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         /* Lock for write access to l2tp_tunnel_idr */
 108         spinlock_t l2tp_tunnel_idr_lock;
 109         struct idr l2tp_tunnel_idr;
 110         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
 111         /* Lock for write access to l2tp_session_hlist */
 112         spinlock_t l2tp_session_hlist_lock;
 113 };
 114
 115 #if IS_ENABLED(CONFIG_IPV6)
 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         tunnel = idr_find(&pn->l2tp_tunnel_idr, tunnel_id);
 212         if (tunnel && refcount_inc_not_zero(&tunnel->ref_count)) {
 213                 rcu_read_unlock_bh();
 214                 return tunnel;
 215         }
 216         rcu_read_unlock_bh();
 217
 218         return NULL;
 219 }
 220 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
 221
 222 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
 223 {
 224         struct l2tp_net *pn = l2tp_pernet(net);
 225         unsigned long tunnel_id, tmp;
 226         struct l2tp_tunnel *tunnel;
 227         int count = 0;
 228
 229         rcu_read_lock_bh();
 230         idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
 231                 if (tunnel && ++count > nth &&
 232                     refcount_inc_not_zero(&tunnel->ref_count)) {
 233                         rcu_read_unlock_bh();
 234                         return tunnel;
 235                 }
 236         }
 237         rcu_read_unlock_bh();
 238
 239         return NULL;
 240 }
 241 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
 242
 243 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
 244                                              u32 session_id)
 245 {
 246         struct hlist_head *session_list;
 247         struct l2tp_session *session;
 248
 249         session_list = l2tp_session_id_hash(tunnel, session_id);
 250
 251         rcu_read_lock_bh();
 252         hlist_for_each_entry_rcu(session, session_list, hlist)
 253                 if (session->session_id == session_id) {
 254                         l2tp_session_inc_refcount(session);
 255                         rcu_read_unlock_bh();
 256
 257                         return session;
 258                 }
 259         rcu_read_unlock_bh();
 260
 261         return NULL;
 262 }
 263 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
 264
 265 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
 266 {
 267         struct hlist_head *session_list;
 268         struct l2tp_session *session;
 269
 270         session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
 271
 272         rcu_read_lock_bh();
 273         hlist_for_each_entry_rcu(session, session_list, global_hlist)
 274                 if (session->session_id == session_id) {
 275                         l2tp_session_inc_refcount(session);
 276                         rcu_read_unlock_bh();
 277
 278                         return session;
 279                 }
 280         rcu_read_unlock_bh();
 281
 282         return NULL;
 283 }
 284 EXPORT_SYMBOL_GPL(l2tp_session_get);
 285
 286 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
 287 {
 288         int hash;
 289         struct l2tp_session *session;
 290         int count = 0;
 291
 292         rcu_read_lock_bh();
 293         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 294                 hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
 295                         if (++count > nth) {
 296                                 l2tp_session_inc_refcount(session);
 297                                 rcu_read_unlock_bh();
 298                                 return session;
 299                         }
 300                 }
 301         }
 302
 303         rcu_read_unlock_bh();
 304
 305         return NULL;
 306 }
 307 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
 308
 309 /* Lookup a session by interface name.
 310  * This is very inefficient but is only used by management interfaces.
 311  */
 312 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
 313                                                 const char *ifname)
 314 {
 315         struct l2tp_net *pn = l2tp_pernet(net);
 316         int hash;
 317         struct l2tp_session *session;
 318
 319         rcu_read_lock_bh();
 320         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 321                 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
 322                         if (!strcmp(session->ifname, ifname)) {
 323                                 l2tp_session_inc_refcount(session);
 324                                 rcu_read_unlock_bh();
 325
 326                                 return session;
 327                         }
 328                 }
 329         }
 330
 331         rcu_read_unlock_bh();
 332
 333         return NULL;
 334 }
 335 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
 336
 337 int l2tp_session_register(struct l2tp_session *session,
 338                           struct l2tp_tunnel *tunnel)
 339 {
 340         struct l2tp_session *session_walk;
 341         struct hlist_head *g_head;
 342         struct hlist_head *head;
 343         struct l2tp_net *pn;
 344         int err;
 345
 346         head = l2tp_session_id_hash(tunnel, session->session_id);
 347
 348         spin_lock_bh(&tunnel->hlist_lock);
 349         if (!tunnel->acpt_newsess) {
 350                 err = -ENODEV;
 351                 goto err_tlock;
 352         }
 353
 354         hlist_for_each_entry(session_walk, head, hlist)
 355                 if (session_walk->session_id == session->session_id) {
 356                         err = -EEXIST;
 357                         goto err_tlock;
 358                 }
 359
 360         if (tunnel->version == L2TP_HDR_VER_3) {
 361                 pn = l2tp_pernet(tunnel->l2tp_net);
 362                 g_head = l2tp_session_id_hash_2(pn, session->session_id);
 363
 364                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
 365
 366                 /* IP encap expects session IDs to be globally unique, while
 367                  * UDP encap doesn't.
 368                  */
 369                 hlist_for_each_entry(session_walk, g_head, global_hlist)
 370                         if (session_walk->session_id == session->session_id &&
 371                             (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP ||
 372                              tunnel->encap == L2TP_ENCAPTYPE_IP)) {
 373                                 err = -EEXIST;
 374                                 goto err_tlock_pnlock;
 375                         }
 376
 377                 l2tp_tunnel_inc_refcount(tunnel);
 378                 hlist_add_head_rcu(&session->global_hlist, g_head);
 379
 380                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 381         } else {
 382                 l2tp_tunnel_inc_refcount(tunnel);
 383         }
 384
 385         hlist_add_head_rcu(&session->hlist, head);
 386         spin_unlock_bh(&tunnel->hlist_lock);
 387
 388         trace_register_session(session);
 389
 390         return 0;
 391
 392 err_tlock_pnlock:
 393         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 394 err_tlock:
 395         spin_unlock_bh(&tunnel->hlist_lock);
 396
 397         return err;
 398 }
 399 EXPORT_SYMBOL_GPL(l2tp_session_register);
 400
 401 /*****************************************************************************
 402  * Receive data handling
 403  *****************************************************************************/
 404
 405 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 406  * number.
