net/l2tp/l2tp_core.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * L2TP core.
   4  *
   5  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
   6  *
   7  * This file contains some code of the original L2TPv2 pppol2tp
   8  * driver, which has the following copyright:
   9  *
  10  * Authors:     Martijn van Oosterhout <kleptog@svana.org>
  11  *              James Chapman (jchapman@katalix.com)
  12  * Contributors:
  13  *              Michal Ostrowski <mostrows@speakeasy.net>
  14  *              Arnaldo Carvalho de Melo <acme@xconectiva.com.br>
  15  *              David S. Miller (davem@redhat.com)
  16  */
  17
  18 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  19
  20 #include <linux/module.h>
  21 #include <linux/string.h>
  22 #include <linux/list.h>
  23 #include <linux/rculist.h>
  24 #include <linux/uaccess.h>
  25
  26 #include <linux/kernel.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/kthread.h>
  29 #include <linux/sched.h>
  30 #include <linux/slab.h>
  31 #include <linux/errno.h>
  32 #include <linux/jiffies.h>
  33
  34 #include <linux/netdevice.h>
  35 #include <linux/net.h>
  36 #include <linux/inetdevice.h>
  37 #include <linux/skbuff.h>
  38 #include <linux/init.h>
  39 #include <linux/in.h>
  40 #include <linux/ip.h>
  41 #include <linux/udp.h>
  42 #include <linux/l2tp.h>
  43 #include <linux/hash.h>
  44 #include <linux/sort.h>
  45 #include <linux/file.h>
  46 #include <linux/nsproxy.h>
  47 #include <net/net_namespace.h>
  48 #include <net/netns/generic.h>
  49 #include <net/dst.h>
  50 #include <net/ip.h>
  51 #include <net/udp.h>
  52 #include <net/udp_tunnel.h>
  53 #include <net/inet_common.h>
  54 #include <net/xfrm.h>
  55 #include <net/protocol.h>
  56 #include <net/inet6_connection_sock.h>
  57 #include <net/inet_ecn.h>
  58 #include <net/ip6_route.h>
  59 #include <net/ip6_checksum.h>
  60
  61 #include <asm/byteorder.h>
  62 #include <linux/atomic.h>
  63
  64 #include "l2tp_core.h"
  65
  66 #define L2TP_DRV_VERSION        "V2.0"
  67
  68 /* L2TP header constants */
  69 #define L2TP_HDRFLAG_T     0x8000
  70 #define L2TP_HDRFLAG_L     0x4000
  71 #define L2TP_HDRFLAG_S     0x0800
  72 #define L2TP_HDRFLAG_O     0x0200
  73 #define L2TP_HDRFLAG_P     0x0100
  74
  75 #define L2TP_HDR_VER_MASK  0x000F
  76 #define L2TP_HDR_VER_2     0x0002
  77 #define L2TP_HDR_VER_3     0x0003
  78
  79 /* L2TPv3 default L2-specific sublayer */
  80 #define L2TP_SLFLAG_S      0x40000000
  81 #define L2TP_SL_SEQ_MASK   0x00ffffff
  82
  83 #define L2TP_HDR_SIZE_MAX               14
  84
  85 /* Default trace flags */
  86 #define L2TP_DEFAULT_DEBUG_FLAGS        0
  87
  88 /* Private data stored for received packets in the skb.
  89  */
  90 struct l2tp_skb_cb {
  91         u32                     ns;
  92         u16                     has_seq;
  93         u16                     length;
  94         unsigned long           expires;
  95 };
  96
  97 #define L2TP_SKB_CB(skb)        ((struct l2tp_skb_cb *) &skb->cb[sizeof(struct inet_skb_parm)])
  98
  99 static struct workqueue_struct *l2tp_wq;
 100
 101 /* per-net private data for this module */
 102 static unsigned int l2tp_net_id;
 103 struct l2tp_net {
 104         struct list_head l2tp_tunnel_list;
 105         spinlock_t l2tp_tunnel_list_lock;
 106         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
 107         spinlock_t l2tp_session_hlist_lock;
 108 };
 109
 110 #if IS_ENABLED(CONFIG_IPV6)
 111 static bool l2tp_sk_is_v6(struct sock *sk)
 112 {
 113         return sk->sk_family == PF_INET6 &&
 114                !ipv6_addr_v4mapped(&sk->sk_v6_daddr);
 115 }
 116 #endif
 117
 118 static inline struct l2tp_tunnel *l2tp_tunnel(struct sock *sk)
 119 {
 120         return sk->sk_user_data;
 121 }
 122
 123 static inline struct l2tp_net *l2tp_pernet(const struct net *net)
 124 {
 125         BUG_ON(!net);
 126
 127         return net_generic(net, l2tp_net_id);
 128 }
 129
 130 /* Session hash global list for L2TPv3.
 131  * The session_id SHOULD be random according to RFC3931, but several
 132  * L2TP implementations use incrementing session_ids.  So we do a real
 133  * hash on the session_id, rather than a simple bitmask.
 134  */
 135 static inline struct hlist_head *
 136 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 137 {
 138         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 139
 140 }
 141
 142 /* Session hash list.
 143  * The session_id SHOULD be random according to RFC2661, but several
 144  * L2TP implementations (Cisco and Microsoft) use incrementing
 145  * session_ids.  So we do a real hash on the session_id, rather than a
 146  * simple bitmask.
 147  */
 148 static inline struct hlist_head *
 149 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 150 {
 151         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 152 }
 153
 154 void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
 155 {
 156         sock_put(tunnel->sock);
 157         /* the tunnel is freed in the socket destructor */
 158 }
 159 EXPORT_SYMBOL(l2tp_tunnel_free);
 160
 161 /* Lookup a tunnel. A new reference is held on the returned tunnel. */
 162 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
 163 {
 164         const struct l2tp_net *pn = l2tp_pernet(net);
 165         struct l2tp_tunnel *tunnel;
 166
 167         rcu_read_lock_bh();
 168         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 169                 if (tunnel->tunnel_id == tunnel_id &&
 170                     refcount_inc_not_zero(&tunnel->ref_count)) {
 171                         rcu_read_unlock_bh();
 172
 173                         return tunnel;
 174                 }
 175         }
 176         rcu_read_unlock_bh();
 177
 178         return NULL;
 179 }
 180 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
 181
 182 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
 183 {
 184         const struct l2tp_net *pn = l2tp_pernet(net);
 185         struct l2tp_tunnel *tunnel;
 186         int count = 0;
 187
 188         rcu_read_lock_bh();
 189         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 190                 if (++count > nth &&
 191                     refcount_inc_not_zero(&tunnel->ref_count)) {
 192                         rcu_read_unlock_bh();
 193                         return tunnel;
 194                 }
 195         }
 196         rcu_read_unlock_bh();
 197
 198         return NULL;
 199 }
 200 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
 201
 202 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
 203                                              u32 session_id)
 204 {
 205         struct hlist_head *session_list;
 206         struct l2tp_session *session;
 207
 208         session_list = l2tp_session_id_hash(tunnel, session_id);
 209
 210         read_lock_bh(&tunnel->hlist_lock);
 211         hlist_for_each_entry(session, session_list, hlist)
 212                 if (session->session_id == session_id) {
 213                         l2tp_session_inc_refcount(session);
 214                         read_unlock_bh(&tunnel->hlist_lock);
 215
 216                         return session;
 217                 }
 218         read_unlock_bh(&tunnel->hlist_lock);
 219
 220         return NULL;
 221 }
 222 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
 223
 224 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
 225 {
 226         struct hlist_head *session_list;
 227         struct l2tp_session *session;
 228
 229         session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
 230
 231         rcu_read_lock_bh();
 232         hlist_for_each_entry_rcu(session, session_list, global_hlist)
 233                 if (session->session_id == session_id) {
 234                         l2tp_session_inc_refcount(session);
 235                         rcu_read_unlock_bh();
 236
 237                         return session;
 238                 }
 239         rcu_read_unlock_bh();
 240
 241         return NULL;
 242 }
 243 EXPORT_SYMBOL_GPL(l2tp_session_get);
 244
 245 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
 246 {
 247         int hash;
 248         struct l2tp_session *session;
 249         int count = 0;
 250
 251         read_lock_bh(&tunnel->hlist_lock);
 252         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 253                 hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
 254                         if (++count > nth) {
 255                                 l2tp_session_inc_refcount(session);
 256                                 read_unlock_bh(&tunnel->hlist_lock);
 257                                 return session;
 258                         }
 259                 }
 260         }
 261
 262         read_unlock_bh(&tunnel->hlist_lock);
 263
 264         return NULL;
 265 }
 266 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
 267
 268 /* Lookup a session by interface name.
