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
 339         head = l2tp_session_id_hash(tunnel, session->session_id);
 340
 341         write_lock_bh(&tunnel->hlist_lock);
 342         hlist_for_each_entry(session_walk, walk, head, hlist)
 343                 if (session_walk->session_id == session->session_id)
 344                         goto exist;
 345
 346         if (tunnel->version == L2TP_HDR_VER_3) {
 347                 pn = l2tp_pernet(tunnel->l2tp_net);
 348                 g_head = l2tp_session_id_hash_2(l2tp_pernet(tunnel->l2tp_net),
 349                                                 session->session_id);
 350
 351                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
 352                 hlist_for_each_entry(session_walk, walk, g_head, global_hlist)
 353                         if (session_walk->session_id == session->session_id)
 354                                 goto exist_glob;
 355
 356                 hlist_add_head_rcu(&session->global_hlist, g_head);
 357                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 358         }
 359
 360         hlist_add_head(&session->hlist, head);
 361         write_unlock_bh(&tunnel->hlist_lock);
 362
 363         return 0;
 364
 365 exist_glob:
 366         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
 367 exist:
 368         write_unlock_bh(&tunnel->hlist_lock);
 369
 370         return -EEXIST;
 371 }
 372
 373 /* Lookup a tunnel by id
 374  */
 375 struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
 376 {
 377         struct l2tp_tunnel *tunnel;
 378         struct l2tp_net *pn = l2tp_pernet(net);
 379
 380         rcu_read_lock_bh();
 381         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 382                 if (tunnel->tunnel_id == tunnel_id) {
 383                         rcu_read_unlock_bh();
 384                         return tunnel;
 385                 }
 386         }
 387         rcu_read_unlock_bh();
 388
 389         return NULL;
 390 }
 391 EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
 392
 393 struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
 394 {
 395         struct l2tp_net *pn = l2tp_pernet(net);
 396         struct l2tp_tunnel *tunnel;
 397         int count = 0;
 398
 399         rcu_read_lock_bh();
 400         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 401                 if (++count > nth) {
 402                         rcu_read_unlock_bh();
 403                         return tunnel;
 404                 }
 405         }
 406
 407         rcu_read_unlock_bh();
 408
 409         return NULL;
 410 }
 411 EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
 412
 413 /*****************************************************************************
 414  * Receive data handling
 415  *****************************************************************************/
 416
 417 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 418  * number.
 419  */
 420 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 421 {
 422         struct sk_buff *skbp;
 423         struct sk_buff *tmp;
 424         u32 ns = L2TP_SKB_CB(skb)->ns;
 425
 426         spin_lock_bh(&session->reorder_q.lock);
 427         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 428                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 429                         __skb_queue_before(&session->reorder_q, skbp, skb);
 430                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 431                                "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 432                                session->name, ns, L2TP_SKB_CB(skbp)->ns,
 433                                skb_queue_len(&session->reorder_q));
 434                         session->stats.rx_oos_packets++;
 435                         goto out;
 436                 }
 437         }
 438
 439         __skb_queue_tail(&session->reorder_q, skb);
 440
 441 out:
 442         spin_unlock_bh(&session->reorder_q.lock);
 443 }
 444
 445 /* Dequeue a single skb.
 446  */
 447 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 448 {
 449         struct l2tp_tunnel *tunnel = session->tunnel;
 450         int length = L2TP_SKB_CB(skb)->length;
 451
 452         /* We're about to requeue the skb, so return resources
 453          * to its current owner (a socket receive buffer).
 454          */
 455         skb_orphan(skb);
 456
 457         tunnel->stats.rx_packets++;
 458         tunnel->stats.rx_bytes += length;
 459         session->stats.rx_packets++;
 460         session->stats.rx_bytes += length;
 461
 462         if (L2TP_SKB_CB(skb)->has_seq) {
 463                 /* Bump our Nr */
 464                 session->nr++;
 465                 if (tunnel->version == L2TP_HDR_VER_2)
 466                         session->nr &= 0xffff;
 467                 else
 468                         session->nr &= 0xffffff;
 469
 470                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 471                        "%s: updated nr to %hu\n", session->name, session->nr);
 472         }
 473
 474         /* call private receive handler */
 475         if (session->recv_skb != NULL)
 476                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 477         else
 478                 kfree_skb(skb);
 479
 480         if (session->deref)
 481                 (*session->deref)(session);
 482 }
 483
 484 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 485  * Skbs that have been in the queue for too long are simply discarded.
 486  */
 487 static void l2tp_recv_dequeue(struct l2tp_session *session)
 488 {
 489         struct sk_buff *skb;
 490         struct sk_buff *tmp;
 491
 492         /* If the pkt at the head of the queue has the nr that we
 493          * expect to send up next, dequeue it and any other
 494          * in-sequence packets behind it.
 495          */
 496 start:
 497         spin_lock_bh(&session->reorder_q.lock);
 498         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 499                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 500                         session->stats.rx_seq_discards++;
 501                         session->stats.rx_errors++;
 502                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 503                                "%s: oos pkt %u len %d discarded (too old), "
 504                                "waiting for %u, reorder_q_len=%d\n",
 505                                session->name, L2TP_SKB_CB(skb)->ns,
 506                                L2TP_SKB_CB(skb)->length, session->nr,
 507                                skb_queue_len(&session->reorder_q));
 508                         __skb_unlink(skb, &session->reorder_q);
 509                         kfree_skb(skb);
 510                         if (session->deref)
 511                                 (*session->deref)(session);
 512                         continue;
 513                 }
 514
 515                 if (L2TP_SKB_CB(skb)->has_seq) {
 516                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 517                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 518                                        "%s: holding oos pkt %u len %d, "
 519                                        "waiting for %u, reorder_q_len=%d\n",
 520                                        session->name, L2TP_SKB_CB(skb)->ns,
 521                                        L2TP_SKB_CB(skb)->length, session->nr,
 522                                        skb_queue_len(&session->reorder_q));
 523                                 goto out;
 524                         }
 525                 }
 526                 __skb_unlink(skb, &session->reorder_q);
 527
 528                 /* Process the skb. We release the queue lock while we
 529                  * do so to let other contexts process the queue.
