net/l2tp/l2tp_core.c

   1 /*
   2  * L2TP core.
   3  *
   4  * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
   5  *
   6  * This file contains some code of the original L2TPv2 pppol2tp
   7  * driver, which has the following copyright:
   8  *
   9  * Authors:     Martijn van Oosterhout <kleptog@svana.org>
  10  *              James Chapman (jchapman@katalix.com)
  11  * Contributors:
  12  *              Michal Ostrowski <mostrows@speakeasy.net>
  13  *              Arnaldo Carvalho de Melo <acme@xconectiva.com.br>
  14  *              David S. Miller (davem@redhat.com)
  15  *
  16  * This program is free software; you can redistribute it and/or modify
  17  * it under the terms of the GNU General Public License version 2 as
  18  * published by the Free Software Foundation.
  19  */
  20
  21 #include <linux/module.h>
  22 #include <linux/string.h>
  23 #include <linux/list.h>
  24 #include <linux/rculist.h>
  25 #include <linux/uaccess.h>
  26
  27 #include <linux/kernel.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/kthread.h>
  30 #include <linux/sched.h>
  31 #include <linux/slab.h>
  32 #include <linux/errno.h>
  33 #include <linux/jiffies.h>
  34
  35 #include <linux/netdevice.h>
  36 #include <linux/net.h>
  37 #include <linux/inetdevice.h>
  38 #include <linux/skbuff.h>
  39 #include <linux/init.h>
  40 #include <linux/in.h>
  41 #include <linux/ip.h>
  42 #include <linux/udp.h>
  43 #include <linux/l2tp.h>
  44 #include <linux/hash.h>
  45 #include <linux/sort.h>
  46 #include <linux/file.h>
  47 #include <linux/nsproxy.h>
  48 #include <net/net_namespace.h>
  49 #include <net/netns/generic.h>
  50 #include <net/dst.h>
  51 #include <net/ip.h>
  52 #include <net/udp.h>
  53 #include <net/inet_common.h>
  54 #include <net/xfrm.h>
  55 #include <net/protocol.h>
  56 #include <net/inet6_connection_sock.h>
  57 #include <net/inet_ecn.h>
  58 #include <net/ip6_route.h>
  59
  60 #include <asm/byteorder.h>
  61 #include <linux/atomic.h>
  62
  63 #include "l2tp_core.h"
  64
  65 #define L2TP_DRV_VERSION        "V2.0"
  66
  67 /* L2TP header constants */
  68 #define L2TP_HDRFLAG_T     0x8000
  69 #define L2TP_HDRFLAG_L     0x4000
  70 #define L2TP_HDRFLAG_S     0x0800
  71 #define L2TP_HDRFLAG_O     0x0200
  72 #define L2TP_HDRFLAG_P     0x0100
  73
  74 #define L2TP_HDR_VER_MASK  0x000F
  75 #define L2TP_HDR_VER_2     0x0002
  76 #define L2TP_HDR_VER_3     0x0003
  77
  78 /* L2TPv3 default L2-specific sublayer */
  79 #define L2TP_SLFLAG_S      0x40000000
  80 #define L2TP_SL_SEQ_MASK   0x00ffffff
  81
  82 #define L2TP_HDR_SIZE_SEQ               10
  83 #define L2TP_HDR_SIZE_NOSEQ             6
  84
  85 /* Default trace flags */
  86 #define L2TP_DEFAULT_DEBUG_FLAGS        0
  87
  88 #define PRINTK(_mask, _type, _lvl, _fmt, args...)                       \
  89         do {                                                            \
  90                 if ((_mask) & (_type))                                  \
  91                         printk(_lvl "L2TP: " _fmt, ##args);             \
  92         } while (0)
  93
  94 /* Private data stored for received packets in the skb.
  95  */
  96 struct l2tp_skb_cb {
  97         u32                     ns;
  98         u16                     has_seq;
  99         u16                     length;
 100         unsigned long           expires;
 101 };
 102
 103 #define L2TP_SKB_CB(skb)        ((struct l2tp_skb_cb *) &skb->cb[sizeof(struct inet_skb_parm)])
 104
 105 static atomic_t l2tp_tunnel_count;
 106 static atomic_t l2tp_session_count;
 107
 108 /* per-net private data for this module */
 109 static unsigned int l2tp_net_id;
 110 struct l2tp_net {
 111         struct list_head l2tp_tunnel_list;
 112         spinlock_t l2tp_tunnel_list_lock;
 113         struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
 114         spinlock_t l2tp_session_hlist_lock;
 115 };
 116
 117 static void l2tp_session_set_header_len(struct l2tp_session *session, int version);
 118 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
 119 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
 120
 121 static inline struct l2tp_net *l2tp_pernet(struct net *net)
 122 {
 123         BUG_ON(!net);
 124
 125         return net_generic(net, l2tp_net_id);
 126 }
 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) do { \
 144                 printk(KERN_DEBUG "l2tp_tunnel_inc_refcount: %s:%d %s: cnt=%d\n", __func__, __LINE__, (_t)->name, atomic_read(&_t->ref_count)); \
 145                 l2tp_tunnel_inc_refcount_1(_t);                         \
 146         } while (0)
 147 #define l2tp_tunnel_dec_refcount(_t) do { \
 148                 printk(KERN_DEBUG "l2tp_tunnel_dec_refcount: %s:%d %s: cnt=%d\n", __func__, __LINE__, (_t)->name, atomic_read(&_t->ref_count)); \
 149                 l2tp_tunnel_dec_refcount_1(_t);                         \
 150         } while (0)
 151 #else
 152 #define l2tp_tunnel_inc_refcount(t) l2tp_tunnel_inc_refcount_1(t)
 153 #define l2tp_tunnel_dec_refcount(t) l2tp_tunnel_dec_refcount_1(t)
 154 #endif
 155
 156 /* Session hash global list for L2TPv3.
 157  * The session_id SHOULD be random according to RFC3931, but several
 158  * L2TP implementations use incrementing session_ids.  So we do a real
 159  * hash on the session_id, rather than a simple bitmask.
 160  */
 161 static inline struct hlist_head *
 162 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
 163 {
 164         return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
 165
 166 }
 167
 168 /* Lookup a session by id in the global session list
 169  */
 170 static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id)
 171 {
 172         struct l2tp_net *pn = l2tp_pernet(net);
 173         struct hlist_head *session_list =
 174                 l2tp_session_id_hash_2(pn, session_id);
 175         struct l2tp_session *session;
 176         struct hlist_node *walk;
 177
 178         rcu_read_lock_bh();
 179         hlist_for_each_entry_rcu(session, walk, session_list, global_hlist) {
 180                 if (session->session_id == session_id) {
 181                         rcu_read_unlock_bh();
 182                         return session;
 183                 }
 184         }
 185         rcu_read_unlock_bh();
 186
 187         return NULL;
 188 }
 189
 190 /* Session hash list.
 191  * The session_id SHOULD be random according to RFC2661, but several
 192  * L2TP implementations (Cisco and Microsoft) use incrementing
 193  * session_ids.  So we do a real hash on the session_id, rather than a
 194  * simple bitmask.
 195  */
 196 static inline struct hlist_head *
 197 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 198 {
 199         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 200 }
 201
 202 /* Lookup a session by id
 203  */
 204 struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id)
 205 {
 206         struct hlist_head *session_list;
 207         struct l2tp_session *session;
 208         struct hlist_node *walk;
 209
 210         /* In L2TPv3, session_ids are unique over all tunnels and we
 211          * sometimes need to look them up before we know the
 212          * tunnel.
