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 /* Lock for write access to l2tp_tunnel_idr */
108 spinlock_t l2tp_tunnel_idr_lock;
109 struct idr l2tp_tunnel_idr;
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 tunnel = idr_find(&pn->l2tp_tunnel_idr, tunnel_id);
212 if (tunnel && refcount_inc_not_zero(&tunnel->ref_count)) {
213 rcu_read_unlock_bh();
214 return tunnel;
215 }
216 rcu_read_unlock_bh();
217
218 return NULL;
219 }
220 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
221
l2tp_tunnel_get_nth(const struct net * net,int nth)222 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
223 {
224 struct l2tp_net *pn = l2tp_pernet(net);
225 unsigned long tunnel_id, tmp;
226 struct l2tp_tunnel *tunnel;
227 int count = 0;
228
229 rcu_read_lock_bh();
230 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
231 if (tunnel && ++count > nth &&
232 refcount_inc_not_zero(&tunnel->ref_count)) {
233 rcu_read_unlock_bh();
234 return tunnel;
235 }
236 }
237 rcu_read_unlock_bh();
238
239 return NULL;
240 }
241 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
242
l2tp_tunnel_get_session(struct l2tp_tunnel * tunnel,u32 session_id)243 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
244 u32 session_id)
245 {
246 struct hlist_head *session_list;
247 struct l2tp_session *session;
248
249 session_list = l2tp_session_id_hash(tunnel, session_id);
250
251 read_lock_bh(&tunnel->hlist_lock);
252 hlist_for_each_entry(session, session_list, hlist)
253 if (session->session_id == session_id) {
254 l2tp_session_inc_refcount(session);
255 read_unlock_bh(&tunnel->hlist_lock);
256
257 return session;
258 }
259 read_unlock_bh(&tunnel->hlist_lock);
260
261 return NULL;
262 }
263 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
264
l2tp_session_get(const struct net * net,u32 session_id)265 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
266 {
267 struct hlist_head *session_list;
268 struct l2tp_session *session;
269
270 session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
271
272 rcu_read_lock_bh();
273 hlist_for_each_entry_rcu(session, session_list, global_hlist)
274 if (session->session_id == session_id) {
275 l2tp_session_inc_refcount(session);
276 rcu_read_unlock_bh();
277
278 return session;
279 }
280 rcu_read_unlock_bh();
281
282 return NULL;
283 }
284 EXPORT_SYMBOL_GPL(l2tp_session_get);
285
l2tp_session_get_nth(struct l2tp_tunnel * tunnel,int nth)286 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
287 {
288 int hash;
289 struct l2tp_session *session;
290 int count = 0;
291
292 read_lock_bh(&tunnel->hlist_lock);
293 for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
294 hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
295 if (++count > nth) {
296 l2tp_session_inc_refcount(session);
297 read_unlock_bh(&tunnel->hlist_lock);
298 return session;
299 }
300 }
301 }
302
303 read_unlock_bh(&tunnel->hlist_lock);
304
305 return NULL;
306 }
307 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
308
309 /* Lookup a session by interface name.
310 * This is very inefficient but is only used by management interfaces.
311 */
l2tp_session_get_by_ifname(const struct net * net,const char * ifname)312 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
313 const char *ifname)
314 {
315 struct l2tp_net *pn = l2tp_pernet(net);
316 int hash;
317 struct l2tp_session *session;
318
319 rcu_read_lock_bh();
320 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
321 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
322 if (!strcmp(session->ifname, ifname)) {
323 l2tp_session_inc_refcount(session);
324 rcu_read_unlock_bh();
325
326 return session;
327 }
328 }
329 }
330
331 rcu_read_unlock_bh();
332
333 return NULL;
334 }
335 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
336
l2tp_session_register(struct l2tp_session * session,struct l2tp_tunnel * tunnel)337 int l2tp_session_register(struct l2tp_session *session,
338 struct l2tp_tunnel *tunnel)
339 {
340 struct l2tp_session *session_walk;
341 struct hlist_head *g_head;
342 struct hlist_head *head;
343 struct l2tp_net *pn;
344 int err;
345
346 head = l2tp_session_id_hash(tunnel, session->session_id);
347
348 write_lock_bh(&tunnel->hlist_lock);
349 if (!tunnel->acpt_newsess) {
350 err = -ENODEV;
351 goto err_tlock;
352 }
353
354 hlist_for_each_entry(session_walk, head, hlist)
355 if (session_walk->session_id == session->session_id) {
356 err = -EEXIST;
357 goto err_tlock;
358 }
359
360 if (tunnel->version == L2TP_HDR_VER_3) {
361 pn = l2tp_pernet(tunnel->l2tp_net);
362 g_head = l2tp_session_id_hash_2(pn, session->session_id);
363
364 spin_lock_bh(&pn->l2tp_session_hlist_lock);
365
366 /* IP encap expects session IDs to be globally unique, while
367 * UDP encap doesn't.
368 */
369 hlist_for_each_entry(session_walk, g_head, global_hlist)
370 if (session_walk->session_id == session->session_id &&
371 (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP ||
372 tunnel->encap == L2TP_ENCAPTYPE_IP)) {
373 err = -EEXIST;
374 goto err_tlock_pnlock;
375 }
376
377 l2tp_tunnel_inc_refcount(tunnel);
378 hlist_add_head_rcu(&session->global_hlist, g_head);
379
380 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
381 } else {
382 l2tp_tunnel_inc_refcount(tunnel);
383 }
384
385 hlist_add_head(&session->hlist, head);
386 write_unlock_bh(&tunnel->hlist_lock);
387
388 trace_register_session(session);
389
390 return 0;
391
392 err_tlock_pnlock:
393 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
394 err_tlock:
395 write_unlock_bh(&tunnel->hlist_lock);
396
397 return err;
398 }
399 EXPORT_SYMBOL_GPL(l2tp_session_register);
400
401 /*****************************************************************************
402 * Receive data handling
403 *****************************************************************************/
404
405 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
406 * number.