 407  */
 408 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 409 {
 410         struct sk_buff *skbp;
 411         struct sk_buff *tmp;
 412         u32 ns = L2TP_SKB_CB(skb)->ns;
 413
 414         spin_lock_bh(&session->reorder_q.lock);
 415         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 416                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 417                         __skb_queue_before(&session->reorder_q, skbp, skb);
 418                         atomic_long_inc(&session->stats.rx_oos_packets);
 419                         goto out;
 420                 }
 421         }
 422
 423         __skb_queue_tail(&session->reorder_q, skb);
 424
 425 out:
 426         spin_unlock_bh(&session->reorder_q.lock);
 427 }
 428
 429 /* Dequeue a single skb.
 430  */
 431 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 432 {
 433         struct l2tp_tunnel *tunnel = session->tunnel;
 434         int length = L2TP_SKB_CB(skb)->length;
 435
 436         /* We're about to requeue the skb, so return resources
 437          * to its current owner (a socket receive buffer).
 438          */
 439         skb_orphan(skb);
 440
 441         atomic_long_inc(&tunnel->stats.rx_packets);
 442         atomic_long_add(length, &tunnel->stats.rx_bytes);
 443         atomic_long_inc(&session->stats.rx_packets);
 444         atomic_long_add(length, &session->stats.rx_bytes);
 445
 446         if (L2TP_SKB_CB(skb)->has_seq) {
 447                 /* Bump our Nr */
 448                 session->nr++;
 449                 session->nr &= session->nr_max;
 450                 trace_session_seqnum_update(session);
 451         }
 452
 453         /* call private receive handler */
 454         if (session->recv_skb)
 455                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 456         else
 457                 kfree_skb(skb);
 458 }
 459
 460 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 461  * Skbs that have been in the queue for too long are simply discarded.
 462  */
 463 static void l2tp_recv_dequeue(struct l2tp_session *session)
 464 {
 465         struct sk_buff *skb;
 466         struct sk_buff *tmp;
 467
 468         /* If the pkt at the head of the queue has the nr that we
 469          * expect to send up next, dequeue it and any other
 470          * in-sequence packets behind it.
 471          */
 472 start:
 473         spin_lock_bh(&session->reorder_q.lock);
 474         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 475                 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
 476
 477                 /* If the packet has been pending on the queue for too long, discard it */
 478                 if (time_after(jiffies, cb->expires)) {
 479                         atomic_long_inc(&session->stats.rx_seq_discards);
 480                         atomic_long_inc(&session->stats.rx_errors);
 481                         trace_session_pkt_expired(session, cb->ns);
 482                         session->reorder_skip = 1;
 483                         __skb_unlink(skb, &session->reorder_q);
 484                         kfree_skb(skb);
 485                         continue;
 486                 }
 487
 488                 if (cb->has_seq) {
 489                         if (session->reorder_skip) {
 490                                 session->reorder_skip = 0;
 491                                 session->nr = cb->ns;
 492                                 trace_session_seqnum_reset(session);
 493                         }
 494                         if (cb->ns != session->nr)
 495                                 goto out;
 496                 }
 497                 __skb_unlink(skb, &session->reorder_q);
 498
 499                 /* Process the skb. We release the queue lock while we
 500                  * do so to let other contexts process the queue.
 501                  */
 502                 spin_unlock_bh(&session->reorder_q.lock);
 503                 l2tp_recv_dequeue_skb(session, skb);
 504                 goto start;
 505         }
 506
 507 out:
 508         spin_unlock_bh(&session->reorder_q.lock);
 509 }
 510
 511 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
 512 {
 513         u32 nws;
 514
 515         if (nr >= session->nr)
 516                 nws = nr - session->nr;
 517         else
 518                 nws = (session->nr_max + 1) - (session->nr - nr);
 519
 520         return nws < session->nr_window_size;
 521 }
 522
 523 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
 524  * acceptable, else non-zero.
 525  */
 526 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
 527 {
 528         struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
 529
 530         if (!l2tp_seq_check_rx_window(session, cb->ns)) {
 531                 /* Packet sequence number is outside allowed window.
 532                  * Discard it.
 533                  */
 534                 trace_session_pkt_outside_rx_window(session, cb->ns);
 535                 goto discard;
 536         }
 537
 538         if (session->reorder_timeout != 0) {
 539                 /* Packet reordering enabled. Add skb to session's
 540                  * reorder queue, in order of ns.
 541                  */
 542                 l2tp_recv_queue_skb(session, skb);
 543                 goto out;
 544         }
 545
 546         /* Packet reordering disabled. Discard out-of-sequence packets, while
 547          * tracking the number if in-sequence packets after the first OOS packet
 548          * is seen. After nr_oos_count_max in-sequence packets, reset the
 549          * sequence number to re-enable packet reception.
 550          */
 551         if (cb->ns == session->nr) {
 552                 skb_queue_tail(&session->reorder_q, skb);
 553         } else {
 554                 u32 nr_oos = cb->ns;
 555                 u32 nr_next = (session->nr_oos + 1) & session->nr_max;
 556
 557                 if (nr_oos == nr_next)
 558                         session->nr_oos_count++;
 559                 else
 560                         session->nr_oos_count = 0;
 561
 562                 session->nr_oos = nr_oos;
 563                 if (session->nr_oos_count > session->nr_oos_count_max) {
 564                         session->reorder_skip = 1;
 565                 }
 566                 if (!session->reorder_skip) {
 567                         atomic_long_inc(&session->stats.rx_seq_discards);
 568                         trace_session_pkt_oos(session, cb->ns);
 569                         goto discard;
 570                 }
 571                 skb_queue_tail(&session->reorder_q, skb);
 572         }
 573
 574 out:
 575         return 0;
 576
 577 discard:
 578         return 1;
 579 }
 580
 581 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 582  * and L2TPv3 data frames here.
 583  *
 584  * L2TPv2 Data Message Header
 585  *
 586  *  0                   1                   2                   3
 587  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 588  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 589  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 590  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 591  * |           Tunnel ID           |           Session ID          |
 592  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 593  * |             Ns (opt)          |             Nr (opt)          |
 594  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 595  * |      Offset Size (opt)        |    Offset pad... (opt)
 596  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 597  *
 598  * Data frames are marked by T=0. All other fields are the same as
 599  * those in L2TP control frames.