 213          */
 214         if (tunnel == NULL)
 215                 return l2tp_session_find_2(net, session_id);
 216
 217         session_list = l2tp_session_id_hash(tunnel, session_id);
 218         read_lock_bh(&tunnel->hlist_lock);
 219         hlist_for_each_entry(session, walk, session_list, hlist) {
 220                 if (session->session_id == session_id) {
 221                         read_unlock_bh(&tunnel->hlist_lock);
 222                         return session;
 223                 }
 224         }
 225         read_unlock_bh(&tunnel->hlist_lock);
 226
 227         return NULL;
 228 }
 229 EXPORT_SYMBOL_GPL(l2tp_session_find);
 230
 231 struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth)
 232 {
 233         int hash;
 234         struct hlist_node *walk;
 235         struct l2tp_session *session;
 236         int count = 0;
 237
 238         read_lock_bh(&tunnel->hlist_lock);
 239         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 240                 hlist_for_each_entry(session, walk, &tunnel->session_hlist[hash], hlist) {
 241                         if (++count > nth) {
 242                                 read_unlock_bh(&tunnel->hlist_lock);
 243                                 return session;
 244                         }
 245                 }
 246         }
 247
 248         read_unlock_bh(&tunnel->hlist_lock);
 249
 250         return NULL;
 251 }
 252 EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
 253
 254 /* Lookup a session by interface name.
 255  * This is very inefficient but is only used by management interfaces.
 256  */
 257 struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
 258 {
 259         struct l2tp_net *pn = l2tp_pernet(net);
 260         int hash;
 261         struct hlist_node *walk;
 262         struct l2tp_session *session;
 263
 264         rcu_read_lock_bh();
 265         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 266                 hlist_for_each_entry_rcu(session, walk, &pn->l2tp_session_hlist[hash], global_hlist) {
 267                         if (!strcmp(session->ifname, ifname)) {
 268                                 rcu_read_unlock_bh();
 269                                 return session;
 270                         }
 271                 }
 272         }
 273
 274         rcu_read_unlock_bh();
 275
 276         return NULL;
 277 }
 278 EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname);
 279
 280 /* Lookup a tunnel by id
 281  */
 282 struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
 283 {
 284         struct l2tp_tunnel *tunnel;
 285         struct l2tp_net *pn = l2tp_pernet(net);
 286
 287         rcu_read_lock_bh();
 288         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 289                 if (tunnel->tunnel_id == tunnel_id) {
 290                         rcu_read_unlock_bh();
 291                         return tunnel;
 292                 }
 293         }
 294         rcu_read_unlock_bh();
 295
 296         return NULL;
 297 }
 298 EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
 299
 300 struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
 301 {
 302         struct l2tp_net *pn = l2tp_pernet(net);
 303         struct l2tp_tunnel *tunnel;
 304         int count = 0;
 305
 306         rcu_read_lock_bh();
 307         list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
 308                 if (++count > nth) {
 309                         rcu_read_unlock_bh();
 310                         return tunnel;
 311                 }
 312         }
 313
 314         rcu_read_unlock_bh();
 315
 316         return NULL;
 317 }
 318 EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
 319
 320 /*****************************************************************************
 321  * Receive data handling
 322  *****************************************************************************/
 323
 324 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 325  * number.
 326  */
 327 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 328 {
 329         struct sk_buff *skbp;
 330         struct sk_buff *tmp;
 331         u32 ns = L2TP_SKB_CB(skb)->ns;
 332
 333         spin_lock_bh(&session->reorder_q.lock);
 334         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 335                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 336                         __skb_queue_before(&session->reorder_q, skbp, skb);
 337                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 338                                "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 339                                session->name, ns, L2TP_SKB_CB(skbp)->ns,
 340                                skb_queue_len(&session->reorder_q));
 341                         session->stats.rx_oos_packets++;
 342                         goto out;
 343                 }
 344         }
 345
 346         __skb_queue_tail(&session->reorder_q, skb);
 347
 348 out:
 349         spin_unlock_bh(&session->reorder_q.lock);
 350 }
 351
 352 /* Dequeue a single skb.
 353  */
 354 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 355 {
 356         struct l2tp_tunnel *tunnel = session->tunnel;
 357         int length = L2TP_SKB_CB(skb)->length;
 358
 359         /* We're about to requeue the skb, so return resources
 360          * to its current owner (a socket receive buffer).
 361          */
 362         skb_orphan(skb);
 363
 364         tunnel->stats.rx_packets++;
 365         tunnel->stats.rx_bytes += length;
 366         session->stats.rx_packets++;
 367         session->stats.rx_bytes += length;
 368
 369         if (L2TP_SKB_CB(skb)->has_seq) {
 370                 /* Bump our Nr */
 371                 session->nr++;
 372                 if (tunnel->version == L2TP_HDR_VER_2)
 373                         session->nr &= 0xffff;
 374                 else
 375                         session->nr &= 0xffffff;
 376
 377                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 378                        "%s: updated nr to %hu\n", session->name, session->nr);
 379         }
 380
 381         /* call private receive handler */
 382         if (session->recv_skb != NULL)
 383                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 384         else
 385                 kfree_skb(skb);
 386
 387         if (session->deref)
 388                 (*session->deref)(session);
 389 }
 390
 391 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 392  * Skbs that have been in the queue for too long are simply discarded.
 393  */
 394 static void l2tp_recv_dequeue(struct l2tp_session *session)
 395 {
 396         struct sk_buff *skb;
 397         struct sk_buff *tmp;
 398
 399         /* If the pkt at the head of the queue has the nr that we
 400          * expect to send up next, dequeue it and any other
 401          * in-sequence packets behind it.
 402          */
 403 start:
 404         spin_lock_bh(&session->reorder_q.lock);
 405         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 406                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 407                         session->stats.rx_seq_discards++;
 408                         session->stats.rx_errors++;
 409                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 410                                "%s: oos pkt %u len %d discarded (too old), "
 411                                "waiting for %u, reorder_q_len=%d\n",
 412                                session->name, L2TP_SKB_CB(skb)->ns,
 413                                L2TP_SKB_CB(skb)->length, session->nr,
 414                                skb_queue_len(&session->reorder_q));
 415                         __skb_unlink(skb, &session->reorder_q);
 416                         kfree_skb(skb);
 417                         if (session->deref)
 418                                 (*session->deref)(session);
 419                         continue;
 420                 }
 421
 422                 if (L2TP_SKB_CB(skb)->has_seq) {
 423                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 424                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 425                                        "%s: holding oos pkt %u len %d, "
 426                                        "waiting for %u, reorder_q_len=%d\n",
 427                                        session->name, L2TP_SKB_CB(skb)->ns,
 428                                        L2TP_SKB_CB(skb)->length, session->nr,
 429                                        skb_queue_len(&session->reorder_q));
 430                                 goto out;
 431                         }
 432                 }
 433                 __skb_unlink(skb, &session->reorder_q);
 434
 435                 /* Process the skb. We release the queue lock while we
 436                  * do so to let other contexts process the queue.