407 */
l2tp_recv_queue_skb(struct l2tp_session * session,struct sk_buff * skb)408 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
409 {
410 struct sk_buff *skbp;
411 struct sk_buff *tmp;
412 u32 ns = L2TP_SKB_CB(skb)->ns;
413
414 spin_lock_bh(&session->reorder_q.lock);
415 skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
416 if (L2TP_SKB_CB(skbp)->ns > ns) {
417 __skb_queue_before(&session->reorder_q, skbp, skb);
418 atomic_long_inc(&session->stats.rx_oos_packets);
419 goto out;
420 }
421 }
422
423 __skb_queue_tail(&session->reorder_q, skb);
424
425 out:
426 spin_unlock_bh(&session->reorder_q.lock);
427 }
428
429 /* Dequeue a single skb.
430 */
l2tp_recv_dequeue_skb(struct l2tp_session * session,struct sk_buff * skb)431 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
432 {
433 struct l2tp_tunnel *tunnel = session->tunnel;
434 int length = L2TP_SKB_CB(skb)->length;
435
436 /* We're about to requeue the skb, so return resources
437 * to its current owner (a socket receive buffer).
438 */
439 skb_orphan(skb);
440
441 atomic_long_inc(&tunnel->stats.rx_packets);
442 atomic_long_add(length, &tunnel->stats.rx_bytes);
443 atomic_long_inc(&session->stats.rx_packets);
444 atomic_long_add(length, &session->stats.rx_bytes);
445
446 if (L2TP_SKB_CB(skb)->has_seq) {
447 /* Bump our Nr */
448 session->nr++;
449 session->nr &= session->nr_max;
450 trace_session_seqnum_update(session);
451 }
452
453 /* call private receive handler */
454 if (session->recv_skb)
455 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
456 else
457 kfree_skb(skb);
458 }
459
460 /* Dequeue skbs from the session's reorder_q, subject to packet order.
461 * Skbs that have been in the queue for too long are simply discarded.
462 */
l2tp_recv_dequeue(struct l2tp_session * session)463 static void l2tp_recv_dequeue(struct l2tp_session *session)
464 {
465 struct sk_buff *skb;
466 struct sk_buff *tmp;
467
468 /* If the pkt at the head of the queue has the nr that we
469 * expect to send up next, dequeue it and any other
470 * in-sequence packets behind it.
471 */
472 start:
473 spin_lock_bh(&session->reorder_q.lock);
474 skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
475 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
476
477 /* If the packet has been pending on the queue for too long, discard it */
478 if (time_after(jiffies, cb->expires)) {
479 atomic_long_inc(&session->stats.rx_seq_discards);
480 atomic_long_inc(&session->stats.rx_errors);
481 trace_session_pkt_expired(session, cb->ns);
482 session->reorder_skip = 1;
483 __skb_unlink(skb, &session->reorder_q);
484 kfree_skb(skb);
485 continue;
486 }
487
488 if (cb->has_seq) {
489 if (session->reorder_skip) {
490 session->reorder_skip = 0;
491 session->nr = cb->ns;
492 trace_session_seqnum_reset(session);
493 }
494 if (cb->ns != session->nr)
495 goto out;
496 }
497 __skb_unlink(skb, &session->reorder_q);
498
499 /* Process the skb. We release the queue lock while we
500 * do so to let other contexts process the queue.
501 */
502 spin_unlock_bh(&session->reorder_q.lock);
503 l2tp_recv_dequeue_skb(session, skb);
504 goto start;
505 }
506
507 out:
508 spin_unlock_bh(&session->reorder_q.lock);
509 }
510
l2tp_seq_check_rx_window(struct l2tp_session * session,u32 nr)511 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
512 {
513 u32 nws;
514
515 if (nr >= session->nr)
516 nws = nr - session->nr;
517 else
518 nws = (session->nr_max + 1) - (session->nr - nr);
519
520 return nws < session->nr_window_size;
521 }
522
523 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
524 * acceptable, else non-zero.
525 */
l2tp_recv_data_seq(struct l2tp_session * session,struct sk_buff * skb)526 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
527 {
528 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
529
530 if (!l2tp_seq_check_rx_window(session, cb->ns)) {
531 /* Packet sequence number is outside allowed window.
532 * Discard it.
533 */
534 trace_session_pkt_outside_rx_window(session, cb->ns);
535 goto discard;
536 }
537
538 if (session->reorder_timeout != 0) {
539 /* Packet reordering enabled. Add skb to session's
540 * reorder queue, in order of ns.
541 */
542 l2tp_recv_queue_skb(session, skb);
543 goto out;
544 }
545
546 /* Packet reordering disabled. Discard out-of-sequence packets, while
547 * tracking the number if in-sequence packets after the first OOS packet
548 * is seen. After nr_oos_count_max in-sequence packets, reset the
549 * sequence number to re-enable packet reception.
550 */
551 if (cb->ns == session->nr) {
552 skb_queue_tail(&session->reorder_q, skb);
553 } else {
554 u32 nr_oos = cb->ns;
555 u32 nr_next = (session->nr_oos + 1) & session->nr_max;
556
557 if (nr_oos == nr_next)
558 session->nr_oos_count++;
559 else
560 session->nr_oos_count = 0;
561
562 session->nr_oos = nr_oos;
563 if (session->nr_oos_count > session->nr_oos_count_max) {
564 session->reorder_skip = 1;
565 }
566 if (!session->reorder_skip) {
567 atomic_long_inc(&session->stats.rx_seq_discards);
568 trace_session_pkt_oos(session, cb->ns);
569 goto discard;
570 }
571 skb_queue_tail(&session->reorder_q, skb);
572 }
573
574 out:
575 return 0;
576
577 discard:
578 return 1;
579 }
580
581 /* Do receive processing of L2TP data frames. We handle both L2TPv2
582 * and L2TPv3 data frames here.
583 *
584 * L2TPv2 Data Message Header
585 *
586 * 0 1 2 3
587 * 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
588 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
589 * |T|L|x|x|S|x|O|P|x|x|x|x| Ver | Length (opt) |
590 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
591 * | Tunnel ID | Session ID |
592 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
593 * | Ns (opt) | Nr (opt) |
594 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
595 * | Offset Size (opt) | Offset pad... (opt)
596 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
597 *
598 * Data frames are marked by T=0. All other fields are the same as
599 * those in L2TP control frames.
600 *
601 * L2TPv3 Data Message Header
602 *
603 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
604 * | L2TP Session Header |
605 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
606 * | L2-Specific Sublayer |
607 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
608 * | Tunnel Payload ...