 269  * This is very inefficient but is only used by management interfaces.
 270  */
 271 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
 272                                                 const char *ifname)
 273 {
 274         struct l2tp_net *pn = l2tp_pernet(net);
 275         int hash;
 276         struct l2tp_session *session;
 277
 278         rcu_read_lock_bh();
 279         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 280                 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
 281                         if (!strcmp(session->ifname, ifname)) {
 282                                 l2tp_session_inc_refcount(session);
 283                                 rcu_read_unlock_bh();
 284
 285                                 return session;
 286                         }
 287                 }
 288         }
 289
 290         rcu_read_unlock_bh();
 291
 292         return NULL;
 293 }
 294 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
 295
 296 int l2tp_session_register(struct l2tp_session *session,
 297                           struct l2tp_tunnel *tunnel)
 298 {
 299         struct l2tp_session *session_walk;
 300         struct hlist_head *g_head;
 301         struct hlist_head *head;
 302         struct l2tp_net *pn;
 303         int err;
 304
 305         head = l2tp_session_id_hash(tunnel, session->session_id);
 306
 307         write_lock_bh(&tunnel->hlist_lock);
 308         if (!tunnel->acpt_newsess) {
 309                 err = -ENODEV;
 310                 goto err_tlock;
 311         }
 312
 313         hlist_for_each_entry(session_walk, head, hlist)
 314                 if (session_walk->session_id == session->session_id) {
 315                         err = -EEXIST;
 316                         goto err_tlock;
 317                 }
 318
 319         if (tunnel->version == L2TP_HDR_VER_3) {
 320                 pn = l2tp_pernet(tunnel->l2tp_net);
 321                 g_head = l2tp_session_id_hash_2(pn, session->session_id);
 322
 323                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
 324
 325                 hlist_for_each_entry(session_walk, g_head, global_hlist)
 326                         if (session_walk->session_id == session->session_id) {
 327                                 err = -EEXIST;
 328                                 goto err_tlock_pnlock;
 329                         }
 330
 331                 l2tp_tunnel_inc_refcount(tunnel);
 332                 hlist_add_head_rcu(&session->global_hlist, g_head);
 333
 334                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 335         } else {
 336                 l2tp_tunnel_inc_refcount(tunnel);
 337         }
 338
 339         hlist_add_head(&session->hlist, head);
 340         write_unlock_bh(&tunnel->hlist_lock);
 341
 342         return 0;
 343
 344 err_tlock_pnlock:
 345         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 346 err_tlock:
 347         write_unlock_bh(&tunnel->hlist_lock);
 348
 349         return err;
 350 }
 351 EXPORT_SYMBOL_GPL(l2tp_session_register);
 352
 353 /*****************************************************************************
 354  * Receive data handling
 355  *****************************************************************************/
 356
 357 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 358  * number.
 359  */
 360 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 361 {
 362         struct sk_buff *skbp;
 363         struct sk_buff *tmp;
 364         u32 ns = L2TP_SKB_CB(skb)->ns;
 365
 366         spin_lock_bh(&session->reorder_q.lock);
 367         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 368                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 369                         __skb_queue_before(&session->reorder_q, skbp, skb);
 370                         l2tp_dbg(session, L2TP_MSG_SEQ,
 371                                  "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 372                                  session->name, ns, L2TP_SKB_CB(skbp)->ns,
 373                                  skb_queue_len(&session->reorder_q));
 374                         atomic_long_inc(&session->stats.rx_oos_packets);
 375                         goto out;
 376                 }
 377         }
 378
 379         __skb_queue_tail(&session->reorder_q, skb);
 380
 381 out:
 382         spin_unlock_bh(&session->reorder_q.lock);
 383 }
 384
 385 /* Dequeue a single skb.
 386  */
 387 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 388 {
 389         struct l2tp_tunnel *tunnel = session->tunnel;
 390         int length = L2TP_SKB_CB(skb)->length;
 391
 392         /* We're about to requeue the skb, so return resources
 393          * to its current owner (a socket receive buffer).
 394          */
 395         skb_orphan(skb);
 396
 397         atomic_long_inc(&tunnel->stats.rx_packets);
 398         atomic_long_add(length, &tunnel->stats.rx_bytes);
 399         atomic_long_inc(&session->stats.rx_packets);
 400         atomic_long_add(length, &session->stats.rx_bytes);
 401
 402         if (L2TP_SKB_CB(skb)->has_seq) {
 403                 /* Bump our Nr */
 404                 session->nr++;
 405                 session->nr &= session->nr_max;
 406
 407                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated nr to %hu\n",
 408                          session->name, session->nr);
 409         }
 410
 411         /* call private receive handler */
 412         if (session->recv_skb != NULL)
 413                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 414         else
 415                 kfree_skb(skb);
 416 }
 417
 418 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 419  * Skbs that have been in the queue for too long are simply discarded.
 420  */
 421 static void l2tp_recv_dequeue(struct l2tp_session *session)
 422 {
 423         struct sk_buff *skb;
 424         struct sk_buff *tmp;
 425
 426         /* If the pkt at the head of the queue has the nr that we
 427          * expect to send up next, dequeue it and any other
 428          * in-sequence packets behind it.
 429          */
 430 start:
 431         spin_lock_bh(&session->reorder_q.lock);
 432         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 433                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 434                         atomic_long_inc(&session->stats.rx_seq_discards);
 435                         atomic_long_inc(&session->stats.rx_errors);
 436                         l2tp_dbg(session, L2TP_MSG_SEQ,
 437                                  "%s: oos pkt %u len %d discarded (too old), waiting for %u, reorder_q_len=%d\n",
 438                                  session->name, L2TP_SKB_CB(skb)->ns,
 439                                  L2TP_SKB_CB(skb)->length, session->nr,
 440                                  skb_queue_len(&session->reorder_q));
 441                         session->reorder_skip = 1;
 442                         __skb_unlink(skb, &session->reorder_q);
 443                         kfree_skb(skb);
 444                         continue;
 445                 }
 446
 447                 if (L2TP_SKB_CB(skb)->has_seq) {
 448                         if (session->reorder_skip) {
 449                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 450                                          "%s: advancing nr to next pkt: %u -> %u",
 451                                          session->name, session->nr,
 452                                          L2TP_SKB_CB(skb)->ns);
 453                                 session->reorder_skip = 0;
 454                                 session->nr = L2TP_SKB_CB(skb)->ns;
 455                         }
 456                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 457                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 458                                          "%s: holding oos pkt %u len %d, waiting for %u, reorder_q_len=%d\n",
 459                                          session->name, L2TP_SKB_CB(skb)->ns,
 460                                          L2TP_SKB_CB(skb)->length, session->nr,
 461                                          skb_queue_len(&session->reorder_q));
 462                                 goto out;
 463                         }
 464                 }
 465                 __skb_unlink(skb, &session->reorder_q);
 466
 467                 /* Process the skb. We release the queue lock while we
 468                  * do so to let other contexts process the queue.