 437                  */
 438                 spin_unlock_bh(&session->reorder_q.lock);
 439                 l2tp_recv_dequeue_skb(session, skb);
 440                 goto start;
 441         }
 442
 443 out:
 444         spin_unlock_bh(&session->reorder_q.lock);
 445 }
 446
 447 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 448                                            struct sk_buff *skb)
 449 {
 450         struct udphdr *uh = udp_hdr(skb);
 451         u16 ulen = ntohs(uh->len);
 452         __wsum psum;
 453
 454         if (sk->sk_no_check || skb_csum_unnecessary(skb))
 455                 return 0;
 456
 457 #if IS_ENABLED(CONFIG_IPV6)
 458         if (sk->sk_family == PF_INET6) {
 459                 if (!uh->check) {
 460                         LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
 461                         return 1;
 462                 }
 463                 if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 464                     !csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 465                                      &ipv6_hdr(skb)->daddr, ulen,
 466                                      IPPROTO_UDP, skb->csum)) {
 467                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 468                         return 0;
 469                 }
 470                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 471                                                          &ipv6_hdr(skb)->daddr,
 472                                                          skb->len, IPPROTO_UDP,
 473                                                          0));
 474         } else
 475 #endif
 476         {
 477                 struct inet_sock *inet;
 478                 if (!uh->check)
 479                         return 0;
 480                 inet = inet_sk(sk);
 481                 psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr,
 482                                           ulen, IPPROTO_UDP, 0);
 483
 484                 if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 485                     !csum_fold(csum_add(psum, skb->csum)))
 486                         return 0;
 487                 skb->csum = psum;
 488         }
 489
 490         return __skb_checksum_complete(skb);
 491 }
 492
 493 /* Do receive processing of L2TP data frames. We handle both L2TPv2
 494  * and L2TPv3 data frames here.
 495  *
 496  * L2TPv2 Data Message Header
 497  *
 498  *  0                   1                   2                   3
 499  *  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
 500  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 501  * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
 502  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 503  * |           Tunnel ID           |           Session ID          |
 504  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 505  * |             Ns (opt)          |             Nr (opt)          |
 506  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 507  * |      Offset Size (opt)        |    Offset pad... (opt)
 508  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 509  *
 510  * Data frames are marked by T=0. All other fields are the same as
 511  * those in L2TP control frames.
 512  *
 513  * L2TPv3 Data Message Header
 514  *
 515  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 516  * |                      L2TP Session Header                      |
 517  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 518  * |                      L2-Specific Sublayer                     |
 519  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 520  * |                        Tunnel Payload                      ...
 521  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 522  *
 523  * L2TPv3 Session Header Over IP
 524  *
 525  *  0                   1                   2                   3
 526  *  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
 527  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 528  * |                           Session ID                          |
 529  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 530  * |               Cookie (optional, maximum 64 bits)...
 531  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 532  *                                                                 |
 533  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 534  *
 535  * L2TPv3 L2-Specific Sublayer Format
 536  *
 537  *  0                   1                   2                   3
 538  *  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
 539  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 540  * |x|S|x|x|x|x|x|x|              Sequence Number                  |
 541  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 542  *
 543  * Cookie value, sublayer format and offset (pad) are negotiated with
 544  * the peer when the session is set up. Unlike L2TPv2, we do not need
 545  * to parse the packet header to determine if optional fields are
 546  * present.
 547  *
 548  * Caller must already have parsed the frame and determined that it is
 549  * a data (not control) frame before coming here. Fields up to the
 550  * session-id have already been parsed and ptr points to the data
 551  * after the session-id.
 552  */
 553 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 554                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
 555                       int length, int (*payload_hook)(struct sk_buff *skb))
 556 {
 557         struct l2tp_tunnel *tunnel = session->tunnel;
 558         int offset;
 559         u32 ns, nr;
 560
 561         /* The ref count is increased since we now hold a pointer to
 562          * the session. Take care to decrement the refcnt when exiting
 563          * this function from now on...
 564          */
 565         l2tp_session_inc_refcount(session);
 566         if (session->ref)
 567                 (*session->ref)(session);
 568
 569         /* Parse and check optional cookie */
 570         if (session->peer_cookie_len > 0) {
 571                 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
 572                         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 573                                "%s: cookie mismatch (%u/%u). Discarding.\n",
 574                                tunnel->name, tunnel->tunnel_id, session->session_id);
 575                         session->stats.rx_cookie_discards++;
 576                         goto discard;
 577                 }
 578                 ptr += session->peer_cookie_len;
 579         }
 580
 581         /* Handle the optional sequence numbers. Sequence numbers are
 582          * in different places for L2TPv2 and L2TPv3.
 583          *
 584          * If we are the LAC, enable/disable sequence numbers under
 585          * the control of the LNS.  If no sequence numbers present but
 586          * we were expecting them, discard frame.
 587          */
 588         ns = nr = 0;
 589         L2TP_SKB_CB(skb)->has_seq = 0;
 590         if (tunnel->version == L2TP_HDR_VER_2) {
 591                 if (hdrflags & L2TP_HDRFLAG_S) {
 592                         ns = ntohs(*(__be16 *) ptr);
 593                         ptr += 2;
 594                         nr = ntohs(*(__be16 *) ptr);
 595                         ptr += 2;
 596
 597                         /* Store L2TP info in the skb */
 598                         L2TP_SKB_CB(skb)->ns = ns;
 599                         L2TP_SKB_CB(skb)->has_seq = 1;
 600
 601                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 602                                "%s: recv data ns=%u, nr=%u, session nr=%u\n",
 603                                session->name, ns, nr, session->nr);
 604                 }
 605         } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 606                 u32 l2h = ntohl(*(__be32 *) ptr);
 607
 608                 if (l2h & 0x40000000) {
 609                         ns = l2h & 0x00ffffff;
 610
 611                         /* Store L2TP info in the skb */
 612                         L2TP_SKB_CB(skb)->ns = ns;
 613                         L2TP_SKB_CB(skb)->has_seq = 1;
 614
 615                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 616                                "%s: recv data ns=%u, session nr=%u\n",
 617                                session->name, ns, session->nr);
 618                 }
 619         }
 620
 621         /* Advance past L2-specific header, if present */
 622         ptr += session->l2specific_len;
 623
 624         if (L2TP_SKB_CB(skb)->has_seq) {
 625                 /* Received a packet with sequence numbers. If we're the LNS,
 626                  * check if we sre sending sequence numbers and if not,
 627                  * configure it so.
 628                  */
 629                 if ((!session->lns_mode) && (!session->send_seq)) {
 630                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 631                                "%s: requested to enable seq numbers by LNS\n",
 632                                session->name);
 633                         session->send_seq = -1;
 634                         l2tp_session_set_header_len(session, tunnel->version);
 635                 }
 636         } else {
 637                 /* No sequence numbers.
 638                  * If user has configured mandatory sequence numbers, discard.
 639                  */
 640                 if (session->recv_seq) {
 641                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 642                                "%s: recv data has no seq numbers when required. "
 643                                "Discarding\n", session->name);
 644                         session->stats.rx_seq_discards++;
 645                         goto discard;
 646                 }
 647
 648                 /* If we're the LAC and we're sending sequence numbers, the
 649                  * LNS has requested that we no longer send sequence numbers.
 650                  * If we're the LNS and we're sending sequence numbers, the
 651                  * LAC is broken. Discard the frame.
 652                  */
 653                 if ((!session->lns_mode) && (session->send_seq)) {
 654                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 655                                "%s: requested to disable seq numbers by LNS\n",
 656                                session->name);
 657                         session->send_seq = 0;
 658                         l2tp_session_set_header_len(session, tunnel->version);
 659                 } else if (session->send_seq) {
 660                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 661                                "%s: recv data has no seq numbers when required. "
 662                                "Discarding\n", session->name);
 663                         session->stats.rx_seq_discards++;
 664                         goto discard;
 665                 }
 666         }
 667
 668         /* Session data offset is handled differently for L2TPv2 and
 669          * L2TPv3. For L2TPv2, there is an optional 16-bit value in
 670          * the header. For L2TPv3, the offset is negotiated using AVPs
 671          * in the session setup control protocol.
