net/l2tp/l2tp_core.c

   1 /*
   2  * L2TP core.
   3  *
   4  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
   5  *
   6  * This file contains some code of the original L2TPv2 pppol2tp
   7  * driver, which has the following copyright:
   8  *
   9  * Authors:     Martijn van Oosterhout <kleptog@svana.org>
  10  *              James Chapman (jchapman@katalix.com)
  11  * Contributors:
  12  *              Michal Ostrowski <mostrows@speakeasy.net>
  13  *              Arnaldo Carvalho de Melo <acme@xconectiva.com.br>
  14  *              David S. Miller (davem@redhat.com)
  15  *
  16  * This program is free software; you can redistribute it and/or modify
  17  * it under the terms of the GNU General Public License version 2 as
  18  * published by the Free Software Foundation.
  19  */
  20
  21 #include <linux/module.h>
  22 #include <linux/string.h>
  23 #include <linux/list.h>
  24 #include <linux/rculist.h>
  25 #include <linux/uaccess.h>
  26
  27 #include <linux/kernel.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/kthread.h>
  30 #include <linux/sched.h>
  31 #include <linux/slab.h>
  32 #include <linux/errno.h>
  33 #include <linux/jiffies.h>
  34
  35 #include <linux/netdevice.h>
  36 #include <linux/net.h>
  37 #include <linux/inetdevice.h>
  38 #include <linux/skbuff.h>
  39 #include <linux/init.h>
  40 #include <linux/in.h>
  41 #include <linux/ip.h>
  42 #include <linux/udp.h>
  43 #include <linux/l2tp.h>
  44 #include <linux/hash.h>
  45 #include <linux/sort.h>
  46 #include <linux/file.h>
  47 #include <linux/nsproxy.h>
  48 #include <net/net_namespace.h>
  49 #include <net/netns/generic.h>
  50 #include <net/dst.h>
  51 #include <net/ip.h>
  52 #include <net/udp.h>
  53 #include <net/inet_common.h>
  54 #include <net/xfrm.h>
  55 #include <net/protocol.h>
  56
  57 #include <asm/byteorder.h>
  58 #include <linux/atomic.h>
  59
  60 #include "l2tp_core.h"
  61
  62 #define L2TP_DRV_VERSION        "V2.0"
  63
  64 /* L2TP header constants */
  65 #define L2TP_HDRFLAG_T     0x8000
  66 #define L2TP_HDRFLAG_L     0x4000
  67 #define L2TP_HDRFLAG_S     0x0800
  68 #define L2TP_HDRFLAG_O     0x0200
  69 #define L2TP_HDRFLAG_P     0x0100
  70
  71 #define L2TP_HDR_VER_MASK  0x000F
  72 #define L2TP_HDR_VER_2     0x0002
  73 #define L2TP_HDR_VER_3     0x0003
  74
  75 /* L2TPv3 default L2-specific sublayer */
  76 #define L2TP_SLFLAG_S      0x40000000
  77 #define L2TP_SL_SEQ_MASK   0x00ffffff
  78
  79 #define L2TP_HDR_SIZE_SEQ               10
  80 #define L2TP_HDR_SIZE_NOSEQ             6
  81
  82 /* Default trace flags */
  83 #define L2TP_DEFAULT_DEBUG_FLAGS        0
  84
  85 #define PRINTK(_mask, _type, _lvl, _fmt, args...)                       \
  86         do {                                                            \
  87                 if ((_mask) & (_type))                                  \
  88                         printk(_lvl "L2TP: " _fmt, ##args);             \
  89         } while (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 atomic_t l2tp_tunnel_count;
 103 static atomic_t l2tp_session_count;
 104
 105 /* per-net private data for this module */
 106 static unsigned int l2tp_net_id;
 107 struct l2tp_net {
 108         struct list_head l2tp_tunnel_list;
 109         spinlock_t l2tp_tunnel_list_lock;
 110         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
 111         spinlock_t l2tp_session_hlist_lock;
 112 };
 113
 114 static void l2tp_session_set_header_len(struct l2tp_session *session, int version);
 115 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
 116
 117 static inline struct l2tp_net *l2tp_pernet(const struct net *net)
 118 {
 119         BUG_ON(!net);
 120
 121         return net_generic(net, l2tp_net_id);
 122 }
 123
 124
 125 /* Session hash global list for L2TPv3.
 126  * The session_id SHOULD be random according to RFC3931, but several
 127  * L2TP implementations use incrementing session_ids.  So we do a real
 128  * hash on the session_id, rather than a simple bitmask.
 129  */
 130 static inline struct hlist_head *
 131 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 132 {
 133         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 134
 135 }
 136
 137 /* Lookup a session by id in the global session list
 138  */
 139 static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id)
 140 {
 141         struct l2tp_net *pn = l2tp_pernet(net);
 142         struct hlist_head *session_list =
 143                 l2tp_session_id_hash_2(pn, session_id);
 144         struct l2tp_session *session;
 145         struct hlist_node *walk;
 146
 147         rcu_read_lock_bh();
 148         hlist_for_each_entry_rcu(session, walk, session_list, global_hlist) {
 149                 if (session->session_id == session_id) {
 150                         rcu_read_unlock_bh();
 151                         return session;
 152                 }
 153         }
 154         rcu_read_unlock_bh();
 155
 156         return NULL;
 157 }
 158
 159 /* Session hash list.
 160  * The session_id SHOULD be random according to RFC2661, but several
 161  * L2TP implementations (Cisco and Microsoft) use incrementing
 162  * session_ids.  So we do a real hash on the session_id, rather than a
 163  * simple bitmask.
 164  */
 165 static inline struct hlist_head *
 166 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 167 {
 168         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 169 }
 170
 171 /* Lookup a session by id
 172  */
 173 struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id)
 174 {
 175         struct hlist_head *session_list;
 176         struct l2tp_session *session;
 177         struct hlist_node *walk;
 178
 179         /* In L2TPv3, session_ids are unique over all tunnels and we
 180          * sometimes need to look them up before we know the
 181          * tunnel.
 182          */
 183         if (tunnel == NULL)
 184                 return l2tp_session_find_2(net, session_id);
 185
 186         session_list = l2tp_session_id_hash(tunnel, session_id);
 187         read_lock_bh(&tunnel->hlist_lock);
 188         hlist_for_each_entry(session, walk, session_list, hlist) {
 189                 if (session->session_id == session_id) {
 190                         read_unlock_bh(&tunnel->hlist_lock);
 191                         return session;
 192                 }
 193         }
 194         read_unlock_bh(&tunnel->hlist_lock);
 195
 196         return NULL;
 197 }
 198 EXPORT_SYMBOL_GPL(l2tp_session_find);
 199
 200 /* Lookup a tunnel. A new reference is held on the returned tunnel. */
 201 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
 202 {
 203         const struct l2tp_net *pn = l2tp_pernet(net);
 204         struct l2tp_tunnel *tunnel;
 205
 206         rcu_read_lock_bh();
 207         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 208                 if (tunnel->tunnel_id == tunnel_id) {
 209                         l2tp_tunnel_inc_refcount(tunnel);
 210                         rcu_read_unlock_bh();
 211
 212                         return tunnel;
 213                 }
 214         }
 215         rcu_read_unlock_bh();
 216
 217         return NULL;
 218 }
 219 EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
 220
 221 /* Like l2tp_session_find() but takes a reference on the returned session.
