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 rcu_read_lock_bh();
252 hlist_for_each_entry_rcu(session, session_list, hlist)
253 if (session->session_id == session_id) {
254 l2tp_session_inc_refcount(session);
255 rcu_read_unlock_bh();
256
257 return session;
258 }
259 rcu_read_unlock_bh();
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 rcu_read_lock_bh();
293 for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
294 hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
295 if (++count > nth) {
296 l2tp_session_inc_refcount(session);
297 rcu_read_unlock_bh();
298 return session;
299 }
300 }
301 }
302
303 rcu_read_unlock_bh();
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 spin_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_rcu(&session->hlist, head);
386 spin_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 spin_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 struct l2tp_tunnel *orig_tunnel = tunnel;
798 unsigned char *ptr, *optr;
799 u16 hdrflags;
800 u32 tunnel_id, session_id;
801 u16 version;
802 int length;
803
804 /* UDP has verified checksum */
805
806 /* UDP always verifies the packet length. */
807 __skb_pull(skb, sizeof(struct udphdr));
808
809 /* Short packet? */
810 if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
811 pr_debug_ratelimited("%s: recv short packet (len=%d)\n",
812 tunnel->name, skb->len);
813 goto invalid;
814 }
815
816 /* Point to L2TP header */
817 optr = skb->data;
818 ptr = skb->data;
819
820 /* Get L2TP header flags */
821 hdrflags = ntohs(*(__be16 *)ptr);
822
823 /* Get protocol version */
824 version = hdrflags & L2TP_HDR_VER_MASK;
825
826 /* Get length of L2TP packet */
827 length = skb->len;
828
829 /* If type is control packet, it is handled by userspace. */
830 if (hdrflags & L2TP_HDRFLAG_T)
831 goto pass;
832
833 /* Skip flags */
834 ptr += 2;
835
836 if (version == L2TP_HDR_VER_2) {
837 /* If length is present, skip it */
838 if (hdrflags & L2TP_HDRFLAG_L)
839 ptr += 2;
840
841 /* Extract tunnel and session ID */
842 tunnel_id = ntohs(*(__be16 *)ptr);
843 ptr += 2;
844
845 if (tunnel_id != tunnel->tunnel_id) {
846 /* We are receiving trafic for another tunnel, probably
847 * because we have several tunnels between the same
848 * IP/port quadruple, look it up.
849 */
850 struct l2tp_tunnel *alt_tunnel;
851
852 alt_tunnel = l2tp_tunnel_get(tunnel->l2tp_net, tunnel_id);
853 if (!alt_tunnel)
854 goto pass;
855 tunnel = alt_tunnel;
856 }
857
858 session_id = ntohs(*(__be16 *)ptr);
859 ptr += 2;
860 } else {
861 ptr += 2; /* skip reserved bits */
862 tunnel_id = tunnel->tunnel_id;
863 session_id = ntohl(*(__be32 *)ptr);
864 ptr += 4;
865 }
866
867 /* Check protocol version */
868 if (version != tunnel->version) {
869 pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n",
870 tunnel->name, version, tunnel->version);
871 goto invalid;
872 }
873
874 /* Find the session context */
875 session = l2tp_tunnel_get_session(tunnel, session_id);
876 if (!session || !session->recv_skb) {
877 if (session)
878 l2tp_session_dec_refcount(session);
879
880 /* Not found? Pass to userspace to deal with */
881 pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n",
882 tunnel->name, tunnel_id, session_id);
883 goto pass;
884 }
885
886 if (tunnel->version == L2TP_HDR_VER_3 &&
887 l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
888 l2tp_session_dec_refcount(session);
889 goto invalid;
890 }
891
892 l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
893 l2tp_session_dec_refcount(session);
894
895 if (tunnel != orig_tunnel)
896 l2tp_tunnel_dec_refcount(tunnel);
897
898 return 0;
899
900 invalid:
901 atomic_long_inc(&tunnel->stats.rx_invalid);
902
903 pass:
904 /* Put UDP header back */
905 __skb_push(skb, sizeof(struct udphdr));
906
907 if (tunnel != orig_tunnel)
908 l2tp_tunnel_dec_refcount(tunnel);
909
910 return 1;
911 }
912
913 /* UDP encapsulation receive and error receive handlers.
914 * See net/ipv4/udp.c for details.
