net/l2tp/l2tp_core.c

   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_MAX               14
  87
  88 /* Default trace flags */
  89 #define L2TP_DEFAULT_DEBUG_FLAGS        0
  90
  91 /* Private data stored for received packets in the skb.
  92  */
  93 struct l2tp_skb_cb {
  94         u32                     ns;
  95         u16                     has_seq;
  96         u16                     length;
  97         unsigned long           expires;
  98 };
  99
 100 #define L2TP_SKB_CB(skb)        ((struct l2tp_skb_cb *) &skb->cb[sizeof(struct inet_skb_parm)])
 101
 102 static struct workqueue_struct *l2tp_wq;
 103
 104 /* per-net private data for this module */
 105 static unsigned int l2tp_net_id;
 106 struct l2tp_net {
 107         struct list_head l2tp_tunnel_list;
 108         spinlock_t l2tp_tunnel_list_lock;
 109         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
 110         spinlock_t l2tp_session_hlist_lock;
 111 };
 112
 113 #if IS_ENABLED(CONFIG_IPV6)
 114 static bool l2tp_sk_is_v6(struct sock *sk)
 115 {
 116         return sk->sk_family == PF_INET6 &&
 117                !ipv6_addr_v4mapped(&sk->sk_v6_daddr);
 118 }
 119 #endif
 120
 121 static inline struct l2tp_tunnel *l2tp_tunnel(struct sock *sk)
 122 {
 123         return sk->sk_user_data;
 124 }
 125
 126 static inline struct l2tp_net *l2tp_pernet(const struct net *net)
 127 {
 128         BUG_ON(!net);
 129
 130         return net_generic(net, l2tp_net_id);
 131 }
 132
 133 /* Session hash global list for L2TPv3.
 134  * The session_id SHOULD be random according to RFC3931, but several
 135  * L2TP implementations use incrementing session_ids.  So we do a real
 136  * hash on the session_id, rather than a simple bitmask.
 137  */
 138 static inline struct hlist_head *
 139 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 140 {
 141         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 142
 143 }
 144
 145 /* Session hash list.
 146  * The session_id SHOULD be random according to RFC2661, but several
 147  * L2TP implementations (Cisco and Microsoft) use incrementing
 148  * session_ids.  So we do a real hash on the session_id, rather than a
 149  * simple bitmask.
 150  */
 151 static inline struct hlist_head *
 152 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 153 {
 154         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 155 }
 156
 157 void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
 158 {
 159         sock_put(tunnel->sock);
 160         /* the tunnel is freed in the socket destructor */
 161 }
 162 EXPORT_SYMBOL(l2tp_tunnel_free);
 163
 164 /* Lookup a tunnel. A new reference is held on the returned tunnel. */
 165 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
 166 {
 167         const struct l2tp_net *pn = l2tp_pernet(net);
 168         struct l2tp_tunnel *tunnel;
 169
 170         rcu_read_lock_bh();
 171         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 172                 if (tunnel->tunnel_id == tunnel_id) {
 173                         l2tp_tunnel_inc_refcount(tunnel);
 174                         rcu_read_unlock_bh();
 175
 176                         return tunnel;
 177                 }
 178         }
 179         rcu_read_unlock_bh();
 180
 181         return NULL;
 182 }
 183 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
 184
 185 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
 186 {
 187         const struct l2tp_net *pn = l2tp_pernet(net);
 188         struct l2tp_tunnel *tunnel;
 189         int count = 0;
 190
 191         rcu_read_lock_bh();
 192         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 193                 if (++count > nth) {
 194                         l2tp_tunnel_inc_refcount(tunnel);
 195                         rcu_read_unlock_bh();
 196                         return tunnel;
 197                 }
 198         }
 199         rcu_read_unlock_bh();
 200
 201         return NULL;
 202 }
 203 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
 204
 205 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
 206                                              u32 session_id)
 207 {
 208         struct hlist_head *session_list;
 209         struct l2tp_session *session;
 210
 211         session_list = l2tp_session_id_hash(tunnel, session_id);
 212
 213         read_lock_bh(&tunnel->hlist_lock);
 214         hlist_for_each_entry(session, session_list, hlist)
 215                 if (session->session_id == session_id) {
 216                         l2tp_session_inc_refcount(session);
 217                         read_unlock_bh(&tunnel->hlist_lock);
 218
 219                         return session;
 220                 }
 221         read_unlock_bh(&tunnel->hlist_lock);
 222
 223         return NULL;
 224 }
 225 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
 226
 227 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
 228 {
 229         struct hlist_head *session_list;
 230         struct l2tp_session *session;
 231
 232         session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
 233
 234         rcu_read_lock_bh();
 235         hlist_for_each_entry_rcu(session, session_list, global_hlist)
 236                 if (session->session_id == session_id) {
 237                         l2tp_session_inc_refcount(session);
 238                         rcu_read_unlock_bh();
 239
 240                         return session;
 241                 }
 242         rcu_read_unlock_bh();
 243
 244         return NULL;
 245 }
 246 EXPORT_SYMBOL_GPL(l2tp_session_get);
 247
 248 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
 249 {
 250         int hash;
 251         struct l2tp_session *session;
 252         int count = 0;
 253
 254         read_lock_bh(&tunnel->hlist_lock);
 255         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 256                 hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
 257                         if (++count > nth) {
 258                                 l2tp_session_inc_refcount(session);
 259                                 read_unlock_bh(&tunnel->hlist_lock);
 260                                 return session;
 261                         }
 262                 }
 263         }
 264
 265         read_unlock_bh(&tunnel->hlist_lock);
 266
 267         return NULL;
 268 }
 269 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
 270
 271 /* Lookup a session by interface name.
 272  * This is very inefficient but is only used by management interfaces.
 273  */
 274 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
 275                                                 const char *ifname)
 276 {
 277         struct l2tp_net *pn = l2tp_pernet(net);
 278         int hash;
 279         struct l2tp_session *session;
 280
 281         rcu_read_lock_bh();
 282         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 283                 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
 284                         if (!strcmp(session->ifname, ifname)) {
 285                                 l2tp_session_inc_refcount(session);
 286                                 rcu_read_unlock_bh();
 287
 288                                 return session;
 289                         }
 290                 }
 291         }
 292
 293         rcu_read_unlock_bh();
 294
 295         return NULL;
 296 }
 297 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
 298
 299 int l2tp_session_register(struct l2tp_session *session,
 300                           struct l2tp_tunnel *tunnel)
 301 {
 302         struct l2tp_session *session_walk;
 303         struct hlist_head *g_head;
 304         struct hlist_head *head;
 305         struct l2tp_net *pn;
 306         int err;
 307
 308         head = l2tp_session_id_hash(tunnel, session->session_id);
 309
 310         write_lock_bh(&tunnel->hlist_lock);
 311         if (!tunnel->acpt_newsess) {
 312                 err = -ENODEV;
 313                 goto err_tlock;
 314         }
 315
 316         hlist_for_each_entry(session_walk, head, hlist)
 317                 if (session_walk->session_id == session->session_id) {
 318                         err = -EEXIST;
 319                         goto err_tlock;
 320                 }
 321
 322         if (tunnel->version == L2TP_HDR_VER_3) {
 323                 pn = l2tp_pernet(tunnel->l2tp_net);
 324                 g_head = l2tp_session_id_hash_2(pn, session->session_id);
 325
 326                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
 327
 328                 hlist_for_each_entry(session_walk, g_head, global_hlist)
 329                         if (session_walk->session_id == session->session_id) {
 330                                 err = -EEXIST;
 331                                 goto err_tlock_pnlock;
 332                         }
 333
 334                 l2tp_tunnel_inc_refcount(tunnel);
 335                 hlist_add_head_rcu(&session->global_hlist, g_head);
 336
 337                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 338         } else {
 339                 l2tp_tunnel_inc_refcount(tunnel);
 340         }
 341
 342         hlist_add_head(&session->hlist, head);
 343         write_unlock_bh(&tunnel->hlist_lock);
 344
 345         return 0;
 346
 347 err_tlock_pnlock:
 348         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 349 err_tlock:
 350         write_unlock_bh(&tunnel->hlist_lock);
 351
 352         return err;
 353 }
 354 EXPORT_SYMBOL_GPL(l2tp_session_register);
 355
 356 /*****************************************************************************
 357  * Receive data handling
 358  *****************************************************************************/
 359
 360 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 361  * number.