 222  * Optionally calls session->ref() too if do_ref is true.
 223  */
 224 struct l2tp_session *l2tp_session_get(const struct net *net,
 225                                       struct l2tp_tunnel *tunnel,
 226                                       u32 session_id, bool do_ref)
 227 {
 228         struct hlist_head *session_list;
 229         struct l2tp_session *session;
 230         struct hlist_node *walk;
 231
 232         if (!tunnel) {
 233                 struct l2tp_net *pn = l2tp_pernet(net);
 234
 235                 session_list = l2tp_session_id_hash_2(pn, session_id);
 236
 237                 rcu_read_lock_bh();
 238                 hlist_for_each_entry_rcu(session, walk, session_list, global_hlist) {
 239                         if (session->session_id == session_id) {
 240                                 l2tp_session_inc_refcount(session);
 241                                 if (do_ref && session->ref)
 242                                         session->ref(session);
 243                                 rcu_read_unlock_bh();
 244
 245                                 return session;
 246                         }
 247                 }
 248                 rcu_read_unlock_bh();
 249
 250                 return NULL;
 251         }
 252
 253         session_list = l2tp_session_id_hash(tunnel, session_id);
 254         read_lock_bh(&tunnel->hlist_lock);
 255         hlist_for_each_entry(session, walk, session_list, hlist) {
 256                 if (session->session_id == session_id) {
 257                         l2tp_session_inc_refcount(session);
 258                         if (do_ref && session->ref)
 259                                 session->ref(session);
 260                         read_unlock_bh(&tunnel->hlist_lock);
 261
 262                         return session;
 263                 }
 264         }
 265         read_unlock_bh(&tunnel->hlist_lock);
 266
 267         return NULL;
 268 }
 269 EXPORT_SYMBOL_GPL(l2tp_session_get);
 270
 271 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth,
 272                                           bool do_ref)
 273 {
 274         int hash;
 275         struct hlist_node *walk;
 276         struct l2tp_session *session;
 277         int count = 0;
 278
 279         read_lock_bh(&tunnel->hlist_lock);
 280         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 281                 hlist_for_each_entry(session, walk, &tunnel->session_hlist[hash], hlist) {
 282                         if (++count > nth) {
 283                                 l2tp_session_inc_refcount(session);
 284                                 if (do_ref && session->ref)
 285                                         session->ref(session);
 286                                 read_unlock_bh(&tunnel->hlist_lock);
 287                                 return session;
 288                         }
 289                 }
 290         }
 291
 292         read_unlock_bh(&tunnel->hlist_lock);
 293
 294         return NULL;
 295 }
 296 EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
 297
 298 /* Lookup a session by interface name.
 299  * This is very inefficient but is only used by management interfaces.
 300  */
 301 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
 302                                                 const char *ifname,
 303                                                 bool do_ref)
 304 {
 305         struct l2tp_net *pn = l2tp_pernet(net);
 306         int hash;
 307         struct hlist_node *walk;
 308         struct l2tp_session *session;
 309
 310         rcu_read_lock_bh();
 311         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 312                 hlist_for_each_entry_rcu(session, walk, &pn->l2tp_session_hlist[hash], global_hlist) {
 313                         if (!strcmp(session->ifname, ifname)) {
 314                                 l2tp_session_inc_refcount(session);
 315                                 if (do_ref && session->ref)
 316                                         session->ref(session);
 317                                 rcu_read_unlock_bh();
 318
 319                                 return session;
 320                         }
 321                 }
 322         }
 323
 324         rcu_read_unlock_bh();
 325
 326         return NULL;
 327 }
 328 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
 329
 330 static int l2tp_session_add_to_tunnel(struct l2tp_tunnel *tunnel,
 331                                       struct l2tp_session *session)
 332 {
 333         struct l2tp_session *session_walk;
 334         struct hlist_head *g_head;
 335         struct hlist_head *head;
 336         struct l2tp_net *pn;
 337         struct hlist_node *walk;
 338         int err;
 339
 340         head = l2tp_session_id_hash(tunnel, session->session_id);
 341
 342         write_lock_bh(&tunnel->hlist_lock);
 343         if (!tunnel->acpt_newsess) {
 344                 err = -ENODEV;
 345                 goto err_tlock;
 346         }
 347
 348         hlist_for_each_entry(session_walk, walk, head, hlist)
 349                 if (session_walk->session_id == session->session_id) {
 350                         err = -EEXIST;
 351                         goto err_tlock;
 352                 }
 353
 354         if (tunnel->version == L2TP_HDR_VER_3) {
 355                 pn = l2tp_pernet(tunnel->l2tp_net);
 356                 g_head = l2tp_session_id_hash_2(l2tp_pernet(tunnel->l2tp_net),
 357                                                 session->session_id);
 358
 359                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
 360
 361                 hlist_for_each_entry(session_walk, walk, g_head, global_hlist)
 362                         if (session_walk->session_id == session->session_id) {
 363                                 err = -EEXIST;
 364                                 goto err_tlock_pnlock;
 365                         }
 366
 367                 l2tp_tunnel_inc_refcount(tunnel);
 368                 sock_hold(tunnel->sock);
 369                 hlist_add_head_rcu(&session->global_hlist, g_head);
 370
 371                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 372         } else {
 373                 l2tp_tunnel_inc_refcount(tunnel);
 374                 sock_hold(tunnel->sock);
 375         }
 376
 377         hlist_add_head(&session->hlist, head);
 378         write_unlock_bh(&tunnel->hlist_lock);
 379
 380         return 0;
 381
 382 err_tlock_pnlock:
 383         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 384 err_tlock:
 385         write_unlock_bh(&tunnel->hlist_lock);
 386
 387         return err;
 388 }
 389
 390 /* Lookup a tunnel by id
 391  */
 392 struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
 393 {
 394         struct l2tp_tunnel *tunnel;
 395         struct l2tp_net *pn = l2tp_pernet(net);
 396
 397         rcu_read_lock_bh();
 398         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 399                 if (tunnel->tunnel_id == tunnel_id) {
 400                         rcu_read_unlock_bh();
 401                         return tunnel;
 402                 }
 403         }
 404         rcu_read_unlock_bh();
 405
 406         return NULL;
 407 }
 408 EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
 409
 410 struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
 411 {
 412         struct l2tp_net *pn = l2tp_pernet(net);
 413         struct l2tp_tunnel *tunnel;
 414         int count = 0;
 415
 416         rcu_read_lock_bh();
 417         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 418                 if (++count > nth) {
 419                         rcu_read_unlock_bh();
 420                         return tunnel;
 421                 }
 422         }
 423
 424         rcu_read_unlock_bh();
 425
 426         return NULL;
 427 }
 428 EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
 429
 430 /*****************************************************************************
 431  * Receive data handling
 432  *****************************************************************************/
 433
 434 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 435  * number.
