net/l2tp/l2tp_core.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* L2TP core.
   3  *
   4  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
   5  *
   6  * This file contains some code of the original L2TPv2 pppol2tp
   7  * driver, which has the following copyright:
   8  *
   9  * Authors:     Martijn van Oosterhout <kleptog@svana.org>
  10  *              James Chapman (jchapman@katalix.com)
  11  * Contributors:
  12  *              Michal Ostrowski <mostrows@speakeasy.net>
  13  *              Arnaldo Carvalho de Melo <acme@xconectiva.com.br>
  14  *              David S. Miller (davem@redhat.com)
  15  */
  16
  17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  18
  19 #include <linux/module.h>
  20 #include <linux/string.h>
  21 #include <linux/list.h>
  22 #include <linux/rculist.h>
  23 #include <linux/uaccess.h>
  24
  25 #include <linux/kernel.h>
  26 #include <linux/spinlock.h>
  27 #include <linux/kthread.h>
  28 #include <linux/sched.h>
  29 #include <linux/slab.h>
  30 #include <linux/errno.h>
  31 #include <linux/jiffies.h>
  32
  33 #include <linux/netdevice.h>
  34 #include <linux/net.h>
  35 #include <linux/inetdevice.h>
  36 #include <linux/skbuff.h>
  37 #include <linux/init.h>
  38 #include <linux/in.h>
  39 #include <linux/ip.h>
  40 #include <linux/udp.h>
  41 #include <linux/l2tp.h>
  42 #include <linux/hash.h>
  43 #include <linux/sort.h>
  44 #include <linux/file.h>
  45 #include <linux/nsproxy.h>
  46 #include <net/net_namespace.h>
  47 #include <net/netns/generic.h>
  48 #include <net/dst.h>
  49 #include <net/ip.h>
  50 #include <net/udp.h>
  51 #include <net/udp_tunnel.h>
  52 #include <net/inet_common.h>
  53 #include <net/xfrm.h>
  54 #include <net/protocol.h>
  55 #include <net/inet6_connection_sock.h>
  56 #include <net/inet_ecn.h>
  57 #include <net/ip6_route.h>
  58 #include <net/ip6_checksum.h>
  59
  60 #include <asm/byteorder.h>
  61 #include <linux/atomic.h>
  62
  63 #include "l2tp_core.h"
  64 #include "trace.h"
  65
  66 #define CREATE_TRACE_POINTS
  67 #include "trace.h"
  68
  69 #define L2TP_DRV_VERSION        "V2.0"
  70
  71 /* L2TP header constants */
  72 #define L2TP_HDRFLAG_T     0x8000
  73 #define L2TP_HDRFLAG_L     0x4000
  74 #define L2TP_HDRFLAG_S     0x0800
  75 #define L2TP_HDRFLAG_O     0x0200
  76 #define L2TP_HDRFLAG_P     0x0100
  77
  78 #define L2TP_HDR_VER_MASK  0x000F
  79 #define L2TP_HDR_VER_2     0x0002
  80 #define L2TP_HDR_VER_3     0x0003
  81
  82 /* L2TPv3 default L2-specific sublayer */
  83 #define L2TP_SLFLAG_S      0x40000000
  84 #define L2TP_SL_SEQ_MASK   0x00ffffff
  85
  86 #define L2TP_HDR_SIZE_MAX               14
  87
  88 /* Default trace flags */
  89 #define L2TP_DEFAULT_DEBUG_FLAGS        0
  90
  91 /* Private data stored for received packets in the skb.
  92  */
  93 struct l2tp_skb_cb {
  94         u32                     ns;
  95         u16                     has_seq;
  96         u16                     length;
  97         unsigned long           expires;
  98 };
  99
 100 #define L2TP_SKB_CB(skb)        ((struct l2tp_skb_cb *)&(skb)->cb[sizeof(struct inet_skb_parm)])
 101
 102 static struct workqueue_struct *l2tp_wq;
 103
 104 /* per-net private data for this module */
 105 static unsigned int l2tp_net_id;
 106 struct l2tp_net {
 107         struct list_head l2tp_tunnel_list;
 108         /* Lock for write access to l2tp_tunnel_list */
 109         spinlock_t l2tp_tunnel_list_lock;
 110         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
 111         /* Lock for write access to l2tp_session_hlist */
 112         spinlock_t l2tp_session_hlist_lock;
 113 };
 114
 115 #if IS_ENABLED(CONFIG_IPV6)
 116 static bool l2tp_sk_is_v6(struct sock *sk)
 117 {
 118         return sk->sk_family == PF_INET6 &&
 119                !ipv6_addr_v4mapped(&sk->sk_v6_daddr);
 120 }
 121 #endif
 122
 123 static inline struct l2tp_net *l2tp_pernet(const struct net *net)
 124 {
 125         return net_generic(net, l2tp_net_id);
 126 }
 127
 128 /* Session hash global list for L2TPv3.
 129  * The session_id SHOULD be random according to RFC3931, but several
 130  * L2TP implementations use incrementing session_ids.  So we do a real
 131  * hash on the session_id, rather than a simple bitmask.
 132  */
 133 static inline struct hlist_head *
 134 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 135 {
 136         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 137 }
 138
 139 /* Session hash list.
 140  * The session_id SHOULD be random according to RFC2661, but several
 141  * L2TP implementations (Cisco and Microsoft) use incrementing
 142  * session_ids.  So we do a real hash on the session_id, rather than a
 143  * simple bitmask.
