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/uaccess.h>
  25
  26 #include <linux/kernel.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/kthread.h>
  29 #include <linux/sched.h>
  30 #include <linux/slab.h>
  31 #include <linux/errno.h>
  32 #include <linux/jiffies.h>
  33
  34 #include <linux/netdevice.h>
  35 #include <linux/net.h>
  36 #include <linux/inetdevice.h>
  37 #include <linux/skbuff.h>
  38 #include <linux/init.h>
  39 #include <linux/ip.h>
  40 #include <linux/udp.h>
  41 #include <linux/hash.h>
  42 #include <linux/sort.h>
  43 #include <linux/file.h>
  44 #include <linux/nsproxy.h>
  45 #include <net/net_namespace.h>
  46 #include <net/netns/generic.h>
  47 #include <net/dst.h>
  48 #include <net/ip.h>
  49 #include <net/udp.h>
  50 #include <net/xfrm.h>
  51
  52 #include <asm/byteorder.h>
  53 #include <asm/atomic.h>
  54
  55 #include "l2tp_core.h"
  56
  57 #define L2TP_DRV_VERSION        "V2.0"
  58
  59 /* L2TP header constants */
  60 #define L2TP_HDRFLAG_T     0x8000
  61 #define L2TP_HDRFLAG_L     0x4000
  62 #define L2TP_HDRFLAG_S     0x0800
  63 #define L2TP_HDRFLAG_O     0x0200
  64 #define L2TP_HDRFLAG_P     0x0100
  65
  66 #define L2TP_HDR_VER_MASK  0x000F
  67 #define L2TP_HDR_VER_2     0x0002
  68
  69 /* L2TPv3 default L2-specific sublayer */
  70 #define L2TP_SLFLAG_S      0x40000000
  71 #define L2TP_SL_SEQ_MASK   0x00ffffff
  72
  73 #define L2TP_HDR_SIZE_SEQ               10
  74 #define L2TP_HDR_SIZE_NOSEQ             6
  75
  76 /* Default trace flags */
  77 #define L2TP_DEFAULT_DEBUG_FLAGS        0
  78
  79 #define PRINTK(_mask, _type, _lvl, _fmt, args...)                       \
  80         do {                                                            \
  81                 if ((_mask) & (_type))                                  \
  82                         printk(_lvl "L2TP: " _fmt, ##args);             \
  83         } while (0)
  84
  85 /* Private data stored for received packets in the skb.
  86  */
  87 struct l2tp_skb_cb {
  88         u16                     ns;
  89         u16                     has_seq;
  90         u16                     length;
  91         unsigned long           expires;
  92 };
  93
  94 #define L2TP_SKB_CB(skb)        ((struct l2tp_skb_cb *) &skb->cb[sizeof(struct inet_skb_parm)])
  95
  96 static atomic_t l2tp_tunnel_count;
  97 static atomic_t l2tp_session_count;
  98
  99 /* per-net private data for this module */
 100 static unsigned int l2tp_net_id;
 101 struct l2tp_net {
 102         struct list_head l2tp_tunnel_list;
 103         rwlock_t l2tp_tunnel_list_lock;
 104 };
 105
 106 static inline struct l2tp_net *l2tp_pernet(struct net *net)
 107 {
 108         BUG_ON(!net);
 109
 110         return net_generic(net, l2tp_net_id);
 111 }
 112
 113 /* Session hash list.
 114  * The session_id SHOULD be random according to RFC2661, but several
 115  * L2TP implementations (Cisco and Microsoft) use incrementing
 116  * session_ids.  So we do a real hash on the session_id, rather than a
 117  * simple bitmask.
 118  */
 119 static inline struct hlist_head *
 120 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
 121 {
 122         return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
 123 }
 124
 125 /* Lookup a session by id
 126  */
 127 struct l2tp_session *l2tp_session_find(struct l2tp_tunnel *tunnel, u32 session_id)
 128 {
 129         struct hlist_head *session_list =
 130                 l2tp_session_id_hash(tunnel, session_id);
 131         struct l2tp_session *session;
 132         struct hlist_node *walk;
 133
 134         read_lock_bh(&tunnel->hlist_lock);
 135         hlist_for_each_entry(session, walk, session_list, hlist) {
 136                 if (session->session_id == session_id) {
 137                         read_unlock_bh(&tunnel->hlist_lock);
 138                         return session;
 139                 }
 140         }
 141         read_unlock_bh(&tunnel->hlist_lock);
 142
 143         return NULL;
 144 }
 145 EXPORT_SYMBOL_GPL(l2tp_session_find);
 146
 147 struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth)
 148 {
 149         int hash;
 150         struct hlist_node *walk;
 151         struct l2tp_session *session;
 152         int count = 0;
 153
 154         read_lock_bh(&tunnel->hlist_lock);
 155         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 156                 hlist_for_each_entry(session, walk, &tunnel->session_hlist[hash], hlist) {
 157                         if (++count > nth) {
 158                                 read_unlock_bh(&tunnel->hlist_lock);
 159                                 return session;
 160                         }
 161                 }
 162         }
 163
 164         read_unlock_bh(&tunnel->hlist_lock);
 165
 166         return NULL;
 167 }
 168 EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
 169
 170 /* Lookup a tunnel by id
 171  */
 172 struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
 173 {
 174         struct l2tp_tunnel *tunnel;
 175         struct l2tp_net *pn = l2tp_pernet(net);
 176
 177         read_lock_bh(&pn->l2tp_tunnel_list_lock);
 178         list_for_each_entry(tunnel, &pn->l2tp_tunnel_list, list) {
 179                 if (tunnel->tunnel_id == tunnel_id) {
 180                         read_unlock_bh(&pn->l2tp_tunnel_list_lock);
 181                         return tunnel;
 182                 }
 183         }
 184         read_unlock_bh(&pn->l2tp_tunnel_list_lock);
 185
 186         return NULL;
 187 }
 188 EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
 189
 190 struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
 191 {
 192         struct l2tp_net *pn = l2tp_pernet(net);
 193         struct l2tp_tunnel *tunnel;
 194         int count = 0;
 195
 196         read_lock_bh(&pn->l2tp_tunnel_list_lock);
 197         list_for_each_entry(tunnel, &pn->l2tp_tunnel_list, list) {
 198                 if (++count > nth) {
 199                         read_unlock_bh(&pn->l2tp_tunnel_list_lock);
 200                         return tunnel;
 201                 }
 202         }
 203
 204         read_unlock_bh(&pn->l2tp_tunnel_list_lock);
 205
 206         return NULL;
 207 }
 208 EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
 209
 210 /*****************************************************************************
 211  * Receive data handling
 212  *****************************************************************************/
 213
 214 /* Queue a skb in order. We come here only if the skb has an L2TP sequence
 215  * number.
