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 static struct workqueue_struct *l2tp_wq;
 105
 106 /* per-net private data for this module */
 107 static unsigned int l2tp_net_id;
 108 struct l2tp_net {
 109         struct list_head l2tp_tunnel_list;
 110         spinlock_t l2tp_tunnel_list_lock;
 111         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
 112         spinlock_t l2tp_session_hlist_lock;
 113 };
 114
 115 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
 116
 117 static inline struct l2tp_tunnel *l2tp_tunnel(struct sock *sk)
 118 {
 119         return sk->sk_user_data;
 120 }
 121
 122 static inline struct l2tp_net *l2tp_pernet(struct net *net)
 123 {
 124         BUG_ON(!net);
 125
 126         return net_generic(net, l2tp_net_id);
 127 }
 128
 129 /* Tunnel reference counts. Incremented per session that is added to
 130  * the tunnel.
 131  */
 132 static inline void l2tp_tunnel_inc_refcount_1(struct l2tp_tunnel *tunnel)
 133 {
 134         atomic_inc(&tunnel->ref_count);
 135 }
 136
 137 static inline void l2tp_tunnel_dec_refcount_1(struct l2tp_tunnel *tunnel)
 138 {
 139         if (atomic_dec_and_test(&tunnel->ref_count))
 140                 l2tp_tunnel_free(tunnel);
 141 }
 142 #ifdef L2TP_REFCNT_DEBUG
 143 #define l2tp_tunnel_inc_refcount(_t)                                    \
 144 do {                                                                    \
 145         pr_debug("l2tp_tunnel_inc_refcount: %s:%d %s: cnt=%d\n",        \
 146                  __func__, __LINE__, (_t)->name,                        \
 147                  atomic_read(&_t->ref_count));                          \
 148         l2tp_tunnel_inc_refcount_1(_t);                                 \
 149 } while (0)
 150 #define l2tp_tunnel_dec_refcount(_t)
 151 do {                                                                    \
 152         pr_debug("l2tp_tunnel_dec_refcount: %s:%d %s: cnt=%d\n",        \
 153                  __func__, __LINE__, (_t)->name,                        \
 154                  atomic_read(&_t->ref_count));                          \
 155         l2tp_tunnel_dec_refcount_1(_t);                                 \
 156 } while (0)
 157 #else
 158 #define l2tp_tunnel_inc_refcount(t) l2tp_tunnel_inc_refcount_1(t)
 159 #define l2tp_tunnel_dec_refcount(t) l2tp_tunnel_dec_refcount_1(t)
 160 #endif
 161
 162 /* Session hash global list for L2TPv3.
 163  * The session_id SHOULD be random according to RFC3931, but several
 164  * L2TP implementations use incrementing session_ids.  So we do a real
 165  * hash on the session_id, rather than a simple bitmask.
 166  */
 167 static inline struct hlist_head *
 168 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 169 {
 170         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 171
 172 }
 173
 174 /* Lookup the tunnel socket, possibly involving the fs code if the socket is
 175  * owned by userspace.  A struct sock returned from this function must be
 176  * released using l2tp_tunnel_sock_put once you're done with it.
 177  */
 178 static struct sock *l2tp_tunnel_sock_lookup(struct l2tp_tunnel *tunnel)
 179 {
 180         int err = 0;
 181         struct socket *sock = NULL;
 182         struct sock *sk = NULL;
 183
 184         if (!tunnel)
 185                 goto out;
 186
 187         if (tunnel->fd >= 0) {
 188                 /* Socket is owned by userspace, who might be in the process
 189                  * of closing it.  Look the socket up using the fd to ensure
 190                  * consistency.
 191                  */
 192                 sock = sockfd_lookup(tunnel->fd, &err);
 193                 if (sock)
 194                         sk = sock->sk;
 195         } else {
 196                 /* Socket is owned by kernelspace */
 197                 sk = tunnel->sock;
 198                 sock_hold(sk);
 199         }
 200
 201 out:
 202         return sk;
 203 }
 204
 205 /* Drop a reference to a tunnel socket obtained via. l2tp_tunnel_sock_put */
 206 static void l2tp_tunnel_sock_put(struct sock *sk)
 207 {
 208         struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk);
 209         if (tunnel) {
 210                 if (tunnel->fd >= 0) {
 211                         /* Socket is owned by userspace */
 212                         sockfd_put(sk->sk_socket);
 213                 }
 214                 sock_put(sk);
 215         }
 216         sock_put(sk);
 217 }
 218
 219 /* Lookup a session by id in the global session list
 220  */
 221 static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id)
 222 {
 223         struct l2tp_net *pn = l2tp_pernet(net);
 224         struct hlist_head *session_list =
 225                 l2tp_session_id_hash_2(pn, session_id);
 226         struct l2tp_session *session;
 227
 228         rcu_read_lock_bh();
 229         hlist_for_each_entry_rcu(session, session_list, global_hlist) {
 230                 if (session->session_id == session_id) {
 231                         rcu_read_unlock_bh();
 232                         return session;
 233                 }
 234         }
 235         rcu_read_unlock_bh();
 236
 237         return NULL;
 238 }
 239
 240 /* Session hash list.
 241  * The session_id SHOULD be random according to RFC2661, but several
 242  * L2TP implementations (Cisco and Microsoft) use incrementing
 243  * session_ids.  So we do a real hash on the session_id, rather than a
 244  * simple bitmask.
 245  */
 246 static inline struct hlist_head *
 247 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 248 {
 249         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 250 }
 251
 252 /* Lookup a session by id
 253  */
 254 struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id)
 255 {
 256         struct hlist_head *session_list;
 257         struct l2tp_session *session;
 258
 259         /* In L2TPv3, session_ids are unique over all tunnels and we
 260          * sometimes need to look them up before we know the
 261          * tunnel.
 262          */
 263         if (tunnel == NULL)
 264                 return l2tp_session_find_2(net, session_id);
 265
 266         session_list = l2tp_session_id_hash(tunnel, session_id);
 267         read_lock_bh(&tunnel->hlist_lock);
 268         hlist_for_each_entry(session, session_list, hlist) {
 269                 if (session->session_id == session_id) {
 270                         read_unlock_bh(&tunnel->hlist_lock);
 271                         return session;
 272                 }
 273         }
 274         read_unlock_bh(&tunnel->hlist_lock);
 275
 276         return NULL;
 277 }
 278 EXPORT_SYMBOL_GPL(l2tp_session_find);
 279
 280 struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth)
 281 {
 282         int hash;
 283         struct l2tp_session *session;
 284         int count = 0;
 285
 286         read_lock_bh(&tunnel->hlist_lock);
 287         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 288                 hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
 289                         if (++count > nth) {
 290                                 read_unlock_bh(&tunnel->hlist_lock);
 291                                 return session;
 292                         }
 293                 }
 294         }
 295
 296         read_unlock_bh(&tunnel->hlist_lock);
 297
 298         return NULL;
 299 }
 300 EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
 301
 302 /* Lookup a session by interface name.
 303  * This is very inefficient but is only used by management interfaces.
 304  */
 305 struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
 306 {
 307         struct l2tp_net *pn = l2tp_pernet(net);
 308         int hash;
 309         struct l2tp_session *session;
 310
 311         rcu_read_lock_bh();
 312         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 313                 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
 314                         if (!strcmp(session->ifname, ifname)) {
 315                                 rcu_read_unlock_bh();
 316                                 return session;
 317                         }
 318                 }
 319         }
 320
 321         rcu_read_unlock_bh();
 322
 323         return NULL;
 324 }
 325 EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname);
 326
 327 /* Lookup a tunnel by id
 328  */
 329 struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
 330 {
 331         struct l2tp_tunnel *tunnel;
 332         struct l2tp_net *pn = l2tp_pernet(net);
 333
 334         rcu_read_lock_bh();
 335         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 336                 if (tunnel->tunnel_id == tunnel_id) {
 337                         rcu_read_unlock_bh();
 338                         return tunnel;
 339                 }
 340         }
 341         rcu_read_unlock_bh();
 342
 343         return NULL;
 344 }
 345 EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
 346
 347 struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
 348 {
 349         struct l2tp_net *pn = l2tp_pernet(net);
 350         struct l2tp_tunnel *tunnel;
 351         int count = 0;
 352
 353         rcu_read_lock_bh();
 354         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 355                 if (++count > nth) {
 356                         rcu_read_unlock_bh();
 357                         return tunnel;
 358                 }
 359         }
 360
 361         rcu_read_unlock_bh();
 362
 363         return NULL;
 364 }
 365 EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
 366
 367 /*****************************************************************************
 368  * Receive data handling
 369  *****************************************************************************/
 370
 371 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 372  * number.
 373  */
 374 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 375 {
 376         struct sk_buff *skbp;
 377         struct sk_buff *tmp;
 378         u32 ns = L2TP_SKB_CB(skb)->ns;
 379
 380         spin_lock_bh(&session->reorder_q.lock);
 381         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 382                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 383                         __skb_queue_before(&session->reorder_q, skbp, skb);
 384                         l2tp_dbg(session, L2TP_MSG_SEQ,
 385                                  "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 386                                  session->name, ns, L2TP_SKB_CB(skbp)->ns,
 387                                  skb_queue_len(&session->reorder_q));
 388                         atomic_long_inc(&session->stats.rx_oos_packets);
 389                         goto out;
 390                 }
 391         }
 392
 393         __skb_queue_tail(&session->reorder_q, skb);
 394
 395 out:
 396         spin_unlock_bh(&session->reorder_q.lock);
 397 }
 398
 399 /* Dequeue a single skb.
 400  */
 401 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 402 {
 403         struct l2tp_tunnel *tunnel = session->tunnel;
 404         int length = L2TP_SKB_CB(skb)->length;
 405
 406         /* We're about to requeue the skb, so return resources
 407          * to its current owner (a socket receive buffer).
 408          */
 409         skb_orphan(skb);
 410
 411         atomic_long_inc(&tunnel->stats.rx_packets);
 412         atomic_long_add(length, &tunnel->stats.rx_bytes);
 413         atomic_long_inc(&session->stats.rx_packets);
 414         atomic_long_add(length, &session->stats.rx_bytes);
 415
 416         if (L2TP_SKB_CB(skb)->has_seq) {
 417                 /* Bump our Nr */
 418                 session->nr++;
 419                 session->nr &= session->nr_max;
 420
 421                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated nr to %hu\n",
 422                          session->name, session->nr);
 423         }
 424
 425         /* call private receive handler */
 426         if (session->recv_skb != NULL)
 427                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 428         else
 429                 kfree_skb(skb);
 430
 431         if (session->deref)
 432                 (*session->deref)(session);
 433 }
 434
 435 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 436  * Skbs that have been in the queue for too long are simply discarded.
 437  */
 438 static void l2tp_recv_dequeue(struct l2tp_session *session)
 439 {
 440         struct sk_buff *skb;
 441         struct sk_buff *tmp;
 442
 443         /* If the pkt at the head of the queue has the nr that we
 444          * expect to send up next, dequeue it and any other
 445          * in-sequence packets behind it.
 446          */
 447 start:
 448         spin_lock_bh(&session->reorder_q.lock);
 449         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 450                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 451                         atomic_long_inc(&session->stats.rx_seq_discards);
 452                         atomic_long_inc(&session->stats.rx_errors);
 453                         l2tp_dbg(session, L2TP_MSG_SEQ,
 454                                  "%s: oos pkt %u len %d discarded (too old), waiting for %u, reorder_q_len=%d\n",
 455                                  session->name, L2TP_SKB_CB(skb)->ns,
 456                                  L2TP_SKB_CB(skb)->length, session->nr,
 457                                  skb_queue_len(&session->reorder_q));
 458                         session->reorder_skip = 1;
 459                         __skb_unlink(skb, &session->reorder_q);
 460                         kfree_skb(skb);
 461                         if (session->deref)
 462                                 (*session->deref)(session);
 463                         continue;
 464                 }
 465
 466                 if (L2TP_SKB_CB(skb)->has_seq) {
 467                         if (session->reorder_skip) {
 468                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 469                                          "%s: advancing nr to next pkt: %u -> %u",
 470                                          session->name, session->nr,
 471                                          L2TP_SKB_CB(skb)->ns);
 472                                 session->reorder_skip = 0;
 473                                 session->nr = L2TP_SKB_CB(skb)->ns;
 474                         }
 475                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 476                                 l2tp_dbg(session, L2TP_MSG_SEQ,
 477                                          "%s: holding oos pkt %u len %d, waiting for %u, reorder_q_len=%d\n",
 478                                          session->name, L2TP_SKB_CB(skb)->ns,
 479                                          L2TP_SKB_CB(skb)->length, session->nr,
 480                                          skb_queue_len(&session->reorder_q));
 481                                 goto out;
 482                         }
 483                 }
 484                 __skb_unlink(skb, &session->reorder_q);
 485
 486                 /* Process the skb. We release the queue lock while we
 487                  * do so to let other contexts process the queue.
 488                  */
 489                 spin_unlock_bh(&session->reorder_q.lock);
 490                 l2tp_recv_dequeue_skb(session, skb);
 491                 goto start;
 492         }
 493
 494 out:
 495         spin_unlock_bh(&session->reorder_q.lock);
 496 }
 497
 498 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 499                                            struct sk_buff *skb)
 500 {
 501         struct udphdr *uh = udp_hdr(skb);
 502         u16 ulen = ntohs(uh->len);
 503         __wsum psum;
 504
 505         if (sk->sk_no_check || skb_csum_unnecessary(skb))
 506                 return 0;
 507
 508 #if IS_ENABLED(CONFIG_IPV6)
 509         if (sk->sk_family == PF_INET6 && !l2tp_tunnel(sk)->v4mapped) {
 510                 if (!uh->check) {
 511                         LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
 512                         return 1;
 513                 }
 514                 if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 515                     !csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 516                                      &ipv6_hdr(skb)->daddr, ulen,
 517                                      IPPROTO_UDP, skb->csum)) {
 518                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 519                         return 0;
 520                 }
 521                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 522                                                          &ipv6_hdr(skb)->daddr,
 523                                                          skb->len, IPPROTO_UDP,
 524                                                          0));
 525         } else
 526 #endif
 527         {
 528                 struct inet_sock *inet;
 529                 if (!uh->check)
 530                         return 0;
 531                 inet = inet_sk(sk);
 532                 psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr,
 533                                           ulen, IPPROTO_UDP, 0);
 534
 535                 if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 536                     !csum_fold(csum_add(psum, skb->csum)))
 537                         return 0;
 538                 skb->csum = psum;
 539         }
 540
 541         return __skb_checksum_complete(skb);
 542 }
 543
 544 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
 545 {
 546         u32 nws;
 547
 548         if (nr >= session->nr)
 549                 nws = nr - session->nr;
 550         else
 551                 nws = (session->nr_max + 1) - (session->nr - nr);
 552
 553         return nws < session->nr_window_size;
 554 }
 555
 556 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if
 557  * acceptable, else non-zero.
 558  */
 559 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
 560 {
 561         if (!l2tp_seq_check_rx_window(session, L2TP_SKB_CB(skb)->ns)) {
 562                 /* Packet sequence number is outside allowed window.
 563                  * Discard it.
 564                  */
 565                 l2tp_dbg(session, L2TP_MSG_SEQ,
 566                          "%s: pkt %u len %d discarded, outside window, nr=%u\n",
 567                          session->name, L2TP_SKB_CB(skb)->ns,
 568                          L2TP_SKB_CB(skb)->length, session->nr);
 569                 goto discard;
 570         }
 571
 572         if (session->reorder_timeout != 0) {
 573                 /* Packet reordering enabled. Add skb to session's
 574                  * reorder queue, in order of ns.
 575                  */
 576                 l2tp_recv_queue_skb(session, skb);
 577                 goto out;
 578         }
 579
 580         /* Packet reordering disabled. Discard out-of-sequence packets, while
 581          * tracking the number if in-sequence packets after the first OOS packet
 582          * is seen. After nr_oos_count_max in-sequence packets, reset the
 583          * sequence number to re-enable packet reception.
 584          */
 585         if (L2TP_SKB_CB(skb)->ns == session->nr) {
 586                 skb_queue_tail(&session->reorder_q, skb);
 587         } else {
 588                 u32 nr_oos = L2TP_SKB_CB(skb)->ns;
 589                 u32 nr_next = (session->nr_oos + 1) & session->nr_max;
 590
 591                 if (nr_oos == nr_next)
 592                         session->nr_oos_count++;
 593                 else
 594                         session->nr_oos_count = 0;
 595
 596                 session->nr_oos = nr_oos;
 597                 if (session->nr_oos_count > session->nr_oos_count_max) {
 598                         session->reorder_skip = 1;
 599                         l2tp_dbg(session, L2TP_MSG_SEQ,
 600                                  "%s: %d oos packets received. Resetting sequence numbers\n",
 601                                  session->name, session->nr_oos_count);
 602                 }
 603                 if (!session->reorder_skip) {
 604                         atomic_long_inc(&session->stats.rx_seq_discards);
 605                         l2tp_dbg(session, L2TP_MSG_SEQ,
 606                                  "%s: oos pkt %u len %d discarded, waiting for %u, reorder_q_len=%d\n",
 607                                  session->name, L2TP_SKB_CB(skb)->ns,
 608                                  L2TP_SKB_CB(skb)->length, session->nr,
 609                                  skb_queue_len(&session->reorder_q));
 610                         goto discard;
 611                 }
 612                 skb_queue_tail(&session->reorder_q, skb);
 613         }
 614
 615 out:
 616         return 0;
 617
 618 discard:
 619         return 1;
 620 }
 621
 622 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 623  * and L2TPv3 data frames here.