 600  *
 601  * L2TPv3 Data Message Header
 602  *
 603  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 604  * |                      L2TP Session Header                      |
 605  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 606  * |                      L2-Specific Sublayer                     |
 607  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 608  * |                        Tunnel Payload                      ...
 609  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 610  *
 611  * L2TPv3 Session Header Over IP
 612  *
 613  *  0                   1                   2                   3
 614  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 615  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 616  * |                           Session ID                          |
 617  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 618  * |               Cookie (optional, maximum 64 bits)...
 619  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 620  *                                                                 |
 621  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 622  *
 623  * L2TPv3 L2-Specific Sublayer Format
 624  *
 625  *  0                   1                   2                   3
 626  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 627  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 628  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 629  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 630  *
 631  * Cookie value and sublayer format are negotiated with the peer when
 632  * the session is set up. Unlike L2TPv2, we do not need to parse the
 633  * packet header to determine if optional fields are present.
 634  *
 635  * Caller must already have parsed the frame and determined that it is
 636  * a data (not control) frame before coming here. Fields up to the
 637  * session-id have already been parsed and ptr points to the data
 638  * after the session-id.
 639  */
 640 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 641                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 642                       int length)
 643 {
 644         struct l2tp_tunnel *tunnel = session->tunnel;
 645         int offset;
 646
 647         /* Parse and check optional cookie */
 648         if (session->peer_cookie_len > 0) {
 649                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 650                         pr_debug_ratelimited("%s: cookie mismatch (%u/%u). Discarding.\n",
 651                                              tunnel->name, tunnel->tunnel_id,
 652                                              session->session_id);
 653                         atomic_long_inc(&session->stats.rx_cookie_discards);
 654                         goto discard;
 655                 }
 656                 ptr += session->peer_cookie_len;
 657         }
 658
 659         /* Handle the optional sequence numbers. Sequence numbers are
 660          * in different places for L2TPv2 and L2TPv3.
 661          *
 662          * If we are the LAC, enable/disable sequence numbers under
 663          * the control of the LNS.  If no sequence numbers present but
 664          * we were expecting them, discard frame.
 665          */
 666         L2TP_SKB_CB(skb)->has_seq = 0;
 667         if (tunnel->version == L2TP_HDR_VER_2) {
 668                 if (hdrflags & L2TP_HDRFLAG_S) {
 669                         /* Store L2TP info in the skb */
 670                         L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr);
 671                         L2TP_SKB_CB(skb)->has_seq = 1;
 672                         ptr += 2;
 673                         /* Skip past nr in the header */
 674                         ptr += 2;
 675
 676                 }
 677         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 678                 u32 l2h = ntohl(*(__be32 *)ptr);
 679
 680                 if (l2h & 0x40000000) {
 681                         /* Store L2TP info in the skb */
 682                         L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff;
 683                         L2TP_SKB_CB(skb)->has_seq = 1;
 684                 }
 685                 ptr += 4;
 686         }
 687
 688         if (L2TP_SKB_CB(skb)->has_seq) {
 689                 /* Received a packet with sequence numbers. If we're the LAC,
 690                  * check if we sre sending sequence numbers and if not,
 691                  * configure it so.
 692                  */
 693                 if (!session->lns_mode && !session->send_seq) {
 694                         trace_session_seqnum_lns_enable(session);
 695                         session->send_seq = 1;
 696                         l2tp_session_set_header_len(session, tunnel->version);
 697                 }
 698         } else {
 699                 /* No sequence numbers.
 700                  * If user has configured mandatory sequence numbers, discard.
 701                  */
 702                 if (session->recv_seq) {
 703                         pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
 704                                              session->name);
 705                         atomic_long_inc(&session->stats.rx_seq_discards);
 706                         goto discard;
 707                 }
 708
 709                 /* If we're the LAC and we're sending sequence numbers, the
 710                  * LNS has requested that we no longer send sequence numbers.
 711                  * If we're the LNS and we're sending sequence numbers, the
 712                  * LAC is broken. Discard the frame.
 713                  */
 714                 if (!session->lns_mode && session->send_seq) {
 715                         trace_session_seqnum_lns_disable(session);
 716                         session->send_seq = 0;
 717                         l2tp_session_set_header_len(session, tunnel->version);
 718                 } else if (session->send_seq) {
 719                         pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
 720                                              session->name);
 721                         atomic_long_inc(&session->stats.rx_seq_discards);
 722                         goto discard;
 723                 }
 724         }
 725
 726         /* Session data offset is defined only for L2TPv2 and is
 727          * indicated by an optional 16-bit value in the header.
 728          */
 729         if (tunnel->version == L2TP_HDR_VER_2) {
 730                 /* If offset bit set, skip it. */
 731                 if (hdrflags & L2TP_HDRFLAG_O) {
 732                         offset = ntohs(*(__be16 *)ptr);
 733                         ptr += 2 + offset;
 734                 }
 735         }
 736
 737         offset = ptr - optr;
 738         if (!pskb_may_pull(skb, offset))
 739                 goto discard;
 740
 741         __skb_pull(skb, offset);
 742
 743         /* Prepare skb for adding to the session's reorder_q.  Hold
 744          * packets for max reorder_timeout or 1 second if not
 745          * reordering.
 746          */
 747         L2TP_SKB_CB(skb)->length = length;
 748         L2TP_SKB_CB(skb)->expires = jiffies +
 749                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 750
 751         /* Add packet to the session's receive queue. Reordering is done here, if
 752          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 753          */
 754         if (L2TP_SKB_CB(skb)->has_seq) {
 755                 if (l2tp_recv_data_seq(session, skb))
 756                         goto discard;
 757         } else {
 758                 /* No sequence numbers. Add the skb to the tail of the
 759                  * reorder queue. This ensures that it will be
 760                  * delivered after all previous sequenced skbs.