 216  */
 217 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
 218 {
 219         struct sk_buff *skbp;
 220         struct sk_buff *tmp;
 221         u16 ns = L2TP_SKB_CB(skb)->ns;
 222
 223         spin_lock_bh(&session->reorder_q.lock);
 224         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
 225                 if (L2TP_SKB_CB(skbp)->ns > ns) {
 226                         __skb_queue_before(&session->reorder_q, skbp, skb);
 227                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 228                                "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
 229                                session->name, ns, L2TP_SKB_CB(skbp)->ns,
 230                                skb_queue_len(&session->reorder_q));
 231                         session->stats.rx_oos_packets++;
 232                         goto out;
 233                 }
 234         }
 235
 236         __skb_queue_tail(&session->reorder_q, skb);
 237
 238 out:
 239         spin_unlock_bh(&session->reorder_q.lock);
 240 }
 241
 242 /* Dequeue a single skb.
 243  */
 244 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
 245 {
 246         struct l2tp_tunnel *tunnel = session->tunnel;
 247         int length = L2TP_SKB_CB(skb)->length;
 248
 249         /* We're about to requeue the skb, so return resources
 250          * to its current owner (a socket receive buffer).
 251          */
 252         skb_orphan(skb);
 253
 254         tunnel->stats.rx_packets++;
 255         tunnel->stats.rx_bytes += length;
 256         session->stats.rx_packets++;
 257         session->stats.rx_bytes += length;
 258
 259         if (L2TP_SKB_CB(skb)->has_seq) {
 260                 /* Bump our Nr */
 261                 session->nr++;
 262                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 263                        "%s: updated nr to %hu\n", session->name, session->nr);
 264         }
 265
 266         /* call private receive handler */
 267         if (session->recv_skb != NULL)
 268                 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 269         else
 270                 kfree_skb(skb);
 271
 272         if (session->deref)
 273                 (*session->deref)(session);
 274 }
 275
 276 /* Dequeue skbs from the session's reorder_q, subject to packet order.
 277  * Skbs that have been in the queue for too long are simply discarded.
 278  */
 279 static void l2tp_recv_dequeue(struct l2tp_session *session)
 280 {
 281         struct sk_buff *skb;
 282         struct sk_buff *tmp;
 283
 284         /* If the pkt at the head of the queue has the nr that we
 285          * expect to send up next, dequeue it and any other
 286          * in-sequence packets behind it.
 287          */
 288         spin_lock_bh(&session->reorder_q.lock);
 289         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
 290                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
 291                         session->stats.rx_seq_discards++;
 292                         session->stats.rx_errors++;
 293                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 294                                "%s: oos pkt %hu len %d discarded (too old), "
 295                                "waiting for %hu, reorder_q_len=%d\n",
 296                                session->name, L2TP_SKB_CB(skb)->ns,
 297                                L2TP_SKB_CB(skb)->length, session->nr,
 298                                skb_queue_len(&session->reorder_q));
 299                         __skb_unlink(skb, &session->reorder_q);
 300                         kfree_skb(skb);
 301                         if (session->deref)
 302                                 (*session->deref)(session);
 303                         continue;
 304                 }
 305
 306                 if (L2TP_SKB_CB(skb)->has_seq) {
 307                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 308                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 309                                        "%s: holding oos pkt %hu len %d, "
 310                                        "waiting for %hu, reorder_q_len=%d\n",
 311                                        session->name, L2TP_SKB_CB(skb)->ns,
 312                                        L2TP_SKB_CB(skb)->length, session->nr,
 313                                        skb_queue_len(&session->reorder_q));
 314                                 goto out;
 315                         }
 316                 }
 317                 __skb_unlink(skb, &session->reorder_q);
 318
 319                 /* Process the skb. We release the queue lock while we
 320                  * do so to let other contexts process the queue.
 321                  */
 322                 spin_unlock_bh(&session->reorder_q.lock);
 323                 l2tp_recv_dequeue_skb(session, skb);
 324                 spin_lock_bh(&session->reorder_q.lock);
 325         }
 326
 327 out:
 328         spin_unlock_bh(&session->reorder_q.lock);
 329 }
 330
 331 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 332                                            struct sk_buff *skb)
 333 {
 334         struct udphdr *uh = udp_hdr(skb);
 335         u16 ulen = ntohs(uh->len);
 336         struct inet_sock *inet;
 337         __wsum psum;
 338
 339         if (sk->sk_no_check || skb_csum_unnecessary(skb) || !uh->check)
 340                 return 0;
 341
 342         inet = inet_sk(sk);
 343         psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr, ulen,
 344                                   IPPROTO_UDP, 0);
 345
 346         if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
 347             !csum_fold(csum_add(psum, skb->csum)))
 348                 return 0;
 349
 350         skb->csum = psum;
 351
 352         return __skb_checksum_complete(skb);
 353 }
 354
 355 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
 356  * here. The skb is not on a list when we get here.
 357  * Returns 0 if the packet was a data packet and was successfully passed on.
 358  * Returns 1 if the packet was not a good data packet and could not be
 359  * forwarded.  All such packets are passed up to userspace to deal with.
 360  */
 361 int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 362                        int (*payload_hook)(struct sk_buff *skb))
 363 {
 364         struct l2tp_session *session = NULL;
 365         unsigned char *ptr, *optr;
 366         u16 hdrflags;
 367         u32 tunnel_id, session_id;
 368         int length;
 369         int offset;
 370         u16 version;
 371         u16 ns, nr;
 372
 373         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
 374                 goto discard_bad_csum;
 375
 376         /* UDP always verifies the packet length. */
 377         __skb_pull(skb, sizeof(struct udphdr));
 378
 379         /* Short packet? */
 380         if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
 381                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 382                        "%s: recv short packet (len=%d)\n", tunnel->name, skb->len);
 383                 goto error;
 384         }
 385
 386         /* Point to L2TP header */
 387         optr = ptr = skb->data;
 388
 389         /* Trace packet contents, if enabled */
 390         if (tunnel->debug & L2TP_MSG_DATA) {
 391                 length = min(32u, skb->len);
 392                 if (!pskb_may_pull(skb, length))
 393                         goto error;
 394
 395                 printk(KERN_DEBUG "%s: recv: ", tunnel->name);
 396
 397                 offset = 0;
 398                 do {
 399                         printk(" %02X", ptr[offset]);
 400                 } while (++offset < length);
 401
 402                 printk("\n");
 403         }
 404
 405         /* Get L2TP header flags */
 406         hdrflags = ntohs(*(__be16 *)ptr);
 407
 408         /* Check protocol version */
 409         version = hdrflags & L2TP_HDR_VER_MASK;
 410         if (version != tunnel->version) {
 411                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 412                        "%s: recv protocol version mismatch: got %d expected %d\n",
 413                        tunnel->name, version, tunnel->version);
 414                 goto error;
 415         }
 416
 417         /* Get length of L2TP packet */
 418         length = skb->len;
 419
 420         /* If type is control packet, it is handled by userspace. */
 421         if (hdrflags & L2TP_HDRFLAG_T) {
 422                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 423                        "%s: recv control packet, len=%d\n", tunnel->name, length);
 424                 goto error;
 425         }
 426
 427         /* Skip flags */
 428         ptr += 2;
 429
 430         /* If length is present, skip it */
 431         if (hdrflags & L2TP_HDRFLAG_L)
 432                 ptr += 2;
 433
 434         /* Extract tunnel and session ID */
 435         tunnel_id = ntohs(*(__be16 *) ptr);
 436         ptr += 2;
 437         session_id = ntohs(*(__be16 *) ptr);
 438         ptr += 2;
 439
 440         /* Find the session context */
 441         session = l2tp_session_find(tunnel, session_id);
 442         if (!session) {
 443                 /* Not found? Pass to userspace to deal with */
 444                 PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 445                        "%s: no session found (%hu/%hu). Passing up.\n",
 446                        tunnel->name, tunnel_id, session_id);
 447                 goto error;
 448         }
 449
 450         /* The ref count is increased since we now hold a pointer to
 451          * the session. Take care to decrement the refcnt when exiting
 452          * this function from now on...
 453          */
 454         l2tp_session_inc_refcount(session);
 455         if (session->ref)
 456                 (*session->ref)(session);
 457
 458         /* Handle the optional sequence numbers. Sequence numbers are
 459          * in different places for L2TPv2 and L2TPv3.
 460          *
 461          * If we are the LAC, enable/disable sequence numbers under
 462          * the control of the LNS.  If no sequence numbers present but
 463          * we were expecting them, discard frame.
 464          */
 465         ns = nr = 0;
 466         L2TP_SKB_CB(skb)->has_seq = 0;
 467         if (hdrflags & L2TP_HDRFLAG_S) {
 468                 ns = (u16) ntohs(*(__be16 *) ptr);
 469                 ptr += 2;
 470                 nr = ntohs(*(__be16 *) ptr);
 471                 ptr += 2;
 472
 473                 /* Store L2TP info in the skb */
 474                 L2TP_SKB_CB(skb)->ns = ns;
 475                 L2TP_SKB_CB(skb)->has_seq = 1;
 476
 477                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 478                        "%s: recv data ns=%hu, nr=%hu, session nr=%hu\n",
 479                        session->name, ns, nr, session->nr);
 480         }
 481
 482         if (L2TP_SKB_CB(skb)->has_seq) {
 483                 /* Received a packet with sequence numbers. If we're the LNS,
 484                  * check if we sre sending sequence numbers and if not,
 485                  * configure it so.
 486                  */
 487                 if ((!session->lns_mode) && (!session->send_seq)) {
 488                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 489                                "%s: requested to enable seq numbers by LNS\n",
 490                                session->name);
 491                         session->send_seq = -1;
 492                 }
 493         } else {
 494                 /* No sequence numbers.
 495                  * If user has configured mandatory sequence numbers, discard.
 496                  */
 497                 if (session->recv_seq) {
 498                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 499                                "%s: recv data has no seq numbers when required. "
 500                                "Discarding\n", session->name);
 501                         session->stats.rx_seq_discards++;
 502                         goto discard;
 503                 }
 504
 505                 /* If we're the LAC and we're sending sequence numbers, the
 506                  * LNS has requested that we no longer send sequence numbers.
 507                  * If we're the LNS and we're sending sequence numbers, the
 508                  * LAC is broken. Discard the frame.
 509                  */
 510                 if ((!session->lns_mode) && (session->send_seq)) {
 511                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_INFO,
 512                                "%s: requested to disable seq numbers by LNS\n",
 513                                session->name);
 514                         session->send_seq = 0;
 515                 } else if (session->send_seq) {
 516                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
 517                                "%s: recv data has no seq numbers when required. "
 518                                "Discarding\n", session->name);
 519                         session->stats.rx_seq_discards++;
 520                         goto discard;
 521                 }
 522         }
 523
 524         /* If offset bit set, skip it. */
 525         if (hdrflags & L2TP_HDRFLAG_O) {
 526                 offset = ntohs(*(__be16 *)ptr);
 527                 ptr += 2 + offset;
 528         }
 529
 530         offset = ptr - optr;
 531         if (!pskb_may_pull(skb, offset))
 532                 goto discard;
 533
 534         __skb_pull(skb, offset);
 535
 536         /* If caller wants to process the payload before we queue the
 537          * packet, do so now.
 538          */
 539         if (payload_hook)
 540                 if ((*payload_hook)(skb))
 541                         goto discard;
 542
 543         /* Prepare skb for adding to the session's reorder_q.  Hold
 544          * packets for max reorder_timeout or 1 second if not
 545          * reordering.
 546          */
 547         L2TP_SKB_CB(skb)->length = length;
 548         L2TP_SKB_CB(skb)->expires = jiffies +
 549                 (session->reorder_timeout ? session->reorder_timeout : HZ);
 550
 551         /* Add packet to the session's receive queue. Reordering is done here, if
 552          * enabled. Saved L2TP protocol info is stored in skb->sb[].
 553          */
 554         if (L2TP_SKB_CB(skb)->has_seq) {
 555                 if (session->reorder_timeout != 0) {
 556                         /* Packet reordering enabled. Add skb to session's
 557                          * reorder queue, in order of ns.
 558                          */
 559                         l2tp_recv_queue_skb(session, skb);
 560                 } else {
 561                         /* Packet reordering disabled. Discard out-of-sequence
 562                          * packets
 563                          */
 564                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
 565                                 session->stats.rx_seq_discards++;
 566                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 567                                        "%s: oos pkt %hu len %d discarded, "
 568                                        "waiting for %hu, reorder_q_len=%d\n",
 569                                        session->name, L2TP_SKB_CB(skb)->ns,
 570                                        L2TP_SKB_CB(skb)->length, session->nr,
 571                                        skb_queue_len(&session->reorder_q));
 572                                 goto discard;
 573                         }
 574                         skb_queue_tail(&session->reorder_q, skb);
 575                 }
 576         } else {
 577                 /* No sequence numbers. Add the skb to the tail of the
 578                  * reorder queue. This ensures that it will be
 579                  * delivered after all previous sequenced skbs.
 580                  */
 581                 skb_queue_tail(&session->reorder_q, skb);
 582         }
 583
 584         /* Try to dequeue as many skbs from reorder_q as we can. */
 585         l2tp_recv_dequeue(session);
 586
 587         l2tp_session_dec_refcount(session);
 588
 589         return 0;
 590
 591 discard:
 592         session->stats.rx_errors++;
 593         kfree_skb(skb);
 594
 595         if (session->deref)
 596                 (*session->deref)(session);
 597
 598         l2tp_session_dec_refcount(session);
 599
 600         return 0;
 601
 602 discard_bad_csum:
 603         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
 604         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
 605         tunnel->stats.rx_errors++;
 606         kfree_skb(skb);
 607
 608         return 0;
 609
 610 error:
 611         /* Put UDP header back */
 612         __skb_push(skb, sizeof(struct udphdr));
 613
 614         return 1;
 615 }
 616 EXPORT_SYMBOL_GPL(l2tp_udp_recv_core);
 617
 618 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
 619  * Return codes:
 620  * 0 : success.
 621  * <0: error
 622  * >0: skb should be passed up to userspace as UDP.
 623  */
 624 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 625 {
 626         struct l2tp_tunnel *tunnel;
 627
 628         tunnel = l2tp_sock_to_tunnel(sk);
 629         if (tunnel == NULL)
 630                 goto pass_up;
 631
 632         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_DEBUG,
 633                "%s: received %d bytes\n", tunnel->name, skb->len);
 634
 635         if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
 636                 goto pass_up_put;
 637
 638         sock_put(sk);
 639         return 0;
 640
 641 pass_up_put:
 642         sock_put(sk);
 643 pass_up:
 644         return 1;
 645 }
 646 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
 647
 648 /************************************************************************
 649  * Transmit handling
 650  ***********************************************************************/
 651
 652 /* Build an L2TP header for the session into the buffer provided.
 653  */
 654 static void l2tp_build_l2tpv2_header(struct l2tp_tunnel *tunnel,
 655                                      struct l2tp_session *session,
 656                                      void *buf)
 657 {
 658         __be16 *bufp = buf;
 659         u16 flags = L2TP_HDR_VER_2;
 660         u32 tunnel_id = tunnel->peer_tunnel_id;
 661         u32 session_id = session->peer_session_id;
 662
 663         if (session->send_seq)
 664                 flags |= L2TP_HDRFLAG_S;
 665
 666         /* Setup L2TP header. */
 667         *bufp++ = htons(flags);
 668         *bufp++ = htons(tunnel_id);
 669         *bufp++ = htons(session_id);
 670         if (session->send_seq) {
 671                 *bufp++ = htons(session->ns);
 672                 *bufp++ = 0;
 673                 session->ns++;
 674                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
 675                        "%s: updated ns to %hu\n", session->name, session->ns);
 676         }
 677 }
 678
 679 void l2tp_build_l2tp_header(struct l2tp_session *session, void *buf)
 680 {
 681         struct l2tp_tunnel *tunnel = session->tunnel;
 682
 683         BUG_ON(tunnel->version != L2TP_HDR_VER_2);
 684         l2tp_build_l2tpv2_header(tunnel, session, buf);
 685 }
 686 EXPORT_SYMBOL_GPL(l2tp_build_l2tp_header);
 687
 688 int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, size_t data_len)
 689 {
 690         struct l2tp_tunnel *tunnel = session->tunnel;
 691         unsigned int len = skb->len;
 692         int error;
 693
 694         /* Debug */
 695         if (session->send_seq)
 696                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
 697                        "%s: send %Zd bytes, ns=%hu\n", session->name,
 698                        data_len, session->ns - 1);
 699         else
 700                 PRINTK(session->debug, L2TP_MSG_DATA, KERN_DEBUG,
 701                        "%s: send %Zd bytes\n", session->name, data_len);
 702
 703         if (session->debug & L2TP_MSG_DATA) {
 704                 int i;
 705                 unsigned char *datap = skb->data + sizeof(struct udphdr);
 706
 707                 printk(KERN_DEBUG "%s: xmit:", session->name);
 708                 for (i = 0; i < (len - sizeof(struct udphdr)); i++) {
 709                         printk(" %02X", *datap++);
 710                         if (i == 31) {
 711                                 printk(" ...");
 712                                 break;
 713                         }
 714                 }
 715                 printk("\n");
 716         }
 717
 718         /* Queue the packet to IP for output */
 719         error = ip_queue_xmit(skb, 1);
 720
 721         /* Update stats */
 722         if (error >= 0) {
 723                 tunnel->stats.tx_packets++;
 724                 tunnel->stats.tx_bytes += len;
 725                 session->stats.tx_packets++;
 726                 session->stats.tx_bytes += len;
 727         } else {
 728                 tunnel->stats.tx_errors++;
 729                 session->stats.tx_errors++;
 730         }
 731
 732         return 0;
 733 }
 734 EXPORT_SYMBOL_GPL(l2tp_xmit_core);
 735
 736 /* Automatically called when the skb is freed.
 737  */
 738 static void l2tp_sock_wfree(struct sk_buff *skb)
 739 {
 740         sock_put(skb->sk);
 741 }
 742
 743 /* For data skbs that we transmit, we associate with the tunnel socket
 744  * but don't do accounting.
 745  */
 746 static inline void l2tp_skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
 747 {
 748         sock_hold(sk);
 749         skb->sk = sk;
 750         skb->destructor = l2tp_sock_wfree;
 751 }
 752
 753 /* If caller requires the skb to have a ppp header, the header must be
 754  * inserted in the skb data before calling this function.
 755  */
 756 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
 757 {
 758         int data_len = skb->len;
 759         struct sock *sk = session->tunnel->sock;
 760         struct udphdr *uh;
 761         unsigned int udp_len;
 762         struct inet_sock *inet;
 763         __wsum csum;
 764         int old_headroom;
 765         int new_headroom;
 766         int headroom;
 767
 768         /* Check that there's enough headroom in the skb to insert IP,
 769          * UDP and L2TP headers. If not enough, expand it to
 770          * make room. Adjust truesize.
 771          */
 772         headroom = NET_SKB_PAD + sizeof(struct iphdr) +
 773                 sizeof(struct udphdr) + hdr_len;
 774         old_headroom = skb_headroom(skb);
 775         if (skb_cow_head(skb, headroom))
 776                 goto abort;
 777
 778         new_headroom = skb_headroom(skb);
 779         skb_orphan(skb);
 780         skb->truesize += new_headroom - old_headroom;
 781
 782         /* Setup L2TP header */
 783         l2tp_build_l2tp_header(session, __skb_push(skb, hdr_len));
 784         udp_len = sizeof(struct udphdr) + hdr_len + data_len;
 785
 786         /* Setup UDP header */
 787         inet = inet_sk(sk);
 788         __skb_push(skb, sizeof(*uh));
 789         skb_reset_transport_header(skb);
 790         uh = udp_hdr(skb);
 791         uh->source = inet->inet_sport;
 792         uh->dest = inet->inet_dport;
 793         uh->len = htons(udp_len);
 794
 795         uh->check = 0;
 796
 797         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 798         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
 799                               IPSKB_REROUTED);
 800         nf_reset(skb);
 801
 802         /* Get routing info from the tunnel socket */
 803         skb_dst_drop(skb);
 804         skb_dst_set(skb, dst_clone(__sk_dst_get(sk)));
 805         l2tp_skb_set_owner_w(skb, sk);
 806
 807         /* Calculate UDP checksum if configured to do so */
 808         if (sk->sk_no_check == UDP_CSUM_NOXMIT)
 809                 skb->ip_summed = CHECKSUM_NONE;
 810         else if ((skb_dst(skb) && skb_dst(skb)->dev) &&
 811                  (!(skb_dst(skb)->dev->features & NETIF_F_V4_CSUM))) {
 812                 skb->ip_summed = CHECKSUM_COMPLETE;
 813                 csum = skb_checksum(skb, 0, udp_len, 0);
 814                 uh->check = csum_tcpudp_magic(inet->inet_saddr,
 815                                               inet->inet_daddr,
 816                                               udp_len, IPPROTO_UDP, csum);
 817                 if (uh->check == 0)
 818                         uh->check = CSUM_MANGLED_0;
 819         } else {
 820                 skb->ip_summed = CHECKSUM_PARTIAL;
 821                 skb->csum_start = skb_transport_header(skb) - skb->head;
 822                 skb->csum_offset = offsetof(struct udphdr, check);
 823                 uh->check = ~csum_tcpudp_magic(inet->inet_saddr,
 824                                                inet->inet_daddr,
 825                                                udp_len, IPPROTO_UDP, 0);
 826         }
 827
 828         l2tp_xmit_core(session, skb, data_len);
 829
 830 abort:
 831         return 0;
 832 }
 833 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
 834
 835 /*****************************************************************************
 836  * Tinnel and session create/destroy.
 837  *****************************************************************************/
 838
 839 /* Tunnel socket destruct hook.
 840  * The tunnel context is deleted only when all session sockets have been
 841  * closed.
 842  */
 843 void l2tp_tunnel_destruct(struct sock *sk)
 844 {
 845         struct l2tp_tunnel *tunnel;
 846
 847         tunnel = sk->sk_user_data;
 848         if (tunnel == NULL)
 849                 goto end;
 850
 851         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
 852                "%s: closing...\n", tunnel->name);
 853
 854         /* Close all sessions */
 855         l2tp_tunnel_closeall(tunnel);
 856
 857         /* No longer an encapsulation socket. See net/ipv4/udp.c */
 858         (udp_sk(sk))->encap_type = 0;
 859         (udp_sk(sk))->encap_rcv = NULL;
 860
 861         /* Remove hooks into tunnel socket */
 862         tunnel->sock = NULL;
 863         sk->sk_destruct = tunnel->old_sk_destruct;
 864         sk->sk_user_data = NULL;
 865
 866         /* Call the original destructor */
 867         if (sk->sk_destruct)
 868                 (*sk->sk_destruct)(sk);
 869
 870         /* We're finished with the socket */
 871         l2tp_tunnel_dec_refcount(tunnel);
 872
 873 end:
 874         return;
 875 }
 876 EXPORT_SYMBOL(l2tp_tunnel_destruct);
 877
 878 /* When the tunnel is closed, all the attached sessions need to go too.
 879  */
 880 void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
 881 {
 882         int hash;
 883         struct hlist_node *walk;
 884         struct hlist_node *tmp;
 885         struct l2tp_session *session;
 886
 887         BUG_ON(tunnel == NULL);
 888
 889         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
 890                "%s: closing all sessions...\n", tunnel->name);
 891
 892         write_lock_bh(&tunnel->hlist_lock);
 893         for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
 894 again:
 895                 hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
 896                         session = hlist_entry(walk, struct l2tp_session, hlist);
 897
 898                         PRINTK(session->debug, L2TP_MSG_CONTROL, KERN_INFO,
 899                                "%s: closing session\n", session->name);
 900
 901                         hlist_del_init(&session->hlist);
 902
 903                         /* Since we should hold the sock lock while
 904                          * doing any unbinding, we need to release the
 905                          * lock we're holding before taking that lock.
 906                          * Hold a reference to the sock so it doesn't
 907                          * disappear as we're jumping between locks.
 908                          */
 909                         if (session->ref != NULL)
 910                                 (*session->ref)(session);
 911
 912                         write_unlock_bh(&tunnel->hlist_lock);
 913
 914                         if (session->session_close != NULL)
 915                                 (*session->session_close)(session);
 916
 917                         if (session->deref != NULL)
 918                                 (*session->deref)(session);
 919
 920                         write_lock_bh(&tunnel->hlist_lock);
 921
 922                         /* Now restart from the beginning of this hash
 923                          * chain.  We always remove a session from the
 924                          * list so we are guaranteed to make forward
 925                          * progress.
 926                          */
 927                         goto again;
 928                 }
 929         }
 930         write_unlock_bh(&tunnel->hlist_lock);
 931 }
 932 EXPORT_SYMBOL_GPL(l2tp_tunnel_closeall);
 933
 934 /* Really kill the tunnel.
 935  * Come here only when all sessions have been cleared from the tunnel.
 936  */
 937 void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
 938 {
 939         struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
 940
 941         BUG_ON(atomic_read(&tunnel->ref_count) != 0);
 942         BUG_ON(tunnel->sock != NULL);
 943
 944         PRINTK(tunnel->debug, L2TP_MSG_CONTROL, KERN_INFO,
 945                "%s: free...\n", tunnel->name);
 946
 947         /* Remove from tunnel list */
 948         write_lock_bh(&pn->l2tp_tunnel_list_lock);
 949         list_del_init(&tunnel->list);
 950         write_unlock_bh(&pn->l2tp_tunnel_list_lock);
 951
 952         atomic_dec(&l2tp_tunnel_count);
 953         kfree(tunnel);
 954 }
 955 EXPORT_SYMBOL_GPL(l2tp_tunnel_free);
 956
 957 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)
 958 {
 959         struct l2tp_tunnel *tunnel = NULL;
 960         int err;
 961         struct socket *sock = NULL;
 962         struct sock *sk = NULL;
 963         struct l2tp_net *pn;
 964
 965         /* Get the tunnel socket from the fd, which was opened by
 966          * the userspace L2TP daemon.
 967          */
 968         err = -EBADF;
 969         sock = sockfd_lookup(fd, &err);
 970         if (!sock) {
 971                 printk(KERN_ERR "tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
 972                        tunnel_id, fd, err);
 973                 goto err;
 974         }
 975
 976         sk = sock->sk;
 977
 978         /* Quick sanity checks */
 979         err = -EPROTONOSUPPORT;
 980         if (sk->sk_protocol != IPPROTO_UDP) {
 981                 printk(KERN_ERR "tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
 982                        tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
 983                 goto err;
 984         }
 985         err = -EAFNOSUPPORT;
 986         if (sock->ops->family != AF_INET) {
 987                 printk(KERN_ERR "tunl %hu: fd %d wrong family, got %d, expected %d\n",
 988                        tunnel_id, fd, sock->ops->family, AF_INET);
 989                 goto err;
 990         }
 991
 992         /* Check if this socket has already been prepped */
 993         tunnel = (struct l2tp_tunnel *)sk->sk_user_data;
 994         if (tunnel != NULL) {
 995                 /* This socket has already been prepped */
 996                 err = -EBUSY;
 997                 goto err;
 998         }
 999
1000         if (version != L2TP_HDR_VER_2)
1001                 goto err;
1002
1003         tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
1004         if (tunnel == NULL) {
1005                 err = -ENOMEM;
1006                 goto err;
1007         }
1008
1009         tunnel->version = version;
1010         tunnel->tunnel_id = tunnel_id;
1011         tunnel->peer_tunnel_id = peer_tunnel_id;
1012         tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
1013
1014         tunnel->magic = L2TP_TUNNEL_MAGIC;
1015         sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
1016         rwlock_init(&tunnel->hlist_lock);
1017
1018         /* The net we belong to */
1019         tunnel->l2tp_net = net;
1020         pn = l2tp_pernet(net);
1021
1022         if (cfg)
1023                 tunnel->debug = cfg->debug;
1024
1025         /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
1026         udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
1027         udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
1028
1029         sk->sk_user_data = tunnel;
1030
1031         /* Hook on the tunnel socket destructor so that we can cleanup
1032          * if the tunnel socket goes away.
1033          */
1034         tunnel->old_sk_destruct = sk->sk_destruct;
1035         sk->sk_destruct = &l2tp_tunnel_destruct;
1036         tunnel->sock = sk;
1037         sk->sk_allocation = GFP_ATOMIC;
1038
1039         /* Add tunnel to our list */
1040         INIT_LIST_HEAD(&tunnel->list);
1041         write_lock_bh(&pn->l2tp_tunnel_list_lock);
1042         list_add(&tunnel->list, &pn->l2tp_tunnel_list);
1043         write_unlock_bh(&pn->l2tp_tunnel_list_lock);
1044         atomic_inc(&l2tp_tunnel_count);
1045
1046         /* Bump the reference count. The tunnel context is deleted
1047          * only when this drops to zero.
1048          */
1049         l2tp_tunnel_inc_refcount(tunnel);
1050
1051         err = 0;
1052 err:
1053         if (tunnelp)
1054                 *tunnelp = tunnel;
1055
1056         if (sock)
1057                 sockfd_put(sock);
1058
1059         return err;
1060 }
1061 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
1062
1063 /* Really kill the session.
1064  */
1065 void l2tp_session_free(struct l2tp_session *session)
1066 {
1067         struct l2tp_tunnel *tunnel;
1068
1069         BUG_ON(atomic_read(&session->ref_count) != 0);
1070
1071         tunnel = session->tunnel;
1072         if (tunnel != NULL) {
1073                 BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
1074
1075                 /* Delete the session from the hash */
1076                 write_lock_bh(&tunnel->hlist_lock);
1077                 hlist_del_init(&session->hlist);
1078                 write_unlock_bh(&tunnel->hlist_lock);
1079
1080                 if (session->session_id != 0)
1081                         atomic_dec(&l2tp_session_count);
1082
1083                 sock_put(tunnel->sock);
1084
1085                 /* This will delete the tunnel context if this
1086                  * is the last session on the tunnel.
1087                  */
1088                 session->tunnel = NULL;
1089                 l2tp_tunnel_dec_refcount(tunnel);
1090         }
1091
1092         kfree(session);
1093
1094         return;
1095 }
1096 EXPORT_SYMBOL_GPL(l2tp_session_free);
1097
1098 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)
1099 {
1100         struct l2tp_session *session;
1101
1102         session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
1103         if (session != NULL) {
1104                 session->magic = L2TP_SESSION_MAGIC;
1105                 session->tunnel = tunnel;
1106
1107                 session->session_id = session_id;
1108                 session->peer_session_id = peer_session_id;
1109
1110                 sprintf(&session->name[0], "sess %u/%u",
1111                         tunnel->tunnel_id, session->session_id);
1112
1113                 skb_queue_head_init(&session->reorder_q);
1114
1115                 INIT_HLIST_NODE(&session->hlist);
1116
1117                 /* Inherit debug options from tunnel */
1118                 session->debug = tunnel->debug;
1119
1120                 if (cfg) {
1121                         session->debug = cfg->debug;
1122                         session->hdr_len = cfg->hdr_len;
1123                         session->mtu = cfg->mtu;
1124                         session->mru = cfg->mru;
1125                         session->send_seq = cfg->send_seq;
1126                         session->recv_seq = cfg->recv_seq;
1127                         session->lns_mode = cfg->lns_mode;
1128                 }
1129
1130                 /* Bump the reference count. The session context is deleted
1131                  * only when this drops to zero.
1132                  */
1133                 l2tp_session_inc_refcount(session);
1134                 l2tp_tunnel_inc_refcount(tunnel);
1135
1136                 /* Ensure tunnel socket isn't deleted */
1137                 sock_hold(tunnel->sock);
1138
1139                 /* Add session to the tunnel's hash list */
1140                 write_lock_bh(&tunnel->hlist_lock);
1141                 hlist_add_head(&session->hlist,
1142                                l2tp_session_id_hash(tunnel, session_id));
1143                 write_unlock_bh(&tunnel->hlist_lock);
1144
1145                 /* Ignore management session in session count value */
1146                 if (session->session_id != 0)
1147                         atomic_inc(&l2tp_session_count);
1148         }
1149
1150         return session;
1151 }
1152 EXPORT_SYMBOL_GPL(l2tp_session_create);
1153
1154 /*****************************************************************************
1155  * Init and cleanup
1156  *****************************************************************************/
1157
1158 static __net_init int l2tp_init_net(struct net *net)
1159 {
1160         struct l2tp_net *pn;
1161         int err;
1162
1163         pn = kzalloc(sizeof(*pn), GFP_KERNEL);
1164         if (!pn)
1165                 return -ENOMEM;
1166
1167         INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
1168         rwlock_init(&pn->l2tp_tunnel_list_lock);
1169
1170         err = net_assign_generic(net, l2tp_net_id, pn);
1171         if (err)
1172                 goto out;
1173
1174         return 0;
1175
1176 out:
1177         kfree(pn);
1178         return err;
1179 }
1180
1181 static __net_exit void l2tp_exit_net(struct net *net)
1182 {
1183         struct l2tp_net *pn;
1184
1185         pn = net_generic(net, l2tp_net_id);
1186         /*
1187          * if someone has cached our net then
1188          * further net_generic call will return NULL
1189          */
1190         net_assign_generic(net, l2tp_net_id, NULL);
1191         kfree(pn);
1192 }
1193
1194 static struct pernet_operations l2tp_net_ops = {
1195         .init = l2tp_init_net,
1196         .exit = l2tp_exit_net,
1197         .id   = &l2tp_net_id,
1198         .size = sizeof(struct l2tp_net),
1199 };
1200
1201 static int __init l2tp_init(void)
1202 {
1203         int rc = 0;
1204
1205         rc = register_pernet_device(&l2tp_net_ops);
1206         if (rc)
1207                 goto out;
1208
1209         printk(KERN_INFO "L2TP core driver, %s\n", L2TP_DRV_VERSION);
1210
1211 out:
1212         return rc;
1213 }
1214
1215 static void __exit l2tp_exit(void)
1216 {
1217         unregister_pernet_device(&l2tp_net_ops);
1218 }
1219
1220 module_init(l2tp_init);
1221 module_exit(l2tp_exit);
1222
1223 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
1224 MODULE_DESCRIPTION("L2TP core");
1225 MODULE_LICENSE("GPL");
1226 MODULE_VERSION(L2TP_DRV_VERSION);
1227