Initial import

10 files changed, 7385 insertions, 0 deletions

diff --git a/net/l2tp/Kconfig b/net/l2tp/Kconfig
new file mode 100644
index 000000000..378c73b26
--- /dev/null
+++ b/net/l2tp/Kconfig
@@ -0,0 +1,109 @@
+#
+# Layer Two Tunneling Protocol (L2TP)
+#
+
+menuconfig L2TP
+	tristate "Layer Two Tunneling Protocol (L2TP)"
+	depends on (IPV6 || IPV6=n)
+	depends on INET
+	select NET_UDP_TUNNEL
+	---help---
+	  Layer Two Tunneling Protocol
+
+	  From RFC 2661 <http://www.ietf.org/rfc/rfc2661.txt>.
+
+	  L2TP facilitates the tunneling of packets across an
+	  intervening network in a way that is as transparent as
+	  possible to both end-users and applications.
+
+	  L2TP is often used to tunnel PPP traffic over IP
+	  tunnels. One IP tunnel may carry thousands of individual PPP
+	  connections. L2TP is also used as a VPN protocol, popular
+	  with home workers to connect to their offices.
+
+	  L2TPv3 allows other protocols as well as PPP to be carried
+	  over L2TP tunnels. L2TPv3 is defined in RFC 3931
+	  <http://www.ietf.org/rfc/rfc3931.txt>.
+
+	  The kernel component handles only L2TP data packets: a
+	  userland daemon handles L2TP the control protocol (tunnel
+	  and session setup). One such daemon is OpenL2TP
+	  (http://openl2tp.org/).
+
+	  If you don't need L2TP, say N. To compile all L2TP code as
+	  modules, choose M here.
+
+config L2TP_DEBUGFS
+	tristate "L2TP debugfs support"
+	depends on L2TP && DEBUG_FS
+	help
+	  Support for l2tp directory in debugfs filesystem. This may be
+	  used to dump internal state of the l2tp drivers for problem
+	  analysis.
+
+	  If unsure, say 'Y'.
+
+	  To compile this driver as a module, choose M here. The module
+	  will be called l2tp_debugfs.
+
+config L2TP_V3
+	bool "L2TPv3 support"
+	depends on L2TP
+	help
+	  Layer Two Tunneling Protocol Version 3
+
+	  From RFC 3931 <http://www.ietf.org/rfc/rfc3931.txt>.
+
+	  The Layer Two Tunneling Protocol (L2TP) provides a dynamic
+	  mechanism for tunneling Layer 2 (L2) "circuits" across a
+	  packet-oriented data network (e.g., over IP).  L2TP, as
+	  originally defined in RFC 2661, is a standard method for
+	  tunneling Point-to-Point Protocol (PPP) [RFC1661] sessions.
+	  L2TP has since been adopted for tunneling a number of other
+	  L2 protocols, including ATM, Frame Relay, HDLC and even raw
+	  ethernet frames.
+
+	  If you are connecting to L2TPv3 equipment, or you want to
+	  tunnel raw ethernet frames using L2TP, say Y here. If
+	  unsure, say N.
+
+config L2TP_IP
+	tristate "L2TP IP encapsulation for L2TPv3"
+	depends on L2TP_V3
+	help
+	  Support for L2TP-over-IP socket family.
+
+	  The L2TPv3 protocol defines two possible encapsulations for
+	  L2TP frames, namely UDP and plain IP (without UDP). This
+	  driver provides a new L2TPIP socket family with which
+	  userspace L2TPv3 daemons may create L2TP/IP tunnel sockets
+	  when UDP encapsulation is not required. When L2TP is carried
+	  in IP packets, it used IP protocol number 115, so this port
+	  must be enabled in firewalls.
+
+	  To compile this driver as a module, choose M here. The module
+	  will be called l2tp_ip.
+
+config L2TP_ETH
+	tristate "L2TP ethernet pseudowire support for L2TPv3"
+	depends on L2TP_V3
+	help
+	  Support for carrying raw ethernet frames over L2TPv3.
+
+	  From RFC 4719 <http://www.ietf.org/rfc/rfc4719.txt>.
+
+	  The Layer 2 Tunneling Protocol, Version 3 (L2TPv3) can be
+	  used as a control protocol and for data encapsulation to set
+	  up Pseudowires for transporting layer 2 Packet Data Units
+	  across an IP network [RFC3931].
+
+	  This driver provides an ethernet virtual interface for each
+	  L2TP ethernet pseudowire instance. Standard Linux tools may
+	  be used to assign an IP address to the local virtual
+	  interface, or add the interface to a bridge.
+
+	  If you are using L2TPv3, you will almost certainly want to
+	  enable this option.
+
+	  To compile this driver as a module, choose M here. The module
+	  will be called l2tp_eth.
diff --git a/net/l2tp/Makefile b/net/l2tp/Makefile
new file mode 100644
index 000000000..2870f41ea
--- /dev/null
+++ b/net/l2tp/Makefile
@@ -0,0 +1,15 @@
+#
+# Makefile for the L2TP.
+#
+
+obj-$(CONFIG_L2TP) += l2tp_core.o
+
+# Build l2tp as modules if L2TP is M
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_PPPOL2TP)) += l2tp_ppp.o
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_IP)) += l2tp_ip.o
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_V3)) += l2tp_netlink.o
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_ETH)) += l2tp_eth.o
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_DEBUGFS)) += l2tp_debugfs.o
+ifneq ($(CONFIG_IPV6),)
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_L2TP_IP)) += l2tp_ip6.o
+endif
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
new file mode 100644
index 000000000..a29a50449
--- /dev/null
+++ b/net/l2tp/l2tp_core.c
@@ -0,0 +1,1901 @@
+/*
+ * L2TP core.
+ *
+ * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
+ *
+ * This file contains some code of the original L2TPv2 pppol2tp
+ * driver, which has the following copyright:
+ *
+ * Authors:	Martijn van Oosterhout <kleptog@svana.org>
+ *		James Chapman (jchapman@katalix.com)
+ * Contributors:
+ *		Michal Ostrowski <mostrows@speakeasy.net>
+ *		Arnaldo Carvalho de Melo <acme@xconectiva.com.br>
+ *		David S. Miller (davem@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/list.h>
+#include <linux/rculist.h>
+#include <linux/uaccess.h>
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/kthread.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/jiffies.h>
+
+#include <linux/netdevice.h>
+#include <linux/net.h>
+#include <linux/inetdevice.h>
+#include <linux/skbuff.h>
+#include <linux/init.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <linux/l2tp.h>
+#include <linux/hash.h>
+#include <linux/sort.h>
+#include <linux/file.h>
+#include <linux/nsproxy.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <net/dst.h>
+#include <net/ip.h>
+#include <net/udp.h>
+#include <net/udp_tunnel.h>
+#include <net/inet_common.h>
+#include <net/xfrm.h>
+#include <net/protocol.h>
+#include <net/inet6_connection_sock.h>
+#include <net/inet_ecn.h>
+#include <net/ip6_route.h>
+#include <net/ip6_checksum.h>
+
+#include <asm/byteorder.h>
+#include <linux/atomic.h>
+
+#include "l2tp_core.h"
+
+#define L2TP_DRV_VERSION	"V2.0"
+
+/* L2TP header constants */
+#define L2TP_HDRFLAG_T	   0x8000
+#define L2TP_HDRFLAG_L	   0x4000
+#define L2TP_HDRFLAG_S	   0x0800
+#define L2TP_HDRFLAG_O	   0x0200
+#define L2TP_HDRFLAG_P	   0x0100
+
+#define L2TP_HDR_VER_MASK  0x000F
+#define L2TP_HDR_VER_2	   0x0002
+#define L2TP_HDR_VER_3	   0x0003
+
+/* L2TPv3 default L2-specific sublayer */
+#define L2TP_SLFLAG_S	   0x40000000
+#define L2TP_SL_SEQ_MASK   0x00ffffff
+
+#define L2TP_HDR_SIZE_SEQ		10
+#define L2TP_HDR_SIZE_NOSEQ		6
+
+/* Default trace flags */
+#define L2TP_DEFAULT_DEBUG_FLAGS	0
+
+/* Private data stored for received packets in the skb.
+ */
+struct l2tp_skb_cb {
+	u32			ns;
+	u16			has_seq;
+	u16			length;
+	unsigned long		expires;
+};
+
+#define L2TP_SKB_CB(skb)	((struct l2tp_skb_cb *) &skb->cb[sizeof(struct inet_skb_parm)])
+
+static atomic_t l2tp_tunnel_count;
+static atomic_t l2tp_session_count;
+static struct workqueue_struct *l2tp_wq;
+
+/* per-net private data for this module */
+static unsigned int l2tp_net_id;
+struct l2tp_net {
+	struct list_head l2tp_tunnel_list;
+	spinlock_t l2tp_tunnel_list_lock;
+	struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
+	spinlock_t l2tp_session_hlist_lock;
+};
+
+static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
+
+static inline struct l2tp_tunnel *l2tp_tunnel(struct sock *sk)
+{
+	return sk->sk_user_data;
+}
+
+static inline struct l2tp_net *l2tp_pernet(struct net *net)
+{
+	BUG_ON(!net);
+
+	return net_generic(net, l2tp_net_id);
+}
+
+/* Tunnel reference counts. Incremented per session that is added to
+ * the tunnel.
+ */
+static inline void l2tp_tunnel_inc_refcount_1(struct l2tp_tunnel *tunnel)
+{
+	atomic_inc(&tunnel->ref_count);
+}
+
+static inline void l2tp_tunnel_dec_refcount_1(struct l2tp_tunnel *tunnel)
+{
+	if (atomic_dec_and_test(&tunnel->ref_count))
+		l2tp_tunnel_free(tunnel);
+}
+#ifdef L2TP_REFCNT_DEBUG
+#define l2tp_tunnel_inc_refcount(_t)					\
+do {									\
+	pr_debug("l2tp_tunnel_inc_refcount: %s:%d %s: cnt=%d\n",	\
+		 __func__, __LINE__, (_t)->name,			\
+		 atomic_read(&_t->ref_count));				\
+	l2tp_tunnel_inc_refcount_1(_t);					\
+} while (0)
+#define l2tp_tunnel_dec_refcount(_t)					\
+do {									\
+	pr_debug("l2tp_tunnel_dec_refcount: %s:%d %s: cnt=%d\n",	\
+		 __func__, __LINE__, (_t)->name,			\
+		 atomic_read(&_t->ref_count));				\
+	l2tp_tunnel_dec_refcount_1(_t);					\
+} while (0)
+#else
+#define l2tp_tunnel_inc_refcount(t) l2tp_tunnel_inc_refcount_1(t)
+#define l2tp_tunnel_dec_refcount(t) l2tp_tunnel_dec_refcount_1(t)
+#endif
+
+/* Session hash global list for L2TPv3.
+ * The session_id SHOULD be random according to RFC3931, but several
+ * L2TP implementations use incrementing session_ids.  So we do a real
+ * hash on the session_id, rather than a simple bitmask.
+ */
+static inline struct hlist_head *
+l2tp_session_id_hash_2(struct l2tp_net *pn, u32 session_id)
+{
+	return &pn->l2tp_session_hlist[hash_32(session_id, L2TP_HASH_BITS_2)];
+
+}
+
+/* Lookup the tunnel socket, possibly involving the fs code if the socket is
+ * owned by userspace.  A struct sock returned from this function must be
+ * released using l2tp_tunnel_sock_put once you're done with it.
+ */
+static struct sock *l2tp_tunnel_sock_lookup(struct l2tp_tunnel *tunnel)
+{
+	int err = 0;
+	struct socket *sock = NULL;
+	struct sock *sk = NULL;
+
+	if (!tunnel)
+		goto out;
+
+	if (tunnel->fd >= 0) {
+		/* Socket is owned by userspace, who might be in the process
+		 * of closing it.  Look the socket up using the fd to ensure
+		 * consistency.
+		 */
+		sock = sockfd_lookup(tunnel->fd, &err);
+		if (sock)
+			sk = sock->sk;
+	} else {
+		/* Socket is owned by kernelspace */
+		sk = tunnel->sock;
+		sock_hold(sk);
+	}
+
+out:
+	return sk;
+}
+
+/* Drop a reference to a tunnel socket obtained via. l2tp_tunnel_sock_put */
+static void l2tp_tunnel_sock_put(struct sock *sk)
+{
+	struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk);
+	if (tunnel) {
+		if (tunnel->fd >= 0) {
+			/* Socket is owned by userspace */
+			sockfd_put(sk->sk_socket);
+		}
+		sock_put(sk);
+	}
+	sock_put(sk);
+}
+
+/* Lookup a session by id in the global session list
+ */
+static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+	struct hlist_head *session_list =
+		l2tp_session_id_hash_2(pn, session_id);
+	struct l2tp_session *session;
+
+	rcu_read_lock_bh();
+	hlist_for_each_entry_rcu(session, session_list, global_hlist) {
+		if (session->session_id == session_id) {
+			rcu_read_unlock_bh();
+			return session;
+		}
+	}
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+
+/* Session hash list.
+ * The session_id SHOULD be random according to RFC2661, but several
+ * L2TP implementations (Cisco and Microsoft) use incrementing
+ * session_ids.  So we do a real hash on the session_id, rather than a
+ * simple bitmask.
+ */
+static inline struct hlist_head *
+l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id)
+{
+	return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)];
+}
+
+/* Lookup a session by id
+ */
+struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id)
+{
+	struct hlist_head *session_list;
+	struct l2tp_session *session;
+
+	/* In L2TPv3, session_ids are unique over all tunnels and we
+	 * sometimes need to look them up before we know the
+	 * tunnel.
+	 */
+	if (tunnel == NULL)
+		return l2tp_session_find_2(net, session_id);
+
+	session_list = l2tp_session_id_hash(tunnel, session_id);
+	read_lock_bh(&tunnel->hlist_lock);
+	hlist_for_each_entry(session, session_list, hlist) {
+		if (session->session_id == session_id) {
+			read_unlock_bh(&tunnel->hlist_lock);
+			return session;
+		}
+	}
+	read_unlock_bh(&tunnel->hlist_lock);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_find);
+
+struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth)
+{
+	int hash;
+	struct l2tp_session *session;
+	int count = 0;
+
+	read_lock_bh(&tunnel->hlist_lock);
+	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
+		hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
+			if (++count > nth) {
+				read_unlock_bh(&tunnel->hlist_lock);
+				return session;
+			}
+		}
+	}
+
+	read_unlock_bh(&tunnel->hlist_lock);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
+
+/* Lookup a session by interface name.
+ * This is very inefficient but is only used by management interfaces.
+ */
+struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+	int hash;
+	struct l2tp_session *session;
+
+	rcu_read_lock_bh();
+	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
+		hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
+			if (!strcmp(session->ifname, ifname)) {
+				rcu_read_unlock_bh();
+				return session;
+			}
+		}
+	}
+
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname);
+
+/* Lookup a tunnel by id
+ */
+struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id)
+{
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_net *pn = l2tp_pernet(net);
+
+	rcu_read_lock_bh();
+	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
+		if (tunnel->tunnel_id == tunnel_id) {
+			rcu_read_unlock_bh();
+			return tunnel;
+		}
+	}
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
+
+struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+	struct l2tp_tunnel *tunnel;
+	int count = 0;
+
+	rcu_read_lock_bh();
+	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
+		if (++count > nth) {
+			rcu_read_unlock_bh();
+			return tunnel;
+		}
+	}
+
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth);
+
+/*****************************************************************************
+ * Receive data handling
+ *****************************************************************************/
+
+/* Queue a skb in order. We come here only if the skb has an L2TP sequence
+ * number.
+ */
+static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *skb)
+{
+	struct sk_buff *skbp;
+	struct sk_buff *tmp;
+	u32 ns = L2TP_SKB_CB(skb)->ns;
+
+	spin_lock_bh(&session->reorder_q.lock);
+	skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
+		if (L2TP_SKB_CB(skbp)->ns > ns) {
+			__skb_queue_before(&session->reorder_q, skbp, skb);
+			l2tp_dbg(session, L2TP_MSG_SEQ,
+				 "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
+				 session->name, ns, L2TP_SKB_CB(skbp)->ns,
+				 skb_queue_len(&session->reorder_q));
+			atomic_long_inc(&session->stats.rx_oos_packets);
+			goto out;
+		}
+	}
+
+	__skb_queue_tail(&session->reorder_q, skb);
+
+out:
+	spin_unlock_bh(&session->reorder_q.lock);
+}
+
+/* Dequeue a single skb.
+ */
+static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *skb)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	int length = L2TP_SKB_CB(skb)->length;
+
+	/* We're about to requeue the skb, so return resources
+	 * to its current owner (a socket receive buffer).
+	 */
+	skb_orphan(skb);
+
+	atomic_long_inc(&tunnel->stats.rx_packets);
+	atomic_long_add(length, &tunnel->stats.rx_bytes);
+	atomic_long_inc(&session->stats.rx_packets);
+	atomic_long_add(length, &session->stats.rx_bytes);
+
+	if (L2TP_SKB_CB(skb)->has_seq) {
+		/* Bump our Nr */
+		session->nr++;
+		session->nr &= session->nr_max;
+
+		l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated nr to %hu\n",
+			 session->name, session->nr);
+	}
+
+	/* call private receive handler */
+	if (session->recv_skb != NULL)
+		(*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
+	else
+		kfree_skb(skb);
+
+	if (session->deref)
+		(*session->deref)(session);
+}
+
+/* Dequeue skbs from the session's reorder_q, subject to packet order.
+ * Skbs that have been in the queue for too long are simply discarded.
+ */
+static void l2tp_recv_dequeue(struct l2tp_session *session)
+{
+	struct sk_buff *skb;
+	struct sk_buff *tmp;
+
+	/* If the pkt at the head of the queue has the nr that we
+	 * expect to send up next, dequeue it and any other
+	 * in-sequence packets behind it.
+	 */
+start:
+	spin_lock_bh(&session->reorder_q.lock);
+	skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
+		if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
+			atomic_long_inc(&session->stats.rx_seq_discards);
+			atomic_long_inc(&session->stats.rx_errors);
+			l2tp_dbg(session, L2TP_MSG_SEQ,
+				 "%s: oos pkt %u len %d discarded (too old), waiting for %u, reorder_q_len=%d\n",
+				 session->name, L2TP_SKB_CB(skb)->ns,
+				 L2TP_SKB_CB(skb)->length, session->nr,
+				 skb_queue_len(&session->reorder_q));
+			session->reorder_skip = 1;
+			__skb_unlink(skb, &session->reorder_q);
+			kfree_skb(skb);
+			if (session->deref)
+				(*session->deref)(session);
+			continue;
+		}
+
+		if (L2TP_SKB_CB(skb)->has_seq) {
+			if (session->reorder_skip) {
+				l2tp_dbg(session, L2TP_MSG_SEQ,
+					 "%s: advancing nr to next pkt: %u -> %u",
+					 session->name, session->nr,
+					 L2TP_SKB_CB(skb)->ns);
+				session->reorder_skip = 0;
+				session->nr = L2TP_SKB_CB(skb)->ns;
+			}
+			if (L2TP_SKB_CB(skb)->ns != session->nr) {
+				l2tp_dbg(session, L2TP_MSG_SEQ,
+					 "%s: holding oos pkt %u len %d, waiting for %u, reorder_q_len=%d\n",
+					 session->name, L2TP_SKB_CB(skb)->ns,
+					 L2TP_SKB_CB(skb)->length, session->nr,
+					 skb_queue_len(&session->reorder_q));
+				goto out;
+			}
+		}
+		__skb_unlink(skb, &session->reorder_q);
+
+		/* Process the skb. We release the queue lock while we
+		 * do so to let other contexts process the queue.
+		 */
+		spin_unlock_bh(&session->reorder_q.lock);
+		l2tp_recv_dequeue_skb(session, skb);
+		goto start;
+	}
+
+out:
+	spin_unlock_bh(&session->reorder_q.lock);
+}
+
+static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
+{
+	u32 nws;
+
+	if (nr >= session->nr)
+		nws = nr - session->nr;
+	else
+		nws = (session->nr_max + 1) - (session->nr - nr);
+
+	return nws < session->nr_window_size;
+}
+
+/* If packet has sequence numbers, queue it if acceptable. Returns 0 if
+ * acceptable, else non-zero.
+ */
+static int l2tp_recv_data_seq(struct l2tp_session *session, struct sk_buff *skb)
+{
+	if (!l2tp_seq_check_rx_window(session, L2TP_SKB_CB(skb)->ns)) {
+		/* Packet sequence number is outside allowed window.
+		 * Discard it.
+		 */
+		l2tp_dbg(session, L2TP_MSG_SEQ,
+			 "%s: pkt %u len %d discarded, outside window, nr=%u\n",
+			 session->name, L2TP_SKB_CB(skb)->ns,
+			 L2TP_SKB_CB(skb)->length, session->nr);
+		goto discard;
+	}
+
+	if (session->reorder_timeout != 0) {
+		/* Packet reordering enabled. Add skb to session's
+		 * reorder queue, in order of ns.
+		 */
+		l2tp_recv_queue_skb(session, skb);
+		goto out;
+	}
+
+	/* Packet reordering disabled. Discard out-of-sequence packets, while
+	 * tracking the number if in-sequence packets after the first OOS packet
+	 * is seen. After nr_oos_count_max in-sequence packets, reset the
+	 * sequence number to re-enable packet reception.
+	 */
+	if (L2TP_SKB_CB(skb)->ns == session->nr) {
+		skb_queue_tail(&session->reorder_q, skb);
+	} else {
+		u32 nr_oos = L2TP_SKB_CB(skb)->ns;
+		u32 nr_next = (session->nr_oos + 1) & session->nr_max;
+
+		if (nr_oos == nr_next)
+			session->nr_oos_count++;
+		else
+			session->nr_oos_count = 0;
+
+		session->nr_oos = nr_oos;
+		if (session->nr_oos_count > session->nr_oos_count_max) {
+			session->reorder_skip = 1;
+			l2tp_dbg(session, L2TP_MSG_SEQ,
+				 "%s: %d oos packets received. Resetting sequence numbers\n",
+				 session->name, session->nr_oos_count);
+		}
+		if (!session->reorder_skip) {
+			atomic_long_inc(&session->stats.rx_seq_discards);
+			l2tp_dbg(session, L2TP_MSG_SEQ,
+				 "%s: oos pkt %u len %d discarded, waiting for %u, reorder_q_len=%d\n",
+				 session->name, L2TP_SKB_CB(skb)->ns,
+				 L2TP_SKB_CB(skb)->length, session->nr,
+				 skb_queue_len(&session->reorder_q));
+			goto discard;
+		}
+		skb_queue_tail(&session->reorder_q, skb);
+	}
+
+out:
+	return 0;
+
+discard:
+	return 1;
+}
+
+/* Do receive processing of L2TP data frames. We handle both L2TPv2
+ * and L2TPv3 data frames here.
+ *
+ * L2TPv2 Data Message Header
+ *
+ *  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
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |T|L|x|x|S|x|O|P|x|x|x|x|  Ver  |          Length (opt)         |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |           Tunnel ID           |           Session ID          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |             Ns (opt)          |             Nr (opt)          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |      Offset Size (opt)        |    Offset pad... (opt)
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * Data frames are marked by T=0. All other fields are the same as
+ * those in L2TP control frames.
+ *
+ * L2TPv3 Data Message Header
+ *
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      L2TP Session Header                      |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      L2-Specific Sublayer                     |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                        Tunnel Payload                      ...
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * 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 L2-Specific Sublayer Format
+ *
+ *  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
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |x|S|x|x|x|x|x|x|              Sequence Number                  |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * Cookie value, sublayer format and offset (pad) are negotiated with
+ * the peer when the session is set up. Unlike L2TPv2, we do not need
+ * to parse the packet header to determine if optional fields are
+ * present.
+ *
+ * Caller must already have parsed the frame and determined that it is
+ * a data (not control) frame before coming here. Fields up to the
+ * session-id have already been parsed and ptr points to the data
+ * after the session-id.
+ */
+void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
+		      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
+		      int length, int (*payload_hook)(struct sk_buff *skb))
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	int offset;
+	u32 ns, nr;
+
+	/* The ref count is increased since we now hold a pointer to
+	 * the session. Take care to decrement the refcnt when exiting
+	 * this function from now on...
+	 */
+	l2tp_session_inc_refcount(session);
+	if (session->ref)
+		(*session->ref)(session);
+
+	/* Parse and check optional cookie */
+	if (session->peer_cookie_len > 0) {
+		if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
+			l2tp_info(tunnel, L2TP_MSG_DATA,
+				  "%s: cookie mismatch (%u/%u). Discarding.\n",
+				  tunnel->name, tunnel->tunnel_id,
+				  session->session_id);
+			atomic_long_inc(&session->stats.rx_cookie_discards);
+			goto discard;
+		}
+		ptr += session->peer_cookie_len;
+	}
+
+	/* Handle the optional sequence numbers. Sequence numbers are
+	 * in different places for L2TPv2 and L2TPv3.
+	 *
+	 * If we are the LAC, enable/disable sequence numbers under
+	 * the control of the LNS.  If no sequence numbers present but
+	 * we were expecting them, discard frame.
+	 */
+	ns = nr = 0;
+	L2TP_SKB_CB(skb)->has_seq = 0;
+	if (tunnel->version == L2TP_HDR_VER_2) {
+		if (hdrflags & L2TP_HDRFLAG_S) {
+			ns = ntohs(*(__be16 *) ptr);
+			ptr += 2;
+			nr = ntohs(*(__be16 *) ptr);
+			ptr += 2;
+
+			/* Store L2TP info in the skb */
+			L2TP_SKB_CB(skb)->ns = ns;
+			L2TP_SKB_CB(skb)->has_seq = 1;
+
+			l2tp_dbg(session, L2TP_MSG_SEQ,
+				 "%s: recv data ns=%u, nr=%u, session nr=%u\n",
+				 session->name, ns, nr, session->nr);
+		}
+	} else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
+		u32 l2h = ntohl(*(__be32 *) ptr);
+
+		if (l2h & 0x40000000) {
+			ns = l2h & 0x00ffffff;
+
+			/* Store L2TP info in the skb */
+			L2TP_SKB_CB(skb)->ns = ns;
+			L2TP_SKB_CB(skb)->has_seq = 1;
+
+			l2tp_dbg(session, L2TP_MSG_SEQ,
+				 "%s: recv data ns=%u, session nr=%u\n",
+				 session->name, ns, session->nr);
+		}
+	}
+
+	/* Advance past L2-specific header, if present */
+	ptr += session->l2specific_len;
+
+	if (L2TP_SKB_CB(skb)->has_seq) {
+		/* Received a packet with sequence numbers. If we're the LNS,
+		 * check if we sre sending sequence numbers and if not,
+		 * configure it so.