 436  */
 437 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 438 {
 439         struct sk_buff *skbp;
 440         struct sk_buff *tmp;
 441         u32 ns = L2TP_SKB_CB(skb)->ns;
 442
 443         spin_lock_bh(&session->reorder_q.lock);
 444         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 445                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 446                         __skb_queue_before(&session->reorder_q, skbp, skb);
 447                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 448                                "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 449                                session->name, ns, L2TP_SKB_CB(skbp)->ns,
 450                                skb_queue_len(&session->reorder_q));
 451                         session->stats.rx_oos_packets++;
 452                         goto out;
 453                 }
 454         }
 455
 456         __skb_queue_tail(&session->reorder_q, skb);
 457
 458 out:
 459         spin_unlock_bh(&session->reorder_q.lock);
 460 }
 461
 462 /* Dequeue a single skb.
 463  */
 464 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 465 {
 466         struct l2tp_tunnel *tunnel = session->tunnel;
 467         int length = L2TP_SKB_CB(skb)->length;
 468
 469         /* We're about to requeue the skb, so return resources
 470          * to its current owner (a socket receive buffer).
 471          */
 472         skb_orphan(skb);
 473
 474         tunnel->stats.rx_packets++;
 475         tunnel->stats.rx_bytes += length;
 476         session->stats.rx_packets++;
 477         session->stats.rx_bytes += length;
 478
 479         if (L2TP_SKB_CB(skb)->has_seq) {
 480                 /* Bump our Nr */
 481                 session->nr++;
 482                 if (tunnel->version == L2TP_HDR_VER_2)
 483                         session->nr &= 0xffff;
 484                 else
 485                         session->nr &= 0xffffff;
 486
 487                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 488                        "%s: updated nr to %hu\n", session->name, session->nr);
 489         }
 490
 491         /* call private receive handler */
 492         if (session->recv_skb != NULL)
 493                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 494         else
 495                 kfree_skb(skb);
 496
 497         if (session->deref)
 498                 (*session->deref)(session);
 499 }
 500
 501 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 502  * Skbs that have been in the queue for too long are simply discarded.
 503  */
 504 static void l2tp_recv_dequeue(struct l2tp_session *session)
 505 {
 506         struct sk_buff *skb;
 507         struct sk_buff *tmp;
 508
 509         /* If the pkt at the head of the queue has the nr that we
 510          * expect to send up next, dequeue it and any other
 511          * in-sequence packets behind it.
 512          */
 513 start:
 514         spin_lock_bh(&session->reorder_q.lock);
 515         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 516                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 517                         session->stats.rx_seq_discards++;
 518                         session->stats.rx_errors++;
 519                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 520                                "%s: oos pkt %u len %d discarded (too old), "
 521                                "waiting for %u, reorder_q_len=%d\n",
 522                                session->name, L2TP_SKB_CB(skb)->ns,
 523                                L2TP_SKB_CB(skb)->length, session->nr,
 524                                skb_queue_len(&session->reorder_q));
 525                         __skb_unlink(skb, &session->reorder_q);
 526                         kfree_skb(skb);
 527                         if (session->deref)
 528                                 (*session->deref)(session);
 529                         continue;
 530                 }
 531
 532                 if (L2TP_SKB_CB(skb)->has_seq) {
 533                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 534                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 535                                        "%s: holding oos pkt %u len %d, "
 536                                        "waiting for %u, reorder_q_len=%d\n",
 537                                        session->name, L2TP_SKB_CB(skb)->ns,
 538                                        L2TP_SKB_CB(skb)->length, session->nr,
 539                                        skb_queue_len(&session->reorder_q));
 540                                 goto out;
 541                         }
 542                 }
 543                 __skb_unlink(skb, &session->reorder_q);
 544
 545                 /* Process the skb. We release the queue lock while we
 546                  * do so to let other contexts process the queue.
 547                  */
 548                 spin_unlock_bh(&session->reorder_q.lock);
 549                 l2tp_recv_dequeue_skb(session, skb);
 550                 goto start;
 551         }
 552
 553 out:
 554         spin_unlock_bh(&session->reorder_q.lock);
 555 }
 556
 557 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 558                                            struct sk_buff *skb)
 559 {
 560         struct udphdr *uh = udp_hdr(skb);
 561         u16 ulen = ntohs(uh->len);
 562         struct inet_sock *inet;
 563         __wsum psum;
 564
 565         if (sk->sk_no_check || skb_csum_unnecessary(skb) || !uh->check)
 566                 return 0;
 567
 568         inet = inet_sk(sk);
 569         psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr, ulen,
 570                                   IPPROTO_UDP, 0);
 571
 572         if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 573             !csum_fold(csum_add(psum, skb->csum)))
 574                 return 0;
 575
 576         skb->csum = psum;
 577
 578         return __skb_checksum_complete(skb);
 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, sublayer format and offset (pad) are negotiated with
 632  * the peer when the session is set up. Unlike L2TPv2, we do not need
 633  * to parse the packet header to determine if optional fields are
 634  * present.
 635  *
 636  * Caller must already have parsed the frame and determined that it is
 637  * a data (not control) frame before coming here. Fields up to the
 638  * session-id have already been parsed and ptr points to the data
 639  * after the session-id.
 640  *
 641  * session->ref() must have been called prior to l2tp_recv_common().
 642  * session->deref() will be called automatically after skb is processed.
 643  */
 644 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 645                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 646                       int length, int (*payload_hook)(struct sk_buff *skb))
 647 {
 648         struct l2tp_tunnel *tunnel = session->tunnel;
 649         int offset;
 650         u32 ns, nr;
 651
 652         /* Parse and check optional cookie */
 653         if (session->peer_cookie_len > 0) {
 654                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 655                         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 656                                "%s: cookie mismatch (%u/%u). Discarding.\n",
 657                                tunnel->name, tunnel->tunnel_id, session->session_id);
 658                         session->stats.rx_cookie_discards++;
 659                         goto discard;
 660                 }
 661                 ptr += session->peer_cookie_len;
 662         }
 663
 664         /* Handle the optional sequence numbers. Sequence numbers are
 665          * in different places for L2TPv2 and L2TPv3.
 666          *
 667          * If we are the LAC, enable/disable sequence numbers under
 668          * the control of the LNS.  If no sequence numbers present but
 669          * we were expecting them, discard frame.
 670          */
 671         ns = nr = 0;
 672         L2TP_SKB_CB(skb)->has_seq = 0;
 673         if (tunnel->version == L2TP_HDR_VER_2) {
 674                 if (hdrflags & L2TP_HDRFLAG_S) {
 675                         ns = ntohs(*(__be16 *) ptr);
 676                         ptr += 2;
 677                         nr = ntohs(*(__be16 *) ptr);
 678                         ptr += 2;
 679
 680                         /* Store L2TP info in the skb */
 681                         L2TP_SKB_CB(skb)->ns = ns;
 682                         L2TP_SKB_CB(skb)->has_seq = 1;
 683
 684                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 685                                "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 686                                session->name, ns, nr, session->nr);
 687                 }
 688         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 689                 u32 l2h = ntohl(*(__be32 *) ptr);
 690
 691                 if (l2h & 0x40000000) {
 692                         ns = l2h & 0x00ffffff;
 693
 694                         /* Store L2TP info in the skb */
 695                         L2TP_SKB_CB(skb)->ns = ns;
 696                         L2TP_SKB_CB(skb)->has_seq = 1;
 697
 698                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 699                                "%s: recv data ns=%u, session nr=%u\n",
 700                                session->name, ns, session->nr);
 701                 }
 702         }
 703
 704         /* Advance past L2-specific header, if present */
 705         ptr += session->l2specific_len;
 706
 707         if (L2TP_SKB_CB(skb)->has_seq) {
 708                 /* Received a packet with sequence numbers. If we're the LNS,
 709                  * check if we sre sending sequence numbers and if not,
 710                  * configure it so.