609 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
610 *
611 * L2TPv3 Session Header Over IP
612 *
613 * 0 1 2 3
614 * 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
615 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
616 * | Session ID |
617 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
618 * | Cookie (optional, maximum 64 bits)...
619 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
620 * |
621 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
622 *
623 * L2TPv3 L2-Specific Sublayer Format
624 *
625 * 0 1 2 3
626 * 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
627 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
628 * |x|S|x|x|x|x|x|x| Sequence Number |
629 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
630 *
631 * Cookie value and sublayer format are negotiated with the peer when
632 * the session is set up. Unlike L2TPv2, we do not need to parse the
633 * packet header to determine if optional fields are present.
634 *
635 * Caller must already have parsed the frame and determined that it is
636 * a data (not control) frame before coming here. Fields up to the
637 * session-id have already been parsed and ptr points to the data
638 * after the session-id.
639 */
l2tp_recv_common(struct l2tp_session * session,struct sk_buff * skb,unsigned char * ptr,unsigned char * optr,u16 hdrflags,int length)640 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
641 unsigned char *ptr, unsigned char *optr, u16 hdrflags,
642 int length)
643 {
644 struct l2tp_tunnel *tunnel = session->tunnel;
645 int offset;
646
647 /* Parse and check optional cookie */
648 if (session->peer_cookie_len > 0) {
649 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
650 pr_debug_ratelimited("%s: cookie mismatch (%u/%u). Discarding.\n",
651 tunnel->name, tunnel->tunnel_id,
652 session->session_id);
653 atomic_long_inc(&session->stats.rx_cookie_discards);
654 goto discard;
655 }
656 ptr += session->peer_cookie_len;
657 }
658
659 /* Handle the optional sequence numbers. Sequence numbers are
660 * in different places for L2TPv2 and L2TPv3.
661 *
662 * If we are the LAC, enable/disable sequence numbers under
663 * the control of the LNS. If no sequence numbers present but
664 * we were expecting them, discard frame.
665 */
666 L2TP_SKB_CB(skb)->has_seq = 0;
667 if (tunnel->version == L2TP_HDR_VER_2) {
668 if (hdrflags & L2TP_HDRFLAG_S) {
669 /* Store L2TP info in the skb */
670 L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr);
671 L2TP_SKB_CB(skb)->has_seq = 1;
672 ptr += 2;
673 /* Skip past nr in the header */
674 ptr += 2;
675
676 }
677 } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
678 u32 l2h = ntohl(*(__be32 *)ptr);
679
680 if (l2h & 0x40000000) {
681 /* Store L2TP info in the skb */
682 L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff;
683 L2TP_SKB_CB(skb)->has_seq = 1;
684 }
685 ptr += 4;
686 }
687
688 if (L2TP_SKB_CB(skb)->has_seq) {
689 /* Received a packet with sequence numbers. If we're the LAC,
690 * check if we sre sending sequence numbers and if not,
691 * configure it so.
692 */
693 if (!session->lns_mode && !session->send_seq) {
694 trace_session_seqnum_lns_enable(session);
695 session->send_seq = 1;
696 l2tp_session_set_header_len(session, tunnel->version);
697 }
698 } else {
699 /* No sequence numbers.
700 * If user has configured mandatory sequence numbers, discard.
701 */
702 if (session->recv_seq) {
703 pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
704 session->name);
705 atomic_long_inc(&session->stats.rx_seq_discards);
706 goto discard;
707 }
708
709 /* If we're the LAC and we're sending sequence numbers, the
710 * LNS has requested that we no longer send sequence numbers.
711 * If we're the LNS and we're sending sequence numbers, the
712 * LAC is broken. Discard the frame.
713 */
714 if (!session->lns_mode && session->send_seq) {
715 trace_session_seqnum_lns_disable(session);
716 session->send_seq = 0;
717 l2tp_session_set_header_len(session, tunnel->version);
718 } else if (session->send_seq) {
719 pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
720 session->name);
721 atomic_long_inc(&session->stats.rx_seq_discards);
722 goto discard;
723 }
724 }
725
726 /* Session data offset is defined only for L2TPv2 and is
727 * indicated by an optional 16-bit value in the header.
728 */
729 if (tunnel->version == L2TP_HDR_VER_2) {
730 /* If offset bit set, skip it. */
731 if (hdrflags & L2TP_HDRFLAG_O) {
732 offset = ntohs(*(__be16 *)ptr);
733 ptr += 2 + offset;
734 }
735 }
736
737 offset = ptr - optr;
738 if (!pskb_may_pull(skb, offset))
739 goto discard;
740
741 __skb_pull(skb, offset);
742
743 /* Prepare skb for adding to the session's reorder_q. Hold
744 * packets for max reorder_timeout or 1 second if not
745 * reordering.
746 */
747 L2TP_SKB_CB(skb)->length = length;
748 L2TP_SKB_CB(skb)->expires = jiffies +
749 (session->reorder_timeout ? session->reorder_timeout : HZ);
750
751 /* Add packet to the session's receive queue. Reordering is done here, if
752 * enabled. Saved L2TP protocol info is stored in skb->sb[].
753 */
754 if (L2TP_SKB_CB(skb)->has_seq) {
755 if (l2tp_recv_data_seq(session, skb))
756 goto discard;
757 } else {
758 /* No sequence numbers. Add the skb to the tail of the
759 * reorder queue. This ensures that it will be
760 * delivered after all previous sequenced skbs.
761 */
762 skb_queue_tail(&session->reorder_q, skb);
763 }
764
765 /* Try to dequeue as many skbs from reorder_q as we can. */
766 l2tp_recv_dequeue(session);
767
768 return;
769
770 discard:
771 atomic_long_inc(&session->stats.rx_errors);
772 kfree_skb(skb);
773 }
774 EXPORT_SYMBOL_GPL(l2tp_recv_common);
775
776 /* Drop skbs from the session's reorder_q
777 */
l2tp_session_queue_purge(struct l2tp_session * session)778 static void l2tp_session_queue_purge(struct l2tp_session *session)
779 {
780 struct sk_buff *skb = NULL;
781
782 while ((skb = skb_dequeue(&session->reorder_q))) {
783 atomic_long_inc(&session->stats.rx_errors);
784 kfree_skb(skb);
785 }
786 }
787
788 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
789 * here. The skb is not on a list when we get here.