+		 */
+		if ((!session->lns_mode) && (!session->send_seq)) {
+			l2tp_info(session, L2TP_MSG_SEQ,
+				  "%s: requested to enable seq numbers by LNS\n",
+				  session->name);
+			session->send_seq = -1;
+			l2tp_session_set_header_len(session, tunnel->version);
+		}
+	} else {
+		/* No sequence numbers.
+		 * If user has configured mandatory sequence numbers, discard.
+		 */
+		if (session->recv_seq) {
+			l2tp_warn(session, L2TP_MSG_SEQ,
+				  "%s: recv data has no seq numbers when required. Discarding.\n",
+				  session->name);
+			atomic_long_inc(&session->stats.rx_seq_discards);
+			goto discard;
+		}
+
+		/* If we're the LAC and we're sending sequence numbers, the
+		 * LNS has requested that we no longer send sequence numbers.
+		 * If we're the LNS and we're sending sequence numbers, the
+		 * LAC is broken. Discard the frame.
+		 */
+		if ((!session->lns_mode) && (session->send_seq)) {
+			l2tp_info(session, L2TP_MSG_SEQ,
+				  "%s: requested to disable seq numbers by LNS\n",
+				  session->name);
+			session->send_seq = 0;
+			l2tp_session_set_header_len(session, tunnel->version);
+		} else if (session->send_seq) {
+			l2tp_warn(session, L2TP_MSG_SEQ,
+				  "%s: recv data has no seq numbers when required. Discarding.\n",
+				  session->name);
+			atomic_long_inc(&session->stats.rx_seq_discards);
+			goto discard;
+		}
+	}
+
+	/* Session data offset is handled differently for L2TPv2 and
+	 * L2TPv3. For L2TPv2, there is an optional 16-bit value in
+	 * the header. For L2TPv3, the offset is negotiated using AVPs
+	 * in the session setup control protocol.
+	 */
+	if (tunnel->version == L2TP_HDR_VER_2) {
+		/* If offset bit set, skip it. */
+		if (hdrflags & L2TP_HDRFLAG_O) {
+			offset = ntohs(*(__be16 *)ptr);
+			ptr += 2 + offset;
+		}
+	} else
+		ptr += session->offset;
+
+	offset = ptr - optr;
+	if (!pskb_may_pull(skb, offset))
+		goto discard;
+
+	__skb_pull(skb, offset);
+
+	/* If caller wants to process the payload before we queue the
+	 * packet, do so now.
+	 */
+	if (payload_hook)
+		if ((*payload_hook)(skb))
+			goto discard;
+
+	/* Prepare skb for adding to the session's reorder_q.  Hold
+	 * packets for max reorder_timeout or 1 second if not
+	 * reordering.
+	 */
+	L2TP_SKB_CB(skb)->length = length;
+	L2TP_SKB_CB(skb)->expires = jiffies +
+		(session->reorder_timeout ? session->reorder_timeout : HZ);
+
+	/* Add packet to the session's receive queue. Reordering is done here, if
+	 * enabled. Saved L2TP protocol info is stored in skb->sb[].
+	 */
+	if (L2TP_SKB_CB(skb)->has_seq) {
+		if (l2tp_recv_data_seq(session, skb))
+			goto discard;
+	} else {
+		/* No sequence numbers. Add the skb to the tail of the
+		 * reorder queue. This ensures that it will be
+		 * delivered after all previous sequenced skbs.
+		 */
+		skb_queue_tail(&session->reorder_q, skb);
+	}
+
+	/* Try to dequeue as many skbs from reorder_q as we can. */
+	l2tp_recv_dequeue(session);
+
+	l2tp_session_dec_refcount(session);
+
+	return;
+
+discard:
+	atomic_long_inc(&session->stats.rx_errors);
+	kfree_skb(skb);
+
+	if (session->deref)
+		(*session->deref)(session);
+
+	l2tp_session_dec_refcount(session);
+}
+EXPORT_SYMBOL(l2tp_recv_common);
+
+/* Drop skbs from the session's reorder_q
+ */
+int l2tp_session_queue_purge(struct l2tp_session *session)
+{
+	struct sk_buff *skb = NULL;
+	BUG_ON(!session);
+	BUG_ON(session->magic != L2TP_SESSION_MAGIC);
+	while ((skb = skb_dequeue(&session->reorder_q))) {
+		atomic_long_inc(&session->stats.rx_errors);
+		kfree_skb(skb);
+		if (session->deref)
+			(*session->deref)(session);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_queue_purge);
+
+/* Internal UDP receive frame. Do the real work of receiving an L2TP data frame
+ * here. The skb is not on a list when we get here.
+ * Returns 0 if the packet was a data packet and was successfully passed on.
+ * Returns 1 if the packet was not a good data packet and could not be
+ * forwarded.  All such packets are passed up to userspace to deal with.
+ */
+static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
+			      int (*payload_hook)(struct sk_buff *skb))
+{
+	struct l2tp_session *session = NULL;
+	unsigned char *ptr, *optr;
+	u16 hdrflags;
+	u32 tunnel_id, session_id;
+	u16 version;
+	int length;
+
+	/* UDP has verifed checksum */
+
+	/* UDP always verifies the packet length. */
+	__skb_pull(skb, sizeof(struct udphdr));
+
+	/* Short packet? */
+	if (!pskb_may_pull(skb, L2TP_HDR_SIZE_SEQ)) {
+		l2tp_info(tunnel, L2TP_MSG_DATA,
+			  "%s: recv short packet (len=%d)\n",
+			  tunnel->name, skb->len);
+		goto error;
+	}
+
+	/* Trace packet contents, if enabled */
+	if (tunnel->debug & L2TP_MSG_DATA) {
+		length = min(32u, skb->len);
+		if (!pskb_may_pull(skb, length))
+			goto error;
+
+		pr_debug("%s: recv\n", tunnel->name);
+		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
+	}
+
+	/* Point to L2TP header */
+	optr = ptr = skb->data;
+
+	/* Get L2TP header flags */
+	hdrflags = ntohs(*(__be16 *) ptr);
+
+	/* Check protocol version */
+	version = hdrflags & L2TP_HDR_VER_MASK;
+	if (version != tunnel->version) {
+		l2tp_info(tunnel, L2TP_MSG_DATA,
+			  "%s: recv protocol version mismatch: got %d expected %d\n",
+			  tunnel->name, version, tunnel->version);
+		goto error;
+	}
+
+	/* Get length of L2TP packet */
+	length = skb->len;
+
+	/* If type is control packet, it is handled by userspace. */
+	if (hdrflags & L2TP_HDRFLAG_T) {
+		l2tp_dbg(tunnel, L2TP_MSG_DATA,
+			 "%s: recv control packet, len=%d\n",
+			 tunnel->name, length);
+		goto error;
+	}
+
+	/* Skip flags */
+	ptr += 2;
+
+	if (tunnel->version == L2TP_HDR_VER_2) {
+		/* If length is present, skip it */
+		if (hdrflags & L2TP_HDRFLAG_L)
+			ptr += 2;
+
+		/* Extract tunnel and session ID */
+		tunnel_id = ntohs(*(__be16 *) ptr);
+		ptr += 2;
+		session_id = ntohs(*(__be16 *) ptr);
+		ptr += 2;
+	} else {
+		ptr += 2;	/* skip reserved bits */
+		tunnel_id = tunnel->tunnel_id;
+		session_id = ntohl(*(__be32 *) ptr);
+		ptr += 4;
+	}
+
+	/* Find the session context */
+	session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
+	if (!session || !session->recv_skb) {
+		/* Not found? Pass to userspace to deal with */
+		l2tp_info(tunnel, L2TP_MSG_DATA,
+			  "%s: no session found (%u/%u). Passing up.\n",
+			  tunnel->name, tunnel_id, session_id);
+		goto error;
+	}
+
+	l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
+
+	return 0;
+
+error:
+	/* Put UDP header back */
+	__skb_push(skb, sizeof(struct udphdr));
+
+	return 1;
+}
+
+/* UDP encapsulation receive handler. See net/ipv4/udp.c.
+ * Return codes:
+ * 0 : success.
+ * <0: error
+ * >0: skb should be passed up to userspace as UDP.
+ */
+int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
+{
+	struct l2tp_tunnel *tunnel;
+
+	tunnel = l2tp_sock_to_tunnel(sk);
+	if (tunnel == NULL)
+		goto pass_up;
+
+	l2tp_dbg(tunnel, L2TP_MSG_DATA, "%s: received %d bytes\n",
+		 tunnel->name, skb->len);
+
+	if (l2tp_udp_recv_core(tunnel, skb, tunnel->recv_payload_hook))
+		goto pass_up_put;
+
+	sock_put(sk);
+	return 0;
+
+pass_up_put:
+	sock_put(sk);
+pass_up:
+	return 1;
+}
+EXPORT_SYMBOL_GPL(l2tp_udp_encap_recv);
+
+/************************************************************************
+ * Transmit handling
+ ***********************************************************************/
+
+/* Build an L2TP header for the session into the buffer provided.
+ */
+static int l2tp_build_l2tpv2_header(struct l2tp_session *session, void *buf)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	__be16 *bufp = buf;
+	__be16 *optr = buf;
+	u16 flags = L2TP_HDR_VER_2;
+	u32 tunnel_id = tunnel->peer_tunnel_id;
+	u32 session_id = session->peer_session_id;
+
+	if (session->send_seq)
+		flags |= L2TP_HDRFLAG_S;
+
+	/* Setup L2TP header. */
+	*bufp++ = htons(flags);
+	*bufp++ = htons(tunnel_id);
+	*bufp++ = htons(session_id);
+	if (session->send_seq) {
+		*bufp++ = htons(session->ns);
+		*bufp++ = 0;
+		session->ns++;
+		session->ns &= 0xffff;
+		l2tp_dbg(session, L2TP_MSG_SEQ, "%s: updated ns to %u\n",
+			 session->name, session->ns);
+	}
+
+	return bufp - optr;
+}
+
+static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	char *bufp = buf;
+	char *optr = bufp;
+
+	/* Setup L2TP header. The header differs slightly for UDP and
+	 * IP encapsulations. For UDP, there is 4 bytes of flags.
+	 */
+	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
+		u16 flags = L2TP_HDR_VER_3;
+		*((__be16 *) bufp) = htons(flags);
+		bufp += 2;
+		*((__be16 *) bufp) = 0;
+		bufp += 2;
+	}
+
+	*((__be32 *) bufp) = htonl(session->peer_session_id);
+	bufp += 4;
+	if (session->cookie_len) {
+		memcpy(bufp, &session->cookie[0], session->cookie_len);
+		bufp += session->cookie_len;
+	}
+	if (session->l2specific_len) {
+		if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
+			u32 l2h = 0;
+			if (session->send_seq) {
+				l2h = 0x40000000 | session->ns;
+				session->ns++;
+				session->ns &= 0xffffff;
+				l2tp_dbg(session, L2TP_MSG_SEQ,
+					 "%s: updated ns to %u\n",
+					 session->name, session->ns);
+			}
+
+			*((__be32 *) bufp) = htonl(l2h);
+		}
+		bufp += session->l2specific_len;
+	}
+	if (session->offset)
+		bufp += session->offset;
+
+	return bufp - optr;
+}
+
+static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
+			  struct flowi *fl, size_t data_len)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	unsigned int len = skb->len;
+	int error;
+
+	/* Debug */
+	if (session->send_seq)
+		l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %Zd bytes, ns=%u\n",
+			 session->name, data_len, session->ns - 1);
+	else
+		l2tp_dbg(session, L2TP_MSG_DATA, "%s: send %Zd bytes\n",
+			 session->name, data_len);
+
+	if (session->debug & L2TP_MSG_DATA) {
+		int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
+		unsigned char *datap = skb->data + uhlen;
+
+		pr_debug("%s: xmit\n", session->name);
+		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET,
+				     datap, min_t(size_t, 32, len - uhlen));
+	}
+
+	/* Queue the packet to IP for output */
+	skb->ignore_df = 1;
+#if IS_ENABLED(CONFIG_IPV6)
+	if (tunnel->sock->sk_family == PF_INET6 && !tunnel->v4mapped)
+		error = inet6_csk_xmit(tunnel->sock, skb, NULL);
+	else
+#endif
+		error = ip_queue_xmit(tunnel->sock, skb, fl);
+
+	/* Update stats */
+	if (error >= 0) {
+		atomic_long_inc(&tunnel->stats.tx_packets);
+		atomic_long_add(len, &tunnel->stats.tx_bytes);
+		atomic_long_inc(&session->stats.tx_packets);
+		atomic_long_add(len, &session->stats.tx_bytes);
+	} else {
+		atomic_long_inc(&tunnel->stats.tx_errors);
+		atomic_long_inc(&session->stats.tx_errors);
+	}
+
+	return 0;
+}
+
+/* If caller requires the skb to have a ppp header, the header must be
+ * inserted in the skb data before calling this function.
+ */
+int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len)
+{
+	int data_len = skb->len;
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	struct sock *sk = tunnel->sock;
+	struct flowi *fl;
+	struct udphdr *uh;
+	struct inet_sock *inet;
+	int headroom;
+	int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
+	int udp_len;
+	int ret = NET_XMIT_SUCCESS;
+
+	/* Check that there's enough headroom in the skb to insert IP,
+	 * UDP and L2TP headers. If not enough, expand it to
+	 * make room. Adjust truesize.
+	 */
+	headroom = NET_SKB_PAD + sizeof(struct iphdr) +
+		uhlen + hdr_len;
+	if (skb_cow_head(skb, headroom)) {
+		kfree_skb(skb);
+		return NET_XMIT_DROP;
+	}
+
+	/* Setup L2TP header */
+	session->build_header(session, __skb_push(skb, hdr_len));
+
+	/* Reset skb netfilter state */
+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
+	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
+			      IPSKB_REROUTED);
+	nf_reset(skb);
+
+	bh_lock_sock(sk);
+	if (sock_owned_by_user(sk)) {
+		kfree_skb(skb);
+		ret = NET_XMIT_DROP;
+		goto out_unlock;
+	}
+
+	/* Get routing info from the tunnel socket */
+	skb_dst_drop(skb);
+	skb_dst_set(skb, dst_clone(__sk_dst_check(sk, 0)));
+
+	inet = inet_sk(sk);
+	fl = &inet->cork.fl;
+	switch (tunnel->encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		/* Setup UDP header */
+		__skb_push(skb, sizeof(*uh));
+		skb_reset_transport_header(skb);
+		uh = udp_hdr(skb);
+		uh->source = inet->inet_sport;
+		uh->dest = inet->inet_dport;
+		udp_len = uhlen + hdr_len + data_len;
+		uh->len = htons(udp_len);
+
+		/* Calculate UDP checksum if configured to do so */
+#if IS_ENABLED(CONFIG_IPV6)
+		if (sk->sk_family == PF_INET6 && !tunnel->v4mapped)
+			udp6_set_csum(udp_get_no_check6_tx(sk),
+				      skb, &inet6_sk(sk)->saddr,
+				      &sk->sk_v6_daddr, udp_len);
+		else
+#endif
+		udp_set_csum(sk->sk_no_check_tx, skb, inet->inet_saddr,
+			     inet->inet_daddr, udp_len);
+		break;
+
+	case L2TP_ENCAPTYPE_IP:
+		break;
+	}
+
+	l2tp_xmit_core(session, skb, fl, data_len);
+out_unlock:
+	bh_unlock_sock(sk);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
+
+/*****************************************************************************
+ * Tinnel and session create/destroy.
+ *****************************************************************************/
+
+/* Tunnel socket destruct hook.
+ * The tunnel context is deleted only when all session sockets have been
+ * closed.
+ */
+static void l2tp_tunnel_destruct(struct sock *sk)
+{
+	struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
+	struct l2tp_net *pn;
+
+	if (tunnel == NULL)
+		goto end;
+
+	l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing...\n", tunnel->name);
+
+
+	/* Disable udp encapsulation */
+	switch (tunnel->encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		/* No longer an encapsulation socket. See net/ipv4/udp.c */
+		(udp_sk(sk))->encap_type = 0;
+		(udp_sk(sk))->encap_rcv = NULL;
+		(udp_sk(sk))->encap_destroy = NULL;
+		break;
+	case L2TP_ENCAPTYPE_IP:
+		break;
+	}
+
+	/* Remove hooks into tunnel socket */
+	sk->sk_destruct = tunnel->old_sk_destruct;
+	sk->sk_user_data = NULL;
+	tunnel->sock = NULL;
+
+	/* Remove the tunnel struct from the tunnel list */
+	pn = l2tp_pernet(tunnel->l2tp_net);
+	spin_lock_bh(&pn->l2tp_tunnel_list_lock);
+	list_del_rcu(&tunnel->list);
+	spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
+	atomic_dec(&l2tp_tunnel_count);
+
+	l2tp_tunnel_closeall(tunnel);
+	l2tp_tunnel_dec_refcount(tunnel);
+
+	/* Call the original destructor */
+	if (sk->sk_destruct)
+		(*sk->sk_destruct)(sk);
+end:
+	return;
+}
+
+/* When the tunnel is closed, all the attached sessions need to go too.
+ */
+void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
+{
+	int hash;
+	struct hlist_node *walk;
+	struct hlist_node *tmp;
+	struct l2tp_session *session;
+
+	BUG_ON(tunnel == NULL);
+
+	l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing all sessions...\n",
+		  tunnel->name);
+
+	write_lock_bh(&tunnel->hlist_lock);
+	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
+again:
+		hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
+			session = hlist_entry(walk, struct l2tp_session, hlist);
+
+			l2tp_info(session, L2TP_MSG_CONTROL,
+				  "%s: closing session\n", session->name);
+
+			hlist_del_init(&session->hlist);
+
+			if (session->ref != NULL)
+				(*session->ref)(session);
+
+			write_unlock_bh(&tunnel->hlist_lock);
+
+			__l2tp_session_unhash(session);
+			l2tp_session_queue_purge(session);
+
+			if (session->session_close != NULL)
+				(*session->session_close)(session);
+
+			if (session->deref != NULL)
+				(*session->deref)(session);
+
+			l2tp_session_dec_refcount(session);
+
+			write_lock_bh(&tunnel->hlist_lock);
+
+			/* Now restart from the beginning of this hash
+			 * chain.  We always remove a session from the
+			 * list so we are guaranteed to make forward
+			 * progress.
+			 */
+			goto again;
+		}
+	}
+	write_unlock_bh(&tunnel->hlist_lock);
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_closeall);
+
+/* Tunnel socket destroy hook for UDP encapsulation */
+static void l2tp_udp_encap_destroy(struct sock *sk)
+{
+	struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk);
+	if (tunnel) {
+		l2tp_tunnel_closeall(tunnel);
+		sock_put(sk);
+	}
+}
+
+/* Really kill the tunnel.
+ * Come here only when all sessions have been cleared from the tunnel.
+ */
+static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
+{
+	BUG_ON(atomic_read(&tunnel->ref_count) != 0);
+	BUG_ON(tunnel->sock != NULL);
+	l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: free...\n", tunnel->name);
+	kfree_rcu(tunnel, rcu);
+}
+
+/* Workqueue tunnel deletion function */
+static void l2tp_tunnel_del_work(struct work_struct *work)
+{
+	struct l2tp_tunnel *tunnel = NULL;
+	struct socket *sock = NULL;
+	struct sock *sk = NULL;
+
+	tunnel = container_of(work, struct l2tp_tunnel, del_work);
+	sk = l2tp_tunnel_sock_lookup(tunnel);
+	if (!sk)
+		return;
+
+	sock = sk->sk_socket;
+
+	/* If the tunnel socket was created by userspace, then go through the
+	 * inet layer to shut the socket down, and let userspace close it.
+	 * Otherwise, if we created the socket directly within the kernel, use
+	 * the sk API to release it here.
+	 * In either case the tunnel resources are freed in the socket
+	 * destructor when the tunnel socket goes away.
+	 */
+	if (tunnel->fd >= 0) {
+		if (sock)
+			inet_shutdown(sock, 2);
+	} else {
+		if (sock)
+			kernel_sock_shutdown(sock, SHUT_RDWR);
+		sk_release_kernel(sk);
+	}
+
+	l2tp_tunnel_sock_put(sk);
+}
+
+/* Create a socket for the tunnel, if one isn't set up by
+ * userspace. This is used for static tunnels where there is no
+ * managing L2TP daemon.
+ *
+ * Since we don't want these sockets to keep a namespace alive by
+ * themselves, we drop the socket's namespace refcount after creation.
+ * These sockets are freed when the namespace exits using the pernet
+ * exit hook.
+ */
+static int l2tp_tunnel_sock_create(struct net *net,
+				u32 tunnel_id,
+				u32 peer_tunnel_id,
+				struct l2tp_tunnel_cfg *cfg,
+				struct socket **sockp)
+{
+	int err = -EINVAL;
+	struct socket *sock = NULL;
+	struct udp_port_cfg udp_conf;
+
+	switch (cfg->encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		memset(&udp_conf, 0, sizeof(udp_conf));
+
+#if IS_ENABLED(CONFIG_IPV6)
+		if (cfg->local_ip6 && cfg->peer_ip6) {
+			udp_conf.family = AF_INET6;
+			memcpy(&udp_conf.local_ip6, cfg->local_ip6,
+			       sizeof(udp_conf.local_ip6));
+			memcpy(&udp_conf.peer_ip6, cfg->peer_ip6,
+			       sizeof(udp_conf.peer_ip6));
+			udp_conf.use_udp6_tx_checksums =
+			    cfg->udp6_zero_tx_checksums;
+			udp_conf.use_udp6_rx_checksums =
+			    cfg->udp6_zero_rx_checksums;
+		} else
+#endif
+		{
+			udp_conf.family = AF_INET;
+			udp_conf.local_ip = cfg->local_ip;
+			udp_conf.peer_ip = cfg->peer_ip;
+			udp_conf.use_udp_checksums = cfg->use_udp_checksums;
+		}
+
+		udp_conf.local_udp_port = htons(cfg->local_udp_port);
+		udp_conf.peer_udp_port = htons(cfg->peer_udp_port);
+
+		err = udp_sock_create(net, &udp_conf, &sock);
+		if (err < 0)
+			goto out;
+
+		break;
+
+	case L2TP_ENCAPTYPE_IP:
+#if IS_ENABLED(CONFIG_IPV6)
+		if (cfg->local_ip6 && cfg->peer_ip6) {
+			struct sockaddr_l2tpip6 ip6_addr = {0};
+
+			err = sock_create_kern(AF_INET6, SOCK_DGRAM,
+					  IPPROTO_L2TP, &sock);
+			if (err < 0)
+				goto out;
+
+			sk_change_net(sock->sk, net);
+
+			ip6_addr.l2tp_family = AF_INET6;
+			memcpy(&ip6_addr.l2tp_addr, cfg->local_ip6,
+			       sizeof(ip6_addr.l2tp_addr));
+			ip6_addr.l2tp_conn_id = tunnel_id;
+			err = kernel_bind(sock, (struct sockaddr *) &ip6_addr,
+					  sizeof(ip6_addr));
+			if (err < 0)
+				goto out;
+
+			ip6_addr.l2tp_family = AF_INET6;
+			memcpy(&ip6_addr.l2tp_addr, cfg->peer_ip6,
+			       sizeof(ip6_addr.l2tp_addr));
+			ip6_addr.l2tp_conn_id = peer_tunnel_id;
+			err = kernel_connect(sock,
+					     (struct sockaddr *) &ip6_addr,
+					     sizeof(ip6_addr), 0);
+			if (err < 0)
+				goto out;
+		} else
+#endif
+		{
+			struct sockaddr_l2tpip ip_addr = {0};
+
+			err = sock_create_kern(AF_INET, SOCK_DGRAM,
+					  IPPROTO_L2TP, &sock);
+			if (err < 0)
+				goto out;
+
+			sk_change_net(sock->sk, net);
+
+			ip_addr.l2tp_family = AF_INET;
+			ip_addr.l2tp_addr = cfg->local_ip;
+			ip_addr.l2tp_conn_id = tunnel_id;
+			err = kernel_bind(sock, (struct sockaddr *) &ip_addr,
+					  sizeof(ip_addr));
+			if (err < 0)
+				goto out;
+
+			ip_addr.l2tp_family = AF_INET;
+			ip_addr.l2tp_addr = cfg->peer_ip;
+			ip_addr.l2tp_conn_id = peer_tunnel_id;
+			err = kernel_connect(sock, (struct sockaddr *) &ip_addr,
+					     sizeof(ip_addr), 0);
+			if (err < 0)
+				goto out;
+		}
+		break;
+
+	default:
+		goto out;
+	}
+
+out:
+	*sockp = sock;
+	if ((err < 0) && sock) {
+		kernel_sock_shutdown(sock, SHUT_RDWR);
+		sk_release_kernel(sock->sk);
+		*sockp = NULL;
+	}
+
+	return err;
+}
+
+static struct lock_class_key l2tp_socket_class;
+
+int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
+{
+	struct l2tp_tunnel *tunnel = NULL;
+	int err;
+	struct socket *sock = NULL;
+	struct sock *sk = NULL;
+	struct l2tp_net *pn;
+	enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
+
+	/* Get the tunnel socket from the fd, which was opened by
+	 * the userspace L2TP daemon. If not specified, create a
+	 * kernel socket.