 144  */
 145 static inline struct hlist_head *
 146 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 147 {
 148         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 149 }
 150
 151 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
 152 {
 153         trace_free_tunnel(tunnel);
 154         sock_put(tunnel->sock);
 155         /* the tunnel is freed in the socket destructor */
 156 }
 157
 158 static void l2tp_session_free(struct l2tp_session *session)
 159 {
 160         trace_free_session(session);
 161         if (session->tunnel)
 162                 l2tp_tunnel_dec_refcount(session->tunnel);
 163         kfree(session);
 164 }
 165
 166 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk)
 167 {
 168         struct l2tp_tunnel *tunnel = sk->sk_user_data;
 169
 170         if (tunnel)
 171                 if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
 172                         return NULL;
 173
 174         return tunnel;
 175 }
 176 EXPORT_SYMBOL_GPL(l2tp_sk_to_tunnel);
 177
 178 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel)
 179 {
 180         refcount_inc(&tunnel->ref_count);
 181 }
 182 EXPORT_SYMBOL_GPL(l2tp_tunnel_inc_refcount);
 183
 184 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel)
 185 {
 186         if (refcount_dec_and_test(&tunnel->ref_count))
 187                 l2tp_tunnel_free(tunnel);
 188 }
 189 EXPORT_SYMBOL_GPL(l2tp_tunnel_dec_refcount);
 190
 191 void l2tp_session_inc_refcount(struct l2tp_session *session)
 192 {
 193         refcount_inc(&session->ref_count);
 194 }
 195 EXPORT_SYMBOL_GPL(l2tp_session_inc_refcount);
 196
 197 void l2tp_session_dec_refcount(struct l2tp_session *session)
 198 {
 199         if (refcount_dec_and_test(&session->ref_count))
 200                 l2tp_session_free(session);
 201 }
 202 EXPORT_SYMBOL_GPL(l2tp_session_dec_refcount);
 203
 204 /* Lookup a tunnel. A new reference is held on the returned tunnel. */
 205 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
 206 {
 207         const struct l2tp_net *pn = l2tp_pernet(net);
 208         struct l2tp_tunnel *tunnel;
 209
 210         rcu_read_lock_bh();
 211         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 212                 if (tunnel->tunnel_id == tunnel_id &&
 213                     refcount_inc_not_zero(&tunnel->ref_count)) {
 214                         rcu_read_unlock_bh();
 215
 216                         return tunnel;
 217                 }
 218         }
 219         rcu_read_unlock_bh();
 220
 221         return NULL;
 222 }
 223 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
 224
 225 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
 226 {
 227         const struct l2tp_net *pn = l2tp_pernet(net);
 228         struct l2tp_tunnel *tunnel;
 229         int count = 0;
 230
 231         rcu_read_lock_bh();
 232         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 233                 if (++count > nth &&
 234                     refcount_inc_not_zero(&tunnel->ref_count)) {
 235                         rcu_read_unlock_bh();
 236                         return tunnel;
 237                 }
 238         }
 239         rcu_read_unlock_bh();
 240
 241         return NULL;
 242 }
 243 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
 244
 245 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
 246                                              u32 session_id)
 247 {
 248         struct hlist_head *session_list;
 249         struct l2tp_session *session;
 250
 251         session_list = l2tp_session_id_hash(tunnel, session_id);
 252
 253         read_lock_bh(&tunnel->hlist_lock);
 254         hlist_for_each_entry(session, session_list, hlist)
 255                 if (session->session_id == session_id) {
 256                         l2tp_session_inc_refcount(session);
 257                         read_unlock_bh(&tunnel->hlist_lock);
 258
 259                         return session;
 260                 }
 261         read_unlock_bh(&tunnel->hlist_lock);
 262
 263         return NULL;
 264 }
 265 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
 266
 267 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
 268 {
 269         struct hlist_head *session_list;
 270         struct l2tp_session *session;
 271
 272         session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
 273
 274         rcu_read_lock_bh();
 275         hlist_for_each_entry_rcu(session, session_list, global_hlist)
 276                 if (session->session_id == session_id) {
 277                         l2tp_session_inc_refcount(session);
 278                         rcu_read_unlock_bh();
 279
 280                         return session;
 281                 }
 282         rcu_read_unlock_bh();
 283
 284         return NULL;
 285 }
 286 EXPORT_SYMBOL_GPL(l2tp_session_get);
 287
 288 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
 289 {
 290         int hash;
 291         struct l2tp_session *session;
 292         int count = 0;
 293
 294         read_lock_bh(&tunnel->hlist_lock);
 295         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 296                 hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
 297                         if (++count > nth) {
 298                                 l2tp_session_inc_refcount(session);
 299                                 read_unlock_bh(&tunnel->hlist_lock);
 300                                 return session;
 301                         }
 302                 }
 303         }
 304
 305         read_unlock_bh(&tunnel->hlist_lock);
 306
 307         return NULL;
 308 }
 309 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
 310
 311 /* Lookup a session by interface name.
 312  * This is very inefficient but is only used by management interfaces.
 313  */
 314 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
 315                                                 const char *ifname)
 316 {
 317         struct l2tp_net *pn = l2tp_pernet(net);
 318         int hash;
 319         struct l2tp_session *session;
 320
 321         rcu_read_lock_bh();
 322         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 323                 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
 324                         if (!strcmp(session->ifname, ifname)) {
 325                                 l2tp_session_inc_refcount(session);
 326                                 rcu_read_unlock_bh();
 327
 328                                 return session;
 329                         }
 330                 }
 331         }
 332
 333         rcu_read_unlock_bh();
 334
 335         return NULL;
 336 }
 337 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
 338
 339 int l2tp_session_register(struct l2tp_session *session,
 340                           struct l2tp_tunnel *tunnel)
 341 {
 342         struct l2tp_session *session_walk;
 343         struct hlist_head *g_head;
 344         struct hlist_head *head;
 345         struct l2tp_net *pn;
 346         int err;
 347
 348         head = l2tp_session_id_hash(tunnel, session->session_id);
 349
 350         write_lock_bh(&tunnel->hlist_lock);
 351         if (!tunnel->acpt_newsess) {
 352                 err = -ENODEV;
 353                 goto err_tlock;
 354         }
 355
 356         hlist_for_each_entry(session_walk, head, hlist)
 357                 if (session_walk->session_id == session->session_id) {
 358                         err = -EEXIST;
 359                         goto err_tlock;
 360                 }
 361
 362         if (tunnel->version == L2TP_HDR_VER_3) {
 363                 pn = l2tp_pernet(tunnel->l2tp_net);
 364                 g_head = l2tp_session_id_hash_2(pn, session->session_id);
 365
 366                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
 367
 368                 /* IP encap expects session IDs to be globally unique, while
 369                  * UDP encap doesn't.
 370                  */
 371                 hlist_for_each_entry(session_walk, g_head, global_hlist)
 372                         if (session_walk->session_id == session->session_id &&
 373                             (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP ||
 374                              tunnel->encap == L2TP_ENCAPTYPE_IP)) {
 375                                 err = -EEXIST;
 376                                 goto err_tlock_pnlock;
 377                         }
 378
 379                 l2tp_tunnel_inc_refcount(tunnel);
 380                 hlist_add_head_rcu(&session->global_hlist, g_head);
 381
 382                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 383         } else {
 384                 l2tp_tunnel_inc_refcount(tunnel);
 385         }
 386
 387         hlist_add_head(&session->hlist, head);
 388         write_unlock_bh(&tunnel->hlist_lock);
 389
 390         trace_register_session(session);
 391
 392         return 0;
 393
 394 err_tlock_pnlock:
 395         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 396 err_tlock:
 397         write_unlock_bh(&tunnel->hlist_lock);
 398
 399         return err;
 400 }
 401 EXPORT_SYMBOL_GPL(l2tp_session_register);
 402
 403 /*****************************************************************************
 404  * Receive data handling
 405  *****************************************************************************/
 406
 407 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 408  * number.
 409  */
 410 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 411 {
 412         struct sk_buff *skbp;
 413         struct sk_buff *tmp;
 414         u32 ns = L2TP_SKB_CB(skb)->ns;
 415
 416         spin_lock_bh(&session->reorder_q.lock);
 417         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 418                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 419                         __skb_queue_before(&session->reorder_q, skbp, skb);
 420                         atomic_long_inc(&session->stats.rx_oos_packets);
 421                         goto out;
 422                 }
 423         }
 424
 425         __skb_queue_tail(&session->reorder_q, skb);
 426
 427 out:
 428         spin_unlock_bh(&session->reorder_q.lock);
 429 }
 430
 431 /* Dequeue a single skb.