 530                  */
 531                 spin_unlock_bh(&session->reorder_q.lock);
 532                 l2tp_recv_dequeue_skb(session, skb);
 533                 goto start;
 534         }
 535
 536 out:
 537         spin_unlock_bh(&session->reorder_q.lock);
 538 }
 539
 540 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 541                                            struct sk_buff *skb)
 542 {
 543         struct udphdr *uh = udp_hdr(skb);
 544         u16 ulen = ntohs(uh->len);
 545         struct inet_sock *inet;
 546         __wsum psum;
 547
 548         if (sk->sk_no_check || skb_csum_unnecessary(skb) || !uh->check)
 549                 return 0;
 550
 551         inet = inet_sk(sk);
 552         psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr, ulen,
 553                                   IPPROTO_UDP, 0);
 554
 555         if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 556             !csum_fold(csum_add(psum, skb->csum)))
 557                 return 0;
 558
 559         skb->csum = psum;
 560
 561         return __skb_checksum_complete(skb);
 562 }
 563
 564 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 565  * and L2TPv3 data frames here.
 566  *
 567  * L2TPv2 Data Message Header
 568  *
 569  *  0                   1                   2                   3
 570  *  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
 571  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 572  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 573  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 574  * |           Tunnel ID           |           Session ID          |
 575  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 576  * |             Ns (opt)          |             Nr (opt)          |
 577  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 578  * |      Offset Size (opt)        |    Offset pad... (opt)
 579  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 580  *
 581  * Data frames are marked by T=0. All other fields are the same as
 582  * those in L2TP control frames.
 583  *
 584  * L2TPv3 Data Message Header
 585  *
 586  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 587  * |                      L2TP Session Header                      |
 588  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 589  * |                      L2-Specific Sublayer                     |
 590  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 591  * |                        Tunnel Payload                      ...
 592  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 593  *
 594  * L2TPv3 Session Header Over IP
 595  *
 596  *  0                   1                   2                   3
 597  *  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
 598  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 599  * |                           Session ID                          |
 600  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 601  * |               Cookie (optional, maximum 64 bits)...
 602  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 603  *                                                                 |
 604  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 605  *
 606  * L2TPv3 L2-Specific Sublayer Format
 607  *
 608  *  0                   1                   2                   3
 609  *  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
 610  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 611  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 612  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 613  *
 614  * Cookie value, sublayer format and offset (pad) are negotiated with
 615  * the peer when the session is set up. Unlike L2TPv2, we do not need
 616  * to parse the packet header to determine if optional fields are
 617  * present.
 618  *
 619  * Caller must already have parsed the frame and determined that it is
 620  * a data (not control) frame before coming here. Fields up to the
 621  * session-id have already been parsed and ptr points to the data
 622  * after the session-id.
 623  *
 624  * session->ref() must have been called prior to l2tp_recv_common().
 625  * session->deref() will be called automatically after skb is processed.
 626  */
 627 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 628                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 629                       int length, int (*payload_hook)(struct sk_buff *skb))
 630 {
 631         struct l2tp_tunnel *tunnel = session->tunnel;
 632         int offset;
 633         u32 ns, nr;
 634
 635         /* Parse and check optional cookie */
 636         if (session->peer_cookie_len > 0) {
 637                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 638                         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 639                                "%s: cookie mismatch (%u/%u). Discarding.\n",
 640                                tunnel->name, tunnel->tunnel_id, session->session_id);
 641                         session->stats.rx_cookie_discards++;
 642                         goto discard;
 643                 }
 644                 ptr += session->peer_cookie_len;
 645         }
 646
 647         /* Handle the optional sequence numbers. Sequence numbers are
 648          * in different places for L2TPv2 and L2TPv3.
 649          *
 650          * If we are the LAC, enable/disable sequence numbers under
 651          * the control of the LNS.  If no sequence numbers present but
 652          * we were expecting them, discard frame.
 653          */
 654         ns = nr = 0;
 655         L2TP_SKB_CB(skb)->has_seq = 0;
 656         if (tunnel->version == L2TP_HDR_VER_2) {
 657                 if (hdrflags & L2TP_HDRFLAG_S) {
 658                         ns = ntohs(*(__be16 *) ptr);
 659                         ptr += 2;
 660                         nr = ntohs(*(__be16 *) ptr);
 661                         ptr += 2;
 662
 663                         /* Store L2TP info in the skb */
 664                         L2TP_SKB_CB(skb)->ns = ns;
 665                         L2TP_SKB_CB(skb)->has_seq = 1;
 666
 667                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 668                                "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 669                                session->name, ns, nr, session->nr);
 670                 }
 671         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 672                 u32 l2h = ntohl(*(__be32 *) ptr);
 673
 674                 if (l2h & 0x40000000) {
 675                         ns = l2h & 0x00ffffff;
 676
 677                         /* Store L2TP info in the skb */
 678                         L2TP_SKB_CB(skb)->ns = ns;
 679                         L2TP_SKB_CB(skb)->has_seq = 1;
 680
 681                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 682                                "%s: recv data ns=%u, session nr=%u\n",
 683                                session->name, ns, session->nr);
 684                 }
 685         }
 686
 687         /* Advance past L2-specific header, if present */
 688         ptr += session->l2specific_len;
 689
 690         if (L2TP_SKB_CB(skb)->has_seq) {
 691                 /* Received a packet with sequence numbers. If we're the LNS,
 692                  * check if we sre sending sequence numbers and if not,
 693                  * configure it so.
 694                  */
 695                 if ((!session->lns_mode) && (!session->send_seq)) {
 696                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 697                                "%s: requested to enable seq numbers by LNS\n",
 698                                session->name);
 699                         session->send_seq = -1;
 700                         l2tp_session_set_header_len(session, tunnel->version);
 701                 }
 702         } else {
 703                 /* No sequence numbers.
