l2tp_ip.c 15 KB

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  1. /*
  2. * L2TPv3 IP encapsulation support
  3. *
  4. * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
  5. *
  6. * This program is free software; you can redistribute it and/or
  7. * modify it under the terms of the GNU General Public License
  8. * as published by the Free Software Foundation; either version
  9. * 2 of the License, or (at your option) any later version.
  10. */
  11. #include <linux/icmp.h>
  12. #include <linux/module.h>
  13. #include <linux/skbuff.h>
  14. #include <linux/random.h>
  15. #include <linux/socket.h>
  16. #include <linux/l2tp.h>
  17. #include <linux/in.h>
  18. #include <net/sock.h>
  19. #include <net/ip.h>
  20. #include <net/icmp.h>
  21. #include <net/udp.h>
  22. #include <net/inet_common.h>
  23. #include <net/inet_hashtables.h>
  24. #include <net/tcp_states.h>
  25. #include <net/protocol.h>
  26. #include <net/xfrm.h>
  27. #include "l2tp_core.h"
  28. struct l2tp_ip_sock {
  29. /* inet_sock has to be the first member of l2tp_ip_sock */
  30. struct inet_sock inet;
  31. u32 conn_id;
  32. u32 peer_conn_id;
  33. };
  34. static DEFINE_RWLOCK(l2tp_ip_lock);
  35. static struct hlist_head l2tp_ip_table;
  36. static struct hlist_head l2tp_ip_bind_table;
  37. static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk)
  38. {
  39. return (struct l2tp_ip_sock *)sk;
  40. }
  41. static struct sock *__l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id)
  42. {
  43. struct hlist_node *node;
  44. struct sock *sk;
  45. sk_for_each_bound(sk, node, &l2tp_ip_bind_table) {
  46. struct inet_sock *inet = inet_sk(sk);
  47. struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk);
  48. if (l2tp == NULL)
  49. continue;
  50. if ((l2tp->conn_id == tunnel_id) &&
  51. net_eq(sock_net(sk), net) &&
  52. !(inet->inet_rcv_saddr && inet->inet_rcv_saddr != laddr) &&
  53. !(sk->sk_bound_dev_if && sk->sk_bound_dev_if != dif))
  54. goto found;
  55. }
  56. sk = NULL;
  57. found:
  58. return sk;
  59. }
  60. static inline struct sock *l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id)
  61. {
  62. struct sock *sk = __l2tp_ip_bind_lookup(net, laddr, dif, tunnel_id);
  63. if (sk)
  64. sock_hold(sk);
  65. return sk;
  66. }
  67. /* When processing receive frames, there are two cases to
  68. * consider. Data frames consist of a non-zero session-id and an
  69. * optional cookie. Control frames consist of a regular L2TP header
  70. * preceded by 32-bits of zeros.
  71. *
  72. * L2TPv3 Session Header Over IP
  73. *
  74. * 0 1 2 3
  75. * 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
  76. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  77. * | Session ID |
  78. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  79. * | Cookie (optional, maximum 64 bits)...
  80. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  81. * |
  82. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  83. *
  84. * L2TPv3 Control Message Header Over IP
  85. *
  86. * 0 1 2 3
  87. * 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
  88. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  89. * | (32 bits of zeros) |
  90. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  91. * |T|L|x|x|S|x|x|x|x|x|x|x| Ver | Length |
  92. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  93. * | Control Connection ID |
  94. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  95. * | Ns | Nr |
  96. * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  97. *
  98. * All control frames are passed to userspace.
  99. */
  100. static int l2tp_ip_recv(struct sk_buff *skb)
  101. {
  102. struct sock *sk;
  103. u32 session_id;
  104. u32 tunnel_id;
  105. unsigned char *ptr, *optr;
  106. struct l2tp_session *session;
  107. struct l2tp_tunnel *tunnel = NULL;
  108. int length;
  109. int offset;
  110. /* Point to L2TP header */
  111. optr = ptr = skb->data;
  112. if (!pskb_may_pull(skb, 4))
  113. goto discard;
  114. session_id = ntohl(*((__be32 *) ptr));
  115. ptr += 4;
  116. /* RFC3931: L2TP/IP packets have the first 4 bytes containing
  117. * the session_id. If it is 0, the packet is a L2TP control
  118. * frame and the session_id value can be discarded.