 672          */
 673         if (tunnel->version == L2TP_HDR_VER_2) {
 674                 /* If offset bit set, skip it. */
 675                 if (hdrflags & L2TP_HDRFLAG_O) {
 676                         offset = ntohs(*(__be16 *)ptr);
 677                         ptr += 2 + offset;
 678                 }
 679         } else
 680                 ptr += session->offset;
 681
 682         offset = ptr - optr;
 683         if (!pskb_may_pull(skb, offset))
 684                 goto discard;
 685
 686         __skb_pull(skb, offset);
 687
 688         /* If caller wants to process the payload before we queue the
 689          * packet, do so now.
 690          */
 691         if (payload_hook)
 692                 if ((*payload_hook)(skb))
 693                         goto discard;
 694
 695         /* Prepare skb for adding to the session's reorder_q.  Hold
 696          * packets for max reorder_timeout or 1 second if not
 697          * reordering.
 698          */
 699         L2TP_SKB_CB(skb)->length = length;
 700         L2TP_SKB_CB(skb)->expires = jiffies +
 701                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 702
 703         /* Add packet to the session's receive queue. Reordering is done here, if
 704          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 705          */
 706         if (L2TP_SKB_CB(skb)->has_seq) {
 707                 if (session->reorder_timeout != 0) {
 708                         /* Packet reordering enabled. Add skb to session's
 709                          * reorder queue, in order of ns.
 710                          */
 711                         l2tp_recv_queue_skb(session, skb);
 712                 } else {
 713                         /* Packet reordering disabled. Discard out-of-sequence
 714                          * packets
 715                          */
 716                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 717                                 session->stats.rx_seq_discards++;
 718                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 719                                        "%s: oos pkt %u len %d discarded, "
 720                                        "waiting for %u, reorder_q_len=%d\n",
 721                                        session->name, L2TP_SKB_CB(skb)->ns,
 722                                        L2TP_SKB_CB(skb)->length, session->nr,
 723                                        skb_queue_len(&session->reorder_q));
 724                                 goto discard;
 725                         }
 726                         skb_queue_tail(&session->reorder_q, skb);
 727                 }
 728         } else {
 729                 /* No sequence numbers. Add the skb to the tail of the
 730                  * reorder queue. This ensures that it will be
 731                  * delivered after all previous sequenced skbs.
 732                  */
 733                 skb_queue_tail(&session->reorder_q, skb);
 734         }
 735
 736         /* Try to dequeue as many skbs from reorder_q as we can. */
 737         l2tp_recv_dequeue(session);
 738
 739         l2tp_session_dec_refcount(session);
 740
 741         return;
 742
 743 discard:
 744         session->stats.rx_errors++;
 745         kfree_skb(skb);
 746
 747         if (session->deref)
 748                 (*session->deref)(session);
 749
 750         l2tp_session_dec_refcount(session);
 751 }
 752 EXPORT_SYMBOL(l2tp_recv_common);
 753
 754 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 755  * here. The skb is not on a list when we get here.
 756  * Returns 0 if the packet was a data packet and was successfully passed on.
 757  * Returns 1 if the packet was not a good data packet and could not be
 758  * forwarded.  All such packets are passed up to userspace to deal with.
 759  */
 760 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 761                               int (*payload_hook)(struct sk_buff *skb))
 762 {
 763         struct l2tp_session *session = NULL;
 764         unsigned char *ptr, *optr;
 765         u16 hdrflags;
 766         u32 tunnel_id, session_id;
 767         int offset;
 768         u16 version;
 769         int length;
 770
 771         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
 772                 goto discard_bad_csum;
 773
 774         /* UDP always verifies the packet length. */
 775         __skb_pull(skb, sizeof(struct udphdr));
 776
 777         /* Short packet? */
 778         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
 779                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 780                        "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
 781                 goto error;
 782         }
 783
 784         /* Trace packet contents, if enabled */
 785         if (tunnel->debug & L2TP_MSG_DATA) {
 786                 length = min(32u, skb->len);
 787                 if (!pskb_may_pull(skb, length))
 788                         goto error;
 789
 790                 printk(KERN_DEBUG "%s: recv: ", tunnel->name);
 791
 792                 offset = 0;
 793                 do {
 794                         printk(" %02X", skb->data[offset]);
 795                 } while (++offset < length);
 796
 797                 printk("\n");
 798         }
 799
 800         /* Point to L2TP header */
 801         optr = ptr = skb->data;
 802
 803         /* Get L2TP header flags */
 804         hdrflags = ntohs(*(__be16 *) ptr);
 805
 806         /* Check protocol version */
 807         version = hdrflags & L2TP_HDR_VER_MASK;
 808         if (version != tunnel->version) {
 809                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 810                        "%s: recv protocol version mismatch: got %d expected %d\n",
 811                        tunnel->name, version, tunnel->version);
 812                 goto error;
 813         }
 814
 815         /* Get length of L2TP packet */
 816         length = skb->len;
 817
 818         /* If type is control packet, it is handled by userspace. */
 819         if (hdrflags & L2TP_HDRFLAG_T) {
 820                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 821                        "%s: recv control packet, len=%d\n", tunnel->name, length);
 822                 goto error;
 823         }
 824
 825         /* Skip flags */
 826         ptr += 2;
 827
 828         if (tunnel->version == L2TP_HDR_VER_2) {
 829                 /* If length is present, skip it */
 830                 if (hdrflags & L2TP_HDRFLAG_L)
 831                         ptr += 2;
 832
 833                 /* Extract tunnel and session ID */
 834                 tunnel_id = ntohs(*(__be16 *) ptr);
 835                 ptr += 2;
 836                 session_id = ntohs(*(__be16 *) ptr);
 837                 ptr += 2;
 838         } else {
 839                 ptr += 2;       /* skip reserved bits */
 840                 tunnel_id = tunnel->tunnel_id;
 841                 session_id = ntohl(*(__be32 *) ptr);
 842                 ptr += 4;
 843         }
 844
 845         /* Find the session context */
 846         session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
 847         if (!session || !session->recv_skb) {
 848                 /* Not found? Pass to userspace to deal with */
 849                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 850                        "%s: no session found (%u/%u). Passing up.\n",
 851                        tunnel->name, tunnel_id, session_id);
 852                 goto error;
 853         }
 854
 855         l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
 856
 857         return 0;
 858
 859 discard_bad_csum:
 860         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
 861         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
 862         tunnel->stats.rx_errors++;
 863         kfree_skb(skb);
 864
 865         return 0;
 866
 867 error:
 868         /* Put UDP header back */
 869         __skb_push(skb, sizeof(struct udphdr));
 870
 871         return 1;
 872 }
 873
 874 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 875  * Return codes:
 876  * 0 : success.
 877  * <0: error
 878  * >0: skb should be passed up to userspace as UDP.
