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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22
  23 #include <linux/module.h>
  24 #include <linux/string.h>
  25 #include <linux/list.h>
  26 #include <linux/rculist.h>
  27 #include <linux/uaccess.h>
  28
  29 #include <linux/kernel.h>
  30 #include <linux/spinlock.h>
  31 #include <linux/kthread.h>
  32 #include <linux/sched.h>
  33 #include <linux/slab.h>
  34 #include <linux/errno.h>
  35 #include <linux/jiffies.h>
  36
  37 #include <linux/netdevice.h>
  38 #include <linux/net.h>
  39 #include <linux/inetdevice.h>
  40 #include <linux/skbuff.h>
  41 #include <linux/init.h>
  42 #include <linux/in.h>
  43 #include <linux/ip.h>
  44 #include <linux/udp.h>
  45 #include <linux/l2tp.h>
  46 #include <linux/hash.h>
  47 #include <linux/sort.h>
  48 #include <linux/file.h>
  49 #include <linux/nsproxy.h>
  50 #include <net/net_namespace.h>
  51 #include <net/netns/generic.h>
  52 #include <net/dst.h>
  53 #include <net/ip.h>
  54 #include <net/udp.h>
  55 #include <net/inet_common.h>
  56 #include <net/xfrm.h>
  57 #include <net/protocol.h>
  58 #include <net/inet6_connection_sock.h>
  59 #include <net/inet_ecn.h>
  60 #include <net/ip6_route.h>
  61 #include <net/ip6_checksum.h>
  62
  63 #include <asm/byteorder.h>
  64 #include <linux/atomic.h>
  65
  66 #include "l2tp_core.h"
  67
  68 #define L2TP_DRV_VERSION        "V2.0"
  69
  70 /* L2TP header constants */
  71 #define L2TP_HDRFLAG_T     0x8000
  72 #define L2TP_HDRFLAG_L     0x4000
  73 #define L2TP_HDRFLAG_S     0x0800
  74 #define L2TP_HDRFLAG_O     0x0200
  75 #define L2TP_HDRFLAG_P     0x0100
  76
  77 #define L2TP_HDR_VER_MASK  0x000F
  78 #define L2TP_HDR_VER_2     0x0002
  79 #define L2TP_HDR_VER_3     0x0003
  80
  81 /* L2TPv3 default L2-specific sublayer */
  82 #define L2TP_SLFLAG_S      0x40000000
  83 #define L2TP_SL_SEQ_MASK   0x00ffffff
  84
  85 #define L2TP_HDR_SIZE_SEQ               10
  86 #define L2TP_HDR_SIZE_NOSEQ             6
  87
  88 /* Default trace flags */
  89 #define L2TP_DEFAULT_DEBUG_FLAGS        0
  90
  91 /* Private data stored for received packets in the skb.
  92  */
  93 struct l2tp_skb_cb {
  94         u32                     ns;
  95         u16                     has_seq;
  96         u16                     length;
  97         unsigned long           expires;
  98 };
  99
 100 #define L2TP_SKB_CB(skb)        ((struct l2tp_skb_cb *) &skb->cb[sizeof(struct inet_skb_parm)])
 101
 102 static 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)                                    \
 141 do {                                                                    \
 142         pr_debug("l2tp_tunnel_inc_refcount: %s:%d %s: cnt=%d\n",        \
 143                  __func__, __LINE__, (_t)->name,                        \
 144                  atomic_read(&_t->ref_count));                          \
 145         l2tp_tunnel_inc_refcount_1(_t);                                 \
 146 } while (0)
 147 #define l2tp_tunnel_dec_refcount(_t)
 148 do {                                                                    \
 149         pr_debug("l2tp_tunnel_dec_refcount: %s:%d %s: cnt=%d\n",        \
 150                  __func__, __LINE__, (_t)->name,                        \
 151                  atomic_read(&_t->ref_count));                          \
 152         l2tp_tunnel_dec_refcount_1(_t);                                 \
 153 } while (0)
 154 #else
 155 #define l2tp_tunnel_inc_refcount(t) l2tp_tunnel_inc_refcount_1(t)
 156 #define l2tp_tunnel_dec_refcount(t) l2tp_tunnel_dec_refcount_1(t)
 157 #endif
 158
 159 /* Session hash global list for L2TPv3.
 160  * The session_id SHOULD be random according to RFC3931, but several
 161  * L2TP implementations use incrementing session_ids.  So we do a real
 162  * hash on the session_id, rather than a simple bitmask.
 163  */
 164 static inline struct hlist_head *
 165 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 166 {
 167         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 168
 169 }
 170
 171 /* Lookup a session by id in the global session list
 172  */
 173 static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id)
 174 {
 175         struct l2tp_net *pn = l2tp_pernet(net);
 176         struct hlist_head *session_list =
 177                 l2tp_session_id_hash_2(pn, session_id);
 178         struct l2tp_session *session;
 179         struct hlist_node *walk;
 180
 181         rcu_read_lock_bh();
 182         hlist_for_each_entry_rcu(session, walk, session_list, global_hlist) {
 183                 if (session->session_id == session_id) {
 184                         rcu_read_unlock_bh();
 185                         return session;
 186                 }
 187         }
 188         rcu_read_unlock_bh();
 189
 190         return NULL;
 191 }
 192
 193 /* Session hash list.
 194  * The session_id SHOULD be random according to RFC2661, but several
 195  * L2TP implementations (Cisco and Microsoft) use incrementing
 196  * session_ids.  So we do a real hash on the session_id, rather than a
 197  * simple bitmask.
 198  */
 199 static inline struct hlist_head *
 200 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 201 {
 202         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 203 }
 204
 205 /* Lookup a session by id
 206  */
 207 struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id)
 208 {
 209         struct hlist_head *session_list;
 210         struct l2tp_session *session;
 211         struct hlist_node *walk;
 212
 213         /* In L2TPv3, session_ids are unique over all tunnels and we
 214          * sometimes need to look them up before we know the
 215          * tunnel.
 216          */
 217         if (tunnel == NULL)
 218                 return l2tp_session_find_2(net, session_id);
 219
 220         session_list = l2tp_session_id_hash(tunnel, session_id);
 221         read_lock_bh(&tunnel->hlist_lock);
 222         hlist_for_each_entry(session, walk, session_list, hlist) {
 223                 if (session->session_id == session_id) {
 224                         read_unlock_bh(&tunnel->hlist_lock);
 225                         return session;
 226                 }
 227         }
 228         read_unlock_bh(&tunnel->hlist_lock);
 229
 230         return NULL;
 231 }
 232 EXPORT_SYMBOL_GPL(l2tp_session_find);
 233
 234 struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth)
 235 {
 236         int hash;
 237         struct hlist_node *walk;
 238         struct l2tp_session *session;
 239         int count = 0;
 240
 241         read_lock_bh(&tunnel->hlist_lock);
 242         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 243                 hlist_for_each_entry(session, walk, &tunnel->session_hlist[hash], hlist) {
 244                         if (++count > nth) {
 245                                 read_unlock_bh(&tunnel->hlist_lock);
 246                                 return session;
 247                         }
 248                 }
 249         }
 250
 251         read_unlock_bh(&tunnel->hlist_lock);
 252
 253         return NULL;
 254 }
 255 EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
 256
 257 /* Lookup a session by interface name.
 258  * This is very inefficient but is only used by management interfaces.