+	 */
+	if (fd < 0) {
+		err = l2tp_tunnel_sock_create(net, tunnel_id, peer_tunnel_id,
+				cfg, &sock);
+		if (err < 0)
+			goto err;
+	} else {
+		sock = sockfd_lookup(fd, &err);
+		if (!sock) {
+			pr_err("tunl %u: sockfd_lookup(fd=%d) returned %d\n",
+			       tunnel_id, fd, err);
+			err = -EBADF;
+			goto err;
+		}
+
+		/* Reject namespace mismatches */
+		if (!net_eq(sock_net(sock->sk), net)) {
+			pr_err("tunl %u: netns mismatch\n", tunnel_id);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+	sk = sock->sk;
+
+	if (cfg != NULL)
+		encap = cfg->encap;
+
+	/* Quick sanity checks */
+	switch (encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		err = -EPROTONOSUPPORT;
+		if (sk->sk_protocol != IPPROTO_UDP) {
+			pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
+			       tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
+			goto err;
+		}
+		break;
+	case L2TP_ENCAPTYPE_IP:
+		err = -EPROTONOSUPPORT;
+		if (sk->sk_protocol != IPPROTO_L2TP) {
+			pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
+			       tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
+			goto err;
+		}
+		break;
+	}
+
+	/* Check if this socket has already been prepped */
+	tunnel = l2tp_tunnel(sk);
+	if (tunnel != NULL) {
+		/* This socket has already been prepped */
+		err = -EBUSY;
+		goto err;
+	}
+
+	tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
+	if (tunnel == NULL) {
+		err = -ENOMEM;
+		goto err;
+	}
+
+	tunnel->version = version;
+	tunnel->tunnel_id = tunnel_id;
+	tunnel->peer_tunnel_id = peer_tunnel_id;
+	tunnel->debug = L2TP_DEFAULT_DEBUG_FLAGS;
+
+	tunnel->magic = L2TP_TUNNEL_MAGIC;
+	sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
+	rwlock_init(&tunnel->hlist_lock);
+
+	/* The net we belong to */
+	tunnel->l2tp_net = net;
+	pn = l2tp_pernet(net);
+
+	if (cfg != NULL)
+		tunnel->debug = cfg->debug;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == PF_INET6) {
+		struct ipv6_pinfo *np = inet6_sk(sk);
+
+		if (ipv6_addr_v4mapped(&np->saddr) &&
+		    ipv6_addr_v4mapped(&sk->sk_v6_daddr)) {
+			struct inet_sock *inet = inet_sk(sk);
+
+			tunnel->v4mapped = true;
+			inet->inet_saddr = np->saddr.s6_addr32[3];
+			inet->inet_rcv_saddr = sk->sk_v6_rcv_saddr.s6_addr32[3];
+			inet->inet_daddr = sk->sk_v6_daddr.s6_addr32[3];
+		} else {
+			tunnel->v4mapped = false;
+		}
+	}
+#endif
+
+	/* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
+	tunnel->encap = encap;
+	if (encap == L2TP_ENCAPTYPE_UDP) {
+		struct udp_tunnel_sock_cfg udp_cfg;
+
+		udp_cfg.sk_user_data = tunnel;
+		udp_cfg.encap_type = UDP_ENCAP_L2TPINUDP;
+		udp_cfg.encap_rcv = l2tp_udp_encap_recv;
+		udp_cfg.encap_destroy = l2tp_udp_encap_destroy;
+
+		setup_udp_tunnel_sock(net, sock, &udp_cfg);
+	} else {
+		sk->sk_user_data = tunnel;
+	}
+
+	/* Hook on the tunnel socket destructor so that we can cleanup
+	 * if the tunnel socket goes away.
+	 */
+	tunnel->old_sk_destruct = sk->sk_destruct;
+	sk->sk_destruct = &l2tp_tunnel_destruct;
+	tunnel->sock = sk;
+	tunnel->fd = fd;
+	lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class, "l2tp_sock");
+
+	sk->sk_allocation = GFP_ATOMIC;
+
+	/* Init delete workqueue struct */
+	INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
+
+	/* Add tunnel to our list */
+	INIT_LIST_HEAD(&tunnel->list);
+	atomic_inc(&l2tp_tunnel_count);
+
+	/* Bump the reference count. The tunnel context is deleted
+	 * only when this drops to zero. Must be done before list insertion
+	 */
+	l2tp_tunnel_inc_refcount(tunnel);
+	spin_lock_bh(&pn->l2tp_tunnel_list_lock);
+	list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
+	spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
+
+	err = 0;
+err:
+	if (tunnelp)
+		*tunnelp = tunnel;
+
+	/* If tunnel's socket was created by the kernel, it doesn't
+	 *  have a file.
+	 */
+	if (sock && sock->file)
+		sockfd_put(sock);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
+
+/* This function is used by the netlink TUNNEL_DELETE command.
+ */
+int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
+{
+	l2tp_tunnel_closeall(tunnel);
+	return (false == queue_work(l2tp_wq, &tunnel->del_work));
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
+
+/* Really kill the session.
+ */
+void l2tp_session_free(struct l2tp_session *session)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+
+	BUG_ON(atomic_read(&session->ref_count) != 0);
+
+	if (tunnel) {
+		BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
+		if (session->session_id != 0)
+			atomic_dec(&l2tp_session_count);
+		sock_put(tunnel->sock);
+		session->tunnel = NULL;
+		l2tp_tunnel_dec_refcount(tunnel);
+	}
+
+	kfree(session);
+}
+EXPORT_SYMBOL_GPL(l2tp_session_free);
+
+/* Remove an l2tp session from l2tp_core's hash lists.
+ * Provides a tidyup interface for pseudowire code which can't just route all
+ * shutdown via. l2tp_session_delete and a pseudowire-specific session_close
+ * callback.
+ */
+void __l2tp_session_unhash(struct l2tp_session *session)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+
+	/* Remove the session from core hashes */
+	if (tunnel) {
+		/* Remove from the per-tunnel hash */
+		write_lock_bh(&tunnel->hlist_lock);
+		hlist_del_init(&session->hlist);
+		write_unlock_bh(&tunnel->hlist_lock);
+
+		/* For L2TPv3 we have a per-net hash: remove from there, too */
+		if (tunnel->version != L2TP_HDR_VER_2) {
+			struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
+			spin_lock_bh(&pn->l2tp_session_hlist_lock);
+			hlist_del_init_rcu(&session->global_hlist);
+			spin_unlock_bh(&pn->l2tp_session_hlist_lock);
+			synchronize_rcu();
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(__l2tp_session_unhash);
+
+/* This function is used by the netlink SESSION_DELETE command and by
+   pseudowire modules.
+ */
+int l2tp_session_delete(struct l2tp_session *session)
+{
+	if (session->ref)
+		(*session->ref)(session);
+	__l2tp_session_unhash(session);
+	l2tp_session_queue_purge(session);
+	if (session->session_close != NULL)
+		(*session->session_close)(session);
+	if (session->deref)
+		(*session->deref)(session);
+	l2tp_session_dec_refcount(session);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_delete);
+
+/* We come here whenever a session's send_seq, cookie_len or
+ * l2specific_len parameters are set.
+ */
+void l2tp_session_set_header_len(struct l2tp_session *session, int version)
+{
+	if (version == L2TP_HDR_VER_2) {
+		session->hdr_len = 6;
+		if (session->send_seq)
+			session->hdr_len += 4;
+	} else {
+		session->hdr_len = 4 + session->cookie_len + session->l2specific_len + session->offset;
+		if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
+			session->hdr_len += 4;
+	}
+
+}
+EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
+
+struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
+{
+	struct l2tp_session *session;
+
+	session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
+	if (session != NULL) {
+		session->magic = L2TP_SESSION_MAGIC;
+		session->tunnel = tunnel;
+
+		session->session_id = session_id;
+		session->peer_session_id = peer_session_id;
+		session->nr = 0;
+		if (tunnel->version == L2TP_HDR_VER_2)
+			session->nr_max = 0xffff;
+		else
+			session->nr_max = 0xffffff;
+		session->nr_window_size = session->nr_max / 2;
+		session->nr_oos_count_max = 4;
+
+		/* Use NR of first received packet */
+		session->reorder_skip = 1;
+
+		sprintf(&session->name[0], "sess %u/%u",
+			tunnel->tunnel_id, session->session_id);
+
+		skb_queue_head_init(&session->reorder_q);
+
+		INIT_HLIST_NODE(&session->hlist);
+		INIT_HLIST_NODE(&session->global_hlist);
+
+		/* Inherit debug options from tunnel */
+		session->debug = tunnel->debug;
+
+		if (cfg) {
+			session->pwtype = cfg->pw_type;
+			session->debug = cfg->debug;
+			session->mtu = cfg->mtu;
+			session->mru = cfg->mru;
+			session->send_seq = cfg->send_seq;
+			session->recv_seq = cfg->recv_seq;
+			session->lns_mode = cfg->lns_mode;
+			session->reorder_timeout = cfg->reorder_timeout;
+			session->offset = cfg->offset;
+			session->l2specific_type = cfg->l2specific_type;
+			session->l2specific_len = cfg->l2specific_len;
+			session->cookie_len = cfg->cookie_len;
+			memcpy(&session->cookie[0], &cfg->cookie[0], cfg->cookie_len);
+			session->peer_cookie_len = cfg->peer_cookie_len;
+			memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
+		}
+
+		if (tunnel->version == L2TP_HDR_VER_2)
+			session->build_header = l2tp_build_l2tpv2_header;
+		else
+			session->build_header = l2tp_build_l2tpv3_header;
+
+		l2tp_session_set_header_len(session, tunnel->version);
+
+		/* Bump the reference count. The session context is deleted
+		 * only when this drops to zero.
+		 */
+		l2tp_session_inc_refcount(session);
+		l2tp_tunnel_inc_refcount(tunnel);
+
+		/* Ensure tunnel socket isn't deleted */
+		sock_hold(tunnel->sock);
+
+		/* Add session to the tunnel's hash list */
+		write_lock_bh(&tunnel->hlist_lock);
+		hlist_add_head(&session->hlist,
+			       l2tp_session_id_hash(tunnel, session_id));
+		write_unlock_bh(&tunnel->hlist_lock);
+
+		/* And to the global session list if L2TPv3 */
+		if (tunnel->version != L2TP_HDR_VER_2) {
+			struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
+
+			spin_lock_bh(&pn->l2tp_session_hlist_lock);
+			hlist_add_head_rcu(&session->global_hlist,
+					   l2tp_session_id_hash_2(pn, session_id));
+			spin_unlock_bh(&pn->l2tp_session_hlist_lock);
+		}
+
+		/* Ignore management session in session count value */
+		if (session->session_id != 0)
+			atomic_inc(&l2tp_session_count);
+	}
+
+	return session;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_create);
+
+/*****************************************************************************
+ * Init and cleanup
+ *****************************************************************************/
+
+static __net_init int l2tp_init_net(struct net *net)
+{
+	struct l2tp_net *pn = net_generic(net, l2tp_net_id);
+	int hash;
+
+	INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
+	spin_lock_init(&pn->l2tp_tunnel_list_lock);
+
+	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
+		INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
+
+	spin_lock_init(&pn->l2tp_session_hlist_lock);
+
+	return 0;
+}
+
+static __net_exit void l2tp_exit_net(struct net *net)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+	struct l2tp_tunnel *tunnel = NULL;
+
+	rcu_read_lock_bh();
+	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
+		(void)l2tp_tunnel_delete(tunnel);
+	}
+	rcu_read_unlock_bh();
+}
+
+static struct pernet_operations l2tp_net_ops = {
+	.init = l2tp_init_net,
+	.exit = l2tp_exit_net,
+	.id   = &l2tp_net_id,
+	.size = sizeof(struct l2tp_net),
+};
+
+static int __init l2tp_init(void)
+{
+	int rc = 0;
+
+	rc = register_pernet_device(&l2tp_net_ops);
+	if (rc)
+		goto out;
+
+	l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
+	if (!l2tp_wq) {
+		pr_err("alloc_workqueue failed\n");
+		unregister_pernet_device(&l2tp_net_ops);
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	pr_info("L2TP core driver, %s\n", L2TP_DRV_VERSION);
+
+out:
+	return rc;
+}
+
+static void __exit l2tp_exit(void)
+{
+	unregister_pernet_device(&l2tp_net_ops);
+	if (l2tp_wq) {
+		destroy_workqueue(l2tp_wq);
+		l2tp_wq = NULL;
+	}
+}
+
+module_init(l2tp_init);
+module_exit(l2tp_exit);
+
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("L2TP core");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(L2TP_DRV_VERSION);
+
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
new file mode 100644
index 000000000..68aa9ffd4
--- /dev/null
+++ b/net/l2tp/l2tp_core.h
@@ -0,0 +1,324 @@
+/*
+ * L2TP internal definitions.
+ *
+ * Copyright (c) 2008,2009 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 version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _L2TP_CORE_H_
+#define _L2TP_CORE_H_
+
+/* Just some random numbers */
+#define L2TP_TUNNEL_MAGIC	0x42114DDA
+#define L2TP_SESSION_MAGIC	0x0C04EB7D
+
+/* Per tunnel, session hash table size */
+#define L2TP_HASH_BITS	4
+#define L2TP_HASH_SIZE	(1 << L2TP_HASH_BITS)
+
+/* System-wide, session hash table size */
+#define L2TP_HASH_BITS_2	8
+#define L2TP_HASH_SIZE_2	(1 << L2TP_HASH_BITS_2)
+
+/* Debug message categories for the DEBUG socket option */
+enum {
+	L2TP_MSG_DEBUG		= (1 << 0),	/* verbose debug (if
+						 * compiled in) */
+	L2TP_MSG_CONTROL	= (1 << 1),	/* userspace - kernel
+						 * interface */
+	L2TP_MSG_SEQ		= (1 << 2),	/* sequence numbers */
+	L2TP_MSG_DATA		= (1 << 3),	/* data packets */
+};
+
+struct sk_buff;
+
+struct l2tp_stats {
+	atomic_long_t		tx_packets;
+	atomic_long_t		tx_bytes;
+	atomic_long_t		tx_errors;
+	atomic_long_t		rx_packets;
+	atomic_long_t		rx_bytes;
+	atomic_long_t		rx_seq_discards;
+	atomic_long_t		rx_oos_packets;
+	atomic_long_t		rx_errors;
+	atomic_long_t		rx_cookie_discards;
+};
+
+struct l2tp_tunnel;
+
+/* Describes a session. Contains information to determine incoming
+ * packets and transmit outgoing ones.
+ */
+struct l2tp_session_cfg {
+	enum l2tp_pwtype	pw_type;
+	unsigned int		data_seq:2;	/* data sequencing level
+						 * 0 => none, 1 => IP only,
+						 * 2 => all
+						 */
+	unsigned int		recv_seq:1;	/* expect receive packets with
+						 * sequence numbers? */
+	unsigned int		send_seq:1;	/* send packets with sequence
+						 * numbers? */
+	unsigned int		lns_mode:1;	/* behave as LNS? LAC enables
+						 * sequence numbers under
+						 * control of LNS. */
+	int			debug;		/* bitmask of debug message
+						 * categories */
+	u16			vlan_id;	/* VLAN pseudowire only */
+	u16			offset;		/* offset to payload */
+	u16			l2specific_len;	/* Layer 2 specific length */
+	u16			l2specific_type; /* Layer 2 specific type */
+	u8			cookie[8];	/* optional cookie */
+	int			cookie_len;	/* 0, 4 or 8 bytes */
+	u8			peer_cookie[8];	/* peer's cookie */
+	int			peer_cookie_len; /* 0, 4 or 8 bytes */
+	int			reorder_timeout; /* configured reorder timeout
+						  * (in jiffies) */
+	int			mtu;
+	int			mru;
+	char			*ifname;
+};
+
+struct l2tp_session {
+	int			magic;		/* should be
+						 * L2TP_SESSION_MAGIC */
+
+	struct l2tp_tunnel	*tunnel;	/* back pointer to tunnel
+						 * context */
+	u32			session_id;
+	u32			peer_session_id;
+	u8			cookie[8];
+	int			cookie_len;
+	u8			peer_cookie[8];
+	int			peer_cookie_len;
+	u16			offset;		/* offset from end of L2TP header
+						   to beginning of data */
+	u16			l2specific_len;
+	u16			l2specific_type;
+	u16			hdr_len;
+	u32			nr;		/* session NR state (receive) */
+	u32			ns;		/* session NR state (send) */
+	struct sk_buff_head	reorder_q;	/* receive reorder queue */
+	u32			nr_max;		/* max NR. Depends on tunnel */
+	u32			nr_window_size;	/* NR window size */
+	u32			nr_oos;		/* NR of last OOS packet */
+	int			nr_oos_count;	/* For OOS recovery */
+	int			nr_oos_count_max;
+	struct hlist_node	hlist;		/* Hash list node */
+	atomic_t		ref_count;
+
+	char			name[32];	/* for logging */
+	char			ifname[IFNAMSIZ];
+	unsigned int		data_seq:2;	/* data sequencing level
+						 * 0 => none, 1 => IP only,
+						 * 2 => all
+						 */
+	unsigned int		recv_seq:1;	/* expect receive packets with
+						 * sequence numbers? */
+	unsigned int		send_seq:1;	/* send packets with sequence
+						 * numbers? */
+	unsigned int		lns_mode:1;	/* behave as LNS? LAC enables
+						 * sequence numbers under
+						 * control of LNS. */
+	int			debug;		/* bitmask of debug message
+						 * categories */
+	int			reorder_timeout; /* configured reorder timeout
+						  * (in jiffies) */
+	int			reorder_skip;	/* set if skip to next nr */
+	int			mtu;
+	int			mru;
+	enum l2tp_pwtype	pwtype;
+	struct l2tp_stats	stats;
+	struct hlist_node	global_hlist;	/* Global hash list node */
+
+	int (*build_header)(struct l2tp_session *session, void *buf);
+	void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
+	void (*session_close)(struct l2tp_session *session);
+	void (*ref)(struct l2tp_session *session);
+	void (*deref)(struct l2tp_session *session);
+#if defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
+	void (*show)(struct seq_file *m, void *priv);
+#endif
+	uint8_t			priv[0];	/* private data */
+};
+
+/* Describes the tunnel. It contains info to track all the associated
+ * sessions so incoming packets can be sorted out
+ */
+struct l2tp_tunnel_cfg {
+	int			debug;		/* bitmask of debug message
+						 * categories */
+	enum l2tp_encap_type	encap;
+
+	/* Used only for kernel-created sockets */
+	struct in_addr		local_ip;
+	struct in_addr		peer_ip;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct in6_addr		*local_ip6;
+	struct in6_addr		*peer_ip6;
+#endif
+	u16			local_udp_port;
+	u16			peer_udp_port;
+	unsigned int		use_udp_checksums:1,
+				udp6_zero_tx_checksums:1,
+				udp6_zero_rx_checksums:1;
+};
+
+struct l2tp_tunnel {
+	int			magic;		/* Should be L2TP_TUNNEL_MAGIC */
+	struct rcu_head rcu;
+	rwlock_t		hlist_lock;	/* protect session_hlist */
+	struct hlist_head	session_hlist[L2TP_HASH_SIZE];
+						/* hashed list of sessions,
+						 * hashed by id */
+	u32			tunnel_id;
+	u32			peer_tunnel_id;
+	int			version;	/* 2=>L2TPv2, 3=>L2TPv3 */
+
+	char			name[20];	/* for logging */
+	int			debug;		/* bitmask of debug message
+						 * categories */
+	enum l2tp_encap_type	encap;
+	struct l2tp_stats	stats;
+
+	struct list_head	list;		/* Keep a list of all tunnels */
+	struct net		*l2tp_net;	/* the net we belong to */
+
+	atomic_t		ref_count;
+#ifdef CONFIG_DEBUG_FS
+	void (*show)(struct seq_file *m, void *arg);
+#endif
+	int (*recv_payload_hook)(struct sk_buff *skb);
+	void (*old_sk_destruct)(struct sock *);
+	struct sock		*sock;		/* Parent socket */
+	int			fd;		/* Parent fd, if tunnel socket
+						 * was created by userspace */
+#if IS_ENABLED(CONFIG_IPV6)
+	bool			v4mapped;
+#endif
+
+	struct work_struct	del_work;
+
+	uint8_t			priv[0];	/* private data */
+};
+
+struct l2tp_nl_cmd_ops {
+	int (*session_create)(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg);
+	int (*session_delete)(struct l2tp_session *session);
+};
+
+static inline void *l2tp_tunnel_priv(struct l2tp_tunnel *tunnel)
+{
+	return &tunnel->priv[0];
+}
+
+static inline void *l2tp_session_priv(struct l2tp_session *session)
+{
+	return &session->priv[0];
+}
+
+static inline struct l2tp_tunnel *l2tp_sock_to_tunnel(struct sock *sk)
+{
+	struct l2tp_tunnel *tunnel;
+
+	if (sk == NULL)
+		return NULL;
+
+	sock_hold(sk);
+	tunnel = (struct l2tp_tunnel *)(sk->sk_user_data);
+	if (tunnel == NULL) {
+		sock_put(sk);
+		goto out;
+	}
+
+	BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
+
+out:
+	return tunnel;
+}
+
+struct l2tp_session *l2tp_session_find(struct net *net,
+				       struct l2tp_tunnel *tunnel,
+				       u32 session_id);
+struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth);
+struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname);
+struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id);
+struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth);
+
+int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
+		       u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
+		       struct l2tp_tunnel **tunnelp);
+void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
+int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
+struct l2tp_session *l2tp_session_create(int priv_size,
+					 struct l2tp_tunnel *tunnel,
+					 u32 session_id, u32 peer_session_id,
+					 struct l2tp_session_cfg *cfg);
+void __l2tp_session_unhash(struct l2tp_session *session);
+int l2tp_session_delete(struct l2tp_session *session);
+void l2tp_session_free(struct l2tp_session *session);
+void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
+		      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
+		      int length, int (*payload_hook)(struct sk_buff *skb));
+int l2tp_session_queue_purge(struct l2tp_session *session);
+int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
+void l2tp_session_set_header_len(struct l2tp_session *session, int version);
+
+int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb,
+		  int hdr_len);
+
+int l2tp_nl_register_ops(enum l2tp_pwtype pw_type,
+			 const struct l2tp_nl_cmd_ops *ops);
+void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
+
+/* Session reference counts. Incremented when code obtains a reference
+ * to a session.