 362  */
 363 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 364 {
 365         struct sk_buff *skbp;
 366         struct sk_buff *tmp;
 367         u32 ns = L2TP_SKB_CB(skb)->ns;
 368
 369         spin_lock_bh(&session->reorder_q.lock);
 370         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 371                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 372                         __skb_queue_before(&session->reorder_q, skbp, skb);
 373                         l2tp_dbg(session, L2TP_MSG_SEQ,
 374                                  "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 375                                  session->name, ns, L2TP_SKB_CB(skbp)->ns,
 376                                  skb_queue_len(&session->reorder_q));
 377                         atomic_long_inc(&session->stats.rx_oos_packets);
 378                         goto out;
 379                 }
 380         }
 381
 382         __skb_queue_tail(&session->reorder_q, skb);
 383
 384 out:
 385         spin_unlock_bh(&session->reorder_q.lock);
 386 }
 387
 388 /* Dequeue a single skb.
 389  */
 390 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 391 {
 392         struct l2tp_tunnel *tunnel = session->tunnel;
 393         int length = L2TP_SKB_CB(skb)->length;
 394
 395         /* We're about to requeue the skb, so return resources
 396          * to its current owner (a socket receive buffer).
 397          */
 398         skb_orphan(skb);
 399
 400         atomic_long_inc(&tunnel->stats.rx_packets);
 401         atomic_long_add(length, &tunnel->stats.rx_bytes);
 402         atomic_long_inc(&session->stats.rx_packets);
 403         atomic_long_add(length, &session->stats.rx_bytes);
 404
 405         if (L2TP_SKB_CB(skb)->has_seq) {
 406                 /* Bump our Nr */
 407                 session->nr++;
 408                 session->nr &= session->nr_max;
 409
 410                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated nr to %hu\n",
 411                          session->name, session->nr);
 412         }
 413
 414         /* call private receive handler */
 415         if (session->recv_skb != NULL)
 416                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 417         else
 418                 kfree_skb(skb);
 419 }
 420
 421 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 422  * Skbs that have been in the queue for too long are simply discarded.
 423  */
 424 static void l2tp_recv_dequeue(struct l2tp_session *session)
 425 {
 426         struct sk_buff *skb;
 427         struct sk_buff *tmp;
 428
 429         /* If the pkt at the head of the queue has the nr that we
 430          * expect to send up next, dequeue it and any other
 431          * in-sequence packets behind it.
 432          */
 433 start:
 434         spin_lock_bh(&session->reorder_q.lock);
 435         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 436                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 437                         atomic_long_inc(&session->stats.rx_seq_discards);
 438                         atomic_long_inc(&session->stats.rx_errors);
 439                         l2tp_dbg(session, L2TP_MSG_SEQ,
 440                                  "%s: oos pkt %u len %d discarded (too old), waiting for %u, reorder_q_len=%d\n",
 441                                  session->name, L2TP_SKB_CB(skb)->ns,
 442                                  L2TP_SKB_CB(skb)->length, session->nr,
 443                                  skb_queue_len(&session->reorder_q));
 444                         session->reorder_skip = 1;
 445                         __skb_unlink(skb, &session->reorder_q);
 446                         kfree_skb(skb);
 447                         continue;
 448                 }
 449
 450                 if (L2TP_SKB_CB(skb)->has_seq) {
 451                         if (session->reorder_skip) {
 452                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 453                                          "%s: advancing nr to next pkt: %u -> %u",
 454                                          session->name, session->nr,
 455                                          L2TP_SKB_CB(skb)->ns);
 456                                 session->reorder_skip = 0;
 457                                 session->nr = L2TP_SKB_CB(skb)->ns;
 458                         }
 459                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 460                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 461                                          "%s: holding oos pkt %u len %d, waiting for %u, reorder_q_len=%d\n",
 462                                          session->name, L2TP_SKB_CB(skb)->ns,
 463                                          L2TP_SKB_CB(skb)->length, session->nr,
 464                                          skb_queue_len(&session->reorder_q));
 465                                 goto out;
 466                         }
 467                 }
 468                 __skb_unlink(skb, &session->reorder_q);
 469
 470                 /* Process the skb. We release the queue lock while we
 471                  * do so to let other contexts process the queue.
 472                  */
 473                 spin_unlock_bh(&session->reorder_q.lock);
 474                 l2tp_recv_dequeue_skb(session, skb);
 475                 goto start;
 476         }
 477
 478 out:
 479         spin_unlock_bh(&session->reorder_q.lock);
 480 }
 481
 482 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
 483 {
 484         u32 nws;
 485
 486         if (nr >= session->nr)
 487                 nws = nr - session->nr;
 488         else
 489                 nws = (session->nr_max + 1) - (session->nr - nr);
 490
 491         return nws < session->nr_window_size;
 492 }
 493
 494 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
 495  * acceptable, else non-zero.
 496  */
 497 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
 498 {
 499         if (!l2tp_seq_check_rx_window(session, L2TP_SKB_CB(skb)->ns)) {
 500                 /* Packet sequence number is outside allowed window.
 501                  * Discard it.
 502                  */
 503                 l2tp_dbg(session, L2TP_MSG_SEQ,
 504                          "%s: pkt %u len %d discarded, outside window, nr=%u\n",
 505                          session->name, L2TP_SKB_CB(skb)->ns,
 506                          L2TP_SKB_CB(skb)->length, session->nr);
 507                 goto discard;
 508         }
 509
 510         if (session->reorder_timeout != 0) {
 511                 /* Packet reordering enabled. Add skb to session's
 512                  * reorder queue, in order of ns.
 513                  */
 514                 l2tp_recv_queue_skb(session, skb);
 515                 goto out;
 516         }
 517
 518         /* Packet reordering disabled. Discard out-of-sequence packets, while
 519          * tracking the number if in-sequence packets after the first OOS packet
 520          * is seen. After nr_oos_count_max in-sequence packets, reset the
 521          * sequence number to re-enable packet reception.