 761                  */
 762                 skb_queue_tail(&session->reorder_q, skb);
 763         }
 764
 765         /* Try to dequeue as many skbs from reorder_q as we can. */
 766         l2tp_recv_dequeue(session);
 767
 768         return;
 769
 770 discard:
 771         atomic_long_inc(&session->stats.rx_errors);
 772         kfree_skb(skb);
 773 }
 774 EXPORT_SYMBOL_GPL(l2tp_recv_common);
 775
 776 /* Drop skbs from the session's reorder_q
 777  */
 778 static void l2tp_session_queue_purge(struct l2tp_session *session)
 779 {
 780         struct sk_buff *skb = NULL;
 781
 782         while ((skb = skb_dequeue(&session->reorder_q))) {
 783                 atomic_long_inc(&session->stats.rx_errors);
 784                 kfree_skb(skb);
 785         }
 786 }
 787
 788 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 789  * here. The skb is not on a list when we get here.
 790  * Returns 0 if the packet was a data packet and was successfully passed on.
 791  * Returns 1 if the packet was not a good data packet and could not be
 792  * forwarded.  All such packets are passed up to userspace to deal with.
 793  */
 794 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 795 {
 796         struct l2tp_session *session = NULL;
 797         unsigned char *ptr, *optr;
 798         u16 hdrflags;
 799         u32 tunnel_id, session_id;
 800         u16 version;
 801         int length;
 802
 803         /* UDP has verified checksum */
 804
 805         /* UDP always verifies the packet length. */
 806         __skb_pull(skb, sizeof(struct udphdr));
 807
 808         /* Short packet? */
 809         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
 810                 pr_debug_ratelimited("%s: recv short packet (len=%d)\n",
 811                                      tunnel->name, skb->len);
 812                 goto invalid;
 813         }
 814
 815         /* Point to L2TP header */
 816         optr = skb->data;
 817         ptr = skb->data;
 818
 819         /* Get L2TP header flags */
 820         hdrflags = ntohs(*(__be16 *)ptr);
 821
 822         /* Check protocol version */
 823         version = hdrflags & L2TP_HDR_VER_MASK;
 824         if (version != tunnel->version) {
 825                 pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n",
 826                                      tunnel->name, version, tunnel->version);
 827                 goto invalid;
 828         }
 829
 830         /* Get length of L2TP packet */
 831         length = skb->len;
 832
 833         /* If type is control packet, it is handled by userspace. */
 834         if (hdrflags & L2TP_HDRFLAG_T)
 835                 goto pass;
 836
 837         /* Skip flags */
 838         ptr += 2;
 839
 840         if (tunnel->version == L2TP_HDR_VER_2) {
 841                 /* If length is present, skip it */
 842                 if (hdrflags & L2TP_HDRFLAG_L)
 843                         ptr += 2;
 844
 845                 /* Extract tunnel and session ID */
 846                 tunnel_id = ntohs(*(__be16 *)ptr);
 847                 ptr += 2;
 848                 session_id = ntohs(*(__be16 *)ptr);
 849                 ptr += 2;
 850         } else {
 851                 ptr += 2;       /* skip reserved bits */
 852                 tunnel_id = tunnel->tunnel_id;
 853                 session_id = ntohl(*(__be32 *)ptr);
 854                 ptr += 4;
 855         }
 856
 857         /* Find the session context */
 858         session = l2tp_tunnel_get_session(tunnel, session_id);
 859         if (!session || !session->recv_skb) {
 860                 if (session)
 861                         l2tp_session_dec_refcount(session);
 862
 863                 /* Not found? Pass to userspace to deal with */
 864                 pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n",
 865                                      tunnel->name, tunnel_id, session_id);
 866                 goto pass;
 867         }
 868
 869         if (tunnel->version == L2TP_HDR_VER_3 &&
 870             l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
 871                 l2tp_session_dec_refcount(session);
 872                 goto invalid;
 873         }
 874
 875         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
 876         l2tp_session_dec_refcount(session);
 877
 878         return 0;
 879
 880 invalid:
 881         atomic_long_inc(&tunnel->stats.rx_invalid);
 882
 883 pass:
 884         /* Put UDP header back */
 885         __skb_push(skb, sizeof(struct udphdr));
 886
 887         return 1;
 888 }
 889
 890 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 891  * Return codes:
 892  * 0 : success.
 893  * <0: error
 894  * >0: skb should be passed up to userspace as UDP.
 895  */
 896 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 897 {
 898         struct l2tp_tunnel *tunnel;
 899
 900         /* Note that this is called from the encap_rcv hook inside an
 901          * RCU-protected region, but without the socket being locked.
 902          * Hence we use rcu_dereference_sk_user_data to access the
 903          * tunnel data structure rather the usual l2tp_sk_to_tunnel
 904          * accessor function.
 905          */
 906         tunnel = rcu_dereference_sk_user_data(sk);
 907         if (!tunnel)
 908                 goto pass_up;
 909         if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
 910                 goto pass_up;
 911
 912         if (l2tp_udp_recv_core(tunnel, skb))
 913                 goto pass_up;
 914
 915         return 0;
 916
 917 pass_up:
 918         return 1;
 919 }
 920 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 921
 922 /************************************************************************
 923  * Transmit handling
 924  ***********************************************************************/
 925
 926 /* Build an L2TP header for the session into the buffer provided.
 927  */
 928 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 929 {
 930         struct l2tp_tunnel *tunnel = session->tunnel;
 931         __be16 *bufp = buf;
 932         __be16 *optr = buf;
 933         u16 flags = L2TP_HDR_VER_2;
 934         u32 tunnel_id = tunnel->peer_tunnel_id;
 935         u32 session_id = session->peer_session_id;
 936
 937         if (session->send_seq)
 938                 flags |= L2TP_HDRFLAG_S;
 939
 940         /* Setup L2TP header. */
 941         *bufp++ = htons(flags);
 942         *bufp++ = htons(tunnel_id);
 943         *bufp++ = htons(session_id);
 944         if (session->send_seq) {
 945                 *bufp++ = htons(session->ns);
 946                 *bufp++ = 0;
 947                 session->ns++;
 948                 session->ns &= 0xffff;
 949                 trace_session_seqnum_update(session);
 950         }
 951
 952         return bufp - optr;
 953 }
 954
 955 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 956 {
 957         struct l2tp_tunnel *tunnel = session->tunnel;
 958         char *bufp = buf;
 959         char *optr = bufp;
 960
 961         /* Setup L2TP header. The header differs slightly for UDP and
 962          * IP encapsulations. For UDP, there is 4 bytes of flags.