+ */
+static inline void l2tp_session_inc_refcount_1(struct l2tp_session *session)
+{
+	atomic_inc(&session->ref_count);
+}
+
+static inline void l2tp_session_dec_refcount_1(struct l2tp_session *session)
+{
+	if (atomic_dec_and_test(&session->ref_count))
+		l2tp_session_free(session);
+}
+
+#ifdef L2TP_REFCNT_DEBUG
+#define l2tp_session_inc_refcount(_s)					\
+do {									\
+	pr_debug("l2tp_session_inc_refcount: %s:%d %s: cnt=%d\n",	\
+		 __func__, __LINE__, (_s)->name,			\
+		 atomic_read(&_s->ref_count));				\
+	l2tp_session_inc_refcount_1(_s);				\
+} while (0)
+#define l2tp_session_dec_refcount(_s)					\
+do {									\
+	pr_debug("l2tp_session_dec_refcount: %s:%d %s: cnt=%d\n",	\
+		 __func__, __LINE__, (_s)->name,			\
+		 atomic_read(&_s->ref_count));				\
+	l2tp_session_dec_refcount_1(_s);				\
+} while (0)
+#else
+#define l2tp_session_inc_refcount(s) l2tp_session_inc_refcount_1(s)
+#define l2tp_session_dec_refcount(s) l2tp_session_dec_refcount_1(s)
+#endif
+
+#define l2tp_printk(ptr, type, func, fmt, ...)				\
+do {									\
+	if (((ptr)->debug) & (type))					\
+		func(fmt, ##__VA_ARGS__);				\
+} while (0)
+
+#define l2tp_warn(ptr, type, fmt, ...)					\
+	l2tp_printk(ptr, type, pr_warn, fmt, ##__VA_ARGS__)
+#define l2tp_info(ptr, type, fmt, ...)					\
+	l2tp_printk(ptr, type, pr_info, fmt, ##__VA_ARGS__)
+#define l2tp_dbg(ptr, type, fmt, ...)					\
+	l2tp_printk(ptr, type, pr_debug, fmt, ##__VA_ARGS__)
+
+#endif /* _L2TP_CORE_H_ */
diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c
new file mode 100644
index 000000000..2d6760a2a
--- /dev/null
+++ b/net/l2tp/l2tp_debugfs.c
@@ -0,0 +1,352 @@
+/*
+ * L2TP subsystem debugfs
+ *
+ * Copyright (c) 2010 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/module.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/hash.h>
+#include <linux/l2tp.h>
+#include <linux/in.h>
+#include <linux/etherdevice.h>
+#include <linux/spinlock.h>
+#include <linux/debugfs.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/tcp_states.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#include "l2tp_core.h"
+
+static struct dentry *rootdir;
+static struct dentry *tunnels;
+
+struct l2tp_dfs_seq_data {
+	struct net *net;
+	int tunnel_idx;			/* current tunnel */
+	int session_idx;		/* index of session within current tunnel */
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;	/* NULL means get next tunnel */
+};
+
+static void l2tp_dfs_next_tunnel(struct l2tp_dfs_seq_data *pd)
+{
+	pd->tunnel = l2tp_tunnel_find_nth(pd->net, pd->tunnel_idx);
+	pd->tunnel_idx++;
+}
+
+static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd)
+{
+	pd->session = l2tp_session_find_nth(pd->tunnel, pd->session_idx);
+	pd->session_idx++;
+
+	if (pd->session == NULL) {
+		pd->session_idx = 0;
+		l2tp_dfs_next_tunnel(pd);
+	}
+
+}
+
+static void *l2tp_dfs_seq_start(struct seq_file *m, loff_t *offs)
+{
+	struct l2tp_dfs_seq_data *pd = SEQ_START_TOKEN;
+	loff_t pos = *offs;
+
+	if (!pos)
+		goto out;
+
+	BUG_ON(m->private == NULL);
+	pd = m->private;
+
+	if (pd->tunnel == NULL)
+		l2tp_dfs_next_tunnel(pd);
+	else
+		l2tp_dfs_next_session(pd);
+
+	/* NULL tunnel and session indicates end of list */
+	if ((pd->tunnel == NULL) && (pd->session == NULL))
+		pd = NULL;
+
+out:
+	return pd;
+}
+
+
+static void *l2tp_dfs_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	return NULL;
+}
+
+static void l2tp_dfs_seq_stop(struct seq_file *p, void *v)
+{
+	/* nothing to do */
+}
+
+static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v)
+{
+	struct l2tp_tunnel *tunnel = v;
+	int session_count = 0;
+	int hash;
+	struct hlist_node *walk;
+	struct hlist_node *tmp;
+
+	read_lock_bh(&tunnel->hlist_lock);
+	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
+		hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
+			struct l2tp_session *session;
+
+			session = hlist_entry(walk, struct l2tp_session, hlist);
+			if (session->session_id == 0)
+				continue;
+
+			session_count++;
+		}
+	}
+	read_unlock_bh(&tunnel->hlist_lock);
+
+	seq_printf(m, "\nTUNNEL %u peer %u", tunnel->tunnel_id, tunnel->peer_tunnel_id);
+	if (tunnel->sock) {
+		struct inet_sock *inet = inet_sk(tunnel->sock);
+
+#if IS_ENABLED(CONFIG_IPV6)
+		if (tunnel->sock->sk_family == AF_INET6) {
+			const struct ipv6_pinfo *np = inet6_sk(tunnel->sock);
+
+			seq_printf(m, " from %pI6c to %pI6c\n",
+				&np->saddr, &tunnel->sock->sk_v6_daddr);
+		} else
+#endif
+		seq_printf(m, " from %pI4 to %pI4\n",
+			   &inet->inet_saddr, &inet->inet_daddr);
+		if (tunnel->encap == L2TP_ENCAPTYPE_UDP)
+			seq_printf(m, " source port %hu, dest port %hu\n",
+				   ntohs(inet->inet_sport), ntohs(inet->inet_dport));
+	}
+	seq_printf(m, " L2TPv%d, %s\n", tunnel->version,
+		   tunnel->encap == L2TP_ENCAPTYPE_UDP ? "UDP" :
+		   tunnel->encap == L2TP_ENCAPTYPE_IP ? "IP" :
+		   "");
+	seq_printf(m, " %d sessions, refcnt %d/%d\n", session_count,
+		   tunnel->sock ? atomic_read(&tunnel->sock->sk_refcnt) : 0,
+		   atomic_read(&tunnel->ref_count));
+
+	seq_printf(m, " %08x rx %ld/%ld/%ld rx %ld/%ld/%ld\n",
+		   tunnel->debug,
+		   atomic_long_read(&tunnel->stats.tx_packets),
+		   atomic_long_read(&tunnel->stats.tx_bytes),
+		   atomic_long_read(&tunnel->stats.tx_errors),
+		   atomic_long_read(&tunnel->stats.rx_packets),
+		   atomic_long_read(&tunnel->stats.rx_bytes),
+		   atomic_long_read(&tunnel->stats.rx_errors));
+
+	if (tunnel->show != NULL)
+		tunnel->show(m, tunnel);
+}
+
+static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
+{
+	struct l2tp_session *session = v;
+
+	seq_printf(m, "  SESSION %u, peer %u, %s\n", session->session_id,
+		   session->peer_session_id,
+		   session->pwtype == L2TP_PWTYPE_ETH ? "ETH" :
+		   session->pwtype == L2TP_PWTYPE_PPP ? "PPP" :
+		   "");
+	if (session->send_seq || session->recv_seq)
+		seq_printf(m, "   nr %hu, ns %hu\n", session->nr, session->ns);
+	seq_printf(m, "   refcnt %d\n", atomic_read(&session->ref_count));
+	seq_printf(m, "   config %d/%d/%c/%c/%s/%s %08x %u\n",
+		   session->mtu, session->mru,
+		   session->recv_seq ? 'R' : '-',
+		   session->send_seq ? 'S' : '-',
+		   session->data_seq == 1 ? "IPSEQ" :
+		   session->data_seq == 2 ? "DATASEQ" : "-",
+		   session->lns_mode ? "LNS" : "LAC",
+		   session->debug,
+		   jiffies_to_msecs(session->reorder_timeout));
+	seq_printf(m, "   offset %hu l2specific %hu/%hu\n",
+		   session->offset, session->l2specific_type, session->l2specific_len);
+	if (session->cookie_len) {
+		seq_printf(m, "   cookie %02x%02x%02x%02x",
+			   session->cookie[0], session->cookie[1],
+			   session->cookie[2], session->cookie[3]);
+		if (session->cookie_len == 8)
+			seq_printf(m, "%02x%02x%02x%02x",
+				   session->cookie[4], session->cookie[5],
+				   session->cookie[6], session->cookie[7]);
+		seq_printf(m, "\n");
+	}
+	if (session->peer_cookie_len) {
+		seq_printf(m, "   peer cookie %02x%02x%02x%02x",
+			   session->peer_cookie[0], session->peer_cookie[1],
+			   session->peer_cookie[2], session->peer_cookie[3]);
+		if (session->peer_cookie_len == 8)
+			seq_printf(m, "%02x%02x%02x%02x",
+				   session->peer_cookie[4], session->peer_cookie[5],
+				   session->peer_cookie[6], session->peer_cookie[7]);
+		seq_printf(m, "\n");
+	}
+
+	seq_printf(m, "   %hu/%hu tx %ld/%ld/%ld rx %ld/%ld/%ld\n",
+		   session->nr, session->ns,
+		   atomic_long_read(&session->stats.tx_packets),
+		   atomic_long_read(&session->stats.tx_bytes),
+		   atomic_long_read(&session->stats.tx_errors),
+		   atomic_long_read(&session->stats.rx_packets),
+		   atomic_long_read(&session->stats.rx_bytes),
+		   atomic_long_read(&session->stats.rx_errors));
+
+	if (session->show != NULL)
+		session->show(m, session);
+}
+
+static int l2tp_dfs_seq_show(struct seq_file *m, void *v)
+{
+	struct l2tp_dfs_seq_data *pd = v;
+
+	/* display header on line 1 */
+	if (v == SEQ_START_TOKEN) {
+		seq_puts(m, "TUNNEL ID, peer ID from IP to IP\n");
+		seq_puts(m, " L2TPv2/L2TPv3, UDP/IP\n");
+		seq_puts(m, " sessions session-count, refcnt refcnt/sk->refcnt\n");
+		seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
+		seq_puts(m, "  SESSION ID, peer ID, PWTYPE\n");
+		seq_puts(m, "   refcnt cnt\n");
+		seq_puts(m, "   offset OFFSET l2specific TYPE/LEN\n");
+		seq_puts(m, "   [ cookie ]\n");
+		seq_puts(m, "   [ peer cookie ]\n");
+		seq_puts(m, "   config mtu/mru/rcvseq/sendseq/dataseq/lns debug reorderto\n");
+		seq_puts(m, "   nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
+		goto out;
+	}
+
+	/* Show the tunnel or session context */
+	if (pd->session == NULL)
+		l2tp_dfs_seq_tunnel_show(m, pd->tunnel);
+	else
+		l2tp_dfs_seq_session_show(m, pd->session);
+
+out:
+	return 0;
+}
+
+static const struct seq_operations l2tp_dfs_seq_ops = {
+	.start		= l2tp_dfs_seq_start,
+	.next		= l2tp_dfs_seq_next,
+	.stop		= l2tp_dfs_seq_stop,
+	.show		= l2tp_dfs_seq_show,
+};
+
+static int l2tp_dfs_seq_open(struct inode *inode, struct file *file)
+{
+	struct l2tp_dfs_seq_data *pd;
+	struct seq_file *seq;
+	int rc = -ENOMEM;
+
+	pd = kzalloc(sizeof(*pd), GFP_KERNEL);
+	if (pd == NULL)
+		goto out;
+
+	/* Derive the network namespace from the pid opening the
+	 * file.
+	 */
+	pd->net = get_net_ns_by_pid(current->pid);
+	if (IS_ERR(pd->net)) {
+		rc = PTR_ERR(pd->net);
+		goto err_free_pd;
+	}
+
+	rc = seq_open(file, &l2tp_dfs_seq_ops);
+	if (rc)
+		goto err_free_net;
+
+	seq = file->private_data;
+	seq->private = pd;
+
+out:
+	return rc;
+
+err_free_net:
+	put_net(pd->net);
+err_free_pd:
+	kfree(pd);
+	goto out;
+}
+
+static int l2tp_dfs_seq_release(struct inode *inode, struct file *file)
+{
+	struct l2tp_dfs_seq_data *pd;
+	struct seq_file *seq;
+
+	seq = file->private_data;
+	pd = seq->private;
+	if (pd->net)
+		put_net(pd->net);
+	kfree(pd);
+	seq_release(inode, file);
+
+	return 0;
+}
+
+static const struct file_operations l2tp_dfs_fops = {
+	.owner		= THIS_MODULE,
+	.open		= l2tp_dfs_seq_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= l2tp_dfs_seq_release,
+};
+
+static int __init l2tp_debugfs_init(void)
+{
+	int rc = 0;
+
+	rootdir = debugfs_create_dir("l2tp", NULL);
+	if (IS_ERR(rootdir)) {
+		rc = PTR_ERR(rootdir);
+		rootdir = NULL;
+		goto out;
+	}
+
+	tunnels = debugfs_create_file("tunnels", 0600, rootdir, NULL, &l2tp_dfs_fops);
+	if (tunnels == NULL)
+		rc = -EIO;
+
+	pr_info("L2TP debugfs support\n");
+
+out:
+	if (rc)
+		pr_warn("unable to init\n");
+
+	return rc;
+}
+
+static void __exit l2tp_debugfs_exit(void)
+{
+	debugfs_remove(tunnels);
+	debugfs_remove(rootdir);
+}
+
+module_init(l2tp_debugfs_init);
+module_exit(l2tp_debugfs_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("L2TP debugfs driver");
+MODULE_VERSION("1.0");
diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
new file mode 100644
index 000000000..4b552873b
--- /dev/null
+++ b/net/l2tp/l2tp_eth.c
@@ -0,0 +1,360 @@
+/*
+ * L2TPv3 ethernet pseudowire driver
+ *
+ * Copyright (c) 2008,2009,2010 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/module.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/hash.h>
+#include <linux/l2tp.h>
+#include <linux/in.h>
+#include <linux/etherdevice.h>
+#include <linux/spinlock.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/tcp_states.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#include "l2tp_core.h"
+
+/* Default device name. May be overridden by name specified by user */
+#define L2TP_ETH_DEV_NAME	"l2tpeth%d"
+
+/* via netdev_priv() */
+struct l2tp_eth {
+	struct net_device	*dev;
+	struct sock		*tunnel_sock;
+	struct l2tp_session	*session;
+	struct list_head	list;
+	atomic_long_t		tx_bytes;
+	atomic_long_t		tx_packets;
+	atomic_long_t		tx_dropped;
+	atomic_long_t		rx_bytes;
+	atomic_long_t		rx_packets;
+	atomic_long_t		rx_errors;
+};
+
+/* via l2tp_session_priv() */
+struct l2tp_eth_sess {
+	struct net_device	*dev;
+};
+
+/* per-net private data for this module */
+static unsigned int l2tp_eth_net_id;
+struct l2tp_eth_net {
+	struct list_head l2tp_eth_dev_list;
+	spinlock_t l2tp_eth_lock;
+};
+
+static inline struct l2tp_eth_net *l2tp_eth_pernet(struct net *net)
+{
+	return net_generic(net, l2tp_eth_net_id);
+}
+
+static struct lock_class_key l2tp_eth_tx_busylock;
+static int l2tp_eth_dev_init(struct net_device *dev)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+
+	priv->dev = dev;
+	eth_hw_addr_random(dev);
+	eth_broadcast_addr(dev->broadcast);
+	dev->qdisc_tx_busylock = &l2tp_eth_tx_busylock;
+	return 0;
+}
+
+static void l2tp_eth_dev_uninit(struct net_device *dev)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+	struct l2tp_eth_net *pn = l2tp_eth_pernet(dev_net(dev));
+
+	spin_lock(&pn->l2tp_eth_lock);
+	list_del_init(&priv->list);
+	spin_unlock(&pn->l2tp_eth_lock);
+	dev_put(dev);
+}
+
+static int l2tp_eth_dev_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+	struct l2tp_session *session = priv->session;
+	unsigned int len = skb->len;
+	int ret = l2tp_xmit_skb(session, skb, session->hdr_len);
+
+	if (likely(ret == NET_XMIT_SUCCESS)) {
+		atomic_long_add(len, &priv->tx_bytes);
+		atomic_long_inc(&priv->tx_packets);
+	} else {
+		atomic_long_inc(&priv->tx_dropped);
+	}
+	return NETDEV_TX_OK;
+}
+
+static struct rtnl_link_stats64 *l2tp_eth_get_stats64(struct net_device *dev,
+						      struct rtnl_link_stats64 *stats)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+
+	stats->tx_bytes   = atomic_long_read(&priv->tx_bytes);
+	stats->tx_packets = atomic_long_read(&priv->tx_packets);
+	stats->tx_dropped = atomic_long_read(&priv->tx_dropped);
+	stats->rx_bytes   = atomic_long_read(&priv->rx_bytes);
+	stats->rx_packets = atomic_long_read(&priv->rx_packets);
+	stats->rx_errors  = atomic_long_read(&priv->rx_errors);
+	return stats;
+}
+
+
+static struct net_device_ops l2tp_eth_netdev_ops = {
+	.ndo_init		= l2tp_eth_dev_init,
+	.ndo_uninit		= l2tp_eth_dev_uninit,
+	.ndo_start_xmit		= l2tp_eth_dev_xmit,
+	.ndo_get_stats64	= l2tp_eth_get_stats64,
+	.ndo_set_mac_address	= eth_mac_addr,
+};
+
+static void l2tp_eth_dev_setup(struct net_device *dev)
+{
+	ether_setup(dev);
+	dev->priv_flags		&= ~IFF_TX_SKB_SHARING;
+	dev->features		|= NETIF_F_LLTX;
+	dev->netdev_ops		= &l2tp_eth_netdev_ops;
+	dev->destructor		= free_netdev;
+}
+
+static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
+{
+	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
+	struct net_device *dev = spriv->dev;
+	struct l2tp_eth *priv = netdev_priv(dev);
+
+	if (session->debug & L2TP_MSG_DATA) {
+		unsigned int length;
+
+		length = min(32u, skb->len);
+		if (!pskb_may_pull(skb, length))
+			goto error;
+
+		pr_debug("%s: eth recv\n", session->name);
+		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
+	}
+
+	if (!pskb_may_pull(skb, ETH_HLEN))
+		goto error;
+
+	secpath_reset(skb);
+
+	/* checksums verified by L2TP */
+	skb->ip_summed = CHECKSUM_NONE;
+
+	skb_dst_drop(skb);
+	nf_reset(skb);
+
+	if (dev_forward_skb(dev, skb) == NET_RX_SUCCESS) {
+		atomic_long_inc(&priv->rx_packets);
+		atomic_long_add(data_len, &priv->rx_bytes);
+	} else {
+		atomic_long_inc(&priv->rx_errors);
+	}
+	return;
+
+error:
+	atomic_long_inc(&priv->rx_errors);
+	kfree_skb(skb);
+}
+
+static void l2tp_eth_delete(struct l2tp_session *session)
+{
+	struct l2tp_eth_sess *spriv;
+	struct net_device *dev;
+
+	if (session) {
+		spriv = l2tp_session_priv(session);
+		dev = spriv->dev;
+		if (dev) {
+			unregister_netdev(dev);
+			spriv->dev = NULL;
+			module_put(THIS_MODULE);
+		}
+	}
+}
+
+#if defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
+static void l2tp_eth_show(struct seq_file *m, void *arg)
+{
+	struct l2tp_session *session = arg;
+	struct l2tp_eth_sess *spriv = l2tp_session_priv(session);
+	struct net_device *dev = spriv->dev;
+
+	seq_printf(m, "   interface %s\n", dev->name);
+}
+#endif
+
+static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
+{
+	struct net_device *dev;
+	char name[IFNAMSIZ];
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;
+	struct l2tp_eth *priv;
+	struct l2tp_eth_sess *spriv;
+	int rc;
+	struct l2tp_eth_net *pn;
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (!tunnel) {
+		rc = -ENODEV;
+		goto out;
+	}
+
+	session = l2tp_session_find(net, tunnel, session_id);
+	if (session) {
+		rc = -EEXIST;
+		goto out;
+	}
+
+	if (cfg->ifname) {
+		dev = dev_get_by_name(net, cfg->ifname);
+		if (dev) {
+			dev_put(dev);
+			rc = -EEXIST;
+			goto out;
+		}
+		strlcpy(name, cfg->ifname, IFNAMSIZ);
+	} else
+		strcpy(name, L2TP_ETH_DEV_NAME);
+
+	session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
+				      peer_session_id, cfg);
+	if (!session) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	dev = alloc_netdev(sizeof(*priv), name, NET_NAME_UNKNOWN,
+			   l2tp_eth_dev_setup);
+	if (!dev) {
+		rc = -ENOMEM;
+		goto out_del_session;
+	}
+
+	dev_net_set(dev, net);
+	if (session->mtu == 0)
+		session->mtu = dev->mtu - session->hdr_len;
+	dev->mtu = session->mtu;
+	dev->needed_headroom += session->hdr_len;
+
+	priv = netdev_priv(dev);
+	priv->dev = dev;
+	priv->session = session;
+	INIT_LIST_HEAD(&priv->list);
+
+	priv->tunnel_sock = tunnel->sock;
+	session->recv_skb = l2tp_eth_dev_recv;
+	session->session_close = l2tp_eth_delete;
+#if defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
+	session->show = l2tp_eth_show;
+#endif
+
+	spriv = l2tp_session_priv(session);
+	spriv->dev = dev;
+
+	rc = register_netdev(dev);
+	if (rc < 0)
+		goto out_del_dev;
+
+	__module_get(THIS_MODULE);
+	/* Must be done after register_netdev() */
+	strlcpy(session->ifname, dev->name, IFNAMSIZ);
+
+	dev_hold(dev);
+	pn = l2tp_eth_pernet(dev_net(dev));
+	spin_lock(&pn->l2tp_eth_lock);
+	list_add(&priv->list, &pn->l2tp_eth_dev_list);
+	spin_unlock(&pn->l2tp_eth_lock);
+
+	return 0;
+
+out_del_dev:
+	free_netdev(dev);
+	spriv->dev = NULL;
+out_del_session:
+	l2tp_session_delete(session);
+out:
+	return rc;
+}
+
+static __net_init int l2tp_eth_init_net(struct net *net)
+{
+	struct l2tp_eth_net *pn = net_generic(net, l2tp_eth_net_id);
+
+	INIT_LIST_HEAD(&pn->l2tp_eth_dev_list);
+	spin_lock_init(&pn->l2tp_eth_lock);
+
+	return 0;
+}
+
+static struct pernet_operations l2tp_eth_net_ops = {
+	.init = l2tp_eth_init_net,
+	.id   = &l2tp_eth_net_id,
+	.size = sizeof(struct l2tp_eth_net),
+};
+
+
+static const struct l2tp_nl_cmd_ops l2tp_eth_nl_cmd_ops = {
+	.session_create	= l2tp_eth_create,
+	.session_delete	= l2tp_session_delete,
+};
+
+
+static int __init l2tp_eth_init(void)
+{
+	int err = 0;
+
+	err = l2tp_nl_register_ops(L2TP_PWTYPE_ETH, &l2tp_eth_nl_cmd_ops);
+	if (err)
+		goto out;
+
+	err = register_pernet_device(&l2tp_eth_net_ops);
+	if (err)
+		goto out_unreg;
+
+	pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
+
+	return 0;
+
+out_unreg:
+	l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
+out:
+	return err;
+}
+
+static void __exit l2tp_eth_exit(void)
+{
+	unregister_pernet_device(&l2tp_eth_net_ops);
+	l2tp_nl_unregister_ops(L2TP_PWTYPE_ETH);
+}
+
+module_init(l2tp_eth_init);
+module_exit(l2tp_eth_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("L2TP ethernet pseudowire driver");
+MODULE_VERSION("1.0");
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
new file mode 100644
index 000000000..79649937e
--- /dev/null
+++ b/net/l2tp/l2tp_ip.c
@@ -0,0 +1,657 @@
+/*
+ * L2TPv3 IP encapsulation support
+ *
+ * Copyright (c) 2008,2009,2010 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 <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/tcp_states.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+
+#include "l2tp_core.h"
+
+struct l2tp_ip_sock {
+	/* inet_sock has to be the first member of l2tp_ip_sock */
+	struct inet_sock	inet;
+
+	u32			conn_id;
+	u32			peer_conn_id;
+};
+
+static DEFINE_RWLOCK(l2tp_ip_lock);
+static struct hlist_head l2tp_ip_table;
+static struct hlist_head l2tp_ip_bind_table;
+
+static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk)
+{
+	return (struct l2tp_ip_sock *)sk;
+}
+
+static struct sock *__l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id)
+{
+	struct sock *sk;
+
+	sk_for_each_bound(sk, &l2tp_ip_bind_table) {
+		struct inet_sock *inet = inet_sk(sk);
+		struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk);
+
+		if (l2tp == NULL)
+			continue;
+
+		if ((l2tp->conn_id == tunnel_id) &&
+		    net_eq(sock_net(sk), net) &&
+		    !(inet->inet_rcv_saddr && inet->inet_rcv_saddr != laddr) &&
+		    !(sk->sk_bound_dev_if && sk->sk_bound_dev_if != dif))
+			goto found;
+	}
+
+	sk = NULL;
+found:
+	return sk;
+}
+
+static inline struct sock *l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id)
+{
+	struct sock *sk = __l2tp_ip_bind_lookup(net, laddr, dif, tunnel_id);
+	if (sk)
+		sock_hold(sk);
+
+	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_ip_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;
+
+	/* Point to L2TP header */
+	optr = ptr = skb->data;
+
+	if (!pskb_may_pull(skb, 4))
+		goto discard;
+
+	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_find(net, NULL, session_id);
+	if (session == NULL)
+		goto discard;
+
+	tunnel = session->tunnel;
+	if (tunnel == NULL)
+		goto discard;
+
+	/* Trace packet contents, if enabled */
+	if (tunnel->debug & L2TP_MSG_DATA) {
+		length = min(32u, skb->len);
+		if (!pskb_may_pull(skb, length))
+			goto discard;
+
+		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);
+
+	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 != NULL)
+		sk = tunnel->sock;
+	else {
+		struct iphdr *iph = (struct iphdr *) skb_network_header(skb);
+
+		read_lock_bh(&l2tp_ip_lock);
+		sk = __l2tp_ip_bind_lookup(net, iph->daddr, 0, tunnel_id);
+		read_unlock_bh(&l2tp_ip_lock);
+	}
+
+	if (sk == NULL)
+		goto discard;
+
+	sock_hold(sk);
+
+	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
+		goto discard_put;
+
+	nf_reset(skb);
+
+	return sk_receive_skb(sk, skb, 1);
+
+discard_put:
+	sock_put(sk);
+
+discard:
+	kfree_skb(skb);
+	return 0;
+}
+
+static int l2tp_ip_open(struct sock *sk)
+{
+	/* Prevent autobind. We don't have ports. */
+	inet_sk(sk)->inet_num = IPPROTO_L2TP;
+
+	write_lock_bh(&l2tp_ip_lock);
+	sk_add_node(sk, &l2tp_ip_table);
+	write_unlock_bh(&l2tp_ip_lock);
+
+	return 0;
+}
+
+static void l2tp_ip_close(struct sock *sk, long timeout)
+{
+	write_lock_bh(&l2tp_ip_lock);
+	hlist_del_init(&sk->sk_bind_node);
+	sk_del_node_init(sk);
+	write_unlock_bh(&l2tp_ip_lock);
+	sk_common_release(sk);
+}
+
+static void l2tp_ip_destroy_sock(struct sock *sk)
+{
+	struct sk_buff *skb;
+	struct l2tp_tunnel *tunnel = l2tp_sock_to_tunnel(sk);
+
+	while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
+		kfree_skb(skb);
+
+	if (tunnel) {
+		l2tp_tunnel_closeall(tunnel);
+		sock_put(sk);
+	}
+
+	sk_refcnt_debug_dec(sk);
+}
+
+static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr;
+	struct net *net = sock_net(sk);
+	int ret;
+	int chk_addr_ret;
+
+	if (!sock_flag(sk, SOCK_ZAPPED))
+		return -EINVAL;
+	if (addr_len < sizeof(struct sockaddr_l2tpip))
+		return -EINVAL;
+	if (addr->l2tp_family != AF_INET)
+		return -EINVAL;
+
+	ret = -EADDRINUSE;
+	read_lock_bh(&l2tp_ip_lock);
+	if (__l2tp_ip_bind_lookup(net, addr->l2tp_addr.s_addr,
+				  sk->sk_bound_dev_if, addr->l2tp_conn_id))
+		goto out_in_use;
+
+	read_unlock_bh(&l2tp_ip_lock);
+
+	lock_sock(sk);
+	if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip))
+		goto out;
+
+	chk_addr_ret = inet_addr_type(net, addr->l2tp_addr.s_addr);
+	ret = -EADDRNOTAVAIL;
+	if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL &&
+	    chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST)
+		goto out;
+
+	if (addr->l2tp_addr.s_addr)
+		inet->inet_rcv_saddr = inet->inet_saddr = addr->l2tp_addr.s_addr;
+	if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST)
+		inet->inet_saddr = 0;  /* Use device */
+	sk_dst_reset(sk);
+
+	l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id;
+
+	write_lock_bh(&l2tp_ip_lock);
+	sk_add_bind_node(sk, &l2tp_ip_bind_table);
+	sk_del_node_init(sk);
+	write_unlock_bh(&l2tp_ip_lock);
+	ret = 0;
+	sock_reset_flag(sk, SOCK_ZAPPED);
+
+out:
+	release_sock(sk);
+
+	return ret;
+
+out_in_use:
+	read_unlock_bh(&l2tp_ip_lock);
+
+	return ret;
+}
+
+static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr;
+	int rc;
+
+	if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */
+		return -EINVAL;
+
+	if (addr_len < sizeof(*lsa))
+		return -EINVAL;
+
+	if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
+		return -EINVAL;
+
+	rc = ip4_datagram_connect(sk, uaddr, addr_len);
+	if (rc < 0)
+		return rc;
+
+	lock_sock(sk);
+
+	l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
+
+	write_lock_bh(&l2tp_ip_lock);
+	hlist_del_init(&sk->sk_bind_node);
+	sk_add_bind_node(sk, &l2tp_ip_bind_table);
+	write_unlock_bh(&l2tp_ip_lock);
+
+	release_sock(sk);
+	return rc;
+}
+
+static int l2tp_ip_disconnect(struct sock *sk, int flags)
+{
+	if (sock_flag(sk, SOCK_ZAPPED))
+		return 0;
+
+	return udp_disconnect(sk, flags);
+}
+
+static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr,
+			   int *uaddr_len, int peer)
+{
+	struct sock *sk		= sock->sk;
+	struct inet_sock *inet	= inet_sk(sk);
+	struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk);
+	struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr;
+
+	memset(lsa, 0, sizeof(*lsa));
+	lsa->l2tp_family = AF_INET;
+	if (peer) {
+		if (!inet->inet_dport)
+			return -ENOTCONN;
+		lsa->l2tp_conn_id = lsk->peer_conn_id;
+		lsa->l2tp_addr.s_addr = inet->inet_daddr;
+	} else {
+		__be32 addr = inet->inet_rcv_saddr;
+		if (!addr)
+			addr = inet->inet_saddr;
+		lsa->l2tp_conn_id = lsk->conn_id;
+		lsa->l2tp_addr.s_addr = addr;
+	}
+	*uaddr_len = sizeof(*lsa);
+	return 0;
+}
+
+static int l2tp_ip_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;
+}
+
+/* Userspace will call sendmsg() on the tunnel socket to send L2TP
+ * control frames.