790 * Returns 0 if the packet was a data packet and was successfully passed on.
791 * Returns 1 if the packet was not a good data packet and could not be
792 * forwarded. All such packets are passed up to userspace to deal with.
793 */
l2tp_udp_recv_core(struct l2tp_tunnel * tunnel,struct sk_buff * skb)794 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
795 {
796 struct l2tp_session *session = NULL;
797 unsigned char *ptr, *optr;
798 u16 hdrflags;
799 u32 tunnel_id, session_id;
800 u16 version;
801 int length;
802
803 /* UDP has verified checksum */
804
805 /* UDP always verifies the packet length. */
806 __skb_pull(skb, sizeof(struct udphdr));
807
808 /* Short packet? */
809 if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
810 pr_debug_ratelimited("%s: recv short packet (len=%d)\n",
811 tunnel->name, skb->len);
812 goto invalid;
813 }
814
815 /* Point to L2TP header */
816 optr = skb->data;
817 ptr = skb->data;
818
819 /* Get L2TP header flags */
820 hdrflags = ntohs(*(__be16 *)ptr);
821
822 /* Check protocol version */
823 version = hdrflags & L2TP_HDR_VER_MASK;
824 if (version != tunnel->version) {
825 pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n",
826 tunnel->name, version, tunnel->version);
827 goto invalid;
828 }
829
830 /* Get length of L2TP packet */
831 length = skb->len;
832
833 /* If type is control packet, it is handled by userspace. */
834 if (hdrflags & L2TP_HDRFLAG_T)
835 goto pass;
836
837 /* Skip flags */
838 ptr += 2;
839
840 if (tunnel->version == L2TP_HDR_VER_2) {
841 /* If length is present, skip it */
842 if (hdrflags & L2TP_HDRFLAG_L)
843 ptr += 2;
844
845 /* Extract tunnel and session ID */
846 tunnel_id = ntohs(*(__be16 *)ptr);
847 ptr += 2;
848 session_id = ntohs(*(__be16 *)ptr);
849 ptr += 2;
850 } else {
851 ptr += 2; /* skip reserved bits */
852 tunnel_id = tunnel->tunnel_id;
853 session_id = ntohl(*(__be32 *)ptr);
854 ptr += 4;
855 }
856
857 /* Find the session context */
858 session = l2tp_tunnel_get_session(tunnel, session_id);
859 if (!session || !session->recv_skb) {
860 if (session)
861 l2tp_session_dec_refcount(session);
862
863 /* Not found? Pass to userspace to deal with */
864 pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n",
865 tunnel->name, tunnel_id, session_id);
866 goto pass;
867 }
868
869 if (tunnel->version == L2TP_HDR_VER_3 &&
870 l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
871 l2tp_session_dec_refcount(session);
872 goto invalid;
873 }
874
875 l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
876 l2tp_session_dec_refcount(session);
877
878 return 0;
879
880 invalid:
881 atomic_long_inc(&tunnel->stats.rx_invalid);
882
883 pass:
884 /* Put UDP header back */
885 __skb_push(skb, sizeof(struct udphdr));
886
887 return 1;
888 }
889
890 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
891 * Return codes:
892 * 0 : success.
893 * <0: error
894 * >0: skb should be passed up to userspace as UDP.
895 */
l2tp_udp_encap_recv(struct sock * sk,struct sk_buff * skb)896 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
897 {
898 struct l2tp_tunnel *tunnel;
899
900 /* Note that this is called from the encap_rcv hook inside an
901 * RCU-protected region, but without the socket being locked.
902 * Hence we use rcu_dereference_sk_user_data to access the
903 * tunnel data structure rather the usual l2tp_sk_to_tunnel
904 * accessor function.
905 */
906 tunnel = rcu_dereference_sk_user_data(sk);
907 if (!tunnel)
908 goto pass_up;
909 if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
910 goto pass_up;
911
912 if (l2tp_udp_recv_core(tunnel, skb))
913 goto pass_up;
914
915 return 0;
916
917 pass_up:
918 return 1;
919 }
920 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
921
922 /************************************************************************
923 * Transmit handling
924 ***********************************************************************/
925
926 /* Build an L2TP header for the session into the buffer provided.
927 */
l2tp_build_l2tpv2_header(struct l2tp_session * session,void * buf)928 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
929 {
930 struct l2tp_tunnel *tunnel = session->tunnel;
931 __be16 *bufp = buf;
932 __be16 *optr = buf;
933 u16 flags = L2TP_HDR_VER_2;
934 u32 tunnel_id = tunnel->peer_tunnel_id;
935 u32 session_id = session->peer_session_id;
936
937 if (session->send_seq)
938 flags |= L2TP_HDRFLAG_S;
939
940 /* Setup L2TP header. */
941 *bufp++ = htons(flags);
942 *bufp++ = htons(tunnel_id);
943 *bufp++ = htons(session_id);
944 if (session->send_seq) {
945 *bufp++ = htons(session->ns);
946 *bufp++ = 0;
947 session->ns++;
948 session->ns &= 0xffff;
949 trace_session_seqnum_update(session);
950 }
951
952 return bufp - optr;
953 }
954
l2tp_build_l2tpv3_header(struct l2tp_session * session,void * buf)955 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
956 {
957 struct l2tp_tunnel *tunnel = session->tunnel;
958 char *bufp = buf;
959 char *optr = bufp;
960
961 /* Setup L2TP header. The header differs slightly for UDP and
962 * IP encapsulations. For UDP, there is 4 bytes of flags.
