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_free(struct l2tp_tunnel *tunnel);
 116 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
 117
 118 static inline struct l2tp_net *l2tp_pernet(struct net *net)
 119 {
 120         BUG_ON(!net);
 121
 122         return net_generic(net, l2tp_net_id);
 123 }
 124
 125
 126 /* Tunnel reference counts. Incremented per session that is added to
 127  * the tunnel.
 128  */
 129 static inline void l2tp_tunnel_inc_refcount_1(struct l2tp_tunnel *tunnel)
 130 {
 131         atomic_inc(&tunnel->ref_count);
 132 }
 133
 134 static inline void l2tp_tunnel_dec_refcount_1(struct l2tp_tunnel *tunnel)
 135 {
 136         if (atomic_dec_and_test(&tunnel->ref_count))
 137                 l2tp_tunnel_free(tunnel);
 138 }
 139 #ifdef L2TP_REFCNT_DEBUG
 140 #define l2tp_tunnel_inc_refcount(_t) do { \
 141                 printk(KERN_DEBUG "l2tp_tunnel_inc_refcount: %s:%d %s: cnt=%d\n", __func__, __LINE__, (_t)->name, atomic_read(&_t->ref_count)); \
 142                 l2tp_tunnel_inc_refcount_1(_t);                         \
 143         } while (0)
 144 #define l2tp_tunnel_dec_refcount(_t) do { \
 145                 printk(KERN_DEBUG "l2tp_tunnel_dec_refcount: %s:%d %s: cnt=%d\n", __func__, __LINE__, (_t)->name, atomic_read(&_t->ref_count)); \
 146                 l2tp_tunnel_dec_refcount_1(_t);                         \
 147         } while (0)
 148 #else
 149 #define l2tp_tunnel_inc_refcount(t) l2tp_tunnel_inc_refcount_1(t)
 150 #define l2tp_tunnel_dec_refcount(t) l2tp_tunnel_dec_refcount_1(t)
 151 #endif
 152
 153 /* Session hash global list for L2TPv3.
 154  * The session_id SHOULD be random according to RFC3931, but several
 155  * L2TP implementations use incrementing session_ids.  So we do a real
 156  * hash on the session_id, rather than a simple bitmask.
 157  */
 158 static inline struct hlist_head *
 159 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 160 {
 161         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 162
 163 }
 164
 165 /* Lookup a session by id in the global session list
 166  */
 167 static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id)
 168 {
 169         struct l2tp_net *pn = l2tp_pernet(net);
 170         struct hlist_head *session_list =
 171                 l2tp_session_id_hash_2(pn, session_id);
 172         struct l2tp_session *session;
 173         struct hlist_node *walk;
 174
 175         rcu_read_lock_bh();
 176         hlist_for_each_entry_rcu(session, walk, session_list, global_hlist) {
 177                 if (session->session_id == session_id) {
 178                         rcu_read_unlock_bh();
 179                         return session;
 180                 }
 181         }
 182         rcu_read_unlock_bh();
 183
 184         return NULL;
 185 }
 186
 187 /* Session hash list.
 188  * The session_id SHOULD be random according to RFC2661, but several
 189  * L2TP implementations (Cisco and Microsoft) use incrementing
 190  * session_ids.  So we do a real hash on the session_id, rather than a
 191  * simple bitmask.
 192  */
 193 static inline struct hlist_head *
 194 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 195 {
 196         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 197 }
 198
 199 /* Lookup a session by id
 200  */
 201 struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id)
 202 {
 203         struct hlist_head *session_list;
 204         struct l2tp_session *session;
 205         struct hlist_node *walk;
 206
 207         /* In L2TPv3, session_ids are unique over all tunnels and we
 208          * sometimes need to look them up before we know the
 209          * tunnel.
 210          */
 211         if (tunnel == NULL)
 212                 return l2tp_session_find_2(net, session_id);
 213
 214         session_list = l2tp_session_id_hash(tunnel, session_id);
 215         read_lock_bh(&tunnel->hlist_lock);
 216         hlist_for_each_entry(session, walk, session_list, hlist) {
 217                 if (session->session_id == session_id) {
 218                         read_unlock_bh(&tunnel->hlist_lock);
 219                         return session;
 220                 }
 221         }
 222         read_unlock_bh(&tunnel->hlist_lock);
 223
 224         return NULL;
 225 }
 226 EXPORT_SYMBOL_GPL(l2tp_session_find);
 227
 228 struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth)
 229 {
 230         int hash;
 231         struct hlist_node *walk;
 232         struct l2tp_session *session;
 233         int count = 0;
 234
 235         read_lock_bh(&tunnel->hlist_lock);
 236         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 237                 hlist_for_each_entry(session, walk, &tunnel->session_hlist[hash], hlist) {
 238                         if (++count > nth) {
 239                                 read_unlock_bh(&tunnel->hlist_lock);
 240                                 return session;
 241                         }
 242                 }
 243         }
 244
 245         read_unlock_bh(&tunnel->hlist_lock);
 246
 247         return NULL;
 248 }
 249 EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
 250
 251 /* Lookup a session by interface name.
 252  * This is very inefficient but is only used by management interfaces.
 253  */
 254 struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
 255 {
 256         struct l2tp_net *pn = l2tp_pernet(net);
 257         int hash;
 258         struct hlist_node *walk;
 259         struct l2tp_session *session;
 260
 261         rcu_read_lock_bh();
 262         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 263                 hlist_for_each_entry_rcu(session, walk, &pn->l2tp_session_hlist[hash], global_hlist) {
 264                         if (!strcmp(session->ifname, ifname)) {
 265                                 rcu_read_unlock_bh();
 266                                 return session;
 267                         }
 268                 }
 269         }
 270
 271         rcu_read_unlock_bh();
 272
 273         return NULL;
 274 }
 275 EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname);
 276
 277 /* Lookup a tunnel by id
 278  */
 279 struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
 280 {
 281         struct l2tp_tunnel *tunnel;
 282         struct l2tp_net *pn = l2tp_pernet(net);
 283
 284         rcu_read_lock_bh();
 285         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 286                 if (tunnel->tunnel_id == tunnel_id) {
 287                         rcu_read_unlock_bh();
 288                         return tunnel;
 289                 }
 290         }
 291         rcu_read_unlock_bh();
 292
 293         return NULL;
 294 }
 295 EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
 296
 297 struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
 298 {
 299         struct l2tp_net *pn = l2tp_pernet(net);
 300         struct l2tp_tunnel *tunnel;
 301         int count = 0;
 302
 303         rcu_read_lock_bh();
 304         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 305                 if (++count > nth) {
 306                         rcu_read_unlock_bh();
 307                         return tunnel;
 308                 }
 309         }
 310
 311         rcu_read_unlock_bh();
 312
 313         return NULL;
 314 }
 315 EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
 316
 317 /*****************************************************************************
 318  * Receive data handling
 319  *****************************************************************************/
 320
 321 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 322  * number.