 432  */
 433 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 434 {
 435         struct l2tp_tunnel *tunnel = session->tunnel;
 436         int length = L2TP_SKB_CB(skb)->length;
 437
 438         /* We're about to requeue the skb, so return resources
 439          * to its current owner (a socket receive buffer).
 440          */
 441         skb_orphan(skb);
 442
 443         atomic_long_inc(&tunnel->stats.rx_packets);
 444         atomic_long_add(length, &tunnel->stats.rx_bytes);
 445         atomic_long_inc(&session->stats.rx_packets);
 446         atomic_long_add(length, &session->stats.rx_bytes);
 447
 448         if (L2TP_SKB_CB(skb)->has_seq) {
 449                 /* Bump our Nr */
 450                 session->nr++;
 451                 session->nr &= session->nr_max;
 452                 trace_session_seqnum_update(session);
 453         }
 454
 455         /* call private receive handler */
 456         if (session->recv_skb)
 457                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 458         else
 459                 kfree_skb(skb);
 460 }
 461
 462 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 463  * Skbs that have been in the queue for too long are simply discarded.
 464  */
 465 static void l2tp_recv_dequeue(struct l2tp_session *session)
 466 {
 467         struct sk_buff *skb;
 468         struct sk_buff *tmp;
 469
 470         /* If the pkt at the head of the queue has the nr that we
 471          * expect to send up next, dequeue it and any other
 472          * in-sequence packets behind it.
 473          */
 474 start:
 475         spin_lock_bh(&session->reorder_q.lock);
 476         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 477                 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
 478
 479                 /* If the packet has been pending on the queue for too long, discard it */
 480                 if (time_after(jiffies, cb->expires)) {
 481                         atomic_long_inc(&session->stats.rx_seq_discards);
 482                         atomic_long_inc(&session->stats.rx_errors);
 483                         trace_session_pkt_expired(session, cb->ns);
 484                         session->reorder_skip = 1;
 485                         __skb_unlink(skb, &session->reorder_q);
 486                         kfree_skb(skb);
 487                         continue;
 488                 }
 489
 490                 if (cb->has_seq) {
 491                         if (session->reorder_skip) {
 492                                 session->reorder_skip = 0;
 493                                 session->nr = cb->ns;
 494                                 trace_session_seqnum_reset(session);
 495                         }
 496                         if (cb->ns != session->nr)
 497                                 goto out;
 498                 }
 499                 __skb_unlink(skb, &session->reorder_q);
 500
 501                 /* Process the skb. We release the queue lock while we
 502                  * do so to let other contexts process the queue.
 503                  */
 504                 spin_unlock_bh(&session->reorder_q.lock);
 505                 l2tp_recv_dequeue_skb(session, skb);
 506                 goto start;
 507         }
 508
 509 out:
 510         spin_unlock_bh(&session->reorder_q.lock);
 511 }
 512
 513 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
 514 {
 515         u32 nws;
 516
 517         if (nr >= session->nr)
 518                 nws = nr - session->nr;
 519         else
 520                 nws = (session->nr_max + 1) - (session->nr - nr);
 521
 522         return nws < session->nr_window_size;
 523 }
 524
 525 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
 526  * acceptable, else non-zero.
 527  */
 528 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
 529 {
 530         struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
 531
 532         if (!l2tp_seq_check_rx_window(session, cb->ns)) {
 533                 /* Packet sequence number is outside allowed window.
 534                  * Discard it.
 535                  */
 536                 trace_session_pkt_outside_rx_window(session, cb->ns);
 537                 goto discard;
 538         }
 539
 540         if (session->reorder_timeout != 0) {
 541                 /* Packet reordering enabled. Add skb to session's
 542                  * reorder queue, in order of ns.
 543                  */
 544                 l2tp_recv_queue_skb(session, skb);
 545                 goto out;
 546         }
 547
 548         /* Packet reordering disabled. Discard out-of-sequence packets, while
 549          * tracking the number if in-sequence packets after the first OOS packet
 550          * is seen. After nr_oos_count_max in-sequence packets, reset the
 551          * sequence number to re-enable packet reception.
 552          */
 553         if (cb->ns == session->nr) {
 554                 skb_queue_tail(&session->reorder_q, skb);
 555         } else {
 556                 u32 nr_oos = cb->ns;
 557                 u32 nr_next = (session->nr_oos + 1) & session->nr_max;
 558
 559                 if (nr_oos == nr_next)
 560                         session->nr_oos_count++;
 561                 else
 562                         session->nr_oos_count = 0;
 563
 564                 session->nr_oos = nr_oos;
 565                 if (session->nr_oos_count > session->nr_oos_count_max) {
 566                         session->reorder_skip = 1;
 567                 }
 568                 if (!session->reorder_skip) {
 569                         atomic_long_inc(&session->stats.rx_seq_discards);
 570                         trace_session_pkt_oos(session, cb->ns);
 571                         goto discard;
 572                 }
 573                 skb_queue_tail(&session->reorder_q, skb);
 574         }
 575
 576 out:
 577         return 0;
 578
 579 discard:
 580         return 1;
 581 }
 582
 583 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 584  * and L2TPv3 data frames here.
 585  *
 586  * L2TPv2 Data Message Header
 587  *
 588  *  0                   1                   2                   3
 589  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 590  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 591  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 592  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 593  * |           Tunnel ID           |           Session ID          |
 594  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 595  * |             Ns (opt)          |             Nr (opt)          |
 596  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 597  * |      Offset Size (opt)        |    Offset pad... (opt)
 598  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 599  *
 600  * Data frames are marked by T=0. All other fields are the same as
 601  * those in L2TP control frames.
 602  *
 603  * L2TPv3 Data Message Header
 604  *
 605  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 606  * |                      L2TP Session Header                      |
 607  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 608  * |                      L2-Specific Sublayer                     |
 609  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 610  * |                        Tunnel Payload                      ...
 611  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 612  *
 613  * L2TPv3 Session Header Over IP
 614  *
 615  *  0                   1                   2                   3
 616  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 617  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 618  * |                           Session ID                          |
 619  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 620  * |               Cookie (optional, maximum 64 bits)...
 621  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 622  *                                                                 |
 623  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 624  *
 625  * L2TPv3 L2-Specific Sublayer Format
 626  *
 627  *  0                   1                   2                   3
 628  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 629  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 630  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 631  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 632  *
 633  * Cookie value and sublayer format are negotiated with the peer when
 634  * the session is set up. Unlike L2TPv2, we do not need to parse the
 635  * packet header to determine if optional fields are present.
 636  *
 637  * Caller must already have parsed the frame and determined that it is
 638  * a data (not control) frame before coming here. Fields up to the
 639  * session-id have already been parsed and ptr points to the data
 640  * after the session-id.
 641  */
 642 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 643                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 644                       int length)
 645 {
 646         struct l2tp_tunnel *tunnel = session->tunnel;
 647         int offset;
 648
 649         /* Parse and check optional cookie */
 650         if (session->peer_cookie_len > 0) {
 651                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 652                         pr_debug_ratelimited("%s: cookie mismatch (%u/%u). Discarding.\n",
 653                                              tunnel->name, tunnel->tunnel_id,
 654                                              session->session_id);
 655                         atomic_long_inc(&session->stats.rx_cookie_discards);
 656                         goto discard;
 657                 }
 658                 ptr += session->peer_cookie_len;
 659         }
 660
 661         /* Handle the optional sequence numbers. Sequence numbers are
 662          * in different places for L2TPv2 and L2TPv3.