963 */
964 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
965 u16 flags = L2TP_HDR_VER_3;
966 *((__be16 *)bufp) = htons(flags);
967 bufp += 2;
968 *((__be16 *)bufp) = 0;
969 bufp += 2;
970 }
971
972 *((__be32 *)bufp) = htonl(session->peer_session_id);
973 bufp += 4;
974 if (session->cookie_len) {
975 memcpy(bufp, &session->cookie[0], session->cookie_len);
976 bufp += session->cookie_len;
977 }
978 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
979 u32 l2h = 0;
980
981 if (session->send_seq) {
982 l2h = 0x40000000 | session->ns;
983 session->ns++;
984 session->ns &= 0xffffff;
985 trace_session_seqnum_update(session);
986 }
987
988 *((__be32 *)bufp) = htonl(l2h);
989 bufp += 4;
990 }
991
992 return bufp - optr;
993 }
994
995 /* 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)996 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
997 {
998 int err;
999
1000 skb->ignore_df = 1;
1001 skb_dst_drop(skb);
1002 #if IS_ENABLED(CONFIG_IPV6)
1003 if (l2tp_sk_is_v6(tunnel->sock))
1004 err = inet6_csk_xmit(tunnel->sock, skb, NULL);
1005 else
1006 #endif
1007 err = ip_queue_xmit(tunnel->sock, skb, fl);
1008
1009 return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
1010 }
1011
l2tp_xmit_core(struct l2tp_session * session,struct sk_buff * skb,unsigned int * len)1012 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len)
1013 {
1014 struct l2tp_tunnel *tunnel = session->tunnel;
1015 unsigned int data_len = skb->len;
1016 struct sock *sk = tunnel->sock;
1017 int headroom, uhlen, udp_len;
1018 int ret = NET_XMIT_SUCCESS;
1019 struct inet_sock *inet;
1020 struct udphdr *uh;
1021
1022 /* Check that there's enough headroom in the skb to insert IP,
1023 * UDP and L2TP headers. If not enough, expand it to
1024 * make room. Adjust truesize.
1025 */
1026 uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
1027 headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
1028 if (skb_cow_head(skb, headroom)) {
1029 kfree_skb(skb);
1030 return NET_XMIT_DROP;
1031 }
1032
1033 /* Setup L2TP header */
1034 if (tunnel->version == L2TP_HDR_VER_2)
1035 l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len));
1036 else
1037 l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len));
1038
1039 /* Reset skb netfilter state */
1040 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1041 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);
1042 nf_reset_ct(skb);
1043
1044 bh_lock_sock_nested(sk);
1045 if (sock_owned_by_user(sk)) {
1046 kfree_skb(skb);
1047 ret = NET_XMIT_DROP;
1048 goto out_unlock;
1049 }
1050
1051 /* The user-space may change the connection status for the user-space
1052 * provided socket at run time: we must check it under the socket lock
1053 */
1054 if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1055 kfree_skb(skb);
1056 ret = NET_XMIT_DROP;
1057 goto out_unlock;
1058 }
1059
1060 /* Report transmitted length before we add encap header, which keeps
1061 * statistics consistent for both UDP and IP encap tx/rx paths.
1062 */
1063 *len = skb->len;
1064
1065 inet = inet_sk(sk);
1066 switch (tunnel->encap) {
1067 case L2TP_ENCAPTYPE_UDP:
1068 /* Setup UDP header */
1069 __skb_push(skb, sizeof(*uh));
1070 skb_reset_transport_header(skb);
1071 uh = udp_hdr(skb);
1072 uh->source = inet->inet_sport;
1073 uh->dest = inet->inet_dport;
1074 udp_len = uhlen + session->hdr_len + data_len;
1075 uh->len = htons(udp_len);
1076
1077 /* Calculate UDP checksum if configured to do so */
1078 #if IS_ENABLED(CONFIG_IPV6)
1079 if (l2tp_sk_is_v6(sk))
1080 udp6_set_csum(udp_get_no_check6_tx(sk),
1081 skb, &inet6_sk(sk)->saddr,
1082 &sk->sk_v6_daddr, udp_len);
1083 else
1084 #endif
1085 udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1086 inet->inet_daddr, udp_len);
1087 break;
1088
1089 case L2TP_ENCAPTYPE_IP:
1090 break;
1091 }
1092
1093 ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
1094
1095 out_unlock:
1096 bh_unlock_sock(sk);
1097
1098 return ret;
1099 }
1100
1101 /* If caller requires the skb to have a ppp header, the header must be
1102 * inserted in the skb data before calling this function.
1103 */
l2tp_xmit_skb(struct l2tp_session * session,struct sk_buff * skb)1104 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
1105 {
1106 unsigned int len = 0;
1107 int ret;
1108
1109 ret = l2tp_xmit_core(session, skb, &len);
1110 if (ret == NET_XMIT_SUCCESS) {
1111 atomic_long_inc(&session->tunnel->stats.tx_packets);
1112 atomic_long_add(len, &session->tunnel->stats.tx_bytes);
1113 atomic_long_inc(&session->stats.tx_packets);
1114 atomic_long_add(len, &session->stats.tx_bytes);
1115 } else {
1116 atomic_long_inc(&session->tunnel->stats.tx_errors);
1117 atomic_long_inc(&session->stats.tx_errors);
1118 }
1119 return ret;
1120 }
1121 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1122
1123 /*****************************************************************************
1124 * Tinnel and session create/destroy.
1125 *****************************************************************************/
1126
1127 /* Tunnel socket destruct hook.
1128 * The tunnel context is deleted only when all session sockets have been
1129 * closed.
1130 */
l2tp_tunnel_destruct(struct sock * sk)1131 static void l2tp_tunnel_destruct(struct sock *sk)
1132 {
1133 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1134
1135 if (!tunnel)
1136 goto end;
1137
1138 /* Disable udp encapsulation */
1139 switch (tunnel->encap) {
1140 case L2TP_ENCAPTYPE_UDP:
1141 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1142 (udp_sk(sk))->encap_type = 0;
1143 (udp_sk(sk))->encap_rcv = NULL;
1144 (udp_sk(sk))->encap_destroy = NULL;
1145 break;
1146 case L2TP_ENCAPTYPE_IP:
1147 break;
1148 }
1149
1150 /* Remove hooks into tunnel socket */
1151 write_lock_bh(&sk->sk_callback_lock);
1152 sk->sk_destruct = tunnel->old_sk_destruct;
1153 sk->sk_user_data = NULL;
1154 write_unlock_bh(&sk->sk_callback_lock);
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 write_lock_bh(&tunnel->hlist_lock);
1174 hlist_del_init(&session->hlist);
1175 write_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 synchronize_rcu();
1185 }
1186 }
1187 }
1188
1189 /* When the tunnel is closed, all the attached sessions need to go too.