 522          */
 523         if (L2TP_SKB_CB(skb)->ns == session->nr) {
 524                 skb_queue_tail(&session->reorder_q, skb);
 525         } else {
 526                 u32 nr_oos = L2TP_SKB_CB(skb)->ns;
 527                 u32 nr_next = (session->nr_oos + 1) & session->nr_max;
 528
 529                 if (nr_oos == nr_next)
 530                         session->nr_oos_count++;
 531                 else
 532                         session->nr_oos_count = 0;
 533
 534                 session->nr_oos = nr_oos;
 535                 if (session->nr_oos_count > session->nr_oos_count_max) {
 536                         session->reorder_skip = 1;
 537                         l2tp_dbg(session, L2TP_MSG_SEQ,
 538                                  "%s: %d oos packets received. Resetting sequence numbers\n",
 539                                  session->name, session->nr_oos_count);
 540                 }
 541                 if (!session->reorder_skip) {
 542                         atomic_long_inc(&session->stats.rx_seq_discards);
 543                         l2tp_dbg(session, L2TP_MSG_SEQ,
 544                                  "%s: oos pkt %u len %d discarded, waiting for %u, reorder_q_len=%d\n",
 545                                  session->name, L2TP_SKB_CB(skb)->ns,
 546                                  L2TP_SKB_CB(skb)->length, session->nr,
 547                                  skb_queue_len(&session->reorder_q));
 548                         goto discard;
 549                 }
 550                 skb_queue_tail(&session->reorder_q, skb);
 551         }
 552
 553 out:
 554         return 0;
 555
 556 discard:
 557         return 1;
 558 }
 559
 560 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 561  * and L2TPv3 data frames here.
 562  *
 563  * L2TPv2 Data Message Header
 564  *
 565  *  0                   1                   2                   3
 566  *  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
 567  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 568  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 569  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 570  * |           Tunnel ID           |           Session ID          |
 571  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 572  * |             Ns (opt)          |             Nr (opt)          |
 573  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 574  * |      Offset Size (opt)        |    Offset pad... (opt)
 575  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 576  *
 577  * Data frames are marked by T=0. All other fields are the same as
 578  * those in L2TP control frames.
 579  *
 580  * L2TPv3 Data Message Header
 581  *
 582  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 583  * |                      L2TP Session Header                      |
 584  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 585  * |                      L2-Specific Sublayer                     |
 586  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 587  * |                        Tunnel Payload                      ...
 588  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 589  *
 590  * L2TPv3 Session Header Over IP
 591  *
 592  *  0                   1                   2                   3
 593  *  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
 594  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 595  * |                           Session ID                          |
 596  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 597  * |               Cookie (optional, maximum 64 bits)...
 598  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 599  *                                                                 |
 600  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 601  *
 602  * L2TPv3 L2-Specific Sublayer Format
 603  *
 604  *  0                   1                   2                   3
 605  *  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
 606  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 607  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 608  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 609  *
 610  * Cookie value and sublayer format are negotiated with the peer when
 611  * the session is set up. Unlike L2TPv2, we do not need to parse the
 612  * packet header to determine if optional fields are present.
 613  *
 614  * Caller must already have parsed the frame and determined that it is
 615  * a data (not control) frame before coming here. Fields up to the
 616  * session-id have already been parsed and ptr points to the data
 617  * after the session-id.
 618  */
 619 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 620                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 621                       int length)
 622 {
 623         struct l2tp_tunnel *tunnel = session->tunnel;
 624         int offset;
 625         u32 ns, nr;
 626
 627         /* Parse and check optional cookie */
 628         if (session->peer_cookie_len > 0) {
 629                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 630                         l2tp_info(tunnel, L2TP_MSG_DATA,
 631                                   "%s: cookie mismatch (%u/%u). Discarding.\n",
 632                                   tunnel->name, tunnel->tunnel_id,
 633                                   session->session_id);
 634                         atomic_long_inc(&session->stats.rx_cookie_discards);
 635                         goto discard;
 636                 }
 637                 ptr += session->peer_cookie_len;
 638         }
 639
 640         /* Handle the optional sequence numbers. Sequence numbers are
 641          * in different places for L2TPv2 and L2TPv3.
 642          *
 643          * If we are the LAC, enable/disable sequence numbers under
 644          * the control of the LNS.  If no sequence numbers present but
 645          * we were expecting them, discard frame.
 646          */
 647         ns = nr = 0;
 648         L2TP_SKB_CB(skb)->has_seq = 0;
 649         if (tunnel->version == L2TP_HDR_VER_2) {
 650                 if (hdrflags & L2TP_HDRFLAG_S) {
 651                         ns = ntohs(*(__be16 *) ptr);
 652                         ptr += 2;
 653                         nr = ntohs(*(__be16 *) ptr);
 654                         ptr += 2;
 655
 656                         /* Store L2TP info in the skb */
 657                         L2TP_SKB_CB(skb)->ns = ns;
 658                         L2TP_SKB_CB(skb)->has_seq = 1;
 659
 660                         l2tp_dbg(session, L2TP_MSG_SEQ,
 661                                  "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 662                                  session->name, ns, nr, session->nr);
 663                 }
 664         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 665                 u32 l2h = ntohl(*(__be32 *) ptr);
 666
 667                 if (l2h & 0x40000000) {
 668                         ns = l2h & 0x00ffffff;
 669
 670                         /* Store L2TP info in the skb */
 671                         L2TP_SKB_CB(skb)->ns = ns;
 672                         L2TP_SKB_CB(skb)->has_seq = 1;
 673
 674                         l2tp_dbg(session, L2TP_MSG_SEQ,
 675                                  "%s: recv data ns=%u, session nr=%u\n",
 676                                  session->name, ns, session->nr);
 677                 }
 678                 ptr += 4;
 679         }
 680
 681         if (L2TP_SKB_CB(skb)->has_seq) {
 682                 /* Received a packet with sequence numbers. If we're the LNS,
 683                  * check if we sre sending sequence numbers and if not,
 684                  * configure it so.
 685                  */
 686                 if ((!session->lns_mode) && (!session->send_seq)) {
 687                         l2tp_info(session, L2TP_MSG_SEQ,
 688                                   "%s: requested to enable seq numbers by LNS\n",
 689                                   session->name);
 690                         session->send_seq = 1;
 691                         l2tp_session_set_header_len(session, tunnel->version);
 692                 }
 693         } else {
 694                 /* No sequence numbers.
 695                  * If user has configured mandatory sequence numbers, discard.
 696                  */
 697                 if (session->recv_seq) {
 698                         l2tp_warn(session, L2TP_MSG_SEQ,
 699                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 700                                   session->name);
 701                         atomic_long_inc(&session->stats.rx_seq_discards);
 702                         goto discard;
 703                 }
 704
 705                 /* If we're the LAC and we're sending sequence numbers, the
 706                  * LNS has requested that we no longer send sequence numbers.
 707                  * If we're the LNS and we're sending sequence numbers, the
 708                  * LAC is broken. Discard the frame.
