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/hash.h> 43 #include <linux/sort.h> 44 #include <linux/file.h> 45 #include <linux/nsproxy.h> 46 #include <net/net_namespace.h> 47 #include <net/netns/generic.h> 48 #include <net/dst.h> 49 #include <net/ip.h> 50 #include <net/udp.h> 51 #include <net/udp_tunnel.h> 52 #include <net/inet_common.h> 53 #include <net/xfrm.h> 54 #include <net/protocol.h> 55 #include <net/inet6_connection_sock.h> 56 #include <net/inet_ecn.h> 57 #include <net/ip6_route.h> 58 #include <net/ip6_checksum.h> 59 60 #include <asm/byteorder.h> 61 #include <linux/atomic.h> 62 63 #include "l2tp_core.h" 64 #include "trace.h" 65 66 #define CREATE_TRACE_POINTS 67 #include "trace.h" 68 69 #define L2TP_DRV_VERSION "V2.0" 70 71 /* L2TP header constants */ 72 #define L2TP_HDRFLAG_T 0x8000 73 #define L2TP_HDRFLAG_L 0x4000 74 #define L2TP_HDRFLAG_S 0x0800 75 #define L2TP_HDRFLAG_O 0x0200 76 #define L2TP_HDRFLAG_P 0x0100 77 78 #define L2TP_HDR_VER_MASK 0x000F 79 #define L2TP_HDR_VER_2 0x0002 80 #define L2TP_HDR_VER_3 0x0003 81 82 /* L2TPv3 default L2-specific sublayer */ 83 #define L2TP_SLFLAG_S 0x40000000 84 #define L2TP_SL_SEQ_MASK 0x00ffffff 85 86 #define L2TP_HDR_SIZE_MAX 14 87 88 /* Default trace flags */ 89 #define L2TP_DEFAULT_DEBUG_FLAGS 0 90 91 #define L2TP_DEPTH_NESTING 2 92 #if L2TP_DEPTH_NESTING == SINGLE_DEPTH_NESTING 93 #error "L2TP requires its own lockdep subclass" 94 #endif 95 96 /* Private data stored for received packets in the skb. 97 */ 98 struct l2tp_skb_cb { 99 u32 ns; 100 u16 has_seq; 101 u16 length; 102 unsigned long expires; 103 }; 104 105 #define L2TP_SKB_CB(skb) ((struct l2tp_skb_cb *)&(skb)->cb[sizeof(struct inet_skb_parm)]) 106 107 static struct workqueue_struct *l2tp_wq; 108 109 /* per-net private data for this module */ 110 static unsigned int l2tp_net_id; 111 struct l2tp_net { 112 /* Lock for write access to l2tp_tunnel_idr */ 113 spinlock_t l2tp_tunnel_idr_lock; 114 struct idr l2tp_tunnel_idr; 115 struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2]; 116 /* Lock for write access to l2tp_session_hlist */ 117 spinlock_t l2tp_session_hlist_lock; 118 }; 119 120 #if IS_ENABLED(CONFIG_IPV6) 121 static bool l2tp_sk_is_v6(struct sock *sk) 122 { 123 return sk->sk_family == PF_INET6 && 124 !ipv6_addr_v4mapped(&sk->sk_v6_daddr); 125 } 126 #endif 127 128 static inline struct l2tp_net *l2tp_pernet(const struct net *net) 129 { 130 return net_generic(net, l2tp_net_id); 131 } 132 133 /* Session hash global list for L2TPv3. 134 * The session_id SHOULD be random according to RFC3931, but several 135 * L2TP implementations use incrementing session_ids. So we do a real 136 * hash on the session_id, rather than a simple bitmask. 137 */ 138 static inline struct hlist_head * 139 l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id) 140 { 141 return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)]; 142 } 143 144 /* Session hash list. 145 * The session_id SHOULD be random according to RFC2661, but several 146 * L2TP implementations (Cisco and Microsoft) use incrementing 147 * session_ids. So we do a real hash on the session_id, rather than a 148 * simple bitmask. 149 */ 150 static inline struct hlist_head * 151 l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id) 152 { 153 return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)]; 154 } 155 156 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel) 157 { 158 trace_free_tunnel(tunnel); 159 sock_put(tunnel->sock); 160 /* the tunnel is freed in the socket destructor */ 161 } 162 163 static void l2tp_session_free(struct l2tp_session *session) 164 { 165 trace_free_session(session); 166 if (session->tunnel) 167 l2tp_tunnel_dec_refcount(session->tunnel); 168 kfree(session); 169 } 170 171 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk) 172 { 173 struct l2tp_tunnel *tunnel = sk->sk_user_data; 174 175 if (tunnel) 176 if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC)) 177 return NULL; 178 179 return tunnel; 180 } 181 EXPORT_SYMBOL_GPL(l2tp_sk_to_tunnel); 182 183 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel) 184 { 185 refcount_inc(&tunnel->ref_count); 186 } 187 EXPORT_SYMBOL_GPL(l2tp_tunnel_inc_refcount); 188 189 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel) 190 { 191 if (refcount_dec_and_test(&tunnel->ref_count)) 192 l2tp_tunnel_free(tunnel); 193 } 194 EXPORT_SYMBOL_GPL(l2tp_tunnel_dec_refcount); 195 196 void l2tp_session_inc_refcount(struct l2tp_session *session) 197 { 198 refcount_inc(&session->ref_count); 199 } 200 EXPORT_SYMBOL_GPL(l2tp_session_inc_refcount); 201 202 void l2tp_session_dec_refcount(struct l2tp_session *session) 203 { 204 if (refcount_dec_and_test(&session->ref_count)) 205 l2tp_session_free(session); 206 } 207 EXPORT_SYMBOL_GPL(l2tp_session_dec_refcount); 208 209 /* Lookup a tunnel. A new reference is held on the returned tunnel. */ 210 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id) 211 { 212 const struct l2tp_net *pn = l2tp_pernet(net); 213 struct l2tp_tunnel *tunnel; 214 215 rcu_read_lock_bh(); 216 tunnel = idr_find(&pn->l2tp_tunnel_idr, tunnel_id); 217 if (tunnel && refcount_inc_not_zero(&tunnel->ref_count)) { 218 rcu_read_unlock_bh(); 219 return tunnel; 220 } 221 rcu_read_unlock_bh(); 222 223 return NULL; 224 } 225 EXPORT_SYMBOL_GPL(l2tp_tunnel_get); 226 227 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth) 228 { 229 struct l2tp_net *pn = l2tp_pernet(net); 230 unsigned long tunnel_id, tmp; 231 struct l2tp_tunnel *tunnel; 232 int count = 0; 233 234 rcu_read_lock_bh(); 235 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) { 236 if (tunnel && ++count > nth && 237 refcount_inc_not_zero(&tunnel->ref_count)) { 238 rcu_read_unlock_bh(); 239 return tunnel; 240 } 241 } 242 rcu_read_unlock_bh(); 243 244 return NULL; 245 } 246 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth); 247 248 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel, 249 u32 session_id) 250 { 251 struct hlist_head *session_list; 252 struct l2tp_session *session; 253 254 session_list = l2tp_session_id_hash(tunnel, session_id); 255 256 rcu_read_lock_bh(); 257 hlist_for_each_entry_rcu(session, session_list, hlist) 258 if (session->session_id == session_id) { 259 l2tp_session_inc_refcount(session); 260 rcu_read_unlock_bh(); 261 262 return session; 263 } 264 rcu_read_unlock_bh(); 265 266 return NULL; 267 } 268 EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session); 269 270 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id) 271 { 272 struct hlist_head *session_list; 273 struct l2tp_session *session; 274 275 session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id); 276 277 rcu_read_lock_bh(); 278 hlist_for_each_entry_rcu(session, session_list, global_hlist) 279 if (session->session_id == session_id) { 280 l2tp_session_inc_refcount(session); 281 rcu_read_unlock_bh(); 282 283 return session; 284 } 285 rcu_read_unlock_bh(); 286 287 return NULL; 288 } 289 EXPORT_SYMBOL_GPL(l2tp_session_get); 290 291 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth) 292 { 293 int hash; 294 struct l2tp_session *session; 295 int count = 0; 296 297 rcu_read_lock_bh(); 298 for (hash = 0; hash < L2TP_HASH_SIZE; hash++) { 299 hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) { 300 if (++count > nth) { 301 l2tp_session_inc_refcount(session); 302 rcu_read_unlock_bh(); 303 return session; 304 } 305 } 306 } 307 308 rcu_read_unlock_bh(); 309 310 return NULL; 311 } 312 EXPORT_SYMBOL_GPL(l2tp_session_get_nth); 313 314 /* Lookup a session by interface name. 315 * This is very inefficient but is only used by management interfaces. 316 */ 317 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net, 318 const char *ifname) 319 { 320 struct l2tp_net *pn = l2tp_pernet(net); 321 int hash; 322 struct l2tp_session *session; 323 324 rcu_read_lock_bh(); 325 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) { 326 hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) { 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 int l2tp_session_register(struct l2tp_session *session, 343 struct l2tp_tunnel *tunnel) 344 { 345 struct l2tp_session *session_walk; 346 struct hlist_head *g_head; 347 struct hlist_head *head; 348 struct l2tp_net *pn; 349 int err; 350 351 head = l2tp_session_id_hash(tunnel, session->session_id); 352 353 spin_lock_bh(&tunnel->hlist_lock); 354 if (!tunnel->acpt_newsess) { 355 err = -ENODEV; 356 goto err_tlock; 357 } 358 359 hlist_for_each_entry(session_walk, head, hlist) 360 if (session_walk->session_id == session->session_id) { 361 err = -EEXIST; 362 goto err_tlock; 363 } 364 365 if (tunnel->version == L2TP_HDR_VER_3) { 366 pn = l2tp_pernet(tunnel->l2tp_net); 367 g_head = l2tp_session_id_hash_2(pn, session->session_id); 368 369 spin_lock_bh(&pn->l2tp_session_hlist_lock); 370 371 /* IP encap expects session IDs to be globally unique, while 372 * UDP encap doesn't. 373 */ 374 hlist_for_each_entry(session_walk, g_head, global_hlist) 375 if (session_walk->session_id == session->session_id && 376 (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP || 377 tunnel->encap == L2TP_ENCAPTYPE_IP)) { 378 err = -EEXIST; 379 goto err_tlock_pnlock; 380 } 381 382 l2tp_tunnel_inc_refcount(tunnel); 383 hlist_add_head_rcu(&session->global_hlist, g_head); 384 385 spin_unlock_bh(&pn->l2tp_session_hlist_lock); 386 } else { 387 l2tp_tunnel_inc_refcount(tunnel); 388 } 389 390 hlist_add_head_rcu(&session->hlist, head); 391 spin_unlock_bh(&tunnel->hlist_lock); 392 393 trace_register_session(session); 394 395 return 0; 396 397 err_tlock_pnlock: 398 spin_unlock_bh(&pn->l2tp_session_hlist_lock); 399 err_tlock: 400 spin_unlock_bh(&tunnel->hlist_lock); 401 402 return err; 403 } 404 EXPORT_SYMBOL_GPL(l2tp_session_register); 405 406 /***************************************************************************** 407 * Receive data handling 408 *****************************************************************************/ 409 410 /* Queue a skb in order. We come here only if the skb has an L2TP sequence 411 * number. 412 */ 413 static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb) 414 { 415 struct sk_buff *skbp; 416 struct sk_buff *tmp; 417 u32 ns = L2TP_SKB_CB(skb)->ns; 418 419 spin_lock_bh(&session->reorder_q.lock); 420 skb_queue_walk_safe(&session->reorder_q, skbp, tmp) { 421 if (L2TP_SKB_CB(skbp)->ns > ns) { 422 __skb_queue_before(&session->reorder_q, skbp, skb); 423 atomic_long_inc(&session->stats.rx_oos_packets); 424 goto out; 425 } 426 } 427 428 __skb_queue_tail(&session->reorder_q, skb); 429 430 out: 431 spin_unlock_bh(&session->reorder_q.lock); 432 } 433 434 /* Dequeue a single skb. 435 */ 436 static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb) 437 { 438 struct l2tp_tunnel *tunnel = session->tunnel; 439 int length = L2TP_SKB_CB(skb)->length; 440 441 /* We're about to requeue the skb, so return resources 442 * to its current owner (a socket receive buffer). 443 */ 444 skb_orphan(skb); 445 446 atomic_long_inc(&tunnel->stats.rx_packets); 447 atomic_long_add(length, &tunnel->stats.rx_bytes); 448 atomic_long_inc(&session->stats.rx_packets); 449 atomic_long_add(length, &session->stats.rx_bytes); 450 451 if (L2TP_SKB_CB(skb)->has_seq) { 452 /* Bump our Nr */ 453 session->nr++; 454 session->nr &= session->nr_max; 455 trace_session_seqnum_update(session); 456 } 457 458 /* call private receive handler */ 459 if (session->recv_skb) 460 (*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length); 461 else 462 kfree_skb(skb); 463 } 464 465 /* Dequeue skbs from the session's reorder_q, subject to packet order. 466 * Skbs that have been in the queue for too long are simply discarded. 467 */ 468 static void l2tp_recv_dequeue(struct l2tp_session *session) 469 { 470 struct sk_buff *skb; 471 struct sk_buff *tmp; 472 473 /* If the pkt at the head of the queue has the nr that we 474 * expect to send up next, dequeue it and any other 475 * in-sequence packets behind it. 476 */ 477 start: 478 spin_lock_bh(&session->reorder_q.lock); 479 skb_queue_walk_safe(&session->reorder_q, skb, tmp) { 480 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb); 481 482 /* If the packet has been pending on the queue for too long, discard it */ 483 if (time_after(jiffies, cb->expires)) { 484 atomic_long_inc(&session->stats.rx_seq_discards); 485 atomic_long_inc(&session->stats.rx_errors); 486 trace_session_pkt_expired(session, cb->ns); 487 session->reorder_skip = 1; 488 __skb_unlink(skb, &session->reorder_q); 489 kfree_skb(skb); 490 continue; 491 } 492 493 if (cb->has_seq) { 494 if (session->reorder_skip) { 495 session->reorder_skip = 0; 496 session->nr = cb->ns; 497 trace_session_seqnum_reset(session); 498 } 499 if (cb->ns != session->nr) 500 goto out; 501 } 502 __skb_unlink(skb, &session->reorder_q); 503 504 /* Process the skb. We release the queue lock while we 505 * do so to let other contexts process the queue. 506 */ 507 spin_unlock_bh(&session->reorder_q.lock); 508 l2tp_recv_dequeue_skb(session, skb); 509 goto start; 510 } 511 512 out: 513 spin_unlock_bh(&session->reorder_q.lock); 514 } 515 516 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr) 517 { 518 u32 nws; 519 520 if (nr >= session->nr) 521 nws = nr - session->nr; 522 else 523 nws = (session->nr_max + 1) - (session->nr - nr); 524 525 return nws < session->nr_window_size; 526 } 527 528 /* If packet has sequence numbers, queue it if acceptable. Returns 0 if 529 * acceptable, else non-zero. 530 */ 531 static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb) 532 { 533 struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb); 534 535 if (!l2tp_seq_check_rx_window(session, cb->ns)) { 536 /* Packet sequence number is outside allowed window. 537 * Discard it. 538 */ 539 trace_session_pkt_outside_rx_window(session, cb->ns); 540 goto discard; 541 } 542 543 if (session->reorder_timeout != 0) { 544 /* Packet reordering enabled. Add skb to session's 545 * reorder queue, in order of ns. 546 */ 547 l2tp_recv_queue_skb(session, skb); 548 goto out; 549 } 550 551 /* Packet reordering disabled. Discard out-of-sequence packets, while 552 * tracking the number if in-sequence packets after the first OOS packet 553 * is seen. After nr_oos_count_max in-sequence packets, reset the 554 * sequence number to re-enable packet reception. 555 */ 556 if (cb->ns == session->nr) { 557 skb_queue_tail(&session->reorder_q, skb); 558 } else { 559 u32 nr_oos = cb->ns; 560 u32 nr_next = (session->nr_oos + 1) & session->nr_max; 561 562 if (nr_oos == nr_next) 563 session->nr_oos_count++; 564 else 565 session->nr_oos_count = 0; 566 567 session->nr_oos = nr_oos; 568 if (session->nr_oos_count > session->nr_oos_count_max) { 569 session->reorder_skip = 1; 570 } 571 if (!session->reorder_skip) { 572 atomic_long_inc(&session->stats.rx_seq_discards); 573 trace_session_pkt_oos(session, cb->ns); 574 goto discard; 575 } 576 skb_queue_tail(&session->reorder_q, skb); 577 } 578 579 out: 580 return 0; 581 582 discard: 583 return 1; 584 } 585 586 /* Do receive processing of L2TP data frames. We handle both L2TPv2 587 * and L2TPv3 data frames here. 588 * 589 * L2TPv2 Data Message Header 590 * 591 * 0 1 2 3 592 * 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 1 593 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 * |T|L|x|x|S|x|O|P|x|x|x|x| Ver | Length (opt) | 595 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 * | Tunnel ID | Session ID | 597 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 * | Ns (opt) | Nr (opt) | 599 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 600 * | Offset Size (opt) | Offset pad... (opt) 601 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 * 603 * Data frames are marked by T=0. All other fields are the same as 604 * those in L2TP control frames. 605 * 606 * L2TPv3 Data Message Header 607 * 608 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 * | L2TP Session Header | 610 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 611 * | L2-Specific Sublayer | 612 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 * | Tunnel Payload ... 614 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 615 * 616 * L2TPv3 Session Header Over IP 617 * 618 * 0 1 2 3 619 * 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 1 620 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 * | Session ID | 622 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 * | Cookie (optional, maximum 64 bits)... 624 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 625 * | 626 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 627 * 628 * L2TPv3 L2-Specific Sublayer Format 629 * 630 * 0 1 2 3 631 * 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 1 632 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 * |x|S|x|x|x|x|x|x| Sequence Number | 634 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 * 636 * Cookie value and sublayer format are negotiated with the peer when 637 * the session is set up. Unlike L2TPv2, we do not need to parse the 638 * packet header to determine if optional fields are present. 639 * 640 * Caller must already have parsed the frame and determined that it is 641 * a data (not control) frame before coming here. Fields up to the 642 * session-id have already been parsed and ptr points to the data 643 * after the session-id. 644 */ 645 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb, 646 unsigned char *ptr, unsigned char *optr, u16 hdrflags, 647 int length) 648 { 649 struct l2tp_tunnel *tunnel = session->tunnel; 650 int offset; 651 652 /* Parse and check optional cookie */ 653 if (session->peer_cookie_len > 0) { 654 if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) { 655 pr_debug_ratelimited("%s: cookie mismatch (%u/%u). Discarding.\n", 656 tunnel->name, tunnel->tunnel_id, 657 session->session_id); 658 atomic_long_inc(&session->stats.rx_cookie_discards); 659 goto discard; 660 } 661 ptr += session->peer_cookie_len; 662 } 663 664 /* Handle the optional sequence numbers. Sequence numbers are 665 * in different places for L2TPv2 and L2TPv3. 666 * 667 * If we are the LAC, enable/disable sequence numbers under 668 * the control of the LNS. If no sequence numbers present but 669 * we were expecting them, discard frame. 670 */ 671 L2TP_SKB_CB(skb)->has_seq = 0; 672 if (tunnel->version == L2TP_HDR_VER_2) { 673 if (hdrflags & L2TP_HDRFLAG_S) { 674 /* Store L2TP info in the skb */ 675 L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr); 676 L2TP_SKB_CB(skb)->has_seq = 1; 677 ptr += 2; 678 /* Skip past nr in the header */ 679 ptr += 2; 680 681 } 682 } else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) { 683 u32 l2h = ntohl(*(__be32 *)ptr); 684 685 if (l2h & 0x40000000) { 686 /* Store L2TP info in the skb */ 687 L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff; 688 L2TP_SKB_CB(skb)->has_seq = 1; 689 } 690 ptr += 4; 691 } 692 693 if (L2TP_SKB_CB(skb)->has_seq) { 694 /* Received a packet with sequence numbers. If we're the LAC, 695 * check if we sre sending sequence numbers and if not, 696 * configure it so. 697 */ 698 if (!session->lns_mode && !session->send_seq) { 699 trace_session_seqnum_lns_enable(session); 700 session->send_seq = 1; 701 l2tp_session_set_header_len(session, tunnel->version); 702 } 703 } else { 704 /* No sequence numbers. 705 * If user has configured mandatory sequence numbers, discard. 706 */ 707 if (session->recv_seq) { 708 pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n", 709 session->name); 710 atomic_long_inc(&session->stats.rx_seq_discards); 711 goto discard; 712 } 713 714 /* If we're the LAC and we're sending sequence numbers, the 715 * LNS has requested that we no longer send sequence numbers. 716 * If we're the LNS and we're sending sequence numbers, the 717 * LAC is broken. Discard the frame. 718 */ 719 if (!session->lns_mode && session->send_seq) { 720 trace_session_seqnum_lns_disable(session); 721 session->send_seq = 0; 722 l2tp_session_set_header_len(session, tunnel->version); 723 } else if (session->send_seq) { 724 pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n", 725 session->name); 726 atomic_long_inc(&session->stats.rx_seq_discards); 727 goto discard; 728 } 729 } 730 731 /* Session data offset is defined only for L2TPv2 and is 732 * indicated by an optional 16-bit value in the header. 733 */ 734 if (tunnel->version == L2TP_HDR_VER_2) { 735 /* If offset bit set, skip it. */ 736 if (hdrflags & L2TP_HDRFLAG_O) { 737 offset = ntohs(*(__be16 *)ptr); 738 ptr += 2 + offset; 739 } 740 } 741 742 offset = ptr - optr; 743 if (!pskb_may_pull(skb, offset)) 744 goto discard; 745 746 __skb_pull(skb, offset); 747 748 /* Prepare skb for adding to the session's reorder_q. Hold 749 * packets for max reorder_timeout or 1 second if not 750 * reordering. 751 */ 752 L2TP_SKB_CB(skb)->length = length; 753 L2TP_SKB_CB(skb)->expires = jiffies + 754 (session->reorder_timeout ? session->reorder_timeout : HZ); 755 756 /* Add packet to the session's receive queue. Reordering is done here, if 757 * enabled. Saved L2TP protocol info is stored in skb->sb[]. 758 */ 759 if (L2TP_SKB_CB(skb)->has_seq) { 760 if (l2tp_recv_data_seq(session, skb)) 761 goto discard; 762 } else { 763 /* No sequence numbers. Add the skb to the tail of the 764 * reorder queue. This ensures that it will be 765 * delivered after all previous sequenced skbs. 766 */ 767 skb_queue_tail(&session->reorder_q, skb); 768 } 769 770 /* Try to dequeue as many skbs from reorder_q as we can. */ 771 l2tp_recv_dequeue(session); 772 773 return; 774 775 discard: 776 atomic_long_inc(&session->stats.rx_errors); 777 kfree_skb(skb); 778 } 779 EXPORT_SYMBOL_GPL(l2tp_recv_common); 780 781 /* Drop skbs from the session's reorder_q 782 */ 783 static void l2tp_session_queue_purge(struct l2tp_session *session) 784 { 785 struct sk_buff *skb = NULL; 786 787 while ((skb = skb_dequeue(&session->reorder_q))) { 788 atomic_long_inc(&session->stats.rx_errors); 789 kfree_skb(skb); 790 } 791 } 792 793 /* Internal UDP receive frame. Do the real work of receiving an L2TP data frame 794 * here. The skb is not on a list when we get here. 795 * Returns 0 if the packet was a data packet and was successfully passed on. 796 * Returns 1 if the packet was not a good data packet and could not be 797 * forwarded. All such packets are passed up to userspace to deal with. 798 */ 799 static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb) 800 { 801 struct l2tp_session *session = NULL; 802 unsigned char *ptr, *optr; 803 u16 hdrflags; 804 u32 tunnel_id, session_id; 805 u16 version; 806 int length; 807 808 /* UDP has verified checksum */ 809 810 /* UDP always verifies the packet length. */ 811 __skb_pull(skb, sizeof(struct udphdr)); 812 813 /* Short packet? */ 814 if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) { 815 pr_debug_ratelimited("%s: recv short packet (len=%d)\n", 816 tunnel->name, skb->len); 817 goto invalid; 818 } 819 820 /* Point to L2TP header */ 821 optr = skb->data; 822 ptr = skb->data; 823 824 /* Get L2TP header flags */ 825 hdrflags = ntohs(*(__be16 *)ptr); 826 827 /* Check protocol version */ 828 version = hdrflags & L2TP_HDR_VER_MASK; 829 if (version != tunnel->version) { 830 pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n", 831 tunnel->name, version, tunnel->version); 832 goto invalid; 833 } 834 835 /* Get length of L2TP packet */ 836 length = skb->len; 837 838 /* If type is control packet, it is handled by userspace. */ 839 if (hdrflags & L2TP_HDRFLAG_T) 840 goto pass; 841 842 /* Skip flags */ 843 ptr += 2; 844 845 if (tunnel->version == L2TP_HDR_VER_2) { 846 /* If length is present, skip it */ 847 if (hdrflags & L2TP_HDRFLAG_L) 848 ptr += 2; 849 850 /* Extract tunnel and session ID */ 851 tunnel_id = ntohs(*(__be16 *)ptr); 852 ptr += 2; 853 session_id = ntohs(*(__be16 *)ptr); 854 ptr += 2; 855 } else { 856 ptr += 2; /* skip reserved bits */ 857 tunnel_id = tunnel->tunnel_id; 858 session_id = ntohl(*(__be32 *)ptr); 859 ptr += 4; 860 } 861 862 /* Find the session context */ 863 session = l2tp_tunnel_get_session(tunnel, session_id); 864 if (!session || !session->recv_skb) { 865 if (session) 866 l2tp_session_dec_refcount(session); 867 868 /* Not found? Pass to userspace to deal with */ 869 pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n", 870 tunnel->name, tunnel_id, session_id); 871 goto pass; 872 } 873 874 if (tunnel->version == L2TP_HDR_VER_3 && 875 l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) { 876 l2tp_session_dec_refcount(session); 877 goto invalid; 878 } 879 880 l2tp_recv_common(session, skb, ptr, optr, hdrflags, length); 881 l2tp_session_dec_refcount(session); 882 883 return 0; 884 885 invalid: 886 atomic_long_inc(&tunnel->stats.rx_invalid); 887 888 pass: 889 /* Put UDP header back */ 890 __skb_push(skb, sizeof(struct udphdr)); 891 892 return 1; 893 } 894 895 /* UDP encapsulation receive handler. See net/ipv4/udp.c. 896 * Return codes: 897 * 0 : success. 898 * <0: error 899 * >0: skb should be passed up to userspace as UDP. 900 */ 901 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb) 902 { 903 struct l2tp_tunnel *tunnel; 904 905 /* Note that this is called from the encap_rcv hook inside an 906 * RCU-protected region, but without the socket being locked. 907 * Hence we use rcu_dereference_sk_user_data to access the 908 * tunnel data structure rather the usual l2tp_sk_to_tunnel 909 * accessor function. 910 */ 911 tunnel = rcu_dereference_sk_user_data(sk); 912 if (!tunnel) 913 goto pass_up; 914 if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC)) 915 goto pass_up; 916 917 if (l2tp_udp_recv_core(tunnel, skb)) 918 goto pass_up; 919 920 return 0; 921 922 pass_up: 923 return 1; 924 } 925 EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv); 926 927 /************************************************************************ 928 * Transmit handling 929 ***********************************************************************/ 930 931 /* Build an L2TP header for the session into the buffer provided. 932 */ 933 static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf) 934 { 935 struct l2tp_tunnel *tunnel = session->tunnel; 936 __be16 *bufp = buf; 937 __be16 *optr = buf; 938 u16 flags = L2TP_HDR_VER_2; 939 u32 tunnel_id = tunnel->peer_tunnel_id; 940 u32 session_id = session->peer_session_id; 941 942 if (session->send_seq) 943 flags |= L2TP_HDRFLAG_S; 944 945 /* Setup L2TP header. */ 946 *bufp++ = htons(flags); 947 *bufp++ = htons(tunnel_id); 948 *bufp++ = htons(session_id); 949 if (session->send_seq) { 950 *bufp++ = htons(session->ns); 951 *bufp++ = 0; 952 session->ns++; 953 session->ns &= 0xffff; 954 trace_session_seqnum_update(session); 955 } 956 957 return bufp - optr; 958 } 959 960 static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf) 961 { 962 struct l2tp_tunnel *tunnel = session->tunnel; 963 char *bufp = buf; 964 char *optr = bufp; 965 966 /* Setup L2TP header. The header differs slightly for UDP and 967 * IP encapsulations. For UDP, there is 4 bytes of flags. 968 */ 969 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) { 970 u16 flags = L2TP_HDR_VER_3; 971 *((__be16 *)bufp) = htons(flags); 972 bufp += 2; 973 *((__be16 *)bufp) = 0; 974 bufp += 2; 975 } 976 977 *((__be32 *)bufp) = htonl(session->peer_session_id); 978 bufp += 4; 979 if (session->cookie_len) { 980 memcpy(bufp, &session->cookie[0], session->cookie_len); 981 bufp += session->cookie_len; 982 } 983 if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) { 984 u32 l2h = 0; 985 986 if (session->send_seq) { 987 l2h = 0x40000000 | session->ns; 988 session->ns++; 989 session->ns &= 0xffffff; 990 trace_session_seqnum_update(session); 991 } 992 993 *((__be32 *)bufp) = htonl(l2h); 994 bufp += 4; 995 } 996 997 return bufp - optr; 998 } 999 1000 /* Queue the packet to IP for output: tunnel socket lock must be held */ 1001 static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl) 1002 { 1003 int err; 1004 1005 skb->ignore_df = 1; 1006 skb_dst_drop(skb); 1007 #if IS_ENABLED(CONFIG_IPV6) 1008 if (l2tp_sk_is_v6(tunnel->sock)) 1009 err = inet6_csk_xmit(tunnel->sock, skb, NULL); 1010 else 1011 #endif 1012 err = ip_queue_xmit(tunnel->sock, skb, fl); 1013 1014 return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP; 1015 } 1016 1017 static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len) 1018 { 1019 struct l2tp_tunnel *tunnel = session->tunnel; 1020 unsigned int data_len = skb->len; 1021 struct sock *sk = tunnel->sock; 1022 int headroom, uhlen, udp_len; 1023 int ret = NET_XMIT_SUCCESS; 1024 struct inet_sock *inet; 1025 struct udphdr *uh; 1026 1027 /* Check that there's enough headroom in the skb to insert IP, 1028 * UDP and L2TP headers. If not enough, expand it to 1029 * make room. Adjust truesize. 1030 */ 1031 uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0; 1032 headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len; 1033 if (skb_cow_head(skb, headroom)) { 1034 kfree_skb(skb); 1035 return NET_XMIT_DROP; 1036 } 1037 1038 /* Setup L2TP header */ 1039 if (tunnel->version == L2TP_HDR_VER_2) 1040 l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len)); 1041 else 1042 l2tp_build_l2tpv3_header(session, __skb_push(skb, session->hdr_len)); 1043 1044 /* Reset skb netfilter state */ 1045 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt)); 1046 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED); 1047 nf_reset_ct(skb); 1048 1049 /* L2TP uses its own lockdep subclass to avoid lockdep splats caused by 1050 * nested socket calls on the same lockdep socket class. This can 1051 * happen when data from a user socket is routed over l2tp, which uses 1052 * another userspace socket. 1053 */ 1054 spin_lock_nested(&sk->sk_lock.slock, L2TP_DEPTH_NESTING); 1055 1056 if (sock_owned_by_user(sk)) { 1057 kfree_skb(skb); 1058 ret = NET_XMIT_DROP; 1059 goto out_unlock; 1060 } 1061 1062 /* The user-space may change the connection status for the user-space 1063 * provided socket at run time: we must check it under the socket lock 1064 */ 1065 if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) { 1066 kfree_skb(skb); 1067 ret = NET_XMIT_DROP; 1068 goto out_unlock; 1069 } 1070 1071 /* Report transmitted length before we add encap header, which keeps 1072 * statistics consistent for both UDP and IP encap tx/rx paths. 1073 */ 1074 *len = skb->len; 1075 1076 inet = inet_sk(sk); 1077 switch (tunnel->encap) { 1078 case L2TP_ENCAPTYPE_UDP: 1079 /* Setup UDP header */ 1080 __skb_push(skb, sizeof(*uh)); 1081 skb_reset_transport_header(skb); 1082 uh = udp_hdr(skb); 1083 uh->source = inet->inet_sport; 1084 uh->dest = inet->inet_dport; 1085 udp_len = uhlen + session->hdr_len + data_len; 1086 uh->len = htons(udp_len); 1087 1088 /* Calculate UDP checksum if configured to do so */ 1089 #if IS_ENABLED(CONFIG_IPV6) 1090 if (l2tp_sk_is_v6(sk)) 1091 udp6_set_csum(udp_get_no_check6_tx(sk), 1092 skb, &inet6_sk(sk)->saddr, 1093 &sk->sk_v6_daddr, udp_len); 1094 else 1095 #endif 1096 udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr, 1097 inet->inet_daddr, udp_len); 1098 break; 1099 1100 case L2TP_ENCAPTYPE_IP: 1101 break; 1102 } 1103 1104 ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl); 1105 1106 out_unlock: 1107 spin_unlock(&sk->sk_lock.slock); 1108 1109 return ret; 1110 } 1111 1112 /* If caller requires the skb to have a ppp header, the header must be 1113 * inserted in the skb data before calling this function. 1114 */ 1115 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb) 1116 { 1117 unsigned int len = 0; 1118 int ret; 1119 1120 ret = l2tp_xmit_core(session, skb, &len); 1121 if (ret == NET_XMIT_SUCCESS) { 1122 atomic_long_inc(&session->tunnel->stats.tx_packets); 1123 atomic_long_add(len, &session->tunnel->stats.tx_bytes); 1124 atomic_long_inc(&session->stats.tx_packets); 1125 atomic_long_add(len, &session->stats.tx_bytes); 1126 } else { 1127 atomic_long_inc(&session->tunnel->stats.tx_errors); 1128 atomic_long_inc(&session->stats.tx_errors); 1129 } 1130 return ret; 1131 } 1132 EXPORT_SYMBOL_GPL(l2tp_xmit_skb); 1133 1134 /***************************************************************************** 1135 * Tinnel and session create/destroy. 1136 *****************************************************************************/ 1137 1138 /* Tunnel socket destruct hook. 1139 * The tunnel context is deleted only when all session sockets have been 1140 * closed. 1141 */ 1142 static void l2tp_tunnel_destruct(struct sock *sk) 1143 { 1144 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk); 1145 1146 if (!tunnel) 1147 goto end; 1148 1149 /* Disable udp encapsulation */ 1150 switch (tunnel->encap) { 1151 case L2TP_ENCAPTYPE_UDP: 1152 /* No longer an encapsulation socket. See net/ipv4/udp.c */ 1153 WRITE_ONCE(udp_sk(sk)->encap_type, 0); 1154 udp_sk(sk)->encap_rcv = NULL; 1155 udp_sk(sk)->encap_destroy = NULL; 1156 break; 1157 case L2TP_ENCAPTYPE_IP: 1158 break; 1159 } 1160 1161 /* Remove hooks into tunnel socket */ 1162 write_lock_bh(&sk->sk_callback_lock); 1163 sk->sk_destruct = tunnel->old_sk_destruct; 1164 sk->sk_user_data = NULL; 1165 write_unlock_bh(&sk->sk_callback_lock); 1166 1167 /* Call the original destructor */ 1168 if (sk->sk_destruct) 1169 (*sk->sk_destruct)(sk); 1170 1171 kfree_rcu(tunnel, rcu); 1172 end: 1173 return; 1174 } 1175 1176 /* Remove an l2tp session from l2tp_core's hash lists. */ 1177 static void l2tp_session_unhash(struct l2tp_session *session) 1178 { 1179 struct l2tp_tunnel *tunnel = session->tunnel; 1180 1181 /* Remove the session from core hashes */ 1182 if (tunnel) { 1183 /* Remove from the per-tunnel hash */ 1184 spin_lock_bh(&tunnel->hlist_lock); 1185 hlist_del_init_rcu(&session->hlist); 1186 spin_unlock_bh(&tunnel->hlist_lock); 1187 1188 /* For L2TPv3 we have a per-net hash: remove from there, too */ 1189 if (tunnel->version != L2TP_HDR_VER_2) { 1190 struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net); 1191 1192 spin_lock_bh(&pn->l2tp_session_hlist_lock); 1193 hlist_del_init_rcu(&session->global_hlist); 1194 spin_unlock_bh(&pn->l2tp_session_hlist_lock); 1195 } 1196 1197 synchronize_rcu(); 1198 } 1199 } 1200 1201 /* When the tunnel is closed, all the attached sessions need to go too. 1202 */ 1203 static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel) 1204 { 1205 struct l2tp_session *session; 1206 int hash; 1207 1208 spin_lock_bh(&tunnel->hlist_lock); 1209 tunnel->acpt_newsess = false; 1210 for (hash = 0; hash < L2TP_HASH_SIZE; hash++) { 1211 again: 1212 hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) { 1213 hlist_del_init_rcu(&session->hlist); 1214 1215 spin_unlock_bh(&tunnel->hlist_lock); 1216 l2tp_session_delete(session); 1217 spin_lock_bh(&tunnel->hlist_lock); 1218 1219 /* Now restart from the beginning of this hash 1220 * chain. We always remove a session from the 1221 * list so we are guaranteed to make forward 1222 * progress. 1223 */ 1224 goto again; 1225 } 1226 } 1227 spin_unlock_bh(&tunnel->hlist_lock); 1228 } 1229 1230 /* Tunnel socket destroy hook for UDP encapsulation */ 1231 static void l2tp_udp_encap_destroy(struct sock *sk) 1232 { 1233 struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk); 1234 1235 if (tunnel) 1236 l2tp_tunnel_delete(tunnel); 1237 } 1238 1239 static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel) 1240 { 1241 struct l2tp_net *pn = l2tp_pernet(net); 1242 1243 spin_lock_bh(&pn->l2tp_tunnel_idr_lock); 1244 idr_remove(&pn->l2tp_tunnel_idr, tunnel->tunnel_id); 1245 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock); 1246 } 1247 1248 /* Workqueue tunnel deletion function */ 1249 static void l2tp_tunnel_del_work(struct work_struct *work) 1250 { 1251 struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel, 1252 del_work); 1253 struct sock *sk = tunnel->sock; 1254 struct socket *sock = sk->sk_socket; 1255 1256 l2tp_tunnel_closeall(tunnel); 1257 1258 /* If the tunnel socket was created within the kernel, use 1259 * the sk API to release it here. 1260 */ 1261 if (tunnel->fd < 0) { 1262 if (sock) { 1263 kernel_sock_shutdown(sock, SHUT_RDWR); 1264 sock_release(sock); 1265 } 1266 } 1267 1268 l2tp_tunnel_remove(tunnel->l2tp_net, tunnel); 1269 /* drop initial ref */ 1270 l2tp_tunnel_dec_refcount(tunnel); 1271 1272 /* drop workqueue ref */ 1273 l2tp_tunnel_dec_refcount(tunnel); 1274 } 1275 1276 /* Create a socket for the tunnel, if one isn't set up by 1277 * userspace. This is used for static tunnels where there is no 1278 * managing L2TP daemon. 1279 * 1280 * Since we don't want these sockets to keep a namespace alive by 1281 * themselves, we drop the socket's namespace refcount after creation. 1282 * These sockets are freed when the namespace exits using the pernet 1283 * exit hook. 1284 */ 1285 static int l2tp_tunnel_sock_create(struct net *net, 1286 u32 tunnel_id, 1287 u32 peer_tunnel_id, 1288 struct l2tp_tunnel_cfg *cfg, 1289 struct socket **sockp) 1290 { 1291 int err = -EINVAL; 1292 struct socket *sock = NULL; 1293 struct udp_port_cfg udp_conf; 1294 1295 switch (cfg->encap) { 1296 case L2TP_ENCAPTYPE_UDP: 1297 memset(&udp_conf, 0, sizeof(udp_conf)); 1298 1299 #if IS_ENABLED(CONFIG_IPV6) 1300 if (cfg->local_ip6 && cfg->peer_ip6) { 1301 udp_conf.family = AF_INET6; 1302 memcpy(&udp_conf.local_ip6, cfg->local_ip6, 1303 sizeof(udp_conf.local_ip6)); 1304 memcpy(&udp_conf.peer_ip6, cfg->peer_ip6, 1305 sizeof(udp_conf.peer_ip6)); 1306 udp_conf.use_udp6_tx_checksums = 1307 !cfg->udp6_zero_tx_checksums; 1308 udp_conf.use_udp6_rx_checksums = 1309 !cfg->udp6_zero_rx_checksums; 1310 } else 1311 #endif 1312 { 1313 udp_conf.family = AF_INET; 1314 udp_conf.local_ip = cfg->local_ip; 1315 udp_conf.peer_ip = cfg->peer_ip; 1316 udp_conf.use_udp_checksums = cfg->use_udp_checksums; 1317 } 1318 1319 udp_conf.local_udp_port = htons(cfg->local_udp_port); 1320 udp_conf.peer_udp_port = htons(cfg->peer_udp_port); 1321 1322 err = udp_sock_create(net, &udp_conf, &sock); 1323 if (err < 0) 1324 goto out; 1325 1326 break; 1327 1328 case L2TP_ENCAPTYPE_IP: 1329 #if IS_ENABLED(CONFIG_IPV6) 1330 if (cfg->local_ip6 && cfg->peer_ip6) { 1331 struct sockaddr_l2tpip6 ip6_addr = {0}; 1332 1333 err = sock_create_kern(net, AF_INET6, SOCK_DGRAM, 1334 IPPROTO_L2TP, &sock); 1335 if (err < 0) 1336 goto out; 1337 1338 ip6_addr.l2tp_family = AF_INET6; 1339 memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6, 1340 sizeof(ip6_addr.l2tp_addr)); 1341 ip6_addr.l2tp_conn_id = tunnel_id; 1342 err = kernel_bind(sock, (struct sockaddr *)&ip6_addr, 1343 sizeof(ip6_addr)); 1344 if (err < 0) 1345 goto out; 1346 1347 ip6_addr.l2tp_family = AF_INET6; 1348 memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6, 1349 sizeof(ip6_addr.l2tp_addr)); 1350 ip6_addr.l2tp_conn_id = peer_tunnel_id; 1351 err = kernel_connect(sock, 1352 (struct sockaddr *)&ip6_addr, 1353 sizeof(ip6_addr), 0); 1354 if (err < 0) 1355 goto out; 1356 } else 1357 #endif 1358 { 1359 struct sockaddr_l2tpip ip_addr = {0}; 1360 1361 err = sock_create_kern(net, AF_INET, SOCK_DGRAM, 1362 IPPROTO_L2TP, &sock); 1363 if (err < 0) 1364 goto out; 1365 1366 ip_addr.l2tp_family = AF_INET; 1367 ip_addr.l2tp_addr = cfg->local_ip; 1368 ip_addr.l2tp_conn_id = tunnel_id; 1369 err = kernel_bind(sock, (struct sockaddr *)&ip_addr, 1370 sizeof(ip_addr)); 1371 if (err < 0) 1372 goto out; 1373 1374 ip_addr.l2tp_family = AF_INET; 1375 ip_addr.l2tp_addr = cfg->peer_ip; 1376 ip_addr.l2tp_conn_id = peer_tunnel_id; 1377 err = kernel_connect(sock, (struct sockaddr *)&ip_addr, 1378 sizeof(ip_addr), 0); 1379 if (err < 0) 1380 goto out; 1381 } 1382 break; 1383 1384 default: 1385 goto out; 1386 } 1387 1388 out: 1389 *sockp = sock; 1390 if (err < 0 && sock) { 1391 kernel_sock_shutdown(sock, SHUT_RDWR); 1392 sock_release(sock); 1393 *sockp = NULL; 1394 } 1395 1396 return err; 1397 } 1398 1399 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id, 1400 struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp) 1401 { 1402 struct l2tp_tunnel *tunnel = NULL; 1403 int err; 1404 enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP; 1405 1406 if (cfg) 1407 encap = cfg->encap; 1408 1409 tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL); 1410 if (!tunnel) { 1411 err = -ENOMEM; 1412 goto err; 1413 } 1414 1415 tunnel->version = version; 1416 tunnel->tunnel_id = tunnel_id; 1417 tunnel->peer_tunnel_id = peer_tunnel_id; 1418 1419 tunnel->magic = L2TP_TUNNEL_MAGIC; 1420 sprintf(&tunnel->name[0], "tunl %u", tunnel_id); 1421 spin_lock_init(&tunnel->hlist_lock); 1422 tunnel->acpt_newsess = true; 1423 1424 tunnel->encap = encap; 1425 1426 refcount_set(&tunnel->ref_count, 1); 1427 tunnel->fd = fd; 1428 1429 /* Init delete workqueue struct */ 1430 INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work); 1431 1432 INIT_LIST_HEAD(&tunnel->list); 1433 1434 err = 0; 1435 err: 1436 if (tunnelp) 1437 *tunnelp = tunnel; 1438 1439 return err; 1440 } 1441 EXPORT_SYMBOL_GPL(l2tp_tunnel_create); 1442 1443 static int l2tp_validate_socket(const struct sock *sk, const struct net *net, 1444 enum l2tp_encap_type encap) 1445 { 1446 if (!net_eq(sock_net(sk), net)) 1447 return -EINVAL; 1448 1449 if (sk->sk_type != SOCK_DGRAM) 1450 return -EPROTONOSUPPORT; 1451 1452 if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6) 1453 return -EPROTONOSUPPORT; 1454 1455 if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) || 1456 (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP)) 1457 return -EPROTONOSUPPORT; 1458 1459 if (sk->sk_user_data) 1460 return -EBUSY; 1461 1462 return 0; 1463 } 1464 1465 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net, 1466 struct l2tp_tunnel_cfg *cfg) 1467 { 1468 struct l2tp_net *pn = l2tp_pernet(net); 1469 u32 tunnel_id = tunnel->tunnel_id; 1470 struct socket *sock; 1471 struct sock *sk; 1472 int ret; 1473 1474 spin_lock_bh(&pn->l2tp_tunnel_idr_lock); 1475 ret = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id, 1476 GFP_ATOMIC); 1477 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock); 1478 if (ret) 1479 return ret == -ENOSPC ? -EEXIST : ret; 1480 1481 if (tunnel->fd < 0) { 1482 ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id, 1483 tunnel->peer_tunnel_id, cfg, 1484 &sock); 1485 if (ret < 0) 1486 goto err; 1487 } else { 1488 sock = sockfd_lookup(tunnel->fd, &ret); 1489 if (!sock) 1490 goto err; 1491 } 1492 1493 sk = sock->sk; 1494 lock_sock(sk); 1495 write_lock_bh(&sk->sk_callback_lock); 1496 ret = l2tp_validate_socket(sk, net, tunnel->encap); 1497 if (ret < 0) 1498 goto err_inval_sock; 1499 rcu_assign_sk_user_data(sk, tunnel); 1500 write_unlock_bh(&sk->sk_callback_lock); 1501 1502 if (tunnel->encap == L2TP_ENCAPTYPE_UDP) { 1503 struct udp_tunnel_sock_cfg udp_cfg = { 1504 .sk_user_data = tunnel, 1505 .encap_type = UDP_ENCAP_L2TPINUDP, 1506 .encap_rcv = l2tp_udp_encap_recv, 1507 .encap_destroy = l2tp_udp_encap_destroy, 1508 }; 1509 1510 setup_udp_tunnel_sock(net, sock, &udp_cfg); 1511 } 1512 1513 tunnel->old_sk_destruct = sk->sk_destruct; 1514 sk->sk_destruct = &l2tp_tunnel_destruct; 1515 sk->sk_allocation = GFP_ATOMIC; 1516 release_sock(sk); 1517 1518 sock_hold(sk); 1519 tunnel->sock = sk; 1520 tunnel->l2tp_net = net; 1521 1522 spin_lock_bh(&pn->l2tp_tunnel_idr_lock); 1523 idr_replace(&pn->l2tp_tunnel_idr, tunnel, tunnel->tunnel_id); 1524 spin_unlock_bh(&pn->l2tp_tunnel_idr_lock); 1525 1526 trace_register_tunnel(tunnel); 1527 1528 if (tunnel->fd >= 0) 1529 sockfd_put(sock); 1530 1531 return 0; 1532 1533 err_inval_sock: 1534 write_unlock_bh(&sk->sk_callback_lock); 1535 release_sock(sk); 1536 1537 if (tunnel->fd < 0) 1538 sock_release(sock); 1539 else 1540 sockfd_put(sock); 1541 err: 1542 l2tp_tunnel_remove(net, tunnel); 1543 return ret; 1544 } 1545 EXPORT_SYMBOL_GPL(l2tp_tunnel_register); 1546 1547 /* This function is used by the netlink TUNNEL_DELETE command. 1548 */ 1549 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel) 1550 { 1551 if (!test_and_set_bit(0, &tunnel->dead)) { 1552 trace_delete_tunnel(tunnel); 1553 l2tp_tunnel_inc_refcount(tunnel); 1554 queue_work(l2tp_wq, &tunnel->del_work); 1555 } 1556 } 1557 EXPORT_SYMBOL_GPL(l2tp_tunnel_delete); 1558 1559 void l2tp_session_delete(struct l2tp_session *session) 1560 { 1561 if (test_and_set_bit(0, &session->dead)) 1562 return; 1563 1564 trace_delete_session(session); 1565 l2tp_session_unhash(session); 1566 l2tp_session_queue_purge(session); 1567 if (session->session_close) 1568 (*session->session_close)(session); 1569 1570 l2tp_session_dec_refcount(session); 1571 } 1572 EXPORT_SYMBOL_GPL(l2tp_session_delete); 1573 1574 /* We come here whenever a session's send_seq, cookie_len or 1575 * l2specific_type parameters are set. 1576 */ 1577 void l2tp_session_set_header_len(struct l2tp_session *session, int version) 1578 { 1579 if (version == L2TP_HDR_VER_2) { 1580 session->hdr_len = 6; 1581 if (session->send_seq) 1582 session->hdr_len += 4; 1583 } else { 1584 session->hdr_len = 4 + session->cookie_len; 1585 session->hdr_len += l2tp_get_l2specific_len(session); 1586 if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP) 1587 session->hdr_len += 4; 1588 } 1589 } 1590 EXPORT_SYMBOL_GPL(l2tp_session_set_header_len); 1591 1592 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id, 1593 u32 peer_session_id, struct l2tp_session_cfg *cfg) 1594 { 1595 struct l2tp_session *session; 1596 1597 session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL); 1598 if (session) { 1599 session->magic = L2TP_SESSION_MAGIC; 1600 session->tunnel = tunnel; 1601 1602 session->session_id = session_id; 1603 session->peer_session_id = peer_session_id; 1604 session->nr = 0; 1605 if (tunnel->version == L2TP_HDR_VER_2) 1606 session->nr_max = 0xffff; 1607 else 1608 session->nr_max = 0xffffff; 1609 session->nr_window_size = session->nr_max / 2; 1610 session->nr_oos_count_max = 4; 1611 1612 /* Use NR of first received packet */ 1613 session->reorder_skip = 1; 1614 1615 sprintf(&session->name[0], "sess %u/%u", 1616 tunnel->tunnel_id, session->session_id); 1617 1618 skb_queue_head_init(&session->reorder_q); 1619 1620 INIT_HLIST_NODE(&session->hlist); 1621 INIT_HLIST_NODE(&session->global_hlist); 1622 1623 if (cfg) { 1624 session->pwtype = cfg->pw_type; 1625 session->send_seq = cfg->send_seq; 1626 session->recv_seq = cfg->recv_seq; 1627 session->lns_mode = cfg->lns_mode; 1628 session->reorder_timeout = cfg->reorder_timeout; 1629 session->l2specific_type = cfg->l2specific_type; 1630 session->cookie_len = cfg->cookie_len; 1631 memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len); 1632 session->peer_cookie_len = cfg->peer_cookie_len; 1633 memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len); 1634 } 1635 1636 l2tp_session_set_header_len(session, tunnel->version); 1637 1638 refcount_set(&session->ref_count, 1); 1639 1640 return session; 1641 } 1642 1643 return ERR_PTR(-ENOMEM); 1644 } 1645 EXPORT_SYMBOL_GPL(l2tp_session_create); 1646 1647 /***************************************************************************** 1648 * Init and cleanup 1649 *****************************************************************************/ 1650 1651 static __net_init int l2tp_init_net(struct net *net) 1652 { 1653 struct l2tp_net *pn = net_generic(net, l2tp_net_id); 1654 int hash; 1655 1656 idr_init(&pn->l2tp_tunnel_idr); 1657 spin_lock_init(&pn->l2tp_tunnel_idr_lock); 1658 1659 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) 1660 INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]); 1661 1662 spin_lock_init(&pn->l2tp_session_hlist_lock); 1663 1664 return 0; 1665 } 1666 1667 static __net_exit void l2tp_exit_net(struct net *net) 1668 { 1669 struct l2tp_net *pn = l2tp_pernet(net); 1670 struct l2tp_tunnel *tunnel = NULL; 1671 unsigned long tunnel_id, tmp; 1672 int hash; 1673 1674 rcu_read_lock_bh(); 1675 idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) { 1676 if (tunnel) 1677 l2tp_tunnel_delete(tunnel); 1678 } 1679 rcu_read_unlock_bh(); 1680 1681 if (l2tp_wq) 1682 flush_workqueue(l2tp_wq); 1683 rcu_barrier(); 1684 1685 for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) 1686 WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash])); 1687 idr_destroy(&pn->l2tp_tunnel_idr); 1688 } 1689 1690 static struct pernet_operations l2tp_net_ops = { 1691 .init = l2tp_init_net, 1692 .exit = l2tp_exit_net, 1693 .id = &l2tp_net_id, 1694 .size = sizeof(struct l2tp_net), 1695 }; 1696 1697 static int __init l2tp_init(void) 1698 { 1699 int rc = 0; 1700 1701 rc = register_pernet_device(&l2tp_net_ops); 1702 if (rc) 1703 goto out; 1704 1705 l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0); 1706 if (!l2tp_wq) { 1707 pr_err("alloc_workqueue failed\n"); 1708 unregister_pernet_device(&l2tp_net_ops); 1709 rc = -ENOMEM; 1710 goto out; 1711 } 1712 1713 pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION); 1714 1715 out: 1716 return rc; 1717 } 1718 1719 static void __exit l2tp_exit(void) 1720 { 1721 unregister_pernet_device(&l2tp_net_ops); 1722 if (l2tp_wq) { 1723 destroy_workqueue(l2tp_wq); 1724 l2tp_wq = NULL; 1725 } 1726 } 1727 1728 module_init(l2tp_init); 1729 module_exit(l2tp_exit); 1730 1731 MODULE_AUTHOR("James Chapman <jchapman@katalix.com>"); 1732 MODULE_DESCRIPTION("L2TP core"); 1733 MODULE_LICENSE("GPL"); 1734 MODULE_VERSION(L2TP_DRV_VERSION); 1735