915 *
916 * Note that these functions are called from inside an
917 * RCU-protected region, but without the socket being locked.
918 *
919 * Hence we use rcu_dereference_sk_user_data to access the
920 * tunnel data structure rather the usual l2tp_sk_to_tunnel
921 * accessor function.
922 */
l2tp_udp_encap_recv(struct sock * sk,struct sk_buff * skb)923 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
924 {
925 struct l2tp_tunnel *tunnel;
926
927 tunnel = rcu_dereference_sk_user_data(sk);
928 if (!tunnel)
929 goto pass_up;
930 if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
931 goto pass_up;
932
933 if (l2tp_udp_recv_core(tunnel, skb))
934 goto pass_up;
935
936 return 0;
937
938 pass_up:
939 return 1;
940 }
941 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
942
l2tp_udp_encap_err_recv(struct sock * sk,struct sk_buff * skb,int err,__be16 port,u32 info,u8 * payload)943 static void l2tp_udp_encap_err_recv(struct sock *sk, struct sk_buff *skb, int err,
944 __be16 port, u32 info, u8 *payload)
945 {
946 struct l2tp_tunnel *tunnel;
947
948 tunnel = rcu_dereference_sk_user_data(sk);
949 if (!tunnel || tunnel->fd < 0)
950 return;
951
952 sk->sk_err = err;
953 sk_error_report(sk);
954
955 if (ip_hdr(skb)->version == IPVERSION) {
956 if (inet_test_bit(RECVERR, sk))
957 return ip_icmp_error(sk, skb, err, port, info, payload);
958 #if IS_ENABLED(CONFIG_IPV6)
959 } else {
960 if (inet6_test_bit(RECVERR6, sk))
961 return ipv6_icmp_error(sk, skb, err, port, info, payload);
962 #endif
963 }
964 }
965
966 /************************************************************************
967 * Transmit handling
968 ***********************************************************************/
969
970 /* Build an L2TP header for the session into the buffer provided.
971 */
l2tp_build_l2tpv2_header(struct l2tp_session * session,void * buf)972 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
973 {
974 struct l2tp_tunnel *tunnel = session->tunnel;
975 __be16 *bufp = buf;
976 __be16 *optr = buf;
977 u16 flags = L2TP_HDR_VER_2;
978 u32 tunnel_id = tunnel->peer_tunnel_id;
979 u32 session_id = session->peer_session_id;
980
981 if (session->send_seq)
982 flags |= L2TP_HDRFLAG_S;
983
984 /* Setup L2TP header. */
985 *bufp++ = htons(flags);
986 *bufp++ = htons(tunnel_id);
987 *bufp++ = htons(session_id);
988 if (session->send_seq) {
989 *bufp++ = htons(session->ns);
990 *bufp++ = 0;
991 session->ns++;
992 session->ns &= 0xffff;
993 trace_session_seqnum_update(session);
994 }
995
996 return bufp - optr;
997 }
998
l2tp_build_l2tpv3_header(struct l2tp_session * session,void * buf)999 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
1000 {
1001 struct l2tp_tunnel *tunnel = session->tunnel;
1002 char *bufp = buf;
1003 char *optr = bufp;
1004
1005 /* Setup L2TP header. The header differs slightly for UDP and
1006 * IP encapsulations. For UDP, there is 4 bytes of flags.
