net/l2tp/l2tp_ip6.c - kernel/msm-4.9 - Gitiles

 /*
  * L2TPv3 IP encapsulation support for IPv6
  *
  * Copyright (c) 2012 Katalix Systems Ltd
  *
  *	This program is free software; you can redistribute it and/or
  *	modify it under the terms of the GNU General Public License
  *	as published by the Free Software Foundation; either version
  *	2 of the License, or (at your option) any later version.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/icmp.h>
 #include <linux/module.h>
 #include <linux/skbuff.h>
 #include <linux/random.h>
 #include <linux/socket.h>
 #include <linux/l2tp.h>
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <net/sock.h>
 #include <net/ip.h>
 #include <net/icmp.h>
 #include <net/udp.h>
 #include <net/inet_common.h>
 #include <net/inet_hashtables.h>
 #include <net/inet6_hashtables.h>
 #include <net/tcp_states.h>
 #include <net/protocol.h>
 #include <net/xfrm.h>

 #include <net/transp_v6.h>
 #include <net/addrconf.h>
 #include <net/ip6_route.h>

 #include "l2tp_core.h"

 struct l2tp_ip6_sock {
 	/* inet_sock has to be the first member of l2tp_ip6_sock */
 	struct inet_sock	inet;

 	u32			conn_id;
 	u32			peer_conn_id;

 	/* ipv6_pinfo has to be the last member of l2tp_ip6_sock, see
 	   inet6_sk_generic */
 	struct ipv6_pinfo	inet6;
 };

 static DEFINE_RWLOCK(l2tp_ip6_lock);
 static struct hlist_head l2tp_ip6_table;
 static struct hlist_head l2tp_ip6_bind_table;

 static inline struct l2tp_ip6_sock *l2tp_ip6_sk(const struct sock *sk)
 {
 	return (struct l2tp_ip6_sock *)sk;
 }

 static struct sock *__l2tp_ip6_bind_lookup(struct net *net,
 					   struct in6_addr *laddr,
 					   const struct in6_addr *raddr,
 					   int dif, u32 tunnel_id)
 {
 	struct sock *sk;

 	sk_for_each_bound(sk, &l2tp_ip6_bind_table) {
 		const struct in6_addr *sk_laddr = inet6_rcv_saddr(sk);
 		const struct in6_addr *sk_raddr = &sk->sk_v6_daddr;
 		struct l2tp_ip6_sock *l2tp = l2tp_ip6_sk(sk);

 		if (l2tp == NULL)
 			continue;

 		if ((l2tp->conn_id == tunnel_id) &&
 		    net_eq(sock_net(sk), net) &&
 		    (!sk_laddr || ipv6_addr_any(sk_laddr) || ipv6_addr_equal(sk_laddr, laddr)) &&
 		    (!raddr || ipv6_addr_any(sk_raddr) || ipv6_addr_equal(sk_raddr, raddr)) &&
 		    (!sk->sk_bound_dev_if || !dif ||
 		     sk->sk_bound_dev_if == dif))
 			goto found;
 	}

 	sk = NULL;
 found:
 	return sk;
 }

 /* When processing receive frames, there are two cases to
  * consider. Data frames consist of a non-zero session-id and an
  * optional cookie. Control frames consist of a regular L2TP header
  * preceded by 32-bits of zeros.
  *
  * L2TPv3 Session Header Over IP
  *
  *  0                   1                   2                   3
  *  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
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |                           Session ID                          |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |               Cookie (optional, maximum 64 bits)...
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *                                                                 |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *
  * L2TPv3 Control Message Header Over IP
  *
  *  0                   1                   2                   3
  *  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
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |                      (32 bits of zeros)                       |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |T|L|x|x|S|x|x|x|x|x|x|x|  Ver  |             Length            |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |                     Control Connection ID                     |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |               Ns              |               Nr              |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *
  * All control frames are passed to userspace.
  */
 static int l2tp_ip6_recv(struct sk_buff *skb)
 {
 	struct net *net = dev_net(skb->dev);
 	struct sock *sk;
 	u32 session_id;
 	u32 tunnel_id;
 	unsigned char *ptr, *optr;
 	struct l2tp_session *session;
 	struct l2tp_tunnel *tunnel = NULL;
 	int length;

 	if (!pskb_may_pull(skb, 4))
 		goto discard;

 	/* Point to L2TP header */
 	optr = ptr = skb->data;
 	session_id = ntohl(*((__be32 *) ptr));
 	ptr += 4;

 	/* RFC3931: L2TP/IP packets have the first 4 bytes containing
 	 * the session_id. If it is 0, the packet is a L2TP control
 	 * frame and the session_id value can be discarded.
 	 */
 	if (session_id == 0) {
 		__skb_pull(skb, 4);
 		goto pass_up;
 	}

 	/* Ok, this is a data packet. Lookup the session. */
 	session = l2tp_session_get(net, NULL, session_id, true);
 	if (!session)
 		goto discard;

 	tunnel = session->tunnel;
 	if (!tunnel)
 		goto discard_sess;

 	/* Trace packet contents, if enabled */
 	if (tunnel->debug & L2TP_MSG_DATA) {
 		length = min(32u, skb->len);
 		if (!pskb_may_pull(skb, length))
 			goto discard_sess;

 		/* Point to L2TP header */
 		optr = ptr = skb->data;
 		ptr += 4;
 		pr_debug("%s: ip recv\n", tunnel->name);
 		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);
 	}

 	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len,
 			 tunnel->recv_payload_hook);
 	l2tp_session_dec_refcount(session);

 	return 0;

 pass_up:
 	/* Get the tunnel_id from the L2TP header */
 	if (!pskb_may_pull(skb, 12))
 		goto discard;

 	if ((skb->data[0] & 0xc0) != 0xc0)
 		goto discard;

 	tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
 	tunnel = l2tp_tunnel_find(net, tunnel_id);
 	if (tunnel) {
 		sk = tunnel->sock;
 		sock_hold(sk);
 	} else {
 		struct ipv6hdr *iph = ipv6_hdr(skb);

 		read_lock_bh(&l2tp_ip6_lock);
 		sk = __l2tp_ip6_bind_lookup(net, &iph->daddr, &iph->saddr,
 					    inet6_iif(skb), tunnel_id);
 		if (!sk) {
 			read_unlock_bh(&l2tp_ip6_lock);
 			goto discard;
 		}

 		sock_hold(sk);
 		read_unlock_bh(&l2tp_ip6_lock);
 	}

 	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
 		goto discard_put;