  119. */
  120. if (session_id == 0) {
  121. __skb_pull(skb, 4);
  122. goto pass_up;
  123. }
  124. /* Ok, this is a data packet. Lookup the session. */
  125. session = l2tp_session_find(&init_net, NULL, session_id);
  126. if (session == NULL)
  127. goto discard;
  128. tunnel = session->tunnel;
  129. if (tunnel == NULL)
  130. goto discard;
  131. /* Trace packet contents, if enabled */
  132. if (tunnel->debug & L2TP_MSG_DATA) {
  133. length = min(32u, skb->len);
  134. if (!pskb_may_pull(skb, length))
  135. goto discard;
  136. printk(KERN_DEBUG "%s: ip recv: ", tunnel->name);
  137. offset = 0;
  138. do {
  139. printk(" %02X", ptr[offset]);
  140. } while (++offset < length);
  141. printk("\n");
  142. }
  143. l2tp_recv_common(session, skb, ptr, optr, 0, skb->len, tunnel->recv_payload_hook);
  144. return 0;
  145. pass_up:
  146. /* Get the tunnel_id from the L2TP header */
  147. if (!pskb_may_pull(skb, 12))
  148. goto discard;
  149. if ((skb->data[0] & 0xc0) != 0xc0)
  150. goto discard;
  151. tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
  152. tunnel = l2tp_tunnel_find(&init_net, tunnel_id);
  153. if (tunnel != NULL)
  154. sk = tunnel->sock;
  155. else {
  156. struct iphdr *iph = (struct iphdr *) skb_network_header(skb);
  157. read_lock_bh(&l2tp_ip_lock);
  158. sk = __l2tp_ip_bind_lookup(&init_net, iph->daddr, 0, tunnel_id);
  159. read_unlock_bh(&l2tp_ip_lock);
  160. }
  161. if (sk == NULL)
  162. goto discard;
  163. sock_hold(sk);
  164. if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
  165. goto discard_put;
  166. nf_reset(skb);
  167. return sk_receive_skb(sk, skb, 1);
  168. discard_put:
  169. sock_put(sk);
  170. discard:
  171. kfree_skb(skb);
  172. return 0;
  173. }
  174. static int l2tp_ip_open(struct sock *sk)
  175. {
  176. /* Prevent autobind. We don't have ports. */
  177. inet_sk(sk)->inet_num = IPPROTO_L2TP;
  178. write_lock_bh(&l2tp_ip_lock);
  179. sk_add_node(sk, &l2tp_ip_table);
  180. write_unlock_bh(&l2tp_ip_lock);
  181. return 0;
  182. }
  183. static void l2tp_ip_close(struct sock *sk, long timeout)
  184. {
  185. write_lock_bh(&l2tp_ip_lock);
  186. hlist_del_init(&sk->sk_bind_node);
  187. sk_del_node_init(sk);
  188. write_unlock_bh(&l2tp_ip_lock);
  189. sk_common_release(sk);
  190. }
  191. static void l2tp_ip_destroy_sock(struct sock *sk)
  192. {
  193. struct sk_buff *skb;
  194. while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
  195. kfree_skb(skb);
  196. sk_refcnt_debug_dec(sk);
  197. }
  198. static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  199. {
  200. struct inet_sock *inet = inet_sk(sk);
  201. struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr;
  202. int ret = -EINVAL;
  203. int chk_addr_ret;
  204. ret = -EADDRINUSE;
  205. read_lock_bh(&l2tp_ip_lock);
  206. if (__l2tp_ip_bind_lookup(&init_net, addr->l2tp_addr.s_addr, sk->sk_bound_dev_if, addr->l2tp_conn_id))
  207. goto out_in_use;
  208. read_unlock_bh(&l2tp_ip_lock);