 259  */
 260 struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
 261 {
 262         struct l2tp_net *pn = l2tp_pernet(net);
 263         int hash;
 264         struct hlist_node *walk;
 265         struct l2tp_session *session;
 266
 267         rcu_read_lock_bh();
 268         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 269                 hlist_for_each_entry_rcu(session, walk, &pn->l2tp_session_hlist[hash], global_hlist) {
 270                         if (!strcmp(session->ifname, ifname)) {
 271                                 rcu_read_unlock_bh();
 272                                 return session;
 273                         }
 274                 }
 275         }
 276
 277         rcu_read_unlock_bh();
 278
 279         return NULL;
 280 }
 281 EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname);
 282
 283 /* Lookup a tunnel by id
 284  */
 285 struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
 286 {
 287         struct l2tp_tunnel *tunnel;
 288         struct l2tp_net *pn = l2tp_pernet(net);
 289
 290         rcu_read_lock_bh();
 291         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 292                 if (tunnel->tunnel_id == tunnel_id) {
 293                         rcu_read_unlock_bh();
 294                         return tunnel;
 295                 }
 296         }
 297         rcu_read_unlock_bh();
 298
 299         return NULL;
 300 }
 301 EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
 302
 303 struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
 304 {
 305         struct l2tp_net *pn = l2tp_pernet(net);
 306         struct l2tp_tunnel *tunnel;
 307         int count = 0;
 308
 309         rcu_read_lock_bh();
 310         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 311                 if (++count > nth) {
 312                         rcu_read_unlock_bh();
 313                         return tunnel;
 314                 }
 315         }
 316
 317         rcu_read_unlock_bh();
 318
 319         return NULL;
 320 }
 321 EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
 322
 323 /*****************************************************************************
 324  * Receive data handling
 325  *****************************************************************************/
 326
 327 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 328  * number.
 329  */
 330 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 331 {
 332         struct sk_buff *skbp;
 333         struct sk_buff *tmp;
 334         u32 ns = L2TP_SKB_CB(skb)->ns;
 335         struct l2tp_stats *sstats;
 336
 337         spin_lock_bh(&session->reorder_q.lock);
 338         sstats = &session->stats;
 339         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 340                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 341                         __skb_queue_before(&session->reorder_q, skbp, skb);
 342                         l2tp_dbg(session, L2TP_MSG_SEQ,
 343                                  "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 344                                  session->name, ns, L2TP_SKB_CB(skbp)->ns,
 345                                  skb_queue_len(&session->reorder_q));
 346                         u64_stats_update_begin(&sstats->syncp);
 347                         sstats->rx_oos_packets++;
 348                         u64_stats_update_end(&sstats->syncp);
 349                         goto out;
 350                 }
 351         }
 352
 353         __skb_queue_tail(&session->reorder_q, skb);
 354
 355 out:
 356         spin_unlock_bh(&session->reorder_q.lock);
 357 }
 358
 359 /* Dequeue a single skb.
 360  */
 361 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 362 {
 363         struct l2tp_tunnel *tunnel = session->tunnel;
 364         int length = L2TP_SKB_CB(skb)->length;
 365         struct l2tp_stats *tstats, *sstats;
 366
 367         /* We're about to requeue the skb, so return resources
 368          * to its current owner (a socket receive buffer).
 369          */
 370         skb_orphan(skb);
 371
 372         tstats = &tunnel->stats;
 373         u64_stats_update_begin(&tstats->syncp);
 374         sstats = &session->stats;
 375         u64_stats_update_begin(&sstats->syncp);
 376         tstats->rx_packets++;
 377         tstats->rx_bytes += length;
 378         sstats->rx_packets++;
 379         sstats->rx_bytes += length;
 380         u64_stats_update_end(&tstats->syncp);
 381         u64_stats_update_end(&sstats->syncp);
 382
 383         if (L2TP_SKB_CB(skb)->has_seq) {
 384                 /* Bump our Nr */
 385                 session->nr++;
 386                 if (tunnel->version == L2TP_HDR_VER_2)
 387                         session->nr &= 0xffff;
 388                 else
 389                         session->nr &= 0xffffff;
 390
 391                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated nr to %hu\n",
 392                          session->name, session->nr);
 393         }
 394
 395         /* call private receive handler */
 396         if (session->recv_skb != NULL)
 397                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 398         else
 399                 kfree_skb(skb);
 400
 401         if (session->deref)
 402                 (*session->deref)(session);
 403 }
 404
 405 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 406  * Skbs that have been in the queue for too long are simply discarded.
 407  */
 408 static void l2tp_recv_dequeue(struct l2tp_session *session)
 409 {
 410         struct sk_buff *skb;
 411         struct sk_buff *tmp;
 412         struct l2tp_stats *sstats;
 413
 414         /* If the pkt at the head of the queue has the nr that we
 415          * expect to send up next, dequeue it and any other
 416          * in-sequence packets behind it.
 417          */
 418 start:
 419         spin_lock_bh(&session->reorder_q.lock);
 420         sstats = &session->stats;
 421         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 422                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 423                         u64_stats_update_begin(&sstats->syncp);
 424                         sstats->rx_seq_discards++;
 425                         sstats->rx_errors++;
 426                         u64_stats_update_end(&sstats->syncp);
 427                         l2tp_dbg(session, L2TP_MSG_SEQ,
 428                                  "%s: oos pkt %u len %d discarded (too old), waiting for %u, reorder_q_len=%d\n",
 429                                  session->name, L2TP_SKB_CB(skb)->ns,
 430                                  L2TP_SKB_CB(skb)->length, session->nr,
 431                                  skb_queue_len(&session->reorder_q));
 432                         session->reorder_skip = 1;
 433                         __skb_unlink(skb, &session->reorder_q);
 434                         kfree_skb(skb);
 435                         if (session->deref)
 436                                 (*session->deref)(session);
 437                         continue;
 438                 }
 439
 440                 if (L2TP_SKB_CB(skb)->has_seq) {
 441                         if (session->reorder_skip) {
 442                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 443                                          "%s: advancing nr to next pkt: %u -> %u",
 444                                          session->name, session->nr,
 445                                          L2TP_SKB_CB(skb)->ns);
 446                                 session->reorder_skip = 0;
 447                                 session->nr = L2TP_SKB_CB(skb)->ns;
 448                         }
 449                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 450                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 451                                          "%s: holding oos pkt %u len %d, waiting for %u, reorder_q_len=%d\n",
 452                                          session->name, L2TP_SKB_CB(skb)->ns,
 453                                          L2TP_SKB_CB(skb)->length, session->nr,
 454                                          skb_queue_len(&session->reorder_q));
 455                                 goto out;
 456                         }
 457                 }
 458                 __skb_unlink(skb, &session->reorder_q);
 459
 460                 /* Process the skb. We release the queue lock while we
 461                  * do so to let other contexts process the queue.