 879  */
 880 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 881 {
 882         struct l2tp_tunnel *tunnel;
 883
 884         tunnel = l2tp_sock_to_tunnel(sk);
 885         if (tunnel == NULL)
 886                 goto pass_up;
 887
 888         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 889                "%s: received %d bytes\n", tunnel->name, skb->len);
 890
 891         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
 892                 goto pass_up_put;
 893
 894         sock_put(sk);
 895         return 0;
 896
 897 pass_up_put:
 898         sock_put(sk);
 899 pass_up:
 900         return 1;
 901 }
 902 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 903
 904 /************************************************************************
 905  * Transmit handling
 906  ***********************************************************************/
 907
 908 /* Build an L2TP header for the session into the buffer provided.
 909  */
 910 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
 911 {
 912         struct l2tp_tunnel *tunnel = session->tunnel;
 913         __be16 *bufp = buf;
 914         __be16 *optr = buf;
 915         u16 flags = L2TP_HDR_VER_2;
 916         u32 tunnel_id = tunnel->peer_tunnel_id;
 917         u32 session_id = session->peer_session_id;
 918
 919         if (session->send_seq)
 920                 flags |= L2TP_HDRFLAG_S;
 921
 922         /* Setup L2TP header. */
 923         *bufp++ = htons(flags);
 924         *bufp++ = htons(tunnel_id);
 925         *bufp++ = htons(session_id);
 926         if (session->send_seq) {
 927                 *bufp++ = htons(session->ns);
 928                 *bufp++ = 0;
 929                 session->ns++;
 930                 session->ns &= 0xffff;
 931                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 932                        "%s: updated ns to %u\n", session->name, session->ns);
 933         }
 934
 935         return bufp - optr;
 936 }
 937
 938 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
 939 {
 940         struct l2tp_tunnel *tunnel = session->tunnel;
 941         char *bufp = buf;
 942         char *optr = bufp;
 943
 944         /* Setup L2TP header. The header differs slightly for UDP and
 945          * IP encapsulations. For UDP, there is 4 bytes of flags.
 946          */
 947         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 948                 u16 flags = L2TP_HDR_VER_3;
 949                 *((__be16 *) bufp) = htons(flags);
 950                 bufp += 2;
 951                 *((__be16 *) bufp) = 0;
 952                 bufp += 2;
 953         }
 954
 955         *((__be32 *) bufp) = htonl(session->peer_session_id);
 956         bufp += 4;
 957         if (session->cookie_len) {
 958                 memcpy(bufp, &session->cookie[0], session->cookie_len);
 959                 bufp += session->cookie_len;
 960         }
 961         if (session->l2specific_len) {
 962                 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
 963                         u32 l2h = 0;
 964                         if (session->send_seq) {
 965                                 l2h = 0x40000000 | session->ns;
 966                                 session->ns++;
 967                                 session->ns &= 0xffffff;
 968                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 969                                        "%s: updated ns to %u\n", session->name, session->ns);
 970                         }
 971
 972                         *((__be32 *) bufp) = htonl(l2h);
 973                 }
 974                 bufp += session->l2specific_len;
 975         }
 976         if (session->offset)
 977                 bufp += session->offset;
 978
 979         return bufp - optr;
 980 }
 981
 982 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
 983                           struct flowi *fl, size_t data_len)
 984 {
 985         struct l2tp_tunnel *tunnel = session->tunnel;
 986         unsigned int len = skb->len;
 987         int error;
 988
 989         /* Debug */
 990         if (session->send_seq)
 991                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
 992                        "%s: send %Zd bytes, ns=%u\n", session->name,
 993                        data_len, session->ns - 1);
 994         else
 995                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
 996                        "%s: send %Zd bytes\n", session->name, data_len);
 997
 998         if (session->debug & L2TP_MSG_DATA) {
 999                 int i;
1000                 int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1001                 unsigned char *datap = skb->data + uhlen;
1002
1003                 printk(KERN_DEBUG "%s: xmit:", session->name);
1004                 for (i = 0; i < (len - uhlen); i++) {
1005                         printk(" %02X", *datap++);
1006                         if (i == 31) {
1007                                 printk(" ...");
1008                                 break;
1009                         }
1010                 }
1011                 printk("\n");
1012         }
1013
1014         /* Queue the packet to IP for output */
1015         skb->local_df = 1;
1016 #if IS_ENABLED(CONFIG_IPV6)
1017         if (skb->sk->sk_family == PF_INET6)
1018                 error = inet6_csk_xmit(skb, NULL);
1019         else
1020 #endif
1021                 error = ip_queue_xmit(skb, fl);
1022
1023         /* Update stats */
1024         if (error >= 0) {
1025                 tunnel->stats.tx_packets++;
1026                 tunnel->stats.tx_bytes += len;
1027                 session->stats.tx_packets++;
1028                 session->stats.tx_bytes += len;
1029         } else {
1030                 tunnel->stats.tx_errors++;
1031                 session->stats.tx_errors++;
1032         }
1033
1034         return 0;
1035 }
1036
1037 /* Automatically called when the skb is freed.
1038  */
1039 static void l2tp_sock_wfree(struct sk_buff *skb)
1040 {
1041         sock_put(skb->sk);
1042 }
1043
1044 /* For data skbs that we transmit, we associate with the tunnel socket
1045  * but don't do accounting.
1046  */
1047 static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
1048 {
1049         sock_hold(sk);
1050         skb->sk = sk;
1051         skb->destructor = l2tp_sock_wfree;
1052 }
1053
1054 #if IS_ENABLED(CONFIG_IPV6)
1055 static void l2tp_xmit_ipv6_csum(struct sock *sk, struct sk_buff *skb,
1056                                 int udp_len)
1057 {
1058         struct ipv6_pinfo *np = inet6_sk(sk);
1059         struct udphdr *uh = udp_hdr(skb);
1060
1061         if (!skb_dst(skb) || !skb_dst(skb)->dev ||
1062             !(skb_dst(skb)->dev->features & NETIF_F_IPV6_CSUM)) {
1063                 __wsum csum = skb_checksum(skb, 0, udp_len, 0);
1064                 skb->ip_summed = CHECKSUM_UNNECESSARY;
1065                 uh->check = csum_ipv6_magic(&np->saddr, &np->daddr, udp_len,
1066                                             IPPROTO_UDP, csum);
1067                 if (uh->check == 0)
1068                         uh->check = CSUM_MANGLED_0;
1069         } else {
1070                 skb->ip_summed = CHECKSUM_PARTIAL;
1071                 skb->csum_start = skb_transport_header(skb) - skb->head;
1072                 skb->csum_offset = offsetof(struct udphdr, check);
1073                 uh->check = ~csum_ipv6_magic(&np->saddr, &np->daddr,
1074                                              udp_len, IPPROTO_UDP, 0);
1075         }
1076 }
1077 #endif
1078
1079 /* If caller requires the skb to have a ppp header, the header must be
1080  * inserted in the skb data before calling this function.
1081  */
1082 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
1083 {
1084         int data_len = skb->len;
1085         struct l2tp_tunnel *tunnel = session->tunnel;
1086         struct sock *sk = tunnel->sock;
1087         struct flowi *fl;
1088         struct udphdr *uh;
1089         struct inet_sock *inet;
1090         __wsum csum;
1091         int old_headroom;
1092         int new_headroom;
1093         int headroom;
1094         int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
1095         int udp_len;
1096
1097         /* Check that there's enough headroom in the skb to insert IP,
1098          * UDP and L2TP headers. If not enough, expand it to
1099          * make room. Adjust truesize.