+ */
+static int l2tp_ip_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
+{
+	struct sk_buff *skb;
+	int rc;
+	struct inet_sock *inet = inet_sk(sk);
+	struct rtable *rt = NULL;
+	struct flowi4 *fl4;
+	int connected = 0;
+	__be32 daddr;
+
+	lock_sock(sk);
+
+	rc = -ENOTCONN;
+	if (sock_flag(sk, SOCK_DEAD))
+		goto out;
+
+	/* Get and verify the address. */
+	if (msg->msg_name) {
+		DECLARE_SOCKADDR(struct sockaddr_l2tpip *, lip, msg->msg_name);
+		rc = -EINVAL;
+		if (msg->msg_namelen < sizeof(*lip))
+			goto out;
+
+		if (lip->l2tp_family != AF_INET) {
+			rc = -EAFNOSUPPORT;
+			if (lip->l2tp_family != AF_UNSPEC)
+				goto out;
+		}
+
+		daddr = lip->l2tp_addr.s_addr;
+	} else {
+		rc = -EDESTADDRREQ;
+		if (sk->sk_state != TCP_ESTABLISHED)
+			goto out;
+
+		daddr = inet->inet_daddr;
+		connected = 1;
+	}
+
+	/* Allocate a socket buffer */
+	rc = -ENOMEM;
+	skb = sock_wmalloc(sk, 2 + NET_SKB_PAD + sizeof(struct iphdr) +
+			   4 + len, 0, GFP_KERNEL);
+	if (!skb)
+		goto error;
+
+	/* Reserve space for headers, putting IP header on 4-byte boundary. */
+	skb_reserve(skb, 2 + NET_SKB_PAD);
+	skb_reset_network_header(skb);
+	skb_reserve(skb, sizeof(struct iphdr));
+	skb_reset_transport_header(skb);
+
+	/* Insert 0 session_id */
+	*((__be32 *) skb_put(skb, 4)) = 0;
+
+	/* Copy user data into skb */
+	rc = memcpy_from_msg(skb_put(skb, len), msg, len);
+	if (rc < 0) {
+		kfree_skb(skb);
+		goto error;
+	}
+
+	fl4 = &inet->cork.fl.u.ip4;
+	if (connected)
+		rt = (struct rtable *) __sk_dst_check(sk, 0);
+
+	rcu_read_lock();
+	if (rt == NULL) {
+		const struct ip_options_rcu *inet_opt;
+
+		inet_opt = rcu_dereference(inet->inet_opt);
+
+		/* Use correct destination address if we have options. */
+		if (inet_opt && inet_opt->opt.srr)
+			daddr = inet_opt->opt.faddr;
+
+		/* If this fails, retransmit mechanism of transport layer will
+		 * keep trying until route appears or the connection times
+		 * itself out.
+		 */
+		rt = ip_route_output_ports(sock_net(sk), fl4, sk,
+					   daddr, inet->inet_saddr,
+					   inet->inet_dport, inet->inet_sport,
+					   sk->sk_protocol, RT_CONN_FLAGS(sk),
+					   sk->sk_bound_dev_if);
+		if (IS_ERR(rt))
+			goto no_route;
+		if (connected) {
+			sk_setup_caps(sk, &rt->dst);
+		} else {
+			skb_dst_set(skb, &rt->dst);
+			goto xmit;
+		}
+	}
+
+	/* We dont need to clone dst here, it is guaranteed to not disappear.
+	 *  __dev_xmit_skb() might force a refcount if needed.
+	 */
+	skb_dst_set_noref(skb, &rt->dst);
+
+xmit:
+	/* Queue the packet to IP for output */
+	rc = ip_queue_xmit(sk, skb, &inet->cork.fl);
+	rcu_read_unlock();
+
+error:
+	if (rc >= 0)
+		rc = len;
+
+out:
+	release_sock(sk);
+	return rc;
+
+no_route:
+	rcu_read_unlock();
+	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
+	kfree_skb(skb);
+	rc = -EHOSTUNREACH;
+	goto out;
+}
+
+static int l2tp_ip_recvmsg(struct sock *sk, struct msghdr *msg,
+			   size_t len, int noblock, int flags, int *addr_len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	size_t copied = 0;
+	int err = -EOPNOTSUPP;
+	DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
+	struct sk_buff *skb;
+
+	if (flags & MSG_OOB)
+		goto out;
+
+	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 (sin) {
+		sin->sin_family = AF_INET;
+		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
+		sin->sin_port = 0;
+		memset(&sin->sin_zero, 0, sizeof(sin->sin_zero));
+		*addr_len = sizeof(*sin);
+	}
+	if (inet->cmsg_flags)
+		ip_cmsg_recv(msg, skb);
+	if (flags & MSG_TRUNC)
+		copied = skb->len;
+done:
+	skb_free_datagram(sk, skb);
+out:
+	return err ? err : copied;
+}
+
+static struct proto l2tp_ip_prot = {
+	.name		   = "L2TP/IP",
+	.owner		   = THIS_MODULE,
+	.init		   = l2tp_ip_open,
+	.close		   = l2tp_ip_close,
+	.bind		   = l2tp_ip_bind,
+	.connect	   = l2tp_ip_connect,
+	.disconnect	   = l2tp_ip_disconnect,
+	.ioctl		   = udp_ioctl,
+	.destroy	   = l2tp_ip_destroy_sock,
+	.setsockopt	   = ip_setsockopt,
+	.getsockopt	   = ip_getsockopt,
+	.sendmsg	   = l2tp_ip_sendmsg,
+	.recvmsg	   = l2tp_ip_recvmsg,
+	.backlog_rcv	   = l2tp_ip_backlog_recv,
+	.hash		   = inet_hash,
+	.unhash		   = inet_unhash,
+	.obj_size	   = sizeof(struct l2tp_ip_sock),
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt = compat_ip_setsockopt,
+	.compat_getsockopt = compat_ip_getsockopt,
+#endif
+};
+
+static const struct proto_ops l2tp_ip_ops = {
+	.family		   = PF_INET,
+	.owner		   = THIS_MODULE,
+	.release	   = inet_release,
+	.bind		   = inet_bind,
+	.connect	   = inet_dgram_connect,
+	.socketpair	   = sock_no_socketpair,
+	.accept		   = sock_no_accept,
+	.getname	   = l2tp_ip_getname,
+	.poll		   = datagram_poll,
+	.ioctl		   = inet_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_ip_protosw = {
+	.type		= SOCK_DGRAM,
+	.protocol	= IPPROTO_L2TP,
+	.prot		= &l2tp_ip_prot,
+	.ops		= &l2tp_ip_ops,
+};
+
+static struct net_protocol l2tp_ip_protocol __read_mostly = {
+	.handler	= l2tp_ip_recv,
+	.netns_ok	= 1,
+};
+
+static int __init l2tp_ip_init(void)
+{
+	int err;
+
+	pr_info("L2TP IP encapsulation support (L2TPv3)\n");
+
+	err = proto_register(&l2tp_ip_prot, 1);
+	if (err != 0)
+		goto out;
+
+	err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
+	if (err)
+		goto out1;
+
+	inet_register_protosw(&l2tp_ip_protosw);
+	return 0;
+
+out1:
+	proto_unregister(&l2tp_ip_prot);
+out:
+	return err;
+}
+
+static void __exit l2tp_ip_exit(void)
+{
+	inet_unregister_protosw(&l2tp_ip_protosw);
+	inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
+	proto_unregister(&l2tp_ip_prot);
+}
+
+module_init(l2tp_ip_init);
+module_exit(l2tp_ip_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("L2TP over IP");
+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_INET, 2, IPPROTO_L2TP);
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
new file mode 100644
index 000000000..d1ded3777
--- /dev/null
+++ b/net/l2tp/l2tp_ip6.c
@@ -0,0 +1,803 @@
+/*
+ * 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/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,
+					   int dif, u32 tunnel_id)
+{
+	struct sock *sk;
+
+	sk_for_each_bound(sk, &l2tp_ip6_bind_table) {
+		const struct in6_addr *addr = inet6_rcv_saddr(sk);
+		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) &&
+		    !(addr && ipv6_addr_equal(addr, laddr)) &&
+		    !(sk->sk_bound_dev_if && sk->sk_bound_dev_if != dif))
+			goto found;
+	}
+
+	sk = NULL;
+found:
+	return sk;
+}
+
+static inline struct sock *l2tp_ip6_bind_lookup(struct net *net,
+						struct in6_addr *laddr,
+						int dif, u32 tunnel_id)
+{
+	struct sock *sk = __l2tp_ip6_bind_lookup(net, laddr, dif, tunnel_id);
+	if (sk)
+		sock_hold(sk);
+
+	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 sock *sk;
+	u32 session_id;
+	u32 tunnel_id;
+	unsigned char *ptr, *optr;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel = NULL;
+	int length;
+
+	/* Point to L2TP header */
+	optr = ptr = skb->data;
+
+	if (!pskb_may_pull(skb, 4))
+		goto discard;
+
+	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_find(&init_net, NULL, session_id);
+	if (session == NULL)
+		goto discard;
+
+	tunnel = session->tunnel;
+	if (tunnel == NULL)
+		goto discard;
+
+	/* Trace packet contents, if enabled */
+	if (tunnel->debug & L2TP_MSG_DATA) {
+		length = min(32u, skb->len);
+		if (!pskb_may_pull(skb, length))
+			goto discard;
+
+		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);
+	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(&init_net, tunnel_id);
+	if (tunnel != NULL)
+		sk = tunnel->sock;
+	else {
+		struct ipv6hdr *iph = ipv6_hdr(skb);
+
+		read_lock_bh(&l2tp_ip6_lock);
+		sk = __l2tp_ip6_bind_lookup(&init_net, &iph->daddr,
+					    0, tunnel_id);
+		read_unlock_bh(&l2tp_ip6_lock);
+	}
+
+	if (sk == NULL)
+		goto discard;
+
+	sock_hold(sk);
+
+	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
+		goto discard_put;
+
+	nf_reset(skb);
+
+	return sk_receive_skb(sk, skb, 1);
+
+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;
+	__be32 v4addr = 0;
+	int addr_type;
+	int err;
+
+	if (!sock_flag(sk, SOCK_ZAPPED))
+		return -EINVAL;
+	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;
+
+	err = -EADDRINUSE;
+	read_lock_bh(&l2tp_ip6_lock);
+	if (__l2tp_ip6_bind_lookup(&init_net, &addr->l2tp_addr,
+				   sk->sk_bound_dev_if, addr->l2tp_conn_id))
+		goto out_in_use;
+	read_unlock_bh(&l2tp_ip6_lock);
+
+	lock_sock(sk);
+
+	err = -EINVAL;
+	if (sk->sk_state != TCP_CLOSE)
+		goto out_unlock;
+
+	/* 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_len >= sizeof(struct sockaddr_in6) &&
+			    addr->l2tp_scope_id) {
+				/* Override any existing binding, if another
+				 * one is supplied by user.
+				 */
+				sk->sk_bound_dev_if = addr->l2tp_scope_id;
+			}
+
+			/* Binding to link-local address requires an
+			   interface */
+			if (!sk->sk_bound_dev_if)
+				goto out_unlock_rcu;
+
+			err = -ENODEV;
+			dev = dev_get_by_index_rcu(sock_net(sk),
+						   sk->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();
+
+	inet->inet_rcv_saddr = inet->inet_saddr = v4addr;
+	sk->sk_v6_rcv_saddr = addr->l2tp_addr;
+	np->saddr = addr->l2tp_addr;
+
+	l2tp_ip6_sk(sk)->conn_id = addr->l2tp_conn_id;
+
+	write_lock_bh(&l2tp_ip6_lock);
+	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;
+
+out_in_use:
+	read_unlock_bh(&l2tp_ip6_lock);
+	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 (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */
+		return -EINVAL;
+
+	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;
+	}
+
+	rc = ip6_datagram_connect(sk, uaddr, addr_len);
+
+	lock_sock(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);
+
+	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(&init_net, 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 = NULL;
+	struct ip6_flowlabel *flowlabel = NULL;
+	struct dst_entry *dst = NULL;
+	struct flowi6 fl6;
+	int addr_len = msg->msg_namelen;
+	int hlimit = -1;
+	int tclass = -1;
+	int dontfrag = -1;
+	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;
+
+	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);
+
+		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, opt,
+					    &hlimit, &tclass, &dontfrag);
+		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 == NULL)
+		opt = np->opt;
+	if (flowlabel)
+		opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	opt = ipv6_fixup_options(&opt_space, 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));
+
+	dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
+	if (IS_ERR(dst)) {
+		err = PTR_ERR(dst);
+		goto out;
+	}
+
+	if (hlimit < 0)
+		hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);
+
+	if (tclass < 0)
+		tclass = np->tclass;
+
+	if (dontfrag < 0)
+		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, hlimit, tclass, opt,
+			      &fl6, (struct rt6_info *)dst,
+			      msg->msg_flags, dontfrag);
+	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);
+
+	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		   = udp_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		   = inet_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);
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
new file mode 100644
index 000000000..9e13c2ff8
--- /dev/null
+++ b/net/l2tp/l2tp_netlink.c
@@ -0,0 +1,999 @@
+/*
+ * L2TP netlink layer, for management
+ *
+ * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
+ *
+ * Partly based on the IrDA nelink implementation
+ * (see net/irda/irnetlink.c) which is:
+ * Copyright (c) 2007 Samuel Ortiz <samuel@sortiz.org>
+ * which is in turn partly based on the wireless netlink code:
+ * Copyright 2006 Johannes Berg <johannes@sipsolutions.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <net/sock.h>
+#include <net/genetlink.h>
+#include <net/udp.h>
+#include <linux/in.h>
+#include <linux/udp.h>
+#include <linux/socket.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <net/net_namespace.h>
+
+#include <linux/l2tp.h>
+
+#include "l2tp_core.h"
+
+
+static struct genl_family l2tp_nl_family = {
+	.id		= GENL_ID_GENERATE,
+	.name		= L2TP_GENL_NAME,
+	.version	= L2TP_GENL_VERSION,
+	.hdrsize	= 0,
+	.maxattr	= L2TP_ATTR_MAX,
+	.netnsok	= true,
+};
+
+static const struct genl_multicast_group l2tp_multicast_group[] = {
+	{
+		.name = L2TP_GENL_MCGROUP,
+	},
+};
+
+static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq,
+			       int flags, struct l2tp_tunnel *tunnel, u8 cmd);
+static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq,
+				int flags, struct l2tp_session *session,
+				u8 cmd);
+
+/* Accessed under genl lock */
+static const struct l2tp_nl_cmd_ops *l2tp_nl_cmd_ops[__L2TP_PWTYPE_MAX];
+
+static struct l2tp_session *l2tp_nl_session_find(struct genl_info *info)
+{
+	u32 tunnel_id;
+	u32 session_id;
+	char *ifname;
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session = NULL;
+	struct net *net = genl_info_net(info);
+
+	if (info->attrs[L2TP_ATTR_IFNAME]) {
+		ifname = nla_data(info->attrs[L2TP_ATTR_IFNAME]);
+		session = l2tp_session_find_by_ifname(net, ifname);
+	} else if ((info->attrs[L2TP_ATTR_SESSION_ID]) &&
+		   (info->attrs[L2TP_ATTR_CONN_ID])) {
+		tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+		session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
+		tunnel = l2tp_tunnel_find(net, tunnel_id);
+		if (tunnel)
+			session = l2tp_session_find(net, tunnel, session_id);
+	}
+
+	return session;
+}
+
+static int l2tp_nl_cmd_noop(struct sk_buff *skb, struct genl_info *info)
+{
+	struct sk_buff *msg;
+	void *hdr;
+	int ret = -ENOBUFS;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
+			  &l2tp_nl_family, 0, L2TP_CMD_NOOP);
+	if (!hdr) {
+		ret = -EMSGSIZE;
+		goto err_out;
+	}
+
+	genlmsg_end(msg, hdr);
+
+	return genlmsg_unicast(genl_info_net(info), msg, info->snd_portid);
+
+err_out:
+	nlmsg_free(msg);
+
+out:
+	return ret;
+}
+
+static int l2tp_tunnel_notify(struct genl_family *family,
+			      struct genl_info *info,
+			      struct l2tp_tunnel *tunnel,
+			      u8 cmd)
+{
+	struct sk_buff *msg;
+	int ret;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	ret = l2tp_nl_tunnel_send(msg, info->snd_portid, info->snd_seq,
+				  NLM_F_ACK, tunnel, cmd);
+
+	if (ret >= 0)
+		return genlmsg_multicast_allns(family, msg, 0,	0, GFP_ATOMIC);
+
+	nlmsg_free(msg);
+
+	return ret;
+}
+
+static int l2tp_session_notify(struct genl_family *family,
+			       struct genl_info *info,
+			       struct l2tp_session *session,
+			       u8 cmd)
+{
+	struct sk_buff *msg;
+	int ret;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	ret = l2tp_nl_session_send(msg, info->snd_portid, info->snd_seq,
+				   NLM_F_ACK, session, cmd);
+
+	if (ret >= 0)
+		return genlmsg_multicast_allns(family, msg, 0,	0, GFP_ATOMIC);
+
+	nlmsg_free(msg);
+
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info)
+{
+	u32 tunnel_id;
+	u32 peer_tunnel_id;
+	int proto_version;
+	int fd;
+	int ret = 0;
+	struct l2tp_tunnel_cfg cfg = { 0, };
+	struct l2tp_tunnel *tunnel;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PEER_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	peer_tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_CONN_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PROTO_VERSION]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	proto_version = nla_get_u8(info->attrs[L2TP_ATTR_PROTO_VERSION]);
+
+	if (!info->attrs[L2TP_ATTR_ENCAP_TYPE]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	cfg.encap = nla_get_u16(info->attrs[L2TP_ATTR_ENCAP_TYPE]);
+
+	fd = -1;
+	if (info->attrs[L2TP_ATTR_FD]) {
+		fd = nla_get_u32(info->attrs[L2TP_ATTR_FD]);
+	} else {
+#if IS_ENABLED(CONFIG_IPV6)
+		if (info->attrs[L2TP_ATTR_IP6_SADDR] &&
+		    info->attrs[L2TP_ATTR_IP6_DADDR]) {
+			cfg.local_ip6 = nla_data(
+				info->attrs[L2TP_ATTR_IP6_SADDR]);
+			cfg.peer_ip6 = nla_data(
+				info->attrs[L2TP_ATTR_IP6_DADDR]);
+		} else
+#endif
+		if (info->attrs[L2TP_ATTR_IP_SADDR] &&
+		    info->attrs[L2TP_ATTR_IP_DADDR]) {
+			cfg.local_ip.s_addr = nla_get_in_addr(
+				info->attrs[L2TP_ATTR_IP_SADDR]);
+			cfg.peer_ip.s_addr = nla_get_in_addr(
+				info->attrs[L2TP_ATTR_IP_DADDR]);
+		} else {
+			ret = -EINVAL;
+			goto out;
+		}
+		if (info->attrs[L2TP_ATTR_UDP_SPORT])
+			cfg.local_udp_port = nla_get_u16(info->attrs[L2TP_ATTR_UDP_SPORT]);
+		if (info->attrs[L2TP_ATTR_UDP_DPORT])
+			cfg.peer_udp_port = nla_get_u16(info->attrs[L2TP_ATTR_UDP_DPORT]);
+		if (info->attrs[L2TP_ATTR_UDP_CSUM])
+			cfg.use_udp_checksums = nla_get_flag(info->attrs[L2TP_ATTR_UDP_CSUM]);
+
+#if IS_ENABLED(CONFIG_IPV6)
+		if (info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX])
+			cfg.udp6_zero_tx_checksums = nla_get_flag(info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX]);
+		if (info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX])
+			cfg.udp6_zero_rx_checksums = nla_get_flag(info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX]);
+#endif
+	}
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		cfg.debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel != NULL) {
+		ret = -EEXIST;
+		goto out;
+	}
+
+	ret = -EINVAL;
+	switch (cfg.encap) {
+	case L2TP_ENCAPTYPE_UDP:
+	case L2TP_ENCAPTYPE_IP:
+		ret = l2tp_tunnel_create(net, fd, proto_version, tunnel_id,
+					 peer_tunnel_id, &cfg, &tunnel);
+		break;
+	}
+
+	if (ret >= 0)
+		ret = l2tp_tunnel_notify(&l2tp_nl_family, info,
+					 tunnel, L2TP_CMD_TUNNEL_CREATE);
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_delete(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_tunnel *tunnel;
+	u32 tunnel_id;
+	int ret = 0;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	l2tp_tunnel_notify(&l2tp_nl_family, info,
+			   tunnel, L2TP_CMD_TUNNEL_DELETE);
+
+	(void) l2tp_tunnel_delete(tunnel);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_modify(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_tunnel *tunnel;
+	u32 tunnel_id;
+	int ret = 0;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		tunnel->debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+	ret = l2tp_tunnel_notify(&l2tp_nl_family, info,
+				 tunnel, L2TP_CMD_TUNNEL_MODIFY);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int flags,
+			       struct l2tp_tunnel *tunnel, u8 cmd)
+{
+	void *hdr;
+	struct nlattr *nest;
+	struct sock *sk = NULL;
+	struct inet_sock *inet;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct ipv6_pinfo *np = NULL;
+#endif
+
+	hdr = genlmsg_put(skb, portid, seq, &l2tp_nl_family, flags, cmd);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (nla_put_u8(skb, L2TP_ATTR_PROTO_VERSION, tunnel->version) ||
+	    nla_put_u32(skb, L2TP_ATTR_CONN_ID, tunnel->tunnel_id) ||
+	    nla_put_u32(skb, L2TP_ATTR_PEER_CONN_ID, tunnel->peer_tunnel_id) ||
+	    nla_put_u32(skb, L2TP_ATTR_DEBUG, tunnel->debug) ||
+	    nla_put_u16(skb, L2TP_ATTR_ENCAP_TYPE, tunnel->encap))
+		goto nla_put_failure;
+
+	nest = nla_nest_start(skb, L2TP_ATTR_STATS);
+	if (nest == NULL)
+		goto nla_put_failure;
+
+	if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS,
+		    atomic_long_read(&tunnel->stats.tx_packets)) ||
+	    nla_put_u64(skb, L2TP_ATTR_TX_BYTES,
+		    atomic_long_read(&tunnel->stats.tx_bytes)) ||
+	    nla_put_u64(skb, L2TP_ATTR_TX_ERRORS,
+		    atomic_long_read(&tunnel->stats.tx_errors)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_PACKETS,
+		    atomic_long_read(&tunnel->stats.rx_packets)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_BYTES,
+		    atomic_long_read(&tunnel->stats.rx_bytes)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
+		    atomic_long_read(&tunnel->stats.rx_seq_discards)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_OOS_PACKETS,
+		    atomic_long_read(&tunnel->stats.rx_oos_packets)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_ERRORS,
+		    atomic_long_read(&tunnel->stats.rx_errors)))
+		goto nla_put_failure;
+	nla_nest_end(skb, nest);
+
+	sk = tunnel->sock;
+	if (!sk)
+		goto out;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == AF_INET6)
+		np = inet6_sk(sk);
+#endif
+
+	inet = inet_sk(sk);
+
+	switch (tunnel->encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		if (nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
+		    nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)) ||
+		    nla_put_u8(skb, L2TP_ATTR_UDP_CSUM, !sk->sk_no_check_tx))
+			goto nla_put_failure;
+		/* NOBREAK */
+	case L2TP_ENCAPTYPE_IP:
+#if IS_ENABLED(CONFIG_IPV6)
+		if (np) {
+			if (nla_put_in6_addr(skb, L2TP_ATTR_IP6_SADDR,
+					     &np->saddr) ||
+			    nla_put_in6_addr(skb, L2TP_ATTR_IP6_DADDR,
+					     &sk->sk_v6_daddr))
+				goto nla_put_failure;
+		} else
+#endif