  209. lock_sock(sk);
  210. if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip))
  211. goto out;
  212. chk_addr_ret = inet_addr_type(&init_net, addr->l2tp_addr.s_addr);
  213. ret = -EADDRNOTAVAIL;
  214. if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL &&
  215. chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST)
  216. goto out;
  217. if (addr->l2tp_addr.s_addr)
  218. inet->inet_rcv_saddr = inet->inet_saddr = addr->l2tp_addr.s_addr;
  219. if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST)
  220. inet->inet_saddr = 0; /* Use device */
  221. sk_dst_reset(sk);
  222. l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id;
  223. write_lock_bh(&l2tp_ip_lock);
  224. sk_add_bind_node(sk, &l2tp_ip_bind_table);
  225. sk_del_node_init(sk);
  226. write_unlock_bh(&l2tp_ip_lock);
  227. ret = 0;
  228. out:
  229. release_sock(sk);
  230. return ret;
  231. out_in_use:
  232. read_unlock_bh(&l2tp_ip_lock);
  233. return ret;
  234. }
  235. static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  236. {
  237. struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr;
  238. int rc;
  239. if (addr_len < sizeof(*lsa))
  240. return -EINVAL;
  241. if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
  242. return -EINVAL;
  243. rc = ip4_datagram_connect(sk, uaddr, addr_len);
  244. if (rc < 0)
  245. return rc;
  246. lock_sock(sk);
  247. l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
  248. write_lock_bh(&l2tp_ip_lock);
  249. hlist_del_init(&sk->sk_bind_node);
  250. sk_add_bind_node(sk, &l2tp_ip_bind_table);
  251. write_unlock_bh(&l2tp_ip_lock);
  252. release_sock(sk);
  253. return rc;
  254. }
  255. static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr,
  256. int *uaddr_len, int peer)
  257. {
  258. struct sock *sk = sock->sk;
  259. struct inet_sock *inet = inet_sk(sk);
  260. struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk);
  261. struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr;
  262. memset(lsa, 0, sizeof(*lsa));
  263. lsa->l2tp_family = AF_INET;
  264. if (peer) {
  265. if (!inet->inet_dport)
  266. return -ENOTCONN;
  267. lsa->l2tp_conn_id = lsk->peer_conn_id;
  268. lsa->l2tp_addr.s_addr = inet->inet_daddr;
  269. } else {
  270. __be32 addr = inet->inet_rcv_saddr;
  271. if (!addr)
  272. addr = inet->inet_saddr;
  273. lsa->l2tp_conn_id = lsk->conn_id;
  274. lsa->l2tp_addr.s_addr = addr;
  275. }
  276. *uaddr_len = sizeof(*lsa);
  277. return 0;
  278. }
  279. static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb)
  280. {
  281. int rc;
  282. /* Charge it to the socket, dropping if the queue is full. */
  283. rc = sock_queue_rcv_skb(sk, skb);
  284. if (rc < 0)
  285. goto drop;
  286. return 0;
  287. drop:
  288. IP_INC_STATS(&init_net, IPSTATS_MIB_INDISCARDS);
  289. kfree_skb(skb);
  290. return -1;
  291. }
  292. /* Userspace will call sendmsg() on the tunnel socket to send L2TP
  293. * control frames.