 663          *
 664          * If we are the LAC, enable/disable sequence numbers under
 665          * the control of the LNS.  If no sequence numbers present but
 666          * we were expecting them, discard frame.
 667          */
 668         L2TP_SKB_CB(skb)->has_seq = 0;
 669         if (tunnel->version == L2TP_HDR_VER_2) {
 670                 if (hdrflags & L2TP_HDRFLAG_S) {
 671                         /* Store L2TP info in the skb */
 672                         L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr);
 673                         L2TP_SKB_CB(skb)->has_seq = 1;
 674                         ptr += 2;
 675                         /* Skip past nr in the header */
 676                         ptr += 2;
 677
 678                 }
 679         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 680                 u32 l2h = ntohl(*(__be32 *)ptr);
 681
 682                 if (l2h & 0x40000000) {
 683                         /* Store L2TP info in the skb */
 684                         L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff;
 685                         L2TP_SKB_CB(skb)->has_seq = 1;
 686                 }
 687                 ptr += 4;
 688         }
 689
 690         if (L2TP_SKB_CB(skb)->has_seq) {
 691                 /* Received a packet with sequence numbers. If we're the LAC,
 692                  * check if we sre sending sequence numbers and if not,
 693                  * configure it so.
 694                  */
 695                 if (!session->lns_mode && !session->send_seq) {
 696                         trace_session_seqnum_lns_enable(session);
 697                         session->send_seq = 1;
 698                         l2tp_session_set_header_len(session, tunnel->version);
 699                 }
 700         } else {
 701                 /* No sequence numbers.
 702                  * If user has configured mandatory sequence numbers, discard.
 703                  */
 704                 if (session->recv_seq) {
 705                         pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
 706                                              session->name);
 707                         atomic_long_inc(&session->stats.rx_seq_discards);
 708                         goto discard;
 709                 }
 710
 711                 /* If we're the LAC and we're sending sequence numbers, the
 712                  * LNS has requested that we no longer send sequence numbers.
 713                  * If we're the LNS and we're sending sequence numbers, the
 714                  * LAC is broken. Discard the frame.
 715                  */
 716                 if (!session->lns_mode && session->send_seq) {
 717                         trace_session_seqnum_lns_disable(session);
 718                         session->send_seq = 0;
 719                         l2tp_session_set_header_len(session, tunnel->version);
 720                 } else if (session->send_seq) {
 721                         pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
 722                                              session->name);
 723                         atomic_long_inc(&session->stats.rx_seq_discards);
 724                         goto discard;
 725                 }
 726         }
 727
 728         /* Session data offset is defined only for L2TPv2 and is
 729          * indicated by an optional 16-bit value in the header.
 730          */
 731         if (tunnel->version == L2TP_HDR_VER_2) {
 732                 /* If offset bit set, skip it. */
 733                 if (hdrflags & L2TP_HDRFLAG_O) {
 734                         offset = ntohs(*(__be16 *)ptr);
 735                         ptr += 2 + offset;
 736                 }
 737         }
 738
 739         offset = ptr - optr;
 740         if (!pskb_may_pull(skb, offset))
 741                 goto discard;
 742
 743         __skb_pull(skb, offset);
 744
 745         /* Prepare skb for adding to the session's reorder_q.  Hold
 746          * packets for max reorder_timeout or 1 second if not
 747          * reordering.
 748          */
 749         L2TP_SKB_CB(skb)->length = length;
 750         L2TP_SKB_CB(skb)->expires = jiffies +
 751                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 752
 753         /* Add packet to the session's receive queue. Reordering is done here, if
 754          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 755          */
 756         if (L2TP_SKB_CB(skb)->has_seq) {
 757                 if (l2tp_recv_data_seq(session, skb))
 758                         goto discard;
 759         } else {
 760                 /* No sequence numbers. Add the skb to the tail of the
 761                  * reorder queue. This ensures that it will be
 762                  * delivered after all previous sequenced skbs.
 763                  */
 764                 skb_queue_tail(&session->reorder_q, skb);
 765         }
 766
 767         /* Try to dequeue as many skbs from reorder_q as we can. */
 768         l2tp_recv_dequeue(session);
 769
 770         return;
 771
 772 discard:
 773         atomic_long_inc(&session->stats.rx_errors);
 774         kfree_skb(skb);
 775 }
 776 EXPORT_SYMBOL_GPL(l2tp_recv_common);
 777
 778 /* Drop skbs from the session's reorder_q
 779  */
 780 static void l2tp_session_queue_purge(struct l2tp_session *session)
 781 {
 782         struct sk_buff *skb = NULL;
 783
 784         while ((skb = skb_dequeue(&session->reorder_q))) {
 785                 atomic_long_inc(&session->stats.rx_errors);
 786                 kfree_skb(skb);
 787         }
 788 }
 789
 790 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 791  * here. The skb is not on a list when we get here.
 792  * Returns 0 if the packet was a data packet and was successfully passed on.
 793  * Returns 1 if the packet was not a good data packet and could not be
 794  * forwarded.  All such packets are passed up to userspace to deal with.
 795  */
 796 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 797 {
 798         struct l2tp_session *session = NULL;
 799         unsigned char *ptr, *optr;
 800         u16 hdrflags;
 801         u32 tunnel_id, session_id;
 802         u16 version;
 803         int length;
 804
 805         /* UDP has verified checksum */
 806
 807         /* UDP always verifies the packet length. */
 808         __skb_pull(skb, sizeof(struct udphdr));
 809
 810         /* Short packet? */
 811         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
 812                 pr_debug_ratelimited("%s: recv short packet (len=%d)\n",
 813                                      tunnel->name, skb->len);
 814                 goto invalid;
 815         }
 816
 817         /* Point to L2TP header */
 818         optr = skb->data;
 819         ptr = skb->data;
 820
 821         /* Get L2TP header flags */
 822         hdrflags = ntohs(*(__be16 *)ptr);
 823
 824         /* Check protocol version */
 825         version = hdrflags & L2TP_HDR_VER_MASK;
 826         if (version != tunnel->version) {
 827                 pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n",
 828                                      tunnel->name, version, tunnel->version);
 829                 goto invalid;
 830         }
 831
 832         /* Get length of L2TP packet */
 833         length = skb->len;
 834
 835         /* If type is control packet, it is handled by userspace. */
 836         if (hdrflags & L2TP_HDRFLAG_T)
 837                 goto pass;
 838
 839         /* Skip flags */
 840         ptr += 2;
 841
 842         if (tunnel->version == L2TP_HDR_VER_2) {
 843                 /* If length is present, skip it */
 844                 if (hdrflags & L2TP_HDRFLAG_L)
 845                         ptr += 2;
 846
 847                 /* Extract tunnel and session ID */
 848                 tunnel_id = ntohs(*(__be16 *)ptr);
 849                 ptr += 2;
 850                 session_id = ntohs(*(__be16 *)ptr);
 851                 ptr += 2;
 852         } else {
 853                 ptr += 2;       /* skip reserved bits */
 854                 tunnel_id = tunnel->tunnel_id;
 855                 session_id = ntohl(*(__be32 *)ptr);
 856                 ptr += 4;
 857         }
 858
 859         /* Find the session context */
 860         session = l2tp_tunnel_get_session(tunnel, session_id);
 861         if (!session || !session->recv_skb) {
 862                 if (session)
 863                         l2tp_session_dec_refcount(session);
 864
 865                 /* Not found? Pass to userspace to deal with */
 866                 pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n",
 867                                      tunnel->name, tunnel_id, session_id);
 868                 goto pass;
 869         }
 870
 871         if (tunnel->version == L2TP_HDR_VER_3 &&
 872             l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
 873                 l2tp_session_dec_refcount(session);
 874                 goto invalid;
 875         }
 876
 877         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
 878         l2tp_session_dec_refcount(session);
 879
 880         return 0;
 881
 882 invalid:
 883         atomic_long_inc(&tunnel->stats.rx_invalid);
 884
 885 pass:
 886         /* Put UDP header back */
 887         __skb_push(skb, sizeof(struct udphdr));
 888
 889         return 1;
 890 }
 891
 892 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 893  * Return codes:
 894  * 0 : success.