+		if (nla_put_in_addr(skb, L2TP_ATTR_IP_SADDR,
+				    inet->inet_saddr) ||
+		    nla_put_in_addr(skb, L2TP_ATTR_IP_DADDR,
+				    inet->inet_daddr))
+			goto nla_put_failure;
+		break;
+	}
+
+out:
+	genlmsg_end(skb, hdr);
+	return 0;
+
+nla_put_failure:
+	genlmsg_cancel(skb, hdr);
+	return -1;
+}
+
+static int l2tp_nl_cmd_tunnel_get(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_tunnel *tunnel;
+	struct sk_buff *msg;
+	u32 tunnel_id;
+	int ret = -ENOBUFS;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = l2tp_nl_tunnel_send(msg, info->snd_portid, info->snd_seq,
+				  NLM_F_ACK, tunnel, L2TP_CMD_TUNNEL_GET);
+	if (ret < 0)
+		goto err_out;
+
+	return genlmsg_unicast(net, msg, info->snd_portid);
+
+err_out:
+	nlmsg_free(msg);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_dump(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	int ti = cb->args[0];
+	struct l2tp_tunnel *tunnel;
+	struct net *net = sock_net(skb->sk);
+
+	for (;;) {
+		tunnel = l2tp_tunnel_find_nth(net, ti);
+		if (tunnel == NULL)
+			goto out;
+
+		if (l2tp_nl_tunnel_send(skb, NETLINK_CB(cb->skb).portid,
+					cb->nlh->nlmsg_seq, NLM_F_MULTI,
+					tunnel, L2TP_CMD_TUNNEL_GET) < 0)
+			goto out;
+
+		ti++;
+	}
+
+out:
+	cb->args[0] = ti;
+
+	return skb->len;
+}
+
+static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *info)
+{
+	u32 tunnel_id = 0;
+	u32 session_id;
+	u32 peer_session_id;
+	int ret = 0;
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;
+	struct l2tp_session_cfg cfg = { 0, };
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (!tunnel) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (!info->attrs[L2TP_ATTR_SESSION_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
+	session = l2tp_session_find(net, tunnel, session_id);
+	if (session) {
+		ret = -EEXIST;
+		goto out;
+	}
+
+	if (!info->attrs[L2TP_ATTR_PEER_SESSION_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	peer_session_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_SESSION_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PW_TYPE]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	cfg.pw_type = nla_get_u16(info->attrs[L2TP_ATTR_PW_TYPE]);
+	if (cfg.pw_type >= __L2TP_PWTYPE_MAX) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (tunnel->version > 2) {
+		if (info->attrs[L2TP_ATTR_OFFSET])
+			cfg.offset = nla_get_u16(info->attrs[L2TP_ATTR_OFFSET]);
+
+		if (info->attrs[L2TP_ATTR_DATA_SEQ])
+			cfg.data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);
+
+		cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
+		if (info->attrs[L2TP_ATTR_L2SPEC_TYPE])
+			cfg.l2specific_type = nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_TYPE]);
+
+		cfg.l2specific_len = 4;
+		if (info->attrs[L2TP_ATTR_L2SPEC_LEN])
+			cfg.l2specific_len = nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_LEN]);
+
+		if (info->attrs[L2TP_ATTR_COOKIE]) {
+			u16 len = nla_len(info->attrs[L2TP_ATTR_COOKIE]);
+			if (len > 8) {
+				ret = -EINVAL;
+				goto out;
+			}
+			cfg.cookie_len = len;
+			memcpy(&cfg.cookie[0], nla_data(info->attrs[L2TP_ATTR_COOKIE]), len);
+		}
+		if (info->attrs[L2TP_ATTR_PEER_COOKIE]) {
+			u16 len = nla_len(info->attrs[L2TP_ATTR_PEER_COOKIE]);
+			if (len > 8) {
+				ret = -EINVAL;
+				goto out;
+			}
+			cfg.peer_cookie_len = len;
+			memcpy(&cfg.peer_cookie[0], nla_data(info->attrs[L2TP_ATTR_PEER_COOKIE]), len);
+		}
+		if (info->attrs[L2TP_ATTR_IFNAME])
+			cfg.ifname = nla_data(info->attrs[L2TP_ATTR_IFNAME]);
+
+		if (info->attrs[L2TP_ATTR_VLAN_ID])
+			cfg.vlan_id = nla_get_u16(info->attrs[L2TP_ATTR_VLAN_ID]);
+	}
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		cfg.debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+	if (info->attrs[L2TP_ATTR_RECV_SEQ])
+		cfg.recv_seq = nla_get_u8(info->attrs[L2TP_ATTR_RECV_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_SEND_SEQ])
+		cfg.send_seq = nla_get_u8(info->attrs[L2TP_ATTR_SEND_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_LNS_MODE])
+		cfg.lns_mode = nla_get_u8(info->attrs[L2TP_ATTR_LNS_MODE]);
+
+	if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
+		cfg.reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
+
+	if (info->attrs[L2TP_ATTR_MTU])
+		cfg.mtu = nla_get_u16(info->attrs[L2TP_ATTR_MTU]);
+
+	if (info->attrs[L2TP_ATTR_MRU])
+		cfg.mru = nla_get_u16(info->attrs[L2TP_ATTR_MRU]);
+
+	if ((l2tp_nl_cmd_ops[cfg.pw_type] == NULL) ||
+	    (l2tp_nl_cmd_ops[cfg.pw_type]->session_create == NULL)) {
+		ret = -EPROTONOSUPPORT;
+		goto out;
+	}
+
+	/* Check that pseudowire-specific params are present */
+	switch (cfg.pw_type) {
+	case L2TP_PWTYPE_NONE:
+		break;
+	case L2TP_PWTYPE_ETH_VLAN:
+		if (!info->attrs[L2TP_ATTR_VLAN_ID]) {
+			ret = -EINVAL;
+			goto out;
+		}
+		break;
+	case L2TP_PWTYPE_ETH:
+		break;
+	case L2TP_PWTYPE_PPP:
+	case L2TP_PWTYPE_PPP_AC:
+		break;
+	case L2TP_PWTYPE_IP:
+	default:
+		ret = -EPROTONOSUPPORT;
+		break;
+	}
+
+	ret = -EPROTONOSUPPORT;
+	if (l2tp_nl_cmd_ops[cfg.pw_type]->session_create)
+		ret = (*l2tp_nl_cmd_ops[cfg.pw_type]->session_create)(net, tunnel_id,
+			session_id, peer_session_id, &cfg);
+
+	if (ret >= 0) {
+		session = l2tp_session_find(net, tunnel, session_id);
+		if (session)
+			ret = l2tp_session_notify(&l2tp_nl_family, info, session,
+						  L2TP_CMD_SESSION_CREATE);
+	}
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_session_delete(struct sk_buff *skb, struct genl_info *info)
+{
+	int ret = 0;
+	struct l2tp_session *session;
+	u16 pw_type;
+
+	session = l2tp_nl_session_find(info);
+	if (session == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	l2tp_session_notify(&l2tp_nl_family, info,
+			    session, L2TP_CMD_SESSION_DELETE);
+
+	pw_type = session->pwtype;
+	if (pw_type < __L2TP_PWTYPE_MAX)
+		if (l2tp_nl_cmd_ops[pw_type] && l2tp_nl_cmd_ops[pw_type]->session_delete)
+			ret = (*l2tp_nl_cmd_ops[pw_type]->session_delete)(session);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *info)
+{
+	int ret = 0;
+	struct l2tp_session *session;
+
+	session = l2tp_nl_session_find(info);
+	if (session == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		session->debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+	if (info->attrs[L2TP_ATTR_DATA_SEQ])
+		session->data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_RECV_SEQ])
+		session->recv_seq = nla_get_u8(info->attrs[L2TP_ATTR_RECV_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_SEND_SEQ]) {
+		session->send_seq = nla_get_u8(info->attrs[L2TP_ATTR_SEND_SEQ]);
+		l2tp_session_set_header_len(session, session->tunnel->version);
+	}
+
+	if (info->attrs[L2TP_ATTR_LNS_MODE])
+		session->lns_mode = nla_get_u8(info->attrs[L2TP_ATTR_LNS_MODE]);
+
+	if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
+		session->reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
+
+	if (info->attrs[L2TP_ATTR_MTU])
+		session->mtu = nla_get_u16(info->attrs[L2TP_ATTR_MTU]);
+
+	if (info->attrs[L2TP_ATTR_MRU])
+		session->mru = nla_get_u16(info->attrs[L2TP_ATTR_MRU]);
+
+	ret = l2tp_session_notify(&l2tp_nl_family, info,
+				  session, L2TP_CMD_SESSION_MODIFY);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int flags,
+				struct l2tp_session *session, u8 cmd)
+{
+	void *hdr;
+	struct nlattr *nest;
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	struct sock *sk = NULL;
+
+	sk = tunnel->sock;
+
+	hdr = genlmsg_put(skb, portid, seq, &l2tp_nl_family, flags, cmd);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(skb, L2TP_ATTR_CONN_ID, tunnel->tunnel_id) ||
+	    nla_put_u32(skb, L2TP_ATTR_SESSION_ID, session->session_id) ||
+	    nla_put_u32(skb, L2TP_ATTR_PEER_CONN_ID, tunnel->peer_tunnel_id) ||
+	    nla_put_u32(skb, L2TP_ATTR_PEER_SESSION_ID,
+			session->peer_session_id) ||
+	    nla_put_u32(skb, L2TP_ATTR_DEBUG, session->debug) ||
+	    nla_put_u16(skb, L2TP_ATTR_PW_TYPE, session->pwtype) ||
+	    nla_put_u16(skb, L2TP_ATTR_MTU, session->mtu) ||
+	    (session->mru &&
+	     nla_put_u16(skb, L2TP_ATTR_MRU, session->mru)))
+		goto nla_put_failure;
+
+	if ((session->ifname[0] &&
+	     nla_put_string(skb, L2TP_ATTR_IFNAME, session->ifname)) ||
+	    (session->cookie_len &&
+	     nla_put(skb, L2TP_ATTR_COOKIE, session->cookie_len,
+		     &session->cookie[0])) ||
+	    (session->peer_cookie_len &&
+	     nla_put(skb, L2TP_ATTR_PEER_COOKIE, session->peer_cookie_len,
+		     &session->peer_cookie[0])) ||
+	    nla_put_u8(skb, L2TP_ATTR_RECV_SEQ, session->recv_seq) ||
+	    nla_put_u8(skb, L2TP_ATTR_SEND_SEQ, session->send_seq) ||
+	    nla_put_u8(skb, L2TP_ATTR_LNS_MODE, session->lns_mode) ||
+#ifdef CONFIG_XFRM
+	    (((sk) && (sk->sk_policy[0] || sk->sk_policy[1])) &&
+	     nla_put_u8(skb, L2TP_ATTR_USING_IPSEC, 1)) ||
+#endif
+	    (session->reorder_timeout &&
+	     nla_put_msecs(skb, L2TP_ATTR_RECV_TIMEOUT, session->reorder_timeout)))
+		goto nla_put_failure;
+
+	nest = nla_nest_start(skb, L2TP_ATTR_STATS);
+	if (nest == NULL)
+		goto nla_put_failure;
+
+	if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS,
+		atomic_long_read(&session->stats.tx_packets)) ||
+	    nla_put_u64(skb, L2TP_ATTR_TX_BYTES,
+		atomic_long_read(&session->stats.tx_bytes)) ||
+	    nla_put_u64(skb, L2TP_ATTR_TX_ERRORS,
+		atomic_long_read(&session->stats.tx_errors)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_PACKETS,
+		atomic_long_read(&session->stats.rx_packets)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_BYTES,
+		atomic_long_read(&session->stats.rx_bytes)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
+		atomic_long_read(&session->stats.rx_seq_discards)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_OOS_PACKETS,
+		atomic_long_read(&session->stats.rx_oos_packets)) ||
+	    nla_put_u64(skb, L2TP_ATTR_RX_ERRORS,
+		atomic_long_read(&session->stats.rx_errors)))
+		goto nla_put_failure;
+	nla_nest_end(skb, nest);
+
+	genlmsg_end(skb, hdr);
+	return 0;
+
+ nla_put_failure:
+	genlmsg_cancel(skb, hdr);
+	return -1;
+}
+
+static int l2tp_nl_cmd_session_get(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_session *session;
+	struct sk_buff *msg;
+	int ret;
+
+	session = l2tp_nl_session_find(info);
+	if (session == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = l2tp_nl_session_send(msg, info->snd_portid, info->snd_seq,
+				   0, session, L2TP_CMD_SESSION_GET);
+	if (ret < 0)
+		goto err_out;
+
+	return genlmsg_unicast(genl_info_net(info), msg, info->snd_portid);
+
+err_out:
+	nlmsg_free(msg);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct net *net = sock_net(skb->sk);
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel = NULL;
+	int ti = cb->args[0];
+	int si = cb->args[1];
+
+	for (;;) {
+		if (tunnel == NULL) {
+			tunnel = l2tp_tunnel_find_nth(net, ti);
+			if (tunnel == NULL)
+				goto out;
+		}
+
+		session = l2tp_session_find_nth(tunnel, si);
+		if (session == NULL) {
+			ti++;
+			tunnel = NULL;
+			si = 0;
+			continue;
+		}
+
+		if (l2tp_nl_session_send(skb, NETLINK_CB(cb->skb).portid,
+					 cb->nlh->nlmsg_seq, NLM_F_MULTI,
+					 session, L2TP_CMD_SESSION_GET) < 0)
+			break;
+
+		si++;
+	}
+
+out:
+	cb->args[0] = ti;
+	cb->args[1] = si;
+
+	return skb->len;
+}
+
+static struct nla_policy l2tp_nl_policy[L2TP_ATTR_MAX + 1] = {
+	[L2TP_ATTR_NONE]		= { .type = NLA_UNSPEC, },
+	[L2TP_ATTR_PW_TYPE]		= { .type = NLA_U16, },
+	[L2TP_ATTR_ENCAP_TYPE]		= { .type = NLA_U16, },
+	[L2TP_ATTR_OFFSET]		= { .type = NLA_U16, },
+	[L2TP_ATTR_DATA_SEQ]		= { .type = NLA_U8, },
+	[L2TP_ATTR_L2SPEC_TYPE]		= { .type = NLA_U8, },
+	[L2TP_ATTR_L2SPEC_LEN]		= { .type = NLA_U8, },
+	[L2TP_ATTR_PROTO_VERSION]	= { .type = NLA_U8, },
+	[L2TP_ATTR_CONN_ID]		= { .type = NLA_U32, },
+	[L2TP_ATTR_PEER_CONN_ID]	= { .type = NLA_U32, },
+	[L2TP_ATTR_SESSION_ID]		= { .type = NLA_U32, },
+	[L2TP_ATTR_PEER_SESSION_ID]	= { .type = NLA_U32, },
+	[L2TP_ATTR_UDP_CSUM]		= { .type = NLA_U8, },
+	[L2TP_ATTR_VLAN_ID]		= { .type = NLA_U16, },
+	[L2TP_ATTR_DEBUG]		= { .type = NLA_U32, },
+	[L2TP_ATTR_RECV_SEQ]		= { .type = NLA_U8, },
+	[L2TP_ATTR_SEND_SEQ]		= { .type = NLA_U8, },
+	[L2TP_ATTR_LNS_MODE]		= { .type = NLA_U8, },
+	[L2TP_ATTR_USING_IPSEC]		= { .type = NLA_U8, },
+	[L2TP_ATTR_RECV_TIMEOUT]	= { .type = NLA_MSECS, },
+	[L2TP_ATTR_FD]			= { .type = NLA_U32, },
+	[L2TP_ATTR_IP_SADDR]		= { .type = NLA_U32, },
+	[L2TP_ATTR_IP_DADDR]		= { .type = NLA_U32, },
+	[L2TP_ATTR_UDP_SPORT]		= { .type = NLA_U16, },
+	[L2TP_ATTR_UDP_DPORT]		= { .type = NLA_U16, },
+	[L2TP_ATTR_MTU]			= { .type = NLA_U16, },
+	[L2TP_ATTR_MRU]			= { .type = NLA_U16, },
+	[L2TP_ATTR_STATS]		= { .type = NLA_NESTED, },
+	[L2TP_ATTR_IP6_SADDR] = {
+		.type = NLA_BINARY,
+		.len = sizeof(struct in6_addr),
+	},
+	[L2TP_ATTR_IP6_DADDR] = {
+		.type = NLA_BINARY,
+		.len = sizeof(struct in6_addr),
+	},
+	[L2TP_ATTR_IFNAME] = {
+		.type = NLA_NUL_STRING,
+		.len = IFNAMSIZ - 1,
+	},
+	[L2TP_ATTR_COOKIE] = {
+		.type = NLA_BINARY,
+		.len = 8,
+	},
+	[L2TP_ATTR_PEER_COOKIE] = {
+		.type = NLA_BINARY,
+		.len = 8,
+	},
+};
+
+static const struct genl_ops l2tp_nl_ops[] = {
+	{
+		.cmd = L2TP_CMD_NOOP,
+		.doit = l2tp_nl_cmd_noop,
+		.policy = l2tp_nl_policy,
+		/* can be retrieved by unprivileged users */
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_CREATE,
+		.doit = l2tp_nl_cmd_tunnel_create,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_DELETE,
+		.doit = l2tp_nl_cmd_tunnel_delete,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_MODIFY,
+		.doit = l2tp_nl_cmd_tunnel_modify,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_GET,
+		.doit = l2tp_nl_cmd_tunnel_get,
+		.dumpit = l2tp_nl_cmd_tunnel_dump,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_CREATE,
+		.doit = l2tp_nl_cmd_session_create,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_DELETE,
+		.doit = l2tp_nl_cmd_session_delete,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_MODIFY,
+		.doit = l2tp_nl_cmd_session_modify,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_GET,
+		.doit = l2tp_nl_cmd_session_get,
+		.dumpit = l2tp_nl_cmd_session_dump,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+};
+
+int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops)
+{
+	int ret;
+
+	ret = -EINVAL;
+	if (pw_type >= __L2TP_PWTYPE_MAX)
+		goto err;
+
+	genl_lock();
+	ret = -EBUSY;
+	if (l2tp_nl_cmd_ops[pw_type])
+		goto out;
+
+	l2tp_nl_cmd_ops[pw_type] = ops;
+	ret = 0;
+
+out:
+	genl_unlock();
+err:
+	return ret;
+}
+EXPORT_SYMBOL_GPL(l2tp_nl_register_ops);
+
+void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type)
+{
+	if (pw_type < __L2TP_PWTYPE_MAX) {
+		genl_lock();
+		l2tp_nl_cmd_ops[pw_type] = NULL;
+		genl_unlock();
+	}
+}
+EXPORT_SYMBOL_GPL(l2tp_nl_unregister_ops);
+
+static int l2tp_nl_init(void)
+{
+	pr_info("L2TP netlink interface\n");
+	return genl_register_family_with_ops_groups(&l2tp_nl_family,
+						    l2tp_nl_ops,
+						    l2tp_multicast_group);
+}
+
+static void l2tp_nl_cleanup(void)
+{
+	genl_unregister_family(&l2tp_nl_family);
+}
+
+module_init(l2tp_nl_init);
+module_exit(l2tp_nl_cleanup);
+
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("L2TP netlink");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0");
+MODULE_ALIAS_GENL_FAMILY("l2tp");
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
new file mode 100644
index 000000000..e9b0dec56
--- /dev/null
+++ b/net/l2tp/l2tp_ppp.c
@@ -0,0 +1,1865 @@
+/*****************************************************************************
+ * Linux PPP over L2TP (PPPoX/PPPoL2TP) Sockets
+ *
+ * PPPoX    --- Generic PPP encapsulation socket family
+ * PPPoL2TP --- PPP over L2TP (RFC 2661)
+ *
+ * Version:	2.0.0
+ *
+ * Authors:	James Chapman (jchapman@katalix.com)
+ *
+ * Based on original work by Martijn van Oosterhout <kleptog@svana.org>
+ *
+ * License:
+ *		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.
+ *
+ */
+
+/* This driver handles only L2TP data frames; control frames are handled by a
+ * userspace application.
+ *
+ * To send data in an L2TP session, userspace opens a PPPoL2TP socket and
+ * attaches it to a bound UDP socket with local tunnel_id / session_id and
+ * peer tunnel_id / session_id set. Data can then be sent or received using
+ * regular socket sendmsg() / recvmsg() calls. Kernel parameters of the socket
+ * can be read or modified using ioctl() or [gs]etsockopt() calls.
+ *
+ * When a PPPoL2TP socket is connected with local and peer session_id values
+ * zero, the socket is treated as a special tunnel management socket.
+ *
+ * Here's example userspace code to create a socket for sending/receiving data
+ * over an L2TP session:-
+ *
+ *	struct sockaddr_pppol2tp sax;
+ *	int fd;
+ *	int session_fd;
+ *
+ *	fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
+ *
+ *	sax.sa_family = AF_PPPOX;
+ *	sax.sa_protocol = PX_PROTO_OL2TP;
+ *	sax.pppol2tp.fd = tunnel_fd;	// bound UDP socket
+ *	sax.pppol2tp.addr.sin_addr.s_addr = addr->sin_addr.s_addr;
+ *	sax.pppol2tp.addr.sin_port = addr->sin_port;
+ *	sax.pppol2tp.addr.sin_family = AF_INET;
+ *	sax.pppol2tp.s_tunnel  = tunnel_id;
+ *	sax.pppol2tp.s_session = session_id;
+ *	sax.pppol2tp.d_tunnel  = peer_tunnel_id;
+ *	sax.pppol2tp.d_session = peer_session_id;
+ *
+ *	session_fd = connect(fd, (struct sockaddr *)&sax, sizeof(sax));
+ *
+ * A pppd plugin that allows PPP traffic to be carried over L2TP using
+ * this driver is available from the OpenL2TP project at
+ * http://openl2tp.sourceforge.net.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/list.h>
+#include <linux/uaccess.h>
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/kthread.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/jiffies.h>
+
+#include <linux/netdevice.h>
+#include <linux/net.h>
+#include <linux/inetdevice.h>
+#include <linux/skbuff.h>
+#include <linux/init.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <linux/if_pppox.h>
+#include <linux/if_pppol2tp.h>
+#include <net/sock.h>
+#include <linux/ppp_channel.h>
+#include <linux/ppp_defs.h>
+#include <linux/ppp-ioctl.h>
+#include <linux/file.h>
+#include <linux/hash.h>
+#include <linux/sort.h>
+#include <linux/proc_fs.h>
+#include <linux/l2tp.h>
+#include <linux/nsproxy.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <net/dst.h>
+#include <net/ip.h>
+#include <net/udp.h>
+#include <net/xfrm.h>
+#include <net/inet_common.h>
+
+#include <asm/byteorder.h>
+#include <linux/atomic.h>
+
+#include "l2tp_core.h"
+
+#define PPPOL2TP_DRV_VERSION	"V2.0"
+
+/* Space for UDP, L2TP and PPP headers */
+#define PPPOL2TP_HEADER_OVERHEAD	40
+
+/* Number of bytes to build transmit L2TP headers.
+ * Unfortunately the size is different depending on whether sequence numbers
+ * are enabled.
+ */
+#define PPPOL2TP_L2TP_HDR_SIZE_SEQ		10
+#define PPPOL2TP_L2TP_HDR_SIZE_NOSEQ		6
+
+/* Private data of each session. This data lives at the end of struct
+ * l2tp_session, referenced via session->priv[].
+ */
+struct pppol2tp_session {
+	int			owner;		/* pid that opened the socket */
+
+	struct sock		*sock;		/* Pointer to the session
+						 * PPPoX socket */
+	struct sock		*tunnel_sock;	/* Pointer to the tunnel UDP
+						 * socket */
+	int			flags;		/* accessed by PPPIOCGFLAGS.
+						 * Unused. */
+};
+
+static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb);
+
+static const struct ppp_channel_ops pppol2tp_chan_ops = {
+	.start_xmit =  pppol2tp_xmit,
+};
+
+static const struct proto_ops pppol2tp_ops;
+
+/* Helpers to obtain tunnel/session contexts from sockets.
+ */
+static inline struct l2tp_session *pppol2tp_sock_to_session(struct sock *sk)
+{
+	struct l2tp_session *session;
+
+	if (sk == NULL)
+		return NULL;
+
+	sock_hold(sk);
+	session = (struct l2tp_session *)(sk->sk_user_data);
+	if (session == NULL) {
+		sock_put(sk);
+		goto out;
+	}
+
+	BUG_ON(session->magic != L2TP_SESSION_MAGIC);
+
+out:
+	return session;
+}
+
+/*****************************************************************************
+ * Receive data handling
+ *****************************************************************************/
+
+static int pppol2tp_recv_payload_hook(struct sk_buff *skb)
+{
+	/* Skip PPP header, if present.	 In testing, Microsoft L2TP clients
+	 * don't send the PPP header (PPP header compression enabled), but
+	 * other clients can include the header. So we cope with both cases
+	 * here. The PPP header is always FF03 when using L2TP.
+	 *
+	 * Note that skb->data[] isn't dereferenced from a u16 ptr here since
+	 * the field may be unaligned.
+	 */
+	if (!pskb_may_pull(skb, 2))
+		return 1;
+
+	if ((skb->data[0] == 0xff) && (skb->data[1] == 0x03))
+		skb_pull(skb, 2);
+
+	return 0;
+}
+
+/* Receive message. This is the recvmsg for the PPPoL2TP socket.