1190 */
l2tp_tunnel_closeall(struct l2tp_tunnel * tunnel)1191 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1192 {
1193 int hash;
1194 struct hlist_node *walk;
1195 struct hlist_node *tmp;
1196 struct l2tp_session *session;
1197
1198 write_lock_bh(&tunnel->hlist_lock);
1199 tunnel->acpt_newsess = false;
1200 for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1201 again:
1202 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1203 session = hlist_entry(walk, struct l2tp_session, hlist);
1204 hlist_del_init(&session->hlist);
1205
1206 write_unlock_bh(&tunnel->hlist_lock);
1207 l2tp_session_delete(session);
1208 write_lock_bh(&tunnel->hlist_lock);
1209
1210 /* Now restart from the beginning of this hash
1211 * chain. We always remove a session from the
1212 * list so we are guaranteed to make forward
1213 * progress.
1214 */
1215 goto again;
1216 }
1217 }
1218 write_unlock_bh(&tunnel->hlist_lock);
1219 }
1220
1221 /* Tunnel socket destroy hook for UDP encapsulation */
l2tp_udp_encap_destroy(struct sock * sk)1222 static void l2tp_udp_encap_destroy(struct sock *sk)
1223 {
1224 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1225
1226 if (tunnel)
1227 l2tp_tunnel_delete(tunnel);
1228 }
1229
l2tp_tunnel_remove(struct net * net,struct l2tp_tunnel * tunnel)1230 static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel)
1231 {
1232 struct l2tp_net *pn = l2tp_pernet(net);
1233
1234 spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1235 idr_remove(&pn->l2tp_tunnel_idr, tunnel->tunnel_id);
1236 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1237 }
1238
1239 /* Workqueue tunnel deletion function */
l2tp_tunnel_del_work(struct work_struct * work)1240 static void l2tp_tunnel_del_work(struct work_struct *work)
1241 {
1242 struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1243 del_work);
1244 struct sock *sk = tunnel->sock;
1245 struct socket *sock = sk->sk_socket;
1246
1247 l2tp_tunnel_closeall(tunnel);
1248
1249 /* If the tunnel socket was created within the kernel, use
1250 * the sk API to release it here.
1251 */
1252 if (tunnel->fd < 0) {
1253 if (sock) {
1254 kernel_sock_shutdown(sock, SHUT_RDWR);
1255 sock_release(sock);
1256 }
1257 }
1258
1259 l2tp_tunnel_remove(tunnel->l2tp_net, tunnel);
1260 /* drop initial ref */
1261 l2tp_tunnel_dec_refcount(tunnel);
1262
1263 /* drop workqueue ref */
1264 l2tp_tunnel_dec_refcount(tunnel);
1265 }
1266
1267 /* Create a socket for the tunnel, if one isn't set up by
1268 * userspace. This is used for static tunnels where there is no
1269 * managing L2TP daemon.
1270 *
1271 * Since we don't want these sockets to keep a namespace alive by
1272 * themselves, we drop the socket's namespace refcount after creation.
1273 * These sockets are freed when the namespace exits using the pernet
1274 * exit hook.
1275 */
l2tp_tunnel_sock_create(struct net * net,u32 tunnel_id,u32 peer_tunnel_id,struct l2tp_tunnel_cfg * cfg,struct socket ** sockp)1276 static int l2tp_tunnel_sock_create(struct net *net,
1277 u32 tunnel_id,
1278 u32 peer_tunnel_id,
1279 struct l2tp_tunnel_cfg *cfg,
1280 struct socket **sockp)
1281 {
1282 int err = -EINVAL;
1283 struct socket *sock = NULL;
1284 struct udp_port_cfg udp_conf;
1285
1286 switch (cfg->encap) {
1287 case L2TP_ENCAPTYPE_UDP:
1288 memset(&udp_conf, 0, sizeof(udp_conf));
1289
1290 #if IS_ENABLED(CONFIG_IPV6)
1291 if (cfg->local_ip6 && cfg->peer_ip6) {
1292 udp_conf.family = AF_INET6;
1293 memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1294 sizeof(udp_conf.local_ip6));
1295 memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1296 sizeof(udp_conf.peer_ip6));
1297 udp_conf.use_udp6_tx_checksums =
1298 !cfg->udp6_zero_tx_checksums;
1299 udp_conf.use_udp6_rx_checksums =
1300 !cfg->udp6_zero_rx_checksums;
1301 } else
1302 #endif
1303 {
1304 udp_conf.family = AF_INET;
1305 udp_conf.local_ip = cfg->local_ip;
1306 udp_conf.peer_ip = cfg->peer_ip;
1307 udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1308 }
1309
1310 udp_conf.local_udp_port = htons(cfg->local_udp_port);
1311 udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1312
1313 err = udp_sock_create(net, &udp_conf, &sock);
1314 if (err < 0)
1315 goto out;
1316
1317 break;
1318
1319 case L2TP_ENCAPTYPE_IP:
1320 #if IS_ENABLED(CONFIG_IPV6)
1321 if (cfg->local_ip6 && cfg->peer_ip6) {
1322 struct sockaddr_l2tpip6 ip6_addr = {0};
1323
1324 err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1325 IPPROTO_L2TP, &sock);
1326 if (err < 0)
1327 goto out;
1328
1329 ip6_addr.l2tp_family = AF_INET6;
1330 memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1331 sizeof(ip6_addr.l2tp_addr));
1332 ip6_addr.l2tp_conn_id = tunnel_id;
1333 err = kernel_bind(sock, (struct sockaddr *)&ip6_addr,
1334 sizeof(ip6_addr));
1335 if (err < 0)
1336 goto out;
1337
1338 ip6_addr.l2tp_family = AF_INET6;
1339 memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1340 sizeof(ip6_addr.l2tp_addr));
1341 ip6_addr.l2tp_conn_id = peer_tunnel_id;
1342 err = kernel_connect(sock,
1343 (struct sockaddr *)&ip6_addr,
1344 sizeof(ip6_addr), 0);
1345 if (err < 0)
1346 goto out;
1347 } else
1348 #endif
1349 {
1350 struct sockaddr_l2tpip ip_addr = {0};
1351
1352 err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1353 IPPROTO_L2TP, &sock);
1354 if (err < 0)
1355 goto out;
1356
1357 ip_addr.l2tp_family = AF_INET;
1358 ip_addr.l2tp_addr = cfg->local_ip;
1359 ip_addr.l2tp_conn_id = tunnel_id;
1360 err = kernel_bind(sock, (struct sockaddr *)&ip_addr,
1361 sizeof(ip_addr));
1362 if (err < 0)
1363 goto out;
1364
1365 ip_addr.l2tp_family = AF_INET;
1366 ip_addr.l2tp_addr = cfg->peer_ip;
1367 ip_addr.l2tp_conn_id = peer_tunnel_id;
1368 err = kernel_connect(sock, (struct sockaddr *)&ip_addr,
1369 sizeof(ip_addr), 0);
1370 if (err < 0)
1371 goto out;
1372 }
1373 break;
1374
1375 default:
1376 goto out;
1377 }
1378
1379 out:
1380 *sockp = sock;
1381 if (err < 0 && sock) {
1382 kernel_sock_shutdown(sock, SHUT_RDWR);
1383 sock_release(sock);
1384 *sockp = NULL;
1385 }
1386
1387 return err;
1388 }
1389
l2tp_tunnel_create(int fd,int version,u32 tunnel_id,u32 peer_tunnel_id,struct l2tp_tunnel_cfg * cfg,struct l2tp_tunnel ** tunnelp)1390 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id,
1391 struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
1392 {
1393 struct l2tp_tunnel *tunnel = NULL;
1394 int err;
1395 enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1396
1397 if (cfg)
1398 encap = cfg->encap;
1399
1400 tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
1401 if (!tunnel) {
1402 err = -ENOMEM;
1403 goto err;
1404 }
1405
1406 tunnel->version = version;
1407 tunnel->tunnel_id = tunnel_id;
1408 tunnel->peer_tunnel_id = peer_tunnel_id;
1409
1410 tunnel->magic = L2TP_TUNNEL_MAGIC;
1411 sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1412 rwlock_init(&tunnel->hlist_lock);
1413 tunnel->acpt_newsess = true;
1414
1415 tunnel->encap = encap;
1416
1417 refcount_set(&tunnel->ref_count, 1);
1418 tunnel->fd = fd;
1419
1420 /* Init delete workqueue struct */
1421 INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1422
1423 INIT_LIST_HEAD(&tunnel->list);
1424
1425 err = 0;
1426 err:
1427 if (tunnelp)
1428 *tunnelp = tunnel;
1429
1430 return err;
1431 }
1432 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1433
l2tp_validate_socket(const struct sock * sk,const struct net * net,enum l2tp_encap_type encap)1434 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1435 enum l2tp_encap_type encap)
1436 {
1437 if (!net_eq(sock_net(sk), net))
1438 return -EINVAL;
1439
1440 if (sk->sk_type != SOCK_DGRAM)
1441 return -EPROTONOSUPPORT;
1442
1443 if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
1444 return -EPROTONOSUPPORT;
1445
1446 if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1447 (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1448 return -EPROTONOSUPPORT;
1449
1450 if (sk->sk_user_data)
1451 return -EBUSY;
1452
1453 return 0;
1454 }
1455
l2tp_tunnel_register(struct l2tp_tunnel * tunnel,struct net * net,struct l2tp_tunnel_cfg * cfg)1456 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1457 struct l2tp_tunnel_cfg *cfg)
1458 {
1459 struct l2tp_net *pn = l2tp_pernet(net);
1460 u32 tunnel_id = tunnel->tunnel_id;
1461 struct socket *sock;
1462 struct sock *sk;
1463 int ret;
1464
1465 spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1466 ret = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id,
1467 GFP_ATOMIC);
1468 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1469 if (ret)
1470 return ret == -ENOSPC ? -EEXIST : ret;
1471
1472 if (tunnel->fd < 0) {
1473 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1474 tunnel->peer_tunnel_id, cfg,
1475 &sock);
1476 if (ret < 0)
1477 goto err;
1478 } else {
1479 sock = sockfd_lookup(tunnel->fd, &ret);
1480 if (!sock)
1481 goto err;
1482 }
1483
1484 sk = sock->sk;
1485 lock_sock(sk);
1486 write_lock_bh(&sk->sk_callback_lock);
1487 ret = l2tp_validate_socket(sk, net, tunnel->encap);
1488 if (ret < 0)
1489 goto err_inval_sock;
1490 rcu_assign_sk_user_data(sk, tunnel);
1491 write_unlock_bh(&sk->sk_callback_lock);
1492
1493 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1494 struct udp_tunnel_sock_cfg udp_cfg = {
1495 .sk_user_data = tunnel,
1496 .encap_type = UDP_ENCAP_L2TPINUDP,
1497 .encap_rcv = l2tp_udp_encap_recv,
1498 .encap_destroy = l2tp_udp_encap_destroy,
1499 };
1500
1501 setup_udp_tunnel_sock(net, sock, &udp_cfg);
1502 }
1503
1504 tunnel->old_sk_destruct = sk->sk_destruct;
1505 sk->sk_destruct = &l2tp_tunnel_destruct;
1506 sk->sk_allocation = GFP_ATOMIC;
1507 release_sock(sk);
1508
1509 sock_hold(sk);
1510 tunnel->sock = sk;
1511 tunnel->l2tp_net = net;
1512
1513 spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1514 idr_replace(&pn->l2tp_tunnel_idr, tunnel, tunnel->tunnel_id);
1515 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1516
1517 trace_register_tunnel(tunnel);
1518
1519 if (tunnel->fd >= 0)
1520 sockfd_put(sock);
1521
1522 return 0;
1523
1524 err_inval_sock:
1525 write_unlock_bh(&sk->sk_callback_lock);
1526 release_sock(sk);
1527
1528 if (tunnel->fd < 0)
1529 sock_release(sock);
1530 else
1531 sockfd_put(sock);
1532 err:
1533 l2tp_tunnel_remove(net, tunnel);
1534 return ret;
1535 }
1536 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1537
1538 /* This function is used by the netlink TUNNEL_DELETE command.
1539 */
l2tp_tunnel_delete(struct l2tp_tunnel * tunnel)1540 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1541 {
1542 if (!test_and_set_bit(0, &tunnel->dead)) {
1543 trace_delete_tunnel(tunnel);
1544 l2tp_tunnel_inc_refcount(tunnel);
1545 queue_work(l2tp_wq, &tunnel->del_work);
1546 }
1547 }
1548 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1549
l2tp_session_delete(struct l2tp_session * session)1550 void l2tp_session_delete(struct l2tp_session *session)
1551 {
1552 if (test_and_set_bit(0, &session->dead))
1553 return;
1554
1555 trace_delete_session(session);
1556 l2tp_session_unhash(session);
1557 l2tp_session_queue_purge(session);
1558 if (session->session_close)
1559 (*session->session_close)(session);
1560
1561 l2tp_session_dec_refcount(session);
1562 }
1563 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1564
1565 /* We come here whenever a session's send_seq, cookie_len or
1566 * l2specific_type parameters are set.
1567 */
l2tp_session_set_header_len(struct l2tp_session * session,int version)1568 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1569 {
1570 if (version == L2TP_HDR_VER_2) {
1571 session->hdr_len = 6;
1572 if (session->send_seq)
1573 session->hdr_len += 4;
1574 } else {
1575 session->hdr_len = 4 + session->cookie_len;
1576 session->hdr_len += l2tp_get_l2specific_len(session);
1577 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1578 session->hdr_len += 4;
1579 }
1580 }
1581 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1582
l2tp_session_create(int priv_size,struct l2tp_tunnel * tunnel,u32 session_id,u32 peer_session_id,struct l2tp_session_cfg * cfg)1583 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id,
1584 u32 peer_session_id, struct l2tp_session_cfg *cfg)
1585 {
1586 struct l2tp_session *session;
1587
1588 session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
1589 if (session) {
1590 session->magic = L2TP_SESSION_MAGIC;
1591 session->tunnel = tunnel;
1592
1593 session->session_id = session_id;
1594 session->peer_session_id = peer_session_id;
1595 session->nr = 0;
1596 if (tunnel->version == L2TP_HDR_VER_2)
1597 session->nr_max = 0xffff;
1598 else
1599 session->nr_max = 0xffffff;
1600 session->nr_window_size = session->nr_max / 2;
1601 session->nr_oos_count_max = 4;
1602
1603 /* Use NR of first received packet */
1604 session->reorder_skip = 1;
1605
1606 sprintf(&session->name[0], "sess %u/%u",
1607 tunnel->tunnel_id, session->session_id);
1608
1609 skb_queue_head_init(&session->reorder_q);
1610
1611 INIT_HLIST_NODE(&session->hlist);
1612 INIT_HLIST_NODE(&session->global_hlist);
1613
1614 if (cfg) {
1615 session->pwtype = cfg->pw_type;
1616 session->send_seq = cfg->send_seq;
1617 session->recv_seq = cfg->recv_seq;
1618 session->lns_mode = cfg->lns_mode;
1619 session->reorder_timeout = cfg->reorder_timeout;
1620 session->l2specific_type = cfg->l2specific_type;
1621 session->cookie_len = cfg->cookie_len;
1622 memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1623 session->peer_cookie_len = cfg->peer_cookie_len;
1624 memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1625 }
1626
1627 l2tp_session_set_header_len(session, tunnel->version);
1628
1629 refcount_set(&session->ref_count, 1);
1630
1631 return session;
1632 }
1633
1634 return ERR_PTR(-ENOMEM);
1635 }
1636 EXPORT_SYMBOL_GPL(l2tp_session_create);
1637
1638 /*****************************************************************************
1639 * Init and cleanup
1640 *****************************************************************************/
1641
l2tp_init_net(struct net * net)1642 static __net_init int l2tp_init_net(struct net *net)
1643 {
1644 struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1645 int hash;
1646
1647 idr_init(&pn->l2tp_tunnel_idr);
1648 spin_lock_init(&pn->l2tp_tunnel_idr_lock);
1649
1650 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1651 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1652
1653 spin_lock_init(&pn->l2tp_session_hlist_lock);
1654
1655 return 0;
1656 }
1657
l2tp_exit_net(struct net * net)1658 static __net_exit void l2tp_exit_net(struct net *net)
1659 {
1660 struct l2tp_net *pn = l2tp_pernet(net);
1661 struct l2tp_tunnel *tunnel = NULL;
1662 unsigned long tunnel_id, tmp;
1663 int hash;
1664
1665 rcu_read_lock_bh();
1666 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
1667 if (tunnel)
1668 l2tp_tunnel_delete(tunnel);
1669 }
1670 rcu_read_unlock_bh();
1671
1672 if (l2tp_wq)
1673 flush_workqueue(l2tp_wq);
1674 rcu_barrier();
1675
1676 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1677 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1678 idr_destroy(&pn->l2tp_tunnel_idr);
1679 }
1680
1681 static struct pernet_operations l2tp_net_ops = {
1682 .init = l2tp_init_net,
1683 .exit = l2tp_exit_net,
1684 .id = &l2tp_net_id,
1685 .size = sizeof(struct l2tp_net),
1686 };
1687
l2tp_init(void)1688 static int __init l2tp_init(void)
1689 {
1690 int rc = 0;
1691
1692 rc = register_pernet_device(&l2tp_net_ops);
1693 if (rc)
1694 goto out;
1695
1696 l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1697 if (!l2tp_wq) {
1698 pr_err("alloc_workqueue failed\n");
1699 unregister_pernet_device(&l2tp_net_ops);
1700 rc = -ENOMEM;
1701 goto out;
1702 }
1703
1704 pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1705
1706 out:
1707 return rc;
1708 }
1709
l2tp_exit(void)1710 static void __exit l2tp_exit(void)
1711 {
1712 unregister_pernet_device(&l2tp_net_ops);
1713 if (l2tp_wq) {
1714 destroy_workqueue(l2tp_wq);
1715 l2tp_wq = NULL;
1716 }
1717 }
1718
1719 module_init(l2tp_init);
1720 module_exit(l2tp_exit);
1721
1722 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1723 MODULE_DESCRIPTION("L2TP core");
1724 MODULE_LICENSE("GPL");
1725 MODULE_VERSION(L2TP_DRV_VERSION);
1726