 	nf_reset(skb);

 	return sk_receive_skb(sk, skb, 1);

 discard_sess:
 	if (session->deref)
 		session->deref(session);
 	l2tp_session_dec_refcount(session);
 	goto discard;

 discard_put:
 	sock_put(sk);

 discard:
 	kfree_skb(skb);
 	return 0;
 }

 static int l2tp_ip6_open(struct sock *sk)
 {
 	/* Prevent autobind. We don't have ports. */
 	inet_sk(sk)->inet_num = IPPROTO_L2TP;

 	write_lock_bh(&l2tp_ip6_lock);
 	sk_add_node(sk, &l2tp_ip6_table);
 	write_unlock_bh(&l2tp_ip6_lock);

 	return 0;
 }

 static void l2tp_ip6_close(struct sock *sk, long timeout)
 {
 	write_lock_bh(&l2tp_ip6_lock);
 	hlist_del_init(&sk->sk_bind_node);
 	sk_del_node_init(sk);
 	write_unlock_bh(&l2tp_ip6_lock);

 	sk_common_release(sk);
 }

 static void l2tp_ip6_destroy_sock(struct sock *sk)
 {
 	struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk);

 	lock_sock(sk);
 	ip6_flush_pending_frames(sk);
 	release_sock(sk);

 	if (tunnel) {
 		l2tp_tunnel_closeall(tunnel);
 		sock_put(sk);
 	}

 	inet6_destroy_sock(sk);
 }

 static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sockaddr_l2tpip6 *addr = (struct sockaddr_l2tpip6 *) uaddr;
 	struct net *net = sock_net(sk);
 	__be32 v4addr = 0;
 	int bound_dev_if;
 	int addr_type;
 	int err;

 	if (addr->l2tp_family != AF_INET6)
 		return -EINVAL;
 	if (addr_len < sizeof(*addr))
 		return -EINVAL;

 	addr_type = ipv6_addr_type(&addr->l2tp_addr);

 	/* l2tp_ip6 sockets are IPv6 only */
 	if (addr_type == IPV6_ADDR_MAPPED)
 		return -EADDRNOTAVAIL;

 	/* L2TP is point-point, not multicast */
 	if (addr_type & IPV6_ADDR_MULTICAST)
 		return -EADDRNOTAVAIL;

 	lock_sock(sk);

 	err = -EINVAL;
 	if (!sock_flag(sk, SOCK_ZAPPED))
 		goto out_unlock;

 	if (sk->sk_state != TCP_CLOSE)
 		goto out_unlock;

 	bound_dev_if = sk->sk_bound_dev_if;

 	/* Check if the address belongs to the host. */
 	rcu_read_lock();
 	if (addr_type != IPV6_ADDR_ANY) {
 		struct net_device *dev = NULL;

 		if (addr_type & IPV6_ADDR_LINKLOCAL) {
 			if (addr->l2tp_scope_id)
 				bound_dev_if = addr->l2tp_scope_id;

 			/* Binding to link-local address requires an
 			 * interface.
 			 */
 			if (!bound_dev_if)
 				goto out_unlock_rcu;

 			err = -ENODEV;
 			dev = dev_get_by_index_rcu(sock_net(sk), bound_dev_if);
 			if (!dev)
 				goto out_unlock_rcu;
 		}

 		/* ipv4 addr of the socket is invalid.  Only the
 		 * unspecified and mapped address have a v4 equivalent.
 		 */
 		v4addr = LOOPBACK4_IPV6;
 		err = -EADDRNOTAVAIL;
 		if (!ipv6_chk_addr(sock_net(sk), &addr->l2tp_addr, dev, 0))
 			goto out_unlock_rcu;
 	}
 	rcu_read_unlock();

 	write_lock_bh(&l2tp_ip6_lock);
 	if (__l2tp_ip6_bind_lookup(net, &addr->l2tp_addr, NULL, bound_dev_if,
 				   addr->l2tp_conn_id)) {
 		write_unlock_bh(&l2tp_ip6_lock);
 		err = -EADDRINUSE;
 		goto out_unlock;
 	}

 	inet->inet_saddr = v4addr;
 	inet->inet_rcv_saddr = v4addr;
 	sk->sk_bound_dev_if = bound_dev_if;
 	sk->sk_v6_rcv_saddr = addr->l2tp_addr;
 	np->saddr = addr->l2tp_addr;

 	l2tp_ip6_sk(sk)->conn_id = addr->l2tp_conn_id;

 	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
 	sk_del_node_init(sk);
 	write_unlock_bh(&l2tp_ip6_lock);

 	sock_reset_flag(sk, SOCK_ZAPPED);
 	release_sock(sk);
 	return 0;

 out_unlock_rcu:
 	rcu_read_unlock();
 out_unlock:
 	release_sock(sk);

 	return err;
 }

 static int l2tp_ip6_connect(struct sock *sk, struct sockaddr *uaddr,
 			    int addr_len)
 {
 	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *) uaddr;
 	struct sockaddr_in6	*usin = (struct sockaddr_in6 *) uaddr;
 	struct in6_addr	*daddr;
 	int	addr_type;
 	int rc;

 	if (addr_len < sizeof(*lsa))
 		return -EINVAL;

 	if (usin->sin6_family != AF_INET6)
 		return -EINVAL;

 	addr_type = ipv6_addr_type(&usin->sin6_addr);
 	if (addr_type & IPV6_ADDR_MULTICAST)
 		return -EINVAL;

 	if (addr_type & IPV6_ADDR_MAPPED) {
 		daddr = &usin->sin6_addr;
 		if (ipv4_is_multicast(daddr->s6_addr32[3]))
 			return -EINVAL;
 	}

 	lock_sock(sk);

