xref: /openbmc/linux/net/l2tp/l2tp_ip6.c (revision 9a29f5fc)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* L2TPv3 IP encapsulation support for IPv6
3  *
4  * Copyright (c) 2012 Katalix Systems Ltd
5  */
6 
7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8 
9 #include <linux/icmp.h>
10 #include <linux/module.h>
11 #include <linux/skbuff.h>
12 #include <linux/random.h>
13 #include <linux/socket.h>
14 #include <linux/l2tp.h>
15 #include <linux/in.h>
16 #include <linux/in6.h>
17 #include <net/sock.h>
18 #include <net/ip.h>
19 #include <net/icmp.h>
20 #include <net/udp.h>
21 #include <net/inet_common.h>
22 #include <net/tcp_states.h>
23 #include <net/protocol.h>
24 #include <net/xfrm.h>
25 
26 #include <net/transp_v6.h>
27 #include <net/addrconf.h>
28 #include <net/ip6_route.h>
29 
30 #include "l2tp_core.h"
31 
32 struct l2tp_ip6_sock {
33 	/* inet_sock has to be the first member of l2tp_ip6_sock */
34 	struct inet_sock	inet;
35 
36 	u32			conn_id;
37 	u32			peer_conn_id;
38 
39 	/* ipv6_pinfo has to be the last member of l2tp_ip6_sock, see
40 	 * inet6_sk_generic
41 	 */
42 	struct ipv6_pinfo	inet6;
43 };
44 
45 static DEFINE_RWLOCK(l2tp_ip6_lock);
46 static struct hlist_head l2tp_ip6_table;
47 static struct hlist_head l2tp_ip6_bind_table;
48 
49 static inline struct l2tp_ip6_sock *l2tp_ip6_sk(const struct sock *sk)
50 {
51 	return (struct l2tp_ip6_sock *)sk;
52 }
53 
54 static struct sock *__l2tp_ip6_bind_lookup(const struct net *net,
55 					   const struct in6_addr *laddr,
56 					   const struct in6_addr *raddr,
57 					   int dif, u32 tunnel_id)
58 {
59 	struct sock *sk;
60 
61 	sk_for_each_bound(sk, &l2tp_ip6_bind_table) {
62 		const struct in6_addr *sk_laddr = inet6_rcv_saddr(sk);
63 		const struct in6_addr *sk_raddr = &sk->sk_v6_daddr;
64 		const struct l2tp_ip6_sock *l2tp = l2tp_ip6_sk(sk);
65 		int bound_dev_if;
66 
67 		if (!net_eq(sock_net(sk), net))
68 			continue;
69 
70 		bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
71 		if (bound_dev_if && dif && bound_dev_if != dif)
72 			continue;
73 
74 		if (sk_laddr && !ipv6_addr_any(sk_laddr) &&
75 		    !ipv6_addr_any(laddr) && !ipv6_addr_equal(sk_laddr, laddr))
76 			continue;
77 
78 		if (!ipv6_addr_any(sk_raddr) && raddr &&
79 		    !ipv6_addr_any(raddr) && !ipv6_addr_equal(sk_raddr, raddr))
80 			continue;
81 
82 		if (l2tp->conn_id != tunnel_id)
83 			continue;
84 
85 		goto found;
86 	}
87 
88 	sk = NULL;
89 found:
90 	return sk;
91 }
92 
93 /* When processing receive frames, there are two cases to
94  * consider. Data frames consist of a non-zero session-id and an
95  * optional cookie. Control frames consist of a regular L2TP header
96  * preceded by 32-bits of zeros.
97  *
98  * L2TPv3 Session Header Over IP
99  *
100  *  0                   1                   2                   3
101  *  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
102  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
103  * |                           Session ID                          |
104  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
105  * |               Cookie (optional, maximum 64 bits)...
106  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
107  *                                                                 |
108  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
109  *
110  * L2TPv3 Control Message Header Over IP
111  *
112  *  0                   1                   2                   3
113  *  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
114  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
115  * |                      (32 bits of zeros)                       |
116  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
117  * |T|L|x|x|S|x|x|x|x|x|x|x|  Ver  |             Length            |
118  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
119  * |                     Control Connection ID                     |
120  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
121  * |               Ns              |               Nr              |
122  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
123  *
124  * All control frames are passed to userspace.