 711                  */
 712                 if ((!session->lns_mode) && (!session->send_seq)) {
 713                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 714                                "%s: requested to enable seq numbers by LNS\n",
 715                                session->name);
 716                         session->send_seq = -1;
 717                         l2tp_session_set_header_len(session, tunnel->version);
 718                 }
 719         } else {
 720                 /* No sequence numbers.
 721                  * If user has configured mandatory sequence numbers, discard.
 722                  */
 723                 if (session->recv_seq) {
 724                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 725                                "%s: recv data has no seq numbers when required. "
 726                                "Discarding\n", session->name);
 727                         session->stats.rx_seq_discards++;
 728                         goto discard;
 729                 }
 730
 731                 /* If we're the LAC and we're sending sequence numbers, the
 732                  * LNS has requested that we no longer send sequence numbers.
 733                  * If we're the LNS and we're sending sequence numbers, the
 734                  * LAC is broken. Discard the frame.
 735                  */
 736                 if ((!session->lns_mode) && (session->send_seq)) {
 737                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 738                                "%s: requested to disable seq numbers by LNS\n",
 739                                session->name);
 740                         session->send_seq = 0;
 741                         l2tp_session_set_header_len(session, tunnel->version);
 742                 } else if (session->send_seq) {
 743                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 744                                "%s: recv data has no seq numbers when required. "
 745                                "Discarding\n", session->name);
 746                         session->stats.rx_seq_discards++;
 747                         goto discard;
 748                 }
 749         }
 750
 751         /* Session data offset is handled differently for L2TPv2 and
 752          * L2TPv3. For L2TPv2, there is an optional 16-bit value in
 753          * the header. For L2TPv3, the offset is negotiated using AVPs
 754          * in the session setup control protocol.
 755          */
 756         if (tunnel->version == L2TP_HDR_VER_2) {
 757                 /* If offset bit set, skip it. */
 758                 if (hdrflags & L2TP_HDRFLAG_O) {
 759                         offset = ntohs(*(__be16 *)ptr);
 760                         ptr += 2 + offset;
 761                 }
 762         } else
 763                 ptr += session->offset;
 764
 765         offset = ptr - optr;
 766         if (!pskb_may_pull(skb, offset))
 767                 goto discard;
 768
 769         __skb_pull(skb, offset);
 770
 771         /* If caller wants to process the payload before we queue the
 772          * packet, do so now.
 773          */
 774         if (payload_hook)
 775                 if ((*payload_hook)(skb))
 776                         goto discard;
 777
 778         /* Prepare skb for adding to the session's reorder_q.  Hold
 779          * packets for max reorder_timeout or 1 second if not
 780          * reordering.
 781          */
 782         L2TP_SKB_CB(skb)->length = length;
 783         L2TP_SKB_CB(skb)->expires = jiffies +
 784                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 785
 786         /* Add packet to the session's receive queue. Reordering is done here, if
 787          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 788          */
 789         if (L2TP_SKB_CB(skb)->has_seq) {
 790                 if (session->reorder_timeout != 0) {
 791                         /* Packet reordering enabled. Add skb to session's
 792                          * reorder queue, in order of ns.
 793                          */
 794                         l2tp_recv_queue_skb(session, skb);
 795                 } else {
 796                         /* Packet reordering disabled. Discard out-of-sequence
 797                          * packets
 798                          */
 799                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 800                                 session->stats.rx_seq_discards++;
 801                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 802                                        "%s: oos pkt %u len %d discarded, "
 803                                        "waiting for %u, reorder_q_len=%d\n",
 804                                        session->name, L2TP_SKB_CB(skb)->ns,
 805                                        L2TP_SKB_CB(skb)->length, session->nr,
 806                                        skb_queue_len(&session->reorder_q));
 807                                 goto discard;
 808                         }
 809                         skb_queue_tail(&session->reorder_q, skb);
 810                 }
 811         } else {
 812                 /* No sequence numbers. Add the skb to the tail of the
 813                  * reorder queue. This ensures that it will be
 814                  * delivered after all previous sequenced skbs.
 815                  */
 816                 skb_queue_tail(&session->reorder_q, skb);
 817         }
 818
 819         /* Try to dequeue as many skbs from reorder_q as we can. */
 820         l2tp_recv_dequeue(session);
 821
 822         return;
 823
 824 discard:
 825         session->stats.rx_errors++;
 826         kfree_skb(skb);
 827
 828         if (session->deref)
 829                 (*session->deref)(session);
 830 }
 831 EXPORT_SYMBOL(l2tp_recv_common);
 832
 833 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 834  * here. The skb is not on a list when we get here.
 835  * Returns 0 if the packet was a data packet and was successfully passed on.
 836  * Returns 1 if the packet was not a good data packet and could not be
 837  * forwarded.  All such packets are passed up to userspace to deal with.
 838  */
 839 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 840                               int (*payload_hook)(struct sk_buff *skb))
 841 {
 842         struct l2tp_session *session = NULL;
 843         unsigned char *ptr, *optr;
 844         u16 hdrflags;
 845         u32 tunnel_id, session_id;
 846         int offset;
 847         u16 version;
 848         int length;
 849
 850         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
 851                 goto discard_bad_csum;
 852
 853         /* UDP always verifies the packet length. */
 854         __skb_pull(skb, sizeof(struct udphdr));
 855
 856         /* Short packet? */
 857         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
 858                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 859                        "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
 860                 goto error;
 861         }
 862
 863         /* Trace packet contents, if enabled */
 864         if (tunnel->debug & L2TP_MSG_DATA) {
 865                 length = min(32u, skb->len);
 866                 if (!pskb_may_pull(skb, length))
 867                         goto error;
 868
 869                 printk(KERN_DEBUG "%s: recv: ", tunnel->name);
 870
 871                 offset = 0;
 872                 do {
 873                         printk(" %02X", skb->data[offset]);
 874                 } while (++offset < length);
 875
 876                 printk("\n");
 877         }
 878
 879         /* Point to L2TP header */
 880         optr = ptr = skb->data;
 881
 882         /* Get L2TP header flags */
 883         hdrflags = ntohs(*(__be16 *) ptr);
 884
 885         /* Check protocol version */
 886         version = hdrflags & L2TP_HDR_VER_MASK;
 887         if (version != tunnel->version) {
 888                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 889                        "%s: recv protocol version mismatch: got %d expected %d\n",
 890                        tunnel->name, version, tunnel->version);
 891                 goto error;
 892         }
 893
 894         /* Get length of L2TP packet */
 895         length = skb->len;
 896
 897         /* If type is control packet, it is handled by userspace. */
 898         if (hdrflags & L2TP_HDRFLAG_T) {
 899                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 900                        "%s: recv control packet, len=%d\n", tunnel->name, length);
 901                 goto error;
 902         }
 903
 904         /* Skip flags */
 905         ptr += 2;
 906
 907         if (tunnel->version == L2TP_HDR_VER_2) {
 908                 /* If length is present, skip it */
 909                 if (hdrflags & L2TP_HDRFLAG_L)
 910                         ptr += 2;
 911
 912                 /* Extract tunnel and session ID */
 913                 tunnel_id = ntohs(*(__be16 *) ptr);
 914                 ptr += 2;
 915                 session_id = ntohs(*(__be16 *) ptr);
 916                 ptr += 2;
 917         } else {
 918                 ptr += 2;       /* skip reserved bits */
 919                 tunnel_id = tunnel->tunnel_id;
 920                 session_id = ntohl(*(__be32 *) ptr);
 921                 ptr += 4;
 922         }
 923
 924         /* Find the session context */
 925         session = l2tp_session_get(tunnel->l2tp_net, tunnel, session_id, true);
 926         if (!session || !session->recv_skb) {
 927                 if (session) {
 928                         if (session->deref)
 929                                 session->deref(session);
 930                         l2tp_session_dec_refcount(session);
 931                 }
 932
 933                 /* Not found? Pass to userspace to deal with */
 934                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 935                        "%s: no session found (%u/%u). Passing up.\n",
 936                        tunnel->name, tunnel_id, session_id);
 937                 goto error;
 938         }
 939
 940         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
 941         l2tp_session_dec_refcount(session);
 942
 943         return 0;
 944
 945 discard_bad_csum:
 946         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
 947         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
 948         tunnel->stats.rx_errors++;
 949         kfree_skb(skb);
 950
 951         return 0;
 952
 953 error:
 954         /* Put UDP header back */
 955         __skb_push(skb, sizeof(struct udphdr));
 956
 957         return 1;
 958 }
 959
 960 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 961  * Return codes:
 962  * 0 : success.