 624  *
 625  * L2TPv2 Data Message Header
 626  *
 627  *  0                   1                   2                   3
 628  *  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
 629  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 630  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 631  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 632  * |           Tunnel ID           |           Session ID          |
 633  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 634  * |             Ns (opt)          |             Nr (opt)          |
 635  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 636  * |      Offset Size (opt)        |    Offset pad... (opt)
 637  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 638  *
 639  * Data frames are marked by T=0. All other fields are the same as
 640  * those in L2TP control frames.
 641  *
 642  * L2TPv3 Data Message Header
 643  *
 644  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 645  * |                      L2TP Session Header                      |
 646  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 647  * |                      L2-Specific Sublayer                     |
 648  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 649  * |                        Tunnel Payload                      ...
 650  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 651  *
 652  * L2TPv3 Session Header Over IP
 653  *
 654  *  0                   1                   2                   3
 655  *  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
 656  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 657  * |                           Session ID                          |
 658  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 659  * |               Cookie (optional, maximum 64 bits)...
 660  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 661  *                                                                 |
 662  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 663  *
 664  * L2TPv3 L2-Specific Sublayer Format
 665  *
 666  *  0                   1                   2                   3
 667  *  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
 668  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 669  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 670  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 671  *
 672  * Cookie value, sublayer format and offset (pad) are negotiated with
 673  * the peer when the session is set up. Unlike L2TPv2, we do not need
 674  * to parse the packet header to determine if optional fields are
 675  * present.
 676  *
 677  * Caller must already have parsed the frame and determined that it is
 678  * a data (not control) frame before coming here. Fields up to the
 679  * session-id have already been parsed and ptr points to the data
 680  * after the session-id.
 681  */
 682 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 683                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 684                       int length, int (*payload_hook)(struct sk_buff *skb))
 685 {
 686         struct l2tp_tunnel *tunnel = session->tunnel;
 687         int offset;
 688         u32 ns, nr;
 689
 690         /* The ref count is increased since we now hold a pointer to
 691          * the session. Take care to decrement the refcnt when exiting
 692          * this function from now on...
 693          */
 694         l2tp_session_inc_refcount(session);
 695         if (session->ref)
 696                 (*session->ref)(session);
 697
 698         /* Parse and check optional cookie */
 699         if (session->peer_cookie_len > 0) {
 700                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 701                         l2tp_info(tunnel, L2TP_MSG_DATA,
 702                                   "%s: cookie mismatch (%u/%u). Discarding.\n",
 703                                   tunnel->name, tunnel->tunnel_id,
 704                                   session->session_id);
 705                         atomic_long_inc(&session->stats.rx_cookie_discards);
 706                         goto discard;
 707                 }
 708                 ptr += session->peer_cookie_len;
 709         }
 710
 711         /* Handle the optional sequence numbers. Sequence numbers are
 712          * in different places for L2TPv2 and L2TPv3.
 713          *
 714          * If we are the LAC, enable/disable sequence numbers under
 715          * the control of the LNS.  If no sequence numbers present but
 716          * we were expecting them, discard frame.
 717          */
 718         ns = nr = 0;
 719         L2TP_SKB_CB(skb)->has_seq = 0;
 720         if (tunnel->version == L2TP_HDR_VER_2) {
 721                 if (hdrflags & L2TP_HDRFLAG_S) {
 722                         ns = ntohs(*(__be16 *) ptr);
 723                         ptr += 2;
 724                         nr = ntohs(*(__be16 *) ptr);
 725                         ptr += 2;
 726
 727                         /* Store L2TP info in the skb */
 728                         L2TP_SKB_CB(skb)->ns = ns;
 729                         L2TP_SKB_CB(skb)->has_seq = 1;
 730
 731                         l2tp_dbg(session, L2TP_MSG_SEQ,
 732                                  "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 733                                  session->name, ns, nr, session->nr);
 734                 }
 735         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 736                 u32 l2h = ntohl(*(__be32 *) ptr);
 737
 738                 if (l2h & 0x40000000) {
 739                         ns = l2h & 0x00ffffff;
 740
 741                         /* Store L2TP info in the skb */
 742                         L2TP_SKB_CB(skb)->ns = ns;
 743                         L2TP_SKB_CB(skb)->has_seq = 1;
 744
 745                         l2tp_dbg(session, L2TP_MSG_SEQ,
 746                                  "%s: recv data ns=%u, session nr=%u\n",
 747                                  session->name, ns, session->nr);
 748                 }
 749         }
 750
 751         /* Advance past L2-specific header, if present */
 752         ptr += session->l2specific_len;
 753
 754         if (L2TP_SKB_CB(skb)->has_seq) {
 755                 /* Received a packet with sequence numbers. If we're the LNS,
 756                  * check if we sre sending sequence numbers and if not,
 757                  * configure it so.
 758                  */
 759                 if ((!session->lns_mode) && (!session->send_seq)) {
 760                         l2tp_info(session, L2TP_MSG_SEQ,
 761                                   "%s: requested to enable seq numbers by LNS\n",
 762                                   session->name);
 763                         session->send_seq = -1;
 764                         l2tp_session_set_header_len(session, tunnel->version);
 765                 }
 766         } else {
 767                 /* No sequence numbers.
 768                  * If user has configured mandatory sequence numbers, discard.
 769                  */
 770                 if (session->recv_seq) {
 771                         l2tp_warn(session, L2TP_MSG_SEQ,
 772                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 773                                   session->name);
 774                         atomic_long_inc(&session->stats.rx_seq_discards);
 775                         goto discard;
 776                 }
 777
 778                 /* If we're the LAC and we're sending sequence numbers, the
 779                  * LNS has requested that we no longer send sequence numbers.
 780                  * If we're the LNS and we're sending sequence numbers, the
 781                  * LAC is broken. Discard the frame.
 782                  */
 783                 if ((!session->lns_mode) && (session->send_seq)) {
 784                         l2tp_info(session, L2TP_MSG_SEQ,
 785                                   "%s: requested to disable seq numbers by LNS\n",
 786                                   session->name);
 787                         session->send_seq = 0;
 788                         l2tp_session_set_header_len(session, tunnel->version);
 789                 } else if (session->send_seq) {
 790                         l2tp_warn(session, L2TP_MSG_SEQ,
 791                                   "%s: recv data has no seq numbers when required. Discarding.\n",
 792                                   session->name);
 793                         atomic_long_inc(&session->stats.rx_seq_discards);
 794                         goto discard;
 795                 }
 796         }
 797
 798         /* Session data offset is handled differently for L2TPv2 and
 799          * L2TPv3. For L2TPv2, there is an optional 16-bit value in
 800          * the header. For L2TPv3, the offset is negotiated using AVPs
 801          * in the session setup control protocol.
 802          */
 803         if (tunnel->version == L2TP_HDR_VER_2) {
 804                 /* If offset bit set, skip it. */
 805                 if (hdrflags & L2TP_HDRFLAG_O) {
 806                         offset = ntohs(*(__be16 *)ptr);
 807                         ptr += 2 + offset;
 808                 }
 809         } else
 810                 ptr += session->offset;
 811
 812         offset = ptr - optr;
 813         if (!pskb_may_pull(skb, offset))
 814                 goto discard;
 815
 816         __skb_pull(skb, offset);
 817
 818         /* If caller wants to process the payload before we queue the
 819          * packet, do so now.
 820          */
 821         if (payload_hook)
 822                 if ((*payload_hook)(skb))
 823                         goto discard;
 824
 825         /* Prepare skb for adding to the session's reorder_q.  Hold
 826          * packets for max reorder_timeout or 1 second if not
 827          * reordering.
 828          */
 829         L2TP_SKB_CB(skb)->length = length;
 830         L2TP_SKB_CB(skb)->expires = jiffies +
 831                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 832
 833         /* Add packet to the session's receive queue. Reordering is done here, if
 834          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 835          */
 836         if (L2TP_SKB_CB(skb)->has_seq) {
 837                 if (l2tp_recv_data_seq(session, skb))
 838                         goto discard;
 839         } else {
 840                 /* No sequence numbers. Add the skb to the tail of the
 841                  * reorder queue. This ensures that it will be
 842                  * delivered after all previous sequenced skbs.
 843                  */
 844                 skb_queue_tail(&session->reorder_q, skb);
 845         }
 846
 847         /* Try to dequeue as many skbs from reorder_q as we can. */
 848         l2tp_recv_dequeue(session);
 849
 850         l2tp_session_dec_refcount(session);
 851
 852         return;
 853
 854 discard:
 855         atomic_long_inc(&session->stats.rx_errors);
 856         kfree_skb(skb);
 857
 858         if (session->deref)
 859                 (*session->deref)(session);
 860
 861         l2tp_session_dec_refcount(session);
 862 }
 863 EXPORT_SYMBOL(l2tp_recv_common);
 864
 865 /* Drop skbs from the session's reorder_q
 866  */
 867 int l2tp_session_queue_purge(struct l2tp_session *session)
 868 {
 869         struct sk_buff *skb = NULL;
 870         BUG_ON(!session);
 871         BUG_ON(session->magic != L2TP_SESSION_MAGIC);
 872         while ((skb = skb_dequeue(&session->reorder_q))) {
 873                 atomic_long_inc(&session->stats.rx_errors);
 874                 kfree_skb(skb);
 875                 if (session->deref)
 876                         (*session->deref)(session);
 877         }
 878         return 0;
 879 }
 880 EXPORT_SYMBOL_GPL(l2tp_session_queue_purge);
 881
 882 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 883  * here. The skb is not on a list when we get here.
 884  * Returns 0 if the packet was a data packet and was successfully passed on.
 885  * Returns 1 if the packet was not a good data packet and could not be
 886  * forwarded.  All such packets are passed up to userspace to deal with.
 887  */
 888 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 889                               int (*payload_hook)(struct sk_buff *skb))
 890 {
 891         struct l2tp_session *session = NULL;
 892         unsigned char *ptr, *optr;
 893         u16 hdrflags;
 894         u32 tunnel_id, session_id;
 895         u16 version;
 896         int length;
 897
 898         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
 899                 goto discard_bad_csum;
 900
 901         /* UDP always verifies the packet length. */
 902         __skb_pull(skb, sizeof(struct udphdr));
 903
 904         /* Short packet? */
 905         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
 906                 l2tp_info(tunnel, L2TP_MSG_DATA,
 907                           "%s: recv short packet (len=%d)\n",
 908                           tunnel->name, skb->len);
 909                 goto error;
 910         }
 911
 912         /* Trace packet contents, if enabled */
 913         if (tunnel->debug & L2TP_MSG_DATA) {
 914                 length = min(32u, skb->len);
 915                 if (!pskb_may_pull(skb, length))
 916                         goto error;
 917
 918                 pr_debug("%s: recv\n", tunnel->name);
 919                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 920         }
 921
 922         /* Point to L2TP header */
 923         optr = ptr = skb->data;
 924
 925         /* Get L2TP header flags */
 926         hdrflags = ntohs(*(__be16 *) ptr);
 927
 928         /* Check protocol version */
 929         version = hdrflags & L2TP_HDR_VER_MASK;
 930         if (version != tunnel->version) {
 931                 l2tp_info(tunnel, L2TP_MSG_DATA,
 932                           "%s: recv protocol version mismatch: got %d expected %d\n",
 933                           tunnel->name, version, tunnel->version);
 934                 goto error;
 935         }
 936
 937         /* Get length of L2TP packet */
 938         length = skb->len;
 939
 940         /* If type is control packet, it is handled by userspace. */
 941         if (hdrflags & L2TP_HDRFLAG_T) {
 942                 l2tp_dbg(tunnel, L2TP_MSG_DATA,
 943                          "%s: recv control packet, len=%d\n",
 944                          tunnel->name, length);
 945                 goto error;
 946         }
 947
 948         /* Skip flags */
 949         ptr += 2;
 950
 951         if (tunnel->version == L2TP_HDR_VER_2) {
 952                 /* If length is present, skip it */
 953                 if (hdrflags & L2TP_HDRFLAG_L)
 954                         ptr += 2;
 955
 956                 /* Extract tunnel and session ID */
 957                 tunnel_id = ntohs(*(__be16 *) ptr);
 958                 ptr += 2;
 959                 session_id = ntohs(*(__be16 *) ptr);
 960                 ptr += 2;
 961         } else {
 962                 ptr += 2;       /* skip reserved bits */
 963                 tunnel_id = tunnel->tunnel_id;
 964                 session_id = ntohl(*(__be32 *) ptr);
 965                 ptr += 4;
 966         }
 967
 968         /* Find the session context */
 969         session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
 970         if (!session || !session->recv_skb) {
 971                 /* Not found? Pass to userspace to deal with */
 972                 l2tp_info(tunnel, L2TP_MSG_DATA,
 973                           "%s: no session found (%u/%u). Passing up.\n",
 974                           tunnel->name, tunnel_id, session_id);
 975                 goto error;
 976         }
 977
 978         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
 979
 980         return 0;
 981
 982 discard_bad_csum:
 983         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
 984         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
 985         atomic_long_inc(&tunnel->stats.rx_errors);
 986         kfree_skb(skb);
 987
 988         return 0;
 989
 990 error:
 991         /* Put UDP header back */
 992         __skb_push(skb, sizeof(struct udphdr));
 993
 994         return 1;
 995 }
 996
 997 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 998  * Return codes:
 999  * 0 : success.
1000  * <0: error
1001  * >0: skb should be passed up to userspace as UDP.
1002  */
1003 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
1004 {
1005         struct l2tp_tunnel *tunnel;
1006
1007         tunnel = l2tp_sock_to_tunnel(sk);
1008         if (tunnel == NULL)
1009                 goto pass_up;
1010
1011         l2tp_dbg(tunnel, L2TP_MSG_DATA, "%s: received %d bytes\n",
1012                  tunnel->name, skb->len);
1013
1014         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
1015                 goto pass_up_put;
1016
1017         sock_put(sk);
1018         return 0;
1019
1020 pass_up_put:
1021         sock_put(sk);
1022 pass_up:
1023         return 1;
1024 }
1025 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
1026
1027 /************************************************************************
1028  * Transmit handling
1029  ***********************************************************************/
1030
1031 /* Build an L2TP header for the session into the buffer provided.
1032  */
1033 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
1034 {
1035         struct l2tp_tunnel *tunnel = session->tunnel;
1036         __be16 *bufp = buf;
1037         __be16 *optr = buf;
1038         u16 flags = L2TP_HDR_VER_2;
1039         u32 tunnel_id = tunnel->peer_tunnel_id;
1040         u32 session_id = session->peer_session_id;
1041
1042         if (session->send_seq)
1043                 flags |= L2TP_HDRFLAG_S;
1044
1045         /* Setup L2TP header. */
1046         *bufp++ = htons(flags);
1047         *bufp++ = htons(tunnel_id);
1048         *bufp++ = htons(session_id);
1049         if (session->send_seq) {
1050                 *bufp++ = htons(session->ns);
1051                 *bufp++ = 0;
1052                 session->ns++;
1053                 session->ns &= 0xffff;
1054                 l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated ns to %u\n",
1055                          session->name, session->ns);
1056         }
1057
1058         return bufp - optr;
1059 }
1060
1061 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
1062 {
1063         struct l2tp_tunnel *tunnel = session->tunnel;
1064         char *bufp = buf;
1065         char *optr = bufp;
1066
1067         /* Setup L2TP header. The header differs slightly for UDP and
1068          * IP encapsulations. For UDP, there is 4 bytes of flags.
1069          */
1070         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
1071                 u16 flags = L2TP_HDR_VER_3;
1072                 *((__be16 *) bufp) = htons(flags);
1073                 bufp += 2;
1074                 *((__be16 *) bufp) = 0;
1075                 bufp += 2;
1076         }
1077
1078         *((__be32 *) bufp) = htonl(session->peer_session_id);
1079         bufp += 4;
1080         if (session->cookie_len) {
1081                 memcpy(bufp, &session->cookie[0], session->cookie_len);
1082                 bufp += session->cookie_len;
1083         }
1084         if (session->l2specific_len) {
1085                 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
1086                         u32 l2h = 0;
1087                         if (session->send_seq) {
1088                                 l2h = 0x40000000 | session->ns;
1089                                 session->ns++;
1090                                 session->ns &= 0xffffff;
1091                                 l2tp_dbg(session, L2TP_MSG_SEQ,
1092                                          "%s: updated ns to %u\n",
1093                                          session->name, session->ns);
1094                         }
1095
1096                         *((__be32 *) bufp) = htonl(l2h);
1097                 }
1098                 bufp += session->l2specific_len;
1099         }
1100         if (session->offset)
1101                 bufp += session->offset;
1102
1103         return bufp - optr;
1104 }
1105
1106 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
1107                           struct flowi *fl, size_t data_len)
1108 {
1109         struct l2tp_tunnel *tunnel = session->tunnel;
1110         unsigned int len = skb->len;
1111         int error;
1112
1113         /* Debug */
1114         if (session->send_seq)
1115                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %Zd bytes, ns=%u\n",
1116                          session->name, data_len, session->ns - 1);
1117         else
1118                 l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %Zd bytes\n",
1119                          session->name, data_len);
1120
1121         if (session->debug & L2TP_MSG_DATA) {
1122                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1123                 unsigned char *datap = skb->data + uhlen;
1124
1125                 pr_debug("%s: xmit\n", session->name);
1126                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET,
1127                                      datap, min_t(size_t, 32, len - uhlen));
1128         }
1129
1130         /* Queue the packet to IP for output */
1131         skb->local_df = 1;
1132 #if IS_ENABLED(CONFIG_IPV6)
1133         if (skb->sk->sk_family == PF_INET6 && !tunnel->v4mapped)
1134                 error = inet6_csk_xmit(skb, NULL);
1135         else
1136 #endif
1137                 error = ip_queue_xmit(skb, fl);
1138
1139         /* Update stats */
1140         if (error >= 0) {
1141                 atomic_long_inc(&tunnel->stats.tx_packets);
1142                 atomic_long_add(len, &tunnel->stats.tx_bytes);
1143                 atomic_long_inc(&session->stats.tx_packets);
1144                 atomic_long_add(len, &session->stats.tx_bytes);
1145         } else {
1146                 atomic_long_inc(&tunnel->stats.tx_errors);
1147                 atomic_long_inc(&session->stats.tx_errors);
1148         }
1149
1150         return 0;
1151 }
1152
1153 /* Automatically called when the skb is freed.
1154  */
1155 static void l2tp_sock_wfree(struct sk_buff *skb)
1156 {
1157         sock_put(skb->sk);
1158 }
1159
1160 /* For data skbs that we transmit, we associate with the tunnel socket
1161  * but don't do accounting.
1162  */
1163 static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
1164 {
1165         sock_hold(sk);
1166         skb->sk = sk;
1167         skb->destructor = l2tp_sock_wfree;
1168 }
1169
1170 #if IS_ENABLED(CONFIG_IPV6)
1171 static void l2tp_xmit_ipv6_csum(struct sock *sk, struct sk_buff *skb,
1172                                 int udp_len)
1173 {
1174         struct ipv6_pinfo *np = inet6_sk(sk);
1175         struct udphdr *uh = udp_hdr(skb);
1176
1177         if (!skb_dst(skb) || !skb_dst(skb)->dev ||
1178             !(skb_dst(skb)->dev->features & NETIF_F_IPV6_CSUM)) {
1179                 __wsum csum = skb_checksum(skb, 0, udp_len, 0);
1180                 skb->ip_summed = CHECKSUM_UNNECESSARY;
1181                 uh->check = csum_ipv6_magic(&np->saddr, &sk->sk_v6_daddr, udp_len,
1182                                             IPPROTO_UDP, csum);
1183                 if (uh->check == 0)
1184                         uh->check = CSUM_MANGLED_0;
1185         } else {
1186                 skb->ip_summed = CHECKSUM_PARTIAL;
1187                 skb->csum_start = skb_transport_header(skb) - skb->head;
1188                 skb->csum_offset = offsetof(struct udphdr, check);
1189                 uh->check = ~csum_ipv6_magic(&np->saddr, &sk->sk_v6_daddr,
1190                                              udp_len, IPPROTO_UDP, 0);
1191         }
1192 }
1193 #endif
1194
1195 /* If caller requires the skb to have a ppp header, the header must be
1196  * inserted in the skb data before calling this function.
1197  */
1198 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1199 {
1200         int data_len = skb->len;
1201         struct l2tp_tunnel *tunnel = session->tunnel;
1202         struct sock *sk = tunnel->sock;
1203         struct flowi *fl;
1204         struct udphdr *uh;
1205         struct inet_sock *inet;
1206         __wsum csum;
1207         int headroom;
1208         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1209         int udp_len;
1210         int ret = NET_XMIT_SUCCESS;
1211
1212         /* Check that there's enough headroom in the skb to insert IP,
1213          * UDP and L2TP headers. If not enough, expand it to
1214          * make room. Adjust truesize.
1215          */
1216         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1217                 uhlen + hdr_len;
1218         if (skb_cow_head(skb, headroom)) {
1219                 kfree_skb(skb);
1220                 return NET_XMIT_DROP;
1221         }
1222
1223         skb_orphan(skb);
1224         /* Setup L2TP header */
1225         session->build_header(session, __skb_push(skb, hdr_len));
1226
1227         /* Reset skb netfilter state */
1228         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1229         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1230                               IPSKB_REROUTED);
1231         nf_reset(skb);
1232
1233         bh_lock_sock(sk);
1234         if (sock_owned_by_user(sk)) {
1235                 kfree_skb(skb);
1236                 ret = NET_XMIT_DROP;
1237                 goto out_unlock;
1238         }
1239
1240         /* Get routing info from the tunnel socket */
1241         skb_dst_drop(skb);
1242         skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
1243
1244         inet = inet_sk(sk);
1245         fl = &inet->cork.fl;
1246         switch (tunnel->encap) {
1247         case L2TP_ENCAPTYPE_UDP:
1248                 /* Setup UDP header */
1249                 __skb_push(skb, sizeof(*uh));
1250                 skb_reset_transport_header(skb);
1251                 uh = udp_hdr(skb);
1252                 uh->source = inet->inet_sport;
1253                 uh->dest = inet->inet_dport;
1254                 udp_len = uhlen + hdr_len + data_len;
1255                 uh->len = htons(udp_len);
1256                 uh->check = 0;
1257
1258                 /* Calculate UDP checksum if configured to do so */
1259 #if IS_ENABLED(CONFIG_IPV6)
1260                 if (sk->sk_family == PF_INET6 && !tunnel->v4mapped)
1261                         l2tp_xmit_ipv6_csum(sk, skb, udp_len);
1262                 else
1263 #endif
1264                 if (sk->sk_no_check == UDP_CSUM_NOXMIT)
1265                         skb->ip_summed = CHECKSUM_NONE;
1266                 else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
1267                          (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
1268                         skb->ip_summed = CHECKSUM_COMPLETE;
1269                         csum = skb_checksum(skb, 0, udp_len, 0);
1270                         uh->check = csum_tcpudp_magic(inet->inet_saddr,
1271                                                       inet->inet_daddr,
1272                                                       udp_len, IPPROTO_UDP, csum);
1273                         if (uh->check == 0)
1274                                 uh->check = CSUM_MANGLED_0;
1275                 } else {
1276                         skb->ip_summed = CHECKSUM_PARTIAL;
1277                         skb->csum_start = skb_transport_header(skb) - skb->head;
1278                         skb->csum_offset = offsetof(struct udphdr, check);
1279                         uh->check = ~csum_tcpudp_magic(inet->inet_saddr,
1280                                                        inet->inet_daddr,
1281                                                        udp_len, IPPROTO_UDP, 0);
1282                 }
1283                 break;
1284
1285         case L2TP_ENCAPTYPE_IP:
1286                 break;
1287         }
1288
1289         l2tp_skb_set_owner_w(skb, sk);
1290
1291         l2tp_xmit_core(session, skb, fl, data_len);
1292 out_unlock:
1293         bh_unlock_sock(sk);
1294
1295         return ret;
1296 }
1297 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1298
1299 /*****************************************************************************
1300  * Tinnel and session create/destroy.
1301  *****************************************************************************/
1302
1303 /* Tunnel socket destruct hook.
1304  * The tunnel context is deleted only when all session sockets have been
1305  * closed.
1306  */
1307 static void l2tp_tunnel_destruct(struct sock *sk)
1308 {
1309         struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
1310         struct l2tp_net *pn;
1311
1312         if (tunnel == NULL)
1313                 goto end;
1314
1315         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing...\n", tunnel->name);
1316
1317
1318         /* Disable udp encapsulation */
1319         switch (tunnel->encap) {
1320         case L2TP_ENCAPTYPE_UDP:
1321                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1322                 (udp_sk(sk))->encap_type = 0;
1323                 (udp_sk(sk))->encap_rcv = NULL;
1324                 (udp_sk(sk))->encap_destroy = NULL;
1325                 break;
1326         case L2TP_ENCAPTYPE_IP:
1327                 break;
1328         }
1329
1330         /* Remove hooks into tunnel socket */
1331         sk->sk_destruct = tunnel->old_sk_destruct;
1332         sk->sk_user_data = NULL;
1333         tunnel->sock = NULL;
1334
1335         /* Remove the tunnel struct from the tunnel list */
1336         pn = l2tp_pernet(tunnel->l2tp_net);
1337         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1338         list_del_rcu(&tunnel->list);
1339         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1340         atomic_dec(&l2tp_tunnel_count);
1341
1342         l2tp_tunnel_closeall(tunnel);
1343         l2tp_tunnel_dec_refcount(tunnel);
1344
1345         /* Call the original destructor */
1346         if (sk->sk_destruct)
1347                 (*sk->sk_destruct)(sk);
1348 end:
1349         return;
1350 }
1351
1352 /* When the tunnel is closed, all the attached sessions need to go too.
1353  */
1354 void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1355 {
1356         int hash;
1357         struct hlist_node *walk;
1358         struct hlist_node *tmp;
1359         struct l2tp_session *session;
1360
1361         BUG_ON(tunnel == NULL);
1362
1363         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing all sessions...\n",
1364                   tunnel->name);
1365
1366         write_lock_bh(&tunnel->hlist_lock);
1367         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1368 again:
1369                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1370                         session = hlist_entry(walk, struct l2tp_session, hlist);
1371
1372                         l2tp_info(session, L2TP_MSG_CONTROL,
1373                                   "%s: closing session\n", session->name);
1374
1375                         hlist_del_init(&session->hlist);
1376
1377                         if (session->ref != NULL)
1378                                 (*session->ref)(session);
1379
1380                         write_unlock_bh(&tunnel->hlist_lock);
1381
1382                         __l2tp_session_unhash(session);
1383                         l2tp_session_queue_purge(session);
1384
1385                         if (session->session_close != NULL)
1386                                 (*session->session_close)(session);
1387
1388                         if (session->deref != NULL)
1389                                 (*session->deref)(session);
1390
1391                         l2tp_session_dec_refcount(session);
1392
1393                         write_lock_bh(&tunnel->hlist_lock);
1394
1395                         /* Now restart from the beginning of this hash
1396                          * chain.  We always remove a session from the
1397                          * list so we are guaranteed to make forward
1398                          * progress.
1399                          */
1400                         goto again;
1401                 }
1402         }
1403         write_unlock_bh(&tunnel->hlist_lock);
1404 }
1405 EXPORT_SYMBOL_GPL(l2tp_tunnel_closeall);
1406
1407 /* Tunnel socket destroy hook for UDP encapsulation */
1408 static void l2tp_udp_encap_destroy(struct sock *sk)
1409 {
1410         struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk);
1411         if (tunnel) {
1412                 l2tp_tunnel_closeall(tunnel);
1413                 sock_put(sk);
1414         }
1415 }
1416
1417 /* Really kill the tunnel.
1418  * Come here only when all sessions have been cleared from the tunnel.
1419  */
1420 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
1421 {
1422         BUG_ON(atomic_read(&tunnel->ref_count) != 0);
1423         BUG_ON(tunnel->sock != NULL);
1424         l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: free...\n", tunnel->name);
1425         kfree_rcu(tunnel, rcu);
1426 }
1427
1428 /* Workqueue tunnel deletion function */
1429 static void l2tp_tunnel_del_work(struct work_struct *work)
1430 {
1431         struct l2tp_tunnel *tunnel = NULL;
1432         struct socket *sock = NULL;
1433         struct sock *sk = NULL;
1434
1435         tunnel = container_of(work, struct l2tp_tunnel, del_work);
1436         sk = l2tp_tunnel_sock_lookup(tunnel);
1437         if (!sk)
1438                 return;
1439
1440         sock = sk->sk_socket;
1441
1442         /* If the tunnel socket was created by userspace, then go through the
1443          * inet layer to shut the socket down, and let userspace close it.
1444          * Otherwise, if we created the socket directly within the kernel, use
1445          * the sk API to release it here.
1446          * In either case the tunnel resources are freed in the socket
1447          * destructor when the tunnel socket goes away.
1448          */
1449         if (tunnel->fd >= 0) {
1450                 if (sock)
1451                         inet_shutdown(sock, 2);
1452         } else {
1453                 if (sock)
1454                         kernel_sock_shutdown(sock, SHUT_RDWR);
1455                 sk_release_kernel(sk);
1456         }
1457
1458         l2tp_tunnel_sock_put(sk);
1459 }
1460
1461 /* Create a socket for the tunnel, if one isn't set up by
1462  * userspace. This is used for static tunnels where there is no
1463  * managing L2TP daemon.
1464  *
1465  * Since we don't want these sockets to keep a namespace alive by
1466  * themselves, we drop the socket's namespace refcount after creation.
1467  * These sockets are freed when the namespace exits using the pernet
1468  * exit hook.
1469  */
1470 static int l2tp_tunnel_sock_create(struct net *net,
1471                                 u32 tunnel_id,
1472                                 u32 peer_tunnel_id,
1473                                 struct l2tp_tunnel_cfg *cfg,
1474                                 struct socket **sockp)
1475 {
1476         int err = -EINVAL;
1477         struct socket *sock = NULL;
1478         struct sockaddr_in udp_addr = {0};
1479         struct sockaddr_l2tpip ip_addr = {0};
1480 #if IS_ENABLED(CONFIG_IPV6)
1481         struct sockaddr_in6 udp6_addr = {0};
1482         struct sockaddr_l2tpip6 ip6_addr = {0};
1483 #endif
1484
1485         switch (cfg->encap) {
1486         case L2TP_ENCAPTYPE_UDP:
1487 #if IS_ENABLED(CONFIG_IPV6)
1488                 if (cfg->local_ip6 && cfg->peer_ip6) {
1489                         err = sock_create_kern(AF_INET6, SOCK_DGRAM, 0, &sock);
1490                         if (err < 0)
1491                                 goto out;
1492
1493                         sk_change_net(sock->sk, net);
1494
1495                         udp6_addr.sin6_family = AF_INET6;
1496                         memcpy(&udp6_addr.sin6_addr, cfg->local_ip6,
1497                                sizeof(udp6_addr.sin6_addr));
1498                         udp6_addr.sin6_port = htons(cfg->local_udp_port);
1499                         err = kernel_bind(sock, (struct sockaddr *) &udp6_addr,
1500                                           sizeof(udp6_addr));
1501                         if (err < 0)
1502                                 goto out;
1503
1504                         udp6_addr.sin6_family = AF_INET6;
1505                         memcpy(&udp6_addr.sin6_addr, cfg->peer_ip6,
1506                                sizeof(udp6_addr.sin6_addr));
1507                         udp6_addr.sin6_port = htons(cfg->peer_udp_port);
1508                         err = kernel_connect(sock,
1509                                              (struct sockaddr *) &udp6_addr,
1510                                              sizeof(udp6_addr), 0);
1511                         if (err < 0)
1512                                 goto out;
1513                 } else
1514 #endif
1515                 {
1516                         err = sock_create_kern(AF_INET, SOCK_DGRAM, 0, &sock);
1517                         if (err < 0)
1518                                 goto out;
1519
1520                         sk_change_net(sock->sk, net);
1521
1522                         udp_addr.sin_family = AF_INET;
1523                         udp_addr.sin_addr = cfg->local_ip;
1524                         udp_addr.sin_port = htons(cfg->local_udp_port);
1525                         err = kernel_bind(sock, (struct sockaddr *) &udp_addr,
1526                                           sizeof(udp_addr));
1527                         if (err < 0)
1528                                 goto out;
1529
1530                         udp_addr.sin_family = AF_INET;
1531                         udp_addr.sin_addr = cfg->peer_ip;
1532                         udp_addr.sin_port = htons(cfg->peer_udp_port);
1533                         err = kernel_connect(sock,
1534                                              (struct sockaddr *) &udp_addr,
1535                                              sizeof(udp_addr), 0);
1536                         if (err < 0)
1537                                 goto out;
1538                 }
1539
1540                 if (!cfg->use_udp_checksums)
1541                         sock->sk->sk_no_check = UDP_CSUM_NOXMIT;
1542
1543                 break;
1544
1545         case L2TP_ENCAPTYPE_IP:
1546 #if IS_ENABLED(CONFIG_IPV6)
1547                 if (cfg->local_ip6 && cfg->peer_ip6) {
1548                         err = sock_create_kern(AF_INET6, SOCK_DGRAM,
1549                                           IPPROTO_L2TP, &sock);
1550                         if (err < 0)
1551                                 goto out;
1552
1553                         sk_change_net(sock->sk, net);
1554
1555                         ip6_addr.l2tp_family = AF_INET6;
1556                         memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
1557                                sizeof(ip6_addr.l2tp_addr));
1558                         ip6_addr.l2tp_conn_id = tunnel_id;
1559                         err = kernel_bind(sock, (struct sockaddr *) &ip6_addr,
1560                                           sizeof(ip6_addr));
1561                         if (err < 0)
1562                                 goto out;
1563
1564                         ip6_addr.l2tp_family = AF_INET6;
1565                         memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
1566                                sizeof(ip6_addr.l2tp_addr));
1567                         ip6_addr.l2tp_conn_id = peer_tunnel_id;
1568                         err = kernel_connect(sock,
1569                                              (struct sockaddr *) &ip6_addr,
1570                                              sizeof(ip6_addr), 0);
1571                         if (err < 0)
1572                                 goto out;
1573                 } else
1574 #endif
1575                 {
1576                         err = sock_create_kern(AF_INET, SOCK_DGRAM,
1577                                           IPPROTO_L2TP, &sock);
1578                         if (err < 0)
1579                                 goto out;
1580
1581                         sk_change_net(sock->sk, net);
1582
1583                         ip_addr.l2tp_family = AF_INET;
1584                         ip_addr.l2tp_addr = cfg->local_ip;
1585                         ip_addr.l2tp_conn_id = tunnel_id;
1586                         err = kernel_bind(sock, (struct sockaddr *) &ip_addr,
1587                                           sizeof(ip_addr));
1588                         if (err < 0)
1589                                 goto out;
1590
1591                         ip_addr.l2tp_family = AF_INET;
1592                         ip_addr.l2tp_addr = cfg->peer_ip;
1593                         ip_addr.l2tp_conn_id = peer_tunnel_id;
1594                         err = kernel_connect(sock, (struct sockaddr *) &ip_addr,
1595                                              sizeof(ip_addr), 0);
1596                         if (err < 0)
1597                                 goto out;
1598                 }
1599                 break;
1600
1601         default:
1602                 goto out;
1603         }
1604
1605 out:
1606         *sockp = sock;
1607         if ((err < 0) && sock) {
1608                 kernel_sock_shutdown(sock, SHUT_RDWR);
1609                 sk_release_kernel(sock->sk);
1610                 *sockp = NULL;
1611         }
1612
1613         return err;
1614 }
1615
1616 static struct lock_class_key l2tp_socket_class;
1617
1618 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)
1619 {
1620         struct l2tp_tunnel *tunnel = NULL;
1621         int err;
1622         struct socket *sock = NULL;
1623         struct sock *sk = NULL;
1624         struct l2tp_net *pn;
1625         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1626
1627         /* Get the tunnel socket from the fd, which was opened by
1628          * the userspace L2TP daemon. If not specified, create a
1629          * kernel socket.
1630          */
1631         if (fd < 0) {
1632                 err = l2tp_tunnel_sock_create(net, tunnel_id, peer_tunnel_id,
1633                                 cfg, &sock);
1634                 if (err < 0)
1635                         goto err;
1636         } else {
1637                 sock = sockfd_lookup(fd, &err);
1638                 if (!sock) {
1639                         pr_err("tunl %u: sockfd_lookup(fd=%d) returned %d\n",
1640                                tunnel_id, fd, err);
1641                         err = -EBADF;
1642                         goto err;
1643                 }
1644
1645                 /* Reject namespace mismatches */
1646                 if (!net_eq(sock_net(sock->sk), net)) {
1647                         pr_err("tunl %u: netns mismatch\n", tunnel_id);
1648                         err = -EINVAL;
1649                         goto err;
1650                 }
1651         }
1652
1653         sk = sock->sk;
1654
1655         if (cfg != NULL)
1656                 encap = cfg->encap;
1657
1658         /* Quick sanity checks */
1659         switch (encap) {
1660         case L2TP_ENCAPTYPE_UDP:
1661                 err = -EPROTONOSUPPORT;
1662                 if (sk->sk_protocol != IPPROTO_UDP) {
1663                         pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1664                                tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
1665                         goto err;
1666                 }
1667                 break;
1668         case L2TP_ENCAPTYPE_IP:
1669                 err = -EPROTONOSUPPORT;
1670                 if (sk->sk_protocol != IPPROTO_L2TP) {
1671                         pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1672                                tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
1673                         goto err;
1674                 }
1675                 break;
1676         }
1677
1678         /* Check if this socket has already been prepped */
1679         tunnel = l2tp_tunnel(sk);
1680         if (tunnel != NULL) {
1681                 /* This socket has already been prepped */
1682                 err = -EBUSY;
1683                 goto err;
1684         }
1685
1686         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1687         if (tunnel == NULL) {
1688                 err = -ENOMEM;
1689                 goto err;
1690         }
1691
1692         tunnel->version = version;
1693         tunnel->tunnel_id = tunnel_id;
1694         tunnel->peer_tunnel_id = peer_tunnel_id;
1695         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1696
1697         tunnel->magic = L2TP_TUNNEL_MAGIC;
1698         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1699         rwlock_init(&tunnel->hlist_lock);
1700
1701         /* The net we belong to */
1702         tunnel->l2tp_net = net;
1703         pn = l2tp_pernet(net);
1704
1705         if (cfg != NULL)
1706                 tunnel->debug = cfg->debug;
1707
1708 #if IS_ENABLED(CONFIG_IPV6)
1709         if (sk->sk_family == PF_INET6) {
1710                 struct ipv6_pinfo *np = inet6_sk(sk);
1711
1712                 if (ipv6_addr_v4mapped(&np->saddr) &&
1713                     ipv6_addr_v4mapped(&sk->sk_v6_daddr)) {
1714                         struct inet_sock *inet = inet_sk(sk);
1715
1716                         tunnel->v4mapped = true;
1717                         inet->inet_saddr = np->saddr.s6_addr32[3];
1718                         inet->inet_rcv_saddr = sk->sk_v6_rcv_saddr.s6_addr32[3];
1719                         inet->inet_daddr = sk->sk_v6_daddr.s6_addr32[3];
1720                 } else {
1721                         tunnel->v4mapped = false;
1722                 }
1723         }
1724 #endif
1725
1726         /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1727         tunnel->encap = encap;
1728         if (encap == L2TP_ENCAPTYPE_UDP) {
1729                 /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1730                 udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
1731                 udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
1732                 udp_sk(sk)->encap_destroy = l2tp_udp_encap_destroy;
1733 #if IS_ENABLED(CONFIG_IPV6)
1734                 if (sk->sk_family == PF_INET6 && !tunnel->v4mapped)
1735                         udpv6_encap_enable();
1736                 else
1737 #endif
1738                 udp_encap_enable();
1739         }
1740
1741         sk->sk_user_data = tunnel;
1742
1743         /* Hook on the tunnel socket destructor so that we can cleanup
1744          * if the tunnel socket goes away.
1745          */
1746         tunnel->old_sk_destruct = sk->sk_destruct;
1747         sk->sk_destruct = &l2tp_tunnel_destruct;
1748         tunnel->sock = sk;
1749         tunnel->fd = fd;
1750         lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class, "l2tp_sock");
1751
1752         sk->sk_allocation = GFP_ATOMIC;
1753
1754         /* Init delete workqueue struct */
1755         INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
1756
1757         /* Add tunnel to our list */
1758         INIT_LIST_HEAD(&tunnel->list);
1759         atomic_inc(&l2tp_tunnel_count);
1760
1761         /* Bump the reference count. The tunnel context is deleted
1762          * only when this drops to zero. Must be done before list insertion
1763          */
1764         l2tp_tunnel_inc_refcount(tunnel);
1765         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1766         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1767         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1768
1769         err = 0;
1770 err:
1771         if (tunnelp)
1772                 *tunnelp = tunnel;
1773
1774         /* If tunnel's socket was created by the kernel, it doesn't
1775          *  have a file.
1776          */
1777         if (sock && sock->file)
1778                 sockfd_put(sock);
1779
1780         return err;
1781 }
1782 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1783
1784 /* This function is used by the netlink TUNNEL_DELETE command.
1785  */
1786 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1787 {
1788         l2tp_tunnel_closeall(tunnel);
1789         return (false == queue_work(l2tp_wq, &tunnel->del_work));
1790 }
1791 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1792
1793 /* Really kill the session.
1794  */
1795 void l2tp_session_free(struct l2tp_session *session)
1796 {
1797         struct l2tp_tunnel *tunnel = session->tunnel;
1798
1799         BUG_ON(atomic_read(&session->ref_count) != 0);
1800
1801         if (tunnel) {
1802                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1803                 if (session->session_id != 0)
1804                         atomic_dec(&l2tp_session_count);
1805                 sock_put(tunnel->sock);
1806                 session->tunnel = NULL;
1807                 l2tp_tunnel_dec_refcount(tunnel);
1808         }
1809
1810         kfree(session);
1811
1812         return;
1813 }
1814 EXPORT_SYMBOL_GPL(l2tp_session_free);
1815
1816 /* Remove an l2tp session from l2tp_core's hash lists.
1817  * Provides a tidyup interface for pseudowire code which can't just route all
1818  * shutdown via. l2tp_session_delete and a pseudowire-specific session_close
1819  * callback.
1820  */
1821 void __l2tp_session_unhash(struct l2tp_session *session)
1822 {
1823         struct l2tp_tunnel *tunnel = session->tunnel;
1824
1825         /* Remove the session from core hashes */
1826         if (tunnel) {
1827                 /* Remove from the per-tunnel hash */
1828                 write_lock_bh(&tunnel->hlist_lock);
1829                 hlist_del_init(&session->hlist);
1830                 write_unlock_bh(&tunnel->hlist_lock);
1831
1832                 /* For L2TPv3 we have a per-net hash: remove from there, too */
1833                 if (tunnel->version != L2TP_HDR_VER_2) {
1834                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1835                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1836                         hlist_del_init_rcu(&session->global_hlist);
1837                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1838                         synchronize_rcu();
1839                 }
1840         }
1841 }
1842 EXPORT_SYMBOL_GPL(__l2tp_session_unhash);
1843
1844 /* This function is used by the netlink SESSION_DELETE command and by
1845    pseudowire modules.
1846  */
1847 int l2tp_session_delete(struct l2tp_session *session)
1848 {
1849         if (session->ref)
1850                 (*session->ref)(session);
1851         __l2tp_session_unhash(session);
1852         l2tp_session_queue_purge(session);
1853         if (session->session_close != NULL)
1854                 (*session->session_close)(session);
1855         if (session->deref)
1856                 (*session->deref)(session);
1857         l2tp_session_dec_refcount(session);
1858         return 0;
1859 }
1860 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1861
1862 /* We come here whenever a session's send_seq, cookie_len or
1863  * l2specific_len parameters are set.
1864  */
1865 void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1866 {
1867         if (version == L2TP_HDR_VER_2) {
1868                 session->hdr_len = 6;
1869                 if (session->send_seq)
1870                         session->hdr_len += 4;
1871         } else {
1872                 session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
1873                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1874                         session->hdr_len += 4;
1875         }
1876
1877 }
1878 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
1879
1880 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)
1881 {
1882         struct l2tp_session *session;
1883
1884         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1885         if (session != NULL) {
1886                 session->magic = L2TP_SESSION_MAGIC;
1887                 session->tunnel = tunnel;
1888
1889                 session->session_id = session_id;
1890                 session->peer_session_id = peer_session_id;
1891                 session->nr = 0;
1892                 if (tunnel->version == L2TP_HDR_VER_2)
1893                         session->nr_max = 0xffff;
1894                 else
1895                         session->nr_max = 0xffffff;
1896                 session->nr_window_size = session->nr_max / 2;
1897                 session->nr_oos_count_max = 4;
1898
1899                 /* Use NR of first received packet */
1900                 session->reorder_skip = 1;
1901
1902                 sprintf(&session->name[0], "sess %u/%u",
1903                         tunnel->tunnel_id, session->session_id);
1904
1905                 skb_queue_head_init(&session->reorder_q);
1906
1907                 INIT_HLIST_NODE(&session->hlist);
1908                 INIT_HLIST_NODE(&session->global_hlist);
1909
1910                 /* Inherit debug options from tunnel */
1911                 session->debug = tunnel->debug;
1912
1913                 if (cfg) {
1914                         session->pwtype = cfg->pw_type;
1915                         session->debug = cfg->debug;
1916                         session->mtu = cfg->mtu;
1917                         session->mru = cfg->mru;
1918                         session->send_seq = cfg->send_seq;
1919                         session->recv_seq = cfg->recv_seq;
1920                         session->lns_mode = cfg->lns_mode;
1921                         session->reorder_timeout = cfg->reorder_timeout;
1922                         session->offset = cfg->offset;
1923                         session->l2specific_type = cfg->l2specific_type;
1924                         session->l2specific_len = cfg->l2specific_len;
1925                         session->cookie_len = cfg->cookie_len;
1926                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1927                         session->peer_cookie_len = cfg->peer_cookie_len;
1928                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1929                 }
1930
1931                 if (tunnel->version == L2TP_HDR_VER_2)
1932                         session->build_header = l2tp_build_l2tpv2_header;
1933                 else
1934                         session->build_header = l2tp_build_l2tpv3_header;
1935
1936                 l2tp_session_set_header_len(session, tunnel->version);
1937
1938                 /* Bump the reference count. The session context is deleted
1939                  * only when this drops to zero.
1940                  */
1941                 l2tp_session_inc_refcount(session);
1942                 l2tp_tunnel_inc_refcount(tunnel);
1943
1944                 /* Ensure tunnel socket isn't deleted */
1945                 sock_hold(tunnel->sock);
1946
1947                 /* Add session to the tunnel's hash list */
1948                 write_lock_bh(&tunnel->hlist_lock);
1949                 hlist_add_head(&session->hlist,
1950                                l2tp_session_id_hash(tunnel, session_id));
1951                 write_unlock_bh(&tunnel->hlist_lock);
1952
1953                 /* And to the global session list if L2TPv3 */
1954                 if (tunnel->version != L2TP_HDR_VER_2) {
1955                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1956
1957                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1958                         hlist_add_head_rcu(&session->global_hlist,
1959                                            l2tp_session_id_hash_2(pn, session_id));
1960                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1961                 }
1962
1963                 /* Ignore management session in session count value */
1964                 if (session->session_id != 0)
1965                         atomic_inc(&l2tp_session_count);
1966         }
1967
1968         return session;
1969 }
1970 EXPORT_SYMBOL_GPL(l2tp_session_create);
1971
1972 /*****************************************************************************
1973  * Init and cleanup
1974  *****************************************************************************/
1975
1976 static __net_init int l2tp_init_net(struct net *net)
1977 {
1978         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1979         int hash;
1980
1981         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1982         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1983
1984         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1985                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1986
1987         spin_lock_init(&pn->l2tp_session_hlist_lock);
1988
1989         return 0;
1990 }
1991
1992 static __net_exit void l2tp_exit_net(struct net *net)
1993 {
1994         struct l2tp_net *pn = l2tp_pernet(net);
1995         struct l2tp_tunnel *tunnel = NULL;
1996
1997         rcu_read_lock_bh();
1998         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
1999                 (void)l2tp_tunnel_delete(tunnel);
2000         }
2001         rcu_read_unlock_bh();
2002 }
2003
2004 static struct pernet_operations l2tp_net_ops = {
2005         .init = l2tp_init_net,
2006         .exit = l2tp_exit_net,
2007         .id   = &l2tp_net_id,
2008         .size = sizeof(struct l2tp_net),
2009 };
2010
2011 static int __init l2tp_init(void)
2012 {
2013         int rc = 0;
2014
2015         rc = register_pernet_device(&l2tp_net_ops);
2016         if (rc)
2017                 goto out;
2018
2019         l2tp_wq = alloc_workqueue("l2tp", WQ_NON_REENTRANT | WQ_UNBOUND, 0);
2020         if (!l2tp_wq) {
2021                 pr_err("alloc_workqueue failed\n");
2022                 rc = -ENOMEM;
2023                 goto out;
2024         }
2025
2026         pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
2027
2028 out:
2029         return rc;
2030 }
2031
2032 static void __exit l2tp_exit(void)
2033 {
2034         unregister_pernet_device(&l2tp_net_ops);
2035         if (l2tp_wq) {
2036                 destroy_workqueue(l2tp_wq);
2037                 l2tp_wq = NULL;
2038         }
2039 }
2040
2041 module_init(l2tp_init);
2042 module_exit(l2tp_exit);
2043
2044 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
2045 MODULE_DESCRIPTION("L2TP core");
2046 MODULE_LICENSE("GPL");
2047 MODULE_VERSION(L2TP_DRV_VERSION);
2048