 704                  * If user has configured mandatory sequence numbers, discard.
 705                  */
 706                 if (session->recv_seq) {
 707                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 708                                "%s: recv data has no seq numbers when required. "
 709                                "Discarding\n", session->name);
 710                         session->stats.rx_seq_discards++;
 711                         goto discard;
 712                 }
 713
 714                 /* If we're the LAC and we're sending sequence numbers, the
 715                  * LNS has requested that we no longer send sequence numbers.
 716                  * If we're the LNS and we're sending sequence numbers, the
 717                  * LAC is broken. Discard the frame.
 718                  */
 719                 if ((!session->lns_mode) && (session->send_seq)) {
 720                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 721                                "%s: requested to disable seq numbers by LNS\n",
 722                                session->name);
 723                         session->send_seq = 0;
 724                         l2tp_session_set_header_len(session, tunnel->version);
 725                 } else if (session->send_seq) {
 726                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 727                                "%s: recv data has no seq numbers when required. "
 728                                "Discarding\n", session->name);
 729                         session->stats.rx_seq_discards++;
 730                         goto discard;
 731                 }
 732         }
 733
 734         /* Session data offset is handled differently for L2TPv2 and
 735          * L2TPv3. For L2TPv2, there is an optional 16-bit value in
 736          * the header. For L2TPv3, the offset is negotiated using AVPs
 737          * in the session setup control protocol.
 738          */
 739         if (tunnel->version == L2TP_HDR_VER_2) {
 740                 /* If offset bit set, skip it. */
 741                 if (hdrflags & L2TP_HDRFLAG_O) {
 742                         offset = ntohs(*(__be16 *)ptr);
 743                         ptr += 2 + offset;
 744                 }
 745         } else
 746                 ptr += session->offset;
 747
 748         offset = ptr - optr;
 749         if (!pskb_may_pull(skb, offset))
 750                 goto discard;
 751
 752         __skb_pull(skb, offset);
 753
 754         /* If caller wants to process the payload before we queue the
 755          * packet, do so now.
 756          */
 757         if (payload_hook)
 758                 if ((*payload_hook)(skb))
 759                         goto discard;
 760
 761         /* Prepare skb for adding to the session's reorder_q.  Hold
 762          * packets for max reorder_timeout or 1 second if not
 763          * reordering.
 764          */
 765         L2TP_SKB_CB(skb)->length = length;
 766         L2TP_SKB_CB(skb)->expires = jiffies +
 767                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 768
 769         /* Add packet to the session's receive queue. Reordering is done here, if
 770          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 771          */
 772         if (L2TP_SKB_CB(skb)->has_seq) {
 773                 if (session->reorder_timeout != 0) {
 774                         /* Packet reordering enabled. Add skb to session's
 775                          * reorder queue, in order of ns.
 776                          */
 777                         l2tp_recv_queue_skb(session, skb);
 778                 } else {
 779                         /* Packet reordering disabled. Discard out-of-sequence
 780                          * packets
 781                          */
 782                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 783                                 session->stats.rx_seq_discards++;
 784                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 785                                        "%s: oos pkt %u len %d discarded, "
 786                                        "waiting for %u, reorder_q_len=%d\n",
 787                                        session->name, L2TP_SKB_CB(skb)->ns,
 788                                        L2TP_SKB_CB(skb)->length, session->nr,
 789                                        skb_queue_len(&session->reorder_q));
 790                                 goto discard;
 791                         }
 792                         skb_queue_tail(&session->reorder_q, skb);
 793                 }
 794         } else {
 795                 /* No sequence numbers. Add the skb to the tail of the
 796                  * reorder queue. This ensures that it will be
 797                  * delivered after all previous sequenced skbs.
 798                  */
 799                 skb_queue_tail(&session->reorder_q, skb);
 800         }
 801
 802         /* Try to dequeue as many skbs from reorder_q as we can. */
 803         l2tp_recv_dequeue(session);
 804
 805         return;
 806
 807 discard:
 808         session->stats.rx_errors++;
 809         kfree_skb(skb);
 810
 811         if (session->deref)
 812                 (*session->deref)(session);
 813 }
 814 EXPORT_SYMBOL(l2tp_recv_common);
 815
 816 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 817  * here. The skb is not on a list when we get here.
 818  * Returns 0 if the packet was a data packet and was successfully passed on.
 819  * Returns 1 if the packet was not a good data packet and could not be
 820  * forwarded.  All such packets are passed up to userspace to deal with.