 963  * <0: error
 964  * >0: skb should be passed up to userspace as UDP.
 965  */
 966 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 967 {
 968         struct l2tp_tunnel *tunnel;
 969
 970         tunnel = l2tp_sock_to_tunnel(sk);
 971         if (tunnel == NULL)
 972                 goto pass_up;
 973
 974         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 975                "%s: received %d bytes\n", tunnel->name, skb->len);
 976
 977         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
 978                 goto pass_up_put;
 979
 980         sock_put(sk);
 981         return 0;
 982
 983 pass_up_put:
 984         sock_put(sk);
 985 pass_up:
 986         return 1;
 987 }
 988 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 989
 990 /************************************************************************
 991  * Transmit handling
 992  ***********************************************************************/
 993
 994 /* Build an L2TP header for the session into the buffer provided.
 995  */
 996 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 997 {
 998         struct l2tp_tunnel *tunnel = session->tunnel;
 999         __be16 *bufp = buf;
1000         __be16 *optr = buf;
1001         u16 flags = L2TP_HDR_VER_2;
1002         u32 tunnel_id = tunnel->peer_tunnel_id;
1003         u32 session_id = session->peer_session_id;
1004
1005         if (session->send_seq)
1006                 flags |= L2TP_HDRFLAG_S;
1007
1008         /* Setup L2TP header. */
1009         *bufp++ = htons(flags);
1010         *bufp++ = htons(tunnel_id);
1011         *bufp++ = htons(session_id);
1012         if (session->send_seq) {
1013                 *bufp++ = htons(session->ns);
1014                 *bufp++ = 0;
1015                 session->ns++;
1016                 session->ns &= 0xffff;
1017                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
1018                        "%s: updated ns to %u\n", session->name, session->ns);
1019         }
1020
1021         return bufp - optr;
1022 }
1023
1024 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
1025 {
1026         struct l2tp_tunnel *tunnel = session->tunnel;
1027         char *bufp = buf;
1028         char *optr = bufp;
1029
1030         /* Setup L2TP header. The header differs slightly for UDP and
1031          * IP encapsulations. For UDP, there is 4 bytes of flags.
1032          */
1033         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1034                 u16 flags = L2TP_HDR_VER_3;
1035                 *((__be16 *) bufp) = htons(flags);
1036                 bufp += 2;
1037                 *((__be16 *) bufp) = 0;
1038                 bufp += 2;
1039         }
1040
1041         *((__be32 *) bufp) = htonl(session->peer_session_id);
1042         bufp += 4;
1043         if (session->cookie_len) {
1044                 memcpy(bufp, &session->cookie[0], session->cookie_len);
1045                 bufp += session->cookie_len;
1046         }
1047         if (session->l2specific_len) {
1048                 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
1049                         u32 l2h = 0;
1050                         if (session->send_seq) {
1051                                 l2h = 0x40000000 | session->ns;
1052                                 session->ns++;
1053                                 session->ns &= 0xffffff;
1054                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
1055                                        "%s: updated ns to %u\n", session->name, session->ns);
1056                         }
1057
1058                         *((__be32 *) bufp) = htonl(l2h);
1059                 }
1060                 bufp += session->l2specific_len;
1061         }
1062         if (session->offset)
1063                 bufp += session->offset;
1064
1065         return bufp - optr;
1066 }
1067
1068 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
1069                           struct flowi *fl, size_t data_len)
1070 {
1071         struct l2tp_tunnel *tunnel = session->tunnel;
1072         unsigned int len = skb->len;
1073         int error;
1074
1075         /* Debug */
1076         if (session->send_seq)
1077                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
1078                        "%s: send %Zd bytes, ns=%u\n", session->name,
1079                        data_len, session->ns - 1);
1080         else
1081                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
1082                        "%s: send %Zd bytes\n", session->name, data_len);
1083
1084         if (session->debug & L2TP_MSG_DATA) {
1085                 int i;
1086                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1087                 unsigned char *datap = skb->data + uhlen;
1088
1089                 printk(KERN_DEBUG "%s: xmit:", session->name);
1090                 for (i = 0; i < (len - uhlen); i++) {
1091                         printk(" %02X", *datap++);
1092                         if (i == 31) {
1093                                 printk(" ...");
1094                                 break;
1095                         }
1096                 }
1097                 printk("\n");
1098         }
1099
1100         /* Queue the packet to IP for output */
1101         skb->local_df = 1;
1102         error = ip_queue_xmit(skb, fl);
1103
1104         /* Update stats */
1105         if (error >= 0) {
1106                 tunnel->stats.tx_packets++;
1107                 tunnel->stats.tx_bytes += len;
1108                 session->stats.tx_packets++;
1109                 session->stats.tx_bytes += len;
1110         } else {
1111                 tunnel->stats.tx_errors++;
1112                 session->stats.tx_errors++;
1113         }
1114
1115         return 0;
1116 }
1117
1118 /* Automatically called when the skb is freed.
1119  */
1120 static void l2tp_sock_wfree(struct sk_buff *skb)
1121 {
1122         sock_put(skb->sk);
1123 }
1124
1125 /* For data skbs that we transmit, we associate with the tunnel socket
1126  * but don't do accounting.
1127  */
1128 static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
1129 {
1130         sock_hold(sk);
1131         skb->sk = sk;
1132         skb->destructor = l2tp_sock_wfree;
1133 }
1134
1135 /* If caller requires the skb to have a ppp header, the header must be
1136  * inserted in the skb data before calling this function.