 709                  */
 710                 if ((!session->lns_mode) && (session->send_seq)) {
 711                         l2tp_info(session, L2TP_MSG_SEQ,
 712                                   "%s: requested to disable seq numbers by LNS\n",
 713                                   session->name);
 714                         session->send_seq = 0;
 715                         l2tp_session_set_header_len(session, tunnel->version);
 716                 } else if (session->send_seq) {
 717                         l2tp_warn(session, L2TP_MSG_SEQ,
 718                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 719                                   session->name);
 720                         atomic_long_inc(&session->stats.rx_seq_discards);
 721                         goto discard;
 722                 }
 723         }
 724
 725         /* Session data offset is defined only for L2TPv2 and is
 726          * indicated by an optional 16-bit value in the header.
 727          */
 728         if (tunnel->version == L2TP_HDR_VER_2) {
 729                 /* If offset bit set, skip it. */
 730                 if (hdrflags & L2TP_HDRFLAG_O) {
 731                         offset = ntohs(*(__be16 *)ptr);
 732                         ptr += 2 + offset;
 733                 }
 734         }
 735
 736         offset = ptr - optr;
 737         if (!pskb_may_pull(skb, offset))
 738                 goto discard;
 739
 740         __skb_pull(skb, offset);
 741
 742         /* Prepare skb for adding to the session's reorder_q.  Hold
 743          * packets for max reorder_timeout or 1 second if not
 744          * reordering.
 745          */
 746         L2TP_SKB_CB(skb)->length = length;
 747         L2TP_SKB_CB(skb)->expires = jiffies +
 748                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 749
 750         /* Add packet to the session's receive queue. Reordering is done here, if
 751          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 752          */
 753         if (L2TP_SKB_CB(skb)->has_seq) {
 754                 if (l2tp_recv_data_seq(session, skb))
 755                         goto discard;
 756         } else {
 757                 /* No sequence numbers. Add the skb to the tail of the
 758                  * reorder queue. This ensures that it will be
 759                  * delivered after all previous sequenced skbs.
 760                  */
 761                 skb_queue_tail(&session->reorder_q, skb);
 762         }
 763
 764         /* Try to dequeue as many skbs from reorder_q as we can. */
 765         l2tp_recv_dequeue(session);
 766
 767         return;
 768
 769 discard:
 770         atomic_long_inc(&session->stats.rx_errors);
 771         kfree_skb(skb);
 772 }
 773 EXPORT_SYMBOL(l2tp_recv_common);
 774
 775 /* Drop skbs from the session's reorder_q
 776  */
 777 static int l2tp_session_queue_purge(struct l2tp_session *session)
 778 {
 779         struct sk_buff *skb = NULL;
 780         BUG_ON(!session);
 781         BUG_ON(session->magic != L2TP_SESSION_MAGIC);
 782         while ((skb = skb_dequeue(&session->reorder_q))) {
 783                 atomic_long_inc(&session->stats.rx_errors);
 784                 kfree_skb(skb);
 785         }
 786         return 0;
 787 }
 788
 789 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 790  * here. The skb is not on a list when we get here.
 791  * Returns 0 if the packet was a data packet and was successfully passed on.
 792  * Returns 1 if the packet was not a good data packet and could not be
 793  * forwarded.  All such packets are passed up to userspace to deal with.
 794  */
 795 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 796 {
 797         struct l2tp_session *session = NULL;
 798         unsigned char *ptr, *optr;
 799         u16 hdrflags;
 800         u32 tunnel_id, session_id;
 801         u16 version;
 802         int length;
 803
 804         /* UDP has verifed 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                 l2tp_info(tunnel, L2TP_MSG_DATA,
 812                           "%s: recv short packet (len=%d)\n",
 813                           tunnel->name, skb->len);
 814                 goto error;
 815         }
 816
 817         /* Trace packet contents, if enabled */
 818         if (tunnel->debug & L2TP_MSG_DATA) {
 819                 length = min(32u, skb->len);
 820                 if (!pskb_may_pull(skb, length))
 821                         goto error;
 822
 823                 pr_debug("%s: recv\n", tunnel->name);
 824                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 825         }
 826
 827         /* Point to L2TP header */
 828         optr = ptr = skb->data;
 829
 830         /* Get L2TP header flags */
 831         hdrflags = ntohs(*(__be16 *) ptr);
 832
 833         /* Check protocol version */
 834         version = hdrflags & L2TP_HDR_VER_MASK;
 835         if (version != tunnel->version) {
 836                 l2tp_info(tunnel, L2TP_MSG_DATA,
 837                           "%s: recv protocol version mismatch: got %d expected %d\n",
 838                           tunnel->name, version, tunnel->version);
 839                 goto error;
 840         }
 841
 842         /* Get length of L2TP packet */
 843         length = skb->len;
 844
 845         /* If type is control packet, it is handled by userspace. */
 846         if (hdrflags & L2TP_HDRFLAG_T) {
 847                 l2tp_dbg(tunnel, L2TP_MSG_DATA,
 848                          "%s: recv control packet, len=%d\n",
 849                          tunnel->name, length);
 850                 goto error;
 851         }
 852
 853         /* Skip flags */
 854         ptr += 2;
 855
 856         if (tunnel->version == L2TP_HDR_VER_2) {
 857                 /* If length is present, skip it */
 858                 if (hdrflags & L2TP_HDRFLAG_L)
 859                         ptr += 2;
 860
 861                 /* Extract tunnel and session ID */
 862                 tunnel_id = ntohs(*(__be16 *) ptr);
 863                 ptr += 2;
 864                 session_id = ntohs(*(__be16 *) ptr);
 865                 ptr += 2;
 866         } else {
 867                 ptr += 2;       /* skip reserved bits */
 868                 tunnel_id = tunnel->tunnel_id;
 869                 session_id = ntohl(*(__be32 *) ptr);
 870                 ptr += 4;
 871         }
 872
 873         /* Find the session context */
 874         session = l2tp_tunnel_get_session(tunnel, session_id);
 875         if (!session || !session->recv_skb) {
 876                 if (session)
 877                         l2tp_session_dec_refcount(session);
 878
 879                 /* Not found? Pass to userspace to deal with */
 880                 l2tp_info(tunnel, L2TP_MSG_DATA,
 881                           "%s: no session found (%u/%u). Passing up.\n",
 882                           tunnel->name, tunnel_id, session_id);
 883                 goto error;
 884         }
 885
 886         if (tunnel->version == L2TP_HDR_VER_3 &&
 887             l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
 888                 goto error;
 889
 890         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
 891         l2tp_session_dec_refcount(session);
 892
 893         return 0;
 894
 895 error:
 896         /* Put UDP header back */
 897         __skb_push(skb, sizeof(struct udphdr));
 898
 899         return 1;
 900 }
 901
 902 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 903  * Return codes:
 904  * 0 : success.
 905  * <0: error
 906  * >0: skb should be passed up to userspace as UDP.