 895  * <0: error
 896  * >0: skb should be passed up to userspace as UDP.
 897  */
 898 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 899 {
 900         struct l2tp_tunnel *tunnel;
 901
 902         /* Note that this is called from the encap_rcv hook inside an
 903          * RCU-protected region, but without the socket being locked.
 904          * Hence we use rcu_dereference_sk_user_data to access the
 905          * tunnel data structure rather the usual l2tp_sk_to_tunnel
 906          * accessor function.
 907          */
 908         tunnel = rcu_dereference_sk_user_data(sk);
 909         if (!tunnel)
 910                 goto pass_up;
 911         if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
 912                 goto pass_up;
 913
 914         if (l2tp_udp_recv_core(tunnel, skb))
 915                 goto pass_up;
 916
 917         return 0;
 918
 919 pass_up:
 920         return 1;
 921 }
 922 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 923
 924 /************************************************************************
 925  * Transmit handling
 926  ***********************************************************************/
 927
 928 /* Build an L2TP header for the session into the buffer provided.
 929  */
 930 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 931 {
 932         struct l2tp_tunnel *tunnel = session->tunnel;
 933         __be16 *bufp = buf;
 934         __be16 *optr = buf;
 935         u16 flags = L2TP_HDR_VER_2;
 936         u32 tunnel_id = tunnel->peer_tunnel_id;
 937         u32 session_id = session->peer_session_id;
 938
 939         if (session->send_seq)
 940                 flags |= L2TP_HDRFLAG_S;
 941
 942         /* Setup L2TP header. */
 943         *bufp++ = htons(flags);
 944         *bufp++ = htons(tunnel_id);
 945         *bufp++ = htons(session_id);
 946         if (session->send_seq) {
 947                 *bufp++ = htons(session->ns);
 948                 *bufp++ = 0;
 949                 session->ns++;
 950                 session->ns &= 0xffff;
 951                 trace_session_seqnum_update(session);
 952         }
 953
 954         return bufp - optr;
 955 }
 956
 957 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 958 {
 959         struct l2tp_tunnel *tunnel = session->tunnel;
 960         char *bufp = buf;
 961         char *optr = bufp;
 962
 963         /* Setup L2TP header. The header differs slightly for UDP and
 964          * IP encapsulations. For UDP, there is 4 bytes of flags.
 965          */
 966         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 967                 u16 flags = L2TP_HDR_VER_3;
 968                 *((__be16 *)bufp) = htons(flags);
 969                 bufp += 2;
 970                 *((__be16 *)bufp) = 0;
 971                 bufp += 2;
 972         }
 973
 974         *((__be32 *)bufp) = htonl(session->peer_session_id);
 975         bufp += 4;
 976         if (session->cookie_len) {
 977                 memcpy(bufp, &session->cookie[0], session->cookie_len);
 978                 bufp += session->cookie_len;
 979         }
 980         if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 981                 u32 l2h = 0;
 982
 983                 if (session->send_seq) {
 984                         l2h = 0x40000000 | session->ns;
 985                         session->ns++;
 986                         session->ns &= 0xffffff;
 987                         trace_session_seqnum_update(session);
 988                 }
 989
 990                 *((__be32 *)bufp) = htonl(l2h);
 991                 bufp += 4;
 992         }
 993
 994         return bufp - optr;
 995 }
 996
 997 /* Queue the packet to IP for output: tunnel socket lock must be held */
 998 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
 999 {
1000         int err;
1001
1002         skb->ignore_df = 1;
1003         skb_dst_drop(skb);
1004 #if IS_ENABLED(CONFIG_IPV6)
1005         if (l2tp_sk_is_v6(tunnel->sock))
1006                 err = inet6_csk_xmit(tunnel->sock, skb, NULL);
1007         else
1008 #endif
1009                 err = ip_queue_xmit(tunnel->sock, skb, fl);
1010
1011         return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
1012 }
1013
1014 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len)
1015 {
1016         struct l2tp_tunnel *tunnel = session->tunnel;
1017         unsigned int data_len = skb->len;
1018         struct sock *sk = tunnel->sock;
1019         int headroom, uhlen, udp_len;
1020         int ret = NET_XMIT_SUCCESS;
1021         struct inet_sock *inet;
1022         struct udphdr *uh;
1023
1024         /* Check that there's enough headroom in the skb to insert IP,
1025          * UDP and L2TP headers. If not enough, expand it to
1026          * make room. Adjust truesize.
1027          */
1028         uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
1029         headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
1030         if (skb_cow_head(skb, headroom)) {
1031                 kfree_skb(skb);
1032                 return NET_XMIT_DROP;
1033         }
1034
1035         /* Setup L2TP header */
1036         if (tunnel->version == L2TP_HDR_VER_2)
1037                 l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len));
1038         else
1039                 l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len));
1040
1041         /* Reset skb netfilter state */
1042         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1043         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);
1044         nf_reset_ct(skb);
1045
1046         bh_lock_sock(sk);
1047         if (sock_owned_by_user(sk)) {
1048                 kfree_skb(skb);
1049                 ret = NET_XMIT_DROP;
1050                 goto out_unlock;
1051         }
1052
1053         /* The user-space may change the connection status for the user-space
1054          * provided socket at run time: we must check it under the socket lock
1055          */
1056         if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1057                 kfree_skb(skb);
1058                 ret = NET_XMIT_DROP;
1059                 goto out_unlock;
1060         }
1061
1062         /* Report transmitted length before we add encap header, which keeps
1063          * statistics consistent for both UDP and IP encap tx/rx paths.
1064          */
1065         *len = skb->len;
1066
1067         inet = inet_sk(sk);
1068         switch (tunnel->encap) {
1069         case L2TP_ENCAPTYPE_UDP:
1070                 /* Setup UDP header */
1071                 __skb_push(skb, sizeof(*uh));
1072                 skb_reset_transport_header(skb);
1073                 uh = udp_hdr(skb);
1074                 uh->source = inet->inet_sport;
1075                 uh->dest = inet->inet_dport;
1076                 udp_len = uhlen + session->hdr_len + data_len;
1077                 uh->len = htons(udp_len);
1078
1079                 /* Calculate UDP checksum if configured to do so */
1080 #if IS_ENABLED(CONFIG_IPV6)
1081                 if (l2tp_sk_is_v6(sk))
1082                         udp6_set_csum(udp_get_no_check6_tx(sk),
1083                                       skb, &inet6_sk(sk)->saddr,
1084                                       &sk->sk_v6_daddr, udp_len);
1085                 else
1086 #endif
1087                         udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1088                                      inet->inet_daddr, udp_len);
1089                 break;
1090
1091         case L2TP_ENCAPTYPE_IP:
1092                 break;
1093         }
1094
1095         ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
1096
1097 out_unlock:
1098         bh_unlock_sock(sk);
1099
1100         return ret;
1101 }
1102
1103 /* If caller requires the skb to have a ppp header, the header must be
1104  * inserted in the skb data before calling this function.
1105  */
1106 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
1107 {
1108         unsigned int len = 0;
1109         int ret;
1110
1111         ret = l2tp_xmit_core(session, skb, &len);
1112         if (ret == NET_XMIT_SUCCESS) {
1113                 atomic_long_inc(&session->tunnel->stats.tx_packets);
1114                 atomic_long_add(len, &session->tunnel->stats.tx_bytes);
1115                 atomic_long_inc(&session->stats.tx_packets);
1116                 atomic_long_add(len, &session->stats.tx_bytes);
1117         } else {
1118                 atomic_long_inc(&session->tunnel->stats.tx_errors);
1119                 atomic_long_inc(&session->stats.tx_errors);
1120         }
1121         return ret;
1122 }
1123 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1124
1125 /*****************************************************************************
1126  * Tinnel and session create/destroy.
1127  *****************************************************************************/
1128
1129 /* Tunnel socket destruct hook.
1130  * The tunnel context is deleted only when all session sockets have been
1131  * closed.
1132  */
1133 static void l2tp_tunnel_destruct(struct sock *sk)
1134 {
1135         struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1136
1137         if (!tunnel)
1138                 goto end;
1139
1140         /* Disable udp encapsulation */
1141         switch (tunnel->encap) {
1142         case L2TP_ENCAPTYPE_UDP:
1143                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1144                 (udp_sk(sk))->encap_type = 0;
1145                 (udp_sk(sk))->encap_rcv = NULL;
1146                 (udp_sk(sk))->encap_destroy = NULL;
1147                 break;
1148         case L2TP_ENCAPTYPE_IP:
1149                 break;
1150         }
1151
1152         /* Remove hooks into tunnel socket */
1153         sk->sk_destruct = tunnel->old_sk_destruct;
1154         sk->sk_user_data = NULL;
1155
1156         /* Call the original destructor */
1157         if (sk->sk_destruct)
1158                 (*sk->sk_destruct)(sk);
1159
1160         kfree_rcu(tunnel, rcu);
1161 end:
1162         return;
1163 }
1164
1165 /* Remove an l2tp session from l2tp_core's hash lists. */
1166 static void l2tp_session_unhash(struct l2tp_session *session)
1167 {
1168         struct l2tp_tunnel *tunnel = session->tunnel;
1169
1170         /* Remove the session from core hashes */
1171         if (tunnel) {
1172                 /* Remove from the per-tunnel hash */
1173                 write_lock_bh(&tunnel->hlist_lock);
1174                 hlist_del_init(&session->hlist);
1175                 write_unlock_bh(&tunnel->hlist_lock);
1176
1177                 /* For L2TPv3 we have a per-net hash: remove from there, too */
1178                 if (tunnel->version != L2TP_HDR_VER_2) {
1179                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1180
1181                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1182                         hlist_del_init_rcu(&session->global_hlist);
1183                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1184                         synchronize_rcu();
1185                 }
1186         }
1187 }
1188
1189 /* When the tunnel is closed, all the attached sessions need to go too.
1190  */
1191 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1192 {
1193         int hash;
1194         struct hlist_node *walk;
1195         struct hlist_node *tmp;
1196         struct l2tp_session *session;
1197
1198         write_lock_bh(&tunnel->hlist_lock);
1199         tunnel->acpt_newsess = false;
1200         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1201 again:
1202                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1203                         session = hlist_entry(walk, struct l2tp_session, hlist);
1204                         hlist_del_init(&session->hlist);
1205
1206                         write_unlock_bh(&tunnel->hlist_lock);
1207                         l2tp_session_delete(session);
1208                         write_lock_bh(&tunnel->hlist_lock);
1209
1210                         /* Now restart from the beginning of this hash
1211                          * chain.  We always remove a session from the
1212                          * list so we are guaranteed to make forward
1213                          * progress.
1214                          */
1215                         goto again;
1216                 }
1217         }
1218         write_unlock_bh(&tunnel->hlist_lock);
1219 }
1220
1221 /* Tunnel socket destroy hook for UDP encapsulation */
1222 static void l2tp_udp_encap_destroy(struct sock *sk)
1223 {
1224         struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1225
1226         if (tunnel)
1227                 l2tp_tunnel_delete(tunnel);
1228 }
1229
1230 /* Workqueue tunnel deletion function */
1231 static void l2tp_tunnel_del_work(struct work_struct *work)
1232 {
1233         struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1234                                                   del_work);
1235         struct sock *sk = tunnel->sock;
1236         struct socket *sock = sk->sk_socket;
1237         struct l2tp_net *pn;
1238
1239         l2tp_tunnel_closeall(tunnel);
1240
1241         /* If the tunnel socket was created within the kernel, use
1242          * the sk API to release it here.
1243          */
1244         if (tunnel->fd < 0) {
1245                 if (sock) {
1246                         kernel_sock_shutdown(sock, SHUT_RDWR);
1247                         sock_release(sock);
1248                 }
1249         }
1250
1251         /* Remove the tunnel struct from the tunnel list */
1252         pn = l2tp_pernet(tunnel->l2tp_net);
1253         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1254         list_del_rcu(&tunnel->list);
1255         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1256
1257         /* drop initial ref */
1258         l2tp_tunnel_dec_refcount(tunnel);
1259
1260         /* drop workqueue ref */
1261         l2tp_tunnel_dec_refcount(tunnel);
1262 }
1263
1264 /* Create a socket for the tunnel, if one isn't set up by
1265  * userspace. This is used for static tunnels where there is no
1266  * managing L2TP daemon.
1267  *
1268  * Since we don't want these sockets to keep a namespace alive by
1269  * themselves, we drop the socket's namespace refcount after creation.
1270  * These sockets are freed when the namespace exits using the pernet
1271  * exit hook.
1272  */
1273 static int l2tp_tunnel_sock_create(struct net *net,
1274                                    u32 tunnel_id,
1275                                    u32 peer_tunnel_id,
1276                                    struct l2tp_tunnel_cfg *cfg,
1277                                    struct socket **sockp)
1278 {
1279         int err = -EINVAL;
1280         struct socket *sock = NULL;
1281         struct udp_port_cfg udp_conf;
1282
1283         switch (cfg->encap) {
1284         case L2TP_ENCAPTYPE_UDP:
1285                 memset(&udp_conf, 0, sizeof(udp_conf));
1286
1287 #if IS_ENABLED(CONFIG_IPV6)
1288                 if (cfg->local_ip6 && cfg->peer_ip6) {
1289                         udp_conf.family = AF_INET6;
1290                         memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1291                                sizeof(udp_conf.local_ip6));
1292                         memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1293                                sizeof(udp_conf.peer_ip6));
1294                         udp_conf.use_udp6_tx_checksums =
1295                           !cfg->udp6_zero_tx_checksums;
1296                         udp_conf.use_udp6_rx_checksums =
1297                           !cfg->udp6_zero_rx_checksums;
1298                 } else
1299 #endif
1300                 {
1301                         udp_conf.family = AF_INET;
1302                         udp_conf.local_ip = cfg->local_ip;
1303                         udp_conf.peer_ip = cfg->peer_ip;
1304                         udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1305                 }
1306
1307                 udp_conf.local_udp_port = htons(cfg->local_udp_port);
1308                 udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1309
1310                 err = udp_sock_create(net, &udp_conf, &sock);
1311                 if (err < 0)
1312                         goto out;
1313
1314                 break;
1315
1316         case L2TP_ENCAPTYPE_IP:
1317 #if IS_ENABLED(CONFIG_IPV6)
1318                 if (cfg->local_ip6 && cfg->peer_ip6) {
1319                         struct sockaddr_l2tpip6 ip6_addr = {0};
1320
1321                         err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1322                                                IPPROTO_L2TP, &sock);
1323                         if (err < 0)
1324                                 goto out;
1325
1326                         ip6_addr.l2tp_family = AF_INET6;
1327                         memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1328                                sizeof(ip6_addr.l2tp_addr));
1329                         ip6_addr.l2tp_conn_id = tunnel_id;
1330                         err = kernel_bind(sock, (struct sockaddr *)&ip6_addr,
1331                                           sizeof(ip6_addr));
1332                         if (err < 0)
1333                                 goto out;
1334
1335                         ip6_addr.l2tp_family = AF_INET6;
1336                         memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1337                                sizeof(ip6_addr.l2tp_addr));
1338                         ip6_addr.l2tp_conn_id = peer_tunnel_id;
1339                         err = kernel_connect(sock,
1340                                              (struct sockaddr *)&ip6_addr,
1341                                              sizeof(ip6_addr), 0);
1342                         if (err < 0)
1343                                 goto out;
1344                 } else
1345 #endif
1346                 {
1347                         struct sockaddr_l2tpip ip_addr = {0};
1348
1349                         err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1350                                                IPPROTO_L2TP, &sock);
1351                         if (err < 0)
1352                                 goto out;
1353
1354                         ip_addr.l2tp_family = AF_INET;
1355                         ip_addr.l2tp_addr = cfg->local_ip;
1356                         ip_addr.l2tp_conn_id = tunnel_id;
1357                         err = kernel_bind(sock, (struct sockaddr *)&ip_addr,
1358                                           sizeof(ip_addr));
1359                         if (err < 0)
1360                                 goto out;
1361
1362                         ip_addr.l2tp_family = AF_INET;
1363                         ip_addr.l2tp_addr = cfg->peer_ip;
1364                         ip_addr.l2tp_conn_id = peer_tunnel_id;
1365                         err = kernel_connect(sock, (struct sockaddr *)&ip_addr,
1366                                              sizeof(ip_addr), 0);
1367                         if (err < 0)
1368                                 goto out;
1369                 }
1370                 break;
1371
1372         default:
1373                 goto out;
1374         }
1375
1376 out:
1377         *sockp = sock;
1378         if (err < 0 && sock) {
1379                 kernel_sock_shutdown(sock, SHUT_RDWR);
1380                 sock_release(sock);
1381                 *sockp = NULL;
1382         }
1383
1384         return err;
1385 }
1386
1387 static struct lock_class_key l2tp_socket_class;
1388
1389 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id,
1390                        struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
1391 {
1392         struct l2tp_tunnel *tunnel = NULL;
1393         int err;
1394         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1395
1396         if (cfg)
1397                 encap = cfg->encap;
1398
1399         tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
1400         if (!tunnel) {
1401                 err = -ENOMEM;
1402                 goto err;
1403         }
1404
1405         tunnel->version = version;
1406         tunnel->tunnel_id = tunnel_id;
1407         tunnel->peer_tunnel_id = peer_tunnel_id;
1408
1409         tunnel->magic = L2TP_TUNNEL_MAGIC;
1410         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1411         rwlock_init(&tunnel->hlist_lock);
1412         tunnel->acpt_newsess = true;
1413
1414         tunnel->encap = encap;
1415
1416         refcount_set(&tunnel->ref_count, 1);
1417         tunnel->fd = fd;
1418
1419         /* Init delete workqueue struct */
1420         INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1421
1422         INIT_LIST_HEAD(&tunnel->list);
1423
1424         err = 0;
1425 err:
1426         if (tunnelp)
1427                 *tunnelp = tunnel;
1428
1429         return err;
1430 }
1431 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1432
1433 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1434                                 enum l2tp_encap_type encap)
1435 {
1436         if (!net_eq(sock_net(sk), net))
1437                 return -EINVAL;
1438
1439         if (sk->sk_type != SOCK_DGRAM)
1440                 return -EPROTONOSUPPORT;
1441
1442         if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
1443                 return -EPROTONOSUPPORT;
1444
1445         if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1446             (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1447                 return -EPROTONOSUPPORT;
1448
1449         if (sk->sk_user_data)
1450                 return -EBUSY;
1451
1452         return 0;
1453 }
1454
1455 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1456                          struct l2tp_tunnel_cfg *cfg)
1457 {
1458         struct l2tp_tunnel *tunnel_walk;
1459         struct l2tp_net *pn;
1460         struct socket *sock;
1461         struct sock *sk;
1462         int ret;
1463
1464         if (tunnel->fd < 0) {
1465                 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1466                                               tunnel->peer_tunnel_id, cfg,
1467                                               &sock);
1468                 if (ret < 0)
1469                         goto err;
1470         } else {
1471                 sock = sockfd_lookup(tunnel->fd, &ret);
1472                 if (!sock)
1473                         goto err;
1474
1475                 ret = l2tp_validate_socket(sock->sk, net, tunnel->encap);
1476                 if (ret < 0)
1477                         goto err_sock;
1478         }
1479
1480         tunnel->l2tp_net = net;
1481         pn = l2tp_pernet(net);
1482
1483         sk = sock->sk;
1484         sock_hold(sk);
1485         tunnel->sock = sk;
1486
1487         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1488         list_for_each_entry(tunnel_walk, &pn->l2tp_tunnel_list, list) {
1489                 if (tunnel_walk->tunnel_id == tunnel->tunnel_id) {
1490                         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1491                         sock_put(sk);
1492                         ret = -EEXIST;
1493                         goto err_sock;
1494                 }
1495         }
1496         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1497         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1498
1499         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1500                 struct udp_tunnel_sock_cfg udp_cfg = {
1501                         .sk_user_data = tunnel,
1502                         .encap_type = UDP_ENCAP_L2TPINUDP,
1503                         .encap_rcv = l2tp_udp_encap_recv,
1504                         .encap_destroy = l2tp_udp_encap_destroy,
1505                 };
1506
1507                 setup_udp_tunnel_sock(net, sock, &udp_cfg);
1508         } else {
1509                 sk->sk_user_data = tunnel;
1510         }
1511
1512         tunnel->old_sk_destruct = sk->sk_destruct;
1513         sk->sk_destruct = &l2tp_tunnel_destruct;
1514         lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class,
1515                                    "l2tp_sock");
1516         sk->sk_allocation = GFP_ATOMIC;
1517
1518         trace_register_tunnel(tunnel);
1519
1520         if (tunnel->fd >= 0)
1521                 sockfd_put(sock);
1522
1523         return 0;
1524
1525 err_sock:
1526         if (tunnel->fd < 0)
1527                 sock_release(sock);
1528         else
1529                 sockfd_put(sock);
1530 err:
1531         return ret;
1532 }
1533 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1534
1535 /* This function is used by the netlink TUNNEL_DELETE command.