 821  */
 822 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 823                               int (*payload_hook)(struct sk_buff *skb))
 824 {
 825         struct l2tp_session *session = NULL;
 826         unsigned char *ptr, *optr;
 827         u16 hdrflags;
 828         u32 tunnel_id, session_id;
 829         int offset;
 830         u16 version;
 831         int length;
 832
 833         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
 834                 goto discard_bad_csum;
 835
 836         /* UDP always verifies the packet length. */
 837         __skb_pull(skb, sizeof(struct udphdr));
 838
 839         /* Short packet? */
 840         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
 841                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 842                        "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
 843                 goto error;
 844         }
 845
 846         /* Trace packet contents, if enabled */
 847         if (tunnel->debug & L2TP_MSG_DATA) {
 848                 length = min(32u, skb->len);
 849                 if (!pskb_may_pull(skb, length))
 850                         goto error;
 851
 852                 printk(KERN_DEBUG "%s: recv: ", tunnel->name);
 853
 854                 offset = 0;
 855                 do {
 856                         printk(" %02X", skb->data[offset]);
 857                 } while (++offset < length);
 858
 859                 printk("\n");
 860         }
 861
 862         /* Point to L2TP header */
 863         optr = ptr = skb->data;
 864
 865         /* Get L2TP header flags */
 866         hdrflags = ntohs(*(__be16 *) ptr);
 867
 868         /* Check protocol version */
 869         version = hdrflags & L2TP_HDR_VER_MASK;
 870         if (version != tunnel->version) {
 871                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 872                        "%s: recv protocol version mismatch: got %d expected %d\n",
 873                        tunnel->name, version, tunnel->version);
 874                 goto error;
 875         }
 876
 877         /* Get length of L2TP packet */
 878         length = skb->len;
 879
 880         /* If type is control packet, it is handled by userspace. */
 881         if (hdrflags & L2TP_HDRFLAG_T) {
 882                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 883                        "%s: recv control packet, len=%d\n", tunnel->name, length);
 884                 goto error;
 885         }
 886
 887         /* Skip flags */
 888         ptr += 2;
 889
 890         if (tunnel->version == L2TP_HDR_VER_2) {
 891                 /* If length is present, skip it */
 892                 if (hdrflags & L2TP_HDRFLAG_L)
 893                         ptr += 2;
 894
 895                 /* Extract tunnel and session ID */
 896                 tunnel_id = ntohs(*(__be16 *) ptr);
 897                 ptr += 2;
 898                 session_id = ntohs(*(__be16 *) ptr);
 899                 ptr += 2;
 900         } else {
 901                 ptr += 2;       /* skip reserved bits */
 902                 tunnel_id = tunnel->tunnel_id;
 903                 session_id = ntohl(*(__be32 *) ptr);
 904                 ptr += 4;
 905         }
 906
 907         /* Find the session context */
 908         session = l2tp_session_get(tunnel->l2tp_net, tunnel, session_id, true);
 909         if (!session || !session->recv_skb) {
 910                 if (session) {
 911                         if (session->deref)
 912                                 session->deref(session);
 913                         l2tp_session_dec_refcount(session);
 914                 }
 915
 916                 /* Not found? Pass to userspace to deal with */
 917                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 918                        "%s: no session found (%u/%u). Passing up.\n",
 919                        tunnel->name, tunnel_id, session_id);
 920                 goto error;
 921         }
 922
 923         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
 924         l2tp_session_dec_refcount(session);
 925
 926         return 0;
 927
 928 discard_bad_csum:
 929         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
 930         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
 931         tunnel->stats.rx_errors++;
 932         kfree_skb(skb);
 933
 934         return 0;
 935
 936 error:
 937         /* Put UDP header back */
 938         __skb_push(skb, sizeof(struct udphdr));
 939
 940         return 1;
 941 }
 942
 943 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 944  * Return codes:
 945  * 0 : success.
 946  * <0: error
 947  * >0: skb should be passed up to userspace as UDP.
 948  */
 949 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 950 {
 951         struct l2tp_tunnel *tunnel;
 952
 953         tunnel = l2tp_sock_to_tunnel(sk);
 954         if (tunnel == NULL)
 955                 goto pass_up;
 956
 957         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 958                "%s: received %d bytes\n", tunnel->name, skb->len);
 959
 960         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
 961                 goto pass_up_put;
 962
 963         sock_put(sk);
 964         return 0;
 965
 966 pass_up_put:
 967         sock_put(sk);
 968 pass_up:
 969         return 1;
 970 }
 971 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 972
 973 /************************************************************************
 974  * Transmit handling
 975  ***********************************************************************/
 976
 977 /* Build an L2TP header for the session into the buffer provided.
 978  */
 979 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 980 {
 981         struct l2tp_tunnel *tunnel = session->tunnel;
 982         __be16 *bufp = buf;
 983         __be16 *optr = buf;
 984         u16 flags = L2TP_HDR_VER_2;
 985         u32 tunnel_id = tunnel->peer_tunnel_id;
 986         u32 session_id = session->peer_session_id;
 987
 988         if (session->send_seq)
 989                 flags |= L2TP_HDRFLAG_S;
 990
 991         /* Setup L2TP header. */
 992         *bufp++ = htons(flags);
 993         *bufp++ = htons(tunnel_id);
 994         *bufp++ = htons(session_id);
 995         if (session->send_seq) {
 996                 *bufp++ = htons(session->ns);
 997                 *bufp++ = 0;
 998                 session->ns++;
 999                 session->ns &= 0xffff;
1000                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
1001                        "%s: updated ns to %u\n", session->name, session->ns);
1002         }
1003
1004         return bufp - optr;
1005 }
1006
1007 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
1008 {
1009         struct l2tp_tunnel *tunnel = session->tunnel;
1010         char *bufp = buf;
1011         char *optr = bufp;
1012
1013         /* Setup L2TP header. The header differs slightly for UDP and
1014          * IP encapsulations. For UDP, there is 4 bytes of flags.
1015          */
1016         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1017                 u16 flags = L2TP_HDR_VER_3;
1018                 *((__be16 *) bufp) = htons(flags);
1019                 bufp += 2;
1020                 *((__be16 *) bufp) = 0;
1021                 bufp += 2;
1022         }
1023
1024         *((__be32 *) bufp) = htonl(session->peer_session_id);
1025         bufp += 4;
1026         if (session->cookie_len) {
1027                 memcpy(bufp, &session->cookie[0], session->cookie_len);
1028                 bufp += session->cookie_len;
1029         }
1030         if (session->l2specific_len) {
1031                 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
1032                         u32 l2h = 0;
1033                         if (session->send_seq) {
1034                                 l2h = 0x40000000 | session->ns;
1035                                 session->ns++;
1036                                 session->ns &= 0xffffff;
1037                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
1038                                        "%s: updated ns to %u\n", session->name, session->ns);
1039                         }
1040
1041                         *((__be32 *) bufp) = htonl(l2h);
1042                 }
1043                 bufp += session->l2specific_len;
1044         }
1045         if (session->offset)
1046                 bufp += session->offset;
1047
1048         return bufp - optr;
1049 }
1050
1051 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
1052                           struct flowi *fl, size_t data_len)
1053 {
1054         struct l2tp_tunnel *tunnel = session->tunnel;
1055         unsigned int len = skb->len;
1056         int error;
1057
1058         /* Debug */
1059         if (session->send_seq)
1060                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
1061                        "%s: send %Zd bytes, ns=%u\n", session->name,
1062                        data_len, session->ns - 1);
1063         else
1064                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
1065                        "%s: send %Zd bytes\n", session->name, data_len);
1066
1067         if (session->debug & L2TP_MSG_DATA) {
1068                 int i;
1069                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1070                 unsigned char *datap = skb->data + uhlen;
1071
1072                 printk(KERN_DEBUG "%s: xmit:", session->name);
1073                 for (i = 0; i < (len - uhlen); i++) {
1074                         printk(" %02X", *datap++);
1075                         if (i == 31) {
1076                                 printk(" ...");
1077                                 break;
1078                         }
1079                 }
1080                 printk("\n");
1081         }
1082
1083         /* Queue the packet to IP for output */
1084         skb->local_df = 1;
1085         error = ip_queue_xmit(skb, fl);
1086
1087         /* Update stats */
1088         if (error >= 0) {
1089                 tunnel->stats.tx_packets++;
1090                 tunnel->stats.tx_bytes += len;
1091                 session->stats.tx_packets++;
1092                 session->stats.tx_bytes += len;
1093         } else {
1094                 tunnel->stats.tx_errors++;
1095                 session->stats.tx_errors++;
1096         }
1097
1098         return 0;
1099 }
1100
1101 /* Automatically called when the skb is freed.
1102  */
1103 static void l2tp_sock_wfree(struct sk_buff *skb)
1104 {
1105         sock_put(skb->sk);
1106 }
1107
1108 /* For data skbs that we transmit, we associate with the tunnel socket
1109  * but don't do accounting.
1110  */
1111 static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
1112 {
1113         sock_hold(sk);
1114         skb->sk = sk;
1115         skb->destructor = l2tp_sock_wfree;
1116 }
1117
1118 /* If caller requires the skb to have a ppp header, the header must be
1119  * inserted in the skb data before calling this function.
1120  */
1121 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1122 {
1123         int data_len = skb->len;
1124         struct l2tp_tunnel *tunnel = session->tunnel;
1125         struct sock *sk = tunnel->sock;
1126         struct flowi *fl;
1127         struct udphdr *uh;
1128         struct inet_sock *inet;
1129         __wsum csum;
1130         int old_headroom;
1131         int new_headroom;
1132         int headroom;
1133         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1134         int udp_len;
1135
1136         /* Check that there's enough headroom in the skb to insert IP,
1137          * UDP and L2TP headers. If not enough, expand it to
1138          * make room. Adjust truesize.
1139          */
1140         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1141                 uhlen + hdr_len;
1142         old_headroom = skb_headroom(skb);
1143         if (skb_cow_head(skb, headroom)) {
1144                 dev_kfree_skb(skb);
1145                 goto abort;
1146         }
1147
1148         new_headroom = skb_headroom(skb);
1149         skb_orphan(skb);
1150         skb->truesize += new_headroom - old_headroom;
1151
1152         /* Setup L2TP header */
1153         session->build_header(session, __skb_push(skb, hdr_len));
1154
1155         /* Reset skb netfilter state */
1156         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1157         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1158                               IPSKB_REROUTED);
1159         nf_reset(skb);
1160
1161         bh_lock_sock(sk);
1162         if (sock_owned_by_user(sk)) {
1163                 dev_kfree_skb(skb);
1164                 goto out_unlock;
1165         }
1166
1167         /* Get routing info from the tunnel socket */
1168         skb_dst_drop(skb);
1169         skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
1170
1171         inet = inet_sk(sk);
1172         fl = &inet->cork.fl;
1173         switch (tunnel->encap) {
1174         case L2TP_ENCAPTYPE_UDP:
1175                 /* Setup UDP header */
1176                 __skb_push(skb, sizeof(*uh));
1177                 skb_reset_transport_header(skb);
1178                 uh = udp_hdr(skb);
1179                 uh->source = inet->inet_sport;
1180                 uh->dest = inet->inet_dport;
1181                 udp_len = uhlen + hdr_len + data_len;
1182                 uh->len = htons(udp_len);
1183                 uh->check = 0;
1184
1185                 /* Calculate UDP checksum if configured to do so */
1186                 if (sk->sk_no_check == UDP_CSUM_NOXMIT)
1187                         skb->ip_summed = CHECKSUM_NONE;
1188                 else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
1189                          (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
1190                         skb->ip_summed = CHECKSUM_COMPLETE;
1191                         csum = skb_checksum(skb, 0, udp_len, 0);
1192                         uh->check = csum_tcpudp_magic(inet->inet_saddr,
1193                                                       inet->inet_daddr,
1194                                                       udp_len, IPPROTO_UDP, csum);
1195                         if (uh->check == 0)
1196                                 uh->check = CSUM_MANGLED_0;
1197                 } else {
1198                         skb->ip_summed = CHECKSUM_PARTIAL;
1199                         skb->csum_start = skb_transport_header(skb) - skb->head;
1200                         skb->csum_offset = offsetof(struct udphdr, check);
1201                         uh->check = ~csum_tcpudp_magic(inet->inet_saddr,
1202                                                        inet->inet_daddr,
1203                                                        udp_len, IPPROTO_UDP, 0);
1204                 }
1205                 break;
1206
1207         case L2TP_ENCAPTYPE_IP:
1208                 break;
1209         }
1210
1211         l2tp_skb_set_owner_w(skb, sk);
1212
1213         l2tp_xmit_core(session, skb, fl, data_len);
1214 out_unlock:
1215         bh_unlock_sock(sk);
1216
1217 abort:
1218         return 0;
1219 }
1220 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1221
1222 /*****************************************************************************
1223  * Tinnel and session create/destroy.
1224  *****************************************************************************/
1225
1226 /* Tunnel socket destruct hook.
1227  * The tunnel context is deleted only when all session sockets have been
1228  * closed.
1229  */
1230 static void l2tp_tunnel_destruct(struct sock *sk)
1231 {
1232         struct l2tp_tunnel *tunnel;
1233
1234         tunnel = sk->sk_user_data;
1235         if (tunnel == NULL)
1236                 goto end;
1237
1238         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1239                "%s: closing...\n", tunnel->name);
1240
1241         /* Close all sessions */
1242         l2tp_tunnel_closeall(tunnel);
1243
1244         switch (tunnel->encap) {
1245         case L2TP_ENCAPTYPE_UDP:
1246                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1247                 (udp_sk(sk))->encap_type = 0;
1248                 (udp_sk(sk))->encap_rcv = NULL;
1249                 break;
1250         case L2TP_ENCAPTYPE_IP:
1251                 break;
1252         }
1253
1254         /* Remove hooks into tunnel socket */
1255         tunnel->sock = NULL;
1256         sk->sk_destruct = tunnel->old_sk_destruct;
1257         sk->sk_user_data = NULL;
1258
1259         /* Call the original destructor */
1260         if (sk->sk_destruct)
1261                 (*sk->sk_destruct)(sk);
1262
1263         /* We're finished with the socket */
1264         l2tp_tunnel_dec_refcount(tunnel);
1265
1266 end:
1267         return;
1268 }
1269
1270 /* When the tunnel is closed, all the attached sessions need to go too.
1271  */
1272 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1273 {
1274         int hash;
1275         struct hlist_node *walk;
1276         struct hlist_node *tmp;
1277         struct l2tp_session *session;
1278
1279         BUG_ON(tunnel == NULL);
1280
1281         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1282                "%s: closing all sessions...\n", tunnel->name);
1283
1284         write_lock_bh(&tunnel->hlist_lock);
1285         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1286 again:
1287                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1288                         session = hlist_entry(walk, struct l2tp_session, hlist);
1289
1290                         PRINTK(session->debug, L2TP_MSG_CONTROL, KERN_INFO,
1291                                "%s: closing session\n", session->name);
1292
1293                         hlist_del_init(&session->hlist);
1294
1295                         /* Since we should hold the sock lock while
1296                          * doing any unbinding, we need to release the
1297                          * lock we're holding before taking that lock.
1298                          * Hold a reference to the sock so it doesn't
1299                          * disappear as we're jumping between locks.
1300                          */
1301                         if (session->ref != NULL)
1302                                 (*session->ref)(session);
1303
1304                         write_unlock_bh(&tunnel->hlist_lock);
1305
1306                         if (tunnel->version != L2TP_HDR_VER_2) {
1307                                 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1308
1309                                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
1310                                 hlist_del_init_rcu(&session->global_hlist);
1311                                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1312                                 synchronize_rcu();
1313                         }
1314
1315                         if (session->session_close != NULL)
1316                                 (*session->session_close)(session);
1317
1318                         if (session->deref != NULL)
1319                                 (*session->deref)(session);
1320
1321                         write_lock_bh(&tunnel->hlist_lock);
1322
1323                         /* Now restart from the beginning of this hash
1324                          * chain.  We always remove a session from the
1325                          * list so we are guaranteed to make forward
1326                          * progress.
1327                          */
1328                         goto again;
1329                 }
1330         }
1331         write_unlock_bh(&tunnel->hlist_lock);
1332 }
1333
1334 /* Really kill the tunnel.
1335  * Come here only when all sessions have been cleared from the tunnel.
1336  */
1337 void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
1338 {
1339         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1340
1341         BUG_ON(atomic_read(&tunnel->ref_count) != 0);
1342         BUG_ON(tunnel->sock != NULL);
1343
1344         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1345                "%s: free...\n", tunnel->name);
1346
1347         /* Remove from tunnel list */
1348         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1349         list_del_rcu(&tunnel->list);
1350         kfree_rcu(tunnel, rcu);
1351         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1352
1353         atomic_dec(&l2tp_tunnel_count);
1354 }
1355 EXPORT_SYMBOL_GPL(l2tp_tunnel_free);
1356
1357 /* Create a socket for the tunnel, if one isn't set up by
1358  * userspace. This is used for static tunnels where there is no
1359  * managing L2TP daemon.
1360  */
1361 static int l2tp_tunnel_sock_create(u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct socket **sockp)
1362 {
1363         int err = -EINVAL;
1364         struct sockaddr_in udp_addr;
1365         struct sockaddr_l2tpip ip_addr;
1366         struct socket *sock = NULL;
1367
1368         switch (cfg->encap) {
1369         case L2TP_ENCAPTYPE_UDP:
1370                 err = sock_create(AF_INET, SOCK_DGRAM, 0, sockp);
1371                 if (err < 0)
1372                         goto out;
1373
1374                 sock = *sockp;
1375
1376                 memset(&udp_addr, 0, sizeof(udp_addr));
1377                 udp_addr.sin_family = AF_INET;
1378                 udp_addr.sin_addr = cfg->local_ip;
1379                 udp_addr.sin_port = htons(cfg->local_udp_port);
1380                 err = kernel_bind(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr));
1381                 if (err < 0)
1382                         goto out;
1383
1384                 udp_addr.sin_family = AF_INET;
1385                 udp_addr.sin_addr = cfg->peer_ip;
1386                 udp_addr.sin_port = htons(cfg->peer_udp_port);
1387                 err = kernel_connect(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr), 0);
1388                 if (err < 0)
1389                         goto out;
1390
1391                 if (!cfg->use_udp_checksums)
1392                         sock->sk->sk_no_check = UDP_CSUM_NOXMIT;
1393
1394                 break;
1395
1396         case L2TP_ENCAPTYPE_IP:
1397                 err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_L2TP, sockp);
1398                 if (err < 0)
1399                         goto out;
1400
1401                 sock = *sockp;
1402
1403                 memset(&ip_addr, 0, sizeof(ip_addr));
1404                 ip_addr.l2tp_family = AF_INET;
1405                 ip_addr.l2tp_addr = cfg->local_ip;
1406                 ip_addr.l2tp_conn_id = tunnel_id;
1407                 err = kernel_bind(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr));
1408                 if (err < 0)
1409                         goto out;
1410
1411                 ip_addr.l2tp_family = AF_INET;
1412                 ip_addr.l2tp_addr = cfg->peer_ip;
1413                 ip_addr.l2tp_conn_id = peer_tunnel_id;
1414                 err = kernel_connect(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr), 0);
1415                 if (err < 0)
1416                         goto out;
1417
1418                 break;
1419
1420         default:
1421                 goto out;
1422         }
1423
1424 out:
1425         if ((err < 0) && sock) {
1426                 sock_release(sock);
1427                 *sockp = NULL;
1428         }
1429
1430         return err;
1431 }
1432
1433 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)
1434 {
1435         struct l2tp_tunnel *tunnel = NULL;
1436         int err;
1437         struct socket *sock = NULL;
1438         struct sock *sk = NULL;
1439         struct l2tp_net *pn;
1440         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1441
1442         /* Get the tunnel socket from the fd, which was opened by
1443          * the userspace L2TP daemon. If not specified, create a
1444          * kernel socket.
1445          */
1446         if (fd < 0) {
1447                 err = l2tp_tunnel_sock_create(tunnel_id, peer_tunnel_id, cfg, &sock);
1448                 if (err < 0)
1449                         goto err;
1450         } else {
1451                 err = -EBADF;
1452                 sock = sockfd_lookup(fd, &err);
1453                 if (!sock) {
1454                         printk(KERN_ERR "tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
1455                                tunnel_id, fd, err);
1456                         goto err;
1457                 }
1458         }
1459
1460         sk = sock->sk;
1461
1462         if (cfg != NULL)
1463                 encap = cfg->encap;
1464
1465         /* Quick sanity checks */
1466         switch (encap) {
1467         case L2TP_ENCAPTYPE_UDP:
1468                 err = -EPROTONOSUPPORT;
1469                 if (sk->sk_protocol != IPPROTO_UDP) {
1470                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1471                                tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
1472                         goto err;
1473                 }
1474                 break;
1475         case L2TP_ENCAPTYPE_IP:
1476                 err = -EPROTONOSUPPORT;
1477                 if (sk->sk_protocol != IPPROTO_L2TP) {
1478                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1479                                tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
1480                         goto err;
1481                 }
1482                 break;
1483         }
1484
1485         /* Check if this socket has already been prepped */
1486         tunnel = (struct l2tp_tunnel *)sk->sk_user_data;
1487         if (tunnel != NULL) {
1488                 /* This socket has already been prepped */
1489                 err = -EBUSY;
1490                 goto err;
1491         }
1492
1493         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1494         if (tunnel == NULL) {
1495                 err = -ENOMEM;
1496                 goto err;
1497         }
1498
1499         tunnel->version = version;
1500         tunnel->tunnel_id = tunnel_id;
1501         tunnel->peer_tunnel_id = peer_tunnel_id;
1502         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1503
1504         tunnel->magic = L2TP_TUNNEL_MAGIC;
1505         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1506         rwlock_init(&tunnel->hlist_lock);
1507
1508         /* The net we belong to */
1509         tunnel->l2tp_net = net;
1510         pn = l2tp_pernet(net);
1511
1512         if (cfg != NULL)
1513                 tunnel->debug = cfg->debug;
1514
1515         /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1516         tunnel->encap = encap;
1517         if (encap == L2TP_ENCAPTYPE_UDP) {
1518                 /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1519                 udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
1520                 udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
1521         }
1522
1523         sk->sk_user_data = tunnel;
1524
1525         /* Hook on the tunnel socket destructor so that we can cleanup
1526          * if the tunnel socket goes away.
1527          */
1528         tunnel->old_sk_destruct = sk->sk_destruct;
1529         sk->sk_destruct = &l2tp_tunnel_destruct;
1530         tunnel->sock = sk;
1531         sk->sk_allocation = GFP_ATOMIC;
1532
1533         /* Add tunnel to our list */
1534         INIT_LIST_HEAD(&tunnel->list);
1535         atomic_inc(&l2tp_tunnel_count);
1536
1537         /* Bump the reference count. The tunnel context is deleted
1538          * only when this drops to zero. Must be done before list insertion
1539          */
1540         l2tp_tunnel_inc_refcount(tunnel);
1541         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1542         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1543         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1544
1545         err = 0;
1546 err:
1547         if (tunnelp)
1548                 *tunnelp = tunnel;
1549
1550         /* If tunnel's socket was created by the kernel, it doesn't
1551          *  have a file.
1552          */
1553         if (sock && sock->file)
1554                 sockfd_put(sock);
1555
1556         return err;
1557 }
1558 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1559
1560 /* This function is used by the netlink TUNNEL_DELETE command.
1561  */
1562 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1563 {
1564         int err = 0;
1565         struct socket *sock = tunnel->sock ? tunnel->sock->sk_socket : NULL;
1566
1567         /* Force the tunnel socket to close. This will eventually
1568          * cause the tunnel to be deleted via the normal socket close
1569          * mechanisms when userspace closes the tunnel socket.
1570          */
1571         if (sock != NULL) {
1572                 err = inet_shutdown(sock, 2);
1573
1574                 /* If the tunnel's socket was created by the kernel,
1575                  * close the socket here since the socket was not
1576                  * created by userspace.
1577                  */
1578                 if (sock->file == NULL)
1579                         err = inet_release(sock);
1580         }
1581
1582         return err;
1583 }
1584 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1585
1586 /* Really kill the session.