 907  */
 908 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 909 {
 910         struct l2tp_tunnel *tunnel;
 911
 912         tunnel = l2tp_tunnel(sk);
 913         if (tunnel == NULL)
 914                 goto pass_up;
 915
 916         l2tp_dbg(tunnel, L2TP_MSG_DATA, "%s: received %d bytes\n",
 917                  tunnel->name, skb->len);
 918
 919         if (l2tp_udp_recv_core(tunnel, skb))
 920                 goto pass_up;
 921
 922         return 0;
 923
 924 pass_up:
 925         return 1;
 926 }
 927 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 928
 929 /************************************************************************
 930  * Transmit handling
 931  ***********************************************************************/
 932
 933 /* Build an L2TP header for the session into the buffer provided.
 934  */
 935 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 936 {
 937         struct l2tp_tunnel *tunnel = session->tunnel;
 938         __be16 *bufp = buf;
 939         __be16 *optr = buf;
 940         u16 flags = L2TP_HDR_VER_2;
 941         u32 tunnel_id = tunnel->peer_tunnel_id;
 942         u32 session_id = session->peer_session_id;
 943
 944         if (session->send_seq)
 945                 flags |= L2TP_HDRFLAG_S;
 946
 947         /* Setup L2TP header. */
 948         *bufp++ = htons(flags);
 949         *bufp++ = htons(tunnel_id);
 950         *bufp++ = htons(session_id);
 951         if (session->send_seq) {
 952                 *bufp++ = htons(session->ns);
 953                 *bufp++ = 0;
 954                 session->ns++;
 955                 session->ns &= 0xffff;
 956                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated ns to %u\n",
 957                          session->name, session->ns);
 958         }
 959
 960         return bufp - optr;
 961 }
 962
 963 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 964 {
 965         struct l2tp_tunnel *tunnel = session->tunnel;
 966         char *bufp = buf;
 967         char *optr = bufp;
 968
 969         /* Setup L2TP header. The header differs slightly for UDP and
 970          * IP encapsulations. For UDP, there is 4 bytes of flags.
 971          */
 972         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 973                 u16 flags = L2TP_HDR_VER_3;
 974                 *((__be16 *) bufp) = htons(flags);
 975                 bufp += 2;
 976                 *((__be16 *) bufp) = 0;
 977                 bufp += 2;
 978         }
 979
 980         *((__be32 *) bufp) = htonl(session->peer_session_id);
 981         bufp += 4;
 982         if (session->cookie_len) {
 983                 memcpy(bufp, &session->cookie[0], session->cookie_len);
 984                 bufp += session->cookie_len;
 985         }
 986         if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 987                 u32 l2h = 0;
 988
 989                 if (session->send_seq) {
 990                         l2h = 0x40000000 | session->ns;
 991                         session->ns++;
 992                         session->ns &= 0xffffff;
 993                         l2tp_dbg(session, L2TP_MSG_SEQ,
 994                                  "%s: updated ns to %u\n",
 995                                  session->name, session->ns);
 996                 }
 997
 998                 *((__be32 *)bufp) = htonl(l2h);
 999                 bufp += 4;
1000         }
1001
1002         return bufp - optr;
1003 }
1004
1005 static void l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
1006                            struct flowi *fl, size_t data_len)
1007 {
1008         struct l2tp_tunnel *tunnel = session->tunnel;
1009         unsigned int len = skb->len;
1010         int error;
1011
1012         /* Debug */
1013         if (session->send_seq)
1014                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %zd bytes, ns=%u\n",
1015                          session->name, data_len, session->ns - 1);
1016         else
1017                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %zd bytes\n",
1018                          session->name, data_len);
1019
1020         if (session->debug & L2TP_MSG_DATA) {
1021                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1022                 unsigned char *datap = skb->data + uhlen;
1023
1024                 pr_debug("%s: xmit\n", session->name);
1025                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET,
1026                                      datap, min_t(size_t, 32, len - uhlen));
1027         }
1028
1029         /* Queue the packet to IP for output */
1030         skb->ignore_df = 1;
1031 #if IS_ENABLED(CONFIG_IPV6)
1032         if (l2tp_sk_is_v6(tunnel->sock))
1033                 error = inet6_csk_xmit(tunnel->sock, skb, NULL);
1034         else
1035 #endif
1036                 error = ip_queue_xmit(tunnel->sock, skb, fl);
1037
1038         /* Update stats */
1039         if (error >= 0) {
1040                 atomic_long_inc(&tunnel->stats.tx_packets);
1041                 atomic_long_add(len, &tunnel->stats.tx_bytes);
1042                 atomic_long_inc(&session->stats.tx_packets);
1043                 atomic_long_add(len, &session->stats.tx_bytes);
1044         } else {
1045                 atomic_long_inc(&tunnel->stats.tx_errors);
1046                 atomic_long_inc(&session->stats.tx_errors);
1047         }
1048 }
1049
1050 /* If caller requires the skb to have a ppp header, the header must be
1051  * inserted in the skb data before calling this function.
1052  */
1053 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1054 {
1055         int data_len = skb->len;
1056         struct l2tp_tunnel *tunnel = session->tunnel;
1057         struct sock *sk = tunnel->sock;
1058         struct flowi *fl;
1059         struct udphdr *uh;
1060         struct inet_sock *inet;
1061         int headroom;
1062         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1063         int udp_len;
1064         int ret = NET_XMIT_SUCCESS;
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         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1071                 uhlen + 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         session->build_header(session, __skb_push(skb, hdr_len));
1079
1080         /* Reset skb netfilter state */
1081         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1082         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1083                               IPSKB_REROUTED);
1084         nf_reset(skb);
1085
1086         bh_lock_sock(sk);
1087         if (sock_owned_by_user(sk)) {
1088                 kfree_skb(skb);
1089                 ret = NET_XMIT_DROP;
1090                 goto out_unlock;
1091         }
1092
1093         /* The user-space may change the connection status for the user-space
1094          * provided socket at run time: we must check it under the socket lock
1095          */
1096         if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1097                 kfree_skb(skb);
1098                 ret = NET_XMIT_DROP;
1099                 goto out_unlock;
1100         }
1101
1102         /* Get routing info from the tunnel socket */
1103         skb_dst_drop(skb);
1104         skb_dst_set(skb, sk_dst_check(sk, 0));
1105
1106         inet = inet_sk(sk);
1107         fl = &inet->cork.fl;
1108         switch (tunnel->encap) {
1109         case L2TP_ENCAPTYPE_UDP:
1110                 /* Setup UDP header */
1111                 __skb_push(skb, sizeof(*uh));
1112                 skb_reset_transport_header(skb);
1113                 uh = udp_hdr(skb);
1114                 uh->source = inet->inet_sport;
1115                 uh->dest = inet->inet_dport;
1116                 udp_len = uhlen + hdr_len + data_len;
1117                 uh->len = htons(udp_len);
1118
1119                 /* Calculate UDP checksum if configured to do so */
1120 #if IS_ENABLED(CONFIG_IPV6)
1121                 if (l2tp_sk_is_v6(sk))
1122                         udp6_set_csum(udp_get_no_check6_tx(sk),
1123                                       skb, &inet6_sk(sk)->saddr,
1124                                       &sk->sk_v6_daddr, udp_len);
1125                 else
1126 #endif
1127                 udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1128                              inet->inet_daddr, udp_len);
1129                 break;
1130
1131         case L2TP_ENCAPTYPE_IP:
1132                 break;
1133         }
1134
1135         l2tp_xmit_core(session, skb, fl, data_len);
1136 out_unlock:
1137         bh_unlock_sock(sk);
1138
1139         return ret;
1140 }
1141 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1142
1143 /*****************************************************************************
1144  * Tinnel and session create/destroy.