125  */
126 static int l2tp_ip6_recv(struct sk_buff *skb)
127 {
128 	struct net *net = dev_net(skb->dev);
129 	struct sock *sk;
130 	u32 session_id;
131 	u32 tunnel_id;
132 	unsigned char *ptr, *optr;
133 	struct l2tp_session *session;
134 	struct l2tp_tunnel *tunnel = NULL;
135 	struct ipv6hdr *iph;
136 
137 	if (!pskb_may_pull(skb, 4))
138 		goto discard;
139 
140 	/* Point to L2TP header */
141 	optr = skb->data;
142 	ptr = skb->data;
143 	session_id = ntohl(*((__be32 *)ptr));
144 	ptr += 4;
145 
146 	/* RFC3931: L2TP/IP packets have the first 4 bytes containing
147 	 * the session_id. If it is 0, the packet is a L2TP control
148 	 * frame and the session_id value can be discarded.
149 	 */
150 	if (session_id == 0) {
151 		__skb_pull(skb, 4);
152 		goto pass_up;
153 	}
154 
155 	/* Ok, this is a data packet. Lookup the session. */
156 	session = l2tp_session_get(net, session_id);
157 	if (!session)
158 		goto discard;
159 
160 	tunnel = session->tunnel;
161 	if (!tunnel)
162 		goto discard_sess;
163 
164 	if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
165 		goto discard_sess;
166 
167 	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
168 	l2tp_session_dec_refcount(session);
169 
170 	return 0;
171 
172 pass_up:
173 	/* Get the tunnel_id from the L2TP header */
174 	if (!pskb_may_pull(skb, 12))
175 		goto discard;
176 
177 	if ((skb->data[0] & 0xc0) != 0xc0)
178 		goto discard;
179 
180 	tunnel_id = ntohl(*(__be32 *)&skb->data[4]);
181 	iph = ipv6_hdr(skb);
182 
183 	read_lock_bh(&l2tp_ip6_lock);
184 	sk = __l2tp_ip6_bind_lookup(net, &iph->daddr, &iph->saddr,
185 				    inet6_iif(skb), tunnel_id);
186 	if (!sk) {
187 		read_unlock_bh(&l2tp_ip6_lock);
188 		goto discard;
189 	}
190 	sock_hold(sk);
191 	read_unlock_bh(&l2tp_ip6_lock);
192 
193 	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
194 		goto discard_put;
195 
196 	nf_reset_ct(skb);
197 
198 	return sk_receive_skb(sk, skb, 1);
199 
200 discard_sess:
201 	l2tp_session_dec_refcount(session);
202 	goto discard;
203 
204 discard_put:
205 	sock_put(sk);
206 
207 discard:
208 	kfree_skb(skb);
209 	return 0;
210 }
211 
212 static int l2tp_ip6_hash(struct sock *sk)
213 {
214 	if (sk_unhashed(sk)) {
215 		write_lock_bh(&l2tp_ip6_lock);
216 		sk_add_node(sk, &l2tp_ip6_table);
217 		write_unlock_bh(&l2tp_ip6_lock);
218 	}
219 	return 0;
220 }
221 
222 static void l2tp_ip6_unhash(struct sock *sk)
223 {
224 	if (sk_unhashed(sk))
225 		return;
226 	write_lock_bh(&l2tp_ip6_lock);
227 	sk_del_node_init(sk);
228 	write_unlock_bh(&l2tp_ip6_lock);
229 }
230 
231 static int l2tp_ip6_open(struct sock *sk)
232 {
233 	/* Prevent autobind. We don't have ports. */
234 	inet_sk(sk)->inet_num = IPPROTO_L2TP;
235 
236 	l2tp_ip6_hash(sk);
237 	return 0;
238 }
239 
240 static void l2tp_ip6_close(struct sock *sk, long timeout)
241 {
242 	write_lock_bh(&l2tp_ip6_lock);
243 	hlist_del_init(&sk->sk_bind_node);
244 	sk_del_node_init(sk);
245 	write_unlock_bh(&l2tp_ip6_lock);
246 
247 	sk_common_release(sk);
248 }
249 
250 static void l2tp_ip6_destroy_sock(struct sock *sk)
251 {
252 	struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
253 
254 	lock_sock(sk);
255 	ip6_flush_pending_frames(sk);
256 	release_sock(sk);
257 
258 	if (tunnel)
259 		l2tp_tunnel_delete(tunnel);
260 
261 	inet6_destroy_sock(sk);
262 }
263 
264 static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
265 {
266 	struct inet_sock *inet = inet_sk(sk);
267 	struct ipv6_pinfo *np = inet6_sk(sk);
268 	struct sockaddr_l2tpip6 *addr = (struct sockaddr_l2tpip6 *)uaddr;
269 	struct net *net = sock_net(sk);
270 	__be32 v4addr = 0;
271 	int bound_dev_if;
272 	int addr_type;
273 	int err;
274 
275 	if (addr->l2tp_family != AF_INET6)
276 		return -EINVAL;
277 	if (addr_len < sizeof(*addr))
278 		return -EINVAL;
279 
280 	addr_type = ipv6_addr_type(&addr->l2tp_addr);
281 
282 	/* l2tp_ip6 sockets are IPv6 only */
283 	if (addr_type == IPV6_ADDR_MAPPED)
284 		return -EADDRNOTAVAIL;
285 
286 	/* L2TP is point-point, not multicast */
287 	if (addr_type & IPV6_ADDR_MULTICAST)
288 		return -EADDRNOTAVAIL;
289 
290 	lock_sock(sk);
291 
292 	err = -EINVAL;
293 	if (!sock_flag(sk, SOCK_ZAPPED))
294 		goto out_unlock;
295 
296 	if (sk->sk_state != TCP_CLOSE)
297 		goto out_unlock;
298 
299 	bound_dev_if = sk->sk_bound_dev_if;
300 
301 	/* Check if the address belongs to the host. */
302 	rcu_read_lock();
303 	if (addr_type != IPV6_ADDR_ANY) {
304 		struct net_device *dev = NULL;
305 
306 		if (addr_type & IPV6_ADDR_LINKLOCAL) {
307 			if (addr->l2tp_scope_id)
308 				bound_dev_if = addr->l2tp_scope_id;
309 
310 			/* Binding to link-local address requires an
311 			 * interface.
312 			 */
313 			if (!bound_dev_if)
314 				goto out_unlock_rcu;
315 
316 			err = -ENODEV;
317 			dev = dev_get_by_index_rcu(sock_net(sk), bound_dev_if);
318 			if (!dev)
319 				goto out_unlock_rcu;
320 		}
321 
322 		/* ipv4 addr of the socket is invalid.  Only the
323 		 * unspecified and mapped address have a v4 equivalent.
324 		 */
325 		v4addr = LOOPBACK4_IPV6;
326 		err = -EADDRNOTAVAIL;
327 		if (!ipv6_chk_addr(sock_net(sk), &addr->l2tp_addr, dev, 0))
328 			goto out_unlock_rcu;
329 	}
330 	rcu_read_unlock();
331 
332 	write_lock_bh(&l2tp_ip6_lock);
333 	if (__l2tp_ip6_bind_lookup(net, &addr->l2tp_addr, NULL, bound_dev_if,
334 				   addr->l2tp_conn_id)) {
335 		write_unlock_bh(&l2tp_ip6_lock);
336 		err = -EADDRINUSE;
337 		goto out_unlock;
338 	}
339 
340 	inet->inet_saddr = v4addr;
341 	inet->inet_rcv_saddr = v4addr;
342 	sk->sk_bound_dev_if = bound_dev_if;
343 	sk->sk_v6_rcv_saddr = addr->l2tp_addr;
344 	np->saddr = addr->l2tp_addr;
345 
346 	l2tp_ip6_sk(sk)->conn_id = addr->l2tp_conn_id;
347 
348 	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
349 	sk_del_node_init(sk);
350 	write_unlock_bh(&l2tp_ip6_lock);
351 
352 	sock_reset_flag(sk, SOCK_ZAPPED);
353 	release_sock(sk);
354 	return 0;
355 
356 out_unlock_rcu:
357 	rcu_read_unlock();
358 out_unlock:
359 	release_sock(sk);
360 
361 	return err;
362 }
363 
364 static int l2tp_ip6_connect(struct sock *sk, struct sockaddr *uaddr,
365 			    int addr_len)
366 {
367 	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)uaddr;
368 	struct sockaddr_in6	*usin = (struct sockaddr_in6 *)uaddr;
369 	struct in6_addr	*daddr;
370 	int	addr_type;
371 	int rc;
372 
373 	if (addr_len < sizeof(*lsa))
374 		return -EINVAL;
375 
376 	if (usin->sin6_family != AF_INET6)
377 		return -EINVAL;
378 
379 	addr_type = ipv6_addr_type(&usin->sin6_addr);
380 	if (addr_type & IPV6_ADDR_MULTICAST)
381 		return -EINVAL;
382 
383 	if (addr_type & IPV6_ADDR_MAPPED) {
384 		daddr = &usin->sin6_addr;
385 		if (ipv4_is_multicast(daddr->s6_addr32[3]))
386 			return -EINVAL;
387 	}
388 
389 	lock_sock(sk);
390 
391 	 /* Must bind first - autobinding does not work */
392 	if (sock_flag(sk, SOCK_ZAPPED)) {
393 		rc = -EINVAL;
394 		goto out_sk;
395 	}
396 
397 	rc = __ip6_datagram_connect(sk, uaddr, addr_len);
398 	if (rc < 0)
399 		goto out_sk;
400 
401 	l2tp_ip6_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
402 
403 	write_lock_bh(&l2tp_ip6_lock);
404 	hlist_del_init(&sk->sk_bind_node);
405 	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
406 	write_unlock_bh(&l2tp_ip6_lock);
407 
408 out_sk:
409 	release_sock(sk);
410 
411 	return rc;
412 }
413 
414 static int l2tp_ip6_disconnect(struct sock *sk, int flags)
415 {
416 	if (sock_flag(sk, SOCK_ZAPPED))
417 		return 0;
418 
419 	return __udp_disconnect(sk, flags);
420 }
421 
422 static int l2tp_ip6_getname(struct socket *sock, struct sockaddr *uaddr,
423 			    int peer)
424 {
425 	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)uaddr;
426 	struct sock *sk = sock->sk;
427 	struct ipv6_pinfo *np = inet6_sk(sk);
428 	struct l2tp_ip6_sock *lsk = l2tp_ip6_sk(sk);
429 
430 	lsa->l2tp_family = AF_INET6;
431 	lsa->l2tp_flowinfo = 0;
432 	lsa->l2tp_scope_id = 0;
433 	lsa->l2tp_unused = 0;
434 	if (peer) {
435 		if (!lsk->peer_conn_id)
436 			return -ENOTCONN;
437 		lsa->l2tp_conn_id = lsk->peer_conn_id;
438 		lsa->l2tp_addr = sk->sk_v6_daddr;
439 		if (np->sndflow)
440 			lsa->l2tp_flowinfo = np->flow_label;
441 	} else {
442 		if (ipv6_addr_any(&sk->sk_v6_rcv_saddr))
443 			lsa->l2tp_addr = np->saddr;
444 		else
445 			lsa->l2tp_addr = sk->sk_v6_rcv_saddr;
446 
447 		lsa->l2tp_conn_id = lsk->conn_id;
448 	}
449 	if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
450 		lsa->l2tp_scope_id = READ_ONCE(sk->sk_bound_dev_if);
451 	return sizeof(*lsa);
452 }
453 
454 static int l2tp_ip6_backlog_recv(struct sock *sk, struct sk_buff *skb)
455 {
456 	int rc;
457 
458 	/* Charge it to the socket, dropping if the queue is full. */
459 	rc = sock_queue_rcv_skb(sk, skb);
460 	if (rc < 0)
461 		goto drop;
462 
463 	return 0;
464 
465 drop:
466 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS);
467 	kfree_skb(skb);
468 	return -1;
469 }
470 
471 static int l2tp_ip6_push_pending_frames(struct sock *sk)
472 {
473 	struct sk_buff *skb;
474 	__be32 *transhdr = NULL;
475 	int err = 0;
476 
477 	skb = skb_peek(&sk->sk_write_queue);
478 	if (!skb)
479 		goto out;
480 
481 	transhdr = (__be32 *)skb_transport_header(skb);
482 	*transhdr = 0;
483 
484 	err = ip6_push_pending_frames(sk);
485 
486 out:
487 	return err;
488 }
489 
490 /* Userspace will call sendmsg() on the tunnel socket to send L2TP
491  * control frames.
492  */
493 static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
494 {
495 	struct ipv6_txoptions opt_space;
496 	DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
497 	struct in6_addr *daddr, *final_p, final;
498 	struct ipv6_pinfo *np = inet6_sk(sk);
499 	struct ipv6_txoptions *opt_to_free = NULL;
500 	struct ipv6_txoptions *opt = NULL;
501 	struct ip6_flowlabel *flowlabel = NULL;
502 	struct dst_entry *dst = NULL;
503 	struct flowi6 fl6;
504 	struct ipcm6_cookie ipc6;
505 	int addr_len = msg->msg_namelen;
506 	int transhdrlen = 4; /* zero session-id */
507 	int ulen;
508 	int err;
509 
510 	/* Rough check on arithmetic overflow,
511 	 * better check is made in ip6_append_data().
512 	 */
513 	if (len > INT_MAX - transhdrlen)
514 		return -EMSGSIZE;
515 	ulen = len + transhdrlen;
516 
517 	/* Mirror BSD error message compatibility */
518 	if (msg->msg_flags & MSG_OOB)
519 		return -EOPNOTSUPP;
520 
521 	/* Get and verify the address */
522 	memset(&fl6, 0, sizeof(fl6));
523 
524 	fl6.flowi6_mark = sk->sk_mark;
525 	fl6.flowi6_uid = sk->sk_uid;
526 
527 	ipcm6_init(&ipc6);
528 
529 	if (lsa) {
530 		if (addr_len < SIN6_LEN_RFC2133)
531 			return -EINVAL;
532 
533 		if (lsa->l2tp_family && lsa->l2tp_family != AF_INET6)
534 			return -EAFNOSUPPORT;
535 
536 		daddr = &lsa->l2tp_addr;
537 		if (np->sndflow) {
538 			fl6.flowlabel = lsa->l2tp_flowinfo & IPV6_FLOWINFO_MASK;
539 			if (fl6.flowlabel & IPV6_FLOWLABEL_MASK) {
540 				flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
541 				if (IS_ERR(flowlabel))
542 					return -EINVAL;
543 			}
544 		}
545 
546 		/* Otherwise it will be difficult to maintain
547 		 * sk->sk_dst_cache.
548 		 */
549 		if (sk->sk_state == TCP_ESTABLISHED &&
550 		    ipv6_addr_equal(daddr, &sk->sk_v6_daddr))
551 			daddr = &sk->sk_v6_daddr;
552 
553 		if (addr_len >= sizeof(struct sockaddr_in6) &&
554 		    lsa->l2tp_scope_id &&
555 		    ipv6_addr_type(daddr) & IPV6_ADDR_LINKLOCAL)
556 			fl6.flowi6_oif = lsa->l2tp_scope_id;
557 	} else {
558 		if (sk->sk_state != TCP_ESTABLISHED)
559 			return -EDESTADDRREQ;
560 
561 		daddr = &sk->sk_v6_daddr;
562 		fl6.flowlabel = np->flow_label;
563 	}
564 
565 	if (fl6.flowi6_oif == 0)
566 		fl6.flowi6_oif = READ_ONCE(sk->sk_bound_dev_if);
567 
568 	if (msg->msg_controllen) {
569 		opt = &opt_space;
570 		memset(opt, 0, sizeof(struct ipv6_txoptions));
571 		opt->tot_len = sizeof(struct ipv6_txoptions);
572 		ipc6.opt = opt;
573 
574 		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6);
575 		if (err < 0) {
576 			fl6_sock_release(flowlabel);
577 			return err;
578 		}
579 		if ((fl6.flowlabel & IPV6_FLOWLABEL_MASK) && !flowlabel) {
580 			flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
581 			if (IS_ERR(flowlabel))
582 				return -EINVAL;
583 		}
584 		if (!(opt->opt_nflen | opt->opt_flen))
585 			opt = NULL;
586 	}
587 
588 	if (!opt) {
589 		opt = txopt_get(np);
590 		opt_to_free = opt;
591 	}
592 	if (flowlabel)
593 		opt = fl6_merge_options(&opt_space, flowlabel, opt);
594 	opt = ipv6_fixup_options(&opt_space, opt);
595 	ipc6.opt = opt;
596 
597 	fl6.flowi6_proto = sk->sk_protocol;
598 	if (!ipv6_addr_any(daddr))
599 		fl6.daddr = *daddr;
600 	else
601 		fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
602 	if (ipv6_addr_any(&fl6.saddr) && !ipv6_addr_any(&np->saddr))
603 		fl6.saddr = np->saddr;
604 
605 	final_p = fl6_update_dst(&fl6, opt, &final);
606 
607 	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
608 		fl6.flowi6_oif = np->mcast_oif;
609 	else if (!fl6.flowi6_oif)
610 		fl6.flowi6_oif = np->ucast_oif;
611 
612 	security_sk_classify_flow(sk, flowi6_to_flowi_common(&fl6));
613 
614 	if (ipc6.tclass < 0)
615 		ipc6.tclass = np->tclass;
616 
617 	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);
618 
619 	dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
620 	if (IS_ERR(dst)) {
621 		err = PTR_ERR(dst);
622 		goto out;
623 	}
624 
625 	if (ipc6.hlimit < 0)
626 		ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);
627 
628 	if (ipc6.dontfrag < 0)
629 		ipc6.dontfrag = np->dontfrag;
630 
631 	if (msg->msg_flags & MSG_CONFIRM)
632 		goto do_confirm;
633 
634 back_from_confirm:
635 	lock_sock(sk);
636 	err = ip6_append_data(sk, ip_generic_getfrag, msg,
637 			      ulen, transhdrlen, &ipc6,
638 			      &fl6, (struct rt6_info *)dst,
639 			      msg->msg_flags);
640 	if (err)
641 		ip6_flush_pending_frames(sk);
642 	else if (!(msg->msg_flags & MSG_MORE))
643 		err = l2tp_ip6_push_pending_frames(sk);
644 	release_sock(sk);
645 done:
646 	dst_release(dst);
647 out:
648 	fl6_sock_release(flowlabel);
649 	txopt_put(opt_to_free);
650 
651 	return err < 0 ? err : len;
652 
653 do_confirm:
654 	if (msg->msg_flags & MSG_PROBE)
655 		dst_confirm_neigh(dst, &fl6.daddr);
656 	if (!(msg->msg_flags & MSG_PROBE) || len)
657 		goto back_from_confirm;
658 	err = 0;
659 	goto done;
660 }
661 
662 static int l2tp_ip6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
663 			    int flags, int *addr_len)
664 {
665 	struct ipv6_pinfo *np = inet6_sk(sk);
666 	DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
667 	size_t copied = 0;
668 	int err = -EOPNOTSUPP;
669 	struct sk_buff *skb;
670 
671 	if (flags & MSG_OOB)
672 		goto out;
673 
674 	if (flags & MSG_ERRQUEUE)
675 		return ipv6_recv_error(sk, msg, len, addr_len);
676 
677 	skb = skb_recv_datagram(sk, flags, &err);
678 	if (!skb)
679 		goto out;
680 
681 	copied = skb->len;
682 	if (len < copied) {
683 		msg->msg_flags |= MSG_TRUNC;
684 		copied = len;
685 	}
686 
687 	err = skb_copy_datagram_msg(skb, 0, msg, copied);
688 	if (err)
689 		goto done;
690 
691 	sock_recv_timestamp(msg, sk, skb);
692 
693 	/* Copy the address. */
694 	if (lsa) {
695 		lsa->l2tp_family = AF_INET6;
696 		lsa->l2tp_unused = 0;
697 		lsa->l2tp_addr = ipv6_hdr(skb)->saddr;
698 		lsa->l2tp_flowinfo = 0;
699 		lsa->l2tp_scope_id = 0;
700 		lsa->l2tp_conn_id = 0;
701 		if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
702 			lsa->l2tp_scope_id = inet6_iif(skb);
703 		*addr_len = sizeof(*lsa);
704 	}
705 
706 	if (np->rxopt.all)
707 		ip6_datagram_recv_ctl(sk, msg, skb);
708 
709 	if (flags & MSG_TRUNC)