1100          */
1101         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
1102                 uhlen + hdr_len;
1103         old_headroom = skb_headroom(skb);
1104         if (skb_cow_head(skb, headroom)) {
1105                 dev_kfree_skb(skb);
1106                 goto abort;
1107         }
1108
1109         new_headroom = skb_headroom(skb);
1110         skb_orphan(skb);
1111         skb->truesize += new_headroom - old_headroom;
1112
1113         /* Setup L2TP header */
1114         session->build_header(session, __skb_push(skb, hdr_len));
1115
1116         /* Reset skb netfilter state */
1117         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1118         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
1119                               IPSKB_REROUTED);
1120         nf_reset(skb);
1121
1122         bh_lock_sock(sk);
1123         if (sock_owned_by_user(sk)) {
1124                 dev_kfree_skb(skb);
1125                 goto out_unlock;
1126         }
1127
1128         /* Get routing info from the tunnel socket */
1129         skb_dst_drop(skb);
1130         skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
1131
1132         inet = inet_sk(sk);
1133         fl = &inet->cork.fl;
1134         switch (tunnel->encap) {
1135         case L2TP_ENCAPTYPE_UDP:
1136                 /* Setup UDP header */
1137                 __skb_push(skb, sizeof(*uh));
1138                 skb_reset_transport_header(skb);
1139                 uh = udp_hdr(skb);
1140                 uh->source = inet->inet_sport;
1141                 uh->dest = inet->inet_dport;
1142                 udp_len = uhlen + hdr_len + data_len;
1143                 uh->len = htons(udp_len);
1144                 uh->check = 0;
1145
1146                 /* Calculate UDP checksum if configured to do so */
1147 #if IS_ENABLED(CONFIG_IPV6)
1148                 if (sk->sk_family == PF_INET6)
1149                         l2tp_xmit_ipv6_csum(sk, skb, udp_len);
1150                 else
1151 #endif
1152                 if (sk->sk_no_check == UDP_CSUM_NOXMIT)
1153                         skb->ip_summed = CHECKSUM_NONE;
1154                 else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
1155                          (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
1156                         skb->ip_summed = CHECKSUM_COMPLETE;
1157                         csum = skb_checksum(skb, 0, udp_len, 0);
1158                         uh->check = csum_tcpudp_magic(inet->inet_saddr,
1159                                                       inet->inet_daddr,
1160                                                       udp_len, IPPROTO_UDP, csum);
1161                         if (uh->check == 0)
1162                                 uh->check = CSUM_MANGLED_0;
1163                 } else {
1164                         skb->ip_summed = CHECKSUM_PARTIAL;
1165                         skb->csum_start = skb_transport_header(skb) - skb->head;
1166                         skb->csum_offset = offsetof(struct udphdr, check);
1167                         uh->check = ~csum_tcpudp_magic(inet->inet_saddr,
1168                                                        inet->inet_daddr,
1169                                                        udp_len, IPPROTO_UDP, 0);
1170                 }
1171                 break;
1172
1173         case L2TP_ENCAPTYPE_IP:
1174                 break;
1175         }
1176
1177         l2tp_skb_set_owner_w(skb, sk);
1178
1179         l2tp_xmit_core(session, skb, fl, data_len);
1180 out_unlock:
1181         bh_unlock_sock(sk);
1182
1183 abort:
1184         return 0;
1185 }
1186 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
1187
1188 /*****************************************************************************
1189  * Tinnel and session create/destroy.
1190  *****************************************************************************/
1191
1192 /* Tunnel socket destruct hook.
1193  * The tunnel context is deleted only when all session sockets have been
1194  * closed.
1195  */
1196 static void l2tp_tunnel_destruct(struct sock *sk)
1197 {
1198         struct l2tp_tunnel *tunnel;
1199
1200         tunnel = sk->sk_user_data;
1201         if (tunnel == NULL)
1202                 goto end;
1203
1204         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1205                "%s: closing...\n", tunnel->name);
1206
1207         /* Close all sessions */
1208         l2tp_tunnel_closeall(tunnel);
1209
1210         switch (tunnel->encap) {
1211         case L2TP_ENCAPTYPE_UDP:
1212                 /* No longer an encapsulation socket. See net/ipv4/udp.c */
1213                 (udp_sk(sk))->encap_type = 0;
1214                 (udp_sk(sk))->encap_rcv = NULL;
1215                 break;
1216         case L2TP_ENCAPTYPE_IP:
1217                 break;
1218         }
1219
1220         /* Remove hooks into tunnel socket */
1221         tunnel->sock = NULL;
1222         sk->sk_destruct = tunnel->old_sk_destruct;
1223         sk->sk_user_data = NULL;
1224
1225         /* Call the original destructor */
1226         if (sk->sk_destruct)
1227                 (*sk->sk_destruct)(sk);
1228
1229         /* We're finished with the socket */
1230         l2tp_tunnel_dec_refcount(tunnel);
1231
1232 end:
1233         return;
1234 }
1235
1236 /* When the tunnel is closed, all the attached sessions need to go too.
1237  */
1238 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
1239 {
1240         int hash;
1241         struct hlist_node *walk;
1242         struct hlist_node *tmp;
1243         struct l2tp_session *session;
1244
1245         BUG_ON(tunnel == NULL);
1246
1247         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1248                "%s: closing all sessions...\n", tunnel->name);
1249
1250         write_lock_bh(&tunnel->hlist_lock);
1251         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
1252 again:
1253                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
1254                         session = hlist_entry(walk, struct l2tp_session, hlist);
1255
1256                         PRINTK(session->debug, L2TP_MSG_CONTROL, KERN_INFO,
1257                                "%s: closing session\n", session->name);
1258
1259                         hlist_del_init(&session->hlist);
1260
1261                         /* Since we should hold the sock lock while
1262                          * doing any unbinding, we need to release the
1263                          * lock we're holding before taking that lock.
1264                          * Hold a reference to the sock so it doesn't
1265                          * disappear as we're jumping between locks.
1266                          */
1267                         if (session->ref != NULL)
1268                                 (*session->ref)(session);
1269
1270                         write_unlock_bh(&tunnel->hlist_lock);
1271
1272                         if (tunnel->version != L2TP_HDR_VER_2) {
1273                                 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1274
1275                                 spin_lock_bh(&pn->l2tp_session_hlist_lock);
1276                                 hlist_del_init_rcu(&session->global_hlist);
1277                                 spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1278                                 synchronize_rcu();
1279                         }
1280
1281                         if (session->session_close != NULL)
1282                                 (*session->session_close)(session);
1283
1284                         if (session->deref != NULL)
1285                                 (*session->deref)(session);
1286
1287                         write_lock_bh(&tunnel->hlist_lock);
1288
1289                         /* Now restart from the beginning of this hash
1290                          * chain.  We always remove a session from the
1291                          * list so we are guaranteed to make forward
1292                          * progress.
1293                          */
1294                         goto again;
1295                 }
1296         }
1297         write_unlock_bh(&tunnel->hlist_lock);
1298 }
1299
1300 /* Really kill the tunnel.
1301  * Come here only when all sessions have been cleared from the tunnel.
1302  */
1303 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
1304 {
1305         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1306
1307         BUG_ON(atomic_read(&tunnel->ref_count) != 0);
1308         BUG_ON(tunnel->sock != NULL);
1309
1310         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
1311                "%s: free...\n", tunnel->name);
1312
1313         /* Remove from tunnel list */
1314         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1315         list_del_rcu(&tunnel->list);
1316         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1317         synchronize_rcu();
1318
1319         atomic_dec(&l2tp_tunnel_count);
1320         kfree(tunnel);
1321 }
1322
1323 /* Create a socket for the tunnel, if one isn't set up by
1324  * userspace. This is used for static tunnels where there is no
1325  * managing L2TP daemon.
