel_id, session->session_id);
1603 
1604 		skb_queue_head_init(&session->reorder_q);
1605 
1606 		INIT_HLIST_NODE(&session->hlist);
1607 		INIT_HLIST_NODE(&session->global_hlist);
1608 
1609 		if (cfg) {
1610 			session->pwtype = cfg->pw_type;
1611 			session->send_seq = cfg->send_seq;
1612 			session->recv_seq = cfg->recv_seq;
1613 			session->lns_mode = cfg->lns_mode;
1614 			session->reorder_timeout = cfg->reorder_timeout;
1615 			session->l2specific_type = cfg->l2specific_type;
1616 			session->cookie_len = cfg->cookie_len;
1617 			memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1618 			session->peer_cookie_len = cfg->peer_cookie_len;
1619 			memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1620 		}
1621 
1622 		l2tp_session_set_header_len(session, tunnel->version);
1623 
1624 		refcount_set(&session->ref_count, 1);
1625 
1626 		return session;
1627 	}
1628 
1629 	return ERR_PTR(-ENOMEM);
1630 }
1631 EXPORT_SYMBOL_GPL(l2tp_session_create);
1632 
1633 /*****************************************************************************
1634  * Init and cleanup
1635  *****************************************************************************/
1636 
l2tp_init_net(struct net * net)1637 static __net_init int l2tp_init_net(struct net *net)
1638 {
1639 	struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1640 	int hash;
1641 
1642 	INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1643 	spin_lock_init(&pn->l2tp_tunnel_list_lock);
1644 
1645 	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1646 		INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1647 
1648 	spin_lock_init(&pn->l2tp_session_hlist_lock);
1649 
1650 	return 0;
1651 }
1652 
l2tp_exit_net(struct net * net)1653 static __net_exit void l2tp_exit_net(struct net *net)
1654 {
1655 	struct l2tp_net *pn = l2tp_pernet(net);
1656 	struct l2tp_tunnel *tunnel = NULL;
1657 	int hash;
1658 
1659 	rcu_read_lock_bh();
1660 	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
1661 		l2tp_tunnel_delete(tunnel);
1662 	}
1663 	rcu_read_unlock_bh();
1664 
1665 	if (l2tp_wq)
1666 		flush_workqueue(l2tp_wq);
1667 	rcu_barrier();
1668 
1669 	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1670 		WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1671 }
1672 
1673 static struct pernet_operations l2tp_net_ops = {
1674 	.init = l2tp_init_net,
1675 	.exit = l2tp_exit_net,
1676 	.id   = &l2tp_net_id,
1677 	.size = sizeof(struct l2tp_net),
1678 };
1679 
l2tp_init(void)1680 static int __init l2tp_init(void)
1681 {
1682 	int rc = 0;
1683 
1684 	rc = register_pernet_device(&l2tp_net_ops);
1685 	if (rc)
1686 		goto out;
1687 
1688 	l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1689 	if (!l2tp_wq) {
1690 		pr_err("alloc_workqueue failed\n");
1691 		unregister_pernet_device(&l2tp_net_ops);
1692 		rc = -ENOMEM;
1693 		goto out;
1694 	}
1695 
1696 	pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1697 
1698 out:
1699 	return rc;
1700 }
1701 
l2tp_exit(void)1702 static void __exit l2tp_exit(void)
1703 {
1704 	unregister_pernet_device(&l2tp_net_ops);
1705 	if (l2tp_wq) {
1706 		destroy_workqueue(l2tp_wq);
1707 		l2tp_wq = NULL;
1708 	}
1709 }
1710 
1711 module_init(l2tp_init);
1712 module_exit(l2tp_exit);
1713 
1714 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1715 MODULE_DESCRIPTION("L2TP core");
1716 MODULE_LICENSE("GPL");
1717 MODULE_VERSION(L2TP_DRV_VERSION);
1718