710 		copied = skb->len;
711 done:
712 	skb_free_datagram(sk, skb);
713 out:
714 	return err ? err : copied;
715 }
716 
717 static struct proto l2tp_ip6_prot = {
718 	.name		   = "L2TP/IPv6",
719 	.owner		   = THIS_MODULE,
720 	.init		   = l2tp_ip6_open,
721 	.close		   = l2tp_ip6_close,
722 	.bind		   = l2tp_ip6_bind,
723 	.connect	   = l2tp_ip6_connect,
724 	.disconnect	   = l2tp_ip6_disconnect,
725 	.ioctl		   = l2tp_ioctl,
726 	.destroy	   = l2tp_ip6_destroy_sock,
727 	.setsockopt	   = ipv6_setsockopt,
728 	.getsockopt	   = ipv6_getsockopt,
729 	.sendmsg	   = l2tp_ip6_sendmsg,
730 	.recvmsg	   = l2tp_ip6_recvmsg,
731 	.backlog_rcv	   = l2tp_ip6_backlog_recv,
732 	.hash		   = l2tp_ip6_hash,
733 	.unhash		   = l2tp_ip6_unhash,
734 	.obj_size	   = sizeof(struct l2tp_ip6_sock),
735 };
736 
737 static const struct proto_ops l2tp_ip6_ops = {
738 	.family		   = PF_INET6,
739 	.owner		   = THIS_MODULE,
740 	.release	   = inet6_release,
741 	.bind		   = inet6_bind,
742 	.connect	   = inet_dgram_connect,
743 	.socketpair	   = sock_no_socketpair,
744 	.accept		   = sock_no_accept,
745 	.getname	   = l2tp_ip6_getname,
746 	.poll		   = datagram_poll,
747 	.ioctl		   = inet6_ioctl,
748 	.gettstamp	   = sock_gettstamp,
749 	.listen		   = sock_no_listen,
750 	.shutdown	   = inet_shutdown,
751 	.setsockopt	   = sock_common_setsockopt,
752 	.getsockopt	   = sock_common_getsockopt,
753 	.sendmsg	   = inet_sendmsg,
754 	.recvmsg	   = sock_common_recvmsg,
755 	.mmap		   = sock_no_mmap,
756 	.sendpage	   = sock_no_sendpage,
757 #ifdef CONFIG_COMPAT
758 	.compat_ioctl	   = inet6_compat_ioctl,
759 #endif
760 };
761 
762 static struct inet_protosw l2tp_ip6_protosw = {
763 	.type		= SOCK_DGRAM,
764 	.protocol	= IPPROTO_L2TP,
765 	.prot		= &l2tp_ip6_prot,
766 	.ops		= &l2tp_ip6_ops,
767 };
768 
769 static struct inet6_protocol l2tp_ip6_protocol __read_mostly = {
770 	.handler	= l2tp_ip6_recv,
771 };
772 
773 static int __init l2tp_ip6_init(void)
774 {
775 	int err;
776 
777 	pr_info("L2TP IP encapsulation support for IPv6 (L2TPv3)\n");
778 
779 	err = proto_register(&l2tp_ip6_prot, 1);
780 	if (err != 0)
781 		goto out;
782 
783 	err = inet6_add_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
784 	if (err)
785 		goto out1;
786 
787 	inet6_register_protosw(&l2tp_ip6_protosw);
788 	return 0;
789 
790 out1:
791 	proto_unregister(&l2tp_ip6_prot);
792 out:
793 	return err;
794 }
795 
796 static void __exit l2tp_ip6_exit(void)
797 {
798 	inet6_unregister_protosw(&l2tp_ip6_protosw);
799 	inet6_del_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
800 	proto_unregister(&l2tp_ip6_prot);
801 }
802 
803 module_init(l2tp_ip6_init);
804 module_exit(l2tp_ip6_exit);
805 
806 MODULE_LICENSE("GPL");
807 MODULE_AUTHOR("Chris Elston <celston@katalix.com>");
808 MODULE_DESCRIPTION("L2TP IP encapsulation for IPv6");
809 MODULE_VERSION("1.0");
810 
811 /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
812  * enums
813  */
814 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 2, IPPROTO_L2TP);
815 MODULE_ALIAS_NET_PF_PROTO(PF_INET6, IPPROTO_L2TP);
816