1536  */
1537 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1538 {
1539         if (!test_and_set_bit(0, &tunnel->dead)) {
1540                 trace_delete_tunnel(tunnel);
1541                 l2tp_tunnel_inc_refcount(tunnel);
1542                 queue_work(l2tp_wq, &tunnel->del_work);
1543         }
1544 }
1545 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1546
1547 void l2tp_session_delete(struct l2tp_session *session)
1548 {
1549         if (test_and_set_bit(0, &session->dead))
1550                 return;
1551
1552         trace_delete_session(session);
1553         l2tp_session_unhash(session);
1554         l2tp_session_queue_purge(session);
1555         if (session->session_close)
1556                 (*session->session_close)(session);
1557
1558         l2tp_session_dec_refcount(session);
1559 }
1560 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1561
1562 /* We come here whenever a session's send_seq, cookie_len or
1563  * l2specific_type parameters are set.
1564  */
1565 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1566 {
1567         if (version == L2TP_HDR_VER_2) {
1568                 session->hdr_len = 6;
1569                 if (session->send_seq)
1570                         session->hdr_len += 4;
1571         } else {
1572                 session->hdr_len = 4 + session->cookie_len;
1573                 session->hdr_len += l2tp_get_l2specific_len(session);
1574                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1575                         session->hdr_len += 4;
1576         }
1577 }
1578 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1579
1580 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id,
1581                                          u32 peer_session_id, struct l2tp_session_cfg *cfg)
1582 {
1583         struct l2tp_session *session;
1584
1585         session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
1586         if (session) {
1587                 session->magic = L2TP_SESSION_MAGIC;
1588                 session->tunnel = tunnel;
1589
1590                 session->session_id = session_id;
1591                 session->peer_session_id = peer_session_id;
1592                 session->nr = 0;
1593                 if (tunnel->version == L2TP_HDR_VER_2)
1594                         session->nr_max = 0xffff;
1595                 else
1596                         session->nr_max = 0xffffff;
1597                 session->nr_window_size = session->nr_max / 2;
1598                 session->nr_oos_count_max = 4;
1599
1600                 /* Use NR of first received packet */
1601                 session->reorder_skip = 1;
1602
1603                 sprintf(&session->name[0], "sess %u/%u",
1604                         tunnel->tunnel_id, session->session_id);
1605
1606                 skb_queue_head_init(&session->reorder_q);
1607
1608                 INIT_HLIST_NODE(&session->hlist);
1609                 INIT_HLIST_NODE(&session->global_hlist);
1610
1611                 if (cfg) {
1612                         session->pwtype = cfg->pw_type;
1613                         session->send_seq = cfg->send_seq;
1614                         session->recv_seq = cfg->recv_seq;
1615                         session->lns_mode = cfg->lns_mode;
1616                         session->reorder_timeout = cfg->reorder_timeout;
1617                         session->l2specific_type = cfg->l2specific_type;
1618                         session->cookie_len = cfg->cookie_len;
1619                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1620                         session->peer_cookie_len = cfg->peer_cookie_len;
1621                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1622                 }
1623
1624                 l2tp_session_set_header_len(session, tunnel->version);
1625
1626                 refcount_set(&session->ref_count, 1);
1627
1628                 return session;
1629         }
1630
1631         return ERR_PTR(-ENOMEM);
1632 }
1633 EXPORT_SYMBOL_GPL(l2tp_session_create);
1634
1635 /*****************************************************************************
1636  * Init and cleanup
1637  *****************************************************************************/
1638
1639 static __net_init int l2tp_init_net(struct net *net)
1640 {
1641         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1642         int hash;
1643
1644         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1645         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1646
1647         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1648                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1649
1650         spin_lock_init(&pn->l2tp_session_hlist_lock);
1651
1652         return 0;
1653 }
1654
1655 static __net_exit void l2tp_exit_net(struct net *net)
1656 {
1657         struct l2tp_net *pn = l2tp_pernet(net);
1658         struct l2tp_tunnel *tunnel = NULL;
1659         int hash;
1660
1661         rcu_read_lock_bh();
1662         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
1663                 l2tp_tunnel_delete(tunnel);
1664         }
1665         rcu_read_unlock_bh();
1666
1667         if (l2tp_wq)
1668                 flush_workqueue(l2tp_wq);
1669         rcu_barrier();
1670
1671         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1672                 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1673 }
1674
1675 static struct pernet_operations l2tp_net_ops = {
1676         .init = l2tp_init_net,
1677         .exit = l2tp_exit_net,
1678         .id   = &l2tp_net_id,
1679         .size = sizeof(struct l2tp_net),
1680 };
1681
1682 static int __init l2tp_init(void)
1683 {
1684         int rc = 0;
1685
1686         rc = register_pernet_device(&l2tp_net_ops);
1687         if (rc)
1688                 goto out;
1689
1690         l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1691         if (!l2tp_wq) {
1692                 pr_err("alloc_workqueue failed\n");
1693                 unregister_pernet_device(&l2tp_net_ops);
1694                 rc = -ENOMEM;
1695                 goto out;
1696         }
1697
1698         pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1699
1700 out:
1701         return rc;
1702 }
1703
1704 static void __exit l2tp_exit(void)
1705 {
1706         unregister_pernet_device(&l2tp_net_ops);
1707         if (l2tp_wq) {
1708                 destroy_workqueue(l2tp_wq);
1709                 l2tp_wq = NULL;
1710         }
1711 }
1712
1713 module_init(l2tp_init);
1714 module_exit(l2tp_exit);
1715
1716 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1717 MODULE_DESCRIPTION("L2TP core");
1718 MODULE_LICENSE("GPL");
1719 MODULE_VERSION(L2TP_DRV_VERSION);