1145  *****************************************************************************/
1146
1147 /* Tunnel socket destruct hook.
1148  * The tunnel context is deleted only when all session sockets have been
1149  * closed.
1150  */
1151 static void l2tp_tunnel_destruct(struct sock *sk)
1152 {
1153         struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
1154
1155         if (tunnel == NULL)
1156                 goto end;
1157
1158         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing...\n", tunnel->name);
1159
1160         /* Disable udp encapsulation */
1161         switch (tunnel->encap) {
1162         case L2TP_ENCAPTYPE_UDP:
1163                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1164                 (udp_sk(sk))->encap_type = 0;
1165                 (udp_sk(sk))->encap_rcv = NULL;
1166                 (udp_sk(sk))->encap_destroy = NULL;
1167                 break;
1168         case L2TP_ENCAPTYPE_IP:
1169                 break;
1170         }
1171
1172         /* Remove hooks into tunnel socket */
1173         sk->sk_destruct = tunnel->old_sk_destruct;
1174         sk->sk_user_data = NULL;
1175
1176         /* Call the original destructor */
1177         if (sk->sk_destruct)
1178                 (*sk->sk_destruct)(sk);
1179
1180         kfree_rcu(tunnel, rcu);
1181 end:
1182         return;
1183 }
1184
1185 /* When the tunnel is closed, all the attached sessions need to go too.
1186  */
1187 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1188 {
1189         int hash;
1190         struct hlist_node *walk;
1191         struct hlist_node *tmp;
1192         struct l2tp_session *session;
1193
1194         BUG_ON(tunnel == NULL);
1195
1196         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing all sessions...\n",
1197                   tunnel->name);
1198
1199         write_lock_bh(&tunnel->hlist_lock);
1200         tunnel->acpt_newsess = false;
1201         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1202 again:
1203                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1204                         session = hlist_entry(walk, struct l2tp_session, hlist);
1205
1206                         l2tp_info(session, L2TP_MSG_CONTROL,
1207                                   "%s: closing session\n", session->name);
1208
1209                         hlist_del_init(&session->hlist);
1210
1211                         if (test_and_set_bit(0, &session->dead))
1212                                 goto again;
1213
1214                         write_unlock_bh(&tunnel->hlist_lock);
1215
1216                         __l2tp_session_unhash(session);
1217                         l2tp_session_queue_purge(session);
1218
1219                         if (session->session_close != NULL)
1220                                 (*session->session_close)(session);
1221
1222                         l2tp_session_dec_refcount(session);
1223
1224                         write_lock_bh(&tunnel->hlist_lock);
1225
1226                         /* Now restart from the beginning of this hash
1227                          * chain.  We always remove a session from the
1228                          * list so we are guaranteed to make forward
1229                          * progress.
1230                          */
1231                         goto again;
1232                 }
1233         }
1234         write_unlock_bh(&tunnel->hlist_lock);
1235 }
1236
1237 /* Tunnel socket destroy hook for UDP encapsulation */
1238 static void l2tp_udp_encap_destroy(struct sock *sk)
1239 {
1240         struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
1241
1242         if (tunnel)
1243                 l2tp_tunnel_delete(tunnel);
1244 }
1245
1246 /* Workqueue tunnel deletion function */
1247 static void l2tp_tunnel_del_work(struct work_struct *work)
1248 {
1249         struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1250                                                   del_work);
1251         struct sock *sk = tunnel->sock;
1252         struct socket *sock = sk->sk_socket;
1253         struct l2tp_net *pn;
1254
1255         l2tp_tunnel_closeall(tunnel);
1256
1257         /* If the tunnel socket was created within the kernel, use
1258          * the sk API to release it here.
1259          */
1260         if (tunnel->fd < 0) {
1261                 if (sock) {
1262                         kernel_sock_shutdown(sock, SHUT_RDWR);
1263                         sock_release(sock);
1264                 }
1265         }
1266
1267         /* Remove the tunnel struct from the tunnel list */
1268         pn = l2tp_pernet(tunnel->l2tp_net);
1269         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1270         list_del_rcu(&tunnel->list);
1271         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1272
1273         /* drop initial ref */
1274         l2tp_tunnel_dec_refcount(tunnel);
1275
1276         /* drop workqueue ref */
1277         l2tp_tunnel_dec_refcount(tunnel);
1278 }
1279
1280 /* Create a socket for the tunnel, if one isn't set up by
1281  * userspace. This is used for static tunnels where there is no
1282  * managing L2TP daemon.
1283  *
1284  * Since we don't want these sockets to keep a namespace alive by
1285  * themselves, we drop the socket's namespace refcount after creation.
1286  * These sockets are freed when the namespace exits using the pernet
1287  * exit hook.