 462                  */
 463                 spin_unlock_bh(&session->reorder_q.lock);
 464                 l2tp_recv_dequeue_skb(session, skb);
 465                 goto start;
 466         }
 467
 468 out:
 469         spin_unlock_bh(&session->reorder_q.lock);
 470 }
 471
 472 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 473                                            struct sk_buff *skb)
 474 {
 475         struct udphdr *uh = udp_hdr(skb);
 476         u16 ulen = ntohs(uh->len);
 477         __wsum psum;
 478
 479         if (sk->sk_no_check || skb_csum_unnecessary(skb))
 480                 return 0;
 481
 482 #if IS_ENABLED(CONFIG_IPV6)
 483         if (sk->sk_family == PF_INET6) {
 484                 if (!uh->check) {
 485                         LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
 486                         return 1;
 487                 }
 488                 if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 489                     !csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 490                                      &ipv6_hdr(skb)->daddr, ulen,
 491                                      IPPROTO_UDP, skb->csum)) {
 492                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 493                         return 0;
 494                 }
 495                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 496                                                          &ipv6_hdr(skb)->daddr,
 497                                                          skb->len, IPPROTO_UDP,
 498                                                          0));
 499         } else
 500 #endif
 501         {
 502                 struct inet_sock *inet;
 503                 if (!uh->check)
 504                         return 0;
 505                 inet = inet_sk(sk);
 506                 psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr,
 507                                           ulen, IPPROTO_UDP, 0);
 508
 509                 if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 510                     !csum_fold(csum_add(psum, skb->csum)))
 511                         return 0;
 512                 skb->csum = psum;
 513         }
 514
 515         return __skb_checksum_complete(skb);
 516 }
 517
 518 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 519  * and L2TPv3 data frames here.
 520  *
 521  * L2TPv2 Data Message Header
 522  *
 523  *  0                   1                   2                   3
 524  *  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
 525  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 526  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 527  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 528  * |           Tunnel ID           |           Session ID          |
 529  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 530  * |             Ns (opt)          |             Nr (opt)          |
 531  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 532  * |      Offset Size (opt)        |    Offset pad... (opt)
 533  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 534  *
 535  * Data frames are marked by T=0. All other fields are the same as
 536  * those in L2TP control frames.
 537  *
 538  * L2TPv3 Data Message Header
 539  *
 540  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 541  * |                      L2TP Session Header                      |
 542  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 543  * |                      L2-Specific Sublayer                     |
 544  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 545  * |                        Tunnel Payload                      ...
 546  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 547  *
 548  * L2TPv3 Session Header Over IP
 549  *
 550  *  0                   1                   2                   3
 551  *  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
 552  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 553  * |                           Session ID                          |
 554  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 555  * |               Cookie (optional, maximum 64 bits)...
 556  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 557  *                                                                 |
 558  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 559  *
 560  * L2TPv3 L2-Specific Sublayer Format
 561  *
 562  *  0                   1                   2                   3
 563  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 564  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 565  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 566  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 567  *
 568  * Cookie value, sublayer format and offset (pad) are negotiated with
 569  * the peer when the session is set up. Unlike L2TPv2, we do not need
 570  * to parse the packet header to determine if optional fields are
 571  * present.
 572  *
 573  * Caller must already have parsed the frame and determined that it is
 574  * a data (not control) frame before coming here. Fields up to the
 575  * session-id have already been parsed and ptr points to the data
 576  * after the session-id.
 577  */
 578 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 579                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 580                       int length, int (*payload_hook)(struct sk_buff *skb))
 581 {
 582         struct l2tp_tunnel *tunnel = session->tunnel;
 583         int offset;
 584         u32 ns, nr;
 585         struct l2tp_stats *sstats = &session->stats;
 586
 587         /* The ref count is increased since we now hold a pointer to
 588          * the session. Take care to decrement the refcnt when exiting
 589          * this function from now on...
 590          */
 591         l2tp_session_inc_refcount(session);
 592         if (session->ref)
 593                 (*session->ref)(session);
 594
 595         /* Parse and check optional cookie */
 596         if (session->peer_cookie_len > 0) {
 597                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 598                         l2tp_info(tunnel, L2TP_MSG_DATA,
 599                                   "%s: cookie mismatch (%u/%u). Discarding.\n",
 600                                   tunnel->name, tunnel->tunnel_id,
 601                                   session->session_id);
 602                         u64_stats_update_begin(&sstats->syncp);
 603                         sstats->rx_cookie_discards++;
 604                         u64_stats_update_end(&sstats->syncp);
 605                         goto discard;
 606                 }
 607                 ptr += session->peer_cookie_len;
 608         }
 609
 610         /* Handle the optional sequence numbers. Sequence numbers are
 611          * in different places for L2TPv2 and L2TPv3.
 612          *
 613          * If we are the LAC, enable/disable sequence numbers under
 614          * the control of the LNS.  If no sequence numbers present but
 615          * we were expecting them, discard frame.
 616          */
 617         ns = nr = 0;
 618         L2TP_SKB_CB(skb)->has_seq = 0;
 619         if (tunnel->version == L2TP_HDR_VER_2) {
 620                 if (hdrflags & L2TP_HDRFLAG_S) {
 621                         ns = ntohs(*(__be16 *) ptr);
 622                         ptr += 2;
 623                         nr = ntohs(*(__be16 *) ptr);
 624                         ptr += 2;
 625
 626                         /* Store L2TP info in the skb */
 627                         L2TP_SKB_CB(skb)->ns = ns;
 628                         L2TP_SKB_CB(skb)->has_seq = 1;
 629
 630                         l2tp_dbg(session, L2TP_MSG_SEQ,
 631                                  "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 632                                  session->name, ns, nr, session->nr);
 633                 }
 634         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 635                 u32 l2h = ntohl(*(__be32 *) ptr);
 636
 637                 if (l2h & 0x40000000) {
 638                         ns = l2h & 0x00ffffff;
 639
 640                         /* Store L2TP info in the skb */
 641                         L2TP_SKB_CB(skb)->ns = ns;
 642                         L2TP_SKB_CB(skb)->has_seq = 1;
 643
 644                         l2tp_dbg(session, L2TP_MSG_SEQ,
 645                                  "%s: recv data ns=%u, session nr=%u\n",
 646                                  session->name, ns, session->nr);
 647                 }
 648         }
 649
 650         /* Advance past L2-specific header, if present */
 651         ptr += session->l2specific_len;
 652
 653         if (L2TP_SKB_CB(skb)->has_seq) {
 654                 /* Received a packet with sequence numbers. If we're the LNS,
 655                  * check if we sre sending sequence numbers and if not,
 656                  * configure it so.
 657                  */
 658                 if ((!session->lns_mode) && (!session->send_seq)) {
 659                         l2tp_info(session, L2TP_MSG_SEQ,
 660                                   "%s: requested to enable seq numbers by LNS\n",
 661                                   session->name);
 662                         session->send_seq = -1;
 663                         l2tp_session_set_header_len(session, tunnel->version);
 664                 }
 665         } else {
 666                 /* No sequence numbers.
 667                  * If user has configured mandatory sequence numbers, discard.
 668                  */
 669                 if (session->recv_seq) {
 670                         l2tp_warn(session, L2TP_MSG_SEQ,
 671                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 672                                   session->name);
 673                         u64_stats_update_begin(&sstats->syncp);
 674                         sstats->rx_seq_discards++;
 675                         u64_stats_update_end(&sstats->syncp);
 676                         goto discard;
 677                 }
 678
 679                 /* If we're the LAC and we're sending sequence numbers, the
 680                  * LNS has requested that we no longer send sequence numbers.
 681                  * If we're the LNS and we're sending sequence numbers, the
 682                  * LAC is broken. Discard the frame.
 683                  */
 684                 if ((!session->lns_mode) && (session->send_seq)) {
 685                         l2tp_info(session, L2TP_MSG_SEQ,
 686                                   "%s: requested to disable seq numbers by LNS\n",
 687                                   session->name);
 688                         session->send_seq = 0;
 689                         l2tp_session_set_header_len(session, tunnel->version);
 690                 } else if (session->send_seq) {
 691                         l2tp_warn(session, L2TP_MSG_SEQ,
 692                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 693                                   session->name);
 694                         u64_stats_update_begin(&sstats->syncp);
 695                         sstats->rx_seq_discards++;
 696                         u64_stats_update_end(&sstats->syncp);
 697                         goto discard;
 698                 }
 699         }
 700
 701         /* Session data offset is handled differently for L2TPv2 and
 702          * L2TPv3. For L2TPv2, there is an optional 16-bit value in
 703          * the header. For L2TPv3, the offset is negotiated using AVPs
 704          * in the session setup control protocol.
 705          */
 706         if (tunnel->version == L2TP_HDR_VER_2) {
 707                 /* If offset bit set, skip it. */
 708                 if (hdrflags & L2TP_HDRFLAG_O) {
 709                         offset = ntohs(*(__be16 *)ptr);
 710                         ptr += 2 + offset;
 711                 }
 712         } else
 713                 ptr += session->offset;
 714
 715         offset = ptr - optr;
 716         if (!pskb_may_pull(skb, offset))
 717                 goto discard;
 718
 719         __skb_pull(skb, offset);
 720
 721         /* If caller wants to process the payload before we queue the
 722          * packet, do so now.
 723          */
 724         if (payload_hook)
 725                 if ((*payload_hook)(skb))
 726                         goto discard;
 727
 728         /* Prepare skb for adding to the session's reorder_q.  Hold
 729          * packets for max reorder_timeout or 1 second if not
 730          * reordering.
 731          */
 732         L2TP_SKB_CB(skb)->length = length;
 733         L2TP_SKB_CB(skb)->expires = jiffies +
 734                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 735
 736         /* Add packet to the session's receive queue. Reordering is done here, if
 737          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 738          */
 739         if (L2TP_SKB_CB(skb)->has_seq) {
 740                 if (session->reorder_timeout != 0) {
 741                         /* Packet reordering enabled. Add skb to session's
 742                          * reorder queue, in order of ns.
 743                          */
 744                         l2tp_recv_queue_skb(session, skb);
 745                 } else {
 746                         /* Packet reordering disabled. Discard out-of-sequence
 747                          * packets
 748                          */
 749                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 750                                 u64_stats_update_begin(&sstats->syncp);
 751                                 sstats->rx_seq_discards++;
 752                                 u64_stats_update_end(&sstats->syncp);
 753                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 754                                          "%s: oos pkt %u len %d discarded, waiting for %u, reorder_q_len=%d\n",
 755                                          session->name, L2TP_SKB_CB(skb)->ns,
 756                                          L2TP_SKB_CB(skb)->length, session->nr,
 757                                          skb_queue_len(&session->reorder_q));
 758                                 goto discard;
 759                         }
 760                         skb_queue_tail(&session->reorder_q, skb);
 761                 }
 762         } else {
 763                 /* No sequence numbers. Add the skb to the tail of the
 764                  * reorder queue. This ensures that it will be
 765                  * delivered after all previous sequenced skbs.
 766                  */
 767                 skb_queue_tail(&session->reorder_q, skb);
 768         }
 769
 770         /* Try to dequeue as many skbs from reorder_q as we can. */
 771         l2tp_recv_dequeue(session);
 772
 773         l2tp_session_dec_refcount(session);
 774
 775         return;
 776
 777 discard:
 778         u64_stats_update_begin(&sstats->syncp);
 779         sstats->rx_errors++;
 780         u64_stats_update_end(&sstats->syncp);
 781         kfree_skb(skb);
 782
 783         if (session->deref)
 784                 (*session->deref)(session);
 785
 786         l2tp_session_dec_refcount(session);
 787 }
 788 EXPORT_SYMBOL(l2tp_recv_common);
 789
 790 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 791  * here. The skb is not on a list when we get here.
 792  * Returns 0 if the packet was a data packet and was successfully passed on.
 793  * Returns 1 if the packet was not a good data packet and could not be
 794  * forwarded.  All such packets are passed up to userspace to deal with.
 795  */
 796 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 797                               int (*payload_hook)(struct sk_buff *skb))
 798 {
 799         struct l2tp_session *session = NULL;
 800         unsigned char *ptr, *optr;
 801         u16 hdrflags;
 802         u32 tunnel_id, session_id;
 803         u16 version;
 804         int length;
 805         struct l2tp_stats *tstats;
 806
 807         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
 808                 goto discard_bad_csum;
 809
 810         /* UDP always verifies the packet length. */
 811         __skb_pull(skb, sizeof(struct udphdr));
 812
 813         /* Short packet? */
 814         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
 815                 l2tp_info(tunnel, L2TP_MSG_DATA,
 816                           "%s: recv short packet (len=%d)\n",
 817                           tunnel->name, skb->len);
 818                 goto error;
 819         }
 820
 821         /* Trace packet contents, if enabled */
 822         if (tunnel->debug & L2TP_MSG_DATA) {
 823                 length = min(32u, skb->len);
 824                 if (!pskb_may_pull(skb, length))
 825                         goto error;
 826
 827                 pr_debug("%s: recv\n", tunnel->name);
 828                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 829         }
 830
 831         /* Point to L2TP header */
 832         optr = ptr = skb->data;
 833
 834         /* Get L2TP header flags */
 835         hdrflags = ntohs(*(__be16 *) ptr);
 836
 837         /* Check protocol version */
 838         version = hdrflags & L2TP_HDR_VER_MASK;
 839         if (version != tunnel->version) {
 840                 l2tp_info(tunnel, L2TP_MSG_DATA,
 841                           "%s: recv protocol version mismatch: got %d expected %d\n",
 842                           tunnel->name, version, tunnel->version);
 843                 goto error;
 844         }
 845
 846         /* Get length of L2TP packet */
 847         length = skb->len;
 848
 849         /* If type is control packet, it is handled by userspace. */
 850         if (hdrflags & L2TP_HDRFLAG_T) {
 851                 l2tp_dbg(tunnel, L2TP_MSG_DATA,
 852                          "%s: recv control packet, len=%d\n",
 853                          tunnel->name, length);
 854                 goto error;
 855         }
 856
 857         /* Skip flags */
 858         ptr += 2;
 859
 860         if (tunnel->version == L2TP_HDR_VER_2) {
 861                 /* If length is present, skip it */
 862                 if (hdrflags & L2TP_HDRFLAG_L)
 863                         ptr += 2;
 864
 865                 /* Extract tunnel and session ID */
 866                 tunnel_id = ntohs(*(__be16 *) ptr);
 867                 ptr += 2;
 868                 session_id = ntohs(*(__be16 *) ptr);
 869                 ptr += 2;
 870         } else {
 871                 ptr += 2;       /* skip reserved bits */
 872                 tunnel_id = tunnel->tunnel_id;
 873                 session_id = ntohl(*(__be32 *) ptr);
 874                 ptr += 4;
 875         }
 876
 877         /* Find the session context */
 878         session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
 879         if (!session || !session->recv_skb) {
 880                 /* Not found? Pass to userspace to deal with */
 881                 l2tp_info(tunnel, L2TP_MSG_DATA,
 882                           "%s: no session found (%u/%u). Passing up.\n",
 883                           tunnel->name, tunnel_id, session_id);
 884                 goto error;
 885         }
 886
 887         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
 888
 889         return 0;
 890
 891 discard_bad_csum:
 892         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
 893         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
 894         tstats = &tunnel->stats;
 895         u64_stats_update_begin(&tstats->syncp);
 896         tstats->rx_errors++;
 897         u64_stats_update_end(&tstats->syncp);
 898         kfree_skb(skb);
 899
 900         return 0;
 901
 902 error:
 903         /* Put UDP header back */
 904         __skb_push(skb, sizeof(struct udphdr));
 905
 906         return 1;
 907 }
 908
 909 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 910  * Return codes:
 911  * 0 : success.