  294. */
  295. static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, size_t len)
  296. {
  297. struct sk_buff *skb;
  298. int rc;
  299. struct inet_sock *inet = inet_sk(sk);
  300. struct rtable *rt = NULL;
  301. struct flowi4 *fl4;
  302. int connected = 0;
  303. __be32 daddr;
  304. lock_sock(sk);
  305. rc = -ENOTCONN;
  306. if (sock_flag(sk, SOCK_DEAD))
  307. goto out;
  308. /* Get and verify the address. */
  309. if (msg->msg_name) {
  310. struct sockaddr_l2tpip *lip = (struct sockaddr_l2tpip *) msg->msg_name;
  311. rc = -EINVAL;
  312. if (msg->msg_namelen < sizeof(*lip))
  313. goto out;
  314. if (lip->l2tp_family != AF_INET) {
  315. rc = -EAFNOSUPPORT;
  316. if (lip->l2tp_family != AF_UNSPEC)
  317. goto out;
  318. }
  319. daddr = lip->l2tp_addr.s_addr;
  320. } else {
  321. rc = -EDESTADDRREQ;
  322. if (sk->sk_state != TCP_ESTABLISHED)
  323. goto out;
  324. daddr = inet->inet_daddr;
  325. connected = 1;
  326. }
  327. /* Allocate a socket buffer */
  328. rc = -ENOMEM;
  329. skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) +
  330. 4 + len, 0, GFP_KERNEL);
  331. if (!skb)
  332. goto error;
  333. /* Reserve space for headers, putting IP header on 4-byte boundary. */
  334. skb_reserve(skb, 2 + NET_SKB_PAD);
  335. skb_reset_network_header(skb);
  336. skb_reserve(skb, sizeof(struct iphdr));
  337. skb_reset_transport_header(skb);
  338. /* Insert 0 session_id */
  339. *((__be32 *) skb_put(skb, 4)) = 0;
  340. /* Copy user data into skb */
  341. rc = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
  342. if (rc < 0) {
  343. kfree_skb(skb);
  344. goto error;
  345. }
  346. fl4 = &inet->cork.fl.u.ip4;
  347. if (connected)
  348. rt = (struct rtable *) __sk_dst_check(sk, 0);
  349. rcu_read_lock();
  350. if (rt == NULL) {
  351. const struct ip_options_rcu *inet_opt;
  352. inet_opt = rcu_dereference(inet->inet_opt);
  353. /* Use correct destination address if we have options. */
  354. if (inet_opt && inet_opt->opt.srr)
  355. daddr = inet_opt->opt.faddr;
  356. /* If this fails, retransmit mechanism of transport layer will
  357. * keep trying until route appears or the connection times
  358. * itself out.
  359. */
  360. rt = ip_route_output_ports(sock_net(sk), fl4, sk,
  361. daddr, inet->inet_saddr,
  362. inet->inet_dport, inet->inet_sport,
  363. sk->sk_protocol, RT_CONN_FLAGS(sk),
  364. sk->sk_bound_dev_if);
  365. if (IS_ERR(rt))
  366. goto no_route;
  367. if (connected)
  368. sk_setup_caps(sk, &rt->dst);
  369. else
  370. dst_release(&rt->dst); /* safe since we hold rcu_read_lock */
  371. }
  372. /* We dont need to clone dst here, it is guaranteed to not disappear.
  373. * __dev_xmit_skb() might force a refcount if needed.
  374. */
  375. skb_dst_set_noref(skb, &rt->dst);
  376. /* Queue the packet to IP for output */
  377. rc = ip_queue_xmit(skb, &inet->cork.fl);
  378. rcu_read_unlock();
  379. error:
  380. if (rc >= 0)
  381. rc = len;
  382. out:
  383. release_sock(sk);
  384. return rc;
  385. no_route:
  386. rcu_read_unlock();
  387. IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
  388. kfree_skb(skb);
  389. rc = -EHOSTUNREACH;
  390. goto out;
  391. }
  392. static int l2tp_ip_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
  393. size_t len, int noblock, int flags, int *addr_len)
  394. {
  395. struct inet_sock *inet = inet_sk(sk);
  396. size_t copied = 0;
  397. int err = -EOPNOTSUPP;
  398. struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
  399. struct sk_buff *skb;
  400. if (flags & MSG_OOB)
  401. goto out;
  402. if (addr_len)
  403. *addr_len = sizeof(*sin);
  404. skb = skb_recv_datagram(sk, flags, noblock, &err);
  405. if (!skb)