1288  */
1289 static int l2tp_tunnel_sock_create(struct net *net,
1290                                 u32 tunnel_id,
1291                                 u32 peer_tunnel_id,
1292                                 struct l2tp_tunnel_cfg *cfg,
1293                                 struct socket **sockp)
1294 {
1295         int err = -EINVAL;
1296         struct socket *sock = NULL;
1297         struct udp_port_cfg udp_conf;
1298
1299         switch (cfg->encap) {
1300         case L2TP_ENCAPTYPE_UDP:
1301                 memset(&udp_conf, 0, sizeof(udp_conf));
1302
1303 #if IS_ENABLED(CONFIG_IPV6)
1304                 if (cfg->local_ip6 && cfg->peer_ip6) {
1305                         udp_conf.family = AF_INET6;
1306                         memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1307                                sizeof(udp_conf.local_ip6));
1308                         memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1309                                sizeof(udp_conf.peer_ip6));
1310                         udp_conf.use_udp6_tx_checksums =
1311                           ! cfg->udp6_zero_tx_checksums;
1312                         udp_conf.use_udp6_rx_checksums =
1313                           ! cfg->udp6_zero_rx_checksums;
1314                 } else
1315 #endif
1316                 {
1317                         udp_conf.family = AF_INET;
1318                         udp_conf.local_ip = cfg->local_ip;
1319                         udp_conf.peer_ip = cfg->peer_ip;
1320                         udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1321                 }
1322
1323                 udp_conf.local_udp_port = htons(cfg->local_udp_port);
1324                 udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1325
1326                 err = udp_sock_create(net, &udp_conf, &sock);
1327                 if (err < 0)
1328                         goto out;
1329
1330                 break;
1331
1332         case L2TP_ENCAPTYPE_IP:
1333 #if IS_ENABLED(CONFIG_IPV6)
1334                 if (cfg->local_ip6 && cfg->peer_ip6) {
1335                         struct sockaddr_l2tpip6 ip6_addr = {0};
1336
1337                         err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1338                                           IPPROTO_L2TP, &sock);
1339                         if (err < 0)
1340                                 goto out;
1341
1342                         ip6_addr.l2tp_family = AF_INET6;
1343                         memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1344                                sizeof(ip6_addr.l2tp_addr));
1345                         ip6_addr.l2tp_conn_id = tunnel_id;
1346                         err = kernel_bind(sock, (struct sockaddr *) &ip6_addr,
1347                                           sizeof(ip6_addr));
1348                         if (err < 0)
1349                                 goto out;
1350
1351                         ip6_addr.l2tp_family = AF_INET6;
1352                         memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1353                                sizeof(ip6_addr.l2tp_addr));
1354                         ip6_addr.l2tp_conn_id = peer_tunnel_id;
1355                         err = kernel_connect(sock,
1356                                              (struct sockaddr *) &ip6_addr,
1357                                              sizeof(ip6_addr), 0);
1358                         if (err < 0)
1359                                 goto out;
1360                 } else
1361 #endif
1362                 {
1363                         struct sockaddr_l2tpip ip_addr = {0};
1364
1365                         err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1366                                           IPPROTO_L2TP, &sock);
1367                         if (err < 0)
1368                                 goto out;
1369
1370                         ip_addr.l2tp_family = AF_INET;
1371                         ip_addr.l2tp_addr = cfg->local_ip;
1372                         ip_addr.l2tp_conn_id = tunnel_id;
1373                         err = kernel_bind(sock, (struct sockaddr *) &ip_addr,
1374                                           sizeof(ip_addr));
1375                         if (err < 0)
1376                                 goto out;
1377
1378                         ip_addr.l2tp_family = AF_INET;
1379                         ip_addr.l2tp_addr = cfg->peer_ip;
1380                         ip_addr.l2tp_conn_id = peer_tunnel_id;
1381                         err = kernel_connect(sock, (struct sockaddr *) &ip_addr,
1382                                              sizeof(ip_addr), 0);
1383                         if (err < 0)
1384                                 goto out;
1385                 }
1386                 break;
1387
1388         default:
1389                 goto out;
1390         }
1391
1392 out:
1393         *sockp = sock;
1394         if ((err < 0) && sock) {
1395                 kernel_sock_shutdown(sock, SHUT_RDWR);
1396                 sock_release(sock);
1397                 *sockp = NULL;
1398         }
1399
1400         return err;
1401 }
1402
1403 static struct lock_class_key l2tp_socket_class;
1404
1405 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)
1406 {
1407         struct l2tp_tunnel *tunnel = NULL;
1408         int err;
1409         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1410
1411         if (cfg != NULL)
1412                 encap = cfg->encap;
1413
1414         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1415         if (tunnel == NULL) {
1416                 err = -ENOMEM;
1417                 goto err;
1418         }
1419
1420         tunnel->version = version;
1421         tunnel->tunnel_id = tunnel_id;
1422         tunnel->peer_tunnel_id = peer_tunnel_id;
1423         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1424
1425         tunnel->magic = L2TP_TUNNEL_MAGIC;
1426         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1427         rwlock_init(&tunnel->hlist_lock);
1428         tunnel->acpt_newsess = true;
1429
1430         if (cfg != NULL)
1431                 tunnel->debug = cfg->debug;
1432
1433         tunnel->encap = encap;
1434
1435         refcount_set(&tunnel->ref_count, 1);
1436         tunnel->fd = fd;
1437
1438         /* Init delete workqueue struct */
1439         INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1440
1441         INIT_LIST_HEAD(&tunnel->list);
1442
1443         err = 0;
1444 err:
1445         if (tunnelp)
1446                 *tunnelp = tunnel;
1447
1448         return err;
1449 }
1450 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1451
1452 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1453                                 enum l2tp_encap_type encap)
1454 {
1455         if (!net_eq(sock_net(sk), net))
1456                 return -EINVAL;
1457
1458         if (sk->sk_type != SOCK_DGRAM)
1459                 return -EPROTONOSUPPORT;
1460
1461         if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1462             (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1463                 return -EPROTONOSUPPORT;
1464
1465         if (sk->sk_user_data)
1466                 return -EBUSY;
1467
1468         return 0;
1469 }
1470
1471 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1472                          struct l2tp_tunnel_cfg *cfg)
1473 {
1474         struct l2tp_tunnel *tunnel_walk;
1475         struct l2tp_net *pn;
1476         struct socket *sock;
1477         struct sock *sk;
1478         int ret;
1479
1480         if (tunnel->fd < 0) {
1481                 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1482                                               tunnel->peer_tunnel_id, cfg,
1483                                               &sock);
1484                 if (ret < 0)
1485                         goto err;
1486         } else {
1487                 sock = sockfd_lookup(tunnel->fd, &ret);
1488                 if (!sock)
1489                         goto err;
1490
1491                 ret = l2tp_validate_socket(sock->sk, net, tunnel->encap);
1492                 if (ret < 0)
1493                         goto err_sock;
1494         }
1495
1496         tunnel->l2tp_net = net;
1497         pn = l2tp_pernet(net);
1498
1499         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1500         list_for_each_entry(tunnel_walk, &pn->l2tp_tunnel_list, list) {
1501                 if (tunnel_walk->tunnel_id == tunnel->tunnel_id) {
1502                         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1503
1504                         ret = -EEXIST;
1505                         goto err_sock;
1506                 }
1507         }
1508         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1509         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1510
1511         sk = sock->sk;
1512         sock_hold(sk);
1513         tunnel->sock = sk;
1514
1515         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1516                 struct udp_tunnel_sock_cfg udp_cfg = {
1517                         .sk_user_data = tunnel,
1518                         .encap_type = UDP_ENCAP_L2TPINUDP,
1519                         .encap_rcv = l2tp_udp_encap_recv,
1520                         .encap_destroy = l2tp_udp_encap_destroy,
1521                 };
1522
1523                 setup_udp_tunnel_sock(net, sock, &udp_cfg);
1524         } else {
1525                 sk->sk_user_data = tunnel;
1526         }
1527
1528         tunnel->old_sk_destruct = sk->sk_destruct;
1529         sk->sk_destruct = &l2tp_tunnel_destruct;
1530         lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class,
1531                                    "l2tp_sock");
1532         sk->sk_allocation = GFP_ATOMIC;
1533
1534         if (tunnel->fd >= 0)
1535                 sockfd_put(sock);
1536
1537         return 0;
1538
1539 err_sock:
1540         if (tunnel->fd < 0)
1541                 sock_release(sock);
1542         else
1543                 sockfd_put(sock);
1544 err:
1545         return ret;
1546 }
1547 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1548
1549 /* This function is used by the netlink TUNNEL_DELETE command.
1550  */
1551 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1552 {
1553         if (!test_and_set_bit(0, &tunnel->dead)) {
1554                 l2tp_tunnel_inc_refcount(tunnel);
1555                 queue_work(l2tp_wq, &tunnel->del_work);
1556         }
1557 }
1558 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1559
1560 /* Really kill the session.