1326  */
1327 static int l2tp_tunnel_sock_create(u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct socket **sockp)
1328 {
1329         int err = -EINVAL;
1330         struct sockaddr_in udp_addr;
1331         struct sockaddr_l2tpip ip_addr;
1332         struct socket *sock = NULL;
1333
1334         switch (cfg->encap) {
1335         case L2TP_ENCAPTYPE_UDP:
1336                 err = sock_create(AF_INET, SOCK_DGRAM, 0, sockp);
1337                 if (err < 0)
1338                         goto out;
1339
1340                 sock = *sockp;
1341
1342                 memset(&udp_addr, 0, sizeof(udp_addr));
1343                 udp_addr.sin_family = AF_INET;
1344                 udp_addr.sin_addr = cfg->local_ip;
1345                 udp_addr.sin_port = htons(cfg->local_udp_port);
1346                 err = kernel_bind(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr));
1347                 if (err < 0)
1348                         goto out;
1349
1350                 udp_addr.sin_family = AF_INET;
1351                 udp_addr.sin_addr = cfg->peer_ip;
1352                 udp_addr.sin_port = htons(cfg->peer_udp_port);
1353                 err = kernel_connect(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr), 0);
1354                 if (err < 0)
1355                         goto out;
1356
1357                 if (!cfg->use_udp_checksums)
1358                         sock->sk->sk_no_check = UDP_CSUM_NOXMIT;
1359
1360                 break;
1361
1362         case L2TP_ENCAPTYPE_IP:
1363                 err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_L2TP, sockp);
1364                 if (err < 0)
1365                         goto out;
1366
1367                 sock = *sockp;
1368
1369                 memset(&ip_addr, 0, sizeof(ip_addr));
1370                 ip_addr.l2tp_family = AF_INET;
1371                 ip_addr.l2tp_addr = cfg->local_ip;
1372                 ip_addr.l2tp_conn_id = tunnel_id;
1373                 err = kernel_bind(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr));
1374                 if (err < 0)
1375                         goto out;
1376
1377                 ip_addr.l2tp_family = AF_INET;
1378                 ip_addr.l2tp_addr = cfg->peer_ip;
1379                 ip_addr.l2tp_conn_id = peer_tunnel_id;
1380                 err = kernel_connect(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr), 0);
1381                 if (err < 0)
1382                         goto out;
1383
1384                 break;
1385
1386         default:
1387                 goto out;
1388         }
1389
1390 out:
1391         if ((err < 0) && sock) {
1392                 sock_release(sock);
1393                 *sockp = NULL;
1394         }
1395
1396         return err;
1397 }
1398
1399 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)
1400 {
1401         struct l2tp_tunnel *tunnel = NULL;
1402         int err;
1403         struct socket *sock = NULL;
1404         struct sock *sk = NULL;
1405         struct l2tp_net *pn;
1406         enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
1407
1408         /* Get the tunnel socket from the fd, which was opened by
1409          * the userspace L2TP daemon. If not specified, create a
1410          * kernel socket.
1411          */
1412         if (fd < 0) {
1413                 err = l2tp_tunnel_sock_create(tunnel_id, peer_tunnel_id, cfg, &sock);
1414                 if (err < 0)
1415                         goto err;
1416         } else {
1417                 err = -EBADF;
1418                 sock = sockfd_lookup(fd, &err);
1419                 if (!sock) {
1420                         printk(KERN_ERR "tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
1421                                tunnel_id, fd, err);
1422                         goto err;
1423                 }
1424         }
1425
1426         sk = sock->sk;
1427
1428         if (cfg != NULL)
1429                 encap = cfg->encap;
1430
1431         /* Quick sanity checks */
1432         switch (encap) {
1433         case L2TP_ENCAPTYPE_UDP:
1434                 err = -EPROTONOSUPPORT;
1435                 if (sk->sk_protocol != IPPROTO_UDP) {
1436                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1437                                tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
1438                         goto err;
1439                 }
1440                 break;
1441         case L2TP_ENCAPTYPE_IP:
1442                 err = -EPROTONOSUPPORT;
1443                 if (sk->sk_protocol != IPPROTO_L2TP) {
1444                         printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
1445                                tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
1446                         goto err;
1447                 }
1448                 break;
1449         }
1450
1451         /* Check if this socket has already been prepped */
1452         tunnel = (struct l2tp_tunnel *)sk->sk_user_data;
1453         if (tunnel != NULL) {
1454                 /* This socket has already been prepped */
1455                 err = -EBUSY;
1456                 goto err;
1457         }
1458
1459         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1460         if (tunnel == NULL) {
1461                 err = -ENOMEM;
1462                 goto err;
1463         }
1464
1465         tunnel->version = version;
1466         tunnel->tunnel_id = tunnel_id;
1467         tunnel->peer_tunnel_id = peer_tunnel_id;
1468         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1469
1470         tunnel->magic = L2TP_TUNNEL_MAGIC;
1471         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1472         rwlock_init(&tunnel->hlist_lock);
1473
1474         /* The net we belong to */
1475         tunnel->l2tp_net = net;
1476         pn = l2tp_pernet(net);
1477
1478         if (cfg != NULL)
1479                 tunnel->debug = cfg->debug;
1480
1481         /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1482         tunnel->encap = encap;
1483         if (encap == L2TP_ENCAPTYPE_UDP) {
1484                 /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1485                 udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
1486                 udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
1487 #if IS_ENABLED(CONFIG_IPV6)
1488                 if (sk->sk_family == PF_INET6)
1489                         udpv6_encap_enable();
1490                 else
1491 #endif
1492                 udp_encap_enable();
1493         }
1494
1495         sk->sk_user_data = tunnel;
1496
1497         /* Hook on the tunnel socket destructor so that we can cleanup
1498          * if the tunnel socket goes away.
1499          */
1500         tunnel->old_sk_destruct = sk->sk_destruct;
1501         sk->sk_destruct = &l2tp_tunnel_destruct;
1502         tunnel->sock = sk;
1503         sk->sk_allocation = GFP_ATOMIC;
1504
1505         /* Add tunnel to our list */
1506         INIT_LIST_HEAD(&tunnel->list);
1507         atomic_inc(&l2tp_tunnel_count);
1508
1509         /* Bump the reference count. The tunnel context is deleted
1510          * only when this drops to zero. Must be done before list insertion
1511          */
1512         l2tp_tunnel_inc_refcount(tunnel);
1513         spin_lock_bh(&pn->l2tp_tunnel_list_lock);
1514         list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
1515         spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
1516
1517         err = 0;
1518 err:
1519         if (tunnelp)
1520                 *tunnelp = tunnel;
1521
1522         /* If tunnel's socket was created by the kernel, it doesn't
1523          *  have a file.
1524          */
1525         if (sock && sock->file)
1526                 sockfd_put(sock);
1527
1528         return err;
1529 }
1530 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1531
1532 /* This function is used by the netlink TUNNEL_DELETE command.
1533  */
1534 int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
1535 {
1536         int err = 0;
1537         struct socket *sock = tunnel->sock ? tunnel->sock->sk_socket : NULL;
1538
1539         /* Force the tunnel socket to close. This will eventually
1540          * cause the tunnel to be deleted via the normal socket close
1541          * mechanisms when userspace closes the tunnel socket.
1542          */
1543         if (sock != NULL) {
1544                 err = inet_shutdown(sock, 2);
1545
1546                 /* If the tunnel's socket was created by the kernel,
1547                  * close the socket here since the socket was not
1548                  * created by userspace.