1587  */
1588 void l2tp_session_free(struct l2tp_session *session)
1589 {
1590         struct l2tp_tunnel *tunnel;
1591
1592         BUG_ON(atomic_read(&session->ref_count) != 0);
1593
1594         tunnel = session->tunnel;
1595         if (tunnel != NULL) {
1596                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1597
1598                 /* Delete the session from the hash */
1599                 write_lock_bh(&tunnel->hlist_lock);
1600                 hlist_del_init(&session->hlist);
1601                 write_unlock_bh(&tunnel->hlist_lock);
1602
1603                 /* Unlink from the global hash if not L2TPv2 */
1604                 if (tunnel->version != L2TP_HDR_VER_2) {
1605                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1606
1607                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1608                         hlist_del_init_rcu(&session->global_hlist);
1609                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1610                         synchronize_rcu();
1611                 }
1612
1613                 if (session->session_id != 0)
1614                         atomic_dec(&l2tp_session_count);
1615
1616                 sock_put(tunnel->sock);
1617
1618                 /* This will delete the tunnel context if this
1619                  * is the last session on the tunnel.
1620                  */
1621                 session->tunnel = NULL;
1622                 l2tp_tunnel_dec_refcount(tunnel);
1623         }
1624
1625         kfree(session);
1626
1627         return;
1628 }
1629 EXPORT_SYMBOL_GPL(l2tp_session_free);
1630
1631 /* This function is used by the netlink SESSION_DELETE command and by
1632    pseudowire modules.
1633  */
1634 int l2tp_session_delete(struct l2tp_session *session)
1635 {
1636         if (session->session_close != NULL)
1637                 (*session->session_close)(session);
1638
1639         l2tp_session_dec_refcount(session);
1640
1641         return 0;
1642 }
1643 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1644
1645
1646 /* We come here whenever a session's send_seq, cookie_len or
1647  * l2specific_len parameters are set.
1648  */
1649 static void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1650 {
1651         if (version == L2TP_HDR_VER_2) {
1652                 session->hdr_len = 6;
1653                 if (session->send_seq)
1654                         session->hdr_len += 4;
1655         } else {
1656                 session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
1657                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1658                         session->hdr_len += 4;
1659         }
1660
1661 }
1662
1663 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)
1664 {
1665         struct l2tp_session *session;
1666         int err;
1667
1668         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1669         if (session != NULL) {
1670                 session->magic = L2TP_SESSION_MAGIC;
1671                 session->tunnel = tunnel;
1672
1673                 session->session_id = session_id;
1674                 session->peer_session_id = peer_session_id;
1675                 session->nr = 1;
1676
1677                 sprintf(&session->name[0], "sess %u/%u",
1678                         tunnel->tunnel_id, session->session_id);
1679
1680                 skb_queue_head_init(&session->reorder_q);
1681
1682                 INIT_HLIST_NODE(&session->hlist);
1683                 INIT_HLIST_NODE(&session->global_hlist);
1684
1685                 /* Inherit debug options from tunnel */
1686                 session->debug = tunnel->debug;
1687
1688                 if (cfg) {
1689                         session->pwtype = cfg->pw_type;
1690                         session->debug = cfg->debug;
1691                         session->mtu = cfg->mtu;
1692                         session->mru = cfg->mru;
1693                         session->send_seq = cfg->send_seq;
1694                         session->recv_seq = cfg->recv_seq;
1695                         session->lns_mode = cfg->lns_mode;
1696                         session->reorder_timeout = cfg->reorder_timeout;
1697                         session->offset = cfg->offset;
1698                         session->l2specific_type = cfg->l2specific_type;
1699                         session->l2specific_len = cfg->l2specific_len;
1700                         session->cookie_len = cfg->cookie_len;
1701                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1702                         session->peer_cookie_len = cfg->peer_cookie_len;
1703                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1704                 }
1705
1706                 if (tunnel->version == L2TP_HDR_VER_2)
1707                         session->build_header = l2tp_build_l2tpv2_header;
1708                 else
1709                         session->build_header = l2tp_build_l2tpv3_header;
1710
1711                 l2tp_session_set_header_len(session, tunnel->version);
1712
1713                 l2tp_session_inc_refcount(session);
1714
1715                 err = l2tp_session_add_to_tunnel(tunnel, session);
1716                 if (err) {
1717                         kfree(session);
1718
1719                         return ERR_PTR(err);
1720                 }
1721
1722                 l2tp_tunnel_inc_refcount(tunnel);
1723
1724                 /* Ensure tunnel socket isn't deleted */
1725                 sock_hold(tunnel->sock);
1726
1727                 /* Ignore management session in session count value */
1728                 if (session->session_id != 0)
1729                         atomic_inc(&l2tp_session_count);
1730
1731                 return session;
1732         }
1733
1734         return ERR_PTR(-ENOMEM);
1735 }
1736 EXPORT_SYMBOL_GPL(l2tp_session_create);
1737
1738 /*****************************************************************************
1739  * Init and cleanup
1740  *****************************************************************************/
1741
1742 static __net_init int l2tp_init_net(struct net *net)
1743 {
1744         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1745         int hash;
1746
1747         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1748         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1749
1750         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1751                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1752
1753         spin_lock_init(&pn->l2tp_session_hlist_lock);
1754
1755         return 0;
1756 }
1757
1758 static struct pernet_operations l2tp_net_ops = {
1759         .init = l2tp_init_net,
1760         .id   = &l2tp_net_id,
1761         .size = sizeof(struct l2tp_net),
1762 };
1763
1764 static int __init l2tp_init(void)
1765 {
1766         int rc = 0;
1767
1768         rc = register_pernet_device(&l2tp_net_ops);
1769         if (rc)
1770                 goto out;
1771
1772         printk(KERN_INFO "L2TP core driver, %s\n", L2TP_DRV_VERSION);
1773
1774 out:
1775         return rc;
1776 }
1777
1778 static void __exit l2tp_exit(void)
1779 {
1780         unregister_pernet_device(&l2tp_net_ops);
1781 }
1782
1783 module_init(l2tp_init);
1784 module_exit(l2tp_exit);
1785
1786 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1787 MODULE_DESCRIPTION("L2TP core");
1788 MODULE_LICENSE("GPL");
1789 MODULE_VERSION(L2TP_DRV_VERSION);
1790