1 // SPDX-License-Identifier: GPL-2.0-only 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 17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 18 19 #include <linux/module.h> 20 #include <linux/string.h> 21 #include <linux/list.h> 22 #include <linux/rculist.h> 23 #include <linux/uaccess.h> 24 25 #include <linux/kernel.h> 26 #include <linux/spinlock.h> 27 #include <linux/kthread.h> 28 #include <linux/sched.h> 29 #include <linux/slab.h> 30 #include <linux/errno.h> 31 #include <linux/jiffies.h> 32 33 #include <linux/netdevice.h> 34 #include <linux/net.h> 35 #include <linux/inetdevice.h> 36 #include <linux/skbuff.h> 37 #include <linux/init.h> 38 #include <linux/in.h> 39 #include <linux/ip.h> 40 #include <linux/udp.h> 41 #include <linux/l2tp.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/udp_tunnel.h> 51 #include <net/inet_common.h> 52 #include <net/xfrm.h> 53 #include <net/protocol.h> 54 #include <net/inet6_connection_sock.h> 55 #include <net/inet_ecn.h> 56 #include <net/ip6_route.h> 57 #include <net/ip6_checksum.h> 58 59 #include <asm/byteorder.h> 60 #include <linux/atomic.h> 61 62 #include "l2tp_core.h" 63 64 #define CREATE_TRACE_POINTS 65 #include "trace.h" 66 67 #define L2TP_DRV_VERSION "V2.0" 68 69 /* L2TP header constants */ 70 #define L2TP_HDRFLAG_T 0x8000 71 #define L2TP_HDRFLAG_L 0x4000 72 #define L2TP_HDRFLAG_S 0x0800 73 #define L2TP_HDRFLAG_O 0x0200 74 #define L2TP_HDRFLAG_P 0x0100 75 76 #define L2TP_HDR_VER_MASK 0x000F 77 #define L2TP_HDR_VER_2 0x0002 78 #define L2TP_HDR_VER_3 0x0003 79 80 /* L2TPv3 default L2-specific sublayer */ 81 #define L2TP_SLFLAG_S 0x40000000 82 #define L2TP_SL_SEQ_MASK 0x00ffffff 83 84 #define L2TP_HDR_SIZE_MAX 14 85 86 /* Default trace flags */ 87 #define L2TP_DEFAULT_DEBUG_FLAGS 0 88 89 /* Private data stored for received packets in the skb. 90 */ 91 struct l2tp_skb_cb { 92 u32 ns; 93 u16 has_seq; 94 u16 length; 95 unsigned long expires; 96 }; 97 98 #define L2TP_SKB_CB(skb) ((struct l2tp_skb_cb *)&(skb)->cb[sizeof(struct inet_skb_parm)]) 99 100 static struct workqueue_struct *l2tp_wq; 101 102 /* per-net private data for this module */ 103 static unsigned int l2tp_net_id; 104 struct l2tp_net { 105 /* Lock for write access to l2tp_tunnel_idr */ 106 spinlock_t l2tp_tunnel_idr_lock; 107 struct idr l2tp_tunnel_idr; 108 /* Lock for write access to l2tp_v[23]_session_idr/htable */ 109 spinlock_t l2tp_session_idr_lock; 110 struct idr l2tp_v2_session_idr; 111 struct idr l2tp_v3_session_idr; 112 struct hlist_head l2tp_v3_session_htable[16]; 113 }; 114 115 static inline u32 l2tp_v2_session_key(u16 tunnel_id, u16 session_id) 116 { 117 return ((u32)tunnel_id) << 16 | session_id; 118 } 119 120 static inline unsigned long l2tp_v3_session_hashkey(struct sock *sk, u32 session_id) 121 { 122 return ((unsigned long)sk) + session_id; 123 } 124 125 #if IS_ENABLED(CONFIG_IPV6) 126 static bool l2tp_sk_is_v6(struct sock *sk) 127 { 128 return sk->sk_family == PF_INET6 && 129 !ipv6_addr_v4mapped(&sk->sk_v6_daddr); 130 } 131 #endif 132 133 static inline struct l2tp_net *l2tp_pernet(const struct net *net) 134 { 135 return net_generic(net, l2tp_net_id); 136 } 137 138 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel) 139 { 140 trace_free_tunnel(tunnel); 141 sock_put(tunnel->sock); 142 /* the tunnel is freed in the socket destructor */ 143 } 144 145 static void l2tp_session_free(struct l2tp_session *session) 146 { 147 trace_free_session(session); 148 if (session->tunnel) 149 l2tp_tunnel_dec_refcount(session->tunnel); 150 kfree(session); 151 } 152 153 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk) 154 { 155 struct l2tp_tunnel *tunnel = sk->sk_user_data; 156 157 if (tunnel) 158 if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC)) 159 return NULL; 160 161 return tunnel; 162 } 163 EXPORT_SYMBOL_GPL(l2tp_sk_to_tunnel); 164 165 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel) 166 { 167 refcount_inc(&tunnel->ref_count); 168 } 169 EXPORT_SYMBOL_GPL(l2tp_tunnel_inc_refcount); 170 171 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel) 172 { 173 if (refcount_dec_and_test(&tunnel->ref_count)) 174 l2tp_tunnel_free(tunnel); 175 } 176 EXPORT_SYMBOL_GPL(l2tp_tunnel_dec_refcount); 177 178 void l2tp_session_inc_refcount(struct l2tp_session *session) 179 { 180 refcount_inc(&session->ref_count); 181 } 182 EXPORT_SYMBOL_GPL(l2tp_session_inc_refcount); 183 184 void l2tp_session_dec_refcount(struct l2tp_session *session) 185 { 186 if (refcount_dec_and_test(&session->ref_count)) 187 l2tp_session_free(session); 188 } 189 EXPORT_SYMBOL_GPL(l2tp_session_dec_refcount); 190 191 /* Lookup a tunnel. A new reference is held on the returned tunnel. */ 192 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id) 193 { 194 const struct l2tp_net *pn = l2tp_pernet(net); 195 struct l2tp_tunnel *tunnel; 196 197 rcu_read_lock_bh(); 198 tunnel = idr_find(&pn->l2tp_tunnel_idr, tunnel_id); 199 if (tunnel && refcount_inc_not_zero(&tunnel->ref_count)) { 200 rcu_read_unlock_bh(); 201 return tunnel; 202 } 203 rcu_read_unlock_bh(); 204 205 return NULL; 206 } 207 EXPORT_SYMBOL_GPL(l2tp_tunnel_get); 208 209 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth) 210 { 211 struct l2tp_net *pn = l2tp_pernet(net); 212 unsigned long tunnel_id, tmp; 213 struct l2tp_tunnel *tunnel; 214 int count = 0; 215 216 rcu_read_lock_bh(); 217 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) { 218 if (tunnel && ++count > nth && 219 refcount_inc_not_zero(&tunnel->ref_count)) { 220 rcu_read_unlock_bh(); 221 return tunnel; 222 } 223 } 224 rcu_read_unlock_bh(); 225 226 return NULL; 227 } 228 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth); 229 230 struct l2tp_session *l2tp_v3_session_get(const struct net *net, struct sock *sk, u32 session_id) 231 { 232 const struct l2tp_net *pn = l2tp_pernet(net); 233 struct l2tp_session *session; 234 235 rcu_read_lock_bh(); 236 session = idr_find(&pn->l2tp_v3_session_idr, session_id); 237 if (session && !hash_hashed(&session->hlist) && 238 refcount_inc_not_zero(&session->ref_count)) { 239 rcu_read_unlock_bh(); 240 return session; 241 } 242 243 /* If we get here and session is non-NULL, the session_id 244 * collides with one in another tunnel. If sk is non-NULL, 245 * find the session matching sk. 246 */ 247 if (session && sk) { 248 unsigned long key = l2tp_v3_session_hashkey(sk, session->session_id); 249 250 hash_for_each_possible_rcu(pn->l2tp_v3_session_htable, session, 251 hlist, key) { 252 if (session->tunnel->sock == sk && 253 refcount_inc_not_zero(&session->ref_count)) { 254 rcu_read_unlock_bh(); 255 return session; 256 } 257 } 258 } 259 rcu_read_unlock_bh(); 260 261 return NULL; 262 } 263 EXPORT_SYMBOL_GPL(l2tp_v3_session_get); 264 265 struct l2tp_session *l2tp_v2_session_get(const struct net *net, u16 tunnel_id, u16 session_id) 266 { 267 u32 session_key = l2tp_v2_session_key(tunnel_id, session_id); 268 const struct l2tp_net *pn = l2tp_pernet(net); 269 struct l2tp_session *session; 270 271 rcu_read_lock_bh(); 272 session = idr_find(&pn->l2tp_v2_session_idr, session_key); 273 if (session && refcount_inc_not_zero(&session->ref_count)) { 274 rcu_read_unlock_bh(); 275 return session; 276 } 277 rcu_read_unlock_bh(); 278 279 return NULL; 280 } 281 EXPORT_SYMBOL_GPL(l2tp_v2_session_get); 282 283 struct l2tp_session *l2tp_session_get(const struct net *net, struct sock *sk, int pver, 284 u32 tunnel_id, u32 session_id) 285 { 286 if (pver == L2TP_HDR_VER_2) 287 return l2tp_v2_session_get(net, tunnel_id, session_id); 288 else 289 return l2tp_v3_session_get(net, sk, session_id); 290 } 291 EXPORT_SYMBOL_GPL(l2tp_session_get); 292 293 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth) 294 { 295 struct l2tp_session *session; 296 int count = 0; 297 298 rcu_read_lock_bh(); 299 list_for_each_entry_rcu(session, &tunnel->session_list, list) { 300 if (++count > nth) { 301 l2tp_session_inc_refcount(session); 302 rcu_read_unlock_bh(); 303 return session; 304 } 305 } 306 rcu_read_unlock_bh(); 307 308 return NULL; 309 } 310 EXPORT_SYMBOL_GPL(l2tp_session_get_nth); 311 312 /* Lookup a session by interface name. 313 * This is very inefficient but is only used by management interfaces. 314 */ 315 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net, 316 const char *ifname) 317 { 318 struct l2tp_net *pn = l2tp_pernet(net); 319 unsigned long tunnel_id, tmp; 320 struct l2tp_session *session; 321 struct l2tp_tunnel *tunnel; 322 323 rcu_read_lock_bh(); 324 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) { 325 if (tunnel) { 326 list_for_each_entry_rcu(session, &tunnel->session_list, list) { 327 if (!strcmp(session->ifname, ifname)) { 328 l2tp_session_inc_refcount(session); 329 rcu_read_unlock_bh(); 330 331 return session; 332 } 333 } 334 } 335 } 336 rcu_read_unlock_bh(); 337 338 return NULL; 339 } 340 EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname); 341 342 static void l2tp_session_coll_list_add(struct l2tp_session_coll_list *clist, 343 struct l2tp_session *session) 344 { 345 l2tp_session_inc_refcount(session); 346 WARN_ON_ONCE(session->coll_list); 347 session->coll_list = clist; 348 spin_lock(&clist->lock); 349 list_add(&session->clist, &clist->list); 350 spin_unlock(&clist->lock); 351 } 352 353 static int l2tp_session_collision_add(struct l2tp_net *pn, 354 struct l2tp_session *session1, 355 struct l2tp_session *session2) 356 { 357 struct l2tp_session_coll_list *clist; 358 359 lockdep_assert_held(&pn->l2tp_session_idr_lock); 360 361 if (!session2) 362 return -EEXIST; 363 364 /* If existing session is in IP-encap tunnel, refuse new session */ 365 if (session2->tunnel->encap == L2TP_ENCAPTYPE_IP) 366 return -EEXIST; 367 368 clist = session2->coll_list; 369 if (!clist) { 370 /* First collision. Allocate list to manage the collided sessions 371 * and add the existing session to the list. 372 */ 373 clist = kmalloc(sizeof(*clist), GFP_ATOMIC); 374 if (!clist) 375 return -ENOMEM; 376 377 spin_lock_init(&clist->lock); 378 INIT_LIST_HEAD(&clist->list); 379 refcount_set(&clist->ref_count, 1); 380 l2tp_session_coll_list_add(clist, session2); 381 } 382 383 /* If existing session isn't already in the session hlist, add it. */ 384 if (!hash_hashed(&session2->hlist)) 385 hash_add(pn->l2tp_v3_session_htable, &session2->hlist, 386 session2->hlist_key); 387 388 /* Add new session to the hlist and collision list */ 389 hash_add(pn->l2tp_v3_session_htable, &session1->hlist, 390 session1->hlist_key); 391 refcount_inc(&clist->ref_count); 392 l2tp_session_coll_list_add(clist, session1); 393 394 return 0; 395 } 396 397 static void l2tp_session_collision_del(struct l2tp_net *pn, 398 struct l2tp_session *session) 399 { 400 struct l2tp_session_coll_list *clist = session->coll_list; 401 unsigned long session_key = session->session_id; 402 struct l2tp_session *session2; 403 404 lockdep_assert_held(&pn->l2tp_session_idr_lock); 405 406 hash_del(&session->hlist); 407 408 if (clist) { 409 /* Remove session from its collision list. If there 410 * are other sessions with the same ID, replace this 411 * session's IDR entry with that session, otherwise 412 * remove the IDR entry. If this is the last session, 413 * the collision list data is freed. 414 */ 415 spin_lock(&clist->lock); 416 list_del_init(&session->clist); 417 session2 = list_first_entry_or_null(&clist->list, struct l2tp_session, clist); 418 if (session2) { 419 void *old = idr_replace(&pn->l2tp_v3_session_idr, session2, session_key); 420 421 WARN_ON_ONCE(IS_ERR_VALUE(old)); 422 } else { 423 void *removed = idr_remove(&pn->l2tp_v3_session_idr, session_key); 424 425 WARN_ON_ONCE(removed != session); 426 } 427 session->coll_list = NULL; 428 spin_unlock(&clist->lock); 429 if (refcount_dec_and_test(&clist->ref_count)) 430 kfree(clist); 431 l2tp_session_dec_refcount(session); 432 } 433 } 434 435 int l2tp_session_register(struct l2tp_session *session, 436 struct l2tp_tunnel *tunnel) 437 { 438 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net); 439 struct l2tp_session *other_session = NULL; 440 u32 session_key; 441 int err; 442 443 spin_lock_bh(&tunnel->list_lock); 444 spin_lock_bh(&pn->l2tp_session_idr_lock); 445 446 if (!tunnel->acpt_newsess) { 447 err = -ENODEV; 448 goto out; 449 } 450 451 if (tunnel->version == L2TP_HDR_VER_3) { 452 session_key = session->session_id; 453 err = idr_alloc_u32(&pn->l2tp_v3_session_idr, NULL, 454 &session_key, session_key, GFP_ATOMIC); 455 /* IP encap expects session IDs to be globally unique, while 456 * UDP encap doesn't. This isn't per the RFC, which says that 457 * sessions are identified only by the session ID, but is to 458 * support existing userspace which depends on it. 459 */ 460 if (err == -ENOSPC && tunnel->encap == L2TP_ENCAPTYPE_UDP) { 461 other_session = idr_find(&pn->l2tp_v3_session_idr, 462 session_key); 463 err = l2tp_session_collision_add(pn, session, 464 other_session); 465 } 466 } else { 467 session_key = l2tp_v2_session_key(tunnel->tunnel_id, 468 session->session_id); 469 err = idr_alloc_u32(&pn->l2tp_v2_session_idr, NULL, 470 &session_key, session_key, GFP_ATOMIC); 471 } 472 473 if (err) { 474 if (err == -ENOSPC) 475 err = -EEXIST; 476 goto out; 477 } 478 479 l2tp_tunnel_inc_refcount(tunnel); 480 list_add(&session->list, &tunnel->session_list); 481 482 if (tunnel->version == L2TP_HDR_VER_3) { 483 if (!other_session) 484 idr_replace(&pn->l2tp_v3_session_idr, session, session_key); 485 } else { 486 idr_replace(&pn->l2tp_v2_session_idr, session, session_key); 487 } 488 489 out: 490 spin_unlock_bh(&pn->l2tp_session_idr_lock); 491 spin_unlock_bh(&tunnel->list_lock); 492 493 if (!err) 494 trace_register_session(session); 495 496 return err; 497 } 498 EXPORT_SYMBOL_GPL(l2tp_session_register); 499 500 /***************************************************************************** 501 * Receive data handling 502 *****************************************************************************/ 503 504 /* Queue a skb in order. We come here only if the skb has an L2TP sequence 505 * number. 506 */ 507 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb) 508 { 509 struct sk_buff *skbp; 510 struct sk_buff *tmp; 511 u32 ns = L2TP_SKB_CB(skb)->ns; 512 513 spin_lock_bh(&session->reorder_q.lock); 514 skb_queue_walk_safe(&session->reorder_q, skbp, tmp) { 515 if (L2TP_SKB_CB(skbp)->ns > ns) { 516 __skb_queue_before(&session->reorder_q, skbp, skb); 517 atomic_long_inc(&session->stats.rx_oos_packets); 518 goto out; 519 } 520 } 521 522 __skb_queue_tail(&session->reorder_q, skb); 523 524 out: 525 spin_unlock_bh(&session->reorder_q.lock); 526 } 527 528 /* Dequeue a single skb. 529 */ 530 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb) 531 { 532 struct l2tp_tunnel *tunnel = session->tunnel; 533 int length = L2TP_SKB_CB(skb)->length; 534 535 /* We're about to requeue the skb, so return resources 536 * to its current owner (a socket receive buffer). 537 */ 538 skb_orphan(skb); 539 540 atomic_long_inc(&tunnel->stats.rx_packets); 541 atomic_long_add(length, &tunnel->stats.rx_bytes); 542 atomic_long_inc(&session->stats.rx_packets); 543 atomic_long_add(length, &session->stats.rx_bytes); 544 545 if (L2TP_SKB_CB(skb)->has_seq) { 546 /* Bump our Nr */ 547 session->nr++; 548 session->nr &= session->nr_max; 549 trace_session_seqnum_update(session); 550 } 551 552 /* call private receive handler */ 553 if (session->recv_skb) 554 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length); 555 else 556 kfree_skb(skb); 557 } 558 559 /* Dequeue skbs from the session's reorder_q, subject to packet order. 560 * Skbs that have been in the queue for too long are simply discarded. 561 */ 562 static void l2tp_recv_dequeue(struct l2tp_session *session) 563 { 564 struct sk_buff *skb; 565 struct sk_buff *tmp; 566 567 /* If the pkt at the head of the queue has the nr that we 568 * expect to send up next, dequeue it and any other 569 * in-sequence packets behind it. 570 */ 571 start: 572 spin_lock_bh(&session->reorder_q.lock); 573 skb_queue_walk_safe(&session->reorder_q, skb, tmp) { 574 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb); 575 576 /* If the packet has been pending on the queue for too long, discard it */ 577 if (time_after(jiffies, cb->expires)) { 578 atomic_long_inc(&session->stats.rx_seq_discards); 579 atomic_long_inc(&session->stats.rx_errors); 580 trace_session_pkt_expired(session, cb->ns); 581 session->reorder_skip = 1; 582 __skb_unlink(skb, &session->reorder_q); 583 kfree_skb(skb); 584 continue; 585 } 586 587 if (cb->has_seq) { 588 if (session->reorder_skip) { 589 session->reorder_skip = 0; 590 session->nr = cb->ns; 591 trace_session_seqnum_reset(session); 592 } 593 if (cb->ns != session->nr) 594 goto out; 595 } 596 __skb_unlink(skb, &session->reorder_q); 597 598 /* Process the skb. We release the queue lock while we 599 * do so to let other contexts process the queue. 600 */ 601 spin_unlock_bh(&session->reorder_q.lock); 602 l2tp_recv_dequeue_skb(session, skb); 603 goto start; 604 } 605 606 out: 607 spin_unlock_bh(&session->reorder_q.lock); 608 } 609 610 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr) 611 { 612 u32 nws; 613 614 if (nr >= session->nr) 615 nws = nr - session->nr; 616 else 617 nws = (session->nr_max + 1) - (session->nr - nr); 618 619 return nws < session->nr_window_size; 620 } 621 622 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if 623 * acceptable, else non-zero. 624 */ 625 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb) 626 { 627 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb); 628 629 if (!l2tp_seq_check_rx_window(session, cb->ns)) { 630 /* Packet sequence number is outside allowed window. 631 * Discard it. 632 */ 633 trace_session_pkt_outside_rx_window(session, cb->ns); 634 goto discard; 635 } 636 637 if (session->reorder_timeout != 0) { 638 /* Packet reordering enabled. Add skb to session's 639 * reorder queue, in order of ns. 640 */ 641 l2tp_recv_queue_skb(session, skb); 642 goto out; 643 } 644 645 /* Packet reordering disabled. Discard out-of-sequence packets, while 646 * tracking the number if in-sequence packets after the first OOS packet 647 * is seen. After nr_oos_count_max in-sequence packets, reset the 648 * sequence number to re-enable packet reception. 649 */ 650 if (cb->ns == session->nr) { 651 skb_queue_tail(&session->reorder_q, skb); 652 } else { 653 u32 nr_oos = cb->ns; 654 u32 nr_next = (session->nr_oos + 1) & session->nr_max; 655 656 if (nr_oos == nr_next) 657 session->nr_oos_count++; 658 else 659 session->nr_oos_count = 0; 660 661 session->nr_oos = nr_oos; 662 if (session->nr_oos_count > session->nr_oos_count_max) { 663 session->reorder_skip = 1; 664 } 665 if (!session->reorder_skip) { 666 atomic_long_inc(&session->stats.rx_seq_discards); 667 trace_session_pkt_oos(session, cb->ns); 668 goto discard; 669 } 670 skb_queue_tail(&session->reorder_q, skb); 671 } 672 673 out: 674 return 0; 675 676 discard: 677 return 1; 678 } 679 680 /* Do receive processing of L2TP data frames. We handle both L2TPv2 681 * and L2TPv3 data frames here. 682 * 683 * L2TPv2 Data Message Header 684 * 685 * 0 1 2 3 686 * 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 1 687 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 688 * |T|L|x|x|S|x|O|P|x|x|x|x| Ver | Length (opt) | 689 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 690 * | Tunnel ID | Session ID | 691 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 692 * | Ns (opt) | Nr (opt) | 693 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 694 * | Offset Size (opt) | Offset pad... (opt) 695 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 696 * 697 * Data frames are marked by T=0. All other fields are the same as 698 * those in L2TP control frames. 699 * 700 * L2TPv3 Data Message Header 701 * 702 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 703 * | L2TP Session Header | 704 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 705 * | L2-Specific Sublayer | 706 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 707 * | Tunnel Payload ... 708 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 709 * 710 * L2TPv3 Session Header Over IP 711 * 712 * 0 1 2 3 713 * 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 1 714 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 715 * | Session ID | 716 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 * | Cookie (optional, maximum 64 bits)... 718 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 719 * | 720 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 721 * 722 * L2TPv3 L2-Specific Sublayer Format 723 * 724 * 0 1 2 3 725 * 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 1 726 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 727 * |x|S|x|x|x|x|x|x| Sequence Number | 728 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 729 * 730 * Cookie value and sublayer format are negotiated with the peer when 731 * the session is set up. Unlike L2TPv2, we do not need to parse the 732 * packet header to determine if optional fields are present. 733 * 734 * Caller must already have parsed the frame and determined that it is 735 * a data (not control) frame before coming here. Fields up to the 736 * session-id have already been parsed and ptr points to the data 737 * after the session-id. 738 */ 739 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb, 740 unsigned char *ptr, unsigned char *optr, u16 hdrflags, 741 int length) 742 { 743 struct l2tp_tunnel *tunnel = session->tunnel; 744 int offset; 745 746 /* Parse and check optional cookie */ 747 if (session->peer_cookie_len > 0) { 748 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) { 749 pr_debug_ratelimited("%s: cookie mismatch (%u/%u). Discarding.\n", 750 tunnel->name, tunnel->tunnel_id, 751 session->session_id); 752 atomic_long_inc(&session->stats.rx_cookie_discards); 753 goto discard; 754 } 755 ptr += session->peer_cookie_len; 756 } 757 758 /* Handle the optional sequence numbers. Sequence numbers are 759 * in different places for L2TPv2 and L2TPv3. 760 * 761 * If we are the LAC, enable/disable sequence numbers under 762 * the control of the LNS. If no sequence numbers present but 763 * we were expecting them, discard frame. 764 */ 765 L2TP_SKB_CB(skb)->has_seq = 0; 766 if (tunnel->version == L2TP_HDR_VER_2) { 767 if (hdrflags & L2TP_HDRFLAG_S) { 768 /* Store L2TP info in the skb */ 769 L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr); 770 L2TP_SKB_CB(skb)->has_seq = 1; 771 ptr += 2; 772 /* Skip past nr in the header */ 773 ptr += 2; 774 775 } 776 } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) { 777 u32 l2h = ntohl(*(__be32 *)ptr); 778 779 if (l2h & 0x40000000) { 780 /* Store L2TP info in the skb */ 781 L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff; 782 L2TP_SKB_CB(skb)->has_seq = 1; 783 } 784 ptr += 4; 785 } 786 787 if (L2TP_SKB_CB(skb)->has_seq) { 788 /* Received a packet with sequence numbers. If we're the LAC, 789 * check if we sre sending sequence numbers and if not, 790 * configure it so. 791 */ 792 if (!session->lns_mode && !session->send_seq) { 793 trace_session_seqnum_lns_enable(session); 794 session->send_seq = 1; 795 l2tp_session_set_header_len(session, tunnel->version); 796 } 797 } else { 798 /* No sequence numbers. 799 * If user has configured mandatory sequence numbers, discard. 800 */ 801 if (session->recv_seq) { 802 pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n", 803 session->name); 804 atomic_long_inc(&session->stats.rx_seq_discards); 805 goto discard; 806 } 807 808 /* If we're the LAC and we're sending sequence numbers, the 809 * LNS has requested that we no longer send sequence numbers. 810 * If we're the LNS and we're sending sequence numbers, the 811 * LAC is broken. Discard the frame. 812 */ 813 if (!session->lns_mode && session->send_seq) { 814 trace_session_seqnum_lns_disable(session); 815 session->send_seq = 0; 816 l2tp_session_set_header_len(session, tunnel->version); 817 } else if (session->send_seq) { 818 pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n", 819 session->name); 820 atomic_long_inc(&session->stats.rx_seq_discards); 821 goto discard; 822 } 823 } 824 825 /* Session data offset is defined only for L2TPv2 and is 826 * indicated by an optional 16-bit value in the header. 827 */ 828 if (tunnel->version == L2TP_HDR_VER_2) { 829 /* If offset bit set, skip it. */ 830 if (hdrflags & L2TP_HDRFLAG_O) { 831 offset = ntohs(*(__be16 *)ptr); 832 ptr += 2 + offset; 833 } 834 } 835 836 offset = ptr - optr; 837 if (!pskb_may_pull(skb, offset)) 838 goto discard; 839 840 __skb_pull(skb, offset); 841 842 /* Prepare skb for adding to the session's reorder_q. Hold 843 * packets for max reorder_timeout or 1 second if not 844 * reordering. 845 */ 846 L2TP_SKB_CB(skb)->length = length; 847 L2TP_SKB_CB(skb)->expires = jiffies + 848 (session->reorder_timeout ? session->reorder_timeout : HZ); 849 850 /* Add packet to the session's receive queue. Reordering is done here, if 851 * enabled. Saved L2TP protocol info is stored in skb->sb[]. 852 */ 853 if (L2TP_SKB_CB(skb)->has_seq) { 854 if (l2tp_recv_data_seq(session, skb)) 855 goto discard; 856 } else { 857 /* No sequence numbers. Add the skb to the tail of the 858 * reorder queue. This ensures that it will be 859 * delivered after all previous sequenced skbs. 860 */ 861 skb_queue_tail(&session->reorder_q, skb); 862 } 863 864 /* Try to dequeue as many skbs from reorder_q as we can. */ 865 l2tp_recv_dequeue(session); 866 867 return; 868 869 discard: 870 atomic_long_inc(&session->stats.rx_errors); 871 kfree_skb(skb); 872 } 873 EXPORT_SYMBOL_GPL(l2tp_recv_common); 874 875 /* Drop skbs from the session's reorder_q 876 */ 877 static void l2tp_session_queue_purge(struct l2tp_session *session) 878 { 879 struct sk_buff *skb = NULL; 880 881 while ((skb = skb_dequeue(&session->reorder_q))) { 882 atomic_long_inc(&session->stats.rx_errors); 883 kfree_skb(skb); 884 } 885 } 886 887 /* UDP encapsulation receive handler. See net/ipv4/udp.c for details. */ 888 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb) 889 { 890 struct l2tp_session *session = NULL; 891 struct l2tp_tunnel *tunnel = NULL; 892 struct net *net = sock_net(sk); 893 unsigned char *ptr, *optr; 894 u16 hdrflags; 895 u16 version; 896 int length; 897 898 /* UDP has verified checksum */ 899 900 /* UDP always verifies the packet length. */ 901 __skb_pull(skb, sizeof(struct udphdr)); 902 903 /* Short packet? */ 904 if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) 905 goto pass; 906 907 /* Point to L2TP header */ 908 optr = skb->data; 909 ptr = skb->data; 910 911 /* Get L2TP header flags */ 912 hdrflags = ntohs(*(__be16 *)ptr); 913 914 /* Get protocol version */ 915 version = hdrflags & L2TP_HDR_VER_MASK; 916 917 /* Get length of L2TP packet */ 918 length = skb->len; 919 920 /* If type is control packet, it is handled by userspace. */ 921 if (hdrflags & L2TP_HDRFLAG_T) 922 goto pass; 923 924 /* Skip flags */ 925 ptr += 2; 926 927 if (version == L2TP_HDR_VER_2) { 928 u16 tunnel_id, session_id; 929 930 /* If length is present, skip it */ 931 if (hdrflags & L2TP_HDRFLAG_L) 932 ptr += 2; 933 934 /* Extract tunnel and session ID */ 935 tunnel_id = ntohs(*(__be16 *)ptr); 936 ptr += 2; 937 session_id = ntohs(*(__be16 *)ptr); 938 ptr += 2; 939 940 session = l2tp_v2_session_get(net, tunnel_id, session_id); 941 } else { 942 u32 session_id; 943 944 ptr += 2; /* skip reserved bits */ 945 session_id = ntohl(*(__be32 *)ptr); 946 ptr += 4; 947 948 session = l2tp_v3_session_get(net, sk, session_id); 949 } 950 951 if (!session || !session->recv_skb) { 952 if (session) 953 l2tp_session_dec_refcount(session); 954 955 /* Not found? Pass to userspace to deal with */ 956 goto pass; 957 } 958 959 tunnel = session->tunnel; 960 961 /* Check protocol version */ 962 if (version != tunnel->version) 963 goto invalid; 964 965 if (version == L2TP_HDR_VER_3 && 966 l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) { 967 l2tp_session_dec_refcount(session); 968 goto invalid; 969 } 970 971 l2tp_recv_common(session, skb, ptr, optr, hdrflags, length); 972 l2tp_session_dec_refcount(session); 973 974 return 0; 975 976 invalid: 977 atomic_long_inc(&tunnel->stats.rx_invalid); 978 979 pass: 980 /* Put UDP header back */ 981 __skb_push(skb, sizeof(struct udphdr)); 982 983 return 1; 984 } 985 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv); 986 987 /* UDP encapsulation receive error handler. See net/ipv4/udp.c for details. */ 988 static void l2tp_udp_encap_err_recv(struct sock *sk, struct sk_buff *skb, int err, 989 __be16 port, u32 info, u8 *payload) 990 { 991 sk->sk_err = err; 992 sk_error_report(sk); 993 994 if (ip_hdr(skb)->version == IPVERSION) { 995 if (inet_test_bit(RECVERR, sk)) 996 return ip_icmp_error(sk, skb, err, port, info, payload); 997 #if IS_ENABLED(CONFIG_IPV6) 998 } else { 999 if (inet6_test_bit(RECVERR6, sk)) 1000 return ipv6_icmp_error(sk, skb, err, port, info, payload); 1001 #endif 1002 } 1003 } 1004 1005 /************************************************************************ 1006 * Transmit handling 1007 ***********************************************************************/ 1008 1009 /* Build an L2TP header for the session into the buffer provided. 1010 */ 1011 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf) 1012 { 1013 struct l2tp_tunnel *tunnel = session->tunnel; 1014 __be16 *bufp = buf; 1015 __be16 *optr = buf; 1016 u16 flags = L2TP_HDR_VER_2; 1017 u32 tunnel_id = tunnel->peer_tunnel_id; 1018 u32 session_id = session->peer_session_id; 1019 1020 if (session->send_seq) 1021 flags |= L2TP_HDRFLAG_S; 1022 1023 /* Setup L2TP header. */ 1024 *bufp++ = htons(flags); 1025 *bufp++ = htons(tunnel_id); 1026 *bufp++ = htons(session_id); 1027 if (session->send_seq) { 1028 *bufp++ = htons(session->ns); 1029 *bufp++ = 0; 1030 session->ns++; 1031 session->ns &= 0xffff; 1032 trace_session_seqnum_update(session); 1033 } 1034 1035 return bufp - optr; 1036 } 1037 1038 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf) 1039 { 1040 struct l2tp_tunnel *tunnel = session->tunnel; 1041 char *bufp = buf; 1042 char *optr = bufp; 1043 1044 /* Setup L2TP header. The header differs slightly for UDP and 1045 * IP encapsulations. For UDP, there is 4 bytes of flags. 1046 */ 1047 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) { 1048 u16 flags = L2TP_HDR_VER_3; 1049 *((__be16 *)bufp) = htons(flags); 1050 bufp += 2; 1051 *((__be16 *)bufp) = 0; 1052 bufp += 2; 1053 } 1054 1055 *((__be32 *)bufp) = htonl(session->peer_session_id); 1056 bufp += 4; 1057 if (session->cookie_len) { 1058 memcpy(bufp, &session->cookie[0], session->cookie_len); 1059 bufp += session->cookie_len; 1060 } 1061 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) { 1062 u32 l2h = 0; 1063 1064 if (session->send_seq) { 1065 l2h = 0x40000000 | session->ns; 1066 session->ns++; 1067 session->ns &= 0xffffff; 1068 trace_session_seqnum_update(session); 1069 } 1070 1071 *((__be32 *)bufp) = htonl(l2h); 1072 bufp += 4; 1073 } 1074 1075 return bufp - optr; 1076 } 1077 1078 /* Queue the packet to IP for output: tunnel socket lock must be held */ 1079 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl) 1080 { 1081 int err; 1082 1083 skb->ignore_df = 1; 1084 skb_dst_drop(skb); 1085 #if IS_ENABLED(CONFIG_IPV6) 1086 if (l2tp_sk_is_v6(tunnel->sock)) 1087 err = inet6_csk_xmit(tunnel->sock, skb, NULL); 1088 else 1089 #endif 1090 err = ip_queue_xmit(tunnel->sock, skb, fl); 1091 1092 return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP; 1093 } 1094 1095 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len) 1096 { 1097 struct l2tp_tunnel *tunnel = session->tunnel; 1098 unsigned int data_len = skb->len; 1099 struct sock *sk = tunnel->sock; 1100 int headroom, uhlen, udp_len; 1101 int ret = NET_XMIT_SUCCESS; 1102 struct inet_sock *inet; 1103 struct udphdr *uh; 1104 1105 /* Check that there's enough headroom in the skb to insert IP, 1106 * UDP and L2TP headers. If not enough, expand it to 1107 * make room. Adjust truesize. 1108 */ 1109 uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0; 1110 headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len; 1111 if (skb_cow_head(skb, headroom)) { 1112 kfree_skb(skb); 1113 return NET_XMIT_DROP; 1114 } 1115 1116 /* Setup L2TP header */ 1117 if (tunnel->version == L2TP_HDR_VER_2) 1118 l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len)); 1119 else 1120 l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len)); 1121 1122 /* Reset skb netfilter state */ 1123 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt)); 1124 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED); 1125 nf_reset_ct(skb); 1126 1127 bh_lock_sock_nested(sk); 1128 if (sock_owned_by_user(sk)) { 1129 kfree_skb(skb); 1130 ret = NET_XMIT_DROP; 1131 goto out_unlock; 1132 } 1133 1134 /* The user-space may change the connection status for the user-space 1135 * provided socket at run time: we must check it under the socket lock 1136 */ 1137 if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) { 1138 kfree_skb(skb); 1139 ret = NET_XMIT_DROP; 1140 goto out_unlock; 1141 } 1142 1143 /* Report transmitted length before we add encap header, which keeps 1144 * statistics consistent for both UDP and IP encap tx/rx paths. 1145 */ 1146 *len = skb->len; 1147 1148 inet = inet_sk(sk); 1149 switch (tunnel->encap) { 1150 case L2TP_ENCAPTYPE_UDP: 1151 /* Setup UDP header */ 1152 __skb_push(skb, sizeof(*uh)); 1153 skb_reset_transport_header(skb); 1154 uh = udp_hdr(skb); 1155 uh->source = inet->inet_sport; 1156 uh->dest = inet->inet_dport; 1157 udp_len = uhlen + session->hdr_len + data_len; 1158 uh->len = htons(udp_len); 1159 1160 /* Calculate UDP checksum if configured to do so */ 1161 #if IS_ENABLED(CONFIG_IPV6) 1162 if (l2tp_sk_is_v6(sk)) 1163 udp6_set_csum(udp_get_no_check6_tx(sk), 1164 skb, &inet6_sk(sk)->saddr, 1165 &sk->sk_v6_daddr, udp_len); 1166 else 1167 #endif 1168 udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr, 1169 inet->inet_daddr, udp_len); 1170 break; 1171 1172 case L2TP_ENCAPTYPE_IP: 1173 break; 1174 } 1175 1176 ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl); 1177 1178 out_unlock: 1179 bh_unlock_sock(sk); 1180 1181 return ret; 1182 } 1183 1184 /* If caller requires the skb to have a ppp header, the header must be 1185 * inserted in the skb data before calling this function. 1186 */ 1187 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb) 1188 { 1189 unsigned int len = 0; 1190 int ret; 1191 1192 ret = l2tp_xmit_core(session, skb, &len); 1193 if (ret == NET_XMIT_SUCCESS) { 1194 atomic_long_inc(&session->tunnel->stats.tx_packets); 1195 atomic_long_add(len, &session->tunnel->stats.tx_bytes); 1196 atomic_long_inc(&session->stats.tx_packets); 1197 atomic_long_add(len, &session->stats.tx_bytes); 1198 } else { 1199 atomic_long_inc(&session->tunnel->stats.tx_errors); 1200 atomic_long_inc(&session->stats.tx_errors); 1201 } 1202 return ret; 1203 } 1204 EXPORT_SYMBOL_GPL(l2tp_xmit_skb); 1205 1206 /***************************************************************************** 1207 * Tinnel and session create/destroy. 1208 *****************************************************************************/ 1209 1210 /* Tunnel socket destruct hook. 1211 * The tunnel context is deleted only when all session sockets have been 1212 * closed. 1213 */ 1214 static void l2tp_tunnel_destruct(struct sock *sk) 1215 { 1216 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk); 1217 1218 if (!tunnel) 1219 goto end; 1220 1221 /* Disable udp encapsulation */ 1222 switch (tunnel->encap) { 1223 case L2TP_ENCAPTYPE_UDP: 1224 /* No longer an encapsulation socket. See net/ipv4/udp.c */ 1225 WRITE_ONCE(udp_sk(sk)->encap_type, 0); 1226 udp_sk(sk)->encap_rcv = NULL; 1227 udp_sk(sk)->encap_destroy = NULL; 1228 break; 1229 case L2TP_ENCAPTYPE_IP: 1230 break; 1231 } 1232 1233 /* Remove hooks into tunnel socket */ 1234 write_lock_bh(&sk->sk_callback_lock); 1235 sk->sk_destruct = tunnel->old_sk_destruct; 1236 sk->sk_user_data = NULL; 1237 write_unlock_bh(&sk->sk_callback_lock); 1238 1239 /* Call the original destructor */ 1240 if (sk->sk_destruct) 1241 (*sk->sk_destruct)(sk); 1242 1243 kfree_rcu(tunnel, rcu); 1244 end: 1245 return; 1246 } 1247 1248 /* Remove an l2tp session from l2tp_core's lists. */ 1249 static void l2tp_session_unhash(struct l2tp_session *session) 1250 { 1251 struct l2tp_tunnel *tunnel = session->tunnel; 1252 1253 if (tunnel) { 1254 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net); 1255 struct l2tp_session *removed = session; 1256 1257 spin_lock_bh(&tunnel->list_lock); 1258 spin_lock_bh(&pn->l2tp_session_idr_lock); 1259 1260 /* Remove from the per-tunnel list */ 1261 list_del_init(&session->list); 1262 1263 /* Remove from per-net IDR */ 1264 if (tunnel->version == L2TP_HDR_VER_3) { 1265 if (hash_hashed(&session->hlist)) 1266 l2tp_session_collision_del(pn, session); 1267 else 1268 removed = idr_remove(&pn->l2tp_v3_session_idr, 1269 session->session_id); 1270 } else { 1271 u32 session_key = l2tp_v2_session_key(tunnel->tunnel_id, 1272 session->session_id); 1273 removed = idr_remove(&pn->l2tp_v2_session_idr, 1274 session_key); 1275 } 1276 WARN_ON_ONCE(removed && removed != session); 1277 1278 spin_unlock_bh(&pn->l2tp_session_idr_lock); 1279 spin_unlock_bh(&tunnel->list_lock); 1280 1281 synchronize_rcu(); 1282 } 1283 } 1284 1285 /* When the tunnel is closed, all the attached sessions need to go too. 1286 */ 1287 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel) 1288 { 1289 struct l2tp_session *session; 1290 1291 spin_lock_bh(&tunnel->list_lock); 1292 tunnel->acpt_newsess = false; 1293 for (;;) { 1294 session = list_first_entry_or_null(&tunnel->session_list, 1295 struct l2tp_session, list); 1296 if (!session) 1297 break; 1298 l2tp_session_inc_refcount(session); 1299 list_del_init(&session->list); 1300 spin_unlock_bh(&tunnel->list_lock); 1301 l2tp_session_delete(session); 1302 spin_lock_bh(&tunnel->list_lock); 1303 l2tp_session_dec_refcount(session); 1304 } 1305 spin_unlock_bh(&tunnel->list_lock); 1306 } 1307 1308 /* Tunnel socket destroy hook for UDP encapsulation */ 1309 static void l2tp_udp_encap_destroy(struct sock *sk) 1310 { 1311 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk); 1312 1313 if (tunnel) 1314 l2tp_tunnel_delete(tunnel); 1315 } 1316 1317 static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel) 1318 { 1319 struct l2tp_net *pn = l2tp_pernet(net); 1320 1321 spin_lock_bh(&pn->l2tp_tunnel_idr_lock); 1322 idr_remove(&pn->l2tp_tunnel_idr, tunnel->tunnel_id); 1323 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock); 1324 } 1325 1326 /* Workqueue tunnel deletion function */ 1327 static void l2tp_tunnel_del_work(struct work_struct *work) 1328 { 1329 struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel, 1330 del_work); 1331 struct sock *sk = tunnel->sock; 1332 struct socket *sock = sk->sk_socket; 1333 1334 l2tp_tunnel_closeall(tunnel); 1335 1336 /* If the tunnel socket was created within the kernel, use 1337 * the sk API to release it here. 1338 */ 1339 if (tunnel->fd < 0) { 1340 if (sock) { 1341 kernel_sock_shutdown(sock, SHUT_RDWR); 1342 sock_release(sock); 1343 } 1344 } 1345 1346 l2tp_tunnel_remove(tunnel->l2tp_net, tunnel); 1347 /* drop initial ref */ 1348 l2tp_tunnel_dec_refcount(tunnel); 1349 1350 /* drop workqueue ref */ 1351 l2tp_tunnel_dec_refcount(tunnel); 1352 } 1353 1354 /* Create a socket for the tunnel, if one isn't set up by 1355 * userspace. This is used for static tunnels where there is no 1356 * managing L2TP daemon. 1357 * 1358 * Since we don't want these sockets to keep a namespace alive by 1359 * themselves, we drop the socket's namespace refcount after creation. 1360 * These sockets are freed when the namespace exits using the pernet 1361 * exit hook. 1362 */ 1363 static int l2tp_tunnel_sock_create(struct net *net, 1364 u32 tunnel_id, 1365 u32 peer_tunnel_id, 1366 struct l2tp_tunnel_cfg *cfg, 1367 struct socket **sockp) 1368 { 1369 int err = -EINVAL; 1370 struct socket *sock = NULL; 1371 struct udp_port_cfg udp_conf; 1372 1373 switch (cfg->encap) { 1374 case L2TP_ENCAPTYPE_UDP: 1375 memset(&udp_conf, 0, sizeof(udp_conf)); 1376 1377 #if IS_ENABLED(CONFIG_IPV6) 1378 if (cfg->local_ip6 && cfg->peer_ip6) { 1379 udp_conf.family = AF_INET6; 1380 memcpy(&udp_conf.local_ip6, cfg->local_ip6, 1381 sizeof(udp_conf.local_ip6)); 1382 memcpy(&udp_conf.peer_ip6, cfg->peer_ip6, 1383 sizeof(udp_conf.peer_ip6)); 1384 udp_conf.use_udp6_tx_checksums = 1385 !cfg->udp6_zero_tx_checksums; 1386 udp_conf.use_udp6_rx_checksums = 1387 !cfg->udp6_zero_rx_checksums; 1388 } else 1389 #endif 1390 { 1391 udp_conf.family = AF_INET; 1392 udp_conf.local_ip = cfg->local_ip; 1393 udp_conf.peer_ip = cfg->peer_ip; 1394 udp_conf.use_udp_checksums = cfg->use_udp_checksums; 1395 } 1396 1397 udp_conf.local_udp_port = htons(cfg->local_udp_port); 1398 udp_conf.peer_udp_port = htons(cfg->peer_udp_port); 1399 1400 err = udp_sock_create(net, &udp_conf, &sock); 1401 if (err < 0) 1402 goto out; 1403 1404 break; 1405 1406 case L2TP_ENCAPTYPE_IP: 1407 #if IS_ENABLED(CONFIG_IPV6) 1408 if (cfg->local_ip6 && cfg->peer_ip6) { 1409 struct sockaddr_l2tpip6 ip6_addr = {0}; 1410 1411 err = sock_create_kern(net, AF_INET6, SOCK_DGRAM, 1412 IPPROTO_L2TP, &sock); 1413 if (err < 0) 1414 goto out; 1415 1416 ip6_addr.l2tp_family = AF_INET6; 1417 memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6, 1418 sizeof(ip6_addr.l2tp_addr)); 1419 ip6_addr.l2tp_conn_id = tunnel_id; 1420 err = kernel_bind(sock, (struct sockaddr *)&ip6_addr, 1421 sizeof(ip6_addr)); 1422 if (err < 0) 1423 goto out; 1424 1425 ip6_addr.l2tp_family = AF_INET6; 1426 memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6, 1427 sizeof(ip6_addr.l2tp_addr)); 1428 ip6_addr.l2tp_conn_id = peer_tunnel_id; 1429 err = kernel_connect(sock, 1430 (struct sockaddr *)&ip6_addr, 1431 sizeof(ip6_addr), 0); 1432 if (err < 0) 1433 goto out; 1434 } else 1435 #endif 1436 { 1437 struct sockaddr_l2tpip ip_addr = {0}; 1438 1439 err = sock_create_kern(net, AF_INET, SOCK_DGRAM, 1440 IPPROTO_L2TP, &sock); 1441 if (err < 0) 1442 goto out; 1443 1444 ip_addr.l2tp_family = AF_INET; 1445 ip_addr.l2tp_addr = cfg->local_ip; 1446 ip_addr.l2tp_conn_id = tunnel_id; 1447 err = kernel_bind(sock, (struct sockaddr *)&ip_addr, 1448 sizeof(ip_addr)); 1449 if (err < 0) 1450 goto out; 1451 1452 ip_addr.l2tp_family = AF_INET; 1453 ip_addr.l2tp_addr = cfg->peer_ip; 1454 ip_addr.l2tp_conn_id = peer_tunnel_id; 1455 err = kernel_connect(sock, (struct sockaddr *)&ip_addr, 1456 sizeof(ip_addr), 0); 1457 if (err < 0) 1458 goto out; 1459 } 1460 break; 1461 1462 default: 1463 goto out; 1464 } 1465 1466 out: 1467 *sockp = sock; 1468 if (err < 0 && sock) { 1469 kernel_sock_shutdown(sock, SHUT_RDWR); 1470 sock_release(sock); 1471 *sockp = NULL; 1472 } 1473 1474 return err; 1475 } 1476 1477 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id, 1478 struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp) 1479 { 1480 struct l2tp_tunnel *tunnel = NULL; 1481 int err; 1482 enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP; 1483 1484 if (cfg) 1485 encap = cfg->encap; 1486 1487 tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL); 1488 if (!tunnel) { 1489 err = -ENOMEM; 1490 goto err; 1491 } 1492 1493 tunnel->version = version; 1494 tunnel->tunnel_id = tunnel_id; 1495 tunnel->peer_tunnel_id = peer_tunnel_id; 1496 1497 tunnel->magic = L2TP_TUNNEL_MAGIC; 1498 sprintf(&tunnel->name[0], "tunl %u", tunnel_id); 1499 spin_lock_init(&tunnel->list_lock); 1500 tunnel->acpt_newsess = true; 1501 INIT_LIST_HEAD(&tunnel->session_list); 1502 1503 tunnel->encap = encap; 1504 1505 refcount_set(&tunnel->ref_count, 1); 1506 tunnel->fd = fd; 1507 1508 /* Init delete workqueue struct */ 1509 INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work); 1510 1511 err = 0; 1512 err: 1513 if (tunnelp) 1514 *tunnelp = tunnel; 1515 1516 return err; 1517 } 1518 EXPORT_SYMBOL_GPL(l2tp_tunnel_create); 1519 1520 static int l2tp_validate_socket(const struct sock *sk, const struct net *net, 1521 enum l2tp_encap_type encap) 1522 { 1523 if (!net_eq(sock_net(sk), net)) 1524 return -EINVAL; 1525 1526 if (sk->sk_type != SOCK_DGRAM) 1527 return -EPROTONOSUPPORT; 1528 1529 if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6) 1530 return -EPROTONOSUPPORT; 1531 1532 if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) || 1533 (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP)) 1534 return -EPROTONOSUPPORT; 1535 1536 if (sk->sk_user_data) 1537 return -EBUSY; 1538 1539 return 0; 1540 } 1541 1542 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net, 1543 struct l2tp_tunnel_cfg *cfg) 1544 { 1545 struct l2tp_net *pn = l2tp_pernet(net); 1546 u32 tunnel_id = tunnel->tunnel_id; 1547 struct socket *sock; 1548 struct sock *sk; 1549 int ret; 1550 1551 spin_lock_bh(&pn->l2tp_tunnel_idr_lock); 1552 ret = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id, 1553 GFP_ATOMIC); 1554 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock); 1555 if (ret) 1556 return ret == -ENOSPC ? -EEXIST : ret; 1557 1558 if (tunnel->fd < 0) { 1559 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id, 1560 tunnel->peer_tunnel_id, cfg, 1561 &sock); 1562 if (ret < 0) 1563 goto err; 1564 } else { 1565 sock = sockfd_lookup(tunnel->fd, &ret); 1566 if (!sock) 1567 goto err; 1568 } 1569 1570 sk = sock->sk; 1571 lock_sock(sk); 1572 write_lock_bh(&sk->sk_callback_lock); 1573 ret = l2tp_validate_socket(sk, net, tunnel->encap); 1574 if (ret < 0) 1575 goto err_inval_sock; 1576 rcu_assign_sk_user_data(sk, tunnel); 1577 write_unlock_bh(&sk->sk_callback_lock); 1578 1579 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) { 1580 struct udp_tunnel_sock_cfg udp_cfg = { 1581 .sk_user_data = tunnel, 1582 .encap_type = UDP_ENCAP_L2TPINUDP, 1583 .encap_rcv = l2tp_udp_encap_recv, 1584 .encap_err_rcv = l2tp_udp_encap_err_recv, 1585 .encap_destroy = l2tp_udp_encap_destroy, 1586 }; 1587 1588 setup_udp_tunnel_sock(net, sock, &udp_cfg); 1589 } 1590 1591 tunnel->old_sk_destruct = sk->sk_destruct; 1592 sk->sk_destruct = &l2tp_tunnel_destruct; 1593 sk->sk_allocation = GFP_ATOMIC; 1594 release_sock(sk); 1595 1596 sock_hold(sk); 1597 tunnel->sock = sk; 1598 tunnel->l2tp_net = net; 1599 1600 spin_lock_bh(&pn->l2tp_tunnel_idr_lock); 1601 idr_replace(&pn->l2tp_tunnel_idr, tunnel, tunnel->tunnel_id); 1602 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock); 1603 1604 trace_register_tunnel(tunnel); 1605 1606 if (tunnel->fd >= 0) 1607 sockfd_put(sock); 1608 1609 return 0; 1610 1611 err_inval_sock: 1612 write_unlock_bh(&sk->sk_callback_lock); 1613 release_sock(sk); 1614 1615 if (tunnel->fd < 0) 1616 sock_release(sock); 1617 else 1618 sockfd_put(sock); 1619 err: 1620 l2tp_tunnel_remove(net, tunnel); 1621 return ret; 1622 } 1623 EXPORT_SYMBOL_GPL(l2tp_tunnel_register); 1624 1625 /* This function is used by the netlink TUNNEL_DELETE command. 1626 */ 1627 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel) 1628 { 1629 if (!test_and_set_bit(0, &tunnel->dead)) { 1630 trace_delete_tunnel(tunnel); 1631 l2tp_tunnel_inc_refcount(tunnel); 1632 queue_work(l2tp_wq, &tunnel->del_work); 1633 } 1634 } 1635 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete); 1636 1637 void l2tp_session_delete(struct l2tp_session *session) 1638 { 1639 if (test_and_set_bit(0, &session->dead)) 1640 return; 1641 1642 trace_delete_session(session); 1643 l2tp_session_unhash(session); 1644 l2tp_session_queue_purge(session); 1645 if (session->session_close) 1646 (*session->session_close)(session); 1647 1648 l2tp_session_dec_refcount(session); 1649 } 1650 EXPORT_SYMBOL_GPL(l2tp_session_delete); 1651 1652 /* We come here whenever a session's send_seq, cookie_len or 1653 * l2specific_type parameters are set. 1654 */ 1655 void l2tp_session_set_header_len(struct l2tp_session *session, int version) 1656 { 1657 if (version == L2TP_HDR_VER_2) { 1658 session->hdr_len = 6; 1659 if (session->send_seq) 1660 session->hdr_len += 4; 1661 } else { 1662 session->hdr_len = 4 + session->cookie_len; 1663 session->hdr_len += l2tp_get_l2specific_len(session); 1664 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP) 1665 session->hdr_len += 4; 1666 } 1667 } 1668 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len); 1669 1670 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id, 1671 u32 peer_session_id, struct l2tp_session_cfg *cfg) 1672 { 1673 struct l2tp_session *session; 1674 1675 session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL); 1676 if (session) { 1677 session->magic = L2TP_SESSION_MAGIC; 1678 session->tunnel = tunnel; 1679 1680 session->session_id = session_id; 1681 session->peer_session_id = peer_session_id; 1682 session->nr = 0; 1683 if (tunnel->version == L2TP_HDR_VER_2) 1684 session->nr_max = 0xffff; 1685 else 1686 session->nr_max = 0xffffff; 1687 session->nr_window_size = session->nr_max / 2; 1688 session->nr_oos_count_max = 4; 1689 1690 /* Use NR of first received packet */ 1691 session->reorder_skip = 1; 1692 1693 sprintf(&session->name[0], "sess %u/%u", 1694 tunnel->tunnel_id, session->session_id); 1695 1696 skb_queue_head_init(&session->reorder_q); 1697 1698 session->hlist_key = l2tp_v3_session_hashkey(tunnel->sock, session->session_id); 1699 INIT_HLIST_NODE(&session->hlist); 1700 INIT_LIST_HEAD(&session->clist); 1701 INIT_LIST_HEAD(&session->list); 1702 1703 if (cfg) { 1704 session->pwtype = cfg->pw_type; 1705 session->send_seq = cfg->send_seq; 1706 session->recv_seq = cfg->recv_seq; 1707 session->lns_mode = cfg->lns_mode; 1708 session->reorder_timeout = cfg->reorder_timeout; 1709 session->l2specific_type = cfg->l2specific_type; 1710 session->cookie_len = cfg->cookie_len; 1711 memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len); 1712 session->peer_cookie_len = cfg->peer_cookie_len; 1713 memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len); 1714 } 1715 1716 l2tp_session_set_header_len(session, tunnel->version); 1717 1718 refcount_set(&session->ref_count, 1); 1719 1720 return session; 1721 } 1722 1723 return ERR_PTR(-ENOMEM); 1724 } 1725 EXPORT_SYMBOL_GPL(l2tp_session_create); 1726 1727 /***************************************************************************** 1728 * Init and cleanup 1729 *****************************************************************************/ 1730 1731 static __net_init int l2tp_init_net(struct net *net) 1732 { 1733 struct l2tp_net *pn = net_generic(net, l2tp_net_id); 1734 1735 idr_init(&pn->l2tp_tunnel_idr); 1736 spin_lock_init(&pn->l2tp_tunnel_idr_lock); 1737 1738 idr_init(&pn->l2tp_v2_session_idr); 1739 idr_init(&pn->l2tp_v3_session_idr); 1740 spin_lock_init(&pn->l2tp_session_idr_lock); 1741 1742 return 0; 1743 } 1744 1745 static __net_exit void l2tp_exit_net(struct net *net) 1746 { 1747 struct l2tp_net *pn = l2tp_pernet(net); 1748 struct l2tp_tunnel *tunnel = NULL; 1749 unsigned long tunnel_id, tmp; 1750 1751 rcu_read_lock_bh(); 1752 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) { 1753 if (tunnel) 1754 l2tp_tunnel_delete(tunnel); 1755 } 1756 rcu_read_unlock_bh(); 1757 1758 if (l2tp_wq) 1759 flush_workqueue(l2tp_wq); 1760 rcu_barrier(); 1761 1762 idr_destroy(&pn->l2tp_v2_session_idr); 1763 idr_destroy(&pn->l2tp_v3_session_idr); 1764 idr_destroy(&pn->l2tp_tunnel_idr); 1765 } 1766 1767 static struct pernet_operations l2tp_net_ops = { 1768 .init = l2tp_init_net, 1769 .exit = l2tp_exit_net, 1770 .id = &l2tp_net_id, 1771 .size = sizeof(struct l2tp_net), 1772 }; 1773 1774 static int __init l2tp_init(void) 1775 { 1776 int rc = 0; 1777 1778 rc = register_pernet_device(&l2tp_net_ops); 1779 if (rc) 1780 goto out; 1781 1782 l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0); 1783 if (!l2tp_wq) { 1784 pr_err("alloc_workqueue failed\n"); 1785 unregister_pernet_device(&l2tp_net_ops); 1786 rc = -ENOMEM; 1787 goto out; 1788 } 1789 1790 pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION); 1791 1792 out: 1793 return rc; 1794 } 1795 1796 static void __exit l2tp_exit(void) 1797 { 1798 unregister_pernet_device(&l2tp_net_ops); 1799 if (l2tp_wq) { 1800 destroy_workqueue(l2tp_wq); 1801 l2tp_wq = NULL; 1802 } 1803 } 1804 1805 module_init(l2tp_init); 1806 module_exit(l2tp_exit); 1807 1808 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>"); 1809 MODULE_DESCRIPTION("L2TP core"); 1810 MODULE_LICENSE("GPL"); 1811 MODULE_VERSION(L2TP_DRV_VERSION); 1812