 323  */
 324 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 325 {
 326         struct sk_buff *skbp;
 327         struct sk_buff *tmp;
 328         u32 ns = L2TP_SKB_CB(skb)->ns;
 329
 330         spin_lock_bh(&session->reorder_q.lock);
 331         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 332                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 333                         __skb_queue_before(&session->reorder_q, skbp, skb);
 334                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 335                                "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 336                                session->name, ns, L2TP_SKB_CB(skbp)->ns,
 337                                skb_queue_len(&session->reorder_q));
 338                         session->stats.rx_oos_packets++;
 339                         goto out;
 340                 }
 341         }
 342
 343         __skb_queue_tail(&session->reorder_q, skb);
 344
 345 out:
 346         spin_unlock_bh(&session->reorder_q.lock);
 347 }
 348
 349 /* Dequeue a single skb.
 350  */
 351 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 352 {
 353         struct l2tp_tunnel *tunnel = session->tunnel;
 354         int length = L2TP_SKB_CB(skb)->length;
 355
 356         /* We're about to requeue the skb, so return resources
 357          * to its current owner (a socket receive buffer).
 358          */
 359         skb_orphan(skb);
 360
 361         tunnel->stats.rx_packets++;
 362         tunnel->stats.rx_bytes += length;
 363         session->stats.rx_packets++;
 364         session->stats.rx_bytes += length;
 365
 366         if (L2TP_SKB_CB(skb)->has_seq) {
 367                 /* Bump our Nr */
 368                 session->nr++;
 369                 if (tunnel->version == L2TP_HDR_VER_2)
 370                         session->nr &= 0xffff;
 371                 else
 372                         session->nr &= 0xffffff;
 373
 374                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 375                        "%s: updated nr to %hu\n", session->name, session->nr);
 376         }
 377
 378         /* call private receive handler */
 379         if (session->recv_skb != NULL)
 380                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 381         else
 382                 kfree_skb(skb);
 383
 384         if (session->deref)
 385                 (*session->deref)(session);
 386 }
 387
 388 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 389  * Skbs that have been in the queue for too long are simply discarded.
 390  */
 391 static void l2tp_recv_dequeue(struct l2tp_session *session)
 392 {
 393         struct sk_buff *skb;
 394         struct sk_buff *tmp;
 395
 396         /* If the pkt at the head of the queue has the nr that we
 397          * expect to send up next, dequeue it and any other
 398          * in-sequence packets behind it.
 399          */
 400         spin_lock_bh(&session->reorder_q.lock);
 401         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 402                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 403                         session->stats.rx_seq_discards++;
 404                         session->stats.rx_errors++;
 405                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 406                                "%s: oos pkt %u len %d discarded (too old), "
 407                                "waiting for %u, reorder_q_len=%d\n",
 408                                session->name, L2TP_SKB_CB(skb)->ns,
 409                                L2TP_SKB_CB(skb)->length, session->nr,
 410                                skb_queue_len(&session->reorder_q));
 411                         __skb_unlink(skb, &session->reorder_q);
 412                         kfree_skb(skb);
 413                         if (session->deref)
 414                                 (*session->deref)(session);
 415                         continue;
 416                 }
 417
 418                 if (L2TP_SKB_CB(skb)->has_seq) {
 419                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 420                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 421                                        "%s: holding oos pkt %u len %d, "
 422                                        "waiting for %u, reorder_q_len=%d\n",
 423                                        session->name, L2TP_SKB_CB(skb)->ns,
 424                                        L2TP_SKB_CB(skb)->length, session->nr,
 425                                        skb_queue_len(&session->reorder_q));
 426                                 goto out;
 427                         }
 428                 }
 429                 __skb_unlink(skb, &session->reorder_q);
 430
 431                 /* Process the skb. We release the queue lock while we
 432                  * do so to let other contexts process the queue.
 433                  */
 434                 spin_unlock_bh(&session->reorder_q.lock);
 435                 l2tp_recv_dequeue_skb(session, skb);
 436                 spin_lock_bh(&session->reorder_q.lock);
 437         }
 438
 439 out:
 440         spin_unlock_bh(&session->reorder_q.lock);
 441 }
 442
 443 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 444                                            struct sk_buff *skb)
 445 {
 446         struct udphdr *uh = udp_hdr(skb);
 447         u16 ulen = ntohs(uh->len);
 448         struct inet_sock *inet;
 449         __wsum psum;
 450
 451         if (sk->sk_no_check || skb_csum_unnecessary(skb) || !uh->check)
 452                 return 0;
 453
 454         inet = inet_sk(sk);
 455         psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr, ulen,
 456                                   IPPROTO_UDP, 0);
 457
 458         if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 459             !csum_fold(csum_add(psum, skb->csum)))
 460                 return 0;
 461
 462         skb->csum = psum;
 463
 464         return __skb_checksum_complete(skb);
 465 }
 466
 467 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 468  * and L2TPv3 data frames here.
 469  *
 470  * L2TPv2 Data Message Header
 471  *
 472  *  0                   1                   2                   3
 473  *  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
 474  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 475  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 476  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 477  * |           Tunnel ID           |           Session ID          |
 478  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 479  * |             Ns (opt)          |             Nr (opt)          |
 480  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 481  * |      Offset Size (opt)        |    Offset pad... (opt)
 482  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 483  *
 484  * Data frames are marked by T=0. All other fields are the same as
 485  * those in L2TP control frames.
 486  *
 487  * L2TPv3 Data Message Header
 488  *
 489  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 490  * |                      L2TP Session Header                      |
 491  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 492  * |                      L2-Specific Sublayer                     |
 493  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 494  * |                        Tunnel Payload                      ...
 495  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 496  *
 497  * L2TPv3 Session Header Over IP
 498  *
 499  *  0                   1                   2                   3
 500  *  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
 501  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 502  * |                           Session ID                          |
 503  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 504  * |               Cookie (optional, maximum 64 bits)...
 505  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 506  *                                                                 |
 507  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 508  *
 509  * L2TPv3 L2-Specific Sublayer Format
 510  *
 511  *  0                   1                   2                   3
 512  *  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
 513  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 514  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 515  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 516  *
 517  * Cookie value, sublayer format and offset (pad) are negotiated with
 518  * the peer when the session is set up. Unlike L2TPv2, we do not need
 519  * to parse the packet header to determine if optional fields are
 520  * present.
 521  *
 522  * Caller must already have parsed the frame and determined that it is
 523  * a data (not control) frame before coming here. Fields up to the
 524  * session-id have already been parsed and ptr points to the data
 525  * after the session-id.
 526  */
 527 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 528                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 529                       int length, int (*payload_hook)(struct sk_buff *skb))
 530 {
 531         struct l2tp_tunnel *tunnel = session->tunnel;
 532         int offset;
 533         u32 ns, nr;
 534
 535         /* The ref count is increased since we now hold a pointer to
 536          * the session. Take care to decrement the refcnt when exiting
 537          * this function from now on...
 538          */
 539         l2tp_session_inc_refcount(session);
 540         if (session->ref)
 541                 (*session->ref)(session);
 542
 543         /* Parse and check optional cookie */
 544         if (session->peer_cookie_len > 0) {
 545                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 546                         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 547                                "%s: cookie mismatch (%u/%u). Discarding.\n",
 548                                tunnel->name, tunnel->tunnel_id, session->session_id);
 549                         session->stats.rx_cookie_discards++;
 550                         goto discard;
 551                 }
 552                 ptr += session->peer_cookie_len;
 553         }
 554
 555         /* Handle the optional sequence numbers. Sequence numbers are
 556          * in different places for L2TPv2 and L2TPv3.
 557          *
 558          * If we are the LAC, enable/disable sequence numbers under
 559          * the control of the LNS.  If no sequence numbers present but
 560          * we were expecting them, discard frame.
 561          */
 562         ns = nr = 0;
 563         L2TP_SKB_CB(skb)->has_seq = 0;
 564         if (tunnel->version == L2TP_HDR_VER_2) {
 565                 if (hdrflags & L2TP_HDRFLAG_S) {
 566                         ns = ntohs(*(__be16 *) ptr);
 567                         ptr += 2;
 568                         nr = ntohs(*(__be16 *) ptr);
 569                         ptr += 2;
 570
 571                         /* Store L2TP info in the skb */
 572                         L2TP_SKB_CB(skb)->ns = ns;
 573                         L2TP_SKB_CB(skb)->has_seq = 1;
 574
 575                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 576                                "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 577                                session->name, ns, nr, session->nr);
 578                 }
 579         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 580                 u32 l2h = ntohl(*(__be32 *) ptr);
 581
 582                 if (l2h & 0x40000000) {
 583                         ns = l2h & 0x00ffffff;
 584
 585                         /* Store L2TP info in the skb */
 586                         L2TP_SKB_CB(skb)->ns = ns;
 587                         L2TP_SKB_CB(skb)->has_seq = 1;
 588
 589                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 590                                "%s: recv data ns=%u, session nr=%u\n",
 591                                session->name, ns, session->nr);
 592                 }
 593         }
 594
 595         /* Advance past L2-specific header, if present */
 596         ptr += session->l2specific_len;
 597
 598         if (L2TP_SKB_CB(skb)->has_seq) {
 599                 /* Received a packet with sequence numbers. If we're the LNS,
 600                  * check if we sre sending sequence numbers and if not,
 601                  * configure it so.
 602                  */
 603                 if ((!session->lns_mode) && (!session->send_seq)) {
 604                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 605                                "%s: requested to enable seq numbers by LNS\n",
 606                                session->name);
 607                         session->send_seq = -1;
 608                         l2tp_session_set_header_len(session, tunnel->version);
 609                 }
 610         } else {
 611                 /* No sequence numbers.
 612                  * If user has configured mandatory sequence numbers, discard.
 613                  */
 614                 if (session->recv_seq) {
 615                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 616                                "%s: recv data has no seq numbers when required. "
 617                                "Discarding\n", session->name);
 618                         session->stats.rx_seq_discards++;
 619                         goto discard;
 620                 }
 621
 622                 /* If we're the LAC and we're sending sequence numbers, the
 623                  * LNS has requested that we no longer send sequence numbers.
 624                  * If we're the LNS and we're sending sequence numbers, the
 625                  * LAC is broken. Discard the frame.
 626                  */
 627                 if ((!session->lns_mode) && (session->send_seq)) {
 628                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 629                                "%s: requested to disable seq numbers by LNS\n",
 630                                session->name);
 631                         session->send_seq = 0;
 632                         l2tp_session_set_header_len(session, tunnel->version);
 633                 } else if (session->send_seq) {
 634                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 635                                "%s: recv data has no seq numbers when required. "
 636                                "Discarding\n", session->name);
 637                         session->stats.rx_seq_discards++;
 638                         goto discard;
 639                 }
 640         }
 641
 642         /* Session data offset is handled differently for L2TPv2 and
 643          * L2TPv3. For L2TPv2, there is an optional 16-bit value in
 644          * the header. For L2TPv3, the offset is negotiated using AVPs
 645          * in the session setup control protocol.
 646          */
 647         if (tunnel->version == L2TP_HDR_VER_2) {
 648                 /* If offset bit set, skip it. */
 649                 if (hdrflags & L2TP_HDRFLAG_O) {
 650                         offset = ntohs(*(__be16 *)ptr);
 651                         ptr += 2 + offset;
 652                 }
 653         } else
 654                 ptr += session->offset;
 655
 656         offset = ptr - optr;
 657         if (!pskb_may_pull(skb, offset))
 658                 goto discard;
 659
 660         __skb_pull(skb, offset);
 661
 662         /* If caller wants to process the payload before we queue the
 663          * packet, do so now.
 664          */
 665         if (payload_hook)
 666                 if ((*payload_hook)(skb))
 667                         goto discard;
 668
 669         /* Prepare skb for adding to the session's reorder_q.  Hold
 670          * packets for max reorder_timeout or 1 second if not
 671          * reordering.
 672          */
 673         L2TP_SKB_CB(skb)->length = length;
 674         L2TP_SKB_CB(skb)->expires = jiffies +
 675                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 676
 677         /* Add packet to the session's receive queue. Reordering is done here, if
 678          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 679          */
 680         if (L2TP_SKB_CB(skb)->has_seq) {
 681                 if (session->reorder_timeout != 0) {
 682                         /* Packet reordering enabled. Add skb to session's
 683                          * reorder queue, in order of ns.