 963          */
 964         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 965                 u16 flags = L2TP_HDR_VER_3;
 966                 *((__be16 *)bufp) = htons(flags);
 967                 bufp += 2;
 968                 *((__be16 *)bufp) = 0;
 969                 bufp += 2;
 970         }
 971
 972         *((__be32 *)bufp) = htonl(session->peer_session_id);
 973         bufp += 4;
 974         if (session->cookie_len) {
 975                 memcpy(bufp, &session->cookie[0], session->cookie_len);
 976                 bufp += session->cookie_len;
 977         }
 978         if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 979                 u32 l2h = 0;
 980
 981                 if (session->send_seq) {
 982                         l2h = 0x40000000 | session->ns;
 983                         session->ns++;
 984                         session->ns &= 0xffffff;
 985                         trace_session_seqnum_update(session);
 986                 }
 987
 988                 *((__be32 *)bufp) = htonl(l2h);
 989                 bufp += 4;
 990         }
 991
 992         return bufp - optr;
 993 }
 994
 995 /* Queue the packet to IP for output: tunnel socket lock must be held */
 996 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
 997 {
 998         int err;
 999
1000         skb->ignore_df = 1;
1001         skb_dst_drop(skb);
1002 #if IS_ENABLED(CONFIG_IPV6)
1003         if (l2tp_sk_is_v6(tunnel->sock))
1004                 err = inet6_csk_xmit(tunnel->sock, skb, NULL);
1005         else
1006 #endif
1007                 err = ip_queue_xmit(tunnel->sock, skb, fl);
1008
1009         return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
1010 }
1011
1012 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len)
1013 {
1014         struct l2tp_tunnel *tunnel = session->tunnel;
1015         unsigned int data_len = skb->len;
1016         struct sock *sk = tunnel->sock;
1017         int headroom, uhlen, udp_len;
1018         int ret = NET_XMIT_SUCCESS;
1019         struct inet_sock *inet;
1020         struct udphdr *uh;
1021
1022         /* Check that there's enough headroom in the skb to insert IP,
1023          * UDP and L2TP headers. If not enough, expand it to
1024          * make room. Adjust truesize.
1025          */
1026         uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
1027         headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
1028         if (skb_cow_head(skb, headroom)) {
1029                 kfree_skb(skb);
1030                 return NET_XMIT_DROP;
1031         }
1032
1033         /* Setup L2TP header */
1034         if (tunnel->version == L2TP_HDR_VER_2)
1035                 l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len));
1036         else
1037                 l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len));
1038
1039         /* Reset skb netfilter state */
1040         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1041         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);
1042         nf_reset_ct(skb);
1043
1044         bh_lock_sock_nested(sk);
1045         if (sock_owned_by_user(sk)) {
1046                 kfree_skb(skb);
1047                 ret = NET_XMIT_DROP;
1048                 goto out_unlock;
1049         }
1050
1051         /* The user-space may change the connection status for the user-space
1052          * provided socket at run time: we must check it under the socket lock
1053          */
1054         if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1055                 kfree_skb(skb);
1056                 ret = NET_XMIT_DROP;
1057                 goto out_unlock;
1058         }
1059
1060         /* Report transmitted length before we add encap header, which keeps
1061          * statistics consistent for both UDP and IP encap tx/rx paths.
1062          */
1063         *len = skb->len;
1064
1065         inet = inet_sk(sk);
1066         switch (tunnel->encap) {
1067         case L2TP_ENCAPTYPE_UDP:
1068                 /* Setup UDP header */
1069                 __skb_push(skb, sizeof(*uh));
1070                 skb_reset_transport_header(skb);
1071                 uh = udp_hdr(skb);
1072                 uh->source = inet->inet_sport;
1073                 uh->dest = inet->inet_dport;
1074                 udp_len = uhlen + session->hdr_len + data_len;
1075                 uh->len = htons(udp_len);
1076
1077                 /* Calculate UDP checksum if configured to do so */
1078 #if IS_ENABLED(CONFIG_IPV6)
1079                 if (l2tp_sk_is_v6(sk))
1080                         udp6_set_csum(udp_get_no_check6_tx(sk),
1081                                       skb, &inet6_sk(sk)->saddr,
1082                                       &sk->sk_v6_daddr, udp_len);
1083                 else
1084 #endif
1085                         udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1086                                      inet->inet_daddr, udp_len);
1087                 break;
1088
1089         case L2TP_ENCAPTYPE_IP:
1090                 break;
1091         }
1092
1093         ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
1094
1095 out_unlock:
1096         bh_unlock_sock(sk);
1097
1098         return ret;
1099 }
1100
1101 /* If caller requires the skb to have a ppp header, the header must be
1102  * inserted in the skb data before calling this function.
1103  */
1104 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
1105 {
1106         unsigned int len = 0;
1107         int ret;
1108
1109         ret = l2tp_xmit_core(session, skb, &len);
1110         if (ret == NET_XMIT_SUCCESS) {
1111                 atomic_long_inc(&session->tunnel->stats.tx_packets);
1112                 atomic_long_add(len, &session->tunnel->stats.tx_bytes);
1113                 atomic_long_inc(&session->stats.tx_packets);
1114                 atomic_long_add(len, &session->stats.tx_bytes);
1115         } else {
1116                 atomic_long_inc(&session->tunnel->stats.tx_errors);
1117                 atomic_long_inc(&session->stats.tx_errors);
1118         }
1119         return ret;
1120 }
1121 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1122
1123 /*****************************************************************************
1124  * Tinnel and session create/destroy.
1125  *****************************************************************************/
1126
1127 /* Tunnel socket destruct hook.
1128  * The tunnel context is deleted only when all session sockets have been
1129  * closed.