1007 */
1008 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1009 u16 flags = L2TP_HDR_VER_3;
1010 *((__be16 *)bufp) = htons(flags);
1011 bufp += 2;
1012 *((__be16 *)bufp) = 0;
1013 bufp += 2;
1014 }
1015
1016 *((__be32 *)bufp) = htonl(session->peer_session_id);
1017 bufp += 4;
1018 if (session->cookie_len) {
1019 memcpy(bufp, &session->cookie[0], session->cookie_len);
1020 bufp += session->cookie_len;
1021 }
1022 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
1023 u32 l2h = 0;
1024
1025 if (session->send_seq) {
1026 l2h = 0x40000000 | session->ns;
1027 session->ns++;
1028 session->ns &= 0xffffff;
1029 trace_session_seqnum_update(session);
1030 }
1031
1032 *((__be32 *)bufp) = htonl(l2h);
1033 bufp += 4;
1034 }
1035
1036 return bufp - optr;
1037 }
1038
1039 /* 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)1040 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
1041 {
1042 int err;
1043
1044 skb->ignore_df = 1;
1045 skb_dst_drop(skb);
1046 #if IS_ENABLED(CONFIG_IPV6)
1047 if (l2tp_sk_is_v6(tunnel->sock))
1048 err = inet6_csk_xmit(tunnel->sock, skb, NULL);
1049 else
1050 #endif
1051 err = ip_queue_xmit(tunnel->sock, skb, fl);
1052
1053 return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
1054 }
1055
l2tp_xmit_core(struct l2tp_session * session,struct sk_buff * skb,unsigned int * len)1056 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len)
1057 {
1058 struct l2tp_tunnel *tunnel = session->tunnel;
1059 unsigned int data_len = skb->len;
1060 struct sock *sk = tunnel->sock;
1061 int headroom, uhlen, udp_len;
1062 int ret = NET_XMIT_SUCCESS;
1063 struct inet_sock *inet;
1064 struct udphdr *uh;
1065
1066 /* Check that there's enough headroom in the skb to insert IP,
1067 * UDP and L2TP headers. If not enough, expand it to
1068 * make room. Adjust truesize.
1069 */
1070 uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
1071 headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
1072 if (skb_cow_head(skb, headroom)) {
1073 kfree_skb(skb);
1074 return NET_XMIT_DROP;
1075 }
1076
1077 /* Setup L2TP header */
1078 if (tunnel->version == L2TP_HDR_VER_2)
1079 l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len));
1080 else
1081 l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len));
1082
1083 /* Reset skb netfilter state */
1084 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1085 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);
1086 nf_reset_ct(skb);
1087
1088 bh_lock_sock_nested(sk);
1089 if (sock_owned_by_user(sk)) {
1090 kfree_skb(skb);
1091 ret = NET_XMIT_DROP;
1092 goto out_unlock;
1093 }
1094
1095 /* The user-space may change the connection status for the user-space
1096 * provided socket at run time: we must check it under the socket lock
1097 */
1098 if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1099 kfree_skb(skb);
1100 ret = NET_XMIT_DROP;
1101 goto out_unlock;
1102 }
1103
1104 /* Report transmitted length before we add encap header, which keeps
1105 * statistics consistent for both UDP and IP encap tx/rx paths.
1106 */
1107 *len = skb->len;
1108
1109 inet = inet_sk(sk);
1110 switch (tunnel->encap) {
1111 case L2TP_ENCAPTYPE_UDP:
1112 /* Setup UDP header */
1113 __skb_push(skb, sizeof(*uh));
1114 skb_reset_transport_header(skb);
1115 uh = udp_hdr(skb);
1116 uh->source = inet->inet_sport;
1117 uh->dest = inet->inet_dport;
1118 udp_len = uhlen + session->hdr_len + data_len;
1119 uh->len = htons(udp_len);
1120
1121 /* Calculate UDP checksum if configured to do so */
1122 #if IS_ENABLED(CONFIG_IPV6)
1123 if (l2tp_sk_is_v6(sk))
1124 udp6_set_csum(udp_get_no_check6_tx(sk),
1125 skb, &inet6_sk(sk)->saddr,
1126 &sk->sk_v6_daddr, udp_len);
1127 else
1128 #endif
1129 udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1130 inet->inet_daddr, udp_len);
1131 break;
1132
1133 case L2TP_ENCAPTYPE_IP:
1134 break;
1135 }
1136
1137 ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
1138
1139 out_unlock:
1140 bh_unlock_sock(sk);
1141
1142 return ret;
1143 }
1144
1145 /* If caller requires the skb to have a ppp header, the header must be
1146 * inserted in the skb data before calling this function.
1147 */
l2tp_xmit_skb(struct l2tp_session * session,struct sk_buff * skb)1148 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
1149 {
1150 unsigned int len = 0;
1151 int ret;
1152
1153 ret = l2tp_xmit_core(session, skb, &len);
1154 if (ret == NET_XMIT_SUCCESS) {
1155 atomic_long_inc(&session->tunnel->stats.tx_packets);
1156 atomic_long_add(len, &session->tunnel->stats.tx_bytes);
1157 atomic_long_inc(&session->stats.tx_packets);
1158 atomic_long_add(len, &session->stats.tx_bytes);
1159 } else {
1160 atomic_long_inc(&session->tunnel->stats.tx_errors);
1161 atomic_long_inc(&session->stats.tx_errors);
1162 }
1163 return ret;
1164 }
1165 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1166
1167 /*****************************************************************************
1168 * Tinnel and session create/destroy.
1169 *****************************************************************************/
1170
1171 /* Tunnel socket destruct hook.
1172 * The tunnel context is deleted only when all session sockets have been
1173 * closed.
1174 */
l2tp_tunnel_destruct(struct sock * sk)1175 static void l2tp_tunnel_destruct(struct sock *sk)
1176 {
1177 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1178
1179 if (!tunnel)
1180 goto end;
1181
1182 /* Disable udp encapsulation */
1183 switch (tunnel->encap) {
1184 case L2TP_ENCAPTYPE_UDP:
1185 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1186 WRITE_ONCE(udp_sk(sk)->encap_type, 0);
1187 udp_sk(sk)->encap_rcv = NULL;
1188 udp_sk(sk)->encap_destroy = NULL;
1189 break;
1190 case L2TP_ENCAPTYPE_IP:
1191 break;
1192 }
1193
1194 /* Remove hooks into tunnel socket */
1195 write_lock_bh(&sk->sk_callback_lock);
1196 sk->sk_destruct = tunnel->old_sk_destruct;
1197 sk->sk_user_data = NULL;
1198 write_unlock_bh(&sk->sk_callback_lock);
1199
1200 /* Call the original destructor */
1201 if (sk->sk_destruct)
1202 (*sk->sk_destruct)(sk);
1203
1204 kfree_rcu(tunnel, rcu);
1205 end:
1206 return;
1207 }
1208
1209 /* Remove an l2tp session from l2tp_core's hash lists. */
l2tp_session_unhash(struct l2tp_session * session)1210 static void l2tp_session_unhash(struct l2tp_session *session)
1211 {
1212 struct l2tp_tunnel *tunnel = session->tunnel;
1213
1214 /* Remove the session from core hashes */
1215 if (tunnel) {
1216 /* Remove from the per-tunnel hash */
1217 spin_lock_bh(&tunnel->hlist_lock);
1218 hlist_del_init_rcu(&session->hlist);
1219 spin_unlock_bh(&tunnel->hlist_lock);
1220
1221 /* For L2TPv3 we have a per-net hash: remove from there, too */
1222 if (tunnel->version != L2TP_HDR_VER_2) {
1223 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1224
1225 spin_lock_bh(&pn->l2tp_session_hlist_lock);
1226 hlist_del_init_rcu(&session->global_hlist);
1227 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1228 }
1229
1230 synchronize_rcu();
1231 }
1232 }
1233
1234 /* When the tunnel is closed, all the attached sessions need to go too.
1235 */
l2tp_tunnel_closeall(struct l2tp_tunnel * tunnel)1236 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1237 {
1238 struct l2tp_session *session;
1239 int hash;
1240
1241 spin_lock_bh(&tunnel->hlist_lock);
1242 tunnel->acpt_newsess = false;
1243 for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1244 again:
1245 hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
1246 hlist_del_init_rcu(&session->hlist);
1247
1248 spin_unlock_bh(&tunnel->hlist_lock);
1249 l2tp_session_delete(session);
1250 spin_lock_bh(&tunnel->hlist_lock);
1251
1252 /* Now restart from the beginning of this hash
1253 * chain. We always remove a session from the
1254 * list so we are guaranteed to make forward
1255 * progress.
1256 */
1257 goto again;
1258 }
1259 }
1260 spin_unlock_bh(&tunnel->hlist_lock);
1261 }
1262
1263 /* Tunnel socket destroy hook for UDP encapsulation */
l2tp_udp_encap_destroy(struct sock * sk)1264 static void l2tp_udp_encap_destroy(struct sock *sk)
1265 {
1266 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1267
1268 if (tunnel)
1269 l2tp_tunnel_delete(tunnel);
1270 }
1271
l2tp_tunnel_remove(struct net * net,struct l2tp_tunnel * tunnel)1272 static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel)
1273 {
1274 struct l2tp_net *pn = l2tp_pernet(net);
1275
1276 spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1277 idr_remove(&pn->l2tp_tunnel_idr, tunnel->tunnel_id);
1278 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1279 }
1280
1281 /* Workqueue tunnel deletion function */
l2tp_tunnel_del_work(struct work_struct * work)1282 static void l2tp_tunnel_del_work(struct work_struct *work)
1283 {
1284 struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1285 del_work);
1286 struct sock *sk = tunnel->sock;
1287 struct socket *sock = sk->sk_socket;
1288
1289 l2tp_tunnel_closeall(tunnel);
1290
1291 /* If the tunnel socket was created within the kernel, use
1292 * the sk API to release it here.