 469                  */
 470                 spin_unlock_bh(&session->reorder_q.lock);
 471                 l2tp_recv_dequeue_skb(session, skb);
 472                 goto start;
 473         }
 474
 475 out:
 476         spin_unlock_bh(&session->reorder_q.lock);
 477 }
 478
 479 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
 480 {
 481         u32 nws;
 482
 483         if (nr >= session->nr)
 484                 nws = nr - session->nr;
 485         else
 486                 nws = (session->nr_max + 1) - (session->nr - nr);
 487
 488         return nws < session->nr_window_size;
 489 }
 490
 491 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
 492  * acceptable, else non-zero.
 493  */
 494 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
 495 {
 496         if (!l2tp_seq_check_rx_window(session, L2TP_SKB_CB(skb)->ns)) {
 497                 /* Packet sequence number is outside allowed window.
 498                  * Discard it.
 499                  */
 500                 l2tp_dbg(session, L2TP_MSG_SEQ,
 501                          "%s: pkt %u len %d discarded, outside window, nr=%u\n",
 502                          session->name, L2TP_SKB_CB(skb)->ns,
 503                          L2TP_SKB_CB(skb)->length, session->nr);
 504                 goto discard;
 505         }
 506
 507         if (session->reorder_timeout != 0) {
 508                 /* Packet reordering enabled. Add skb to session's
 509                  * reorder queue, in order of ns.
 510                  */
 511                 l2tp_recv_queue_skb(session, skb);
 512                 goto out;
 513         }
 514
 515         /* Packet reordering disabled. Discard out-of-sequence packets, while
 516          * tracking the number if in-sequence packets after the first OOS packet
 517          * is seen. After nr_oos_count_max in-sequence packets, reset the
 518          * sequence number to re-enable packet reception.
 519          */
 520         if (L2TP_SKB_CB(skb)->ns == session->nr) {
 521                 skb_queue_tail(&session->reorder_q, skb);
 522         } else {
 523                 u32 nr_oos = L2TP_SKB_CB(skb)->ns;
 524                 u32 nr_next = (session->nr_oos + 1) & session->nr_max;
 525
 526                 if (nr_oos == nr_next)
 527                         session->nr_oos_count++;
 528                 else
 529                         session->nr_oos_count = 0;
 530
 531                 session->nr_oos = nr_oos;
 532                 if (session->nr_oos_count > session->nr_oos_count_max) {
 533                         session->reorder_skip = 1;
 534                         l2tp_dbg(session, L2TP_MSG_SEQ,
 535                                  "%s: %d oos packets received. Resetting sequence numbers\n",
 536                                  session->name, session->nr_oos_count);
 537                 }
 538                 if (!session->reorder_skip) {
 539                         atomic_long_inc(&session->stats.rx_seq_discards);
 540                         l2tp_dbg(session, L2TP_MSG_SEQ,
 541                                  "%s: oos pkt %u len %d discarded, waiting for %u, reorder_q_len=%d\n",
 542                                  session->name, L2TP_SKB_CB(skb)->ns,
 543                                  L2TP_SKB_CB(skb)->length, session->nr,
 544                                  skb_queue_len(&session->reorder_q));
 545                         goto discard;
 546                 }
 547                 skb_queue_tail(&session->reorder_q, skb);
 548         }
 549
 550 out:
 551         return 0;
 552
 553 discard:
 554         return 1;
 555 }
 556
 557 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 558  * and L2TPv3 data frames here.
 559  *
 560  * L2TPv2 Data Message Header
 561  *
 562  *  0                   1                   2                   3
 563  *  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
 564  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 565  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 566  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 567  * |           Tunnel ID           |           Session ID          |
 568  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 569  * |             Ns (opt)          |             Nr (opt)          |
 570  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 571  * |      Offset Size (opt)        |    Offset pad... (opt)
 572  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 573  *
 574  * Data frames are marked by T=0. All other fields are the same as
 575  * those in L2TP control frames.
 576  *
 577  * L2TPv3 Data Message Header
 578  *
 579  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 580  * |                      L2TP Session Header                      |
 581  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 582  * |                      L2-Specific Sublayer                     |
 583  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 584  * |                        Tunnel Payload                      ...
 585  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 586  *
 587  * L2TPv3 Session Header Over IP
 588  *
 589  *  0                   1                   2                   3
 590  *  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
 591  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 592  * |                           Session ID                          |
 593  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 594  * |               Cookie (optional, maximum 64 bits)...
 595  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 596  *                                                                 |
 597  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 598  *
 599  * L2TPv3 L2-Specific Sublayer Format
 600  *
 601  *  0                   1                   2                   3
 602  *  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
 603  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 604  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 605  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 606  *
 607  * Cookie value and sublayer format are negotiated with the peer when
 608  * the session is set up. Unlike L2TPv2, we do not need to parse the
 609  * packet header to determine if optional fields are present.
 610  *
 611  * Caller must already have parsed the frame and determined that it is
 612  * a data (not control) frame before coming here. Fields up to the
 613  * session-id have already been parsed and ptr points to the data
 614  * after the session-id.
 615  */
 616 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 617                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 618                       int length)
 619 {
 620         struct l2tp_tunnel *tunnel = session->tunnel;
 621         int offset;
 622         u32 ns, nr;
 623
 624         /* Parse and check optional cookie */
 625         if (session->peer_cookie_len > 0) {
 626                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 627                         l2tp_info(tunnel, L2TP_MSG_DATA,
 628                                   "%s: cookie mismatch (%u/%u). Discarding.\n",
 629                                   tunnel->name, tunnel->tunnel_id,
 630                                   session->session_id);
 631                         atomic_long_inc(&session->stats.rx_cookie_discards);
 632                         goto discard;
 633                 }
 634                 ptr += session->peer_cookie_len;
 635         }
 636
 637         /* Handle the optional sequence numbers. Sequence numbers are
 638          * in different places for L2TPv2 and L2TPv3.
 639          *
 640          * If we are the LAC, enable/disable sequence numbers under
 641          * the control of the LNS.  If no sequence numbers present but
 642          * we were expecting them, discard frame.
 643          */
 644         ns = nr = 0;
 645         L2TP_SKB_CB(skb)->has_seq = 0;
 646         if (tunnel->version == L2TP_HDR_VER_2) {
 647                 if (hdrflags & L2TP_HDRFLAG_S) {
 648                         ns = ntohs(*(__be16 *) ptr);
 649                         ptr += 2;
 650                         nr = ntohs(*(__be16 *) ptr);
 651                         ptr += 2;
 652
 653                         /* Store L2TP info in the skb */
 654                         L2TP_SKB_CB(skb)->ns = ns;
 655                         L2TP_SKB_CB(skb)->has_seq = 1;
 656
 657                         l2tp_dbg(session, L2TP_MSG_SEQ,
 658                                  "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 659                                  session->name, ns, nr, session->nr);
 660                 }
 661         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 662                 u32 l2h = ntohl(*(__be32 *) ptr);
 663
 664                 if (l2h & 0x40000000) {
 665                         ns = l2h & 0x00ffffff;
 666
 667                         /* Store L2TP info in the skb */
 668                         L2TP_SKB_CB(skb)->ns = ns;
 669                         L2TP_SKB_CB(skb)->has_seq = 1;
 670
 671                         l2tp_dbg(session, L2TP_MSG_SEQ,
 672                                  "%s: recv data ns=%u, session nr=%u\n",
 673                                  session->name, ns, session->nr);
 674                 }
 675                 ptr += 4;
 676         }
 677
 678         if (L2TP_SKB_CB(skb)->has_seq) {
 679                 /* Received a packet with sequence numbers. If we're the LNS,
 680                  * check if we sre sending sequence numbers and if not,
 681                  * configure it so.