+ */
+static int pppol2tp_recvmsg(struct socket *sock, struct msghdr *msg,
+			    size_t len, int flags)
+{
+	int err;
+	struct sk_buff *skb;
+	struct sock *sk = sock->sk;
+
+	err = -EIO;
+	if (sk->sk_state & PPPOX_BOUND)
+		goto end;
+
+	err = 0;
+	skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
+				flags & MSG_DONTWAIT, &err);
+	if (!skb)
+		goto end;
+
+	if (len > skb->len)
+		len = skb->len;
+	else if (len < skb->len)
+		msg->msg_flags |= MSG_TRUNC;
+
+	err = skb_copy_datagram_msg(skb, 0, msg, len);
+	if (likely(err == 0))
+		err = len;
+
+	kfree_skb(skb);
+end:
+	return err;
+}
+
+static void pppol2tp_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
+{
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+	struct sock *sk = NULL;
+
+	/* If the socket is bound, send it in to PPP's input queue. Otherwise
+	 * queue it on the session socket.
+	 */
+	sk = ps->sock;
+	if (sk == NULL)
+		goto no_sock;
+
+	if (sk->sk_state & PPPOX_BOUND) {
+		struct pppox_sock *po;
+		l2tp_dbg(session, PPPOL2TP_MSG_DATA,
+			 "%s: recv %d byte data frame, passing to ppp\n",
+			 session->name, data_len);
+
+		/* We need to forget all info related to the L2TP packet
+		 * gathered in the skb as we are going to reuse the same
+		 * skb for the inner packet.
+		 * Namely we need to:
+		 * - reset xfrm (IPSec) information as it applies to
+		 *   the outer L2TP packet and not to the inner one
+		 * - release the dst to force a route lookup on the inner
+		 *   IP packet since skb->dst currently points to the dst
+		 *   of the UDP tunnel
+		 * - reset netfilter information as it doesn't apply
+		 *   to the inner packet either
+		 */
+		secpath_reset(skb);
+		skb_dst_drop(skb);
+		nf_reset(skb);
+
+		po = pppox_sk(sk);
+		ppp_input(&po->chan, skb);
+	} else {
+		l2tp_dbg(session, PPPOL2TP_MSG_DATA,
+			 "%s: recv %d byte data frame, passing to L2TP socket\n",
+			 session->name, data_len);
+
+		if (sock_queue_rcv_skb(sk, skb) < 0) {
+			atomic_long_inc(&session->stats.rx_errors);
+			kfree_skb(skb);
+		}
+	}
+
+	return;
+
+no_sock:
+	l2tp_info(session, PPPOL2TP_MSG_DATA, "%s: no socket\n", session->name);
+	kfree_skb(skb);
+}
+
+static void pppol2tp_session_sock_hold(struct l2tp_session *session)
+{
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+
+	if (ps->sock)
+		sock_hold(ps->sock);
+}
+
+static void pppol2tp_session_sock_put(struct l2tp_session *session)
+{
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+
+	if (ps->sock)
+		sock_put(ps->sock);
+}
+
+/************************************************************************
+ * Transmit handling
+ ***********************************************************************/
+
+/* This is the sendmsg for the PPPoL2TP pppol2tp_session socket.  We come here
+ * when a user application does a sendmsg() on the session socket. L2TP and
+ * PPP headers must be inserted into the user's data.
+ */
+static int pppol2tp_sendmsg(struct socket *sock, struct msghdr *m,
+			    size_t total_len)
+{
+	static const unsigned char ppph[2] = { 0xff, 0x03 };
+	struct sock *sk = sock->sk;
+	struct sk_buff *skb;
+	int error;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	struct pppol2tp_session *ps;
+	int uhlen;
+
+	error = -ENOTCONN;
+	if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
+		goto error;
+
+	/* Get session and tunnel contexts */
+	error = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (session == NULL)
+		goto error;
+
+	ps = l2tp_session_priv(session);
+	tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
+	if (tunnel == NULL)
+		goto error_put_sess;
+
+	uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
+
+	/* Allocate a socket buffer */
+	error = -ENOMEM;
+	skb = sock_wmalloc(sk, NET_SKB_PAD + sizeof(struct iphdr) +
+			   uhlen + session->hdr_len +
+			   sizeof(ppph) + total_len,
+			   0, GFP_KERNEL);
+	if (!skb)
+		goto error_put_sess_tun;
+
+	/* Reserve space for headers. */
+	skb_reserve(skb, NET_SKB_PAD);
+	skb_reset_network_header(skb);
+	skb_reserve(skb, sizeof(struct iphdr));
+	skb_reset_transport_header(skb);
+	skb_reserve(skb, uhlen);
+
+	/* Add PPP header */
+	skb->data[0] = ppph[0];
+	skb->data[1] = ppph[1];
+	skb_put(skb, 2);
+
+	/* Copy user data into skb */
+	error = memcpy_from_msg(skb_put(skb, total_len), m, total_len);
+	if (error < 0) {
+		kfree_skb(skb);
+		goto error_put_sess_tun;
+	}
+
+	local_bh_disable();
+	l2tp_xmit_skb(session, skb, session->hdr_len);
+	local_bh_enable();
+
+	sock_put(ps->tunnel_sock);
+	sock_put(sk);
+
+	return total_len;
+
+error_put_sess_tun:
+	sock_put(ps->tunnel_sock);
+error_put_sess:
+	sock_put(sk);
+error:
+	return error;
+}
+
+/* Transmit function called by generic PPP driver.  Sends PPP frame
+ * over PPPoL2TP socket.
+ *
+ * This is almost the same as pppol2tp_sendmsg(), but rather than
+ * being called with a msghdr from userspace, it is called with a skb
+ * from the kernel.
+ *
+ * The supplied skb from ppp doesn't have enough headroom for the
+ * insertion of L2TP, UDP and IP headers so we need to allocate more
+ * headroom in the skb. This will create a cloned skb. But we must be
+ * careful in the error case because the caller will expect to free
+ * the skb it supplied, not our cloned skb. So we take care to always
+ * leave the original skb unfreed if we return an error.
+ */
+static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
+{
+	static const u8 ppph[2] = { 0xff, 0x03 };
+	struct sock *sk = (struct sock *) chan->private;
+	struct sock *sk_tun;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	struct pppol2tp_session *ps;
+	int uhlen, headroom;
+
+	if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
+		goto abort;
+
+	/* Get session and tunnel contexts from the socket */
+	session = pppol2tp_sock_to_session(sk);
+	if (session == NULL)
+		goto abort;
+
+	ps = l2tp_session_priv(session);
+	sk_tun = ps->tunnel_sock;
+	if (sk_tun == NULL)
+		goto abort_put_sess;
+	tunnel = l2tp_sock_to_tunnel(sk_tun);
+	if (tunnel == NULL)
+		goto abort_put_sess;
+
+	uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
+	headroom = NET_SKB_PAD +
+		   sizeof(struct iphdr) + /* IP header */
+		   uhlen +		/* UDP header (if L2TP_ENCAPTYPE_UDP) */
+		   session->hdr_len +	/* L2TP header */
+		   sizeof(ppph);	/* PPP header */
+	if (skb_cow_head(skb, headroom))
+		goto abort_put_sess_tun;
+
+	/* Setup PPP header */
+	__skb_push(skb, sizeof(ppph));
+	skb->data[0] = ppph[0];
+	skb->data[1] = ppph[1];
+
+	local_bh_disable();
+	l2tp_xmit_skb(session, skb, session->hdr_len);
+	local_bh_enable();
+
+	sock_put(sk_tun);
+	sock_put(sk);
+	return 1;
+
+abort_put_sess_tun:
+	sock_put(sk_tun);
+abort_put_sess:
+	sock_put(sk);
+abort:
+	/* Free the original skb */
+	kfree_skb(skb);
+	return 1;
+}
+
+/*****************************************************************************
+ * Session (and tunnel control) socket create/destroy.
+ *****************************************************************************/
+
+/* Called by l2tp_core when a session socket is being closed.
+ */
+static void pppol2tp_session_close(struct l2tp_session *session)
+{
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+	struct sock *sk = ps->sock;
+	struct socket *sock = sk->sk_socket;
+
+	BUG_ON(session->magic != L2TP_SESSION_MAGIC);
+
+	if (sock) {
+		inet_shutdown(sock, 2);
+		/* Don't let the session go away before our socket does */
+		l2tp_session_inc_refcount(session);
+	}
+}
+
+/* Really kill the session socket. (Called from sock_put() if
+ * refcnt == 0.)
+ */
+static void pppol2tp_session_destruct(struct sock *sk)
+{
+	struct l2tp_session *session = sk->sk_user_data;
+	if (session) {
+		sk->sk_user_data = NULL;
+		BUG_ON(session->magic != L2TP_SESSION_MAGIC);
+		l2tp_session_dec_refcount(session);
+	}
+}
+
+/* Called when the PPPoX socket (session) is closed.
+ */
+static int pppol2tp_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct l2tp_session *session;
+	int error;
+
+	if (!sk)
+		return 0;
+
+	error = -EBADF;
+	lock_sock(sk);
+	if (sock_flag(sk, SOCK_DEAD) != 0)
+		goto error;
+
+	pppox_unbind_sock(sk);
+
+	/* Signal the death of the socket. */
+	sk->sk_state = PPPOX_DEAD;
+	sock_orphan(sk);
+	sock->sk = NULL;
+
+	session = pppol2tp_sock_to_session(sk);
+
+	/* Purge any queued data */
+	if (session != NULL) {
+		__l2tp_session_unhash(session);
+		l2tp_session_queue_purge(session);
+		sock_put(sk);
+	}
+	skb_queue_purge(&sk->sk_receive_queue);
+	skb_queue_purge(&sk->sk_write_queue);
+
+	release_sock(sk);
+
+	/* This will delete the session context via
+	 * pppol2tp_session_destruct() if the socket's refcnt drops to
+	 * zero.
+	 */
+	sock_put(sk);
+
+	return 0;
+
+error:
+	release_sock(sk);
+	return error;
+}
+
+static struct proto pppol2tp_sk_proto = {
+	.name	  = "PPPOL2TP",
+	.owner	  = THIS_MODULE,
+	.obj_size = sizeof(struct pppox_sock),
+};
+
+static int pppol2tp_backlog_recv(struct sock *sk, struct sk_buff *skb)
+{
+	int rc;
+
+	rc = l2tp_udp_encap_recv(sk, skb);
+	if (rc)
+		kfree_skb(skb);
+
+	return NET_RX_SUCCESS;
+}
+
+/* socket() handler. Initialize a new struct sock.
+ */
+static int pppol2tp_create(struct net *net, struct socket *sock)
+{
+	int error = -ENOMEM;
+	struct sock *sk;
+
+	sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppol2tp_sk_proto);
+	if (!sk)
+		goto out;
+
+	sock_init_data(sock, sk);
+
+	sock->state  = SS_UNCONNECTED;
+	sock->ops    = &pppol2tp_ops;
+
+	sk->sk_backlog_rcv = pppol2tp_backlog_recv;
+	sk->sk_protocol	   = PX_PROTO_OL2TP;
+	sk->sk_family	   = PF_PPPOX;
+	sk->sk_state	   = PPPOX_NONE;
+	sk->sk_type	   = SOCK_STREAM;
+	sk->sk_destruct	   = pppol2tp_session_destruct;
+
+	error = 0;
+
+out:
+	return error;
+}
+
+#if defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
+static void pppol2tp_show(struct seq_file *m, void *arg)
+{
+	struct l2tp_session *session = arg;
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+
+	if (ps) {
+		struct pppox_sock *po = pppox_sk(ps->sock);
+		if (po)
+			seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
+	}
+}
+#endif
+
+/* connect() handler. Attach a PPPoX socket to a tunnel UDP socket
+ */
+static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
+			    int sockaddr_len, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct sockaddr_pppol2tp *sp = (struct sockaddr_pppol2tp *) uservaddr;
+	struct pppox_sock *po = pppox_sk(sk);
+	struct l2tp_session *session = NULL;
+	struct l2tp_tunnel *tunnel;
+	struct pppol2tp_session *ps;
+	struct dst_entry *dst;
+	struct l2tp_session_cfg cfg = { 0, };
+	int error = 0;
+	u32 tunnel_id, peer_tunnel_id;
+	u32 session_id, peer_session_id;
+	int ver = 2;
+	int fd;
+
+	lock_sock(sk);
+
+	error = -EINVAL;
+	if (sp->sa_protocol != PX_PROTO_OL2TP)
+		goto end;
+
+	/* Check for already bound sockets */
+	error = -EBUSY;
+	if (sk->sk_state & PPPOX_CONNECTED)
+		goto end;
+
+	/* We don't supporting rebinding anyway */
+	error = -EALREADY;
+	if (sk->sk_user_data)
+		goto end; /* socket is already attached */
+
+	/* Get params from socket address. Handle L2TPv2 and L2TPv3.
+	 * This is nasty because there are different sockaddr_pppol2tp
+	 * structs for L2TPv2, L2TPv3, over IPv4 and IPv6. We use
+	 * the sockaddr size to determine which structure the caller
+	 * is using.
+	 */
+	peer_tunnel_id = 0;
+	if (sockaddr_len == sizeof(struct sockaddr_pppol2tp)) {
+		fd = sp->pppol2tp.fd;
+		tunnel_id = sp->pppol2tp.s_tunnel;
+		peer_tunnel_id = sp->pppol2tp.d_tunnel;
+		session_id = sp->pppol2tp.s_session;
+		peer_session_id = sp->pppol2tp.d_session;
+	} else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpv3)) {
+		struct sockaddr_pppol2tpv3 *sp3 =
+			(struct sockaddr_pppol2tpv3 *) sp;
+		ver = 3;
+		fd = sp3->pppol2tp.fd;
+		tunnel_id = sp3->pppol2tp.s_tunnel;
+		peer_tunnel_id = sp3->pppol2tp.d_tunnel;
+		session_id = sp3->pppol2tp.s_session;
+		peer_session_id = sp3->pppol2tp.d_session;
+	} else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpin6)) {
+		struct sockaddr_pppol2tpin6 *sp6 =
+			(struct sockaddr_pppol2tpin6 *) sp;
+		fd = sp6->pppol2tp.fd;
+		tunnel_id = sp6->pppol2tp.s_tunnel;
+		peer_tunnel_id = sp6->pppol2tp.d_tunnel;
+		session_id = sp6->pppol2tp.s_session;
+		peer_session_id = sp6->pppol2tp.d_session;
+	} else if (sockaddr_len == sizeof(struct sockaddr_pppol2tpv3in6)) {
+		struct sockaddr_pppol2tpv3in6 *sp6 =
+			(struct sockaddr_pppol2tpv3in6 *) sp;
+		ver = 3;
+		fd = sp6->pppol2tp.fd;
+		tunnel_id = sp6->pppol2tp.s_tunnel;
+		peer_tunnel_id = sp6->pppol2tp.d_tunnel;
+		session_id = sp6->pppol2tp.s_session;
+		peer_session_id = sp6->pppol2tp.d_session;
+	} else {
+		error = -EINVAL;
+		goto end; /* bad socket address */
+	}
+
+	/* Don't bind if tunnel_id is 0 */
+	error = -EINVAL;
+	if (tunnel_id == 0)
+		goto end;
+
+	tunnel = l2tp_tunnel_find(sock_net(sk), tunnel_id);
+
+	/* Special case: create tunnel context if session_id and
+	 * peer_session_id is 0. Otherwise look up tunnel using supplied
+	 * tunnel id.
+	 */
+	if ((session_id == 0) && (peer_session_id == 0)) {
+		if (tunnel == NULL) {
+			struct l2tp_tunnel_cfg tcfg = {
+				.encap = L2TP_ENCAPTYPE_UDP,
+				.debug = 0,
+			};
+			error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, &tcfg, &tunnel);
+			if (error < 0)
+				goto end;
+		}
+	} else {
+		/* Error if we can't find the tunnel */
+		error = -ENOENT;
+		if (tunnel == NULL)
+			goto end;
+
+		/* Error if socket is not prepped */
+		if (tunnel->sock == NULL)
+			goto end;
+	}
+
+	if (tunnel->recv_payload_hook == NULL)
+		tunnel->recv_payload_hook = pppol2tp_recv_payload_hook;
+
+	if (tunnel->peer_tunnel_id == 0)
+		tunnel->peer_tunnel_id = peer_tunnel_id;
+
+	/* Create session if it doesn't already exist. We handle the
+	 * case where a session was previously created by the netlink
+	 * interface by checking that the session doesn't already have
+	 * a socket and its tunnel socket are what we expect. If any
+	 * of those checks fail, return EEXIST to the caller.
+	 */
+	session = l2tp_session_find(sock_net(sk), tunnel, session_id);
+	if (session == NULL) {
+		/* Default MTU must allow space for UDP/L2TP/PPP
+		 * headers.
+		 */
+		cfg.mtu = cfg.mru = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+
+		/* Allocate and initialize a new session context. */
+		session = l2tp_session_create(sizeof(struct pppol2tp_session),
+					      tunnel, session_id,
+					      peer_session_id, &cfg);
+		if (session == NULL) {
+			error = -ENOMEM;
+			goto end;
+		}
+	} else {
+		ps = l2tp_session_priv(session);
+		error = -EEXIST;
+		if (ps->sock != NULL)
+			goto end;
+
+		/* consistency checks */
+		if (ps->tunnel_sock != tunnel->sock)
+			goto end;
+	}
+
+	/* Associate session with its PPPoL2TP socket */
+	ps = l2tp_session_priv(session);
+	ps->owner	     = current->pid;
+	ps->sock	     = sk;
+	ps->tunnel_sock = tunnel->sock;
+
+	session->recv_skb	= pppol2tp_recv;
+	session->session_close	= pppol2tp_session_close;
+#if defined(CONFIG_L2TP_DEBUGFS) || defined(CONFIG_L2TP_DEBUGFS_MODULE)
+	session->show		= pppol2tp_show;
+#endif
+
+	/* We need to know each time a skb is dropped from the reorder
+	 * queue.
+	 */
+	session->ref = pppol2tp_session_sock_hold;
+	session->deref = pppol2tp_session_sock_put;
+
+	/* If PMTU discovery was enabled, use the MTU that was discovered */
+	dst = sk_dst_get(tunnel->sock);
+	if (dst != NULL) {
+		u32 pmtu = dst_mtu(dst);
+
+		if (pmtu != 0)
+			session->mtu = session->mru = pmtu -
+				PPPOL2TP_HEADER_OVERHEAD;
+		dst_release(dst);
+	}
+
+	/* Special case: if source & dest session_id == 0x0000, this
+	 * socket is being created to manage the tunnel. Just set up
+	 * the internal context for use by ioctl() and sockopt()
+	 * handlers.
+	 */
+	if ((session->session_id == 0) &&
+	    (session->peer_session_id == 0)) {
+		error = 0;
+		goto out_no_ppp;
+	}
+
+	/* The only header we need to worry about is the L2TP
+	 * header. This size is different depending on whether
+	 * sequence numbers are enabled for the data channel.
+	 */
+	po->chan.hdrlen = PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
+
+	po->chan.private = sk;
+	po->chan.ops	 = &pppol2tp_chan_ops;
+	po->chan.mtu	 = session->mtu;
+
+	error = ppp_register_net_channel(sock_net(sk), &po->chan);
+	if (error)
+		goto end;
+
+out_no_ppp:
+	/* This is how we get the session context from the socket. */
+	sk->sk_user_data = session;
+	sk->sk_state = PPPOX_CONNECTED;
+	l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: created\n",
+		  session->name);
+
+end:
+	release_sock(sk);
+
+	return error;
+}
+
+#ifdef CONFIG_L2TP_V3
+
+/* Called when creating sessions via the netlink interface.
+ */
+static int pppol2tp_session_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
+{
+	int error;
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;
+	struct pppol2tp_session *ps;
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+
+	/* Error if we can't find the tunnel */
+	error = -ENOENT;
+	if (tunnel == NULL)
+		goto out;
+
+	/* Error if tunnel socket is not prepped */
+	if (tunnel->sock == NULL)
+		goto out;
+
+	/* Check that this session doesn't already exist */
+	error = -EEXIST;
+	session = l2tp_session_find(net, tunnel, session_id);
+	if (session != NULL)
+		goto out;
+
+	/* Default MTU values. */
+	if (cfg->mtu == 0)
+		cfg->mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+	if (cfg->mru == 0)
+		cfg->mru = cfg->mtu;
+
+	/* Allocate and initialize a new session context. */
+	error = -ENOMEM;
+	session = l2tp_session_create(sizeof(struct pppol2tp_session),
+				      tunnel, session_id,
+				      peer_session_id, cfg);
+	if (session == NULL)
+		goto out;
+
+	ps = l2tp_session_priv(session);
+	ps->tunnel_sock = tunnel->sock;
+
+	l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: created\n",
+		  session->name);
+
+	error = 0;
+
+out:
+	return error;
+}
+
+#endif /* CONFIG_L2TP_V3 */
+
+/* getname() support.
+ */
+static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
+			    int *usockaddr_len, int peer)
+{
+	int len = 0;
+	int error = 0;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	struct sock *sk = sock->sk;
+	struct inet_sock *inet;
+	struct pppol2tp_session *pls;
+
+	error = -ENOTCONN;
+	if (sk == NULL)
+		goto end;
+	if (sk->sk_state != PPPOX_CONNECTED)
+		goto end;
+
+	error = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (session == NULL)
+		goto end;
+
+	pls = l2tp_session_priv(session);
+	tunnel = l2tp_sock_to_tunnel(pls->tunnel_sock);
+	if (tunnel == NULL) {
+		error = -EBADF;
+		goto end_put_sess;
+	}
+
+	inet = inet_sk(tunnel->sock);
+	if ((tunnel->version == 2) && (tunnel->sock->sk_family == AF_INET)) {
+		struct sockaddr_pppol2tp sp;
+		len = sizeof(sp);
+		memset(&sp, 0, len);
+		sp.sa_family	= AF_PPPOX;
+		sp.sa_protocol	= PX_PROTO_OL2TP;
+		sp.pppol2tp.fd  = tunnel->fd;
+		sp.pppol2tp.pid = pls->owner;
+		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+		sp.pppol2tp.s_session = session->session_id;
+		sp.pppol2tp.d_session = session->peer_session_id;
+		sp.pppol2tp.addr.sin_family = AF_INET;
+		sp.pppol2tp.addr.sin_port = inet->inet_dport;
+		sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
+		memcpy(uaddr, &sp, len);
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if ((tunnel->version == 2) &&
+		   (tunnel->sock->sk_family == AF_INET6)) {
+		struct sockaddr_pppol2tpin6 sp;
+
+		len = sizeof(sp);
+		memset(&sp, 0, len);
+		sp.sa_family	= AF_PPPOX;
+		sp.sa_protocol	= PX_PROTO_OL2TP;
+		sp.pppol2tp.fd  = tunnel->fd;
+		sp.pppol2tp.pid = pls->owner;
+		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+		sp.pppol2tp.s_session = session->session_id;
+		sp.pppol2tp.d_session = session->peer_session_id;
+		sp.pppol2tp.addr.sin6_family = AF_INET6;
+		sp.pppol2tp.addr.sin6_port = inet->inet_dport;
+		memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
+		       sizeof(tunnel->sock->sk_v6_daddr));
+		memcpy(uaddr, &sp, len);
+	} else if ((tunnel->version == 3) &&
+		   (tunnel->sock->sk_family == AF_INET6)) {
+		struct sockaddr_pppol2tpv3in6 sp;
+
+		len = sizeof(sp);
+		memset(&sp, 0, len);
+		sp.sa_family	= AF_PPPOX;
+		sp.sa_protocol	= PX_PROTO_OL2TP;
+		sp.pppol2tp.fd  = tunnel->fd;
+		sp.pppol2tp.pid = pls->owner;
+		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+		sp.pppol2tp.s_session = session->session_id;
+		sp.pppol2tp.d_session = session->peer_session_id;
+		sp.pppol2tp.addr.sin6_family = AF_INET6;
+		sp.pppol2tp.addr.sin6_port = inet->inet_dport;
+		memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
+		       sizeof(tunnel->sock->sk_v6_daddr));
+		memcpy(uaddr, &sp, len);
+#endif
+	} else if (tunnel->version == 3) {
+		struct sockaddr_pppol2tpv3 sp;
+		len = sizeof(sp);
+		memset(&sp, 0, len);
+		sp.sa_family	= AF_PPPOX;
+		sp.sa_protocol	= PX_PROTO_OL2TP;
+		sp.pppol2tp.fd  = tunnel->fd;
+		sp.pppol2tp.pid = pls->owner;
+		sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
+		sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
+		sp.pppol2tp.s_session = session->session_id;
+		sp.pppol2tp.d_session = session->peer_session_id;
+		sp.pppol2tp.addr.sin_family = AF_INET;
+		sp.pppol2tp.addr.sin_port = inet->inet_dport;
+		sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
+		memcpy(uaddr, &sp, len);
+	}
+
+	*usockaddr_len = len;
+
+	sock_put(pls->tunnel_sock);
+end_put_sess:
+	sock_put(sk);
+	error = 0;
+
+end:
+	return error;
+}
+
+/****************************************************************************
+ * ioctl() handlers.
+ *
+ * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
+ * sockets. However, in order to control kernel tunnel features, we allow
+ * userspace to create a special "tunnel" PPPoX socket which is used for
+ * control only.  Tunnel PPPoX sockets have session_id == 0 and simply allow
+ * the user application to issue L2TP setsockopt(), getsockopt() and ioctl()
+ * calls.
+ ****************************************************************************/
+
+static void pppol2tp_copy_stats(struct pppol2tp_ioc_stats *dest,
+				struct l2tp_stats *stats)
+{
+	dest->tx_packets = atomic_long_read(&stats->tx_packets);
+	dest->tx_bytes = atomic_long_read(&stats->tx_bytes);
+	dest->tx_errors = atomic_long_read(&stats->tx_errors);
+	dest->rx_packets = atomic_long_read(&stats->rx_packets);
+	dest->rx_bytes = atomic_long_read(&stats->rx_bytes);
+	dest->rx_seq_discards = atomic_long_read(&stats->rx_seq_discards);
+	dest->rx_oos_packets = atomic_long_read(&stats->rx_oos_packets);
+	dest->rx_errors = atomic_long_read(&stats->rx_errors);
+}
+
+/* Session ioctl helper.