1130  */
1131 static void l2tp_tunnel_destruct(struct sock *sk)
1132 {
1133         struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1134
1135         if (!tunnel)
1136                 goto end;
1137
1138         /* Disable udp encapsulation */
1139         switch (tunnel->encap) {
1140         case L2TP_ENCAPTYPE_UDP:
1141                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1142                 (udp_sk(sk))->encap_type = 0;
1143                 (udp_sk(sk))->encap_rcv = NULL;
1144                 (udp_sk(sk))->encap_destroy = NULL;
1145                 break;
1146         case L2TP_ENCAPTYPE_IP:
1147                 break;
1148         }
1149
1150         /* Remove hooks into tunnel socket */
1151         write_lock_bh(&sk->sk_callback_lock);
1152         sk->sk_destruct = tunnel->old_sk_destruct;
1153         sk->sk_user_data = NULL;
1154         write_unlock_bh(&sk->sk_callback_lock);
1155
1156         /* Call the original destructor */
1157         if (sk->sk_destruct)
1158                 (*sk->sk_destruct)(sk);
1159
1160         kfree_rcu(tunnel, rcu);
1161 end:
1162         return;
1163 }
1164
1165 /* Remove an l2tp session from l2tp_core's hash lists. */
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                 spin_lock_bh(&tunnel->hlist_lock);
1174                 hlist_del_init_rcu(&session->hlist);
1175                 spin_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                 }
1185
1186                 synchronize_rcu();
1187         }
1188 }
1189
1190 /* When the tunnel is closed, all the attached sessions need to go too.
1191  */
1192 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1193 {
1194         struct l2tp_session *session;
1195         int hash;
1196
1197         spin_lock_bh(&tunnel->hlist_lock);
1198         tunnel->acpt_newsess = false;
1199         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1200 again:
1201                 hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
1202                         hlist_del_init_rcu(&session->hlist);
1203
1204                         spin_unlock_bh(&tunnel->hlist_lock);
1205                         l2tp_session_delete(session);
1206                         spin_lock_bh(&tunnel->hlist_lock);
1207
1208                         /* Now restart from the beginning of this hash
1209                          * chain.  We always remove a session from the
1210                          * list so we are guaranteed to make forward
1211                          * progress.
1212                          */
1213                         goto again;
1214                 }
1215         }
1216         spin_unlock_bh(&tunnel->hlist_lock);
1217 }
1218
1219 /* Tunnel socket destroy hook for UDP encapsulation */
1220 static void l2tp_udp_encap_destroy(struct sock *sk)
1221 {
1222         struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
1223
1224         if (tunnel)
1225                 l2tp_tunnel_delete(tunnel);
1226 }
1227
1228 static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel)
1229 {
1230         struct l2tp_net *pn = l2tp_pernet(net);
1231
1232         spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1233         idr_remove(&pn->l2tp_tunnel_idr, tunnel->tunnel_id);
1234         spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1235 }
1236
1237 /* Workqueue tunnel deletion function */
1238 static void l2tp_tunnel_del_work(struct work_struct *work)
1239 {
1240         struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1241                                                   del_work);
1242         struct sock *sk = tunnel->sock;
1243         struct socket *sock = sk->sk_socket;
1244
1245         l2tp_tunnel_closeall(tunnel);
1246
1247         /* If the tunnel socket was created within the kernel, use
1248          * the sk API to release it here.
1249          */
1250         if (tunnel->fd < 0) {
1251                 if (sock) {
1252                         kernel_sock_shutdown(sock, SHUT_RDWR);
1253                         sock_release(sock);
1254                 }
1255         }
1256
1257         l2tp_tunnel_remove(tunnel->l2tp_net, tunnel);
1258         /* drop initial ref */
1259         l2tp_tunnel_dec_refcount(tunnel);
1260
1261         /* drop workqueue ref */
1262         l2tp_tunnel_dec_refcount(tunnel);
1263 }
1264
1265 /* Create a socket for the tunnel, if one isn't set up by
1266  * userspace. This is used for static tunnels where there is no
1267  * managing L2TP daemon.
1268  *
1269  * Since we don't want these sockets to keep a namespace alive by
1270  * themselves, we drop the socket's namespace refcount after creation.
1271  * These sockets are freed when the namespace exits using the pernet
1272  * exit hook.
1273  */
1274 static int l2tp_tunnel_sock_create(struct net *net,
1275                                    u32 tunnel_id,
1276                                    u32 peer_tunnel_id,
1277                                    struct l2tp_tunnel_cfg *cfg,
1278                                    struct socket **sockp)
1279 {
1280         int err = -EINVAL;
1281         struct socket *sock = NULL;
1282         struct udp_port_cfg udp_conf;
1283
1284         switch (cfg->encap) {
1285         case L2TP_ENCAPTYPE_UDP:
1286                 memset(&udp_conf, 0, sizeof(udp_conf));
1287
1288 #if IS_ENABLED(CONFIG_IPV6)
1289                 if (cfg->local_ip6 && cfg->peer_ip6) {
1290                         udp_conf.family = AF_INET6;
1291                         memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1292                                sizeof(udp_conf.local_ip6));
1293                         memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1294                                sizeof(udp_conf.peer_ip6));
1295                         udp_conf.use_udp6_tx_checksums =
1296                           !cfg->udp6_zero_tx_checksums;
1297                         udp_conf.use_udp6_rx_checksums =
1298                           !cfg->udp6_zero_rx_checksums;
1299                 } else
1300 #endif
1301                 {
1302                         udp_conf.family = AF_INET;
1303                         udp_conf.local_ip = cfg->local_ip;
1304                         udp_conf.peer_ip = cfg->peer_ip;
1305                         udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1306                 }
1307
1308                 udp_conf.local_udp_port = htons(cfg->local_udp_port);
1309                 udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1310
1311                 err = udp_sock_create(net, &udp_conf, &sock);
1312                 if (err < 0)
1313                         goto out;
1314
1315                 break;
1316
1317         case L2TP_ENCAPTYPE_IP:
1318 #if IS_ENABLED(CONFIG_IPV6)
1319                 if (cfg->local_ip6 && cfg->peer_ip6) {
1320                         struct sockaddr_l2tpip6 ip6_addr = {0};
1321
1322                         err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1323                                                IPPROTO_L2TP, &sock);
1324                         if (err < 0)
1325                                 goto out;
1326
1327                         ip6_addr.l2tp_family = AF_INET6;
1328                         memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1329                                sizeof(ip6_addr.l2tp_addr));
1330                         ip6_addr.l2tp_conn_id = tunnel_id;
1331                         err = kernel_bind(sock, (struct sockaddr *)&ip6_addr,
1332                                           sizeof(ip6_addr));
1333                         if (err < 0)
1334                                 goto out;
1335
1336                         ip6_addr.l2tp_family = AF_INET6;
1337                         memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1338                                sizeof(ip6_addr.l2tp_addr));
1339                         ip6_addr.l2tp_conn_id = peer_tunnel_id;
1340                         err = kernel_connect(sock,
1341                                              (struct sockaddr *)&ip6_addr,
1342                                              sizeof(ip6_addr), 0);
1343                         if (err < 0)
1344                                 goto out;
1345                 } else
1346 #endif
1347                 {
1348                         struct sockaddr_l2tpip ip_addr = {0};
1349
1350                         err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1351                                                IPPROTO_L2TP, &sock);
1352                         if (err < 0)
1353                                 goto out;
1354
1355                         ip_addr.l2tp_family = AF_INET;
1356                         ip_addr.l2tp_addr = cfg->local_ip;
1357                         ip_addr.l2tp_conn_id = tunnel_id;
1358                         err = kernel_bind(sock, (struct sockaddr *)&ip_addr,
1359                                           sizeof(ip_addr));
1360                         if (err < 0)
1361                                 goto out;
1362
1363                         ip_addr.l2tp_family = AF_INET;
1364                         ip_addr.l2tp_addr = cfg->peer_ip;
1365                         ip_addr.l2tp_conn_id = peer_tunnel_id;
1366                         err = kernel_connect(sock, (struct sockaddr *)&ip_addr,
1367                                              sizeof(ip_addr), 0);
1368                         if (err < 0)
1369                                 goto out;
1370                 }
1371                 break;
1372
1373         default:
1374                 goto out;
1375         }
1376
1377 out:
1378         *sockp = sock;
1379         if (err < 0 && sock) {
1380                 kernel_sock_shutdown(sock, SHUT_RDWR);
1381                 sock_release(sock);
1382                 *sockp = NULL;
1383         }
1384
1385         return err;
1386 }
1387
1388 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id,
1389                        struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
1390 {
1391         struct l2tp_tunnel *tunnel = NULL;
1392         int err;
1393         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1394
1395         if (cfg)
1396                 encap = cfg->encap;
1397
1398         tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
1399         if (!tunnel) {
1400                 err = -ENOMEM;
1401                 goto err;
1402         }
1403
1404         tunnel->version = version;
1405         tunnel->tunnel_id = tunnel_id;
1406         tunnel->peer_tunnel_id = peer_tunnel_id;
1407
1408         tunnel->magic = L2TP_TUNNEL_MAGIC;
1409         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1410         spin_lock_init(&tunnel->hlist_lock);
1411         tunnel->acpt_newsess = true;
1412
1413         tunnel->encap = encap;
1414
1415         refcount_set(&tunnel->ref_count, 1);
1416         tunnel->fd = fd;
1417
1418         /* Init delete workqueue struct */
1419         INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1420
1421         INIT_LIST_HEAD(&tunnel->list);
1422
1423         err = 0;
1424 err:
1425         if (tunnelp)
1426                 *tunnelp = tunnel;
1427
1428         return err;
1429 }
1430 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1431
1432 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1433                                 enum l2tp_encap_type encap)
1434 {
1435         if (!net_eq(sock_net(sk), net))
1436                 return -EINVAL;
1437
1438         if (sk->sk_type != SOCK_DGRAM)
1439                 return -EPROTONOSUPPORT;
1440
1441         if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
1442                 return -EPROTONOSUPPORT;
1443
1444         if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1445             (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1446                 return -EPROTONOSUPPORT;
1447
1448         if (sk->sk_user_data)
1449                 return -EBUSY;
1450
1451         return 0;
1452 }
1453
1454 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1455                          struct l2tp_tunnel_cfg *cfg)
1456 {
1457         struct l2tp_net *pn = l2tp_pernet(net);
1458         u32 tunnel_id = tunnel->tunnel_id;
1459         struct socket *sock;
1460         struct sock *sk;
1461         int ret;
1462
1463         spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1464         ret = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id,
1465                             GFP_ATOMIC);
1466         spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1467         if (ret)
1468                 return ret == -ENOSPC ? -EEXIST : ret;
1469
1470         if (tunnel->fd < 0) {
1471                 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1472                                               tunnel->peer_tunnel_id, cfg,
1473                                               &sock);
1474                 if (ret < 0)
1475                         goto err;
1476         } else {
1477                 sock = sockfd_lookup(tunnel->fd, &ret);
1478                 if (!sock)
1479                         goto err;
1480         }
1481
1482         sk = sock->sk;
1483         lock_sock(sk);
1484         write_lock_bh(&sk->sk_callback_lock);
1485         ret = l2tp_validate_socket(sk, net, tunnel->encap);
1486         if (ret < 0)
1487                 goto err_inval_sock;
1488         rcu_assign_sk_user_data(sk, tunnel);
1489         write_unlock_bh(&sk->sk_callback_lock);
1490
1491         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1492                 struct udp_tunnel_sock_cfg udp_cfg = {
1493                         .sk_user_data = tunnel,
1494                         .encap_type = UDP_ENCAP_L2TPINUDP,
1495                         .encap_rcv = l2tp_udp_encap_recv,
1496                         .encap_destroy = l2tp_udp_encap_destroy,
1497                 };
1498
1499                 setup_udp_tunnel_sock(net, sock, &udp_cfg);
1500         }
1501
1502         tunnel->old_sk_destruct = sk->sk_destruct;
1503         sk->sk_destruct = &l2tp_tunnel_destruct;
1504         sk->sk_allocation = GFP_ATOMIC;
1505         release_sock(sk);
1506
1507         sock_hold(sk);
1508         tunnel->sock = sk;
1509         tunnel->l2tp_net = net;
1510
1511         spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
1512         idr_replace(&pn->l2tp_tunnel_idr, tunnel, tunnel->tunnel_id);
1513         spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
1514
1515         trace_register_tunnel(tunnel);
1516
1517         if (tunnel->fd >= 0)
1518                 sockfd_put(sock);
1519
1520         return 0;
1521
1522 err_inval_sock:
1523         write_unlock_bh(&sk->sk_callback_lock);
1524         release_sock(sk);
1525
1526         if (tunnel->fd < 0)
1527                 sock_release(sock);
1528         else
1529                 sockfd_put(sock);
1530 err:
1531         l2tp_tunnel_remove(net, tunnel);
1532         return ret;
1533 }
1534 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1535
1536 /* This function is used by the netlink TUNNEL_DELETE command.
1537  */
1538 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1539 {
1540         if (!test_and_set_bit(0, &tunnel->dead)) {
1541                 trace_delete_tunnel(tunnel);
1542                 l2tp_tunnel_inc_refcount(tunnel);
1543                 queue_work(l2tp_wq, &tunnel->del_work);
1544         }
1545 }
1546 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1547
1548 void l2tp_session_delete(struct l2tp_session *session)
1549 {
1550         if (test_and_set_bit(0, &session->dead))
1551                 return;
1552
1553         trace_delete_session(session);
1554         l2tp_session_unhash(session);
1555         l2tp_session_queue_purge(session);
1556         if (session->session_close)
1557                 (*session->session_close)(session);
1558
1559         l2tp_session_dec_refcount(session);
1560 }
1561 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1562
1563 /* We come here whenever a session's send_seq, cookie_len or
1564  * l2specific_type parameters are set.
1565  */
1566 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1567 {
1568         if (version == L2TP_HDR_VER_2) {
1569                 session->hdr_len = 6;
1570                 if (session->send_seq)
1571                         session->hdr_len += 4;
1572         } else {
1573                 session->hdr_len = 4 + session->cookie_len;
1574                 session->hdr_len += l2tp_get_l2specific_len(session);
1575                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1576                         session->hdr_len += 4;
1577         }
1578 }
1579 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1580
1581 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id,
1582                                          u32 peer_session_id, struct l2tp_session_cfg *cfg)
1583 {
1584         struct l2tp_session *session;
1585
1586         session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
1587         if (session) {
1588                 session->magic = L2TP_SESSION_MAGIC;
1589                 session->tunnel = tunnel;
1590
1591                 session->session_id = session_id;
1592                 session->peer_session_id = peer_session_id;
1593                 session->nr = 0;
1594                 if (tunnel->version == L2TP_HDR_VER_2)
1595                         session->nr_max = 0xffff;
1596                 else
1597                         session->nr_max = 0xffffff;
1598                 session->nr_window_size = session->nr_max / 2;
1599                 session->nr_oos_count_max = 4;
1600
1601                 /* Use NR of first received packet */
1602                 session->reorder_skip = 1;
1603
1604                 sprintf(&session->name[0], "sess %u/%u",
1605                         tunnel->tunnel_id, session->session_id);
1606
1607                 skb_queue_head_init(&session->reorder_q);
1608
1609                 INIT_HLIST_NODE(&session->hlist);
1610                 INIT_HLIST_NODE(&session->global_hlist);
1611
1612                 if (cfg) {
1613                         session->pwtype = cfg->pw_type;
1614                         session->send_seq = cfg->send_seq;
1615                         session->recv_seq = cfg->recv_seq;
1616                         session->lns_mode = cfg->lns_mode;
1617                         session->reorder_timeout = cfg->reorder_timeout;
1618                         session->l2specific_type = cfg->l2specific_type;
1619                         session->cookie_len = cfg->cookie_len;
1620                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1621                         session->peer_cookie_len = cfg->peer_cookie_len;
1622                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1623                 }
1624
1625                 l2tp_session_set_header_len(session, tunnel->version);
1626
1627                 refcount_set(&session->ref_count, 1);
1628
1629                 return session;
1630         }
1631
1632         return ERR_PTR(-ENOMEM);
1633 }
1634 EXPORT_SYMBOL_GPL(l2tp_session_create);
1635
1636 /*****************************************************************************
1637  * Init and cleanup
1638  *****************************************************************************/
1639
1640 static __net_init int l2tp_init_net(struct net *net)
1641 {
1642         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1643         int hash;
1644
1645         idr_init(&pn->l2tp_tunnel_idr);
1646         spin_lock_init(&pn->l2tp_tunnel_idr_lock);
1647
1648         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1649                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1650
1651         spin_lock_init(&pn->l2tp_session_hlist_lock);
1652
1653         return 0;
1654 }
1655
1656 static __net_exit void l2tp_exit_net(struct net *net)
1657 {
1658         struct l2tp_net *pn = l2tp_pernet(net);
1659         struct l2tp_tunnel *tunnel = NULL;
1660         unsigned long tunnel_id, tmp;
1661         int hash;
1662
1663         rcu_read_lock_bh();
1664         idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
1665                 if (tunnel)
1666                         l2tp_tunnel_delete(tunnel);
1667         }
1668         rcu_read_unlock_bh();
1669
1670         if (l2tp_wq)
1671                 flush_workqueue(l2tp_wq);
1672         rcu_barrier();
1673
1674         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1675                 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1676         idr_destroy(&pn->l2tp_tunnel_idr);
1677 }
1678
1679 static struct pernet_operations l2tp_net_ops = {
1680         .init = l2tp_init_net,
1681         .exit = l2tp_exit_net,
1682         .id   = &l2tp_net_id,
1683         .size = sizeof(struct l2tp_net),
1684 };
1685
1686 static int __init l2tp_init(void)
1687 {
1688         int rc = 0;
1689
1690         rc = register_pernet_device(&l2tp_net_ops);
1691         if (rc)
1692                 goto out;
1693
1694         l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1695         if (!l2tp_wq) {
1696                 pr_err("alloc_workqueue failed\n");
1697                 unregister_pernet_device(&l2tp_net_ops);
1698                 rc = -ENOMEM;
1699                 goto out;
1700         }
1701
1702         pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1703
1704 out:
1705         return rc;
1706 }
1707
1708 static void __exit l2tp_exit(void)
1709 {
1710         unregister_pernet_device(&l2tp_net_ops);
1711         if (l2tp_wq) {
1712                 destroy_workqueue(l2tp_wq);
1713                 l2tp_wq = NULL;
1714         }
1715 }
1716
1717 module_init(l2tp_init);
1718 module_exit(l2tp_exit);
1719
1720 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1721 MODULE_DESCRIPTION("L2TP core");
1722 MODULE_LICENSE("GPL");
1723 MODULE_VERSION(L2TP_DRV_VERSION);