 682                  */
 683                 if ((!session->lns_mode) && (!session->send_seq)) {
 684                         l2tp_info(session, L2TP_MSG_SEQ,
 685                                   "%s: requested to enable seq numbers by LNS\n",
 686                                   session->name);
 687                         session->send_seq = 1;
 688                         l2tp_session_set_header_len(session, tunnel->version);
 689                 }
 690         } else {
 691                 /* No sequence numbers.
 692                  * If user has configured mandatory sequence numbers, discard.
 693                  */
 694                 if (session->recv_seq) {
 695                         l2tp_warn(session, L2TP_MSG_SEQ,
 696                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 697                                   session->name);
 698                         atomic_long_inc(&session->stats.rx_seq_discards);
 699                         goto discard;
 700                 }
 701
 702                 /* If we're the LAC and we're sending sequence numbers, the
 703                  * LNS has requested that we no longer send sequence numbers.
 704                  * If we're the LNS and we're sending sequence numbers, the
 705                  * LAC is broken. Discard the frame.
 706                  */
 707                 if ((!session->lns_mode) && (session->send_seq)) {
 708                         l2tp_info(session, L2TP_MSG_SEQ,
 709                                   "%s: requested to disable seq numbers by LNS\n",
 710                                   session->name);
 711                         session->send_seq = 0;
 712                         l2tp_session_set_header_len(session, tunnel->version);
 713                 } else if (session->send_seq) {
 714                         l2tp_warn(session, L2TP_MSG_SEQ,
 715                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 716                                   session->name);
 717                         atomic_long_inc(&session->stats.rx_seq_discards);
 718                         goto discard;
 719                 }
 720         }
 721
 722         /* Session data offset is defined only for L2TPv2 and is
 723          * indicated by an optional 16-bit value in the header.
 724          */
 725         if (tunnel->version == L2TP_HDR_VER_2) {
 726                 /* If offset bit set, skip it. */
 727                 if (hdrflags & L2TP_HDRFLAG_O) {
 728                         offset = ntohs(*(__be16 *)ptr);
 729                         ptr += 2 + offset;
 730                 }
 731         }
 732
 733         offset = ptr - optr;
 734         if (!pskb_may_pull(skb, offset))
 735                 goto discard;
 736
 737         __skb_pull(skb, offset);
 738
 739         /* Prepare skb for adding to the session's reorder_q.  Hold
 740          * packets for max reorder_timeout or 1 second if not
 741          * reordering.
 742          */
 743         L2TP_SKB_CB(skb)->length = length;
 744         L2TP_SKB_CB(skb)->expires = jiffies +
 745                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 746
 747         /* Add packet to the session's receive queue. Reordering is done here, if
 748          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 749          */
 750         if (L2TP_SKB_CB(skb)->has_seq) {
 751                 if (l2tp_recv_data_seq(session, skb))
 752                         goto discard;
 753         } else {
 754                 /* No sequence numbers. Add the skb to the tail of the
 755                  * reorder queue. This ensures that it will be
 756                  * delivered after all previous sequenced skbs.
 757                  */
 758                 skb_queue_tail(&session->reorder_q, skb);
 759         }
 760
 761         /* Try to dequeue as many skbs from reorder_q as we can. */
 762         l2tp_recv_dequeue(session);
 763
 764         return;
 765
 766 discard:
 767         atomic_long_inc(&session->stats.rx_errors);
 768         kfree_skb(skb);
 769 }
 770 EXPORT_SYMBOL(l2tp_recv_common);
 771
 772 /* Drop skbs from the session's reorder_q
 773  */
 774 static int l2tp_session_queue_purge(struct l2tp_session *session)
 775 {
 776         struct sk_buff *skb = NULL;
 777         BUG_ON(!session);
 778         BUG_ON(session->magic != L2TP_SESSION_MAGIC);
 779         while ((skb = skb_dequeue(&session->reorder_q))) {
 780                 atomic_long_inc(&session->stats.rx_errors);
 781                 kfree_skb(skb);
 782         }
 783         return 0;
 784 }
 785
 786 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 787  * here. The skb is not on a list when we get here.
 788  * Returns 0 if the packet was a data packet and was successfully passed on.
 789  * Returns 1 if the packet was not a good data packet and could not be
 790  * forwarded.  All such packets are passed up to userspace to deal with.
 791  */
 792 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 793 {
 794         struct l2tp_session *session = NULL;
 795         unsigned char *ptr, *optr;
 796         u16 hdrflags;
 797         u32 tunnel_id, session_id;
 798         u16 version;
 799         int length;
 800
 801         /* UDP has verifed checksum */
 802
 803         /* UDP always verifies the packet length. */
 804         __skb_pull(skb, sizeof(struct udphdr));
 805
 806         /* Short packet? */
 807         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
 808                 l2tp_info(tunnel, L2TP_MSG_DATA,
 809                           "%s: recv short packet (len=%d)\n",
 810                           tunnel->name, skb->len);
 811                 goto error;
 812         }
 813
 814         /* Trace packet contents, if enabled */
 815         if (tunnel->debug & L2TP_MSG_DATA) {
 816                 length = min(32u, skb->len);
 817                 if (!pskb_may_pull(skb, length))
 818                         goto error;
 819
 820                 pr_debug("%s: recv\n", tunnel->name);
 821                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 822         }
 823
 824         /* Point to L2TP header */
 825         optr = ptr = skb->data;
 826
 827         /* Get L2TP header flags */
 828         hdrflags = ntohs(*(__be16 *) ptr);
 829
 830         /* Check protocol version */
 831         version = hdrflags & L2TP_HDR_VER_MASK;
 832         if (version != tunnel->version) {
 833                 l2tp_info(tunnel, L2TP_MSG_DATA,
 834                           "%s: recv protocol version mismatch: got %d expected %d\n",
 835                           tunnel->name, version, tunnel->version);
 836                 goto error;
 837         }
 838
 839         /* Get length of L2TP packet */
 840         length = skb->len;
 841
 842         /* If type is control packet, it is handled by userspace. */
 843         if (hdrflags & L2TP_HDRFLAG_T) {
 844                 l2tp_dbg(tunnel, L2TP_MSG_DATA,
 845                          "%s: recv control packet, len=%d\n",
 846                          tunnel->name, length);
 847                 goto error;
 848         }
 849
 850         /* Skip flags */
 851         ptr += 2;
 852
 853         if (tunnel->version == L2TP_HDR_VER_2) {
 854                 /* If length is present, skip it */
 855                 if (hdrflags & L2TP_HDRFLAG_L)
 856                         ptr += 2;
 857
 858                 /* Extract tunnel and session ID */
 859                 tunnel_id = ntohs(*(__be16 *) ptr);
 860                 ptr += 2;
 861                 session_id = ntohs(*(__be16 *) ptr);
 862                 ptr += 2;
 863         } else {
 864                 ptr += 2;       /* skip reserved bits */
 865                 tunnel_id = tunnel->tunnel_id;
 866                 session_id = ntohl(*(__be32 *) ptr);
 867                 ptr += 4;
 868         }
 869
 870         /* Find the session context */
 871         session = l2tp_tunnel_get_session(tunnel, session_id);
 872         if (!session || !session->recv_skb) {
 873                 if (session)
 874                         l2tp_session_dec_refcount(session);
 875
 876                 /* Not found? Pass to userspace to deal with */
 877                 l2tp_info(tunnel, L2TP_MSG_DATA,
 878                           "%s: no session found (%u/%u). Passing up.\n",
 879                           tunnel->name, tunnel_id, session_id);
 880                 goto error;
 881         }
 882
 883         if (tunnel->version == L2TP_HDR_VER_3 &&
 884             l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
 885                 goto error;
 886
 887         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
 888         l2tp_session_dec_refcount(session);
 889
 890         return 0;
 891
 892 error:
 893         /* Put UDP header back */
 894         __skb_push(skb, sizeof(struct udphdr));
 895
 896         return 1;
 897 }
 898
 899 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 900  * Return codes:
 901  * 0 : success.
 902  * <0: error
 903  * >0: skb should be passed up to userspace as UDP.
 904  */
 905 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 906 {
 907         struct l2tp_tunnel *tunnel;
 908
 909         tunnel = rcu_dereference_sk_user_data(sk);
 910         if (tunnel == NULL)
 911                 goto pass_up;
 912
 913         l2tp_dbg(tunnel, L2TP_MSG_DATA, "%s: received %d bytes\n",
 914                  tunnel->name, skb->len);
 915
 916         if (l2tp_udp_recv_core(tunnel, skb))
 917                 goto pass_up;
 918
 919         return 0;
 920
 921 pass_up:
 922         return 1;
 923 }
 924 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 925
 926 /************************************************************************
 927  * Transmit handling
 928  ***********************************************************************/
 929
 930 /* Build an L2TP header for the session into the buffer provided.
 931  */
 932 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 933 {
 934         struct l2tp_tunnel *tunnel = session->tunnel;
 935         __be16 *bufp = buf;
 936         __be16 *optr = buf;
 937         u16 flags = L2TP_HDR_VER_2;
 938         u32 tunnel_id = tunnel->peer_tunnel_id;
 939         u32 session_id = session->peer_session_id;
 940
 941         if (session->send_seq)
 942                 flags |= L2TP_HDRFLAG_S;
 943
 944         /* Setup L2TP header. */
 945         *bufp++ = htons(flags);
 946         *bufp++ = htons(tunnel_id);
 947         *bufp++ = htons(session_id);
 948         if (session->send_seq) {
 949                 *bufp++ = htons(session->ns);
 950                 *bufp++ = 0;
 951                 session->ns++;
 952                 session->ns &= 0xffff;
 953                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated ns to %u\n",
 954                          session->name, session->ns);
 955         }
 956
 957         return bufp - optr;
 958 }
 959
 960 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 961 {
 962         struct l2tp_tunnel *tunnel = session->tunnel;
 963         char *bufp = buf;
 964         char *optr = bufp;
 965
 966         /* Setup L2TP header. The header differs slightly for UDP and
 967          * IP encapsulations. For UDP, there is 4 bytes of flags.
 968          */
 969         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 970                 u16 flags = L2TP_HDR_VER_3;
 971                 *((__be16 *) bufp) = htons(flags);
 972                 bufp += 2;
 973                 *((__be16 *) bufp) = 0;
 974                 bufp += 2;
 975         }
 976
 977         *((__be32 *) bufp) = htonl(session->peer_session_id);
 978         bufp += 4;
 979         if (session->cookie_len) {
 980                 memcpy(bufp, &session->cookie[0], session->cookie_len);
 981                 bufp += session->cookie_len;
 982         }
 983         if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 984                 u32 l2h = 0;
 985
 986                 if (session->send_seq) {
 987                         l2h = 0x40000000 | session->ns;
 988                         session->ns++;
 989                         session->ns &= 0xffffff;
 990                         l2tp_dbg(session, L2TP_MSG_SEQ,
 991                                  "%s: updated ns to %u\n",
 992                                  session->name, session->ns);
 993                 }
 994
 995                 *((__be32 *)bufp) = htonl(l2h);
 996                 bufp += 4;
 997         }
 998
 999         return bufp - optr;
1000 }
1001
1002 static void l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
1003                            struct flowi *fl, size_t data_len)
1004 {
1005         struct l2tp_tunnel *tunnel = session->tunnel;
1006         unsigned int len = skb->len;
1007         int error;
1008
1009         /* Debug */
1010         if (session->send_seq)
1011                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %zd bytes, ns=%u\n",
1012                          session->name, data_len, session->ns - 1);
1013         else
1014                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %zd bytes\n",
1015                          session->name, data_len);
1016
1017         if (session->debug & L2TP_MSG_DATA) {
1018                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1019                 unsigned char *datap = skb->data + uhlen;
1020
1021                 pr_debug("%s: xmit\n", session->name);
1022                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET,
1023                                      datap, min_t(size_t, 32, len - uhlen));
1024         }
1025
1026         /* Queue the packet to IP for output */
1027         skb->ignore_df = 1;
1028 #if IS_ENABLED(CONFIG_IPV6)
1029         if (l2tp_sk_is_v6(tunnel->sock))
1030                 error = inet6_csk_xmit(tunnel->sock, skb, NULL);
1031         else
1032 #endif
1033                 error = ip_queue_xmit(tunnel->sock, skb, fl);
1034
1035         /* Update stats */
1036         if (error >= 0) {
1037                 atomic_long_inc(&tunnel->stats.tx_packets);
1038                 atomic_long_add(len, &tunnel->stats.tx_bytes);
1039                 atomic_long_inc(&session->stats.tx_packets);
1040                 atomic_long_add(len, &session->stats.tx_bytes);
1041         } else {
1042                 atomic_long_inc(&tunnel->stats.tx_errors);
1043                 atomic_long_inc(&session->stats.tx_errors);
1044         }
1045 }
1046
1047 /* If caller requires the skb to have a ppp header, the header must be
1048  * inserted in the skb data before calling this function.
1049  */
1050 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1051 {
1052         int data_len = skb->len;
1053         struct l2tp_tunnel *tunnel = session->tunnel;
1054         struct sock *sk = tunnel->sock;
1055         struct flowi *fl;
1056         struct udphdr *uh;
1057         struct inet_sock *inet;
1058         int headroom;
1059         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1060         int udp_len;
1061         int ret = NET_XMIT_SUCCESS;
1062
1063         /* Check that there's enough headroom in the skb to insert IP,
1064          * UDP and L2TP headers. If not enough, expand it to
1065          * make room. Adjust truesize.
1066          */
1067         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1068                 uhlen + hdr_len;
1069         if (skb_cow_head(skb, headroom)) {
1070                 kfree_skb(skb);
1071                 return NET_XMIT_DROP;
1072         }
1073
1074         /* Setup L2TP header */
1075         session->build_header(session, __skb_push(skb, hdr_len));
1076
1077         /* Reset skb netfilter state */
1078         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1079         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1080                               IPSKB_REROUTED);
1081         nf_reset_ct(skb);
1082
1083         bh_lock_sock(sk);
1084         if (sock_owned_by_user(sk)) {
1085                 kfree_skb(skb);
1086                 ret = NET_XMIT_DROP;
1087                 goto out_unlock;
1088         }
1089
1090         /* The user-space may change the connection status for the user-space
1091          * provided socket at run time: we must check it under the socket lock
1092          */
1093         if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
1094                 kfree_skb(skb);
1095                 ret = NET_XMIT_DROP;
1096                 goto out_unlock;
1097         }
1098
1099         /* Get routing info from the tunnel socket */
1100         skb_dst_drop(skb);
1101         skb_dst_set(skb, sk_dst_check(sk, 0));
1102
1103         inet = inet_sk(sk);
1104         fl = &inet->cork.fl;
1105         switch (tunnel->encap) {
1106         case L2TP_ENCAPTYPE_UDP:
1107                 /* Setup UDP header */
1108                 __skb_push(skb, sizeof(*uh));
1109                 skb_reset_transport_header(skb);
1110                 uh = udp_hdr(skb);
1111                 uh->source = inet->inet_sport;
1112                 uh->dest = inet->inet_dport;
1113                 udp_len = uhlen + hdr_len + data_len;
1114                 uh->len = htons(udp_len);
1115
1116                 /* Calculate UDP checksum if configured to do so */
1117 #if IS_ENABLED(CONFIG_IPV6)
1118                 if (l2tp_sk_is_v6(sk))
1119                         udp6_set_csum(udp_get_no_check6_tx(sk),
1120                                       skb, &inet6_sk(sk)->saddr,
1121                                       &sk->sk_v6_daddr, udp_len);
1122                 else
1123 #endif
1124                 udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
1125                              inet->inet_daddr, udp_len);
1126                 break;
1127
1128         case L2TP_ENCAPTYPE_IP:
1129                 break;
1130         }
1131
1132         l2tp_xmit_core(session, skb, fl, data_len);
1133 out_unlock:
1134         bh_unlock_sock(sk);
1135
1136         return ret;
1137 }
1138 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1139
1140 /*****************************************************************************
1141  * Tinnel and session create/destroy.
1142  *****************************************************************************/
1143
1144 /* Tunnel socket destruct hook.
1145  * The tunnel context is deleted only when all session sockets have been
1146  * closed.
1147  */
1148 static void l2tp_tunnel_destruct(struct sock *sk)
1149 {
1150         struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
1151
1152         if (tunnel == NULL)
1153                 goto end;
1154
1155         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing...\n", tunnel->name);
1156
1157         /* Disable udp encapsulation */
1158         switch (tunnel->encap) {
1159         case L2TP_ENCAPTYPE_UDP:
1160                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1161                 (udp_sk(sk))->encap_type = 0;
1162                 (udp_sk(sk))->encap_rcv = NULL;
1163                 (udp_sk(sk))->encap_destroy = NULL;
1164                 break;
1165         case L2TP_ENCAPTYPE_IP:
1166                 break;
1167         }
1168
1169         /* Remove hooks into tunnel socket */
1170         sk->sk_destruct = tunnel->old_sk_destruct;
1171         sk->sk_user_data = NULL;
1172
1173         /* Call the original destructor */
1174         if (sk->sk_destruct)
1175                 (*sk->sk_destruct)(sk);
1176
1177         kfree_rcu(tunnel, rcu);
1178 end:
1179         return;
1180 }
1181
1182 /* When the tunnel is closed, all the attached sessions need to go too.
1183  */
1184 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1185 {
1186         int hash;
1187         struct hlist_node *walk;
1188         struct hlist_node *tmp;
1189         struct l2tp_session *session;
1190
1191         BUG_ON(tunnel == NULL);
1192
1193         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing all sessions...\n",
1194                   tunnel->name);
1195
1196         write_lock_bh(&tunnel->hlist_lock);
1197         tunnel->acpt_newsess = false;
1198         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1199 again:
1200                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1201                         session = hlist_entry(walk, struct l2tp_session, hlist);
1202
1203                         l2tp_info(session, L2TP_MSG_CONTROL,
1204                                   "%s: closing session\n", session->name);
1205
1206                         hlist_del_init(&session->hlist);
1207
1208                         if (test_and_set_bit(0, &session->dead))
1209                                 goto again;
1210
1211                         write_unlock_bh(&tunnel->hlist_lock);
1212
1213                         __l2tp_session_unhash(session);
1214                         l2tp_session_queue_purge(session);
1215
1216                         if (session->session_close != NULL)
1217                                 (*session->session_close)(session);
1218
1219                         l2tp_session_dec_refcount(session);
1220
1221                         write_lock_bh(&tunnel->hlist_lock);
1222
1223                         /* Now restart from the beginning of this hash
1224                          * chain.  We always remove a session from the
1225                          * list so we are guaranteed to make forward
1226                          * progress.
1227                          */
1228                         goto again;
1229                 }
1230         }
1231         write_unlock_bh(&tunnel->hlist_lock);
1232 }
1233
1234 /* Tunnel socket destroy hook for UDP encapsulation */
1235 static void l2tp_udp_encap_destroy(struct sock *sk)
1236 {
1237         struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
1238
1239         if (tunnel)
1240                 l2tp_tunnel_delete(tunnel);
1241 }
1242
1243 /* Workqueue tunnel deletion function */
1244 static void l2tp_tunnel_del_work(struct work_struct *work)
1245 {
1246         struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
1247                                                   del_work);
1248         struct sock *sk = tunnel->sock;
1249         struct socket *sock = sk->sk_socket;
1250         struct l2tp_net *pn;
1251
1252         l2tp_tunnel_closeall(tunnel);
1253
1254         /* If the tunnel socket was created within the kernel, use
1255          * the sk API to release it here.
1256          */
1257         if (tunnel->fd < 0) {
1258                 if (sock) {
1259                         kernel_sock_shutdown(sock, SHUT_RDWR);
1260                         sock_release(sock);
1261                 }
1262         }
1263
1264         /* Remove the tunnel struct from the tunnel list */
1265         pn = l2tp_pernet(tunnel->l2tp_net);
1266         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1267         list_del_rcu(&tunnel->list);
1268         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1269
1270         /* drop initial ref */
1271         l2tp_tunnel_dec_refcount(tunnel);
1272
1273         /* drop workqueue ref */
1274         l2tp_tunnel_dec_refcount(tunnel);
1275 }
1276
1277 /* Create a socket for the tunnel, if one isn't set up by
1278  * userspace. This is used for static tunnels where there is no
1279  * managing L2TP daemon.
1280  *
1281  * Since we don't want these sockets to keep a namespace alive by
1282  * themselves, we drop the socket's namespace refcount after creation.
1283  * These sockets are freed when the namespace exits using the pernet
1284  * exit hook.
1285  */
1286 static int l2tp_tunnel_sock_create(struct net *net,
1287                                 u32 tunnel_id,
1288                                 u32 peer_tunnel_id,
1289                                 struct l2tp_tunnel_cfg *cfg,
1290                                 struct socket **sockp)
1291 {
1292         int err = -EINVAL;
1293         struct socket *sock = NULL;
1294         struct udp_port_cfg udp_conf;
1295
1296         switch (cfg->encap) {
1297         case L2TP_ENCAPTYPE_UDP:
1298                 memset(&udp_conf, 0, sizeof(udp_conf));
1299
1300 #if IS_ENABLED(CONFIG_IPV6)
1301                 if (cfg->local_ip6 && cfg->peer_ip6) {
1302                         udp_conf.family = AF_INET6;
1303                         memcpy(&udp_conf.local_ip6, cfg->local_ip6,
1304                                sizeof(udp_conf.local_ip6));
1305                         memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
1306                                sizeof(udp_conf.peer_ip6));
1307                         udp_conf.use_udp6_tx_checksums =
1308                           ! cfg->udp6_zero_tx_checksums;
1309                         udp_conf.use_udp6_rx_checksums =
1310                           ! cfg->udp6_zero_rx_checksums;
1311                 } else
1312 #endif
1313                 {
1314                         udp_conf.family = AF_INET;
1315                         udp_conf.local_ip = cfg->local_ip;
1316                         udp_conf.peer_ip = cfg->peer_ip;
1317                         udp_conf.use_udp_checksums = cfg->use_udp_checksums;
1318                 }
1319
1320                 udp_conf.local_udp_port = htons(cfg->local_udp_port);
1321                 udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
1322
1323                 err = udp_sock_create(net, &udp_conf, &sock);
1324                 if (err < 0)
1325                         goto out;
1326
1327                 break;
1328
1329         case L2TP_ENCAPTYPE_IP:
1330 #if IS_ENABLED(CONFIG_IPV6)
1331                 if (cfg->local_ip6 && cfg->peer_ip6) {
1332                         struct sockaddr_l2tpip6 ip6_addr = {0};
1333
1334                         err = sock_create_kern(net, AF_INET6, SOCK_DGRAM,
1335                                           IPPROTO_L2TP, &sock);
1336                         if (err < 0)
1337                                 goto out;
1338
1339                         ip6_addr.l2tp_family = AF_INET6;
1340                         memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1341                                sizeof(ip6_addr.l2tp_addr));
1342                         ip6_addr.l2tp_conn_id = tunnel_id;
1343                         err = kernel_bind(sock, (struct sockaddr *) &ip6_addr,
1344                                           sizeof(ip6_addr));
1345                         if (err < 0)
1346                                 goto out;
1347
1348                         ip6_addr.l2tp_family = AF_INET6;
1349                         memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1350                                sizeof(ip6_addr.l2tp_addr));
1351                         ip6_addr.l2tp_conn_id = peer_tunnel_id;
1352                         err = kernel_connect(sock,
1353                                              (struct sockaddr *) &ip6_addr,
1354                                              sizeof(ip6_addr), 0);
1355                         if (err < 0)
1356                                 goto out;
1357                 } else
1358 #endif
1359                 {
1360                         struct sockaddr_l2tpip ip_addr = {0};
1361
1362                         err = sock_create_kern(net, AF_INET, SOCK_DGRAM,
1363                                           IPPROTO_L2TP, &sock);
1364                         if (err < 0)
1365                                 goto out;
1366
1367                         ip_addr.l2tp_family = AF_INET;
1368                         ip_addr.l2tp_addr = cfg->local_ip;
1369                         ip_addr.l2tp_conn_id = tunnel_id;
1370                         err = kernel_bind(sock, (struct sockaddr *) &ip_addr,
1371                                           sizeof(ip_addr));
1372                         if (err < 0)
1373                                 goto out;
1374
1375                         ip_addr.l2tp_family = AF_INET;
1376                         ip_addr.l2tp_addr = cfg->peer_ip;
1377                         ip_addr.l2tp_conn_id = peer_tunnel_id;
1378                         err = kernel_connect(sock, (struct sockaddr *) &ip_addr,
1379                                              sizeof(ip_addr), 0);
1380                         if (err < 0)
1381                                 goto out;
1382                 }
1383                 break;
1384
1385         default:
1386                 goto out;
1387         }
1388
1389 out:
1390         *sockp = sock;
1391         if ((err < 0) && sock) {
1392                 kernel_sock_shutdown(sock, SHUT_RDWR);
1393                 sock_release(sock);
1394                 *sockp = NULL;
1395         }
1396
1397         return err;
1398 }
1399
1400 static struct lock_class_key l2tp_socket_class;
1401
1402 int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
1403 {
1404         struct l2tp_tunnel *tunnel = NULL;
1405         int err;
1406         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1407
1408         if (cfg != NULL)
1409                 encap = cfg->encap;
1410
1411         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1412         if (tunnel == NULL) {
1413                 err = -ENOMEM;
1414                 goto err;
1415         }
1416
1417         tunnel->version = version;
1418         tunnel->tunnel_id = tunnel_id;
1419         tunnel->peer_tunnel_id = peer_tunnel_id;
1420         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1421
1422         tunnel->magic = L2TP_TUNNEL_MAGIC;
1423         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1424         rwlock_init(&tunnel->hlist_lock);
1425         tunnel->acpt_newsess = true;
1426
1427         if (cfg != NULL)
1428                 tunnel->debug = cfg->debug;
1429
1430         tunnel->encap = encap;
1431
1432         refcount_set(&tunnel->ref_count, 1);
1433         tunnel->fd = fd;
1434
1435         /* Init delete workqueue struct */
1436         INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1437
1438         INIT_LIST_HEAD(&tunnel->list);
1439
1440         err = 0;
1441 err:
1442         if (tunnelp)
1443                 *tunnelp = tunnel;
1444
1445         return err;
1446 }
1447 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1448
1449 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
1450                                 enum l2tp_encap_type encap)
1451 {
1452         if (!net_eq(sock_net(sk), net))
1453                 return -EINVAL;
1454
1455         if (sk->sk_type != SOCK_DGRAM)
1456                 return -EPROTONOSUPPORT;
1457
1458         if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
1459             (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
1460                 return -EPROTONOSUPPORT;
1461
1462         if (sk->sk_user_data)
1463                 return -EBUSY;
1464
1465         return 0;
1466 }
1467
1468 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
1469                          struct l2tp_tunnel_cfg *cfg)
1470 {
1471         struct l2tp_tunnel *tunnel_walk;
1472         struct l2tp_net *pn;
1473         struct socket *sock;
1474         struct sock *sk;
1475         int ret;
1476
1477         if (tunnel->fd < 0) {
1478                 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
1479                                               tunnel->peer_tunnel_id, cfg,
1480                                               &sock);
1481                 if (ret < 0)
1482                         goto err;
1483         } else {
1484                 sock = sockfd_lookup(tunnel->fd, &ret);
1485                 if (!sock)
1486                         goto err;
1487
1488                 ret = l2tp_validate_socket(sock->sk, net, tunnel->encap);
1489                 if (ret < 0)
1490                         goto err_sock;
1491         }
1492
1493         tunnel->l2tp_net = net;
1494         pn = l2tp_pernet(net);
1495
1496         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1497         list_for_each_entry(tunnel_walk, &pn->l2tp_tunnel_list, list) {
1498                 if (tunnel_walk->tunnel_id == tunnel->tunnel_id) {
1499                         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1500
1501                         ret = -EEXIST;
1502                         goto err_sock;
1503                 }
1504         }
1505         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1506         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1507
1508         sk = sock->sk;
1509         sock_hold(sk);
1510         tunnel->sock = sk;
1511
1512         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1513                 struct udp_tunnel_sock_cfg udp_cfg = {
1514                         .sk_user_data = tunnel,
1515                         .encap_type = UDP_ENCAP_L2TPINUDP,
1516                         .encap_rcv = l2tp_udp_encap_recv,
1517                         .encap_destroy = l2tp_udp_encap_destroy,
1518                 };
1519
1520                 setup_udp_tunnel_sock(net, sock, &udp_cfg);
1521         } else {
1522                 sk->sk_user_data = tunnel;
1523         }
1524
1525         tunnel->old_sk_destruct = sk->sk_destruct;
1526         sk->sk_destruct = &l2tp_tunnel_destruct;
1527         lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class,
1528                                    "l2tp_sock");
1529         sk->sk_allocation = GFP_ATOMIC;
1530
1531         if (tunnel->fd >= 0)
1532                 sockfd_put(sock);
1533
1534         return 0;
1535
1536 err_sock:
1537         if (tunnel->fd < 0)
1538                 sock_release(sock);
1539         else
1540                 sockfd_put(sock);
1541 err:
1542         return ret;
1543 }
1544 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
1545
1546 /* This function is used by the netlink TUNNEL_DELETE command.
1547  */
1548 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1549 {
1550         if (!test_and_set_bit(0, &tunnel->dead)) {
1551                 l2tp_tunnel_inc_refcount(tunnel);
1552                 queue_work(l2tp_wq, &tunnel->del_work);
1553         }
1554 }
1555 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1556
1557 /* Really kill the session.
1558  */
1559 void l2tp_session_free(struct l2tp_session *session)
1560 {
1561         struct l2tp_tunnel *tunnel = session->tunnel;
1562
1563         BUG_ON(refcount_read(&session->ref_count) != 0);
1564
1565         if (tunnel) {
1566                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1567                 l2tp_tunnel_dec_refcount(tunnel);
1568         }
1569
1570         kfree(session);
1571 }
1572 EXPORT_SYMBOL_GPL(l2tp_session_free);
1573
1574 /* Remove an l2tp session from l2tp_core's hash lists.
1575  * Provides a tidyup interface for pseudowire code which can't just route all
1576  * shutdown via. l2tp_session_delete and a pseudowire-specific session_close
1577  * callback.
1578  */
1579 void __l2tp_session_unhash(struct l2tp_session *session)
1580 {
1581         struct l2tp_tunnel *tunnel = session->tunnel;
1582
1583         /* Remove the session from core hashes */
1584         if (tunnel) {
1585                 /* Remove from the per-tunnel hash */
1586                 write_lock_bh(&tunnel->hlist_lock);
1587                 hlist_del_init(&session->hlist);
1588                 write_unlock_bh(&tunnel->hlist_lock);
1589
1590                 /* For L2TPv3 we have a per-net hash: remove from there, too */
1591                 if (tunnel->version != L2TP_HDR_VER_2) {
1592                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1593                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1594                         hlist_del_init_rcu(&session->global_hlist);
1595                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1596                         synchronize_rcu();
1597                 }
1598         }
1599 }
1600 EXPORT_SYMBOL_GPL(__l2tp_session_unhash);
1601
1602 /* This function is used by the netlink SESSION_DELETE command and by
1603    pseudowire modules.
1604  */
1605 int l2tp_session_delete(struct l2tp_session *session)
1606 {
1607         if (test_and_set_bit(0, &session->dead))
1608                 return 0;
1609
1610         __l2tp_session_unhash(session);
1611         l2tp_session_queue_purge(session);
1612         if (session->session_close != NULL)
1613                 (*session->session_close)(session);
1614
1615         l2tp_session_dec_refcount(session);
1616
1617         return 0;
1618 }
1619 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1620
1621 /* We come here whenever a session's send_seq, cookie_len or
1622  * l2specific_type parameters are set.
1623  */
1624 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1625 {
1626         if (version == L2TP_HDR_VER_2) {
1627                 session->hdr_len = 6;
1628                 if (session->send_seq)
1629                         session->hdr_len += 4;
1630         } else {
1631                 session->hdr_len = 4 + session->cookie_len;
1632                 session->hdr_len += l2tp_get_l2specific_len(session);
1633                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1634                         session->hdr_len += 4;
1635         }
1636
1637 }
1638 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1639
1640 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
1641 {
1642         struct l2tp_session *session;
1643
1644         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1645         if (session != NULL) {
1646                 session->magic = L2TP_SESSION_MAGIC;
1647                 session->tunnel = tunnel;
1648
1649                 session->session_id = session_id;
1650                 session->peer_session_id = peer_session_id;
1651                 session->nr = 0;
1652                 if (tunnel->version == L2TP_HDR_VER_2)
1653                         session->nr_max = 0xffff;
1654                 else
1655                         session->nr_max = 0xffffff;
1656                 session->nr_window_size = session->nr_max / 2;
1657                 session->nr_oos_count_max = 4;
1658
1659                 /* Use NR of first received packet */
1660                 session->reorder_skip = 1;
1661
1662                 sprintf(&session->name[0], "sess %u/%u",
1663                         tunnel->tunnel_id, session->session_id);
1664
1665                 skb_queue_head_init(&session->reorder_q);
1666
1667                 INIT_HLIST_NODE(&session->hlist);
1668                 INIT_HLIST_NODE(&session->global_hlist);
1669
1670                 /* Inherit debug options from tunnel */
1671                 session->debug = tunnel->debug;
1672
1673                 if (cfg) {
1674                         session->pwtype = cfg->pw_type;
1675                         session->debug = cfg->debug;
1676                         session->send_seq = cfg->send_seq;
1677                         session->recv_seq = cfg->recv_seq;
1678                         session->lns_mode = cfg->lns_mode;
1679                         session->reorder_timeout = cfg->reorder_timeout;
1680                         session->l2specific_type = cfg->l2specific_type;
1681                         session->cookie_len = cfg->cookie_len;
1682                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1683                         session->peer_cookie_len = cfg->peer_cookie_len;
1684                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1685                 }
1686
1687                 if (tunnel->version == L2TP_HDR_VER_2)
1688                         session->build_header = l2tp_build_l2tpv2_header;
1689                 else
1690                         session->build_header = l2tp_build_l2tpv3_header;
1691
1692                 l2tp_session_set_header_len(session, tunnel->version);
1693
1694                 refcount_set(&session->ref_count, 1);
1695
1696                 return session;
1697         }
1698
1699         return ERR_PTR(-ENOMEM);
1700 }
1701 EXPORT_SYMBOL_GPL(l2tp_session_create);
1702
1703 /*****************************************************************************
1704  * Init and cleanup
1705  *****************************************************************************/
1706
1707 static __net_init int l2tp_init_net(struct net *net)
1708 {
1709         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1710         int hash;
1711
1712         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1713         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1714
1715         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1716                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1717
1718         spin_lock_init(&pn->l2tp_session_hlist_lock);
1719
1720         return 0;
1721 }
1722
1723 static __net_exit void l2tp_exit_net(struct net *net)
1724 {
1725         struct l2tp_net *pn = l2tp_pernet(net);
1726         struct l2tp_tunnel *tunnel = NULL;
1727         int hash;
1728
1729         rcu_read_lock_bh();
1730         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
1731                 l2tp_tunnel_delete(tunnel);
1732         }
1733         rcu_read_unlock_bh();
1734
1735         if (l2tp_wq)
1736                 flush_workqueue(l2tp_wq);
1737         rcu_barrier();
1738
1739         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1740                 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
1741 }
1742
1743 static struct pernet_operations l2tp_net_ops = {
1744         .init = l2tp_init_net,
1745         .exit = l2tp_exit_net,
1746         .id   = &l2tp_net_id,
1747         .size = sizeof(struct l2tp_net),
1748 };
1749
1750 static int __init l2tp_init(void)
1751 {
1752         int rc = 0;
1753
1754         rc = register_pernet_device(&l2tp_net_ops);
1755         if (rc)
1756                 goto out;
1757
1758         l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
1759         if (!l2tp_wq) {
1760                 pr_err("alloc_workqueue failed\n");
1761                 unregister_pernet_device(&l2tp_net_ops);
1762                 rc = -ENOMEM;
1763                 goto out;
1764         }
1765
1766         pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1767
1768 out:
1769         return rc;
1770 }
1771
1772 static void __exit l2tp_exit(void)
1773 {
1774         unregister_pernet_device(&l2tp_net_ops);
1775         if (l2tp_wq) {
1776                 destroy_workqueue(l2tp_wq);
1777                 l2tp_wq = NULL;
1778         }
1779 }
1780
1781 module_init(l2tp_init);
1782 module_exit(l2tp_exit);
1783
1784 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1785 MODULE_DESCRIPTION("L2TP core");
1786 MODULE_LICENSE("GPL");
1787 MODULE_VERSION(L2TP_DRV_VERSION);