1137  */
1138 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1139 {
1140         int data_len = skb->len;
1141         struct l2tp_tunnel *tunnel = session->tunnel;
1142         struct sock *sk = tunnel->sock;
1143         struct flowi *fl;
1144         struct udphdr *uh;
1145         struct inet_sock *inet;
1146         __wsum csum;
1147         int old_headroom;
1148         int new_headroom;
1149         int headroom;
1150         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1151         int udp_len;
1152
1153         /* Check that there's enough headroom in the skb to insert IP,
1154          * UDP and L2TP headers. If not enough, expand it to
1155          * make room. Adjust truesize.
1156          */
1157         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1158                 uhlen + hdr_len;
1159         old_headroom = skb_headroom(skb);
1160         if (skb_cow_head(skb, headroom)) {
1161                 dev_kfree_skb(skb);
1162                 goto abort;
1163         }
1164
1165         new_headroom = skb_headroom(skb);
1166         skb_orphan(skb);
1167         skb->truesize += new_headroom - old_headroom;
1168
1169         /* Setup L2TP header */
1170         session->build_header(session, __skb_push(skb, hdr_len));
1171
1172         /* Reset skb netfilter state */
1173         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1174         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1175                               IPSKB_REROUTED);
1176         nf_reset(skb);
1177
1178         bh_lock_sock(sk);
1179         if (sock_owned_by_user(sk)) {
1180                 dev_kfree_skb(skb);
1181                 goto out_unlock;
1182         }
1183
1184         /* Get routing info from the tunnel socket */
1185         skb_dst_drop(skb);
1186         skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
1187
1188         inet = inet_sk(sk);
1189         fl = &inet->cork.fl;
1190         switch (tunnel->encap) {
1191         case L2TP_ENCAPTYPE_UDP:
1192                 /* Setup UDP header */
1193                 __skb_push(skb, sizeof(*uh));
1194                 skb_reset_transport_header(skb);
1195                 uh = udp_hdr(skb);
1196                 uh->source = inet->inet_sport;
1197                 uh->dest = inet->inet_dport;
1198                 udp_len = uhlen + hdr_len + data_len;
1199                 uh->len = htons(udp_len);
1200                 uh->check = 0;
1201
1202                 /* Calculate UDP checksum if configured to do so */
1203                 if (sk->sk_no_check == UDP_CSUM_NOXMIT)
1204                         skb->ip_summed = CHECKSUM_NONE;
1205                 else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
1206                          (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
1207                         skb->ip_summed = CHECKSUM_COMPLETE;
1208                         csum = skb_checksum(skb, 0, udp_len, 0);
1209                         uh->check = csum_tcpudp_magic(inet->inet_saddr,
1210                                                       inet->inet_daddr,
1211                                                       udp_len, IPPROTO_UDP, csum);
1212                         if (uh->check == 0)
1213                                 uh->check = CSUM_MANGLED_0;
1214                 } else {
1215                         skb->ip_summed = CHECKSUM_PARTIAL;
1216                         skb->csum_start = skb_transport_header(skb) - skb->head;
1217                         skb->csum_offset = offsetof(struct udphdr, check);
1218                         uh->check = ~csum_tcpudp_magic(inet->inet_saddr,
1219                                                        inet->inet_daddr,
1220                                                        udp_len, IPPROTO_UDP, 0);
1221                 }
1222                 break;
1223
1224         case L2TP_ENCAPTYPE_IP:
1225                 break;
1226         }
1227
1228         l2tp_skb_set_owner_w(skb, sk);
1229
1230         l2tp_xmit_core(session, skb, fl, data_len);
1231 out_unlock:
1232         bh_unlock_sock(sk);
1233
1234 abort:
1235         return 0;
1236 }
1237 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1238
1239 /*****************************************************************************
1240  * Tinnel and session create/destroy.
1241  *****************************************************************************/
1242
1243 /* Tunnel socket destruct hook.
1244  * The tunnel context is deleted only when all session sockets have been
1245  * closed.
1246  */
1247 static void l2tp_tunnel_destruct(struct sock *sk)
1248 {
1249         struct l2tp_tunnel *tunnel;
1250
1251         tunnel = sk->sk_user_data;
1252         if (tunnel == NULL)
1253                 goto end;
1254
1255         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1256                "%s: closing...\n", tunnel->name);
1257
1258         /* Close all sessions */
1259         l2tp_tunnel_closeall(tunnel);
1260
1261         switch (tunnel->encap) {
1262         case L2TP_ENCAPTYPE_UDP:
1263                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1264                 (udp_sk(sk))->encap_type = 0;
1265                 (udp_sk(sk))->encap_rcv = NULL;
1266                 break;
1267         case L2TP_ENCAPTYPE_IP:
1268                 break;
1269         }
1270
1271         /* Remove hooks into tunnel socket */
1272         tunnel->sock = NULL;
1273         sk->sk_destruct = tunnel->old_sk_destruct;
1274         sk->sk_user_data = NULL;
1275
1276         /* Call the original destructor */
1277         if (sk->sk_destruct)
1278                 (*sk->sk_destruct)(sk);
1279
1280         /* We're finished with the socket */
1281         l2tp_tunnel_dec_refcount(tunnel);
1282
1283 end:
1284         return;
1285 }
1286
1287 /* When the tunnel is closed, all the attached sessions need to go too.
1288  */
1289 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1290 {
1291         int hash;
1292         struct hlist_node *walk;
1293         struct hlist_node *tmp;
1294         struct l2tp_session *session;
1295
1296         BUG_ON(tunnel == NULL);
1297
1298         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1299                "%s: closing all sessions...\n", tunnel->name);
1300
1301         write_lock_bh(&tunnel->hlist_lock);
1302         tunnel->acpt_newsess = false;
1303         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1304 again:
1305                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1306                         session = hlist_entry(walk, struct l2tp_session, hlist);
1307
1308                         PRINTK(session->debug, L2TP_MSG_CONTROL, KERN_INFO,
1309                                "%s: closing session\n", session->name);
1310
1311                         hlist_del_init(&session->hlist);
1312
1313                         /* Since we should hold the sock lock while
1314                          * doing any unbinding, we need to release the
1315                          * lock we're holding before taking that lock.
1316                          * Hold a reference to the sock so it doesn't
1317                          * disappear as we're jumping between locks.
1318                          */
1319                         if (session->ref != NULL)
1320                                 (*session->ref)(session);
1321
1322                         write_unlock_bh(&tunnel->hlist_lock);
1323
1324                         if (tunnel->version != L2TP_HDR_VER_2) {
1325                                 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1326
1327                                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
1328                                 hlist_del_init_rcu(&session->global_hlist);
1329                                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1330                                 synchronize_rcu();
1331                         }
1332
1333                         if (session->session_close != NULL)
1334                                 (*session->session_close)(session);
1335
1336                         if (session->deref != NULL)
1337                                 (*session->deref)(session);
1338
1339                         write_lock_bh(&tunnel->hlist_lock);
1340
1341                         /* Now restart from the beginning of this hash
1342                          * chain.  We always remove a session from the
1343                          * list so we are guaranteed to make forward
1344                          * progress.
1345                          */
1346                         goto again;
1347                 }
1348         }
1349         write_unlock_bh(&tunnel->hlist_lock);
1350 }
1351
1352 /* Really kill the tunnel.
1353  * Come here only when all sessions have been cleared from the tunnel.
1354  */
1355 void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
1356 {
1357         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1358
1359         BUG_ON(atomic_read(&tunnel->ref_count) != 0);
1360         BUG_ON(tunnel->sock != NULL);
1361
1362         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1363                "%s: free...\n", tunnel->name);
1364
1365         /* Remove from tunnel list */
1366         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1367         list_del_rcu(&tunnel->list);
1368         kfree_rcu(tunnel, rcu);
1369         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1370
1371         atomic_dec(&l2tp_tunnel_count);
1372 }
1373 EXPORT_SYMBOL_GPL(l2tp_tunnel_free);
1374
1375 /* Create a socket for the tunnel, if one isn't set up by
1376  * userspace. This is used for static tunnels where there is no
1377  * managing L2TP daemon.
1378  */
1379 static int l2tp_tunnel_sock_create(u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct socket **sockp)
1380 {
1381         int err = -EINVAL;
1382         struct sockaddr_in udp_addr;
1383         struct sockaddr_l2tpip ip_addr;
1384         struct socket *sock = NULL;
1385
1386         switch (cfg->encap) {
1387         case L2TP_ENCAPTYPE_UDP:
1388                 err = sock_create(AF_INET, SOCK_DGRAM, 0, sockp);
1389                 if (err < 0)
1390                         goto out;
1391
1392                 sock = *sockp;
1393
1394                 memset(&udp_addr, 0, sizeof(udp_addr));
1395                 udp_addr.sin_family = AF_INET;
1396                 udp_addr.sin_addr = cfg->local_ip;
1397                 udp_addr.sin_port = htons(cfg->local_udp_port);
1398                 err = kernel_bind(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr));
1399                 if (err < 0)
1400                         goto out;
1401
1402                 udp_addr.sin_family = AF_INET;
1403                 udp_addr.sin_addr = cfg->peer_ip;
1404                 udp_addr.sin_port = htons(cfg->peer_udp_port);
1405                 err = kernel_connect(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr), 0);
1406                 if (err < 0)
1407                         goto out;
1408
1409                 if (!cfg->use_udp_checksums)
1410                         sock->sk->sk_no_check = UDP_CSUM_NOXMIT;
1411
1412                 break;
1413
1414         case L2TP_ENCAPTYPE_IP:
1415                 err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_L2TP, sockp);
1416                 if (err < 0)
1417                         goto out;
1418
1419                 sock = *sockp;
1420
1421                 memset(&ip_addr, 0, sizeof(ip_addr));
1422                 ip_addr.l2tp_family = AF_INET;
1423                 ip_addr.l2tp_addr = cfg->local_ip;
1424                 ip_addr.l2tp_conn_id = tunnel_id;
1425                 err = kernel_bind(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr));
1426                 if (err < 0)
1427                         goto out;
1428
1429                 ip_addr.l2tp_family = AF_INET;
1430                 ip_addr.l2tp_addr = cfg->peer_ip;
1431                 ip_addr.l2tp_conn_id = peer_tunnel_id;
1432                 err = kernel_connect(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr), 0);
1433                 if (err < 0)
1434                         goto out;
1435
1436                 break;
1437
1438         default:
1439                 goto out;
1440         }
1441
1442 out:
1443         if ((err < 0) && sock) {
1444                 sock_release(sock);
1445                 *sockp = NULL;
1446         }
1447
1448         return err;
1449 }
1450
1451 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)
1452 {
1453         struct l2tp_tunnel *tunnel = NULL;
1454         int err;
1455         struct socket *sock = NULL;
1456         struct sock *sk = NULL;
1457         struct l2tp_net *pn;
1458         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1459
1460         /* Get the tunnel socket from the fd, which was opened by
1461          * the userspace L2TP daemon. If not specified, create a
1462          * kernel socket.
1463          */
1464         if (fd < 0) {
1465                 err = l2tp_tunnel_sock_create(tunnel_id, peer_tunnel_id, cfg, &sock);
1466                 if (err < 0)
1467                         goto err;
1468         } else {
1469                 err = -EBADF;
1470                 sock = sockfd_lookup(fd, &err);
1471                 if (!sock) {
1472                         printk(KERN_ERR "tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
1473                                tunnel_id, fd, err);
1474                         goto err;
1475                 }
1476         }
1477
1478         sk = sock->sk;
1479
1480         if (cfg != NULL)
1481                 encap = cfg->encap;
1482
1483         /* Quick sanity checks */
1484         switch (encap) {
1485         case L2TP_ENCAPTYPE_UDP:
1486                 err = -EPROTONOSUPPORT;
1487                 if (sk->sk_protocol != IPPROTO_UDP) {
1488                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1489                                tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
1490                         goto err;
1491                 }
1492                 break;
1493         case L2TP_ENCAPTYPE_IP:
1494                 err = -EPROTONOSUPPORT;
1495                 if (sk->sk_protocol != IPPROTO_L2TP) {
1496                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1497                                tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
1498                         goto err;
1499                 }
1500                 break;
1501         }
1502
1503         /* Check if this socket has already been prepped */
1504         tunnel = (struct l2tp_tunnel *)sk->sk_user_data;
1505         if (tunnel != NULL) {
1506                 /* This socket has already been prepped */
1507                 err = -EBUSY;
1508                 goto err;
1509         }
1510
1511         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1512         if (tunnel == NULL) {
1513                 err = -ENOMEM;
1514                 goto err;
1515         }
1516
1517         tunnel->version = version;
1518         tunnel->tunnel_id = tunnel_id;
1519         tunnel->peer_tunnel_id = peer_tunnel_id;
1520         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1521
1522         tunnel->magic = L2TP_TUNNEL_MAGIC;
1523         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1524         rwlock_init(&tunnel->hlist_lock);
1525         tunnel->acpt_newsess = true;
1526
1527         /* The net we belong to */
1528         tunnel->l2tp_net = net;
1529         pn = l2tp_pernet(net);
1530
1531         if (cfg != NULL)
1532                 tunnel->debug = cfg->debug;
1533
1534         /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1535         tunnel->encap = encap;
1536         if (encap == L2TP_ENCAPTYPE_UDP) {
1537                 /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1538                 udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
1539                 udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
1540         }
1541
1542         sk->sk_user_data = tunnel;
1543
1544         /* Hook on the tunnel socket destructor so that we can cleanup
1545          * if the tunnel socket goes away.
1546          */
1547         tunnel->old_sk_destruct = sk->sk_destruct;
1548         sk->sk_destruct = &l2tp_tunnel_destruct;
1549         tunnel->sock = sk;
1550         sk->sk_allocation = GFP_ATOMIC;
1551
1552         /* Add tunnel to our list */
1553         INIT_LIST_HEAD(&tunnel->list);
1554         atomic_inc(&l2tp_tunnel_count);
1555
1556         /* Bump the reference count. The tunnel context is deleted
1557          * only when this drops to zero. Must be done before list insertion
1558          */
1559         l2tp_tunnel_inc_refcount(tunnel);
1560         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1561         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1562         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1563
1564         err = 0;
1565 err:
1566         if (tunnelp)
1567                 *tunnelp = tunnel;
1568
1569         /* If tunnel's socket was created by the kernel, it doesn't
1570          *  have a file.