  406. goto out;
  407. copied = skb->len;
  408. if (len < copied) {
  409. msg->msg_flags |= MSG_TRUNC;
  410. copied = len;
  411. }
  412. err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
  413. if (err)
  414. goto done;
  415. sock_recv_timestamp(msg, sk, skb);
  416. /* Copy the address. */
  417. if (sin) {
  418. sin->sin_family = AF_INET;
  419. sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
  420. sin->sin_port = 0;
  421. memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
  422. }
  423. if (inet->cmsg_flags)
  424. ip_cmsg_recv(msg, skb);
  425. if (flags & MSG_TRUNC)
  426. copied = skb->len;
  427. done:
  428. skb_free_datagram(sk, skb);
  429. out:
  430. return err ? err : copied;
  431. }
  432. static struct proto l2tp_ip_prot = {
  433. .name = "L2TP/IP",
  434. .owner = THIS_MODULE,
  435. .init = l2tp_ip_open,
  436. .close = l2tp_ip_close,
  437. .bind = l2tp_ip_bind,
  438. .connect = l2tp_ip_connect,
  439. .disconnect = udp_disconnect,
  440. .ioctl = udp_ioctl,
  441. .destroy = l2tp_ip_destroy_sock,
  442. .setsockopt = ip_setsockopt,
  443. .getsockopt = ip_getsockopt,
  444. .sendmsg = l2tp_ip_sendmsg,
  445. .recvmsg = l2tp_ip_recvmsg,
  446. .backlog_rcv = l2tp_ip_backlog_recv,
  447. .hash = inet_hash,
  448. .unhash = inet_unhash,
  449. .obj_size = sizeof(struct l2tp_ip_sock),
  450. #ifdef CONFIG_COMPAT
  451. .compat_setsockopt = compat_ip_setsockopt,
  452. .compat_getsockopt = compat_ip_getsockopt,
  453. #endif
  454. };
  455. static const struct proto_ops l2tp_ip_ops = {
  456. .family = PF_INET,
  457. .owner = THIS_MODULE,
  458. .release = inet_release,
  459. .bind = inet_bind,
  460. .connect = inet_dgram_connect,
  461. .socketpair = sock_no_socketpair,
  462. .accept = sock_no_accept,
  463. .getname = l2tp_ip_getname,
  464. .poll = datagram_poll,
  465. .ioctl = inet_ioctl,
  466. .listen = sock_no_listen,
  467. .shutdown = inet_shutdown,
  468. .setsockopt = sock_common_setsockopt,
  469. .getsockopt = sock_common_getsockopt,
  470. .sendmsg = inet_sendmsg,
  471. .recvmsg = sock_common_recvmsg,
  472. .mmap = sock_no_mmap,
  473. .sendpage = sock_no_sendpage,
  474. #ifdef CONFIG_COMPAT
  475. .compat_setsockopt = compat_sock_common_setsockopt,
  476. .compat_getsockopt = compat_sock_common_getsockopt,
  477. #endif
  478. };
  479. static struct inet_protosw l2tp_ip_protosw = {
  480. .type = SOCK_DGRAM,
  481. .protocol = IPPROTO_L2TP,
  482. .prot = &l2tp_ip_prot,
  483. .ops = &l2tp_ip_ops,
  484. .no_check = 0,
  485. };
  486. static struct net_protocol l2tp_ip_protocol __read_mostly = {
  487. .handler = l2tp_ip_recv,
  488. };
  489. static int __init l2tp_ip_init(void)
  490. {
  491. int err;
  492. printk(KERN_INFO "L2TP IP encapsulation support (L2TPv3)\n");
  493. err = proto_register(&l2tp_ip_prot, 1);
  494. if (err != 0)
  495. goto out;
  496. err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
  497. if (err)
  498. goto out1;
  499. inet_register_protosw(&l2tp_ip_protosw);
  500. return 0;
  501. out1:
  502. proto_unregister(&l2tp_ip_prot);
  503. out:
  504. return err;
  505. }
  506. static void __exit l2tp_ip_exit(void)
  507. {
  508. inet_unregister_protosw(&l2tp_ip_protosw);
  509. inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
  510. proto_unregister(&l2tp_ip_prot);
  511. }
  512. module_init(l2tp_ip_init);
  513. module_exit(l2tp_ip_exit);
  514. MODULE_LICENSE("GPL");
  515. MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
  516. MODULE_DESCRIPTION("L2TP over IP");
  517. MODULE_VERSION("1.0");
  518. /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
  519. * enums
  520. */
  521. MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP);