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TOMOYO Linux Cross Reference
Linux/net/l2tp/l2tp_core.c

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  1 /*
  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  * This program is free software; you can redistribute it and/or modify
 17  * it under the terms of the GNU General Public License version 2 as
 18  * published by the Free Software Foundation.
 19  */
 20 
 21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 22 
 23 #include <linux/module.h>
 24 #include <linux/string.h>
 25 #include <linux/list.h>
 26 #include <linux/rculist.h>
 27 #include <linux/uaccess.h>
 28 
 29 #include <linux/kernel.h>
 30 #include <linux/spinlock.h>
 31 #include <linux/kthread.h>
 32 #include <linux/sched.h>
 33 #include <linux/slab.h>
 34 #include <linux/errno.h>
 35 #include <linux/jiffies.h>
 36 
 37 #include <linux/netdevice.h>
 38 #include <linux/net.h>
 39 #include <linux/inetdevice.h>
 40 #include <linux/skbuff.h>
 41 #include <linux/init.h>
 42 #include <linux/in.h>
 43 #include <linux/ip.h>
 44 #include <linux/udp.h>
 45 #include <linux/l2tp.h>
 46 #include <linux/hash.h>
 47 #include <linux/sort.h>
 48 #include <linux/file.h>
 49 #include <linux/nsproxy.h>
 50 #include <net/net_namespace.h>
 51 #include <net/netns/generic.h>
 52 #include <net/dst.h>
 53 #include <net/ip.h>
 54 #include <net/udp.h>
 55 #include <net/udp_tunnel.h>
 56 #include <net/inet_common.h>
 57 #include <net/xfrm.h>
 58 #include <net/protocol.h>
 59 #include <net/inet6_connection_sock.h>
 60 #include <net/inet_ecn.h>
 61 #include <net/ip6_route.h>
 62 #include <net/ip6_checksum.h>
 63 
 64 #include <asm/byteorder.h>
 65 #include <linux/atomic.h>
 66 
 67 #include "l2tp_core.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_SEQ               10
 87 #define L2TP_HDR_SIZE_NOSEQ             6
 88 
 89 /* Default trace flags */
 90 #define L2TP_DEFAULT_DEBUG_FLAGS        0
 91 
 92 /* Private data stored for received packets in the skb.
 93  */
 94 struct l2tp_skb_cb {
 95         u32                     ns;
 96         u16                     has_seq;
 97         u16                     length;
 98         unsigned long           expires;
 99 };
100 
101 #define L2TP_SKB_CB(skb)        ((struct l2tp_skb_cb *) &skb->cb[sizeof(struct inet_skb_parm)])
102 
103 static struct workqueue_struct *l2tp_wq;
104 
105 /* per-net private data for this module */
106 static unsigned int l2tp_net_id;
107 struct l2tp_net {
108         struct list_head l2tp_tunnel_list;
109         spinlock_t l2tp_tunnel_list_lock;
110         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
111         spinlock_t l2tp_session_hlist_lock;
112 };
113 
114 #if IS_ENABLED(CONFIG_IPV6)
115 static bool l2tp_sk_is_v6(struct sock *sk)
116 {
117         return sk->sk_family == PF_INET6 &&
118                !ipv6_addr_v4mapped(&sk->sk_v6_daddr);
119 }
120 #endif
121 
122 static inline struct l2tp_tunnel *l2tp_tunnel(struct sock *sk)
123 {
124         return sk->sk_user_data;
125 }
126 
127 static inline struct l2tp_net *l2tp_pernet(const struct net *net)
128 {
129         BUG_ON(!net);
130 
131         return net_generic(net, l2tp_net_id);
132 }
133 
134 /* Session hash global list for L2TPv3.
135  * The session_id SHOULD be random according to RFC3931, but several
136  * L2TP implementations use incrementing session_ids.  So we do a real
137  * hash on the session_id, rather than a simple bitmask.
138  */
139 static inline struct hlist_head *
140 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
141 {
142         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
143 
144 }
145 
146 /* Session hash list.
147  * The session_id SHOULD be random according to RFC2661, but several
148  * L2TP implementations (Cisco and Microsoft) use incrementing
149  * session_ids.  So we do a real hash on the session_id, rather than a
150  * simple bitmask.
151  */
152 static inline struct hlist_head *
153 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
154 {
155         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
156 }
157 
158 void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
159 {
160         sock_put(tunnel->sock);
161         /* the tunnel is freed in the socket destructor */
162 }
163 EXPORT_SYMBOL(l2tp_tunnel_free);
164 
165 /* Lookup a tunnel. A new reference is held on the returned tunnel. */
166 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
167 {
168         const struct l2tp_net *pn = l2tp_pernet(net);
169         struct l2tp_tunnel *tunnel;
170 
171         rcu_read_lock_bh();
172         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
173                 if (tunnel->tunnel_id == tunnel_id) {
174                         l2tp_tunnel_inc_refcount(tunnel);
175                         rcu_read_unlock_bh();
176 
177                         return tunnel;
178                 }
179         }
180         rcu_read_unlock_bh();
181 
182         return NULL;
183 }
184 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
185 
186 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
187 {
188         const struct l2tp_net *pn = l2tp_pernet(net);
189         struct l2tp_tunnel *tunnel;
190         int count = 0;
191 
192         rcu_read_lock_bh();
193         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
194                 if (++count > nth) {
195                         l2tp_tunnel_inc_refcount(tunnel);
196                         rcu_read_unlock_bh();
197                         return tunnel;
198                 }
199         }
200         rcu_read_unlock_bh();
201 
202         return NULL;
203 }
204 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
205 
206 /* Lookup a session. A new reference is held on the returned session. */
207 struct l2tp_session *l2tp_session_get(const struct net *net,
208                                       struct l2tp_tunnel *tunnel,
209                                       u32 session_id)
210 {
211         struct hlist_head *session_list;
212         struct l2tp_session *session;
213 
214         if (!tunnel) {
215                 struct l2tp_net *pn = l2tp_pernet(net);
216 
217                 session_list = l2tp_session_id_hash_2(pn, session_id);
218 
219                 rcu_read_lock_bh();
220                 hlist_for_each_entry_rcu(session, session_list, global_hlist) {
221                         if (session->session_id == session_id) {
222                                 l2tp_session_inc_refcount(session);
223                                 rcu_read_unlock_bh();
224 
225                                 return session;
226                         }
227                 }
228                 rcu_read_unlock_bh();
229 
230                 return NULL;
231         }
232 
233         session_list = l2tp_session_id_hash(tunnel, session_id);
234         read_lock_bh(&tunnel->hlist_lock);
235         hlist_for_each_entry(session, session_list, hlist) {
236                 if (session->session_id == session_id) {
237                         l2tp_session_inc_refcount(session);
238                         read_unlock_bh(&tunnel->hlist_lock);
239 
240                         return session;
241                 }
242         }
243         read_unlock_bh(&tunnel->hlist_lock);
244 
245         return NULL;
246 }
247 EXPORT_SYMBOL_GPL(l2tp_session_get);
248 
249 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
250 {
251         int hash;
252         struct l2tp_session *session;
253         int count = 0;
254 
255         read_lock_bh(&tunnel->hlist_lock);
256         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
257                 hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
258                         if (++count > nth) {
259                                 l2tp_session_inc_refcount(session);
260                                 read_unlock_bh(&tunnel->hlist_lock);
261                                 return session;
262                         }
263                 }
264         }
265 
266         read_unlock_bh(&tunnel->hlist_lock);
267 
268         return NULL;
269 }
270 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
271 
272 /* Lookup a session by interface name.
273  * This is very inefficient but is only used by management interfaces.
274  */
275 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
276                                                 const char *ifname)
277 {
278         struct l2tp_net *pn = l2tp_pernet(net);
279         int hash;
280         struct l2tp_session *session;
281 
282         rcu_read_lock_bh();
283         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
284                 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
285                         if (!strcmp(session->ifname, ifname)) {
286                                 l2tp_session_inc_refcount(session);
287                                 rcu_read_unlock_bh();
288 
289                                 return session;
290                         }
291                 }
292         }
293 
294         rcu_read_unlock_bh();
295 
296         return NULL;
297 }
298 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
299 
300 int l2tp_session_register(struct l2tp_session *session,
301                           struct l2tp_tunnel *tunnel)
302 {
303         struct l2tp_session *session_walk;
304         struct hlist_head *g_head;
305         struct hlist_head *head;
306         struct l2tp_net *pn;
307         int err;
308 
309         head = l2tp_session_id_hash(tunnel, session->session_id);
310 
311         write_lock_bh(&tunnel->hlist_lock);
312         if (!tunnel->acpt_newsess) {
313                 err = -ENODEV;
314                 goto err_tlock;
315         }
316 
317         hlist_for_each_entry(session_walk, head, hlist)
318                 if (session_walk->session_id == session->session_id) {
319                         err = -EEXIST;
320                         goto err_tlock;
321                 }
322 
323         if (tunnel->version == L2TP_HDR_VER_3) {
324                 pn = l2tp_pernet(tunnel->l2tp_net);
325                 g_head = l2tp_session_id_hash_2(l2tp_pernet(tunnel->l2tp_net),
326                                                 session->session_id);
327 
328                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
329 
330                 hlist_for_each_entry(session_walk, g_head, global_hlist)
331                         if (session_walk->session_id == session->session_id) {
332                                 err = -EEXIST;
333                                 goto err_tlock_pnlock;
334                         }
335 
336                 l2tp_tunnel_inc_refcount(tunnel);
337                 hlist_add_head_rcu(&session->global_hlist, g_head);
338 
339                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
340         } else {
341                 l2tp_tunnel_inc_refcount(tunnel);
342         }
343 
344         hlist_add_head(&session->hlist, head);
345         write_unlock_bh(&tunnel->hlist_lock);
346 
347         return 0;
348 
349 err_tlock_pnlock:
350         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
351 err_tlock:
352         write_unlock_bh(&tunnel->hlist_lock);
353 
354         return err;
355 }
356 EXPORT_SYMBOL_GPL(l2tp_session_register);
357 
358 /*****************************************************************************
359  * Receive data handling
360  *****************************************************************************/
361 
362 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
363  * number.
364  */
365 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
366 {
367         struct sk_buff *skbp;
368         struct sk_buff *tmp;
369         u32 ns = L2TP_SKB_CB(skb)->ns;
370 
371         spin_lock_bh(&session->reorder_q.lock);
372         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
373                 if (L2TP_SKB_CB(skbp)->ns > ns) {
374                         __skb_queue_before(&session->reorder_q, skbp, skb);
375                         l2tp_dbg(session, L2TP_MSG_SEQ,
376                                  "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
377                                  session->name, ns, L2TP_SKB_CB(skbp)->ns,
378                                  skb_queue_len(&session->reorder_q));
379                         atomic_long_inc(&session->stats.rx_oos_packets);
380                         goto out;
381                 }
382         }
383 
384         __skb_queue_tail(&session->reorder_q, skb);
385 
386 out:
387         spin_unlock_bh(&session->reorder_q.lock);
388 }
389 
390 /* Dequeue a single skb.
391  */
392 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
393 {
394         struct l2tp_tunnel *tunnel = session->tunnel;
395         int length = L2TP_SKB_CB(skb)->length;
396 
397         /* We're about to requeue the skb, so return resources
398          * to its current owner (a socket receive buffer).
399          */
400         skb_orphan(skb);
401 
402         atomic_long_inc(&tunnel->stats.rx_packets);
403         atomic_long_add(length, &tunnel->stats.rx_bytes);
404         atomic_long_inc(&session->stats.rx_packets);
405         atomic_long_add(length, &session->stats.rx_bytes);
406 
407         if (L2TP_SKB_CB(skb)->has_seq) {
408                 /* Bump our Nr */
409                 session->nr++;
410                 session->nr &= session->nr_max;
411 
412                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated nr to %hu\n",
413                          session->name, session->nr);
414         }
415 
416         /* call private receive handler */
417         if (session->recv_skb != NULL)
418                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
419         else
420                 kfree_skb(skb);
421 }
422 
423 /* Dequeue skbs from the session's reorder_q, subject to packet order.
424  * Skbs that have been in the queue for too long are simply discarded.
425  */
426 static void l2tp_recv_dequeue(struct l2tp_session *session)
427 {
428         struct sk_buff *skb;
429         struct sk_buff *tmp;
430 
431         /* If the pkt at the head of the queue has the nr that we
432          * expect to send up next, dequeue it and any other
433          * in-sequence packets behind it.
434          */
435 start:
436         spin_lock_bh(&session->reorder_q.lock);
437         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
438                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
439                         atomic_long_inc(&session->stats.rx_seq_discards);
440                         atomic_long_inc(&session->stats.rx_errors);
441                         l2tp_dbg(session, L2TP_MSG_SEQ,
442                                  "%s: oos pkt %u len %d discarded (too old), waiting for %u, reorder_q_len=%d\n",
443                                  session->name, L2TP_SKB_CB(skb)->ns,
444                                  L2TP_SKB_CB(skb)->length, session->nr,
445                                  skb_queue_len(&session->reorder_q));
446                         session->reorder_skip = 1;
447                         __skb_unlink(skb, &session->reorder_q);
448                         kfree_skb(skb);
449                         continue;
450                 }
451 
452                 if (L2TP_SKB_CB(skb)->has_seq) {
453                         if (session->reorder_skip) {
454                                 l2tp_dbg(session, L2TP_MSG_SEQ,
455                                          "%s: advancing nr to next pkt: %u -> %u",
456                                          session->name, session->nr,
457                                          L2TP_SKB_CB(skb)->ns);
458                                 session->reorder_skip = 0;
459                                 session->nr = L2TP_SKB_CB(skb)->ns;
460                         }
461                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
462                                 l2tp_dbg(session, L2TP_MSG_SEQ,
463                                          "%s: holding oos pkt %u len %d, waiting for %u, reorder_q_len=%d\n",
464                                          session->name, L2TP_SKB_CB(skb)->ns,
465                                          L2TP_SKB_CB(skb)->length, session->nr,
466                                          skb_queue_len(&session->reorder_q));
467                                 goto out;
468                         }
469                 }
470                 __skb_unlink(skb, &session->reorder_q);
471 
472                 /* Process the skb. We release the queue lock while we
473                  * do so to let other contexts process the queue.
474                  */
475                 spin_unlock_bh(&session->reorder_q.lock);
476                 l2tp_recv_dequeue_skb(session, skb);
477                 goto start;
478         }
479 
480 out:
481         spin_unlock_bh(&session->reorder_q.lock);
482 }
483 
484 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
485 {
486         u32 nws;
487 
488         if (nr >= session->nr)
489                 nws = nr - session->nr;
490         else
491                 nws = (session->nr_max + 1) - (session->nr - nr);
492 
493         return nws < session->nr_window_size;
494 }
495 
496 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
497  * acceptable, else non-zero.
498  */
499 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
500 {
501         if (!l2tp_seq_check_rx_window(session, L2TP_SKB_CB(skb)->ns)) {
502                 /* Packet sequence number is outside allowed window.
503                  * Discard it.
504                  */
505                 l2tp_dbg(session, L2TP_MSG_SEQ,
506                          "%s: pkt %u len %d discarded, outside window, nr=%u\n",
507                          session->name, L2TP_SKB_CB(skb)->ns,
508                          L2TP_SKB_CB(skb)->length, session->nr);
509                 goto discard;
510         }
511 
512         if (session->reorder_timeout != 0) {
513                 /* Packet reordering enabled. Add skb to session's
514                  * reorder queue, in order of ns.
515                  */
516                 l2tp_recv_queue_skb(session, skb);
517                 goto out;
518         }
519 
520         /* Packet reordering disabled. Discard out-of-sequence packets, while
521          * tracking the number if in-sequence packets after the first OOS packet
522          * is seen. After nr_oos_count_max in-sequence packets, reset the
523          * sequence number to re-enable packet reception.
524          */
525         if (L2TP_SKB_CB(skb)->ns == session->nr) {
526                 skb_queue_tail(&session->reorder_q, skb);
527         } else {
528                 u32 nr_oos = L2TP_SKB_CB(skb)->ns;
529                 u32 nr_next = (session->nr_oos + 1) & session->nr_max;
530 
531                 if (nr_oos == nr_next)
532                         session->nr_oos_count++;
533                 else
534                         session->nr_oos_count = 0;
535 
536                 session->nr_oos = nr_oos;
537                 if (session->nr_oos_count > session->nr_oos_count_max) {
538                         session->reorder_skip = 1;
539                         l2tp_dbg(session, L2TP_MSG_SEQ,
540                                  "%s: %d oos packets received. Resetting sequence numbers\n",
541                                  session->name, session->nr_oos_count);
542                 }
543                 if (!session->reorder_skip) {
544                         atomic_long_inc(&session->stats.rx_seq_discards);
545                         l2tp_dbg(session, L2TP_MSG_SEQ,
546                                  "%s: oos pkt %u len %d discarded, waiting for %u, reorder_q_len=%d\n",
547                                  session->name, L2TP_SKB_CB(skb)->ns,
548                                  L2TP_SKB_CB(skb)->length, session->nr,
549                                  skb_queue_len(&session->reorder_q));
550                         goto discard;
551                 }
552                 skb_queue_tail(&session->reorder_q, skb);
553         }
554 
555 out:
556         return 0;
557 
558 discard:
559         return 1;
560 }
561 
562 /* Do receive processing of L2TP data frames. We handle both L2TPv2
563  * and L2TPv3 data frames here.
564  *
565  * L2TPv2 Data Message Header
566  *
567  *  0                   1                   2                   3
568  *  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
569  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
570  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
571  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
572  * |           Tunnel ID           |           Session ID          |
573  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
574  * |             Ns (opt)          |             Nr (opt)          |
575  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
576  * |      Offset Size (opt)        |    Offset pad... (opt)
577  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
578  *
579  * Data frames are marked by T=0. All other fields are the same as
580  * those in L2TP control frames.
581  *
582  * L2TPv3 Data Message Header
583  *
584  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
585  * |                      L2TP Session Header                      |
586  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
587  * |                      L2-Specific Sublayer                     |
588  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
589  * |                        Tunnel Payload                      ...
590  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
591  *
592  * L2TPv3 Session Header Over IP
593  *
594  *  0                   1                   2                   3
595  *  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
596  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
597  * |                           Session ID                          |
598  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
599  * |               Cookie (optional, maximum 64 bits)...
600  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
601  *                                                                 |
602  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
603  *
604  * L2TPv3 L2-Specific Sublayer Format
605  *
606  *  0                   1                   2                   3
607  *  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
608  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
609  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
610  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
611  *
612  * Cookie value and sublayer format are negotiated with the peer when
613  * the session is set up. Unlike L2TPv2, we do not need to parse the
614  * packet header to determine if optional fields are present.
615  *
616  * Caller must already have parsed the frame and determined that it is
617  * a data (not control) frame before coming here. Fields up to the
618  * session-id have already been parsed and ptr points to the data
619  * after the session-id.
620  */
621 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
622                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
623                       int length, int (*payload_hook)(struct sk_buff *skb))
624 {
625         struct l2tp_tunnel *tunnel = session->tunnel;
626         int offset;
627         u32 ns, nr;
628 
629         /* Parse and check optional cookie */
630         if (session->peer_cookie_len > 0) {
631                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
632                         l2tp_info(tunnel, L2TP_MSG_DATA,
633                                   "%s: cookie mismatch (%u/%u). Discarding.\n",
634                                   tunnel->name, tunnel->tunnel_id,
635                                   session->session_id);
636                         atomic_long_inc(&session->stats.rx_cookie_discards);
637                         goto discard;
638                 }
639                 ptr += session->peer_cookie_len;
640         }
641 
642         /* Handle the optional sequence numbers. Sequence numbers are
643          * in different places for L2TPv2 and L2TPv3.
644          *
645          * If we are the LAC, enable/disable sequence numbers under
646          * the control of the LNS.  If no sequence numbers present but
647          * we were expecting them, discard frame.
648          */
649         ns = nr = 0;
650         L2TP_SKB_CB(skb)->has_seq = 0;
651         if (tunnel->version == L2TP_HDR_VER_2) {
652                 if (hdrflags & L2TP_HDRFLAG_S) {
653                         ns = ntohs(*(__be16 *) ptr);
654                         ptr += 2;
655                         nr = ntohs(*(__be16 *) ptr);
656                         ptr += 2;
657 
658                         /* Store L2TP info in the skb */
659                         L2TP_SKB_CB(skb)->ns = ns;
660                         L2TP_SKB_CB(skb)->has_seq = 1;
661 
662                         l2tp_dbg(session, L2TP_MSG_SEQ,
663                                  "%s: recv data ns=%u, nr=%u, session nr=%u\n",
664                                  session->name, ns, nr, session->nr);
665                 }
666         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
667                 u32 l2h = ntohl(*(__be32 *) ptr);
668 
669                 if (l2h & 0x40000000) {
670                         ns = l2h & 0x00ffffff;
671 
672                         /* Store L2TP info in the skb */
673                         L2TP_SKB_CB(skb)->ns = ns;
674                         L2TP_SKB_CB(skb)->has_seq = 1;
675 
676                         l2tp_dbg(session, L2TP_MSG_SEQ,
677                                  "%s: recv data ns=%u, session nr=%u\n",
678                                  session->name, ns, session->nr);
679                 }
680                 ptr += 4;
681         }
682 
683         if (L2TP_SKB_CB(skb)->has_seq) {
684                 /* Received a packet with sequence numbers. If we're the LNS,
685                  * check if we sre sending sequence numbers and if not,
686                  * configure it so.
687                  */
688                 if ((!session->lns_mode) && (!session->send_seq)) {
689                         l2tp_info(session, L2TP_MSG_SEQ,
690                                   "%s: requested to enable seq numbers by LNS\n",
691                                   session->name);
692                         session->send_seq = 1;
693                         l2tp_session_set_header_len(session, tunnel->version);
694                 }
695         } else {
696                 /* No sequence numbers.
697                  * If user has configured mandatory sequence numbers, discard.
698                  */
699                 if (session->recv_seq) {
700                         l2tp_warn(session, L2TP_MSG_SEQ,
701                                   "%s: recv data has no seq numbers when required. Discarding.\n",
702                                   session->name);
703                         atomic_long_inc(&session->stats.rx_seq_discards);
704                         goto discard;
705                 }
706 
707                 /* If we're the LAC and we're sending sequence numbers, the
708                  * LNS has requested that we no longer send sequence numbers.
709                  * If we're the LNS and we're sending sequence numbers, the
710                  * LAC is broken. Discard the frame.
711                  */
712                 if ((!session->lns_mode) && (session->send_seq)) {
713                         l2tp_info(session, L2TP_MSG_SEQ,
714                                   "%s: requested to disable seq numbers by LNS\n",
715                                   session->name);
716                         session->send_seq = 0;
717                         l2tp_session_set_header_len(session, tunnel->version);
718                 } else if (session->send_seq) {
719                         l2tp_warn(session, L2TP_MSG_SEQ,
720                                   "%s: recv data has no seq numbers when required. Discarding.\n",
721                                   session->name);
722                         atomic_long_inc(&session->stats.rx_seq_discards);
723                         goto discard;
724                 }
725         }
726 
727         /* Session data offset is defined only for L2TPv2 and is
728          * indicated by an optional 16-bit value in the header.
729          */
730         if (tunnel->version == L2TP_HDR_VER_2) {
731                 /* If offset bit set, skip it. */
732                 if (hdrflags & L2TP_HDRFLAG_O) {
733                         offset = ntohs(*(__be16 *)ptr);
734                         ptr += 2 + offset;
735                 }
736         }
737 
738         offset = ptr - optr;
739         if (!pskb_may_pull(skb, offset))
740                 goto discard;
741 
742         __skb_pull(skb, offset);
743 
744         /* If caller wants to process the payload before we queue the
745          * packet, do so now.
746          */
747         if (payload_hook)
748                 if ((*payload_hook)(skb))
749                         goto discard;
750 
751         /* Prepare skb for adding to the session's reorder_q.  Hold
752          * packets for max reorder_timeout or 1 second if not
753          * reordering.
754          */
755         L2TP_SKB_CB(skb)->length = length;
756         L2TP_SKB_CB(skb)->expires = jiffies +
757                 (session->reorder_timeout ? session->reorder_timeout : HZ);
758 
759         /* Add packet to the session's receive queue. Reordering is done here, if
760          * enabled. Saved L2TP protocol info is stored in skb->sb[].
761          */
762         if (L2TP_SKB_CB(skb)->has_seq) {
763                 if (l2tp_recv_data_seq(session, skb))
764                         goto discard;
765         } else {
766                 /* No sequence numbers. Add the skb to the tail of the
767                  * reorder queue. This ensures that it will be
768                  * delivered after all previous sequenced skbs.
769                  */
770                 skb_queue_tail(&session->reorder_q, skb);
771         }
772 
773         /* Try to dequeue as many skbs from reorder_q as we can. */
774         l2tp_recv_dequeue(session);
775 
776         return;
777 
778 discard:
779         atomic_long_inc(&session->stats.rx_errors);
780         kfree_skb(skb);
781 }
782 EXPORT_SYMBOL(l2tp_recv_common);
783 
784 /* Drop skbs from the session's reorder_q
785  */
786 int l2tp_session_queue_purge(struct l2tp_session *session)
787 {
788         struct sk_buff *skb = NULL;
789         BUG_ON(!session);
790         BUG_ON(session->magic != L2TP_SESSION_MAGIC);
791         while ((skb = skb_dequeue(&session->reorder_q))) {
792                 atomic_long_inc(&session->stats.rx_errors);
793                 kfree_skb(skb);
794         }
795         return 0;
796 }
797 EXPORT_SYMBOL_GPL(l2tp_session_queue_purge);
798 
799 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
800  * here. The skb is not on a list when we get here.
801  * Returns 0 if the packet was a data packet and was successfully passed on.
802  * Returns 1 if the packet was not a good data packet and could not be
803  * forwarded.  All such packets are passed up to userspace to deal with.
804  */
805 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
806                               int (*payload_hook)(struct sk_buff *skb))
807 {
808         struct l2tp_session *session = NULL;
809         unsigned char *ptr, *optr;
810         u16 hdrflags;
811         u32 tunnel_id, session_id;
812         u16 version;
813         int length;
814 
815         /* UDP has verifed checksum */
816 
817         /* UDP always verifies the packet length. */
818         __skb_pull(skb, sizeof(struct udphdr));
819 
820         /* Short packet? */
821         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
822                 l2tp_info(tunnel, L2TP_MSG_DATA,
823                           "%s: recv short packet (len=%d)\n",
824                           tunnel->name, skb->len);
825                 goto error;
826         }
827 
828         /* Trace packet contents, if enabled */
829         if (tunnel->debug & L2TP_MSG_DATA) {
830                 length = min(32u, skb->len);
831                 if (!pskb_may_pull(skb, length))
832                         goto error;
833 
834                 pr_debug("%s: recv\n", tunnel->name);
835                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
836         }
837 
838         /* Point to L2TP header */
839         optr = ptr = skb->data;
840 
841         /* Get L2TP header flags */
842         hdrflags = ntohs(*(__be16 *) ptr);
843 
844         /* Check protocol version */
845         version = hdrflags & L2TP_HDR_VER_MASK;
846         if (version != tunnel->version) {
847                 l2tp_info(tunnel, L2TP_MSG_DATA,
848                           "%s: recv protocol version mismatch: got %d expected %d\n",
849                           tunnel->name, version, tunnel->version);
850                 goto error;
851         }
852 
853         /* Get length of L2TP packet */
854         length = skb->len;
855 
856         /* If type is control packet, it is handled by userspace. */
857         if (hdrflags & L2TP_HDRFLAG_T) {
858                 l2tp_dbg(tunnel, L2TP_MSG_DATA,
859                          "%s: recv control packet, len=%d\n",
860                          tunnel->name, length);
861                 goto error;
862         }
863 
864         /* Skip flags */
865         ptr += 2;
866 
867         if (tunnel->version == L2TP_HDR_VER_2) {
868                 /* If length is present, skip it */
869                 if (hdrflags & L2TP_HDRFLAG_L)
870                         ptr += 2;
871 
872                 /* Extract tunnel and session ID */
873                 tunnel_id = ntohs(*(__be16 *) ptr);
874                 ptr += 2;
875                 session_id = ntohs(*(__be16 *) ptr);
876                 ptr += 2;
877         } else {
878                 ptr += 2;       /* skip reserved bits */
879                 tunnel_id = tunnel->tunnel_id;
880                 session_id = ntohl(*(__be32 *) ptr);
881                 ptr += 4;
882         }
883 
884         /* Find the session context */
885         session = l2tp_session_get(tunnel->l2tp_net, tunnel, session_id);
886         if (!session || !session->recv_skb) {
887                 if (session)
888                         l2tp_session_dec_refcount(session);
889 
890                 /* Not found? Pass to userspace to deal with */
891                 l2tp_info(tunnel, L2TP_MSG_DATA,
892                           "%s: no session found (%u/%u). Passing up.\n",
893                           tunnel->name, tunnel_id, session_id);
894                 goto error;
895         }
896 
897         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
898         l2tp_session_dec_refcount(session);
899 
900         return 0;
901 
902 error:
903         /* Put UDP header back */
904         __skb_push(skb, sizeof(struct udphdr));
905 
906         return 1;
907 }
908 
909 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
910  * Return codes:
911  * 0 : success.
912  * <0: error
913  * >0: skb should be passed up to userspace as UDP.
914  */
915 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
916 {
917         struct l2tp_tunnel *tunnel;
918 
919         tunnel = l2tp_tunnel(sk);
920         if (tunnel == NULL)
921                 goto pass_up;
922 
923         l2tp_dbg(tunnel, L2TP_MSG_DATA, "%s: received %d bytes\n",
924                  tunnel->name, skb->len);
925 
926         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
927                 goto pass_up;
928 
929         return 0;
930 
931 pass_up:
932         return 1;
933 }
934 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
935 
936 /************************************************************************
937  * Transmit handling
938  ***********************************************************************/
939 
940 /* Build an L2TP header for the session into the buffer provided.
941  */
942 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
943 {
944         struct l2tp_tunnel *tunnel = session->tunnel;
945         __be16 *bufp = buf;
946         __be16 *optr = buf;
947         u16 flags = L2TP_HDR_VER_2;
948         u32 tunnel_id = tunnel->peer_tunnel_id;
949         u32 session_id = session->peer_session_id;
950 
951         if (session->send_seq)
952                 flags |= L2TP_HDRFLAG_S;
953 
954         /* Setup L2TP header. */
955         *bufp++ = htons(flags);
956         *bufp++ = htons(tunnel_id);
957         *bufp++ = htons(session_id);
958         if (session->send_seq) {
959                 *bufp++ = htons(session->ns);
960                 *bufp++ = 0;
961                 session->ns++;
962                 session->ns &= 0xffff;
963                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated ns to %u\n",
964                          session->name, session->ns);
965         }
966 
967         return bufp - optr;
968 }
969 
970 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
971 {
972         struct l2tp_tunnel *tunnel = session->tunnel;
973         char *bufp = buf;
974         char *optr = bufp;
975 
976         /* Setup L2TP header. The header differs slightly for UDP and
977          * IP encapsulations. For UDP, there is 4 bytes of flags.
978          */
979         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
980                 u16 flags = L2TP_HDR_VER_3;
981                 *((__be16 *) bufp) = htons(flags);
982                 bufp += 2;
983                 *((__be16 *) bufp) = 0;
984                 bufp += 2;
985         }
986 
987         *((__be32 *) bufp) = htonl(session->peer_session_id);
988         bufp += 4;
989         if (session->cookie_len) {
990                 memcpy(bufp, &session->cookie[0], session->cookie_len);
991                 bufp += session->cookie_len;
992         }
993         if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
994                 u32 l2h = 0;
995 
996                 if (session->send_seq) {
997                         l2h = 0x40000000 | session->ns;
998                         session->ns++;
999                         session->ns &= 0xffffff;
1000                         l2tp_dbg(session, L2TP_MSG_SEQ,
1001                                  "%s: updated ns to %u\n",
1002                                  session->name, session->ns);
1003                 }
1004 
1005                 *((__be32 *)bufp) = htonl(l2h);
1006                 bufp += 4;
1007         }
1008 
1009         return bufp - optr;
1010 }
1011 
1012 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
1013                           struct flowi *fl, size_t data_len)
1014 {
1015         struct l2tp_tunnel *tunnel = session->tunnel;
1016         unsigned int len = skb->len;
1017         int error;
1018 
1019         /* Debug */
1020         if (session->send_seq)
1021                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %zd bytes, ns=%u\n",
1022                          session->name, data_len, session->ns - 1);
1023         else
1024                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %zd bytes\n",
1025                          session->name, data_len);
1026 
1027         if (session->debug & L2TP_MSG_DATA) {
1028                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1029                 unsigned char *datap = skb->data + uhlen;
1030 
1031                 pr_debug("%s: xmit\n", session->name);
1032                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET,
1033                                      datap, min_t(size_t, 32, len - uhlen));
1034         }
1035 
1036         /* Queue the packet to IP for output */
1037         skb->ignore_df = 1;
1038 #if IS_ENABLED(CONFIG_IPV6)
1039         if (l2tp_sk_is_v6(tunnel->sock))
1040                 error = inet6_csk_xmit(tunnel->sock, skb, NULL);
1041         else
1042 #endif
1043                 error = ip_queue_xmit(tunnel->sock, skb, fl);
1044 
1045         /* Update stats */
1046         if (error >= 0) {
1047                 atomic_long_inc(&tunnel->stats.tx_packets);
1048                 atomic_long_add(len, &tunnel->stats.tx_bytes);
1049                 atomic_long_inc(&session->stats.tx_packets);
1050                 atomic_long_add(len, &session->stats.tx_bytes);
1051         } else {
1052                 atomic_long_inc(&tunnel->stats.tx_errors);
1053                 atomic_long_inc(&session->stats.tx_errors);
1054         }
1055 
1056         return 0;
1057 }
1058 
1059 /* If caller requires the skb to have a ppp header, the header must be
1060  * inserted in the skb data before calling this function.
1061  */
1062 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1063 {
1064         int data_len = skb->len;
1065         struct l2tp_tunnel *tunnel = session->tunnel;
1066         struct sock *sk = tunnel->sock;
1067         struct flowi *fl;
1068         struct udphdr *uh;
1069         struct inet_sock *inet;
1070         int headroom;
1071         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1072         int udp_len;
1073         int ret = NET_XMIT_SUCCESS;
1074 
1075         /* Check that there's enough headroom in the skb to insert IP,
1076          * UDP and L2TP headers. If not enough, expand it to
1077          * make room. Adjust truesize.
1078          */
1079         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1080                 uhlen + hdr_len;
1081         if (skb_cow_head(skb, headroom)) {
1082                 kfree_skb(skb);
1083                 return NET_XMIT_DROP;
1084         }
1085 
1086         /* Setup L2TP header */
1087         session->build_header(session, __skb_push(skb, hdr_len));
1088 
1089         /* Reset skb netfilter state */
1090         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1091         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1092                               IPSKB_REROUTED);
1093         nf_reset(skb);
1094 
1095         bh_lock_sock(sk);
1096         if (sock_owned_by_user(sk)) {
1097                 kfree_skb(skb);
1098                 ret = NET_XMIT_DROP;
1099                 goto out_unlock;
1100         }
1101 
1102         /* The user-space may change the connection status for the user-space
1103          * provided socket at run time: we must check it under the socket lock
1104          */
1105         if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1106                 kfree_skb(skb);
1107                 ret = NET_XMIT_DROP;
1108                 goto out_unlock;
1109         }
1110 
1111         /* Get routing info from the tunnel socket */
1112         skb_dst_drop(skb);
1113         skb_dst_set(skb, sk_dst_check(sk, 0));
1114 
1115         inet = inet_sk(sk);
1116         fl = &inet->cork.fl;
1117         switch (tunnel->encap) {
1118         case L2TP_ENCAPTYPE_UDP:
1119                 /* Setup UDP header */
1120                 __skb_push(skb, sizeof(*uh));
1121                 skb_reset_transport_header(skb);
1122                 uh = udp_hdr(skb);
1123                 uh->source = inet->inet_sport;
1124                 uh->dest = inet->inet_dport;
1125                 udp_len = uhlen + hdr_len + data_len;
1126                 uh->len = htons(udp_len);
1127 
1128                 /* Calculate UDP checksum if configured to do so */
1129 #if IS_ENABLED(CONFIG_IPV6)
1130                 if (l2tp_sk_is_v6(sk))
1131                         udp6_set_csum(udp_get_no_check6_tx(sk),
1132                                       skb, &inet6_sk(sk)->saddr,
1133                                       &sk->sk_v6_daddr, udp_len);
1134                 else
1135 #endif
1136                 udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1137                              inet->inet_daddr, udp_len);
1138                 break;
1139 
1140         case L2TP_ENCAPTYPE_IP:
1141                 break;
1142         }
1143 
1144         l2tp_xmit_core(session, skb, fl, data_len);
1145 out_unlock:
1146         bh_unlock_sock(sk);
1147 
1148         return ret;
1149 }
1150 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1151 
1152 /*****************************************************************************
1153  * Tinnel and session create/destroy.
1154  *****************************************************************************/
1155 
1156 /* Tunnel socket destruct hook.
1157  * The tunnel context is deleted only when all session sockets have been
1158  * closed.
1159  */
1160 static void l2tp_tunnel_destruct(struct sock *sk)
1161 {
1162         struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
1163 
1164         if (tunnel == NULL)
1165                 goto end;
1166 
1167         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing...\n", tunnel->name);
1168 
1169         /* Disable udp encapsulation */
1170         switch (tunnel->encap) {
1171         case L2TP_ENCAPTYPE_UDP:
1172                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1173                 (udp_sk(sk))->encap_type = 0;
1174                 (udp_sk(sk))->encap_rcv = NULL;
1175                 (udp_sk(sk))->encap_destroy = NULL;
1176                 break;
1177         case L2TP_ENCAPTYPE_IP:
1178                 break;
1179         }
1180 
1181         /* Remove hooks into tunnel socket */
1182         sk->sk_destruct = tunnel->old_sk_destruct;
1183         sk->sk_user_data = NULL;
1184 
1185         /* Call the original destructor */
1186         if (sk->sk_destruct)
1187                 (*sk->sk_destruct)(sk);
1188 
1189         kfree_rcu(tunnel, rcu);
1190 end:
1191         return;
1192 }
1193 
1194 /* When the tunnel is closed, all the attached sessions need to go too.
1195  */
1196 void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1197 {
1198         int hash;
1199         struct hlist_node *walk;
1200         struct hlist_node *tmp;
1201         struct l2tp_session *session;
1202 
1203         BUG_ON(tunnel == NULL);
1204 
1205         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing all sessions...\n",
1206                   tunnel->name);
1207 
1208         write_lock_bh(&tunnel->hlist_lock);
1209         tunnel->acpt_newsess = false;
1210         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1211 again:
1212                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1213                         session = hlist_entry(walk, struct l2tp_session, hlist);
1214 
1215                         l2tp_info(session, L2TP_MSG_CONTROL,
1216                                   "%s: closing session\n", session->name);
1217 
1218                         hlist_del_init(&session->hlist);
1219 
1220                         if (test_and_set_bit(0, &session->dead))
1221                                 goto again;
1222 
1223                         write_unlock_bh(&tunnel->hlist_lock);
1224 
1225                         __l2tp_session_unhash(session);
1226                         l2tp_session_queue_purge(session);
1227 
1228                         if (session->session_close != NULL)
1229                                 (*session->session_close)(session);
1230 
1231                         l2tp_session_dec_refcount(session);
1232 
1233                         write_lock_bh(&tunnel->hlist_lock);
1234 
1235                         /* Now restart from the beginning of this hash
1236                          * chain.  We always remove a session from the
1237                          * list so we are guaranteed to make forward
1238                          * progress.
1239                          */
1240                         goto again;
1241                 }
1242         }
1243         write_unlock_bh(&tunnel->hlist_lock);
1244 }
1245 EXPORT_SYMBOL_GPL(l2tp_tunnel_closeall);
1246 
1247 /* Tunnel socket destroy hook for UDP encapsulation */
1248 static void l2tp_udp_encap_destroy(struct sock *sk)
1249 {
1250         struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
1251 
1252         if (tunnel)
1253                 l2tp_tunnel_delete(tunnel);
1254 }
1255 
1256 /* Workqueue tunnel deletion function */
1257 static void l2tp_tunnel_del_work(struct work_struct *work)
1258 {
1259         struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1260                                                   del_work);
1261         struct sock *sk = tunnel->sock;
1262         struct socket *sock = sk->sk_socket;
1263         struct l2tp_net *pn;
1264 
1265         l2tp_tunnel_closeall(tunnel);
1266 
1267         /* If the tunnel socket was created within the kernel, use
1268          * the sk API to release it here.
1269          */
1270         if (tunnel->fd < 0) {
1271                 if (sock) {
1272                         kernel_sock_shutdown(sock, SHUT_RDWR);
1273                         sock_release(sock);
1274                 }
1275         }
1276 
1277         /* Remove the tunnel struct from the tunnel list */
1278         pn = l2tp_pernet(tunnel->l2tp_net);
1279         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1280         list_del_rcu(&tunnel->list);
1281         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1282 
1283         /* drop initial ref */
1284         l2tp_tunnel_dec_refcount(tunnel);
1285 
1286         /* drop workqueue ref */
1287         l2tp_tunnel_dec_refcount(tunnel);
1288 }
1289 
1290 /* Create a socket for the tunnel, if one isn't set up by
1291  * userspace. This is used for static tunnels where there is no
1292  * managing L2TP daemon.
1293  *
1294  * Since we don't want these sockets to keep a namespace alive by
1295  * themselves, we drop the socket's namespace refcount after creation.
1296  * These sockets are freed when the namespace exits using the pernet
1297  * exit hook.
1298  */
1299 static int l2tp_tunnel_sock_create(struct net *net,
1300                                 u32 tunnel_id,
1301                                 u32 peer_tunnel_id,
1302                                 struct l2tp_tunnel_cfg *cfg,
1303                                 struct socket **sockp)
1304 {
1305         int err = -EINVAL;
1306         struct socket *sock = NULL;
1307         struct udp_port_cfg udp_conf;
1308 
1309         switch (cfg->encap) {
1310         case L2TP_ENCAPTYPE_UDP:
1311                 memset(&udp_conf, 0, sizeof(udp_conf));
1312 
1313 #if IS_ENABLED(CONFIG_IPV6)
1314                 if (cfg->local_ip6 && cfg->peer_ip6) {
1315                         udp_conf.family = AF_INET6;
1316                         memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1317                                sizeof(udp_conf.local_ip6));
1318                         memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1319                                sizeof(udp_conf.peer_ip6));
1320                         udp_conf.use_udp6_tx_checksums =
1321                           ! cfg->udp6_zero_tx_checksums;
1322                         udp_conf.use_udp6_rx_checksums =
1323                           ! cfg->udp6_zero_rx_checksums;
1324                 } else
1325 #endif
1326                 {
1327                         udp_conf.family = AF_INET;
1328                         udp_conf.local_ip = cfg->local_ip;
1329                         udp_conf.peer_ip = cfg->peer_ip;
1330                         udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1331                 }
1332 
1333                 udp_conf.local_udp_port = htons(cfg->local_udp_port);
1334                 udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1335 
1336                 err = udp_sock_create(net, &udp_conf, &sock);
1337                 if (err < 0)
1338                         goto out;
1339 
1340                 break;
1341 
1342         case L2TP_ENCAPTYPE_IP:
1343 #if IS_ENABLED(CONFIG_IPV6)
1344                 if (cfg->local_ip6 && cfg->peer_ip6) {
1345                         struct sockaddr_l2tpip6 ip6_addr = {0};
1346 
1347                         err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1348                                           IPPROTO_L2TP, &sock);
1349                         if (err < 0)
1350                                 goto out;
1351 
1352                         ip6_addr.l2tp_family = AF_INET6;
1353                         memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1354                                sizeof(ip6_addr.l2tp_addr));
1355                         ip6_addr.l2tp_conn_id = tunnel_id;
1356                         err = kernel_bind(sock, (struct sockaddr *) &ip6_addr,
1357                                           sizeof(ip6_addr));
1358                         if (err < 0)
1359                                 goto out;
1360 
1361                         ip6_addr.l2tp_family = AF_INET6;
1362                         memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1363                                sizeof(ip6_addr.l2tp_addr));
1364                         ip6_addr.l2tp_conn_id = peer_tunnel_id;
1365                         err = kernel_connect(sock,
1366                                              (struct sockaddr *) &ip6_addr,
1367                                              sizeof(ip6_addr), 0);
1368                         if (err < 0)
1369                                 goto out;
1370                 } else
1371 #endif
1372                 {
1373                         struct sockaddr_l2tpip ip_addr = {0};
1374 
1375                         err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1376                                           IPPROTO_L2TP, &sock);
1377                         if (err < 0)
1378                                 goto out;
1379 
1380                         ip_addr.l2tp_family = AF_INET;
1381                         ip_addr.l2tp_addr = cfg->local_ip;
1382                         ip_addr.l2tp_conn_id = tunnel_id;
1383                         err = kernel_bind(sock, (struct sockaddr *) &ip_addr,
1384                                           sizeof(ip_addr));
1385                         if (err < 0)
1386                                 goto out;
1387 
1388                         ip_addr.l2tp_family = AF_INET;
1389                         ip_addr.l2tp_addr = cfg->peer_ip;
1390                         ip_addr.l2tp_conn_id = peer_tunnel_id;
1391                         err = kernel_connect(sock, (struct sockaddr *) &ip_addr,
1392                                              sizeof(ip_addr), 0);
1393                         if (err < 0)
1394                                 goto out;
1395                 }
1396                 break;
1397 
1398         default:
1399                 goto out;
1400         }
1401 
1402 out:
1403         *sockp = sock;
1404         if ((err < 0) && sock) {
1405                 kernel_sock_shutdown(sock, SHUT_RDWR);
1406                 sock_release(sock);
1407                 *sockp = NULL;
1408         }
1409 
1410         return err;
1411 }
1412 
1413 static struct lock_class_key l2tp_socket_class;
1414 
1415 int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
1416 {
1417         struct l2tp_tunnel *tunnel = NULL;
1418         int err;
1419         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1420 
1421         if (cfg != NULL)
1422                 encap = cfg->encap;
1423 
1424         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1425         if (tunnel == NULL) {
1426                 err = -ENOMEM;
1427                 goto err;
1428         }
1429 
1430         tunnel->version = version;
1431         tunnel->tunnel_id = tunnel_id;
1432         tunnel->peer_tunnel_id = peer_tunnel_id;
1433         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1434 
1435         tunnel->magic = L2TP_TUNNEL_MAGIC;
1436         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1437         rwlock_init(&tunnel->hlist_lock);
1438         tunnel->acpt_newsess = true;
1439 
1440         if (cfg != NULL)
1441                 tunnel->debug = cfg->debug;
1442 
1443         tunnel->encap = encap;
1444 
1445         refcount_set(&tunnel->ref_count, 1);
1446         tunnel->fd = fd;
1447 
1448         /* Init delete workqueue struct */
1449         INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1450 
1451         INIT_LIST_HEAD(&tunnel->list);
1452 
1453         err = 0;
1454 err:
1455         if (tunnelp)
1456                 *tunnelp = tunnel;
1457 
1458         return err;
1459 }
1460 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1461 
1462 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1463                                 enum l2tp_encap_type encap)
1464 {
1465         if (!net_eq(sock_net(sk), net))
1466                 return -EINVAL;
1467 
1468         if (sk->sk_type != SOCK_DGRAM)
1469                 return -EPROTONOSUPPORT;
1470 
1471         if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1472             (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1473                 return -EPROTONOSUPPORT;
1474 
1475         if (sk->sk_user_data)
1476                 return -EBUSY;
1477 
1478         return 0;
1479 }
1480 
1481 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1482                          struct l2tp_tunnel_cfg *cfg)
1483 {
1484         struct l2tp_tunnel *tunnel_walk;
1485         struct l2tp_net *pn;
1486         struct socket *sock;
1487         struct sock *sk;
1488         int ret;
1489 
1490         if (tunnel->fd < 0) {
1491                 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1492                                               tunnel->peer_tunnel_id, cfg,
1493                                               &sock);
1494                 if (ret < 0)
1495                         goto err;
1496         } else {
1497                 sock = sockfd_lookup(tunnel->fd, &ret);
1498                 if (!sock)
1499                         goto err;
1500 
1501                 ret = l2tp_validate_socket(sock->sk, net, tunnel->encap);
1502                 if (ret < 0)
1503                         goto err_sock;
1504         }
1505 
1506         sk = sock->sk;
1507 
1508         sock_hold(sk);
1509         tunnel->sock = sk;
1510         tunnel->l2tp_net = net;
1511 
1512         pn = l2tp_pernet(net);
1513 
1514         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1515         list_for_each_entry(tunnel_walk, &pn->l2tp_tunnel_list, list) {
1516                 if (tunnel_walk->tunnel_id == tunnel->tunnel_id) {
1517                         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1518 
1519                         ret = -EEXIST;
1520                         goto err_sock;
1521                 }
1522         }
1523         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1524         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1525 
1526         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1527                 struct udp_tunnel_sock_cfg udp_cfg = {
1528                         .sk_user_data = tunnel,
1529                         .encap_type = UDP_ENCAP_L2TPINUDP,
1530                         .encap_rcv = l2tp_udp_encap_recv,
1531                         .encap_destroy = l2tp_udp_encap_destroy,
1532                 };
1533 
1534                 setup_udp_tunnel_sock(net, sock, &udp_cfg);
1535         } else {
1536                 sk->sk_user_data = tunnel;
1537         }
1538 
1539         tunnel->old_sk_destruct = sk->sk_destruct;
1540         sk->sk_destruct = &l2tp_tunnel_destruct;
1541         lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class,
1542                                    "l2tp_sock");
1543         sk->sk_allocation = GFP_ATOMIC;
1544 
1545         if (tunnel->fd >= 0)
1546                 sockfd_put(sock);
1547 
1548         return 0;
1549 
1550 err_sock:
1551         if (tunnel->fd < 0)
1552                 sock_release(sock);
1553         else
1554                 sockfd_put(sock);
1555 err:
1556         return ret;
1557 }
1558 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1559 
1560 /* This function is used by the netlink TUNNEL_DELETE command.
1561  */
1562 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1563 {
1564         if (!test_and_set_bit(0, &tunnel->dead)) {
1565                 l2tp_tunnel_inc_refcount(tunnel);
1566                 queue_work(l2tp_wq, &tunnel->del_work);
1567         }
1568 }
1569 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1570 
1571 /* Really kill the session.
1572  */
1573 void l2tp_session_free(struct l2tp_session *session)
1574 {
1575         struct l2tp_tunnel *tunnel = session->tunnel;
1576 
1577         BUG_ON(refcount_read(&session->ref_count) != 0);
1578 
1579         if (tunnel) {
1580                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1581                 l2tp_tunnel_dec_refcount(tunnel);
1582         }
1583 
1584         kfree(session);
1585 }
1586 EXPORT_SYMBOL_GPL(l2tp_session_free);
1587 
1588 /* Remove an l2tp session from l2tp_core's hash lists.
1589  * Provides a tidyup interface for pseudowire code which can't just route all
1590  * shutdown via. l2tp_session_delete and a pseudowire-specific session_close
1591  * callback.
1592  */
1593 void __l2tp_session_unhash(struct l2tp_session *session)
1594 {
1595         struct l2tp_tunnel *tunnel = session->tunnel;
1596 
1597         /* Remove the session from core hashes */
1598         if (tunnel) {
1599                 /* Remove from the per-tunnel hash */
1600                 write_lock_bh(&tunnel->hlist_lock);
1601                 hlist_del_init(&session->hlist);
1602                 write_unlock_bh(&tunnel->hlist_lock);
1603 
1604                 /* For L2TPv3 we have a per-net hash: remove from there, too */
1605                 if (tunnel->version != L2TP_HDR_VER_2) {
1606                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1607                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1608                         hlist_del_init_rcu(&session->global_hlist);
1609                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1610                         synchronize_rcu();
1611                 }
1612         }
1613 }
1614 EXPORT_SYMBOL_GPL(__l2tp_session_unhash);
1615 
1616 /* This function is used by the netlink SESSION_DELETE command and by
1617    pseudowire modules.
1618  */
1619 int l2tp_session_delete(struct l2tp_session *session)
1620 {
1621         if (test_and_set_bit(0, &session->dead))
1622                 return 0;
1623 
1624         __l2tp_session_unhash(session);
1625         l2tp_session_queue_purge(session);
1626         if (session->session_close != NULL)
1627                 (*session->session_close)(session);
1628 
1629         l2tp_session_dec_refcount(session);
1630 
1631         return 0;
1632 }
1633 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1634 
1635 /* We come here whenever a session's send_seq, cookie_len or
1636  * l2specific_type parameters are set.
1637  */
1638 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1639 {
1640         if (version == L2TP_HDR_VER_2) {
1641                 session->hdr_len = 6;
1642                 if (session->send_seq)
1643                         session->hdr_len += 4;
1644         } else {
1645                 session->hdr_len = 4 + session->cookie_len;
1646                 session->hdr_len += l2tp_get_l2specific_len(session);
1647                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1648                         session->hdr_len += 4;
1649         }
1650 
1651 }
1652 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1653 
1654 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
1655 {
1656         struct l2tp_session *session;
1657 
1658         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1659         if (session != NULL) {
1660                 session->magic = L2TP_SESSION_MAGIC;
1661                 session->tunnel = tunnel;
1662 
1663                 session->session_id = session_id;
1664                 session->peer_session_id = peer_session_id;
1665                 session->nr = 0;
1666                 if (tunnel->version == L2TP_HDR_VER_2)
1667                         session->nr_max = 0xffff;
1668                 else
1669                         session->nr_max = 0xffffff;
1670                 session->nr_window_size = session->nr_max / 2;
1671                 session->nr_oos_count_max = 4;
1672 
1673                 /* Use NR of first received packet */
1674                 session->reorder_skip = 1;
1675 
1676                 sprintf(&session->name[0], "sess %u/%u",
1677                         tunnel->tunnel_id, session->session_id);
1678 
1679                 skb_queue_head_init(&session->reorder_q);
1680 
1681                 INIT_HLIST_NODE(&session->hlist);
1682                 INIT_HLIST_NODE(&session->global_hlist);
1683 
1684                 /* Inherit debug options from tunnel */
1685                 session->debug = tunnel->debug;
1686 
1687                 if (cfg) {
1688                         session->pwtype = cfg->pw_type;
1689                         session->debug = cfg->debug;
1690                         session->mtu = cfg->mtu;
1691                         session->mru = cfg->mru;
1692                         session->send_seq = cfg->send_seq;
1693                         session->recv_seq = cfg->recv_seq;
1694                         session->lns_mode = cfg->lns_mode;
1695                         session->reorder_timeout = cfg->reorder_timeout;
1696                         session->l2specific_type = cfg->l2specific_type;
1697                         session->cookie_len = cfg->cookie_len;
1698                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1699                         session->peer_cookie_len = cfg->peer_cookie_len;
1700                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1701                 }
1702 
1703                 if (tunnel->version == L2TP_HDR_VER_2)
1704                         session->build_header = l2tp_build_l2tpv2_header;
1705                 else
1706                         session->build_header = l2tp_build_l2tpv3_header;
1707 
1708                 l2tp_session_set_header_len(session, tunnel->version);
1709 
1710                 refcount_set(&session->ref_count, 1);
1711 
1712                 return session;
1713         }
1714 
1715         return ERR_PTR(-ENOMEM);
1716 }
1717 EXPORT_SYMBOL_GPL(l2tp_session_create);
1718 
1719 /*****************************************************************************
1720  * Init and cleanup
1721  *****************************************************************************/
1722 
1723 static __net_init int l2tp_init_net(struct net *net)
1724 {
1725         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1726         int hash;
1727 
1728         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1729         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1730 
1731         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1732                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1733 
1734         spin_lock_init(&pn->l2tp_session_hlist_lock);
1735 
1736         return 0;
1737 }
1738 
1739 static __net_exit void l2tp_exit_net(struct net *net)
1740 {
1741         struct l2tp_net *pn = l2tp_pernet(net);
1742         struct l2tp_tunnel *tunnel = NULL;
1743         int hash;
1744 
1745         rcu_read_lock_bh();
1746         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
1747                 l2tp_tunnel_delete(tunnel);
1748         }
1749         rcu_read_unlock_bh();
1750 
1751         flush_workqueue(l2tp_wq);
1752         rcu_barrier();
1753 
1754         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1755                 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1756 }
1757 
1758 static struct pernet_operations l2tp_net_ops = {
1759         .init = l2tp_init_net,
1760         .exit = l2tp_exit_net,
1761         .id   = &l2tp_net_id,
1762         .size = sizeof(struct l2tp_net),
1763 };
1764 
1765 static int __init l2tp_init(void)
1766 {
1767         int rc = 0;
1768 
1769         rc = register_pernet_device(&l2tp_net_ops);
1770         if (rc)
1771                 goto out;
1772 
1773         l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1774         if (!l2tp_wq) {
1775                 pr_err("alloc_workqueue failed\n");
1776                 unregister_pernet_device(&l2tp_net_ops);
1777                 rc = -ENOMEM;
1778                 goto out;
1779         }
1780 
1781         pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1782 
1783 out:
1784         return rc;
1785 }
1786 
1787 static void __exit l2tp_exit(void)
1788 {
1789         unregister_pernet_device(&l2tp_net_ops);
1790         if (l2tp_wq) {
1791                 destroy_workqueue(l2tp_wq);
1792                 l2tp_wq = NULL;
1793         }
1794 }
1795 
1796 module_init(l2tp_init);
1797 module_exit(l2tp_exit);
1798 
1799 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1800 MODULE_DESCRIPTION("L2TP core");
1801 MODULE_LICENSE("GPL");
1802 MODULE_VERSION(L2TP_DRV_VERSION);
1803 
1804 

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