 	 /* Must bind first - autobinding does not work */
 	if (sock_flag(sk, SOCK_ZAPPED)) {
 		rc = -EINVAL;
 		goto out_sk;
 	}

 	rc = __ip6_datagram_connect(sk, uaddr, addr_len);
 	if (rc < 0)
 		goto out_sk;

 	l2tp_ip6_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;

 	write_lock_bh(&l2tp_ip6_lock);
 	hlist_del_init(&sk->sk_bind_node);
 	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
 	write_unlock_bh(&l2tp_ip6_lock);

 out_sk:
 	release_sock(sk);

 	return rc;
 }

 static int l2tp_ip6_disconnect(struct sock *sk, int flags)
 {
 	if (sock_flag(sk, SOCK_ZAPPED))
 		return 0;

 	return __udp_disconnect(sk, flags);
 }

 static int l2tp_ip6_getname(struct socket *sock, struct sockaddr *uaddr,
 			    int *uaddr_len, int peer)
 {
 	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)uaddr;
 	struct sock *sk = sock->sk;
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct l2tp_ip6_sock *lsk = l2tp_ip6_sk(sk);

 	lsa->l2tp_family = AF_INET6;
 	lsa->l2tp_flowinfo = 0;
 	lsa->l2tp_scope_id = 0;
 	lsa->l2tp_unused = 0;
 	if (peer) {
 		if (!lsk->peer_conn_id)
 			return -ENOTCONN;
 		lsa->l2tp_conn_id = lsk->peer_conn_id;
 		lsa->l2tp_addr = sk->sk_v6_daddr;
 		if (np->sndflow)
 			lsa->l2tp_flowinfo = np->flow_label;
 	} else {
 		if (ipv6_addr_any(&sk->sk_v6_rcv_saddr))
 			lsa->l2tp_addr = np->saddr;
 		else
 			lsa->l2tp_addr = sk->sk_v6_rcv_saddr;

 		lsa->l2tp_conn_id = lsk->conn_id;
 	}
 	if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
 		lsa->l2tp_scope_id = sk->sk_bound_dev_if;
 	*uaddr_len = sizeof(*lsa);
 	return 0;
 }

 static int l2tp_ip6_backlog_recv(struct sock *sk, struct sk_buff *skb)
 {
 	int rc;

 	/* Charge it to the socket, dropping if the queue is full. */
 	rc = sock_queue_rcv_skb(sk, skb);
 	if (rc < 0)
 		goto drop;

 	return 0;

 drop:
 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS);
 	kfree_skb(skb);
 	return -1;
 }

 static int l2tp_ip6_push_pending_frames(struct sock *sk)
 {
 	struct sk_buff *skb;
 	__be32 *transhdr = NULL;
 	int err = 0;

 	skb = skb_peek(&sk->sk_write_queue);
 	if (skb == NULL)
 		goto out;

 	transhdr = (__be32 *)skb_transport_header(skb);
 	*transhdr = 0;

 	err = ip6_push_pending_frames(sk);

 out:
 	return err;
 }

 /* Userspace will call sendmsg() on the tunnel socket to send L2TP
  * control frames.
  */
 static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 {
 	struct ipv6_txoptions opt_space;
 	DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
 	struct in6_addr *daddr, *final_p, final;
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct ipv6_txoptions *opt_to_free = NULL;
 	struct ipv6_txoptions *opt = NULL;
 	struct ip6_flowlabel *flowlabel = NULL;
 	struct dst_entry *dst = NULL;
 	struct flowi6 fl6;
 	struct sockcm_cookie sockc_unused = {0};
 	struct ipcm6_cookie ipc6;
 	int addr_len = msg->msg_namelen;
 	int transhdrlen = 4; /* zero session-id */
 	int ulen = len + transhdrlen;
 	int err;

 	/* Rough check on arithmetic overflow,
 	   better check is made in ip6_append_data().
 	 */
 	if (len > INT_MAX)
 		return -EMSGSIZE;

 	/* Mirror BSD error message compatibility */
 	if (msg->msg_flags & MSG_OOB)
 		return -EOPNOTSUPP;

 	/*
 	 *	Get and verify the address.
 	 */
 	memset(&fl6, 0, sizeof(fl6));

 	fl6.flowi6_mark = sk->sk_mark;
 	fl6.flowi6_uid = sk->sk_uid;

 	ipc6.hlimit = -1;
 	ipc6.tclass = -1;
 	ipc6.dontfrag = -1;

 	if (lsa) {
 		if (addr_len < SIN6_LEN_RFC2133)
 			return -EINVAL;

 		if (lsa->l2tp_family && lsa->l2tp_family != AF_INET6)
 			return -EAFNOSUPPORT;

 		daddr = &lsa->l2tp_addr;
 		if (np->sndflow) {
 			fl6.flowlabel = lsa->l2tp_flowinfo & IPV6_FLOWINFO_MASK;
 			if (fl6.flowlabel&IPV6_FLOWLABEL_MASK) {
 				flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
 				if (flowlabel == NULL)
 					return -EINVAL;
 			}
 		}

 		/*
 		 * Otherwise it will be difficult to maintain
 		 * sk->sk_dst_cache.
 		 */
 		if (sk->sk_state == TCP_ESTABLISHED &&
 		    ipv6_addr_equal(daddr, &sk->sk_v6_daddr))
 			daddr = &sk->sk_v6_daddr;

 		if (addr_len >= sizeof(struct sockaddr_in6) &&
 		    lsa->l2tp_scope_id &&
 		    ipv6_addr_type(daddr) & IPV6_ADDR_LINKLOCAL)
 			fl6.flowi6_oif = lsa->l2tp_scope_id;
 	} else {
 		if (sk->sk_state != TCP_ESTABLISHED)
 			return -EDESTADDRREQ;

 		daddr = &sk->sk_v6_daddr;
 		fl6.flowlabel = np->flow_label;
 	}

 	if (fl6.flowi6_oif == 0)
 		fl6.flowi6_oif = sk->sk_bound_dev_if;

 	if (msg->msg_controllen) {
 		opt = &opt_space;
 		memset(opt, 0, sizeof(struct ipv6_txoptions));
 		opt->tot_len = sizeof(struct ipv6_txoptions);
 		ipc6.opt = opt;

 		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6,
 					    &sockc_unused);
 		if (err < 0) {
 			fl6_sock_release(flowlabel);
 			return err;
 		}
 		if ((fl6.flowlabel & IPV6_FLOWLABEL_MASK) && !flowlabel) {
 			flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
 			if (flowlabel == NULL)
 				return -EINVAL;
 		}
 		if (!(opt->opt_nflen|opt->opt_flen))
 			opt = NULL;
 	}

 	if (!opt) {
 		opt = txopt_get(np);
 		opt_to_free = opt;
 	}
 	if (flowlabel)
 		opt = fl6_merge_options(&opt_space, flowlabel, opt);
 	opt = ipv6_fixup_options(&opt_space, opt);
 	ipc6.opt = opt;

 	fl6.flowi6_proto = sk->sk_protocol;
 	if (!ipv6_addr_any(daddr))
 		fl6.daddr = *daddr;
 	else
 		fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
 	if (ipv6_addr_any(&fl6.saddr) && !ipv6_addr_any(&np->saddr))
 		fl6.saddr = np->saddr;

 	final_p = fl6_update_dst(&fl6, opt, &final);