1571          */
1572         if (sock && sock->file)
1573                 sockfd_put(sock);
1574
1575         return err;
1576 }
1577 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1578
1579 /* This function is used by the netlink TUNNEL_DELETE command.
1580  */
1581 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1582 {
1583         int err = 0;
1584         struct socket *sock = tunnel->sock ? tunnel->sock->sk_socket : NULL;
1585
1586         /* Force the tunnel socket to close. This will eventually
1587          * cause the tunnel to be deleted via the normal socket close
1588          * mechanisms when userspace closes the tunnel socket.
1589          */
1590         if (sock != NULL) {
1591                 err = inet_shutdown(sock, 2);
1592
1593                 /* If the tunnel's socket was created by the kernel,
1594                  * close the socket here since the socket was not
1595                  * created by userspace.
1596                  */
1597                 if (sock->file == NULL)
1598                         err = inet_release(sock);
1599         }
1600
1601         return err;
1602 }
1603 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1604
1605 /* Really kill the session.
1606  */
1607 void l2tp_session_free(struct l2tp_session *session)
1608 {
1609         struct l2tp_tunnel *tunnel;
1610
1611         BUG_ON(atomic_read(&session->ref_count) != 0);
1612
1613         tunnel = session->tunnel;
1614         if (tunnel != NULL) {
1615                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1616
1617                 /* Delete the session from the hash */
1618                 write_lock_bh(&tunnel->hlist_lock);
1619                 hlist_del_init(&session->hlist);
1620                 write_unlock_bh(&tunnel->hlist_lock);
1621
1622                 /* Unlink from the global hash if not L2TPv2 */
1623                 if (tunnel->version != L2TP_HDR_VER_2) {
1624                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1625
1626                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1627                         hlist_del_init_rcu(&session->global_hlist);
1628                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1629                         synchronize_rcu();
1630                 }
1631
1632                 if (session->session_id != 0)
1633                         atomic_dec(&l2tp_session_count);
1634
1635                 sock_put(tunnel->sock);
1636
1637                 /* This will delete the tunnel context if this
1638                  * is the last session on the tunnel.
1639                  */
1640                 session->tunnel = NULL;
1641                 l2tp_tunnel_dec_refcount(tunnel);
1642         }
1643
1644         kfree(session);
1645
1646         return;
1647 }
1648 EXPORT_SYMBOL_GPL(l2tp_session_free);
1649
1650 /* This function is used by the netlink SESSION_DELETE command and by
1651    pseudowire modules.
1652  */
1653 int l2tp_session_delete(struct l2tp_session *session)
1654 {
1655         if (session->session_close != NULL)
1656                 (*session->session_close)(session);
1657
1658         l2tp_session_dec_refcount(session);
1659
1660         return 0;
1661 }
1662 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1663
1664
1665 /* We come here whenever a session's send_seq, cookie_len or
1666  * l2specific_len parameters are set.
1667  */
1668 static void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1669 {
1670         if (version == L2TP_HDR_VER_2) {
1671                 session->hdr_len = 6;
1672                 if (session->send_seq)
1673                         session->hdr_len += 4;
1674         } else {
1675                 session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
1676                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1677                         session->hdr_len += 4;
1678         }
1679
1680 }
1681
1682 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)
1683 {
1684         struct l2tp_session *session;
1685         int err;
1686
1687         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1688         if (session != NULL) {
1689                 session->magic = L2TP_SESSION_MAGIC;
1690                 session->tunnel = tunnel;
1691
1692                 session->session_id = session_id;
1693                 session->peer_session_id = peer_session_id;
1694                 session->nr = 1;
1695
1696                 sprintf(&session->name[0], "sess %u/%u",
1697                         tunnel->tunnel_id, session->session_id);
1698
1699                 skb_queue_head_init(&session->reorder_q);
1700
1701                 INIT_HLIST_NODE(&session->hlist);
1702                 INIT_HLIST_NODE(&session->global_hlist);
1703
1704                 /* Inherit debug options from tunnel */
1705                 session->debug = tunnel->debug;
1706
1707                 if (cfg) {
1708                         session->pwtype = cfg->pw_type;
1709                         session->debug = cfg->debug;
1710                         session->mtu = cfg->mtu;
1711                         session->mru = cfg->mru;
1712                         session->send_seq = cfg->send_seq;
1713                         session->recv_seq = cfg->recv_seq;
1714                         session->lns_mode = cfg->lns_mode;
1715                         session->reorder_timeout = cfg->reorder_timeout;
1716                         session->offset = cfg->offset;
1717                         session->l2specific_type = cfg->l2specific_type;
1718                         session->l2specific_len = cfg->l2specific_len;
1719                         session->cookie_len = cfg->cookie_len;
1720                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1721                         session->peer_cookie_len = cfg->peer_cookie_len;
1722                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1723                 }
1724
1725                 if (tunnel->version == L2TP_HDR_VER_2)
1726                         session->build_header = l2tp_build_l2tpv2_header;
1727                 else
1728                         session->build_header = l2tp_build_l2tpv3_header;
1729
1730                 l2tp_session_set_header_len(session, tunnel->version);
1731
1732                 l2tp_session_inc_refcount(session);
1733
1734                 err = l2tp_session_add_to_tunnel(tunnel, session);
1735                 if (err) {
1736                         kfree(session);
1737
1738                         return ERR_PTR(err);
1739                 }
1740
1741                 /* Ignore management session in session count value */
1742                 if (session->session_id != 0)
1743                         atomic_inc(&l2tp_session_count);
1744
1745                 return session;
1746         }
1747
1748         return ERR_PTR(-ENOMEM);
1749 }
1750 EXPORT_SYMBOL_GPL(l2tp_session_create);
1751
1752 /*****************************************************************************
1753  * Init and cleanup
1754  *****************************************************************************/
1755
1756 static __net_init int l2tp_init_net(struct net *net)
1757 {
1758         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1759         int hash;
1760
1761         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1762         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1763
1764         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1765                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1766
1767         spin_lock_init(&pn->l2tp_session_hlist_lock);
1768
1769         return 0;
1770 }
1771
1772 static struct pernet_operations l2tp_net_ops = {
1773         .init = l2tp_init_net,
1774         .id   = &l2tp_net_id,
1775         .size = sizeof(struct l2tp_net),
1776 };
1777
1778 static int __init l2tp_init(void)
1779 {
1780         int rc = 0;
1781
1782         rc = register_pernet_device(&l2tp_net_ops);
1783         if (rc)
1784                 goto out;
1785
1786         printk(KERN_INFO "L2TP core driver, %s\n", L2TP_DRV_VERSION);
1787
1788 out:
1789         return rc;
1790 }
1791
1792 static void __exit l2tp_exit(void)
1793 {
1794         unregister_pernet_device(&l2tp_net_ops);
1795 }
1796
1797 module_init(l2tp_init);
1798 module_exit(l2tp_exit);
1799
1800 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1801 MODULE_DESCRIPTION("L2TP core");
1802 MODULE_LICENSE("GPL");
1803 MODULE_VERSION(L2TP_DRV_VERSION);
1804