1293 */
1294 if (tunnel->fd < 0) {
1295 if (sock) {
1296 kernel_sock_shutdown(sock, SHUT_RDWR);
1297 sock_release(sock);
1298 }
1299 }
1300
1301 l2tp_tunnel_remove(tunnel->l2tp_net, tunnel);
1302 /* drop initial ref */
1303 l2tp_tunnel_dec_refcount(tunnel);
1304
1305 /* drop workqueue ref */
1306 l2tp_tunnel_dec_refcount(tunnel);
1307 }
1308
1309 /* Create a socket for the tunnel, if one isn't set up by
1310 * userspace. This is used for static tunnels where there is no
1311 * managing L2TP daemon.
1312 *
1313 * Since we don't want these sockets to keep a namespace alive by
1314 * themselves, we drop the socket's namespace refcount after creation.
1315 * These sockets are freed when the namespace exits using the pernet
1316 * exit hook.
1317 */
l2tp_tunnel_sock_create(struct net * net,u32 tunnel_id,u32 peer_tunnel_id,struct l2tp_tunnel_cfg * cfg,struct socket ** sockp)1318 static int l2tp_tunnel_sock_create(struct net *net,
1319 u32 tunnel_id,
1320 u32 peer_tunnel_id,
1321 struct l2tp_tunnel_cfg *cfg,
1322 struct socket **sockp)
1323 {
1324 int err = -EINVAL;
1325 struct socket *sock = NULL;
1326 struct udp_port_cfg udp_conf;
1327
1328 switch (cfg->encap) {
1329 case L2TP_ENCAPTYPE_UDP:
1330 memset(&udp_conf, 0, sizeof(udp_conf));
1331
1332 #if IS_ENABLED(CONFIG_IPV6)
1333 if (cfg->local_ip6 && cfg->peer_ip6) {
1334 udp_conf.family = AF_INET6;
1335 memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1336 sizeof(udp_conf.local_ip6));
1337 memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1338 sizeof(udp_conf.peer_ip6));
1339 udp_conf.use_udp6_tx_checksums =
1340 !cfg->udp6_zero_tx_checksums;
1341 udp_conf.use_udp6_rx_checksums =
1342 !cfg->udp6_zero_rx_checksums;
1343 } else
1344 #endif
1345 {
1346 udp_conf.family = AF_INET;
1347 udp_conf.local_ip = cfg->local_ip;
1348 udp_conf.peer_ip = cfg->peer_ip;
1349 udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1350 }
1351
1352 udp_conf.local_udp_port = htons(cfg->local_udp_port);
1353 udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1354
1355 err = udp_sock_create(net, &udp_conf, &sock);
1356 if (err < 0)
1357 goto out;
1358
1359 break;
1360
1361 case L2TP_ENCAPTYPE_IP:
1362 #if IS_ENABLED(CONFIG_IPV6)
1363 if (cfg->local_ip6 && cfg->peer_ip6) {
1364 struct sockaddr_l2tpip6 ip6_addr = {0};
1365
1366 err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1367 IPPROTO_L2TP, &sock);
1368 if (err < 0)
1369 goto out;
1370
1371 ip6_addr.l2tp_family = AF_INET6;
1372 memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1373 sizeof(ip6_addr.l2tp_addr));
1374 ip6_addr.l2tp_conn_id = tunnel_id;
1375 err = kernel_bind(sock, (struct sockaddr *)&ip6_addr,
1376 sizeof(ip6_addr));
1377 if (err < 0)
1378 goto out;
1379
1380 ip6_addr.l2tp_family = AF_INET6;
1381 memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1382 sizeof(ip6_addr.l2tp_addr));
1383 ip6_addr.l2tp_conn_id = peer_tunnel_id;
1384 err = kernel_connect(sock,
1385 (struct sockaddr *)&ip6_addr,
1386 sizeof(ip6_addr), 0);
1387 if (err < 0)
1388 goto out;
1389 } else
1390 #endif
1391 {
1392 struct sockaddr_l2tpip ip_addr = {0};