1549                  */
1550                 if (sock->file == NULL)
1551                         err = inet_release(sock);
1552         }
1553
1554         return err;
1555 }
1556 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
1557
1558 /* Really kill the session.
1559  */
1560 void l2tp_session_free(struct l2tp_session *session)
1561 {
1562         struct l2tp_tunnel *tunnel;
1563
1564         BUG_ON(atomic_read(&session->ref_count) != 0);
1565
1566         tunnel = session->tunnel;
1567         if (tunnel != NULL) {
1568                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1569
1570                 /* Delete the session from the hash */
1571                 write_lock_bh(&tunnel->hlist_lock);
1572                 hlist_del_init(&session->hlist);
1573                 write_unlock_bh(&tunnel->hlist_lock);
1574
1575                 /* Unlink from the global hash if not L2TPv2 */
1576                 if (tunnel->version != L2TP_HDR_VER_2) {
1577                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1578
1579                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1580                         hlist_del_init_rcu(&session->global_hlist);
1581                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1582                         synchronize_rcu();
1583                 }
1584
1585                 if (session->session_id != 0)
1586                         atomic_dec(&l2tp_session_count);
1587
1588                 sock_put(tunnel->sock);
1589
1590                 /* This will delete the tunnel context if this
1591                  * is the last session on the tunnel.
1592                  */
1593                 session->tunnel = NULL;
1594                 l2tp_tunnel_dec_refcount(tunnel);
1595         }
1596
1597         kfree(session);
1598
1599         return;
1600 }
1601 EXPORT_SYMBOL_GPL(l2tp_session_free);
1602
1603 /* This function is used by the netlink SESSION_DELETE command and by
1604    pseudowire modules.
1605  */
1606 int l2tp_session_delete(struct l2tp_session *session)
1607 {
1608         if (session->session_close != NULL)
1609                 (*session->session_close)(session);
1610
1611         l2tp_session_dec_refcount(session);
1612
1613         return 0;
1614 }
1615 EXPORT_SYMBOL_GPL(l2tp_session_delete);
1616
1617
1618 /* We come here whenever a session's send_seq, cookie_len or
1619  * l2specific_len parameters are set.
1620  */
1621 static void l2tp_session_set_header_len(struct l2tp_session *session, int version)
1622 {
1623         if (version == L2TP_HDR_VER_2) {
1624                 session->hdr_len = 6;
1625                 if (session->send_seq)
1626                         session->hdr_len += 4;
1627         } else {
1628                 session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
1629                 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
1630                         session->hdr_len += 4;
1631         }
1632
1633 }
1634
1635 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)
1636 {
1637         struct l2tp_session *session;
1638
1639         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1640         if (session != NULL) {
1641                 session->magic = L2TP_SESSION_MAGIC;
1642                 session->tunnel = tunnel;
1643
1644                 session->session_id = session_id;
1645                 session->peer_session_id = peer_session_id;
1646                 session->nr = 1;
1647
1648                 sprintf(&session->name[0], "sess %u/%u",
1649                         tunnel->tunnel_id, session->session_id);
1650
1651                 skb_queue_head_init(&session->reorder_q);
1652
1653                 INIT_HLIST_NODE(&session->hlist);
1654                 INIT_HLIST_NODE(&session->global_hlist);
1655
1656                 /* Inherit debug options from tunnel */
1657                 session->debug = tunnel->debug;
1658
1659                 if (cfg) {
1660                         session->pwtype = cfg->pw_type;
1661                         session->debug = cfg->debug;
1662                         session->mtu = cfg->mtu;
1663                         session->mru = cfg->mru;
1664                         session->send_seq = cfg->send_seq;
1665                         session->recv_seq = cfg->recv_seq;
1666                         session->lns_mode = cfg->lns_mode;
1667                         session->reorder_timeout = cfg->reorder_timeout;
1668                         session->offset = cfg->offset;
1669                         session->l2specific_type = cfg->l2specific_type;
1670                         session->l2specific_len = cfg->l2specific_len;
1671                         session->cookie_len = cfg->cookie_len;
1672                         memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
1673                         session->peer_cookie_len = cfg->peer_cookie_len;
1674                         memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
1675                 }
1676
1677                 if (tunnel->version == L2TP_HDR_VER_2)
1678                         session->build_header = l2tp_build_l2tpv2_header;
1679                 else
1680                         session->build_header = l2tp_build_l2tpv3_header;
1681
1682                 l2tp_session_set_header_len(session, tunnel->version);
1683
1684                 /* Bump the reference count. The session context is deleted
1685                  * only when this drops to zero.
1686                  */
1687                 l2tp_session_inc_refcount(session);
1688                 l2tp_tunnel_inc_refcount(tunnel);
1689
1690                 /* Ensure tunnel socket isn't deleted */
1691                 sock_hold(tunnel->sock);
1692
1693                 /* Add session to the tunnel's hash list */
1694                 write_lock_bh(&tunnel->hlist_lock);
1695                 hlist_add_head(&session->hlist,
1696                                l2tp_session_id_hash(tunnel, session_id));
1697                 write_unlock_bh(&tunnel->hlist_lock);
1698
1699                 /* And to the global session list if L2TPv3 */
1700                 if (tunnel->version != L2TP_HDR_VER_2) {
1701                         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
1702
1703                         spin_lock_bh(&pn->l2tp_session_hlist_lock);
1704                         hlist_add_head_rcu(&session->global_hlist,
1705                                            l2tp_session_id_hash_2(pn, session_id));
1706                         spin_unlock_bh(&pn->l2tp_session_hlist_lock);
1707                 }
1708
1709                 /* Ignore management session in session count value */
1710                 if (session->session_id != 0)
1711                         atomic_inc(&l2tp_session_count);
1712         }
1713
1714         return session;
1715 }
1716 EXPORT_SYMBOL_GPL(l2tp_session_create);
1717
1718 /*****************************************************************************
1719  * Init and cleanup
1720  *****************************************************************************/
1721
1722 static __net_init int l2tp_init_net(struct net *net)
1723 {
1724         struct l2tp_net *pn = net_generic(net, l2tp_net_id);
1725         int hash;
1726
1727         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1728         spin_lock_init(&pn->l2tp_tunnel_list_lock);
1729
1730         for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
1731                 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
1732
1733         spin_lock_init(&pn->l2tp_session_hlist_lock);
1734
1735         return 0;
1736 }
1737
1738 static struct pernet_operations l2tp_net_ops = {
1739         .init = l2tp_init_net,
1740         .id   = &l2tp_net_id,
1741         .size = sizeof(struct l2tp_net),
1742 };
1743
1744 static int __init l2tp_init(void)
1745 {
1746         int rc = 0;
1747
1748         rc = register_pernet_device(&l2tp_net_ops);
1749         if (rc)
1750                 goto out;
1751
1752         printk(KERN_INFO "L2TP core driver, %s\n", L2TP_DRV_VERSION);
1753
1754 out:
1755         return rc;
1756 }
1757
1758 static void __exit l2tp_exit(void)
1759 {
1760         unregister_pernet_device(&l2tp_net_ops);
1761 }
1762
1763 module_init(l2tp_init);
1764 module_exit(l2tp_exit);
1765
1766 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1767 MODULE_DESCRIPTION("L2TP core");
1768 MODULE_LICENSE("GPL");
1769 MODULE_VERSION(L2TP_DRV_VERSION);
1770