+ */
+static int pppol2tp_session_ioctl(struct l2tp_session *session,
+				  unsigned int cmd, unsigned long arg)
+{
+	struct ifreq ifr;
+	int err = 0;
+	struct sock *sk;
+	int val = (int) arg;
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	struct pppol2tp_ioc_stats stats;
+
+	l2tp_dbg(session, PPPOL2TP_MSG_CONTROL,
+		 "%s: pppol2tp_session_ioctl(cmd=%#x, arg=%#lx)\n",
+		 session->name, cmd, arg);
+
+	sk = ps->sock;
+	sock_hold(sk);
+
+	switch (cmd) {
+	case SIOCGIFMTU:
+		err = -ENXIO;
+		if (!(sk->sk_state & PPPOX_CONNECTED))
+			break;
+
+		err = -EFAULT;
+		if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
+			break;
+		ifr.ifr_mtu = session->mtu;
+		if (copy_to_user((void __user *) arg, &ifr, sizeof(struct ifreq)))
+			break;
+
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: get mtu=%d\n",
+			  session->name, session->mtu);
+		err = 0;
+		break;
+
+	case SIOCSIFMTU:
+		err = -ENXIO;
+		if (!(sk->sk_state & PPPOX_CONNECTED))
+			break;
+
+		err = -EFAULT;
+		if (copy_from_user(&ifr, (void __user *) arg, sizeof(struct ifreq)))
+			break;
+
+		session->mtu = ifr.ifr_mtu;
+
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: set mtu=%d\n",
+			  session->name, session->mtu);
+		err = 0;
+		break;
+
+	case PPPIOCGMRU:
+		err = -ENXIO;
+		if (!(sk->sk_state & PPPOX_CONNECTED))
+			break;
+
+		err = -EFAULT;
+		if (put_user(session->mru, (int __user *) arg))
+			break;
+
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: get mru=%d\n",
+			  session->name, session->mru);
+		err = 0;
+		break;
+
+	case PPPIOCSMRU:
+		err = -ENXIO;
+		if (!(sk->sk_state & PPPOX_CONNECTED))
+			break;
+
+		err = -EFAULT;
+		if (get_user(val, (int __user *) arg))
+			break;
+
+		session->mru = val;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: set mru=%d\n",
+			  session->name, session->mru);
+		err = 0;
+		break;
+
+	case PPPIOCGFLAGS:
+		err = -EFAULT;
+		if (put_user(ps->flags, (int __user *) arg))
+			break;
+
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: get flags=%d\n",
+			  session->name, ps->flags);
+		err = 0;
+		break;
+
+	case PPPIOCSFLAGS:
+		err = -EFAULT;
+		if (get_user(val, (int __user *) arg))
+			break;
+		ps->flags = val;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: set flags=%d\n",
+			  session->name, ps->flags);
+		err = 0;
+		break;
+
+	case PPPIOCGL2TPSTATS:
+		err = -ENXIO;
+		if (!(sk->sk_state & PPPOX_CONNECTED))
+			break;
+
+		memset(&stats, 0, sizeof(stats));
+		stats.tunnel_id = tunnel->tunnel_id;
+		stats.session_id = session->session_id;
+		pppol2tp_copy_stats(&stats, &session->stats);
+		if (copy_to_user((void __user *) arg, &stats,
+				 sizeof(stats)))
+			break;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: get L2TP stats\n",
+			  session->name);
+		err = 0;
+		break;
+
+	default:
+		err = -ENOSYS;
+		break;
+	}
+
+	sock_put(sk);
+
+	return err;
+}
+
+/* Tunnel ioctl helper.
+ *
+ * Note the special handling for PPPIOCGL2TPSTATS below. If the ioctl data
+ * specifies a session_id, the session ioctl handler is called. This allows an
+ * application to retrieve session stats via a tunnel socket.
+ */
+static int pppol2tp_tunnel_ioctl(struct l2tp_tunnel *tunnel,
+				 unsigned int cmd, unsigned long arg)
+{
+	int err = 0;
+	struct sock *sk;
+	struct pppol2tp_ioc_stats stats;
+
+	l2tp_dbg(tunnel, PPPOL2TP_MSG_CONTROL,
+		 "%s: pppol2tp_tunnel_ioctl(cmd=%#x, arg=%#lx)\n",
+		 tunnel->name, cmd, arg);
+
+	sk = tunnel->sock;
+	sock_hold(sk);
+
+	switch (cmd) {
+	case PPPIOCGL2TPSTATS:
+		err = -ENXIO;
+		if (!(sk->sk_state & PPPOX_CONNECTED))
+			break;
+
+		if (copy_from_user(&stats, (void __user *) arg,
+				   sizeof(stats))) {
+			err = -EFAULT;
+			break;
+		}
+		if (stats.session_id != 0) {
+			/* resend to session ioctl handler */
+			struct l2tp_session *session =
+				l2tp_session_find(sock_net(sk), tunnel, stats.session_id);
+			if (session != NULL)
+				err = pppol2tp_session_ioctl(session, cmd, arg);
+			else
+				err = -EBADR;
+			break;
+		}
+#ifdef CONFIG_XFRM
+		stats.using_ipsec = (sk->sk_policy[0] || sk->sk_policy[1]) ? 1 : 0;
+#endif
+		pppol2tp_copy_stats(&stats, &tunnel->stats);
+		if (copy_to_user((void __user *) arg, &stats, sizeof(stats))) {
+			err = -EFAULT;
+			break;
+		}
+		l2tp_info(tunnel, PPPOL2TP_MSG_CONTROL, "%s: get L2TP stats\n",
+			  tunnel->name);
+		err = 0;
+		break;
+
+	default:
+		err = -ENOSYS;
+		break;
+	}
+
+	sock_put(sk);
+
+	return err;
+}
+
+/* Main ioctl() handler.
+ * Dispatch to tunnel or session helpers depending on the socket.
+ */
+static int pppol2tp_ioctl(struct socket *sock, unsigned int cmd,
+			  unsigned long arg)
+{
+	struct sock *sk = sock->sk;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	struct pppol2tp_session *ps;
+	int err;
+
+	if (!sk)
+		return 0;
+
+	err = -EBADF;
+	if (sock_flag(sk, SOCK_DEAD) != 0)
+		goto end;
+
+	err = -ENOTCONN;
+	if ((sk->sk_user_data == NULL) ||
+	    (!(sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND))))
+		goto end;
+
+	/* Get session context from the socket */
+	err = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (session == NULL)
+		goto end;
+
+	/* Special case: if session's session_id is zero, treat ioctl as a
+	 * tunnel ioctl
+	 */
+	ps = l2tp_session_priv(session);
+	if ((session->session_id == 0) &&
+	    (session->peer_session_id == 0)) {
+		err = -EBADF;
+		tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
+		if (tunnel == NULL)
+			goto end_put_sess;
+
+		err = pppol2tp_tunnel_ioctl(tunnel, cmd, arg);
+		sock_put(ps->tunnel_sock);
+		goto end_put_sess;
+	}
+
+	err = pppol2tp_session_ioctl(session, cmd, arg);
+
+end_put_sess:
+	sock_put(sk);
+end:
+	return err;
+}
+
+/*****************************************************************************
+ * setsockopt() / getsockopt() support.
+ *
+ * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
+ * sockets. In order to control kernel tunnel features, we allow userspace to
+ * create a special "tunnel" PPPoX socket which is used for control only.
+ * Tunnel PPPoX sockets have session_id == 0 and simply allow the user
+ * application to issue L2TP setsockopt(), getsockopt() and ioctl() calls.
+ *****************************************************************************/
+
+/* Tunnel setsockopt() helper.
+ */
+static int pppol2tp_tunnel_setsockopt(struct sock *sk,
+				      struct l2tp_tunnel *tunnel,
+				      int optname, int val)
+{
+	int err = 0;
+
+	switch (optname) {
+	case PPPOL2TP_SO_DEBUG:
+		tunnel->debug = val;
+		l2tp_info(tunnel, PPPOL2TP_MSG_CONTROL, "%s: set debug=%x\n",
+			  tunnel->name, tunnel->debug);
+		break;
+
+	default:
+		err = -ENOPROTOOPT;
+		break;
+	}
+
+	return err;
+}
+
+/* Session setsockopt helper.
+ */
+static int pppol2tp_session_setsockopt(struct sock *sk,
+				       struct l2tp_session *session,
+				       int optname, int val)
+{
+	int err = 0;
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+
+	switch (optname) {
+	case PPPOL2TP_SO_RECVSEQ:
+		if ((val != 0) && (val != 1)) {
+			err = -EINVAL;
+			break;
+		}
+		session->recv_seq = val ? -1 : 0;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: set recv_seq=%d\n",
+			  session->name, session->recv_seq);
+		break;
+
+	case PPPOL2TP_SO_SENDSEQ:
+		if ((val != 0) && (val != 1)) {
+			err = -EINVAL;
+			break;
+		}
+		session->send_seq = val ? -1 : 0;
+		{
+			struct sock *ssk      = ps->sock;
+			struct pppox_sock *po = pppox_sk(ssk);
+			po->chan.hdrlen = val ? PPPOL2TP_L2TP_HDR_SIZE_SEQ :
+				PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
+		}
+		l2tp_session_set_header_len(session, session->tunnel->version);
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: set send_seq=%d\n",
+			  session->name, session->send_seq);
+		break;
+
+	case PPPOL2TP_SO_LNSMODE:
+		if ((val != 0) && (val != 1)) {
+			err = -EINVAL;
+			break;
+		}
+		session->lns_mode = val ? -1 : 0;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: set lns_mode=%d\n",
+			  session->name, session->lns_mode);
+		break;
+
+	case PPPOL2TP_SO_DEBUG:
+		session->debug = val;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: set debug=%x\n",
+			  session->name, session->debug);
+		break;
+
+	case PPPOL2TP_SO_REORDERTO:
+		session->reorder_timeout = msecs_to_jiffies(val);
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: set reorder_timeout=%d\n",
+			  session->name, session->reorder_timeout);
+		break;
+
+	default:
+		err = -ENOPROTOOPT;
+		break;
+	}
+
+	return err;
+}
+
+/* Main setsockopt() entry point.
+ * Does API checks, then calls either the tunnel or session setsockopt
+ * handler, according to whether the PPPoL2TP socket is a for a regular
+ * session or the special tunnel type.
+ */
+static int pppol2tp_setsockopt(struct socket *sock, int level, int optname,
+			       char __user *optval, unsigned int optlen)
+{
+	struct sock *sk = sock->sk;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	struct pppol2tp_session *ps;
+	int val;
+	int err;
+
+	if (level != SOL_PPPOL2TP)
+		return -EINVAL;
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
+	if (get_user(val, (int __user *)optval))
+		return -EFAULT;
+
+	err = -ENOTCONN;
+	if (sk->sk_user_data == NULL)
+		goto end;
+
+	/* Get session context from the socket */
+	err = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (session == NULL)
+		goto end;
+
+	/* Special case: if session_id == 0x0000, treat as operation on tunnel
+	 */
+	ps = l2tp_session_priv(session);
+	if ((session->session_id == 0) &&
+	    (session->peer_session_id == 0)) {
+		err = -EBADF;
+		tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
+		if (tunnel == NULL)
+			goto end_put_sess;
+
+		err = pppol2tp_tunnel_setsockopt(sk, tunnel, optname, val);
+		sock_put(ps->tunnel_sock);
+	} else
+		err = pppol2tp_session_setsockopt(sk, session, optname, val);
+
+	err = 0;
+
+end_put_sess:
+	sock_put(sk);
+end:
+	return err;
+}
+
+/* Tunnel getsockopt helper. Called with sock locked.
+ */
+static int pppol2tp_tunnel_getsockopt(struct sock *sk,
+				      struct l2tp_tunnel *tunnel,
+				      int optname, int *val)
+{
+	int err = 0;
+
+	switch (optname) {
+	case PPPOL2TP_SO_DEBUG:
+		*val = tunnel->debug;
+		l2tp_info(tunnel, PPPOL2TP_MSG_CONTROL, "%s: get debug=%x\n",
+			  tunnel->name, tunnel->debug);
+		break;
+
+	default:
+		err = -ENOPROTOOPT;
+		break;
+	}
+
+	return err;
+}
+
+/* Session getsockopt helper. Called with sock locked.
+ */
+static int pppol2tp_session_getsockopt(struct sock *sk,
+				       struct l2tp_session *session,
+				       int optname, int *val)
+{
+	int err = 0;
+
+	switch (optname) {
+	case PPPOL2TP_SO_RECVSEQ:
+		*val = session->recv_seq;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: get recv_seq=%d\n", session->name, *val);
+		break;
+
+	case PPPOL2TP_SO_SENDSEQ:
+		*val = session->send_seq;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: get send_seq=%d\n", session->name, *val);
+		break;
+
+	case PPPOL2TP_SO_LNSMODE:
+		*val = session->lns_mode;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: get lns_mode=%d\n", session->name, *val);
+		break;
+
+	case PPPOL2TP_SO_DEBUG:
+		*val = session->debug;
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL, "%s: get debug=%d\n",
+			  session->name, *val);
+		break;
+
+	case PPPOL2TP_SO_REORDERTO:
+		*val = (int) jiffies_to_msecs(session->reorder_timeout);
+		l2tp_info(session, PPPOL2TP_MSG_CONTROL,
+			  "%s: get reorder_timeout=%d\n", session->name, *val);
+		break;
+
+	default:
+		err = -ENOPROTOOPT;
+	}
+
+	return err;
+}
+
+/* Main getsockopt() entry point.
+ * Does API checks, then calls either the tunnel or session getsockopt
+ * handler, according to whether the PPPoX socket is a for a regular session
+ * or the special tunnel type.
+ */
+static int pppol2tp_getsockopt(struct socket *sock, int level, int optname,
+			       char __user *optval, int __user *optlen)
+{
+	struct sock *sk = sock->sk;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	int val, len;
+	int err;
+	struct pppol2tp_session *ps;
+
+	if (level != SOL_PPPOL2TP)
+		return -EINVAL;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	len = min_t(unsigned int, len, sizeof(int));
+
+	if (len < 0)
+		return -EINVAL;
+
+	err = -ENOTCONN;
+	if (sk->sk_user_data == NULL)
+		goto end;
+
+	/* Get the session context */
+	err = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (session == NULL)
+		goto end;
+
+	/* Special case: if session_id == 0x0000, treat as operation on tunnel */
+	ps = l2tp_session_priv(session);
+	if ((session->session_id == 0) &&
+	    (session->peer_session_id == 0)) {
+		err = -EBADF;
+		tunnel = l2tp_sock_to_tunnel(ps->tunnel_sock);
+		if (tunnel == NULL)
+			goto end_put_sess;
+
+		err = pppol2tp_tunnel_getsockopt(sk, tunnel, optname, &val);
+		sock_put(ps->tunnel_sock);
+	} else
+		err = pppol2tp_session_getsockopt(sk, session, optname, &val);
+
+	err = -EFAULT;
+	if (put_user(len, optlen))
+		goto end_put_sess;
+
+	if (copy_to_user((void __user *) optval, &val, len))
+		goto end_put_sess;
+
+	err = 0;
+
+end_put_sess:
+	sock_put(sk);
+end:
+	return err;
+}
+
+/*****************************************************************************
+ * /proc filesystem for debug
+ * Since the original pppol2tp driver provided /proc/net/pppol2tp for
+ * L2TPv2, we dump only L2TPv2 tunnels and sessions here.
+ *****************************************************************************/
+
+static unsigned int pppol2tp_net_id;
+
+#ifdef CONFIG_PROC_FS
+
+struct pppol2tp_seq_data {
+	struct seq_net_private p;
+	int tunnel_idx;			/* current tunnel */
+	int session_idx;		/* index of session within current tunnel */
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;	/* NULL means get next tunnel */
+};
+
+static void pppol2tp_next_tunnel(struct net *net, struct pppol2tp_seq_data *pd)
+{
+	for (;;) {
+		pd->tunnel = l2tp_tunnel_find_nth(net, pd->tunnel_idx);
+		pd->tunnel_idx++;
+
+		if (pd->tunnel == NULL)
+			break;
+
+		/* Ignore L2TPv3 tunnels */
+		if (pd->tunnel->version < 3)
+			break;
+	}
+}
+
+static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
+{
+	pd->session = l2tp_session_find_nth(pd->tunnel, pd->session_idx);
+	pd->session_idx++;
+
+	if (pd->session == NULL) {
+		pd->session_idx = 0;
+		pppol2tp_next_tunnel(net, pd);
+	}
+}
+
+static void *pppol2tp_seq_start(struct seq_file *m, loff_t *offs)
+{
+	struct pppol2tp_seq_data *pd = SEQ_START_TOKEN;
+	loff_t pos = *offs;
+	struct net *net;
+
+	if (!pos)
+		goto out;
+
+	BUG_ON(m->private == NULL);
+	pd = m->private;
+	net = seq_file_net(m);
+
+	if (pd->tunnel == NULL)
+		pppol2tp_next_tunnel(net, pd);
+	else
+		pppol2tp_next_session(net, pd);
+
+	/* NULL tunnel and session indicates end of list */
+	if ((pd->tunnel == NULL) && (pd->session == NULL))
+		pd = NULL;
+
+out:
+	return pd;
+}
+
+static void *pppol2tp_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	return NULL;
+}
+
+static void pppol2tp_seq_stop(struct seq_file *p, void *v)
+{
+	/* nothing to do */
+}
+
+static void pppol2tp_seq_tunnel_show(struct seq_file *m, void *v)
+{
+	struct l2tp_tunnel *tunnel = v;
+
+	seq_printf(m, "\nTUNNEL '%s', %c %d\n",
+		   tunnel->name,
+		   (tunnel == tunnel->sock->sk_user_data) ? 'Y' : 'N',
+		   atomic_read(&tunnel->ref_count) - 1);
+	seq_printf(m, " %08x %ld/%ld/%ld %ld/%ld/%ld\n",
+		   tunnel->debug,
+		   atomic_long_read(&tunnel->stats.tx_packets),
+		   atomic_long_read(&tunnel->stats.tx_bytes),
+		   atomic_long_read(&tunnel->stats.tx_errors),
+		   atomic_long_read(&tunnel->stats.rx_packets),
+		   atomic_long_read(&tunnel->stats.rx_bytes),
+		   atomic_long_read(&tunnel->stats.rx_errors));
+}
+
+static void pppol2tp_seq_session_show(struct seq_file *m, void *v)
+{
+	struct l2tp_session *session = v;
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+	struct pppox_sock *po = pppox_sk(ps->sock);
+	u32 ip = 0;
+	u16 port = 0;
+
+	if (tunnel->sock) {
+		struct inet_sock *inet = inet_sk(tunnel->sock);
+		ip = ntohl(inet->inet_saddr);
+		port = ntohs(inet->inet_sport);
+	}
+
+	seq_printf(m, "  SESSION '%s' %08X/%d %04X/%04X -> "
+		   "%04X/%04X %d %c\n",
+		   session->name, ip, port,
+		   tunnel->tunnel_id,
+		   session->session_id,
+		   tunnel->peer_tunnel_id,
+		   session->peer_session_id,
+		   ps->sock->sk_state,
+		   (session == ps->sock->sk_user_data) ?
+		   'Y' : 'N');
+	seq_printf(m, "   %d/%d/%c/%c/%s %08x %u\n",
+		   session->mtu, session->mru,
+		   session->recv_seq ? 'R' : '-',
+		   session->send_seq ? 'S' : '-',
+		   session->lns_mode ? "LNS" : "LAC",
+		   session->debug,
+		   jiffies_to_msecs(session->reorder_timeout));
+	seq_printf(m, "   %hu/%hu %ld/%ld/%ld %ld/%ld/%ld\n",
+		   session->nr, session->ns,
+		   atomic_long_read(&session->stats.tx_packets),
+		   atomic_long_read(&session->stats.tx_bytes),
+		   atomic_long_read(&session->stats.tx_errors),
+		   atomic_long_read(&session->stats.rx_packets),
+		   atomic_long_read(&session->stats.rx_bytes),
+		   atomic_long_read(&session->stats.rx_errors));
+
+	if (po)
+		seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
+}
+
+static int pppol2tp_seq_show(struct seq_file *m, void *v)
+{
+	struct pppol2tp_seq_data *pd = v;
+
+	/* display header on line 1 */
+	if (v == SEQ_START_TOKEN) {
+		seq_puts(m, "PPPoL2TP driver info, " PPPOL2TP_DRV_VERSION "\n");
+		seq_puts(m, "TUNNEL name, user-data-ok session-count\n");
+		seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
+		seq_puts(m, "  SESSION name, addr/port src-tid/sid "
+			 "dest-tid/sid state user-data-ok\n");
+		seq_puts(m, "   mtu/mru/rcvseq/sendseq/lns debug reorderto\n");
+		seq_puts(m, "   nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
+		goto out;
+	}
+
+	/* Show the tunnel or session context.
+	 */
+	if (pd->session == NULL)
+		pppol2tp_seq_tunnel_show(m, pd->tunnel);
+	else
+		pppol2tp_seq_session_show(m, pd->session);
+
+out:
+	return 0;
+}
+
+static const struct seq_operations pppol2tp_seq_ops = {
+	.start		= pppol2tp_seq_start,
+	.next		= pppol2tp_seq_next,
+	.stop		= pppol2tp_seq_stop,
+	.show		= pppol2tp_seq_show,
+};
+
+/* Called when our /proc file is opened. We allocate data for use when
+ * iterating our tunnel / session contexts and store it in the private
+ * data of the seq_file.
+ */
+static int pppol2tp_proc_open(struct inode *inode, struct file *file)
+{
+	return seq_open_net(inode, file, &pppol2tp_seq_ops,
+			    sizeof(struct pppol2tp_seq_data));
+}
+
+static const struct file_operations pppol2tp_proc_fops = {
+	.owner		= THIS_MODULE,
+	.open		= pppol2tp_proc_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release_net,
+};
+
+#endif /* CONFIG_PROC_FS */
+
+/*****************************************************************************
+ * Network namespace
+ *****************************************************************************/
+
+static __net_init int pppol2tp_init_net(struct net *net)
+{
+	struct proc_dir_entry *pde;
+	int err = 0;
+
+	pde = proc_create("pppol2tp", S_IRUGO, net->proc_net,
+			  &pppol2tp_proc_fops);
+	if (!pde) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+out:
+	return err;
+}
+
+static __net_exit void pppol2tp_exit_net(struct net *net)
+{
+	remove_proc_entry("pppol2tp", net->proc_net);
+}
+
+static struct pernet_operations pppol2tp_net_ops = {
+	.init = pppol2tp_init_net,
+	.exit = pppol2tp_exit_net,
+	.id   = &pppol2tp_net_id,
+};
+
+/*****************************************************************************
+ * Init and cleanup
+ *****************************************************************************/
+
+static const struct proto_ops pppol2tp_ops = {
+	.family		= AF_PPPOX,
+	.owner		= THIS_MODULE,
+	.release	= pppol2tp_release,
+	.bind		= sock_no_bind,
+	.connect	= pppol2tp_connect,
+	.socketpair	= sock_no_socketpair,
+	.accept		= sock_no_accept,
+	.getname	= pppol2tp_getname,
+	.poll		= datagram_poll,
+	.listen		= sock_no_listen,
+	.shutdown	= sock_no_shutdown,
+	.setsockopt	= pppol2tp_setsockopt,
+	.getsockopt	= pppol2tp_getsockopt,
+	.sendmsg	= pppol2tp_sendmsg,
+	.recvmsg	= pppol2tp_recvmsg,
+	.mmap		= sock_no_mmap,
+	.ioctl		= pppox_ioctl,
+};
+
+static const struct pppox_proto pppol2tp_proto = {
+	.create		= pppol2tp_create,
+	.ioctl		= pppol2tp_ioctl,
+	.owner		= THIS_MODULE,
+};
+
+#ifdef CONFIG_L2TP_V3
+
+static const struct l2tp_nl_cmd_ops pppol2tp_nl_cmd_ops = {
+	.session_create	= pppol2tp_session_create,
+	.session_delete	= l2tp_session_delete,
+};
+
+#endif /* CONFIG_L2TP_V3 */
+
+static int __init pppol2tp_init(void)
+{
+	int err;
+
+	err = register_pernet_device(&pppol2tp_net_ops);
+	if (err)
+		goto out;
+
+	err = proto_register(&pppol2tp_sk_proto, 0);
+	if (err)
+		goto out_unregister_pppol2tp_pernet;
+
+	err = register_pppox_proto(PX_PROTO_OL2TP, &pppol2tp_proto);
+	if (err)
+		goto out_unregister_pppol2tp_proto;
+
+#ifdef CONFIG_L2TP_V3
+	err = l2tp_nl_register_ops(L2TP_PWTYPE_PPP, &pppol2tp_nl_cmd_ops);
+	if (err)
+		goto out_unregister_pppox;
+#endif
+
+	pr_info("PPPoL2TP kernel driver, %s\n", PPPOL2TP_DRV_VERSION);
+
+out:
+	return err;
+
+#ifdef CONFIG_L2TP_V3
+out_unregister_pppox:
+	unregister_pppox_proto(PX_PROTO_OL2TP);
+#endif
+out_unregister_pppol2tp_proto:
+	proto_unregister(&pppol2tp_sk_proto);
+out_unregister_pppol2tp_pernet:
+	unregister_pernet_device(&pppol2tp_net_ops);
+	goto out;
+}
+
+static void __exit pppol2tp_exit(void)
+{
+#ifdef CONFIG_L2TP_V3
+	l2tp_nl_unregister_ops(L2TP_PWTYPE_PPP);
+#endif
+	unregister_pppox_proto(PX_PROTO_OL2TP);
+	proto_unregister(&pppol2tp_sk_proto);
+	unregister_pernet_device(&pppol2tp_net_ops);
+}
+
+module_init(pppol2tp_init);
+module_exit(pppol2tp_exit);
+
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("PPP over L2TP over UDP");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(PPPOL2TP_DRV_VERSION);
+MODULE_ALIAS("pppox-proto-" __stringify(PX_PROTO_OL2TP));