 	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
 		fl6.flowi6_oif = np->mcast_oif;
 	else if (!fl6.flowi6_oif)
 		fl6.flowi6_oif = np->ucast_oif;

 	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

 	if (ipc6.tclass < 0)
 		ipc6.tclass = np->tclass;

 	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);

 	dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
 	if (IS_ERR(dst)) {
 		err = PTR_ERR(dst);
 		goto out;
 	}

 	if (ipc6.hlimit < 0)
 		ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);

 	if (ipc6.dontfrag < 0)
 		ipc6.dontfrag = np->dontfrag;

 	if (msg->msg_flags & MSG_CONFIRM)
 		goto do_confirm;

 back_from_confirm:
 	lock_sock(sk);
 	err = ip6_append_data(sk, ip_generic_getfrag, msg,
 			      ulen, transhdrlen, &ipc6,
 			      &fl6, (struct rt6_info *)dst,
 			      msg->msg_flags, &sockc_unused);
 	if (err)
 		ip6_flush_pending_frames(sk);
 	else if (!(msg->msg_flags & MSG_MORE))
 		err = l2tp_ip6_push_pending_frames(sk);
 	release_sock(sk);
 done:
 	dst_release(dst);
 out:
 	fl6_sock_release(flowlabel);
 	txopt_put(opt_to_free);

 	return err < 0 ? err : len;

 do_confirm:
 	dst_confirm(dst);
 	if (!(msg->msg_flags & MSG_PROBE) || len)
 		goto back_from_confirm;
 	err = 0;
 	goto done;
 }

 static int l2tp_ip6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 			    int noblock, int flags, int *addr_len)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
 	size_t copied = 0;
 	int err = -EOPNOTSUPP;
 	struct sk_buff *skb;

 	if (flags & MSG_OOB)
 		goto out;

 	if (addr_len)
 		*addr_len = sizeof(*lsa);

 	if (flags & MSG_ERRQUEUE)
 		return ipv6_recv_error(sk, msg, len, addr_len);

 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb)
 		goto out;

 	copied = skb->len;
 	if (len < copied) {
 		msg->msg_flags |= MSG_TRUNC;
 		copied = len;
 	}

 	err = skb_copy_datagram_msg(skb, 0, msg, copied);
 	if (err)
 		goto done;

 	sock_recv_timestamp(msg, sk, skb);

 	/* Copy the address. */
 	if (lsa) {
 		lsa->l2tp_family = AF_INET6;
 		lsa->l2tp_unused = 0;
 		lsa->l2tp_addr = ipv6_hdr(skb)->saddr;
 		lsa->l2tp_flowinfo = 0;
 		lsa->l2tp_scope_id = 0;
 		lsa->l2tp_conn_id = 0;
 		if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
 			lsa->l2tp_scope_id = inet6_iif(skb);
 	}

 	if (np->rxopt.all)
 		ip6_datagram_recv_ctl(sk, msg, skb);

 	if (flags & MSG_TRUNC)
 		copied = skb->len;
 done:
 	skb_free_datagram(sk, skb);
 out:
 	return err ? err : copied;
 }

 static struct proto l2tp_ip6_prot = {
 	.name		   = "L2TP/IPv6",
 	.owner		   = THIS_MODULE,
 	.init		   = l2tp_ip6_open,
 	.close		   = l2tp_ip6_close,
 	.bind		   = l2tp_ip6_bind,
 	.connect	   = l2tp_ip6_connect,
 	.disconnect	   = l2tp_ip6_disconnect,
 	.ioctl		   = l2tp_ioctl,
 	.destroy	   = l2tp_ip6_destroy_sock,
 	.setsockopt	   = ipv6_setsockopt,
 	.getsockopt	   = ipv6_getsockopt,
 	.sendmsg	   = l2tp_ip6_sendmsg,
 	.recvmsg	   = l2tp_ip6_recvmsg,
 	.backlog_rcv	   = l2tp_ip6_backlog_recv,
 	.hash		   = inet6_hash,
 	.unhash		   = inet_unhash,
 	.obj_size	   = sizeof(struct l2tp_ip6_sock),
 #ifdef CONFIG_COMPAT
 	.compat_setsockopt = compat_ipv6_setsockopt,
 	.compat_getsockopt = compat_ipv6_getsockopt,
 #endif
 };

 static const struct proto_ops l2tp_ip6_ops = {
 	.family		   = PF_INET6,
 	.owner		   = THIS_MODULE,
 	.release	   = inet6_release,
 	.bind		   = inet6_bind,
 	.connect	   = inet_dgram_connect,
 	.socketpair	   = sock_no_socketpair,
 	.accept		   = sock_no_accept,
 	.getname	   = l2tp_ip6_getname,
 	.poll		   = datagram_poll,
 	.ioctl		   = inet6_ioctl,
 	.listen		   = sock_no_listen,
 	.shutdown	   = inet_shutdown,
 	.setsockopt	   = sock_common_setsockopt,
 	.getsockopt	   = sock_common_getsockopt,
 	.sendmsg	   = inet_sendmsg,
 	.recvmsg	   = sock_common_recvmsg,
 	.mmap		   = sock_no_mmap,
 	.sendpage	   = sock_no_sendpage,
 #ifdef CONFIG_COMPAT
 	.compat_setsockopt = compat_sock_common_setsockopt,
 	.compat_getsockopt = compat_sock_common_getsockopt,
 #endif
 };

 static struct inet_protosw l2tp_ip6_protosw = {
 	.type		= SOCK_DGRAM,
 	.protocol	= IPPROTO_L2TP,
 	.prot		= &l2tp_ip6_prot,
 	.ops		= &l2tp_ip6_ops,
 };

 static struct inet6_protocol l2tp_ip6_protocol __read_mostly = {
 	.handler	= l2tp_ip6_recv,
 };

 static int __init l2tp_ip6_init(void)
 {
 	int err;

 	pr_info("L2TP IP encapsulation support for IPv6 (L2TPv3)\n");

 	err = proto_register(&l2tp_ip6_prot, 1);
 	if (err != 0)
 		goto out;

 	err = inet6_add_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
 	if (err)
 		goto out1;

 	inet6_register_protosw(&l2tp_ip6_protosw);
 	return 0;

 out1:
 	proto_unregister(&l2tp_ip6_prot);
 out:
 	return err;
 }

 static void __exit l2tp_ip6_exit(void)
 {
 	inet6_unregister_protosw(&l2tp_ip6_protosw);
 	inet6_del_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
 	proto_unregister(&l2tp_ip6_prot);
 }

 module_init(l2tp_ip6_init);
 module_exit(l2tp_ip6_exit);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Chris Elston <celston@katalix.com>");
 MODULE_DESCRIPTION("L2TP IP encapsulation for IPv6");
 MODULE_VERSION("1.0");

 /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
  * enums
  */
 MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 2, IPPROTO_L2TP);
 MODULE_ALIAS_NET_PF_PROTO(PF_INET6, IPPROTO_L2TP);
	/*
	* L2TPv3 IP encapsulation support for IPv6
	*
	* Copyright (c) 2012 Katalix Systems Ltd
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/icmp.h>
	#include <linux/module.h>
	#include <linux/skbuff.h>
	#include <linux/random.h>
	#include <linux/socket.h>
	#include <linux/l2tp.h>
	#include <linux/in.h>
	#include <linux/in6.h>
	#include <net/sock.h>
	#include <net/ip.h>
	#include <net/icmp.h>
	#include <net/udp.h>
	#include <net/inet_common.h>
	#include <net/inet_hashtables.h>
	#include <net/inet6_hashtables.h>
	#include <net/tcp_states.h>
	#include <net/protocol.h>
	#include <net/xfrm.h>

	#include <net/transp_v6.h>
	#include <net/addrconf.h>
	#include <net/ip6_route.h>

	#include "l2tp_core.h"

	struct l2tp_ip6_sock {
	/* inet_sock has to be the first member of l2tp_ip6_sock */
	struct inet_sock inet;

	u32 conn_id;
	u32 peer_conn_id;

	/* ipv6_pinfo has to be the last member of l2tp_ip6_sock, see
	inet6_sk_generic */
	struct ipv6_pinfo inet6;
	};

	static DEFINE_RWLOCK(l2tp_ip6_lock);
	static struct hlist_head l2tp_ip6_table;
	static struct hlist_head l2tp_ip6_bind_table;

	static inline struct l2tp_ip6_sock l2tp_ip6_sk(const struct sock sk)
	{
	return (struct l2tp_ip6_sock *)sk;
	}

	static struct sock __l2tp_ip6_bind_lookup(struct net net,
	struct in6_addr *laddr,
	const struct in6_addr *raddr,
	int dif, u32 tunnel_id)
	{
	struct sock *sk;

	sk_for_each_bound(sk, &l2tp_ip6_bind_table) {
	const struct in6_addr *sk_laddr = inet6_rcv_saddr(sk);
	const struct in6_addr *sk_raddr = &sk->sk_v6_daddr;
	struct l2tp_ip6_sock *l2tp = l2tp_ip6_sk(sk);

	if (l2tp == NULL)
	continue;

	if ((l2tp->conn_id == tunnel_id) &&
	net_eq(sock_net(sk), net) &&
	(!sk_laddr \|\| ipv6_addr_any(sk_laddr) \|\| ipv6_addr_equal(sk_laddr, laddr)) &&
	(!raddr \|\| ipv6_addr_any(sk_raddr) \|\| ipv6_addr_equal(sk_raddr, raddr)) &&
	(!sk->sk_bound_dev_if \|\| !dif \|\|
	sk->sk_bound_dev_if == dif))
	goto found;
	}

	sk = NULL;
	found:
	return sk;
	}

	/* When processing receive frames, there are two cases to
	* consider. Data frames consist of a non-zero session-id and an
	* optional cookie. Control frames consist of a regular L2TP header
	* preceded by 32-bits of zeros.
	*
	* L2TPv3 Session Header Over IP
	*
	* 0 1 2 3
	* 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
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Session ID \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Cookie (optional, maximum 64 bits)...
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	*
	* L2TPv3 Control Message Header Over IP
	*
	* 0 1 2 3
	* 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
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| (32 bits of zeros) \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \|T\|L\|x\|x\|S\|x\|x\|x\|x\|x\|x\|x\| Ver \| Length \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Control Connection ID \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Ns \| Nr \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	*
	* All control frames are passed to userspace.
	*/
	static int l2tp_ip6_recv(struct sk_buff *skb)
	{
	struct net *net = dev_net(skb->dev);
	struct sock *sk;
	u32 session_id;
	u32 tunnel_id;
	unsigned char ptr, optr;
	struct l2tp_session *session;
	struct l2tp_tunnel *tunnel = NULL;
	int length;

	if (!pskb_may_pull(skb, 4))
	goto discard;

	/* Point to L2TP header */
	optr = ptr = skb->data;
	session_id = ntohl(((__be32 ) ptr));
	ptr += 4;

	/* RFC3931: L2TP/IP packets have the first 4 bytes containing
	* the session_id. If it is 0, the packet is a L2TP control
	* frame and the session_id value can be discarded.
	*/
	if (session_id == 0) {
	__skb_pull(skb, 4);
	goto pass_up;
	}

	/* Ok, this is a data packet. Lookup the session. */
	session = l2tp_session_get(net, NULL, session_id, true);
	if (!session)
	goto discard;

	tunnel = session->tunnel;
	if (!tunnel)
	goto discard_sess;

	/* Trace packet contents, if enabled */
	if (tunnel->debug & L2TP_MSG_DATA) {
	length = min(32u, skb->len);
	if (!pskb_may_pull(skb, length))
	goto discard_sess;

	/* Point to L2TP header */
	optr = ptr = skb->data;
	ptr += 4;
	pr_debug("%s: ip recv\n", tunnel->name);
	print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);
	}

	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len,
	tunnel->recv_payload_hook);
	l2tp_session_dec_refcount(session);

	return 0;

	pass_up:
	/* Get the tunnel_id from the L2TP header */
	if (!pskb_may_pull(skb, 12))
	goto discard;

	if ((skb->data[0] & 0xc0) != 0xc0)
	goto discard;

	tunnel_id = ntohl((__be32 ) &skb->data[4]);
	tunnel = l2tp_tunnel_find(net, tunnel_id);
	if (tunnel) {
	sk = tunnel->sock;
	sock_hold(sk);
	} else {
	struct ipv6hdr *iph = ipv6_hdr(skb);

	read_lock_bh(&l2tp_ip6_lock);
	sk = __l2tp_ip6_bind_lookup(net, &iph->daddr, &iph->saddr,
	inet6_iif(skb), tunnel_id);
	if (!sk) {
	read_unlock_bh(&l2tp_ip6_lock);
	goto discard;
	}

	sock_hold(sk);
	read_unlock_bh(&l2tp_ip6_lock);
	}

	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
	goto discard_put;

	nf_reset(skb);

	return sk_receive_skb(sk, skb, 1);

	discard_sess:
	if (session->deref)
	session->deref(session);
	l2tp_session_dec_refcount(session);
	goto discard;

	discard_put:
	sock_put(sk);

	discard:
	kfree_skb(skb);
	return 0;
	}

	static int l2tp_ip6_open(struct sock *sk)
	{
	/* Prevent autobind. We don't have ports. */
	inet_sk(sk)->inet_num = IPPROTO_L2TP;

	write_lock_bh(&l2tp_ip6_lock);
	sk_add_node(sk, &l2tp_ip6_table);
	write_unlock_bh(&l2tp_ip6_lock);

	return 0;
	}

	static void l2tp_ip6_close(struct sock *sk, long timeout)
	{
	write_lock_bh(&l2tp_ip6_lock);
	hlist_del_init(&sk->sk_bind_node);
	sk_del_node_init(sk);
	write_unlock_bh(&l2tp_ip6_lock);

	sk_common_release(sk);
	}

	static void l2tp_ip6_destroy_sock(struct sock *sk)
	{
	struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk);

	lock_sock(sk);
	ip6_flush_pending_frames(sk);
	release_sock(sk);

	if (tunnel) {
	l2tp_tunnel_closeall(tunnel);
	sock_put(sk);
	}

	inet6_destroy_sock(sk);
	}

	static int l2tp_ip6_bind(struct sock sk, struct sockaddr uaddr, int addr_len)
	{
	struct inet_sock *inet = inet_sk(sk);
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct sockaddr_l2tpip6 addr = (struct sockaddr_l2tpip6 ) uaddr;
	struct net *net = sock_net(sk);
	__be32 v4addr = 0;
	int bound_dev_if;
	int addr_type;
	int err;

	if (addr->l2tp_family != AF_INET6)
	return -EINVAL;
	if (addr_len < sizeof(*addr))
	return -EINVAL;

	addr_type = ipv6_addr_type(&addr->l2tp_addr);

	/* l2tp_ip6 sockets are IPv6 only */
	if (addr_type == IPV6_ADDR_MAPPED)
	return -EADDRNOTAVAIL;

	/* L2TP is point-point, not multicast */
	if (addr_type & IPV6_ADDR_MULTICAST)
	return -EADDRNOTAVAIL;

	lock_sock(sk);

	err = -EINVAL;
	if (!sock_flag(sk, SOCK_ZAPPED))
	goto out_unlock;

	if (sk->sk_state != TCP_CLOSE)
	goto out_unlock;

	bound_dev_if = sk->sk_bound_dev_if;

	/* Check if the address belongs to the host. */
	rcu_read_lock();
	if (addr_type != IPV6_ADDR_ANY) {
	struct net_device *dev = NULL;

	if (addr_type & IPV6_ADDR_LINKLOCAL) {
	if (addr->l2tp_scope_id)
	bound_dev_if = addr->l2tp_scope_id;

	/* Binding to link-local address requires an
	* interface.
	*/
	if (!bound_dev_if)
	goto out_unlock_rcu;

	err = -ENODEV;
	dev = dev_get_by_index_rcu(sock_net(sk), bound_dev_if);
	if (!dev)
	goto out_unlock_rcu;
	}

	/* ipv4 addr of the socket is invalid. Only the
	* unspecified and mapped address have a v4 equivalent.
	*/
	v4addr = LOOPBACK4_IPV6;
	err = -EADDRNOTAVAIL;
	if (!ipv6_chk_addr(sock_net(sk), &addr->l2tp_addr, dev, 0))
	goto out_unlock_rcu;
	}
	rcu_read_unlock();

	write_lock_bh(&l2tp_ip6_lock);
	if (__l2tp_ip6_bind_lookup(net, &addr->l2tp_addr, NULL, bound_dev_if,
	addr->l2tp_conn_id)) {
	write_unlock_bh(&l2tp_ip6_lock);
	err = -EADDRINUSE;
	goto out_unlock;
	}

	inet->inet_saddr = v4addr;
	inet->inet_rcv_saddr = v4addr;
	sk->sk_bound_dev_if = bound_dev_if;
	sk->sk_v6_rcv_saddr = addr->l2tp_addr;
	np->saddr = addr->l2tp_addr;

	l2tp_ip6_sk(sk)->conn_id = addr->l2tp_conn_id;

	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
	sk_del_node_init(sk);
	write_unlock_bh(&l2tp_ip6_lock);

	sock_reset_flag(sk, SOCK_ZAPPED);
	release_sock(sk);
	return 0;

	out_unlock_rcu:
	rcu_read_unlock();
	out_unlock:
	release_sock(sk);

	return err;
	}

	static int l2tp_ip6_connect(struct sock sk, struct sockaddr uaddr,
	int addr_len)
	{
	struct sockaddr_l2tpip6 lsa = (struct sockaddr_l2tpip6 ) uaddr;
	struct sockaddr_in6 usin = (struct sockaddr_in6 ) uaddr;
	struct in6_addr *daddr;
	int addr_type;
	int rc;

	if (addr_len < sizeof(*lsa))
	return -EINVAL;

	if (usin->sin6_family != AF_INET6)
	return -EINVAL;

	addr_type = ipv6_addr_type(&usin->sin6_addr);
	if (addr_type & IPV6_ADDR_MULTICAST)
	return -EINVAL;

	if (addr_type & IPV6_ADDR_MAPPED) {
	daddr = &usin->sin6_addr;
	if (ipv4_is_multicast(daddr->s6_addr32[3]))
	return -EINVAL;
	}

	lock_sock(sk);

	/* Must bind first - autobinding does not work */
	if (sock_flag(sk, SOCK_ZAPPED)) {
	rc = -EINVAL;
	goto out_sk;
	}

	rc = __ip6_datagram_connect(sk, uaddr, addr_len);
	if (rc < 0)
	goto out_sk;

	l2tp_ip6_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;

	write_lock_bh(&l2tp_ip6_lock);
	hlist_del_init(&sk->sk_bind_node);
	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
	write_unlock_bh(&l2tp_ip6_lock);

	out_sk:
	release_sock(sk);

	return rc;
	}

	static int l2tp_ip6_disconnect(struct sock *sk, int flags)
	{
	if (sock_flag(sk, SOCK_ZAPPED))
	return 0;

	return __udp_disconnect(sk, flags);
	}

	static int l2tp_ip6_getname(struct socket sock, struct sockaddr uaddr,
	int *uaddr_len, int peer)
	{
	struct sockaddr_l2tpip6 lsa = (struct sockaddr_l2tpip6 )uaddr;
	struct sock *sk = sock->sk;
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct l2tp_ip6_sock *lsk = l2tp_ip6_sk(sk);

	lsa->l2tp_family = AF_INET6;
	lsa->l2tp_flowinfo = 0;
	lsa->l2tp_scope_id = 0;
	lsa->l2tp_unused = 0;
	if (peer) {
	if (!lsk->peer_conn_id)
	return -ENOTCONN;
	lsa->l2tp_conn_id = lsk->peer_conn_id;
	lsa->l2tp_addr = sk->sk_v6_daddr;
	if (np->sndflow)
	lsa->l2tp_flowinfo = np->flow_label;
	} else {
	if (ipv6_addr_any(&sk->sk_v6_rcv_saddr))
	lsa->l2tp_addr = np->saddr;
	else
	lsa->l2tp_addr = sk->sk_v6_rcv_saddr;

	lsa->l2tp_conn_id = lsk->conn_id;
	}
	if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
	lsa->l2tp_scope_id = sk->sk_bound_dev_if;
	uaddr_len = sizeof(lsa);
	return 0;
	}

	static int l2tp_ip6_backlog_recv(struct sock sk, struct sk_buff skb)
	{
	int rc;

	/* Charge it to the socket, dropping if the queue is full. */
	rc = sock_queue_rcv_skb(sk, skb);
	if (rc < 0)
	goto drop;

	return 0;

	drop:
	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS);
	kfree_skb(skb);
	return -1;
	}

	static int l2tp_ip6_push_pending_frames(struct sock *sk)
	{
	struct sk_buff *skb;
	__be32 *transhdr = NULL;
	int err = 0;

	skb = skb_peek(&sk->sk_write_queue);
	if (skb == NULL)
	goto out;

	transhdr = (__be32 *)skb_transport_header(skb);
	*transhdr = 0;

	err = ip6_push_pending_frames(sk);

	out:
	return err;
	}

	/* Userspace will call sendmsg() on the tunnel socket to send L2TP
	* control frames.
	*/
	static int l2tp_ip6_sendmsg(struct sock sk, struct msghdr msg, size_t len)
	{
	struct ipv6_txoptions opt_space;
	DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
	struct in6_addr daddr, final_p, final;
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct ipv6_txoptions *opt_to_free = NULL;
	struct ipv6_txoptions *opt = NULL;
	struct ip6_flowlabel *flowlabel = NULL;
	struct dst_entry *dst = NULL;
	struct flowi6 fl6;
	struct sockcm_cookie sockc_unused = {0};
	struct ipcm6_cookie ipc6;
	int addr_len = msg->msg_namelen;
	int transhdrlen = 4; /* zero session-id */
	int ulen = len + transhdrlen;
	int err;

	/* Rough check on arithmetic overflow,
	better check is made in ip6_append_data().
	*/
	if (len > INT_MAX)
	return -EMSGSIZE;

	/* Mirror BSD error message compatibility */
	if (msg->msg_flags & MSG_OOB)
	return -EOPNOTSUPP;

	/*
	* Get and verify the address.
	*/
	memset(&fl6, 0, sizeof(fl6));

	fl6.flowi6_mark = sk->sk_mark;
	fl6.flowi6_uid = sk->sk_uid;

	ipc6.hlimit = -1;
	ipc6.tclass = -1;
	ipc6.dontfrag = -1;

	if (lsa) {
	if (addr_len < SIN6_LEN_RFC2133)
	return -EINVAL;

	if (lsa->l2tp_family && lsa->l2tp_family != AF_INET6)
	return -EAFNOSUPPORT;

	daddr = &lsa->l2tp_addr;
	if (np->sndflow) {
	fl6.flowlabel = lsa->l2tp_flowinfo & IPV6_FLOWINFO_MASK;
	if (fl6.flowlabel&IPV6_FLOWLABEL_MASK) {
	flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
	if (flowlabel == NULL)
	return -EINVAL;
	}
	}

	/*
	* Otherwise it will be difficult to maintain
	* sk->sk_dst_cache.
	*/
	if (sk->sk_state == TCP_ESTABLISHED &&
	ipv6_addr_equal(daddr, &sk->sk_v6_daddr))
	daddr = &sk->sk_v6_daddr;

	if (addr_len >= sizeof(struct sockaddr_in6) &&
	lsa->l2tp_scope_id &&
	ipv6_addr_type(daddr) & IPV6_ADDR_LINKLOCAL)
	fl6.flowi6_oif = lsa->l2tp_scope_id;
	} else {
	if (sk->sk_state != TCP_ESTABLISHED)
	return -EDESTADDRREQ;

	daddr = &sk->sk_v6_daddr;
	fl6.flowlabel = np->flow_label;
	}

	if (fl6.flowi6_oif == 0)
	fl6.flowi6_oif = sk->sk_bound_dev_if;

	if (msg->msg_controllen) {
	opt = &opt_space;
	memset(opt, 0, sizeof(struct ipv6_txoptions));
	opt->tot_len = sizeof(struct ipv6_txoptions);
	ipc6.opt = opt;

	err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6,
	&sockc_unused);
	if (err < 0) {
	fl6_sock_release(flowlabel);
	return err;
	}
	if ((fl6.flowlabel & IPV6_FLOWLABEL_MASK) && !flowlabel) {
	flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
	if (flowlabel == NULL)
	return -EINVAL;
	}
	if (!(opt->opt_nflen\|opt->opt_flen))
	opt = NULL;
	}

	if (!opt) {
	opt = txopt_get(np);
	opt_to_free = opt;
	}
	if (flowlabel)
	opt = fl6_merge_options(&opt_space, flowlabel, opt);
	opt = ipv6_fixup_options(&opt_space, opt);
	ipc6.opt = opt;

	fl6.flowi6_proto = sk->sk_protocol;
	if (!ipv6_addr_any(daddr))
	fl6.daddr = *daddr;
	else
	fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
	if (ipv6_addr_any(&fl6.saddr) && !ipv6_addr_any(&np->saddr))
	fl6.saddr = np->saddr;

	final_p = fl6_update_dst(&fl6, opt, &final);

	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
	fl6.flowi6_oif = np->mcast_oif;
	else if (!fl6.flowi6_oif)
	fl6.flowi6_oif = np->ucast_oif;

	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

	if (ipc6.tclass < 0)
	ipc6.tclass = np->tclass;

	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);

	dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
	if (IS_ERR(dst)) {
	err = PTR_ERR(dst);
	goto out;
	}

	if (ipc6.hlimit < 0)
	ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);

	if (ipc6.dontfrag < 0)
	ipc6.dontfrag = np->dontfrag;

	if (msg->msg_flags & MSG_CONFIRM)
	goto do_confirm;

	back_from_confirm:
	lock_sock(sk);
	err = ip6_append_data(sk, ip_generic_getfrag, msg,
	ulen, transhdrlen, &ipc6,
	&fl6, (struct rt6_info *)dst,
	msg->msg_flags, &sockc_unused);
	if (err)
	ip6_flush_pending_frames(sk);
	else if (!(msg->msg_flags & MSG_MORE))
	err = l2tp_ip6_push_pending_frames(sk);
	release_sock(sk);
	done:
	dst_release(dst);
	out:
	fl6_sock_release(flowlabel);
	txopt_put(opt_to_free);

	return err < 0 ? err : len;

	do_confirm:
	dst_confirm(dst);
	if (!(msg->msg_flags & MSG_PROBE) \|\| len)
	goto back_from_confirm;
	err = 0;
	goto done;
	}

	static int l2tp_ip6_recvmsg(struct sock sk, struct msghdr msg, size_t len,
	int noblock, int flags, int *addr_len)
	{
	struct ipv6_pinfo *np = inet6_sk(sk);
	DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
	size_t copied = 0;
	int err = -EOPNOTSUPP;
	struct sk_buff *skb;

	if (flags & MSG_OOB)
	goto out;

	if (addr_len)
	addr_len = sizeof(lsa);

	if (flags & MSG_ERRQUEUE)
	return ipv6_recv_error(sk, msg, len, addr_len);

	skb = skb_recv_datagram(sk, flags, noblock, &err);
	if (!skb)
	goto out;

	copied = skb->len;
	if (len < copied) {
	msg->msg_flags \|= MSG_TRUNC;
	copied = len;
	}

	err = skb_copy_datagram_msg(skb, 0, msg, copied);
	if (err)
	goto done;

	sock_recv_timestamp(msg, sk, skb);

	/* Copy the address. */
	if (lsa) {
	lsa->l2tp_family = AF_INET6;
	lsa->l2tp_unused = 0;
	lsa->l2tp_addr = ipv6_hdr(skb)->saddr;
	lsa->l2tp_flowinfo = 0;
	lsa->l2tp_scope_id = 0;
	lsa->l2tp_conn_id = 0;
	if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
	lsa->l2tp_scope_id = inet6_iif(skb);
	}

	if (np->rxopt.all)
	ip6_datagram_recv_ctl(sk, msg, skb);

	if (flags & MSG_TRUNC)
	copied = skb->len;
	done:
	skb_free_datagram(sk, skb);
	out:
	return err ? err : copied;
	}

	static struct proto l2tp_ip6_prot = {
	.name = "L2TP/IPv6",
	.owner = THIS_MODULE,
	.init = l2tp_ip6_open,
	.close = l2tp_ip6_close,
	.bind = l2tp_ip6_bind,
	.connect = l2tp_ip6_connect,
	.disconnect = l2tp_ip6_disconnect,
	.ioctl = l2tp_ioctl,
	.destroy = l2tp_ip6_destroy_sock,
	.setsockopt = ipv6_setsockopt,
	.getsockopt = ipv6_getsockopt,
	.sendmsg = l2tp_ip6_sendmsg,
	.recvmsg = l2tp_ip6_recvmsg,
	.backlog_rcv = l2tp_ip6_backlog_recv,
	.hash = inet6_hash,
	.unhash = inet_unhash,
	.obj_size = sizeof(struct l2tp_ip6_sock),
	#ifdef CONFIG_COMPAT
	.compat_setsockopt = compat_ipv6_setsockopt,
	.compat_getsockopt = compat_ipv6_getsockopt,
	#endif
	};

	static const struct proto_ops l2tp_ip6_ops = {
	.family = PF_INET6,
	.owner = THIS_MODULE,
	.release = inet6_release,
	.bind = inet6_bind,
	.connect = inet_dgram_connect,
	.socketpair = sock_no_socketpair,
	.accept = sock_no_accept,
	.getname = l2tp_ip6_getname,
	.poll = datagram_poll,
	.ioctl = inet6_ioctl,
	.listen = sock_no_listen,
	.shutdown = inet_shutdown,
	.setsockopt = sock_common_setsockopt,
	.getsockopt = sock_common_getsockopt,
	.sendmsg = inet_sendmsg,
	.recvmsg = sock_common_recvmsg,
	.mmap = sock_no_mmap,
	.sendpage = sock_no_sendpage,
	#ifdef CONFIG_COMPAT
	.compat_setsockopt = compat_sock_common_setsockopt,
	.compat_getsockopt = compat_sock_common_getsockopt,
	#endif
	};

	static struct inet_protosw l2tp_ip6_protosw = {
	.type = SOCK_DGRAM,
	.protocol = IPPROTO_L2TP,
	.prot = &l2tp_ip6_prot,
	.ops = &l2tp_ip6_ops,
	};

	static struct inet6_protocol l2tp_ip6_protocol __read_mostly = {
	.handler = l2tp_ip6_recv,
	};

	static int __init l2tp_ip6_init(void)
	{
	int err;

	pr_info("L2TP IP encapsulation support for IPv6 (L2TPv3)\n");

	err = proto_register(&l2tp_ip6_prot, 1);
	if (err != 0)
	goto out;

	err = inet6_add_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
	if (err)
	goto out1;

	inet6_register_protosw(&l2tp_ip6_protosw);
	return 0;

	out1:
	proto_unregister(&l2tp_ip6_prot);
	out:
	return err;
	}

	static void __exit l2tp_ip6_exit(void)
	{
	inet6_unregister_protosw(&l2tp_ip6_protosw);
	inet6_del_protocol(&l2tp_ip6_protocol, IPPROTO_L2TP);
	proto_unregister(&l2tp_ip6_prot);
	}

	module_init(l2tp_ip6_init);
	module_exit(l2tp_ip6_exit);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Chris Elston <celston@katalix.com>");
	MODULE_DESCRIPTION("L2TP IP encapsulation for IPv6");
	MODULE_VERSION("1.0");

	/* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
	* enums
	*/
	MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 2, IPPROTO_L2TP);
	MODULE_ALIAS_NET_PF_PROTO(PF_INET6, IPPROTO_L2TP);