 912  * <0: error
 913  * >0: skb should be passed up to userspace as UDP.
 914  */
 915 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 916 {
 917         struct l2tp_tunnel *tunnel;
 918
 919         tunnel = l2tp_sock_to_tunnel(sk);
 920         if (tunnel == NULL)
 921                 goto pass_up;
 922
 923         l2tp_dbg(tunnel, L2TP_MSG_DATA, "%s: received %d bytes\n",
 924                  tunnel->name, skb->len);
 925
 926         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
 927                 goto pass_up_put;
 928
 929         sock_put(sk);
 930         return 0;
 931
 932 pass_up_put:
 933         sock_put(sk);
 934 pass_up:
 935         return 1;
 936 }
 937 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 938
 939 /************************************************************************
 940  * Transmit handling
 941  ***********************************************************************/
 942
 943 /* Build an L2TP header for the session into the buffer provided.
 944  */
 945 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 946 {
 947         struct l2tp_tunnel *tunnel = session->tunnel;
 948         __be16 *bufp = buf;
 949         __be16 *optr = buf;
 950         u16 flags = L2TP_HDR_VER_2;
 951         u32 tunnel_id = tunnel->peer_tunnel_id;
 952         u32 session_id = session->peer_session_id;
 953
 954         if (session->send_seq)
 955                 flags |= L2TP_HDRFLAG_S;
 956
 957         /* Setup L2TP header. */
 958         *bufp++ = htons(flags);
 959         *bufp++ = htons(tunnel_id);
 960         *bufp++ = htons(session_id);
 961         if (session->send_seq) {
 962                 *bufp++ = htons(session->ns);
 963                 *bufp++ = 0;
 964                 session->ns++;
 965                 session->ns &= 0xffff;
 966                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated ns to %u\n",
 967                          session->name, session->ns);
 968         }
 969
 970         return bufp - optr;
 971 }
 972
 973 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 974 {
 975         struct l2tp_tunnel *tunnel = session->tunnel;
 976         char *bufp = buf;
 977         char *optr = bufp;
 978
 979         /* Setup L2TP header. The header differs slightly for UDP and
 980          * IP encapsulations. For UDP, there is 4 bytes of flags.
 981          */
 982         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 983                 u16 flags = L2TP_HDR_VER_3;
 984                 *((__be16 *) bufp) = htons(flags);
 985                 bufp += 2;
 986                 *((__be16 *) bufp) = 0;
 987                 bufp += 2;
 988         }
 989
 990         *((__be32 *) bufp) = htonl(session->peer_session_id);
 991         bufp += 4;
 992         if (session->cookie_len) {
 993                 memcpy(bufp, &session->cookie[0], session->cookie_len);
 994                 bufp += session->cookie_len;
 995         }
 996         if (session->l2specific_len) {
 997                 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 998                         u32 l2h = 0;
 999                         if (session->send_seq) {
1000                                 l2h = 0x40000000 | session->ns;
1001                                 session->ns++;
1002                                 session->ns &= 0xffffff;
1003                                 l2tp_dbg(session, L2TP_MSG_SEQ,
1004                                          "%s: updated ns to %u\n",
1005                                          session->name, session->ns);
1006                         }
1007
1008                         *((__be32 *) bufp) = htonl(l2h);
1009                 }
1010                 bufp += session->l2specific_len;
1011         }
1012         if (session->offset)
1013                 bufp += session->offset;
1014
1015         return bufp - optr;
1016 }
1017
1018 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
1019                           struct flowi *fl, size_t data_len)
1020 {
1021         struct l2tp_tunnel *tunnel = session->tunnel;
1022         unsigned int len = skb->len;
1023         int error;
1024         struct l2tp_stats *tstats, *sstats;
1025
1026         /* Debug */
1027         if (session->send_seq)
1028                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %Zd bytes, ns=%u\n",
1029                          session->name, data_len, session->ns - 1);
1030         else
1031                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %Zd bytes\n",
1032                          session->name, data_len);
1033
1034         if (session->debug & L2TP_MSG_DATA) {
1035                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1036                 unsigned char *datap = skb->data + uhlen;
1037
1038                 pr_debug("%s: xmit\n", session->name);
1039                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET,
1040                                      datap, min_t(size_t, 32, len - uhlen));
1041         }
1042
1043         /* Queue the packet to IP for output */
1044         skb->local_df = 1;
1045 #if IS_ENABLED(CONFIG_IPV6)
1046         if (skb->sk->sk_family == PF_INET6)
1047                 error = inet6_csk_xmit(skb, NULL);
1048         else
1049 #endif
1050                 error = ip_queue_xmit(skb, fl);
1051
1052         /* Update stats */
1053         tstats = &tunnel->stats;
1054         u64_stats_update_begin(&tstats->syncp);
1055         sstats = &session->stats;
1056         u64_stats_update_begin(&sstats->syncp);
1057         if (error >= 0) {
1058                 tstats->tx_packets++;
1059                 tstats->tx_bytes += len;
1060                 sstats->tx_packets++;
1061                 sstats->tx_bytes += len;
1062         } else {
1063                 tstats->tx_errors++;
1064                 sstats->tx_errors++;
1065         }
1066         u64_stats_update_end(&tstats->syncp);
1067         u64_stats_update_end(&sstats->syncp);
1068
1069         return 0;
1070 }
1071
1072 /* Automatically called when the skb is freed.
1073  */
1074 static void l2tp_sock_wfree(struct sk_buff *skb)
1075 {
1076         sock_put(skb->sk);
1077 }
1078
1079 /* For data skbs that we transmit, we associate with the tunnel socket
1080  * but don't do accounting.
1081  */
1082 static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
1083 {
1084         sock_hold(sk);
1085         skb->sk = sk;
1086         skb->destructor = l2tp_sock_wfree;
1087 }
1088
1089 #if IS_ENABLED(CONFIG_IPV6)
1090 static void l2tp_xmit_ipv6_csum(struct sock *sk, struct sk_buff *skb,
1091                                 int udp_len)
1092 {
1093         struct ipv6_pinfo *np = inet6_sk(sk);
1094         struct udphdr *uh = udp_hdr(skb);
1095
1096         if (!skb_dst(skb) || !skb_dst(skb)->dev ||
1097             !(skb_dst(skb)->dev->features & NETIF_F_IPV6_CSUM)) {
1098                 __wsum csum = skb_checksum(skb, 0, udp_len, 0);
1099                 skb->ip_summed = CHECKSUM_UNNECESSARY;
1100                 uh->check = csum_ipv6_magic(&np->saddr, &np->daddr, udp_len,
1101                                             IPPROTO_UDP, csum);
1102                 if (uh->check == 0)
1103                         uh->check = CSUM_MANGLED_0;
1104         } else {
1105                 skb->ip_summed = CHECKSUM_PARTIAL;
1106                 skb->csum_start = skb_transport_header(skb) - skb->head;
1107                 skb->csum_offset = offsetof(struct udphdr, check);
1108                 uh->check = ~csum_ipv6_magic(&np->saddr, &np->daddr,
1109                                              udp_len, IPPROTO_UDP, 0);
1110         }
1111 }
1112 #endif
1113
1114 /* If caller requires the skb to have a ppp header, the header must be
1115  * inserted in the skb data before calling this function.
1116  */
1117 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1118 {
1119         int data_len = skb->len;
1120         struct l2tp_tunnel *tunnel = session->tunnel;
1121         struct sock *sk = tunnel->sock;
1122         struct flowi *fl;
1123         struct udphdr *uh;
1124         struct inet_sock *inet;
1125         __wsum csum;
1126         int old_headroom;
1127         int new_headroom;
1128         int headroom;
1129         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1130         int udp_len;
1131
1132         /* Check that there's enough headroom in the skb to insert IP,
1133          * UDP and L2TP headers. If not enough, expand it to
1134          * make room. Adjust truesize.
1135          */
1136         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1137                 uhlen + hdr_len;
1138         old_headroom = skb_headroom(skb);
1139         if (skb_cow_head(skb, headroom)) {
1140                 dev_kfree_skb(skb);
1141                 goto abort;
1142         }
1143
1144         new_headroom = skb_headroom(skb);
1145         skb_orphan(skb);
1146         skb->truesize += new_headroom - old_headroom;
1147
1148         /* Setup L2TP header */
1149         session->build_header(session, __skb_push(skb, hdr_len));
1150
1151         /* Reset skb netfilter state */
1152         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1153         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1154                               IPSKB_REROUTED);
1155         nf_reset(skb);
1156
1157         bh_lock_sock(sk);
1158         if (sock_owned_by_user(sk)) {
1159                 dev_kfree_skb(skb);
1160                 goto out_unlock;
1161         }
1162
1163         /* Get routing info from the tunnel socket */
1164         skb_dst_drop(skb);
1165         skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
1166
1167         inet = inet_sk(sk);
1168         fl = &inet->cork.fl;
1169         switch (tunnel->encap) {
1170         case L2TP_ENCAPTYPE_UDP:
1171                 /* Setup UDP header */
1172                 __skb_push(skb, sizeof(*uh));
1173                 skb_reset_transport_header(skb);
1174                 uh = udp_hdr(skb);
1175                 uh->source = inet->inet_sport;
1176                 uh->dest = inet->inet_dport;
1177                 udp_len = uhlen + hdr_len + data_len;
1178                 uh->len = htons(udp_len);
1179                 uh->check = 0;
1180
1181                 /* Calculate UDP checksum if configured to do so */
1182 #if IS_ENABLED(CONFIG_IPV6)
1183                 if (sk->sk_family == PF_INET6)
1184                         l2tp_xmit_ipv6_csum(sk, skb, udp_len);
1185                 else
1186 #endif
1187                 if (sk->sk_no_check == UDP_CSUM_NOXMIT)
1188                         skb->ip_summed = CHECKSUM_NONE;
1189                 else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
1190                          (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
1191                         skb->ip_summed = CHECKSUM_COMPLETE;
1192                         csum = skb_checksum(skb, 0, udp_len, 0);
1193                         uh->check = csum_tcpudp_magic(inet->inet_saddr,
1194                                                       inet->inet_daddr,
1195                                                       udp_len, IPPROTO_UDP, csum);
1196                         if (uh->check == 0)
1197                                 uh->check = CSUM_MANGLED_0;
1198                 } else {
1199                         skb->ip_summed = CHECKSUM_PARTIAL;
1200                         skb->csum_start = skb_transport_header(skb) - skb->head;
1201                         skb->csum_offset = offsetof(struct udphdr, check);
1202                         uh->check = ~csum_tcpudp_magic(inet->inet_saddr,
1203                                                        inet->inet_daddr,
1204                                                        udp_len, IPPROTO_UDP, 0);
1205                 }
1206                 break;
1207
1208         case L2TP_ENCAPTYPE_IP:
1209                 break;
1210         }
1211
1212         l2tp_skb_set_owner_w(skb, sk);
1213
1214         l2tp_xmit_core(session, skb, fl, data_len);
1215 out_unlock:
1216         bh_unlock_sock(sk);
1217
1218 abort:
1219         return 0;
1220 }
1221 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1222
1223 /*****************************************************************************
1224  * Tinnel and session create/destroy.
1225  *****************************************************************************/
1226
1227 /* Tunnel socket destruct hook.
1228  * The tunnel context is deleted only when all session sockets have been
1229  * closed.
1230  */
1231 static void l2tp_tunnel_destruct(struct sock *sk)
1232 {
1233         struct l2tp_tunnel *tunnel;
1234
1235         tunnel = sk->sk_user_data;
1236         if (tunnel == NULL)
1237                 goto end;
1238
1239         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%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         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing all sessions...\n",
1282                   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                         l2tp_info(session, L2TP_MSG_CONTROL,
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 static 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         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: free...\n", tunnel->name);
1345
1346         /* Remove from tunnel list */
1347         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1348         list_del_rcu(&tunnel->list);
1349         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1350         synchronize_rcu();
1351
1352         atomic_dec(&l2tp_tunnel_count);
1353         kfree(tunnel);
1354 }
1355
1356 /* Create a socket for the tunnel, if one isn't set up by
1357  * userspace. This is used for static tunnels where there is no
1358  * managing L2TP daemon.
1359  */
1360 static int l2tp_tunnel_sock_create(u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct socket **sockp)
1361 {
1362         int err = -EINVAL;
1363         struct sockaddr_in udp_addr;
1364 #if IS_ENABLED(CONFIG_IPV6)
1365         struct sockaddr_in6 udp6_addr;
1366         struct sockaddr_l2tpip6 ip6_addr;
1367 #endif
1368         struct sockaddr_l2tpip ip_addr;
1369         struct socket *sock = NULL;
1370
1371         switch (cfg->encap) {
1372         case L2TP_ENCAPTYPE_UDP:
1373 #if IS_ENABLED(CONFIG_IPV6)
1374                 if (cfg->local_ip6 && cfg->peer_ip6) {
1375                         err = sock_create(AF_INET6, SOCK_DGRAM, 0, sockp);
1376                         if (err < 0)
1377                                 goto out;
1378
1379                         sock = *sockp;
1380
1381                         memset(&udp6_addr, 0, sizeof(udp6_addr));
1382                         udp6_addr.sin6_family = AF_INET6;
1383                         memcpy(&udp6_addr.sin6_addr, cfg->local_ip6,
1384                                sizeof(udp6_addr.sin6_addr));
1385                         udp6_addr.sin6_port = htons(cfg->local_udp_port);
1386                         err = kernel_bind(sock, (struct sockaddr *) &udp6_addr,
1387                                           sizeof(udp6_addr));
1388                         if (err < 0)
1389                                 goto out;
1390
1391                         udp6_addr.sin6_family = AF_INET6;
1392                         memcpy(&udp6_addr.sin6_addr, cfg->peer_ip6,
1393                                sizeof(udp6_addr.sin6_addr));
1394                         udp6_addr.sin6_port = htons(cfg->peer_udp_port);
1395                         err = kernel_connect(sock,
1396                                              (struct sockaddr *) &udp6_addr,
1397                                              sizeof(udp6_addr), 0);
1398                         if (err < 0)
1399                                 goto out;
1400                 } else
1401 #endif
1402                 {
1403                         err = sock_create(AF_INET, SOCK_DGRAM, 0, sockp);
1404                         if (err < 0)
1405                                 goto out;
1406
1407                         sock = *sockp;
1408
1409                         memset(&udp_addr, 0, sizeof(udp_addr));
1410                         udp_addr.sin_family = AF_INET;
1411                         udp_addr.sin_addr = cfg->local_ip;
1412                         udp_addr.sin_port = htons(cfg->local_udp_port);
1413                         err = kernel_bind(sock, (struct sockaddr *) &udp_addr,
1414                                           sizeof(udp_addr));
1415                         if (err < 0)
1416                                 goto out;
1417
1418                         udp_addr.sin_family = AF_INET;
1419                         udp_addr.sin_addr = cfg->peer_ip;
1420                         udp_addr.sin_port = htons(cfg->peer_udp_port);
1421                         err = kernel_connect(sock,
1422                                              (struct sockaddr *) &udp_addr,
1423                                              sizeof(udp_addr), 0);
1424                         if (err < 0)
1425                                 goto out;
1426                 }
1427
1428                 if (!cfg->use_udp_checksums)
1429                         sock->sk->sk_no_check = UDP_CSUM_NOXMIT;
1430
1431                 break;
1432
1433         case L2TP_ENCAPTYPE_IP:
1434 #if IS_ENABLED(CONFIG_IPV6)
1435                 if (cfg->local_ip6 && cfg->peer_ip6) {
1436                         err = sock_create(AF_INET6, SOCK_DGRAM, IPPROTO_L2TP,
1437                                           sockp);
1438                         if (err < 0)
1439                                 goto out;
1440
1441                         sock = *sockp;
1442
1443                         memset(&ip6_addr, 0, sizeof(ip6_addr));
1444                         ip6_addr.l2tp_family = AF_INET6;
1445                         memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1446                                sizeof(ip6_addr.l2tp_addr));
1447                         ip6_addr.l2tp_conn_id = tunnel_id;
1448                         err = kernel_bind(sock, (struct sockaddr *) &ip6_addr,
1449                                           sizeof(ip6_addr));
1450                         if (err < 0)
1451                                 goto out;
1452
1453                         ip6_addr.l2tp_family = AF_INET6;
1454                         memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1455                                sizeof(ip6_addr.l2tp_addr));
1456                         ip6_addr.l2tp_conn_id = peer_tunnel_id;
1457                         err = kernel_connect(sock,
1458                                              (struct sockaddr *) &ip6_addr,
1459                                              sizeof(ip6_addr), 0);
1460                         if (err < 0)
1461                                 goto out;
1462                 } else
1463 #endif
1464                 {
1465                         err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_L2TP,
1466                                           sockp);
1467                         if (err < 0)
1468                                 goto out;
1469
1470                         sock = *sockp;
1471
1472                         memset(&ip_addr, 0, sizeof(ip_addr));
1473                         ip_addr.l2tp_family = AF_INET;
1474                         ip_addr.l2tp_addr = cfg->local_ip;
1475                         ip_addr.l2tp_conn_id = tunnel_id;
1476                         err = kernel_bind(sock, (struct sockaddr *) &ip_addr,
1477                                           sizeof(ip_addr));
1478                         if (err < 0)
1479                                 goto out;
1480
1481                         ip_addr.l2tp_family = AF_INET;
1482                         ip_addr.l2tp_addr = cfg->peer_ip;
1483                         ip_addr.l2tp_conn_id = peer_tunnel_id;
1484                         err = kernel_connect(sock, (struct sockaddr *) &ip_addr,
1485                                              sizeof(ip_addr), 0);
1486                         if (err < 0)
1487                                 goto out;
1488                 }
1489                 break;
1490
1491         default:
1492                 goto out;
1493         }
1494
1495 out:
1496         if ((err < 0) && sock) {
1497                 sock_release(sock);
1498                 *sockp = NULL;
1499         }
1500
1501         return err;
1502 }
1503
1504 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)
1505 {
1506         struct l2tp_tunnel *tunnel = NULL;
1507         int err;
1508         struct socket *sock = NULL;
1509         struct sock *sk = NULL;
1510         struct l2tp_net *pn;
1511         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1512
1513         /* Get the tunnel socket from the fd, which was opened by
1514          * the userspace L2TP daemon. If not specified, create a
1515          * kernel socket.
1516          */
1517         if (fd < 0) {
1518                 err = l2tp_tunnel_sock_create(tunnel_id, peer_tunnel_id, cfg, &sock);
1519                 if (err < 0)
1520                         goto err;
1521         } else {
1522                 err = -EBADF;
1523                 sock = sockfd_lookup(fd, &err);
1524                 if (!sock) {
1525                         pr_err("tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
1526                                tunnel_id, fd, err);
1527                         goto err;
1528                 }
1529         }
1530
1531         sk = sock->sk;
1532
1533         if (cfg != NULL)
1534                 encap = cfg->encap;
1535
1536         /* Quick sanity checks */
1537         switch (encap) {
1538         case L2TP_ENCAPTYPE_UDP:
1539                 err = -EPROTONOSUPPORT;
1540                 if (sk->sk_protocol != IPPROTO_UDP) {
1541                         pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1542                                tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
1543                         goto err;
1544                 }
1545                 break;
1546         case L2TP_ENCAPTYPE_IP:
1547                 err = -EPROTONOSUPPORT;
1548                 if (sk->sk_protocol != IPPROTO_L2TP) {
1549                         pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1550                                tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
1551                         goto err;
1552                 }
1553                 break;
1554         }
1555
1556         /* Check if this socket has already been prepped */
1557         tunnel = (struct l2tp_tunnel *)sk->sk_user_data;
1558         if (tunnel != NULL) {
1559                 /* This socket has already been prepped */
1560                 err = -EBUSY;
1561                 goto err;
1562         }
1563
1564         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1565         if (tunnel == NULL) {
1566                 err = -ENOMEM;
1567                 goto err;
1568         }
1569
1570         tunnel->version = version;
1571         tunnel->tunnel_id = tunnel_id;
1572         tunnel->peer_tunnel_id = peer_tunnel_id;
1573         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1574
1575         tunnel->magic = L2TP_TUNNEL_MAGIC;
1576         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1577         rwlock_init(&tunnel->hlist_lock);
1578
1579         /* The net we belong to */
1580         tunnel->l2tp_net = net;
1581         pn = l2tp_pernet(net);
1582
1583         if (cfg != NULL)
1584                 tunnel->debug = cfg->debug;
1585
1586         /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1587         tunnel->encap = encap;
1588         if (encap == L2TP_ENCAPTYPE_UDP) {
1589                 /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1590                 udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
1591                 udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
1592 #if IS_ENABLED(CONFIG_IPV6)
1593                 if (sk->sk_family == PF_INET6)
1594                         udpv6_encap_enable();
1595                 else
1596 #endif
1597                 udp_encap_enable();
1598         }
1599
1600         sk->sk_user_data = tunnel;
1601
1602         /* Hook on the tunnel socket destructor so that we can cleanup
1603          * if the tunnel socket goes away.
1604          */
1605         tunnel->old_sk_destruct = sk->sk_destruct;
1606         sk->sk_destruct = &l2tp_tunnel_destruct;
1607         tunnel->sock = sk;
1608         sk->sk_allocation = GFP_ATOMIC;
1609
1610         /* Add tunnel to our list */
1611         INIT_LIST_HEAD(&tunnel->list);
1612         atomic_inc(&l2tp_tunnel_count);
1613
1614         /* Bump the reference count. The tunnel context is deleted
1615          * only when this drops to zero. Must be done before list insertion
1616          */
1617         l2tp_tunnel_inc_refcount(tunnel);
1618         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1619         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1620         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1621
1622         err = 0;
1623 err:
1624         if (tunnelp)
1625                 *tunnelp = tunnel;
1626
1627         /* If tunnel's socket was created by the kernel, it doesn't
1628          *  have a file.
1629          */
1630         if (sock && sock->file)
1631                 sockfd_put(sock);
1632
1633         return err;
1634 }
1635 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1636
1637 /* This function is used by the netlink TUNNEL_DELETE command.
1638  */
1639 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1640 {
1641         int err = 0;
1642         struct socket *sock = tunnel->sock ? tunnel->sock->sk_socket : NULL;
1643
1644         /* Force the tunnel socket to close. This will eventually
1645          * cause the tunnel to be deleted via the normal socket close
1646          * mechanisms when userspace closes the tunnel socket.
1647          */
1648         if (sock != NULL) {
1649                 err = inet_shutdown(sock, 2);
1650
1651                 /* If the tunnel's socket was created by the kernel,
1652                  * close the socket here since the socket was not
1653                  * created by userspace.
1654                  */
1655                 if (sock->file == NULL)
1656                         err = inet_release(sock);
1657         }
1658
1659         return err;
1660 }
1661 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1662
1663 /* Really kill the session.
1664  */
1665 void l2tp_session_free(struct l2tp_session *session)
1666 {
1667         struct l2tp_tunnel *tunnel;
1668
1669         BUG_ON(atomic_read(&session->ref_count) != 0);
1670
1671         tunnel = session->tunnel;
1672         if (tunnel != NULL) {
1673                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1674
1675                 /* Delete the session from the hash */
1676                 write_lock_bh(&tunnel->hlist_lock);
1677                 hlist_del_init(&session->hlist);
1678                 write_unlock_bh(&tunnel->hlist_lock);
1679
1680                 /* Unlink from the global hash if not L2TPv2 */
1681                 if (tunnel->version != L2TP_HDR_VER_2) {
1682                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1683
1684                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1685                         hlist_del_init_rcu(&session->global_hlist);
1686                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1687                         synchronize_rcu();
1688                 }
1689
1690                 if (session->session_id != 0)
1691                         atomic_dec(&l2tp_session_count);
1692
1693                 sock_put(tunnel->sock);
1694
1695                 /* This will delete the tunnel context if this
1696                  * is the last session on the tunnel.
1697                  */
1698                 session->tunnel = NULL;
1699                 l2tp_tunnel_dec_refcount(tunnel);
1700         }
1701
1702         kfree(session);
1703
1704         return;
1705 }
1706 EXPORT_SYMBOL_GPL(l2tp_session_free);
1707
1708 /* This function is used by the netlink SESSION_DELETE command and by
1709    pseudowire modules.
1710  */
1711 int l2tp_session_delete(struct l2tp_session *session)
1712 {
1713         if (session->session_close != NULL)
1714                 (*session->session_close)(session);
1715
1716         l2tp_session_dec_refcount(session);
1717
1718         return 0;
1719 }
1720 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1721
1722
1723 /* We come here whenever a session's send_seq, cookie_len or
1724  * l2specific_len parameters are set.
1725  */
1726 static void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1727 {
1728         if (version == L2TP_HDR_VER_2) {
1729                 session->hdr_len = 6;
1730                 if (session->send_seq)
1731                         session->hdr_len += 4;
1732         } else {
1733                 session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
1734                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1735                         session->hdr_len += 4;
1736         }
1737
1738 }
1739
1740 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)
1741 {
1742         struct l2tp_session *session;
1743
1744         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1745         if (session != NULL) {
1746                 session->magic = L2TP_SESSION_MAGIC;
1747                 session->tunnel = tunnel;
1748
1749                 session->session_id = session_id;
1750                 session->peer_session_id = peer_session_id;
1751                 session->nr = 0;
1752
1753                 sprintf(&session->name[0], "sess %u/%u",
1754                         tunnel->tunnel_id, session->session_id);
1755
1756                 skb_queue_head_init(&session->reorder_q);
1757
1758                 INIT_HLIST_NODE(&session->hlist);
1759                 INIT_HLIST_NODE(&session->global_hlist);
1760
1761                 /* Inherit debug options from tunnel */
1762                 session->debug = tunnel->debug;
1763
1764                 if (cfg) {
1765                         session->pwtype = cfg->pw_type;
1766                         session->debug = cfg->debug;
1767                         session->mtu = cfg->mtu;
1768                         session->mru = cfg->mru;
1769                         session->send_seq = cfg->send_seq;
1770                         session->recv_seq = cfg->recv_seq;
1771                         session->lns_mode = cfg->lns_mode;
1772                         session->reorder_timeout = cfg->reorder_timeout;
1773                         session->offset = cfg->offset;
1774                         session->l2specific_type = cfg->l2specific_type;
1775                         session->l2specific_len = cfg->l2specific_len;
1776                         session->cookie_len = cfg->cookie_len;
1777                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1778                         session->peer_cookie_len = cfg->peer_cookie_len;
1779                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1780                 }
1781
1782                 if (tunnel->version == L2TP_HDR_VER_2)
1783                         session->build_header = l2tp_build_l2tpv2_header;
1784                 else
1785                         session->build_header = l2tp_build_l2tpv3_header;
1786
1787                 l2tp_session_set_header_len(session, tunnel->version);
1788
1789                 /* Bump the reference count. The session context is deleted
1790                  * only when this drops to zero.
1791                  */
1792                 l2tp_session_inc_refcount(session);
1793                 l2tp_tunnel_inc_refcount(tunnel);
1794
1795                 /* Ensure tunnel socket isn't deleted */
1796                 sock_hold(tunnel->sock);
1797
1798                 /* Add session to the tunnel's hash list */
1799                 write_lock_bh(&tunnel->hlist_lock);
1800                 hlist_add_head(&session->hlist,
1801                                l2tp_session_id_hash(tunnel, session_id));
1802                 write_unlock_bh(&tunnel->hlist_lock);
1803
1804                 /* And to the global session list if L2TPv3 */
1805                 if (tunnel->version != L2TP_HDR_VER_2) {
1806                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1807
1808                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1809                         hlist_add_head_rcu(&session->global_hlist,
1810                                            l2tp_session_id_hash_2(pn, session_id));
1811                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1812                 }
1813
1814                 /* Ignore management session in session count value */
1815                 if (session->session_id != 0)
1816                         atomic_inc(&l2tp_session_count);
1817         }
1818
1819         return session;
1820 }
1821 EXPORT_SYMBOL_GPL(l2tp_session_create);
1822
1823 /*****************************************************************************
1824  * Init and cleanup
1825  *****************************************************************************/
1826
1827 static __net_init int l2tp_init_net(struct net *net)
1828 {
1829         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1830         int hash;
1831
1832         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1833         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1834
1835         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1836                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1837
1838         spin_lock_init(&pn->l2tp_session_hlist_lock);
1839
1840         return 0;
1841 }
1842
1843 static struct pernet_operations l2tp_net_ops = {
1844         .init = l2tp_init_net,
1845         .id   = &l2tp_net_id,
1846         .size = sizeof(struct l2tp_net),
1847 };
1848
1849 static int __init l2tp_init(void)
1850 {
1851         int rc = 0;
1852
1853         rc = register_pernet_device(&l2tp_net_ops);
1854         if (rc)
1855                 goto out;
1856
1857         pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
1858
1859 out:
1860         return rc;
1861 }
1862
1863 static void __exit l2tp_exit(void)
1864 {
1865         unregister_pernet_device(&l2tp_net_ops);
1866 }
1867
1868 module_init(l2tp_init);
1869 module_exit(l2tp_exit);
1870
1871 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1872 MODULE_DESCRIPTION("L2TP core");
1873 MODULE_LICENSE("GPL");
1874 MODULE_VERSION(L2TP_DRV_VERSION);
1875