 684                          */
 685                         l2tp_recv_queue_skb(session, skb);
 686                 } else {
 687                         /* Packet reordering disabled. Discard out-of-sequence
 688                          * packets
 689                          */
 690                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 691                                 session->stats.rx_seq_discards++;
 692                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 693                                        "%s: oos pkt %u len %d discarded, "
 694                                        "waiting for %u, reorder_q_len=%d\n",
 695                                        session->name, L2TP_SKB_CB(skb)->ns,
 696                                        L2TP_SKB_CB(skb)->length, session->nr,
 697                                        skb_queue_len(&session->reorder_q));
 698                                 goto discard;
 699                         }
 700                         skb_queue_tail(&session->reorder_q, skb);
 701                 }
 702         } else {
 703                 /* No sequence numbers. Add the skb to the tail of the
 704                  * reorder queue. This ensures that it will be
 705                  * delivered after all previous sequenced skbs.
 706                  */
 707                 skb_queue_tail(&session->reorder_q, skb);
 708         }
 709
 710         /* Try to dequeue as many skbs from reorder_q as we can. */
 711         l2tp_recv_dequeue(session);
 712
 713         l2tp_session_dec_refcount(session);
 714
 715         return;
 716
 717 discard:
 718         session->stats.rx_errors++;
 719         kfree_skb(skb);
 720
 721         if (session->deref)
 722                 (*session->deref)(session);
 723
 724         l2tp_session_dec_refcount(session);
 725 }
 726 EXPORT_SYMBOL(l2tp_recv_common);
 727
 728 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 729  * here. The skb is not on a list when we get here.
 730  * Returns 0 if the packet was a data packet and was successfully passed on.
 731  * Returns 1 if the packet was not a good data packet and could not be
 732  * forwarded.  All such packets are passed up to userspace to deal with.
 733  */
 734 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 735                               int (*payload_hook)(struct sk_buff *skb))
 736 {
 737         struct l2tp_session *session = NULL;
 738         unsigned char *ptr, *optr;
 739         u16 hdrflags;
 740         u32 tunnel_id, session_id;
 741         int offset;
 742         u16 version;
 743         int length;
 744
 745         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
 746                 goto discard_bad_csum;
 747
 748         /* UDP always verifies the packet length. */
 749         __skb_pull(skb, sizeof(struct udphdr));
 750
 751         /* Short packet? */
 752         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
 753                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 754                        "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
 755                 goto error;
 756         }
 757
 758         /* Point to L2TP header */
 759         optr = ptr = skb->data;
 760
 761         /* Trace packet contents, if enabled */
 762         if (tunnel->debug & L2TP_MSG_DATA) {
 763                 length = min(32u, skb->len);
 764                 if (!pskb_may_pull(skb, length))
 765                         goto error;
 766
 767                 printk(KERN_DEBUG "%s: recv: ", tunnel->name);
 768
 769                 offset = 0;
 770                 do {
 771                         printk(" %02X", ptr[offset]);
 772                 } while (++offset < length);
 773
 774                 printk("\n");
 775         }
 776
 777         /* Get L2TP header flags */
 778         hdrflags = ntohs(*(__be16 *) ptr);
 779
 780         /* Check protocol version */
 781         version = hdrflags & L2TP_HDR_VER_MASK;
 782         if (version != tunnel->version) {
 783                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 784                        "%s: recv protocol version mismatch: got %d expected %d\n",
 785                        tunnel->name, version, tunnel->version);
 786                 goto error;
 787         }
 788
 789         /* Get length of L2TP packet */
 790         length = skb->len;
 791
 792         /* If type is control packet, it is handled by userspace. */
 793         if (hdrflags & L2TP_HDRFLAG_T) {
 794                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 795                        "%s: recv control packet, len=%d\n", tunnel->name, length);
 796                 goto error;
 797         }
 798
 799         /* Skip flags */
 800         ptr += 2;
 801
 802         if (tunnel->version == L2TP_HDR_VER_2) {
 803                 /* If length is present, skip it */
 804                 if (hdrflags & L2TP_HDRFLAG_L)
 805                         ptr += 2;
 806
 807                 /* Extract tunnel and session ID */
 808                 tunnel_id = ntohs(*(__be16 *) ptr);
 809                 ptr += 2;
 810                 session_id = ntohs(*(__be16 *) ptr);
 811                 ptr += 2;
 812         } else {
 813                 ptr += 2;       /* skip reserved bits */
 814                 tunnel_id = tunnel->tunnel_id;
 815                 session_id = ntohl(*(__be32 *) ptr);
 816                 ptr += 4;
 817         }
 818
 819         /* Find the session context */
 820         session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
 821         if (!session || !session->recv_skb) {
 822                 /* Not found? Pass to userspace to deal with */
 823                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 824                        "%s: no session found (%u/%u). Passing up.\n",
 825                        tunnel->name, tunnel_id, session_id);
 826                 goto error;
 827         }
 828
 829         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
 830
 831         return 0;
 832
 833 discard_bad_csum:
 834         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
 835         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
 836         tunnel->stats.rx_errors++;
 837         kfree_skb(skb);
 838
 839         return 0;
 840
 841 error:
 842         /* Put UDP header back */
 843         __skb_push(skb, sizeof(struct udphdr));
 844
 845         return 1;
 846 }
 847
 848 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 849  * Return codes:
 850  * 0 : success.
 851  * <0: error
 852  * >0: skb should be passed up to userspace as UDP.
 853  */
 854 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 855 {
 856         struct l2tp_tunnel *tunnel;
 857
 858         tunnel = l2tp_sock_to_tunnel(sk);
 859         if (tunnel == NULL)
 860                 goto pass_up;
 861
 862         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 863                "%s: received %d bytes\n", tunnel->name, skb->len);
 864
 865         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
 866                 goto pass_up_put;
 867
 868         sock_put(sk);
 869         return 0;
 870
 871 pass_up_put:
 872         sock_put(sk);
 873 pass_up:
 874         return 1;
 875 }
 876 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 877
 878 /************************************************************************
 879  * Transmit handling
 880  ***********************************************************************/
 881
 882 /* Build an L2TP header for the session into the buffer provided.
 883  */
 884 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 885 {
 886         struct l2tp_tunnel *tunnel = session->tunnel;
 887         __be16 *bufp = buf;
 888         __be16 *optr = buf;
 889         u16 flags = L2TP_HDR_VER_2;
 890         u32 tunnel_id = tunnel->peer_tunnel_id;
 891         u32 session_id = session->peer_session_id;
 892
 893         if (session->send_seq)
 894                 flags |= L2TP_HDRFLAG_S;
 895
 896         /* Setup L2TP header. */
 897         *bufp++ = htons(flags);
 898         *bufp++ = htons(tunnel_id);
 899         *bufp++ = htons(session_id);
 900         if (session->send_seq) {
 901                 *bufp++ = htons(session->ns);
 902                 *bufp++ = 0;
 903                 session->ns++;
 904                 session->ns &= 0xffff;
 905                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 906                        "%s: updated ns to %u\n", session->name, session->ns);
 907         }
 908
 909         return bufp - optr;
 910 }
 911
 912 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 913 {
 914         struct l2tp_tunnel *tunnel = session->tunnel;
 915         char *bufp = buf;
 916         char *optr = bufp;
 917
 918         /* Setup L2TP header. The header differs slightly for UDP and
 919          * IP encapsulations. For UDP, there is 4 bytes of flags.
 920          */
 921         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 922                 u16 flags = L2TP_HDR_VER_3;
 923                 *((__be16 *) bufp) = htons(flags);
 924                 bufp += 2;
 925                 *((__be16 *) bufp) = 0;
 926                 bufp += 2;
 927         }
 928
 929         *((__be32 *) bufp) = htonl(session->peer_session_id);
 930         bufp += 4;
 931         if (session->cookie_len) {
 932                 memcpy(bufp, &session->cookie[0], session->cookie_len);
 933                 bufp += session->cookie_len;
 934         }
 935         if (session->l2specific_len) {
 936                 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 937                         u32 l2h = 0;
 938                         if (session->send_seq) {
 939                                 l2h = 0x40000000 | session->ns;
 940                                 session->ns++;
 941                                 session->ns &= 0xffffff;
 942                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 943                                        "%s: updated ns to %u\n", session->name, session->ns);
 944                         }
 945
 946                         *((__be32 *) bufp) = htonl(l2h);
 947                 }
 948                 bufp += session->l2specific_len;
 949         }
 950         if (session->offset)
 951                 bufp += session->offset;
 952
 953         return bufp - optr;
 954 }
 955
 956 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
 957                           struct flowi *fl, size_t data_len)
 958 {
 959         struct l2tp_tunnel *tunnel = session->tunnel;
 960         unsigned int len = skb->len;
 961         int error;
 962
 963         /* Debug */
 964         if (session->send_seq)
 965                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
 966                        "%s: send %Zd bytes, ns=%u\n", session->name,
 967                        data_len, session->ns - 1);
 968         else
 969                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
 970                        "%s: send %Zd bytes\n", session->name, data_len);
 971
 972         if (session->debug & L2TP_MSG_DATA) {
 973                 int i;
 974                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
 975                 unsigned char *datap = skb->data + uhlen;
 976
 977                 printk(KERN_DEBUG "%s: xmit:", session->name);
 978                 for (i = 0; i < (len - uhlen); i++) {
 979                         printk(" %02X", *datap++);
 980                         if (i == 31) {
 981                                 printk(" ...");
 982                                 break;
 983                         }
 984                 }
 985                 printk("\n");
 986         }
 987
 988         /* Queue the packet to IP for output */
 989         skb->local_df = 1;
 990         error = ip_queue_xmit(skb, fl);
 991
 992         /* Update stats */
 993         if (error >= 0) {
 994                 tunnel->stats.tx_packets++;
 995                 tunnel->stats.tx_bytes += len;
 996                 session->stats.tx_packets++;
 997                 session->stats.tx_bytes += len;
 998         } else {
 999                 tunnel->stats.tx_errors++;
1000                 session->stats.tx_errors++;
1001         }
1002
1003         return 0;
1004 }
1005
1006 /* Automatically called when the skb is freed.
1007  */
1008 static void l2tp_sock_wfree(struct sk_buff *skb)
1009 {
1010         sock_put(skb->sk);
1011 }
1012
1013 /* For data skbs that we transmit, we associate with the tunnel socket
1014  * but don't do accounting.
1015  */
1016 static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
1017 {
1018         sock_hold(sk);
1019         skb->sk = sk;
1020         skb->destructor = l2tp_sock_wfree;
1021 }
1022
1023 /* If caller requires the skb to have a ppp header, the header must be
1024  * inserted in the skb data before calling this function.
1025  */
1026 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1027 {
1028         int data_len = skb->len;
1029         struct l2tp_tunnel *tunnel = session->tunnel;
1030         struct sock *sk = tunnel->sock;
1031         struct flowi *fl;
1032         struct udphdr *uh;
1033         struct inet_sock *inet;
1034         __wsum csum;
1035         int old_headroom;
1036         int new_headroom;
1037         int headroom;
1038         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1039         int udp_len;
1040
1041         /* Check that there's enough headroom in the skb to insert IP,
1042          * UDP and L2TP headers. If not enough, expand it to
1043          * make room. Adjust truesize.
1044          */
1045         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1046                 uhlen + hdr_len;
1047         old_headroom = skb_headroom(skb);
1048         if (skb_cow_head(skb, headroom))
1049                 goto abort;
1050
1051         new_headroom = skb_headroom(skb);
1052         skb_orphan(skb);
1053         skb->truesize += new_headroom - old_headroom;
1054
1055         /* Setup L2TP header */
1056         session->build_header(session, __skb_push(skb, hdr_len));
1057
1058         /* Reset skb netfilter state */
1059         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1060         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1061                               IPSKB_REROUTED);
1062         nf_reset(skb);
1063
1064         bh_lock_sock(sk);
1065         if (sock_owned_by_user(sk)) {
1066                 dev_kfree_skb(skb);
1067                 goto out_unlock;
1068         }
1069
1070         /* Get routing info from the tunnel socket */
1071         skb_dst_drop(skb);
1072         skb_dst_set(skb, dst_clone(__sk_dst_get(sk)));
1073
1074         inet = inet_sk(sk);
1075         fl = &inet->cork.fl;
1076         switch (tunnel->encap) {
1077         case L2TP_ENCAPTYPE_UDP:
1078                 /* Setup UDP header */
1079                 __skb_push(skb, sizeof(*uh));
1080                 skb_reset_transport_header(skb);
1081                 uh = udp_hdr(skb);
1082                 uh->source = inet->inet_sport;
1083                 uh->dest = inet->inet_dport;
1084                 udp_len = uhlen + hdr_len + data_len;
1085                 uh->len = htons(udp_len);
1086                 uh->check = 0;
1087
1088                 /* Calculate UDP checksum if configured to do so */
1089                 if (sk->sk_no_check == UDP_CSUM_NOXMIT)
1090                         skb->ip_summed = CHECKSUM_NONE;
1091                 else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
1092                          (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
1093                         skb->ip_summed = CHECKSUM_COMPLETE;
1094                         csum = skb_checksum(skb, 0, udp_len, 0);
1095                         uh->check = csum_tcpudp_magic(inet->inet_saddr,
1096                                                       inet->inet_daddr,
1097                                                       udp_len, IPPROTO_UDP, csum);
1098                         if (uh->check == 0)
1099                                 uh->check = CSUM_MANGLED_0;
1100                 } else {
1101                         skb->ip_summed = CHECKSUM_PARTIAL;
1102                         skb->csum_start = skb_transport_header(skb) - skb->head;
1103                         skb->csum_offset = offsetof(struct udphdr, check);
1104                         uh->check = ~csum_tcpudp_magic(inet->inet_saddr,
1105                                                        inet->inet_daddr,
1106                                                        udp_len, IPPROTO_UDP, 0);
1107                 }
1108                 break;
1109
1110         case L2TP_ENCAPTYPE_IP:
1111                 break;
1112         }
1113
1114         l2tp_skb_set_owner_w(skb, sk);
1115
1116         l2tp_xmit_core(session, skb, fl, data_len);
1117 out_unlock:
1118         bh_unlock_sock(sk);
1119
1120 abort:
1121         return 0;
1122 }
1123 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1124
1125 /*****************************************************************************
1126  * Tinnel and session create/destroy.
1127  *****************************************************************************/
1128
1129 /* Tunnel socket destruct hook.
1130  * The tunnel context is deleted only when all session sockets have been
1131  * closed.
1132  */
1133 static void l2tp_tunnel_destruct(struct sock *sk)
1134 {
1135         struct l2tp_tunnel *tunnel;
1136
1137         tunnel = sk->sk_user_data;
1138         if (tunnel == NULL)
1139                 goto end;
1140
1141         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1142                "%s: closing...\n", tunnel->name);
1143
1144         /* Close all sessions */
1145         l2tp_tunnel_closeall(tunnel);
1146
1147         switch (tunnel->encap) {
1148         case L2TP_ENCAPTYPE_UDP:
1149                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1150                 (udp_sk(sk))->encap_type = 0;
1151                 (udp_sk(sk))->encap_rcv = NULL;
1152                 break;
1153         case L2TP_ENCAPTYPE_IP:
1154                 break;
1155         }
1156
1157         /* Remove hooks into tunnel socket */
1158         tunnel->sock = NULL;
1159         sk->sk_destruct = tunnel->old_sk_destruct;
1160         sk->sk_user_data = NULL;
1161
1162         /* Call the original destructor */
1163         if (sk->sk_destruct)
1164                 (*sk->sk_destruct)(sk);
1165
1166         /* We're finished with the socket */
1167         l2tp_tunnel_dec_refcount(tunnel);
1168
1169 end:
1170         return;
1171 }
1172
1173 /* When the tunnel is closed, all the attached sessions need to go too.
1174  */
1175 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1176 {
1177         int hash;
1178         struct hlist_node *walk;
1179         struct hlist_node *tmp;
1180         struct l2tp_session *session;
1181
1182         BUG_ON(tunnel == NULL);
1183
1184         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1185                "%s: closing all sessions...\n", tunnel->name);
1186
1187         write_lock_bh(&tunnel->hlist_lock);
1188         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1189 again:
1190                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1191                         session = hlist_entry(walk, struct l2tp_session, hlist);
1192
1193                         PRINTK(session->debug, L2TP_MSG_CONTROL, KERN_INFO,
1194                                "%s: closing session\n", session->name);
1195
1196                         hlist_del_init(&session->hlist);
1197
1198                         /* Since we should hold the sock lock while
1199                          * doing any unbinding, we need to release the
1200                          * lock we're holding before taking that lock.
1201                          * Hold a reference to the sock so it doesn't
1202                          * disappear as we're jumping between locks.
1203                          */
1204                         if (session->ref != NULL)
1205                                 (*session->ref)(session);
1206
1207                         write_unlock_bh(&tunnel->hlist_lock);
1208
1209                         if (tunnel->version != L2TP_HDR_VER_2) {
1210                                 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1211
1212                                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
1213                                 hlist_del_init_rcu(&session->global_hlist);
1214                                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1215                                 synchronize_rcu();
1216                         }
1217
1218                         if (session->session_close != NULL)
1219                                 (*session->session_close)(session);
1220
1221                         if (session->deref != NULL)
1222                                 (*session->deref)(session);
1223
1224                         write_lock_bh(&tunnel->hlist_lock);
1225
1226                         /* Now restart from the beginning of this hash
1227                          * chain.  We always remove a session from the
1228                          * list so we are guaranteed to make forward
1229                          * progress.
1230                          */
1231                         goto again;
1232                 }
1233         }
1234         write_unlock_bh(&tunnel->hlist_lock);
1235 }
1236
1237 /* Really kill the tunnel.
1238  * Come here only when all sessions have been cleared from the tunnel.
1239  */
1240 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
1241 {
1242         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1243
1244         BUG_ON(atomic_read(&tunnel->ref_count) != 0);
1245         BUG_ON(tunnel->sock != NULL);
1246
1247         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1248                "%s: free...\n", tunnel->name);
1249
1250         /* Remove from tunnel list */
1251         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1252         list_del_rcu(&tunnel->list);
1253         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1254         synchronize_rcu();
1255
1256         atomic_dec(&l2tp_tunnel_count);
1257         kfree(tunnel);
1258 }
1259
1260 /* Create a socket for the tunnel, if one isn't set up by
1261  * userspace. This is used for static tunnels where there is no
1262  * managing L2TP daemon.
1263  */
1264 static int l2tp_tunnel_sock_create(u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct socket **sockp)
1265 {
1266         int err = -EINVAL;
1267         struct sockaddr_in udp_addr;
1268         struct sockaddr_l2tpip ip_addr;
1269         struct socket *sock = NULL;
1270
1271         switch (cfg->encap) {
1272         case L2TP_ENCAPTYPE_UDP:
1273                 err = sock_create(AF_INET, SOCK_DGRAM, 0, sockp);
1274                 if (err < 0)
1275                         goto out;
1276
1277                 sock = *sockp;
1278
1279                 memset(&udp_addr, 0, sizeof(udp_addr));
1280                 udp_addr.sin_family = AF_INET;
1281                 udp_addr.sin_addr = cfg->local_ip;
1282                 udp_addr.sin_port = htons(cfg->local_udp_port);
1283                 err = kernel_bind(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr));
1284                 if (err < 0)
1285                         goto out;
1286
1287                 udp_addr.sin_family = AF_INET;
1288                 udp_addr.sin_addr = cfg->peer_ip;
1289                 udp_addr.sin_port = htons(cfg->peer_udp_port);
1290                 err = kernel_connect(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr), 0);
1291                 if (err < 0)
1292                         goto out;
1293
1294                 if (!cfg->use_udp_checksums)
1295                         sock->sk->sk_no_check = UDP_CSUM_NOXMIT;
1296
1297                 break;
1298
1299         case L2TP_ENCAPTYPE_IP:
1300                 err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_L2TP, sockp);
1301                 if (err < 0)
1302                         goto out;
1303
1304                 sock = *sockp;
1305
1306                 memset(&ip_addr, 0, sizeof(ip_addr));
1307                 ip_addr.l2tp_family = AF_INET;
1308                 ip_addr.l2tp_addr = cfg->local_ip;
1309                 ip_addr.l2tp_conn_id = tunnel_id;
1310                 err = kernel_bind(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr));
1311                 if (err < 0)
1312                         goto out;
1313
1314                 ip_addr.l2tp_family = AF_INET;
1315                 ip_addr.l2tp_addr = cfg->peer_ip;
1316                 ip_addr.l2tp_conn_id = peer_tunnel_id;
1317                 err = kernel_connect(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr), 0);
1318                 if (err < 0)
1319                         goto out;
1320
1321                 break;
1322
1323         default:
1324                 goto out;
1325         }
1326
1327 out:
1328         if ((err < 0) && sock) {
1329                 sock_release(sock);
1330                 *sockp = NULL;
1331         }
1332
1333         return err;
1334 }
1335
1336 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)
1337 {
1338         struct l2tp_tunnel *tunnel = NULL;
1339         int err;
1340         struct socket *sock = NULL;
1341         struct sock *sk = NULL;
1342         struct l2tp_net *pn;
1343         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1344
1345         /* Get the tunnel socket from the fd, which was opened by
1346          * the userspace L2TP daemon. If not specified, create a
1347          * kernel socket.
1348          */
1349         if (fd < 0) {
1350                 err = l2tp_tunnel_sock_create(tunnel_id, peer_tunnel_id, cfg, &sock);
1351                 if (err < 0)
1352                         goto err;
1353         } else {
1354                 err = -EBADF;
1355                 sock = sockfd_lookup(fd, &err);
1356                 if (!sock) {
1357                         printk(KERN_ERR "tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
1358                                tunnel_id, fd, err);
1359                         goto err;
1360                 }
1361         }
1362
1363         sk = sock->sk;
1364
1365         if (cfg != NULL)
1366                 encap = cfg->encap;
1367
1368         /* Quick sanity checks */
1369         switch (encap) {
1370         case L2TP_ENCAPTYPE_UDP:
1371                 err = -EPROTONOSUPPORT;
1372                 if (sk->sk_protocol != IPPROTO_UDP) {
1373                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1374                                tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
1375                         goto err;
1376                 }
1377                 break;
1378         case L2TP_ENCAPTYPE_IP:
1379                 err = -EPROTONOSUPPORT;
1380                 if (sk->sk_protocol != IPPROTO_L2TP) {
1381                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1382                                tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
1383                         goto err;
1384                 }
1385                 break;
1386         }
1387
1388         /* Check if this socket has already been prepped */
1389         tunnel = (struct l2tp_tunnel *)sk->sk_user_data;
1390         if (tunnel != NULL) {
1391                 /* This socket has already been prepped */
1392                 err = -EBUSY;
1393                 goto err;
1394         }
1395
1396         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1397         if (tunnel == NULL) {
1398                 err = -ENOMEM;
1399                 goto err;
1400         }
1401
1402         tunnel->version = version;
1403         tunnel->tunnel_id = tunnel_id;
1404         tunnel->peer_tunnel_id = peer_tunnel_id;
1405         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1406
1407         tunnel->magic = L2TP_TUNNEL_MAGIC;
1408         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1409         rwlock_init(&tunnel->hlist_lock);
1410
1411         /* The net we belong to */
1412         tunnel->l2tp_net = net;
1413         pn = l2tp_pernet(net);
1414
1415         if (cfg != NULL)
1416                 tunnel->debug = cfg->debug;
1417
1418         /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1419         tunnel->encap = encap;
1420         if (encap == L2TP_ENCAPTYPE_UDP) {
1421                 /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1422                 udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
1423                 udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
1424         }
1425
1426         sk->sk_user_data = tunnel;
1427
1428         /* Hook on the tunnel socket destructor so that we can cleanup
1429          * if the tunnel socket goes away.
1430          */
1431         tunnel->old_sk_destruct = sk->sk_destruct;
1432         sk->sk_destruct = &l2tp_tunnel_destruct;
1433         tunnel->sock = sk;
1434         sk->sk_allocation = GFP_ATOMIC;
1435
1436         /* Add tunnel to our list */
1437         INIT_LIST_HEAD(&tunnel->list);
1438         atomic_inc(&l2tp_tunnel_count);
1439
1440         /* Bump the reference count. The tunnel context is deleted
1441          * only when this drops to zero. Must be done before list insertion
1442          */
1443         l2tp_tunnel_inc_refcount(tunnel);
1444         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1445         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1446         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1447
1448         err = 0;
1449 err:
1450         if (tunnelp)
1451                 *tunnelp = tunnel;
1452
1453         /* If tunnel's socket was created by the kernel, it doesn't
1454          *  have a file.
1455          */
1456         if (sock && sock->file)
1457                 sockfd_put(sock);
1458
1459         return err;
1460 }
1461 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1462
1463 /* This function is used by the netlink TUNNEL_DELETE command.
1464  */
1465 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1466 {
1467         int err = 0;
1468         struct socket *sock = tunnel->sock ? tunnel->sock->sk_socket : NULL;
1469
1470         /* Force the tunnel socket to close. This will eventually
1471          * cause the tunnel to be deleted via the normal socket close
1472          * mechanisms when userspace closes the tunnel socket.
1473          */
1474         if (sock != NULL) {
1475                 err = inet_shutdown(sock, 2);
1476
1477                 /* If the tunnel's socket was created by the kernel,
1478                  * close the socket here since the socket was not
1479                  * created by userspace.
1480                  */
1481                 if (sock->file == NULL)
1482                         err = inet_release(sock);
1483         }
1484
1485         return err;
1486 }
1487 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1488
1489 /* Really kill the session.
1490  */
1491 void l2tp_session_free(struct l2tp_session *session)
1492 {
1493         struct l2tp_tunnel *tunnel;
1494
1495         BUG_ON(atomic_read(&session->ref_count) != 0);
1496
1497         tunnel = session->tunnel;
1498         if (tunnel != NULL) {
1499                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1500
1501                 /* Delete the session from the hash */
1502                 write_lock_bh(&tunnel->hlist_lock);
1503                 hlist_del_init(&session->hlist);
1504                 write_unlock_bh(&tunnel->hlist_lock);
1505
1506                 /* Unlink from the global hash if not L2TPv2 */
1507                 if (tunnel->version != L2TP_HDR_VER_2) {
1508                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1509
1510                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1511                         hlist_del_init_rcu(&session->global_hlist);
1512                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1513                         synchronize_rcu();
1514                 }
1515
1516                 if (session->session_id != 0)
1517                         atomic_dec(&l2tp_session_count);
1518
1519                 sock_put(tunnel->sock);
1520
1521                 /* This will delete the tunnel context if this
1522                  * is the last session on the tunnel.
1523                  */
1524                 session->tunnel = NULL;
1525                 l2tp_tunnel_dec_refcount(tunnel);
1526         }
1527
1528         kfree(session);
1529
1530         return;
1531 }
1532 EXPORT_SYMBOL_GPL(l2tp_session_free);
1533
1534 /* This function is used by the netlink SESSION_DELETE command and by
1535    pseudowire modules.
1536  */
1537 int l2tp_session_delete(struct l2tp_session *session)
1538 {
1539         if (session->session_close != NULL)
1540                 (*session->session_close)(session);
1541
1542         l2tp_session_dec_refcount(session);
1543
1544         return 0;
1545 }
1546 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1547
1548
1549 /* We come here whenever a session's send_seq, cookie_len or
1550  * l2specific_len parameters are set.
1551  */
1552 static void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1553 {
1554         if (version == L2TP_HDR_VER_2) {
1555                 session->hdr_len = 6;
1556                 if (session->send_seq)
1557                         session->hdr_len += 4;
1558         } else {
1559                 session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
1560                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1561                         session->hdr_len += 4;
1562         }
1563
1564 }
1565
1566 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)
1567 {
1568         struct l2tp_session *session;
1569
1570         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1571         if (session != NULL) {
1572                 session->magic = L2TP_SESSION_MAGIC;
1573                 session->tunnel = tunnel;
1574
1575                 session->session_id = session_id;
1576                 session->peer_session_id = peer_session_id;
1577                 session->nr = 1;
1578
1579                 sprintf(&session->name[0], "sess %u/%u",
1580                         tunnel->tunnel_id, session->session_id);
1581
1582                 skb_queue_head_init(&session->reorder_q);
1583
1584                 INIT_HLIST_NODE(&session->hlist);
1585                 INIT_HLIST_NODE(&session->global_hlist);
1586
1587                 /* Inherit debug options from tunnel */
1588                 session->debug = tunnel->debug;
1589
1590                 if (cfg) {
1591                         session->pwtype = cfg->pw_type;
1592                         session->debug = cfg->debug;
1593                         session->mtu = cfg->mtu;
1594                         session->mru = cfg->mru;
1595                         session->send_seq = cfg->send_seq;
1596                         session->recv_seq = cfg->recv_seq;
1597                         session->lns_mode = cfg->lns_mode;
1598                         session->reorder_timeout = cfg->reorder_timeout;
1599                         session->offset = cfg->offset;
1600                         session->l2specific_type = cfg->l2specific_type;
1601                         session->l2specific_len = cfg->l2specific_len;
1602                         session->cookie_len = cfg->cookie_len;
1603                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1604                         session->peer_cookie_len = cfg->peer_cookie_len;
1605                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1606                 }
1607
1608                 if (tunnel->version == L2TP_HDR_VER_2)
1609                         session->build_header = l2tp_build_l2tpv2_header;
1610                 else
1611                         session->build_header = l2tp_build_l2tpv3_header;
1612
1613                 l2tp_session_set_header_len(session, tunnel->version);
1614
1615                 /* Bump the reference count. The session context is deleted
1616                  * only when this drops to zero.
1617                  */
1618                 l2tp_session_inc_refcount(session);
1619                 l2tp_tunnel_inc_refcount(tunnel);
1620
1621                 /* Ensure tunnel socket isn't deleted */
1622                 sock_hold(tunnel->sock);
1623
1624                 /* Add session to the tunnel's hash list */
1625                 write_lock_bh(&tunnel->hlist_lock);
1626                 hlist_add_head(&session->hlist,
1627                                l2tp_session_id_hash(tunnel, session_id));
1628                 write_unlock_bh(&tunnel->hlist_lock);
1629
1630                 /* And to the global session list if L2TPv3 */
1631                 if (tunnel->version != L2TP_HDR_VER_2) {
1632                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1633
1634                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1635                         hlist_add_head_rcu(&session->global_hlist,
1636                                            l2tp_session_id_hash_2(pn, session_id));
1637                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1638                 }
1639
1640                 /* Ignore management session in session count value */
1641                 if (session->session_id != 0)
1642                         atomic_inc(&l2tp_session_count);
1643         }
1644
1645         return session;
1646 }
1647 EXPORT_SYMBOL_GPL(l2tp_session_create);
1648
1649 /*****************************************************************************
1650  * Init and cleanup
1651  *****************************************************************************/
1652
1653 static __net_init int l2tp_init_net(struct net *net)
1654 {
1655         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1656         int hash;
1657
1658         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1659         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1660
1661         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1662                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1663
1664         spin_lock_init(&pn->l2tp_session_hlist_lock);
1665
1666         return 0;
1667 }
1668
1669 static struct pernet_operations l2tp_net_ops = {
1670         .init = l2tp_init_net,
1671         .id   = &l2tp_net_id,
1672         .size = sizeof(struct l2tp_net),
1673 };
1674
1675 static int __init l2tp_init(void)
1676 {
1677         int rc = 0;
1678
1679         rc = register_pernet_device(&l2tp_net_ops);
1680         if (rc)
1681                 goto out;
1682
1683         printk(KERN_INFO "L2TP core driver, %s\n", L2TP_DRV_VERSION);
1684
1685 out:
1686         return rc;
1687 }
1688
1689 static void __exit l2tp_exit(void)
1690 {
1691         unregister_pernet_device(&l2tp_net_ops);
1692 }
1693
1694 module_init(l2tp_init);
1695 module_exit(l2tp_exit);
1696
1697 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1698 MODULE_DESCRIPTION("L2TP core");
1699 MODULE_LICENSE("GPL");
1700 MODULE_VERSION(L2TP_DRV_VERSION);
1701