1393
1394 err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1395 IPPROTO_L2TP, &sock);
1396 if (err < 0)
1397 goto out;
1398
1399 ip_addr.l2tp_family = AF_INET;
1400 ip_addr.l2tp_addr = cfg->local_ip;
1401 ip_addr.l2tp_conn_id = tunnel_id;
1402 err = kernel_bind(sock, (struct sockaddr *)&ip_addr,
1403 sizeof(ip_addr));
1404 if (err < 0)
1405 goto out;
1406
1407 ip_addr.l2tp_family = AF_INET;
1408 ip_addr.l2tp_addr = cfg->peer_ip;
1409 ip_addr.l2tp_conn_id = peer_tunnel_id;
1410 err = kernel_connect(sock, (struct sockaddr *)&ip_addr,
1411 sizeof(ip_addr), 0);
1412 if (err < 0)
1413 goto out;
1414 }
1415 break;
1416
1417 default:
1418 goto out;
1419 }
1420
1421 out:
1422 *sockp = sock;
1423 if (err < 0 && sock) {
1424 kernel_sock_shutdown(sock, SHUT_RDWR);
1425 sock_release(sock);
1426 *sockp = NULL;
1427 }
1428
1429 return err;
1430 }
1431
l2tp_tunnel_create(int fd,int version,u32 tunnel_id,u32 peer_tunnel_id,struct l2tp_tunnel_cfg * cfg,struct l2tp_tunnel ** tunnelp)1432 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id,
1433 struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
1434 {
1435 struct l2tp_tunnel *tunnel = NULL;
1436 int err;
1437 enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1438
1439 if (cfg)
1440 encap = cfg->encap;
1441
1442 tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
1443 if (!tunnel) {
1444 err = -ENOMEM;
1445 goto err;
1446 }
1447
1448 tunnel->version = version;
1449 tunnel->tunnel_id = tunnel_id;
1450 tunnel->peer_tunnel_id = peer_tunnel_id;
1451
1452 tunnel->magic = L2TP_TUNNEL_MAGIC;
1453 sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1454 spin_lock_init(&tunnel->hlist_lock);
1455 tunnel->acpt_newsess = true;
1456
1457 tunnel->encap = encap;
1458
1459 refcount_set(&tunnel->ref_count, 1);
1460 tunnel->fd = fd;
1461
1462 /* Init delete workqueue struct */
1463 INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1464
1465 INIT_LIST_HEAD(&tunnel->list);
1466
1467 err = 0;
1468 err:
1469 if (tunnelp)
1470 *tunnelp = tunnel;
1471
1472 return err;
1473 }
1474 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1475
l2tp_validate_socket(const struct sock * sk,const struct net * net,enum l2tp_encap_type encap)1476 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1477 enum l2tp_encap_type encap)
1478 {
1479 if (!net_eq(sock_net(sk), net))
1480 return -EINVAL;
1481
1482 if (sk->sk_type != SOCK_DGRAM)
1483 return -EPROTONOSUPPORT;
1484
1485 if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
1486 return -EPROTONOSUPPORT;
1487
1488 if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1489 (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1490 return -EPROTONOSUPPORT;
1491
1492 if (sk->sk_user_data)
1493 return -EBUSY;
1494
1495 return 0;
1496 }
1497
l2tp_tunnel_register(struct l2tp_tunnel * tunnel,struct net * net,struct l2tp_tunnel_cfg * cfg)1498 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1499 struct l2tp_tunnel_cfg *cfg)
1500 {
1501 struct l2tp_net *pn = l2tp_pernet(net);
1502 u32 tunnel_id = tunnel->tunnel_id;
1503 struct socket *sock;
1504 struct sock *sk;
1505 int ret;
1506
1507 spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1508 ret = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id,
1509 GFP_ATOMIC);
1510 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1511 if (ret)
1512 return ret == -ENOSPC ? -EEXIST : ret;
1513
1514 if (tunnel->fd < 0) {
1515 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1516 tunnel->peer_tunnel_id, cfg,
1517 &sock);
1518 if (ret < 0)
1519 goto err;
1520 } else {
1521 sock = sockfd_lookup(tunnel->fd, &ret);
1522 if (!sock)
1523 goto err;
1524 }
1525
1526 sk = sock->sk;
1527 lock_sock(sk);
1528 write_lock_bh(&sk->sk_callback_lock);
1529 ret = l2tp_validate_socket(sk, net, tunnel->encap);
1530 if (ret < 0)
1531 goto err_inval_sock;
1532 rcu_assign_sk_user_data(sk, tunnel);
1533 write_unlock_bh(&sk->sk_callback_lock);
1534
1535 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1536 struct udp_tunnel_sock_cfg udp_cfg = {
1537 .sk_user_data = tunnel,
1538 .encap_type = UDP_ENCAP_L2TPINUDP,
1539 .encap_rcv = l2tp_udp_encap_recv,
1540 .encap_err_rcv = l2tp_udp_encap_err_recv,
1541 .encap_destroy = l2tp_udp_encap_destroy,
1542 };
1543
1544 setup_udp_tunnel_sock(net, sock, &udp_cfg);
1545 }
1546
1547 tunnel->old_sk_destruct = sk->sk_destruct;
1548 sk->sk_destruct = &l2tp_tunnel_destruct;
1549 sk->sk_allocation = GFP_ATOMIC;
1550 release_sock(sk);
1551
1552 sock_hold(sk);
1553 tunnel->sock = sk;
1554 tunnel->l2tp_net = net;
1555
1556 spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1557 idr_replace(&pn->l2tp_tunnel_idr, tunnel, tunnel->tunnel_id);
1558 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1559
1560 trace_register_tunnel(tunnel);
1561
1562 if (tunnel->fd >= 0)
1563 sockfd_put(sock);
1564
1565 return 0;
1566
1567 err_inval_sock:
1568 write_unlock_bh(&sk->sk_callback_lock);
1569 release_sock(sk);
1570
1571 if (tunnel->fd < 0)
1572 sock_release(sock);
1573 else
1574 sockfd_put(sock);
1575 err:
1576 l2tp_tunnel_remove(net, tunnel);
1577 return ret;
1578 }
1579 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1580
1581 /* This function is used by the netlink TUNNEL_DELETE command.
1582 */
l2tp_tunnel_delete(struct l2tp_tunnel * tunnel)1583 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1584 {
1585 if (!test_and_set_bit(0, &tunnel->dead)) {
1586 trace_delete_tunnel(tunnel);
1587 l2tp_tunnel_inc_refcount(tunnel);
1588 queue_work(l2tp_wq, &tunnel->del_work);
1589 }
1590 }
1591 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1592
l2tp_session_delete(struct l2tp_session * session)1593 void l2tp_session_delete(struct l2tp_session *session)
1594 {
1595 if (test_and_set_bit(0, &session->dead))
1596 return;
1597
1598 trace_delete_session(session);
1599 l2tp_session_unhash(session);
1600 l2tp_session_queue_purge(session);
1601 if (session->session_close)
1602 (*session->session_close)(session);
1603
1604 l2tp_session_dec_refcount(session);
1605 }
1606 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1607
1608 /* We come here whenever a session's send_seq, cookie_len or
1609 * l2specific_type parameters are set.
1610 */
l2tp_session_set_header_len(struct l2tp_session * session,int version)1611 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1612 {
1613 if (version == L2TP_HDR_VER_2) {
1614 session->hdr_len = 6;
1615 if (session->send_seq)
1616 session->hdr_len += 4;
1617 } else {
1618 session->hdr_len = 4 + session->cookie_len;
1619 session->hdr_len += l2tp_get_l2specific_len(session);
1620 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1621 session->hdr_len += 4;
1622 }
1623 }
1624 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1625
l2tp_session_create(int priv_size,struct l2tp_tunnel * tunnel,u32 session_id,u32 peer_session_id,struct l2tp_session_cfg * cfg)1626 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id,
1627 u32 peer_session_id, struct l2tp_session_cfg *cfg)
1628 {
1629 struct l2tp_session *session;
1630
1631 session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
1632 if (session) {
1633 session->magic = L2TP_SESSION_MAGIC;
1634 session->tunnel = tunnel;
1635
1636 session->session_id = session_id;
1637 session->peer_session_id = peer_session_id;
1638 session->nr = 0;
1639 if (tunnel->version == L2TP_HDR_VER_2)
1640 session->nr_max = 0xffff;
1641 else
1642 session->nr_max = 0xffffff;
1643 session->nr_window_size = session->nr_max / 2;
1644 session->nr_oos_count_max = 4;
1645
1646 /* Use NR of first received packet */
1647 session->reorder_skip = 1;
1648
1649 sprintf(&session->name[0], "sess %u/%u",
1650 tunnel->tunnel_id, session->session_id);
1651
1652 skb_queue_head_init(&session->reorder_q);
1653
1654 INIT_HLIST_NODE(&session->hlist);
1655 INIT_HLIST_NODE(&session->global_hlist);
1656
1657 if (cfg) {
1658 session->pwtype = cfg->pw_type;
1659 session->send_seq = cfg->send_seq;
1660 session->recv_seq = cfg->recv_seq;
1661 session->lns_mode = cfg->lns_mode;
1662 session->reorder_timeout = cfg->reorder_timeout;
1663 session->l2specific_type = cfg->l2specific_type;
1664 session->cookie_len = cfg->cookie_len;
1665 memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1666 session->peer_cookie_len = cfg->peer_cookie_len;
1667 memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1668 }
1669
1670 l2tp_session_set_header_len(session, tunnel->version);
1671
1672 refcount_set(&session->ref_count, 1);
1673
1674 return session;
1675 }
1676
1677 return ERR_PTR(-ENOMEM);
1678 }
1679 EXPORT_SYMBOL_GPL(l2tp_session_create);
1680
1681 /*****************************************************************************
1682 * Init and cleanup
1683 *****************************************************************************/
1684
l2tp_init_net(struct net * net)1685 static __net_init int l2tp_init_net(struct net *net)
1686 {
1687 struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1688 int hash;
1689
1690 idr_init(&pn->l2tp_tunnel_idr);
1691 spin_lock_init(&pn->l2tp_tunnel_idr_lock);
1692
1693 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1694 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1695
1696 spin_lock_init(&pn->l2tp_session_hlist_lock);
1697
1698 return 0;
1699 }
1700
l2tp_exit_net(struct net * net)1701 static __net_exit void l2tp_exit_net(struct net *net)
1702 {
1703 struct l2tp_net *pn = l2tp_pernet(net);
1704 struct l2tp_tunnel *tunnel = NULL;
1705 unsigned long tunnel_id, tmp;
1706 int hash;
1707
1708 rcu_read_lock_bh();
1709 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
1710 if (tunnel)
1711 l2tp_tunnel_delete(tunnel);
1712 }
1713 rcu_read_unlock_bh();
1714
1715 if (l2tp_wq)
1716 flush_workqueue(l2tp_wq);
1717 rcu_barrier();
1718
1719 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1720 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1721 idr_destroy(&pn->l2tp_tunnel_idr);
1722 }
1723
1724 static struct pernet_operations l2tp_net_ops = {
1725 .init = l2tp_init_net,
1726 .exit = l2tp_exit_net,
1727 .id = &l2tp_net_id,
1728 .size = sizeof(struct l2tp_net),
1729 };
1730
l2tp_init(void)1731 static int __init l2tp_init(void)
1732 {
1733 int rc = 0;
1734
1735 rc = register_pernet_device(&l2tp_net_ops);
1736 if (rc)
1737 goto out;
1738
1739 l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1740 if (!l2tp_wq) {
1741 pr_err("alloc_workqueue failed\n");
1742 unregister_pernet_device(&l2tp_net_ops);
1743 rc = -ENOMEM;
1744 goto out;
1745 }
1746
1747 pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1748
1749 out:
1750 return rc;
1751 }
1752
l2tp_exit(void)1753 static void __exit l2tp_exit(void)
1754 {
1755 unregister_pernet_device(&l2tp_net_ops);
1756 if (l2tp_wq) {
1757 destroy_workqueue(l2tp_wq);
1758 l2tp_wq = NULL;
1759 }
1760 }
1761
1762 module_init(l2tp_init);
1763 module_exit(l2tp_exit);
1764
1765 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1766 MODULE_DESCRIPTION("L2TP core");
1767 MODULE_LICENSE("GPL");
1768 MODULE_VERSION(L2TP_DRV_VERSION);
1769