1561  */
1562 void l2tp_session_free(struct l2tp_session *session)
1563 {
1564         struct l2tp_tunnel *tunnel = session->tunnel;
1565
1566         BUG_ON(refcount_read(&session->ref_count) != 0);
1567
1568         if (tunnel) {
1569                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1570                 l2tp_tunnel_dec_refcount(tunnel);
1571         }
1572
1573         kfree(session);
1574 }
1575 EXPORT_SYMBOL_GPL(l2tp_session_free);
1576
1577 /* Remove an l2tp session from l2tp_core's hash lists.
1578  * Provides a tidyup interface for pseudowire code which can't just route all
1579  * shutdown via. l2tp_session_delete and a pseudowire-specific session_close
1580  * callback.
1581  */
1582 void __l2tp_session_unhash(struct l2tp_session *session)
1583 {
1584         struct l2tp_tunnel *tunnel = session->tunnel;
1585
1586         /* Remove the session from core hashes */
1587         if (tunnel) {
1588                 /* Remove from the per-tunnel hash */
1589                 write_lock_bh(&tunnel->hlist_lock);
1590                 hlist_del_init(&session->hlist);
1591                 write_unlock_bh(&tunnel->hlist_lock);
1592
1593                 /* For L2TPv3 we have a per-net hash: remove from there, too */
1594                 if (tunnel->version != L2TP_HDR_VER_2) {
1595                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1596                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1597                         hlist_del_init_rcu(&session->global_hlist);
1598                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1599                         synchronize_rcu();
1600                 }
1601         }
1602 }
1603 EXPORT_SYMBOL_GPL(__l2tp_session_unhash);
1604
1605 /* This function is used by the netlink SESSION_DELETE command and by
1606    pseudowire modules.
1607  */
1608 int l2tp_session_delete(struct l2tp_session *session)
1609 {
1610         if (test_and_set_bit(0, &session->dead))
1611                 return 0;
1612
1613         __l2tp_session_unhash(session);
1614         l2tp_session_queue_purge(session);
1615         if (session->session_close != NULL)
1616                 (*session->session_close)(session);
1617
1618         l2tp_session_dec_refcount(session);
1619
1620         return 0;
1621 }
1622 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1623
1624 /* We come here whenever a session's send_seq, cookie_len or
1625  * l2specific_type parameters are set.
1626  */
1627 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1628 {
1629         if (version == L2TP_HDR_VER_2) {
1630                 session->hdr_len = 6;
1631                 if (session->send_seq)
1632                         session->hdr_len += 4;
1633         } else {
1634                 session->hdr_len = 4 + session->cookie_len;
1635                 session->hdr_len += l2tp_get_l2specific_len(session);
1636                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1637                         session->hdr_len += 4;
1638         }
1639
1640 }
1641 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1642
1643 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)
1644 {
1645         struct l2tp_session *session;
1646
1647         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1648         if (session != NULL) {
1649                 session->magic = L2TP_SESSION_MAGIC;
1650                 session->tunnel = tunnel;
1651
1652                 session->session_id = session_id;
1653                 session->peer_session_id = peer_session_id;
1654                 session->nr = 0;
1655                 if (tunnel->version == L2TP_HDR_VER_2)
1656                         session->nr_max = 0xffff;
1657                 else
1658                         session->nr_max = 0xffffff;
1659                 session->nr_window_size = session->nr_max / 2;
1660                 session->nr_oos_count_max = 4;
1661
1662                 /* Use NR of first received packet */
1663                 session->reorder_skip = 1;
1664
1665                 sprintf(&session->name[0], "sess %u/%u",
1666                         tunnel->tunnel_id, session->session_id);
1667
1668                 skb_queue_head_init(&session->reorder_q);
1669
1670                 INIT_HLIST_NODE(&session->hlist);
1671                 INIT_HLIST_NODE(&session->global_hlist);
1672
1673                 /* Inherit debug options from tunnel */
1674                 session->debug = tunnel->debug;
1675
1676                 if (cfg) {
1677                         session->pwtype = cfg->pw_type;
1678                         session->debug = cfg->debug;
1679                         session->send_seq = cfg->send_seq;
1680                         session->recv_seq = cfg->recv_seq;
1681                         session->lns_mode = cfg->lns_mode;
1682                         session->reorder_timeout = cfg->reorder_timeout;
1683                         session->l2specific_type = cfg->l2specific_type;
1684                         session->cookie_len = cfg->cookie_len;
1685                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1686                         session->peer_cookie_len = cfg->peer_cookie_len;
1687                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1688                 }
1689
1690                 if (tunnel->version == L2TP_HDR_VER_2)
1691                         session->build_header = l2tp_build_l2tpv2_header;
1692                 else
1693                         session->build_header = l2tp_build_l2tpv3_header;
1694
1695                 l2tp_session_set_header_len(session, tunnel->version);
1696
1697                 refcount_set(&session->ref_count, 1);
1698
1699                 return session;
1700         }
1701
1702         return ERR_PTR(-ENOMEM);
1703 }
1704 EXPORT_SYMBOL_GPL(l2tp_session_create);
1705
1706 /*****************************************************************************
1707  * Init and cleanup
1708  *****************************************************************************/
1709
1710 static __net_init int l2tp_init_net(struct net *net)
1711 {
1712         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1713         int hash;
1714
1715         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1716         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1717
1718         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1719                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1720
1721         spin_lock_init(&pn->l2tp_session_hlist_lock);
1722
1723         return 0;
1724 }
1725
1726 static __net_exit void l2tp_exit_net(struct net *net)
1727 {
1728         struct l2tp_net *pn = l2tp_pernet(net);
1729         struct l2tp_tunnel *tunnel = NULL;
1730         int hash;
1731
1732         rcu_read_lock_bh();
1733         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
1734                 l2tp_tunnel_delete(tunnel);
1735         }
1736         rcu_read_unlock_bh();
1737
1738         flush_workqueue(l2tp_wq);
1739         rcu_barrier();
1740
1741         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1742                 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1743 }
1744
1745 static struct pernet_operations l2tp_net_ops = {
1746         .init = l2tp_init_net,
1747         .exit = l2tp_exit_net,
1748         .id   = &l2tp_net_id,
1749         .size = sizeof(struct l2tp_net),
1750 };
1751
1752 static int __init l2tp_init(void)
1753 {
1754         int rc = 0;
1755
1756         rc = register_pernet_device(&l2tp_net_ops);
1757         if (rc)
1758                 goto out;
1759
1760         l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1761         if (!l2tp_wq) {
1762                 pr_err("alloc_workqueue failed\n");
1763                 unregister_pernet_device(&l2tp_net_ops);
1764                 rc = -ENOMEM;
1765                 goto out;
1766         }
1767
1768         pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1769
1770 out:
1771         return rc;
1772 }
1773
1774 static void __exit l2tp_exit(void)
1775 {
1776         unregister_pernet_device(&l2tp_net_ops);
1777         if (l2tp_wq) {
1778                 destroy_workqueue(l2tp_wq);
1779                 l2tp_wq = NULL;
1780         }
1781 }
1782
1783 module_init(l2tp_init);
1784 module_exit(l2tp_exit);
1785
1786 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1787 MODULE_DESCRIPTION("L2TP core");
1788 MODULE_LICENSE("GPL");
1789 MODULE_VERSION(L2TP_DRV_VERSION);